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Sample records for longitudinal self-electric field

  1. PREPROCESSING MAGNETIC FIELDS WITH CHROMOSPHERIC LONGITUDINAL FIELDS

    SciTech Connect

    Yamamoto, Tetsuya T.; Kusano, K.

    2012-06-20

    Nonlinear force-free field (NLFFF) extrapolation is a powerful tool for the modeling of the magnetic field in the solar corona. However, since the photospheric magnetic field does not in general satisfy the force-free condition, some kind of processing is required to assimilate data into the model. In this paper, we report the results of new preprocessing for the NLFFF extrapolation. Through this preprocessing, we expect to obtain magnetic field data similar to those in the chromosphere. In our preprocessing, we add a new term concerning chromospheric longitudinal fields into the optimization function proposed by Wiegelmann et al. We perform a parameter survey of six free parameters to find minimum force- and torque-freeness with the simulated-annealing method. Analyzed data are a photospheric vector magnetogram of AR 10953 observed with the Hinode spectropolarimeter and a chromospheric longitudinal magnetogram observed with SOLIS spectropolarimeter. It is found that some preprocessed fields show the smallest force- and torque-freeness and are very similar to the chromospheric longitudinal fields. On the other hand, other preprocessed fields show noisy maps, although the force- and torque-freeness are of the same order. By analyzing preprocessed noisy maps in the wave number space, we found that small and large wave number components balance out on the force-free index. We also discuss our iteration limit of the simulated-annealing method and magnetic structure broadening in the chromosphere.

  2. Optical encryption in the longitudinal domain of focused fields.

    PubMed

    Carnicer, Artur; Juvells, Ignasi; Javidi, Bahram; Martínez-Herrero, Rosario

    2016-04-01

    We develop a method for encoding information in the longitudinal component of a focused field. Focused beams display a non-zero contribution of the electric field in the direction of propagation. However, the associated irradiance is very weak and difficult to isolate from the transverse part of the beam. For these reasons, the longitudinal component of a focused field could be a good choice for encoding and securing information. Using the Richards and Wolf formalism we show how to encrypt information in the longitudinal domain of the focal area. In addition, we use quantum imaging techniques to enhance the security and to prevent unauthorized access to the information. To the best of our knowledge, this is the first report on using the longitudinal component of the focused fields in optical security. PMID:27136978

  3. ABRUPT LONGITUDINAL MAGNETIC FIELD CHANGES IN FLARING ACTIVE REGIONS

    SciTech Connect

    Petrie, G. J. D.; Sudol, J. J.

    2010-12-01

    We characterize the changes in the longitudinal photospheric magnetic field during 38 X-class and 39 M-class flares within 65{sup 0} of disk center using 1 minute GONG magnetograms. In all 77 cases, we identify at least one site in the flaring active region where clear, permanent, stepwise field changes occurred. The median duration of the field changes was about 15 minutes and was approximately equal for X-class and for M-class flares. The absolute values of the field changes ranged from the detection limit of {approx}10 G to as high as {approx}450 G in two exceptional cases. The median value was 69 G. Field changes were significantly stronger for X-class than for M-class flares and for limb flares than for disk-center flares. Longitudinal field changes less than 100 G tended to decrease longitudinal field strengths, both close to disk center and close to the limb, while field changes greater than 100 G showed no such pattern. Likewise, longitudinal flux strengths tended to decrease during flares. Flux changes, particularly net flux changes near disk center, correlated better than local field changes with GOES peak X-ray flux. The strongest longitudinal field and flux changes occurred in flares observed close to the limb. We estimate the change of Lorentz force associated with each flare and find that this is large enough in some cases to power seismic waves. We find that longitudinal field decreases would likely outnumber increases at all parts of the solar disk within 65{sup 0} of disk center, as in our observations, if photospheric field tilts increase during flares as predicted by Hudson et al.

  4. On the Longitudinal Component of Paraxial Fields

    ERIC Educational Resources Information Center

    Carnicer, Artur; Juvells, Ignasi; Maluenda, David; Martinez-Herrero, Rosario; Mejias, Pedro M.

    2012-01-01

    The analysis of paraxial Gaussian beams features in most undergraduate courses in laser physics, advanced optics and photonics. These beams provide a simple model of the field generated in the resonant cavities of lasers, thus constituting a basic element for understanding laser theory. Usually, uniformly polarized beams are considered in the…

  5. Electron beam guiding by strong longitudinal magnetic fields

    NASA Astrophysics Data System (ADS)

    Johzaki, T.; Mima, K.; Fujioka, S.; Sakagami, H.; Sunahara, A.; Nagatomo, H.; Shiraga, H.

    2016-03-01

    In electron-driven fast ignition, the guiding of fast electron beam having significantly large beam divergence is one of the most critical issues for efficient core heating. To guide the fast electron beam to the core, we consider to externally apply longitudinal magnetic fields. From the 2D PIC simulations applying uniform magnetic fields, it was shown that the field strength of 1∼10kT is required for efficient guiding for the heating laser intensity of 1018∼1020W/cm2.

  6. Magnetization and diamagnetism of a longitudinal autosoliton in p-InSb in an external longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Kamilov, I. K.; Stepurenko, A. A.; Gummetov, A. E.

    2016-07-01

    It has been experimentally shown that a longitudinal thermal-diffusion autosoliton, which is generated in a nonequilibrium electron-hole plasma in p-InSb, in an external longitudinal magnetic field acquires diamagnetic properties. The results of the calculation and numerical estimates of the diamagnetism have been presented.

  7. Absorption line CW EPR using an amplitude modulated longitudinal field.

    PubMed

    Fedin, Matvey; Gromov, Igor; Schweiger, Arthur

    2004-11-01

    In standard continuous wave electron paramagnetic resonance (CW-EPR) experiments, the first derivative of absorption lines is detected. This type of a line shape is caused by the magnetic field modulation and is usually an undesired feature, since the sensitivity of CW-EPR drastically decreases with increasing linewidth. A new approach is introduced, which allows for the measurement of absorption line EPR spectra in systems with broad inhomogeneous lines. The method makes use of multiple-photon transitions that are induced in spin systems when a transverse microwave and a longitudinal radio frequency field are simultaneously applied. The absorption lines are obtained by using amplitude modulation of the radio frequency field and slight saturation of the spectral lines. The basics of the new approach are discussed and experimental examples are given. PMID:15504685

  8. Near-field ptychography using lateral and longitudinal shifts

    NASA Astrophysics Data System (ADS)

    Robisch, A.-L.; Kröger, K.; Rack, A.; Salditt, T.

    2015-07-01

    Image reconstruction of in-line holography depends crucially on the probing wave front used to illuminate an object. Aberrations inherent to the illumination can mix with the features imposed by the object. Conventional raw data processing methods rely on the division of the measured hologram by the intensity profile of the probe and are not able to fully eliminate artifacts caused by the illumination. Here we present a generalized ptychography approach to simultaneously reconstruct object and probe in the optical near-field. Combining the ideas of ptychographic lateral shifts of the object with variations of the propagation distance by longitudinal shifts, simultaneous reconstruction of object and probe was achieved equally well for a highly aberrated and a mildly disturbed probe without the need for an additional wave front diffuser. The method overcomes the image deterioration by a non-ideal probe and at the same time any restrictions due to linearization of the object’s transmission function or the Fresnel propagator. The method is demonstrated experimentally using visible light and hard x-rays, in both parallel beam and cone beam geometry, which is relevant for high resolution x-ray imaging. It also opens up a new approach to characterize extended wave fronts by phase retrieval.

  9. Longitudinal Dispersivity in a Radial Diverging Flow Field

    NASA Astrophysics Data System (ADS)

    Seaman, J. C.; Wilson, M.; Bertsch, P. M.; Aburime, S. A.

    2005-12-01

    Hydrodynamic dispersion is an important factor controlling contaminant migration in the subsurface environment. However, few comprehensive data sets exist for evaluating the impact of travel distance and site heterogeneity on solute dispersion under non-uniform flow conditions. In addition, anionic tracers are often used to estimate physical transport parameters based on an erroneous assumption of conservative (i.e., non-reactive) behavior. Therefore, a series of field experiments using tritiated water and several other commonly used hydrologic tracers (Br, Cl, FBAs) were conducted in the water-table aquifer on the U.S. Department of Energy's Savannah River Site (Aiken, SC) to evaluate solute transport processes in a diverging radial flow field. For each experiment, tracer-free groundwater was injected for approximately 24 hours at a fixed rate of 56.7 L/min (15 gpm) to establish a forced radial gradient prior to the introduction of a tracer pulse. After the tracer pulse, the forced gradient was maintained throughout the experiment using non-labeled groundwater. Tracer migration was monitored using a set of six sampling wells radially spaced at approximate distances of 1.5, 3, and 4.5 meters from a central injection well. Each sampling well was further divided into three discrete sampling depths that were monitored continuously throughout the course of the tracer experiment. At various time intervals, discrete groundwater samples were collected from all 18 sampling ports for tritium analysis. Longitudinal dispersivity for tritium breakthrough at each sampling location was estimated using analytical approximations of the convection dispersion equation (CDE) for radial flow assuming an instantaneous Dirac pulse and a pulse of known duration. The results were also compared to dispersivity values derived from fitting the tracer data to analytical solutions derived from assuming uniform flow conditions. Tremendous variation in dispersivity values and tracer arrival

  10. Energetic electron-bunch generation in a phase-locked longitudinal laser electric field

    NASA Astrophysics Data System (ADS)

    Xiao, K. D.; Huang, T. W.; Ju, L. B.; Li, R.; Yang, S. L.; Yang, Y. C.; Wu, S. Z.; Zhang, H.; Qiao, B.; Ruan, S. C.; Zhou, C. T.; He, X. T.

    2016-04-01

    Energetic electron acceleration processes in a plasma hollow tube irradiated by an ultraintense laser pulse are investigated. It is found that the longitudinal component of the laser field is much enhanced when a linear polarized Gaussian laser pulse propagates through the plasma tube. This longitudinal field is of π /2 phase shift relative to the transverse electric field and has a π phase interval between its upper and lower parts. The electrons in the plasma tube are first pulled out by the transverse electric field and then trapped by the longitudinal electric field. The trapped electrons can further be accelerated to higher energy in the presence of the longitudinal electric field. This acceleration mechanism is clearly illustrated by both particle-in-cell simulations and single particle modelings.

  11. MHD flows in the channels of plasma accelerators with a longitudinal magnetic field

    SciTech Connect

    Brushlinskii, K. V.; Zhdanova, N. S.

    2008-12-15

    Plasma flows caused by the interaction of the discharge current with the azimuthal magnetic self-field in coaxial channels (nozzles) of plasma accelerators are strongly affected by the longitudinal field produced by external conductors. A two-dimensional MHD model of flows in channels in the presence of a longitudinal magnetic field is proposed. Depending on the ratio between the characteristic values of the longitudinal and azimuthal field components, one of three types of flow is established in the channel: super-Alfven, sub-Alfven, or combined. The properties of different types of flows are analyzed. The acceleration process in sub-Alfven flows differs qualitatively from that in regimes without a longitudinal field in transitions between the kinetic, thermal, and magnetic energy components.

  12. MHD flows in the channels of plasma accelerators with a longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Brushlinskii, K. V.; Zhdanova, N. S.

    2008-12-01

    Plasma flows caused by the interaction of the discharge current with the azimuthal magnetic self-field in coaxial channels (nozzles) of plasma accelerators are strongly affected by the longitudinal field produced by external conductors. A two-dimensional MHD model of flows in channels in the presence of a longitudinal magnetic field is proposed. Depending on the ratio between the characteristic values of the longitudinal and azimuthal field components, one of three types of flow is established in the channel: super-Alfvén, sub-Alfvén, or combined. The properties of different types of flows are analyzed. The acceleration process in sub-Alfvén flows differs qualitatively from that in regimes without a longitudinal field in transitions between the kinetic, thermal, and magnetic energy components.

  13. Generation of longitudinally polarized terahertz pulses with field amplitudes exceeding 2 kV/cm

    SciTech Connect

    Cliffe, M. J. Rodak, A.; Graham, D. M.; Jamison, S. P.

    2014-11-10

    We demonstrate the generation of near-single cycle longitudinally polarized terahertz radiation using a large-area radially biased photoconductive antenna with a longitudinal field amplitude in excess of 2 kV/cm. The 76 mm diameter antenna was photo-excited by a 0.5 mJ amplified near-infrared femtosecond laser system and biased with a voltage of up to 100 kV applied over concentric electrodes. Amplitudes for both the transverse and longitudinal field components of the source were measured using a calibrated electro-optic detection scheme. By tightly focusing the radiation emitted from the photoconductive antenna, we obtained a maximum longitudinal field amplitude of 2.22 kV/cm with an applied bias field of 38.5 kV/cm.

  14. Linearization of the longitudinal phase space without higher harmonic field

    NASA Astrophysics Data System (ADS)

    Zeitler, Benno; Floettmann, Klaus; Grüner, Florian

    2015-12-01

    Accelerator applications like free-electron lasers, time-resolved electron diffraction, and advanced accelerator concepts like plasma acceleration desire bunches of ever shorter longitudinal extent. However, apart from space charge repulsion, the internal bunch structure and its development along the beam line can limit the achievable compression due to nonlinear phase space correlations. In order to improve such a limited longitudinal focus, a correction by properly linearizing the phase space is required. At large scale facilities like Flash at Desy or the European Xfel, a higher harmonic cavity is installed for this purpose. In this paper, another method is described and evaluated: Expanding the beam after the electron source enables a higher order correction of the longitudinal focus by a subsequent accelerating cavity which is operated at the same frequency as the electron gun. The elaboration of this idea presented here is based on a ballistic bunching scheme, but can be extended to bunch compression based on magnetic chicanes. The core of this article is an analytic model describing this approach, which is verified by simulations, predicting possible bunch length below 1 fs at low bunch charge. Minimizing the energy spread down to σE/E <1 0-5 while keeping the bunch long is another interesting possibility, which finds applications, e.g., in time resolved transmission electron microscopy concepts.

  15. Longitudinally polarized single-cycle terahertz pulses generated with high electric field strengths

    NASA Astrophysics Data System (ADS)

    Cliffe, M. J.; Graham, D. M.; Jamison, S. P.

    2016-05-01

    We demonstrate the generation of single-cycle longitudinally polarized terahertz pulses with field amplitudes in excess of 11 kV/cm using the interferometric recombination of two linearly polarized terahertz beams. High field strength transversely polarized pulses were generated by optical rectification in a matched pair of magnesium-oxide doped stoichiometric lithium niobate (MgO:SLN) crystals with a reversal in the χ333 ( 2 ) orientation. The discontinuity in χ333 ( 2 ) produces a polarity flip in the transverse field; the longitudinal field produced as a consequence of the transverse field discontinuity was measured in the far-field. Both the spatial and temporal profiles of the measured longitudinally polarized terahertz radiation were consistent with the propagation of the transverse discontinuity.

  16. The electromagnetic field in conductive slabs and cylinders submitted to a harmonic longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Íñiguez, J.; Raposo, V.; Zazo, M.; García-Flores, A.; Hernández-Gómez, P.

    2009-11-01

    The analysis of the induced current distribution in conducting wires subjected to a harmonic axial voltage is important in designing many electrical devices such as transformers and transmission lines. The azimuthal magnetic field induces axial electric currents and therefore the impedance of the wire depends on the excitation frequency. The current density is increasingly confined to a thin layer at the boundary of the wire as the frequency increases. To minimize this effect at higher frequencies it is necessary to enhance the surface-to-volume ratio by using thin high-conductivity wires. The study of induction phenomena in conducting samples subjected to a harmonic longitudinal magnetic field has attracted less attention. The time-varying magnetic flux induces eddy currents, which flow perpendicularly to the axis of the sample. We study the electromagnetic field in samples of simple geometry, making the usual approximations in good conductors. The validity of our calculations extends to several GHz and allows us to propose a method for determining the electrical conductivity by measuring the phase angle of the complex mutual inductance between a primary coil, responsible for the external magnetic field, and a secondary winding around the sample.

  17. Tracing ultrafast dynamics of strong fields at plasma-vacuum interfaces with longitudinal proton probing

    SciTech Connect

    Abicht, F.; Braenzel, J.; Koschitzki, Ch.; Schnürer, M.; Priebe, G.; Andreev, A. A.; Nickles, P. V.; Sandner, W.

    2014-07-21

    If regions of localized strong fields at plasma-vacuum interfaces are probed longitudinally with laser accelerated proton beams their velocity distribution changes sensitively and very fast. Its measured variations provide indirectly a higher temporal resolution as deduced from deflection geometries which rely on the explicit temporal resolution of the proton beam at the position of the object to probe. With help of reasonable models and comparative measurements changes of proton velocity can trace the field dynamics even at femtosecond time scale. In longitudinal probing, the very low longitudinal emittance together with a broad band kinetic energy distribution of laser accelerated protons is the essential prerequisite of the method. With a combination of energy and one-dimensional spatial resolution, we resolve fast field changes down to 100 fs. The used pump probe setup extends previous schemes and allows discriminating simultaneously between electric and magnetic fields in their temporal evolution.

  18. Measured Effects of a Longitudinal Solenoidal Field on an Iron Quadrupole

    NASA Astrophysics Data System (ADS)

    Ecklund, S.; Seeman, J. T.; Wolf, Z.

    1997-05-01

    We have measured the effects of a longitudinal solenoidal field on the field harmonics of an iron dominated quadrupole. These measurements are useful when designing a colliding beam interaction region where the first quadrupole is very near the solenoidal field of the physics detector. The effects of mirror plates, quadrupole excition, skew quadrupole windings, dipole windings, and solenoidal fields that enter at an angle have been measured. Conclusions and interpretations are given.

  19. Critical Current Properties in Longitudinal Magnetic Field of YBCO Superconductor with APC

    NASA Astrophysics Data System (ADS)

    Kido, R.; Kiuchi, M.; Otabe, E. S.; Matsushita, T.; Jha, A. K.; Matsumoto, K.

    The critical current density (Jc) properties of the Artificial Pinning Center (APC) introduced YBa2Cu3O7 (YBCO) films in the longitudinal magnetic field were measured. Y2O3 or Y2BaCuO5 (Y211) was introduced as APCs to YBCO, and YBCO films with APC were fabricated on SrTiO3 single crystal substrate. The sizes of Y2O3 and Y211 were 5-10 nm and 10-20 nm, respectively. As a result, Jc enhancement in the longitudinal magnetic field was observed in Y2O3 introduced YBCO films. However, it was not observed in Y211 introduced YBCO films. Therefore, it was considered that Jc properties in the longitudinal magnetic field were affected by introducing of small size APC, and it was necessary that APC does not disturb the current pathway in the superconductor.

  20. Scaling of the Longitudinal Electric Field and Transformer Ratio in a Nonlinear Plasma Wakefield Accelerator

    SciTech Connect

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

    2012-06-12

    The scaling of the two important figures of merit, the transformer ratio T and the longitudinal electric field E{sub z}, with the peak drive-bunch current I{sub p}, in a nonlinear plasma wakefield accelerator is presented for the first time. The longitudinal field scales as I{sub P}{sup 0.623{+-}0.007}, in good agreement with nonlinear wakefield theory ({approx}I{sub P}{sup 0.5}), while the unloaded transformer ratio is shown to be greater than unity and scales weakly with the bunch current. The effect of bunch head erosion on both parameters is also discussed.

  1. Streamlined mean field variational Bayes for longitudinal and multilevel data analysis.

    PubMed

    Lee, Cathy Yuen Yi; Wand, Matt P

    2016-07-01

    Streamlined mean field variational Bayes algorithms for efficient fitting and inference in large models for longitudinal and multilevel data analysis are obtained. The number of operations is linear in the number of groups at each level, which represents a two orders of magnitude improvement over the naïve approach. Storage requirements are also lessened considerably. We treat models for the Gaussian and binary response situations. Our algorithms allow the fastest ever approximate Bayesian analyses of arbitrarily large longitudinal and multilevel datasets, with little degradation in accuracy compared with Markov chain Monte Carlo. The modularity of mean field variational Bayes allows relatively simple extension to more complicated scenarios. PMID:27214238

  2. ON THE PERIODIC VARIABILITY OF THE LONGITUDINAL MAGNETIC FIELDS OF STARS

    SciTech Connect

    Bychkov, V. D.; Bychkova, L. V.; Madej, J. E-mail: lbych@sao.ru

    2013-10-01

    There exist 218 stars with measured phase curves of their longitudinal (effective) magnetic field B{sub e} . In that group, 172 objects are classified as magnetic chemically peculiar stars. The remaining objects are stars of various spectral types, from the most massive hot Of?p supergiants to low-mass red dwarfs and stars with planets. In this paper, we discuss the behavior of the longitudinal magnetic field B{sub e} and present estimated parameters of the apparent magnetic variability for stars of each spectral type. This paper also aims to briefly review the properties of the observed magnetic behavior among various types of stars.

  3. A survey of Ap stars for weak longitudinal magnetic fields

    NASA Astrophysics Data System (ADS)

    Auriere, M.; Silvester, J.; Wade, G. A.; Bagnulo, S.; Donati, J. F.; Johnson, N.; Landstreet, J. D.; Lignieres, F.; Lueftinger, T.; Mouillet, M.; Paletou, F.; Petit, P.; Strasser, S.

    2004-10-01

    We are conducting a magnetic survey of a sample of about 30 spectroscopically-identified Ap stars (selected from the HD catalogue), but with faint or previously undetected magnetic fields. We use the MuSiCoS spectropolarimeter at Telescope Bernard Lyot (Pic du Midi Observatory, France) and the cross-correlation technique Least Squares Deconvolution (LSD; Donati et al. 1997). For 24 studied stars, we have obtained 21 detections of Stokes V Zeeman signatures (data quality and phase coverage may explain our lack of detection of any field in some objects). Our results suggest that all Ap stars are magnetic and, furthermore, that there may exist a minimum field strength for which Ap-type characteristics are produced.

  4. Images of Imaging: Notes on Doing Longitudinal Field Work.

    ERIC Educational Resources Information Center

    Barley, Stephen R.

    1990-01-01

    Discusses the processes involved in a field study of technological change in radiology and how researchers can design a qualitative study and then collect data in a systematic and explicit manner. Illustrates the social and human problems of gaining entry into a research site, constructing a research role, and managing relationships. (63…

  5. The influence of longitudinal space charge fields on the modulation process of coherent electron cooling

    SciTech Connect

    Wang, G.; Blaskiewicz, M.; Litvinenko, V. N.

    2014-05-21

    Initial modulation in Coherent electron cooling (CeC) scheme relies on ion charge screening by electrons. In a CeC system with bunched electron beam, the long-range longitudinal space charge force is inevitably induced. For a relatively dense electron beam, it can be comparable or even greater than the attractive force from the ion. Hence, space-charge field influence to the modulation process could be important. If the longitudinal Debye length is much smaller than the electron bunch length, the modulation induced by the ion happens locally. In this case, the long-range longitudinal space charge field can be approximated as a uniform electric field across the region. In this paper we developed an analytical model to study the dynamics of ion shielding in the presence of a uniform electric field. We are solving the coupled Vlasov-Poisson equation system for infinite anisotropic electron plasma and estimate the influences of the longitudinal space charge field to the modulation process. We present numerical estimates for a case of the proof of CeC principle experiment at RHIC.

  6. A Longitudinal Investigation of Field Dependence-Independence and the Development of Formal Operational Thought.

    ERIC Educational Resources Information Center

    Flexer, B.K.; Roberge, J.J.

    1983-01-01

    A longitudinal study among American adolescents revealed (1) an insignificant impact of field dependence-independence on the development of formal operational thought; (2) continuous development of combinatorial reasoning and propositional logic abilities, but little increase in comprehension of proportionality; and (3) sex differences in formal…

  7. Dose response of selected solid state detectors in applied homogeneous transverse and longitudinal magnetic fields

    SciTech Connect

    Reynolds, M.; Fallone, B. G.; Rathee, S.

    2014-09-15

    Purpose: MR-Linac devices under development worldwide will require standard calibration, commissioning, and quality assurance. Solid state radiation detectors are often used for dose profiles and percent depth dose measurements. The dose response of selected solid state detectors is therefore evaluated in varying transverse and longitudinal magnetic fields for this purpose. Methods: The Monte Carlo code PENELOPE was used to model irradiation of a PTW 60003 diamond detector and IBA PFD diode detector in the presence of a magnetic field. The field itself was varied in strength, and oriented both transversely and longitudinally with respect to the incident photon beam. The long axis of the detectors was oriented either parallel or perpendicular to the photon beam. The dose to the active volume of each detector in air was scored, and its ratio to dose with zero magnetic field strength was determined as the “dose response” in magnetic field. Measurements at low fields for both detectors in transverse magnetic fields were taken to evaluate the accuracy of the simulations. Additional simulations were performed in a water phantom to obtain few representative points for beam profile and percent depth dose measurements. Results: Simulations show significant dose response as a function of magnetic field in transverse field geometries. This response can be near 20% at 1.5 T, and it is highly dependent on the detectors’ relative orientation to the magnetic field, the energy of the photon beam, and detector composition. Measurements at low transverse magnetic fields verify the simulations for both detectors in their relative orientations to radiation beam. Longitudinal magnetic fields, in contrast, show little dose response, rising slowly with magnetic field, and reaching 0.5%–1% at 1.5 T regardless of detector orientation. Water tank and in air simulation results were the same within simulation uncertainty where lateral electronic equilibrium is present and expectedly

  8. Field distortion in a longitudinal slot radiator in a slotted-waveguide array

    NASA Astrophysics Data System (ADS)

    Wang, Hanyang; Sangster, A. J.

    1992-12-01

    A comprehensive solution to the tangential field distribution within a longitudinal slot in the presence of its neighboring slots in a linear slotted-waveguide array is presented which is based on the direct method of moments. A set of basic functions is used to simulate the field in the slots as a group. It is concluded that the mutual coupling has little impact on the shape of the field even when the interfering slots are asymmetrically distributed in relation to the slot under consideration. However, it significantly affects the amplitude of the slot aperture field.

  9. Plasmonic lens focused longitudinal field excitation for tip-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Mingqian; Wang, Jia

    2015-04-01

    A novel tip-enhanced Raman spectroscopy setup with longitudinal field excitation generated by a plasmonic lens is investigated. A symmetry-breaking structure plasmonic lens that is expected to realize a strong longitudinal electric field focus has been designed to generate suitable excitation for enhancement in a tip antenna. The focusing performance of the plasmonic lens is theoretically simulated by the finite-difference time-domain method and experimentally verified by the detection of optical near-field distribution. A plasmonic lens assisted tip-enhanced Raman spectroscopy setup has been constructed and used to investigate specimens of carbon nanotubes. Tip-enhanced Raman spectra with distinct excitation wavelengths show similar Raman shifts but different intensities. Experimental results presented in this paper demonstrate that the Raman signal is considerably enhanced. It indicates that the novel tip-enhanced Raman spectroscopy configuration is feasible and is a promising technique for tip-enhanced Raman spectroscopy measurements and characterizations.

  10. Plasmonic lens focused longitudinal field excitation for tip-enhanced Raman spectroscopy.

    PubMed

    Zhang, Mingqian; Wang, Jia

    2015-01-01

    A novel tip-enhanced Raman spectroscopy setup with longitudinal field excitation generated by a plasmonic lens is investigated. A symmetry-breaking structure plasmonic lens that is expected to realize a strong longitudinal electric field focus has been designed to generate suitable excitation for enhancement in a tip antenna. The focusing performance of the plasmonic lens is theoretically simulated by the finite-difference time-domain method and experimentally verified by the detection of optical near-field distribution. A plasmonic lens assisted tip-enhanced Raman spectroscopy setup has been constructed and used to investigate specimens of carbon nanotubes. Tip-enhanced Raman spectra with distinct excitation wavelengths show similar Raman shifts but different intensities. Experimental results presented in this paper demonstrate that the Raman signal is considerably enhanced. It indicates that the novel tip-enhanced Raman spectroscopy configuration is feasible and is a promising technique for tip-enhanced Raman spectroscopy measurements and characterizations. PMID:25977661

  11. Hamiltonian Analysis of the Particle Motion in an Accelerator with the Longitudinal Magnetic Field

    SciTech Connect

    Reva, V. B.

    2006-03-20

    The particle motion at a presence of a large magnetic field directed along the particle trajectory demands the special description. This article deals with the decomposition of the Hamiltonian on the two parts: fast and slow motion. The first part describes the fast rotation around the magnetic line of longitudinal field. The second part describes the slow drift of rotation center from one magnetic line to another. The supposed method enables to write the simple Hamiltonian to each motion type and to formulate the matrix formalism for any element of an accelerator device (quadruple, skew- quadruple, drift gap, bend with a filed index). The Hamiltonian decomposition has physical clearness when the longitudinal field is larger than another fields but it is correct for the arbitrary parameters. At the small longitudinal field the coupling term in Hamiltonian between two modes is essential. The dispersion property of fast and slow modes is derived easy from Hamiltonian also. This method expands easily for nonlinear motion of such modes. This results may be used at analyzed the electron motion in the cooling device, the muon motion in the muon ionization cooler or another system with strong solenoidal coupling.

  12. Symplectic tracking using point magnets in the presence of a longitudinal magnetic field

    SciTech Connect

    Parzen, G.

    1993-09-01

    In the absence of a longitudinal magnetic field, symplectic tracking can be achieved by replacing the magnets by a series of point magnets and drift spaces. To treat the case when a longitudinal magnetic field is also present, this procedure is modified in this paper by replacing the drift space by a solenoidal drift, which is defined as the motion of a particle in a uniform longitudinal magnetic field. A symplectic integrator can be obtained by subdividing each magnet into pieces and replacing each magnet piece by point magnets, with only transverse fields, and solenoidal drift spaces. The reference orbit used here is made up of arcs of circles and straight lines which join smoothly with each other. For this choice of reference orbit, the required results are obtained to track particles, which are the transfer functions, and the transfer time for the different elements. It is shown that these results provide a symplectic integrator, and they are exact in the sense that as the number of magnet pieces is increased, the particle motion will converge to the particle motion of the exact equations of motion.

  13. Discharge rate measurements for Micromegas detectors in the presence of a longitudinal magnetic field

    SciTech Connect

    B. Moreno, S. Aune, J. Ball, G. Charles, A. Giganon, P. Konczykowski, C. Lahonde-Hamdoun, H. Moutarde, S. Procureur, F. Sabatie

    2011-10-01

    We present first discharge rate measurements for Micromegas detectors in the presence of a high longitudinal magnetic field in the GeV kinematical region. Measurements were performed by using two Micromegas detectors and a photon beam impinging a CH{sub 2} target in the Hall B of the Jefferson Laboratory. One detector was equipped with an additional GEM foil, and a reduction of the discharge probability by two orders of magnitude compared to the stand-alone Micromegas was observed. The detectors were p laced in the FROST solenoid providing a longitudinal magnetic field up to 5T. It allowed for precise measurements of the discharge probability dependence with a diffusion-reducing magnetic field. Between 0 and 5T, the discharge probability increased by a factor of 10 for polar angles between 19{degrees} and 34{degrees}. A GEANT4-based simulation developed for sparking rate calculation was calibrated against these data in order to predict the sparking rate in a high longitudinal magnetic field environment. This simulati on is then used to investigate the possible use of Micromegas in the Forward Vertex Tracker (FVT) of the future CLAS12 spectrometer. In the case of the FVT a sparking rate of 1Hz per detector was obtained at the anticipated CLAS12 luminosity.

  14. Thermodynamic properties of anisotropic spin ladder in a longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Rezania, H.

    2015-08-01

    We address thermodynamic properties of quasi-one dimensional two leg antiferromagnetic ladder in the presence of magnetic field. A generalized bond operator formalism is used to transform the spin model to a hard core bosonic gas. We have implemented Green's function approach to obtain the temperature dependence of spin excitation spectrum in field induced spin polarized phase. The results show energy gap that vanishes at critical magnetic field for fixed values of temperatures. We have also found the temperature dependence of the specific heat and magnetization component in the magnetic field direction for various magnetic field strengths and anisotropies in the Heisenberg interactions on both leg and rung couplings. At low temperatures, the specific heat is found to be monotonically increasing with temperature for magnetic fields in the spin polarized phase region. Furthermore we studied the temperature dependence of the longitudinal magnetization for different magnetic field and anisotropy parameters.

  15. Influence of a strong longitudinal magnetic field on laser wakefield acceleration

    SciTech Connect

    Rassou, S.; Bourdier, A.; Drouin, M.

    2015-07-15

    Optimization of the beam quality and electronic trapped charge in the cavity are key issues of laser wake field acceleration. The effect of an initially applied uniform magnetic field, parallel to the direction of propagation of the pump pulse, on the laser wakefield is explored. First, an analytic model for the laser wakefield is built up in the case when such an external magnetic field is applied. Then, simulations are performed with a 3D quasi-cylindrical particle in cell code in the blowout (or bubble) regime. Transverse currents are generated at the rear of the bubble which amplify the longitudinal magnetic field. For several plasma and laser parameters, the wake shape is altered and trapping can be reduced or cancelled by the magnetic field. When considering optical injection, and when two counterpropagating waves interact with a rather high plasma density, trapping is not affected by the magnetic field. In this range of plasma and laser parameters, it is shown that the longitudinal magnetic field can reduce or even prevent self-injection and enhance beam quality.

  16. Dispersal of G-band Bright Points at Different Longitudinal Magnetic Field Strengths

    NASA Astrophysics Data System (ADS)

    Yang, Yunfei; Ji, Kaifai; Feng, Song; Deng, Hui; Wang, Feng; Lin, Jiaben

    2015-09-01

    G-band bright points (GBPs) are thought to be the foot-points of magnetic flux tubes. The aim of this paper is to investigate the relation between the diffusion regimes of GBPs and the associated longitudinal magnetic field strengths. Two high resolution observations of different magnetized environments were acquired with the Hinode/Solar Optical Telescope. Each observation was recorded simultaneously with G-band filtergrams and Narrow-band Filter Imager (NFI) Stokes I and V images. GBPs are identified and tracked automatically, and then categorized into several groups by their longitudinal magnetic field strengths, which are extracted from the calibrated NFI magnetograms using a point-by-point method. The Lagrangian approach and the distribution of diffusion indices approach are adopted separately to explore the diffusion regime of GBPs for each group. It is found that the values of diffusion index and diffusion coefficient both decrease exponentially with the increasing longitudinal magnetic field strengths whichever approach is used. The empirical formulas deduced from the fitting equations are proposed to describe these relations. Stronger elements tend to diffuse more slowly than weak elements, independently of the magnetic flux of the surrounding medium. This may be because the magnetic energy of stronger elements is not negligible compared with the kinetic energy of the gas, and therefore the flows cannot perturb them so easily.

  17. Self-mapping the longitudinal field structure of a nonlinear plasma accelerator cavity.

    PubMed

    Clayton, C E; Adli, E; Allen, J; An, W; Clarke, C I; Corde, S; Frederico, J; Gessner, S; Green, S Z; Hogan, M J; Joshi, C; Litos, M; Lu, W; Marsh, K A; Mori, W B; Vafaei-Najafabadi, N; Xu, X; Yakimenko, V

    2016-01-01

    The preservation of emittance of the accelerating beam is the next challenge for plasma-based accelerators envisioned for future light sources and colliders. The field structure of a highly nonlinear plasma wake is potentially suitable for this purpose but has not been yet measured. Here we show that the longitudinal variation of the fields in a nonlinear plasma wakefield accelerator cavity produced by a relativistic electron bunch can be mapped using the bunch itself as a probe. We find that, for much of the cavity that is devoid of plasma electrons, the transverse force is constant longitudinally to within ±3% (r.m.s.). Moreover, comparison of experimental data and simulations has resulted in mapping of the longitudinal electric field of the unloaded wake up to 83 GV m(-1) to a similar degree of accuracy. These results bode well for high-gradient, high-efficiency acceleration of electron bunches while preserving their emittance in such a cavity. PMID:27527569

  18. Self-mapping the longitudinal field structure of a nonlinear plasma accelerator cavity

    PubMed Central

    Clayton, C. E.; Adli, E.; Allen, J.; An, W.; Clarke, C. I.; Corde, S.; Frederico, J.; Gessner, S.; Green, S. Z.; Hogan, M. J.; Joshi, C.; Litos, M.; Lu, W.; Marsh, K. A.; Mori, W. B.; Vafaei-Najafabadi, N.; Xu, X.; Yakimenko, V.

    2016-01-01

    The preservation of emittance of the accelerating beam is the next challenge for plasma-based accelerators envisioned for future light sources and colliders. The field structure of a highly nonlinear plasma wake is potentially suitable for this purpose but has not been yet measured. Here we show that the longitudinal variation of the fields in a nonlinear plasma wakefield accelerator cavity produced by a relativistic electron bunch can be mapped using the bunch itself as a probe. We find that, for much of the cavity that is devoid of plasma electrons, the transverse force is constant longitudinally to within ±3% (r.m.s.). Moreover, comparison of experimental data and simulations has resulted in mapping of the longitudinal electric field of the unloaded wake up to 83 GV m−1 to a similar degree of accuracy. These results bode well for high-gradient, high-efficiency acceleration of electron bunches while preserving their emittance in such a cavity. PMID:27527569

  19. Hemispherical and Longitudinal Asymmetries in the Heliospheric Magnetic Field: Flip-flops of a Bashful Ballerina

    NASA Astrophysics Data System (ADS)

    Hiltula, T.; Mursula, K.

    2004-12-01

    Several studies during many decennia have studied possible longitudinal and hemispherical asymmetries in various forms of solar activity. E.g., there are well known periods when one of the solar hemispheres has dominated the other in sunspot numbers, flare occurrence or some other form of solar activity. However, the solar asymmetries have not been found to be very conclusive, or to form any clear systematical patterns (e.g., relation to solar cycle). On the contrary, recent studies of similar longitudinal and hemispherical asymmetries in the heliospheric magnetic field have shown a very clear and systematic behaviour. E.g., it was found recently that the dominance of the two HMF sectors experiences an oscillation with a period of about 3.2 years. This new flip-flop periodicity in the heliospheric magnetic field is most likely related to a similar periodicity recently found in sunspots. Also, it has recently been found that the HMF sector coming from the northern solar hemisphere systematically dominates at 1AU during solar minimum times. This leads to a persistent southward shift or coning of the heliospheric current sheet at these times that can be picturesquely described by the concept of a Bashful Ballerina. This result also implies that the Sun has a large-scale quadrupole magnetic moment. Here we review these recent developments concerning the longitudinal and hemispherical asymmetries in the heliospheric magnetic field and study their inter-connection.

  20. Visualization of Longitudinal and Transverse Components of Strongly Focused Optical Field by means of Photo-Reactive Azopolymers

    NASA Astrophysics Data System (ADS)

    Kharitonov, A. V.; Kharintsev, S. S.

    2015-09-01

    Most important problems in modern photonics are fabrication, visualization and characterization of nanomaterials at optical frequencies. A number of optical techniques uses tightly focused laser beams to access longitudinal electromagnetic fields, which are directed towards the wave vector. In this Letter, the distribution of transverse and longitudinal optical fields in tightly focused laser beams, polarized in a new fashion, is investigated. Polarization dependent fingerprints of transverse and longitudinal optical fields are experimentally captured by means of photoinduced surface deformations in azobenzene polymer thin films.

  1. Electric field generated by longitudinal axial microtubule vibration modes with high spatial resolution microtubule model

    NASA Astrophysics Data System (ADS)

    Cifra, M.; Havelka, D.; Deriu, M. A.

    2011-12-01

    Microtubules are electrically polar structures fulfilling prerequisites for generation of oscillatory electric field in the kHz to GHz region. Energy supply for excitation of elasto-electrical vibrations in microtubules may be provided from GTP-hydrolysis; motor protein-microtubule interactions; and energy efflux from mitochondria. It recently was determined from anisotropic elastic network modeling of entire microtubules that the frequencies of microtubule longitudinal axial eigenmodes lie in the region of tens of GHz for the physiologically common microtubule lengths. We calculated electric field generated by axial longitudinal vibration modes of microtubule, which model is based on subnanometer precision of charge distribution. Due to elastoelectric nature of the vibrations, the vibration wavelength is million-fold shorter than that of the electromagnetic field in free space and the electric field around the microtubule manifests rich spatial structure with multiple minima. The dielectrophoretic force exerted by electric field on the surrounding molecules will influence the kinetics of reactions via change in the probability of the transport of charge and mass particles. The electric field generated by vibrations of electrically polar cellular structures is expected to play a role in biological self-organization.

  2. Transverse and longitudinal characterization of electron beams using interaction with optical near-fields.

    PubMed

    Kozák, Martin; McNeur, Joshua; Leedle, Kenneth J; Deng, Huiyang; Schönenberger, Norbert; Ruehl, Axel; Hartl, Ingmar; Hoogland, Heinar; Holzwarth, Ronald; Harris, James S; Byer, Robert L; Hommelhoff, Peter

    2016-08-01

    We demonstrate an experimental technique for both transverse and longitudinal characterization of bunched femtosecond free electron beams. The operation principle is based on monitoring of the current of electrons that obtained an energy gain during the interaction with the synchronized optical near-field wave excited by femtosecond laser pulses. The synchronous accelerating/decelerating fields confined to the surface of a silicon nanostructure are characterized using a highly focused sub-relativistic electron beam. Here the transverse spatial resolution of 450 nm and femtosecond temporal resolution of 480 fs (sub-optical-cycle temporal regime is briefly discussed) achievable by this technique are demonstrated. PMID:27472587

  3. Creating order with the help of randomness: generating transversely random, longitudinally invariant vector optical fields.

    PubMed

    Khonina, Svetlana N; Golub, Ilya

    2015-09-01

    We show that it is possible to generate transversely random, diffraction-free/longitudinally invariant vector optical fields. The randomness in transverse polarization distribution complements a previously studied one in intensity of scalar Bessel-type beams, adding another degree of freedom to control these beams. Moreover, we show that the relative transversely random phase distribution is also conserved along the optical axis. Thus, intensity, phase, and polarization of Bessel-type beams can be transversely random/arbitrary while invariant upon propagation. Such fields may find applications in encryption/secure communications, optical trapping, etc. PMID:26368714

  4. Longitudinal wave function control in single quantum dots with an applied magnetic field

    PubMed Central

    Cao, Shuo; Tang, Jing; Gao, Yunan; Sun, Yue; Qiu, Kangsheng; Zhao, Yanhui; He, Min; Shi, Jin-An; Gu, Lin; Williams, David A.; Sheng, Weidong; Jin, Kuijuan; Xu, Xiulai

    2015-01-01

    Controlling single-particle wave functions in single semiconductor quantum dots is in demand to implement solid-state quantum information processing and spintronics. Normally, particle wave functions can be tuned transversely by an perpendicular magnetic field. We report a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field along the base-apex direction, the hole wave function shrinks in the base plane. Because of the linear changing of the confinement for hole wave function from base to apex, the center of effective mass moves up during shrinking process. Due to the uniform confine potential for electrons, the center of effective mass of electrons does not move much, which results in a permanent dipole moment change and an inverted electron-hole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electron-hole interaction in single quantum dots. PMID:25624018

  5. Longitudinal Changes in Quality of Life and Rates of Progressive Visual Field Loss in Glaucoma Patients

    PubMed Central

    Medeiros, Felipe A.; Gracitelli, Carolina P. B.; Boer, Erwin R.; Weinreb, Robert N.; Zangwill, Linda M.; Rosen, Peter N.

    2014-01-01

    Purpose To evaluate the association between longitudinal changes in quality of life and rates of progressive visual field loss in glaucoma. Design Prospective observational cohort study. Participants 322 eyes of 161 patients with glaucomatous visual field loss recruited from the Diagnostic Innovations Glaucoma Study (DIGS) followed for an average of 3.5 ± 0.7 years. Methods All subjects had NEI VFQ-25 performed annually and standard automated perimetry (SAP) at 6-month intervals. Subjects were included if they had a minimum of 2 NEI VFQ-25 and at least 5 standard automated perimetry (SAP) during follow up. Evaluation of rates of visual field change was performed using the mean sensitivity (MS) of the integrated binocular visual field. Rasch analysis was performed to obtain final scores of disability as measured by the NEI VFQ-25. A joint longitudinal multivariate mixed model was used to investigate the association between change in NEI VFQ-25 Rasch-calibrated scores and change in binocular visual field sensitivity. Potentially confounding socio-economic and clinical variables were also analyzed. Main outcome measures The relationship between change in NEI VFQ-25 Rasch-calibrated scores and change in binocular SAP MS. Results There was a statistically significant correlation between change in the NEI VFQ-25 Rasch scores during follow-up and change in binocular SAP sensitivity. Each 1db change in binocular SAP MS per year was associated with a change of 2.9 units per year in the NEI VFQ-25 Rasch scores during the follow-up period (R2=26%; P<0.001). Eyes with more severe disease at baseline were also more likely to have a decrease in NEI VFQ-25 scores during follow-up (P<0.001). For subjects with the same amount of change in SAP sensitivity, those with shorter follow-up times had larger changes in NEI VFQ-25 scores (P=0.005). A multivariable model containing baseline and rate of change in binocular MS had an adjusted-R2 of 50% in predicting change in NEI VFQ-25

  6. E8 spectrum and the finite temperature spin dynamics in the transverse field Ising chain with a small longitudinal field

    NASA Astrophysics Data System (ADS)

    Wu, Jianda; Kormos, Marton; Si, Qimiao

    2013-03-01

    When the transverse field Ising chain at its quantum critical point is subjected to a small longitudinal field, the perturbed conformal field theory led to a field theory with an exotic E8 symmetry. Recent neutron scattering experiments have provided evidence for the lightest two particles in this E8 model in the quasi-1D Ising ferromagnet CoNb2O6. While the zero temperature dynamics of the model is well known, its finite-temperature counterpart has not yet been systematically studied. We study the low-frequency dynamical structure factor at finite temperatures using the form-factor method. We show that the dominant contribution to the dynamical structure factor comes from the scattering between two lightest particles, and discuss the implications of our results for the NMR relaxation rate.

  7. AC current distribution and losses in multifilamentary superconductors exposed to longitudinal magnetic field

    SciTech Connect

    Le Naour, S.; Lacaze, A.; Laumond, Y.; Estop, P.; Verhaege, T.

    1996-07-01

    The current distribution and also AC losses, in a multifilamentary superconductor carrying a transport current, are influenced by the self and the external magnetic field. By using the Maxwell equations, a model has been developed in order to calculate the temporal evolution of current distribution in a single wire exposed or not to external magnetic field. This model is based on the actual relationship of electrical field E with current density J and takes into account the twist pitch of the wire. AC losses are calculated by adding all local losses through the cross section. This paper presents calculations of the influence of the cable twist coupled with the longitudinal magnetic field, and also gives some ideas how to decrease losses.

  8. Observations of the longitudinal magnetic field in the transition region and photosphere of a sunspot

    NASA Technical Reports Server (NTRS)

    Henze, W., Jr.; Tandberg-Hanssen, E.; Hagyard, M. J.; West, E. A.; Woodgate, B. E.; Shine, R. A.; Beckers, J. M.; Bruner, M.; Hyder, C. L.; West, E. A.

    1982-01-01

    The Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission spacraft has observed for the first time the longitudinal component of the magnetic field by means of the Zeeman effect in the transition region above a sunspot. The data presented here were obtained on three days in one sunspot, have spatial resolutions of 10 arcsec and 3 arcsec, and yield maximum field strengths greater than 1000 G above the umbrae in the spot. The method of analysis, including a line-width calibration feature used during some of the observations, is described in some detail in an appendix; the line width is required for the determination of the longitudinal magnetic field from the observed circular polarization. The transition region data for one day are compared with photospheric magnetograms from the Marshall Space Flight Center. Vertical gradients of the magnetic field are compared from the two sets of data; the maximum gradients of 0.41 to 0.62 G/km occur above the umbra and agree with or are smaller than values observed previously in the photosphere and low chromosphere.

  9. The Effects of Magnetic-field Geometry on Longitudinal Oscillaitons of Solar Prominences

    NASA Technical Reports Server (NTRS)

    Luna, M.; Diaz, A. J.; Karpen, J.

    2013-01-01

    We investigate the influence of the geometry of the solar filament magnetic structure on the large-amplitude longitudinal oscillations. A representative filament flux tube is modeled as composed of a cool thread centered in a dipped part with hot coronal regions on either side.We have found the normal modes of the system and establish that the observed longitudinal oscillations are well described with the fundamental mode. For small and intermediate curvature radii and moderate to large density contrast between the prominence and the corona, the main restoring force is the solar gravity. In this full wave description of the oscillation a simple expression for the oscillation frequencies is derived in which the pressure-driven term introduces a small correction. We have also found that the normal modes are almost independent of the geometry of the hot regions of the tube. We conclude that observed large-amplitude longitudinal oscillations are driven by the projected gravity along the flux tubes and are strongly influenced by the curvature of the dips of the magnetic field in which the threads reside.

  10. ABRUPT LONGITUDINAL MAGNETIC FIELD CHANGES AND ULTRAVIOLET EMISSIONS ACCOMPANYING SOLAR FLARES

    SciTech Connect

    Johnstone, B. M.; Petrie, G. J. D.; Sudol, J. J.

    2012-11-20

    We have used Transition Region and Coronal Explorer 1600 A images and Global Oscillation Network Group (GONG) magnetograms to compare ultraviolet (UV) emissions from the chromosphere to longitudinal magnetic field changes in the photosphere during four X-class solar flares. An abrupt, significant, and persistent change in the magnetic field occurred across more than 10 pixels in the GONG magnetograms for each flare. These magnetic changes lagged the GOES flare start times in all cases, showing that they were consequences and not causes of the flares. Ultraviolet emissions were spatially coincident with the field changes. The UV emissions tended to lag the GOES start times for the flares and led the changes in the magnetic field in all pixels except one. The UV emissions led the photospheric field changes by 4 minutes on average with the longest lead being 9 minutes; however, the UV emissions continued for tens of minutes, and more than an hour in some cases, after the field changes were complete. The observations are consistent with the picture in which an Alfven wave from the field reconnection site in the corona propagates field changes outward in all directions near the onset of the impulsive phase, including downward through the chromosphere and into the photosphere, causing the photospheric field changes, whereas the chromosphere emits in the UV in the form of flare kernels, ribbons, and sequential chromospheric brightenings during all phases of the flare.

  11. Impact of longitudinal fields on second harmonic generation in lithium niobate nanopillars

    NASA Astrophysics Data System (ADS)

    Baghban, Mohammad Amin; Gallo, Katia

    2016-09-01

    An optimized focused ion beam process is used to fabricate micrometer-long LiNbO3 nanopillars with diameters varying between 150 and 325 nm. Polarimetric mappings of second harmonic generation from a wavelength of 850 nm demonstrate the ability to modify the polarization features of the nonlinear response through a fine adjustment of the pillar size. The effect is ascribed to the non-negligible contribution of the longitudinal fields associated with sub-wavelength light confinement in the LiNbO3 nanopillars. The results also highlight the importance of a fine control over the nanopillar size in order to effectively engineer their nonlinear response.

  12. Interaction of oppositely directed plasma streams in a longitudinal magnetic field

    SciTech Connect

    Zhitlukhin, A.M.; Ilyushin, I.V.; Safronov, V.M.; Skvortsov, Y.V.

    1982-05-01

    Streams of a deuterium plasma with a density 10/sup 15/ cm/sup -3/ and directed velocities from 3 x 10/sup 7/ to 8 x 10/sup 7/ cm/s were made to collide in a uniform longitudinal magnetic field. Complete randomization of the directed energy of the stream was observed, and a hot ''steady-state'' plasma with a density n = 10/sup 15/ cm/sup -3/ and T/sub i/ = 2--3 keV was formed. The neutron yield reached 4 x 10/sup 9/ neutrons per shot. The stopping of the colliding streams is ascribed to a firehose instability.

  13. Longitudinal static optical properties of hydrogen chains: finite field extrapolations of matrix product state calculations.

    PubMed

    Wouters, Sebastian; Limacher, Peter A; Van Neck, Dimitri; Ayers, Paul W

    2012-04-01

    We have implemented the sweep algorithm for the variational optimization of SU(2) U(1) (spin and particle number) invariant matrix product states (MPS) for general spin and particle number invariant fermionic Hamiltonians. This class includes non-relativistic quantum chemical systems within the Born-Oppenheimer approximation. High-accuracy ab initio finite field results of the longitudinal static polarizabilities and second hyperpolarizabilities of one-dimensional hydrogen chains are presented. This allows to assess the performance of other quantum chemical methods. For small basis sets, MPS calculations in the saturation regime of the optical response properties can be performed. These results are extrapolated to the thermodynamic limit. PMID:22482543

  14. Suppression of electron scattering by the longitudinal components of tightly focused laser fields

    SciTech Connect

    Masuda, S.; Kando, M.; Kotaki, H.; Nakajima, K.

    2005-01-01

    Relativistic electron scattering by a high intensity linearly polarized Gaussian (TEM{sub 00} mode) laser beam is studied in detail using three-dimensional numerical simulations. It is observed that the longitudinal components of the electromagnetic field in a tight focus effectively suppress transverse electron scattering in the relativistic laser ponderomotive acceleration scheme. The simulations show that the relativistic ponderomotive acceleration can produce high quality electron bunches characterized by an extremely short bunch length of subfemtosecond, energy spread less than 1%, and normalized transverse emittance less than 10{pi} mm mrad.

  15. Ion Species and Charge States of Vacuum Arc Plasma with Gas Feed and Longitudinal Magnetic Field

    SciTech Connect

    Oks, Efim; Anders, Andre

    2010-06-23

    The evolution of copper ion species and charge state distributions is measured for a long vacuum arc discharge plasma operated in the presence of a longitudinal magnetic field of several 10 mT and working gas (Ar). It was found that changing the cathode-anode distance within 20 cm as well as increasing the gas pressure did not affect the arc burning voltage and power dissipation by much. In contrast, burning voltage and power dissipation were greatly increased as the magnetic field was increased. The longer the discharge gap the greater was the fraction of gaseous ions and the lower the fraction of metal ions, while the mean ion charge state was reduced. It is argued that the results are affected by charge exchange collisions and electron impact ionization.

  16. SU-E-J-51: Dose Response of Common Solid State Detectors in Homogeneous Transverse and Longitudinal Magnetic Fields

    SciTech Connect

    Reynolds, M; Fallone, B; Rathee, S

    2014-06-01

    Purpose: Solid state radiation detectors are often used for dose profiles and percent depth dose measurements. The dose response of selected solid state detectors is evaluated in varying transverse and longitudinal magnetic fields for eventual use in MR-Linac devices. Methods: A PTW 60003 and IBA PFD detector were modeled in the Monte Carlo code PENELOPE, incorporating a magnetic field which was varied in strength and oriented both transversely and longitudinally with respect to the incident photon beam. The detectors' long axis was in turn oriented either parallel or perpendicular to the photon beam. Dose to the active volume of each detector was scored, and its ratio to dose with zero magnetic field strength (dose response) was determined. Accuracy of the simulations was evaluated by measurements using both chambers taken at low field with a small electromagnet. Simulations were also performed in a water phantom to compare to the in air results. Results: Significant dose response was found in transverse field geometries, nearing 20% at 1.5T. The response is highly dependent on relative orientations to the magnetic field and photon beam, and on detector composition. Low field measurements confirm these results. In the presence of longitudinal magnetic fields, the detectors exhibit little dose response, reaching 0.5–1% at 1.5T regardless of detector orientation. Water tank simulations compared well to the in air simulations when not at the beam periphery, where in transverse magnetic fields only, the water tank simulations differed from the in air results. Conclusion: Transverse magnetic fields can cause large deviations in dose response, and are highly position orientation dependent. Comparatively, longitudinal magnetic fields exhibit little to no dose response in each detector as a function of magnetic field strength. Water tank simulations show longitudinal fields are generally easier to work with, but each detector must be evaluated separately.

  17. Breast dosimetry in transverse and longitudinal field MRI-Linac radiotherapy systems

    SciTech Connect

    Mahdavi, S. R.; Esmaeeli, A. D.; Pouladian, M.; Sardari, D.; Bagheri, S.; Monfared, A. S.

    2015-02-15

    Purpose: In the framework of developing the integration of a MRI-Linac system, configurations of MRI-Linac units were simulated in order to improve the dose distribution in tangential breast radiotherapy using transverse and longitudinal magnetic field geometries of Lorentz force for both medial and lateral tangential fields. Methods: In this work, the GEANT4 Monte Carlo (MC) code was utilized to compare dose distributions in breast radiotherapy for Linac-MR systems in the transverse and longitudinal geometries within humanoid phantoms across a range of magnetic field strengths of 0.5 and 1.5 T. The dose increment due to scattering from the coils was investigated for both geometries as well. Computed tomography images of two patients were used for MC simulations. One patient had intact breast while the other was mastectomized. In the simulations, planning and methods of chest wall irradiation were similar to the actual clinical planning. Results: In a longitudinal geometry, the magnetic field is shown to restrict the lateral spread of secondary electrons to the lung, heart, and contralateral organs, which reduced the mean dose of the ipsilateral lung and heart by means of 17.2% and 6% at 1.5 T, respectively. The transverse configuration exhibits a significant increase in tissue interface effects, which increased dose buildup in the entrance regions of the lateral and medial tangent beams to the planning target volume (PTV) and improved dose homogeneity within the PTV. The improved relative average homogeneity index for two patients to the PTV at magnetic field strength of 1.5 T with respect to no magnetic field case evaluated was 11.79% and 34.45% in the LRBP and TRBP geometries, respectively. In both geometries, the simulations show significant mean dose reductions in the contralateral breast and chest wall skin, respectively, by a mean of 16.6% and 24.9% at 0.5 T and 17.2% and 28.1% at 1.5 T in the transverse geometry, and 10.56% and 14.6% at 0.5 T and 11.3% and

  18. Basis of the quasi-steady plasma accelerator theory in the presence of a longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Kozlov, Andrey N.

    2008-04-01

    The analytic and numerical approaches to the investigation of the two-dimensional steady-state plasma flows are analyzed and compared with reference to a plasma accelerator channel in the presence of a longitudinal magnetic field. The present study continues a cycle of research into the plasma flows in the coaxial channels with the traditional azimuthal magnetic field. The additional longitudinal field opens new possibilities for controlling the dynamic processes and achieving the transonic flows. The research is based on the magnetohydrodynamic equations.

  19. Quasi-Static Magnetic Field Shielding Using Longitudinal Mu-Near-Zero Metamaterials

    PubMed Central

    Lipworth, Guy; Ensworth, Joshua; Seetharam, Kushal; Lee, Jae Seung; Schmalenberg, Paul; Nomura, Tsuyoshi; Reynolds, Matthew S.; Smith, David R.; Urzhumov, Yaroslav

    2015-01-01

    The control of quasi-static magnetic fields is of considerable interest in applications including the reduction of electromagnetic interference (EMI), wireless power transfer (WPT), and magnetic resonance imaging (MRI). The shielding of static or quasi-static magnetic fields is typically accomplished through the use of inherently magnetic materials with large magnetic permeability, such as ferrites, used sometimes in combination with metallic sheets and/or active field cancellation. Ferrite materials, however, can be expensive, heavy and brittle. Inspired by recent demonstrations of epsilon-, mu- and index-near-zero metamaterials, here we show how a longitudinal mu-near-zero (LMNZ) layer can serve as a strong frequency-selective reflector of magnetic fields when operating in the near-field region of dipole-like sources. Experimental measurements with a fabricated LMNZ sheet constructed from an artificial magnetic conductor – formed from non-magnetic, conducting, metamaterial elements – confirm that the artificial structure provides significantly improved shielding as compared with a commercially available ferrite of the same size. Furthermore, we design a structure to shield simultaneously at the fundamental and first harmonic frequencies. Such frequency-selective behavior can be potentially useful for shielding electromagnetic sources that may also generate higher order harmonics, while leaving the transmission of other frequencies unaffected. PMID:26234929

  20. Quasi-Static Magnetic Field Shielding Using Longitudinal Mu-Near-Zero Metamaterials

    NASA Astrophysics Data System (ADS)

    Lipworth, Guy; Ensworth, Joshua; Seetharam, Kushal; Lee, Jae Seung; Schmalenberg, Paul; Nomura, Tsuyoshi; Reynolds, Matthew S.; Smith, David R.; Urzhumov, Yaroslav

    2015-08-01

    The control of quasi-static magnetic fields is of considerable interest in applications including the reduction of electromagnetic interference (EMI), wireless power transfer (WPT), and magnetic resonance imaging (MRI). The shielding of static or quasi-static magnetic fields is typically accomplished through the use of inherently magnetic materials with large magnetic permeability, such as ferrites, used sometimes in combination with metallic sheets and/or active field cancellation. Ferrite materials, however, can be expensive, heavy and brittle. Inspired by recent demonstrations of epsilon-, mu- and index-near-zero metamaterials, here we show how a longitudinal mu-near-zero (LMNZ) layer can serve as a strong frequency-selective reflector of magnetic fields when operating in the near-field region of dipole-like sources. Experimental measurements with a fabricated LMNZ sheet constructed from an artificial magnetic conductor - formed from non-magnetic, conducting, metamaterial elements - confirm that the artificial structure provides significantly improved shielding as compared with a commercially available ferrite of the same size. Furthermore, we design a structure to shield simultaneously at the fundamental and first harmonic frequencies. Such frequency-selective behavior can be potentially useful for shielding electromagnetic sources that may also generate higher order harmonics, while leaving the transmission of other frequencies unaffected.

  1. Quasi-Static Magnetic Field Shielding Using Longitudinal Mu-Near-Zero Metamaterials.

    PubMed

    Lipworth, Guy; Ensworth, Joshua; Seetharam, Kushal; Lee, Jae Seung; Schmalenberg, Paul; Nomura, Tsuyoshi; Reynolds, Matthew S; Smith, David R; Urzhumov, Yaroslav

    2015-01-01

    The control of quasi-static magnetic fields is of considerable interest in applications including the reduction of electromagnetic interference (EMI), wireless power transfer (WPT), and magnetic resonance imaging (MRI). The shielding of static or quasi-static magnetic fields is typically accomplished through the use of inherently magnetic materials with large magnetic permeability, such as ferrites, used sometimes in combination with metallic sheets and/or active field cancellation. Ferrite materials, however, can be expensive, heavy and brittle. Inspired by recent demonstrations of epsilon-, mu- and index-near-zero metamaterials, here we show how a longitudinal mu-near-zero (LMNZ) layer can serve as a strong frequency-selective reflector of magnetic fields when operating in the near-field region of dipole-like sources. Experimental measurements with a fabricated LMNZ sheet constructed from an artificial magnetic conductor - formed from non-magnetic, conducting, metamaterial elements - confirm that the artificial structure provides significantly improved shielding as compared with a commercially available ferrite of the same size. Furthermore, we design a structure to shield simultaneously at the fundamental and first harmonic frequencies. Such frequency-selective behavior can be potentially useful for shielding electromagnetic sources that may also generate higher order harmonics, while leaving the transmission of other frequencies unaffected. PMID:26234929

  2. Baccalaureate and Beyond Longitudinal Study: 2000/01 Follow-Up Field Test Methodology Report. Working Paper Series.

    ERIC Educational Resources Information Center

    Biber, Melissa R.; Link, Michael W.; Riccobono, John A.; Siegel, Peter H.

    This report describes and evaluates the methods and procedures used for the field test of the Baccalaureate and Beyond Longitudinal Study (B&B:2000/01). The B&B:2000/01 field test included important changes from previous B&B surveys (conducted in 1994 and 1997) in its sample design and collection of data. The introductory chapter describes the…

  3. Generation of longitudinal current by a transverse electromagnetic field in classical and quantum plasmas

    SciTech Connect

    Latyshev, A. V. Yushkanov, A. A.

    2015-09-15

    A distribution function for collisionless plasma is derived from the Vlasov kinetic equation in the quadratic approximation with respect to the electromagnetic field. Formulas for calculation of the electric current at an arbitrary temperature (arbitrary degree of degeneration of the electron gas) are deduced. The case of small wavenumbers is considered. It is shown that nonlinearity leads to the generation of an electric current directed along the wave vector. This longitudinal current is orthogonal to the classical transverse current, well known in the linear theory. A distribution function for collisionless quantum plasma is derived from the kinetic equation with the Wigner integral in the quadratic approximation with respect to the vector potential. Formulas for calculation of the electric current at an arbitrary temperature are deduced. The case of small wavenumbers is considered. It is shown that, at small values of the wavenumber, the value of the longitudinal current for quantum plasma coincides with that for classical plasma. The dimensionless currents in quantum and classical plasmas are compared graphically.

  4. Finite-temperature spin dynamics near the quantum critical point of transverse field Ising chain with a small longitudinal field

    NASA Astrophysics Data System (ADS)

    Kormos, Márton; Wu, Jianda; Si, Qimiao

    2014-03-01

    When the transverse-field Ising chain at its quantum critical point is subjected to a small longitudinal field, the perturbed conformal field theory led to a field theory with an exotic E8 symmetry. Recent neutron scattering experiments have provided evidence for the lightest two particles in this E8 model in the quasi-1D Ising ferromagnet CoNb2O6. While the zero temperature dynamic of the model is well known, its finite-temperature counterpart has not yet been systematically studied. We study the low-frequency dynamical spin structure factor at finite temperatures using the form-factor method. We show that the dominant contribution to the spin dynamics comes from the channel between two lightest particles, and demonstrate how the spin dynamics differ from a diffusion form. Using these results, we determine the temperature dependence of the NMR relaxation rate. We suggest that, for CoNb2O6, measurements of the NMR relaxation rate provide a means to further test the applicability of the E8 model.

  5. Acoustic Longitudinal Field NIF Optic Feature Detection Map Using Time-Reversal & MUSIC

    SciTech Connect

    Lehman, S K

    2006-02-09

    We developed an ultrasonic longitudinal field time-reversal and MUltiple SIgnal Classification (MUSIC) based detection algorithm for identifying and mapping flaws in fused silica NIF optics. The algorithm requires a fully multistatic data set, that is one with multiple, independently operated, spatially diverse transducers, each transmitter of which, in succession, launches a pulse into the optic and the scattered signal measured and recorded at every receiver. We have successfully localized engineered ''defects'' larger than 1 mm in an optic. We confirmed detection and localization of 3 mm and 5 mm features in experimental data, and a 0.5 mm in simulated data with sufficiently high signal-to-noise ratio. We present the theory, experimental results, and simulated results.

  6. Transverse-longitudinal coherence function of a sound field for line-of-sight propagation in a turbulent atmosphere

    NASA Astrophysics Data System (ADS)

    Ostashev, Vladimir E.; Collier, Sandra L.; Keith Wilson, D.

    Using the narrow-angle and Markov approximations, a formula for the transverse-longitudinal coherence function of a sound field propagating in a turbulent atmosphere with temperature and wind velocity fluctuations is derived. This function, which applies to observation points that are arbitrarily located in space, generalizes the transverse coherence function (coherence when the observation points are in a plane perpendicular to the sound propagation path), which has been studied extensively. The new result is expressed in terms of the transverse coherence function and the extinction coefficient of the mean sound field. The transverse-longitudinal coherence function of a plane sound wave is then calculated and studied in detail for the Gaussian and von Kármán spectra of temperature and wind velocity fluctuations. It is shown, for relatively small propagation distances, that the magnitude of the coherence function decreases in the longitudinal direction but remains almost constant in the transverse direction. On the other hand, for moderate and large propagation distances, the magnitude of the coherence decreases faster in the transverse direction than in the longitudinal. For some parameters of the problem, the coherence function has relatively large local maxima and minima as the transverse and longitudinal coordinates are varied. With small modifications, many results obtained in the paper can be applied to studies of electromagnetic wave propagation in a turbulent atmosphere.

  7. Spacetimes with longitudinal and angular magnetic fields in third order Lovelock gravity

    SciTech Connect

    Dehghani, M. H.; Bostani, N.

    2007-04-15

    We obtain two new classes of magnetic solutions in third order Lovelock gravity. The first class of solutions yields an (n+1)-dimensional spacetime with a longitudinal magnetic field generated by a static source. We generalize this class of solutions to the case of spinning magnetic strings with one or more rotation parameters. These solutions have no curvature singularity and no horizons, but have a conic geometry. For the spinning string, when one or more rotation parameters are nonzero, the string has a net electric charge which is proportional to the magnitude of the rotation parameters, while the static string has no net electric charge. The second class of solutions yields a spacetime with an angular magnetic field. These solutions have no curvature singularity, no horizon, and no conical singularity. Although the second class of solutions may be made electrically charged by a boost transformation, the transformed solutions do not present new spacetimes. Finally, we use the counterterm method in third order Lovelock gravity and compute the conserved quantities of these spacetimes.

  8. Magnetic confinement of electron and photon radiotherapy dose: A Monte Carlo simulation with a nonuniform longitudinal magnetic field

    SciTech Connect

    Chen Yu; Bielajew, Alex F.; Litzenberg, Dale W.; Moran, Jean M.; Becchetti, Frederick D.

    2005-12-15

    It recently has been shown experimentally that the focusing provided by a longitudinal nonuniform high magnetic field can significantly improve electron beam dose profiles. This could permit precise targeting of tumors near critical areas and minimize the radiation dose to surrounding healthy tissue. The experimental results together with Monte Carlo simulations suggest that the magnetic confinement of electron radiotherapy beams may provide an alternative to proton or heavy ion radiation therapy in some cases. In the present work, the external magnetic field capability of the Monte Carlo code PENELOPE was utilized by providing a subroutine that modeled the actual field produced by the solenoid magnet used in the experimental studies. The magnetic field in our simulation covered the region from the vacuum exit window to the phantom including surrounding air. In a longitudinal nonuniform magnetic field, it is observed that the electron dose can be focused in both the transverse and longitudinal directions. The measured dose profiles of the electron beam are generally reproduced in the Monte Carlo simulations to within a few percent in the region of interest provided that the geometry and the energy of the incident electron beam are accurately known. Comparisons for the photon beam dose profiles with and without the magnetic field are also made. The experimental results are qualitatively reproduced in the simulation. Our simulation shows that the excessive dose at the beam entrance is due to the magnetic field trapping and focusing scattered secondary electrons that were produced in the air by the incident photon beam. The simulations also show that the electron dose profile can be manipulated by the appropriate control of the beam energy together with the strength and displacement of the longitudinal magnetic field.

  9. The Application of Intensive Longitudinal Methods to Investigate Change: Stimulating the Field of Applied Family Research.

    PubMed

    Bamberger, Katharine T

    2016-03-01

    The use of intensive longitudinal methods (ILM)-rapid in situ assessment at micro timescales-can be overlaid on RCTs and other study designs in applied family research. Particularly, when done as part of a multiple timescale design-in bursts over macro timescales-ILM can advance the study of the mechanisms and effects of family interventions and processes of family change. ILM confers measurement benefits in accurately assessing momentary and variable experiences and captures fine-grained dynamic pictures of time-ordered processes. Thus, ILM allows opportunities to investigate new research questions about intervention effects on within-subject (i.e., within-person, within-family) variability (i.e., dynamic constructs) and about the time-ordered change process that interventions induce in families and family members beginning with the first intervention session. This paper discusses the need and rationale for applying ILM to family intervention evaluation, new research questions that can be addressed with ILM, example research using ILM in the related fields of basic family research and the evaluation of individual-based interventions. Finally, the paper touches on practical challenges and considerations associated with ILM and points readers to resources for the application of ILM. PMID:26541560

  10. Longitudinal correlation properties of an optical field with broad angular and frequency spectra and their manifestation in interference microscopy

    SciTech Connect

    Lyakin, D V; Ryabukho, V P

    2013-10-31

    The results of theoretical and experimental studies of the longitudinal correlation properties of an optical field with broad angular and frequency spectra and manifestations of these properties in interference microscopy are presented. The joint and competitive influence of the angular and frequency spectra of the object-probing field on the longitudinal resolution and on the amplitude of the interference microscope signals from the interfaces between the media inside a multilayer object is demonstrated. The method of compensating the so-called defocusing effect that arises in the interference microscopy using objectives with a large numerical aperture is experimentally demonstrated, which consists in using as a light source in the interference microscope an illuminating interferometer with a frequency-broadband light source. This method of compensation may be used as the basis of simultaneous determination of geometric thickness and refractive index of media forming a multilayer object. (optical fields)

  11. A longitudinal study of auditory evoked field and language development in young children.

    PubMed

    Yoshimura, Yuko; Kikuchi, Mitsuru; Ueno, Sanae; Shitamichi, Kiyomi; Remijn, Gerard B; Hiraishi, Hirotoshi; Hasegawa, Chiaki; Furutani, Naoki; Oi, Manabu; Munesue, Toshio; Tsubokawa, Tsunehisa; Higashida, Haruhiro; Minabe, Yoshio

    2014-11-01

    The relationship between language development in early childhood and the maturation of brain functions related to the human voice remains unclear. Because the development of the auditory system likely correlates with language development in young children, we investigated the relationship between the auditory evoked field (AEF) and language development using non-invasive child-customized magnetoencephalography (MEG) in a longitudinal design. Twenty typically developing children were recruited (aged 36-75 months old at the first measurement). These children were re-investigated 11-25 months after the first measurement. The AEF component P1m was examined to investigate the developmental changes in each participant's neural brain response to vocal stimuli. In addition, we examined the relationships between brain responses and language performance. P1m peak amplitude in response to vocal stimuli significantly increased in both hemispheres in the second measurement compared to the first measurement. However, no differences were observed in P1m latency. Notably, our results reveal that children with greater increases in P1m amplitude in the left hemisphere performed better on linguistic tests. Thus, our results indicate that P1m evoked by vocal stimuli is a neurophysiological marker for language development in young children. Additionally, MEG is a technique that can be used to investigate the maturation of the auditory cortex based on auditory evoked fields in young children. This study is the first to demonstrate a significant relationship between the development of the auditory processing system and the development of language abilities in young children. PMID:25067819

  12. Mixed-mode toughness of human cortical bone containing a longitudinal crack in far-field compression.

    PubMed

    Olvera, Diana; Zimmermann, Elizabeth A; Ritchie, Robert O

    2012-01-01

    Bone is generally loaded under multiaxial conditions in vivo; as it invariably contains microcracks, this leads to complex mixed-mode stress-states involving combinations of tension, compression and shear. In previous work on the mixed-mode loading of human cortical bone (using an asymmetric bend test geometry), we found that the bone toughness was lower when loaded in far-field shear than in tension (opposite to the trend in most brittle materials), although only for the transverse orientation. This is a consequence of the competition between preferred mechanical vs. microstructural crack-path directions, the former dictated by the direction of the maximum mechanical "driving force" (which changes with the mode-mixity), and the latter by the "weakest" microstructural path (which in human bone is along the osteonal interfaces or cement lines). As most microcracks are oriented longitudinally, we investigate here the corresponding mixed-mode toughness of human cortical bone in the longitudinal (proximal-distal) orientation using a "double cleavage drilled compression" test geometry, which provides a physiologically-relevant loading condition for bone in that it characterizes the toughness of a longitudinal crack loaded in far-field compression. In contrast to the transverse toughness, results show that the longitudinal toughness, measured using the strain-energy release rate, is significantly higher in shear (mode II) than in tension (mode I). This is consistent, however, with the individual criteria of preferred mechanical vs. microstructural crack paths being commensurate in this orientation. PMID:22115793

  13. Two-fluid magnetohydrodynamic model of plasma flows in a quasi-steady-state accelerator with a longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Kozlov, A. N.

    2009-05-01

    This paper reports the results of numerical studies of axisymmetric flows in a coaxial plasma accelerator in the presence of a longitudinal magnetic field. The calculations were performed using a two-dimensional two-fluid magnetohydrodynamic model taking into account the Hall effect and the conductivity tensor of the medium. The numerical experiments confirmed the main features of the plasmadynamic processes found previously using analytical and one-fluid models and made it possible to study plasma flows near the electrodes.

  14. Soft X-Ray Stimulated Bremsstrahlung In Traveling Longitudinal Electric Wake-Fields Of Two-Beam Pill-Box Cavities

    NASA Astrophysics Data System (ADS)

    Kim, S. H.; Chen, K. W.; Wilhelm, H. E.

    1986-01-01

    The amplification of laser light in a free electron laser (FEL) due to stimulated bremsstrahlung in a traveling longitudinal undulating electric field is derived. It is shown that this FEL provides sufficient gain to be used as a coherent radiation source down to the soft x-ray regime. It is suggested that, among other possibilities, the wake-field produced in a two-beam elliptical or annular pill-box cavity is suitable for the required traveling longitudinal undulating electric field.

  15. Soft X-ray stimulated bremsstrahlung in traveling longitudinal electric wake-fields of two-beam pill-box cavities

    NASA Astrophysics Data System (ADS)

    Kim, S. H.; Chen, K. W.; Wilhelm, H. E.

    The amplification of laser light in a free electron laser (FEL) due to stimulated bremsstrahlung in a traveling longitudinal undulating electric field is derived. It is shown that this FEL provides sufficient gain to be used as a coherent radiation source down to the soft X-ray regime. It is suggested that, among other possibilities, the wake-field produced in a two-beam elliptical or annular pill-box cavity is suitable for the required traveling longitudinal undulating electric field.

  16. Electron contamination modeling and skin dose in 6 MV longitudinal field MRIgRT: Impact of the MRI and MRI fringe field

    SciTech Connect

    Oborn, B. M.; Metcalfe, P. E.; Butson, M. J.; Rosenfeld, A. B.; Keall, P. J.

    2012-02-15

    Purpose: In recent times, longitudinal field MRI-linac systems have been proposed for 6 MV MRI-guided radiotherapy (MRIgRT). The magnetic field is parallel with the beam axis and so will alter the transport properties of any electron contamination particles. The purpose of this work is to provide a first investigation into the potential effects of the MR and fringe magnetic fields on the electron contamination as it is transported toward a phantom, in turn, providing an estimate of the expected patient skin dose changes in such a modality. Methods: Geant4 Monte Carlo simulations of a water phantom exposed to a 6 MV x-ray beam were performed. Longitudinal magnetic fields of strengths between 0 and 3 T were applied to a 30 x 30 x 20 cm{sup 3} phantom. Surrounding the phantom there is a region where the magnetic field is at full MRI strength, consistent with clinical MRI systems. Beyond this the fringe magnetic field entering the collimation system is also modeled. The MRI-coil thickness, fringe field properties, and isocentric distance are varied and investigated. Beam field sizes of 5 x 5, 10 x 10, 15 x 15 and 20 x 20 cm{sup 2} were simulated. Central axis dose, 2D virtual entry skin dose films, and 70 {mu}m skin depth doses were calculated using high resolution scoring voxels. Results: In the presence of a longitudinal magnetic field, electron contamination from the linear accelerator is encouraged to travel almost directly toward the patient surface with minimal lateral spread. This results in a concentration of electron contamination within the x-ray beam outline. This concentration is particularly encouraged if the fringe field encompasses the collimation system. Skin dose increases of up to 1000% were observed for certain configurations and increases above Dmax were common. In nonmagnetically shielded cases, electron contamination generated from the jaw faces and air column is trapped and propagated almost directly to the phantom entry region, giving rise to

  17. Education Longitudinal Study of 2002 (ELS:2002/12) Third Follow-up Field Test Report. Working Paper Series. NCES 2012-03

    ERIC Educational Resources Information Center

    Ingels, Steven J.; Pratt, Daniel J.; Jewell, Donna M.; Mattox, Tiffany; Dalton, Ben; Rosen, Jeffrey; Lauff, Erich; Hill, Jason

    2012-01-01

    This report describes the methodologies and results of the third follow-up Education Longitudinal Study of 2002 (ELS:2002/12) field test which was conducted in the summer of 2011. The field test report is divided into six chapters: (1) Introduction; (2) Field Test Survey Design and Preparation; (3) Data Collection Procedures and Results; (4) Field…

  18. Longitudinal field characterization of converging terahertz vortices with linear and circular polarizations.

    PubMed

    Wang, Xinke; Shi, Jing; Sun, Wenfeng; Feng, Shengfei; Han, Peng; Ye, Jiasheng; Zhang, Yan

    2016-04-01

    Linearly and circularly polarized terahertz (THz) vortex beams are generated by adopting a THz quarter wave plate and spiral phase plates with topological charges 1 and 2. Taking advantage of a THz digital holographic imaging system, longitudinal components of THz vortices with different polarizations and topological charges are coherently measured and systemically analyzed in a focusing condition. The application potential of circularly polarized THz vortex beams in microscopy is experimentally demonstrated and the transformation between the spin angular momentums and orbital angular momentums of THz waves is also checked. Modified Richards-Wolf vector diffraction integration equations are applied to successfully simulate experimental phenomena. PMID:27137010

  19. Conductance and resonant tunneling in multi-channel double barrier structures under transverse and longitudinal electric fields

    SciTech Connect

    Pereyra, Pedro Mendoza-Figueroa, M. G.

    2015-03-21

    Transport properties of electrons through biased double barrier semiconductor structures with finite transverse width w{sub y}, in the presence of a channel-mixing transverse electric field E{sub T} (along the y-axis), were studied. We solve the multichannel Schrödinger equation using the transfer matrix method and transport properties, like the conductance G and the transmission coefficients T{sub ij} have been evaluated as functions of the electrons' energy E and the transverse and longitudinal (bias) electric forces, f{sub T} and f{sub b}. We show that peak-suppression effects appear, due to the applied bias. Similarly, coherent interference of wave-guide states induced by the transverse field is obtained. We show also that the coherent interference of resonant wave-guide states gives rise to resonant conductance, which can be tuned to produce broad resonant peaks, implying operation frequencies of the order of 10 THz or larger.

  20. Effect of longitudinal density structure on a straight magnetic field modelling coronal arcade oscillations

    NASA Astrophysics Data System (ADS)

    Donnelly, G. R.; Díaz, A. J.; Roberts, B.

    2007-09-01

    Aims:Motivated by recent observations of oscillations in coronal arcades, we investigate analytically the influence of longitudinal structuring on the modes of oscillation of a straight coronal loop arcade. As a first step towards more complicated models, we use a simple structure to obtain analytical solutions. Methods: A partial differential equation is derived for the total pressure perturbation of the fast modes in a zero beta plasma and it is solved analytically. We first recover the results for a homogeneous structure, and then study an equilibrium with an exponentially structured density profile, solving it in terms of Bessel functions of non-integer order and exponential argument, thus obtaining a dispersion relation. The properties of this dispersion relation are discussed and some limits studied, leading to analytical approximations to the eigenfrequencies. Results: The introduction of longitudinal structuring results in a modification to the oscillatory frequencies of the modes of oscillation in such structures when compared with the uniform case. Regarding the oscillatory periods P_n, n=1,2, dots, the period ratios P_1/2P2 and P_1/3P3 are both shifted from unity. Other properties described in structured coronal loops are also found in an arcade: the occurrence of avoided crossings in the dispersion diagram and the displacement of the extrema towards the footpoints in the spatial structure of the eigenmodes. Conclusions: We show analytically for simple arcade modes that the shift in the fundamental period proves to be small, but the ratio P_1/2P2 depends strongly on the density structure. Moreover, transversal propagation also shifts the ratio P_1/2P2 from unity, so it can be used in the coronal seismology of arcades in which transversal propagation is present. We use the currently available observational data to illustrate this application. Appendix A is only available in electronic form at http://www.aanda.org

  1. Improved longitudinal gray and white matter atrophy assessment via application of a 4-dimensional hidden Markov random field model.

    PubMed

    Dwyer, Michael G; Bergsland, Niels; Zivadinov, Robert

    2014-04-15

    SIENA and similar techniques have demonstrated the utility of performing "direct" measurements as opposed to post-hoc comparison of cross-sectional data for the measurement of whole brain (WB) atrophy over time. However, gray matter (GM) and white matter (WM) atrophy are now widely recognized as important components of neurological disease progression, and are being actively evaluated as secondary endpoints in clinical trials. Direct measures of GM/WM change with advantages similar to SIENA have been lacking. We created a robust and easily-implemented method for direct longitudinal analysis of GM/WM atrophy, SIENAX multi-time-point (SIENAX-MTP). We built on the basic halfway-registration and mask composition components of SIENA to improve the raw output of FMRIB's FAST tissue segmentation tool. In addition, we created LFAST, a modified version of FAST incorporating a 4th dimension in its hidden Markov random field model in order to directly represent time. The method was validated by scan-rescan, simulation, comparison with SIENA, and two clinical effect size comparisons. All validation approaches demonstrated improved longitudinal precision with the proposed SIENAX-MTP method compared to SIENAX. For GM, simulation showed better correlation with experimental volume changes (r=0.992 vs. 0.941), scan-rescan showed lower standard deviations (3.8% vs. 8.4%), correlation with SIENA was more robust (r=0.70 vs. 0.53), and effect sizes were improved by up to 68%. Statistical power estimates indicated a potential drop of 55% in the number of subjects required to detect the same treatment effect with SIENAX-MTP vs. SIENAX. The proposed direct GM/WM method significantly improves on the standard SIENAX technique by trading a small amount of bias for a large reduction in variance, and may provide more precise data and additional statistical power in longitudinal studies. PMID:24333394

  2. High School Longitudinal Study of 2009 (HSLS:09) Base-Year Field Test Report. Working Paper Series. NCES 2011-01

    ERIC Educational Resources Information Center

    Ingels, Steven J.; Herget, Deborah; Pratt, Daniel J.; Dever, Jill; Copello, Elizabeth; Leinwand, Steve

    2010-01-01

    This report examines the results of the field test for the base year of the High School Longitudinal Study of 2009 (HSLS:09). The general purposes of the field test were, in anticipation of the base-year full-scale effort, to test instruments, forms, and procedures; to experiment with different approaches to questionnaire content and survey…

  3. Slow light, open-cavity formation, and large longitudinal electric field on a slab waveguide made of indefinite permittivity metamaterials

    NASA Astrophysics Data System (ADS)

    Lu, W. T.; Sridhar, S.

    2010-07-01

    The optical properties of slab waveguides made of indefinite permittivity (ɛ) materials (IEMs) are considered. In this medium, the real part of the transverse permittivity is negative while that of the longitudinal permittivity is positive. At any given frequency, the IEM waveguide supports an infinite number of transverse magnetic (TM) eigenmodes. For a slab waveguide with a fixed thickness, at most only one TM mode is forward wave. The remainder are backward waves which can have a very large phase index. At a critical thickness, the waveguide supports degenerate forward- and backward-wave modes with zero group velocity if loss is absent. Above the critical thickness, the waveguide supports complex-conjugate decay modes instead of propagating modes. The presence of loss in IEMs will lift the TM mode degeneracy, resulting in modes with finite group velocity. A feasible realization is proposed. The performance of the IEM waveguide is analyzed and possible applications are discussed, which are supported by numerical calculations. These slab waveguides can be used to make optical delay lines in optical buffers to slow down and trap light, to form open cavities, to generate strong longitudinal electric fields, and as phase shifters in optical integrated circuits. Although the presence of loss will hinder these applications, gain can be introduced to compensate the loss and enhance the performance.

  4. Assessing the playing field: a prospective longitudinal study of internet sports gambling behavior.

    PubMed

    LaBrie, Richard A; LaPlante, Debi A; Nelson, Sarah E; Schumann, Anja; Shaffer, Howard J

    2007-09-01

    Internet gambling is growing rapidly, as is concern about its possible effect on the public's health. This paper reports the results of the first prospective longitudinal study of actual Internet sports gambling behavior during eight study months. Data include recorded fixed-odds bets on the outcome of sporting contests and live-action bets on the outcome of events within contests for 40,499 Internet sports gambling service subscribers who enrolled during February 2005. We tracked the following primary gambling behaviors: daily totals of the number of bets made, money bet, and money won. We transformed these variables into measures of gambling involvement. We analyzed behavior for both fixed-odds and live-action bets. The median betting behavior of the 39,719 fixed-odds bettors was to place 2.5 bets of 4 euro (approximately $5.3 US) every fourth day during the median 4 months from first to last bet. This typical pattern incurred a loss of 29% of the amount wagered. The median betting behavior of the 24,794 live-action bettors was to place 2.8 wagers of 4 euro every fourth day during the median duration of 6 weeks at a loss of 18% of the amount wagered. We also examined the behavior of empirically determined groups of heavily involved bettors whose activity exceeded that of 99% of the sample. PMID:17574522

  5. Metabolic T1 dynamics and longitudinal relaxation enhancement in vivo at ultrahigh magnetic fields on ischemia.

    PubMed

    Shemesh, Noam; Rosenberg, Jens T; Dumez, Jean-Nicolas; Grant, Samuel C; Frydman, Lucio

    2014-11-01

    Interruptions in cerebral blood flow may lead to devastating neural outcomes. Magnetic resonance has a central role in diagnosing and monitoring these insufficiencies, as well as in understanding their underlying metabolic consequences. Magnetic resonance spectroscopy (MRS) in particular can probe ischemia via the signatures of endogenous metabolites including lactic acid (Lac), N-acetylaspartate, creatine (Cre), and cholines. Typically, MRS reports on these metabolites' concentrations. This study focuses on establishing the potential occurrence of in vivo longitudinal relaxation enhancement (LRE) effects-a phenomenon involving a reduction of the apparent T1 with selective bandwidth excitations- in a rat stroke model at 21.1 T. Statistically significant reductions in Cre's apparent T1s were observed at all the examined post-ischemia time points for both ipsi- and contralateral hemispheres, thereby establishing the existence of LREs for this metabolite in vivo. Ischemia-dependent LRE trends were also noted for Lac in the ipsilateral hemisphere only 24 hours after ischemia. Metabolic T1s were also found to vary significantly as a function of post-stroke recovery time, with the most remarkable and rapid changes observed for Lac T1s. The potential of such measurements to understand stroke at a molecular level and assist in its diagnosis, is discussed. PMID:25204392

  6. Metabolic T1 dynamics and longitudinal relaxation enhancement in vivo at ultrahigh magnetic fields on ischemia

    PubMed Central

    Shemesh, Noam; Rosenberg, Jens T; Dumez, Jean-Nicolas; Grant, Samuel C; Frydman, Lucio

    2014-01-01

    Interruptions in cerebral blood flow may lead to devastating neural outcomes. Magnetic resonance has a central role in diagnosing and monitoring these insufficiencies, as well as in understanding their underlying metabolic consequences. Magnetic resonance spectroscopy (MRS) in particular can probe ischemia via the signatures of endogenous metabolites including lactic acid (Lac), N-acetylaspartate, creatine (Cre), and cholines. Typically, MRS reports on these metabolites' concentrations. This study focuses on establishing the potential occurrence of in vivo longitudinal relaxation enhancement (LRE) effects—a phenomenon involving a reduction of the apparent T1 with selective bandwidth excitations— in a rat stroke model at 21.1 T. Statistically significant reductions in Cre's apparent T1s were observed at all the examined post-ischemia time points for both ipsi- and contralateral hemispheres, thereby establishing the existence of LREs for this metabolite in vivo. Ischemia-dependent LRE trends were also noted for Lac in the ipsilateral hemisphere only 24 hours after ischemia. Metabolic T1s were also found to vary significantly as a function of post-stroke recovery time, with the most remarkable and rapid changes observed for Lac T1s. The potential of such measurements to understand stroke at a molecular level and assist in its diagnosis, is discussed. PMID:25204392

  7. Influence of Frequency and Induction of Longitudinal Magnetic Field on The Electrode Metal Loss and its Spattering During MAG-Welding

    NASA Astrophysics Data System (ADS)

    Nosov, D. G.; Peremitko, V. V.

    2015-09-01

    It is possible to increase the MAG-welding efficiency by controlling the electrode metal mass transfer at the reduction of discharge coefficient on spattering by influence of longitudinal magnetic field on the arc. The paper identifies a range of longitudinal magnetic field frequencies and induction which provide the discharge coefficient reduction of the electrode metal; it has also been found the characteristics of their mutual influence on electrode metal mass transfer process; mathematical models correlating the frequency and induction of longitudinal magnetic field length with loss coefficient of electrode metal on spattering are presented; technological recommendations, the implementation of which will allow to improve the efficiency of MAG-welding in industrial environments, are given.

  8. Monte Carlo study of internal energy and specific heat of a nano-graphene bilayer in a longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Luo, Xiao-hong; Wang, Wei; Chen, Dong-dong; Xu, Si-yuan

    2016-06-01

    The thermodynamic properties of a nano-graphene bilayer, consisting of the upper layer A of spin-3/2 with antiferromagnetic intralayer exchange coupling and the bottom layer B of spin-5/2 with ferromagnetic intralayer exchange coupling, have been studied by the use of Monte Carlo simulation. We find a number of characteristic phenomena. The effects of the exchange coupling, the single-ion anisotropy and the longitudinal magnetic field on the internal energy, the specific heat and the blocking temperature of the mixed-spin bilayer system have been investigated in detail. The internal energy and the specific heat profiles are clarified. In particular, we have found that the specific heat curve may show two peaks phenomenon for appropriate values of the system parameters.

  9. Ontogeny of spatial discrimination in mice: a longitudinal analysis in the modified open-field with objects.

    PubMed

    Ricceri, L; Colozza, C; Calamandrei, G

    2000-09-01

    The present longitudinal study investigated the emergence of spatial discrimination and reaction to novelty in CD-1 mice, using a modified open-field test with four objects, a test in which responses to both spatial rearrangement of familiar objects and object novelty are assessed. Male and female mice were tested on postnatal days (pnd) 18, 28, 46 and 90. Locomotor activity was highest on pnd 90, whereas time spent on objects before rearrangement was highest on pnd 46. Eighteen-day old mice were unable to detect both object rearrangement and object novelty, suggesting immaturity in processing spatial information. On days 28 and 46 mice showed a clear response to object novelty, actively exploring the unfamiliar object placed in the arena, while at these ages object displacement elicited a generalized increase of exploration, not directed towards the displaced objects. A clear and selective response to object displacement emerged only at adulthood (day 90). PMID:10954836

  10. Promotion of solar water disinfection: comparing the effectiveness of different strategies in a longitudinal field study in Bolivia.

    PubMed

    Tamas, Andrea; Tobias, Robert; Mosler, Hans-Joachim

    2009-12-01

    Solar water disinfection (SODIS) is a simple method designed to treat microbiologically contaminated drinking water at the household level. This study focused on the effective promotion of the SODIS method using various strategies. In a longitudinal field study, we compared 2 interpersonal strategies (promoters and opinion leaders) and a centralized strategy (health fair) with a control group. Indicators of effectiveness were SODIS knowledge, SODIS adoption rate, and potential reach. The results suggest that use of promoters is the most successful strategy in terms of reaching people and changing their behavior toward SODIS use. The opinion leaders-although less effective-show some potential to stimulate communication among people about SODIS. Only the health fair did not have a big impact on behavior. Further discussion includes the costs of the various promotional activities, limitations, and recommendations for future projects. PMID:20183380

  11. Perceived mathematical ability under challenge: a longitudinal perspective on sex segregation among STEM degree fields

    PubMed Central

    Nix, Samantha; Perez-Felkner, Lara; Thomas, Kirby

    2015-01-01

    Students' perceptions of their mathematics ability vary by gender and seem to influence science, technology, engineering, and mathematics (STEM) degree choice. Related, students' perceptions during academic difficulty are increasingly studied in educational psychology, suggesting a link between such perceptions and task persistence. Despite interest in examining the gender disparities in STEM, these concepts have not been considered in tandem. In this manuscript, we investigate how perceived ability under challenge—in particular in mathematics domains—influences entry into the most sex-segregated and mathematics-intensive undergraduate degrees: physics, engineering, mathematics, and computer science (PEMC). Using nationally representative Education Longitudinal Study of 2002 (ELS) data, we estimate the influence of perceived ability under challenging conditions on advanced high school science course taking, selection of an intended STEM major, and specific major type 2 years after high school. Demonstrating the importance of specificity when discussing how gender influences STEM career pathways, the intersecting effects of gender and perceived ability under mathematics challenge were distinct for each scientific major category. Perceived ability under challenge in secondary school varied by gender, and was highly predictive of selecting PEMC and health sciences majors. Notably, women's 12th grade perceptions of their ability under mathematics challenge increased their probability of selecting PEMC majors over and above biology. In addition, gender moderated the effect of growth mindset on students' selection of health science majors. Perceptions of ability under challenge in general and verbal domains also influenced retention in and declaration of certain STEM majors. The implications of these results are discussed, with particular attention to access to advanced scientific coursework in high school and interventions aimed at enhancing young women

  12. Perceived mathematical ability under challenge: a longitudinal perspective on sex segregation among STEM degree fields.

    PubMed

    Nix, Samantha; Perez-Felkner, Lara; Thomas, Kirby

    2015-01-01

    Students' perceptions of their mathematics ability vary by gender and seem to influence science, technology, engineering, and mathematics (STEM) degree choice. Related, students' perceptions during academic difficulty are increasingly studied in educational psychology, suggesting a link between such perceptions and task persistence. Despite interest in examining the gender disparities in STEM, these concepts have not been considered in tandem. In this manuscript, we investigate how perceived ability under challenge-in particular in mathematics domains-influences entry into the most sex-segregated and mathematics-intensive undergraduate degrees: physics, engineering, mathematics, and computer science (PEMC). Using nationally representative Education Longitudinal Study of 2002 (ELS) data, we estimate the influence of perceived ability under challenging conditions on advanced high school science course taking, selection of an intended STEM major, and specific major type 2 years after high school. Demonstrating the importance of specificity when discussing how gender influences STEM career pathways, the intersecting effects of gender and perceived ability under mathematics challenge were distinct for each scientific major category. Perceived ability under challenge in secondary school varied by gender, and was highly predictive of selecting PEMC and health sciences majors. Notably, women's 12th grade perceptions of their ability under mathematics challenge increased their probability of selecting PEMC majors over and above biology. In addition, gender moderated the effect of growth mindset on students' selection of health science majors. Perceptions of ability under challenge in general and verbal domains also influenced retention in and declaration of certain STEM majors. The implications of these results are discussed, with particular attention to access to advanced scientific coursework in high school and interventions aimed at enhancing young women's perceptions of

  13. Mean-field thalamocortical modeling of longitudinal EEG acquired during intensive meditation training.

    PubMed

    Saggar, Manish; Zanesco, Anthony P; King, Brandon G; Bridwell, David A; MacLean, Katherine A; Aichele, Stephen R; Jacobs, Tonya L; Wallace, B Alan; Saron, Clifford D; Miikkulainen, Risto

    2015-07-01

    Meditation training has been shown to enhance attention and improve emotion regulation. However, the brain processes associated with such training are poorly understood and a computational modeling framework is lacking. Modeling approaches that can realistically simulate neurophysiological data while conforming to basic anatomical and physiological constraints can provide a unique opportunity to generate concrete and testable hypotheses about the mechanisms supporting complex cognitive tasks such as meditation. Here we applied the mean-field computational modeling approach using the scalp-recorded electroencephalogram (EEG) collected at three assessment points from meditating participants during two separate 3-month-long shamatha meditation retreats. We modeled cortical, corticothalamic, and intrathalamic interactions to generate a simulation of EEG signals recorded across the scalp. We also present two novel extensions to the mean-field approach that allow for: (a) non-parametric analysis of changes in model parameter values across all channels and assessments; and (b) examination of variation in modeled thalamic reticular nucleus (TRN) connectivity over the retreat period. After successfully fitting whole-brain EEG data across three assessment points within each retreat, two model parameters were found to replicably change across both meditation retreats. First, after training, we observed an increased temporal delay between modeled cortical and thalamic cells. This increase provides a putative neural mechanism for a previously observed reduction in individual alpha frequency in these same participants. Second, we found decreased inhibitory connection strength between the TRN and secondary relay nuclei (SRN) of the modeled thalamus after training. This reduction in inhibitory strength was found to be associated with increased dynamical stability of the model. Altogether, this paper presents the first computational approach, taking core aspects of physiology and

  14. Characterization of argon direct-current glow discharge with a longitudinal electric field applied at ambient air

    PubMed Central

    Jiang, Weiman; Tang, Jie; Wang, Yishan; Zhao, Wei; Duan, Yixiang

    2014-01-01

    A direct-current-driven plasma jet is developed by applying a longitudinal electric field on the flowing argon at ambient air. This plasma shows a torch shape with its cross-section increased from the anode to the cathode. Comparison with its counterparts indicates that the gas flow plays a key role in variation of the plasma structure and contributes much to enlarging the plasma volume. It is also found that the circular hollow metal base promotes generation of plasma with a high-power volume density in a limited space. The optical emission spectroscopy (OES) diagnosis indicates that the plasma comprises many reactive species, such as OH, O, excited N2, and Ar metastables. Examination of the rotational and vibrational temperature indicates that the plasma is under nonequilibrium condition and the excited species OH(A 2Σ+), O(5P), and N2(C 3Πu) are partly generated by energy transfer from argon metastables. The spatially resolved OES of plasma reveals that the negative glow, Faraday dark space, and positive column are distributed across the gas gap. The absence of the anode glow is attributed to the fact that many electrons in the vicinity of the anode follow ions into the positive column due to the ambipolar diffusion in the flowing gas. PMID:25205176

  15. Characterization of argon direct-current glow discharge with a longitudinal electric field applied at ambient air.

    PubMed

    Jiang, Weiman; Tang, Jie; Wang, Yishan; Zhao, Wei; Duan, Yixiang

    2014-01-01

    A direct-current-driven plasma jet is developed by applying a longitudinal electric field on the flowing argon at ambient air. This plasma shows a torch shape with its cross-section increased from the anode to the cathode. Comparison with its counterparts indicates that the gas flow plays a key role in variation of the plasma structure and contributes much to enlarging the plasma volume. It is also found that the circular hollow metal base promotes generation of plasma with a high-power volume density in a limited space. The optical emission spectroscopy (OES) diagnosis indicates that the plasma comprises many reactive species, such as OH, O, excited N2, and Ar metastables. Examination of the rotational and vibrational temperature indicates that the plasma is under nonequilibrium condition and the excited species OH(A (2)Σ(+)), O((5)P), and N2(C (3)Πu) are partly generated by energy transfer from argon metastables. The spatially resolved OES of plasma reveals that the negative glow, Faraday dark space, and positive column are distributed across the gas gap. The absence of the anode glow is attributed to the fact that many electrons in the vicinity of the anode follow ions into the positive column due to the ambipolar diffusion in the flowing gas. PMID:25205176

  16. Application of an Extended Parabolic Equation to the Calculation of the Mean Field and the Transverse and Longitudinal Mutual Coherence Functions Within Atmospheric Turbulence

    NASA Technical Reports Server (NTRS)

    Manning, Robert M.

    2005-01-01

    Solutions are derived for the generalized mutual coherence function (MCF), i.e., the second order moment, of a random wave field propagating through a random medium within the context of the extended parabolic equation. Here, "generalized" connotes the consideration of both the transverse as well as the longitudinal second order moments (with respect to the direction of propagation). Such solutions will afford a comparison between the results of the parabolic equation within the pararaxial approximation and those of the wide-angle extended theory. To this end, a statistical operator method is developed which gives a general equation for an arbitrary spatial statistical moment of the wave field. The generality of the operator method allows one to obtain an expression for the second order field moment in the direction longitudinal to the direction of propagation. Analytical solutions to these equations are derived for the Kolmogorov and Tatarskii spectra of atmospheric permittivity fluctuations within the Markov approximation.

  17. A field-based technique for the longitudinal profiling of ultrarelativistic electron or positron bunches down to lengths of {le}10 microns

    SciTech Connect

    Tatchyn, R.

    1993-05-01

    Present and future generations of particle accelerating and storage machines are expected to develop ever-decreasing electron/positron bunch lengths, down to 100 {mu} and beyond. In this paper a method for measuring the longitudinal profiles of ultrashort (1000 {mu} {approx} 10 {mu}) bunches, based on: (1) the extreme field compaction attained by ultrarelativistic particles, and (2) the reduction of the group velocity of a visible light pulse in a suitably-chosen dielectric medium, is outline.

  18. Longitudinal assessment of occupational exposures to the organophosphorous insecticides chlorpyrifos and profenofos in Egyptian cotton field workers.

    PubMed

    Singleton, Steven T; Lein, Pamela J; Dadson, Oswald A; McGarrigle, Barbara P; Farahat, Fayssal M; Farahat, Taghreed; Bonner, Matthew R; Fenske, Richard A; Galvin, Kit; Lasarev, Michael R; Anger, W Kent; Rohlman, Diane S; Olson, James R

    2015-03-01

    Chlorpyrifos (CPF) and profenofos (PFF) are organophosphorus (OP) insecticides that are applied seasonally in Egypt to cotton fields. Urinary trichloro-2-pyridinol (TCPy), a specific CPF metabolite, and 4-bromo-2-chlorophenol (BCP), a specific PFF metabolite, are biomarkers of exposure, while inhibition of blood butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) activities are effect biomarkers that may be associated with neurotoxicity. Urinary TCPy and BCP and blood BChE and AChE activities were measured in 37 adult Egyptian Ministry of Agriculture workers during and after 9-17 consecutive days of CPF application followed by an application of PFF (9-11 days), and a second CPF application (5 days) in 2008. During the OP applications, urinary TCPy and BCP levels were significantly higher than baseline levels, remained elevated following the application periods, and were associated with an exposure related inhibition of blood BChE and AChE. Analysis of blood AChE levels before and after the PFF application period suggests that individual workers with peak BCP levels greater than 1000 μg/g creatinine exhibited further inhibition of blood AChE with PFF application, demonstrating that PFF exposure had a negative impact on AChE activity in this highly exposed worker population. While large interindividual differences in exposure were observed throughout this longitudinal study (peak urinary BCP and peak TCPy levels for individuals ranging from 13.4 to 8052 and 16.4 to 30,107 μg/g creatinine, respectively), these urinary biomarkers were highly correlated within workers (r=0.75, p<0.001). This suggests that the relative exposures to CPF and PFF were highly correlated for a given worker. The variable exposures between job classification and work site suggest that job title and work location should not be used as the sole basis for categorizing OP exposures when assessing neurobehavioral and other health outcomes in Egyptian cotton field workers. Together, these

  19. Longitudinal assessment of occupational exposures to the organophosphorous insecticides chlorpyrifos and profenofos in Egyptian cotton field workers

    PubMed Central

    Singleton, Steven T.; Lein, Pamela J.; Dadson, Oswald A.; McGarrigle, Barbara P.; Farahat, Fayssal M.; Farahat, Taghreed; Bonner, Matthew R.; Fenske, Richard A.; Galvin, Kit; Lasarev, Michael R.; Anger, W. Kent; Rohlman, Diane S.; Olson, James R.

    2014-01-01

    Chlorpyrifos (CPF) and profenofos (PFF) are organophosphorus (OP) insecticides that are applied seasonally in Egypt to cotton fields. Urinary trichloro-2-pyridinol (TCPy), a specific CPF metabolite, and 4-bromo-2-chlorophenol (BCP), a specific PFF metabolite, are biomarkers of exposure, while inhibition of blood butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) activities are effect biomarkers that may be associated with neurotoxicity. Urinary TCPy and BCP and blood BChE and AChE activities were measured in 37 adult Egyptian Ministry of Agriculture workers during and after 9-17 consecutive days of CPF application followed by an application of PFF (9-11 days), and a second CPF application (5 days) in 2008. During the OP applications, urinary TCPy and BCP levels were significantly higher than baseline levels, remained elevated following the application periods, and were associated with an exposure related inhibition of blood BChE and AChE. Analysis of blood AChE levels before and after the PFF application period suggests that individual workers with peak BCP levels greater than 1000 μg/g creatinine exhibited further inhibition of blood AChE with PFF application, demonstrating that PFF exposure had a negative impact on AChE activity in this highly exposed worker population. While large interindividual differences in exposure were observed throughout this longitudinal study (peak urinary BCP and peak TCPy levels for individuals ranging from 13.4 to 8,052 and 16.4 to 30,107 μg/g creatinine, respectively), these urinary biomarkers were highly correlated within workers (r= 0.75, p<0.001). This suggests that the relative exposures to CPF and PFF were highly correlated for a given worker. The variable exposures between job classification and work site suggest that job title and work location should not be used as the sole basis for categorizing OP exposures when assessing neurobehavioral and other health outcomes in Egyptian cotton field workers. Together

  20. Effect of Longitudinal Optical Phonon--Plasmon Coupling on the Transient Self-Consistent Field in GaAs p--i--n Diodes

    NASA Astrophysics Data System (ADS)

    Thao, Dinh Nhu; The, Nguyen Phuoc

    2013-10-01

    The effect of longitudinal optical (LO) phonon--coherent plasmon coupling on the transient self-consistent field and then on frequency spectra of collective oscillations in GaAs p--i--n diodes without a biased field is investigated by the self-consistent ensemble Monte Carlo method. The frequency spectra of collective oscillations in the diodes show that there are two new strong peaks in the terahertz range when the coupling is taken into account. These peaks replace the coupled phonon--plasmon peaks in the bulk semiconductor.

  1. High-aperture binary axicons for the formation of the longitudinal electric field component on the optical axis for linear and circular polarizations of the illuminating beam

    SciTech Connect

    Khonina, S. N. Savelyev, D. A.

    2013-10-15

    Diffraction of uniformly polarized laser beams with vortex phase singularity is theoretically analyzed using the plane wave expansion. It is shown that for a high numerical aperture, an intense longitudinal electric field component is formed on the optical axis in this case. It is numerically demonstrated that an analogous effect is ensured for diffraction of a conventional Gaussian beam from asymmetric binary axicons. The field intensity on the optical axis can be varied either by rotating the optical element or by changing the direction of polarization of radiation.

  2. Longitudinal Analysis of Image Time Series with Diffeomorphic Deformations: A Computational Framework Based on Stationary Velocity Fields

    PubMed Central

    Hadj-Hamou, Mehdi; Lorenzi, Marco; Ayache, Nicholas; Pennec, Xavier

    2016-01-01

    We propose and detail a deformation-based morphometry computational framework, called Longitudinal Log-Demons Framework (LLDF), to estimate the longitudinal brain deformations from image data series, transport them in a common space and perform statistical group-wise analyses. It is based on freely available software and tools, and consists of three main steps: (i) Pre-processing, (ii) Position correction, and (iii) Non-linear deformation analysis. It is based on the LCC log-Demons non-linear symmetric diffeomorphic registration algorithm with an additional modulation of the similarity term using a confidence mask to increase the robustness with respect to brain boundary intensity artifacts. The pipeline is exemplified on the longitudinal Open Access Series of Imaging Studies (OASIS) database and all the parameters values are given so that the study can be reproduced. We investigate the group-wise differences between the patients with Alzheimer's disease and the healthy control group, and show that the proposed pipeline increases the sensitivity with no decrease in the specificity of the statistical study done on the longitudinal deformations. PMID:27375408

  3. Longitudinal Analysis of Image Time Series with Diffeomorphic Deformations: A Computational Framework Based on Stationary Velocity Fields.

    PubMed

    Hadj-Hamou, Mehdi; Lorenzi, Marco; Ayache, Nicholas; Pennec, Xavier

    2016-01-01

    We propose and detail a deformation-based morphometry computational framework, called Longitudinal Log-Demons Framework (LLDF), to estimate the longitudinal brain deformations from image data series, transport them in a common space and perform statistical group-wise analyses. It is based on freely available software and tools, and consists of three main steps: (i) Pre-processing, (ii) Position correction, and (iii) Non-linear deformation analysis. It is based on the LCC log-Demons non-linear symmetric diffeomorphic registration algorithm with an additional modulation of the similarity term using a confidence mask to increase the robustness with respect to brain boundary intensity artifacts. The pipeline is exemplified on the longitudinal Open Access Series of Imaging Studies (OASIS) database and all the parameters values are given so that the study can be reproduced. We investigate the group-wise differences between the patients with Alzheimer's disease and the healthy control group, and show that the proposed pipeline increases the sensitivity with no decrease in the specificity of the statistical study done on the longitudinal deformations. PMID:27375408

  4. Shielding of longitudinal magnetic fields with thin, closely, spaced concentric cylindrical shells with applications to atomic clocks

    NASA Technical Reports Server (NTRS)

    Wolf, S. A.; Gubser, D. U.; Cox, J. E.

    1978-01-01

    A general formula is given for the longitudinal shielding effectiveness of N closed concentric cylinders. The use of these equations is demonstrated by application to the design of magnetic shields for hydrogen maser atomic clocks. Examples of design tradeoffs such as size, weight, and material thickness are discussed. Experimental results on three sets of shields fabricated by three manufacturers are presented. Two of the sets were designed employing the techniques described. Agreement between the experimental results and the design calculations is then demonstrated.

  5. Experimental studies of transonic flow field near a longitudinally slotted wind tunnel wall. Ph.D. Thesis - George Washington Univ., 1988

    NASA Technical Reports Server (NTRS)

    Everhart, Joel L.; Bobbitt, Percy J.

    1994-01-01

    The results of detailed parametric experiments are presented for the near-wall flow field of a longitudinally slotted transonic wind tunnel. Existing data are reevaluated and new data obtained in the Langley 6- by 19-inch Transonic Wind Tunnel are presented and analyzed. In the experiments, researchers systematically investigate many pertinent wall-geometry variables such as the wall openness and the number of slots along with the free stream Mach number and model angle of attack. Flow field surveys on the plane passing through the centerline of the slot were conducted and are presented. The effects of viscosity on the slot flow are considered in the analysis. The present experiments, combined with those of previous investigations, give a more complete physical characterization of the flow near and through the slotted wall of a transonic wind tunnel.

  6. Longitudinal Field μSR Study of Spin Dynamics and Onset of Magnetic Correlations in LiHoxY1-xF4

    NASA Astrophysics Data System (ADS)

    Chen, K.; Johnson, R. C.; Giblin, S. R.; Lord, J. S.; Amato, A.; Baines, C.; Lascialfari, A.; Tkachuk, A. M.; Barbara, B.; Malkin, B. Z.; Graf, M. J.

    2010-03-01

    Nanomagnets - non-interacting spins typically imbedded in a solid host material - are intensely studied for applications ranging from high density data storage to quantum computing. We are studying the magnetic ion Ho^3+ spin dynamics in LiHoxY1-xF4 in the dilute limit (x << 1) using the muon spin relaxation in applied longitudinal magnetic fields as a function of temperature and magnetic field strength. At low concentrations (x <= 0.01) and for all magnetic field values studied, the spin lattice relaxation rate, 1/T1, shows a characteristic peak, usually associated with relaxation by spin fluctuations, near T = 10 K; this peak is consistent with the single-ion energy level diagram of Ho^3+. At larger x this peak is lost in low fields; stronger fields (> 600 G) restore the peak but show qualitatively different low temperature behavior. This suggests that both magnetic disorder and Ho-Ho interactions play an increasingly important role at larger x values.

  7. Quantum states of charge carriers and longitudinal conductivity in double periodic n-type semiconductor lattice structures in electric field

    SciTech Connect

    Perov, A. A. Penyagin, I. V.

    2015-07-15

    Quantum states of charge carriers in double periodic semiconductor superlattices of n-type quantum dots with Rashba spin–orbit coupling in an electron gas have been calculated in the one-electron approximation in the presence of mutually perpendicular electric and magnetic fields. For these structures in weak constant electric field, the solution to the quasi-classical kinetic Boltzmann equation shows that the states of carriers in magnetic Landau minibands with negative differential conductivity are possible.

  8. The intellectual structure and substance of the knowledge utilization field: A longitudinal author co-citation analysis, 1945 to 2004

    PubMed Central

    Estabrooks, Carole A; Derksen, Linda; Winther, Connie; Lavis, John N; Scott, Shannon D; Wallin, Lars; Profetto-McGrath, Joanne

    2008-01-01

    Background It has been argued that science and society are in the midst of a far-reaching renegotiation of the social contract between science and society, with society becoming a far more active partner in the creation of knowledge. On the one hand, new forms of knowledge production are emerging, and on the other, both science and society are experiencing a rapid acceleration in new forms of knowledge utilization. Concomitantly since the Second World War, the science underpinning the knowledge utilization field has had exponential growth. Few in-depth examinations of this field exist, and no comprehensive analyses have used bibliometric methods. Methods Using bibliometric analysis, specifically first author co-citation analysis, our group undertook a domain analysis of the knowledge utilization field, tracing its historical development between 1945 and 2004. Our purposes were to map the historical development of knowledge utilization as a field, and to identify the changing intellectual structure of its scientific domains. We analyzed more than 5,000 articles using citation data drawn from the Web of Science®. Search terms were combinations of knowledge, research, evidence, guidelines, ideas, science, innovation, technology, information theory and use, utilization, and uptake. Results We provide an overview of the intellectual structure and how it changed over six decades. The field does not become large enough to represent with a co-citation map until the mid-1960s. Our findings demonstrate vigorous growth from the mid-1960s through 2004, as well as the emergence of specialized domains reflecting distinct collectives of intellectual activity and thought. Until the mid-1980s, the major domains were focused on innovation diffusion, technology transfer, and knowledge utilization. Beginning slowly in the mid-1980s and then growing rapidly, a fourth scientific domain, evidence-based medicine, emerged. The field is dominated in all decades by one individual, Everett

  9. Nonlocal vibration of axially moving graphene sheet resting on orthotropic visco-Pasternak foundation under longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Arani, A. Ghorbanpour; Haghparast, E.; BabaAkbar Zarei, H.

    2016-08-01

    In the present research, vibration and instability of axially moving single-layered graphene sheet (SLGS) subjected to magnetic field is investigated. Orthotropic visco-Pasternak foundation is developed to consider the influences of orthotropy angle, damping coefficient, normal and shear modulus. Third order shear deformation theory (TSDT) is utilized due to its accuracy of polynomial functions than other plate theories. Motion equations are obtained by means of Hamilton's principle and solved analytically. Influences of various parameters such as axially moving speed, magnetic field, orthotropic viscoelastic surrounding medium, thickness and aspect ratio of SLGS on the vibration characteristics of moving system are discussed in details. The results indicated that the critical speed of moving SLGS is strongly dependent on the moving speed. Therefore, the critical speed of moving SLGS can be improved by applying magnetic field. The results of this investigation can be used in design and manufacturing of marine vessels in nanoscale.

  10. Technology-Assisted Learning: A Longitudinal Field Study of Knowledge Category, Learning Effectiveness and Satisfaction in Language Learning

    ERIC Educational Resources Information Center

    Hui, W.; Hu, P. J.-H.; Clark, T. H. K.; Tam, K. Y.; Milton, J.

    2008-01-01

    A field experiment compares the effectiveness and satisfaction associated with technology-assisted learning with that of face-to-face learning. The empirical evidence suggests that technology-assisted learning effectiveness depends on the target knowledge category. Building on Kolb's experiential learning model, we show that technology-assisted…

  11. Use of a force-sensing automated open field apparatus in a longitudinal study of multiple behavioral deficits in CAG140 Huntington's disease model mice.

    PubMed

    Fowler, Stephen C; Muma, Nancy A

    2015-11-01

    Behavioral testing of mouse models of Huntington's disease (HD) is a key component of preclinical assessment for potential pharmacological intervention. An open field with a force plate floor was used to quantify numerous spontaneous behaviors in a slowly progressing model of HD. CAG140 (+/+, +/-, -/-) male and female mice were compared in a longitudinal study from 6 to 65 weeks of age. Distance traveled, wall rears, wall rear duration, number of low mobility bouts, in-place movements, number of high velocity runs, and gait parameters (stride rate, stride length, and velocity) were extracted from the ground reaction forces recorded in 20-min actometer sessions. Beginning at 11 weeks, HD mice (both +/- and +/+) were consistently hypoactive throughout testing. Robust hypoactivity at 39 weeks of age was not accompanied by gait disturbances. By 52 and 65 weeks of age the duration of wall rears increased and in-place tremor-like movements emerged at 65 weeks of age in the +/+, but not in the +/- HD mice. Taken together, these results suggest that hypoactivity preceding frank motor dysfunction is a characteristic of CAG140 mice that may correspond to low motivation to move seen clinically in the premanifest/prediagnostic stage in human HD. The results also show that the force plate method provides a means for tracking the progression of behavioral dysfunction in HD mice beyond the stage when locomotion is lost while enabling quantification of tremor-like and similar in-place behaviors without a change in instrumentation. Use of force plate actometry also minimizes testing-induced enrichment effects when batteries of different tests are carried out longitudinally. PMID:26210937

  12. Spectropolarimetric measurements of the mean longitudinal magnetic field of chemically peculiar stars. II. Phase relating the magnetic and luminosity variabilities

    NASA Astrophysics Data System (ADS)

    Leone, F.; Catanzaro, G.

    2001-01-01

    For a sample of chemically peculiar stars, we report time-resolved measurements of the effective magnetic field which were obtained with the spectropolarimetry operating at the Catania Astrophysical Observatory. These observations are combined with data from the literature for better pointing out that periodic magnetic variability which characterises this class of stars. Periods given in the literature have been checked and, if possible, re-determined, not only by means of the magnetic measurements but referring also to the Hipparcos photometry. The variability of the effective magnetic field of the already known magnetic star 25 Sex is pointed out for the first time. As to the suspected magnetic chemically peculiar star EP UMa, our measurements confirm that this is really a magnetic star and we indicate a possible variability period. The accuracy of the variability period for CS Vir and FF Vir is improved. The suggestion that light variability is due to the re-distribution of ultraviolet flux towards the visible wavelengths in metal rich regions, which are not homogeneously distributed on the stellar surface, appears not always and straightly valid. Local line-blocking is certainly important in the case of CS Vir and a direct influence of the magnetic field on the infrared photometric variability cannot be ruled out for 25 Sex. Based on observations collected at the Catania Astrophysical Observatory, Italy.

  13. The thermionic energy converter as a topping cycle for more efficient heat engines—new triode designs with a longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Moyzhes, B. Y.; Geballe, T. H.

    2005-03-01

    A new concept for converting heat energy to electrical energy using thermionic energy converters (TECs) is proposed. It has potential for increasing the Carnot efficiency to an unprecedented 80% when the TEC is combined as a topping cycle with a conventional external combustion engine. The optimal electrical power density, 5-20 W cm-2, is satisfactory for many applications including stationary power generators and propulsion drives for vehicles. But unfortunately the substantial losses, ~50% of the output power, that have been needed to compensate the space charge have prevented the TEC from realizing its thermodynamic potential. We present two ways of overcoming this limitation. Both utilize a triode configuration (rather than a simple diode) with a longitudinal magnetic field. In the first method the magnetic field together with the grid separate the relatively few hot electrons required for volume generation of Cs ions used for the space charge compensation from the majority of the thermal electrons which constitute the current to the collector. In the second method the Cs ions are generated on the surface of the grid wires and injected into the space between the electrodes. Grid wires with high work functions are required for this.

  14. Motion of a charged particle in an axisymmetric longitudinal magnetic field that is inversely proportional to the radius

    NASA Astrophysics Data System (ADS)

    Kabin, K.; Bonner, G.

    2015-04-01

    An exact solution to the equations of motion of a charged particle in an axisymmetric magnetic field inversely proportional to the distance from the axis of symmetry is described and a FORTRAN code computing this solution is provided. This solution involves only elementary mathematical functions, however, it requires finding a root of a transcendental equation numerically. Although not particularly complicated in principle, this process is tedious in implementation as it requires considering several distinct types of solutions determined by the initial conditions as well as developing procedures for selecting the correct branches of the inverse trigonometric functions at multiple turning points. While this exact solution has been mentioned in the literature, its detailed description has been lacking.

  15. COMPUTERIZED EXPERT SYSTEM FOR EVALUATION OF AUTOMATED VISUAL FIELDS FROM THE ISCHEMIC OPTIC NEUROPATHY DECOMPRESSION TRIAL: METHODS, BASELINE FIELDS, AND SIX-MONTH LONGITUDINAL FOLLOW-UP

    PubMed Central

    Feldon, Steven E

    2004-01-01

    ABSTRACT Purpose To validate a computerized expert system evaluating visual fields in a prospective clinical trial, the Ischemic Optic Neuropathy Decompression Trial (IONDT). To identify the pattern and within-pattern severity of field defects for study eyes at baseline and 6-month follow-up. Design Humphrey visual field (HVF) change was used as the outcome measure for a prospective, randomized, multi-center trial to test the null hypothesis that optic nerve sheath decompression was ineffective in treating nonarteritic anterior ischemic optic neuropathy and to ascertain the natural history of the disease. Methods An expert panel established criteria for the type and severity of visual field defects. Using these criteria, a rule-based computerized expert system interpreted HVF from baseline and 6-month visits for patients randomized to surgery or careful follow-up and for patients who were not randomized. Results A computerized expert system was devised and validated. The system was then used to analyze HVFs. The pattern of defects found at baseline for patients randomized to surgery did not differ from that of patients randomized to careful follow-up. The most common pattern of defect was a superior and inferior arcuate with central scotoma for randomized eyes (19.2%) and a superior and inferior arcuate for nonrandomized eyes (30.6%). Field patterns at 6 months and baseline were not different. For randomized study eyes, the superior altitudinal defects improved (P = .03), as did the inferior altitudinal defects (P = .01). For nonrandomized study eyes, only the inferior altitudinal defects improved (P = .02). No treatment effect was noted. Conclusions A novel rule-based expert system successfully interpreted visual field defects at baseline of eyes enrolled in the IONDT. PMID:15747764

  16. Longitudinal Cell Tracking and Simultaneous Monitoring of Tissue Regeneration after Cell Treatment of Natural Tendon Disease by Low-Field Magnetic Resonance Imaging

    PubMed Central

    Berner, Dagmar; Brehm, Walter; Gerlach, Kerstin; Gittel, Claudia; Offhaus, Julia; Paebst, Felicitas; Scharner, Doreen; Burk, Janina

    2016-01-01

    Treatment of tendon disease with multipotent mesenchymal stromal cells (MSC) is a promising option to improve tissue regeneration. To elucidate the mechanisms by which MSC support regeneration, longitudinal tracking of MSC labelled with superparamagnetic iron oxide (SPIO) by magnetic resonance imaging (MRI) could provide important insight. Nine equine patients suffering from tendon disease were treated with SPIO-labelled or nonlabelled allogeneic umbilical cord-derived MSC by local injection. Labelling of MSC was confirmed by microscopy and MRI. All animals were subjected to clinical, ultrasonographical, and low-field MRI examinations before and directly after MSC application as well as 2, 4, and 8 weeks after MSC application. Hypointense artefacts with characteristically low signal intensity were identified at the site of injection of SPIO-MSC in T1- and T2∗-weighted gradient echo MRI sequences. They were visible in all 7 cases treated with SPIO-MSC directly after injection, but not in the control cases treated with nonlabelled MSC. Furthermore, hypointense artefacts remained traceable within the damaged tendon tissue during the whole follow-up period in 5 out of 7 cases. Tendon healing could be monitored at the same time. Clinical and ultrasonographical findings as well as T2-weighted MRI series indicated a gradual improvement of tendon function and structure. PMID:26880932

  17. Salmonella enterica Subclinical Infection: Bacteriological, Serological, Pulsed-Field Gel Electrophoresis, and Antimicrobial Resistance Profiles—Longitudinal Study in a Three-Site Farrow-to-Finish Farm

    PubMed Central

    Vigo, German B.; Cappuccio, Javier A.; Salve, Angela; Machuca, Mariana A.; Quiroga, Maria A.; Moredo, Fabiana; Giacoboni, Gabriel; Cancer, Jose L.; Caffer, Ines G.; Binsztein, Norma; Pichel, Mariana; Perfumo, Carlos J.

    2009-01-01

    Abstract The aim of this surveillance was to study both Salmonella spp. shedding patterns and the time course of serological response in farrow-to-finish reared pigs from a subclinically infected farm. Antimicrobial resistance profile, molecular subtyping, and the relationship among the isolates were determined by pulsed-field gel electrophoresis (PFGE). A farrow-to-finish farm of 6000 sows, with a history of Salmonella Typhimurium septicemia, was selected. A longitudinal bacteriological and serological study was conducted in 25 sows before farrowing (M/S1) and in 50 offspring at 21 (M/S2), 35 (M/S3), 65 (M/S4), 86 (M/S5), 128 (M/S6), and 165 (M/S7) days of age. Serum antibodies were tested using Herdcheck® Swine Salmonella antibody test kit (Idexx Laboratories, ME). Bacteria were isolated from pooled fecal samples. Suspected isolates were confirmed by conventional biochemical assays, and those identified as Salmonella spp. were serotyped. A variation between seropositive percentages and positive fecal samples was observed. Serologically positive pigs decreased from S1 to S4, and subsequently increased from S4 to S7. The percentages of fecal positive culture increased from M1 to M3, and then declined in M4, increased in M5, and were negative in M6 and M7. In the study three serovars, Salmonella 3,10:e,h:-, Salmonella Muenster, and Salmonella Bovismorbificans, were identified with low pathogenicity for swine. Three multidrug resistance strains (one belonged to Salmonella 3,10:e,h:- and two belonged to Salmonella Muenster) were found. PFGE results showed three different but closely related patterns among the 13 isolates of Salmonella Bovismorbificans, and two patterns for the three Salmonella Muenster and Salmonella 3,10:e,h:- isolates. This longitudinal study established critical points of Salmonella spp. infection in the farm and the production stages, where appropriate control measures must be taken. PFGE showed clonal relationships in each serovar. Antibiotic

  18. 1993/03 Baccalaureate and Beyond Longitudinal Study (B&B:93/03) Field Test Methodology Report. Working Paper Series. NCES 2004-02

    ERIC Educational Resources Information Center

    Wine, J.; Cominole, M.; Carwile, S.; Franklin, J.; Carley-Baxter, L.; and Wheeless, S.

    2004-01-01

    The 1993/03 Baccalaureate and Beyond Longitudinal Study (B&B:93/03), sponsored by the National Center for Education Statistics (NCES), U.S. Department of Education, followed a cohort of students who earned bachelor's degrees during the 1992?93 academic year. These students were first interviewed in 1993, as part of the 1993 National Postsecondary…

  19. Symposium on the National Education Longitudinal Study of 1988 (NELS:88) and the NELS:88 Field Test (New Orleans, Louisiana, April 5-9, 1988).

    ERIC Educational Resources Information Center

    Ingels, Steven J.; And Others

    The National Education Longitudinal Study of 1988 (NELS:88) is a major new panel study of educational outcomes sponsored by the Center for Education Statistics of the United States Department of Education. The NELS:88 is designed to provide trend data about critical transitions experienced by young people as they develop, attend school, and embark…

  20. Longitudinal Stern-Gerlach

    NASA Astrophysics Data System (ADS)

    Higinbotham, Douglas

    2006-11-01

    In 1922 Otto Stern and Walther Gerlach split a beam of silver atoms using a transverse gradient field. This experiment, which lead to the understanding that electrons have intrinsic spin, oddly enough does not work for free electrons due to the interplay between the Lorentz force and Heisenberg uncertainly principle. Recent calculations, Phys. Rev. Lett. 79 (1997) 4517 and Phys. Rev. Lett. 86 (2001) 4508, have shown that a dismissed idea of L. Brillouin from 1928 to use a longitudinal gradient field to minimize the effect of the Lorentz force may in fact be possible. The history of the Stern-Gerlach device will be presented along with the revived ideas for separating a beam of free electrons into its two spin states.

  1. Longitudinal emittance in high-current ion accelerators

    SciTech Connect

    Wangler, T.P.; Bhatia, T.S.; Neuschaefer, G.H.; Pabst, M.

    1989-01-01

    The control of longitudinal emittance in an ion linear accelerator is important for minimizing both chromatic aberrations and beam halo. The root-mean-square (rms) longitudinal emittance grouth can result from either the nonlinear rf focusing fields or the nonlinear space-charge fields. We will present conclusions based on numerical beam-dynamics studies for both the radio-frequency quadrupole (RFQ), and the drift-tube linac (DTL). We will discuss the scaling of longitudinal emittance produced during the adiabatic bunching in an RFQ and will show the benefits of ramped DTL accelerating field designs to maintain high longitudinal focusing strength with increasing particle energy. 15 refs., 8 figs.

  2. Restoration of longitudinal images.

    PubMed

    Hu, Y; Frieden, B R

    1988-01-15

    In this paper, a method of restoring longitudinal images is developed. By using the transfer function for longitudinal objects, and inverse filtering, a longitudinal image may be restored. The Fourier theory and sampling theorems for transverse images cannot be used directly in the longitudinal case. A modification and reasonable approximation are introduced. We have numerically established a necessary relationship between just-resolved longitudinal separation (after inverse filtering), noise level, and the taking conditions of object distance and lens diameter. An empirical formula is also found to well-fit the computed results. This formula may be of use for designing optical systems which are to image longitudinal details, such as in robotics or microscopy. PMID:20523607

  3. The Importance of Longitudinal Studies

    NASA Astrophysics Data System (ADS)

    Knezek, Patricia

    2014-01-01

    It has been eight years since the AAS Council unanimously endorsed the document, known as "Equity Now: The Pasadena Recommendations for Gender Equality in Astronomy," in January 2005. This document was the main product of the conference entitled “Women in Astronomy II: Ten Years After” (WIA II), held in June 2003 in Pasadena, CA. One of the key recommendations represented in that document was the need for a longitudinal study of astronomers. It was recognized that in order to understand our own field, how it is evolving, and the impact on individuals, we need to track people over time. I will discuss the fundamental questions that led to the recommendation, and set the stage for the current (ongoing) longitudinal study.

  4. Longitudinal impedance of RHIC

    SciTech Connect

    Blaskiewicz, M.; Brennan, J. M.; Mernick, K.

    2015-05-03

    The longitudinal impedance of the two RHIC rings has been measured using the effect of potential well distortion on longitudinal Schottky measurements. For the blue RHIC ring Im(Z/n) = 1.5±0.2Ω. For the yellow ring Im(Z/n) = 5.4±1Ω.

  5. Longitudinal Multistage Testing

    ERIC Educational Resources Information Center

    Pohl, Steffi

    2013-01-01

    This article introduces longitudinal multistage testing (lMST), a special form of multistage testing (MST), as a method for adaptive testing in longitudinal large-scale studies. In lMST designs, test forms of different difficulty levels are used, whereas the values on a pretest determine the routing to these test forms. Since lMST allows for…

  6. Theoretical and Experimental Studies of the Transonic Flow Field and Associated Boundary Conditions near a Longitudinally-Slotted Wind-Tunnel Wall. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Everhart, Joel Lee

    1988-01-01

    A theoretical examination of the slotted-wall flow field is conducted to determine the appropriate wall pressure drop (or boundary condition) equation. This analysis improves the understanding of the fluid physics of these types of flow fields and helps in evaluating the uncertainties and limitations existing in previous mathematical developments. It is shown that the resulting slotted-wall boundary condition contains contributions from the airfoil-induced streamline curvature and the non-linear, quadratic, slot crossflow in addition to an often neglected linear term which results from viscous shearing in the slot. Existing and newly acquired experimental data are examined in the light of this formulation and theoretical developments.

  7. Longitudinal evaluation of Ocimum and other plants effects on the feeding behavioral response of mosquitoes (Diptera: Culicidae) in the field in Tanzania

    PubMed Central

    Kweka, Eliningaya J; Mosha, Franklin W; Lowassa, Asanterabi; Mahande, Aneth M; Mahande, Michael J; Massenga, Charles P; Tenu, Filemoni; Lyatuu, Ester E; Mboya, Michael A; Temu, Emmanuel A

    2008-01-01

    Background The use of repellent materials from plants against nuisance insects is common with great potential to compliment existing malaria control programmes and this requires evaluation in the field. Ocimum plant species, Ocimum suave (Willd) and O. kilimandscharicum (Guerke) materials and their essential oils extracted by steam distillation were evaluated in the field and experimental huts for repellence, exophily and feeding inhibition effects against three mosquito species, Anopheles arabiensis (Patton), An. gambiae ss (Giles) and Culex quinquefasciatus (Say). The protective effect of essential oils from Ocimum plants were compared with N, N-diethly-3- methylbenzamide (DEET), a standard synthetic repellent. Also, the protective effect of fumigation by burning of repellent plants; Ocimum suave, Ocimum kilimandscharicum, Azadirachta indica, Eucalyptus globules and Lantana camara were tested in experimental huts and selected local houses. Results In the field, protection by Ocimum plants from mosquito bites was high and there was small variation among different mosquito species. Protection efficiency was 93.4%, 91.98% and 89.75% for An. arabiensis while for Cx. quinquefaciatus it was 91.30%, 88.65% and 90.50% for DEET, Ocimum suave and O. kilimandscharicum respectively. In the experimental hut, deterrence induced by burning of Ocimum and other plants ranged from 73.1.0% to 81.9% for An. arabiensis and 56.5% to 67.8% for Cx. quinquefaciatus, while feeding inhibition was 61.1% to 100% for An. arabiensis and 50% to 100% for Cx. quinquefaciatus. Evaluations under field conditions confirmed high protective efficacy, enhanced feeding inhibition and house entry inhibition (Deterrence). Conclusion This study shows the potential of Ocimum suave and Ocimum kilimandscharicum crude extracts and whole plants of Ocimum suave, Ocimum kilimandscharicum, Azadirachta indica, Eucalyptus globules and Lantana camara for use in protecting against human biting while the burning of

  8. In vivo wide-field multispectral scanning laser ophthalmoscopy-optical coherence tomography mouse retinal imager: longitudinal imaging of ganglion cells, microglia, and Müller glia, and mapping of the mouse retinal and choroidal vasculature.

    PubMed

    Zhang, Pengfei; Zam, Azhar; Jian, Yifan; Wang, Xinlei; Li, Yuanpei; Lam, Kit S; Burns, Marie E; Sarunic, Marinko V; Pugh, Edward N; Zawadzki, Robert J

    2015-01-01

    Scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) provide complementary views of the retina, with the former collecting fluorescence data with good lateral but relatively low-axial resolution, and the latter collecting label-free backscattering data with comparable lateral but much higher axial resolution. To take maximal advantage of the information of both modalities in mouse retinal imaging, we have constructed a compact, four-channel, wide-field (∼50  deg) system that simultaneously acquires and automatically coregisters three channels of confocal SLO and Fourier domain OCT data. The scanner control system allows “zoomed” imaging of a region of interest identified in a wide-field image, providing efficient digital sampling and localization of cellular resolution features in longitudinal imaging of individual mice. The SLO is equipped with a “flip-in” spectrometer that enables spectral “fingerprinting” of fluorochromes. Segmentation of retina layers and en face display facilitate spatial comparison of OCT data with SLO fluorescence patterns. We demonstrate that the system can be used to image an individual retinal ganglion cell over many months, to simultaneously image microglia and Müller glia expressing different fluorochromes, to characterize the distinctive spatial distributions and clearance times of circulating fluorochromes with different molecular sizes, and to produce unequivocal images of the heretofore uncharacterized mouse choroidal vasculature. PMID:26677070

  9. In vivowide-field multispectral scanning laser ophthalmoscopy-optical coherence tomography mouse retinal imager: longitudinal imaging of ganglion cells, microglia, and Müller glia, and mapping of the mouse retinal and choroidal vasculature

    NASA Astrophysics Data System (ADS)

    Zhang, Pengfei; Zam, Azhar; Jian, Yifan; Wang, Xinlei; Li, Yuanpei; Lam, Kit S.; Burns, Marie E.; Sarunic, Marinko V.; Pugh, Edward N., Jr.; Zawadzki, Robert J.

    2015-12-01

    Scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) provide complementary views of the retina, with the former collecting fluorescence data with good lateral but relatively low-axial resolution, and the latter collecting label-free backscattering data with comparable lateral but much higher axial resolution. To take maximal advantage of the information of both modalities in mouse retinal imaging, we have constructed a compact, four-channel, wide-field (˜50 deg) system that simultaneously acquires and automatically coregisters three channels of confocal SLO and Fourier domain OCT data. The scanner control system allows "zoomed" imaging of a region of interest identified in a wide-field image, providing efficient digital sampling and localization of cellular resolution features in longitudinal imaging of individual mice. The SLO is equipped with a "flip-in" spectrometer that enables spectral "fingerprinting" of fluorochromes. Segmentation of retina layers and en face display facilitate spatial comparison of OCT data with SLO fluorescence patterns. We demonstrate that the system can be used to image an individual retinal ganglion cell over many months, to simultaneously image microglia and Müller glia expressing different fluorochromes, to characterize the distinctive spatial distributions and clearance times of circulating fluorochromes with different molecular sizes, and to produce unequivocal images of the heretofore uncharacterized mouse choroidal vasculature.

  10. The effects of canard-wing flow-field interactions on longitudinal stability, effective dihedral and potential deep-stall trim

    NASA Technical Reports Server (NTRS)

    Muchmore, C. B., Jr.

    1988-01-01

    The literature available on high aspect ratio canard configurations shows them to have some unique stability characteristics. Using a generic canard-wing model, the effects of canard-wing flow-field interactions on stability were investigated in the NASA Langley Twelve-Foot Low-Speed Wind Tunnel. Results for the attached flow regime indicate linear interactions shift the neutral point of a canard configuration forward, but the effect of a canard on a wing can change significantly when the flow over the surface begins to separate, even several degrees below stall. The asymmetry of the canard downwash in a sideslip condition can result in an increment in effective dihedral roughly proportional to canard lift coefficient. At very high angles of attack the presence of a wing can cause an incremental normal force on a canard, contributing to the possibility of a deep-stall trim point. This effect is greater for a high canard and less for a low one.

  11. Persistent Longitudinal Variations of Plasma Density and DC Electric Fields in the Low Latitude Ionosphere Observed with Probes on the C/NOFS Satellite

    NASA Astrophysics Data System (ADS)

    Pfaff, R. F.; Freudenreich, H.; Klenzing, J. H.; Rowland, D. E.; Liebrecht, M. C.; Bromund, K. R.; Roddy, P. A.

    2010-12-01

    Continuous measurements using in situ probes on consecutive orbits of the C/NOFS satellite reveal that the plasma density is persistently organized by longitude, in both day and night conditions and at all locations within the satellite orbit, defined by its perigee and apogee of 401 km and 867 km, respectively, and its inclination of 13 degrees. Typical variations are a factor of 2 or 3 compared to mean values. Furthermore, simultaneous observations of DC electric fields and their associated E x B drifts in the low latitude ionosphere also reveal that their amplitudes are also strongly organized by longitude in a similar fashion. The drift variations with longitude are particularly pronounced in the meridional component perpendicular to the magnetic field although they are also present in the zonal component as well. The longitudes of the peak meridional drift and density values are significantly out of phase with respect to each other. Time constants for the plasma accumulation at higher altitudes with respect to the vertical drift velocity must be taken into account in order to properly interpret the detailed comparisons of the phase relationship of the plasma density and plasma velocity variations. Although for a given period corresponding to that of several days, typically one longitude region dominates the structuring of the plasma density and plasma drift data, there is also evidence for variations organized about multiple longitudes at the same time. Statistical averages will be shown that suggest a tidal “wave 4” structuring is present in both the plasma drift and plasma density data. We interpret the apparent association of the modulation of the E x B drifts with longitude as well as that of the ambient plasma density as a manifestation of tidal forces at work in the low latitude upper atmosphere. The observations demonstrate how the high duty cycle of the C/NOFS observations and its unique orbit expose fundamental processes at work in the low

  12. Persistent Longitudinal Variations of Plasma Density and DC Electric Fields in the Low Latitude Ionosphere Observed with Probes on the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Klenzing, J.; Rowland, D.; Liebrecht, C.; Bromund, K.; Roddy, P.

    2010-01-01

    Continuous measurements using in situ probes on consecutive orbits of the C/N0FS satellite reveal that the plasma density is persistently organized by longitude, in both day and night conditions and at all locations within the satellite orbit, defined by its perigee and apogee of 401 km and 867 km, respectively, and its inclination of 13 degrees. Typical variations are a factor of 2 or 3 compared to mean values. Furthermore, simultaneous observations of DC electric fields and their associated E x B drifts in the low latitude ionosphere also reveal that their amplitudes are also strongly organized by longitude in a similar fashion. The drift variations with longitude are particularly pronounced in the meridional component perpendicular to the magnetic field although they are also present in the zonal component as well. The longitudes of the peak meridional drift and density values are significantly out of phase with respect to each other. Time constants for the plasma accumulation at higher altitudes with respect to the vertical drift velocity must be taken into account in order to properly interpret the detailed comparisons of the phase relationship of the plasma density and plasma velocity variations. Although for a given period corresponding to that of several days, typically one longitude region dominates the structuring of the plasma density and plasma drift data, there is also evidence for variations organized about multiple longitudes at the same time. Statistical averages will be shown that suggest a tidal "wave 4" structuring is present in both the plasma drift and plasma density data. We interpret the apparent association of the modulation of the E x B drifts with longitude as well as that of the ambient plasma density as a manifestation of tidal forces at work in the low latitude upper atmosphere. The observations demonstrate how the high duty cycle of the C/NOFS observations and its unique orbit expose fundamental processes at work in the low latitude

  13. Longitudinal Lisfranc injury.

    PubMed

    Oak, Nikhil R; Manoli, Arthur; Holmes, James R

    2014-01-01

    Most Lisfranc or tarsometatarsal (TMT) joint injuries result from a horizontally directed force in which the metatarsals are displaced relative to the midfoot. The injury pattern that is described in this article is one of a longitudinal force through the first ray and cuneiform. A reliable measure to recognize the longitudinal Lisfranc variant injury has been the height difference between the distal articular surfaces of the first and second cuneiform bones in an anteroposterior (AP) weight-bearing radiograph. This measure helps identify subtle injuries in which there is a proximal and medial subluxation of the first cuneiform-metatarsal complex. Delayed diagnosis and treatment have been associated with poorer results and significant functional consequences. This article describes a simple radiographic measurement to recognize the longitudinal injury pattern and to aid in determining whether operative intervention is required. PMID:25785475

  14. Idiopathic Polydactylous Longitudinal Erythronychia

    PubMed Central

    2011-01-01

    Objective: To describe the clinical features of idiopathic polydactylous longitudinal erythronychia. Introduction: Longitudinal erythronychia presents as a linear red band on the nail plate. Idiopathic polydactylous longitudinal erythronychia is a rarely described manifestation of longitudinal erythronychia in which one or more linear red bands present on the nails of multiple digits without any associated subungual malignant tumor, dermatological condition, or systemic disease. Methods: As part of a total body skin examination, the fingernails and toenails were evaluated for linear red bands. Results: One or more asymptomatic linear red bands (longitudinal erythronychia) was observed on multiple digits of the hands in one percent (3 men of 134 men and 112 women) of patients examined during a period of 75 days. The author also noted similar changes of his own nails. Between 3 to 10 digits were affected. Multiple linear red bands per nail were usually narrow (less than 1mm wide), whereas a single band on a nail often ranged from 4 to 6mm wide. The intensity of an individual wider linear red band was position-dependent in three individuals in whom the distal portion appeared less prominent when the affected digit was held upward above the level of the patient's heart—pseudolongitudinal erythronychia. Other nail changes in these patients included distal subungual hyperkeratosis, fissuring at the free end of the nail, leukonychia, red lunula, and splinter hemorrhages. Discussion: Idiopathic polydactylous longitudinal erythronychia is a benign, usually asymptomatic, condition of undetermined etiology characterized by one or more linear red bands originating at the proximal nail fold or distal lunula and extending to the free edge of the nail. It appears to be more prevalent in men over 50 years of age and its incidence was noted to be one percent of adults attending a dermatology clinic. Patients are either unaware of the nail changes or seek medical attention because

  15. Longitudinal discharge laser baffles

    DOEpatents

    Warner, B.E.; Ault, E.R.

    1994-06-07

    The IR baffles placed between the window and the electrode of a longitudinal discharge laser improve laser performance by intercepting off-axis IR radiation from the laser and in doing so reduce window heating and subsequent optical distortion of the laser beam. 1 fig.

  16. Longitudinal discharge laser baffles

    DOEpatents

    Warner, Bruce E.; Ault, Earl R.

    1994-01-01

    The IR baffles placed between the window and the electrode of a longitudinal discharge laser improve laser performance by intercepting off-axis IR radiation from the laser and in doing so reduce window heating and subsequent optical distortion of the laser beam.

  17. Longitudinal discharge laser electrodes

    DOEpatents

    Warner, B.E.; Miller, J.L.; Ault, E.R.

    1994-08-23

    The improved longitudinal discharge laser electrode with IR baffle includes an electrode made up of washers spaced along the laser axis in order to form inter-washer spaces for hollow cathode discharge to take place and for IR radiation to be trapped. Additional IR baffles can be placed between the electrode ann the window. 2 figs.

  18. Longitudinal discharge laser electrodes

    DOEpatents

    Warner, Bruce E.; Miller, John L.; Ault, Earl R.

    1994-01-01

    The improved longitudinal discharge laser electrode with IR baffle includes an electrode made up of washers spaced along the laser axis in order to form inter-washer spaces for hollow cathode discharge to take place and for IR radiation to be trapped. Additional IR baffles can be placed between the electrode ann the window.

  19. WISCONSIN LONGITUDINAL STUDY (WLS)

    EPA Science Inventory

    The Wisconsin Longitudinal Study (WLS) is a long-term study of a random sample of 10,317 men and women who graduated from Wisconsin high schools in 1957. The WLS provides an opportunity to study of the life course, intergenerational transfers and relationships, family functioning...

  20. Experimental Demonstration of Longitudinal Magnification

    ERIC Educational Resources Information Center

    Razpet, Nada; Susman, Katarina; Cepic, Mojca

    2009-01-01

    We describe an experiment which enables the observation of longitudinal magnification for the real image of a three-dimensional (3D) object formed by a converging lens. The experiment also shows the absence of longitudinal inversion. Possible reasons for misconceptions with respect to real images and longitudinal inversions are discussed and a…

  1. Longitudinal epiphyseal bracket.

    PubMed

    Nguyen, Jimmy Q; Gatewood, Jason B; Beall, Douglas; Herndon, William; Puffinberger, William R; Ly, Justin; Fish, Jon R

    2007-10-01

    A longitudinal epiphyseal bracket (LEB) is a defect of the tubular bones and has been primarily described in the hands and feet, especially the proximal phalanges, metacarpals, and metatarsals. The LEB results from a defective C-shaped secondary ossification center that brackets the diaphysis and metaphysis, causing restricted longitudinal growth in these bones with resultant shortening and angular deformities. Deformities associated with metatarsal epiphyseal bracket include a short, broad metatarsal and medial deviation of the metatarsophalangeal joint (hallux varus deformity). Excision of the cartilaginous LEB has been proposed to prevent future soft tissue contractures and osseous deformities. The LEB has been associated with numerous syndromes including Rubinstein-Taybi syndrome, Cenani-Lenz syndactyly, isolated oligosyndactyly, and Nievergelt syndrome. We describe a two-month-old patient in whom plain film and MR imaging demonstrated bilateral bracketed first metatarsals with associated hallux varus deformities. Bilateral bracket excision was performed with excellent clinical results. PMID:18085094

  2. Longitudinal structure of ballooning MHD disturbances in a model magnetosphere

    NASA Astrophysics Data System (ADS)

    Mazur, N. G.; Fedorov, E. N.; Pilipenko, V. A.

    2014-05-01

    Large-scale toroidal Pc5 pulsations are commonly treated as Alfven oscillations of a magnetic field line. According to observations, their longitudinal structure is described well by theory. At the same time, the longitudinal structure of azimuthal small-scale poloidal Pc5 pulsations is virtually unknown. These pulsations are associated with ballooning disturbances described by a system of coupled equations for Alfvenic and slow magnetosonic (SMS) modes. In this work, the Voigt model is used to describe the equilibrium finite-pressure plasma configuration in an inhomogeneous magnetosphere plasma in a curved magnetic field. Spectral characteristics and the spatial structure of natural ballooning modes are calculated for this model. The model calculations demonstrate the possibility of different longitudinal scales for transverse and longitudinal magnetic components of oscillations near the top of the field line.

  3. A new hybrid longitudinal-torsional magnetostrictive ultrasonic transducer

    NASA Astrophysics Data System (ADS)

    Karafi, Mohammad Reza; Hojjat, Yousef; Sassani, Farrokh

    2013-06-01

    In this paper, a novel hybrid longitudinal-torsional magnetostrictive ultrasonic transducer (HL-TMUT) is introduced. The transducer is composed of a magnetostrictive exponential horn and a stainless steel tail mass. In this transducer a spiral magnetic field made up of longitudinal and circumferential magnetic fields is applied to the magnetostrictive horn. As a result, the magnetostrictive horn oscillates simultaneously both longitudinally and torsionally in accordance with the Joule and Wiedemann effects. The magnetostrictive exponential horn is designed in such a manner that it has the same longitudinal and torsional resonant frequency. It is made up of ‘2V Permendur’, which has isotropic magnetic properties. The differential equations of the torsional and longitudinal vibration of the horn are derived, and a HL-TMUT is designed with a resonant frequency of 20 573 Hz. The natural frequency and mode shapes of the transducer are considered theoretically and numerically. The experimental results show that this transducer resonates torsionally and longitudinally with frequencies of 20 610 Hz and 20 830 Hz respectively. The maximum torsional displacement is 1.5 mrad m-1 and the maximum longitudinal displacement is 0.6 μm. These are promising features for industrial applications.

  4. Longitudinal Variations in Jupiter's Winds

    NASA Technical Reports Server (NTRS)

    Simon-Miller, Amy A.; Gierasch, P. J.; Tierney, G.

    2010-01-01

    Long-term studies of Jupiter's zonal wind field revealed temporal variations on the order of 20 to 40 m/s at many latitudes, greater than the typical data uncertainties of 1 to 10 m/s. No definitive periodicities were evident, however, though some latitudinally-confined signals did appear at periods relevant to the Quasi- Quadrennial Oscillation (Simon-Miller & Gierasch, Icarus, in press). As the QQO appears, from vertical temperature profiles, to propagate downward, it is unclear why a signal is not more obvious, unless other processes dominate over possibly weaker forcing from the QQO. An additional complication is that zonal wind profiles represent an average over some particular set of longitudes for an image pair and most data sets do not offer global wind coverage. Lien avoiding known features, such as the large anticyclonic vortices especially prevalent in the south, there can be distinct variations in longitude. We present results on the full wind field from Voyager and Cassini data, showing apparent longitudinal variations of up to 60 m/s or more. These are particularly obvious near disruptions such as the South Equatorial Disturbance, even when the feature itself is not clearly visible. These two dates represent very different states of the planet for comparison: Voyagers 1 & 2 flew by Jupiter shortly after a global upheaval, while many regions were in a disturbed state, while the Cassini view is typical of a more quiescent period present during much of the 1990s and early 2000s.

  5. Enhanced magnetoelectric effect in longitudinal-longitudinal mode laminate with cofired interdigitated electrodes

    NASA Astrophysics Data System (ADS)

    Yan, Yongke; Zhou, Yuan; Priya, Shashank

    2014-01-01

    In this letter, we describe a low-temperature cofiring technique to embed the interdigitated electrodes (IDE) inside the piezoelectric ceramic layer to achieve longitudinally (L) poled magnetoelectric (ME) laminates. The ME voltage coefficient of this L-L mode composite was found to be 4.41 V cm-1 Oe-1 at 1 kHz, which is 340% higher than that of L-T (transversal) mode. IDE based longitudinal poling and piezoelectric response was evaluated by impedance changes and piezoresponse force microscopy, illustrating the effect of inactive/ineffective zone in the range beneath and above the fingers with vanishing fields. At an electric field of 50 V/cm, the composite was found to generate magnetic field on the order of 175 μG at 1 kHz.

  6. Digital Longitudinal Tomosynthesis

    NASA Astrophysics Data System (ADS)

    Rimkus, Daniel Steven

    1985-12-01

    The purpose of this dissertation was to investigate the clinical utility of digital longitudinal tomosynthesis in radiology. By acquiring a finite group of digital images during a longitudinal tomographic exposure, and processing these images, tomographic planes, other than the fulcrum plane, can be reconstructed. This process is now termed "tomosynthesis". A prototype system utilizing this technique was developed. Both phantom and patient studies were done with this system. The phantom studies were evaluated by subjective, visual criterion and by quantitative analysis of edge sharpness and noise in the reconstructions. Two groups of patients and one volunteer were studied. The first patient group consisted of 8 patients undergoing intravenous urography (IVU). These patients had digital tomography and film tomography of the abdomen. The second patient group consisted of 4 patients with lung cancer admitted to the hospital for laser resection of endobronchial tumor. These patients had mediastinal digital tomograms to evaluate the trachea and mainstem bronchi. The knee of one volunteer was imaged by film tomography and digital tomography. The results of the phantom studies showed that the digital reconstructions accurately produced images of the desired planes. The edge sharpness of the reconstructions approached that of the acquired images. Adequate reconstructions were achieved with as few as 5 images acquired during the exposure, with the quality of the reconstructions improving as the number of images acquired increased. The IVU patients' digital studies had less contrast and spatial resolution than the film tomograms. The single renal lesion visible on the film tomograms was also visible in the digital images. The digital mediastinal studies were felt by several radiologists to be superior to a standard chest xray in evaluating the airways. The digital images of the volunteer's knee showed many of the same anatomic features as the film tomogram, but the digital

  7. A Longitudinal Support Vector Regression for Prediction of ALS Score

    PubMed Central

    Du, Wei; Cheung, Huey; Goldberg, Ilya; Thambisetty, Madhav; Becker, Kevin; Johnson, Calvin A.

    2015-01-01

    Longitudinal studies play a key role in various fields, including epidemiology, clinical research, and genomic analysis. Currently, the most popular methods in longitudinal data analysis are model-driven regression approaches, which impose strong prior assumptions and are unable to scale to large problems in the manner of machine learning algorithms. In this work, we propose a novel longitudinal support vector regression (LSVR) algorithm that not only takes the advantage of one of the most popular machine learning methods, but also is able to model the temporal nature of longitudinal data by taking into account observational dependence within subjects. We test LSVR on publicly available data from the DREAM-Phil Bowen ALS Prediction Prize4Life challenge. Results suggest that LSVR is at a minimum competitive with favored machine learning methods and is able to outperform those methods in predicting ALS score one month in advance. PMID:27042700

  8. Propagation of radially localized helicon waves in longitudinally nonuniform plasmas

    SciTech Connect

    Arefiev, Alexey V.; Breizman, Boris N.

    2006-06-15

    A gradient in the plasma density across the guiding magnetic field can support a low-frequency radially localized helicon (RLH) wave in a plasma column. If the radial density gradient changes along the magnetic field, this wave can undergo reflection and also excite conventional whistlers. This paper presents calculations of the corresponding reflection coefficient, including the effect of whistler radiation. It is shown that a sharp longitudinal density drop causes a nearly complete reflection of the RLH wave. The longitudinal wavelength of the excited whistlers is much greater than that of the RLH wave, and, as a result, only a small fraction of the RLH wave energy is transferred to the whistlers.

  9. Longitudinal dynamics and stability in beams for heavy-ion fusion

    SciTech Connect

    Sharp, W.M.; Callahan, D.A.; Grote, D.P.

    1996-01-05

    Successful transport of induction-driven beams for heavy-ion fusion requires careful control of the longitudinal space charge. The usual control technique is the periodic application of time-varying longitudinal electric fields, called `ears`, that on the average, balance the space-charge field. this technique is illustrated using a fluid/envelope code CIRCE, and the sensitivity of the method to errors in these ear fields is illustrated. The possibility that periodic ear fields also excite the longitudinal instability is examined.

  10. Modeling Longitudinal Data Containing Non-Normal Within Subject Errors

    NASA Technical Reports Server (NTRS)

    Feiveson, Alan; Glenn, Nancy L.

    2013-01-01

    The mission of the National Aeronautics and Space Administration’s (NASA) human research program is to advance safe human spaceflight. This involves conducting experiments, collecting data, and analyzing data. The data are longitudinal and result from a relatively few number of subjects; typically 10 – 20. A longitudinal study refers to an investigation where participant outcomes and possibly treatments are collected at multiple follow-up times. Standard statistical designs such as mean regression with random effects and mixed–effects regression are inadequate for such data because the population is typically not approximately normally distributed. Hence, more advanced data analysis methods are necessary. This research focuses on four such methods for longitudinal data analysis: the recently proposed linear quantile mixed models (lqmm) by Geraci and Bottai (2013), quantile regression, multilevel mixed–effects linear regression, and robust regression. This research also provides computational algorithms for longitudinal data that scientists can directly use for human spaceflight and other longitudinal data applications, then presents statistical evidence that verifies which method is best for specific situations. This advances the study of longitudinal data in a broad range of applications including applications in the sciences, technology, engineering and mathematics fields.

  11. Longitudinal beam dynamics for heavy ion fusion using WARPrz

    SciTech Connect

    Callahan, D.A.; Langdon, A.B.; Friedman, A.; Haber, I.

    1993-02-22

    WARPrz is a 2.5 dimensional, cylindrically symmetric, electrostatic, particle-in-cell code. It is part of the WARP family of codes which has been developed to study heavy ion fusion driver issues. WARPrz is being used to study the longitudinal dynamics of heavy ion beams including a longitudinal instability that is driven by the impedance of the LINAC accelerating modules. This instability is of concern because it can enhance longitudinal momentum spread; chromatic abhoration in the lens system restricts the amount of momentum spread allowed in the beam in the final focusing system. The impedance of the modules is modeled by a continuum of resistors and capacitors in parallel in WARPrz. We discuss simulations of this instability including the effect of finite temperature and reflection of perturbations off the beam ends. We also discuss intermittency of axial confining fields (``ears`` fields) as a seed for this instability.

  12. Negative Ion Drift Velocity and Longitudinal Diffusion in Mixtures of Carbon Disulfide and Methane

    NASA Technical Reports Server (NTRS)

    Dion, Michael P.; Son, S.; Hunter, S. D.; deNolfo, G. A.

    2011-01-01

    Negative ion drift velocity and longitudinal diffusion has been measured for gas mixtures of carbon disulfide (CS2) and methane (CH4)' Measurements were made as a function of total pressure, CS2 partial pressure and electric field. Constant mobility and thermal-limit longitudinal diffusion is observed for all gas mixtures tested. Gas gain for some of the mixtures is also included.

  13. Longitudinal seam weld characterization by focused ultrasonics

    NASA Astrophysics Data System (ADS)

    Bisbee, Laney H.; Nottingham, Lawrence

    1996-11-01

    Increasingly, the detectability limits placed on inspection methodologies applied to the assessment of critical high energy components in fossil fuelled power plants are being forced to lower values. Most notably, recent events involving longitudinal seam welded piping have raised the question of lowering the detectibility limit for ultrasonics to a level necessary for resolving incipient creep damage. Historically, several testing methods were required for the detection of defects over the range of anticipated flaw sizes in an economically and technically acceptable manner. However, unyielding limitations exist for several of these currently used methods. While accepting that the detection of isolated creep cavities is not technically feasible with current conventional ultrasonic methods, the detection of high density cavitation sheets or zones prior to microcrack initiation has been demonstrated and successfully applied to field inspection of critical welds using focused ultrasonics. This paper describes the equipment and verification process used to extend the detectability limit of a field ultrasonic systems for longitudinal seam weld evaluations to approaching that of an acoustic microscope for the identification of incipient creep cavitation.

  14. Longitudinal dynamics in storage rings

    SciTech Connect

    Colton, E.P.

    1986-01-01

    The single-particle equations of motion are derived for charged particles in a storage ring. Longitudinal space charge is included in the potential assuming an infinitely conducting circular beam pipe with a distributed inductance. The framework uses Hamilton's equations with the canonical variables phi and W. The Twiss parameters for longitudinal motion are also defined for the small amplitude synchrotron oscillations. The space-charge Hamiltonian is calculated for both parabolic bunches and ''matched'' bunches. A brief analysis including second-harmonic rf contributions is also given. The final sections supply calculations of dynamical quantities and particle simulations with the space-charge effects neglected.

  15. Transverse-longitudinal coupling by space charge in cyclotrons

    NASA Astrophysics Data System (ADS)

    Baumgarten, C.

    2011-11-01

    A method is presented that enables one to compute the parameters of matched beams with space charge in cyclotrons with emphasis on the effect of the transverse-longitudinal coupling. Equations describing the transverse-longitudinal coupling and corresponding tune shifts in first order are derived for the model of an azimuthally symmetric cyclotron. The eigenellipsoid of the beam is calculated and the transfer matrix is transformed into block-diagonal form. The influence of the slope of the phase curve on the transverse-longitudinal coupling is accounted for. The results are generalized and numerical procedures for the case of an azimuthally varying field cyclotron are presented. The algorithm is applied to the PSI injector II and ring cyclotron and the results are compared to TRANSPORT.

  16. Generation of flux tube waves in stellar convection zones. 1: Longitudinal tube waves

    NASA Technical Reports Server (NTRS)

    Musielak, Z. E.; Rosner, R.; Ulmschneider, P.

    1987-01-01

    The source functions and the energy fluxes are derived for wave generation in magnetic flux tubes embedded in an otherwise magnetic- field free, turbulent, and compressible fluid. Specific results for the generation of longitudinal tube waves are presented.

  17. LONGITUDINAL STUDY OF AGING (LSOA)

    EPA Science Inventory

    The Longitudinal Study of Aging (LSOA) is a collaborative effort of the National Center for Health Statistics (NCHS) and the National Institute on Aging (NIA). The Supplement on Aging (SOA), conducted in conjunction with the 1984 National Health Interview Survey (NHIS), served as...

  18. Longitudinally-vibrating surgical microelectrode

    NASA Technical Reports Server (NTRS)

    Feldstein, C.; Crawford, D.; Kawabus, E. W.

    1977-01-01

    Microelectrode attached to cone of loudspeaker imparting longitudinal vibrations, penetrates relatively tough tissue of arterial walls easier and with more precise depth control because dimpling is eliminated. Vibrating microelectrode has been successfully used to make accurate oxygen-content measurements in arterial walls.

  19. The National Longitudinal Surveys Handbook.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center for Human Resource Research.

    This volume discussed the research methodology used in the National Longitudinal Surveys of Labor Market Ecperience (NLS). The survey studied employment market conditions for four groups in the labor force: men, aged 45-59; women, aged 30-44; young men, aged 14-24; and young women, aged 14-24. Data were collected on 20,000 individuals over a five…

  20. Longitudinal Diagnostics for Short Electron Beam Bunches

    SciTech Connect

    Loos, H.; /SLAC

    2010-06-11

    Single-pass free electron lasers require high peak currents from ultra-short electron bunches to reach saturation and an accurate measurement of bunch length and longitudinal bunch profile is necessary to control the bunch compression process from low to high beam energy. The various state-of-the-art diagnostics methods from ps to fs time scales using coherent radiation detection, RF deflection, and other techniques are presented. The use of linear accelerators as drivers for free electron lasers (FEL) and the advent of single-pass (SASE) FELs has driven the development of a wide range of diagnostic techniques for measuring the length and longitudinal distribution of short and ultra-short electron bunches. For SASE FELs the radiation power and the length of the undulator needed to achieve saturation depend strongly on the charge density of the electron beam. In the case of X-ray FELs, this requires the accelerator to produce ultra-high brightness beams with micron size transverse normalized emittances and peak currents of several kA through several stages of magnetic bunch compression. Different longitudinal diagnostics are employed to measure the peak current and bunch profile along these stages. The measurement techniques can be distinguished into different classes. Coherent methods detect the light emitted from the beam by some coherent radiation process (spectroscopic measurement), or directly measure the Coulomb field traveling with the beam (electro-optic). Phase space manipulation techniques map the time coordinate onto a transverse dimension and then use conventional transverse beam diagnostics (transverse deflector, rf zero-phasing). Further methods measure the profile or duration of an incoherent light pulse emitted by the bunch at wavelengths much shorted than the bunch length (streak camera, fluctuation technique) or modulate the electron beam at an optical wavelength and then generate a narrow bandwidth radiation pulse with the longitudinal profile of

  1. Single longitudinal mode operation of semiconductor laser arrays with etalon feedback

    NASA Technical Reports Server (NTRS)

    Hemmati, H.

    1987-01-01

    The multiple longitudinal mode output of high-power diode-laser arrays is converted into single mode with 97 percent efficiency by optical feedback from a thin (less than 200-micron thick) etalon external to the laser. The coupled cavities formed by addition of the etalon favor a single longitudinal mode. Single-mode operation is retained at 0.1 MHz pulsed rates. Both the near-field and the far-field patterns of the laser array remain nearly unchanged while the array operates in a single longitudinal mode.

  2. Charge and Current Neutralization of an Ion-Beam Pulse Propagating in a Background Plasma along a Solenoidal Magnetic Field

    SciTech Connect

    Kaganovich, I. D.; Startsev, E. A.; Sefkow, A. B.; Davidson, R. C.

    2007-12-07

    The analytical studies show that the application of a small solenoidal magnetic field can drastically change the self-magnetic and self-electric fields of the beam pulse propagating in a background plasma. Theory predicts that when {omega}{sub ce}{approx}{omega}{sub pe}{beta}{sub b}, where {omega}{sub ce} is the electron gyrofrequency, {omega}{sub pe} is the electron plasma frequency, and {beta}{sub b} is the ion-beam velocity relative to the speed of light, there is a sizable enhancement of the self-electric and self-magnetic fields due to the dynamo effect. Furthermore, the combined ion-beam-plasma system acts as a paramagnetic medium; i.e., the solenoidal magnetic field inside the beam pulse is enhanced.

  3. LONGITUDINAL LASER WIRE AT SNS

    SciTech Connect

    Aleksandrov, Alexander V; Liu, Yun; Zhukov, Alexander P

    2014-01-01

    This paper describes a longitudinal H- beam profile scanner that utilizes laser light to detach convoy electrons and an MCP to collect and measure these electrons. The scanner is located in MEBT with H- energy of 2.5MeV and an RF frequency 402.5MHz. The picosecond pulsed laser runs at 80.5MHz in sync with the accelerator RF. The laser beam is delivered to the beam line through a 30m optical fiber. The pulse width after the fiber transmission measures about 10ps. Scanning the laser phase effectively allows measurements to move along ion bunch longitudinal position. We are able to reliably measure production beam bunch length with this method. The biggest problem we have encountered is background signal from electrons being stripped by vacuum. Several techniques of signal detection are discussed.

  4. Longitudinal spin fluctuations in nickel

    SciTech Connect

    Boeni, P. , Villigen ); Martinez, J.L. ); Tranquada, J.M. )

    1989-10-10

    The longitudinal and transverse spin fluctuations in Ni have been measured below {Tc} by means of polarized neutron scattering in the momentum range 0.06 < q < 0.18 {angstrom}{sup -1}. In transverse scans spin wave peaks at E{sub q} = Dq{sup 2} appear as expected from early measurements performed with unpolarized neutrons. The longitudinal magnetic scattering {sub {chi}L}(q, E), on the other hand, is quasielastic without any signature of inelastic peaks near E{sub q}. The q and T dependences of {sub {chi}L}(q, E) resemble the paramagnetic scattering above {Tc}, i.e., the linewidth is roughly proportional to q{sup 2.5} and the integrated intensity I(q) is proportional to (q{sup 2} + {kappa}{sub z}{sup 2}){sup -1}. 8 refs., 3 figs.

  5. Longitudinal bulk acoustic mass sensor

    SciTech Connect

    Hales, J. H.; Teva, J.; Boisen, A.; Davis, Z. J.

    2009-07-20

    A polycrystalline silicon longitudinal bulk acoustic cantilever is fabricated and operated in air at 51 MHz. A mass sensitivity of 100 Hz/fg (1 fg=10{sup -15} g) is obtained from the preliminary experiments where a minute mass is deposited on the device by means of focused ion beam. The total noise in the currently applied measurement system allows for a minimum detectable mass of 0.5 fg in air.

  6. Parameterized Linear Longitudinal Airship Model

    NASA Technical Reports Server (NTRS)

    Kulczycki, Eric; Elfes, Alberto; Bayard, David; Quadrelli, Marco; Johnson, Joseph

    2010-01-01

    A parameterized linear mathematical model of the longitudinal dynamics of an airship is undergoing development. This model is intended to be used in designing control systems for future airships that would operate in the atmospheres of Earth and remote planets. Heretofore, the development of linearized models of the longitudinal dynamics of airships has been costly in that it has been necessary to perform extensive flight testing and to use system-identification techniques to construct models that fit the flight-test data. The present model is a generic one that can be relatively easily specialized to approximate the dynamics of specific airships at specific operating points, without need for further system identification, and with significantly less flight testing. The approach taken in the present development is to merge the linearized dynamical equations of an airship with techniques for estimation of aircraft stability derivatives, and to thereby make it possible to construct a linearized dynamical model of the longitudinal dynamics of a specific airship from geometric and aerodynamic data pertaining to that airship. (It is also planned to develop a model of the lateral dynamics by use of the same methods.) All of the aerodynamic data needed to construct the model of a specific airship can be obtained from wind-tunnel testing and computational fluid dynamics

  7. Theory of longitudinal beam halo in RF linacs: II. envelope-particle resonances

    SciTech Connect

    Lund, S.M.; Barnard, J.J.

    1997-05-01

    Using the core/test-particle model described in a companion paper in these proceedings (``Theory of Longitudinal Halo in rf Linacs: I. Core/Test Particle Formulation,`` by J. J. Barnard and S. M. Lund), we analyze longitudinal beam halo produced by resonant self-field interactions in intense, ion-beam rf linacs. It is shown that particles moving in the presence of the space-charge forces of an oscillating, mismatched ellipsoidal beam bunch can be resonantly driven to large longitudinal amplitude. This resonantly produced halo is first analyzed in a limit where it is most simply understood, with particles moving purely longitudinally and with linear rf focusing. Then modifications of the resonance induced by nonlinear rf and transverse-longitudinal coupling are explored.

  8. Measurement of longitudinal electron diffusion in liquid argon

    NASA Astrophysics Data System (ADS)

    Li, Yichen; Tsang, Thomas; Thorn, Craig; Qian, Xin; Diwan, Milind; Joshi, Jyoti; Kettell, Steve; Morse, William; Rao, Triveni; Stewart, James; Tang, Wei; Viren, Brett

    2016-04-01

    We report the measurement of longitudinal electron diffusion coefficients in liquid argon for electric fields between 100 and 2000 V/cm with a gold photocathode as a bright electron source. The measurement principle, apparatus, and data analysis are described. In the region between 100 and 350 V/cm, our results show a discrepancy with the previous measurement [1]. In the region between 350 and 2000 V/cm, our results represent the world's best measurement. Over the entire measured electric field range, our results are systematically higher than the calculation of Atrazhev-Timoshkin [2]. The quantum efficiency of the gold photocathode, the drift velocity and longitudinal diffusion coefficients in gas argon are also presented.

  9. Using Hand Grip Force as a Correlate of Longitudinal Acceleration Comfort for Rapid Transit Trains

    PubMed Central

    Guo, Beiyuan; Gan, Weide; Fang, Weining

    2015-01-01

    Longitudinal acceleration comfort is one of the essential metrics used to evaluate the ride comfort of train. The aim of this study was to investigate the effectiveness of using hand grip force as a correlate of longitudinal acceleration comfort of rapid transit trains. In the paper, a motion simulation system was set up and a two-stage experiment was designed to investigate the role of the grip force on the longitudinal comfort of rapid transit trains. The results of the experiment show that the incremental grip force was linearly correlated with the longitudinal acceleration value, while the incremental grip force had no correlation with the direction of the longitudinal acceleration vector. The results also show that the effects of incremental grip force and acceleration duration on the longitudinal comfort of rapid transit trains were significant. Based on multiple regression analysis, a step function model was established to predict the longitudinal comfort of rapid transit trains using the incremental grip force and the acceleration duration. The feasibility and practicably of the model was verified by a field test. Furthermore, a comparative analysis shows that the motion simulation system and the grip force based model were valid to support the laboratory studies on the longitudinal comfort of rapid transit trains. PMID:26147730

  10. Nanofocusing of longitudinally polarized light using absorbance modulation

    SciTech Connect

    Li, Qiang; Zhao, Xing Zhang, Bo; Zheng, Yi; Zhou, Liqiu; Fang, Zhiliang; Wang, Lingjie; Wu, Yanxiong

    2014-02-10

    Recently, many methods based on amplitude or phase modulation to reduce the focal spot and enhance the longitudinal field component of a tight-focused radially polarized light beam have been suggested. But they all suffer from spot size limit 0.36λ/NA and large side lobes strength in longitudinal component. Here, we report a method of generating a tighter focused spot by focusing radially polarized and azimuthally polarized beams of different wavelengths on a thin photochromic film through a high-numerical-aperture lens simultaneously. In this method, by suppressing the radial component and compressing the longitudinal component of radially polarized beam, absorbance modulation makes the ultimate spot size break the size limit of 0.36λ/NA with side-lobe intensity of longitudinal component below 1% of central-peak intensity. The theoretical analysis and simulation demonstrate that the focal spot size could be smaller than 0.1λ with nearly all radial component blocked at high intensity ratio of the two illuminating beams.

  11. Longitudinal Oscillations in Density Stratified and Expanding Solar Waveguides

    NASA Astrophysics Data System (ADS)

    Luna-Cardozo, M.; Verth, G.; Erdélyi, R.

    2012-04-01

    Waves and oscillations can provide vital information about the internal structure of waveguides in which they propagate. Here, we analytically investigate the effects of density and magnetic stratification on linear longitudinal magnetohydrodynamic (MHD) waves. The focus of this paper is to study the eigenmodes of these oscillations. It is our specific aim to understand what happens to these MHD waves generated in flux tubes with non-constant (e.g., expanding or magnetic bottle) cross-sectional area and density variations. The governing equation of the longitudinal mode is derived and solved analytically and numerically. In particular, the limit of the thin flux tube approximation is examined. The general solution describing the slow longitudinal MHD waves in an expanding magnetic flux tube with constant density is found. Longitudinal MHD waves in density stratified loops with constant magnetic field are also analyzed. From analytical solutions, the frequency ratio of the first overtone and fundamental mode is investigated in stratified waveguides. For small expansion, a linear dependence between the frequency ratio and the expansion factor is found. From numerical calculations it was found that the frequency ratio strongly depends on the density profile chosen and, in general, the numerical results are in agreement with the analytical results. The relevance of these results for solar magneto-seismology is discussed.

  12. LONGITUDINAL OSCILLATIONS IN DENSITY STRATIFIED AND EXPANDING SOLAR WAVEGUIDES

    SciTech Connect

    Luna-Cardozo, M.; Verth, G.; Erdelyi, R. E-mail: robertus@sheffield.ac.uk

    2012-04-01

    Waves and oscillations can provide vital information about the internal structure of waveguides in which they propagate. Here, we analytically investigate the effects of density and magnetic stratification on linear longitudinal magnetohydrodynamic (MHD) waves. The focus of this paper is to study the eigenmodes of these oscillations. It is our specific aim to understand what happens to these MHD waves generated in flux tubes with non-constant (e.g., expanding or magnetic bottle) cross-sectional area and density variations. The governing equation of the longitudinal mode is derived and solved analytically and numerically. In particular, the limit of the thin flux tube approximation is examined. The general solution describing the slow longitudinal MHD waves in an expanding magnetic flux tube with constant density is found. Longitudinal MHD waves in density stratified loops with constant magnetic field are also analyzed. From analytical solutions, the frequency ratio of the first overtone and fundamental mode is investigated in stratified waveguides. For small expansion, a linear dependence between the frequency ratio and the expansion factor is found. From numerical calculations it was found that the frequency ratio strongly depends on the density profile chosen and, in general, the numerical results are in agreement with the analytical results. The relevance of these results for solar magneto-seismology is discussed.

  13. Generalized longitudinal susceptibility for magnetic monopoles in spin ice

    PubMed Central

    Bramwell, Steven T.

    2012-01-01

    The generalized longitudinal susceptibility χ(q,ω) affords a sensitive measure of the spatial and temporal correlations of magnetic monopoles in spin ice. Starting with the monopole model, a mean field expression for χ(q,ω) is derived as well as expressions for the mean square longitudinal field and induction at a point. Monopole motion is shown to be strongly correlated, and both spatial and temporal correlations are controlled by the dimensionless monopole density x which defines the ratio of the magnetization relaxation rate and the monopole hop rate. Thermal effects and spin-lattice relaxation are also considered. The derived equations are applicable in the temperature range where the Wien effect for magnetic monopoles is negligible. They are discussed in the context of existing theories of spin ice and the following experimental techniques: DC and AC magnetization, neutron scattering, neutron spin echo and longitudinal and transverse field μSR. The monopole theory is found to unify diverse experimental results, but several discrepancies between theory and experiment are identified. One of these, concerning the neutron scattering line shape, is explained by means of a phenomenological modification to the theory. PMID:23166378

  14. Chiral current generation in QED by longitudinal photons

    NASA Astrophysics Data System (ADS)

    Acosta Avalo, J. L.; Pérez Rojas, H.

    2016-08-01

    We report the generation of a pseudovector electric current having imbalanced chirality in an electron-positron strongly magnetized gas in QED. It propagates along the external applied magnetic field B as a chiral magnetic effect in QED. It is triggered by a perturbative electric field parallel to B, associated to a pseudovector longitudinal mode propagating along B. An electromagnetic chemical potential was introduced, but our results remain valid even when it vanishes. A nonzero fermion mass was assumed, which is usually considered vanishing in the literature. In the quantum field theory formalism at finite temperature and density, an anomaly relation for the axial current was found for a medium of massive fermions. It bears some analogy to the Adler-Bell-Jackiw anomaly. From the expression for the chiral current in terms of the photon self-energy tensor in a medium, it is obtained that electrons and positrons scattered by longitudinal photons (inside the light cone) contribute to the chiral current, as well as the to pair creation due to longitudinal photons (out of light cone). In the static limit, an electric pseudovector current is obtained in the lowest Landau level.

  15. Analysis of critically refracted longitudinal waves

    NASA Astrophysics Data System (ADS)

    Pei, Ning; Bond, Leonard J.

    2015-03-01

    Fabrication processes, such as, welding, forging, and rolling can induce residual stresses in metals that will impact product performance and phenomena such as cracking and corrosion. To better manage residual stress tools are needed to map their distribution. The critically refracted ultrasonic longitudinal (LCR) wave is one such approach that has been used for residual stress characterization. It has been shown to be sensitive to stress and less sensitive to the effects of the texture of the material. Although the LCR wave is increasingly widely applied, the factors that influence the formation of the LCR beam are seldom discussed. This paper reports a numerical model used to investigate the transducers' parameters that can contribute to the directionality of the LCR wave and hence enable performance optimization when used for industrial applications. An orthogonal test method is used to study the transducer parameters which influence the LCR wave beams. This method provides a design tool that can be used to study and optimize multiple parameter experiments and it can identify which parameter or parameters are of most significance. The simulation of the sound field in a 2-D "water-steel" model is obtained using a Spatial Fourier Analysis method. The effects of incident angle, standoff, the aperture and the center frequency of the transducer were studied. Results show that the aperture of the transducer, the center frequency and the incident angle are the most important factors in controlling the directivity of the resulting LCR wave fields.

  16. Analysis of critically refracted longitudinal waves

    SciTech Connect

    Pei, Ning Bond, Leonard J.

    2015-03-31

    Fabrication processes, such as, welding, forging, and rolling can induce residual stresses in metals that will impact product performance and phenomena such as cracking and corrosion. To better manage residual stress tools are needed to map their distribution. The critically refracted ultrasonic longitudinal (LCR) wave is one such approach that has been used for residual stress characterization. It has been shown to be sensitive to stress and less sensitive to the effects of the texture of the material. Although the LCR wave is increasingly widely applied, the factors that influence the formation of the LCR beam are seldom discussed. This paper reports a numerical model used to investigate the transducers' parameters that can contribute to the directionality of the LCR wave and hence enable performance optimization when used for industrial applications. An orthogonal test method is used to study the transducer parameters which influence the LCR wave beams. This method provides a design tool that can be used to study and optimize multiple parameter experiments and it can identify which parameter or parameters are of most significance. The simulation of the sound field in a 2-D 'water-steel' model is obtained using a Spatial Fourier Analysis method. The effects of incident angle, standoff, the aperture and the center frequency of the transducer were studied. Results show that the aperture of the transducer, the center frequency and the incident angle are the most important factors in controlling the directivity of the resulting LCR wave fields.

  17. Plasma laser accelerator: longitudinal dynamics, the plasma/laser interaction, and a qualitative design

    SciTech Connect

    Ruth, R.D.; Chao, A.W.

    1982-04-01

    In this paper we present our studies on a plasma laser accelerator. First we look at the longitudinal dynamics and the trapping of particles in the potential well due to the longitudinal electric field in a plasma density wave. Next we study the plasma/laser interaction to obtain power requirements. Lastly, we qualitatively design a plasma/laser accelerator with parameters somewhat more modest than existing suggestions.

  18. Longitudinal Space Charge Effects in the JLAB IR FEL SRF LINAC

    SciTech Connect

    C. Hernandez-Garcia; K. Beard; C. Behre; S. Benson; G. Biallas; J. Boyce; D. Douglas; H. F. Dylla; R. Evans; A. Grippo; J. Gubeli; D. Hardy; K. Jordan; L. Merminga; G. Neil; J. Preble; Michelle D. Shinn; T. Siggins; R. Walker; G. P. Williams; B. Yunn; S. Zhang

    2004-09-01

    Observations of energy spread asymmetry when operating the Linac on either side of crest and longitudinal emittance growth have been confirmed by extending PARMELA simulations from the injector to the end of the first SRF Linac module. The asymmetry can be explained by the interaction of the accelerating electric field with that from longitudinal space charge effects within the electron bunch. This can be a major limitation to performance in FEL accelerators.

  19. Excitation of kinetic Alfven waves by resonant mode conversion and longitudinal heating of magnetized plasmas

    NASA Technical Reports Server (NTRS)

    Tanaka, Motohiko; Sato, Tetsuya; Hasegawa, A.

    1989-01-01

    The excitation of the kinetic Alfven wave by resonant mode conversion and longitudinal heating of the plasma by the kinetic Alfven wave were demonstrated on the basis of a macroscale particle simulation. The longitudinal electron current was shown to be cancelled by the ions. The kinetic Alfven wave produced an ordered motion of the plasma particles in the wave propagation direction. The electrons were pushed forward along the ambient magnetic field by absorbing the kinetic Alfven wave through the Landau resonance.

  20. Longitudinal study of fingerprint recognition

    PubMed Central

    Yoon, Soweon; Jain, Anil K.

    2015-01-01

    Human identification by fingerprints is based on the fundamental premise that ridge patterns from distinct fingers are different (uniqueness) and a fingerprint pattern does not change over time (persistence). Although the uniqueness of fingerprints has been investigated by developing statistical models to estimate the probability of error in comparing two random samples of fingerprints, the persistence of fingerprints has remained a general belief based on only a few case studies. In this study, fingerprint match (similarity) scores are analyzed by multilevel statistical models with covariates such as time interval between two fingerprints in comparison, subject’s age, and fingerprint image quality. Longitudinal fingerprint records of 15,597 subjects are sampled from an operational fingerprint database such that each individual has at least five 10-print records over a minimum time span of 5 y. In regard to the persistence of fingerprints, the longitudinal analysis on a single (right index) finger demonstrates that (i) genuine match scores tend to significantly decrease when time interval between two fingerprints in comparison increases, whereas the change in impostor match scores is negligible; and (ii) fingerprint recognition accuracy at operational settings, nevertheless, tends to be stable as the time interval increases up to 12 y, the maximum time span in the dataset. However, the uncertainty of temporal stability of fingerprint recognition accuracy becomes substantially large if either of the two fingerprints being compared is of poor quality. The conclusions drawn from 10-finger fusion analysis coincide with the conclusions from single-finger analysis. PMID:26124106

  1. Longitudinal heritability of childhood aggression.

    PubMed

    Porsch, Robert M; Middeldorp, Christel M; Cherny, Stacey S; Krapohl, Eva; van Beijsterveldt, Catharina E M; Loukola, Anu; Korhonen, Tellervo; Pulkkinen, Lea; Corley, Robin; Rhee, Soo; Kaprio, Jaakko; Rose, Richard R; Hewitt, John K; Sham, Pak; Plomin, Robert; Boomsma, Dorret I; Bartels, Meike

    2016-07-01

    The genetic and environmental contributions to the variation and longitudinal stability in childhood aggressive behavior were assessed in two large twin cohorts, the Netherlands Twin Register (NTR), and the Twins Early Development Study (TEDS; United Kingdom). In NTR, maternal ratings on aggression from the Child Behavior Checklist (CBCL) were available for 10,765 twin pairs at age 7, for 8,557 twin pairs at age 9/10, and for 7,176 twin pairs at age 12. In TEDS, parental ratings of conduct disorder from the Strength and Difficulty Questionnaire (SDQ) were available for 6,897 twin pairs at age 7, for 3,028 twin pairs at age 9 and for 5,716 twin pairs at age 12. In both studies, stability and heritability of aggressive behavioral problems was high. Heritability was on average somewhat, but significantly, lower in TEDS (around 60%) than in NTR (between 50% and 80%) and sex differences were slightly larger in the NTR sample. In both studies, the influence of shared environment was similar: in boys shared environment explained around 20% of the variation in aggression across all ages while in girls its influence was absent around age 7 and only came into play at later ages. Longitudinal genetic correlations were the main reason for stability of aggressive behavior. Individual differences in CBCL-Aggressive Behavior and SDQ-Conduct disorder throughout childhood are driven by a comparable but significantly different genetic architecture. © 2016 Wiley Periodicals, Inc. PMID:26786601

  2. Comparison of Earth-Based Longitudinal Studies and Cassini CIRS Observations of Saturn's Temperature Field: Modifications of Seasonal Forcing Models and the Discovery of Nonseasonal Low-Latitude Thermal Oscillations

    NASA Astrophysics Data System (ADS)

    Orton, G.; Parrish, P.; Yanamandra-Fisher, P.; Fisher, B.; Fletcher, L.; Irwin, P.; Nelson, J.; Gezari, D.; Fuse, T.; Fujiyoshi, T.

    2006-12-01

    During the sequence of observations made by Cassini CIRS from 2004 to the present, supporting observations of Saturn have been made in the same spectral region. Most of these were taken at NASA's 3-m Infrared Telescope Facility (IRTF), but they were supplemented by observations from the 8.2-m Subaru Telescope. An examination of temperature field retrieved from form spacecraft and earth-based observations has required us to assess carefully the limitation of vertical sensitivity for the ground-based images and the calibration of both geometry and absolute radiance. Keeping those limitations in mind, the combination of the two data sets has provided evidence that is consistent with the absence of effective cloud opacity in the mid- and far-infrared. Furthermore, the full sequence of ground-based imaging stretches back as early as 1990. These observations clearly indicate the expected hemispherically antisymmetric seasonal forcing, but with relaxation times considerably shorter than the 9-year scales in both the stratosphere and upper troposphere expected from gaseous constituents alone. An important non- seasonal effect was also noted in the long-term behavior of the equator and low-latitude regions which undergo a periodic oscillation with an alternating phases of thermal waves at the equator and at latitudes 5-25 degrees poleward in both hemispheres over a period of 20 years or longer. The observed behavior is consistent with the different stratospheric temperature profiles of these regions. This phenomenon is best explained by the presence of upwelling thermal waves which are similar to the Earth's quasi-biennial oscillation (QBO) and Jupiter's quasi-quadrennial oscillation (QQO).

  3. Longitudinal confinement and matching of an intense electron beam

    NASA Astrophysics Data System (ADS)

    Beaudoin, B.; Haber, I.; Kishek, R. A.; Bernal, S.; Koeth, T.; Sutter, D.; O'Shea, P. G.; Reiser, M.

    2011-01-01

    An induction cell has successfully been demonstrated to longitudinally confine a space-charge dominated bunch for over a thousand turns (>11.52 km) in the University of Maryland Electron Ring [Haber et al., Nucl. Instrum. Methods Phys. Res. A 606, 64 (2009) and R. A. Kishek et al., Int. J. Mod. Phys. A 22, 3838 (2007)]. With the use of synchronized periodic focusing fields, the beam is confined for multiple turns overcoming the longitudinal space-charge forces. Experimental results show that an optimum longitudinal match is obtained when the focusing frequency for containment of the 0.52 mA beam is applied at every fifth turn. Containment of the beam bunch is achievable at lower focusing frequencies, at the cost of a reduction in the transported charge from the lack of sufficient focusing. Containment is also obtainable, if the confinement fields overfocus the bunch, exciting multiple waves at the bunch ends, which propagate into the central region of the beam, distorting the overall constant current beam shape.

  4. Generation of a global longitudinal asymmetry in Saturn's magnetosphere

    NASA Astrophysics Data System (ADS)

    Hill, T. W.; Jaggi, A.; Wolf, R.; Sazykin, S. Y.

    2014-12-01

    Numerous empirical studies have indicated that a global longitudinal asymmetry of Saturn's magnetospheric plasma population (the m=1 term in a Fourier expansion, where m is the azimuthal wavenumber) is required to explain observed spin-periodic modulations (~ 10.7 hr) of magnetospheric behavior (e.g., Carbary and Mitchell [2013], Rev. Geophys., 51, doi:10.1029/2012RG000416, and references therein). This is true in spite of the fact that Saturn's intrinsic magnetic field is well described by a perfectly spin-aligned dipole. The Rice Convection Model (RCM) has been used previously to simulate plasma transport in Saturn's magnetosphere with a spin-aligned dipole field and a longitudinally symmetric plasma source that is largely confined to the radial range L ~ 5 - 8 (e.g., Liu et al. [2010], J. Geophys. Res., 115, doi:10.1029/2010JA015859; Liu and Hill [2012], J. Geophys. Res., 117, doi:10.1029/2012JA017827). We have begun to explore the consequences of a global-scale longitudinal asymmetry of the plasma source. Preliminary results indicate that a small (~1%) asymmetry of the imposed plasma source produces a magnetospherically significant (factor ~2) m=1 asymmetry of the resultant plasma distribution in the middle magnetosphere (L ~ 8-15). Our objective is not to explain the (still mysterious) underlying cause of the source asymmetry, but rather to investigate the effects of a given source asymmetry on the plasma distribution in the more distant magnetosphere.

  5. Transverse-longitudinal integrated resonator

    SciTech Connect

    Hutchinson, Donald P; Simpson, Marcus L; Simpson, John T

    2003-03-11

    A transverse-longitudinal integrated optical resonator (TLIR) is disclosed which includes a waveguide, a first and a second subwavelength resonant grating in the waveguide, and at least one photonic band gap resonant structure (PBG) in the waveguide. The PBG is positioned between the first and second subwavelength resonant gratings. An electro-optic waveguide material may be used to permit tuning the TLIR and to permit the TLIR to perform signal modulation and switching. The TLIR may be positioned on a bulk substrate die with one or more electronic and optical devices and may be communicably connected to the same. A method for fabricating a TLIR including fabricating a broadband reflective grating is disclosed. A method for tuning the TLIR's transmission resonance wavelength is also disclosed.

  6. Laser wakefield excitation and measurement by femtosecond longitudinal interferometry

    SciTech Connect

    Siders, C.W.; Le Blanc, S.P.; Fisher, D.; Tajima, T.; Downer, M.C.; Babine, A.; Stepanov, A.; Sergeev, A.

    1996-04-01

    Plasma density oscillations (Langmuir waves) in the wake of an intense (I{sub peak} {approximately} 3 {times} 10{sup 17}W/cm{sup 2}) laser pulse (100 fs) are measured with ultrafast time resolution using a longitudinal interferometric technique. Phase shifts consistent with large amplitude ({delta}n{sub e}/n{sub e} {approximately} 1) density waves at the electron plasma frequency were observed in a fully tunnel-ionized He plasma, corresponding to longitudinal electric fields of {approximately} 10 GV/m. Strong radial ponderomotive forces enhance the density oscillations. As this technique utilizes a necessary component of any laser-based plasma accelerator, it promises to be a powerful tool for on-line monitoring and control of future plasma-based particle accelerators.

  7. Longitudinal Proximity Effects in Superconducting Transition-Edge Sensors

    NASA Technical Reports Server (NTRS)

    Sadlier, John E.; Smith, Stephen J.; Bandler, Simon R.; Chervenak, James A.; Clem, John R.

    2009-01-01

    We have found experimentally that the critical current of a square thin-film superconducting transition-edge sensor (TES) depends exponentially upon the side length L and the square root of the temperature T, a behavior that has a natural theoretical explanation in terms of longitudinal proximity effects if the TES is regarded as a weak link between superconducting leads. As a consequence, the effective transition temperature T(sub c) of the TES is current-dependent and at fixed current scales as 1/L(sup 2). We also have found that the critical current can show clear Fraunhofer-like oscillations in an applied magnetic field, similar to those found in Josephson junctions. We have observed the longitudinal proximity effect in these devices over extraordinarily long lengths up to 290 micrometers, 1450 times the mean-free path.

  8. Longitudinal Proximity Effects in Superconducting Transition-Edge Sensors

    NASA Technical Reports Server (NTRS)

    Sadleir, John E.; Smith, Stephen J.; Bandler, Simon R.; Chervenak, James A.; Clem, John R.

    2010-01-01

    We have found experimentally that the critical current of a square thin-film superconducting transition-edge sensor (TES) depends exponentially upon the side length L and the square root of the temperature T, a behavior that has a natural theoretical explanation in terms of longitudinal proximity effects if the TES is regarded as a weak link between superconducting leads. As a consequence, the effective transition temperature T(sub c) of the TES is current-dependent and at fixed current scales as 1/L(sup 2). We also have found that the critical current can show clear Fraunhofer-like oscillations in an applied magnetic field, similar to those found in Josephson junctions. We have observed the longitudinal proximity effect in these devices over extraordinarily long lengths up to 290 micrometers, 1450 times the mean-free path.

  9. First measurement of laser Wakefield oscillations by longitudinal interferometry

    SciTech Connect

    Siders, C.W.; Le Blanc, S.P.; Rau, B.; Fisher, D.; Tajima, T.; Downer, M.C.; Babine, A.; Stepanov, A.; Sergeev, A.

    1996-12-31

    Because the electrostatic fields present in plasma waves can exceed those achievable in conventional accelerators and approach atomic scale values (E{sub a} {approximately} 500 GV/m), plasma based accelerators have received considerable attention as compact sources of high-energy electron pulses. Although stimulated Raman scattering or terahertz radiation at {ital w{sub p}} provided spatially averaged optical signatures of the plasma wave`s existence, new diagnostic techniques are required to map the the temporal and spatial structure of the plasma wave directly since such information is vital for addressing fundamental issues of wakefield generation and propagation. In this paper, we report femtosecond time resolved measurements of the longitudinal and radial structure of laser wakefield oscillations using an all optical technique known as interferometric ``photon acceleration`` or Longitudinal Interferometry.

  10. Fears in Czech Adolescents: A Longitudinal Study

    ERIC Educational Resources Information Center

    Michalcáková, Radka; Lacinová, Lenka; Kyjonková, Hana; Bouša, Ondrej; Jelínek, Martin

    2013-01-01

    The present study investigates developmental patterns of fear in adolescence. It is based on longitudinal data collected as a part of the European Longitudinal Study of Pregnancy and Childhood (ELSPAC) project. A total of 186 Czech adolescents (43% girls) were assessed repeatedly at the age of 11, 13, and 15 years. The free-response method was…

  11. 14 CFR 25.145 - Longitudinal control.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Longitudinal control. 25.145 Section 25.145 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Controllability and Maneuverability § 25.145 Longitudinal control. (a) It must be possible,...

  12. Modeling a Longitudinal Relational Research Data Systems

    ERIC Educational Resources Information Center

    Olsen, Michelle D. Hunt

    2010-01-01

    A study was conducted to propose a research-based model for a longitudinal data research system that addressed recommendations from a synthesis of literature related to: (1) needs reported by the U.S. Department of Education, (2) the twelve mandatory elements that define federally approved state longitudinal data systems (SLDS), (3) the…

  13. Transverse and longitudinal vibrations in amorphous silicon

    NASA Astrophysics Data System (ADS)

    Beltukov, Y. M.; Fusco, C.; Tanguy, A.; Parshin, D. A.

    2015-12-01

    We show that harmonic vibrations in amorphous silicon can be decomposed to transverse and longitudinal components in all frequency range even in the absence of the well defined wave vector q. For this purpose we define the transverse component of the eigenvector with given ω as a component, which does not change the volumes of Voronoi cells around atoms. The longitudinal component is the remaining orthogonal component. We have found the longitudinal and transverse components of the vibrational density of states for numerical model of amorphous silicon. The vibrations are mostly transverse below 7 THz and above 15 THz. In the frequency interval in between the vibrations have a longitudinal nature. Just this sudden transformation of vibrations at 7 THz from almost transverse to almost longitudinal ones explains the prominent peak in the diffusivity of the amorphous silicon just above 7 THz.

  14. LSTGEE: longitudinal analysis of neuroimaging data

    NASA Astrophysics Data System (ADS)

    Li, Yimei; Zhu, Hongtu; Chen, Yasheng; An, Hongyu; Gilmore, John; Lin, Weili; Shen, Dinggang

    2009-02-01

    Longitudinal imaging studies are essential to understanding the neural development of neuropsychiatric disorders, substance use disorders, and normal brain. Using appropriate image processing and statistical tools to analyze the imaging, behavioral, and clinical data is critical for optimally exploring and interpreting the findings from those imaging studies. However, the existing imaging processing and statistical methods for analyzing imaging longitudinal measures are primarily developed for cross-sectional neuroimaging studies. The simple use of these cross-sectional tools to longitudinal imaging studies will significantly decrease the statistical power of longitudinal studies in detecting subtle changes of imaging measures and the causal role of time-dependent covariate in disease process. The main objective of this paper is to develop longitudinal statistics toolbox, called LSTGEE, for the analysis of neuroimaging data from longitudinal studies. We develop generalized estimating equations for jointly modeling imaging measures with behavioral and clinical variables from longitudinal studies. We develop a test procedure based on a score test statistic and a resampling method to test linear hypotheses of unknown parameters, such as associations between brain structure and function and covariates of interest, such as IQ, age, gene, diagnostic groups, and severity of disease. We demonstrate the application of our statistical methods to the detection of the changes of the fractional anisotropy across time in a longitudinal neonate study. Particularly, our results demonstrate that the use of longitudinal statistics can dramatically increase the statistical power in detecting the changes of neuroimaging measures. The proposed approach can be applied to longitudinal data with multiple outcomes and accommodate incomplete and unbalanced data, i.e., subjects with different number of measurements.

  15. Statistical image analysis of longitudinal RAVENS images

    PubMed Central

    Lee, Seonjoo; Zipunnikov, Vadim; Reich, Daniel S.; Pham, Dzung L.

    2015-01-01

    Regional analysis of volumes examined in normalized space (RAVENS) are transformation images used in the study of brain morphometry. In this paper, RAVENS images are analyzed using a longitudinal variant of voxel-based morphometry (VBM) and longitudinal functional principal component analysis (LFPCA) for high-dimensional images. We demonstrate that the latter overcomes the limitations of standard longitudinal VBM analyses, which does not separate registration errors from other longitudinal changes and baseline patterns. This is especially important in contexts where longitudinal changes are only a small fraction of the overall observed variability, which is typical in normal aging and many chronic diseases. Our simulation study shows that LFPCA effectively separates registration error from baseline and longitudinal signals of interest by decomposing RAVENS images measured at multiple visits into three components: a subject-specific imaging random intercept that quantifies the cross-sectional variability, a subject-specific imaging slope that quantifies the irreversible changes over multiple visits, and a subject-visit specific imaging deviation. We describe strategies to identify baseline/longitudinal variation and registration errors combined with covariates of interest. Our analysis suggests that specific regional brain atrophy and ventricular enlargement are associated with multiple sclerosis (MS) disease progression. PMID:26539071

  16. Bayesian response adaptive randomization using longitudinal outcomes.

    PubMed

    Hatayama, Tomoyoshi; Morita, Satoshi; Sakamaki, Kentaro

    2015-01-01

    The response adaptive randomization (RAR) method is used to increase the number of patients assigned to more efficacious treatment arms in clinical trials. In many trials evaluating longitudinal patient outcomes, RAR methods based only on the final measurement may not benefit significantly from RAR because of its delayed initiation. We propose a Bayesian RAR method to improve RAR performance by accounting for longitudinal patient outcomes (longitudinal RAR). We use a Bayesian linear mixed effects model to analyze longitudinal continuous patient outcomes for calculating a patient allocation probability. In addition, we aim to mitigate the loss of statistical power because of large patient allocation imbalances by embedding adjusters into the patient allocation probability calculation. Using extensive simulation we compared the operating characteristics of our proposed longitudinal RAR method with those of the RAR method based only on the final measurement and with an equal randomization method. Simulation results showed that our proposed longitudinal RAR method assigned more patients to the presumably superior treatment arm compared with the other two methods. In addition, the embedded adjuster effectively worked to prevent extreme patient allocation imbalances. However, our proposed method may not function adequately when the treatment effect difference is moderate or less, and still needs to be modified to deal with unexpectedly large departures from the presumed longitudinal data model. PMID:26099995

  17. Longitudinal oscillation of launch vehicles

    NASA Technical Reports Server (NTRS)

    Glaser, R. F.

    1973-01-01

    During powered flight a vehicle may develop longitudinal self-excited oscillations, so-called oscillations, of its structure. The energy supplying the vibration is tapped from the thrust by the activity of the system itself; that is, oscillation of the structure causes oscillation of the propellant system, especially of the pumps. In this way an oscillating thrust can be created that, by a feedback loop, may sustain the structural oscillation under certain circumstances. Two special features of the system proved to be essential for creation of instability. One is the effect of the inherent time interval that the thrust oscillation is lagging behind the structural oscillation. The other is the decreased of system mass caused by the exhausting of gas. The latter feature may cause an initially stable system to become unstable. To examine the stability of the system, a single mass-spring model, which is the result of a one-term Galerkin approach to the equation of motion, has been considered. The Nyquist stability criterion leads to a stability graph that shows the stability conditions in terms of the system parameter and also demonstrates the significance of time lag, feedback magnitude, and loss of mass. An important conclusion can be drawn from the analysis: large relative displacements of the pump-engine masses favor instability. This is also confirmed by flight measurements.

  18. Psychiatric resilience: longitudinal twin study†

    PubMed Central

    Amstadter, Ananda B.; Myers, John M.; Kendler, Kenneth S.

    2014-01-01

    Background The source of variability in people’s response to stressful life events is poorly understood. Aims We examine the genetic and environmental underpinning of resilience (i.e. the difference between the twins’ internalising symptoms and their predicted symptoms based on cumulative stressful life events). Method Stressful life event exposure and internalising symptoms were assessed at two time points in 7500 adult twins. Using the residual between actual and predicted internalising symptom total score, twin modelling was conducted for each wave separately and longitudinally. Results Resilience was found to have a moderate genetic heritability at each wave (∼31%). Qualitative gender effects were found. Incorporating error of measurement into the model increased the estimated heritability for the latent construct of resilience (∼50%). When measurement error and occasion-specific effects were removed, environmental influences contributed roughly equally to level of resilience. Conclusions Both genes and environment influence level of psychiatric resilience, and are largely stable over time. Environmental influences can have an enduring effect on resilience. PMID:24723629

  19. Breaking of Longitudinal Akhiezer-Polovin Waves

    NASA Astrophysics Data System (ADS)

    Verma, Prabal Singh; Sengupta, Sudip; Kaw, Predhiman

    2012-03-01

    The breaking of longitudinal Akhiezer-Polovin (AP) waves is demonstrated using a one-dimensional simulation based on the Dawson sheet model. It is found that the AP longitudinal waves break through the process of phase mixing at an amplitude well below the breaking amplitude for AP waves, when subjected to arbitrarily small longitudinal perturbations. Results from the simulation show a good agreement with the Dawson phase mixing formula modified to include relativistic mass variation effects. This result may be of direct relevance to the laser- or particle-beam plasma wakefield experiments.

  20. TRANSVERSE OSCILLATIONS OF A LONGITUDINALLY STRATIFIED CORONAL LOOP SYSTEM

    SciTech Connect

    Fathalian, N.; Safari, H. E-mail: safari@znu.ac.i

    2010-11-20

    Collective transverse coronal loop oscillations seem to be detected in observational studies. In this regard, Luna et al. modeled the collective kink-like normal modes of several cylindrical loop systems using the T-matrix theory. This paper investigates the effects of longitudinal density stratification along the loop axis on the collective kink-like modes of the system of coronal loops. The coronal loop system is modeled as cylinders of parallel flux tubes, with two ends of each loop at the dense photosphere. The flux tubes are considered as uniform magnetic fields, with stratified density along the loop axis which changes discontinuously at the lateral surface of each cylinder. The MHD equations are reduced to solve a set of two coupled dispersion relations for frequencies and wavenumbers, in the presence of a stratification parameter. The fundamental and first overtone frequencies and longitudinal wavenumbers are computed. The previous results are verified for an unstratified coronal loop system. Finally, we conclude that an increased longitudinal density stratification parameter will result in an increase of the frequencies. The frequency ratios, first overtones to fundamentals, are very sensitive functions of the density scale height parameter. Therefore, stratification should be included in dynamics of coronal loop systems. For unstratified coronal loop systems, these ratios are the same as monoloop ones.

  1. Atmospheric lateral and longitudinal turbulent length scales (measured at 600 to 800 meters above grade level)

    NASA Technical Reports Server (NTRS)

    Cliff, W. C.; Skarda, J. R.

    1987-01-01

    NASA's Airborne Doppler Lidar System has been used to obtain a detailed 'instantaneous' mapping of horizontal spatial wind fields at 600-800 m elevations on the east side of the San Gorgonio Pass in California, in the form of checkerboard-fashion horizontal wind vectors spaced at 300 m intervals along and normal to the flight path. Spatial autocorrelations for the lateral and longitudinal components are ensemble-averaged, and integral turbulent length scales are computed for the wind fields' longitudinal and lateral directions. The flow in the region studied does not appear to be isotropic.

  2. Controlling charge and current neutralization of an ion beam pulse in a background plasma by application of a solenoidal magnetic field: Weak magnetic field limit

    SciTech Connect

    Kaganovich, I. D.; Startsev, E. A.; Sefkow, A. B.; Davidson, R. C.

    2008-10-15

    Propagation of an intense charged particle beam pulse through a background plasma is a common problem in astrophysics and plasma applications. The plasma can effectively neutralize the charge and current of the beam pulse, and thus provides a convenient medium for beam transport. The application of a small solenoidal magnetic field can drastically change the self-magnetic and self-electric fields of the beam pulse, thus allowing effective control of the beam transport through the background plasma. An analytic model is developed to describe the self-magnetic field of a finite-length ion beam pulse propagating in a cold background plasma in a solenoidal magnetic field. The analytic studies show that the solenoidal magnetic field starts to influence the self-electric and self-magnetic fields when {omega}{sub ce} > or approx. {omega}{sub pe}{beta}{sub b}, where {omega}{sub ce}=eB/m{sub e}c is the electron gyrofrequency, {omega}{sub pe} is the electron plasma frequency, and {beta}{sub b}=V{sub b}/c is the ion beam velocity relative to the speed of light. This condition typically holds for relatively small magnetic fields (about 100 G). Analytical formulas are derived for the effective radial force acting on the beam ions, which can be used to minimize beam pinching. The results of analytic theory have been verified by comparison with the simulation results obtained from two particle-in-cell codes, which show good agreement.

  3. Controlling Charge and Current Neutralization of an Ion Beam Pulse in a Background Plasma by Application of a Solenoidal Magnetic Field I: Weak Magnetic Field Limit

    SciTech Connect

    Kaganovich, I. D., Startsev, E. A., Sefkow, A. B., Davidson, R. C.

    2008-10-10

    Propagation of an intense charged particle beam pulse through a background plasma is a common problem in astrophysics and plasma applications. The plasma can effectively neutralize the charge and current of the beam pulse, and thus provides a convenient medium for beam transport. The application of a small solenoidal magnetic field can drastically change the self-magnetic and self- electric fields of the beam pulse, thus allowing effective control of the beam transport through the background plasma. An analytic model is developed to describe the self-magnetic field of a finite- length ion beam pulse propagating in a cold background plasma in a solenoidal magnetic field. The analytic studies show that the solenoidal magnetic field starts to infuence the self-electric and self-magnetic fields when ωce > ωpeβb, where ωce = eβ/mec is the electron gyrofrequency, ωpe is the electron plasma frequency, and βb = Vb/c is the ion beam velocity relative to the speed of light. This condition typically holds for relatively small magnetic fields (about 100G). Analytical formulas are derived for the effective radial force acting on the beam ions, which can be used to minimize beam pinching. The results of analytic theory have been verified by comparison with the simulation results obtained from two particle-in-cell codes, which show good agreement.

  4. Transverse-longitudinal coupling in intense beams

    SciTech Connect

    Wang, T.S.F.; Smith, L.

    1981-03-01

    The coupling between transverse and longitudinal perturbations is studied self-consistently by considering a beam of K-V distribution. The analysis is carried out within the context of linearized Vlasov-Maxwell equations and electrostatic approximation. The perturbation is assumed to be azimuthally symmetric but axially non-uniform (k/sub z/ is not equal to 0). It is shown that the coupling affects both the longitudinal and transverse modes significantly in the high density and low frequency region. Two new classes of longitudinal modes are found which would not exist if the transverse motions of particles are neglected. The effect of resistive wall impedance on beam stability is also studied. It is found that the longitudinal impedance can cause the transverse modes also to be weakly unstable.

  5. The Lighthouse Program: A Longitudinal Research Project.

    ERIC Educational Resources Information Center

    LaRose, Barbara

    1986-01-01

    Longitudinal data are presented from the Lighthouse Program for gifted students which features cluster grouping and a quota identification systems to ensure proportionate inclusion of minority students. (Author/CL)

  6. ADDHEALTH - NATIONAL LONGITUDINAL STUDY OF ADOLESCENT HEALTH

    EPA Science Inventory

    This study provides a comprehensive view of the health and health behaviors of adolescents and the antecedents - personal, interpersonal, familial, and environmental of these outcomes. The study features a longitudinal, multi-level design with independent measurement at the indiv...

  7. Analysis of Longitudinal Space Charge Effects With Radial Dependence

    SciTech Connect

    Wu, Juhao; Huang, Z.; Emma, P.; /SLAC

    2005-09-30

    Longitudinal space charge (LSC) force can be a main effect driving the microbunching instability in the linac for an x-ray free-electron laser (FEL). In this paper, the LSC-induced beam modulation is studied using an integral equation approach that takes into account the transverse (radial) variation of LSC field for both the coasting beam limit and bunched beam. Changes of beam energy and the transverse beam size can be also incorporated. We discuss the validity of this approach and compare it with other analyses as well as numerical simulations.

  8. Longitudinal variations of the magnetic flux in the heliosphere

    NASA Astrophysics Data System (ADS)

    Dósa, Melinda; Erdős, Géza

    2015-04-01

    The heliospheric magnetic flux is determined from the radial component of the magnetic field vector measured onboard interplanetary space probes. Earlier Ulysses research has shown remarkable independence of the flux from heliographic latitude. Here we investigate whether any longitudinal variation exist in the 50 year long OMNI magnetic data set. When determining the heliographic longitude of the plasma source, correction was applied for the solar wind travel time. Significant recurrent enhancements of the magnetic flux was observed during the declining phase of the solar cycles. These flux enhancements are associated with co-rotating interaction regions (CIRs), lasting several years. The recurrence period equals the equatorial rotation period of the Sun. The same, long lasting recurring features can be observed in the deviation angle of the solar wind velocity vector from the radial direction. However, the deviation angle is small, in the order of few degrees, which cannot account for the observed flux increases. An increase of the magnetic field is clearly caused by the plasma compression associated to CIRs, however the increase of the radial component is not obvious. It is suggested that the origin of that increase is caused by the compression of the plasma in the direction perpendicular to the Parker field line rather than the radial direction. The longitudinal variation of the magnetic flux during the declining phase of the solar cycle has impact on the modulation of cosmic rays as well as on the frequency and intensity of space weather events.

  9. 14 CFR 23.145 - Longitudinal control.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Longitudinal control. 23.145 Section 23.145... Maneuverability § 23.145 Longitudinal control. (a) With the airplane as nearly as possible in trim at 1.3 VS1, it... application of single-handed control forces exceeding those specified in § 23.143(c). The trimming...

  10. 14 CFR 23.145 - Longitudinal control.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Longitudinal control. 23.145 Section 23.145... Maneuverability § 23.145 Longitudinal control. (a) With the airplane as nearly as possible in trim at 1.3 VS1, it... application of single-handed control forces exceeding those specified in § 23.143(c). The trimming...

  11. Longitudinal space charge effects near transition

    SciTech Connect

    Pozdeyev,E.; Rodriguez, J.A.; Marti, F.; York, R.C.

    2009-05-04

    Experimental and numerical studies of the longitudinal beam dynamics in the Small Isochronous Ring (SIR) at Michigan State University revealed a fast, space-charge driven instability that did not fit the model of the negative mass instability. This paper proposes a simple analytical model explaining these results. Also, the paper compares the model to result s of experimental and numerical studies of the longitudinal beam dynamics in SIR.

  12. Digital Longitudinal Tomography Using Backprojection.

    NASA Astrophysics Data System (ADS)

    Kampp, Thomas Dalton

    1987-09-01

    Conventional tomography allows a single section to be demonstrated on film with a single sweep of an x -ray tube. Each sweep of the x-ray tube exposes the patient to approximately one rad of radiation dose. This tomographic method has been extended by using a backprojection method to allow six degrees of freedom in the selection of the plane to be synthesized. As many planes as desired can be retrospectively tomosynthesized from a single sweep of the apparatus. This can greatly reduce the dose to the patient as well as eliminate patient motion artifacts that would occur with individually acquired slices using the traditional analogue film method. A linear tomographic table was modified by the addition of a digital imaging chain so that a set of projection images could be acquired with each sweep of the apparatus. The digital images were manipulated by a computer to tomosynthesize retrospectively any desired plane. This advanced tomographic system would complement CT which cannot yet match the resolution of this system for longitudinal studies. Various special phantoms were imaged in order to provide data which were used to determine the operating characteristics of this particular system. The characteristics measured are the system gray level response, sampling density, modulation transfer function, small area contrast, detection limits, signal-to-noise ratio, noise Wiener spectrum, and slice thickness. This laboratory piece of equipment could significantly detect approximately 1.7% contrast with a 1 mm pixel size. The MTF values and limiting resolution were approximately one -third of what can be obtained with current CT scanners. The system performed precisely as the computer simulations indicated. The dynamic range of the display is less than that of the image. Windowing of the final image can increase displayed contrast up to the limits imposed by noise. This is an improvement compared to film. With current state -of-the-art equipment, a little engineering and

  13. Longitudinal Excitons in GaN

    NASA Astrophysics Data System (ADS)

    Reynolds, D. C.; Jogai, B.; Collins, T. C.

    2002-05-01

    Many of the previous investigations of longitudinal excitons have involved reflection and absorption measurements rather than emission. In these measurements it is more difficult to resolve the longitudinal exciton from the Γ5 and Γ6 free excitons in wurtzite material. The longitudinal excitons have energies and oscillator strengths that depend on the direction of propagation and they are not observable along the principal axis of the crystal. In the wurtzite structure, such as GaN, the Γ5 exciton is the pure transverse mode, whereas the longitudinal is a mixed mode going from pure longitudinal, for the propogation direction K perpendicular to C, to pure transverse for K parallel to C. If more than one orientation is present in the sample, it is clear that more than one longitudinal exciton may be seen since it is a mixed mode. In the current experiment we observe more than one mode, which we associate with more than one crystal orientation. This may result from the columnar growth often observed in GaN.

  14. Anharmonic longitudinal motion of bases and dynamics of nonlinear excitation in DNA.

    PubMed

    Di Garbo, Angelo

    2016-01-01

    The dynamics of the transcription bubble in DNA is studied by using a nonlinear model in which torsional and longitudinal conformations of the biomolecule are coupled. In the absence of forcing and dissipation the torsional dynamics is described by a perturbed kink of the Sine-Gordon DNA model, while the longitudinal conformational energy propagate as phonons. It was found that for random initial conditions of the longitudinal conformational field the presence of the kink promotes the creation of phonons propagating along the chain axis. Moreover, the presence of forcing, describing the active role of RNA polymerase, determines in agreement to the experimental data a modulation of the velocity of the transcription bubble. Lastly, it was shown that the presence of dissipation impacts the dynamic of the phonon by reducing the amplitude of the corresponding conformational field. On the contrary, dissipation and forcing modulate the velocity of the transcription bubble alone. PMID:26453257

  15. End fields of CBA superconducting magnets

    SciTech Connect

    Kirk, H.G.; Herrera, J.; Willen, E.

    1983-01-01

    Measurements of the two dimensional harmonic content of the end fields generated by the Brookhaven CBA dipole and quadrupole superconducting magnets are presented. Both the local longitudinal structure and the integrated end effects are examined.

  16. Landau levels and longitudinal magnetoresistance in generalized Weyl semimetals

    NASA Astrophysics Data System (ADS)

    Li, Xiao; Roy, Bitan

    The notion of axial anomaly is a venerable concept in quantum field theory that has received ample attention in condensed matter physics due to the discovery of Weyl materials (WSMs). In such systems Kramers non-degenerate bands touch at isolated points in the Brillouin zone that act as (anti)monopoles of Berry flux, and the monopole number (m) defines the topological invariant of the system. Although so far only simple WSMs (with m = 1) has been found in various inversion and/or time-reversal asymmetric systems, generalized Weyl semimetals with m > 1 can also be found in nature, for example double-Weyl semimetals in HgCr2Se4 and SrSi2 and triple-Weyl semimetals. In this work, we demonstrate the Landau level spectrum in generalized Weyl systems and its ramification on longitudinal magnetotransport measurements. We show that in the quantum limit generalized Weyl semimetals display negative longitudinal magnetoresistance due to the chiral anomaly. Moreover, the magnetoresistance has nontrivial dependence on the relative orientation of the external fields with the crystallographic axis, stemming from underlying anisotropic quasiparticle dispersion in the pristine system. Our theory can thus provide diagnostic tools to pin the quasiparticle properties in Weyl systems.

  17. Annual and longitudinal variations of the Pacific North Equatorial Countercurrent

    NASA Technical Reports Server (NTRS)

    Lolk, Nina K.

    1992-01-01

    The climatological annual cycle of the Pacific North Equatorial Countercurrent (NECC) simulated by an ocean general circulation model (OGCM) was studied. The longitudinal variation of transports, degree of geostrophy, and the relationship between Ekman pumping and vertical displacement of the thermocline were emphasized. The longitudinal variation was explored using six sections along 150 deg E, 180 deg, 160 deg W, 140 deg W, 125 deg W, and 110 deg W. A primitive equation OGCM of the Pacific Ocean was run for three years and the fields used were from the third year. The fields consisted of zonal, meridional, and vertical current components and temperature and salinity averaged every three days. The model was forced with the Hellerman and Rosenstein climatological wind stress. The mean annual eastward transport (19.9 Sv) was largest at 160 deg W. The maximum-current boundaries along 160 deg W were 9.2 deg N (1.0 deg), 5.1 deg N (1.1 deg), and 187 m (90.6 m). The annual-cycle amplitude of the NECC was greatest between 160 deg W and 140 deg W. Although the NECC is geostrophic to the first order, deviations from geostrophy were found in the boreal spring and summer near the southern boundary and near the surface. Meridional local acceleration played a role between 3 deg N-5 deg N.

  18. Joint multiple imputation for longitudinal outcomes and clinical events that truncate longitudinal follow-up.

    PubMed

    Hu, Bo; Li, Liang; Greene, Tom

    2016-07-30

    Longitudinal cohort studies often collect both repeated measurements of longitudinal outcomes and times to clinical events whose occurrence precludes further longitudinal measurements. Although joint modeling of the clinical events and the longitudinal data can be used to provide valid statistical inference for target estimands in certain contexts, the application of joint models in medical literature is currently rather restricted because of the complexity of the joint models and the intensive computation involved. We propose a multiple imputation approach to jointly impute missing data of both the longitudinal and clinical event outcomes. With complete imputed datasets, analysts are then able to use simple and transparent statistical methods and standard statistical software to perform various analyses without dealing with the complications of missing data and joint modeling. We show that the proposed multiple imputation approach is flexible and easy to implement in practice. Numerical results are also provided to demonstrate its performance. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26179943

  19. Phoning Logistics in a Longitudinal Follow-Up of Batterers and Their Partners

    ERIC Educational Resources Information Center

    Gondolf, Edward W.; Deemer, Crystal

    2004-01-01

    More needs to be known about the phoning logistics of interviewing subjects for longitudinal follow-up studies in the domestic violence field. Using phoning logs from a 4-year follow-up of batterer intervention, the authors calculated the number, results, and costs of phone calls from a sub sample of 100 men and 138 women. The number of calls is…

  20. Educational Participation Post-16: A Longitudinal Analysis of Intentions and Outcomes

    ERIC Educational Resources Information Center

    Croll, Paul

    2009-01-01

    The issue of levels of participation in post-compulsory education has been emphasised by the current policy initiatives to increase the age to which some form of participation is compulsory. One of the acknowledged weaknesses of research in the field of children's intentions with regard to participation is the lack of longitudinal data. This paper…

  1. A Longitudinal Study of the Determinants and Outcomes of Career Change

    ERIC Educational Resources Information Center

    Carless, Sally A.; Arnup, Jessica L.

    2011-01-01

    The present longitudinal field study investigated the antecedents and consequences of an actual career change. The framework for this study was Rhodes and Doering's (1983) model of career change. We examined the effect of individual and organisational characteristics on career change behaviour. The individual characteristics were: traits (Openness…

  2. Longitudinal Investigation of Perceptions towards University Concept through Metaphors: A University Sample in Turkey

    ERIC Educational Resources Information Center

    Argon, Türkan

    2015-01-01

    This study aims to fill the gap in the field of observation-based longitudinal studies about metaphors in educational literature and investigates students' perceptions about the concept of university before and after university by identifying and comparing the change and the direction of change observed in perceptions. The phenomenological…

  3. Characteristics of Schools Successful in STEM: Evidence from Two States' Longitudinal Data

    ERIC Educational Resources Information Center

    Hansen, Michael

    2014-01-01

    Present federal education policies promote learning in science, technology, engineering, and mathematics (STEM) and the participation of minority students in these fields. Using longitudinal data on students in Florida and North Carolina, value-added estimates in mathematics and science are generated to categorize schools into performance levels…

  4. The effect of space charge fields due to finite length electron beams in the free-electron laser

    NASA Technical Reports Server (NTRS)

    Tang, C.-M.; Sprangle, P.; Freund, H.; Colson, W.

    1982-01-01

    The space charge electric field of a finite length electron beam in the free electron laser amplifier with a tapered wiggler is analyzed. In the free drift region between the accelerator and laser, expressions for the increase of energy spread due to the self field are presented. In the FEL interaction region, the general conditions on the importance of the self electric field in the equations of motion is obtained. A numerical example of the FEL experiment at 10.6 microns is given.

  5. Longitudinal surface structures (flowstripes) on Antarctic glaciers

    NASA Astrophysics Data System (ADS)

    Glasser, N. F.; Gudmundsson, G. H.

    2012-03-01

    Longitudinal surface structures ("flowstripes") are common on many glaciers but their origin and significance are poorly understood. In this paper we present observations of the development of these longitudinal structures from four different Antarctic glacier systems; the Lambert Glacier/Amery Ice Shelf area, the Taylor and Ferrar Glaciers in the Ross Sea sector, Crane and Jorum Glaciers (ice-shelf tributary glaciers) on the Antarctic Peninsula, and the onset zone of a tributary to the Recovery Glacier Ice Stream in the Filchner Ice Shelf area. Mapping from optical satellite images demonstrates that longitudinal surface structures develop in two main situations: (1) as relatively wide flow stripes within glacier flow units and (2) as relatively narrow flow stripes where there is convergent flow around nunataks or at glacier confluence zones. Our observations indicate that the confluence features are narrower, sharper, and more clearly defined features. They are characterised by linear troughs or depressions on the ice surface and are much more common than the former type. Longitudinal surface structures within glacier flow units have previously been explained as the surface expression of localised bed perturbations but a universal explanation for those forming at glacier confluences is lacking. Here we propose that these features are formed at zones of ice acceleration and extensional flow at glacier confluences. We provide a schematic model for the development of longitudinal surface structures based on extensional flow that can explain their ridge and trough morphology as well as their down-ice persistence.

  6. Longitudinal dispersion modeling in small streams

    NASA Astrophysics Data System (ADS)

    Pekarova, Pavla; Pekar, Jan; Miklanek, Pavol

    2014-05-01

    The environmental problems caused by the increasing of pollutant loads discharged into natural water bodies are very complex. For that reason the cognition of transport mechanism and mixing characteristics in natural streams is very important. The mathematical and numerical models have become very useful tools for solving the water management problems. The mathematical simulations based on numerical models of pollution mixing in streams can be used (for example) for prediction of spreading of accidental contaminant waves in rivers. The paper deals with the estimation of the longitudinal dispersion coefficients and with the numerical simulation of transport and transformation of accidental pollution in the small natural streams. There are different ways of solving problems of pollution spreading in open channels, in natural rivers. One of them is the hydrodynamic approach, which endeavours to understand and quantify the spreading phenomenon in a stream. The hydrodynamic models are based on advection-diffusion equation and the majority of them are one-dimensional models. Their disadvantage is inability to simulate the spread of pollution until complete dispersion of pollutant across the stream section is finished. Two-dimensional mixing models do not suffer from these limitations. On the other hand, the one-dimensional models are simpler than two-dimensional ones, they need not so much input data and they are often swifter. Three-dimensional models under conditions of natural streams are applicable with difficulties (or inapplicable) for their complexity and demands on accuracy and amount of input data. As there was mentioned above the two-dimensional models can be used also until complete dispersion of pollutant across the stream section is not finished, so we decided to apply the two-dimensional model SIRENIE. Experimental microbasin Rybarik is the part of the experimental Mostenik brook basin of IH SAS Bratislava. It was established as a Field Hydrological

  7. Evidence of Longitudinal Acoustic Phonon Generation in Si Doping Superlattices by Ge Prism-Coupled THz Laser Radiation

    NASA Astrophysics Data System (ADS)

    Wilson, T.; Kasper, E.; Oehme, M.; Schulze, J.; Korolev, K.

    2014-11-01

    We report on the direct excitation of 246 GHz longitudinal acoustic phonons in silicon doping superlattices by the resonant absorption of nanosecond-pulsed far-infrared laser radiation of the same frequency. A longitudinally polarized evanescent laser light field is coupled to the superlattice through a germanium prism providing total internal reflection at the superlattice interface. The ballistic phonon signal is detected by a superconducting aluminum bolometer. The sample is immersed in low-temperature liquid helium.

  8. Visual analysis of longitudinal brain tumor perfusion

    NASA Astrophysics Data System (ADS)

    Glaßer, Sylvia; Oeltze, Steffen; Preim, Uta; Bjørnerud, Atle; Hauser, Helwig; Preim, Bernhard

    2013-02-01

    In clinical research on diagnosis and evaluation of brain tumors, longitudinal perfusion MRI studies are acquired for tumor grading as well as to monitor and assess treatment response and patient prognosis. Within this work, we demonstrate how visual analysis techniques can be adapted to multidimensional datasets from such studies within a framework to support the computer-aided diagnosis of brain tumors. Our solution builds on two innovations: First, we introduce a pipeline yielding comparative, co-registered quantitative perfusion parameter maps over all time steps of the longitudinal study. Second, based on these time-dependent parameter maps, visual analysis methods were developed and adapted to reveal valuable insight into tumor progression, especially regarding the clinical research area of low grade glioma transformation into high grade gliomas. Our examination of four longitudinal brain studies demonstrates the suitability of the presented visual analysis methods and comprises new possibilities for the clinical researcher to characterize the development of low grade gliomas.

  9. Bunched beam longitudinal instability: Coherent dipole motion

    SciTech Connect

    Zhang, S.Y.; Weng, W.T.

    1993-04-23

    In this paper, the authors present a new formulation for the longitudinal coherent dipole motion, where a quadrature response of the environmental impedance is shown to be the effective longitudinal impedance for the beam instability. The Robinson-Pedersen formulation for the longitudinal dipole motion is also presented, the difference of the two approaches is discussed in the comparison. The results by using the Sacherer integral equation for the coherent dipole motion can generate the same results as by using the other two approaches, except for a scaling difference. The formulation is further generalized to the rigid bunch motion using signal analysis method, where a form factor shows up naturally. Finally, the formulation is applied to solve the coupled bunch instabilities. Examples of the AGS Booster and the AGS coupled bunch instabilities are used to illustrate the applications of the formulation.

  10. Longitudinal structure of substorm injections at synchronous orbit

    SciTech Connect

    Arnoldy, R.L.; Moore, T.E.

    1983-08-01

    From multiple-spacecraft measurements it is shown that the synchronous orbit manifestation of a substorm, i.e., plasma injection and magnetic field reconfiguration to dipolar, has an onset which expands both eastward and westward from a relatively narrow sector near midnight. For low-to-moderate geomagnetic activity the earliest onset sector at synchronous orbit is about 3 hours wide, skewed toward the evening side of midnight. Using the extensive International Magnetospheric Study ground magnetometer network beneath the satellites, it is found that simultaneous westward motion of electrojet intensification is seen in the ground data over a large longitudinal range than the magnetospheric signatures. This might be explained in terms of distortion of the nightside magnetic field at synchronous orbit. Plasma that might be explained in terms of distortion of the nightside magnetic field at synchronous orbit. Plasma that has already been injected near midnight at synchronous altitude undergoes no further change as a result of the westward and eastward motion of the borders of the plasma. This suggest that the expansion does not represent new substorm activation. One can intepret these results in terms of an injection front wedge which makes hot plasma accessible to the inner magnetosphere and which spatially expands or propagates with time. The origin of plasma behind the front is not addressed. Detailed pitch angle data do, however, show that strong precipitation would be expected from the front for about the first 10 min after the front passes over an observer. Finally, as a result of longitudinal expansion of plasma injections from midnight toward evening or morning and the continuation or even enhancement of field inflation in the evening or morning sectors, growth and expansive phase substorm signatures can occur simultaneously.

  11. Velocity profile similarity for viscous flow development along a longitudinally slotted wind-tunnel wall

    NASA Technical Reports Server (NTRS)

    Everhart, Joel L.; Goradia, Suresh H.

    1988-01-01

    A discussion of the flow field measurements on the slot centerline of two different longitudinally slotted wind-tunnel walls is presented. The longitudinal and transverse components of these data are then transformed using the concept of flow similarity to demonstrate the applicability of the technique to the development of the viscous shear flow along and through a slotted wall. Results are presented showing the performance of the similarity transformations with variations in tunnel station, Mach number, and airfoil-induced curvature of the tunnel free stream.

  12. Three-Dimensional Analysis of Longitudinal Space Charge Microbunching Starting From Shot Noise

    SciTech Connect

    Ratner, D.; Chao, A.; Huang, Z.

    2008-09-24

    The commissioning of the Linac Coherent Light Source (LCLS) injector showed unexpected coherent optical transition radiation (COTR) for an uncompressed electron bunch downstream of a dog-leg transport line. In this paper, we develop a three-dimensional analysis of longitudinal space charge microbunching to explain the phenomenon. Our analysis takes into account the transverse correlation of the longitudinal space charge field due to shot-noise startup and finite observation angles of the radiation. We also apply this analysis to the LCLS COTR observations.

  13. Longitudinal stent deformation during coronary bifurcation stenting.

    PubMed

    Vijayvergiya, Rajesh; Sharma, Prafull; Gupta, Ankush; Goyal, Praveg; Panda, Prashant

    2016-03-01

    A distortion of implanted coronary stent along its longitudinal axis during coronary intervention is known as longitudinal stent deformation (LSD). LSD is frequently seen with newer drug eluting stents (DES), specifically with PROMUS Element stent. It is usually caused by impact of guide catheter tip, or following passage of catheters like balloon catheter, IVUS catheter, guideliner, etc. We hereby report a case of LSD during coronary bifurcation lesion intervention, using two-stents technique. Patient had acute stent thrombosis as a complication of LSD, which was successfully managed. PMID:26811144

  14. What Can We Learn From Longitudinal Studies of Adult Development?

    PubMed Central

    Schaie, K. Warner

    2005-01-01

    This article distinguishes between normal and pathological aging, provides an interdisciplinary context, and then considers a sample case of cognitive aging. Developmental influences on cognition include the physiological infrastructure, genetic predispositions, and environmental influences. Different types of longitudinal studies are distinguished, and contrasting findings of cross-sectional and longitudinal are examined in the sample case of the Seattle Longitudinal Study. Also considered is the longitudinal context for intervention studies and the role of longitudinal family studies in assessing rate of aging and generational differences in rates of aging. Finally, attention is given to the role of longitudinal studies in the early detection of risk for dementia in advanced age. PMID:16467912

  15. Longitudinal modes along thin piezoelectric waveguides for liquid sensing applications.

    PubMed

    Caliendo, Cinzia

    2015-01-01

    The propagation of longitudinally polarized acoustic modes along thin piezoelectric plates (BN, ZnO, InN, AlN and GaN) is theoretically studied, aiming at the design of high frequency electroacoustic devices suitable for work in liquid environments. The investigation of the acoustic field profile across the plate revealed the presence of longitudinally polarized Lamb modes, travelling at velocities close to that of the longitudinal bulk acoustic wave propagating in the same direction. Such waves are suitable for the implementation of high-frequency, low-loss electroacoustic devices operating in liquid environments. The time-averaged power flow density, the phase velocity and the electroacoustic coupling coefficient K2 dispersion curves were studied, for the first (S0) and four higher order (S1, S2, S3, S4) symmetrical modes for different electrical boundary conditions. Two electroacoustic coupling configurations were investigated, based on interdigitated transducers, with or without a metal floating electrode at the opposite plate surface. Enhanced performances, such as a K2 as high as 8.5% and a phase velocity as high as 16,700 m/s, were demostrated for the ZnO- and BN-based waveguides, as an example. The relative velocity changes, and the inertial and viscous sensitivities of the first symmetric and anti-symmetric mode, S0 and A0, propagating along thin plates bordered by a viscous liquid were derived using the perturbation approach. The present study highlights the feasibility of the piezoelectric waveguides to the development of high-frequency, integrated-circuits compatible electroacoustic devices suitable for working in liquid environment. PMID:26043174

  16. Longitudinal Modes along Thin Piezoelectric Waveguides for Liquid Sensing Applications

    PubMed Central

    Caliendo, Cinzia

    2015-01-01

    The propagation of longitudinally polarized acoustic modes along thin piezoelectric plates (BN, ZnO, InN, AlN and GaN) is theoretically studied, aiming at the design of high frequency electroacoustic devices suitable for work in liquid environments. The investigation of the acoustic field profile across the plate revealed the presence of longitudinally polarized Lamb modes, travelling at velocities close to that of the longitudinal bulk acoustic wave propagating in the same direction. Such waves are suitable for the implementation of high-frequency, low-loss electroacoustic devices operating in liquid environments. The time-averaged power flow density, the phase velocity and the electroacoustic coupling coefficient K2 dispersion curves were studied, for the first (S0) and four higher order (S1, S2, S3, S4) symmetrical modes for different electrical boundary conditions. Two electroacoustic coupling configurations were investigated, based on interdigitated transducers, with or without a metal floating electrode at the opposite plate surface. Enhanced performances, such as a K2 as high as 8.5% and a phase velocity as high as 16,700 m/s, were demostrated for the ZnO- and BN-based waveguides, as an example. The relative velocity changes, and the inertial and viscous sensitivities of the first symmetric and anti-symmetric mode, S0 and A0, propagating along thin plates bordered by a viscous liquid were derived using the perturbation approach. The present study highlights the feasibility of the piezoelectric waveguides to the development of high-frequency, integrated-circuits compatible electroacoustic devices suitable for working in liquid environment. PMID:26043174

  17. Long-path-length experimental studies of longitudinal phenomena in intense beams

    NASA Astrophysics Data System (ADS)

    Beaudoin, Brian

    2015-11-01

    Intense charged particle beams are nonneutral plasmas and they can support a host of plasma waves and instabilities. For a long beam bunch, the longitudinal physics can often be reasonably described by a 1-D cold-fluid model, with a geometry factor to account for the transverse effects. The plasma physics of such beams has been extensively studied theoretically and computationally for decades, but until recently, the only experimental measurements were carried out on relatively short linacs. This work reviews experimental studies over the past 5 years on the U. Maryland Electron Ring, investigating longitudinal phenomena, for the first time, over time scales of hundreds and thousands of plasma periods. These results are in good agreement with theory and simulation. Topics that will be discussed are: Longitudinal confinement of a long bunch using barrier fields. The generation of space charge waves from barrier field mismatches, their propagation along the bunch and reflection at the beam ends, as well as their long-term dissipation. The characterization of solitary waves from density/velocity perturbations in the center of the bunch. Compression of solitary wave trains with velocity ``tilts'' (head-to-tail gradient). Observation of a multi-stream instability driven by the longitudinal merging of bunches and the characterization of the onset of the instability with a PIC code. The shock-wave compression of a bunch using rapidly-moving barrier fields.

  18. Negative longitudinal magnetoresistance in Dirac and Weyl metals

    NASA Astrophysics Data System (ADS)

    Burkov, A. A.

    2015-06-01

    It has recently been found that Dirac and Weyl metals are characterized by an unusual weak-field longitudinal magnetoresistance: large, negative, and quadratic in the magnetic field. This has been shown to arise from the chiral anomaly, i.e., nonconservation of the chiral charge in the presence of external electric and magnetic fields, oriented collinearly. In this paper we report on a theory of this effect in both Dirac and Weyl metals. We demonstrate that this phenomenon contains two important ingredients. One is the magnetic-field-induced coupling between the chiral and the total (or vector, in relativistic field theory terminology) charge densities. This arises from the Berry curvature and is present in principle whenever the Berry curvature is nonzero, i.e., is nonspecific to Dirac and Weyl metals. This coupling, however, leads to a large negative quadratic magnetoresistance only when the second ingredient is present, namely when the chiral charge density is a nearly conserved quantity with a long relaxation time. This property is specific to Dirac and Weyl metals and is realized only when the Fermi energy is close to Dirac or Weyl nodes, expressing an important low-energy property of these materials, emergent chiral symmetry.

  19. Longitudinal Predictors of Implicit Phonological Awareness Skills

    ERIC Educational Resources Information Center

    Rvachew, Susan

    2006-01-01

    Purpose: The purpose of this study was to examine the longitudinal predictive relationships among variables that may contribute to poor phonological awareness skills in preschool-age children with speech-sound disorders. Method: Forty-seven children with speech-sound disorders were assessed during the spring of their prekindergarten year and again…

  20. ECEAP 1991 Longitudinal Study and Annual Report.

    ERIC Educational Resources Information Center

    Washington State Office of Community Development, Olympia.

    Washington State's Early Childhood Education and Assistance Program (ECEAP) provides a comprehensive, family-focused preschool program designed to help low-income children succeed in the public school system and help families support and participate in their children's success. Findings from an ongoing longitudinal study of the ECEAP program…

  1. Investigating Ceiling Effects in Longitudinal Data Analysis

    ERIC Educational Resources Information Center

    Wang, Lijuan; Zhang, Zhiyong; McArdle, John J.; Salthouse, Timothy A.

    2008-01-01

    Score limitation at the top of a scale is commonly termed "ceiling effect." Ceiling effects can lead to serious artifactual parameter estimates in most data analysis. This study examines the consequences of ceiling effects in longitudinal data analysis and investigates several methods of dealing with ceiling effects through Monte Carlo simulations…

  2. Delinquency Prone Youth: Longitudinal and Preventive Research.

    ERIC Educational Resources Information Center

    Benning, James J.; And Others

    The first two phases of the EAU Claire County Youth Study were concerned with the relationships between classroom behavior and various facets of the child's family life. Phase II took two forms: (1) a major longitudinal evaluation of the relationships among classroom aggression, social adjustment, subsequent academic achievement, and juvenile…

  3. Teaching Technology Longitudinally to Virtual Children

    ERIC Educational Resources Information Center

    Matthews, Lynley

    2010-01-01

    Children of Generation Y are entering our schooling system. These children have always known instant communication and the internet. They possess basic skills in using technology, but they still need to develop a deeper understanding of technology. Teaching longitudinally will increase the learner's confidence and develop a deeper understanding.…

  4. Longitudinal Predictors of High School Completion

    ERIC Educational Resources Information Center

    Barry, Melissa; Reschly, Amy L.

    2012-01-01

    This longitudinal study examined predictors of dropout assessed in elementary school. Student demographic data, achievement, attendance, and ratings of behavior from the Behavior Assessment System for Children were used to predict dropout and completion. Two models, which varied on student sex and race, predicted dropout at rates ranging from 75%…

  5. Longitudinal photosynthetic gradient in crust lichens' thalli.

    PubMed

    Wu, Li; Zhang, Gaoke; Lan, Shubin; Zhang, Delu; Hu, Chunxiang

    2014-05-01

    In order to evaluate the self-shading protection for inner photobionts, the photosynthetic activities of three crust lichens were detected using Microscope-Imaging-PAM. The false color images showed that longitudinal photosynthetic gradient was found in both the green algal lichen Placidium sp. and the cyanolichen Peltula sp. In longitudinal direction, all the four chlorophyll fluorescence parameters Fv/Fm, Yield, qP, and rETR gradually decreased with depth in the thalli of both of these two lichens. In Placidium sp., qN values decreased with depth, whereas an opposite trend was found in Peltula sp. However, no such photosynthetic heterogeneity was found in the thalli of Collema sp. in longitudinal direction. Microscope observation showed that photobiont cells are compactly arranged in Placidium sp. and Peltula sp. while loosely distributed in Collema sp. It was considered that the longitudinal photosynthetic heterogeneity was ascribed to the result of gradual decrease of incidence caused by the compact arrangement of photobiont cells in the thalli. The results indicate a good protection from the self-shading for the inner photobionts against high radiation in crust lichens. PMID:24477924

  6. An Early Intervention Project: A Longitudinal Look.

    ERIC Educational Resources Information Center

    Gordon, Ira J.

    This report describes the longitudinal research conducted in an early intervention program since 1966. The program is characterized by the use of paraprofessionals serving as home visitors and parent educators. Data collection has included measures of children's behavior and development, parent-child interactions, and parent variables such as…

  7. Design and Implementation Issues in Longitudinal Research

    ERIC Educational Resources Information Center

    Ludlow, Larry H.; Pedulla, Joseph; Reagan, Emile Mitescu; Enterline, Sarah; Cannady, Mac; Chappe, Stephanie

    2011-01-01

    To meet demands for accountability, most schools and departments of education at institutions of higher education (IHEs) gather information on their current students and graduates. This paper describes issues to consider when designing a longitudinal data collection and management system, drawing on seven years' experience developing such a…

  8. 14 CFR 23.145 - Longitudinal control.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Longitudinal control. 23.145 Section 23.145 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Flight Controllability and Maneuverability § 23.145...

  9. The Tevatron bunch by bunch longitudinal dampers

    SciTech Connect

    Cheng-Yang Tan and James Steimel

    2002-09-25

    We describe in this paper the Tevatron bunch by bunch dampers. The goal of the dampers is to stop the spontaneous longitudinal beam size blowup of the protons during a store. We will go through the theory and also show the measured results during the commissioning of this system. The system is currently operational and have stopped the beam blowups during a store.

  10. 14 CFR 25.145 - Longitudinal control.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Longitudinal control. 25.145 Section 25.145... control. (a) It must be possible, at any point between the trim speed prescribed in § 25.103(b)(6) and..., no change in trim control, or exertion of more than 50 pounds control force (representative of...