Science.gov

Sample records for dynamics reflect influences

  1. Seasonal Dynamics of Hyperspectral Reflectance Patterns Influencing Detection of Imported Fire Ant (Hymenoptera: Formicidae) Mound Features in Turfgrass

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Invasive mound-building imported fire ants impact soil quality and turfgrass nutrient management affecting an estimated 8.1 million hectares in sod production, recreational, and residential settings in the southeastern U.S. Reflectance characteristics of imported fire ant mound features (i.e., ant m...

  2. Asymptotic dynamics of reflecting spiral waves.

    PubMed

    Langham, Jacob; Biktasheva, Irina; Barkley, Dwight

    2014-12-01

    Resonantly forced spiral waves in excitable media drift in straight-line paths, their rotation centers behaving as pointlike objects moving along trajectories with a constant velocity. Interaction with medium boundaries alters this velocity and may often result in a reflection of the drift trajectory. Such reflections have diverse characteristics and are known to be highly nonspecular in general. In this context we apply the theory of response functions, which via numerically computable integrals, reduces the reaction-diffusion equations governing the whole excitable medium to the dynamics of just the rotation center and rotation phase of a spiral wave. Spiral reflection trajectories are computed by this method for both small- and large-core spiral waves in the Barkley model. Such calculations provide insight into the process of reflection as well as explanations for differences in trajectories across parameters, including the effects of incidence angle and forcing amplitude. Qualitative aspects of these results are preserved far beyond the asymptotic limit of weak boundary effects and slow resonant drift. PMID:25615159

  3. Estimating the noise influence on recovering reflectances

    NASA Astrophysics Data System (ADS)

    Hironaga, Mikiya; Shimano, Noriyuki

    2010-01-01

    The evaluation of the noise present in the image acquisition system and the influence of the noise is essential to image acquisition. However the mean square errors (MSE) is not divided into two terms, i.e., the noise independent MSE (MSEfree) and noise dependent MSE (MSEnoise) were not discussed separately before. The MSEfree depends on the spectral characteristics of a set of sensors, illuminations and reflectances of imaged objects and the MSEfree arises in the noise free case, however MSEnoise originates from the noise present image acquisition system. One of the authors (N.S.) already proposed a model to separate the MSE into the two factors and also proposed a model to estimate noise variance present in image acquisition systems. By the use of this model, we succeeded in the expression of the MSEnoise as a function of the noise variance and showed that the experimental results agreed fairly well with the expression when the Wiener estimation was used for the recovery. The present paper shows the extended expression for the influence of the system noise on the MSEnoise and the experimental results to show the trustworthiness of the expression for the regression model, Imai-Berns model and finite dimensional linear model.

  4. Practitioners Influence Curriculum Theory: Autobiographical Reflections.

    ERIC Educational Resources Information Center

    Schubert, William H.

    1992-01-01

    Examines dimensions of theoretical perspective on curriculum, noting influences of teachers who were the author's graduate students. The article covers curriculum theorizing, synoptic and historical portrayals, comparative orientations, ideological considerations, teacher/student lore, outside curriculum, preservice/inservice teacher education…

  5. Self-Reflections on Group Dynamics

    ERIC Educational Resources Information Center

    Torosyan, Roben

    2008-01-01

    This article provides a first-person account of a training program in group dynamics. It is deliberately written in the first-person to capture the highly personal nature of group dynamic analysis. Proceeding through an intensive account of six days of T-groups, module facilitation, and facilitator feedback sessions, the author examines painful…

  6. The Influence of Particle Size on Infrared Reflectance Spectra

    SciTech Connect

    Myers, Tanya L.; Brauer, Carolyn S.; Su, Yin-Fong; Blake, Thomas A.; Johnson, Timothy J.; Richardson, Robert L.

    2014-06-13

    Reflectance spectra of solids are influenced by the absorption coefficient as well as the particle size and morphology. In the infrared, spectral features may be observed as either maxima or minima: in general, the upward-going peaks in the reflectance spectrum result from surface scattering, which are rays that have reflected from the surface without penetration, whereas downward-going peaks result from either absorption or volume scattering, i.e. rays that have penetrated into the sample or refracted into the sample interior and are not reflected. The light signal reflected from solids usually encompasses all these effects which include dependencies on particle size, morphology and sample density. This paper measures the reflectance spectra in the 1.3 – 16 micron range for various bulk materials that have a combination of strong and weak absorption bands in order to understand the effects on the spectral features as a function of the mean grain size of the sample. The bulk materials were ground with a mortar and pestle and then sieved to separate the samples into various size fractions: 0-45, 45-90, 90-180, 180-250, 250-500, and >500 microns. The directional-hemispherical spectra were recorded using a Fourier transform infrared spectrometer equipped with an integrating sphere to measure the reflectance for all of the particle-size fractions. We have studied both organic and inorganic materials, but this paper focuses on inorganic salts, NaNO3 in particular. Our studies clearly show that particle size has an enormous influence on the measured reflectance spectra for bulk materials and that successful identification requires sufficient representative reflectance data so as to include the particle size(s) of interest. Origins of the effects are discussed.

  7. Postmodern Influence in Family Therapy Research: Reflections of Graduate Students

    ERIC Educational Resources Information Center

    Hertlein, Katherine M.; Lambert-Shute, Jennifer; Benson, Kristen

    2004-01-01

    Postmodernism has influenced family therapy in significant ways, from clinical work to family therapy research. Little has been written, however, on how to conduct postmodern research in a manner reflecting marriage and family therapy inquiries. The present study seeks to investigate doctoral students understanding of postmodern family therapy…

  8. Influencing and Facilitating Conditions for Developing Reflective Assessment Practice

    ERIC Educational Resources Information Center

    Rønsen, Anne Kristin; Smith, Kari

    2014-01-01

    By following a professional development project focusing on enhancing assessment competence amongst teachers, the current study examines how teachers use reflective writing and systematic discussions as tools for developing competence in assessment. More specifically, the article aims at identifying conditions that influence and facilitate…

  9. Dynamical Symmetries Reflected in Realistic Interactions

    SciTech Connect

    Sviratcheva, K.D.; Draayer, J.P.; Vary, J.P.; /Iowa State U. /LLNL, Livermore /SLAC

    2007-04-06

    Realistic nucleon-nucleon (NN) interactions, derived within the framework of meson theory or more recently in terms of chiral effective field theory, yield new possibilities for achieving a unified microscopic description of atomic nuclei. Based on spectral distribution methods, a comparison of these interactions to a most general Sp(4) dynamically symmetric interaction, which previously we found to reproduce well that part of the interaction that is responsible for shaping pairing-governed isobaric analog 0{sup +} states, can determine the extent to which this significantly simpler model Hamiltonian can be used to obtain an approximate, yet very good description of low-lying nuclear structure. And furthermore, one can apply this model in situations that would otherwise be prohibitive because of the size of the model space. In addition, we introduce a Sp(4) symmetry breaking term by including the quadrupole-quadrupole interaction in the analysis and examining the capacity of this extended model interaction to imitate realistic interactions. This provides a further step towards gaining a better understanding of the underlying foundation of realistic interactions and their ability to reproduce striking features of nuclei such as strong pairing correlations or collective rotational motion.

  10. Concert halls with strong lateral reflections enhance musical dynamics.

    PubMed

    Pätynen, Jukka; Tervo, Sakari; Robinson, Philip W; Lokki, Tapio

    2014-03-25

    One of the most thrilling cultural experiences is to hear live symphony-orchestra music build up from a whispering passage to a monumental fortissimo. The impact of such a crescendo has been thought to depend only on the musicians' skill, but here we show that interactions between the concert-hall acoustics and listeners' hearing also play a major role in musical dynamics. These interactions contribute to the shoebox-type concert hall's established success, but little prior research has been devoted to dynamic expression in this three-part transmission chain as a complete system. More forceful orchestral playing disproportionately excites high frequency harmonics more than those near the note's fundamental. This effect results in not only more sound energy, but also a different tone color. The concert hall transmits this sound, and the room geometry defines from which directions acoustic reflections arrive at the listener. Binaural directional hearing emphasizes high frequencies more when sound arrives from the sides of the head rather than from the median plane. Simultaneously, these same frequencies are emphasized by higher orchestral-playing dynamics. When the room geometry provides reflections from these directions, the perceived dynamic range is enhanced. Current room-acoustic evaluation methods assume linear behavior and thus neglect this effect. The hypothesis presented here is that the auditory excitation by reflections is emphasized with an orchestra forte most in concert halls with strong lateral reflections. The enhanced dynamic range provides an explanation for the success of rectangularly shaped concert-hall geometry. PMID:24591584

  11. Using Dynamic Software in Mathematics: The Case of Reflection Symmetry

    ERIC Educational Resources Information Center

    Tatar, Enver; Akkaya, Adnan; Kagizmanli, Türkan Berrin

    2014-01-01

    This study was carried out to examine the effects of computer-assisted instruction (CAI) using dynamic software on the achievement of students in mathematics in the topic of reflection symmetry. The study also aimed to ascertain the pre-service mathematics teachers' opinions on the use of CAI in mathematics lessons. In the study, a mixed…

  12. Concert halls with strong lateral reflections enhance musical dynamics

    PubMed Central

    Pätynen, Jukka; Tervo, Sakari; Robinson, Philip W.; Lokki, Tapio

    2014-01-01

    One of the most thrilling cultural experiences is to hear live symphony-orchestra music build up from a whispering passage to a monumental fortissimo. The impact of such a crescendo has been thought to depend only on the musicians’ skill, but here we show that interactions between the concert-hall acoustics and listeners’ hearing also play a major role in musical dynamics. These interactions contribute to the shoebox-type concert hall’s established success, but little prior research has been devoted to dynamic expression in this three-part transmission chain as a complete system. More forceful orchestral playing disproportionately excites high frequency harmonics more than those near the note’s fundamental. This effect results in not only more sound energy, but also a different tone color. The concert hall transmits this sound, and the room geometry defines from which directions acoustic reflections arrive at the listener. Binaural directional hearing emphasizes high frequencies more when sound arrives from the sides of the head rather than from the median plane. Simultaneously, these same frequencies are emphasized by higher orchestral-playing dynamics. When the room geometry provides reflections from these directions, the perceived dynamic range is enhanced. Current room-acoustic evaluation methods assume linear behavior and thus neglect this effect. The hypothesis presented here is that the auditory excitation by reflections is emphasized with an orchestra forte most in concert halls with strong lateral reflections. The enhanced dynamic range provides an explanation for the success of rectangularly shaped concert-hall geometry. PMID:24591584

  13. Polarization influence on reflectance measurements in the spatial frequency domain.

    PubMed

    Wiest, J; Bodenschatz, N; Brandes, A; Liemert, A; Kienle, A

    2015-08-01

    In this work, we quantify the influence of crossed polarizers on reflectance measurements in the spatial frequency domain. The use of crossed polarizers is a very common approach for suppression of specular surface reflections. However, measurements are typically evaluated using a non-polarized scalar theory. The consequences of this discrepancy are the focus of our study, and we also quantify the related errors of the derived optical properties. We used polarized Monte Carlo simulations for forward calculation of the reflectance from different samples. The samples' scatterers are assumed to be spherical, allowing for the calculation of the scattering functions by Mie theory. From the forward calculations, the reduced scattering coefficient [Formula: see text] and the absorption coefficient μa were derived by means of a scalar theory, as commonly used. Here, we use the analytical solution of the scalar radiative transfer equation. With this evaluation approach, which does not consider polarization, we found large errors in [Formula: see text] and μa in the range of 25% and above. Furthermore, we investigated the applicability of the use of a reference measurement to reduce these errors as suggested in literature. We found that this method is not able to generally improve the accuracy of measurements in the spatial frequency domain. Our general recommendation is to apply a polarized theory when using crossed polarizers. PMID:26158399

  14. Dynamical Outcomes of Quenching: Reflections on a Conical Intersection

    NASA Astrophysics Data System (ADS)

    Lehman, Julia H.; Lester, Marsha I.

    2014-04-01

    This review focuses on experimental studies of the dynamical outcomes following collisional quenching of electronically excited OH A2Σ+ radicals by molecular partners. The experimental observables include the branching between reactive and nonreactive decay channels, kinetic energy release, and quantum state distributions of the products. Complementary theoretical investigations reveal regions of strong nonadiabatic coupling, known as conical intersections, which facilitate the quenching process. The dynamical outcomes observed experimentally are connected to the local forces and geometric properties of the nuclei in the conical intersection region. Dynamical calculations for the benchmark OH-H2 system are in good accord with experimental observations, demonstrating that the outcomes reflect the strong coupling in the conical intersection region as the system evolves from the excited electronic state to quenched products.

  15. Neutron Reflectivity Measurement for Polymer Dynamics near Graphene Oxide Monolayers

    NASA Astrophysics Data System (ADS)

    Koo, Jaseung

    We investigated the diffusion dynamics of polymer chains confined between graphene oxide layers using neutron reflectivity (NR). The bilayers of polymethylmetacrylate (PMMA)/ deuterated PMMA (d-PMMA) films and polystyrene (PS)/d-PS films with various film thickness sandwiched between Langmuir-Blodgett (LB) monolayers of graphene oxide (GO) were prepared. From the NR results, we found that PMMA diffusion dynamics was reduced near the GO surface while the PS diffusion was not significantly changed. This is due to the different strength of GO-polymer interaction. In this talk, these diffusion results will be compared with dewetting dynamics of polymer thin films on the GO monolayers. This has given us the basis for development of graphene-based nanoelectronics with high efficiency, such as heterojunction devices for polymer photovoltaic (OPV) applications.

  16. Dynamics of directional reflectance factor distributions for vegetation canopies

    NASA Technical Reports Server (NTRS)

    Kimes, D. S.

    1983-01-01

    Directional reflectance factors that span the entire exitance hemisphere are collected on the ground for a variety of homogeneous vegetation canopies and bare soils. NOAA 6/7 AVHRR bands 1 (0.58-0.68 micron) and 2 (0.73-1.1 microns) are used. When possible, geometric measurements of leaf orientation distributions are taken simultaneously with each spectral measurement. Other supporting structural and optical measurements are made. These data sets are taken at various times of the day for each cover type. These unique sets, together with pertinent data in the literature, are used to investigate the dynamics of the directional reflectance factor distribution as a function of the geometric structure of the scene, solar zenith angle, and optical properties of the scene components (leaves and soil). For complete homogeneous vegetation canopies, the principal trend observed at all sun angles and spectral bands is a minimum reflectance near nadir and increasing reflectance with increasing off-nadir view angle for all azimuth directions.

  17. Influence of realistic atom wall potentials in quantum reflection traps

    NASA Astrophysics Data System (ADS)

    Madroñero, Javier; Friedrich, Harald

    2007-02-01

    We study the influence of atom-surface interactions close to the surface on the confinement properties in a recently proposed model [A. Jurisch and H. Friedrich, Phys. Lett. A 349, 230 (2006)] for quantum reflection traps and test the reliability of the sharp-step approximation used there. Accurate numerical calculations show a dependence of the surviving particle fraction on characteristic potential lengths determined by the behavior of the interaction in the limits r→0 and r→∞ of the atom-surface distance r . For interactions dominated by the retarded potential proportional to 1/r4 we find that the simplified sharp-step potential reproduces the behavior of the trapped atoms well, both qualitatively and quantitatively.

  18. Using dynamic software in mathematics: the case of reflection symmetry

    NASA Astrophysics Data System (ADS)

    Tatar, Enver; Akkaya, Adnan; Berrin Kağizmanli, Türkan

    2014-10-01

    This study was carried out to examine the effects of computer-assisted instruction (CAI) using dynamic software on the achievement of students in mathematics in the topic of reflection symmetry. The study also aimed to ascertain the pre-service mathematics teachers' opinions on the use of CAI in mathematics lessons. In the study, a mixed research method was used. The study group of this research consists of 30 pre-service mathematics teachers. The data collection tools used include a reflection knowledge test, a survey and observations. Based on the analysis of the data obtained from the study, the use of CAI had a positive effect on achievement in the topic of reflection symmetry of the pre-service mathematics teachers. The pre-service mathematics teachers were found to largely consider that a mathematics education which is carried out utilizing CAI will be more beneficial in terms of 'visualization', 'saving of time' and 'increasing interest/attention in the lesson'. In addition, it was found that the vast majority of them considered using computers in their teaching on the condition that the learning environment in which they would be operating has the appropriate technological equipment.

  19. Influence of Interlocutor/Reader on Utterance in Reflective Writing and Interview

    ERIC Educational Resources Information Center

    Collyer, Vivian M.

    2010-01-01

    The influence of the Other on utterance is foundational to language study. This analysis contrasts this influence within two modes of communication: reflective writing and interview. The data source is derived from the reflective writings and interview transcripts of a twelfth-grade physics student. In this student's case, reflective writing…

  20. Dynamic speckle illumination wide-field reflection phase microscopy

    PubMed Central

    Choi, Youngwoon; Hosseini, Poorya; Choi, Wonshik; Dasari, Ramachandra R.; So, Peter T. C.; Yaqoob, Zahid

    2014-01-01

    We demonstrate a quantitative reflection-phase microscope based on time-varying speckle-field illumination. Due to the short spatial coherence length of the speckle field, the proposed imaging system features superior lateral resolution, 520 nm, as well as high-depth selectivity, 1.03 µm. Off-axis interferometric detection enables wide-field and single-shot imaging appropriate for high-speed measurements. In addition, the measured phase sensitivity of this method, which is the smallest measurable axial motion, is more than 40 times higher than that available using a transmission system. We demonstrate the utility of our method by successfully distinguishing the motion of the top surface from that of the bottom in red blood cells. The proposed method will be useful for studying membrane dynamics in complex eukaryotic cells. PMID:25361156

  1. Using Network Dynamical Influence to Drive Consensus

    NASA Astrophysics Data System (ADS)

    Punzo, Giuliano; Young, George F.; MacDonald, Malcolm; Leonard, Naomi E.

    2016-05-01

    Consensus and decision-making are often analysed in the context of networks, with many studies focusing attention on ranking the nodes of a network depending on their relative importance to information routing. Dynamical influence ranks the nodes with respect to their ability to influence the evolution of the associated network dynamical system. In this study it is shown that dynamical influence not only ranks the nodes, but also provides a naturally optimised distribution of effort to steer a network from one state to another. An example is provided where the “steering” refers to the physical change in velocity of self-propelled agents interacting through a network. Distinct from other works on this subject, this study looks at directed and hence more general graphs. The findings are presented with a theoretical angle, without targeting particular applications or networked systems; however, the framework and results offer parallels with biological flocks and swarms and opportunities for design of technological networks.

  2. Using Network Dynamical Influence to Drive Consensus.

    PubMed

    Punzo, Giuliano; Young, George F; Macdonald, Malcolm; Leonard, Naomi E

    2016-01-01

    Consensus and decision-making are often analysed in the context of networks, with many studies focusing attention on ranking the nodes of a network depending on their relative importance to information routing. Dynamical influence ranks the nodes with respect to their ability to influence the evolution of the associated network dynamical system. In this study it is shown that dynamical influence not only ranks the nodes, but also provides a naturally optimised distribution of effort to steer a network from one state to another. An example is provided where the "steering" refers to the physical change in velocity of self-propelled agents interacting through a network. Distinct from other works on this subject, this study looks at directed and hence more general graphs. The findings are presented with a theoretical angle, without targeting particular applications or networked systems; however, the framework and results offer parallels with biological flocks and swarms and opportunities for design of technological networks. PMID:27210291

  3. Using Network Dynamical Influence to Drive Consensus

    PubMed Central

    Punzo, Giuliano; Young, George F.; Macdonald, Malcolm; Leonard, Naomi E.

    2016-01-01

    Consensus and decision-making are often analysed in the context of networks, with many studies focusing attention on ranking the nodes of a network depending on their relative importance to information routing. Dynamical influence ranks the nodes with respect to their ability to influence the evolution of the associated network dynamical system. In this study it is shown that dynamical influence not only ranks the nodes, but also provides a naturally optimised distribution of effort to steer a network from one state to another. An example is provided where the “steering” refers to the physical change in velocity of self-propelled agents interacting through a network. Distinct from other works on this subject, this study looks at directed and hence more general graphs. The findings are presented with a theoretical angle, without targeting particular applications or networked systems; however, the framework and results offer parallels with biological flocks and swarms and opportunities for design of technological networks. PMID:27210291

  4. Cenozoic climate change influences mammalian evolutionary dynamics

    PubMed Central

    Figueirido, Borja; Janis, Christine M.; Pérez-Claros, Juan A.; De Renzi, Miquel; Palmqvist, Paul

    2012-01-01

    Global climate change is having profound impacts on the natural world. However, climate influence on faunal dynamics at macroevolutionary scales remains poorly understood. In this paper we investigate the influence of climate over deep time on the diversity patterns of Cenozoic North American mammals. We use factor analysis to identify temporally correlated assemblages of taxa, or major evolutionary faunas that we can then study in relation to climatic change over the past 65 million years. These taxa can be grouped into six consecutive faunal associations that show some correspondence with the qualitative mammalian chronofaunas of previous workers. We also show that the diversity pattern of most of these chronofaunas can be correlated with the stacked deep-sea benthic foraminiferal oxygen isotope (δ18O) curve, which strongly suggests climatic forcing of faunal dynamics over a large macroevolutionary timescale. This study demonstrates the profound influence of climate on the diversity patterns of North American terrestrial mammals over the Cenozoic. PMID:22203974

  5. Influence of atmospheric aerosols and desert reflectance properties on satellite radiance measurements

    NASA Technical Reports Server (NTRS)

    Bowker, D. E.; Davis, R. E.

    1992-01-01

    The influence of surface bidirectional reflectance factors, including shadowing, and of atmospheric aerosol variability are modeled for their effects on the remote sensing of desert targets from space in the 0.7-micron region at high spatial resolution. The white sand reflectance data of Salomonson (1968) are used as the basis for the simulation. The effects of the surface bi-directional reflectance and atmospheric aerosol on the nadir-normalized reflectance measured at the satellite are discussed individually and jointly. The net influence of these two factors is shown to depend on the magnitude of other parameters, such as the surface reflectance and solar zenith angle.

  6. Total internal reflection and dynamic light scattering microscopy of gels

    NASA Astrophysics Data System (ADS)

    Gregor, Brian F.

    Two different techniques which apply optical microscopy in novel ways to the study of biological systems and materials were built and applied to several samples. The first is a system for adapting the well-known technique of dynamic light scattering (DLS) to an optical microscope. This can detect and scatter light from very small volumes, as compared to standard DLS which studies light scattering from volumes 1000x larger. The small scattering volume also allows for the observation of nonergodic dynamics in appropriate samples. Porcine gastric mucin (PGM) forms a gel at low pH which lines the epithelial cell layer and acts as a protective barrier against the acidic stomach environment. The dynamics and microscopic viscosity of PGM at different pH levels is studied using polystyrene microspheres as tracer particles. The microscopic viscosity and microrheological properties of the commercial basement membrane Matrigel are also studied with this instrument. Matrigel is frequently used to culture cells and its properties remain poorly determined. Well-characterized and purely synthetic Matrigel substitutes will need to have the correct rheological and morphological characteristics. The second instrument designed and built is a microscope which uses an interferometry technique to achieve an improvement in resolution 2.5x better in one dimension than the Abbe diffraction limit. The technique is based upon the interference of the evanescent field generated on the surface of a prism by a laser in a total internal reflection geometry. The enhanced resolution is demonstrated with fluorescent samples. Additionally. Raman imaging microscopy is demonstrated using the evanescent field in resonant and non-resonant samples, although attempts at applying the enhanced resolution technique to the Raman images were ultimately unsuccessful. Applications of this instrument include high resolution imaging of cell membranes and macroscopic structures in gels and proteins. Finally, a third

  7. The Mirror Reflects both Ways: Action Influences Perception of Others

    ERIC Educational Resources Information Center

    Blaesi, Sabine; Wilson, Margaret

    2010-01-01

    Substantial evidence links perception of others' bodies and mental representation of the observer's own body; however, the overwhelming majority of this evidence is unidirectional, showing influence from perception to action. It has been proposed that the influence also runs from action to perception, but to date the evidence is scant. Here we…

  8. Influence of Controlled Reflected Power on Gyrotron Performance

    NASA Astrophysics Data System (ADS)

    Kharchev, N.; Cappa, Á.; Malakhov, D.; Martínez, J.; Konchekov, E.; Tolkachev, A.; Borzosekov, V.; Sarksyan, K.; Petelin, M.

    2015-12-01

    This paper describes the reaction of a gyrotron oscillator when a very small fraction of its radiation, extracted from the main beam, is phase-modulated in a controlled way and is finally redirected back to the gyrotron. The gyrotron may exhibit a 10 % modulation of its total power even if the reflected power is lower than 1 %. Moreover, radial probing of the beam power distribution shows that the amplitude of the power modulation differs at different radial positions across the beam.

  9. Counterfactual and Factual Reflection: The Influence of Past Misdeeds on Future Immoral Behavior.

    PubMed

    Gaspar, Joseph P; Seabright, Mark A; Reynolds, Scott J; Yam, Kai Chi

    2015-01-01

    Though the decision to behave immorally is situated within the context of prior immoral behavior, research has provided contradictory insights into this process. In a series of experiments, we demonstrate that the effects of prior immoral behavior depend on how individuals think about, or reflect on, their immoral behavior. In Experiment 1, participants who reflected counterfactually on their prior moral lapses morally disengaged (i.e., rationalized) less than participants who reflected factually. In Experiment 2, participants who reflected counterfactually on their prior moral lapses experienced more guilt than those who reflected factually. Finally, in Experiments 3 and 4, participants who reflected counterfactually lied less on unrelated tasks with real monetary stakes than those who reflected factually. Our studies provide important insights into moral rationalization and moral compensation processes and demonstrate the profound influence of reflection in everyday moral life. PMID:25668142

  10. Soybean canopy reflectance as influenced by cultural practices. [West Lafayette, Indiana

    NASA Technical Reports Server (NTRS)

    Bauer, M. E. (Principal Investigator); Kollenkark, J. C.; Daughtry, C. S. T.

    1981-01-01

    Experiments were conducted at West Lafayette, Indiana in 1978 and 1979 to study the reflectance factor of soybean canopies as affected by differences in row width, population, planting date, cultivar and soil type. Reflectance factor data were acquired throughout the growing season with a LANDSAT-band radiometer. Agronomic data included plant height, leaf area index, development stage, total fresh and dry biomass, percent soil cover, and grain yield. The results indicate that row width, planting date, and cultivar influence the percent soil cover, leaf area index, and biomass present, which are in turn related to the multispectral reflectance. Additionally, the reflectance data were quite sensitive to the onset of senescence. Soil color and moisture were found to be important factors influencing the reflectance in single LANDSAT bands, but the near infrared/red reflectance ratio and the greeness transformation were less sensitive than the single bands to the soil background present.

  11. Canopy reflectance as influenced by solar illumination angle

    NASA Technical Reports Server (NTRS)

    Bauer, M. E. (Principal Investigator); Kollenkark, J. C.; Vanderbilt, V. C.; Daughtry, C. S. T.

    1981-01-01

    The interaction of the solar illumination angle and row azimuth angle of the measured reflectance factor (RF) of soybean canopies was investigated. Diurnal changes of nearly 140% were observed in the red wavelength region when canopies covered 64% of the soil. The amount of shadow observed was a function of the plant geometry and row width. As soil cover approached 100%, the diurnal changes diminished. A function tht describes the solar illumination angle with respect to the row azimuth explained most of the diurnal variation in the measured RF. Variation in near infrared response was much less and did not appear to be as strongly related to Sun-row angle interactions. The near infrared/red ratio was highly sensitive to Sun angle-row direction interactions, whereas the greenness function, utilizing all four spectral bands, was not.

  12. Influence of gas humidity on the reflection coefficient of multilayer dielectric mirrors.

    PubMed

    Serdyukov, V I; Sinitsa, L N; Lugovskoi, A A

    2016-06-10

    The influence of water vapor on the reflection coefficient of multilayer mirrors was studied using a gas cell with multiple reflections from the mirrors. A strong change in the reflection coefficient of the mirrors (up to 0.9%) was found when water vapor under a pressure of 23 mbar was injected into the cell, which was interpreted as a change in the refraction index of the layers of multilayer coatings when water vapor penetrated into the porous coating structure. PMID:27409037

  13. Teacher Reflection in a Hall of Mirrors: Historical Influences and Political Reverberations.

    ERIC Educational Resources Information Center

    Fendler, Lynn

    2003-01-01

    Traces the history of reflection in teacher education, focusing on its emergence through the influences of Descartes, Dewey, Schon, and feminism. Uses the critical lenses of Foucaultian genealogy and the sociology of scientific knowledge to investigate how the complicated meanings of reflection play out in complex ways through research practice.…

  14. REMOTE ISCHEMIC CONDITIONING INFLUENCES MITOCHONDRIAL DYNAMICS

    PubMed Central

    Cellier, Laura; Tamareille, Sophie; Kalakech, Hussein; Guillou, Sophie; Lenaers, Guy; Prunier, Fabrice; Mirebeau-Prunier, Delphine

    2016-01-01

    ABSTRACT Remote ischemic preconditioning (RIPC) has emerged as an attractive strategy to protect the heart against ischemia-reperfusion (I/R) injury. The mechanisms by which remote ischemic conditioning (RIC) is protective are to date unknown, yet a well-accepted theory holds that the mitochondria play a central role. Mitochondria are dynamic organelles that undergo fusion and fission. Interventions that decrease mitochondrial fission or increase mitochondrial fusion have been associated with reduced I/R injury. However, whether RIPC influences mitochondrial dynamics or not has yet to be ascertained. We sought to determine the role played by mitochondrial dynamics in RIPC-induced cardioprotection. Male adult rats exposed in vivo to myocardial I/R were assigned to one of two groups, either undergoing 40 min of myocardial ischemia followed by 120 min of reperfusion (MI group) or four 5-min cycles of limb ischemia interspersed by 5 min of limb reperfusion, immediately prior to myocardial ischemia and 120 min of reperfusion (MI+RIPC group). After reperfusion, infarct size was assessed and myocardial tissue was analyzed by Western blot and electron microscopy. RIPC induced smaller infarct size (−28%), increased mitochondrial fusion protein OPA1, and preserved mitochondrial morphology. These findings suggest that mitochondrial dynamics play a role in the mechanisms of RIPC-induced cardioprotection. PMID:26555744

  15. Recognizing dynamic scenes: influence of processing orientation.

    PubMed

    Huff, Markus; Schwan, Stephan; Garsoffky, Bärbel

    2011-04-01

    From face recognition studies, it is known that instructions are able to change processing orientation of stimuli, leading to an impairment of recognition performance. The present study examined instructional influences on the visual recognition of dynamic scenes. A global processing orientation without any instruction was assumed to lead to highest recognition performance, whereas instructions focusing participants' attention on certain characteristics of the event should lead to a local processing orientation with an impairment of visual recognition performance as a direct consequence. Since the pattern of results provided evidence for this hypothesis, theoretical contributions were discussed. PMID:21667754

  16. Node influence identification via resource allocation dynamics

    NASA Astrophysics Data System (ADS)

    Ma, Shu-Jiao; Ren, Zhuo-Ming; Ye, Chun-Ming; Guo, Qiang; Liu, Jian-Guo

    2014-07-01

    Identifying the node influence in complex networks is an important task to optimally use the network structure and ensure the more efficient spreading in information. In this paper, by taking into account the resource allocation dynamics (RAD) and the k-shell decomposition method, we present an improved method namely RAD to generate the ranking list to evaluate the node influence. First, comparing with the epidemic process results for four real networks, the RAD method could identify the node influence more accurate than the ones generated by the topology-based measures including the degree, k-shell, closeness and the betweenness. Then, a growing scale-free network model with tunable assortative coefficient is introduced to analyze the effect of the assortative coefficient on the accuracy of the RAD method. Finally, the positive correlation is found between the RAD method and the k-shell values which display an exponential form. This work would be helpful for deeply understanding the node influence of a network.

  17. A Reflection High Energy Electron Diffraction-Reflectance Anisotropy Spectroscopy Study of Silicon Growth Dynamics During Gas Source Molecular Beam Epitaxy from Silanes

    NASA Astrophysics Data System (ADS)

    Joyce, B. A.; Zhang, J.; Taylor, A. G.; Lees, A. K.

    Molecular beam epitaxy (MBE) provides an ideal experimental vehicle for the in situ study of thin film growth dynamics. By using a combination of reflection high energy electron diffraction (RHEED) and reflectance anisotropy (difference) spectroscopy [RA(D)S], it is possible to separate morphological (long range order) and local electronic structure effects, which we demonstrate with the growth of silicon films from disilane (Si2H6) on Si(001) (2 × 1)+(1 × 2) reconstructed surfaces. The rate-limiting step in Si growth from both monosilane (SiH4) and disilane is the desorption of molecular hydrogen and we have found using RAS that, over a significant range of temperature and coverage, hydrogen desorption follows zeroth order kinetics as the result of a step-mediated process. Finally, we show how this influences the growth rate on substrates of differing degrees of vicinality.

  18. Influence of interlocutor/reader on utterance in reflective writing and interview

    NASA Astrophysics Data System (ADS)

    Collyer, Vivian M.

    2010-03-01

    The influence of the Other on utterance is foundational to language study. This analysis contrasts this influence within two modes of communication: reflective writing and interview. The data source is derived from the reflective writings and interview transcripts of a twelfth-grade physics student. In this student's case, reflective writing includes extensive utterances, utilizing rhetorical devices to persuade and reconcile with his reader. In the interview, on-going back-and-forth utterances allow the two participants to negotiate a co-constructed meaning for religion. Implications for the classroom are briefly discussed.

  19. Fostering an Action-Reflection Dynamic amongst Student Practitioners

    ERIC Educational Resources Information Center

    Francis, Helen; Cowan, John

    2008-01-01

    Purpose: This paper seeks to explore changes taking place in a curriculum design for postgraduate teaching in personnel and development, aimed at enhancing lifelong learning. A scheme is described which aims to improve the alignment for professional development of students, in ways that facilitate critically reflective practice.…

  20. Trophic dynamics influence climate at high latitudes

    NASA Astrophysics Data System (ADS)

    Oksanen, L.; Tuomi, M.; Hoset, K.; Oksanen, T.; Olofsson, J.; Dahlgren, J.; Nordic Center of Excellence-Tundra

    2011-12-01

    Abundance relationships between tall woody plants and low herbaceous plants influence ground albedo. Increasing abundance of erect woody plants on the tundra increase the amount of solar energy converted to heat, thus speeding up global warming. By transplanting vegetation blocks from an island with predatory mammals and gray-sided voles (Myodes rufocanus) to similar habitats on islands with gray-sided voles but no resident predators and to islands with neither voles nor predators, we show that changing trophic dynamics radically change the abundance relationships between woody and herbaceous plants. Impacts of food limited gray-sided voles result to devastation of all erect woody plants, regardless of their palatability, thus differing both quantitatively and qualitatively from the selective impacts of the same species in the presence of predators. The shift from vegetation dominated by erect woody plants to vegetation dominated by herbs or trailing dwarf shrubs also increases ground albedo. The relationship between climate and trophic dynamics is thus no one way street. Rather than responding passively to changes in climate, food webs can also influence climate via their impacts on ground albedo.

  1. Dynamically deformable reflective membrane for laser beam shaping and smoothing

    NASA Astrophysics Data System (ADS)

    Masson, J.; Bitterli, R.; Bich, A.; Noell, W.; Voelkel, R.; Weible, K.; de Rooij, N.

    2012-03-01

    We show a laser beam shaping device made of a deformable continuous reflective membrane fabricated over a scanning stage. The combination of two actuator schemes enables shaping and smoothing of a laser beam with a unique compact device. It is designed to shape an input laser beam into a flat top or Gaussian intensity profile, to support high optical load and to potentially reduce speckle contrast. One single electrode is needed to deform the whole membrane into multiple sub-reflecting concave elements. The scanning stage is used simultaneously to smooth out the remaining interference patterns. The fabrication process is based on SOI wafer and parylene refilling to enable the fabrication of a 100 % fill factor 5 by 5 mm2 deformable membrane. Applications for such device are laser machining and laser display.

  2. Influence of frame inelasticity on poroviscoelastic reflections from a gas-water contact

    NASA Astrophysics Data System (ADS)

    Zhou, Rui; Chesnokov, Evgeny; Brown, Raymon

    2016-01-01

    As a natural extension of Biot theory, poroviscoelasticity is more comprehensive. The only difference between them is frame inelasticity, which influences wave dispersion, attenuation, reflection, and transmission. Hence we compute the influence, which uses the data of typical sand with gas and water saturation in the Gulf of Mexico with four values of frame inelasticity. The graphically illustrated results show that frame inelasticity has a small influence on the dispersion of P1- and S-waves and almost no influence on the dispersion of P2-wave. The frame inelasticity's influence on the P1- and S-wave attenuation is substantial with only a relatively small impact on the P2-wave attenuation. In some frequency and incident-angle ranges, frame inelasticity's influence on the reflection and transmission coefficients is considerable.

  3. Influence of ionization on reflection of solitary waves in a magnetized plasma

    SciTech Connect

    Jyoti,; Malik, Hitendra K.; Kumar, Ravinder; Dahiya, Raj P.

    2013-09-15

    The reflection of nonlinear solitary waves is studied in a nonuniform, magnetized plasma diffusing from an ionization source along the magnetic field lines. Contribution of the ionization term is included in the continuity equation. The behavior of solitary waves is governed by modified form of Korteweg–de Vries equation (called mKdV equation). In order to investigate the reflection of solitary waves, the mKdV equations for the right and left going waves are derived, and solved by finding new transformations coupled at the point of reflection, for obtaining the expression of reflection coefficient. Contrary to the case of usual inhomogeneous plasma, the present analysis shows that a combination of usual sech{sup 2} structure and tanh structure (called the tail of soliton) arises due to the influence of ionization term. Interestingly, this tailing structure disappears after the reflection of the soliton and hence, the soliton is downshifted prominently.

  4. Investigation of acoustic beam reflection influence on the collinear acousto-optic interaction characteristics.

    PubMed

    Mantsevich, S N

    2016-08-01

    Significant part of acousto-optic devices apply the acoustic beam reflection to arouse the desired type of acoustic mode propagating along the required direction in crystal. The influence of acoustic beam reflection process on the ultrasound field structure in the acousto-optic cell and the collinear acousto-optic diffraction characteristics is examined in this paper. The investigation is carried on the example of the collinear acousto-optic filter fabricated on the base of calcium molybdate crystal. It is shown that the reflection process changes the acoustic field structure and affects the acousto-optic filter transmission function shape and diffraction efficiency. PMID:27153373

  5. Influence of contact state on NIR diffuse reflectance spectroscopy in vivo

    NASA Astrophysics Data System (ADS)

    Chen, Wenliang; Liu, Rong; Xu, Kexin; Wang, Ruikang K.

    2005-08-01

    In the practice of non-invasive blood glucose measurement by near-infrared (NIR) diffuse reflectance spectroscopy, an optical probe usually directly contacts skin in order to eliminate specular reflection. In this paper, the influence of contact state on the diffuse reflectance in vivo and the variation trend of diffuse reflectance with contact time under the same contact pressure, are investigated at wavelengths ranging from 1100 to 1700 nm. The result shows that the diffuse reflectance decreases with increasing contact pressure under the contact state. At a certain applied pressure, the diffuse reflectance fluctuates significantly at the beginning of contact, and the fluctuation becomes stable with elapsing contacting time. It is our aim in this paper to find out the optimal contact state and optimal measuring time, in order to reduce the influence of contact pressure on diffuse reflectance measurements. It is found from our experiments that, for in vivo measurement, the optimal contact state appears when the skin is pressed to about 0.5 mm by the probe, where the probe contacts the palm entirely, and that the optimal measuring time is at the 30th second since the probe contacting with the measuring site. Putting the above conclusions into practice, the repeatability of spectra is improved greatly.

  6. Influence of spatial differential reflection parameters on 2,4,6- trinitrotoluene (TNT) absorption spectra

    NASA Astrophysics Data System (ADS)

    Dubroca, Thierry; Guetard, Ga"l.; Hummel, Rolf E.

    2012-06-01

    Differential reflectometry has been shown to be a sensitive and fast tool to detect explosive substances on surfaces such as luggage and parcel. This paper elucidates the influence of several parameters on the sensitivity of the technique. An expression for the reflected intensity that contains the influence of angle of incidence, wavelength of the incident light, and surface roughness has been established. The feature used to identify and detect TNT stems mainly from the diffuse component of the reflected light. This spectral "finger-print" shape does not change by varying these parameters. The maximum sensitivity is obtained for samples which are strongly diffusive and weakly specular.

  7. Disrupted modular brain dynamics reflect cognitive dysfunction in Alzheimer's disease.

    PubMed

    de Haan, W; van der Flier, W M; Koene, T; Smits, L L; Scheltens, P; Stam, C J

    2012-02-15

    The relation between pathology and cognitive dysfunction in dementia is still poorly understood, although disturbed communication between different brain regions is almost certainly involved. In this study we combine magneto-encephalography (MEG) and network analysis to investigate the role of functional sub-networks (modules) in the brain with regard to cognitive failure in Alzheimer's disease. Whole-head resting-state (MEG) was performed in 18 Alzheimer patients (age 67 ± 9, 6 females, MMSE 23 ± 5) and 18 healthy controls (age 66 ± 9, 11 females, MMSE 29 ± 1). We constructed functional brain networks based on interregional synchronization measurements, and performed graph theoretical analysis with a focus on modular organization. The overall modular strength and the number of modules changed significantly in Alzheimer patients. The parietal cortex was the most highly connected network area, but showed the strongest intramodular losses. Nonetheless, weakening of intermodular connectivity was even more outspoken, and more strongly related to cognitive impairment. The results of this study demonstrate that particularly the loss of communication between different functional brain regions reflects cognitive decline in Alzheimer's disease. These findings imply the relevance of regarding dementia as a functional network disorder. PMID:22154957

  8. Dissolution dynamics of thin films measured by optical reflectance

    NASA Astrophysics Data System (ADS)

    Punckt, Christian; Aksay, Ilhan A.

    2009-12-01

    Measuring the dissolution dynamics of thin films in situ both with spatial and temporal resolution can be a challenging task. Available methods such as scanning electrochemical microscopy rely on scanning the specimen and are intrinsically slow. We developed a characterization technique employing only an optical microscope, a digital charge coupled device camera, and a computer for image processing. It is capable of detecting dissolution rates of the order of nm/min and has a spatial and temporal resolution which is limited by the imaging and recording setup. We demonstrate the capabilities of our method by analyzing the electrochemical dissolution of copper thin films on gold substrates in a mild hydrochloric acid solution. Due to its simplicity, our technique can be implemented in any laboratory and can be applied to a variety of systems such as thin film sensors or passive coatings.

  9. INFLUENCES OF CARTILAGINOUS RINGS ON TRACHEOBRONCHIAL FLUID DYNAMICS

    EPA Science Inventory

    Fluid dynamics patterns within tracheobronchial airways reflect interactions between cartilaginous rings and inspiratory flow rates. The results of supercomputer simulations performed herein were complex, yet systematic. The effects of cartilaginous rings upon tracheobronchial fl...

  10. Influence of Cultural Norms and Collaborative Discussions on Children's Reflective Essays

    ERIC Educational Resources Information Center

    Kim, Il-Hee; Anderson, Richard C.; Miller, Brian; Jeong, Jongseong; Swim, Terri

    2011-01-01

    This study investigated the influence of culture and discussion participation on rhetorical patterns in the reflective essays of 238 Korean and 196 American 4th-graders. Results showed significant differences between Korean children's essays and American children's essays in types of reasons, uses of argument elements, and uses of rhetorical…

  11. The influence of inhomogeneity of the reflectivity distribution on the accuracy of its measurement

    NASA Technical Reports Server (NTRS)

    Salman, Y. M.

    1975-01-01

    The influence of pulse volume dimensions on the accuracy of reflectivity from various clouds is considered. It is shown that due to the spatial averaging and the inhomogeneities of the clouds, the dependence frequently breaks down, which is a cause of lower values of the spatial distribution estimate. Values of the corrections calculated for various conditions are presented.

  12. An Evaluation of the Influence of Case Method Instruction on the Reflective Thinking of MSW Students

    ERIC Educational Resources Information Center

    Milner, Marleen

    2009-01-01

    Social work practice requires that graduates be prepared to deal with complex, multifaceted problems which cannot be defined completely, do not have absolute, correct answers and can be approached from multiple perspectives. This study evaluated the influence of case-based instruction on MSW students' reflective judgment, an aspect of critical…

  13. Learning about University Teaching: Reflections on a Research Study Investigating Influences for Change

    ERIC Educational Resources Information Center

    Pickering, Angela M.

    2006-01-01

    This article reflects on findings from research involving case studies of four novice lecturers enrolled on a one-year university teaching development programme. The study sought to contribute to an understanding of the "process" of pedagogic change and the influences which affect it. Findings suggest that key aspects of the lecturers' experience…

  14. Qualitative Career Assessment: Developing the My System of Career Influences Reflection Activity

    ERIC Educational Resources Information Center

    McMahon, Mary; Watson, Mark; Patton, Wendy

    2005-01-01

    This article reports on the development of a qualitative career assessment activity, the My System of Career Influences (MSCI) Reflection Activity. The article describes the process of developing and testing the instrument. The testing was conducted in two stages with adults and adolescents. Findings from Stage 1 indicate that the MSCI (pilot…

  15. Influence of measurement geometry on the human skin reflectance spectra detection

    NASA Astrophysics Data System (ADS)

    Borisova, E.; Troyanova, P.; Avramov, L.

    2007-06-01

    One of the optical techniques applied in skin lesion investigations is reflectance spectroscopy of cutaneous tissues. Diffuse reflectance signals could be applied for absolute determination of absorption and scattering coefficients of biological tissue and give reliable results for wide range of wavelengths. However, light distribution anisotropy leads to significant influence over the reflectance spectra appearance depending on the used geometry. To obtain good reproducibility and repeatability of the results, one needs to fix carefully the geometrical conditions. We present skin reflectance spectra obtained at different angles and distances from tissue surface and discuss possible reasons for differences observed. In the case of small angles of incidence, we have significant losses of the backscattered light related to the anisotropy of the tissue and the intensity observed of the reflected signal is much lower than in the case of diffuse reflectance signal detected at higher angles. In the case of direct contact between skin surface and end tip of the fibers great reduction of the short wavelength component is observed. The appearance of higher intensity blue signal as the distance between end tip of the optical fibers and skin surface is increased could be related to the specular component of the reflectance spectra. An optimum distance exists where the registered signal has the greatest value, which is related to the specific parameters of the optical fibers used, such as diameter and optical aperture.

  16. Influence of target reflection on three-dimensional range gated reconstruction.

    PubMed

    Chua, Sing Yee; Wang, Xin; Guo, Ningqun; Tan, Ching Seong

    2016-08-20

    The range gated technique is a promising laser ranging method that is widely used in different fields such as surveillance, industry, and military. In a range gated system, a reflected laser pulse returned from the target scene contains key information for range reconstruction, which directly affects the system performance. Therefore, it is necessary to study the characteristics and effects of the target reflection factor. In this paper, theoretical and experimental analyses are performed to investigate the influence of target reflection on three-dimensional (3D) range gated reconstruction. Based on laser detection and ranging (LADAR) and bidirectional reflection distribution function (BRDF) theory, a 3D range gated reconstruction model is derived and the effect on range accuracy is analyzed from the perspectives of target surface reflectivity and angle of laser incidence. Our theoretical and experimental study shows that the range accuracy is proportional to the target surface reflectivity, but it decreases when the angle of incidence increases to adhere to the BRDF model. The presented findings establish a comprehensive understanding of target reflection in 3D range gated reconstruction, which is of interest to various applications such as target recognition and object modeling. This paper provides a reference for future improvement to perform accurate range compensation or correction. PMID:27556975

  17. Misconceptions about coercion and undue influence: reflections on the views of IRB members.

    PubMed

    Largent, Emily; Grady, Christine; Miller, Franklin G; Wertheimer, Alan

    2013-11-01

    Payment to recruit research subjects is a common practice but raises ethical concerns relating to the potential for coercion or undue influence. We conducted the first national study of IRB members and human subjects protection professionals to explore attitudes as to whether and why payment of research participants constitutes coercion or undue influence. Upon critical evaluation of the cogency of ethical concerns regarding payment, as reflected in our survey results, we found expansive or inconsistent views about coercion and undue influence that may interfere with valuable research. In particular, respondents appear to believe that coercion and undue influence lie on a continuum; by contrast, we argue that they are wholly distinct: whereas undue influence is a cognitive distortion relating to assessment of risks and benefits, coercion is a threat of harm. Because payment is an offer, rather than a threat, payment is never coercive. PMID:22493972

  18. MISCONCEPTIONS ABOUT COERCION AND UNDUE INFLUENCE: REFLECTIONS ON THE VIEWS OF IRB MEMBERS

    PubMed Central

    LARGENT, EMILY; GRADY, CHRISTINE; MILLER, FRANKLIN G.; WERTHEIMER, ALAN

    2016-01-01

    Payment to recruit research subjects is a common practice but raises ethical concerns relating to the potential for coercion or undue influence. We conducted the first national study of IRB members and human subjects protection professionals to explore attitudes as to whether and why payment of research participants constitutes coercion or undue influence. Upon critical evaluation of the cogency of ethical concerns regarding payment, as reflected in our survey results, we found expansive or inconsistent views about coercion and undue influence that may interfere with valuable research. In particular, respondents appear to believe that coercion and undue influence lie on a continuum; by contrast, we argue that they are wholly distinct: whereas undue influence is a cognitive distortion relating to assessment of risks and benefits, coercion is a threat of harm. Because payment is an offer, rather than a threat, payment is never coercive. PMID:22493972

  19. Probing carrier dynamics of individual layers in a heterostructure using transient reflectivity

    SciTech Connect

    Khan, Salahuddin; Jayabalan, J. Singh, Asha; Yogi, Rachana; Chari, Rama

    2015-09-21

    We report the wavelength dependent transient reflectivity measurements in AlGaAs-GaAs heterostructures having two-dimensional electron (or hole) gas near the interface. Using a multilayer model for transient reflectivity, we show that the magnitude and sign of contributions from the carriers in two-dimensional electron (or hole) gas and GaAs to the total signal depends on the wavelength. Further, it has been shown that it is possible to study the carrier dynamics in a given layer of a heterostructure by performing transient reflectivity at specific wavelengths.

  20. Fiber Bragg grating dynamic strain sensor using an adaptive reflective semiconductor optical amplifier source.

    PubMed

    Wei, Heming; Tao, Chuanyi; Zhu, Yinian; Krishnaswamy, Sridhar

    2016-04-01

    In this paper, a reflective semiconductor optical amplifier (RSOA) is configured to demodulate dynamic spectral shifts of a fiber Bragg grating (FBG) dynamic strain sensor. The FBG sensor and the RSOA source form an adaptive fiber cavity laser. As the reflective spectrum of the FBG sensor changes due to dynamic strains, the wavelength of the laser output shifts accordingly, which is subsequently converted into a corresponding phase shift and demodulated by an unbalanced Michelson interferometer. Due to the short transition time of the RSOA, the RSOA-FBG cavity can respond to dynamic strains at high frequencies extending to megahertz. A demodulator using a PID controller is used to compensate for low-frequency drifts induced by temperature and large quasi-static strains. As the sensitivity of the demodulator is a function of the optical path difference and the FBG spectral width, optimal parameters to obtain high sensitivity are presented. Multiplexing to demodulate multiple FBG sensors is also discussed. PMID:27139682

  1. Directed dynamical influence is more detectable with noise.

    PubMed

    Jiang, Jun-Jie; Huang, Zi-Gang; Huang, Liang; Liu, Huan; Lai, Ying-Cheng

    2016-01-01

    Successful identification of directed dynamical influence in complex systems is relevant to significant problems of current interest. Traditional methods based on Granger causality and transfer entropy have issues such as difficulty with nonlinearity and large data requirement. Recently a framework based on nonlinear dynamical analysis was proposed to overcome these difficulties. We find, surprisingly, that noise can counterintuitively enhance the detectability of directed dynamical influence. In fact, intentionally injecting a proper amount of asymmetric noise into the available time series has the unexpected benefit of dramatically increasing confidence in ascertaining the directed dynamical influence in the underlying system. This result is established based on both real data and model time series from nonlinear ecosystems. We develop a physical understanding of the beneficial role of noise in enhancing detection of directed dynamical influence. PMID:27066763

  2. Directed dynamical influence is more detectable with noise

    PubMed Central

    Jiang, Jun-Jie; Huang, Zi-Gang; Huang, Liang; Liu, Huan; Lai, Ying-Cheng

    2016-01-01

    Successful identification of directed dynamical influence in complex systems is relevant to significant problems of current interest. Traditional methods based on Granger causality and transfer entropy have issues such as difficulty with nonlinearity and large data requirement. Recently a framework based on nonlinear dynamical analysis was proposed to overcome these difficulties. We find, surprisingly, that noise can counterintuitively enhance the detectability of directed dynamical influence. In fact, intentionally injecting a proper amount of asymmetric noise into the available time series has the unexpected benefit of dramatically increasing confidence in ascertaining the directed dynamical influence in the underlying system. This result is established based on both real data and model time series from nonlinear ecosystems. We develop a physical understanding of the beneficial role of noise in enhancing detection of directed dynamical influence. PMID:27066763

  3. Directed dynamical influence is more detectable with noise

    NASA Astrophysics Data System (ADS)

    Jiang, Jun-Jie; Huang, Zi-Gang; Huang, Liang; Liu, Huan; Lai, Ying-Cheng

    2016-04-01

    Successful identification of directed dynamical influence in complex systems is relevant to significant problems of current interest. Traditional methods based on Granger causality and transfer entropy have issues such as difficulty with nonlinearity and large data requirement. Recently a framework based on nonlinear dynamical analysis was proposed to overcome these difficulties. We find, surprisingly, that noise can counterintuitively enhance the detectability of directed dynamical influence. In fact, intentionally injecting a proper amount of asymmetric noise into the available time series has the unexpected benefit of dramatically increasing confidence in ascertaining the directed dynamical influence in the underlying system. This result is established based on both real data and model time series from nonlinear ecosystems. We develop a physical understanding of the beneficial role of noise in enhancing detection of directed dynamical influence.

  4. Influence of community experiences on first-year medical students' reflective writing.

    PubMed

    Beylefeld, Adriana A; Nena, Kali D; Prinsloo, Engela A M

    2005-03-01

    The purpose of this research was to investigate the usefulness of providing students with community-located experiences as a basis for reflection by observing the degree to which community-located experiences influenced the quality of a reflective writing exercise. Students were prepared for reflection by means of a lecture and a handout on the meaning, function and process of reflection. One hundred and twenty-eight students (66 Afrikaans-speaking, and 62 English-speaking) took part in the study. Initially, most students (71%) who revealed affect prior to the visit reported negative emotional states. For 54% of the students who revealed emotions upon arrival, positive emotional states replaced the negative and this increased to 67% as the visit continued. This represented the most important stage of the personal growth continuum, signifying awareness of perspective 'distortions'. The majority (94.3%) regarded the visit as being important prior to immersing themselves in the theory of primary healthcare. In the questionnaire survey, students were asked for their opinions on the value of reflective writing as a tool for promoting deep learning, as students' attitudes were considered an important determinant of increased uptake of this kind of activity. Reflective writing can be promoted through using a real-world experience as stimulus, and a framework for guiding students' thoughts. PMID:16019336

  5. A Universal Dynamic Threshold Cloud Detection Algorithm (UDTCDA) supported by a prior surface reflectance database

    NASA Astrophysics Data System (ADS)

    Sun, Lin; Wei, Jing; Wang, Jian; Mi, Xueting; Guo, Yamin; Lv, Yang; Yang, Yikun; Gan, Ping; Zhou, Xueying; Jia, Chen; Tian, Xinpeng

    2016-06-01

    Conventional cloud detection methods are easily affected by mixed pixels, complex surface structures, and atmospheric factors, resulting in poor cloud detection results. To minimize these problems, a new Universal Dynamic Threshold Cloud Detection Algorithm (UDTCDA) supported by a priori surface reflectance database is proposed in this paper. A monthly surface reflectance database is constructed using long-time-sequenced MODerate resolution Imaging Spectroradiometer surface reflectance product (MOD09A1) to provide the surface reflectance of the underlying surfaces. The relationships between the apparent reflectance changes and the surface reflectance are simulated under different observation and atmospheric conditions with the 6S (Second Simulation of the Satellite Signal in the Solar Spectrum) model, and the dynamic threshold cloud detection models are developed. Two typical remote sensing data with important application significance and different sensor parameters, MODIS and Landsat 8, are selected for cloud detection experiments. The results were validated against the visual interpretation of clouds and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation cloud measurements. The results showed that the UDTCDA can obtain a high precision in cloud detection, correctly identifying cloudy pixels and clear-sky pixels at rates greater than 80% with error rate and missing rate of less than 20%. The UDTCDA cloud product overall shows less estimation uncertainty than the current MODIS cloud mask products. Moreover, the UDTCDA can effectively reduce the effects of atmospheric factors and mixed pixels and can be applied to different satellite sensors to realize long-term, large-scale cloud detection operations.

  6. Dynamics and control of flexible spinning solar sails under reflectivity modulation

    NASA Astrophysics Data System (ADS)

    Mu, Junshan; Gong, Shengping; Ma, Pengbin; Li, Junfeng

    2015-10-01

    Electrochromic devices have been used for the attitude control of a spinning solar sail in a deep space mission by modulating the reflectivity of the sail membrane. As a flexible spinning solar sail has no rigid structure to support its membrane, the distributed load due to solar radiation will lead to the deformation of the sail membrane, and the control torque generated by reflectivity modulation can introduce oscillatory motion to the membrane. By contrast, the deformation and oscillatory motion of the sail membrane have an impact on the performance of the reflectivity control. This paper investigates the dynamics and control of flexible spinning solar sails under reflectivity modulation. The static deformation of a spinning sail membrane subjected to solar radiation pressure in an equilibrium state is analyzed. The von Karman theory is used to obtain the displacements and the stress distribution in the equilibrium states. A simplified analytical first-order mode is chosen to model the membrane oscillation. The coupled membrane oscillation-attitude-orbit dynamics are considered for a GeoSail formation flying mission. The relative attitude and orbit control of flexible spinning solar sails under reflectivity modulation are numerically tested. The simulations indicate that the membrane deformation and oscillation have a lower impact on the control of the reflectivity modulated sails than the increase of the spinning rate.

  7. Oblique shock reflection from an axis of symmetry: shock dynamics and relation to the Guderley singularity

    NASA Astrophysics Data System (ADS)

    Hornung, H. G.; Schwendeman, D. W.

    2001-07-01

    Oblique shock reflection from an axis of symmetry is studied using Whitham's theory of geometrical shock dynamics, and the results are compared with previous numerical simulations of the phenomenon by Hornung (2000). The shock shapes (for strong and weak shocks), and the location of the shock-shock (for strong shocks), are in good agreement with the numerical results, though the detail of the shock reflection structure is, of course, not resolved by shock dynamics. A guess at a mathematical form of the shock shape based on an analogy with the Guderley singularity in cylindrical shock implosion, in the form of a generalized hyperbola, fits the shock shape very well. The smooth variation of the exponent in this equation with initial shock angle from the Guderley value at zero to 0.5 at 90° supports the analogy. Finally, steady-flow shock reflection from a symmetry axis is related to the self-similar flow.

  8. Opinion dynamics model with weighted influence: Exit probability and dynamics

    NASA Astrophysics Data System (ADS)

    Biswas, Soham; Sinha, Suman; Sen, Parongama

    2013-08-01

    We introduce a stochastic model of binary opinion dynamics in which the opinions are determined by the size of the neighboring domains. The exit probability here shows a step function behavior, indicating the existence of a separatrix distinguishing two different regions of basin of attraction. This behavior, in one dimension, is in contrast to other well known opinion dynamics models where no such behavior has been observed so far. The coarsening study of the model also yields novel exponent values. A lower value of persistence exponent is obtained in the present model, which involves stochastic dynamics, when compared to that in a similar type of model with deterministic dynamics. This apparently counterintuitive result is justified using further analysis. Based on these results, it is concluded that the proposed model belongs to a unique dynamical class.

  9. Andreev reflection, a tool to investigate vortex dynamics and quantum turbulence in 3He-B

    PubMed Central

    Fisher, Shaun Neil; Jackson, Martin James; Sergeev, Yuri A.; Tsepelin, Viktor

    2014-01-01

    Andreev reflection of quasiparticle excitations provides a sensitive and passive probe of flow in superfluid 3He-B. It is particularly useful for studying complex flows generated by vortex rings and vortex tangles (quantum turbulence). We describe the reflection process and discuss the results of numerical simulations of Andreev reflection from vortex rings and from quantum turbulence. We present measurements of vortices generated by a vibrating grid resonator at very low temperatures. The Andreev reflection is measured using an array of vibrating wire sensors. At low grid velocities, ballistic vortex rings are produced. At higher grid velocities, the rings collide and reconnect to produce quantum turbulence. We discuss spatial correlations of the fluctuating vortex signals measured by the different sensor wires. These reveal detailed information about the formation of quantum turbulence and about the underlying vortex dynamics. PMID:24704872

  10. Dynamical measurement of refractive index distribution using digital holographic interferometry based on total internal reflection.

    PubMed

    Zhang, Jiwei; Di, Jianglei; Li, Ying; Xi, Teli; Zhao, Jianlin

    2015-10-19

    We present a method for dynamically measuring the refractive index distribution in a large range based on the combination of digital holographic interferometry and total internal reflection. A series of holograms, carrying the index information of mixed liquids adhered on a total reflection prism surface, are recorded with CCD during the diffusion process. Phase shift differences of the reflected light are reconstructed exploiting the principle of double-exposure holographic interferometry. According to the relationship between the reflection phase shift difference and the liquid index, two dimensional index distributions can be directly figured out, assuming that the index of air near the prism surface is constant. The proposed method can also be applied to measure the index of solid media and monitor the index variation during some chemical reaction processes. PMID:26480394

  11. Andreev reflection, a tool to investigate vortex dynamics and quantum turbulence in 3He-B.

    PubMed

    Fisher, Shaun Neil; Jackson, Martin James; Sergeev, Yuri A; Tsepelin, Viktor

    2014-03-25

    Andreev reflection of quasiparticle excitations provides a sensitive and passive probe of flow in superfluid (3)He-B. It is particularly useful for studying complex flows generated by vortex rings and vortex tangles (quantum turbulence). We describe the reflection process and discuss the results of numerical simulations of Andreev reflection from vortex rings and from quantum turbulence. We present measurements of vortices generated by a vibrating grid resonator at very low temperatures. The Andreev reflection is measured using an array of vibrating wire sensors. At low grid velocities, ballistic vortex rings are produced. At higher grid velocities, the rings collide and reconnect to produce quantum turbulence. We discuss spatial correlations of the fluctuating vortex signals measured by the different sensor wires. These reveal detailed information about the formation of quantum turbulence and about the underlying vortex dynamics. PMID:24704872

  12. Photonic sensing of organic solvents through geometric study of dynamic reflection spectrum

    PubMed Central

    Zhang, Yuqi; Fu, Qianqian; Ge, Jianping

    2015-01-01

    Traditional photonic sensing based on the change of balanced reflection of photonic structures can hardly distinguish chemical species with similar refractive indices. Here a sensing method based on the dynamic reflection spectra (DRS) of photonic crystal gel has been developed to distinguish even homologues, isomers and solvents with similar structures and physical properties. There are inherent relationships between solvent properties, diffusion behaviour and evolution of reflection signals, so that the geometric characteristics of DRS pattern including ascending/descending, colour changes, splitting/merging and curvature of reflection band can be utilized to recognize different organic solvents. With adequate solvents being tested, a database of DRS patterns can be established, which provide a standard to identify an unknown solvent. PMID:26082186

  13. Influence of Cenozoic Plateau Growth on Precipitation and Atmospheric Dynamics

    NASA Astrophysics Data System (ADS)

    Insel, N.; Poulsen, C. J.; Rowley, D. B.

    2011-12-01

    Large mountain ranges exhibit a first-order control on climate, but it is unclear how climate may have changed over time as topography developed. In this work we use global and regional general circulation models (Genesis3.0, RegCM4) to evaluate dynamical and physical atmospheric changes associated with variations in the Andean and Himalayan topography during the Cenozoic. Our model results show that orogenic plateaus play a critical role in the evolution of climate by affecting atmospheric circulation and precipitation patterns. The influence of high topography on regional climate is not purely mechanical through orographic lifting, but also due to modifications of dynamical processes. The uplift of the Andes and Himalaya influence atmospheric flow in the following ways: (1) Orogens act as a barrier to atmospheric flow, thereby changing low-level (800 mbar) wind patterns by causing a reversal and/or significant strengthening of the prevailing winds. The establishment and strength of low-level jets is directly related to mountain elevations. (2) In contrast, monsoonal circulations form without the existence of a plateau, but are modified by high topography through thermal and mechanical effects (e.g. sensible or latent heating, orographic blocking). (3) An increase in the surface pressure gradient between high mountain ranges and the foreland enhances convergence of low-level flow and draws in moisture from adjacent regions. The increase in moisture transport provides the latent heat required to drive convective updrafts and enhances convection and precipitation along the windward flanks of high topography. (4) Regional atmospheric circulation similar to modern are established and amplify as the mountains rise to ~50-75% of their modern elevation. Our model results are largely consistent with proxy evidence of regional climate change, and have implications for the timing and rate of surface plateau uplift. Most importantly, simulated changes in paleoclimate alter

  14. Performance limitations of bilateral force reflection imposed by operator dynamic characteristics

    NASA Technical Reports Server (NTRS)

    Chapel, Jim D.

    1989-01-01

    A linearized, single-axis model is presented for bilateral force reflection which facilitates investigation into the effects of manipulator, operator, and task dynamics, as well as time delay and gain scaling. Structural similarities are noted between this model and impedance control. Stability results based upon this model impose requirements upon operator dynamic characteristics as functions of system time delay and environmental stiffness. An experimental characterization reveals the limited capabilities of the human operator to meet these requirements. A procedure is presented for determining the force reflection gain scaling required to provide stability and acceptable operator workload. This procedure is applied to a system with dynamics typical of a space manipulator, and the required gain scaling is presented as a function of environmental stiffness.

  15. Femtosecond laser ablation dynamics of fused silica extracted from oscillation of time-resolved reflectivity

    SciTech Connect

    Kumada, Takayuki Akagi, Hiroshi; Itakura, Ryuji; Otobe, Tomohito; Yokoyama, Atsushi

    2014-03-14

    Femtosecond laser ablation dynamics of fused silica is examined via time-resolved reflectivity measurements. After optical breakdown was caused by irradiation of a pump pulse with fluence F{sub pump} = 3.3–14.9 J/cm{sup 2}, the reflectivity oscillated with a period of 63 ± 2 ps for a wavelength λ = 795 nm. The period was reduced by half for λ = 398 nm. We ascribe the oscillation to the interference between the probe pulses reflected from the front and rear surfaces of the photo-excited molten fused silica layer. The time-resolved reflectivity agrees closely with a model comprising a photo-excited layer which expands due to the formation of voids, and then separates into two parts, one of which is left on the sample surface and the other separated as a molten thin layer from the surface by the spallation mechanism. Such oscillations were not observed in the reflectivity of soda-lime glass. Whether the reflectivity oscillates or not probably depends on the layer viscosity while in a molten state. Since viscosity of the molten fused silica is several orders of magnitude higher than that of the soda-lime glass at the same temperature, fused silica forms a molten thin layer that reflects the probe pulse, whereas the soda-lime glass is fragmented into clusters.

  16. Dynamic reflectance of tin shocked from its beta to BCT phase

    NASA Astrophysics Data System (ADS)

    Stevens, Gerald; La Lone, Brandon; Veeser, Lynn; Turley, Dale

    2015-06-01

    Shock-induced phase transitions have historically been inferred by features in loading/unloading velocity wave profiles, which arise due to volume or sound speed differences between phases. In 2010, we used a flash-lamp illuminated multi-band reflectometer to demonstrate that iron, tin, cerium, and gallium have measureable reflectance changes at phase boundaries. We have improved upon our prior technique, utilizing an integrating sphere with an internal xenon flash lamp to illuminate a shocked metal beneath a LiF window. The new reflectance system is insensitive to motion, tilt, or curvature and measures the absolute (not relative) reflectance within five bands centered at 500, 700, 850, 1300, and 1550 nm. We have made dynamic reflectance measurements of tin samples shocked to pressures above and below the beta-bct phase transition using either high explosives or a gas gun. Below the transition, the visible reflectance decreases with pressure. At and above the transition, the visible reflectance increases to values higher than the ambient values. Reflectance can therefore be used to locate the beta-bct phase transition boundary for tin, independent of the velocity wave profile. This work was done by National Security Technologies, LLC, under Contract No. DE-AC52-06NA25946 with the U.S. Department of Energy, and supported by the Site-Directed Research and Development Program.

  17. The Influence of Dynamic Contact Angle on Wetting Dynamics

    NASA Technical Reports Server (NTRS)

    Rame, Enrique; Garoff, Steven

    2005-01-01

    When surface tension forces dominate, and regardless of whether the situation is static or dynamic, the contact angle (the angle the interface between two immiscible fluids makes when it contacts a solid) is the key parameter that determines the shape of a fluid-fluid interface. The static contact angle is easy to measure and implement in models predicting static capillary surface shapes and such associated quantities as pressure drops. By contrast, when the interface moves relative to the solid (as in dynamic wetting processes) the dynamic contact angle is not identified unambiguously because it depends on the geometry of the system Consequently, its determination becomes problematic and measurements in one geometry cannot be applied in another for prediction purposes. However, knowing how to measure and use the dynamic contact angle is crucial to determine such dynamics as a microsystem throughput reliably. In this talk we will present experimental and analytical efforts aimed at resolving modeling issues present in dynamic wetting. We will review experiments that show the inadequacy of the usual hydrodynamic model when a fluid-fluid meniscus moves over a solid surface such as the wall of a small tube or duct. We will then present analytical results that show how to parametrize these problems in a predictive manner. We will illustrate these ideas by showing how to implement the method in numerical fluid mechanical calculations.

  18. A functional-dynamic reflection on participatory processes in modeling projects.

    PubMed

    Seidl, Roman

    2015-12-01

    The participation of nonscientists in modeling projects/studies is increasingly employed to fulfill different functions. However, it is not well investigated if and how explicitly these functions and the dynamics of a participatory process are reflected by modeling projects in particular. In this review study, I explore participatory modeling projects from a functional-dynamic process perspective. The main differences among projects relate to the functions of participation-most often, more than one per project can be identified, along with the degree of explicit reflection (i.e., awareness and anticipation) on the dynamic process perspective. Moreover, two main approaches are revealed: participatory modeling covering diverse approaches and companion modeling. It becomes apparent that the degree of reflection on the participatory process itself is not always explicit and perfectly visible in the descriptions of the modeling projects. Thus, the use of common protocols or templates is discussed to facilitate project planning, as well as the publication of project results. A generic template may help, not in providing details of a project or model development, but in explicitly reflecting on the participatory process. It can serve to systematize the particular project's approach to stakeholder collaboration, and thus quality management. PMID:25999270

  19. Release Path Temperatures of Shock-Compressed Tin from Dynamic Reflectance and Radiance Measurements

    SciTech Connect

    La Lone, B. M.; Stevens, G. D.; Turley, W. D.; Holtkamp, D. B.; Iverson, A. J.; Hixson, R. S.; Veeser, L. R.

    2013-08-01

    Dynamic reflectance and radiance measurements were conducted for tin samples shock compressed to 35 GPa and released to 15 GPa using high explosives. We determined the reflectance of the tin samples glued to lithium fluoride windows using an integrating sphere with an internal xenon flashlamp as an illumination source. The dynamic reflectance (R) was determined at near normal incidence in four spectral bands with coverage in visible and near-infrared spectra. Uncertainties in R/R0 are < 2%, and uncertainties in absolute reflectance are < 5%. In complementary experiments, thermal radiance from the tin/glue/lithium fluoride interface was recorded with similar shock stress and spectral coverage as the reflectance measurements. The two sets of experiments were combined to obtain the temperature history of the tin surface with an uncertainty of < 2%. The stress at the interface was determined from photonic Doppler velocimetry and combined with the temperatures to obtain temperature-stress release paths for tin. We discuss the relationship between the experimental release paths and release isentropes that begin on the principal shock Hugoniot.

  20. Geophysical flows as dynamical systems: the influence of Hide's experiments

    NASA Astrophysics Data System (ADS)

    Ghil, Michael; Read, Peter; Smith, Leonard

    2010-08-01

    Michael Ghil, Peter L Read and Leonard A Smith recount the many and various ways that Raymond Hide has influenced their life and work in geophysical fluid dynamics, meteorology, climatology and planetary sciences, as well as in developing the study of dynamical systems in general.

  1. Dynamics of surface thermal expansion and diffusivity using two-color reflection transient gratings

    SciTech Connect

    Pennington, D.M.; Harris, C.B.

    1993-02-01

    We report ultrafast measurements of the dynamic thermal expansion of a surface and the temperature dependent surface thermal diffusivity using a two-color reflection transient grating technique. Studies were performed on p-type, n-type, and undoped GaAs(100) samples at several temperatures. Using a 75 fs ultraviolet probe with visible excitation beams, the electronic effects that dominate single color experiments become negligible; thus surface expansion due to heating and the subsequent contraction caused by cooling provide the dominant influence on the diffracted probe. The diffracted signal was composed of two components, thermal expansion of the surface and heat flow away from the surface, allowing the determination of the rate of expansion as well as the surface thermal diffusivity. At room temperature a signal rise due to thermal expansion was observed, corresponding to a maximum average displacement of {approx} 1 {angstrom} at 32 ps. Large fringe spacings were used, thus the dominant contributions to the signal were expansion and diffusion perpendicular to the surface. Values for the surface thermal diffusivity of GaAs were measured and found to be in reasonable agreement with bulk values above 50{degrees}K. Below 50{degrees}K, the diffusivity at the surface was more than an order of magnitude slower than in the bulk due to increased phonon boundary scattering. Comparison of the results with a straightforward thermal model yields good agreement over a range of temperatures (12--300{degrees}K). The applicability and advantages of the transient grating technique for studying photothermal and photoacoustic phenomena are discussed.

  2. The Influence of Group Dynamics on Collaborative Scientific Argumentation

    ERIC Educational Resources Information Center

    Ryu, Suna; Sandoval, William A.

    2015-01-01

    Research has addressed what instructional conditions may inhibit or promote scientific argumentation. Little research, however, has paid attention to interpersonal factors that influence collaborative argumentation. The present study examines the ways interpersonal factors affected group dynamics, which influence the features of collaborative…

  3. Reflective SOA fiber cavity adaptive laser source for measuring dynamic strains

    NASA Astrophysics Data System (ADS)

    Wei, Heming; Tao, Chuanyi; Krishnaswamy, Sridhar

    2016-04-01

    Smart sensors based on Optical fiber Bragg gratings (FBGs) are suitable for structural health monitoring of dynamic strains in civil, aerospace, and mechanical structures. In these structures, dynamic strains with high frequencies reveal acoustic emissions cracking or impact loading. It is necessary to find a practical tool for monitoring such structural damages. In this work, we explore an intelligent system based on a reflective semiconductor optical amplifier (RSOA)- FBG composed as a fiber cavity for measuring dynamic strain in intelligent structures. The ASE light emitted from a RSOA laser and reflected by a FBG is amplified in the fiber cavity and coupled out by a 90:10 coupler, which is demodulated by a low frequency compensated Michelson interferometer using a proportional-integral-derivative (PID) controller and is monitored via a photodetector. As the wavelength of the FBG shifts due to dynamic strain, the wavelength of the optical output from the laser cavity shifts accordingly, which is demodulated by the Michelson Interferometer. Because the RSOA has a quick transition time, the RSOA- FBG fiber cavity shows an ability of high frequency response to the FBG reflective spectrum shift, with frequency response extending to megahertz.

  4. Influence of human behavior on cholera dynamics

    PubMed Central

    Wang, Xueying; Gao, Daozhou; Wang, Jin

    2015-01-01

    This paper is devoted to studying the impact of human behavior on cholera infection. We start with a cholera ordinary differential equation (ODE) model that incorporates human behavior via modeling disease prevalence dependent contact rates for direct and indirect transmissions and infectious host shedding. Local and global dynamics of the model are analyzed with respect to the basic reproduction number. We then extend the ODE model to a reaction-convection-diffusion partial differential equation (PDE) model that accounts for the movement of both human hosts and bacteria. Particularly, we investigate the cholera spreading speed by analyzing the traveling wave solutions of the PDE model, and disease threshold dynamics by numerically evaluating the basic reproduction number of the PDE model. Our results show that human behavior can reduce (a) the endemic and epidemic levels, (b) cholera spreading speeds and (c) the risk of infection (characterized by the basic reproduction number). PMID:26119824

  5. On the influence of reflective boundary conditions on the statistics of Poisson-Kac diffusion processes

    NASA Astrophysics Data System (ADS)

    Giona, Massimiliano; Brasiello, Antonio; Crescitelli, Silvestro

    2016-05-01

    We analyze the influence of reflective boundary conditions on the statistics of Poisson-Kac diffusion processes, and specifically how they modify the Poissonian switching-time statistics. After addressing simple cases such as diffusion in a channel, and the switching statistics in the presence of a polarization potential, we thoroughly study Poisson-Kac diffusion in fractal domains. Diffusion in fractal spaces highlights neatly how the modification in the switching-time statistics associated with reflections against a complex and fractal boundary induces new emergent features of Poisson-Kac diffusion leading to a transition from a regular behavior at shorter timescales to emerging anomalous diffusion properties controlled by walk dimensionality of the fractal set.

  6. Flash Lamp Integrating Sphere Technique for Measuring the Dynamic Reflectance of Shocked Materials

    SciTech Connect

    Stevens, Gerald; La Lone, Brandon; Veeser, Lynn; Hixson, Rob; Holtkamp, David

    2013-07-08

    Accurate reflectance (R) measurements of metals undergoing shock wave compression can benefit high pressure research in several ways. For example, pressure dependent reflectance measurements can be used to deduce electronic band structure, and discrete changes with pressure or temperature may indicate the occurrence of a phase boundary. Additionally, knowledge of the wavelength dependent emissivity (1 -R, for opaque samples) of the metal surface is essential for accurate pyrometric temperature measurement because the radiance is a function of both the temperature and emissivity. We have developed a method for measuring dynamic reflectance in the visible and near IR spectral regions with nanosecond response time and less than 1.5% uncertainty. The method utilizes an integrating sphere fitted with a xenon flash-lamp illumination source. Because of the integrating sphere, the measurements are insensitive to changes in surface curvature or tilt. The in-situ high brightness of the flash-lamp exceeds the sample’s thermal radiance and also enables the use of solid state detectors for recording the reflectance signals with minimal noise. Using the method, we have examined the dynamic reflectance of gallium and tin subjected to shock compression from high explosives. The results suggest significant reflectance changes across phase boundaries for both metals. We have also used the method to determine the spectral emissivity of shock compressed tin at the interface between tin and a LiF window. The results were used to perform emissivity corrections to previous pyrometry data and obtain shock temperatures of the tin/LiF interface with uncertainties of less than 2%.

  7. Influence of tissue parameters on visual reflectance spectra of port wine stains and normal skin

    NASA Astrophysics Data System (ADS)

    Norvang Nilsen, Lill T.; Fiskerstrand, Elisanne J.; Bakken, B.; Grini, D.; Standahl, O.; Milner, Thomas E.; Berns, Michael W.; Nelson, J. Stuart; Svaasand, Lars O.

    1996-01-01

    The visual appearance of port-wine stain lesions is often a red to purple color due to an enlarged blood volume in the upper dermis. The purpose of the treatment is to re-establish normal skin coloration. Visual reflectance spectra should therefore, in principle, contain all relevant information about the lesion. The influence on the spectra from the different tissue parameters, such as melanin, blood content and scattering, is rather composite. However, a simple mathematical model can give a good understanding of the relevance of the different components. This knowledge can be used to optimize the laser treatment of port-wine stain. In vivo reflectance spectra were obtained using an integrating sphere spectrophotometer. A simple mathematical model based on the diffusion approximation was used to simulate port- wine stain and normal skin reflectance spectra. The absorption coefficients of epidermis and dermis are mainly due to melanin and blood. These parameters were measured in separate in vivo experiments and obtained from skin biopsies. The scattering coefficients were based on reported values. Simulated reflectance spectra show good agreement with the measured ones. Even though the diffusion model has limited validity for wavelengths shorter than 600 nm, the simulated spectra from 450 to 600 nm give a qualitative understanding of the influence of the tissue parameters. The results show that dark red to almost dark grey port-wine stains contain enlarged blood fraction in the entire upper dermis. The red port-wine stains appear when the abnormal density of blood is confined to a thin layer. High amount of epidermal melanin results in reduced reflectance throughout the visible spectrum. The characteristic spectrum due to the blood is suppressed. The reflectance spectra are strongly dependent on the dermal and epidermal scattering coefficient; even minor changes as naturally occurring with age, might have a significant impact. A permanently reduced scattering

  8. Imogene M. King's scholars reflect on her wisdom and influence on nursing science.

    PubMed

    Clarke, Pamela N; Killeen, Mary B; Messmer, Patricia R; Leibold Sieloff, Christina

    2009-04-01

    Reflections on the impact of the work of great leaders are vital for both scientists and practitioners to gain important perspectives on the progress of the evolution of the discipline. Recognizing the influence of a particular theorist's impact is particularly important at the time of death, which is the time where the development of a particular theory moves from the originator to the followers. This column serves as a tribute to Imogene M. King, and is dedicated to her wisdom in promoting the conceptual system she developed. PMID:19342711

  9. Dynamic influences of changing gear tooth stiffness

    SciTech Connect

    Morguel, O.K.; Esat, I.

    1997-07-01

    One of the principal sources of vibratory excitation of gear a system is due to the angular speed fluctuation of meshing gears due to non-linearities and profile errors and tooth and supporting bearings flexibility. The transmission error is also influenced by the varying force at the contact point of the meshing gear teeth. The varying contact force itself is influenced by the varying tooth stiffness due to change of orientation of teeth relative to each other, during the contact phase of each pair. This paper presents a simplified single degree of freedom gear system. It is assumed that one member of the gear pair is rigid and flexibility of the gear tooth is attributed only to one section of the gear system. This enables the equation to be simplified to a single degree of freedom system. The resulting non-linear equation is solved iteratively by employing a method which combines piecewise linearization for the stiffness and resulting contact orientation shift due to shaft and tooth flexibility. The contact shift will be referred as the phase shift in this report. The early finding indicates that there are significant differences between the response of the system incorporating three different tooth stiffness, namely, constant tooth stiffness, rectangular wave tooth stiffness and sinusoidal tooth stiffness. The results also implies that any design specification associated with gears has to include gear tooth influences, especially if the excitation is of a major concern. The rectangular stiffness variation which most accurately describes the tooth stiffness gives a response fluctuation, studied in the frequency domain shows that the effective natural frequencies fluctuates between certain upper and lower limits. Thus the paper suggest that any design study should consider these limits.

  10. Concentration of Elements in Food: How Can It Reflect Impact of Environmental and Other Influencing Factors?

    NASA Astrophysics Data System (ADS)

    Vincevica-Gaile, Zane; Klavins, Maris

    2013-12-01

    Element content of food is variable and can be influenced by different factors. The aim of the present study was to discover the linkage between macro- and microelement concentrations in food produced in Latvia, and possible impacts of environmental factors. More than 300 fresh food samples such as eggs, cottage cheese, honey, root vegetables, apple juice, apple wine were collected in the time period from 2009 to 2011. Samples were mineralised or analysed directly by appropriate method of quantitative analysis: atomic absorption spectrometry, inductively coupled plasma mass spectrometry or total reflection X-ray fluorescence spectrometry. Statistical analysis of data revealed that food elemental content can be influenced by sitespecific factors such as geographical origin, seasonality, environmental pollution.

  11. Dynamics of influence on hierarchical structures

    NASA Astrophysics Data System (ADS)

    Fotouhi, Babak; Rabbat, Michael G.

    2013-08-01

    Dichotomous spin dynamics on a pyramidal hierarchical structure (the Bethe lattice) are studied. The system embodies a number of classes, where a class comprises nodes that are equidistant from the root (head node). Weighted links exist between nodes from the same and different classes. The spin (hereafter state) of the head node is fixed. We solve for the dynamics of the system for different boundary conditions. We find necessary conditions so that the classes eventually repudiate or acquiesce in the state imposed by the head node. The results indicate that to reach unanimity across the hierarchy, it suffices that the bottommost class adopts the same state as the head node. Then the rest of the hierarchy will inevitably comply. This also sheds light on the importance of mass media as a means of synchronization between the topmost and bottommost classes. Surprisingly, in the case of discord between the head node and the bottommost classes, the average state over all nodes inclines towards that of the bottommost class regardless of the link weights and intraclass configurations. Hence the role of the bottommost class is signified.

  12. Use of a Remote Sensing Method to Estimate the Influence of Anthropogenic Factors on the Spectral Reflectance of Plant Species

    NASA Astrophysics Data System (ADS)

    Krezhova, Dora D.; Yanev, Tony K.

    2007-04-01

    Results from a remote sensing study of the influence of stress factors on the leaf spectral reflectance of wheat and tomato plants contaminated by viruses and pea plants treated with herbicides are presented and discussed. The changes arising in the spectral reflectance characteristics of control and treated plants are estimated through statistical methods as well as through derivative analysis to determine specific reflectance features in the red edge region.

  13. Influence of Temperature on the Dynamic Tensile Behavior of Zirconium

    NASA Astrophysics Data System (ADS)

    Escobedo, Juan P.; Cerreta, Ellen K.; Martinez, Daniel T.; Trujillo, Carl P.; Lebensohn, Ricardo A.; Gray, George T.

    2014-12-01

    The influence of temperature on the dynamic tensile behavior of Zr has been investigated. Bullet-shaped Zr samples with two different textures were dynamically extruded at room temperature and 523 K (250 °C). A higher ductility was measured for samples deformed at elevated temperature as compared to those extruded at room temperature. This difference in ductility is discussed in terms of zirconium's ability to accommodate plastic deformation via thermally enhanced slip activity, as evidenced by examination of the deformed microstructures.

  14. Situating social influence processes: dynamic, multidirectional flows of influence within social networks.

    PubMed

    Mason, Winter A; Conrey, Frederica R; Smith, Eliot R

    2007-08-01

    Social psychologists have studied the psychological processes involved in persuasion, conformity, and other forms of social influence, but they have rarely modeled the ways influence processes play out when multiple sources and multiple targets of influence interact over time. However, workers in other fields from sociology and economics to cognitive science and physics have recognized the importance of social influence and have developed models of influence flow in populations and groups-generally without relying on detailed social psychological findings. This article reviews models of social influence from a number of fields, categorizing them using four conceptual dimensions to delineate the universe of possible models. The goal is to encourage interdisciplinary collaborations to build models that incorporate the detailed, microlevel understanding of influence processes derived from focused laboratory studies but contextualized in ways that recognize how multidirectional, dynamic influences are situated in people's social networks and relationships. PMID:18453465

  15. Total-Internal-Reflection-Fluorescence Microscopy for the Study of Nanobubble Dynamics

    NASA Astrophysics Data System (ADS)

    Chan, Chon U.; Ohl, Claus-Dieter

    2012-10-01

    Nanobubbles can be observed with optical microscopy using the total-internal-reflection-fluorescence excitation. We report on total-internal-reflection-fluorescence visualization using rhodamine 6G at 5μM concentration which results in strongly contrasting pictures. The preferential absorption and the high spatial resolution allow us to detect nanobubbles with diameters of 230 nm and above. We resolve the nucleation dynamics during the water-ethanol-water exchange: within 4 min after exchange the bubbles nucleate and form a stable population. Additionally, we demonstrate that tracer particles near to the nanobubbles are following Brownian motion: the remaining drift flow is weaker than a few micrometers per second at a distance of 400 nm from the nanobubble’s center.

  16. External Dynamics Influencing Tattooing among College Students: A Qualitative Analysis

    ERIC Educational Resources Information Center

    Firmin, Michael; Tse, Luke; Foster, Janna; Angelini, Tammy

    2012-01-01

    The study utilized qualitative research methodology to assess external dynamics and their influences on tattooing practices among college students. Twenty-four undergraduates supplied in-depth interviews regarding the external variables related to college students' decisions to tattoo. The present research follows (Tse, Firmin, Angelini, & Foster,…

  17. Popularity and Adolescent Friendship Networks: Selection and Influence Dynamics

    ERIC Educational Resources Information Center

    Dijkstra, Jan Kornelis; Cillessen, Antonius H. N.; Borch, Casey

    2013-01-01

    This study examined the dynamics of popularity in adolescent friendship networks across 3 years in middle school. Longitudinal social network modeling was used to identify selection and influence in the similarity of popularity among friends. It was argued that lower status adolescents strive to enhance their status through befriending higher…

  18. Switch programming of reflectivity control devices for the coupled dynamics of a solar sail

    NASA Astrophysics Data System (ADS)

    Hu, Tianjian; Gong, Shengping; Mu, Junshan; Li, Junfeng; Wang, Tianshu; Qian, Weiping

    2016-03-01

    As demonstrated in the Interplanetary Kite-craft Accelerated by Radiation Of the Sun (IKAROS), reflectivity control devices (RCDs) are switched on or off independently with each other, which has nevertheless been ignored by many previous researches. This paper emphasizes the discrete property of RCDs, and aims to obtain an appropriate switch law of RCDs for a rigid spinning solar sail. First, the coupled attitude-orbit dynamics is derived from the basic solar force and torque model into an underdetermined linear system with a binary set constraint. Subsequently, the coupled dynamics is reformulated into a constrained quadratic programming and a basic gradient projection method is designed to search for the optimal solution. Finally, a circular sail flying in the Venus rendezvous mission demonstrates the model and method numerically, which illustrates approximately 103 km terminal position error and 0.5 m/s terminal velocity error as 80 independent RCDs are switched on or off appropriately.

  19. Popularity and adolescent friendship networks: selection and influence dynamics.

    PubMed

    Dijkstra, Jan Kornelis; Cillessen, Antonius H N; Borch, Casey

    2013-07-01

    This study examined the dynamics of popularity in adolescent friendship networks across 3 years in middle school. Longitudinal social network modeling was used to identify selection and influence in the similarity of popularity among friends. It was argued that lower status adolescents strive to enhance their status through befriending higher status adolescents, whereas higher status adolescents strive to maintain their status by keeping lower status adolescents at a distance. The results largely supported these expectations. Selection partially accounted for similarity in popularity among friends; adolescents preferred to affiliate with similar-status or higher status peers, reinforcing the attractiveness of popular adolescents and explaining stability of popularity at the individual level. Influence processes also accounted for similarity in popularity over time, showing that peers increase in popularity and become more similar to their friends. The results showed how selection and influence processes account for popularity dynamics in adolescent networks over time. PMID:22985296

  20. Autism spectrum disorder severity reflects the average contribution of de novo and familial influences.

    PubMed

    Robinson, Elise B; Samocha, Kaitlin E; Kosmicki, Jack A; McGrath, Lauren; Neale, Benjamin M; Perlis, Roy H; Daly, Mark J

    2014-10-21

    Autism spectrum disorders (ASDs) are a highly heterogeneous group of conditions--phenotypically and genetically--although the link between phenotypic variation and differences in genetic architecture is unclear. This study aimed to determine whether differences in cognitive impairment and symptom severity reflect variation in the degree to which ASD cases reflect de novo or familial influences. Using data from more than 2,000 simplex cases of ASD, we examined the relationship between intelligence quotient (IQ), behavior and language assessments, and rate of de novo loss of function (LOF) mutations and family history of broadly defined psychiatric disease (depressive disorders, bipolar disorder, and schizophrenia; history of psychiatric hospitalization). Proband IQ was negatively associated with de novo LOF rate (P = 0.03) and positively associated with family history of psychiatric disease (P = 0.003). Female cases had a higher frequency of sporadic genetic events across the severity distribution (P = 0.01). High rates of LOF mutation and low frequencies of family history of psychiatric illness were seen in individuals who were unable to complete a traditional IQ test, a group with the greatest degree of language and behavioral impairment. These analyses provide strong evidence that familial risk for neuropsychiatric disease becomes more relevant to ASD etiology as cases become higher functioning. The findings of this study reinforce that there are many routes to the diagnostic category of autism and could lead to genetic studies with more specific insights into individual cases. PMID:25288738

  1. Influence of precipitation pulses on long-term Prosopis ferox dynamics in the Argentinean intermontane subtropics.

    PubMed

    Morales, Mariano S; Villalba, Ricardo

    2012-02-01

    Biological processes in arid communities are associated with episodic precipitation pulses. We postulate that annual to decadal-scale precipitation pulses modulate the dynamics of the intermontane Prepuna woodlands. To study this hypothesis, we have assessed the influence of precipitation pulses on the rates of growth and survival of Prosopis ferox in the Prepuna woodlands during the past century. Tree ages from several P. ferox stands were used to reconstruct the establishment patterns at each sampling site. Ring-width chronologies provided the basis to assess the influence of annual versus multiannual precipitation pulses on radial growth and establishment over time. Both the radial growth and the stand dynamics of P. ferox at the regional scale were found to be largely modulated by climate, with precipitation the dominant factor influencing interannual variations in P. ferox ring-widths. Our analysis of dendrochronological dating data on 885 individuals of P. ferox revealed a period of abundant establishment from the mid-1970s to beginning of 1990 s, which is coincident with an interval of remarkable above-average precipitation. However, tree-growth and establishment patterns at the local scale in the Prepuna also reflected land-use changes, particularly long-term variations in livestock intensity. The P. ferox dynamics documented here substantiates the hierarchical concept of "resource-pulse" in dry ecosystems, with precipitation pulses of different lengths modulating distinct dynamic processes in the P. ferox woodlands. Interannual variations in precipitation influence year-to-year patterns of P. ferox radial growth, whereas multiannual oscillations in rainfall influence episodic events of tree establishment. The long-term interval considered in this study enabled us to disentangle the roles of natural versus human controls on P. ferox dynamics in the region. PMID:21805299

  2. Influence of credit scoring on the dynamics of Markov chain

    NASA Astrophysics Data System (ADS)

    Galina, Timofeeva

    2015-11-01

    Markov processes are widely used to model the dynamics of a credit portfolio and forecast the portfolio risk and profitability. In the Markov chain model the loan portfolio is divided into several groups with different quality, which determined by presence of indebtedness and its terms. It is proposed that dynamics of portfolio shares is described by a multistage controlled system. The article outlines mathematical formalization of controls which reflect the actions of the bank's management in order to improve the loan portfolio quality. The most important control is the organization of approval procedure of loan applications. The credit scoring is studied as a control affecting to the dynamic system. Different formalizations of "good" and "bad" consumers are proposed in connection with the Markov chain model.

  3. Simulating food web dynamics along a gradient: quantifying human influence.

    PubMed

    Jordán, Ferenc; Gjata, Nerta; Mei, Shu; Yule, Catherine M

    2012-01-01

    Realistically parameterized and dynamically simulated food-webs are useful tool to explore the importance of the functional diversity of ecosystems, and in particular relations between the dynamics of species and the whole community. We present a stochastic dynamical food web simulation for the Kelian River (Borneo). The food web was constructed for six different locations, arrayed along a gradient of increasing human perturbation (mostly resulting from gold mining activities) along the river. Along the river, the relative importance of grazers, filterers and shredders decreases with increasing disturbance downstream, while predators become more dominant in governing eco-dynamics. Human activity led to increased turbidity and sedimentation which adversely impacts primary productivity. Since the main difference between the study sites was not the composition of the food webs (structure is quite similar) but the strengths of interactions and the abundance of the trophic groups, a dynamical simulation approach seemed to be useful to better explain human influence. In the pristine river (study site 1), when comparing a structural version of our model with the dynamical model we found that structurally central groups such as omnivores and carnivores were not the most important ones dynamically. Instead, primary consumers such as invertebrate grazers and shredders generated a greater dynamical response. Based on the dynamically most important groups, bottom-up control is replaced by the predominant top-down control regime as distance downstream and human disturbance increased. An important finding, potentially explaining the poor structure to dynamics relationship, is that indirect effects are at least as important as direct ones during the simulations. We suggest that our approach and this simulation framework could serve systems-based conservation efforts. Quantitative indicators on the relative importance of trophic groups and the mechanistic modeling of eco-dynamics

  4. Neutron reflectivity as a tool to study the interdigitation of grafted polymer chains and its dynamics

    NASA Astrophysics Data System (ADS)

    Leger, Liliane; Restagno, Frédéric; Cousin, Fabrice; Boue, François; Chenneviere, Alexis

    Three series of experiments aimed at characterizing the interdigitation between a brush and a melt, and based on neutron reflectivity, are presented and discussed. The density profile of brush chains has been analysed for series of annealing times, on h-PS brushes in contact with d-PS melts, as a function of molecular weights and grafting densities. We show that the relaxation dynamics of the brush chains can be modelled taking into account the long relaxation time of end tethered chains along with the reptation of the melt chains which accelerates the arm retraction process. Using a non-grafted layer with a thickness smaller than the equilibrium size of the brush when immersed into a thick melt allows one to apply chosen degrees of confinement to the brush. We show that the interdigitation dynamics is affected by such confinements, in a way reminiscent of the change of the glass transition temperature in nanometric PS films. Finally, when the upper d-PS layer is sheared above Tg, flow with large slip at the wall has been observed and interpreted in terms of stretching and expulsion of the grafted chains from the melt. We show how neutron reflectivity directly evidence this expulsion.

  5. Effects of surface reflectance on local second order shape estimation in dynamic scenes.

    PubMed

    Dövencioğlu, Dicle N; Wijntjes, Maarten W A; Ben-Shahar, Ohad; Doerschner, Katja

    2015-10-01

    In dynamic scenes, relative motion between the object, the observer, and/or the environment projects as dynamic visual information onto the retina (optic flow) that facilitates 3D shape perception. When the object is diffusely reflective, e.g. a matte painted surface, this optic flow is directly linked to object shape, a property found at the foundations of most traditional shape-from-motion (SfM) schemes. When the object is specular, the corresponding specular flow is related to shape curvature, a regime change that challenges the visual system to determine concurrently both the shape and the distortions of the (sometimes unknown) environment reflected from its surface. While human observers are able to judge the global 3D shape of most specular objects, shape-from-specular-flow (SFSF) is not veridical. In fact, recent studies have also shown systematic biases in the perceived motion of such objects. Here we focus on the perception of local shape from specular flow and compare it to that of matte-textured rotating objects. Observers judged local surface shape by adjusting a rotation and scale invariant shape index probe. Compared to shape judgments of static objects we find that object motion decreases intra-observer variability in local shape estimation. Moreover, object motion introduces systematic changes in perceived shape between matte-textured and specular conditions. Taken together, this study provides a new insight toward the contribution of motion and surface material to local shape perception. PMID:25645965

  6. Influence of nozzle random side loads on launch vehicle dynamics

    NASA Astrophysics Data System (ADS)

    Srivastava, Nilabh; Tkacik, Peter T.; Keanini, Russell G.

    2010-08-01

    It is well known that the dynamic performance of a rocket or launch vehicle is enhanced when the length of the divergent section of its nozzle is reduced or the nozzle exit area ratio is increased. However, there exists a significant performance trade-off in such rocket nozzle designs due to the presence of random side loads under overexpanded nozzle operating conditions. Flow separation and the associated side-load phenomena have been extensively investigated over the past five decades; however, not much has been reported on the effect of side loads on the attitude dynamics of rocket or launch vehicle. This paper presents a quantitative investigation on the influence of in-nozzle random side loads on the attitude dynamics of a launch vehicle. The attitude dynamics of launch vehicle motion is captured using variable-mass control-volume formulation on a cylindrical rigid sounding rocket model. A novel physics-based stochastic model of nozzle side-load force is developed and embedded in the rigid-body model of rocket. The mathematical model, computational scheme, and results corresponding to side loading scenario are subsequently discussed. The results highlight the influence of in-nozzle random side loads on the roll, pitch, yaw, and translational dynamics of a rigid-body rocket model.

  7. Correlation between Ultrasound Reflection Intensity and Tumor Ablation Ratio of Late-Stage Pancreatic Carcinoma in HIFU Therapy: Dynamic Observation on Ultrasound Reflection Intensity

    PubMed Central

    Ge, Hui-Yu; Miao, Li-Ying; Wang, Jin-Rui; Xiong, Liu-Lin; Yan, Fang; Zheng, Cui-Shan; Jia, Jian-Wen; Cui, Li-Gang; Chen, Wen

    2013-01-01

    The minimally invasive high-intensity focused ultrasound (HIFU) therapy is thermal ablation treatment for late-stage pancreatic carcinoma with widely recognized safety and effectiveness, but there are currently no instant assessment methods for its ablation effect. It is vital to find a real-time high-sensitive assessment method. This research aims to dynamically observe the variation rules of ultrasound reflection intensity, analyze the correlation between ultrasound reflection intensity and tumor ablation ratio, and find out the value of ultrasound reflection intensity in prognosis of HIFU ablation effect. HIFU intermittent therapies were retrospectively analyzed for 31 subjects with late-stage pancreatic carcinoma from March 2007 to December 2009 in the study. The variation rules of the ultrasound reflection intensity during HIFU therapy were summarized and the correlation between ultrasound reflection intensity and tumor ablation ratio was analyzed based on the tumor ablation ratio indicated by CT scanning. The conclusion is that variation of ultrasound reflection intensity can be used for initial assessment of tumor ablation in HIFU therapy and early prognosis of overall HIFU ablation, providing important clinical basis for improving safety and effectiveness of HIFU therapy. Ultrasound can work as a real-time imaging instrument for observation of HIFU ablation effect in treating late-stage pancreatic carcinoma. PMID:24453916

  8. Influence of process parameter variation on the reflectivity of sputter-deposited W-C multilayer diffraction gratings

    NASA Technical Reports Server (NTRS)

    Sager, B.; Benson, P.; Jahoda, K.; Jacobs, J. R.; Bloch, J. J.

    1986-01-01

    Multilayer W-C diffraction gratings with nominal d spacings of 35 A have been fabricated by magnetron sputter deposition. The peak and integrated reflectivities of these films have been measured with Al K-alpha X-rays and compared to theoretical values. The rms surface roughness has been evaluated. The influence of several sputtering-system process parameters on the reflectivities has been investigated.

  9. Dynamic behaviour of HPFRCC: The influence of fibres dispersion

    NASA Astrophysics Data System (ADS)

    Caverzan, Alessio; di Prisco, Marco; Cadoni, Ezio

    2015-09-01

    The promise of fibre-reinforced cementitious composites for dynamic loading application stems from their observed good response under static loading mainly due to fibre contribution. An experimental research aimed at contributing to the understanding of the behaviour of advanced fibre-reinforced cementitious composites subjected to low and high strain rates was carried out underlining the influence of fibres. The material behaviour was investigated at three strain rates (0.1, 1, and 150 s-1) and the tests results were compared with their static behaviour. Tests at intermediate strain rates (0.1-1 s-1) were carried out by means of a hydro-pneumatic machine (HPM), while high strain rates (150 s-1) were investigated by exploiting a modified Hopkinson bar (MHB). Particular attention has been placed on the influence of fibre and fibre dispersion on the dynamic behaviour of the materials: matrix, HPFRCC with random fibre distribution and aligned fibres were compared. The comparison between static and dynamic tests highlighted several relevant aspects regarding the influence of fibres on the peak strength and post-peak behaviour at high strain rates.

  10. Influence of surface clinker on the crustal structures and dynamics of 'a'ā lava flows

    NASA Astrophysics Data System (ADS)

    Applegarth, L. J.; James, M. R.; van Wyk de Vries, B.; Pinkerton, H.

    2010-07-01

    Surface structures on 'a'ā and blocky lavas reflect the internal flow dynamics during emplacement and also influence the dynamics of developing flows. To investigate the effects of brittle, clinkery 'a'ā flow crusts on flow dynamics and surface structures, we conducted sand and silicone laboratory experiments that simulated the advance of lava into a preexisting channelized flow with a surface crust. Experiments carried out with relatively thin crusts produced apparently ductile surface deformation structures, while thick crusts behaved dominantly in a brittle manner. Increased crustal thickness led to increased strength under compression but favored more disruption under tension, as the flow core welled up through tensile fractures, entraining crustal material. At lava flow fronts, upwelling and entrainment would increase heat losses by radiation and advection, respectively, resulting in a positive-feedback cooling loop. Fracturing caused heterogeneous crustal distribution near the flow front, which resulted in lobate flow advance, despite the absence of the viscoelastic layer that has previously been inferred as the primary control on flow advance and lobe formation. We therefore conclude that the influence of a purely brittle crust on the dynamics and surface morphologies of lava flows is more significant than often thought. All of the surface structures produced in the experiments have been observed on lavas or glaciers and many also on landslides and debris flows, suggesting the results can assist in the understanding of a range of natural flows.

  11. Mesoscopic dynamics of diffusion-influenced enzyme kinetics.

    PubMed

    Chen, Jiang-Xing; Kapral, Raymond

    2011-01-28

    A particle-based mesoscopic model for enzyme kinetics is constructed and used to investigate the influence of diffusion on the reactive dynamics. Enzymes and enzyme-substrate complexes are modeled as finite-size soft spherical particles, while substrate, product, and solvent molecules are point particles. The system is evolved using a hybrid molecular dynamics-multiparticle collision dynamics scheme. Both the nonreactive and reactive dynamics are constructed to satisfy mass, momentum, and energy conservation laws, and reversible reaction steps satisfy detailed balance. Hydrodynamic interactions among the enzymes and complexes are automatically accounted for in the dynamics. Diffusion manifests itself in various ways, notably in power-law behavior in the evolution of the species concentrations. In accord with earlier investigations, regimes where the product production rate exhibits either monotonic or nonmonotonic behavior as a function of time are found. In addition, the species concentrations display both t(-1/2) and t(-3/2) power-law behavior, depending on the dynamical regime under investigation. For high enzyme volume fractions, cooperative effects influence the enzyme kinetics. The time dependent rate coefficient determined from the mass action rate law is computed and shown to depend on the enzyme concentration. Lifetime distributions of substrate molecules newly released in complex dissociation events are determined and shown to have either a power-law form for rebinding to the same enzyme from which they were released or an exponential form for rebinding to different enzymes. The model can be used and extended to explore a variety of issues related concentration effects and diffusion on enzyme kinetics. PMID:21280744

  12. An accurate dynamical electron diffraction algorithm for reflection high-energy electron diffraction

    NASA Astrophysics Data System (ADS)

    Huang, J.; Cai, C. Y.; Lv, C. L.; Zhou, G. W.; Wang, Y. G.

    2015-12-01

    The conventional multislice method (CMS) method, one of the most popular dynamical electron diffraction calculation procedures in transmission electron microscopy, was introduced to calculate reflection high-energy electron diffraction (RHEED) as it is well adapted to deal with the deviations from the periodicity in the direction parallel to the surface. However, in the present work, we show that the CMS method is no longer sufficiently accurate for simulating RHEED with the accelerating voltage 3-100 kV because of the high-energy approximation. An accurate multislice (AMS) method can be an alternative for more accurate RHEED calculations with reasonable computing time. A detailed comparison of the numerical calculation of the AMS method and the CMS method is carried out with respect to different accelerating voltages, surface structure models, Debye-Waller factors and glancing angles.

  13. Molecular Dynamics Calculation of Carbon/Hydrocarbon Reflection Coefficients on a Graphite Surface Employing Distributed Computing

    NASA Astrophysics Data System (ADS)

    Alman, D. A.; Ruzic, D. N.; Brooks, J. N.

    2001-10-01

    Reflection coefficients of carbon and hydrocarbon molecules have been calculated with a molecular dynamics code. The code uses the Brenner hydrocarbon potential, an empirical many-body potential that can model the chemical bonding in small hydrocarbon molecules and graphite surfaces. A variety of incident energies and angles have been studied. Typical results for carbon show reflection coefficients 0.4 at thermal energy, decreasing to a minimum of 0.15 at 10-20 eV, and then increasing again. Distributed computing is used to distribute the work among 10-20 desktop PCs in the laboratory. The system consists of a client application run on all of the PCs and a single server machine that distributes work and compiles the results sent back from the clients. The client-server software is written in Java and requires no commercial software packages. Thus, the MD code benefits from multiprocessor-like speed-up at no additional cost by using the idle CPU cycles that would otherwise be wasted. These calculations represent an important improvement to the WBC code, which has been used to model surface erosion, core plasma contamination, and tritium codeposition in many fusion design studies and experiments.

  14. The National Board Certification Portfolio Process and Its Influence on Teacher Reflection

    ERIC Educational Resources Information Center

    Palmer, Jennifer L.

    2012-01-01

    This study examined the types of teacher reflections and the changes in reflective levels as 15 candidates for National Board Certification worked through the portfolio process. This study also examined how the portfolio requirements and mentoring from candidate support providers helped teachers deepen their levels of reflection. Study findings…

  15. Early Childhood Teachers' Views of Nature of Science: The Influence of Intellectual Levels, Cultural Values, and Explicit Reflective Teaching

    ERIC Educational Resources Information Center

    Akerson, Valarie L.; Buzzelli, Cary A.; Donnelly, Lisa A.

    2008-01-01

    This study tracked the influence of explicit reflective instructional methods on cultural values, ethical and intellectual development, and the relationship of these with preservice teachers' views of nature of science (NOS). The researchers used the Views of Nature of Science Form B (VNOS B) to describe NOS views, the Learning Context…

  16. In vivo skin absorption dynamics of topically applied pharmaceuticals monitored by fiber-optic diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Kim, Ki-Hong; Jheon, Sanghoon; Kim, Jong-Ki

    2007-03-01

    A simple non-invasive ultra-violet/visible (UV/vis) diffusive reflectance spectroscopy combined with fiber-optics was investigated to elicit the dynamics of skin penetration in vivo of a pharmaceutical, aminolevulinic acid polyethylene glycol cream (5-ALA-PEG cream). Temporal data of the reflectance, R( λ), were measured from a bare skin region and from a skin region treated with 5-ALA cream. The difference in apparent optical density [(ΔAOD) = Δ log[1/ R( λ)

  17. The high heritability of educational achievement reflects many genetically influenced traits, not just intelligence

    PubMed Central

    Krapohl, Eva; Rimfeld, Kaili; Shakeshaft, Nicholas G.; Trzaskowski, Maciej; McMillan, Andrew; Pingault, Jean-Baptiste; Asbury, Kathryn; Harlaar, Nicole; Kovas, Yulia; Dale, Philip S.; Plomin, Robert

    2014-01-01

    Because educational achievement at the end of compulsory schooling represents a major tipping point in life, understanding its causes and correlates is important for individual children, their families, and society. Here we identify the general ingredients of educational achievement using a multivariate design that goes beyond intelligence to consider a wide range of predictors, such as self-efficacy, personality, and behavior problems, to assess their independent and joint contributions to educational achievement. We use a genetically sensitive design to address the question of why educational achievement is so highly heritable. We focus on the results of a United Kingdom-wide examination, the General Certificate of Secondary Education (GCSE), which is administered at the end of compulsory education at age 16. GCSE scores were obtained for 13,306 twins at age 16, whom we also assessed contemporaneously on 83 scales that were condensed to nine broad psychological domains, including intelligence, self-efficacy, personality, well-being, and behavior problems. The mean of GCSE core subjects (English, mathematics, science) is more heritable (62%) than the nine predictor domains (35–58%). Each of the domains correlates significantly with GCSE results, and these correlations are largely mediated genetically. The main finding is that, although intelligence accounts for more of the heritability of GCSE than any other single domain, the other domains collectively account for about as much GCSE heritability as intelligence. Together with intelligence, these domains account for 75% of the heritability of GCSE. We conclude that the high heritability of educational achievement reflects many genetically influenced traits, not just intelligence. PMID:25288728

  18. The high heritability of educational achievement reflects many genetically influenced traits, not just intelligence.

    PubMed

    Krapohl, Eva; Rimfeld, Kaili; Shakeshaft, Nicholas G; Trzaskowski, Maciej; McMillan, Andrew; Pingault, Jean-Baptiste; Asbury, Kathryn; Harlaar, Nicole; Kovas, Yulia; Dale, Philip S; Plomin, Robert

    2014-10-21

    Because educational achievement at the end of compulsory schooling represents a major tipping point in life, understanding its causes and correlates is important for individual children, their families, and society. Here we identify the general ingredients of educational achievement using a multivariate design that goes beyond intelligence to consider a wide range of predictors, such as self-efficacy, personality, and behavior problems, to assess their independent and joint contributions to educational achievement. We use a genetically sensitive design to address the question of why educational achievement is so highly heritable. We focus on the results of a United Kingdom-wide examination, the General Certificate of Secondary Education (GCSE), which is administered at the end of compulsory education at age 16. GCSE scores were obtained for 13,306 twins at age 16, whom we also assessed contemporaneously on 83 scales that were condensed to nine broad psychological domains, including intelligence, self-efficacy, personality, well-being, and behavior problems. The mean of GCSE core subjects (English, mathematics, science) is more heritable (62%) than the nine predictor domains (35-58%). Each of the domains correlates significantly with GCSE results, and these correlations are largely mediated genetically. The main finding is that, although intelligence accounts for more of the heritability of GCSE than any other single domain, the other domains collectively account for about as much GCSE heritability as intelligence. Together with intelligence, these domains account for 75% of the heritability of GCSE. We conclude that the high heritability of educational achievement reflects many genetically influenced traits, not just intelligence. PMID:25288728

  19. Influence of dissolved organic materials on turbid water optical properties and remote-sensing reflectance

    NASA Technical Reports Server (NTRS)

    Witte, W. G.; Whitlock, C. H.; Harriss, R. C.; Usry, J. W.; Poole, L. R.; Houghton, W. M.; Morris, W. D.; Gurganus, E. A.

    1982-01-01

    The effects of dissolved organic materials on turbid-water optical properties are assessed, by means of field measurements and laboratory simulations in which upwelled reflectance, attenuation, absorption, and backscatter spectral properties at wavelengths from 450 to 800 nm are examined in relation to water chemistry. The data show that dissolved organic materials decrease upwelled reflectance from turbid waters, and that the decrease in reflectance is a nonlinear function of concentration with the largest gradients at low carbon concentrations, depending on wavelength. Upwelled reflectance is found to be highly correlated with two backscatter-absorption parameters used in some optical models, which are nonlinear with dissolved organic material concentration change.

  20. Disturbance frequency influences patch dynamics in stream benthic algal communities.

    PubMed

    Ledger, Mark E; Harris, Rebecca M L; Armitage, Patrick D; Milner, Alexander M

    2008-04-01

    Disturbance is integral to the organisation of riverine ecosystems. Fluctuating low flows caused by supra-seasonal drought and water management periodically dewater habitat patches, potentially creating heterogeneity in the taxonomic composition and successional dynamics of benthic communities. The frequency of disturbance induced by low flows is contingent upon the topography of the river bed and thus varies among patches. We investigated whether the frequency of patch dewatering influenced the structure and temporal dynamics of benthic algal communities attached to the upper surfaces of stones in stream mesocosms (4 m2). In a 693-day disturbance experiment, we applied short dewatering disturbances (6 days) at high (33-day cycles) and low frequencies (99-day cycles) and compared algal assemblages with undisturbed controls at 21 endpoints. In the absence of disturbance, epilithic space was dominated by the green encrusting alga Gongrosira incrustans. However, drying disturbances consistently reduced the dominance of the green alga, and crust abundance decreased with increasing disturbance frequency, thereby opening space for a diversity of mat-forming diatoms. The response of mat diatoms to disturbance varied markedly during the experiment, from strong reductions in the abundance of loosely attached mats in mid-late 2000 to the exploitation of open space by closely adhering mats in 2001. Contrary responses were attributed to changes in the species composition of mat diatoms, which influenced the physiognomy and hence stress-resistance and resilience of the assemblage. Our results indicate that patchy dewatering of habitat patches during periods of low flow influences the successional dynamics of algae, thereby creating distinctive mosaics on the stream bed. PMID:18193289

  1. Influence of snow-cover properties on avalanche dynamics

    NASA Astrophysics Data System (ADS)

    Steinkogler, W.; Sovilla, B.; Lehning, M.

    2012-04-01

    Snow avalanches with the potential of reaching traffic routes and settlements are a permanent winter threat for many mountain communities. Snow safety officers have to take the decision whether to close a road, a railway line or a ski slope. Those decisions are often very difficult as they demand the ability to interpret weather forecasts, to establish their implication for the stability and the structure of the snow cover and to evaluate the influence of the snow cover on avalanche run-out distances. In the operational programme 'Italy-Switzerland, project STRADA' we focus on the effects of snow cover on avalanche dynamics, and thus run-out distance, with the aim to provide a better understanding of this influence and to ultimately develop tools to support snow safety officers in their decision process. We selected five avalanches, measured at the Vallée de la Sionne field site, with similar initial mass and topography but different flow dynamics and run-out distances. Significant differences amongst the individual avalanches could be observed for front and internal velocities, impact pressures, flow regimes, deposition volumes and run-out distances. For each of these avalanches, the prevailing snow conditions at release were reconstructed using field data from local snowpits or were modeled with SNOWPACK. Combining flow dynamical data with snow cover properties shows that erodible snow depth, snow density and snow temperature in the snow pack along the avalanche track are among the decisive variables that appear to explain the observed differences. It is further discussed, how these influencing factors can be quantified and used for improved predictions of site and time specific avalanche hazard.

  2. Lattice dynamics of neodymium: Influence of 4 f electron correlations

    NASA Astrophysics Data System (ADS)

    Waller, O.; Piekarz, P.; Bosak, A.; Jochym, P. T.; Ibrahimkutty, S.; Seiler, A.; Krisch, M.; Baumbach, T.; Parlinski, K.; Stankov, S.

    2016-07-01

    Incorporation of strong electron correlations into the density functional theory (DFT) for the electronic structure calculations of light lanthanides leads to a modification of interatomic forces and consequently the lattice dynamics. Using first-principles theory we demonstrate the substantial influence of the 4 f electron correlations on the phonon dispersion relations of Nd. The calculations are verified by an inelastic x-ray scattering experiment performed on a single-crystalline Nd(0001) film. We show that very good agreement between the calculated and measured data is achieved when electron-electron interactions are treated by the DFT +U approach.

  3. Vestibular ontogeny: Measuring the influence of the dynamic environment

    NASA Technical Reports Server (NTRS)

    Jones, Timothy A.; Devries, Sherri M.; Dubois, Linda M.; Nelson, Rick C.

    1993-01-01

    In comparison to other special senses, we are only meagerly informed about the development of vestibular function and the mechanisms that may operate to control or influence the course of vestibular ontogeny. Perhaps one contributing factor to this disparity is the difficulty of evaluating vestibular sense organs directly and noninvasively. The present report describes a recently developed direct noninvasive vestibular function test that can be used to address many basic questions about the developing vestibular system. More particularly, the test can be used to examine the effects of the dynamic environment (e.g. gravitational field and vibration) on vestibular ontogeny.

  4. Multiparticle collision dynamics for diffusion-influenced signaling pathways

    NASA Astrophysics Data System (ADS)

    Strehl, R.; Rohlf, K.

    2016-08-01

    An efficient yet accurate simulation method for modeling diffusion-influenced reaction networks is presented. The method extends existing reactive multiparticle collision dynamics by incorporating species-dependent diffusion coefficients, and developing theoretical expressions for the reactant-dependent diffusion control. This off-lattice particle-based mesoscopic simulation tool is particularly suited for problems in which detailed descriptions of particle trajectories and local reactions are required. Numerical simulations of an intracellular signaling pathway for bacterial chemotaxis are carried out to validate our approach, and to demonstrate its efficiency.

  5. The influence of acoustic reflections from diffusive architectural surfaces on spatial auditory perception

    NASA Astrophysics Data System (ADS)

    Robinson, Philip W.

    This thesis addresses the effect of reflections from diffusive architectural surfaces on the perception of echoes and on auditory spatial resolution. Diffusive architectural surfaces play an important role in performance venue design for architectural expression and proper sound distribution. Extensive research has been devoted to the prediction and measurement of the spatial dispersion. However, previous psychoacoustic research on perception of reflections and the precedence effect has focused on specular reflections. This study compares the echo threshold of specular reflections, against those for reflections from realistic architectural surfaces, and against synthesized reflections that isolate individual qualities of reflections from diffusive surfaces, namely temporal dispersion and spectral coloration. In particular, the activation of the precedence effect, as indicated by the echo threshold is measured. Perceptual tests are conducted with direct sound, and simulated or measured reflections with varying temporal dispersion. The threshold for reflections from diffusive architectural surfaces is found to be comparable to that of a specular re ection of similar energy rather than similar amplitude. This is surprising because the amplitude of the dispersed re ection is highly attenuated, and onset cues are reduced. This effect indicates that the auditory system is integrating re ection response energy dispersed over many milliseconds into a single stream. Studies on the effect of a single diffuse reflection are then extended to a full architectural enclosure with various surface properties. This research utilizes auralizations from measured and simulated performance venues to investigate spatial discrimination of multiple acoustic sources in rooms. It is found that discriminating the lateral arrangement of two sources is possible at narrower separation angles when reflections come from at rather than diffusive surfaces. Additionally, subjective impressions are

  6. The Influence of Reflective Self-Explanations on Problem-Solving Performance

    ERIC Educational Resources Information Center

    Kwon, Kyungbin; Jonassen, David H.

    2011-01-01

    In this study, the effects of reflective self-explanations on conceptual understanding and problem solving are investigated in a domain of computer programming. After completing a multiple-choice test, 33 students were asked to reflect on and explain why their answers were correct or incorrect. Groups were divided for post hoc analysis based on…

  7. Influence of MR damper modeling on vehicle dynamics

    NASA Astrophysics Data System (ADS)

    de-J Lozoya-Santos, Jorge; Morales-Menendez, Ruben; Ramirez-Mendoza, Ricardo A.; Vivas-Lopez, Carlos A.

    2013-12-01

    The influence of magneto-rheological damper modeling in vehicle dynamics analysis is studied. Several tests using CarSim™ compare a four-corner controlled semi-active suspension for two different magneto-rheological damper models. The magneto-rheological damper characteristics were identified from experimental data. A model-free controller discards the influence of control and emphasizes the compliance of the magneto-rheological damper model; the characteristics of the vehicle index performance considered were comfort, road holding, handling, roll and suspension deflection. The comparison for magneto-rheological damper dynamics and semi-active suspension covers the automotive bandwidth. The results show that high precision of a magneto-rheological damper model as an isolated feature is not enough. The magneto-rheological damper model, as a component of a vehicle suspension, needs to simulate with passive precision and variable damping forces. The findings exhibit the requisite of accurate models for evaluation of semi-active control systems in classic tests. The lack of the friction component in a magneto-rheological damper model leads to an overestimation in handling and stability.

  8. Molecular dynamics simulations and neutron reflectivity as an effective approach to characterize biological membranes and related macromolecular assemblies.

    PubMed

    Darré, L; Iglesias-Fernandez, J; Kohlmeyer, A; Wacklin, H; Domene, C

    2015-10-13

    In combination with other spectroscopy, microscopy, and scattering techniques, neutron reflectivity is a powerful tool to characterize biological systems. Specular reflection of neutrons provides structural information at the nanometer and subnanometer length scales, probing the composition and organization of layered materials. Currently, analysis of neutron reflectivity data involves several simplifying assumptions about the structure of the sample under study, affecting the extraction and interpretation of information from the experimental data. Computer simulations can be used as a source of structural and dynamic data with atomic resolution. We present a novel tool to compare the structural properties determined by neutron reflectivity experiments with those obtained from molecular simulations. This tool allows benchmarking the ability of molecular dynamics simulations to reproduce experimental data, but it also promotes unbiased interpretation of experimentally determined quantities. Two application examples are presented to illustrate the capabilities of the new tool. The first example is the generation of reflectivity profiles for a 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid bilayer from molecular dynamics simulations using data from both atomistic and coarse-grained models, and comparison with experimentally measured data. The second example is the calculation of lipid volume changes with temperature and composition from all atoms simulations of single and mixed 1,2-di-palmitoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dihexadecanoyl-sn-glycero-3-phosphocholine (DPPC) bilayers. PMID:26574275

  9. Diurnal and seasonal dynamics of canopy-level solar-induced chlorophyll fluorescence and spectral reflectance indices in a cornfield

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A collaborative field campaign was undertaken to examine the temporal dynamics of canopy-level solar-induced fluorescence (SIF) and the Photochemical Reflectance Index (PRI) in conjunction with photosynthetic light use efficiency (LUE) obtained from fluxes measured at an instrumented tower. We condu...

  10. Genetic Influences on Dynamic Complexity of Brain Oscillations

    PubMed Central

    Anokhin, Andrey P.; Müller, Viktor; Lindenberger, Ulman; Heath, Andrew C.; Myers, Erin

    2007-01-01

    Human electroencephalogram (EEG) consists of complex aperiodic oscillations that are assumed to indicate underlying neural dynamics such as the number and the degree of independence of oscillating neuronal networks. EEG complexity can be estimated using measures derived from non-linear dynamic systems theory. Variations in such measures have been shown to be associated with normal individual differences in cognition and some neuropsychiatric disorders. Despite the increasing use of EEG complexity measures for the study of normal and abnormal brain functioning, little is known about genetic and environmental influences on these measures. Using the pointwise dimension (PD2) algorithm, this study assessed heritability of EEG complexity at rest in a sample of 214 young female twins consisting of 51 monozygotic (MZ) and 56 dizygotic (DZ) pairs. In MZ twins, intrapair correlations were high and statistically significant; in DZ twins, correlations were substantially smaller. Genetic analyses using linear structural equation modeling revealed high and significant heritability of EEG complexity: 62–68 % in the eyes closed condition, and 46–60 % in the eyes open condition. Results suggest that individual differences in the complexity of resting electrocortical dynamics are largely determined by genetic factors. Neurophysiological mechanisms mediating genetic variation in EEG complexity may include the degree of structural connectivity and functional differentiation among cortical neuronal assemblies. PMID:16442730

  11. Racial identity and reflected appraisals as influences on Asian Americans' racial adjustment.

    PubMed

    Alvarez, A N; Helms, J E

    2001-08-01

    J. E. Helms's (1990) racial identity psychodiagnostic model was used to examine the contribution of racial identity schemas and reflected appraisals to the development of healthy racial adjustment of Asian American university students (N = 188). Racial adjustment was operationally defined as collective self-esteem and awareness of anti-Asian racism. Multiple regression analyses suggested that racial identity schemas and reflected appraisals were significantly predictive of Asian Americans' racial adjustment. Implications for counseling and future research are discussed. PMID:11506069

  12. Beryllium deposition on International Thermonuclear Experimental Reactor first mirrors: Layer morphology and influence on mirror reflectivity

    NASA Astrophysics Data System (ADS)

    De Temmerman, G.; Baldwin, M. J.; Doerner, R. P.; Nishijima, D.; Seraydarian, R.; Schmid, K.; Kost, F.; Linsmeier, Ch.; Marot, L.

    2007-10-01

    Metallic mirrors will be essential components of the optical diagnostic systems in the International Thermonuclear Experimental Reactor (ITER). Reliability of these systems may be affected by mirror reflectivity changes induced by erosion and/or deposition of impurities (carbon, beryllium). The present study aims to assess the effect of beryllium (Be) deposition on the reflectivity of metallic mirrors and to collect data on the optical quality of these layers in terms of morphology, roughness, etc. Mirrors from molybdenum and copper were exposed in the PISCES-B linear plasma device to collect eroded material from graphite and beryllium targets exposed to beryllium-seeded deuterium plasma. After exposure, relative reflectivity of the mirrors was measured and different surface analysis techniques were used to investigate the properties of the deposited layers. Be layers formed in PISCES-B exhibit high levels of porosity which makes the reflectivity of the Be layers much lower than the reflectivity of pure Be. It is found that if Be deposition occurs on ITER first mirrors, the reflectivity of the coated mirrors will strongly depend on the layer morphology, which in turn depends on the deposition conditions.

  13. Communication: The influence of vibrational parity in chiral photoionization dynamics

    SciTech Connect

    Powis, Ivan

    2014-03-21

    A pronounced vibrational state dependence of photoelectron angular distributions observed in chiral photoionization experiments is explored using a simple, yet realistic, theoretical model based upon the transiently chiral molecule H{sub 2}O{sub 2}. The adiabatic approximation is used to separate vibrational and electronic wavefunctions. The full ionization matrix elements are obtained as an average of the electronic dipole matrix elements over the vibrational coordinate, weighted by the product of neutral and ion state vibrational wavefunctions. It is found that the parity of the vibrational Hermite polynomials influences not just the amplitude, but also the phase of the transition matrix elements, and the latter is sufficient, even in the absence of resonant enhancements, to account for enhanced vibrational dependencies in the chiral photoionization dynamics.

  14. Radiative Influences On The Dynamical Structure of Cirrus Clouds

    NASA Astrophysics Data System (ADS)

    Dobbie, S.; Jonas, P. R.

    The results of a study will be presented which investigates the role of radiative and la- tent heating processes on the dynamical and microphysical evolution of cirrus clouds. The UK Met. Office's LES model run in 2D is used as the cloud resolving model for this work. Results will be shown pertaining to the effects that solar and IR radiation have on cloud stability, morphology, microphysics, time evolution, and cloud lifetime. In an attempt to generalize the results beyond the model calculations, stability num- bers will be presented that help to assess the influence that these diabatic processes have on the cloud stability. Recent work will also be shown pertaining to full 3D model simulations and a study showing a comparison of results from the LES double moment microphysics scheme to observations.

  15. Mcl-1 dynamics influence mitotic slippage and death in mitosis

    PubMed Central

    Sloss, Olivia; Topham, Caroline; Diez, Maria; Taylor, Stephen

    2016-01-01

    Microtubule-binding drugs such as taxol are frontline treatments for a variety of cancers but exactly how they yield patient benefit is unclear. In cell culture, inhibiting microtubule dynamics prevents spindle assembly, leading to mitotic arrest followed by either apoptosis in mitosis or slippage, whereby a cell returns to interphase without dividing. Myeloid cell leukaemia-1 (Mcl-1), a pro-survival member of the Bcl-2 family central to the intrinsic apoptosis pathway, is degraded during a prolonged mitotic arrest and may therefore act as a mitotic death timer. Consistently, we show that blocking proteasome-mediated degradation inhibits taxol-induced mitotic apoptosis in a Mcl-1-dependent manner. However, this degradation does not require the activity of either APC/C-Cdc20, FBW7 or MULE, three separate E3 ubiquitin ligases implicated in targeting Mcl-1 for degradation. This therefore challenges the notion that Mcl-1 undergoes regulated degradation during mitosis. We also show that Mcl-1 is continuously synthesized during mitosis and that blocking protein synthesis accelerates taxol induced death-in-mitosis. Modulating Mcl-1 levels also influences slippage; overexpressing Mcl-1 extends the time from mitotic entry to mitotic exit in the presence of taxol, while inhibiting Mcl-1 accelerates it. We suggest that Mcl-1 competes with Cyclin B1 for binding to components of the proteolysis machinery, thereby slowing down the slow degradation of Cyclin B1 responsible for slippage. Thus, modulating Mcl-1 dynamics influences both death-in-mitosis and slippage. However, because mitotic degradation of Mcl-1 appears not to be under the control of an E3 ligase, we suggest that the notion of network crosstalk is used with caution. PMID:26769847

  16. Oxidation-resistant reflective surfaces for solar dynamic power generation in near earth orbit

    NASA Technical Reports Server (NTRS)

    Gulino, Daniel A.; Egger, Robert A.; Banholzer, William F.

    1987-01-01

    Reflective surfaces for Space Station power generation systems are required to withstand the atomic oxygen-dominated environment of near earth orbit. Thin films of platinum and rhodium, which are corrosion resistant reflective metals, have been deposited by ion beam sputter deposition onto various substrate materials. Solar reflectances were then measured as a function of time of exposure to a RF-generated air plasma.

  17. Transformation of the Strongly Hydrogen Bonded System into van der Waals one Reflected in Molecular Dynamics

    NASA Astrophysics Data System (ADS)

    Kamiński, K.; Kamińska, E.; Grzybowska, K.; Włodarczyk, P.; Pawlus, S.; Paluch, M.; Zioło, J.; Rzoska, S. J.; Pilch, J.; Kasprzycka, A.; Szeja, W.

    Dielectric relaxation studies on disaccharides lactose and octa-O-acetyl-lactose are reported. The latter is a hydrogen bonded system while the former is a van der Waals glass former. The transformation between them was arranged by substituting hydrogen atoms in lactose by acetyl groups. Hereby the influence of differences in bounding on dynamics of both systems is discussed. We showed that the faster secondary relaxation (labeled γ) in octa-O-acetyl-lactose has much lower amplitude than that of lactose. The relaxation time and activation energy remain unchanged in comparison to the γ- relaxation of lactose. We did not observe the slow secondary relaxation (labeled β), clearly visible in lactose, in its acethyl derivative. Detailed analysis of the dielectric spectra measured for octa-O-acetyl-lactose in its glassy state (not standard change in the shape of the γ- peak with lowering temperature) enabled us to provide probable explanation of our finding. No credible comparative analysis of the α- relaxation process of the lactose and octa-O-acetyl-lactose are presented, because loss spectra of the former carbohydrate were affected by the huge contribution of the dc conductivity. Notwithstanding, one can expect that octa-O-acetyl-lactose has lower glass transition temperature and steepness index than lactose.

  18. Influence of unsteady aerodynamics on driving dynamics of passenger cars

    NASA Astrophysics Data System (ADS)

    Huemer, Jakob; Stickel, Thomas; Sagan, Erich; Schwarz, Martin; Wall, Wolfgang A.

    2014-11-01

    Recent approaches towards numerical investigations with computational fluid dynamics methods on unsteady aerodynamic loads of passenger cars identified major differences compared with steady-state aerodynamic excitations. Furthermore, innovative vehicle concepts such as electric-vehicles or hybrid drives further challenge the basic layout of passenger cars. Therefore, the relevance of unsteady aerodynamic loads on cross-wind stability of changing basic vehicle architectures should be analysed. In order to assure and improve handling and ride characteristics at high velocity of the actual range of vehicle layouts, the influence of unsteady excitations on the vehicle response was investigated. For this purpose, a simulation of the vehicle dynamics through multi-body simulation was used. The impact of certain unsteady aerodynamic load characteristics on the vehicle response was quantified and key factors were identified. Through a series of driving simulator tests, the identified differences in the vehicle response were evaluated regarding their significance on the subjective driver perception of cross-wind stability. Relevant criteria for the subjective driver assessment of the vehicle response were identified. As a consequence, a design method for the basic layout of passenger cars and chassis towards unsteady aerodynamic excitations was defined.

  19. Influence of follicular dendritic cells on HIV dynamics.

    PubMed Central

    Hlavacek, W S; Stilianakis, N I; Perelson, A S

    2000-01-01

    In patients infected with human immunodeficiency virus type 1 (HIV-1), a large amount of virus is associated with follicular dendritic cells (FDCs) in lymphoid tissue. To assess the influence of FDCs on viral dynamics during antiretroviral therapy we have developed a mathematical model for treatment of HIV-1 infection that includes FDCs. Here, we use this model to analyse measurements of HIV-1 dynamics in the blood and lymphoid tissue of a representative patient, who was treated with a combination of HIV-1 reverse transcriptase and protease inhibitors. We show that loss of virus from FDCs during therapy can make a much larger contribution to plasma virus than production of virus by infected cells. This result challenges the notion that long-lived infected cells are a significant source of HIV-1 during drug therapy. Due to release of FDC-associated virus, we find that it is necessary to revise upward previous estimates of c, the rate at which free virus is cleared, and delta, the rate at which productively infected cells die. Furthermore, we find that potentially infectious virus, present before treatment, is released from FDCs during therapy and that the persistence of this virus can be affected by whether therapy includes reverse transcriptase inhibitors. PMID:11186306

  20. Microphysical and Dynamical Influences on Cirrus Cloud Optical Depth Distributions

    SciTech Connect

    Kay, J.; Baker, M.; Hegg, D.

    2005-03-18

    Cirrus cloud inhomogeneity occurs at scales greater than the cirrus radiative smoothing scale ({approx}100 m), but less than typical global climate model (GCM) resolutions ({approx}300 km). Therefore, calculating cirrus radiative impacts in GCMs requires an optical depth distribution parameterization. Radiative transfer calculations are sensitive to optical depth distribution assumptions (Fu et al. 2000; Carlin et al. 2002). Using raman lidar observations, we quantify cirrus timescales and optical depth distributions at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site in Lamont, OK (USA). We demonstrate the sensitivity of outgoing longwave radiation (OLR) calculations to assumed optical depth distributions and to the temporal resolution of optical depth measurements. Recent work has highlighted the importance of dynamics and nucleation for cirrus evolution (Haag and Karcher 2004; Karcher and Strom 2003). We need to understand the main controls on cirrus optical depth distributions to incorporate cirrus variability into model radiative transfer calculations. With an explicit ice microphysics parcel model, we aim to understand the influence of ice nucleation mechanism and imposed dynamics on cirrus optical depth distributions.

  1. Deriving seasonal dynamics in ecosystem properties of semi-arid savannas using in situ based hyperspectral reflectance

    NASA Astrophysics Data System (ADS)

    Tagesson, T.; Fensholt, R.; Huber, S.; Horion, S.; Guiro, I.; Ehammer, A.; Ardö, J.

    2015-02-01

    This paper investigates how seasonal hyperspectral reflectance data (between 350 and 1800 nm) can be used to infer ecosystem properties for a semi-arid savanna ecosystem in West Africa using a unique in situ based dataset. Relationships between seasonal dynamics in hyperspectral reflectance, and ecosystem properties (biomass, gross primary productivity (GPP), light use efficiency (LUE), and fraction of photosynthetically active radiation absorbed by vegetation (FAPAR)) were analysed. Reflectance data (ρ) were used to study the relationship between normalised difference spectral indices (NDSI) and the measured ecosystem properties. Finally, also the effects of variable sun sensor viewing geometry on different NDSI wavelength combinations were analysed. The wavelengths with the strongest correlation to seasonal dynamics in ecosystem properties were shortwave infrared (biomass), the peak absorption band for chlorophyll a and b (at 682 nm) (GPP), the oxygen A-band at 761 nm used for estimating chlorophyll fluorescence (GPP, and LUE), and blue wavelengths (FAPAR). The NDSI with the strongest correlation to: (i) biomass combined red edge reflectance (ρ705) with green reflectance (ρ587), (ii) GPP combined wavelengths at the peak of green reflection (ρ518, ρ556), (iii) the LUE combined red (ρ688) with blue reflectance (ρ436), and (iv) FAPAR combined blue (ρ399) and near infrared (ρ1295) wavelengths. NDSI combining near infrared and shortwave infrared were strongly affected by solar zenith angles and sensor viewing geometry, as were many combinations of visible wavelengths. This study provides analyses based upon novel multi-angular hyperspectral data for validation of Earth Observation based properties of semi-arid ecosystems, as well as insights for designing spectral characteristics of future sensors for ecosystem monitoring.

  2. Monitoring ecosystem dynamics in an Arctic tundra ecosystem using hyperspectral reflectance and a robotic tram system

    NASA Astrophysics Data System (ADS)

    Goswami, Santonu

    ) Is NDVI a good predictor for aboveground biomass and leaf area index (LAI) for plant species that are common in an arctic landscape? (4) How can cyberinfrastructure tools be developed to optimize ground-based remote sensing data collection, management and processing associated with a large scale experimental infrastructure? The Biocomplexity project experimentally manipulated the water table (drained, flooded, and control treatments) of a vegetated thaw lake basin to investigate the effects of altered hydrology on land-atmosphere carbon balance. In each experimental treatment, hyperspectral reflectance data were collected in the visible and near IR range of the spectrum using a robotic tram system that operated along a 300m tramline during the snow free growing period between June and August 2005-09. Water table depths (WTD) and soil volumetric water content were also collected along these transects. During 2005-2007, measurements were made without experimental treatments. Experimental treatments were run in 2008 and 2009, which involved water table being raised (+10cm) and lowered (-10cm) in flooding and draining treatments respectively. A new spectral index, the normalized difference surface water index (NDSWI) was developed and tested at multiple spatial and temporal scales. NDSWI uses the 460nm (blue) and 1000nm (IR) bands and was to capture surface hydrological dynamics in the study area using the robotic tram system. When applied to high spatial resolution satellite imagery, NDSWI was also able to capture changes in surface hydrology at the landscape scale. Interannual patterns of land-surface phenology (measured with the normalized difference vegetation index - NDVI) unexpectedly lacked marked differences under experimental conditions. Measurement of NDVI was, however, compromised when WTD was above ground level. NDVI and NDSWI were negatively correlated when WTD was above ground level, which held when scaled to MODIS imagery collected from satellite

  3. INFLUENCE OF INJURY ON DYNAMIC POSTURAL CONTROL IN RUNNERS

    PubMed Central

    Klusendorf, Anna; Kernozek, Thomas

    2016-01-01

    ABSTRACT Background Injury has been linked with altered postural control in active populations. The association between running injury and dynamic postural control has not been examined. Hypothesis/Purpose The purpose of this study was to examine dynamic postural control in injured and uninjured runners using the Star Excursion Balance Test (SEBT), Time to Stabilization (TTS) of ground reaction forces following a single-leg landing, and postural stability indices reflecting the fluctuations in GRFs during single-leg landing and stabilization tasks (forward and lateral hop). It was hypothesized that dynamic postural control differences would exist between runners with a history of injury that interrupted training for ≥7 days (INJ) when compared to runners without injury (CON). Design Case-control study Methods Twenty-two INJ (14 F, 8 M; 23.7 ± 2.1 y; 22.3 ± 2.8 kg/m2; 29.5 ± 16.3 mi/wk) currently running > 50% pre-injury mileage without pain were compared with twenty-two matched CON (14F, 8M; 22.7 ± 1.2 y; 22.7 ± 2.7 kg/m2; 31.2 ± 19.6 mi/wk). INJ group was stratified by site of injury into two groups (Hip/Thigh/Knee and Lower Leg/Ankle/Foot) for secondary analysis. Leg length-normalized anterior, posterolateral, and posteromedial reach distances on the SEBT, medial/lateral and anterior/posterior ground reaction force TTS, directional postural stability indices, and a composite dynamic postural stability index (DPSI), were assessed using mixed model ANOVA (α=0.05) and effect sizes (d). Results No group X direction interaction or group differences were observed for the SEBT (p=0.51, 0.71) or TTS (p=0.83, 0.72) measures. A group X direction interaction was found for postural stability indices during the forward landing task (p<0.01). Both Hip/Thigh/Knee and Lower leg/Ankle/Foot INJ groups demonstrated a greater vertical postural stability index (VPSI) (p=0.01 for both, d=0.80, 0.95) and DPSI (p=0.01, 0.02, d=0.75, 0.93) when

  4. Fluoropolymer Microstructure and Dynamics: Influence of Molecular Orientation Induced by Uniaxial Drawing

    NASA Astrophysics Data System (ADS)

    Miranda, Daniel; Yin, Chaoqing; Runt, James

    Fluorinated semi-crystalline polymer films are attractive for dielectric film applications due to their chemical inertness, heat resistance, and high thermal stability. In the present investigation we explore the influence of orientation induced by uniaxial drawing on the crystalline microstructure and relaxation processes of poly(ethylene-tetrafluoroethylene) (ETFE), in order to ascertain how morphological control can benefit polymer dielectric design. When drawn below or near the Tg, the crystallinity of the drawn films is unchanged, and oriented amorphous structures and crystalline microfibrils form at high draw ratios. This orientation slows segmental relaxation, reflected by an increase in the dynamic Tg, and also delays the transition to the high temperature crystalline form of ETFE. When drawing above the Tg, the films undergo strain-induced crystallization at high draw ratios. For these films an increase in the dynamic Tg is also observed, in addition to a second segmental relaxation process, appearing as a shoulder on the primary process. We propose that this represents a contribution from a rigid amorphous fraction, having slowed chain dynamics. Supported by Office of Naval Research.

  5. Aortic Wave Dynamics and Its Influence on Left Ventricular Workload

    NASA Astrophysics Data System (ADS)

    Pahlevan, Niema; Gharib, Morteza

    2010-11-01

    Clinical and epidemiologic studies have shown that hypertension plays a key role in development of left ventricular (LV) hypertrophy and ultimately heart failure mostly due to increased LV workload. Therefore, it is crucial to diagnose and treat abnormal high LV workload at early stages. The pumping mechanism of the heart is pulsatile, thus it sends pressure and flow wave into the compliant aorta. The wave dynamics in the aorta is dominated by interplay of heart rate (HR), aortic rigidity, and location of reflection sites. We hypothesized that for a fixed cardiac output (CO) and peripheral resistance (PR), interplay of HR and aortic compliance can create conditions that minimize LV power requirement. We used a computational approach to test our hypothesis. Finite element method with direct coupling method of fluid-structure interaction (FSI) was used. Blood was assumed to be incompressible Newtonian fluid and aortic wall was considered elastic isotropic. Simulations were performed for various heart rates and aortic rigidities while inflow wave, CO, and PR were kept constant. For any aortic compliance, LV power requirement becomes minimal at a specific heart rate. The minimum shifts to higher heart rates as aortic rigidity increases.

  6. Determination of the dynamic stress intensity factors for 7075-T6 aluminum alloy using the reflected caustic method

    SciTech Connect

    Tsukagoshi, Seiji; Takahashi, Susumu; Shimamoto, Akira

    1996-12-31

    Dynamic fracture initiation and propagation in Al 7075-T6 was investigated experimentally using the optical method of reflected caustics combined with a simplified high speed photography. A crack propagation testing configuration consisting of a three point bending specimen loaded In a drop weighting was used. It was found that prior to crack initiation the stress intensity factor time record calculated using the dynamic impact load and a static formula disagrees with the actual stress Intensity factor measured by caustics. The impact fracture tests are performed. With use of Al 7075-T6 band plate test specimens with a V-notch on their one side. The dynamic stress intensity factor K{sub id} are given. With this, the authors experimentally calculated the dynamic fracture toughness K{sub ID}.

  7. Study of the reflectivity of neutron supermirrors influenced by surface oil layers.

    PubMed

    Veres, Tamás; Cser, László

    2010-06-01

    Neutron guides made of supermirror-coated glass are important components of most neutron scattering instruments, thus their quality and possible deterioration due to various deleterious effects (e.g., surface contamination or defects) deserve careful examination. The modification of the reflectivity of supermirrors and the transmission of neutron guides due to surface contamination with hydrocarbon oil has been investigated using neutron reflectometry together with model calculations. A significant loss in the neutron reflectivity was observed for supermirrors covered with thin hydrocarbon oil films, which were confirmed in model calculations. Simulations carried out for several typical arrangements show drastic decreases in the transmitted neutron flux of neutron guides. These simulations show that determining the distortion of the beam profile (using a slit or a pin hole) enables the detection of oil contamination even in an operating neutron guide. PMID:20590233

  8. Systematic spectral analysis of GX 339-4: Influence of Galactic background and reflection models

    NASA Astrophysics Data System (ADS)

    Clavel, M.; Rodriguez, J.; Corbel, S.; Coriat, M.

    2016-05-01

    Black hole X-ray binaries display large outbursts, during which their properties are strongly variable. We develop a systematic spectral analysis of the 3-40 keV {RXTE}/PCA data in order to study the evolution of these systems and apply it to GX 339-4. Using the low count rate observations, we provide a precise model of the Galactic background at GX 339-4's location and discuss its possible impact on the source spectral parameters. At higher fluxes, the use of a Gaussian line to model the reflection component can lead to the detection of a high-temperature disk, in particular in the high-hard state. We demonstrate that this component is an artifact arising from an incomplete modeling of the reflection spectrum.

  9. Influence of Si doping on the infrared reflectance characteristics of GaN grown on sapphire

    NASA Astrophysics Data System (ADS)

    Hou, Y. T.; Feng, Z. C.; Chua, S. J.; Li, M. F.; Akutsu, N.; Matsumoto, K.

    1999-11-01

    Si-doped GaN films grown on sapphire are investigated by infrared reflectance. A damping behavior of the interference fringes is observed, and interpreted to be due to the presence of an interface layer between the film and the substrate. A theoretical calculation using a two-layer model to take into account the interface layer resulted in this damping in agreement with the experiment. The damping behavior and an improvement of interface properties by Si incorporation are demonstrated.

  10. Dynamic balancing of isoprene carbon sources reflects photosynthetic and photorespiratory responses to temperature stress.

    PubMed

    Jardine, Kolby; Chambers, Jeffrey; Alves, Eliane G; Teixeira, Andrea; Garcia, Sabrina; Holm, Jennifer; Higuchi, Niro; Manzi, Antonio; Abrell, Leif; Fuentes, Jose D; Nielsen, Lars K; Torn, Margaret S; Vickers, Claudia E

    2014-12-01

    The volatile gas isoprene is emitted in teragrams per annum quantities from the terrestrial biosphere and exerts a large effect on atmospheric chemistry. Isoprene is made primarily from recently fixed photosynthate; however, alternate carbon sources play an important role, particularly when photosynthate is limiting. We examined the relative contribution of these alternate carbon sources under changes in light and temperature, the two environmental conditions that have the strongest influence over isoprene emission. Using a novel real-time analytical approach that allowed us to examine dynamic changes in carbon sources, we observed that relative contributions do not change as a function of light intensity. We found that the classical uncoupling of isoprene emission from net photosynthesis at elevated leaf temperatures is associated with an increased contribution of alternate carbon. We also observed a rapid compensatory response where alternate carbon sources compensated for transient decreases in recently fixed carbon during thermal ramping, thereby maintaining overall increases in isoprene production rates at high temperatures. Photorespiration is known to contribute to the decline in net photosynthesis at high leaf temperatures. A reduction in the temperature at which the contribution of alternate carbon sources increased was observed under photorespiratory conditions, while photosynthetic conditions increased this temperature. Feeding [2-(13)C]glycine (a photorespiratory intermediate) stimulated emissions of [(13)C1-5]isoprene and (13)CO2, supporting the possibility that photorespiration can provide an alternate source of carbon for isoprene synthesis. Our observations have important implications for establishing improved mechanistic predictions of isoprene emissions and primary carbon metabolism, particularly under the predicted increases in future global temperatures. PMID:25318937

  11. Reflective and impulsive influences on unhealthy snacking. The moderating effects of food related self-control.

    PubMed

    Honkanen, Pirjo; Olsen, Svein Ottar; Verplanken, Bas; Tuu, Ho Huy

    2012-04-01

    This study proposes that snacking behaviour may be either reflective and deliberate or impulsive, thus following a dual-process account. We hypothesised that chronic individual differences in food related self-control would moderate the relationships between reflective and impulsive processes. The reflective route was represented by an attitude toward unhealthy snacking, while the impulsive route was represented by the tendency to buy snack on impulse. A web survey was conducted with 207 students and employees at a Norwegian university, and a moderated hierarchical regression analysis using structural equation modelling was used to estimate the theoretical model. The findings showed that both attitudes towards unhealthy snacking and impulsive snack buying tendency were positively related to snack consumption. Food related self-control moderated the relation between attitude and behaviour, as well as the relation between impulsive snack buying tendency and behaviour. The effect of attitude on consumption was relatively strong when food related self-control was strong, while the effect of impulsive snack buying on consumption was relatively strong when food related self-control was weak. The results thus suggest that while weak self-control exposes individuals vulnerable to impulsive tendencies, strong self-control does not necessarily lead to less unhealthy snacking, but this depends on the valence of an individual's attitude. PMID:22138115

  12. Influence of Subpixel Scale Cloud Top Structure on Reflectances from Overcast Stratiform Cloud Layers

    NASA Technical Reports Server (NTRS)

    Loeb, N. G.; Varnai, Tamas; Winker, David M.

    1998-01-01

    Recent observational studies have shown that satellite retrievals of cloud optical depth based on plane-parallel model theory suffer from systematic biases that depend on viewing geometry, even when observations are restricted to overcast marine stratus layers, arguably the closest to plane parallel in nature. At moderate to low sun elevations, the plane-parallel model significantly overestimates the reflectance dependence on view angle in the forward-scattering direction but shows a similar dependence in the backscattering direction. Theoretical simulations are performed that show that the likely cause for this discrepancy is because the plane-parallel model assumption does not account for subpixel, scale variations in cloud-top height (i.e., "cloud bumps"). Monte Carlo simulation, comparing ID model radiances to radiances from overcast cloud field with 1) cloud-top height variation, but constant cloud volume extinction; 2) flat tops but horizontal variations in cloud volume extinction; and 3) variations in both cloud top height and cloud extinction are performed over a approximately equal to 4 km x 4 km domain (roughly the size of an individual GAC AVHRR pixel). The comparisons show that when cloud-top height variations are included, departures from 1D theory are remarkably similar (qualitatively) to those obtained observationally. In contrast, when clouds are assumed flat and only cloud extinction is variable, reflectance differences are much smaller and do not show any view-angle dependence. When both cloud-top height and cloud extinction variations are included, however, large increases in cloud extinction variability can enhance reflectance difference. The reason 3D-1D reflectance differences are more sensitive to cloud-top height variations in the forward-scattering direction (at moderate to low, sun elevations) is because photons leaving the cloud field in that direction experience fewer scattering events (low-order scattering) and are restricted to the

  13. Study of the influence of glucose on diffuse reflection of ultrashort laser pulses from a medium simulating a biological tissue

    SciTech Connect

    Bykov, A V; Indukaev, A K; Priezzhev, A V; Myllylae, R

    2008-05-31

    The influence of glucose on the diffuse reflection of near-IR femtosecond laser radiation from single- and three-layer media simulating biological tissues is studied experimentally. Based on a 800-nm femtosecond Ti:sapphire laser emitting 40-fs pulses and a VUV Agat streak camera, a setup is built for time and spatially resolved detection of radiation diffusely reflected from the volume of a strongly scattering medium. A multichannel fibreoptic system is developed for detecting pulses simultaneously at several fixed distances between a radiation source and detector. It is shown that the peak intensity and total energy of detected pulses are sensitive to variations in the glucose concentration in the medium under study from 0 to 1000 mg dL{sup -1}. The relative sensitivity in our experiments achieved 0.030% mg dL{sup -1}. (biophotonics)

  14. The Influence of Repeated Teaching and Reflection on Preservice Teachers' Views of Inquiry and Nature of Science

    NASA Astrophysics Data System (ADS)

    Lotter, Christine; Singer, Jonathan; Godley, Jenice

    2009-12-01

    This study describes the influence of a secondary science methods program on secondary science preservice teachers’ views and enactment of nature of science and inquiry-based instructional practices. Built into the structure of this program were three cycles of practice teaching and reflection in which the preservice teachers focused on key pedagogical ideas in classroom settings with middle and high school students. The nine secondary preservice teachers improved both their understanding and enactment of inquiry and nature of science throughout the program period. This study provides evidence of the importance of incorporating multiple low-stakes practicum experiences that are closely tied to methods course goals that are highly scaffolded through both methods instructor and cooperating teacher support and tied to analytic self-reflection.

  15. Influence of plasma composition on reflectance anisotropy spectra for in situ III-V semiconductor dry-etch monitoring

    NASA Astrophysics Data System (ADS)

    Barzen, Lars; Kleinschmidt, Ann-Kathrin; Strassner, Johannes; Doering, Christoph; Fouckhardt, Henning; Bock, Wolfgang; Wahl, Michael; Kopnarski, Michael

    2015-12-01

    Reflectance anisotropy spectroscopy (RAS) can be used to monitor (reactive) ion etching (RIE) of semiconductor samples. We present results on the influence of the Cl2 content of the plasma gas on the RAS spectra during reactive ion etching. In a first step GaAs samples have been used and the RAS spectra are compared to results of secondary ion mass spectrometry (SIMS) on sample surfaces and depth profiles. In a second step a III-V semiconductor multilayer system has been investigated using the time-evolution of the average reflected intensity as an indication for the etch rate. In both cases usually even a high amount of Cl2 does not disturb the surface-sensitivity of the RAS signal.

  16. Social influences in opinion dynamics: The role of conformity

    NASA Astrophysics Data System (ADS)

    Javarone, Marco Alberto

    2014-11-01

    We study the effects of social influences in opinion dynamics. In particular, we define a simple model, based on the majority rule voting, in order to consider the role of conformity. Conformity is a central issue in social psychology as it represents one of people’s behaviors that emerges as a result of their interactions. The proposed model represents agents, arranged in a network and provided with an individual behavior, that change opinion in function of those of their neighbors. In particular, agents can behave as conformists or as nonconformists. In the former case, agents change opinion in accordance with the majority of their social circle (i.e., their neighbors); in the latter case, they do the opposite, i.e., they take the minority opinion. Moreover, we investigate the nonconformity both on a global and on a local perspective, i.e., in relation to the whole population and to the social circle of each nonconformist agent, respectively. We perform a computational study of the proposed model, with the aim to observe if and how the conformity affects the related outcomes. Moreover, we want to investigate whether it is possible to achieve some kind of equilibrium, or of order, during the evolution of the system. Results highlight that the amount of nonconformist agents in the population plays a central role in these dynamics. In particular, conformist agents play the role of stabilizers in fully-connected networks, whereas the opposite happens in complex networks. Furthermore, by analyzing complex topologies of the agent network, we found that in the presence of radical nonconformist agents the topology of the system has a prominent role; otherwise it does not matter since we observed that a conformist behavior is almost always more convenient. Finally, we analyze the results of the model by considering that agents can change also their behavior over time, i.e., conformists can become nonconformists and vice versa.

  17. Oxidation-resistant reflective surfaces for solar dynamic power generation in near Earth orbit

    NASA Technical Reports Server (NTRS)

    Gulino, D. A.; Mgf2, Sio2, Al2o3, and si3n4, we

    1986-01-01

    Reflective surfaces for space station power generation systems are required to withstand the atomic oxygen-dominated environment of near Earth orbit. Thin films of platinum and rhodium, which are corrosion resistant reflective metals, have been deposited by ion beam sputter deposition onto various substrate materials. Solar reflectances were then measured as a function of time of exposure to a RF-generated air plasma. Similarly, various protective coating materials, including MgF2, SiO2, Al2O3, and Si3N4, were deposited onto silver-coated substrates and then exposed to the plasma. Analysis of the films both before and after exposure by both ESCA and Auger spectroscopy was also performed. The results indicate that Pt and Rh do not suffer any loss in reflectance over the duration of the tests. Also, each of the coating materials survived the plasma environment. The ESCA and Auger analyses are discussed as well.

  18. In vitro dynamic solubility test: influence of various parameters.

    PubMed Central

    Thélohan, S; de Meringo, A

    1994-01-01

    This article discusses the dissolution of mineral fibers in simulated physiological fluids (SPF), and the parameters that affect the solubility measurement in a dynamic test where an SPF runs through a cell containing fibers (Scholze and Conradt test). Solutions simulate either the extracellular fluid (pH 7.6) or the intracellular fluid (pH 4.5). The fibers have various chemical compositions and are either continuously drawn or processed as wool. The fiber solubility is determined by the amount of SiO2 (and occasionally other ions) released in the solution. Results are stated as percentage of the initial silica content released or as dissolution rate v in nm/day. The reproducibility of the test is higher with the less soluble fibers (10% solubility), than with highly soluble fibers (20% solubility). The influence of test parameters, including SPF, test duration, and surface area/volume (SA/V), has been studied. The pH and the inorganic buffer salts have a major influence: industrial glasswool composition is soluble at pH 7.6 but not at pH 4.5. The opposite is true for rock- (basalt) wool composition. For slightly soluble fibers, the dissolution rate v remains constant with time, whereas for highly soluble fibers, the dissolution rate decreases rapidly. The dissolution rates believed to occur are v1, initial dissolution rate, and v2, dissolution rate of the residual fibers. The SA of fibers varies with the mass of the fibers tested, or with the fiber diameter at equal mass. Volume, V, is the chosen flow rate. An increase in the SA/V ratio leads to a decrease in the dissolution rate.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7882964

  19. Reflectance measurements of port-wine stains: influence of selective cooling

    NASA Astrophysics Data System (ADS)

    Norvang Nilsen, Lill T.; Fiskerstrand, Elisanne J.; Svaasand, Lars O.

    1996-12-01

    Port wine stain birthmark removal is based on selective photothermolysis. The most common technique utilizes 0.45 ms laser pulses at 585 nm wavelength. High incident energy doses are often needed to reach the ectatic blood vessels in dermis. This might induce changes in pigmentation or even epidermal necrosis. However, the epidermis can be protected by selectively cooling it down prior to laser exposure. Short cooling pulses ensure epidermal protection while preserving the temperature in dermis. Visible reflectance spectra of the birthmark are dependent on the melanin content, the blood volume and the scattering properties. these parameters also determine the fluence underneath the skin during laser exposure. Threshold fluence values can therefore be predicted for each specific lesion. Eight Scandinavian patients with red to purple macular port wine stains were treated with a pulsed dye laser at the energy density 6 J/cm2. Seven patients have developed hyperpigmentation in earlier treatments at this energy dose. One site in each lesion was cooled with a 20 ms cryogen spray immediately prior to laser exposure. Visible reflectance spectra were measured before and eight weeks after treatment. A simulation model based on diffusion approximation was used to estimate blood volume, skin pigmentation and scattering properties each time. The measured reflectance spectra, as well as the clinical observations, showed no significant differences between the cooled and uncooled sites. Estimated blood volume fractions and melanin pigmentations were about the same, and the short cooling spurts did not prevent hyperpigmentation. A light brown color was seen in both sites for 7 patients, and could be detected in the spectra for two patients. However, the estimated increases in pigmentation were small also for these patients. Calculated threshold fluence values were almost the same for cooled and uncooled sites after treatment.

  20. Dynamic shear-influenced collagen self-assembly.

    PubMed

    Saeidi, Nima; Sander, Edward A; Ruberti, Jeffrey W

    2009-12-01

    The ability to influence the direction of polymerization of a self-assembling biomolecular system has the potential to generate materials with extremely high anisotropy. In biological systems where highly-oriented cellular populations give rise to aligned and often load-bearing tissue such organized molecular scaffolds could aid in the contact guidance of cells for engineered tissue constructs (e.g. cornea and tendon). In this investigation we examine the detailed dynamics of pepsin-extracted type I bovine collagen assembly on a glass surface under the influence of flow between two plates. Differential Interference Contrast (DIC) imaging (60x-1.4NA) with focal plane stabilization was used to resolve and track the growth of collagen aggregates on borosilicate glass for 4 different shear rates (500, 80, 20, and 9s(-1)). The detailed morphology of the collagen fibrils/aggregates was examined using Quick Freeze Deep Etch (QFDE) electron microscopy. Nucleation of fibrils on the glass was observed to occur rapidly (approximately 2 min) followed by continued growth of the fibrils. The growth rates were dependent on flow in a complex manner with the highest rate of axial growth (0.1 micro/s) occurring at a shear rate of 9s(-1). The lowest growth rate occurred at the highest shear. Fibrils were observed to both branch and join during the experiments. The best alignment of fibrils was observed at intermediate shear rates of 20 and 80s(-1). However, the investigation revealed that fibril directional growth was not stable. At high shear rates, fibrils would often turn downstream forming what we term "hooks" which are likely the combined result of monomer interaction with the initial collagen layer or "mat" and the high shear rate. Further, QFDE examination of fibril morphology demonstrated that the assembled fibrillar structure did not possess native D-periodicity. Instead, fibrils comprised a collection of generally aligned, monomers which were self-assembled to form a fibril

  1. Model for Vortex Ring State Influence on Rotorcraft Flight Dynamics

    NASA Technical Reports Server (NTRS)

    Johnson, Wayne

    2005-01-01

    The influence of vortex ring state (VRS) on rotorcraft flight dynamics is investigated, specifically the vertical velocity drop of helicopters and the roll-off of tiltrotors encountering VRS. The available wind tunnel and flight test data for rotors in vortex ring state are reviewed. Test data for axial flow, non-axial flow, two rotors, unsteadiness, and vortex ring state boundaries are described and discussed. Based on the available measured data, a VRS model is developed. The VRS model is a parametric extension of momentum theory for calculation of the mean inflow of a rotor, hence suitable for simple calculations and real-time simulations. This inflow model is primarily defined in terms of the stability boundary of the aircraft motion. Calculations of helicopter response during VRS encounter were performed, and good correlation is shown with the vertical velocity drop measured in flight tests. Calculations of tiltrotor response during VRS encounter were performed, showing the roll-off behavior characteristic of tiltrotors. Hence it is possible, using a model of the mean inflow of an isolated rotor, to explain the basic behavior of both helicopters and tiltrotors in vortex ring state.

  2. Model for Vortex Ring State Influence on Rotorcraft Flight Dynamics

    NASA Technical Reports Server (NTRS)

    Johnson, Wayne

    2004-01-01

    The influence of vortex ring state (VRS) on rotorcraft flight dynamics is investigated, specifically the vertical velocity drop of helicopters and the roll-off of tiltrotors encountering VRS. The available wind tunnel and flight test data for rotors in vortex ring state are reviewed. Test data for axial flow, nonaxial flow, two rotors, unsteadiness, and vortex ring state boundaries are described and discussed. Based on the available measured data, a VRS model is developed. The VRS model is a parametric extension of momentum theory for calculation of the mean inflow of a rotor, hence suitable for simple calculations and real-time simulations. This inflow model is primarily defined in terms of the stability boundary of the aircraft motion. Calculations of helicopter response during VRS encounter were performed, and good correlation is shown with the vertical velocity drop measured in flight tests. Calculations of tiltrotor response during VRS encounter were performed, showing the roll-off behavior characteristic of tiltrotors. Hence it is possible, using a model of the mean inflow of an isolated rotor, to explain the basic behavior of both helicopters and tiltrotors in vortex ring state.

  3. Influence of impeller shroud forces on turbopump rotor dynamics

    NASA Technical Reports Server (NTRS)

    Williams, Jim P.; Childs, Dara W.

    1989-01-01

    The shrouded-impeller leakage path forces calculated by Childs (1987) have been analyzed to answer two questions. First, because of certain characteristics of the results of Childs, the forces could not be modeled with traditional approaches. Therefore, an approach has been devised to include the forces in conventional rotordynamic analyses. The forces were approximated by traditional stiffness, damping and inertia coefficients with the addition of whirl-frequency-dependent direct and cross-coupled stiffness terms. The forces were found to be well-modeled with this approach. Finally, the effect these forces had on a simple rotor-bearing system was analyzed, and, therefore, they, in addition to seal forces, were applied to a Jeffcott rotor. The traditional methods of dynamic system analysis were modified to incorporate the impeller forces and yielded results for the eigenproblem, frequency response, critical speed, transient response and an iterative technique for finding the frequency of free vibration as well as system stability. All results lead to the conclusion that the forces have little influence on natural frequency but can have appreciable effects on system stability. Specifically, at higher values of fluid swirl at the leakage path entrance, relative stability is reduced. The only unexpected response characteristics that occurred are attributed to the nonlinearity of the model.

  4. Influence of impeller shroud forces on turbopump rotor dynamics

    NASA Technical Reports Server (NTRS)

    Williams, J. P.; Childs, Dara W.

    1993-01-01

    The shrouded-impeller leakage path forces calculated by Childs have been analyzed to answer two questions. First, because of certain characteristics or the results of Childs, the forces could not be modeled with traditional approaches. Therefore, an approach has been devised to include the forces in conventional rotordynamic analyses. The forces were found to be well-modeled with this approach. Finally, the effect these forces had on a simple rotor-bearing system was analyzed, and, therefore, they, in addition to seal forces, were applied to a Jeffcott rotor. The traditional methods of dynamic system analysis were modified to incorporate the impeller forces and yielded results for the eigenproblem, frequency response, critical speed, transient response, and an iterative technique for finding the frequency of free vibration as well as system stability. All results lead to the conclusion that the forces have little influence on natural frequency but can have appreciable effects on system stability. Specifically, at higher values of fluid swirl at the leakage path entrance, relative stability is reduced. The only unexpected response characteristics that occurred are attributed to the nonlinearity of the model.

  5. The Influence of AAC Device Type, Dynamic vs. Static Screen, on Peer Attitudes

    ERIC Educational Resources Information Center

    Dudek, Karen; Beck, Ann R.; Thompson, James R.

    2006-01-01

    This study examined how children's attitudes toward a peer who used augmentative and alternative communication (AAC) were influenced by type of AAC device accessed by the child for communication. Specifically, the influence of dynamic screens vs. static screens was investigated. Two videotapes were created. In one a child used a dynamic screen…

  6. Modification of the surface state of rough substrates by two different varnishes and influence on the reflected light

    NASA Astrophysics Data System (ADS)

    Elias, Mady; René de la Rie, E.; Delaney, John K.; Charron, Eric; Morales, Kathryn M.

    2006-10-01

    Modification of the visual appearance when a rough surface is covered by a varnish is mostly attributed to the levelling of the substrate surface, which depends on the molecular weight of the varnish. The topography of varnished surfaces, however, has never been measured directly. Surfaces of varnishes applied over glass substrates of varying roughness were studied, therefore, using mechanical profilometry. Two different varnishes made with a low and a high molecular weight resin were studied. Both varnishes lower the r.m.s. roughness of the substrates and filter the high spatial frequencies. These results are amplified for the varnish containing the low molecular weight resin. The light reflected by the varnished samples is modelled from these topographical data. Its angular distribution, calculated from the probability density of slopes is presented, taking into account separately the air/varnish and the varnish/substrate interfaces. These analyses are presented in a back-scattering configuration. They show that varnishing significantly reduces the angular width of the reflected light and that this effect is magnified for the low molecular weight resin. Modelling furthermore shows that the influence of the roughness of the varnish/substrate interface is negligible in the total reflected light.

  7. Variation in normal mood state influences sensitivity to dynamic changes in emotional expression.

    PubMed

    Jackson, Margaret C; Arlegui-Prieto, Maritxu

    2016-03-01

    Normal social functioning depends on the ability to efficiently and accurately detect when someone's facial expression changes to convey positive or negative emotion. While observer mood state has been shown to influence emotion recognition, how variations in normal mood might influence sensitivity to the dynamic emergence of expressions has not yet been addressed. To investigate this, we modified an existing face-morphing paradigm in which a central face gradually changes from neutral to expressive (angry, sad, happy, surprised). Our sample comprised healthy young adults, and current mood state was measured using the PANAS-X. Participants pressed a key as soon as they (1) noticed a physical change in expression (perceptual sensitivity-novel task element), and (2) could clearly conceptualize which expression was emerging (conceptual sensitivity). A final unspeeded response required participants to explicitly label the expression as a measure of recognition accuracy. We measured the percentage morph (expression intensity) at which a perceptual and conceptual change was detected, where greater intensity equates to poorer sensitivity. Increased positive mood reduced perceptual and conceptual sensitivity to angry and sad expressions only (a mood incongruency effect). Of particular interest, increased negative mood decreased conceptual sensitivity for all expressions, but had limited impact on perceptual sensitivity. Thus, heightened negative mood is particularly detrimental for effectively decoding someone else's mood change. This may reflect greater introspection and consumption of attentional resources directed toward the negative self, leaving fewer resources to process emotional signals conveyed by others. This could have important consequences for human social interaction. PMID:26479773

  8. Analysis of the influence of tool dynamics in diamond turning

    SciTech Connect

    Fawcett, S.C.; Luttrell, D.E.; Keltie, R.F.

    1988-12-01

    This report describes the progress in defining the role of machine and interface dynamics on the surface finish in diamond turning. It contains a review of literature from conventional and diamond machining processes relating tool dynamics, material interactions and tool wear to surface finish. Data from experimental measurements of tool/work piece interface dynamics are presented as well as machine dynamics for the DTM at the Center.

  9. Rethinking the Christian Studies Classroom: Reflections on the Dynamics of Teaching Religion in Southern Public Universities

    ERIC Educational Resources Information Center

    Gravett, Sandie; Hulsether, Mark; Medine, Carolyn

    2011-01-01

    An extended set of conversations conducted by three religious studies faculty teaching at large public universities in the Southern United States spurred these reflections on how their institutional locations inflected issues such as the cultural expectations students bring to the classroom, how these expectations interact with the evolving…

  10. Dynamic Tensions: Early Reflections from MDRC's Evaluation of the Innovative Professional Development Challenge

    ERIC Educational Resources Information Center

    MDRC, 2015

    2015-01-01

    In the Innovative Professional Development (iPD) Challenge, the Bill & Melinda Gates Foundation has invested in helping school districts and networks redesign their instructional support systems to better support educators in increasing student success. This Issue Focus, the second in a series, presents early reflections from MDRC's evaluation…

  11. The Influence of Information Acquisition on the Complex Dynamics of Market Competition

    NASA Astrophysics Data System (ADS)

    Guo, Zhanbing; Ma, Junhai

    In this paper, we build a dynamical game model with three bounded rational players (firms) to study the influence of information on the complex dynamics of market competition, where useful information is about rival’s real decision. In this dynamical game model, one information-sharing team is composed of two firms, they acquire and share the information about their common competitor, however, they make their own decisions separately, where the amount of information acquired by this information-sharing team will determine the estimation accuracy about the rival’s real decision. Based on this dynamical game model and some creative 3D diagrams, the influence of the amount of information on the complex dynamics of market competition such as local dynamics, global dynamics and profits is studied. These results have significant theoretical and practical values to realize the influence of information.

  12. Influences to System and Superiority of Model Parameters in Dynamic Setting AGC

    NASA Astrophysics Data System (ADS)

    Xu, LI; Hao-yu, Zhang; Jin, Zhang; Jian-fei, Guo; Cui-hong, Liu; Ping-wen, Cheng

    Dynamic setting AGC is based on the improvement of the BISRA-AGC model. Based on the control algorithms and control models of dynamic setting AGC, the influences of the model parameters to system performance were analyzed using the GUI in MATLAB. At the same time, the superiority and limitation of the dynamic setting AGC were analyzed.

  13. Daily MODIS 500 m Reflectance Anisotropy Direct Broadcast (DB) Products for Monitoring Vegetation Phenology Dynamics

    NASA Technical Reports Server (NTRS)

    Shuai, Yanmin; Schaaf, Crystal; Zhang, Xiaoyang; Strahler, Alan; Roy, David; Morisette, Jeffrey; Wang, Zhuosen; Nightingale, Joanne; Nickeson, Jaime; Richardson, Andrew D.; Xie, Donghui; Wang, Jindi; Li, Xiaowen; Strabala, Kathleen; Davies, James E.

    2013-01-01

    Land surface vegetation phenology is an efficient bio-indicator for monitoring ecosystem variation in response to changes in climatic factors. The primary objective of the current article is to examine the utility of the daily MODIS 500 m reflectance anisotropy direct broadcast (DB) product for monitoring the evolution of vegetation phenological trends over selected crop, orchard, and forest regions. Although numerous model-fitted satellite data have been widely used to assess the spatio-temporal distribution of land surface phenological patterns to understand phenological process and phenomena, current efforts to investigate the details of phenological trends, especially for natural phenological variations that occur on short time scales, are less well served by remote sensing challenges and lack of anisotropy correction in satellite data sources. The daily MODIS 500 m reflectance anisotropy product is employed to retrieve daily vegetation indices (VI) of a 1 year period for an almond orchard in California and for a winter wheat field in northeast China, as well as a 2 year period for a deciduous forest region in New Hampshire, USA. Compared with the ground records from these regions, the VI trajectories derived from the cloud-free and atmospherically corrected MODIS Nadir BRDF (bidirectional reflectance distribution function) adjusted reflectance (NBAR) capture not only the detailed footprint and principal attributes of the phenological events (such as flowering and blooming) but also the substantial inter-annual variability. This study demonstrates the utility of the daily 500 m MODIS reflectance anisotropy DB product to provide daily VI for monitoring and detecting changes of the natural vegetation phenology as exemplified by study regions comprising winter wheat, almond trees, and deciduous forest.

  14. The influence of micronutrients in cell culture: a reflection on viability and genomic stability.

    PubMed

    Arigony, Ana Lúcia Vargas; de Oliveira, Iuri Marques; Machado, Miriana; Bordin, Diana Lilian; Bergter, Lothar; Prá, Daniel; Henriques, João Antonio Pêgas

    2013-01-01

    Micronutrients, including minerals and vitamins, are indispensable to DNA metabolic pathways and thus are as important for life as macronutrients. Without the proper nutrients, genomic instability compromises homeostasis, leading to chronic diseases and certain types of cancer. Cell-culture media try to mimic the in vivo environment, providing in vitro models used to infer cells' responses to different stimuli. This review summarizes and discusses studies of cell-culture supplementation with micronutrients that can increase cell viability and genomic stability, with a particular focus on previous in vitro experiments. In these studies, the cell-culture media include certain vitamins and minerals at concentrations not equal to the physiological levels. In many common culture media, the sole source of micronutrients is fetal bovine serum (FBS), which contributes to only 5-10% of the media composition. Minimal attention has been dedicated to FBS composition, micronutrients in cell cultures as a whole, or the influence of micronutrients on the viability and genetics of cultured cells. Further studies better evaluating micronutrients' roles at a molecular level and influence on the genomic stability of cells are still needed. PMID:23781504

  15. The Influence of Micronutrients in Cell Culture: A Reflection on Viability and Genomic Stability

    PubMed Central

    Arigony, Ana Lúcia Vargas; de Oliveira, Iuri Marques; Bordin, Diana Lilian; Prá, Daniel; Pêgas Henriques, João Antonio

    2013-01-01

    Micronutrients, including minerals and vitamins, are indispensable to DNA metabolic pathways and thus are as important for life as macronutrients. Without the proper nutrients, genomic instability compromises homeostasis, leading to chronic diseases and certain types of cancer. Cell-culture media try to mimic the in vivo environment, providing in vitro models used to infer cells' responses to different stimuli. This review summarizes and discusses studies of cell-culture supplementation with micronutrients that can increase cell viability and genomic stability, with a particular focus on previous in vitro experiments. In these studies, the cell-culture media include certain vitamins and minerals at concentrations not equal to the physiological levels. In many common culture media, the sole source of micronutrients is fetal bovine serum (FBS), which contributes to only 5–10% of the media composition. Minimal attention has been dedicated to FBS composition, micronutrients in cell cultures as a whole, or the influence of micronutrients on the viability and genetics of cultured cells. Further studies better evaluating micronutrients' roles at a molecular level and influence on the genomic stability of cells are still needed. PMID:23781504

  16. Topographic Influence and Atmospheric Dynamics in the Indian Wells Valley

    NASA Astrophysics Data System (ADS)

    Uher, Erich J.

    Indian Wells Valley (IWV) is home to the China Lake Naval Air Weapons Station (NAWS) whose operations necessitate regional forecasting and weather analysis relevant to aviation and plume release scenarios. In order to better understand the terrain influenced mesoscale circulations in the varied complex terrain of Indian Wells Valley surrounding Ridgecrest, four seasonal WRF simulations were analyzed using linear shallow water theory and nonlinear theory for flows over two-dimensional mountains. The goal is to better understand the relationships between atmospheric dynamical processes and the wind/thermal structure of the mesoscale at Indian Wells Valley. This will involve exploring relationships linking theoretical meteorology in complex terrain and advanced high resolution atmospheric modeling in this region. The WRF simulation results show several distinct circulations which rely on the interaction between complex terrain and the background weather conditions: 1) In calm synoptic conditions, diurnal processes guide the evolution of boundary layer stability and slope flows. 2) In periods of greatest seasonal surface heating (i.e. summer), the pressure gradient across the Sierra Nevada drives near surface westerlies across IWV. 3) In conditions with strong synoptic scale increase in stability and meridional winds across the Sierra Nevada, a downslope windstorm can develop in IWV. The downslope winds and compensatory gravity wave activity over IWV will conclude once there is a significant change in conditions aloft, or an increase in convective instability at the surface of IWV which prevents air aloft from sinking towards the surface. These results provide a better understanding of the mesoscale meteorology in this region and improve forecast and analysis for plume transport and aviation needs while also laying the groundwork for future projects managing environmental concerns in this region.

  17. Soil porosity correlation and its influence in percolation dynamics

    NASA Astrophysics Data System (ADS)

    Rodriguez, Alfredo; Capa-Morocho, Mirian; Ruis-Ramos, Margarita; Tarquis, Ana M.

    2016-04-01

    The prediction of percolation in natural soils is relevant for modeling root growth and optimizing infiltration of water and nutrients. Also, it would improve our understanding on how pollutants as pesticides, and virus and bacteria (Darnault et al., 2003) reach significant depths without being filtered out by the soil matrix (Beven and Germann, 2013). Random walk algorithms have been used successfully to date to characterize the dynamical characteristics of disordered media. This approach has been used here to describe how soil at different bulk densities and with different threshold values applied to the 3D gray images influences the structure of the pore network and their implications on particle flow and distribution (Ruiz-Ramos et al., 2009). In order to do so first we applied several threshold values to each image analyzed and characterized them through Hurst exponents, then we computed random walks algorithms to calculate distances reached by the particles and speed of those particles. At the same time, 3D structures with a Hurst exponent of ca 0.5 and with different porosities were constructed and the same random walks simulations were replicated over these generated structures. We have found a relationship between Hurst exponents and the speed distribution of the particles reaching percolation of the total soil depth. REFERENCES Darnault, C.J. G., P. Garnier, Y.J. Kim, K.L. Oveson, T.S. Steenhuis, J.Y. Parlange, M. Jenkins, W.C. Ghiorse, and P. Baveye (2003), Preferential transport of Cryptosporidium parvum oocysts in variably saturated subsurface environments, Water Environ. Res., 75, 113-120. Beven, Keith and Germann, Peter. 2013. Macropores and water flow in soils revisited. Water Resources Research, 49(6), 3071-3092. DOI: 10.1002/wrcr.20156. Ruiz-Ramos, M., D. del Valle, D. Grinev, and A.M. Tarquis. 2009. Soil hydraulic behaviour at different bulk densities. Geophysical Research Abstracts, 11, EGU2009-6234.

  18. Oxidation of basaltic tephras: Influence on reflectance in the 1 micron region

    NASA Technical Reports Server (NTRS)

    Farrand, William H.; Singer, Robert B.

    1991-01-01

    As part of a ongoing study into the products of hydrovolcanism, tuffs were examined from the Cerro Colorado and Pavant Butte tuff cones. The former resides in the northeastern corner of the Pinacate Volcanic Field in Sonara, Mexico and the latter is in the Black Rock Desert of southern Utah. Numerous samples were collected and many of these had their Vis/IR reflectance measured. It seems likely that in the palagonite tuffs there is a combination of nanocrystalline ferric oxide phases contributing to the UV absorption edge, but not to the 1 micron band, plus more crystalline ferric oxides which do contribute to that band as well as ferrous iron within unaltered sideromelane which is skewing the band center to longer wavelengths. This work has implications for the study of Mars. The present work indicates that when ferrous and ferric iron phases are both present, their combined spectral contribution is a single band in the vicinity of 1 micron. The center, depth, and width of that feature has potential to be used to gauge the relative proportions of ferrous and ferric iron phases.

  19. Genetic data from algae sedimentary DNA reflect the influence of environment over geography

    PubMed Central

    Stoof-Leichsenring, Kathleen R.; Herzschuh, Ulrike; Pestryakova, Luidmila A.; Klemm, Juliane; Epp, Laura S.; Tiedemann, Ralph

    2015-01-01

    Genetic investigations on eukaryotic plankton confirmed the existence of modern biogeographic patterns, but analyses of palaeoecological data exploring the temporal variability of these patterns have rarely been presented. Ancient sedimentary DNA proved suitable for investigations of past assemblage turnover in the course of environmental change, but genetic relatedness of the identified lineages has not yet been undertaken. Here, we investigate the relatedness of diatom lineages in Siberian lakes along environmental gradients (i.e. across treeline transects), over geographic distance and through time (i.e. the last 7000 years) using modern and ancient sedimentary DNA. Our results indicate that closely-related Staurosira lineages occur in similar environments and less-related lineages in dissimilar environments, in our case different vegetation and co-varying climatic and limnic variables across treeline transects. Thus our study reveals that environmental conditions rather than geographic distance is reflected by diatom-relatedness patterns in space and time. We tentatively speculate that the detected relatedness pattern in Staurosira across the treeline could be a result of adaptation to diverse environmental conditions across the arctic boreal treeline, however, a geographically-driven divergence and subsequent repopulation of ecologically different habitats might also be a potential explanation for the observed pattern. PMID:26261899

  20. Genetic data from algae sedimentary DNA reflect the influence of environment over geography

    NASA Astrophysics Data System (ADS)

    Stoof-Leichsenring, Kathleen R.; Herzschuh, Ulrike; Pestryakova, Luidmila A.; Klemm, Juliane; Epp, Laura S.; Tiedemann, Ralph

    2015-08-01

    Genetic investigations on eukaryotic plankton confirmed the existence of modern biogeographic patterns, but analyses of palaeoecological data exploring the temporal variability of these patterns have rarely been presented. Ancient sedimentary DNA proved suitable for investigations of past assemblage turnover in the course of environmental change, but genetic relatedness of the identified lineages has not yet been undertaken. Here, we investigate the relatedness of diatom lineages in Siberian lakes along environmental gradients (i.e. across treeline transects), over geographic distance and through time (i.e. the last 7000 years) using modern and ancient sedimentary DNA. Our results indicate that closely-related Staurosira lineages occur in similar environments and less-related lineages in dissimilar environments, in our case different vegetation and co-varying climatic and limnic variables across treeline transects. Thus our study reveals that environmental conditions rather than geographic distance is reflected by diatom-relatedness patterns in space and time. We tentatively speculate that the detected relatedness pattern in Staurosira across the treeline could be a result of adaptation to diverse environmental conditions across the arctic boreal treeline, however, a geographically-driven divergence and subsequent repopulation of ecologically different habitats might also be a potential explanation for the observed pattern.

  1. Retrieval of seasonal dynamics of forest understory reflectance from semi-arid to boreal forests using MODIS BRDF data

    NASA Astrophysics Data System (ADS)

    Pisek, Jan; Chen, Jing; Kobayashi, Hideki; Rautiainen, Miina; Schaepman, Michael; Karnieli, Arnon; Sprintsin, Michael; Ryu, Youngryel; Nikopensius, Maris; Raabe, Kairi

    2016-04-01

    Ground vegetation (understory) provides an essential contribution to the whole-stand reflectance signal in many boreal, sub-boreal, and temperate forests. Accurate knowledge about forest understory reflectance is urgently needed in various forest reflectance modelling efforts. However, systematic collections of understory reflectance data covering different sites and ecosystems are almost missing. Measurement of understory reflectance is a real challenge because of an extremely high variability of irradiance at the forest floor, weak signal in some parts of the spectrum, spectral separability issues of over- and understory and its variable nature. Understory can consist of several sub-layers (regenerated tree, shrub, grasses or dwarf shrub, mosses, lichens, litter, bare soil), it has spatially-temporally variable species composition and ground coverage. Additional challenges are introduced by patchiness of ground vegetation, ground surface roughness, and understory-overstory relations. Due to this variability, remote sensing might be the only means to provide consistent data at spatially relevant scales. In this presentation, we report on retrieving seasonal courses of understory Normalized Difference Vegetation Index (NDVI) from multi-angular MODIS BRDF/Albedo data. We compared satellite-based seasonal courses of understory NDVI against an extended collection of different types of forest sites with available in-situ understory reflectance measurements. These sites are distributed along a wide latitudinal gradient on the Northern hemisphere: a sparse and dense black spruce forests in Alaska and Canada, a northern European boreal forest in Finland, hemiboreal needleleaf and deciduous stands in Estonia, a mixed temperate forest in Switzerland, a cool temperate deciduous broadleaf forest in Korea, and a semi-arid pine plantation in Israel. Our results indicated the retrieval method performs well particularly over open forests of different types. We also demonstrated

  2. Pervasive influence of large-scale climate in the dynamics of a terrestrial vertebrate community

    PubMed Central

    Post, Eric; Forchhammer, Mads C

    2001-01-01

    Background Large-scale climatic variability has been implicated in the population dynamics of many vertebrates throughout the Northern Hemisphere, but has not been demonstrated to directly influence dynamics at multiple trophic levels of any single system. Using data from Isle Royale, USA, comprising time series on the long-term dynamics at three trophic levels (wolves, moose, and balsam fir), we analyzed the relative contributions of density dependence, inter-specific interactions, and climate to the dynamics of each level of the community. Results Despite differences in dynamic complexity among the predator, herbivore, and vegetation levels, large-scale climatic variability influenced dynamics directly at all three levels. The strength of the climatic influence on dynamics was, however, strongest at the top and bottom trophic levels, where density dependence was weakest. Conclusions Because of the conflicting influences of environmental variability and intrinsic processes on population stability, a direct influence of climate on the dynamics at all three levels suggests that climate change may alter stability of this community. Theoretical considerations suggest that if it does, such alteration is most likely to result from changes in stability at the top or bottom trophic levels, where the influence of climate was strongest. PMID:11782292

  3. Structures, Organization, and Function of Reflectin Proteins in Dynamically Tunable Reflective Cells*

    PubMed Central

    DeMartini, Daniel G.; Izumi, Michi; Weaver, Aaron T.; Pandolfi, Erica; Morse, Daniel E.

    2015-01-01

    The reversible assembly of reflectin proteins drives dynamic iridescence in cephalopods. Squid dynamically tune the intensity and colors of iridescence generated by constructive interference from intracellular Bragg reflectors in specialized skin cells called iridocytes. Analysis of the tissue specificity of reflectin subtypes reveals that tunability is correlated with the presence of one specific reflectin sequence. Differential phosphorylation and dephosphorylation of the reflectins in response to activation by acetylcholine, as well as differences in their tissue-specific and subcellular spatial distributions, further support the suggestion of different roles for the different reflectin subtypes. PMID:25918159

  4. Some reflections on the influence of Chinese thought on Jung and his psychological theory.

    PubMed

    Stein, Murray

    2005-04-01

    Jung claimed that Richard Wilhelm, whose masterful translations of Chinese wisdom literature into a European language (German) and thence into Western consciousness have brought Chinese modes of thinking to so many, was one of the most important influences on his own life and work. The contacts between the two men, which took place from the early 1920's until Wilhelm's death in 1930, were few but intense and for Jung decisive in several ways. Wilhelm's translations of the I Ching and The Secret of the Golden Flower opened new avenues for Jung that had far-reaching consequences on his research and writing after 1930. The latter opened the door to the study of alchemy as a key to the archetypal process of individuation as rooted in the collective unconscious. 'Synchronicity' is a term that grew out of his contact with Chinese thought, in particular with the I Ching. From his contact with Chinese thought, additionally, he received confirmation of the view, independently arrived at, that adult psychological development is not linear but rather circular and spiral-like. The letters between Jung and Wilhelm illuminate the great importance Jung ascribed to Wilhelm's contribution toward bridging East and West and the potential value of Chinese philosophy for psychotherapy. PMID:15817043

  5. Dynamics of continental collision: influence of the plate contact

    NASA Astrophysics Data System (ADS)

    De Franco, Roberta; Govers, Rob; Wortel, Rinus

    2008-09-01

    Observations shows that continental collision may evolve in different ways, resulting in a wide range of tectonic responses. In search of the controlling conditions and parameters, we start from the results of our previous work, which demonstrated that the properties of the plate contact are important for the overall dynamics of convergent plate margins. Two fundamental types of subduction plate contact can be distinguished: one based on a fault and the other based on a weak subduction channel. In this study, we investigate how the plate contact affects the initial stage of continental collision. We use a finite element method to solve the heat and the time-dependent momentum equations for elastic, (power-law) viscous and plastic rheologies. For the same rheological properties and driving forces, varying the nature of the plate contact leads to three types of responses. The presence of a subduction channel promotes coherent and, when the boundary conditions allow it, plate-like subduction of the continental margin. In models with a subduction fault, coherent subduction of the incoming continental lithosphere occurs when the colliding passive margin has a gentle slope. The approaching continental sliver starts to subduct and the subduction is characterized by a non-plate like behaviour-slower subduction velocity than in channel models and strong slab deformation. If the continental margin is steep and the strength of the incoming continental crust is high, fault models result in locking of the trench, eventually leading to slab break-off. If the crustal strength is relatively low, shear delamination of part of the crust is expected. In the channel model, this type of delamination never occurs. The tectonic settings used in our experiments (prescribed plate velocity of the subducting plate versus fixed subducting plate corresponding to a landlocked basin setting) do not significantly influence the nature of the model response. We conclude that initial stages of

  6. Reflections on the Development of a Dynamic Learning, Teaching and Assessment Strategy

    ERIC Educational Resources Information Center

    Strickland, Karen; McLatchie, Joan; Pelik, Rowena

    2011-01-01

    Purpose: This paper aims to demonstrate how an institutional learning, teaching and assessment (LTA) strategy was developed and a "dynamic" strategy created in order to achieve the ongoing enhancement of the quality of the student learning experience. Developing LTA strategies that foster ongoing engagement and provide inspiration to academic…

  7. How Reflected Wave Fronts Dynamically Establish Hooke's Law in a Spring

    ERIC Educational Resources Information Center

    Fahy, Stephen; O'Riordan, John; O'Sullivan, Colm; Twomey, Patrick

    2012-01-01

    A simple benchtop experiment in which a moving cart collides with a fixed spring is described. Force-time and force-distance data recorded during the collision display the transit of compression wave fronts through the spring following impact. These data can be used by students to develop a computational model of the dynamics of this simple…

  8. POST ASYMPTOTIC GIANT BRANCH BIPOLAR REFLECTION NEBULAE: RESULT OF DYNAMICAL EJECTION OR SELECTIVE ILLUMINATION?

    SciTech Connect

    Koning, N.; Kwok, Sun; Steffen, W. E-mail: sunkwok@hku.hk

    2013-03-10

    A model for post asymptotic giant branch bipolar reflection nebulae has been constructed based on a pair of evacuated cavities in a spherical dust envelope. Many of the observed features of bipolar nebulae, including filled bipolar lobes, an equatorial torus, searchlight beams, and a bright central light source, can be reproduced. The effects on orientation and dust densities are studied and comparisons with some observed examples are offered. We suggest that many observed properties of bipolar nebulae are the result of optical effects and any physical modeling of these nebulae has to take these factors into consideration.

  9. Evaluation of self-focusing influence on laser-induced damage threshold of anti-reflective coated windows

    NASA Astrophysics Data System (ADS)

    Rakickas, T.; Kudriašov, V.; Sirutkaitis, V.; Grigonis, R.; Gaižauskas, E.

    2005-12-01

    For high intensity lasers it is very important to choose appropriate optical elements. Since invention of high power lasers laser-induced damage of optical coatings was subject of extensive investigations. At high laser intensities the self-focusing in optical elements appears and intensity at rear optics surface can be much higher than at the front surface. Due to this damage of rear-surface can be reached much faster than damage of the front surface. We investigated the influence of self-focusing on damage threshold in fused-silica windows with anti-reflective coatings on both sides. In our experiments we used titanium-sapphire chirped pulse amplification system (130 fs, 2 mJ, 1 kHz repetition rate pulses at 800 nm). We have tested 1 mm, 3 mm and 6 mm thickness fused-silica windows with identical anti-reflective coatings. The front surface of the samples was placed in the waist of focused beam. The experiments were performed for effective spot diameters on the front 145 μm, 95 μm and 43 μm respectively. The experiments showed the self-focusing of beam inside the fused silica window and self-focusing dependence on initial beam diameter. The damage behavior was dependent on irradiation history. Also we found quite strong nonlinear absorption in fused silica.

  10. Distribution of chemical elements in attic dust and soil as reflection of lithology and anthropogenic influence in Slovenia

    NASA Astrophysics Data System (ADS)

    Sajn, R.

    2003-05-01

    The aim of this study was to establish contents and distribution of chemical elements in attic dust in Slovenia, and to define them according to geology and anthiopogenic influence. Attic dust and topsoil (0-5 cm) samples were collected in the rural area in settlements without known industry and in six largest towns in Slovenia. Analysis of 42 chemical elements was performed. For estimation of the association between elements and sampling materials the R mode factor analysis was applied. Al, Ba, Co, Ci, Fe, La, Mn, Na, Nb, Ni, Sc, Th, Ti, Y, V and Zr in attic dust reflect the natural distribution. The highest elemental contents in attic dust occur in the areas of igneous and metmoiphic rocks and of flysch formation. High contents of the elemental association Co, Ci, Fe, Mn, and Ni reflect also centuries of ferrous metallurgy. Distribution of As, Cd, Cu, Hg, Mo, Sb, Sn, Sr, Pb and Zn represents the anthropogenically introduced chemical elements. Their averages in attic dust are higher compared to topsoil. High contents of these elements are a result of historical Pb-Zn mining and smelting.

  11. Community, intervention and provider support influences on implementation: reflections from a South African illustration of safety, peace and health promotion

    PubMed Central

    2014-01-01

    Background The development, implementation and evaluation of community interventions are important for reducing child violence and injuries in low- to middle-income contexts, with successful implementation critical to effective intervention outcomes. The assessment of implementation processes is required to identify the factors that influence effective implementation. This article draws on a child safety, peace and health initiative to examine key factors that enabled or hindered its implementation, in a context characterised by limited resources. Methods A case study approach was employed. The research team was made up of six researchers and intervention coordinators, who led the development and implementation of the Ukuphepha Child Study in South Africa, and who are also the authors of this article. The study used author observations, reflections and discussions of the factors perceived to influence the implementation of the intervention. The authors engaged in an in-depth and iterative dialogic process aimed at abstracting the experiences of the intervention, with a recursive cycle of reflection and dialogue. Data were analysed utilising inductive content analysis, and categorised using classification frameworks for understanding implementation. Results The study highlights key factors that enabled or hindered implementation. These included the community context and concomitant community engagement processes; intervention compatibility and adaptability issues; community service provider perceptions of intervention relevance and expectations; and the intervention support system, characterised by training and mentorship support. Conclusions This evaluation illustrated the complexity of intervention implementation. The study approach sought to support intervention fidelity by fostering and maintaining community endorsement and support, a prerequisite for the unfolding implementation of the intervention. PMID:25081088

  12. Influence of dynamic immunization on epidemic spreading in networks

    NASA Astrophysics Data System (ADS)

    Wu, Qingchu; Fu, Xinchu; Jin, Zhen; Small, Michael

    2015-02-01

    We introduce a new dynamic immunization method based on the static immunization algorithm and study the relationship between dynamic and static immunization. By nodes to be immunized according to static immunization strategies, we build a connection between dynamic and static immunization. Using theoretical arguments and computational simulation we show that dynamic immunization (from a finite vaccine reservoir) is not sufficient to prevent epidemic outbreak, nor does it significantly change the asymptotic prevalence. Nonetheless, we do find that less total vaccine is required to implement this strategy. To help understand this better, we examine the extent and distribution of dynamic immunization required to achieve this reduced vaccine demand. Our results suggest that it is not necessary to increase the immunization rate when the infection rate is relatively small.

  13. Medial prefrontal cortical activity reflects dynamic re-evaluation during voluntary persistence

    PubMed Central

    McGuire, Joseph T.; Kable, Joseph W.

    2015-01-01

    Deciding how long to keep waiting for future rewards is a nontrivial problem, especially when the timing of rewards is uncertain. We report an experiment in which human decision makers waited for rewards in two environments, in which reward-timing statistics favored either a greater or lesser degree of behavioral persistence. We found that decision makers adaptively calibrated their level of persistence for each environment. Functional neuroimaging revealed signals that evolved differently during physically identical delays in the two environments, consistent with a dynamic and context-sensitive reappraisal of subjective value. This effect was observed in a region of ventromedial prefrontal cortex that is sensitive to subjective value in other contexts, demonstrating continuity between valuation mechanisms involved in discrete choice and in temporally extended decisions analogous to foraging. Our findings support a model in which voluntary persistence emerges from dynamic cost/benefit evaluation rather than from a control process that overrides valuation mechanisms. PMID:25849988

  14. Aeroelasticity matters: Some reflections on two decades of testing in the NASA Langley transonic dynamics tunnel

    NASA Technical Reports Server (NTRS)

    Reed, W. H., III

    1981-01-01

    Testing of wind-tunnel aeroelastic models is a well established, widely used means of studying flutter trends, validating theory and investigating flutter margins of safety of new vehicle designs. The Langley Transonic Dynamics Tunnel was designed specifically for work on dynamics and aeroelastic problems of aircraft and space vehicles. A cross section of aeroelastic research and testing in the facility since it became operational more than two decades ago is presented. Examples selected from a large store of experience illustrate the nature and purpose of some major areas of work performed in the tunnel. These areas include: specialized experimental techniques; development testing of new aircraft and launch vehicle designs; evaluation of proposed "fixes" to solve aeroelastic problems uncovered during development testing; study of unexpected aeroelastic phenomena (i.e., "surprises"); control of aeroelastic effects by active and passive means; and, finally, fundamental research involving measurement of unsteady pressures on oscillating wings and control surface.

  15. Medial prefrontal cortical activity reflects dynamic re-evaluation during voluntary persistence.

    PubMed

    McGuire, Joseph T; Kable, Joseph W

    2015-05-01

    Deciding how long to keep waiting for future rewards is a nontrivial problem, especially when the timing of rewards is uncertain. We carried out an experiment in which human decision makers waited for rewards in two environments in which reward-timing statistics favored either a greater or lesser degree of behavioral persistence. We found that decision makers adaptively calibrated their level of persistence for each environment. Functional neuroimaging revealed signals that evolved differently during physically identical delays in the two environments, consistent with a dynamic and context-sensitive reappraisal of subjective value. This effect was observed in a region of ventromedial prefrontal cortex that is sensitive to subjective value in other contexts, demonstrating continuity between valuation mechanisms involved in discrete choice and in temporally extended decisions analogous to foraging. Our findings support a model in which voluntary persistence emerges from dynamic cost/benefit evaluation rather than from a control process that overrides valuation mechanisms. PMID:25849988

  16. The influence of climatic variability on local population dynamics of Cercidium microphyllum (foothill paloverde)

    USGS Publications Warehouse

    Bowers, Janice E.; Turner, R.M.

    2002-01-01

    This study investigated correlations among climatic variability, population age structure, and seedling survival of a dominant Sonoran Desert tree, Cercidium microphyllum (foothill paloverde), at Tucson, Arizona, USA. A major goal was to determine whether wet years promote seedling establishment and thereby determine population structure. Plant age was estimated from basal circumference for a sample of 980 living and dead trees in twelve 0.5-ha plots. Ages ranged from 1 to 181 years. Age frequency distribution showed that the population is in decline. Most (51.2%) of the 814 living trees were 40-80 years old; only 6.5% were younger than 20 years. The average age of the 166 dead trees was 78 years. Fifty-nine percent of dead trees were aged 60-100 years. Survival of newly emerged seedlings was monitored for 7 years in a 557-m2 permanent plot. Mean survival in the 1st year of life was 1.7%. Only 2 of 1,008 seedlings lived longer than 1 year. Length of survival was not correlated with rainfall. Residual regeneration, an index of the difference between predicted and observed cohort size, showed that regeneration was high during the first half of the twentieth century and poor after the mid-1950s. Trends in regeneration did not reflect interannual variation in seasonal temperature or rain before 1950, that is, in the years before urban warming. Taken together, the seedling study and the regeneration analysis suggest that local population dynamics reflect biotic factors to such an extent that population age structure might not always be a reliable clue to past climatic influences.

  17. Synaptic dynamics and neuronal network connectivity are reflected in the distribution of times in Up states.

    PubMed

    Dao Duc, Khanh; Parutto, Pierre; Chen, Xiaowei; Epsztein, Jérôme; Konnerth, Arthur; Holcman, David

    2015-01-01

    The dynamics of neuronal networks connected by synaptic dynamics can sustain long periods of depolarization that can last for hundreds of milliseconds such as Up states recorded during sleep or anesthesia. Yet the underlying mechanism driving these periods remain unclear. We show here within a mean-field model that the residence time of the neuronal membrane potential in cortical Up states does not follow a Poissonian law, but presents several peaks. Furthermore, the present modeling approach allows extracting some information about the neuronal network connectivity from the time distribution histogram. Based on a synaptic-depression model, we find that these peaks, that can be observed in histograms of patch-clamp recordings are not artifacts of electrophysiological measurements, but rather are an inherent property of the network dynamics. Analysis of the equations reveals a stable focus located close to the unstable limit cycle, delimiting a region that defines the Up state. The model further shows that the peaks observed in the Up state time distribution are due to winding around the focus before escaping from the basin of attraction. Finally, we use in vivo recordings of intracellular membrane potential and we recover from the peak distribution, some information about the network connectivity. We conclude that it is possible to recover the network connectivity from the distribution of times that the neuronal membrane voltage spends in Up states. PMID:26283956

  18. Eocene prevalence of monsoon-like climate over eastern China reflected by hydrological dynamics

    NASA Astrophysics Data System (ADS)

    Wang, Dehai; Lu, Shicong; Han, Shuang; Sun, Xiaoyan; Quan, Cheng

    2013-01-01

    Hydrological dynamics of sedimentary basins are essential for understanding regional climatic pattern in the geological past. In previous qualitative studies lithologically depending on the occurrence of featured sedimentary rocks, the Eocene climate of China had been subdivided into three latitudinal zones, with one subtropical high-controlled arid zone throughout middle China, and two humid zones respectively in the north and south. However, recent advances on mammalian fauna distribution, plant fossil-based quantitative paleoclimatic reconstruction, and modeling experiment jointly suggest that the relatively humid monsoonal climate might have prevailed over the territory. Here we examine and compare sedimentary sequences of 10 Eocene sections across eastern China, and hence the lake level fluctuations, to discuss the nature of climate type. Our results show that, instead of the categorically zonal pattern, the hydroclimate dynamics is intensified landward. This is demonstrated by the fact that, in contrast to the wide developed coal layers around the periphery, evaporites are growingly occurred endocentrically to the central part of middle China. However, although we have had assumed that all evaporites are indicator of extreme aridity, the highly oscillated climate in the central part of middle China was humid in the majority of the Eocene, distinct from permanent arid as seen in deserts or steppe along modern horse latitude. From the upcountry distribution pattern of the Eocene hydrological dynamics, it appears that the relatively dry climate in central China was caused by the impact of continentality or rain shadow effect under monsoonal, or monsoon-like climate.

  19. Shifts of Gamma Phase across Primary Visual Cortical Sites Reflect Dynamic Stimulus-Modulated Information Transfer

    PubMed Central

    Besserve, Michel; Lowe, Scott C.; Logothetis, Nikos K.; Schölkopf, Bernhard; Panzeri, Stefano

    2015-01-01

    Distributed neural processing likely entails the capability of networks to reconfigure dynamically the directionality and strength of their functional connections. Yet, the neural mechanisms that may allow such dynamic routing of the information flow are not yet fully understood. We investigated the role of gamma band (50–80 Hz) oscillations in transient modulations of communication among neural populations by using measures of direction-specific causal information transfer. We found that the local phase of gamma-band rhythmic activity exerted a stimulus-modulated and spatially-asymmetric directed effect on the firing rate of spatially separated populations within the primary visual cortex. The relationships between gamma phases at different sites (phase shifts) could be described as a stimulus-modulated gamma-band wave propagating along the spatial directions with the largest information transfer. We observed transient stimulus-related changes in the spatial configuration of phases (compatible with changes in direction of gamma wave propagation) accompanied by a relative increase of the amount of information flowing along the instantaneous direction of the gamma wave. These effects were specific to the gamma-band and suggest that the time-varying relationships between gamma phases at different locations mark, and possibly causally mediate, the dynamic reconfiguration of functional connections. PMID:26394205

  20. Synaptic dynamics and neuronal network connectivity are reflected in the distribution of times in Up states

    PubMed Central

    Dao Duc, Khanh; Parutto, Pierre; Chen, Xiaowei; Epsztein, Jérôme; Konnerth, Arthur; Holcman, David

    2015-01-01

    The dynamics of neuronal networks connected by synaptic dynamics can sustain long periods of depolarization that can last for hundreds of milliseconds such as Up states recorded during sleep or anesthesia. Yet the underlying mechanism driving these periods remain unclear. We show here within a mean-field model that the residence time of the neuronal membrane potential in cortical Up states does not follow a Poissonian law, but presents several peaks. Furthermore, the present modeling approach allows extracting some information about the neuronal network connectivity from the time distribution histogram. Based on a synaptic-depression model, we find that these peaks, that can be observed in histograms of patch-clamp recordings are not artifacts of electrophysiological measurements, but rather are an inherent property of the network dynamics. Analysis of the equations reveals a stable focus located close to the unstable limit cycle, delimiting a region that defines the Up state. The model further shows that the peaks observed in the Up state time distribution are due to winding around the focus before escaping from the basin of attraction. Finally, we use in vivo recordings of intracellular membrane potential and we recover from the peak distribution, some information about the network connectivity. We conclude that it is possible to recover the network connectivity from the distribution of times that the neuronal membrane voltage spends in Up states. PMID:26283956

  1. Decisions in Motion: Decision Dynamics during Intertemporal Choice reflect Subjective Evaluation of Delayed Rewards

    PubMed Central

    O’Hora, Denis; Carey, Rachel; Kervick, Aoife; Crowley, David; Dabrowski, Maciej

    2016-01-01

    People tend to discount rewards or losses that occur in the future. Such delay discounting has been linked to many behavioral and health problems, since people choose smaller short-term gains over greater long-term gains. We investigated whether the effect of delays on the subjective value of rewards is expressed in how people move when they make choices. Over 600 patrons of the RISK LAB exhibition hosted by the Science Gallery DublinTM played a short computer game in which they used a computer mouse to choose between amounts of money at various delays. Typical discounting effects were observed and decision dynamics indicated that choosing smaller short-term rewards became easier (i.e., shorter response times, tighter trajectories, less vacillation) as the delays until later rewards increased. Based on a sequence of choices, subjective values of delayed outcomes were estimated and decision dynamics during initial choices predicted these values. Decision dynamics are affected by subjective values of available options and thus provide a means to estimate such values. PMID:26867497

  2. Deriving seasonal dynamics in ecosystem properties of semi-arid savanna grasslands from in situ-based hyperspectral reflectance

    NASA Astrophysics Data System (ADS)

    Tagesson, T.; Fensholt, R.; Huber, S.; Horion, S.; Guiro, I.; Ehammer, A.; Ardo, J.

    2015-08-01

    This paper investigates how hyperspectral reflectance (between 350 and 1800 nm) can be used to infer ecosystem properties for a semi-arid savanna grassland in West Africa using a unique in situ-based multi-angular data set of hemispherical conical reflectance factor (HCRF) measurements. Relationships between seasonal dynamics in hyperspectral HCRF and ecosystem properties (biomass, gross primary productivity (GPP), light use efficiency (LUE), and fraction of photosynthetically active radiation absorbed by vegetation (FAPAR)) were analysed. HCRF data (ρ) were used to study the relationship between normalised difference spectral indices (NDSIs) and the measured ecosystem properties. Finally, the effects of variable sun sensor viewing geometry on different NDSI wavelength combinations were analysed. The wavelengths with the strongest correlation to seasonal dynamics in ecosystem properties were shortwave infrared (biomass), the peak absorption band for chlorophyll a and b (at 682 nm) (GPP), the oxygen A band at 761 nm used for estimating chlorophyll fluorescence (GPP and LUE), and blue wavelengths (ρ412) (FAPAR). The NDSI with the strongest correlation to (i) biomass combined red-edge HCRF (ρ705) with green HCRF (ρ587), (ii) GPP combined wavelengths at the peak of green reflection (ρ518, ρ556), (iii) LUE combined red (ρ688) with blue HCRF (ρ436), and (iv) FAPAR combined blue (ρ399) and near-infrared (ρ1295) wavelengths. NDSIs combining near infrared and shortwave infrared were strongly affected by solar zenith angles and sensor viewing geometry, as were many combinations of visible wavelengths. This study provides analyses based upon novel multi-angular hyperspectral data for validation of Earth-observation-based properties of semi-arid ecosystems, as well as insights for designing spectral characteristics of future sensors for ecosystem monitoring.

  3. Influence of rubbing on rotor dynamics, part 2

    NASA Technical Reports Server (NTRS)

    Muszynska, Agnes; Bently, Donald E.; Franklin, Wesley D.; Hayashida, Robert D.; Kingsley, Lori M.; Curry, Arthur E.

    1989-01-01

    Rotor dynamic behavior depends considerably on how much the specific physical phenomena accompanying rotor rubbing against the stator is involved. The experimental results of rotor-to-stator rubbing contact are analyzed. The computer code is described for obtaining numerical calculations of rotor-to-stator rubbing system dynamic responses. Computer generated results are provided. The reduced dynamic data from High Pressure Fuel Turbo Pump (HPFTP) hot fire test are given. The results provide some significant conclusions. Information is provided on the electronic instrumentation used in the experimental testing.

  4. Assessing Static and Dynamic Influences on Inmate Violence Levels

    ERIC Educational Resources Information Center

    Steiner, Benjamin

    2009-01-01

    Inmate misconduct creates problems for other inmates as well as correctional staff. Most empirical assessments of the correlates of inmate misconduct have been conducted at the individual level; however, a facility's level of misconduct may be of equal importance to prison management and state officials because these numbers can reflect order, or…

  5. Adaptive optics optical coherence tomography for measuring phase and reflectance dynamics of photoreceptors

    NASA Astrophysics Data System (ADS)

    Kocaoglu, Omer P.; Jonnal, Ravi S.; Lee, Sangyeol; Wang, Qiang; Liu, Zhuolin; Miller, Donald T.

    2012-03-01

    Optical coherence tomography with adaptive optics (AO-OCT) is a noninvasive method for imaging the living retina at the microscopic level. We used AO-OCT technology to follow changes in cone photoreceptor outer segment (OS) length and reflectance. To substantially increase sensitivity of the length measurements, a novel phase retrieval technique was demonstrated, capable of detecting changes on a nanometer scale. We acquired volume videos of 0.65°x0.65° retinal patches at 1.5° temporal to the fovea over 75 and 105 minutes in two subjects. Volumes were dewarped and registered, after which the cone intensity, OS length, and referenced phase difference were tracked over time. The reflections from inner segment/OS junction (IS/OS) and posterior tips of OS (PT) showed significant intensity variations over time. In contrast, the OS length as measured from the intensity images did not change, indicative of a highly stable OS length at least down to the level of the system's axial resolution (3μm). Smaller axial changes, however, were detected with our phase retrieval technique. Specifically, the PT-IS/OS phase difference for the same cones showed significant variation, suggesting real sub-wavelength changes in OS length of 125+/-46 nm/hr for the 22 cones followed. We believe these length changes are due to the normal renewal process of the cone OS that elongate the OS at a rate of about 100 nm/hr. The phase difference measurements were strongly correlated among Alines within the same cone (0.65 radians standard deviation) corresponding to a length sensitivity of 31 nm, or ~100 times smaller than the axial resolution of our system.

  6. Ultrafast Carrier Dynamics Measured by the Transient Change in the Reflectance of InP and GaAs Film

    SciTech Connect

    John Klopf

    2005-10-31

    the dynamics of the hot carrier distributions in these materials, but also provide the basis for future development of better diagnostic instruments for the non-destructive evaluation of these important materials. A theoretical model describing the change in reflectance due to the photoexcited hot carrier distribution has also been developed. By applying this model to the experimental results, several important material parameters such as the electron-phonon scattering time and the rates for diffusion and several recombination processes are determined. These values are compared with those reported for similar materials, and the validity of the results is discussed. A complete description of the experimental technique as well as the theoretical reflectance model is presented.

  7. Influence of dynamic conditions on biofilm formation by staphylococci.

    PubMed

    Stepanović, S; Vuković, D; Jezek, P; Pavlović, M; Svabic-Vlahović, M

    2001-07-01

    The modified microtiter plate test was used to investigate biofilm formation by staphylococci under both static and dynamic conditions. The quantity of biofilm produced under static conditions was used as a reference. Dynamic conditions, which were achieved by incubating microtiter plates on a horizontal shaker with and without the presence of glass beads in wells, either reduced biofilm formation or left it unchanged. Dynamic conditions particularly affected the capacity of certain species to produce biofilm: these species included the causative agents of infections associated with a foreign body (Staphylococcus epidermidis, Staphylococcus aureus). On the basis of these results, dynamic conditions should be included as a parameter for evaluating biofilm formation by staphylococci in vitro. PMID:11561809

  8. Analyzing the influence of median cross-section design on highway safety using vehicle dynamics simulations.

    PubMed

    Stine, Jason S; Hamblin, Bridget C; Brennan, Sean N; Donnell, Eric T

    2010-11-01

    Although vehicle dynamics simulations have long been used in vehicle design and crash reconstruction, their use for highway design is rare. This paper investigates the safety of highway medians through iterative simulations of off-road median encroachments. The commercially available software CarSim was used to simulate over one hundred thousand encroachments, representing the entire passenger vehicle fleet and a wide range of encroachment angles, departure speeds, steering inputs, and braking inputs. Each individual simulation output was then weighted using data from previous studies to reflect the probability of each specific accident scenario occurring in a real-life median encroachment. Results of this analysis illustrate the relative influence of median cross-section geometry on the resulting accident outcomes. The simulations indicate that the overall safety of a highway median depends on the occurrence of both vehicle rollover and median crossover events, and the cross-section shape, slope, and width are all shown to greatly affect each of these incidents. An evaluation of the simulation results was conducted with vehicle trajectories from previous experimental crash tests. Further assessment of the aggregate simulation results to actual crash data was achieved through comparison with several databases of crash statistics. Both efforts showed a strong agreement between the simulations and the real-life crash data. PMID:20728628

  9. Host polymer influence on dilute polystyrene segmental dynamics

    NASA Astrophysics Data System (ADS)

    Lutz, T. R.

    2005-03-01

    We have utilized deuterium NMR to investigate the segmental dynamics of dilute (2%) d3-polystyrene (PS) chains in miscible polymer blends with polybutadiene, poly(vinyl ethylene), polyisoprene, poly(vinyl methylether) and poly(methyl methacrylate). In the dilute limit, we find qualitative differences depending upon whether the host polymer has dynamics that are faster or slower than that of pure PS. In blends where PS is the fast (low Tg) component, segmental dynamics are slowed upon blending and can be fit by the Lodge-McLeish model. When PS is the slow (high Tg) component, PS segmental dynamics speed up upon blending, but cannot be fit by the Lodge-McLeish model unless a temperature dependent self-concentration is employed. These results are qualitatively consistent with a recent suggestion by Kant, Kumar and Colby (Macromolecules, 2003, 10087), based upon data at higher concentrations. Furthermore, as the slow component, we find the segmental dynamics of PS has a temperature dependence similar to that of its host. This suggests viewing the high Tg component dynamics in a miscible blend as similar to a polymer in a low molecular weight solvent.

  10. The dynamical influences of cloud shading on simulated supercell thunderstorms

    NASA Astrophysics Data System (ADS)

    Frame, Jeffrey

    2008-10-01

    supercells with radiation because varying surface characteristics alter the amount of frictional drag experienced by the low-level flow. Additionally, the propagation of the rear-flank gust front is heavily modulated by both the strength and the location of the outflow, which are influenced by the choice of the storm-relative wind profile and the microphysics package. If shortwave radiation is excluded from the model, a shallow stable layer forms over the entire domain and the storm becomes elevated and weakens. The direct absorption and emission of radiation by clouds does not significantly affect the simulated supercells. The base-state environment is changed to see under which conditions cloud shading and friction combine to force the undercutting of the updraft. Neither a morning model initialization nor a cold season model initialization prevent this from occurring in any of the simulations which produce an anvil shadow. The ground-relative wind is also varied because the surface fluxes of both heat and momentum are not Galilean invariant. A storm in which both the rear-flank gust front and updraft slowly move along the major axis of the anvil shadow becomes undercut, much like the stationary storm. A fast moving storm, however, does not become undercut because less time exists to cool the model surface and to decouple the surface layer if the storm moves faster. If the gust front moves into the anvil shadow and the updraft moves normal to the shadow (i.e., the northward movement of the updraft for an eastward-extending anvil), cyclic behavior can result, although this is highly dependent on storm motion. If the gust front propagates into the full sun (i.e., southward movement), the storm is relatively unaffected by the presence of radiation because the dynamics that govern gust front propagation remain relatively unchanged.

  11. Dynamics of layer-by-layer growth of a polyelectrolyte multilayer studied in situ using attenuated total reflectance infrared spectroscopy.

    PubMed

    Owusu-Nkwantabisah, Silas; Gammana, Madhira; Tripp, Carl P

    2014-10-01

    Attenuated total reflectance infrared spectroscopy (ATR-IR) was used to study the dynamic layer-by-layer (LBL) growth of a sodium polyacrylate (NaPA)/poly(diallydimethylammonium) chloride (PDADMAC) multilayer on TiO2 particles. Molecular weights (Mw) used were 30 and 60 kDa for NaPA and 8.5 and 150 kDa for PDADMAC. IR spectra were recorded in situ as a function of time and were used to obtain the dynamic mass adsorbed and bound fraction of the polymers during each deposition step. For 30 kDa NaPA layers, the dynamics of adsorption show an initial rapid rise in mass followed by a slow increase toward a plateau value upon LBL with 150 kDa PDADMAC. In contrast, the 60 kDa NaPA layers achieve a plateau quickly and do not show a slow increase toward a plateau. In the case of LBL with 150 kDa PDADMAC, the dynamics of the bound fraction of polymer per layer suggest that polymer diffusion and conformational rearrangement occur for the layers of 30 kDa NaPA but not for the 60 kDa NaPA layers. Furthermore, PDADMAC adsorption profiles show that there is no diffusion of the PDADMAC layers and that PDADMAC flattens onto the underlying layer. A linear growth in the mass adsorbed per layer was observed for 150 kDa PDADMAC with both molecular weights of NaPA. In the case of 8.5 kDa PDADMAC, smaller growth increments and the desorption of underlying layers were observed. This work demonstrates the use of ATR-IR in obtaining the dynamics of LBL multilayer formation. Furthermore, it provides an example in which polymer diffusion during LBL film formation does not lead to exponential growth. PMID:25203136

  12. Dynamic properties influence the perception of facial expressions.

    PubMed

    Kamachi, Miyuki; Bruce, Vicki; Mukaida, Shigeru; Gyoba, Jiro; Yoshikawa, Sakiko; Akamatsu, Shigeru

    2013-01-01

    Two experiments were conducted to investigate the role played by dynamic information in identifying facial expressions of emotion. Dynamic expression sequences were created by generating and displaying morph sequences which changed the face from neutral to a peak expression in different numbers of intervening intermediate stages, to create fast (6 frames), medium (26 frames), and slow (101 frames) sequences. In experiment 1, participants were asked to describe what the person shown in each sequence was feeling. Sadness was more accurately identified when slow sequences were shown. Happiness, and to some extent surprise, was better from faster sequences, while anger was most accurately detected from the sequences of medium pace. In experiment 2 we used an intensity-rating task and static images as well as dynamic ones to examine whether effects were due to total time of the displays or to the speed of sequence. Accuracies of expression judgments were derived from the rated intensities and the results were similar to those of experiment 1 for angry and sad expressions (surprised and happy were close to ceiling). Moreover, the effect of display time was found only for dynamic expressions and not for static ones, suggesting that it was speed, not time, which was responsible for these effects. These results suggest that representations of basic expressions of emotion encode information about dynamic as well as static properties. PMID:24601038

  13. Predicting agricultural management influence on long-term soil organic carbon dynamics: implications for biofuel production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Long-term field experiments (LTE) are ideal for predicting the influence of agricultural management on soil organic carbon (SOC) dynamics and examining biofuel crop residue removal policy questions. Our objectives were (i) to simulate SOC dynamics in LTE soils under various climates, crop rotations,...

  14. Reflections on urban science teacher-student self-efficacy dynamics

    NASA Astrophysics Data System (ADS)

    Hagiwara, Sumi; Maulucci, Maria S. Rivera; Ramos, S. Lizette

    2011-12-01

    This forum article consists of commentaries—authored by Sumi Hagiwara, Maria S. Rivera Maulucci and Lizette Ramos—on the feature article by Virginia Jennings Bolshakova, Carla C. Johnson, and Charlene M. Czerniak. We reflect on a series of questions that take retrospective, introspective, and prospective views of self-efficacy in science education. We review selected studies that explore some of the historical developments and methodological approaches in the literature and examine a teacher-student self-efficacy system model that shows the ways in which teachers' and students' self-efficacy judgments are based upon multiple individual and shared components, such as identity and social interaction within the classroom and school. We close with a call for the design of measures of teacher-student self-efficacy systems, so that we can begin to tailor professional development experiences to the goals and motivations of individual and collective groups of teachers and students in ways that accommodate the unique cultural features of their classrooms and foster student self-efficacy.

  15. Dynamic blastomere behaviour reflects human embryo ploidy by the four-cell stage

    PubMed Central

    Chavez, Shawn L.; Loewke, Kevin E.; Han, Jinnuo; Moussavi, Farshid; Colls, Pere; Munne, Santiago; Behr, Barry; Reijo Pera, Renee A.

    2012-01-01

    Previous studies have demonstrated that aneuploidy in human embryos is surprisingly frequent with 50–80% of cleavage-stage human embryos carrying an abnormal chromosome number. Here we combine non-invasive time-lapse imaging with karyotypic reconstruction of all blastomeres in four-cell human embryos to address the hypothesis that blastomere behaviour may reflect ploidy during the first two cleavage divisions. We demonstrate that precise cell cycle parameter timing is observed in all euploid embryos to the four-cell stage, whereas only 30% of aneuploid embryos exhibit parameter values within normal timing windows. Further, we observe that the generation of human embryonic aneuploidy is complex with contribution from chromosome-containing fragments/micronuclei that frequently emerge and may persist or become reabsorbed during interphase. These findings suggest that cell cycle and fragmentation parameters of individual blastomeres are diagnostic of ploidy, amenable to automated tracking algorithms, and likely of clinical relevance in reducing transfer of embryos prone to miscarriage. PMID:23212380

  16. High temperature far-infrared dynamics of orthorhombic NdMnO3: emissivity and reflectivity.

    PubMed

    Massa, Néstor E; del Campo, Leire; Meneses, Domingos De Sousa; Echegut, Patrick; Martínez-Lope, María Jesús; Alonso, José Antonio

    2013-06-12

    We report on near normal far- and mid-infrared emission and reflectivity of NdMnO3 perovskite from room temperature to sample decomposition above 1800 K. At 300 K the number of infrared active phonons is in close agreement with the 25 calculated for the orthorhombic D(2h)(16)-Pbnm (Z = 4) space group. Their number gradually decreases as we approach the temperature of orbital disorder at ~1023 K where the orthorhombic O' lower temperature cooperative phase coexists with the cubic orthorhombic O. At above ~1200 K, the three infrared active phonons coincide with that expected for cubic Pm-3m (Z = 1) in the high temperature insulating regime. Heating samples in dry air triggers double exchange conductivity by Mn(3+) and Mn(4+) ions and a small polaron mid-infrared band. Fits to the optical conductivity single out the octahedral antisymmetric and symmetric vibrational modes as the main phonons in the electron-phonon interactions at 875 K. For 1745 K, it is enough to consider the symmetric stretching internal mode. An overdamped defect induced Drude component is clearly outlined at the highest temperatures. We conclude that rare earth manganite eg electrons are prone to spin, charge, orbital, and lattice couplings in an intrinsic orbital distorted perovskite lattice, favoring embryonic low energy collective excitations. PMID:23676242

  17. Aeroelasticity matters - Some reflections on two decades of testing in the NASA Langley Transonic Dynamics Tunnel

    NASA Technical Reports Server (NTRS)

    Reed, W. H., III

    1981-01-01

    In 1955, work was started on the conversion of a subsonic wind tunnel to a 16-foot transonic tunnel with Freon-12 or air as the test medium. The new facility, designated the Transonic Dynamics Tunnel (TDT), became fully operational in 1960. A description is presented of aeroelastic testing and research performed in the TDT since 1960. It is pointed out that wind-tunnel tests of aeroelastic models require specialized experimental techniques seldom found in other types of wind-tunnel studies. Attention is given to model mount systems, launch vehicle models, aircraft models, aircraft buffet, gust response, stability derivative measurements, and subcritical testing techniques. Aspects of vehicle development testing are considered along with aeroelastic 'fixes', aeroelastic 'surprises', approaches for controlling aeroelastic effects, and unsteady pressure measurements.

  18. Electronically non-adiabatic influences in surface chemistry and dynamics.

    PubMed

    Wodtke, Alec M

    2016-07-01

    Electronically nonadiabatic interactions between molecules and metal surfaces are now well known. Evidence is particularly clear from studies of diatomic molecules that molecular vibration can be strongly coupled to electrons of the metal leading to efficient energy transfer between these two kinds of motion. Since molecular vibration is the same motion needed for bond breaking, it is logical to postulate that electronically nonadiabatic influences on surface chemical reaction probabilities would be strong. Still there are few if any examples where such influences have been clearly investigated. This review recounts the evidence for and against the aforementioned postulate emphasizing reacting systems that have yet to receive full attention and where electronically nonadiabatic influence of reaction probabilities might be clearly demonstrated. PMID:27152489

  19. Spatial asymmetries in connectivity influence colonization-extinction dynamics.

    PubMed

    Acevedo, Miguel A; Fletcher, Robert J; Tremblay, Raymond L; Meléndez-Ackerman, Elvia J

    2015-10-01

    Movement has broad implications for many areas of biology, including evolution, community and population ecology. Movement is crucial in metapopulation ecology because it facilitates colonization and reduces the likelihood of local extinction via rescue effects. Most metapopulation modeling approaches describe connectivity using pair-wise Euclidean distances resulting in the simplifying assumption of a symmetric connectivity pattern. Yet, assuming symmetric connectivity when populations show net asymmetric movement patterns may result in biased estimates of colonization and extinction, and may alter interpretations of the dynamics and conclusions regarding the viability of metapopulations. Here, we use a 10-year time series on a wind-dispersed orchid Lepanthes rupestris that anchors its roots in patches of moss growing on trees or boulders along streams, to test for the role of connectivity asymmetries in explaining the colonization-extinction dynamics of this orchid in a network of 975 patches. We expected that wind direction could highly alter dispersal direction in this orchid. To account for this potential asymmetry, we modified the connectivity measure traditionally used in metapopulation models to allow for asymmetric effective distances between patches and subsequently estimated colonization and extinction probabilities using a dynamic occupancy modeling approach. Asymmetric movement was prevalent in the L. rupestris metapopulation and incorporating potential dispersal asymmetries resulted in higher colonization estimates in larger patches and more accurate models. Accounting for dispersal asymmetries may reveal connectivity effects where they were previously assumed to be negligible and may provide more reliable conclusions regarding the role of connectivity in patch dynamics. PMID:26054613

  20. On the dynamical influence of ocean eddy potential vorticity fluxes

    NASA Astrophysics Data System (ADS)

    Maddison, J. R.; Marshall, D. P.; Shipton, J.

    2015-08-01

    The impact of eddy potential vorticity fluxes on the dynamical evolution of the flow is obscured by the presence of large and dynamically-inert rotational fluxes. However, the decomposition of eddy potential vorticity fluxes into rotational and divergent components is non-unique in a bounded domain and requires the imposition of an additional boundary condition. Here it is proposed to invoke a one-to-one correspondence between divergent eddy potential vorticity fluxes and non-divergent eddy momentum tendencies in the quasi-geostrophic residual-mean equations in order to select a unique divergent eddy potential vorticity flux. The divergent eddy potential vorticity flux satisfies a zero tangential component boundary condition. In a simply connected domain, the resulting divergent eddy potential vorticity flux satisfies a powerful optimality condition: it is the horizontally oriented divergent flux with minimum L2 norm. Hence there is a well-defined sense in which this approach removes as much of the dynamically inactive eddy potential vorticity flux as possible, and extracts an underlying dynamically active divergent eddy potential vorticity flux. It is shown that this approach leads to a divergent eddy potential vorticity flux which has an intuitive physical interpretation, via a direct relationship to the resulting forcing of the mean circulation.

  1. About compensation the electronic beam dynamic stratification influence in super-power relativistic Cherenkov oscillators

    SciTech Connect

    Kurayev, Alexander A.; Rak, Alexey O.; Sinitsyn, Anatoly K.

    2011-07-01

    On the basis of the exact nonlinear theory relativistic TWT and BWO on irregular hollow waveguides with cathode filters-modulators with the account as propagating, and beyond cut-off waves, with the account of losses in walls of a waveguide and inhomogeneity directing an electronic beam magnetostatic fields finds out influence of dynamic stratification influence on efficiency of the generator. Possibility of almost fill compensation the electronic beam dynamic stratification influence on efficiency by optimization of an electronic beam arrangement in inhomogeneous high frequency and magnetic fields and characteristics of the irregular corrugated waveguide is shown. (author)

  2. Encoding of Physics Concepts: Concreteness and Presentation Modality Reflected by Human Brain Dynamics

    PubMed Central

    Lai, Kevin; She, Hsiao-Ching; Chen, Sheng-Chang; Chou, Wen-Chi; Huang, Li-Yu; Jung, Tzyy-Ping; Gramann, Klaus

    2012-01-01

    Previous research into working memory has focused on activations in different brain areas accompanying either different presentation modalities (verbal vs. non-verbal) or concreteness (abstract vs. concrete) of non-science concepts. Less research has been conducted investigating how scientific concepts are learned and further processed in working memory. To bridge this gap, the present study investigated human brain dynamics associated with encoding of physics concepts, taking both presentation modality and concreteness into account. Results of this study revealed greater theta and low-beta synchronization in the anterior cingulate cortex (ACC) during encoding of concrete pictures as compared to the encoding of both high and low imageable words. In visual brain areas, greater theta activity accompanying stimulus onsets was observed for words as compared to pictures while stronger alpha suppression was observed in responses to pictures as compared to words. In general, the EEG oscillation patterns for encoding words of different levels of abstractness were comparable but differed significantly from encoding of pictures. These results provide insights into the effects of modality of presentation on human encoding of scientific concepts and thus might help in developing new ways to better teach scientific concepts in class. PMID:22848602

  3. Movement dynamics reflect a functional role for weak coupling and role structure in dyadic problem solving.

    PubMed

    Abney, Drew H; Paxton, Alexandra; Dale, Rick; Kello, Christopher T

    2015-11-01

    Successful interaction requires complex coordination of body movements. Previous research has suggested a functional role for coordination and especially synchronization (i.e., time-locked movement across individuals) in different types of human interaction contexts. Although such coordination has been shown to be nearly ubiquitous in human interaction, less is known about its function. One proposal is that synchrony supports and facilitates communication (Topics Cogn Sci 1:305-319, 2009). However, questions still remain about what the properties of coordination for optimizing communication might look like. In the present study, dyads worked together to construct towers from uncooked spaghetti and marshmallows. Using cross-recurrence quantification analysis, we found that dyads with loosely coupled gross body movements performed better, supporting recent work suggesting that simple synchrony may not be the key to effective performance (Riley et al. 2011). We also found evidence that leader-follower dynamics-when sensitive to the specific role structure of the interaction-impact task performance. We discuss our results with respect to the functional role of coordination in human interaction. PMID:25757891

  4. Activity of striatal neurons reflects dynamic encoding and recoding of procedural memories.

    PubMed

    Barnes, Terra D; Kubota, Yasuo; Hu, Dan; Jin, Dezhe Z; Graybiel, Ann M

    2005-10-20

    Learning to perform a behavioural procedure as a well-ingrained habit requires extensive repetition of the behavioural sequence, and learning not to perform such behaviours is notoriously difficult. Yet regaining a habit can occur quickly, with even one or a few exposures to cues previously triggering the behaviour. To identify neural mechanisms that might underlie such learning dynamics, we made long-term recordings from multiple neurons in the sensorimotor striatum, a basal ganglia structure implicated in habit formation, in rats successively trained on a reward-based procedural task, given extinction training and then given reacquisition training. The spike activity of striatal output neurons, nodal points in cortico-basal ganglia circuits, changed markedly across multiple dimensions during each of these phases of learning. First, new patterns of task-related ensemble firing successively formed, reversed and then re-emerged. Second, task-irrelevant firing was suppressed, then rebounded, and then was suppressed again. These changing spike activity patterns were highly correlated with changes in behavioural performance. We propose that these changes in task representation in cortico-basal ganglia circuits represent neural equivalents of the explore-exploit behaviour characteristic of habit learning. PMID:16237445

  5. SOLAR DYNAMICS OBSERVATORY/ATMOSPHERIC IMAGING ASSEMBLY OBSERVATIONS OF A REFLECTING LONGITUDINAL WAVE IN A CORONAL LOOP

    SciTech Connect

    Kumar, Pankaj; Innes, D. E.; Inhester, B.

    2013-12-10

    We report high resolution observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) of intensity oscillations in a hot, T ∼ 8-10 MK, loop. The AIA images show a large coronal loop that was rapidly heated following plasma ejection from one of the loop's footpoints. A wave-like intensity enhancement, seen very clearly in the 131 and 94 Å channel images, propagated ahead of the ejecta along the loop, and was reflected at the opposite footpoint. The wave reflected four times before fading. It was only seen in the hot, 131 and 94 Å channels. The characteristic period and the decay time of the oscillation were ∼630 and ∼440 s, respectively. The phase speed was about 460-510 km s{sup –1} which roughly matches the sound speed of the loop (430-480 km s{sup –1}). The observed properties of the oscillation are consistent with the observations of Dopper-shift oscillations discovered by the Solar and Heliospheric Observatory/Solar Ultraviolet Measurement of Emitted Radiation and with their interpretation as slow magnetoacoustic waves. We suggest that the impulsive injection of plasma, following reconnection at one of the loop footpoints, led to rapid heating and the propagation of a longitudinal compressive wave along the loop. The wave bounces back and forth a couple of times before fading.

  6. Influence of subducted components on back-arc melting dynamics in the Manus Basin

    NASA Astrophysics Data System (ADS)

    Beier, Christoph; Turner, Simon P.; Sinton, John M.; Gill, James B.

    2010-06-01

    Lavas erupted in back-arc basins afford the opportunity to explore the extent to which decompression and subduction-related components influence partial melting in this setting. We present U-Th-Ra disequilibria data from 24 well-characterized lavas from the Manus Basin behind the New Britain volcanic arc, supplemented by some additional trace element and Sr-Nd-Pb isotope data. The lavas range in composition from 49.6 to 57.7 wt % SiO2 and can be subdivided into those that are broadly like mid-ocean ridge basalts (MORB) with Ba/Nb < 16 and back-arc basin basalts (BABB) that are variably influenced by subduction components and have Ba/Nb > 16. Rifts closest to the arc are dominated by BABB, whereas both lavas types erupt further away at the Manus Spreading Center. The MORB have small 230Th excesses (up to 5%) and are displaced below the global correlation of (230Th/238U) with ridge depth. In most respects the BABB closely resemble lavas erupted along the New Britain arc front, including 238U excesses that reach 26%. The Pb isotope data can be explained by mixing of a subduction component into an Indian MORB mantle source. The Pb in the subduction component is derived from both the subducted sediment (5%) and fluids from the subducting altered Solomon Sea oceanic crust (95%), and these were mixed prior to addition to the mantle wedge. U/Th ratios, Fe3+/ΣFe, and H2O contents all increase with increasing 206Pb/204Pb. A model in which addition of the subduction component to the mantle wedge is followed by 230Th in-growth during decompression and dynamic melting all less than 140 kyr prior to eruption can simulate the data. However, our preferred model is one of dynamic decompression melting in which subduction-modified, more oxidized mantle had DU ≪ DTh leading to 238U excesses in contrast to unmodified mantle that yields 230Th excess. Large 226Ra excesses in some southern rift samples require addition of a fluid <8 kyr ago but elsewhere reflect melting under low

  7. Walking in simulated Martian gravity: influence of the portable life support system's design on dynamic stability.

    PubMed

    Scott-Pandorf, Melissa M; O'Connor, Daniel P; Layne, Charles S; Josić, Kresimir; Kurz, Max J

    2009-09-01

    With human exploration of the moon and Mars on the horizon, research considerations for space suit redesign have surfaced. The portable life support system (PLSS) used in conjunction with the space suit during the Apollo missions may have influenced the dynamic balance of the gait pattern. This investigation explored potential issues with the PLSS design that may arise during the Mars exploration. A better understanding of how the location of the PLSS load influences the dynamic stability of the gait pattern may provide insight, such that space missions may have more productive missions with a smaller risk of injury and damaging equipment while falling. We explored the influence the PLSS load position had on the dynamic stability of the walking pattern. While walking, participants wore a device built to simulate possible PLSS load configurations. Floquet and Lyapunov analysis techniques were used to quantify the dynamic stability of the gait pattern. The dynamic stability of the gait pattern was influenced by the position of load. PLSS loads that are placed high and forward on the torso resulted in less dynamically stable walking patterns than loads placed evenly and low on the torso. Furthermore, the kinematic results demonstrated that all joints of the lower extremity may be important for adjusting to different load placements and maintaining dynamic stability. Space scientists and engineers may want to consider PLSS designs that distribute loads evenly and low, and space suit designs that will not limit the sagittal plane range of motion at the lower extremity joints. PMID:19725694

  8. Dynamics of 2013 Sudden Stratospheric Warming event and its impact on cold weather over Eurasia: Role of planetary wave reflection.

    PubMed

    Nath, Debashis; Chen, Wen; Zelin, Cai; Pogoreltsev, Alexander Ivanovich; Wei, Ke

    2016-01-01

    In the present study, we investigate the impact of stratospheric planetary wave reflection on tropospheric weather over Central Eurasia during the 2013 Sudden Stratospheric Warming (SSW) event. We analyze EP fluxes and Plumb wave activity fluxes to study the two and three dimensional aspects of wave propagation, respectively. The 2013 SSW event is excited by the combined influence of wavenumber 1 (WN1) and wavenumber 2 (WN2) planetary waves, which makes the event an unusual one and seems to have significant impact on tropospheric weather regime. We observe an extraordinary development of a ridge over the Siberian Tundra and the North Pacific during first development stage (last week of December 2012) and later from the North Atlantic in the second development stage (first week of January 2013), and these waves appear to be responsible for the excitation of the WN2 pattern during the SSW. The wave packets propagated upward and were then reflected back down to central Eurasia due to strong negative wind shear in the upper stratospheric polar jet, caused by the SSW event. Waves that propagated downward led to the formation of a deep trough over Eurasia and brought extreme cold weather over Kazakhstan, the Southern part of Russia and the Northwestern part of China during mid-January 2013. PMID:27051997

  9. Dynamics of 2013 Sudden Stratospheric Warming event and its impact on cold weather over Eurasia: Role of planetary wave reflection

    PubMed Central

    Nath, Debashis; Chen, Wen; Zelin, Cai; Pogoreltsev, Alexander Ivanovich; Wei, Ke

    2016-01-01

    In the present study, we investigate the impact of stratospheric planetary wave reflection on tropospheric weather over Central Eurasia during the 2013 Sudden Stratospheric Warming (SSW) event. We analyze EP fluxes and Plumb wave activity fluxes to study the two and three dimensional aspects of wave propagation, respectively. The 2013 SSW event is excited by the combined influence of wavenumber 1 (WN1) and wavenumber 2 (WN2) planetary waves, which makes the event an unusual one and seems to have significant impact on tropospheric weather regime. We observe an extraordinary development of a ridge over the Siberian Tundra and the North Pacific during first development stage (last week of December 2012) and later from the North Atlantic in the second development stage (first week of January 2013), and these waves appear to be responsible for the excitation of the WN2 pattern during the SSW. The wave packets propagated upward and were then reflected back down to central Eurasia due to strong negative wind shear in the upper stratospheric polar jet, caused by the SSW event. Waves that propagated downward led to the formation of a deep trough over Eurasia and brought extreme cold weather over Kazakhstan, the Southern part of Russia and the Northwestern part of China during mid-January 2013. PMID:27051997

  10. Opinion dynamics and influencing on random geometric graphs.

    PubMed

    Zhang, Weituo; Lim, Chjan C; Korniss, G; Szymanski, Boleslaw K

    2014-01-01

    We investigate the two-word Naming Game on two-dimensional random geometric graphs. Studying this model advances our understanding of the spatial distribution and propagation of opinions in social dynamics. A main feature of this model is the spontaneous emergence of spatial structures called opinion domains which are geographic regions with clear boundaries within which all individuals share the same opinion. We provide the mean-field equation for the underlying dynamics and discuss several properties of the equation such as the stationary solutions and two-time-scale separation. For the evolution of the opinion domains we find that the opinion domain boundary propagates at a speed proportional to its curvature. Finally we investigate the impact of committed agents on opinion domains and find the scaling of consensus time. PMID:24993655

  11. The influence of surface adsorption on microbubble dynamics.

    PubMed

    Stride, E

    2008-06-28

    In a pure liquid, the behaviour of a gas or vapour microbubble is determined primarily by its size, the ambient pressure and the properties of the surrounding liquid. In practice, however, adsorption of a dissolved substance from the surrounding liquid onto the microbubble surface will often take place, producing a thin coating which can significantly affect both the microbubble's stability and its dynamic response. This can have important implications in a wide range of applications, including underwater acoustics, cavitation detection, medical imaging and drug delivery. The aim of this paper is to review the existing theoretical treatments of coated microbubbles and to present and discuss some recent developments. It will be shown that the presence of the coating can substantially modify the amplitude of microbubble volumetric oscillation, resonance characteristics and relative amplitude in tension and compression. Finally, the need for improved understanding of the dynamic behaviour of surface coatings at high frequencies will be discussed. PMID:18348975

  12. Using directed information for influence discovery in interconnected dynamical systems

    NASA Astrophysics Data System (ADS)

    Rao, Arvind; Hero, Alfred O.; States, David J.; Engel, James Douglas

    2008-08-01

    Structure discovery in non-linear dynamical systems is an important and challenging problem that arises in various applications such as computational neuroscience, econometrics, and biological network discovery. Each of these systems have multiple interacting variables and the key problem is the inference of the underlying structure of the systems (which variables are connected to which others) based on the output observations (such as multiple time trajectories of the variables). Since such applications demand the inference of directed relationships among variables in these non-linear systems, current methods that have a linear assumption on structure or yield undirected variable dependencies are insufficient. Hence, in this work, we present a methodology for structure discovery using an information-theoretic metric called directed time information (DTI). Using both synthetic dynamical systems as well as true biological datasets (kidney development and T-cell data), we demonstrate the utility of DTI in such problems.

  13. Opinion Dynamics and Influencing on Random Geometric Graphs

    PubMed Central

    Zhang, Weituo; Lim, Chjan C.; Korniss, G.; Szymanski, Boleslaw K.

    2014-01-01

    We investigate the two-word Naming Game on two-dimensional random geometric graphs. Studying this model advances our understanding of the spatial distribution and propagation of opinions in social dynamics. A main feature of this model is the spontaneous emergence of spatial structures called opinion domains which are geographic regions with clear boundaries within which all individuals share the same opinion. We provide the mean-field equation for the underlying dynamics and discuss several properties of the equation such as the stationary solutions and two-time-scale separation. For the evolution of the opinion domains we find that the opinion domain boundary propagates at a speed proportional to its curvature. Finally we investigate the impact of committed agents on opinion domains and find the scaling of consensus time. PMID:24993655

  14. Influence of initial conditions on compressible vorticity dynamics

    NASA Astrophysics Data System (ADS)

    Virk, D.; Hussain, F.

    1993-11-01

    Prompted by the lack of a unique choice of pressure ( P) and density (ρ) fields for a compressible free vortex and by the observed dependence of turbulence dynamics on initial P and ρ in compressible simulations, we address the effects of initial conditions on the evolution of a single vortex, on the prototypical phenomenon of vortex reconnection, and on two-dimensional turbulence. Two previous choices of initial conditions used for numerical simulations of compressible turbulence have been: (i) both P and ρ uniform (constant initial conditions, CIC), and (ii) uniform ρ with P determined from the Poisson equation (constant density initial conditions, CDIC). We find these initial conditions to be inappropriate for compressible vorticity dynamics studies. Specifically, in compressible reconnection, the effects of baroclinic vorticity generation and shocklet formation cancel each other during early evolution for CDIC, thus leading to almost incompressible behavior. Although CIC captures compressibility effects, it incorrectly changes the initial vorticity distribution by introducing strong acoustic transients, thereby significantly altering the evolving dynamics. Here, a new initial condition, called polytropic initial condition (PIC), is proposed, for which the Poisson equation is solved for initially polytropically related P and ρ fields. PIC provides P and ρ distributions within vortices which are consistent with those observed in shock-wedge interaction experiment and also leads to compressible solutions with no acoustic transients. At low Mach number ( M), we show that the effects of all these three initial conditions can be predicted by low- M asymptotic theories of the Navier-Stokes equations. At high M, it is shown here that inappropriate initial conditions may alter the evolutionary dynamics and, hence, lead to wrong conclusions regarding compressibility effects. We argue that PIC is a more appropriate choice.

  15. Investigation of Influence of Modeling Fidelities on Supply Chain Dynamics

    SciTech Connect

    Kulvatunyou, Boonserm; Son, Young Jun; Venkatestwaran, Jayendran

    2002-12-01

    In this paper, a three-echelon supply chain model is analyzed to determine strategies to reduce the total supply chain system dynamics. Many researchers have attempted to improve the system performance by simulation of an abstract model representing the actual supply chain. Uniqueness of the research in this paper stems from the usage of multiple models with varying degrees of detail representing the same supply chain. The significance of a detailed supply chain model on the quality of experimental result obtained is made clear. Combinations of the factors employed to build an abstract to a detailed supply chain model include: (i) Transportation and production delay, (ii) Demand at the retailer, and (iii) Production and transportation capacity. It is shown that the system dynamics itself varies with increasing detail in the supply chain model. In addition, it is examined to see if a strategy found effective in improving the system dynamics with an abstract supply chain model is also effective with a detailed supply chain model. For this purpose, the following strategies are identified: Inventory level determination, Lead time reduction, Access to Point of Sale (PoS) data I, Access to PoS data II and Vendor Managed Inventory. It is established that the strategy found to be the most effective on an abstract model of the supply chain is not always the best strategy for the real supply chain.

  16. Influence of rubbing on rotor dynamics, part 1

    NASA Technical Reports Server (NTRS)

    Muszynska, Agnes; Bently, Donald E.; Franklin, Wesley D.; Hayashida, Robert D.; Kingsley, Lori M.; Curry, Arthur E.

    1989-01-01

    The results of analytical and experimental research on rotor-to-stationary element rubbing in rotating machines are presented. A characterization of physical phenomena associated with rubbing, as well as a literature survey on the subject of rub is given. The experimental results were obtained from two rubbing rotor rigs: one, which dynamically simulates the space shuttle main engine high pressure fuel turbopump (HPFTP), and the second one, much simpler, a two-mode rotor rig, designed for more generic studies on rotor-to-stator rubbing. Two areas were studied: generic rotor-to-stator rub-related dynamic phenomena affecting rotating machine behavior and applications to the space shuttle HPFTP. An outline of application of dynamic stiffness methodology for identification of rotor/bearing system modal parameters is given. The mathematical model of rotor/bearing/seal system under rub condition is given. The computer program was developed to calculate rotor responses. Compared with experimental results the computed results prove an adequacy of the model.

  17. Cluster influences on the internal dynamics of a galaxy

    NASA Technical Reports Server (NTRS)

    Miller, R. H.; Smith, B. F.

    1988-01-01

    As part of a study of cluster influences, an attempt is made to map out damage to a galaxy under several different kinds of buffeting a galaxy suffers as it sweeps along its orbit through a cluster. It is shown that a cluster's observational characteristics are determined by the shape of its gravitational potential. It is noted the model galaxy must have full freedom to do whatever the physical galaxy wants to do.

  18. 15N Content Reflects Development of Mycorrhizae and Nitrogen Dynamics During Primary Succession

    NASA Astrophysics Data System (ADS)

    Hobbie, E. A.; Jumpponen, A.

    2004-05-01

    influence of mycorrhizal fungi on plant N supply, and 3) 15N content of mycorrhizal fungi may be a marker of proteolytic capabilities, and may therefore indicate the importance of organic nitrogen cycling to plant nitrogen supply.

  19. Spectral reflectance patterns and temporal dynamics of common understory types in hemi-boreal forests in Järvselja, Estonia

    NASA Astrophysics Data System (ADS)

    Nikopensius, Maris; Raabe, Kairi; Pisek, Jan

    2014-05-01

    The knowledge about spectral properties and seasonal dynamics of understory layers in boreal forests currently holds several gaps. This introduces severe uncertainties while modelling the carbon balance of this ecosystem, which is expected to be prone to major shifts with climate change in the future. In this work the seasonal reflectance dynamics in European hemi-boreal forests are studied. The data for this study was collected at Järvselja Training and Experimental Forestry District (Estonia, 27.26°E 58.30°N). Measurements were taken in three different stands. The silver birch (Betula Pendula Roth) stand grows on typical brown gley-soil and its understory vegetation is dominated by a mixture of several grass species. The Scots pine (Pinus sylvestris) stand grows on a bog with understory vegetation composed of sparse labrador tea, cotton grass, and a continuous Sphagnum moss layer. The third stand, Norway spruce (Picea abies), grows on a Gleyi Ferric Podzol site with understory vegetation either partially missing or consisting of mosses such as Hylocomium splendens or Pleurozium schreberi [1]. The sampling design was similar to the study by Rautiainen et al. [3] in northern European boreal forests. At each study site, a 100 m long permanent transect was marked with flags. In addition, four intensive study plots (1 m × 1 m) were marked next to the transects at 20 m intervals. The field campaign lasted from May to September 2013. For each site the fractional cover of understory and understory spectra were estimated ten times i.e. every 2 to 3 weeks. Results from Järvselja forest were compared with the seasonal profiles from boreal forests in Hyytiälä, Finland [2]. References [1] A. Kuusk, M. Lang, J. Kuusk, T. Lükk, T. Nilson, M. Mõttus, M. Rautiainen, and A. Eenmäe, "Database of optical and structural data for validation of radiative transfer models", Technical Report, September 2009 [2] M. Rautiainen, M. Mõttus, J. Heiskanen, A. Akujärvi, T. Majasalmi

  20. Autumn leaf subsidies influence spring dynamics of freshwater plankton communities.

    PubMed

    Fey, Samuel B; Mertens, Andrew N; Cottingham, Kathryn L

    2015-07-01

    While ecologists primarily focus on the immediate impact of ecological subsidies, understanding the importance of ecological subsidies requires quantifying the long-term temporal dynamics of subsidies on recipient ecosystems. Deciduous leaf litter transferred from terrestrial to aquatic ecosystems exerts both immediate and lasting effects on stream food webs. Recently, deciduous leaf additions have also been shown to be important subsidies for planktonic food webs in ponds during autumn; however, the inter-seasonal effects of autumn leaf subsidies on planktonic food webs have not been studied. We hypothesized that autumn leaf drop will affect the spring dynamics of freshwater pond food webs by altering the availability of resources, water transparency, and the metabolic state of ponds. We created leaf-added and no-leaf-added field mesocosms in autumn 2012, allowed mesocosms to ice-over for the winter, and began sampling the physical, chemical, and biological properties of mesocosms immediately following ice-off in spring 2013. At ice-off, leaf additions reduced dissolved oxygen, elevated total phosphorus concentrations and dissolved materials, and did not alter temperature or total nitrogen. These initial abiotic effects contributed to higher bacterial densities and lower chlorophyll concentrations, but by the end of spring, the abiotic environment, chlorophyll and bacterial densities converged. By contrast, zooplankton densities diverged between treatments during the spring, with leaf additions stimulating copepods but inhibiting cladocerans. We hypothesized that these differences between zooplankton orders resulted from resource shifts following leaf additions. These results suggest that leaf subsidies can alter both the short- and long-term dynamics of planktonic food webs, and highlight the importance of fully understanding how ecological subsidies are integrated into recipient food webs. PMID:25761444

  1. Know yourself and you shall know the other... to a certain extent: multiple paths of influence of self-reflection on mindreading.

    PubMed

    Dimaggio, Giancarlo; Lysaker, Paul H; Carcione, Antonino; Nicolò, Giuseppe; Semerari, Antonio

    2008-09-01

    Social and neurocognitive research suggests that thinking about one's own thinking and thinking about the thinking of others-termed 'mindreading', 'metacognition', 'social cognition' or 'mentalizing' are not identical activities. The ability though to think about thinking in the first person is nevertheless related to the ability to think about other's thoughts in the third person. Unclear is how these phenomena influence one another. In this review, we explore how self-reflection and autobiographical memory influence the capacity to think about the thoughts and emotions of others. We review studies suggesting that the more individuals are able to reflect on and retrieve episodes from their life narratives, the more they are likely to grasp others' thoughts and emotions. We discuss evidence supporting this possibility including studies of the neurocognitive bases of empathy and self-awareness and how different aspects of self-reflection may impact on mindreading. We also draw from clinical reports how improved self-reflection may result in a more nuanced mindreading, namely persons suffering from schizophrenia and narcissistic personality disorder. We finally discuss the implications for research and practice and consider whether there are conditions in which the reverse is true, where self-reflection might impair mindreading or in which mindreading may facilitate self-reflection. PMID:18394921

  2. Influence of the Difficulty of the Matching Familiar Figures Test-20 on the Assessment of Reflection-Impulsivity: An Item Analysis

    ERIC Educational Resources Information Center

    Carretero-Dios, Hugo; Macarena, De los Santos-Roig; Buela-Casal, Gualberto

    2008-01-01

    This study is an item analysis of the Matching Familiar Figures Test-20. We examined error scores in the Matching Familiar Figures Test-20 to determine the influence of the difficulty of the test on the assessment of reflection-impulsivity. The sample included 700 participants aged between 6 and 12 years. The results obtained from the corrected…

  3. The Influence of Reflective Opposite-Sex Norms and Importance of Opposite-Sex Approval on Adjudicated Student Drinking: Theoretical Extensions and Implications

    ERIC Educational Resources Information Center

    Hummer, Justin F.; LaBrie, Joseph W.; Lac, Andrew; Louie, Brian

    2013-01-01

    This study examines the salience and influence of reflective norms regarding opposite- sex friends, dating, and sexual partners on drinking behaviors of heterosexual college students sanctioned for violating the campus alcohol policy (i.e., adjudicated students). Results revealed that the level of importance placed on approval from the opposite…

  4. What's in Your Box? Promoting Self-Reflection and Analysis of External Influences on Gender Expression and Sexual Orientation Attitudes

    ERIC Educational Resources Information Center

    Priest, Hannah M.

    2014-01-01

    This lesson plan is designed to stimulate awareness and reflection on personal attitudes toward gender expression and sexual orientation. Participants are guided to identify and analyze how external influences from various socialization agents shape gender and sexual orientation norms and, consequently, personal attitudes about gender expression…

  5. Modelling of snow avalanche dynamics: influence of model parameters

    NASA Astrophysics Data System (ADS)

    Bozhinskiy, A. N.

    The three-parameter hydraulic model of snow avalanche dynamics including the coefficients of dry and turbulent friction and the coefficient of new-snow-mass entrainment was investigated. The 'Domestic' avalanche site in Elbrus region, Caucasus, Russia, was chosen as the model avalanche range. According to the model, the fixed avalanche run-out can be achieved with various combinations of model parameters. At the fixed value of the coefficient of entrainment me, we have a curve on a plane of the coefficients of dry and turbulent friction. It was found that the family of curves (me is a parameter) are crossed at the single point. The value of the coefficient of turbulent friction at the cross-point remained practically constant for the maximum and average avalanche run-outs. The conclusions obtained are confirmed by the results of modelling for six arbitrarily chosen avalanche sites: three in the Khibiny mountains, Kola Peninsula, Russia, two in the Elbrus region and one idealized site with an exponential longitudinal profile. The dependences of run-out on the coefficient of dry friction are constructed for all the investigated avalanche sites. The results are important for the statistical simulation of avalanche dynamics since they suggest the possibility of using only one random model parameter, namely, the coefficient of dry friction, in the model. The histograms and distribution functions of the coefficient of dry friction are constructed and presented for avalanche sites Nos 22 and 43 (Khibiny mountains) and 'Domestic', with the available series of field data.

  6. Opinion dynamics on interacting networks: media competition and social influence

    NASA Astrophysics Data System (ADS)

    Quattrociocchi, Walter; Caldarelli, Guido; Scala, Antonio

    2014-05-01

    The inner dynamics of the multiple actors of the informations systems - i.e, T.V., newspapers, blogs, social network platforms, - play a fundamental role on the evolution of the public opinion. Coherently with the recent history of the information system (from few main stream media to the massive diffusion of socio-technical system), in this work we investigate how main stream media signed interaction might shape the opinion space. In particular we focus on how different size (in the number of media) and interaction patterns of the information system may affect collective debates and thus the opinions' distribution. We introduce a sophisticated computational model of opinion dynamics which accounts for the coexistence of media and gossip as separated mechanisms and for their feedback loops. The model accounts also for the effect of the media communication patterns by considering both the simple case where each medium mimics the behavior of the most successful one (to maximize the audience) and the case where there is polarization and thus competition among media memes. We show that plurality and competition within information sources lead to stable configurations where several and distant cultures coexist.

  7. Opinion dynamics on interacting networks: media competition and social influence.

    PubMed

    Quattrociocchi, Walter; Caldarelli, Guido; Scala, Antonio

    2014-01-01

    The inner dynamics of the multiple actors of the informations systems - i.e, T.V., newspapers, blogs, social network platforms, - play a fundamental role on the evolution of the public opinion. Coherently with the recent history of the information system (from few main stream media to the massive diffusion of socio-technical system), in this work we investigate how main stream media signed interaction might shape the opinion space. In particular we focus on how different size (in the number of media) and interaction patterns of the information system may affect collective debates and thus the opinions' distribution. We introduce a sophisticated computational model of opinion dynamics which accounts for the coexistence of media and gossip as separated mechanisms and for their feedback loops. The model accounts also for the effect of the media communication patterns by considering both the simple case where each medium mimics the behavior of the most successful one (to maximize the audience) and the case where there is polarization and thus competition among media memes. We show that plurality and competition within information sources lead to stable configurations where several and distant cultures coexist. PMID:24861995

  8. Influence of Opinion Dynamics on the Evolution of Games

    PubMed Central

    Gargiulo, Floriana; Ramasco, José J.

    2012-01-01

    Under certain circumstances such as lack of information or bounded rationality, human players can take decisions on which strategy to choose in a game on the basis of simple opinions. These opinions can be modified after each round by observing own or others payoff results but can be also modified after interchanging impressions with other players. In this way, the update of the strategies can become a question that goes beyond simple evolutionary rules based on fitness and become a social issue. In this work, we explore this scenario by coupling a game with an opinion dynamics model. The opinion is represented by a continuous variable that corresponds to the certainty of the agents respect to which strategy is best. The opinions transform into actions by making the selection of an strategy a stochastic event with a probability regulated by the opinion. A certain regard for the previous round payoff is included but the main update rules of the opinion are given by a model inspired in social interchanges. We find that the fixed points of the dynamics of the coupled model are different from those of the evolutionary game or the opinion models alone. Furthermore, new features emerge such as the independence of the fraction of cooperators with respect to the topology of the social interaction network or the presence of a small fraction of extremist players. PMID:23166600

  9. Dynamics of public opinion under the influence of epidemic spreading

    NASA Astrophysics Data System (ADS)

    Wu, Junhui; Ni, Shunjiang; Shen, Shifei

    2016-02-01

    In this paper, we propose a novel model with dynamically adjusted confidence level of others to investigate the propagation of public opinion on whether to buy chicken in the case of avian influenza infection in humans. We study how people adjust their confidence level in other people’s opinions according to their perceived infection risk and how the opinion evolution and epidemic spreading affect each other on different complex networks by taking into account the spreading feature of avian influenza, that is, only people who buy chicken are possible to be infected. The simulation results show that in a closed system, people who support buying chicken and people who are infected can achieve a dynamic balance after a few time-steps, and the final stable state is mainly dependent on the level of people’s risk perception, rather than the initial distribution of the different opinions. Our results imply that in the course of the epidemic spread, transparent and timely announcement of the number of infections and the risk of infection can help people take the right self-protection actions, and thus help control the spread of avian influenza.

  10. Opinion dynamics on interacting networks: media competition and social influence

    PubMed Central

    Quattrociocchi, Walter; Caldarelli, Guido; Scala, Antonio

    2014-01-01

    The inner dynamics of the multiple actors of the informations systems – i.e, T.V., newspapers, blogs, social network platforms, – play a fundamental role on the evolution of the public opinion. Coherently with the recent history of the information system (from few main stream media to the massive diffusion of socio-technical system), in this work we investigate how main stream media signed interaction might shape the opinion space. In particular we focus on how different size (in the number of media) and interaction patterns of the information system may affect collective debates and thus the opinions' distribution. We introduce a sophisticated computational model of opinion dynamics which accounts for the coexistence of media and gossip as separated mechanisms and for their feedback loops. The model accounts also for the effect of the media communication patterns by considering both the simple case where each medium mimics the behavior of the most successful one (to maximize the audience) and the case where there is polarization and thus competition among media memes. We show that plurality and competition within information sources lead to stable configurations where several and distant cultures coexist. PMID:24861995