WorldWideScience

Sample records for temporally dispersed slow

  1. Atom slowing via dispersive optical interactions

    Science.gov (United States)

    Hamamda, M.; Boustimi, M.; Correia, F.; Baudon, J.; Taillandier-Loize, T.; Dutier, G.; Perales, F.; Ducloy, M.

    2012-02-01

    A promising technique of atom slowing is proposed. It is based upon the dispersive interaction of atoms with optical potential pulses generated by a far-off-resonance standing wave modulated in time. Each pulse reduces the velocity by a small amount. By repeating the process thousands of times, the velocity can be lowered from several hundreds of meters per second down to almost zero, over a path as short as 20cm. In the absence of any random recoil process, the initial characteristics of the beam are preserved.

  2. Tunable temporal gap based on simultaneous fast and slow light in electro-optic photonic crystals.

    Science.gov (United States)

    Li, Guangzhen; Chen, Yuping; Jiang, Haowei; Liu, Yi'an; Liu, Xiao; Chen, Xianfeng

    2015-07-13

    We demonstrated a tunable temporal gap based on simultaneous fast and slow light in electro-optic photonic crystals. The light experiences an anomalous dispersion near the transmission center and a normal dispersion away from the center, where it can be accelerated and slowed down, respectively. We also obtained the switch between fast and slow light by adjusting the external electric filed. The observed largest temporal gap is 541 ps, which is crucial in practical event operation inside the gap. The results offer a new solution for temporal cloak.

  3. Temporal imaging based on four-wave mixing in slow-light photonic crystal waveguide

    Science.gov (United States)

    Zhou, Mingyang; Liu, Hongjun; Wang, Zhaolu; Huang, Nan; Han, Jing

    2017-12-01

    We have proposed a temporal imaging system based on four-wave mixing (FWM) in the dispersion engineered slow-light photonic crystal waveguide (PCW). Dispersion relations of the modified PCW are calculated through the 3D plane wave expansion method. Time lens is demonstrated by solving the couple-mode equations describing the FWM process inside the PCW directly. Intensity and phase evolutions of the signal, pump and idler waves during the FWM process are calculated to investigate temporal imaging. Meanwhile, temporal magnifications with different magnification factors are realized by tuning the total dispersion of the input signals. Furthermore, influences of dispersion and free-carrier effects inside PCW on the temporal imaging performance are analyzed. The simulation results show the capability to realize temporal imaging system based on the FWM process in slow-light engineered PCW.

  4. Slow light pulse propagation in dispersive media

    DEFF Research Database (Denmark)

    Nielsen, Torben Roland; Mørk, Jesper; Lavrinenko, Andrei

    2009-01-01

    We present a theoretical and numerical analysis of pulse propagation in a semiconductor photonic crystal waveguide with embedded quantum dots in a regime where the pulse is subjected to both waveguide and material dispersion. The group index and the transmission are investigated by finite...... broadening or break-up of the pulse may be observed. The transition from linear to nonlinear pulse propagation is quantified in terms of the spectral width of the pulse. To cite this article: T.R. Nielsen et al., C. R. Physique 10 (2009). (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All...

  5. Slow features nonnegative matrix factorization for temporal data decomposition

    NARCIS (Netherlands)

    Zafeiriou, Lazaros; Nikitidis, Symeon; Zafeiriou, Stefanos; Pantic, Maja

    2014-01-01

    In this paper, we combine the principles of temporal slowness and nonnegative parts-based learning into a single framework that aims to learn slow varying parts-based representations of time varying sequences. We demonstrate that the proposed algorithm arises naturally by embedding the Slow Features

  6. Dispersion-controlled slow light in photonic crystal waveguides.

    Science.gov (United States)

    Baba, Toshihiko; Adachi, Jun; Ishikura, Norihiro; Hamachi, Yohei; Sasaki, Hirokazu; Kawasaki, Takashi; Mori, Daisuke

    2009-01-01

    Slow light with a markedly low group velocity is a promising solution for optical buffering and advanced time-domain optical signal processing. It is also anticipated to enhance linear and nonlinear effects and so miniaturize functional photonic devices because slow light compresses optical energy in space. Photonic crystal waveguide devices generate on-chip slow light at room temperature with a wide bandwidth and low dispersion suitable for short pulse transmission. This paper first explains the delay-bandwidth product, fractional delay, and tunability as crucial criteria for buffering capacity of slow light devices. Then the paper describes experimental observations of slow light pulse, exhibiting their record high values. It also demonstrates the nonlinear enhancement based on slow light pulse transmission.

  7. Enhanced circular dichroism via slow light in dispersive structured media

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Mortensen, Asger

    2007-01-01

    Circular dichroism (CD) is in widespread use as a means of determining enantiomeric excess. We show how slow-light phenomena in dispersive structured media allow for a reduction in the required optical path length of an order of magnitude. The same ideas may be used to enhance the sensitivity of CD...

  8. Slow light based on material and waveguide dispersion

    DEFF Research Database (Denmark)

    Nielsen, Torben Roland; Lavrinenko, Andrei; Mørk, Jesper

    2009-01-01

    We study slow light pulse propagation in a photonic crystal structure consisting of a dispersive and absorptive dielectric material and compare it with the constant wave case. The group index and the trasmission are investigated for the example of an ensemble of semiconductor quantum dots embedde...... in a photonic crystal waveguide by FDTD Maxwell-Bloch simulations. The total group index scales linearly with the material based group index whicle the transmission has a power dependency on the material based absorption coefficient....

  9. A New Approach to Charged Particle Slowing Down and Dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Stevens, David E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-03-24

    The process by which super-thermal ions slow down against background Coulomb potentials arises in many fields of study. In particular, this is one of the main mechanisms by which the mass and energy from the reaction products of fusion reactions is deposited back into the background. Many of these fields are characterized by length and time scales that are the same magnitude as the range and duration of the trajectory of these particles, before they thermalize into the background. This requires numerical simulation of this slowing down process through numerically integrating the velocities and energies of these particles. This paper first presents a simple introduction to the required plasma physics, followed by the description of the numerical integration used to integrate a beam of particles. This algorithm is unique in that it combines in an integrated manner both a second-order integration of the slowing down with the particle beam dispersion. These two processes are typically computed in isolation from each other. A simple test problem of a beam of alpha particles slowing down against an inert background of deuterium and tritium with varying properties of both the beam and the background illustrate the utility of the algorithm. This is followed by conclusions and appendices. The appendices define the notation, units, and several useful identities.

  10. The Localizing Value Of Focal Delta Slowing In Temporal Lobe ...

    African Journals Online (AJOL)

    Background Clinical and structural correlates of lateralized interictal delta activity in patients with temporal lobe epilepsy (TLE) have been well documented in the literature. Nevertheless, its occurrence has not been considered a significant clinical feature. Objective To evaluate the significance of focal delta- range slowing ...

  11. Dispersing billiards with cusps slow decay of correlations

    CERN Document Server

    Chernov, N

    2006-01-01

    Dispersing billiards introduced by Sinai are uniformly hyperbolic and have strong statistical properties (exponential decay of correlations and various limit theorems). However, if the billiard table has cusps (corner points with zero interior angles), then its hyperbolicity is nonuniform and statistical properties deteriorate. Until now only heuristic and experiments results existed predicting the decay of correlations as $\\cO(1/n)$. We present a first rigorous analysis of correlations for dispersing billiards with cusps.

  12. Comparison between different dispersion engineering methods in slow light photonic crystal waveguides

    DEFF Research Database (Denmark)

    Wang, Fengwen; Jensen, Jakob Søndergaard; Sigmund, Ole

    2011-01-01

    This paper compares the performance of different dispersion engineering methods in slow light photonic crystal waveguides, i.e., geometrical parameter optimization and topology optimization. In both methods, the design robustness is enforced by considering the dilated, intermediate and eroded...

  13. Wideband and low-dispersion engineered slow light using liquid infiltration of a modified photonic crystal waveguide.

    Science.gov (United States)

    Pourmand, Mohammad; Karimkhani, Arash; Nazari, Fakhroddin

    2016-12-10

    We present a wideband and low-dispersion slow-light photonic crystal waveguide with a large normalized delay-bandwidth product that can be exploited in many ultra-compact all-optical devices, such as modulators and switches. The proposed new approach is based on infiltrating optical fluid into the first and second rows of the shifted air holes adjacent to the line-defect waveguide in a hexagonal lattice of photonic crystal. The simulation results show that the normalized delay-bandwidth product can be enhanced to a large value of 0.469 with a wide bandwidth operation of 36.8 nm in the C-band frequency optical communication window. Furthermore, by means of two-dimensional finite-difference time-domain calculations, the low-dispersion slow-light propagation is demonstrated by simulating the temporal Gaussian pulse width broadening.

  14. Longitudinal and angular dispersions in photonic crystals: a synergistic perspective on slow light and superprism effects.

    Science.gov (United States)

    Integlia, Ryan A; Song, Weiwei; Tan, Jun; Jiang, Wei

    2010-03-01

    The slow-light effect and the superprism effect are two important effects in photonic crystal structures. In this paper, we will review some of our recent works on the fundamental physics and device applications of these two effects. We will present a synergistic perspective that examines these two effects as a whole. Apparently, the slow light effect is due to the dispersion of a photonic crystal along the direction of light propagation, namely the longitudinal direction, and the superprism effect is related to angular dispersion. However, a deep analysis will show that the superprism effect has an elusive dependence on the longitudinal dispersion as well. Some subtle connections and distinctions between the slow-light effect and the superprism effect will be revealed through our physical analysis. This allows us to treat these two effects under a common theoretical framework. As an example, we will apply this framework to make a direct comparison of the slow-light optical phase array approach and the superprism approach to beam steering applications. Dispersive effects are frequently accompanied by high optical loss and/or narrow bandwidths. We will discuss these issues for both longitudinal and angular dispersions. For the slow light effect, we will give a simple proof of the scaling of fabrication-imperfection related random scattering losses in a slow-light photonic crystal waveguide. Similar to the bandwidth-delay product for the longitudinal dispersion, we will introduce a simple, yet fundamental, limit that governs the bandwidth and angular sensitivities of the superprism effect. We will also discuss the application of the slow-light effect to making compact silicon optical modulators and switches.

  15. REVIEW ARTICLE: Dispersion engineered slow light in photonic crystals: a comparison

    Science.gov (United States)

    Schulz, S. A.; O'Faolain, L.; Beggs, D. M.; White, T. P.; Melloni, A.; Krauss, T. F.

    2010-10-01

    We review the different types of dispersion engineered photonic crystal waveguides that have been developed for slow light applications. We introduce the group index bandwidth product (GBP) and the loss per delay in terms of dB ns - 1 as two key figures of merit to describe such structures and compare the different experimental realizations based on these figures. A key outcome of the comparison is that slow light based on photonic crystals performs as well or better than slow light based on coupled ring resonators.

  16. Uni-directional optical pulses, temporal propagation, and spatial and temporal dispersion

    Science.gov (United States)

    Kinsler, P.

    2018-02-01

    I derive a temporally propagated uni-directional optical pulse equation valid in the few cycle limit. Temporal propagation is advantageous because it naturally preserves causality, unlike the competing spatially propagated models. The exact coupled bi-directional equations that this approach generates can be efficiently approximated down to a uni-directional form in cases where an optical pulse changes little over one optical cycle. They also permit a direct term-to-term comparison of the exact bi-directional theory with its corresponding approximate uni-directional theory. Notably, temporal propagation handles dispersion in a different way, and this difference serves to highlight existing approximations inherent in spatially propagated treatments of dispersion. Accordingly, I emphasise the need for future work in clarifying the limitations of the dispersion conversion required by these types of approaches; since the only alternative in the few cycle limit may be to resort to the much more computationally intensive full Maxwell equation solvers.

  17. Aging Slows Access to Temporal Information From Working Memory.

    Science.gov (United States)

    Kiliç, Asli; Sayali, Zeynep Ceyda; Öztekin, Ilke

    2017-10-01

    To evaluate the impact of aging on controlled memory search operations, we investigated the retrieval of temporal order information from working memory (WM). Young and older adults completed a relative judgments-of-recency (JOR) task. In each trial, participants studied 5-item lists and were presented with two probes from the study list. Participants indicated the probe that had appeared more recently in the study list. Analyses of accuracy data showed that young adults were more successful in correctly detecting the more recent probe compared with older adults. To evaluate the retrieval dynamics, we applied Hacker's (1980) serial scanning model on reaction time data. Results from the model fits revealed that older adults were slower in engaging in the serial memory search operations required to access temporal order information from WM. These findings suggest that this age-related impairment in a JOR task might arise from a slower deployment of controlled memory operations, such as serial search.

  18. Photonic crystal waveguides with semi-slow light and tailored dispersion properties

    DEFF Research Database (Denmark)

    Frandsen, Lars Hagedorn; Lavrinenko, Andrei; Fage-Pedersen, Jacob

    2006-01-01

    waveguide with either vanishing, positive, or negative group velocity dispersion and semi-slow light. We realize experimentally a silicon-on-insulator photonic crystal waveguide having nearly constant group velocity [similar to]c$-0$//34 in an 11-nm bandwidth below the silica-line. $CPY@2006 Optical Society......We demonstrate a concept for tailoring the group velocity and dispersion properties for light propagating in a planar photonic crystal waveguide. By perturbing the holes adjacent to the waveguide core it is possible to increase the useful bandwidth below the light-line and obtain a photonic crystal...

  19. Slowing and stopping of wave in dispersive metamaterial loaded helical guide.

    Science.gov (United States)

    Sharma, Dushyant K; Pathak, Surya K

    2016-02-08

    We propose a dispersive metamaterial loaded helical waveguide (DMLHG) structure that supports slowing and stopping of Electromagnetic (EM) wave. Analytical and computational characterizations have been done to visualize various modal characteristics in detail using the Drude model as a dispersive parameter. It is observed that metamaterial insertion enhances helical guide slow wave behaviour and it supports both forward wave (FW) and backward wave (BW) as well as mode degeneracy. Obtained mode degeneracy mechanism leads to trapping of EM wave. The proposed guide structure provides a dynamic control of wave velocity by varying its physical parameters. Two possible structures are designed and simulated using CST Microwave Studio Software. The simulation results verify the presence of similar characteristics as observed in analytical study such as FW, BW, mode-degeneracy, but in slightly shifted frequency spectrum.

  20. Topology-optimized and dispersion-tailored photonic crystal slow-light devices

    DEFF Research Database (Denmark)

    Frandsen, Lars Hagedorn; Lavrinenko, Andrei; Borel, Peter Ingo

    2007-01-01

    not guarantee optimal solutions. The systematic design method based on topology optimization [1] allows creation of improved PhCW components with previously unseen low transmission losses, high operational bandwidths,and/or with wavelength selective functionalities. The method was originally developed...... sophisticated possibilities for realizing complex nanophotonic circuits. Potentially,PhCWs may facilitate delay lines for package synchronization, dispersion compensation, and enhanced light-matter interactions in nanophotonic circuits by exploiting slow-light phenomena. The practical utilization of ultra...... distribution for the target mode and through a simple structural tuning of the waveguide geometry [3]. In this way, it is possible to realize a silicon-on-insulator PhCW with semi-slow light having a group velocity in the range ~(c0/15 – c0/100); vanishing, positive, or negative group velocity dispersion (GVD...

  1. Wideband slow light with low dispersion in asymmetric slotted photonic crystal waveguides.

    Science.gov (United States)

    Liu, Bo; Wang, Tao; Tang, Jian; Li, Xiaoming; Dong, Chuanbo; He, Yu

    2013-12-01

    A new procedure of designing slotted photonic crystal waveguides is proposed to achieve slow light with improved normalized delay-bandwidth product and low group velocity dispersion that is suitable for both the W1 defect mode and the slot mode. The lateral symmetry of the waveguide in our study is broken by shifting the air holes periodically along the slot axis. The conversion of the "flat band" from band-up slow light to band-down slow light is achieved for the W1 defect mode. The group index curves of the W1 mode change from U-like to step-like and the group indices of 47, 67 and 130 are obtained with the bandwidth over 7.2, 4.8, and 2.3 nm around 1550 nm, respectively. We also obtain the group indices of 42, 55, and 108 for the slot mode with the bandwidth over 6.2, 5.6, and 2.2 nm, respectively. Then the low dispersion slow light propagation is numerically demonstrated by the finite-difference time-domain method.

  2. Controls of Plume Dispersal at the Slow Spreading Mid-Atlantic Ridge

    Science.gov (United States)

    Walter, M.; Mertens, C.; Koehler, J.; Sueltenfuss, J.; Rhein, M.; Keir, R. S.; Schmale, O.; Schneider v. Deimling, J.; German, C. R.; Yoerger, D. R.; Baker, E. T.

    2011-12-01

    The slow-spreading Mid-Atlantic Ridges hosts a multitude of different types of hydrothermal systems. Here, we compare the fluxes and the plume dispersal at three high temperature sites located in very diverse settings at comparable depths (~3000m): The recently discovered sites Turtle Pits, and Nibelungen on the southern MAR, and the Logatchev field in the North Atlantic. Plume mapping for these sites on cruises between 2004 and 2009 consisted of CTD Towyo-, Yoyo,- and station work, including velocity profiling, as well as water sampling for analysis of trace gases (CH4, H2, 3He/4He) and metals; temperature measurements and fluid sampling at the vent sites were carried out with an ROV. The aim of this work is to gain a better understanding of how the setting of a vent site affects the dispersal of the particle plume, and what means can be used to infer possible locations of vent sites based on the hydrographic properties and plume observations, using high resolution bathymetric mapping and hydrographic information. The ultramafic-hosted Nibelungen site (8°18'S) consists of a single active smoking crater, along with several extinct smokers, which is located off-axis south of a non-transform offset. The setting is characterized by rugged topography, favorable for the generation of internal tides, internal wave breaking, and vertical mixing. Elevated mixing with turbulent diffusivities Kρ up to 0.1 m2 s-1, 3 to 4 orders of magnitude higher than open ocean values, was observed close to the vent site. The mixing as well as the flow field exhibited a strong tidal cycle; the plume dispersal is thus dominated by the fast and intermittent vertical exchange and characterized by small scale spatial and temporal variability. The Turtle Pits vent fields (4°48'S) are located on a sill in a north-south orientated rift valley. The site consists of three (known) high temperature fields: Turtle Pits, Comfortless Cove, and Red Lion. The particle plume is confined to the rift

  3. Wideband slow light and dispersion control in oblique lattice photonic crystal waveguides.

    Science.gov (United States)

    Leng, Feng-Chun; Liang, Wen-Yao; Liu, Bin; Wang, Tong-Biao; Wang, He-Zhou

    2010-03-15

    We find that the angle between elementary lattice vectors obviously affects the bandwidth and dispersion of slow light in photonic crystal line-defect waveguides. When the fluctuation of group index is strictly limited in a +/-1% range, the oblique lattice structures with the angle between elementary lattice vectors slightly larger than 60 degrees have broader available bandwidth of flat band slow light than triangular lattice structures. For example, for the angle 66 degrees , there are increases of the available bandwidth from 20% to 68% for several different structures. For the same angle and a +/-10% variation in group velocity, when group indices are nearly constants of 30, 48.5, 80 and 130, their corresponding bandwidths of flat band reach 20 nm, 11.8 nm, 7.3 nm and 3.9 nm around 1550 nm, respectively. The increasing of bandwidth is related to the shift of the anticrossing point towards smaller wave numbers.

  4. NLO dispersion laws for slow-moving quarks in HTL QCD

    Energy Technology Data Exchange (ETDEWEB)

    Abada, Abdessamad [Laboratoire de Physique des Particules et Physique Statistique, Ecole Normale Supérieure,BP 92 Vieux Kouba, 16050 Alger (Algeria); Physics Department, United Arab Emirates University,POB 17551 Al Ain (United Arab Emirates); Benchallal, Karima; Bouakaz, Karima [Laboratoire de Physique des Particules et Physique Statistique, Ecole Normale Supérieure,BP 92 Vieux Kouba, 16050 Alger (Algeria)

    2015-03-11

    We determine the next-to-leading order dispersion laws for slow-moving quarks in hard-thermal-loop perturbation of high-temperature QCD where weak coupling is assumed. Real-time formalism is used. The next-to-leading order quark self-energy is written in terms of three and four HTL-dressed vertex functions. The hard thermal loops contributing to these vertex functions are calculated ab initio and expressed using the Feynman parametrization which allows the calculation of the solid-angle integrals involved. We use a prototype of the resulting integrals to indicate how finite results are obtained in the limit of vanishing regularizer.

  5. The effects of temporally variable dispersal and landscape structure on invasive species spread.

    Science.gov (United States)

    Andrew, Margaret E; Ustin, Susan L

    2010-04-01

    Many invasive species are too widespread to realistically eradicate. For such species, a viable management strategy is to slow the rate of spread. However, to be effective, this will require detailed spread data and an understanding of the influence of environmental conditions and landscape structure on invasion rates. We used a time series of remotely sensed distribution maps and a spatial simulation model to study spread of the invasive Lepidium latifolium (perennial pepperweed) in California's Sacramento-San Joaquin River Delta. L. latifolium is a noxious weed and exhibited rapid, explosive spread. Annual infested area and empirical dispersal kernels were derived from the remotely sensed distributions in order to assess the influence of weather conditions on spread and to parameterize the simulation model. Spread rates and dispersal distances were highest for nascent infestations and in years with wet springs. Simulations revealed that spread rates were more strongly influenced by the length of long-distance dispersal than by temporal variation in its likelihood. It is thus important to capture long-distance dispersal and the conditions that facilitate spread when collecting data to parameterize spread models. Additionally, management actions performed in high-spread years, targeting long-distance recruits, can effectively contain infestations. Corridors were relatively unimportant to spread rates; their effectiveness at enhancing rate of spread was limited by the species' dispersal ability and the time needed to travel through the corridor. In contrast, habitat abundance and shape surrounding the introduction site strongly influenced invasion dynamics. Satellite patches invading large areas of invasible habitat present especially high risk.

  6. Dispersive waves induced by self-defocusing temporal solitons in a beta-barium-borate crystal

    DEFF Research Database (Denmark)

    Zhou, Binbin; Bache, Morten

    2015-01-01

    We experimentally observe dispersive waves in the anomalous dispersion regime of a beta-barium-borate (BBO) crystal, induced by a self-defocusing few-cycle temporal soliton. Together the soliton and dispersive waves form an energetic octave-spanning supercontinuum. The soliton was excited...

  7. Temporal slow-growth formulation for direct numerical simulation of compressible wall-bounded flows

    Science.gov (United States)

    Topalian, Victor; Oliver, Todd A.; Ulerich, Rhys; Moser, Robert D.

    2017-08-01

    A slow-growth formulation for DNS of wall-bounded turbulent flow is developed and demonstrated to enable extension of slow-growth modeling concepts to wall-bounded flows with complex physics. As in previous slow-growth approaches, the formulation assumes scale separation between the fast scales of turbulence and the slow evolution of statistics such as the mean flow. This separation enables the development of approaches where the fast scales of turbulence are directly simulated while the forcing provided by the slow evolution is modeled. The resulting model admits periodic boundary conditions in the streamwise direction, which avoids the need for extremely long domains and complex inflow conditions that typically accompany spatially developing simulations. Further, it enables the use of efficient Fourier numerics. Unlike previous approaches [Guarini, Moser, Shariff, and Wray, J. Fluid Mech. 414, 1 (2000), 10.1017/S0022112000008466; Maeder, Adams, and Kleiser, J. Fluid Mech. 429, 187 (2001), 10.1017/S0022112000002718; Spalart, J. Fluid Mech. 187, 61 (1988), 10.1017/S0022112088000345], the present approach is based on a temporally evolving boundary layer and is specifically tailored to give results for calibration and validation of Reynolds-averaged Navier-Stokes (RANS) turbulence models. The use of a temporal homogenization simplifies the modeling, enabling straightforward extension to flows with complicating features, including cold and blowing walls. To generate data useful for calibration and validation of RANS models, special care is taken to ensure that the mean slow-growth forcing is closed in terms of the mean and other quantities that appear in standard RANS models, ensuring that there is no confounding between typical RANS closures and additional closures required for the slow-growth problem. The performance of the method is demonstrated on two problems: an essentially incompressible, zero-pressure-gradient boundary layer and a transonic boundary layer over

  8. Dispersal Ability Determines the Role of Environmental, Spatial and Temporal Drivers of Metacommunity Structure

    NARCIS (Netherlands)

    Padial, André A.; Ceschin, Fernanda; Declerck, Steven A. J.; De Meester, Luc; Bonecker, Cláudia C.; Lansac-Tôha, Fabio A.; Rodrigues, Liliana; Rodrigues, Luzia C.; Train, Sueli; Velho, Luiz F. M.; Bini, Luis M.

    2014-01-01

    Recently, community ecologists are focusing on the relative importance of local environmental factors and proxies to dispersal limitation to explain spatial variation in community structure. Albeit less explored, temporal processes may also be important in explaining species composition variation in

  9. Slow Temporal Integration Enables Robust Neural Coding and Perception of a Cue to Sound Source Location.

    Science.gov (United States)

    Brown, Andrew D; Tollin, Daniel J

    2016-09-21

    In mammals, localization of sound sources in azimuth depends on sensitivity to interaural differences in sound timing (ITD) and level (ILD). Paradoxically, while typical ILD-sensitive neurons of the auditory brainstem require millisecond synchrony of excitatory and inhibitory inputs for the encoding of ILDs, human and animal behavioral ILD sensitivity is robust to temporal stimulus degradations (e.g., interaural decorrelation due to reverberation), or, in humans, bilateral clinical device processing. Here we demonstrate that behavioral ILD sensitivity is only modestly degraded with even complete decorrelation of left- and right-ear signals, suggesting the existence of a highly integrative ILD-coding mechanism. Correspondingly, we find that a majority of auditory midbrain neurons in the central nucleus of the inferior colliculus (of chinchilla) effectively encode ILDs despite complete decorrelation of left- and right-ear signals. We show that such responses can be accounted for by relatively long windows of bilateral excitatory-inhibitory interaction, which we explicitly measure using trains of narrowband clicks. Neural and behavioral data are compared with the outputs of a simple model of ILD processing with a single free parameter, the duration of excitatory-inhibitory interaction. Behavioral, neural, and modeling data collectively suggest that ILD sensitivity depends on binaural integration of excitation and inhibition within a ≳3 ms temporal window, significantly longer than observed in lower brainstem neurons. This relatively slow integration potentiates a unique role for the ILD system in spatial hearing that may be of particular importance when informative ITD cues are unavailable. In mammalian hearing, interaural differences in the timing (ITD) and level (ILD) of impinging sounds carry critical information about source location. However, natural sounds are often decorrelated between the ears by reverberation and background noise, degrading the fidelity of

  10. Temporally variable dispersal and demography can accelerate the spread of invading species.

    Science.gov (United States)

    Ellner, Stephen P; Schreiber, Sebastian J

    2012-12-01

    We analyze how temporal variability in local demography and dispersal combine to affect the rate of spread of an invading species. Our model combines state-structured local demography (specified by an integral or matrix projection model) with general dispersal distributions that may depend on the state of the individual or its parent. It allows very general patterns of stationary temporal variation in both local demography and in the frequency and distribution of dispersal distances. We show that expressions for the asymptotic spread rate and its sensitivity to parameters, which have been derived previously for less general models, continue to hold. Using these results we show that random temporal variability in dispersal can accelerate population spread. Demographic variability can further accelerate spread if it is positively correlated with dispersal variability, for example if high-fecundity years are also years in which juveniles tend to settle further away from their parents. A simple model for the growth and spread of patches of an invasive plant (perennial pepperweed, Lepidium latifolium) illustrates these effects and shows that they can have substantial impacts on the predicted speed of an invasion wave. Temporal variability in dispersal has received very little attention in both the theoretical and empirical literature on invasive species spread. Our results suggest that this needs to change.

  11. Spatio-temporal organization of vehicles in a cellular automata model of traffic with `slow-to-start' rule

    Science.gov (United States)

    Chowdhury, Debashish; Santen, Ludger; Schadschneider, Andreas; Sinha, Shishir; Pasupathy, Abhay

    1999-05-01

    The spatio-temporal organizations of vehicular traffic in cellular-automata models with `slow-to-start' rules are qualitatively different from those in the Nagel-Schreckenberg (NaSch) model of highway traffic. Here we study the effects of such a slow-to-start rule, introduced by Benjamin, Johnson and Hui (BJH), on the distributions of the distance-headways, time-headways, jam sizes and sizes of the gaps between successive jams by a combination of approximate analytical calculations and extensive computer simulations. We compare these results for the BJH model with the corresponding results for the NaSch model and interpret the qualitative differences in the nature of the spatio-temporal organizations of traffic in these two models in terms of a phase separation of the traffic caused by the slow-to-start rule in the BJH model.

  12. Extremely large bandwidth and ultralow-dispersion slow light in photonic crystal waveguides with magnetically controllability

    DEFF Research Database (Denmark)

    Pu, Shengli; Wang, Haotian; Wang, Ning

    2013-01-01

    of the lattice and the light speed in vacuum, respectively). Simultaneously, the normalized delay-bandwidth product is relatively large and almost invariant with magnetic field strength. It is indicated that using magnetic fluid as one of the constitutive materials of the photonic crystal structures can enable......A line-defect waveguide within a two-dimensional magnetic-fluid-based photonic crystal with 45o-rotated square lattice is presented to have excellent slow light properties. The bandwidth centered at $$ \\lambda_{0} $$ = 1,550 nm of our designed W1 waveguide is around 66 nm, which is very large than...... the magnetically fine tunability of the slow light in online mode. The concept and results of this work may give a guideline for studying and realizing tunable slow light based on the external-stimulus-responsive materials....

  13. Demographic Fluctuations versus Spatial Variation in the Competition between Fast and Slow Dispersers

    Science.gov (United States)

    Doering, Charles R.; Waddell, Jack N.; Sander, Leonard M.

    2010-03-01

    Dispersal is an important strategy employed by populations to locate and exploit favorable habitats. Given competition in a spatially heterogeneous landscape, what is the optimal rate of dispersal? Continuous population models predict that, all other features the same, a species with a lower dispersal rate always drives a competing species to extinction in the presence of spatial variation of resources. But the introduction of intrinsic demographic fluctuations can reverse this conclusion. We present a simple model in which competition between the exploitation of resources and population birth-death fluctuations leads to victory by either the faster or slower of two species depending on the environmental parameters. A simplified limiting case of the model, analyzed by closing the moment and correlation hierarchy, quantitatively predicts which species will win in the complete model under given parameters of spatial variation and average carrying capacity.

  14. Effect of Particular Nonlinear Dispersion in Photorefractive Four wave Mixing on Slow and Fast Light (Preprint)

    Science.gov (United States)

    2018-01-31

    coupling strength increases. The conclusions of the theoretical analysis are confirmed experimentally for photorefractive four-wave mixing in...fast light Konstantin Shcherbin*a, Pierre Matheyb, and Dean R. Evansc aInstitute of Physics , National Academy of Sciences, Prospekt Nauki 46, 03680...conclusions of the theoretical analysis are confirmed experimentally for photorefractive four-wave mixing in barium titanate. Keywords: slow light

  15. Evolution of dispersal in spatially and temporally variable environments: The importance of life cycles.

    Science.gov (United States)

    Massol, François; Débarre, Florence

    2015-07-01

    Spatiotemporal variability of the environment is bound to affect the evolution of dispersal, and yet model predictions strongly differ on this particular effect. Recent studies on the evolution of local adaptation have shown that the life cycle chosen to model the selective effects of spatiotemporal variability of the environment is a critical factor determining evolutionary outcomes. Here, we investigate the effect of the order of events in the life cycle on the evolution of unconditional dispersal in a spatially heterogeneous, temporally varying landscape. Our results show that the occurrence of intermediate singular strategies and disruptive selection are conditioned by the temporal autocorrelation of the environment and by the life cycle. Life cycles with dispersal of adults versus dispersal of juveniles, local versus global density regulation, give radically different evolutionary outcomes that include selection for total philopatry, evolutionary bistability, selection for intermediate stable states, and evolutionary branching points. Our results highlight the importance of accounting for life-cycle specifics when predicting the effects of the environment on evolutionarily selected trait values, such as dispersal, as well as the need to check the robustness of model conclusions against modifications of the life cycle. © 2015 The Author(s). Evolution © 2015 The Society for the Study of Evolution.

  16. Electromagnetic and Optical Pulse Propagation 1 Spectral Representations in Temporally Dispersive Media

    CERN Document Server

    Oughstun, Kurt E

    2007-01-01

    Electromagnetic & Optical Pulse Propagation presents a systematic treatment of the radiation and propagation of transient electromagnetic and optical wave fields (such as those used in ultrawideband radar and communications sysyems as well as in ultrashort pulsed optics) through causal, locally linear media which exhibit both temporal dispersion and absorption. Volume I presents a detailed, rigorous development of the fundamental theory of both time and frequency-domain electromagnetics, beginning with the classical Maxwell-Lorentz theory of microscopic electromagnetic fields and ist invariance in the special theory of relativity, the correlation of the microscopic and macroscopic fields, and the angular spectrum representation of pulsed radiation fields in causally dispersive media. The theory provides a rigorous framework for applied research treating temporally pulsed wave fields in dielectric, conducting and semiconducting materials. Volume II presents the asymptotic description of specific pulsed wav...

  17. A dispersion-balanced Discrete Fourier Transform of repetitive pulse sequences using temporal Talbot effect

    Science.gov (United States)

    Fernández-Pousa, Carlos R.

    2017-11-01

    We propose a processor based on the concatenation of two fractional temporal Talbot dispersive lines with balanced dispersion to perform the DFT of a repetitive electrical sequence, for its use as a controlled source of optical pulse sequences. The electrical sequence is used to impart the amplitude and phase of a coherent train of optical pulses by use of a modulator placed between the two Talbot lines. The proposal has been built on a representation of the action of fractional Talbot effect on repetitive pulse sequences and a comparison with related results and proposals. It is shown that the proposed system is reconfigurable within a few repetition periods, has the same processing rate as the input optical pulse train, and requires the same technical complexity in terms of dispersion and pulse width as the standard, passive pulse-repetition rate multipliers based on fractional Talbot effect.

  18. Limited capacity of working memory in unihemispheric random walks implies conceivable slow dispersal.

    Science.gov (United States)

    Wei, Kun; Zhong, Suchuan

    2017-08-01

    Phenomenologically inspired by dolphins' unihemispheric sleep, we introduce a minimal model for random walks with physiological memory. The physiological memory consists of long-term memory which includes unconscious implicit memory and conscious explicit memory, and working memory which serves as a multi-component system for integrating, manipulating and managing short-term storage. The model assumes that the sleeping state allows retrievals of episodic objects merely from the episodic buffer where these memory objects are invoked corresponding to the ambient objects and are thus object-oriented, together with intermittent but increasing use of implicit memory in which decisions are unconsciously picked up from historical time series. The process of memory decay and forgetting is constructed in the episodic buffer. The walker's risk attitude, as a product of physiological heuristics according to the performance of objected-oriented decisions, is imposed on implicit memory. The analytical results of unihemispheric random walks with the mixture of object-oriented and time-oriented memory, as well as the long-time behavior which tends to the use of implicit memory, are provided, indicating the common sense that a conservative risk attitude is inclinable to slow movement.

  19. Reflections of hunger and satiation in the structure of temporal organization of slow electrical and spike activities of fundal and antral stomach muscles in rabbits.

    Science.gov (United States)

    Kromin, A A; Zenina, O Yu

    2012-11-01

    Manifestations of hunger and satiation in myoelectric activity patterns in different portions of the stomach were studied in chronic experiments. The state of hunger manifested in the structure of temporal organization of slow electric activity of muscles in the stomach body and antrum in the form of bimodal distributions of slow electric wave periods, while satiation as unimodal distribution. In hunger-specific bimodal distribution of slow electric wave periods generated by muscles of the stomach body and antrum, the position of the first maximum carries the information about oncoming food reinforcement, since this particular range of slow wave fluctuations determines temporal parameters of slow electric activity of muscles in all stomach regions in the course of subsequent successive food-procuring behavior. Under conditions of hunger, the pacemaker features of muscles in the lesser curvature are realized incompletely. Complete realization is achieved in the course of food intake and at the state of satiation.

  20. Multi-temporal mapping of a large, slow-moving earth flow for kinematic interpretation

    Science.gov (United States)

    Guerriero, Luigi; Coe, Jeffrey A.; Revellino, Paola; Guadagno, Francesco M.

    2014-01-01

    lowest in the upper and lower parts. As the velocity of movement initiated and increased, stretching of the earth flow body induced the formation of normal faults. Conversely, decreasing velocity and shortening of the earth flow induced the formation of thrust faults. A zone with relatively few structures, bounded by strike-slip faults, was located between stretching and shortening areas. These kinematic elements indicate that the overall earth flow was actually composed of numerous linked internal earth flows, with each internal flow having a distinct pattern of structures representative of stretching and shortening (Guerriero et al., in review). These observations indicated that the spatial variation in movement velocity associated with each internal earth flow, mimicked the pattern of movement for the overall earth flow. That is, the earth flow displayed a self-similar pattern at different scales. Furthermore, the presence of other structures such as back-tilted surfaces, flank-ridges, and hydrological elements provide specific information about the shape of the basal topographic surface. Our multi-temporal maps provided a basis for interpretation of the long-term kinematic evolution of the earth flow and the influence of the basal-slip surface on the earth flow movement. Our maps showed that main faults remained stationary through time, despite extensive mobilization and movement of material. This observation indicated that the slip-surface has remained relatively stationary since at least 1954.

  1. Slow-oscillatory Transcranial Direct Current Stimulation Modulates Memory in Temporal Lobe Epilepsy by Altering Sleep Spindle Generators: A Possible Rehabilitation Tool.

    Science.gov (United States)

    Del Felice, Alessandra; Magalini, Alessandra; Masiero, Stefano

    2015-01-01

    Temporal lobe epilepsy (TLE) is often associated with memory deficits. Given the putative role for sleep spindles memory consolidation, spindle generators skewed toward the affected lobe in TLE subjects may be a neurophysiological marker of defective memory. Slow-oscillatory transcranial direct current stimulation (sotDCS) during slow waves sleep (SWS) has previously been shown to enhance sleep-dependent memory consolidation by increasing slow-wave sleep and modulating sleep spindles. To test if anodal sotDCS over the affected TL prior to a nap affects sleep spindles and whether this improves memory consolidation. Randomized controlled cross-over study. 12 people with TLE underwent sotDCS (0.75 Hz; 0-250 μV, 30 min) or sham before daytime nap. Declarative verbal and visuospatial learning were tested. Fast and slow spindle signals were recorded by 256-channel EEG during sleep. In both study arms, electrical source imaging (ESI) localized cortical generators. Neuropsychological data were analyzed with general linear model statistics or the Kruskal-Wallis test (P or Z memory performance (P = 0.048) emerged after sotDCS. SotDCS increased slow spindle generators current density (Z = 0.001), with a shift to the anterior cortical areas. Anodal sotDCS over the affected temporal lobe improves declarative and visuospatial memory performance by modulating slow sleep spindles cortical source generators. SotDCS appears a promising tool for memory rehabilitation in people with TLE. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Sensitivity of honeybee hygroreceptors to slow humidity changes and temporal humidity variation detected in high resolution by mobile measurements.

    Science.gov (United States)

    Tichy, Harald; Kallina, Wolfgang

    2014-01-01

    The moist cell and the dry cell on the antenna of the male honeybee were exposed to humidities slowly rising and falling at rates between -1.5%/s and +1.5%/s and at varying amplitudes in the 10 to 90% humidity range. The two cells respond to these slow humidity oscillations with oscillations in impulse frequency which depend not only on instantaneous humidity but also on the rate with which humidity changes. The impulse frequency of each cell was plotted as a function of these two parameters and regression planes were fitted to the data points of single oscillation periods. The regression slopes, which estimate sensitivity, rose with the amplitude of humidity oscillations. During large-amplitude oscillations, moist and dry cell sensitivity for instantaneous humidity and its rate of change was high. During small-amplitude oscillations, their sensitivity for both parameters was low, less exactly reflecting humidity fluctuations. Nothing is known about the spatial and temporal humidity variations a honeybee may encounter when flying through natural environments. Microclimatic parameters (absolute humidity, temperature, wind speed) were measured from an automobile traveling through different landscapes of Lower Austria. Landscape type affected extremes and mean values of humidity. Differences between peaks and troughs of humidity fluctuations were generally smaller in open grassy fields or deciduous forests than in edge habitats or forest openings. Overall, fluctuation amplitudes were small. In this part of the stimulus range, hygroreceptor sensitivity is not optimal for encoding instantaneous humidity and the rate of humidity change. It seems that honeybee's hygroreceptors are specialized for detecting large-amplitude fluctuations that are relevant for a specific behavior, namely, maintaining a sufficiently stable state of water balance. The results suggest that optimal sensitivity of both hygroreceptors is shaped not only by humidity oscillation amplitudes but also

  3. Epileptic encephalopathy with continuous spikes and waves in the occipito-temporal region during slow-wave sleep in two patients with acquired Kanji dysgraphia.

    Science.gov (United States)

    Kuki, Ichiro; Kawawaki, Hisashi; Okazaki, Shin; Ikeda, Hiroko; Tomiwa, Kiyotaka

    2014-12-01

    We encountered two patients with acquired Kanji dysgraphia in whom continuous spikes and waves, dominant in the occipito-temporal region, were recorded during slow-wave sleep. Electrical status epileptics during sleep (ESES) was demonstrated on overnight electroencephalography, and dipoles clustered in and around the posterior inferior temporal cortex on magnetoencephalography. Functional neuroimaging suggested dysfunction in the left posterior temporal lobe, including the posterior inferior temporal cortex. The patients had normal intelligence with no problems in reading and writing Kana, as well as copying, reading aloud, and identifying Kanjis, but showed Kanji dysgraphia (morphological, phonemic, and semantic error) accompanied by impaired visual processing. ESES was resolved by sodium valproate, clonazepam, and acetazolamide in Patient 1, and by adrenocorticotropic hormone, sodium valproate, and clorazepate in Patient 2. The present cases had the unique cognitive dysfunction of Kanji dysgraphia, which is distinct from that of Landau-Kleffner syndrome and continuous spikes and waves during slow-wave sleep. However, the present cases also share common features with these two encephalopathies in terms of the clinical course, pathophysiology, neuroimaging, and response to steroids and antiepileptic drugs. In the context of the Japanese language, acquired Kanji dysgraphia may occur due to electrical dysfunction of left posterior inferior temporal cortex in patients with ESES.

  4. A pace of our own. Becoming through speeds and slows: investigating living through temporal ontologies of the university

    DEFF Research Database (Denmark)

    Juelskjær, Malou; Rogowska-Stangret, Monika

    2017-01-01

    possibilities of thinking through new materialist theorising and concepts for examining conditions of the im/possibilities of living live-able academic lives in current political climates. As a response to those conditions a cry for slowing down has surfaced and manifestos for slow scholarship, reading...

  5. Validity of a Wireless Gait Analysis Tool (Wi-GAT) in assessing spatio-temporal gait parameters at slow, preferred and fast walking speeds.

    Science.gov (United States)

    DesJardins, Ashley M; Schiller, Martha; Eraqi, Enas; Samuels, Amanda Nicole; Galen, Sujay S

    2016-11-14

    The wireless gait assessment tool (Wi-GAT) measures have been shown to have good to excellent concurrent validity with preferred walking speeds, however, the validity of the Wi-GAT measures at slow and fast walking speeds is unknown. To establish validity of the Wi-GAT spatio-temporal gait measures at slow, fast, and preferred walking speeds. Twenty two healthy adult volunteers, with a mean age of 25.7 (± 5.3) participated in this study. The spatio-temporal gait variables of each participant were concurrently recorded using the GAITrite and the Wi-GAT system, while the participants performed 3 trials for each walking speed in a randomized order. Intraclass correlation analyses were performed to establish the agreement between the measures recorded by the GAITrite and Wi-GAT systems. Walking speed measured both by the Wi-GAT and the GAITrite systems showed excellent agreement for preferred (ICC = 0.979 pgait parameters recorded at slow walking speed showed good (ICC > 0.70) to excellent (ICC > 0.85) agreement. Gait parameters recorded by the Wi-GAT system showed fair to excellent validity for preferred and slow walking speeds.

  6. Spatial and temporal effects on seed dispersal and seed predation of Musa acuminata in southern Yunnan, China.

    Science.gov (United States)

    Meng, Lingzeng; Gao, Xiuxia; Chen, Jin; Martin, Konrad

    2012-03-01

    Wild bananas are abundant in tropical areas and many ecologists have observed that the succession process is quicker following increased disturbance. This study was conducted to analyze animal-seed interactions and their effects on the seed fate of a wild banana species (Musa acuminata) in tropical southern Yunnan (China) through experiments considering spatial (site and habitat) and temporal (seasons) variation. The largest proportion of fruits (81%) was removed by frugivorous seed dispersers, especially by bats at nighttime. Only 13% of the fruits were removed by climbing seed predators (different species of rats). In the exclosure treatment, rodents accounted for a significantly higher total artificially exposed seed removal number than ants, but with spatial and temporal differences. The highest seed predation rate by rodents (70%) was found in forest with wild banana stands, corresponding with the highest rodent diversity (species numbers and abundance) among the habitat types. In contrast, the seed removal number by ants (57%) was highest in the open land habitats, but there was no close correlation with ant diversity. Seed removal numbers by ants were significantly higher in the dry compared to the rainy season, but rodent activity showed no differences between seasons. The overall results suggest that the largest proportion of seeds produced by wild banana are primarily dispersed by bats. Primary seed dispersal by bats at nighttime is essential for wild banana seeds to escape seed predation. © 2012 ISZS, Blackwell Publishing and IOZ/CAS.

  7. A Comprehensive Study on Fast Dispersible and Slow-Releasing Characteristic of Orange Peel Pectin in Relation to Established Synthetic Polymer.

    Science.gov (United States)

    Srivastava, Pranati; Singh, Mahendra; Bhargava, Shilpi

    2017-10-01

    In the present work, the method to extract, isolate, and characterize orange peel pectin using soxhlation, and thereafter, the use of this polymer-polymer in the formulation of fast dispersable and slow-releasing tablet has been studied. Thereafter, the evaluation and comparison of fast dispersible/slow-releasing tablets using orange peel pectin versus prepared using sodium starch glycolate (SSG) were carried out. In the present investigation, extraction methodology was employed for isolation of pectin from orange peels. Four different batches with each polymer were prepared with varying concentration of superdisintegrant and bulking agent using diclofenac sodium as model drug. Diclofenac sodium stands as easily available, cheap, and good candidate to demonstrate disintegrant property. The formulation involved wet granulation method for the preparation of tablets of each batch. The tablets were evaluated for hardness, friability, thickness, wetting time, deaggregation time, and in vitro release characteristic data. It was observed that parameters for batch O2* were comparable with that of synthetic superdisintegrant. This batch gave around 92.12% drug release in period of 90 min. The study showed that orange peel pectin could be a potential candidate for formulation of orodispersible dosage forms in competence to SSG, which is established superdisintegrant. The results led to the conclusion that the use of natural polymers in formulation of pharmaceutical dosage form can be put into practice on industrial scale meeting the similar requirements as done by synthetic polymers. The present work aims to demonstrate and establish the use of naturally derived polymer, i.e., orange peel pectin as a superdisintegrant. The extraction methodology has been discussed followed by comparative analysis with a synthetic polymer. Abbreviations used: O1-O2: Batches Containing Orange peel pectin, S1-S2: Batches containing SSG, SSG: Sodium starch glycolate, NDDS: Novel drug delivery

  8. Spatial and temporal seed dispersal of squarrose knapweed (Centaurea virgata Lam. ssp. squarrosa (Willd.) Gugler) in west central Utah, a case study

    Science.gov (United States)

    Scott L. Jensen; Stephen B. Monsen; Pat Fosse

    2008-01-01

    This case study documents temporal and spatial squarrose knapweed (Centaurea virgata Lam. spp. squarrosa (Willd.) Gugler) seed dispersal from study sites in central Utah. Felt seed traps were placed along transects extending from sites occupied by squarrose knapweed into adjacent plant communities. Seed dispersal from knapweed...

  9. Similarity in temporal variation in sex-biased dispersal over short and long distances in the dark-eyed junco, Junco hyemalis.

    Science.gov (United States)

    Liebgold, Eric B; Gerlach, Nicole M; Ketterson, Ellen D

    2013-11-01

    Patterns of sex-biased dispersal (SBD) are typically consistent within taxa, for example female-biased in birds and male-biased in mammals, leading to theories about the evolutionary pressures that lead to SBD. However, generalizations about the evolution of sex biases tend to overlook that dispersal is mediated by ecological factors that vary over time. We examined potential temporal variation in between- and within-population dispersal over an 11-year period in a bird, the dark-eyed junco (Junco hyemalis). We measured between-population dispersal patterns using genetic assignment indices and found yearly variation in which sex was more likely to have immigrated. When we measured within-population spatial genetic structure and mark–recapture dispersal distances, we typically found yearly SBD patterns that mirrored between-population dispersal, indicating common eco-evolutionary causes despite expected differences due to the scale of dispersal. However, in years without detectable between-population sex biases, we found genetic similarity between nearby males within our population. This suggests that, in certain circumstances, ecological pressures may act on within-population dispersal without affecting dispersal between populations. Alternatively, current analytical tools may be better able to detect within-population SBD. Future work will investigate potential causes of the observed temporal variation in dispersal patterns and whether they have greater effects on within-population dispersal.

  10. Slow and Fast Light in Coupled Microresonators

    Science.gov (United States)

    Chang, Hongrok; Smith, David D.; Fuller, Kirk A.; Dimmock, John O.; Gregory, Don A.; Frazier, Donald O.

    2005-01-01

    We predict the propagation of slow and fast light in two co-resonant coupled optical resonators. In coupled resonators, slow light can propagate without attenuation by a cancellation of absorption as a result of mode splitting and destructive interference, whereas transparent fast light propagation can be achieved by the assistance of gain and splitting of the intracavity resonances, which consequently change the dispersion from normal to anomalous. The effective steady-state response of coupled-resonators is derived using the temporal coupled-mode formalism, and the absorptive and dispersive responses are described. Specifically, the occurrence of slow light via coupled-resonator-induced transparency and gain-assisted fast light are discussed.

  11. Temporal interactive response is resistant to cloudy ocular media in the slow double-stimulation multifocal electroretinogram.

    Science.gov (United States)

    Ho, Wing-Cheung; Chu, Patrick H W; Ng, Yiu-Fai; Tong, Patrick P C; Woo, Victor C P; Chan, Henry H L

    2012-07-01

    To examine the influence of cloudy media on the slow double-stimulation multifocal electroretinogram (mfERG). Slow double-stimulation mfERG responses were measured from 26 subjects with normal ocular health under normal and light scattering conditions (induced using acrylic sheets) (Experiment 1) and another nine cataract patients before and after cataract surgery (Experiment 2). The amplitudes and implicit times of the first (M(1)) and second (M(2)) stimulation were compared under normal and light scattering conditions in Experiment 1 and they were compared under precataract and postcataract surgery in Experiment 2. Compared with control conditions (normal and postcataract surgery), the M(1) amplitude in the central region was significantly reduced in light scattering conditions (acrylic sheets and precataract surgery); the M(2) amplitude and both M(1) and M(2) implicit times of all regions examined were moderately affected in precataract surgery. The M(1):M(2) amplitude ratio and implicit time ratio were virtually unaffected in cloudy media for either central or mid-peripheral regions. Cloudy media affects the mfERG amplitude and implicit time in the slow double-stimulation, but does not affect the response ratio (ie, M(1):M(2) amplitude ratio and implicit time ratio) between the two stimulations. This suggests that the ratio analysis can be applied in patients with mild to moderately cloudy ocular media to evaluate the functional integrity of the retina.

  12. Indexes of temporal myocardial repolarization dispersion and sudden cardiac death in heart failure: any difference?

    Science.gov (United States)

    Piccirillo, Gianfranco; Rossi, Pietro; Mitra, Marilena; Quaglione, Raffaele; Dell'Armi, Annalaura; Di Barba, Daniele; Maisto, Damiana; Lizio, Andrea; Barillà, Francesco; Magrì, Damiano

    2013-03-01

    The QT variability index, calculated between Q- and the T-wave end (QTend VI), is an index of temporal myocardial repolarization lability associated with sudden cardiac death (SCD) in chronic heart failure (CHF). Little is known about temporal variability in the other two temporal myocardial repolarization descriptors obtained from Q-Tpeak and Tpeak -Tend intervals. We therefore investigated differences between these indexes in patients with CHF who died suddenly and in those who survived with a left ventricular ejection fraction (LVEF) ≤35% or >35%. We selected 127 ECG and systolic blood pressure (SPB) recordings from outpatients with CHF all of whom had been followed up for 30 months. We calculated RR and SPB variability by power spectral analysis and QTend VI, QTpeak VI, Tpeak Tend VI. We then subdivided data patients into three groups SCD, LVEF ≤ 35%, and LVEF > 35%. The LVEF was higher in the SCD than in the LVEF ≤ 35% group, whereas no difference was found between the SCD and LVEF > 35% groups. QTend VI, QTpeak VI, and Tpeak Tend VI were higher in the SCD and LVEF ≤ 35% groups than in the LVEF > 35% group. Multivariate analysis detected a negative relationship between all repolarization variability indexes, low frequency obtained from RR intervals and LVEF. Our data show that variability in the first (QTpeak VI) and second halves of the QT interval (Tpeak -Tend VI) significantly contributes to the QTend VI in patients with CHF. Further studies should investigate whether these indexes might help stratify the risk of SCD in patients with a moderately depressed LVEF. ©2012, Wiley Periodicals, Inc.

  13. Temporal and spatial patterns of seed dispersal in two Cistus species (Cistaceae).

    Science.gov (United States)

    Bastida, Fernando; Talavera, Salvador

    2002-04-01

    Cistus species are obligate seeding, early colonizers that follow disturbance, particularly fire, in Mediterranean ecosystems. We studied seed release, seed dispersal and soil seed populations in stands of Cistus ladanifer and C. libanotis. Seed release started in mid- to late summer (C. ladanifer) or in early autumn (C libanotis), and continued for a very extended period: 8-10 months in C. ladanifer, and for a mean of 16 months in C. libanotis. The xerochastic capsules of both species released seeds by successive dehiscence of the locules. All capsules begin to dehisce simultaneously at the start of the seed release period, but in C. libanotis capsule fragmentation replaced dehiscence early in the seed release period. In plants of both species, seed shadows were characterized by a peak of density beneath the plant canopy and a very short tail of much lower densities, indicating that seeds are concentrated beneath mother plants when dispersed. Nevertheless, in late May, at the onset of the fire season, soil seed densities beneath plant canopies were low compared with densities expected from seed shadows, but were apparently high enough to allow recovery of the stands if a disturbance, such as fire, had taken place. Seed-eating Bruchidae in summer and granivorous ants during the seed release period were apparently the main causes of seed losses. Results suggest that in both Cistus species, the staggered seed release could constitute an efficient risk-reducing trait. The plant pool of seeds existing throughout most of the year could be a relevant component of Cistus seed banks.

  14. Temporal and Spatial Dispersal of Cladobotryum Conidia in the Controlled Environment of a Mushroom Growing Room▿

    Science.gov (United States)

    Adie, Bruce; Grogan, Helen; Archer, Simon; Mills, Peter

    2006-01-01

    Cladobotryum spp. are responsible for cobweb disease of mushrooms. In two commercial and one experimental mushroom-growing room, Cladobotryum conidia were released into the air in direct response to physical disturbance of disease colonies during either crop watering or treatment by covering with salt to 10 mm. Conidia were detected using a Burkard spore trap or agar-based trap plates. A maximum concentration of ∼25,000 conidia m−3 was recorded in a small (75-m3) experimental growing room in the hour following the salting of 16 cobweb patches (0.55 m2). Concentrations of 100 and 40 conidia m−3 were recorded in the two larger commercial growing rooms in the hour following the salting of 18 and 11 patches of cobweb (diameter, approximately 50 to 200 mm), respectively. In controlled experiments, disturbed conidia were dispersed rapidly throughout a small growing room, with 91 to 97% of conidia settling out within 15 min. Eighty-five percent of conidia settled out within a 0.5-m radius when air-conditioning fans were switched off, consistent with airborne spore dispersal. Alternative methods for treating diseased areas to minimize conidial release and distribution were investigated and included covering disease colonies with damp paper tissue prior to salt application (tissue salting) and holding a dust extractor above disease colonies during salt application. Both methods resulted in no detectable airborne conidia, but the tissue paper salting technique was more convenient. Prevention of airborne conidial release and distribution is essential to avoid mushroom spotting symptoms, secondary colonies, and early crop termination. PMID:16980426

  15. Spatial-temporal variations in regional ambient sulfur dioxide concentration and source-contribution analysis: A dispersion modeling approach

    Science.gov (United States)

    Zou, Bin; Wilson, J. Gaines; Zhan, F. Benjamin; Zeng, Yongnian; Wu, Kongjiang

    2011-09-01

    An understanding of the complexity of spatial-temporal variations in regional air quality and its respective source contributors is one of the priority research areas due to the adverse effects of air pollution on human health and the environment. In this paper, we integrate air dispersion modeling and Geographic Information System (GIS) based spatial analysis methods to characterize regional ambient air quality at a relatively fine geographical scale (1 km × 1 km) while ascertaining source contributors. The temporal variation analysis shows that sulfur dioxide (SO 2) pollution in Dallas County, Texas did not consistently increase or decrease from 1996 to 2002. The lowest and highest mean levels of annual SO 2 concentrations at all the receptors ( n = 2000) were 0.39 μg m -3 and 2.32 μg m -3 in 2001 and 2002, respectively. Meanwhile, analysis results suggest that the annual SO 2 concentrations in a small part of Dallas County slightly declined with the highest value of -1.00 μg m -3 over the 1996-2002 period, while most of the county experienced increased SO 2 concentration levels from 0.00 to 0.25 μg m -3. In addition, the source apportionment analysis demonstrated that the variations in total annual SO 2 concentrations in Dallas County from 1996 to 2002 were significantly different from those by source classification. That is, compared to industrial emission sources, on-road vehicle emission sources caused variations in annual SO 2 concentrations with relatively larger extents (power of determinant = 0.42). However, extreme variations in concentrations were due to industrial emission sources (3.45% vs. 0.00%). Based on these observations, it can be concluded that the combination of air dispersion modeling and GIS-based spatial analysis shows promise to overcome the drawbacks of sparse intraurban air quality monitoring in characterizing the spatial-temporal micro-variations in regional ambient air quality and ascertaining roles of source contributors over

  16. A Research Program on the Asymptotic Description of Electromagnetic Pulse Propagation in Spatially Inhomogeneous Temporally Dispersive, Attenuative Media

    Science.gov (United States)

    2007-09-01

    of law, no person shall be subject to any penalty for failing to comply with a c control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE...frequency dispersion of the propagation factor fl((o) about the carrier frequency within the passband where the dispersion is normal when (o, = cow ...IN WAVE PROPAGATION 21 [18] -L A. LowRrz, The Theory of.Blectrons, .Toubner, Leipzig, 1906. [19] E. Moms ~, M. KRAoALwrr, AND K. GURLACH, ED,-Ultra

  17. Endozoochorous seed dispersal by Japanese macaques (Macaca fuscata): Effects of temporal variation in ranging and seed characteristics on seed shadows.

    Science.gov (United States)

    Tsuji, Yamato; Morimoto, Mayumi

    2016-02-01

    Variation in seed shadows generated by frugivores is caused by daily, seasonal, and inter-annual variation in ranging, as well as inter-specific variability in gut passage times according to seed characteristics. We studied the extent to which seed weight, specific gravity, and daily (morning, afternoon, and evening) and inter-annual (2004 vs. 2005) variation in ranging affected seed shadows generated by wild Japanese macaques (Macaca fuscata) in northern Japan. The macaques ingested fleshy fruits of 11 species during the two year study period; Viburnum dilatatum (Caprifoliaceae: heavier seeds with higher specific gravity) and Rosa multiflora (Rosaceae: lighter seeds with lower specific gravity) were eaten frequently in both years. The travel distances of macaques after feeding on V. dilatatum and R. multiflora fruits were estimated by combining feeding locations and ranging patterns measured in the field with gut passage times of model seeds in captive animals. Median travel distances after fruit feeding were 431 (quantile range: 277-654) and 478 m (265-646), respectively, with a maximum of 1,261 m. Neither year nor time of day affected travel distances. The gut passage time of model V. dilatatum seeds was longer than that of model R. multiflora seed, but this did not affect dispersal distances. Seed shadows for both species over 2 years showed unimodal distribution (peak: 101-500 m) and more than 90%, 20%, and 3% of ingested seeds were estimated to be dispersed >100, >500, and >1000 m, respectively, the longest known distances among macaque species. R. multiflora seeds tended to be dispersed further in 2004 than 2005, but V. dilatatum seeds were not, implying that inter-annual variations in ranging pattern due to the distribution and abundance of nut fruiting could affect dispersal distance. © 2015 Wiley Periodicals, Inc.

  18. On the influence of temporal and spatial resolution of aircraft emission inventories for mesoscale modeling of pollutant dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Franzkowiak, V.; Petry, H.; Ebel, A. [Cologne Univ. (Germany). Inst. for Geophysics and Meteorology

    1997-12-31

    The sensitivity of a mesoscale chemistry transport model to the temporal and spatial resolution of aircraft emission inventories is evaluated. A statistical analysis of air traffic in the North-Atlantic flight corridor is carried out showing a highly variable, fine structured spatial distribution and a pronounced daily variation. Sensitivity studies comparing different emission scenarios reveal a strong dependency to the emission time and location of both transport and response in chemical formation of subsequent products. The introduction of a pronounced daily variation leads to a 30% higher ozone production in comparison to uniformly distributed emissions. (author) 9 refs.

  19. Spatial vs. temporal effects on demographic and genetic structures: the roles of dispersal, masting and differential mortality on patterns of recruitment in Fagus sylvatica.

    Science.gov (United States)

    Oddou-Muratorio, Sylvie; Klein, Etienne K; Vendramin, Giovanni G; Fady, Bruno

    2011-05-01

    Trees' long lifespan, long-distance dispersal abilities and high year-to-year variability in fecundity are thought to have pervasive consequences for the demographic and genetic structure of recruited seedlings. However, we still lack experimental studies quantifying the respective roles of spatial processes such as restricted seed and pollen dispersal and temporal processes such as mast seeding on patterns of regeneration. Dynamics of European beech (Fagus sylvatica) seedling recruitment was monitored in three plots from 2004 to 2006. Six polymorphic microsatellite genetic markers were used to characterize seedlings and their potential parents in a 7.2-ha stand. These seedlings were shown to result from 12 years of recruitment, with one predominant year of seedling recruitment in 2002 and several years without significant recruitment. Using a spatially explicit mating model based on parentage assignment, short average dispersal distances for seed (δ(s) = 10.9 m) and pollen (43.7 m < δ(p) <57.3 m) were found, but there was also a non-negligible immigration rate from outside the plot (m(s) = 20.5%; 71.6% < m(p) < 77.9%). Hierarchical analyses of seedling genetic structure showed that (i) most of the genetic variation was within plots; (ii) the genetic differentiation among seedling plots was significant (F(ST) = 2.6%) while (iii) there was no effect of year-to-year seed rain variation on genetic structure. In addition, no significant effect of genetic structure on mortality was detected. The consequences of these results for the prediction of population dynamics at ecological timescales are discussed. © 2011 Blackwell Publishing Ltd.

  20. Temporal and spatial variations of 134Cs and 137Cs levels in the Sea of Japan and Pacific coastal region: Implications for dispersion of FDNPP-derived radiocesium.

    Science.gov (United States)

    Inoue, M; Shirotani, Y; Yamashita, S; Takata, H; Kofuji, H; Ambe, D; Honda, N; Yagi, Y; Nagao, S

    2018-02-01

    To investigate the dispersion of Fukushima Dai-ichi Nuclear Power Plant (FDNPP)-derived radiocesium in the Sea of Japan and western Pacific coastal region and determine the sources of radiocesium in these areas, we examined the temporal and spatial variations of 134Cs and 137Cs concentrations (activities) during 2011-2016 in seawaters around the western Japanese Archipelago, particularly in the Sea of Japan. In May 2013, the surface concentration of 134Cs was ∼0.5 mBq/L (decay-corrected to March 11, 2011), and that of 137Cs exceeded the pre-accident level in this study area, where the effects of radiocesium depositions just after the FDNPP accident disappeared in surface waters in October 2011. Subsequently, radiocesium concentrations gradually increased during 2013-2016 (∼0.5-1 mBq/L for 134Cs), exhibiting approximately homogeneous distributions in each year. The temporal and spatial variations of 134Cs and 137Cs concentrations indicated that FDNPP-derived radiocesium around the western Japanese Archipelago, including the Sea of Japan, has been supported by the Kuroshio Current and its branch, Tsushima Warm Current, during 2013-2016. However, in the Sea of Japan, the penetration of 134Cs was limited to depths of less than ∼200 m during three years following the re-delivery of FDNPP-derived radiocesium. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Slow Meteors

    Science.gov (United States)

    Dubs, Martin; Sposetti, Stefano; Spinner, Roger; Booz, Beat

    2017-04-01

    Slow meteors are studied with video observations and spectroscopy. A comparison of their orbits and spectra points to a common origin. Although they do not belong to some meteor stream, they deserve to be studied in more detail. The present paper tries to make a first attempt to characterize the common properties of this class of meteors.

  2. Slow Learner.

    Science.gov (United States)

    Howie, Mark

    2002-01-01

    Discusses the author's success in teaching English. Describes his experiences in achievement, including what has sometimes felt like a slow and even painful process of professional development. Presents an outline of a unit that illustrates a movement through approaches: from personal growth type activities, to post-structuralist and critical…

  3. Slow light with large group index-bandwidth product in ellipse-hole photonic crystal waveguides.

    Science.gov (United States)

    Han, Xu; Wang, Tao; Tang, Jian; Liu, Bo; Wang, BoYun; He, Yu; Zhu, Youjiang

    2015-02-20

    In this study, we propose a new type of slow light photonic crystal waveguide structure to achieve wideband slow light with low dispersion. The waveguide is based on a triangular lattice ellipse-hole photonic crystal imposed simply by a selective altering of the locations of the holes adjacent to the line defect. Under a constant group index criterion of ±10% variation, when group indices are nearly constants of 54, 69, and 80, their corresponding bandwidths of the flat band reach 12.7, 10.0, and 8.6 nm around 1550 nm, respectively. A nearly constant large group index-bandwidth product of 0.44 is achieved for all cases. Low dispersion slow light propagation is confirmed by studying the relative temporal pulse-width spreading with the two-dimensional finite-difference time-domain method.

  4. Temporal variation in the dispersion patterns of metazoan parasites of a coastal fish species from the Gulf of Mexico.

    Science.gov (United States)

    Vidal-Martínez, V M; Pal, P; Aguirre-Macedo, M L; May-Tec, A L; Lewis, J W

    2014-03-01

    Global climate change (GCC) is expected to affect key environmental variables such as temperature and rainfall, which in turn influence the infection dynamics of metazoan parasites in tropical aquatic hosts. Thus, our aim was to determine how temporal patterns of temperature and rainfall influence the mean abundance and aggregation of three parasite species of the fish Cichlasoma urophthalmus from Yucatán, México. We calculated mean abundance and the aggregation parameter of the negative binomial distribution k for the larval digeneans Oligogonotylus manteri and Ascocotyle (Phagicola) nana and the ectoparasite Argulus yucatanus monthly from April 2005 to December 2010. Fourier analysis of time series and cross-correlations were used to determine potential associations between mean abundance and k for the three parasite species with water temperature and rainfall. Both O. manteri and A. (Ph.) nana exhibited their highest frequency peaks in mean abundance at 6 and 12 months, respectively, while their peak in k occurred every 24 months. For A. yucatanus the frequency peaks in mean abundance and k occurred every 12 months. We suggest that the level of aggregation at 24 months of O. manteri increases the likelihood of fish mortality. Such a scenario is less likely for A. (Ph.) nana and A. yucatanus, due to their low infection levels. Our findings suggest that under the conditions of GCC it would be reasonable to expect higher levels of parasite aggregation in tropical aquatic hosts, in turn leading to a potential increase in parasite-induced host mortality.

  5. Chronologic implications for slow cooling of troctolite 76535 and temporal relationships between the Mg-suite and the ferroan anorthosite suite

    Science.gov (United States)

    Borg, Lars E.; Connelly, James N.; Cassata, William S.; Gaffney, Amy M.; Bizzarro, Martin

    2017-03-01

    Ages have been obtained using the 87Rb-87Sr, 147Sm-143Nd, and 146Sm-142Nd isotopic systems for one of the most slowly cooled lunar rocks, Apollo 17 Mg-suite troctolite 76535. The 147Sm-143Nd, 146Sm-142Nd, and Rb-Sr ages derived from plagioclase, olivine, and pyroxene mineral isochrons yield concordant ages of 4307 ± 11 Ma, 4299+29/-35 Ma, and 4279 ± 52 Ma, respectively. These ages are slightly younger than the age determined on ferroan anorthosite suite (FAS) rock 60025 and are therefore consistent with the traditional magma ocean model of lunar differentiation in which the Mg-suite is intruded into the anorthositic crust. However, the Sm-Nd ages record when the rock passed below the closing temperature of the Sm-Nd system in this rock at ∼825 °C, whereas the Rb-Sr age likely records the closure temperature of ∼650 °C. A cooling rate of 3.9 °C/Ma is determined using the ages reported here and in the literature and calculated closure temperatures for the Ar-Ar, Pb-Pb, Rb-Sr, and Sm-Nd systems. This cooling rate is in good agreement with cooling rates estimated from petrographic observations. Slow cooling can lower apparent Sm-Nd crystallization ages by up to ∼80 Ma in the slowest cooled rocks like 76535, and likely accounts for some of the variation of ages reported for lunar crustal rocks. Nevertheless, slow cooling cannot account for the overlap in FAS and Mg-suite rock ages. Instead, this overlap appears to reflect the concordance of Mg-suite and FAS magmatism in the lunar crust as indicated by ages calculated for the solidus temperature of 76535 and 60025 of 4384 ± 24 Ma and 4383 ± 17, respectively. Not only are the solidus ages of 76535 and 60025 nearly concordant, but the Sm-Nd isotopic systematics suggest they are derived from reservoirs that were minimally differentiated prior to ∼4.38 Ga. Although the Sr isotopic composition of 60025 indicates its source was minimally differentiated, the Sr isotopic composition of 76535 indicates it underwent

  6. Slow light engineering in photonic crystals

    OpenAIRE

    Baba, Toshihiko; Mori, Daisuke

    2007-01-01

    Light showing extremely slow propagation (known as slow light) provides various effects such as spatial compression of optical signals, buffering, convolution integral calculation, beam forming, and enhancement of optical absorption, gain, nonlinearity, and so on. To generate such light, very large material or structural dispersion is used. Photonic crystal waveguides are good candidates for many device applications since they can easily generate slow light at room temperature. This paper dis...

  7. Control of Granule Cell Dispersion by Natural Materials Such as Eugenol and Naringin: A Potential Therapeutic Strategy Against Temporal Lobe Epilepsy.

    Science.gov (United States)

    Kim, Sang Ryong

    2016-08-01

    The hippocampus is an important brain area where abnormal morphological characteristics are often observed in patients with temporal lobe epilepsy (TLE), typically showing the loss of the principal neurons in the CA1 and CA3 areas of the hippocampus. TLE is frequently associated with widening of the granule cell layer of the dentate gyrus (DG), termed granule cell dispersion (GCD), in the hippocampus, suggesting that the control of GCD with protection of hippocampal neurons may be useful for preventing and inhibiting epileptic seizures. We previously reported that eugenol (EUG), which is an essential component of medicinal herbs and has anticonvulsant activity, is beneficial for treating epilepsy through its ability to inhibit GCD via suppression of mammalian target of rapamycin complex 1 (mTORC1) activation in the hippocampal DG in a kainic acid (KA)-treated mouse model of epilepsy in vivo. In addition, we reported that naringin, a bioflavonoid in citrus fruits, could exert beneficial effects, such as antiautophagic stress and antineuroinflammation, in the KA mouse model of epilepsy, even though it was unclear whether naringin might also attenuate the seizure-induced morphological changes of GCD in the DG. Similar to the effects of EUG, we recently observed that naringin treatment significantly reduced KA-induced GCD and mTORC1 activation, which are both involved in epileptic seizures, in the hippocampus of mouse brain. Therefore, these observations suggest that the utilization of natural materials, which have beneficial properties such as inhibition of GCD formation and protection of hippocampal neurons, may be useful in developing a novel therapeutic agent against TLE.

  8. Wideband slow light in chirped slot photonic-crystal coupled waveguides.

    Science.gov (United States)

    Hou, Jin; Wu, Huaming; Citrin, D S; Mo, Wenqin; Gao, Dingshan; Zhou, Zhiping

    2010-05-10

    Wideband dispersion-free slow light in chirped-slot photonic-crystal coupled waveguides is proposed and theoretically investigated in detail. By systematically analyzing the dependence of band shape on various structure parameters, unique inflection points in the key photonic band with approximate zero group velocity can be obtained in an optimized slot photonic-crystal coupled waveguide. By simply chirping the widths of the photonic-crystal waveguides in the optimized structure, wideband (up to 20 nm) slow-light with optical confinement in the low dielectric slot is demonstrated numerically with relative temporal pulse-width spreading well below 8% as obtained from two-dimensional finite-difference time-domain simulations. The wideband slow-light operation of the proposed structures would offer significant potential for novel compact high-speed optical-signal-processing devices in silicon-based systems. (c) 2010 Optical Society of America.

  9. Slow light in quantum dot photonic crystal waveguides

    DEFF Research Database (Denmark)

    Nielsen, Torben Roland; Lavrinenko, Andrei; Mørk, Jesper

    2009-01-01

    A theoretical analysis of pulse propagation in a semiconductor quantum dot photonic crystal waveguide in the regime of electromagnetically induced transparency is presented. The slow light mechanism considered here is based on both material and waveguide dispersion. The group index n......(g) for the combined system is significantly enhanced relative to slow light based on purely material or waveguide dispersion....

  10. The TTI slowness surface approximation

    KAUST Repository

    Stovas, A.

    2011-01-01

    The relation between the vertical and horizontal slownesses, better known as the dispersion relation, for a transversely isotropic media with titled symmetry axis {left parenthesis, less than bracket}TTI{right parenthesis, greater than bracket} requires solving a quartic polynomial, which does not admit a practical explicit solution to be used, for example, in downward continuation. Using a combination of perturbation theory with respect to the anelliptic parameter and Shanks transform to improve the accuracy of the expansion, we develop an explicit formula for the dispersion relation that is highly accurate for all practical purposes. It also reveals some insights into the anisotropy parameter dependency of the dispersion relation including the low impact that the anelliptic parameter has on the vertical placement of reflectors for small tilt in the symmetry angle. © 2011 Society of Exploration Geophysicists.

  11. FROM SLOW FOOD TO SLOW TOURISM

    Directory of Open Access Journals (Sweden)

    Bac Dorin Paul

    2014-12-01

    Full Text Available One of the effects of globalization is the faster pace of our lives. This rhythm can be noticed in all aspects of life: travel, work, shopping, etc. and it has serious negative effects. It has become common knowledge that stress and speed generate serious medical issues. Food and eating habits in the modern world have taken their toll on our health. However, some people took a stand and argued for a new kind of lifestyle. It all started in the field of gastronomy, where a new movement emerged – Slow Food, based on the ideas and philosophy of Carlo Petrini. Slow Food represents an important adversary to the concept of fast food, and is promoting local products, enjoyable meals and healthy food. The philosophy of the Slow Food movement developed in several directions: Cittaslow, slow travel and tourism, slow religion and slow money etc. The present paper will account the evolution of the concept and its development during the most recent years. We will present how the philosophy of slow food was applied in all the other fields it reached and some critical points of view. Also we will focus on the presence of the slow movement in Romania, although it is in a very early stage of development. The main objectives of the present paper are: to present the chronological and ideological evolution of the slow movement; to establish a clear separation of slow travel and slow tourism, as many mistake on for the other; to review the presence of the slow movement in Romania. Regarding the research methodology, information was gathered from relevant academic papers and books and also from interviews and discussions with local entrepreneurs. The research is mostly theoretical and empirical, as slow food and slow tourism are emerging research themes in academic circles.

  12. Improved Slow Light Capacity In Graphene-based Waveguide.

    Science.gov (United States)

    Hao, Ran; Peng, Xi-Liang; Li, Er-Ping; Xu, Yang; Jin, Jia-Min; Zhang, Xian-Min; Chen, Hong-Sheng

    2015-10-19

    We have systematically investigated the wideband slow light in two-dimensional material graphene, revealing that graphene exhibits much larger slow light capability than other materials. The slow light performances including material dispersion, bandwidth, dynamic control ability, delay-bandwidth product, propagation loss, and group-velocity dispersion are studied, proving graphene exhibits significant advantages in these performances. A large delay-bandwidth product has been obtained in a simple yet functional grating waveguide with slow down factor c/v(g) at 163 and slow light bandwidth Δω at 94.4 nm centered at 10.38 μm, which is several orders of magnitude larger than previous results. Physical explanation of the enhanced slow light in graphene is given. Our results indicate graphene is an excellent platform for slow light applications, promoting various future slow light devices based on graphene.

  13. Temporal and Spatial Variability in Composition of Polar Components of Oil and Dispersants During and After the Deepwater Horizon Oil Spill

    Science.gov (United States)

    Kujawinski, E. B.; Longnecker, K.; Kido Soule, M. C.; Boysen, A. K.

    2010-12-01

    Oil and dispersants are complex mixtures of organic compounds with a wide range of physico-chemical properties. During the Deepwater Horizon oil spill, extremely large volumes of both crude oil and dispersants were released at the seafloor of the Gulf of Mexico. Although a minor fraction, polar components of both crude oil and dispersants are more likely to dissolve in the water column during transit to shallower waters. These components are also less biodegradable and may be more toxic to marine fauna and thus they may have a disproportional impact on the Gulf of Mexico ecosystem. As a result, it is important to examine the composition of these components as well as to assess their fate in the water column over time. We have employed ultrahigh resolution mass spectrometry to characterize the complex mixtures of oil, dispersants and dissolved organic matter (DOM) in water samples collected from a variety of depths and distances from the wellhead. Our technique couples negative ion mode electrospray ionization (ESI) to a Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer (MS). This method resolves thousands of polar components per spectrum and has sufficient mass resolution and accuracy to enable the assignment of elemental formulas based on the mass measurement alone. Our preliminary results indicate that heteroatom-containing compounds such as naphthenic and sulfonic acids, including the surfactant used in Corexit 9500, are present and enhanced in surface and deepwater samples with high hydrocarbon content. We are in the process of examining additional samples collected during the active spill as well as after the spill had ceased in order to identify compounds (1) that may be selectively degraded, (2) that may be produced from bacterial metabolism of other hydrocarbons or (3) that may remain refractory in the Gulf of Mexico. In this presentation, we will summarize our findings to date and will propose compounds that merit further examination

  14. Unambiguous demonstration of soliton evolution in slow-light silicon photonic crystal waveguides with SFG-XFROG.

    Science.gov (United States)

    Li, Xiujian; Liao, Jiali; Nie, Yongming; Marko, Matthew; Jia, Hui; Liu, Ju; Wang, Xiaochun; Wong, Chee Wei

    2015-04-20

    We demonstrate the temporal and spectral evolution of picosecond soliton in the slow light silicon photonic crystal waveguides (PhCWs) by sum frequency generation cross-correlation frequency resolved optical grating (SFG-XFROG) and nonlinear Schrödinger equation (NLSE) modeling. The reference pulses for the SFG-XFROG measurements are unambiguously pre-characterized by the second harmonic generation frequency resolved optical gating (SHG-FROG) assisted with the combination of NLSE simulations and optical spectrum analyzer (OSA) measurements. Regardless of the inevitable nonlinear two photon absorption, high order soliton compressions have been observed remarkably owing to the slow light enhanced nonlinear effects in the silicon PhCWs. Both the measurements and the further numerical analyses of the pulse dynamics indicate that, the free carrier dispersion (FCD) enhanced by the slow light effects is mainly responsible for the compression, the acceleration, and the spectral blue shift of the soliton.

  15. Holographic Gratings for Slow-Neutron Optics

    Science.gov (United States)

    Klepp, Juergen; Pruner, Christian; Tomita, Yasuo; Geltenbort, Peter; Drevenšek-Olenik, Irena; Gyergyek, Saso; Kohlbrecher, Joachim; Fally, Martin

    2012-01-01

    Recent progress in the development of holographic gratings for neutron-optics applications is reviewed. We summarize the properties of gratings recorded in deuterated (poly)methylmethacrylate, holographic polymer-dispersed liquid crystals and nanoparticle-polymer composites revealed by diffraction experiments with slow neutrons. Existing and anticipated neutron-optical instrumentations based on holographic gratings are discussed.

  16. Improving temporal profiles of anthropogenic emissions influenced by human activities and meteorological drivers for atmospheric dispersion modelling - a case study for the UK

    Science.gov (United States)

    Vieno, M.; Reis, S.; Ambelas Skjøth, C.; Lang, M.; Geels, C.

    2010-12-01

    Emissions of trace gases originating from anthropogenic activities are vital input data for chemical transport models (CTMs). Other key input datasets such as meteorological drivers, and biogeochemical and physical processes have been subject to detailed investigation and research in the recent past, while the representation of emission data in CTMs has been somewhat neglected. Arguably, this has less impact on the regional to hemispheric or global scale, where the grid sizes of currently applied CTMs represent well mixed average concentrations or deposition values. Evaluating model output against ground-based observations or remote sensing results on these spatial levels appears not to be overly sensitive to the temporal (and spatial) profiles of emission input data. With increasing level of detail and spatiotemporal resolution, CTMs applied to determine national or local scale air quality are likely prone to be more sensitive to the spatial and temporal patterns of anthropogenic emissions. This paper discusses results of the application of the EMEP4UK CTM on a 5 km x 5 km resolution for the whole of the United Kingdom. In a first instance, detailed temporal profiles for emissions from road transport, power generation and other stationary sources have been developed. Depending on typical sectoral activities, hourly to seasonal variations have been quantified and (sub-)sectoral time curves generated. Here, we will discuss how these improved time curves influence modelled concentrations of NO2, Ozone and PM10 for selected episodes in the year 2007. In a second application, both anthropogenic activities (e.g. manure spreading and fertilizer application) and meteorological factors (e.g. temperature and seasonality) have been investigated regarding their influence on the spatiotemporal distribution of NH3 emissions (Skjøth et al., 2004; see as well Pinder et al., 2004; Gilliland et al., 2006). The discussion of results in this case will focus on the impact on the

  17. Fundamental limitations to gain enhancement in slow-light photonic structures

    DEFF Research Database (Denmark)

    Grgic, Jure; Ott, Johan Raunkjar; Wang, Fengwen

    2012-01-01

    We present a non-perturbative analysis of light-matter interaction in active photonic crystal waveguides in the slow-light regime. Inclusion of gain is shown to modify the underlying dispersion law, thereby degrading the slow-light enhancement.......We present a non-perturbative analysis of light-matter interaction in active photonic crystal waveguides in the slow-light regime. Inclusion of gain is shown to modify the underlying dispersion law, thereby degrading the slow-light enhancement....

  18. On the use of slow light for enhancing waveguide properties

    DEFF Research Database (Denmark)

    Mørk, Jesper; Nielsen, Torben Roland

    2010-01-01

    On the basis of a general analysis of waveguides containing a dispersive material, we identify conditions under which slow-light propagation may enhance the gain, absorption, or phase change. The enhancement is shown to depend on the slow-light mechanism and the translational symmetry...... of the waveguide. A combination of material and waveguide dispersion may strongly enhance the control of light speed, e.g., using electromagnetically induced transparency in quantum dots embedded in a photonic crystal waveguide....

  19. Experimental arrangement to measure dispersion in optical fiber devices

    Energy Technology Data Exchange (ETDEWEB)

    Armas Rivera, Ivan [Benemerita Universidad Autonoma de Puebla, Facultad de Ciencias de la Electronica (Mexico); Beltran Perez, Georgina; Castillo Mixcoatl, Juan; Munoz Aguirre, Severino [Benemerita Universidad Autonoma de Puebla, Facultad de Ciencias Fisico Matematicas (Mexico); Zaca Moran, Placido, E-mail: ivan_rr1@hotmail.com [Benemerita Universidad Autonoma de Puebla, Fisicoquimica de Materiales ICUAP (Mexico)

    2011-01-01

    Dispersion is a quite important parameter in systems based on optical fiber, especially in pulsed emission lasers, where the temporal width is affected by such parameter. Therefore, it is necessary to consider the dispersion provoked by each component in the cavity. There are various experimental interferometric arrangements to evaluate this parameter. Generally, these systems modify the wavelength to obtain information about the n({lambda}) dependency, which is contained in the interferogram phase. However, this makes the system quite slow and it requires tunable and narrow bandwidth laser sources. In the present work, results obtained from an arrangement based on Mach-Zehnder interferometer where one of the arms is the optical fiber under study, while the reference one is air, are presented. In order to determine the n({lambda}) dependency, a wide spectrum light source was used in the wavelength range of interest. The phase information was evaluated from the interferometric signal measured by an optical spectrum analyzer.

  20. Dispersal and metapopulation stability

    Directory of Open Access Journals (Sweden)

    Shaopeng Wang

    2015-10-01

    Full Text Available Metapopulation dynamics are jointly regulated by local and spatial factors. These factors may affect the dynamics of local populations and of the entire metapopulation differently. Previous studies have shown that dispersal can stabilize local populations; however, as dispersal also tends to increase spatial synchrony, its net effect on metapopulation stability has been controversial. Here we present a simple metapopulation model to study how dispersal, in interaction with other spatial and local processes, affects the temporal variability of metapopulations in a stochastic environment. Our results show that in homogeneous metapopulations, the local stabilizing and spatial synchronizing effects of dispersal cancel each other out, such that dispersal has no effect on metapopulation variability. This result is robust to moderate heterogeneities in local and spatial parameters. When local and spatial dynamics exhibit high heterogeneities, however, dispersal can either stabilize or destabilize metapopulation dynamics through various mechanisms. Our findings have important theoretical and practical implications. We show that dispersal functions as a form of spatial intraspecific mutualism in metapopulation dynamics and that its effect on metapopulation stability is opposite to that of interspecific competition on local community stability. Our results also suggest that conservation corridors should be designed with appreciation of spatial heterogeneities in population dynamics in order to maximize metapopulation stability.

  1. The Slow Learner.

    Science.gov (United States)

    Roucek, Joseph S., Ed.

    Papers on the slow learner treat physical defects and learning abilities, social and economic background as an obstacle to learning, the causes of dropouts and lapses in study, and the limitations and potential of the ungifted. The contribution interest in the slow learner has made to education is discussed; also discussed are problems of the…

  2. STUDY OF SLOW LEARNERS.

    Science.gov (United States)

    MIDANIK, J. SYDNEY

    A SPECIAL COMMITTEE REPORT TO THE BOARD OF EDUCATION, TORONTO, CANADA, REVIEWS THE PRESENT PROGRAM FOR SLOW LEARNERS (IQ 59 TO 90) AND RECOMMENDS A NEW TYPE OF EXPERIMENTAL HIGH SCHOOL. THE PROBLEM OF SLOW LEARNERS, THE USE AND MEANING OF INTELLIGENCE TESTS, AND THE DISTRIBUTION OF LEARNING CAPACITIES AMONG STUDENTS IN SCHOOL ARE DISCUSSED. THE…

  3. Temporal variations of flux and altitude of sulfur dioxide emissions during volcanic eruptions: implications for long-range dispersal of volcanic clouds

    Directory of Open Access Journals (Sweden)

    M. Boichu

    2015-07-01

    Full Text Available Sulfur-rich degassing, which is mostly composed of sulfur dioxide (SO2, plays a major role in the overall impact of volcanism on the atmosphere and climate. The accurate assessment of this impact is currently hampered by the poor knowledge of volcanic SO2 emissions. Here, using an inversion procedure, we show how assimilating snapshots of the volcanic SO2 load derived from the Infrared Atmospheric Sounding Interferometer (IASI allows for reconstructing both the flux and altitude of the SO2 emissions with an hourly resolution. For this purpose, the regional chemistry-transport model CHIMERE is used to describe the dispersion of SO2 when released in the atmosphere. As proof of concept, we study the 10 April 2011 eruption of the Etna volcano (Italy, which represents one of the few volcanoes instrumented on the ground for the continuous monitoring of SO2 degassing. We find that the SO2 flux time-series retrieved from satellite imagery using the inverse scheme is in agreement with ground observations during ash-poor phases of the eruption. However, large discrepancies are observed during the ash-rich paroxysmal phase as a result of enhanced plume opacity affecting ground-based ultraviolet (UV spectroscopic retrievals. As a consequence, the SO2 emission rate derived from the ground is underestimated by almost one order of magnitude. Altitudes of the SO2 emissions predicted by the inverse scheme are validated against an RGB image of the Moderate Resolution Imaging Spectroradiometer (MODIS capturing the near-source atmospheric pathways followed by Etna plumes, in combination with forward trajectories from the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT model. At a large distance from the source, modelled SO2 altitudes are compared with independent information on the volcanic cloud height. We find that the altitude predicted by the inverse scheme is in agreement with snapshots of the SO2 height retrieved from recent algorithms

  4. A tilted transversely isotropic slowness surface approximation

    KAUST Repository

    Stovas, A.

    2012-05-09

    The relation between vertical and horizontal slownesses, better known as the dispersion relation, for transversely isotropic media with a tilted symmetry axis (TTI) requires solving a quartic polynomial equation, which does not admit a practical explicit solution to be used, for example, in downward continuation. Using a combination of the perturbation theory with respect to the anelliptic parameter and Shanks transform to improve the accuracy of the expansion, we develop an explicit formula for the vertical slowness that is highly accurate for all practical purposes. It also reveals some insights into the anisotropy parameter dependency of the dispersion relation including the low impact that the anelliptic parameter has on the vertical placement of reflectors for a small tilt in the symmetry angle. © 2012 European Association of Geoscientists & Engineers.

  5. Frozen and broadband slow light in coupled periodic nanowire waveguides.

    Science.gov (United States)

    Gutman, Nadav; Dupree, W Hugo; Sun, Yue; Sukhorukov, Andrey A; de Sterke, C Martijn

    2012-02-13

    We develop novel designs enabling slow-light propagation with vanishing group-velocity dispersion ("frozen light") and slow-light with large delay-bandwidth product, in periodic nanowires. Our design is based on symmetry-breaking of periodic nanowire waveguides and we demonstrate its vailidy through two- and three-dimensional simulations. The slow-light is associated with a stationary inflection point which appears through coupling between forward and backward waveguide modes. The mode coupling also leads to evanescent modes, which enable efficient light coupling to the slow mode.

  6. Transformer Industry Productivity Slows.

    Science.gov (United States)

    Otto, Phyllis Flohr

    1981-01-01

    Annual productivity increases averaged 2.4 percent during 1963-79, slowing since 1972 to 1.5 percent; computer-assisted design and product standardization aided growth in output per employee-hour. (Author)

  7. Systematic Design of Slow Light Waveguides

    DEFF Research Database (Denmark)

    Wang, Fengwen

    Light can propagate much slower in photonic crystal waveguides and plasmonic waveguides than in vacuum. Slow light propagation in waveguides shows broad prospects in the terabit communication systems. However, it causes severe signal distortions and displays large propagation loss. Moreover......, an optimization formulation is presented to tailor the slope of the dispersion curve. The design robustness is enforced by considering different manufacturing realizations in the optimization procedure. Both free- and fixed-topology (circular-hole based) slow light photonic crystal waveguides are obtained using...... two different parameterizations. Detailed comparisons show that the bandwidth of slow light propagation can be significantly enhanced by allowing irregular geometries in the waveguides. To mitigate the propagation loss due to scattering in the photonic crystal waveg- uides, an optimization problem...

  8. Slow medical education.

    Science.gov (United States)

    Wear, Delese; Zarconi, Joseph; Kumagai, Arno; Cole-Kelly, Kathy

    2015-03-01

    Slow medical education borrows from other "slow" movements by offering a complementary orientation to medical education that emphasizes the value of slow and thoughtful reflection and interaction in medical education and clinical care. Such slow experiences, when systematically structured throughout the curriculum, offer ways for learners to engage in thoughtful reflection, dialogue, appreciation, and human understanding, with the hope that they will incorporate these practices throughout their lives as physicians. This Perspective offers several spaces in the medical curriculum where slowing down is possible: while reading and writing at various times in the curriculum and while providing clinical care, focusing particularly on conducting the physical exam and other dimensions of patient care. Time taken to slow down in these ways offers emerging physicians opportunities to more fully incorporate their experiences into a professional identity that embodies reflection, critical awareness, cultural humility, and empathy. The authors argue that these curricular spaces must be created in a very deliberate manner, even on busy ward services, throughout the education of physicians.

  9. Biofilm Dispersal

    Science.gov (United States)

    2010-01-01

    Like all sessile organisms, surface-attached communities of bacteria known as biofilms must release and disperse cells into the environment to colonize new sites. For many pathogenic bacteria, biofilm dispersal plays an important role in the transmission of bacteria from environmental reservoirs to human hosts, in horizontal and vertical cross-host transmission, and in the exacerbation and spread of infection within a host. The molecular mechanisms of bacterial biofilm dispersal are only beginning to be elucidated. Biofilm dispersal is a promising area of research that may lead to the development of novel agents that inhibit biofilm formation or promote biofilm cell detachment. Such agents may be useful for the prevention and treatment of biofilms in a variety of industrial and clinical settings. This review describes the current status of research on biofilm dispersal, with an emphasis on studies aimed to characterize dispersal mechanisms, and to identify environmental cues and inter- and intracellular signals that regulate the dispersal process. The clinical implications of biofilm dispersal and the potential therapeutic applications of some of the most recent findings will also be discussed. PMID:20139339

  10. Ivory Osteoma Of Temporal Bone

    Directory of Open Access Journals (Sweden)

    Ravi Meher

    2006-03-01

    Full Text Available Osteomas are slow growing bony tumors common in fronto-ethmoid regions and rare in temporal bone. These are usually asymptomatic and require treatment mainly for cosmetic reasons. We describe a case of temporal bone osteoma in a female.

  11. Slow earthquakes linked along dip in the Nankai subduction zone.

    Science.gov (United States)

    Hirose, Hitoshi; Asano, Youichi; Obara, Kazushige; Kimura, Takeshi; Matsuzawa, Takanori; Tanaka, Sachiko; Maeda, Takuto

    2010-12-10

    We identified a strong temporal correlation between three distinct types of slow earthquakes distributed over 100 kilometers along the dip of the subducting oceanic plate at the western margin of the Nankai megathrust rupture zone, southwest Japan. In 2003 and 2010, shallow very-low-frequency earthquakes near the Nankai trough as well as nonvolcanic tremor at depths of 30 to 40 kilometers were triggered by the acceleration of a long-term slow slip event in between. This correlation suggests that the slow slip might extend along-dip between the source areas of deeper and shallower slow earthquakes and thus could modulate the stress buildup on the adjacent megathrust rupture zone.

  12. Regional Slow Waves and Spindles in Human Sleep

    Science.gov (United States)

    Nir, Yuval; Staba, Richard J.; Andrillon, Thomas; Vyazovskiy, Vladyslav V.; Cirelli, Chiara; Fried, Itzhak; Tononi, Giulio

    2011-01-01

    SUMMARY The most prominent EEG events in sleep are slow waves, reflecting a slow (waves and the underlying active and inactive neuronal states occur locally. Thus, especially in late sleep, some regions can be active while others are silent. We also find that slow waves can propagate, usually from medial prefrontal cortex to the medial temporal lobe and hippocampus. Sleep spindles, the other hallmark of NREM sleep EEG, are likewise predominantly local. Thus, intracerebral communication during sleep is constrained because slow and spindle oscillations often occur out-of-phase in different brain regions. PMID:21482364

  13. Dispersion Forces

    CERN Document Server

    Buhmann, Stefan Yoshi

    2012-01-01

    In this book, a modern unified theory of dispersion forces on atoms and bodies is presented which covers a broad range of advanced aspects and scenarios. Macroscopic quantum electrodynamics is shown to provide a powerful framework for dispersion forces which allows for discussing general properties like their non-additivity and the relation between microscopic and macroscopic interactions. It is demonstrated how the general results can be used to obtain dispersion forces on atoms in the presence of bodies of various shapes and materials. Starting with a brief recapitulation of volume I, this volume II deals especially with bodies of irregular shapes, universal scaling laws, dynamical forces on excited atoms, enhanced forces in cavity quantum electrodynamics, non-equilibrium forces in thermal environments and quantum friction. The book gives both the specialist and those new to the field a thorough overview over recent results in the field. It provides a toolbox for studying dispersion forces in various contex...

  14. Sediment dispersal in the macro tidal Gulf of Kachchh, India

    Digital Repository Service at National Institute of Oceanography (India)

    Chauhan, O.S.

    and their dispersal patterns have been determined and presented. The results of the study have application for sequential interpretation of satellite images for separating out macro-tide induced temporal and spatial changes in the dispersal patterns and physiographic...

  15. Slow light enhancement and limitations in periodic media

    DEFF Research Database (Denmark)

    Grgic, Jure

    to longer interaction time in the periodic media. Due to this reason, weak light-matter interaction is enhanced. The enhancement due to slow light has been studied for loss and gain. By introducing gain/loss, dispersive properties, in the slow light region, are severely influenced. The minimum attainable......Properties of periodic dielectric media have attracted a big interest in the last two decades due to numerous exciting physical phenomena that cannot occur in homogeneous media. Due to their strong dispersive properties, the speed of light can be significantly slowed down in periodic structures...... and significant structures with numerical and analytical methods. By analyzing different structures, we show very general properties for limitation and enhancement in the slow light regime. Inherent imperfections of fabricated structures such as a material loss and structural disorder have a strong influence...

  16. Slow Learners Speed Up

    Science.gov (United States)

    Becker, Leonard

    1975-01-01

    The article describes a work/study program for slow learners where the students spend a month at the Brooklyn Bureau's Department for the Handicapped, an agency where the physically and emotionally handicapped are given a comprehensive program of work training, job placement, homemaker training, and recreation. (Author/JB)

  17. SPS slow extraction septa

    CERN Multimedia

    CERN PhotoLab

    1979-01-01

    SPS long straight section (LSS) with a series of 5 septum tanks for slow extraction (view in the direction of the proton beam). There are 2 of these: in LSS2, towards the N-Area; in LSS6 towards the W-Area. See also Annual Report 1975, p.175.

  18. Human gamma oscillations during slow wave sleep.

    Directory of Open Access Journals (Sweden)

    Mario Valderrama

    Full Text Available Neocortical local field potentials have shown that gamma oscillations occur spontaneously during slow-wave sleep (SWS. At the macroscopic EEG level in the human brain, no evidences were reported so far. In this study, by using simultaneous scalp and intracranial EEG recordings in 20 epileptic subjects, we examined gamma oscillations in cerebral cortex during SWS. We report that gamma oscillations in low (30-50 Hz and high (60-120 Hz frequency bands recurrently emerged in all investigated regions and their amplitudes coincided with specific phases of the cortical slow wave. In most of the cases, multiple oscillatory bursts in different frequency bands from 30 to 120 Hz were correlated with positive peaks of scalp slow waves ("IN-phase" pattern, confirming previous animal findings. In addition, we report another gamma pattern that appears preferentially during the negative phase of the slow wave ("ANTI-phase" pattern. This new pattern presented dominant peaks in the high gamma range and was preferentially expressed in the temporal cortex. Finally, we found that the spatial coherence between cortical sites exhibiting gamma activities was local and fell off quickly when computed between distant sites. Overall, these results provide the first human evidences that gamma oscillations can be observed in macroscopic EEG recordings during sleep. They support the concept that these high-frequency activities might be associated with phasic increases of neural activity during slow oscillations. Such patterned activity in the sleeping brain could play a role in off-line processing of cortical networks.

  19. Stationary waves and slow cloud features challenge Venus's night side superrotation

    Science.gov (United States)

    Peralta, J.; Hueso, R.; Sánchez-Lavega, A.; Lee, Y. J.; García-Muñoz, A.; Kouyama, T.; Sagawa, H.; Sato, T. M.; Piccioni, G.; Tellmann, S.; Satoh, T.

    2017-09-01

    We present the first global measurements of the night side circulation of Venus at the upper cloud level from the tracking of individual features in thermal emission images at 3.8 and 5.0 μm during 2006-2008 (Venus Express/VIRTIS) and 2015 (IRTF/SpeX). The zonal motions range from -110 to -60 m/s, consistent with those found for the dayside but with larger dispersion6. Slow motions (-50 to -20 m/s) are also found and may indicate temporal changes in the vertical structure of the superrotation. Abundant stationary wave patterns with zonal speeds from -10 to +10 m/s clearly dominate the night upper clouds.

  20. Chemical dispersants

    NARCIS (Netherlands)

    Rahsepar, Shokouhalsadat; Smit, Martijn P.J.; Murk, Albertinka J.; Rijnaarts, Huub H.M.; Langenhoff, Alette A.M.

    2016-01-01

    Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil

  1. Grating-assisted superresolution of slow waves in Fourier space

    DEFF Research Database (Denmark)

    Thomas, N. Le; Houdré, R.; Frandsen, Lars Hagedorn

    2007-01-01

    We present a far-field optical technique allowing the measurement of the dispersion relation of electromagnetic fields propagating under the light cone in photonic nanostuctures. It relies on the use of a one-dimensional grating to probe the evanescent tail of the guided field in combination...... with a high numerical aperture Fourier space imaging set-up. A high-resolution spectroscopy of the far-field emission diagram allows us to accurately and efficiently determine the dispersion curve and the group-index dispersion of planar photonic waveguides operating in the slow light regime....

  2. Slow-light solitons revisited

    OpenAIRE

    Rybin, A. V.; Vadeiko, I. P.; Bishop, A. R.

    2006-01-01

    We investigate propagation of slow-light solitons in atomic media described by the nonlinear $\\Lambda$-model. Under a physical assumption, appropriate to the slow light propagation, we reduce the $\\Lambda$-scheme to a simplified nonlinear model, which is also relevant to 2D dilatonic gravity. Exact solutions describing various regimes of stopping slow-light solitons can then be readily derived.

  3. Slow Scan Telemedicine

    Science.gov (United States)

    1984-01-01

    Originally developed under contract for NASA by Ball Bros. Research Corporation for acquiring visual information from lunar and planetary spacecraft, system uses standard closed circuit camera connected to a device called a scan converter, which slows the stream of images to match an audio circuit, such as a telephone line. Transmitted to its destination, the image is reconverted by another scan converter and displayed on a monitor. In addition to assist scans, technique allows transmission of x-rays, nuclear scans, ultrasonic imagery, thermograms, electrocardiograms or live views of patient. Also allows conferencing and consultation among medical centers, general practitioners, specialists and disease control centers. Commercialized by Colorado Video, Inc., major employment is in business and industry for teleconferencing, cable TV news, transmission of scientific/engineering data, security, information retrieval, insurance claim adjustment, instructional programs, and remote viewing of advertising layouts, real estate, construction sites or products.

  4. Temporal Heterogeneity and the Value of Slowness in Robotic Systems

    Science.gov (United States)

    2015-11-01

    Abstract— Robot teaming is a well-studied area, but little research to date has been conducted on the fundamental benefits of heterogeneous... establish it through theoretical analysis and experimental results conducted in simulation and actual robotic platforms. REFERENCES [1] J.D. Madden...with an Ecological Augmented Virtuality Interface, Proceedings of AISB-HRI Symposium: New Frontiers in Human- Robot Interaction, Scotland , 2009. [18

  5. Reducing disorder-induced losses for slow light photonic crystal waveguides through Bloch mode engineering

    DEFF Research Database (Denmark)

    Mann, Nishan; Combrié, Sylvian; Colman, Pierre

    2013-01-01

    We present theory and measurements ofdisorder-induced losses for low loss 1.5 mmlong slow light photonic crystal waveguides. A recent class of dispersion engineered waveguides increases the bandwidth of slow light and shows lower propagation losses for the same group index. Our theory and experim...

  6. Gravity slows light

    Science.gov (United States)

    O'Sullivan, Ian

    2014-03-01

    The speed of light is measured as a constant number of metres per second. However, a meter is a measure of how far light travels in a second. That is, light always travels as far as it does in a second every second. This is a circular definition. When measured against other things, light speed must change. Gravity is usually described as a consequence of a curve in spacetime. The word ``space'' has two distinct meanings. In geometry, space is a continuous area. In relativity, ``space'' refers exclusively to geometric spaces measured with light. ``Time'' in a relativistic sense also refers exclusively to the passage of time as measured against light. So a curve in spacetime (a relativistic concept) is a gradual deviation in the thing we use to measure geometric spaces and the passage of time, i.e. the speed of light. I show how Newtonian gravity can explain observable phenomena if the speed of light is inversely proportional to the strength of the gravitational field. For example, we would also expect light to refract as it changes speed passing near massive bodies. Boundary conditions are also discussed, for example, very high gravity will slow light to a stop, making it impossible to measure anything against light, giving a gravitational singularity.

  7. Slow frictional waves

    Science.gov (United States)

    Viswanathan, Koushik; Sundaram, Narayan; Chandrasekar, Srinivasan

    Stick-slip, manifest as intermittent tangential motion between two dry solid surfaces, is a friction instability that governs diverse phenomena from automobile brake squeals to earthquakes. We show, using high-speed in situ imaging of an adhesive polymer interface, that low velocity stick-slip is fundamentally of three kinds, corresponding to passage of three different surface waves -- separation pulses, slip pulses and the well-known Schallamach waves. These waves, traveling much slower than elastic waves, have clear distinguishing properties. Separation pulses and Schallamach waves involve local interface separation, and propagate in opposite directions while slip pulses are characterized by a sharp stress front and do not display any interface detachment. A change in the stick-slip mode from separation to slip pulse is effected simply by increasing the normal force. Together, these three waves constitute all possible stick-slip modes in adhesive friction and are shown to have direct analogues in muscular locomotory waves in soft bodied invertebrates. A theory for slow wave propagation is also presented which is capable of explaining the attendant interface displacements, velocities and stresses.

  8. Slowing Ocean Acidification

    Science.gov (United States)

    Bravo, A.

    2016-12-01

    Currently our ocean's pH is 8.1, a decrease from 8.2 in the past 200 years since the beginning of the industrial revolution. The ocean absorbs about a third of the carbon dioxide (CO2) from the atmosphere, which is helpful to us, since reducing the amount of CO2 in the atmosphere shows global warming. However, what is the impact of all that CO2 on the ocean? I evaluated the effect of acidic water on bivalves, and found that the shells were broken down with exposure to increased acidity. I am concerned that continued ocean acidification will impact organisms that are unable to adapt to the changing ocean chemistry. While the US currently invests in alternative forms of energy including solar and wind, approximately 66% of our energy comes from sources that are releasing CO2 into the atmosphere. I want to explore the potential of wave energy as another form of renewable energy. When wind blows over the surface of the ocean, it creates a wave. Could this wave energy be a consistent clean energy source? Could a strategy to slow and reverse ocean acidification be found in the ocean?

  9. A Case for Slow Reading

    Directory of Open Access Journals (Sweden)

    Matthew J Ostercamp

    2014-05-01

    Full Text Available This essay makes a case for the value of slow or deep reading.  Inspired by the Slow Food movement it seeks to apply their principles to reading.  It begins by exploring the meaning of information and how like food, information has come to be regarded as a commodity.  Drawing upon the philosophy of Albert Borgmann, it counters the prevalent commodity view of information by offering an alternative paradigm that connects careful reading to human flourishing.  It argues that by connecting information to pleasure and community, slow reading advocates can have comparable success to that enjoyed by the slow food movement.

  10. Coaxial slow source

    Energy Technology Data Exchange (ETDEWEB)

    Brooks, R.D.; Jarboe, T.R.

    1990-01-01

    Field reversed configurations (FRCs) are a class of compact toroid with not toroidal field. The field reversed theta pinch technique has been successfully used for formation of FRCs since their inception in 1958. In this method an initial bias field is produced. After ionization of the fill gas, the current in the coil is rapidly reversed producing the radial implosion of a current sheath. At the ends of the coil the reversed field lines rapidly tear and reconnect with the bias field lines until no more bias flux remains. At this point, vacuum reversed field accumulates around the configuration which contracts axially until an equilibrium is reached. When extrapolating the use of such a technique to reactor size plasmas two main shortcomings are found. First, the initial bias field, and hence flux in a given device, which can be reconnected to form the configuration is limited from above by destructive axial dynamics. Second, the voltages required to produce rapid current reversal in the coil are very large. Clearly, a low voltage formation technique without limitations on flux addition is desirable. The Coaxial Slow Source (CSS) device was designed to meet this need. It has two coaxial theta pinch coils. Coaxial coil geometry allows for the addition of as much magnetic flux to the annular plasma between them as can be generated inside the inner coil. Furthermore the device can be operated at charging voltages less than 10 kV and on resistive diffusion, rather than implosive time scales. The inner coil is a novel, concentric, helical design so as to allow it to be cantilevered on one end to permit translation of the plasma. Following translation off the inner coil the Annular Field Reversed Configuration would be re-formed as a true FRC. In this paper we investigate the formation process in the new parallel configuration., CSSP, in which the inner and outer coils are connected in parallel to the main capacitor bank.

  11. Coaxial slow source

    Science.gov (United States)

    Brooks, R. D.; Jarboe, T. R.

    Field reversed configurations (FRC's) are a class of compact toroid with no toroidal field. The field reversed theta pinch technique has been successfully used for formation of FRC's since their inception in 1958. In this method an initial bias field is produced. After ionization of the fill gas, the current in the coil is rapidly reversed producing the radial implosion of a current sheath. At the ends of the coil the reversed field lines rapidly tear and reconnect with the bias field lines until no more bias flux remains. At this point, vacuum reversed field accumulates around the configuration which contracts axially until an equilibrium is reached. When extrapolating the use of such a technique to reactor size plasmas two main shortcomings are found. First, the initial bias field, and hence flux in a given device, which can be reconnected to form the configuration is limited from above by destructive axial dynamics. Second, the voltages required to produce rapid current reversal in the coil are very large. Clearly, a low voltage formation technique without limitations on flux addition is desirable. The Coaxial Slow Source (CSS) device was designed to meet this need. It has two coaxial theta pinch coils. Coaxial coil geometry allows for the addition of as much magnetic flux to the annular plasma between them as can be generated inside the inner coil. Furthermore the device can be operated at charging voltages less than 10 kV and on resistive diffusion, rather than implosive time scales. The inner coil is a novel, concentric, helical design so as to allow it to be cantilevered on one end to permit translation of the plasma. Following translation off the inner coil the Annular Field Reversed Configuration would be re-formed as a true FRC. In this paper, we investigate the formation process in the new parallel configuration, CSSP, in which the inner and outer coils are connected in parallel to the main capacitor bank.

  12. Switching feature of EIT-based slow light giant phase-sensitive Kerr nonlinearity in a semiconductor quantum well

    Science.gov (United States)

    Hamedi, H. R.; Mehmannavaz, Mohammad Reza

    2015-02-01

    A four level inverted Y-type quantum well semiconductor is proposed based on phase-sensitive Kerr nonlinearity with a closed-loop configuration. It is found that as the Rabi-frequency of coupling field increases, the maximal Kerr nonlinearity intensifies and at the same time the probe linear and nonlinear absorption decreases at Telecom wavelength λ = 1550 nm . The impact of an incoherent pumping field as well as the relative phase of the applied fields on nonlinear optical properties of the QW medium is then discussed. The temporal behavior of the Kerr nonlinearity and the required switching time for switching the nonlinear dispersion are also discussed. The results may be useful for understanding the switching feature of EIT-based slow light Kerr nonlinearity enhancement systems and have potential application in optical information processing and transmission.

  13. REVIEW ARTICLE: Slow light enhanced nonlinear optics in periodic structures

    Science.gov (United States)

    Monat, C.; de Sterke, M.; Eggleton, B. J.

    2010-10-01

    We review recent advances related to slow light in periodic structures, where the refractive index varies along one or two directions, i.e. gratings and planar photonic crystals. We focus on how these geometries are conducive to enhancing the nonlinear interaction between light and matter. We describe the underlying theory developed for shallow gratings, but whose conclusions can be extended to planar photonic crystal waveguides, in particular the enhancement of third-order nonlinear processes with slow light. We review some experiments showing how gratings have been used for pulse compression and the generation of slow gap solitons. We then present recent nonlinear experiments performed in photonic crystal waveguides that demonstrate the strong reinforcement of nonlinear third-order optical phenomena with slow light. We discuss the challenges associated with slow light in these 2D structures and their unique advantage—dispersion engineering—for creating broadband nonlinear devices for all-optical signal processing. By breaking down the relation between dispersion and group velocity imposed in gratings, these structures also offer new opportunities for generating soliton-like effects over short length scales, at low powers and with short pulses.

  14. Integrating Slow Learners in Wales.

    Science.gov (United States)

    Lowden, Gordon

    1984-01-01

    Results of interviews, attitude scales, questionnaires, and school record reviews revealed that teachers (N=120) generally approved of the principle of integration of slow learners while viewing the practice as impractical and sometimes undesirable. Students were not particularly antagonistic to slow learners, and parents were generally satisfied…

  15. Colloidal Dispersions

    Science.gov (United States)

    Russel, W. B.; Saville, D. A.; Schowalter, W. R.

    1992-03-01

    The book covers the physical side of colloid science from the individual forces acting between submicron particles suspended in a liquid through the resulting equilibrium and dynamic properties. The relevant forces include Brownian motion, electrostatic repulsion, dispersion attraction, both attraction and repulsion due to soluble polymer, and viscous forces due to relative motion between the particles and the liquid. The balance among Brownian motion and the interparticle forces decides the questions of stability and phase behavior. Imposition of external fields produces complex effects, i.e. electrokinetic phenomena (electric field), sedimentation (gravitational field), diffusion (concentration/chemical potential gradient), and non-Newtonian rheology (shear field). The treatment aims to impart a sound, quantitative understanding based on fundamental theory and experiments with well-characterized model systems. This broad grasp of the fundamentals lends insight and helps to develop the intuitive sense needed to isolate essential features of technological problems and design critical experiments. Some exposure to fluid mechanics, statistical mechanics, and electricity and magnetism is assumed, but each subject is reintroduced in a self-contained manner.

  16. Slow Tourism: Exploring the discourses

    Directory of Open Access Journals (Sweden)

    J. Guiver

    2016-05-01

    Full Text Available ‘Slow travel’ and ‘slow tourism’ are relatively new, but contested, concepts. This paper examines the meanings ascribed to them in the academic literature and websites targeted at potential tourists. It finds concurrence on aspects of savouring time at the destination and investing time to appreciate the locality, its people, history, culture and products, but detects different emphases. The academic literature stresses the benefits to the destination and global sustainability, while the websites focus on the personal benefits and ways of becoming a ‘slow tourist’. Food and drink epitomise the immersion in and absorption of the destination and the multi-dimensional tourism experience, contrasted with the superficiality of mainstream tourism. The paper discusses whether tourists practising slow tourism without using the label are slow tourists or not.

  17. Tailoring Dispersion properties of photonic crystal waveguides by topology optimization

    DEFF Research Database (Denmark)

    Stainko, Roman; Sigmund, Ole

    2007-01-01

    The paper describes a systematic method for the tailoring of dispersion properties of slab-based photonic crystal waveguides. The method is based on the topology optimization method which consists in repeated finite element frequency domain analyzes, analytical sensitivity analyzes and gradient...... based design updates. The goal of the optimization process is to come up with slow light, zero group velocity dispersion photonic waveguides or photonic waveguides with tailored dispersion properties for dispersion compensation purposes. Two examples concerning reproduction of a specific dispersion...... curve and design of a wide bandwidth, constant low group velocity waveguide demonstrate the efficiency of the method....

  18. Ultrafast slow-light tuning beyond the carrier lifetime using photonic crystal waveguides.

    Science.gov (United States)

    Kondo, K; Shinkawa, M; Hamachi, Y; Saito, Y; Arita, Y; Baba, T

    2013-02-01

    We demonstrate ultrafast delay tuning of a slow-light pulse with a response time slow light: dispersion-compensated slow light for the signal pulse, and low-dispersion slow light to enhance nonlinear effects of the control pulse. These two types of slow light are generated simultaneously in Si lattice-shifted photonic crystal waveguides, arising from flat and straight photonic bands, respectively. The control pulse blueshifts the signal pulse spectrum, through dynamic tuning caused by the plasma effect of two-photon-absorption-induced carriers. This changes the delay by up to 10 ps only when the two pulses overlap within the waveguide and enables ultrafast tuning that is not limited by the carrier lifetime. Using this, we succeeded in tuning the delay of one target pulse within a pulse train with 12 ps intervals.

  19. Seed dispersal in fens

    NARCIS (Netherlands)

    Middleton, Beth; van Diggelen, Rudy; Jensen, Kai

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and

  20. Using Nonuniform Fiber to Generate Slow Light via SBS

    Directory of Open Access Journals (Sweden)

    Wenhai Li

    2008-01-01

    Full Text Available The data pulse delay based on slow light induced by stimulated Brillouin scattering (SBS in a nonuniform dispersion decreasing fiber (DDF is demonstrated experimentally, and the distortions of data pulses at different beat frequencies are studied. We found that a delay exceeding a pulse width can be achieved at particular beat frequency, and the DDF has larger delay versus gain slope coefficient with much better output pulse quality than single-mode fiber.

  1. Source Modeling Sleep Slow Waves

    National Research Council Canada - National Science Library

    Michael Murphy; Brady A. Riedner; Reto Huber; Marcello Massimini; Fabio Ferrarelli; Giulio Tononi; Marcus E. Raichle

    2009-01-01

    .... Here we use high-density EEG (hd-EEG) source modeling to show that individual spontaneous slow waves have distinct cortical origins, propagate uniquely across the cortex, and involve unique subsets of cortical structures...

  2. Dispersal and metapopulation stability

    National Research Council Canada - National Science Library

    Wang, Shaopeng; Haegeman, Bart; Loreau, Michel

    2015-01-01

    .... Previous studies have shown that dispersal can stabilize local populations; however, as dispersal also tends to increase spatial synchrony, its net effect on metapopulation stability has been controversial...

  3. Dynamic coupling between slow waves and sleep spindles during slow wave sleep in humans is modulated by functional pre-sleep activation.

    Science.gov (United States)

    Yordanova, Juliana; Kirov, Roumen; Verleger, Rolf; Kolev, Vasil

    2017-11-03

    Co-existent sleep spindles and slow waves have been viewed as a mechanism for offline information processing. Here we explored if the temporal synchronization between slow waves and spindle activity during slow wave sleep (SWS) in humans was modulated by preceding functional activations during pre-sleep learning. We activated differentially the left and right hemisphere before sleep by using a lateralized variant of serial response time task (SRTT) and verified these inter-hemispheric differences by analysing alpha and beta electroencephalographic (EEG) activities during learning. The stability and timing of coupling between positive and negative phases of slow waves and sleep spindle activity during SWS were quantified. Spindle activity was temporally synchronized with both positive (up-state) and negative (down-state) slow half waves. Synchronization of only the fast spindle activity was laterally asymmetric after learning, corresponding to hemisphere-specific activations before sleep. However, the down state was associated with decoupling, whereas the up-state was associated with increased coupling of fast spindle activity over the pre-activated hemisphere. These observations provide original evidence that (1) the temporal grouping of fast spindles by slow waves is a dynamic property of human SWS modulated by functional pre-sleep activation patterns, and (2) fast spindles synchronized by slow waves are functionally distinct.

  4. Study and analysis on slow light in photonic crystal waveguide

    Science.gov (United States)

    Dang, Shuzhen; Shu, Jing

    2017-02-01

    Slow light is to reduce the light propagation speed in the medium. In recent years, because slow light technology is the key to achieving all-optical network technologies constitute optics, it attracted people's attention. Compared with other methods, photonic crystal waveguides provide slow light with many adventages, especially we can fine tune the structure to control the performance of the slow-light. Because the two-dimensional triangular lattice photonic crystal is easier to form band gaps than two-dimensional cubic lattice photonic crystal, the circular dielectric rod is easier to form band gaps than square dielectric cylinder, when the photonic crystal lattice vector angle is greater than 60 degrees, it can make the performance of slow light more excellent. So in this paper,we will rotate the cubic lattice 45 degrees counterclockwise. By reducing the radius of middle row of medium column to form the line defect; Additionly, we design a coupled cavity waveguide. Using the plane wave expansion method (PWE), we have analyzed the dispersion curves of the guided mode, the corresponding group refractive index and group velocity dispersion of slow light. For the line defected waveguide, we have realized the group refractive index changing from 8.1 to 84.8 by fine tuning the radius of the defective rod, the position and radius of the first row of the dielectric cylinder close to the waveguide. For the coupled cavity waveguide, we have realized the group refractive index changing from 16 to 79 by fine tuning the radius of the defective rod.

  5. Abyssal near-bottom dispersal stages of benthic invertebrates in the Clarion-Clipperton polymetallic nodule province

    Science.gov (United States)

    Kersten, Oliver; Smith, Craig R.; Vetter, Eric W.

    2017-09-01

    Growing interest in polymetallic nodule mining has intensified the need to characterize the abundance, community structure and vertical flux of meroplankton in the Clarion-Clipperton Zone (CCZ) to facilitate the estimation of larval supply and potential connectivity of benthic populations. These ecological parameters are essential to predict recolonization processes following the expected large-scale, high intensity disturbances associated with nodule extraction. Here, we present the first description of the composition, abundance, temporal variability, and mesoscale distribution of dispersing stages of the benthos in two study areas in the eastern CCZ. Samples from free-vehicle plankton pumps showed little variation in meroplankton diversity and abundance over scales of 30-100 km for time scales of days to weeks. However, sediment-trap samples revealed high temporal variability in vertical flux over weeks to months. Larval abundances and fluxes measured in the abyssal CCZ are 1-2 orders of magnitude lower than observed at deep-sea ridge and hydrothermal-vent habitats. We found significantly higher downward larval fluxes at 11 m above the bottom (mab) than at 146 mab, indicating accumulation or retention of meroplankton within the Benthic Boundary Layer (BBL). The high abundance of meroplankton in the BBL emphasizes its importance to dispersing stages and suggests that the creation of large sediment plumes in the BBL during nodule mining could compromise the dispersal and recruitment abilities of the abyssal benthos, potentially slowing rates and altering patterns of benthic community recovery following mining disturbance.

  6. Nonlinear theory of slow light.

    Science.gov (United States)

    Rybin, Andrei; Timonen, Jussi

    2011-03-28

    In the framework of the nonlinear Λ model, propagation of solitons was analysed in atomic vapours and Bose-Einstein condensates. The complicated nonlinear interplay between fast and slow-light solitons in a Λ-type medium was shown to facilitate control of its optical transparency and formation of optical gates. An exact analytical description was given for the deceleration, stopping and revival of slow-light solitons in the experimentally relevant non-adiabatic regime. A stopping slow-light soliton imprints a localized immobile polarization pattern in the medium, which, as explicitly demonstrated here, can be used as a bit of readable optical memory. The whole process can be controlled with the background field and an auxiliary laser field. The latter regulates the signal velocity, while the slow-light soliton can be stopped by switching off the former. The location and shape of the imprinted memory bit were also determined. With few assumptions characteristic of slow light, the Λ model was reduced to a simpler nonlinear model that also describes two-dimensional dilatonic gravity. Exact solutions could now be derived also in the presence of relaxation. Spontaneous decay of the upper atomic level was found to be strongly suppressed, and the spatial form of the decelerating slow-light soliton was preserved, even if the optical relaxation time was much shorter than the typical time scale of the soliton. The effective relaxation coefficient of the slow-light soliton was significantly smaller than that of an arbitrary optical pulse. Such features are obviously of great importance when this kind of system is applied, in practice, to information processing. A number of experimentally observable properties of the solutions reported were found to be in good agreement with recent experimental results, and a few suggestions are also made for future experiments.

  7. Propagated infra-slow intrinsic brain activity reorganizes across wake and slow wave sleep.

    Science.gov (United States)

    Mitra, Anish; Snyder, Abraham Z; Tagliazucchi, Enzo; Laufs, Helmut; Raichle, Marcus E

    2015-11-09

    Propagation of slow intrinsic brain activity has been widely observed in electrophysiogical studies of slow wave sleep (SWS). However, in human resting state fMRI (rs-fMRI), intrinsic activity has been understood predominantly in terms of zero-lag temporal synchrony (functional connectivity) within systems known as resting state networks (RSNs). Prior rs-fMRI studies have found that RSNs are generally preserved across wake and sleep. Here, we use a recently developed analysis technique to study propagation of infra-slow intrinsic blood oxygen level dependent (BOLD) signals in normal adults during wake and SWS. This analysis reveals marked changes in propagation patterns in SWS vs. wake. Broadly, ordered propagation is preserved within traditionally defined RSNs but lost between RSNs. Additionally, propagation between cerebral cortex and subcortical structures reverses directions, and intra-cortical propagation becomes reorganized, especially in visual and sensorimotor cortices. These findings show that propagated rs-fMRI activity informs theoretical accounts of the neural functions of sleep.

  8. The Potential of/for 'Slow': Slow Tourists and Slow Destinations

    Directory of Open Access Journals (Sweden)

    J. Guiver

    2016-05-01

    Full Text Available Slow tourism practices are nothing new; in fact, they were once the norm and still are for millions of people whose annual holiday is spent camping, staying in caravans, rented accommodation, with friends and relations or perhaps in a second home, who immerse themselves in their holiday environment, eat local food, drink local wine and walk or cycle around the area. So why a special edition about slow tourism? Like many aspects of life once considered normal (such as organic farming or free-range eggs, the emergence of new practices has highlighted differences and prompted a re-evaluation of once accepted practices and values. In this way, the concept of ‘slow tourism’ has recently appeared as a type of tourism that contrasts with many contemporary mainstream tourism practices. It has also been associated with similar trends already ‘branded’ slow: slow food and cittaslow (slow towns and concepts such as mindfulness, savouring and well-being.

  9. Primordial black holes and slow-roll violation

    Science.gov (United States)

    Motohashi, Hayato; Hu, Wayne

    2017-09-01

    For primordial black holes (PBH) to be the dark matter in single-field inflation, the slow-roll approximation must be violated by at least O (1 ) in order to enhance the curvature power spectrum within the required number of e -folds between cosmic microwave background scales and PBH mass scales. Power spectrum predictions which rely on the inflaton remaining on the slow-roll attractor can fail dramatically leading to qualitatively incorrect conclusions in models like an inflection potential and misestimate the mass scale in a running mass model. We show that an optimized temporal evaluation of the Hubble slow-roll parameters to second order remains a good description for a wide range of PBH formation models where up to a 1 07 amplification of power occurs in 10 e -folds or more.

  10. Project Temporalities

    DEFF Research Database (Denmark)

    Tryggestad, Kjell; Justesen, Lise; Mouritsen, Jan

    2013-01-01

    Purpose – The purpose of this paper is to explore how animals can become stakeholders in interaction with project management technologies and what happens with project temporalities when new and surprising stakeholders become part of a project and a recognized matter of concern to be taken...... into account. Design/methodology/approach – The paper is based on a qualitative case study of a project in the building industry. The authors use actor-network theory (ANT) to analyze the emergence of animal stakeholders, stakes and temporalities. Findings – The study shows how project temporalities can...... multiply in interaction with project management technologies and how conventional linear conceptions of project time may be contested with the emergence of new non-human stakeholders and temporalities. Research limitations/implications – The study draws on ANT to show how animals can become stakeholders...

  11. Temporal genetic structure in a poecilogonous polychaete: the interplay of developmental mode and environmental stochasticity

    DEFF Research Database (Denmark)

    Hansen, Benni Winding; Kesäniemi, Jenni E; Mustonen, Marina

    2014-01-01

    variation: species with dispersive planktonic larvae are expected to be more likely to show temporal genetic variation than species with benthic or brooded non-dispersive larvae, due to differences in larval mortality and dispersal ability. We examined temporal genetic structure in populations of Pygospio...

  12. Modified dispersion relations, inflation, and scale invariance

    Science.gov (United States)

    Bianco, Stefano; Friedhoff, Victor Nicolai; Wilson-Ewing, Edward

    2018-02-01

    For a certain type of modified dispersion relations, the vacuum quantum state for very short wavelength cosmological perturbations is scale-invariant and it has been suggested that this may be the source of the scale-invariance observed in the temperature anisotropies in the cosmic microwave background. We point out that for this scenario to be possible, it is necessary to redshift these short wavelength modes to cosmological scales in such a way that the scale-invariance is not lost. This requires nontrivial background dynamics before the onset of standard radiation-dominated cosmology; we demonstrate that one possible solution is inflation with a sufficiently large Hubble rate, for this slow roll is not necessary. In addition, we also show that if the slow-roll condition is added to inflation with a large Hubble rate, then for any power law modified dispersion relation quantum vacuum fluctuations become nearly scale-invariant when they exit the Hubble radius.

  13. The effect of Kerr nonlinearity and Doppler broadening on slow light propagation

    Science.gov (United States)

    Ali, Hazrat; Ziauddin; Ahmad, Iftikhar

    2014-02-01

    The influence of Kerr nonlinearity and Doppler broadening on the slow light propagation of a dispersive atomic medium is revisited using a four-level Λ-type (87Rb) atomic system under the condition of electromagnetically induced transparency (EIT). The medium exhibits an EIT process which is accompanied by normal dispersion, i.e., sub-luminal (slow light) pulse propagation. In the presence of Kerr nonlinearity and the Doppler broadening effect the dispersion property of the proposed atomic medium is modified, which leads to enhancement of the positive group index of the medium. The combined effect of Kerr nonlinearity and Doppler broadening on slow light propagation inside the medium is the major motivation for this work.

  14. Ultra-slow and superluminal light propagation in solids at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Bigelow, M S; Lepeshkin, N N; Boyd, R W [Institute of Optics, University of Rochester, Rochester, NY 14627 (United States)

    2004-11-24

    Slow and superluminal group velocities can be observed in any material that has large normal or anomalous dispersion. While this fact has been known for more than a century, recent experiments have shown that the dispersion can be very large without dramatically deforming a pulse. As a result, the significance and nature of pulse velocity is being reevaluated. In this review, we discuss some of the current techniques used for generating ultra-slow, superluminal, and even stopped light. While ultra-slow and superluminal group velocities have been observed in complicated systems, from an applications point of view it is highly desirable to do have this done in a solid that can operate at room temperature. We describe how coherent population oscillations can produce ultra-slow and superluminal light under these conditions. (topical review)

  15. Reading and the Slow Learner.

    Science.gov (United States)

    Ediger, Marlow

    Advocates of high standards and expectations usually believe that gaps in reading achievement can be eliminated with good teaching, but slow readers need a specially designed reading curriculum. The teacher first needs to use an informal reading inventory to determine the student's reading level. Functioning generally on a higher level than…

  16. Programmed Instruction for Slow Learners

    Science.gov (United States)

    Holden, Eric; Roberts, Ted

    1973-01-01

    A description of a project which produced and provided programed learning materials for slow learners. These programs have been printed and distributed in over 30,000 free copies throughout Canada and have been a source of hope and assistance to teachers and parents. (Author)

  17. More Questions and Answers about Slow Learners

    Science.gov (United States)

    Abramowitz, Jack

    1977-01-01

    Presented are responses to questions often asked about slow learners, including: What kinds of materials can be used with slow learners? Is it advisable to deliver lecture lessons to slow learners? How do you start a class lesson? Can the teacher of slow learners reach every student? Teaching techniques and learning activities are described.…

  18. Genetics of dispersal

    Science.gov (United States)

    Bocedi, Greta; Cote, Julien; Legrand, Delphine; Guillaume, Frédéric; Wheat, Christopher W.; Fronhofer, Emanuel A.; Garcia, Cristina; Henry, Roslyn; Husby, Arild; Baguette, Michel; Bonte, Dries; Coulon, Aurélie; Kokko, Hanna; Matthysen, Erik; Niitepõld, Kristjan; Nonaka, Etsuko; Stevens, Virginie M.; Travis, Justin M. J.; Donohue, Kathleen; Bullock, James M.; del Mar Delgado, Maria

    2017-01-01

    ABSTRACT Dispersal is a process of central importance for the ecological and evolutionary dynamics of populations and communities, because of its diverse consequences for gene flow and demography. It is subject to evolutionary change, which begs the question, what is the genetic basis of this potentially complex trait? To address this question, we (i) review the empirical literature on the genetic basis of dispersal, (ii) explore how theoretical investigations of the evolution of dispersal have represented the genetics of dispersal, and (iii) discuss how the genetic basis of dispersal influences theoretical predictions of the evolution of dispersal and potential consequences. Dispersal has a detectable genetic basis in many organisms, from bacteria to plants and animals. Generally, there is evidence for significant genetic variation for dispersal or dispersal‐related phenotypes or evidence for the micro‐evolution of dispersal in natural populations. Dispersal is typically the outcome of several interacting traits, and this complexity is reflected in its genetic architecture: while some genes of moderate to large effect can influence certain aspects of dispersal, dispersal traits are typically polygenic. Correlations among dispersal traits as well as between dispersal traits and other traits under selection are common, and the genetic basis of dispersal can be highly environment‐dependent. By contrast, models have historically considered a highly simplified genetic architecture of dispersal. It is only recently that models have started to consider multiple loci influencing dispersal, as well as non‐additive effects such as dominance and epistasis, showing that the genetic basis of dispersal can influence evolutionary rates and outcomes, especially under non‐equilibrium conditions. For example, the number of loci controlling dispersal can influence projected rates of dispersal evolution during range shifts and corresponding demographic impacts

  19. A slow-light laser radar system with two-dimensional scanning.

    Science.gov (United States)

    Schweinsberg, Aaron; Shi, Zhimin; Vornehm, Joseph E; Boyd, Robert W

    2012-02-01

    We propose a multi-aperture slow-light laser radar with two-dimensional scanning. We demonstrate experimentally that we can use two independent slow-light mechanisms, namely dispersive delay and stimulated Brillouin scattering, to dynamically compensate the group delay mismatch among different apertures, while we use optical phase locking to control the relative phases of the optical signals emitted from different apertures, as the system steers the beam in two dimensions.

  20. The unappreciated slowness of conventional tourism

    Directory of Open Access Journals (Sweden)

    G.R. Larsen

    2016-05-01

    Full Text Available Most tourists are not consciously engaging in ‘slow travel’, but a number of travel behaviours displayed by conventional tourists can be interpreted as slow travel behaviour. Based on Danish tourists’ engagement with the distances they travel across to reach their holiday destination, this paper explores unintended slow travel behaviours displayed by these tourists. None of the tourists participating in this research were consciously doing ‘slow travel’, and yet some of their most valued holiday memories are linked to slow travel behaviours. Based on the analysis of these unintended slow travel behaviours, this paper will discuss the potential this insight might hold for promotion of slow travel. If unappreciated and unintentional slow travel behaviours could be utilised in the deliberate effort of encouraging more people to travel slow, ‘slow travel’ will be in a better position to become integrated into conventional travel behaviour.

  1. Wide band dispersionless slow light in hetero-MIM plasmonic waveguide.

    Science.gov (United States)

    Li, Dacheng; Du, Kang; Liang, Shuhai; Zhang, Wending; Mei, Ting

    2016-10-03

    A flat slow-light band over a wide frequency range is obtained in the hetero-MIM (metal-insulator-metal) waveguide with zero group velocity dispersion (GVD). The zero GVD originates from dispersion compensation by the photonic mode and the plasmonic mode, the mechanism of which does not exist in the homo-MIM structure. By changing dielectric permittivity of the insulator or the difference of two different metallic plasma frequencies, the group index and the bandwidth can be tuned. The dispersionless slow light characteristic in the hetero-MIM waveguide may be useful in the new design of plasmonic devices.

  2. Dispersal and migration

    Directory of Open Access Journals (Sweden)

    Schwarz, C.

    2004-06-01

    Full Text Available Ringing of birds unveiled many aspects of avian migration and dispersal movements. However, there is even much more to be explored by the use of ringing and other marks. Dispersal is crucial in understanding the initial phase of migration in migrating birds as it is to understand patterns and processes of distribution and gene flow. So far, the analysis of migration was largely based on analysing spatial and temporal patters of recoveries of ringed birds. However, there are considerable biases and pitfalls in using recoveries due to spatial and temporal variation in reporting probabilities. Novel methods are required for future studies separating the confounding effects of spatial and temporal heterogeneity of recovery data and heterogeneity of the landscape as well. These novel approaches should aim a more intensive and novel use of the existing recovery data by taking advantage of, for instance, dynamic and multistate modeling, should elaborate schemes for future studies, and should also include other marks that allow a more rapid data collection, like telemetry, geolocation and global positioning systems, and chemical and molecular markers. The latter appear to be very useful in the delineating origin of birds and connectivity between breeding and non–breeding grounds. Many studies of migration are purely descriptive. However, King and Brooks (King & Brooks, 2004 examine if movement patterns of dolphins change after the introduction of a gillnet ban. Bayesian methods are an interesting approach to this problem as they provide a meaningful measure of the probability that such a change occurred rather than simple yes/no response that is often the result of classical statistical methods. However, the key difficulty of a general implementation of Bayesian methods is the complexity of the modelling —there is no general userfriendly package that is easily accessible to most scientists. Drake and Alisauskas (Drake & Alisauskas, 2004 examine the

  3. Lectures on Dispersion Theory

    Science.gov (United States)

    Salam, A.

    1956-04-01

    Lectures with mathematical analysis are given on Dispersion Theory and Causality and Dispersion Relations for Pion-nucleon Scattering. The appendix includes the S-matrix in terms of Heisenberg Operators. (F. S.)

  4. The trajectory of dispersal research in conservation biology. Systematic review.

    Science.gov (United States)

    Driscoll, Don A; Banks, Sam C; Barton, Philip S; Ikin, Karen; Lentini, Pia; Lindenmayer, David B; Smith, Annabel L; Berry, Laurence E; Burns, Emma L; Edworthy, Amanda; Evans, Maldwyn J; Gibson, Rebecca; Heinsohn, Rob; Howland, Brett; Kay, Geoff; Munro, Nicola; Scheele, Ben C; Stirnemann, Ingrid; Stojanovic, Dejan; Sweaney, Nici; Villaseñor, Nélida R; Westgate, Martin J

    2014-01-01

    Dispersal knowledge is essential for conservation management, and demand is growing. But are we accumulating dispersal knowledge at a pace that can meet the demand? To answer this question we tested for changes in dispersal data collection and use over time. Our systematic review of 655 conservation-related publications compared five topics: climate change, habitat restoration, population viability analysis, land planning (systematic conservation planning) and invasive species. We analysed temporal changes in the: (i) questions asked by dispersal-related research; (ii) methods used to study dispersal; (iii) the quality of dispersal data; (iv) extent that dispersal knowledge is lacking, and; (v) likely consequences of limited dispersal knowledge. Research questions have changed little over time; the same problems examined in the 1990s are still being addressed. The most common methods used to study dispersal were occupancy data, expert opinion and modelling, which often provided indirect, low quality information about dispersal. Although use of genetics for estimating dispersal has increased, new ecological and genetic methods for measuring dispersal are not yet widely adopted. Almost half of the papers identified knowledge gaps related to dispersal. Limited dispersal knowledge often made it impossible to discover ecological processes or compromised conservation outcomes. The quality of dispersal data used in climate change research has increased since the 1990s. In comparison, restoration ecology inadequately addresses large-scale process, whilst the gap between knowledge accumulation and growth in applications may be increasing in land planning. To overcome apparent stagnation in collection and use of dispersal knowledge, researchers need to: (i) improve the quality of available data using new approaches; (ii) understand the complementarities of different methods and; (iii) define the value of different kinds of dispersal information for supporting management

  5. The trajectory of dispersal research in conservation biology. Systematic review.

    Directory of Open Access Journals (Sweden)

    Don A Driscoll

    Full Text Available Dispersal knowledge is essential for conservation management, and demand is growing. But are we accumulating dispersal knowledge at a pace that can meet the demand? To answer this question we tested for changes in dispersal data collection and use over time. Our systematic review of 655 conservation-related publications compared five topics: climate change, habitat restoration, population viability analysis, land planning (systematic conservation planning and invasive species. We analysed temporal changes in the: (i questions asked by dispersal-related research; (ii methods used to study dispersal; (iii the quality of dispersal data; (iv extent that dispersal knowledge is lacking, and; (v likely consequences of limited dispersal knowledge. Research questions have changed little over time; the same problems examined in the 1990s are still being addressed. The most common methods used to study dispersal were occupancy data, expert opinion and modelling, which often provided indirect, low quality information about dispersal. Although use of genetics for estimating dispersal has increased, new ecological and genetic methods for measuring dispersal are not yet widely adopted. Almost half of the papers identified knowledge gaps related to dispersal. Limited dispersal knowledge often made it impossible to discover ecological processes or compromised conservation outcomes. The quality of dispersal data used in climate change research has increased since the 1990s. In comparison, restoration ecology inadequately addresses large-scale process, whilst the gap between knowledge accumulation and growth in applications may be increasing in land planning. To overcome apparent stagnation in collection and use of dispersal knowledge, researchers need to: (i improve the quality of available data using new approaches; (ii understand the complementarities of different methods and; (iii define the value of different kinds of dispersal information for supporting

  6. Quantitative dispersion microscopy

    OpenAIRE

    Fu, Dan; Choi, Wonshik; Sung, Yongjin; Yaqoob, Zahid; Ramachandra R Dasari; Feld, Michael

    2010-01-01

    Refractive index dispersion is an intrinsic optical property and a useful source of contrast in biological imaging studies. In this report, we present the first dispersion phase imaging of living eukaryotic cells. We have developed quantitative dispersion microscopy based on the principle of quantitative phase microscopy. The dual-wavelength quantitative phase microscope makes phase measurements at 310 nm and 400 nm wavelengths to quantify dispersion (refractive index increment ratio) of live...

  7. Dispersing powders in liquids

    CERN Document Server

    Nelson, RD

    1988-01-01

    This book provides powder technologists with laboratory procedures for selecting dispersing agents and preparing stable dispersions that can then be used in particle size characterization instruments. Its broader goal is to introduce industrial chemists and engineers to the phenomena, terminology, physical principles, and chemical considerations involved in preparing and handling dispersions on a commercial scale. The book introduces novices to: - industrial problems due to improper degree of dispersion; - the nomenclature used in describing particles; - the basic physica

  8. Generalized Slow Roll for Tensors

    OpenAIRE

    Hu, Wayne

    2014-01-01

    The recent BICEP2 detection of degree scale CMB B-mode polarization, coupled with a deficit of observed power in large angle temperature anisotropy, suggest that the slow-roll parameter $\\epsilon_H$, the fractional variation in the Hubble rate per efold, is both relatively large and may evolve from an even larger value on scales greater than the horizon at recombination. The relatively large tensor contribution implied also requires finite matching features in the tensor power spectrum for an...

  9. Slow Light in Coupled Resonator Optical Waveguides

    Science.gov (United States)

    Chang, Hongrok; Gates, Amanda L.; Fuller, Kirk A.; Gregory, Don A.; Witherow, William K.; Paley, Mark S.; Frazier, Donald O.; Smith, David D.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    Recently, we discovered that a splitting of the whispering gallery modes (WGMs) occurs in coupled resonator optical waveguides (CROWs), and that these split modes are of a higher Q than the single-resonator modes, leading to enormous circulating intensity magnification factors that dramatically reduce thresholds for nonlinear optical (NLO) processes. As a result of the enhancements in Q, pulses propagating at a split resonance can propagate much slower (faster) for over (under)-coupled structures, due to the modified dispersion near the split resonance. Moreover, when loss is considered, the mode-splitting may be thought of as analogous to the Autler-Townes splitting that occurs in atomic three-level lambda systems, i.e., it gives rise to induced transparency as a result of destructive interference. In under- or over-coupled CROWs, this coupled resonator induced transparency (CRIT) allows slow light to be achieved at the single-ring resonance with no absorption, while maintaining intensities such that NLO effects are maximized. The intensity magnification of the circulating fields and phase transfer characteristics are examined in detail.

  10. Enhanced spectral sensitivity of a chip-scale photonic-crystal slow-light interferometer.

    Science.gov (United States)

    Magaña-Loaiza, Omar S; Gao, Boshen; Schulz, Sebastian A; Awan, Kashif M; Upham, Jeremy; Dolgaleva, Ksenia; Boyd, Robert W

    2016-04-01

    We experimentally demonstrate that the spectral sensitivity of a Mach-Zehnder (MZ) interferometer can be enhanced through structural slow light. We observe a 20-fold resolution enhancement by placing a dispersion-engineered, slow-light, photonic-crystal waveguide in one arm of a fiber-based MZ interferometer. The spectral sensitivity of the interferometer increases roughly linearly with the group index, and we have quantified the resolution in terms of the spectral density of interference fringes. These results show promise for the use of slow-light methods for developing novel tools for optical metrology and, specifically, for compact high-resolution spectrometers.

  11. Role of slow oscillatory activity and slow wave sleep in consolidation of episodic-like memory in rats.

    Science.gov (United States)

    Oyanedel, Carlos N; Binder, Sonja; Kelemen, Eduard; Petersen, Kimberley; Born, Jan; Inostroza, Marion

    2014-12-15

    Our previous experiments showed that sleep in rats enhances consolidation of hippocampus dependent episodic-like memory, i.e. the ability to remember an event bound into specific spatio-temporal context. Here we tested the hypothesis that this enhancing effect of sleep is linked to the occurrence of slow oscillatory and spindle activity during slow wave sleep (SWS). Rats were tested on an episodic-like memory task and on three additional tasks covering separately the where (object place recognition), when (temporal memory), and what (novel object recognition) components of episodic memory. In each task, the sample phase (encoding) was followed by an 80-min retention interval that covered either a period of regular morning sleep or sleep deprivation. Memory during retrieval was tested using preferential exploration of novelty vs. familiarity. Consistent with previous findings, the rats which had slept during the retention interval showed significantly stronger episodic-like memory and spatial memory, and a trend of improved temporal memory (although not significant). Object recognition memory was similarly retained across sleep and sleep deprivation retention intervals. Recall of episodic-like memory was associated with increased slow oscillatory activity (0.85-2.0Hz) during SWS in the retention interval. Spatial memory was associated with increased proportions of SWS. Against our hypothesis, a relationship between spindle activity and episodic-like memory performance was not detected, but spindle activity was associated with object recognition memory. The results provide support for the role of SWS and slow oscillatory activity in consolidating hippocampus-dependent memory, the role of spindles in this process needs to be further examined. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

  12. Millisecond Photon Lifetime in a Slow-Light Microcavity

    Science.gov (United States)

    Huet, V.; Rasoloniaina, A.; Guillemé, P.; Rochard, P.; Féron, P.; Mortier, M.; Levenson, A.; Bencheikh, K.; Yacomotti, A.; Dumeige, Y.

    2016-04-01

    Optical microcavities with ultralong photon storage times are of central importance for integrated nanophotonics. To date, record quality (Q ) factors up to 1011 have been measured in millimetric-size single-crystal whispering-gallery-mode (WGM) resonators, and 1010 in silica or glass microresonators. We show that, by introducing slow-light effects in an active WGM microresonator, it is possible to enhance the photon lifetime by several orders of magnitude, thus circumventing both fabrication imperfections and residual absorption. The slow-light effect is obtained from coherent population oscillations in an erbium-doped fluoride glass microsphere, producing strong dispersion of the WGM (group index ng˜106). As a result, a photon lifetime up to 2.5 ms at room temperature has been measured, corresponding to a Q factor of 3 ×1012 at 1530 nm. This system could yield a new type of optical memory microarray with ultralong storage times.

  13. Pupil dilation deconvolution reveals the dynamics of attention at high temporal resolution

    NARCIS (Netherlands)

    Wierda, Stefan M.; van Rijn, Hedderik; Taatgen, Niels A.; Martens, Sander

    2012-01-01

    The size of the human pupil increases as a function of mental effort. However, this response is slow, and therefore its use is thought to be limited to measurements of slow tasks or tasks in which meaningful events are temporally well separated. Here we show that high-temporal-resolution tracking of

  14. Does time really slow down during a frightening event?

    Directory of Open Access Journals (Sweden)

    Chess Stetson

    2007-12-01

    Full Text Available Observers commonly report that time seems to have moved in slow motion during a life-threatening event. It is unknown whether this is a function of increased time resolution during the event, or instead an illusion of remembering an emotionally salient event. Using a hand-held device to measure speed of visual perception, participants experienced free fall for 31 m before landing safely in a net. We found no evidence of increased temporal resolution, in apparent conflict with the fact that participants retrospectively estimated their own fall to last 36% longer than others' falls. The duration dilation during a frightening event, and the lack of concomitant increase in temporal resolution, indicate that subjective time is not a single entity that speeds or slows, but instead is composed of separable subcomponents. Our findings suggest that time-slowing is a function of recollection, not perception: a richer encoding of memory may cause a salient event to appear, retrospectively, as though it lasted longer.

  15. Temporal naturalism

    Science.gov (United States)

    Smolin, Lee

    2015-11-01

    Two people may claim both to be naturalists, but have divergent conceptions of basic elements of the natural world which lead them to mean different things when they talk about laws of nature, or states, or the role of mathematics in physics. These disagreements do not much affect the ordinary practice of science which is about small subsystems of the universe, described or explained against a background, idealized to be fixed. But these issues become crucial when we consider including the whole universe within our system, for then there is no fixed background to reference observables to. I argue here that the key issue responsible for divergent versions of naturalism and divergent approaches to cosmology is the conception of time. One version, which I call temporal naturalism, holds that time, in the sense of the succession of present moments, is real, and that laws of nature evolve in that time. This is contrasted with timeless naturalism, which holds that laws are immutable and the present moment and its passage are illusions. I argue that temporal naturalism is empirically more adequate than the alternatives, because it offers testable explanations for puzzles its rivals cannot address, and is likely a better basis for solving major puzzles that presently face cosmology and physics. This essay also addresses the problem of qualia and experience within naturalism and argues that only temporal naturalism can make a place for qualia as intrinsic qualities of matter.

  16. Photonic fractional Fourier transformer with a single dispersive device.

    Science.gov (United States)

    Cuadrado-Laborde, C; Carrascosa, A; Díez, A; Cruz, J L; Andres, M V

    2013-04-08

    In this work we used the temporal analog of spatial Fresnel diffraction to design a temporal fractional Fourier transformer with a single dispersive device, in this way avoiding the use of quadratic phase modulators. We demonstrate that a single dispersive passive device inherently provides the fractional Fourier transform of an incident optical pulse. The relationships linking the fractional Fourier transform order and scaling factor with the dispersion parameters are derived. We first provide some numerical results in order to prove the validity of our proposal, using a fiber Bragg grating as the dispersive device. Next, we experimentally demonstrate the feasibility of this proposal by using a spool of a standard optical fiber as the dispersive device.

  17. Life-history syndromes: integrating dispersal through space and time.

    Science.gov (United States)

    Buoro, Mathieu; Carlson, Stephanie M

    2014-06-01

    Recent research has highlighted interdependencies between dispersal and other life-history traits, i.e. dispersal syndromes, thereby revealing constraints on the evolution of dispersal and opportunities for improved ability to predict dispersal by considering suites of dispersal-related traits. This review adds to the growing list of life-history traits linked to spatial dispersal by emphasising the interdependence between dispersal through space and time, i.e. life-history diversity that distributes individuals into separate reproductive events. We reviewed the literature that has simultaneously investigated spatial and temporal dispersal to examine the prediction that traits of these two dispersal strategies are negatively correlated. Our results suggest that negative covariation is widely anticipated from theory. Empirical studies often reported evidence of weak negative covariation, although more complicated patterns were also evident, including across levels of biological organisation. Existing literature has largely focused on plants with dormancy capability, one or two phases of the dispersal process (emigration and/or transfer) and a single level of biological organisation (theory: individual; empirical: species). We highlight patterns of covariation across levels of organisation and conclude with a discussion of the consequences of dispersal through space and time and future research areas that should improve our understanding of dispersal-related life-history syndromes. © 2014 John Wiley & Sons Ltd/CNRS.

  18. The CUORE slow monitoring systems

    Science.gov (United States)

    Gladstone, L.; Biare, D.; Cappelli, L.; Cushman, J. S.; Del Corso, F.; Fujikawa, B. K.; Hickerson, K. P.; Moggi, N.; Pagliarone, C. E.; Schmidt, B.; Wagaarachchi, S. L.; Welliver, B.; Winslow, L. A.

    2017-09-01

    CUORE is a cryogenic experiment searching primarily for neutrinoless double decay in 130Te. It will begin data-taking operations in 2016. To monitor the cryostat and detector during commissioning and data taking, we have designed and developed Slow Monitoring systems. In addition to real-time systems using LabVIEW, we have an alarm, analysis, and archiving website that uses MongoDB, AngularJS, and Bootstrap software. These modern, state of the art software packages make the monitoring system transparent, easily maintainable, and accessible on many platforms including mobile devices.

  19. Corpuscular slow-roll inflation

    Science.gov (United States)

    Casadio, Roberto; Giugno, Andrea; Giusti, Andrea

    2018-01-01

    We show that a corpuscular description of gravity can lead to an inflationary scenario similar to Starobinsky's model without requiring the introduction of the inflaton field. All relevant properties are determined by the number of gravitons in the cosmological condensate or, equivalently, by their Compton length. In particular, the relation between the Hubble parameter H and its time derivative H ˙ required by cosmic microwave background observations at the end of inflation, as well as the (minimum) initial value of the slow-roll parameter, are naturally obtained from the Compton size of the condensate.

  20. Experimental observation of critical slowing down before population collapse

    Science.gov (United States)

    Dai, Lei; Vorselen, Daan; Dudley, Carmel; Ornek, Onur; Korolev, Kirill; Gore, Jeff

    2012-02-01

    Tipping points marking population collapse and other critical transitions in natural systems (e.g. ecosystems, the climate) can be described by a fold bifurcation in the dynamics of the system. Theory predicts that the approach of bifurcations will result in an increasingly slow recovery from small perturbations, a phenomenon called critical slowing down. Here we demonstrate the direct observation of critical slowing down before population collapse using replicate laboratory populations of the budding yeast Saccharomyces cerevisiae. We mapped the bifurcation diagram experimentally and found a significant increase in both the size and timescale of the fluctuations of population density near a fold bifurcation, in agreement with the theory. We further confirmed the utility of theoretically predicted warning signals by observing them in two different slowly deteriorating environments. To extend the application of warning signals to spatially extended populations, we proposed and identified several indicators based on the emergence of spatial patterns. Our results suggest that generic temporal and spatial indicators of critical slowing down can be useful in predicting tipping points in population dynamics.

  1. Slow oscillations orchestrating fast oscillations and memory consolidation.

    Science.gov (United States)

    Mölle, Matthias; Born, Jan

    2011-01-01

    Slow-wave sleep (SWS) facilitates the consolidation of hippocampus-dependent declarative memory. Based on the standard two-stage memory model, we propose that memory consolidation during SWS represents a process of system consolidation which is orchestrated by the neocortical memory. The slow oscillations temporally group neuronal activity into up-states of strongly enhanced neuronal activity and down-states of neuronal silence. In a feed-forward efferent action, this grouping is induced not only in the neocortex but also in other structures relevant to consolidation, namely the thalamus generating 10-15Hz spindles, and the hippocampus generating sharp wave-ripples, with the latter well known to accompany a replay of newly encoded memories taking place in hippocampal circuitries. The feed-forward synchronizing effect of the slow oscillation enables the formation of spindle-ripple events where ripples and accompanying reactivated hippocampal memory information become nested into the single troughs of spindles. Spindle-ripple events thus enable reactivated memory-related hippocampal information to be fed back to neocortical networks in the excitable slow oscillation up-state where they can induce enduring plastic synaptic changes underlying the effective formation of long-term memories. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Resistance Training May Slow MS, Study Says

    Science.gov (United States)

    ... page: https://medlineplus.gov/news/fullstory_167617.html Resistance Training May Slow MS, Study Says Scans revealed ... 4, 2017 FRIDAY, Aug. 4, 2017 (HealthDay News) -- Resistance training may help slow progression of multiple sclerosis, ...

  3. Integrated Photonics Enabled by Slow Light

    DEFF Research Database (Denmark)

    Mørk, Jesper; Chen, Yuntian; Ek, Sara

    2012-01-01

    In this talk we will discuss the physics of slow light in semiconductor materials and in particular the possibilities offered for integrated photonics. This includes ultra-compact slow light enabled optical amplifiers, lasers and pulse sources....

  4. Lifestyle Changes Might Prevent or Slow Dementia

    Science.gov (United States)

    ... 166825.html Lifestyle Changes Might Prevent or Slow Dementia The public should be aware of this encouraging ... to your lifestyle might delay the start of dementia or slow its progression, a new report suggests. ...

  5. Factors Contributing Decreased Performance Of Slow Learners

    National Research Council Canada - National Science Library

    Dr. L. Kannan; Dr. P. V. Vijayaragavan; Dr. Pankaj. B. Shah; Dr. Suganathan. S; Dr. Praveena .P

    2015-01-01

    ... these students are called as slow learnersStruggle learners. There should be a designed study to foster discussion about diagnosing particular problems that contribute with meeting objectives of slow learners...

  6. Connecting slow earthquakes to huge earthquakes

    OpenAIRE

    Obara, Kazushige; Kato, Aitaro

    2016-01-01

    Slow earthquakes are characterized by a wide spectrum of fault slip behaviors and seismic radiation patterns that differ from those of traditional earthquakes. However, slow earthquakes and huge megathrust earthquakes can have common slip mechanisms and are located in neighboring regions of the seismogenic zone. The frequent occurrence of slow earthquakes may help to reveal the physics underlying megathrust events as useful analogs. Slow earthquakes may function as stress meters because of th...

  7. Nanocavity Linewidth Narrowing and Group Delay Enhancement by Slow Light Propagation and Nonlinear Effects

    Science.gov (United States)

    Grinberg, P.; Bencheikh, K.; Brunstein, M.; Yacomotti, A. M.; Dumeige, Y.; Sagnes, I.; Raineri, F.; Bigot, L.; Levenson, J. A.

    2012-09-01

    Slow light induced by coherent population oscillations and cavity dispersive nonlinear response are combined achieving 2 orders of magnitude enhancement of the group delay and an equivalent decreasing of the spectral linewidth of a L3 two-dimensional photonic crystal nanocavity.

  8. Slow Learners: Are Educators Leaving Them Behind?

    Science.gov (United States)

    Kaznowski, Kimberly

    2004-01-01

    This study compared the school performance of a sample of slow learners who qualified for special education as learning disabled with a sample of slow learners who did not qualify for special education. The intent of the study was to determine which group of slow learners was more successful in school in order to know if special education or…

  9. Don't Forget the Slow Learner.

    Science.gov (United States)

    Watson, Daniel L.; Rangel, Lyle

    1989-01-01

    Advocates cooperative learning as an effective tool for reaching slow learners, by bridging the gaps between the learning styles of slow learners and the teaching requirements of the classroom, resulting in improved academic performance for both slow learners and high achievers. (SR)

  10. Loss engineered slow light waveguides.

    Science.gov (United States)

    O'Faolain, L; Schulz, S A; Beggs, D M; White, T P; Spasenović, M; Kuipers, L; Morichetti, F; Melloni, A; Mazoyer, S; Hugonin, J P; Lalanne, P; Krauss, T F

    2010-12-20

    Slow light devices such as photonic crystal waveguides (PhCW) and coupled resonator optical waveguides (CROW) have much promise for optical signal processing applications and a number of successful demonstrations underpinning this promise have already been made. Most of these applications are limited by propagation losses, especially for higher group indices. These losses are caused by technological imperfections ("extrinsic loss") that cause scattering of light from the waveguide mode. The relationship between this loss and the group velocity is complex and until now has not been fully understood. Here, we present a comprehensive explanation of the extrinsic loss mechanisms in PhC waveguides and address some misconceptions surrounding loss and slow light that have arisen in recent years. We develop a theoretical model that accurately describes the loss spectra of PhC waveguides. One of the key insights of the model is that the entire hole contributes coherently to the scattering process, in contrast to previous models that added up the scattering from short sections incoherently. As a result, we have already realised waveguides with significantly lower losses than comparable photonic crystal waveguides as well as achieving propagation losses, in units of loss per unit time (dB/ns) that are even lower than those of state-of-the-art coupled resonator optical waveguides based on silicon photonic wires. The model will enable more advanced designs with further loss reduction within existing technological constraints.

  11. Further Investigations of Slow Lightning

    Science.gov (United States)

    Stephan, Karl; Sheleg, Gil

    2013-09-01

    The phenomenon of ``slow lightning'' is a new type of tracking or sliding atmospheric-pressure resistive-barrier discharge on the surface of a weakly conducting electrolyte. It occurs during the production of water plasmoids (also called ``Gatchina discharges'') in which a high-voltage capacitor is discharged into an insulated cathode in limited surface contact with the electrolyte. Unlike conventional dielectric-barrier and most other resistive-barrier discharges, these novel discharges propagate on the surface relatively slowly, spreading at a speed of 1-10 meters per second. We have investigated this phenomenon in several ways, using high-speed videography, time- and space-resolved spectroscopy, and current-density profiling. The plasma produced at cathode spots forms the plasmoid, and this plasma is distinct from the plasma in the slow-lightning discharge above the electrolyte. The primary visible emission from the latter discharge is a continuum, probably due to free-bound transitions, although an N2 + band is also present as well as intense emission from OH radicals under certain conditions. Possible applications of this phenomenon include water purification and pollution control.

  12. Exclusion Process with Slow Boundary

    Science.gov (United States)

    Baldasso, Rangel; Menezes, Otávio; Neumann, Adriana; Souza, Rafael R.

    2017-06-01

    We study the hydrodynamic and the hydrostatic behavior of the simple symmetric exclusion process with slow boundary. The term slow boundary means that particles can be born or die at the boundary sites, at a rate proportional to N^{-θ }, where θ > 0 and N is the scaling parameter. In the bulk, the particles exchange rate is equal to 1. In the hydrostatic scenario, we obtain three different linear profiles, depending on the value of the parameter θ ; in the hydrodynamic scenario, we obtain that the time evolution of the spatial density of particles, in the diffusive scaling, is given by the weak solution of the heat equation, with boundary conditions that depend on θ . If θ \\in (0,1), we get Dirichlet boundary conditions, (which is the same behavior if θ =0, see Farfán in Hydrostatics, statical and dynamical large deviations of boundary driven gradient symmetric exclusion processes, 2008); if θ =1, we get Robin boundary conditions; and, if θ \\in (1,∞), we get Neumann boundary conditions.

  13. Slow Monitoring Systems for CUORE

    Science.gov (United States)

    Dutta, Suryabrata; Cuore Collaboration

    2016-09-01

    The Cryogenic Underground Observatory for Rare Events (CUORE) is a ton-scale neutrinoless double-beta decay experiment under construction at the Laboratori Nazionali del Gran Sasso (LNGS). The experiment is comprised of 988 TeO2 bolometric crystals arranged into 19 towers and operated at a temperature of 10 mK. We have developed slow monitoring systems to monitor the cryostat during detector installation, commissioning, data taking, and other crucial phases of the experiment. Our systems use responsive LabVIEW virtual instruments and video streams of the cryostat. We built a website using the Angular, Bootstrap, and MongoDB frameworks to display this data in real-time. The website can also display archival data and send alarms. I will present how we constructed these slow monitoring systems to be robust, accurate, and secure, while maintaining reliable access for the entire collaboration from any platform in order to ensure efficient communications and fast diagnoses of all CUORE systems.

  14. Uncertainty in spatially explicit animal dispersal models

    Science.gov (United States)

    Mooij, Wolf M.; DeAngelis, Donald L.

    2003-01-01

    Uncertainty in estimates of survival of dispersing animals is a vexing difficulty in conservation biology. The current notion is that this uncertainty decreases the usefulness of spatially explicit population models in particular. We examined this problem by comparing dispersal models of three levels of complexity: (1) an event-based binomial model that considers only the occurrence of mortality or arrival, (2) a temporally explicit exponential model that employs mortality and arrival rates, and (3) a spatially explicit grid-walk model that simulates the movement of animals through an artificial landscape. Each model was fitted to the same set of field data. A first objective of the paper is to illustrate how the maximum-likelihood method can be used in all three cases to estimate the means and confidence limits for the relevant model parameters, given a particular set of data on dispersal survival. Using this framework we show that the structure of the uncertainty for all three models is strikingly similar. In fact, the results of our unified approach imply that spatially explicit dispersal models, which take advantage of information on landscape details, suffer less from uncertainly than do simpler models. Moreover, we show that the proposed strategy of model development safeguards one from error propagation in these more complex models. Finally, our approach shows that all models related to animal dispersal, ranging from simple to complex, can be related in a hierarchical fashion, so that the various approaches to modeling such dispersal can be viewed from a unified perspective.

  15. Dispersion management with metamaterials

    Science.gov (United States)

    Tassin, Philippe; Koschny, Thomas; Soukoulis, Costas M.

    2017-03-07

    An apparatus, system, and method to counteract group velocity dispersion in fibers, or any other propagation of electromagnetic signals at any wavelength (microwave, terahertz, optical, etc.) in any other medium. A dispersion compensation step or device based on dispersion-engineered metamaterials is included and avoids the need of a long section of specialty fiber or the need for Bragg gratings (which have insertion loss).

  16. Modal theory of slow light enhanced third-order nonlinear effects in photonic crystal waveguides.

    Science.gov (United States)

    Chen, Tao; Sun, Junqiang; Li, Linsen

    2012-08-27

    In this paper, we derive the couple-mode equations for third-order nonlinear effects in photonic crystal waveguides by employing the modal theory. These nonlinear interactions include self-phase modulation, cross-phase modulation and degenerate four-wave mixing. The equations similar to that in nonlinear fiber optics could be expanded and applied for third-order nonlinear processes in other periodic waveguides. Based on the equations, we systematically analyze the group-velocity dispersion, optical propagation loss, effective interaction area, slow light enhanced factor and phase mismatch for a slow light engineered silicon photonic crystal waveguide. Considering the two-photon and free-carrier absorptions, the wavelength conversion efficiencies in two low-dispersion regions are numerically simulated by utilizing finite difference method. Finally, we investigate the influence of slow light enhanced multiple four-wave-mixing process on the conversion efficiency.

  17. Reconstruction of constant slow-roll inflation

    Science.gov (United States)

    Gao, Qing

    2017-09-01

    Using the relations between the slow-roll parameters and the power spectra for the single field slow-roll inflation, we derive the scalar spectral tilt n s and the tensor to scalar ratio r for the constant slow-roll inflation, and obtain the constraint on the slow-roll parameter η from the Planck 2015 results. The inflationary potential for the constant slow-roll inflation is then reconstructed in the framework of both general relativity and the scalar-tensor theory of gravity, and compared with the recently reconstructed E model potential. In the strong coupling limit, we show that the η attractor is reached.

  18. A model for simulating the active dispersal of juvenile sea turtles with a case study on western Pacific leatherback turtles.

    Science.gov (United States)

    Gaspar, Philippe; Lalire, Maxime

    2017-01-01

    Oceanic currents are known to broadly shape the dispersal of juvenile sea turtles during their pelagic stage. Accordingly, simple passive drift models are widely used to investigate the distribution at sea of various juvenile sea turtle populations. However, evidence is growing that juveniles do not drift purely passively but also display some swimming activity likely directed towards favorable habitats. We therefore present here a novel Sea Turtle Active Movement Model (STAMM) in which juvenile sea turtles actively disperse under the combined effects of oceanic currents and habitat-driven movements. This model applies to all sea turtle species but is calibrated here for leatherback turtles (Dermochelys coriacea). It is first tested in a simulation of the active dispersal of juveniles originating from Jamursba-Medi, a main nesting beach of the western Pacific leatherback population. Dispersal into the North Pacific Ocean is specifically investigated. Simulation results demonstrate that, while oceanic currents broadly shape the dispersal area, modeled habitat-driven movements strongly structure the spatial and temporal distribution of juveniles within this area. In particular, these movements lead juveniles to gather in the North Pacific Transition Zone (NPTZ) and to undertake seasonal north-south migrations. More surprisingly, juveniles in the NPTZ are simulated to swim mostly towards west which considerably slows down their progression towards the American west coast. This increases their residence time, and hence the risk of interactions with fisheries, in the central and eastern part of the North Pacific basin. Simulated habitat-driven movements also strongly reduce the risk of cold-induced mortality. This risk appears to be larger among the juveniles that rapidly circulate into the Kuroshio than among those that first drift into the North Equatorial Counter Current (NECC). This mechanism might induce marked interannual variability in juvenile survival as the

  19. A model for simulating the active dispersal of juvenile sea turtles with a case study on western Pacific leatherback turtles.

    Directory of Open Access Journals (Sweden)

    Philippe Gaspar

    Full Text Available Oceanic currents are known to broadly shape the dispersal of juvenile sea turtles during their pelagic stage. Accordingly, simple passive drift models are widely used to investigate the distribution at sea of various juvenile sea turtle populations. However, evidence is growing that juveniles do not drift purely passively but also display some swimming activity likely directed towards favorable habitats. We therefore present here a novel Sea Turtle Active Movement Model (STAMM in which juvenile sea turtles actively disperse under the combined effects of oceanic currents and habitat-driven movements. This model applies to all sea turtle species but is calibrated here for leatherback turtles (Dermochelys coriacea. It is first tested in a simulation of the active dispersal of juveniles originating from Jamursba-Medi, a main nesting beach of the western Pacific leatherback population. Dispersal into the North Pacific Ocean is specifically investigated. Simulation results demonstrate that, while oceanic currents broadly shape the dispersal area, modeled habitat-driven movements strongly structure the spatial and temporal distribution of juveniles within this area. In particular, these movements lead juveniles to gather in the North Pacific Transition Zone (NPTZ and to undertake seasonal north-south migrations. More surprisingly, juveniles in the NPTZ are simulated to swim mostly towards west which considerably slows down their progression towards the American west coast. This increases their residence time, and hence the risk of interactions with fisheries, in the central and eastern part of the North Pacific basin. Simulated habitat-driven movements also strongly reduce the risk of cold-induced mortality. This risk appears to be larger among the juveniles that rapidly circulate into the Kuroshio than among those that first drift into the North Equatorial Counter Current (NECC. This mechanism might induce marked interannual variability in juvenile

  20. Slow viscoelastic relaxation and aging in aqueous foam

    Science.gov (United States)

    Vincent-Bonnieu, S.; Höhler, R.; Cohen-Addad, S.

    2006-05-01

    Like emulsions, pastes and many other forms of soft condensed matter, aqueous foams present slow mechanical relaxations when subjected to a stress too small to induce any plastic flow. To identify the physical origin of this viscoelastic behaviour, we have simulated how dry disordered coarsening 2D foams respond to a small applied stress. We show that the mechanism of long time relaxation is driven by coarsening-induced rearrangements of small bubble clusters. These findings are in full agreement with a scaling law previously derived from experimental creep data for 3D foams. Moreover, we find that the temporal statistics of coarsening-induced bubble rearrangements are described by a Poisson process.

  1. The role of individual variation in marine larval dispersal

    KAUST Repository

    Nanninga, Gerrit B.

    2014-12-08

    The exchange of individuals among patchy habitats plays a central role in spatial ecology and metapopulation dynamics. Dispersal is frequently observed to vary non-randomly within populations (e.g., short vs. long), indicating that variability among individuals may shape heterogeneity in patterns of connectivity. The concept of context- and condition-dependent dispersal describes the balance between the costs and benefits of dispersal that arises from the interaction of temporal and spatial landscape heterogeneity (the context) with phenotypic variability among individuals (the condition). While this hypothesis is widely accepted in terrestrial theory, it remains questionable to what extent the concept of adaptive dispersal strategies may apply to marine larval dispersal, a process that is largely determined by stochastic forces. Yet, larvae of many taxa exhibit strong navigational capabilities and there is mounting evidence of widespread intra-specific variability in biological traits that are potentially correlated with dispersal potential. While so far there are few known examples of real larval dispersal polymorphisms, intra-specifically variable dispersal strategies may be common in marine systems. Whether adaptive or not, it is becoming apparent that inter-individual heterogeneity in morphology, behavior, condition, and life history traits may have critical effects on population-level heterogeneity in dispersal. Here, we explore the eco-evolutionary causes and consequences of intrinsic and extrinsic variability on larval dispersal by synthesizing the existing literature and drawing conceptual parallels from terrestrial theory. We emphasize the potential importance of larval dispersal polymorphisms in marine population dynamics.

  2. Lagrangian scale of particle dispersion in turbulence.

    Science.gov (United States)

    Xia, Hua; Francois, Nicolas; Punzmann, Horst; Shats, Michael

    2013-01-01

    Transport of mass, heat and momentum in turbulent flows by far exceeds that in stable laminar fluid motions. As turbulence is a state of a flow dominated by a hierarchy of scales, it is not clear which of these scales mostly affects particle dispersion. Also, it is not uncommon that turbulence coexists with coherent vortices. Here we report on Lagrangian statistics in laboratory two-dimensional turbulence. Our results provide direct experimental evidence that fluid particle dispersion is determined by a single measurable Lagrangian scale related to the forcing scale. These experiments offer a new way of predicting dispersion in turbulent flows in which one of the low energy scales possesses temporal coherency. The results are applicable to oceanographic and atmospheric data, such as those obtained from trajectories of free-drifting instruments in the ocean.

  3. Taylor dispersion in wind-driven current

    Science.gov (United States)

    Li, Gang; Wang, Ping; Jiang, Wei-Quan; Zeng, Li; Li, Zhi; Chen, G. Q.

    2017-12-01

    Taylor dispersion associated with wind-driven currents in channels, shallow lakes and estuaries is essential to hydrological environmental management. For solute dispersion in a wind-driven current, presented in this paper is an analytical study of the evolution of concentration distribution. The concentration moments are intensively derived for an accurate presentation of the mean concentration distribution, up to the effect of kurtosis. The vertical divergence of concentration is then deduced by Gill's method of series expansion up to the fourth order. Based on the temporal evolution of the vertical concentration distribution, the dispersion process in the wind-driven current is concretely characterized. The uniform shear leads to a special symmetrical distribution of mean concentration free of skewness. The non-uniformity of vertical concentration is caused by convection and smeared out gradually by the effect of diffusion, but fails to disappear even at large times.

  4. Slow light optofluidics: a proposal.

    Science.gov (United States)

    Sumetsky, M

    2014-10-01

    The resonant slow light structures created along a thin-walled optical capillary by nanoscale deformation of its surface can perform comprehensive simultaneous detection and manipulation of microfluidic components. This concept is illustrated with a model of a 0.5 mm long, 5 nm high, triangular bottle resonator created at a 50 μm radius silica capillary containing floating microparticles. The developed theory shows that the microparticle positions can be determined from the bottle resonator spectrum. In addition, the microparticles can be driven and simultaneously positioned at predetermined locations by the localized electromagnetic field created by the optimized superposition of eigenstates of this resonator, thus exhibiting a multicomponent, near-field optical tweezer.

  5. Incoherent "slow and fast light".

    Science.gov (United States)

    Zapasskii, Valerii; Kozlov, Gleb

    2009-11-23

    We show experimentally that the effects of pulse delay and advancement usually ascribed to the "slow and fast light" under conditions of the coherent population oscillations (CPO) can be universally observed with incoherent light fields on objects with the pure-intensity nonlinearity. As a light source, we used an incandescent lamp and as objects for study, a photochromic glass and a thermochromic coating. The response of the objects to intensity modulation of the incident light reproduced in all details the commonly accepted experimental evidences of the "light with a negative group velocity" and "ultraslow light". Thus we show that observations of the pulse delay (advancement) and characteristic changes in the light intensity modulation spectrum are not enough to make conclusion about modification of the light group velocity in the medium.

  6. Traditional Procurement is too Slow

    Directory of Open Access Journals (Sweden)

    Ann Kong

    2012-11-01

    Full Text Available This paper reports on an exploratory interview survey of construction project participants aimed at identifying the reasons for the decrease in use of the traditional, lump-sum, procurement system in Malaysia. The results show that most people believe it is too slow. This appears to be in part due to the contiguous nature of the various phase and stages of the process and especially the separation of the design and construction phases. The delays caused by disputes between the various parties are also seen as a contributory factor - the most prominent cause being the frequency of variations, with design and scope changes being a particular source of discontent. It is concluded that an up scaling of the whole of the time related reward/penalty system may be the most appropriate measure for the practice in future.

  7. Slow molecular recognition by RNA.

    Science.gov (United States)

    Gleitsman, Kristin R; Sengupta, Raghuvir N; Herschlag, Daniel

    2017-12-01

    Molecular recognition is central to biological processes, function, and specificity. Proteins associate with ligands with a wide range of association rate constants, with maximal values matching the theoretical limit set by the rate of diffusional collision. As less is known about RNA association, we compiled association rate constants for all RNA/ligand complexes that we could find in the literature. Like proteins, RNAs exhibit a wide range of association rate constants. However, the fastest RNA association rates are considerably slower than those of the fastest protein associations and fall well below the diffusional limit. The apparently general observation of slow association with RNAs has implications for evolution and for modern-day biology. Our compilation highlights a quantitative molecular property that can contribute to biological understanding and underscores our need to develop a deeper physical understanding of molecular recognition events. © 2017 Gleitsman et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

  8. Dispersion relations of cytoskeleton dynamics

    Directory of Open Access Journals (Sweden)

    Wang R

    2016-01-01

    Full Text Available Ru Wang,1,2 Lei Lei,3 Shamira Sridharan,1,3 Yingxiao Wang,3 Alex J Levine,4,5 Gabriel Popescu,1,3,6 1Quantitative Light Imaging Laboratory, Beckman Institute for Advanced Science and Technology, 2Department of Mechanical Science and Engineering, 3Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, 4Department of Chemistry and Biochemistry, 5Department of Physics and Astronomy, University of California, Los Angeles, CA, 6Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA Abstract: While it is well known that the cytoskeleton plays a fundamental role in maintaining cell shape, performing cell division, and intracellular transport, its spatiotemporal dynamics are insufficiently understood. The dispersion relation, which is fundamental for understanding the connection between spatial and temporal scales of a dynamic system, was employed here for the first time to study the activity of actin and microtubules. Using green fluorescence protein for time-lapse imaging of the cytoskeleton, we showed that the dispersion relation can distinguish between diffusive and active transport of actin and microtubule filaments. Our analysis revealed that along the filaments, the transport was deterministic, as one might expect as the result of the active polymerization process, while across the filaments diffusion was dominant. Furthermore, using drugs to block the polymerization–depolymerization of both actin and microtubules, we measured that the transport immediately became diffusive, as expected. However, unexpectedly, our results indicated that within a few minutes from blocking its polymerization, actin recovered an active transport component. This deterministic component vanished upon treatment with nocodazole, indicating that fragments of actin were actively transported along microtubules. Because it provides information over broad temporal and spatial scales

  9. Synaptic Mechanisms of Memory Consolidation during Sleep Slow Oscillations.

    Science.gov (United States)

    Wei, Yina; Krishnan, Giri P; Bazhenov, Maxim

    2016-04-13

    Sleep is critical for regulation of synaptic efficacy, memories, and learning. However, the underlying mechanisms of how sleep rhythms contribute to consolidating memories acquired during wakefulness remain unclear. Here we studied the role of slow oscillations, 0.2-1 Hz rhythmic transitions between Up and Down states during stage 3/4 sleep, on dynamics of synaptic connectivity in the thalamocortical network model implementing spike-timing-dependent synaptic plasticity. We found that the spatiotemporal pattern of Up-state propagation determines the changes of synaptic strengths between neurons. Furthermore, an external input, mimicking hippocampal ripples, delivered to the cortical network results in input-specific changes of synaptic weights, which persisted after stimulation was removed. These synaptic changes promoted replay of specific firing sequences of the cortical neurons. Our study proposes a neuronal mechanism on how an interaction between hippocampal input, such as mediated by sharp wave-ripple events, cortical slow oscillations, and synaptic plasticity, may lead to consolidation of memories through preferential replay of cortical cell spike sequences during slow-wave sleep. Sleep is critical for memory and learning. Replay during sleep of temporally ordered spike sequences related to a recent experience was proposed to be a neuronal substrate of memory consolidation. However, specific mechanisms of replay or how spike sequence replay leads to synaptic changes that underlie memory consolidation are still poorly understood. Here we used a detailed computational model of the thalamocortical system to report that interaction between slow cortical oscillations and synaptic plasticity during deep sleep can underlie mapping hippocampal memory traces to persistent cortical representation. This study provided, for the first time, a mechanistic explanation of how slow-wave sleep may promote consolidation of recent memory events. Copyright © 2016 the authors 0270-6474/16/364231-17$15.00/0.

  10. Some Observational and Modeling Studies of the Atmospheric Boundary Layer at Mississippi Gulf Coast for Air Pollution Dispersion Assessment

    Directory of Open Access Journals (Sweden)

    Anjaneyulu Yerramilli

    2008-12-01

    Full Text Available Coastal atmospheric conditions widely vary from those over inland due to the land-sea interface, temperature contrast and the consequent development of local circulations. In this study a field meteorological experiment was conducted to measure vertical structure of boundary layer during the period 25-29 June, 2007 at three locations Seabee base, Harrison and Wiggins sites in the Mississippi coast. A GPS Sonde along with slow ascent helium balloon and automated weather stations equipped with slow and fast response sensors were used in the experiment. GPS sonde were launched at three specific times (0700 LT, 1300 LT and 1800 LT during the experiment days. The observations indicate shallow boundary layer near the coast which gradually develops inland. The weather research and forecasting (WRF meso-scale atmospheric model and a Lagrangian particle dispersion model (HYSPLIT are used to simulate the lower atmospheric flow and dispersion in a range of 100 km from the coast for 28-30 June, 2007. The simulated meteorological parameters were compared with the experimental observations. The meso-scale model results show significant temporal and spatial variations in the meteorological fields as a result of development of sea breeze flow, its coupling with the large scale flow field and the ensuing alteration in the mixing depth across the coast. Simulated ground-level concentrations of SO2 from four elevated point sources located along the coast indicate diurnal variation and impact of the local sea-land breeze on the direction of the plume. Model concentration levels were highest during the stable morning condition and during the sea-breeze time in the afternoon. The highest concentrations were found up to 40 km inland during sea breeze time. The study illustrates the application of field meteorological observations for the validation of WRF which is coupled to HYSPLIT for dispersion assessment in the coastal region.

  11. Dispersal of forest insects

    Science.gov (United States)

    Mcmanus, M. L.

    1979-01-01

    Dispersal flights of selected species of forest insects which are associated with periodic outbreaks of pests that occur over large contiguous forested areas are discussed. Gypsy moths, spruce budworms, and forest tent caterpillars were studied for their massive migrations in forested areas. Results indicate that large dispersals into forested areas are due to the females, except in the case of the gypsy moth.

  12. Quasi-asymptotic Dispersion

    Science.gov (United States)

    Scheven, U. M.; Harris, R.; Johns, M. L.

    2008-12-01

    The experimental characterization of voidspaces in porous media generally includes measurements of volume averaged scalar properties such as porosity, dispersivity, or the hydrodynamic radius rh = V/S, where V and S are the volume and surface area of the pore space respectively. Displacement encoding NMR experiments have made significant contributions to this characterization. It is clear, however, that NMR derived dispersivities in packed beds—the one random porous system for which there exist canonical but incompatible theoretical predictions with few or no adjustable parameters—can be affected by the same experimental complications which have substantially contributed to the puzzling scatter in published dispersion results based on elution experiments. Notable among these are macroscopic flow heterogeneities near walls, and inhomogeneous flow injection. Using the first three cumulants we delineate a transition from a pre-asymptotic to a quasi-asymptotic dispersion regime and determine the true dispersivity of the random pack of spheres.

  13. Absorption and dispersion of ultrasonic waves

    CERN Document Server

    Herzfeld, Karl F; Massey, H S W; Brueckner, Keith A

    1959-01-01

    Absorption and Dispersion of Ultrasonic Waves focuses on the influence of ultrasonics on molecular processes in liquids and gases, including hydrodynamics, energy exchange, and chemical reactions. The book first offers information on the Stokes-Navier equations of hydrodynamics, as well as equations of motion, viscosity, formal introduction of volume viscosity, and linearized wave equation for a nonviscous fluid. The manuscript then ponders on energy exchange between internal and external degrees of freedom as relaxation phenomenon; effect of slow energy exchange on sound propagation; differe

  14. Dual-channel dispersionless slow light based on plasmon-induced transparency.

    Science.gov (United States)

    Han, Xiaoxiang

    2014-01-01

    I have proposed a dual-channel dispersionless slow-light waveguide system based on plasmon-induced transparency. By appropriately tuning the stub depth, two transparency windows in the transmission spectrum can be achieved due to the destructive interference between the electromagnetic fields from the three stubs. Two flat bands can be achieved in the transparency windows, which have nearly constant group indices over the bandwidth of 2 THz. The analytical results show that the group velocity dispersion parameters of the two channels equal zero, which indicates that the incident pulse can be slowed down without distortion. The proposed plasmonic waveguide system can realize slow-light effect without pulse distortion, and thus can find important applications on slow-light systems, optical buffers, and all-optical signal processors in highly integrated optical circuits.

  15. Limited predator-induced dispersal in whiteflies.

    Directory of Open Access Journals (Sweden)

    Rui-Xia Meng

    Full Text Available Whereas prey are known to avoid habitats with their predators, it is less well established whether they are triggered to emigrate to new habitats when exposed to predators in their current habitat. We studied plant-to-plant dispersal of adult whiteflies in response to the presence of predatory mites on the plant on which the whiteflies were released. These predators attack whitefly eggs and crawlers, but not the adults, which can fly to other plants and can learn to avoid plants with predators. Being tiny and wingless, the predatory mites are slow dispersers compared to adult whiteflies. This offers the whiteflies the opportunity to escape from plants with predatory mites to plants without predators, thus avoiding predation of their offspring. To test for this escape response, a greenhouse experiment was carried out, where whiteflies were released on the first of a row of 5 cucumber plants, 0.6 m or 2 m apart, and predators either on the same plant, on the next plant, or nowhere (control. Adult whiteflies dispersed significantly faster from plants with predatory mites onto neighbouring plants when the plants were 0.6 m apart, but not when plants were 2 m apart. However, the final numbers of whiteflies that had successfully dispersed at the end of the experiments did not differ significantly for either of the two interplant distances. Overall, the proportion of whiteflies that did disperse was low, suggesting that adult whiteflies were apparently reluctant to disperse, even from plants with predators. Our results suggest that this reluctance increases with the distance between the plants, so most likely depends on the uncertainty to find a new plant. Thus, whiteflies do not always venture to fly even when they can easily bridge the distance to another plant.

  16. Emergence of Slow-Switching Assemblies in Structured Neuronal Networks.

    Directory of Open Access Journals (Sweden)

    Michael T Schaub

    2015-07-01

    Full Text Available Unraveling the interplay between connectivity and spatio-temporal dynamics in neuronal networks is a key step to advance our understanding of neuronal information processing. Here we investigate how particular features of network connectivity underpin the propensity of neural networks to generate slow-switching assembly (SSA dynamics, i.e., sustained epochs of increased firing within assemblies of neurons which transition slowly between different assemblies throughout the network. We show that the emergence of SSA activity is linked to spectral properties of the asymmetric synaptic weight matrix. In particular, the leading eigenvalues that dictate the slow dynamics exhibit a gap with respect to the bulk of the spectrum, and the associated Schur vectors exhibit a measure of block-localization on groups of neurons, thus resulting in coherent dynamical activity on those groups. Through simple rate models, we gain analytical understanding of the origin and importance of the spectral gap, and use these insights to develop new network topologies with alternative connectivity paradigms which also display SSA activity. Specifically, SSA dynamics involving excitatory and inhibitory neurons can be achieved by modifying the connectivity patterns between both types of neurons. We also show that SSA activity can occur at multiple timescales reflecting a hierarchy in the connectivity, and demonstrate the emergence of SSA in small-world like networks. Our work provides a step towards understanding how network structure (uncovered through advancements in neuroanatomy and connectomics can impact on spatio-temporal neural activity and constrain the resulting dynamics.

  17. Emergence of Slow-Switching Assemblies in Structured Neuronal Networks.

    Science.gov (United States)

    Schaub, Michael T; Billeh, Yazan N; Anastassiou, Costas A; Koch, Christof; Barahona, Mauricio

    2015-07-01

    Unraveling the interplay between connectivity and spatio-temporal dynamics in neuronal networks is a key step to advance our understanding of neuronal information processing. Here we investigate how particular features of network connectivity underpin the propensity of neural networks to generate slow-switching assembly (SSA) dynamics, i.e., sustained epochs of increased firing within assemblies of neurons which transition slowly between different assemblies throughout the network. We show that the emergence of SSA activity is linked to spectral properties of the asymmetric synaptic weight matrix. In particular, the leading eigenvalues that dictate the slow dynamics exhibit a gap with respect to the bulk of the spectrum, and the associated Schur vectors exhibit a measure of block-localization on groups of neurons, thus resulting in coherent dynamical activity on those groups. Through simple rate models, we gain analytical understanding of the origin and importance of the spectral gap, and use these insights to develop new network topologies with alternative connectivity paradigms which also display SSA activity. Specifically, SSA dynamics involving excitatory and inhibitory neurons can be achieved by modifying the connectivity patterns between both types of neurons. We also show that SSA activity can occur at multiple timescales reflecting a hierarchy in the connectivity, and demonstrate the emergence of SSA in small-world like networks. Our work provides a step towards understanding how network structure (uncovered through advancements in neuroanatomy and connectomics) can impact on spatio-temporal neural activity and constrain the resulting dynamics.

  18. Spontaneous K-Complex Density in Slow-Wave Sleep.

    Science.gov (United States)

    Manzar, Md Dilshad; Rajput, Mohammad Muntafa; Zannat, Wassilatul; Pandi-Perumal, Seithikurippu R; BaHammam, Ahmed S; Hussain, M Ejaz

    2016-01-01

    To study spontaneous K-complex (KC) densities during slow-wave sleep. The secondary objective was to estimate intra-non-rapid eye movement (NREM) sleep differences in KC density. It is a retrospective study using EEG data included in polysomnographic records from the archive at the sleep research laboratory of the Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia, India. The EEG records of 4459 minutes were used. The study presents a manual identification investigation of KCs in 17 healthy young adult male volunteers (age = 23.82±3.40 years and BMI = 23.42±4.18 kg/m2). N3 had a higher KC density than N2 (Z = -2.485, p = 0.013) for all of the probes taken together. Four EEG probes had a higher probe-specific KC density during N3. The inter-probe KC density differed significantly during N2 (χ2 = 67.91, p theory of KC generation. The significantly higher KC density during N3 may imply that the neuro-anatomical origin of slow-wave activity and KC is the same. This temporal alignment with slow-wave activity supports the sleep-promoting function of the KC.

  19. Electroencephalographic slow waves prior to sleepwalking episodes.

    Science.gov (United States)

    Perrault, Rosemarie; Carrier, Julie; Desautels, Alex; Montplaisir, Jacques; Zadra, Antonio

    2014-12-01

    Recent studies have suggested that the onset of sleepwalking episodes may be preceded by fluctuations in slow-wave sleep electroencephalographic characteristics. However, whether or not such fluctuations are specific to sleepwalking episodes or generalized to all sleep-wake transitions in sleepwalkers remains unknown. The goal of this study was to compare spectral power for delta (1-4 Hz) and slow delta (0.5-1 Hz) as well as slow oscillation density before the onset of somnambulistic episodes versus non-behavioral awakenings recorded from the same group of sleepwalkers. A secondary aim was to describe the time course of observed changes in slow-wave activity and slow oscillations during the 3 min immediately preceding the occurrence of somnambulistic episodes. Twelve adult sleepwalkers were investigated polysomnographically during the course of one night. Slow-wave activity and slow oscillation density were significantly greater prior to patients' somnambulistic episodes as compared with non-behavioral awakenings. However, there was no evidence for a gradual increase over the 3 min preceding the episodes. Increased slow-wave activity and slow oscillation density appear to be specific to sleepwalking episodes rather than generalized to all sleep-wake transitions in sleepwalkers. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Generation and evolution of interplanetary slow shocks

    Directory of Open Access Journals (Sweden)

    C.-C. Wu

    1996-04-01

    Full Text Available It is well known that most MHD shocks observed within 1 AU are MHD fast shocks. Only a very limited number of MHD slow shocks are observed within 1 AU. In order to understand why there are only a few MHD slow shocks observed within 1 AU, we use a one-dimensional, time-dependent MHD code with an adaptive grid to study the generation and evolution of interplanetary slow shocks (ISS in the solar wind. Results show that a negative, nearly square-wave perturbation will generate a pair of slow shocks (a forward and a reverse slow shock. In addition, the forward and the reverse slow shocks can pass through each other without destroying their characteristics, but the propagating speeds for both shocks are decreased. A positive, square-wave perturbation will generate both slow and fast shocks. When a forward slow shock (FSS propagates behind a forward fast shock (FFS, the former experiences a decreasing Mach number. In addition, the FSS always disappears within a distance of 150R⊙ (where R⊙ is one solar radius from the Sun when there is a forward fast shock (with Mach number ≥1.7 propagating in front of the FSS. In all tests that we have performed, we have not discovered that the FSS (or reverse slow shock evolves into a FFS (or reverse fast shock. Thus, we do not confirm the FSS-FFS evolution as suggested by Whang (1987.

  1. Applications of Slow Light in Telecommunications

    National Research Council Canada - National Science Library

    Boyd, Robert W; Gauthier, Daniel J; Gaeta, Alexander L

    2006-01-01

    .... Now, optical scientists are turning their attention toward developing useful applications of slow light, including controllable optical delay lines, optical buffers and true time delay methods...

  2. Holographic analysis of dispersive pupils in space--time optics

    Energy Technology Data Exchange (ETDEWEB)

    Calatroni, J.; Vienot, J.C.

    1981-06-01

    Extension of space--time optics to objects whose transparency is a function of the temporal frequency v = c/lambda is examined. Considering the effects of such stationary pupils on white light waves, they are called temporal pupils. It is shown that simultaneous encoding both in the space and time frequency domains is required to record pupil parameters. The space-time impulse response and transfer functions are calculated for a dispersive nonabsorbent material. An experimental method providing holographic recording of the dispersion curve of any transparent material is presented.

  3. REVIEW ARTICLE: Slow light modes for optical delay lines: 2D photonic crystal-based design structures, performances and challenges

    Science.gov (United States)

    Talneau, A.

    2010-10-01

    This paper presents an overview of 2D photonic crystal-based structures designed to display low group velocity as well as reduced group velocity dispersions. Their main envisioned applications are optical delay lines for telecom transmissions at 1.55 µm. Optical mechanisms responsible for slowing down the optical modes and encountered in the slow light regime serve as a guideline for this paper.

  4. Sustained eye closure slows saccades

    Science.gov (United States)

    Shaikh, Aasef G.; Wong, Aaron L.; Optican, Lance M.; Miura, Kenichiro; Solomon, David; Zee, David S.

    2010-01-01

    Saccadic eye movements rapidly orient the line of sight towards the object of interest. Pre-motor burst neurons (BNs) controlling saccades receive excitation from superior colliculus and cerebellum, but inhibition by omnipause neurons (OPNs) prevents saccades. When the OPNs pause, BNs begin to fire. It has been presumed that part of the BN burst comes from post-inhibitory rebound (PIR). We hypothesized that in the absence of prior inhibition from OPNs there would be no PIR, and thus the increase in initial firing rate of BNs would be reduced. Consequently, saccade acceleration would be reduced. We measured eye movements and showed that sustained eye closure, which inhibits the activity of OPNs and thus hypothetically should weaken PIR, reduced the peak velocity, acceleration, and deceleration of saccades in healthy human subjects. Saccades under closed eyelids also had irregular trajectories; the frequency of the oscillations underlying this irregularity was similar to that of high-frequency ocular flutter (back-to-back saccades) often seen in normal subjects during attempted fixation at straight ahead while eyes are closed. Saccades and quick phases of nystagmus are generated by the same pre-motor neurons, and we found that the quick-phase velocity of nystagmus was also reduced by lid closure. These changes were not due to a mechanical hindrance to the eyes, because lid closure did not affect the peak velocities or accelerations of the eyes in the “slow-phase” response to rapid head movements of comparable speeds to those of saccades. These results indicate a role for OPNs in generating the abrupt onset and high velocities of saccades. We hypothesize that the mechanism involved is PIR in pre-motor burst neurons. PMID:20573593

  5. Slow Movement/Slow University: Critical Engagements. Introduction to the Thematic Section

    Directory of Open Access Journals (Sweden)

    Maggie O'Neill

    2014-09-01

    Full Text Available This thematic section emerged from two seminars that took place at Durham University in England in November 2013 and March 2014 on the possibilities for thinking through what a change movement towards slow might mean for the University. Slow movements have emerged in relation to a number of topics: Slow food, Citta slow and more recently, slow science. What motivated us in the seminars was to explore how far these movements could help us address the acceleration and intensification of work within our own and other universities, and indeed, what new learning, research, philosophies, practices, structures and governance might emerge. This editorial introduction presents the concept of the "slow university" and introduces our critical engagements with slow. The articles presented here interrogate the potentialities, challenges, problems and pitfalls of the slow university in an era of corporate culture and management rationality. URN: http://nbn-resolving.de/urn:nbn:de:0114-fqs1403166

  6. Obsessional Slowness in College Students: Case Studies

    Science.gov (United States)

    Johnson, Aleta

    2014-01-01

    Cases of obsessional slowness, a variant of obsessive compulsive disorder, have been documented in case literature regarding relatively low functioning populations. However, obsessional slowness can also present in higher functioning populations, including college and graduate students, as illustrated here by three case examples from a competitive…

  7. Slow-light vortices in periodic waveguides

    DEFF Research Database (Denmark)

    Sukhorukov, Andrey A.; Ha, Sangwoo; Desyatnikov, Anton S.

    2009-01-01

    We reveal that the reduction of the group velocity of light in periodic waveguides is generically associated with the presence of vortex energy flows. We show that the energy flows are gradually frozen for slow-light at the Brillouin zone edge, whereas vortices persist for slow-light states havin...

  8. The Slow Learner and the Reading Problem.

    Science.gov (United States)

    Cawley, John F.; And Others

    The purpose of this book is to provide the special educator and the general educator with a basic reference tool concerning the slow learner and the reading problem. The text is divided into two sections. The first section, "An Overview of Selected Factors Relative to Reading and the Slow Learner," includes six chapters that discuss selected…

  9. Staff Development for Teaching Slow Learners

    Science.gov (United States)

    Leff, Rhona

    2008-01-01

    If you have noticed that your teachers need more "tricks up their sleeves" for working with slow learners, you can initiate a staff-development plan for changing that. Here are some suggestions for using the time, resources, and staff that you already have to improve the teaching of slow learners.

  10. Slow Learners' Attitudes toward Fundamental Freedoms.

    Science.gov (United States)

    Curtis, Charles K.

    1981-01-01

    This article reports a study that compared slow learners' attitudes toward the freedoms described in the Canadian Bill of Rights with those of vocational and academic students. As a group, slow learners in Canada scored significantly below vocational and academic students, and the scores for each group suggested only a slight libertarian bias.…

  11. VERY SLOW SPEED AXIAL MOTION RELUCTANCE MOTOR

    African Journals Online (AJOL)

    Dr Obe

    1984-09-01

    Sep 1, 1984 ... VERY SLOW SPEED AXIAL MOTION RELUCTANCE MOTOR by. L. A. Agu. Electrical Engineering Department. University of Nigeria, Nsukka. ABSTRACT. This paper presents the scheme for a very slow speed linear machine which uses conventional laminations and with which speeds of the same low.

  12. Tandem queue with server slow-down

    NARCIS (Netherlands)

    Miretskiy, D.I.; Scheinhardt, W.R.W.; Mandjes, M.R.H.

    2007-01-01

    We study how rare events happen in the standard two-node tandem Jackson queue and in a generalization, the socalled slow-down network, see [2]. In the latter model the service rate of the first server depends on the number of jobs in the second queue: the first server slows down if the amount of

  13. Observaton of tunneling of slow and fast electromagnetic modes in coupled periodic waveguides

    DEFF Research Database (Denmark)

    Ha, Sangwoo; Sukhorukov, Andrey A.; Lavrinenko, Andrei

    2011-01-01

    We report the experimental observation of tunneling of slow and fast electromagnetic modes in coupled periodic waveguides shifted longitudinally by half of modulation period. According to the symmetry analysis, such a coupler supports two electromagnetic modes with exactly matched slow or fast...... group velocities but different phase velocities for frequencies close to the edge of the photonic band. We confirm the predicted properties of the modes by directly extracting their dispersion and group velocities from the near-field measurements using specialized Bloch-wave spectral analysis method....

  14. Why material slow light does not improve cavity-enhanced atom detection

    Science.gov (United States)

    Megyeri, B.; Lampis, A.; Harvie, G.; Culver, R.; Goldwin, J.

    2018-01-01

    We discuss the prospects for enhancing absorption and scattering of light from a weakly coupled atom in a high-finesse optical cavity by adding a medium with large, positive group index of refraction. The slow-light effect is known to narrow the cavity transmission spectrum and increase the photon lifetime, but the quality factor of the cavity may not be increased in a metrologically useful sense. Specifically, detection of the weakly coupled atom through either cavity ringdown measurements or the Purcell effect fails to improve with the addition of material slow light. A single-atom model of the dispersive medium helps elucidate why this is the case.

  15. Single-mode dispersive waves and soliton microcomb dynamics

    CERN Document Server

    Yi, Xu; Zhang, Xueyue; Yang, Ki Youl; Vahala, Kerry

    2016-01-01

    Dissipative Kerr solitons are self-sustaining optical wavepackets in resonators. They use the Kerr nonlinearity to both compensate dispersion and to offset optical loss. Besides providing insights into nonlinear resonator physics, they can be applied in frequency metrology, precision clocks, and spectroscopy. Like other optical solitons, the dissipative Kerr soliton can radiate power in the form of a dispersive wave through a process that is the optical analogue of Cherenkov radiation. Dispersive waves typically consist of an ensemble of optical modes. A limiting case is demonstrated in which the dispersive wave is concentrated into a single cavity mode. In this limit, its interaction with the soliton is shown to induce bistable behavior in the spectral and temporal properties of the soliton. Also, an operating point of enhanced repetition-rate stability is predicted and observed. The single-mode dispersive wave can therefore provide quiet states of soliton comb operation useful in many applications.

  16. Slow Rotating Trojans: Tidally Synchronized Binaries?

    Science.gov (United States)

    Noll, Keith

    2017-08-01

    We propose HST observations of six slow-rotating Trojans to search for tidally synchronous binaries similar to the Patroclus binary system. A significant excess of slow rotators over Maxwellian suggests that additional binaries may be present. If any of the targets are binary, they can be resolved by HST. This target selection strategy has recently yielded the third known resolved Trojan binary, detected in a sample of seven slow-rotating Trojans. We wish to extend this successful strategy with another similarly selected sample. Even one additional resolved binary in the Trojans, which would become the fourth, would be of extreme interest. The discovery of no binaries among this group of slow rotators would challenge the understanding of the source of the excess slow rotators in the Trojans.

  17. Connecting slow earthquakes to huge earthquakes.

    Science.gov (United States)

    Obara, Kazushige; Kato, Aitaro

    2016-07-15

    Slow earthquakes are characterized by a wide spectrum of fault slip behaviors and seismic radiation patterns that differ from those of traditional earthquakes. However, slow earthquakes and huge megathrust earthquakes can have common slip mechanisms and are located in neighboring regions of the seismogenic zone. The frequent occurrence of slow earthquakes may help to reveal the physics underlying megathrust events as useful analogs. Slow earthquakes may function as stress meters because of their high sensitivity to stress changes in the seismogenic zone. Episodic stress transfer to megathrust source faults leads to an increased probability of triggering huge earthquakes if the adjacent locked region is critically loaded. Careful and precise monitoring of slow earthquakes may provide new information on the likelihood of impending huge earthquakes. Copyright © 2016, American Association for the Advancement of Science.

  18. Exponential estimates of symplectic slow manifolds

    DEFF Research Database (Denmark)

    Kristiansen, Kristian Uldall; Wulff, C.

    2016-01-01

    In this paper we prove the existence of an almost invariant symplectic slow manifold for analytic Hamiltonian slow-fast systems with finitely many slow degrees of freedom for which the error field is exponentially small. We allow for infinitely many fast degrees of freedom. The method we use...... is motivated by a paper of MacKay from 2004. The method does not notice resonances, and therefore we do not pose any restrictions on the motion normal to the slow manifold other than it being fast and analytic. We also present a stability result and obtain a generalization of a result of Gelfreich and Lerman...... on an invariant slow manifold to (finitely) many fast degrees of freedom....

  19. Spatial heterogeneity in landscape structure influences dispersal and genetic structure: empirical evidence from a grasshopper in an agricultural landscape.

    Science.gov (United States)

    Gauffre, Bertrand; Mallez, Sophie; Chapuis, Marie-Pierre; Leblois, Raphael; Litrico, Isabelle; Delaunay, Sabrina; Badenhausser, Isabelle

    2015-04-01

    Dispersal may be strongly influenced by landscape and habitat characteristics that could either enhance or restrict movements of organisms. Therefore, spatial heterogeneity in landscape structure could influence gene flow and the spatial structure of populations. In the past decades, agricultural intensification has led to the reduction in grassland surfaces, their fragmentation and intensification. As these changes are not homogeneously distributed in landscapes, they have resulted in spatial heterogeneity with generally less intensified hedged farmland areas remaining alongside streams and rivers. In this study, we assessed spatial pattern of abundance and population genetic structure of a flightless grasshopper species, Pezotettix giornae, based on the surveys of 363 grasslands in a 430-km² agricultural landscape of western France. Data were analysed using geostatistics and landscape genetics based on microsatellites markers and computer simulations. Results suggested that small-scale intense dispersal allows this species to survive in intensive agricultural landscapes. A complex spatial genetic structure related to landscape and habitat characteristics was also detected. Two P. giornae genetic clusters bisected by a linear hedged farmland were inferred from clustering analyses. This linear hedged farmland was characterized by high hedgerow and grassland density as well as higher grassland temporal stability that were suspected to slow down dispersal. Computer simulations demonstrated that a linear-shaped landscape feature limiting dispersal could be detected as a barrier to gene flow and generate the observed genetic pattern. This study illustrates the relevance of using computer simulations to test hypotheses in landscape genetics studies. © 2015 John Wiley & Sons Ltd.

  20. Wideband slow-light modes for time delay of ultrashort pulses in symmetrical metal-cladding optical waveguide.

    Science.gov (United States)

    Zheng, Yuanlin; Yuan, Wen; Chen, Xianfeng; Cao, Zhuangqi

    2012-04-23

    A widebandwidth optical delay line is a useful device for various fascinating applications, such as optical buffering and processing of ultrafast signal. Here, we experimentally demonstrated effective slow light of sub-picosecond signal over 10 THz frequency range by employing the wide slow light modes in thick symmetrical metal-cladding optical waveguide (SMCOW). Ultrahigh-order guided modes travelling as slow light in waveguide together with strong confinement provided by metal-cladding makes this scheme nearly material dispersion independent and compatible with wide bandwidth operation. © 2012 Optical Society of America

  1. Slow shock interactions in the heliosphere using an adaptive grid MHD model

    Directory of Open Access Journals (Sweden)

    C.-C. Wu

    2005-03-01

    Full Text Available A one-dimensional (1-D, time-dependent, adaptive-grid MHD model with solar wind structure has been used in the past to study the interaction of shocks. In the present study, we wish to study some fundamental processes that may be associated with slow shock genesis and their possible interactions with other discontinuities. This adaptive-grid model, suitable for appropriate spatial and temporal numerical simulations, is used for this purpose because its finer grid sizes in the vicinity of the steep gradients at shocks make it possible to delineate the physical parameters on both sides of the shocks. We found that a perturbation with deceleration of solar wind will generate an ensemble consisting of a forward slow shock, a fast forward wave and a reverse slow shock. On the other hand, a perturbation with an increase in acceleration of solar wind will generate both a slow shock and a fast shock. These two perturbations, although not unique, may be representative of momentum and pressure changes at the solar surface. During the transition of a fast shock overtaking a slow shock from behind, the slow shock might disappear temporarily. Also, during the process of the merging of two slow shocks, a slow shock-like structure is formed first; later, the slow shock-like structure evolves into an intermediate shock-like structure. This intermediate shock-like structure then evolves into an intermediate wave and a slow shock-like structure. Finally, the slow shock-like structure evolves into a slow shock, but the intermediate wave disappears by interacting with the non-uniform solar wind. This complex behavior demonstrates the non-unique nature of the formation of slow shocks, intermediate shocks and their derivative structures. We emphasize the main aim of this work to be both: (a non-unique input physical parameters to explain the paucity of observed slow shocks, as well as (b the impossibility of backward tracing to the history of input boundary

  2. Slow shock interactions in the heliosphere using an adaptive grid MHD model

    Directory of Open Access Journals (Sweden)

    C.-C. Wu

    2005-03-01

    Full Text Available A one-dimensional (1-D, time-dependent, adaptive-grid MHD model with solar wind structure has been used in the past to study the interaction of shocks. In the present study, we wish to study some fundamental processes that may be associated with slow shock genesis and their possible interactions with other discontinuities. This adaptive-grid model, suitable for appropriate spatial and temporal numerical simulations, is used for this purpose because its finer grid sizes in the vicinity of the steep gradients at shocks make it possible to delineate the physical parameters on both sides of the shocks. We found that a perturbation with deceleration of solar wind will generate an ensemble consisting of a forward slow shock, a fast forward wave and a reverse slow shock. On the other hand, a perturbation with an increase in acceleration of solar wind will generate both a slow shock and a fast shock. These two perturbations, although not unique, may be representative of momentum and pressure changes at the solar surface.

    During the transition of a fast shock overtaking a slow shock from behind, the slow shock might disappear temporarily. Also, during the process of the merging of two slow shocks, a slow shock-like structure is formed first; later, the slow shock-like structure evolves into an intermediate shock-like structure. This intermediate shock-like structure then evolves into an intermediate wave and a slow shock-like structure. Finally, the slow shock-like structure evolves into a slow shock, but the intermediate wave disappears by interacting with the non-uniform solar wind. This complex behavior demonstrates the non-unique nature of the formation of slow shocks, intermediate shocks and their derivative structures.

    We emphasize the main aim of this work to be both: (a non-unique input physical parameters to explain the paucity of observed slow shocks, as well as (b the impossibility

  3. Fiber Based Dispersion Compensation

    CERN Document Server

    Ramachandran, Siddharth

    2007-01-01

    Dispersion management is a critical design criterion that characterizes the performance of an optical network, and has impacted almost every aspect of the physical layer of an optical transmission line. The past 10 years have seen an explosion in the variety of device effects exploited to obtain optimal performance from dispersion compensators, and this is the first book that deals exclusively with this technology. It starts with an exposition on the fundamental physics underlying dispersion and its effects on optical pulses, followed by at least one chapter devoted to each of the fiber-based dispersion-compensating devices that have either been deployed or are considered as serious candidates for future networks. The final section of this book then describes the systems-level impact of these devices, hence providing a one-stop reference for all aspects of optical-communication-network design pertaining to dispersion-management. Each chapter is written by the leading experts in the field, drawn from both acad...

  4. Highly coherent octave-spanning supercontinuum generation in CS2-filled photonic crystal fiber with strong slow nonlinearity

    Science.gov (United States)

    Wang, Liyun; Yuan, Jinhui; Wang, Kuiru; Kang, Zhe; Sang, Xinzhu; Yu, Chongxiu; Yan, Binbin

    2016-11-01

    In this paper, the supercontinuum (SC) generation in a carbon disulfide (CS2)-filled photonic crystal fiber (PCF) with strong slow nonlinearity is investigated. When the PCF is pumped at 1.55 μm in the anomalous dispersion region, we obtain highly coherent SC spanning from 0.99 to 2.32 μm, at -40 dB level. Moreover, the influences of the slow nonlinearity, the input pulse width, the pulse peak power, the fiber length, and the temperature on the supercontinuum generation (SCG) are studied. The role of the slow nonlinearity in enhancing the coherence of SC is proved. To our best knowledge, this is the first demonstration on generating the octave-spanning SC with high coherence using the slow nonlinearity of CS2. CS2 is a material that has high nonlinearity coefficient and well transparency in infrared. What's more, the slow nonlinearity is very strong in this material.

  5. Copropagating superluminal and slow light manifested by electromagnetically assisted nonlinear optical processes.

    Science.gov (United States)

    Zhang, Jiepeng; Hernandez, Gessler; Zhu, Yifu

    2006-09-01

    We report an experimental observation of nonlinear optical gain and loss assisted by electromagnetically induced transparency (EIT) and simultaneous superluminal and subluminal light propagations. Two circular components of a linearly polarized light initiate third-order nonlinear processes in which one circular component is attenuated while the other component is amplified in a three-level EIT system. Near the atomic resonance, the attenuated circular component experiences steep normal dispersion and propagates with a slow group velocity, while the amplified circular component experiences steep anomalous dispersion and propagates with a superluminal group velocity.

  6. Multiple scattering of slow muons in an electron gas

    Science.gov (United States)

    Archubi, Claudio Darío; Arista, Nestor R.

    2017-09-01

    A comparative study of the angular dispersion of slow muons in an electron gas is performed using three dielectric models which represent the case of metals (Lindhard model for a free electron gas) and the cases of semiconductors and insulators (Levine and Louie model and Brandt and Reinheimer model for systems with a band gap) and a non-linear model for both cases at very low velocities. The contribution of collective electronic excitations according to the dielectric model are found to be negligible. The results from the calculation using Lindhard expressions for the angular half width are coincident with the result of a multiple scattering model. In particular, the effects produced by the band gap of the material are analyzed in detail. Finally, as the recoil effect is negligible, there is an almost exact scaling, for a given velocity, between the proton and the muon results.

  7. KEK-IMSS Slow Positron Facility

    Energy Technology Data Exchange (ETDEWEB)

    Hyodo, T; Wada, K; Yagishita, A; Kosuge, T; Saito, Y; Kurihara, T; Kikuchi, T; Shirakawa, A; Sanami, T; Ikeda, M; Ohsawa, S; Kakihara, K; Shidara, T, E-mail: toshio.hyodo@kek.jp [High Energy Accelerator Research Organization (KEK) 1-1 Oho, Tsukuba, Ibaraki, 305-0801 (Japan)

    2011-12-01

    The Slow Positron Facility at the Institute of Material Structure Science (IMSS) of High Energy Accelerator Research Organization (KEK) is a user dedicated facility with an energy tunable (0.1 - 35 keV) slow positron beam produced by a dedicated 55MeV linac. The present beam line branches have been used for the positronium time-of-flight (Ps-TOF) measurements, the transmission positron microscope (TPM) and the photo-detachment of Ps negative ions (Ps{sup -}). During the year 2010, a reflection high-energy positron diffraction (RHEPD) measurement station is going to be installed. The slow positron generator (converter/ moderator) system will be modified to get a higher slow positron intensity, and a new user-friendly beam line power-supply control and vacuum monitoring system is being developed. Another plan for this year is the transfer of a {sup 22}Na-based slow positron beam from RIKEN. This machine will be used for the continuous slow positron beam applications and for the orientation training of those who are interested in beginning researches with a slow positron beam.

  8. KEK-IMSS Slow Positron Facility

    Science.gov (United States)

    Hyodo, T.; Wada, K.; Yagishita, A.; Kosuge, T.; Saito, Y.; Kurihara, T.; Kikuchi, T.; Shirakawa, A.; Sanami, T.; Ikeda, M.; Ohsawa, S.; Kakihara, K.; Shidara, T.

    2011-12-01

    The Slow Positron Facility at the Institute of Material Structure Science (IMSS) of High Energy Accelerator Research Organization (KEK) is a user dedicated facility with an energy tunable (0.1 - 35 keV) slow positron beam produced by a dedicated 55MeV linac. The present beam line branches have been used for the positronium time-of-flight (Ps-TOF) measurements, the transmission positron microscope (TPM) and the photo-detachment of Ps negative ions (Ps-). During the year 2010, a reflection high-energy positron diffraction (RHEPD) measurement station is going to be installed. The slow positron generator (converter/ moderator) system will be modified to get a higher slow positron intensity, and a new user-friendly beam line power-supply control and vacuum monitoring system is being developed. Another plan for this year is the transfer of a 22Na-based slow positron beam from RIKEN. This machine will be used for the continuous slow positron beam applications and for the orientation training of those who are interested in beginning researches with a slow positron beam.

  9. Coping with power dispersion?

    DEFF Research Database (Denmark)

    2014-01-01

    The last decades have witnessed a significant shift in policy competences away from central governments in Europe. The reallocation of competences spans over three dimensions: upwards; sideways; and downwards. This collection takes the dispersion of powers as a starting point and seeks to assess...... how the actors involved cope with the new configurations. In this introduction, we discuss the conceptualization of power dispersion and highlight the ways in which the contributions add to this research agenda. We then outline some general conclusions and end by indicating future avenues of research....... Taken together, the collection contributes some answers to the challenge of defining and measuring – in a comparative way – the control and co-ordination mechanisms which power dispersion generates. It also explores the tension between political actors' quest for autonomy and the acknowledgement...

  10. Characterizing Thalamocortical Disturbances in Cervical Spondylotic Myelopathy: Revealed by Functional Connectivity under Two Slow Frequency Bands.

    Directory of Open Access Journals (Sweden)

    Fuqing Zhou

    Full Text Available Recent advanced MRI studies on cervical spondylotic myelopathy (CSM revealed alterations of sensorimotor cortex, but the disturbances of large-scale thalamocortical systems remains elusive. The purpose of this study was to characterizing the CSM-related thalamocortical disturbances, which were associated with spinal cord structural injury, and clinical measures.A total of 17 patients with degenerative CSM and well-matched control subjects participated. Thalamocortical disturbances were quantified using thalamus seed-based functional connectivity in two distinct low frequencies bands (slow-5 and slow-4, with different neural manifestations. The clinical measures were evaluated by Japanese Orthopaedic Association (JOA score system and Neck Disability Index (NDI questionnaires.Decreased functional connectivity was found in the thalamo-motor, -somatosensory, and -temporal circuits in the slow-5 band, indicating impairment of thalamo-cortical circuit degeneration or axon/synaptic impairment. By contrast, increased functional connectivity between thalami and the bilateral primary motor (M1, primary and secondary somatosensory (S1/S2, premotor cortex (PMC, and right temporal cortex was detected in the slow-4 band, and were associated with higher fractional anisotropy values in the cervical cord, corresponding to mild spinal cord structural injury.These thalamocortical disturbances revealed by two slow frequency bands inform basic understanding and vital clues about the sensorimotor dysfunction in CSM. Further work is needed to evaluate its contribution in central functional reorganization during spinal cord degeneration.

  11. Smooth pursuit eye movements and motion perception share motion signals in slow and fast motion mechanisms.

    Science.gov (United States)

    Matsumiya, Kazumichi; Shioiri, Satoshi

    2015-08-01

    Pursuit eye movements correlate with perceived motion in both velocity and direction, even without retinal motion. Cortical cells in the monkey medial temporal region generate signals for initiating pursuit eye movements and respond to retinal motion for perception. However, recent studies suggest multiple motion processes, fast and slow, even for low-level motion. Here we investigated whether the relationship with pursuit eye movements is different for fast and slow motion processes, using a motion aftereffect technique with superimposed low- and high-spatial-frequency gratings. A previous study showed that the low- and high-spatial-frequency gratings adapt the fast and slow motion processes, respectively, and that a static test probes the slow motion process and a flicker test probes the fast motion process (Shioiri & Matsumiya, 2009). In the present study, an adaptation stimulus was composed of two gratings with different spatial frequencies and orientations but the same temporal frequency, moving in the orthogonal direction of ±45° from the vertical. We measured the directions of perceived motion and pursuit eye movements to a test stimulus presented after motion adaptation with changing relative contrasts of the two adapting gratings. Pursuit eye movements were observed in the same direction as that of the motion aftereffects, independent of the relative contrasts of the two adapting gratings, for both the static and flicker tests. These results suggest that pursuit eye movements and perception share motion signals in both slow and fast motion processes.

  12. Generation and evolution of interplanetary slow shocks

    Directory of Open Access Journals (Sweden)

    C.-C. Wu

    Full Text Available It is well known that most MHD shocks observed within 1 AU are MHD fast shocks. Only a very limited number of MHD slow shocks are observed within 1 AU. In order to understand why there are only a few MHD slow shocks observed within 1 AU, we use a one-dimensional, time-dependent MHD code with an adaptive grid to study the generation and evolution of interplanetary slow shocks (ISS in the solar wind. Results show that a negative, nearly square-wave perturbation will generate a pair of slow shocks (a forward and a reverse slow shock. In addition, the forward and the reverse slow shocks can pass through each other without destroying their characteristics, but the propagating speeds for both shocks are decreased. A positive, square-wave perturbation will generate both slow and fast shocks. When a forward slow shock (FSS propagates behind a forward fast shock (FFS, the former experiences a decreasing Mach number. In addition, the FSS always disappears within a distance of 150R (where R is one solar radius from the Sun when there is a forward fast shock (with Mach number ≥1.7 propagating in front of the FSS. In all tests that we have performed, we have not discovered that the FSS (or reverse slow shock evolves into a FFS (or reverse fast shock. Thus, we do not confirm the FSS-FFS evolution as suggested by Whang (1987.

  13. Slow media. Comunicación, cambio social y sostenibilidad en la era del torrente mediático

    Directory of Open Access Journals (Sweden)

    Alejandro Barranquero-Carretero

    2013-01-01

    Full Text Available Desde una crítica al culto a la velocidad en el moderno sistema capitalista, el movimiento slow insiste en la raíz temporal de la crisis sistémica planetaria. Este artículo ofrece una primera aproximación al origen y fundamentos de los slow media, que abogan por un abordaje en clave lenta, reflexiva y sostenible de la comunicación humana, mediada y digital.

  14. Slow light vortices in periodic waveguides

    DEFF Research Database (Denmark)

    Sukhorukov, Andrey A.; Ha, Sangwoo; Desyatnikov, Anton S.

    2009-01-01

    We reveal that the reduction of the group velocity of light in periodic waveguides is generically associated with the presence of vortex energy flows. We show that the energy flows are gradually frozen for slow-light at the Brillouin zone edge, whereas vortices persist for slow-light states having...... non-vanishing phase velocity inside the Brillouin zone. We also demonstrate that presence of vortices can be linked to the absence of slow-light at the zone edge, and present calculations illustrating these general results....

  15. Dystonia Associated with Idiopathic Slow Orthostatic Tremor

    Directory of Open Access Journals (Sweden)

    Christopher Kobylecki

    2016-02-01

    Full Text Available Background: We aimed to characterize the clinical and electrophysiological features of patients with slow orthostatic tremor.Case Report: The clinical and neurophysiological data of patients referred for lower limb tremor on standing were reviewed. Patients with symptomatic or primary orthostatic tremor were excluded. Eight patients were identified with idiopathic slow 4–8 Hz orthostatic tremor, which was associated with tremor and dystonia in cervical and upper limb musculature. Coherence analysis in two patients showed findings different to those seen in primary orthostatic tremor.Discussion: Slow orthostatic tremor may be associated with dystonia and dystonic tremor.

  16. Millisecond Photon Lifetime in a Slow-Light Microcavity.

    Science.gov (United States)

    Huet, V; Rasoloniaina, A; Guillemé, P; Rochard, P; Féron, P; Mortier, M; Levenson, A; Bencheikh, K; Yacomotti, A; Dumeige, Y

    2016-04-01

    Optical microcavities with ultralong photon storage times are of central importance for integrated nanophotonics. To date, record quality (Q) factors up to 10^{11} have been measured in millimetric-size single-crystal whispering-gallery-mode (WGM) resonators, and 10^{10} in silica or glass microresonators. We show that, by introducing slow-light effects in an active WGM microresonator, it is possible to enhance the photon lifetime by several orders of magnitude, thus circumventing both fabrication imperfections and residual absorption. The slow-light effect is obtained from coherent population oscillations in an erbium-doped fluoride glass microsphere, producing strong dispersion of the WGM (group index n_{g}∼10^{6}). As a result, a photon lifetime up to 2.5 ms at room temperature has been measured, corresponding to a Q factor of 3×10^{12} at 1530 nm. This system could yield a new type of optical memory microarray with ultralong storage times.

  17. Towards General Temporal Aggregation

    DEFF Research Database (Denmark)

    Boehlen, Michael H.; Gamper, Johann; Jensen, Christian Søndergaard

    2008-01-01

    Most database applications manage time-referenced, or temporal, data. Temporal data management is difficult when using conventional database technology, and many contributions have been made for how to better model, store, and query temporal data. Temporal aggregation illustrates well the problem...

  18. Simultaneous observation of superluminal and slow light propagation in a nested fiber ring resonator.

    Science.gov (United States)

    Wang, Jinfang; Zhang, Yundong; Zhang, Jing; Cai, Yuanxue; Zhang, Xuenan; Yuan, Ping

    2010-06-07

    We observe both superluminal and slow light propagation simultaneously in a nested fiber ring resonator. The two outputs of the resonator exhibit different absorption characteristics that produce opposite dispersion performance. The transmission spectra of two outputs are demonstrated experimentally for a variety of coupler settings. In particular, the group delays of the resonator for various values of the coupling coefficients are demonstrated theoretically and experimentally. We also discuss potential applications of the resonator.

  19. Multi-band slow light metamaterial.

    Science.gov (United States)

    Zhu, Lei; Meng, Fan-Yi; Fu, Jia-Hui; Wu, Qun; Hua, Jun

    2012-02-13

    In this paper, a multi-band slow light metamaterial is presented and investigated. The metamaterial unit cell is composed of three cut wires of different sizes and parallel to each other. Two transparency windows induced by two-two overlaps of absorption bands of three cut wires are observed. The multi-band transmission characteristics and the slow light properties of metamaterial are verified by numerical simulation, which is in a good agreement with theoretical predictions. The impacts of structure parameters on transparency windows are also investigated. Simulation results show the spectral properties can be tuned by adjusting structure parameters of metamaterial. The equivalent circuit model and the synthesis method of the multi-band slow light metamaterial are presented. It is seen from simulation results that the synthesis method accurately predicts the center frequency of the multi-band metamaterial, which opens a door to a quick and accurate construction for multi-band slow light metamaterial.

  20. Helping Parents Help the Slow Learner

    Science.gov (United States)

    Warnemuende, Carolyn

    2008-01-01

    Parents of struggling learners are often unsure of how to assist their children at home. The author provides useful strategies and tips for principals to help parents support and encourage their children who are slow learners.

  1. Teaching the Third World to Slow Learners.

    Science.gov (United States)

    Clabrough, Peter

    1978-01-01

    Describes a simulation game about the third world which can be valuable to slow learners because it enables them to acquire abstract concepts using a concrete method (induction). For journal availability, see SO 507 289. (Author/CK)

  2. Development of slowed down beams at GSI

    Energy Technology Data Exchange (ETDEWEB)

    Boutachkov, Plamen; Farinon, Fabio; Gorska, Magdalena; Gerl, Juergen; Kojouharov, Ivan; Naqvi, Farheen; Nociforo, Chiara; Prokopowicz, Wawrzyniec; Pietri, Stephane; Prochazka, Andrej; Schaffner, Henning; Weick, Helmut [GSI, Darmstadt (Germany); Hadynska, Katarzyna; Napiorkowski, Pawel; Pietak, Daniel [Warsaw University, Warsaw (Poland); Janik, Rudo; Strmen, Peter [Komenskeho University, Bratislava (Slovakia); Kondratyev, Nikolai A. [FLNR, JINR, Dubna (Russian Federation); Alvarez, Marcos A.G. [CNA, Seville (Spain); Mukha, Ivan [Seville University, Seville (Spain)

    2009-07-01

    The NUSTAR/HISPEC slowed down beam project at GSI/FAIR is dedicated to rare isotopes with energies of upto 10 MeV/u. These radioactive beams will be used for spectroscopy and reactions studies. The setup for slowing down will utilize a thick degrader positioned after the FRS/Super-FRS separators at GSI/FAIR, followed by transmission detectors for energy and trajectory reconstruction. As a test, Coulomb excitation of a slowed down {sup 64}Ni beam on a gold target was performed in Sep-Oct 2008 at GSI. TPC and MCP detectors were used for the tracking of the beam before and after slowing it down. The gold target, placed after the tracking setup, was surrounded partially with two DSSSDs and NaI {gamma}-detectors. The results from the test experiment and a comparison to simulations are presented.

  3. Slow-Scan TV Bibliography, 1988.

    Science.gov (United States)

    Colorado Video, Inc., Boulder.

    This 175-item bibliography on slow-scan television lists journal articles, monographs, research reports, and conference proceedings under the following headings: (1) Instructional Applications; (2) Medical Applications; and (3) General Applications. (MES)

  4. A vertebrate slow skeletal muscle actin isoform

    National Research Council Canada - National Science Library

    Mudalige, Wasana A. K. A; Jackman, Donna M; Waddleton, Deena M; Heeley, David H

    2007-01-01

    Salmonids utilize a unique, class II isoactin in slow skeletal muscle. This actin contains 12 replacements when compared with those from salmonid fast skeletal muscle, salmonid cardiac muscle and rabbit skeletal muscle...

  5. Slow living and the green economy

    Directory of Open Access Journals (Sweden)

    Diana-Eugenia Ioncică

    2016-05-01

    Full Text Available The current paper explores the relationship between some relatively new concepts in the field of economics – slow living, slow food, slow writing and the green economy. The goal of the paper is twofold – discussing the possibilities opened by these exciting new concepts, in terms of an increase in the quality of life combined with an environmentally sustainable lifestyle, as well as ascertaining what the concepts may entail in the context in which the effects of the recent economic crisis may make green and slow living seem like a distant dream. It is this holistic view that we shall attempt to enlarge upon in the paper, with the avowed purpose of weighing out the possibilities presented in the complicated, crisis-fraught global context.

  6. Depression Can Slow Hospital Patients' Recovery

    Science.gov (United States)

    ... page: https://medlineplus.gov/news/fullstory_166427.html Depression Can Slow Hospital Patients' Recovery: Study Screening for ... 9, 2017 FRIDAY, June 9, 2017 (HealthDay News) -- Depression affects about one-third of hospital patients and ...

  7. Universally dispersible carbon nanotubes.

    Science.gov (United States)

    Prevoteau, Alexandre; Soulié-Ziakovic, Corinne; Leibler, Ludwik

    2012-12-12

    We show that supramolecular chemistry provides a convenient tool to prepare carbone nanotubes (CNTs) that can be dispersed in solvents of any chemical nature, easily recovered and redispersed. Thymine-modified CNTs (CNT-Thy) can be dispersed in solution in the presence of diaminotriazine (DAT) end-functionalized polymers, through supramolecular Thy/DAT association. DAT-polymer chains are selected according to the solvent chemical nature: polystyrene (PS) for hydrophobic/low polarity solvents and a propylene oxide/ethylene oxide copolymer (predominantly propylene oxide based, PPO/PEO) for polar solvents or water. Long-term stable supramolecular CNT dispersions are reversibly aggregated by adding a few droplets of a selective dissociating agent of the Thy/DAT association (DMSO). CNT-Thy, simply recycled by centrifugation or filtration, can be redispersed in another solvent in presence of a suitable soluble DAT-polymer. Dispersion and aggregation can also be switched on and off by choosing a polymer for which a given solvent is close to Θ-conditions, e.g., PS in cyclohexane or PPO/PEO in water.

  8. A dispersion control chart

    NARCIS (Netherlands)

    Riaz, M.

    2008-01-01

    The study proposes a Shewhart-type control chart, namely Q chart, based on inter-quartile range, for monitoring changes (especially of moderate and large amounts which is major concern of Shewhart-type control charts) in process dispersion assuming normality of quality characteristic to be

  9. Interface, a dispersed architecture

    NARCIS (Netherlands)

    Vissers, C.A.

    1976-01-01

    Past and current specification techniques use timing diagrams and written text to describe the phenomenology of an interface. This paper treats an interface as the architecture of a number of processes, which are dispersed over the related system parts and the message path. This approach yields a

  10. Turbulence and Dispersion

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 9; Issue 10. Turbulence and Dispersion. K S Gandhi. General Article Volume 9 Issue 10 October 2004 pp 48-61. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/009/10/0048-0061. Keywords. Turbulent ...

  11. Octave spanning wedge dispersive mirrors with low dispersion oscillations.

    Science.gov (United States)

    Habel, Florian; Shirvanyan, Vage; Trubetskov, Michael; Burger, Christian; Sommer, Annkatrin; Kling, Matthias F; Schultze, Martin; Pervak, Vladimir

    2016-05-02

    A novel concept for octave spanning dispersive mirrors with low spectral dispersion oscillations is presented. The key element of the so-called wedge dispersive mirror is a slightly wedged layer which is coated on a specially optimized dispersive multilayer stack by a common sputter coating process. The group delay dispersion (GDD) of a pulse reflected on a wedge dispersive mirror is nearly free of oscillations. Fabricated mirrors with negative GDD demonstrate the compression of a pulse down to 3.8 fs as good as double angled mirrors optimized for the same bandwidth.

  12. Triggering of the 2014 Mw7.3 Papanoa earthquake by a slow slip event in Guerrero, Mexico

    Science.gov (United States)

    Radiguet, M.; Perfettini, H.; Cotte, N.; Gualandi, A.; Valette, B.; Kostoglodov, V.; Lhomme, T.; Walpersdorf, A.; Cabral Cano, E.; Campillo, M.

    2016-11-01

    Since their discovery two decades ago, slow slip events have been shown to play an important role in accommodating strain in subduction zones. However, the physical mechanisms that generate slow slip and the relationships with earthquakes are unclear. Slow slip events have been recorded in the Guerrero segment of the Cocos-North America subduction zone. Here we use inversion of position time series recorded by a continuous GPS network to reconstruct the evolution of aseismic slip on the subduction interface of the Guerrero segment. We find that a slow slip event began in February 2014, two months before the magnitude (Mw) 7.3 Papanoa earthquake on 18 April. The slow slip event initiated in a region adjacent to the earthquake hypocentre and extended into the vicinity of the seismogenic zone. This spatio-temporal proximity strongly suggests that the Papanoa earthquake was triggered by the ongoing slow slip event. We demonstrate that the triggering mechanism could be either static stress increases in the hypocentral region, as revealed by Coulomb stress modelling, or enhanced weakening of the earthquake hypocentral area by the slow slip. We also show that the plate interface in the Guerrero area is highly coupled between slow slip events, and that most of the accumulated strain is released aseismically during the slow slip episodes.

  13. Factors Contributing Decreased Performance Of Slow Learners

    OpenAIRE

    Dr. L. Kannan; Dr. P. V. Vijayaragavan.; Dr. Pankaj. B. Shah; Dr. Suganathan. S; Dr. Praveena .P

    2015-01-01

    Back ground Even experienced teaching faculty and administrators can be challenged by learners who have not able to perform up to expected need in their annual performance of their students these students are called as slow learnersStruggle learners. There should be a designed study to foster discussion about diagnosing particular problems that contribute with meeting objectives of slow learners. Methodology The study was performed on the entire current first year of Medical students were all...

  14. Blinks slow memory-guided saccades

    OpenAIRE

    Powers, Alice S.; Basso, Michele A.; Evinger, Craig

    2012-01-01

    Memory-guided saccades are slower than visually guided saccades. The usual explanation for this slowing is that the absence of a visual drive reduces the discharge of neurons in the superior colliculus. We tested a related hypothesis: that the slowing of memory-guided saccades was due also to the more frequent occurrence of gaze-evoked blinks with memory-guided saccades compared with visually guided saccades. We recorded gaze-evoked blinks in three monkeys while they performed visually guided...

  15. Suppression of displacement in severely slowed saccades

    OpenAIRE

    MacAskill, Michael R; Tim J. Anderson; Jones, Richard D

    2000-01-01

    Severely slowed saccades in spinocerebellar ataxia have previously been shown to be at least partially closed-loop in nature: their long duration means that they can be modified in-flight in response to intrasaccadic target movements. In this study, a woman with these pathologically slowed saccades could modify them in-flight in response to target movements, even when saccadic suppression of displacement prevented conscious awareness of those movements. Thus saccadic suppression of displace...

  16. Slow Slip Events and degree of coupling along the Mexican subduction zone in Guerrero and Oaxaca areas: role of the slab geometry and its lateral variations, spatio-temporal evolution, slip budget, determined from cGPS time series inversion using PCAIM code

    Science.gov (United States)

    Cotte, N.; Perfettini, H.; Rousset, B.; Kostoglodov, V.; Lasserre, C.; Walpersdorf, A.; Cabral, E.

    2014-12-01

    Since the first cGPS have been installed in 1997 in the Guerrero-Oaxaca region of the Central American subduction zone in Mexico, several slow slip events (SSE) have been observed there. Further studies showed that the SSE characteristics are disparate in Guerrero and Oaxaca in terms of duration, amplitude and depth. In particular, recent investigations show that the slip during SSE intrudes the seismogenic zone in Guerrero, but barely in Oaxaca. The SSE lateral and depth extent has important implications on the seismic cycle. It affects the redistribution of stress (increasing or decreasing it) within the seismogenic zone, thus the timing and magnitude of future earthquakes. It is thus important to constrain a degree of coupling on the subduction interface and how the coupling evolves in space and time. This can be achieved by refining coupling models based on the observations and exploring a sensitivity of the models to variations of their main parameters.To better understand the effect of the SSE on the seismic cycle along the Mexican subduction zone, we analyze cGPS data and invert the time series, using a method based on a principal component analysis: PCAIM (Principal Component Analysis-based Inversion Method). For both Guerrero and Oaxaca areas, we first discuss the geometry of the plates' interface. Then we investigate in particular the effect of possible lateral and down-dip variations of the subduction interface on coupling models. Subsequent modeling using the PCAIM of the sequential SSEs that occurred in the past decade permitted to compare our results with the inferences of previously published works. We present the first analysis of the latest large SSE that started in January 2014 in Guerrero. We show that the PCAIM allows to describe a complex slip history in space and time of different SSEs and to provide a comparative analysis of behavior of the individual SSEs. We then discuss the potential interplay between SSE in Guerrero and Oaxaca, and the

  17. Implications of waterbird ecology for the dispersal of aquatic organisms

    Science.gov (United States)

    Green, Andy J.; Figuerola, Jordi; Sánchez, Marta I.

    2002-06-01

    In this paper, we review some potential implications of waterbird ecology for their role as dispersers of aquatic plants and invertebrates. We focus particularly on internal transport (endozoochory) by the Anatidae (mainly ducks) and shorebirds, groups especially important for dispersal processes owing to their abundance, migratory habitats and diets. We conduct a literature review to assess the seasonal patterns shown by Anatidae in consumption of seeds and plankton, the interspecific patterns in such consumption (including the effects of body size, bill morphology, etc.), and differences in habitat use (e.g., shoreline vs. open water specialists) and migration patterns between species (e.g., true migrants vs. nomads). We show that many shorebirds are important consumers of seeds as well as plankton, and suggest that their role in plant dispersal has been underestimated. This review confirms that Anatidae, shorebirds and other waterbirds have great potential as dispersers of aquatic organisms, but illustrates how closely related, sympatric bird species can have very different roles in dispersal of specific aquatic organisms. Furthermore, great spatial and temporal variation is likely in dispersal patterns realized by a given bird population. We present evidence suggesting that northbound dispersal of aquatic propagules by endozoochory during spring migration is a frequent process in the northern hemisphere. Much more systematic fieldwork and reanalysis of the existing data sets (e.g., from diet studies) are needed before the relative roles of various waterbird species as dispersers can be fully assessed.

  18. Tunable flat band slow light in reconfigurable photonic crystal waveguides based on magnetic fluids

    DEFF Research Database (Denmark)

    Pu, Shengli; Wang, Haotian; Wang, Ning

    2013-01-01

    and the light speed in vacuum, respectively). Simultaneously, the normalized delay-bandwidth product is relatively large compared with other works. Reconfiguring the photonic crystal waveguide with magnetic fluids of different concentrations can remarkably tune the slow light parameters and the trade......A kind of two-dimensional photonic crystal line-defect waveguide with 45 -rotated square lattice is proposed to present slow light phenomena. Infiltrating the photonic crystal waveguide with appropriate magnetic fluids can generate very wide flat bands of guided modes, which give rise...... to the excellent slow light properties. The bandwidth centered at λ0=1550 nm of the designed W1 waveguide is considerably large (around 54 nm). The obtained group velocity dispersion β2 within the bandwidth is ultralow (varying from -2118a/2πc2 to 1845a/2πc2, where a and c are the period of the lattice...

  19. Slow light Mach-Zehnder interferometer as label-free biosensor with scalable sensitivity.

    Science.gov (United States)

    Qin, Kun; Hu, Shuren; Retterer, Scott T; Kravchenko, Ivan I; Weiss, Sharon M

    2016-02-15

    The design, fabrication, and characterization of a label-free Mach-Zehnder interferometer (MZI) optical biosensor that incorporates a highly dispersive one-dimensional (1D) photonic crystal in one arm are presented. The sensitivity of this slow light MZI-based sensor scales with the length of the slow light photonic crystal region. The numerically simulated sensitivity of a MZI sensor with a 16 μm long slow light region is 115,000 rad/RIU-cm, which is sevenfold higher than traditional MZI biosensors with millimeter-length sensing regions. An experimental bulk refractive index detection sensitivity of 84,000 rad/RIU-cm is realized and nucleic acid detection is also demonstrated.

  20. Slow Activity in Focal Epilepsy During Sleep and Wakefulness

    DEFF Research Database (Denmark)

    Pellegrino, Giovanni; Tombini, Mario; Curcio, Giuseppe

    2017-01-01

    Introduction We aimed to test differences between healthy subjects and patients with respect to slow wave activity during wakefulness and sleep. Methods Fifteen patients affected by nonlesional focal epilepsy originating within temporal areas and fourteen matched controls underwent a 24-hour EEG...... recording. We studied the EEG power spectral density during wakefulness and sleep in delta (1-4 Hz), theta (5-7 Hz), alpha (8-11 Hz), sigma (12-15 Hz), and beta (16-20 Hz) bands. Results During sleep, patients with focal epilepsy showed higher power from delta to beta frequency bands compared with controls...... was the delta band during the first 2 sleep cycles (sleep cycle 1, P = .014; sleep cycle 2, P = .002). During wakefulness, patients showed higher delta/theta activity over the affected regions compared with controls. Conclusions Patients with focal epilepsy showed a pattern of power increases characterized...

  1. Enhancement of a nano cavity lifetime by induced slow light and nonlinear dispersions.

    Science.gov (United States)

    Grinberg, P; Bencheikh, K; Brunstein, M; Yacomotti, A M; Dumeige, Y; Sagnes, I; Raineri, F; Bigot, L; Levenson, J A

    2012-11-19

    We start from a 2D photonic crystal nanocavity with moderate Q-factor and dynamically increase it by two order of magnitude by the joint action of coherent population oscillations and nonlinear refractive index.

  2. Between-site differences in the scale of dispersal and gene flow in red oak.

    Directory of Open Access Journals (Sweden)

    Emily V Moran

    Full Text Available BACKGROUND: Nut-bearing trees, including oaks (Quercus spp., are considered to be highly dispersal limited, leading to concerns about their ability to colonize new sites or migrate in response to climate change. However, estimating seed dispersal is challenging in species that are secondarily dispersed by animals, and differences in disperser abundance or behavior could lead to large spatio-temporal variation in dispersal ability. Parentage and dispersal analyses combining genetic and ecological data provide accurate estimates of current dispersal, while spatial genetic structure (SGS can shed light on past patterns of dispersal and establishment. METHODOLOGY AND PRINCIPAL FINDINGS: In this study, we estimate seed and pollen dispersal and parentage for two mixed-species red oak populations using a hierarchical bayesian approach. We compare these results to those of a genetic ML parentage model. We also test whether observed patterns of SGS in three size cohorts are consistent with known site history and current dispersal patterns. We find that, while pollen dispersal is extensive at both sites, the scale of seed dispersal differs substantially. Parentage results differ between models due to additional data included in bayesian model and differing genotyping error assumptions, but both indicate between-site dispersal differences. Patterns of SGS in large adults, small adults, and seedlings are consistent with known site history (farmed vs. selectively harvested, and with long-term differences in seed dispersal. This difference is consistent with predator/disperser satiation due to higher acorn production at the low-dispersal site. While this site-to-site variation results in substantial differences in asymptotic spread rates, dispersal for both sites is substantially lower than required to track latitudinal temperature shifts. CONCLUSIONS: Animal-dispersed trees can exhibit considerable spatial variation in seed dispersal, although patterns may

  3. The influence of male takeovers on female dispersal in Colobus vellerosus.

    Science.gov (United States)

    Sicotte, Pascale; Teichroeb, Julie A; Vayro, Josie V; Fox, Stephanie A; Bădescu, Iulia; Wikberg, Eva C

    2017-07-01

    Male takeovers affect male tenure, female mate choice and ultimately, individual reproductive success in group-living primates. In social systems with female philopatry and high male reproductive skew, male takeovers largely determine female mate choice, whereas in species with female dispersal, females have the option of deserting a new male. We focused on a species with facultative female dispersal to investigate which factors promote female desertion of males after takeover, using 15 cases (12 for which we have complete data on the takeover process and the female dispersal outcome). These cases took place in nine groups of Colobus vellerosus between 2001 and 2013 at the Boabeng-Fiema Monkey Sanctuary, Ghana. Quick takeovers were usually achieved by single adult males and were never followed by female dispersal. Slow takeovers involved several males, and these takeovers were regularly accompanied by female emigration. Infant attacks and infanticide by males occurred during both kinds of takeovers, but females with dependent offspring never dispersed, regardless of whether their infant was attacked or killed by the new male(s). Subadult females, who were not constrained by the presence of infants, dispersed more often after slow takeovers than after quick takeovers. Whether female dispersal post-takeover is an expression of female mate choice, or occurs to avoid the social upheaval surrounding slow takeovers, remains to be investigated. Am. J. Primatol. 79:e22436, 2017. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

  4. Spontaneous K-Complex Density in Slow-Wave Sleep.

    Directory of Open Access Journals (Sweden)

    Md Dilshad Manzar

    Full Text Available To study spontaneous K-complex (KC densities during slow-wave sleep. The secondary objective was to estimate intra-non-rapid eye movement (NREM sleep differences in KC density.It is a retrospective study using EEG data included in polysomnographic records from the archive at the sleep research laboratory of the Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia, India. The EEG records of 4459 minutes were used. The study presents a manual identification investigation of KCs in 17 healthy young adult male volunteers (age = 23.82±3.40 years and BMI = 23.42±4.18 kg/m2.N3 had a higher KC density than N2 (Z = -2.485, p = 0.013 for all of the probes taken together. Four EEG probes had a higher probe-specific KC density during N3. The inter-probe KC density differed significantly during N2 (χ2 = 67.91, p < .001, N3 (χ2 = 70.62, p < .001 and NREM (χ2 = 68.50, p < .001. The percent distribution of KC decreased uniformly with sleep cycles.The inter-probe differences during N3 establish the fronto-central dominance of the KC density regardless of sleep stage. This finding supports one local theory of KC generation. The significantly higher KC density during N3 may imply that the neuro-anatomical origin of slow-wave activity and KC is the same. This temporal alignment with slow-wave activity supports the sleep-promoting function of the KC.

  5. Slow Activity in Focal Epilepsy During Sleep and Wakefulness.

    Science.gov (United States)

    Pellegrino, Giovanni; Tombini, Mario; Curcio, Giuseppe; Campana, Chiara; Di Pino, Giovanni; Assenza, Giovanni; Tomasevic, Leo; Di Lazzaro, Vincenzo

    2017-05-01

    We aimed to test differences between healthy subjects and patients with respect to slow wave activity during wakefulness and sleep. Fifteen patients affected by nonlesional focal epilepsy originating within temporal areas and fourteen matched controls underwent a 24-hour EEG recording. We studied the EEG power spectral density during wakefulness and sleep in delta (1-4 Hz), theta (5-7 Hz), alpha (8-11 Hz), sigma (12-15 Hz), and beta (16-20 Hz) bands. During sleep, patients with focal epilepsy showed higher power from delta to beta frequency bands compared with controls. The effect was widespread for alpha band and above, while localized over the affected hemisphere for delta (sleep cycle 1, P = .006; sleep cycle 2, P = .008; sleep cycle 3, P = .017). The analysis of interhemispheric differences showed that the only frequency band stronger over the affected regions was the delta band during the first 2 sleep cycles (sleep cycle 1, P = .014; sleep cycle 2, P = .002). During wakefulness, patients showed higher delta/theta activity over the affected regions compared with controls. Patients with focal epilepsy showed a pattern of power increases characterized by a selective slow wave activity enhancement over the epileptic regions during daytime and sleep. This phenomenon was stronger and asymmetric during the first sleep cycles.

  6. Genetic detection of sex-specific dispersal in historical and contemporary populations of anadromous brown trout Salmo trutta

    DEFF Research Database (Denmark)

    Bekkevold, Dorte; Hansen, Michael Møller; Mensberg, Karen-Lise Dons

    2004-01-01

    The study of sex-biased dispersal has attracted considerable attention in birds and mammals, but less in other taxa, including fishes. We analysed sex-specific dispersal in historical (1910s and 1950s) and contemporary (1990s) samples of anadromous brown trout Salmo trutta. We tested the hypothesis...... that dispersal is unbiased using information from microsatellite DNA and applying an assignment index for 11 temporally and spatially separated samples. Our results are most consistent with brown trout dispersal being male biased, and provide no evidence of female bias. We found no evidence that dispersal...... patterns changed over time, indicating that stocking with hatchery strains did not affect sex-specific dispersal...

  7. Disabling Radiological Dispersal Terror

    Energy Technology Data Exchange (ETDEWEB)

    Hart, M

    2002-11-08

    Terror resulting from the use of a radiological dispersal device (RDD) relies upon an individual's lack of knowledge and understanding regarding its significance. Disabling this terror will depend upon realistic reviews of the current conservative radiation protection regulatory standards. It will also depend upon individuals being able to make their own informed decisions merging perceived risks with reality. Preparation in these areas will reduce the effectiveness of the RDD and may even reduce the possibility of its use.

  8. Taylor dispersion of nanoparticles

    Science.gov (United States)

    Balog, Sandor; Urban, Dominic A.; Milosevic, Ana M.; Crippa, Federica; Rothen-Rutishauser, Barbara; Petri-Fink, Alke

    2017-08-01

    The ability to detect and accurately characterize particles is required by many fields of nanotechnology, including materials science, nanotoxicology, and nanomedicine. Among the most relevant physicochemical properties of nanoparticles, size and the related surface-to-volume ratio are fundamental ones. Taylor dispersion combines three independent phenomena to determine particle size: optical extinction, translational diffusion, and sheer-enhanced dispersion of nanoparticles subjected to a steady laminar flow. The interplay of these defines the apparent size. Considering that particles in fact are never truly uniform nor monodisperse, we rigorously address particle polydispersity and calculate the apparent particle size measured by Taylor dispersion analysis. We conducted case studies addressing aqueous suspensions of model particles and large-scale-produced "industrial" particles of both academic and commercial interest of various core materials and sizes, ranging from 15 to 100 nm. A comparison with particle sizes determined by transmission electron microscopy confirms that our approach is model-independent, non-parametric, and of general validity that provides an accurate account of size polydispersity—independently on the shape of the size distribution and without any assumption required a priori.

  9. Dispersal ghosts in Oceania.

    Science.gov (United States)

    Cann, Rebecca L; Lum, J Koji

    2004-01-01

    Anthropological genetics helps expand our understanding of human phenotypes in the Pacific, in part because of its focus on gene genealogies to infer past episodes of dispersal and to differentiate these events from adaptations due to long-duration directional selection. Sewall Wright's 1949 seminal paper on population structure emphasized that there were two strong forces that exerted systematic and therefore determinant pressure on the gene pool: recurrent immigration and gene flow. These are important topics to all discussions of human dispersal in any region of the world. Furthermore, Wright listed five unique kinds of events that produced indeterminate or unpredictable changes that could lead to phenotypic and genotypic effects. In this category, he placed unique selective incidents, unique hybridization events, unique reductions in number, swamping by mass immigration, and mutational drive due to an allele always being favored since its origin or introduction. This discussion of human dispersal in the Pacific will touch on these topics, since they provide a second level of complexity in knowing who moved about a region of the world found already settled when rediscovered by colonial explorers during the 16-18th centuries. Copyright 2004 Wiley-Liss, Inc.

  10. Magnon Inflation: Slow Roll with Steep Potentials

    CERN Document Server

    Adshead, Peter; Burgess, C P; Hayman, Peter; Patil, Subodh P

    2016-01-01

    We find multi-scalar effective field theories (EFTs) that can achieve a slow inflationary roll despite having a scalar potential that does not satisfy the usual slow-roll condition (d V)^2 << V^2/Mp^2. They evade the usual slow-roll conditions on $V$ because their kinetic energies are dominated by single-derivative terms rather than the usual two-derivative terms. Single derivatives dominate during slow roll and so do not require a breakdown of the usual derivative expansion that underpins calculational control in much of cosmology. The presence of such terms requires some sort of UV Lorentz-symmetry breaking during inflation (besides the usual cosmological breaking). Chromo-natural inflation provides an example of a UV theory that can generate the multi-field single-derivative terms we consider, and we argue that the EFT we find indeed captures the slow-roll conditions for the background evolution for Chromo-natural inflation. We also show that our EFT can be understood as a multi-field generalization ...

  11. Fate of dispersants associated with the deepwater horizon oil spill.

    Science.gov (United States)

    Kujawinski, Elizabeth B; Kido Soule, Melissa C; Valentine, David L; Boysen, Angela K; Longnecker, Krista; Redmond, Molly C

    2011-02-15

    Response actions to the Deepwater Horizon oil spill included the injection of ∼771,000 gallons (2,900,000 L) of chemical dispersant into the flow of oil near the seafloor. Prior to this incident, no deepwater applications of dispersant had been conducted, and thus no data exist on the environmental fate of dispersants in deepwater. We used ultrahigh resolution mass spectrometry and liquid chromatography with tandem mass spectrometry (LC/MS/MS) to identify and quantify one key ingredient of the dispersant, the anionic surfactant DOSS (dioctyl sodium sulfosuccinate), in the Gulf of Mexico deepwater during active flow and again after flow had ceased. Here we show that DOSS was sequestered in deepwater hydrocarbon plumes at 1000-1200 m water depth and did not intermingle with surface dispersant applications. Further, its concentration distribution was consistent with conservative transport and dilution at depth and it persisted up to 300 km from the well, 64 days after deepwater dispersant applications ceased. We conclude that DOSS was selectively associated with the oil and gas phases in the deepwater plume, yet underwent negligible, or slow, rates of biodegradation in the affected waters. These results provide important constraints on accurate modeling of the deepwater plume and critical geochemical contexts for future toxicological studies.

  12. Semantics of Temporal Models with Multiple Temporal Dimensions

    DEFF Research Database (Denmark)

    Kraft, Peter; Sørensen, Jens Otto

    Semantics of temporal models with multi temporal dimensions are examined progressing from non-temporal models unto uni-temporal, and further unto bi- and tri-temporal models. An example of a uni-temporal model is the valid time model, an example of a bi-temporal model is the valid time/transactio...

  13. Wakefield and wave propagation at non-linear dispersion

    CERN Document Server

    Smirnov, A V

    2002-01-01

    Synchronous wakefield excitation and wave propagation along a dispersive slow-wave structure is considered. An explicit form for wakefields is obtained for a single bunch in the second and third approximations of dispersion while taking into account the effect of substantial group velocity with respect to charge velocity. Generalized differential equations describing diffused fields induced by a beam current or generated by an external source are derived. Field excitation and propagation near the cut-off is considered including trapped modes in the stopband. This theory can be applied to the fields induced by single bunch and bunch train in Standing Wave and Traveling Wave devices operating near pi-mode, self-consistent beam break-up simulations, RF-generation, pulse propagation, and breakdown study in waveguides as well as some of new methods of acceleration in a dispersive medium.

  14. What Causes Animals to Disperse?

    Indian Academy of Sciences (India)

    Dispersal thus produces homeless travelers (vagrants) who are in search of a new home." Dispersal has been at the forefront of research involving animal behaviour and ecology for a very long time. In a more general sense, dispersal speaks of the tendency of some animals to move away from their existing groups or from ...

  15. Slow light by Bloch surface wave tunneling.

    Science.gov (United States)

    Koju, Vijay; Robertson, William M

    2014-06-30

    We demonstrate a slow light configuration that makes use of Bloch Surface Waves as an intermediate excitation in a double-prism tunneling configuration. This method is simple compared to the more usual technique for slowing light using the phenomenon of electromagnetically induced transparency in atomic gases or doped ionic crystals operated at temperatures below 4 K. Using a semi-numerical approach, we show that a 1D photonic crystal, a multilayer structure composed of alternating layers of TiO(2) and SiO(2), can be used to slow down light by a factor of up to 400. The results also show that better control of the speed of light can be achieved by changing the number of bilayers and the air-gap thickness appropriately.

  16. Kinetic slow mode-type solitons

    Directory of Open Access Journals (Sweden)

    K. Baumgärtel

    2005-01-01

    Full Text Available One-dimensional hybrid code simulations are presented, carried out in order both to study solitary waves of the slow mode branch in an isotropic, collisionless, medium-β plasma (βi=0.25 and to test the fluid based soliton interpretation of Cluster observed strong magnetic depressions (Stasiewicz et al., 2003; Stasiewicz, 2004 against kinetic theory. In the simulations, a variety of strongly oblique, large amplitude, solitons are seen, including solitons with Alfvenic polarization, similar to those predicted by the Hall-MHD theory, and robust, almost non-propagating, solitary structures of slow magnetosonic type with strong magnetic field depressions and perpendicular ion heating, which have no counterpart in fluid theory. The results support the soliton-based interpretation of the Cluster observations, but reveal substantial deficiencies of Hall-MHD theory in describing slow mode-type solitons in a plasma of moderate beta.

  17. Slow and fast light in semiconductor waveguides

    DEFF Research Database (Denmark)

    Mørk, Jesper; Hansen, Per Lunnemann; Xue, Weiqi

    2010-01-01

    transparency and coherent population oscillations. While electromagnetically induced transparency has been the most important effect in realizing slowdown effects in atomic gasses, progress has been comparatively slow in semiconductors due to inherent problems of fast dephasing times and inhomogeneous......Investigations of slow and fast light effects in semiconductor waveguides entail interesting physics and point to a number of promising applications. In this review we give an overview of recent progress in the field, in particular focusing on the physical mechanisms of electromagnetically induced...

  18. Periodic orbits near a bifurcating slow manifold

    DEFF Research Database (Denmark)

    Kristiansen, Kristian Uldall

    2015-01-01

    (\\epsilon^{1/3})$-distance from the union of the normally elliptic slow manifolds that occur as a result of the bifurcation. Here $\\epsilon\\ll 1$ measures the time scale separation. These periodic orbits are predominantly unstable. The proof is based on averaging of two blowup systems, allowing one to estimate...... the effect of the singularity, combined with results on asymptotics of the second Painleve equation. The stable orbits of smallest amplitude that are {persistently} obtained by these methods remain slightly further away from the slow manifold being distant by an order $\\mathcal O(\\epsilon^{1/3}\\ln^{1/2}\\ln...

  19. Critical slowing down of topological modes

    CERN Document Server

    Del Debbio, L; Vicari, E; Debbio, Luigi Del; Manca, Gian Mario; Vicari, Ettore

    2004-01-01

    We investigate the critical slowing down of the topological modes using local updating algorithms in lattice 2-d CP^(N-1) models. We show that the topological modes experience a critical slowing down that is much more severe than the one of the quasi-Gaussian modes relevant to the magnetic susceptibility, which is characterized by $\\tau_{\\rm mag} \\sim \\xi^z$ with $z\\approx 2$. We argue that this may be a general feature of Monte Carlo simulations of lattice theories with non-trivial topological properties, such as QCD, as also suggested by recent Monte Carlo simulations of 4-d SU(N) lattice gauge theories.

  20. Transverse-electric and transverse-magnetic mode slow light propagation in a two-dimensional photonic crystal waveguide.

    Science.gov (United States)

    Wang, Donglin; Yu, Zhongyuan; Liu, Yumin; Guo, Xiaotao; Shu, Changgan; Zhou, Shuai

    2013-09-10

    A two-dimensional photonic crystal waveguide structure is designed for both TE- and TM-mode slow light propagation. The minimum group index of the waveguide for TE and TM modes can reach to 137.8 and 126.4, and the two polarizations have the same slow light frequency region. The designed structure can provide a large bandwidth range with very low group velocity dispersion for both TE and TM modes. The transmission property investigation for a suspended two-dimensional slab photonic crystal waveguide (PCW) indicates that such slow light character may be retained when perfect reflectors can be fixed on the horizontal surfaces of the slab. Such high group index for both TE and TM modes in two-dimensional PCWs is, to the best of our knowledge, first reported here, and may provide some useful guides for slow light research in theory.

  1. Coagulation of highly turbid suspensions using magnesium hydroxide: effects of slow mixing conditions.

    Science.gov (United States)

    Ayoub, George M; BinAhmed, Sara W; Al-Hindi, Mahmoud; Azizi, Fouad

    2014-09-01

    Laboratory experiments were carried out to study the effects of slow mixing conditions on magnesium hydroxide floc size and strength and to determine the turbidity and total suspended solid (TSS) removal efficiencies during coagulation of highly turbid suspensions. A highly turbid kaolin clay suspension (1,213 ± 36 nephelometric turbidity units (NTU)) was alkalized to pH 10.5 using a 5 M NaOH solution; liquid bittern (LB) equivalent to 536 mg/L of Mg(2+) was added as a coagulant, and the suspension was then subjected to previously optimized fast mixing conditions of 100 rpm and 60 s. Slow mixing speed (20, 30, 40, and 50 rpm) and time (10, 20, and 30 min) were then varied, while the temperature was maintained at 20.7 ± 1 °C. The standard practice for coagulation-flocculation jar test ASTM D2035-13 (2013) was followed in all experiments. Relative floc size was monitored using an optical measuring device, photometric dispersion analyzer (PDA 2000). Larger and more shear resistant flocs were obtained at 20 rpm for both 20- and 30-min slow mixing times; however, given the shorter duration for the former, the 20-min slow mixing time was considered to be more energy efficient. For slow mixing camp number (Gt) values in the range of 8,400-90,000, it was found that the mixing speed affected floc size and strength more than the time. Higher-turbidity removal efficiencies were achieved at 20 and 30 rpm, while TSS removal efficiency was higher for the 50-rpm slow mixing speed. Extended slow mixing time of 30 min yielded better turbidity and TSS removal efficiencies at the slower speeds.

  2. Developing a dispersant spraying capability

    Energy Technology Data Exchange (ETDEWEB)

    Gill, S.D.

    1979-01-01

    In developing a national dispersant spraying capability, the Canadian Coast Guard (CCG) has undertaken a modification program to enable the conventional offshore spraying gear to be mounted on almost any vessel of convenience. Smaller, more versatile inshore spraying vessels and pumps have been designed and built. With the popularization of concentrated dispersants, the inshore pumping equipment can be used aboard hovercraft for special application situations. A program of acquiring mobile dispersant storage tanks has been undertaken with auxiliary equipment that will facilitate the shipment of dispersants in bulk by air freight. Work also has commenced on extending the dispersant application program to include the CCG fleet of helicopters.

  3. Spatially Dispersed Employee Recovery

    DEFF Research Database (Denmark)

    Hvass, Kristian Anders; Torfadóttir, Embla

    2014-01-01

    Employee recovery addresses either employee well-being or management's practices in aiding employees in recovering themselves following a service failure. This paper surveys the cabin crew at a small, European, low-cost carrier and investigates employees' perceptions of management practices to aid...... personnel achieve service recovery. Employee recovery within service research often focuses on front-line employees that work in a fixed location, however a contribution to the field is made by investigating the recovery of spatially dispersed personnel, such as operational personnel in the transport sector...

  4. Spurious dispersion effects at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Prat, Eduard

    2009-07-15

    The performance of the Free-Electron Laser (FEL) process imposes stringent demands on the transverse trajectory and size of the electron beam. Since transverse dispersion changes off-energy particle trajectories and increases the effective beam size, dispersion must be controlled. This thesis treats the concept of dispersion in linacs, and analyses the impact of dispersion on the electron beam and on the FEL process. It presents generation mechanisms for spurious dispersion, quantifying its importance for FLASH (Free-electron Laser in Hamburg) and the XFEL (European X-ray Free-Electron Laser). A method for measuring and correcting dispersion and its implementation in FLASH is described. Experiments of dispersion e ects on the transverse beam quality and on the FEL performance are presented. (orig.)

  5. Dispersion stability of thermal nanofluids

    Directory of Open Access Journals (Sweden)

    Fan Yu

    2017-10-01

    Full Text Available Thermal nanofluids, the engineered fluids with dispersed functional nanoparticles, have exhibited extraordinary thermophysical properties and added functionalities, and thus have enabled a broad range of important applications. The poor dispersion stability of thermal nanofluids, however, has been considered as a long-existing issue that limits their further development and practical application. This review overviews the recent efforts and progresses in improving the dispersion stability of thermal nanofluids such as mechanistic understanding of dispersion behavior of nanofluids, examples of both water-based and oil-based nanofluids, strategies to stabilize nanofluids, and characterization techniques for dispersion behavior of nanofluids. Finally, on-going research needs, and possible solutions to research challenges and future research directions in exploring stably dispersed thermal nanofluids are discussed. Keywords: Thermal nanofluids, Dispersion, Aggregation, Electrostatic stabilization, Steric stabilization

  6. Dispersive Dam-Break Flow of a Photon Fluid

    Science.gov (United States)

    Xu, Gang; Conforti, Matteo; Kudlinski, Alexandre; Mussot, Arnaud; Trillo, Stefano

    2017-06-01

    We investigate the temporal photonic analogue of the dam-break phenomenon for shallow water by exploiting a fiber optics setup. We clearly observe the decay of the steplike input (photonic dam) into a pair of oppositely propagating rarefaction wave and dispersive shock wave. Our results show evidence for a critical transition of the dispersive shock into a self-cavitating state. The detailed observation of the cavitating state dynamics allows for a fully quantitative test of the Whitham modulation theory applied to the universal defocusing nonlinear Schrödinger equation.

  7. Experimental demonstration of spinor slow light.

    Science.gov (United States)

    Lee, Meng-Jung; Ruseckas, Julius; Lee, Chin-Yuan; Kudriašov, Viačeslav; Chang, Kao-Fang; Cho, Hung-Wen; Juzeliānas, Gediminas; Yu, Ite A

    2014-11-24

    Slow light based on the effect of electromagnetically induced transparency is of great interest due to its applications in low-light-level nonlinear optics and quantum information manipulation. The previous experiments all dealt with the single-component slow light. Here, we report the experimental demonstration of two-component or spinor slow light using a double-tripod atom-light coupling scheme. The scheme involves three atomic ground states coupled to two excited states by six light fields. The oscillation due to the interaction between the two components was observed. On the basis of the stored light, our data showed that the double-tripod scheme behaves like the two outcomes of an interferometer enabling precision measurements of frequency detuning. We experimentally demonstrated a possible application of the double-tripod scheme as quantum memory/rotator for the two-colour qubit. Our study also suggests that the spinor slow light is a better method than a widely used scheme in the nonlinear frequency conversion.

  8. Slow Reading: Reading along "Lectio" Lines

    Science.gov (United States)

    Badley, K. Jo-Ann; Badley, Ken

    2011-01-01

    The medieval monastic movement preserved and developed reading practices--lectio--from ancient Greek pedagogy as a slow, mindful approach to reading for formation. This ancient way of reading, now better known as lectio divina, challenges the fast, pragmatic reading so characteristic of our time. We propose that the present moment may be ripe for…

  9. Rescuing Students from the Slow Learner Trap

    Science.gov (United States)

    Shaw, Steven R.

    2010-01-01

    Slow learners, such as students with borderline intellectual functioning, represent one of the most challenging student populations for administrators and teachers. Standard systems and supports are often ineffective--even counterproductive--because they fail to meet students' specific learning needs and instead create a cycle of failure. This…

  10. Visual evoked potential study in slow learners.

    Science.gov (United States)

    Khaliq, Farah; Anjana, Yumnam; Vaney, Neelam

    2009-01-01

    Slow learners are individuals with low achievement and comparably low IQ scores. It may be a symptom reflecting a larger underlying problem in them. Sensory neural processing of visual information can be one of the contributory factors for their underachievement. The present study was undertaken to examine the integrity and function of visual pathway by means of Visual Evoked Potential (VEP). Pattern reversal VEP was performed on seventeen slow learners. Fifteen age and sex matched children with good school performance and normal IQ were taken as controls. There was significant prolongation of N75 component of VEP in slow learners. The latencies of P100 and N145 were also increased but could not reach the level of significance. Our findings are suggestive of the presence of a weaker VEP response in slow learners indicative of a deficit early in the visual processing. There is some abnormality in the geniculate afferents to V1 which is consistent with a defect in the magnocellular pathway at the level of Visual Area 1 or earlier.

  11. Slow Learner Education in New Zealand.

    Science.gov (United States)

    Tagg, Mary

    A survey of slow learner education in state secondary schools was conducted in Auckland and North Auckland, New Zealand. Thirty-five schools containing 30,787 pupils replied to the questionnaire which covered the following areas: assessment prior to placement, educational objectives, identification methods, special classes, teaching groups,…

  12. Visual-Motor Abilities of Slow Learners.

    Science.gov (United States)

    Hetrick, Ethel W.

    The Bender Gestalt protocols of 134 rural and 140 children (6-18 years old) found to have IQ scores in the slow learner range (IQ 70-84) were compared. The Bender Gestalt Test, used in psychoeducational evaluation to determine eligibility for special education placement, was administered to determine Ss' level of visual motor skills. Rural slow…

  13. Retention by "Fast" and "Slow" Learners.

    Science.gov (United States)

    Gentile, J. Ronald; And Others

    1982-01-01

    In four experiments to replicate and extend the findings of Shuell and Keppel (EJ 016 150), "fast" and "slow" learners were brought to a similar learning criterion, with the result that their forgetting curves were parallel. The experiments involved American and Nigerian students in learning word lists and poems. (Author/CM)

  14. Limits of slow light in photonic crystals

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Xiao, Sanshui; Mortensen, N. Asger

    2008-01-01

    While ideal photonic crystals would support modes with a vanishing group velocity, state-of-the-art structures have still only provided a slow down by roughly two orders of magnitude. We find that the induced density of states caused by lifetime broadening of the electromagnetic modes results in ...

  15. Preliminary characterization of slow growing rhizobial strains ...

    African Journals Online (AJOL)

    In this paper, we did some preliminary characterization of six slow growing rhizobial strains, isolated from Retama monosperma (L.) Boiss. root nodules sampled from 3 sites along the coast of Oran (CapeFalcon, Bousfer and MersElHadjadj) in Northwestern Algeria. Results of this study showed that all strains had a very ...

  16. Probabilistic Slow Features for Behavior Analysis

    NARCIS (Netherlands)

    Zafeiriou, Lazaros; Nicolaou, Mihalis A.; Zafeiriou, Stefanos; Nikitidis, Symeon; Pantic, Maja

    A recently introduced latent feature learning technique for time-varying dynamic phenomena analysis is the so-called slow feature analysis (SFA). SFA is a deterministic component analysis technique for multidimensional sequences that, by minimizing the variance of the first-order time derivative

  17. Slowed ageing, welfare, and population problems.

    Science.gov (United States)

    Wareham, Christopher

    2015-10-01

    Biological studies have demonstrated that it is possible to slow the ageing process and extend lifespan in a wide variety of organisms, perhaps including humans. Making use of the findings of these studies, this article examines two problems concerning the effect of life extension on population size and welfare. The first--the problem of overpopulation--is that as a result of life extension too many people will co-exist at the same time, resulting in decreases in average welfare. The second--the problem of underpopulation--is that life extension will result in too few people existing across time, resulting in decreases in total welfare. I argue that overpopulation is highly unlikely to result from technologies that slow ageing. Moreover, I claim that the problem of underpopulation relies on claims about life extension that are false in the case of life extension by slowed ageing. The upshot of these arguments is that the population problems discussed provide scant reason to oppose life extension by slowed ageing.

  18. Impact of multiple bird partners on the seed dispersal effectiveness of China's relic trees.

    Science.gov (United States)

    Li, Ning; Li, Xin-Hai; An, Shu-Qing; Lu, Chang-Hu

    2016-01-04

    Frugivorous birds generally exhibit an unequal contribution to dispersal effectiveness of plant species as a function of their habitat adaptation and body size. In our study, we compared the effectiveness of multiple bird species that contribute to the dispersal of the endangered relic Chinese yew, Taxus chinensis. Seven bird species dispersed T. chinensis seeds, with Picus canus, Turdus hortulorum, and Urocissa erythrorhyncha being the main dispersers. The quantity part of dispersal effectiveness was strongly influenced by two inherent characteristics of disperser species: body size and habitat adaptation. However, the quality part of dispersal effectiveness was only influenced by disperser type. For instance, small generalist birds and large specialist birds removed more seeds than other type dispersers. Moreover, small birds and specialist birds contributed slightly more to the dispersal quality of T. chinensis than large birds and generalist birds respectively; however, these differences were not significant. Our results suggest that dispersal effectiveness is affected by variety in the body size and habitat adaptation of different dispersers. Therefore, such variation should be incorporated into spatial and temporal management actions of relic plant species in patchy, human-disturbed habitats.

  19. Impact of multiple bird partners on the seed dispersal effectiveness of China’s relic trees

    Science.gov (United States)

    Li, Ning; Li, Xin-hai; An, Shu-qing; Lu, Chang-hu

    2016-01-01

    Frugivorous birds generally exhibit an unequal contribution to dispersal effectiveness of plant species as a function of their habitat adaptation and body size. In our study, we compared the effectiveness of multiple bird species that contribute to the dispersal of the endangered relic Chinese yew, Taxus chinensis. Seven bird species dispersed T. chinensis seeds, with Picus canus, Turdus hortulorum, and Urocissa erythrorhyncha being the main dispersers. The quantity part of dispersal effectiveness was strongly influenced by two inherent characteristics of disperser species: body size and habitat adaptation. However, the quality part of dispersal effectiveness was only influenced by disperser type. For instance, small generalist birds and large specialist birds removed more seeds than other type dispersers. Moreover, small birds and specialist birds contributed slightly more to the dispersal quality of T. chinensis than large birds and generalist birds respectively; however, these differences were not significant. Our results suggest that dispersal effectiveness is affected by variety in the body size and habitat adaptation of different dispersers. Therefore, such variation should be incorporated into spatial and temporal management actions of relic plant species in patchy, human-disturbed habitats. PMID:26725517

  20. Blinks slow memory-guided saccades.

    Science.gov (United States)

    Powers, Alice S; Basso, Michele A; Evinger, Craig

    2013-02-01

    Memory-guided saccades are slower than visually guided saccades. The usual explanation for this slowing is that the absence of a visual drive reduces the discharge of neurons in the superior colliculus. We tested a related hypothesis: that the slowing of memory-guided saccades was due also to the more frequent occurrence of gaze-evoked blinks with memory-guided saccades compared with visually guided saccades. We recorded gaze-evoked blinks in three monkeys while they performed visually guided and memory-guided saccades and compared the kinematics of the different saccade types with and without blinks. Gaze-evoked blinks were more common during memory-guided saccades than during visually guided saccades, and the well-established relationship between peak and average velocity for saccades was disrupted by blinking. The occurrence of gaze-evoked blinks was associated with a greater slowing of memory-guided saccades compared with visually guided saccades. Likewise, when blinks were absent, the peak velocity of visually guided saccades was only slightly higher than that of memory-guided saccades. Our results reveal interactions between circuits generating saccades and blink-evoked eye movements. The interaction leads to increased curvature of saccade trajectories and a corresponding decrease in saccade velocity. Consistent with this interpretation, the amount of saccade curvature and slowing increased with gaze-evoked blink amplitude. Thus, although the absence of vision decreases the velocity of memory-guided saccades relative to visually guided saccades somewhat, the cooccurrence of gaze-evoked blinks produces the majority of slowing for memory-guided saccades.

  1. Blinks slow memory-guided saccades

    Science.gov (United States)

    Basso, Michele A.; Evinger, Craig

    2013-01-01

    Memory-guided saccades are slower than visually guided saccades. The usual explanation for this slowing is that the absence of a visual drive reduces the discharge of neurons in the superior colliculus. We tested a related hypothesis: that the slowing of memory-guided saccades was due also to the more frequent occurrence of gaze-evoked blinks with memory-guided saccades compared with visually guided saccades. We recorded gaze-evoked blinks in three monkeys while they performed visually guided and memory-guided saccades and compared the kinematics of the different saccade types with and without blinks. Gaze-evoked blinks were more common during memory-guided saccades than during visually guided saccades, and the well-established relationship between peak and average velocity for saccades was disrupted by blinking. The occurrence of gaze-evoked blinks was associated with a greater slowing of memory-guided saccades compared with visually guided saccades. Likewise, when blinks were absent, the peak velocity of visually guided saccades was only slightly higher than that of memory-guided saccades. Our results reveal interactions between circuits generating saccades and blink-evoked eye movements. The interaction leads to increased curvature of saccade trajectories and a corresponding decrease in saccade velocity. Consistent with this interpretation, the amount of saccade curvature and slowing increased with gaze-evoked blink amplitude. Thus, although the absence of vision decreases the velocity of memory-guided saccades relative to visually guided saccades somewhat, the cooccurrence of gaze-evoked blinks produces the majority of slowing for memory-guided saccades. PMID:23155174

  2. Analysis of slow-wave activity and slow-wave oscillations prior to somnambulism.

    Science.gov (United States)

    Jaar, Olivier; Pilon, Mathieu; Carrier, Julie; Montplaisir, Jacques; Zadra, Antonio

    2010-11-01

    STUDY OBJECTIVIES: several studies have investigated slow wave sleep EEG parameters, including slow-wave activity (SWA) in relation to somnambulism, but results have been both inconsistent and contradictory. The first goal of the present study was to conduct a quantitative analysis of sleepwalkers' sleep EEG by studying fluctuations in spectral power for delta (1-4 Hz) and slow delta (0.5-1 Hz) before the onset of somnambulistic episodes. A secondary aim was to detect slow-wave oscillations to examine changes in their amplitude and density prior to behavioral episodes. twenty-two adult sleepwalkers were investigated polysomnographically following 25 h of sleep deprivation. analysis of patients' sleep EEG over the 200 sec prior to the episodes' onset revealed that the episodes were not preceded by a gradual increase in spectral power for either delta or slow delta over frontal, central, or parietal leads. However, time course comparisons revealed significant changes in the density of slow-wave oscillations as well as in very slow oscillations with significant increases occurring during the final 20 sec immediately preceding episode onset. the specificity of these sleep EEG parameters for the occurrence and diagnosis of NREM parasomnias remains to be determined.

  3. Hollow core photonic bandgap fiber with microfluid-infiltrated air holes for slow-light propagation

    Science.gov (United States)

    Ren, Liyong; Liang, Jian; Yun, Maojin

    2012-10-01

    Slow light plays an important role in the fields of all-optical signal processing and integration photonics. It has shown many potential applications, such as realizing optical delay lines or buffers, enhancing linear and nonlinear light-matter interactions, as well as increasing the sensitivity of the interferometers and transducers. In this paper, hollow-core photonic bandgap fibers made from high index glasses are designed by infiltrating microfluid into the air-holes to tailor the fiber dispersion for slow-light propagation under low pulse distortion. In such a fiber made from Si material, group index ng~8 is obtained with a bandwidth up to 30 nm, where the group index fluctuation is restricted in ±10 % of the ng, while ng~6 is obtained with a bandwidth over 100 nm when the chalcogenide material is selected instead. Such a ±10 % criterion determines a regarded flatland region accordingly, and in this region the group velocity dispersion can be negligible. It is found that for the same fiber length the slow-light time delay in the photonic bandgap fiber is much larger as compared with that in the single mode fiber. This kind of photonic bandgap fiber may have many potential applications in short-distance fiber communications and delay lines.

  4. Deterministic tuning of slow-light in photonic-crystal waveguides through the C and L bands by atomic layer deposition

    CERN Document Server

    Chen, Charlton J; Meric, Inanc; Shepard, Ken L; Wong, Chee Wei; Green, William M J; Vlasov, Yurii A; Assefa, Solomon

    2009-01-01

    We demonstrate digital tuning of the slow-light regime in silicon photonic-crystal waveguides by performing atomic layer deposition of hafnium oxide. The high group-index regime was deterministically controlled (red-shift of 140 +/- 10 pm per atomic layer) without affecting the group-velocity dispersion and third-order dispersion. Additionally, differential tuning of 110 +/- 30 pm per monolayer of the slow-light TE-like and TM-like modes was observed. This passive post-fabrication process has potential applications including the tuning of chip-scale optical interconnects, as well as Raman and parametric amplification.

  5. QT dispersion and P wave dispersion in patients with fibromyalgia.

    Science.gov (United States)

    Yolbaş, Servet; Yıldırım, Ahmet; Düzenci, Deccane; Karakaya, Bülent; Dağlı, Mustafa Necati; Koca, Süleyman Serdar

    2016-12-01

    Fibromyalgia (FM) is a chronic disease characterized by widespread pain. Somatic complaints associated with the cardiovascular system, such as chest pain and palpitations, are frequently seen in FM patients. P and QT dispersions are simple and inexpensive measurements reflecting the regional heterogeneity of atrial and ventricular repolarization, respectively. QT dispersion can cause serious ventricular arrhythmias. The aim of the present study was to evaluate QT dispersion and P wave dispersion in patients with FM. The study involved 48 FM patients who fulfilled the established criteria and 32 healthy controls (HC). A standard 12-lead electrocardiogram was performed on all participants. QT dispersion was defined as the difference between the longest and the shortest QT intervals. Similarly, the differences between the shortest and longest P waves were defined as P wave dispersion. The QT dispersion and corrected QT dispersion were shorter in the FM group compared with the HC group (pQT and P wave dispersions are not problems in patients with FM. Therefore, it may be concluded that fibromyalgia does not include an increased risk of atrial and/or ventricular arrhythmias.

  6. Escape for the Slow Solar Wind

    Science.gov (United States)

    Kohler, Susanna

    2017-05-01

    Plasma from the Sun known as the slow solar wind has been observed far away from where scientists thought it was produced. Now new simulations may have resolved the puzzle of where the slow solar wind comes from and how it escapes the Sun to travel through our solar system.An Origin PuzzleA full view of a coronal hole (dark portion) from SDO. The edges of the coronal hole mark the boundary between open and closed magnetic field lines. [SDO; adapted from Higginson et al. 2017]The Suns atmosphere, known as the corona, is divided into two types of regions based on the behavior of magnetic field lines. In closed-field regions, the magnetic field is firmly anchored in the photosphere at both ends of field lines, so traveling plasma is confined to coronal loops and must return to the Suns surface. In open-field regions, only one end of each magnetic field line is anchored in the photosphere, so plasma is able to stream from the Suns surface out into the solar system.This second type of region known as a coronal hole is thought to be the origin of fast-moving plasma measured in our solar system and known as the fast solar wind. But we also observe a slow solar wind: plasma that moves at speeds of less than 500 km/s.The slow solar wind presents a conundrum. Its observational properties strongly suggest it originates in the hot, closed corona rather than the cooler, open regions. But if the slow solar wind plasma originates in closed-field regions of the Suns atmosphere, then how does it escape from the Sun?Slow Wind from Closed FieldsA team of scientists led by Aleida Higginson (University of Michigan) has now used high-resolution, three-dimensional magnetohydrodynamic simulations to show how the slow solar wind can be generated from plasma that starts outin closed-field parts of the Sun.A simulated heliospheric arc, composed of open magnetic field lines. [Higginson et al. 2017]Motions on the Suns surface near the boundary between open and closed-field regions the boundary

  7. Polarization Mode Dispersion

    CERN Document Server

    Galtarossa, Andrea

    2005-01-01

    This book contains a series of tutorial essays on polarization mode dispersion (PMD) by the leading experts in the field. It starts with an introductory review of the basic concepts and continues with more advanced topics, including a thorough review of PMD mitigation techniques. Topics covered include mathematical representation of PMD, how to properly model PMD in numerical simulations, how to accurately measure PMD and other related polarization effects, and how to infer fiber properties from polarization measurements. It includes discussions of other polarization effects such as polarization-dependent loss and the interaction of PMD with fiber nonlinearity. It additionally covers systems issues like the impact of PMD on wavelength division multiplexed systems. This book is intended for research scientists or engineers who wish to become familiar with PMD and its system impacts.

  8. Temporal super resolution using variational methods

    DEFF Research Database (Denmark)

    Keller, Sune Høgild; Lauze, Francois Bernard; Nielsen, Mads

    2010-01-01

    Temporal super resolution (TSR) is the ability to convert video from one frame rate to another and is as such a key functionality in modern video processing systems. A higher frame rate than what is recorded is desired for high frame rate displays, for super slow-motion, and for video/film format...... and intensities are calculated simultaneously in a multiresolution setting. A frame doubling version of our algorithm is implemented and in testing it, we focus on making the motion of high contrast edges to seem smooth and thus reestablish the illusion of motion pictures....

  9. Fan-beam steering device using a photonic crystal slow-light waveguide with surface diffraction grating.

    Science.gov (United States)

    Kondo, Keisuke; Tatebe, Tomoki; Hachuda, Shoji; Abe, Hiroshi; Koyama, Fumio; Baba, Toshihiko

    2017-12-01

    Compact non-mechanical beam steering devices are desired not only for current common applications, but also for advanced applications such as light detection and ranging. We use a Si photonic crystal slow-light waveguide with a diffraction grating, which radiates the guided mode to free space and steers a fan beam by sweeping the wavelength. Due to its large angular dispersion, slow light enhances the steering range without degrading the beam quality, resulting in more resolution points. We fabricated 600 μm devices and observed a 23° steering range and a beam divergence of 0.23°, which resulted in 100 resolution points.

  10. The Slow Learner in Mathematics: Characteristics and Needs of the Slow Learner

    Science.gov (United States)

    Schulz, Richard W.

    1973-01-01

    Strengths and weaknesses of students classified as slow learners'' are presented with emphasis on affective concerns. The teacher, as strategic change-agent, is given suggestions for managing instruction. (LS)

  11. Dispersal of the emerald ash borer, Agrilus planipennis, in newly-colonized sites

    Science.gov (United States)

    Rodrigo J. Mercader; Andrew M. Siegert; Andrew M. Liebhold; Deborah G. McCullough

    2009-01-01

    Emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is an invasive forest insect pest threatening more than 8 billion ash (Fraxinus spp.) trees in North America. Development of effective survey methods and strategies to slow the spread of A. planipennis requires an understanding of dispersal...

  12. Polygamy slows down population divergence in shorebirds

    Science.gov (United States)

    Jackson, Josephine D'Urban; dos Remedios, Natalie; Maher, Kathryn; Zefania, Sama; Haig, Susan M.; Oyler-McCance, Sara J.; Blomqvist, Donald; Burke, Terry; Bruford, Michael W.; Székely, Tamás; Küpper, Clemens

    2017-01-01

    Sexual selection may act as a promotor of speciation since divergent mate choice and competition for mates can rapidly lead to reproductive isolation. Alternatively, sexual selection may also retard speciation since polygamous individuals can access additional mates by increased breeding dispersal. High breeding dispersal should hence increase gene flow and reduce diversification in polygamous species. Here, we test how polygamy predicts diversification in shorebirds using genetic differentiation and subspecies richness as proxies for population divergence. Examining microsatellite data from 79 populations in 10 plover species (Genus: Charadrius) we found that polygamous species display significantly less genetic structure and weaker isolation-by-distance effects than monogamous species. Consistent with this result, a comparative analysis including 136 shorebird species showed significantly fewer subspecies for polygamous than for monogamous species. By contrast, migratory behavior neither predicted genetic differentiation nor subspecies richness. Taken together, our results suggest that dispersal associated with polygamy may facilitate gene flow and limit population divergence. Therefore, intense sexual selection, as occurs in polygamous species, may act as a brake rather than an engine of speciation in shorebirds. We discuss alternative explanations for these results and call for further studies to understand the relationships between sexual selection, dispersal, and diversification.

  13. Ionization of atoms by slow heavy particles

    CERN Document Server

    Roberts, B M; Gribakin, G F

    2016-01-01

    Atoms and molecules can become ionized during the scattering of a slow, heavy particle off a bound electron. Such an interaction involving leptophilic weakly interacting massive particles (WIMPs) is a promising possible explanation for the anomalous 9 sigma annual modulation in the DAMA dark matter direct detection experiment [R. Bernabei et al., Eur. Phys. J. C 73, 2648 (2013)]. We demonstrate the applicability of the Born approximation for such an interaction by showing its equivalence to the semiclassical adiabatic treatment of atomic ionization by slow-moving WIMPs. Conventional wisdom has it that the ionization probability for such a process should be exponentially small. We show, however, that due to nonanalytic, cusp-like behaviour of Coulomb functions close to the nucleus this suppression is removed, leading to an effective atomic structure enhancement. We also show that electron relativistic effects actually give the dominant contribution to such a process, meaning that nonrelativistic calculations m...

  14. Critical slowing down in a dynamic duopoly

    Science.gov (United States)

    Escobido, M. G. O.; Hatano, N.

    2015-01-01

    Anticipating critical transitions is very important in economic systems as it can mean survival or demise of firms under stressful competition. As such identifying indicators that can provide early warning to these transitions are very crucial. In other complex systems, critical slowing down has been shown to anticipate critical transitions. In this paper, we investigate the applicability of the concept in the heterogeneous quantity competition between two firms. We develop a dynamic model where the duopoly can adjust their production in a logistic process. We show that the resulting dynamics is formally equivalent to a competitive Lotka-Volterra system. We investigate the behavior of the dominant eigenvalues and identify conditions that critical slowing down can provide early warning to the critical transitions in the dynamic duopoly.

  15. NPK Fertilizer with Slow Release Fly Ash

    Directory of Open Access Journals (Sweden)

    Nadhira Izzatur Silmi

    2018-01-01

    Full Text Available Fly ash is the solid of the remaining coal combustion carried along with the exhaust gas and captured by the air controller. Fluids in fly ash are Al2O3, SiO2, Fe2O3, CaO, MgO, Na2, and SO3 which are similar to zeolites. So that fly ash can be used as a substitute for zeolite for various carrier of fertilizer. The result of slow release test is known that N element has higher release level. The NPK fertilizer activity test of Fly Ash Slow Release was done on chilli plant with parameter of variation of fertilizer composition and plant height. Based on research result, fly ash-TSP 2: 1 fertilizer has the best result.

  16. Statistical Thermodynamics of Disperse Systems

    DEFF Research Database (Denmark)

    Shapiro, Alexander

    1996-01-01

    Principles of statistical physics are applied for the description of thermodynamic equilibrium in disperse systems. The cells of disperse systems are shown to possess a number of non-standard thermodynamic parameters. A random distribution of these parameters in the system is determined....... On the basis of this distribution, it is established that the disperse system has an additional degree of freedom called the macro-entropy. A large set of bounded ideal disperse systems allows exact evaluation of thermodynamic characteristics. The theory developed is applied to the description of equilibrium...

  17. Optical biosensor with dispersion compensation.

    Science.gov (United States)

    Zong, W; Thirstrup, C; Sørensen, M H; Pedersen, H C

    2005-05-15

    Dispersion limits performance in many optical systems. In surface plasmon resonance (SPR) biosensors, the sensing area is an optical element in which the dispersion depends on the effective refractive index of the biochemical compounds to be measured. We report a method of compensating for wavelength dispersion in SPR biosensors employing two integrated diffractive optical coupling elements in a polymer substrate. The dispersion compensation is achieved over the whole dynamic measurement range and provides a biosensor more robust to wavelength fluctuations than prism-coupler SPR systems. The concept can readily be employed in other types of sensor measuring refractive-index changes.

  18. Inductive Temporal Logic Programming

    OpenAIRE

    Kolter, Robert

    2009-01-01

    We study the extension of techniques from Inductive Logic Programming (ILP) to temporal logic programming languages. Therefore we present two temporal logic programming languages and analyse the learnability of programs from these languages from finite sets of examples. In first order temporal logic the following topics are analysed: - How can we characterize the denotational semantics of programs? - Which proof techniques are best suited? - How complex is the learning task? In propositional ...

  19. Dynamics of social balance under temporal interaction

    Science.gov (United States)

    Nishi, Ryosuke; Masuda, Naoki

    2014-08-01

    Real social contacts are often intermittent such that a link between a pair of nodes in a social network is only temporarily used. The effects of such temporal networks on social dynamics have been investigated for several phenomenological models such as epidemic spreading, linear diffusion processes, and nonlinear oscillations. Here, we numerically investigate nonlinear social balance dynamics in such a situation. Social balance is a classical psychological theory, which dictates that a triad is balanced if the three agents are mutual friends or if the two of them are the friends of each other and hostile to the other agent. We show that the social balance dynamics is slowed down on the temporal complete graph as compared to the corresponding static complete graph.

  20. SOFTWARE Manual for VMM3 Slow Control

    CERN Document Server

    Guth, Manuel

    2017-01-01

    For the New Small Wheel upgrade of the ATLAS detector a new readout chip, called VMM3(a), was developed. In order to provide this new technology to a larger community, the RD51 collaboration is integrating the VMM3 in their scalable readout system (SRS). For this purpose, a new slow control and calibration tool is necessary. This new software was developed and improved within a CERN Summer Student project.

  1. MIND diet slows cognitive decline with aging

    OpenAIRE

    Morris, Martha Clare; Tangney, Christy C; Wang, Yamin; Sacks, Frank Martin; Barnes, Lisa L.; Bennett, David William; Aggarwal, Neelum T.

    2015-01-01

    INTRODUCTION: The Mediterranean and dash diets have been shown to slow cognitive decline; however, neither diet is specific to the nutrition literature on dementia prevention. METHODS: We devised the Mediterranean-Dietary Approach to Systolic Hypertension (DASH) diet intervention for neurodegenerative delay (MIND) diet score that specifically captures dietary components shown to be neuroprotective and related it to change in cognition over an average 4.7 years among 960 participants ...

  2. Indeterministic Temporal Logic

    Directory of Open Access Journals (Sweden)

    Trzęsicki Kazimierz

    2015-09-01

    Full Text Available The questions od determinism, causality, and freedom have been the main philosophical problems debated since the beginning of temporal logic. The issue of the logical value of sentences about the future was stated by Aristotle in the famous tomorrow sea-battle passage. The question has inspired Łukasiewicz’s idea of many-valued logics and was a motive of A. N. Prior’s considerations about the logic of tenses. In the scheme of temporal logic there are different solutions to the problem. In the paper we consider indeterministic temporal logic based on the idea of temporal worlds and the relation of accessibility between them.

  3. Imbricated slip rate processes during slow slip transients imaged by low-frequency earthquakes

    Science.gov (United States)

    Lengliné, O.; Frank, W. B.; Marsan, D.; Ampuero, J.-P.

    2017-10-01

    Low Frequency Earthquakes (LFEs) often occur in conjunction with transient strain episodes, or Slow Slip Events (SSEs), in subduction zones. Their focal mechanism and location consistent with shear failure on the plate interface argue for a model where LFEs are discrete dynamic ruptures in an otherwise slowly slipping interface. SSEs are mostly observed by surface geodetic instruments with limited resolution and it is likely that only the largest ones are detected. The time synchronization of LFEs and SSEs suggests that we could use the recorded LFEs to constrain the evolution of SSEs, and notably of the geodetically-undetected small ones. However, inferring slow slip rate from the temporal evolution of LFE activity is complicated by the strong temporal clustering of LFEs. Here we apply dedicated statistical tools to retrieve the temporal evolution of SSE slip rates from the time history of LFE occurrences in two subduction zones, Mexico and Cascadia, and in the deep portion of the San Andreas fault at Parkfield. We find temporal characteristics of LFEs that are similar across these three different regions. The longer term episodic slip transients present in these datasets show a slip rate decay with time after the passage of the SSE front possibly as t - 1 / 4. They are composed of multiple short term transients with steeper slip rate decay as t-α with α between 1.4 and 2. We also find that the maximum slip rate of SSEs has a continuous distribution. Our results indicate that creeping faults host intermittent deformation at various scales resulting from the imbricated occurrence of numerous slow slip events of various amplitudes.

  4. Nonlinear dynamical triggering of slow slip

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Paul A [Los Alamos National Laboratory; Knuth, Matthew W [WISCONSIN; Kaproth, Bryan M [PENN STATE; Carpenter, Brett [PENN STATE; Guyer, Robert A [Los Alamos National Laboratory; Le Bas, Pierre - Yves [Los Alamos National Laboratory; Daub, Eric G [Los Alamos National Laboratory; Marone, Chris [PENN STATE

    2010-12-10

    Among the most fascinating, recent discoveries in seismology have been the phenomena of triggered slip, including triggered earthquakes and triggered-tremor, as well as triggered slow, silent-slip during which no seismic energy is radiated. Because fault nucleation depths cannot be probed directly, the physical regimes in which these phenomena occur are poorly understood. Thus determining physical properties that control diverse types of triggered fault sliding and what frictional constitutive laws govern triggered faulting variability is challenging. We are characterizing the physical controls of triggered faulting with the goal of developing constitutive relations by conducting laboratory and numerical modeling experiments in sheared granular media at varying load conditions. In order to simulate granular fault zone gouge in the laboratory, glass beads are sheared in a double-direct configuration under constant normal stress, while subject to transient perturbation by acoustic waves. We find that triggered, slow, silent-slip occurs at very small confining loads ({approx}1-3 MPa) that are smaller than those where dynamic earthquake triggering takes place (4-7 MPa), and that triggered slow-slip is associated with bursts of LFE-like acoustic emission. Experimental evidence suggests that the nonlinear dynamical response of the gouge material induced by dynamic waves may be responsible for the triggered slip behavior: the slip-duration, stress-drop and along-strike slip displacement are proportional to the triggering wave amplitude. Further, we observe a shear-modulus decrease corresponding to dynamic-wave triggering relative to the shear modulus of stick-slips. Modulus decrease in response to dynamical wave amplitudes of roughly a microstrain and above is a hallmark of elastic nonlinear behavior. We believe that the dynamical waves increase the material non-affine elastic deformation during shearing, simultaneously leading to instability and slow-slip. The inferred

  5. Analysis of Rectangular Folded-Waveguide Millimeter-Wave Slow-wave Structures using Conformal Transformations

    Science.gov (United States)

    Sumathy, M.; Vinoy, K. J.; Datta, S. K.

    2009-03-01

    An analysis of rectangular folded-waveguide slow-wave structure was developed using conformal mapping technique through Schwarz’s polygon transformation and closed form expressions for the lumped capacitance and inductance per period of the slow-wave structure were derived in terms of the physical dimensions of the structure, incorporating the effects of the beam hole in the lumped parameters. The lumped parameters were subsequently interpreted for obtaining the dispersion and interaction impedance characteristics of the structure. The analysis was benchmarked for two typical millimeter-wave structures, one operating in Ka-band and the other operating in Q-band, against measurement and 3D electromagnetic modeling using MAFIA.

  6. Fano resonance and slow light in hybrid optomechanics mediated by a two-level system

    Science.gov (United States)

    Jiang, Cheng; Jiang, Lei; Yu, Hualing; Cui, Yuanshun; Li, Xiaowei; Chen, Guibin

    2017-11-01

    We study the Fano resonance and slow light in a hybrid optomechanical system, where a mechanical resonator is coupled to a cavity via radiation pressure and to a two-level system (qubit) via the Jaynes-Cummings coupling. The absorption spectra of the weak probe field can exhibit a series of asymmetric Fano line shapes when the frequency of the strong control field varies. The positions of the double Fano resonances can be determined by the cavity-control-field detuning, the qubit-resonator coupling strength, and the transition frequency of the qubit. Furthermore, the transparency windows in the probe transmission spectrum are accompanied by the rapid normal phase dispersion, which indicates the slow light effect. We find that the group delay of the transmitted probe field can be tuned by the frequency and amplitude of the control field and is inversely proportional to the decay rate of the qubit.

  7. Bender visual-motor abilities of slow learners.

    Science.gov (United States)

    Hetrick, E W

    1979-08-01

    The Bender-Gestalt protocols of 134 rural and 140 urban slow learners (IQ 70 to 84) are compared. Rural slow learners performed significantly below their mental ages more frequently than urban slow learners. Rural and urban slow learners performed developmentally below chronological ages, but as expected for mental ages until CA 10 (MA 8). At this point urban slow learners appeared to perform as expected from MAs, but a significant number of rural slow learners performed below expectations. After CA 14 (MA 11-0) the differences between the urban and rural groups, however, were not significant.

  8. Life-stage differences in spatial genetic structure in an irruptive forest insect: implications for dispersal and spatial synchrony

    Science.gov (United States)

    Patrick M.A. James; Barry Cooke; Bryan M.T. Brunet; Lisa M. Lumley; Felix A.H. Sperling; Marie-Josee Fortin; Vanessa S. Quinn; Brian R. Sturtevant

    2015-01-01

    Dispersal determines the flux of individuals, energy and information and is therefore a key determinant of ecological and evolutionary dynamics. Yet, it remains difficult to quantify its importance relative to other factors. This is particularly true in cyclic populations in which demography, drift and dispersal contribute to spatio-temporal variability in genetic...

  9. The Processing and Interpretation of Verb Phrase Ellipsis Constructions by Children at Normal and Slowed Speech Rates

    Science.gov (United States)

    Callahan, Sarah M.; Walenski, Matthew; Love, Tracy

    2013-01-01

    Purpose To examine children’s comprehension of verb phrase (VP) ellipsis constructions in light of their automatic, online structural processing abilities and conscious, metalinguistic reflective skill. Method Forty-two children ages 5 through 12 years listened to VP ellipsis constructions involving the strict/sloppy ambiguity (e.g., “The janitor untangled himself from the rope and the fireman in the elementary school did too after the accident.”) in which the ellipsis phrase (“did too”) had 2 interpretations: (a) strict (“untangled the janitor”) and (b) sloppy (“untangled the fireman”). We examined these sentences at a normal speech rate with an online cross-modal picture priming task (n = 14) and an offline sentence–picture matching task (n = 11). Both tasks were also given with slowed speech input (n = 17). Results Children showed priming for both the strict and sloppy interpretations at a normal speech rate but only for the strict interpretation with slowed input. Offline, children displayed an adultlike preference for the sloppy interpretation with normal-rate input but a divergent pattern with slowed speech. Conclusions Our results suggest that children and adults rely on a hybrid syntax-discourse model for the online comprehension and offline interpretation of VP ellipsis constructions. This model incorporates a temporally sensitive syntactic process of VP reconstruction (disrupted with slow input) and a temporally protracted discourse effect attributed to parallelism (preserved with slow input). PMID:22223886

  10. Temporal properties of stereopsis

    NARCIS (Netherlands)

    Gheorghiu, E.

    2005-01-01

    The goal of the research presented in this thesis was to investigate temporal properties of disparity processing and depth perception in human subjects, in response to dynamic stimuli. The results presented in various chapters, reporting findings about different temporal aspects of disparity

  11. Temporal Linear System Structure

    NARCIS (Netherlands)

    Willigenburg, van L.G.; Koning, de W.L.

    2008-01-01

    Piecewise constant rank systems and the differential Kalman decomposition are introduced in this note. Together these enable the detection of temporal uncontrollability/unreconstructability of linear continuous-time systems. These temporal properties are not detected by any of the four conventional

  12. Taylor dispersion in peristaltic pumping

    Science.gov (United States)

    Saintillan, David; Chakrabarti, Brato

    2017-11-01

    The diffusivity of a Brownian tracer in unidirectional flow is generally enhanced due to shear by the classic phenomenon of Taylor dispersion. At long times, the average concentration of the tracer follows a simplified advection-diffusion equation with an effective shear-dependent dispersivity. In this work, we make use of Brenner's generalized Taylor theory for periodic domains to study dispersion in peristaltic pumping. In channels with small aspect ratios, asymptotic expansions are employed to obtain analytical expressions for the dispersivity at both small and high Peclet numbers. Channels of arbitrary aspect ratios are also considered using a boundary integral formulation for the flow coupled to a hyperbolic conservation equation for the effective dispersivity, which is solved by the finite-volume method. Our numerical results show good agreement with theoretical predictions and provide a basis for understanding passive scalar transport in peristaltic flow, for instance in the ureter or in microfluidic peristaltic pumps.

  13. Subwavelength-Diameter Silica Wire and Photonic Crystal Waveguide Slow Light Coupling

    Directory of Open Access Journals (Sweden)

    Ziyang Zhang

    2007-01-01

    Full Text Available Counter-directional coupling between subwavelength-diameter silica wire and single-line-defect two-dimensional photonic crystal slab waveguide is studied numerically using parallel three-dimensional finite-different time-domain method. By modifying silica wire properties or engineering photonic crystal waveguide dispersion band, the coupling central wavelength can be moved to the slow light region and the coupling efficiency improves simultaneously. One design gives 82% peak power transmission from silica wire to photonic crystal waveguide over an interacting distance of 50 lattice constants. The group velocity is estimated as 1/35 of light speed in vacuum.

  14. Slow to superluminal light waves in thin 3D photonic crystals.

    Science.gov (United States)

    Galisteo-López, J F; Galli, M; Balestreri, A; Patrini, M; Andreani, L C; López, C

    2007-11-12

    Phase measurements on self-assembled three-dimensional photonic crystals show that the group velocity of light can flip from small positive (slow) to negative (superluminal) values in samples of a few mum size. This phenomenon takes place in a narrow spectral range around the second-order stop band and follows from coupling to weakly dispersive photonic bands associated with multiple Bragg diffraction. The observations are well accounted for by theoretical calculations of the phase delay and of photonic states in the finite-sized systems.

  15. Polarization-independent waveguides in air holes photonic crystals and its slow light

    Science.gov (United States)

    Fan, Qingbin; Li, Chuanqi; Liu, Wei; Lu, Ye; Zhang, Dongchuang

    2016-12-01

    A line-defect waveguide in a triangular lattice photonic crystal (PC) made of air holes in dielectric is demonstrated to support transverse magnetic (TM) as well as transverse electric (TE) guided modes simultaneously. A group of suitable geometric parameters were found to make the guided bands overlapped by means of Genetic Algorithm. The optimized waveguide realizes a polarization-independent single-mode transmission and wide operating bandwidth which reaches 0.012 Δ ω a / (2 π c) . Moreover, the guided modes are shown to exhibit a wide-bandwidth slow light and an extremely low group velocity dispersion in most frequency range.

  16. Mode spectrum and temporal soliton formation in optical microresonators

    CERN Document Server

    Herr, T; Jost, J D; Mirgorodskiy, I; Lihachev, G; Gorodetsky, M L; Kippenberg, T J

    2013-01-01

    The formation of temporal dissipative solitons in optical microresonators enables compact, high repetition rate sources of ultra-short pulses as well as low noise, broadband optical frequency combs with smooth spectral envelopes. Here we study the influence of the resonator mode spectrum on temporal soliton formation. Using frequency comb assisted diode laser spectroscopy, the measured mode structure of crystalline MgF2 resonators are correlated with temporal soliton formation. While an overal general anomalous dispersion is required, it is found that higher order dispersion can be tolerated as long as it does not dominate the resonator's mode structure. Mode coupling induced avoided crossings in the resonator mode spectrum are found to prevent soliton formation, when affecting resonator modes close to the pump laser. The experimental observations are in excellent agreement with numerical simulations based on the nonlinear coupled mode equations, which reveal the rich interplay of mode crossings and soliton f...

  17. Temporal Photon Differentials

    DEFF Research Database (Denmark)

    Schjøth, Lars; Frisvad, Jeppe Revall; Erleben, Kenny

    2010-01-01

    , constituting a temporal smoothing of rapidly changing illumination. In global illumination temporal smoothing can be achieved with distribution ray tracing (Cook et al., 1984). Unfortunately, this, and resembling methods, requires a high temporal resolution as samples has to be drawn from in-between frames. We...... present a novel method which is able to produce high quality temporal smoothing for indirect illumination without using in-between frames. Our method is based on ray differentials (Igehy, 1999) as it has been extended in (Sporring et al., 2009). Light rays are traced as bundles creating footprints, which......The finite frame rate also used in computer animated films is cause of adverse temporal aliasing effects. Most noticeable of these is a stroboscopic effect that is seen as intermittent movement of fast moving illumination. This effect can be mitigated using non-zero shutter times, effectively...

  18. Investigation of phase matching for third-harmonic generation in silicon slow light photonic crystal waveguides using Fourier optics.

    Science.gov (United States)

    Monat, Christelle; Grillet, Christian; Corcoran, Bill; Moss, David J; Eggleton, Benjamin J; White, Thomas P; Krauss, Thomas F

    2010-03-29

    Using Fourier optics, we retrieve the wavevector dependence of the third-harmonic (green) light generated in a slow light silicon photonic crystal waveguide. We show that quasi-phase matching between the third-harmonic signal and the fundamental mode is provided in this geometry by coupling to the continuum of radiation modes above the light line. This process sustains third-harmonic generation with a relatively high efficiency and a substantial bandwidth limited only by the slow light window of the fundamental mode. The results give us insights into the physics of this nonlinear process in the presence of strong absorption and dispersion at visible wavelengths where bandstructure calculations are problematic. Since the characteristics (e.g. angular pattern) of the third-harmonic light primarily depend on the fundamental mode dispersion, they could be readily engineered.

  19. Gain-assisted slow to superluminal group velocity manipulation in nanowaveguides.

    Science.gov (United States)

    Govyadinov, Alexander A; Podolskiy, Viktor A

    2006-12-01

    We study the energy propagation in subwavelength waveguides and demonstrate that the mechanism of material gain, previously suggested for loss compensation, is also a powerful tool to manipulate dispersion and propagation characteristics of electromagnetic pulses at the nanoscale. We show theoretically that the group velocity in lossy nanowaveguides can be controlled from slow to superluminal values by the material gain and waveguide geometry and develop an analytical description of the relevant physics. We utilize the developed formalism to show that gain-assisted dispersion management can be used to control the transition between "photonic-funnel" and "photonic-compressor" regimes in tapered nanowaveguides. The phenomenon of strong modulation of group velocity in subwavelength structures can be realized in waveguides with different geometries and is present for both volume and surface modes.

  20. Slow diffusive dynamics in a chaotic balanced neural network.

    Science.gov (United States)

    Shaham, Nimrod; Burak, Yoram

    2017-05-01

    It has been proposed that neural noise in the cortex arises from chaotic dynamics in the balanced state: in this model of cortical dynamics, the excitatory and inhibitory inputs to each neuron approximately cancel, and activity is driven by fluctuations of the synaptic inputs around their mean. It remains unclear whether neural networks in the balanced state can perform tasks that are highly sensitive to noise, such as storage of continuous parameters in working memory, while also accounting for the irregular behavior of single neurons. Here we show that continuous parameter working memory can be maintained in the balanced state, in a neural circuit with a simple network architecture. We show analytically that in the limit of an infinite network, the dynamics generated by this architecture are characterized by a continuous set of steady balanced states, allowing for the indefinite storage of a continuous parameter. In finite networks, we show that the chaotic noise drives diffusive motion along the approximate attractor, which gradually degrades the stored memory. We analyze the dynamics and show that the slow diffusive motion induces slowly decaying temporal cross correlations in the activity, which differ substantially from those previously described in the balanced state. We calculate the diffusivity, and show that it is inversely proportional to the system size. For large enough (but realistic) neural population sizes, and with suitable tuning of the network connections, the proposed balanced network can sustain continuous parameter values in memory over time scales larger by several orders of magnitude than the single neuron time scale.

  1. Deciphering Lower Mantle Structure With the Dispersion of Core-Diffracted Waves

    Science.gov (United States)

    Euler, G. G.; Wysession, M. E.; Aleqabi, G. I.; Shore, P. J.

    2005-12-01

    We investigate lateral variations of the D'' region beneath the West Coast of North America using the dispersion signatures of Pdiff and Sdiff waves originating from the Western Pacific Rim. Data come from large earthquakes recorded by over 50 3-component broadband seismic stations stretched across North America as part of seismic networks including the IRIS Global Seismograph Network, U.S. National Seismic Network, Canadian National Seismic Network, and the IRIS PASSCAL Florida-to-Edmonton Seismic Experiment. All data were obtained from the IRIS DMC, resampled at a constant sample rate (20 sps), converted to displacements, and had the instrument responses removed. When the seismic energy of core-diffracted waves occupies a wide frequency band, the structure at the base of the mantle is sampled differently by the energy at various frequencies. The higher-frequency waves stay closer to the core-mantle boundary, while the longer-frequency waves sample more of the lower mantle. This creates dispersion because of the differences in mantle velocities as a function of depth. Using dispersion slowness curves derived from diffracted body waves sampling the thermal and chemical boundary layer region at the base of the mantle, lateral structural variations can not only be resolved but also their nature may be inferred through comparison with synthetic seismic modeling. For this study, the determination of slownesses of incoming diffracted body waves at periods ranging from 150 to 5 seconds was facilitated by an iterative multiple cross-correlation algorithm. Typical results in our calculation of slownesses show r-squared correlations between arrival times and distances above 0.999. We find that dispersion overall causes the slowness to decrease with shorter periods (also found in the synthetic models) and that the dispersion curves we found for different paths resemble the dispersion curves from several different synthetic structural models of D'', thus quantifying the

  2. Temporal properties of stereopsis

    Science.gov (United States)

    Gheorghiu, E.

    2005-03-01

    The goal of the research presented in this thesis was to investigate temporal properties of disparity processing and depth perception in human subjects, in response to dynamic stimuli. The results presented in various chapters, reporting findings about different temporal aspects of disparity processing, are based on psychophysical experiments and computational model analysis. In chapter 1 we investigated which processes of binocular depth perception in dynamic random-dot stereograms (DRS), i.e., tolerance for interocular delays and temporal integration of correlation, are responsible for the temporal flexibility of the stereoscopic system. Our results demonstrate that (i) disparities from simultaneous monocular inputs dominate those from interocular delayed inputs; (ii) stereopsis is limited by temporal properties of monocular luminance mechanisms; (iii) depth perception in DRS results from cross-correlation-like operation on two simultaneous monocular inputs that represent the retinal images after having been subjected to a process of monocular temporal integration of luminance. In chapter 2 we examined what temporal information is exploited by the mechanisms underlying stereoscopic motion in depth. We investigated systematically the influence of temporal frequency on binocular depth perception in temporally correlated and temporally uncorrelated DRS. Our results show that disparity-defined depth is judged differently in temporally correlated and uncorrelated DRS above a temporal frequency of about 3 Hz. The results and simulations indicate that: (i) above about 20 Hz, the complete absence of stereomotion is caused by temporal integration of luminance; (ii) the difference in perceived depth in temporally correlated and temporally uncorrelated DRS for temporal frequencies between 20 and 3 Hz, is caused by temporal integration of disparity. In chapter 3 we investigated temporal properties of stereopsis at different spatial scales in response to sustained and

  3. Slow Wave Sleep and Long Duration Spaceflight

    Science.gov (United States)

    Whitmire, Alexandra; Orr, Martin; Arias, Diana; Rueger, Melanie; Johnston, Smith; Leveton, Lauren

    2012-01-01

    While ground research has clearly shown that preserving adequate quantities of sleep is essential for optimal health and performance, changes in the progression, order and /or duration of specific stages of sleep is also associated with deleterious outcomes. As seen in Figure 1, in healthy individuals, REM and Non-REM sleep alternate cyclically, with stages of Non-REM sleep structured chronologically. In the early parts of the night, for instance, Non-REM stages 3 and 4 (Slow Wave Sleep, or SWS) last longer while REM sleep spans shorter; as night progresses, the length of SWS is reduced as REM sleep lengthens. This process allows for SWS to establish precedence , with increases in SWS seen when recovering from sleep deprivation. SWS is indeed regarded as the most restorative portion of sleep. During SWS, physiological activities such as hormone secretion, muscle recovery, and immune responses are underway, while neurological processes required for long term learning and memory consolidation, also occur. The structure and duration of specific sleep stages may vary independent of total sleep duration, and changes in the structure and duration have been shown to be associated with deleterious outcomes. Individuals with narcolepsy enter sleep through REM as opposed to stage 1 of NREM. Disrupting slow wave sleep for several consecutive nights without reducing total sleep duration or sleep efficiency is associated with decreased pain threshold, increased discomfort, fatigue, and the inflammatory flare response in skin. Depression has been shown to be associated with a reduction of slow wave sleep and increased REM sleep. Given research that shows deleterious outcomes are associated with changes in sleep structure, it is essential to characterize and mitigate not only total sleep duration, but also changes in sleep stages.

  4. Contact lenses to slow progression of myopia.

    Science.gov (United States)

    Sankaridurg, Padmaja

    2017-09-01

    The prevalence of myopia has been steadily rising, with 28 per cent of the global population said to be affected in 2010 and to rise to affect nearly 50 per cent by 2050. Increasing levels of myopia increase the risk of vision impairment and in particular, high myopia is associated with the risk of serious and permanent visual disability due to associated sight-threatening complications. To stem the burden associated with higher levels of myopia, there are efforts to slow the progression of myopia, and several optical and pharmaceutical strategies have been found useful in slowing myopia to varying degrees. More recently, numerous multifocal soft contact lenses and extended depth of focus soft contact lenses (collectively referred to as myopia control contact lenses) were found effective in slowing myopia. As opposed to overnight orthokeratology, myopia control contact lenses are worn during the day and the hypotheses proposed to explain the efficacy of these lenses are generally based on the premise that the stimulus for eye growth is a defocused retinal image with hyperopic blur either centrally or peripherally. Although the individual power profiles of the lenses vary, the contact lens generally incorporates 'positive power' to reduce the hyperopic blur and/or impose myopic defocus or in the case of the extended depth of focus lens, has a power profile designed to optimise retinal image quality for points on or in front of the retina. The use of soft contact lenses as a platform for myopia control offers an exciting and effective avenue to manage myopia but there is a need for further research on issues such as the mechanism underlying control of myopia, improving efficacy with lenses, and understanding rebound on discontinuation. More significantly, although contact lenses are generally safe and improve quality of life in older children, one of the major challenges for improved uptake and acceptance of contact lenses centres on the perceived risk of

  5. Counting graphene layers with very slow electrons

    Energy Technology Data Exchange (ETDEWEB)

    Frank, Ludĕk; Mikmeková, Eliška; Müllerová, Ilona [Institute of Scientific Instruments AS CR, v.v.i., Královopolská 147, 61264 Brno (Czech Republic); Lejeune, Michaël [Laboratoire de Physique de la Matière Condensée, Faculté des Sciences d' Amiens, Universite de Picardie Jules Verne, 33 rue Saint Leu, 80039 Amiens Cedex 2 (France)

    2015-01-05

    The study aimed at collection of data regarding the transmissivity of freestanding graphene for electrons across their full energy scale down to the lowest energies. Here, we show that the electron transmissivity of graphene drops with the decreasing energy of the electrons and remains below 10% for energies below 30 eV, and that the slow electron transmissivity value is suitable for reliable determination of the number of graphene layers. Moreover, electrons incident below 50 eV release adsorbed hydrocarbon molecules and effectively clean graphene in contrast to faster electrons that decompose these molecules and create carbonaceous contamination.

  6. Application of slow positrons to coating degradation

    Energy Technology Data Exchange (ETDEWEB)

    Cao, H.; Zhang, R.; Chen, H.M.; Mallon, P.; Huang, C.-M.; He, Y.; Sandreczki, T.C.; Jean, Y.C. E-mail: jeany@umkc.edu; Nielsen, B.; Friessnegg, T.; Suzuki, R.; Ohdaira, T

    2000-06-01

    Photodegradation of a polyurethane-based topcoat induced by accelerated UV irradiation is studied using Doppler broadened energy spectra (DBES) and positron annihilation lifetime (PAL) spectroscopies coupled with slow positron technique. Significant and similar variations of S-parameter and ortho-positronium intensity (I{sub 3}) in coatings are observed as functions of depth and of exposure time. The decrease of S is interpreted as a result of an increase of crosslink density and a reduction of free-volume and hole fraction during the degradation process.

  7. Not slowing down | Center for Cancer Research

    Science.gov (United States)

    Nine and-a-half-year-old Travis Carpenter gets a lot of speeding tickets. (He stresses that “and-a-half” part, too). These speeding tickets don’t come from a law enforcement officer but Jesse, one of his nurses at the NIH Clinical Center. Travis uses a power chair that he’s adorned with racing stickers, and his speeding tickets come from him zooming down the Clinical Center’s hallways, dodging the steady traffic of doctors, nurses, patients and families. He loves all things racing, NASCAR and pit crews. Neurofibromatosis type 1 isn’t slowing him down. Read more...

  8. Dragging cylinders in slow viscous flows

    Science.gov (United States)

    Luca, Elena; Crowdy, Darren

    2015-11-01

    The so-called ``dragging problem'' in slow viscous fluids is an important basic flow with many applications. In two dimensions, the Stokes paradox means there is no solution to the dragging problem for a cylinder in free space. The presence of walls changes this; the solutions exist, but are not easy to find without purely numerical methods. This talk describes new ``transform methods'' that produce convenient, semi-analytical solutions to dragging problems for cylinders in various geometries. We apply the techniques to low-Reynolds-number swimming where dragging problem solutions can be combined with the reciprocal theorem to compute swimmer dynamics in confined domains.

  9. Dispersive suspended microextraction.

    Science.gov (United States)

    Yang, Zhong-Hua; Liu, Yu; Lu, Yue-Le; Wu, Tong; Zhou, Zhi-Qiang; Liu, Dong-Hui

    2011-11-14

    A novel sample pre-treatment technique termed dispersive suspended microextraction (DSME) coupled with gas chromatography-flame photometric detection (GC-FPD) has been developed for the determination of eight organophosphorus pesticides (ethoprophos, malathion, chlorpyrifos, isocarbophos, methidathion, fenamiphos, profenofos, triazophos) in aqueous samples. In this method, both extraction and two phases' separation process were performed by the assistance of magnetic stirring. After separating the two phases, 1 μL of the suspended phase was injected into GC for further instrument analysis. Varieties of experiment factors which could affect the experiment results were optimized and the following were selected: 12.0 μL p-xylene was selected as extraction solvent, extraction speed was 1200 rpm, extraction time was 30 s, the restoration speed was 800 rpm, the restoration time was 8 min, and no salt was added. Under the optimum conditions, limits of detections (LODs) varied between 0.01 and 0.05 μg L(-1). The relative standard deviation (RSDs, n=6) ranged from 4.6% to 12.1%. The linearity was obtained by five points in the concentration range of 0.1-100.0 μg L(-1). Correlation coefficients (r) varied from 0.9964 to 0.9995. The enrichment factors (EFs) were between 206 and 243. In the final experiment, the developed method has been successfully applied to the determination of organophosphorus pesticides in wine and tap water samples and the obtained recoveries were between 83.8% and 101.3%. Compared with other pre-treatment methods, DSME has its own features and could achieve satisfied results for the analysis of trace components in complicated matrices. Copyright © 2011 Elsevier B.V. All rights reserved.

  10. Slow and Fast Light in Optical Fibers: Review and Perspectives

    OpenAIRE

    Thévenaz, Luc

    2009-01-01

    Fiber slow light systems are at a turning point moving from a laboratory research to real applications. The possibility to shape the spectral resonance in Brillouin slow light leads to optimized configurations and innovative solutions.

  11. Slow-plasmon resonant nano-strip antennas

    DEFF Research Database (Denmark)

    Søndergaard, Thomas; Beermann, Jonas; Boltasseva, Alexandra

    2008-01-01

    Resonant scattering by gold nanostrip antennas due to constructive interference of counterpropagating slow surface plasmon polaritons SPPs is analyzed, including the quasistatic limit of ultrasmall antennas, and experimentally demonstrated. The phase of slow SPP reflection by strip ends is found...

  12. Sustainable Development of Slow Fashion Businesses: Customer Value Approach

    Directory of Open Access Journals (Sweden)

    Sojin Jung

    2016-06-01

    Full Text Available As an alternative to the prevalent fast fashion model, slow fashion has emerged as a way of enhancing sustainability in the fashion industry, yet how slow fashion can enhance profitability is still largely unknown. Based on a customer value creation framework, this study empirically tested a structural model that specified the slow fashion attributes that contribute to creating perceived customer value, which subsequently increases a consumer’s intention to buy and pay a price premium for slow fashion products. An analysis of 221 U.S. consumer data revealed that delivering exclusive product value is significantly critical in creating customer value for slow fashion, and customer value, in turn, positively affects consumers’ purchase intentions. Further analysis also revealed that different slow fashion attributes distinctively affect customer value. This provides potential strategies on which slow fashion businesses can focus to secure an economically sustainable business model, thereby continuously improving environmental and social sustainability with the slow fashion ideal.

  13. Slow-light dynamics in nonlinear periodic waveguides couplers

    DEFF Research Database (Denmark)

    Sukhorukov, A.A.; Ha, S.; Powell, D.A.

    2009-01-01

    We predict pulse switching and reshaping through nonlinear mixing of two slow-light states with different phase velocities in the same frequency range, and report on the first experimental observation of slow-light tunneling between coupled periodic waveguides.......We predict pulse switching and reshaping through nonlinear mixing of two slow-light states with different phase velocities in the same frequency range, and report on the first experimental observation of slow-light tunneling between coupled periodic waveguides....

  14. Nonlinear Gain Saturation in Active Slow Light Photonic Crystal Waveguides

    DEFF Research Database (Denmark)

    Chen, Yaohui; Mørk, Jesper

    2013-01-01

    We present a quantitative three-dimensional analysis of slow-light enhanced traveling wave amplification in an active semiconductor photonic crystal waveguides. The impact of slow-light propagation on the nonlinear gain saturation of the device is investigated.......We present a quantitative three-dimensional analysis of slow-light enhanced traveling wave amplification in an active semiconductor photonic crystal waveguides. The impact of slow-light propagation on the nonlinear gain saturation of the device is investigated....

  15. Slow-light effects in photonic crystal membrane lasers

    DEFF Research Database (Denmark)

    Xue, Weiqi; Yu, Yi; Ottaviano, Luisa

    2015-01-01

    In this paper, we present a systematic investigation of photonic crystal cavity laser operating in the slow-light regime. The dependence of lasing threshold on the effect of slow-light will be particularly highlighted.......In this paper, we present a systematic investigation of photonic crystal cavity laser operating in the slow-light regime. The dependence of lasing threshold on the effect of slow-light will be particularly highlighted....

  16. Wave-equation dispersion inversion

    KAUST Repository

    Li, Jing

    2016-12-08

    We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained from Rayleigh waves recorded by vertical-component geophones. Similar to wave-equation traveltime tomography, the complicated surface wave arrivals in traces are skeletonized as simpler data, namely the picked dispersion curves in the phase-velocity and frequency domains. Solutions to the elastic wave equation and an iterative optimization method are then used to invert these curves for 2-D or 3-D S-wave velocity models. This procedure, denoted as wave-equation dispersion inversion (WD), does not require the assumption of a layered model and is significantly less prone to the cycle-skipping problems of full waveform inversion. The synthetic and field data examples demonstrate that WD can approximately reconstruct the S-wave velocity distributions in laterally heterogeneous media if the dispersion curves can be identified and picked. The WD method is easily extended to anisotropic data and the inversion of dispersion curves associated with Love waves.

  17. High-performance slow light photonic crystal waveguides with topology optimized or circular-hole based material layouts

    DEFF Research Database (Denmark)

    Wang, Fengwen; Jensen, Jakob Søndergaard; Sigmund, Ole

    2012-01-01

    energy located in air regions. It is demonstrated that slow light with a group index up to ng=278 can be achieved by topology optimized waveguides with promising modal confinement and restricted group-velocity-dispersion. All the topology optimized waveguides achieve a normalized group-index bandwidth......Photonic crystal waveguides are optimized for modal confinement and loss related to slow light with high group index. A detailed comparison between optimized circular-hole based waveguides and optimized waveguides with free topology is performed. Design robustness with respect to manufacturing...... imperfections is enforced by considering different design realizations generated from under-, standard- and over-etching processes in the optimization procedure. A constraint ensures a certain modal confinement, and loss related to slow light with high group index is indirectly treated by penalizing field...

  18. Estimating landscape resistance to dispersal

    Science.gov (United States)

    Graves, Tabitha A.; Chandler, Richard B.; Royle, J. Andrew; Beier, Paul; Kendall, Katherine C.

    2014-01-01

    Dispersal is an inherently spatial process that can be affected by habitat conditions in sites encountered by dispersers. Understanding landscape resistance to dispersal is important in connectivity studies and reserve design, but most existing methods use resistance functions with cost parameters that are subjectively chosen by the investigator. We develop an analytic approach allowing for direct estimation of resistance parameters that folds least cost path methods typically used in simulation approaches into a formal statistical model of dispersal distributions. The core of our model is a frequency distribution of dispersal distances expressed as least cost distance rather than Euclidean distance, and which includes terms for feature-specific costs to dispersal and sex (or other traits) of the disperser. The model requires only origin and settlement locations for multiple individuals, such as might be obtained from mark–recapture studies or parentage analyses, and maps of the relevant habitat features. To evaluate whether the model can estimate parameters correctly, we fit our model to data from simulated dispersers in three kinds of landscapes (in which resistance of environmental variables was categorical, continuous with a patchy configuration, or continuous in a trend pattern). We found maximum likelihood estimators of resistance and individual trait parameters to be approximately unbiased with moderate sample sizes. We applied the model to a small grizzly bear dataset to demonstrate how this approach could be used when the primary interest is in the prediction of costs and found that estimates were consistent with expectations based on bear ecology. Our method has important practical applications for testing hypotheses about dispersal ecology and can be used to inform connectivity planning efforts, via the resistance estimates and confidence intervals, which can be used to create a data-driven resistance surface.

  19. An 8 month slow slip event triggers progressive nucleation of the 2014 Chile megathrust

    Science.gov (United States)

    Socquet, Anne; Valdes, Jesus Piña.; Jara, Jorge; Cotton, Fabrice; Walpersdorf, Andrea; Cotte, Nathalie; Specht, Sebastian; Ortega-Culaciati, Francisco; Carrizo, Daniel; Norabuena, Edmundo

    2017-05-01

    The mechanisms leading to large earthquakes are poorly understood and documented. Here we characterize the long-term precursory phase of the 1 April 2014 Mw8.1 North Chile megathrust. We show that a group of coastal GPS stations accelerated westward 8 months before the main shock, corresponding to a Mw6.5 slow slip event on the subduction interface, 80% of which was aseismic. Concurrent interface foreshocks underwent a diminution of their radiation at high frequency, as shown by the temporal evolution of Fourier spectra and residuals with respect to ground motions predicted by recent subduction models. Such ground motions change suggests that in response to the slow sliding of the subduction interface, seismic ruptures are progressively becoming smoother and/or slower. The gradual propagation of seismic ruptures beyond seismic asperities into surrounding metastable areas could explain these observations and might be the precursory mechanism eventually leading to the main shock.

  20. Excitation of surface plasma waves over corrugated slow-wave ...

    Indian Academy of Sciences (India)

    A microwave propagating along vacuum–dielectric–plasma interface excites surface plasma wave (SPW). A periodic slow-wave structure placed over dielectric slows down the SPW. The phase velocity of slow SPW is sensitive to height, periodicity, number of periods, thickness and the separation between dielectric and ...

  1. Good, Clean, Fair: The Rhetoric of the Slow Food Movement

    Science.gov (United States)

    Schneider, Stephen

    2008-01-01

    This article outlines the origins of the Slow Food movement before examining the ways in which Slow Food rhetoric seeks to redefine gastronomy and combat the more deleterious effects of globalization. In articulating a new gastronomy, Slow Food founder Carlo Petrini attempts to reconstruct the gastronomy of Jean Anthelme Brillat-Savarin, at once…

  2. Threshold Characteristics of Slow-Light Photonic Crystal Lasers

    DEFF Research Database (Denmark)

    Xue, Weiqi; Yu, Yi; Ottaviano, Luisa

    2016-01-01

    results are explained by an analytical theory for the laser threshold that takes into account the effects of slow light and random disorder due to unavoidable fabrication imperfections. Longer lasers are found to operate deeper into the slow-light region, leading to a trade-off between slow-light induced...

  3. Teaching Slow Learners in the Social Studies Class.

    Science.gov (United States)

    Graham, Dr. Tony; Cline, Dr, Paul C.

    1987-01-01

    Identifies the characteristics of a slow learner and gives a basic philosophy and techniques for teaching the slow learners in social studies. Includes a list of 11 tips for teaching slow learners and offers a lesson format designed for their instruction. (AEM)

  4. Excitation of surface plasma waves over corrugated slow-wave ...

    Indian Academy of Sciences (India)

    Abstract. A microwave propagating along vacuum–dielectric–plasma interface excites surface plasma wave (SPW). A periodic slow-wave structure placed over dielectric slows down the SPW. The phase velocity of slow SPW is sensitive to height, periodicity, number of periods, thickness and the separation between ...

  5. Towards Temporal Graph Databases

    OpenAIRE

    Campos, Alexander; Mozzino, Jorge; Vaisman, Alejandro

    2016-01-01

    In spite of the extensive literature on graph databases (GDBs), temporal GDBs have not received too much attention so far. Temporal GBDs can capture, for example, the evolution of social networks across time, a relevant topic in data analysis nowadays. In this paper we propose a data model and query language (denoted TEG-QL) for temporal GDBs, based on the notion of attribute graphs. This allows a straightforward translation to Neo4J, a well-known GBD. We present extensive examples of the use...

  6. MIND diet slows cognitive decline with aging.

    Science.gov (United States)

    Morris, Martha Clare; Tangney, Christy C; Wang, Yamin; Sacks, Frank M; Barnes, Lisa L; Bennett, David A; Aggarwal, Neelum T

    2015-09-01

    The Mediterranean and dash diets have been shown to slow cognitive decline; however, neither diet is specific to the nutrition literature on dementia prevention. We devised the Mediterranean-Dietary Approach to Systolic Hypertension (DASH) diet intervention for neurodegenerative delay (MIND) diet score that specifically captures dietary components shown to be neuroprotective and related it to change in cognition over an average 4.7 years among 960 participants of the Memory and Aging Project. In adjusted mixed models, the MIND score was positively associated with slower decline in global cognitive score (β = 0.0092; P diet scores versus the lowest was equivalent to being 7.5 years younger in age. The study findings suggest that the MIND diet substantially slows cognitive decline with age. Replication of these findings in a dietary intervention trial would be required to verify its relevance to brain health. Copyright © 2015 The Alzheimer's Association. Published by Elsevier Inc. All rights reserved.

  7. Maxwell Equations for Slow-Moving Media

    Science.gov (United States)

    Rozov, Andrey

    2015-12-01

    In the present work, the Minkowski equations obtained on the basis of theory of relativity are used to describe electromagnetic fields in moving media. But important electromagnetic processes run under non-relativistic conditions of slow-moving media. Therefore, one should carry out its description in terms of classical mechanics. Hertz derived electrodynamic equations for moving media within the frame of classical mechanics on the basis of the Maxwell theory. His equations disagree with the experimental data concerned with the moving dielectrics. In the paper, a way of description of electromagnetic fields in slow-moving media on the basis of the Maxwell theory within the frame of classical mechanics is offered by combining the Hertz approach and the experimental data concerned with the movement of dielectrics in electromagnetic fields. Received Maxwell equations lack asymmetry in the description of the reciprocal electrodynamic action of a magnet and a conductor and conform to known experimental data. Comparative analysis of the Minkowski and Maxwell models is carried out.

  8. Slow waves in mutually inhibitory neuronal networks

    Science.gov (United States)

    Jalics, Jozsi

    2004-05-01

    A variety of experimental and modeling studies have been performed to investigate wave propagation in networks of thalamic neurons and their relationship to spindle sleep rhythms. It is believed that spindle oscillations result from the reciprocal interaction between thalamocortical (TC) and thalamic reticular (RE) neurons. We consider a network of TC and RE cells reduced to a one-layer network model and represented by a system of singularly perturbed integral-differential equations. Geometric singular perturbation methods are used to prove the existence of a locally unique slow wave pulse that propagates along the network. By seeking a slow pulse solution, we reformulate the problem to finding a heteroclinic orbit in a 3D system of ODEs with two additional constraints on the location of the orbit at two distinct points in time. In proving the persistence of the singular heteroclinic orbit, difficulties arising from the solution passing near points where normal hyperbolicity is lost on a 2D critical manifold are overcome by employing results by Wechselberger [Singularly perturbed folds and canards in R3, Thesis, TU-Wien, 1998].

  9. Pulse Dispersion in Phased Arrays

    Directory of Open Access Journals (Sweden)

    Randy L. Haupt

    2017-01-01

    Full Text Available Phased array antennas cause pulse dispersion when receiving or transmitting wideband signals, because phase shifting the signals does not align the pulse envelopes from the elements. This paper presents two forms of pulse dispersion that occur in a phased array antenna. The first results from the separation distance between the transmit and receive antennas and impacts the definition of far field in the time domain. The second is a function of beam scanning and array size. Time delay units placed at the element and/or subarrays limit the pulse dispersion.

  10. Progress in urban dispersion studies

    DEFF Research Database (Denmark)

    Batchvarova, E.; Gryning, Sven-Erik

    2006-01-01

    The present Study addresses recent achievements in better representation Of the urban area structure in meteorology and dispersion parameterisations. The setup and Main Outcome of several recent dispersion experiments in Urban areas and their use in model validation are discussed. The maximum con...... BUBBLE Tracer Experiment) the horizontal spread of the plume corresponds to a Lagrangian time scale bigger than the value for ground Sources. Turbulence measurements LIP to 3-5 times the building height Lire needed for direct use in dispersion Calculations....

  11. Dispersion Decay and Scattering Theory

    CERN Document Server

    Komech, Alexander

    2012-01-01

    A simplified, yet rigorous treatment of scattering theory methods and their applications Dispersion Decay and Scattering Theory provides thorough, easy-to-understand guidance on the application of scattering theory methods to modern problems in mathematics, quantum physics, and mathematical physics. Introducing spectral methods with applications to dispersion time-decay and scattering theory, this book presents, for the first time, the Agmon-Jensen-Kato spectral theory for the Schr?dinger equation, extending the theory to the Klein-Gordon equation. The dispersion decay plays a crucial role i

  12. Factors Contributing Decreased Performance Of Slow Learners

    Directory of Open Access Journals (Sweden)

    Dr. L. Kannan

    2015-03-01

    Full Text Available Back ground Even experienced teaching faculty and administrators can be challenged by learners who have not able to perform up to expected need in their annual performance of their students these students are called as slow learnersStruggle learners. There should be a designed study to foster discussion about diagnosing particular problems that contribute with meeting objectives of slow learners. Methodology The study was performed on the entire current first year of Medical students were all the three internal assessments of 250 students performance is taken in to consideration for the study. This study is of cross section type.After obtaining the list of all students marks in internal examination from medical education unit supporting mentors are contacted to meet the students and confidentiality is maintained throughout the study. After obtaining informed consent a questionnaire was administered to the students by the investigator. The questionnaire contains the following sections. Section I will be on the background characteristics of the student name age sex type of family. Section II will be on the details of their learning capabilities. Section III will focus on the awareness of the slow learners in which the precipitating factors contributing to them. Results The prevalence of slow learners as low achievers were contributed to be 32.4 percentages.The performance of the students is based on combination of all three internal assessment marks including theory and practical performance. In this the students age ranges from 17 to 21 years the mean age of student was contributed to be 17.81 and majority of the students were in the age group of 18 years which contributed to be 16867.2.In the present study majority were males 13252.8 compared to females 11847.2.but when study is compared to percentage of attendance majority of the individual 15177 scored more than 50 percentage of marks have more than 80 percentage of attendance but when

  13. Species dispersal rates alter diversity and ecosystem stability in pond metacommunities.

    Science.gov (United States)

    Howeth, Jennifer G; Leibold, Mathew A

    2010-09-01

    Metacommunity theory suggests that relationships between diversity and ecosystem stability can be determined by the rate of species dispersal among local communities. The predicted relationships, however, may depend upon the relative strength of local environmental processes and disturbance. Here we evaluate the role of dispersal frequency and local predation perturbations in affecting patterns of diversity and stability in pond plankton metacommunities. Pond metacommunities were composed of three mesocosm communities: one of the three communities maintained constant "press" predation from a selective predator, bluegill sunfish (Lepomis macrochirus); the second community maintained "press" conditions without predation; and the third community experienced recurrent "pulsed" predation from bluegill sunfish. The triads of pond communities were connected at either no, low (0.7%/d), or high (20%/d) planktonic dispersal. Richness and composition of zooplankton and stability of plankton biomass and ecosystem productivity were measured at local and regional spatial scales. Dispersal significantly affected diversity such that local and regional biotas at the low dispersal rate maintained the greatest number of species. The unimodal local dispersal-diversity relationship was predator-dependent, however, as selective press predation excluded species regardless of dispersal. Further, there was no effect of dispersal on beta diversity because predation generated local conditions that selected for distinct community assemblages. Spatial and temporal ecosystem stability responded to dispersal frequency but not predation. Low dispersal destabilized the spatial stability of producer biomass but stabilized temporal ecosystem productivity. The results indicate that selective predation can prevent species augmentation from mass effects but has no apparent influence on stability. Dispersal rates, in contrast, can have significant effects on both species diversity and ecosystem

  14. Temporal Lobe Seizure

    Science.gov (United States)

    ... pregnancy Temporal lobe seizure Symptoms & causes Diagnosis & treatment Advertisement Mayo Clinic does not endorse companies or products. ... a Job Site Map About This Site Twitter Facebook Google YouTube Pinterest Mayo Clinic is a not- ...

  15. Temporal Lobe Seizure

    Science.gov (United States)

    ... functions, including having odd feelings — such as euphoria, deja vu or fear. During a temporal lobe seizure, you ... include: A sudden sense of unprovoked fear A deja vu experience — a feeling that what's happening has happened ...

  16. Multisensory temporal numerosity judgment

    NARCIS (Netherlands)

    Philippi, T.; Erp, J.B.F. van; Werkhoven, P.J.

    2008-01-01

    In temporal numerosity judgment, observers systematically underestimate the number of pulses. The strongest underestimations occur when stimuli are presented with a short interstimulus interval (ISI) and are stronger for vision than for audition and touch. We investigated if multisensory

  17. Neocortical Temporal Lobe Epilepsy

    Science.gov (United States)

    Bercovici, Eduard; Kumar, Balagobal Santosh; Mirsattari, Seyed M.

    2012-01-01

    Complex partial seizures (CPSs) can present with various semiologies, while mesial temporal lobe epilepsy (mTLE) is a well-recognized cause of CPS, neocortical temporal lobe epilepsy (nTLE) albeit being less common is increasingly recognized as separate disease entity. Differentiating the two remains a challenge for epileptologists as many symptoms overlap due to reciprocal connections between the neocortical and the mesial temporal regions. Various studies have attempted to correctly localize the seizure focus in nTLE as patients with this disorder may benefit from surgery. While earlier work predicted poor outcomes in this population, recent work challenges those ideas yielding good outcomes in part due to better localization using improved anatomical and functional techniques. This paper provides a comprehensive review of the diagnostic workup, particularly the application of recent advances in electroencephalography and functional brain imaging, in neocortical temporal lobe epilepsy. PMID:22953057

  18. Massive temporal lobe cholesteatoma

    National Research Council Canada - National Science Library

    Waidyasekara, Pasan; Dowthwaite, Samuel A; Stephenson, Ellison; Bhuta, Sandeep; McMonagle, Brent

    2015-01-01

    .... There had been no relevant symptoms in the interim until 6 weeks prior to this presentation. Imaging demonstrated a large right temporal lobe mass contiguous with the middle ear and mastoid cavity with features consistent with cholesteatoma...

  19. Massive Temporal Lobe Cholesteatoma

    National Research Council Canada - National Science Library

    Waidyasekara, Pasan; Dowthwaite, Samuel A; Stephenson, Ellison; Bhuta, Sandeep; McMonagle, Brent

    2015-01-01

    .... There had been no relevant symptoms in the interim until 6 weeks prior to this presentation. Imaging demonstrated a large right temporal lobe mass contiguous with the middle ear and mastoid cavity with features consistent with cholesteatoma...

  20. Wireless Communication over Dispersive Channels

    NARCIS (Netherlands)

    Fang, K.

    2010-01-01

    Broadband wireless communication systems require high transmission rates, where the bandwidth of the transmitted signal is larger than the channel coherence bandwidth. This gives rise to time dispersion of the transmitted symbols or frequency-selectivity with different frequency components

  1. Threshold Characteristics of Slow-Light Photonic Crystal Lasers.

    Science.gov (United States)

    Xue, Weiqi; Yu, Yi; Ottaviano, Luisa; Chen, Yaohui; Semenova, Elizaveta; Yvind, Kresten; Mork, Jesper

    2016-02-12

    The threshold properties of photonic crystal quantum dot lasers operating in the slow-light regime are investigated experimentally and theoretically. Measurements show that, in contrast to conventional lasers, the threshold gain attains a minimum value for a specific cavity length. The experimental results are explained by an analytical theory for the laser threshold that takes into account the effects of slow light and random disorder due to unavoidable fabrication imperfections. Longer lasers are found to operate deeper into the slow-light region, leading to a trade-off between slow-light induced reduction of the mirror loss and slow-light enhancement of disorder-induced losses.

  2. Great earthquakes hazard in slow subduction zones

    Science.gov (United States)

    Marcaillou, B.; Gutscher, M.; Westbrook, G. K.

    2008-12-01

    Research on the Sumatra-Andaman earthquake of 2004 has challenged two popular paradigms; that the strongest subduction earthquakes strike in regions of rapid plate convergence and that rupture occurs primarily along the contact between the basement of the overriding plate and the downgoing plate. Subduction zones presenting similar structural and geodynamic characteristics (slow convergence and thick wedges of accreted sediment) may be capable of generating great megathrust earthquakes (M>8.5) despite an absence of thrust type earthquakes over the past 40 years. Existing deep seismic sounding data and hypocenters are used to constrain the geometry of several key slow subduction zones (Antilles, Hellenic, Sumatra). This geometry forms the basis for numerical modelling of fore-arc thermal structure, which is applied to calculate the estimated width of the seismogenic portion of the subduction fault plane. The margins with the thickest accretionary wedges are commonly found to have the widest (predicted) seismogenic zone. Furthermore, for these margins there exists a substantial (20-60 km wide) region above the up-dip limit for which the contribution to tsunami generation is poorly understood. As the rigidity (mu) of these high-porosity sediments is low, co-seismic slip here can be expected to be slow. Accordingly, the contribution to seismic moment will be low, but the contribution to tsunami generation may be very high. Indeed, recent seismological data from Nankai indicate very low frequency shallow-thrust earthquakes beneath this portion of the accretionary wedge, long-considered to be "aseismic". We propose that thick accumulations of sediment on the downgoing plate and the presence of a thick accretionary wedge can increase the maximum size of the potential rupture fault plane in two ways; 1) by thermally insulating the downgoing plate and thereby increasing the total downdip length of the fault which can rupture seismically and 2) by "smoothing out" the

  3. Birefringent dispersive FDTD subgridding scheme

    OpenAIRE

    De Deckere, B; Van Londersele, Arne; De Zutter, Daniël; Vande Ginste, Dries

    2016-01-01

    A novel 2D finite difference time domain (FDTD) subgridding method is proposed, only subject to the Courant limit of the coarse grid. By making mu or epsilon inside the subgrid dispersive, unconditional stability is induced at the cost of a sparse, implicit set of update equations. By only adding dispersion along preferential directions, it is possible to dramatically reduce the rank of the matrix equation that needs to be solved.

  4. Information, Search, and Price Dispersion

    OpenAIRE

    Baye, Michael R; John Morgan; Patrick Scholten

    2006-01-01

    We provide a unified treatment of alternative models of information acquisition/transmission that have been advanced to rationalize price dispersion in online and offline markets for homogeneous products. These different frameworks -- which include sequential search, fixed sample search, and clearinghouse models -- reveal that reductions in (or the elimination of) consumer search costs need not reduce (or eliminate) price dispersion. Our treatment highlights a "duality" between search-theoret...

  5. Dispersion engineering for integrated nanophotonics

    CERN Document Server

    Vanbésien, Olivier

    2014-01-01

    This book shows how dispersion engineering in two dimensional dielectric photonic crystals can provide new effects for the precise control of light propagation for integrated nanophotonics.Dispersion engineering in regular and graded photonic crystals to promote anomalous refraction effects is studied from the concepts to experimental demonstration via nanofabrication considerations. Self collimation, ultra and negative refraction, second harmonic generation, mirage and invisibility effects which lead to an unprecedented control of light propagation at the (sub-)wavelength scale for the

  6. Dispersion properties of photonic bandgap guiding fibers

    DEFF Research Database (Denmark)

    Barkou, Stig Eigil; Broeng, Jes; Bjarklev, Anders Overgaard

    1999-01-01

    We investigate low-index core photonic crystal fibers. Dispersion properties very different from standard fibers are found. Both Zero dispersion are very large dispersion is shown possible at 1550 nm wavelength.......We investigate low-index core photonic crystal fibers. Dispersion properties very different from standard fibers are found. Both Zero dispersion are very large dispersion is shown possible at 1550 nm wavelength....

  7. Role of mastoid pneumatization in temporal bone fractures.

    Science.gov (United States)

    Ilea, A; Butnaru, A; Sfrângeu, S A; Hedeşiu, M; Dudescu, C M; Berce, P; Chezan, H; Hurubeanu, L; Trombiţaş, V E; Câmpian, R S; Albu, S

    2014-07-01

    The mastoid portion of the temporal bone has multiple functional roles in the organism, including regulation of pressure in the middle ear and protection of the inner ear. We investigated whether mastoid pneumatization plays a role in the protection of vital structures in the temporal bone during direct lateral trauma. The study was performed on 20 human temporal bones isolated from cadavers. In the study group formed by 10 temporal bone samples, mastoid cells were removed and the resulting neocavities were filled. The mastoids were maintained intact in the control group. All samples were impacted at the same speed and kinetic energy. The resultant temporal bone fractures were evaluated by CT. Temporal squama fractures were 2.88 times more frequent, and mastoid fractures were 2.76 times more frequent in the study group. Facial nerve canal fractures were 6 times more frequent in the study group and involved all the segments of the facial nerve. Carotid canal fractures and jugular foramen fractures were 2.33 and 2.5 times, respectively, more frequent in the study group. The mastoid portion of the temporal bone plays a role in the absorption and dispersion of kinetic energy during direct lateral trauma to the temporal bone, reducing the incidence of fracture in the setting of direct trauma. © 2014 by American Journal of Neuroradiology.

  8. A Flexible Spatio-Temporal Model for Air Pollution with Spatial and Spatio-Temporal Covariates.

    Science.gov (United States)

    Lindström, Johan; Szpiro, Adam A; Sampson, Paul D; Oron, Assaf P; Richards, Mark; Larson, Tim V; Sheppard, Lianne

    2014-09-01

    The development of models that provide accurate spatio-temporal predictions of ambient air pollution at small spatial scales is of great importance for the assessment of potential health effects of air pollution. Here we present a spatio-temporal framework that predicts ambient air pollution by combining data from several different monitoring networks and deterministic air pollution model(s) with geographic information system (GIS) covariates. The model presented in this paper has been implemented in an R package, SpatioTemporal, available on CRAN. The model is used by the EPA funded Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air) to produce estimates of ambient air pollution; MESA Air uses the estimates to investigate the relationship between chronic exposure to air pollution and cardiovascular disease. In this paper we use the model to predict long-term average concentrations of NOx in the Los Angeles area during a ten year period. Predictions are based on measurements from the EPA Air Quality System, MESA Air specific monitoring, and output from a source dispersion model for traffic related air pollution (Caline3QHCR). Accuracy in predicting long-term average concentrations is evaluated using an elaborate cross-validation setup that accounts for a sparse spatio-temporal sampling pattern in the data, and adjusts for temporal effects. The predictive ability of the model is good with cross-validated R2 of approximately 0.7 at subject sites. Replacing four geographic covariate indicators of traffic density with the Caline3QHCR dispersion model output resulted in very similar prediction accuracy from a more parsimonious and more interpretable model. Adding traffic-related geographic covariates to the model that included Caline3QHCR did not further improve the prediction accuracy.

  9. Dispersant and salinity effects on weathering and acute toxicity of South Louisiana crude oil.

    Science.gov (United States)

    Kuhl, Adam J; Nyman, J Andrew; Kaller, Michael D; Green, Christopher C

    2013-11-01

    Chemical dispersants are an important technology in the remediation of oil spills in the aquatic environment, facilitating degradation of crude oil and salinity is an important factor in dispersant effectiveness. The aim of the present study was to explore the role of salinity on the degradation chemistry of crude oil polycyclic aromatic hydrocarbons (PAHs) and acute toxicity of the water accommodated fraction (WAF) of the dispersant COREXIT 9500A and chemically dispersed crude oil on a common estuarine fish. Laboratory microcosms were designed at salinities of 4 parts per thousand (ppt), 12 ppt, or 18 ppt and spiked with crude oil, COREXIT 9500A, or a combined exposure to crude oil and COREXIT and allowed to biodegrade for 1 wk, 4 wk, and 16 wk. The WAF was harvested for analytical PAH analysis and acute toxicity testing in juvenile Fundulus grandis. Compared with undispersed oil, COREXIT exponentially increased the PAH concentrations in the WAF for up to 16 wk; hopane-normalized concentrations indicated that biodegradation was slowed for the first 4 wk. Dispersed crude oil and COREXIT were acutely toxic following 1 wk of biodegradation with no correlation between PAH concentrations and crude oil WAF mortality. Both dispersant and dispersant oil mixtures remained toxic for at least 4 wk at the lowest salinity tested, suggesting increased sensitivity or reduced biodegradation of toxic components in low-saline environments. At the lowest salinity, oil dispersed with COREXIT was more toxic than either the COREXIT alone or oil alone, even after 16 wk of biodegradation.

  10. Slow creep in soft granular packings.

    Science.gov (United States)

    Srivastava, Ishan; Fisher, Timothy S

    2017-05-14

    Transient creep mechanisms in soft granular packings are studied numerically using a constant pressure and constant stress simulation method. Rapid compression followed by slow dilation is predicted on the basis of a logarithmic creep phenomenon. Characteristic scales of creep strain and time exhibit a power-law dependence on jamming pressure, and they diverge at the jamming point. Microscopic analysis indicates the existence of a correlation between rheology and nonaffine fluctuations. Localized regions of large strain appear during creep and grow in magnitude and size at short times. At long times, the spatial structure of highly correlated local deformation becomes time-invariant. Finally, a microscale connection between local rheology and local fluctuations is demonstrated in the form of a linear scaling between granular fluidity and nonaffine velocity.

  11. Joint Attention is Slowed in Older Adults.

    Science.gov (United States)

    Deroche, Thomas; Castanier, Carole; Perrot, Alexandra; Hartley, Alan

    2016-01-01

    The automatic propensity to orient to the location where other people are looking is the main way of establishing joint attention with others. Whereas joint attention has been mostly investigated with young adults, the present study examines age-related differences in the magnitude and time course of joint attention. Forty-three community-dwelling seniors and 43 younger adults performed a visuospatial task. The procedures closely follow those of gaze-cueing tasks commonly used to investigate joint attention. The findings revealed that a gaze-cueing effect occurs for both younger and older adults, with an equivalent average magnitude but with different time courses. The effect peaks later in older adults. Age-related differences in joint attention could be linked to a more general cognitive slowing rather than to poorer basic social skills. The present study adds to the growing interest in gerontological research regarding social attention.

  12. Selective attention in fast and slow learners.

    Science.gov (United States)

    Hunt, D; Randhawa, B S; Fitzgerald, D

    1977-06-01

    64 children aged 8 yr. were trained on a tactile simultaneous discrimination task. Selective attention was measured in terms of percentage contact time per trial to the relevant dimension. Inter- and intra-couplings per trial were also recorded. Multivariate analyses were carried out to examine the role of component factor scores, obtained from a component curve analysis of the percentage touching time per trial, and selected cognitive variables in differentiating between the fast and slow learner groups. Percentage touching time factor scores and a memory factor were significant, but there was no significant difference between the groups in the number of couplings made. As learning progressed the number of inter- and intra-couplings decreased.

  13. Environmentally friendly slow-release nitrogen fertilizer.

    Science.gov (United States)

    Ni, Boli; Liu, Mingzhu; Lü, Shaoyu; Xie, Lihua; Wang, Yanfang

    2011-09-28

    To sustain the further world population, more fertilizers are required, which may become an environmental hazard, unless adequate technical and socioeconomic impacts are addressed. In the current study, slow-release formulations of nitrogen fertilizer were developed on the basis of natural attapulgite (APT) clay, ethylcellulose (EC) film, and sodium carboxymethylcellulose/hydroxyethylcellulose (CMC/HEC) hydrogel. The structural and chemical characteristics of the product were examined. The release profiles of urea, ammonium sulfate, and ammonium chloride as nitrogen fertilizer substrates were determined in soil. To further compare the release profiles of nitrogen from different fertilizer substrates, a mathematical model for nutrient release from the coated fertilizer was applied to calculate the diffusion coefficient D. The influence of the product on water-holding and water-retention capacities of soil was determined. The experimental data indicated that the product can effectively reduce nutrient loss, improve use efficiency of water, and prolong irrigation cycles in drought-prone environments.

  14. Predation risk increases dispersal distance in prey

    Science.gov (United States)

    Otsuki, Hatsune; Yano, Shuichi

    2014-06-01

    Understanding the ecological factors that affect dispersal distances allows us to predict the consequences of dispersal. Although predator avoidance is an important cause of prey dispersal, its effects on dispersal distance have not been investigated. We used simple experimental setups to test dispersal distances of the ambulatory dispersing spider mite ( Tetranychus kanzawai) in the presence or absence of a predator ( Neoseiulus womersleyi). In the absence of predators, most spider mites settled in adjacent patches, whereas the majority of those dispersing in the presence of predators passed through adjacent patches and settled in distant ones. This is the first study to experimentally demonstrate that predators induce greater dispersal distance in prey.

  15. Reversible Fano resonance by transition from fast light to slow light in a coupled-resonator-induced transparency structure.

    Science.gov (United States)

    Zhang, Yundong; Zhang, Xuenan; Wang, Ying; Zhu, Ruidong; Gai, Yulong; Liu, Xiaoqi; Yuan, Ping

    2013-04-08

    We theoretically propose and experimentally perform a novel dispersion tuning scheme to realize a tunable Fano resonance in a coupled-resonator-induced transparency (CRIT) structure coupled Mach-Zehnder interferometer. We reveal that the profile of the Fano resonance in the resonator coupled Mach-Zehnder interferometers (RCMZI) is determined not only by the phase shift difference between the two arms of the RCMZI but also by the dispersion (group delay) of the CRIT structure. Furthermore, it is theoretically predicted and experimentally demonstrated that the slope and the asymmetry parameter (q) describing the Fano resonance spectral line shape of the RCMZI experience a sign reversal when the dispersion of the CRIT structure is tuned from abnormal dispersion (fast light) to normal dispersion (slow light). These theoretical and experimental results indicate that the reversible Fano resonance which holds significant implications for some attractive device applications such as highly sensitive biochemical sensors, ultrafast optical switches and routers can be realized by the dispersion tuning scheme in the RCMZI.

  16. Role of sources and temporal sinks in a marine amphipod.

    Science.gov (United States)

    Munguia, Pablo

    2015-02-01

    Spatially structured habitats challenge populations to have positive growth rates and species often rely on dispersing propagules to occupy habitats outside their fundamental niche. Most marine species show two main life stages, a dispersing stage and a sedentary stage affecting distribution and abundance patterns. An experimental study on Corophium acherusicum, a colonial tube-building amphipod, showed the strong influence that a source population can have on new habitats. More importantly, this study shows the effect of temporal sinks where newly established populations can show reduced growth rates if the propagule supply from a source is removed. Sink populations had a reduction in abundance and became male-biased as females left colonies. The consequences arising from short-term dispersal and temporal sinks could be due to different selection pressures at the source and sink populations. These consequences can become reflected in long-term dynamics of marine populations if we shift focus to non-random dispersal models incorporating behaviour and stage-dependent dispersal. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  17. How spatio-temporal habitat connectivity affects amphibian genetic structure

    Science.gov (United States)

    Watts, Alexander G.; Schlichting, P; Billerman, S; Jesmer, B; Micheletti, S; Fortin, M.-J.; Funk, W.C.; Hapeman, P; Muths, Erin L.; Murphy, M.A.

    2015-01-01

    Heterogeneous landscapes and fluctuating environmental conditions can affect species dispersal, population genetics, and genetic structure, yet understanding how biotic and abiotic factors affect population dynamics in a fluctuating environment is critical for species management. We evaluated how spatio-temporal habitat connectivity influences dispersal and genetic structure in a population of boreal chorus frogs (Pseudacris maculata) using a landscape genetics approach. We developed gravity models to assess the contribution of various factors to the observed genetic distance as a measure of functional connectivity. We selected (a) wetland (within-site) and (b) landscape matrix (between-site) characteristics; and (c) wetland connectivity metrics using a unique methodology. Specifically, we developed three networks that quantify wetland connectivity based on: (i) P. maculata dispersal ability, (ii) temporal variation in wetland quality, and (iii) contribution of wetland stepping-stones to frog dispersal. We examined 18 wetlands in Colorado, and quantified 12 microsatellite loci from 322 individual frogs. We found that genetic connectivity was related to topographic complexity, within- and between-wetland differences in moisture, and wetland functional connectivity as contributed by stepping-stone wetlands. Our results highlight the role that dynamic environmental factors have on dispersal-limited species and illustrate how complex asynchronous interactions contribute to the structure of spatially-explicit metapopulations.

  18. Complete compensation of pulse broadening in an amplifier-based slow light system using a nonlinear regeneration element.

    Science.gov (United States)

    Chin, Sanghooon; Gonzalez-Herraez, Miguel; Thévenaz, Luc

    2009-11-23

    We experimentally demonstrate complete compensation of pulse broadening in an amplifier-based slow light system. The configuration of the delay line basically consists of two stages: a conventional Brillouin slow light system and a nonlinear regeneration element. Signal pulses experienced both time delay and temporal broadening through the Brillouin delay line and then the delayed pulses were delivered into a nonlinear optical loop mirror. Due to the nonlinear response of the transmission of the fiber loop, the inevitably broadened pulses were moderately compressed in the output of the loop, without loss in the capacity to delay the pulses. The overall result is that, for the maximum delay, the width of the pulse could be kept below the input width while the time delays introduced by the slow light element were preserved. Using this delay line, a signal pulse with duration of 27 ns at full width at half maximum was delayed up to 1.3-bits without suffering from signal distortion.

  19. The success of failed Homo sapiens dispersals out of Africa and into Asia.

    Science.gov (United States)

    Rabett, Ryan J

    2018-02-01

    The evidence for an early dispersal of Homo sapiens from Africa into the Levant during Marine Isotope Stage 5 (MIS-5) 126-74 ka (thousand years ago) was characterized for many years as an 'abortive' expansion: a precursor to a sustained dispersal from which all extant human populations can be traced. Recent archaeological and genetic data from both western and eastern parts of Eurasia and from Australia are starting to challenge that interpretation. This Perspective reviews the current evidence for a scenario where the MIS-5 dispersal encompassed a much greater geographic distribution and temporal duration. The implications of this for tracking and understanding early human dispersal in Southeast Asia specifically are considered, and the validity of measuring dispersal success only through genetic continuity into the present is examined.

  20. Slow waves in microchannel metal waveguides and application to particle acceleration

    Directory of Open Access Journals (Sweden)

    L. C. Steinhauer

    2003-06-01

    Full Text Available Conventional metal-wall waveguides support waveguide modes with phase velocities exceeding the speed of light. However, for infrared frequencies and guide dimensions of a fraction of a millimeter, one of the waveguide modes can have a phase velocity equal to or less than the speed of light. Such a metal microchannel then acts as a slow-wave structure. Furthermore, if it is a transverse magnetic mode, the electric field has a component along the direction of propagation. Therefore, a strong exchange of energy can occur between a beam of charged particles and this slow-waveguide mode. Moreover, the energy exchange can be sustained over a distance limited only by the natural damping of the wave. This makes the microchannel metal waveguide an attractive possibility for high-gradient electron laser acceleration because the wave can be directly energized by a long-wavelength laser. Indeed the frequency of CO_{2} lasers lies at a fortuitous wavelength that produces a strong laser-particle interaction in a channel of reasonable macroscopic size (e.g., ∼0.6  mm. The dispersion properties including phase velocity and damping for the slow wave are developed. The performance and other issues related to laser accelerator applications are discussed.

  1. The use of semiochemical slow-release devices in integrated pest management strategies

    Directory of Open Access Journals (Sweden)

    Heuskin, S.

    2011-01-01

    Full Text Available The development of integrated pest management (IPM strategies is increasing since many problems appeared with the use of synthetic pesticides. Semiochemicals – informative molecules used in insect-insect or plant-insect interaction – are more and more considered within IPM strategies as alternative or complementary approach to insecticide treatments. Indeed, these species-specific compounds do not present any related adversely affectation of beneficial organisms and do not generate any risk of pest insect resistance as observed with insecticides. Because of their complex biological activity, their dispersion in the environment to be protected or monitored needs the elaboration of slow-release devices ensuring a controlled release of the biologically active volatile compounds. These sensitive molecules also need to be protected from degradation by UV light and oxygen. Many studies were conducted on estimation of release-rate from commercialized or experimental slow-release devices. The influence of climatic parameters and dispenser type were estimated by previous authors in order to provide indications about the on-field longevity of lures. The present review outlines a list of slow-release studies conducted by many authors followed by a critical analysis of these studies.

  2. U-shaped meander-line slow-wave structure with stub-loading

    Science.gov (United States)

    Bian, Xingwang; Miao, Min; Li, Zhensong; Cui, Xiaole

    2017-06-01

    In this paper, a U-shaped meander-line slow-wave structure (SWS) with stub-loading is proposed for applications in Ka-band traveling-wave tube (TWT). This new slow-wave structure, loaded with a stub at the center of the U-turn section, has higher interaction impedance and lower phase velocity compared with conventional U-shaped meander-line SWSs, indicating that the devices based on this structure may have a lower operating voltage and higher output power. The dispersion characteristic, interaction impedance, transmission characteristics, and beam-wave interaction are simulated by utilizing simulation tool. The simulation result predicts that the millimeter-wave traveling-wave tube design based on this slow-wave structure is capable of delivering over 200 W with a gain of 33 dB and interaction efficiency 14.5% at the center frequency 34 GHz. This design, more compact and powerful in comparison with those based on more conventional vacuum electronic mechanisms, is demonstrated as a prospective option for integrated millimeter-wave power modules (MMPMs) empowering a broad spectrum of fields, from target detection, to imaging and telecommunications, among others.

  3. Slow waves in microchannel metal waveguides and application to particle acceleration

    Science.gov (United States)

    Steinhauer, L. C.; Kimura, W. D.

    2003-06-01

    Conventional metal-wall waveguides support waveguide modes with phase velocities exceeding the speed of light. However, for infrared frequencies and guide dimensions of a fraction of a millimeter, one of the waveguide modes can have a phase velocity equal to or less than the speed of light. Such a metal microchannel then acts as a slow-wave structure. Furthermore, if it is a transverse magnetic mode, the electric field has a component along the direction of propagation. Therefore, a strong exchange of energy can occur between a beam of charged particles and this slow-waveguide mode. Moreover, the energy exchange can be sustained over a distance limited only by the natural damping of the wave. This makes the microchannel metal waveguide an attractive possibility for high-gradient electron laser acceleration because the wave can be directly energized by a long-wavelength laser. Indeed the frequency of CO2 lasers lies at a fortuitous wavelength that produces a strong laser-particle interaction in a channel of reasonable macroscopic size (e.g., ˜0.6 mm). The dispersion properties including phase velocity and damping for the slow wave are developed. The performance and other issues related to laser accelerator applications are discussed.

  4. Slow and Fast Light in Semiconductor Quantum-Well and Quantum-Dot Devices

    Science.gov (United States)

    Chang-Hasnain, Connie J.; Chuang, Shun Lien

    2006-12-01

    The ability to manipulate the speed of light has recently become one of the most exciting emergent topics in optics. There are several experimental demonstrations showing the capability to slow down light more than six orders of magnitude in a variety of media, ranging from atomic vapor, solid state crystal, to semiconductors. These results have led to intensive research into new materials, devices, and system studies that examine their impact to new applications. It is believed that we are on the verge of a dramatic change in the way we envision and construct communication, processing and control systems. One direct application of slow and fast light devices is in the area of communications. One grand challenge remaining in information technology today is to store and buffer optical signals directly in optical format. As such, optical signals must be converted to electronic signals to route, switch, or be processed. This resulted in significant latencies and traffic congestions in current networks. In addition, keeping the data in optical domain during the routing process can greatly reduce the power, complexity and size of the routers. To this end, a controllable optical delay line can effectively function as an optical buffer, and the storage is proportional to the variability of the group velocity. In addition to optical buffers, slow and fast light devices can be used as tunable true-time delay elements in microwave photonics, which are important for remotely controlling phased array antenna. Other novel applications include nonlinear optics, optical signal processing, and quantum information processing. There are various approaches that can be used to vary the optical group velocity. Ultraslow or fast group velocity may result from a large material dispersion, waveguide dispersion, or both. In this paper, the authors provide a review of recent progress of slow and fast light using semiconductor devices. Specifically, they will discuss results obtained using

  5. Microsurgical treatment of temporal lobe arachnoid cysts complicated with epilepsy

    Directory of Open Access Journals (Sweden)

    Yong-qin KUANG

    2011-02-01

    Full Text Available Objective To explore the technique and precautions of microsurgical treatment of temporal lobe arachnoid cysts complicated with spilepsy.Methods The clinical data of 32 patients with temporal lobe arachnoid cysts complicated with epilepsy,admitted from Nov.2007 to Apr.2010,were analyzed retrospectively.The diagnosis of temporal lobe arachnoid cysts was confirmed before surgical operation by cranial MRI or CT.Continual video-electroencephalogram monitoring with sphenoidal electrodes were employed in all patients,and spike-wave,polyspike-wave and/or sharp-slow-wave was detected at arachnoid cyst side.Craniotomy was performed under general anesthesia,the temporal lobe arachnoid cysts were treated by microsurgical excision.Besides,partial anterior temporal lobectomy,hippocampectomy,amygdalotomy and bipolar electrogulation on functional cortex were conducted in all cases.Intraoperative electroencephalography(EEG monitoring was used in all patients.And an one year follow-up after surgery was carried out.Results No postoperative death occurred.Transient aphasia and hemiplegia were found in 14 patients(10 in left and 4 in right and recovered 7-10 days after treatment.A one-year MRI follow-up showed the temporal lobe arachnoid cysts disappeared in 12 patients(37.5%,shrank in 8(25.0%,and unchanged in 12(37.5%.Epileptic symptom disappeared in 27 cases(84.4% and temporary symptoms could be observed in 5 cases(15.6%.Continual video-electroencephalogram monitoring with sphenoidal electrodes showed no spike-wave,but sharp wave was detected in 8 cases and sharp-slow wave complexes were detected in 4 cases.Conclusion Microsurgery used in resection of the cysts and epileptic foci may achieve good therapeutic effects for temporal lobe arachnoid cysts complicated with epilepsy.

  6. Circular motion of electromagnetic power shaping the dispersion of Surface Plasmon Polaritons.

    Science.gov (United States)

    Rosenblatt, Gilad; Feigenbaum, Eyal; Orenstein, Meir

    2010-12-06

    A circular zero-time-averaged power component, coupling the forward (dielectric) and backward (metal) power channels of Surface Plasmon Polaritons (SPPs), is shown to be the core ingredient for the slow-light characteristic of SPPs at the surface plasmon frequency, for both a lossless and lossy metal. Additional slow-light regimes emerging in configurations where few SPPs are strongly coupled, such as in a narrow plasmonic gap and slab, forming local extrema of the dispersion curve (branch points for positive and negative index branches), are also propelled by the circular motion of the plasmonic power.

  7. The role of non-rapid eye movement slow-wave activity in prefrontal metabolism across young and middle-aged adults.

    Science.gov (United States)

    Wilckens, Kristine A; Aizenstein, Howard J; Nofzinger, Eric A; James, Jeffrey A; Hasler, Brant P; Rosario-Rivera, Bedda L; Franzen, Peter L; Germain, Anne; Hall, Martica H; Kupfer, David J; Price, Julie C; Siegle, Greg J; Buysse, Daniel J

    2016-06-01

    Electroencephalographic slow-wave activity (0.5-4 Hz) during non-rapid eye movement (NREM) sleep is a marker for cortical reorganization, particularly within the prefrontal cortex. Greater slow wave activity during sleep may promote greater waking prefrontal metabolic rate and, in turn, executive function. However, this process may be affected by age. Here we examined whether greater NREM slow wave activity was associated with higher prefrontal metabolism during wakefulness and whether this relationship interacted with age. Fifty-two participants aged 25-61 years were enrolled into studies that included polysomnography and a (18) [F]-fluoro-deoxy-glucose positron emission tomography scan during wakefulness. Absolute and relative measures of NREM slow wave activity were assessed. Semiquantitative and relative measures of cerebral metabolism were collected to assess whole brain and regional metabolism, focusing on two regions of interest: the dorsolateral prefrontal cortex and the orbitofrontal cortex. Greater relative slow wave activity was associated with greater dorsolateral prefrontal metabolism. Age and slow wave activity interacted significantly in predicting semiquantitative whole brain metabolism and outside regions of interest in the posterior cingulate, middle temporal gyrus and the medial frontal gyrus, such that greater slow-wave activity was associated with lower metabolism in the younger participants and greater metabolism in the older participants. These results suggest that slow-wave activity is associated with cerebral metabolism during wakefulness across the adult lifespan within regions important for executive function. © 2016 European Sleep Research Society.

  8. Slow diffusive dynamics in a chaotic balanced neural network.

    Directory of Open Access Journals (Sweden)

    Nimrod Shaham

    2017-05-01

    Full Text Available It has been proposed that neural noise in the cortex arises from chaotic dynamics in the balanced state: in this model of cortical dynamics, the excitatory and inhibitory inputs to each neuron approximately cancel, and activity is driven by fluctuations of the synaptic inputs around their mean. It remains unclear whether neural networks in the balanced state can perform tasks that are highly sensitive to noise, such as storage of continuous parameters in working memory, while also accounting for the irregular behavior of single neurons. Here we show that continuous parameter working memory can be maintained in the balanced state, in a neural circuit with a simple network architecture. We show analytically that in the limit of an infinite network, the dynamics generated by this architecture are characterized by a continuous set of steady balanced states, allowing for the indefinite storage of a continuous parameter. In finite networks, we show that the chaotic noise drives diffusive motion along the approximate attractor, which gradually degrades the stored memory. We analyze the dynamics and show that the slow diffusive motion induces slowly decaying temporal cross correlations in the activity, which differ substantially from those previously described in the balanced state. We calculate the diffusivity, and show that it is inversely proportional to the system size. For large enough (but realistic neural population sizes, and with suitable tuning of the network connections, the proposed balanced network can sustain continuous parameter values in memory over time scales larger by several orders of magnitude than the single neuron time scale.

  9. Relationship between slow visual processing and reading speed in people with macular degeneration.

    Science.gov (United States)

    Cheong, Allen M Y; Legge, Gordon E; Lawrence, Mary G; Cheung, Sing-Hang; Ruff, Mary A

    2007-10-01

    People with macular degeneration (MD) often read slowly even with adequate magnification to compensate for acuity loss. Oculomotor deficits may affect reading in MD, but cannot fully explain the substantial reduction in reading speed. Central-field loss (CFL) is often a consequence of macular degeneration, necessitating the use of peripheral vision for reading. We hypothesized that slower temporal processing of visual patterns in peripheral vision is a factor contributing to slow reading performance in MD patients. Fifteen subjects with MD, including 12 with CFL, and five age-matched control subjects were recruited. Maximum reading speed and critical print size were measured with rapid serial visual presentation (RSVP). Temporal processing speed was studied by measuring letter-recognition accuracy for strings of three randomly selected letters centered at fixation for a range of exposure times. Temporal threshold was defined as the exposure time yielding 80% recognition accuracy for the central letter. Temporal thresholds for the MD subjects ranged from 159 to 5881 ms, much longer than values for age-matched controls in central vision (13 ms, preading speed (preading speed is consistent with the hypothesis that slower visual processing of letter recognition is one of the factors limiting reading speed in MD subjects.

  10. Temporal network epidemiology

    CERN Document Server

    Holme, Petter

    2017-01-01

    This book covers recent developments in epidemic process models and related data on temporally varying networks. It is widely recognized that contact networks are indispensable for describing, understanding, and intervening to stop the spread of infectious diseases in human and animal populations; “network epidemiology” is an umbrella term to describe this research field. More recently, contact networks have been recognized as being highly dynamic. This observation, also supported by an increasing amount of new data, has led to research on temporal networks, a rapidly growing area. Changes in network structure are often informed by epidemic (or other) dynamics, in which case they are referred to as adaptive networks. This volume gathers contributions by prominent authors working in temporal and adaptive network epidemiology, a field essential to understanding infectious diseases in real society.

  11. Vivienda temporal para refugiados

    OpenAIRE

    Amonarraiz Gutiérrez, Ana

    2015-01-01

    El proyecto se centra en el diseño y desarrollo de un espacio destinado a vivienda temporal para dar hogar a personas que han perdido su casa. Este tipo de vivienda es fundamental dentro del proceso de recuperación post-desastre ya que la construcción inmediata de viviendas permanentes es utópica. El objetivo principal es la construcción de una vivienda temporal formada por elementos prefabricados, logrando así una mayor rapidez en su montaje. Esto también permitirá que cualquier component...

  12. Dielectric spectroscopy of isotropic liquids and liquid crystal phases with dispersed graphene oxide

    Science.gov (United States)

    Al-Zangana, Shakhawan; Iliut, Maria; Boran, Gökçen; Turner, Michael; Vijayaraghavan, Aravind; Dierking, Ingo

    2016-08-01

    Graphene oxide (GO) flakes of different sizes were prepared and dispersed in isotropic and nematic (anisotropic) fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature (25-60 oC) and frequency range (100 Hz-2 MHz). The mixtures containing GO flakes exhibited varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. Relaxation frequencies of the GO doped isotropic media, such as isopropanol IPA, were observed to be much lower than the GO doped thermotropic nematic medium 5CB. It is anticipated that the slow relaxation frequencies (~10 kHz) could be resulting from the relaxation modes of the GO flakes while the fast relaxation frequencies (~100 kHz) could indicate strongly slowed down molecular modes of the nematogenic molecules, which are anchored to the GO flakes via dispersion interactions. The relaxation frequencies decreased as the size of the GO flakes in the isotropic solvent was increased. Polarizing microscopy showed that GO flakes with a mean diameter of 10 μm, dispersed in water, formed a lyotropic nematic liquid crystal phase. This lyotropic nematic exhibited the slowest dielectric relaxation process, with relaxation frequencies in the order of 2 kHz, as compared to the GO-isotropic suspension and the GO-doped 5CB.

  13. Slow-roll approximation in loop quantum cosmology

    CERN Document Server

    Luc, Joanna

    2016-01-01

    The slow-roll approximation is an analytical approach to study dynamical properties of the inflationary universe. In this article, systematic construction of the slow-roll expansion for effective loop quantum cosmology is presented. The analysis is performed up to the fourth order in both slow-roll parameters and the parameter controlling the strength of deviation from the classical case. The expansion is performed for three types of the slow-roll parameters: Hubble slow-roll parameters, Hubble flow parameters and potential slow-roll parameters. An accuracy of the approximation is verified by comparison with the numerical phase space trajectories for the case with a massive potential term. The results obtained in this article may be helpful in the search for the subtle quantum gravitational effects with use of the cosmological data.

  14. The nature of subslab slow velocity anomalies beneath South America

    Science.gov (United States)

    Portner, Daniel Evan; Beck, Susan; Zandt, George; Scire, Alissa

    2017-05-01

    Slow seismic velocity anomalies are commonly imaged beneath subducting slabs in tomographic studies, yet a unifying explanation for their distribution has not been agreed upon. In South America two such anomalies have been imaged associated with subduction of the Nazca Ridge in Peru and the Juan Fernández Ridge in Chile. Here we present new seismic images of the subslab slow velocity anomaly beneath Chile, which give a unique view of the nature of such anomalies. Slow seismic velocities within a large hole in the subducted Nazca slab connect with a subslab slow anomaly that appears correlated with the extent of the subducted Juan Fernández Ridge. The hole in the slab may allow the subslab material to rise into the mantle wedge, revealing the positive buoyancy of the slow material. We propose a new model for subslab slow velocity anomalies beneath the Nazca slab related to the entrainment of hot spot material.

  15. Contrasting evolutionary histories of the legless lizards slow worms (Anguis) shaped by the topography of the Balkan Peninsula.

    Science.gov (United States)

    Jablonski, Daniel; Jandzik, David; Mikulíček, Peter; Džukić, Georg; Ljubisavljević, Katarina; Tzankov, Nikolay; Jelić, Dušan; Thanou, Evanthia; Moravec, Jiří; Gvoždík, Václav

    2016-05-10

    Genetic architecture of a species is a result of historical changes in population size and extent of distribution related to climatic and environmental factors and contemporary processes of dispersal and gene flow. Population-size and range contractions, expansions and shifts have a substantial effect on genetic diversity and intraspecific divergence, which is further shaped by gene-flow limiting barriers. The Balkans, as one of the most important sources of European biodiversity, is a region where many temperate species persisted during the Pleistocene glaciations and where high topographic heterogeneity offers suitable conditions for local adaptations of populations. In this study, we investigated the phylogeographical patterns and demographic histories of four species of semifossorial slow-worm lizards (genus Anguis) present in the Balkan Peninsula, and tested the relationship between genetic diversity and topographic heterogeneity of the inhabited ranges. We inferred phylogenetic relationships, compared genetic structure and historical demography of slow worms using nucleotide sequence variation of mitochondrial DNA. Four Anguis species with mostly parapatric distributions occur in the Balkan Peninsula. They show different levels of genetic diversity. A signature of population growth was detected in all four species but with various courses in particular populations. We found a strong correlation between genetic diversity of slow-worm populations and topographic ruggedness of the ranges (mountain systems) they inhabit. Areas with more rugged terrain harbour higher genetic diversity. Phylogeographical pattern of the genus Anguis in the Balkans is concordant with the refugia-within-refugia model previously proposed for both several other taxa in the region and other main European Peninsulas. While slow-worm populations from the southern refugia mostly have restricted distributions and have not dispersed much from their refugial areas, populations from the extra

  16. Slow positron beam at the JINR, Dubna

    Directory of Open Access Journals (Sweden)

    Horodek Paweł

    2015-12-01

    Full Text Available The Low Energy Positron Toroidal Accumulator (LEPTA at the Joint Institute for Nuclear Research (JINR proposed for generation of positronium in flight has been adopted for positron annihilation spectroscopy (PAS. The positron injector generates continuous slow positron beam with positron energy range between 50 eV and 35 keV. The radioactive 22Na isotope is used. In distinction to popular tungsten foil, here the solid neon is used as moderator. It allows to obtain the beam intensity of about 105 e+/s width energy spectrum characterized by full width at half maximum (FWHM of 3.4 eV and a tail to lower energies of about 30 eV. The paper covers the characteristic of variable energy positron beam at the LEPTA facility: parameters, the rule of moderation, scheme of injector, and transportation of positrons into the sample chamber. Recent status of the project and its development in the field of PAS is discussed. As an example, the measurement of the positron diffusion length in pure iron is demonstrated.

  17. Vestibular perception is slow: a review.

    Science.gov (United States)

    Barnett-Cowan, Michael

    2013-01-01

    Multisensory stimuli originating from the same event can be perceived asynchronously due to differential physical and neural delays. The transduction of and physiological responses to vestibular stimulation are extremely fast, suggesting that other stimuli need to be presented prior to vestibular stimulation in order to be perceived as simultaneous. There is, however, a recent and growing body of evidence which indicates that the perceived onset of vestibular stimulation is slow compared to the other senses, such that vestibular stimuli need to be presented prior to other sensory stimuli in order to be perceived synchronously. From a review of this literature it is speculated that this perceived latency of vestibular stimulation may reflect the fact that vestibular stimulation is most often associated with sensory events that occur following head movement, that the vestibular system rarely works alone, that additional computations are required for processing vestibular information, and that the brain prioritizes physiological response to vestibular stimulation over perceptual awareness of stimulation onset. Empirical investigation of these theoretical predictions is encouraged in order to fully understand this surprising result, its implications, and to advance the field.

  18. A slow gravity compensated atom laser

    DEFF Research Database (Denmark)

    Kleine Büning, G.; Will, J.; Ertmer, W.

    2010-01-01

    We report on a slow guided atom laser beam outcoupled from a Bose–Einstein condensate of 87Rb atoms in a hybrid trap. The acceleration of the atom laser beam can be controlled by compensating the gravitational acceleration and we reach residual accelerations as low as 0.0027 g. The outcoupling...... mechanism allows for the production of a constant flux of 4.5×106 atoms per second and due to transverse guiding we obtain an upper limit for the mean beam width of 4.6 μm. The transverse velocity spread is only 0.2 mm/s and thus an upper limit for the beam quality parameter is M 2=2.5. We demonstrate...... the potential of the long interrogation times available with this atom laser beam by measuring the trap frequency in a single measurement. The small beam width together with the long evolution and interrogation time makes this atom laser beam a promising tool for continuous interferometric measurements....

  19. Deciding about fast and slow decisions.

    Science.gov (United States)

    Croskerry, Pat; Petrie, David A; Reilly, James B; Tait, Gordon

    2014-02-01

    Two reports in this issue address the important topic of clinical decision making. Dual process theory has emerged as the dominant model for understanding the complex processes that underlie human decision making. This theory distinguishes between the reflexive, autonomous processes that characterize intuitive decision making and the deliberate reasoning of an analytical approach. In this commentary, the authors address the polarization of viewpoints that has developed around the relative merits of the two systems. Although intuitive processes are typically fast and analytical processes slow, speed alone does not distinguish them. In any event, the majority of decisions in clinical medicine are not dependent on very short response times. What does appear relevant to diagnostic ease and accuracy is the degree to which the symptoms of the disease being diagnosed are characteristic ones. There are also concerns around some methodological issues related to research design in this area of enquiry. Reductionist approaches that attempt to isolate dependent variables may create such artificial experimental conditions that both external and ecological validity are sacrificed. Clinical decision making is a complex process with many independent (and interdependent) variables that need to be separated out in a discrete fashion and then reflected on in real time to preserve the fidelity of clinical practice. With these caveats in mind, the authors believe that research in this area should promote a better understanding of clinical practice and teaching by focusing less on the deficiencies of intuitive and analytical systems and more on their adaptive strengths.

  20. Micro growth slows; early converts gain advantage

    Energy Technology Data Exchange (ETDEWEB)

    Moore, W.D.

    1986-03-03

    The drilling industry recession has stopped expansions and slowed new microcomputing projects. But firms already are inching up the learning curve, gaining a competitive advantage over latecomers and smaller firms unable to afford new directions. Rather than enjoying widespread, universal acceptance, micros are filling a few specific niches in drilling. They serve companies too small for real-time, mainframe links and too big to manage all their business and engineering on paper. Where micros have made inroads in drilling, they are performing many useful services, becoming indispensable in daily operations. But where micros have not yet been adopted, their application seems further away than it did several years ago. Current drilling economics overshadow progress in computing. The drilling industry has experienced 4 years of serious recession. Over this period, activity slumped as petroleum prices declined. Profits evaporated. Most drilling companies were already in dire straits when the downturn accelerated in 1986. Service companies have begun yet another round of painful retrenchment. So even minor capital expenditures or expansions are beyond the hopes of most drilling-related firms in 1986. Yet microcomputing remains a growing part of drilling. For now, growth is concentrated in better-off companies.

  1. Evidence for a large phononic band gap leading to slow hot carrier thermalisation

    Science.gov (United States)

    Chung, S.; Shrestha, S.; Wen, X.; Feng, Y.; Gupta, N.; Xia, H.; Yu, P.; Tang, J.; Conibeer, G.

    2014-11-01

    It has been proposed that the rate of hot carrier thermalisation can be slowed down if there is a sufficiently large gap in the phonon dispersion for a bulk material. This phenomenon is critical for the development of high efficiency hot carrier solar cells to minimise energy loss to thermalisation. A gap where the minimum of the optical branches is at least twice that of the maximum of the acoustic branches can prevent the primary pathway where optical phonons loses energy, the Klemens' decay mechanism. The large gap in the phonon dispersion eliminates the Klemens' decay pathway due to energy and momentum conservation laws. This enables the electron population to remain hot by allowing sufficient time for optical phonons to re-scatter its energy to electrons. Binary compounds with a large mass difference between the two constituent atoms and high level of crystal symmetry such as zirconium nitride and hafnium nitride (HfN) have such a gap in their phonon dispersion. HfN thin films have been sputtered on silicon and quartz substrates. Characterisation of hot electron lifetimes in HfN films have been performed using ultrafast transient absorption spectroscopy. Preliminary analysis of transient absorption data, both spectra and time evolution has indicated high carrier temperatures with a nanosecond long decay time. It is postulated the long hot carrier lifetime is due to the large phononic gap.

  2. Hyperbranched polymeric dispersants and non-aqueous pigment dispersions

    NARCIS (Netherlands)

    ANDRE, XAVIER; Bernaerts, Katrien

    2012-01-01

    The invention discloses a polymeric dispersant having a hyperbranched polyurethane architecture obtained by reacting a polyisocyanate core with a mixture of a) 40 to 65 mol% of an anchor represented by Formula (I) and/or (II) wherein n represents an integer selected from 0 to 7; and X and Y each

  3. HYPERBRANCHED POLYMERIC DISPERSANTS AND NON-AQUEOUS PIGMENT DISPERSIONS

    NARCIS (Netherlands)

    ANDRE, XAVIER; Bernaerts, Katrien

    2011-01-01

    A polymeric dispersant having a hyperbranched polyurethane architecture obtained by reacting a polyisocyanate core with a mixture of a) 40 to 65 mol% of an anchor represented by Formula (I) and/or (II) wherein n represents an integer selected from 0 to 7; and X and Y each independently represent a

  4. HYPERBRANCHED POLYMERIC DISPERSANTS AND NON-AQUEOUS PIGMENT DISPERSIONS

    NARCIS (Netherlands)

    ANCRE, XAVIER; BERNAERTS, KATRIEN; ANDRE, XAVIER

    2012-01-01

    A polymeric dispersant having a hyperbranched polyurethane architecture obtained by reacting a polyisocyanate core with a mixture of: a) 40 to 65 mol % of an anchor represented by Formula (I) and/or (II): wherein n represents an integer selected from 0 to 7; and X and Y each independently represent

  5. Slow feature analysis on retinal waves leads to V1 complex cells.

    Directory of Open Access Journals (Sweden)

    Sven Dähne

    2014-05-01

    Full Text Available The developing visual system of many mammalian species is partially structured and organized even before the onset of vision. Spontaneous neural activity, which spreads in waves across the retina, has been suggested to play a major role in these prenatal structuring processes. Recently, it has been shown that when employing an efficient coding strategy, such as sparse coding, these retinal activity patterns lead to basis functions that resemble optimal stimuli of simple cells in primary visual cortex (V1. Here we present the results of applying a coding strategy that optimizes for temporal slowness, namely Slow Feature Analysis (SFA, to a biologically plausible model of retinal waves. Previously, SFA has been successfully applied to model parts of the visual system, most notably in reproducing a rich set of complex-cell features by training SFA with quasi-natural image sequences. In the present work, we obtain SFA units that share a number of properties with cortical complex-cells by training on simulated retinal waves. The emergence of two distinct properties of the SFA units (phase invariance and orientation tuning is thoroughly investigated via control experiments and mathematical analysis of the input-output functions found by SFA. The results support the idea that retinal waves share relevant temporal and spatial properties with natural visual input. Hence, retinal waves seem suitable training stimuli to learn invariances and thereby shape the developing early visual system such that it is best prepared for coding input from the natural world.

  6. Ability Dispersion and Team Performance

    DEFF Research Database (Denmark)

    Hoogendoorn, Sander; Parker, Simon C.; Van Praag, Mirjam

    What is the effect of dispersed levels of cognitive ability of members of a (business) team on their team's performance? This paper reports the results of a field experiment in which 573 students in 49 teams start up and manage real companies under identical circumstances. We ensured exogenous...... increases and then decreases with ability dispersion. We seek to understand this finding by developing a model in which team members of different ability levels form sub-teams with other team members with similar ability levels to specialize in different productive tasks. Diversity spreads production over...

  7. Stochastic models for atmospheric dispersion

    DEFF Research Database (Denmark)

    Ditlevsen, Ove Dalager

    2003-01-01

    Simple stochastic differential equation models have been applied by several researchers to describe the dispersion of tracer particles in the planetary atmospheric boundary layer and to form the basis for computer simulations of particle paths. To obtain the drift coefficient, empirical vertical...... velocity distributions that depend on height above the ground both with respect to standard deviation and skewness are substituted into the stationary Fokker/Planck equation. The particle position distribution is taken to be uniform *the well/mixed condition( and also a given dispersion coefficient...

  8. Ability Dispersion and Team Performance

    DEFF Research Database (Denmark)

    Hoogendoorn, Sander; Parker, Simon C.; Van Praag, Mirjam

    What is the effect of dispersed levels of cognitive ability of members of a (business) team on their team's performance? This paper reports the results of a field experiment in which 573 students in 49 teams start up and manage real companies under identical circumstances for one year. We ensured...... increases and then decreases with ability dispersion. We seek to understand this finding by developing a model in which team members of different ability levels form sub-teams with other team members with similar ability levels to specialize in different productive tasks. Diversity spreads production over...

  9. Ability Dispersion and Team Performance

    DEFF Research Database (Denmark)

    Hoogendoorn, Sander; Parker, Simon C.; Van Praag, Mirjam

    What is the effect of dispersed levels of cognitive ability of members of a (business) team on their team's performance? This paper reports the results of a field experiment in which 573 students in 49 (student) teams start up and manage real companies under identical circumstances for one year. We...... increases and then decreases with ability dispersion. We seek to understand this finding by developing a model in which team members of different ability levels form sub- teams with other team members with similar ability levels to specialize in different productive tasks. Diversity spreads production over...

  10. Printed circuit dispersive transmission line

    Science.gov (United States)

    Ikezi, Hiroyuki; Lin-Liu, Yuh-Ren; DeGrassie, John S.

    1991-01-01

    A printed circuit dispersive transmission line structure is disclosed comprising an insulator, a ground plane formed on one surface of the insulator, a first transmission line formed on a second surface of the insulator, and a second transmission line also formed on the second surface of the insulator and of longer length than the first transmission line and periodically intersecting the first transmission line. In a preferred embodiment, the transmission line structure exhibits highly dispersive characteristics by designing the length of one of the transmission line between two adjacent periodic intersections to be longer than the other.

  11. Instabilities in passive dispersion oscillating fiber ring cavities

    Science.gov (United States)

    Copie, François; Conforti, Matteo; Kudlinski, Alexandre; Mussot, Arnaud; Biancalana, Fabio; Trillo, Stefano

    2017-05-01

    We investigate theoretically and experimentally the development of instabilities in passive ring cavities with stepwise longitudinal variation of the dispersion. We derive an extended version of the Lugiato-Lefever equation that permits to model dispersion oscillating cavities and we demonstrate that this equation is valid well beyond the mean field approximation. We review the theory of Turing (modulational) and Faraday (parametric) instability in inhomogeneous fiber cavities. We report the experimental demonstration of the generation of stable Turing and Faraday temporal patterns in the same device, which can be controlled by changing the detuning and/or the input power. Moreover, we experimentally record the round-trip-to-round-trip dynamics of the spectrum, which shows that Turing and Faraday instabilities not only differ by their characteristic frequency but also by their dynamical behavior. Contribution to the Topical Issue: "Theory and Applications of the Lugiato-Lefever Equation", edited by Yanne K. Chembo, Damia Gomila, Mustapha Tlidi, Curtis R. Menyuk.

  12. Unexpected collective larval dispersal but little support for sweepstakes reproductive success in the highly dispersive brooding mollusc Crepidula fornicata.

    Science.gov (United States)

    Riquet, Florentine; Comtet, Thierry; Broquet, Thomas; Viard, Frédérique

    2017-10-01

    In many marine invertebrates, long-distance dispersal is achieved during an extended pelagic larval phase. Although such dispersal should result in high gene flow over broad spatial scales, fine-scale genetic structure has often been reported, a pattern attributed to interfamilial variance in reproductive success and limited homogenization during dispersal. To examine this hypothesis, the genetic diversity of dispersing larvae must be compared with the postdispersal stages, that is benthic recruits and adults. Such data remain, however, scarce due to the difficulty to sample and analyse larvae of minute size. Here, we carried out such an investigation using the marine gastropod Crepidula fornicata. Field sampling of three to four larval pools was conducted over the reproductive season and repeated over 3 years. The genetic composition of larval pools, obtained with 16 microsatellite loci, was compared with that of recruits and adults sampled from the same site and years. In contrast to samples of juveniles and adults, large genetic temporal variations between larval pools produced at different times of the same reproductive season were observed. In addition, full- and half-sibs were detected in early larvae and postdispersal juveniles, pointing to correlated dispersal paths between several pairs of individuals. Inbred larvae were also identified. Such collective larval dispersal was unexpected given the long larval duration of the study species. Our results suggest that each larval pool is produced by a small effective number of reproducers but that, over a reproductive season, the whole larval pool is produced by large numbers of reproducers across space and time. © 2017 John Wiley & Sons Ltd.

  13. Parasitic slow extraction of extremely weak beam from a high-intensity proton rapid cycling synchrotron

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Ye [University of Science and Technology of China, Hefei, Anhui 230029 (China); Institute of High Energy Physics, CAS, Yuquan Road 19B, Beijing 100049 (China); Tang, Jingyu, E-mail: tangjy@ihep.ac.cn [University of Science and Technology of China, Hefei, Anhui 230029 (China); Institute of High Energy Physics, CAS, Yuquan Road 19B, Beijing 100049 (China); Yang, Zheng; Jing, Hantao [Institute of High Energy Physics, CAS, Yuquan Road 19B, Beijing 100049 (China)

    2014-02-11

    This paper proposes a novel method to extract extremely weak beam from a high-intensity proton rapid cycling synchrotron (RCS) in the parasitic mode, while maintaining the normal fast extraction. The usual slow extraction method from a synchrotron by employing third-order resonance cannot be applied in a high-intensity RCS due to a very short flat-top at the extraction energy and the strict control on beam loss. The proposed parasitic slow extraction method moves the beam to scrape a scattering foil prior to the fast beam extraction by employing either a local orbit bump or momentum deviation or their combination, so that the halo part of the beam will be scattered. A part of the scattered particles will be extracted from the RCS and guided to the experimental area. The slow extraction process can last about a few milliseconds before the beam is extracted by the fast extraction system. The method has been applied to the RCS of China Spallation Neutron Source. With 1.6 GeV in the extraction energy, 62.5 μA in the average current and 25 Hz in the repetition rate for the RCS, the proton intensity by the slow extraction method can be up to 2×10{sup 4} protons per cycle or 5×10{sup 5} protons per second. The extracted beam has also a good time structure of approximately uniform in a spill which is required for many applications such as detector tests. Detailed studies including the scattering effect in the foil, the local orbit bump by the bump magnets and dispersive orbit bump by modifying the RF pattern, the multi-particle simulations by ORBIT and TURTLE codes, and some technical features for the extraction magnets are presented.

  14. The slow demise of Easter Island: insights from a modelling investigation

    Directory of Open Access Journals (Sweden)

    Gunnar eBrandt

    2015-02-01

    Full Text Available The history of Easter Island and its supposed social-ecological collapse is often taken as a grim warning for the modern world. However, while the loss of a once lush palm forest is largely uncontested, causes and timing of the collapse remain controversial, because many paleoeological and archaeological data are afflicted with considerable uncertainties. According to a scenario named ecocide, the overharvesting of palm trees triggered a dramatic population decline, whereas a contrasting view termed genocide deems diseases and enslavement introduced by Europeans as the main reasons for the collapse. We propose here a third possibility, a slow demise, in which aspects of both ecocide and genocide concur to produce a long and slow decline of the society. We use a dynamic model to illustrate the consequences of the three alternatives with respect to the fate of the paleoecological system of the island.While none of the three model scenarios can be safely ruled out given the uncertainties of the available data, the slow demise appears to be the most plausible model scenario, in particular when considering the temporal pattern of deforestation as inferred from radiocarbon dates of charcoal remains.

  15. Auditory cortical areas activated by slow frequency-modulated sounds in mice.

    Directory of Open Access Journals (Sweden)

    Yuusuke Honma

    Full Text Available Species-specific vocalizations in mice have frequency-modulated (FM components slower than the lower limit of FM direction selectivity in the core region of the mouse auditory cortex. To identify cortical areas selective to slow frequency modulation, we investigated tonal responses in the mouse auditory cortex using transcranial flavoprotein fluorescence imaging. For differentiating responses to frequency modulation from those to stimuli at constant frequencies, we focused on transient fluorescence changes after direction reversal of temporally repeated and superimposed FM sweeps. We found that the ultrasonic field (UF in the belt cortical region selectively responded to the direction reversal. The dorsoposterior field (DP also responded weakly to the reversal. Regarding the responses in UF, no apparent tonotopic map was found, and the right UF responses were significantly larger in amplitude than the left UF responses. The half-max latency in responses to FM sweeps was shorter in UF compared with that in the primary auditory cortex (A1 or anterior auditory field (AAF. Tracer injection experiments in the functionally identified UF and DP confirmed that these two areas receive afferent inputs from the dorsal part of the medial geniculate nucleus (MG. Calcium imaging of UF neurons stained with fura-2 were performed using a two-photon microscope, and the presence of UF neurons that were selective to both direction and direction reversal of slow frequency modulation was demonstrated. These results strongly suggest a role for UF, and possibly DP, as cortical areas specialized for processing slow frequency modulation in mice.

  16. Population genetics strategies to characterize long-distance dispersal of insects

    Science.gov (United States)

    Population genetics strategies offer an alternative and powerful approach for obtaining information about long-distance movement, and have been widely used for examining patterns and magnitude of insect dispersal over geographic and temporal scales. Such strategies are based on the principle that ge...

  17. Spatiotemporal coupled-mode theory in dispersive media under a dynamic modulation

    CERN Document Server

    Dana, Brenda; Bahabad, Alon

    2014-01-01

    A simple and general formalism for mode coupling by a spatial, temporal or spatiotemporal perturbation in dispersive materials is developed. This formalism can be used for studying various linear and non-linear optical interactions involving a dynamic modulation of the interaction parameters such as non-reciprocal phenomena, time reversal of signals and spatiotemporal quasi phase matching

  18. Application of Planar Broadband Slow-Wave Systems

    Directory of Open Access Journals (Sweden)

    Edvardas Metlevskis

    2012-04-01

    Full Text Available Different types of planar broadband slow-wave systems are used for designing microwave devices. The papers published by Lithuanian scientists analyze and investigate the models of helical and meander slow-wave systems. The article carefully examines the applications of meander slow-wave systems and presents the areas where similar systems, e.g. mobile devices, RFID, wireless technologies are used and reviewed nowadays. The paper also focuses on the examples of the papers discussing antennas, filters and couplers that contain designed and fabricated meander slow-wave systems.Article in Lithuanian

  19. Graphene-based active slow surface plasmon polaritons

    National Research Council Canada - National Science Library

    Lu, Hua; Zeng, Chao; Zhang, Qiming; Liu, Xueming; Hossain, Md Muntasir; Reineck, Philipp; Gu, Min

    2015-01-01

    .... For the design of plasmonic slow light structures, graphene represents an attractive alternative to metals due to its strong field confinement, comparably low ohmic loss and versatile tunability...

  20. Sustainable Development of Slow Fashion Businesses: Customer Value Approach

    National Research Council Canada - National Science Library

    Jung, Sojin; Jin, Byoungho

    2016-01-01

    ... fashion can enhance protability is still largely unknown. Based on a customer value creation framework, this study empirically tested a structural model that specied the slow fashion attributes ...

  1. The Persistence of a Slow Manifold with Bifurcation

    DEFF Research Database (Denmark)

    Kristiansen, Kristian Uldall; Palmer, P.; Robert, M.

    2012-01-01

    his paper considers the persistence of a slow manifold with bifurcation in a slow-fast two degree of freedom Hamiltonian system. In particular, we consider a system with a supercritical pitchfork bifurcation in the fast space which is unfolded by the slow coordinate. The model system is motivated...... by tethered satellites. It is shown that an almost full measure subset of a neighborhood of the slow manifold's normally elliptic branches persists in an adiabatic sense. We prove this using averaging and a blow-up near the bifurcation....

  2. The Analysis and Calculation Method of Urban Rail Transit Carrying Capacity Based on Express-Slow Mode

    Directory of Open Access Journals (Sweden)

    Xiaobing Ding

    2016-01-01

    Full Text Available Urban railway transport that connects suburbs and city areas is characterized by uneven temporal and spatial distribution in terms of passenger flow and underutilized carrying capacity. This paper aims to develop methodologies to measure the carrying capacity of the urban railway by introducing a concept of the express-slow mode. We first explore factors influencing the carrying capacity under the express-slow mode and the interactive relationships among these factors. Then we establish seven different scenarios to measure the carrying capacity by considering the ratio of the number of the express trains and the slow trains, the station where overtaking takes place, and the number of overtaking maneuvers. Taking Shanghai Metro Line 16 as an empirical study, the proposed methods to measure the carrying capacity under different express-slow mode are proved to be valid. This paper contributes to the literature by remodifying the traditional methods to measure the carrying capacity when different express-slow modes are applied to improve the carrying capacity of the suburban railway.

  3. Temporal compressive sensing systems

    Energy Technology Data Exchange (ETDEWEB)

    Reed, Bryan W.

    2017-12-12

    Methods and systems for temporal compressive sensing are disclosed, where within each of one or more sensor array data acquisition periods, one or more sensor array measurement datasets comprising distinct linear combinations of time slice data are acquired, and where mathematical reconstruction allows for calculation of accurate representations of the individual time slice datasets.

  4. Temporal Concurrent Constraint Programming

    DEFF Research Database (Denmark)

    Nielsen, Mogens; Palamidessi, Catuscia; Valencia, Frank Dan

    2002-01-01

    The ntcc calculus is a model of non-deterministic temporal concurrent constraint programming. In this paper we study behavioral notions for this calculus. In the underlying computational model, concurrent constraint processes are executed in discrete time intervals. The behavioral notions studied...

  5. Temporal Concurrent Constraint Programming

    DEFF Research Database (Denmark)

    Valencia, Frank Dan

    Concurrent constraint programming (ccp) is a formalism for concurrency in which agents interact with one another by telling (adding) and asking (reading) information in a shared medium. Temporal ccp extends ccp by allowing agents to be constrained by time conditions. This dissertation studies...

  6. Mesial temporal sclerosis

    African Journals Online (AJOL)

    Kurt

    2005-07-29

    Jul 29, 2005 ... Introduction. Mesial temporal sclerosis is the commonest cause of partial complex seizures. The aetiology of this condi- tion is controversial, but it is postulat- ed that both acquired and develop- mental processes may be involved. Familial cases have also been reported. Magnetic resonance imaging. (MRI) ...

  7. Temporal bone imaging

    Energy Technology Data Exchange (ETDEWEB)

    Lemmerling, Marc [Algemeen Ziekenhuis Sint-Lucas, Gent (Belgium). Dept. of Radiology; Foer, Bert de (ed.) [Sint-Augustinus Ziekenhuis, Wilrijk (Belgium). Dept. of Radiology

    2015-04-01

    Complete overview of imaging of normal and diseased temporal bone. Straightforward structure to facilitate learning. Detailed consideration of newer imaging techniques, including the hot topic of diffusion-weighted imaging. Includes a chapter on anatomy that will be of great help to the novice interpreter of imaging findings. Excellent illustrations throughout. This book provides a complete overview of imaging of normal and diseased temporal bone. After description of indications for imaging and the cross-sectional imaging anatomy of the area, subsequent chapters address the various diseases and conditions that affect the temporal bone and are likely to be encountered regularly in clinical practice. The classic imaging methods are described and discussed in detail, and individual chapters are included on newer techniques such as functional imaging and diffusion-weighted imaging. There is also a strong focus on postoperative imaging. Throughout, imaging findings are documented with the aid of numerous informative, high-quality illustrations. Temporal Bone Imaging, with its straightforward structure based essentially on topography, will prove of immense value in daily practice.

  8. Backtracking and Mixing Rate of Diffusion on Uncorrelated Temporal Networks

    Directory of Open Access Journals (Sweden)

    Martin Gueuning

    2017-10-01

    Full Text Available We consider the problem of diffusion on temporal networks, where the dynamics of each edge is modelled by an independent renewal process. Despite the apparent simplicity of the model, the trajectories of a random walker exhibit non-trivial properties. Here, we quantify the walker’s tendency to backtrack at each step (return where he/she comes from, as well as the resulting effect on the mixing rate of the process. As we show through empirical data, non-Poisson dynamics may significantly slow down diffusion due to backtracking, by a mechanism intrinsically different from the standard bus paradox and related temporal mechanisms. We conclude by discussing the implications of our work for the interpretation of results generated by null models of temporal networks.

  9. Atypical effects of incorporated surfactants on stability and dissolution properties of amorphous polymeric dispersions.

    Science.gov (United States)

    Al-Obaidi, Hisham; Lawrence, M Jayne; Buckton, Graham

    2016-11-01

    To understand the impact of ionic and non-ionic surfactants on the dissolution and stability properties of amorphous polymeric dispersions using griseofulvin (GF) as a model for poorly soluble drugs. Solid dispersions of the poorly water-soluble drug, griseofulvin (GF) and the polymers, poly(vinylpyrrolidone) (PVP) and poly(2-hydroxypropyl methacrylate) (PHPMA), have been prepared by spray drying and bead milling and the effect of the ionic and non-ionic surfactants, namely sodium dodecyl sulphate (SDS) and Tween-80, on the physico-chemical properties of the solid dispersions studied. The X-ray powder diffraction data and hot-stage microscopy showed a fast re-crystallisation of GF. While dynamic vapour sorption (DVS) measurements indicated an increased water uptake, slow dissolution rates were observed for the solid dispersions incorporating surfactants. The order by which surfactants free dispersions were prepared seemed critical as indicated by DVS and thermal analysis. Dispersions prepared by milling with SDS showed significantly better stability than spray-dried dispersions (drug remained amorphous for more than 6 months) as well as improved dissolution profile. We suggest that surfactants can hinder the dissolution by promoting aggregation of polymeric chains, however that effect depends mainly on how the particles were prepared. © 2016 Royal Pharmaceutical Society.

  10. Graphene dispersions in alkanes: toward fast drying conducting inks.

    Science.gov (United States)

    Al Shboul, A; Trudeau, C; Cloutier, S; Siaj, M; Claverie, J P

    2017-07-20

    Graphene inks are becoming widely popular. However the vast majority of these inks are formulated in polar solvents with high-boiling points. Their slow evaporation is a bottleneck factor in roll-to-roll printing processes. Here, we developed a highly-conductive fast-drying graphene ink in isooctane, a non-polar and low-boiling solvent. For this purpose, a diblock copolymer containing pendant cholesterol groups was used during the exfoliation of natural graphite in isooctane. The polymer develops non-covalent supramolecular interactions with the graphene conjugated system, resulting in the formation of stable graphene dispersions (up to c = 4 mg mL(-1)). These dispersions were used for direct writing on a variety of substrates, and were shown to dry instantly after application. The influence of polymer concentration on graphene characteristics, on colloidal stability and on electrochemical characteristics has been studied. The lowest sheet resistance (80 Ω □(-1)) was obtained when 23% of the graphene surface was covered by the polymer. In this case, the flakes were constituted of 2-5 graphene layers. More extensive exfoliation, down to single-layer graphene, was achieved at greater surface coverage, but led to inks with higher sheet resistance. Thus, by combining a tailored polymeric dispersant, a smooth exfoliation process and a low-boiling non-polar ink solvent, we were able to prepare highly-conductive fast-drying graphene inks which should have a high potentital for the development of roll-to-roll printed electronics.

  11. Investigation of growth rate dispersion in lactose crystallisation by AFM

    Science.gov (United States)

    Dincer, T. D.; Ogden, M. I.; Parkinson, G. M.

    2014-09-01

    α-Lactose monohydrate crystals have been reported to exhibit growth rate dispersion (GRD). Variation in surface dislocations has been suggested as the cause of GRD, but this has not been further investigated to date. In this study, growth rate dispersion and the change in morphology were investigated in situ and via bottle roller experiments. The surfaces of the (0 1 0) faces of crystals were examined with Atomic Force Microscopy. Smaller, slow growing crystals tend to have smaller (0 1 0) faces with narrow bases and displayed a single double spiral in the centre of the crystal with 2 nm high steps. Additional double spirals in other crystals resulted in faster growth rates. Large, fast growing crystals were observed to have larger (0 1 0) faces with fast growth in both the a and b directions (giving a broader crystal base) with macro steps parallel to the (c direction). The number and location of spirals or existence of macro steps appears to influence the crystal morphology, growth rates and growth rate dispersion in lactose crystals.

  12. Communication, Technology, Temporality

    Directory of Open Access Journals (Sweden)

    Mark A. Martinez

    2012-08-01

    Full Text Available This paper proposes a media studies that foregrounds technological objects as communicative and historical agents. Specifically, I take the digital computer as a powerful catalyst of crises in communication theories and certain key features of modernity. Finally, the computer is the motor of “New Media” which is at once a set of technologies, a historical epoch, and a field of knowledge. As such the computer shapes “the new” and “the future” as History pushes its origins further in the past and its convergent quality pushes its future as a predominate medium. As treatment of information and interface suggest, communication theories observe computers, and technologies generally, for the mediated languages they either afford or foreclose to us. My project describes the figures information and interface for the different ways they can be thought of as aspects of communication. I treat information not as semantic meaning, formal or discursive language, but rather as a physical organism. Similarly an interface is not a relationship between a screen and a human visual intelligence, but is instead a reciprocal, affective and physical process of contact. I illustrate that historically there have been conceptions of information and interface complimentary to mine, fleeting as they have been in the face of a dominant temporality of mediation. I begin with a theoretically informed approach to media history, and extend it to a new theory of communication. In doing so I discuss a model of time common to popular, scientific, and critical conceptions of media technologies especially in theories of computer technology. This is a predominate model with particular rules of temporal change and causality for thinking about mediation, and limits the conditions of possibility for knowledge production about communication. I suggest a new model of time as integral to any event of observation and analysis, and that human mediation does not exhaust the

  13. Dispersive MHD waves and alfvenons in charge non-neutral plasmas

    Directory of Open Access Journals (Sweden)

    K. Stasiewicz

    2008-08-01

    Full Text Available Dispersive properties of linear and nonlinear MHD waves, including shear, kinetic, electron inertial Alfvén, and slow and fast magnetosonic waves are analyzed using both analytical expansions and a novel technique of dispersion diagrams. The analysis is extended to explicitly include space charge effects in non-neutral plasmas. Nonlinear soliton solutions, here called alfvenons, are found to represent either convergent or divergent electric field structures with electric potentials and spatial dimensions similar to those observed by satellites in auroral regions. Similar solitary structures are postulated to be created in the solar corona, where fast alfvenons can provide acceleration of electrons to hundreds of keV during flares. Slow alfvenons driven by chromospheric convection produce positive potentials that can account for the acceleration of solar wind ions to 300–800 km/s. New results are discussed in the context of observations and other theoretical models for nonlinear Alfvén waves in space plasmas.

  14. Evolution of Modulated Dispersive Electron Waves in a Plasma

    DEFF Research Database (Denmark)

    Sugai, H.; Lynov, Jens-Peter; Michelsen, Poul

    1979-01-01

    The linear propagation of amplitude-modulated electron waves was examined in a low-density Q-machine plasma. Three effects of the strong dispersion on the modulated wave have been demonstrated: (i) a wavepacket expands along its direction of propagation, followed by a shift of the frequency through...... the wavepacket, (ii) the number of oscillations in the temporally observed packet is not identical with that in the spatially observed packet and (iii) continuously modulated waves exhibit recurrence of modulation. The experimental results agree with both a simple analysis based on the Schrodinger equation...

  15. The spatio-temporal dynamics of neutral genetic diversity

    OpenAIRE

    Bonnefon, Olivier; Coville, Jérôme; Garnier, Jimmy; Hamel, François; Roques, Lionel

    2014-01-01

    International audience; The notions of pulled and pushed solutions of reaction-dispersal equations introduced by Garnier et al. (2012) and Roques et al. (2012) are based on a decomposition of the solutions into several components. In the framework of population dynamics, this decomposition is related to the spatio-temporal evolution of the genetic structure of a population. The pulled solutions describe a rapid erosion of neutral genetic diversity, while the pushed solutions are associated wi...

  16. Retrieval of dispersive and convective transport phenomena in fluids using stationary and nonstationary time domain analysis

    Science.gov (United States)

    Stephens, J. B.; St.john, R. M.

    1973-01-01

    Simultaneously occuring dispersive and convective components of fluid kinematics are obtained by a time domain analysis of optically retrieved temporal histories of the transport phenomena. Utilizing triangulation of collimated optical fields of view from two radiometers to obtain the temporal histories of the intensity fluctuations associated with the transport phenomena has enabled investigators to retrieve the local convective transport by employing correlation statistics. The location of the peak in the covariance curve determines the transit time from which the convection velocity is calculated; whereas, the change in shape of the peak in the covariance curve determines the change in average frequency of the wave packet from which the dispersion velocity is calculated. Thus, two-component analysis requires the maximum possible enhancement of the delineation for the transport. The convection velocity is the result of a fixed reference frame calculation whereas, the dispersion velocity is the result of a moving reference frame calcuation.

  17. Slow contractions characterize failing rat hearts.

    Science.gov (United States)

    Bøkenes, Janny; Aronsen, Jan Magnus; Birkeland, Jon Arne; Henriksen, Unni Lie; Louch, William E; Sjaastad, Ivar; Sejersted, Ole M

    2008-07-01

    The reduced power of the failing heart can be ascribed to a combination of reduced force and slower contraction. We hypothesized that these two properties are due to different cellular mechanisms. We measured contraction parameters both in vivo and in isolated left ventricular (LV) cardiomyocytes from a rat model of post infarction congestive heart failure (CHF). ECG was measured simultaneously with echocardiography and LV pressure, respectively. Shortening and shortening velocity (SV) in isolated cardiomyocytes were measured during different stimulation protocols. LV end diastolic pressure (LVEDP) was 24.6 +/- 0.7 mmHg in CHF. LV systolic pressure was decreased by 20%, maximum rate of pressure development in the LV (+dP/dtmax) by 36% and time in systole increased by 20% in CHF compared to sham. Electrical remodelling occurred in CHF cells, which were depolarized and had prolonged action potentials (AP) compared to sham cells. Fractional shortening (FS) was increased in CHF compared to sham independent of stimulation protocol. Larger FS was accompanied by increased sarcoplasmic reticulum (SR) Ca2+ load and depended on the electrical remodelling. Time to peak contraction (TTP) was increased in CHF compared to sham cells, but in contrast to FS, TTP was only slightly affected when the cells were stimulated with sham APs and sham diastolic membrane potential (DMP). Contraction duration (corresponding to systolic duration) was 25% longer in CHF than in sham independent on stimulation protocol. We conclude that electrical remodelling affecting DMP and AP duration (APD) significantly affects the size of contraction, whereas the mechanism for slowing of contraction in CHF is different.

  18. Rapid identification of slow healing wounds.

    Science.gov (United States)

    Jung, Kenneth; Covington, Scott; Sen, Chandan K; Januszyk, Michael; Kirsner, Robert S; Gurtner, Geoffrey C; Shah, Nigam H

    2016-01-01

    Chronic nonhealing wounds have a prevalence of 2% in the United States, and cost an estimated $50 billion annually. Accurate stratification of wounds for risk of slow healing may help guide treatment and referral decisions. We have applied modern machine learning methods and feature engineering to develop a predictive model for delayed wound healing that uses information collected during routine care in outpatient wound care centers. Patient and wound data was collected at 68 outpatient wound care centers operated by Healogics Inc. in 26 states between 2009 and 2013. The dataset included basic demographic information on 59,953 patients, as well as both quantitative and categorical information on 180,696 wounds. Wounds were split into training and test sets by randomly assigning patients to training and test sets. Wounds were considered delayed with respect to healing time if they took more than 15 weeks to heal after presentation at a wound care center. Eleven percent of wounds in this dataset met this criterion. Prognostic models were developed on training data available in the first week of care to predict delayed healing wounds. A held out subset of the training set was used for model selection, and the final model was evaluated on the test set to evaluate discriminative power and calibration. The model achieved an area under the curve of 0.842 (95% confidence interval 0.834-0.847) for the delayed healing outcome and a Brier reliability score of 0.00018. Early, accurate prediction of delayed healing wounds can improve patient care by allowing clinicians to increase the aggressiveness of intervention in patients most at risk. © 2015 by the Wound Healing Society.

  19. Dispersion-Enhanced Laser Gyroscope

    Science.gov (United States)

    Smith, David D.; Chang, Hongrok; Arissian, L.; Diels, J. C.

    2008-01-01

    We analyze the effect of a highly dispersive element placed inside a modulated optical cavity on the frequency and amplitude of the output modulation to determine the conditions for enhanced gyroscopic sensitivities. The element is treated as both a phase and amplitude filter, and the time-dependence of the cavity field is considered. Both atomic gases (two-level and multi-level) and optical resonators (single and coupled) are considered and compared as dispersive elements. We find that it is possible to simultaneously enhance the gyro scale factor sensitivity and suppress the dead band by using an element with anomalous dispersion that has greater loss at the carrier frequency than at the side-band frequencies, i.e., an element that simultaneously pushes and intensifies the perturbed cavity modes, e.g. a two-level absorber or an under-coupled optical resonator. The sensitivity enhancement is inversely proportional to the effective group index, becoming infinite at a group index of zero. However, the number of round trips required to reach a steady-state also becomes infinite when the group index is zero (or two). For even larger dispersions a steady-state cannot be achieved, and nonlinear dynamic effects such as bistability and periodic oscillations are predicted in the gyro response.

  20. DIMO, a plant dispersal model

    NARCIS (Netherlands)

    Wamelink, G.W.W.; Jochem, R.; Greft, van der J.G.M.; Franke, J.; Malinowska, A.H.; Geertsema, W.; Prins, A.H.; Ozinga, W.A.; Hoek, van der D.C.J.; Grashof-Bokdam, C.J.

    2014-01-01

    Due to human activities many natural habitats have become isolated. As a result the dispersal of many plant species is hampered. Isolated populations may become extinct and have a lower probability to become reestablished in a natural way. Moreover, plant species may be forced to migrate to new

  1. Creep in dispersion strengthened aluminium

    Energy Technology Data Exchange (ETDEWEB)

    Orlova, A.; Kucharova, K.; Cadek, J.; Besterci, M.; Slesar, M.

    1986-01-01

    Results of an investigation of creep at 623 and 723 K in two DISPAL type dispersion strengthened aluminium alloys containing nominal concentrations of 2.5 and 10 vol. pct of dispersed Al4C3 and 2.1 and 3.8 vol. pct of Al2O3, respectively, are presented. The dispersoid particles 25-85 nm in diameter are situated predominantly in grain boundaries and to a less extent as clusters inside the grains. Steady state creep rate, which is strongly applied stress dependent, is most probably controlled by lattice diffusion. A threshold stress characterizing the creep can be identified with the Orowan bowing stress for lattice dislocations. It is shown that creep can be described in terms of lattice diffusion controlled climb of Orowan dislocation loops around dispersed particles. A comparison with creep behavior of dispersion strengthened alloys SAP and NOVAMET shows better resistance of DISPAL as compared to these alloys though its creep ductility is relatively low. 27 references.

  2. Chameleon radiation by oceanic dispersal.

    Science.gov (United States)

    Raxworthy, C J; Forstner, M R J; Nussbaum, R A

    2002-02-14

    Historical biogeography is dominated by vicariance methods that search for a congruent pattern of fragmentation of ancestral distributions produced by shared Earth history. A focus of vicariant studies has been austral area relationships and the break-up of the supercontinent Gondwana. Chameleons are one of the few extant terrestrial vertebrates thought to have biogeographic patterns that are congruent with the Gondwanan break-up of Madagascar and Africa. Here we show, using molecular and morphological evidence for 52 chameleon taxa, support for a phylogeny and area cladogram that does not fit a simple vicariant history. Oceanic dispersal--not Gondwanan break-up--facilitated species radiation, and the most parsimonious biogeographic hypothesis supports a Madagascan origin for chameleons, with multiple 'out-of-Madagascar' dispersal events to Africa, the Seychelles, the Comoros archipelago, and possibly Reunion Island. Although dispersal is evident in other Indian Ocean terrestrial animal groups, our study finds substantial out-of-Madagascar species radiation, and further highlights the importance of oceanic dispersal as a potential precursor for speciation.

  3. Dispersed publication of editorial research

    DEFF Research Database (Denmark)

    Rosenberg, Jacob; Pommergaard, Hans-Christian; Vinther, Siri

    2015-01-01

    journals with a median of one article per journal (range: 1-17). CONCLUSION: The publication of papers on editorial research seems to be dispersed. In order to increase the visibility of this research field, it may be reasonable to establish well-defined platforms such as dedicated journals or journal...

  4. Magnetic exciton dispersion in praseodymium

    DEFF Research Database (Denmark)

    Rainford, B. D.; Houmann, Jens Christian Gylden

    1971-01-01

    Measurements of the dispersion of magnetic excitons have been made in a single crystal of praseodymium metal using inelastic neutron scattering. A preliminary analysis of the data yields the first detailed information about the exchange interactions and the crystal field splittings in the light...

  5. On Dispersion in Visual Photoreceptors

    NARCIS (Netherlands)

    Stavenga, D.G.; Barneveld, H.H. van

    1975-01-01

    An idealized visual pigment absorbance spectrum is used together with a Kramers-Kronig dispersion relation to calculate the contribution of the visual pigment to the refractive index of the fly photoreceptor. It appears that an absorption coefficient of 0.010 µm-1 results in a refractive index

  6. Coupling constant in dispersive model

    Indian Academy of Sciences (India)

    perturbative theory using the dispersive model. By fitting the experimental data, the values of ( M Z ° ) = 0.1171 ± 0.00229 and 0 ( I = 2 GeV ) = 0.5068 ± 0.0440 are found. Our results are consistent with the above model. Our results are also ...

  7. Multiscale temporal integrators for fluctuating hydrodynamics

    Science.gov (United States)

    Delong, Steven; Sun, Yifei; Griffith, Boyce E.; Vanden-Eijnden, Eric; Donev, Aleksandar

    2014-12-01

    Following on our previous work [S. Delong, B. E. Griffith, E. Vanden-Eijnden, and A. Donev, Phys. Rev. E 87, 033302 (2013), 10.1103/PhysRevE.87.033302], we develop temporal integrators for solving Langevin stochastic differential equations that arise in fluctuating hydrodynamics. Our simple predictor-corrector schemes add fluctuations to standard second-order deterministic solvers in a way that maintains second-order weak accuracy for linearized fluctuating hydrodynamics. We construct a general class of schemes and recommend two specific schemes: an explicit midpoint method and an implicit trapezoidal method. We also construct predictor-corrector methods for integrating the overdamped limit of systems of equations with a fast and slow variable in the limit of infinite separation of the fast and slow time scales. We propose using random finite differences to approximate some of the stochastic drift terms that arise because of the kinetic multiplicative noise in the limiting dynamics. We illustrate our integrators on two applications involving the development of giant nonequilibrium concentration fluctuations in diffusively mixing fluids. We first study the development of giant fluctuations in recent experiments performed in microgravity using an overdamped integrator. We then include the effects of gravity and find that we also need to include the effects of fluid inertia, which affects the dynamics of the concentration fluctuations greatly at small wave numbers.

  8. The Temporal Tipping Point

    DEFF Research Database (Denmark)

    Hermann, A. K.

    2016-01-01

    and analyses of their journalistic works, this paper offers a study of ethnographic journalism suggesting that slow time operates in at least three separate registers. First, in terms of regimentation, ethnographic journalism is mostly long-form pieces that demand time-consuming research and careful writing...... and editing. Second, in terms of representation, practitioners report on the quotidian rather than urgent events. Third, deceleration is an essential tool for acquiring an insider's perspective. Ethnographic journalists describe a point during reporting at which their attitudes begin to change and they start...

  9. Surface Wave Dispersion Measurements and Tomography from Ambient Seismic Noise Correlation in China

    Science.gov (United States)

    2010-03-15

    dispersion maps .......................................................... 8 7. S velocities of our model at the depth of CRUST 2.0 Moho ...The 3D model shows some remarkable features, including slow sedimentary layers of all the major basins in China at the shallow depth, Moho depth...strong blocks thus seem to play an important role in confining the deformation of the TP to be a triangular shape. The Moho change from plateau to the

  10. Physicochemical considerations in the preparation of amorphous ritonavir-poly(ethylene glycol) 8000 solid dispersions.

    Science.gov (United States)

    Law, D; Krill, S L; Schmitt, E A; Fort, J J; Qiu, Y; Wang, W; Porter, W R

    2001-08-01

    A systematic study of the properties of ritonavir and the influence of polyethylene glycol 8000 (PEG) on ritonavir revealed that amorphous ritonavir dispersions in PEG would have an improved dissolution profile and could exhibit long-term stability. Ritonavir, a human immunodeficiency virus (HIV) protease inhibitor, is highly lipophilic [distribution coefficient (log D)= 4.3, 25 degrees C, pH 6.8], poorly water soluble (400 microg/mL in 0.1 N HCl, 1 microg/mL at pH 6.8, 37 degrees C), and exhibits an exceedingly slow dissolution rate (0.03 mg/cm(2)-min in 0.1 N HCl at 37 degrees C). These properties indicated that a solid dispersion containing ritonavir might be useful for overcoming problems associated with slow dissolution. In addition, ritonavir is a good glass former [glass-transition temperature (T(g))/melting point (T(m)) > 0.7]. Amorphous ritonavir has an apparent solubility of 4 mg/mL in 0.1 N HCl at 37 degrees C and shows reasonable stability at 25 degrees C. Amorphous ritonavir, therefore, has properties desirable for preparing a solid dispersion containing this phase. Since PEG, a commonly used polymer, improved the aqueous solubility of crystalline ritonavir, it was expected to have a positive influence on the dissolution rate of ritonavir. Moreover, PEG was found to have negligible plasticizing effect on amorphous ritonavir, which was beneficial for the stability of the dispersion. Finally, solid dispersions of amorphous ritonavir in PEG were prepared, and these dispersions had improved in vitro dissolution rate and were physically stable for > 1.5 years at 25 degrees C when protected from moisture. The performance of this solid dispersion has been attributed to the physicochemical properties of amorphous ritonavir. Copyright 2001 Wiley-Liss, Inc.

  11. Electrostatic Stabilization of Graphene in Organic Dispersions.

    Science.gov (United States)

    Rodgers, Andrew N J; Velický, Matěj; Dryfe, Robert A W

    2015-12-08

    The exfoliation of graphite to give graphene dispersions in nonaqueous solvents is an important area with regards to scalable production of graphene in bulk quantities and its ultimate application in devices. Understanding the mechanisms governing the stability of these dispersions is therefore of both scientific interest and technological importance. Herein, we have used addition of an indifferent electrolyte to perturb few-layer graphene dispersions in a nonaqueous solvent (1,2-dichloroethane) as a way to probe the importance of interparticle electrostatic repulsions toward the overall dispersion stability. At a sufficient electrolyte concentration, complete sedimentation of the dispersions occurred over 24 h, and the relationship between dispersed graphene concentration and electrolyte concentration was consistent with a dispersion stabilized by electrostatic repulsions. We also found that an increased oxygen content in the graphite starting material produced dispersions of greater stability, indicating that the extent of oxidation is an important parameter in determining the extent of electrostatic stabilization in nonaqueous graphene dispersions.

  12. Different neural manifestations of two slow frequency bands in resting functional magnetic resonance imaging: a systemic survey at regional, interregional, and network levels.

    Science.gov (United States)

    Xue, Shao-Wei; Li, Da; Weng, Xu-Chu; Northoff, Georg; Li, Dian-Wen

    2014-05-01

    Temporal and spectral perspectives are two fundamental facets in deciphering fluctuating signals. In resting state, the dynamics of blood oxygen level-dependent (BOLD) signals recorded by functional magnetic resonance imaging (fMRI) have been proven to be strikingly informative (0.01-0.1 Hz). The distinction between slow-4 (0.027-0.073 Hz) and slow-5 (0.01-0.027 Hz) has been described, but the pertinent data have never been systematically investigated. This study used fMRI to measure spontaneous brain activity and to explore the different spectral characteristics of slow-4 and slow-5 at regional, interregional, and network levels, respectively assessed by regional homogeneity (ReHo) and mean amplitude of low-frequency fluctuation (mALFF), functional connectivity (FC) patterns, and graph theory. Results of paired t-tests supported/replicated recent research dividing low-frequency BOLD fluctuation into slow-4 and slow-5 for ReHo and mALFF. Interregional analyses showed that for brain regions reaching statistical significance, FC strengths at slow-4 were always weaker than those at slow-5. Community detection algorithm was applied to FC data and unveiled two modules sensitive to frequency effects: one comprised sensorimotor structure, and the other encompassed limbic/paralimbic system. Graph theoretical analysis verified that slow-4 and slow-5 differed in local segregation measures. Although the manifestation of frequency differences seemed complicated, the associated brain regions can be grossly categorized into limbic/paralimbic, midline, and sensorimotor systems. Our results suggest that future resting fMRI research addressing the three above systems either from neuropsychiatric or psychological perspectives may consider using spectrum-specific analytical strategies.

  13. Slow Light at High Frequencies in an Amplifying Semiconductor Waveguide

    DEFF Research Database (Denmark)

    Öhman, Filip; Yvind, Kresten; Mørk, Jesper

    2006-01-01

    We demonstrate slow-down of a modulated light signal in a semiconductor waveguide. Concatenated amplifying and absorbing sections simultaneously achieve both amplification and a controllable time delay at 15 GHz.......We demonstrate slow-down of a modulated light signal in a semiconductor waveguide. Concatenated amplifying and absorbing sections simultaneously achieve both amplification and a controllable time delay at 15 GHz....

  14. Dynamics of slow and fast systems on complex networks

    Indian Academy of Sciences (India)

    .35(green), 0.5(blue). Region 2, where = 0 corre- sponds to AD. are coupled to form the network, the emergent frequency may depend also on the number of slow systems m. ... slow (red) systems, while fast (green) systems show large.

  15. hippocampal slow rhythms in ongoing behaviour and during

    African Journals Online (AJOL)

    1971-02-06

    Feb 6, 1971 ... HIPPOCAMPAL SLOW RHYTHMS IN ONGOING BEHAVIOUR AND DURING CLASSICAL. CONDITIONING*. R. C. ALBINO AND K. CAIGER, Psychology Department, University of Natal, Durban. Experiments on the relationships between hippocampal slow (or theta) rhythms and phases of approach ...

  16. EDUCATION FOR THE SLOW LEARNERS. PRENTICE-HALL PSYCHOLOGY SERIES.

    Science.gov (United States)

    JOHNSON, G. ORVILLE

    THIS VOLUME IS DESIGNED TO DEFINE, FROM AN EDUCATIONAL POINT OF VIEW, THE PROBLEM POSED BY SLOW LEARNERS. IT PRESENTS THE CLINICAL EDUCATION APPROACH AS A TOOL IN THE PLANNING OF SOLUTIONS RELATING TO THE FUNDAMENTAL PROBLEM OF PROVIDING AN APPROPRIATE SCHOOL EXPERIENCE FOR THE SLOW LEARNER THROUGH CURRICULUM PLANNING. PART ONE FOCUSES ON THE…

  17. METHODS AND PSYCHOLOGY OF TEACHING THE SLOW LEARNER.

    Science.gov (United States)

    MARTIN, RUTH; MARTIN, WILLIAM

    THE SPECIAL PSYCHOLOGICAL AND EDUCATIONAL NEEDS OF THE SLOW LEARNER ARE EMPHASIZED IN THIS PUBLIC SCHOOL CURRICULUM GUIDE. FOR THIS TYPE OF STUDENT MORE FOCUS MUST BE PLACED ON PERSONALITY DEVELOPMENT AND ADEQUACY IN BASIC SKILLS THAN ON ACADEMIC ACHIEVEMENT. THEREFORE THE OBJECTIVES OF A "BASIC WORK PROGRAM" FOR SLOW LEARNERS SHOULD STRESS THE…

  18. Role Distance of Classroom Teachers of Slow Learners

    Science.gov (United States)

    Khleif, Bud B.

    1976-01-01

    Study suggests that teachers judge pupils in terms of an ideal, a student with average or above-average aptitude. Hostile attitudes toward slow learners may be a result of this expectation, rather than indication of personality, with role distance being a particular adjustment made by untrained teachers of slow learners. (RW)

  19. A MODEL VOCATIONAL EDUCATION PROGRAM FOR THE SLOW LEARNER.

    Science.gov (United States)

    KITZMILLER, RICHARD L.

    THE TERM "SLOW LEARNER" IS USED IN THIS REPORT TO DESIGNATE THE 18 TO 20 PERCENT OF SCHOOL CHILDREN WHO MEASURE APPROXIMATELY 50 TO 89 IQ ON INDIVIDUAL INTELLIGENCE TESTS. THE PURPOSES OF THE PROJECT WERE TO IDENTIFY AREAS OF VOCATIONAL OPPORTUNITY BEST SUITED TO THE ABILITIES AND INTERESTS OF THE SLOW LEARNER, ADOPT CRITERIA FOR OPTIMUM…

  20. Damping of Slow Magnetoacoustic Waves in an Inhomogeneous ...

    Indian Academy of Sciences (India)

    Abstract. We study the propagation and dissipation of slow magneto- acoustic waves in an inhomogeneous viscous coronal loop plasma permeated by uniform magnetic field. Only viscosity and thermal con- ductivity are taken into account as dissipative processes in the coronal loop. The damping length of slow-mode ...

  1. Experimental determination of the slow-neutron wavelength distribution

    DEFF Research Database (Denmark)

    Lebech, Bente; Mikke, K.; Sledziewska-Blocka, D.

    1970-01-01

    Different experiments for determining the slow-neutron wavelength distribution in the region 227-3 meV have been carried out, and the results compared. It is concluded that the slow-neutron wave-length distribution can be determined accurately by elastic scattering on a pure incoherent or a pure...

  2. ADHD and temporality

    DEFF Research Database (Denmark)

    Nielsen, Mikka

    According to the official diagnostic manual, ADHD is defined by symptoms of inattention, hyperactivity, and impulsivity and patterns of behaviour are characterized as failure to pay attention to details, excessive talking, fidgeting, or inability to remain seated in appropriate situations (DSM-5......). In this paper, however, I will ask if we can understand what we call ADHD in a different way than through the symptom descriptions and will advocate for a complementary, phenomenological understanding of ADHD as a certain being in the world – more specifically as a matter of a phenomenological difference...... in temporal experience and/or rhythm. Inspired by both psychiatry’s experiments with people diagnosed with ADHD and their assessment of time and phenomenological perspectives on mental disorders and temporal disorientation I explore the experience of ADHD as a disruption in the phenomenological experience...

  3. Temporal lobe epilepsy semiology.

    Science.gov (United States)

    Blair, Robert D G

    2012-01-01

    Epilepsy represents a multifaceted group of disorders divided into two broad categories, partial and generalized, based on the seizure onset zone. The identification of the neuroanatomic site of seizure onset depends on delineation of seizure semiology by a careful history together with video-EEG, and a variety of neuroimaging technologies such as MRI, fMRI, FDG-PET, MEG, or invasive intracranial EEG recording. Temporal lobe epilepsy (TLE) is the commonest form of focal epilepsy and represents almost 2/3 of cases of intractable epilepsy managed surgically. A history of febrile seizures (especially complex febrile seizures) is common in TLE and is frequently associated with mesial temporal sclerosis (the commonest form of TLE). Seizure auras occur in many TLE patients and often exhibit features that are relatively specific for TLE but few are of lateralizing value. Automatisms, however, often have lateralizing significance. Careful study of seizure semiology remains invaluable in addressing the search for the seizure onset zone.

  4. Dispersion modeling by kinematic simulation: Cloud dispersion model

    Energy Technology Data Exchange (ETDEWEB)

    Fung, J C H [Department of Mathematics, Hong Kong University of Science and Technology, Clear Water Bay (Hong Kong); Perkins, R J [Laboratoire de Mecanique des Fluides et d' Acoustique, Ecole Centrale de Lyon (France)], E-mail: majfung@ust.hk

    2008-04-30

    A new technique has been developed to compute mean and fluctuating concentrations in complex turbulent flows (tidal current near a coast and deep ocean). An initial distribution of material is discretized into any small clouds which are advected by a combination of the mean flow and large scale turbulence. The turbulence can be simulated either by kinematic simulation (KS) or direct numerical simulation. The clouds also diffuse relative to their centroids; the statistics for this are obtained from a separate calculation of the growth of individual clouds in small scale turbulence, generated by KS. The ensemble of discrete clouds is periodically re-discretized, to limit the size of the small clouds and prevent overlapping. The model is illustrated with simulations of dispersion in uniform flow, and the results are compared with analytic, steady state solutions. The aim of this study is to understand how pollutants disperses in a turbulent flow through a numerical simulation of fluid particle motion in a random flow field generated by Fourier modes. Although this homogeneous turbulent is rather a 'simple' flow, it represents a building block toward understanding pollutant dispersion in more complex flow. The results presented here are preliminary in nature, but we expect that similar qualitative results should be observed in a genuine turbulent flow.

  5. Slow dynamics perspectives on the Embodied-Brain Systems Science.

    Science.gov (United States)

    Yano, Shiro; Maeda, Takaki; Kondo, Toshiyuki

    2016-03-01

    Recent researches point out the importance of the fast-slow cognitive process and learning process of self-body. Bayesian perspectives on the cognitive system also attract research attentions. The view of fast-slow dynamical system has long attracted wide range of attentions from physics to the neurobiology. In many research fields, there is a vast well-organized and coherent behavior in the multi degrees-of-freedom. This behavior matches the mathematical fact that fast-slow system is essentially described with a few variables. In this paper, we review the mathematical basis for understanding the fast-slow dynamical systems. Additionally, we review the basis of Bayesian statistics and provide a fast-slow perspective on the Bayesian inference. Copyright © 2015 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

  6. Involvement of cytokines in slow wave sleep.

    Science.gov (United States)

    Krueger, James M; Clinton, James M; Winters, Bradley D; Zielinski, Mark R; Taishi, Ping; Jewett, Kathryn A; Davis, Christopher J

    2011-01-01

    Cytokines such as tumor necrosis factor alpha (TNFα) and interleukin-1 beta (IL1β) play a role in sleep regulation in health and disease. TNFα or IL1β injection enhances non-rapid eye movement sleep. Inhibition of TNFα or IL1β reduces spontaneous sleep. Mice lacking TNFα or IL1β receptors sleep less. In normal humans and in multiple disease states, plasma levels of TNFα covary with EEG slow wave activity (SWA) and sleep propensity. Many of the symptoms induced by sleep loss, for example, sleepiness, fatigue, poor cognition, enhanced sensitivity to pain, are elicited by injection of exogenous TNFα or IL1β. IL1β or TNFα applied unilaterally to the surface of the cortex induces state-dependent enhancement of EEG SWA ipsilaterally, suggesting greater regional sleep intensity. Interventions such as unilateral somatosensory stimulation enhance localized sleep EEG SWA, blood flow, and somatosensory cortical expression of IL1β and TNFα. State oscillations occur within cortical columns. One such state shares properties with whole animal sleep in that it is dependent on prior cellular activity, shows homeostasis, and is induced by TNFα. Extracellular ATP released during neuro- and gliotransmission enhances cytokine release via purine type 2 receptors. An ATP agonist enhances sleep, while ATP antagonists inhibit sleep. Mice lacking the P2X7 receptor have attenuated sleep rebound responses after sleep loss. TNFα and IL1β alter neuron sensitivity by changing neuromodulator/neurotransmitter receptor expression, allowing the neuron to scale its activity to the presynaptic neurons. TNFα's role in synaptic scaling is well characterized. Because the sensitivity of the postsynaptic neuron is changed, the same input will result in a different network output signal and this is a state change. The top-down paradigm of sleep regulation requires intentional action from sleep/wake regulatory brain circuits to initiate whole-organism sleep. This raises unresolved

  7. Dispersity in Polymer Science (IUPAC Recommendations 2009

    Directory of Open Access Journals (Sweden)

    Translated by Rogošić, M.

    2012-05-01

    Full Text Available This recommendation defines just three terms, viz., (1 molar-mass dispersity, relative-molecu- lar-mass dispersity, or molecular-weight dispersity; (2 degree-of-polymerization dispersity; and (3 dispersity. “Dispersity” is a new word, coined to replace the misleading, but widely used term “polydispersity index” for Mw / Mn and Xw/ Xn. The document, although brief, also has a broader significance in that it seeks to put the terminology describing dispersions of distributions of properties of polymeric (and non-polymeric materials on an unambiguous and justifiable footing.

  8. Nanocomposites from Stable Dispersions of Carbon Nanotubes in Polymeric Matrices Using Dispersion Interaction

    Science.gov (United States)

    Wise, Kristopher Eric (Inventor); Park, Cheol (Inventor); Kang, Jin Ho (Inventor); Siochi, Emilie J. (Inventor); Harrison, Joycelyn S. (Inventor)

    2016-01-01

    Stable dispersions of carbon nanotubes (CNTs) in polymeric matrices include CNTs dispersed in a host polymer or copolymer whose monomers have delocalized electron orbitals, so that a dispersion interaction results between the host polymer or copolymer and the CNTs dispersed therein. Nanocomposite products, which are presented in bulk, or when fabricated as a film, fiber, foam, coating, adhesive, paste, or molding, are prepared by standard means from the present stable dispersions of CNTs in polymeric matrices, employing dispersion interactions, as presented hereinabove.

  9. Enhancement of sleep slow waves: underlying mechanisms and practical consequences.

    Directory of Open Access Journals (Sweden)

    Michele eBellesi

    2014-10-01

    Full Text Available Even modest sleep restriction, especially the loss of sleep slow wave activity, is invariably associated with slower EEG activity during wake, the occurrence of local sleep in an otherwise awake brain, and impaired performance due to cognitive and memory deficits. Recent studies not only confirm the beneficial role of sleep in memory consolidation, but also point to a specific role for sleep slow waves. Thus, the implementation of methods to enhance sleep slow waves without unwanted arousals or lightening of sleep could have significant practical implications. Here we first review the evidence that it is possible to enhance sleep slow waves in humans using transcranial direct-current stimulation and transcranial magnetic stimulation. Since these methods are currently impractical and their safety is questionable, especially for chronic long-term exposure, we then discuss novel data suggesting that it is possible to enhance slow waves using sensory stimuli. We consider the physiology of the K-complex, a peripheral evoked slow wave, and show that, among different sensory modalities, acoustic stimulation is the most effective in increasing the magnitude of slow waves, likely through the activation of non-lemniscal ascending pathways to the thalamo-cortical system. In addition, we discuss how intensity and frequency of the acoustic stimuli, as well as exact timing and pattern of stimulation, affect sleep enhancement. Finally, we discuss automated algorithms that read the EEG and, in real-time, adjust the stimulation parameters in a closed-loop manner to obtain an increase in sleep slow waves and avoid undesirable arousals. In conclusion, while discussing the mechanisms that underlie the generation of sleep slow waves, we review the converging evidence showing that acoustic stimulation is safe and represents an ideal tool for slow wave sleep enhancement.

  10. Fragile Spectral and Temporal Auditory Processing in Adolescents with Autism Spectrum Disorder and Early Language Delay

    Science.gov (United States)

    Boets, Bart; Verhoeven, Judith; Wouters, Jan; Steyaert, Jean

    2015-01-01

    We investigated low-level auditory spectral and temporal processing in adolescents with autism spectrum disorder (ASD) and early language delay compared to matched typically developing controls. Auditory measures were designed to target right versus left auditory cortex processing (i.e. frequency discrimination and slow amplitude modulation (AM)…

  11. Unexpected diversity of slow lorises (Nycticebus spp.) within the Javan pet trade: implications for slow loris taxonomy

    NARCIS (Netherlands)

    Nekaris, K.A.I.; Jaffe, S.

    2007-01-01

    Since the 1950s, Sundaland (Borneo, Java, Sumatra and their surrounding islands) was thought to be inhabited by a single slow loris species, the greater slow loris Nycticebus coucang. Early taxonomies as well as recent morphological and genetic studies, however, point to at least three species

  12. Dispersive Readout of Adiabatic Phases

    Science.gov (United States)

    Kohler, Sigmund

    2017-11-01

    We propose a protocol for the measurement of adiabatic phases of periodically driven quantum systems coupled to an open cavity that enables dispersive readout. It turns out that the cavity transmission exhibits peaks at frequencies determined by a resonance condition that involves the dynamical and the geometric phase. Since these phases scale differently with the driving frequency, one can determine them by fitting the peak positions to the theoretically expected behavior. For the derivation of the resonance condition and for a numerical study, we develop a Floquet theory for the dispersive readout of ac driven quantum systems. The feasibility is demonstrated for two test cases that generalize Landau-Zener-Stückelberg-Majorana interference to two-parameter driving.

  13. Faraday anomalous dispersion optical tuners

    Science.gov (United States)

    Wanninger, P.; Valdez, E. C.; Shay, T. M.

    1992-01-01

    Common methods for frequency stabilizing diode lasers systems employ gratings, etalons, optical electric double feedback, atomic resonance, and a Faraday cell with low magnetic field. Our method, the Faraday Anomalous Dispersion Optical Transmitter (FADOT) laser locking, is much simpler than other schemes. The FADOT uses commercial laser diodes with no antireflection coatings, an atomic Faraday cell with a single polarizer, and an output coupler to form a compound cavity. This method is vibration insensitive, thermal expansion effects are minimal, and the system has a frequency pull in range of 443.2 GHz (9A). Our technique is based on the Faraday anomalous dispersion optical filter. This method has potential applications in optical communication, remote sensing, and pumping laser excited optical filters. We present the first theoretical model for the FADOT and compare the calculations to our experimental results.

  14. Sex-biased dispersal at different geographical scales in a cooperative breeder from fragmented rainforest.

    Directory of Open Access Journals (Sweden)

    Carl Vangestel

    Full Text Available Dispersal affects both social behavior and population structure and is therefore a key determinant of long-term population persistence. However, dispersal strategies and responses to spatial habitat alteration may differ between sexes. Here we analyzed spatial and temporal variation in ten polymorphic microsatellite DNA loci of male and female Cabanis's greenbuls (Phyllastrephuscabanisi, a cooperative breeder of Afrotropical rainforest, to quantify rates of gene flow and fine-grained genetic structuring within and among fragmented populations. We found genetic evidence for female-biased dispersal at small spatial scales, but not at the landscape level. Local autocorrelation analysis provided evidence of positive genetic structure within 300 m distance ranges, which is consistent with behavioral observations of short-distance natal dispersal. At a landscape scale, individual-based autocorrelation values decreased over time while levels of admixture increased, possibly indicating increased gene flow over the past decade.

  15. Dispersal of Plants by Waterbirds

    OpenAIRE

    Green, Andy J.; Soons, Merel B.; Brochet, Anne-Laure; Kleyheeg, Erik

    2016-01-01

    The widespread distribution of fresh-water plants and of the lower animals, whether retaining the same identical form or in some degree modified, I believe mainly depends on the wide dispersal of their seeds and eggs by animals, more especially by fresh-water birds, which have large powers of flight, and naturally travel from one to another and often distant piece of water. — Charles Darwin (1859)

  16. Hydrodynamic dispersion within porous biofilms

    KAUST Repository

    Davit, Y.

    2013-01-23

    Many microorganisms live within surface-associated consortia, termed biofilms, that can form intricate porous structures interspersed with a network of fluid channels. In such systems, transport phenomena, including flow and advection, regulate various aspects of cell behavior by controlling nutrient supply, evacuation of waste products, and permeation of antimicrobial agents. This study presents multiscale analysis of solute transport in these porous biofilms. We start our analysis with a channel-scale description of mass transport and use the method of volume averaging to derive a set of homogenized equations at the biofilm-scale in the case where the width of the channels is significantly smaller than the thickness of the biofilm. We show that solute transport may be described via two coupled partial differential equations or telegrapher\\'s equations for the averaged concentrations. These models are particularly relevant for chemicals, such as some antimicrobial agents, that penetrate cell clusters very slowly. In most cases, especially for nutrients, solute penetration is faster, and transport can be described via an advection-dispersion equation. In this simpler case, the effective diffusion is characterized by a second-order tensor whose components depend on (1) the topology of the channels\\' network; (2) the solute\\'s diffusion coefficients in the fluid and the cell clusters; (3) hydrodynamic dispersion effects; and (4) an additional dispersion term intrinsic to the two-phase configuration. Although solute transport in biofilms is commonly thought to be diffusion dominated, this analysis shows that hydrodynamic dispersion effects may significantly contribute to transport. © 2013 American Physical Society.

  17. Coupling constant in dispersive model

    Indian Academy of Sciences (India)

    Abstract. The average of the moments for event shapes in e+e− → hadrons within the con- text of next-to-leading order (NLO) perturbative QCD prediction in dispersive model is studied. Moments used in this article are 〈1 − T〉, 〈ρ〉, 〈BT〉 and 〈BW〉. We extract αs, the coupling con- stant in perturbative theory and α0 in the ...

  18. Faraday anomalous dispersion optical filters

    Science.gov (United States)

    Shay, T. M.; Yin, B.; Alvarez, L. S.

    1993-01-01

    The effect of Faraday anomalous dispersion optical filters on infrared and blue transitions of some alkali atoms is calculated. A composite system is designed to further increase the background noise rejection. The measured results of the solar background rejection and image quality through the filter are presented. The results show that the filter may provide high transmission and high background noise rejection with excellent image quality.

  19. Spatial and temporal variations of the high-altitude cusp precipitation

    Directory of Open Access Journals (Sweden)

    Z. Němeček

    2004-07-01

    Full Text Available Structured dispersion patterns of the ion precipitation in low- and mid-altitude cusp regions have been reported by many authors. These patterns are interpreted either as temporal features in terms of the pulsed reconnection model or as spatial changes caused by a combination of the particle velocity with the convection of magnetic field lines. It is generally expected that the spatial dispersion is predominantly observed in lower altitudes where the spacecraft crosses a wide range of geomagnetic coordinates in a short time, whereas the high-altitude spacecraft observes temporal changes because it stays nearly on the same field line for a long time. We have analyzed one pass of the INTERBALL-1/MAGION-4 satellite pair through the high-altitude cusp and found that both temporal and spatial dispersion effects are important even in the magnetopause vicinity. The analysis of the present event shows a spatial nature of the observed dispersion in the LLBL and in the plasma mantle. We have identified two sources of a mantle precipitation operating simultaneously. Our investigations suggest that besides already reported latitudinal dispersion, the longitudinal dispersion can be observed during intervals of sufficiently high east-west interplanetary magnetic field component.

  20. Slowing down the speed of light using an electromagnetically-induced-transparency mechanism in a modified reservoir

    Science.gov (United States)

    Liu, Ronggang; Liu, Tong; Wang, Yingying; Li, Yujie; Gai, Bingzheng

    2017-11-01

    We propose an effective method to achieve extremely slow light by using both the mechanism of electromagnetically induced transparency (EIT) and the localization of a coupled cavity waveguide (CCW). Based on quantum mechanics theory and the dispersion relation of a CCW, we derive a group-velocity formula that reveals both the effects of the EIT and CCW. Results show that ultralow light velocity at the order of several meters per second or even static light, could be obtained feasibly. In comparison with the EIT mechanism in a background of vacuum, this proposed method is more effective and realistic to achieve extremely slow light. And it exhibits potential values in the field of light storage.