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Sample records for high-velocity low-amplitude spinal

  1. Neural responses to the mechanical characteristics of high velocity, low amplitude spinal manipulation: effect of specific contact site

    PubMed Central

    Reed, William R.; Long, Cynthia R.; Kawchuk, Gregory N.; Pickar, Joel G.

    2015-01-01

    Background Systematic investigations are needed identifying how variability in the biomechanical characteristics of spinal manipulation affects physiological responses. Such knowledge may inform future clinical practice and research study design. Objective To determine how contact site for high velocity, low amplitude spinal manipulation (HVLA-SM) affects sensory input to the central nervous system. Design HVLA-SM was applied to 4 specific anatomic locations using a no-HVLA-SM control at each location randomized in an 8×8 Latin square design in an animal model. Methods Neural activity from muscle spindles in the multifidus and longissimus muscles were recorded from L6 dorsal rootlets in 16 anesthetized cats. A posterior to anterior HVLA-SM was applied through the intact skin overlying the L6 spinous process, lamina, inferior articular process and L7 spinous process. HVLA-SMs were preceded and followed by simulated spinal movement applied to the L6 vertebra. Change in mean instantaneous discharge frequency (ΔMIF) was determined during the thrust and the simulated spinal movement. Results All contact sites increased L6 muscle spindle discharge during the thrust. Contact at all L6 sites significantly increased spindle discharge more than at the L7 site when recording at L6. There were no differences between L6 contact sites. For simulated movement, the L6 contact sites but not the L7 contact site significantly decreased L6 spindle responses to a change in vertebral position but not to movement to that position. Conclusions This animal study showed that contact site for an HVLA-SM can have a significant effect on the magnitude of sensory input arising from muscle spindles in the back. PMID:25841562

  2. Neural responses to the mechanical parameters of a high velocity, low amplitude spinal manipulation: effect of preload parameters

    PubMed Central

    Reed, William. R.; Long, Cynthia R.; Kawchuk, Gregory N.; Pickar, Joel G.

    2014-01-01

    Objective The purpose of this study was to determine how the preload that precedes a high velocity low amplitude spinal manipulation (HVLA-SM) affects muscle spindle input from lumbar paraspinal muscles both during and after the HVLA-SM. Methods Primary afferent activity from muscle spindles in lumbar paraspinal muscles were recorded from the L6 dorsal root in anesthetized cats. HVLA-SM of the L6 vertebra was preceded either by no preload or by systematic changes in the preload magnitude, duration, and the presence or absence of a downward incisural point (DIP). Immediate effects of preload on muscle spindle responses to the HVLA-SM were determined by comparing mean instantaneous discharge frequencies (MIF) during the HVLA-SM’s thrust phase with baseline. Longer lasting effects of preload on spindle responses to the HVLA-SM were determined by comparing MIF during slow ramp and hold movement of the L6 vertebra before and following the HVLA-SM. Results The smaller compared to the larger preload magnitude and the longer compared to the shorter preload duration significantly increased (P=0.02 and P=0.04) respectively) muscle spindle responses during the HVLA-SM thrust. The absence of preload had the greatest effect on the change in MIF. Interactions between preload magnitude, duration and DIP often produced statistically significant but arguably physiologically modest changes in the passive signaling properties of the muscle spindle following the manipulation. Conclusion Because preload parameters in this animal model were shown to affect neural responses to an HVLA-SM, preload characteristics should be taken into consideration when judging this intervention’s therapeutic benefit in both clinical efficacy studies and in clinical practice. PMID:24387888

  3. Establishing force and speed training targets for lumbar spine high-velocity, low-amplitude chiropractic adjustments*

    PubMed Central

    Owens, Edward F.; Hosek, Ronald S.; Sullivan, Stephanie G.B.; Russell, Brent S.; Mullin, Linda E.; Dever, Lydia L.

    2016-01-01

    Objective: We developed an adjusting bench with a force plate supporting the lumbar portion to measure loads transmitted during lumbar manual adjustment. It will be used to provide force-feedback to enhance student learning in technique labs. The study goal is to define the learning target loads and speeds, with instructors as expert models. Methods: A total of 11 faculty members experienced in teaching Gonstead technique methods performed 81 simulated adjustments on a mannequin on the force plate. Adjustments were along 9 lumbopelvic “listings” at 3 load levels: light, normal, and heavy. We analyzed the thrusts to find preload, peak load, duration, and thrust rate. Results: Analysis of 891 thrusts showed wide variations between doctors. Peak loads ranged from 100 to 1400 N. All doctors showed clear distinctions between peak load levels, but there was overlap between high and low loads. Thrust rates were more uniform across doctors, averaging 3 N/ms. Conclusion: These faculty members delivered a range of thrusts, not unlike those seen in the literature for high velocity, low amplitude manipulation. We have established at least minimum force and speed targets for student performance, but more work must be done to create a normative adjustment to guide refinement of student learning. PMID:26600272

  4. The relationship of the audible pop to hypoalgesia associated with high velocity, low amplitude thrust manipulation: A secondary analysis of an experimental study in pain free participants

    PubMed Central

    Bishop, Mark D; Robinson, Michael E; George, Steven Z

    2010-01-01

    Objective High velocity, low amplitude (HVLA) manipulation is an effective treatment for low back pain (LBP); however, the corresponding mechanisms are undetermined. Hypoalgesia is associated with HVLA manipulation and suggests specific mechanisms of action. An audible pop (AP) is also associated with HVLA manipulation; however, the influence of the AP on the hypoalgesia associated with HVLA manipulation is not established. The purpose of the current study was to observe the influence of the AP on hypoalgesia associated with HVLA manipulation. Methods The current study represents a secondary analysis of 40 participants. All participants underwent thermal pain sensitivity testing to their leg and low back using protocols specific to Aδ fiber mediated pain and temporal summation. Next, participants received HVLA manipulation to their low back and the examiner recorded whether or not an AP was perceived. Finally, participants underwent immediate follow up thermal pain sensitivity testing using the same protocols. Separate repeated measure ANOVAs were used to observe changes in pain sensitivity prior to and immediately following HVLA manipulation. Results Hypoalgesia of Aδ fiber mediated pain was observed in the low back following HVLA (p< 0.05) and this was independent of whether an AP was perceived (p> 0.05). Hypoalgesia of temporal summation was observed in the lower extremity following HVLA (p< 0.05) and this was independent of whether an AP was perceived (p= 0.08). However, a moderate effect size for temporal summation was observed favoring participants in whom an AP was perceived. Conclusion The current study suggests hypoalgesia is associated with HVLA manipulation and occurs independently of a perceived AP. Inhibition of lower extremity temporal summation may be larger in individuals in whom an AP is perceived, but further study is necessary to confirm this finding. PMID:20170777

  5. Kinematics of the upper cervical spine during high velocity-low amplitude manipulation. Analysis of intra- and inter-operator reliability for pre-manipulation positioning and impulse displacements.

    PubMed

    Dugailly, Pierre-Michel; Beyer, Benoît; Sobczak, Stéphane; Salvia, Patrick; Rooze, Marcel; Feipel, Véronique

    2014-10-01

    To date, kinematics data analyzing continuous 3D motion of upper cervical spine (UCS) manipulation is lacking. This in vitro study aims at investigating inter- and intra-operator reliability of kinematics during high velocity low amplitude manipulation of the UCS. Three fresh specimens were used. Restricted dissection was realized to attach technical clusters to each bone (skull to C2). Motion data was obtained using an optoelectronic system during manipulation. Kinematics data were integrated into specific-subject 3D models to provide anatomical motion representation during thrust manipulation. The reliability of manipulation kinematics was assessed for three practitioners performing two sessions of three repetitions on two separate days. For pre-manipulation positioning, average UCS ROM (SD) were 10° (5°), 22° (5°) and 14° (4°) for lateral bending, axial rotation and flexion-extension, respectively. For the impulse phase, average axial rotation magnitude ranged from 7° to 12°. Reliability analysis showed average RMS up to 8° for pre-manipulation positioning and up to 5° for the impulse phase. As compared to physiological ROM, this study supports the limited angular displacement during manipulation for UCS motion components, especially for axial rotation. Kinematics reliability confirms intra- and inter-operator consistency although pre-manipulation positioning reliability is slightly lower between practitioners and sessions.

  6. High Velocity Gas Gun

    NASA Technical Reports Server (NTRS)

    1988-01-01

    A video tape related to orbital debris research is presented. The video tape covers the process of loading a High Velocity Gas Gun and firing it into a mounted metal plate. The process is then repeated in slow motion.

  7. Particle Distribution Modification by Low Amplitude Modes

    SciTech Connect

    White, R. B.; Gorelenkov, N.; Heidbrink, W. W.; Van Zeeland, M. A.

    2009-08-28

    Modification of a high energy particle distribution by a spectrum of low amplitude modes is investigated using a guiding center code. Only through resonance are modes effective in modifying the distribution. Diagnostics are used to illustrate the mode-particle interaction and to find which effects are relevant in producing significant resonance, including kinetic Poincare plots and plots showing those orbits with time averaged mode-particle energy transfer. Effects of pitch angle scattering and drag are studied, as well as plasma rotation and time dependence of the equilibrium and mode frequencies. A specific example of changes observed in a DIII-D deuterium beam distribution in the presence of low amplitude experimentally validated Toroidal Alfven (TAE) eigenmodes and Reversed Shear Alfven (RSAE) eigenmodes is examined in detail. Comparison with experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam profile modification, and that the experimental amplitudes are only slightly above this threshold.

  8. Low Amplitude Impact of Damaged PBX 9501

    NASA Astrophysics Data System (ADS)

    Idar, Deanne

    1999-06-01

    Low amplitude impact tests on damaged, baseline and aged, PBX 9501 specimens have been performed to determine the critical impact-velocity threshold for violent reaction. Tests were performed using 3.0-in. diameter, 2 kg. mild-steel projectiles launched from a spigot gun at lightly confined modified Steven targets. Prior damage on the seven targets was induced by a single impact ranging in velocity from 36.9 to 52.7 m/s. External blast gauge data were coupled with ballistic pendulum data to evaluate the level of reaction violence relative to a steady-state detonation. Strain gage data were used to evaluate the response of the explosive to impact and characterize subsequent reaction profiles. The effect of PBX 9501 lots, age, and prior level of damage on threshold behavior will be discussed and compared to single impact test results.

  9. Virchow's Triad and spinal manipulative therapy of the cervical spine

    PubMed Central

    Symons, Bruce P; Westaway, Michael

    2001-01-01

    The objective of this review paper is to borrow Virchow's Triad as a conceptual framework to examine the state of the art in research on thrombosis, specifically in the vertebrobasilar system as a consequence of high velocity, low amplitude spinal manipulation of the cervical spine. A revised Virchow's Triad is presented which emphasizes the interactions between various risk factors, as a tool for clinicians and researchers to use in their analyses of vertebrobasilar stroke. Endothelial injury, abnormal blood flow and hypercoagulability are discussed.

  10. High Velocity Clouds

    NASA Technical Reports Server (NTRS)

    Wolfire, M. G.; McKee, C. F.; Hollenbach, D. J.; Tielens, A. G. G. M.; Morrison, David (Technical Monitor)

    1994-01-01

    We calculate the thermal equilibrium gas temperature of high velocity clouds (HVCs) in the Galactic Halo. Our method accounts for the photoelectric heating from small grains and PAHs, and includes a detailed treatment of the ionization rates and heating due to the soft X-ray background and due to cosmic rays. Phase diagrams (thermal pressure P versus gas density n) are presented for gas with a range of dust/gas ratios (D/G) and a range of metallicities (Z). Variations in D/G affect mainly the photoelectric heating rate, while variations in Z affect both the photoelectric heating and gas cooling. Curves are shown for D/G = 1 (local value) to D/G less than approx. equal to 0.005 and for Z=1 (local value) to Z= 0.005. We find that a two phase medium (CNM + WNM) can be in pressure equilibrium with a hot (T approximately 1-2 x 10(exp 6) K) halo within a range of permitted pressures, P(sup min) to P(sup max). We take halo parameters consistent with observed properties of the soft X-ray background. In general, both P(sup min) and P(sup max) decrease with lower D/G due to a drop in photoelectric heating from grains, while. P(sup min) and P(sup max) increase with lower Z due to a drop in gas coolants. We demonstrate that successful two phase models can be constructed with pressure in the range 10(exp 3) less than approximately equal to P/k less than approximately equal to 10(exp 4) K cm(exp -3) consistent with the thermal pressure in the Galactic disk. In addition, using the observed relation between CNM density and distance in HVCs, (n = 75/fDkpc cm(exp -3); Wakker & Schwarz 1991, AA, 250, 484) we show that our pressure curves constrain the allowed range of HVC heights to be between 0.3 - 16 kpc.

  11. Effect of Spinal Manipulation Thrust Duration on Trunk Mechanical Activation Thresholds of Nociceptive-Specific Lateral Thalamic Neurons

    PubMed Central

    Reed, William R.; Sozio, Randall; Pickar, Joel G.; Onifer, Stephen M.

    2015-01-01

    Objective The objective of this preliminary study was to determine if high-velocity, low-amplitude spinal manipulation (HVLA-SM) thrust duration alters mechanical trunk activation thresholds of nociceptive-specific (NS) lateral thalamic neurons. Methods Extracellular recordings were obtained from 18 NS neurons located in 2 lateral thalamic nuclei (ventrolateral [n = 12] and posterior [n = 6]) in normal anesthetized Wistar rats. Response thresholds to electronic von Frey anesthesiometer (rigid tip) mechanical trunk stimuli applied in 3 lumbar directions (dorsal-ventral, 45° caudal, and 45° cranial) were determined before and immediately after the delivery of 3 HVLA-SM thrust durations (time control 0, 100, and 400 milliseconds). Mean changes in mechanical trunk activation thresholds were compared using a mixed model analysis of variance. Results High-velocity, low-amplitude spinal manipulation duration did not significantly alter NS lateral thalamic neurons’ mechanical trunk responses to any of the 3 directions tested with the anesthesiometer. Conclusions This study is the first to examine the effect of HVLA-SM thrust duration on NS lateral thalamic mechanical response thresholds. High-velocity, low-amplitude spinal manipulation thrust duration did not affect mechanical trunk thresholds. PMID:25220757

  12. Two-color pyrometry for low amplitude periodic heating

    NASA Astrophysics Data System (ADS)

    Bennett, T. D.; Silveira, V. B.; Valdes, R.

    2017-02-01

    Specimens subject to periodic heating must be probed for a calibrated temperature response if standard measurements of thermal diffusivity are to be extended to determine thermal conductivity. A variation on two-color pyrometry is developed to measure both the offset and harmonic amplitudes of temperature fluctuations caused by periodic heating. The requisite pyrometric formulae are derived for low amplitude heating using an expansion of the nonlinear thermal emission. Well-defined uncertainties in the temperature values are determined from experimental uncertainties in radiometric measurements. The accuracy demonstrated in this work is better than 2% for the temperature offset and 3%-8% for the fluctuating temperature amplitude.

  13. Development of vibration isolation platform for low amplitude vibration

    NASA Astrophysics Data System (ADS)

    Lee, Dae-Oen; Park, Geeyong; Han, Jae-Hung

    2014-03-01

    The performance of high precision payloads on board a satellite is extremely sensitive to vibration. Although vibration environment of a satellite on orbit is very gentle compared to the launch environment, even a low amplitude vibration disturbances generated by reaction wheel assembly, cryocoolers, etc may cause serious problems in performing tasks such as capturing high resolution images. The most commonly taken approach to protect sensitive payloads from performance degrading vibration is application of vibration isolator. In this paper, development of vibration isolation platform for low amplitude vibration is discussed. Firstly, single axis vibration isolator is developed by adapting three parameter model using bellows and viscous fluid. The isolation performance of the developed single axis isolator is evaluated by measuring force transmissibility. The measured transmissibility shows that both the low Q-factor (about 2) and the high roll-off rate (about -40 dB/dec) are achieved with the developed isolator. Then, six single axis isolators are combined to form Stewart platform in cubic configuration to provide multi-axis vibration isolation. The isolation performance of the developed multi-axis isolator is evaluated using a simple prototype reaction wheel model in which wheel imbalance is the major source of vibration. The transmitted force without vibration isolator is measured and compared with the transmitted force with vibration isolator. More than 20 dB reduction of the X and Y direction (radial direction of flywheel) disturbance is observed for rotating wheel speed of 100 Hz and higher.

  14. High velocity collisions of nanoparticles

    NASA Astrophysics Data System (ADS)

    Johnson, Donald F.; Mattson, William D.

    2017-01-01

    Nanoparticles (NPs) are a unique class of material with highly functionalizable surfaces and exciting applications. With a large surface-to-volume ratio and potentially high surface tension, shocked nanoparticles might display unique materials behavior. Using density functional theory, we have simulated high-velocity NP collisions under a variety of conditions. NPs composed of diamond-C, cubic-BN, and diamond-Si were considered with particle sizes up to 3.5 nm diameter. Additional simulations involved NPs that were destabilized by incorporating internal strain. The initial spherical NP structures were carved out of bulk crystals while the NPs with internal strain were constructed as a dense core (compressive strain) encompassed by a thin shell (tensile strain). Both on-axis and off-axis collisions were simulated at 10 km/s relative velocity. The amount of internal strain was artificially increased by creating a dense inner core with bond lengths compressed up to 8%. Collision dynamics, shock propagation, and fragmentation will be analyzed, but the simulation are ongoing and results are not finalized. The effect of material properties, internal strain, and collision velocity will be discussed.

  15. High velocity impact experiment (HVIE)

    SciTech Connect

    Toor, A.; Donich, T.; Carter, P.

    1998-02-01

    The HVIE space project was conceived as a way to measure the absolute EOS for approximately 10 materials at pressures up to {approximately}30 Mb with order-of-magnitude higher accuracy than obtainable in any comparable experiment conducted on earth. The experiment configuration is such that each of the 10 materials interacts with all of the others thereby producing one-hundred independent, simultaneous EOS experiments The materials will be selected to provide critical information to weapons designers, National Ignition Facility target designers and planetary and geophysical scientists. In addition, HVIE will provide important scientific information to other communities, including the Ballistic Missile Defense Organization and the lethality and vulnerability community. The basic HVIE concept is to place two probes in counter rotating, highly elliptical orbits and collide them at high velocity (20 km/s) at 100 km altitude above the earth. The low altitude of the experiment will provide quick debris strip-out of orbit due to atmospheric drag. The preliminary conceptual evaluation of the HVIE has found no show stoppers. The design has been very easy to keep within the lift capabilities of commonly available rides to low earth orbit including the space shuttle. The cost of approximately 69 million dollars for 100 EOS experiment that will yield the much needed high accuracy, absolute measurement data is a bargain!

  16. Contrast and spatial resolution in MREIT using low amplitude current.

    PubMed

    Birgul, Ozlem; Hamamura, Mark J; Muftuler, L Tugan; Nalcioglu, Orhan

    2006-10-07

    Magnetic resonance-electrical impedance tomography employs low amplitude currents injected or induced inside an object. The additional magnetic field due to these currents results in a phase in the MR images. In this study, a modified fast spin-echo sequence was used to measure this magnetic field, which is obtained by scaling the MR phase image. A finite element method with first order triangular elements was used for the solution of the forward problem. An iterated sensitivity matrix-based algorithm was developed for the inverse problem. The resulting ill-conditioned matrix equation was regularized using the Tikhonov method and solved using a conjugate gradient solver. The spatial and contrast resolution of the technique was tested using agarose gel phantoms. A circular phantom with 7 cm diameter and 1 cm thickness is used in the phantom experiments. The amplitude of the injected current was 1 mA. 3, 5 and 8 mm diameter insulators and high conductor objects are used for the spatial resolution study and an average full-width half-maximum value of 4.7 mm is achieved for the 3 mm insulator case. For the contrast analysis, the conductivity of a 15 mm object is varied between 44% and 500% with respect to the background and results are compared to the ideal reconstruction.

  17. Immediate and lasting improvements in weight distribution seen in baropodometry following a high-velocity, low-amplitude thrust manipulation of the sacroiliac joint.

    PubMed

    Grassi, Daniel de Oliveira; de Souza, Marcial Zanelli; Ferrareto, Silvia Belissa; Montebelo, Maria Imaculada de Lima; Guirro, Elaine Caldeira de Oliveira

    2011-10-01

    The biomechanics of the sacroiliac joint makes the pelvic segment responsible for proper weight distribution between lower extremities; however, it is known to be susceptible to altered mobility. The objective of this study was to analyze baropodometric responses following thrust manipulation on subjects with sacroiliac joint restrictions. Twenty asymptomatic subjects were submitted to computerized baropodometric analysis before, after, and seven days following sacroiliac manipulation. The variables peak pressure and contact area were obtained at each of these periods as the average of absolute values of the difference between the right and left foot based on three trials. Data revealed significant reduction only in peak pressure immediately after manipulation and at follow-up when compared to pre-manipulative values (p < 0.05). Strong correlation was found between the dominant foot and the foot with greater contact area (r = 0.978), as well as between the side of joint restriction and the foot with greater contact area (r = 0.884). Weak correlation was observed between the dominant foot and the foot with greater peak pressure (r = 0.501), as well as between the side of joint restriction and the foot with greater peak pressure (r = 0.694). The results suggest that sacroiliac joint manipulation can influence peak pressure distribution between feet, but contact area does not seem to be related to the biomechanical aspects addressed in this study.

  18. Cervical radiculopathy: a systematic review on treatment by spinal manipulation and measurement with the Neck Disability Index

    PubMed Central

    Rodine, Robert J.; Vernon, Howard

    2012-01-01

    Cervical radiculopathy (CR), while less common than conditions with neck pain alone, can be a significant cause of neck pain and disability; thus the determination of adequate treatment options for patients is essential. Currently, inadequate scientific literature restricts specific conservative management recommendations for CR. Despite a paucity of evidence for high-velocity low-amplitude (HVLA) spinal manipulation in the treatment for CR, this strategy has been frequently labeled as contraindicated. Scientific support for appropriate outcome measures for CR is equally deficient. While more scientific data is needed to draw firm conclusions, the present review suggests that spinal manipulation may be cautiously considered as a therapeutic option for patients suffering from CR. With respect to outcome measures, the Neck Disability Index appears well-suited for spinal manipulative treatment of CR. PMID:22457538

  19. High velocity formability and factors affecting it

    NASA Astrophysics Data System (ADS)

    Dehra, Mala Seth

    High velocity forming methods successfully address problems faced in conventional forming techniques. They can be effectively used for forming metals with low formability like aluminum alloys and high strength steel. They can be instrumental is manufacturing of lighter vehicles with higher fuel efficiency. Electromagnetic forming (EMF) is an HVF method that is gaining wide acceptance due to its advantages and scope for commercialization. A number of experimental studies were carried out with EMF with the main goal of exploring fundamentals about material formability at high velocities, which can be used to establish practical design guidelines and to make models of high velocity formability. Thus the main factors that influence high velocity formability-inertia/size effects; changes in constitutive behavior; impact; and dynamic failure modes, were studied mainly with experiments. The role of changes in constitutive behavior in improving formability was studied from existing studies and new theoretical studies involving High velocity Forming Limit Diagram (FLD) and through solving an inverse problem of ring expansion. Tube free-expansion experiments were carried out to demonstrate enhanced metal formability even in the absence of die impact. To further establish the significance of inertia, electromagnetic ring free-expansion experiments with rings of different aspect ratios were carried out. A higher aspect ratio sample had better formability in terms of uniform and total elongation and also had fewer necks than a low aspect ratio (more slender) ring at the same velocity. The results clearly demonstrated the influence of sample aspect ratio (dimensions) and hence inertia on high velocity formability. Die impact experiments were carried out with tubes and rings to show the beneficial influence of die arrest of a moving sample. It was revealed that die impact in an appropriate range of velocities can significantly suppress failure and reduce the number of tears and

  20. High velocity pulsed wire-arc spray

    NASA Technical Reports Server (NTRS)

    Witherspoon, F. Douglas (Inventor); Massey, Dennis W. (Inventor); Kincaid, Russell W. (Inventor)

    1999-01-01

    Wire arc spraying using repetitively pulsed, high temperature gas jets, usually referred to as plasma jets, and generated by capillary discharges, substantially increases the velocity of atomized and entrained molten droplets. The quality of coatings produced is improved by increasing the velocity with which coating particles impact the coated surface. The effectiveness of wire-arc spraying is improved by replacing the usual atomizing air stream with a rapidly pulsed high velocity plasma jet. Pulsed power provides higher coating particle velocities leading to improved coatings. 50 micron aluminum droplets with velocities of 1500 m/s are produced. Pulsed plasma jet spraying provides the means to coat the insides of pipes, tubes, and engine block cylinders with very high velocity droplet impact.

  1. Instrumented impact testing at high velocities

    SciTech Connect

    Delfosse, D.; Pageau, G.; Bennett, R.; Poursartip, A. Defence Research Establishment Valcartier, Courcelette )

    1993-01-01

    Impact loading of carbon fiber-reinforced plastic (CFRP) aircraft parts is a major concern. Birds or hailstones striking an aircraft generally have a low mass and a high velocity, whereas typically instrumented impact experiments are performed with a high mass and a low velocity. Our aim has been to build an instrumented impact facility with a low-mass projectile capable of simulating these impact events, since there is evidence that a low-velocity impact will not always result in the same amount or even type of damage as a high-velocity impact. This paper provides a detailed description of the instrumented low-mass impact facility at The University of British Columbia (UBC). A gas gun is used to accelerate the instrumented projectile to impact velocities as high as 50 m/s, corresponding to an energy level of 350 J. The contact force during the impact event is measured by an incorporated load cell. The necessary mathematical operations to determine the real load-displacement curves are outlined, and the results of some impact events at different velocities are shown. 23 refs.

  2. Consideration of wear rates at high velocity

    NASA Astrophysics Data System (ADS)

    Hale, Chad S.

    The development of the research presented here is one in which high velocity relative sliding motion between two bodies in contact has been considered. Overall, the wear environment is truly three-dimensional. The attempt to characterize three-dimensional wear was not economically feasible because it must be analyzed at the micro-mechanical level to get results. Thus, an engineering approximation was carried out. This approximation was based on a metallographic study identifying the need to include viscoplasticity constitutive material models, coefficient of friction, relationships between the normal load and velocity, and the need to understand wave propagation. A sled test run at the Holloman High Speed Test Track (HHSTT) was considered for the determination of high velocity wear rates. In order to adequately characterize high velocity wear, it was necessary to formulate a numerical model that contained all of the physical events present. The experimental results of a VascoMax 300 maraging steel slipper sliding on an AISI 1080 steel rail during a January 2008 sled test mission were analyzed. During this rocket sled test, the slipper traveled 5,816 meters in 8.14 seconds and reached a maximum velocity of 1,530 m/s. This type of environment was never considered previously in terms of wear evaluation. Each of the features of the metallography were obtained through micro-mechanical experimental techniques. The byproduct of this analysis is that it is now possible to formulate a model that contains viscoplasticity, asperity collisions, temperature and frictional features. Based on the observations of the metallographic analysis, these necessary features have been included in the numerical model, which makes use of a time-dynamic program which follows the movement of a slipper during its experimental test run. The resulting velocity and pressure functions of time have been implemented in the explicit finite element code, ABAQUS. Two-dimensional, plane strain models

  3. Experimental high-velocity missile head injury.

    PubMed

    Allen, I V; Scott, R; Tanner, J A

    1982-09-01

    A standardized experimental high-velocity penetrating head-injury model has been produced in which pathological lesions were observed, not only in the wound track but at sites more remote from the track in the hypothalamus, brain stem and cerebellum. Diffuse subarachnoid haemorrhage was common and intraventricular haemorrhage was a constant feature. Other constant histological abnormalities were:L 1. Perivascular "ring' haemorrhages. 2. Perivascular haemorrhage with a surrounding zone of decreased staining intensity. 3. Perivascular increased staining intensity. 4. Areas of decreased staining intensity apparently dissociated from areas of haemorrhage. The pathogenesis of the perivascular lesions is discussed and preliminary studies suggest that these may be the site of early oedema. The implications of this experiment for military surgery and for ballistic protection of the head are discussed.

  4. High-Velocity Collisions of Nanoparticles

    NASA Astrophysics Data System (ADS)

    Johnson, Donald; Mattson, William

    Nanoparticles (NPs) are interesting materials with exciting applications due to their large surface-to-volume ratio and functionalizable surfaces. The large surface area and potentially high surface tension might result in unique materials behavior when subject to shock loading. Using density functional theory, we have simulated high-velocity NP collisions producing high-pressure, high-temperature, and extreme shock conditions. NPs composed of diamond-C, cubic-BN, and diamond-Si were considered with particle sizes up to 3.5 nm diameter. Some simulations involved NPs that were destabilized by incorporating internal strain. Normal, spherical NPs were carved out of bulk crystals and structurally optimized while the NPs with internal strain were constructed as a dense core (compressive strain) encompassed by a thin shell (tensile strain). Both on-axis and off-axis collisions were simulated at various speeds. Collision dynamics, shock propagation, and fragmentation will be presented and analyzed. The effect of material properties, internal strain, and collision velocity on the final temperature of the fragments will be discussed.

  5. NGC 1275, High Velocity Filamentary System

    NASA Astrophysics Data System (ADS)

    Caulet, Adeline

    The extensive filamentary system surrounding NGC 1275 is known to exhibit two velocity components, one at 5200 km/s which is the same as the velocity of NGC 1275 itself, and one at 8300 km/s. The low velocity (LV) system has been studied extensively with a view to elucidating the nature of a putative cooling flow of intracluster (A426) gas into NGC1275. A plausible hypothesis based on optical and radio data describes the high velocity (HV) system as a late-type galaxy caught in the gravitational potential well of NGC 1275 and falling into it with a velocity of about 3000 km/s. In this picture the HV filaments are composed of giant HII regions which have been imaged in H-alpha and observed spectroscopically in other optical lines. Our lack of certainty about the morphology of the HV system, the dynamical relationship between the HV and LV systems, and the optical spectral characteristics of the HV filaments coupled with the fact that spiral galaxies are rare in the inner regions of A426 make this hypothesis tentative. Yet it is important to understand the nature of the HV system in order to properly interpret observations of the LV system in terms of a cooling flow. We propose to obtain vacuum ultraviolet spectra with the IUE of several emission regions of the HV system. The objectives are: a) to use any observed vacuum ultraviolet emission lines together with existing optical emission line data to infer the physical processes by which the emission lines are produced, b) to use any vacuum ultraviolet emission line data to help determine abundances, particularly that of carbon, with a view to finding evidence bearing on the origin of the HV system, and c) and to search for an ultraviolet continuum characteristic of an OB stellar population. The proposed work is part of a larger effort to obtain groundbased Fabry-Perot imagery and sounding rocket vacuum ultraviolet imagery of the HV and LV systems.

  6. Correlation of expertise with error detection skills of force application during spinal manipulation learning*

    PubMed Central

    Loranger, Michel; Treboz, Julien; Boucher, Jean-Alexandre; Nougarou, François; Dugas, Claude; Descarreaux, Martin

    2016-01-01

    Objective: Most studies on spinal manipulation learning demonstrate the relevance of including motor learning strategies in chiropractic curricula. Two outcomes of practice are the production of movement in an efficient manner and the improved capability of learners to evaluate their own motor performance. The goals of this study were to evaluate if expertise is associated with increased spinal manipulation proficiency and if error detection skills of force application during a high-velocity low-amplitude spinal manipulation are related to expertise. Methods: Three groups of students and 1 group of expert chiropractors completed 10 thoracic spine manipulations on an instrumented device with the specific goal of reaching a maximum peak force of 300 N after a brief period of practice. After each trial, participants were asked to give an estimate of their maximal peak force. Force-time profiles were analyzed to determine the biomechanical parameters of each participant and the participant's capacity to estimate his or her own performance. Results: Significant between-group differences were found for each biomechanical parameter. No significant difference was found between groups for the error detection variables (p > .05). The lack of significant effects related to the error detection capabilities with expertise could be related to the specificity of the task and how the training process was structured. Conclusion: This study confirms that improvements in biomechanical parameters of spinal manipulation are related to expertise. Feedback based on error detection could be implemented in chiropractic curricula to improve trainee abilities in detecting motor execution errors. PMID:26270897

  7. Low amplitude impact of PBX 9501: Modified Steven spigot gun tests

    SciTech Connect

    Idar, D.J.; Lucht, R.A.; Straight, J.W.

    1998-12-01

    Low-velocity mechanical impact and subsequent high explosive (HE) reaction are of concern in credible accident scenarios involving the handling, transport, and storage of nuclear weapons. Using modified Steven spigot gun tests, the authors have investigated the high-explosive violent-reaction (HEVR) potential of PBX 9501 to low-amplitude insult. Reliable modeling predictions require that one identify the relevant parameters and behavioral responses that are key to the reaction mechanism(s) in PBX 9501. Additional efforts have been targeted at identifying relevant differences in the response between baseline and stockpile-aged PBX 9501 to low-velocity impacts.

  8. Anomalously low amplitude of S waves produced by the 3D structures in the lower mantle

    NASA Astrophysics Data System (ADS)

    To, Akiko; Capdeville, Yann; Romanowicz, Barbara

    2016-07-01

    Direct S and Sdiff phases with anomalously low amplitudes are recorded for the earthquakes in Papua New Guinea by seismographs in northern America. According to the prediction by a standard 1D model, the amplitudes are the lowest at stations in southern California, at a distance and azimuth of around 95° and 55°, respectively, from the earthquake. The amplitude anomaly is more prominent at frequencies higher than 0.03 Hz. We checked and ruled out the possibility of the anomalies appearing because of the errors in the focal mechanism used in the reference synthetic waveform calculations. The observed anomaly distribution changes drastically with a relatively small shift in the location of the earthquake. The observations indicate that the amplitude reduction is likely due to the 3D shear velocity (Vs) structure, which deflects the wave energy away from the original ray paths. Moreover, some previous studies suggested that some of the S and Sdiff phases in our dataset are followed by a prominent postcursor and show a large travel time delay, which was explained by placing a large ultra-low velocity zone (ULVZ) located on the core-mantle boundary southwest of Hawaii. In this study, we evaluated the extent of amplitude anomalies that can be explained by the lower mantle structures in the existing models, including the previously proposed ULVZ. In addition, we modified and tested some models and searched for the possible causes of low amplitudes. Full 3D synthetic waveforms were calculated and compared with the observations. Our results show that while the existing models explain the trends of the observed amplitude anomalies, the size of such anomalies remain under-predicted especially at large distances. Adding a low velocity zone, which is spatially larger and has less Vs reduction than ULVZ, on the southwest side of ULVZ, contributes to explain the low amplitudes observed at distances larger than 100° from the earthquake. The newly proposed low velocity zone

  9. Comparison of damping in buildings under low-amplitude and strong motions

    USGS Publications Warehouse

    Celebi, M.

    1996-01-01

    This paper presents a comprehensive assessment of damping values and other dynamic characteristics of five buildings using strong-motion and low-amplitude (ambient vibration) data. The strong-motion dynamic characteristics of five buildings within the San Francisco Bay area are extracted from recordings of the 17 October 1989 Loma Prieta earthquake (LPE). Ambient vibration response characteristics for the same five buildings were inferred using data collected in 1990 following LPE. Additional earthquake data other than LPE for one building and ambient vibration data collected before LPE for two other buildings provide additional confirmation of the results obtained. For each building, the percentages of critical damping and the corresponding fundamental periods determined from low-amplitude test data are appreciably lower than those determined from strong-motion recordings. These differences are attributed mainly to soil-structure interaction and other non-linear behavior affecting the structures during strong shaking. Significant contribution of radiation damping to the effective damping of a specific building is discussed in detail.

  10. Speckle interferometric sensor to measure low-amplitude high frequency Ocular Microtremor (OMT)

    NASA Astrophysics Data System (ADS)

    Ryle, James P.; Al-Kalbani, Mohammed; Gopinathan, Unnikrishnan; Boyle, Gerard; Coakley, Davis; Sheridan, John T.

    2009-08-01

    Ocular microtremor (OMT) is a physiological high frequency (up to 150Hz) low amplitude (150-2500nm) involuntary tremor of the human eye. It is one of the three fixational ocular motions described by Adler and Fliegelman in 1934 as well as microsaccades and drift. Clinical OMT investigations to date have used eye-contacting piezoelectric probes or piezoelectric strain gauges. Before contact can be made, the eye must first be anaesthetised. In some cases, this induces eyelid spasms (blepharospasm) making it impossible to measure OMT. Using the contact probe method, the eye motion is mechanically damped. In addition to this, it is not possible to obtain exact information about the displacement. Results from clinical studies to date have given electrical signal amplitudes from the probe. Recent studies suggest a number of clinical applications for OMT, these include monitoring the depth of anaesthesia of a patient in surgery, prediction of outcome in coma, diagnosis of brainstem death. In addition to this, abnormal OMT frequency content is present in patients with neurological disorders such as Multiple sclerosis and Parkinson's disease. However for ongoing clinical investigations the contact probe method falls short of a non-contact accurate measurement solution. In this paper, we design a compact non contact phase modulating optical fiber speckle interferometer to measure eye motions. We present our calibration results using a calibrated piezoelectric vibration simulator. Digital signal processing is then performed to extract the low amplitude high frequency displacement information.

  11. High Velocity Absorption during Eta Car B's Periastron Passage

    NASA Technical Reports Server (NTRS)

    Nielsen, Krister E.; Groh, J. H.; Hillier, J.; Gull, Theodore R.; Owocki, S. P.; Okazaki, A. T.; Damineli, A.; Teodoro, M.; Weigelt, G.; Hartman, H.

    2010-01-01

    Eta Car is one of the most luminous massive stars in the Galaxy, with repeated eruptions with a 5.5 year periodicity. These events are caused by the periastron passage of a massive companion in an eccentric orbit. We report the VLT/CRIRES detection of a strong high-velocity, (<1900 km/s) , broad absorption wing in He I at 10833 A during the 2009.0 periastron passage. Previous observations during the 2003.5 event have shown evidence of such high-velocity absorption in the He I 10833 transition, allowing us to conclude that the high-velocity gas is crossing the line-of-sight toward Eta Car over a time period of approximately 2 months. Our analysis of HST/STlS archival data with observations of high velocity absorption in the ultraviolet Si IV and C IV resonance lines, confirm the presence of a high-velocity material during the spectroscopic low state. The observations provide direct detection of high-velocity material flowing from the wind-wind collision zone around the binary system, and we discuss the implications of the presence of high-velocity gas in Eta Car during periastron

  12. Method for Estimating the Acoustic Pressure in Tissues Using Low-Amplitude Measurements in Water.

    PubMed

    Keravnou, Christina P; Izamis, Maria-Louisa; Averkiou, Michalakis A

    2015-11-01

    The aim of this study was to evaluate a simple, reliable and reproducible method for accuracy in estimating the acoustic pressure delivered in tissue exposed to ultrasound. Such a method would be useful for therapeutic applications of ultrasound with microbubbles, for example, sonoporation. The method is based on (i) low-amplitude water measurements that are easily made and do not suffer from non-linear propagation effects, and (ii) the attenuation coefficient of the tissue of interest. The range of validity of the extrapolation method for different attenuation and pressure values was evaluated with a non-linear propagation theoretical model. Depending on the specific tissue attenuation, the method produces good estimates of pressures in excess of 10 MPa. Ex vivo machine-perfused pig liver tissue was used to validate the method for source pressures up to 3.5 MPa. The method can be used to estimate the delivered pressure in vivo in diagnostic and therapeutic applications of ultrasound.

  13. Low amplitude insult project: Structural analysis and prediction of low order reaction

    SciTech Connect

    Scammon, R.J.; Browning, R.V.; Middleditch, J.; Dienes, J.K.; Haberman, K.S.; Bennett, J.G.

    1998-12-31

    The low velocity impact sensitivity of PBX 9501 has been investigated through a series of experiments based on the Steven Test targets and a set of Shear Impact experiments. The authors describe calculations done using DYNA2D, SPRONTO and DYNA3D to support these, and other, low amplitude insult experiments. The calculations allow them to study pressure and strain rate variables, to investigate structural aspects of the experiment, and to predict velocities required for reaction. Structural analyses have played an active role in this project beginning with the original target design and continuing through analyses of the experimental results. Alternative designs and various ideas for active instrumentation were examined as part of the experiment evolution process. Predictions of reaction are used to guide these design studies, even though the authors do not yet have enough experimental data to fully calibrate any of the models.

  14. Pilot Test of a Novel Method for Assessing Community Response to Low-Amplitude Sonic Booms

    NASA Technical Reports Server (NTRS)

    Fidell, Sanford; Horonjeff, Richard D.; Harris, Michael

    2012-01-01

    A pilot test of a novel method for assessing residents annoyance to sonic booms was performed. During a two-week period, residents of the base housing area at Edwards Air Force Base provided data on their reactions to sonic booms using Smartphone-based interviews. Noise measurements were conducted at the same time. The report presents information about data collection methods and about test participants reactions to low-amplitude sonic booms. The latter information should not be viewed as definitive for several reasons. It may not be reliably generalized to the wider U.S. residential population (because it was not derived from a representative random sample) and the sample itself was not large.

  15. Low-Amplitude Craniofacial EMG Power Spectral Density and 3D Muscle Reconstruction from MRI

    PubMed Central

    Wiedemann, Lukas; Chaberova, Jana; Edmunds, Kyle; Einarsdóttir, Guðrún; Ramon, Ceon

    2015-01-01

    Improving EEG signal interpretation, specificity, and sensitivity is a primary focus of many current investigations, and the successful application of EEG signal processing methods requires a detailed knowledge of both the topography and frequency spectra of low-amplitude, high-frequency craniofacial EMG. This information remains limited in clinical research, and as such, there is no known reliable technique for the removal of these artifacts from EEG data. The results presented herein outline a preliminary investigation of craniofacial EMG high-frequency spectra and 3D MRI segmentation that offers insight into the development of an anatomically-realistic model for characterizing these effects. The data presented highlights the potential for confounding signal contribution from around 60 to 200 Hz, when observed in frequency space, from both low and high-amplitude EMG signals. This range directly overlaps that of both low γ (30-50 Hz) and high γ (50-80 Hz) waves, as defined traditionally in standatrd EEG measurements, and mainly with waves presented in dense-array EEG recordings. Likewise, average EMG amplitude comparisons from each condition highlights the similarities in signal contribution of low-activity muscular movements and resting, control conditions. In addition to the FFT analysis performed, 3D segmentation and reconstruction of the craniofacial muscles whose EMG signals were measured was successful. This recapitulation of the relevant EMG morphology is a crucial first step in developing an anatomical model for the isolation and removal of confounding low-amplitude craniofacial EMG signals from EEG data. Such a model may be eventually applied in a clinical setting to ultimately help to extend the use of EEG in various clinical roles. PMID:26913150

  16. On optical studies of high-velocity clouds

    NASA Technical Reports Server (NTRS)

    York, D. G.; Burks, G. S.; Gibney, T. B.

    1986-01-01

    Lists of distant objects that can be used to study physical conditions in, and distances of, 21 cm (Oort) high-velocity clouds are presented. Recent published observations are used to compile positions, velocities, and distances of the clouds.

  17. 46 CFR 153.353 - High velocity vents.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false High velocity vents. 153.353 Section 153.353 Shipping... Systems § 153.353 High velocity vents. The discharge point of a B/3 or 4m venting system must be located..., unimpeded jet; (b) The jet has a minimum exit velocity of 30 m/sec (approx. 98.4 ft/sec); and (c) The...

  18. 46 CFR 153.353 - High velocity vents.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false High velocity vents. 153.353 Section 153.353 Shipping... Systems § 153.353 High velocity vents. The discharge point of a B/3 or 4m venting system must be located..., unimpeded jet; (b) The jet has a minimum exit velocity of 30 m/sec (approx. 98.4 ft/sec); and (c) The...

  19. Cryogenic Testing of High-Velocity Spoke Cavities

    SciTech Connect

    Hopper, Christopher S.; Delayen, Jean R.; Park, HyeKyoung

    2014-12-01

    Spoke-loaded cavities are being investigated for the high-velocity regime. The relative compactness at low-frequency makes them attractive for applications requiring, or benefiting from, 4 K operation. Additionally, the large velocity acceptance makes them good candidates for the acceleration of high-velocity protons and ions. Here we present the results of cryogenic testing of a 325 MHz, β0= 0.82 single-spoke cavity and a 500 MHz, β0 = 1 double-spoke cavity.

  20. 46 CFR 153.353 - High velocity vents.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false High velocity vents. 153.353 Section 153.353 Shipping... Systems § 153.353 High velocity vents. The discharge point of a B/3 or 4m venting system must be located..., unimpeded jet; (b) The jet has a minimum exit velocity of 30 m/sec (approx. 98.4 ft/sec); and (c) The...

  1. 46 CFR 153.353 - High velocity vents.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false High velocity vents. 153.353 Section 153.353 Shipping... Systems § 153.353 High velocity vents. The discharge point of a B/3 or 4m venting system must be located..., unimpeded jet; (b) The jet has a minimum exit velocity of 30 m/sec (approx. 98.4 ft/sec); and (c) The...

  2. 46 CFR 153.353 - High velocity vents.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false High velocity vents. 153.353 Section 153.353 Shipping... Systems § 153.353 High velocity vents. The discharge point of a B/3 or 4m venting system must be located..., unimpeded jet; (b) The jet has a minimum exit velocity of 30 m/sec (approx. 98.4 ft/sec); and (c) The...

  3. Golden Gate Bridge response: a study with low-amplitude data from three earthquakes

    USGS Publications Warehouse

    Celebi, Mehmet

    2012-01-01

    The dynamic response of the Golden Gate Bridge, located north of San Francisco, CA, has been studied previously using ambient vibration data and finite element models. Since permanent seismic instrumentation was installed in 1993, only small earthquakes that originated at distances varying between ~11 to 122 km have been recorded. Nonetheless, these records prompted this study of the response of the bridge to low amplitude shaking caused by three earthquakes. Compared to previous ambient vibration studies, the earthquake response data reveal a slightly higher fundamental frequency (shorter-period) for vertical vibration of the bridge deck center span (~7.7–8.3 s versus 8.2–10.6 s), and a much higher fundamental frequency (shorter period) for the transverse direction of the deck (~11.24–16.3 s versus ~18.2 s). In this study, it is also shown that these two periods are dominant apparent periods representing interaction between tower, cable, and deck.

  4. Experimental study of low amplitude, long-duration mechanical loading of reactive materials

    SciTech Connect

    Urtiew, P A; Forbes, J W

    2000-10-03

    Studies of the low amplitude, long-duration mechanical loading of reactive materials rely very heavily on the experimental data in general and in particular on the data obtained from gauges placed within the experimental test sample to measure accurately the local changes of parameters of the investigated material. For a complete description of these changes taking place in a dynamically loaded material one would like to know both the spatial and the temporal resolution of pressure, temperature, volume, wave and mass velocity. However, temperature and volume are not easily attainable. Therefore, most of the in-situ work is limited to measurements of pressure and both wave and mass velocities. Various types of these gauges will be discussed and their records will be illustrated. Some of these gauges have limitations but are better suited for particular applications than others. These aspects will also be discussed. Main limitation of most in-situ gauges is that they are built for one-dimensional application. However, some work is being done to develop two-dimensional gauges. This work will also be briefly discussed. While these experiments are necessary to validate theoretical models of the phenomenon, they can also provide sufficient amount of data to yield complete information on material characteristics such as its equation of state (EOS), its phase change under certain loads and its sensitivity to shock loading. Processing of these data to get important information on the behavior of both reactive and non-reactive materials will also be demonstrated.

  5. Laboratory Headphone Studies of Human Response to Low-Amplitude Sonic Booms and Rattle Heard Indoors

    NASA Technical Reports Server (NTRS)

    Loubeau, Alexandra; Sullivan, Brenda M.; Klos, Jacob; Rathsam, Jonathan; Gavin, Joseph R.

    2013-01-01

    Human response to sonic booms heard indoors is affected by the generation of contact-induced rattle noise. The annoyance caused by sonic boom-induced rattle noise was studied in a series of psychoacoustics tests. Stimuli were divided into three categories and presented in three different studies: isolated rattles at the same calculated Perceived Level (PL), sonic booms combined with rattles with the mixed sound at a single PL, and sonic booms combined with rattles with the mixed sound at three different PL. Subjects listened to sounds over headphones and were asked to report their annoyance. Annoyance to different rattles was shown to vary significantly according to rattle object size. In addition, the combination of low-amplitude sonic booms and rattles can be more annoying than the sonic boom alone. Correlations and regression analyses for the combined sonic boom and rattle sounds identified the Moore and Glasberg Stationary Loudness (MGSL) metric as a primary predictor of annoyance for the tested sounds. Multiple linear regression models were developed to describe annoyance to the tested sounds, and simplifications for applicability to a wider range of sounds are presented.

  6. A high-stability non-contact dilatometer for low-amplitude temperature-modulated measurements

    NASA Astrophysics Data System (ADS)

    Luckabauer, Martin; Sprengel, Wolfgang; Würschum, Roland

    2016-07-01

    Temperature modulated thermophysical measurements can deliver valuable insights into the phase transformation behavior of many different materials. While especially for non-metallic systems at low temperatures numerous powerful methods exist, no high-temperature device suitable for modulated measurements of bulk metallic alloy samples is available for routine use. In this work a dilatometer for temperature modulated isothermal and non-isothermal measurements in the temperature range from room temperature to 1300 K is presented. The length measuring system is based on a two-beam Michelson laser interferometer with an incremental resolution of 20 pm. The non-contact measurement principle allows for resolving sinusoidal length change signals with amplitudes in the sub-500 nm range and physically decouples the length measuring system from the temperature modulation and heating control. To demonstrate the low-amplitude capabilities, results for the thermal expansion of nickel for two different modulation frequencies are presented. These results prove that the novel method can be used to routinely resolve length-change signals of metallic samples with temperature amplitudes well below 1 K. This high resolution in combination with the non-contact measurement principle significantly extends the application range of modulated dilatometry towards high-stability phase transformation measurements on complex alloys.

  7. High Velocity White Dwarfs from Type Ia Supernovae

    NASA Astrophysics Data System (ADS)

    Hansen, B.

    2002-12-01

    The single degenerate scenario for Type Ia supernovae predicts the post-supernova release of the donor star with a space velocity determined by the original binary orbital velocity. The mass transfer criteria for successful supernova ignition also place constraints on the mass of the donor. The combination of these two factors means that the great majority of high velocity donor remnants will be white dwarfs. We present models of the Type Ia supernova progenitors and antecedents in the Galaxy, and examine the donor remnant white dwarf population in the light of the current interest in high velocity white dwarfs. One potential discriminant between donor remnants and normal high velocity white dwarfs (from a thick disk or spheroid stellar population) is a determination of the binary fraction. White dwarfs which have their origin in disrupted close binaries will always be single.

  8. Superconducting spoke cavities for high-velocity applications

    SciTech Connect

    Hopper, Christopher S.; Delayen, Jean R.

    2013-10-01

    To date, superconducting spoke cavities have been designed, developed, and tested for particle velocities up to {beta}{sub 0}~0.6, but there is a growing interest in possible applications of multispoke cavities for high-velocity applications. We have explored the design parameter space for low-frequency, high-velocity, double-spoke superconducting cavities in order to determine how each design parameter affects the electromagnetic properties, in particular the surface electromagnetic fields and the shunt impedance. We present detailed design for cavities operating at 325 and 352 MHz and optimized for {beta}{sub 0}~=0.82 and 1.

  9. Punch valve development testing: Low and high velocity test results

    SciTech Connect

    Replogle, W.C.; Brandon, S.L.

    1996-09-01

    This is a report on the use of quasi-static tests to predict fundamental parameters for punch valve development. This report summarizes the results from low and high velocity tests performed with 0.63 and 0.38 cm diameter plungers, 5 cm long penetrating aluminium and composite targets. The low velocity tests, 0.025 m/s, were performed to understand the effects and interactions of plunger diameter plunger tip shape, target material, and target support on penetration energy and plunger functionality. High velocity tests, 75 m/s, were compared to low velocity results.

  10. High-Velocity Clouds Merging with the Milky Way

    NASA Astrophysics Data System (ADS)

    Lockman, Felix J.

    HI observations with the Green Bank Telescope have now given us two clear examples of high-velocity HI clouds which are encountering the Milky Way disk and losing matter to it: Complex H, passing through the plane of the Milky Way in the far outer Galaxy, and Smith's Cloud, just entering the disk in the inner Galaxy. These clouds may give unique insights into the ongoing formation of the Milky Way, its chemical history, and the nature of the high-velocity cloud phenomenon.

  11. Overview of historical recurring low-amplitude floods in Lower Provence, Southeastern France (1700-1950)

    NASA Astrophysics Data System (ADS)

    Maughan, Nicolas

    2015-04-01

    In the Mediterranean world, water plays a prominent role as a « prime mover » in the development of urban and rural spaces. But, the specificities of the typical climate require a management of a natural resource that varies permanently between scarcity and abundance. Since Antiquity, the chronic lack of freshwater could be limited thanks to large hydraulic infrastructures while the flood risk management has always been a recurring problem for rural and urban communities. Because of brief, intense and irregularly distributed rain, amplified by a mountainous topography, stream floods often are heavy and flash with catastrophic consequences. However, often only past extremefloods were studied because both their consequences and available archival materials they have left while many recurring low-amplitude floodshave resulted in severe damagesto hydraulic and road infrastructures, in loss of agricultural soils and inconflicts between citizens and administration. Indeed, these ones were a central problem for rural and urban settlements and for the managementof water bodies.It seems interesting to present adetailed overview of historical recurring low-amplitude floods and consider how local societies have chosen to manage these questions and how these small hydrological events have contributed to shape existing current hydrological and geomorphologicalstructure of hydrosystems. In this context, the Lower Provence area (especially the Bouches-du-Rhône district, southeastern France), subject to recurring floods for centuries, appears to be a perfect place to explore and understand these questions. The decision to start the study at the dawn of the Eighteenth Century is especially interesting because it's a turning point for economic, scientific and engineering development in many European countries during whichdisasters and environmental health risks, including flooding, begin to become a real social and technical problem for authorities and citizens. Moreover, from

  12. Removal of residual nuclei following a cavitation event using low-amplitude ultrasound.

    PubMed

    Duryea, Alexander P; Cain, Charles A; Tamaddoni, Hedieh A; Roberts, William W; Hall, Timothy L

    2014-10-01

    Microscopic residual bubble nuclei can persist on the order of 1 s following a cavitation event. These bubbles can limit the efficacy of ultrasound therapies such as shock wave lithotripsy and histotripsy, because they attenuate pulses that arrive subsequent to their formation and seed repetitive cavitation activity at a discrete set of sites (cavitation memory). Here, we explore a strategy for the removal of these residual bubbles following a cavitation event, using low-amplitude ultrasound pulses to stimulate bubble coalescence. All experiments were conducted in degassed water and monitored using high-speed photography. In each case, a 2-MHz histotripsy transducer was used to initiate cavitation activity (a cavitational bubble cloud), the collapse of which generated a population of residual bubble nuclei. This residual nuclei population was then sonicated using a 1 ms pulse from a separate 500-kHz transducer, which we term the bubble removal pulse. Bubble removal pulse amplitudes ranging from 0 to 1.7 MPa were tested, and the backlit area of shadow from bubbles remaining in the field following bubble removal was calculated to quantify efficacy. It was found that an ideal amplitude range exists (roughly 180 to 570 kPa) in which bubble removal pulses stimulate the aggregation and subsequent coalescence of residual bubble nuclei, effectively removing them from the field. Further optimization of bubble removal pulse sequences stands to provide an adjunct to cavitation-based ultrasound therapies such as shock wave lithotripsy and histotripsy, mitigating the effects of residual bubble nuclei that currently limit their efficacy.

  13. Harmonics of Low Amplitude Anisotropic Wave Train Events in Cosmic Ray Intensity

    NASA Astrophysics Data System (ADS)

    Mishra, Rajesh K.; Agarwal, Rekha

    2008-12-01

    The unusually low amplitude anisotropic wave train events (LAWEs) in cosmic ray intensity using the ground based Deep River neutron monitor data has been studied during the period 1991 1994. It has been observed that the amplitude of the diurnal anisotropy for LAWE events significantly remains quite low and statistically constant as compared to the quiet day annual average amplitude for majority of the events. The time of maximum of the diurnal anisotropy of LAWE significantly shifts towards earlier hours as compared to the co-rotational direction and remains in the direction of quiet day annual average anisotropy for majority of the events. On the other hand, the amplitude of the semi/tri-diurnal anisotropy remains statistically the same and high whereas, phase shift towards later hours as compared to the quiet day annual average values for majority of the LAWEs. The diurnal anisotropy vectors are found to shifts towards earlier hours for 50% of the events; whereas they are found to shifts towards later hours for rest of the events (50%) relative to the average vector for the entire period. It is also noted that the amplitude of these vectors are found to increase significantly with the shift of the diurnal anisotropy vectors towards later hours. The high-speed solar wind streams do not play a significant role in causing the LAWE events on short-term basis, however it may be responsible in causing these events on long-term basis (Mishra and Mishra 2007). Occurrence of LAWE is dominant, when the polarity of Bx and Bz remains positive and polarity of By remains negative, which is never been reported earlier. The amplitude of first harmonic shows good anti-correlation and direction of first and third harmonic shows nearly good anti-correlation with solar wind velocity, whereas the direction of second harmonic shows nearly good anti-correlation with interplanetary magnetic field strength.

  14. Removal of Residual Nuclei Following a Cavitation Event using Low-Amplitude Ultrasound

    PubMed Central

    Duryea, Alexander P.; Cain, Charles A.; Tamaddoni, Hedieh A.; Roberts, William W.; Hall, Timothy L.

    2014-01-01

    Microscopic residual bubble nuclei can persist on the order of 1 second following a cavitation event. These bubbles can limit the efficacy of ultrasound therapies such as shock wave lithotripsy and histotripsy, as they attenuate pulses that arrive subsequent to their formation and seed repetitive cavitation activity at a discrete set of sites (cavitation memory). Here, we explore a strategy for the removal of these residual bubbles following a cavitation event, using low amplitude ultrasound pulses to stimulate bubble coalescence. All experiments were conducted in degassed water and monitored using high speed photography. In each case, a 2 MHz histotripsy transducer was used to initiate cavitation activity (a cavitational bubble cloud), the collapse of which generated a population of residual bubble nuclei. This residual nuclei population was then sonicated using a 1 ms pulse from a separate 500 kHz transducer, which we term the ‘bubble removal pulse.’ Bubble removal pulse amplitudes ranging from 0 to 1.7 MPa were tested, and the backlit area of shadow from bubbles remaining in the field following bubble removal was calculated to quantify efficacy. It was found that an ideal amplitude range exists (roughly 180 – 570 kPa) in which bubble removal pulses stimulate the aggregation and subsequent coalescence of residual bubble nuclei, effectively removing them from the field. Further optimization of bubble removal pulse sequences stands to provide an adjunct to cavitation-based ultrasound therapies such as shock wave lithotripsy and histotripsy, mitigating the effects of residual bubble nuclei that currently limit their efficacy. PMID:25265172

  15. Low amplitude entrainment of mice and the impact of circadian phase on behavior tests.

    PubMed

    Beeler, Jeff A; Prendergast, Brian; Zhuang, Xiaoxi

    2006-05-30

    A tremendous increase in the use of genetically engineered mice as experimental animals has led to increased scrutiny of mouse models generally and mouse behavioral paradigms specifically. Although mice are nocturnal, for practical reasons, most experimental procedures, including behavioral studies, are conducted during their inactive, sleep phase. Accumulating evidence indicates that myriad behavioral, cellular and biochemical processes fluctuate with circadian rhythmicity; however, time of day at which experiments are conducted is rarely controlled. The impact of circadian phase on the reliability of experimental results has received little attention and the present data are conflicting. This study addressed two questions. First, will laboratory mice in a typical animal care facility entrain to a low amplitude light cycle using bright/dim rather than light/dark cycles? A positive answer will make reversing photocycle easy to implement in any facility as dim light suitable for animal husbandry and behavioral testing can substitute for darkness during work hours. By monitoring home cage wheel running, we examined the effectiveness of a dim/bright photocycle as a zeitgeiber. We found that mice subjected to dim/bright photocycles effectively entrained such that their subjective night and activity onset coincided with the beginning of the dim light period, suggesting a potential strategy for standardization and management of circadian phase in nocturnal animals. In a second experiment, we asked what effect circadian phase has on behavioral performance in commonly used mouse behavioral tests. We found no main effect of circadian phase on outcome in open field activity, elevated plus maze emotionality, water maze spatial memory, novel object exploration and hyperactivity in response to amphetamine; however, we observed occasional interactions between circadian phase and both strain and sex that were neither consistent nor systematic. These data suggest that the tests

  16. Acceleration of objects to high velocity by electromagnetic forces

    DOEpatents

    Post, Richard F

    2017-02-28

    Two exemplary approaches to the acceleration of projectiles are provided. Both approaches can utilize concepts associated with the Inductrack maglev system. Either of them provides an effective means of accelerating multi-kilogram projectiles to velocities of several kilometers per second, using launchers of order 10 meters in length, thus enabling the acceleration of projectiles to high velocities by electromagnetic forces.

  17. High-velocity pulsars in the galactic halo.

    PubMed

    Eichler, D; Silk, J

    1992-08-14

    It is proposed that high-velocity pulsars are produced in extended galactic halos, and possibly in extragalactic space, from primordial (population III) stars. Such a population of neutron stars could provide an explanation for the gamma-ray bursters and would then accommodate the possibility that most bursters are not in the visible parts of galaxies.

  18. A High-Velocity Collision With Our Galaxy's Disk

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-08-01

    What caused the newly discovered supershell in the outskirts of our galaxy? A new study finds evidence that a high-velocity cloud may have smashed into the Milky Ways disk millions of years ago.Mysterious Gas ShellsA single velocity-channel map of the supershell GS040.2+00.670, with red contours marking the high-velocity cloud at its center. [Adapted from Park et al. 2016]The neutral hydrogen gas that fills interstellar space is organized into structures like filaments, loops, and shells. Supershells are enormous shells of hydrogen gas that can have radii of a thousand light-years or more; weve spotted about 20 of these in our own galaxy, and more in nearby dwarfs and spiral galaxies.How do these structures form? One theory is that they result from several supernovae explosions occurring in the same area. But the energy needed to create a supershell is more than 3 x 1052 erg, which corresponds to over 30 supernovae quite a lot to have exploding in the same region.Theres an interesting alternative scenario: the supershells might instead be caused by the impacts of high-velocity clouds that fall into the galactic disk.Velocity data for the compact high-velocity cloud CHVC040. The cloud is moving fast enough to create the supershell observed. [Adapted from Park et al. 2016]The Milky Ways Speeding CloudsHigh-velocity clouds are clouds of mostly hydrogen that speed through the Milky Way with radial velocities that are very different from the material in the galactic disk. The origins of these clouds are unknown, but its proposed that they come from outside the galaxy they might be fragments of a nearby, disrupting galaxy, or they might have originated from flows of accreting gas in the space in between galaxies.Though high-velocity clouds have long been on the list of things that might cause supershells, weve yet to find conclusive evidence of this. But that might have just changed, with a recent discovery by a team of scientists led by Geumsook Park (Seoul National

  19. HD 69686: A MYSTERIOUS HIGH VELOCITY B STAR

    SciTech Connect

    Huang, Wenjin; Gies, D. R.; McSwain, M. V. E-mail: gies@chara.gsu.ed

    2009-09-20

    We report on the discovery of a high velocity B star, HD 69686. We estimate its space velocity, distance, surface temperature, gravity, and age. With these data, we are able to reconstruct the trajectory of the star and to trace it back to its birthplace. We use evolutionary tracks for single stars to estimate that HD 69686 was born 73 Myr ago in the outer part of our Galaxy (r {approx} 12 kpc) at a position well below the Galactic plane (z {approx} -1.8 kpc), a very unusual birthplace for a B star. Along the star's projected path in the sky, we also find about 12 other stars having similar proper motions, and their photometry data suggest that they are located at the same distance as HD 69686 and probably have the same age. We speculate on the origin of this group by star formation in a high velocity cloud or as a Galactic merger fragment.

  20. High Velocity Forming of Magnesium and Titanium Sheets

    SciTech Connect

    Revuelta, A.; Larkiola, J.; Korhonen, A. S.; Kanervo, K.

    2007-04-07

    Cold forming of magnesium and titanium is difficult due to their hexagonal crystal structure and limited number of available slip systems. However, high velocity deformation can be quite effective in increasing the forming limits. In this study, electromagnetic forming (EMF) of thin AZ31B-O magnesium and CP grade 1 titanium sheets were compared with normal deep drawing. Same dies were used in both forming processes. Finite element (FE) simulations were carried out to improve the EMF process parameters. Constitutive data was determined using Split Hopkinson Pressure Bar tests (SHPB). To study formability, sample sheets were electromagnetically launched to the female die, using a flat spiral electromagnetic coil and aluminum driver sheets. Deep drawing tests were made by a laboratory press-machine.Results show that high velocity forming processes increase the formability of Magnesium and Titanium sheets although process parameters have to be carefully tuned to obtain good results.

  1. Mixing between high velocity clouds and the galactic halo

    SciTech Connect

    Gritton, Jeffrey A.; Shelton, Robin L.; Kwak, Kyujin E-mail: rls@physast.uga.edu

    2014-11-01

    In the Galactic halo, metal-bearing Galactic halo material mixes into high velocity clouds (HVCs) as they hydrodynamically interact. This interaction begins long before the clouds completely dissipate and long before they slow to the velocity of the Galactic material. In order to make quantitative estimates of the mixing efficiency and resulting metal enrichment of HVCs, we made detailed two- and three-dimensional simulations of cloud-interstellar medium interactions. Our simulations track the hydrodynamics and time-dependent ionization levels. They assume that the cloud originally has a warm temperature and extremely low metallicity while the surrounding medium has a high temperature, low density, and substantial metallicity, but our simulations can be generalized to other choices of initial metallicities. In our simulations, mixing between cloud and halo gas noticeably raises the metallicity of the high velocity material. We present plots of the mixing efficiency and metal enrichment as a function of time.

  2. 3D finite element simulations of high velocity projectile impact

    NASA Astrophysics Data System (ADS)

    Ožbolt, Joško; İrhan, Barış; Ruta, Daniela

    2015-09-01

    An explicit three-dimensional (3D) finite element (FE) code is developed for the simulation of high velocity impact and fragmentation events. The rate sensitive microplane material model, which accounts for large deformations and rate effects, is used as a constitutive law. In the code large deformation frictional contact is treated by forward incremental Lagrange multiplier method. To handle highly distorted and damaged elements the approach based on the element deletion is employed. The code is then used in 3D FE simulations of high velocity projectile impact. The results of the numerical simulations are evaluated and compared with experimental results. It is shown that it realistically predicts failure mode and exit velocities for different geometries of plain concrete slab. Moreover, the importance of some relevant parameters, such as contact friction, rate sensitivity, bulk viscosity and deletion criteria are addressed.

  3. Simple Motor Control Concept Results High Efficiency at High Velocities

    NASA Astrophysics Data System (ADS)

    Starin, Scott; Engel, Chris

    2013-09-01

    The need for high velocity motors in space applications for reaction wheels and detectors has stressed the limits of Brushless Permanent Magnet Motors (BPMM). Due to inherent hysteresis core losses, conventional BPMMs try to balance the need for torque verses hysteresis losses. Cong-less motors have significantly less hysteresis losses but suffer from lower efficiencies. Additionally, the inherent low inductance in cog-less motors result in high ripple currents or high switching frequencies, which lowers overall efficiency and increases performance demands on the control electronics.However, using a somewhat forgotten but fully qualified technology of Isotropic Magnet Motors (IMM), extremely high velocities may be achieved at low power input using conventional drive electronics. This paper will discuss the trade study efforts and empirical test data on a 34,000 RPM IMM.

  4. Gouge initiation in high-velocity rocket sled testing

    NASA Astrophysics Data System (ADS)

    Tachau, R. D. M.; Trucano, T. G.; Yew, C. H.

    1994-07-01

    A model is presented which describes the formation of surface damage 'gouging' on the rails that guide rocket sleds. An unbalanced sled can randomly cause a very shallow-angle, oblique impact between the sled shoe and the rail. This damage phenomenon has also been observed in high-velocity guns where the projectile is analogous to the moving sled shoe and the gun barrel is analogous to the stationary rail. At sufficiently high velocity, the oblique impact will produce a thin hot layer of soft material on the contact surfaces. Under the action of a normal moving load, the soft layer lends itself to an anti-symmetric deformation and the formation of a 'hump' in front of the moving load. A gouge is formed when this hump is overrun by the sled shoe. The phenomenon is simulated numerically using the CTH strong shock physics code, and the results are in good agreement with experimental observation.

  5. Gouge initiation in high-velocity rocket sled testing

    SciTech Connect

    Tachau, R.D.M.; Trucano, T.G.; Yew, C.H.

    1994-07-01

    A model is presented which describes the formation of surface damage ``gouging`` on the rails that guide rocket sleds. An unbalanced sled can randomly cause a very shallow-angle, oblique impact between the sled shoe and the rail. This damage phenomenon has also been observed in high-velocity guns where the projectile is analogous to the moving sled shoe and the gun barrel is analogous to the stationary rail. At sufficiently high velocity, the oblique impact will produce a thin hot layer of soft material on the contact surfaces. Under the action of a normal moving load, the soft layer lends itself to an anti-symmetric deformation and the formation of a ``hump`` in front of the moving load. A gouge is formed when this hump is overrun by the sled shoe. The phenomenon is simulated numerically using the CTH strong shock physics code, and the results are in good agreement with experimental observation.

  6. Gentle protein ionization assisted by high-velocity gas flow.

    PubMed

    Yang, Pengxiang; Cooks, R Graham; Ouyang, Zheng; Hawkridge, Adam M; Muddiman, David C

    2005-10-01

    Gentle protein electrospray ionization is achieved using the high-velocity gas flow of an air amplifier to improve desolvation in conventional ESI and generate intact folded protein ions in the gas phase. Comparisons are made between the ESI spectra of a number of model proteins, including ubiquitin, cytochrome c, lysozyme, and myoglobin, over a range of pH values under optimized conditions, with and without using an air amplifier to achieve high-velocity gas flow. Previously reported increased ion signals are confirmed. In addition, the peaks recorded using the air amplifier are shown to be narrower, corresponding to more complete desolvation. Significant changes in the charge-state distribution also are observed, with a shift to lower charge state at high-velocity flow. The relationship between the observed charge-state distribution and protein conformation was explored by comparing the charge-state shifts and the distributions of charge states for proteins that are or are not stable in their native conformations in low pH solutions. The data suggest retention of native or nativelike protein conformations using the air amplifier in all cases examined. This is explained by a mechanism in which the air amplifier rapidly creates small droplets from the original large ESI droplets and these microdroplets then desolvate without a significant decrease in pH, resulting in retention of the folded protein conformations. Furthermore, the holoform of ionized myoglobin is visible at pH 3.5, a much lower value than the minimum needed to see this form in conventional ESI. These results provide evidence for the importance of the conditions used in the desolvation process for the preservation of the protein conformation and suggest that the conditions achieved when using high-velocity gas flows to assist droplet evaporation and ion desolvation are much gentler than those in conventional ESI experiments.

  7. Spinal Headaches

    MedlinePlus

    ... undergo a spinal tap (lumbar puncture) or spinal anesthesia. Both procedures require a puncture of the tough ... is withdrawn from your spinal canal. During spinal anesthesia, medication is injected into your spinal canal to ...

  8. Electric rail gun projectile acceleration to high velocity

    NASA Technical Reports Server (NTRS)

    Bauer, D. P.; Mccormick, T. J.; Barber, J. P.

    1982-01-01

    Electric rail accelerators are being investigated for application in electric propulsion systems. Several electric propulsion applications require that the rail accelerator be capable of launching projectiles at velocities above 10 km/s. An experimental program was conducted to develop rail accelerator technology for high velocity projectile launch. Several 6 mm bore, 3 m long rail accelerators were fabricated. Projectiles with a mass of 0.2 g were accelerated by plasmas, carrying currents up to 150 kA. Experimental design and results are described. Results indicate that the accelerator performed as predicted for a fraction of the total projectile acceleration. The disparity between predicted and measured results are discussed.

  9. Analysis of high velocity impact on hybrid composite fan blades

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1979-01-01

    Recent developments in the analysis of high velocity impact of composite blades are described, using a computerized capability which consists of coupling a composites mechanics code with the direct-time integration features of NASTRAN. The application of the capability to determine the linear dynamic response of an interply hybrid composite aircraft engine fan blade is described in detail. The results also show that the impact stresses reach sufficiently high magnitudes to cause failures in the impact region at early times of the impact event.

  10. Analysis of high velocity impact on hybrid composite fan blades

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1979-01-01

    This paper describes recent developments in the analysis of high velocity impact of composite blades using a computerized capability which consists of coupling a composites mechanics code with the direct-time integration features of NASTRAN. The application of the capability to determine the linear dynamic response of an intraply hybrid composite aircraft engine fan blade is described in detail. The predicted results agree with measured data. The results also show that the impact stresses reach sufficiently high magnitudes to cause failures in the impact region at early times of the impact event.

  11. High-Velocity Star Formation in the Large Magellanic Cloud.

    PubMed

    Graff; Gould

    2000-05-01

    Light-echo measurements show that SN 1987A is 425 pc behind the LMC disk. It is continuing to move away from the disk at 18 km s-1. Thus, it has been suggested that SN 1987A was ejected from the LMC disk. However, SN 1987A is a member of a star cluster, so this entire cluster would have to have been ejected from the disk. We show that the cluster was formed in the LMC disk, with a velocity perpendicular to the disk of about 50 km s-1. Such high-velocity formation of a star cluster is unusual, having no known counterpart in the Milky Way.

  12. High-velocity streams of dust originating from Saturn.

    PubMed

    Kempf, Sascha; Srama, Ralf; Horányi, Mihaly; Burton, Marcia; Helfert, Stefan; Moragas-Klostermeyer, Georg; Roy, Mou; Grün, Eberhard

    2005-01-20

    High-velocity submicrometre-sized dust particles expelled from the jovian system have been identified by dust detectors on board several spacecraft. On the basis of periodicities in the dust impact rate, Jupiter's moon Io was found to be the dominant source of the streams. The grains become positively charged within the plasma environment of Jupiter's magnetosphere, and gain energy from its co-rotational electric field. Outside the magnetosphere, the dynamics of the grains are governed by the interaction with the interplanetary magnetic field that eventually forms the streams. A similar process was suggested for Saturn. Here we report the discovery by the Cassini spacecraft of bursts of high-velocity dust particles (> or = 100 km s(-1)) within approximately 70 million kilometres of Saturn. Most of the particles detected at large distances appear to originate from the outskirts of Saturn's outermost main ring. All bursts of dust impacts detected within 150 Saturn radii are characterized by impact directions markedly different from those measured between the bursts, and they clearly coincide with the spacecraft's traversals through streams of compressed solar wind.

  13. Effect of State of Stress on Velocity of Low-Amplitude Shear Waves Propagating along Principal Stress Directions in Dry Sand.

    DTIC Science & Technology

    1982-03-01

    amplitude, and confining pressure. 4.4.1 Low-Amplitude Dinamic Properties Three series of low-amplitude tests were performed to determine the effect of...integrity of the wire in the cube during testing, a soil specimen of the same sand used in the cube was prepared for static triaxial soil testing with a

  14. Low and high velocity impact response of thick hybrid composites

    NASA Technical Reports Server (NTRS)

    Hiel, Clement; Ishai, Ori

    1993-01-01

    The effects of low and high velocity impact on thick hybrid composites (THC's) were experimentally compared. Test Beams consisted of CFRP skins which were bonded onto an interleaved syntactic foam core and cured at 177 C (350 F). The impactor tip for both cases was a 16 mm (0.625 inch) steel hemisphere. In spite of the order of magnitude difference in velocity ranges and impactor weights, similar relationships between impact energy, damage size, and residual strength were found. The dependence of the skin compressive strength on damage size agree well with analytical open hole models for composite laminates and may enable the prediction of ultimate performance for the damaged composite, based on visual inspection.

  15. Response of Cable Harnesses Subjected to High-velocity Impacts

    NASA Astrophysics Data System (ADS)

    Nitta, Kumi; Kawakita, Shirou; Takeba, Atsushi; Katayama, Masahide

    We compared numerical simulation results obtained using AUTODYN-3D, which is used for impact analysis of complex physical systems including fluid and solid materials, with experimental results obtained using a two-stage light gas gun. The response of electric power supply cable harnesses subjected to high-velocity impact at 4.01 km/s is shown and discussed. In addition, AUTODYN-3D was applied to the numerical simulation of the hypervelocity impact of micrometeoroids and space debris (M/OD) at 15 km/s and 20 km/s, respectively. Material models used in the numerical simulation are also discussed and investigated in order to cover a wide range of impact velocities, including shock-induced vaporization.

  16. The distance to the high velocity clouds of neutral hydrogen

    NASA Technical Reports Server (NTRS)

    Bregman, Joel N.

    1992-01-01

    The goal of this project was to determine the distance to high velocity gas clouds. These clouds are believed to lie in the halo of the galaxy, but this is a matter of controversy. The technique was used to look for the effect of absorption by these clouds against the light of stars at various distances along the line of sight to these clouds. This was done in the ultraviolet using the International Ultraviolet Explorer. Absorption at the velocity of the clouds was not found in any of the stars, which have kiloparsec distances. It was concluded that the vertical distance to these clouds is at least 1.5 kpc, putting them firmly in the halo of the galaxy.

  17. Heterogeneous fragmentation of metallic liquid microsheet with high velocity gradient

    NASA Astrophysics Data System (ADS)

    An-Min, He; Pei, Wang; Jian-Li, Shao

    2016-01-01

    Large-scale molecular dynamics simulations are performed to study the fragmentation of metallic liquid sheets with high velocity gradient. Dynamic fragmentation of the system involves the formation of a network of fragments due to the growth and coalescence of holes, decomposition of the network into filaments, and further breakup of the filaments into spherical clusters. The final size distribution of the fragmented clusters in the large volume limit is found to obey a bilinear exponential form, which is resulted from the heterogeneous breakup of quasi-cylindrical filaments. The main factors contributing to fragmentation heterogeneity are introduced, including strain rate inhomogeneity and matter distribution nonuniformity of fragments produced during decomposition of the network structure. Project supported by the Science and Technology Development Foundation of China Academy of Engineering Physics (Grant Nos. 2013A0201010 and 2015B0201039) and the National Natural Science Foundation of China (Grant No. 11402032).

  18. Fluid shielding of high-velocity jet noise

    NASA Technical Reports Server (NTRS)

    Goodykoontz, J. H.

    1984-01-01

    Experimental noise data for a nozzle exhaust system incorporating a thermal acoustic shield (TAS) are presented to show the effect of changes in geometric and flow parameters on attenuation of high-velocity jet exhaust noise in the flyover plane. The results are presented for a 10.00-cm-diameter primary conical nozzle with a TAS configuration consisting of a 2.59- or 5.07-cm-wide annular gap. Shield-stream exhaust velocity was varied from 157 to 248 m/sec to investigate the effect of velocity ratio. The results showed that increasing the annular gap width increases attenuation of high-frequency noise when comparisons are made on the same ideal thrust basis. Varying the velocity ratio had a minor effect on the noise characteristics of the nozzles investigated.

  19. Resonant Orbits and the High Velocity Peaks toward the Bulge

    NASA Astrophysics Data System (ADS)

    Molloy, Matthew; Smith, Martin C.; Evans, N. Wyn; Shen, Juntai

    2015-10-01

    We extract the resonant orbits from an N-body bar that is a good representation of the Milky Way, using the method recently introduced by Molloy et al. By decomposing the bar into its constituent orbit families, we show that they are intimately connected to the boxy-peanut shape of the density. We highlight the imprint due solely to resonant orbits on the kinematic landscape toward the Galactic center. The resonant orbits are shown to have distinct kinematic features and may be used to explain the cold velocity peak seen in the Apache Point Observatory Galactic Evolution Experiment commissioning data. We show that high velocity peaks are a natural consequence of the motions of stars in the 2:1 orbit family and that stars on other higher order resonances can contribute to the peaks. The locations of the peaks vary with bar angle and, with the tacit assumption that the observed peaks are due to the 2:1 family, we find that the locations of the high velocity peaks correspond to bar angles in the range {10}\\circ ≲ {θ }{bar}≲ 25^\\circ . However, some important questions about the nature of the peaks remain, such as their apparent absence in other surveys of the Bulge and the deviations from symmetry between equivalent fields in the north and south. We show that the absence of a peak in surveys at higher latitudes is likely due to the combination of a less prominent peak and a lower number density of bar supporting orbits at these latitudes.

  20. Dynamic weakening by nanoscale smoothing during high velocity fault slip

    NASA Astrophysics Data System (ADS)

    Chen, X.; Madden, A. S.; Bickmore, B. R.; Reches, Z.

    2012-12-01

    Rock friction is commonly determined through measurements on rock samples with areas from a few cm^2 to 1 m^2. On the other hand, theoretical models suggest that frictional processes are scale-dependent, and active at scales of a few microns or less. We used Atomic Force Microscope (AFM) to determine the frictional strength and roughness of experimental fault surfaces that slipped under high velocity (< 0.9 m/s) and moderate normal stress (< 7.0 MPa). The high velocity tests (Reches and Lockner, 2010) were conducted on experimental faults made of Sierra White granite (SWG) and Kasota dolomite (KD), and the sheared surfaces were sampled for the nanoscale measurements by the AFM. The friction coefficient (FC) at the sub-micron scale was measured by using the AFM to press & shear a tiny silica glass bead against the rock surface (Stiernstedt et al., 2005). The 3D morphology of the fault surfaces at the nano- to microscale was measured with the standard AFM intermittent contact mode with sharp tip probe. In the AFM friction measurements, a total of 43 sites have been measured and each site was repeated hundreds of times; 33 of these sites were measured under air and 10 sites were measured under deionized water. The SWG and KD samples display FC values that vary systematically with orientation and conditions. Room-dry, un-sheared surfaces have FC = 0.64 ± 0.05 for both rock types. KD normal to striations has FC = 0.60 ± 0.15. SWG rough, sheared surface display FC = 0.71 ± 0.02. Significant friction drop was observed under dry, parallel to striations, with FC = 0.34 ± 0.08 (KD) and FC = 0.52 ± 0.03 (SWG). Under wet (water covered) conditions parallel to slickensides, the friction dropped even further to FC = 0.15 ± 0.05 (dolomite) and FC = 0.31 ± 0.05 (granite). The nanoscale FC (room dry, parallel to striations) is comparable to the macroscopic FC for the host experiments. Roughness calculations are based on AFM topographic images, and analyzed by both Power

  1. Collisional Disruption of Ice by High-Velocity Impact

    NASA Astrophysics Data System (ADS)

    Arakawa, Masahiko

    1999-11-01

    High-velocity impact among icy planetesimals is a physical phenomenon important to the planetary evolution process in the outer Solar System. In order to study this phenomenon, impact experiments on water ice were made by using a two-stage light gas gun installed in a cold room (-10°C) to clarify the elementary processes of collisional disruption and to study the reaccumulation and the escape conditions of the impact fragments. Cubic ice targets ranging in size from 15 to 100 mm were impacted by a nylon projectile of 7 mg with an impact velocity ( vi) from 2.3 to 4.7 km/s. The corresponding mass ratio of the projectile to the target ( mp/ Mt) ranged from 10 -3 to 10 -6, which is two orders of magnitude lower than that used in previous studies (Arakawa et al. 1995, Icarus118, 341-354). As a result, we obtained data on elementary processes such as attenuation of the shock wave and fragmentation dynamics. We found that the shock pressure attenuates in the ice target according to the relation of P∝( Lp/ r2, irrespective of the mass ratio between 10 -3 and 10 -5, where Lp is the projectile size and r is a propagation distance. The largest fragment mass ( ml) normalized by the original target mass has a good relationship to a nondimensional impact stress ( PI, NDIS) defined as the ratio of the antipodal pressure to the material strength. This relationship is described as ml/ Mt ∝ PI-1.7 for a wide range of impact conditions (50 m/s< vi<4 km/s and 10 -1< ml/ Mt<10 -6), and shows the utility of NDIS. Using a measured shock wave decay constant of 2, the reaccumulation and the escape conditions of icy bodies in high-velocity collisions were estimated. As a result, it was clarified that a rubble pile could be formed when large icy bodies (radius>20 km) reaccumulated. On the other hand, when smaller icy bodies (radius<2 km) disrupted catastrophically, all fragments escaped and a rubble pile was never formed.

  2. High-velocity features in Type Ia supernova spectra

    NASA Astrophysics Data System (ADS)

    Childress, Michael J.; Filippenko, Alexei V.; Ganeshalingam, Mohan; Schmidt, Brian P.

    2014-01-01

    We use a sample of 58 low-redshift (z ≤ 0.03) Type Ia supernovae (SNe Ia) having well-sampled light curves and spectra near maximum light to examine the behaviour of high-velocity features (HVFs) in SN Ia spectra. We take advantage of the fact that Si II λ6355 is free of HVFs at maximum light in all SNe Ia, while HVFs are still strong in the Ca II near-infrared feature in many SNe, allowing us to quantify the strength of HVFs by comparing the structure of these two lines. We find that the average HVF strength increases with decreasing light-curve decline rate, and rapidly declining SNe Ia (Δm15(B) ≥ 1.4 mag) show no HVFs in their maximum-light spectra. Comparison of HVF strength to the light-curve colour of the SNe Ia in our sample shows no evidence of correlation. We find a correlation of HVF strength with the velocity of Si II λ6355 at maximum light (vSi), such that SNe Ia with lower vSi have stronger HVFs, while those SNe Ia firmly in the `high-velocity' (i.e. vSi ≥ 12 000 km s-1) subclass exhibit no HVFs in their maximum-light spectra. While vSi and Δm15(B) show no correlation in the full sample of SNe Ia, we find a significant correlation between these quantities in the subset of SNe Ia having weak HVFs. In general, we find that slowly declining (low Δm15(B)) SNe Ia, which are more luminous and more energetic than average SNe Ia, tend to produce either high photospheric ejecta velocities (i.e. high vSi) or strong HVFs at maximum light, but not both. Finally, we examine the evolution of HVF strength for a sample of SNe Ia having extensive pre-maximum spectroscopic coverage and find significant diversity of the pre-maximum HVF behaviour.

  3. High velocity compact clouds in the sagittarius C region

    SciTech Connect

    Tanaka, Kunihiko; Oka, Tomoharu; Matsumura, Shinji; Nagai, Makoto; Kamegai, Kazuhisa

    2014-03-01

    We report the detection of extremely broad emission toward two molecular clumps in the Galactic central molecular zone. We have mapped the Sagittarius C complex (–0.°61 < l < –0.°27, –0.°29 < b < 0.°04) in the HCN J = 4-3, {sup 13}CO J = 3-2, and H{sup 13}CN J = 1-0 lines with the ASTE 10 m and NRO 45 m telescopes, detecting bright emission with 80-120 km s{sup –1} velocity width (in full-width at zero intensity) toward CO–0.30–0.07 and CO–0.40–0.22, which are high velocity compact clouds (HVCCs) identified with our previous CO J = 3-2 survey. Our data reveal an interesting internal structure of CO–0.30–0.07 comprising a pair of high velocity lobes. The spatial-velocity structure of CO–0.40–0.22 can be also understood as a multiple velocity component, or a velocity gradient across the cloud. They are both located on the rims of two molecular shells of about 10 pc in radius. Kinetic energies of CO–0.30–0.07 and CO–0.40–0.22 are (0.8-2) × 10{sup 49} erg and (1-4) × 10{sup 49} erg, respectively. We propose several interpretations of their broad emission: collision between clouds associated with the shells, bipolar outflow, expansion driven by supernovae (SNe), and rotation around a dark massive object. These scenarios cannot be discriminated because of the insufficient angular resolution of our data, though the absence of a visible energy source associated with the HVCCs seems to favor the cloud-cloud collision scenario. Kinetic energies of the two molecular shells are 1 × 10{sup 51} erg and 0.7 × 10{sup 51} erg, which can be furnished by multiple SN or hypernova explosions in 2 × 10{sup 5} yr. These shells are candidates of molecular superbubbles created after past active star formation.

  4. Two high-velocity encounters of elliptical galaxies

    NASA Technical Reports Server (NTRS)

    Balcells, Marc; Borne, Kirk D.; Hoessel, John G.

    1989-01-01

    This paper describes results obtained on a simulation of two high-velocity encounters of NGC 4782/4783 and NGC 2672/2673 binary elliptical galaxies which differ substantially in mass ratio (about 1 for the first pair, and about 10 for the second). CCD images and velocities obtained from digital spectra were used to constrain simulations of the galaxy collisions. The binary orbital elements, the orientation of the orbit in the sky, the time since pericenter, and the dynamical mass of the pair were derived. Results suggested that the dumb-bell galaxy NGC 4782/4783 is not a supermassive galaxy, as was claimed earlier on the basis of the high relative velocity and high central dispersion, but has a moderate mass to luminosity ratio M/L(B) of about 10. It was concluded that its trajectory changed from hyperbolic to elliptical as a result of energy lost during the collision. It was found that the NGC 2672/2673 also has a moderate M/L(B) of about 7.

  5. High velocity electromagnetic particle launcher for aerosol production studies

    SciTech Connect

    Benson, D.A.; Rader, D.J.

    1986-05-01

    This report describes the development of a new device for study of metal combustion, breakup and production of aerosols in a high velocity environment. Metal wires are heated and electromagnetically launched with this device to produce molten metal droplets moving at velocities ranging up to about Mach 1. Such tests are presently intended to simulate the behavior of metal streamers ejected from a high-explosive detonation. A numerical model of the launcher performance in terms of sample properties, sample geometry and pulser electrical parameters is presented which can be used as a tool for design of specific test conditions. Results from several tests showing the range of sample velocities accessible with this device are described and compared with the model. Photographic measurements showing the behavior of tungsten and zirconium metal droplets are presented. Estimates of the Weber breakup and drag on the droplets, as well as calculations of the droplet trajectories, are described. Such studies may ultimately be useful in assessing environmental hazards in the handling and storage of devices containing metallic plutonium.

  6. Orbital Transfer Vehicle Engine Technology High Velocity Ratio Diffusing Crossover

    NASA Technical Reports Server (NTRS)

    Lariviere, Brian W.

    1992-01-01

    High speed, high efficiency head rise multistage pumps require continuous passage diffusing crossovers to effectively convey the pumped fluid from the exit of one impeller to the inlet of the next impeller. On Rocketdyne's Orbital Transfer Vehicle (OTV), the MK49-F, a three stage high pressure liquid hydrogen turbopump, utilizes a 6.23 velocity ratio diffusing crossover. This velocity ratio approaches the diffusion limits for stable and efficient flow over the operating conditions required by the OTV system. The design of the high velocity ratio diffusing crossover was based on advanced analytical techniques anchored by previous tests of stationary two-dimensional diffusers with steady flow. To secure the design and the analytical techniques, tests were required with the unsteady whirling characteristics produced by an impeller. A tester was designed and fabricated using a 2.85 times scale model of the MK49-F turbopumps first stage, including the inducer, impeller, and the diffusing crossover. Water and air tests were completed to evaluate the large scale turbulence, non-uniform velocity, and non-steady velocity on the pump and crossover head and efficiency. Suction performance tests from 80 percent to 124 percent of design flow were completed in water to assess these pump characteristics. Pump and diffuser performance from the water and air tests were compared with the actual MK49-F test data in liquid hydrogen.

  7. Orbital transfer vehicle engine technology high velocity ratio diffusing crossover

    NASA Astrophysics Data System (ADS)

    Lariviere, Brian W.

    1992-12-01

    High speed, high efficiency head rise multistage pumps require continuous passage diffusing crossovers to effectively convey the pumped fluid from the exit of one impeller to the inlet of the next impeller. On Rocketdyne's Orbital Transfer Vehicle (OTV), the MK49-F, a three stage high pressure liquid hydrogen turbopump, utilizes a 6.23 velocity ratio diffusing crossover. This velocity ratio approaches the diffusion limits for stable and efficient flow over the operating conditions required by the OTV system. The design of the high velocity ratio diffusing crossover was based on advanced analytical techniques anchored by previous tests of stationary two-dimensional diffusers with steady flow. To secure the design and the analytical techniques, tests were required with the unsteady whirling characteristics produced by an impeller. A tester was designed and fabricated using a 2.85 times scale model of the MK49-F turbopumps first stage, including the inducer, impeller, and the diffusing crossover. Water and air tests were completed to evaluate the large scale turbulence, non-uniform velocity, and non-steady velocity on the pump and crossover head and efficiency. Suction performance tests from 80 percent to 124 percent of design flow were completed in water to assess these pump characteristics. Pump and diffuser performance from the water and air tests were compared with the actual MK49-F test data in liquid hydrogen.

  8. The effects of photobiomodulation and low-amplitude high-frequency vibration on bone healing process: a comparative study.

    PubMed

    Rajaei Jafarabadi, M; Rouhi, G; Kaka, G; Sadraie, S H; Arum, J

    2016-12-01

    This study aimed at investigating the effects of photobiomodulation (PBM) and low-amplitude high-frequency (LAHF) whole body mechanical vibration on bone fracture healing process when metallic plates are implanted in rats' femurs. Forty male rats weighing between 250 and 350 g, 12 weeks old, were employed in this study. A transverse critical size defect (CSD) was made in their right femurs that were fixed by stainless steel plates. After the surgery, the rats were divided equally into four groups: low-level laser therapy group (GaAlAs laser, 830 nm, 40 mW, 4 J/cm(2), 0.35 cm beam diameter, LLLT), whole body vibration group (60 Hz, 0.1 mm amplitude, 1.5 g, WBV), a combination of laser and vibration group (LV), and the control group (C). Each group was divided into two subgroups based on sacrifice dates. The rats were sacrificed at intervals of 3 and 6 weeks after the surgery to extract their right femurs for radiography and biomechanical and histological analyses, and the results were analyzed using standard statistical methods. Radiographic analyses showed greater callus formation in the LLLT and WBV groups than in control group at both 3 (P < 0.05 and P < 0.001, respectively) and 6 weeks after surgery (P < 0.05 and P < 0.05, respectively). Histological evaluations showed a higher amount of new bone formation and better maturity in the LLLT and WBV groups than the control groups at 3 and 6 weeks after surgery. Biomechanical tests showed that the maximum force at fracture in the LLLT (P < 0.05 in 3 weeks and P < 0.05 in 6 weeks) and WBV (P < 0.001 in 3 weeks and P < 0.05 in 6 weeks) groups was greater than that in the control groups at both time intervals. But a combination of laser and vibration therapy, LV, did not show a positive interaction on bone fracture healing process. The biostimulation effects of PBM or LLLT and of low-amplitude high-frequency WBV both had a positive impact on bone healing process, for

  9. Coherent control of the route of an ultrafast magnetic phase transition via low-amplitude spin precession.

    PubMed

    de Jong, J A; Razdolski, I; Kalashnikova, A M; Pisarev, R V; Balbashov, A M; Kirilyuk, A; Rasing, Th; Kimel, A V

    2012-04-13

    Time-resolved magneto-optical imaging of laser-excited rare-earth orthoferrite (SmPr)FeO3 demonstrates that a single 60 fs circularly polarized laser pulse is capable of creating a magnetic domain on a picosecond time scale with a magnetization direction determined by the helicity of light. Depending on the light intensity and sample temperature, pulses of the same helicity can create domains with opposite magnetizations. We argue that this phenomenon relies on a twofold effect of light which (i) instantaneously excites coherent low-amplitude spin precession and (ii) triggers a spin reorientation phase transition. The former dynamically breaks the equivalence between two otherwise degenerate states with opposite magnetizations in the high-temperature phase and thus controls the route of the phase transition.

  10. Low-Amplitude Topographic Features and Textures on the Moon: Initial Results from Detrended Lunar Orbiter Laser Altimeter (LOLA) Topography

    NASA Technical Reports Server (NTRS)

    Kreslavsky, Mikhail A.; Head, James W.; Neumann, Gregory A.; Zuber, Maria T.; Smith, David E.

    2016-01-01

    Global lunar topographic data derived from ranging measurements by the Lunar Orbiter Laser Altimeter (LOLA) onboard LRO mission to the Moon have extremely high vertical precision. We use detrended topography as a means for utilization of this precision in geomorphological analysis. The detrended topography was calculated as a difference between actual topography and a trend surface defined as a median topography in a circular sliding window. We found that despite complicated distortions caused by the non-linear nature of the detrending procedure, visual inspection of these data facilitates identification of low-amplitude gently-sloping geomorphic features. We present specific examples of patterns of lava flows forming the lunar maria and revealing compound flow fields, a new class of lava flow complex on the Moon. We also highlight the identification of linear tectonic features that otherwise are obscured in the images and topographic data processed in a more traditional manner.

  11. Low-amplitude topographic features and textures on the Moon: Initial results from detrended Lunar Orbiter Laser Altimeter (LOLA) topography

    NASA Astrophysics Data System (ADS)

    Kreslavsky, Mikhail A.; Head, James W.; Neumann, Gregory A.; Zuber, Maria T.; Smith, David E.

    2017-02-01

    Global lunar topographic data derived from ranging measurements by the Lunar Oribter Laser Altimeter (LOLA) onboard LRO mission to the Moon have extremely high vertical precision. We use detrended topography as a means for utilization of this precision in geomorphological analysis. The detrended topography was calculated as a difference between actual topography and a trend surface defined as a median topography in a circular sliding window. We found that despite complicated distortions caused by the non-linear nature of the detrending procedure, visual inspection of these data facilitates identification of low-amplitude gently-sloping geomorphic features. We present specific examples of patterns of lava flows forming the lunar maria and revealing compound flow fields, a new class of lava flow complex on the Moon. We also highlight the identification of linear tectonic features that otherwise are obscured in the images and topographic data processed in a more traditional manner.

  12. Low-amplitude variations detected by CoRoT in the B8IIIe star HD 175869

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Soto, J.; Floquet, M.; Samadi, R.; Neiner, C.; Garrido, R.; Fabregat, J.; Frémat, Y.; Diago, P. D.; Huat, A.-L.; Leroy, B.; Emilio, M.; Hubert, A.-M.; Andrade, O. Thizy L.; de Batz, B.; Janot-Pacheco, E.; Espinosa Lara, F.; Martayan, C.; Semaan, T.; Suso, J.; Auvergne, M.; Chaintreuil, S.; Michel, E.; Catala, C.

    2009-10-01

    Context: The origin of the short-term variability in Be stars remains a matter of controversy. Pulsations and rotational modulation are the components of the favored hypothesis. Aims: We present our analysis of CoRoT data of the B8IIIe star HD 175869 observed during the first short run in the center direction (SRC1). Methods: We review both the instrumental effects visible in the CoRoT light curve and the analysis methods used by the CoRoT Be team. We applied these methods to the CoRoT light curve of the star HD 175869. A search for line-profile variations in the spectroscopic data was also performed. We also searched for a magnetic field, by applying the LSD technique to spectropolarimetric data. Results: The light curve exhibits low-amplitude variations of the order of 300 μmag with a double wave shape. A frequency within the range determined for the rotational frequency and 6 of its harmonics are detected. The main frequency and its first harmonic exhibit amplitude variations of a few days. Other significant frequencies of low-amplitude from 25 to a few μmag are also found. The analysis of line profiles from ground-based spectroscopic data does not detect any variation. In addition, no Zeeman signature was found. Conclusions: Inhomogeneities caused by stellar activity in or just above the photosphere are proposed to produce the photometric variability detected by CoRoT in the Be star HD 175869. The hypothesis that non-radial pulsations are the origin of these variations cannot be excluded.

  13. Numerical Investigation of High Velocity Suspension Flame Spraying

    NASA Astrophysics Data System (ADS)

    Taleby, M.; Hossainpour, S.

    2012-12-01

    High-velocity suspension flame spraying (HVSFS) has recently developed as a possible alternative to conventional HVOF-spraying employing liquid suspensions instead of dry powder feedstock enables the use of nanoparticles. From the fluid dynamics point of view, the HVSFS system is complex and involves three-phase (gas, liquid and solid particles) turbulent flow, heat transfer, evaporation of the suspension solvent, chemical reactions of main fuel (propane) and suspension solvent (ethanol) and supersonic/subsonic flow transitions. Computational fluid dynamic techniques were carried out to solve the mass, momentum, and energy conservation equations. The realizable k-ɛ turbulence model was used to account for the effect of turbulence. The HVSFS process involves two combustion reactions. A primary combustion process is the premixed oxygen-propane reaction and secondary process is the non-premixed oxygen-gaseous ethanol reaction. For each reaction, one step global reaction, which takes dissociations and intermediate reactions into account, was derived from the equilibrium chemistry code developed by Gordon and McBride and eddy dissipation model was used to calculate the rate of reactions based on the transport equations for all species (10 species) mass fractions. Droplets were tracked in the continuum in a Lagrangian approach. In this paper, flow field inside and outside the gun simulated to provide clear and complete insight about the HVSFS processes. Moreover, the effect of some operative parameters (oxy-fuel flow rate, ethanol flow rate, droplets injection velocity and droplets size) on the gas flow field along the centerline and droplets evaporation behavior was discussed.

  14. Fault gouge rheology under confined, high-velocity conditions

    NASA Astrophysics Data System (ADS)

    Reches, Z.; Madden, A. S.; Chen, X.

    2012-12-01

    We recently developed the experimental capability to investigate the shear properties of fine-grain gouge under confined conditions and high-velocity. The experimental system includes a rotary apparatus that can apply large displacements of tens of meters, slip velocity of 0.001- 2.0 m/s, and normal stress of 35 MPa (Reches and Lockner, 2010). The key new component is a Confined ROtary Cell (CROC) that can shear a gouge layer either dry or under pore-pressure. The pore pressure is controlled by two syringe pumps. CROC includes a ring-shape gouge chamber of 62.5 mm inner diameter, 81.25 mm outer diameter, and up to 3 mm thick gouge sample. The lower, rotating part of CROC contains the sample chamber, and the upper, stationary part includes the loading, hollow cylinder and setting for temperature, and dilation measurements, and pore-pressure control. Each side of the gouge chamber has two pairs of industrial, spring-energized, self-lubricating, teflon-graphite seals, built for particle media and can work at temperature up to 250 ded C. The space between each of the two sets of seals is pressurized by nitrogen. This design generates 'zero-differential pressure' on the inner seal (which is in contact with the gouge powder), and prevents gouge leaks. For the preliminary dry experiments, we used ~2.0 mm thick layers of room-dry kaolinite powder. Total displacements were on the order of meters and normal stress up to 4 MPa. The initial shear was accommodated by multiple internal slip surfaces within the kaolinite layer accommodated as oriented Riedel shear structures. Later, the shear was localized within a thin, plate-parallel Y-surface. The kaolinite layer was compacted at a quasi-asymptotic rate, and displayed a steady-state friction coefficient of ~ 0.5 with no clear dependence on slip velocity up to 0.15 m/s. Further experiments with loose quartz sand (grain size ~ 125 micron) included both dry runs and pore-pressure (distilled water) controlled runs. The sand was

  15. Experimental investigation of high velocity impacts on brittle materials

    NASA Astrophysics Data System (ADS)

    Nathenson, David Isaac

    Experiments were conducted on soda lime glass and AS800 grade silicon nitride. Soda lime glass is often used in windows of military vehicles and aircraft where integrity in the event of shrapnel impacts is of vital concern. AS800 grade silicon nitride is considered one of the leading material candidates for the next generation of aircraft engine turbine blades because of its superior high temperature properties when compared with nickel based super-alloys. The suitability of these materials for their applications depends upon their response to point and planar dynamic impact loading. An experimental apparatus was constructed to fire one-sixteenth inch diameter hardened chrome steel ball bearings at 50 mm square soda lime glass blocks of thicknesses between 3 mm and 25.4 mm. Inelasticity due to the crushed zone effects the coefficients of restitution and the surface strains. The change in severity of cracking with velocity and specimen thickness is observed. Shock compression and pressure-shear experiments were conducted by means of a single stage gas gun capable of attaining impact velocities of 600 m/s. High velocity planar shock compression experiments on soda lime glass reveal a lack of spall strength, and a decrease of shear impedance and shear strength in the presence of a failure wave. The longitudinal impedance remains nearly constant. The spall strength of glass is 3.49 GPa and is sensitive to the presence of shear. Shock compression studies on silicon nitride using normal shock compression show that the material has a Hugoniot Elastic Limit of 12 GPa and that the spall strength decreases with increasing impact velocity due to damage below the HEL. The presence of inelastic deformation stops this trend, while the presence of shear increases the rate of spall strength drop by five times because of more severe microscopic damage. Experiments involving multiple shocks on silicon nitride show that material loading and unloading follows the shock Hugoniot

  16. High-Velocity H I Gas in Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Koo, Bon-Chul

    1993-05-01

    Using the Hat Creek 85 foot telescope, we had carried out a survey of H I 21 cm emission lines toward all 103 known northern supernova remnants (SNRs) in order to find rapidly expanding SNR shells (Koo & Heiles 1991). We detected 15 SNRs that have associated high-velocity (HV) H I gas, most of which are quite likely the gas accelerated by the SN blast wave. Although the large beam-size (FWHM~ 30') of the 85 foot telescope prevented us to see the structure of the HV H I gas, the H I mass distribution in line-of-sight velocity suggested clumpy shell structures in several SNRs. In order to resolve the structure of the HV H I gas, we have been carrying out high-resolution H I 21 cm line observations using the Arecibo telescope and the VLA. We report preliminary results on two SNRs, CTB 80 and W51. In CTB 80, the VLA observations revealed fast moving H I clumps, which have a dense (n_H ~ 100 cm(-3) ) core surrounded by a relatively diffuse envelope. The clumps are small, 3 pc to 5 pc, and have velocities between +40 km s(-1) and +80 km s(-1) with respect to the systematic velocity of CTB 80. The clumps have relatively large momentum per unit volume, which implies that they have been swept-up at an early stage of the SNR evolution. By analyzing the Arecibo data, we found that the interstellar medium around CTB 80 is far from being uniform and homogeneous, which explains the peculiar morphology of CTB 80 in infrared and radio continuum. In W51, HV H I gas moving up to v_LSR>+150 km s(-1) has been detected. The H I distribution is elongated along the northwest-southeast direction, and the peak is very close to an X-ray bright region. We discuss the implications of our results in relation to the X-ray and the radio continuum morphology of W51. This work was supported in part by NON DIRECTED RESEARCH FUND, Korea Research Foundation, 1992.

  17. ``But I am constant as the North Star*'' - The Return of Polaris as a Low Amplitude Classical Cepheid

    NASA Astrophysics Data System (ADS)

    Davis, J. J.; Tracey, J. C.; Engle, S. G.; Guinan, E. F.

    2002-12-01

    * Julius Caesar, William Shakespeare Polaris ( ≈ +2.0 mag; B-V = +0.60; F7 Ib) is a low amplitude Classical Cepheid with a pulsation period of P = 3.97 days. Polaris is one of the nearest (dHipparcos = 132 +/- 8 pc) and brightest Cepheid. This Cepheid (Polaris A) is the luminous member of the multiple star system (ADS 1477). Over the last century amazing changing have been occurring for this famous star. The pulsation period has been increasing a rate of dP/dt = +3.2 sec/yr while the light amplitude has decreased from ~0.12 mag (1900s) to ~0.02 mag (early1990s). A recent summary and thorough discussion of Polaris's interesting properties are given by Evans et al. (2002, ApJ, 567, 1121). We have been carrying out photoelectric photometry of Polaris starting in early 2002. This photometry is a continuation of the work done on Polaris by Kamper and Fernie. Our observations were made to obtain new epochal light curves and accurate times of maximum light. We secured well defined 450 nm and 550 nm light curves from which we extracted accurate measures of light amplitudes of 0.033 +/- 0.004 mag and 0.028 +/- 0.003 mag, respectively. These light amplitudes are slightly larger than those observed during the early 1990s. So it appears that the century long decrease in the light amplitude has halted (or paused). Our time of maximum light was combined with previous timings and reaffirms the increase in period of +3.2 sec/yr. These observations lend strong support to overtone nature of Polaris's pulsations, whose transition from moderate to low amplitude pulsator will be discussed in more detail in this poster. In addition to the long-term secular increase in the Polaris's pulsation period, an analysis of the O-Cs indicates +/-0.25 day cyclic oscillations in the apparent period with time scale of 11-12 years. The nature of these period oscillations is being investigated and will be discussed. We gratefully acknowledge the support for this research from NSF/RUI Grant AST 00

  18. Spinal Stenosis

    MedlinePlus

    ... center of the column of bones (vertebral or spinal column) through which the spinal cord and nerve roots ... be acquired at birth. Poor alignment of the spinal column when a vertebra slips forward onto the one ...

  19. The glycolytic metabolite methylglyoxal induces changes in vigilance by generating low-amplitude non-REM sleep.

    PubMed

    Jakubcakova, Vladimira; Curzi, M Letizia; Flachskamm, Cornelia; Hambsch, Boris; Landgraf, Rainer; Kimura, Mayumi

    2013-11-01

    Methylglyoxal (MG), an essential by-product of glycolysis, is a highly reactive endogenous α-oxoaldehyde. Although high levels of MG are cytotoxic, physiological doses of MG were shown to reduce anxiety-related behavior through selective activation of γ-aminobutyric acid type A (GABAA) receptors. Because the latter play a major role in sleep induction, this study examined the potential of MG to regulate sleep. Specifically, we assessed how MG influences sleep-wake behavior in CD1 mice that received intracerebroventricular injections of either vehicle or 0.7 µmol MG at onset of darkness. We used electroencephalogram (EEG) and electromyogram (EMG) recordings to monitor changes in vigilance states, sleep architecture and the EEG spectrum, for 24 h after receipt of injections. Administration of MG rapidly induced non-rapid eye movement sleep (NREMS) and, concomitantly, decreased wakefulness and suppressed EEG delta power during NREMS. In addition, MG robustly enhanced the amount and number of episodes of an unclassified state of vigilance in which EMG, as well as EEG delta and theta power, were very low. MG did not affect overall rapid eye movement sleep (REMS) in a given 24-h period, but significantly reduced the power of theta activity during REMS. Our results provide the first evidence that MG can exert sleep-promoting properties by triggering low-amplitude NREMS.

  20. Axial and Torsional Load-Type Sequencing in Cumulative Fatigue: Low Amplitude Followed by High Amplitude Loading

    NASA Technical Reports Server (NTRS)

    Bonacuse, Peter J.; Kalluri, Sreeramesh

    2001-01-01

    The experiments described herein were performed to determine whether damage imposed by axial loading interacts with damage imposed by torsional loading. This paper is a follow on to a study that investigated effects of load-type sequencing on the cumulative fatigue behavior of a cobalt base superalloy, Haynes 188 at 538 C Both the current and the previous study were used to test the applicability of cumulative fatigue damage models to conditions where damage is imposed by different loading modes. In the previous study, axial and torsional two load level cumulative fatigue experiments were conducted, in varied combinations, with the low-cycle fatigue (high amplitude loading) applied first. In present study, the high-cycle fatigue (low amplitude loading) is applied initially. As in the previous study, four sequences (axial/axial, torsion/torsion, axial/torsion, and torsion/axial) of two load level cumulative fatigue experiments were performed. The amount of fatigue damage contributed by each of the imposed loads was estimated by both the Palmgren-Miner linear damage rule (LDR) and the non-linear damage curve approach (DCA). Life predictions for the various cumulative loading combinations are compared with experimental results.

  1. THE TAIWAN-AMERICAN OCCULTATION SURVEY PROJECT STELLAR VARIABILITY. I. DETECTION OF LOW-AMPLITUDE {delta} SCUTI STARS

    SciTech Connect

    Kim, D.-W.; Protopapas, P.; Alcock, C.; Wright, N. J.; Bianco, F. B.; Lehner, M. J.; Byun, Y.-I.; Kyeong, J.; Lee, B.-C.; Axelrod, T.; Chen, W.-P.; Lin, H.-C.; Coehlo, N. K.; Rice, J. A.; Cook, K. H.; Marshall, S. L.; Dave, R.; King, S.-K.; Lee, T.; Porrata, R.

    2010-02-15

    We analyzed data accumulated during 2005 and 2006 by the Taiwan-American Occultation Survey (TAOS) in order to detect short-period variable stars (periods of {approx}<1 hr) such as {delta} Scuti. TAOS is designed for the detection of stellar occultation by small-size Kuiper Belt Objects and is operating four 50 cm telescopes at an effective cadence of 5 Hz. The four telescopes simultaneously monitor the same patch of the sky in order to reduce false positives. To detect short-period variables, we used the fast Fourier transform algorithm (FFT) in as much as the data points in TAOS light curves are evenly spaced. Using FFT, we found 41 short-period variables with amplitudes smaller than a few hundredths of a magnitude and periods of about an hour, which suggest that they are low-amplitude {delta} Scuti stars. The light curves of TAOS {delta} Scuti stars are accessible online at the Time Series Center Web site (http://timemachine.iic.harvard.edu)

  2. Effect of Spinal Manipulation Thrust Magnitude on Trunk Mechanical Thresholds of Lateral Thalamic Neurons

    PubMed Central

    Reed, William R.; Pickar, Joel G.; Sozio, Randall S.; Long, Cynthia R.

    2014-01-01

    Objectives High velocity low amplitude spinal manipulation (HVLA-SM), as performed by manual therapists (eg, doctors of chiropractic and osteopathy) results in mechanical hypoalgesia in clinical settings. This hypoalgesic effect has previously been attributed to alterations in peripheral and/or central pain processing. The objective of this study was to determine whether thrust magnitude of a simulated HVLA-SM alters mechanical trunk response thresholds in wide dynamic range (WDR) and/or nociceptive specific (NS) lateral thalamic neurons. Methods Extracellular recordings were carried out in the thalamus of 15 anesthetized Wistar rats. Lateral thalamic neurons having receptive fields which included the lumbar dorsal-lateral trunk were characterized as either WDR (n=22) or NS (n=25). Response thresholds to electronic von Frey (rigid tip) mechanical trunk stimuli were determined in three directions (dorsal-ventral, 45°caudalward, and 45°cranialward) prior to and immediately following the dorsal-ventral delivery of a 100ms HVLA-SM at three thrust magnitudes (control, 55%, 85% body weight; (BW)). Results There was a significant difference in mechanical threshold between 85% BW manipulation and control thrust magnitudes in the dorsal-ventral direction in NS neurons (p=.01). No changes were found in WDR neurons at either HVLA-SM thrust magnitude. Conclusions This study is the first to investigate the effect of HVLA-SM thrust magnitude on WDR and NS lateral thalamic mechanical response threshold. Our data suggest that at the single lateral thalamic neuron level, there may be a minimal spinal manipulative thrust magnitude required to elicit an increase in trunk mechanical response thresholds. PMID:24928636

  3. The biomechanics of spinal manipulation.

    PubMed

    Herzog, Walter

    2010-07-01

    Biomechanics is the science that deals with the external and internal forces acting on biological systems and the effects produced by these forces. Here, we describe the forces exerted by chiropractors on patients during high-speed, low-amplitude manipulations of the spine and the physiological responses produced by the treatments. The external forces were found to vary greatly among clinicians and locations of treatment on the spine. Spinal manipulative treatments produced reflex responses far from the treatment site, caused movements of vertebral bodies in the "para-physiological" zone, and were associated with cavitation of facet joints. Stresses and strains on the vertebral artery during chiropractic spinal manipulation of the neck were always much smaller than those produced during passive range of motion testing and diagnostic procedures.

  4. High velocity properties of the dynamic frictional force between ductile metals

    SciTech Connect

    Hammerberg, James Edward; Hollan, Brad L; Germann, Timothy C; Ravelo, Ramon J

    2010-01-01

    The high velocity properties of the tangential frictional force between ductile metal interfaces seen in large-scale NonEquilibrium Molecular Dynamics (NEMD) simulations are characterized by interesting scaling behavior. In many cases a power law decrease in the frictional force with increasing velocity is observed at high velocities. We discuss the velocity dependence of the high velocity branch of the tangential force in terms of structural transformation and ultimate transition, at the highest velocities, to confined fluid behavior characterized by a critical strain rate. The particular case of an Al/Al interface is discussed.

  5. Paraspinal muscle spindle response to intervertebral fixation and segmental thrust level during spinal manipulation in an animal model

    PubMed Central

    Reed, William R.; Pickar, Joel G.

    2015-01-01

    Study Design In vivo cat model study. Objective To determine whether intervertebral facet joint fixation and segmental thrust level alter paraspinal muscle spindle activity during simulated spinal manipulation. Summary of Background Data Intervertebral motion is commonly assessed by manual therapy practitioners during clinical evaluation and treatment. Mechanoreceptor activity elicited during spinal manipulation has been theorized as a potential mechanism of its efficacy. The degree to which intervertebral fixation and segmental thrust level alter paraspinal muscle spindle activity during high velocity low amplitude spinal manipulation (HVLA-SM) is unclear. Methods Intervertebral fixation was created by inserting facet screws through the left L5–6, L6–7 and left L4–5, L5–6, L6–7, facet joints of a cat spine. Changes in the mean instantaneous frequency of L6 muscle spindle discharge were determined during five HVLA-SM thrust durations ((0-control, 75, 100, 150, 250ms) delivered at the L4 or L6 spinous process in each of 3 conditions within the same preparation: laminectomy-only (surgical control; n=23), L5–6 and L6–7 fixations (n=20), and L4–5, L5–6, and L6–7 fixations (n=7). Comparisons were made between thrust levels, thrust durations and spinal joint conditions using a linear mixed model. Results Insertion of facet screws compared to laminectomy-only significantly increased (P<.001) lumbar spinal stiffness during L6 HVLA-SM. Compared to laminectomy-only, both the 2 facet screw (100ms; P<.05) and 3 screw conditions [75 and 100ms (P<.001), 150 ms (P<.005), and 250 ms (P<.05)] significantly decreased L6 spindle response during the L6 HVLA-SM. HVLA-SM delivered 2 segments rostral to the level of muscle spindle input significantly decreases spindle response compared to HVLA-SM delivered at-level, however non-target HVLA-SM still elicits 60–80% of at-level muscle spindle response. Conclusions Intervertebral fixation decreases paraspinal muscle

  6. Effects of unilateral facet fixation and facetectomy on muscle spindle responsiveness during simulated spinal manipulation in an animal model

    PubMed Central

    Reed, William R.; Long, Cynthia R.; Pickar, Joel G.

    2013-01-01

    Objectives Manual therapy practitioners commonly assess lumbar intervertebral mobility before deciding treatment regimens. Changes in mechanoreceptor activity during the manipulative thrust are theorized to be an underlying mechanism of spinal manipulation (SM) efficacy. The objective of this study was to determine if facet fixation or facetectomy at a single lumbar level alters muscle spindle activity during 5 SM thrust durations in an animal model. Methods Spinal stiffness was determined using the slope of a force-displacement curve. Changes in the mean instantaneous frequency of spindle discharge were measured during simulated SM of the L6 vertebra in the same 20 afferents for laminectomy-only, 19 laminectomy & facet screw conditions; only 5 also had data for the laminectomy & facetectomy condition. Neural responses were compared across conditions and five thrust durations (≤ 250ms) using linear mixed models. Results Significant decreases in afferent activity between the laminectomy-only and laminectomy & facet screw conditions were seen during 75ms (P<.001), 100ms (P=.04) and 150ms (P=.02) SM thrust durations. Significant increases in spindle activity between the laminectomy-only and laminectomy & facetectomy conditions were seen during the 75ms (P<.001) and 100ms (P<.001) thrust durations. Conclusion Intervertebral mobility at a single segmental level alters paraspinal sensory response during clinically relevant high velocity low amplitude SM thrust durations (≤150ms). The relationship between intervertebral joint mobility and alterations of primary afferent activity during and following various manual therapy interventions may be used to help to identify patient subpopulations who respond to different types of manual therapy and better inform practitioners (eg, chiropractic, osteopathic) delivering the therapeutic intervention. PMID:24161386

  7. An Approach for Measuring and Modeling of Plastic Deformation of Metallic Plates during High Velocity Impacts

    SciTech Connect

    O'Toole, Brendan J.; Trabia, Mohamed B.; Roy, Shawoon K.; Somasundarum, Deepak; Jennings, Richard; Matthes, Melissa; Hixson, Robert S.; Becker, Steven; Daykin, Edward P.; Pena, Michael T.; Machorro, Eric A.

    2014-05-29

    During high velocity impact experiments, projectile impact creates extreme pressure waves that results in a significant localized deformation within a short period of time. Experiments under these conditions require sophisticated data acquisition technique to better understand the materials deformation mechanisms. Since these experiments are expensive, it is also beneficial to develop accurate computational models that can predict this kind of deformation in high velocity impact events.

  8. CELFE/NASTRAN Code for the Analysis of Structures Subjected to High Velocity Impact

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1978-01-01

    CELFE (Coupled Eulerian Lagrangian Finite Element)/NASTRAN Code three-dimensional finite element code has the capability for analyzing of structures subjected to high velocity impact. The local response is predicted by CELFE and, for large problems, the far-field impact response is predicted by NASTRAN. The coupling of the CELFE code with NASTRAN (CELFE/NASTRAN code) and the application of the code to selected three-dimensional high velocity impact problems are described.

  9. Spinal Stenosis

    MedlinePlus

    ... Spinal stenosis is a narrowing of the open spaces within your spine, which can put pressure on ... stenosis, doctors may recommend surgery to create additional space for the spinal cord or nerves. Many people ...

  10. Spinal stenosis

    MedlinePlus

    ... stenosis; Foraminal spinal stenosis; Degenerative spine disease; Back pain - spinal stenosis; Low back pain - stenosis; LBP - stenosis ... involve both legs. Symptoms include: Numbness , cramping, or pain in the back, buttocks, thighs, or calves, or ...

  11. Spinal injury

    MedlinePlus

    ... and drive. Do not dive into pools, lakes, rivers, and other bodies of water, particularly if you cannot determine the depth of the ... Central nervous system Spinal cord injury Spinal anatomy Two person roll - ...

  12. Are High Velocity Peaks in the Milky Way Bulge due to the Bar?

    NASA Astrophysics Data System (ADS)

    Li, Zhao-Yu; Shen, Juntai; Rich, R. Michael; Kunder, Andrea; Mao, Shude

    2014-04-01

    Recently the commissioning APOGEE observations of the Galactic bulge reported that a significant fraction of stars (~10%) are in a cold (σV ≈ 30 km s-1) high velocity peak (Galactocentric radial velocity ≈200 km s-1). These stars are speculated to reflect the stellar orbits in the Galactic bar. In this study, we use two N-body models of a Milky Way-like disk galaxy with different bar strengths to critically examine this possibility. The general trends of the Galactocentric radial velocity distribution in observations and simulations are similar, but neither our models nor the BRAVA data reveal a statistically significant cold high velocity peak. A Monte Carlo test further suggests that it is possible for a spurious high velocity peak to appear if there are only a limited number of stars observed. Thus, the reported cold high velocity peak, even if it is real, is unlikely due to stars on the bar-supporting orbits. Our models do predict an excess of stars with high radial velocity, but not in a distinct peak. In the distance-velocity diagram, the high velocity particles in different fields exist at a similar distance ~8.5 ± 1 kpc away from the Sun. This result may be explained by geometric intersections between the line-of-sight and the particle orbits; high velocity stars naturally exist approximately at the tangent point, without constituting a distinct peak. We further demonstrate that even without the presence of a bar structure, particle motions in an axisymmetric disk can also exhibit an excess of high velocity stars.

  13. ARE HIGH VELOCITY PEAKS IN THE MILKY WAY BULGE DUE TO THE BAR?

    SciTech Connect

    Li, Zhao-Yu; Shen, Juntai; Rich, R. Michael; Kunder, Andrea; Mao, Shude

    2014-04-10

    Recently the commissioning APOGEE observations of the Galactic bulge reported that a significant fraction of stars (∼10%) are in a cold (σ{sub V} ≈ 30 km s{sup –1}) high velocity peak (Galactocentric radial velocity ≈200 km s{sup –1}). These stars are speculated to reflect the stellar orbits in the Galactic bar. In this study, we use two N-body models of a Milky Way-like disk galaxy with different bar strengths to critically examine this possibility. The general trends of the Galactocentric radial velocity distribution in observations and simulations are similar, but neither our models nor the BRAVA data reveal a statistically significant cold high velocity peak. A Monte Carlo test further suggests that it is possible for a spurious high velocity peak to appear if there are only a limited number of stars observed. Thus, the reported cold high velocity peak, even if it is real, is unlikely due to stars on the bar-supporting orbits. Our models do predict an excess of stars with high radial velocity, but not in a distinct peak. In the distance-velocity diagram, the high velocity particles in different fields exist at a similar distance ∼8.5 ± 1 kpc away from the Sun. This result may be explained by geometric intersections between the line-of-sight and the particle orbits; high velocity stars naturally exist approximately at the tangent point, without constituting a distinct peak. We further demonstrate that even without the presence of a bar structure, particle motions in an axisymmetric disk can also exhibit an excess of high velocity stars.

  14. High velocity HI in the inner 5 KPC of M31

    NASA Astrophysics Data System (ADS)

    Brinks, E.

    New radio frequency position-velocity maps of HI whithin 5 kpc of the M31 galactic center are reported. The maps were generated from 21 cm line studies performed with the Westerbork Synthesis Radio Telescope directed at regions +6 arcmin, 0 arcmin, and -6 arcmin distance from the nucleus. High velocity neutral hydrogen displayed the same signature at high velocities previously observed in the visible range (Rubin and Ford, 1970), but no HI was detected within the inner 500 pc. The data indicate that rotation produces the high velocities rather than an infall to or an ejection from the nucleus. The region around the M31 nucleus is suggested to be similar to that of the Galaxy.

  15. High-Velocity Estimates for the Scattering Operator and Aharonov-Bohm Effect in Three Dimensions

    NASA Astrophysics Data System (ADS)

    Ballesteros, Miguel; Weder, Ricardo

    2009-01-01

    We obtain high-velocity estimates with error bounds for the scattering operator of the Schrödinger equation in three dimensions with electromagnetic potentials in the exterior of bounded obstacles that are handlebodies. A particular case is a finite number of tori. We prove our results with time-dependent methods. We consider high-velocity estimates where the direction of the velocity of the incoming electrons is kept fixed as its absolute value goes to infinity. In the case of one torus our results give a rigorous proof that quantum mechanics predicts the interference patterns observed in the fundamental experiments of Tonomura et al. that gave conclusive evidence of the existence of the Aharonov-Bohm effect using a toroidal magnet. We give a method for the reconstruction of the flux of the magnetic field over a cross-section of the torus modulo 2π. Equivalently, we determine modulo 2π the difference in phase for two electrons that travel to infinity, when one goes inside the hole and the other outside it. For this purpose we only need the high-velocity limit of the scattering operator for one direction of the velocity of the incoming electrons. When there are several tori-or more generally handlebodies-the information that we obtain in the fluxes, and on the difference of phases, depends on the relative position of the tori and on the direction of the velocities when we take the high-velocity limit of the incoming electrons. For some locations of the tori we can determine all the fluxes modulo 2π by taking the high-velocity limit in only one direction. We also give a method for the unique reconstruction of the electric potential and the magnetic field outside the handlebodies from the high-velocity limit of the scattering operator.

  16. Search for auroral belt E-parallel fields with high-velocity barium ion injections

    NASA Technical Reports Server (NTRS)

    Heppner, J. P.; Ledley, B. G.; Miller, M. L.; Marionni, P. A.; Pongratz, M. B.

    1989-01-01

    In April 1984, four high-velocity shaped-charge Ba(+) injections were conducted from two sounding rockets at 770-975 km over northern Alaska under conditions of active auroral and magnetic disturbance. Spatial ionization (brightness) profiles of high-velocity Ba(+) clouds from photometric scans following each release were found to be consistent with the 28-sec theoretical time constant for Ba photoionization determined by Carlsten (1975). These observations therefore revealed no evidence of anomalous fast ionization predicted by the Alfven critical velocity hypothesis.

  17. Spinal infections.

    PubMed

    Tay, Bobby K-B; Deckey, Jeffrey; Hu, Serena S

    2002-01-01

    Spinal infections can occur in a variety of clinical situations. Their presentation ranges from the infant with diskitis who is unwilling to crawl or walk to the adult who develops an infection after a spinal procedure. The most common types of spinal infections are hematogenous bacterial or fungal infections, pediatric diskitis, epidural abscess, and postoperative infections. Prompt and accurate diagnosis of spinal infections, the cornerstone of treatment, requires a high index of suspicion in at-risk patients and the appropriate evaluation to identify the organism and determine the extent of infection. Neurologic function and spinal stability also should be carefully evaluated. The goals of therapy should include eradicating the infection, relieving pain, preserving or restoring neurologic function, improving nutrition, and maintaining spinal stability.

  18. Spinal brucellosis.

    PubMed

    Tali, E Turgut; Koc, A Murat; Oner, A Yusuf

    2015-05-01

    Spinal involvement in human brucellosis is a common condition and a significant cause of morbidity and mortality, particularly in endemic areas, because it is often associated with therapeutic failure. Most chronic brucellosis cases are the result of inadequate treatment of the initial episode. Recognition of spinal brucellosis is challenging. Early diagnosis is important to ensure proper treatment and decrease morbidity and mortality. Radiologic evaluation has gained importance in diagnosis and treatment planning, including interventional procedures and monitoring of all spinal infections.

  19. Experimental verification of vapor deposition rate theory in high velocity burner rigs

    NASA Technical Reports Server (NTRS)

    Gokoglu, Suleyman A.; Santoro, Gilbert J.

    1985-01-01

    The main objective has been the experimental verification of the corrosive vapor deposition theory in high-temperature, high-velocity environments. Towards this end a Mach 0.3 burner-rig appartus was built to measure deposition rates from salt-seeded (mostly Na salts) combustion gases on the internally cooled cylindrical collector. Deposition experiments are underway.

  20. Warm spraying—a novel coating process based on high-velocity impact of solid particles

    PubMed Central

    Kuroda, Seiji; Kawakita, Jin; Watanabe, Makoto; Katanoda, Hiroshi

    2008-01-01

    In recent years, coating processes based on the impact of high-velocity solid particles such as cold spraying and aerosol deposition have been developed and attracting much industrial attention. A novel coating process called ‘warm spraying’ has been developed, in which coatings are formed by the high-velocity impact of solid powder particles heated to appropriate temperatures below the melting point of the powder material. The advantages of such process are as follows: (1) the critical velocity needed to form a coating can be significantly lowered by heating, (2) the degradation of feedstock powder such as oxidation can be significantly controlled compared with conventional thermal spraying where powder is molten, and (3) various coating structures can be realized from porous to dense ones by controlling the temperature and velocity of the particles. The principles and characteristics of this new process are discussed in light of other existing spray processes such as high-velocity oxy-fuel spraying and cold spraying. The gas dynamics of particle heating and acceleration by the spraying apparatus as well as the high-velocity impact phenomena of powder particles are discussed in detail. Several examples of depositing heat sensitive materials such as titanium, metallic glass, WC–Co cermet and polymers are described with potential industrial applications. PMID:27877996

  1. Characterization and evaluation of silicon carbide for high-velocity impact

    NASA Astrophysics Data System (ADS)

    Holmquist, Timothy J.; Johnson, Gordon R.

    2005-05-01

    This article presents a characterization and evaluation of silicon carbide for high-velocity impact. This includes a wide range of loading conditions that produce large strains, high strain rates, and high pressures. Experimental data from the literature are used to determine constants for the Johnson-Holmquist-Beissel (JHB) constitutive model for brittle materials. A previous article by the authors presented a characterization of silicon carbide for high-velocity impact using an earlier version of the model (JH-1). The previous work provided good agreement with a broad range of experimental data with the exception of high-velocity penetration data. The current work uses the more recently developed JHB constitutive model, a target geometry that more closely matches the experimental design, and a computational technique that allows for target prestress. These recent developments (primarily the prestress) produce computed results that agree with all the experimental data, including the high-velocity penetration data. The computed results also provide a detailed analysis of the penetration process into a prestressed target and show why it is necessary to include the target prestress. A specific result is the ability to reproduce the nonsteady penetration rate that occurs in the prestressed target.

  2. Temporary Network Development Capability in High Velocity Environments: A Dynamic Capability Study of Disaster Relief Organizations

    ERIC Educational Resources Information Center

    O'Brien, William Ross

    2010-01-01

    Organizations involved in crisis relief after a natural disaster face the multifaceted challenge of significantly changing needs of their various stakeholders, limited, ambiguous and even incorrect information, and highly compressed time limitations. Yet the performance of these organization in these high velocity environments is critical for the…

  3. Relationship between Biomechanical Characteristics of Spinal Manipulation and Neural Responses in an Animal Model: Effect of Linear Control of Thrust Displacement versus Force, Thrust Amplitude, Thrust Duration, and Thrust Rate.

    PubMed

    Reed, William R; Cao, Dong-Yuan; Long, Cynthia R; Kawchuk, Gregory N; Pickar, Joel G

    2013-01-01

    High velocity low amplitude spinal manipulation (HVLA-SM) is used frequently to treat musculoskeletal complaints. Little is known about the intervention's biomechanical characteristics that determine its clinical benefit. Using an animal preparation, we determined how neural activity from lumbar muscle spindles during a lumbar HVLA-SM is affected by the type of thrust control and by the thrust's amplitude, duration, and rate. A mechanical device was used to apply a linear increase in thrust displacement or force and to control thrust duration. Under displacement control, neural responses during the HVLA-SM increased in a fashion graded with thrust amplitude. Under force control neural responses were similar regardless of the thrust amplitude. Decreasing thrust durations at all thrust amplitudes except the smallest thrust displacement had an overall significant effect on increasing muscle spindle activity during the HVLA-SMs. Under force control, spindle responses specifically and significantly increased between thrust durations of 75 and 150 ms suggesting the presence of a threshold value. Thrust velocities greater than 20-30 mm/s and thrust rates greater than 300 N/s tended to maximize the spindle responses. This study provides a basis for considering biomechanical characteristics of an HVLA-SM that should be measured and reported in clinical efficacy studies to help define effective clinical dosages.

  4. The frequency and distribution of high-velocity gas in the Galaxy

    NASA Technical Reports Server (NTRS)

    Nichols, Joy S.

    1995-01-01

    The purpose of this study was to estimate the frequency and distribution of high-velocity gas in the Galaxy using UV absorption line measurements from archival high-dispersion IUE spectra and to identify particularly interesting regions for future study. Approximately 500 spectra have been examined. The study began with the creation of a database of all 0 and B stars with b less than or = to 30 deg observed with IUE at high dispersion over its 18-year lifetime. The original database of 2500 unique objects was reduced to 1200 objects which had optimal exposures available. The next task was to determine the distances of these stars so the high-velocity structures could be mapped in the Galaxy. Spectroscopic distances were calculated for each star for which photometry was available. The photometry was acquired for each star using the SIMBAD database. Preference was given to the ubvy system where available; otherwise the UBV system was used.

  5. High Velocity Impact Interaction of Metal Particles with Porous Heterogeneous Materials with an Inorganic Matrix

    NASA Astrophysics Data System (ADS)

    Glazunov, A. A.; Ishchenko, A. N.; Afanasyeva, S. A.; Belov, N. N.; Burkin, V. V.; Rogaev, K. S.; Tabachenko, A. N.; Khabibulin, M. V.; Yugov, N. T.

    2016-03-01

    A computational-experimental investigation of stress-strain state and fracture of a porous heterogeneous material with an inorganic matrix, used as a thermal barrier coating of flying vehicles, under conditions of a high-velocity impact by a spherical steel projectile imitating a meteorite particle is discussed. Ballistic tests are performed at the velocities about 2.5 km/s. Numerical modeling of the high-velocity impact is described within the framework of a porous elastoplastic model including fracture and different phase states of the materials. The calculations are performed using the Euler and Lagrange numerical techniques for the velocities up to 10 km/s in a complete-space problem statement.

  6. High Velocity Tensile Test for Thin Plate Specimen with One Bar Method

    NASA Astrophysics Data System (ADS)

    Itabashi, Masaaki

    In order to design thin-walled impact-resistant structure, for example, an automotive body, dynamic behavior of thin plate is essential. So far, except for laminated composite materials, high velocity tensile test of thin plate specimen did not attract impact researchers' and engineers' attention very much. In this paper, the previous thin plate specimen assembly for the one bar method was improved. The one bar method has been utilized for cylindrical specimens of various solid materials and is known as an effective high velocity tensile testing technique. Unfortunately, the previous assembly introduced a tremendous initial peak on stress-strain curves, even for aluminum alloys. With a new specimen assembly, stress-strain curves for IF (Interstitial-atom Free) steel and 7075-T6 aluminum alloy obtained by the one bar method were almost equivalent to those obtained by the tensile version of the split Hopkinson pressure bar method.

  7. Electrical method and apparatus for impelling the extruded ejection of high-velocity material jets

    DOEpatents

    Weingart, Richard C.

    1989-01-01

    A method and apparatus (10, 40) for producing high-velocity material jets provided. An electric current pulse generator (14, 42) is attached to an end of a coaxial two-conductor transmission line (16, 44) having an outer cylindrical conductor (18), an inner cylindrical conductor (20), and a solid plastic or ceramic insulator (21) therebetween. A coxial, thin-walled metal structure (22, 30) is conductively joined to the two conductors (18, 20) of the transmission line (16, 44). An electrical current pulse applies magnetic pressure to and possibly explosively vaporizes metal structure (22), thereby collapsing it and impelling the extruded ejection of a high-velocity material jet therefrom. The jet is comprised of the metal of the structure (22), together with the material that comprises any covering layers (32, 34) disposed on the structure. An electric current pulse generator of the explosively driven magnetic flux compression type or variety (42) may be advantageously used in the practice of this invention.

  8. Measuring densities of high-velocity metallic sprays using piezoelectric sensors

    SciTech Connect

    Lloyd, C. E.; Proud, W. G.

    2007-12-12

    Recent research efforts in large-scale hydrodynamic experiments have concentrated on the possibility of using piezoelectric sensors to study the evolution of ejecta. Ejecta are small (<100 m diameter) particulates that are ejected at high velocity (>1 km s{sup -1}) from a shocked surface. This paper investigates whether Dynasen PZT piezoelectric sensors are reliable and robust enough to measure accurate time-resolved stresses and densities in high-velocity metallic sprays. The sprays are assumed to have similar characteristics to ejecta sprays, and are generated by a gas gun and in a safe and reproducible manner. A complimentary diagnostic technique, utilising high-speed photography and fast x-radiography, measures the densities of the sprays independently, allowing the accuracy of the sensors to be assessed. The Dynasen sensors have been shown to perform relatively well in spray environments. Their accuracy can be improved by taking their mechanical impedance characteristics into account.

  9. The Guitar nebula - A bow shock from a slow-spin, high-velocity neutron star

    NASA Technical Reports Server (NTRS)

    Cordes, James M.; Romani, Roger W.; Lundgren, Scott C.

    1993-01-01

    The discovery is reported of a prominent nebula produced by the motion of a high-velocity pulsar, PSR 2224 + 65, through partially neutral gas. The pulsar's transverse speed of over about 800 km/s makes it arguably the fastest known star in the Galaxy and guarantees that it will ultimately escape the Galactic potential well. A deep H-alpha image reveals a bright head and a giant limb-brightened 'body' whose variable width suggests that the ambient interstellar gas has density variations on length scales less than 0.1 pc. Thermalization of shock energy occurs at a rate of about 0.01 times the pulsar's spindown loss rate. These observations provide some insights into the likelihood of finding shocks around other pulsars and the use of nebulae to find high-velocity neutron stars either not acting as pulsars or with their radiation beamed away from the earth.

  10. The Guitar nebula - A bow shock from a slow-spin, high-velocity neutron star

    NASA Astrophysics Data System (ADS)

    Cordes, James M.; Romani, Roger W.; Lundgren, Scott C.

    1993-03-01

    The discovery is reported of a prominent nebula produced by the motion of a high-velocity pulsar, PSR 2224 + 65, through partially neutral gas. The pulsar's transverse speed of over about 800 km/s makes it arguably the fastest known star in the Galaxy and guarantees that it will ultimately escape the Galactic potential well. A deep H-alpha image reveals a bright head and a giant limb-brightened 'body' whose variable width suggests that the ambient interstellar gas has density variations on length scales less than 0.1 pc. Thermalization of shock energy occurs at a rate of about 0.01 times the pulsar's spindown loss rate. These observations provide some insights into the likelihood of finding shocks around other pulsars and the use of nebulae to find high-velocity neutron stars either not acting as pulsars or with their radiation beamed away from the earth.

  11. Intermediate-metallicity, high-velocity stars and Galactic chemical evolution

    NASA Astrophysics Data System (ADS)

    Ryan, S. G.; Smith, I. M.

    2003-05-01

    High signal-to-noise ratio spectra were obtained of 10 high-proper-motion stars having -1 <~[Fe/H] < 0, and a comparable number of disc stars. All but two of the high-proper-motion stars were confirmed to have [Fe/H] > -1.0, some approaching solar metallicity, but, even so, earlier measurements overestimated the metallicities and velocities of some of these stars. Models of stellar populations were used to assign membership probabilities to the Galactic components to which the high-velocity stars might belong. Many were found to be more probably thick-disc than halo objects, despite their large space motions, and two might be associated with the inner Galaxy. It may be necessary to reassess contamination of previous halo samples, such as those used to define the metallicity distribution, to account for contamination by high-velocity thick-disc stars, and to consider possible subcomponents of the halo. The change in [α/Fe] ratios at [Fe/H]~=-1.0 is often used to constrain the degree and timing of Type Ia supernova nucleosynthesis in Galactic chemical-evolution models. [Ti/Fe] values were measured for eight of the high-velocity stars. Both high- and low-[Ti/Fe] halo stars exist; likewise high- and low-[Ti/Fe] thick-disc stars exist. We conclude that the [Ti/Fe]`break' is not well defined for a given population; nor is there a simple, continuous evolutionary sequence through the break. Implications for the interpretation of the [α/Fe] break in terms of SN Ia time-scales and progenitors are discussed. The range of [Ti/Fe] found for high-velocity (low rotation) thick-disc stars contrasts with that for the low-velocity (high rotation) thick-disc sample studied by Prochaska et al.

  12. Chronic symptoms after vestibular neuritis and the high velocity vestibulo-ocular reflex

    PubMed Central

    Patel, Mitesh; Arshad, Qadeer; Roberts, R Edward; Ahmad, Hena; Bronstein, Adolfo M.

    2015-01-01

    Hypothesis As the anterior and posterior semicircular canals are vital to the regulation of gaze stability, particularly during locomotion or vehicular travel, we tested whether the high velocity vestibulo-ocular reflex (VOR) of the three ipsilesional semicircular canals elicited by the modified Head Impulse Test would correlate with subjective dizziness or vertigo scores after vestibular neuritis (VN). Background Recovery following acute VN varies with around half reporting persistent symptoms long after the acute episode. However, an unanswered question is whether chronic symptoms are associated with impairment of the high velocity VOR of the anterior or posterior canals. Methods Twenty patients who had experienced an acute episode of VN at least three months earlier were included in this study. Participants were assessed with the video head impulse test (vHIT) of all six canals, bithermal caloric irrigation, the Dizziness Handicap Inventory (DHI) and the Vertigo Symptoms Scale short-form (VSS). Results Of these 20 patients, 12 felt that they had recovered from the initial episode whereas 8 did not and reported elevated DHI and VSS scores. However, we found no correlation between DHI or VSS scores and the ipsilesional single or combined vHIT gain, vHIT gain asymmetry or caloric paresis. The high velocity VOR was not different between patients who felt they had recovered and patients who felt they had not. Conclusions Our findings suggest that chronic symptoms of dizziness following VN are not associated with the high velocity VOR of the single or combined ipsilesional horizontal, anterior or posterior semicircular canals. PMID:26719963

  13. Treatment Protocol for High Velocity/High Energy Gunshot Injuries to the Face

    PubMed Central

    Peled, Micha; Leiser, Yoav; Emodi, Omri; Krausz, Amir

    2011-01-01

    Major causes of facial combat injuries include blasts, high-velocity/high-energy missiles, and low-velocity missiles. High-velocity bullets fired from assault rifles encompass special ballistic properties, creating a transient cavitation space with a small entrance wound and a much larger exit wound. There is no dispute regarding the fact that primary emergency treatment of ballistic injuries to the face commences in accordance with the current advanced trauma life support (ATLS) recommendations; the main areas in which disputes do exist concern the question of the timing, sequence, and modes of surgical treatment. The aim of the present study is to present the treatment outcome of high-velocity/high-energy gunshot injuries to the face, using a protocol based on the experience of a single level I trauma center. A group of 23 injured combat soldiers who sustained bullet and shrapnel injuries to the maxillofacial region during a 3-week regional military conflict were evaluated in this study. Nine patients met the inclusion criteria (high-velocity/high-energy injuries) and were included in the study. According to our protocol, upon arrival patients underwent endotracheal intubation and were hemodynamically stabilized in the shock-trauma unit and underwent total-body computed tomography with 3-D reconstruction of the head and neck and computed tomography angiography. All patients underwent maxillofacial surgery upon the day of arrival according to the protocol we present. In view of our treatment outcomes, results, and low complication rates, we conclude that strict adherence to a well-founded and structured treatment protocol based on clinical experience is mandatory in providing efficient, appropriate, and successful treatment to a relatively large group of patients who sustain various degrees of maxillofacial injuries during a short period of time. PMID:23449809

  14. Heat Transfer and Hydraulic Flow Resistance for Streams of High Velocity

    NASA Technical Reports Server (NTRS)

    Lelchuk, V. L.

    1943-01-01

    Problems of hydraulic flow resistance and heat transfer for streams with velocities comparable with acoustic have present great importance for various fields of technical science. Especially, they have great importance for the field of heat transfer in designing and constructing boilers.of the "Velox" type. In this article a description of experiments and their results as regards definition of the laws of heat transfer in differential form for high velocity air streams inside smooth tubes are given.

  15. High-velocity frictional strength across the Tohoku-Oki megathrust determined from surface drilling torque

    NASA Astrophysics Data System (ADS)

    Ujiie, Kohtaro; Inoue, Tomoya; Ishiwata, Junya

    2016-03-01

    High-velocity frictional strength is one of the primary factors controlling earthquake faulting. The Japan Trench Fast Drilling Project drilled through the shallow plate boundary fault, where displacement was ~50 m during the 2011 Tohoku-Oki earthquake. To determine downhole frictional strength, we analyzed the surface drilling torque data acquired at rotation rates equivalent to seismic slip rates (0.8-1.3 m/s). The results show a clear contrast in high-velocity frictional strength across the plate boundary fault: the apparent friction coefficient of frontal prism sediments (hemipelagic mudstones) in the hanging wall is 0.1-0.3, while that of the underthrust sediments (mudstone, laminar pelagic claystone, and chert) in the footwall increases to 0.2-0.4. The apparent friction coefficient of the smectite-rich pelagic clay in the plate boundary fault is 0.08-0.19, which is consistent with that determined from high-velocity (1.1-1.3 m/s) friction experiments. This suggests that surface drilling torque is useful in obtaining downhole frictional strength.

  16. Real-time dynamics of high-velocity micro-particle impact

    NASA Astrophysics Data System (ADS)

    Veysset, David; Hsieh, Alex; Kooi, Steve; Maznev, Alex A.; Tang, Shengchang; Olsen, Bradley D.; Nelson, Keith A.

    High-velocity micro-particle impact is important for many areas of science and technology, from space exploration to the development of novel drug delivery platforms. We present real-time observations of supersonic micro-particle impacts using multi-frame imaging. In an all optical laser-induced projectile impact test, a monolayer of micro-particles is placed on a transparent substrate coated with a laser absorbing polymer layer. Ablation of a laser-irradiated polymer region accelerates the micro-particles into free space with speeds up to 1.0 km/s. The particles are monitored during the impact on the target with an ultrahigh-speed multi-frame camera that can record up to 16 images with time resolution as short as 3 ns. In particular, we investigated the high-velocity impact deformation response of poly(urethane urea) (PUU) elastomers to further the fundamental understanding of the molecular influence on dynamical behaviors of PUUs. We show the dynamic-stiffening response of the PUUs and demonstrate the significance of segmental dynamics in the response. We also present movies capturing individual particle impact and penetration in gels, and discuss the observed dynamics. The results will provide an impetus for modeling high-velocity microscale impact responses and high strain rate deformation in polymers, gels, and other materials.

  17. Auditory velocity discrimination in the horizontal plane at very high velocities.

    PubMed

    Frissen, Ilja; Féron, François-Xavier; Guastavino, Catherine

    2014-10-01

    We determined velocity discrimination thresholds and Weber fractions for sounds revolving around the listener at very high velocities. Sounds used were a broadband white noise and two harmonic sounds with fundamental frequencies of 330 Hz and 1760 Hz. Experiment 1 used velocities ranging between 288°/s and 720°/s in an acoustically treated room and Experiment 2 used velocities between 288°/s and 576°/s in a highly reverberant hall. A third experiment addressed potential confounds in the first two experiments. The results show that people can reliably discriminate velocity at very high velocities and that both thresholds and Weber fractions decrease as velocity increases. These results violate Weber's law but are consistent with the empirical trend observed in the literature. While thresholds for the noise and 330 Hz harmonic stimulus were similar, those for the 1760 Hz harmonic stimulus were substantially higher. There were no reliable differences in velocity discrimination between the two acoustical environments, suggesting that auditory motion perception at high velocities is robust against the effects of reverberation.

  18. A Investigation of Gouge Initiation in High-Velocity Sliding Contact

    NASA Astrophysics Data System (ADS)

    Tachau, Robert David Mazur

    1991-02-01

    Surface damage has been observed on the rails of rocket sled tracks and on the barrels of high-velocity guns. The phenomenon is generally referred to as "gouging". Damage to a stationary surface (guider) is created from the oblique impact of a high-velocity object (slider) moving over its surface. The surface damage (gouge) is typically a shallow crater in the shape of a teardrop with the leading edge characterized by the wider end and a slightly raised lip. For rocket sleds, rail gouging occurs when the sled velocity is greater than 1.5 km/sec; while in guns, barrel gouging occurs when the velocity exceeds 4 km/sec. A model is developed to describe the phenomenon of gouging. An unbalanced slider randomly causes a shallow -angle, oblique impact between the slider and the guider. At sufficiently high velocity, the impact produces a thin, but very hot, layer of soft material at the contact surface. Under the action of a moving load, the soft layer lends itself to an antisymmetric deformation and a gouge is formed when this soft material is over-run by the slider. The model is simulated numerically with a hydrodynamic (CTH) code. The results of the simulations are in good agreement with the observed phenomena. Based on the simulated temperature and pressure profiles at the contact surface, design criteria for gouge mitigation are developed in this study.

  19. Effects of spinal manipulation on sensorimotor function in low back pain patients – a randomized controlled trial

    PubMed Central

    Goertz, Christine M.; Xia, Ting; Long, Cynthia R.; Vining, Robert D.; Pohlman, Katherine A.; DeVocht, James W.; Gudavalli, M. Ram; Owens, Edward F.; Meeker, William C.; Wilder, David G.

    2015-01-01

    Background Low back pain (LBP) is a major health problem in industrialized societies. Spinal manipulation (SM) is often used for treating LBP, though the therapeutic mechanisms remain elusive. Research suggests that sensorimotor changes may be involved in LBP. It is hypothesized that SM may generate its beneficial effects by affecting sensorimotor functions. Objectives To compare changes in sensorimotor function, as measured by postural sway and response to sudden load, in LBP patients following the delivery of high-velocity low amplitude (HVLA)-SM or low-velocity variable amplitude (LVVA)-SM versus a sham control intervention. Design A three-arm (1:1:1 ratio) randomized controlled trial. Methods A total of 221 participants who were between 21-65 years, having LBP intensity (numerical rating scale) ≥4 at either phone screen or the first baseline visit and ≥2 at phone screen and both baseline visits, and Quebec Task Force diagnostic classifications of 1, 2, 3 or 7 were enrolled to receive four SM treatments over two weeks. Study outcomes were measured at the first and fifth visits with the examiners blinded from participant group assignment. Results The LVVA-SM group demonstrated a significant increase in medial-to-lateral postural excursion on the soft surface at the first visit when compared to the control group. No other significant between-group differences were found for the two sensorimotor tests, whether during the first visit or over two weeks. Conclusions It appears that short-term SM does not affect the sensorimotor functions as measured by postural sway and response to sudden load in this study. PMID:26319101

  20. Understanding inhibitory mechanisms of lumbar spinal manipulation using H-reflex and F-wave responses: a methodological approach.

    PubMed

    Dishman, J Donald; Weber, Kenneth A; Corbin, Roger L; Burke, Jeanmarie R

    2012-09-30

    The purpose of this research was to characterize unique neurophysiologic events following a high velocity, low amplitude (HVLA) spinal manipulation (SM) procedure. Descriptive time series analysis techniques of time plots, outlier detection and autocorrelation functions were applied to time series of tibial nerve H-reflexes that were evoked at 10-s intervals from 100 s before the event until 100 s after three distinct events L5-S1 HVLA SM, or a L5-S1 joint pre-loading procedure, or the control condition. Sixty-six subjects were randomly assigned to three procedures, i.e., 22 time series per group. If the detection of outliers and correlograms revealed a pattern of non-randomness that was only time-locked to a single, specific event in the normalized time series, then an experimental effect would be inferred beyond the inherent variability of H-reflex responses. Tibial nerve F-wave responses were included to determine if any new information about central nervous function following a HVLA SM procedure could be ascertained. Time series analyses of H(max)/M(max) ratios, pre-post L5-S1 HVLA SM, substantiated the hypothesis that the specific aspects of the manipulative thrust lead to a greater attenuation of the H(max)/M(max) ratio as compared to the non-specific aspects related to the postural perturbation and joint pre-loading. The attenuation of the H(max)/M(max) ratio following the HVLA SM procedure was reliable and may hold promise as a translational tool to measure the consistency and accuracy of protocol implementation involving SM in clinical trials research. F-wave responses were not sensitive to mechanical perturbations of the lumbar spine.

  1. Quasi-static and multi-site high velocity impact response of composite structures

    NASA Astrophysics Data System (ADS)

    Deka, Lakshya

    Understanding of low and high velocity transverse impact of laminated fiber reinforced composites is of interest in military, aerospace, marine and civilian structures. Recent advances in the field of numerical simulation provide a means of predicting the performance characteristics of layered materials for impact protection. The overall objective of this work is to investigate the behavior of laminated composites which include both thermoplastic and thermoset systems subjected to quasi-static, low and high velocity impact; both from an experimental and numerical modeling view point. To analyze this problem, a series of quasi-static, low and high velocity impact tests have been performed on laminated composite plates namely E-glass/polypropylene, S2-glass/epoxy and carbon/polyphenylene sulphide. To analyze the perforation mechanism, ballistic limit and damage evolution, an explicit three-dimensional finite element code LS-DYNA is used. Selecting proper material models and contact definition is one of the major criteria for obtaining accurate numerical simulation. Material model 162 (MAT 162), a progressive failure model based on modified Hashin's criteria and continuum damage mechanics (CDM) has been assigned to predict failure of the laminate. This approach is used because during transverse impact, a composite laminate undergoes progressive damage. The laminate and the projectile are meshed using brick elements with single integration points. The impact velocity ranges from 180 to 400 m s -1. This work focuses on three main aspects; (i) To obtain static and dynamic material properties to incorporate into the finite element model and predict the ballistic limit of a composite laminate based on the information from quasi-static punch shear test; (ii) To understand penetration, material erosion, ballistic limit and delamination mechanisms for single and multi-site high velocity (or ballistic) impact of composite laminates; (iii) To investigate the different failure

  2. Spinal Fusion

    MedlinePlus

    ... concept of fusion is similar to that of welding in industry. Spinal fusion surgery, however, does not ... bone taken from the patient has a long history of use and results in predictable healing. Autograft ...

  3. Spinal tumor

    MedlinePlus

    ... Livingstone; 2014:chap 49. Read More Brain tumor - children Hodgkin lymphoma Metastasis Spinal cord trauma Review Date 8/15/2016 Updated by: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review ...

  4. Spinal Infections

    MedlinePlus

    ... spinal infection include fever, chills, headache, neck stiffness, pain, wound redness and tenderness, and wound drainage. In some cases, patients may notice new weakness, numbness or tingling sensations in the arms and/or legs. The symptoms ...

  5. Spinal deformity.

    PubMed

    Bunnell, W P

    1986-12-01

    Spinal deformity is a relatively common disorder, particularly in teenage girls. Early detection is possible by a simple, quick visual inspection that should be a standard part of the routine examination of all preteen and teenage patients. Follow-up observation will reveal those curvatures that are progressive and permit orthotic treatment to prevent further increase in the deformity. Spinal fusion offers correction and stabilization of more severe degrees of scoliosis.

  6. Spinal fusion - series (image)

    MedlinePlus

    ... vertebrae are the bones that make up the spinal column, which surrounds and protects the spinal cord. The ... cushions between vertebrae, and absorb energy while the spinal column flexes, extends, and twists. Nerves from the spinal ...

  7. Spinal Cord Tumor

    MedlinePlus

    Spinal cord tumor Overview By Mayo Clinic Staff A spinal tumor is a growth that develops within your ... as vertebral tumors. Tumors that begin within the spinal cord itself are called spinal cord tumors. There are ...

  8. A Gravitational Double-scattering Mechanism for Generating High-velocity Objects during Halo Mergers

    NASA Astrophysics Data System (ADS)

    Samsing, Johan

    2015-02-01

    We present a dynamical model that describes how halo particles can receive a significant energy kick from the merger between their own host halo and a target halo. This could provide a possible explanation for some high-velocity objects, including extended systems like globular clusters (GCs). In the model we especially introduce a double-scattering mechanism, where a halo particle receives a significant part of its total energy kick by first undergoing a gravitational deflection by the target halo and subsequently by its original host halo. This generates an energy kick that is due to the relative velocity between the halos during the deflections. We derive analytically the total kick energy of the particle, which is composed of energy from the double-scattering mechanism and tidal fields, as a function of its position in its original host halo just before merger. In the case of a 1:10 merger, we find that the presented mechanisms can easily generate particles with a velocity approximately two times the virial velocity of the target halo. This motivates us to suggest that the high velocity of the recently discovered GC HVGC-1 can be explained by a head-on halo merger. Finally, we illustrate the orbital evolution of high-velocity particles outside the virial sphere of the target halo by solving the equation of motion in an expanding universe. We find a sweet spot around a scale factor of 0.3-0.5 for ejecting particles into large orbits, which can easily reach beyond approximately five virial radii.

  9. A GRAVITATIONAL DOUBLE-SCATTERING MECHANISM FOR GENERATING HIGH-VELOCITY OBJECTS DURING HALO MERGERS

    SciTech Connect

    Samsing, Johan

    2015-02-01

    We present a dynamical model that describes how halo particles can receive a significant energy kick from the merger between their own host halo and a target halo. This could provide a possible explanation for some high-velocity objects, including extended systems like globular clusters (GCs). In the model we especially introduce a double-scattering mechanism, where a halo particle receives a significant part of its total energy kick by first undergoing a gravitational deflection by the target halo and subsequently by its original host halo. This generates an energy kick that is due to the relative velocity between the halos during the deflections. We derive analytically the total kick energy of the particle, which is composed of energy from the double-scattering mechanism and tidal fields, as a function of its position in its original host halo just before merger. In the case of a 1:10 merger, we find that the presented mechanisms can easily generate particles with a velocity approximately two times the virial velocity of the target halo. This motivates us to suggest that the high velocity of the recently discovered GC HVGC-1 can be explained by a head-on halo merger. Finally, we illustrate the orbital evolution of high-velocity particles outside the virial sphere of the target halo by solving the equation of motion in an expanding universe. We find a sweet spot around a scale factor of 0.3-0.5 for ejecting particles into large orbits, which can easily reach beyond approximately five virial radii.

  10. Experimental verification of corrosive vapor deposition rate theory in high velocity burner rigs

    NASA Technical Reports Server (NTRS)

    Gokoglu, S. A.; Santoro, G. J.

    1986-01-01

    The ability to predict deposition rates is required to facilitate modelling of high temperature corrosion by fused salt condensates in turbine engines. A corrosive salt vapor deposition theory based on multicomponent chemically frozen boundary layers (CFBL) has been successfully verified by high velocity burner rig experiments. The experiments involved internally air-impingement cooled, both rotating full and stationary segmented cylindrical collectors located in the crossflow of sodium-seeded combustion gases. Excellent agreement is found between the CFBL theory an the experimental measurements for both the absolute amounts of Na2SO4 deposition rates and the behavior of deposition rate with respect to collector temperature, mass flowrate (velocity) and Na concentration.

  11. Variables Affecting Smooth Particle Hydrodynamics Simulation of High-Velocity Flyer Plate Impact Experiments

    SciTech Connect

    Somasundaram, Deepak S; Trabia, Mohamed; O'Toole, Brendan; Hixson, Robert S

    2014-01-23

    This paper describes our work to characterize the variables affecting the smoothed particle hydrodynamics (SPH) method in the LS-DYNA package for simulating high-velocity flyer plate impact experiments. LS-DYNA simulations are compared with one-dimensional experimental data of an oxygen-free high-conductivity (OFHC) copper flyer plate impacting another plate of the same material. The comparison is made by measuring the velocity of a point on the back surface of the impact plate using the velocity interferometer system for any reflector (VISAR) technique.

  12. High-Velocity Absorption Features in FUSE Spectra of Eta Carinae

    NASA Technical Reports Server (NTRS)

    Sonneborn, G.; Iping, R. C.; Gull, T. R.; Vieira, G.

    2003-01-01

    Numerous broad (200 to 1000 km/sec) features in the FUSE spectrum (905-1187 A) of eta Carinae are identified as absorption by a forest of high-velocity narrow lines formed in the expanding circumstellar envelope. These features were previously thought to be P-Cygni lines arising in the wind of the central star. The features span a heliocentric velocity range of -140 to -580 km/sec and are seen prominently in low-ionization ground-state transitions (e.g. N I 1134-35, Fe II 1145-42, 1133, 1127- 22, P II 1153, C I 1158) in addition to C III] 1176 A. The high-velocity components of the FUSE transitions have depths about 50% below the continuum. The identifications are consistent with the complex velocity structures seen in ground- and excited-state transitions of Mg I, Mg 11, Fe II, V II, etc observed in STIS/E230H spectra. The origin of other broad features of similar width and depth in the FUSE spectrum, but without low-velocity ISM absorption, are unidentified. However, they are suspected of being absorption of singly-ionized iron-peak elements (e.g. Fe II, V II, Cr II) out of excited levels 1,000 to 20,000 cmE-l above the ground state. The high-velocity features seen in Fe II 1145 are also present in Fe II 1608 (STIS/E140M), but are highly saturated in the latter. Since these transitions have nearly identical log (flambda) (1.998 vs. 2.080), the differences in the profiles are attributable to the different aperture sizes used (30 x 30 arcsec for FUSE, 0.2 x 0.2 arcsec for STIS/E140M). The high-velocity gas appears to be very patchy or has a small covering factor near the central star. Eta Carinae has been observed several times by FUSE over the past three years. The FUSE flux levels and spectral features in eta Car are essentially unchanged over the 2000 March to June 2002 period, establishing a baseline far-UV spectrum in advance of the predicted spectroscopic minimum in 2003.

  13. Carbon nanotube reinforced aluminum nanocomposite via plasma and high velocity oxy-fuel spray forming.

    PubMed

    Laha, T; Liu, Y; Agarwal, A

    2007-02-01

    Free standing structures of hypereutectic aluminum-23 wt% silicon nanocomposite with multiwalled carbon nanotubes (MWCNT) reinforcement have been successfully fabricated by two different thermal spraying technique viz Plasma Spray Forming (PSF) and High Velocity Oxy-Fuel (HVOF) Spray Forming. Comparative microstructural and mechanical property evaluation of the two thermally spray formed nanocomposites has been carried out. Presence of nanosized grains in the Al-Si alloy matrix and physically intact and undamaged carbon nanotubes were observed in both the nanocomposites. Excellent interfacial bonding between Al alloy matrix and MWCNT was observed. The elastic modulus and hardness of HVOF sprayed nanocomposite is found to be higher than PSF sprayed composites.

  14. PTF 12gzk—A rapidly declining, high-velocity type Ic radio supernova

    SciTech Connect

    Horesh, Assaf; Kulkarni, Shrinivas R.; Corsi, Alessandra; Frail, Dale A.; Cenko, S. Bradley; Ben-Ami, Sagi; Gal-Yam, Avishay; Yaron, Ofer; Arcavi, Iair; Ofek, Eran O.; Kasliwal, Mansi M.

    2013-11-20

    Only a few cases of Type Ic supernovae (SNe) with high-velocity ejecta (≥0.2 c) have been discovered and studied. Here, we present our analysis of radio and X-ray observations of the Type Ic SN PTF 12gzk. The radio emission declined less than 10 days after explosion, suggesting SN ejecta expanding at high velocity (∼0.3 c). The radio data also indicate that the density of the circumstellar material (CSM) around the supernova is lower by a factor of ∼10 than the CSM around normal Type Ic SNe. PTF 12gzk may therefore be an intermediate event between a 'normal' SN Ic and a gamma-ray-burst-SN-like event. Our observations of this rapidly declining radio SN at a distance of 58 Mpc demonstrates the potential to detect many additional radio SNe, given the new capabilities of the Very Large Array (improved sensitivity and dynamic scheduling), which are currently missed, leading to a biased view of radio SNe Ic. Early optical discovery followed by rapid radio observations would provide a full description of the ejecta velocity distribution and CSM densities around stripped massive star explosions as well as strong clues about the nature of their progenitor stars.

  15. A novel platform to study magnetized high-velocity collisionless shocks

    SciTech Connect

    Higginson, D. P.; Korneev, Ph; Béard, J.; Chen, S. N.; d'Humières, E.; Pépin, H.; Pikuz, S.; Pollock, B.; Riquier, R.; Tikhonchuk, V.; Fuchs, J.

    2014-12-13

    An experimental platform to study the interaction of two colliding high-velocity (0.01–0.2c; 0.05–20 MeV) proton plasmas in a high strength (20 T) magnetic field is introduced. This platform aims to study the collision of magnetized plasmas accelerated via the Target-Normal-Sheath-Acceleration mechanism and initially separated by distances of a few hundred microns. The plasmas are accelerated from solid targets positioned inside a few cubic millimeter cavity located within a Helmholtz coil that provides up to 20 T magnetic fields. Various parameters of the plasmas at their interaction location are estimated. These show an interaction that is highly non-collisional, and that becomes more and more dominated by the magnetic fields as time progresses (from 5 to 60 ps). Particle-in-cell simulations are used to reproduce the initial acceleration of the plasma both via simulations including the laser interaction and via simulations that start with preheated electrons (to save dramatically on computational expense). The benchmarking of such simulations with the experiment and with each other will be used to understand the physical interaction when a magnetic field is applied. In conclusion, the experimental density profile of the interacting plasmas is shown in the case without an applied magnetic magnetic field, so to show that without an applied field that the development of high-velocity shocks, as a result of particle-to-particle collisions, is not achievable in the configuration considered.

  16. A SPITZER-MIPS SEARCH FOR DUST IN COMPACT HIGH-VELOCITY H I CLOUDS

    SciTech Connect

    Williams, Rik J.; Mathur, Smita; Poindexter, Shawn; Elvis, Martin; Nicastro, Fabrizio

    2012-04-15

    We employ three-band Spitzer-MIPS observations to search for cold dust emission in three neutral hydrogen compact high-velocity clouds (CHVCs) in the vicinity of the Milky Way. Far-infrared emission correlated with H I column density was previously reported in HVC Complex C, indicating that this object contains dust heated by the Galactic radiation field at its distance of {approx}10 kpc. Assuming published Spitzer, IRAS, and Planck, IR-H I correlations for Complex C, our Spitzer observations are of sufficient depth to directly detect 160 {mu}m dust emission in the CHVCs if it is present at the same level as in Complex C, but no emission is detected in any of the targets. For one of the targets (CHVC289) which has well-localized H I clumps, we therefore conclude that it is fundamentally different from Complex C, with either a lower dust-to-gas ratio or a greater distance from the Galactic disk (and consequently cooler dust temperature). Firm conclusions cannot be drawn for the other two Spitzer-observed CHVCs since their small-scale H I structures are not sufficiently well known; nonetheless, no extended dust emission is apparent despite their relatively high H I column densities. The lack of dust emission in CHVC289 suggests that at least some compact high-velocity clouds objects may exhibit very low dust-to-gas ratios and/or greater Galactocentric distances than large HVC complexes.

  17. Ultrafine particle generation by high-velocity impact of metal projectiles

    NASA Astrophysics Data System (ADS)

    Stabile, L.; Iannitti, G.; Vigo, P.; Ruggiero, A.; Russi, A.; Buonanno, G.

    2014-05-01

    Ultrafine particle generation through mechanical processes was not carefully deepened so far, even if it could be related to the human health-based researches. In particular, the evaluation of ultrafine particles produced in battlefield scenarios can be useful to quantify the exposure of soldiers to particles carrying toxic heavy metals. In the present work ultrafine particle generation during high-velocity impact of metal projectiles was deepened performing symmetrical high velocity Taylor impacts of copper cylinder tests (Rod-on-Rod tests) by means of a gas-gun facility. Particle number distributions and total concentrations were measured through one-second-time resolution instruments in a chamber where impact events at different velocities were performed. Particle number generation per impact was also evaluated. Particle concentrations in the 106 part. cm-3 range were measured corresponding to particle generations higher than 1012 particles per impact, then comparable to those typical of combustion sources. Particle number distribution showed a unimodal distribution with a 10 nm mode. Summarizing, the performed experimental campaign revealed an extremely high generation of ultrafine particles from mechanical processes.

  18. On projectile fragmentation at high-velocity perforation of a thin bumper

    NASA Astrophysics Data System (ADS)

    Myagkov, N. N.; Stepanov, V. V.

    2014-09-01

    By means of 3D numerical simulations, we study the statistical properties of the fragments cloud formed during high-velocity impact of a spherical projectile on a mesh bumper. We present a quantitative description of the projectile fragmentation, and study the nature of the transition from the damage to the fragmentation of the projectile when the impact velocity varies. A distinctive feature of the present work is that the calculations are carried out by smoothed particle hydrodynamics (SPH) method applied to the equations of mechanics of deformable solids (MDS). We describe the materials behavior by the Mie-Grüneisen equation of state and the Johnson-Cook model for the yield strength. The maximum principal stress spall model is used as the fracture model. It is shown that the simulation results of fragmentation based on the MDS equations by the SPH method are qualitatively consistent with the results obtained earlier on the basis of the molecular dynamics and discrete element models. It is found that the power-law distribution exponent does not depend on energy imparted to the projectile during the high-velocity impact. At the same time, our calculations show that the critical impact velocity, the power-law exponent and other critical exponents depend on the fracture criterion.

  19. Characterization of High-Velocity Single Particle Impacts on Plasma-Sprayed Ceramic Coatings

    NASA Astrophysics Data System (ADS)

    Kiilakoski, Jarkko; Lindroos, Matti; Apostol, Marian; Koivuluoto, Heli; Kuokkala, Veli-Tapani; Vuoristo, Petri

    2016-08-01

    High-velocity impact wear can have a significant effect on the lifetime of thermally sprayed coatings in multiple applications, e.g., in the process and paper industries. Plasma-sprayed oxide coatings, such as Cr2O3- and TiO2-based coatings, are often used in these industries in wear and corrosion applications. An experimental impact study was performed on thermally sprayed ceramic coatings using the High-Velocity Particle Impactor (HVPI) at oblique angles to investigate the damage, failure, and deformation of the coated structures. The impact site was characterized by profilometry, optical microscopy, and scanning electron microscopy (SEM). Furthermore, the connection between the microstructural details and impact behavior was studied in order to reveal the damage and failure characteristics at a more comprehensive level. Differences in the fracture behavior were found between the thermally sprayed Cr2O3 and TiO2 coatings, and a concept of critical impact energy is presented here. The superior cohesion of the TiO2 coating inhibited interlamellar cracking while the Cr2O3 coating suffered greater damage at high impact energies. The HVPI experiment has proven to be able to produce valuable information about the deformation behavior of coatings under high strain rates and could be utilized further in the development of wear-resistant coatings.

  20. Target responses to the impact of high-velocity, non-abrasive water jets

    SciTech Connect

    Kang, S.W.; Reitter, T.; Carlson, G.; Crutchmer, J.; Garrett, D.; Kramer, P.; Do, B.

    1993-04-01

    Theoretical and experimental investigations have been performed on the effects of a non-abrasive water jet impinging on a solid surface. The theoretical analysis treats the time-dependent, twodimensional case of an axisymmetric jet impacting on a rigid or non-rigid surface at various velocities, up to 1500 m/s. The numerical results obtained include time-dependent pressure distributions and jet geometry near the surface. The maximum calculated pressures agree well with the ``water-hammer`` values when modified for high-velocity jets. Impact and machining experiments were conducted with various materials with water jet reservoir pressures up to 276 MPa (40,000 psi). Test results show that maximum mass removal rate takes place when the standoff distance is several hundred nozzle diameters from the nozzle, suggesting that at this long distance the jet has disintegrated into a series of ligaments and drops impinging on the surface. Analytical and experimental efforts are continuing on determining the dominant mechanisms for the target response to high-velocity jets.

  1. Target responses to the impact of high-velocity, non-abrasive water jets

    SciTech Connect

    Kang, S.W.; Reitter, T.; Carlson, G. ); Crutchmer, J.; Garrett, D.; Kramer, P.; Do, B. )

    1993-04-01

    Theoretical and experimental investigations have been performed on the effects of a non-abrasive water jet impinging on a solid surface. The theoretical analysis treats the time-dependent, twodimensional case of an axisymmetric jet impacting on a rigid or non-rigid surface at various velocities, up to 1500 m/s. The numerical results obtained include time-dependent pressure distributions and jet geometry near the surface. The maximum calculated pressures agree well with the water-hammer'' values when modified for high-velocity jets. Impact and machining experiments were conducted with various materials with water jet reservoir pressures up to 276 MPa (40,000 psi). Test results show that maximum mass removal rate takes place when the standoff distance is several hundred nozzle diameters from the nozzle, suggesting that at this long distance the jet has disintegrated into a series of ligaments and drops impinging on the surface. Analytical and experimental efforts are continuing on determining the dominant mechanisms for the target response to high-velocity jets.

  2. High-Velocity Features in Type Ia Supernovae from a Compact Circumstellar Shell

    NASA Astrophysics Data System (ADS)

    Mulligan, Brian W.; Wheeler, J. Craig

    2017-01-01

    High-velocity features (HVF) of Ca prior to B-band maximum light are a ubiquitous property of Type Ia supernovae (SN Ia), but the origin of this high-velocity material is unknown. It may result from ejection of material during the explosion, detonation of material on the surface prior to the supernova, or interaction with a companion or material in the nearby environment. Here we introduce the methods we use to simulate the interaction of SN Ia ejecta with a shell of material surrounding the progenitor at a distance of less than 1 R⊙. Assuming free expansion, constant ion state and excitation temperature, we generate synthetic spectra from the data showing the effect of equation of state, explosion model, and the width, initial density profile, and mass of the shell on the appearance and temporal evolution of the Ca II near-infrared triplet (CaNIR). The Ca abundance of the shell is taken to be a free parameter. We compare the evolution of the pseudo-equivalent width (pEW) of the CaNIR feature resulting from these models to observational results. We find that the mass of the shell must be less than 0.012 ± 0.004 M⊙. We discuss potential ambiguities in observational methods of determining the pEW of the HVF.

  3. Aerosol formation from high-velocity uranium drops: Comparison of number and mass distributions. Final report

    SciTech Connect

    Rader, D.J.; Benson, D.A.

    1995-05-01

    This report presents the results of an experimental study of the aerosol produced by the combustion of high-velocity molten-uranium droplets produced by the simultaneous heating and electromagnetic launch of uranium wires. These tests are intended to simulate the reduction of high-velocity fragments into aerosol in high-explosive detonations or reactor accidents involving nuclear materials. As reported earlier, the resulting aerosol consists mainly of web-like chain agglomerates. A condensation nucleus counter was used to investigate the decay of the total particle concentration due to coagulation and losses. Number size distributions based on mobility equivalent diameter obtained soon after launch with a Differential Mobility Particle Sizer showed lognormal distributions with an initial count median diameter (CMD) of 0.3 {mu}m and a geometric standard deviation, {sigma}{sub g} of about 2; the CMD was found to increase and {sigma}{sub g} decrease with time due to coagulation. Mass size distributions based on aerodynamic diameter were obtained for the first time with a Microorifice Uniform Deposit Impactor, which showed lognormal distributions with mass median aerodynamic diameters of about 0.5 {mu}m and an aerodynamic geometric standard deviation of about 2. Approximate methods for converting between number and mass distributions and between mobility and aerodynamic equivalent diameters are presented.

  4. Investigation of high velocity separator for particle removal in coal gasification plants. Phase II report

    SciTech Connect

    Linhardt, H.D.

    1980-01-15

    This report summarizes the results of Phase II of the High Velocity Particle Separator Program performed under Contract EF-77-C-01-2709. This high velocity wedge separator has the potential to reduce equipment size and cost of high temperature and pressurized particulate removal equipment for coal derived gases. Phase II has been directed toward testing and detailed conceptual design of an element suitable for a commercial scale high temperature, high pressure particle separator (HTPS). Concurrently, Phase IA has been conducted, which utilized the ambient analog method (AAM) for aerodynamic and collection performance investigation of each HTPS configuration prior and during hot testing. This report summarizes the results of Phase IA and II. The AAM effort established correlation of theoretical analysis and experiment for HTPS pressure drop, purge flow ratio and collection efficiency potential. Task I defined the initial test conditions to be the contract design point of 1800/sup 0/F and 350 psia. The 1800/sup 0/F, 350 psia testing represents the main high temperature testing with coal-derived particulates in the 2 to 10 micron range. Phase IA and Phase II have demonstrated efficient particle collection with acceptable pressure drop. In view of these encouraging results, it is reasonable to apply the developed technology toward future hot gas particulate cleanup requirements.

  5. Development of a high-velocity free-flight launcher : the Ames light-gas gun

    NASA Technical Reports Server (NTRS)

    Charters, A C; Denardo, B Pat; Rossow, Vernon J

    1955-01-01

    Recent interest in long-range missiles has stimulated a search for new experimental techniques which can reproduce in the laboratory the high temperatures and Mach numbers associated with the missiles' flight. One promising possibility lies in free-flight testing of laboratory models which are flown at the full velocity of the missile. In this type of test, temperatures are approximated and aerodynamic heating of the model is representative of that experienced by the missile in high-velocity flight. A prime requirement of the free-flight test technique is a device which had the capacity for launching models at the velocities desired. In response to thie need, a gun firing light models at velocities up to 15,000 feet per second has been developed at the Ames Aeronautical Laboratory. The design of this gun, the analysis of its performance, and the results of the initial firing trials are described in this paper. The firing trials showed that the measured velocities and pressures agreed well with the predicted values. Also, the erosion of the launch tube was very small for the eleven rounds fired. The performance of the gun suggests that it will prove to be a satisfactory launcher for high-velocity free-flight tests. However, it should be mentioned that only the gross performance has been evaluated so far, and, consequently, the operation of the gun must be investigated in further detail before its performance can be reliably predicted over its full operating range.

  6. High-velocity frictional experiments on dolerite and quartzite under controlled pore pressure

    NASA Astrophysics Data System (ADS)

    Togo, T.; Shimamoto, T.; Ma, S.

    2013-12-01

    High-velocity friction experiments on rocks with or without gouge have been conducted mostly under dry conditions and demonstrated dramatic weakening of faults at high velocities (e.g., Di Toro et al., 2011, Nature). Recent experiments under wet conditions (e.g., Ujiie and Tsutsumi, 2010, GRL; Faulkner et al., 2011, GRL) revealed very different behaviors from those of dry faults, but those experiments were done under drained conditions. Experiments with controlled pore pressure Pp are definitely needed to determine mechanical properties of faults under fluid-rich environments such as those in subduction zones. Thus we have developed a pressure vessel that can be attached to our rotary-shear low to high-velocity friction apparatus (Marui Co Ltd., MIS-233-1-76). With a current specimen holder, friction experiments can be done on hollow-cylindrical specimens of 15 and 40 mm in inner and outer diameters, respectively, at controlled Pp to 35 MPa, at effective normal stresses of 3~9 MPa, and at slip rates of 60 mm/year to 2 m/s. An effective normal stress can be applied with a 100 kN hydraulic actuator. We report an outline of the experimental system and preliminary high-velocity experiments on Shanxi dolerite and a quartzite from China that are composed of pyroxene and plagioclase and of almost pure quartz, respectively. High-velocity friction experiments were performed on hollow-cylindrical specimens of Shanxi dolerite at effective normal stresses of 0.13~1.07 MPa and at slip rates of 1, 10, 100 and 1000 mm/sec. All experiments were conducted first with the nitrogen gas filling the pressure vessel (dry tests) and then with a controlled pore-water pressure (wet tests). In the dry tests an axial force was kept at 1 kN and the nitrogen gas pressure was increased in steps to 5 MPa to change an effective normal stress. In the wet tests the specimens were soaked in distilled water in the vessel and Pp was applied by nitrogen gas in a similar manner as in the dry tests

  7. Continuous exposure to low amplitude extremely low frequency electrical fields characterizing the vascular streaming potential alters elastin accumulation in vascular smooth muscle cells.

    PubMed

    Bergethon, Peter R; Kindler, Dean D; Hallock, Kevin; Blease, Susan; Toselli, Paul

    2013-07-01

    In normal development and pathology, the vascular system depends on complex interactions between cellular elements, biochemical molecules, and physical forces. The electrokinetic vascular streaming potential (EVSP) is an endogenous extremely low frequency (ELF) electrical field resulting from blood flowing past the vessel wall. While generally unrecognized, it is a ubiquitous electrical biophysical force to which the vascular tree is exposed. Extracellular matrix elastin plays a central role in normal blood vessel function and in the development of atherosclerosis. It was hypothesized that ELF fields of low amplitude would alter elastin accumulation, supporting a link between the EVSP and the biology of vascular smooth muscle cells. Neonatal rat aortic smooth muscle cell cultures were exposed chronically to electrical fields characteristic of the EVSP. Extracellular protein accumulation, DNA content, and electron microscopic (EM) evaluation were performed after 2 weeks of exposure. Stimulated cultures showed no significant change in cellular proliferation as measured by the DNA concentration. The per-DNA normalized protein in the extracellular matrix was unchanged while extracellular elastin accumulation decreased 38% on average. EM analysis showed that the stimulated cells had a 2.85-fold increase in mitochondrial number. These results support the formulation that ELF fields are a potential factor in both normal vessel biology and in the pathogenesis of atherosclerotic diseases including heart disease, stroke, and peripheral vascular disease.

  8. The differentiation of human adipose-derived stem cells (hASCs) into osteoblasts is promoted by low amplitude, high frequency vibration treatment.

    PubMed

    Prè, D; Ceccarelli, G; Gastaldi, G; Asti, A; Saino, E; Visai, L; Benazzo, F; Cusella De Angelis, M G; Magenes, G

    2011-08-01

    Several studies have demonstrated that tissue culture conditions influence the differentiation of human adipose-derived stem cells (hASCs). Recently, studies performed on SAOS-2 and bone marrow stromal cells (BMSCs) have shown the effectiveness of high frequency vibration treatment on cell differentiation to osteoblasts. The aim of this study was to evaluate the effects of low amplitude, high frequency vibrations on the differentiation of hASCs toward bone tissue. In view of this goal, hASCs were cultured in proliferative or osteogenic media and stimulated daily at 30Hz for 45min for 28days. The state of calcification of the extracellular matrix was determined using the alizarin assay, while the expression of extracellular matrix and associated mRNA was determined by ELISA assays and quantitative RT-PCR (qRT-PCR). The results showed the osteogenic effect of high frequency vibration treatment in the early stages of hASC differentiation (after 14 and 21days). On the contrary, no additional significant differences were observed after 28days cell culture. Transmission Electron Microscopy (TEM) images performed on 21day samples showed evidence of structured collagen fibers in the treated samples. All together, these results demonstrate the effectiveness of high frequency vibration treatment on hASC differentiation toward osteoblasts.

  9. Low-amplitude high frequency vibration down-regulates myostatin and atrogin-1 expression, two components of the atrophy pathway in muscle cells.

    PubMed

    Ceccarelli, Gabriele; Benedetti, Laura; Galli, Daniela; Prè, Deborah; Silvani, Giulia; Crosetto, Nicola; Magenes, Giovanni; Cusella De Angelis, Maria Gabriella

    2014-05-01

    Whole body vibration (WBV) is a very widespread mechanical stimulus used in physical therapy, rehabilitation and fitness centres. It has been demonstrated that vibration induces improvements in muscular strength and performance and increases bone density. We investigated the effects of low-amplitude, high frequency vibration (HFV) at the cellular and tissue levels in muscle. We developed a system to produce vibrations adapted to test several parameters in vitro and in vivo. For in vivo experiments, we used newborn CD1 wild-type mice, for in vitro experiments, we isolated satellite cells from 6-day-old CD1 mice, while for proliferation studies, we used murine cell lines. Animals and cells were treated with high frequency vibration at 30 Hz. We analyzed the effects of mechanical stimulation on muscle hypertrophy/atrophy pathways, fusion enhancement of myoblast cells and modifications in the proliferation rate of cells. Results demonstrated that mechanical vibration strongly down-regulates atrophy genes both in vivo and in vitro. The in vitro experiments indicated that mechanical stimulation promotes fusion of satellite cells treated directly in culture compared to controls. Finally, proliferation experiments indicated that stimulated cells had a decreased growth rate compared to controls. We concluded that vibration treatment at 30 Hz is effective in suppressing the atrophy pathway both in vivo and in vitro and enhances fusion of satellite muscle cells.

  10. Wide Binaries among High-Velocity and Metal-Poor Stars

    NASA Astrophysics Data System (ADS)

    Allen, C.; Herrera, M. A.; Poveda, A.

    1998-11-01

    The properties of old disk and halo binaries are of interest for the understanding of the processes of formation and early dynamical evolution of the Galaxy. The luminosity function of the components of wide binaries and multiples, their mass function, the fraction of halo or old disk stars that are members of wide binaries, and the distribution of their separations are some of the basic properties that are poorly understood, mainly because of the paucity of known wide binaries among halo and old disk stars. The present work is an attempt to ameliorate this situation. We have elaborated a list of 133 wide binaries mostly belonging to the halo or high-velocity disk, by searching for common proper motion companions to the high-velocity and metal-poor stars studied by Schuster and collaborators (1988, 1993). Based on Stromgren photometry, these authors have derived distances, metallicities and ages for their stars. Since each star has a large and well determined proper motion, it was possible to compare this value with that of NLTT stars of its vicinity. In this way we were able to identify over 100 high-velocity and metal-poor common proper motion binary systems. Each system was carefully checked to avoid misidentifications; in most of the cases, distances were improved using the Hipparcos trigonometric parallaxes. We have determined the distribution of angular separations for our wide binaries. Reliable distances are available for all of our systems, so this distribution can be converted into a separation distribution in AU. We find 11 systems that have projected semiaxes in excess of 10000 AU, or 16 systems with expected semiaxes larger than 10000 AU, their existence poses interesting dynamical problems. Since many systems also have known radial velocities, space velocities for them can be determined, and galactic orbits have been computed and characterized. The secondaries of these wide binaries are interesting by themselves, since they represent a sampling of the

  11. A study of two high-velocity red horizontal branch stars

    NASA Astrophysics Data System (ADS)

    Pereira, C. B.; Jilinski, E. G.; Drake, N. A.; Ortega, V. G.; Roig, F.

    2013-11-01

    Context. High-velocity halo stars provide important information about the properties of the extreme Galactic halo. The study of Population II unbound and bound stars enables us better estimate the mass of the halo. Aims: We carried out a detailed spectroscopic and kinematic study of two red horizontal branch stars, CD-41°15048 and HD 214362. Methods: The atmospheric parameters, chemical abundances, and kinematical properties were determined using high-resolution optical spectroscopy and employing the local thermodynamic equilibrium model atmospheres of Kurucz and the spectral analysis code moog. Results: We found that CD-41°15048 and HD 214362 are metal-poor red horizontal branch stars. Their abundance patterns are similar to other metal-poor halo stars already investigated. Our kinematic analysis of the 3D space motions shows that HD 214362 has a highly eccentric (e = 0.95) orbit and passes at 2 kpc from the Galactic center. CD-41°15048, for an adopted distance of 1.3 kpc, has an extreme retrograde motion and travels with very high velocity relative to the Galactocentric reference frame (VGRF = 583 km s-1). Conclusions: CD-41°15048 is a bound or an unbound star, depending on the adopted Galactic potential. We also show that the red horizontal branch star BD+09°3223 is another example of a hypervelocity star. Whether it is bound or unbound to the Galaxy depends on the assumed mass and adopted Galactic potential. Possible origins of these two high-velocity stars are briefly discussed. CD-41°15048 and BD+09°3223 are further examples of evolved stars to join the restricted group of hypervelocity stars. Finally, our results seem to contradict the idea that a passage of a star very close to the Galactic center is the only possible origin of hypervelocity stars. Based on observations made with the 2.2 m telescope at the European Southern Observatory (La Silla, Chile) under the agreement between ESO and Observatório Nacional (2007-2010).Figures 3-5, 8, 10

  12. What Happens to a High Velocity Cloud When it Hits the Milky Way's Disk: Is Dark Matter Necessary for Survival?

    NASA Astrophysics Data System (ADS)

    Shelton, Robin L.; Galyardt, Jason

    2015-01-01

    Dark matter halos enshroud some of the most massive high velocity clouds. Their gravitational pull confines the clouds as they pass through the intergalactic medium. Given the ability of dark matter halos to stabilize their embedded baryonic clouds against hydrodynamic interactions that would otherwise disrupt them, it has further been suggested that dark matter halos could enable high velocity clouds to survive impacts with the Milky Way's disk. The survival of high velocity clouds, such as the Smith Cloud, during a passage through the disk has been cited as evidence for the presence of dark matter. However, a second actor, the magnetic field, may also be at play. In order to characterize, measure, and disentangle their effects, we have performed magnetohydrodynamic simulations of massive high velocity clouds as they impact a galactic disk. Here, we present the rate at which material dissipates in a variety of situations that include or exclude dark matter and magnetic fields.

  13. Ringlike spin segregation of binary mixtures in a high-velocity rotating drum

    NASA Astrophysics Data System (ADS)

    Decai, Huang; Ming, Lu; Gang, Sun; Yaodong, Feng; Min, Sun; Haiping, Wu; Kaiming, Deng

    2012-03-01

    This study presents molecular dynamics simulations on the segregation of binary mixtures in a high-velocity rotating drum. Depending on the ratio between the particle radius and density, similarities to the Brazil-nut effect and its reverse form are shown in the ringlike spin segregation patterns in radial direction. The smaller and heavier particles accumulated toward the drum wall, whereas the bigger and lighter particles accumulated toward the drum center. The effects of particle radius and density on the segregation states were quantified and the phase diagram of segregation in the ρb/ρs - rb/rs space was plotted. The observed phenomena can be explained by the combined percolation and the buoyancy effects.

  14. Simulation of High Velocity Impact on Composite Structures - Model Implementation and Validation

    NASA Astrophysics Data System (ADS)

    Schueler, Dominik; Toso-Pentecôte, Nathalie; Voggenreiter, Heinz

    2016-08-01

    High velocity impact on composite aircraft structures leads to the formation of flexural waves that can cause severe damage to the structure. Damage and failure can occur within the plies and/or in the resin rich interface layers between adjacent plies. In the present paper a modelling methodology is documented that captures intra- and inter-laminar damage and their interrelations by use of shell element layers representing sub-laminates that are connected with cohesive interface layers to simulate delamination. This approach allows the simulation of large structures while still capturing the governing damage mechanisms and their interactions. The paper describes numerical algorithms for the implementation of a Ladevèze continuum damage model for the ply and methods to derive input parameters for the cohesive zone model. By comparison with experimental results from gas gun impact tests the potential and limitations of the modelling approach are discussed.

  15. Erosive wear of ductile metals by a particle-laden high velocity liquid jet

    SciTech Connect

    Ka-Keung Li, Simon; Humphrey, Joseph A. C.; Levy, Alan V.

    1981-11-30

    In this paper, a liquid-solid particle jet impingement flow apparatus is described and experimental measurements are reported for the accelerated erosion of copper, aluminum and mild steel sheet metal by coal suspensions in kerosene and Al2O3 and SiC suspensions in water. Slurry velocities of up to 130 ft s-1 (40 m s-1) and impingement angles of 15°–90° were investigated. The maximum particle concentration used was 40 wt.%. For high velocity the results of this work show two erosion maxima; these are found at impingement angles of 90° and 40°. However, in corresponding gas-solid particle investigations maximum erosion occurs at approximately 20°. In this work both particle concentration and composition were varied. Finally, a polynomial regression technique was used to calculate empirical and semitheoretical correlation constants.

  16. LP 400-22, A Very Low Mass and High-Velocity White Dwarf

    NASA Technical Reports Server (NTRS)

    Kawka, Adela; Vennes, Stephane; Oswalt, Terry D.; Smith, J. Allyn; Silvestri, Nicole M.

    2006-01-01

    We report the identification of LP 400-22 (WD 2234+222) as a very low mass and high-velocity white dwarf. The ultraviolet GALEX and optical photometric colors and a spectral line analysis of LP 400-22 show this star to have an effective temperature of 11,080+/-140 K and a surface gravity of log g = 6.32 +/-0.08. Therefore, this is a helium-core white dwarf with a mass of 0.17 M,. The tangential velocity of this white dwarf is 414+/-43 km/s, making it one of the fastest moving white dwarfs known. We discuss probable evolutionary scenarios for this remarkable object.

  17. The kinematics of the high velocity bipolar nebulae NGC 6537 and HB 5

    NASA Astrophysics Data System (ADS)

    Corradi, Romano L. M.; Schwarz, Hugo E.

    1993-03-01

    The velocity structure of the bipolar planetary nebulae (PNe) NGC 6537 and Hb 5 has been investigated by means of medium dispersion long slit spectra. We have derived kinematical parameters and the deprojected shapes of the two nebulae by applying the kinematical model introduced by Solf and Ulrich (1985). In the direction of the polar axis of the nebulae, the deprojected expansion velocity is computed to be 300 km/s for NGC 6537 and about 250 km/s for Hb 5. These are very high velocities, but not unusual in the class of bipolar nebulae. The observed shapes and the velocity fields, in particular the one of Hb 5, are nicely reproduced by the interacting winds models by Icke et al. (1989). These imply a strongly aspherical initial mass distribution, i.e. equatorial to polar density contrasts larger than five. We espouse the idea that these initial conditions are created in interacting binary systems.

  18. IUE observations of high velocity gas towards the M16 nebula

    NASA Astrophysics Data System (ADS)

    Welsh, B. Y.

    1984-03-01

    The star HD 168183, which is part of the giant H II region-molecular cloud complex of M16 (NGC 6611), has been observed at high resolution using the IUE satellite. High velocity interstellar absorption components have been detected at velocities of -83, -38 and +40 km s-1 and it is proposed that a stellar wind-driven shock-front, interacting with the ambient neutral interstellar gas, is responsible for such complex velocity structure. Strong absorption from five of the 12C16O UV molecular lines has also been detected and the present UV absorption line data seem consistent with radio observations of M16 in which the Tenorio-Tagle 'champagne' model has been invoked to explain the ionized and neutral gas outflows from the nebula.

  19. Analysis of possible improvement of acceleration of a high-velocity air-breathing flying vehicle

    NASA Astrophysics Data System (ADS)

    Goonko, Yu. P.; Mazhul, I. I.

    2008-09-01

    Results of parametric calculations of the total aeropropulsive characteristics and characteristics of acceleration of a small-scale high-velocity flying vehicle with an air-breathing engine are presented. Integral parameters of acceleration from the flight Mach number M∞ = 4 to M∞ = 7 are determined, namely, the time required fuel stock, and range. A schematic configuration of the vehicle is considered, which allows studying the basic parameters, such as the forebody shape, the angles of surfaces of compression of the stream captured by the inlet, angles of external aerodynamic surfaces of the airframe, relative planform area of the wing panels, and relative area of the nozzle cross section. A comparative estimate of the effect of these parameters shows that it is possible to improve the characteristics of acceleration of vehicles of the type considered.

  20. The Draco Nebula, a Molecular Cloud Associated with a High Velocity Cloud?

    NASA Technical Reports Server (NTRS)

    Mebold, U.; Kalberla, P. W. M.

    1984-01-01

    Extended and very faint bright nebulae are found in high galactic latitudes at the Palomar Observatory Sky Survey. Such a nebula, located in the constellation Draco and called Draco Nebula or Dracula, was found to be in detailed positional coincidence with a 21 cm emission line feature. Estimates of the minimum visual extinction from star counts ON and OFF Dracula and an estimated visual surface brightness indicate that Dracula fits the relation SBV = 24.2 - 2.5 log AV for dust clouds located above the galactic plane and reflecting the integrated starlight of the galactic disk. Hence Dracula is probably a reflection nebula. Indicators of molecular hydrogen in Dracula, molecules such as CO, were searched for by using a 2.5-m mm-telescope. Molecular hydrogen column densities were estimated. The dynamics of CO clumps was studied. Dracula has a close positional and possibly even astrophysical relationship to the high velocity cloud phenomenon.

  1. HIGH-VELOCITY OUTFLOWS WITHOUT AGN FEEDBACK: EDDINGTON-LIMITED STAR FORMATION IN COMPACT MASSIVE GALAXIES

    SciTech Connect

    Diamond-Stanic, Aleksandar M.; Moustakas, John; Coil, Alison L.; Tremonti, Christy A.; Sell, Paul H.; Hickox, Ryan C.; Robaina, Aday R.; Rudnick, Gregory H.

    2012-08-20

    We present the discovery of compact, obscured star formation in galaxies at z {approx} 0.6 that exhibit {approx}> 1000 km s{sup -1} outflows. Using optical morphologies from the Hubble Space Telescope and infrared photometry from the Wide-field Infrared Survey Explorer, we estimate star formation rate (SFR) surface densities that approach {Sigma}{sub SFR} Almost-Equal-To 3000 M{sub Sun} yr{sup -1} kpc{sup -2}, comparable to the Eddington limit from radiation pressure on dust grains. We argue that feedback associated with a compact starburst in the form of radiation pressure from massive stars and ram pressure from supernovae and stellar winds is sufficient to produce the high-velocity outflows we observe, without the need to invoke feedback from an active galactic nucleus.

  2. The detection of high-velocity outflows from M8E-IR

    NASA Technical Reports Server (NTRS)

    Mitchell, George F.; Allen, Mark; Beer, Reinhard; Dekany, Richard; Huntress, Wesley

    1988-01-01

    A high-resolution (0.059/cm) M band (4.6 micron) spectrum of the embedded young stellar object M8E-IR is presented and discussed. The spectrum shows strong absorption to large blueshifts in the rotational lines of the fundamental vibrational band, v = 1-0, of CO. The absorption is interpreted as being due to gas near to, and flowing from, the central object. The outflowing gas is warm (95-330 K) and consists of discrete velocity components with the very high velocities of 90, 130, 150, and 160 km/s. On the basis of a simple model, it is estimated that the observed outflows are less than 100 yr old.

  3. The quest for TPa Hugoniot data: using the DEMG in high velocity pulsed power experiments

    SciTech Connect

    Peterson, Jeff H; Rousculp, Christopher L; Holtkamp, David B; Oro, David M; Griego, Jeffrey R; Atchison, Walter L; Reinovsky, Robert E

    2010-12-20

    ALT-3 is an experiment being designed in collaboration between Russian VNIIEF scientists and LANL that aims to conduct high velocity material experiments to measure shock velocities at pressures near 1 TPa. The DEMG (Disk Explosive Magnetic Generator) is used to drive >60MA currents to accelerate an aluminum liner to speeds in excess of 20 km/s. The 1-D model of the DEMG has been refined from a given current profile to a time-varying inductance. Various techniques are used to model the FOS (Foil Opening Switch) on the DEMG and a refined DEMG model is then used to drive a liner into various targets to determine the optimum design for the experiment and analyze the possible conditions and complications.

  4. Three-dimensional finite element analysis for high velocity impact. [of projectiles from space debris

    NASA Technical Reports Server (NTRS)

    Chan, S. T. K.; Lee, C. H.; Brashears, M. R.

    1975-01-01

    A finite element algorithm for solving unsteady, three-dimensional high velocity impact problems is presented. A computer program was developed based on the Eulerian hydroelasto-viscoplastic formulation and the utilization of the theorem of weak solutions. The equations solved consist of conservation of mass, momentum, and energy, equation of state, and appropriate constitutive equations. The solution technique is a time-dependent finite element analysis utilizing three-dimensional isoparametric elements, in conjunction with a generalized two-step time integration scheme. The developed code was demonstrated by solving one-dimensional as well as three-dimensional impact problems for both the inviscid hydrodynamic model and the hydroelasto-viscoplastic model.

  5. Design and test of a superconducting structure for high-velocity ions

    SciTech Connect

    Delayen, J.R.; Kennedy, W.L.; Roche, C.T.

    1992-10-01

    Following the successful development of a niobium coaxial half-wave structure we have designed, built and tested a new half-wave geometry: the spoke resonator. This geometry is better suited for high frequency resonators and for the acceleration of high velocity ions. The prototype cavity is a 2-gap structure resonating at 855 MHz, and optimized for particle velocity of 0.30 c. It is easier to manufacture than the coaxial half-wave resonator and the geometry can be straightforwardly extended to multigap designs. Rf-tests have been performed on this cavity both prior to and after high temperature annealing. An accelerating gradient of 7.2 MV/m (cw) and 7.8 MV/m (pulsed) was observed at 4.2 K. After annealing, a low power Q{sub 0} of 1.2 {times}10{sup 8} was observed with small Q degradation due to field emission at high accelerating fields.

  6. Design and test of a superconducting structure for high-velocity ions

    SciTech Connect

    Delayen, J.R.; Kennedy, W.L.; Roche, C.T.

    1992-01-01

    Following the successful development of a niobium coaxial half-wave structure we have designed, built and tested a new half-wave geometry: the spoke resonator. This geometry is better suited for high frequency resonators and for the acceleration of high velocity ions. The prototype cavity is a 2-gap structure resonating at 855 MHz, and optimized for particle velocity of 0.30 c. It is easier to manufacture than the coaxial half-wave resonator and the geometry can be straightforwardly extended to multigap designs. Rf-tests have been performed on this cavity both prior to and after high temperature annealing. An accelerating gradient of 7.2 MV/m (cw) and 7.8 MV/m (pulsed) was observed at 4.2 K. After annealing, a low power Q{sub 0} of 1.2 {times}10{sup 8} was observed with small Q degradation due to field emission at high accelerating fields.

  7. Method and apparatus for direct high velocity preparation of completion/workover systems

    SciTech Connect

    Richard, B.M.; Johnson, M.H.

    1990-07-31

    This patent describes apparatus for direct high velocity preparation of completion/workover systems incorporating a solid particulate matter into a carrier fluid for use in subterranean wells. It comprises: fluid pump means having inlet and outlet members; a conveyor system; a cylindrical mixing housing secured relative to the pump means; an inlet through the cylindrical mixing housing for receipt of the conveyor housing; first fluid flow passages defined through the cylindrical mixing housing and in fluid communication with the inlet members of the pump means; second fluid flow passages defined through the conveyor housing and in relative axial alignment with the first fluid flow passages; a mixing annulus ; means for transmission and receipt of a carrier fluid through the mixing housing and into the mixing annulus; means for activation of the rotable conveyor; and means for introduction of particulate matter into the cylindrical conveyor housing upstream of the means for transmission of the carrier fluid.

  8. Ongoing Search for Metal Line Emission in Intermediate and High Velocity Clouds with WHAM

    NASA Astrophysics Data System (ADS)

    Barger, K. A.; Haffner, L. M.; Madsen, G. J.; Hill, A. S.; Wakker, B. P.

    2010-01-01

    We present new observations of the ionized gas in Complexes A, K, and L obtained with the Wisconsin H-Alpha Mapper (WHAM). To date, there have been only a limited number of studies of the ionized components of intermediate and high velocity clouds. Investigating their emission provides a rare probe of the physical conditions of the clouds and the halo they are embedded within. These types of measurements will help guide discussion of the origin and evolution of these neutral halo structures. Here we follow up on the H-alpha maps we have presented elsewhere with deeper observations in H-alpha, [S II], [N II], and [O I]. Distance constraints from absorption studies place this gas in the mid to lower Galactic halo. Complex A has been constrained to a distance of 8-10 kpc (Wakker et al. 2008); Complex K has an upper limit of 6.8 kpc; and Complex L at a distance of 8-15 kpc (Wakker 2000). Some halo gas structures have clear metal line emission (e.g., Smith Cloud; Hill et al. 2009 and this meeting); however, the lack of [S II] emission toward Complex C combined with absorption-line observations demonstrates that it has very low metallically (Wakker, et al. 1999). Such discoveries reveal ongoing gas replenishment of the evolving Milky Way. Here, we find a similar lack of emission toward the high-velocity Complex A. In particular, the cores of its cloud components designated III and IV show no evidence for metal line emission in our new observations, which places new constraints on the metallically of this complex. These observations were taken with WHAM at Kitt Peak, and we thank the excellent, decade-long support from its staff. WHAM operations are supported through NSF award AST-0607512.

  9. Mapping High-Velocity H-alpha and Lyman-alpha Emission from Supernova 1987A

    NASA Technical Reports Server (NTRS)

    France, Kevin; McCray, Richard; Fransson, Claes; Larsson, Josefin; Frank, Kari A.; Burrows, David N.; Challis, Peter; Kirshner, Robert P.; Chevalier, Roger A.; Garnavich, Peter; Heng, Kevin; Lawrence, Stephen S.; Lundqvist, Peter; Smith, Nathan; Sonneborn, George

    2015-01-01

    We present new Hubble Space Telescope images of high-velocity H-alpha and Lyman-alpha emission in the outer debris of SN 1987A. The H-alpha images are dominated by emission from hydrogen atoms crossing the reverse shock. For the first time we observe emission from the reverse shock surface well above and below the equatorial ring, suggesting a bipolar or conical structure perpendicular to the ring plane. Using the H-alpha imaging, we measure the mass flux of hydrogen atoms crossing the reverse shock front, in the velocity intervals (-7,500 < V(sub obs) < -2,800 km/s) and (1,000 < V(sub obs) < 7,500 km/s), ?M(sub H) = 1.2 × 10(exp -3) M/ y. We also present the first Lyman-alpha imaging of the whole remnant and new Chandra X-ray observations. Comparing the spatial distribution of the Lyman-alpha and X-ray emission, we observe that the majority of the high-velocity Lyman-alpha emission originates interior to the equatorial ring. The observed Lyman-alpha/H-alpha photon ratio, R(L-alpha/H-alpha) approx. = 17, is significantly higher than the theoretically predicted ratio of approx. = 5 for neutral atoms crossing the reverse shock front. We attribute this excess to Lyman-alpha emission produced by X-ray heating of the outer debris. The spatial orientation of the Lyman-alpha and X-ray emission suggests that X-ray heating of the outer debris is the dominant Lyman-alpha production mechanism in SN 1987A at this phase in its evolution.

  10. High-velocity Interstellar Bullets in IRAS 05506+2414: A Very Young Protostar

    NASA Technical Reports Server (NTRS)

    Sahai, Raghvendra; Claussen, Mark; Sanchez Contreras, Carmen; Morris, Mark; Sarkar, Geetanjali

    2008-01-01

    We have made a serendipitous discovery of an enigmatic outflow source, IRAS 05506+2414 (hereafter IRAS 05506), as part of a multiwavelength survey of pre-planetary nebulae (PPNs). The HST optical and near-infrared images show a bright compact central source with a jet-like extension, and a fan-like spray of high-velocity (with radial velocities up to 350 km/s) elongated knots which appear to emanate from it. These structures are possibly analogous to the near-IR bullets'' seen in the Orion Nebula. Interferometric observations at 2.6 mm show the presence of a continuum source and a high-velocity CO outflow, which is aligned with the optical jet structure. IRAS 05506 is most likely not a PPN. We find extended NH3 (1,1) emission toward IRAS 05506; these data, together with the combined presence of far-IR emission, H2O and OH masers, and CO and CS J=2-1 emission, strongly argue for a dense, dusty star-forming core associated with IRAS 05506. IRAS 05506 is probably an intermediate-mass or massive protostar, and the very short timescale (200 yr) of its outflows indicates that it is very young. If IRAS 05506 is a massive star, then the lack of radio continuum and the late G to early K spectral type we find from our optical spectra imply that in this object we are witnessing the earliest stages of its life, while its temperature is still too low to provide sufficient UV flux for ionization.

  11. Wide Binaries among High-Velocity and Metal-Poor Stars

    NASA Astrophysics Data System (ADS)

    Allen, C.; Herrera, M. A.; Poveda, A.

    The properties of old disk and halo binaries are of interest for the understanding of the processes of formation and early dynamical evolution of the Galaxy. The luminosity function of the components of wide binaries and multiples, their mass function, the fraction of halo or old disk stars that are members of wide binaries, and the distribution of its separations are some of the basic properties that are poorly understood, mainly because of the paucity of known wide binaries among halo and old disk stars. The present work is an attempt to ameliorate this situation. We have elaborated a list of 130 halo and old disk wide binaries by searching for common proper motion companions to the high-velocity and metal-poor stars studied by Schuster and Nissen (1988, 1993). Based on Stromgren photometry, these authors have derived distances, metallicities and ages for their stars. Since each star has a large and well determined proper motion it was possible to compare this value with that of NLTT stars of its vicinity. In this way we were able to identify 130 high-velocity and metal-poor common proper motion binary systems. Each system was carefully checked to avoid misidentifications, and when possible, distances were updated using the Hipparcos trigonometric parallaxes. We have determined the distribution of angular separations for our wide binaries. Reliable distances are available for all of our systems, so this distribution can be converted into a separation distribution in AU. We find that 12 systems have separations in excess of 10000 AU, and their existence poses interesting dynamical problems. Since many systems also have known radial velocities, space velocities for them can be determined, and galactic orbits have been computed and characterized. The secondaries of these wide binaries are interesting in themselves, since they represent a sampling of the faint end of the main sequence of old disk and halo stars.

  12. A novel platform to study magnetized high-velocity collisionless shocks

    DOE PAGES

    Higginson, D. P.; Korneev, Ph; Béard, J.; ...

    2014-12-13

    An experimental platform to study the interaction of two colliding high-velocity (0.01–0.2c; 0.05–20 MeV) proton plasmas in a high strength (20 T) magnetic field is introduced. This platform aims to study the collision of magnetized plasmas accelerated via the Target-Normal-Sheath-Acceleration mechanism and initially separated by distances of a few hundred microns. The plasmas are accelerated from solid targets positioned inside a few cubic millimeter cavity located within a Helmholtz coil that provides up to 20 T magnetic fields. Various parameters of the plasmas at their interaction location are estimated. These show an interaction that is highly non-collisional, and that becomesmore » more and more dominated by the magnetic fields as time progresses (from 5 to 60 ps). Particle-in-cell simulations are used to reproduce the initial acceleration of the plasma both via simulations including the laser interaction and via simulations that start with preheated electrons (to save dramatically on computational expense). The benchmarking of such simulations with the experiment and with each other will be used to understand the physical interaction when a magnetic field is applied. In conclusion, the experimental density profile of the interacting plasmas is shown in the case without an applied magnetic magnetic field, so to show that without an applied field that the development of high-velocity shocks, as a result of particle-to-particle collisions, is not achievable in the configuration considered.« less

  13. Chemical reactions induced by high-velocity molecular impacts: challenges for closed-source mass spectrometry

    NASA Astrophysics Data System (ADS)

    Austin, Daniel

    2016-07-01

    Analysis of upper atmosphere composition using closed-source neutral mass spectrometers (e.g., Cassini INMS, MAVEN NGIMS) is subject to error due to chemical reactions caused by the high-velocity impacts of neutral molecules on the source surfaces. In addition to species traditionally considered "surface reactive" (e.g., O, N) it is likely that many or all impacting molecules are vibrationally excited to the point that chemical changes can occur. Dissociation, fragmentation, formation of radicals and ions, and other reactions likely obscure analysis of the native atmospheric composition, particularly of organic compounds. Existing techniques are not capable of recreating the relevant impact chemistry in the lab. We report on the development of a new capability allowing reactions of high-velocity neutrals impacting surfaces to be characterized directly. Molecules introduced into a vacuum chamber are impacted at several km/s by the surface of a high-speed rotor. These molecules subsequently impact multiple times on other surfaces within the vacuum chamber until they are thermalized, after which they are cryogenically collected and analyzed. Reaction pathways and thermodynamics for volatile compounds are then determined. We will present current results on this project, including data from low- and mid-range velocity experiments. This type of information is critical to clarify prior flight results and plan for future missions. Finally, we present a new type of inlet intended to significantly reduce fragmentation for impact velocities typical of a fly-by mission. Theoretical analysis indicates that this new inlet may reduce fragmentation by more than an order of magnitude for any encounter velocity.

  14. High-velocity gas toward the LMC resides in the Milky Way halo

    NASA Astrophysics Data System (ADS)

    Richter, P.; de Boer, K. S.; Werner, K.; Rauch, T.

    2015-12-01

    Aims: To explore the origin of high-velocity gas in the direction of the Large Magellanic Cloud, (LMC) we analyze absorption lines in the ultraviolet spectrum of a Galactic halo star that is located in front of the LMC at d = 9.2+4.1-7.2 kpc distance. Methods: We study the velocity-component structure of low and intermediate metal ions (C ii, Si ii, Si iii) in the spectrum of RX J0439.8-6809, as obtained with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope (HST), and measure equivalent widths and column densities for these ions. We supplement our COS data with a Far-Ultraviolet Spectroscopic Explorer (FUSE) spectrum of the nearby LMC star Sk -69 59 and with H i 21 cm data from the Leiden-Argentina-Bonn (LAB) survey. Results: Metal absorption toward RX J0439.8-6809 is unambiguously detected in three different velocity components near vLSR = 0, + 60, and + 150 km s-1. The presence of absorption proves that all three gas components are situated in front of the star, thus located in the disk and inner halo of the Milky Way. For the high-velocity cloud (HVC) at vLSR = + 150 km s-1, we derive an oxygen abundance of [O/H] =-0.63 (~0.2 solar) from the neighboring Sk -69 59 sight line, in accordance with previous abundance measurements for this HVC. From the observed kinematics we infer that the HVC hardly participates in the Galactic rotation. Conclusions: Our study shows that the HVC toward the LMC represents a Milky Way halo cloud that traces low column density gas with relatively low metallicity. We rule out scenarios in which the HVC represents material close to the LMC that stems from a LMC outflow.

  15. Simulation of compact circumstellar shells around Type Ia supernovae and the resulting high-velocity features

    NASA Astrophysics Data System (ADS)

    Mulligan, Brian W.; Wheeler, J. Craig

    2017-01-01

    For Type Ia supernovae that are observed prior to B-band maximum (approximately 18-20 days after the explosion) Ca absorption features are observed at velocities of order 10,000 km/s faster than the typical photospheric features. These high velocity features weaken in the first couple of weeks, disappearing entirely by a week after B-band maximum. The source of this high velocity material is uncertain: it may be the result of interaction between the supernova and circumstellar material or may be the result of plumes or bullets of material ejected during the course of the explosion. We simulate interaction between a supernova and several compact circumstellar shells, located within 0.03 solar radii of the progenitor white dwarf and having masses of 0.02 solar masses or less. We use FLASH to perform hydrodynamic simulations of the system to determine the structure of the ejecta and shell components after the interaction, then use these results to generate synthetic spectra with 1 day cadence for the first 25 days after the explosion. We compare the evolution of the velocity and pseudo-equivalent width of the Ca near-infrared triplet features in the synthetic spectra to observed values, demonstrating that these models are consistent with observations. Additionally, we fit the observed spectra of SN 2011fe (Parrent 2012, Pereira 2013) prior to B-band maximum using these models and synthetic spectra and provide an estimate for Ca abundance within the circumstellar material with implications for the mechanism by which the white dwarf explodes.

  16. Optical Emission from High Velocity Clouds and the Nature of HVCs

    NASA Astrophysics Data System (ADS)

    Weiner, B. J.; Vogel, S. N.; Williams, T. B.

    1999-12-01

    The nature and origin of the high-velocity clouds of neutral hydrogen remain controversial, and the distances of most HVCs are poorly constrained. Only the large northern HVC complexes M and A have upper distance limits, of <5 and 4--10 kpc, from absorption against halo stars (Danly et al 1993, van Woerden et al 1999). These HVCs have diffuse H-alpha emission of 80--200 milli-Rayleighs (mR) (Tufte, Reynolds & Haffner 1998). We report results from a search of 20 high velocity clouds for faint diffuse optical emission lines in H-alpha and [N II], using a Fabry-Perot at the Las Campanas 2.5-m telescope. A few small complexes are ``bright,'' with H-alpha emission from 100--400 mR and high [N II]/H-alpha. Many HVCs are very faint in H-alpha: HVCs from the Anticenter, Galactic Center Negative, and Extreme Positive complexes have H-alpha from <15 to 30 mR. We construct a simple model for the ionizing flux emergent from the galaxy, normalized by the northern ``bright'' HVCs with known distances and H-alpha fluxes. If the H-alpha from HVCs is produced by ionizing flux escaping from the Galaxy, the H-alpha flux can be used to infer distances for HVCs. The model places the very faint HVCs at distances of 20--60 kpc, in the outer Galactic halo. If H-alpha can be produced by other mechanisms, than these distances could be lower limits. Independent of the model or mechanism, the HVCs that are very faint in H-alpha should be much farther away than the nearby ``bright'' HVCs. The faint HVCs are too far away to be produced by a Galactic fountain, and represent a significant amount of gas accreting onto the Galaxy. This work has been supported by a Carnegie Barbara McClintock Fellowship.

  17. High-velocity OH megamasers in IRAS 20100-4156: evidence for a supermassive black hole

    NASA Astrophysics Data System (ADS)

    Harvey-Smith, L.; Allison, J. R.; Green, J. A.; Bannister, K. W.; Chippendale, A.; Edwards, P. G.; Heywood, I.; Hotan, A. W.; Lenc, E.; Marvil, J.; McConnell, D.; Phillips, C. J.; Sault, R. J.; Serra, P.; Stevens, J.; Voronkov, M.; Whiting, M.

    2016-08-01

    We report the discovery of new, high-velocity narrow-line components of the OH megamaser in IRAS 20100-4156. Results from the Australian Square Kilometre Array Pathfinder (ASKAP)'s Boolardy Engineering Test Array (BETA) and the Australia Telescope Compact Array (ATCA) provide two independent measurements of the OH megamaser spectrum. We found evidence for OH megamaser clumps at -409 and -562 km s-1 (blue-shifted) from the systemic velocity of the galaxy, in addition to the lines previously known. The presence of such high velocities in the molecular emission from IRAS 20100-4156 could be explained by a ˜50 pc molecular ring enclosing a ˜3.8 billion solar mass black hole. We also discuss two alternatives, i.e. that the narrow-line masers are dynamically coupled to the wind driven by the active galactic nucleus or they are associated with two separate galactic nuclei. The comparison between the BETA and ATCA spectra provides another scientific verification of ASKAP's BETA. Our data, combined with previous measurements of the source enabled us to study the variability of the source over a 26 yr period. The flux density of the brightest OH maser components has reduced by more than a factor of 2 between 1988 and 2015, whereas a secondary narrow-line component has more than doubled in the same time. Plans for high-resolution very long baseline interferometry follow-up of this source are discussed, as are prospects for discovering new OH megamasers during the ASKAP early science programme.

  18. Influence of low amplitude/high frequency relative sea-level changes in a wave-dominated estuary (Miocene), São Luis Basin, northern Brazil

    NASA Astrophysics Data System (ADS)

    de Fátima Rossetti, D.

    2000-06-01

    Miocene deposits exceptionally well exposed along several coastal cliffs between the towns of Alcântara and Guimarães, Maranhão State, northern Brazil, record the history of low-amplitude/high-frequency sea-level changes in a wave-dominated incised valley estuarine setting. These deposits are interpreted as estuarine in origin, based on: (i) depauparated ichnological assemblage and occurrence of Gyrolithes, both typical of highly stressed brackish water conditions; (ii) dominance of sedimentary structures diagnostic of tidal processes (e.g. alternating thicker/thinner sand bundles marked by reactivation surfaces and/or mud drapes); and (iii) presence of widespread channel deposits. This estuarine fill consists of three stratigraphic units (Units 1-3): (1) Unit 1—shoaling shoreline (SH) and tidal channel (CH); (2) Unit 2—shoaling shoreline (SH), tidal channel (CH) facies associations, lagoon (LG), and flood-tidal delta/washover (FTD/W) facies associations; and (3) Unit 3—tidal channel (CH), estuarine bay (EB), and fluvial-influenced channel (FCH) facies associations. The individual units internally show a dominantly prograding character, a pattern also reflected throughout the succession by the overall upward stacking of units showing successively more restricted conditions. These characteristics, combined with the position in the uppermost portion of the valley fill succession, led to suggest that the deposits exposed in the study area likely formed during the transition from rising to highstand stages of relative sea level. Mapping of regionally significant discontinuity surfaces led to the recognition of a sequence boundary (i.e. discontinuity surface DS1) marked by erosion and subaerial exposure at the valley floor. This surface separates the Miocene succession from underlying Cretaceous rocks, and it is attributed to a major period of incision that led to the genesis of the incised valley during relative sea level fall. Unit 1 onlaps against DS1 and is

  19. Spinal Osteosarcoma

    PubMed Central

    Katonis, P.; Datsis, G.; Karantanas, A.; Kampouroglou, A.; Lianoudakis, S.; Licoudis, S.; Papoutsopoulou, E.; Alpantaki, K.

    2013-01-01

    Although osteosarcoma represents the second most common primary bone tumor, spinal involvement is rare, accounting for 3%–5% of all osteosarcomas. The most frequent symptom of osteosarcoma is pain, which appears in almost all patients, whereas more than 70% exhibit neurologic deficit. At a molecular level, it is a tumor of great genetic complexity and several genetic disorders have been associated with its appearance. Early diagnosis and careful surgical staging are the most important factors in accomplishing sufficient management. Even though overall prognosis remains poor, en-block tumor removal combined with adjuvant radiotherapy and chemotherapy is currently the treatment of choice. This paper outlines histopathological classification, epidemiology, diagnostic procedures, and current concepts of management of spinal osteosarcoma. PMID:24179411

  20. Spinal Bracing

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Dr. Arthur Copes of the Copes Foundation, Baton Rouge, LA, says that 35 percent of the 50 technical reports he received from the NASA/Southern University Industrial Applications Center in Baton Rouge and the Central Industrial Applications Center, Durant, OK, were vital to the development of his Copes Scoliosis Braces, which are custom designed and feature a novel pneumatic bladder that exerts constant corrective pressure to the torso to slowly reduce or eliminate the spinal curve.

  1. Spinal Cord Injury

    MedlinePlus

    ... Types of illnesses and disabilities Spinal cord injury Spinal cord injury Read advice from Dr. Jeffrey Rabin , a ... your health on a daily basis. Living with spinal cord injury — your questions answered top What are pediatric ...

  2. Tethered Spinal Cord Syndrome

    MedlinePlus

    ... the movement of the spinal cord within the spinal column. Attachments may occur congenitally at the base of ... or may be due to narrowing of the spinal column (stenosis) with age. Tethering may also develop after ...

  3. Spinal Cord Injury Map

    MedlinePlus

    ... Counseling About Blog Facing Disability Jeff Shannon Donate Spinal Cord Injury Map Loss of function depends on what ... control. Learn more about spinal cord injuries. A spinal cord injury affects the entire family FacingDisability is designed ...

  4. Spinal injury - resources

    MedlinePlus

    Resources - spinal injury ... The following organizations are good resources for information on spinal injury : National Institute of Neurological Disorders and Stroke -- www.ninds.nih.gov/Disorders/All-Disorders/Spinal-Cord- ...

  5. Far-infrared Study of High Velocity Ejecta Associated with Cold Dust in Young Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Rho, Jeonghee

    2014-10-01

    Whether supernovae (SNe) are a significant source of dust has been a long-standing debate. Large quantities of dust observed in high-redshift galaxies raises a fundamental astrophysical question of the origin of dust in the Universe, since AGB stars, which are thought to produce most interstellar dust in the modern Milky Way, are too old to have evolved in high-redshift galaxies. In contrast, SNe, the end point of massive stars, can occur within millions of years after the onset of star formation. Our Spitzer observations of the young supernova remnant (YSNR) Cas A revealed that the ejecta maps show a remarkable similarity to the dust maps, confirming for the first time that significant quantities of dust forms in SN ejecta. The shape and composition of the dust continuum and type of dust is closely correlated with the nucleosynthetic layers of different heavy elements in the ejecta lines. Recent Herschel observations of YSNRs including Crab Nebula, Cas A, SN 1987A and G54.1+0.3 further confirmed that SNe are important dust factories. These results imply that SN dust could be responsible for the large dust masses detected in high redshift galaxies and in galaxies today, but only a handful of such observations exist, and it is not clear how much of this dust was formed in the previous stellar wind phase. Identifying SN ejecta and examining its physical conditions are the fundamental steps in developing an understanding of dust formation and dust evolution in ejecta. We searched for high velocity ejecta emission from ISO/LWS archival data, and identified four young SNRs which exhibit evidence for such emission in their spectra (G21.5-0.9, G54.1+0.3, MSH 11-54, and MSH15-52). These SNRs form a valuable sample for the study of cold dust emission from SNRs: in fact, we have studied such emission from these sources using Herschel archival imaging data, and so far two of these SNRs indeed feature a significant amount of dust in ejecta. The far-infrared ISO detected high

  6. Spinal surgery -- cervical - series (image)

    MedlinePlus

    The cervical spinal column is made up of vertebral bodies which protect the spinal cord. ... spinal nerves, trauma, and narrowing (stenosis) of the spinal column around the spinal cord. Symptoms of cervical spine ...

  7. High-velocity, high-excitation neutral carbon in a cloud in the Vela supernova remnant

    NASA Technical Reports Server (NTRS)

    Jenkins, Edward B.; Wallerstein, George

    1995-01-01

    HD 72089 is situated behind the Vela supernova remnant, and the interstellar absorption lines in the spectrum of this star are remarkable for two reasons. First, there are six distinct velocity components that span the (heliocentric) velocity range -60 to +121 km/s in the lines of Na I and Ca II. Second, two of the components at high velocity, one at +85 km/s and another at +121.5 km/s, have densities that are large enough to produce observable lines from neutral carbon. The gas moving at +121.5 km/s has such a large pressure that the excited fine-structure levels of the ground electronic state of C I are collisionally populated nearly in proportion to their level degeneracies. This high-velocity gas exhibits unusually low column densities of Mg I and Na I, compared to that of C I. We propose that the +121.5 km/s component represents gas that has cooled and recombined in a zone that follows a shock driven into a cloud by the very recent passage of a supernova blast wave. A representative preshock density of n(sub H) approximately = 13/cc and velocity v(sub s) = 100 km/s is indicated by the strength of diffuse (O III) emission lines seen in directions very near HD 72089. The strong collisional population of excited C I and apparent absence of excited levels of O I give a most favorable fit to the conditions 1000 less than n(sub H) less than 2900/cc over a temperature range 300 less than T less than 1000 K. The fact that the compression is not substantially more than this indicates that the preshock gas may have had an embedded, transverse magnetic field with a strength B greater than or approximately = 1 micro-G. The large dynamical pressure of the supernova blast wave that would be needed to create the cloud shock that we describe implies that the energy of the supernova was 8 x 10(exp 51) ergs, if the Vela remnant is 500 pc away. We can bring this value much closer to typical supernova energies E less than or approximately = 10(exp 51) ergs if the distance to the

  8. Effects of High-Velocity Resistance Training on Athletic Performance in Prepuberal Male Soccer Athletes.

    PubMed

    Negra, Yassine; Chaabene, Helmi; Hammami, Mehréz; Hachana, Younés; Granacher, Urs

    2016-12-01

    Negra, Y, Chaabene, H, Hammami, M, Hachana, Y, and Granacher, U. Effects of high-velocity resistance training on athletic performance in prepuberal male soccer athletes. J Strength Cond Res 30(12): 3290-3297, 2016-The aim of this study was to assess the effectiveness of a 12-week in-season low-to-moderate load high-velocity resistance training (HVRT) in addition to soccer training as compared with soccer training only on proxies of athletic performance in prepubertal soccer players. Twenty-four male soccer players performed 2 different protocols: (a) regular soccer training with 5 sessions per week (n = 11; age = 12.7 ± 0.3 years) and (b) regular soccer training with 3 sessions per week and HVRT with 2 sessions per week (n = 13; age = 12.8 ± 0.2 years). The outcome measures included tests for the assessment of muscle strength (e.g., 1 repetition maximum [1RM] half-squat tests), jump ability (e.g., countermovement jump, squat jump [SJ], standing long jump [SLJ], and multiple 5-bound tests [MB5s]), linear speed (e.g., 5-, 10-, 20-, and 30-m sprint tests), and change of direction (e.g., T-test and Illinois change of direction test). Results revealed significant group × test interactions for the SJ test (p ≤ 0.05, d = 0.59) and the SLJ test (p < 0.01, d = 0.83). Post hoc tests illustrated significant pre-post changes in the HVRT group (SJ: [INCREMENT]22%, p < 0.001, d = 1.26; SLJ: [INCREMENT]15%, p < 0.001, d = 1.30) but not in the control group. In addition, tendencies toward significant interaction effects were found for the 1RM half-squat (p = 0.08, d = 0.54) and the 10-m sprint test (p = 0.06, d = 0.57). Significant pre-post changes were found for both parameters in the HVRT group only (1RM: [INCREMENT]25%, p < 0.001, d = 1.23; 10-m sprint: [INCREMENT]7%, p < 0.0001, d = 1.47). In summary, in-season low-to-moderate load HVRT conducted in combination with regular soccer training is a safe and feasible intervention that has positive effects on maximal strength

  9. High-velocity stimulation evokes "dense" population response in layer 2/3 vibrissal cortex.

    PubMed

    Ranjbar-Slamloo, Yadollah; Arabzadeh, Ehsan

    2017-03-01

    Supragranular layers of sensory cortex are known to exhibit sparse firing. In rodent vibrissal cortex, a small fraction of neurons in layer 2 and 3 (L2/3) respond to whisker stimulation. In this study, we combined whole cell recording and two-photon imaging in anesthetized mice and quantified the synaptic response and spiking profile of L2/3 neurons. Previous literature has shown that neurons across layers of vibrissal cortex are tuned to the velocity of whisker movement. We therefore used a broad range of stimuli that included the standard range of velocities (0-1.2 deg/ms) and extended to a "sharp" high-velocity deflection (3.8 deg/ms). Consistent with previous literature, whole cell recording revealed a sparse response to the standard range of velocities: although all recorded cells showed tuning to velocity in their postsynaptic potentials, only a small fraction produced stimulus-evoked spikes. In contrast, the sharp stimulus evoked reliable spiking in the majority of neurons. The action potential threshold of spikes evoked by the sharp stimulus was significantly lower than that of the spontaneous spikes. Juxtacellular recordings confirmed that application of sharp stimulus to single or multiple whiskers produced temporally precise spiking with minimal trial-to-trial spike count variability (Fano factors equal or close to the theoretical minimum). Two-photon imaging further confirmed that most neurons that were not responsive to the standard deflections responded to the sharp stimulus. Altogether, our results indicate that sparseness in L2/3 cortex depends on the choice of stimulus: strong single- or multiwhisker stimulation can induce the transition from sparse to "dense" population response.NEW & NOTEWORTHY In superficial layers of sensory cortex, only a small fraction of neurons fire most of the spontaneous and sensory evoked spikes. However, the functional relevance of such "sparse" activity remains unknown. We found that a "dense" population response is

  10. The StEllar Counterparts of COmpact high velocity clouds (SECCO) survey. I. Photos of ghosts

    NASA Astrophysics Data System (ADS)

    Bellazzini, M.; Beccari, G.; Battaglia, G.; Martin, N.; Testa, V.; Ibata, R.; Correnti, M.; Cusano, F.; Sani, E.

    2015-03-01

    We present an imaging survey that searches for the stellar counterparts of recently discovered ultra-compact high-velocity H i clouds (UCHVC). It has been proposed that these clouds are candidate mini-haloes in the Local Group and its surroundings within a distance range of 0.25-2.0 Mpc. Using the Large Binocular Telescope we obtained wide-field (≃ 23' × 23') g- and r-band images of the twenty-five most promising and most compact clouds amongst the fifty-nine that have been identified. Careful visual inspection of all the images does not reveal any stellar counterpart that even slightly resembles Leo P, the only local dwarf galaxy that was found as a counterpart to a previously detected high-velocity cloud. Only a possible distant (D> 3.0 Mpc) counterpart to HVC274.68+74.70-123 has been identified in our images. The point source photometry in the central 17.3' × 7.7' chips reaches r ≤ 26.5 and is expected to contain most of the stellar counterparts to the UCHVCs. However, no obvious stellar over-density is detected in any of our fields, in marked contrast to our comparison Leo P field, in which the dwarf galaxy is detected at a >30σ-significance level. Only HVC352.45+59.06+263 may be associated with a weak over-density, whose nature cannot be ascertained with our data. Sensitivity tests show that our survey would have detected any dwarf galaxy dominated by an old stellar population, with an integrated absolute magnitude of MV ≤ - 8.0 and a half-light radius of rh ≤ 300 pc that lies within 1.5 Mpc of us, thereby confirming that it is unlikely that the observed UCHVCs are associated with the stellar counterparts typical of known Local Group dwarf galaxies. Based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration amongst institutions in the United States, Italy, and Germany. LBT Corporation partners are The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica

  11. A dynamic study of fragmentation and energy loss during high velocity impact

    NASA Technical Reports Server (NTRS)

    Zee, Ralph H.

    1992-01-01

    Research conducted under this contract can be divided into two main areas: hypervelocity (in the range up to 7 km/s) and high velocity (less than 1 km/s). Work in the former was performed at NASA-MSFC using the Light Gas Gun Facility. The lower velocity studies were conducted at Auburn University using the ballistic gun. The emphasis of the project was on the hypervelocity phenomenon especially in the characterization of the debris cloud formed by the primary impact events. Special devices were made to determine the angular distributions of momentum and energy of the debris cloud as a function of impact conditions. After several iteration processes, it was decided to concentrate on the momentum effort. Prototype devices were designed, fabricated, and tested. These devices were based on the conservation of momentum. Distributions of the debris cloud formed were measured by determining the amount of momentum transferred from the debris cloud to strategically placed pendulum measurement devices. The motion of the pendula was monitored using itegrated opto-interrupters. The distribution of momentum in the debris cloud was found to be a strong function of the impact condition. Small projectiles at high velocities were observed to produce finely dispersed debris whereas large projectiles generated discrete particles in the debris. Results also show that the momentum in the forward direction was enhanced due to the impact. This phenomenon of momentum multiplication was also observed in other studies and in computer simulations. It was initially planned to determine the energy distribution using deformation energy in a rod with strain gauges. Results from preliminary studies show that this technique is acceptable but too tedious. A new technique was explored based on measuring the heating effect of the debris cloud using an IR camera. The feasibility and sensitivity was established at Auburn University. This type of energy distribution measurement method can easily be

  12. Formation and transformation of amino acids and amino acid precursors by high-velocity impacts

    NASA Astrophysics Data System (ADS)

    Kaneko, T.; Kobayashi, K.; Yamori, A.

    A wide variety of organic compounds have been found in extraterrestrial bodies such as comets and carbonaceous chondrites. It is plausible that these extraterrestrial bodies carried organic compounds such as amino acids or their precursors to the early Earth. It is claimed, however, that these extraterrestrial organics were destroyed during impacts to the Earth. We therefore examined possible transformation of amino acids and their precursors during high-velocity impacts by using a rail gun "HYPAC" in ISAS. Starting materials used in the impact experiments were (i) aqueous solution of glycine (10 mM or 1.0 M), and (ii) a mixture of ammonia, methanol and water. The target materials were sealed in stainless steel capsules, and shocked by impact with a polycarbonate projectile accelerated with "HYPAC" to the velocities of 2.5 - 7.0 km/s. A part of the products was acid-hydrolyzed. Both hydrolyzed an unhydrolyzed products were analyzed by mass spectrometry, high performance liquid chromatography and capillary electrophoresis and chromatography. When an aqueous solution containing ammonia, methanol and water was shocked by impact at the velocity of 6.4 km/s, a number of amino acids (e.g., serine and glycine) were detected after hydrolysis. The present results suggest that amino acid precursors could be formed during cometary impacts. When glycine solution was used as a starting material, about 40 % of glycine was recovered even after 6 km/s impact. Methylamine and ammonia, which are known as pyrolytic products of glycine, were detected, besides them, diketopiperazine and an unidentified product whose molecular weight was 134, were detected, while no glycine peptides were identified in them. It was shown that the impact processes resulted in the formation of amino acid condensates. Thermal stability of glycine precursor is comparable with glycine. The present results suggest that organic material could survive and/or formed during an impact process. Most of organic

  13. Study of mechanisms of electric field-induced DNA transfection. II. Transfection by low-amplitude, low-frequency alternating electric fields.

    PubMed

    Xie, T D; Tsong, T Y

    1990-10-01

    Electroporation for DNA transfection generally uses short intense electric pulses (direct current of kilovolts per centimeter, microseconds to milliseconds), or intense dc shifted radio-frequency oscillating fields. These methods, while remarkably effective, often cause death of certain cell populations. Previously it was shown that a completely reversible, high ionic permeation state of membranes could be induced by a low-frequency alternating electric field (ac) with a strength one-tenth, or less, of the critical breakdown voltage of the cell membrane (Teissie, J., and T. Y. Tsong. 1981. J. Physiol. (Paris). 77:1043-1053). We report the transfection of E. coli (JM105) by plasmid PUC18 DNA, which carries an ampicillin-resistance gene, using low-amplitude, low-frequency ac fields. E. coli transformants confer the ampicillin resistance and the efficiency of the transfection can be conveniently assayed by counting colonies in a selection medium containing ampicillin. For the range of ac fields employed (peak-to-peak amplitude 50-200 V/cm, frequency 0.1 Hz-1 MHz, duration 1-100 s), 100% of the E. coli survived the electric field treatment. Transfection efficiencies varied with field strength and frequency, and as high as 1 x 10(5)/micrograms DNA was obtained with a 200 V/cm square wave, 1 Hz ac field, 30 s exposure time, when the DNA/cell ratio was 50-75. Control samples gave a background transfection of much less than 10/micrograms DNA. With a square wave ac field, the transfection efficiency showed a frequency window: the optimal frequency was 1 Hz with a 200 V/cm field, and was approximately 0.1 Hz with a 50 V/cm field. Transfection efficiency varied with the waveform: square wave > sine wave > triangle wave. If the DNA was added after the ac field was turned off, transfection efficiency was reduced to the background level within 1 min. The field intensity used in this study was low and insufficient to cause electric breakdown of cell membranes. Thus, DNA

  14. High-Velocity Ly(Alpha) Emission from SMR 1987A

    NASA Technical Reports Server (NTRS)

    Michael, Eli; McCray, Richard; Borkowski, Kazimierz J.; Pun, Chu S. J.; Sonneborn, George

    1998-01-01

    The high-velocity Ly(Alpha) emission from SN 1987A observed with the Space Telescope Imaging Spectrograph (STIS) evidently comes from a reverse shock formed where the outer envelope of SN 1987A strikes ionized gas inside the inner circumstellar ring. The observations can be explained by a simple kinematic model, in which the Ly(Alpha) emission comes from hydrogen atoms with radial velocity approximately 15,000 km s(exp -1) crossing a reverse shock in the shape of a slightly prolate ellipsoid with equatorial radius 4.8 x 10(exp 17) cm or approximately 80% of the distance to the inner surface of the inner ring. N v double Lambda 1239, 1243 emission, if present, has a net luminosity approximately less than 30% times that of the Ly(Alpha) emission. Future STIS observations should enable us to predict the time of impact with the inner ring and to determine unambiguously whether or not N v emission is present. These observations will offer a unique opportunity to probe the structure of SN 1987A's circumstellar environment and the hydrodynamics and kinetics of very fast shocks.

  15. Searching for Dark Matter Annihilation in the Smith High-Velocity Cloud

    NASA Technical Reports Server (NTRS)

    Drlica-Wagner, Alex; Gomez-Vargas, German A.; Hewitt, John W.; Linden, Tim; Tibaldo, Luigi

    2014-01-01

    Recent observations suggest that some high-velocity clouds may be confined by massive dark matter halos. In particular, the proximity and proposed dark matter content of the Smith Cloud make it a tempting target for the indirect detection of dark matter annihilation. We argue that the Smith Cloud may be a better target than some Milky Way dwarf spheroidal satellite galaxies and use gamma-ray observations from the Fermi Large Area Telescope to search for a dark matter annihilation signal. No significant gamma-ray excess is found coincident with the Smith Cloud, and we set strong limits on the dark matter annihilation cross section assuming a spatially extended dark matter profile consistent with dynamical modeling of the Smith Cloud. Notably, these limits exclude the canonical thermal relic cross section (approximately 3 x 10 (sup -26) cubic centimeters per second) for dark matter masses less than or approximately 30 gigaelectronvolts annihilating via the B/B- bar oscillation or tau/antitau channels for certain assumptions of the dark matter density profile; however, uncertainties in the dark matter content of the Smith Cloud may significantly weaken these constraints.

  16. The Smith Stream: A High Velocity Cloud crossing the Milky Way Disk

    NASA Astrophysics Data System (ADS)

    Lockman, Felix J.

    2012-05-01

    The Smith Cloud is a high-velocity HI cloud with the following extraordinary properties: it is located about 12 kpc from the Sun but less than 8 kpc from the Galactic Center, and it's tip is currently about 2 kpc below the Galactic plane. Its complete space motion is known and it is on a trajectory to cross the Galactic plane in about 30 Myr. Its size is >3 x >1 kpc, and it contains more than two million solar masses of ionized and neutral Hydrogen. Recent new HI observations with the NRAO Green Bank Telescope have revealed a series of small HI clouds over an area ahead of the Smith Cloud that have kinematics and locations consistent with following the same trajectory as the Cloud. Their spectra suggests that they are interacting strongly with the local ISM. The implication is that that the Smith Cloud is the largest object along a stream of gas more than 6 kpc in extent, some of which has already passed through the Galactic plane. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under a cooperative agreement by Associated Universities, Inc.

  17. VLA Observations of the Magnetic Field of the Smith High Velocity Cloud

    NASA Astrophysics Data System (ADS)

    Betti, Sarah; Hill, Alex S.; Mao, Sui Ann; McClure-Griffiths, Naomi M.; Lockman, Felix J.; Benjamin, Robert A.; Gaensler, Bryan M.

    2017-01-01

    High velocity clouds (HVCs) are hydrogen gas clouds around galaxies with velocities inconsistent with Galactic rotation. HVCs may fuel future star formation and drive galaxy evolution. The Smith Cloud is an HVC with an orbit suggesting it has made at least one passage through the disk. A measured magnetic field suggests how it survived passage through the Galactic halo. The Faraday rotation measure (RM) provides information about the strength and direction of the magnetic field. We use the Karl G. Jansky Very Large Array (VLA) to obtain reliable RMs towards ~950 background point sources to measure the geometry of the magnetic field of the Smith Cloud. These RMs constrain the strength of the magnetic field at the head, tail, and body of the Smith Cloud while RMs directly behind the Smith Cloud suggest there is ionized gas associated with the cloud that has not previously been detected. The confirmation of the magnetic field of the Smith Cloud along with a detailed morphology of the magnetic field structure will constrain how HVCs pass through the Galactic halo without losing their gas and survive the passage through the intergalactic and interstellar media.

  18. Production of a high-velocity water slug using an impacting technique.

    PubMed

    Dehkhoda, S; Bourne, N K

    2014-02-01

    A pulsed water jet consists of a series of discrete water slugs travelling at high velocity. Immediately after striking a target, these slugs apply high-intensity, short-duration transient stress pulses reaching an amplitude known as the water hammer pressure, followed by low-intensity, long-duration stationary stress at a lower stagnation pressure. The magnitude and duration of the water hammer and stagnation pressures are controlled by the size and quality of the water slugs. The use of water jets for rock cutting in mining operations is a centuries-old technology; however, practical methods for producing high-energy water slugs repeatedly have proven difficult. This can be partly due to the fact that the geometrical properties of a jet and so its effectiveness in creating damage is controlled and influenced by the method that is employed to generate the water slugs. This paper investigates the quality of a single water slug produced using an impacting technique where a hammer strikes a piston, resting on top of a water-filled chamber. The coherence and integrity of the jet core was of concern in this study. The impact impulse of the formed water jet was measured in a Kel-F target material using an embedded PVDF (Polyvinylidene fluoride) shock gauge. The recorded stress waveform was then used to determine the unity and endurance of the water slug stream once travelled through air.

  19. Effect of Operating Parameters on a Dual-Stage High Velocity Oxygen Fuel Thermal Spray System

    NASA Astrophysics Data System (ADS)

    Khan, Mohammed N.; Shamim, Tariq

    2014-08-01

    High velocity oxygen fuel (HVOF) thermal spray systems are being used to apply coatings to prevent surface degradation. The coatings of temperature sensitive materials such as titanium and copper, which have very low melting points, cannot be applied using a single-stage HVOF system. Therefore, a dual-stage HVOF system has been introduced and modeled computationally. The dual-spray system provides an easy control of particle oxidation by introducing a mixing chamber. In addition to the materials being sprayed, the thermal spray coating quality depends to a large extent on flow behavior of reacting gases and the particle dynamics. The present study investigates the influence of various operating parameters on the performance of a dual-stage thermal spray gun. The objective is to develop a predictive understanding of various parameters. The gas flow field and the free jet are modeled by considering the conservation of mass, momentum, and energy with the turbulence and the equilibrium combustion sub models. The particle phase is decoupled from the gas phase due to very low particle volume fractions. The results demonstrate the advantage of a dual-stage system over a single-stage system especially for the deposition of temperature sensitive materials.

  20. The collision of high-velocity clouds with a galactic disk

    NASA Technical Reports Server (NTRS)

    Tenorio-Tagle, G.; Bodenheimer, P.; Rozyczka, M.; Franco, J.

    1986-01-01

    Two-dimensional hydrodynamic simulations for the interaction of high-velocity clouds with a galactic disk are presented. The impinging clouds are assumed to be spherical and the target disk is represented by a constant density slab, n(g) = 1/cu cm, with a total width W(g) = 200 pc. The numerical experiments cover a wide range of cloud densities, between 0.1 and 100/cu cm, and velocities between 100 and 300 km/s. At a time approximately 10 to the 7th yr after impact, two types of final configurations are found. In the first case, the infalling cloud is completely shocked in a time short compared with the crossing time of the disk. Then, the generated cavity has time to grow sideways and large scale structures with a round shape, and in some cases nearly spherical, are produced. In the second case, which occurs for high density clouds, the cloud is shocked on a time scale longer than or comparable to the crossing time. The resultant cylindrical holes drilled across the entire disk have the dimensions of the impinging cloud. Cloud-galaxy interactions are compared with other energy sources and the morphologies of the resultant structures are suggested to resemble the large scale structures observed in H I.

  1. Suspension High Velocity Oxy-Fuel (SHVOF)-Sprayed Alumina Coatings: Microstructure, Nanoindentation and Wear

    NASA Astrophysics Data System (ADS)

    Murray, J. W.; Ang, A. S. M.; Pala, Z.; Shaw, E. C.; Hussain, T.

    2016-12-01

    Suspension high velocity oxy-fuel spraying can be used to produce thermally sprayed coatings from powdered feedstocks too small to be processed by mechanical feeders, allowing formation of nanostructured coatings with improved density and mechanical properties. Here, alumina coatings were produced from submicron-sized feedstock in aqueous suspension, using two flame combustion parameters yielding contrasting microstructures. Both coatings were tested in dry sliding wear conditions with an alumina counterbody. The coating processed with high combustion power of 101 kW contained 74 wt.% amorphous phase and 26 wt.% crystalline phase (95 wt.% gamma and 3 wt.% alpha alumina), while the 72-kW coating contained lower 58 wt.% amorphous phase and 42 wt.% crystalline phases (73 wt.% was alpha and 26 wt.% gamma). The 101-kW coating had a dry sliding specific wear rate between 4 and 4.5 × 10-5 mm3/Nm, 2 orders of magnitude higher than the 72-kW coating wear rate of 2-4.2 × 10-7 mm3/Nm. A severe wear regime dominated by brittle fracture and grain pullout of the coating was responsible for the wear of the 101-kW coating, explained by mean fracture toughness three times lower than the 72-kW coating, owing to the almost complete absence of alpha alumina.

  2. The Smith Cloud: A High-Velocity Cloud Colliding with the Milky Way

    NASA Astrophysics Data System (ADS)

    Lockman, Felix J.; Benjamin, Robert A.; Heroux, A. J.; Langston, Glen I.

    2008-05-01

    New 21 cm H I observations made with the Green Bank Telescope show that the high-velocity cloud known as the Smith Cloud has a striking cometary appearance and many indications of interaction with the Galactic interstellar medium. The velocities of interaction give a kinematic distance of 12.4 +/- 1.3 kpc, consistent with the distance derived from other methods. The Cloud is >3 × 1 kpc in size, and its tip at (l, b) ≈ 39°, -13° is 7.6 kpc from the Galactic center and 2.9 kpc below the Galactic plane. It has >106 M⊙ in H I. Its leading section has a total space velocity near 300 km s-1, is moving toward the Galactic plane with a velocity of 73 +/- 26 km s-1, and is shedding material to the Galaxy. In the absence of drag, the Cloud will cross the plane in about 27 Myr. The Smith Cloud may be an example of the accretion of gas by the Milky Way that is needed to explain certain persistant anomalies in Galactic chemical evolution.

  3. Smith's Cloud: A High Velocity HI Cloud Entering The Galactic Disk

    NASA Astrophysics Data System (ADS)

    Lockman, Felix J.; Benjamin, R. A.; Heroux, A.; Langston, G. I.

    2007-12-01

    HI observations using the Green Bank Telescope at 21cm of the high-velocity cloud known as Smith's Cloud show that it has a large, cometary morphology pointing toward the Galactic disk, and shows clear signs of interaction with the Milky Way. From the velocity range of the interaction we can estimate the rest velocity of the ambient medium into which Smith's Cloud moves. This gives a kinematic distance to the interaction site of 12 kpc, a value which is essentially identical to other distance estimates for the cloud. The main portion of Smith's Cloud is located about 3 kpc below the Galactic plane and only 7.6 kpc from the Galactic center. Its total extent is more than 3 kpc. It is bring more than a million solar masses of gas to the star-forming regions of the inner Galaxy. From the projected differential velocity of the cloud we can estimate its trajectory: its total space velocity appears to be at least 275 km/s and it has a peculiar velocity with respect to its environment of at least 95 km/s.

  4. Episodic High-velocity Outflows from V899 Mon: A Constraint On The Outflow Mechanisms

    NASA Astrophysics Data System (ADS)

    Ninan, J. P.; Ojha, D. K.; Philip, N. S.

    2016-07-01

    We report the detection of large variations in the outflow wind velocity from a young eruptive star, V899 Mon, during its ongoing high accretion outburst phase. Such large variations in the outflow velocity (from -722 to -425 km s-1) have never been reported previously in this family of objects. Our continuous monitoring of this source shows that the multi-component, clumpy, and episodic high velocity outflows are stable in the timescale of a few days, and vary over the timescale of a few weeks to months. We detect significant decoupling in the instantaneous outflow strength to accretion rate. From the comparison of various possible outflow mechanisms in magnetospheric accretion of young stellar objects, we conclude magnetically driven polar winds to be the most consistent mechanism for the outflows seen in V899 Mon. The large scale fluctuations in outflow over the short period makes V899 Mon the most ideal source to constrain various magnetohydrodynamics simulations of magnetospheric accretion. Based on observations made with the Southern African Large Telescope (SALT).

  5. Studying counterstreaming high velocity plasma flows relevant to astrophysical collisionless shock

    NASA Astrophysics Data System (ADS)

    Ross, James Steven; Amendt, Peter; Divol, Laurent; Pollock, Brad; Remington, Bruce; Ryutov, Dmitri; rozmus, Wojciech; Turnbull, David; Froula, Dustin; morita, taichi; Sakawa, Youichi; Takabe, Hideke; Drake, R. Paul; Kuranz, Carolyn C.; Gregori, Gianluca; Meinecke, Jena; Koenig, Michel; Spitkovsky, Anatoly; Park, Hye-Sook

    2015-08-01

    In a broad range of low-density astrophysical plasmas the flow has a high Mach number, making the ion-ion collisional mean free path very large compared to the scale lengths of various observed astrophysical shocks. These shocks are believed to be “collisionless,” driven by plasma instabilities and self-generated magnetic fields. A series of experiments at the NIF and Omega laser facilities is underway to study the formation of collisionless shocks under scaled laboratory conditions, using high velocity counterstreaming and interpenetrating plasma flows. Double CH2, and CH/CD planar foils have been irradiated with a laser intensity of ~1016 W/cm2. The laser-ablated plasma between the two foils was characterized using a suite of diagnostics, including Thomson scattering and x-ray radiography. On the Omega laser facility clear interpenetration and instability growth are observed, although our experimental conditions reached only ~50 ion skin depths (c/wpi) and were insufficient to fully form a collisionless shock. Initial NIF experimental results using 50x more laser energy than the Omega experiments will be presented.

  6. Microstructure of surface zones subjected to high-velocity parting-off

    NASA Astrophysics Data System (ADS)

    Ryttberg, K.; Knutson Wedel, M.; Dahlman, P.; Nyborg, L.

    2006-08-01

    A hydraulic high-velocity pressing machine with a parting-off tool was used for adiabatic cutting with impact velocities ranging from 5 to 10 m/s. In this study the associated fracture mechanisms and microstructures of three different materials (100Cr6, 100CrMn6 and C56) in the form of wire or bar were investigated. It was concluded that the parting-off is initiated through a shearing effect resulting in ductile shear fracture being responsible for the cutting. In all of the samples microcracks were found in the severely deformed region around the cut, which became larger with increasing sample diameter. Evidence of heating was not observed in the cut zone of samples having 6 mm diameter. However, for samples with a diameter of 70 mm and above, a white-etching band could be found, indicating that the temperature had increased considerably in this region. Analysis of the fracture surfaces using scanning optical microscopy showed that the fracture mode had mostly been ductile shear, with exception of the largest samples where some evidence of tensile fracture could be observed.

  7. Searching for dark matter annihilation in the Smith high-velocity cloud

    SciTech Connect

    Drlica-Wagner, Alex; Gómez-Vargas, Germán A.; Hewitt, John W.; Linden, Tim; Tibaldo, Luigi

    2014-07-20

    Recent observations suggest that some high-velocity clouds may be confined by massive dark matter halos. In particular, the proximity and proposed dark matter content of the Smith Cloud make it a tempting target for the indirect detection of dark matter annihilation. We argue that the Smith Cloud may be a better target than some Milky Way dwarf spheroidal satellite galaxies and use γ-ray observations from the Fermi Large Area Telescope to search for a dark matter annihilation signal. No significant γ-ray excess is found coincident with the Smith Cloud, and we set strong limits on the dark matter annihilation cross section assuming a spatially extended dark matter profile consistent with dynamical modeling of the Smith Cloud. Notably, these limits exclude the canonical thermal relic cross section (∼ 3 × 10{sup –26} cm{sup 3} s{sup –1}) for dark matter masses ≲ 30 GeV annihilating via the b b-bar or τ{sup +}τ{sup –} channels for certain assumptions of the dark matter density profile; however, uncertainties in the dark matter content of the Smith Cloud may significantly weaken these constraints.

  8. Radio jets and high velocity gas in the Seyfert Galaxy NGC 1068

    NASA Astrophysics Data System (ADS)

    Wilson, A. S.; Ulvestad, J. S.

    1983-12-01

    New, high sensitivity VLA maps of the central regions of NGC 1068 at 4.9 GHz (total intensity and linear polarization) and 15.0 GHz (total intensity only) are presented. As found by van der Hulst, Hummel, and Dickey (1982), the bright radio emission coincident with the galaxy nucleus is resolved into a bent triple of total extent 0.7 arcsec, with the central source apparently associated with the nucleus proper. It is found that the 13 arcsec scale linear source comprises oppositely directed radio jets feeding a 'hot spot' and radio lobes. The radio emission of the NE lobe seems to be concentrated near the surface of a conically shaped region, which is also closely associated with some of the high velocity, optical line emitting clouds, and may relate to a bow shock, blast wave, or cocoon of material shed by the jet as it propagates through the interstellar medium. Two models for the ionization of the optical clouds are discussed either ionizing photons eacape preferentially along the rotation axis of the disk which collimates the radio jets, or the excitation is effected by the kinetic energy of the jets or lobes themselves.

  9. Residual stresses in high-velocity oxy-fuel metallic coatings

    NASA Astrophysics Data System (ADS)

    Totemeier, T. C.; Wright, R. N.; Swank, W. D.

    2004-06-01

    X-ray based residual stress measurements were made on type 316 stainless steel and Fe3Al coatings that were high-velocity oxy-fuel (HVOF) sprayed onto low-carbon and stainless steel substrates. Nominal coating thicknesses varied from 250 to 1500 µm. The effect of HVOF spray particle velocity on residual stress and deposition efficiency was assessed by preparing coatings at three different torch chamber pressures. The effect of substrate thickness on residual stress was determined by spraying coatings onto thick (6.4 mm) and thin (1.4 mm) substrates. Residual stresses were compressive for both coating materials and increased in magnitude with spray velocity. For coatings applied to thick substrates, near-surface residual stresses were essentially constant with increasing coating thickness. Differences in thermal expansion coefficient between low-carbon and stainless steels led to a 180 MPa difference in residual stress for Fe3Al coatings. Deposition efficiency for both materials is maximized at an intermediate (˜600 m/s) velocity. Considerations for X-ray measurement of residual stresses in HVOF coatings are also presented.

  10. Fabry-Perot images of NGC 1275 and its puzzling high-velocity system

    NASA Technical Reports Server (NTRS)

    Caulet, Adeline; Woodgate, Bruce E.; Brown, Larry W.; Gull, Theodore R.; Hintzen, Paul; Lowenthal, James D.; Oliversen, Ronald J.; Ziegler, Michael M.

    1992-01-01

    The Fabry-Perot imager is used to obtain a velocity sequence of calibrated narrow-band CCD images to cover 3000 km/s velocity space between the redshifted H-alpha emission lines of NGC 1275, its extended associated system of low-velocity (LV) filaments, and the high-velocity (HV) system of knots, projected on the same line of sight in the sky. The lack of intermediate-velocity emission-line gas between the two systems leads to an upper limit of 1.5 x 10 exp -16 ergs/sq cm s sq arcsec (3 sigma) on stripped ionized gas due to the dynamical interaction between NGC 1275 and its HV companion galaxy. It also confirms previous reports that the level of continuum light arising from stellar and nonstellar sources must be very low in otherwise bright, strongly concentrated emission-line knots with unresolved diameters of 425/h pc. The H-alpha luminosities of the emission-line regions of the two systems were measured and star formation rates derived in order to investigate quantitatively the physical relation between the HV galaxy, NGC 1275, and the surrounding cooling flow filaments.

  11. Removal of interproximal dental biofilms by high-velocity water microdrops.

    PubMed

    Rmaile, A; Carugo, D; Capretto, L; Aspiras, M; De Jager, M; Ward, M; Stoodley, P

    2014-01-01

    The influence of the impact of a high-velocity water microdrop on the detachment of Streptococcus mutans UA159 biofilms from the interproximal (IP) space of teeth in a training typodont was studied experimentally and computationally. Twelve-day-old S. mutans biofilms in the IP space were exposed to a prototype AirFloss delivering 115 µL water at a maximum exit velocity of 60 m/sec in a 30-msec burst. Using confocal microscopy and image analysis, we obtained quantitative measurements of the percentage removal of biofilms from different locations in the IP space. The 3D geometry of the typodont and the IP spaces was obtained by micro-computed tomography (µ-CT) imaging. We performed computational fluid dynamics (CFD) simulations to calculate the wall shear stress (τw ) distribution caused by the drops on the tooth surface. A qualitative agreement and a quantitative relationship between experiments and simulations were achieved. The wall shear stress (τw ) generated by the prototype AirFloss and its spatial distribution on the teeth surface played a key role in dictating the efficacy of biofilm removal in the IP space.

  12. Fabricating Aluminum Bronze Rotating Band for Large-Caliber Projectiles by High Velocity Arc Spraying

    NASA Astrophysics Data System (ADS)

    Wu, Bin; Fang, Ling-hui; Chen, Xiao-lei; Zou, Zhi-qiang; Yu, Xu-hua; Chen, Gang

    2014-02-01

    The necessity of finding new rotating band materials and developing corresponding joining technologies for large-caliber projectiles has been revealed by the recent increase in the ballistic performance of high loads. In this paper, aluminum bronze coatings were fabricated by the high velocity arc spraying (HVAS) technique. Microstructure and microhardness of the prepared coatings were investigated. Ring-on-disk dry sliding wear tests were conducted in an ambient condition to examine the tribological behavior of the coatings. Quasi-static engraving processes of rotating bands made of as-sprayed aluminum bronze coating and bulk copper were studied using rate-controlled push test methodology on an MTS 810 Material Testing System. The results show that the as-sprayed aluminum bronze coatings have a dense microstructure with porosity of about 1.6%. Meanwhile, the as-sprayed coating presents a higher microhardness than pure copper. The friction coefficient of coatings is about 0.2-0.3 in the steady state. Tribological mechanisms of the as-sprayed coatings were discussed. The engraving test results show that the aluminum bronze rotating band presents high bonding strength and good plasticity. The HVAS aluminum bronze coating should be a possible substitute for the state-of-the-art copper rotating band.

  13. Abrasive wear of high velocity oxygen fuel (HVOF) superalloy coatings under vibration load

    NASA Astrophysics Data System (ADS)

    Kandeva, M.; Ivanova, B.; Karastoyanov, D.; Grozdanova, T.; Assenova, E.

    2017-02-01

    The present paper considers wear of coatings deposited by HVOF (High velocity oxy-fuel) technology, under conditions of dry friction against abrasive surface accompanied with the action of vibrations perpendicular to the sliding axis. Results are obtained with four type coatings: two types with Ni matrix of composition 602P – without preliminary heating of the basic surface (the substrate) and after substrate heating up to 650°C in a chamber; coating WC-12Co with tungsten matrix and coating obtained by 1:1 proportion powder mixture of both compositions 602P and WC-12Co. Results about the thickness, hardness and coating’ morphology are presented, as well as dependences of the wear and the relative wear resistance on vibration speeds in the interval 3.03 to 21.08 mm/s. New results are obtained about the nonlinear relationship between abrasive wear and vibration speed showing minimal wear for all specimens by 6.04 mm/s. It is found that lowest wear shows WC-12Co coating in the entire interval of vibration speed variation: 3.03 to 21.08 mm/s. The obtained results are new in the literature; they are not presented and published by the authors.

  14. High velocity features in Type Ia supernovae via interaction with circumstellar shell

    NASA Astrophysics Data System (ADS)

    Mulligan, Brian W.; Wheeler, J. Craig

    2015-01-01

    Observations of Type Ia supernovae (SN Ia) in the weeks before B-band maximum (Bmax) have shown the presence of Ca, Si, and Fe features with velocities of 8,000-14,000 km/s faster than that associated with the photospheric features (PSF). Suggestions for the source of the high velocity features include interaction of the ejecta with a circumstellar material. We perform hydrodynamic simulation of a supernova interacting with a shell consisting of 5×10-3 M⊙ of material and an outer radius of 0.028 R⊙ as well as a supernova in a low density circumstellar medium (LDCSM) without a shell. We present the synthetic spectra of the Ca II near-IR feature generated from both models fit to the observed features in SN 2011fe in the epoch before Bmax. The shell interaction model consistently fits the observed spectra better than the LDCSM model at all times before Bmax, and satisfies the observed velocity evolution of both the HVF and PSF.

  15. Analysis of a High Velocity Oxygen-Fuel (HVOF) thermal spray torch. Part 1, Numerical formulation

    SciTech Connect

    Oberkampf, W.L.; Talpallikar, M.

    1994-01-01

    The fluid and particle dynamics of a High Velocity Oxygen-Fuel (HVOF) torch are analyzed using computational fluid dynamic (CFD) techniques. The thermal spray device analyzed is similar to a Metco Diamond Jet torch with powder injection. The spray nozzle is axisymmetric with powder injection on the centerline, premixed fuel and oxygen fed from an annulus, and air cooling injected along the interior surface of the aircap. Choked flow conditions occur at the exit of the aircap and a supersonic, under-expanded jet develops externally. The CFD simulation assumes three injection streams (solid metal particles with argon as a carrier gas, premixed oxygen/fuel, and air) inside the aircap and solves the combusting two-phase flow until the external spray stream decays to sonic conditions. The numerical formulation solves the mass, momentum, and energy transfer for both the gas and particle phase and strongly couples each phase. The combustion process is modeled using approximate equilibrium chemistry with dissociation of the gas with a total of nine species. Melting and re-solidification of the metal panicles is modeled as a lumped-mass system. Turbulent flow is modeled by a two equation k-{epsilon} turbulence model, including compressibility effects on turbulent dissipation. A time iterative, implicit, finite volume numerical method is used to solve the partial differential equations. A companion paper [10] presents the results of the numerical simulation and gives a detailed discussion of the gas and panicle dynamics.

  16. H ii REGIONS WITHIN A COMPACT HIGH VELOCITY CLOUD. A NEARLY STARLESS DWARF GALAXY?

    SciTech Connect

    Bellazzini, M.; Magrini, L.; Mucciarelli, A.; Fraternali, F.; Ibata, R.; Martin, N.; Battaglia, G.; Testa, V.; Fumana, M.; Marchetti, A.; Correnti, M.

    2015-02-10

    Within the SECCO survey we identified a candidate stellar counterpart to the Ultra Compact High Velocity Cloud (UCHVC) HVC274.68+74.70-123 that was suggested by Adams et al. to be a possible mini halo within the Local Group of galaxies. The spectroscopic follow-up of the brightest sources within the candidate reveals the presence of two H ii regions whose radial velocity is compatible with a physical association with the UVHVC. The available data do not allow us to give a definite answer on the nature of the newly identified system. A few alternative hypotheses are discussed. However, the most likely possibility is that we have found a new faint dwarf galaxy residing in the Virgo cluster of galaxies, which we name SECCO 1. Independently of its actual distance, SECCO 1 displays a ratio of neutral hydrogen mass to V luminosity of M{sub H} {sub I}/L{sub V}≳20, by far the largest among local dwarfs. Hence, it appears to be a nearly starless galaxy and it may be an example of the missing links between normal dwarfs and the dark mini halos that are predicted to exist in large numbers according to the currently accepted cosmological model.

  17. Numerical Analysis of Multicomponent Suspension Droplets in High-Velocity Flame Spray Process

    NASA Astrophysics Data System (ADS)

    Gozali, Ebrahim; Mahrukh, Mahrukh; Gu, Sai; Kamnis, Spyros

    2014-08-01

    The liquid feedstock or suspension as a different mixture of liquid fuel ethanol and water is numerically studied in high-velocity suspension flame spray (HVSFS) process, and the results are compared for homogenous liquid feedstock of ethanol and water. The effects of mixture on droplet aerodynamic breakup, evaporation, combustion, and gas dynamics of HVSFS process are thoroughly investigated. The exact location where the particle heating is initiated (above the carrier liquid boiling point) can be controlled by increasing the water content in the mixture. In this way, the particle inflight time in the high-temperature gas regions can be adjusted avoiding adverse effects from surface chemical transformations. The mixture is modeled as a multicomponent droplet, and a convection/diffusion model, which takes into account the convective flow of evaporating material from droplet surface, is used to simulate the suspension evaporation. The model consists of several sub-models that include premixed combustion of propane-oxygen, non-premixed ethanol-oxygen combustion, modeling of multicomponent droplet breakup and evaporation, as well as heat and mass transfer between liquid droplets and gas phase.

  18. Variability of the high-velocity outflow in the quasar PDS 456

    SciTech Connect

    Reeves, J. N.; Gofford, J.; Costa, M.; Matzeu, G.; Braito, V.; Sim, S. A.; Behar, E.; Kaspi, S.; Miller, L.; O'Brien, P.; Turner, T. J.; Ward, M.

    2014-01-01

    We present a comparison of two Suzaku X-ray observations of the nearby (z = 0.184), luminous (L {sub bol} ∼ 10{sup 47} erg s{sup –1}) type I quasar, PDS 456. A new 125 ks Suzaku observation in 2011 caught the quasar during a period of low X-ray flux and with a hard X-ray spectrum, in contrast with a previous 190 ks Suzaku observation in 2007 when the quasar appeared brighter and had a steep (Γ > 2) X-ray spectrum. The 2011 X-ray spectrum contains a pronounced trough near 9 keV in the quasar rest frame, which can be modeled with blueshifted iron K-shell absorption, most likely from the He- and H-like transitions of iron. The absorption trough is observed at a similar rest-frame energy as in the earlier 2007 observation, which appears to confirm the existence of a persistent high-velocity wind in PDS 456, at an outflow velocity of 0.25-0.30c. The spectral variability between 2007 and 2011 can be accounted for by variations in a partial covering absorber, increasing in covering fraction from the brighter 2007 observation to the hard and faint 2011 observation. Overall, the low-flux 2011 observation can be explained if PDS 456 is observed at relatively low inclination angles through a Compton-thick wind, originating from the accretion disk, which significantly attenuates the X-ray flux from the quasar.

  19. Production of a high-velocity water slug using an impacting technique

    NASA Astrophysics Data System (ADS)

    Dehkhoda, S.; Bourne, N. K.

    2014-02-01

    A pulsed water jet consists of a series of discrete water slugs travelling at high velocity. Immediately after striking a target, these slugs apply high-intensity, short-duration transient stress pulses reaching an amplitude known as the water hammer pressure, followed by low-intensity, long-duration stationary stress at a lower stagnation pressure. The magnitude and duration of the water hammer and stagnation pressures are controlled by the size and quality of the water slugs. The use of water jets for rock cutting in mining operations is a centuries-old technology; however, practical methods for producing high-energy water slugs repeatedly have proven difficult. This can be partly due to the fact that the geometrical properties of a jet and so its effectiveness in creating damage is controlled and influenced by the method that is employed to generate the water slugs. This paper investigates the quality of a single water slug produced using an impacting technique where a hammer strikes a piston, resting on top of a water-filled chamber. The coherence and integrity of the jet core was of concern in this study. The impact impulse of the formed water jet was measured in a Kel-F target material using an embedded PVDF (Polyvinylidene fluoride) shock gauge. The recorded stress waveform was then used to determine the unity and endurance of the water slug stream once travelled through air.

  20. Integrity of high-velocity water slug generated by an impacting technique

    NASA Astrophysics Data System (ADS)

    Dehkhoda, Sevda; Bourne, Neil

    2013-06-01

    A pulsed water jet is a series of discrete water slugs travelling at high velocity. Immediately after striking a target, these slugs apply high-intensity, short-duration transient stress known as the water hammer pressure, followed by low-intensity, long-duration stationary stress at the stagnation pressure. The magnitude and duration of the water hammer and stagnation pressures are controlled by the size and quality of the water slugs. The use of water jets for rock cutting in mining operations is a centuries-old technology; however, practical methods for producing high-energy water slugs repeatedly have proven difficult. This can be partly due to the fact that the geometrical properties of a jet and so its effectiveness in creating damage is controlled and influenced by the method that is employed to generate the water slugs. This paper investigates the integrity of a single water slug produced using an impacting technique where a hammer strikes a piston, resting on top of a water-filled chamber. The coherence of the generated water pulse was of concern in this study. If repeated shock reflections within the chamber were transmitted or were carried into the internal geometry of nozzle, the emerging jet could pulsate. The impact impulse of the formed water jet was measured in a Kel-F target material using an embedded PVDF (Polyvinylidene fluoride) shock gauge. The recorded stress waveform was then used to study the quality and endurance of the water pulse stream as it travelled through air.

  1. Computational fluid dynamic analysis of a High-Velocity Oxygen-Fuel (HVOF) thermal spray torch

    SciTech Connect

    Hassan, B.; Oberkampf, W.L.; Neiser, R.A.; Roemer, T.J.

    1995-09-01

    The gas dynamics of a High-Velocity Oxygen-Fuel (HVOF) torch are analyzed using computational fluid dynamics (CFD) techniques. The thermal spray device analyzed is similar to a Metco Diamond Jet torch with powder feed. The injection nozzle is assumed to be axisymmetric with premixed fuel and oxygen fed from an annulus, and air cooling injected along the interior surface of the aircap. The aircap, a cronically converging nozzle, achieves choked flow conditions at the exit and a supersonic, under-expanded jet develops externally. Finite difference equations for mass, momentum, and energy conservation are solved for the gas dynamics. The combustion process is modeled using a single-step and a 12-step quasi-global finite-rate chemistry model with dissociation of the gas and a total of nine species. Turbulent flow inside the aircap and in the free-jet decay is modeled using a two-equation k-{epsilon} model. An iterative, implicit, finite volume numerical method is used to solve the gas dynamic equations inside and outside the torch . The CFD results are compared with recent experimental measurements of pressure inside the HVOF aircap. Comparisons are made for two flow rates of premixed fuel and oxygen and air cooling. This paper presents the first published comparisons of CFD predictions and experimental measurements for HVOF tbermal spraying.

  2. Cryogenic spray vaporization in high-velocity helium, argon and nitrogen gasflows

    NASA Technical Reports Server (NTRS)

    Ingebo, Robert D.

    1993-01-01

    Effects of gas properties on cryogenic liquid-jet atomization in high-velocity helium, nitrogen, and argon gas flows were investigated. Volume median diameter, D(sub v.5e), data were obtained with a scattered-light scanning instrument. By calculating the change in spray drop size, -Delta D(sub v.5)(exp 2), due to droplet vaporization, it was possible to calculate D(sub v.5C). D(sub v.5C) is the unvaporized characteristic drop size formed at the fuel-nozzle orifice. This drop size was normalized with respect to liquid-jet diameter, D(sub O). It was then correlated with several dimensionless groups to give an expression for the volume median diameter of cryogenic LN2 sprays. This expression correlates drop size D(sub v.5c) with aerodynamic and liquid-surface forces so that it can be readily determined in the design of multiphase-flow propellant injectors for rocket combustors.

  3. Experimental and analytical study of high velocity impact on Kevlar/Epoxy composite plates

    NASA Astrophysics Data System (ADS)

    Sikarwar, Rahul; Velmurugan, Raman; Madhu, Velmuri

    2012-12-01

    In the present study, impact behavior of Kevlar/Epoxy composite plates has been carried out experimentally by considering different thicknesses and lay-up sequences and compared with analytical results. The effect of thickness, lay-up sequence on energy absorbing capacity has been studied for high velocity impact. Four lay-up sequences and four thickness values have been considered. Initial velocities and residual velocities are measured experimentally to calculate the energy absorbing capacity of laminates. Residual velocity of projectile and energy absorbed by laminates are calculated analytically. The results obtained from analytical study are found to be in good agreement with experimental results. It is observed from the study that 0/90 lay-up sequence is most effective for impact resistance. Delamination area is maximum on the back side of the plate for all thickness values and lay-up sequences. The delamination area on the back is maximum for 0/90/45/-45 laminates compared to other lay-up sequences.

  4. HIGH-VELOCITY CLOUDS IN THE GALACTIC ALL SKY SURVEY. I. CATALOG

    SciTech Connect

    Moss, V. A.; Kummerfeld, J. K.; McClure-Griffiths, N. M.; Murphy, T.; Pisano, D. J.; Curran, J. R.

    2013-11-01

    We present a catalog of high-velocity clouds (HVCs) from the Galactic All Sky Survey (GASS) of southern sky neutral hydrogen, which has 57 mK sensitivity and 1 km s{sup –1} velocity resolution and was obtained with the Parkes Telescope. Our catalog has been derived from the stray-radiation-corrected second release of GASS. We describe the data and our method of identifying HVCs and analyze the overall properties of the GASS population. We catalog a total of 1693 HVCs at declinations <0°, including 1111 positive velocity HVCs and 582 negative velocity HVCs. Our catalog also includes 295 anomalous velocity clouds (AVCs). The cloud line-widths of our HVC population have a median FWHM of ∼19 km s{sup –1}, which is lower than that found in previous surveys. The completeness of our catalog is above 95% based on comparison with the HIPASS catalog of HVCs upon which we improve by an order of magnitude in spectral resolution. We find 758 new HVCs and AVCs with no HIPASS counterpart. The GASS catalog will shed unprecedented light on the distribution and kinematic structure of southern sky HVCs, as well as delve further into the cloud populations that make up the anomalous velocity gas of the Milky Way.

  5. AXAOTHER XL -- A spreadsheet for determining doses for incidents caused by tornadoes or high-velocity straight winds

    SciTech Connect

    Simpkins, A.A.

    1996-09-01

    AXAOTHER XL is an Excel Spreadsheet used to determine dose to the maximally exposed offsite individual during high-velocity straight winds or tornado conditions. Both individual and population doses may be considered. Potential exposure pathways are inhalation and plume shine. For high-velocity straight winds the spreadsheet has the capability to determine the downwind relative air concentration, however for the tornado conditions, the user must enter the relative air concentration. Theoretical models are discussed and hand calculations are performed to ensure proper application of methodologies. A section has also been included that contains user instructions for the spreadsheet.

  6. Grain size distribution of fault rocks: implication from natural gouges and high velocity friction experiments

    NASA Astrophysics Data System (ADS)

    Yang, X.; Chen, J.; Duan, B.

    2011-12-01

    The grain size distribution (GSD) is considered as an important parameter for the characterization of fault rocks. The relative magnitude of energy radiated as seismic waves to fracture energy plays a fundamental role to influence earthquake rupture dynamics. Currently, the details of grain size reduction mechanism and energy-budget are not well known. Here we present GSD measurements on fault rocks (gouge and breccias) in the main slip zone associated with the Wenchuan earthquake happened on 12 May, 2008, and on the gouges produced by high velocity friction (HVF) experiments. High velocity friction experiments were carried out on air dry granitic powder with grain size of 150 - 300 μm at normal stress of 1.0 MPa, a slip rate of 1.0 m / s and slip distances from 10 m to 30 m. On log-log plots of N(r) versus equivalent radius, two distinct linear parts can be discriminated with their intersection at 1 - 2 μm, defined as critical radius rc. One of power-law regime spans about 4 decades from 4 μm to 16 mm and the other covers a range of 0.2 - 2.0 μm. Larger fractal dimension from 2.7 to 3.5 are obtained for larger grain size regime, while lower values ranging from 1.7 to 2.1 for smaller size one. This two-stage distribution means the GSD is not self-similar (scale invariant) and the dominant ways of reducing grain size may be different from one another. XRD data show that the content of quartz drops greatly or disappears at 0.5 - 0.25 μm. GSD of HVF experimental products demonstrates similar feature to natural gouges. For instance, they all show the two-stage GSD with 1 - 2 μm of critical radius rc. The grains with their sizes of less than 1 μm appear rounded edges and equiaxial shapes. A variation in grain shapes can be observed in the grains larger than 5 μm. Some implications could be obtained from the measurements and experiments. (1) rc corresponds to the average value of grinding limit of rock-forming minerals. Further grain size reducing could be

  7. COLLISIONS BETWEEN DARK MATTER CONFINED HIGH VELOCITY CLOUDS AND MAGNETIZED GALACTIC DISKS: THE SMITH CLOUD

    SciTech Connect

    Galyardt, Jason; Shelton, Robin L. E-mail: rls@physast.uga.edu

    2016-01-01

    The Galaxy’s population of High Velocity Clouds (HVCs) may include a subpopulation that is confined by dark matter minihalos and falling toward the Galactic disk. We present the first magnetohydrodynamic simulational study of dark-matter-dominated HVCs colliding with a weakly magnetized galactic disk. Our HVCs have baryonic masses of 5 × 10{sup 6}M{sub ⊙} and dark matter minihalo masses of 0, 3 × 10{sup 8}, or 1 × 10{sup 9} M{sub ⊙}. They are modeled on the Smith Cloud, which is said to have collided with the disk 70 Myr ago. We find that, in all cases, the cloud’s collision with the galactic disk creates a hole in the disk, completely disperses the cloud, and forms a bubble-shaped structure on the far side of the disk. In contrast, when present, the dark matter minihalo continues unimpeded along its trajectory. Later, as the minihalo passes through the bubble structure and galactic halo, it accretes up to 6.0 × 10{sup 5} M{sub ⊙} in baryonic material, depending on the strengths of the magnetic field and minihalo gravity. These simulations suggest that if the Smith Cloud is associated with a dark matter minihalo and collided with the Galactic disk, the minihalo has accreted the observed gas. However, if the Smith Cloud is dark-matter-free, it is on its first approach toward the disk. These simulations also suggest that the dark matter is most concentrated either at the head of the cloud or near the cloud, depending upon the strength of the magnetic field, a point that could inform indirect dark matter searches.

  8. Wire melting and droplet atomization in a high velocity oxy-fuel jet

    SciTech Connect

    Neiser, R.A.; Brockmann, J.E.; O`Hern, T.J.

    1995-07-01

    Coatings produced by feeding a steel wire into a high-velocity oxy-fuel (HVOF) torch are being intensively studied by the automotive industry as a cost-effective alternative to the more expensive cast iron sleeves currently used in aluminum engine blocks. The microstructure and properties of the sprayed coatings and the overall economics of the process depend critically on the melting and atomization occurring at the wire tip. This paper presents results characterizing several aspects of wire melting and droplet breakup in an HVOF device. Fluctuations in the incandescent emission of the plume one centimeter downstream from the wire tip were recorded using a fast photodiode. A Fourier transform of the light traces provided a measure of the stripping rate of molten material from the wire tip. Simultaneous in-flight measurement of atomized particle size and velocity distributions were made using a Phase Doppler Particle Analyzer (PDPA). The recorded size distributions approximate a log-normal distribution. Small particles traveled faster than large particles, but the difference was considerably smaller than simple aerodynamic drag arguments would suggest. A set of experiments was carried out to determine the effect that variations in torch gas flow rates have on wire melt rate, average particle size, and average particle velocity. The observed variation of particle size with spray condition is qualitatively consistent with a Weber breakup of the droplets coming off the wire. The measurements also showed that it was possible to significantly alter atomized particle size and velocity without appreciably changing the wire melt rate.

  9. A Discovery of a Compact High Velocity Cloud-Galactic Supershell System

    NASA Astrophysics Data System (ADS)

    Park, Geumsook; Koo, Bon-Chul; Kang, Ji-hyun; Gibson, Steven J.; Peek, Joshua Eli Goldston; Douglas, Kevin A.; Korpela, Eric J.; Heiles, Carl E.

    2017-01-01

    High velocity clouds (HVCs) are neutral hydrogen (HI) gas clouds having very different radial velocities from those of the Galactic disk material. While some large HVC complexes are known to be gas streams tidally stripped from satellite galaxies of the Milky Way, there are relatively isolated and small angular-sized HVCs, so called “compact HVCs (CHVCs)”, the origin of which remains controversial. There are about 300 known CHVCs in the Milky Way, and many of them show a head-tail structure, implying a ram pressure interaction with the diffuse Galactic halo gas. It is, however, not clear whether CHVCs are completely dissipated in the Galactic halo to feed the multi-phase circumgalactic medium or they can survive their trip through the halo and collide with the Galactic disk. The colliding CHVCs may leave a gigantic trail in the disk, and it had been suggested that some of HI supershells that require ≧ 3 x 1052 erg may be produced by the collision of such HVCs.Here we report the detection of a kiloparsec (kpc)-size supershell in the outskirts of the Milky Way with the compact HVC 040+01-282 (hereafter, CHVC040) at its geometrical center using the “Inner-Galaxy Arecibo L-band Feed Array” HI 21 cm survey data. The morphological and physical properties of both objects suggest that CHVC040, which is either a fragment of a nearby disrupted galaxy or a cloud that originated from an intergalactic accreting flow, collided with the disk ˜5 Myr ago to form the supershell. Our results show that some compact HVCs can survive their trip through the Galactic halo and inject energy and momentum into the Milky Way disk.

  10. A comprehensive statistical investigation of schlieren image velocimetry (SIV) using high-velocity helium jet

    NASA Astrophysics Data System (ADS)

    Biswas, Sayan; Qiao, Li

    2017-03-01

    A detailed statistical assessment of seedless velocity measurement using Schlieren Image Velocimetry (SIV) was explored using open source Robust Phase Correlation (RPC) algorithm. A well-known flow field, an axisymmetric turbulent helium jet, was analyzed near and intermediate region (0≤ x/d≤ 20) for two different Reynolds numbers, Re d = 11,000 and Re d = 22,000 using schlieren with horizontal knife-edge, schlieren with vertical knife-edge and shadowgraph technique, and the resulted velocity fields from SIV techniques were compared to traditional Particle Image Velocimetry (PIV) measurements. A novel, inexpensive, easy to setup two-camera SIV technique had been demonstrated to measure high-velocity turbulent jet, with jet exit velocities 304 m/s (Mach = 0.3) and 611 m/s (Mach = 0.6), respectively. Several image restoration and enhancement techniques were tested to improve signal to noise ratio (SNR) in schlieren and shadowgraph images. Processing and post-processing parameters for SIV techniques were examined in detail. A quantitative comparison between self-seeded SIV techniques and traditional PIV had been made using correlation statistics. While the resulted flow field from schlieren with horizontal knife-edge and shadowgraph showed excellent agreement with PIV measurements, schlieren with vertical knife-edge performed poorly. The performance of spatial cross-correlations at different jet locations using SIV techniques and PIV was evaluated. Turbulence quantities like turbulence intensity, mean velocity fields, Reynolds shear stress influenced spatial correlations and correlation plane SNR heavily. Several performance metrics such as primary peak ratio (PPR), peak to correlation energy (PCE), the probability distribution of signal and noise were used to compare capability and potential of different SIV techniques.

  11. Chemical abundances in a high-velocity RR Lyrae star near the bulge

    NASA Astrophysics Data System (ADS)

    Hansen, C. J.; Rich, R. M.; Koch, A.; Xu, S.; Kunder, A.; Ludwig, H.-G.

    2016-05-01

    Low-mass variable high-velocity stars are interesting study cases for many aspects of Galactic structure and evolution. Until recently, the only known high- or hyper-velocity stars were young stars thought to originate from the Galactic center. Wide-area surveys such as APOGEE and BRAVA have found several low-mass stars in the bulge with Galactic rest-frame velocities higher than 350 km s-1. In this study we present the first abundance analysis of a low-mass RR Lyrae star that is located close to the Galactic bulge, with a space motion of ~-400 km s-1. Using medium-resolution spectra, we derived abundances (including upper limits) of 11 elements. These allowed us to chemically tag the star and discuss its origin, although our derived abundances and metallicity, at [Fe/H] =-0.9 dex, do not point toward one unambiguous answer. Based on the chemical tagging, we cannot exclude that it originated in the bulge. However, its retrograde orbit and the derived abundances combined suggest that the star was accelerated from the outskirts of the inner (or even outer) halo during many-body interactions. Other possible origins include the bulge itself, or the star might have been stripped from a stellar cluster or the Sagittarius dwarf galaxy when it merged with the Milky Way. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  12. Energy Productivity of the High Velocity Algae Raceway Integrated Design (ARID-HV)

    SciTech Connect

    Attalah, Said; Waller, Peter M.; Khawam, George; Ryan, Randy D.; Huesemann, Michael H.

    2015-06-03

    The original Algae Raceway Integrated Design (ARID) raceway was an effective method to increase algae culture temperature in open raceways. However, the energy input was high and flow mixing was poor. Thus, the High Velocity Algae Raceway Integrated Design (ARID-HV) raceway was developed to reduce energy input requirements and improve flow mixing in a serpentine flow path. A prototype ARID-HV system was installed in Tucson, Arizona. Based on algae growth simulation and hydraulic analysis, an optimal ARID-HV raceway was designed, and the electrical energy input requirement (kWh ha-1 d-1) was calculated. An algae growth model was used to compare the productivity of ARIDHV and conventional raceways. The model uses a pond surface energy balance to calculate water temperature as a function of environmental parameters. Algae growth and biomass loss are calculated based on rate constants during day and night, respectively. A 10 year simulation of DOE strain 1412 (Chlorella sorokiniana) showed that the ARID-HV raceway had significantly higher production than a conventional raceway for all months of the year in Tucson, Arizona. It should be noted that this difference is species and climate specific and is not observed in other climates and with other algae species. The algae growth model results and electrical energy input evaluation were used to compare the energy productivity (algae production rate/energy input) of the ARID-HV and conventional raceways for Chlorella sorokiniana in Tucson, Arizona. The energy productivity of the ARID-HV raceway was significantly greater than the energy productivity of a conventional raceway for all months of the year.

  13. Monitoring High Velocity Salt Tracer via 4D Electrical Resistivity Tomography - Possibility for Salt Tracer Tomography

    NASA Astrophysics Data System (ADS)

    Doro, K. O.; Cirpka, O. A.; Patzelt, A.; Leven, C.

    2014-12-01

    Hydrogeological testing in a tomographic sequence as shown by the use of hydraulic tomography, allows an improvement of the spatial resolution of subsurface parameters. In this regard, recent studies show increasing interest in tracer tomography which involves sequential and spatially separated tracer injections and the measurement of their corresponding tracer breakthrough at different locations and depths. Such concentration measurements however require large experimental efforts and can be simplified by geophysical tracer monitoring techniques such as electrical resistivity. In this study, we present the use of 4-D, cross-hole electrical resistivity tomography (ERT) for monitoring salt tracer experiments in high velocity flow fields. For our study, we utilized a set up that enables the conduction of salt tracer experiments with complete recovery within 84 hours over a transport distance of 16 m. This allows the repetition of the experiments with different injection depths for a tomographic salt tracer testing. For ERT monitoring, we designed modular borehole electrodes for repeated usage in a flexible manner. We also assess the use of a high speed resistivity data acquisition mode for field scale tracer monitoring ensuring high spatial and temporal resolution without sacrificing data accuracy. We applied our approach at the Lauswiesen test site, Tübingen, Germany. In our 10 m × 10 m tracer monitoring domain with 16 borehole electrodes, we acquired 4650 data points in less than 18 minutes for each monitoring cycle. Inversion results show that the tracer could be successfully imaged using this approach. The results show that repeated salt tracer tests can be efficiently monitored at a high resolution with ERT which gives the possibility for salt tracer tomography at field scale. Our results also provide a data base for extending current hydrogeophysical inversion approaches to field scale data.

  14. Petrophysical models of high velocity lower crust on the South Atlantic rifted margins: whence the asymmetry?

    NASA Astrophysics Data System (ADS)

    Trumbull, Robert B.; Franke, Dieter; Bauer, Klaus; Sobolev, Stephan V.

    2015-04-01

    Lower crustal bodies with high seismic velocity (Vp > 7km/s) underlie seaward-dipping reflector wedges on both margins of the South Atlantic, as on many other volcanic rifted margins worldwide. A comprehensive geophysical study of the South Atlantic margins by Becker et al. (Solid Earth, 5: 1011-1026, 2014) showed a strong asymmetry in the development of high-velocity lower crust (HVLC), with about 4 times larger volumes of HVLC on the African margin. That study also found interesting variations in the vertical position of HVLC relative to seaward-dipping reflectors which question a simple intrusive vs. extrusive relationship between these lower- and upper crustal features. The asymmetry of HVLC volumes on the conjugate margins is paradoxically exactly the opposite to that of surface lavas in the Paraná-Etendeka flood basalt province, which are much more voluminous on the South American margin. This contribution highlights the asymmetric features of magma distribution on the South Atlantic margins and explores their geodynamic significance. Petrophysical models of the HVLC are presented in the context of mantle melt generation, based on thickness-velocity (H-Vp) relations. These suggest that the greater volumes and average Vp values of HVLC on the African margin are due to active upwelling and high temperature, whereas passive upwelling under a thick lithospheric lid suppressed magma generation on the South American margin. The contrast in mantle upwelling rate and lithospheric thickness on the two margins predictably causes differential uplift, and this may help explain the greater accomodation space for surface lavas on the South American side although melt generation was strongest under the African margin.

  15. Uvby-B Photometry of High Velocity Stars. Photometric Parallaxes and Preliminary Kinematic Results

    NASA Astrophysics Data System (ADS)

    Schuster, W. J.

    1990-11-01

    RESUMEN. Se han explorado dos metodos para la determinaci6n de paralajes fotometricos usando fotometrfa uv - . Estos metodos dependen de las relaciones estandar de Crawford (1975) y de Olsen (1984) y de colores y magnitudes sinteticas de VandenBerg y Bell (1985). Ambos metodos incluyen una correcci6n evolucionaria de forma f6c0. Se calculan las distancias para las 711 estrellas de alta velocidad y pobres en metales en el catalogo uvby-p de Schuster y Nissen (1988). Se comparan estas con las distancias de Sandage y Fouts (1987) y Laird, Carney y Latham (1988) para las estrellas en comtfin. Tambien son aplicables nuestros metodos a estrellas de paralaje. En general las comparaciones son satisfactorias y las sistematicas son despreciables o pequefias. Las distancias finales de nuestras 711 estrellas se aplican a un numero de problemas cinematicos. Se estudian algunos diagramas interesantes, tales como el diagrama de energia de Toomre y el diagrama V(rot) versus [Fe/H]. ABSTRACT Two methods for the determination of parallaxes using uvbyP photometry are being explored. These methods depend upon the standard relations of Crawford (1975) and of Olsen (1984) and upon synthetic colors and magnitudes of VandenBerg and Bell (1985). Both include an evolutionary correction of the form f6c0. Distances are calculated for the 711 high-velocity and metal-poor stars in the uvby-P catalogue of Schuster and Nissen (1988). These are compared to the distances of Sandage and Fouts (1987) and Laird, Carney, and Lathain (1988) for stars in common. Also our methods are applied to parallax stars. In general the comparisons are good with negligible or small systematic differences. The final distances of our 711 stars are applied to a number of kinematical problems. Several interesting diagrams are studied, sucl as Toomre energy diagram and the plot of V(rot) versus [Fe/H]. Key words: DISTANCES - PHOTOMETRY - STARS-POPULATION II

  16. A Detailed Kinematic Map of Cassiopeia A's Optical Main Shell and Outer High-velocity Ejecta

    NASA Astrophysics Data System (ADS)

    Milisavljevic, Dan; Fesen, Robert A.

    2013-08-01

    We present three-dimensional (3D) kinematic reconstructions of optically emitting material in the young Galactic supernova remnant Cassiopeia A (Cas A). These Doppler maps have the highest spectral and spatial resolutions of any previous survey of Cas A and represent the most complete catalog of its optically emitting material to date. We confirm that the bulk of Cas A's optically bright ejecta populate a torus-like geometry tilted approximately 30° with respect to the plane of the sky with a -4000 to +6000 km s-1 radial velocity asymmetry. Near-tangent viewing angle effects and an inhomogeneous surrounding circumstellar material/interstellar medium environment suggest that this geometry and velocity asymmetry may not be faithfully representative of the remnant's true 3D structure or the kinematic properties of the original explosion. The majority of the optical ejecta are arranged in several well-defined and nearly circular ring-like structures with diameters between approximately 30'' (0.5 pc) and 2' (2 pc). These ejecta rings appear to be a common phenomenon of young core-collapse remnants and may be associated with post-explosion input of energy from plumes of radioactive 56Ni-rich ejecta that rise, expand, and compress non-radioactive material. Our optical survey encompasses Cas A's faint outlying ejecta knots and exceptionally high-velocity NE and SW streams of S-rich debris often referred to as "jets." These outer knots, which exhibit a chemical make-up suggestive of an origin deep within the progenitor star, appear to be arranged in opposing and wide-angle outflows with opening half-angles of ≈40°.

  17. High-velocity Line Forming Regions in the Type Ia Supernova 2009ig

    NASA Astrophysics Data System (ADS)

    Marion, G. H.; Vinko, Jozsef; Wheeler, J. Craig; Foley, Ryan J.; Hsiao, Eric Y.; Brown, Peter J.; Challis, Peter; Filippenko, Alexei V.; Garnavich, Peter; Kirshner, Robert P.; Landsman, Wayne B.; Parrent, Jerod T.; Pritchard, Tyler A.; Roming, Peter W. A.; Silverman, Jeffrey M.; Wang, Xiaofeng

    2013-11-01

    We report measurements and analysis of high-velocity (HVF) (>20,000 km s-1) and photospheric absorption features in a series of spectra of the Type Ia supernova (SN) 2009ig obtained between -14 days and +13 days with respect to the time of maximum B-band luminosity (B-max). We identify lines of Si II, Si III, S II, Ca II, and Fe II that produce both HVF and photospheric-velocity (PVF) absorption features. SN 2009ig is unusual for the large number of lines with detectable HVF in the spectra, but the light-curve parameters correspond to a slightly overluminous but unexceptional SN Ia (MB = -19.46 mag and Δm 15(B) = 0.90 mag). Similarly, the Si II λ6355 velocity at the time of B-max is greater than "normal" for an SN Ia, but it is not extreme (v Si = 13,400 km s-1). The -14 days and -13 days spectra clearly resolve HVF from Si II λ6355 as separate absorptions from a detached line forming region. At these very early phases, detached HVF are prevalent in all lines. From -12 days to -6 days, HVF and PVF are detected simultaneously, and the two line forming regions maintain a constant separation of about 8000 km s-1. After -6 days all absorption features are PVF. The observations of SN 2009ig provide a complete picture of the transition from HVF to PVF. Most SNe Ia show evidence for HVF from multiple lines in spectra obtained before -10 days, and we compare the spectra of SN 2009ig to observations of other SNe. We show that each of the unusual line profiles for Si II λ6355 found in early-time spectra of SNe Ia correlate to a specific phase in a common development sequence from HVF to PVF.

  18. A DETAILED KINEMATIC MAP OF CASSIOPEIA A'S OPTICAL MAIN SHELL AND OUTER HIGH-VELOCITY EJECTA

    SciTech Connect

    Milisavljevic, Dan; Fesen, Robert A.

    2013-08-01

    We present three-dimensional (3D) kinematic reconstructions of optically emitting material in the young Galactic supernova remnant Cassiopeia A (Cas A). These Doppler maps have the highest spectral and spatial resolutions of any previous survey of Cas A and represent the most complete catalog of its optically emitting material to date. We confirm that the bulk of Cas A's optically bright ejecta populate a torus-like geometry tilted approximately 30 Degree-Sign with respect to the plane of the sky with a -4000 to +6000 km s{sup -1} radial velocity asymmetry. Near-tangent viewing angle effects and an inhomogeneous surrounding circumstellar material/interstellar medium environment suggest that this geometry and velocity asymmetry may not be faithfully representative of the remnant's true 3D structure or the kinematic properties of the original explosion. The majority of the optical ejecta are arranged in several well-defined and nearly circular ring-like structures with diameters between approximately 30'' (0.5 pc) and 2' (2 pc). These ejecta rings appear to be a common phenomenon of young core-collapse remnants and may be associated with post-explosion input of energy from plumes of radioactive {sup 56}Ni-rich ejecta that rise, expand, and compress non-radioactive material. Our optical survey encompasses Cas A's faint outlying ejecta knots and exceptionally high-velocity NE and SW streams of S-rich debris often referred to as ''jets''. These outer knots, which exhibit a chemical make-up suggestive of an origin deep within the progenitor star, appear to be arranged in opposing and wide-angle outflows with opening half-angles of Almost-Equal-To 40 Degree-Sign.

  19. The Gas Dynamics of High-Velocity Oxy-Fuel Thermal Sprays

    NASA Astrophysics Data System (ADS)

    Hackett, Charles Marcou

    An experimental study of the gas dynamics of the High-Velocity Oxy-Fuel (HVOF) thermal spray process has been performed. With this process, a hot, combustion-driven, supersonic jet is used to propel particles onto a surface, thus forming metal coatings that provide wear, temperature, and corrosion resistance. The fundamental physics of the spray process were studied and several key areas of interest were identified for in-depth study. Optical diagnostic techniques, including microsecond -exposure schlieren and shadowgraph imaging, were used to visualize the hot supersonic jet produced during the spray process. Energetic turbulent mixing of the jet with the surrounding atmosphere was observed. Measurements of oxide levels in aluminum and mild steel coatings sprayed for a range of conditions indicated that the turbulent mixing influences coating oxidation. However, experiments conducted with a low-speed coaxial shroud of inert gas demonstrated that coating oxide formation can be effectively controlled during the spray process. A simple numerical model was developed to predict the behavior of a spray particle in the HVOF jet. The results of computations indicated that independent control of spray particle velocity and temperature was possible through systematic variations in combustion chamber pressure and particle injection location within the nozzle. This hypothesis was confirmed through a series of experiments in which stainless steel particle velocity and temperature were measured using trace velocimetry and two-color radiative pyrometry, respectively. Combustion chamber pressure had a strong effect on particle velocity. Injection location was used to control the residence time of a particle within the flow, thus allowing manipulation of particle temperature without a measurable effect on velocity. Thus, the results of these experiments revealed that the gas dynamics--the behavior of the compressible gas flow--of the HVOF spray process strongly influenced spray

  20. THE SMITH CLOUD: HIGH-VELOCITY ACCRETION AND DARK MATTER CONFINEMENT

    SciTech Connect

    Nichols, M.; Bland-Hawthorn, J.

    2009-12-20

    The Smith Cloud is a massive system of metal-poor neutral and ionized gas (M{sub gas} approx> 2 x 10{sup 6} M{sub sun}) that is presently moving at high velocity (V{sub GSR}approx 300 km s{sup -1}) with respect to the Galaxy at a distance of 12 kpc from the Sun. The kinematics of the cloud's cometary tail indicates that the gas is in the process of accretion onto the Galaxy, as first discussed by Lockman et al. Here, we re-investigate the cloud's orbit by considering the possibility that the cloud is confined by a dark matter halo. This is required for the cloud to survive its passage through the Galactic corona. We consider three possible models for the dark matter halo (Navarro-Frenk-White (NFW), Einasto, and Burkert) including the effects of tidal disruption and ram pressure stripping during the cloud's infall onto and passage through the Galactic disk. For the NFW and Einasto dark matter models, we are able to determine reasonable initial conditions for the Smith Cloud, although this is only marginally possible with the Burkert model. For all three models, the progenitor had an initial (gas+dark matter) mass that was an order-of-magnitude higher than inferred today. In agreement with Lockman et al., the cloud appears to have punched through the disk approx70 Myr ago. For our most successful models, the baryon-to-dark matter ratio is fairly constant during an orbital period but drops by a factor of 2-5 after transiting the disk. The cloud appears to have only marginally survived its transit and is unlikely to retain its integrity during the next transit approx 30 Myr from now.

  1. The Formation of the Local Group and the High Velocity Clouds

    NASA Astrophysics Data System (ADS)

    Spergel, D. N.; Blitz, L.; Teuben, P. J.; Hartmann, D.; Burton, B.

    1996-12-01

    We simulate the formation and evolution of the Local Group. The dynamics of the Local Group is governed primarily by the its two largest members, Andromeda (M31) and the Galaxy (M0) and secondarily by the tidal effects of neighboring galaxies. In the simulation, a long filament forms which contains M31 and M0. While the gas near M31 and M0 is likely shock heated, we expect that much of the gas in the filament is cold. The kinematics of this gas in the simulation is remarkably similar to the kinematics of the High Velocity Clouds (HVCs). This similarity suggests reinterpreting the HVCs as primarily extragalactic. In this model, the HVCs are similar to the Lyman alpha clouds. Recent work (Hernquist et al. 996) suggests that the Lyman alpha clouds are primarily condensations in the filaments between galaxies. We suggest a similar picture for most of the HVCs: they are gravitationally confined, rather than pressure confined, clouds infalling into the Local Group and are likely associated with a substantial amount of dark matter. In this picture, the two phase structure seen in some of the HVCs (Wakker & Schwarz 1991) would be due to self shielding that arises in gas clouds ionized by external UV (Murakami & Ikeuchi 1990). This model suggests that there is a substantial amount of gas in the HVCs: ~ 1 x 10(10) M_sun. This gas is and was a reservoir of relatively unprocessed gas for both M31 and our Galaxy and likely plays an important role in the evolution of both galaxies. Hernquist, L, Katz, N., Weinberg, D. & Miralda-Escude, J. 1996, ApJ L 457, 51 Murakami, I. & Ikeuchi, S. 1990 PASJ, 41 , L11. Wakker, B.P. & Schwarz, U.J. 1991 A & A, 250, 48.

  2. The Guitar Nebula, Bow Shocks From High Velocity Pulsars, and Companions of Recycled Pulsars

    NASA Astrophysics Data System (ADS)

    Lundgren, S. C.; Cordes, J. M.; Romani, R. W.

    1992-12-01

    We report results of optical studies of neutron star interactions with companion objects and the surrounding medium. In Hα observations of 11 high velocity, high spindown energy pulsars we have discovered one spectacular bow shock nebula, the Guitar Nebula, produced by the motion of the pulsar, PSR 2224+65, through partially neutral gas. One other pulsar, PSR 0136+57, has a faint feature near the pulsar position with a nonstellar morphology. We discuss the possibility that this is another shock and give upper limits on shock emission for the rest of the pulsars. Further, we consider possible scaling of shock emission with pulsar spindown energy and velocity, and detectability of shocks in other pulsars. Shocks may even reveal the existence of neutron stars not detectable as pulsars due to beaming or lack of pulsed radio emission. Our observations of several binary millisecond pulsars show some intriquing counterparts in some cases and allow strong limits to be placed on the magnitude of any counterparts in others. In pulsars 1534+12 and 1953+29 optical counterparts near the pulsar position are most likely chance coincidence with foreground stars. We imaged PSR 1257+12 in the hope of seeing the remnants of the disk which resulted in formation of planets or another pulsar wind driven shock nebula. We place upper limits on optical emission from nebulosity in the vicinity of the pulsar. This work was supported by grants from NSF, NASA and the National Astronomy and Ionosphere Center which operates Arecibo Observatory under contract with the NSF.

  3. High- and low-temperature-stable thermite composition for producing high-pressure, high-velocity gases

    DOEpatents

    Halcomb, Danny L.; Mohler, Jonathan H.

    1990-10-16

    A high- and low-temperature-stable thermite composition for producing high-pressure and high-velocity gases comprises an oxidizable metal, an oxidizing reagent, and a high-temperature-stable gas-producing additive selected from the group consisting of metal carbides and metal nitrides.

  4. Hyperfine interactions in soybean and lupin oxy-leghemoglobins studied using Mössbauer spectroscopy with a high velocity resolution

    NASA Astrophysics Data System (ADS)

    Kumar, A.; Alenkina, I. V.; Zakharova, A. P.; Oshtrakh, M. I.; Semionkin, V. A.

    2015-04-01

    A comparative study of monomeric soybean and lupin leghemoglobins in the oxy-form was carried out using Mössbauer spectroscopy with a high velocity resolution at 90 K. The 57Fe hyperfine parameters of measured spectra were evaluated and compared with possible structural differences in the heme Fe(II)-O 2 bond.

  5. High Velocity Linear Induction Launcher with Exit-Edge Compensation for Testing of Aerospace Components

    NASA Technical Reports Server (NTRS)

    Kuznetsov, Stephen; Marriott, Darin

    2008-01-01

    Advances in ultra high speed linear induction electromagnetic launchers over the past decade have focused on magnetic compensation of the exit and entry-edge transient flux wave to produce efficient and compact linear electric machinery. The paper discusses two approaches to edge compensation in long-stator induction catapults with typical end speeds of 150 to 1,500 m/s. In classical linear induction machines, the exit-edge effect is manifest as two auxiliary traveling waves that produce a magnetic drag on the projectile and a loss of magnetic flux over the main surface of the machine. In the new design for the Stator Compensated Induction Machine (SCIM) high velocity launcher, the exit-edge effect is nulled by a dual wavelength machine or alternately the airgap flux is peaked at a location prior to the exit edge. A four (4) stage LIM catapult is presently being constructed for 180 m/s end speed operation using double-sided longitudinal flux machines. Advanced exit and entry edge compensation is being used to maximize system efficiency, and minimize stray heating of the reaction armature. Each stage will output approximately 60 kN of force and produce over 500 G s of acceleration on the armature. The advantage of this design is there is no ablation to the projectile and no sliding contacts, allowing repeated firing of the launcher without maintenance of any sort. The paper shows results of a parametric study for 500 m/s and 1,500 m/s linear induction launchers incorporating two of the latest compensation techniques for an air-core stator primary and an iron-core primary winding. Typical thrust densities for these machines are in the range of 150 kN/sq.m. to 225 kN/sq.m. and these compete favorably with permanent magnet linear synchronous machines. The operational advantages of the high speed SCIM launcher are shown by eliminating the need for pole-angle position sensors as would be required by synchronous systems. The stator power factor is also improved.

  6. The Serendipitous Discovery of High-Velocity Shocks in the Galactic Center

    NASA Astrophysics Data System (ADS)

    Simpson, Janet P.

    2015-01-01

    Previous studies with Spitzer have shown that the Galactic Center (GC) contains widespread (although of low abundance) lines from high-excitation gas, such as [O IV] (ionization potential IP = 55 eV), even though most of its diffuse ionized interstellar medium is low excitation, dominated by singly ionized species like Ne+ or doubly ionized species whose singly ionized IP is below the 13.6 eV needed to ionize hydrogen, like S++. Because of the O3+, the GC cannot be considered a normal H II region, which is ionized by massive O and B stars whose extreme ultraviolet spectra essentially cut off at 54 eV, owing to the high opacity of the helium and metals in their atmospheres. The consequence is that highly ionized species, like He++, O3+, etc, with IP > 54 are not seen in Milky Way H II regions, whereas such gas is commonly found in AGN with their hard radiation fields. In order to investigate the energy inputs to the Galactic Center, we have reduced all the Infrared Spectrograph data in the Spitzer archive with positions in the GC. We find that the highest excitation gas isn't uniformly distributed over the GC but is concentrated in compact clumps, unlike the low-excitation gas. Ten of these highly-excited regions have [Ne V] (IP = 97 eV) lines. Such high-energy gas cannot be excited by the OB stars that ionize H II regions, but is found only in high-velocity shocks and high-excitation planetary nebulae (PNe). The shocks could be due to outflows from massive young stellar objects or red supergiants. Analysis of the emission lines reveals that the energies of the clumped gas range from 1036 to 1037 erg/s for assumed GC distances of 8 kpc if the high-excitation regions are shocks with velocities of order several hundred km/s and similar energies if the regions are excited by the hot stars required for PNe. We will show examples of the high-excitation regions, which range from the bubble surrounding the Sgr B1-C ultra-compact H II region to several high

  7. Earthquake Energy Dissipation in Light of High-Velocity, Slip-Pulse Shear Experiments

    NASA Astrophysics Data System (ADS)

    Reches, Z.; Liao, Z.; Chang, J. C.

    2014-12-01

    We investigated the energy dissipation during earthquakes by analysis of high-velocity shear experiments conducted on room-dry, solid samples of granite, tonalite, and dolomite sheared at slip-velocity of 0.0006-1m/s, and normal stress of 1-11.5MPa. The experimental fault were loaded in one of three modes: (1) Slip-pulse of abrupt, intense acceleration followed by moderate deceleration; (2) Impact by a spinning, heavy flywheel (225 kg); and (3) Constant velocity loading. We refer to energy dissipation in terms of power-density (PD=shear stress*slip-velocity; units of MW/m^2), and Coulomb-energy-density (CED= mechanical energy/normal stress; units of m). We present two aspects: Relative energy dissipation of the above loading modes, and relative energy dissipation between impact experiments and moderate earthquakes. For the first aspect, we used: (i) the lowest friction coefficient of the dynamic weakening; (ii) the work dissipated before reaching the lowest friction; and (iii) the cumulative mechanical work during the complete run. The results show that the slip-pulse/impact modes are energy efficient relatively to the constant-velocity mode as manifested by faster, more intense weakening and 50-90% lower energy dissipation. Thus, for a finite amount of pre-seismic crustal energy, the efficiency of slip-pulse would amplify earthquake instability. For the second aspect, we compare the experimental CED of the impact experiments to the reported breakdown energy (EG) of moderate earthquakes, Mw = 5.6 to 7.2 (Chang et al., 2012). In is commonly assumed that the seismic EG is a small fraction of the total earthquake energy, and as expected in 9 out of 11 examined earthquakes, EG was 0.005 to 0.07 of the experimental CED. We thus speculate that the experimental relation of Coulomb-energy-density to total slip distance, D, CED = 0.605 × D^0.933, is a reasonable estimate of total earthquake energy, a quantity that cannot be determined from seismic data.

  8. High-Velocity Frictional Behavior of Incoming Pelagic Sediments to the Tohoku Subduction zone

    NASA Astrophysics Data System (ADS)

    Sawai, M.; Hirose, T.

    2012-12-01

    The 2011 Tohoku earthquake (Mw 9.0) off the Pacific coast of Japan produced huge slip (~50 m) on the shallow part of the fault close to the toe of the megathrust (e.g., Fujiwara et al., 2011), resulting in destructive tsunamis. Although the multiple causes of such large slip at shallow depths is expected, the frictional property of sediments around the fault, especially at coseismic slip velocities, may significantly contribute to large slip along the fault. We thus investigate the frictional properties of pelagic sediments to be subducting beneath the Tohoku region at high velocities and large displacement toward understanding the rupture processes to cause large slip at the shallow portion of subduction zone. We have conducted friction experiments on incoming pelagic sediment on the Pacific plate (DSDP, Site 436, Leg56, 378 mbsf) that consider as simulated fault gouge. The site locates about 100 km northeast from the Hole C0019E drilled during the IODP Expedition 343 (J-FAST). The sediment contains mainly montmorillonite and its blackish color is quite similar to the sheared sediments in the plate boundary fault recovered during the Expedition 343. Experiments are performed at slip velocities of 2.5 x 10-4 to 1.3 m/s, normal stresses of 0.5 to 2.0 MPa and slip displacement of about 16 m under brine saturated conditions, using a rotary-shear friction apparatus. One gram of gouge was placed between rock cylinders of sandstone or gabbro of 25 mm diameter with Teflon sleeve outside to contain gouge. Both gouge sample and host rock were saturated with brine. At slip velocity of 1.3 m/s and normal stresses of 0.5 to 2.0 MPa, a typical slip weakening behavior is observed; friction coefficient of the sediment rapidly increases 0.1 - 0.3 at the onset of sliding and subsequently decreases to 0.06 - 0.15 over the displacement of > 1 m. However, peak friction and frictional work during slip-weakening (fracture energy) are markedly lower as compared to similar studies

  9. Identifying galaxy candidates in WSRT H i imaging of ultra-compact high velocity clouds

    NASA Astrophysics Data System (ADS)

    Adams, Elizabeth A. K.; Oosterloo, Tom A.; Cannon, John M.; Giovanelli, Riccardo; Haynes, Martha P.

    2016-12-01

    Ultra-compact high velocity clouds (UCHVCs) were identified in the Arecibo Legacy Fast ALFA (ALFALFA) H i survey as potential gas-bearing dark matter halos. Here we present higher resolution neutral hydrogen (H i) observations of twelve UCHVCS with the Westerbork Synthesis Radio Telescope (WSRT). The UCHVCs were selected based on a combination of size, isolation, large recessional velocity and high column density as the best candidate dark matter halos. The WSRT data were tapered to image the UCHVCs at 210'' (comparable to the Arecibo resolution) and 105'' angular resolution. In a comparison of the single-dish to interferometer data, we find that the integrated line flux recovered in the WSRT observations is generally comparable to that from the single-dish ALFALFA data. In addition, any structure seen in the ALFALFA data is reproduced in the WSRT maps at the same angular resolution. At 210'' resolution all the sources are generally compact with a smooth H i morphology, as expected from their identification as UCHVCs. At the higher angular resolution, a majority of the sources break into small clumps contained in a diffuse envelope. These UCHVCs also have no ordered velocity motion and are most likely Galactic halo clouds. We identify two UCHVCs, AGC 198606 and AGC 249525, as excellent galaxy candidates based on maintaining a smooth H i morphology at higher angular resolution and showing ordered velocity motion consistent with rotation. A third source, AGC 249565, lies between these two populations in properties and is a possible galaxy candidate. If interpreted as gas-bearing dark matter halos, the three candidate galaxies have rotation velocities of 8-15 km s-1, H i masses of 0.6-50 × 105M⊙, H i radii of 0.3-2 kpc, and dynamical masses of 2-20 × 107M⊙ for a range of plausible distances. These are the UCHVCs with the highest column density values in the ALFALFA H i data and we suggest this is the best way to identify further candidates.

  10. HIGH-VELOCITY LINE FORMING REGIONS IN THE TYPE Ia SUPERNOVA 2009ig

    SciTech Connect

    Marion, G. H.; Foley, Ryan J.; Challis, Peter; Kirshner, Robert P.; Vinko, Jozsef; Wheeler, J. Craig; Silverman, Jeffrey M.; Hsiao, Eric Y.; Brown, Peter J.; Filippenko, Alexei V.; Garnavich, Peter; Landsman, Wayne B.; Parrent, Jerod T.; Pritchard, Tyler A.; Roming, Peter W. A.; Wang, Xiaofeng

    2013-11-01

    We report measurements and analysis of high-velocity (HVF) (>20,000 km s{sup –1}) and photospheric absorption features in a series of spectra of the Type Ia supernova (SN) 2009ig obtained between –14 days and +13 days with respect to the time of maximum B-band luminosity (B-max). We identify lines of Si II, Si III, S II, Ca II, and Fe II that produce both HVF and photospheric-velocity (PVF) absorption features. SN 2009ig is unusual for the large number of lines with detectable HVF in the spectra, but the light-curve parameters correspond to a slightly overluminous but unexceptional SN Ia (M{sub B} = –19.46 mag and Δm{sub 15}(B) = 0.90 mag). Similarly, the Si II λ6355 velocity at the time of B-max is greater than 'normal' for an SN Ia, but it is not extreme (v{sub Si} = 13,400 km s{sup –1}). The –14 days and –13 days spectra clearly resolve HVF from Si II λ6355 as separate absorptions from a detached line forming region. At these very early phases, detached HVF are prevalent in all lines. From –12 days to –6 days, HVF and PVF are detected simultaneously, and the two line forming regions maintain a constant separation of about 8000 km s{sup –1}. After –6 days all absorption features are PVF. The observations of SN 2009ig provide a complete picture of the transition from HVF to PVF. Most SNe Ia show evidence for HVF from multiple lines in spectra obtained before –10 days, and we compare the spectra of SN 2009ig to observations of other SNe. We show that each of the unusual line profiles for Si II λ6355 found in early-time spectra of SNe Ia correlate to a specific phase in a common development sequence from HVF to PVF.

  11. Frictional Behavior of Amphibolite at Seismic Slip Rates from High-velocity Rotary Shear Experiments

    NASA Astrophysics Data System (ADS)

    Jung, S.; Ree, J.; Hirose, T.; Lee, S.

    2012-12-01

    Gabbroic rocks of oceanic crust transform into amphibolite with depth at subduction zone, and thus frictional property of amphibolite may be important for a better understanding of subduction zone earthquakes. We report preliminary results of high-velocity rotary shear experiments on amphibolite at a seismic slip rate (~1.05 m/s) and normal stresses of 2-15 MPa. Amphibolite from the Imjingang belt of South Korea is composed of hornblende (0.5-1.5 mm) and plagioclase (0.25-0.5 mm) with rare occurrence of quartz. The frictional behavior of the amphibolite is characterized by two phases of unstable slip weakening separated by strengthening, followed by a final weakening with a very low steady-state friction coefficient of 0.07. The average coefficient of the first, second and final peak frictions is 0.48, 0.36 and 0.22, respectively. The fault zone consists of a principal slip zone (PSZ, 200-300 μm thick) with molten material mantled by damage zone (1-3 mm thick). In the damage zone, the color of hornblende grains becomes darker toward the PSZ and thin, black stripes occur along cleavage planes of hornblende in plane-polarized light. Also fracture density of hornblende and plagioclase increases relative to those of wall rock. The PSZ comprises molten material and mineral clasts (25-50 μm) and the clasts tend to concentrate along the center of the PSZ. The surface temperature of the fault zones measured by a radiation thermography during experiments is about 1060°C and the internal temperature of the fault zones could be higher than the measured temperature in view of the melting of hornblende and plagioclase. The frictional behavior of amphibolite is much different from that of gabbro where the overall friction is much higher with the final peak friction of 0.84-1.09 and steady-state friction of ~0.6 (Hirose and Shimamoto, 2005 in Journal of Geophysical Research). This difference may be due to dehydration of hornblende by frictional heating and lower viscosity of

  12. The high-velocity outflow in the proto-planetary nebula Hen 3-1475

    NASA Astrophysics Data System (ADS)

    Riera, A.; García-Lario, P.; Manchado, A.; Bobrowsky, M.; Estalella, R.

    2003-04-01

    The proto-planetary nebula Hen 3-1475 shows a remarkable highly collimated optical jet with an S-shaped string of three pairs of knots and extremely high velocities. We present here a detailed analysis of the overall morphology, kinematic structure and the excitation conditions of these knots based on deep ground-based high dispersion spectroscopy complemented with high spatial resolution spectroscopy obtained with STIS onboard HST, and WFPC2 [N II] images. The spectra obtained show double-peaked, extremely wide emission line profiles, and a decrease of the radial velocities with distance to the source in a step-like fashion. We find that the emission line ratios observed in the intermediate knots are consistent with a spectrum arising from the recombination region of a shock wave with shock velocities ranging from 100 to 150 km s-1. We propose that the ejection velocity is varying as a function of time with a quasi-periodic variability (with timescale of the order of 100 years) and the direction of ejection is also varying with a precession period of the order of 1500 years. Some slowing down with distance along the axis of the Hen 3-1475 jet may be due to the entrainment process and/or to the enviromental drag. This scenario is supported by geometric and kinematic evidence: firstly, the decrease of the radial velocities along the Hen 3-1475 jet in a step like fashion; secondly, the kinematic structure observed in the knots; thirdly, the point-symmetric morphology together with the high proper motions shown by several knots; and finally the fact that the shock velocity predicted from the observed spectra of the shocked knots is much slower than the velocities at which these knots move outwards with respect to the central source. Based on observations made during service time with the 2.5 m Isaac Newton Telescope operated on La Palma by the Isaac Newton Group of Telescopes in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de

  13. ULTRA-COMPACT HIGH VELOCITY CLOUDS AS MINIHALOS AND DWARF GALAXIES

    SciTech Connect

    Faerman, Yakov; Sternberg, Amiel; McKee, Christopher F.

    2013-11-10

    We present dark matter minihalo models for the Ultra-Compact, High-Velocity H I Clouds (UCHVCs) recently discovered in the 21 cm ALFALFA survey. We assume gravitational confinement of 10{sup 4} K H I gas by flat-cored dark-matter subhalos within the Local Group. We show that for flat cores, typical (median) tidally stripped cosmological subhalos at redshift z = 0 have dark-matter masses of ∼10{sup 7} M{sub ☉} within the central 300 pc (independent of total halo mass), consistent with the 'Strigari mass scale' observed in low-luminosity dwarf galaxies. Flat-cored subhalos also resolve the mass discrepancy between simulated and observed satellites around the Milky Way. For the UCHVCs, we calculate the photoionization-limited hydrostatic gas profiles for any distance-dependent total observed H I mass and predict the associated (projected) H I half-mass radii, assuming the clouds are embedded in distant (d ∼> 300 kpc) and unstripped subhalos. For a typical UCHVC (0.9 Jy km s{sup –1}), we predict physical H I half-mass radii of 0.18 to 0.35 kpc (or angular sizes of 0.'6 to 2.'1) for distances ranging from 300 kpc to 2 Mpc. As a consistency check, we model the gas-rich dwarf galaxy Leo T, for which there is a well-resolved H I column density profile and a known distance (420 kpc). For Leo T, we find that a subhalo with M{sub 300} = 8 (± 0.2) × 10{sup 6} M{sub ☉} best fits the observed H I profile. We derive an upper limit of P{sub HIM} ∼< 150 cm{sup –3} K for the pressure of any enveloping hot intergalactic medium gas at the distance of Leo T. Our analysis suggests that some of the UCHVCs may in fact constitute a population of 21 cm-selected but optically faint dwarf galaxies in the Local Group.

  14. The microstructural evolution of clay-bearing carbonate faults during high-velocity friction experiments

    NASA Astrophysics Data System (ADS)

    Bullock, Rachael; De Paola, Nicola; Holdsworth, Robert

    2014-05-01

    Seismicity in the Northern Apennines, Italy, nucleates within and propagates through a multilayer sequence comprising limestones with marl interbeds. Observations from the Gubbio fault (1984, Ms = 5.2) indicate that the majority of earthquake displacement is localized within principal slip zones (PSZs), <1.5 mm wide, characterized by cataclasites and gouges containing up to 50% phyllosilicate. To assess the effect of clay content on the frictional behaviour of such carbonate faults during earthquake propagation, we performed high-velocity friction experiments, using a rotary-shear apparatus, on gouges containing 50:50, 80:20 and 90:10 ratios of calcite:montmorillonite and calcite:illite-smectite (mixed-layer). Starting grain size was 180-250 µm. Experiments were conducted at 1.3 m/s slip rate, 9 MPa normal load and under both dry and water-saturated conditions. The dry calcite+clay gouges produce a typical slip-weakening curve comprising a slip-hardening phase during the early stages of slip, during which friction evolves to a peak value (µp) of 0.62-0.76. µp is followed by a dramatic decrease in frictional strength within the first 0.5 m of slip to a constant steady-state value (µss) of 0.23-0.33. The frictional behaviour of the wet calcite+clay gouges is profoundly different, in that they undergo negligible slip-hardening, and instead attain steady-state sliding almost immediately at the onset of slip with µss <<0.2. As little as 10-20 wt.% phyllosilicate is enough to produce this dramatic weakening. The dry and wet gouges show significant microstructural differences in both the initial (post-compaction, pre-shearing) phase and after shearing. Initial microstructure of the dry gouges is characterized by discrete calcite grains and irregular 'clumps' of clay. The microstructure of the sheared dry gouges is then characterized by a sharp principal slip surface (PSS) and the development of a strong fabric and localized PSZ, up to 65 µm wide, composed of

  15. Anomalous high-velocity outbursts ejected from the surface of tungsten microdroplets in a flow of argon-air plasma

    NASA Astrophysics Data System (ADS)

    Gulyaev, I. P.; Dolmatov, A. V.; Gulyaev, P. Yu; Iordan, V. I.; Kharlamov, M. Yu; Krivtsun, I. V.

    2016-02-01

    For the first time, a phenomenon of high-velocity outbursts ejected from the surface of liquid tungsten microparticles in a flow of argon-air plasma under atmospheric pressure was observed. As tungsten particles sized 50 to 200 μm moved in a plasma flow, stratified radiating spheres up to 9 mm in diameter formed around such particles. The spheres were sources of high-velocity outbursts whose ejection direction coincided with the direction of the plasma flow. The velocity of the anomalous outbursts amounted to 3-20 km/s. In the outburst images, the distribution of glow intensity along outburst tracks exhibited a wavy decaying behavior with a wavelength of 5-15 mm. Possible physical factors that could be the cause of the phenomenon are discussed.

  16. New Hubble Space Telescope Observations of High-Velocity Ly(alpha) and H(alpha) in SNR 1987A

    NASA Technical Reports Server (NTRS)

    Michael, Eli; McCray, Richard; Pun, C. S. J.; Borkowski, Kazimierz; Garnavich, Peter; Challis, Peter; Kirshner, Robert P.; Chevalier, Roger; Filippenko, Alexei V.; Fransson, Claes; Panagia, Nino; Phillips, Mark; Schmidt, Brian; Suntzef, Nicholas

    1998-01-01

    We describe and model high-velocity (approximately 15,000 km S(exp -1)) Ly Alpha and H Alpha emission from the supernova remnant SNR 1987A seen in 1997 September and October with the Space Telescope Imaging Spectrograph. Part of this emission comes from a reverse shock located at approximately 75% of the radius of the inner boundary ofthe innercircumstellar ring and confined within + or - 30 degrees of the equatorial plane. Departure from axisymmetry in the Ly Alpha and H Alpha emission correlates with that seen in nonthermal radio emission and reveals an asymmetry in the circumstellar gas distribution. We also see diffuse high-velocity Ly-Alpha emission from supernova debris inside the reverse shock that may be due to excitation by nonthermal particles accelerated by the shock.

  17. Effect of spinal manipulation on sensorimotor functions in back pain patients: study protocol for a randomised controlled trial

    PubMed Central

    2011-01-01

    Background Low back pain (LBP) is a recognized public health problem, impacting up to 80% of US adults at some point in their lives. Patients with LBP are utilizing integrative health care such as spinal manipulation (SM). SM is the therapeutic application of a load to specific body tissues or structures and can be divided into two broad categories: SM with a high-velocity low-amplitude load, or an impulse "thrust", (HVLA-SM) and SM with a low-velocity variable-amplitude load (LVVA-SM). There is evidence that sensorimotor function in people with LBP is altered. This study evaluates the sensorimotor function in the lumbopelvic region, as measured by postural sway, response to sudden load and repositioning accuracy, following SM to the lumbar and pelvic region when compared to a sham treatment. Methods/Design A total of 219 participants with acute, subacute or chronic low back pain are being recruited from the Quad Cities area located in Iowa and Illinois. They are allocated through a minimization algorithm in a 1:1:1 ratio to receive either 13 HVLA-SM treatments over 6 weeks, 13 LVVA-SM treatments over 6 weeks or 2 weeks of a sham treatment followed by 4 weeks of full spine "doctor's choice" SM. Sensorimotor function tests are performed before and immediately after treatment at baseline, week 2 and week 6. Self-report outcome assessments are also collected. The primary aims of this study are to 1) determine immediate pre to post changes in sensorimotor function as measured by postural sway following delivery of a single HVLA-SM or LVVA-SM treatment when compared to a sham treatment and 2) to determine changes from baseline to 2 weeks (4 treatments) of HVLA-SM or LVVA-SM compared to a sham treatment. Secondary aims include changes in response to sudden loads and lumbar repositioning accuracy at these endpoints, estimating sensorimotor function in the SM groups after 6 weeks of treatment, and exploring if changes in sensorimotor function are associated with changes in

  18. Mössbauer spectroscopy with a high velocity resolution in the study of iron-containing proteins and model compounds.

    PubMed

    Oshtrakh, M I; Alenkina, I V; Milder, O B; Semionkin, V A

    2011-08-15

    Mössbauer spectroscopy with a high velocity resolution was used for comparative studies of human adult, rabbit and pig oxyhemoglobins, human liver ferritin and its pharmaceutically important models Imferon and Maltofer(®) as well as liver and spleen tissues from normal and lymphoid leukemia chicken. These studies revealed small variations of Mössbauer hyperfine parameters which were related to small variations of iron electronic structure and stereochemistry in these samples.

  19. Effects of pulsed, high-velocity water flow on larval robust redhorse and V-lip redhorse

    USGS Publications Warehouse

    Weyers, R.S.; Jennings, C.A.; Freeman, Mary C.

    2003-01-01

    The pulsed, high-velocity water flow characteristic of water-flow patterns downstream from hydropower-generating dams has been implicated in the declining abundance of both aquatic insects and fishes in dam-regulated rivers. This study examined the effects of 0, 4, and 12 h per day of pulsed, high-velocity water flow on the egg mortality, hatch length, final length, and survival of larval robust redhorse Moxostoma robusturn, a presumedly extinct species that was rediscovered in the 1990s, and V-lip redhorse M. collapsum (previously synonomized with the silver redhorse M. anisurum) over a 3-5 week period in three separate experiments. Twelve 38.0-L aquaria (four per treatment) were modified to simulate pulsed, high-velocity water flow (>35 cm/s) and stable, low-velocity water flow (<10 cm/s). Temperature, dissolved oxygen, zooplankton density, and water quality variables were kept the same across treatments. Fertilized eggs were placed in gravel nests in each aquarium. Hatch success was estimated visually at greater than 90%, and the mean larval length at 24 h posthatch was similar in each experiment. After emergence from the gravel nest, larvae exposed to 4 and 12 h of pulsed, high-velocity water flow grew significantly more slowly and had lower survival than those in the 0-h treatment. These results demonstrate that the altered water-flow patterns that typically occur when water is released during hydropower generation can have negative effects on the growth and survival of larval catostomid suckers.

  20. Anomalous resistivity due to low-frequency turbulence. [of collisionless plasma with limited acceleration of high velocity runaway electrons

    NASA Technical Reports Server (NTRS)

    Rowland, H. L.; Palmadesso, P. J.

    1983-01-01

    Large amplitude ion cyclotron waves have been observed on auroral field lines. In the presence of an electric field parallel to the ambient magnetic field these waves prevent the acceleration of the bulk of the plasma electrons leading to the formation of a runaway tail. It is shown that low-frequency turbulence can also limit the acceleration of high-velocity runaway electrons via pitch angle scattering at the anomalous Doppler resonance.

  1. Study of maghemite nanoparticles as prepared and coated with DMSA using Mössbauer spectroscopy with a high velocity resolution

    NASA Astrophysics Data System (ADS)

    Oshtrakh, M. I.; Ushakov, M. V.; Semionkin, V. A.; Lima, E. C. D.; Morais, P. C.

    2014-04-01

    Study of maghemite nanoparticles, native and coated with DMSA as magnetic fluid for biomedical applications, was carried out using Mössbauer spectroscopy with a high velocity resolution at 295 and 90 K. The obtained results demonstrated differences in Mössbauer hyperfine parameters for uncoated and DMSA-coated nanoparticles which were related to the interactions of DMSA molecules with Fe3+ ions on maghemite nanoparticle's surface.

  2. Spinal Cord Injury

    MedlinePlus

    ... care for people with spinal cord injuries and aggressive treatment and rehabilitation can minimize damage to the ... care for people with spinal cord injuries and aggressive treatment and rehabilitation can minimize damage to the ...

  3. Spinal Cord Diseases

    MedlinePlus

    ... diseases Autoimmune diseases Degenerative diseases such as amyotrophic lateral sclerosis and spinal muscular atrophy Symptoms vary but might include pain, numbness, loss of sensation and muscle weakness. These symptoms can occur around the spinal ...

  4. THE HIGH-VELOCITY MOLECULAR OUTFLOWS IN MASSIVE CLUSTER-FORMING REGION G10.6-0.4

    SciTech Connect

    Liu Hauyu Baobab; Ho, Paul T. P.; Zhang Qizhou E-mail: pho@asiaa.sinica.edu.t

    2010-12-20

    We report the arcsecond resolution Submillimeter Array observations of the {sup 12}CO (2-1) transition in the massive cluster-forming region G10.6-0.4. In these observations, the high-velocity {sup 12}CO emission is resolved into individual outflow systems, which have a typical size scale of a few arcseconds. These molecular outflows are energetic and are interacting with the ambient molecular gas. By inspecting the shock signatures traced by CH{sub 3}OH, SiO, and HCN emissions, we suggest that abundant star formation activities are distributed over the entire 0.5 pc scale dense molecular envelope. The star formation efficiency over one global free-fall timescale (of the 0.5 pc molecular envelope, {approx}10{sup 5} years) is about a few percent. The total energy feedback of these high-velocity outflows is higher than 10{sup 47} erg, which is comparable to the total kinetic energy in the rotational motion of the dense molecular envelope. From order-of-magnitude estimations, we suggest that the energy injected from the protostellar outflows is capable of balancing the turbulent energy dissipation. No high-velocity bipolar molecular outflow associated with the central OB cluster is directly detected, which can be due to the photoionization.

  5. Use of a visual guide to improve the quality of VOR responses evoked by high-velocity rotational stimuli

    PubMed Central

    Gianna-Poulin, C.C.; Peterka, R.J.

    2008-01-01

    High-velocity rotational stimuli have the potential to improve the diagnostic capabilities of clinical rotation testing by revealing nonlinear vestibulo-ocular reflex (VOR) responses that are indicative of asymmetric vestibular function. However, eye movements evoked by high-velocity rotations often are inconsistent over time and therefore do not yield reliable diagnostic measures. This study investigated whether use of a novel “visual guide” could improve the consistency and quality of VORs obtained during testing with pulse-step-sine (PSS) stimuli providing periodic high-velocity, horizontal-plane rotations with peak velocities up to 290 deg/s. The visual guide (narrow phosphorescent line spanning 180° field of view) was mounted horizontally on the rotation chair at the subject's eye level. Eight healthy human subjects were tested either in complete darkness while performing an alerting task, or while viewing the visual guide in an otherwise dark room. We found that the visual guide improved the quality of VOR responses as shown by an increased proportion of slow-phase velocity data segments retained for analysis, by a decreased variance of the processed eye velocity data, and by a reduction of outlying VOR response measures. We also found that the visual guide did not induce visual suppression because VOR gain measures were not diminished. PMID:18776595

  6. Phase contrast ultrashort TE: A more reliable technique for measurement of high-velocity turbulent stenotic jets.

    PubMed

    O'Brien, Kieran R; Myerson, Saul G; Cowan, Brett R; Young, Alistair A; Robson, Matthew D

    2009-09-01

    Accurate measurement of peak velocity is critical to the assessment of patients with stenotic valvular disease. Conventional phase contrast (PC) methods for imaging high-velocity jets in aortic stenosis are susceptible to intravoxel dephasing signal loss, which can result in unreliable measurements. The most effective method for reducing intravoxel dephasing is to shorten the echo time (TE); however, the amount that TE can be shortened in conventional sequences is limited. A new sequence incorporating velocity-dependent slice excitation and ultrashort TE (UTE) centric radial readout trajectories is proposed that reduces TE from 2.85 to 0.65 ms. In a high-velocity stenotic jet phantom, a conventional sequence had >5% flow error at a flow rate of only 400 mL/s (velocity >358 cm/s), whereas the PC-UTE showed excellent agreement (<5% error) at much higher flow rates (1080 mL/s, 965 cm/s). In vivo feasibility studies demonstrated that by measuring velocity over a shorter time the PC-UTE approach is more robust to intravoxel dephasing signal loss. It also has less inherent higher-order motion encoding. This sequence therefore demonstrates potential as a more robust method for measuring peak velocity and flow in high-velocity turbulent stenotic jets.

  7. Spinal Cord Injuries

    MedlinePlus

    ... your body and your brain. A spinal cord injury disrupts the signals. Spinal cord injuries usually begin with a blow that fractures or ... bone disks that make up your spine. Most injuries don't cut through your spinal cord. Instead, ...

  8. RESPONSE OF LUMBAR PARASPINAL MUSCLES SPINDLES IS GREATER TO SPINAL MANIPULATIVE LOADING COMPARED WITH SLOWER LOADING UNDER LENGTH CONTROL

    PubMed Central

    Pickar, Joel G.; Sung, Paul S.; Kang, Yu-Ming; Ge, Weiqing

    2007-01-01

    Background Context Spinal manipulation (SM) is a form of manual therapy used clinically to treat patients with low back and neck pain. The most common form of this maneuver is characterized as a high velocity (duration < 150ms), low amplitude (segmental translation < 2mm, rotation < 4°, and applied force 220-889N) impulse thrust (HVLA-SM). Clinical skill in applying an HVLA-SM lies in the practitioner's ability to control the duration and magnitude of the load (i.e., the rate of loading), the direction in which the load is applied, and the contact point at which the load is applied. Control over its mechanical delivery presumably related to its clinical effects. Biomechanical changes evoked by an HVLA-SM are thought to have physiological consequences caused, at least in part, by changes in sensory signaling from paraspinal tissues. Purpose If activation of afferent pathways does contribute to the effects of an HVLA-SM, it seems reasonable to anticipate that neural discharge might increase or decrease in a non-linear fashion as the thrust duration thrust approaches a threshold value. We hypothesized that the relationship between the duration of an impulsive thrust to a vertebra and paraspinal muscle spindle discharge would be non-linear with an inflection near the duration of an HVLA-SM delivered clinically (<150ms). In addition, we anticipated that muscle spindle discharge would be more sensitive to larger amplitude thrusts. Study Design/Setting A neurophysiological study of spinal manipulation using the lumbar spine of a feline model. Methods Impulse thrusts (duration: 12.5, 25, 50, 100, 200, and 400 ms; amplitude 1 or 2mm posterior to anterior) were applied to the spinous process of the L6 vertebra of deeply anesthetized cats while recording single unit activity from dorsal root filaments of muscle spindle afferents innervating the lumbar paraspinal muscles. A feedback motor was used in displacement control mode to deliver the impulse thrusts. The motor's drive

  9. Investigations on spinal cord fMRI of cats under ketamine.

    PubMed

    Cohen-Adad, J; Hoge, R D; Leblond, H; Xie, G; Beaudoin, G; Song, A W; Krueger, G; Doyon, J; Benali, H; Rossignol, S

    2009-01-15

    Functional magnetic resonance imaging (fMRI) of the spinal cord has been the subject of intense research for the last ten years. An important motivation for this technique is its ability to detect non-invasively neuronal activity in the spinal cord related to sensorimotor functions in various conditions, such as after spinal cord lesions. Although promising results of spinal cord fMRI have arisen from previous studies, the poor reproducibility of BOLD activations and their characteristics remain a major drawback. In the present study we investigated the reproducibility of BOLD fMRI in the spinal cord of cats (N=9) by repeating the same stimulation protocol over a long period (approximately 2 h). Cats were anaesthetized with ketamine, and spinal cord activity was induced by electrical stimulation of cutaneous nerves of the hind limbs. As a result, task-related signals were detected in most cats with relatively good spatial specificity. However, BOLD response significantly varied within and between cats. This variability was notably attributed to the moderate intensity of the stimulus producing a low amplitude haemodynamic response, variation in end-tidal CO(2) during the session, low signal-to-noise ratio (SNR) in spinal fMRI time series and animal-specific vascular anatomy. Original contributions of the present study are: (i) first spinal fMRI experiment in ketamine-anaesthetized animals, (ii) extensive study of intra- and inter-subject variability of activation, (iii) characterisation of static and temporal SNR in the spinal cord and (iv) investigation on the impact of CO(2) end-tidal level on the amplitude of BOLD response.

  10. Flow mechanism of Forchheimer's cubic equation in high-velocity radial gas flow through porous media. [High-velocity, high-pressure gas flow through porous media near the wellbore

    SciTech Connect

    Ezeudembah; Dranchuk, P.M.

    1982-09-01

    Until recently, the visco-inertial flow equation, which is an adaptation of Forchheimer's quadratic equation, has been used to describe gas flow behavior at higher flow rates and pressures. The inability of this equation, in some cases, to fully describe high-velocity, high-pressure gas flow behavior, especially around the well bore, led to the consideration of other empirical equations. In this paper, formal derivation of Forchheimer's cubic equation is made by considering the kinetic energy equation of mean flow and dimensional relations for one-dimensional, linear, incompressible fluid flow. By the addition of the cubic term, this equation is regarded as a modified Forchheimer's quadratic equation which accounts for the flow rates obtained beyond the laminar flow condition. The cubic equation spans a wide range of flow rates and regimes, i.e. Darcy type, inertial type, and turbulent. For suitable use in gas flow studies, this equation has been adapted, modified, and corrected for the gas slippage effect. The physical basis of the cubic term has been established by using boundary layer theory to explain the high-velocity, high-pressure flow behavior through a porous path. Gamma, the main parameter in the cubic term, is directly related to a characteristic, dimensionless shape factor which is significant at higher flow rates. It is inversely related to viscosity, but has no dependence on the gas slippage coefficient in the higher flow regime.

  11. High velocity flyer plates launched by magnetic pressure on pulsed power generator CQ-4 and applied in shock Hugoniot experiments

    NASA Astrophysics Data System (ADS)

    Zhang, Xuping; Wang, Guiji; Zhao, Jianheng; Tan, Fuli; Luo, Binqiang; Sun, Chengwei

    2014-05-01

    High velocity flyer plates with good flatness and some thickness have being widely used to the field of shock physics for characterizations of materials under dynamical loading. The techniques of magnetically driven high-velocity flyer plates are further researched based on our pulsed power generators CQ-4 and some good results got on Sandia's Z machine. With large current of several mega-amperes, the loading surface of electrode panel will suffer acute phase transitions caused from magnetic diffusion and Joule heating, and the thickness and flatness of the flyer plates will change with time. In order to obtain the flyer plates with high performances for shock physics, some researches on electrode panels were done by means of LS-DYNA980 software with electro-magnetic package. Two typical configurations for high velocity flyer plates were compared from distribution uniformity of magnetic field in simulation. The results show that the configuration with counter-bore with "notch" and "ear" is better than the other. Then, with the better configuration panels, some experiments were designed and done to validate the simulation results and obtain high velocity flyer plates with good flatness for one-dimensional strain shock experiments on CQ-4. The velocity profiles of the flyer plates were measured by displacement interferometer systems for any reflectors. And the planarity of flyer plates was measured by using the optical fiber pins array for recording the flyer arrival time. The peak velocities of 8.7 km/s with initial dimension of 10 × 7.2 × 0.62 mm for aluminum flyer plates have been achieved. And the flyer plate with initial size of 12 × 9.2 × 0.73 mm was accelerated to velocity of 6.5 km/s with the flatness of less than 11 ns in the central region of 6 mm in diameter and the effective thickness of about 0.220 mm. Based on these work, the symmetrical impact experiments were performed to obtain the high accuracy Hugoniot data of OFHC (oxygen free high conductance

  12. Integral Field Spectroscopy of Markarian 273: Mapping High-Velocity Gas Flows and an Off-Nucleus Seyfert 2 Nebula.

    PubMed

    Colina; Arribas; Borne

    1999-12-10

    Integral field optical spectroscopy with the INTEGRAL fiber-based system is used to map the extended ionized regions and gas flows in Mrk 273, one of the closest ultraluminous infrared galaxies. The Hbeta and [O iii] lambda5007 maps show the presence of two distinct regions separated by 4&arcsec; (3.1 kpc) along position angle (P.A.) 240 degrees. The northeastern region coincides with the optical nucleus of the galaxy and shows the spectral characteristics of LINERs. The southwestern region is dominated by [O iii] emission and is classified as a Seyfert 2. Therefore, in the optical, Mrk 273 is an ultraluminous infrared galaxy with a LINER nucleus and an extended off-nucleus Seyfert 2 nebula. The kinematics of the [O iii] ionized gas shows (1) the presence of highly disturbed gas in the regions around the LINER nucleus, (2) a high-velocity gas flow with a peak-to-peak amplitude of 2.4x103 km s-1, and (3) quiescent gas in the outer regions (at 3 kpc). We hypothesize that the high-velocity flow is the starburst-driven superwind generated in an optically obscured nuclear starburst and that the quiescent gas is directly ionized by a nuclear source, similar to the ionization cones typically seen in Seyfert galaxies.

  13. GALACTIC ALL-SKY SURVEY HIGH-VELOCITY CLOUDS IN THE REGION OF THE MAGELLANIC LEADING ARM

    SciTech Connect

    For, Bi-Qing; Staveley-Smith, Lister; McClure-Griffiths, N. M.

    2013-02-10

    We present a catalog of high-velocity clouds in the region of the Magellanic Leading Arm. The catalog is based on neutral hydrogen (H I) observations from the Parkes Galactic All-Sky Survey. Excellent spectral resolution allows clouds with narrow-line components to be resolved. The total number of detected clouds is 419. We describe the method of cataloging and present the basic parameters of the clouds. We discuss the general distribution of the high-velocity clouds and classify the clouds based on their morphological type. The presence of a significant number of head-tail clouds and their distribution in the region is discussed in the context of Magellanic System simulations. We suggest that ram-pressure stripping is a more important factor than tidal forces for the morphology and formation of the Magellanic Leading Arm and that different environmental conditions might explain the morphological difference between the Magellanic Leading Arm and Magellanic Stream. We also discuss a newly identified population of clouds that forms the LA IV and a new diffuse bridge-like feature connecting the LA II and III complexes.

  14. An experimental study of non-destructive testing on glass fibre reinforced polymer composites after high velocity impact event

    NASA Astrophysics Data System (ADS)

    Razali, N.; Sultan, M. T. H.; Cardona, F.

    2016-10-01

    A non-destructive testing method on Glass Fibre Reinforced Polymer (GFRP) after high velocity impact event using single stage gas gun (SSGG) is presented. Specimens of C- type and E-type fibreglass reinforcement, which were fabricated with 6mm, 8mm, 10mm and 12mm thicknesses and size 100 mm x 100 mm, were subjected to a high velocity impact with three types of bullets: conical, hemispherical and blunt at various gas gun pressure levels from 6 bar to 60 bar. Visual observation techniques using a lab microscope were used to determine the infringed damage by looking at the crack zone. Dye penetrants were used to inspect the area of damage, and to evaluate internal and external damages on the specimens after impact. The results from visual analysis of the impacted test laminates were discussed and presented. It was found that the impact damage started with induced delamination, fibre cracking and then failure, simultaneously with matrix cracking and breakage, and finally followed by the fibres pulled out. C-type experienced more damaged areas compared to E-type of GFRP.

  15. 3 mm band line survey toward the high-velocity compact cloud CO-0.40-0.22

    NASA Astrophysics Data System (ADS)

    Oka, T.; Tanaka, K.; Matsumura, S.; Miura, K.; Takekawa, S.; Takahata, Y.; Nishino, Akihiko

    2014-05-01

    High-velocity compact clouds (HVCCs) are a population of molecular clouds which have compact appearance (d < 10 pc) and large velocity width (Δ V > 50 km s-1), and are found in the central molecular zone of our Galaxy. We performed a 3 mm band line survey toward CO-0.40-0.22, a spatially unresolved HVCC with an extremely large velocity width (Δ V ≃ 90 km s-1), using the Mopra 22 m telescope. We surveyed the frequency range between 76 GHz and 116 GHz with a 0.27 MHz frequency resolution. We detect at least 54 lines from 32 molecules. Many line profiles show a prominent peak at vLSR ˜ 70 km s-1 with very large velocity width, indicating they are emitted by the HVCC. Detections of largish molecules are indicative of non-equilibrium chemistry. We extracted some prominent lines based on velocity structure, intensity ratios, and PCA analyses. Shock diagnostic lines (SiO, SO, CH3OH, HNCO) and dense gas probes (HCN, HCO+) appear to be prominent. Excitation analysis of CH3OH lines show an enhancement in T rot in the negative high-velocity end of the profile. These results suggest that CO-0.40-0.22 has experienced a shock, acceleration, compression, and heating in the recent past.

  16. Theoretical model for high-power diamond laser optics using high-velocity liquid-metal jet impingement cooling

    NASA Astrophysics Data System (ADS)

    Palmer, James R.

    1993-02-01

    In 1988 I presented a paper, `Fly's Eye Modular Optic,' in the Los Angeles Symposium that described an optic for high power laser systems that provided for a modular system of hexagonal components that were independently cooled using a high velocity jet pointed normal to the back surface of the optical faceplate. In this paper we look at the use of diamond optical materials in concert with high velocity jet impingement heat transfer of various liquid metal mediums. By using this combination of techniques and materials we can push the laser damage threshold of optical components to even higher levels of absorbed flux density. The thrust of this paper is to develop a theoretical model for use on optical elements subject to very high continuous flux density lasers and to evaluate the use of commercial diamond substrates with conventional optical thin films and conventional substrates with CVD diamond films. In order to assume the very high absorbed flux densities, it is necessary to have a heat transfer technique capable of maintaining the optical component at a stable temperature and below the damage threshold of the optical materials. For the more common materials, thermal shock and subsequent failure in bi-axial shear have proven to be one of the major constituents of the optical damage. In this paper we look at the thermal shock, vis-a-vis, the melting point of some of the materials.

  17. MULTIPLE HIGH-VELOCITY SiO MASER FEATURES FROM THE HIGH-MASS PROTOSTAR W51 NORTH

    SciTech Connect

    Cho, Se-Hyung; Kim, Jaeheon; Byun, Do-Young E-mail: jhkim@kasi.re.kr

    2011-02-01

    We present the detection of multiple high-velocity silicon monoxide (SiO v = 1, 2, J = 1-0) maser features in the high-mass protostar W51 North which are distributed over an exceedingly large velocity range from 105 to 230 km s{sup -1}. The SiO v = 1, J = 1-0 maser emission shows 3-5 narrow components which span a velocity range from 154 to 230 km s{sup -1} according to observational epochs. The SiO v = 2, J = 1-0 maser also shows 3-5 narrow components that do not correspond to the SiO v = 1 maser and span a velocity range from 105 to 154 km s{sup -1}. The multiple maser components show significant changes on very short timescales (<1 month) from epoch to epoch. We suggest that the high-velocity SiO masers may be emanated from massive star-forming activity of the W51 North protostar as SiO maser jets and will be a good probe of the earliest evolutionary stages of high-mass star formation via an accretion model. Further high angular resolution observations will be required for confirmation.

  18. An experimental and computational study of the hydrodynamics of high-velocity water microdrops for interproximal tooth cleaning.

    PubMed

    Rmaile, A; Carugo, D; Capretto, L; Wharton, J A; Thurner, P J; Aspiras, M; Ward, M; De Jager, M; Stoodley, P

    2015-06-01

    The flow field and local hydrodynamics of high-velocity water microdrops impacting the interproximal (IP) space of typodont teeth were studied experimentally and computationally. Fourteen-day old Streptococcus mutans biofilms in the IP space were treated by a prototype AirFloss delivering 115 µL of water at a maximum exit-velocity of 60 ms(-1) in a 33-ms burst. Using high-speed imaging, footage was generated showing the details of the burst, and demonstrating the removal mechanism of the biofilms. Footage was also generated to characterize the viscoelastic behavior of the biofilms when impacted by an air-only burst, which was compared to the water burst. Image analysis demonstrated the importance of fluid forces on the removal pattern of interdental biofilms. X-ray micro-Computed Tomography (µ-CT) was used to obtain 3D images of the typodont and the IP spaces. Computational Fluid Dynamics (CFD) simulations were performed to study the effect of changing the nozzle position and design on the hydrodynamics within the IP space. Results confirmed our previous data regarding the wall shear stress generated by high-velocity water drops which dictated the efficacy of biofilm detachment. Finally, we showed how CFD models could be used to optimize water drop or burst design towards a more effective biofilm removal performance.

  19. High-velocity frictional properties and microstructures of clay-rich fault gouge in megasplay fault zone, Nankai subduction zone

    NASA Astrophysics Data System (ADS)

    Ujiie, K.; Tsutsumi, A.

    2010-12-01

    In accretionary margins, a large out-of-sequence fault system (the megasplay fault) commonly branches from the megathrust and intersects the seafloor along the lower slope of the margin. Detailed seismic reflection surveys and theoretical studies have suggested that the propagation of earthquake rupture occurred repeatedly along the megasplay fault during great subduction earthquakes. Recently, IODP Expedition 316 drilled into the shallow portion of the megasplay fault zone in the Nankai subduction zone offshore the Kii Peninsula, southwest Japan and found the evidence for the slip localization and past frictional heating along ~10-mm-thick dark gouges in the microbreccia. Thus, high-velocity frictional properties of the megasplay fault material are crucial for understanding whether the megasplay fault efficiently transfers displacement toward the seafloor and fosters a tsunami genesis during a subduction earthquake. We conducted high-velocity friction experiments on clay-rich fault gouge taken from the Nankai megasplay fault zone at a slip rate of 1.3 m/s and normal stresses of 0.6-2.0 MPa under dry and wet conditions. After the experiments, the microstructures of the fault gouges were examined by optical microscope and SEM. In the dry tests, dehydration of clay minerals occurred by frictional heating, and the slip weakening is related to the fault gouge expansion due to a water phase transition from liquid to vapor. The water is derived from the dehydration of clay minerals by frictional heating. The resulting microstructure in the gouge layer is a random distribution of spherical clay-clast aggregates (CCA) in the optically isotropic, dark matrix. In the wet tests, the slip weakening is caused by pore-fluid pressurization resulting from shear-enhanced compaction of the water-saturated gouge and frictional heating. Compared to the dry tests, the wet tests show smaller dynamic stress drops and slip weakening distance. The steady-state shear stress in the wet tests

  20. Detection of High Velocity Absorption Components in the He I Lines of Eta Carinae near the Time of Periastron

    NASA Technical Reports Server (NTRS)

    Richardson, Noel D.; St-Jean, Lucas; Gull, Theodore R.; Madura, Thomas; Hillier, D. John; Teodoro, Mairan; Moffat, Anthony; Corcoran, Michael; Damineli, Augusto

    2014-01-01

    We have obtained a total of 58 high spectral resolution (R90,000) spectra of the massive binary star eta Carinae since 2012 in an effort to continue our orbital and long-term echelle monitoring of this extreme binary (Richardson et al. 2010, AJ, 139, 1534) with the CHIRON spectrograph on the CTIO 1.5 m telescope (Tokovinin et al. 2013, PASP, 125, 1336) in the 45507500A region. We have increased our monitoring efforts and observation frequency as the periastron event of 2014 has approached. We note that there were multiple epochs this year where we observe unusual absorption components in the P Cygni troughs of the He I triplet lines. In particular, we note high velocity absorption components related to the following epochs for the following lines: He I 4713: HJD 2456754- 2456795 (velocity -450 to -560 kms) He I 5876: HJD 2456791- 2456819 (velocity -690 to -800 kms) He I 7065: HJD 2456791- 2456810 (velocity -665 to -730 kms) Figures: Note that red indicates a high-velocity component noted above. He I 4713: http:www.astro.umontreal.carichardson4713.png He I 5876: http:www.astro.umontreal.carichardson5876.png He I 7065: http:www.astro.umontreal.carichardson7065.png These absorptions are likely related to the wind-wind collision region and bow shock, as suggested by the high-velocity absorption observed by Groh et al. (2010, AA, 519, 9) in the He I 10830 Atransition. In these cases, we suspect that we look along an arm of the shock cone and that we will see a fast absorption change from the other collision region shortly after periastron. We suspect that this is related to the multiple-components of the He II 4686 line that was noted by Walter (ATel6334), and is confirmed in our data. Further, high spectral resolution data are highly encouraged,especially for resolving powers greater than 50,000.These observations were obtained with the CTIO 1.5 m telescope, operated by the SMARTS Consortium, and were obtained through both SMARTS and NOAO programs 2012A-0216,2012B-0194

  1. Properties of Ejecta Generated at High-Velocity Perforation of Thin Bumpers made from Different Constructional Materials

    NASA Astrophysics Data System (ADS)

    Myagkov, N. N.; Shumikhin, T. A.; Bezrukov, L. N.

    2013-08-01

    The series of impact experiments were performed to study the properties of ejecta generated at high-velocity perforation of thin bumpers. The bumpers were aluminum plates, fiber-glass plastic plates, and meshes weaved of steel wire. The projectiles were 6.35 mm diameter aluminum spheres. The impact velocities ranged from 1.95 to 3.52 km/s. In the experiments the ejecta particles were captured with low-density foam collectors or registered with the use of aluminum foils. The processing of the experimental results allowed us to estimate the total masses, spatial and size distributions, and perforating abilities of the ejecta produced from these different bumpers. As applied to the problem of reducing the near-Earth space pollution caused by the ejecta, the results obtained argue against the use of aluminum plates as first (outer) bumper in spacecraft shield protection.

  2. Deposition of Na2SO4 from salt-seeded combustion gases of a high velocity burner rig

    NASA Technical Reports Server (NTRS)

    Santoro, G. J.; Kohl, F. J.; Stearns, C. A.; Gokoglu, S. A.; Rosner, D. A.

    1985-01-01

    With a view to developing simulation criteria for the laboratory testing of high-temperature materials for gas turbine engines, the deposition rates of sodium sulfate from sodium salt-seeded combustion gases were determined experimentally using a well instrumented high-velocity burner. In the experiments, Na2SO4, NaCl, NaNO3, and simulated sea salt solutions were injected into the combustor of the Mach 0.3 burner rig operating at constant fuel/air ratios. The deposits formed on an inert rotating collector were then weighed and analyzed. The experimental results are compared to Rosner's vapor diffusion theory. Some additional test results, including droplet size distribution of an atomized salt spray, are used in interpreting the deposition rate data.

  3. Deposition and properties of high-velocity-oxygen-fuel and plasma-sprayed Mo-Mo2C composite coatings

    NASA Astrophysics Data System (ADS)

    Prchlik, L.; Gutleber, J.; Sampath, S.

    2001-12-01

    Molybdenum thermal-spray coatings, dispersion strengthened by molybdenum oxides and molybdenum carbides, play an important role in industrial tribological applications. Traditionally, they have been prepared by plasma and wire flame spraying. High porosity and lower cohesion strength limit their application in situations where both galling and abrasion wear is involved. In this study, high-velocity-oxygen-fuel (HVOF) deposition of molybdenum and molybdenum carbide coatings was attempted. Deposition was achieved for all powders used. Composition, microstructure, mechanical, and wear properties of the HVOF synthesized coatings were evaluated and compared with plasma-sprayed counterparts. The HVOF coatings possessed a very good abrasion resistance, whereas plasma deposits performed better in dry sliding tests. Measurements showed a close relationship between the coating surface hardness and its abrasion resistance. Results also suggested correlation between molybdenum carbide distribution in the molybdenum matrix and the sliding friction response of Mo-Mo2C coatings.

  4. Gel versus aerogel to collect high velocity ejectas from laser shock-loaded metallic targets for postrecovery analyses

    NASA Astrophysics Data System (ADS)

    Lescoute, Emilien; De Rességuier, Thibaut; Chevalier, Jean-Marc

    2012-03-01

    Soft recovery of fast objects is an issue of considerable interest for many applications involving shock wave loading, such as ballistics, armor design, or more recently laser-driven inertial confinement fusion, where the characterization of the debris ejected from metallic shells subjected to intense laser irradiation conditions the design of the experiments. In this work, we compare the high velocity ejecta recovery efficiency of two materials: silica aerogel (density 0.03 g/cm3), which has been used as fragment collector for many years, and "varagel" (density 0.9 g/cm3), which we have tested recently in laser shock experiments. Ejected fragments have been recovered in both types of collectors. Then, samples have been analyzed by X-ray tomography at the European Synchrotron Radiation Facility (ESRF). Three-dimensional reconstructions of the fragments populations have been achieved, and quantitative comparisons between both collecting materials, used in the same conditions, have been performed.

  5. Gas motions within high-velocity cloud Complex A reveal that it is dissolving into the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Huey-You, Cannan; Barger, Kathleen; Nidever, David L.; Rueff, Katherine Meredith

    2017-01-01

    A massive gas cloud, known as Complex A, is headed towards our Galaxy. This high-velocity cloud is made up of 2 million solar masses of neutral and ionized hydrogen. This cloud is traveling through the Galactic halo, which causes a headwind that damages the cloud. Light escaping the Milky Way’s disk also hits the cloud and ionizes it. Using 21-cm radio observations from the Green Bank Telescope, we studied the motions of the gas. We found that diffuse gas is lagging behind the denser parts of the cloud. These motions suggest that gas is being stripped off the cloud and that it is dissolving into the Galactic halo. This disruptive process means that less gas will safely reach the disk of Milky Way and therefore the cloud will provide less gas for making future stars.

  6. Gamma-ray bursts from the accretion of solid bodies onto high-velocity Galactic neutron stars

    SciTech Connect

    Colgate, S.A.; Leonard, P.J.T.

    1993-12-31

    We propose a simple model for the gamma-ray bursts based on high- velocity Galactic neutron stars that have accretion disks. The latter are formed from a mixture of material from the supernova shell and that ablated from a pre-supernova binary companion. Accretion onto the neutron star from this disk when the disk is still largely gaseous may result in a soft gamma-ray repeater phase. Much later, after the neutron star has moved away from its birthplace, solid bodies form in the disk, and some are perturbed into hitting the neutron star to create gamma-ray bursts. This model makes several predictions that are consistent with the observations. The observed combination of a high degree of isotropy on the sky coupled with the observed value of < V/V{sub max}> is not, at first glance, predicted, but is not impossible to attain in our model.

  7. Statistical Study of High-Velocity Compact Clouds Based on the Complete CO Imagings of the Central Molecular Zone

    NASA Astrophysics Data System (ADS)

    Tokuyama, Sekito; Oka, Tomoharu; Takekawa, Shunya; Yamada, Masaya; Iwata, Yuhei; Tsujimoto, Shiho

    2017-01-01

    High-velocity compact clouds (HVCCs) is one of the populations of peculiar clouds detected in the Central Molecular Zone (CMZ) of our Galaxy. They have compact appearances (< 5 pc) and large velocity widths (> 50 km s-1). Several explanations for the origin of HVCC were proposed; e.g., a series of supernovae (SN) explosions (Oka et al. 1999) or a gravitational kick by a point-like gravitational source (Oka et al. 2016). To investigate the statistical property of HVCCs, a complete list of them is acutely necessary. However, the previous list is not complete since the identification procedure included automated processes and manual selection (Nagai 2008). Here we developed an automated procedure to identify HVCCs in a spectral line data.

  8. Kinematics of the Ultra-High-Velocity Gas in the Expanding Molecular Shell Adjacent to the W44 Supernova Remnant

    NASA Astrophysics Data System (ADS)

    Yamada, Masaya; Oka, Tomoharu; Tanaka, Kunihiko; Nomura, Mariko; Takekawa, Shunya; Iwata, Yuhei; Tokuyama, Sekito; Tanabe, Keisuke; Tsujimoto, Shiho; Furusawa, Maiko

    2017-01-01

    High-velocity compact cloud (HVCC) is a peculiar category of molecular clouds detected in the central molecular zone of our Galaxy (Oka et al. 1998, 2007, and 2012). They are characterized by compact appearances (d < 5 pc) and very large velocity widths (Δ V > 50 km s-1). Some of them show high CO J=3-2/J=1-0 intensity ratios (>= 1.5), indicating that they consist of dense and warm molecular gas. Dispite a number of efforts, we have not reached a comprehensive interpretation of HVCCs. Recently, we detected an extraordinaly broad velocity width feature, the `Bullet', in the molecular cloud interacting with the W44 supernova remnant. The Bullet shares essential properties with HVCCs. Because of its proximity, a close inspection of the Bullet must contribute to the understanding of HVCCs.

  9. A statistical study on the occurrence of discrete frequencies in the high velocity solar wind and in the magnetosphere

    NASA Astrophysics Data System (ADS)

    Di Matteo, Simone; Villante, Umberto

    2016-04-01

    The possible occurrence of oscillations at discrete frequencies in the solar wind and their possible correspondence with magnetospheric field oscillations represent an interesting aspect of the solar wind/magnetopheric research. We analyze a large set of high velocity streams following interplanetary shocks in order to ascertain the possible occurrence of preferential sets of discrete frequencies in the oscillations of the solar wind pressure in such structures. We evaluate, for each event, the power spectrum of the dynamic pressure by means of two methods (Welch and multitaper windowing) and accept the common spectral peaks that also pass a harmonic F-test at the 95% confidence level. We compare these frequencies with those detected at geosynchronous orbit in the magnetospheric field components soon after the manifestation of the corresponding Sudden Impulses.

  10. THE 21 cm 'OUTER ARM' AND THE OUTER-GALAXY HIGH-VELOCITY CLOUDS: CONNECTED BY KINEMATICS, METALLICITY, AND DISTANCE

    SciTech Connect

    Tripp, Todd M.; Song Limin

    2012-02-20

    Using high-resolution ultraviolet spectra obtained with the Hubble Space Telescope Space Telescope Imaging Spectrograph and the Far Ultraviolet Spectroscopic Explorer, we study the metallicity, kinematics, and distance of the gaseous 'outer arm' (OA) and the high-velocity clouds (HVCs) in the outer Galaxy. We detect the OA in a variety of absorption lines toward two QSOs, H1821+643 and HS0624+6907. We search for OA absorption toward eight Galactic stars and detect it in one case, which constrains the OA Galactocentric radius to 9 kpc high velocities that are not consistent with Galactic rotation, suggests that the OA and outer-Galaxy HVCs could have a common origin.

  11. Dynamic weakening of fault gouge affected by thermal conductivity of host specimen: implications for the high-velocity weakening mechanisms

    NASA Astrophysics Data System (ADS)

    Yao, Lu; Ma, Shengli; Shimamoto, Toshihiko; Niemeijer, André

    2015-04-01

    Since many high-velocity weakening mechanisms are thermal in origin, we study the effects of thermal conductivity of host specimen on fault gouge friction behavior at seismic slip rates. By using host specimens made of brass, stainless steel, Ti-Al-V alloy and gabbro with thermal conductivities of 123, 15, 5.8 and 3.25 W/m/K, respectively, the experiments in this study produce completely different temperature conditions within the same gouge under the same slip rates and normal stresses. Fault gouges used in the experiments are a natural illite- and quartz-rich gouge from Longmenshan fault zone and pure periclase (MgO) nanopowder. High-velocity weakening of gouges were more pronounced with decreasing thermal conductivity of the specimens. Particularly, almost no dynamic weakening was observed in the tests performed with brass host specimens, while tests with specimens of gabbro and Ti-Al-V alloy exhibits quite similar dramatic weakening behaviors. Such differences in gouge frictional behavior cannot be explained by original flash heating model, since asperity contacts within the slip zone and experimental conditions are still same, even though host specimens are different. Microstructure observations under scanning and transmission electron microscopes reveal that slip zone materials tend to change from individual ultrafine nanograins to larger sintered grains or aggregates, with decreasing thermal conductivities of host specimens. Calculated temperature together with observed microstructure indicate that bulk temperature rise may be also play an important role in fault weakening, as predicted by a recent theoretical analysis of the role of flash heating within the gouge zone [Proctor et al., 2014]. Current results demonstrate the importance of frictional heating in causing the dynamic weakening of gouge, and the powder lubrication hypothesis is not consistent with our experimental data.

  12. Large- and small-scale structure of the intermediate- and high-velocity clouds towards the LMC and SMC

    NASA Astrophysics Data System (ADS)

    Smoker, J. V.; Fox, A. J.; Keenan, F. P.

    2015-08-01

    We employ Ca II K and Na I D interstellar absorption-line spectroscopy of early-type stars in the Large and Small Magellanic Clouds (LMC, SMC) to investigate the large- and small-scale structure in foreground intermediate- and high-velocity clouds (I/HVCs). Data include FLAMES-GIRAFFE Ca II K observations of 403 stars in four open clusters, plus FEROS or UVES spectra of 156 stars in the LMC and SMC. The FLAMES observations are amongst the most extensive probes to date of Ca II structures on ˜20 arcsec scales in Magellanic I/HVCs. From the FLAMES data within a 0.5° field of view, the Ca II K equivalent width in the I/HVC components towards three clusters varies by factors of ≥10. There are no detections of molecular gas in absorption at intermediate or high velocities, although molecular absorption is present at LMC and Galactic velocities towards some sightlines. The FEROS/UVES data show Ca II K I/HVC absorption in ˜60 per cent of sightlines. The range in the Ca II/Na I ratio in I/HVCs is from -0.45 to +1.5 dex, similar to previous measurements for I/HVCs. In 10 sightlines we find Ca II/O I ratios in I/HVC gas ranging from 0.2 to 1.5 dex below the solar value, indicating either dust or ionization effects. In nine sightlines I/HVC gas is detected in both H I and Ca II at similar velocities, implying that the two elements form part of the same structure.

  13. Application of TiC reinforced Fe-based coatings by means of High Velocity Air Fuel Spraying

    NASA Astrophysics Data System (ADS)

    Bobzin, K.; Öte, M.; Knoch, M. A.; Liao, X.; Sommer, J.

    2017-03-01

    In the field of hydraulic applications, different development trends can cause problems for coatings currently used as wear and corrosion protection for piston rods. Aqueous hydraulic fluids and rising raw material prices necessitate the search for alternatives to conventional coatings like galvanic hard chrome or High Velocity Oxygen Fuel (HVOF)-sprayed WC/Co coatings. In a previous study, Fe/TiC coatings sprayed by a HVOF-process, were identified to be promising coating systems for wear and corrosion protection in hydraulic systems. In this feasibility study, the novel High Velocity Air Fuel (HVAF)-process, a modification of the HVOF-process, is investigated using the same feedstock material, which means the powder is not optimized for the HVAF-process. The asserted benefits of the HVAF-process are higher particle velocities and lower process temperatures, which can result in a lower porosity and oxidation of the coating. Further benefits of the HVAF process are claimed to be lower process costs and higher deposition rates. In this study, the focus is set on to the applicability of Fe/TiC coatings by HVAF in general. The Fe/TiC HVAF coating could be produced, successfully. The HVAF- and HVOF-coatings, produced with the same powder, were investigated using micro-hardness, porosity, wear and corrosion tests. A similar wear coefficient and micro-hardness for both processes could be achieved. Furthermore the propane/hydrogen proportion of the HVAF process and its influence on the coating thickness and the porosity was investigated.

  14. Spinal Muscular Atrophy (SMA)

    MedlinePlus

    ... Lessons? Visit KidsHealth in the Classroom What Other Parents Are Reading Your Child's Development (Birth to 3 Years) Feeding Your 1- to 3-Month-Old Feeding Your 4- to 7-Month-Old Feeding Your 8- to 12-Month-Old Feeding Your 1- to 2-Year-Old Spinal ... > For Parents > Spinal Muscular Atrophy (SMA) Print A A A ...

  15. What Is Spinal Stenosis?

    MedlinePlus

    ... and problems with joints. Rheumatoid arthritis:  Affects most people at a younger age than osteoarthritis.  Causes the soft tissues of the joints to swell and can affect the internal organs and systems.  Is not a common cause of spinal ... Conditions Some people are born with conditions that cause spinal stenosis. ...

  16. Spinal Myoclonus After Spinal Cord Injury

    PubMed Central

    Calancie, Blair

    2006-01-01

    Background/Objective: In the course of examining spinal motor function in many hundreds of people with traumatic spinal cord injury, we encountered 6 individuals who developed involuntary and rhythmic contractions in muscles of their legs. Although there are many reports of unusual muscle activation patterns associated with different forms of myoclonus, we believe that certain aspects of the patterns seen with these 6 subjects have not been previously reported. These patterns share many features with those associated with a spinal central pattern generator for walking. Methods: Subjects in this case series had a history of chronic injury to the cervical spinal cord, resulting in either complete (ASIA A; n = 4) or incomplete (ASIA D; n = 2) quadriplegia. We used multi-channel electromyography recordings of trunk and leg muscles of each subject to document muscle activation patterns associated with different postures and as influenced by a variety of sensory stimuli. Results: Involuntary contractions spanned multiple leg muscles bilaterally, sometimes including weak abdominal contractions. Contractions were smooth and graded and were highly reproducible in rate for a given subject (contraction rates were 0.3–0.5 Hz). These movements did not resemble the brief rapid contractions (ie, "jerks") ascribed to some forms of spinal myoclonus. For all subjects, the onset of involuntary muscle contraction was dependent upon hip angle; contractions did not occur unless the hips (and knees) were extended (ie, subjects were supine). In the 4 ASIA A subjects, contractions occurred simultaneously in all muscles (agonists and antagonists) bilaterally. In sharp contrast, contractions in the 2 ASIA D subjects were reciprocal between agonists and antagonists within a limb and alternated between limbs, such that movements in these 2 subjects looked just like repetitive stepping. Finally, each of the 6 subjects had a distinct pathology of their spinal cord, nerve roots, distal trunk

  17. Analysis of the flux and polarization spectra of the type Ia supernova SN 2001el: Exploring the geometry of the high-velocity Ejecta

    SciTech Connect

    Kasen, Daniel; Nugent, Peter; Wang, Lifan; Howell, D.A.; Wheeler, J. Craig; Hoeflich, Peter; Baade, Dietrich; Baron, E.; Hauschildt, P.H.

    2003-01-15

    SN 2001el is the first normal Type Ia supernova to show a strong, intrinsic polarization signal. In addition, during the epochs prior to maximum light, the CaII IR triplet absorption is seen distinctly and separately at both normal photospheric velocities and at very high velocities. The unusual, high-velocity triplet absorption is highly polarized, with a different polarization angle than the rest of the spectrum. The unique observation allows us to construct a relatively detailed picture of the layered geometrical structure of the supernova ejecta: in our interpretation, the ejecta layers near the photosphere (v approximately 10,000 km/s) obey a near axial symmetry, while a detached, high-velocity structure (v approximately 18,000-25,000 $ km/s) of CaII line opacity deviates from the photospheric axisymmetry. By partially obscuring the underlying photosphere, the high-velocity structure causes a more incomplete cancellation of the polarization of the photospheric light, and so gives rise to the polarization peak of the high-velocity IR triplet feature. In an effort to constrain the ejecta geometry, we develop a technique for calculating 3-D synthetic polarization spectra and use it to generate polarization profiles for several parameterized configurations. In particular, we examine the case where the inner ejecta layers are ellipsoidal and the outer, high-velocity structure is one of four possibilities: a spherical shell, an ellipsoidal shell, a clumped shell, or a toroid. The synthetic spectra rule out the clearly discriminated if observations are obtained from several different lines of sight. Thus, assuming the high velocity structure observed for SN 2001el is a consistent feature of at least known subset of type Ia supernovae, future observations and analyses such as these may allow one to put strong constraints on the ejecta geometry and hence on supernova progenitors and explosion mechanisms.

  18. Seismic Technology Adapted to Analyzing and Developing Geothermal Systems Below Surface-Exposed High-Velocity Rocks Final Report

    SciTech Connect

    Hardage, Bob A.; DeAngelo, Michael V.; Ermolaeva, Elena; Hardage, Bob A.; Remington, Randy; Sava, Diana; Wagner, Donald; Wei, Shuijion

    2013-02-01

    The objective of our research was to develop and demonstrate seismic data-acquisition and data-processing technologies that allow geothermal prospects below high-velocity rock outcrops to be evaluated. To do this, we acquired a 3-component seismic test line across an area of exposed high-velocity rocks in Brewster County, Texas, where there is high heat flow and surface conditions mimic those found at numerous geothermal prospects. Seismic contractors have not succeeded in creating good-quality seismic data in this area for companies who have acquired data for oil and gas exploitation purposes. Our test profile traversed an area where high-velocity rocks and low-velocity sediment were exposed on the surface in alternating patterns that repeated along the test line. We verified that these surface conditions cause non-ending reverberations of Love waves, Rayleigh waves, and shallow critical refractions to travel across the earth surface between the boundaries of the fast-velocity and slow-velocity material exposed on the surface. These reverberating surface waves form the high level of noise in this area that does not allow reflections from deep interfaces to be seen and utilized. Our data-acquisition method of deploying a box array of closely spaced geophones allowed us to recognize and evaluate these surface-wave noise modes regardless of the azimuth direction to the surface anomaly that backscattered the waves and caused them to return to the test-line profile. With this knowledge of the surface-wave noise, we were able to process these test-line data to create P-P and SH-SH images that were superior to those produced by a skilled seismic data-processing contractor. Compared to the P-P data acquired along the test line, the SH-SH data provided a better detection of faults and could be used to trace these faults upward to the boundaries of exposed surface rocks. We expanded our comparison of the relative value of S-wave and P-wave seismic data for geothermal

  19. The influence of slip velocity and temperature on permeability during and after high-velocity fault slip

    NASA Astrophysics Data System (ADS)

    Tanikawa, W.; Mukoyoshi, H.; Tadai, O.; Hirose, T.; Lin, W.

    2011-12-01

    Fluid transport properties in fault zones play an important role in dynamic processes during large earthquakes. If the permeability in a fault zone is low, high pore-fluid pressures caused by thermal pressurization (Sibson, 1973) or shear-induced compaction (Blanpied et al., 1992) can lead to an apparent reduction of fault strength. Changes in porosity and permeability of fault rocks within a fault zone during earthquakes and the subsequent progressive recovery of these properties may have a large influence on earthquake recurrence (Sleep and Blanpied, 1992). A rotary shear apparatus was used to investigate changes of fluid transport properties in a fault zone by real-time measurement of gas flow rates during and after shearing of hollow sandstone and granite cylinders at various slip rates. Our apparatus measures permeability parallel to the slip plane in both the slip zone and wall rocks. In all cases, permeability decreased rapidly with an increase of friction, but recovered soon after slip, reaching a steady state within several tens of minutes. The rate of reduction of permeability increased with increasing slip velocity. Permeability did not recover to pre-slip levels after low-velocity tests but recovered to exceed them after high-velocity tests. Frictional heating of gases at the slip surface increased gas viscosity, which increased gas flow rate to produce an apparent permeability increase. The irreversible permeability changes of the low-velocity tests were caused by gouge formation due to wearing and smoothing of the slip surface. The increase of permeability after high-velocity tests was caused by mesoscale fracturing in response to rapid temperature rise. Changes of pore fluid viscosity contributed more to changes of flow rate than did permeability changes caused by shear deformation, although test results from different rocks and pore fluids might be different. References Blanpied, M.L., Lockner, D.A., Byerlee, J.D., 1992. An earthquake mechanism

  20. High-velocity Frictional Behavior of Dunite, Biotite Gneiss, Phyllite and Coal Show Evidence for Melting and Thermal Degasing

    NASA Astrophysics Data System (ADS)

    O'Hara, K. D.; Mizoguchi, K.; Shimamoto, T.

    2004-12-01

    We conducted high-velocity frictional experiments on dunite, biotite gneiss, phyllite gouge and coal gouge at Kyoto University using a rotary high-velocity frictional testing machine. The purpose was to examine the effect of frictional melting in various rock types and to explore the effect of thermal degassing using coal as an analogue for a volatile fault zone. Experiments were conducted dry at equivalent slip rates of 1 m/s (1200 rpm) at normal stresses of 0.6-16 MPa for distances up to 90 m. Solid cylinders (25 mm diameter) of dunite and biotite gneiss were sheared with aluminum-alloy jackets at high stress, whereas phyllite and coal gouges were sheared with Teflon sleeves at low stress. The metal jackets allow high stress experiments to be performed and are inferred to melt before rock melting occurs. Dunite sheared at 10-16 MPa shows a weakening-strengthening followed by second weakening on melting, similar to previous experiments on gabbro without a metal jacket. Dunite melting is confirmed by, as yet unidentified, dendritic microlites, and a rapid reduction of steady-state frictional strength to 0.15. Under similar conditions, biotite gneiss shows apparent melting, but undergoes continuous strengthening without reaching steady state. Bituminous coal gouge sheared at 0.6 MPa undergoes a highly reproducible rapid weakening from 0.75 to 0.2, with odorous white gas emissions, sometimes accompanied by liquid hydrocarbons. Shear stress decreases prior to gasification and rapidly oscillating sample shortening/elongation occurs during gas emission. A slowly sheared sample (15 rpm) did not show weakening or gas emission. This is the first experimental demonstration of weakening associated with devolatilization during rapid slip. Vitrinite reflectance measurements on sheared coal samples may provide constraints on the temperature during gasification. Phyllite gouge sheared under the same conditions shows a gradual weakening to a steady-state strength of about 0

  1. On the Derivation of a High-Velocity Tail from the Boltzmann-Fokker-Planck Equation for Shear Flow

    NASA Astrophysics Data System (ADS)

    Acedo, L.; Santos, A.; Bobylev, A. V.

    2002-12-01

    Uniform shear flow is a paradigmatic example of a nonequilibrium fluid state exhibiting non-Newtonian behavior. It is characterized by uniform density and temperature and a linear velocity profile U x ( y)= ay, where a is the constant shear rate. In the case of a rarefied gas, all the relevant physical information is represented by the one-particle velocity distribution function f( r, v)= f( V), with V≡ v- U( r), which satisfies the standard nonlinear integro-differential Boltzmann equation. We have studied this state for a two-dimensional gas of Maxwell molecules with a collision rate K( θ)∝lim ∈→0 ∈ -2 δ( θ- ∈), where θ is the scattering angle, in which case the nonlinear Boltzmann collision operator reduces to a Fokker-Planck operator. We have found analytically that for shear rates larger than a certain threshold value a th≃0.3520 ν (where ν is an average collision frequency and a th/ ν is the real root of the cubic equation 64 x 3+16 x 2+12 x-9=0) the velocity distribution function exhibits an algebraic high-velocity tail of the form f( V; a)˜| V|-4- σ( a) Φ( ϕ; a), where ϕ≡tan V y / V x and the angular distribution function Φ( ϕ; a) is the solution of a modified Mathieu equation. The enforcement of the periodicity condition Φ( ϕ; a)= Φ( ϕ+ π; a) allows one to obtain the exponent σ( a) as a function of the shear rate. It diverges when a→ a th and tends to a minimum value σ min≃1.252 in the limit a→∞. As a consequence of this power-law decay for a> a th, all the velocity moments of a degree equal to or larger than 2+ σ( a) are divergent. In the high-velocity domain the velocity distribution is highly anisotropic, with the angular distribution sharply concentrated around a preferred orientation angle ~ϕ( a), which rotates from ~ϕ=- π/4,3 π/4 when a→ a th to ~ϕ=0, π in the limit a→∞.

  2. Spinal cordectomy: A new hope for morbid spinal conditions.

    PubMed

    Konar, Subhas K; Maiti, Tanmoy K; Bir, Shyamal C; Nanda, Anil

    2017-01-01

    A spinal cordectomy is a treatment option for several disorders of the spinal cord like post-traumatic syringomyelia, spinal cord tumor and myelomeningocele. We have done a systematic analysis of all reported cases of spinal cordectomy to investigate the possible outcomes and complications. A PubMed search was performed for literature published from 1949 to 2015 with search words "spinal cordectomy", "spinal cord transection" and "cordectomy for malignant spinal cord tumors" to select articles containing information about the indication, outcome and complication of spinal cordectomy performed for diverse etiologies. Spinal cordectomy was performed for post-traumatic syrinx (76 cases), SPAM (2 cases), Central pain of spinal cord origin (22 cases), Spasticity (8 cases), Spinal tumors (16 cases) and Myelomeningocele (30 cases). Among the 76 cases, 60 cases fulfilled the inclusion criteria for our outcome analysis in terms of improvement, stabilization or deterioration after spinal cordectomy. The results showed 78.3% excellent improvement, 13.4% stable and 8.3% (5 cases) deterioration. The reported causes of failure of spinal cordectomy for post-traumatic syrinx were scarring of a proximal stump and severe arachnoid adhesion. Sixteen cases of spinal cordectomy related with spinal cord tumors have been reported. Also reported were seven cases of GBM, two cases of AA and one each case of anaplastic tanycytic ependymoma, schwanoma, neurofibroma, atypical meningioma and malignant ganglioglioma. Cordectomy shouldbe strongly considered in patients having malignant spinal cord tumors with complete motor loss and sensory loss below the level of the lesion as a means of preventing the spread of disease from the original tumor focus. Spinal cordectomy is a treatment option with a good outcome for post-traumatic spinal morbidity, spinal cord tumors and myelomeningocele. However, since it is an invasive and irreversible procedure, it is only considered when other options have

  3. Spinal epidural abscess.

    PubMed

    Johnson, Katherine G

    2013-09-01

    Spinal epidural abscess is a rare bacterial infection located within the spinal canal. Early diagnosis and rapid treatment are important because of its potential to cause rapidly progressive spinal cord compression and irreversible paralysis. A staphylococcus bacterial infection is the cause in most cases. Treatment includes antibiotics and possible surgical drainage of the abscess. A favorable neurologic outcome correlates with the severity and duration of neurologic deficits before surgery and the timeliness of the chosen intervention. It is important for the critical care nurse to monitor the patient's neurologic status and provide appropriate interventions.

  4. Burst Speed of Wild Fishes under High-Velocity Flow Conditions Using Stamina Tunnel with Natural Guidance System in River

    NASA Astrophysics Data System (ADS)

    Izumi, Mattashi; Yamamoto, Yasuyuki; Yataya, Kenichi; Kamiyama, Kohhei

    Swimming experiments were conducted on wild fishes in a natural guidance system stamina tunnel (cylindrical pipe) installed in a fishway of a local river under high-velocity flow conditions (tunnel flow velocity : 211 to 279 cm·s-1). In this study, the swimming characteristics of fishes were observed. The results show that (1) the swimming speeds of Tribolodon hakonensis (Japanese dace), Phoxinus lagowshi steindachneri (Japanese fat-minnow), Plecoglossus altivelis (Ayu), and Zacco platypus (Pale chub) were in proportion to their body length under identical water flow velocity conditions; (2) the maximum burst speed of Japanese dace and Japanese fat-minnow (measuring 4 to 6 cm in length) was 262 to 319 cm·s-1 under high flow velocity conditions (225 to 230 cm·s-1), while the maximum burst speed of Ayu and Pale chub (measuring 5 cm to 12 cm in length) was 308 to 355 cm·s-1 under high flow velocity conditions (264 to 273 cm·s-1) ; (3) the 50cm-maximum swimming speed of swimming fishes was 1.07 times faster than the pipe-swimming speed; (4) the faster the flow velocity, the shorter the swimming distance became.

  5. Survivability of bare, individual Bacillus subtilis spores to high-velocity surface impact: Implications for microbial transfer through space

    NASA Astrophysics Data System (ADS)

    Barney, Brandon L.; Pratt, Sara N.; Austin, Daniel E.

    2016-06-01

    Laboratory experiments show that endospores of Bacillus subtilis survive impact against a solid surface at velocities as high as 299 ±28 m/s. During impact, spores experience and survive accelerations of at least 1010 m/s2. The spores were introduced into a vacuum chamber using an electrospray source and accelerated to a narrow velocity distribution by entrainment in a differentially pumped gas flow. Different velocity ranges were studied by modifying the gas flow parameters. The spores were electrically charged, allowing direct measurement of the velocity of each spore as it passed through an image charge detector prior to surface impact. Spores impacted a glass surface and were collected for subsequent analysis by culturing. Most spores survived impact at all measured velocities. These experiments differ fundamentally from other studies that show either shock or impact survivability of bacteria embedded within or on the surface of a projectile. Bacteria in the present experiments undergo a single interaction with a solid surface at the full impact velocity, in the absence of any other effects such as cushioning due to microbe agglomerations, deceleration due to air or vapor, or transfer of impact shock through solid or liquid media. During these full-velocity impact events, the spores experience extremely high decelerations. This study is the first reported instance of accelerations of this magnitude experienced during a bacteria impact event. These results are discussed in the context of potential transfer of viable microbes in space and other scenarios involving surface impacts at high velocities.

  6. Numerical Investigation of Combustion and Flow Dynamics in a High Velocity Oxygen-Fuel Thermal Spray Gun

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoguang; Song, Qiuzhi; Yu, Zhiyi

    2016-02-01

    The combustion and flow behavior within a high velocity oxygen-fuel (HVOF) thermal spray gun is very complex and involves multiphase flow, heat transfer, chemical reactions, and supersonic/subsonic transitions. Additionally, this behavior has a significant effect on the formation of a coating. Non-premixed combustion models have been developed and are able to provide insight into the underlying physics of the process. Therefore, this investigation employs a non-premixed combustion model and the SST k - ω turbulence model to simulate the flow field of the JP5000 (Praxair-TAFA, US) HVOF thermal spray gun. The predicted temperature and velocity have a high level of agreement with experimental data when using the non-premixed combustion model. The results are focused on the fuel combustion, the subsequent gas dynamics within the HVOF gun, and the development of a supersonic free jet outside the gun. Furthermore, the oxygen/fuel inlet turbulence intensity, the fuel droplet size, and the oxygen/fuel ratio are investigated to determine their effect on the supersonic flow characteristics of the combustion gas.

  7. Evaluation of High Velocity Oxygen Fuel (HVOF) Al/SiCp Coatings as Corrosion Control Coatings for Magnesium Alloys

    NASA Astrophysics Data System (ADS)

    Taltavull, C.; Lopez, A. J.; Torres, B.; Rams, J.

    2014-06-01

    High velocity oxygen-fuel (HVOF) thermal spray technique has been used to fabricate Al and MMC (Al/SiCp) coatings on the AZ91 Mg alloy as a corrosion-control coatings. Corrosion behaviour of the coated specimens had been evaluated by electrochemical tests which revealed that some coated specimens presented an improvement on the corrosion behaviour of the AZ91 substrate. Taguchi DOE method has been used to analyse the relationship between the spraying conditions, i.e. spraying distance, % SiCp in feedstock, number of layers deposited and gun speed, and the corrosion behaviour of the coated specimens. In addition, a relationship between the coating characteristic, i.e. thickness, porosity, adhesion and roughness, and the corrosion behaviour of the coated specimens had also been studied. Optimum spraying conditions were fabricated and corrosion tested to validate the Taguchi DOE method analysis. Among the different coatings features, thickness and compactness seems to be the most relevant ones in terms of corrosion.

  8. AN EXTREME HIGH-VELOCITY BIPOLAR OUTFLOW IN THE PRE-PLANETARY NEBULA IRAS 08005-2356

    SciTech Connect

    Sahai, R.; Patel, N. A.

    2015-09-01

    We report interferometric mapping of the bipolar pre-planetary nebula IRAS 08005-2356 (I 08005) with an angular resolution of ∼1″–5″, using the Submillimeter Array, in the {sup 12}CO J = 2–1, 3–2, {sup 13}CO J = 2–1, and SiO J = 5–4 (v = 0) lines. Single-dish observations, using the SMT 10 m, were made in these lines as well as in the CO J = 4–3 and SiO J = 6–5 (v = 0) lines. The line profiles are very broad, showing the presence of a massive (>0.1 M{sub ⊙}), extreme high velocity outflow (V ∼ 200 km s{sup −1}) directed along the nebular symmetry axis derived from the Hubble Space Telescope imaging of this object. The outflow's scalar momentum far exceeds that available from radiation pressure of the central post-AGB star, and it may be launched from an accretion disk around a main-sequence companion. We provide indirect evidence for such a disk from its previously published, broad Hα emission profile, which we propose results from Lyβ emission generated in the disk followed by Raman-scattering in the innermost regions of a fast, neutral wind.

  9. High-Velocity Oxygen Fuel Thermal Spray of Fe-Based Amorphous Alloy: a Numerical and Experimental Study

    NASA Astrophysics Data System (ADS)

    Ajdelsztajn, L.; Dannenberg, J.; Lopez, J.; Yang, N.; Farmer, J.; Lavernia, E. J.

    2009-09-01

    The fabrication of dense coatings with appropriate properties using a high velocity oxygen fuel (HVOF) spray process requires an in-depth understanding of the complete gas flow field and particle behavior during the process. A computational fluid dynamics (CFD) model is implemented to investigate the gas flow behavior that occurs during the HVOF process and a simplified one-dimensional decoupled model of the in-flight thermal behavior of the amorphous Fe-based powder particles was developed and applied for three different spray conditions. The numerical results were used to rationalize the different coating microstructures described in the experimental results. Low porosity and amorphous coatings were produced using two different particle size distributions (16 to 25 μm and 25 to 53 μm). The amorphous characteristics of the powder were retained in the coating due to melting and rapid solidification in the case of very fine powder or ligaments (<16 μm) and to the fact that the crystallization temperature was not reached in the case of the large particles (16 to 53 μm).

  10. High-velocity stars as a result of encounters between stars and massive binary black holes in galactic nuclei

    NASA Astrophysics Data System (ADS)

    Zhuiko, S. V.; Orlov, V. V.; Shirokova, K. S.

    2017-01-01

    Numerical simulations of the motions of stars in the gravitational fields of binary black holes with various component mass ratios have been carried out. Two models are considered: (1) the two-body problem with two fixed centers; (2) the general three-body problem. The first model is applicable only over short times Δ t ≫ T, where T is the period of the binary system. The second model is applicable at all times except for during close encounters of stars with one of the binary components, r ≤ 0.00002 pc, where r is the distance from the star to the nearer black hole. In very close passages, relativistic corrections must be taken into account. Estimates of the probability of formation of high-velocity stars as a result of such interactions are obtained. It is shown that this mechanism is not suitable for the nucleus of our Galaxy due to the probable absence of a second massive black hole in the central region of the Galaxy.

  11. The corrosion behavior and microstructure of high-velocity oxy-fuel sprayed nickel-base amorphous/nanocrystalline coatings

    NASA Astrophysics Data System (ADS)

    Dent, A. H.; Horlock, A. J.; McCartney, D. G.; Harris, S. J.

    1999-09-01

    The corrosion characteristics of two Ni-Cr-Mo-B alloy powders sprayed by the high-velocity oxy-fuel (HVOF) process have been studied using potentiodynamic and potentiostatic corrosion analysis in 0.5 M H2SO4. The deposits were also microstructurally characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM) (utilizing both secondary electron and backscattered electron modes), and transmission electron microscopy (TEM). Results from the microstructural examination of the two alloys have revealed a predominantly amorphous/nanocrystalline face centered cubic (fcc) matrix containing submicron boride precipitates as well as regions of martensitically transformed laths. Apparent recrystallization of the amorphous matrix has also been observed in the form of cellular crystals with a fcc structure. The oxide stringers observed at splat boundaries were found to be columnar grained α-Cr2O3, though regions of the spinel oxide NiCr2O4 with a globular morphology were also observed. The coatings of the two alloys exhibited comparable resistance to corrosion in 0.5 M H2SO4, as revealed by potentiodynamic tests. They both had rest potentials approximately equal to -300 mV saturated calomel electrode (SCE) and passive region current densities of ˜1 mA/cm2. Microstructural examination of samples tested potentiostatically revealed the prevalence of degradation at splat boundaries, especially those where significant oxidation of the deposit occurred.

  12. Detection of an Optical Counterpart to the ALFALFA Ultra-compact High-velocity Cloud AGC 249525

    NASA Astrophysics Data System (ADS)

    Janesh, William; Rhode, Katherine L.; Salzer, John J.; Janowiecki, Steven; Adams, Elizabeth A. K.; Haynes, Martha P.; Giovanelli, Riccardo; Cannon, John M.

    2017-03-01

    We report on the detection at >98% confidence of an optical counterpart to AGC 249525, an ultra-compact high-velocity cloud (UCHVC) discovered by the Arecibo Legacy Fast ALFA survey blind neutral hydrogen survey. UCHVCs are compact, isolated H i clouds with properties consistent with their being nearby low-mass galaxies, but without identified counterparts in extant optical surveys. Analysis of the resolved stellar sources in deep g- and i-band imaging from the WIYN pODI camera reveals a clustering of possible red giant branch stars associated with AGC 249525 at a distance of 1.64 ± 0.45 Mpc. Matching our optical detection with the H i synthesis map of AGC 249525 from Adams et al. shows that the stellar overdensity is exactly coincident with the highest-density H i contour from that study. Combining our optical photometry and the H i properties of this object yields an absolute magnitude of -7.1≤slant {M}V≤slant -4.5, a stellar mass between 2.2+/- 0.6× {10}4 {M}ȯ and 3.6+/- 1.0× {10}5 {M}ȯ , and an H i to stellar mass ratio between 9 and 144. This object has stellar properties within the observed range of gas-poor ultra-faint dwarfs in the Local Group, but is gas-dominated.

  13. Kinematics of Ultra-high-velocity Gas in the Expanding Molecular Shell Adjacent to the W44 Supernova Remnant

    NASA Astrophysics Data System (ADS)

    Yamada, Masaya; Oka, Tomoharu; Takekawa, Shunya; Iwata, Yuhei; Tsujimoto, Shiho; Tokuyama, Sekito; Furusawa, Maiko; Tanabe, Keisuke; Nomura, Mariko

    2017-01-01

    We mapped the ultra-high-velocity feature (the “Bullet”) detected in the expanding molecular shell associated with the W44 supernova remnant using the Nobeyama Radio Observatory 45 m telescope and the Atacama Submillimeter Telescope Experiment 10 m telescope. The Bullet clearly appears in the CO J = 1–0, CO J = 3–2, CO J = 4–3, and HCO+ J = 1–0 maps with a compact appearance (0.5 × 0.8 pc2) and an extremely broad-velocity width (ΔV ≃ 100 km s‑1). The line intensities indicate that the Bullet has a higher density and temperature than those in the expanding molecular shell. The kinetic energy of the Bullet amounts to 1048.0 erg, which is approximately 1.5 orders of magnitude greater than the kinetic energy shared to the small solid angle of it. Two possible formation scenarios with an inactive isolated black hole are presented.

  14. Computational fluid dynamics analysis of a wire-feed, high-velocity oxygen-fuel (HVOF) thermal spray torch

    SciTech Connect

    Lopez, A.R.; Hassan, B.; Oberkampf, W.L.; Neiser, R.A.; Roemer, T.J.

    1996-09-01

    The fluid and particle dynamics of a High-Velocity Oxygen-Fuel Thermal Spray torch are analyzed using computational and experimental techniques. Three-dimensional Computational Fluid Dynamics (CFD) results are presented for a curved aircap used for coating interior surfaces such as engine cylinder bores. The device analyzed is similar to the Metco Diamond Jet Rotating Wire (DJRW) torch. The feed gases are injected through an axisymmetric nozzle into the curved aircap. Premixed propylene and oxygen are introduced from an annulus in the nozzle, while cooling air is injected between the nozzle and the interior wall of the aircap. The combustion process is modeled using a single-step finite-rate chemistry model with a total of 9 gas species which includes dissociation of combustion products. A continually-fed steel wire passes through the center of the nozzle and melting occurs at a conical tip near the exit of the aircap. Wire melting is simulated computationally by injecting liquid steel particles into the flow field near the tip of the wire. Experimental particle velocity measurements during wire feed were also taken using a Laser Two-Focus (L2F) velocimeter system. Flow fields inside and outside the aircap are presented and particle velocity predictions are compared with experimental measurements outside of the aircap.

  15. Computational analysis of a three-dimensional High-Velocity Oxygen-Fuel (HVOF) Thermal Spray torch

    SciTech Connect

    Hassan, B.; Lopez, A.R.; Oberkampf, W.L.

    1995-07-01

    An analysis of a High-Velocity Oxygen-Fuel Thermal Spray torch is presented using computational fluid dynamics (CFD). Three-dimensional CFD results are presented for a curved aircap used for coating interior surfaces such as engine cylinder bores. The device analyzed is similar to the Metco Diamond Jet Rotating Wire torch, but wire feed is not simulated. To the authors` knowledge, these are the first published 3-D results of a thermal spray device. The feed gases are injected through an axisymmetric nozzle into the curved aircap. Argon is injected through the center of the nozzle. Pre-mixed propylene and oxygen are introduced from an annulus in the nozzle, while cooling air is injected between the nozzle and the interior wall of the aircap. The combustion process is modeled assuming instantaneous chemistry. A standard, two-equation, K-{var_epsilon} turbulence model is employed for the turbulent flow field. An implicit, iterative, finite volume numerical technique is used to solve the coupled conservation of mass, momentum, and energy equations for the gas in a sequential manner. Flow fields inside and outside the aircap are presented and discussed.

  16. X-ray imaging of high velocity moving objects by scanning summation using a single photon processing system

    NASA Astrophysics Data System (ADS)

    Thim, J.; Reza, S.; O'Nils, M.; Norlin, B.

    2015-04-01

    X-ray imaging has been used extensively in the manufacturing industry. In the paper and paperboard industry X-ray imaging has been used for measuring parameters such as coat weight, using mean values of X-ray absorption inline in the manufacturing machines. Recently, an interest has surfaced to image paperboard coating with pixel resolved images showing material distribution in the coating on the paperboard, and to do this inline in the paper machine. Naturally, imaging with pixel resolution in an application where the paperboard web travels with velocities in the order of 10 m/s sets harsh demands on the X-ray source and the detector system to be used. This paper presents a scanning imaging method for single photon imaging systems that lower the demands on the source flux by hundreds of times, enabling a system to be developed for high velocity industrial measurement applications. The paper presents the imaging method, a discussion of system limitations, simulations and real measurements in a laboratory environment with a moving test object of low velocity, all to verify the potential and limits of the proposed method.

  17. A Computational Study of Segmented Tungsten Rod Penetration into a Thick Steel Target Plate at High Velocities

    NASA Astrophysics Data System (ADS)

    Presnell, M.; Rajendran, A.

    2011-06-01

    This paper presents results from computational simulations of tungsten alloy segmented rod projectiles (SRP) penetrating an RHA semi-infinite target plate at high velocities. For SRP with an aspect ratio (L/D) = 1/8, a loss in penetration efficiency was seen upon successive segment impacts. Numerical simulations of a configuration in which a tungsten heavy alloy SRP penetrated a thick RHA 4340 steel at 2.6 km/s were performed using the 2006 version of the EPIC - a Lagrangian code. The configuration consisted of eight collinear impacts of discs which measured 2 mm thick and 16mm in diameter. The numerical simulations considered a range of parameters including element-particle conversion, spacing and number of fragments, failure criterion, and mesh resolution that influenced the Depth of Penetration (DOP). The EPIC results using the element-to-particle conversion capability in the EPIC code are also compared with open-literature DOP data from simulations using an Eulerian finite element code, AUTODYN for a similar configuration. The present results showed a unique phenomenon of back-flowing ejecta from the crater and fragmented segments penetrating the in-coming subsequent segment. The penetration efficiency seems to be influenced by the back-flowing ejecta. Further computational investigation considered additional simulations with an impact configuration designed to minimize the ejecta effects by using washer-shaped segments; however, the results showed insignificant improvement.

  18. Synthesis of nanostructured WC-12 pct Co coating using mechanical milling and high velocity oxygen fuel thermal spraying

    SciTech Connect

    He, J. Ice, M.; Dallek, S.; Lavernia, E.J.

    2000-02-01

    A nanostructured WC-12 pct Co coating was synthesized using mechanical milling and high velocity oxygen fuel (HVOF) thermal spraying. The variation of powder characteristics with milling time and the performance of the coatings were investigated using scanning electron microscope (SEM), X-ray, transmission electron microscope (TEM), thermogravimetric analyzer (TGA), and microhardness measurements. There is no evidence that indicates the presence of an amorphous phase in the sintered WC-12 pct Co powder, and the binder phase in this powder is still crystalline Co. Mechanical milling of up to 20 hours did not lead to the formation of an amorphous phase in the sintered WC-12 pct Co powder. During the initial stages of the milling, the brittle carbide particles were first fractured into fragments and then embedded into the binder phase. This process gradually formed polycrystal nanocomposite powders of the Co binder phase and W carbide particles. The conventional cold welding and fracturing processes primarily occurred among the Co binder powders and polycrystal composite powders. The nanostructured WC-12 pct Co coatings, synthesized in the present study, consist of an amorphous matrix and carbides with an average particle diameter of 35 nm. The coating possesses an average microhardness of 1135 HV and higher resistance to indentation fracture than that of its conventional counterpart.

  19. An Extremely High Velocity Molecular Jet Surrounded by an Ionized Cavity in the Protostellar Source Serpens SMM1

    NASA Astrophysics Data System (ADS)

    Hull, Charles L. H.; Girart, Josep M.; Kristensen, Lars E.; Dunham, Michael M.; Rodríguez-Kamenetzky, Adriana; Carrasco-González, Carlos; Cortés, Paulo C.; Li, Zhi-Yun; Plambeck, Richard L.

    2016-06-01

    We report Atacama Large Millimeter/submillimeter Array (ALMA) observations of a one-sided, high-velocity (˜80 km s-1) CO(J = 2\\to 1) jet powered by the intermediate-mass protostellar source Serpens SMM1-a. The highly collimated molecular jet is flanked at the base by a wide-angle cavity; the walls of the cavity can be seen in both 4 cm free-free emission detected by the Very Large Array and 1.3 mm thermal dust emission detected by ALMA. This is the first time that ionization of an outflow cavity has been directly detected via free-free emission in a very young, embedded Class 0 protostellar source that is still powering a molecular jet. The cavity walls are ionized either by UV photons escaping from the accreting protostellar source or by the precessing molecular jet impacting the walls. These observations suggest that ionized outflow cavities may be common in Class 0 protostellar sources, shedding further light on the radiation, outflow, and jet environments in the youngest, most embedded forming stars.

  20. HIGH-VELOCITY H I IS NOT ASSOCIATED WITH THE TeV SUPERNOVA REMNANT W51C

    SciTech Connect

    Tian, W. W.; Leahy, D. A.

    2013-05-20

    The recently detected TeV {gamma}-ray source HESS J1923+141 coincides with supernova remnant (SNR) W51C and the star-forming region W51B of the W51 complex. We construct H I absorption spectra of SNR W51C, H II regions G49.2-0.35 and G49.1-0.38 in W51B, and a nearby compact extragalactic source. Our study detects high-velocity (HV) H I clouds (above 83 km s{sup -1}) that coincide with W51B, but finds that the clouds are behind W51B. Both W51C and G49.2-0.35 have similar highest velocity absorption features at {approx}70 km s{sup -1}. The H II region G49.1-0.38 is behind the SNR because its H I absorption spectrum has a feature at 83 km s{sup -1}. These new results argue against previous claims that the SNR has shocked the HV H I clouds. Therefore, the TeV emission from the complex should not be associated with the HV H I clouds. W51C has a distance of about 4.3 kpc, smaller than the tangent point distance of 5.5 kpc in that direction, but still in the Sagittarius spiral arm.

  1. AN EXPERIMENTAL STUDY OF SHOCK WAVES RESULTING FROM THE IMPACT OF HIGH VELOCITY MISSILES ON ANIMAL TISSUES

    PubMed Central

    Harvey, E. Newton; McMillen, J. Howard

    1947-01-01

    The spark shadowgram method of studying shock waves is described. It has been used to investigate the properties of such waves produced by the impact of a high velocity missile on the surface of water. The method can be adapted for study of behavior of shock waves in tissue by placing the tissue on a water surface or immersing it in water. Spark shadowgrams then reveal waves passing from tissue to water or reflected from tissue surfaces. Reflection and transmission of shock waves from muscle, liver, stomach, and intestinal wall are compared with reflection from non-living surfaces such as gelatin gel, steel, plexiglas, cork, and air. Because of its heterogeneous structure, waves transmitted by tissue are dispersed and appear as a series of wavelets. When the accoustical impedance (density x wave velocity) of a medium is less than that in which the wave is moving, reflection will occur with inversion of the wave; i.e., a high pressure wave will become a low pressure wave. This inversion occurs at an air surface and is illustrated by shadowgrams of reflection from stomach wall, from a segment of colon filled with gas, and from air-filled rubber balloons. Bone (human skull and beef ribs) shows good reflection and some transmission of shock waves. When steel is directly hit by a missile, clearly visible elastic waves pass from metal to water, but a similar direct hit on bone does not result in elastic waves strong enough to be detected by a spark shadowgram. PMID:19871617

  2. Discovery of star formation in the extreme outer galaxy possibly induced by a high-velocity cloud impact

    SciTech Connect

    Izumi, Natsuko; Kobayashi, Naoto; Hamano, Satoshi; Yasui, Chikako; Tokunaga, Alan T.; Saito, Masao

    2014-11-01

    We report the discovery of star formation activity in perhaps the most distant molecular cloud in the extreme outer galaxy. We performed deep near-infrared imaging with the Subaru 8.2 m telescope, and found two young embedded clusters at two CO peaks of 'Digel Cloud 1' at the kinematic distance of D = 16 kpc (Galactocentric radius R {sub G} = 22 kpc). We identified 18 and 45 cluster members in the two peaks, and the estimated stellar densities are ∼5 and ∼3 pc{sup –2}, respectively. The observed K-band luminosity function suggests that the age of the clusters is less than 1 Myr and also that the distance to the clusters is consistent with the kinematic distance. On the sky, Cloud 1 is located very close to the H I peak of high-velocity cloud Complex H, and there are some H I intermediate velocity structures between the Complex H and the Galactic disk, which could indicate an interaction between them. We suggest the possibility that Complex H impacting on the Galactic disk has triggered star formation in Cloud 1 as well as the formation of the Cloud 1 molecular cloud.

  3. THE APACHE POINT OBSERVATORY GALACTIC EVOLUTION EXPERIMENT: FIRST DETECTION OF HIGH-VELOCITY MILKY WAY BAR STARS

    SciTech Connect

    Nidever, David L.; Zasowski, Gail; Majewski, Steven R.; Beaton, Rachael L.; Wilson, John C.; Skrutskie, Michael F.; O'Connell, Robert W.; Bird, Jonathan; Schoenrich, Ralph; Johnson, Jennifer A.; Sellgren, Kris; Robin, Annie C.; Schultheis, Mathias; Martinez-Valpuesta, Inma; Gerhard, Ortwin; Shetrone, Matthew; Schiavon, Ricardo P.; Weiner, Benjamin; Schneider, Donald P.; Allende Prieto, Carlos; and others

    2012-08-20

    Commissioning observations with the Apache Point Observatory Galactic Evolution Experiment (APOGEE), part of the Sloan Digital Sky Survey III, have produced radial velocities (RVs) for {approx}4700 K/M-giant stars in the Milky Way (MW) bulge. These high-resolution (R {approx} 22, 500), high-S/N (>100 per resolution element), near-infrared (NIR; 1.51-1.70 {mu}m) spectra provide accurate RVs ({epsilon}{sub V} {approx} 0.2 km s{sup -1}) for the sample of stars in 18 Galactic bulge fields spanning -1 Degree-Sign -32 Degree-Sign . This represents the largest NIR high-resolution spectroscopic sample of giant stars ever assembled in this region of the Galaxy. A cold ({sigma}{sub V} {approx} 30 km s{sup -1}), high-velocity peak (V{sub GSR} Almost-Equal-To +200 km s{sup -1}) is found to comprise a significant fraction ({approx}10%) of stars in many of these fields. These high RVs have not been detected in previous MW surveys and are not expected for a simple, circularly rotating disk. Preliminary distance estimates rule out an origin from the background Sagittarius tidal stream or a new stream in the MW disk. Comparison to various Galactic models suggests that these high RVs are best explained by stars in orbits of the Galactic bar potential, although some observational features remain unexplained.

  4. Discovery of a high velocity, spatially extended emission ``shell'' in front of the southeast lobe of the eta Carinae Homunculus

    NASA Astrophysics Data System (ADS)

    Currie, D. G.; Dorland, B. N.; Kaufer, A.

    2002-07-01

    We report the discovery of the eta Carinae ``Ghost Shell,'' a high-velocity, spatially extended emission feature that lies in front of the southeast lobe of the eta Carinae Homunculus. Using data obtained with ``Kueyen,'' one of the European Southern Observatory's Very Large Telescope 8.2 m telescopes and its Ultraviolet and Visible Echelle Spectrograph instrument, we have observed a structure in velocity space of width ~35 km s-1 and with Doppler velocities ranging from -675 <= v <= -850 km s-1. This is up to 500 km s-1 faster than the Homunculus front wall. The structure is distinct from the front wall in velocity space, and extends beyond the Homunculus' spatial boundaries. The Ghost Shell has been detected in emission for multiple allowed Balmer lines and in forbidden lines of [NII], [SII], and [ArIII]. The feature is also associated with a complex absorption structure in Ca H and K lines. We propose that the Ghost Shell lies outside the Homunculus and represents the forward shock between the fast stellar wind of the Great Eruption epoch and the older slow massive stellar wind. Based on observations collected at the European Southern Observatory at Paranal, Chile (UVES commissioning II).

  5. EXTREMELY BROAD RADIO RECOMBINATION MASER LINES TOWARD THE HIGH-VELOCITY IONIZED JET IN CEPHEUS A HW2

    SciTech Connect

    Jimenez-Serra, I.; Patel, N.; Martin-Pintado, J.; Baez-Rubio, A.; Thum, C. E-mail: npatel@cfa.harvard.edu E-mail: baezra@cab.inta-csic.es

    2011-05-10

    We present the first detection of the H40{alpha}, H34{alpha}, and H31{alpha} radio recombination lines (RRLs) at millimeter wavelengths toward the high-velocity ionized jet in the Cepheus A HW2 star-forming region. From our single-dish and interferometric observations, we find that the measured RRLs show extremely broad asymmetric line profiles with zero-intensity line widths of {approx}1100 km s{sup -1}. From the line widths, we estimate a terminal velocity for the ionized gas in the jet of {>=}500 km s{sup -1}, consistent with that obtained from the proper motions of the HW2 radio jet. The total integrated line-to-continuum flux ratios of the H40{alpha}, H34{alpha}, and H31{alpha} lines are 43, 229, and 280 km s{sup -1}, clearly deviating from LTE predictions. These ratios are very similar to those observed for the RRL masers toward MWC349A, suggesting that the intensities of the RRLs toward HW2 are affected by maser emission. Our radiative transfer modeling of the RRLs shows that their asymmetric profiles could be explained by maser emission arising from a bi-conical radio jet with a semi-opening angle of 18 deg., electron density distribution varying as r {sup -2.11}, and turbulent and expanding wind velocities of 60 and 500 km s{sup -1}.

  6. Hubble Space Telescope observations of the optical counterpart to a ultra-compact high-velocity cloud

    NASA Astrophysics Data System (ADS)

    Sand, David J.

    2017-01-01

    As part of a comprehensive archival search for optical counterparts to ultra-compact high-velocity clouds (UCHVCs), our team has uncovered five Local Volume dwarf galaxies, two of which were not previously known. Among these was AGC 226067, also known as ALFALFA-Dw1, which appeared to be made up of several HI and blue optical clumps based on ground-based data, with at least one HII region. Here we present Hubble Space Telescope Advanced Camera for Surveys data of AGC 226067. The data show that AGC 226067 is made up of a ~7-30 Myr old stellar population with a [Fe/H]~-0.6. Further, there is no evidence for an old stellar population associated with the system, down to a limit of MV>-8. Based on this and the position of AGC 226067 in the outskirts of the M86 subgroup of the Virgo cluster we present various arguments for the origin of this strange stellar system.

  7. Manufacturing and Properties of High-Velocity Oxygen Fuel (HVOF)-Sprayed FeVCrC Coatings

    NASA Astrophysics Data System (ADS)

    Sassatelli, Paolo; Bolelli, Giovanni; Lusvarghi, Luca; Manfredini, Tiziano; Rigon, Rinaldo

    2016-10-01

    This paper studies the microstructure, sliding wear behavior and corrosion resistance of high-velocity oxygen fuel (HVOF)-sprayed FeVCrC-based coatings. Various process parameters were tested to evaluate their effects on the coating properties, which were also compared to those of HVOF-sprayed NiCrBSi and Stellite-6 coatings. The Fe alloy coatings are composed of flattened splats, originating from molten droplets and consisting of a super-saturated solid solution, together with rounded particles, coming from partially unmolten material and containing V- and Fe-based carbide precipitates. All process parameters, apart from "extreme" settings with excess comburent in the flame, produce dense coatings, indicating that the feedstock powder is quite easily processable by HVOF. These coatings, with a microhardness of 650-750 HV0.3, exhibit wear rates of ≈2 × 10-6 mm3/(Nm) in ball-on-disk tests against sintered Al2O3 spheres. They perform far better than the reference coatings, and better than other Fe- and Ni-based alloy coatings tested in previous research. On the other hand, the corrosion resistance of the coating material (tested by electrochemical polarization in 0.1 M HCl solution) is quite low. Even in the absence of interconnected porosity, this results in extensive, selective damage to the Fe-based matrix. This coating material is therefore unadvisable for severely corrosive environments.

  8. Catastrophic detachment and high-velocity long-runout flow of Kolka Glacier, Caucasus Mountains, Russia in 2002

    NASA Astrophysics Data System (ADS)

    Evans, Stephen G.; Tutubalina, Olga V.; Drobyshev, Valery N.; Chernomorets, Sergey S.; McDougall, Scott; Petrakov, Dmitry A.; Hungr, Oldrich

    2009-04-01

    In September 2002, a catastrophic geomorphic event occurred in the Caucasus Mountains, southern Russia, in which almost the entire mass of Kolka Glacier detached from its bed, accelerated to a very high velocity (max. 65-80 m/s), and traveled a total distance of 19 km downstream as a glacier-debris flow. Based on the interpretation of satellite imagery obtained only 8.5 h before the event occurred, the analysis of seismograms from nearby seismic stations, and subsequent detailed field observations and measurements, we suggest that this remarkable event was not a response to impulse loading from a rock avalanche in the mountainside above the glacier, or to glacier surging, but due entirely to the static and delayed catastrophic response of the Kolka glacier to ice and debris loading over a period of months prior to the September 20 detachment. We reconstruct the glacier-debris flow using field observations in conjunction with the interpretation of seismographs from nearby seismic stations and successfully simulate the behaviour (runout, velocity, and deposition) of the post-detachment glacier-debris flow using a three-dimensional analytical model. Our demonstration of a standing-start hypothesis in the 2002 Kolka Glacier detachment has substantial implications for glacier hazard assessment and risk management strategies in valleys downstream from unstable debris-covered glaciers in the mountain regions of the world.

  9. What Is Spinal Stenosis?

    MedlinePlus

    ... To order the Sports Injuries Handout on Health full-text version, please contact NIAMS using the contact information ... publication. To order the Spinal Stenosis Q&A full-text version, please contact NIAMS using the contact information ...

  10. Spinal cord trauma

    MedlinePlus

    ... Oh's Intensive Care Manual . 7th ed. Philadelphia, PA: Elsevier; 2014:chap 78. Bryce TN. Spinal cord injury. ... Physical Medicine and Rehabilitation . 5th ed. Philadelphia, PA: Elsevier; 2016:chap 49. Dalzell K, Nouri A, Fehlings ...

  11. Spinal Cord Injury 101

    MedlinePlus Videos and Cool Tools

    ... is "Braingate" research? What is the status of stem-cell research? How would stem-cell therapies work in the treatment of spinal cord injuries? What does stem-cell research on animals tell us? When can we ...

  12. Spinal Muscular Atrophy (SMA)

    MedlinePlus

    ... children with SMA develop spinal deformities, such as scoliosis (sideways curvature of the spine) and kyphosis (front- ... Magnetic Resonance Imaging (MRI) Brain and Nervous System Scoliosis Contact Us Print Resources Send to a friend ...

  13. [Meningitis after spinal anesthesia].

    PubMed

    Mouchrif, Issam; Berdaii, Adnane; Labib, Ismail; Harrandou, Moustapha

    2016-01-01

    Meningitis is a rare but serious complication of epidural and spinal anesthesia. Bacterial meningitis is mainly caused by Gram-positive cocci, implying an exogenous contamination which suggests a lack of asepsis. The evolution is usually favorable after treatment, but at the expense of increased health care costs and, sometimes, of significant neurological sequelae. We report a case of bacterial meningitis after spinal anesthesia for caesarean section.

  14. Modeling spinal cord biomechanics

    NASA Astrophysics Data System (ADS)

    Luna, Carlos; Shah, Sameer; Cohen, Avis; Aranda-Espinoza, Helim

    2012-02-01

    Regeneration after spinal cord injury is a serious health issue and there is no treatment for ailing patients. To understand regeneration of the spinal cord we used a system where regeneration occurs naturally, such as the lamprey. In this work, we analyzed the stress response of the spinal cord to tensile loading and obtained the mechanical properties of the cord both in vitro and in vivo. Physiological measurements showed that the spinal cord is pre-stressed to a strain of 10%, and during sinusoidal swimming, there is a local strain of 5% concentrated evenly at the mid-body and caudal sections. We found that the mechanical properties are homogeneous along the body and independent of the meninges. The mechanical behavior of the spinal cord can be characterized by a non-linear viscoelastic model, described by a modulus of 20 KPa for strains up to 15% and a modulus of 0.5 MPa for strains above 15%, in agreement with experimental data. However, this model does not offer a full understanding of the behavior of the spinal cord fibers. Using polymer physics we developed a model that relates the stress response as a function of the number of fibers.

  15. Canine spinal cord glioma.

    PubMed

    Rissi, Daniel R; Barber, Renee; Burnum, Annabelle; Miller, Andrew D

    2017-01-01

    Spinal cord glioma is uncommonly reported in dogs. We describe the clinicopathologic and diagnostic features of 7 cases of canine spinal cord glioma and briefly review the veterinary literature on this topic. The median age at presentation was 7.2 y. Six females and 1 male were affected and 4 dogs were brachycephalic. The clinical course lasted from 3 d to 12 wk, and clinical signs were progressive and associated with multiple suspected neuroanatomic locations in the spinal cord. Magnetic resonance imaging of 6 cases revealed T2-weighted hyperintense lesions with variable contrast enhancement in the spinal cord. All dogs had a presumptive clinical diagnosis of intraparenchymal neoplasia or myelitis based on history, advanced imaging, and cerebrospinal fluid analysis. Euthanasia was elected in all cases because of poor outcome despite anti-inflammatory or immunosuppressive treatment or because of poor prognosis at the time of diagnosis. Tumor location during autopsy ranged from C1 to L6, with no clear predilection for a specific spinal cord segment. The diagnosis was based on histopathology and the immunohistochemistry expression of glial fibrillary acidic protein, oligodendrocyte lineage transcription factor 2, 2',3'-cyclic-nucleotide 3'-phosphodiesterase, neuron-specific enolase, synaptophysin, and Ki-67. Diagnoses consisted of 4 cases of oligodendroglioma, 2 cases of gliomatosis cerebri, and 1 astrocytoma. This case series further defines the clinicopathologic features of canine spinal glioma and highlights the need for comprehensive immunohistochemistry in addition to routine histopathology to confirm the diagnosis of these tumors.

  16. High-Velocity Frictional Properties of Westerly Granite and the Role of Thermal Cracking on Gouge Production

    NASA Astrophysics Data System (ADS)

    Passelegue, Francois; Spanuolo, Elena; Violay, Marie; Nielsen, Stefan; Di Toro, Giulio; Schubnel, Alexandre

    2016-04-01

    With the advent of high-velocity shear apparatus, several experimental studies have been conducted in recent years improving our understanding of fault friction at seismic slip rates (0.1-10 m/s). Here, we present the results of a series of tests conducted on Westerly granite, at INGV Roma, on a Slow to HIgh Velocity Apparatus (SHIVA), coupled with a high frequency monitoring (4MHz sampling rate). Experiments were conducted under normal stress (σn) ranging from 5 to 20 MPa and at sliding velocities (V) comprised between 3 mm/s and 3 m/s. Additional experiments were conducted in the presence of pore fluid at equivalent effective normal stress. In dry conditions, two friction drops are observed. The first drop is independent of the normal stress and occurs when V become higher than a critical value (Vc≈0.15 m/s). The second friction drop occurs after a critical slip weakening distance which decreases as a power law with the power density (τV). The first, abrupt, drop is explained by flash heating and weakening mechanism while the second, smooth, drop is due to the formation and growth of molten patches on the fault surface. In wet conditions, only the second drop of friction is observed. Average values of the fracture energy are independent of normal stress and sliding velocity at V > 0.01 m/s. However, measurements of elastic wave velocities travelling through the fault strongly suggest that higher damage is induced for 0.1 < V < 0.3 m/s for a same finite displacement. This observation is also supported by acoustic emission (AE) recordings. Indeed, most the AEs are recorded after the initiation of the second friction drop, that is, once the fault surface temperature is high. Some AEs are even recorded few seconds after the end of the experiments, suggesting they may be due to thermal cracking induced by heat diffusion. In addition, the presence of pore fluid pressure (water) delayed the apparition of AEs at equivalent effective pressure, supporting the link

  17. Friction and wear properties of high-velocity oxygen fuel sprayed WC-17Co coating under rotational fretting conditions

    NASA Astrophysics Data System (ADS)

    Luo, Jun; Cai, Zhenbing; Mo, Jiliang; Peng, Jinfang; Zhu, Minhao

    2016-05-01

    Rotational fretting which exist in many engineering applications has incurred enormous economic loss. Thus, accessible methods are urgently needed to alleviate or eliminate damage by rotational fretting. Surface engineering is an effective approach that is successfully adopted to enhance the ability of components to resist the fretting damage. In this paper, using a high-velocity oxygen fuel sprayed (HVOF) technique WC-17Co coating is deposited on an LZ50 steel surface to study its properties through Vickers hardness testing, scanning electric microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffractrometry (XRD). Rotational fretting wear tests are conducted under normal load varied from 10 N to 50 N, and angular displacement amplitudes vary from 0.125° to 1°. Wear scars are examined using SEM, EDX, optical microscopy (OM), and surface topography. The experimental results reveal that the WC-17Co coating adjusted the boundary between the partial slip regime (PSR) and the slip regime (SR) to the direction of smaller amplitude displacement. As a result, the coefficients of friction are consistently lower than the substrate's coefficients of friction both in the PSR and SR. The damage to the coating in the PSR is very slight. In the SR, the coating exhibits higher debris removal efficiency and load-carrying capacity. The bulge is not found for the coating due to the coating's higher hardness to restrain plastic flow. This research could provide experimental bases for promoting industrial application of WC-17Co coating in prevention of rotational fretting wear.

  18. Present-day Galactic Evolution: Low-metallicity, Warm, Ionized Gas Inflow Associated with High-velocity Cloud Complex A

    NASA Astrophysics Data System (ADS)

    Barger, K. A.; Haffner, L. M.; Wakker, B. P.; Hill, Alex. S.; Madsen, G. J.; Duncan, A. K.

    2012-12-01

    The high-velocity cloud Complex A is a probe of the physical conditions in the Galactic halo. The kinematics, morphology, distance, and metallicity of Complex A indicate that it represents new material that is accreting onto the Galaxy. We present Wisconsin Hα Mapper kinematically resolved observations of Complex A over the velocity range of -250 to -50 km s-1 in the local standard of rest reference frame. These observations include the first full Hα intensity map of Complex A across (\\mathit {l, b}) = (124{^\\circ }, 18{^\\circ }) to (171°, 53°) and deep targeted observations in Hα, [S II] λ6716, [N II] λ6584, and [O I] λ6300 toward regions with high H I column densities, background quasars, and stars. The Hα data imply that the masses of neutral and ionized material in the cloud are similar, both being greater than 106 M ⊙. We find that the Bland-Hawthorn & Maloney model for the intensity of the ionizing radiation near the Milky Way is consistent with the known distance of the high-latitude part of Complex A and an assumed cloud geometry that puts the lower-latitude parts of the cloud at a distance of 7-8 kpc. This compatibility implies a 5% ionizing photon escape fraction from the Galactic disk. We also provide the nitrogen and sulfur upper abundance solutions for a series of temperatures, metallicities, and cloud configurations for purely photoionized gas; these solutions are consistent with the sub-solar abundances found by previous studies, especially for temperatures above 104 K or for gas with a high fraction of singly ionized nitrogen and sulfur.

  19. The Silicon and Calcium High-velocity Features in Type Ia Supernovae from Early to Maximum Phases

    NASA Astrophysics Data System (ADS)

    Zhao, Xulin; Wang, Xiaofeng; Maeda, Keiichi; Sai, Hanna; Zhang, Tianmeng; Zhang, Jujia; Huang, Fang; Rui, Liming; Zhou, Qi; Mo, Jun

    2015-09-01

    The high-velocity features (HVFs) in optical spectra of type Ia supernovae (SNe Ia) are examined with a large sample including very early-time spectra (e.g., t < -7 days). Multiple Gaussian fits are applied to examine the HVFs and their evolutions, using constraints on expansion velocities for the same species (i.e., Si ii 5972 and Si ii 6355). We find that strong HVFs tend to appear in SNe Ia with smaller decline rates (e.g., Δm15(B) ≲ 1.4 {mag}), clarifying that the finding by Childress et al. for the Ca-HVFs in near-maximum-light spectra applies both to the Si-HVFs and Ca-HVFs in the earlier phase. The Si-HVFs seem to be more common in rapidly expanding SNe Ia, which is different from the earlier result that Ca-HVFs are associated with SNe Ia that have slower Si ii 6355 velocities at maximum light (i.e., VSimax). Moreover, SNe Ia with both stronger HVFs at early phases and larger VSimax are found to have noticeably redder B-V colors and to occur preferentially in the inner regions of their host galaxies, while those with stronger HVFs but smaller VSimax show opposite tendencies, suggesting that these two subclasses have different explosion environments and their HVFs may have different origins. We further examine the relationships between the absorption features of Si ii 6355 and Ca ii IR lines, and find that their photospheric components are well correlated in velocity and strength but that the corresponding HVFs show larger scatter. These results cannot be explained with ionization and/or thermal processes alone, and different mechanisms are required for the creation of HVF-forming regions in SNe Ia.

  20. Optimization of magnetically accelerated, ultra-high velocity aluminum flyer plates for use in plate impact, shock wave experiments.

    SciTech Connect

    Cochrane, Kyle Robert; Knudson, Marcus D.; Slutz, Stephen A.; Lemke, Raymond William; Davis, J. P.; Harjes, Henry Charles III; Giunta, Anthony Andrew; Bliss, David Emery

    2005-05-01

    The intense magnetic field produced by the 20 MA Z accelerator is used as an impulsive pressure source to accelerate metal flyer plates to high velocity for the purpose of performing plate impact, shock wave experiments. This capability has been significantly enhanced by the recently developed pulse shaping capability of Z, which enables tailoring the rise time to peak current for a specific material and drive pressure to avoid shock formation within the flyer plate during acceleration. Consequently, full advantage can be taken of the available current to achieve the maximum possible magnetic drive pressure. In this way, peak magnetic drive pressures up to 490 GPa have been produced, which shocklessly accelerated 850 {micro}m aluminum (6061-T6) flyer plates to peak velocities of 34 km/s. We discuss magnetohydrodynamic (MHD) simulations that are used to optimize the magnetic pressure for a given flyer load and to determine the shape of the current rise time that precludes shock formation within the flyer during acceleration to peak velocity. In addition, we present results pertaining to plate impact, shock wave experiments in which the aluminum flyer plates were magnetically accelerated across a vacuum gap and impacted z-cut, {alpha}-quartz targets. Accurate measurements of resulting quartz shock velocities are presented and analyzed through high-fidelity MHD simulations enhanced using optimization techniques. Results show that a fraction of the flyer remains at solid density at impact, that the fraction of material at solid density decreases with increasing magnetic pressure, and that the observed abrupt decrease in the quartz shock velocity is well correlated with the melt transition in the aluminum flyer.

  1. Spatially Extended and High-Velocity Dispersion Molecular Component in Spiral Galaxies: Single-Dish Versus Interferometric Observations

    NASA Astrophysics Data System (ADS)

    Caldú-Primo, Anahi; Schruba, Andreas; Walter, Fabian; Leroy, Adam; Bolatto, Alberto D.; Vogel, Stuart

    2015-02-01

    Recent studies of the molecular medium in nearby galaxies have provided mounting evidence that the molecular gas can exist in two phases: one that is clumpy and organized as molecular clouds and another one that is more diffuse. This last component has a higher velocity dispersion than the clumpy one. In order to investigate these two molecular components further, we compare the fluxes and line widths of CO in NGC 4736 and NGC 5055, two nearby spiral galaxies for which high-quality interferometric as well as single-dish data sets are available. Our analysis leads to two main results: (1) employing three different methods, we determine the flux recovery of the interferometer as compared to the single-dish to be within a range of 35%-74% for NGC 4736 and 81%-92% for NGC 5055, and (2) when focusing on high (S/N ≥ 5) lines of sight (LOSs), the single-dish line widths are larger by ˜(40 ± 20)% than the ones derived from interferometric data, which is in agreement with stacking all LOSs. These results point to a molecular gas component that is distributed over spatial scales larger than 30″(˜1 kpc), and is therefore filtered out by the interferometer. The available observations do not allow us to distinguish between a truly diffuse gas morphology and a uniform distribution of small clouds that are separated by less than the synthesized beam size (˜3″ or ˜100 pc), as they would both be invisible for the interferometer. This high velocity dispersion component has a dispersion similar to what is found in the atomic medium, as traced through observations of the H i line.

  2. Spatially extended and high-velocity dispersion molecular component in spiral galaxies: Single-dish versus interferometric observations

    SciTech Connect

    Caldú-Primo, Anahi; Walter, Fabian; Schruba, Andreas; Leroy, Adam; Bolatto, Alberto D.; Vogel, Stuart

    2015-02-01

    Recent studies of the molecular medium in nearby galaxies have provided mounting evidence that the molecular gas can exist in two phases: one that is clumpy and organized as molecular clouds and another one that is more diffuse. This last component has a higher velocity dispersion than the clumpy one. In order to investigate these two molecular components further, we compare the fluxes and line widths of CO in NGC 4736 and NGC 5055, two nearby spiral galaxies for which high-quality interferometric as well as single-dish data sets are available. Our analysis leads to two main results: (1) employing three different methods, we determine the flux recovery of the interferometer as compared to the single-dish to be within a range of 35%–74% for NGC 4736 and 81%–92% for NGC 5055, and (2) when focusing on high (S/N ≥ 5) lines of sight (LOSs), the single-dish line widths are larger by ∼(40 ± 20)% than the ones derived from interferometric data, which is in agreement with stacking all LOSs. These results point to a molecular gas component that is distributed over spatial scales larger than 30″(∼1 kpc), and is therefore filtered out by the interferometer. The available observations do not allow us to distinguish between a truly diffuse gas morphology and a uniform distribution of small clouds that are separated by less than the synthesized beam size (∼3″ or ∼100 pc), as they would both be invisible for the interferometer. This high velocity dispersion component has a dispersion similar to what is found in the atomic medium, as traced through observations of the H i line.

  3. Epidural Injections for Spinal Pain

    MedlinePlus

    ... back or leg pain after spinal surgery) Other injuries to spinal nerves, vertebrae and surrounding tissues Bone ... Bleeding if a blood vessel is inadvertently damaged. Injury to the nerves at the injection site. Temporary ...

  4. Living with Spinal Cord Injury

    MedlinePlus

    ... to send and receive messages to and from the brain. About 200,000 people in the United States have spinal cord injuries. Most injuries occur from a traumatic event, according to the National Spinal Cord Injury ...

  5. Proper motion with HST: Searching for high-velocity stars in the core of the globular cluster 47 Tucanae

    SciTech Connect

    Meylan, G.; Minniti, D.; Pryor, C.; Tinney, C.G.; Phinney, E.S.; Sams, B.

    1996-02-13

    Binary stars play an essential role during the late phases of the dynamical evolution of a globular cluster. They transfer energy to passing stars and so can strongly influence the cluster evolution, enough to delay, halt, and even reverse core collapse. Hard binaries are known to exist in cluster cores, e.g., in the form of millisecond pulsars (about half of the millisecond pulsars observed in 47 Tucanae are such hard binaries). The presence of hard binaries may also be revealed by searching for the by-products of close encounters: high- velocity stars, such as those discovered in the core of 47 Tuc by Meylan et al. (1991) and Gebhardt et al. (1995). These studies represent the limit of the radial velocity data which can be obtained from the ground. If more progress is to be made, it must come through obtaining proper motions--a task for which {ital only} the Hubble Space Telescope (HST) is suitable. We are using WFPC2 to obtain deep U (F300W) images of the core of 47 Tuc at three different epochs over two years, with which we will measure differential proper motions to a 1-{sigma} limit of 0.23 mas/yr. This--rather conservative--estimate corresponds to a 5-{sigma} detection of all stars with tangential velocities greater than 22 km s{sup -1}. By using the F300W filter we can measure stars over the whole color-magnitude diagram, from the red-giant branch to well down the main sequence. Such a complete census will provide unique constraints as a function of the stellar mass on relaxation processes, collision and ejection rates, and the velocity distribution. Here we report on the first-epoch (Cycle 5) observations of this project. Although no proper motions are available yet, some preliminary by-product results are presented. These include luminosity functions and color-magnitude diagrams for the core of 47 Tuc and the light curves of variable blue straggler stars and of a candidate X-ray source. 32 refs., 5 figs.

  6. MRK 1216 and NGC 1277 - an orbit-based dynamical analysis of compact, high-velocity dispersion galaxies

    NASA Astrophysics Data System (ADS)

    Yıldırım, Akın; van den Bosch, Remco C. E.; van de Ven, Glenn; Husemann, Bernd; Lyubenova, Mariya; Walsh, Jonelle L.; Gebhardt, Karl; Gültekin, Kayhan

    2015-09-01

    We present a dynamical analysis to infer the structural parameters and properties of the two nearby, compact, high-velocity dispersion galaxies MRK 1216 and NGC 1277. Combining deep Hubble Space Telescope imaging, wide-field integral field unit stellar kinematics, and complementary long-slit spectroscopic data out to three effective radii, we construct orbit-based models to constrain their black hole masses, dark matter content and stellar mass-to-light ratios. We obtain a black hole mass of log(M•/M⊙) = 10.1_{-0.2}^{+0.1} for NGC 1277 and an upper limit of log(M•/M⊙) = 10.0 for MRK 1216, within 99.7 per cent (3σ) confidence. The stellar mass-to-light ratios span a range of ΥV = 6.5_{-1.5}^{+1.5} in NGC 1277 and ΥH = 1.8_{-0.8}^{+0.5} in MRK 1216 and are in good agreement with single stellar population models of a single power-law Salpeter initial mass function. Even though our models do not place strong constraints on the dark halo parameters, they suggest that dark matter is a necessary ingredient in MRK 1216, with a dark matter contribution of 22^{+30}_{-20} per cent to the total mass budget within one effective radius. NGC 1277, on the other hand, can be reproduced without the need for a dark halo, and a maximal dark matter fraction of 13 per cent within the same radial extent. In addition, we investigate the orbital structures of both galaxies, which are rotationally supported and consistent with photometric multi-Sérsic decompositions, indicating that these compact objects do not host classical, non-rotating bulges formed during recent (z ≤ 2) dissipative events or through violent relaxation. Finally, both MRK 1216 and NGC 1277 are anisotropic, with a global anisotropy parameter δ of 0.33 and 0.58, respectively. While MRK 1216 follows the trend of fast-rotating, oblate galaxies with a flattened velocity dispersion tensor in the meridional plane of the order of βz ˜ δ, NGC 1277 is highly tangentially anisotropic and seems to belong

  7. Characterizing high-velocity angular vestibulo-ocular reflex function in service members post-blast exposure

    PubMed Central

    Scherer, Matthew R.; Shelhamer, Mark J.; Schubert, Michael C.

    2011-01-01

    Blasts (explosions) are the most common mechanism of injury in modern warfare. Traumatic brain injury (TBI) and dizziness are common sequelae associated with blasts, and many service members (SMs) report symptoms worsen with activity. The purpose of this study was to measure angular vestibulo-ocular reflex gain (aVOR) of blast-exposed SMs with TBI during head impulse testing. We also assessed their symptoms during exertion. Twenty-four SMs recovering from TBI were prospectively assigned to one of two groups based on the presence or absence of dizziness. Wireless monocular scleral search coil and rate sensor were used to characterize active and passive yaw and pitch head and eye rotations. Visual analog scale (VAS) was used to monitor symptoms during fast walking/running. For active yaw head impulses, aVOR gains were significantly lower in the symptomatic group (0.79 ± 0.15) versus asymptomatic (0.87 ± 0.18), but not for passive head rotation. For pitch head rotation, the symptomatic group had both active (0.915 ± 0.24) and passive (0.878 ± 0.22) aVOR gains lower than the asymptomatic group (active 1.03 ± 0.27, passive 0.97 ± 0.23). Some SMs had elevated aVOR gain. VAS scores for all symptoms were highest during exertion. Our data suggest symptomatic SMs with TBI as a result of blast have varied aVOR gain during high-velocity head impulses and provide compelling evidence of pathology affecting the vestibular system. Potential loci of injury in this population include the following: disruption of pathways relaying vestibular efference signals, differential destruction of type I vestibular hair cells, or selective damage to irregular afferent pathways—any of which may explain the common discrepancy between reports of vestibular-like symptoms and laboratory testing results. significantly reduced pitch aVOR in symptomatic SMs and peak symptom severity during exertional testing support earlier findings in the chronic blast-exposed active duty SMs. PMID:21113582

  8. Pyrometamorphism of Fault Zone Rocks Induced by Frictional Heating in High-velocity Friction Tests: Reliable Records of Seismic Slip?

    NASA Astrophysics Data System (ADS)

    Ree, J.; Ando, J.; Kim, J.; Han, R.; Shimamoto, T.

    2008-12-01

    Recognition of seismic slip zone is important for a better understanding of earthquake generation processes in fault zones and paleoseismology. However, there has been no reliable record of ancient seismic slip except pseudotachylyte. Recently, it has been suggested that decomposition (dehydration or decarbonation) products due to frictional heating can be used as a seismic slip record. The decomposition products, however, can be easily rehydrated or recarbonated with pervasive fluid migration in the fault zone after seismic slip, raising some question about their stability as a seismic slip record. Here, we review microstructural and mineralogical changes of the simulated fault zones induced by frictional heating (pyrometamorphism) from high-velocity friction tests (HVFT) on siltstone, sandstone and carbonates at seismic slip rates, and discuss on their stability after seismic slip. HVFT on siltstone generates pseuodotachylyte in the principal slip zone (0.30-0.75 mm thick) with 'damage' layer (0.1-0.2 mm thick) along its margins. Chlorite in the damage layer suffers an incipient dehydration with many voids (0.2-1.0 μm in diameter) in transmission electron microscopy (TEM), appearing as dark tiny spots both in plane-polarized light and back-scattered electron (BSE) photomicrographs. HVFT on brown sandstone induces a color change of wall rocks adjacent to the principal slip zone (brown to red) due to the dehydration of iron hydroxides with frictional heating. These dehydration products in siltstone and sandstone due to frictional heating may be unstable since they would be easily rehydrated with fluid infiltration after a seismic slip. HVFT on carbonates including Carrara marble and siderite-bearing gouges produces decarbonation products of nano-scale lime (CaO) and magnetite (Fe3O4), respectively. Lime is a very unstable phase whereas magnetite is a stable and thus may be used as an indicator of seismic slip. The simulated fault zones of Carrara marble contain

  9. Characterizing high-velocity angular vestibulo-ocular reflex function in service members post-blast exposure.

    PubMed

    Scherer, Matthew R; Shelhamer, Mark J; Schubert, Michael C

    2011-02-01

    Blasts (explosions) are the most common mechanism of injury in modern warfare. Traumatic brain injury (TBI) and dizziness are common sequelae associated with blasts, and many service members (SMs) report symptoms worsen with activity. The purpose of this study was to measure angular vestibulo-ocular reflex gain (aVOR) of blast-exposed SMs with TBI during head impulse testing. We also assessed their symptoms during exertion. Twenty-four SMs recovering from TBI were prospectively assigned to one of two groups based on the presence or absence of dizziness. Wireless monocular scleral search coil and rate sensor were used to characterize active and passive yaw and pitch head and eye rotations. Visual analog scale (VAS) was used to monitor symptoms during fast walking/running. For active yaw head impulses, aVOR gains were significantly lower in the symptomatic group (0.79 ± 0.15) versus asymptomatic (0.87 ± 0.18), but not for passive head rotation. For pitch head rotation, the symptomatic group had both active (0.915 ± 0.24) and passive (0.878 ± 0.22) aVOR gains lower than the asymptomatic group (active 1.03 ± 0.27, passive 0.97 ± 0.23). Some SMs had elevated aVOR gain. VAS scores for all symptoms were highest during exertion. Our data suggest symptomatic SMs with TBI as a result of blast have varied aVOR gain during high-velocity head impulses and provide compelling evidence of pathology affecting the vestibular system. Potential loci of injury in this population include the following: disruption of pathways relaying vestibular efference signals, differential destruction of type I vestibular hair cells, or selective damage to irregular afferent pathways-any of which may explain the common discrepancy between reports of vestibular-like symptoms and laboratory testing results. Significantly reduced pitch aVOR in symptomatic SMs and peak symptom severity during exertional testing support earlier findings in the chronic blast-exposed active duty SMs.

  10. Spinal Injuries in Children

    PubMed Central

    Basu, Saumyajit

    2012-01-01

    About 5% of spinal injuries occur in children – however the consequences to the society are devastating, all the more so because the cervical spine is more commonly affected. Anatomical differences with adults along with the inherent elasticity of the pediatric spine, makes these injuries a biomechanically separate entity. Hence clinical manifestations are unique, one of which is the Spinal Cord Injury Without Radiological Abnormality. With the advent of high quality MRI and CT scan along with digital X-ray, it is now possible to exactly delineate the anatomical location, geometrical configuration, and the pathological extent of the injury. This has improved the management strategies of these unfortunate children and the role of surgical stabilization in unstable injuries can be more sharply defined. However these patients should be followed up diligently because of the recognized long term complications of spinal deformity and syringomyelia. PMID:22855681

  11. Lumbar spinal stenosis.

    PubMed Central

    Ciricillo, S F; Weinstein, P R

    1993-01-01

    Lumbar spinal stenosis, the results of congenital and degenerative constriction of the neural canal and foramina leading to lumbosacral nerve root or cauda equina compression, is a common cause of disability in middle-aged and elderly patients. Advanced neuroradiologic imaging techniques have improved our ability to localize the site of nerve root entrapment in patients presenting with neurogenic claudication or painful radiculopathy. Although conservative medical management may be successful initially, surgical decompression by wide laminectomy or an intralaminar approach should be done in patients with serious or progressive pain or neurologic dysfunction. Because the early diagnosis and treatment of lumbar spinal stenosis may prevent intractable pain and the permanent neurologic sequelae of chronic nerve root entrapment, all physicians should be aware of the different neurologic presentations and the treatment options for patients with spinal stenosis. Images PMID:8434469

  12. Changes in spinal alignment.

    PubMed

    Veintemillas Aráiz, M T; Beltrán Salazar, V P; Rivera Valladares, L; Marín Aznar, A; Melloni Ribas, P; Valls Pascual, R

    2016-04-01

    Spinal misalignments are a common reason for consultation at primary care centers and specialized departments. Misalignment has diverse causes and is influenced by multiple factors: in adolescence, the most frequent misalignment is scoliosis, which is idiopathic in 80% of cases and normally asymptomatic. In adults, the most common cause is degenerative. It is important to know the natural history and to detect factors that might predict progression. The correct diagnosis of spinal deformities requires specific imaging studies. The degree of deformity determines the type of treatment. The aim is to prevent progression of the deformity and to recover the flexibility and balance of the body.

  13. Use of an arm weight-bearing combined with upper-limb reaching apparatus to facilitate motor paralysis recovery in an incomplete spinal cord injury patient: a single case report

    PubMed Central

    Hoei, Takashi; Kawahira, Kazumi; Fukuda, Hidefumi; Sihgenobu, Keizo; Shimodozono, Megumi; Ogura, Tadashi

    2017-01-01

    [Purpose] Training using an arm weight-bearing device combined with upper-limb reaching apparatus to facilitate motor paralysis recovery, named the “Reaching Robot”, as well as Repetitive Facilitation Exercise were applied to a patient with severe impairment of the shoulder and elbow due to incomplete spinal cord injury and the effects were examined. [Subjects and Methods] A 66-year-old man with incomplete spinal cord injury participated in an upper extremity rehabilitation program involving a Reaching Robot. The program was comprised of active motor suspension, continuous low amplitude neuromuscular electrical stimulation and functional vibratory stimulation, as well as Repetitive Facilitation Exercise combined with continuous low amplitude neuromuscular electrical stimulation. This protocol used a crossover design following an A1-B1-A2-B2. “A” consisted of 2 weeks of Repetitive Facilitation Exercise, and “B” consisted of 2 weeks of Reaching Robot training. [Results] Improvements were observed after all sessions. Active range of motion for shoulder flexion improved after 2 weeks of Reaching Robot sessions only. There were no adverse events. [Conclusion] Reaching Robot training for severe paretic upper-extremity after incomplete spinal cord injury was a safe and effective treatment. Reaching Robot training may be useful for rehabilitation of paretic upper-extremity after incomplete spinal cord injury. PMID:28210068

  14. Spinal tuberculosis: diagnosis and management.

    PubMed

    Rasouli, Mohammad R; Mirkoohi, Maryam; Vaccaro, Alexander R; Yarandi, Kourosh Karimi; Rahimi-Movaghar, Vafa

    2012-12-01

    The spinal column is involved in less than 1% of all cases of tuberculosis (TB). Spinal TB is a very dangerous type of skeletal TB as it can be associated with neurologic deficit due to compression of adjacent neural structures and significant spinal deformity. Therefore, early diagnosis and management of spinal TB has special importance in preventing these serious complications. In order to extract current trends in diagnosis and medical or surgical treatment of spinal TB we performed a narrative review with analysis of all the articles available for us which were published between 1990 and 2011. Althoug h the development of more accurate imaging modalities such as magnetic resonance imaging and advanced surgical techniques have made the early diagnosis and management of spinal TB much easier, these are still very challenging topics. In this review we aim to discuss the diagnosis and management of spinal TB based on studies with acceptable design, clearly explained results and justifiable conclusions.

  15. Spinal epidural abscess.

    PubMed

    Miftode, E; Luca, V; Mihalache, D; Leca, D; Stefanidis, E; Anuţa, C; Sabadis, L

    2001-01-01

    In a retrospective study, 68 patients with Spinal Epidural Abscess (SEA) were reviewed. Of these, 66% had different predisposing factors such as staphylococcal skin infections, surgical procedures, rachicentesis, trauma, spondilodiscitis. Abscess had a lumbar region location in 53% of cases. Staphylococcus aureus was the most frequent etiological agent (81%). The overall rate of mortality in SEA patients was 13.2%.

  16. Numerical Simulation of the Twin-Wire Arc Spraying Process: Modeling the High Velocity Gas Flow Field Distribution and Droplets Transport

    NASA Astrophysics Data System (ADS)

    Chen, Yongxiong; Liang, Xiubing; Wei, Shicheng; Chen, Xi; Xu, Binshi

    2012-03-01

    During the twin-wire arc spraying, a high velocity gas stream is used to accelerate the arc-melting materials and propel the droplets toward the substrate surface. This study is aimed at investigating the gas flow formation and droplets transport processes using numerical simulation method. Results from the 3-D gas flow field model show that the distribution of the gas flow velocity on the twin-wire intersection plane is quite different from that on the twin-wire vertical plane. Based on the 3-D model, the convergence amplitude of the high velocity zone in the jet center is improved by modifying the gun head design. It is also observed that a flat substrate existed downstream from the gas nozzle exit results in decreasing close to zero in velocity of the gas jet near the substrate. In addition, the predicted droplet trajectories and velocity distributions exhibited good agreement with experimentally observations.

  17. Characterization of impact damage resistance of CF/PEEK and CF/toughened epoxy laminates under low and high velocity impact tests

    SciTech Connect

    Morita, Hideo; Adachi, Tadaharu; Tateishi, Yasuhiro; Matsumoto, Hiroyuki

    1995-12-31

    In order to use composite materials in aeronautical turbo engines, their resistance to impact damage must be understood. In this work the subperforation flat-wise impact resistance of three kinds of high resistance material systems were evaluated under low and high velocity impact tests. Tested systems were AS4/PEEK (APC-2/AS4, ICI-Fiberite), AS4/PEEK+IL, which consists of APC-2 prepreg and PEEK film inserted between layers as an interleave, and toughened epoxy system T800/{number_sign}3900 (Toray). To investigate the effects of stacking sequence on resistance, three lay-ups -- (0/+30/0/{minus}30)s, (0/+60/0/{minus}60)s, and (0/+45/90/{minus}45)s -- were tested. A drop weight system was used for the low velocity tests, where the velocity ranged from 1.5 to 3.1 m/s. An air gun system was used for the high velocity tests, where the velocity range was between 50 and 100 m/s. The relation between damage area (DA) and impact energy (IE) was linear, and the ratio of the DA/IE quantified the impact resistance of each specimen. The value of DA/IE for the high velocity tests was larger than the value for low velocity tests. To estimate the lay-up effect, a stacking parameter {beta}, which indicates the difference of the inplane stiffness between the adjacent laminae, was proposed. A proportional relation between the DA/IE and the {beta} was obtained. The value of (DA/IE)/{beta}, which was independent of stacking sequence, indicated the impact resistance of the tested material systems for both velocity levels. The ratio of (DA/IE)/{beta} for the high velocity to the value for the low velocity changed with material systems.

  18. Prediction of the consequences of a high-velocity collision between meteoric particles and elements of a titanium alloy protective structure

    NASA Astrophysics Data System (ADS)

    Ishchenko, A. N.; Afanas'eva, S. A.; Burkin, V. V.; Dudarev, E. F.; Rogaev, K. S.; Tabachenko, A. N.; Khabibullin, M. V.

    2016-11-01

    Calculation-experimental studies of a high-velocity collision between VT1-0 titanium plates and ultrafine- and coarse-grained structures with a steel spherical impactor are illustrated. Fine-grained VT1-0 titanium plate samples have been obtained using the abc pressing method. Ballistic measurements have been performed using a 30-mm smooth-bore ballistic installation at velocities of about 2500 m/s. A high-velocity collision has been calculated in the scope of an elastoplastic model of interacting materials with regard to destruction and a different phase state at velocities reaching 15 km/s. It has been indicated that the mechanical properties of the VT1-0 alloy are improved when proceeding from a coarse-grained structure to an ultrafine- grained structure; however, in this case, the result of shock loading is hardly affected in the considered velocity range. Titanium plates can be used as screens to protect the main structure of the aircraft from a high-velocity collision.

  19. Real-Time Thermographic-Phosphor-Based Temperature Measurements of Thermal Barrier Coating Surfaces Subjected to a High-Velocity Combustor Burner Environment

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey I.; Jenkins, Thomas P.; Allison, Stephen W.; Cruzen, Scott; Condevaux, J. J.; Senk, J. R.; Paul, A. D.

    2011-01-01

    Surface temperature measurements were conducted on metallic specimens coated with an yttria-stabilized zirconia (YSZ) thermal barrier coating (TBC) with a YAG:Dy phosphor layer that were subjected to an aggressive high-velocity combustor burner environment. Luminescence-based surface temperature measurements of the same TBC system have previously been demonstrated for specimens subjected to static furnace or laser heating. Surface temperatures were determined from the decay time of the luminescence signal of the YAG:Dy phosphor layer that was excited by a pulsed laser source. However, the furnace and laser heating provides a much more benign environment than that which exists in a turbine engine, where there are additional challenges of a highly radiant background and high velocity gases. As the next step in validating the suitability of luminescence-based temperature measurements for turbine engine environments, new testing was performed where heating was provided by a high-velocity combustor burner rig at Williams International. Real-time surface temperature measurements during burner rig heating were obtained from the decay of the luminescence from the YAG:Dy surface layer. The robustness of several temperature probe designs in the sonic velocity, high radiance flame environment was evaluated. In addition, analysis was performed to show whether the luminescence decay could be satisfactorily extracted from the high radiance background.

  20. Spinal Arteriovenous Fistula with Progressive Paraplegia after Spinal Anaesthesia

    PubMed Central

    Argyrakis, Nikolaos; Matis, Georgios K.; Mpata-Tshibemba, Stephanie

    2014-01-01

    A case of an iatrogenic spinal arteriovenous fistula with progressive paraplegia in a young woman is reported. The fistula was eventually created after repetitive lumbar punctures performed in the process of spinal anaesthesia. Her symptoms were progressed to paraplegia over a period of 2 years. The digital subtraction angiography demonstrated a single-hole fistula, involving the anterior spinal artery and vein. The lesion was occluded by embolization with immediate improvement. The potential mechanism is discussed. PMID:24653807

  1. [Therapy progress of spinal cord compression by metastatic spinal tumor].

    PubMed

    Liu, Yao-sheng; He, Qi-zhen; Liu, Shu-bin; Jiang, Wei-gang; Lei, Ming-xing

    2016-01-01

    Metastatic epidural compression of the spinal cord is a significant source of morbidity in patients with systemic cancer. With improvment of oncotheray, survival period in the patients is improving and metastatic cord compression is en- countered increasingly often. Surgical management performed for early circumferential decompression for the spinal cord com- pression with spine instability, and spine reconstruction performed. Patients with radiosensitive tumours without spine instabili- ty, radiotherapy is an effective therapy. Spinal stereotactic radiosurgery and minimally invasive techniques, such as vertebro- plasty and kyphoplasty, percutaneous pedicle screw fixation, radiofrequency ablation are promising options for treatment of cer- tain selected patients with spinal metastases.

  2. Spinal epidural abscess.

    PubMed

    Krishnamohan, Prashanth; Berger, Joseph R

    2014-11-01

    Spinal epidural abscess (SEA) remains a relatively infrequent diagnosis. Staphylococcus aureus is the most common organism identified, and the infectious source in SEA emanates from skin and soft tissue infections in about 20 % of instances. The thoracic spine is most often involved followed by the lumbar spine. The classic triad of fever, spinal pain, and neurological deficit is present in but a minority of patients. The appearance of neurological deficits with SEA has a significant impact on the prognosis; therefore, early diagnosis is imperative. Magnetic resonance imaging has permitted earlier diagnosis, although significant delays in diagnosis are common due to the nonspecific symptoms that frequently attend the disorder. Due to the rarity of this condition, there have been few randomized controlled trials to evaluate new treatment strategies, and most recommendations regarding treatment are based on case series studies often derived from the experiences at a single center.

  3. Aspergillus spinal epidural abscess

    SciTech Connect

    Byrd, B.F. III; Weiner, M.H.; McGee, Z.A.

    1982-12-17

    A spinal epidural abscess developed in a renal transplant recipient; results of a serum radioimmunoassay for Aspergillus antigen were positive. Laminectomy disclosed an abscess of the L4-5 interspace and L-5 vertebral body that contained hyphal forms and from which Aspergillus species was cultured. Serum Aspergillus antigen radioimmunoassay may be a valuable, specific early diagnostic test when systemic aspergillosis is a consideration in an immunosuppressed host.

  4. Spontaneous spinal epidural abscess.

    PubMed

    Ellanti, P; Morris, S

    2011-10-01

    Spinal epidural abscess is an uncommon entity, the frequency of which is increasing. They occur spontaneously or as a complication of intervention. The classical triad of fever, back pain and neurological symptoms are not always present. High index of suspicion is key to diagnosis. Any delay in diagnosis and treatment can have significant neurological consequences. We present the case of a previously well man with a one month history of back pain resulting from an epidural abscess.

  5. Spinal arteriovenous shunts in children.

    PubMed

    Davagnanam, Indran; Toma, Ahmed K; Brew, Stefan

    2013-11-01

    Pediatric spinal arteriovenous shunts are rare and, in contrast to those in adults, are often congenital or associated with underlying genetic disorders. These are thought to be a more severe and complete phenotypic spectrum of all spinal arteriovenous shunts seen in the overall spinal shunt population. The pediatric presentation thus accounts for its association with significant morbidity and, in general, a more challenging treatment process compared with the adult presentation.

  6. [Information analysis of spinal ganglia].

    PubMed

    Lobko, P I; Kovaleva, D V; Kovalchuk, I E; Pivchenko, P G; Rudenok, V V; Davydova, L A

    2000-01-01

    Information parameters (entropia and redundancy) of cervical and thoracic spinal ganglia of albino rat foetuses, mature animals (cat and dog) and human subjects were analysed. Information characteristics of spinal ganglia were shown to be level-specified and to depend on their functional peculiarities. Information parameters of thoracic spinal ganglia of man and different animals are specie specified and may be used in assessment of morphological structures as information systems.

  7. Medicolegal cases for spinal epidural hematoma and spinal epidural abscess.

    PubMed

    French, Keisha L; Daniels, Eldra W; Ahn, Uri M; Ahn, Nicholas U

    2013-01-01

    Spinal epidural hematoma and spinal epidural abscess are rare surgical emergencies resulting in significant neurologic deficits. Making the diagnosis for spinal epidural hematoma and spinal epidural abscess can be challenging; however, a delay in recognition and treatment can be devastating. The objective of this retrospective analysis study was to identify risk factors for an adverse outcome for the provider. The LexisNexis Academic legal search database was used to identify a total of 19 cases of spinal epidural hematoma and spinal epidural abscess filed against medical providers. Outcome data on trial verdicts, age, sex, initial site of injury, time to consultation, time to appropriate imaging studies, time to surgery, and whether a rectal examination was performed or not were recorded. The results demonstrated a significant association between time to surgery more than 48 hours and an unfavorable verdict for the provider. The degree of permanent neurologic impairment did not appear to affect the verdicts. Fifty-eight percent of the cases did not present with an initial deficit, including loss of bowel or bladder control. All medical professionals must maintain a high level of suspicion and act quickly. Physicians who are able to identify early clinical features, appropriately image, and treat within a 48 hour time frame have demonstrated a more favorable medicolegal outcome compared with their counterparts in filed lawsuits for spinal epidural hematoma and spinal epidural abscess cases.

  8. THE M81 GROUP DWARF IRREGULAR GALAXY DDO 165. I. HIGH-VELOCITY NEUTRAL GAS IN A POST-STARBURST SYSTEM

    SciTech Connect

    Cannon, John M.; Most, Hans P.; Skillman, Evan D.; Weisz, Daniel R.; Warren, Steven R.; Cook, David; Dolphin, Andrew E.; Kennicutt, Robert C.; Lee, Janice; Seth, Anil; Walter, Fabian E-mail: skillman@astro.umn.edu E-mail: warren@astro.umn.edu E-mail: adolphin@raytheon.com E-mail: jlee@obs.carnegiescience.edu E-mail: walter@mpia.de

    2011-07-01

    We present new multi-configuration Very Large Array H I spectral line observations of the M81 group dwarf irregular post-starburst galaxy DDO 165. The H I morphology is complex, with multiple column density peaks surrounding a large region of very low H I surface density that is offset from the center of the stellar distribution. The bulk of the neutral gas is associated with the southern section of the galaxy; a secondary peak in the north contains {approx}15% of the total H I mass. These components appear to be kinematically distinct, suggesting that either tidal processes or large-scale blowout have recently shaped the interstellar medium (ISM) of DDO 165. Using spatially resolved position-velocity maps, we find multiple localized high-velocity gas features. Cross-correlating with radius-velocity analyses, we identify eight shell/hole structures in the ISM with a range of sizes ({approx}400-900 pc) and expansion velocities ({approx}7-11 km s{sup -1}). These structures are compared with narrow- and broadband imaging from the Kitt Peak National Observatory and the Hubble Space Telescope (HST). Using the latter data, recent works have shown that DDO 165's previous 'burst' phase was extended temporally ({approx}>1 Gyr). We thus interpret the high-velocity gas features, H I holes, and kinematically distinct components of the galaxy in the context of the immediate effects of 'feedback' from recent star formation (SF). In addition to creating H I holes and shells, extended SF events are capable of creating localized high-velocity motion of the surrounding interstellar material. A companion paper connects the energetics from the H I and HST data.

  9. Comparison of iron-bearing minerals in ordinary chondrites from H, L and LL groups using Mössbauer spectroscopy with a high velocity resolution.

    PubMed

    Maksimova, A A; Oshtrakh, M I; Petrova, E V; Grokhovsky, V I; Semionkin, V A

    2017-02-05

    Ordinary chondrites from H, L and LL groups were studied using Mössbauer spectroscopy with a high velocity resolution. Mössbauer parameters of spectral components were obtained using new fitting model excluding the effect of previous misfits of troilite component. Obtained parameters were related to corresponding iron-bearing minerals in ordinary chondrites. The differences of these minerals content as well as small differences in the hyperfine parameters of the same iron-bearing minerals were revealed for different meteorites. The temperatures of equilibrium cations distribution in silicates were estimated and suitable parameters for classification of H, L and LL chondrites were supposed using Mössbauer parameters.

  10. Signs of interaction of the NGC 1275 nucleus with the high-velocity system according to 0.7 sec seeing observations

    NASA Technical Reports Server (NTRS)

    Dudinov, V. N.; Tsvetkova, V. S.; Novikov, S. B.; Pronik, I. I.

    1990-01-01

    The nucleus of the Seyfert galaxy NGC 1275 was observed in the B system on 1 December 1989 with seeing 0, 7 seconds using the Zeiss-1000 telescope on Mount Majdanak in Central Asia. Special methods of processing reveal low-contrast details. The nucleus and circumnucleus are stretched in NW-SE direction. There are two narrow filaments near the nucleus in position angles roughly 340 degrees and 320 degrees. The first is directed near the radio jet of the nucleus, the second has broken details curved to the NW or toward the high-velocity system of NGC 1275.

  11. Re-examination of Dronino iron meteorite and its weathering products using Mössbauer spectroscopy with a high velocity resolution

    NASA Astrophysics Data System (ADS)

    Oshtrakh, M. I.; Yakovlev, G. A.; Grokhovsky, V. I.; Semionkin, V. A.

    2016-12-01

    Re-examination of Dronino iron meteorite and products of its weathering in the internal and external surface layers was carried out using Mössbauer spectroscopy with a high velocity resolution. New results showed the presence of α-Fe(Ni, Co), α 2-Fe(Ni, Co) and γ-Fe(Ni, Co) phases with variations in Ni concentration in Dronino metallic iron alloy. The surface weathering products were supposed as magnetite and/or maghemite, goethite with different particles size and probably ferrihydrite in the internal layer and goethite with different particles size and probably ferrihydrite in the external layer.

  12. Comparison of iron-bearing minerals in ordinary chondrites from H, L and LL groups using Mössbauer spectroscopy with a high velocity resolution

    NASA Astrophysics Data System (ADS)

    Maksimova, A. A.; Oshtrakh, M. I.; Petrova, E. V.; Grokhovsky, V. I.; Semionkin, V. A.

    2017-02-01

    Ordinary chondrites from H, L and LL groups were studied using Mössbauer spectroscopy with a high velocity resolution. Mössbauer parameters of spectral components were obtained using new fitting model excluding the effect of previous misfits of troilite component. Obtained parameters were related to corresponding iron-bearing minerals in ordinary chondrites. The differences of these minerals content as well as small differences in the hyperfine parameters of the same iron-bearing minerals were revealed for different meteorites. The temperatures of equilibrium cations distribution in silicates were estimated and suitable parameters for classification of H, L and LL chondrites were supposed using Mössbauer parameters.

  13. High-velocity-oxidation performance of metal-chromium-aluminum (MCrAl), cermet, and modified aluminide coatings on IN-100 and type VIA alloys at 1093 C

    NASA Technical Reports Server (NTRS)

    Deadmore, D. L.

    1974-01-01

    Cermet, MCrAl, and modified aluminide types of coatings applied to IN-100 and NASA-TRW-VIA alloy specimens were cyclically oxidation tested in a high velocity (Mach 1) gas flame at 1093 C. Several coating compositions of each type were evaluated for oxidation resistance. The modified aluminide coating, Pt-Al, applied to alloy 6A proved to be the best, providing oxidation protection to approximately 750 hours based on weight change measurements. The second best, a CoCrAlY coating applied to 6A, provided protection to 450 hours. The third best was a cermet + aluminide coating on 6A with a protection time to 385 hours.

  14. Imaging modalities in spinal disorders

    SciTech Connect

    Kricun, M.E.

    1986-01-01

    This book provides an approach to the various imaging modalities used to view the spine. It discusses the indications, limitations and practical use of each in the diagnosis, work-up and staging of various spinal disorders, and compares each of them in various clinical settings. Topics covered include low back pain syndrome, disk disease, spinal cord lesions, congenital abnormalities, and trauma.

  15. Spinal adhesive arachnoiditis.

    PubMed

    Dolan, R A

    1993-06-01

    Forty-one cases of spinal adhesive arachnoiditis are presented. The key points are, first, that lumbar disc lesions, their investigations and surgical treatment and the use of nonabsorbable contrast materials are the most common etiological factors and, secondly, that operation is the best treatment. It is our contention that the majority of patients so treated do experience some improvement in what otherwise can be an unbearable amount of pain and disability. The use of adsorbable, nonirritative contrast materials such as Iohexol Parenteral will result in a marked reduction in the frequency of occurrence of arachnoiditis.

  16. CNS and spinal tumors.

    PubMed

    Furtado, Andre D; Panigrahy, Ashok; Fitz, Charles R

    2016-01-01

    Primary CNS tumors consist of a diverse group of neoplasms originating from various cell types in the CNS. Brain tumors are the most common solid malignancy in children under the age of 15 years and the second leading cause of cancer death after leukemia. The most common brain neoplasms in children differ consistently from those in older age groups. Pediatric brain tumors demonstrate distinct patterns of occurrence and biologic behavior according to sex, age, and race. This chapter highlights the imaging features of the most common tumors that affect the child's CNS (brain and spinal cord).

  17. Totally Ossified Metaplastic Spinal Meningioma

    PubMed Central

    Hida, Kazutoshi; Yamauchi, Tomohiro; Houkin, Kiyohiro

    2013-01-01

    A 61-year-old woman with a very rare case of totally ossified large thoracic spinal metaplastic meningioma, showing progressing myelopathy is presented. Computed tomographic images showed a large totally ossfied intradural round mass occupying the spinal canal on T9-10 level. Magnetic resonance imaging revealed a large T9-10 intradural extramedullary mass that was hypointense to spinal cord on T1- and T2-weighted sequences, partial enhancement was apparent after Gadolinium administration. The spinal cord was severely compressed and displaced toward the right at the level of T9-10. Surgical removal of the tumor was successfully accomplished via the posterior midline approach and the histological diagnosis verified an ossified metaplastic meningioma. The clinical neurological symptoms of patient were improved postoperatively. In this article we discuss the surgical and pathological aspects of rare case of spinal totally ossified metaplastic meningioma. PMID:24278660

  18. Retraining the injured spinal cord

    NASA Technical Reports Server (NTRS)

    Edgerton, V. R.; Leon, R. D.; Harkema, S. J.; Hodgson, J. A.; London, N.; Reinkensmeyer, D. J.; Roy, R. R.; Talmadge, R. J.; Tillakaratne, N. J.; Timoszyk, W.; Tobin, A.

    2001-01-01

    The present review presents a series of concepts that may be useful in developing rehabilitative strategies to enhance recovery of posture and locomotion following spinal cord injury. First, the loss of supraspinal input results in a marked change in the functional efficacy of the remaining synapses and neurons of intraspinal and peripheral afferent (dorsal root ganglion) origin. Second, following a complete transection the lumbrosacral spinal cord can recover greater levels of motor performance if it has been exposed to the afferent and intraspinal activation patterns that are associated with standing and stepping. Third, the spinal cord can more readily reacquire the ability to stand and step following spinal cord transection with repetitive exposure to standing and stepping. Fourth, robotic assistive devices can be used to guide the kinematics of the limbs and thus expose the spinal cord to the new normal activity patterns associated with a particular motor task following spinal cord injury. In addition, such robotic assistive devices can provide immediate quantification of the limb kinematics. Fifth, the behavioural and physiological effects of spinal cord transection are reflected in adaptations in most, if not all, neurotransmitter systems in the lumbosacral spinal cord. Evidence is presented that both the GABAergic and glycinergic inhibitory systems are up-regulated following complete spinal cord transection and that step training results in some aspects of these transmitter systems being down-regulated towards control levels. These concepts and observations demonstrate that (a) the spinal cord can interpret complex afferent information and generate the appropriate motor task; and (b) motor ability can be defined to a large degree by training.

  19. Juxtafacet Spinal Synovial Cysts

    PubMed Central

    2016-01-01

    Study Design This was a retrospective study. Purpose To study the surgical outcome of synovial cysts of the lumbar spine through posterior laminectomy in combination with transpedicular screw fixation. Overview of Literature Synovial cysts of the lumbar spine contribute significantly to narrowing of the spinal canal and lateral thecal sac and nerve root compression. Cysts form as a result of arthrotic disruption of the facet joint, leading to degenerative spondylolisthesis in up to 40% of patients. Methods Retrospective data from 6 patients, treated during the period of March 2007 to February 2011, were analyzed. All preoperative and postoperative manifestations, extension/flexion radiographs, magnetic resonance imaging, and computed tomography records were reviewed. All underwent surgery for synovial cysts with excision and decompression combined with posterior fixation. The result of surgery was evaluated with Macnab's classification. An excellent or good outcome was considered as satisfactory. Japanese Orthopedic Association Scale was used for evaluation of back pain. Results All patients included in this study had excellent outcomes as regarding to improvement of all preoperative manifestations and returning to normal daily activities. Only 2 cases developed postoperative transient cerebro-spinal fluid leak and were treated conservatively and improved during the follow up period. Conclusions Although this study included a small number of cases and we could not have statistically significant results, the good outcome of decompression of synovial cysts combined with posterior fixation and fusion encouraged us to recommend this approach for patients with juxtafacet synovial cysts. PMID:26949457

  20. [Surgical anatomy of spinal cord tumors].

    PubMed

    Peltier, J; Chenin, L; Hannequin, P; Page, C; Havet, É; Foulon, P; Le Gars, D

    2015-08-03

    In this article, we respectively describe the morphology of the spinal cord, spinal meningeal layers, main fiber tracts, and both arterial and venous distribution in order to explain signs of spinal cord compression. We will then describe a surgical technique for spinal cord tumor removal.

  1. Attitudes Towards Individuals with Spinal Cord Injuries

    ERIC Educational Resources Information Center

    Conway, Cassandra Sligh D.; Gooden, Randy; Nowell, Jennifer; Wilson, Navodda

    2010-01-01

    This paper will shed light on the lives of persons with spinal cord injuries by revealing the literature on spinal cord injuries that focuses on research that can shed light on attitudes towards persons with spinal cord injuries. The background literature related to incidences, the definition of spinal cord injury, and vocational opportunities are…

  2. Spinal Cord Repair with Engineered Nervous Tissue

    DTIC Science & Technology

    2014-04-01

    in order to minimize scarring and injected dissociated adult DRGs rostral to a dorsal column transection of the spinal cord. From the sensory... columns were dissected and post-fixed overnight in 4% paraformaldehyde, and then spinal cords were dissected from spinal columns and cryoprotected...AD______________ Award Number: W81XWH-10-1-0941 TITLE: Spinal Cord Repair with Engineered Nervous Tissue

  3. Potential Clinical Applications for Spinal Functional MRI

    PubMed Central

    Kornelsen, Jennifer; Mackey, Sean

    2010-01-01

    Functional MRI (fMRI) of the spinal cord is a noninvasive technique for obtaining information regarding spinal cord neuronal function. This article provides a brief overview of recent developments in spinal cord fMRI and outlines potential applications, as well as the limitations that must be overcome, for using spinal fMRI in the clinic. This technique is currently used for research purposes, but significant potential exists for spinal fMRI to become an important clinical tool. PMID:17504642

  4. DISCUSSION ON SPINAL INJURIES

    PubMed Central

    1928-01-01

    (1).—Varieties of spinal injuries, the three groups of common usage: fractures, dislocations, fracture-dislocations. Shall not refer in detail to fractures of the spinous or transverse processes. (2) Mechanics of injury to vertebræ. Two variables: (1) the nature of the bones; (2) the qualities of the force. Spinal injury usually caused by indirect violence. (3) The different results of injuries applied to the head; may break skull, failing that, the neck. Atlas fracture. Difference in qualities of the force causing atlas fracture and low cervical dislocation. (4) The compound nature of the vertebral body. The two columns, anterior, spongy; posterior, compact. The nature of wedge-compression of the vertebral body. Variations in the shape of the wedge. Reasons. Occur at all levels, including cervical spine. (5) Frequency of injury at different levels of vertebral column. “Localization” of injury. The two places of the graph of injury. The cervical at C. 5. Reason. The thoracic-lumbar peak at T. 12, L. 1 industrial. Is there a third peak at C. 2? (6) The effects of violent flexion of the spine: cervical flexion causes luxation at C. 5 or so. Extension causes fracture of odontoid. Violent flexion and extension therefore cause injury at very different levels. Thoracic region, why is there no “peak” of injury at T.6, 7? Lumbar region. (7) Displacement of fragments. Continuation of violence after the essential injury has been effected. Kümmell's disease, no inflammatory process involved. (8) Injury to the intervertebral discs, essential for displacement. Imperfect rupture a cause for difficulty in reducing luxations. The worst cases those in which it is most easily done, but most of these have cord damage. (9) Spinal injury from minimal violence. Examples of trivial cases, diving, brushing hair and so forth. Vertebral displacement in disease a much more serious thing. (10) Curious stability of many cervical luxations. Reasons. Locking of the inferior

  5. Crustal high-velocity anomaly at the East European Craton margin in SE Poland (TESZ) modelled by 3-D seismic tomography of refracted and reflected arrivals

    NASA Astrophysics Data System (ADS)

    Środa, Piotr; Dec, Monika

    2016-04-01

    The area of Trans-European Suture Zone in SE Poland represents a contact of major tectonic units of different consolidation age - from the Precambrian East European Craton, through Palaeozoic West European Platform to Cenozoic Carpathian orogen. The region was built by several phases of crustal accretion, which resulted in a complex collage of tectonic blocks. In 2000, this region was studied by several seismic wide-angle profiles of CELEBRATION 2000 experiment, providing a dense coverage of seismic data in SE Poland and allowing for detailed investigations of the crustal structure and properties in this area. Beneath the marginal part of the EEC, the 2-D modelling of in-line data form several CELEBRATION profiles revealed a prominent high P-wave velocity anomaly in the upper crust, with Vp of 6.7-7.1 km/s, starting at 10-16 km depth (e.g., Środa et al., 2006). Anomalously high velocities are observed in the area located approximately beneath Lublin trough, to the NE of Teisseyre-Tornquist Zone. Based on 3-D tomography of first arrivals of in- and off-line CELEBRATION 2000 recordings (Malinowski et al., 2008), elevated velocities are also reported in the same area and seem to continue to the SW, off the craton margin. Gravimetric modelling also revealed anomalously high density in the same region at similar depths. High seismic velocities and densities are interpreted as indicative for a pronounced mafic intrusion, possibly related to extensional processes at the EEC margin. Previous 3-D models of the high-velocity intrusion were based on first arrivals (crustal refractions) only. In this study, also off-line reflections (not modelled up to now) are used, in order to enlarge the data set and to better constrain the geometry and properties of the velocity anomaly. A code for 3-D joint tomographic inversion of refracted and reflected arrivals, with model parametrization allowing for velocity discontinuities was used (Rawlinson, 2007). With this approach, besides the

  6. The dura causes spinal cord compression after spinal cord injury.

    PubMed

    Saadoun, Samira; Werndle, Melissa C; Lopez de Heredia, Luis; Papadopoulos, Marios C

    2016-10-01

    MR scans from 65 patients with traumatic spinal cord injury were analysed; on admission 95% had evidence of cord compression - in 26% due to the dura, and in the remaining 74% due to extradural factors. Compression due to dural factors resolved with a half-life of 5.5 days. These findings suggest that bony decompression alone may not relieve spinal cord compression in the quarter of patients in whom dural factors are significant.

  7. Simulation in spinal diseases.

    PubMed

    Aso Escario, José; Martínez Quiñones, José Vicente; Aso Vizán, Alberto; Arregui Calvo, Ricardo; Bernal Lafuente, Marta; Alcázar Crevillén, Andrés

    2014-01-01

    Simulation is frequent in spinal disease, resulting in problems for specialists like Orthopedic Surgeons, Neurosurgeons, Reumathologists, etc. Simulation requires demonstration of the intentional production of false or exaggerated symptoms following an external incentive. The clinician has difficulties in demonstrating these criteria, resulting in misdiagnosis of simulation or misinterpretation of the normal patient as a simulator, with the possibility of iatrogenic distress and litigation. We review simulation-related problems in spine, proposing a terminological, as well as a diagnostic strategy including clinical and complementary diagnosis, as a way to avoid misinterpretation and minimize the iatrogenic distress and liability Based on the clinical-Forensic author's expertise, the literature is analyzed and the terminology readdressed to develop new terms (inconsistences, incongruences, discrepancies and contradictions). Clinical semiology and complementary test are adapted to the new scenario. Diagnostic strategy relies on anamnesis, clinical and complementary tests, adapting them to a uniform terminology with clear meaning of signs and symptoms.

  8. Slurry Erosion Behavior of F6NM Stainless Steel and High-Velocity Oxygen Fuel-Sprayed WC-10Co-4Cr Coating

    NASA Astrophysics Data System (ADS)

    Cui, S. Y.; Miao, Q.; Liang, W. P.; Huang, B. Z.; Ding, Z.; Chen, B. W.

    2016-12-01

    WC-10Co-4Cr coating was applied to the surface of F6NM stainless steel by high-velocity oxygen-fuel spraying. The slurry erosion behavior of the matrix and coating was examined at different rotational speeds using a self-made machine. This experiment effectively simulates real slurry erosion in an environment with high silt load. At low velocity (<6 m/s), the main failure mechanism was cavitation. Small bubbles acted as an air cushion, obstructing direct contact between sand and the matrix surface. However, at velocity above 9 m/s, abrasive wear was the dominant failure mechanism. The results indicate that WC-10Co-4Cr coating significantly improved the slurry resistance at higher velocity, because it created a thin and dense WC coating on the surface.

  9. History of high-velocity impact water trauma at Letterman Army Medical Center: a 54-year experience with the Golden Gate Bridge.

    PubMed

    Lafave, M; LaPorta, A J; Hutton, J; Mallory, P L

    1995-04-01

    Three time frames were studied during the 54-year history of the Golden Gate Bridge from 1937 to 1991. During that period of time, there were 918 documented jumps from this majestic structure to the water 250 feet below. The last 15 years provided us with 297 consecutive patients, all brought to one institution, which were retrospectively reviewed and categorized as to site and type of injury for survivors and fatalities. This is the largest high-velocity water impact trauma series in the world. Certain unique characteristics of the Golden Gate Bridge and the San Francisco Bay lend itself to this extremely popular and successful form of suicide. These characteristics, as well as personal factors of free-fall water impact from each patient, are summarized and discussed in this paper.

  10. Study of Chelyabinsk LL5 meteorite fragment with a light lithology and its fusion crust using Mössbauer spectroscopy with a high velocity resolution

    NASA Astrophysics Data System (ADS)

    Maksimova, Alevtina A.; Oshtrakh, Michael I.; Petrova, Evgeniya V.; Grokhovsky, Victor I.; Semionkin, Vladimir A.

    2014-10-01

    Study of Chelyabinsk LL5 ordinary chondrite fragment with a light lithology and its fusion crust, fallen on February 15, 2013, in Russian Federation, was carried out using Mössbauer spectroscopy with a high velocity resolution. The Mössbauer spectra of the internal matter and fusion crust were fitted and all components were related to iron-bearing phases such as olivine, pyroxene, troilite, Fe-Ni-Co alloy, and chromite in the internal matter and olivine, pyroxene, troilite, Fe-Ni-Co alloy, and magnesioferrite in the fusion crust. A comparison of the content of different phases in the internal matter and in the fusion crust of this fragment showed that ferric compounds resulted from olivine, pyroxene, and troilite combustion in the atmosphere.

  11. Study of Chelyabinsk LL5 meteorite fragment with a light lithology and its fusion crust using Mössbauer spectroscopy with a high velocity resolution

    SciTech Connect

    Maksimova, Alevtina A.; Petrova, Evgeniya V.; Grokhovsky, Victor I.; Oshtrakh, Michael I. Semionkin, Vladimir A.

    2014-10-27

    Study of Chelyabinsk LL5 ordinary chondrite fragment with a light lithology and its fusion crust, fallen on February 15, 2013, in Russian Federation, was carried out using Mössbauer spectroscopy with a high velocity resolution. The Mössbauer spectra of the internal matter and fusion crust were fitted and all components were related to iron-bearing phases such as olivine, pyroxene, troilite, Fe-Ni-Co alloy, and chromite in the internal matter and olivine, pyroxene, troilite, Fe-Ni-Co alloy, and magnesioferrite in the fusion crust. A comparison of the content of different phases in the internal matter and in the fusion crust of this fragment showed that ferric compounds resulted from olivine, pyroxene, and troilite combustion in the atmosphere.

  12. Four frictional regimes as a function of slip rate in halite and halite-muscovite gouge deformed from low to high velocities

    NASA Astrophysics Data System (ADS)

    Buijze, Loes; Niemeijer, Andre R.; Han, Raehee; Shimamoto, Toshihiko; Spiers, Christopher J.

    2014-05-01

    The evolution of friction as a function of slip velocity is an important factor in understanding earthquake nucleation and propagation. The velocity dependence of the coefficient of friction may not be constant but vary with slip rate. When such variations in the sign (velocity weakening vs. strengthening) and/or magnitude of the velocity dependence of friction are included in numerical modelling of rupture, it is observed that more complex and more realistic rupture patterns are produced compared to using a single constant velocity dependence. It is thus important to study the coefficient of friction over the entire range of velocities relevant to earthquake nucleation and propagation, which may be done in the laboratory. Most laboratory experiments are either conducted at low velocities (10-8 - 10-4 ms-1) or high velocities (0.01 - 1 ms-1). Few experiments however bridge the gap between these two regimes. Also, reproducing in situ conditions is difficult during high velocity experiments since normal stress is often limited, pore pressure is hard to control and often room temperature is used. In this research we aim to study the evolution of friction of a single material from low to high slip rates, which deforms via processes representative to upper crustal deformation of quartzite fault rock (with phyllosilicates) at conditions accessible at low and high velocities. Analogue halite and halite-muscovite gouges were deformed over a 7 orders of magnitude slip range (0.1 μms-1 - 1 ms-1) using a low-to-high velocity rotary shear apparatus at Hiroshima University. The applied normal stress was 5 MPa, the experiments took place at room temperature and gouges were room-dry. Microstructural analysis was conducted to study the deformation mechanisms. Four frictional regimes as a function of slip rate could be recognized from the mechanical data, and each regime was associated with a distinct microstructure, reflecting a transition from mainly brittle-dominated to more

  13. Effect of ultrasonic cavitation erosion on corrosion behavior of high-velocity oxygen-fuel (HVOF) sprayed near-nanostructured WC-10Co-4Cr coating.

    PubMed

    Hong, Sheng; Wu, Yuping; Zhang, Jianfeng; Zheng, Yugui; Qin, Yujiao; Lin, Jinran

    2015-11-01

    The effect of ultrasonic cavitation erosion on electrochemical corrosion behavior of high-velocity oxygen-fuel (HVOF) sprayed near-nanostructured WC-10Co-4Cr coating in 3.5 wt.% NaCl solution, was investigated using free corrosion potential, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) in comparison with stainless steel 1Cr18Ni9Ti. The results showed that cavitation erosion strongly enhanced the cathodic current density, shifted the free corrosion potential in the anodic direction, and reduced the magnitude of impedance of the coating. The impedance of the coating decreased more slowly under cavitation conditions than that of the stainless steel 1Cr18Ni9Ti, suggesting that corrosion behavior of the coating was less affected by cavitation erosion than that of the stainless steel.

  14. Cyclic oxidation of cobalt-chromium-aluminum-yttrium and aluminide coatings on IN-100 and VIA alloys in high velocity gases

    NASA Technical Reports Server (NTRS)

    Deadmore, D. L.

    1972-01-01

    Embedded-alumina-particle aluminide (EAPA) coated and CoCrAlY coated IN-100 and NASA-TRW-VIA specimens were cyclically oxidation tested in a high velocity (approximately Mach 1) gas flame at 1093 C (2000 F). The EAPA coatings on both alloys performed very similarly to commercial pack aluminide coatings with respect to weight change and thermal fatigue cracking. The CoCrAlY coating on IN-100 had weight changes similar to commercial pack aluminide coatings but no thermal fatigue cracks appeared at 300 hours. The CoCrAlY coating on VIA performed significantly better than the commercial aluminide coatings, providing oxidation protection (based on weight change) to 450 hours and thermal fatigue crack prevention to at least 600 hours.

  15. Slurry Erosion Behavior of F6NM Stainless Steel and High-Velocity Oxygen Fuel-Sprayed WC-10Co-4Cr Coating

    NASA Astrophysics Data System (ADS)

    Cui, S. Y.; Miao, Q.; Liang, W. P.; Huang, B. Z.; Ding, Z.; Chen, B. W.

    2017-02-01

    WC-10Co-4Cr coating was applied to the surface of F6NM stainless steel by high-velocity oxygen-fuel spraying. The slurry erosion behavior of the matrix and coating was examined at different rotational speeds using a self-made machine. This experiment effectively simulates real slurry erosion in an environment with high silt load. At low velocity (<6 m/s), the main failure mechanism was cavitation. Small bubbles acted as an air cushion, obstructing direct contact between sand and the matrix surface. However, at velocity above 9 m/s, abrasive wear was the dominant failure mechanism. The results indicate that WC-10Co-4Cr coating significantly improved the slurry resistance at higher velocity, because it created a thin and dense WC coating on the surface.

  16. SHORT-DURATION LENSING EVENTS. I. WIDE-ORBIT PLANETS? FREE-FLOATING LOW-MASS OBJECTS? OR HIGH-VELOCITY STARS?

    SciTech Connect

    Di Stefano, Rosanne

    2012-08-01

    Short-duration lensing events tend to be generated by low-mass lenses or by lenses with high transverse velocities. Furthermore, for any given lens mass and speed, events of short duration are preferentially caused by nearby lenses (mesolenses) that can be studied in detail, or else by lenses so close to the source star that finite-source-size effects may be detected, yielding information about both the Einstein ring radius and the surface of the lensed star. Planets causing short-duration events may be in orbits with any orientation, and may have semimajor axes smaller than 1 AU, or they may reach the outer limits of their planetary systems, in the region corresponding to the solar system's Oort Cloud. They can have masses larger than Jupiter's or smaller than Pluto's. Lensing therefore has a unique potential to expand our understanding of planetary systems. A particular advantage of lensing is that it can provide precision measurements of system parameters, including the masses of and projected separation between star and planet. We demonstrate how the parameters can be extracted and show that a great deal can be learned. For example, it is remarkable that the gravitational mass of nearby free-floating planet-mass lenses can be measured by complementing observations of a photometric event with deep images that detect the planet itself. A fraction of short events may be caused by high-velocity stars located within a kiloparsec. Many high-velocity lenses are likely to be neutron stars that received large natal kicks. Other high-speed stars may be members of the halo population. Still others may be hypervelocity stars that have been ejected from the Galactic center, or runaway stars escaped from close binaries, possibly including the progenitor binaries of Type Ia supernovae.

  17. Spectroscopic Observations of SN 2012fr: A Luminous, Normal Type Ia Supernova with Early High-velocity Features and a Late Velocity Plateau

    NASA Astrophysics Data System (ADS)

    Childress, M. J.; Scalzo, R. A.; Sim, S. A.; Tucker, B. E.; Yuan, F.; Schmidt, B. P.; Cenko, S. B.; Silverman, J. M.; Contreras, C.; Hsiao, E. Y.; Phillips, M.; Morrell, N.; Jha, S. W.; McCully, C.; Filippenko, A. V.; Anderson, J. P.; Benetti, S.; Bufano, F.; de Jaeger, T.; Forster, F.; Gal-Yam, A.; Le Guillou, L.; Maguire, K.; Maund, J.; Mazzali, P. A.; Pignata, G.; Smartt, S.; Spyromilio, J.; Sullivan, M.; Taddia, F.; Valenti, S.; Bayliss, D. D. R.; Bessell, M.; Blanc, G. A.; Carson, D. J.; Clubb, K. I.; de Burgh-Day, C.; Desjardins, T. D.; Fang, J. J.; Fox, O. D.; Gates, E. L.; Ho, I.-T.; Keller, S.; Kelly, P. L.; Lidman, C.; Loaring, N. S.; Mould, J. R.; Owers, M.; Ozbilgen, S.; Pei, L.; Pickering, T.; Pracy, M. B.; Rich, J. A.; Schaefer, B. E.; Scott, N.; Stritzinger, M.; Vogt, F. P. A.; Zhou, G.

    2013-06-01

    We present 65 optical spectra of the Type Ia SN 2012fr, 33 of which were obtained before maximum light. At early times, SN 2012fr shows clear evidence of a high-velocity feature (HVF) in the Si II λ6355 line that can be cleanly decoupled from the lower velocity "photospheric" component. This Si II λ6355 HVF fades by phase -5 subsequently, the photospheric component exhibits a very narrow velocity width and remains at a nearly constant velocity of ~12,000 km s-1 until at least five weeks after maximum brightness. The Ca II infrared triplet exhibits similar evidence for both a photospheric component at v ≈ 12,000 km s-1 with narrow line width and long velocity plateau, as well as an HVF beginning at v ≈ 31,000 km s-1 two weeks before maximum. SN 2012fr resides on the border between the "shallow silicon" and "core-normal" subclasses in the Branch et al. classification scheme, and on the border between normal and high-velocity Type Ia supernovae (SNe Ia) in the Wang et al. system. Though it is a clear member of the "low velocity gradient" group of SNe Ia and exhibits a very slow light-curve decline, it shows key dissimilarities with the overluminous SN 1991T or SN 1999aa subclasses of SNe Ia. SN 2012fr represents a well-observed SN Ia at the luminous end of the normal SN Ia distribution and a key transitional event between nominal spectroscopic subclasses of SNe Ia.

  18. Short-duration Lensing Events. I. Wide-orbit Planets? Free-floating Low-mass Objects? Or High-velocity Stars?

    NASA Astrophysics Data System (ADS)

    Di Stefano, Rosanne

    2012-08-01

    Short-duration lensing events tend to be generated by low-mass lenses or by lenses with high transverse velocities. Furthermore, for any given lens mass and speed, events of short duration are preferentially caused by nearby lenses (mesolenses) that can be studied in detail, or else by lenses so close to the source star that finite-source-size effects may be detected, yielding information about both the Einstein ring radius and the surface of the lensed star. Planets causing short-duration events may be in orbits with any orientation, and may have semimajor axes smaller than 1 AU, or they may reach the outer limits of their planetary systems, in the region corresponding to the solar system's Oort Cloud. They can have masses larger than Jupiter's or smaller than Pluto's. Lensing therefore has a unique potential to expand our understanding of planetary systems. A particular advantage of lensing is that it can provide precision measurements of system parameters, including the masses of and projected separation between star and planet. We demonstrate how the parameters can be extracted and show that a great deal can be learned. For example, it is remarkable that the gravitational mass of nearby free-floating planet-mass lenses can be measured by complementing observations of a photometric event with deep images that detect the planet itself. A fraction of short events may be caused by high-velocity stars located within a kiloparsec. Many high-velocity lenses are likely to be neutron stars that received large natal kicks. Other high-speed stars may be members of the halo population. Still others may be hypervelocity stars that have been ejected from the Galactic center, or runaway stars escaped from close binaries, possibly including the progenitor binaries of Type Ia supernovae.

  19. Relationship between Spinal Cord Volume and Spinal Cord Injury due to Spinal Shortening

    PubMed Central

    Qiu, Feng; Yang, Jin-Cheng; Ma, Xiang-Yang; Xu, Jun-Jie; Yang, Qing-Lei; Zhou, Xin; Xiao, Yao-Sheng; Hu, Hai-Sheng; Xia, Li-Hui

    2015-01-01

    Vertebral column resection is associated with a risk of spinal cord injury. In the present study, using a goat model, we aimed to investigate the relationship between changes in spinal cord volume and spinal cord injury due to spinal shortening, and to quantify the spinal cord volume per 1-mm height in order to clarify a safe limit for shortening. Vertebral column resection was performed at T10 in 10 goats. The spinal cord was shortened until the somatosensory-evoked potential was decreased by 50% from the baseline amplitude or delayed by 10% relative to the baseline peak latency. A wake-up test was performed, and the goats were observed for two days postoperatively. Magnetic resonance imaging was used to measure the spinal cord volume, T10 height, disc height, osteotomy segment height, and spinal segment height pre- and postoperatively. Two of the 10 goats were excluded, and hence, only data from eight goats were analyzed. The somatosensory-evoked potential of these eight goats demonstrated meaningful changes. With regard to neurologic function, five and three goats were classified as Tarlov grades 5 and 4 at two days postoperatively. The mean shortening distance was 23.6 ± 1.51 mm, which correlated with the d-value (post-pre) of the spinal cord volume per 1-mm height of the osteotomy segment (r = 0.95, p < 0.001) and with the height of the T10 body (r = 0.79, p = 0.02). The mean d-value (post-pre) of the spinal cord volume per 1-mm height of the osteotomy segment was 142.87 ± 0.59 mm3 (range, 142.19–143.67 mm3). The limit for shortening was approximately 106% of the vertebral height. The mean volumes of the osteotomy and spinal segments did not significantly change after surgery (t = 0.310, p = 0.765 and t = 1.241, p = 0.255, respectively). Thus, our results indicate that the safe limit for shortening can be calculated using the change in spinal cord volume per 1-mm height. PMID:26001196

  20. Currarino syndrome and spinal dysraphism.

    PubMed

    Kole, Matthew J; Fridley, Jared S; Jea, Andrew; Bollo, Robert J

    2014-06-01

    Currarino syndrome is a rare constellation of congenital anomalies characterized by the triad of sacral dysgenesis, presacral mass, and anorectal malformation. It is frequently associated with other congenital anomalies, often including occult spinal dysraphism. Mutations in the MNX1 gene are identified in the majority of cases. The authors report a rare case of Currarino syndrome in an infant with tethered cord syndrome and a dorsal lipomyelomeningocele continuous with a presacral intradural spinal lipoma, in addition to an imperforate anus and a scimitar sacrum. They review the literature to highlight patterns of occult spinal dysraphism in patients with Currarino syndrome and their relationship to tethered cord syndrome. Approximately 60% of the patients with Currarino syndrome reported in the literature have an occult spinal dysraphism. Published studies suggest that the risk of tethered cord syndrome may be higher among patients with a lipoma and lower among those with a teratoma or anterior meningocele.

  1. Overview of Spinal Cord Disorders

    MedlinePlus

    ... cord consists of gray matter shaped like a butterfly: The front "wings" (anterior or motor horns) contain ... In the center of the spinal cord, a butterfly-shaped area of gray matter helps relay impulses ...

  2. Depression and Spinal Cord Injury

    MedlinePlus

    ... colleagues, with an educational grant from Pfizer Inc. University of Washington-operated SCI Clinics: Harborview Medical Center ... Spinal Cord Injury Clinic nurses: 206-744-5862 University of Washington Medical Center Rehabilitation Medicine Clinic 1959 ...

  3. Spinal anomalies in Pfeiffer syndrome.

    PubMed

    Moore, M H; Lodge, M L; Clark, B E

    1995-05-01

    Review of the spinal radiographs of a consecutive series of 11 patients with Pfeiffer syndrome presenting to the Australian Craniofacial Unit was performed. The prevalence of cervical spine fusions was high, and the pattern of fusion complex. Isolated anomalies were evident at lower levels, including two cases of sacrococcygeal eversion. Spinal anomalies occur more frequently in the more severely involved cases of Pfeiffer syndrome emphasizing the generalized dysostotic nature of this condition.

  4. High Velocity Implanting of Anchors

    DTIC Science & Technology

    2007-11-02

    pi’ech us~inq cold high pressure gas to s’jppl y -the, energy, instead of propllant gs. This turned .ne. "* "UNCLASSIFIED *SECJQ" : SSI FICA’ION O.TH.IS... pressure gun propulsor now used. These alternate ýropulsion systems all have the capability to propel the PEA’s and to eliminate the recoil problems that...EXIT AND AT GAS-WATER INTERFACE AS A FUNCTION OF TIME ..... ......... 34 11 REQUIRED INSIDE DIAMETER OF LAUNCH, TUBE AS A FUNCTION OF DRIVE PRESSURE

  5. Role of spinal metabotropic glutamate receptor 5 in pudendal inhibition of the nociceptive bladder reflex in cats.

    PubMed

    Reese, Jeremy N; Rogers, Marc J; Xiao, Zhiying; Shen, Bing; Wang, Jicheng; Schwen, Zeyad; Roppolo, James R; de Groat, William C; Tai, Changfeng

    2015-04-15

    This study examined the role of spinal metabotropic glutamate receptor 5 (mGluR5) in the nociceptive C-fiber afferent-mediated spinal bladder reflex and in the inhibtion of this reflex by pudendal nerve stimulation (PNS). In α-chloralose-anesthetized cats after spinal cord transection at the T9/T10 level, intravesical infusion of 0.25% acetic acid irritated the bladder, activated nociceptive C-fiber afferents, and induced spinal reflex bladder contractions of low amplitude (<50 cmH2O) and short duration (<20 s) at a smaller bladder capacity ∼80% of saline control capacity. PNS significantly (P < 0.01) increased bladder capacity from 85.5 ± 10.1 to 137.3 ± 14.1 or 148.2 ± 11.2% at 2T or 4T stimulation, respectively, where T is the threshold intensity for PNS to induce anal twitch. MTEP {3-[(2-methyl-4-thiazolyl)ethynyl]pyridine; 3 mg/kg iv, a selective mGluR5 antagonist} completely removed the PNS inhibition and significantly (P < 0.05) increased bladder capacity from 71.8 ± 9.9 to 94.0 ± 13.9% of saline control, but it did not change the bladder contraction amplitude. After propranolol (3 mg/kg iv, a β1/β2-adrenergic receptor antagonist) treatment, PNS inhibition remained but MTEP significantly (P < 0.05) reduced the bladder contraction amplitude from 18.6 ± 2.1 to 6.6 ± 1.2 cmH2O and eliminated PNS inhibition. At the end of experiments, hexamethonium (10 mg/kg iv, a ganglionic blocker) significantly (P < 0.05) reduced the bladder contraction amplitude from 20.9 ± 3.2 to 8.1 ± 1.5 cmH2O on average demonstrating that spinal reflexes were responsible for a major component of the contractions. This study shows that spinal mGluR5 plays an important role in the nociceptive C-fiber afferent-mediated spinal bladder reflex and in pudendal inhibition of this spinal reflex.

  6. Spinal muscular atrophy

    PubMed Central

    2011-01-01

    Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease characterized by degeneration of alpha motor neurons in the spinal cord, resulting in progressive proximal muscle weakness and paralysis. Estimated incidence is 1 in 6,000 to 1 in 10,000 live births and carrier frequency of 1/40-1/60. This disease is characterized by generalized muscle weakness and atrophy predominating in proximal limb muscles, and phenotype is classified into four grades of severity (SMA I, SMAII, SMAIII, SMA IV) based on age of onset and motor function achieved. This disease is caused by homozygous mutations of the survival motor neuron 1 (SMN1) gene, and the diagnostic test demonstrates in most patients the homozygous deletion of the SMN1 gene, generally showing the absence of SMN1 exon 7. The test achieves up to 95% sensitivity and nearly 100% specificity. Differential diagnosis should be considered with other neuromuscular disorders which are not associated with increased CK manifesting as infantile hypotonia or as limb girdle weakness starting later in life. Considering the high carrier frequency, carrier testing is requested by siblings of patients or of parents of SMA children and are aimed at gaining information that may help with reproductive planning. Individuals at risk should be tested first and, in case of testing positive, the partner should be then analyzed. It is recommended that in case of a request on carrier testing on siblings of an affected SMA infant, a detailed neurological examination should be done and consideration given doing the direct test to exclude SMA. Prenatal diagnosis should be offered to couples who have previously had a child affected with SMA (recurrence risk 25%). The role of follow-up coordination has to be managed by an expert in neuromuscular disorders and in SMA who is able to plan a multidisciplinary intervention that includes pulmonary, gastroenterology/nutrition, and orthopedic care. Prognosis depends on the phenotypic

  7. Spinal trauma. Pathophysiology and management of traumatic spinal injuries.

    PubMed

    Shores, A

    1992-07-01

    Spinal trauma can originate from internal or external sources. Injuries to the spinal cord can be classified as either concussive or compressive and concussive. The pathophysiologic events surrounding spinal cord injury include the primary injury (compression, concussion) and numerous secondary injury mechanisms (vascular, biochemical, electrolyte), which are mediated by excessive oxygen free radicles, neurotransmitter and electrolyte alterations in cell membrane permeability, excitotoxic amino acids, and various other biochemical factors that collectively result in reduced SCBF, ischemia, and eventual necrosis of the gray and white matter. Management of acute spinal cord injuries includes the use of a high-dose corticosteroid regimen within the initial 8 hours after trauma. Sodium prednisolone and methylprednisolone, at recommended doses, act as oxygen radical scavengers and are anti-inflammatory. Additional considerations are the stability of the vertebral column, other conditions associated with trauma (i.e., pneumothorax), and the presence or absence of spinal cord compression, which may warrant surgical therapy. Vertebral fractures or luxations can occur in any area of the spine but most commonly occur at the junction of mobile and immobile segments. Dorsal and dorsolateral surgical approaches are applicable to the lumbosacral and thoracolumbar spine and dorsal and ventral approaches to the cervical spine. Indications for surgical intervention include spinal cord compression and vertebral instability. Instability can be determined from the type of fracture, how many of the three compartments of the vertebrae are disrupted, and on occasion, by carefully positioned stress studies of fluoroscopy. Decompression (dorsal laminectomy, hemilaminectomy, or ventral cervical slot) is employed when compression of the spinal cord exists. The hemilaminectomy (unilateral or bilateral) causes less instability than dorsal laminectomy and therefore should be used when practical

  8. [Acute spinal subdural hematoma after attempted spinal anesthesia].

    PubMed

    Likar, R; Mathiaschitz, K; Spendel, M; Krumpholz, R; Martin, E

    1996-01-01

    This is a report of a case of a subdural haematoma with resulting paraplegia after attempted spinal anaesthesia. Epidural and subdural haematomas are rare complications after central neural blockade. The complication described here was the result of an unsuccessful attempt to puncture the spinal channel. The patient was a 72-year-old woman with a fracture of the left femoral neck, which it was intended to stabilize operatively. Findings that made lumbar spinal puncture difficult were severe overweight, and lordosis and scoliosis of the lumbar spine resulting from degenerative changes. Spinal anaesthesia was suggested because the patient had eaten shortly before and because she suffered from asthma. From the aspect of haemostasis no contraindications were present, and the anaesthesist was experienced in spinal anaesthesia even under difficult anatomical conditions. Several unsuccessful attempts were made to puncture the lumbar spinal channel while the patient was lying on her right side. It was also impossible to reach the spinal channel from a median or left paramedian approach. We used atraumatic pencil-point needles (Sprotte gauge 24, 90 mm). No blood was aspirated during any of the attempts. The surgical intervention was finally performed under a general anaesthetic in view of the urgency. No significant complications occurred during the operation, and no neurological abnormalities were observed immediately after or in the next 8 h after the operation. At 12 h after the operation a paraparesis was found caudal to L3. After this had been verified by radiological and neurological tests, neurosurgical decompression was carried out as quickly as possible. During the operation a distinct subdural haematoma without any detectable source of bleeding was discovered. Even after surgical revision and evacuation of the remaining haematoma it was not possible to reverse the paraplegia, in spite of rehabilitation measures. Despite a certain fragility of the vessel and

  9. Spinal fixation. Part 3. Complications of spinal instrumentation.

    PubMed

    Slone, R M; MacMillan, M; Montgomery, W J

    1993-07-01

    Spinal fixation devices can be used to form a rigid construct with the spine to replace bone, restore alignment, maintain position, and prevent motion in the treatment of fractures, degenerative disease, neoplasm, and congenital deformities. Because most spinal constructs will eventually fail if bone fusion does not occur, bone graft material is often used along with the implant to promote fusion. Conventional radiographs, obtained in two projections, remain the mainstay of implant evaluation, demonstrating the position of the spinal elements, hardware, graft material, and evidence of complication. Possible complications connected with use of fixation devices include intraoperative soft-tissue injuries, postoperative hematomas, and infection. The components (through incorrect use, malpositioning at surgery, and later dislodgment or fracture) may also contribute to complications such as instability; failure of fusion; or pain, with possible resultant neurologic damage. Bone graft material can migrate or hypertrophy, resulting in impingement on the spinal canal or neural foramen. Radiologists should be familiar with the various spinal fixation devices and techniques to better identify evolving complications.

  10. Spinal Extradural Arachnoid Cyst

    PubMed Central

    Woo, Joon Bum; Kang, Kyung Taek; Lee, Jun Seok; Song, Geun Seong; Sung, Soon Ki; Lee, Sang Weon

    2016-01-01

    A spinal extradural arachnoid cyst (SEAC) results from a rare small defect of the dura matter that leads to cerebrospinal fluid accumulation and communication defects between the cyst and the subarachnoid space. There is consensus for the treatment of the dural defect, but not for the treatment of the cyst. Some advocate a total resection of the cysts and repair of the communication site to prevent the recurrence of a SEAC, while others recommended more conservative therapy. Here we report the outcomes of selective laminectomy and closure of the dural defect for a 72-year-old and a 33-year-old woman. Magnetic resonance imaging of these patients showed an extradural cyst from T12 to L4 and an arachnoid cyst at the posterior epidural space of T12 to L2. For both patients, we surgically fenestrated the cyst and repaired the dural defect using a partial hemi-laminectomy. The patient’s symptoms dramatically subsided, and follow-up radiological images show a complete disappearance of the cyst in both patients. Our results suggest that fenestration of the cyst can be a safe and effective approach in treating SEACs compared to a classical complete resection of the cyst wall with multilevel laminectomy. PMID:27857934

  11. Spinal Extradural Arachnoid Cyst

    PubMed Central

    Choi, Seung Won; Seong, Han Yu

    2013-01-01

    Spinal extradural arachnoid cyst (SEAC) is a rare disease and uncommon cause of compressive myelopathy. The etiology remains still unclear. We experienced 2 cases of SEACs and reviewed the cases and previous literatures. A 59-year-old man complained of both leg radiating pain and paresthesia for 4 years. His MRI showed an extradural cyst from T12 to L3 and we performed cyst fenestration and repaired the dural defect with tailored laminectomy. Another 51-year-old female patient visited our clinical with left buttock pain and paresthesia for 3 years. A large extradural cyst was found at T1-L2 level on MRI and a communication between the cyst and subarachnoid space was illustrated by CT-myelography. We performed cyst fenestration with primary repair of dural defect. Both patients' symptoms gradually subsided and follow up images taken 1-2 months postoperatively showed nearly disappeared cysts. There has been no documented recurrence in these two cases so far. Tailored laminotomy with cyst fenestration can be a safe and effective alternative choice in treating SEACs compared to traditional complete resection of cyst wall with multi-level laminectomy. PMID:24294463

  12. Initiation and runaway process of Tsaoling landslide, triggered by the 1999 Taiwan Chi-Chi earthquake, as studied by high-velocity friction experiments (Invited)

    NASA Astrophysics Data System (ADS)

    Togo, T.; Shimamoto, T.; Dong, J.; Lee, C.

    2013-12-01

    High-velocity friction experiments in the last two decades have demonstrated dramatic weakening of simulated faults at seismic slip rates on the order of 1 m/s (e.g., Di Toro et al., 2011, Nature). Similar experiments revealed very low friction of landslide materials (0.05-0.2 in friction coefficient) that can cause catastrophic landslides with velocity exceeding even 10 m/s (e.g., Miyamoto et al. (2009) on the 1999 Tsaoling landslide in Taiwan; Yano et al. (2009) on the 1999 Jiufengershan landslide in Taiwan,; Ferri et al. (2010, 2011) on the 1963 Vaiont landslide in Italy; Kuo et al. (2011) on the 2009 Hsiaolin landslide in Taiwan). Those studies strongly suggest that there are common processes operative in fault zones and along slip surfaces of catastrophic landslides along bedding planes, fractures or joints. As for catastrophic landslides triggered by an earthquake, an important issue to be addressed is how a landslide initiates during seismic ground motion. Thus we have studied the initiation and runaway process of the Tsaoling landslide by idealizing the initial landslide movement during seismic ground motion as an oscillating accelerating/decelerating motion. Tsaoling landslide is the largest landslide among those triggered by the Chi-Chi earthquake with its volume of about 130 Mm3. The landslide took place along very planar bedding planes of the porous Pliocene sedimentary rocks (mostly siltstone and sandstone), with a dip angle of 14 degree. A seismic record at a station about 500 m away from the landslide and a witness of a survivor who slid on top of the landslide mass indicate that the average speed of the landslide reached 20~40 m/s. A simple analysis of sliding block indicates that the kinetic friction has to be 0.05~0.15 to produce such a high-velocity. Moreover, Tang et al. (2009, Eng. Geol.) analyzed landslide motion with the discrete element method and showed that the landslide mass must have slid nearly as an intact mass, without much

  13. High-Velocity Friction Experiments on the Longmenshan Fault Gouge towards the Understanding of Dynamic Rupture Propagation of the 2008 Wenchuan Earthquake

    NASA Astrophysics Data System (ADS)

    Togo, T.; Shimamoto, T.; Ma, S.; Wen, X.; Hirose, T.; Lei, X.

    2009-12-01

    Disastrous Wenchuan earthquake (12 May 2009, Mw 7.9) was accompanied by surface ruptures of about 280 km in EW extension along existing Longmenshan fault system (e.g., Lin et al., 2009, Tectonophysics). We have conducted high-velocity friction experiments on fault gouge from this fault in order to understand the mechanisms of dynamic fault motion that caused this earthquake. Fault gouge was collected from Hongkou outcrop of Yingxiu-Beichuan fault on the western part of the Longmenshan fault system (site 6 of Lin et al., 2009). XRD analyses revealed that gouge contains quartz, muscovite, kaolinite and chlorite. Experiments were done on gouge of about 1 mm in thickness between a pair of solid cylindrical specimens of Belfast gabbro of about 25 mm in diameter under dry or wet conditions, using the first high-velocity testing machine and a rotary-shear low-to-high-velocity friction apparatus (the second machine). Slip rates and normal stresses were varied, respectively, from 0.009 to 1.30 m/s and from 0.6 to 4.9 MPa. Deionized water of 0.25grams in weight was added to gouge for wet runs. Dry fault gouge exhibit quite similar behaviors to those reported previously, characterized by dramatic slip weakening at high slip rates. A series of tests at slip rate of 0.3 m/s with normal stresses varied from 0.61 to 3.04 MPa shows that Coulomb’s law of friction holds for both peak and steady-state friction with frictional coefficients of 0.65 and 0.12, respectively. The steady-state friction markedly decreases from around 0.75 to about 0.2 as slip rate increases from 0.01 to 1.3 m/s, even though the peak frictional coefficient remains at around 0.8 for the same range of slip rates. The change in friction from peak to steady state is characterized by nearly exponential decay from peak to steady-state. The slip-weakening distance, Dc, defined as the displacement required for 95% reduction from peak to steady-state friction, decreases very systematically with increasing slip rate

  14. Effects of mechanical horseback riding velocity on spinal alignment in young adults

    PubMed Central

    Lim, Jae-Heon; Cho, Woon-Su; Lee, Seong-Jin; Park, Chi-Bok; Park, Jang-Sung

    2016-01-01

    [Purpose] This study aimed to determine if the velocity of mechanical horseback-riding training can improve spinal alignment in young adults. [Subjects and Methods] Thirty-six subjects were enrolled in this study. The subjects were randomly allocated into high-, moderate-, and low-velocity mechanical horseback-riding training groups. All participants completed one 20-minute session per day, 3 days per week, for 6 weeks. The evaluation was performed before and 6 weeks after the training intervention. The spinal alignment was measured by a Formetric III device. The measurement items were kyphotic angle, lordotic angle, trunk inclination, pelvic torsion, pelvic rotation, and lateral deviation. The data were analyzed using analysis of covariance to determine the statistical significance. [Results] The kyphotic angle and trunk inclination were significantly different among the groups. The kyphotic angles of the high- and moderate-velocity groups were significantly lower than that of the low-velocity group after the intervention. The trunk inclination of the high-velocity group was significantly lower than that of the low-velocity group after intervention. [Conclusion] Higher-velocity mechanical horseback-riding training is more effective than lower-velocity mechanical horseback-riding training for improving spinal alignment. PMID:27390428

  15. Effects of mechanical horseback riding velocity on spinal alignment in young adults.

    PubMed

    Lim, Jae-Heon; Cho, Woon-Su; Lee, Seong-Jin; Park, Chi-Bok; Park, Jang-Sung

    2016-06-01

    [Purpose] This study aimed to determine if the velocity of mechanical horseback-riding training can improve spinal alignment in young adults. [Subjects and Methods] Thirty-six subjects were enrolled in this study. The subjects were randomly allocated into high-, moderate-, and low-velocity mechanical horseback-riding training groups. All participants completed one 20-minute session per day, 3 days per week, for 6 weeks. The evaluation was performed before and 6 weeks after the training intervention. The spinal alignment was measured by a Formetric III device. The measurement items were kyphotic angle, lordotic angle, trunk inclination, pelvic torsion, pelvic rotation, and lateral deviation. The data were analyzed using analysis of covariance to determine the statistical significance. [Results] The kyphotic angle and trunk inclination were significantly different among the groups. The kyphotic angles of the high- and moderate-velocity groups were significantly lower than that of the low-velocity group after the intervention. The trunk inclination of the high-velocity group was significantly lower than that of the low-velocity group after intervention. [Conclusion] Higher-velocity mechanical horseback-riding training is more effective than lower-velocity mechanical horseback-riding training for improving spinal alignment.

  16. Directing Spinal Cord Plasticity: The Impact of Stretch Therapy on Functional Recovery after Spinal Cord Injury

    DTIC Science & Technology

    2014-10-01

    AWARD NUMBER: W81XWH-12-1-0587 TITLE: Directing Spinal Cord Plasticity: The Impact of Stretch ...Directing Spinal Cord Plasticity: The Impact of Stretch Therapy on Functional Recovery after Spinal Cord Injury. 5b. GRANT NUMBER W81XWH-12-1...ABSTRACT Essentially all spinal cord injured patients receive stretching therapies beginning within the first few weeks post-injury. Despite

  17. Subdural Thoracolumbar Spine Hematoma after Spinal Anesthesia: A Rare Occurrence and Literature Review of Spinal Hematomas after Spinal Anesthesia

    PubMed Central

    Maddali, Prasanthi; Walker, Blake; Fisahn, Christian; Page, Jeni; Diaz, Vicki; Zwillman, Michael E; Oskouian, Rod J; Tubbs, R. Shane

    2017-01-01

    Spinal hematomas are a rare but serious complication of spinal epidural anesthesia and are typically seen in the epidural space; however, they have been documented in the subdural space. Spinal subdural hematomas likely exist within a traumatically induced space within the dural border cell layer, rather than an anatomical subdural space. Spinal subdural hematomas present a dangerous clinical situation as they have the potential to cause significant compression of neural elements and can be easily mistaken for spinal epidural hematomas. Ultrasound can be an effective modality to diagnose subdural hematoma when no epidural blood is visualized. We have reviewed the literature and present a full literature review and a case presentation of an 82-year-old male who developed a thoracolumbar spinal subdural hematoma after spinal epidural anesthesia. Anticoagulant therapy is an important predisposing risk factor for spinal epidural hematomas and likely also predispose to spinal subdural hematomas. It is important to consider spinal subdural hematomas in addition to spinal epidural hematomas in patients who develop weakness after spinal epidural anesthesia, especially in patients who have received anticoagulation. PMID:28357164

  18. Subdural Thoracolumbar Spine Hematoma after Spinal Anesthesia: A Rare Occurrence and Literature Review of Spinal Hematomas after Spinal Anesthesia.

    PubMed

    Maddali, Prasanthi; Walker, Blake; Fisahn, Christian; Page, Jeni; Diaz, Vicki; Zwillman, Michael E; Oskouian, Rod J; Tubbs, R Shane; Moisi, Marc

    2017-02-16

    Spinal hematomas are a rare but serious complication of spinal epidural anesthesia and are typically seen in the epidural space; however, they have been documented in the subdural space. Spinal subdural hematomas likely exist within a traumatically induced space within the dural border cell layer, rather than an anatomical subdural space. Spinal subdural hematomas present a dangerous clinical situation as they have the potential to cause significant compression of neural elements and can be easily mistaken for spinal epidural hematomas. Ultrasound can be an effective modality to diagnose subdural hematoma when no epidural blood is visualized. We have reviewed the literature and present a full literature review and a case presentation of an 82-year-old male who developed a thoracolumbar spinal subdural hematoma after spinal epidural anesthesia. Anticoagulant therapy is an important predisposing risk factor for spinal epidural hematomas and likely also predispose to spinal subdural hematomas. It is important to consider spinal subdural hematomas in addition to spinal epidural hematomas in patients who develop weakness after spinal epidural anesthesia, especially in patients who have received anticoagulation.

  19. FAQs about Spinal Cord Injury (SCI)

    MedlinePlus

    ... spinal cord injury? Where is the nearest SCI Model System of Care? Emergency Medical Services Hospital (Acute) Care Rehabilitation More ... spinal cord injury? Where is the nearest SCI Model System of Care? Follow Us! Get Email Updates Questions & Comments Suggest ...

  20. Genetics Home Reference: spinal muscular atrophy

    MedlinePlus

    ... by a loss of specialized nerve cells, called motor neurons , in the spinal cord and the part ... the spinal cord ( the brainstem ). The loss of motor neurons leads to weakness and wasting ( atrophy ) of ...

  1. Rehabilitation in spinal infection diseases

    PubMed Central

    Nas, Kemal; Karakoç, Mehmet; Aydın, Abdulkadir; Öneş, Kadriye

    2015-01-01

    Spinal cord infections were the diseases defined by Hypocrite yet the absence of modern medicine and there was not a real protocol in rehabilitation although there were many aspects in surgical treatment options. The patients whether surgically or conservatively treated had a lot of neurological, motor, and sensory disturbances. Our clinic has quite experience from our previous researchs. Unfortunately, serious spinal cord infections are still present in our region. In these patients the basic rehabilitation approaches during early, pre-operation, post-operation period and in the home environment will provide significant contributions to improve the patients’ sensory and motor skills, develop the balance and proriocaption, increase the independence of patients in daily living activities and minimize the assistance of other people. There is limited information in the literature related with the nature of the rehabilitation programmes to be applied for patients with spinal infections. The aim of this review is to share our clinic experience and summarise the publications about spinal infection rehabilitation. There are very few studies about the rehabilitation of spinal infections. There are still not enough studies about planning and performing rehabilitation programs in these patients. Therefore, a comprehensive rehabilitation programme during the hospitalisation and home periods is emphasised in order to provide optimal management and prevent further disability. PMID:25621205

  2. Rehabilitation in spinal infection diseases.

    PubMed

    Nas, Kemal; Karakoç, Mehmet; Aydın, Abdulkadir; Öneş, Kadriye

    2015-01-18

    Spinal cord infections were the diseases defined by Hypocrite yet the absence of modern medicine and there was not a real protocol in rehabilitation although there were many aspects in surgical treatment options. The patients whether surgically or conservatively treated had a lot of neurological, motor, and sensory disturbances. Our clinic has quite experience from our previous researchs. Unfortunately, serious spinal cord infections are still present in our region. In these patients the basic rehabilitation approaches during early, pre-operation, post-operation period and in the home environment will provide significant contributions to improve the patients' sensory and motor skills, develop the balance and proriocaption, increase the independence of patients in daily living activities and minimize the assistance of other people. There is limited information in the literature related with the nature of the rehabilitation programmes to be applied for patients with spinal infections. The aim of this review is to share our clinic experience and summarise the publications about spinal infection rehabilitation. There are very few studies about the rehabilitation of spinal infections. There are still not enough studies about planning and performing rehabilitation programs in these patients. Therefore, a comprehensive rehabilitation programme during the hospitalisation and home periods is emphasised in order to provide optimal management and prevent further disability.

  3. Timing of Surgery After Spinal Cord Injury.

    PubMed

    Piazza, Matthew; Schuster, James

    2017-01-01

    Although timing for surgical intervention after spinal cord injury remains controversial, there is accumulating evidence suggesting that early surgery may improve neurologic outcomes, particularly with incomplete spinal cord injury, and may reduce non-neurologic complications and health care resource utilization. Moreover, even in patients with complete spinal cord injury, minor improvement in neurologic function can lead to significant changes in quality of life. This article reviews the experimental and clinical data examining surgical timing after spinal cord injury.

  4. Recurrence of spinal schwannoma: Is it preventable?

    PubMed Central

    Senapati, Satya B.; Mishra, Sudhansu S.; Dhir, Manmath K.; Patnaik, Ashis; Panigrahi, Souvagya

    2016-01-01

    Spinal schwannomas account for about 25% of primary intradural spinal cord tumors in adult. The prognosis for spinal schwannomas is excellent in most cases. Complete resection is curative. However following subtotal removal, recurrence develops after several years. We describe a case of recurrent spinal schwannoma who had been operated twice before for same disease. The possible cause of recurrence and difficulties in reoperation are discussed. PMID:27695564

  5. Experimental and numerical evaluation of the performance of supersonic two-stage high-velocity oxy-fuel thermal spray (Warm Spray) gun

    NASA Astrophysics Data System (ADS)

    Katanoda, H.; Morita, H.; Komatsu, M.; Kuroda, S.

    2011-03-01

    The water-cooled supersonic two-stage high-velocity oxy-fuel (HVOF) thermal spray gun was developed to make a coating of temperature-sensitive material, such as titanium, on a substrate. The gun has a combustion chamber (CC) followed by a mixing chamber (MC), in which the combustion gas is mixed with the nitrogen gas at room temperature. The mixed gas is accelerated to supersonic speed through a converging-diverging (C-D) nozzle followed by a straight passage called the barrel. This paper proposes an experimental procedure to estimate the cooling rate of CC, MC and barrel separately. Then, the mathematical model is presented to predict the pressure and temperature in the MC for the specific mass flow rates of fuel, oxygen and nitrogen by assuming chemical equilibrium with water-cooling in the CC and MC, and frozen flow with constant specific heat from stagnant condition to the throat in the CC and MC. Finally, the present mathematical model was validated by comparing the calculated and measured stagnant pressures of the CC of the two-stage HVOF gun.

  6. CELFE: Coupled Eulerian-Lagrangian Finite Element program for high velocity impact. Part 1: Theory and formulation. [hydroelasto-viscoplastic model

    NASA Technical Reports Server (NTRS)

    Lee, C. H.

    1978-01-01

    A 3-D finite element program capable of simulating the dynamic behavior in the vicinity of the impact point, together with predicting the dynamic response in the remaining part of the structural component subjected to high velocity impact is discussed. The finite algorithm is formulated in a general moving coordinate system. In the vicinity of the impact point contained by a moving failure front, the relative velocity of the coordinate system will approach the material particle velocity. The dynamic behavior inside the region is described by Eulerian formulation based on a hydroelasto-viscoplastic model. The failure front which can be regarded as the boundary of the impact zone is described by a transition layer. The layer changes the representation from the Eulerian mode to the Lagrangian mode outside the failure front by varying the relative velocity of the coordinate system to zero. The dynamic response in the remaining part of the structure described by the Lagrangian formulation is treated using advanced structural analysis. An interfacing algorithm for coupling CELFE with NASTRAN is constructed to provide computational capabilities for large structures.

  7. The effect of post-treatment of a high-velocity oxy-fuel Ni-Cr-Mo-Si-B coating part 2: Erosion-corrosion behavior

    NASA Astrophysics Data System (ADS)

    Shrestha, S.; Hodgkiess, T.; Neville, A.

    2001-12-01

    In this paper, a study of the erosion-corrosion characteristics of a Ni-Cr-Mo-Si-B coating applied by the high-velocity oxy-fuel (HVOF) process on to an austenitic stainless steel (UNS S31603) substrate are reported. The coatings were studied in the as-sprayed condition, after vacuum sealing with polymer impregnation and after vacuum furnace fusion. The erosion-corrosion characteristics were assessed in an impinging liquid jet of 3.5% NaCl solution at 18 °C at a velocity of 17 m/s at normal incidence in two conditions: (1) free from added solids and (2) containing 800 ppm silica sand. The methodology employed electrochemical control and monitoring to facilitate the identification of the separate and interrelated erosion and corrosion contributions to the erosion-corrosion process. The rates of erosion-corrosion damage were drastically accelerated in the presence of the suspended solids. The application of cathodic protection significantly reduced the deterioration process. The study showed the effect of sealing with polymer impregnation did not significantly alter the erosion-corrosion behavior of the sprayed coating. However, there was a significant improvement in erosion-corrosion durability afforded by the postfusion process. The mechanisms by which the improved performance of vacuum-fused coatings is achieved are discussed.

  8. Effect of the increase in the entrance convergent section length of the gun nozzle on the high-velocity oxygen fuel and cold spray process

    NASA Astrophysics Data System (ADS)

    Sakaki, K.; Shimizu, Y.

    2001-09-01

    Nozzle geometry, which influences combustion gas dynamics and, therefore, sprayed particle behavior, is one of the most important parameters in the high-velocity oxygen-fuel (HVOF) thermal spray process. The nozzle geometry is also important in the cold spray method. The gas flows in the entrance convergent section of the nozzle exhibit a relatively higher temperature and are subsonic; thus, this region is most suitable for heating spray particles. In this study, numerical simulation and experiments investigated the effect of the entrance geometry of the gun nozzle on the HVOF process. The process changes inside the nozzle, as obtained by numerical simulation studies, were related to the coating properties. An Al2O3-40 mass% TiO2 powder was used for the experimental studies. The change in entrance convergent section length (rather than barrel part length or total length) of the gun nozzle had a significant effect on the deposition efficiency, microstructure, and hardness. The deposition efficiency and hardness increased as this geometry increased. On the other hand, the calculated and measured particle velocity showed a slight decrease. This effect on the HVOF process will also be applied to the nozzle design for the cold spray method.

  9. Sensitivities of phase-velocity dispersion curves of surface waves due to high-velocity-layer and low-velocity-layer models

    NASA Astrophysics Data System (ADS)

    Shen, Chao; Xu, Yixian; Pan, Yudi; Wang, Ao; Gao, Lingli

    2016-12-01

    High-velocity-layer (HVL) and low-velocity-layer (LVL) models are two kinds of the most common irregular layered models in near-surface geophysical applications. When calculating dispersion curves of some extreme irregular models, current algorithms (e.g., Knopoff transfer matrix algorithm) should be modified. We computed the correct dispersion curves and analyzed their sensitivities due to several synthetic HVL and LVL models. The results show that phase-velocity dispersion curves of both Rayleigh and Love waves are sensitive to variations in S-wave velocity of an LVL, but insensitive to that of an HVL. In addition, they are both insensitive to those of layers beneath the HVL or LVL. With an increase in velocity contrast between the irregular layer and its neighboring layers, the sensitivity effects (high sensitivity for the LVL and low sensitivity for the HVL) will amplify. These characteristics may significantly influence the inversion stability, leading to an inverted result with a low level of confidence. To invert surface-wave phase velocities for a more accurate S-wave model with an HVL or LVL, priori knowledge may be required and an inversion algorithm should be treated with extra caution.

  10. APEX CO (9-8) MAPPING OF AN EXTREMELY HIGH VELOCITY AND JET-LIKE OUTFLOW IN A HIGH-MASS STAR-FORMING REGION

    SciTech Connect

    Qiu Keping; Wyrowski, Friedrich; Menten, Karl M.; Guesten, Rolf; Leurini, Silvia; Leinz, Christian

    2011-12-10

    Atacama Pathfinder Experiment (APEX) mapping observations in CO (9-8) and (4-3) toward a high-mass star-forming region, NGC 6334 I, are presented. The CO (9-8) map has a 6.''4 resolution, revealing a {approx}0.5 pc, jet-like, and bipolar outflow. This is the first map of a molecular outflow in a THz line. The CO (9-8) and (4-3) lines arising from the outflow lobes both show extremely high velocity line wings, and their ratios indicate a gas temperature greater than 100 K and a density higher than 10{sup 4} cm{sup -3}. The spatial-velocity structure of the CO (9-8) data is typical of a bow-shock-driven flow, which is consistent with the association between the bipolar outflow and the infrared bow-shaped tips. In short, the observations unveil a highly excited and collimated component in a bipolar outflow that is powered by a high-mass protostar, and provide insights into the driving mechanism of the outflow. Meanwhile, the observations demonstrate that high-quality mapping observations can be performed with the new THz receiver on APEX.

  11. Comparison of the Mechanical and Electrochemical Properties of WC-25Co Coatings Obtained by High Velocity Oxy-Fuel and Cold Gas Spraying

    NASA Astrophysics Data System (ADS)

    Couto, M.; Dosta, S.; Fernández, J.; Guilemany, J. M.

    2014-12-01

    Cold gas spray (CGS) coatings were previously produced by spraying WC-25Co cermet powders onto Al7075-T6 and low-carbon steel substrates. Unlike conventional flame spray techniques (e.g., high-velocity oxy-fuel; HVOF), no melting of the powder occurs; the particles are deformed and bond together after being sprayed by a supersonic jet of compressed gas, thereby building up several layers and forming a coating. WC-Co cermets are used in wear-resistant parts, because of their combination of mechanical, physical, and chemical properties. XRD tests were previously run on the initial powder and the coatings to determine possible phase changes during spraying. The bonding strength of the coatings was measured by adhesion tests. Here, WC-25Co coatings were also deposited on the same substrates by HVOF spraying. The wear resistance and fracture toughness of the coatings obtained previously by CGS and the HVOF coatings obtained here were studied. Their corrosion resistance was determined by electrochemical measurements. It was possible to achieve thick, dense, and hard CGS coatings on Al7075-T6 and low-carbon steel substrates, with better or the same mechanical and electrochemical properties as those of the HVOF coatings; making the former a highly competitive method for producing WC-25Co coatings.

  12. ALMA Observations of the Water Fountain Pre-Planetary Nebula IRAS 16342-3814: High-Velocity Bipolar Jets and an Expanding Torus.

    PubMed

    Sahai, R; Vlemmings, W H T; Gledhill, T; Sánchez Contreras, C; Lagadec, E; Nyman, L-Å; Quintana-Lacaci, G

    2017-01-20

    We have mapped (12)CO J=3-2 and other molecular lines from the "water-fountain" bipolar pre-planetary nebula (PPN) IRAS 16342-3814 with [Formula: see text] resolution using ALMA. We find (i) two very high-speed knotty, jet-like molecular outflows, (ii) a central high-density (> few × 10(6) cm(-3)), expanding torus of diameter 1300 AU, and (iii) the circumstellar envelope of the progenitor AGB, generated by a sudden, very large increase in the mass-loss rate to > 3.5 × 10(-4)M⊙ yr(-1) in the past ~455 yr. Strong continuum emission at 0.89 mm from a central source (690 mJy), if due to thermally-emitting dust, implies a substantial mass (0.017 M⊙) of very large (~mm-sized) grains. The measured expansion ages of the above structural components imply that the torus (age~160 yr) and the younger high-velocity outflow (age~110 yr) were formed soon after the sharp increase in the AGB mass-loss rate. Assuming a binary model for the jets in IRAS 16342, the high momentum rate for the dominant jet-outflow in IRAS 16342 implies a high minimum accretion rate, ruling out standard Bondi-Hoyle-Lyttleton wind accretion and wind Roche lobe overflow (RLOF) models with white-dwarf or main-sequence companions. Most likely, enhanced RLOF from the primary or accretion modes operating within common envelope evolution are needed.

  13. Microstructural Characterization and Wear Behavior of Nano-Boride Dispersed Coating on AISI 304 Stainless Steel by Hybrid High Velocity Oxy-Fuel Spraying Laser Surface Melting

    NASA Astrophysics Data System (ADS)

    Sharma, Prashant; Majumdar, Jyotsna Dutta

    2015-07-01

    The current study concerns the detailed microstructural characterization and investigation of wear behavior of nano-boride dispersed coating developed on AISI 304 stainless steel by high velocity oxy-fuel spray deposition of nickel-based alloy and subsequent laser melting. There is a significant refinement and homogenization of microstructure with improvement in microhardness due to laser surface melting (1200 VHN as compared to 945 VHN of as-sprayed and 250 VHN of as-received substrate). The high temperature phase stability of the as-coated and laser melted surface has been studied by differential scanning calorimeter followed by detailed phase analysis at room and elevated temperature. There is a significant improvement in wear resistance of laser melted surface as compared to as-sprayed and the as-received one due to increased hardness and reduced coefficient of friction. The mechanism of wear has been investigated in details. Corrosion resistance of the coating in a 3.56 wt pct NaCl solution is significantly improved (4.43 E-2 mm/year as compared to 5 E-1 mm/year of as-sprayed and 1.66 mm/year of as-received substrate) due to laser surface melting as compared to as-sprayed surface.

  14. Intramedullary spinal metastasis of a carcinoid tumor.

    PubMed

    Kumar, Jay I; Yanamadala, Vijay; Shin, John H

    2015-12-01

    We report an intramedullary spinal cord metastasis from a bronchial carcinoid, and discuss its mechanisms and management. Intramedullary spinal cord metastases from any cancer are rare, and bronchial carcinoids account for only a small fraction of lung cancers. To our knowledge, an intramedullary spinal cord metastasis from a bronchial carcinoid has been described only once previously.

  15. Cervical epidural hematoma after chiropractic spinal manipulation.

    PubMed

    Heiner, Jason D

    2009-10-01

    Spinal epidural hematoma is a rare but potentially devastating complication of spinal manipulation therapy. This is a case report of a healthy pregnant female who presented to the emergency department with a cervical epidural hematoma resulting from chiropractic spinal manipulation therapy that responded to conservative treatment rather than the more common route of surgical management.

  16. Brain and Spinal Cord Tumors in Adults

    MedlinePlus

    ... Search Search En Español Category Cancer A-Z Brain and Spinal Cord Tumors in Adults If you have a brain or spinal cord tumor or are close to ... cope. Here you can find out all about brain and spinal cord tumors in adults, including risk ...

  17. Evaluation of spinal cord injury animal models

    PubMed Central

    Zhang, Ning; Fang, Marong; Chen, Haohao; Gou, Fangming; Ding, Mingxing

    2014-01-01

    Because there is no curative treatment for spinal cord injury, establishing an ideal animal model is important to identify injury mechanisms and develop therapies for individuals suffering from spinal cord injuries. In this article, we systematically review and analyze various kinds of animal models of spinal cord injury and assess their advantages and disadvantages for further studies. PMID:25598784

  18. Motorcycle-related spinal injury: crash characteristics.

    PubMed

    Zulkipli, Zarir Hafiz; Abdul Rahmat, Abdul Manap; Mohd Faudzi, Siti Atiqah; Paiman, Noor Faradila; Wong, Shaw Voon; Hassan, Ahamedali

    2012-11-01

    This study presents an analysis of crash characteristics of motorcyclists who sustained spinal injuries in motorcycle crashes. The aim of the study is to identify the salient crash characteristics that would help explain spinal injury risks for motorcyclists. Data were retrospectively collected from police case reports that were archived at MIROS from year 2005 to 2007. The data were categorized into two subcategories; the first group was motorcycle crashes with spinal injury (case) and the second group was motorcycle crashes without spinal injury (control). A total of 363 motorcyclists with spinal injury and 873 motorcyclists without spinal injury were identified and analyzed. Descriptive analysis and multivariate analysis were performed in order to determine the odds of each characteristic in contributing to spinal injury. Single vehicle crash, collision with fixed objects and crash configuration were found to have significant influence on motorcyclists in sustaining spinal injury (p<0.05). Although relatively few than other impact configurations, the rear-end impacted motorcyclist shows the highest risk of spinal injury. Helmets have helped to reduce head injury but they did not seem to offer corresponding protection for the spine in the study. With a growing number of young motorcyclists, further efforts are needed to find effective measures to help reduce the crash incidents and severity of spinal injury. In sum, the study provides some insights on some vital crash characteristics associated with spinal injury that can be further investigated to determine the appropriate counter-measures and prevention strategies to reduce spinal injury.

  19. Aquaporins in the Spinal Cord

    PubMed Central

    Oklinski, Michal K.; Skowronski, Mariusz T.; Skowronska, Agnieszka; Rützler, Michael; Nørgaard, Kirsten; Nieland, John D.; Kwon, Tae-Hwan; Nielsen, Søren

    2016-01-01

    Aquaporins (AQPs) are water channel proteins robustly expressed in the central nervous system (CNS). A number of previous studies described the cellular expression sites and investigated their major roles and function in the brain and spinal cord. Among thirteen different mammalian AQPs, AQP1 and AQP4 have been mainly studied in the CNS and evidence has been presented that they play important roles in the pathogenesis of CNS injury, edema and multiple diseases such as multiple sclerosis, neuromyelitis optica spectrum disorders, amyotrophic lateral sclerosis, glioblastoma multiforme, Alzheimer’s disease and Parkinson’s disease. The objective of this review is to highlight the current knowledge about AQPs in the spinal cord and their proposed roles in pathophysiology and pathogenesis related to spinal cord lesions and injury. PMID:27941618

  20. Spinal reflexes in brain death.

    PubMed

    Beckmann, Yesim; Çiftçi, Yeliz; Incesu, Tülay Kurt; Seçil, Yaprak; Akhan, Galip

    2014-12-01

    Spontaneous and reflex movements have been described in brain death and these unusual movements might cause uncertainties in diagnosis. In this study we evaluated the presence of spinal reflexes in patients who fulfilled the criteria for brain death. Thirty-two (22 %) of 144 patients presented unexpected motor movements spontaneously or during examinations. These patients exhibited the following signs: undulating toe, increased deep tendon reflexes, plantar responses, Lazarus sign, flexion-withdrawal reflex, facial myokymia, neck-arm flexion, finger jerks and fasciculations. In comparison, there were no significant differences in age, sex, etiology of brain death and hemodynamic laboratory findings in patients with and without reflex motor movement. Spinal reflexes should be well recognized by physicians and it should be born in mind that brain death can be determined in the presence of spinal reflexes.

  1. [Spinal column: implants and revisions].

    PubMed

    Krieg, S M; Meyer, H S; Meyer, B

    2016-03-01

    Non-fusion spinal implants are designed to reduce the commonly occurring risks and complications of spinal fusion surgery, e.g. long duration of surgery, high blood loss, screw loosening and adjacent segment disease, by dynamic or movement preserving approaches. This principle could be shown for interspinous spacers, cervical and lumbar total disc replacement and dynamic stabilization; however, due to the continuing high rate of revision surgery, the indications for surgery require as much attention and evidence as comparative data on the surgical technique itself.

  2. Progress in the last 25 years and future perspectives in the low to high-velocity friction studies of faults; a time to shift from dry to wet experiments

    NASA Astrophysics Data System (ADS)

    Shimamoto, T.; Ma, S.; Yao, L.; Togo, T.

    2014-12-01

    High-velocity friction experiments in the last 25 years have contributed greatly to the understanding of the physical processes and mechanical properties of fault zones during seismic fault motion. But most experiments have been done at low normal stresses, under dry conditions, and at room temperature. A rationale for conducting experiments under controlled pore-pressure conditions is that specific fracture energy at a 100 MPa normal stress, extrapolated from the experimental results at low normal-stresses, is smaller than the fracture energy estimated for natural earthquakes by about one order of magnitude. Thus dry data are not consistent with earthquakes with respect to the specific fracture energy, and wet experiments may lead to a completely different framework of fault mechanics. We review nineteen existing friction apparatuses having high-velocity capabilities. Velocity regimes are conventionally classified into low velocity below 10-7 m/s, intermediate velocity between 10-7~10-4 m/s, and high velocity above 10-4 m/s. Then there are six high-velocity friction apparatuses, five intermediate to high-velocity apparatuses, and eight low to high-velocity apparatuses currently in use. Seven apparatuses can cover plate velocities on the order of 10-9 m/s to high velocities to allow studies of earthquake nucleation to dynamic rupture processes. Six apparatuses are equipped with pressure vessels and experiments with pore pressures are becoming possible. Use of Ti-Al alloy with a thermal conductivity almost as low as that of rock will open a way to expand the high-normal stress capability dramatically. We also report a rotary-shear low to high-velocity friction apparatus at IGCEA, capable of producing plate to seismic velocities (44 mm/yr to 2.1 m/s), and velocity jumps by 103 or 106 by using five electromagnetic clutches without stopping the motor. A unique feature of the apparatus is a large specimen chamber where different specimen assemblies can be installed

  3. Management of Chronic Spinal Cord Dysfunction

    PubMed Central

    Abrams, Gary M.; Ganguly, Karunesh

    2015-01-01

    Purpose of Review: Both acute and chronic spinal cord disorders present multisystem management problems to the clinician. This article highlights key issues associated with chronic spinal cord dysfunction. Recent Findings: Advances in symptomatic management for chronic spinal cord dysfunction include use of botulinum toxin to manage detrusor hyperreflexia, pregabalin for management of neuropathic pain, and intensive locomotor training for improved walking ability in incomplete spinal cord injuries. Summary: The care of spinal cord dysfunction has advanced significantly over the past 2 decades. Management and treatment of neurologic and non-neurologic complications of chronic myelopathies ensure that each patient will be able to maximize their functional independence and quality of life. PMID:25651225

  4. Pediatric Spinal Ultrasound: Neonatal and Intraoperative Applications.

    PubMed

    Alvarado, Enrique; Leach, James; Caré, Marguerite; Mangano, Francesco; O Hara, Sara

    2017-04-01

    The purpose of this article is to review the use of ultrasound as a screening tool for spinal diseases in neonates and infants and its intraoperative value in selected pediatric neurosurgical disorders. A review of spinal embryology followed by a description of common spinal diseases in neonates assessed with ultrasound is presented. Indications for spinal ultrasound in neonates, commonly identified conditions, and the importance of magnetic resonance imaging in selected cases are emphasized. Additionally, the use of ultrasound in selected neurosurgical spinal diseases in pediatric patients is presented with magnetic resonance imaging and intraoperative correlation. Technique, limitations, and pitfalls are discussed.

  5. The StEllar Counterparts of COmpact high velocity clouds (SECCO) survey. II. Sensitivity of the survey and the atlas of synthetic dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Beccari, G.; Bellazzini, M.; Battaglia, G.; Ibata, R.; Martin, N.; Testa, V.; Cignoni, M.; Correnti, M.

    2016-06-01

    The searching for StEllar Counterparts of COmpact high velocity clouds (SECCO) survey is devoted to the search for stellar counterparts within ultra compact high velocity clouds that are candidate low-mass, low-luminosity galaxies. We present the results of a set of simulations aimed at the quantitative estimate of the sensitivity of the survey as a function of the total luminosity, size, and distance of the stellar systems we are looking for. For all of our synthetic galaxies we assumed an exponential surface brightness profile and an old and metal-poor population. The synthetic galaxies are simulated both on the images and on the photometric catalogues, taking all the observational effects into account. In the fields where the available observational material is of top quality (≃36% of the SECCO fields), we detect synthetic galaxies as ≥5σ over-densities of resolved stars down to μV,h ≃ 30.0 mag/arcsec2, for D ≤ 1.5 Mpc, and down to μV,h ≃ 29.5 mag/arcsec2, for D ≤ 2.5 Mpc. In the field with the worst observational material of the whole survey, we detect synthetic galaxies with μV,h ≤ 28.8 mag/arcsec2 out to D ≤ 1.0 Mpc, and those with μV,h ≤ 27.5 mag/arcsec2 out to D ≤ 2.5 Mpc. Dwarf galaxies with MV = -10.0, with sizes in the range spanned by known dwarfs, are detected by visual inspection of the images up to D = 5 Mpc independent of the image quality. In the best quality images, dwarfs are partially resolved into stars up to D = 3.0 Mpc and completely unresolved at D = 5 Mpc. As an independent test of the sensitivity of our images to low surface brightness galaxies, we report on the detection of several dwarf spheroidal galaxies probably located in the Virgo cluster with MV ≲ -8.0 and μV,h ≲ 26.8 mag/arcsec2. The nature of the previously discovered SECCO 1 stellar system, also likely located in the Virgo cluster, is rediscussed in comparison with these dwarfs. While specific for the SECCO survey, our study may also provide general

  6. Influence of slip rate and normal stress on off-fault damage in high-velocity friction experiments on crustal rocks

    NASA Astrophysics Data System (ADS)

    Passelègue, F. X.; Spagnuolo, E.; Violay, M.; Nielsen, S. B.; Di Toro, G.; Schubnel, A.

    2013-12-01

    With the advent of high-velocity shear apparatus, several experimental studies have been conducted in recent years improving our understanding of fault friction at seismic slip rates (0.1-10 m/s). Here, we present the results of a series of tests conducted on Westerly granite, at INGV Roma, on a Slow to HIgh Velocity Apparatus (SHIVA), coupled with a high frequency monitoring (4MHz sampling rate). Experiments were conducted under normal stress (σn) ranging from 5 to 20 MPa and at sliding velocities (V) comprised between 3 mm/s and 3 m/s. Additional experiments were conducted in the presence of pore fluid at equivalent effective normal stress. In dry conditions, two friction drops are observed. The first drop is independent of the normal stress and occurs when V become higher than a critical value (Vc≈0.15 m/s). The second friction drop occurs after a critical slip weakening distance which decreases as a power law with the power density (τV). The first, abrupt, drop is explained by flash heating and weakening mechanism while the second, smooth, drop is due to the formation and growth of molten patches on the fault surface. In wet conditions, only the second drop of friction is observed. Average values of the fracture energy are independent of normal stress and sliding velocity at V > 0.01 m/s. However, measurements of elastic wave velocities travelling through the fault strongly suggest that higher damage is induced for 0.1 < V < 0.3 m/s for a same finite displacement. This observation is also supported by acoustic emission (AE) recordings. Indeed, most the AEs are recorded after the initiation of the second friction drop, that is, once the fault surface temperature is high. Some AEs are even recorded few seconds after the end of the experiments, suggesting they may be due to thermal cracking induced by heat diffusion. In addition, the presence of pore fluid pressure (water) delayed the apparition of AEs at equivalent effective pressure, supporting the link

  7. Purely extradural spinal nerve root hemangioblastomas

    PubMed Central

    Aytar, Murat Hamit; Yener, Ulaş; Ekşi, Murat Şakir; Kaya, Behram; Özgen, Serdar; Sav, Aydin; Alanay, Ahmet

    2016-01-01

    Spinal nerve root hemangioblastomas present mostly as intradural-extradurally. Purely extradural spinal nerve root hemangioblastoma is a very rare entity. In this study, we aimed to analyze epidemiological perspectives of purely extradural spinal nerve root hemangioblastomas presented in English medical literature in addition to our own exemplary case. PubMed/MEDLINE was searched using the terms “hemangioblastoma,” “extradural,” “spinal,” and “nerve root.” Demographical variables of age, gender, concomitant presence of von Hippel–Lindau (VHL) disease; spinal imaging and/or intraoperative findings for tumor location were surveyed from retrieved articles. There are 38 patients with purely extradural spinal nerve root hemangioblastoma. The median age is 45 years (range = 24–72 years). Female:male ratio is 0.6. Spinal levels for purely extradural spinal nerve root hemangioblastomas, in order of decreasing frequency, are thoracic (48.6%), cervical (13.5%), lumbar (13.5%), lumbosacral (10.8%), sacral (8.1%), and thoracolumbar (5.4%). Concomitant presence of VHL disease is 45%. Purely extradural spinal nerve root hemangioblastomas are very rare and can be confused with other more common extradural spinal cord tumors. Concomitant presence of VHL disease is observed in less than half of the patients with purely extradural spinal nerve root hemangioblastomas. Surgery is the first-line treatment in these tumors. PMID:27891027

  8. Fe-Al Weld Overlay and High Velocity Oxy-Fuel Thermal Spray Coatings for Corrosion Protection of Waterwalls in Fossil Fired Plants with Low NOx Burners

    SciTech Connect

    Regina, J.R.

    2002-02-08

    Iron-aluminum-chromium coatings were investigated to determine the best candidates for coatings of boiler tubes in Low NOx fossil fueled power plants. Ten iron-aluminum-chromium weld claddings with aluminum concentrations up to 10wt% were tested in a variety of environments to evaluate their high temperature corrosion resistance. The weld overlay claddings also contained titanium additions to investigate any beneficial effects from these ternary and quaternary alloying additions. Several High-Velocity Oxy-Fuel (HVOF) thermal spray coatings with higher aluminum concentrations were investigated as well. Gaseous corrosion testing revealed that at least 10wt%Al is required for protection in the range of environments examined. Chromium additions were beneficial in all of the environments, but additions of titanium were beneficial only in sulfur rich atmospheres. Similar results were observed when weld claddings were in contact with corrosive slag while simultaneously, exposed to the corrosive environments. An aluminum concentration of 10wt% was required to prevent large amounts of corrosion to take place. Again chromium additions were beneficial with the greatest corrosion protection occurring for welds containing both 10wt%Al and 5wt%Cr. The exposed thermal spray coatings showed either significant cracking within the coating, considerable thickness loss, or corrosion products at the coating substrate interface. Therefore, the thermal spray coatings provided the substrate very little protection. Overall, it was concluded that of the coatings studied weld overlay coatings provide superior protection in these Low NOx environments; specifically, the ternary weld composition of 10wt%Al and 5wt%Cr provided the best corrosion protection in all of the environments tested.

  9. Entrance and exit wounds of high velocity bullet: An autopsy analysis in the event of dispersing the mass rally in Bangkok Thailand, May 2010.

    PubMed

    Peonim, Vichan; Srisont, Smith; Udnoon, Jitta; Wongwichai, Sompong; Thapon, Arisa; Worasuwannarak, Wisarn

    2016-11-01

    Fatal mass casualties by high velocity bullets (HVBs) are rare events in peaceful countries. This study presents 27 forensic autopsy cases with 32 shots fired by 5.56×45mm. HVB (M-16 rifle bullets) during the dispersing the mass rally in Bangkok Thailand, May 2010. It was found that twenty-three (71.88%) typical entrance HVB wounds had round sizes less than the bullet diameters. Most entrance wounds had microtears but no collar abrasion since a HVB has a small streamlined spitzer tip and full metal jacket. For exit wounds, there were various sizes and shapes depending on which section of wound ballistics presented when the bullet exited the body. If a bullet exited in the section of temporally cavity formation, there would be a large size exit wound in accordance with the degree of bullet yaw. This is different from civilian bullets whereby the shape looks like a cylindrical round nose and at low velocity that causes entrance wounds with a similar size to the bullet diameter and is usually round or oval shape with collar abrasion. The temporary cavity is not as large as in a HVB so exit wounds are not quite as large and present a ragged border compared to a HVB. We also reported 9 out of 32 shots (28.13%) of atypical entrance wounds that had various characteristics depending on site of injury and destabilization of bullets. These findings may be helpful to forensic pathologists and to give physicians, who need to diagnose HVB wounds, more confidence.

  10. Origin of three-dimensional shapes of chondrules. I. Hydrodynamics simulations of rotating droplet exposed to high-velocity rarefied gas flow

    NASA Astrophysics Data System (ADS)

    Miura, Hitoshi; Nakamoto, Taishi; Doi, Masao

    2008-09-01

    The origin of three-dimensional shapes of chondrules is an important information to identify their formation mechanism in the early solar nebula. The measurement of their shapes by using X-ray computed topography suggested that they are usually close to perfect spheres, however, some of them have rugby-ball-like (prolate) shapes [Tsuchiyama, A., Shigeyoshi, R., Kawabata, T., Nakano, T., Uesugi, K., Shirono, S., 2003. Lunar Planet. Sci. 34, 1271-1272]. We considered that the prolate shapes reflect the deformations of chondrule precursor dust particles when they are heated and melted in the high velocity gas flow. In order to reveal the origin of chondrule shapes, we carried out the three-dimensional hydrodynamics simulations of a rotating molten chondrule exposed to the gas flow in the framework of the shock-wave heating model for chondrule formation. We adopted the gas ram pressure acting on the chondrule surface of p=10 dyncm in a typical shock wave. Considering that the chondrule precursor dust particle has an irregular shape before melting, the ram pressure causes a net torque to rotate the particle. The estimated angular velocity is ω=140 rads for the precursor radius of r=1 mm, though it has a different value depending on the irregularity of the shape. In addition, the rotation axis is likely to be perpendicular to the direction of the gas flow. Our calculations showed that the rotating molten chondrule elongates along the rotation axis, in contrast, shrinks perpendicularly to it. It is a prolate shape. The reason why the molten chondrule is deformed to a prolate shape was clearly discussed. Our study gives a complementary constraint for chondrule formation mechanisms, comparing with conventional chemical analyses and dynamic crystallization experiments that have mainly constrained the thermal evolutions of chondrules.

  11. ALMA Observations of the Water Fountain Pre-planetary Nebula IRAS 16342-3814: High-velocity Bipolar Jets and an Expanding Torus

    NASA Astrophysics Data System (ADS)

    Sahai, R.; Vlemmings, W. H. T.; Gledhill, T.; Sánchez Contreras, C.; Lagadec, E.; Nyman, L.-Å; Quintana-Lacaci, G.

    2017-01-01

    We have mapped 12CO J = 3–2 and other molecular lines from the “water fountain” bipolar pre-planetary nebula (PPN) IRAS 16342-3814 with ∼0.″35 resolution using Atacama Large Millimeter/submillimeter Array. We find (i) two very high-speed knotty, jet-like molecular outflows; (ii) a central high-density (> {few}× {10}6 cm‑3), expanding torus of diameter 1300 au; and (iii) the circumstellar envelope of the progenitor AGB, generated by a sudden, very large increase in the mass-loss rate to > 3.5× {10}-4 M⊙ yr‑1 in the past ∼455 years. Strong continuum emission at 0.89 mm from a central source (690 mJy), if due to thermally emitting dust, implies a substantial mass (0.017 M⊙) of very large (∼millimeter-sized) grains. The measured expansion ages of the above structural components imply that the torus (age ∼160 years) and the younger high-velocity outflow (age ∼110 years) were formed soon after the sharp increase in the AGB mass-loss rate. Assuming a binary model for the jets in IRAS 16342, the high momentum rate for the dominant jet-outflow in IRAS 16342 implies a high minimum accretion rate, ruling out standard Bondi–Hoyle–Lyttleton wind accretion and wind Roche-lobe overflow (RLOF) models with white-dwarf or main-sequence companions. Most likely, enhanced RLOF from the primary or accretion modes operating within common-envelope evolution are needed.

  12. The origin of the X-ray emission from the high-velocity cloud MS30.7–81.4–118

    SciTech Connect

    Henley, David B.; Shelton, Robin L.; Kwak, Kyujin E-mail: rls@physast.uga.edu

    2014-08-10

    A soft X-ray enhancement has recently been reported toward the high-velocity cloud MS30.7–81.4–118 (MS30.7), a constituent of the Magellanic Stream. In order to investigate the origin of this enhancement, we have analyzed two overlapping XMM-Newton observations of this cloud. We find that the X-ray enhancement is ∼6' or ∼100 pc across, and is concentrated to the north and west of the densest part of the cloud. We modeled the X-ray enhancement with a variety of spectral models. A single-temperature equilibrium plasma model yields a temperature of (3.69{sub −0.44}{sup +0.47})×10{sup 6} K and a 0.4-2.0 keV luminosity of 7.9 × 10{sup 33} erg s{sup –1}. However, this model underpredicts the on-enhancement emission around 1 keV, which may indicate the additional presence of hotter plasma (T ≳ 10{sup 7} K), or that recombination emission is important. We examined several different physical models for the origin of the X-ray enhancement. We find that turbulent mixing of cold cloud material with hot ambient material, compression or shock heating of a hot ambient medium, and charge exchange reactions between cloud atoms and ions in a hot ambient medium all lead to emission that is too faint. In addition, shock heating in a cool or warm medium leads to emission that is too soft (for reasonable cloud speeds). We find that magnetic reconnection could plausibly power the observed X-ray emission, but resistive magnetohydrodynamical simulations are needed to test this hypothesis. If magnetic reconnection is responsible for the X-ray enhancement, the observed spectral properties could potentially constrain the magnetic field in the vicinity of the Magellanic Stream.

  13. Full-scale-wind-tunnel Tests of a 35 Degree Sweptback Wing Airplane with High-velocity Blowing over the Training-edge Flaps

    NASA Technical Reports Server (NTRS)

    Kelley, Mark W; Tolhurst, William H JR

    1955-01-01

    A wind-tunnel investigation was made to determine the effects of ejecting high-velocity air near the leading edge of plain trailing-edge flaps on a 35 degree sweptback wing. The tests were made with flap deflections from 45 degrees to 85 degrees and with pressure ratios across the flap nozzles from sub-critical up to 2.9. A limited study of the effects of nozzle location and configuration on the efficiency of the flap was made. Measurements of the lift, drag, and pitching moment were made for Reynolds numbers from 5.8 to 10.1x10(6). Measurements were also made of the weight rate of flow, pressure, and temperature of the air supplied to the flap nozzles.The results show that blowing on the deflected flap produced large flap lift increments. The amount of air required to prevent flow separation on the flap was significantly less than that estimated from published two-dimensional data. When the amount of air ejected over the flap was just sufficient to prevent flow separation, the lift increment obtained agreed well with linear inviscid fluid theory up to flap deflections of 60 degrees. The flap lift increment at 85 degrees flap deflection was about 80 percent of that predicted theoretically.With larger amounts of air blown over the flap, these lift increments could be significantly increased. It was found that the performance of the flap was relatively insensitive to the location of the flap nozzle, to spacers in the nozzle, and to flow disturbances such as those caused by leading-edge slats or discontinuities on the wing or flap surfaces. Analysis of the results indicated that installation of this system on an F-86 airplane is feasible.

  14. Constraints from sill intrusions and their deeper source magma chambers (seismic high velocity bodies) on the origins of volcanic rifted margins

    NASA Astrophysics Data System (ADS)

    Rohrman, M.

    2015-12-01

    Volcanic rifted margins are characterized by massive igneous activity originating from the rift margin, characterized by seaward dipping reflectors. These consist of basalt flows and associated magmatic products, from deep magma chambers imaged on seismic data as High Velocity Bodies (HVB) with seismic velocities between 7 and 7.5 km/s. The relationship between rifting and decompression melting have been well quantified, using the HVB's as constraints on magmatic production to match extension models. Crucial in this approach are the relationship between extension and mantle plumes, with HVB's generated by mantle plumes often indicative of velocities between 7.5 - 7.8 km/s. Here I address information that can be obtained from sill complexes in sedimentary basins associated with rifting, representing the earliest phase of magmatism. I use a simple crustal scale hydrostatic model for dikes while incorporating the presence of sills by calculating magmatic overpressures from differences in pressure gradients. It transpires that the presence of sills as observed on seismic reflection and outcrop data, can be predicted. Modelling further suggests that the source of these sill complexes are large magma chambers at or near the Moho, and equate to HVB's observed on seismic data. Utilizing simple mass balance calculations, the ratio of cumulate thickness (from HVB thickness) and expelled melt (from accumulated sill thicknesses) can be related to MgO content in expelled liquids, primary magma and cumulates. Higher MgO content translates in higher seismic velocities. Thus, HVB velocity can subsequently be used to discriminate between mantle plume, or shallow rift related melting. The theory is applied to various basins bordering the northern North Atlantic (Vøring Basin, Jameson Land Basin and Rockall Basin) and South Atlantic rifts (Namibia), associated with the Paleocene/Eocene Iceland mantle plume and the Early Cretaceous Tristan da Cunha mantle plume magmatism respectively.

  15. ALMA Observations of the Water Fountain Pre-Planetary Nebula IRAS 16342-3814: High-Velocity Bipolar Jets and an Expanding Torus

    PubMed Central

    Sahai, R.; Vlemmings, W.H.T.; Gledhill, T.; Sánchez Contreras, C.; Lagadec, E.; Nyman, L-Å; Quintana-Lacaci, G.

    2017-01-01

    We have mapped 12CO J=3–2 and other molecular lines from the “water-fountain” bipolar pre-planetary nebula (PPN) IRAS 16342-3814 with ∼0⋅″35 resolution using ALMA. We find (i) two very high-speed knotty, jet-like molecular outflows, (ii) a central high-density (> few × 106 cm−3), expanding torus of diameter 1300 AU, and (iii) the circumstellar envelope of the progenitor AGB, generated by a sudden, very large increase in the mass-loss rate to > 3.5 × 10−4 M⊙ yr−1 in the past ~455 yr. Strong continuum emission at 0.89 mm from a central source (690 mJy), if due to thermally-emitting dust, implies a substantial mass (0.017 M⊙) of very large (~mm-sized) grains. The measured expansion ages of the above structural components imply that the torus (age~160 yr) and the younger high-velocity outflow (age~110 yr) were formed soon after the sharp increase in the AGB mass-loss rate. Assuming a binary model for the jets in IRAS 16342, the high momentum rate for the dominant jet-outflow in IRAS 16342 implies a high minimum accretion rate, ruling out standard Bondi-Hoyle-Lyttleton wind accretion and wind Roche lobe overflow (RLOF) models with white-dwarf or main-sequence companions. Most likely, enhanced RLOF from the primary or accretion modes operating within common envelope evolution are needed. PMID:28191303

  16. THE HIGH-VELOCITY SYSTEM: INFALL OF A GIANT LOW-SURFACE-BRIGHTNESS GALAXY TOWARD THE CENTER OF THE PERSEUS CLUSTER

    SciTech Connect

    Yu, Alice P.-Y.; Lim, Jeremy; Chan, Jeffrey C.-C.; Ohyama, Youichi; Broadhurst, T.

    2015-12-01

    The high-velocity system (HVS) lies just north-west of the center and is moving at a speed of 3000 km s{sup −1} toward NGC 1275, the central giant elliptical galaxy in the Perseus cluster. We report imaging spectroscopy of the HVS in Hα and [N ii] that resolves both the nature of this galaxy and its physical relationship with NGC 1275. The HVS exhibits a distorted disk having a projected rotational velocity that rises steadily to ∼200 km s{sup −1} at a radius of ∼12 kpc, the same maximal extent detectable in neutral gas and dust. We discover highly blueshifted emission at relative velocities of up to ∼800 km s{sup −1} distributed throughout and confined almost entirely within the projected area of the disk, tracing gas stripped by ram pressure. The distribution of the stripped gas implies that the HVS is moving essentially along our sightline closely toward the center of NGC 1275. We show that the speed of the HVS is consistent with it having fallen from rest at the virial radius of the Perseus cluster and reached ∼100 kpc from the cluster center. Despite having an overall metallicity (inferred from [N ii]/Hα) significantly lower than that of star-forming disk galaxies, the HVS exhibits a current star formation rate of ∼3.6 M{sub ⊙} yr{sup −1} and numerous young star clusters projected against giant H ii regions. The evidence assembled implicates a progenitor giant low-surface-brightness galaxy that, because of galaxy harassment and/or the cluster tidal field, has developed two prominent spiral arms along which star formation is strongly elevated.

  17. Spinal Schwannoma with Intradural Intramedullary Hemorrhage

    PubMed Central

    Nadeem, Muhammad; Mansoor, Salman; Assad, Salman; Qavi, Ahmed H; Saadat, Shoab

    2017-01-01

    Patients with spinal abnormalities infrequently present with intradural intramedullary bleeding. The more common causes include spinal trauma, arteriovenous malformations and saccular aneurysms of spinal arteries. On occasion, spinal cord tumors either primary or metastatic may cause intramedullary bleed with ependymoma of the conus medullaris. Spinal nerve sheath tumors such as schwannomas only rarely cause intradural intramedullary bleed, especially in the absence of spinal cord or nerve root symptoms. We report a case of spinal intradural schwannoma presenting with acute onset of quadriparesis. Cerebral angiography studies were negative but magnetic resonance imaging (MRI) of the spine revealed a large hemorrhagic tumor in the thoracolumbar junction. However, we suggest that the patients with intradural intramedullary bleed should be evaluated for underlying spine disease.

  18. Pain following spinal cord injury.

    PubMed

    Ullrich, Philip M

    2007-05-01

    Pain is one of the most common, severe, and treatment-resistant complications that follows SCI. Recent years have seen a surge of research on methods for assessing and treating spinal cord injury pain. In this article, pain after SCI is reviewed in terms of nature, scope, assessment techniques, and treatment strategies.

  19. Learning about Spinal Muscular Atrophy

    MedlinePlus

    ... causes the disorder. Top of page NHGRI Clinical Research on Spinal Muscular Atrophy Currently, NHGRI is not conducting studies on SMA. The National Institutes of Health is conducting clinical trials identified as enrolling individuals with SMA: Quantitative Analysis of SMN1 and SMN2 Gene Based on ...

  20. Vestibulo-spinal reflex mechanisms

    NASA Technical Reports Server (NTRS)

    Reschke, M. F.

    1981-01-01

    The specific objectives of experiments designed to investigate postural reflex behavior during sustained weightlessness are discussed. The first is to investigate, during prolonged weightlessness with Hoffmann response (H-reflex) measurement procedures, vestibulo-spinal reflexes associated with vestibular (otolith) responses evoked during an applied linear acceleration. This objective includes not only an evaluation of otolith-induced changes in a major postural muscle but also an investigation with this technique of the adaptive process of the vestibular system and spinal reflex mechanisms to this unique environment. The second objective is to relate space motion sickness to the results of this investigation. Finally, a return to the vestibulo-spinal and postural reflexes to normal values following the flight will be examined. The flight experiment involves activation of nerve tissue (tibial N) with electrical shock and the recording of resulting muscle activity (soleus) with surface electrodes. Soleus/spinal H-reflex testing procedures will be used in conjuction with linear acceleration through the subject's X-axis.

  1. DELTAE+. Design Environment for Low-Amplitude Thermoacoustic Engines

    SciTech Connect

    Ward, W.C; Swift, G.W.

    1993-10-01

    In thermoacoustic engines and refrigerators, and in many simple acoustic systems, a one dimensional wave equation determines the spatial dependence of the acoustic pressure and velocity. DELTAE numerically integrates such wave equations in the acoustic approximation, in gases or liquids, in user-defined geometries. Boundary conditions can include conventional acoustic boundary conditions of geometry and impedance, as well as temperature and thermal power in thermoacoustic systems. DELTAE can be used easily for apparatus ranging from simple duct networks and resonators to thermoacoustic engines refrigerators and combinations thereof. It can predict how a given apparatus will perform, or can allow the user to design an apparatus to achieve desired performance. DELTAE views systems as a series of segments; twenty segment types are supported. The purely acoustic segments include ducts and cones, and lumped impedances including compliances, series impedances, and endcaps. Electroacoustics tranducer segments can be defined using either frequency-independent coefficients or the conventional parameters of loudspeaker-style drivers: mass, spring constant, magnetic field strength, etc. Tranducers can be current driven, voltage driven, or connected to an electrical load impedance. Thermoacoustic segment geometries include parallel plates, circular and rectangular pores, and pin arrays. Side branches can be defined with fixed impedances, frequency-dependent radiation impedances, or as an auxiliary series of segments of any types. The user can select working fluids from among air, helium, neon, argon, hydrogen, deuterium, carbon dioxide, nitrogen, helium-argon mixtures, helium-xenon mixtures, liquid sodium, and eutectic sodium-potassium. Additional fluids and solids can be defined by the user.

  2. DELTAE. Design Environment for Low-Amplitude Thermoacoustic Engines

    SciTech Connect

    Ward, W.C.; Swift, G.W.

    1993-10-01

    In thermoacoustic engines and refrigerators, and in many simple acoustic systems, a one dimensional wave equation determines the spatial dependence of the acoustic pressure and velocity. DELTAE numerically integrates such wave equations in the acoustic approximation, in gases or liquids, in user-defined geometries. Boundary conditions can include conventional acoustic boundary conditions of geometry and impedance, as well as temperature and thermal power in thermoacoustic systems. DELTAE can be used easily for apparatus ranging from simple duct networks and resonators to thermoacoustic engines refrigerators and combinations thereof. It can predict how a given apparatus will perform, or can allow the user to design an apparatus to achieve desired performance. DELTAE views systems as a series of segments; twenty segment types are supported. The purely acoustic segments include ducts and cones, and lumped impedances including compliances, series impedances, and endcaps. Electroacoustics tranducer segments can be defined using either frequency-independent coefficients or the conventional parameters of loudspeaker-style drivers: mass, spring constant, magnetic field strength, etc. Tranducers can be current driven, voltage driven, or connected to an electrical load impedance. Thermoacoustic segment geometries include parallel plates, circular and rectangular pores, and pin arrays. Side branches can be defined with fixed impedances, frequency-dependent radiation impedances, or as an auxiliary series of segments of any types. The user can select working fluids from among air, helium, neon, argon, hydrogen, deuterium, carbon dioxide, nitrogen, helium-argon mixtures, helium-xenon mixtures, liquid sodium, and eutectic sodium-potassium. Additional fluids and solids can be defined by the user.

  3. DELTAE. Design Environment for Low-Amplitude Thermoacoustic Engines

    SciTech Connect

    Ward, W.C.

    1993-10-10

    In thermoacoustic engines and refrigerators, and in many simple acoustic systems, a one dimensional wave equation determines the spatial dependence of the acoustic pressure and velocity. DELTAE numerically integrates such wave equations in the acoustic approximation, in gases or liquids, in user-defined geometries. Boundary conditions can include conventional acoustic boundary conditions of geometry and impedance, as well as temperature and thermal power in thermoacoustic systems. DELTAE can be used easily for apparatus ranging from simple duct networks and resonators to thermoacoustic engines refrigerators and combinations thereof. It can predict how a given apparatus will perform, or can allow the user to design an apparatus to achieve desired performance. DELTAE views systems as a series of segments; twenty segment types are supported. The purely acoustic segments include ducts and cones, and lumped impedances including compliances, series impedances, and endcaps. Electroacoustics tranducer segments can be defined using either frequency-independent coefficients or the conventional parameters of loudspeaker-style drivers: mass, spring constant, magnetic field strength, etc. Tranducers can be current driven, voltage driven, or connected to an electrical load impedance. Thermoacoustic segment geometries include parallel plates, circular and rectangular pores, and pin arrays. Side branches can be defined with fixed impedances, frequency-dependent radiation impedances, or as an auxiliary series of segments of any types. The user can select working fluids from among air, helium, neon, argon, hydrogen, deuterium, carbon dioxide, nitrogen, helium-argon mixtures, helium-xenon mixtures, liquid sodium, and eutectic sodium-potassium. Additional fluids and solids can be defined by the user.

  4. Biomechanics of Degenerative Spinal Disorders

    PubMed Central

    Iorio, Justin A.; Jakoi, Andre M.

    2016-01-01

    The spine has several important functions including load transmission, permission of limited motion, and protection of the spinal cord. The vertebrae form functional spinal units, which represent the smallest segment that has characteristics of the entire spinal column. Discs and paired facet joints within each functional unit form a three-joint complex between which loads are transmitted. Surrounding the spinal motion segment are ligaments, composed of elastin and collagen, and joint capsules which restrict motion to within normal limits. Ligaments have variable strengths and act via different lever arm lengths to contribute to spinal stability. As a consequence of the longer moment arm from the spinous process to the instantaneous axis of rotation, inherently weaker ligaments (interspinous and supraspinous) are able to provide resistance to excessive flexion. Degenerative processes of the spine are a normal result of aging and occur on a spectrum. During the second decade of life, the intervertebral disc demonstrates histologic evidence of nucleus pulposus degradation caused by reduced end plate blood supply. As disc height decreases, the functional unit is capable of an increased range of axial rotation which subjects the posterior facet capsules to greater mechanical loads. A concurrent change in load transmission across the end plates and translation of the instantaneous axis of rotation further increase the degenerative processes at adjacent structures. The behavior of the functional unit is impacted by these processes and is reflected by changes in the stress-strain relationship. Back pain and other clinical symptoms may occur as a result of the biomechanical alterations of degeneration. PMID:27114783

  5. Therapeutic approaches for spinal cord injury

    PubMed Central

    Cristante, Alexandre Fogaça; de Barros Filho, Tarcísio Eloy Pessoa; Marcon, Raphael Martus; Letaif, Olavo Biraghi; da Rocha, Ivan Dias

    2012-01-01

    This study reviews the literature concerning possible therapeutic approaches for spinal cord injury. Spinal cord injury is a disabling and irreversible condition that has high economic and social costs. There are both primary and secondary mechanisms of damage to the spinal cord. The primary lesion is the mechanical injury itself. The secondary lesion results from one or more biochemical and cellular processes that are triggered by the primary lesion. The frustration of health professionals in treating a severe spinal cord injury was described in 1700 BC in an Egyptian surgical papyrus that was translated by Edwin Smith; the papyrus reported spinal fractures as a “disease that should not be treated.” Over the last two decades, several studies have been performed to obtain more effective treatments for spinal cord injury. Most of these studies approach a patient with acute spinal cord injury in one of four manners: corrective surgery or a physical, biological or pharmacological treatment method. Science is unraveling the mechanisms of cell protection and neuroregeneration, but clinically, we only provide supportive care for patients with spinal cord injuries. By combining these treatments, researchers attempt to enhance the functional recovery of patients with spinal cord injuries. Advances in the last decade have allowed us to encourage the development of experimental studies in the field of spinal cord regeneration. The combination of several therapeutic strategies should, at minimum, allow for partial functional recoveries for these patients, which could improve their quality of life. PMID:23070351

  6. An Analytical Means of Determining Mass Loss from High Velocity Rigid Penetrators based on the Thermodynamic and Mechanical Properties of the Penetrator and Target

    NASA Astrophysics Data System (ADS)

    Foster, Joseph C., Jr.; Jones, S. E.; Rule, William; Toness, Odin

    1999-06-01

    Sub-scale experimentation is commonly used as a cost-effective means of conducting terminal ballistics research. Analytical models of the penetration process focus on calculating the depth of penetration based on target density, target strength represented by the unconfined compressive-strength (f”c), the areal density of the penetrator (W/A), and the impact velocity.1 Forrestal, et. al. have documented the mass loss from the penetrator during the penetration process and employed improved equations of motion.2 Various researchers have investigated the upper limits of rigid body penetration and identified the onset of instabilities.3 In an effort to better understand the physical processes associated with this instability, experimental techniques have been developed to capture the details of the penetrator and target and subject them to microscopic analysis.4 These results have served as motivation to explore new forms for the physics included in the penetration equation as a means of identifying the processes associated with high velocity instability. We have included target shear and nose friction in the formulation of the fundamental load function expressions.5 When the resulting equations of motion are integrated and combined with the thermodynamics indicated by microscopic analysis, methods are identified to calculated penetrator mass loss. A comparison of results with experimental data serves as an indicator of the thermodynamic state variables associated with the quasi-steady state penetrator target interface conditions. 1 Young, C. W. , “Depth Predictions for Earth Penetrating Projectiles,” Journal of Soil Mechanics and Foundations, Division of ASCE, May 1998 pp 803-817 2. M.J. Forrestal, D.J. Frew, S.J. Hanchak, amd Brar, “ Pentration of Grout and Concrete Targets with Ogive-Nose Steel Projectiles,” Inrt. J. Impact Engng. Vol 18, pp. 465-476,1996 3. Andrew J. Piekutowski, Michael J. Forrestal, Kevin L. Poormon, and Thomas L. Warren,

  7. Spontaneous Spinal Epidural Hematoma on the Ventral Portion of Whole Spinal Canal: A Case Report

    PubMed Central

    Lee, Hyun-Ho; Kim, Young; Ha, Young-Soo

    2015-01-01

    Spontaneous spinal epidural hematoma is an uncommon but disabling disease. This paper reports a case of spontaneous spinal epidural hematoma and treatment by surgical management. A 32-year-old male presented with a 30-minute history of sudden headache, back pain, chest pain, and progressive quadriplegia. Whole-spinal sagittal magnetic resonance imaging (MRI) revealed spinal epidural hematoma on the ventral portion of the spinal canal. Total laminectomy from T5 to T7 was performed, and hematoma located at the ventral portion of the spinal cord was evacuated. Epidural drainages were inserted in the upper and lower epidural spaces. The patient improved sufficiently to ambulate, and paresthesia was fully recovered. Spontaneous spinal epidural hematoma should be considered when patients present symptoms of spinal cord compression after sudden back pain or chest pain. To prevent permanent neurologic deficits, early and correct diagnosis with timely surgical management is necessary. PMID:26512277

  8. Part 1: recognizing neonatal spinal cord injury.

    PubMed

    Brand, M Colleen

    2006-02-01

    Neonatal spinal cord injury can occur in utero, as well as after either a difficult delivery or a nontraumatic delivery. Spinal cord injury can also be related to invasive nursery procedures or underlying neonatal pathology. Early clinical signs of spinal cord injury that has occurred in utero or at delivery includes severe respiratory compromise and profound hypotonia. Knowledge of risk factors and awareness of symptoms is required for early recognition and appropriate treatment. This article reviews the embryological development of the spinal column highlighting mechanisms of injury and identifying underlying factors that increase the risk of spinal cord injury in newborns. Signs and symptoms of injury, cervical spine immobilization, and the differential diagnosis are discussed. Nursing implications, general prognosis, and research in spinal cord injury are provided.

  9. Survival Rates for Selected Childhood Brain and Spinal Cord Tumors

    MedlinePlus

    ... Diagnosis, and Staging Survival Rates for Selected Childhood Brain and Spinal Cord Tumors Survival rates are often ... Childhood Brain and Spinal Cord Tumors More In Brain and Spinal Cord Tumors in Children About Brain ...

  10. Testosterone Plus Finasteride Treatment After Spinal Cord Injury

    ClinicalTrials.gov

    2017-01-24

    Spinal Cord Injury; Spinal Cord Injuries; Trauma, Nervous System; Wounds and Injuries; Central Nervous System Diseases; Nervous System Diseases; Spinal Cord Diseases; Gonadal Disorders; Endocrine System Diseases; Hypogonadism; Genital Diseases, Male

  11. Acute non-traumatic spinal subdural haematoma: an unusual aetiology.

    PubMed

    Seizeur, Romuald; Ahmed, Seddik Sid; Simon, Alexandre; Besson, Gérard; Forlodou, Pierre

    2009-06-01

    We report an unusual case of a spinal subdural haematoma associated with a ruptured spinal aneurysm. The delayed diagnosis or misdiagnosis of this rare entity can have disastrous consequences. We discuss various possible aetiologies and its association with spinal aneurysms.

  12. [Osteoporosis associated with spinal cord lesion].

    PubMed

    Miladinović, Ksenija; Vavra-Hadziahmetović, Narcisa; Muftić, Mirsad; Sakota, Slavica

    2007-01-01

    One of the complications caused by spinal lesion is osteoporosis which development is induced by lesion itself, and its mechanism is not explained enough. Risk factor of this kind of osteoporosis is fracture which management is difficult and is cause of further complications which aggravate already damaged quality of life of patients with spinal cord injury, and demand additional health insurance expenses. Importance of prevention and treatment of spinal cord injury induced osteoporosis is enlightened by case report.

  13. The shortened spinal cord in tetraodontiform fishes.

    PubMed

    Uehara, Masato; Hosaka, Yoshinao Z; Doi, Hiroyuki; Sakai, Harumi

    2015-03-01

    In teleosts, the spinal cord generally extends along the entire vertebral canal. The Tetraodontiformes, in which the spinal cord is greatly reduced in length with a distinct long filum terminale and cauda equina, have been regarded as an aberration. The aims of this study are: 1) to elucidate whether the spinal cord in all tetraodontiform fishes shorten with the filum terminale, and 2) to describe the gross anatomical and histological differences in the spinal cord among all families of the Tetraodontiformes. Representative species from all families of the Tetraodontiformes, and for comparison the carp as a common teleost, were investigated. In the Triacanthodidae, Triacanthidae, and Triodontidae, which are the more ancestral taxa of the Tetraodontiformes, the spinal cord extends through the entire vertebral canal. In the Triacanthidae and Triodontidae, the caudal half or more spinal segments of the spinal cord, however, lack gray matter and consist largely of nerve fibers. In the other tetraodontiform families, the spinal cord is shortened forming a filum terminale with the cauda equina, which is prolonged as far as the last vertebra. The shortened spinal cord is divided into three groups. In the Ostraciidae and Molidae, the spinal cord tapers abruptly at the cranium or first vertebra forming a cord-like filum terminale. In the Monacanthidae, Tetraodontidae, and Diodontidae, it abruptly flattens at the rostral vertebrae forming a flat filum terminale. The spinal cord is relatively longer in the Monacanthidae than that in the other two families. It is suggested by histological features of the flat filum terminale that shortening of the spinal cord in this group progresses in order of the Monacanthidae, Tetraodontidae, and Diodontidae. In the Balistidae and Aracanidae, the cord is relatively long and then gradually decreased in dorso-ventral thickness.

  14. Spinal Cord Repair with Engineered Nervous Tissue

    DTIC Science & Technology

    2011-10-01

    funded grant, we demonstrated proof-of-concept success of bridging a lateral hemisection of the rat spinal cord with engineered (“stretch-grown...AD_________________ Award Number: W81XWH-10-1-0941 TITLE: Spinal Cord Repair with Engineered...5a. CONTRACT NUMBER Spinal Cord Repair with Engineered Nervous Tissue 5b. GRANT NUMBER W81XWH-10-1-0941 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR

  15. Spinal Cord Repair with Engineered Nervous Tissue

    DTIC Science & Technology

    2012-10-01

    success of bridging a lateral hemisection in the rat spinal cord with engineered (“stretch-grown”) living nervous tissue constructs 2 . For the current...AD_________________ Award Number: W81XWH-10-1-0941 TITLE: Spinal Cord Repair with Engineered...SUBTITLE Spinal Cord Repair with Engineered Nervous Tissue 5a. CONTRACT NUMBER 5b. GRANT NUMBER W81XWH-10-1-0941 5c. PROGRAM ELEMENT NUMBER 6

  16. Surgical Outcome of Spinal Neurilemmoma

    PubMed Central

    Yeh, Kuang-Ting; Lee, Ru-Ping; Yu, Tzai-Chiu; Chen, Ing-Ho; Peng, Cheng-Huan; Liu, Kuan-Lin; Wang, Jen-Hung; Wu, Wen-Tien

    2015-01-01

    Abstract Neurilemmoma commonly occurs from the fourth to sixth decades of life with an incidence of 3 to 10 per 100,000 people, and is rare in adolescence. This case report describes the clinical and radiographic features of 2 rare cases with intraspinal neurilemmoma of the cervical and thoracic spine. A 29-year-old man who experienced middle back pain with prominent right lower limb weakness, and an 11-year-old boy who suffered from sudden onset neck pain with left arm weakness and hand clawing for 2 weeks before admission to our department were included in this case report. Magnetic resonance imaging of both patients revealed an intraspinal mass causing spinal cord compression at the cervical and thoracic spine. The patients subsequently received urgent posterior spinal cord decompression and tumor resection surgery. The histopathology reports revealed neurilemmoma. The 2 patients recovered and resumed their normal lives within 1 year. Intraspinal neurilemmoma is rare but should be considered in the differential diagnosis of spinal cord compression. Advances in imaging techniques and surgical procedures have yielded substantially enhanced clinical outcomes in intraspinal neoplasm cases. Delicate preoperative study and surgical skill with rehabilitation and postoperative observation are critical. PMID:25654395

  17. Spinal myoclonus resembling belly dance.

    PubMed

    Kono, I; Ueda, Y; Araki, K; Nakajima, K; Shibasaki, H

    1994-05-01

    A 63-year-old man presented with an 11-month history of progressive myoclonus in the right abdominal wall. Administration of clonazepam reduced the frequency and amplitude. When the therapy was discontinued, the frequency and amplitude of the myoclonus increased, and synchronous and weak myoclonus also was observed in the left abdomen. The trunk was twisted just after the appearance of the abdominal myoclonus associated with myoclonic jerks spreading from the rostral to caudal paraspinal muscles. Later in the clinical course, the myoclonus became stimulus sensitive and was induced by tendon tap given anywhere on the body, with the latency ranging from 50 to 150 ms irrespective of the sites of tapping. Myoclonus seen in the abdominal wall was segmental and considered to be of spinal origin. The reflex myoclonus had a 150-ms refractory period. It can be postulated that increased excitability of anterior horn cells at a certain segment might make a spino-bulbo-spinal reflex manifest at the corresponding segment. This myoclonus is considered to be a new form of spinal reflex myoclonus, because the abdominal myoclonic jerk seems to trigger another myoclonic jerk involving the paraspinal muscles.

  18. Investigation of spinal pathology in notalgia paresthetica.

    PubMed

    Savk, Oner; Savk, Ekin

    2005-06-01

    A possible association of spinal pathology with notalgia paresthetica (NP) was investigated through clinical and radiographic evaluation. Forty-three NP patients underwent dermatologic and orthopedic examination accompanied by radiography of the spine. Sixty-one lesions in 43 patients were evaluated. In 34 patients, various vertebral pathologies were observed radiographically by a blinded investigator, and in 28 of these cases these changes were most prominent in the vertebrae which corresponded to a lesional dermatome. Thirty-seven lesions were accompanied by spinal changes decided to be relevant (60.7%). The striking correlation of NP localization with spinal pathology suggests that spinal nerve impingement may contribute to the pathogenesis of this entity.

  19. Spinal infections: clinical and imaging features.

    PubMed

    Arbelaez, Andres; Restrepo, Feliza; Castillo, Mauricio

    2014-10-01

    Spinal infections represent a group of rare conditions affecting vertebral bodies, intervertebral discs, paraspinal soft tissues, epidural space, meninges, and spinal cord. The causal factors, clinical presentations, and imaging features are a challenge because the difficulty to differentiate them from other conditions, such as degenerative and inflammatory disorders and spinal neoplasm. They require early recognition because delay diagnosis, imaging, and intervention may have devastating consequences especially in children and the elderly. This article reviews the most common spinal infections, their pathophysiologic, clinical manifestation, and their imaging findings.

  20. Spinal cord astrocytoma mimicking multifocal myelitis

    PubMed Central

    Neutel, Dulce; Teodoro, Tiago; Coelho, Miguel; Pimentel, José; Albuquerque, Luísa

    2014-01-01

    Introduction Differential diagnosis of acute/subacute intrinsic spinal cord lesions can be challenging. In addition, intramedullary neoplasms typically show gadolinium enhancement, mass effect, and cord expansion. Case report We report a patient with spinal cord and brain stem lesions resembling multifocal myelitis. Magnetic resonance imaging showed no spinal cord enlargement or gadolinium enhancing. Treatment of myelitis was undertaken without stopping the progression of the disease. Biopsy was made and led to a histological diagnosis of astrocytoma. Discussion Astrocytoma must remain as a possible diagnosis of spinal cord lesions, even without typical characteristics of neoplasms. Furthermore, biopsy should always be considered when diagnosis is uncertain. PMID:24621037