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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. On the longitudinal polarization of non-paraxial electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Martínez-Herrero, R.; Mejías, P. M.; Manjavacas, A.

    2010-05-01

    Within the framework of the angular plane-wave spectrum of the electromagnetic field, the general form is given for the freely-propagating beams, exact solution of the Maxwell equations, that closely approach (in an algebraic sense) to a purely-longitudinal vectorial distribution at some transverse plane. In the rotationally symmetric case, such a field is written as the combination of radial and longitudinal components, whose propagation can be analysed independently. Several illustrative examples are also considered.

  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. Contribution of longitudinal electric field of a gaussian beam to second harmonic generation

    NASA Astrophysics Data System (ADS)

    Mishra, S. R.; Rustagi, K. C.

    1990-01-01

    A laser beam with a nonuniform transverse intensity profile necessarily has a longitudinal component of the electric field. We show that a detectable second harmonic can be generated due to coupling of this longitudinal component with the transverse field of a gaussian beam in a configuration in which second harmonic generation is forbidden for plane wave interaction.

  6. 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.

  7. 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.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

    2016-08-01

    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.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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…

  15. 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.

  16. 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

  17. Dynamics and instability of current-carrying microbeams in a longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Wang, Lin; Liu, Wen-Bo; Dai, Hu-Liang

    2015-02-01

    The dynamics and instability of current-carrying slender microbeams immersed in a longitudinal magnetic field is investigated by considering the material length scale effect of the microbeam. On the basis of modified couple stress theory, a theoretical model considering the effect of Lorentz forces is developed to analyze the free vibration and possible instability of the microbeam. Using the differential quadrature method, the governing equations of motion are solved and the lowest three natural frequencies are determined. The obtained results reveal that the electric current and the longitudinal magnetic field tend to reduce the microbeam's flexural stiffness. It is therefore shown that the lowest natural frequencies would decrease with increasing magnetic field parameter. The mode shapes of the microbeam are found to be generally three-dimensional spatial in the presence of the longitudinal magnetic field. It is interesting that buckling instability would concurrently occur in the first mode or in the higher-order modes when the magnetic field parameter becomes sufficiently large.

  18. The effect of longitudinal conductance variations on the ionospheric prompt penetration electric fields

    NASA Astrophysics Data System (ADS)

    Sazykin, S.; Wolf, R.; Spiro, R.; Fejer, B.

    Ionospheric prompt penetration electric fields of magnetospheric origin, together with the atmospheric disturbance dynamo, represent the most important parameters controlling the storm-time dynamics of the low and mid-latitude ionosphere. These prompt penetration fields result from the disruption of region-2 field-aligned shielding currents during geomagnetically disturbed conditions. Penetration electric fields con- trol, to a large extent, the generation and development of equatorial spread-F plasma instabilities as well as other dynamic space weather phenomena in the ionosphere equatorward of the auroral zone. While modeling studies typically agree with average patterns of prompt penetration fields, experimental results suggest that longitudinal variations of the ionospheric con- ductivities play a non-negligible role in controlling spread-F phenomena, an effect that has not previously been modeled. We present first results of modeling prompt pene- tration electric fields using a version of the Rice Convection Model (RCM) that allows for longitudinal variations in the ionospheric conductance tensor. The RCM is a first- principles numerical ionosphere-magnetosphere coupling model that solves for the electric fields, field-aligned currents, and particle distributions in the ionosphere and inner/middle magnetosphere. We compare these new theoretical results with electric field observations.

  19. 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.

  20. 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.

  1. Generation of a longitudinal current by a transverse electromagnetic field in collisional degenerate plasma

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    From the Vlasov-Boltzmann kinetic equation for a collisional degenerate plasma, the electron distribution function is constructed in the quadratic approximation in the electric field strength. A formula for calculating the electric current is derived. It is shown that nonlinearity leads to the rise of a longitudinal electric current directed along the wave vector. The longitudinal current is orthogonal to the known transverse classical current obtained in the linear analysis. When the collision frequency tends to zero, all results obtained for a collisional plasma pass into the corresponding results for a collisionless plasma. The case of small wavenumbers is considered. It is shown that, when the collision frequency tends to zero, the expression for the current passes into the corresponding expression for the current in a collisionless plasma. Graphic analysis of the real and imaginary parts of the current density is performed. The dependence of the electromagnetic field oscillation frequency and electron-plasma-particle collision frequency on the wavenumber is studied.

  2. 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.

  3. 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

  4. 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.

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

    DOE PAGESBeta

    Clayton, C. E.; Adli, E.; Allen, J.; An, W.; Clarke, C. I.; Corde, S.; Frederico, J.; Gessner, S.; Green, S. Z.; Hogan, M. J.; et al

    2016-08-16

    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.).more » 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. Lastly, these results bode well for high-gradient, high-efficiency acceleration of electron bunches while preserving their emittance in such a cavity.« less

  6. 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

  7. 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

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

    PubMed

    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

  9. 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

  10. 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.

  11. 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.

  12. The Effects of Magnetic-field Geometry on Longitudinal Oscillations of Solar Prominences

    NASA Astrophysics Data System (ADS)

    Luna, M.; Díaz, A. J.; Karpen, J.

    2012-09-01

    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.

  13. 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.

  14. THE EFFECTS OF MAGNETIC-FIELD GEOMETRY ON LONGITUDINAL OSCILLATIONS OF SOLAR PROMINENCES

    SciTech Connect

    Luna, M.; Karpen, J.

    2012-09-20

    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.

  15. 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.

  16. Polarization dependent extinction coefficients of superparamagnetic colloids in transverse and longitudinal configurations of magnetic field

    NASA Astrophysics Data System (ADS)

    Mehta, R. V.

    2013-05-01

    We review here, our work on the light scattering by ferrofluids and mixture of ferrofluids and other nonmagnetic suspensions subjected to an external static magnetic field. Detailed derivation of extinction coefficients of the systems when incident light is propagating along transverse and longitudinal direction of the field are carried out. In case of inclusion of anisotropic diamagnetic micron sized particles in a ferrofluids, effects of'magnetic holes' generated in the system on the extinction are discussed. The present work is analyzed in light of other similar investigations. It is shown that the study of polarization dependence of extinction coefficients in transverse field configuration is useful to arrive at an unambiguous conclusion regarding chain formation in a ferrofluid.

  17. 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.

  18. 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.

  19. 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

  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. 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

  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. Monte Carlo simulation of magnetic properties of a nano-graphene bilayer in a longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Liu, Ruijia; Lv, Dan; Luo, Xiaohong

    2016-10-01

    Monte Carlo simulation has been used to study the magnetic properties of a nano-graphene bilayer which consists of the upper layer A with spin-3/2 and the bottom layer B with spin-5/2. The effects of the single-ion anisotropy, the intralayer exchange coupling and the longitudinal magnetic field on the magnetization, the susceptibility, the blocking temperature and hysteresis loops of the mixed-spin nano-graphene bilayer system have been examined detailedly. In particular, the variations of the blocking temperature with different intralayer exchange couplings, single-ion anisotropies, and the longitudinal magnetic field are obtained for the present system. Many multiple hysteresis loop behaviors have also been found, depending on the combinations of both the upper and bottom layer magnetizations in the longitudinal magnetic field. Through a comparison, our results obtained are according well with other theoretical researches and experimental results.

  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. ρ -meson longitudinal leading-twist distribution amplitude within QCD background field theory

    NASA Astrophysics Data System (ADS)

    Fu, Hai-Bing; Wu, Xing-Gang; Cheng, Wei; Zhong, Tao

    2016-10-01

    We revisit the ρ -meson longitudinal leading-twist distribution amplitude (DA) ϕ2;ρ ∥ by using the QCD sum rules approach within the background field theory. To improve the accuracy of the sum rules for its moments ⟨ξn;ρ ∥⟩ , we include the next-to-leading order QCD correction to the perturbative part and keep all nonperturbative condensates up to dimension-six consistently within the background field theory. The first two moments read ⟨ξ2;ρ ∥⟩|1 GeV=0.241 (28 ) and ⟨ξ4;ρ ∥⟩|1 GeV=0.109 (10 ) , indicating a double humped behavior for ϕ2;ρ ∥ at small energy scale. As an application, we apply them to the B →ρ transition form factors within the QCD light-cone sum rules, which are key components for the decay width Γ (B →ρ ℓνℓ) . To compare with the world average of Γ (B →ρ ℓνℓ) issued by Particle Data Group, we predict |Vub|=3.1 9-0.62+0.65 , which agrees with the BABAR and Omnès parametrization prediction within errors.

  8. 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.

  9. Adaptive quantification and longitudinal analysis of pulmonary emphysema with a hidden Markov measure field model.

    PubMed

    Hame, Yrjo; Angelini, Elsa D; Hoffman, Eric A; Barr, R Graham; Laine, Andrew F

    2014-07-01

    The extent of pulmonary emphysema is commonly estimated from CT scans by computing the proportional area of voxels below a predefined attenuation threshold. However, the reliability of this approach is limited by several factors that affect the CT intensity distributions in the lung. This work presents a novel method for emphysema quantification, based on parametric modeling of intensity distributions and a hidden Markov measure field model to segment emphysematous regions. The framework adapts to the characteristics of an image to ensure a robust quantification of emphysema under varying CT imaging protocols, and differences in parenchymal intensity distributions due to factors such as inspiration level. Compared to standard approaches, the presented model involves a larger number of parameters, most of which can be estimated from data, to handle the variability encountered in lung CT scans. The method was applied on a longitudinal data set with 87 subjects and a total of 365 scans acquired with varying imaging protocols. The resulting emphysema estimates had very high intra-subject correlation values. By reducing sensitivity to changes in imaging protocol, the method provides a more robust estimate than standard approaches. The generated emphysema delineations promise advantages for regional analysis of emphysema extent and progression.

  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.

  12. Longitudinal and transverse magnetic field program procedure and detailed specification for Sigma 5

    NASA Technical Reports Server (NTRS)

    Wang, C. K.

    1980-01-01

    A computer program and procedure for plotting the contour of the data transferred from the Marshall Space Flight Center solar magnetography is presented. The plotted data then can be easily compared with solar data from other sources, such as the Solar Maximum Mission. From the data file for circular polarization the longitudinal program plots the contours for filtered longitudinal plot and intensity plot by choosing the positive and negative contour levels, intensity levels, and also X,Y plotting ranges which need to be used. In a similar manner the transverse program generates the transverse contour plot, azimuth plot, and intensity plot from the linear polarization data files.

  13. Early Career Secondary Science Teachers: A Longitudinal Study of Beliefs in Relation to Field Experiences

    ERIC Educational Resources Information Center

    Fletcher, Steven S.; Luft, Julie A.

    2011-01-01

    This 3-year longitudinal study explores the evolving beliefs of five prospective secondary science teachers in a university preparation program from recruitment through their first year in the classroom. As an interpretive qualitative study, data were collected through semistructured interviews and an array of artifacts. The data sources were used…

  14. 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

  15. Skin Dose in Longitudinal and Transverse Linac-MRIs using Monte-Carlo and realistic 3D MRI field models

    NASA Astrophysics Data System (ADS)

    Keyvanloo Shahrestanaky, Amirmohamad

    The integration of a clinical linear accelerator (linac) with a magnetic resonance imaging (MRI) system would provide real-time tumor tracking. The magnetic fields of linac-MR systems modify the path of contaminant electrons in photon beams, which alters patient skin dose. In this work, we used Monte Carlo calculations that incorporate realistic 3D magnetic field models of longitudinal and transverse linac-MR systems to accurately quantify the changes in skin dose. The results show that fringe fields of realistic 3D B-fields decay rapidly and have a very small magnitude at the linac’s head. As a result, for longitudinal linac-MR systems only a small increase in the entrance skin dose is predicted. For transverse linac-MR systems, changes to the entrance skin dose are small for most scenarios. On the exit side, however, a fairly large increase is observed for perpendicular beams due to the electron return effect, but significantly drops for large oblique angles of incidence.

  16. Control of longitudinal electric field intensity and of the electron temperature in a weakly ionized decaying plasma

    SciTech Connect

    Ivanov, V.A.; Skoblo, Y.E.

    1981-07-01

    The possibility is considered of controlling the intensity of a longitudinal electric field and the electron temperature in a decaying gas-discharge plasma. It is proposed to feed the discharge from a simple circuit that makes possible the control of the electric field in wide dynamic and frequency ranges. The procedure for controlling the field intensity and the electron temperature is experimentally investigated in the afterglow of a discharge in neon at pressures 2--30 torr and currents 10--100 mA. The possibility of arbitrarily varying the electron temperature can be used to investigate the temperature dependences of the constants of the elementary processes that take place in a decaying plasma.

  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. Nonlinear upper hybrid drift waves for a longitudinal electric field perpendicular to a uniform magnetic field in the Vlasov-Maxwell approximation

    NASA Technical Reports Server (NTRS)

    Abraham-Shrauner, B.

    1986-01-01

    Upper hybrid drift waves are found as a special solution to a Vlasov-Maxwell plasma which has a longitudinal electric field and a perpendicular uniform magnetic field. A single-species plasma with a constant-density mobile neutralizing background supports spatially varying disturbances that oscillate at the upper hybrid frequency. The general functional dependences of the electric field, the plasma number density, and the one-particle distribution function for the special case are found from more general Vlasov-Maxwell equations invariant under a Lie group point transformation. The one-particle distribution function for the plasma is a function of the Liouville invariant, which is the energy in the generalized Bernstein-Greene-Kruskal (BGK) reference frame, and the momentum in the drift direction.

  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.

  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. Characterizing longitudinal and transverse relaxation rates of ferrofluids in microtesla magnetic fields

    NASA Astrophysics Data System (ADS)

    Chen, Ming-Jye; Liao, Shu-Hsien; Yang, Hong-Chang; Lee, Hsin-Yi; Liu, Yi-Jia; Chen, Hsin-Hsien; Horng, Herng-Er; Yang, Shieh-Yueh

    2011-12-01

    Shortening spin-lattice relaxation rates (1/T1) or spin-spin relaxation rates (1/T2) is the purpose of magnetic resonance imaging contrast agents. In this work, an ultralow field nuclear magnetic resonance spectrometer and imager are set up to characterize the spin relaxation rates of Fe3O4 superparamagnetic iron oxide (SPIO) for image contrast. It was found that both 1/T1 and 1/T2 increase linearly when the magnetic susceptibility χ of SPIO increases by increasing the concentration of SPIO dispersed in water. In an applied field, magnetic moments of SPIO generate microscopic field gradients that weaken the field homogeneity, in turn de-phasing the proton's nuclear spin and enhancing the relaxation rates. A T1-contrast image is demonstrated, using SPIO as the contrast agent and high-Tc superconducting quantum interference devices as the detector. T1-contrast imaging in microtesla fields might provide a potential modality for discriminating cancer.

  4. The effects of magnetic-field geometry on longitudinal oscillations of solar prominences: Cross-sectional area variation for thin tubes

    NASA Astrophysics Data System (ADS)

    Luna, M.; Díaz, A. J.; Oliver, R.; Terradas, J.; Karpen, J.

    2016-09-01

    Context. Solar prominences are subject to both field-aligned (longitudinal) and transverse oscillatory motions, as evidenced by an increasing number of observations. Large-amplitude longitudinal motions provide valuable information on the geometry of the filament-channel magnetic structure that supports the cool prominence plasma against gravity. Our pendulum model, in which the restoring force is the gravity projected along the dipped field lines of the magnetic structure, best explains these oscillations. However, several factors can influence the longitudinal oscillations, potentially invalidating the pendulum model. Aims: The aim of this work is to study the influence of large-scale variations in the magnetic field strength along the field lines, i.e., variations of the cross-sectional area along the flux tubes supporting prominence threads. Methods: We studied the normal modes of several flux tube configurations, using linear perturbation analysis, to assess the influence of different geometrical parameters on the oscillation properties. Results: We found that the influence of the symmetric and asymmetric expansion factors on longitudinal oscillations is small. Conclusions: We conclude that the longitudinal oscillations are not significantly influenced by variations of the cross-section of the flux tubes, validating the pendulum model in this context.

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. Generation and subwavelength focusing of longitudinal magnetic fields in a metallized fiber tip.

    PubMed

    Ploss, Daniel; Kriesch, Arian; Pfeifer, Hannes; Banzer, Peter; Peschel, Ulf

    2014-06-01

    We demonstrate experimentally and numerically that in fiber tips as they are used in NSOMs azimuthally polarized electrical fields (|E(azi)|2 / |E(tot)|2 ≈55% ± 5% for λ0 = 1550 nm), respectively subwavelength confined (FWHM ≈450 nm ≈λ0/3.5) magnetic fields, are generated for a certain tip aperture diameter (d = 1.4 μm). We attribute the generation of this field distribution in metal-coated fiber tips to symmetry breaking in the bend and subsequent plasmonic mode filtering in the truncated conical taper. PMID:24921567

  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.

  11. 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

  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. 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

  14. Effect of Some Overlay Welding Regime With Longitudinal Magnetic Field on Hardness, Phase Composition And Welded Layer Wear By Arc Method With Flux Metal Wire

    NASA Astrophysics Data System (ADS)

    Nosov, D. G.; Peremitko, V. V.; Barashkin, M. H.

    2016-08-01

    The paper defines the range of overlay welding current, frequencies and induction of a longitudinal magnetic field that enhance the wear resistance of welded layer additing the flux. The conditions of their mutual influence on the process of structure formation are stated as well as the mathematical models linking the overlay welding current, frequency and induction of a longitudinal magnetic field with hardness, wear resistance and phase composition of the welded layer, the use of which will allow to determine the welding modes to provide the necessary properties of the weld metal.

  15. Quantum criticality in single crystalline YFe2 Al10 determined from zero-field and longitudinal-field muon spin relaxation

    NASA Astrophysics Data System (ADS)

    Huang, Kevin; Tan, Cheng; Zhang, Jian; Ding, Zhaofeng; Maclaughlin, Douglas; Bernal, Oscar; Ho, Pei-Chun; Wu, Liusuo; Aronson, Meigan; Shu, Lei

    Muon spin relaxation (μSR) measurements were performed on single crystalline YFe2Al10 down to 19 mK and in magnetic fields up to ~100 Oe. Zero-field- μSR measurements showed no evidence of magnetic order down to 19 mK, consistent with previous measurements. However, we also find that the depolarization rate Λ is temperature independent above 1 K but increases in an exponential behavior for T < 1 K. Longitudinal-field μSR measurements also reveals a time-field scaling where G (t , H) = G (t /Hγ), with γ = 0.67. This is further confirmed from the magnetic field dependence of Λ, which finds Λ (H) ~H0. 67 at 19 mK. This is further evidence that single crystalline YFe2Al10 is in close proximity to a ferromagnetic quantum critical point. The research performed in this study was supported by the National NSF of China under Grant No. 11474060 and STCSM of China (No. 15XD1500200). Work at CSULA funded by NSF/DMR-1105380. Research at CSU-Fresno is supported by NSF DMR-1506677.

  16. Nonresonant kinetic instabilities of a relativistic plasma in a uniform magnetic field: Longitudinal and transverse mode coupling effects

    SciTech Connect

    Tautz, R. C.; Schlickeiser, R.; Lerche, I.

    2007-01-15

    The stability properties of relativistic plasmas embedded in a uniform magnetic field are investigated for longitudinal and transverse modes and with coupling effects between these modes. The direction of wave propagation in the plasma is not necessarily either parallel or transverse to the ambient magnetic field. The basic dispersion relation equations are given for arbitrary propagation directions. Detailed examination is focused on perpendicular wave propagation in this paper. The concept of neutral points in wave number space, introduced by Harris [Phys. Rev. Lett. 2, 34 (1959)], is generalized to allow for the inclusion of ion effects and the effects of fluctuating magnetic fields. Starting from the relativistic conductivity tensor, an expansion procedure for low wave frequencies is used to determine the stability properties in the neighborhood of neutral points and in the frequency regime below the ion cyclotron frequency. The bulk plasma properties determine stability or instability but the mode structure is derivable only from a particle kinetic picture, as with Weibel [Phys. Rev. Lett. 2, 83 (1959)] instabilities, and not from a magnetohydrodynamic description. For monoenergetic plasma distribution functions of electrons and ions, as well as for electrons and positrons, numerical examples are given to illustrate the neutral points and the unstable wave number regimes.

  17. Ground state energy and scaling behaviour of spin gap in the XXZ spin-12 antiferromagnetic chain in longitudinal staggered field

    NASA Astrophysics Data System (ADS)

    Paul, Susobhan; Ghosh, Asim Kumar

    2014-08-01

    The ground state energy and the spin gap of a spin-12 Heisenberg antiferromagnetic XXZ chain in the presence of longitudinal staggered field (hz) have been estimated by using Jordan-Wigner representation, exact diagonalization and perturbative analysis. All those quantities have been obtained for a region of anisotropic parameter (Δ) defined by 0≤Δ≤1. For Δ=0, the exact value of ground state energy is found for finite values of hz. The spin gap is found to develop as soon as the staggered field is switched on. The magnitude of spin gap is compared with the field induced gap measured in magnetic compounds CuBenzoate and Yb4As3 when Δ=1. The dependence of spin gap on both Δ and hz has been found which gives rise to scaling laws associated with hz. Scaling exponents obtained in two different cases show excellent agreements with the previously determined values. The variation of scaling exponents with Δ can be fitted with a regular function.

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. 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

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. 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.

  10. Longitudinal field investigation of the moderating and mediating effects of self-efficacy on the relationship between training and newcomer adjustment.

    PubMed

    Saks, A M

    1995-04-01

    A longitudinal field study examined the moderating and mediating effects of self-efficacy on the relationship between training and the adjustment of newcomers during their 1st year of employment. The results provided some support for the hypothesis that initial self-efficacy moderates the relationship between training and adjustment. Training was more strongly related to posttraining self-efficacy, ability to cope, job performance, and intention to quit the profession for newcomers with low levels of initial self-efficacy mediates the relationship between training and adjustment; however, evidence of complete mediation was found only for ability to cope. Posttraining self-efficacy partially mediated the relationships between training and job satisfaction, organizational and professional commitment, and intention to quit the organization and the profession. Research and practical implications of these findings for the training and the socialization of newcomers are discussed.

  11. 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

  12. 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.

  13. 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…

  14. Equity Education: A Longitudinal Study Comparing Multicultural Knowledge and Dispositions of Field-Based and Campus-Based Teacher Candidates

    ERIC Educational Resources Information Center

    Thompson, Johnnie; Bakken, Linda; Mau, Wei-Cheng

    2009-01-01

    Two groups of teacher candidates, enrolled either in a field-based or campus-based program, were measured before and after their first semester of teacher education courses and again at the end of their student teaching semester. The two groups were compared regarding their knowledge of multicultural education issues, dispositions towards diverse…

  15. Latitudinal and longitudinal behavior of the geomagnetic field during a disturbed period: A case study using wavelet techniques

    NASA Astrophysics Data System (ADS)

    Klausner, Virginia; Domingues, Margarete Oliveira; Mendes, Odim; Mendes da Costa, Aracy; Papa, Andres Reinaldo Rodriguez; Ojeda Gonzalez, Arian

    2016-11-01

    Coronal mass ejections are the primary cause of the highly disturbed conditions observed in the magnetosphere. Momentum and energy from the solar wind are transferred to the Earth's magnetosphere mainly via magnetic reconnection which produces open field lines connecting the Earth magnetic field to the solar wind. Magnetospheric currents are coupled to the ionosphere through field-aligned currents. This particular characteristic of the magnetosphere-ionosphere interconnection is discussed here on the basis of the energy transfer from high (auroral currents) to low-latitudes (ring current). The objective of this work is to examine how the conditions during a magnetic storm can affect the global space and time configuration of the ring current, and, how these processes can affect the region of the South Atlantic Magnetic Anomaly. The H- or X-components of the Earth's magnetic field were examined using a set of six magnetometers approximately aligned around the geographic longitude at about 10 °, 140 ° and 295 ° from latitudes of 70 ° N to 70 ° S and aligned throughout the equatorial region, for the event of October 18-22, 1998. The investigation of simultaneous observations of data measured at different locations makes it possible to determine the effects of the magnetosphere-ionosphere coupling, and, it tries to establish some relationships among them. This work also compares the responses of the aligned magnetic observatories to the responses in the South Atlantic Magnetic Anomaly region. The major contribution of this paper is related to the applied methodology of the discrete wavelet transform. The wavelet coefficients are used as a filter to extract the information in high frequencies of the analyzed magnetogram. They also better represent information about the injections of energy and, consequently, the disturbances of the geomagnetic field measured on the ground. As a result, we present a better way to visualize the correlation between the X- or H

  16. Muon cooling: longitudinal compression.

    PubMed

    Bao, Yu; Antognini, Aldo; Bertl, Wilhelm; Hildebrandt, Malte; Khaw, Kim Siang; Kirch, Klaus; Papa, Angela; Petitjean, Claude; Piegsa, Florian M; Ritt, Stefan; Sedlak, Kamil; Stoykov, Alexey; Taqqu, David

    2014-06-01

    A 10  MeV/c positive muon beam was stopped in helium gas of a few mbar in a magnetic field of 5 T. The muon "swarm" has been efficiently compressed from a length of 16 cm down to a few mm along the magnetic field axis (longitudinal compression) using electrostatic fields. The simulation reproduces the low energy interactions of slow muons in helium gas. Phase space compression occurs on the order of microseconds, compatible with the muon lifetime of 2  μs. This paves the way for the preparation of a high-quality low-energy muon beam, with an increase in phase space density relative to a standard surface muon beam of 10^{7}. The achievable phase space compression by using only the longitudinal stage presented here is of the order of 10^{4}.

  17. Muon Cooling: Longitudinal Compression

    NASA Astrophysics Data System (ADS)

    Bao, Yu; Antognini, Aldo; Bertl, Wilhelm; Hildebrandt, Malte; Khaw, Kim Siang; Kirch, Klaus; Papa, Angela; Petitjean, Claude; Piegsa, Florian M.; Ritt, Stefan; Sedlak, Kamil; Stoykov, Alexey; Taqqu, David

    2014-06-01

    A 10 MeV/c positive muon beam was stopped in helium gas of a few mbar in a magnetic field of 5 T. The muon "swarm" has been efficiently compressed from a length of 16 cm down to a few mm along the magnetic field axis (longitudinal compression) using electrostatic fields. The simulation reproduces the low energy interactions of slow muons in helium gas. Phase space compression occurs on the order of microseconds, compatible with the muon lifetime of 2 μs. This paves the way for the preparation of a high-quality low-energy muon beam, with an increase in phase space density relative to a standard surface muon beam of 107. The achievable phase space compression by using only the longitudinal stage presented here is of the order of 104.

  18. 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

  19. Longitudinal 2 years field study of conventional vaccination against highly pathogenic avian influenza H5N1 in layer hens.

    PubMed

    Rudolf, Miriam; Pöppel, Manfred; Fröhlich, Andreas; Breithaupt, Angele; Teifke, Jens; Blohm, Ulrike; Mettenleiter, Thomas; Beer, Martin; Harder, Timm

    2010-10-01

    A licensed, inactivated vaccine based on a low pathogenic avian influenza virus strain (H5N2) was evaluated in layer hens kept under field conditions during a 2-year period. Vaccine efficacy was investigated by specific antibodies and by challenge-contact experiments using highly pathogenic avian influenza viruses (HPAIV) H5N1. Basic immunization with two applications induced clinical protection. Virus excretion by vaccinated hens was significantly reduced compared to non-vaccinated controls; transmission to non-vaccinated and vaccinated contact birds was not fully interrupted. Vaccination efficacy is influenced by several factors including antigenic relatedness between vaccine and field strains, but also by species, age and type of commercial uses of the host. Limitations and risks of HPAIV vaccination as silent spread of HPAIV and emergence of escape mutants must be considered a priori and appropriate corrective measures have to be installed. PMID:20727963

  20. 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

  1. 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

  2. Increasing the yield of Ar((sup 3)P(sub 2, 0)) and Ne((sub 3)P(sub 2, 0)) effusing from a glow discharge by using a longitudinal magnetic field

    NASA Technical Reports Server (NTRS)

    Barrios, A.; Ramos, G. B.; Hardy, K. A.; Sheldon, J. W.

    1994-01-01

    It is demonstrated that a longitudinal magnetic field applied to a low-pressure, low-voltage, hot cathode glow discharge will substantially increase the intensity of metastable atoms effusing from a central anode slit. For an argon discharge there is a fourfold increase in the effusing Ar((sup 3)P(sub 2, 0)) atom intensity and for neon there is a 14-fold increase in Ne((sup 3)P(sub 2, 0)) intensity.

  3. 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…

  4. 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…

  5. 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.

  6. 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.

  7. 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.

  8. 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…

  9. 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.

  10. Open Field Test; Technical Report 14. Disadvantaged Children and Their First School Experiences. ETS-Head Start Longitudinal Study. Technical Report Series.

    ERIC Educational Resources Information Center

    Ward, William C.

    The Open Field Test was used to assess variables that might not be manifested in a more standard testing situation. In this test, the child was shown 10 standard play objects in the room, and was told to do anything he wished with the toys. The tester initiated no interaction with the child and responded minimally to any overture made by the…

  11. 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.

  12. Longitudinal Magnification Drawing Mistake

    NASA Astrophysics Data System (ADS)

    Rabal, Héctor; Cap, Nelly; Trivi, Marcelo

    2004-01-01

    Lateral magnification in image formation by positive lenses, mirrors, and dioptrics is usually appropriately developed in most optics textbooks.1-9 However, the image of a three-dimensional object occupies a three-dimensional region of space. The optical system affects both the transverse and the longitudinal dimensions of the object and, in general, does it in different ways. The magnification in the direction of the optical axis (the longitudinal magnification) is seldom treated. In several texts, the concept of longitudinal magnification is not even considered. Symmetrical objects (such as arrows) are used and their images appear laterally inverted. It is not shown how a longitudinally nonsymmetric object is imaged. One of the few books where this subject is well treated is in the textbook by Hecht.10 We have repeatedly verified in our classes that there is some confusion related to this subject. Students tend to believe that the image is longitudinally symmetric with respect to the lens optic center. Some prestigious texts commit the same mistake. In addition, a very nice optics book,11 a catalogue of optical hardware,12 a worldwide scientific magazine,13 a paper in an optics journal,14 and a Spanish encyclopedia,15 for example, have also been found to contain this error in drawing the image of a three-dimensional object formed by a positive lens. In this paper we suggest that the teaching of longitudinal magnification should be done with some care and we include a figure showing a properly drawn image.

  13. 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.

  14. 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

  15. Longitudinal coupling effect in microfiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Zhao, Ping; Zhang, Jihua; Wang, Guanghui; Jiang, Meng; Ping Shum, Perry; Zhang, Xinliang

    2012-10-01

    We theoretically present longitudinal coupling effect (LCE) in air-cladding microfiber Bragg gratings (MFBGs). Distinct from conventional weakly-guiding optical fibers, large longitudinal electric field (Ez) exists in wavelength-scale microfibers. Due to LCE, MFBG reflectivity can be reduced by more than 30% within the band-gap and the full width at half maximum (FWHM) is obviously narrowed. This theoretical analytical work is instructive to precisely design and fabricate MFBGs that are promising in the areas of optical sensing and nanophotonics.

  16. Entanglement from longitudinal and scalar photons

    SciTech Connect

    Franson, J. D

    2011-09-15

    The covariant quantization of the electromagnetic field in the Lorentz gauge gives rise to longitudinal and scalar photons in addition to the usual transverse photons. It is shown here that the exchange of longitudinal and scalar photons can produce entanglement between two distant atoms or harmonic oscillators. The form of the entangled states produced in this way is very different from that obtained in the Coulomb gauge, where the longitudinal and scalar photons do not exist. A generalized gauge transformation is used to show that all physically observable effects are the same in the two gauges, despite the differences in the form of the entangled states. An approach of this kind may be useful for a covariant description of the dynamics of quantum information processing.

  17. Longitudinal stability in multiharmonic standing wave linacs

    NASA Astrophysics Data System (ADS)

    Carver, L. R.; Jones, R. M.; Jiang, Y.; Hirshfield, J. L.

    2016-09-01

    Accelerating cavities that excite multiple modes at integer harmonics of the fundamental frequency have the potential to be used to suppress the onset of rf breakdown and reduce the pulsed surface heating at high accelerating gradients. Understanding the effect of an additional harmonic cavity mode on the longitudinal beam dynamics is important to their development and use. A Hamiltonian that describes the longitudinal motion of a particle as it traverses a chain of multiharmonic cavities has been derived and is applied to the case of a second harmonic cavity. The Hamiltonian is based upon formalisms found in literature for the fundamental harmonic and is extended to include different longitudinal field distributions and harmonic frequencies. The study initially explores the longitudinal motion for moderate accelerating gradients with high-β protons, as this will allow fundamental properties of the stable region (acceptance and shape of the rf bucket) to be determined. High accelerating gradients are also investigated but the focus will be on phase stability throughout. This work concludes by considering the longitudinal dynamics of a modified European Spallation Source accelerator, comprised of multiharmonic cavities that has specifications broadly consistent with the accelerator.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. LONGITUDINAL SOLUTIONS IN RHIC.

    SciTech Connect

    BLASKIEWICZ,M.BRENNAN,J.M.FISCHER,W.CAMERON,P.WEI,J.LUQUE,A.SCHAMEL,H.

    2003-05-12

    Stable, coherent, longitudinal oscillations have been observed in the RHIC accelerator. Within the context of perturbation theory, the beam parameters and machine impedance suggest these oscillations should be Landau damped. When nonlinear effects are included, long lived, stable oscillations become possible for low intensity beams. Simulations and theory are compared with data.

  3. Longitudinal variations of the equatorial electojet

    NASA Astrophysics Data System (ADS)

    Shume, Esayas

    We have utilized a three dimensional electrostatic potential model to explain the longitudinal variations of the equatorial electrojet. The model runs were constrained by net H component magnetic field measurements from three equatorial stations, namely, Huancayo (Peru) 12.05 S, 284.67 E; Addis Ababa (Ethiopia) 9.8 N, 38.8 E; Tirunelveli (India) 8.42 N, 77.48 E. The model runs were done in an iterative fashion until the computed and measured H component magnetic field values come into a close agreement. The physical mechanisms for the longitudinal variations of the equatorial electrojet were inferred by comparing and contrasting the resulting computed vertical polarization electric field (which drives the equatorial electrojet), and zonal current density profiles for the three stations mentioned above.

  4. 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…

  5. Longitudinal vortices beneath breaking waves

    NASA Astrophysics Data System (ADS)

    Nepf, H. M.; Cowen, E. A.; Kimmel, S. J.; Monismith, S. G.

    1995-08-01

    The formation of longitudinal vortices has been observed in a wavy channel flow and appears to be linked to spilling breaking and/or to vertical vorticity generated by a wave instability at the wave maker. Both conditions were present when the wave slope, ak exceeded 0.25. The wave instability produced velocity jets beneath and just downstream of the plunger that could provide the initial perturbation for the CL2 instability mechanism (Faller and Caponi, 1978). The breaker activity could also contribute to the CL2 production mechanism by eliminating the negative, stabilizing shear observed within the wave maker wake and by providing seed perturbations to the vorticity field. As the cells evolved downstream, they were maintained through interaction with the bottom boundary layer. When the vortices were present, both vertical mixing and turbulent kinetic energy were enhanced. Despite some differences in scale these results suggest that Langmuir circulation may produce similar changes in the mixed layer.

  6. Regional flux analysis of longitudinal atrophy in Alzheimer's disease.

    PubMed

    Lorenzi, Marco; Ayache, Nicholas; Xavier, Pennec

    2012-01-01

    The longitudinal analysis of the brain morphology in Alzheimer's disease(AD) is fundamental for understanding and quantifying the dynamics of the pathology. This study provides a new measure of the brain longitudinal changes based on the Helmholtz decomposition of deformation fields. We used the scalar pressure map associated to the irrotational component in order to identify a consistent group-wise set of areas of maximal volume change. The atrophy was then quantified in these areas for each subject by the probabilistic integration of the flux of the longitudinal deformations across the boundaries. The presented framework unifies voxel-based and regional approaches, and robustly describes the longitudinal atrophy at group level as a spatial process governed by consistently defined regions. Our experiments showed that the resulting regional flux analysis is able to detect the differential atrophy patterns across populations, and leads to precise and statistically powered quantifications of the longitudinal changes in AD, even in mild/premorbid cases.

  7. 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.

  8. Modeling nonstationary longitudinal data.

    PubMed

    Núñez-Antón, V; Zimmerman, D L

    2000-09-01

    An important theme of longitudinal data analysis in the past two decades has been the development and use of explicit parametric models for the data's variance-covariance structure. A variety of these models have been proposed, of which most are second-order stationary. A few are flexible enough to accommodate nonstationarity, i.e., nonconstant variances and/or correlations that are not a function solely of elapsed time between measurements. We review five nonstationary models that we regard as most useful: (1) the unstructured covariance model, (2) unstructured antedependence models, (3) structured antedependence models, (4) autoregressive integrated moving average and similar models, and (5) random coefficients models. We evaluate the relative strengths and limitations of each model, emphasizing when it is inappropriate or unlikely to be useful. We present three examples to illustrate the fitting and comparison of the models and to demonstrate that nonstationary longitudinal data can be modeled effectively and, in some cases, quite parsimoniously. In these examples, the antedependence models generally prove to be superior and the random coefficients models prove to be inferior. We conclude that antedependence models should be given much greater consideration than they have historically received.

  9. 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.

  10. Longitudinal profiles in simple alluvial systems

    NASA Astrophysics Data System (ADS)

    Rice, Stephen P.; Church, Michael

    2001-02-01

    Theoretical considerations suggest that exponential or quadratic functions are apt for describing the longitudinal profiles of aggrading, alluvial systems that are unaffected by significant lateral inputs of water or sediment. A new set of field data confirms this for individual sedimentary links along a wandering gravel-bed river in British Columbia, Canada. Each link is viewed as a simple alluvial system, without major water or sediment inputs, within which grain size typically fines downstream in a relatively systematic manner. Such homogeneous reaches are suitable for the investigation of simple profile form. It is found that quadratic approximations are the most flexible descriptor for link longitudinal profiles. Overall, the river forms an irregularly cuspate long profile structured by these fundamental length-scale units. Both link gradients and link fining rate reflect size-selective aggradation associated with the bounding lateral inputs.

  11. 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

  12. Modeling HIF relevant longitudinal dynamics in UMER

    NASA Astrophysics Data System (ADS)

    Beaudoin, B. L.; Bernal, S.; Blanco, C.; Haber, I.; Kishek, R. A.; Koeth, T.; Mo, Y.

    2014-01-01

    The foremost challenge for Heavy-Ion Fusion (HIF) is achieving sufficiently low emittances and small energy spreads in the presence of intense space-charge, to achieve the high deposition densities necessary for pellet ignition. The University of Maryland Electron Ring (UMER) uses intense low-energy electron beams to access the scaled physics of HIF drivers. In particular, the long path-length propagation in UMER presents an opportunity to study, at realistic scales, the longitudinal beam dynamics and manipulations required for such a driver. With the use of induction modules, as in the ion machines such as NDCX-II, the resulting bunch dynamics show evidence of space-charge waves excited by an initial mismatch between the detailed initial beam distribution at the bunch ends and the applied focusing waveforms, persisting with multiple damped reflections propagating along the bunch flat-top. Using the induction module we are able to suppress space-charge waves with great accuracy, at amplitudes that include wave steepening prior to the formation of solitary wave trains. The longitudinal dynamics largely dominates when no containment fields are applied, coupling through the natural chromaticity of the ring even within the first turn. After subsequent turns, the bunch elongates and wraps the circumference of the machine multiple times; eventually reaching a point of instability that has also been shown through simulation, obtaining excellent agreement when the detailed longitudinal dynamics of the experiment are carefully incorporated into the model.

  13. 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.

  14. 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.

  15. The Identity and Learning Programme: "Principled Pragmatism" in a 12-Year Longitudinal Ethnography

    ERIC Educational Resources Information Center

    Pollard, Andrew

    2007-01-01

    This paper offers a case study of the evolution of what is believed to be the earliest UK longitudinal ethnography in the field of education--and discussion of some issues arising. As such, it is a contribution to the contemporary methodological development of qualitative longitudinal research. The Identity and Learning Programme tracked the…

  16. 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.

  17. 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.

  18. Longitudinal instability of the forearm.

    PubMed

    Phadnis, J; Watts, A C

    2016-10-01

    The Essex Lopresti lesion is a rare triad of injury to the radial head, interosseous membrane of the forearm and distal radio-ulnar joint, which results in longitudinal instability of the radius. If unrecognized this leads to chronic pain and disability which is difficult to salvage. Early recognition and appropriate treatment is therefore desirable to prevent long-term problems. The aim of this article is to review the pathoanatomy of longitudinal radius instability and use the existing literature and authors' experience to provide recommendations for recognition and treatment of acute and chronic forearm instability, including description of the author's technique for interosseous membrane reconstruction. PMID:27628434

  19. Procedure of measuring the longitudinal emittance of electron beam

    NASA Astrophysics Data System (ADS)

    Vladimirov, I. Yu

    2016-09-01

    The procedure of measuring the longitudinal emittance of electron beam generated by RF gun and reconstruction of its longitudinal phase portrait is proposed. Measuring system consists of vertical deflecting RF cavity, horizontal bending dipole and screen. The beam spot on the screen is used to reconstruct the longitudinal phase portrait. In the proposed procedure an electromagnetic field of the vertical deflecting RF cavity can be approximated by the TM110 mode of pillbox cavity. This approximation allows analytically solve the motion equations of the electron motion in the vertical deflecting RF cavity. The report contains description of the vertical deflecting RF cavity and the dipole, the formulae underlying the procedure and the results of numerical simulation.

  20. Measurement of electron longitudinal diffusion coefficient in liquid argon

    NASA Astrophysics Data System (ADS)

    Li, Yichen; Tang, Wei; Qian, Xin

    2016-03-01

    The electron longitudinal diffusion coefficients in Liquid Argon (LAr) are measured for a range of electric fields from 0.05 to 2.0 kV/cm up to a maximum drift distance of 120 mm using the two experimental setups at BNL. The measurement principle, apparatus, and data analysis are described. Our result represents the world's best measurement of electron longitudinal coefficients in this range. The measured longitudinal diffusion results are directly applicable to the existing experiments such as MicroBooNE and are essential for the future LAr based experiment detector design such as SBN and DUNE. We also report the performance of the gas purification system, which is important for the design of the purification system of future large LArTPCs.

  1. 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.

  2. 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.

  3. Set-based tests for genetic association in longitudinal studies.

    PubMed

    He, Zihuai; Zhang, Min; Lee, Seunggeun; Smith, Jennifer A; Guo, Xiuqing; Palmas, Walter; Kardia, Sharon L R; Diez Roux, Ana V; Mukherjee, Bhramar

    2015-09-01

    Genetic association studies with longitudinal markers of chronic diseases (e.g., blood pressure, body mass index) provide a valuable opportunity to explore how genetic variants affect traits over time by utilizing the full trajectory of longitudinal outcomes. Since these traits are likely influenced by the joint effect of multiple variants in a gene, a joint analysis of these variants considering linkage disequilibrium (LD) may help to explain additional phenotypic variation. In this article, we propose a longitudinal genetic random field model (LGRF), to test the association between a phenotype measured repeatedly during the course of an observational study and a set of genetic variants. Generalized score type tests are developed, which we show are robust to misspecification of within-subject correlation, a feature that is desirable for longitudinal analysis. In addition, a joint test incorporating gene-time interaction is further proposed. Computational advancement is made for scalable implementation of the proposed methods in large-scale genome-wide association studies (GWAS). The proposed methods are evaluated through extensive simulation studies and illustrated using data from the Multi-Ethnic Study of Atherosclerosis (MESA). Our simulation results indicate substantial gain in power using LGRF when compared with two commonly used existing alternatives: (i) single marker tests using longitudinal outcome and (ii) existing gene-based tests using the average value of repeated measurements as the outcome.

  4. 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.

  5. Longitudinal Studies of Spelling Development.

    ERIC Educational Resources Information Center

    Ellis, Nick

    Noting that proposed models of literacy development suggest that reading and writing mutually influence and grow from each other, this paper summarizes aspects of stage theories of literacy development and an integrative model, and considers how the model fared in empirical longitudinal tests. The paper begins with a summary of the modal aspects…

  6. 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... multiengine airplanes, without the use of the primary longitudinal control system. (2) For...

  7. Robust solid 129Xe longitudinal relaxation times

    NASA Astrophysics Data System (ADS)

    Limes, M. E.; Ma, Z. L.; Sorte, E. G.; Saam, B.

    2016-09-01

    We find that if solid xenon is formed from liquid xenon, denoted "ice," there is a 10% increase in 129Xe longitudinal relaxation T1 time (taken at 77 K and 2 T) over a trickle-freeze formation, denoted "snow." Forming xenon ice also gives an unprecedented reproducibility of 129Xe T1 measurements across a range of 77-150 K. This temperature dependence roughly follows the theory of spin rotation mediated by Raman scattering of harmonic phonons, though it results in a smaller-than-predicted spin-rotation coupling strength cK 0/h . Enriched ice 129Xe T1 experiments show no isotopic dependence of bulk relaxation mechanisms at 77 K and at kilogauss fields.

  8. Quantization and Excitation of Longitudinal Electrostatic Waves in Magnetized Quantum Plasmas

    NASA Astrophysics Data System (ADS)

    Tsintsadze, Levan N.

    2010-12-01

    Effects of the Landau diamagnetism and the Pauli paramagnetism on the longitudinal electric wave characteristics in a quantum plasma are studied. It is shown that a dispersion relation of the longitudinal wave propagating along a magnetic field strongly depends on the magnetic field, in radical contrast to the classical case. Instabilities of the quantized longitudinal electric waves are studied by a newly derived dispersion equation. Novel branches of longitudinal waves are found, which have no analogies without the Landau quantization. Growth rates of these new modes are obtained. The excitation of the zero sound by an electron beam is discussed and found that the quantization of the energy of electrons imposes a new condition. Furthermore, the excitation of Bogolyubov's type of spectrum by a strong electric field is considered.

  9. 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.

  10. 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

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

    PubMed

    Guo, Beiyuan; Gan, Weide; Fang, Weining

    2015-07-02

    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.

  12. 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

  13. 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.

  14. 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.

  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. 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

  18. Longitudinal study of fingerprint recognition.

    PubMed

    Yoon, Soweon; Jain, Anil K

    2015-07-14

    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.

  19. Longitudinal and Shear Mode Ultrasound Propagation in Human Skull Bone

    NASA Astrophysics Data System (ADS)

    White, P. J.; Hynynen, K.; Clement, G. T.

    2006-05-01

    Recent studies have attempted to dispel the idea of the longitudinal mode being the only significant mode of ultrasound energy transport through the skull bone. The inclusion of shear waves in propagation models has been largely ignored because of an assumption that shear mode conversions from the skull interfaces to the surrounding media rendered the resulting acoustic field insignificant in amplitude and overly distorted. Experimental investigations with isotropic phantom materials and ex vivo human skulls demonstrated that in certain cases, a shear mode propagation scenario not only can be less distorted, but at times allowed for a substantial (as much as 36% of the longitudinal pressure amplitude) transmission of energy. The phase speed of 1.0-MHz shear mode propagation through ex vivo human skull specimens has been measured to be nearly half of that of the longitudinal mode (shear sound speed = 1500±140 m/s, longitudinal sound speed = 2820±40 m/s), demonstrating that a closer match in impedance can be achieved between the skull and surrounding soft tissues with shear mode transmission. By comparing propagation model results with measurements of transcranial ultrasound transmission obtained by a radiation force method, the attenuation coefficients for the longitudinal mode of propagation was determined to between 14 Np/m and 70 Np/m for the frequency range studied while the same for shear waves were found to be between 94 Np/m and 213 Np/m. This study was performed within the frequency range of 0.2-0.9 MHz.

  20. Transverse and longitudinal angular momenta of light

    NASA Astrophysics Data System (ADS)

    Bliokh, Konstantin Y.; Nori, Franco

    2015-08-01

    We review basic physics and novel types of optical angular momentum. We start with a theoretical overview of momentum and angular momentum properties of generic optical fields, and discuss methods for their experimental measurements. In particular, we describe the well-known longitudinal (i.e., aligned with the mean momentum) spin and orbital angular momenta in polarized vortex beams. Then, we focus on the transverse (i.e., orthogonal to the mean momentum) spin and orbital angular momenta, which were recently actively discussed in theory and observed in experiments. First, the recently-discovered transverse spin angular momenta appear in various structured fields: evanescent waves, interference fields, and focused beams. We show that there are several kinds of transverse spin angular momentum, which differ strongly in their origins and physical properties. We describe extraordinary features of the transverse optical spins and overview recent experiments. In particular, the helicity-independent transverse spin inherent in edge evanescent waves offers robust spin-direction coupling at optical interfaces (the quantum spin Hall effect of light). Second, we overview the transverse orbital angular momenta of light, which can be both extrinsic and intrinsic. These two types of the transverse orbital angular momentum are produced by spatial shifts of the optical beams (e.g., in the spin Hall effect of light) and their Lorentz boosts, respectively. Our review is underpinned by a unified theory of the angular momentum of light based on the canonical momentum and spin densities, which avoids complications associated with the separation of spin and orbital angular momenta in the Poynting picture. It allows us to construct a comprehensive classification of all known optical angular momenta based on their key parameters and main physical properties.

  1. Longitudinal dispersion in open channel flow with suspended canopies.

    PubMed

    Huai, Wenxin; Li, Chengguang

    2016-01-01

    Suspended canopies can cause flow disturbances such as reducing velocities within the canopy, and increasing flow beneath the canopy. Flow modifications by canopies dramatically affect the fate and transport of sediment, nutrients, contaminants, dissolved oxygen, and fauna in aquatic systems. A three-zone model is presented here to predict the longitudinal dispersion coefficient by simplifying Chikwendu's N-zone model. To validate the model, both flow field and tracer experiments were conducted using a straight rectangular Plexiglas flume, with rigid circular rods as the modeled suspended canopies. The result shows that velocities increased above the flume bed and maximized at a point between the canopies and flume bed. Above that point, streamwise velocities decreased into and within the canopies. Reynolds shear stresses were largest at the canopy interface and smallest (zero) at the velocity maximum point. Good agreement between the modeled results and experimental data shows that the model can effectively predict the longitudinal dispersion coefficient in open channels with suspended canopies.

  2. 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.

  3. 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.

  4. Nonlinear dynamics of microtubules —A longitudinal model

    NASA Astrophysics Data System (ADS)

    Zdravković, S.; Satarić, M. V.; Zeković, S.

    2013-05-01

    In the present letter we describe a model of nonlinear dynamics of microtubules (MTs) assuming a single longitudinal degree of freedom per tubulin dimer. This is a longitudinal displacement of a dimer at a certain position with respect to the neighbouring one. A nonlinear partial differential equation, describing dimer's dynamics within MT, is solved both analytically and numerically. It is shown that such a nonlinear model can lead to the existence of kink solitons moving along the MTs. The internal electrical field strength is calculated using two procedures and a perfect agreement between the results is demonstrated. This enabled the estimation of the total energy, kink velocity and kink width. To simplify the calculation of the total energy we stated and proved a useful auxiliary theorem.

  5. 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.

  6. Transverse-longitudinal integrated resonator

    DOEpatents

    Hutchinson, Donald P [Knoxville, TN; Simpson, Marcus L [Knoxville, TN; Simpson, John T [Knoxville, TN

    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.

  7. 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…

  8. Vergence instabilities and the longitudinal horopter.

    PubMed

    Reading, R W

    1986-01-01

    The method of averaging was applied to the results of repeated measures of the longitudinal horopter for four subjects classified as binocularly normal and one anisometropic amblyope. The results produced a refined horopter locus and suggested that the so-called Vieth-Mueller circle is an adequate describer of the empirical longitudinal horopter, except in those cases involving uncorrected aniseikonia.

  9. 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…

  10. Experimental demonstration of electron longitudinal-phase-space linearization by shaping the photoinjector laser pulse.

    PubMed

    Penco, G; Danailov, M; Demidovich, A; Allaria, E; De Ninno, G; Di Mitri, S; Fawley, W M; Ferrari, E; Giannessi, L; Trovó, M

    2014-01-31

    Control of the electron-beam longitudinal-phase-space distribution is of crucial importance in a number of accelerator applications, such as linac-driven free-electron lasers, colliders and energy recovery linacs. Some longitudinal-phase-space features produced by nonlinear electron beam self- fields, such as a quadratic energy chirp introduced by geometric longitudinal wakefields in radio-frequency (rf) accelerator structures, cannot be compensated by ordinary tuning of the linac rf phases nor corrected by a single high harmonic accelerating cavity. In this Letter we report an experimental demonstration of the removal of the quadratic energy chirp by properly shaping the electron beam current at the photoinjector. Specifically, a longitudinal ramp in the current distribution at the cathode linearizes the longitudinal wakefields in the downstream linac, resulting in a flat electron current and energy distribution. We present longitudinal-phase-space measurements in this novel configuration compared to those typically obtained without longitudinal current shaping at the FERMI linac.

  11. 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.

  12. Recruiting and Training Undergraduate Research Assistants for Longitudinal Field Investigations.

    ERIC Educational Resources Information Center

    Evans, Richard I.; And Others

    1981-01-01

    Discusses a research training project for undergraduate psychology students in the development, administration, and evaluation of strategies to deter addictive smoking in adolescents. Students worked closely with faculty and graduate student researchers and became aware of the constraints of institutional regulations and logistical problems…

  13. 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.

  14. 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.

  15. Magnetic fields and coronal heating

    NASA Technical Reports Server (NTRS)

    Golub, L.; Maxson, C.; Rosner, R.; Vaiana, G. S.; Serio, S.

    1980-01-01

    General considerations concerning the scaling properties of magnetic-field-related coronal heating mechanisms are used to build a two-parameter model for the heating of closed coronal regions. The model predicts the way in which coronal temperature and electron density are related to photospheric magnetic field strength and the size of the region, using the additional constraint provided by the scaling law of Rosner, Tucker, and Vaiana. The model duplicates the observed scaling of total thermal energy content with total longitudinal flux; it also predicts a relation between the coronal energy density (or pressure) and the longitudinal field strength modified by the region scale size.

  16. 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.

  17. 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.

  18. Modeling Disease Progression with Longitudinal Markers.

    PubMed

    Inoue, Lurdes Y T; Etzioni, Ruth; Morrell, Christopher; Müller, Peter

    2008-01-01

    In this paper we propose a Bayesian natural history model for disease progression based on the joint modeling of longitudinal biomarker levels, age at clinical detection of disease and disease status at diagnosis. We establish a link between the longitudinal responses and the natural history of the disease by using an underlying latent disease process which describes the onset of the disease and models the transition to an advanced stage of the disease as dependent on the biomarker levels. We apply our model to the data from the Baltimore Longitudinal Study of Aging on prostate specific antigen (PSA) to investigate the natural history of prostate cancer. PMID:24453387

  19. Longitudinal dynamics and tomography in the Tevatron

    SciTech Connect

    Stogin, J.; Sen, T.; Moore, R. S.

    2012-01-10

    Motivated by the desire to understand the longitudinal effects of beam-beam forces, we study the longitudinal dynamics of protons and anti-protons at injection and top energy in the Tevatron. Multi-turn data of the longitudinal profiles are captured to reveal information about frequencies of oscillation, and changes in the bunch distributions. Tomographic reconstruction is used to create phase space maps which are subsequently used to find the momentum distributions. Changes in these distributions for both proton and anti-proton beams are also followed through the operational cycle. We report too on the details of interesting dynamics and some unexpected findings.

  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. Longitudinal asymmetry of the Jovian magnetosphere and the periodic escape of energetic particles

    NASA Technical Reports Server (NTRS)

    Hill, T. W.; Dessler, A. J.

    1976-01-01

    An earlier model of the Jovian magnetosphere is utilized in which the centrifugal stress of corotating plasma distends the outer magnetosphere and opens the tail field. Because of a longitudinal asymmetry in the ionospheric plasma source strength, caused principally by the nonaxisymmetric surface field, the closed-field region in the tail expands and contracts with the rotation period, resulting in a 10-hour modulation of the flux of energetic particles escaping from the magnetosphere into interplanetary space.

  2. 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)

  3. 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.

  4. 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

  5. 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...

  6. Marital assortment and phenotypic convergence: longitudinal evidence.

    PubMed

    Caspi, A; Herbener, E S

    1993-01-01

    This study provides a direct test of whether the observed similarity of spouses is due to initial assortment rather than to convergence of phenotypes. With data from three well-known longitudinal studies, phenotypic convergence is examined using both variable- and person-centered analyses. The longitudinal evidence does not support the hypothesis that couples increasingly resemble each other with time. Spouse correlations most likely reflect initial assortment at marriage and not the convergence of phenotypes.

  7. 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.

  8. 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

  9. Traveltime and longitudinal dispersion in Illinois streams

    USGS Publications Warehouse

    Graf, Julia B.

    1986-01-01

    Twenty-seven measurements of traveltime and longitudinal dispersion in 10 Illinois streams made from 1975 to 1982 provide data needed for estimating traveltime of peak concentration of a conservative solute, traveltime of the leading edge of a solute cloud, peak concentration resulting from injection of a given quantity of solute, and passage time of solute past a given point on a stream. These four variables can be estimated graphically for each stream from distance of travel and either discharge at the downstream end of the reach or flow-duration frequency. From equations developed from field measurements, the traveltime and dispersion characteristics also can be estimated for other unregulated streams in Illinois that have drainage areas less than about 1,500 square miles. For unmeasured streams, traveltime of peak concentration and of the leading edge of the cloud are related to discharge at the downstream end of the reach and to distance of travel. For both measured and unmeasured streams, peak concentration and passage time are best estimated from the relation of each to traveltime. In measured streams, dispersion efficiency is greater than that predicted by Fickian diffusion theory. The rate of decrease in peak concentration with traveltime is about equal to the rate of increase in passage time. Average velocity in a stream reach, given by the velocity of the center of solute mass in that reach, can be estimated from an equation developed from measured values. The equation relates average reach velocity to discharge at the downstream end of the reach. Average reach velocities computed for 9 of the 10 streams from available equations that are based on hydraulic-geometry relations are high relative to measured values. The estimating equation developed from measured velocities provides estimates of average reach velocity that are closer to measured velocities than are those computed using equations developed from hydraulic-geometry relations.

  10. 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.

  11. 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…

  12. 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…

  13. A Longitudinal Analysis of an Out-of-School Science Experience

    ERIC Educational Resources Information Center

    Knapp, Doug

    2007-01-01

    A phenomenological approach was used to investigate the longitudinal recollections of participants of an out-of-school science program. The experience was a field trip to the Shenandoah National Park (USA) conducted in the fall of 2004. The science topic was geologic history and features related to the Shenandoah Valley. Two major themes relating…

  14. 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…

  15. Newspapers and Adult Understanding of Public Affairs: Two Longitudinal Community Studies.

    ERIC Educational Resources Information Center

    Tichenor, P. J.; And Others

    Two longitudinal field studies of the process of information dissemination through newspapers were conducted on two different public affairs topics (regional planning and routing of a high voltage power line) in four communities to examine the role of newspapers in increasing levels of conflict and in creating greater levels of awareness and…

  16. 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…

  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. 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.

  19. RESONANTLY DAMPED PROPAGATING KINK WAVES IN LONGITUDINALLY STRATIFIED SOLAR WAVEGUIDES

    SciTech Connect

    Soler, R.; Verth, G.; Goossens, M.; Terradas, J.

    2011-07-20

    It has been shown that resonant absorption is a robust physical mechanism for explaining the observed damping of magnetohydrodynamic kink waves in the solar atmosphere due to naturally occurring plasma inhomogeneity in the direction transverse to the direction of the magnetic field. Theoretical studies of this damping mechanism were greatly inspired by the first observations of post-flare standing kink modes in coronal loops using the Transition Region and Coronal Explorer. More recently, these studies have been extended to explain the attenuation of propagating coronal kink waves observed by the Coronal Multi-Channel Polarimeter. In the present study, for the first time we investigate the properties of propagating kink waves in solar waveguides including the effects of both longitudinal and transverse plasma inhomogeneity. Importantly, it is found that the wavelength is only dependent on the longitudinal stratification and the amplitude is simply a product of the two effects. In light of these results the advancement of solar atmospheric magnetoseismology by exploiting high spatial/temporal resolution observations of propagating kink waves in magnetic waveguides to determine the length scales of the plasma inhomogeneity along and transverse to the direction of the magnetic field is discussed.

  20. 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.

  1. Response-adaptive regression for longitudinal data.

    PubMed

    Wu, Shuang; Müller, Hans-Georg

    2011-09-01

    We propose a response-adaptive model for functional linear regression, which is adapted to sparsely sampled longitudinal responses. Our method aims at predicting response trajectories and models the regression relationship by directly conditioning the sparse and irregular observations of the response on the predictor, which can be of scalar, vector, or functional type. This obliterates the need to model the response trajectories, a task that is challenging for sparse longitudinal data and was previously required for functional regression implementations for longitudinal data. The proposed approach turns out to be superior compared to previous functional regression approaches in terms of prediction error. It encompasses a variety of regression settings that are relevant for the functional modeling of longitudinal data in the life sciences. The improved prediction of response trajectories with the proposed response-adaptive approach is illustrated for a longitudinal study of Kiwi weight growth and by an analysis of the dynamic relationship between viral load and CD4 cell counts observed in AIDS clinical trials. PMID:21133880

  2. 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

  3. 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.

  4. 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

  5. Numerical studies of high current beam compression in heavy ion fusion

    SciTech Connect

    Bisognano, J.; Lee, E.P.; Mark, J.W.K.

    1985-05-10

    The process of longitudinal compression of a drifting heavy ion pulse to be used as an ICF driver is examined with the aid of particle simulation. Space charge forces play a vital role in halting compression before the final focus lens system is reached. This must take place with minimal growth of transverse emittance and momentum spread. Of particular concern is the distortion of longitudinal phase space by the rounded transverse profile of the longitudinal self-electric field.

  6. 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

  7. 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

  8. Beam breakup with longitudinal halo

    SciTech Connect

    Delayen, J.R.; Bohn, C.L.

    1991-01-01

    We have developed an analytical model of cumulative beam breakup in linear accelerators that predicts the displacement of particles between bunches. Beam breakup is assumed to be caused by a periodic current consisting of an infinite bunch train. The particles in the halo do not contribute to the breakup but experience the deflecting fields and are displaced by them. Under certain circumstances, the displacement of particles in the halo can be considerably larger than that of the bunches. This may have important consequences for the design of high-current cw accelerators where even a small flux of particles striking components of the accelerator cannot be tolerated because of activation. 11 refs., 2 figs.

  9. 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.

  10. [Posterior longitudinal ligament ossification: case report].

    PubMed

    Tella, Oswaldo Inácio de; Herculano, Marco Antonio; Paiva Neto, Manoel Antonio; Faedo Neto, Atílio; Crosera, João Francisco

    2006-03-01

    Posterior longitudinal ligament ossification of cervical spine is a rare condition among caucasians. A 42 years old japanese patient with progressive walking difficulty was diagnosed with this pathology by CT scan and MRI and treated surgically by an anterior approach with arthrodesis. Pathophysiology, racial prevalence, clinical picture, radiological characteristics and surgical approaches options are revised.

  11. Longitudinal emittance measurements at REX-ISOLDE

    NASA Astrophysics Data System (ADS)

    Fraser, M. A.; Zocca, F.; Jones, R. M.; Pasini, M.; Posocco, P. A.; Voulot, D.; Wenander, F.

    2012-01-01

    We report on measurements of the longitudinal emittance at the Radioactive ion beam EXperiment (REX) at ISOLDE, CERN. The rms longitudinal emittance was measured as 0.34±0.08 π ns keV/u at the output of the RFQ and as 0.36±0.04 π ns keV/ u in front of the third 7-gap split-ring resonator (7G3) using the three-gradient technique; systematic errors are not included but are estimated at approximately 10%. The 86% emittance was measured a factor of approximately 4.4 times larger than the rms emittance at 1.48±0.2 and 1.55±0.12 π ns keV/ u at the RFQ and 7G3, respectively. The REX switchyard magnet was used as a spectrometer to analyse the energy spread of the beam as it was manipulated by varying the voltage of the rebuncher (ReB) and 7G3 cavities operating at non-accelerating phases. The transfer matrix for a multi-gap bunching cavity is derived and suitably truncated to allow for the accurate reconstruction of the beam parameters from measurement. The technique for measuring the energy spread was rigorously simulated and validated. A silicon detector, in its development phase, was also exploited to measure the longitudinal beam properties. The measured longitudinal emittance is compatible with the acceptance of the HIE-ISOLDE superconducting linac upgrade.

  12. Mother-Child Interactions: A Longitudinal Microanalysis.

    ERIC Educational Resources Information Center

    Velleman, Shelley L.

    This longitudinal pilot study, which extends Veneziano's (1987) work on phonetically and semantically contingent maternal response types, compared, microanalytically and globally, maternal response types and mother-child dyadic interactions of normally developing and Down syndrome children. Participants were three normally developing infants, five…

  13. Are Sibling Relationships Protective? A Longitudinal Study

    ERIC Educational Resources Information Center

    Gass, Krista; Jenkins, Jennifer; Dunn, Judy

    2007-01-01

    Background: Although the protective effects of familial and parental support have been studied extensively in the child psychopathology literature, few studies have explored the protective quality of positive sibling relationships. Methods: A two-wave longitudinal design was used to examine the protective effect of positive sibling relationships…

  14. 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...

  15. Longitudinal studies based on vital registration records.

    PubMed

    Fox, A J

    1989-01-01

    We describe here the increased use of routine vital event and census records to construct national follow-up and longitudinal studies. The strengths and weaknesses of these studies are discussed and examples given of their use in research into relationships between employment and mortality and socio-economic differences in mortality. PMID:2626588

  16. Religion and Aging in a Longitudinal Panel

    ERIC Educational Resources Information Center

    Blazer, Dan; Palmore, Erdman

    1976-01-01

    Analysis of religious activities and attitudes in a longitudinal panel of 272 community residents showed there were several significant and substantial correlations between religion and happiness, feelings of usefulness, and adjustment; these correlations also tended to be stronger for older persons and tended to increase over time. (Author)

  17. Biomechanics of Distance Running: A Longitudinal Study

    ERIC Educational Resources Information Center

    Nelson, Richard C.; Gregor, Robert J.

    1976-01-01

    Training for distance running over a long period produces meaningful changes in the running mechanics of experienced runners, as revealed in this longitudinal study of the biomechanical components of stride length, stride rate, stride time, and support and nonsupport time. (MB)

  18. NLS Handbook, 2005. National Longitudinal Surveys

    ERIC Educational Resources Information Center

    Bureau of Labor Statistics, 2006

    2006-01-01

    The National Longitudinal Surveys (NLS), sponsored by the U.S. Bureau of Labor Statistics (BLS), are a set of surveys designed to gather information at multiple points in time on the labor market experiences of groups of men and women. Each of the cohorts has been selected to represent all people living in the United States at the initial…

  19. 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.

  20. Emotion Regulation and Childhood Aggression: Longitudinal Associations

    ERIC Educational Resources Information Center

    Roll, Judith; Koglin, Ute; Petermann, Franz

    2012-01-01

    Accumulating evidence suggests that emotion dysregulation is associated with psychopathology. This paper provides a review of recent longitudinal studies that investigate the relationship between emotion regulation and aggressive behavior in childhood age. While there is substantial evidence for assuming a close relation of emotion regulation and…

  1. 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…

  2. Psychodynamic Psychotherapy: A Quantitative, Longitudinal Perspective

    ERIC Educational Resources Information Center

    Roseborough, David J.; McLeod, Jeffrey T.; Bradshaw, William H.

    2012-01-01

    This effectiveness study examined the course of treatment longitudinally and outcomes associated with psychodynamic psychotherapy for a sample of 1,050 people undertaking this treatment in a community setting, over the course of 4 years, at 3-month intervals, using the Outcome Questionnaire (OQ)-45.2. The authors used multilevel modeling to look…

  3. Managing Organizational Commitment: Insights from Longitudinal Research

    ERIC Educational Resources Information Center

    Morrow, Paula C.

    2011-01-01

    This article summarizes what is known about the "active" management of affective organizational commitment (AOC) through a review of 58 studies employing longitudinal research designs. The review yields six broad categories of antecedents that have empirically demonstrated effects on AOC: socialization practices, organizational changes, human…

  4. Empirical data on longitudinal dispersion in rivers

    USGS Publications Warehouse

    Nordin, Carl F.; Sabol, George V.

    1974-01-01

    Empirical data on longitudinal dispersion process in rivers are compiled from published and unpublished sources. Fifty-one sets of data, covering flows from about 30 cubic feet per second to 241,000 cubic feet per second (0.85 to 6,820 cubic meters per second), are analyzed graphically.

  5. 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…

  6. Collaborative Knowledge-Building: A Longitudinal Study

    ERIC Educational Resources Information Center

    Li, Qing

    2009-01-01

    The focus of this paper is on knowledge-building in a technology-supported learning environment in higher education through a longitudinal study of a graduate course from 2003 to 2007. The primary question is: how do learning conditions designed into a graduate course contribute to collaborative knowledge building? In particular, two major…

  7. 14 CFR 25.145 - 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. 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...

  8. 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%…

  9. 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.…

  10. Self-field effects on instability of wave modes in a two-stream free-electron laser with an axial magnetic field

    SciTech Connect

    Mohsenpour, Taghi Rezaee Rami, Omme Kolsoum

    2014-07-15

    Free electron lasers (FEL) play major roles in the Raman Regime, due to the charge and current densities of the beam self-field. The method of perturbation has been applied to study the influence of self-electric and self-magnetic fields. A dispersion relation for two-stream free electron lasers with a helical wiggler and an axial magnetic field has been found. This dispersion relation is solved numerically to investigate the influence of self-fields on the FEL coupling and the two-stream instability. It was found that self-fields can produce very large effects on the FEL coupling, but they have almost negligible effects on two-stream instability.

  11. FDTD analysis of dielectric-loaded longitudinally slotted rectangular waveguides.

    PubMed

    Al-Rizzo, Hussain M; Younies, Hassan Z; Clark, Ken G; Tranquilla, Jim M

    2003-01-01

    A versatile electromagnetic (EM) computational algorithm, based on the Finite-Difference Time-Domain (FDTD) technique, is developed to analyze longitudinally oriented, square-ended, single slot fixtures and slot-pair configurations cut in the broad wall of a WR-975 guide operating at a frequency of 915 MHz. The finite conductivity of the waveguide walls is accounted for by employing a time-domain Surface-Impedance Boundary Conditions (SIBC) formulation. The proposed FDTD algorithm has been validated against measurements performed on a probe-excited slot cut along the center line of the broad wall of a WR-284 guide and available experimental data for energy coupled from a longitudinal slot pair in the broad wall of a WR-340 guide. Numerical results are-presented to exploit the influence of the constitutive parameters of the processed material as well as protective insulating window slabs mounted on the exterior surface of the slots. Particular attention is given to the resonant length, scattering parameters, and the electric field distribution within lossy objects placed in the near-field region over a range of slot offsets and workloads with extensive results being reported for the first time. It is shown that the FDTD technique can accurately predict the coupling and power absorption characteristics in loads located in the near field zone of the slotted waveguide structures and, therefore, should prove to be a powerful design tool applicable to a wide class of slotted waveguide applicators that may be difficult to analyze using other available techniques.

  12. Longitudinal dispersion in open channel flow with suspended canopies.

    PubMed

    Huai, Wenxin; Li, Chengguang

    2016-01-01

    Suspended canopies can cause flow disturbances such as reducing velocities within the canopy, and increasing flow beneath the canopy. Flow modifications by canopies dramatically affect the fate and transport of sediment, nutrients, contaminants, dissolved oxygen, and fauna in aquatic systems. A three-zone model is presented here to predict the longitudinal dispersion coefficient by simplifying Chikwendu's N-zone model. To validate the model, both flow field and tracer experiments were conducted using a straight rectangular Plexiglas flume, with rigid circular rods as the modeled suspended canopies. The result shows that velocities increased above the flume bed and maximized at a point between the canopies and flume bed. Above that point, streamwise velocities decreased into and within the canopies. Reynolds shear stresses were largest at the canopy interface and smallest (zero) at the velocity maximum point. Good agreement between the modeled results and experimental data shows that the model can effectively predict the longitudinal dispersion coefficient in open channels with suspended canopies. PMID:27508377

  13. The Longitudinal Effective CSR Force for a Tilted Thin Bunch

    SciTech Connect

    Rui Li

    2005-05-01

    In the scheme of magnetic bunch compression, an electron bunch with linear energy chirp (energy-bunch length correlation), imposed by an upstream RF cavity, is sent to a magnetic chicane. The bunch length at the exit of the chicane can thus be manipulated via the pathlength-energy dependence due to chicane dispersion. As a linear energy-chirped bunch ({delta}-z correlation) being transported through a dispersive region (x-{delta} correlation), the bunch will have a linear horizontal-longitudinal (x-z) correlation in the configuration space (bunch tilt). Comparing to the case of a nontilted bunch, this x-z correlation modifies the geometry of particle interaction with respect to the direction of particle motion, which consequently modifies the retardation solution and the effective CSR forces. The simulation result of the CSR field for a tilted thin beam was presented earlier by Dohlus [1]. In this paper, we first give an example of the bunch x-z correlation, or bunch tilt, in a bunch compression chicane. The effect of this x-z correlation on the retardation solution and the longitudinal effective force are then analyzed for a line bunch with linear energy chirp transported by design optics.

  14. Using the Longitudinal Study as a Central Teaching Focus.

    ERIC Educational Resources Information Center

    Demchik, Michael J.

    1999-01-01

    Argues that treatment of one investigative longitudinal topic from start to finish in a high school biology class can illustrate many major ideas and concepts. Discusses ways to use various longitudinal studies of plant growth with General Biology classes. (WRM)

  15. 14 CFR 23.175 - Demonstration of static longitudinal stability.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Demonstration of static longitudinal stability. 23.175 Section 23.175 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF... Flight Stability § 23.175 Demonstration of static longitudinal stability. Static longitudinal...

  16. 46 CFR 172.095 - Intact longitudinal stability.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Intact longitudinal stability. 172.095 Section 172.095... Under Subchapter O of This Chapter § 172.095 Intact longitudinal stability. Each tank barge must be shown by design calculations to have a longitudinal metacentric height (GM) in feet (meters) in...

  17. Coupled bunch instability in Fermilab Booster: Longitudinal phase-space simulation

    SciTech Connect

    Bogacz, S.A.; Stahl, S.

    1988-06-09

    The physical presence of vacuum structures can be expressed in terms of a coupling impedance experienced by the beam. The beam environment considered here consist of parasitic higher order modes of the r.f. cavities. These resonances may have high enough Q's to allow consecutive bunches to interact through mutually induced fields. The cumulative effect of such fields as the particles pass through the cavity may be to induce a coherent buildup in synchrotron motion of the bunches, i.e., a longitudinal coupled-bunch instability. The colliding mode operation of the present generation of high energy synchrotrons and the accompanying r.f. manipulations, make considerations of individual bunch area of paramount importance. Thus, a longitudinal instability in one of a chain of accelerators, while not leading to any immediate reduction in the intensity of the beam in that accelerator, may cause such a reduction of beam quality that later operations are inhibited (resulting in a degradation performance). In this paper we employ a longitudinal phase-space tracking code (ESME) as an effective tool to simulate specific coupled bunch modes arising in a circular accelerator. One of the obvious advantages of the simulation compared to existing analytic formalisms, e.g., based on the Vlasov equation, is that it allows consideration of the instability in a self-consistent manner with respect to the changing accelerating conditions. Furthermore this scheme allows to model nonlinearities of the longitudinal beam dynamics, which are usually not tractable analytically. 5 refs., 3 figs.

  18. Longitudinal distribution of cosmic rays in the heliosphere

    NASA Technical Reports Server (NTRS)

    Gold, R. E.; Venkatesan, D.

    1985-01-01

    The longitudinal distribution of cosmic ray intensity was examined during the years 1974-1976 when the persistent high speed solar wind stream structures produced a well ordered inner heliosphere. Solar wind velocity is mapped back to the Sun and compared with cosmic ray intensity which is represented relative to the solar rotation average. Low solar wind velocity is observed to be a necessary, but not sufficient, condition for the occurrence of higher cosmic ray intensities at 1 AU. These relative enhancements cover a restricted range of heliographic longitudes and persist for several solar rotations. The observed solar wind and cosmic ray intensity relationships are consistent with a simple model suggested here in which cosmic ray modulation is very weak in the inner heliosphere, sunward of the first shock crossing on each field line and more intense in the outer heliosphere.

  19. 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.

    2009-01-01

    We have found experimentally that the critical current of a square superconducting transition-edge sensor (TES) depends exponentially upon the side length L and the square root of the temperature T. 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. The observed behavior has a natural theoretical explanation in terms of longitudinal proximity effects if the TES is regarded as a weak link between superconducting leads. We have observed the proximity effect in these devices over extraordinarily long lengths exceeding 100 microns.

  20. Tunable Laser Plasma Accelerator based on Longitudinal Density Tailoring

    SciTech Connect

    Gonsalves, Anthony; Nakamura, Kei; Lin, Chen; Panasenko, Dmitriy; Shiraishi, Satomi; Sokollik, Thomas; Benedetti, Carlo; Schroeder, Carl; Geddes, Cameron; Tilborg, Jeroen van; Osterhoff, Jens; Esarey, Eric; Toth, Csaba; Leemans, Wim

    2011-07-15

    Laser plasma accelerators have produced high-quality electron beams with GeV energies from cm-scale devices and are being investigated as hyperspectral fs light sources producing THz to {gamma}-ray radiation and as drivers for future high-energy colliders. These applications require a high degree of stability, beam quality and tunability. Here we report on a technique to inject electrons into the accelerating field of a laser-driven plasma wave and coupling of this injector to a lower-density, separately tunable plasma for further acceleration. The technique relies on a single laser pulse powering a plasma structure with a tailored longitudinal density profile, to produce beams that can be tuned in the range of 100-400 MeV with percent-level stability, using laser pulses of less than 40 TW. The resulting device is a simple stand-alone accelerator or the front end for a multistage higher-energy accelerator.

  1. Longitudinal, multimodal functional imaging of microvascular response to photothermal therapy

    PubMed Central

    Bui, Albert K.; Teves, Kathleen M.; Indrawan, Elmer; Jia, Wangcun; Choi, Bernard

    2012-01-01

    Although studies have shown that photothermal therapy can coagulate selectively abnormal vasculature, the ability of this method to achieve consistent, complete removal of the vasculature is questionable. We present the use of multimodal, wide-field functional imaging to study, in greater detail, the biological response to selective laser injury. Specifically, a single-platform instrument capable of coregistered fluorescence imaging and laser speckle imaging was utilized to monitor vascular endothelial growth factor gene expression and blood flow, respectively, in a transgenic rodent model. Collectively, the longitudinal, in vivo data collected with our instrument suggest that the biological response to selective laser injury involves early-stage redistribution of blood flow, followed by increased vascular endothelial growth factor promoter activity to stimulate pro-angiogenic events. PMID:20890338

  2. Longitudinal Gradient Dipole Magnet Prototype for APS at ANL

    DOE PAGESBeta

    Kashikhin, V. S.; Borland, M.; Chlachidze, G.; Decker, G.; Dejus, R.; DiMarco, J.; Doose, C. L.; Gardner, T. J.; Harding, D. J.; Jaski, M. S.; et al

    2016-01-26

    We planned an upgrade of the Advanced Photon Source at Argonne National Laboratory (ANL). The main goal of the upgrade is to improve the storage ring performance based on more advanced optics. One of the key magnet system elements is bending dipole magnets having a field strength change along the electron beam path. Moreover, a prototype of one such longitudinal gradient dipole magnet has been designed, built, and measured in a collaborative effort of ANL and Fermilab. Our paper discusses various magnetic design options, the selected magnet design, and the fabrication technology. The prototype magnet has been measured by rotationalmore » coils, a stretched wire, and a Hall probe. Measurement results are discussed and compared with simulations.« less

  3. Non-equilibrium Thermodynamics of the Longitudinal Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Basso, Vittorio; Ferraro, Elena; Sola, Alessandro; Magni, Alessandro; Kuepferling, Michaela; Pasquale, Massimo

    In this paper we employ non equilibrium thermodynamics of fluxes and forces to describe magnetization and heat transport. By the theory we are able to identify the thermodynamic driving force of the magnetization current as the gradient of the effective field ▿H*. This definition permits to define the spin Seebeck coefficient ɛM which relates ▿H* and the temperature gradient ▿T. By applying the theory to the geometry of the longitudinal spin Seebeck effect we are able to obtain the optimal conditions for generating large magnetization currents. Furthermore, by using the results of recent experiments, we obtain an order of magnitude for the value of ɛM ∼ 10-2 TK-1 for yttrium iron garnet (Y3Fe5O12).

  4. Spiradenoma causing longitudinal splitting of the nail.

    PubMed

    Jha, A K; Sinha, R; Kumar, A; Bhadani, P; Kumar, S

    2016-10-01

    Longitudinal splitting of the nails can occur as a result of any growth arising in the nail matrix. We present a case of a 50-year-old woman who presented with an 18-month history of longitudinal splitting of the nail on her right little finger, along with pain in the proximal nail fold region, which was extremely tender to touch. Magnetic resonance imaging revealed an intensely enhancing lesion, while colour Doppler imaging revealed hypervascularity within the mass. A provisional diagnosis of glomus tumour was considered. Histopathology demonstrated presence of a well-circumscribed tumour comprising a dual population of cells, which stained negatively with periodic-acid-Schiff. The histopathological features were consistent with those of eccrine spiradenoma (ES). In this case, glomus tumour was considered as the first differential diagnosis, but histopathology confirmed it as an ES. PMID:27663150

  5. Longitudinal Trajectories of Cigarette Smoking Following Rape

    PubMed Central

    Amstadter, Ananda B.; Resnick, Heidi S.; Nugent, Nicole R.; Acierno, Ron; Rheingold, Alyssa A.; Minhinnett, Robin; Kilpatrick, Dean G.

    2009-01-01

    Although prior research has identified increases in cigarette smoking following trauma exposure, no studies have examined longitudinal trajectories of smoking following rape. The present investigation identifies and characterizes longitudinal (< 3 months, 3-6 months, and > 6 months post-assault) trajectories of smoking (N = 152) following a rape in a sample of 268 sexual assault victims participating in a forensic medical exam. Further, we examine acute predictors of subsequent smoking trajectories. Of participants endorsing smoking post-rape, a two-class solution was identified, with the majority of participants (74.6%) evidencing moderate smoking with a slight decrease over time and remaining participants showing heavy smoking with a slight increase over time. Having sustained an injury, minority status, and post-exam distress all predicted subsequent smoking trajectory. PMID:19370699

  6. Longitudinal spin dynamics in ferrimagnets: Multiple spin wave nature of longitudinal spin excitations

    NASA Astrophysics Data System (ADS)

    Krivoruchko, V. N.

    2016-08-01

    Motivated by the existing controversy about the physical mechanisms that govern longitudinal magnetization dynamics under the effect of ultrafast laser pulses, in this paper we study the microscopic model of longitudinal spin excitations in a two-sublattice ferrimagnet using the diagrammatic technique for spin operators. The diagrammatic approach provides us with an efficient procedure to derive graphical representations for perturbation expansion series for different spin Green's functions and thus to overcome limitations typical for phenomenological approaches. The infinite series involving all distinct loops built from spin wave propagators are summed up. These result in an expression for the longitudinal spin susceptibility χz z(q ,ω ) applicable in all regions of frequency ω and wave vector q space beyond the hydrodynamical and critical regimes. A strong renormalization of the longitudinal spin oscillations due to processes of virtual creation and annihilation of transverse spin waves has been found. We have shown that the spectrum of longitudinal excitations consists of a quasirelaxation mode forming a central peak in χz z(q ,ω ) and two (acoustic and exchange) precessionlike modes. As the main result, it is predicted that both acoustic and exchange longitudinal excitations are energetically above similar modes of transverse spin waves at the same temperature and wave vector. The existence of the exchange longitudinal mode at such frequencies can result in a new form of excitation behavior in ferrimagnetic system, which could be important for understanding the physics of nonequilibrium magnetic dynamics under the effect of ultrafast laser pulses in multisublattice magnetic materials.

  7. A synthetic Longitudinal Study dataset for England and Wales.

    PubMed

    Dennett, Adam; Norman, Paul; Shelton, Nicola; Stuchbury, Rachel

    2016-12-01

    This article describes the new synthetic England and Wales Longitudinal Study 'spine' dataset designed for teaching and experimentation purposes. In the United Kingdom, there exist three Census-based longitudinal micro-datasets, known collectively as the Longitudinal Studies. The England and Wales Longitudinal Study (LS) is a 1% sample of the population of England and Wales (around 500,000 individuals), linking individual person records from the 1971 to 2011 Censuses. The synthetic data presented contains a similar number of individuals to the original data and accurate longitudinal transitions between 2001 and 2011 for key demographic variables, but unlike the original data, is open access. PMID:27656667

  8. A synthetic Longitudinal Study dataset for England and Wales.

    PubMed

    Dennett, Adam; Norman, Paul; Shelton, Nicola; Stuchbury, Rachel

    2016-12-01

    This article describes the new synthetic England and Wales Longitudinal Study 'spine' dataset designed for teaching and experimentation purposes. In the United Kingdom, there exist three Census-based longitudinal micro-datasets, known collectively as the Longitudinal Studies. The England and Wales Longitudinal Study (LS) is a 1% sample of the population of England and Wales (around 500,000 individuals), linking individual person records from the 1971 to 2011 Censuses. The synthetic data presented contains a similar number of individuals to the original data and accurate longitudinal transitions between 2001 and 2011 for key demographic variables, but unlike the original data, is open access.

  9. RADON reconstruction in longitudinal phase space

    SciTech Connect

    Mane, V.; Peggs, S.; Wei, J.

    1997-07-01

    Longitudinal particle motion in circular accelerators is typically monitoring by one dimensional (1-D) profiles. Adiabatic particle motion in two dimensional (2-D) phase space can be reconstructed with tomographic techniques, using 1-D profiles. A computer program RADON has been developed in C++ to process digitized mountain range data and perform the phase space reconstruction for the AGS, and later for Relativistic Heavy Ion Collider (RHIC).

  10. Longitudinal ABR in the NICU infant.

    PubMed

    Cox, L C; Hack, M; Metz, D A

    1982-08-01

    To assess the reliability of ABR testing of NICU infants, longitudinal ABR testing was accomplished on 50 NICU infants while hospitalized and subsequently at 4 and at 20-24 months of age. The results indicate that ABR testing in the NICU may be a poor predictor of subsequent permanent hearing loss. The implications of these findings are discussed with the recommendation that ABR testing in the NICU be used in concert with follow-up testing.

  11. Nonlinear longitudinal control of a supermaneuverable aircraft

    NASA Technical Reports Server (NTRS)

    Garrard, William L.; Snell, Anthony; Enns, Dale F.

    1989-01-01

    A technique is described which can be used for design of feedback controllers for high-performance aircraft operating in flight conditions in which nonlinearities significantly affect performance. Designs are performed on a mathematical model of the longitudinal dynamics of a hypothetical aircraft similar to proposed supermaneuverable flight test vehicles. Nonlinear controller designs are performed using truncated solutions of the Hamilton-Jacobi-Bellman equation. Preliminary results show that the method yields promising results.

  12. Operation of PEP longitudinal feedback system

    SciTech Connect

    Allen, M.A.; Karvonen, L.G.; McConnell, R.A.; Schwarz, H.

    1981-03-01

    In order to suppress longitudinal coupled-bunch oscillations which might limit the capabilities of PEP, the 18 GeV e/sup +/e/sup -/ storage ring at SLAC, a longitudinal feedback system is utilized. A frequency domain feedback system was chosen with the frequency spectrum of the stored beam being sampled close to a symmetry point in the ring where the feedback cavity itself is also located. The symmetry point chosen is symmetry point 5 which lies half-way between interaction regions 4 and 6. The system has been installed in PEP and is now operational. However, at stored currents up to the maximum stored in PEP to date at 14.5 GeV (approximately 40 mA in 6 bunches), the ring has been stable to all modes of longitudinal coupled-bunch oscillations both barycentric and the other fundamental modes. By deliberately detuning the main accelerating cavities, small multibunch oscillations can be introduced which, in turn, can be damped by the feedback system. Under optimized beam conditions the feedback system could be adjusted to positive feedback and excite oscillations with relatively small power to the feedback cavity. This will be described along with other details of the system.

  13. Longitudinal Electroproduction of Charged Pions from

    SciTech Connect

    David Gaskell; Abdellah Ahmidouch; Pawel Ambrozewicz; H. Anklin; John Arrington; K. Assamagan; Steven Avery; Kevin Bailey; Oliver K. Baker; Shelton Beedoe; Elizabeth Beise; Herbert Breuer; D. S. Brown; Roger Carlini; Jinseok Cha; Nicholas Chant; Anthony Cowley; Samuel Danagoulian; D. De Schepper; Jim Dunne; Dipangkar Dutta; Rolf Ent; Liping Gan; Ashot Gasparian; Donald Geesaman; Ron Gilman; Charles Glashausser; Paul Gueye; M. Harvey; O. Hashimoto; Wendy Hinton; G. Hofman; Ceasar Jackson; Hal Jackson; Cynthia Keppel; Ed Kinney; Doug Koltenuk; G. Kyle; Allison Lung; David Mack; D. McKee; Joseph Mitchell; Hamlet Mkrtchyan; B. Mueller; Gabriel Niculescu; Ioana Niculescu; Tom O'Neill; V. Papavassiliou; Dave Potterveld; Juerg Reinhold; Philip Roos; Reyad Sawafta; Ralph Segel; Stepan Stepanyan; Vardan Tadevosyan; T. Takahashi; Liguang Tang; B. Terburg; D. Van Westrum; J. Volmer; T. P. Welch; Stephen Wood; Lulin Yuan; Ben Zeidman; Beni Zihlmann

    2001-11-12

    Separated longitudinal and transverse cross sections for charged pion electroproduction from {sup 1}H, {sup 2}H, and {sup 3}He were measured at Q{sup 2} = 0.4 (GeV/c){sup 2} for two values of the invariant mass, {bar W} = 1.15 GeV and {bar W} = 1.60 GeV, in a search for a mass dependence which would signal the effect of nuclear pions. This is the first such study that includes recoil momenta significantly above the Fermi surface. The longitudinal cross section, if dominated by the pion-pole process, should be sensitive to nuclear pion currents. Comparisons of the longitudinal cross section target ratios to a quasifree calculation reveal a significant suppression in {sup 3>}He at {bar W} = 1.60 GeV. The {bar W} = 1.15 GeV results are consistent with simple estimates of the effect of nuclear pion currents, but are also consistent with pure quasifree production.

  14. Identifying longitudinal trends within EEG experiments.

    PubMed

    Hasenstab, Kyle; Sugar, Catherine A; Telesca, Donatello; McEvoy, Kevin; Jeste, Shafali; Şentürk, Damla

    2015-12-01

    Differential brain response to sensory stimuli is very small (a few microvolts) compared to the overall magnitude of spontaneous electroencephalogram (EEG), yielding a low signal-to-noise ratio (SNR) in studies of event-related potentials (ERP). To cope with this phenomenon, stimuli are applied repeatedly and the ERP signals arising from the individual trials are averaged at the subject level. This results in loss of information about potentially important changes in the magnitude and form of ERP signals over the course of the experiment. In this article, we develop a meta-preprocessing step utilizing a moving average of ERP across sliding trial windows, to capture such longitudinal trends. We embed this procedure in a weighted linear mixed effects model to describe longitudinal trends in features such as ERP peak amplitude and latency across trials while adjusting for the inherent heteroskedasticity created at the meta-preprocessing step. The proposed unified framework, including the meta-processing and the weighted linear mixed effects modeling steps, is referred to as MAP-ERP (moving-averaged-processed ERP). We perform simulation studies to assess the performance of MAP-ERP in reconstructing existing longitudinal trends and apply MAP-ERP to data from young children with autism spectrum disorder (ASD) and their typically developing counterparts to examine differences in patterns of implicit learning, providing novel insights about the mechanisms underlying social and/or cognitive deficits in this disorder.

  15. Nucleon Spin Structure: Longitudinal and Transverse

    SciTech Connect

    Jian-Ping Chen

    2011-02-01

    Inclusive Deep-Inelastic Scattering (DIS) experiments have provided us with the most extensive information on the unpolarized and longitudinal polarized parton (quark and gluon) distributions in the nucleon. It has becoming clear that transverse spin and transverse momentum dependent distributions (TMDs) study are crucial for a more complete understanding of the nucleon structure and the dynamics of the strong interaction. The transverse spin structure and the TMDs are the subject of increasingly intense theoretical and experimental study recently. With a high luminosity electron beam facility, JLab has played a major role in the worldwide effort to study both the longitudinal and transverse spin structure. Highlights of recent results will be presented. With 12-GeV energy upgrade, JLab will provide the most precise measurements in the valence quark region to close a chapter in longitudinal spin study. JLab will also perform a multi-dimensional mapping of the transverse spin structure and TMDs in the valence quark region through Semi-Inclusive DIS (SIDIS) experiments, providing a 3-d partonic picture of the nucleon in momentum space and extracting the u and d quark tensor charges of the nucleon. The precision mapping of TMDs will also allow a detailed study of the quark orbital motion and its dynamics.

  16. Magnetization Transfer Induced Biexponential Longitudinal Relaxation

    PubMed Central

    Prantner, Andrew M.; Bretthorst, G. Larry; Neil, Jeffrey J.; Garbow, Joel R.; Ackerman, Joseph J.H.

    2009-01-01

    Longitudinal relaxation of brain water 1H magnetization in mammalian brain in vivo is typically analyzed on a per voxel basis using a monoexponential model, thereby assigning a single relaxation time constant to all 1H magnetization within a given voxel. This approach was tested by obtaining inversion recovery data from grey matter of rats at 64 exponentially-spaced recovery times. Using Bayesian probability for model selection, brain water data were best represented by a biexponential function characterized by fast and slow relaxation components. At 4.7 T, the amplitude fraction of the rapidly relaxing component is 3.4 ± 0.7 % with a rate constant of 44 ± 12 s-1 (mean ± SD; 174 voxels from 4 rats). The rate constant of the slow relaxing component is 0.66 ± 0.04 s-1. At 11.7 T, the corresponding values are 6.9 ± 0.9 %, 19 ± 5 s-1, and 0.48 ± 0.02 s-1 (151 voxels from 4 rats). Several putative mechanisms for biexponential relaxation behavior were evaluated, and magnetization transfer between bulk water protons and non-aqueous protons was determined to be the source of biexponential longitudinal relaxation. MR methods requiring accurate quantification of longitudinal relaxation may need to take this effect explicitly into account. PMID:18759367

  17. Complete Suppression of Longitudinal Spin Seebeck Effect by Frozen Magnetization Dynamics in Y3Fe5O12

    NASA Astrophysics Data System (ADS)

    Kikkawa, Takashi; Uchida, Ken-ichi; Daimon, Shunsuke; Saitoh, Eiji

    2016-06-01

    The spin Seebeck effect (SSE) in a Pt-film/Y3Fe5O12 (YIG)-slab junction system has been investigated at low temperatures and under various magnetic fields in the longitudinal configuration. We found that, by increasing applied magnetic fields, the SSE signal gradually decreases and converges to zero without showing sign reversal. The complete field-induced suppression of the SSE is interpreted in terms of the effect of the Zeeman gap in magnon excitation.

  18. Self-induced acoustic transparency of three-component longitudinal-transverse pulses

    SciTech Connect

    Sazonov, S. V.; Ustinov, N. V.

    2012-04-15

    The features of the nonlinear dynamics of three-component elastic pulses in a low-temperature crystal containing paramagnetic impurities of electron and nuclear spins have been analyzed in the slowly varying envelope approximation. The presence of the electron spin subsystem makes it possible to equate the velocities of longitudinal sound and transverse acoustic waves; as a result, all components of the strain field efficiently interact with each other through the nuclear spin subsystem. The system of equations for envelopes of harmonics of the components of the strain field and the spin variables has been derived. The relations between the amplitudes and phases of the components have been obtained, the spectral composition has been analyzed, and the regimes of acoustic transparency of three-component longitudinal-transverse pulses have been discussed.

  19. A scaled experiment to study energy dissipation process during longitudinal compression of charged particle beams

    NASA Astrophysics Data System (ADS)

    Sakai, Y.; Nakajima, M.; Hasegawa, J.; Kikuchi, T.; Horioka, K.

    2016-03-01

    Beam behavior during longitudinal bunch compression of charged particles was investigated using a compact simulator device based on electron beams. Beam current waveforms and bunch compression ratios were measured as a function of the initial beam current. We found that the current waveform became blunt and the compression ratio degraded at higher beam currents. These results indicate that space-charge fields dissipate the kinetic energy of beam particles.

  20. Using quasiphotons to compute wave fields in an elastic medium

    SciTech Connect

    Kachalov, A.P.

    1987-07-10

    Quasiphoton solutions are constructed for longitudinal and transversal waves in an elastic medium. The quasiphotons are then applied to determine the fields of nonstationary high-frequency point sources in a medium with parameters dependent on two Euclidean coordinates.

  1. Effect of longitudinal ridges on the aerodynamic performance of a leatherback turtle model

    NASA Astrophysics Data System (ADS)

    Bang, Kyeongtae; Kim, Jooha; Kim, Heesu; Lee, Sang-Im; Choi, Haecheon

    2012-11-01

    Leatherback sea turtles (Dermochelys coriacea) are known as the fastest swimmer and the deepest diver in the open ocean among marine turtles. Unlike other marine turtles, leatherback sea turtles have five longitudinal ridges on their carapace. To investigate the effect of these longitudinal ridges on the aerodynamic performance of a leatherback turtle model, the experiment is conducted in a wind tunnel at Re = 1.0 × 105 - 1.4 × 106 (including that of real leatherback turtle in cruising condition) based on the model length. We measure the drag and lift forces on the leatherback turtle model with and without longitudinal ridges. The presence of longitudinal ridges increases both the lift and drag forces on the model, but increases the lift-to-drag ratio by 15 - 40%. We also measure the velocity field around the model with and without the ridges using particle image velocimetry. More details will be shown in the presentation. Supported by the NRF program (2011-0028032).

  2. First evidence of interaction between longitudinal and transverse waves in solar magnetic elements

    NASA Astrophysics Data System (ADS)

    Stangalini, M.; Solanki, S. K.; Cameron, R.; Martínez Pillet, V.

    2013-06-01

    Small-scale magnetic fields are thought to play an important role in the heating of the outer solar atmosphere. By taking advantage of the unprecedented high-spatial and temporal cadence of the Imaging Magnetograph eXperiment (IMaX), the filter vector polarimeter on board the Sunrise balloon-borne observatory, we study the transversal and longitudinal velocity oscillations in small magnetic elements. The results of this analysis are then compared to magnetohydrodynamic (MHD) simulations, showing excellent agreement. We found buffeting-induced transverse oscillations with velocity amplitudes of the order of 1-2 km s-1 to be common along with longitudinal oscillations with amplitudes ~0.4 km s-1. Moreover, we also found an interaction between transverse oscillations and longitudinal velocity oscillations, showing a ± 90° phase lag at the frequency at which they exhibit the maximum coherence in the power spectrum. Our results are consistent with the theoretical picture in which MHD longitudinal waves are excited inside small magnetic elements as a response of the flux tube to the forcing action of the granular flows.

  3. Regional vulnerability of longitudinal cortical association connectivity

    PubMed Central

    Ceschin, Rafael; Lee, Vince K.; Schmithorst, Vince; Panigrahy, Ashok

    2015-01-01

    Preterm born children with spastic diplegia type of cerebral palsy and white matter injury or periventricular leukomalacia (PVL), are known to have motor, visual and cognitive impairments. Most diffusion tensor imaging (DTI) studies performed in this group have demonstrated widespread abnormalities using averaged deterministic tractography and voxel-based DTI measurements. Little is known about structural network correlates of white matter topography and reorganization in preterm cerebral palsy, despite the availability of new therapies and the need for brain imaging biomarkers. Here, we combined novel post-processing methodology of probabilistic tractography data in this preterm cohort to improve spatial and regional delineation of longitudinal cortical association tract abnormalities using an along-tract approach, and compared these data to structural DTI cortical network topology analysis. DTI images were acquired on 16 preterm children with cerebral palsy (mean age 5.6 ± 4) and 75 healthy controls (mean age 5.7 ± 3.4). Despite mean tract analysis, Tract-Based Spatial Statistics (TBSS) and voxel-based morphometry (VBM) demonstrating diffusely reduced fractional anisotropy (FA) reduction in all white matter tracts, the along-tract analysis improved the detection of regional tract vulnerability. The along-tract map-structural network topology correlates revealed two associations: (1) reduced regional posterior–anterior gradient in FA of the longitudinal visual cortical association tracts (inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, optic radiation, posterior thalamic radiation) correlated with reduced posterior–anterior gradient of intra-regional (nodal efficiency) metrics with relative sparing of frontal and temporal regions; and (2) reduced regional FA within frontal–thalamic–striatal white matter pathways (anterior limb/anterior thalamic radiation, superior longitudinal fasciculus and cortical spinal tract) correlated

  4. A new formulation of longitudinal coherent instabilities

    SciTech Connect

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

    1993-01-01

    The quadrature response of longitudinal impedance is shown to be the effective impedance for the beam instability. The results of the application of this formulation are compared with that obtained using the Robinson-Pedersen approach and the Sacherer integral equation. 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.

  5. A new formulation of longitudinal coherent instabilities

    SciTech Connect

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

    1993-06-01

    The quadrature response of longitudinal impedance is shown to be the effective impedance for the beam instability. The results of the application of this formulation are compared with that obtained using the Robinson-Pedersen approach and the Sacherer integral equation. 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.

  6. Nature of the strong field capabilities of lasers

    NASA Astrophysics Data System (ADS)

    Reiss, H. R.

    2013-05-01

    Research with lasers of extremely high intensity has been proposed in terms of tunneling and the "Schwinger Limit", which refers to breakdown of the vacuum into electron-positron pairs caused by a static or quasistatic electric field. The difficulty is that lasers produce transverse fields, wherein the electric and magnetic fields form a mutually orthogonal triad with the direction of propagation. Tunneling, including the Schwinger Limit, relates to longitudinal fields, in which the direction of the electric field vector is the only preferred direction. Transverse fields propagate indefinitely without inputs from source or current distributions. By contrast, longitudinal fields require continuing contributions from external source or current distributions. Failure to distinguish between longitudinal and transverse fields is consequential in that some proposed applications of very high intensity lasers pertain only to tunneling processes, but not to laser fields. A related difficulty is the flawed notion that tunneling constitutes a low-frequency limit of laser-induced processes. A counter-indication is that the ponderomotive potential of a charged particle in a laser field is proportional to the inverse square of the field frequency. Thus there is no possible approach to a zero-frequency laser field. The Göppert-Mayer gauge transformation of atomic physics makes possible a limited correspondence between transverse and longitudinal fields. The correspondence fails at both high and, most importantly, at low field frequencies. Vacuum pair production does not require the Schwinger Limit, but can be achieved at much lower intensities.

  7. Cultural Mediation of Children's Cosmologies: A Longitudinal Study of the Astronomy Concepts of Chinese and New Zealand Children

    ERIC Educational Resources Information Center

    Bryce, T. G. K.; Blown, E. J.

    2006-01-01

    These longitudinal studies investigated the cultural mediation of children's thinking about the Earth using an interview technique designed to elicit responses from children from all "levels" of their conceptual organization (intuitive, cultural, and scientific). Close scrutiny of the research literature in this field reveals that some strategies…

  8. Time-to-Event Analysis of Individual Variables Associated with Nursing Students' Academic Failure: A Longitudinal Study

    ERIC Educational Resources Information Center

    Dante, Angelo; Fabris, Stefano; Palese, Alvisa

    2013-01-01

    Empirical studies and conceptual frameworks presented in the extant literature offer a static imagining of academic failure. Time-to-event analysis, which captures the dynamism of individual factors, as when they determine the failure to properly tailor timely strategies, impose longitudinal studies which are still lacking within the field. The…

  9. Results from the Longitudinal Study of Astronomy Graduate Students

    NASA Astrophysics Data System (ADS)

    Ivie, Rachel

    2014-01-01

    The Longitudinal Study of Astronomy Graduate Students (LSAGS), an ongoing, joint project of the American Astronomical Society (AAS) and the American Institute of Physics (AIP), first collected survey data from astronomy and astrophysics graduate students in 2007-08. The LSAGS follows the same people, all of whom were in graduate school in 2006-07, over time as they start their careers. Most of the respondents are currently working as postdocs. There have been two rounds of the survey so far, and we have recently received funding for a third round from the National Science Foundation (AST-1347723). Results from the first round showed the importance of mentoring for graduate students. Data collection for the second round has been completed, and AIP has just begun analysis of these data. At this talk, I will present the results of the second survey. Ultimately, the LSAGS will *provide detailed data on trends in employment over 10+ years for a single cohort, *collect data on people who leave the field of astronomy during or after graduate school, *determine whether there are sex differences in attrition from astronomy and reasons for this, and *examine factors that precede decisions to persist in, or leave, the field of astronomy.

  10. Response of fiber Bragg gratings to longitudinal ultrasonic waves.

    PubMed

    Minardo, Aldo; Cusano, Andrea; Bernini, Romeo; Zeni, Luigi; Giordano, Michele

    2005-02-01

    In the last years, fiber optic sensors have been widely exploited for several sensing applications, including static and dynamic strain measurements up to acoustic detection. Among these, fiber Bragg grating sensors have been indicated as the ideal candidate for practical structural health monitoring in light of their unique advantages over conventional sensing devices. Although this class of sensors has been successfully tested for static and low-frequency measurements, the identification of sensor performances for high-frequency detection, including acoustic emission and ultrasonic investigations, is required. To this aim, the analysis of feasibilty on the use of fiber Bragg grating sensors as ultrasonic detectors has been carried out. In particular, the response of fiber Bragg gratings subjected to the longitudinal ultrasonic (US) field has been theoretically and numerically investigated. Ultrasonic field interaction has been modeled, taking into account the direct deformation of the grating pitch combined with changes in local refractive index due to the elasto-optic effect. Numerical results, obtained for both uniform and Gaussian-apodized fiber Bragg gratings, show that the grating spectrum is strongly influenced by the US field in terms of shape and central wavelength. In particular, a key parameter affecting the grating response is the ratio between the US wavelength and the grating length. Normal operation characterized by changes in wavelength of undistorted Bragg peak is possible only for US wavelengths longer than the grating length. For US wavelengths approaching the grating length, the wavelength change is accompanied by subpeaks formation and main peak amplitude modulation. This effect can be attributed to the nonuniformity of the US perturbation along the grating length. At very high US frequencies, the grating is not sensitive any longer. The results of this analysis provide useful tools for the design of grating-based ultrasound sensors for

  11. Bootstrap inference longitudinal semiparametric regression model

    NASA Astrophysics Data System (ADS)

    Pane, Rahmawati; Otok, Bambang Widjanarko; Zain, Ismaini; Budiantara, I. Nyoman

    2016-02-01

    Semiparametric regression contains two components, i.e. parametric and nonparametric component. Semiparametric regression model is represented by yt i=μ (x˜'ti,zt i)+εt i where μ (x˜'ti,zt i)=x˜'tiβ ˜+g (zt i) and yti is response variable. It is assumed to have a linear relationship with the predictor variables x˜'ti=(x1 i 1,x2 i 2,…,xT i r) . Random error εti, i = 1, …, n, t = 1, …, T is normally distributed with zero mean and variance σ2 and g(zti) is a nonparametric component. The results of this study showed that the PLS approach on longitudinal semiparametric regression models obtain estimators β˜^t=[X'H(λ)X]-1X'H(λ )y ˜ and g˜^λ(z )=M (λ )y ˜ . The result also show that bootstrap was valid on longitudinal semiparametric regression model with g^λ(b )(z ) as nonparametric component estimator.

  12. Multivariate Longitudinal Analysis with Bivariate Correlation Test.

    PubMed

    Adjakossa, Eric Houngla; Sadissou, Ibrahim; Hounkonnou, Mahouton Norbert; Nuel, Gregory

    2016-01-01

    In the context of multivariate multilevel data analysis, this paper focuses on the multivariate linear mixed-effects model, including all the correlations between the random effects when the dimensional residual terms are assumed uncorrelated. Using the EM algorithm, we suggest more general expressions of the model's parameters estimators. These estimators can be used in the framework of the multivariate longitudinal data analysis as well as in the more general context of the analysis of multivariate multilevel data. By using a likelihood ratio test, we test the significance of the correlations between the random effects of two dependent variables of the model, in order to investigate whether or not it is useful to model these dependent variables jointly. Simulation studies are done to assess both the parameter recovery performance of the EM estimators and the power of the test. Using two empirical data sets which are of longitudinal multivariate type and multivariate multilevel type, respectively, the usefulness of the test is illustrated. PMID:27537692

  13. Transversal and longitudinal mixing in compound channels

    NASA Astrophysics Data System (ADS)

    Besio, G.; Stocchino, A.; Angiolani, S.; Brocchini, M.

    2012-12-01

    An experimental campaign, based on particle image velocimetry (PIV) measurements of free-surface velocities, forms the basis for an analysis of the mixing processes which occur in a compound-channel flow. The flow mixing is characterized in terms of Lagrangian statistics (absolute dispersion and diffusivity) and of the related mean flow characteristics. Mixing properties strongly depend on the ratiorh between the main channel flow depth (h*mc) and the floodplain depth (h*fp), and three flow classes can be identified, namely shallow, intermediate, and deep flows. In the present study the large time asymptotic behavior of the mixing characteristics is analyzed in terms of the absolute diffusivity in order to characterize typical values of longitudinal and transversal diffusivity coefficients. Various sets of experiments, which cover a wide range of the governing physical parameters, have been performed and the asymptotic values of the absolute diffusivity have been evaluated. The results are then compared with several studies of flow dispersion for both the longitudinal diffusivity coefficient and the transversal turbulent mixing coefficient. The present results highlight a stronger dependence of such coefficients with the flow-depth ratio than with the flow regime (Froude number).

  14. Longitudinal residual stresses in boron fibers

    NASA Technical Reports Server (NTRS)

    Behrendt, D. R.

    1976-01-01

    A technique is proposed for measuring the longitudinal residual stress distribution in commercial CVD (Chemical Vapor Deposition) boron on tungsten fibers of 102, 142, and 203 microns in diameter. The experimental apparatus is so designed that continuous measurements are made of the length changes of a boron fiber specimen as the surface of the fiber is removed by electropolishing. The effects of surface removal on core residual stress and core-initiated fracture are discussed. The three sizes of boron fibers investigated show similar residual stress distributions, i.e., compressive at the surface, tensile near the core, and for the 102-micron fiber compressive again in the core. It is shown that an increase in UTS is due to the increase in the compressive stress at the core produced by fiber contraction during surface removal. An expression is derived for calculating the longitudinal residual stress at a given radius for an as-received fiber of a certain radius from measurements of the axial strain produced by removal of the surface by electropolishing.

  15. Sufficient dimension reduction for longitudinally measured predictors.

    PubMed

    Pfeiffer, Ruth M; Forzani, Liliana; Bura, Efstathia

    2012-09-28

    We propose a method to combine several predictors (markers) that are measured repeatedly over time into a composite marker score without assuming a model and only requiring a mild condition on the predictor distribution. Assuming that the first and second moments of the predictors can be decomposed into a time and a marker component via a Kronecker product structure that accommodates the longitudinal nature of the predictors, we develop first-moment sufficient dimension reduction techniques to replace the original markers with linear transformations that contain sufficient information for the regression of the predictors on the outcome. These linear combinations can then be combined into a score that has better predictive performance than a score built under a general model that ignores the longitudinal structure of the data. Our methods can be applied to either continuous or categorical outcome measures. In simulations, we focus on binary outcomes and show that our method outperforms existing alternatives by using the AUC, the area under the receiver-operator characteristics (ROC) curve, as a summary measure of the discriminatory ability of a single continuous diagnostic marker for binary disease outcomes.

  16. Longitudinal Predictors of Institutionalization in Old Age

    PubMed Central

    Hajek, André; Brettschneider, Christian; Lange, Carolin; Posselt, Tina; Wiese, Birgitt; Steinmann, Susanne; Weyerer, Siegfried; Werle, Jochen; Pentzek, Michael; Fuchs, Angela; Stein, Janine; Luck, Tobias; Bickel, Horst; Mösch, Edelgard; Wagner, Michael; Jessen, Frank; Maier, Wolfgang; Scherer, Martin

    2015-01-01

    Objective To investigate time-dependent predictors of institutionalization in old age using a longitudinal approach. Methods In a representative survey of the German general population aged 75 years and older predictors of institutionalization were observed every 1.5 years over six waves. Conditional fixed-effects logistic regressions (with 201 individuals and 960 observations) were performed to estimate the effects of marital status, depression, dementia, and physical impairments (mobility, hearing and visual impairments) on the risk of admission to old-age home or nursing home. By exploiting the longitudinal data structure using panel econometric models, we were able to control for unobserved heterogeneity such as genetic predisposition and personality traits. Results The probability of institutionalization increased significantly with occurrence of widowhood, depression, dementia, as well as walking and hearing impairments. In particular, the occurrence of widowhood (OR = 78.3), dementia (OR = 154.1) and substantial mobility impairment (OR = 36.7) were strongly associated with institutionalization. Conclusion Findings underline the strong influence of loss of spouse as well as dementia on institutionalization. This is relevant as the number of old people (a) living alone and (b) suffering from dementia is expected to increase rapidly in the next decades. Consequently, it is supposed that the demand for institutionalization among the elderly will increase considerably. Practitioners as well as policy makers should be aware of these upcoming challenges. PMID:26658776

  17. MULTILINEAR TENSOR REGRESSION FOR LONGITUDINAL RELATIONAL DATA

    PubMed Central

    Hoff, Peter D.

    2016-01-01

    A fundamental aspect of relational data, such as from a social network, is the possibility of dependence among the relations. In particular, the relations between members of one pair of nodes may have an effect on the relations between members of another pair. This article develops a type of regression model to estimate such effects in the context of longitudinal and multivariate relational data, or other data that can be represented in the form of a tensor. The model is based on a general multilinear tensor regression model, a special case of which is a tensor autoregression model in which the tensor of relations at one time point are parsimoniously regressed on relations from previous time points. This is done via a separable, or Kronecker-structured, regression parameter along with a separable covariance model. In the context of an analysis of longitudinal multivariate relational data, it is shown how the multilinear tensor regression model can represent patterns that often appear in relational and network data, such as reciprocity and transitivity. PMID:27458495

  18. Multivariate Longitudinal Analysis with Bivariate Correlation Test

    PubMed Central

    Adjakossa, Eric Houngla; Sadissou, Ibrahim; Hounkonnou, Mahouton Norbert; Nuel, Gregory

    2016-01-01

    In the context of multivariate multilevel data analysis, this paper focuses on the multivariate linear mixed-effects model, including all the correlations between the random effects when the dimensional residual terms are assumed uncorrelated. Using the EM algorithm, we suggest more general expressions of the model’s parameters estimators. These estimators can be used in the framework of the multivariate longitudinal data analysis as well as in the more general context of the analysis of multivariate multilevel data. By using a likelihood ratio test, we test the significance of the correlations between the random effects of two dependent variables of the model, in order to investigate whether or not it is useful to model these dependent variables jointly. Simulation studies are done to assess both the parameter recovery performance of the EM estimators and the power of the test. Using two empirical data sets which are of longitudinal multivariate type and multivariate multilevel type, respectively, the usefulness of the test is illustrated. PMID:27537692

  19. Splinting of Longitudinal Fracture: An Innovative Approach

    PubMed Central

    Bansal, Rashmi; Chowdhary, Priyanka; Gurtu, Anuraag; Mehrotra, Nakul; Kishore, Abhinav

    2016-01-01

    Trauma may result in craze lines on the enamel surface, one or more fractured cusps of posterior teeth, cracked tooth syndrome, splitting of posterior teeth, and vertical fracture of root. Out of these, management of some fractures is of great challenge and such teeth are generally recommended for extraction. Literature search reveals attempts to manage such fractures by full cast crown, orthodontic wires, and so forth, in which consideration was given to extracoronal splinting only. However, due to advancement in materials and technologies, intracoronal splinting can be achieved as well. In this case report, longitudinal fractures in tooth #27, tooth #37, and tooth #46 had occurred. In #27, fracture line was running mesiodistally involving the pulpal floor resulting in a split tooth. In teeth 37 and 46, fractures of the mesiobuccal cusp and mesiolingual cusp were observed, respectively. They were restored with cast gold inlay and full cast crown, respectively. Longitudinal fracture of 27 was treated with an innovative approach using intracanal reinforced composite with Ribbond, external reinforcement with an orthodontic band, and full cast metal crown to splint the split tooth. PMID:27247808

  20. Perception of longitudinal components in piano string vibrations.

    PubMed

    Bank, Balázs; Lehtonen, Heidi-Maria

    2010-09-01

    This paper investigates the audibility of longitudinal components in piano string vibrations with listening tests. The recorded fortissimo sounds of two grand and one upright pianos have been resynthesized with and without longitudinal components and used in ABX type listening tests. Results suggest that the longitudinal components are audible up to note C(5). However, a second test seeking the importance of the difference shows that the effect of longitudinal components for the range A(3)-C(5) is subtle. This means that modeling the phenomenon up to around note A(3) only is acceptable for sound synthesis applications. PMID:20815427

  1. Coupling and degenerating modes in longitudinal-torsional step horns.

    PubMed

    Harkness, Patrick; Lucas, Margaret; Cardoni, Andrea

    2012-12-01

    Longitudinal-torsional vibration is used and proposed for a variety of ultrasonic applications including motors, welding, and rock-cutting. To obtain this behavior in an ultrasonic step horn one can either, (i) couple the longitudinal and torsional modes of the horn by incorporating a ring of diagonal slits in the thick base section or, (ii) place helical flutes in the thin stem section to degenerate the longitudinal mode into a modified behavior with a longitudinal-torsional motion. This paper compares the efficacy of these two design approaches using both numerical and experimental techniques.

  2. Estimation and visualization of longitudinal muscle motion using ultrasonography: a feasibility study.

    PubMed

    Li, Jizhou; Zhou, Yongjin; Ivanov, Kamen; Zheng, Yong-Ping

    2014-03-01

    Ultrasonography is a convenient and widely used technique to look into the longitudinal muscle motion as it is radiation-free and real-time. The motion of localized parts of the muscle, disclosed by ultrasonography, spatially reflects contraction activities of the corresponding muscles. However, little attention was paid to the estimation of longitudinal muscle motion, especially towards estimation of dense deformation field at different depths under the skin. Yet fewer studies on the visualization of such muscle motion or further clinical applications were reported in the literature. A primal-dual algorithm was used to estimate the motion of gastrocnemius muscle (GM) in longitudinal direction in this study. To provide insights into the rules of longitudinal muscle motion, we proposed a novel framework including motion estimation, visualization and quantitative analysis to interpret synchronous activities of collaborating muscles with spatial details. The proposed methods were evaluated on ultrasound image sequences, captured at a rate of 25 frames per second from eight healthy subjects. In order to estimate and visualize the GM motion in longitudinal direction, each subject was asked to perform isometric plantar flexion twice. Preliminary results show that the proposed visualization methods provide both spatial and temporal details and they are helpful to study muscle contractions. One of the proposed quantitative measures was also tested on a patient with unilateral limb dysfunction caused by cerebral infarction. The measure revealed distinct patterns between the normal and the dysfunctional lower limb. The proposed framework and its associated quantitative measures could potentially be used to complement electromyography (EMG) and torque signals in functional assessment of skeletal muscles.

  3. Longitudinal Muscle Dysfunction in Achalasia Esophagus and Its Relevance

    PubMed Central

    Hong, Su Jin; Bhargava, Valmik

    2013-01-01

    Muscularis propria of the esophagus is organized into circular and longitudinal muscle layers. Goal of this review is to summarize the role of longitudinal muscle in physiology and pathophysiology of esophageal sensory and motor function. Simultaneous manometry and ultrasound imaging that measure circular and longitudinal muscle contraction respectively reveal that during peristalsis 2 layers of the esophagus contract in perfect synchrony. On the other hand, during transient relaxation of the lower esophageal sphincter (LES), longitudinal muscle contracts independently of circular muscle. Recent studies provide novel insights, i.e., longitudinal muscle contraction of the esophagus induces LES relaxation and possibly descending relaxation of the esophagus. In achalasia esophagus and other motility disorders there is discoordination between the 2 muscle layers. Longitudinal muscle contraction patterns are different in the recently described three types of achalasia identified by high-resolution manometry. Robust contraction of the longitudinal muscle in type II achalasia causes pan-esophageal pressurization and is the mechanism of whatever little esophageal emptying that take place in the absence of peristalsis and impaired LES relaxation. It may be that preserved longitudinal muscle contraction is also the reason for superior outcome to medical/surgical therapy in type II achalasia esophagus. Prolonged contractions of longitudinal muscles of the esophagus is a possible mechanism of heartburn and "angina like" pain seen in esophageal motility disorders and possibly achalasia esophagus. Novel techniques to record longitudinal muscle contraction are on the horizon. Neuro-pharmacologic control of circular and longitudinal muscles is different, which provides an important opportunity for the development of novel pharmacological therapies to treat sensory and motor disorders of the esophagus. PMID:23667744

  4. NUMERICAL STUDY OF THE LONGITUDINALLY ASYMMETRIC DISTRIBUTION OF SOLAR ENERGETIC PARTICLES IN THE HELIOSPHERE

    SciTech Connect

    He, H.-Q.; Wan, W. E-mail: wanw@mail.iggcas.ac.cn

    2015-06-22

    Solar energetic particles (SEPs) affect the solar–terrestrial space environment and are very important to space weather research. In this work, we numerically investigate the transport processes of SEPs in the three-dimensional interplanetary magnetic field, with an emphasis on the longitudinal distribution of SEPs in the heliosphere. We confirm our previous finding that there exists an east–west longitudinal asymmetry in the SEP intensities, i.e., with the same longitude separations between the solar source centers and the magnetic footpoint of the observer, the fluxes of SEP events originating from solar sources located on the eastern side of the nominal magnetic footpoint of the observer are systematically larger than those of the SEP events originating from sources located on the western side. We discuss the formation mechanism of this phenomenon, and conclude that the longitudinally asymmetric distribution of SEPs results from the east–west azimuthal asymmetry in the topology of the heliospheric magnetic field as well as the effects of perpendicular diffusion on the transport of SEPs in the heliosphere. Our results will be valuable to understanding Sun–Earth relations and useful for space weather forecasting.

  5. Longitudinal Differences of Ionospheric Vertical Density Distribution and Equatorial Electrodynamics

    NASA Technical Reports Server (NTRS)

    Yizengaw, E.; Zesta, E.; Moldwin, M. B.; Damtie, B.; Mebrahtu, A.; Valledares, C.E.; Pfaff, R. F.

    2012-01-01

    Accurate estimation of global vertical distribution of ionospheric and plasmaspheric density as a function of local time, season, and magnetic activity is required to improve the operation of space-based navigation and communication systems. The vertical density distribution, especially at low and equatorial latitudes, is governed by the equatorial electrodynamics that produces a vertical driving force. The vertical structure of the equatorial density distribution can be observed by using tomographic reconstruction techniques on ground-based global positioning system (GPS) total electron content (TEC). Similarly, the vertical drift, which is one of the driving mechanisms that govern equatorial electrodynamics and strongly affect the structure and dynamics of the ionosphere in the low/midlatitude region, can be estimated using ground magnetometer observations. We present tomographically reconstructed density distribution and the corresponding vertical drifts at two different longitudes: the East African and west South American sectors. Chains of GPS stations in the east African and west South American longitudinal sectors, covering the equatorial anomaly region of meridian approx. 37 deg and 290 deg E, respectively, are used to reconstruct the vertical density distribution. Similarly, magnetometer sites of African Meridian B-field Education and Research (AMBER) and INTERMAGNET for the east African sector and South American Meridional B-field Array (SAMBA) and Low Latitude Ionospheric Sensor Network (LISN) are used to estimate the vertical drift velocity at two distinct longitudes. The comparison between the reconstructed and Jicamarca Incoherent Scatter Radar (ISR) measured density profiles shows excellent agreement, demonstrating the usefulness of tomographic reconstruction technique in providing the vertical density distribution at different longitudes. Similarly, the comparison between magnetometer estimated vertical drift and other independent drift observation

  6. THE INFLUENCE OF PARTICULATE MATTER OF AMBIENT ORIGIN UPON INDOOR RESIDENTIAL MASS CONCENTRATIONS INVOLVING SENSITIVE SUBPOPULATIONS-RESULTS FROM LONGITUDINAL PANEL STUDIES

    EPA Science Inventory

    The US EPA has completed field data collections from a series of longitudinal particulate matter (PM) exposure panel field studies. These studies were conducted in Baltimore, Maryland (1998), Fresno, California (1999), and Research Triangle Park (RTP), North Carolina (2000-2001) ...

  7. Jointly Modeling Event Time and Skewed-Longitudinal Data with Missing Response and Mismeasured Covariate for AIDS Studies.

    PubMed

    Huang, Yangxin; Yan, Chunning; Xing, Dongyuan; Zhang, Nanhua; Chen, Henian

    2015-01-01

    In longitudinal studies it is often of interest to investigate how a repeatedly measured marker in time is associated with a time to an event of interest. This type of research question has given rise to a rapidly developing field of biostatistics research that deals with the joint modeling of longitudinal and time-to-event data. Normality of model errors in longitudinal model is a routine assumption, but it may be unrealistically obscuring important features of subject variations. Covariates are usually introduced in the models to partially explain between- and within-subject variations, but some covariates such as CD4 cell count may be often measured with substantial errors. Moreover, the responses may encounter nonignorable missing. Statistical analysis may be complicated dramatically based on longitudinal-survival joint models where longitudinal data with skewness, missing values, and measurement errors are observed. In this article, we relax the distributional assumptions for the longitudinal models using skewed (parametric) distribution and unspecified (nonparametric) distribution placed by a Dirichlet process prior, and address the simultaneous influence of skewness, missingness, covariate measurement error, and time-to-event process by jointly modeling three components (response process with missing values, covariate process with measurement errors, and time-to-event process) linked through the random-effects that characterize the underlying individual-specific longitudinal processes in Bayesian analysis. The method is illustrated with an AIDS study by jointly modeling HIV/CD4 dynamics and time to viral rebound in comparison with potential models with various scenarios and different distributional specifications. PMID:24905593

  8. A Non-Intrusive Pressure Sensor by Detecting Multiple Longitudinal Waves

    PubMed Central

    Zhou, Hongliang; Lin, Weibin; Ge, Xiaocheng; Zhou, Jian

    2016-01-01

    Pressure vessels are widely used in industrial fields, and some of them are safety-critical components in the system—for example, those which contain flammable or explosive material. Therefore, the pressure of these vessels becomes one of the critical measurements for operational management. In the paper, we introduce a new approach to the design of non-intrusive pressure sensors, based on ultrasonic waves. The model of this sensor is built based upon the travel-time change of the critically refracted longitudinal wave (LCR wave) and the reflected longitudinal waves with the pressure. To evaluate the model, experiments are carried out to compare the proposed model with other existing models. The results show that the proposed model can improve the accuracy compared to models based on a single wave. PMID:27527183

  9. A U-statistics-based approach for modeling Cronbach coefficient alpha within a longitudinal data setting.

    PubMed

    Yan, Ma; Alejandro, Gonzalez Della Valle; Hui, Zhang; Tu, X M

    2010-03-15

    Cronbach coefficient alpha (CCA) is a classic measure of item internal consistency of an instrument and is used in a wide range of behavioral, biomedical, psychosocial, and health-care-related research. Methods are available for making inference about one CCA or multiple CCAs from correlated outcomes. However, none of the existing approaches effectively address missing data. As longitudinal study designs become increasingly popular and complex in modern-day clinical studies, missing data have become a serious issue, and the lack of methods to systematically address this problem has hampered the progress of research in the aforementioned fields. In this paper, we develop a novel approach to tackle the complexities involved in addressing missing data (at the instrument level due to subject dropout) within a longitudinal data setting. The approach is illustrated with both clinical and simulated data.

  10. Exact evaluation of the quadratic longitudinal response function for an unmagnetized Maxwellian plasma

    SciTech Connect

    Layden, B.; Cairns, Iver H.; Robinson, P. A.; Percival, D. J.

    2012-07-15

    The quadratic longitudinal response function describes the second-order nonlinear response of a plasma to electrostatic wave fields. An explicit expression for this function in the weak-turbulence regime requires the evaluation of velocity-space integrals involving the velocity distribution function and various resonant denominators. Previous calculations of the quadratic longitudinal response function were performed by approximating the resonant denominators to facilitate the integration. Here, we evaluate these integrals exactly for a non-relativistic collisionless unmagnetized isotropic Maxwellian plasma in terms of generalized plasma dispersion functions, and correct certain aspects of expressions previously derived for these functions. We show that in the appropriate limits the exact expression reduces to the approximate form used for interactions between two fast waves and one slow wave, such as the electrostatic decay of Langmuir waves into Langmuir waves and ion sound waves, and the scattering of Langmuir waves off thermal ions.

  11. A Non-Intrusive Pressure Sensor by Detecting Multiple Longitudinal Waves.

    PubMed

    Zhou, Hongliang; Lin, Weibin; Ge, Xiaocheng; Zhou, Jian

    2016-01-01

    Pressure vessels are widely used in industrial fields, and some of them are safety-critical components in the system-for example, those which contain flammable or explosive material. Therefore, the pressure of these vessels becomes one of the critical measurements for operational management. In the paper, we introduce a new approach to the design of non-intrusive pressure sensors, based on ultrasonic waves. The model of this sensor is built based upon the travel-time change of the critically refracted longitudinal wave (LCR wave) and the reflected longitudinal waves with the pressure. To evaluate the model, experiments are carried out to compare the proposed model with other existing models. The results show that the proposed model can improve the accuracy compared to models based on a single wave. PMID:27527183

  12. A Non-Intrusive Pressure Sensor by Detecting Multiple Longitudinal Waves.

    PubMed

    Zhou, Hongliang; Lin, Weibin; Ge, Xiaocheng; Zhou, Jian

    2016-08-05

    Pressure vessels are widely used in industrial fields, and some of them are safety-critical components in the system-for example, those which contain flammable or explosive material. Therefore, the pressure of these vessels becomes one of the critical measurements for operational management. In the paper, we introduce a new approach to the design of non-intrusive pressure sensors, based on ultrasonic waves. The model of this sensor is built based upon the travel-time change of the critically refracted longitudinal wave (LCR wave) and the reflected longitudinal waves with the pressure. To evaluate the model, experiments are carried out to compare the proposed model with other existing models. The results show that the proposed model can improve the accuracy compared to models based on a single wave.

  13. Longitudinal residual stresses in boron fibers

    NASA Technical Reports Server (NTRS)

    Behrendt, D. R.

    1976-01-01

    A method of measuring the longitudinal residual stress distribution in boron fibers is presented. The residual stresses in commercial CVD boron on tungsten fibers of 102, 142, and 203 microns (4, 5.6, and 8 mil) diameters were determined. Results for the three sizes show a compressive stress at the surface 800 to -1400 MN/sq m 120 to -200 ksi), changing monotonically to a region of tensile stress within the boron. At approximately 25 percent of the original radius, the stress reaches a maximum tensile 600 to 1000 MN/sq m(90 to 150 ksi) and then decreases to compressive near the tungsten boride core. The core itself is under a compressive stress of approximately -1300 MN/sq m (-190 ksi). The effects of surface removal on core residual stress and core-initiated fracture are discussed.

  14. Simulation of longitudinal coupled-bunch instabilities

    SciTech Connect

    Thompson, K.A.

    1991-02-07

    The purpose of this note is to document some work done as part of the effort directed at designing and simulating a bunch-by-bunch feedback system to control longitudinal coupled bunch instabilities in the B-factory. In particular, I discuss the ring model used in the simulation program developed to study this feedback system. Basically the simulation is a simple tracking program in which the rf drive voltage, the wakefields due to all the bunches, the synchrotron radiation losses, and the kicks applied to the bunches by the bunch-by-bunch feedback are all modelled as voltages applied at a single, discrete point in the ring. The computation of the bunch-by-bunch feedback voltages may of course be done by any desired algorithms. An example and discussion of the general behavior without bunch-by-bunch feedback is given at the end of this report.

  15. Beam Tomography in Longitudinal Phase Space

    NASA Astrophysics Data System (ADS)

    Mane, V.; Wei, J.; Peggs, S.

    1997-05-01

    Longitudinal particle motion in circular accelerators is typically monitored by one dimensional (1-D) profiles. Adiabatic particle motion in 2-D phase space can be reconstructed with tomographic techniques, using 1-D profiles. In this paper, we discuss a filtered backprojection algorithm, with a high pass ramp or Hann filter, for phase space reconstruction. The algorithm uses several projections of the beam at equally spaced angles over half a synchrotron period. A computer program RADON has been developed to process digitized mountain range data and do the phase space reconstruction for the AGS, and later for Relativistic Heavy Ion Collider (RHIC). Analysis has been performed to determine the sensitivity to machine parameters and data acquisition errors. During the Sextant test of RHIC in early 1997, this program has been successfully employed to reconstruct the motion of Au^77+ beam in the AGS.

  16. Random-effects models for longitudinal data

    SciTech Connect

    Laird, N.M.; Ware, J.H.

    1982-12-01

    Models for the analysis of longitudinal data must recognize the relationship between serial observations on the same unit. Multivariate models with general covariance structure are often difficult to apply to highly unbalanced data, whereas two-stage random-effects models can be used easily. In two-stage models, the probability distributions for the response vectors of different individuals belong to a single family, but some random-effects parameters vary across individuals, with a distribution specified at the second stage. A general family of models is discussed, which includes both growth models and repeated-measures models as special cases. A unified approach to fitting these models, based on a combination of empirical Bayes and maximum likelihood estimation of model parameters and using the EM algorithm, is discussed. Two examples are taken from a current epidemiological study of the health effects of air pollution.

  17. Van Kampen modes for bunch longitudinal motion

    SciTech Connect

    Burov, A.; /Fermilab

    2010-09-01

    Conditions for existence, uniqueness and stability of bunch steady states are considered. For the existence uniqueness problem, simple algebraic equations are derived, showing the result both for the action and Hamiltonian domain distributions. For the stability problem, van Kampen theory is used. Emerging of discrete van Kampen modes show either loss of Landau damping, or instability. This method can be applied for an arbitrary impedance, RF shape and beam distribution function Available areas on intensity-emittance plane are shown for resistive wall wake and single harmonic, bunch shortening and bunch lengthening RF configurations. Language of van Kampen modes is a powerful tool for studying beam stability. Its unique efficiency reveals itself in those complicated cases, when the dielectric function cannot be obtained, as it is for the longitudinal bunch motion. Emergence of a discrete mode means either loss of Landau damping or instability. By definition, the discrete modes lie outside the continuous incoherent spectrum, but they still may stay within the bucket. In the last case, the discrete mode would disappear after a tiny portion of resonant particles would be added. However, if the discrete mode lie outside the bucket, the Landau damping cannot be restored by tiny perturbation of the particle distribution; LLD is called radical in that case. For a given bunch emittance and RF voltage, the intensity is limited either by reduction of the bucket acceptance or by (radical) LLD. In this paper, results are presented for longitudinal bunch stability in weak head-tail approximation and resistive wall impedance; three RF configurations are studied: single harmonic, bunch shortening and bunch lengthening. It is shown that every RF configuration may be preferable, depending on the bunch emittance and intensity.

  18. Longitudinal gradients along a reservoir cascade

    USGS Publications Warehouse

    Miranda, L.E.; Habrat, M.D.; Miyazono, S.

    2008-01-01

    Reservoirs have traditionally been regarded as spatially independent entities rather than as longitudinal segments of a river system that are connected upstream and downstream to the river and other reservoirs. This view has frustrated advancement in reservoir science by impeding adequate organization of available information and by hindering interchanges with allied disciplines that often consider impounded rivers at the basin scale. We analyzed reservoir morphology, water quality, and fish assemblage data collected in 24 reservoirs of the Tennessee River; we wanted to describe longitudinal changes occurring at the scale of the entire reservoir series (i.e., cascade) and to test the hypothesis that fish communities and environmental factors display predictable gradients like those recognized for unimpounded rivers. We used a data set collected over a 7-year period; over 3 million fish representing 94 species were included in the data set. Characteristics such as reservoir mean depth, relative size of the limnetic zone, water retention time, oxygen stratification, thermal stratification, substrate size, and water level fluctuations increased in upstream reservoirs. Conversely, reservoir area, extent of riverine and littoral zones, access to floodplains and associated wetlands, habitat diversity, and nutrient and sediment inputs increased in downstream reservoirs. Upstream reservoirs included few, largely lacustrine, ubiquitous fish taxa that were characteristic of the lentic upper reaches of the basin. Fish species richness increased in a downstream direction from 12 to 67 species/ reservoir as riverine species became more common. Considering impoundments at a basin scale by viewing them as sections in a river or links in a chain may generate insight that is not always available when the impoundments are viewed as isolated entities. Basin-scale variables are rarely controllable but constrain the expression of processes at smaller scales and can facilitate the

  19. Prospective, longitudinal assessment of developmental neurotoxicity.

    PubMed Central

    Jacobson, J L; Jacobson, S W

    1996-01-01

    Methodological issues in the design of prospective, longitudinal studies of developmental neurotoxicity in humans are reviewed. A comprehensive assessment of potential confounding influences is important in these studies because inadequate assessment of confounders can threaten the validity of causal inferences drawn from the data. Potential confounders typically include demographic background variables, alcohol and smoking during pregnancy, the quality of parental stimulation, the child's age at test, and the examiner. Exposure to other substances is assessed where significant exposure is expected in the target population. In most studies, control variables even weakly related to outcome are included in all multivariate statistical analyses, and a toxic effect is inferred only if the effect of exposure is significant after controlling for the potential confounders. Once a neurotoxic effect has been identified, suspected mediating variables may be added to the analysis to examine underlying processes or mechanisms through which the exposure may impact on developmental outcome. Individual differences in vulnerability may be examined in terms of either an additive compensatory model or a synergistic "risk and resilience" approach. Failure to detect real effects (Type II error) is of particular concern in these studies because public policy considerations make it likely that negative findings will be interpreted to mean that the exposure is safe. Important sources of Type II error include inadequate representation of highly exposed individuals, overcontrol for confounders, and inappropriate correction for multiple comparisons. Given the high cost and complexity of prospective, longitudinal investigations, cross-sectional pilot studies focusing on highly exposed individuals can be valuable for the initial identification of salient domains of impairment. PMID:9182034

  20. Psychosocial adjustment to ALS: a longitudinal study

    PubMed Central

    Matuz, Tamara; Birbaumer, Niels; Hautzinger, Martin; Kübler, Andrea

    2015-01-01

    For the current study the Lazarian stress-coping theory and the appendant model of psychosocial adjustment to chronic illness and disabilities (Pakenham, 1999) has shaped the foundation for identifying determinants of adjustment to ALS. We aimed to investigate the evolution of psychosocial adjustment to ALS and to determine its long-term predictors. A longitudinal study design with four measurement time points was therefore, used to assess patients' quality of life, depression, and stress-coping model related aspects, such as illness characteristics, social support, cognitive appraisals, and coping strategies during a period of 2 years. Regression analyses revealed that 55% of the variance of severity of depressive symptoms and 47% of the variance in quality of life at T2 was accounted for by all the T1 predictor variables taken together. On the level of individual contributions, protective buffering, and appraisal of own coping potential accounted for a significant percentage in the variance in severity of depressive symptoms, whereas problem management coping strategies explained variance in quality of life scores. Illness characteristics at T2 did not explain any variance of both adjustment outcomes. Overall, the pattern of the longitudinal results indicated stable depressive symptoms and quality of life indices reflecting a successful adjustment to the disease across four measurement time points during a period of about two years. Empirical evidence is provided for the predictive value of social support, cognitive appraisals, and coping strategies, but not illness parameters such as severity and duration for adaptation to ALS. The current study contributes to a better conceptualization of adjustment, allowing us to provide evidence-based support beyond medical and physical intervention for people with ALS. PMID:26441696

  1. Longitudinal Research with Sexual Assault Survivors: A Methodological Review

    ERIC Educational Resources Information Center

    Campbell, Rebecca; Sprague, Heather Brown; Cottrill, Sara; Sullivan, Cris M.

    2011-01-01

    Longitudinal research designs are relatively rare in the academic literature on rape and sexual assault despite their tremendous methodological rigor and scientific utility. In the interest of promoting wider use of such methods, we conducted a methodological review of projects that have used prospective longitudinal designs to study the…

  2. Objectives, Design, and History of the National Longitudinal Study.

    ERIC Educational Resources Information Center

    Davis, J. A.; Collins, Elmer

    The National Longitudinal Study of the High School Class of 1972 (NLS) is a federally supported longitudinal study of a national sample of some 23,000 young people first surveyed as high school seniors in the spring of 1972. The historical precedents of such a study include the work of Friend and Haggert in a Boston settlement house, Louis…

  3. Longitudinal and transverse mode evolution in free electron laser

    SciTech Connect

    Dattoli, G.; Giannessi, L.; Georgii, R.

    1995-12-31

    We use the method of Padg approximants and Fourier transform techniques to treat analytically the problem of transverse and longitudinal mode evolution in FELs. We obtain simple relations providing a transparent understanding of the dynamic of pulse propagation effects and of transverse mode guiding. We discuss the interplay with inhomogeneous broadening effects and derive gain formulae including longitudinal and transverse mode couplings.

  4. Beyond Terman: Contemporary Longitudinal Studies of Giftedness and Talent.

    ERIC Educational Resources Information Center

    Subotnik, Rena F., Ed.; Arnold, Karen D., Ed.

    This volume presents 16 papers describing recent longitudinal studies of giftedness. Papers have the following titles and authors: (1) "Longitudinal Study of Giftedness and Talent" (Rena F. Subotnik and Karen D. Arnold); (2) "The Illinois Valedictorian Project: Early Adult Careers of Academically Talented Male High School Students" (Karen D.…

  5. A Longitudinal Investigation of Individual Implementation of Educational Innovations.

    ERIC Educational Resources Information Center

    Hall, Gene E.

    Implementation is a key factor in shaping school policies. The Procedures for Adopting Educational Innovations Project conducted longitudinal studies of innovation implementation based on the Concerns-Based Adoption Model (CBAM). A key dimension of CBAM, Levels of Use of the Innovation (LoU), was assessed in three longitudinal studies over a…

  6. A Longitudinal Study of Adolescent Adjustment Following Family Transitions

    ERIC Educational Resources Information Center

    Ruschena, Eda; Prior, Margot; Sanson, Ann; Smart, Diana

    2005-01-01

    Background: This study examined the impact of family transitions, that is, parental separation, divorce, remarriage and death, upon the lives of Australian children and adolescents in a longitudinal study of temperament and development. Methods: Using longitudinal and concurrent questionnaire data, outcomes for young people experiencing…

  7. Longitudinal Predictors of Very Early Chinese Literacy Acquisition

    ERIC Educational Resources Information Center

    Tong, Xiuli; McBride-Chang, Catherine; Wong, Anita M.-Y.; Shu, Hua; Reitsma, Pieter; Rispens, Judith

    2011-01-01

    This 2-year longitudinal study examined both concurrent and longitudinal relations of a variety of reading-related cognitive tasks and Chinese word reading and word dictation among 187 Hong Kong Chinese kindergarteners aged 4-6. Homophone awareness, visual skills and syllable awareness were all uniquely associated with Chinese word reading across…

  8. Longitudinal Outcomes for Mathematics Achievement for Students with Learning Disabilities

    ERIC Educational Resources Information Center

    Judge, Sharon; Watson, Silvana M. R.

    2011-01-01

    Using longitudinal data from the first 6 waves of the Early Childhood Longitudinal Study-Kindergarten Cohort (ECLS-K), the authors examined mathematics achievement and growth trajectories by learning disability (LD) subgroups. The 2-level (time-student) growth curve model showed that lower levels of mathematics achievement were already evident at…

  9. Learning from Longitudinal Research in Criminology and the Health Sciences

    ERIC Educational Resources Information Center

    Vanderstaay, Steven L.

    2006-01-01

    This article reviews longitudinal research within criminology and the health sciences on the relationship between reading and criminal, delinquent, or antisocial behavior. Longitudinal research in criminology, medicine, and psychology examines the role of reading within a broad set of interactive processes, connecting literacy to public health via…

  10. 14 CFR 25.173 - Static longitudinal stability.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Static longitudinal stability. 25.173... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Stability § 25.173 Static longitudinal stability. Under the conditions specified in § 25.175, the characteristics of the elevator...

  11. 14 CFR 25.173 - Static longitudinal stability.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Static longitudinal stability. 25.173... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Stability § 25.173 Static longitudinal stability. Under the conditions specified in § 25.175, the characteristics of the elevator...

  12. 14 CFR 23.173 - Static longitudinal stability.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Static longitudinal stability. 23.173 Section 23.173 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... Stability § 23.173 Static longitudinal stability. Under the conditions specified in § 23.175 and with...

  13. 46 CFR 172.095 - Intact longitudinal stability.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 7 2014-10-01 2014-10-01 false Intact longitudinal stability. 172.095 Section 172.095 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SUBDIVISION AND STABILITY SPECIAL RULES... Under Subchapter O of This Chapter § 172.095 Intact longitudinal stability. Each tank barge must...

  14. 46 CFR 172.095 - Intact longitudinal stability.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Intact longitudinal stability. 172.095 Section 172.095 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SUBDIVISION AND STABILITY SPECIAL RULES... Under Subchapter O of This Chapter § 172.095 Intact longitudinal stability. Each tank barge must...

  15. 14 CFR 23.173 - Static longitudinal stability.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Static longitudinal stability. 23.173 Section 23.173 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... Stability § 23.173 Static longitudinal stability. Under the conditions specified in § 23.175 and with...

  16. 14 CFR 25.173 - Static longitudinal stability.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Static longitudinal stability. 25.173... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Stability § 25.173 Static longitudinal stability. Under the conditions specified in § 25.175, the characteristics of the elevator...

  17. 14 CFR 23.173 - Static longitudinal stability.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Static longitudinal stability. 23.173 Section 23.173 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... Stability § 23.173 Static longitudinal stability. Under the conditions specified in § 23.175 and with...

  18. 46 CFR 172.095 - Intact longitudinal stability.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Intact longitudinal stability. 172.095 Section 172.095 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SUBDIVISION AND STABILITY SPECIAL RULES... Under Subchapter O of This Chapter § 172.095 Intact longitudinal stability. Each tank barge must...

  19. 46 CFR 172.095 - Intact longitudinal stability.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 7 2012-10-01 2012-10-01 false Intact longitudinal stability. 172.095 Section 172.095 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SUBDIVISION AND STABILITY SPECIAL RULES... Under Subchapter O of This Chapter § 172.095 Intact longitudinal stability. Each tank barge must...

  20. 14 CFR 23.173 - Static longitudinal stability.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Static longitudinal stability. 23.173 Section 23.173 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... Stability § 23.173 Static longitudinal stability. Under the conditions specified in § 23.175 and with...

  1. Mt. Druitt Longitudinal Study: Second Major Report, 1983.

    ERIC Educational Resources Information Center

    O'Brien, Peter

    Sections of this report introduce many of the activities undertaken in 1982 within the purview of the Mt. Druitt (Australia) longitudinal study. Included are reports of (1) the 1982 math investigation, (2) a longitudinal study of child growth and development and the incidence of physical defects at ages 9 and 10, (3) an investigation of classroom…

  2. A Cautionary Note on Modeling Growth Trends in Longitudinal Data

    ERIC Educational Resources Information Center

    Kuljanin, Goran; Braun, Michael T.; DeShon, Richard P.

    2011-01-01

    Random coefficient and latent growth curve modeling are currently the dominant approaches to the analysis of longitudinal data in psychology. The application of these models to longitudinal data assumes that the data-generating mechanism behind the psychological process under investigation contains only a deterministic trend. However, if a…

  3. Antisocial Behavior and Depressive Symptoms: Longitudinal and Concurrent Relations

    ERIC Educational Resources Information Center

    Vieno, Alessio; Kiesner, Jeff; Pastore, Massimiliano; Santinello, Massimo

    2008-01-01

    The relations between antisocial behavior and depressive symptoms were examined both longitudinally and concurrently in a sample of Italian early-adolescents. Structural equation modelling was applied to 10-month longitudinal data from a sample of 107 youths (54 girls; mean age at baseline = M = 12.5). Early adolescents completed a questionnaire…

  4. Longitudinal Trajectories of Perceived Body Weight: Adolescence to Early Adulthood

    ERIC Educational Resources Information Center

    Seo, Dong-Chul; Li, Kaigang

    2012-01-01

    Objective: To examine longitudinal trajectories of perceived weight from adolescence to early adulthood by gender. Methods: We analyzed 9 waves (1997-2005) of data from the National Longitudinal Survey of Youth (N = 8302) using Mplus. Results: Perceived overweight increased over time among girls and did not level off until 23 years of age. Blacks…

  5. 14 CFR 25.231 - Longitudinal stability and control.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Longitudinal stability and control. 25.231 Section 25.231 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... Characteristics § 25.231 Longitudinal stability and control. (a) Landplanes may have no uncontrollable tendency...

  6. 14 CFR 23.173 - Static longitudinal stability.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Static longitudinal stability. 23.173 Section 23.173 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... Stability § 23.173 Static longitudinal stability. Under the conditions specified in § 23.175 and with...

  7. 14 CFR 25.173 - Static longitudinal stability.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Static longitudinal stability. 25.173 Section 25.173 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... longitudinal stability. Under the conditions specified in § 25.175, the characteristics of the elevator...

  8. 14 CFR 23.231 - Longitudinal stability and control.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Longitudinal stability and control. 23.231 Section 23.231 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... and Water Handling Characteristics § 23.231 Longitudinal stability and control. (a) A landplane...

  9. Longitudinal and transverse coupling in infrared gold nanoantenna arrays: long range versus short range interaction regimes.

    PubMed

    Weber, Daniel; Albella, Pablo; Alonso-González, Pablo; Neubrech, Frank; Gui, Han; Nagao, Tadaaki; Hillenbrand, Rainer; Aizpurua, Javier; Pucci, Annemarie

    2011-08-01

    Interaction between micrometer-long nanoantennas within an array considerably modifies the plasmonic resonant behaviour; for fundamental resonances in the infrared already at micrometer distances. In order to get systematic knowledge on the relationship between infrared plasmonic resonances and separation distances dx and dy in longitudinal and transverse direction, respectively, we experimentally studied the optical extinction spectra for rectangularly ordered lithographic gold nanorod arrays on silicon wafers. For small dy, strong broadening of resonances and strongly decreased values of far-field extinction are detected which come along with a decreased near-field intensity, as indicated by near-field amplitude maps of the interacting nanoantennas. In contrast, near-field interaction over small dx does only marginally broaden the resonance. Our findings set a path for optimum design of rectangular nanorod lattices for surface enhanced infrared spectroscopy. PMID:21934866

  10. Stimulated emission from a relativistic electron beam in a variable-parameter longitudinal magnetic wiggler

    NASA Astrophysics Data System (ADS)

    McMullin, W. A.; Davidson, R. C.; Johnston, G. L.

    1983-08-01

    The single-particle equations of motion are used to study the stimulated emission from a tenuous relativistic electron beam propagating in the combined solenoidal and variable-parameter longitudinal wiggler magnetic fields produced near the axis of a multiple-mirror (undulator) field configuration. The specific case of constant field amplitude and variable wiggler periodicity is studied. It is found that the efficiency of radiation generation can be increased by orders of magnitude relative to the case where the wiggler periodicity is constant. This is due to the fact that the phase velocity of the ponderomotive potential in which the electrons are trapped is decreasing, allowing the electrons to exchange energy with the radiation field.

  11. Large-Amplitude Longitudinal Oscillations in a Solar Filament

    NASA Technical Reports Server (NTRS)

    Luna, M.; Karpen, J.

    2012-01-01

    We have developed the first self-consistent model for the observed large-amplitude oscillations along filament axes that explains the restoring force and damping mechanism. We have investigated the oscillations of multiple threads formed in long, dipped flux tubes through the thermal nonequilibrium process, and found that the oscillation properties predicted by our simulations agree with the observed behavior. We then constructed a model for the large-amplitude longitudinal oscillations that demonstrates that the restoring force is the projected gravity in the tube where the threads oscillate. Although the period is independent of the tube length and the constantly growing mass, the motions are strongly damped by the steady accretion of mass onto the threads by thermal nonequilibrium. The observations and our model suggest that a nearby impulsive event drives the existing prominence threads along their supporting tubes, away from the heating deposition site, without destroying them. The subsequent oscillations occur because the displaced threads reside in magnetic concavities with large radii of curvature. Our model yields a powerful seismological method for constraining the coronal magnetic field and radius of curvature of dips. Furthermore, these results indicate that the magnetic structure is most consistent with the sheared-arcade model for filament channels.

  12. Elastic energy loss and longitudinal straggling of a hard jet

    SciTech Connect

    Majumder, A.

    2009-09-15

    The elastic energy loss encountered by jets produced in deep-inelastic scattering (DIS) off a large nucleus is studied in the collinear limit. In close analogy to the case of (nonradiative) transverse momentum broadening, which is dependent on the medium transport coefficient q, a class of medium enhanced higher twist operators which contribute to the nonradiative loss of the forward light-cone momentum of the jet (q{sup -}) are identified and the leading correction in the limit of asymptotically high q{sup -} is isolated. Based on these operator products, a new transport coefficient e is motivated which quantifies the energy loss per unit length encountered by the hard jet. These operator products are then computed, explicitly, in the case of a similar hard jet traversing a deconfined quark-gluon plasma (QGP) in the hard-thermal-loop (HTL) approximation. This is followed by an evaluation of subleading contributions which are suppressed by the inverse light-cone momentum q{sup -}, which yields the longitudinal 'straggling', i.e., a slight change in light cone momentum due to the Brownian propagation through a medium with a fluctuating color field.

  13. LARGE-AMPLITUDE LONGITUDINAL OSCILLATIONS IN A SOLAR FILAMENT

    SciTech Connect

    Luna, M.

    2012-05-01

    We have developed the first self-consistent model for the observed large-amplitude oscillations along filament axes that explains the restoring force and damping mechanism. We have investigated the oscillations of multiple threads formed in long, dipped flux tubes through the thermal nonequilibrium process, and found that the oscillation properties predicted by our simulations agree with the observed behavior. We then constructed a model for the large-amplitude longitudinal oscillations that demonstrates that the restoring force is the projected gravity in the tube where the threads oscillate. Although the period is independent of the tube length and the constantly growing mass, the motions are strongly damped by the steady accretion of mass onto the threads by thermal nonequilibrium. The observations and our model suggest that a nearby impulsive event drives the existing prominence threads along their supporting tubes, away from the heating deposition site, without destroying them. The subsequent oscillations occur because the displaced threads reside in magnetic concavities with large radii of curvature. Our model yields a powerful seismological method for constraining the coronal magnetic field and radius of curvature of dips. Furthermore, these results indicate that the magnetic structure is most consistent with the sheared-arcade model for filament channels.

  14. 77 FR 2349 - Proposed Information Collection (Vocational Rehabilitation and Employment Longitudinal Study...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-17

    ... AFFAIRS Proposed Information Collection (Vocational Rehabilitation and Employment Longitudinal Study... . Please refer to ``OMB Control No. 2900--New (VR&E Longitudinal Study Survey)'' in any correspondence...: Vocational Rehabilitation and Employment Longitudinal Study Survey. OMB Control Number: 2900--New...

  15. On the search for the chiral anomaly in Weyl semimetals: the negative longitudinal magnetoresistance

    NASA Astrophysics Data System (ADS)

    dos Reis, R. D.; Ajeesh, M. O.; Kumar, N.; Arnold, F.; Shekhar, C.; Naumann, M.; Schmidt, M.; Nicklas, M.; Hassinger, E.

    2016-08-01

    Recently, the existence of massless chiral (Weyl) fermions has been postulated in a class of semi-metals with a non-trivial energy dispersion. These materials are now commonly dubbed Weyl semi-metals (WSM). One predicted property of Weyl fermions is the chiral or Adler-Bell-Jackiw anomaly, a chirality imbalance in the presence of parallel magnetic and electric fields. In WSM, it is expected to induce a negative longitudinal magnetoresistance (MR). Here, we present experimental evidence that the observation of the chiral anomaly can be hindered by an effect called ‘current jetting’. This effect also leads to a strong apparent negative longitudinal MR, but it is characterized by a highly non-uniform current distribution inside the sample. It appears in materials possessing a large field-induced anisotropy of the resistivity tensor, such as almost compensated high-mobility semimetals due to the orbital effect. In case of a non-homogeneous current injection, the potential distribution is strongly distorted in the sample. As a consequence, an experimentally measured potential difference is not proportional to the intrinsic resistance. Our results on the MR of the Weyl semimetal candidate materials NbP, NbAs, TaAs, and TaP exhibit distinct signatures of an inhomogeneous current distribution, such as a field-induced ‘zero resistance’ and a strong dependence of the ‘measured resistance’ on the position, shape, and type of the voltage and current contacts on the sample. A misalignment between the current and the magnetic-field directions can even induce a ‘negative resistance’. Finite-element simulations of the potential distribution inside the sample, using typical resistance anisotropies, are in good agreement with the experimental findings. Our study demonstrates that great care must be taken before interpreting measurements of a negative longitudinal MR as evidence for the chiral anomaly in putative Weyl semimetals.

  16. On the search for the chiral anomaly in Weyl semimetals: the negative longitudinal magnetoresistance

    NASA Astrophysics Data System (ADS)

    dos Reis, R. D.; Ajeesh, M. O.; Kumar, N.; Arnold, F.; Shekhar, C.; Naumann, M.; Schmidt, M.; Nicklas, M.; Hassinger, E.

    2016-08-01

    Recently, the existence of massless chiral (Weyl) fermions has been postulated in a class of semi-metals with a non-trivial energy dispersion. These materials are now commonly dubbed Weyl semi-metals (WSM). One predicted property of Weyl fermions is the chiral or Adler–Bell–Jackiw anomaly, a chirality imbalance in the presence of parallel magnetic and electric fields. In WSM, it is expected to induce a negative longitudinal magnetoresistance (MR). Here, we present experimental evidence that the observation of the chiral anomaly can be hindered by an effect called ‘current jetting’. This effect also leads to a strong apparent negative longitudinal MR, but it is characterized by a highly non-uniform current distribution inside the sample. It appears in materials possessing a large field-induced anisotropy of the resistivity tensor, such as almost compensated high-mobility semimetals due to the orbital effect. In case of a non-homogeneous current injection, the potential distribution is strongly distorted in the sample. As a consequence, an experimentally measured potential difference is not proportional to the intrinsic resistance. Our results on the MR of the Weyl semimetal candidate materials NbP, NbAs, TaAs, and TaP exhibit distinct signatures of an inhomogeneous current distribution, such as a field-induced ‘zero resistance’ and a strong dependence of the ‘measured resistance’ on the position, shape, and type of the voltage and current contacts on the sample. A misalignment between the current and the magnetic-field directions can even induce a ‘negative resistance’. Finite-element simulations of the potential distribution inside the sample, using typical resistance anisotropies, are in good agreement with the experimental findings. Our study demonstrates that great care must be taken before interpreting measurements of a negative longitudinal MR as evidence for the chiral anomaly in putative Weyl semimetals.

  17. Data-driven regions of interest for longitudinal change in frontotemporal lobar degeneration.

    PubMed

    Pankov, Aleksandr; Binney, Richard J; Staffaroni, Adam M; Kornak, John; Attygalle, Suneth; Schuff, Norbert; Weiner, Michael W; Kramer, Joel H; Dickerson, Bradford C; Miller, Bruce L; Rosen, Howard J

    2016-01-01

    Current research is investigating the potential utility of longitudinal measurement of brain structure as a marker of drug effect in clinical trials for neurodegenerative disease. Recent studies in Alzheimer's disease (AD) have shown that measurement of change in empirically derived regions of interest (ROIs) allows more reliable measurement of change over time compared with regions chosen a-priori based on known effects of AD on brain anatomy. Frontotemporal lobar degeneration (FTLD) is a devastating neurodegenerative disorder for which there are no approved treatments. The goal of this study was to identify an empirical ROI that maximizes the effect size for the annual rate of brain atrophy in FTLD compared with healthy age matched controls, and to estimate the effect size and associated power estimates for a theoretical study that would use change within this ROI as an outcome measure. Eighty six patients with FTLD were studied, including 43 who were imaged twice at 1.5 T and 43 at 3 T, along with 105 controls (37 imaged at 1.5 T and 67 at 3 T). Empirically-derived maps of change were generated separately for each field strength and included the bilateral insula, dorsolateral, medial and orbital frontal, basal ganglia and lateral and inferior temporal regions. The extent of regions included in the 3 T map was larger than that in the 1.5 T map. At both field strengths, the effect sizes for imaging were larger than for any clinical measures. At 3 T, the effect size for longitudinal change measured within the empirically derived ROI was larger than the effect sizes derived from frontal lobe, temporal lobe or whole brain ROIs. The effect size derived from the data-driven 1.5 T map was smaller than at 3 T, and was not larger than the effect size derived from a-priori ROIs. It was estimated that measurement of longitudinal change using 1.5 T MR systems requires approximately a 3-fold increase in sample size to obtain effect sizes equivalent to those seen at

  18. Second-harmonic generation from the longitudinal component of vectorial laser beams: a theoretical framework

    NASA Astrophysics Data System (ADS)

    Fortin, Pierre-Yves

    2008-06-01

    Vectorial laser beams propagating beyond the paraxial limit exhibit an intensity profile at focus that depends upon their field structure and the width of their plane wave spectrum. Under tight focussing conditions, the longitudinal component of the lowest order transverse magnetic laser beam has a field amplitude that becomes comparable to that of the transverse components of the beam; the global intensity profile is then narrower than that produced by a Gaussian beam, thus enabling hyperresolution. With a general polarization eigenmode approach for all propagating directions in anisotropic media, we can show that privileged propagating directions exist, allowing preservation of the transverse magnetic polarization state despite birefringence. Using wave functions satisfying the non-paraxial wave equation, we can also find exact expressions for the field components. During propagation of tightly focussed beams along those privileged directions inside an appropriate anisotropic nonlinear crystal, the longitudinal electric field component may then be used to take advantage of nonlinear tensor terms otherwise ineffective with a paraxial beam. In this work, spectral conversion rate and power conversion efficiency of second-harmonic generation are characterized as a function of effective and undepleted nonlinear pumping in the case of propagation along the anisotropic axis of an uniaxial nonlinear crystal. Even if the phase matching condition is not fully satisfied for propagation along this privileged direction, we show to which extent the nonlinear properties are preserved for a restricted interaction volume.

  19. High field - low energy muon ionization cooling channel

    NASA Astrophysics Data System (ADS)

    Kamal Sayed, Hisham; Palmer, Robert B.; Neuffer, David

    2015-09-01

    Muon beams are generated with large transverse and longitudinal emittances. In order to achieve the low emittances required by a muon collider, within the short lifetime of the muons, ionization cooling is required. Cooling schemes have been developed to reduce the muon beam 6D emittances to ≈300 μ m -rad in transverse and ≈1 - 1.5 mm in longitudinal dimensions. The transverse emittance has to be further reduced to ≈50 - 25 μ m -rad with an upper limit on the longitudinal emittance of ≈76 mm in order to meet the high-energy muon collider luminosity requirements. Earlier studies of the transverse cooling of low energy muon beams in high field magnets showed a promising performance, but did not include transverse or longitudinal matching between the stages. In this study we present the first complete design of the high field-low energy ionization cooling channel with transverse and longitudinal matching. The channel design was based on strong focusing solenoids with fields of 25-30 T and low momentum muon beam starting at 135 MeV /c and gradually decreasing. The cooling channel design presented here is the first to reach ≈50 micron scale emittance beam. We present the channel's optimized design parameters including the focusing solenoid fields, absorber parameters and the transverse and longitudinal matching.

  20. Longitudinal phase space tomography with space charge

    NASA Astrophysics Data System (ADS)

    Hancock, S.; Lindroos, M.; Koscielniak, S.

    2000-12-01

    Tomography is now a very broad topic with a wealth of algorithms for the reconstruction of both qualitative and quantitative images. In an extension in the domain of particle accelerators, one of the simplest algorithms has been modified to take into account the nonlinearity of large-amplitude synchrotron motion. This permits the accurate reconstruction of longitudinal phase space density from one-dimensional bunch profile data. The method is a hybrid one which incorporates particle tracking. Hitherto, a very simple tracking algorithm has been employed because only a brief span of measured profile data is required to build a snapshot of phase space. This is one of the strengths of the method, as tracking for relatively few turns relaxes the precision to which input machine parameters need to be known. The recent addition of longitudinal space charge considerations as an optional refinement of the code is described. Simplicity suggested an approach based on the derivative of bunch shape with the properties of the vacuum chamber parametrized by a single value of distributed reactive impedance and by a geometrical coupling coefficient. This is sufficient to model the dominant collective effects in machines of low to moderate energy. In contrast to simulation codes, binning is not an issue since the profiles to be differentiated are measured ones. The program is written in Fortran 90 with high-performance Fortran extensions for parallel processing. A major effort has been made to identify and remove execution bottlenecks, for example, by reducing floating-point calculations and recoding slow intrinsic functions. A pointerlike mechanism which avoids the problems associated with pointers and parallel processing has been implemented. This is required to handle the large, sparse matrices that the algorithm employs. Results obtained with and without the inclusion of space charge are presented and compared for proton beams in the CERN protron synchrotron booster. Comparisons

  1. Longitudinal static stability requirements for wing in ground effect vehicle

    NASA Astrophysics Data System (ADS)

    Yang, Wei; Yang, Zhigang; Collu, Maurizio

    2015-06-01

    The issue of the longitudinal stability of a WIG vehicle has been a very critical design factor since the first experimental WIG vehicle has been built. A series of studies had been performed and focused on the longitudinal stability analysis. However, most studies focused on the longitudinal stability of WIG vehicle in cruise phase, and less is available on the longitudinal static stability requirement of WIG vehicle when hydrodynamics are considered: WIG vehicle usually take off from water. The present work focuses on stability requirement for longitudinal motion from taking off to landing. The model of dynamics for a WIG vehicle was developed taking into account the aerodynamic, hydrostatic and hydrodynamic forces, and then was analyzed. Following with the longitudinal static stability analysis, effect of hydrofoil was discussed. Locations of CG, aerodynamic center in pitch, aerodynamic center in height and hydrodynamic center in heave were illustrated for a stabilized WIG vehicle. The present work will further improve the longitudinal static stability theory for WIG vehicle.

  2. Longitudinal variability of black carbon vertical profiles

    NASA Astrophysics Data System (ADS)

    Schwarz, J. P.; Weinzierl, B.; Samset, B. H.; Perring, A. E.; Dollner, M.; Heimerl, K.; Markovic, M. Z.; Ziemba, L. D.

    2015-12-01

    Black carbon (BC) aerosol contributes substantially to both climate forcing and climate forcing uncertainty. An important source of this uncertainty derives from the difficulty in predicting BC's global abundance and vertical distribution. Here we present a multi-year record of black carbon (BC) vertical concentration profiles from both sides of the Atlantic, obtained from airborne Single Particle Soot Photometers (SP2s) flown on the NASA DC-8, and the DLR Falcon research aircraft from the CONCERT, ACCESS, DC3, SEAC4RS, and SALTRACE campaigns. The measurements constrain the relative rates of BC transport/removal from, and zonal mixing in, the upper troposphere, as well as the range of BC loadings in these regions. They also constrain the time-rates of change of BC loads in altitudes at which it is a highly efficient (although sparse) climate forcer, and a relatively long-lived aerosol tracer. We find that concentration of BC in the upper troposphere can vary by a factor 10. Over the Northern mid-latitudes concentrations are however consistent to a fraction of this range over wide longitudinal ranges, over month-long timescales. The data show that BC becomes zonally mixed here starting at 500 hPa and extending to near the tropopause. These results imply broader value than previously associated with measured vertical profiles in constraining global scale BC loadings aloft.

  3. Semiparametric Bayesian classification with longitudinal markers

    PubMed Central

    De la Cruz-Mesía, Rolando; Quintana, Fernando A.; Müller, Peter

    2013-01-01

    Summary We analyse data from a study involving 173 pregnant women. The data are observed values of the β human chorionic gonadotropin hormone measured during the first 80 days of gestational age, including from one up to six longitudinal responses for each woman. The main objective in this study is to predict normal versus abnormal pregnancy outcomes from data that are available at the early stages of pregnancy. We achieve the desired classification with a semiparametric hierarchical model. Specifically, we consider a Dirichlet process mixture prior for the distribution of the random effects in each group. The unknown random-effects distributions are allowed to vary across groups but are made dependent by using a design vector to select different features of a single underlying random probability measure. The resulting model is an extension of the dependent Dirichlet process model, with an additional probability model for group classification. The model is shown to perform better than an alternative model which is based on independent Dirichlet processes for the groups. Relevant posterior distributions are summarized by using Markov chain Monte Carlo methods. PMID:24368871

  4. Longitudinal performance of an implantable vestibular prosthesis

    PubMed Central

    Phillips, Christopher; Ling, Leo; Oxford, Trey; Nowack, Amy; Nie, Kaibao; Rubinstein, Jay T.; Phillips, James O.

    2014-01-01

    Loss of vestibular function may be treatable with an implantable vestibular prosthesis that stimulates semicircular canal afferents with biphasic pulse trains. Several studies have demonstrated short-term activation of the vestibulo-ocular reflex (VOR) with electrical stimulation. Fewer long-term studies have been restricted to small numbers of animals and stimulation designed to produce adaptive changes in the electrically elicited response. This study is the first large consecutive series of implanted rhesus macaque to be studied longitudinally using brief stimuli designed to limit adaptive changes in response, so that the efficacy of electrical activation can be studied over time, across surgeries, canals and animals. The implantation of a vestibular prosthesis in animals with intact vestibular end organs produces variable responses to electrical stimulation across canals and animals, which change in threshold for electrical activation of eye movements and in elicited slow phase velocities over time. These thresholds are consistently lower, and the slow phase velocities higher, than those obtained in human subjects. The changes do not appear to be correlated with changes in electrode impedance. The variability in response suggests that empirically derived transfer functions may be required to optimize the response of individual canals to a vestibular prosthesis, and that this function may need to be remapped over time. PMID:25245586

  5. Automatic parcellation of longitudinal cortical surfaces

    NASA Astrophysics Data System (ADS)

    Alassaf, Manal H.; Hahn, James K.

    2015-03-01

    We present a novel automatic method to parcellate the cortical surfaces of the neonatal brain longitudinal atlas at different stages of development. A labeled brain atlas of newborn at 41 weeks gestational age (GA) is used to propagate labels of anatomical regions of interest to an unlabeled spatio-temporal atlas, which provides a dynamic model of brain development at each week between 28-44 GA weeks. First, labels from the cortical volume of the labeled newborn brain are propagated to an age-matched cortical surface from the spatio-temporal atlas. Then, labels are propagated across the cortical surfaces of each week of the spatio-temporal atlas by registering successive cortical surfaces using a novel approach and an energy optimization function. This procedure incorporates local and global, spatial and temporal information when assigning the labels to each surface. The result is a complete parcellation of 17 neonatal brain surfaces of the spatio-temporal atlas with similar points per labels distributions across weeks.

  6. Endocrine regulation of longitudinal bone growth.

    PubMed

    Wit, Jan M; Camacho-Hübner, Cecilia

    2011-01-01

    Longitudinal growth is primarily influenced by the GH-IGF-I axis, which is a mixed endocrine-paracrine-autocrine system. Further, classical hormones such as thyroxine, glucocorticosteroids and sex steroids play a role, as well as primarily paracrine systems. In the GH-IGF-I axis, seven disorders can be differentiated: (1) GH deficiency; (2) GHR defects; (3) defects in the GH signal transduction pathway; (4) IGF1 defects; (5) IGFALS defects; (6) IGF1R defects, and (7) IGF2 defects. Children with one of the first 3 disorders have near-normal prenatal growth, while children with defects of IGF1, IGF1R or IGF2 show prenatal as well as postnatal growth retardation. Hypothyroidism or a thyroid hormone resistance cause growth failure, but the effect of hyperthyroidism on growth is modest. Hypercortisolism causes poor growth, while FGD caused by ACTH insensitivity is associated with tall stature. Increased sex steroids in childhood cause advanced growth but even more skeletal maturation, so that adult height is decreased. Finally, the paracrine-autocrine SHOX-BNP pathway and the related CNP-NPR2 pathway are also involved in growth, as very many other growth factors and their receptors and mediators. PMID:21865752

  7. Analyzing River Longitudinal Profiles Around the World

    NASA Astrophysics Data System (ADS)

    Hannon, M. T.; Syvitski, J. P.; Kettner, A. J.

    2009-12-01

    River longitudinal profiles can reveal areas of bedload erosion and deposition. Zones of erosion and deposition, and knowing how to locate them, are of interest to geoscientists, hydrologists, and petrologists. For this study the worldwide SRTM 3 arc-second DEM satellite derived data was analyzed using GIS software to identify general large-scale patterns (slope, slope change, sinuosity) along a river’s course. This analysis uses other data sets to develop an understanding of the external and internal influences that are pressed upon and inherent within the lower 100 meters of the river systems. Changes in the slopes of seven rivers were examined for external controls by overlaying geological data of rock type and fault locations. Faulting occurring in several river systems, such as the Mississippi, Niger, and Magdalena, appears to impact the slope and/or sinuosity of the river. The Magdalena has several regions where a strike-slip fault crosses the river, resulting in increased slopes with the more parallel the encounter. Additionally, stretches of each river were broken into different segment lengths based on meander wavelengths to compare sinuosity with the river’s slope. Preliminary results indicate that sinuosity is influenced by the growth faulting found in the mud dominated systems of the Mississippi and Niger. The resulting sinuosity is greatest in these rivers where the growth faulting is occurring. Contradictory to previous findings, the seven rivers studied here show that slope and sinuosity are not strongly correlated (R^2 of 0.29).

  8. Dual imputation model for incomplete longitudinal data.

    PubMed

    Jolani, Shahab; Frank, Laurence E; van Buuren, Stef

    2014-05-01

    Missing values are a practical issue in the analysis of longitudinal data. Multiple imputation (MI) is a well-known likelihood-based method that has optimal properties in terms of efficiency and consistency if the imputation model is correctly specified. Doubly robust (DR) weighing-based methods protect against misspecification bias if one of the models, but not necessarily both, for the data or the mechanism leading to missing data is correct. We propose a new imputation method that captures the simplicity of MI and protection from the DR method. This method integrates MI and DR to protect against misspecification of the imputation model under a missing at random assumption. Our method avoids analytical complications of missing data particularly in multivariate settings, and is easy to implement in standard statistical packages. Moreover, the proposed method works very well with an intermittent pattern of missingness when other DR methods can not be used. Simulation experiments show that the proposed approach achieves improved performance when one of the models is correct. The method is applied to data from the fireworks disaster study, a randomized clinical trial comparing therapies in disaster-exposed children. We conclude that the new method increases the robustness of imputations. PMID:23909566

  9. Results on longitudinal spin physics at COMPASS

    NASA Astrophysics Data System (ADS)

    Wilfert, Malte

    2016-03-01

    The COMPASS experiment at the CERN SPS has taken data on deep inelastic scattering of polarised muons on a polarised NH3 target in 2007 and 2011 and on a polarised LiD target in 2002-2004 and 2006. The new results on the longitudinal double spin asymmetry A1p and the spin-dependent structure function g1p obtained from the 2011 data set are presented. These results are used in a NLO QCD fit to the world data to obtain the polarised parton distributions. Also an update of the results on the Bjorken sum rule, connecting the integral of the non-singlet spin-dependent structure function with the ratio of the weak coupling constants, will be given. Direct access to the gluon polarisation is possible via the photon gluon fusion process in semi-inclusive deep inelastic scattering. This process is studied using the pT dependence of charged hadron asymmetries. The latest results indicate a positive gluon polarisation in the kinematic region of COMPASS

  10. Longitudinal wheel slip during ABS braking

    NASA Astrophysics Data System (ADS)

    Hartikainen, Lassi; Petry, Frank; Westermann, Stephan

    2015-02-01

    Anti-lock braking system (ABS) braking tests with two subcompact passenger cars were performed on dry and wet asphalt, as well as on snow and ice surfaces. The operating conditions of the tyres in terms of wheel slip were evaluated using histograms of the wheel slip data. The results showed different average slip levels for different road surfaces. It was also found that changes in the tyre tread stiffness affected the slip operating range through a modification of the slip value at which the maximum longitudinal force is achieved. Variation of the tyre footprint length through modifications in the inflation pressure affected the slip operating range as well. Differences in the slip distribution between vehicles with different brake controllers were also observed. The changes in slip operating range in turn modified the relative local sliding speeds between the tyre and the road. The results highlight the importance of the ABS controller's ability to adapt to changing slip-force characteristics of tyres and provide estimates of the magnitude of the effects of different tyre and road operating conditions.

  11. NASA Planetary Science Summer School: Longitudinal Study

    NASA Astrophysics Data System (ADS)

    Giron, Jennie M.; Sohus, A.

    2006-12-01

    NASA’s Planetary Science Summer School is a program designed to prepare the next generation of scientists and engineers to participate in future missions of solar system exploration. The opportunity is advertised to science and engineering post-doctoral and graduate students with a strong interest in careers in planetary exploration. Preference is given to U.S. citizens. The “school” consists of a one-week intensive team exercise learning the process of developing a robotic mission concept into reality through concurrent engineering, working with JPL’s Advanced Project Design Team (Team X). This program benefits the students by providing them with skills, knowledge and the experience of collaborating with a concept mission design. A longitudinal study was conducted to assess the impact of the program on the past participants of the program. Data collected included their current contact information, if they are currently part of the planetary exploration community, if participation in the program contributed to any career choices, if the program benefited their career paths, etc. Approximately 37% of 250 past participants responded to the online survey. Of these, 83% indicated that they are actively involved in planetary exploration or aerospace in general; 78% said they had been able to apply what they learned in the program to their current job or professional career; 100% said they would recommend this program to a colleague.

  12. Endocrine regulation of longitudinal bone growth.

    PubMed

    Wit, Jan M; Camacho-Hübner, Cecilia

    2011-01-01

    Longitudinal growth is primarily influenced by the GH-IGF-I axis, which is a mixed endocrine-paracrine-autocrine system. Further, classical hormones such as thyroxine, glucocorticosteroids and sex steroids play a role, as well as primarily paracrine systems. In the GH-IGF-I axis, seven disorders can be differentiated: (1) GH deficiency; (2) GHR defects; (3) defects in the GH signal transduction pathway; (4) IGF1 defects; (5) IGFALS defects; (6) IGF1R defects, and (7) IGF2 defects. Children with one of the first 3 disorders have near-normal prenatal growth, while children with defects of IGF1, IGF1R or IGF2 show prenatal as well as postnatal growth retardation. Hypothyroidism or a thyroid hormone resistance cause growth failure, but the effect of hyperthyroidism on growth is modest. Hypercortisolism causes poor growth, while FGD caused by ACTH insensitivity is associated with tall stature. Increased sex steroids in childhood cause advanced growth but even more skeletal maturation, so that adult height is decreased. Finally, the paracrine-autocrine SHOX-BNP pathway and the related CNP-NPR2 pathway are also involved in growth, as very many other growth factors and their receptors and mediators.

  13. THz wiggler applied for measurements of electron bunch longitudinal structure in FEL

    NASA Astrophysics Data System (ADS)

    Syresin, E.; Kostromin, S.; Krasilnikov, M.; Makarov, R.; Morozov, N.; Petrov, D.

    2015-01-01

    The infrared undulator manufactured at JINR and installed at FLASH in 2007 is used for longitudinal bunch shape measurements in the range of several tenths of a micrometer. The presented electromagnetic wiggler is intended for generating a narrow-band THz radiation to measure the longitudinal electron bunch structure in FELs with an electron energy of several tens of MeV. This is a planar electromagnetic device with six regular periods, each 30 cm long. The K parameter is varied in the range 0.5-7.12 corresponding to the range B = 0.025-0.356 T of the peak field on the axis. The wiggler is simulated for 19.8 MeV/ c corresponding to the possible FEL option at PITZ. The wavelength range is 126 μm - 5.1 mm for this electron beam momentum. The 3D Opera simulations of the THz wiggler are discussed. A new PITZ photocathode laser system is proposed for the optimized performance of the high-brightness electron beam. The main goal is a production of 3D ellipsoidal electron bunches with homogeneous charge density. The electromagnetic wiggler is supposed to be used for measuring the longitudinal shape of these electron bunches.

  14. A low-cost method to identify tubewells for longitudinal research on arsenic in groundwater.

    PubMed

    Sugimoto, Jonathan D; Ahmad, Salahuddin; Rashid, Mahbubur; Shamim, Abu Ahmed; Labrique, Alain B

    2007-09-01

    Exposure to high concentrations of arsenic in tubewell groundwater from the shallow aquifers of Bangladesh could result in up to 300,000 arsenic-related cancer cases over the next four decades. Understanding the magnitude and temporal dynamics of this exposure, via longitudinal studies, is imperative for planning effective mitigation and management strategies. Appropriate methods are needed to identify tubewells for longitudinal sampling. A plastic band marked with a unique identification number was developed, and various methods for attaching the band to the tubewell were tested, resulting in the choice of a galvanized-iron split-rivet. Two follow-up surveys at two and 14 months post-banding assessed the durability and longevity under field conditions in the JiVitA Project area in rural, northwestern Bangladesh. After two months, approximately 96.0% of the original bands on 1,063 tubewells were functional, although the rivets were partially corroded. After 14 months, approximately 65% of a subsample of the bands were functional. With further improvements to the rivets, these bands offer an inexpensive, durable, enumeration technology for longitudinal studies on groundwater arsenic.

  15. Relation between Longitudinal and Transverse Diffusion Coefficients of Alkali Ions in Noble Gases

    NASA Astrophysics Data System (ADS)

    Hogan, M. J.

    1997-10-01

    The relation between longitudinal and transverse diffusion coefficients of ions drifting in a neutral gas under the influence of an electric field has been investigated for alkali ions in noble gases. The 125 combinations of ions of Li, Na, K, Rb, and Cs in the neutral gases He, Ne, Ar, Kr, and Xe at gas temperatures of 100, 200, 300, 400 and 500 K were included in this study. Plots of the ratio of the longitudinal-to-transverse diffusion coefficients versus E/N exhibited similar variation in the values of the ratios. As the value of E/N increased from zero, the value of the ratio increased rapidly from one for all ion/neutral/temperature combinations. The ratio peaked at values mostly in the range of 1.2 to 2.5 at E/N values in the range of 20 to 120 Td. As E/N increased further, the ratio values decreased, at an ever lower rate, to values ranging from 0.8 to 1.2. These results suggest the existence of a single function relating the longitudinal and transverse diffusion coefficients.

  16. THE LONGITUDINAL TRANSPORT OF ENERGETIC IONS FROM IMPULSIVE SOLAR FLARES IN INTERPLANETARY SPACE

    SciTech Connect

    Giacalone, J.; Jokipii, J. R.

    2012-06-01

    We present a study of the longitudinal spread of energetic charged particles from a localized instantaneous compact source on the Sun. Our study utilizes a diffusive-transport model for the propagation of energetic ions in interplanetary space. We show that even for very small values of the ratio of perpendicular to parallel diffusion coefficients-a few percent-the particles spread significantly in longitude. Spatial diffusion and adiabatic energy loss of ions in the interplanetary plasma cause impulsive particle events at Earth's orbit to last a few days. In this time, the combination of transport both along and across the local Parker-spiral magnetic field and the longitudinal motion of the magnetic lines of forces rooted at the Sun as it rotates leads to substantial longitudinal transport of the particles. We show that spacecraft separated by as much as 180 Degree-Sign or more may observe events associated with compact solar sources, such as those from impulsive solar flares. Our results are qualitatively consistent with recent multi-spacecraft observations.

  17. A Low-cost Method to Identify Tubewells for Longitudinal Research on Arsenic in Groundwater

    PubMed Central

    Sugimoto, Jonathan D.; Ahmad, Salahuddin; Rashid, Mahbubur; Shamim, Abu Ahmed; Labrique, Alain B.

    2007-01-01

    Exposure to high concentrations of arsenic in tubewell groundwater from the shallow aquifers of Bangladesh could result in up to 300,000 arsenic-related cancer cases over the next four decades. Understanding the magnitude and temporal dynamics of this exposure, via longitudinal studies, is imperative for planning effective mitigation and management strategies. Appropriate methods are needed to identify tubewells for longitudinal sampling. A plastic band marked with a unique identification number was developed, and various methods for attaching the band to the tubewell were tested, resulting in the choice of a galvanized-iron split-rivet. Two follow-up surveys at two and 14 months post-banding assessed the durability and longevity under field conditions in the JiVitA Project area in rural, northwestern Bangladesh. After two months, ~96.0% of the original bands on 1,063 tubewells were functional, although the rivets were partially corroded. After 14 months, ~65% of a subsample of the bands were functional. With further improvements to the rivets, these bands offer an inexpensive, durable, enumeration technology for longitudinal studies on groundwater arsenic. PMID:18330072

  18. Longitudinal health record: a pediatrician's viewpoint of the longitudinal health record.

    PubMed

    Oberst, B B

    1989-01-01

    This paper will discuss the Health Record in terms of content, value of a Longitudinal Record, need for a dynamic and interactive record versus the current archived chronological repository of information, areas of application in research, clinical benefits and population related research concerning present and future influences upon a person's health. It will contain the categories of information utilized in a model Health Record, what facts should be contained within a brief Synopsis or Record Abstract and the contents of a master Pediatric Database. Areas of uses, abuses, potential problems, security needs, privacy and confidentiality issues, legal aspects, transfer of information, technical considerations, computerization of the Record and other matters will be discussed.

  19. Tectonic Escape and Present-Day Crustal Deformation in Northernmost Longitudinal Valley, Hualien Taiwan

    NASA Astrophysics Data System (ADS)

    Lee, J. C.; Chen, C. Y.; Chen, Y. G.; Chen, R. F.; Chen, H. Y.

    2014-12-01

    The Longitudinal Valley in Eastern Taiwan sits at the collision suture between the Eurasian and Philippine Sea plates. Based on repeated GPS campaigned measurements from 25 stations six times in 2007-2014 and 10 continuous GPS single-frequency stations recorded in 2011-2014, we characterize the surface deformation in the northernmost Longitudinal Valley where the Coastal Range of the Philippine Sea plate turns northward diving under the Eurasian plate producing two major active faults: the Milun fault and the Longitudinal Valley fault. We reconstructed a GPS velocity field and conducted strain analyses and elastic block modeling. Our results suggest a clockwise rotation at a rate of 33° M/yr and an eastward tectonic escape in the small Hualien City block (HUAL) area of ~10 × 10 km, which is apparently detached from the regional rotating RYUK block (~ 100 x 100 km) defined by previous studies. Combining the levelling data that indicated the Coastal Range is going down toward the north, we interpret the tectonic escape of the northernmost Longitudinal Valley as being initiated locally by the northwest indentation of the Coastal Range, which pushed the HUAL block to move upward and eastward. According to our strain analyses, the HUAL block shows a significant internal elastic strain inside the Milun Tableland, the hanging wall of the Milun fault. No significant deformation was observed across the surface trace of the fault, indicating that the Milun fault is now probably locked in the near surface. The deformation in the footwall of the fault was accommodated by pure-shear strain with a major NNW-compression and a minor ENE-extension. The deformation in the hanging wall is characterized by simple-shear strain with ENE-extension in its northern part and little deformation in the southern part, separated by a little known NW-trending active fault zone (Dongmingyi fault), which needs further investigation.

  20. On the East-West Longitudinally Asymmetric Distribution of Solar Proton Events

    NASA Astrophysics Data System (ADS)

    He, H.-Q.; Wan, W.

    2016-09-01

    A large data set of 78 solar proton events observed near the Earth's orbit during 1996-2011 is investigated. An East-West longitudinal (azimuthal) asymmetry is found to exist in the distribution of flare sources of solar proton events. With the same longitudinal separation between the flare sources and the magnetic field line footpoint of observer, the number of the solar proton events originating from solar sources located on the eastern side of the nominal magnetic footpoint of observer is larger than the number of the solar proton events from solar sources located on the western side. We emphasize the importance of this statistical investigation in two aspects. On the one hand, this statistical finding confirms our previous simulation results obtained by numerically solving five-dimensional Fokker-Planck equation of solar energetic particle (SEP) transport. On the other hand, the East-West longitudinally (azimuthally) asymmetric distribution of solar proton events accumulated over a long time period provides an observational evidence for the effects of perpendicular diffusion on the SEP propagation in the heliosphere. We further point out that, in the sense of perpendicular diffusion, our numerical simulations and statistical results of SEP events confirm each other. We discuss in detail the important effects of perpendicular diffusion on the formation of the East-West azimuthal (longitudinal) asymmetry of SEP distribution in two physical scenarios, i.e., "multiple SEP events with one spacecraft" and "one SEP event with multiple spacecraft". A functional relation Imax(r) = kr-1.7 quantifying the radial dependence of SEP peak intensities is obtained and utilized in the analysis of physical mechanism. The relationship between our results and those of Dresing et al. (2014, Astronomy & Astrophysics, 567, A27) is also discussed.

  1. Material laws and related uncommon phenomena in the electromagnetic response of type-II superconductors in longitudinal geometry

    NASA Astrophysics Data System (ADS)

    Ruiz, H. S.; Badía-Majós, A.; López, C.

    2011-11-01

    Relying on our theoretical approach for the superconducting critical state problem in 3D magnetic field configurations, we present an exhaustive analysis of the electrodynamic response for the so-called longitudinal transport problem in the slab geometry. A wide set of experimental conditions have been considered, including modulation of the applied magnetic field either perpendicular or parallel (longitudinal) to the transport current density. The main objective of our work was to characterize the role of the macroscopic material law that should properly account for the underlying mechanisms of flux cutting and depinning. The intriguing occurrence of negative current patterns and the enhancement of the transport current flow along the center of the superconducting sample are reproduced as a straightforward consequence of the magnetically induced internal anisotropy. Moreover, we show that, related to a maximal projection of the current density vector onto the local magnetic field, a maximal transport current density occurs somewhere within the sample. The elusive measurement of the flux cutting threshold (critical value of such parallel component J_{ {c} \\parallel } ) is suggested on the basis of local measurements of the transport current density. Finally, we show that a high correlation exists between the evolution of the transport current density and the appearance of paramagnetic peak structures in terms of the applied longitudinal magnetic field.

  2. [Comparative study of N, P output and eutrophication risk in runoff water in cross ridge and longitudinal ridge].

    PubMed

    Yu, Xing-Xiu; Ma, Qian; Liu, Qian-Jin; Lü, Guo-An

    2011-02-01

    Field in-situ rainfall simulation tests with two rainfall intensities (40 mm x h(-1) and 70 mm x h(-1)), which were conducted at typical sloping cropland in Yimeng mountainous area, were designed to analyze the output characteristics of dissolved inorganic nitrogen, Inorganic-N (NO3(-)-N, NH4(+) -N) and dissolved phosphorus (DP) in runoff water, as well as to compare the eutrophication risk in this water by calculating three ratios of Inorganic-N/DP, NO3(-) -N/DP, and NH4(+)-N/DP, respectively, in cross ridge and longitudinal ridge tillage methods. Results showed that, under the same rainfall intensity, the DP level in runoff water was higher in cross ridge than longitudinal ridge, while the change of different Inorganic-N level between the two tillage methods were not consistent. Cross ridge could effectively reduce runoff and the output rate of Inorganic-N and DP when compared to the longitudinal ridge tillage, which would be more outstanding with the increases of rainfall intensities. The losses of Inorganic-N and DP in runoff water were 43% and 5% less, respectively, in cross ridge than longitudinal ridge at the 40 mm x h(-1) rainfall intensity, and were 68% and 55%, respectively, at 70 mm x h(-1). The higher Inorganic-N/DP and NO3(-) -N/DP ratios suggest that runoff water from either cross ridge or longitudinal ridge tillage have a certain eutrophication risk, which present an increasing trend during the precipitation-runoff process. Compared with longitudinal ridge, cross ridge can not only hinder the increasing trend of eutrophication risk, but also can significantly lower it, and thus effectively reduce the effect of sloping cropland runoff on the eutrophication processes of receiving waters.

  3. Dune fields in central Western Argentina

    NASA Astrophysics Data System (ADS)

    Suvires, Graciela M.

    Important accumulations of wind blown sands extend over some sections of plains and pediments. The three dune fields existing in the area are called: Medanos Grandes (great dunes) in the south end of Pie de Palo range between 660 to 750 masl; Las Chacras dune to the southwestern end of Valle Fertil range between 690 to 800 masl; and Mascasin dunes between 450 to 550 masl. These dune fields contain longitudinal, transverse, parabolic, and barchanoid sand dunes with interdune basins.

  4. Analyzing Longitudinal Magnetoresistance Asymmetry to Quantify Doping Gradients: Generalization of the van der Pauw Method

    NASA Astrophysics Data System (ADS)

    Zhou, Wang; Yoo, H. M.; Prabhu-Gaunkar, S.; Tiemann, L.; Reichl, C.; Wegscheider, W.; Grayson, M.

    2015-10-01

    A longitudinal magnetoresistance asymmetry (LMA) between a positive and negative magnetic field is known to occur in both the extreme quantum limit and the classical Drude limit in samples with a nonuniform doping density. By analyzing the current stream function in van der Pauw measurement geometry, it is shown that the electron density gradient can be quantitatively deduced from this LMA in the Drude regime. Results agree with gradients interpolated from local densities calibrated across an entire wafer, establishing a generalization of the van der Pauw method to quantify density gradients.

  5. Self-healing of Bessel-like beams with longitudinally dependent cone angles

    NASA Astrophysics Data System (ADS)

    Litvin, I.; Burger, L.; Forbes, A.

    2015-10-01

    Bessel beams have been extensively studied, but to date have been created over a finite region inside the laboratory. Recently Bessel-like beams with longitudinally dependent cone angles have been introduced allowing for a potentially infinite quasi non-diffracting propagation region. Here we show that such beams can self-heal. Moreover, in contrast to Bessel beams where the self-healing distance is constant, here the self-healing distance is dependent on where the obstruction is placed in the field, with the distance increasing as the Bessel-like beam propagates farther. We outline the theoretical concept for this self-healing and confirm it experimentally.

  6. Introduction to longitudinal data analysis in psychiatric research.

    PubMed

    Liu, Xian

    2015-08-25

    The onset, course, and management of mental health problems typically occur over relatively long periods of time, so a substantial proportion of psychiatric research - particularly the research that can provide clear answers about the complex interaction of biological, psychological, and social factors - requires multiple assessments of individuals and the environments in which they live over time. However, many psychiatric researchers use incorrect statistical methods to analyze this type of longitudinal data, a problem that can result in unrecognized bias in analytic results and, thus, incorrect conclusions. This paper provides an introduction to the topic of longitudinal data analysis. It discusses the different dataset structures used in the analysis of longitudinal data, the classification and management of missing data, and methods of adjusting for intra-individual correlation when developing multivariate regression models using longitudinal data. PMID:26549964

  7. Multivariate longitudinal data analysis with mixed effects hidden Markov models.

    PubMed

    Raffa, Jesse D; Dubin, Joel A

    2015-09-01

    Multiple longitudinal responses are often collected as a means to capture relevant features of the true outcome of interest, which is often hidden and not directly measurable. We outline an approach which models these multivariate longitudinal responses as generated from a hidden disease process. We propose a class of models which uses a hidden Markov model with separate but correlated random effects between multiple longitudinal responses. This approach was motivated by a smoking cessation clinical trial, where a bivariate longitudinal response involving both a continuous and a binomial response was collected for each participant to monitor smoking behavior. A Bayesian method using Markov chain Monte Carlo is used. Comparison of separate univariate response models to the bivariate response models was undertaken. Our methods are demonstrated on the smoking cessation clinical trial dataset, and properties of our approach are examined through extensive simulation studies. PMID:25761965

  8. A NEW METHOD OF LONGITUDINAL DIARY ASSEMBLY FOR EXPOSURE MODELING

    EPA Science Inventory

    Many stochastic human exposure models require the construction of longitudinal time-activity diaries to evaluate the time sequence of concentrations encountered, and hence, the pollutant exposure for the simulated individuals. However, most of the available data on human activiti...

  9. Room 106, A laboratory with longitudinal arrangement of benches. View ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Room 106, A laboratory with longitudinal arrangement of benches. View to west. - San Bernardino Valley College, Life Science Building, 701 South Mount Vernon Avenue, San Bernardino, San Bernardino County, CA

  10. Coupling of transverse and longitudinal waves in piano strings.

    PubMed

    Etchenique, Nikki; Collin, Samantha R; Moore, Thomas R

    2015-04-01

    The existence of longitudinal waves in vibrating piano strings has been previously established, as has their importance in producing the characteristic sound of the piano. Modeling of the coupling between the transverse and longitudinal motion of strings indicates that the amplitude of the longitudinal waves are quadratically related to the transverse displacement of the string, however, experimental verification of this relationship is lacking. In the work reported here this relationship is tested by driving the transverse motion of a piano string at only two frequencies, which simplifies the task of unambiguously identifying the constituent signals. The results indicate that the generally accepted relationship between the transverse motion and the longitudinal motion is valid. It is further shown that this dependence on transverse displacement is a good approximation when a string is excited by the impact of the hammer during normal play. PMID:25920829

  11. LONGITUDINAL VIEW OF THE SOAKING PIT BUILDING INTERIOR WITH OPEN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    LONGITUDINAL VIEW OF THE SOAKING PIT BUILDING INTERIOR WITH OPEN HEARTH IN BACKGROUND AND FURNACE PIT/ STACK AREA TO THE LEFT. - Pittsburgh Steel Company, Monessen Works, Open Hearth Plant, Donner Avenue, Monessen, Westmoreland County, PA

  12. Longitudinal emittance measurements in the Fermilab Recycler Ring

    SciTech Connect

    C. M. Bhat; John P. Marriner

    2003-06-10

    The Recycler Ring (RR) is a new 8Gev antiproton storage ring at Fermilab. Presently, this machine is being commissioned using protons from the Booster. It uses barrier buckets for stacking, un-stacking and storing the beam. At any given time, the RR is capable of storing proton or antiproton beams in multiple segments azimuthally. These segments of the beam may have widely differing longitudinal emittance and beam intensities and bunch lengths. It is highly essential to be able to measure the longitudinal emittance and keep track of the longitudinal dynamics at various stages of the operation of the RR. In this paper, the authors discuss a few methods of longitudinal emittance measurements in barrier buckets and discuss their merits and demerits

  13. Photocopy of longitudinal, cross sections and roof plan of the ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Photocopy of longitudinal, cross sections and roof plan of the C.B. & Q. R.R. roundhouse and locomotive shops. June 1980. - Chicago, Burlington & Quincy Railroad, Roundhouse & Shops, Broadway & Spring Streets, Aurora, Kane County, IL

  14. Longitudinal Section AA; Reflected Deck Plan; Reflected Ceiling Plan ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Longitudinal Section A-A; Reflected Deck Plan; Reflected Ceiling Plan - Shoreham Railroad Bridge, Former Addison County Railroad (later, Rutland Railroad, Addison Branch), spanning Lemon Fair River above Richville Pond, west of East Shoreham Road, Shoreham, Addison County, VT

  15. 2. LONGITUDINAL VIEW OF THE CONCRETE ARCH (ONEWAY BRIDGE), LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. LONGITUDINAL VIEW OF THE CONCRETE ARCH (ONE-WAY BRIDGE), LOOKING NORTHEAST. - Washington Water Power Company Post Falls Power Plant, Concrete Arch Bridge, West of intersection of Spokane & Fourth Streets, Post Falls, Kootenai County, ID

  16. Longitudinal view, looking east through inclinded end posts of eastern ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Longitudinal view, looking east through inclinded end posts of eastern portal. - Monongahela Railroad, New Geneva Bridge, Spanning Monongahela River, South of Lock & Dam No. 7, New Geneva, Fayette County, PA

  17. 5. UNDERSIDE OF VIADUCT AT WEST END. LONGITUDINAL TROLLEY BEAMS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. UNDERSIDE OF VIADUCT AT WEST END. LONGITUDINAL TROLLEY BEAMS ARE BEING SUPPORTED BY FLOOR BEAMS AT THE PANEL POINTS. - Marshall Street Viaduct, Marshall Street from College through Twenty-first Streets, Richmond, Independent City, VA

  18. 29. HAWSER DEVICE, DEVELOPED AT WES FOR MEASURING LONGITUDINAL AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    29. HAWSER DEVICE, DEVELOPED AT WES FOR MEASURING LONGITUDINAL AND TRANSVERSE STRESS OF BARGES IN CANAL LOCKS. - Waterways Experiment Station, Hydraulics Laboratory, Halls Ferry Road, 2 miles south of I-20, Vicksburg, Warren County, MS

  19. 15. Photocopy of longitudinal sections, March 7, 1950. Original drawing ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. Photocopy of longitudinal sections, March 7, 1950. Original drawing property of Continental Airlines. - Newark International Airport, Brewster Hangar, Brewster Road between Route 21 & New Jersey Turnpike Exchange No. 14, Newark, Essex County, NJ

  20. Coupling of transverse and longitudinal waves in piano strings.

    PubMed

    Etchenique, Nikki; Collin, Samantha R; Moore, Thomas R

    2015-04-01

    The existence of longitudinal waves in vibrating piano strings has been previously established, as has their importance in producing the characteristic sound of the piano. Modeling of the coupling between the transverse and longitudinal motion of strings indicates that the amplitude of the longitudinal waves are quadratically related to the transverse displacement of the string, however, experimental verification of this relationship is lacking. In the work reported here this relationship is tested by driving the transverse motion of a piano string at only two frequencies, which simplifies the task of unambiguously identifying the constituent signals. The results indicate that the generally accepted relationship between the transverse motion and the longitudinal motion is valid. It is further shown that this dependence on transverse displacement is a good approximation when a string is excited by the impact of the hammer during normal play.

  1. Viability of longitudinal trenches for capturing contaminated groundwater.

    PubMed

    Hudak, Paul F

    2010-04-01

    Using a groundwater flow and mass transport model, this study compared the capability of trenches with permeable backfill for capturing hypothetical contaminant plumes in homogeneous and heterogeneous unconfined aquifers. Longitudinal (parallel to groundwater flow), as well as conventional transverse (perpendicular to groundwater flow) trench configurations were considered. Alternate trench configurations intercepted the leading tip of an initial contaminant plume and had identical length, equal to the cross-gradient width of the plume. A longitudinal trench required 31% less time than its transverse counterpart to remediate a homogeneous aquifer. By contrast, in simulated heterogeneous aquifers, longitudinal remediation timeframes ranged from 41% less to 33% more than transverse trenches. Results suggest that longitudinal trenches may be a viable alternative for narrow contaminant plumes under low-groundwater velocity conditions, but may be impractical for plumes with wide leading tips, or in complex heterogeneous aquifers with divergent flow.

  2. Unusual longitudinal relaxation time behaviour of colloidal solutions of superparamagnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Carvalho, A.; Taborda, A.

    2007-12-01

    Superparamagnetic nanoparticles are very interesting objects having many applications among which MRI contrast agents are one of the more important. In this work the longitudinal relaxation times of Endorem and Lumirem, two colloidal solutions of iron oxide nanoparticles used as contrast agents for magnetic resonance imaging were measured at magnetic field intensities similar to the ones used in MRI. T1 was seen to depend on nanoparticle concentrations as expected but, for the Lumirem, also on the time spend by the sample under the influence of the static magnetic field. The T1 evolution was measured for colloidal solutions both different concentrations and different viscosities. The strange T1 dependence is presented and discussed relating to the nanoparticles superparamagnetic properties. It is shown that one of the possible reasons for the fact is the formation of local field enhanced linear arrays of SPIO.

  3. Higher harmonic emission by a relativistic electron beam in a longitudinal magnetic wiggler

    NASA Astrophysics Data System (ADS)

    Davidson, Ronald C.; McMullin, Wayne A.

    1982-10-01

    The classical limit of the Einstein-coefficient method is used in the low-gain regime to calculate the stimulated emission from a tenuous relativistic electron beam propagating in the combined solenoidal and longitudinal wiggler fields (B0+δB k0z)e^z produced near the axis of a multiple-mirror (undulator) field configuration. Emission is found to occur at all harmonics of the wiggler wave number k0 with Doppler upshifted output frequency given by ω=(lk0Vb+ωcb)(1+Vbc)γ2b(1+γ2bV2⊥c2), where l>=1. The emission is compared to the low-gain cyclotron maser with δB=0 and to the low-gain free-electron laser (operating at higher harmonics) utilizing a transverse linearly polarized wiggler field.

  4. Visual field

    MedlinePlus

    Perimetry; Tangent screen exam; Automated perimetry exam; Goldmann visual field exam; Humphrey visual field exam ... Confrontation visual field exam : This is a quick and basic check of the visual field. The health care provider ...

  5. Global longitudinal strain: a useful everyday measurement?

    PubMed Central

    Thambyrajah, J; Leng, E; Stewart, M J

    2016-01-01

    Herceptin (Trastuzumab) is a widely used and effective drug for the treatment of Her2+ breast cancer but its cardiotoxic side effects require regular monitoring by echocardiography. A 10% reduction in left ventricular ejection fraction can lead to suspension of treatment and therefore has significant implications for patient prognosis in terms of cardiac and cancer outcomes. Assessment of LV function by conventional 2D biplane method of discs (2DEF) has limitations in accuracy and reproducibility. Global longitudinal strain (GLS) is becoming more widely available and user friendly. It has been shown to demonstrate myocardial damage earlier in treatment than 2DEF, allowing the option of pharmacological intervention at a pre-clinical stage and preventing the interruption of Herceptin. This study compares the reproducibility of GLS with that of 2DEF in a routine clinical environment. Fifty echocardiograms performed on female patients undergoing Herceptin treatment were used to measure both 2DEF and GLS within the recommended standard appointment time of 40 min. The data were re-measured (blind) by the same operator a minimum of 14 days later to determine intra-operator variation. These data were also measured by a second operator (blind), to assess inter-operator variation. Analysis by direct comparison, intra-class correlation (ICC), coefficient of variation (CV) and Bland–Altman plots demonstrated that GLS is a more reproducible measurement than 2DEF. This is important to prevent clinical decisions being erroneously based on variation in operator measurement. The investigation also shows that with advances in machine software this is a practical addition to routine assessment rather than merely a research tool. PMID:27628098

  6. Longitudinal structures in lower thermosphere density

    NASA Astrophysics Data System (ADS)

    Forbes, J. M.; Palo, S. E.; Marcos, F. A.

    1999-03-01

    Thermospheric densities near 200 km from the Satellite Electrostatic Triaxial Accelerometer (SETA) experiment during July and December 1983 are analyzed to reveal two types of longitude structures: (1) the so-called ``longitude/UT'' variation which has been noted in higher-altitude satellite data and incorporated into the mass spectrometer incoherent scatter extension-90 (MSISE-90) empirical model [Hedin, 1991] and (2) ``higher-order structures'' in the form of longitudinal wave patterns which have not previously been mentioned in the thermosphere-ionosphere literature. The longitude/UT variation in the SETA densities shares many similarities with that embodied in the MSISE-90 model, except for some differences in symmetry about the equator. Interpretation concerning the origin of the observed variation is handicapped by the Sun-synchronous limitations of the satellite orbit and by the convolution of high-latitude heating effects being mapped into the geographic frame while solar-driven latitudinal variations are mapped into the geomagnetic frame. An unambiguous separation of these effects is not possible with the present orbital constraints. The space-time Fourier analysis method of Salby [1982a, b] is applied in an attempt to quantitatively characterize the higher-order structure in the data. The nature of the satellite sampling introduces ambiguities into the determination of zonal wavenumbers and periodicities. There is, evidence of s=1 and s=2 stationary features, eastward propagating Kelvin waves, and a number of westward propagating waves with zonal wavenumbers s=0 to s=6 and periods between 6 to 10 hours. Meyer and Forbes [1997] have recently shown the latter class of waves, referred to as Lamb waves in an isothermal nondissipative atmosphere, to represent the preferred response to broadband forcing of the thermosphere. The present observations may represent the existence of Lamb waves in the thermosphere.

  7. Longitudinal Increase in Anisometropia in Older Adults

    PubMed Central

    Haegerstrom-Portnoy, Gunilla; Schneck, Marilyn E.; Lott, Lori A.; Hewlett, Susan E.; Brabyn, John A.

    2014-01-01

    Purpose Anisometropia shows an exponential increase in prevalence with increasing age based on cross-sectional studies. The purpose of this study was to evaluate longitudinal changes in anisometropia in all refractive components in older observers and to assess the influence of early cataract development. Methods Refractive error was assessed at two time points separated by ~12 years in 118 older observers (ages 67.1 and 79.3 years at the two test times). Anisometropia defined as ≥1.00 D was calculated for all refractive components. The subjects had intact ocular lenses in both eyes throughout the study. Lens evaluations were performed at the second test using LOCS III. Results All refractive components approximately doubled in prevalence of anisometropia. Spherical equivalent anisometropia changed from 16.1% to 32.2%. Similar changes were found for spherical error (17% to 38.1%), primary astigmatism (7.6% to 17.8%) and oblique astigmatism (14.4% to 29.7%). Many who did not have anisometropia at the first visit subsequently developed anisometropia (for ex. 26.3% for spherical error and 22.9% for oblique cylinder). The onset of anisometropia occurred at all ages within the studied age range with no particular preference for any one age. A small number lost anisometropia over time. Individual comparisons of refractive error changes in the two eyes in combination with nuclear lens changes showed that early changes in nuclear sclerosis in the two eyes could account for a large proportion of anisometropia (~40%) but unequal hyperopic shift in the spherical component in the two eyes was the primary cause of the anisometropia. Conclusions Anisometropia is at least 10 times more common in the elderly than in children and anisometropia develops in all refractive components in the oldest observers. Clinicians need to be aware of this common condition that could lead to binocular vision problems and potentially cause falls in the elderly. PMID:24276578

  8. Longitudinal Beam Diagnostics for the ILC Injectors and Bunch Compressors

    SciTech Connect

    Piot, Philippe; Bracke, Adam; Demir, Veysel; Maxwell, Timothy; Rihaoui, Marwan; Jing, Chunguang; Power, John

    2010-12-01

    We present a diagnostics suite and analyze techniques for setting up the longitudinal beam dynamics in ILC e⁻ injectors and e⁺ and e⁻ bunch compressors. Techniques to measure the first order moments and recover the first order longitudinal transfer map of the injector's intricate bunching scheme are presented. Coherent transition radiation diagnostics needed to measure and monitor the bunch length downstream of the ~5 GeV bunch compressor are investigated using a vector diffraction model.

  9. Longitudinal interfacial shearing of a unidirectional fiber composite

    SciTech Connect

    Yang, M.; Kurth, R.E.

    1995-12-31

    In this work, longitudinal interfacial shearing of a unidirectional fiber composite which sustains slippage at the interface between fiber and matrix is analyzed. Based on the experimental work on the fiber pull-out, the interface between the fiber and the matrix can be divided as three regions, depending on the longitudinal shear stress. These three regions are the bonded region, frictional slip regions, and the free-friction slid region. The problem is formulated as a nonlinear system of singular integral equations and solved numerically. It has been shown that when the longitudinal shear stress is less than a critical value, the fiber and the matrix can be assumed to be bonded perfectly. When the longitudinal shear stress is greater than this critical value, the slippage at the interface between the fiber and the interface takes place. From the recent fiber pull-out test, the phenomena of fiber frictional slip followed by free slide has been observed and analyzed. Thus, there are three stages for the deformation of interfacial shearing of a unidirectional fiber composite under longitudinal shearing. The first stage occurs when the applied longitudinal shear stress is less than the critical value corresponding to the onset of slippage. In the second stage, the interface is divided into two regions, namely, the bonded region and the frictional slip region in which the shear stress is either assumed to be constant or governed by a friction law. The third stage occurs when the longitudinal shear stress is greater than the critical value corresponding to free sliding or when the friction limit is exceeded. In the third stage, the interface between the fiber and the matrix can be divided into three regions, depending on the longitudinal shear stress. These three regions are the bonded region, the frictional slip regions, and the free-friction slide region in which the shear stress is neglected.

  10. Definition and application of longitudinal stability derivatives for elastic airplanes

    NASA Technical Reports Server (NTRS)

    Kemp, W. B., Jr.

    1972-01-01

    A set of longitudinal stability derivatives for elastic airplanes is defined from fundamental principles allowing perturbations in forward speed. Application of these derivatives to longitudinal stability analysis by use of approximate expressions for static stability and control parameters as well as the dynamic equations of motion is illustrated. One commonly used alternative formulation for elastic airplanes is shown to yield significant inaccuracies because of inappropriate interpretation of inertial effects.

  11. Dynamics of heavy ion beams during longitudinal compression

    SciTech Connect

    Ho, D.D.M.; Bangerter, R.O.; Lee, E.P.; Brandon, S.; Mark, J.W.K.

    1987-03-13

    Heavy ion beams with initially uniform line charge density can be compressed longitudinally by an order of magnitude in such a way that the compressed beam has uniform line charge density and velocity-tilt profiles. There are no envelope mismatch oscillations during compression. Although the transverse temperature varies along the beam and also varies with time, no substantial longitudinal and transverse emittance growth has been observed. Scaling laws for beam radius and transport system parameters are given.

  12. Technical Note: Response measurement for select radiation detectors in magnetic fields

    SciTech Connect

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

    2015-06-15

    Purpose: Dose response to applied magnetic fields for ion chambers and solid state detectors has been investigated previously for the anticipated use in linear accelerator–magnetic resonance devices. In this investigation, the authors present the measured response of selected radiation detectors when the magnetic field is applied in the same direction as the radiation beam, i.e., a longitudinal magnetic field, to verify previous simulation only data. Methods: The dose response of a PR06C ion chamber, PTW60003 diamond detector, and IBA PFD diode detector is measured in a longitudinal magnetic field. The detectors are irradiated with buildup caps and their long axes either parallel or perpendicular to the incident photon beam. In each case, the magnetic field dose response is reported as the ratio of detector signals with to that without an applied longitudinal magnetic field. The magnetic field dose response for each unique orientation as a function of magnetic field strength was then compared to the previous simulation only studies. Results: The measured dose response of each detector in longitudinal magnetic fields shows no discernable response up to near 0.21 T. This result was expected and matches the previously published simulation only results, showing no appreciable dose response with magnetic field. Conclusions: Low field longitudinal magnetic fields have been shown to have little or no effect on the dose response of the detectors investigated and further lend credibility to previous simulation only studies.

  13. Factors affecting longitudinal trajectories of plasma sphingomyelins: the Baltimore Longitudinal Study of Aging

    PubMed Central

    Mielke, Michelle M; Bandaru, Veera Venkata Ratnam; Han, Dingfen; An, Yang; Resnick, Susan M; Ferrucci, Luigi; Haughey, Norman J

    2015-01-01

    Sphingomyelin metabolism has been linked to several diseases and to longevity. However, few epidemiological studies have quantified individual plasma sphingomyelin species (identified by acyl-chain length and saturation) or their relationship between demographic factors and disease processes. In this study, we determined plasma concentrations of distinct sphingomyelin species in 992 individuals, aged 55 and older, enrolled in the Baltimore Longitudinal Study of Aging. Participants were followed, with serial measures, up to 6 visits and 38 years (3972 total samples). Quantitative analyses were performed on a high-performance liquid chromatography-coupled electrospray ionization tandem mass spectrometer. Linear mixed models were used to assess variation in specific sphingomyelin species and associations with demographics, diseases, medications or lifestyle factors, and plasma cholesterol and triglyceride levels. We found that most sphingomyelin species increased with age. Women had higher plasma levels of all sphingomyelin species and showed steeper trajectories of age-related increases compared to men. African Americans also showed higher circulating sphingomyelin concentrations compared to Caucasians. Diabetes, smoking, and plasma triglycerides were associated with lower levels of many sphingomyelins and dihydrosphingomyelins. Notably, these associations showed specificity to sphingomyelin acyl-chain length and saturation. These results demonstrate that longitudinal changes in circulating sphingomyelin levels are influenced by age, sex, race, lifestyle factors, and diseases. It will be important to further establish the intra-individual age- and sex-specific changes in each sphingomyelin species in relation to disease onset and progression. PMID:25345489

  14. Longitudinal changes in white matter microstructure after heavy cannabis use.

    PubMed

    Becker, Mary P; Collins, Paul F; Lim, Kelvin O; Muetzel, R L; Luciana, M

    2015-12-01

    Diffusion tensor imaging (DTI) studies of cannabis users report alterations in brain white matter microstructure, primarily based on cross-sectional research, and etiology of the alterations remains unclear. We report findings from longitudinal voxelwise analyses of DTI data collected at baseline and at a 2-year follow-up on 23 young adult (18-20 years old at baseline) regular cannabis users and 23 age-, sex-, and IQ-matched non-using controls with limited substance use histories. Onset of cannabis use was prior to age 17. Cannabis users displayed reduced longitudinal growth in fractional anisotropy in the central and parietal regions of the right and left superior longitudinal fasciculus, in white matter adjacent to the left superior frontal gyrus, in the left corticospinal tract, and in the right anterior thalamic radiation lateral to the genu of the corpus callosum, along with less longitudinal reduction of radial diffusion in the right central/posterior superior longitudinal fasciculus, corticospinal tract, and posterior cingulum. Greater amounts of cannabis use were correlated with reduced longitudinal growth in FA as was relatively impaired performance on a measure of verbal learning. These findings suggest that continued heavy cannabis use during adolescence and young adulthood alters ongoing development of white matter microstructure, contributing to functional impairment. PMID:26602958

  15. Longitudinal changes in white matter microstructure after heavy cannabis use.

    PubMed

    Becker, Mary P; Collins, Paul F; Lim, Kelvin O; Muetzel, R L; Luciana, M

    2015-12-01

    Diffusion tensor imaging (DTI) studies of cannabis users report alterations in brain white matter microstructure, primarily based on cross-sectional research, and etiology of the alterations remains unclear. We report findings from longitudinal voxelwise analyses of DTI data collected at baseline and at a 2-year follow-up on 23 young adult (18-20 years old at baseline) regular cannabis users and 23 age-, sex-, and IQ-matched non-using controls with limited substance use histories. Onset of cannabis use was prior to age 17. Cannabis users displayed reduced longitudinal growth in fractional anisotropy in the central and parietal regions of the right and left superior longitudinal fasciculus, in white matter adjacent to the left superior frontal gyrus, in the left corticospinal tract, and in the right anterior thalamic radiation lateral to the genu of the corpus callosum, along with less longitudinal reduction of radial diffusion in the right central/posterior superior longitudinal fasciculus, corticospinal tract, and posterior cingulum. Greater amounts of cannabis use were correlated with reduced longitudinal growth in FA as was relatively impaired performance on a measure of verbal learning. These findings suggest that continued heavy cannabis use during adolescence and young adulthood alters ongoing development of white matter microstructure, contributing to functional impairment.

  16. Joint Analysis of Survival Time and Longitudinal Categorical Outcomes

    PubMed Central

    Choi, Jaeun; Cai, Jianwen; Zeng, Donglin; Olshan, Andrew F.

    2013-01-01

    In biomedical or public health research, it is common for both survival time and longitudinal categorical outcomes to be collected for a subject, along with the subject’s characteristics or risk factors. Investigators are often interested in finding important variables for predicting both survival time and longitudinal outcomes which could be correlated within the same subject. Existing approaches for such joint analyses deal with continuous longitudinal outcomes. New statistical methods need to be developed for categorical longitudinal outcomes. We propose to simultaneously model the survival time with a stratified Cox proportional hazards model and the longitudinal categorical outcomes with a generalized linear mixed model. Random effects are introduced to account for the dependence between survival time and longitudinal outcomes due to unobserved factors. The Expectation-Maximization (EM) algorithm is used to derive the point estimates for the model parameters, and the observed information matrix is adopted to estimate their asymptotic variances. Asymptotic properties for our proposed maximum likelihood estimators are established using the theory of empirical processes. The method is demonstrated to perform well in finite samples via simulation studies. We illustrate our approach with data from the Carolina Head and Neck Cancer Study (CHANCE) and compare the results based on our simultaneous analysis and the separately conducted analyses using the generalized linear mixed model and the Cox proportional hazards model. Our proposed method identifies more predictors than by separate analyses. PMID:26052353

  17. An investigation into student understanding of longitudinal standing waves

    NASA Astrophysics Data System (ADS)

    Dostal, Jack Alan

    This study investigates the difficulties that introductory university physics students have with the concept of longitudinal standing waves in the context of standing waves in pipes. My goal is to identify difficulties that persist even after standard instruction on longitudinal standing waves and attempt to improve upon that method of instruction. The study follows a four-step design. I first use exploratory surveys and interviews with students to elicit the difficulties present in students' understanding of longitudinal standing waves in pipes. I then use the information gained to create and assessment instrument, the Standing Waves Diagnostic Test, and a curricular intervention, the Longitudinal Standing Waves Tutorial. I then undertake a three-step process of pre-testing students with the Standing Wave Diagnostic Test, intervention with the Longitudinal Standing Waves Tutorial, and post-testing again with the Standing Wave Diagnostic Test to determine the impact of the intervention. This is then compared to data from students in classes where the intervention is not used. Students using the intervention significantly outperform their non-intervention counterparts on the Standing Wave Diagnostic Test. The results of the students pre- and post-tests indicate that significant improvement in students' understandings of longitudinal standing waves can be achieved by the use of the tutorial.

  18. Trajectories of electrons with large longitudinal momenta in the phase plane during surfatron acceleration by an electromagnetic wave

    SciTech Connect

    Mkrtichyan, G. S.

    2015-07-15

    The trajectories of electrons with large longitudinal momenta in the phase plane in the course of their surfatron acceleration by an electromagnetic wave propagating in space plasma across the external magnetic field are analyzed. Electrons with large longitudinal momenta are trapped immediately if the initial wave phase Ψ(0) on the particle trajectory is positive. For negative values of Ψ(0), no electrons trapping by the wave is observed over the available computational times. According to numerical calculations, the trajectories of trapped particles in the phase plane have a singular point of the stable focus type and the behavior of the trajectory corresponds to the motion in a complex nonstationary effective potential well. For some initial phases, electrons are confined in the region of the accelerating electric field for relatively short time, the energy gain being about 50–130% and more.

  19. Direct longitudinal laser acceleration of electrons in free space

    NASA Astrophysics Data System (ADS)

    Carbajo, Sergio; Nanni, Emilio A.; Wong, Liang Jie; Moriena, Gustavo; Keathley, Phillip D.; Laurent, Guillaume; Miller, R. J. Dwayne; Kärtner, Franz X.

    2016-02-01

    Compact laser-driven accelerators are pursued heavily worldwide because they make novel methods and tools invented at national laboratories widely accessible in science, health, security, and technology [V. Malka et al., Principles and applications of compact laser-plasma accelerators, Nat. Phys. 4, 447 (2008)]. Current leading laser-based accelerator technologies [S. P. D. Mangles et al., Monoenergetic beams of relativistic electrons from intense laser-plasma interactions, Nature (London) 431, 535 (2004); T. Toncian et al., Ultrafast laser-driven microlens to focus and energy-select mega-electron volt protons, Science 312, 410 (2006); S. Tokita et al. Single-shot ultrafast electron diffraction with a laser-accelerated sub-MeV electron pulse, Appl. Phys. Lett. 95, 111911 (2009)] rely on a medium to assist the light to particle energy transfer. The medium imposes material limitations or may introduce inhomogeneous fields [J. R. Dwyer et al., Femtosecond electron diffraction: "Making the molecular movie,", Phil. Trans. R. Soc. A 364, 741 (2006)]. The advent of few cycle ultraintense radially polarized lasers [S. Carbajo et al., Efficient generation of ultraintense few-cycle radially polarized laser pulses, Opt. Lett. 39, 2487 (2014)] has ushered in a novel accelerator concept [L. J. Wong and F. X. Kärtner, Direct acceleration of an electron in infinite vacuum by a pulsed radially polarized laser beam, Opt. Express 18, 25035 (2010); F. Pierre-Louis et al. Direct-field electron acceleration with ultrafast radially polarized laser beams: Scaling laws and optimization, J. Phys. B 43, 025401 (2010); Y. I. Salamin, Electron acceleration from rest in vacuum by an axicon Gaussian laser beam, Phys. Rev. A 73, 043402 (2006); C. Varin and M. Piché, Relativistic attosecond electron pulses from a free-space laser-acceleration scheme, Phys. Rev. E 74, 045602 (2006); A. Sell and F. X. Kärtner, Attosecond electron bunches accelerated and compressed by radially polarized laser

  20. Longitudinal magnetohydrodynamics oscillations in dissipative, cooling coronal loops

    SciTech Connect

    Al-Ghafri, K. S.; Ruderman, M. S.; Williamson, A.; Erdélyi, R. E-mail: m.s.ruderman@sheffield.ac.uk E-mail: robertus@sheffield.ac.uk

    2014-05-01

    This paper investigates the effect of cooling on standing slow magnetosonic waves in coronal magnetic loops. The damping mechanism taken into account is thermal conduction that is a viable candidate for dissipation of slow magnetosonic waves in coronal loops. In contrast to earlier studies, here we assume that the characteristic damping time due to thermal conduction is not small, but arbitrary, and can be of the order of the oscillation period, i.e., a temporally varying plasma is considered. The approximation of low-beta plasma enables us to neglect the magnetic field perturbation when studying longitudinal waves and consider, instead, a one-dimensional motion that allows a reliable first insight into the problem. The background plasma temperature is assumed to be decaying exponentially with time, with the characteristic cooling timescale much larger than the oscillation period. This assumption enables us to use the WKB method to study the evolution of the oscillation amplitude analytically. Using this method we obtain the equation governing the oscillation amplitude. The analytical expressions determining the wave properties are evaluated numerically to investigate the evolution of the oscillation frequency and amplitude with time. The results show that the oscillation period increases with time due to the effect of plasma cooling. The plasma cooling also amplifies the amplitude of oscillations in relatively cool coronal loops, whereas, for very hot coronal loop oscillations the damping rate is enhanced by the cooling. We find that the critical point for which the amplification becomes dominant over the damping is in the region of 4 MK. These theoretical results may serve as impetus for developing the tools of solar magneto-seismology in dynamic plasmas.

  1. Coronal Magnetic Fields Derived from Simultaneous Microwave and EUV Observations and Comparison with the Potential Field Model

    NASA Astrophysics Data System (ADS)

    Miyawaki, Shun; iwai, Kazumasa; Shibasaki, Kiyoto; Shiota, Daikou; Nozawa, Satoshi

    2016-02-01

    We estimated the accuracy of coronal magnetic fields derived from radio observations by comparing them to potential field calculations and the differential emission measure measurements using EUV observations. We derived line-of-sight components of the coronal magnetic field from polarization observations of the thermal bremsstrahlung in the NOAA active region 11150, observed around 3:00 UT on 2011 February 3 using the Nobeyama Radioheliograph at 17 GHz. Because the thermal bremsstrahlung intensity at 17 GHz includes both chromospheric and coronal components, we extracted only the coronal component by measuring the coronal emission measure in EUV observations. In addition, we derived only the radio polarization component of the corona by selecting the region of coronal loops and weak magnetic field strength in the chromosphere along the line of sight. The upper limits of the coronal longitudinal magnetic fields were determined as 100-210 G. We also calculated the coronal longitudinal magnetic fields from the potential field extrapolation using the photospheric magnetic field obtained from the Helioseismic and Magnetic Imager. However, the calculated potential fields were certainly smaller than the observed coronal longitudinal magnetic field. This discrepancy between the potential and the observed magnetic field strengths can be explained consistently by two reasons: (1) the underestimation of the coronal emission measure resulting from the limitation of the temperature range of the EUV observations, and (2) the underestimation of the coronal magnetic field resulting from the potential field assumption.

  2. Longitudinal nonlinear wave propagation through soft tissue.

    PubMed

    Valdez, M; Balachandran, B

    2013-04-01

    In this paper, wave propagation through soft tissue is investigated. A primary aim of this investigation is to gain a fundamental understanding of the influence of soft tissue nonlinear material properties on the propagation characteristics of stress waves generated by transient loadings. Here, for computational modeling purposes, the soft tissue is modeled as a nonlinear visco-hyperelastic material, the geometry is assumed to be one-dimensional rod geometry, and uniaxial propagation of longitudinal waves is considered. By using the linearized model, a basic understanding of the characteristics of wave propagation is developed through the dispersion relation and in terms of the propagation speed and attenuation. In addition, it is illustrated as to how the linear system can be used to predict brain tissue material parameters through the use of available experimental ultrasonic attenuation curves. Furthermore, frequency thresholds for wave propagation along internal structures, such as axons in the white matter of the brain, are obtained through the linear analysis. With the nonlinear material model, the authors analyze cases in which one of the ends of the rods is fixed and the other end is subjected to a loading. Two variants of the nonlinear model are analyzed and the associated predictions are compared with the predictions of the corresponding linear model. The numerical results illustrate that one of the imprints of the nonlinearity on the wave propagation phenomenon is the steepening of the wave front, leading to jump-like variations in the stress wave profiles. This phenomenon is a consequence of the dependence of the local wave speed on the local deformation of the material. As per the predictions of the nonlinear material model, compressive waves in the structure travel faster than tensile waves. Furthermore, it is found that wave pulses with large amplitudes and small elapsed times are attenuated over shorter spans. This feature is due to the elevated

  3. Longitudinal Predictors of Homelessness: Findings from the National Longitudinal Survey of Youth-97

    PubMed Central

    Sznajder-Murray, Brittany; Jang, Joy Bohyun; Slesnick, Natasha; Snyder, Anastasia

    2016-01-01

    Homeless youth represent a vulnerable and understudied population. Little research has prospectively identified factors that may place youth at risk for experiencing homelessness. The current study utilizes data from the National Longitudinal Survey of Youth-97 (NLSY-97) to examine predictors of experiencing homelessness as a young adult (before age 25). The NLSY-97 includes a nationally representative sample of 8,984 youth. Data were first collected from these youth when they were between the ages of 12 to 18 years. The current study examined whether individual and family risk factors reported during adolescence predict homelessness by the age of 25. The findings showed that multiple runaway episodes, non-traditional family structure, lower educational attainment, and parental work limitations due to health increased the risk of homelessness. A permissive parenting style and being Hispanic protected against homelessness. This study offers unique insight into risk and protective factors for youth homelessness, and has important clinical implications. PMID:27774034

  4. Information Systems in Teacher Preparation Programs: What Can We Learn from a 5-Year Longitudinal Case Study of an Electronic Portfolio Database?

    ERIC Educational Resources Information Center

    Swan, Gerry

    2009-01-01

    In 2003, a portfolio system was implemented to manage the data associated with the field experiences in a teacher education program at a research institution in the southeast region of the United States. In this longitudinal study, the implementation trends from usage data extracted from the system are used to discuss the implications for the use…

  5. Longitudinal structure of the northern higher latitude middle stratosphere to lower mesosphere

    NASA Astrophysics Data System (ADS)

    Lastovicka, Jan; Krizan, Peter; Kozubek, Michal

    2016-07-01

    The meridional wind is relatively little studied but important quantity in the stratosphere and mesosphere. We found a two-core longitudinal structure in meridional wind at northern higher middle latitudes based on MERRA data. The two-core structure covers the middle stratosphere (lower boundary ~50 hPa), upper stratosphere and lower mesosphere (up to at least 0.1 hPa, probably somewhat higher). It is circulation response to the appearance of the blocking Aleutian pressure high, which affects more or less also the zonal wind, temperature and ozone fields. The well-pronounced two core structure occurs only in the winter half of the year (October-March) and only at the Northern Hemisphere. The two-core longitudinal structure in meridional wind is persistent feature. Only a few winters (Januaries) reveal more complex structure; all these winters were observed during the positive phase of the Pacific PNA index. The two core structure and Aleutian pressure high display a westward shift with increasing altitude, which allows the interpretation of the blocking Aleutian pressure high as a stationary planetary wave with the two core structure of meridional wind as a response of the overall circulation to the appearance of this stationary planetary wave in pressure field. Its existence could influence the Brewer-Dobson circulation and also the zonal mean approach to investigations of the middle atmosphere.

  6. Beam Loss and Longitudinal Emittance Growth in SIS

    NASA Astrophysics Data System (ADS)

    Kirk, M.; Hofmann, I.; Boine-Frankenheim, O.; Spiller, P.; Hülsmann, P.; Franchetti, G.; Damerau, H.; König, H. Günter; Klingbeil, H.; Kumm, M.; Moritz, P.; Schütt, P.; Redelbach, A.

    2005-06-01

    Beam losses of several percent occur regularly in SIS. The onset occurs during the RF capture of the beam. Previous studies have revealed that the losses can come from the RF bucket at the start of acceleration being over filled due to the longitudinal bucket acceptance being too small, or due to the mismatch between the mean energy from the UNILAC and synchronous energy of the SIS. The beam losses as measured by a DC beam transformer however show in addition to the sharp initial drop, for the above reasons, a much slower decay in the beam intensity. The speculated cause comes from the incoherent transverse tune shift of the bunched beam, which forces particles into transverse resonant conditions. The longitudinal emittance growth is also another important issue for SIS. Past measurements from Schottky-noise pick-ups have shown a factor of 3-5 increase in the longitudinal emittance depending on the extraction energy; a large factor when compared against expectations from theory. These factors were calculated from the ratio between the normalized relative momentum spread of the DC beam before RF capture and after debunching. In this present work, tomographical techniques have been used to reconstruct the phasespace from a series of bunch profile measurements from a Beam Position Monitor (BPM). Therefore one can find the rate of growth in the longitudinal emittance from a series of high resolution BPM measurements along the RF ramp. Furthermore the initial phasespace density matrix from these reconstructions has been used to generate the initial population of macroparticles for the ESME longitudinal dynamics Particle-In-Cell code, thereby enabling a comparison between the longitudinal emittance growth of the beam under ideal conditions and that of the experiment. The longitudinal emittance growth (rms) during the acceleration (˜540ms) was approximately 20%, and that during the RF capture was estimated to have an upper limit of about 40%. Later measurements have also

  7. Theoretical study of transverse-longitudinal emittance coupling

    SciTech Connect

    Qin, H; Davidson, R C; Chung, M; Barnard, J J; Wang, T F

    2011-04-14

    The effect of a weakly coupled periodic lattice in terms of achieving emittance exchange between the transverse and longitudinal directions is investigated using the generalized Courant-Snyder theory for coupled lattices. Recently, the concept and technique of transverse-longitudinal emittance coupling have been proposed for applications in the Linac Coherent Light Source and other free-electron lasers to reduce the transverse emittance of the electron beam. Such techniques can also be applied to the driver beams for the heavy ion fusion and beam-driven high energy density physics, where the transverse emittance budget is typically tighter than the longitudinal emittance. The proposed methods consist of one or several coupling components which completely swap the emittances of one of the transverse directions and the longitudinal direction at the exit of the coupling components. The complete emittance exchange is realized in one pass through the coupling components. In the present study, we investigate the effect of a weakly coupled periodic lattice in terms of achieving emittance exchange between the transverse and longitudinal directions. A weak coupling component is introduced at every focusing lattice, and we would like to determine if such a lattice can realize the function of emittance exchange.

  8. A Bayesian semiparametric survival model with longitudinal markers.

    PubMed

    Zhang, Song; Müller, Peter; Do, Kim-Anh

    2010-06-01

    We consider inference for data from a clinical trial of treatments for metastatic prostate cancer. Patients joined the trial with diverse prior treatment histories. The resulting heterogeneous patient population gives rise to challenging statistical inference problems when trying to predict time to progression on different treatment arms. Inference is further complicated by the need to include a longitudinal marker as a covariate. To address these challenges, we develop a semiparametric model for joint inference of longitudinal data and an event time. The proposed approach includes the possibility of cure for some patients. The event time distribution is based on a nonparametric Pólya tree prior. For the longitudinal data we assume a mixed effects model. Incorporating a regression on covariates in a nonparametric event time model in general, and for a Pólya tree model in particular, is a challenging problem. We exploit the fact that the covariate itself is a random variable. We achieve an implementation of the desired regression by factoring the joint model for the event time and the longitudinal outcome into a marginal model for the event time and a regression of the longitudinal outcomes on the event time, i.e., we implicitly model the desired regression by modeling the reverse conditional distribution.

  9. Diseased Region Detection of Longitudinal Knee Magnetic Resonance Imaging Data

    PubMed Central

    Huang, Chao; Shan, Liang; Charles, H. Cecil; Wirth, Wolfgang; Niethammer, Marc; Zhu, Hongtu

    2015-01-01

    Magnetic resonance imaging (MRI) has become an important imaging technique for quantifying the spatial location and magnitude/direction of longitudinal cartilage morphology changes in patients with osteoarthritis (OA). Although several analytical methods, such as subregion-based analysis, have been developed to refine and improve quantitative cartilage analyses, they can be suboptimal due to two major issues: the lack of spatial correspondence across subjects and time and the spatial heterogeneity of cartilage progression across subjects. The aim of this paper is to present a statistical method for longitudinal cartilage quantification in OA patients, while addressing these two issues. The 3D knee image data is preprocessed to establish spatial correspondence across subjects and/or time. Then, a Gaussian hidden Markov model (GHMM) is proposed to deal with the spatial heterogeneity of cartilage progression across both time and OA subjects. To estimate unknown parameters in GHMM, we employ a pseudo-likelihood function and optimize it by using an expectation-maximization (EM) algorithm. The proposed model can effectively detect diseased regions in each OA subject and present a localized analysis of longitudinal cartilage thickness within each latent subpopulation. Our GHMM integrates the strengths of two standard statistical methods including the local subregion-based analysis and the ordered value approach. We use simulation studies and the Pfizer longitudinal knee MRI dataset to evaluate the finite sample performance of GHMM in the quantification of longitudinal cartilage morphology changes. Our results indicate that GHMM significantly outperforms several standard analytical methods. PMID:25823031

  10. Analysis of the Longitudinal Microwave Instability for Heavy Ion Fusion

    NASA Astrophysics Data System (ADS)

    Majeed, Tariq

    A theoretical model has been developed to analyze the experimental observations of the longitudinal microwave instabilities in reference to the joint experiment between the Argonne National Laboratory and the Rutherford Appleton Laboratory in the UK. The longitudinal microwave instability (LMI) of a coasting beam is created by the interaction of the electromagnetic fields of the ion beam and the surrounding cavity structures in an accelerator storage ring. The Keil-Schnell stability criteria have been used in the present analysis in predicting the LMI threshold limits and the LMI saturation points in the ISIS storage rings for 70 -MeV coasting proton beams. The higher and lower values of the LMI threshold limits have been attributed to the magnitudes of the initial Deltap/p of the beam. The LMI saturation point is almost unaffected by the initial conditions of the beam, and the theoretically calculated values are 3.795 times 10^{12} for debuncher -off case and 3.935 times 10 ^{12} for debuncher-on case. With the sweeper magnet-on, the calculated values of the saturation points are 3.924 times 10 ^{12} and 3.883 times 10^{12} for debuncher -off and debuncher-on, respectively. The differences of the number of particles related with the initial threshold limits and the saturation point (though very close) are believed to be the reason of the difference in the signal height from the spectrum analyzer. The calculated values of LMI rise time are within 5% to 12% of the experimentally observed values. With the sweeper magnet-on, a delay in the start of LMI and the faster growth rates of Deltap/p in the later stages of injection have been observed experimentally and are predicted by the developed analytical model. The difference of the LMI signal height between the debuncher on and off cases, while the sweeper magnet is on, is about 20%. It has also been observed in the experiment that the application of external RF voltage of 120 volts/turn was able to reduce the signal

  11. Achievement, motivation, and educational choices: A longitudinal study of expectancy and value using a multiplicative perspective.

    PubMed

    Guo, Jiesi; Parker, Philip D; Marsh, Herbert W; Morin, Alexandre J S

    2015-08-01

    Drawing on the expectancy-value model, the present study explored individual and gender differences in university entry and selection of educational pathway (e.g., science, technology, engineering, and mathematics [STEM] course selection). In particular, we examined the multiplicative effects of expectancy and task values on educational outcomes during the transition into early adulthood. Participants were from a nationally representative longitudinal sample of 15-year-old Australian youths (N = 10,370). The results suggest that (a) both math self-concept and intrinsic value interact in predicting advanced math course selection, matriculation results, entrance into university, and STEM fields of study; (b) prior reading achievement has negative effects on advanced math course selection and STEM fields through math motivational beliefs; and (c) gender differences in educational outcomes are mediated by gender differences in motivational beliefs and prior academic achievement, while the processes underlying choice of educational pathway were similar for males and females.

  12. Relativistic electron beam driven longitudinal wake-wave breaking in a cold plasma

    NASA Astrophysics Data System (ADS)

    Bera, Ratan Kumar; Mukherjee, Arghya; Sengupta, Sudip; Das, Amita

    2016-08-01

    Space-time evolution of a relativistic electron beam driven wake-field in a cold, homogeneous plasma is studied using 1D-fluid simulation techniques. It is observed that the wake wave gradually evolves and eventually breaks, exhibiting sharp spikes in the density profile and sawtooth like features in the electric field profile [Bera et al., Phys. Plasmas 22, 073109 (2015)]. It is shown here that the excited wakefield is a longitudinal Akhiezer-Polovin mode [A. I. Akhiezer and R. V. Polovin, Sov. Phys. JETP 3, 696 (1956)] and its steepening (breaking) can be understood in terms of phase mixing of this mode, which arises because of relativistic mass variation effects. Further, the phase mixing time (breaking time) is studied as a function of beam density and beam velocity and is found to follow the well known scaling presented by Mukherjee and Sengupta [Phys. Plasmas 21, 112104 (2014)].

  13. Achievement, motivation, and educational choices: A longitudinal study of expectancy and value using a multiplicative perspective.

    PubMed

    Guo, Jiesi; Parker, Philip D; Marsh, Herbert W; Morin, Alexandre J S

    2015-08-01

    Drawing on the expectancy-value model, the present study explored individual and gender differences in university entry and selection of educational pathway (e.g., science, technology, engineering, and mathematics [STEM] course selection). In particular, we examined the multiplicative effects of expectancy and task values on educational outcomes during the transition into early adulthood. Participants were from a nationally representative longitudinal sample of 15-year-old Australian youths (N = 10,370). The results suggest that (a) both math self-concept and intrinsic value interact in predicting advanced math course selection, matriculation results, entrance into university, and STEM fields of study; (b) prior reading achievement has negative effects on advanced math course selection and STEM fields through math motivational beliefs; and (c) gender differences in educational outcomes are mediated by gender differences in motivational beliefs and prior academic achievement, while the processes underlying choice of educational pathway were similar for males and females. PMID:26053150

  14. Longitudinal effects of ionospheric responses to substorms at middle and lower latitudes: a case study

    NASA Astrophysics Data System (ADS)

    Pi, Xiaoqing; Mendillo, Michael; Spalla, Paolo; Anderson, David N.

    1995-08-01

    An ionospheric model is used to simulate total electron content (TEC) disturbance events observed at middle and lower latitude sites near 75°W and 7°E longitudes. Within this longitudinal range, daytime TEC disturbances show patterns that are correlated with substrom activity seen in both auroral electrojet and ring current behavior. In modeling studies of the observed ionospheric effects, both electric field and neutral wind perturbations are examined as possible mechanisms. The morphological features of the required electric field perturbations near drawn and dusk are compared with those at other times to examine the local time characteristics of magnetospheric influence. Large-scale traveling atmospheric disturbances (TADs), an alternative candidate for the disturbance source, are also characterized and compared with known thermospheric behavior.

  15. Nonlinear Cascade Strategy for Longitudinal Control of Electric Vehicle.

    PubMed

    El Majdoub, K; Giri, F; Ouadi, H; Chaoui, F Z

    2014-01-01

    The problem of controlling the longitudinal motion of front-wheels electric vehicle (EV) is considered making the focus on the case where a single dc motor is used for both front wheels. Chassis dynamics are modelled applying relevant fundamental laws taking into account the aerodynamic effects and the road slope variation. The longitudinal slip, resulting from tire deformation, is captured through Kiencke's model. Despite its highly nonlinear nature the complete model proves to be utilizable in longitudinal control design. The control objective is to achieve a satisfactory vehicle speed regulation in acceleration/deceleration stages, despite wind speed and other parameters uncertainty. An adaptive controller is developed using the backstepping design technique. The obtained adaptive controller is shown to meet its objectives in presence of the changing aerodynamics efforts and road slope.

  16. [The problem of repeated measurements. Longitudinal analysis in epidemiology].

    PubMed

    Sáez, M

    2001-01-01

    In longitudinal analyses subjects are repeatedly measured along time. They are mixed designs, characterised for their simultaneous consideration of two or more dimensions of analysis, in which time is one of the dimensions.Longitudinal analyses have important advantages with respect other designs. The most important is that they are more efficient, since they allow to distinguish between-individual and within-individual variation.Longitudinal analyses can be approached marginal and conditionally. Whereas the former allows to draw poblational, or average, inferences, the latter permits to draw individual inferences.The statistical models to use depend on the type of response variable. If the dependent variable is normally distributed one will use linear mixed models. When the response is a count one will use mixed Poisson regressions. Mixed binomial or multinomial logistic regressions should be used when the response would be categorical.

  17. Using Administrative Data for Longitudinal Substance Abuse Research

    PubMed Central

    Evans, Elizabeth; Grella, Christine E.; Murphy, Debra A.; Hser, Yih-Ing

    2008-01-01

    The utilization of administrative data in substance abuse research has become more widespread than ever. This selective review synthesizes recent extant research from 31 articles to consider what has been learned from using administrative data to conduct longitudinal substance abuse research in four overlapping areas: (1) service access and utilization, (2) underrepresented populations, (3) treatment outcomes, and (4) cost analysis. Despite several notable limitations, administrative data contribute valuable information, particularly in the investigation of service system interactions and outcomes among substance abusers as they unfold and influence each other over the long term. This critical assessment of the advantages and disadvantages of using existing administrative data within a longitudinal framework should stimulate innovative thinking regarding future applications of administrative data for longitudinal substance abuse research purposes. PMID:18679805

  18. Young's modulus of BF wood material by longitudinal vibration

    NASA Astrophysics Data System (ADS)

    Phadke, Sushil; Darshan Shrivastava, Bhakt; Mishra, Ashutosh; Dagaonkar, N.

    2014-09-01

    All engineered structures are designed and built with consideration of resisting the same fundamental forces of tension, compression, shear, bending and torsion. Structural design is a balance of these internal and external forces. So, it is interesting to calculate the Young's moduli of Borassus Flabellifier BF wood are quite important from the application point of view. The ultrasonic waves are closely related with the elastic and inelastic properties of the materials. In the present study, we measured longitudinal wave ultrasonic velocities in BF wood material by longitudinal vibration method. After measuring ultrasonic velocity in BF wood material, we calculated Young's modulus of Borassus Flabellifier BF wood material. We used ultrasonic interferometer for measuring longitudinal wave ultrasonic velocity in BF wood material made by Mittal Enterprises, New Delhi, India in our laboratory. Borassus Flabellifier BF wood material was collected from Dhar district of Madhya Pradesh, India.

  19. Decorrelation of anisotropic flow along the longitudinal direction

    NASA Astrophysics Data System (ADS)

    Pang, Long-Gang; Petersen, Hannah; Qin, Guang-You; Roy, Victor; Wang, Xin-Nian

    2016-04-01

    The initial energy density distribution and fluctuations in the transverse direction lead to anisotropic flow of final hadrons through collective expansion in high-energy heavy-ion collisions. Fluctuations along the longitudinal direction, on the other hand, can result in decorrelation of anisotropic flow in different regions of pseudorapidity ( η . Decorrelation of the 2nd- and 3rd-order anisotropic flow with different η gaps for final charged hadrons in high-energy heavy-ion collisions is studied in an event-by-event (3+1)D ideal hydrodynamic model with fully fluctuating initial conditions from A Multi-Phase Transport (AMPT) model. The decorrelation of anisotropic flow of final hadrons with large η gaps is found to originate from the spatial decorrelation along the longitudinal direction in the AMPT initial conditions through hydrodynamic evolution. The decorrelation is found to consist of both a linear twist and random fluctuation of the event plane angles. The agreement between our results and recent CMS data in most centralities suggests that the string-like mechanism of initial parton production in AMPT model captures the initial longitudinal fluctuation that is responsible for the measured decorrelation of anisotropic flow in Pb+Pb collisions at LHC. Our predictions for Au+Au collisions at the highest RHIC energy show stronger longitudinal decorrelation, indicating larger longitudinal fluctuations at lower beam energies. Our study also calls into question some of the current experimental methods for measuring anisotropic flow and the quantitative extraction of transport coefficients through comparisons to hydrodynamic simulations that do not include longitudinal fluctuations.

  20. Positive illusions in marital relationships: a 13-year longitudinal study.

    PubMed

    Miller, Paul J E; Niehuis, Sylvia; Huston, Ted L

    2006-12-01

    This study examined the long-term consequences of idealization in marriage, using both daily diary and questionnaire data collected from a sample of 168 newlywed couples who participated in a 4-wave, 13-year longitudinal study of marriage. Idealization was operationalized as the tendency for people to perceive their partner as more agreeable than would be expected based on their reports of their partner's agreeable and disagreeable behaviors. Spouses who idealized one another were more in love with each other as newlyweds. Longitudinal analyses suggested that spouses were less likely to suffer declines in love when they idealized one another as newlyweds. Newlywed levels of idealization did not predict divorce.

  1. Longitudinal phase space experiments on the ELSA photoinjector

    SciTech Connect

    Dowell, D.H.; Joly, S.; Brion, J.P. de

    1995-12-31

    The excellent beam quality produced by RF photocathode injectors is well established, andhas been verified by numerous measurements of the transverse emittance. However, there are few experimental determinations of the longitudinal phase space. This paper reports on experiments performed at the ELSA FEL facility to emasure the longitudinal phase space distribution at the exit of the 144 MHz photoinjector cavity. Phase spaces were determined by the analysis of beam energy spectra and pulse shapes at 17.5 MeV for micropulse charges between 0.5 and 5 nC.

  2. Longitudinal cerebral blood flow and amyloid deposition: an emerging pattern?

    PubMed Central

    Sojkova, Jitka; Beason-Held, Lori; Zhou, Yun; An, Yang; Kraut, Michael A; Ye, Weigo; Ferrucci, Luigi; Mathis, Chester A; Klunk, William E; Wong, Dean F; Resnick, Susan M

    2008-01-01

    Although cerebral amyloid deposition may precede cognitive impairment by decades, the relationship between amyloid deposition and longitudinal change in neuronal function has not been studied. The aim of this paper is to determine whether nondemented individuals with high and low amyloid burden show different patterns of longitudinal regional cerebral blood flow (rCBF) changes in the years preceding measurement of amyloid deposition. Methods Twenty-eight nondemented participants (mean (SD) age at [11C] PIB 82.5(4.8) yrs; 6 mildly impaired) from the Baltimore Longitudinal Study of Aging underwent yearly resting-state [15O]H2O PET scans for up to 8 years. [11C]PIB images of amyloid deposition were acquired on average 10.8(0.8) years after the first CBF scan. [11C]PIB distribution volume ratios (DVR) of regions of interest were estimated by fitting a reference tissue model to the measured time activity curves. Based on mean cortical DVR, participants were divided into high and low [11C]PIB retention groups. Differences in longitudinal rCBF changes between high and low [11C]PIB groups were investigated by voxel-based analysis. Results Longitudinal rCBF changes differed significantly between high (n=10) and low (n=18) [11C]PIB groups (p<=0.001). Greater longitudinal decreases in rCBF in the high [11C]PIB group were seen in right anterior/mid cingulate, right supramarginal gyrus, left thalamus and midbrain bilaterally relative to the low group. Greater increases in rCBF over time in the high [11C]PIB group were found in left medial and inferior frontal gyri, right precuneus, left inferior parietal lobule, and the left postcentral gyrus. Conclusion In this group of nondemented older adults, those with high [11C]PIB show greater longitudinal declines in rCBF in certain areas, representing regions with greater decrements in neuronal function. Greater longitudinal increases in rCBF are also observed in those with higher amyloid load and may represent an attempt to preserve

  3. Inference for longitudinal data with nonignorable nonmonotone missing responses

    PubMed Central

    Sinha, Sanjoy K.; Kaushal, Amit; Xiao, Wenzhong

    2014-01-01

    For the analysis of longitudinal data with nonignorable and nonmonotone missing responses, a full likelihood method often requires intensive computation, especially when there are many follow-up times. The authors propose and explore a Monte Carlo method, based on importance sampling, for approximating the maximum likelihood estimators. The finite-sample properties of the proposed estimators are studied using simulations. An application of the proposed method is also provided using longitudinal data on peptide intensities obtained from a proteomics experiment of trauma patients. PMID:25435599

  4. 3. Framework for the longitudinal phases of disasters.

    PubMed

    2014-05-01

    The longitudinal framework facilitates the analysis of disasters by providing a series of phases based on properties rather than on absolute times. This framework allows the comparison of similar phases of a disaster regardless of the hazard involved and the society impacted. The phases, which may overlap include the: (1) pre-event state; (2) event; (3) damage; (4) changes in societal functions; (5) relief interventions; and (6) recovery interventions. Development is not a phase of a disaster and is addressed separately. For research and evaluation purposes, assessments, plans, and interventions must be described in relation to only one of the longitudinal phases of a disaster.

  5. Longitudinal vector form factors in weak decays of nuclei

    SciTech Connect

    Šimkovic, F.; Kovalenko, S.; Krivoruchenko, M. I.

    2015-10-28

    The longitudinal form factors of the weak vector current of particles with spin J = 1/2 and isospin I = 1/2 are determined by the mass difference and the charge radii of members of the isotopic doublets. The most promising reactions to measure these form factors are the reactions with large momentum transfers involving the spin-1/2 isotopic doublets with a maximum mass splitting. Numerical estimates of longitudinal form factors are given for nucleons and eight nuclear spin-1/2 isotopic doublets.

  6. A Simple, Low Cost Longitudinal Phase Space Diagnostic

    SciTech Connect

    Bertsche, Kirk; Emma, Paul; Shevchenko, Oleg; /Novosibirsk, IYF

    2009-05-15

    For proper operation of the LCLS [1] x-ray free-electron laser (FEL), and other similar machines, measurement and control of the electron bunch longitudinal phase space is critical. The LCLS accelerator includes two bunch compressor chicanes to magnify the peak current. These magnetic chicanes can generate significant coherent synchrotron radiation (CSR), which can distort the phase space distribution. We propose a diagnostic scheme by exciting a weak skew quadrupole at an energy-chirped, high dispersion point in the first LCLS bunch compressor (BC1) to reconstruct longitudinal phase space on an OTR screen after BC1, allowing a time-resolved characterization of CSR effects.

  7. Longitudinal fMRI analysis: A review of methods

    PubMed Central

    Skup, Martha

    2010-01-01

    Functional magnetic resonance imaging (fMRI) investigations of a longitudinal nature, where participants are scanned repeatedly over time and imaging data are obtained at more than one time-point, are essential to understanding functional changes and development in healthy and pathological brains. The main objective of this paper is to provide a brief summary of common longitudinal analysis approaches, develop an overview of fMRI by introducing how such data manifest, and explore the statistical challenges that arise at the intersection of these two techniques. PMID:21691445

  8. Longitudinal fMRI analysis: A review of methods

    PubMed Central

    Skup, Martha

    2011-01-01

    Functional magnetic resonance imaging (fMRI) investigations of a longitudinal nature, where participants are scanned repeatedly over time and imaging data are obtained at more than one time-point, are essential to understanding functional changes and development in healthy and pathological brains. The main objective of this paper is to provide a brief summary of common longitudinal analysis approaches, develop an overview of fMRI by introducing how such data manifest, and explore the statistical challenges that arise at the intersection of these two techniques. PMID:22655113

  9. Wake Fields in the Super B Factory Interaction Region

    SciTech Connect

    Weathersby, Stephen; Novokhatski, Alexander; /SLAC

    2011-06-02

    The geometry of storage ring collider interaction regions present an impedance to beam fields resulting in the generation of additional electromagnetic fields (higher order modes or wake fields) which affect the beam energy and trajectory. These affects are computed for the Super B interaction region by evaluating longitudinal loss factors and averaged transverse kicks for short range wake fields. Results indicate at least a factor of 2 lower wake field power generation in comparison with the interaction region geometry of the PEP-II B-factory collider. Wake field reduction is a consderation in the Super B design. Transverse kicks are consistent with an attractive potential from the crotch nearest the beam trajectory. The longitudinal loss factor scales as the -2.5 power of the bunch length. A factor of 60 loss factor reduction is possible with crotch geometry based on an intersecting tubes model.

  10. Magnetic field control of the spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Ritzmann, Ulrike; Hinzke, Denise; Kehlberger, Andreas; Guo, Er-Jia; Kläui, Mathias; Nowak, Ulrich

    2015-11-01

    The origin of the suppression of the longitudinal spin Seebeck effect by applied magnetic fields is studied. We perform numerical simulations of the stochastic Landau-Lifshitz-Gilbert equation of motion for an atomistic spin model and calculate the magnon accumulation in linear temperature gradients for different strengths of applied magnetic fields and different length scales of the temperature gradient. We observe a decrease of the magnon accumulation with increasing magnetic field and we reveal that the origin of this effect is a field dependent change of the frequency distribution of the propagating magnons. With increasing field the magnonic spin currents are reduced due to a suppression of parts of the frequency spectrum. By comparison with measurements of the magnetic field dependent longitudinal spin Seebeck effect in YIG thin films with various thicknesses, we find qualitative agreement between our model and the experimental data, demonstrating the importance of this effect for experimental systems.

  11. Nonlinear amplification of instabilities with longitudinal expansion

    NASA Astrophysics Data System (ADS)

    Berges, Jürgen; Boguslavski, Kirill; Schlichting, Sören

    2012-04-01

    We study the dynamics of nonequilibrium instabilities in anisotropically expanding systems. The most prominent example of such a system is the “glasma” in the context of relativistic heavy-ion collision experiments, where the expansion is a consequence of approximately boost-invariant initial conditions. Here we consider the problem of parametric resonance in scalar N-component quantum field theories with boost-invariant initial conditions, which is similar in spirit. We find that many aspects of the dynamics can be treated analytically by introducing a generalized conformal time. Primary instabilities, which are described by the linearized evolution equations, are seen to lead to a secondary regime of amplifications with strongly enhanced growth rates due to nonlinear corrections. For the secondary instabilities we present a power-counting scheme for weak coupling, and discuss their role for the question of isotropization and the establishment of an equation of state.

  12. The effect of a liquid layer and tides on the longitudinal libration of Mercury and of large icy satellites

    NASA Astrophysics Data System (ADS)

    Van Hoolst, T.

    2012-09-01

    The gravitational forcing from a central primary body not only induces tides in secondary bodies in spinorbit resonance around the primary but also small periodic variations in the rotation rate, or forced longitudinal librations. In view of the recent observations of these librations and of the low-degree gravitational field for Mercury, we study the effect of tides and the existence of a solid inner core on the librations of Mercury, which is in a 3:2 spin-orbit resonance. We also theoretically estimate the amplitude of longitudinal librations of Titan and the Galilean satellites, satellites for which accurate rotation data is already available thanks to the Cassini mission or will be measured in the future by the JUICE mission to the Jupiter system, recently selected as the first L-class mission of the cosmic vision program of ESA. We show that observations of rotation data can yield important information on the interior structure.

  13. [Longitudinal change in independence in the elderly--Kahoku Longitudinal Aging Study (KLAS)].

    PubMed

    Matsubayashi, K; Okumiya, K; Kawamoto, A; Kimura, S; Wada, T; Fujisawa, M; Doi, Y; Shimada, K; Ozawa, T

    1994-10-01

    A community based study named Kahoku Longitudinal Aging Study (KLAS) was conducted since 1990 for the purpose of evaluating the comprehensive geriatric functional assessment (CGA) and preventing a decline in CGA in the community-dwelling elderly population. It was carried out in a Japanese rural town, in which 32% of the population was over 65 years of age. This study included a questionnaire about activity of daily living (ADL), information-related physical function, mental (cognitive and affective) and social functional domains. In addition to subjective informative instruments, various types of objective assessment such as quantitative neuro-behavioral function tests and medical examinations were performed. Subjects were all the eligible elderly aged over 65 years in the community. Although the ratio of subjects who were independent in ADL decreased with advancing age in both 1991 and 1993, the ratio of the independent elderly in ADL became significant higher (74%) in 1993 than in 1991 (71%). Scores on 2 kinds of neurobehavioral function tests in the 159 subjects aged over 75 years who attended the examination every year showed a significant and slight decrease during two years. However, some test indices significantly improved during the 2 years. These results suggested that age-related dependency in ADL and some kind of neurobehavioral functions might be prevented, in part, by health promoting education and improvement of life style. PMID:7853739

  14. On the Robustness of the Pendulum Model for Large-amplitude Longitudinal Oscillations in Prominences

    NASA Astrophysics Data System (ADS)

    Luna, M.; Terradas, J.; Khomenko, E.; Collados, M.; de Vicente, A.

    2016-02-01

    Large-amplitude longitudinal oscillations (LALOs) in prominences are spectacular manifestations of solar activity. In such events nearby energetic disturbances induce periodic motions on filaments with displacements comparable to the size of the filaments themselves and with velocities larger than 20 {km} {{{s}}}-1. The pendulum model, in which the gravity projected along a rigid magnetic field is the restoring force, was proposed to explain these events. However, it can be objected that in a realistic situation where the magnetic field reacts to the mass motion of the heavy prominence, the simplified pendulum model could be no longer valid. We have performed nonlinear time-dependent numerical simulations of LALOs considering a dipped magnetic field line structure. In this work we demonstrate that for even relatively weak magnetic fields the pendulum model works very well. We therefore validate the pendulum model and show its robustness, with important implications for prominence seismology purposes. With this model it is possible to infer the geometry of the dipped field lines that support the prominence.

  15. Longitudinal spin relaxation of donor-bound electrons in direct band-gap semiconductors

    NASA Astrophysics Data System (ADS)

    Linpeng, Xiayu; Karin, Todd; Durnev, M. V.; Barbour, Russell; Glazov, M. M.; Sherman, E. Ya.; Watkins, S. P.; Seto, Satoru; Fu, Kai-Mei C.

    2016-09-01

    We measure the donor-bound electron longitudinal spin-relaxation time (T1) as a function of magnetic field (B ) in three high-purity direct band-gap semiconductors: GaAs, InP, and CdTe, observing a maximum T1 of 1.4, 0.4, and 1.2 ms, respectively. In GaAs and InP at low magnetic field, up to ˜2 T, the spin-relaxation mechanism is strongly density and temperature dependent and is attributed to the random precession of the electron spin in hyperfine fields caused by the lattice nuclear spins. In all three semiconductors at high magnetic field, we observe a power-law dependence T1∝B-ν with 3 ≲ν ≲4 . Our theory predicts that the direct spin-phonon interaction is important in all three materials in this regime in contrast to quantum dot structures. In addition, the "admixture" mechanism caused by Dresselhaus spin-orbit coupling combined with single-phonon processes has a comparable contribution in GaAs. We find excellent agreement between high-field theory and experiment for GaAs and CdTe with no free parameters, however a significant discrepancy exists for InP.

  16. A biophysical model of brain deformation to simulate and analyze longitudinal MRIs of patients with Alzheimer's disease.

    PubMed

    Khanal, Bishesh; Lorenzi, Marco; Ayache, Nicholas; Pennec, Xavier

    2016-07-01

    We propose a framework for developing a comprehensive biophysical model that could predict and simulate realistic longitudinal MRIs of patients with Alzheimer's disease (AD). The framework includes three major building blocks: i) atrophy generation, ii) brain deformation, and iii) realistic MRI generation. Within this framework, this paper focuses on a detailed implementation of the brain deformation block with a carefully designed biomechanics-based tissue loss model. For a given baseline brain MRI, the model yields a deformation field imposing the desired atrophy at each voxel of the brain parenchyma while allowing the CSF to expand as required to globally compensate for the locally prescribed volume loss. Our approach is inspired by biomechanical principles and involves a system of equations similar to Stokes equations in fluid mechanics but with the presence of a non-zero mass source term. We use this model to simulate longitudinal MRIs by prescribing complex patterns of atrophy. We present experiments that provide an insight into the role of different biomechanical parameters in the model. The model allows simulating images with exactly the same tissue atrophy but with different underlying deformation fields in the image. We explore the influence of different spatial distributions of atrophy on the image appearance and on the measurements of atrophy reported by various global and local atrophy estimation algorithms. We also present a pipeline that allows evaluating atrophy estimation algorithms by simulating longitudinal MRIs from large number of real subject MRIs with complex subject-specific atrophy patterns. The proposed framework could help understand the implications of different model assumptions, regularization choices, and spatial priors for the detection and measurement of brain atrophy from longitudinal brain MRIs.

  17. Hexamethonium-induced augmentation of the electrical twitch response in the guinea-pig ileum longitudinal muscle-myenteric plexus strip.

    PubMed

    Donnerer, Josef; Liebmann, Ingrid; Holzer-Petsche, Ulrike

    2014-08-01

    Longitudinal muscle-myenteric plexus strips of the guinea-pig ileum were used to investigate the nature of the hexamethonium-induced augmentation of the twitch response. All preparations were set up in Tyrode solution and intermittent longitudinal twitch contractions were evoked by single pulse electrical field stimulation. Hexamethonium, a blocker of nicotinic ganglionic transmission, at 300 μmol/l and 1 mmol/l augmented the twitch contractions by 21% and 35%, respectively. First we tested for a possible nicotinic drive onto an inhibitory neuronal component to the longitudinal smooth muscle cells. However, guanethidine (5 μmol/l), naloxone (1 μmol/l), or l-NAME (300 μmol/l) were without effect on the hexamethonium-induced augmentation. The P2 purinoceptor antagonist pyridoxalphosphate-6-azophenyl-2'-4'-disulphonic acid (PPADS), 25-100 μmol/l, without altering the control twitch responses, dose-dependently reduced the hexamethonium-induced augmentation; at 100 μmol/l a statistically significantly inhibition was observed. Based on these functional experiments we found no evidence that blocking nicotinic transmission removed a tonic adrenergic, opioidergic or nitrergic inhibitory input to the longitudinal muscle. However, we provide evidence for a hexamethonium-induced augmentation of the P2 purinergic input to cholinergic motoneurons of the guinea-pig ileum longitudinal muscle. The P2-nicotinic receptor interaction presents a novel modulatory mechanism to cholinergic myenteric motor neurons. PMID:24933535

  18. Sex Differences in the Longitudinal Prediction of Adult Personality.

    ERIC Educational Resources Information Center

    Sutton-Smith, B.; Rosenberg, B. G.

    This paper deals with two sets of data-one that fails to find any long-term sex differences in adults, and another which seems to find such differences. The Berkeley Guidance Study offers longitudinal data in which no variables differentiate between the two sexes at all age levels. From these results, the authors conclude that the normal course of…

  19. Children's Perceptions of Live Arts Performances: A Longitudinal Study

    ERIC Educational Resources Information Center

    Schiller, Wendy

    2005-01-01

    "Children?s Voices" is a longitudinal research project to document and understand children's perceptions of live arts performance and the impact on their teachers and school communities. The research conducted in South Australia with 135 5?12-year-olds in four schools involves collaboration between the South Australian Department of Education and…

  20. A Longitudinal Investigation of Peer Sexual Harassment Victimization in Adolescence

    ERIC Educational Resources Information Center

    Petersen, Jennifer L.; Hyde, Janet Shibley

    2009-01-01

    The current study describes longitudinal trends in sexual harassment by adolescent peers and highlights gender, pubertal status, attractiveness, and power as predictors of harassment victimization. At the end of 5th, 7th, and 9th grades, 242 adolescents completed questionnaires about sexual harassment victimization, pubertal status, and perceived…

  1. 46 CFR 154.176 - Longitudinal contiguous hull structure.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... (2) Maintained by the heating system under § 154.178, if, without heat, the contiguous hull structure... hull structure of a vessel having cargo containment systems without secondary barriers must meet the...”, 1981. (b) The longitudinal contiguous hull structure of a vessel having cargo containment systems...

  2. 46 CFR 154.176 - Longitudinal contiguous hull structure.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... (2) Maintained by the heating system under § 154.178, if, without heat, the contiguous hull structure... hull structure of a vessel having cargo containment systems without secondary barriers must meet the...”, 1981. (b) The longitudinal contiguous hull structure of a vessel having cargo containment systems...

  3. 46 CFR 154.176 - Longitudinal contiguous hull structure.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... (2) Maintained by the heating system under § 154.178, if, without heat, the contiguous hull structure... hull structure of a vessel having cargo containment systems without secondary barriers must meet the...”, 1981. (b) The longitudinal contiguous hull structure of a vessel having cargo containment systems...

  4. 46 CFR 154.176 - Longitudinal contiguous hull structure.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... (2) Maintained by the heating system under § 154.178, if, without heat, the contiguous hull structure... hull structure of a vessel having cargo containment systems without secondary barriers must meet the...”, 1981. (b) The longitudinal contiguous hull structure of a vessel having cargo containment systems...

  5. Traumatic longitudinal splitting of the inferior rectus muscle

    PubMed Central

    Laursen, Jessica; Demer, Joseph L.

    2011-01-01

    Orbital floor fractures and associated injuries can cause strabismus. We present the case of a 34-year-old man with incomitant strabismus following orbital reconstruction after a high-impact baseball injury. Multipositional, high-resolution magnetic resonance imaging (MRI) revealed extensive longitudinal splitting of the inferior rectus muscle by an orbital floor implant that separated its orbital and global layers. PMID:21463958

  6. First Results of the LHC Longitudinal Density Monitor

    SciTech Connect

    Jeff, A.; Boccardi, A.; Bravin, E.; Fisher, A.S.; Lefevre, T.; Rabiller, A.; Roncarolo, F.; Welsch, C.P.; /Liverpool U. /Cockcroft Inst. Accel. Sci. Tech.

    2012-04-19

    The Large Hadron Collider (LHC) at CERN is the world's largest particle accelerator. It is designed to accelerate and collide protons or heavy ions up to the center-of-mass energies of 14 TeV. Knowledge of the longitudinal distribution of particles is important for various aspects of accelerator operation, in particular to check the injection quality and to measure the proportion of charge outside the nominally filled bunches during the physics periods. In order to study this so-called ghost charge at levels very much smaller than the main bunches, a longitudinal profile measurement with a very high dynamic range is needed. A new detector, the LHC Longitudinal Density Monitor (LDM) is a single-photon counting system measuring synchrotron light by means of an avalanche photodiode detector. The unprecedented energies reached in the LHC allow synchrotron light diagnostics to be used with both protons and heavy ions. A prototype was installed during the 2010 LHC run and was able to longitudinally profile the whole ring with a resolution close to the target of 50 ps. On-line correction for the effects of the detector deadtime, pile-up and afterpulsing allow a dynamic range of 105 to be achieved. First measurements with the LDM are presented here along with an analysis of its performance and an outlook for future upgrades.

  7. Assessing Longitudinal Change: Adjustment for Regression to the Mean Effects

    ERIC Educational Resources Information Center

    Rocconi, Louis M.; Ethington, Corinna A.

    2009-01-01

    Pascarella (J Coll Stud Dev 47:508-520, 2006) has called for an increase in use of longitudinal data with pretest-posttest design when studying effects on college students. However, such designs that use multiple measures to document change are vulnerable to an important threat to internal validity, regression to the mean. Herein, we discuss a…

  8. A Longitudinal Study of Children's Social Adjustment during Elementary School.

    ERIC Educational Resources Information Center

    Battistich, Victor; Solomon, Daniel

    A 7-year, longitudinal study of children's social development from kindergarten through sixth grade was designed to identify unusually prosocial children and characteristics that differentiated them from average and antisocial peers. Another objective was to identify functional socioemotional predictors of changes in children's social adjustment.…

  9. A Longitudinal Study of ESL Learners' Fluency and Comprehensibility Development

    ERIC Educational Resources Information Center

    Derwing, Tracey M.; Munro, Murray J.; Thomson, Ron I.

    2008-01-01

    This longitudinal mixed-methods study compared the oral fluency of well-educated adult immigrants from Mandarin and Slavic language backgrounds (16 per group) enrolled in introductory English as a second language (ESL) classes. Speech samples were collected over a 2-year period, together with estimates of weekly English use. We also conducted…

  10. 15. DETAIL OF UNDERSIDE OF BRIDGE, SHOWING LONGITUDINAL STRINGERS SUPPORTING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. DETAIL OF UNDERSIDE OF BRIDGE, SHOWING LONGITUDINAL STRINGERS SUPPORTING WOODEN DECK AND RESTING ON TRANSVERSE FLOOR BEAMS. DIAGONAL EYE BARS FOR REINFORCEMENT ARE SEEN AT CENTER; VIEW FROM SOUTH BANK. - Mitchell's Mill Bridge, Spanning Winter's Run on Carrs Mill Road, west of Bel Air, Bel Air, Harford County, MD

  11. Nonlinear Latent Curve Models for Multivariate Longitudinal Data

    ERIC Educational Resources Information Center

    Blozis, Shelley A.; Conger, Katherine J.; Harring, Jeffrey R.

    2007-01-01

    Latent curve models have become a useful approach to analyzing longitudinal data, due in part to their allowance of and emphasis on individual differences in features that describe change. Common applications of latent curve models in developmental studies rely on polynomial functions, such as linear or quadratic functions. Although useful for…

  12. Predictors of Longitudinal Growth in Inhibitory Control in Early Childhood

    ERIC Educational Resources Information Center

    Moilanen, Kristin L.; Shaw, Daniel S.; Dishion, Thomas J.; Gardner, Frances; Wilson, Melvin

    2010-01-01

    In the current study, we examined latent growth in 731 young children's inhibitory control from the ages of two to four years, and whether demographic characteristics or parenting behaviors were related to initial levels and growth in inhibitory control. As part of an ongoing longitudinal evaluation of the family check-up, children's inhibitory…

  13. Suprasegmental Phonology Development and Reading Acquisition: A Longitudinal Study

    ERIC Educational Resources Information Center

    Calet, Nuria; Gutiérrez-Palma, Nicolás; Simpson, Ian C.; González-Trujillo, M. Carmen; Defior, Sylvia

    2015-01-01

    Previous studies implicate suprasegmental phonology in reading acquisition. However, little is known about how suprasegmental sensitivity develops or how it contributes to reading. Here, 130 Spanish primary-school children participated in this 2-year longitudinal study. Nonlinguistic rhythm, lexical-stress sensitivity and metrical-stress…

  14. English as a Foreign Language Spelling Development: A Longitudinal Study

    ERIC Educational Resources Information Center

    Kahn-Horwitz, Janina; Sparks, Richard L.; Goldstein, Zahava

    2012-01-01

    English as a foreign language (EFL) spelling was examined longitudinally three times (4th, 9th, 12th grades) during 9 years of EFL study among Hebrew first language (L1) students. The study examined the impact of L1 literacy variables including phonemic awareness, word attack, and spelling on EFL spelling and the relationship between EFL literacy…

  15. A Longitudinal Study of Pretend Play in Autism

    ERIC Educational Resources Information Center

    Rutherford, M. D.; Young, Gregory S.; Hepburn, Susan; Rogers, Sally J.

    2007-01-01

    This study describes a longitudinal design (following subjects described in Rutherford & Rogers [2003, "Journal of Autism and Developmental Disorder", 33, 289-302]) to test for predictors of pretend play competence in a group of children with autism. We tested the hypothesis that developmental change in pretend play performance can be predicted by…

  16. Career Trajectories of Dutch Pop Musicians: A Longitudinal Study

    ERIC Educational Resources Information Center

    Zwaan, Koos; ter Bogt, Tom F. M.; Raaijmakers, Quinten

    2010-01-01

    Systematic studies of artistic careers are scarce and this is the first large-scale study on the career development of pop musicians. Using a prospective longitudinal approach we followed a sample of aspiring pop musicians in the Netherlands (N=369) over a three-year period. First we identified four groups of pop musicians with different career…

  17. A Longitudinal Study of Engineering Students' Approaches to Their Studies

    ERIC Educational Resources Information Center

    Jungert, Tomas

    2008-01-01

    This longitudinal study draws on data from a larger project and examines how students' perceptions of their opportunities to influence their study environment may be enacted in approaches aimed at influencing their studies, and whether this changes during the course of their studies. Ten students from a 4.5-year Master's program in Engineering…

  18. 49 CFR 238.405 - Longitudinal static compressive strength.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... crash refuge for crewmembers occupying the cab of a power car, the underframe of the cab of a power car... volumes of a power car or a trailer car designed to crush as part of the crash energy management design...) The underframe of the occupied volume of each trailer car shall resist a minimum longitudinal...

  19. Conduct, Biological Factors and Adult Delinquency in a Longitudinal Perspective.

    ERIC Educational Resources Information Center

    Magnusson, David

    In the course of a longitudinal research program conducted in Sweden, data were being collected on biological and psychological aspects of individual functioning and on environmental factors for a fairly large representative sample (approximately 1,000) of Swedish males and females between 10 and 27 years of age. Based on data from the…

  20. Longitudinal stress fracture of the femur: A rare presentation

    PubMed Central

    Bilreiro, Carlos; Bahia, Carla; Castro, Miguel Oliveira e

    2016-01-01

    We present the case of an 80 year old woman with hip pain, caused by a longitudinal femoral insufficiency stress fracture, depicted with radiographs, CT and MR. This type of fracture is very rare, with only a few cases reported. We conducted a literature review and compared the findings with the present case. PMID:27069976

  1. Structural Damage Detection Using Slopes of Longitudinal Vibration Shapes

    DOE PAGESBeta

    Xu, W.; Zhu, W. D.; Smith, S. A.; Cao, M. S.

    2016-03-18

    While structural damage detection based on flexural vibration shapes, such as mode shapes and steady-state response shapes under harmonic excitation, has been well developed, little attention is paid to that based on longitudinal vibration shapes that also contain damage information. This study originally formulates a slope vibration shape for damage detection in bars using longitudinal vibration shapes. To enhance noise robustness of the method, a slope vibration shape is transformed to a multiscale slope vibration shape in a multiscale domain using wavelet transform, which has explicit physical implication, high damage sensitivity, and noise robustness. These advantages are demonstrated in numericalmore » cases of damaged bars, and results show that multiscale slope vibration shapes can be used for identifying and locating damage in a noisy environment. A three-dimensional (3D) scanning laser vibrometer is used to measure the longitudinal steady-state response shape of an aluminum bar with damage due to reduced cross-sectional dimensions under harmonic excitation, and results show that the method can successfully identify and locate the damage. Slopes of longitudinal vibration shapes are shown to be suitable for damage detection in bars and have potential for applications in noisy environments.« less

  2. Longitudinal Links between Early Coparenting and Infant Behaviour Problems

    ERIC Educational Resources Information Center

    LeRoy, Michelle; Mahoney, Annette; Pargament, Kenneth I.; DeMaris, Alfred

    2013-01-01

    This study of 164 married couples examined longitudinal links between parents' perceptions of coparenting support and undermining by spouse at 6 months postpartum and infant behaviour problems at the age of 12 months after controlling for marital quality, individual parenting, and infant temperament. Multiple methods (i.e. parent reports and…

  3. Longitudinal Analyses of Achievement Data from Durham County (NC) Schools.

    ERIC Educational Resources Information Center

    Williamson, Gary L.; And Others

    A longitudinal study of achievement data from public schools in Durham County, North Carolina, was undertaken to examine individual growth curves as well as to chart the progress of educational institutions and the effects of aggregation on the study of growth. A two-level hierarchical linear model was used in the study to specify individual…

  4. Generalization of Rare Variant Association Tests for Longitudinal Family Studies.

    PubMed

    Chien, Li-Chu; Hsu, Fang-Chi; Bowden, Donald W; Chiu, Yen-Feng

    2016-02-01

    Given the functional relevance of many rare variants, their identification is frequently critical for dissecting disease etiology. Functional variants are likely to be aggregated in family studies enriched with affected members, and this aggregation increases the statistical power to detect rare variants associated with a trait of interest. Longitudinal family studies provide additional information for identifying genetic and environmental factors associated with disease over time. However, methods to analyze rare variants in longitudinal family data remain fairly limited. These methods should be capable of accounting for different sources of correlations and handling large amounts of sequencing data efficiently. To identify rare variants associated with a phenotype in longitudinal family studies, we extended pedigree-based burden (BT) and kernel (KS) association tests to genetic longitudinal studies. Generalized estimating equation (GEE) approaches were used to generalize the pedigree-based BT and KS to multiple correlated phenotypes under the generalized linear model framework, adjusting for fixed effects of confounding factors. These tests accounted for complex correlations between repeated measures of the same phenotype (serial correlations) and between individuals in the same family (familial correlations). We conducted comprehensive simulation studies to compare the proposed tests with mixed-effects models and marginal models, using GEEs under various configurations. When the proposed tests were applied to data from the Diabetes Heart Study, we found exome variants of POMGNT1 and JAK1 genes were associated with type 2 diabetes. PMID:26783077

  5. Delineating the Average Rate of Change in Longitudinal Models

    ERIC Educational Resources Information Center

    Kelley, Ken; Maxwell, Scott E.

    2008-01-01

    The average rate of change is a concept that has been misunderstood in the literature. This article attempts to clarify the concept and show unequivocally the mathematical definition and meaning of the average rate of change in longitudinal models. The slope from the straight-line change model has at times been interpreted as if it were always the…

  6. A Longitudinal Study of Idiom and Text Comprehension

    ERIC Educational Resources Information Center

    Levorato, M. Chiara; Roch, Maja; Nesi, Barbara

    2007-01-01

    The relation between text and idiom comprehension in children with poor text comprehension skills was investigated longitudinally. In the first phase of the study, six-year-old first graders with different levels of text comprehension were compared in an idiom and sentence comprehension task. Text comprehension was shown to be more closely related…

  7. 15. Dry Dock No. 4. Longitudinal Section. Subdivision Nos. I ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. Dry Dock No. 4. Longitudinal Section. Subdivision Nos. I and II (Frederic R. Harris, Inc., January 10, 1941). In Files of Cushman & Wakefield, Building no. 501, Philadelphia Naval Business Center. - Naval Base Philadelphia-Philadelphia Naval Shipyard, Dry Dock No. 4, Broad Street south of Government Avenue, Philadelphia, Philadelphia County, PA

  8. 16. Dry Dock No. 4. Longitudinal Section. Subdivision Nos. III ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    16. Dry Dock No. 4. Longitudinal Section. Subdivision Nos. III and IV (Frederic R. Harris, Inc., January 10, 1941). In Files of Cushman & Wakefield, Building no. 501, Philadelphia Naval Business Center. - Naval Base Philadelphia-Philadelphia Naval Shipyard, Dry Dock No. 4, Broad Street south of Government Avenue, Philadelphia, Philadelphia County, PA

  9. 17. Dry Dock No. 4. Longitudinal Section. Subdivision V and ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. Dry Dock No. 4. Longitudinal Section. Subdivision V and Stair Details (Frederic R. Harris, Inc., January 10, 1941). In Files of Cushman & Wakefield, Building No. 501, Philadelphia Naval Business Center. - Naval Base Philadelphia-Philadelphia Naval Shipyard, Dry Dock No. 4, Broad Street south of Government Avenue, Philadelphia, Philadelphia County, PA

  10. A Bayesian semiparametric model for bivariate sparse longitudinal data.

    PubMed

    Das, Kiranmoy; Li, Runze; Sengupta, Subhajit; Wu, Rongling

    2013-09-30

    Mixed-effects models have recently become popular for analyzing sparse longitudinal data that arise naturally in biological, agricultural and biomedical studies. Traditional approaches assume independent residuals over time and explain the longitudinal dependence by random effects. However, when bivariate or multivariate traits are measured longitudinally, this fundamental assumption is likely to be violated because of intertrait dependence over time. We provide a more general framework where the dependence of the observations from the same subject over time is not assumed to be explained completely by the random effects of the model. We propose a novel, mixed model-based approach and estimate the error-covariance structure nonparametrically under a generalized linear model framework. We use penalized splines to model the general effect of time, and we consider a Dirichlet process mixture of normal prior for the random-effects distribution. We analyze blood pressure data from the Framingham Heart Study where body mass index, gender and time are treated as covariates. We compare our method with traditional methods including parametric modeling of the random effects and independent residual errors over time. We conduct extensive simulation studies to investigate the practical usefulness of the proposed method. The current approach is very helpful in analyzing bivariate irregular longitudinal traits. PMID:23553747

  11. 11. Photograph of a line drawing. SHEET 11, LONGITUDINAL SECTION ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. Photograph of a line drawing. SHEET 11, LONGITUDINAL SECTION ON LINE FF; 9-16-1940. Assembly Building for Tank Plant for the Chrysler Corporation, Macomb County, Michigan. Delineator: E.B. - Detroit Arsenal, 6501 East Eleven Mile Road, Warren, Macomb County, MI

  12. 9. Photograph of a line drawing. SHEET 9, LONGITUDINAL SECTION ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. Photograph of a line drawing. SHEET 9, LONGITUDINAL SECTION ON LINE AA; 9-16-1940. Assembly Building for Tank Plant for the Chrysler Corporation, Macomb County, Michigan. Delineator: E.B. - Detroit Arsenal, 6501 East Eleven Mile Road, Warren, Macomb County, MI

  13. A Longitudinal Study of Accounting Students' Ethical Judgement Making Ability

    ERIC Educational Resources Information Center

    Mohamed Saat, Maisarah; Porter, Stacey; Woodbine, Gordon

    2012-01-01

    This paper reports the effect of a moral education programme on the ethical judgement making ability of university students. The programme comprises two forms of intervention: a dedicated ethics course and subsequent practical training. A total of 113 accounting students from six Malaysian universities participated in a longitudinal study…

  14. Chicago EARLY Program Follow-Up: A Longitudinal Analysis.

    ERIC Educational Resources Information Center

    Perlman, Carole L.; And Others

    Since 1975, the Chicago public schools have been conducting ongoing research and development related to the identification and remediation of prekindergarten children with potential learning problems. The present study describes initial efforts toward the creation of a longitudinal data base aimed at determining (1) prekindergarten-age…

  15. Longitudinal Associations among Child Maltreatment, Social Functioning, and Cortisol Regulation

    ERIC Educational Resources Information Center

    Alink, Lenneke R. A.; Cicchetti, Dante; Kim, Jungmeen; Rogosch, Fred A.

    2012-01-01

    Child maltreatment increases the risk for impaired social functioning and cortisol regulation. However, the longitudinal interplay among these factors is still unclear. This study aimed to shed light on the effect of maltreatment on social functioning and cortisol regulation over time. The sample consisted of 236 children (mean age 7.64 years, SD…

  16. Accumulation of Welfare Problems in a Longitudinal Perspective

    ERIC Educational Resources Information Center

    Hallerod, Bjorn; Bask, Miia

    2008-01-01

    The central aim of the present paper is to analyse the degree to which welfare problems accumulate over time and to what extent such an accumulation is related to class position and household formation. We utilize longitudinal data from the Swedish Survey of Living Conditions, following a panel that was first interviewed in 1979 and, thereafter,…

  17. 34. 'Firing Pier, Longitudinal Sectional Elevation, Looking East,' submitted 29 ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    34. 'Firing Pier, Longitudinal Sectional Elevation, Looking East,' submitted 29 December 1941 by John Brackett, Consulting Engineer, to Public Works Department, Bureau of Yards & Docks. PW Drawing 3873-46, Y&D Drawing 190847. Scale 1/8' = 1'. - Naval Torpedo Station, Firing Pier, North end of Gould Island in Narragansett Bay, Newport, Newport County, RI

  18. A Longitudinal Study of Judge Leniency and Consistency.

    ERIC Educational Resources Information Center

    Lunz, Mary E.; O'Neill, Thomas R.

    This retrospective longitudinal study was designed to show grading leniency patterns of judges within and across clinical examination administrations. Data from 17 different administrations of the histology examination of the American Society of Clinical Pathologists over 10 years were studied. Over the 10 years there were 4,683 candidates and 57…

  19. A Bayesian Approach for Analyzing Longitudinal Structural Equation Models

    ERIC Educational Resources Information Center

    Song, Xin-Yuan; Lu, Zhao-Hua; Hser, Yih-Ing; Lee, Sik-Yum

    2011-01-01

    This article considers a Bayesian approach for analyzing a longitudinal 2-level nonlinear structural equation model with covariates, and mixed continuous and ordered categorical variables. The first-level model is formulated for measures taken at each time point nested within individuals for investigating their characteristics that are dynamically…

  20. Longitudinal Course of Rapid Naming in Disabled and Nondisabled Readers.

    ERIC Educational Resources Information Center

    Meyer, Marianne S.; Wood, Frank B.; Hart, Lesley A.; Felton, Rebecca H.

    1998-01-01

    The Rapid Automatized Naming Test was studied cross sectionally in a sample of kindergartners (n=342) at risk for reading disability and longitudinally in an epidemiologically normal sample of children (n=160). Findings indicate the absolute color/object naming speed was strongly related to reading level and vocabulary across grades. (Author/CR)

  1. Social Class Differentiation in Cognitive Development: A Longitudinal Study.

    ERIC Educational Resources Information Center

    Golden, Mark; And Others

    In an effort to isolate the emergence and causes of social class differences in intellectual performance, this longitudinal study was undertaken as a follow-up on a cross-sectional study that yielded no social class differences on the Cattell Infant Intelligence Scale for 12-, 18-, and 24-month-old black children. In the present study, 89 children…

  2. A Longitudinal Study of Gender-Related Cognition and Behaviour

    ERIC Educational Resources Information Center

    Campbell, Anne; Shirley, Louisa; Candy, Julia

    2004-01-01

    Gender schema theory proposes that children's acquisition of gender labels and gender stereotypes informs gender-congruent behaviour. Most previous studies have been cross-sectional and do not address the temporal relationship between knowledge and behaviour. We report the results of a longitudinal study of gender knowledge and sex-typed behaviour…

  3. Analyzing Longitudinal Item Response Data via the Pairwise Fitting Method

    ERIC Educational Resources Information Center

    Fu, Zhi-Hui; Tao, Jian; Shi, Ning-Zhong; Zhang, Ming; Lin, Nan

    2011-01-01

    Multidimensional item response theory (MIRT) models can be applied to longitudinal educational surveys where a group of individuals are administered different tests over time with some common items. However, computational problems typically arise as the dimension of the latent variables increases. This is especially true when the latent variable…

  4. Investigating Sexual Abuse: Findings of a 15-Year Longitudinal Study

    ERIC Educational Resources Information Center

    McCormack, Bob; Kavanagh, Denise; Caffrey, Shay; Power, Anne

    2005-01-01

    Background: There is a lack of longitudinal large-scale studies of sexual abuse in intellectual disability services. Such studies offer opportunities to examine patterns in disclosure, investigation and outcomes, and to report on incidence and trends. Methods: All allegations of sexual abuse (n = 250) involving service users as victims or…

  5. Students with Reading Difficulties/Dyslexia: A Longitudinal Swedish Example

    ERIC Educational Resources Information Center

    Mattson, Eva Heimdahl; Fischbein, Siv; Roll-Pettersson, Lise

    2010-01-01

    The aim of this study was to investigate the longitudinal development of students having difficulties with reading and their decoding ability in Swedish compulsory school. Another aim was to relate this to the experiences of educational activities expressed by students and parents. The decoding ability was assessed by a word chain test given at…

  6. Helping Rural Adolescents Make Successful Postsecondary Transitions: A Longitudinal Study

    ERIC Educational Resources Information Center

    Lapan, Richard T.; Aoyagi, Mark; Kayson, Marc

    2007-01-01

    The longitudinal study in this article tested whether advantages in the career development of high school seniors resulted in better transition outcomes for these young adults 3 years after they graduated from high school. Enhanced career development in high school was significantly connected to more successful transitions into the adult roles of…

  7. Stages of Headship: A Longitudinal Study of the Principalship.

    ERIC Educational Resources Information Center

    Weindling, Dick

    This paper uses socialization theory to re-examine a unique, 10-year longitudinal study of headteachers so as to describe the stages of headship transition. It outlines prior models of leadership succession in both business and schools and produces a stage theory of headship that can be used not only as a research tool, but also as a way to assist…

  8. Longitudinal variations of thermospheric composition at the solstices

    NASA Astrophysics Data System (ADS)

    Qian, Liying; Burns, Alan G.; Wang, Wenbin; Solomon, Stanley C.; Zhang, Yongliang

    2016-07-01

    O/N2, measured by the Global Ultraviolet Imager on board the Thermosphere Ionosphere Mesosphere Energetics Dynamics satellite, has large longitudinal variations at the solstices, which are simulated well in upper atmosphere general circulation models. These longitudinal variations are caused by the displacement of the Earth's magnetic poles from the geographic ones. The location of a magnetic pole affects the latitude at which the winds, driven by heating in summer, converge in the subauroral region of the winter hemisphere. In the magnetic pole's longitude sector, this convergence occurs at relatively low latitudes, which results in the maximum values of O/N2 also occurring at relatively low latitudes. These latitudes have a relatively small solar zenith angle, contributing to a strong winter anomaly. In the zonally opposite longitude sector, maximum values of O/N2 occur at relatively high latitudes because the summer-to-winter wind convergence also occurs at relatively high latitudes. These high latitudes have a relatively large solar zenith angle, so ionization is weak, contributing to a weak winter anomaly. Therefore, the displacement between the magnetic and geographic poles not only results in a strong longitudinal variation of O/N2 but also results in a strong longitudinal variation of the ionosphere winter anomaly.

  9. Predictors of Educational Attainment in the Chicago Longitudinal Study

    ERIC Educational Resources Information Center

    Ou, Suh-Ruu; Reynolds, Arthur J.

    2008-01-01

    The authors investigated a comprehensive set of predictors of high school completion and years of completed education for youth in the Chicago Longitudinal Study, an ongoing investigation of over 1500 low-income, minority children who grew up on high-poverty neighborhoods. The study sample included 1286 youth for whom educational attainment could…

  10. School Mobility and Achievement: Longitudinal Findings from an Urban Cohort.

    ERIC Educational Resources Information Center

    Temple, Judy A.; Reynolds, Arthur J.

    1999-01-01

    Investigates effects of school mobility on reading and math achievement for low-income Black children in Chicago Longitudinal Study. Children who frequently changed schools between kindergarten and seventh grade performed approximately one year behind their nonmobile peers on reading and mathematics achievement tests. Findings indicate that it is…

  11. Early Cognitive Profiles of Emergent Readers: A Longitudinal Study

    ERIC Educational Resources Information Center

    Brunswick, Nicola; Martin, G. Neil; Rippon, Georgina

    2012-01-01

    This longitudinal study examined the contribution of phonological awareness, phonological memory, and visuospatial ability to reading development in 142 English-speaking children from the start of kindergarten to the middle of Grade 2. Partial cross-lagged analyses revealed significant relationships between early performance on block design and…

  12. Longitudinal Effects of Parental Bereavement on Adolescent Developmental Competence

    ERIC Educational Resources Information Center

    Brent, David A.; Melhem, Nadine M.; Masten, Ann S.; Porta, Giovanna; Walker Payne, Monica

    2012-01-01

    The aim of this study is to assess the impact of sudden parental bereavement on subsequent attainment of developmental competencies. This longitudinal study reports on 126 youth bereaved by sudden parental death (suicide, accident, or natural death) and 116 demographically similar nonbereaved controls assessed at 9, 21, 33, and 62 months after…

  13. Thought Suppression and Meaning in Life: A Longitudinal Investigation

    ERIC Educational Resources Information Center

    Krause, Neal

    2007-01-01

    The purpose of this study is to see if older adults who experience problems with thought suppression tend to encounter greater difficulty deriving a sense of meaning in life. Data from a longitudinal nationwide survey of older people (N = 988) indicate that greater difficulty with thought suppression is associated with a decline in meaning over…

  14. 15. Photograph of a line drawing. SHEET 15, LONGITUDINAL SECTION ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. Photograph of a line drawing. SHEET 15, LONGITUDINAL SECTION XX, SWITCHBOARD ROOM, TRANSFORMER PLATFORM, AND 1 1/2' SCALE DETAILS; 9-16-1940. Assembly Building for Tank Plant for the Chrysler Corporation, Macomb County, Michigan. Delineator: S. R. B. - Detroit Arsenal, 6501 East Eleven Mile Road, Warren, Macomb County, MI

  15. A Longitudinal Study of Welfare Exit among American Indian Families

    ERIC Educational Resources Information Center

    Pandey, Shanta; Guo, Baorong

    2007-01-01

    Data from a longitudinal survey of families from three reservations (Navajo Nation, San Carlos, and Salt River) in Arizona were used to examine their probability of welfare use. Logistic regression models were used to estimate the effects of individual, family, and structural factors on welfare exit. Results indicate that their probability of…

  16. Experimental study of the longitudinal instability for beam transport

    SciTech Connect

    Reiser, M.; Wang, J.G.; Guo, W.M.; Wang, D.X.

    1990-01-01

    Theoretical model for beam longitudinal instability in a transport pipe with general wall impedance is considered. The result shows that a capacitive wall tends to stabilize the beam. The experimental study of the instability for a pure resistive-wall is presented, including the design parameters, setup and components for the experiment. 6 refs., 3 figs.

  17. Longitudinal trial functions and the cosmic ray energy scale

    NASA Technical Reports Server (NTRS)

    Linsley, J.

    1985-01-01

    Formulae which were proposed to represent the longitudinal profiles of cosmic ray air showers are compared, and the physical interpretation of their parameters is examined. Applications to the problem of energy calibration are pointed out. Adoption of a certain especially simple formula is recommended, and its use is illustrated.

  18. Anxiety Sensitivity and Panic Attacks: A 1-Year Longitudinal Study

    ERIC Educational Resources Information Center

    Li, Wen; Zinbarg, Richard E.

    2007-01-01

    The hypothesis that anxiety sensitivity (AS) is a risk factor for panic genesis has obtained compelling support, but the clinical/practical importance of AS in panic genesis has been questioned. In addition, the association between panic experience and AS increase has not been clearly demonstrated. Through this 1-year longitudinal study among…

  19. A Longitudinal Study on Internship Effectiveness in Vocational Higher Education

    ERIC Educational Resources Information Center

    Wan, Chin-Sheng; Yang, Jen-te; Cheng, Shu-yun; Su, Chiakai

    2013-01-01

    A cooperative education experience (or internship placement) is an essential component of the curricula of vocational higher education. The efficacy of internship placements has become one of the major concerns facing those who develop education curricula. The purpose of this longitudinal study was to explore the relationships among the…

  20. Application of optical longitudinal tomography for dental introscopy

    NASA Astrophysics Data System (ADS)

    Levin, Gennady G.; Burgansky, Alexander A.; Levandovski, Alexei G.

    1997-08-01

    A new method of dental introscopy in-vitro is suggested by the authors. This method implies the usage of longitudinal tomography techniques and is characterized by non-invasive and non-harmful diagnostics features, as well as interactive regime of image reconstruction which lets an operator (doctor) to control the diagnostics process in real time. He-Ne laser emission is used for obtaining of the projections. By the means of longitudinal tomography, images of different sections of an object (tooth) can be reconstructed. An experiment was held by the authors in which 100 projections of a tooth (premolar) were obtained and images of 10 different sections were reconstructed. These images were later compared to real sections of the tooth. This experiment proved that optical longitudinal tomography can be successfully used for dental introscopy. Authors claim that optical tomographic methods can be used for diagnostics of other biological objects as well. Such objects are characterized by spatial geometrical anisotropy (tubular bones, phalanxes of fingers, penis, etc.). It is especially promising to use this method for children's dentistry. the authors discuss some features of the data acquisition system for optical longitudinal tomography. Reconstruction algorithms are described. The results of experimental reconstruction are presented and advantages of this diagnostics method are discussed.