Pitch Angle Dependence of Drift Resonant Ions Observed by the Van Allen Probes

Science.gov (United States)

Rankin, R.; Wang, C.; Wang, Y.; Zong, Q. G.; Zhou, X.

2017-12-01

Acceleration and modulation of ring current ions by poloidal mode ULF waves is investigated. A simplified MHD model of ULF waves in a dipole magnetic field is presented that includes phase mixing to perpendicular scales determined by the ionospheric Pedersen conductivity. The wave model is combined with a full Lorentz force test particle code to study drift and drift bounce resonance wave-particle interactions. Ion trajectories are traced backward-in-time to an assumed form of the distribution function, and Liouville's method is used to reconstruct the phase space density response (PSD) poloidal mode waves observed by the Van Allen Probes. In spite of its apparent simplicity, simulations using the wave and test particle models are able to explain the acceleration of ions and energy dispersion observed by the Van Allen Probes. The paper focuses on the pitch angle evolution of the initial PSD as it responds to the action of ULF waves. An interesting aspect of the study is the formation of butterfly ion distributions as ions make periodic radial oscillations across L. Ions become trapped in an effective potential well across a limited range of L and follow trajectories that cause them to surf along constant phase fronts. The impications of this new trapping mechanism for both ions and electrons is discussed.

Cross-scale observations of the 2015 St. Patrick's day storm: THEMIS, Van Allen Probes, and TWINS

International Nuclear Information System (INIS)

Goldstein, J.

2016-01-01

In this paper, we present cross-scale magnetospheric observations of the 17 March 2015 (St. Patrick's Day) storm, by Time History of Events and Macroscale Interactions during Substorms (THEMIS), Van Allen Probes (Radiation Belt Storm Probes), and Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS), plus upstream ACE/Wind solar wind data. THEMIS crossed the bow shock or magnetopause 22 times and observed the magnetospheric compression that initiated the storm. Empirical models reproduce these boundary locations within 0.7 R E . Van Allen Probes crossed the plasmapause 13 times; test particle simulations reproduce these encounters within 0.5 R E . Before the storm, Van Allen Probes measured quiet double-nose proton spectra in the region of corotating cold plasma. About 15 min after a 0605 UT dayside southward turning, Van Allen Probes captured the onset of inner magnetospheric convection, as a density decrease at the moving corotation-convection boundary (CCB) and a steep increase in ring current (RC) proton flux. During the first several hours of the storm, Van Allen Probes measured highly dynamic ion signatures (numerous injections and multiple spectral peaks). Sustained convection after ~1200 UT initiated a major buildup of the midnight-sector ring current (measured by RBSP A), with much weaker duskside fluxes (measured by RBSP B, THEMIS a and THEMIS d). A close conjunction of THEMIS d, RBSP A, and TWINS 1 at 1631 UT shows good three-way agreement in the shapes of two-peak spectra from the center of the partial RC. A midstorm injection, observed by Van Allen Probes and TWINS at 1740 UT, brought in fresh ions with lower average energies (leading to globally less energetic spectra in precipitating ions) but increased the total pressure. Finally, the cross-scale measurements of 17 March 2015 contain significant spatial, spectral, and temporal structure.

Multipoint Observations of Energetic Particle Injections and Substorm Activity During a Conjunction Between Magnetospheric Multiscale (MMS) and Van Allen Probes

Science.gov (United States)

Turner, D. L.; Fennell, J. F.; Blake, J. B.; Claudepierre, S. G.; Clemmons, J. H.; Jaynes, A. N.; Leonard, T.; Baker, D. N.; Cohen, I. J.; Gkioulidou, M.; Ukhorskiy, A. Y.; Mauk, B. H.; Gabrielse, C.; Angelopoulos, V.; Strangeway, R. J.; Kletzing, C. A.; Le Contel, O.; Spence, H. E.; Torbert, R. B.; Burch, J. L.; Reeves, G. D.

2017-11-01

This study examines multipoint observations during a conjunction between Magnetospheric Multiscale (MMS) and Van Allen Probes on 7 April 2016 in which a series of energetic particle injections occurred. With complementary data from Time History of Events and Macroscale Interactions during Substorms, Geotail, and Los Alamos National Laboratory spacecraft in geosynchronous orbit (16 spacecraft in total), we develop new insights on the nature of energetic particle injections associated with substorm activity. Despite this case involving only weak substorm activity (maximum AE energy wave activity is also established from Van Allen Probes and MMS. Drift mapping using a simplified magnetic field model provides estimates of the dispersionless injection boundary locations as a function of universal time, magnetic local time, and L shell. The analysis reveals that at least five electron injections, which were localized in magnetic local time, preceded a larger injection of both electrons and ions across nearly the entire nightside of the magnetosphere near geosynchronous orbit. The larger ion and electron injection did not penetrate to L < 6.6, but several of the smaller electron injections penetrated to L < 6.6. Due to the discrepancy between the number, penetration depth, and complexity of electron versus ion injections, this event presents challenges to the current conceptual models of energetic particle injections.

Transitional behavior of different energy protons based on Van Allen Probes observations

International Nuclear Information System (INIS)

Yue, Chao; Bortnik, Jacob; Chen, Lunjin; Ma, Qianli

2016-01-01

Understanding the dynamical behavior of ~1 eV to 50 keV ions and identifying the energies at which the morphologies transit are important in that they involve the relative intensities and distributions of the large-scale electric and magnetic fields, the outflow, and recombination rates. However, there have been only few direct observational investigations of the transition in drift behaviors of different energy ions before the Van Allen Probes era. In this paper, we statistically analyze ~1 eV to 50 keV hydrogen (H + ) differential flux distributions near geomagnetic equator by using Van Allen Probes observations to investigate the H + dynamics under the regulation of large-scale electric and magnetic fields. Our survey clearly indicates three types of H + behaviors within different energy ranges, which is consistent with previous theory predictions. Finally, using simple electric and magnetic field models in UBK coordinates, we have further constrained the source regions of different energy ions and their drift directions.

Van Allen Probes Measurements of Energetic Particle Deep Penetration Into the Low L Region (L Storm on 8 April 2016

Science.gov (United States)

Zhao, H.; Baker, D. N.; Califf, S.; Li, X.; Jaynes, A. N.; Leonard, T.; Kanekal, S. G.; Blake, J. B.; Fennell, J. F.; Claudepierre, S. G.; Turner, D. L.; Reeves, G. D.; Spence, H. E.

2017-12-01

Using measurements from the Van Allen Probes, a penetration event of tens to hundreds of keV electrons and tens of keV protons into the low L shells (L electric field represented by the Volland-Stern model or a uniform dawn-dusk electric field model based on the electric field measurements. It suggests that the underlying physical mechanism responsible for energetic electron deep penetration, which is very important for fully understanding energetic electron dynamics in the low L shells, should be MLT localized.

Modeling the Proton Radiation Belt With Van Allen Probes Relativistic Electron-Proton Telescope Data

Science.gov (United States)

Selesnick, R. S.; Baker, D. N.; Kanekal, S. G.; Hoxie, V. C.; Li, X.

2018-01-01

An empirical model of the proton radiation belt is constructed from data taken during 2013-2017 by the Relativistic Electron-Proton Telescopes on the Van Allen Probes satellites. The model intensity is a function of time, kinetic energy in the range 18-600 MeV, equatorial pitch angle, and L shell of proton guiding centers. Data are selected, on the basis of energy deposits in each of the nine silicon detectors, to reduce background caused by hard proton energy spectra at low L. Instrument response functions are computed by Monte Carlo integration, using simulated proton paths through a simplified structural model, to account for energy loss in shielding material for protons outside the nominal field of view. Overlap of energy channels, their wide angular response, and changing satellite orientation require the model dependencies on all three independent variables be determined simultaneously. This is done by least squares minimization with a customized steepest descent algorithm. Model uncertainty accounts for statistical data error and systematic error in the simulated instrument response. A proton energy spectrum is also computed from data taken during the 8 January 2014 solar event, to illustrate methods for the simpler case of an isotropic and homogeneous model distribution. Radiation belt and solar proton results are compared to intensities computed with a simplified, on-axis response that can provide a good approximation under limited circumstances.

Comparison of species-resolved energy spectra from ACE EPAM and Van Allen Probes RBSPICE

Science.gov (United States)

Patterson, J.; Manweiler, J. W.; Armstrong, T. P.; Lanzerotti, L. J.; Gerrard, A. J.; Gkioulidou, M.

2013-12-01

We present a comparison between energy spectra measured by the Advanced Composition Explorer (ACE) Electron Proton Alpha Monitor (EPAM) instrument and the Van Allen Probe Ion Composition Experiment (RBSPICE) for two significant and distinct events in early 2013. The first is an impulsive solar particle event on March 17th. While intense, this event presented no significant surprises in terms of its composition or anisotropy characteristics, thus providing a good baseline for response of the trapped radiation belts as observed by the Van Allen Probes. The second solar event occurred late May 22nd and early May 23rd. This event has a much greater concentration of medium and heavy ions than the St. Patrick's Day event, as well as having very peculiar energy spectra with evidence of two distinct populations. During the St. Patrick's Day Event, the energy spectra for helium, carbon, oxygen, neon, silicon, and iron all show the same spectral power law slope -3.1. The event shows strong anisotropy with intensities differing by a factor of four for both protons and Z>1 ions. The late May event also has strong anisotropy, and in the same directions as the St. Patrick's Day Event, but with very different composition and energy spectra. The spectra are much harder with power law spectral slopes of -0.5. Additionally, there is a significant spectral bump at 3 MeV/nuc for helium that is not present in the spectra of the heavier ions. The intensities of the heavier ions, however, show an increase that is an order of magnitude greater than the increase seen for helium. The March 17 RBSPICE observations show multiple injection events lasting for less than an hour each during the Van Allen Probes B apogees. These injections are seen in protons as well as Helium and only somewhat observed in Oxygen. Spectral slopes for the observations range from approximately -5 during quiet times to double peaked events with a spectral slope of approximately -2 at the beginning of the injection

Spatial characterization of relativistic electron enhancements in the Earth's outer radiation belt during the Van Allen Probes era

Science.gov (United States)

Pinto, V. A.; Bortnik, J.; Moya, P. S.; Lyons, L. R.; Sibeck, D. G.; Kanekal, S. G.

2017-12-01

Using Van Allen Probes Relativistic Electron-Proton Telescope (REPT) instrument we have identified 73 relativistic electron enhancement events in the outer radiation belt that occurred at different L values between L = 2.5 and L = 6.0. To determine an enhancement, we have used three different identification methods. We then determine the radial location, MLT location, timing and strength of those enhancements. We discuss the differences of each of the methods and test them to pinpoint the origin and spatial propagation of each enhancement. We have classified the events based on the radial propagation, speed of enhancement and intensity of fluxes and response for energy channels ranging from 1.8 MeV to 6.3 MeV. In addition, we have used OMNI data to study the statistical properties of the solar wind during each event and have classified similarities and differences that might be relevant for each group of enhancements and help us determine the physical process responsible for different types of enhancements. Additionally, we have used >2 MeV electron fluxes at geostationary orbit as measured by the GOES 13 and 15 Energetic Particle Sensor (EPS) instrument to compare our results with the geostationary orbit. Our results suggest that under certain conditions GOES data can be used to predict fluxes at the core of the radiation belt and vice-versa.

Van Allen Probes Science Gateway: Single-Point Access to Long-Term Radiation Belt Measurements and Space Weather Nowcasting

Science.gov (United States)

Romeo, G.; Barnes, R. J.; Ukhorskiy, A. Y.; Sotirelis, T.; Stephens, G.

2017-12-01

The Science Gateway gives single-point access to over 4.5 years of comprehensive wave and particle measurements from the Van Allen Probes NASA twin-spacecraft mission. The Gateway provides a set of visualization and data analysis tools including: HTML5-based interactive visualization of high-level data products from all instrument teams in the form of: line plots, orbital content plots, dynamical energy spectra, L-shell context plots (including two-spacecraft plotting), FFT spectra of wave data, solar wind and geomagnetic indices data, etc.; download custom multi-instrument CDF data files of selected data products; publication quality plots of digital data; combined orbit predicts for mission planning and coordination including: Van Allen Probes, MMS, THEMIS, Arase (ERG), Cluster, GOES, Geotail, FIREBIRD; magnetic footpoint calculator for coordination with LEO and ground-based assets; real-time computation and processing of empirical magnetic field models - computation of magnetic ephemeris, computation of adiabatic invariants. Van Allen Probes is the first spacecraft mission to provide a nowcast of the radiation environment in the heart of the radiation belts, where the radiation levels are the highest and most dangerous for spacecraft operations. For this purpose, all instruments continuously broadcast a subset of their science data in real time. Van Allen Probes partners with four foreign institutions who operate ground stations that receive the broadcast: Korea (KASI), the Czech republic (CAS), Argentina (CONAE), and Brazil (INPE). The SpWx broadcast is then collected at APL and delivered to the community via the Science Gateway.

Void structure of O+ ions in the inner magnetosphere observed by the Van Allen Probes

Science.gov (United States)

Nakayama, Y.; Ebihara, Y.; Ohtani, S.; Gkioulidou, M.; Takahashi, K.; Kistler, L. M.; Tanaka, T.

2016-12-01

The Van Allen Probes Helium Oxygen Proton Electron instrument observed a new type of enhancement of O+ ions in the inner magnetosphere during substorms. As the satellite moved outward in the premidnight sector, the flux of the O+ ions with energy 10 keV appeared first in the energy-time spectrograms. Then, the enhancement of the flux spread toward high and low energies. The enhanced flux of the O+ ions with the highest energy remained, whereas the flux of the ions with lower energy vanished near apogee, forming what we call the void structure. The structure cannot be found in the H+ spectrogram. We studied the generation mechanism of this structure by using numerical simulation. We traced the trajectories of O+ ions in the electric and magnetic fields from the global magnetohydrodynamics simulation and calculated the flux of O+ ions in the inner magnetosphere in accordance with the Liouville theorem. The simulated spectrograms are well consistent with the ones observed by Van Allen Probes. We suggest the following processes. (1) When magnetic reconnection starts, an intensive equatorward and tailward plasma flow appears in the plasma lobe. (2) The flow transports plasma from the lobe to the plasma sheet where the radius of curvature of the magnetic field line is small. (3) The intensive dawn-dusk electric field transports the O+ ions earthward and accelerates them nonadiabatically to an energy threshold; (4) the void structure appears at energies below the threshold.

Space Weather Operation at KASI With Van Allen Probes Beacon Signals

Science.gov (United States)

Lee, Jongkil; Kim, Kyung-Chan; Giuseppe, Romeo; Ukhorskiy, Sasha; Sibeck, David; Kessel, Ramona; Mauk, Barry; Giles, Barbara; Gu, Bon-Jun; Lee, Hyesook; Park, Young-Deuk; Lee, Jaejin

2018-02-01

The Van Allen Probes (VAPs) are the only modern National Aeronautics and Space Administration (NASA) spacecraft broadcasting real-time data on the Earth's radiation belts for space weather operations. Since 2012, the Korea Astronomy and Space Science Institute (KASI) has contributed to the receipt of these data via a 7 m satellite-tracking antenna and used these beacon data for space weather operations. An approximately 15 min period is required from measurement to acquisition of Level-1 data. In this paper, we demonstrate the use of VAP data for monitoring space weather conditions at geostationary orbit (GEO) by highlighting the Saint Patrick's Day storm of 2015. During that storm, Probe-A observed a significant increase in the relativistic electron flux at 3 RE. Those electrons diffused outward resulting in a large increase of the electron flux >2 MeV at GEO, which potentially threatened satellite operations. Based on this study, we conclude that the combination of VAP data and National Oceanic and Atmospheric Administration-Geostationary Operational Environmental Satellite (NOAA-GOES) data can provide improved space environment information to geostationary satellite operators. In addition, the findings obtained indicate that more data-receiving sites would be necessary and data connections improved if this or a similar system were to be used as an operational data service.

In situ observations of Pc1 pearl pulsations by the Van Allen Probes

Science.gov (United States)

Paulson, K. W.; Smith, C. W.; Lessard, M. R.; Engebretson, M. J.; Torbert, R. B.; Kletzing, C. A.

2014-03-01

We present in situ observations of Pc1 pearl pulsations using the Van Allen Probes. These waves are often observed using ground-based magnetometers, but are rarely observed by orbiting satellites. With the Van Allen Probes, we have seen at least 14 different pearl pulsation events during the first year of operations. These new in situ measurements allow us to identify the wave classification based on local magnetic field conditions. Additionally, by using two spacecraft, we are able to observe temporal changes in the region of observation. The waves appear to be generated at an overall central frequency, as often observed on the ground, and change polarization from left- to right-handedness as they propagate into a region where they are resonant with the crossover frequency (where R- and L-mode waves have the same phase velocity). By combining both in situ and ground-based data, we have found that the region satisfying electromagnetic ion cyclotron wave generation conditions is azimuthally large while radially narrow. The observation of a similar modulation period on the ground as in the magnetosphere contradicts the bouncing wave packet mechanism of generation.

Van Allen Probe Observations of Chorus Wave Activity, Source and Seed electrons, and the Radiation Belt Response During ICME and CIR Storms

Science.gov (United States)

Bingham, S.; Mouikis, C.; Kistler, L. M.; Farrugia, C. J.; Paulson, K. W.; Huang, C. L.; Boyd, A. J.; Spence, H. E.; Kletzing, C.

2017-12-01

Whistler mode chorus waves are electromagnetic waves that have been shown to be a major contributor to enhancements in the outer radiation belt during geomagnetic storms. The temperature anisotropy of source electrons (10s of keV) provides the free energy for chorus waves, which can accelerate sub-relativistic seed electrons (100s of keV) to relativistic energies. This study uses Van Allen Probe observations to examine the excitation and plasma conditions associated with chorus wave observations, the development of the seed population, and the outer radiation belt response in the inner magnetosphere, for 25 ICME and 35 CIR storms. Plasma data from the Helium Oxygen Proton Electron (HOPE) instrument and magnetic field measurements from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) are used to identify chorus wave activity and to model a linear theory based proxy for chorus wave growth. A superposed epoch analysis shows a peak of chorus wave power on the dawnside during the storm main phase that spreads towards noon during the storm recovery phase. According to the linear theory results, this wave activity is driven by the enhanced convection driving plasma sheet electrons across the dayside. Both ICME and CIR storms show comparable levels of wave growth. Plasma data from the Magnetic Electron Ion Spectrometer (MagEIS) and the Relativistic Electron Proton Telescope (REPT) are used to observe the seed and relativistic electrons. A superposed epoch analysis of seed and relativistic electrons vs. L shows radiation belt enhancements with much greater frequency in the ICME storms, coinciding with a much stronger and earlier seed electron enhancement in the ICME storms.

Detection of Chorus Elements and other Wave Signatures Using Geometric Computational Techniques in the Van Allen radiation belts

Science.gov (United States)

Sengupta, A.; Kletzing, C.; Howk, R.; Kurth, W. S.

2017-12-01

An important goal of the Van Allen Probes mission is to understand wave particle interactions that can energize relativistic electron in the Earth's Van Allen radiation belts. The EMFISIS instrumentation suite provides measurements of wave electric and magnetic fields of wave features such as chorus that participate in these interactions. Geometric signal processing discovers structural relationships, e.g. connectivity across ridge-like features in chorus elements to reveal properties such as dominant angles of the element (frequency sweep rate) and integrated power along the a given chorus element. These techniques disambiguate these wave features against background hiss-like chorus. This enables autonomous discovery of chorus elements across the large volumes of EMFISIS data. At the scale of individual or overlapping chorus elements, topological pattern recognition techniques enable interpretation of chorus microstructure by discovering connectivity and other geometric features within the wave signature of a single chorus element or between overlapping chorus elements. Thus chorus wave features can be quantified and studied at multiple scales of spectral geometry using geometric signal processing techniques. We present recently developed computational techniques that exploit spectral geometry of chorus elements and whistlers to enable large-scale automated discovery, detection and statistical analysis of these events over EMFISIS data. Specifically, we present different case studies across a diverse portfolio of chorus elements and discuss the performance of our algorithms regarding precision of detection as well as interpretation of chorus microstructure. We also provide large-scale statistical analysis on the distribution of dominant sweep rates and other properties of the detected chorus elements.

Deterministic methods for the relativistic Vlasov-Maxwell equations and the Van Allen belts dynamics

International Nuclear Information System (INIS)

Le Bourdiec, S.

2007-03-01

Artificial satellites operate in an hostile radiation environment, the Van Allen radiation belts, which partly condition their reliability and their lifespan. In order to protect them, it is necessary to characterize the dynamics of the energetic electrons trapped in these radiation belts. This dynamics is essentially determined by the interactions between the energetic electrons and the existing electromagnetic waves. This work consisted in designing a numerical scheme to solve the equations modelling these interactions: the relativistic Vlasov-Maxwell system of equations. Our choice was directed towards methods of direct integration. We propose three new spectral methods for the momentum discretization: a Galerkin method and two collocation methods. All of them are based on scaled Hermite functions. The scaling factor is chosen in order to obtain the proper velocity resolution. We present in this thesis the discretization of the one-dimensional Vlasov-Poisson system and the numerical results obtained. Then we study the possible extensions of the methods to the complete relativistic problem. In order to reduce the computing time, parallelization and optimization of the algorithms were carried out. Finally, we present 1Dx-3Dv (mono-dimensional for x and three-dimensional for velocity) computations of Weibel and whistler instabilities with one or two electrons species. (author)

Energetic Proton Spectra Measured by the Van Allen Probes

Science.gov (United States)

Summers, Danny; Shi, Run; Engebretson, Mark J.; Oksavik, Kjellmar; Manweiler, Jerry W.; Mitchell, Donald G.

2017-10-01

We test the hypothesis that pitch angle scattering by electromagnetic ion cyclotron (EMIC) waves can limit ring current proton fluxes. For two chosen magnetic storms, during 17-20 March 2013 and 17-20 March 2015, we measure proton energy spectra in the region 3 ≤ L ≤ 6 using the RBSPICE-B instrument on the Van Allen Probes. The most intense proton spectra are observed to occur during the recovery periods of the respective storms. Using proton precipitation data from the POES (NOAA and MetOp) spacecraft, we deduce that EMIC wave action was prevalent at the times and L-shell locations of the most intense proton spectra. We calculate limiting ring current proton energy spectra from recently developed theory. Comparisons between the observed proton energy spectra and the theoretical limiting spectra show reasonable agreement. We conclude that the measurements of the most intense proton spectra are consistent with self-limiting by EMIC wave scattering.

Ion spectral structures observed by the Van Allen Probes

Science.gov (United States)

Ferradas, C.; Zhang, J.; Spence, H. E.; Kistler, L. M.; Larsen, B.; Reeves, G. D.; Skoug, R. M.; Funsten, H. O.

2015-12-01

During the last decades several missions have recorded the presence of dynamic spectral features of energetic ions in the inner magnetosphere. Previous studies have reported single "nose-like" structures occurring alone and simultaneous nose-like structures (up to three). These ion structures are named after the characteristic shapes of energy bands or gaps in the energy-time spectrograms of in situ measured ion fluxes. They constitute the observational signatures of ion acceleration, transport, and loss in the global magnetosphere. The HOPE mass spectrometer onboard the Van Allen Probes measures energetic hydrogen, helium, and oxygen ions near the inner edge of the plasma sheet, where these ion structures are observed. We present a statistical study of nose-like structures, using 2-years measurements from the HOPE instrument. The results provide important details about the spatial distribution (dependence on geocentric distance), spectral features of the structures (differences among species), and geomagnetic conditions under which these structures occur.

Deterministic methods for the relativistic Vlasov-Maxwell equations and the Van Allen belts dynamics; Methodes deterministes de resolution des equations de Vlasov-Maxwell relativistes en vue du calcul de la dynamique des ceintures de Van Allen

Energy Technology Data Exchange (ETDEWEB)

Le Bourdiec, S

2007-03-15

Artificial satellites operate in an hostile radiation environment, the Van Allen radiation belts, which partly condition their reliability and their lifespan. In order to protect them, it is necessary to characterize the dynamics of the energetic electrons trapped in these radiation belts. This dynamics is essentially determined by the interactions between the energetic electrons and the existing electromagnetic waves. This work consisted in designing a numerical scheme to solve the equations modelling these interactions: the relativistic Vlasov-Maxwell system of equations. Our choice was directed towards methods of direct integration. We propose three new spectral methods for the momentum discretization: a Galerkin method and two collocation methods. All of them are based on scaled Hermite functions. The scaling factor is chosen in order to obtain the proper velocity resolution. We present in this thesis the discretization of the one-dimensional Vlasov-Poisson system and the numerical results obtained. Then we study the possible extensions of the methods to the complete relativistic problem. In order to reduce the computing time, parallelization and optimization of the algorithms were carried out. Finally, we present 1Dx-3Dv (mono-dimensional for x and three-dimensional for velocity) computations of Weibel and whistler instabilities with one or two electrons species. (author)

Propagation of Dipolarization Signatures Observed by the Van Allen Probes in the Inner Magnetosphere

Science.gov (United States)

Ohtani, S.; Motoba, T.; Gkioulidou, M.; Takahashi, K.; Kletzing, C.

2017-12-01

Dipolarization, the change of the local magnetic field from a stretched to a more dipolar configuration, is one of the most fundamental processes of magnetospheric physics. It is especially critical for the dynamics of the inner magnetosphere. The associated electric field accelerates ions and electrons and transports them closer to Earth. Such injected ions intensify the ring current, and electrons constitute the seed population of the radiation belt. Those ions and electrons may also excite various waves that play important roles in the enhancement and loss of the radiation belt electrons. Despite such critical consequences, the general characteristics of dipolarization in the inner magnetosphere still remain to be understood. The Van Allen Probes mission, which consists of two probes that orbit through the equatorial region of the inner magnetosphere, provides an ideal opportunity to examine dipolarization signatures in the core of the ring current. In the present study we investigate the spatial expansion of the dipolarization region by examining the correlation and time delay of dipolarization signatures observed by the two probes. Whereas in general it requires three-point measurements to deduce the propagation of a signal on a certain plane, we statically examined the observed time delays and found that dipolarization signatures tend to propagate radially inward as well as away from midnight. In this paper we address the propagation of dipolarization signatures quantitatively and compare with the propagation velocities reported previously based on observations made farther away from Earth. We also discuss how often and under what conditions the dipolarization region expands.

Estimating Outer Zone Radial Diffusion Coefficients from Drift Scale Fluctuations in Van Allen Particle Data

Science.gov (United States)

O'Brien, T. P., III; Claudepierre, S. G.

2017-12-01

During geomagnetic storms, the Earth's outer radiation belt experiences enhanced radial transport. This transport occurs via phase-dependent radial displacements of particles, either by impulsive events or drift resonant waves. Because transport is phase dependent, it produces drift phase bunching, which can be observed with in situ particle detectors. We provide bounds on the radial diffusion coefficients derived from this drift phase structure as seen by NASA's Van Allen Probes. We compare these bounds to published radial diffusion coefficient models, particularly those derived independently from electromagnetic field observations.

Shielding of manned space stations against Van Allen Belt protons: a preliminary scoping study

International Nuclear Information System (INIS)

Santoro, R.T.; Alsmiller, R.G. Jr.; Barnes, J.M.; Corbin, J.M.

1986-09-01

Calculated results are presented to aid in the design of the shielding required to protect astronauts in a space station that is orbiting through the Van Allen proton belt. The geometry considered - a spherical shell shield with a spherical tissue phantom at its center - is only a very approximate representation of an actual space station, but this simple geometry makes it possible to consider a wide range of possible shield materials. Both homogeneous and laminated shields are considered. Also, an approximation procedure - the equivalent thickness approximation - that allows dose rates to be estimated for any shield material or materials from the dose rates for an aluminum shield is presented and discussed

A Telescopic and Microscopic Examination of Acceleration in the June 2015 Geomagnetic Storm: Magnetospheric Multiscale and Van Allen Probes Study of Substorm Particle Injection

Science.gov (United States)

Baker, D. N.; Jaynes, A. N.; Turner, D. L.; Nakamura, R.; Schmid, D.; Mauk, B. H.; Cohen, I. J.; Fennell, J. F.; Blake, J. B.; Strangeway, R. J.;

An improved sheath impedance model for the Van Allen Probes EFW instrument: Effects of the spin axis antenna

Czech Academy of Sciences Publication Activity Database

Hartley, D. P.; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.; Bounds, S. R.; Averkamp, T. F.; Bonnell, J. W.; Santolík, Ondřej; Wygant, J. R.

2017-01-01

Roč. 122, č. 4 (2017), s. 4420-4429 ISSN 2169-9380 R&D Projects: GA MŠk(CZ) LH15304 Grant - others:AV ČR(CZ) AP1401 Program:Akademická prémie - Praemium Academiae Institutional support: RVO:68378289 Keywords : antenna sheath impedance * electric field * Van Allen Probes * EFW * EMFISIS * whistler mode waves Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.733, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/2016JA023597/abstract

Magnetosphere dynamics during the 14 November 2012 storm inferred from TWINS, AMPERE, Van Allen Probes, and BATS-R-US-CRCM

Science.gov (United States)

Buzulukova, Natalia; Goldstein, Jerry; Fok, Mei-Ching; Glocer, Alex; Valek, Phil; McComas, David; Korth, Haje; Anderson, Brian

2018-01-01

During the 14 November 2012 geomagnetic storm, the Van Allen Probes spacecraft observed a number of sharp decreases (dropouts) in particle fluxes for ions and electrons of different energies. In this paper, we investigate the global magnetosphere dynamics and magnetosphere-ionosphere (M-I) coupling during the dropout events using multipoint measurements by Van Allen Probes, TWINS, and AMPERE together with the output of the two-way coupled global BATS-R-US-CRCM model. We find different behavior for two pairs of dropouts. For one pair, the same pattern was repeated: (1) weak nightside Region 1 and 2 Birkeland currents before and during the dropout; (2) intensification of Region 2 currents after the dropout; and (3) a particle injection detected by TWINS after the dropout. The model predicted similar behavior of Birkeland currents. TWINS low-altitude emissions demonstrated high variability during these intervals, indicating high geomagnetic activity in the near-Earth tail region. For the second pair of dropouts, the structure of both Birkeland currents and ENA emissions was relatively stable. The model also showed quasi-stationary behavior of Birkeland currents and simulated ENA emissions with gradual ring current buildup. We confirm that the first pair of dropouts was caused by large-scale motions of the OCB (open-closed boundary) during substorm activity. We show the new result that this OCB motion was associated with global changes in Birkeland (M-I coupling) currents and strong modulation of low-altitude ion precipitation. The second pair of dropouts is the result of smaller OCB disturbances not related to magnetospheric substorms. The local observations of the first pair of dropouts result from a global magnetospheric reconfiguration, which is manifested by ion injections and enhanced ion precipitation detected by TWINS and changes in the structure of Birkeland currents detected by AMPERE. This study demonstrates that multipoint measurements along with the global

Van Allen Probes Mission Space Academy: Educating middle school students about Earth's mysterious radiation belts

Science.gov (United States)

Butler, L.; Turney, D.; Matiella Novak, A.; Smith, D.; Simon, M.

2013-12-01

How's the weather in space? Why on Earth did NASA send two satellites above Earth to study radiation belts and space weather? To learn the answer to questions about NASA's Van Allen Probes mission, 450 students and their teachers from Maryland middle schools attended Space Academy events highlighting the Van Allen Probes mission. Sponsored by the Applied Physics Laboratory (APL) and Discovery Education, the events are held at the APL campus in Laurel, MD. Space Academies take students and teachers on behind-the-scenes exploration of how spacecraft are built, what they are designed to study, and introduces them to the many professionals that work together to create some of NASA's most exciting projects. Moderated by a public relations representative in the format of an official NASA press conference, the daylong event includes a student press conference with students as reporters and mission experts as panelists. Lunch with mission team members gives students a chance to ask more questions. After lunch, students don souvenir clean room suits, enjoy interactive science demonstrations, and tour APL facilities where the Van Allen Probes were built and tested before launch. Students may even have an opportunity to peek inside a clean room to view spacecraft being assembled. Prior to the event, teachers are provided with classroom activities, lesson plans, and videos developed by APL and Discovery Education to help prepare students for the featured mission. The activities are aligned to National Science Education Standards and appropriate for use in the classroom. Following their visit, student journalists are encouraged to write a short article about their field trip; selections are posted on the Space Academy web site. Designed to engage, inspire, and influence attitudes about space science and STEM careers, Space Academies provide an opportunity to attract underserved populations and emphasize that space science is for everyone. Exposing students to a diverse group of

Using the cold plasma dispersion relation and whistler mode waves to quantify the antenna sheath impedance of the Van Allen Probes EFW instrument

Czech Academy of Sciences Publication Activity Database

Hartley, D. P.; Kletzing, C. A.; Kurth, W. S.; Bounds, S. R.; Averkamp, T. F.; Hospodarsky, G. B.; Wygant, J. R.; Bonnell, J. W.; Santolík, Ondřej; Watt, C. E. J.

2016-01-01

Roč. 121, č. 5 (2016), s. 4590-4606 ISSN 2169-9380 R&D Projects: GA MŠk(CZ) LH15304 Institutional support: RVO:68378289 Keywords : EFW * EMFISIS * plasmaspheric hiss * sheath impedance * Van Allen Probes * whistler mode chorus Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.733, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/2016JA022501/abstract

Using ACE Observations of Interplanetary Particles and Magnetic Fields as Possible Contributors to Variations Observed at Van Allen Probes during Major events in 2013

Science.gov (United States)

Armstrong, T. P.; Manweiler, J. W.; Gerrard, A. J.; Gkioulidou, M.; Lanzerotti, L. J.; Patterson, J. D.

2013-12-01

Observations from ACE EPAM including energy spectra of protons, helium, and oxygen will be prepared for coordinated use in estimating the direct and indirect access of energetic particles to inner and outer geomagnetic trapping zones. Complete temporal coverage from ACE at 12 seconds, 5 minutes, 17 minutes, hourly and daily cadences will be used to catalog interplanetary events arriving at Earth including interplanetary magnetic field sector boundaries, interplanetary shocks, and interplanetary coronal mass ejections, ICMEs. The first 6 months of 2013 have included both highly disturbed times, March 17 and May 22, and extended quiet periods of little or no variations. Among the specific questions that ACE and Van Allen Probes coordinated observations may aid in resolving are: 1. How much, if any, direct capture of interplanetary energetic particles occurs and what conditions account for it? 2. How much influence do interplanetary field and particle variations have on energization and/or loss of geomagnetically trapped populations? The poster will also present important links and describe methods and important details of access to numerically expressed ACE EPAM and Van Allen Probes RBSPICE observations that can be flexibly and easily accessed via the internet for student and senior researcher use.

Ring Current Response to Different Storm Drivers. Van Allen Probes and Cluster Observations.

Science.gov (United States)

Bingham, S.; Mouikis, C.; Kistler, L. M.; Spence, H. E.; Gkioulidou, M.; Claudepierre, S. G.; Farrugia, C. J.

2015-12-01

The ring current responds differently to the different solar and interplanetary storm drivers such as coronal mass injections, (CME's), co-rotating interaction regions (CIR's), high-speed streamers and other structures. The resulting changes in the ring current particle pressure change the global magnetic field, which affects the transport of the radiation belts. In order to determine the field changes during a storm it is necessary to understand the transport, sources and losses of the particles that contribute to the ring current. The source population of the storm time ring current is the night side plasma sheet. However, it is not clear how these convecting particles affect the storm time ring current pressure development. We use Van Allen Probes and Cluster observations together with the Volland-Stern and dipole magnetic field models to determine the contribution in the ring current pressure of the plasma sheet particles convecting from the night side that are on open drift paths, during the storm evolution. We compare storms that are related to different interplanetary drivers, CME and CIR, as observed at different local times.

Subauroral Polarization Streams (SAPS) Duration as Determined From Van Allen Probe Successive Electric Drift Measurements

Science.gov (United States)

Lejosne, Solène; Mozer, F. S.

2017-09-01

We examine a characteristic feature of the magnetosphere-ionosphere coupling, namely, the persistent and latitudinally narrow bands of rapid westward ion drifts called the subauroral polarization streams (SAPS). Despite countless works on SAPS, information relative to their durations is lacking. Here we report on the first statistical analysis of more than 200 near-equatorial SAPS observations based on more than 2 years of Van Allen Probe electric drift measurements. First, we present results relative to SAPS radial locations and amplitudes. Then, we introduce two different ways to estimate SAPS durations. In both cases, SAPS activity is estimated to last for about 9 h on average. However, our estimates for SAPS duration are limited either by the relatively long orbital periods of the spacecraft or by the relatively small number of observations involved. Fifty percent of the events fit within the time interval [0;18] hours.

Rapid flattening of butterfly pitch angle distributions of radiation belt electrons by whistler-mode chorus

Science.gov (United States)

Yang, Chang; Su, Zhenpeng; Xiao, Fuliang; Zheng, Huinan; Wang, Yuming; Wang, Shui; Spence, H. E.; Reeves, G. D.; Baker, D. N.; Blake, J. B.; Funsten, H. O.

2016-08-01

Van Allen radiation belt electrons exhibit complex dynamics during geomagnetically active periods. Investigation of electron pitch angle distributions (PADs) can provide important information on the dominant physical mechanisms controlling radiation belt behaviors. Here we report a storm time radiation belt event where energetic electron PADs changed from butterfly distributions to normal or flattop distributions within several hours. Van Allen Probes observations showed that the flattening of butterfly PADs was closely related to the occurrence of whistler-mode chorus waves. Two-dimensional quasi-linear STEERB simulations demonstrate that the observed chorus can resonantly accelerate the near-equatorially trapped electrons and rapidly flatten the corresponding electron butterfly PADs. These results provide a new insight on how chorus waves affect the dynamic evolution of radiation belt electrons.

Rapid flattening of butterfly pitch angle distributions of radiation belt electrons by whistler-mode chorus

International Nuclear Information System (INIS)

Yang, Chang; Changsha University of Science and Technology, Changsha; Su, Zhenpeng; Xiao, Fuliang; Zheng, Huinan

2016-01-01

Van Allen radiation belt electrons exhibit complex dynamics during geomagnetically active periods. Investigation of electron pitch angle distributions (PADs) can provide important information on the dominant physical mechanisms controlling radiation belt behaviors. In this paper, we report a storm time radiation belt event where energetic electron PADs changed from butterfly distributions to normal or flattop distributions within several hours. Van Allen Probes observations showed that the flattening of butterfly PADs was closely related to the occurrence of whistler-mode chorus waves. Two-dimensional quasi-linear STEERB simulations demonstrate that the observed chorus can resonantly accelerate the near-equatorially trapped electrons and rapidly flatten the corresponding electron butterfly PADs. Finally, these results provide a new insight on how chorus waves affect the dynamic evolution of radiation belt electrons.

Energy resolution in liquid argon doped with allene

International Nuclear Information System (INIS)

Ichinose, H.; Doke, T.; Masuda, K.; Shibamura, E.

1989-01-01

Studies have been made on liquid argon as detection medium with large volume and good energy and position resolution. It is advantageous to dope liquid argon with molecules with an ionization potential lower than the energy of scintillation light. In the present work, the energy resolution for 5.305MeV alpha particles is examined, and the effect of allene added to liquid argon is investigated. Some preliminary results for 976 KeV electrons are also presented. Allene is purified by two methods: (a) small-quantity purification and (b) mass purification. Three methods are tried for mixing allene with argon. Results concerning the allene purification methods, effect of allene concentration, and allene-argon mixing methods are presented. Discussion is made of the collected charge and energy resolution. It is concluded that the addition of allene to liquid argon greatly improves the energy resolution of 5.305 MeV alpha particles. The best intrinsic resolution is 1.4 percent FWHM obtained for 4 ppm allene doped liquid argon. In the case of 976 KeV electron radiation, energy resolution is not improved by adding allene to liquid argon. The best resolution is 31 KeV FWHM obtaiend for 65ppm allene doped liquid argon. (N.K.)

Kalman Filtering and Smoothing of the Van Allen Probes Observations to Estimate the Radial, Energy and Pitch Angle Diffusion Rates

Science.gov (United States)

Podladchikova, T.; Shprits, Y.; Kellerman, A. C.

2015-12-01

The Kalman filter technique combines the strengths of new physical models of the Earth's radiation belts with long-term spacecraft observations of electron fluxes and therefore provide an extremely useful method for the analysis of the state and evolution of the electron radiation belts. However, to get the reliable data assimilation output, the Kalman filter application is confronted with a set of fundamental problems. E.g., satellite measurements are usually limited to a single location in space, which confines the reconstruction of the global evolution of the radiation environment. The uncertainties arise from the imperfect description of the process dynamics and the presence of observation errors, which may cause the failure of data assimilation solution. The development of adaptive Kalman filter that combines the Van Allen Probes data and 3-D VERB code, its accurate customizations in the reconstruction of model describing the phase space density (PSD) evolution, extension of the possibilities to use measurement information, and the model adjustment by developing the identification techniques of model and measurement errors allowed us to reveal hidden and implicit regularities of the PSD dynamics and obtain quantitative and qualitative estimates of radial, energy and pitch angle diffusion characteristics from satellite observations. In this study we propose an approach to estimate radial, energy and pitch angle diffusion rates, as well as the direction of their propagation.

Fast Magnetosonic Waves Observed by Van Allen Probes: Testing Local Wave Excitation Mechanism

Science.gov (United States)

Min, Kyungguk; Liu, Kaijun; Wang, Xueyi; Chen, Lunjin; Denton, Richard E.

2018-01-01

Linear Vlasov theory and particle-in-cell (PIC) simulations for electromagnetic fluctuations in a homogeneous, magnetized, and collisionless plasma are used to investigate a fast magnetosonic wave event observed by the Van Allen Probes. The fluctuating magnetic field observed exhibits a series of spectral peaks at harmonics of the proton cyclotron frequency Ωp and has a dominant compressional component, which can be classified as fast magnetosonic waves. Furthermore, the simultaneously observed proton phase space density exhibits positive slopes in the perpendicular velocity space, ∂fp/∂v⊥>0, which can be a source for these waves. Linear theory analyses and PIC simulations use plasma and field parameters measured in situ except that the modeled proton distribution is modified to have larger ∂fp/∂v⊥ under the assumption that the observed distribution corresponds to a marginally stable state when the distribution has already been scattered by the excited waves. The results show that the positive slope is the source of the proton cyclotron harmonic waves at propagation quasi-perpendicular to the background magnetic field, and as a result of interactions with the excited waves the evolving proton distribution progresses approximately toward the observed distribution.

Substituent effects on dynamics at conical intersections: Allene and methyl allenes

Energy Technology Data Exchange (ETDEWEB)

Neville, Simon P. [Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada); Wang, Yanmei [State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Boguslavskiy, Andrey E.; Stolow, Albert, E-mail: albert.stolow@nrc-cnrc.gc.ca [Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada); National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa ON K1N 6N5 (Canada); Schuurman, Michael S., E-mail: michael.schuurman@nrc-cnrc.gc.ca [Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada); National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada)

2016-01-07

We report a joint experimental and theoretical study on the ultrafast excited state dynamics of allene and a series of its methylated analogues (1,2-butadiene, 1,1-dimethylallene, and tetramethylallene) in order to elucidate the conical intersection mediated dynamics that give rise to ultrafast relaxation to the ground electronic state. We use femtosecond time-resolved photoelectron spectroscopy (TRPES) to probe the coupled electronic-vibrational dynamics following UV excitation at 200 nm (6.2 eV). Ab initio multiple spawning (AIMS) simulations are employed to determine the mechanistic details of two competing dynamical pathways to the ground electronic state. In all molecules, these pathways are found to involve as follows: (i) twisting about the central allenic C–C–C axis followed by pyramidalization at one of the terminal carbon atoms and (ii) bending of allene moiety. Importantly, the AIMS trajectory data were used for ab initio simulations of the TRPES, permitting direct comparison with experiment. For each molecule, the decay of the TRPES signal is characterized by short (30 fs, 52 fs, 23 fs) and long (1.8 ps, 3.5 ps, [306 fs, 18 ps]) time constants for 1,2-butadiene, 1,1-dimethylallene, and tetramethylallene, respectively. However, AIMS simulations show that these time constants are only loosely related to the evolution of electronic character and actually more closely correlate to large amplitude motions on the electronic excited state, modulating the instantaneous vertical ionization potentials. Furthermore, the fully substituted tetramethylallene is observed to undergo qualitatively different dynamics, as displacements involving the relatively massive methyl groups impede direct access to the conical intersections which give rise to the ultrafast relaxation dynamics observed in the other species. These results show that the branching between the “twisting” and “bending” pathways can be modified via the selective methylation of the terminal

Charging of the Van Allen Probes: Theory and Simulations

Science.gov (United States)

Delzanno, G. L.; Meierbachtol, C.; Svyatskiy, D.; Denton, M.

2017-12-01

The electrical charging of spacecraft has been a known problem since the beginning of the space age. Its consequences can vary from moderate (single event upsets) to catastrophic (total loss of the spacecraft) depending on a variety of causes, some of which could be related to the surrounding plasma environment, including emission processes from the spacecraft surface. Because of its complexity and cost, this problem is typically studied using numerical simulations. However, inherent unknowns in both plasma parameters and spacecraft material properties can lead to inaccurate predictions of overall spacecraft charging levels. The goal of this work is to identify and study the driving causes and necessary parameters for particular spacecraft charging events on the Van Allen Probes (VAP) spacecraft. This is achieved by making use of plasma theory, numerical simulations, and on-board data. First, we present a simple theoretical spacecraft charging model, which assumes a spherical spacecraft geometry and is based upon the classical orbital-motion-limited approximation. Some input parameters to the model (such as the warm plasma distribution function) are taken directly from on-board VAP data, while other parameters are either varied parametrically to assess their impact on the spacecraft potential, or constrained through spacecraft charging data and statistical techniques. Second, a fully self-consistent numerical simulation is performed by supplying these parameters to CPIC, a particle-in-cell code specifically designed for studying plasma-material interactions. CPIC simulations remove some of the assumptions of the theoretical model and also capture the influence of the full geometry of the spacecraft. The CPIC numerical simulation results will be presented and compared with on-board VAP data. This work will set the foundation for our eventual goal of importing the full plasma environment from the LANL-developed SHIELDS framework into CPIC, in order to more accurately

Understanding the Driver of Energetic Electron Precipitation Using Coordinated Multi-Satellite Measurements

Science.gov (United States)

Capannolo, L.; Li, W.; Ma, Q.

2017-12-01

Electron precipitation into the upper atmosphere is one of the important loss mechanisms in the Earth's inner magnetosphere. Various magnetospheric plasma waves (i.e., chorus, plasmaspheric hiss, electromagnetic ion cyclotron waves, etc.) play an important role in scattering energetic electrons into the loss cone, thus enhance ionization in the upper atmosphere and affect ring current and radiation belt dynamics. The present study evaluates conjunction events where low-earth-orbiting satellites (twin AeroCube-6) and near-equatorial satellites (twin Van Allen Probes) are located roughly along the same magnetic field line. By analyzing electron flux variation at various energies (> 35 keV) measured by AeroCube-6 and wave and electron measurements by Van Allen Probes, together with quasilinear diffusion theory and modeling, we determine the physical process of driving the observed energetic electron precipitation for the identified electron precipitation events. Moreover, the twin AeroCube-6 also helps us understand the spatiotemporal effect and constrain the coherent size of each electron precipitation event.

Propagation of lower-band whistler-mode waves in the outer Van Allen belt: Systematic analysis of 11 years of multi-component data from the Cluster spacecraft

Czech Academy of Sciences Publication Activity Database

Santolík, Ondřej; Macúšová, Eva; Kolmašová, Ivana; Cornilleau-Wehrlin, N.; De Conchy, Y.

2014-01-01

Roč. 41, č. 8 (2014), s. 2729-2737 ISSN 0094-8276 R&D Projects: GA MŠk 7E12026; GA ČR GAP205/10/2279 Institutional support: RVO:68378289 Keywords : whistler-mode chorus * wave vector directions * Van Allen radiation belts Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 4.456, year: 2013 http://onlinelibrary.wiley.com/doi/10.1002/2014GL059815/abstract

Evaluatie pilot toepassing van technieken op gebied van electronic monitoring binnen een penitentiaire inrichting

NARCIS (Netherlands)

Bekkers, R.N.A.; te Velde, R.; Segers, J.; Bilderbeek, R.

2008-01-01

Publicatienummer 2006.051-0713; Een evaluatie van een pilot inzake de toepassing van technieken op gebied van electronic monitoring binnen een penitentiaire inrichting. Wat zijn de gevolgen voor de veiligheid (incidenten, ontvluchtingen) en welk inzicht biedt een kosten-batenanalyse?

Generation of Nonlinear Electric Field Bursts in the Outer Radiation Belt through Electrons Trapping by Oblique Whistler Waves

Science.gov (United States)

Agapitov, Oleksiy; Drake, James; Mozer, Forrest

2016-04-01

Huge numbers of different nonlinear structures (double layers, electron holes, non-linear whistlers, etc. referred to as Time Domain Structures - TDS) have been observed by the electric field experiment on board the Van Allen Probes. A large part of the observed non-linear structures are associated with whistler waves and some of them can be directly driven by whistlers. The parameters favorable for the generation of TDS were studied experimentally as well as making use of 2-D particle-in-cell (PIC) simulations for the system with inhomogeneous magnetic field. It is shown that an outward propagating front of whistlers and hot electrons amplifies oblique whistlers which collapse into regions of intense parallel electric field with properties consistent with recent observations of TDS from the Van Allen Probe satellites. Oblique whistlers seed the parallel electric fields that are driven by the beams. The resulting parallel electric fields trap and heat the precipitating electrons. These electrons drive spikes of intense parallel electric field with characteristics similar to the TDSs seen in the VAP data. The decoupling of the whistler wave and the nonlinear electrostatic component is shown in PIC simulation in the inhomogeneous magnetic field system. These effects are observed by the Van Allen Probes in the radiation belts. The precipitating hot electrons propagate away from the source region in intense bunches rather than as a smooth flux.

The evolution of ring current ion energy density and energy content during geomagnetic storms based on Van Allen Probes measurements

International Nuclear Information System (INIS)

Zhao, H.; University of Colorado, Boulder, CO; Li, X.; University of Colorado, Boulder, CO; Baker, D. N.

2015-01-01

Enabled by the comprehensive measurements from the Magnetic Electron Ion Spectrometer (MagEIS), Helium Oxygen Proton Electron mass spectrometer (HOPE), and Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instruments onboard Van Allen Probes in the heart of the radiation belt, the relative contributions of ions with different energies and species to the ring current energy density and their dependence on the phases of geomagnetic storms are quantified. The results show that lower energy (<50 keV) protons enhance much more often and also decay much faster than higher-energy protons. During the storm main phase, ions with energies <50 keV contribute more significantly to the ring current than those with higher energies; while the higher-energy protons dominate during the recovery phase and quiet times. The enhancements of higher-energy proton fluxes as well as energy content generally occur later than those of lower energy protons, which could be due to the inward radial diffusion. For the 29 March 2013 storm we investigated in detail that the contribution from O + is ~25% of the ring current energy content during the main phase and the majority of that comes from <50 keV O + . This indicates that even during moderate geomagnetic storms the ionosphere is still an important contributor to the ring current ions. Using the Dessler-Parker-Sckopke relation, the contributions of ring current particles to the magnetic field depression during this geomagnetic storm are also calculated. In conclusion, the results show that the measured ring current ions contribute about half of the Dst depression.

Study the Precipitation of Radiation Belt Electrons during the Rapid Dropout Events

Science.gov (United States)

Tu, W.; Cunningham, G.; Li, X.; Chen, Y.

2015-12-01

During the main phase of storms, the relativistic electron flux in the radiation belt can drop by orders of magnitude on timescales of a few hours. Where do the electrons go? This is one of the most important outstanding questions in radiation belt studies. Radiation belt electrons can be lost either by transport across the magnetopause into interplanetary space or by precipitation into the atmosphere. In this work we first conduct a survey of the MeV electron dropouts using the Van Allen Probes data in conjunction with the low-altitude measurements of precipitating electrons by 6 NOAA/POES satellites. The dropout events are categorized into three types: precipitation-loss dominant, outward radial diffusion dominant, or with contributions from both mechanisms. The survey results suggest the relative importance of precipitation and outward radial diffusion to the fast dropouts of radiation belt electrons, and their extent in L-shell and electron energy. Then, for specific events identified as dominated by precipitation loss, we use the Drift-Diffusion model, which includes the effects of azimuthal drift and pitch angle diffusion, to simulate both the electron dropout observed by Van Allen Probes and the distributions of drift-loss-cone electrons observed by multiple low-earth-orbit satellites (6 POES and the Colorado Student Space Weather Experiment). The model quantifies the electron precipitation loss and pitch angle diffusion coefficient, Dxx, with high temporal and spatial resolution. Finally, by comparing the Dxx derived from the model with those estimated from the quasi-linear theory using wave data from Van Allen Probes and other event-specific wave models, we are able to test the validity of quasi-linear theory and seek direct evidence of the wave-particle interactions during the dropouts.

Flow of Energy through the Inner Magnetosphere during the March 17, 2015 solar storm as observed by the Van Allen Probes Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE)

Science.gov (United States)

Manweiler, J. W.; Madanian, H.; Gerrard, A. J.; Patterson, J. D.; Mitchell, D. G.; Lanzerotti, L. J.

2017-12-01

On March 17, 2015, a large solar storm impacted the Earth's magnetosphere with a maximum negative Dst of -232 nT. We report on the temporal and spatial evolution of the proton energetic particle distributions in phase space during this storm, as measured by the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instrument on board each of the Van Allen Probes. We characterize the distribution prior to onset of the storm to provide a definition of quiet time conditions. We then show how the distribution evolves during the storm noting key changes of the distribution as a function of L and MLT and showing how the pitch angle distributions change throughout the storm. These observations displayed a number of interesting features of the storm including high beta plasma conditions and multiple injections of protons into the inner magnetosphere. We present the radial changes of the distribution at storm onset and following the evolution of the distribution during storm recovery. We compare observations of the East/West asymmetry in the proton distribution before versus after onset using both Van Allen Probes A and B spacecraft observations. Finally, we note interesting changes in the distribution showing an anomalous dropout in mid-energies of the distribution and observe an outward radial propagation of this dropout during recovery.

Van Allen Probe observations of drift-bounce resonances with Pc 4 pulsations and wave–particle interactions in the pre-midnight inner magnetosphere

Directory of Open Access Journals (Sweden)

G. I. Korotova

2015-08-01

Full Text Available We present Van Allen Probe B observations of azimuthally limited, antisymmetric, poloidal Pc 4 electric and magnetic field pulsations in the pre-midnight sector of the magnetosphere from 05:40 to 06:00 UT on 1 May 2013. Oscillation periods were similar for the magnetic and electric fields and proton fluxes. The flux of energetic protons exhibited an energy-dependent response to the pulsations. Energetic proton variations were anticorrelated at medium and low energies. Although we attribute the pulsations to a drift-bounce resonance, we demonstrate that the energy-dependent response of the ion fluxes results from pulsation-associated velocities sweeping energy-dependent radial ion flux gradients back and forth past the spacecraft.

Statistical investigation of the efficiency of EMIC waves in precipitating relativistic electrons

Science.gov (United States)

Hudson, M. K.; Qin, M.; Millan, R. M.; Woodger, L. A.; Shekhar, S.

2017-12-01

Electromagnetic ion cyclotron (EMIC) waves have been proposed as an effective way to scatter relativistic electrons into the atmospheric loss cone. In our study, however, among the total 399 coincidence events when NOAA satellites goes through the region of EMIC wave activity, only 103 are associated with Relativistic Electron Precipitation (REP) events, which indicates that the link between EMIC waves and relativistic electrons is much weaker than expected. Most of the studies so far have been focused on the He+ band EMIC waves, and H+ band EMIC waves have been regarded as less important to the precipitation of electrons. In our study, we demonstrate that among the 103 EMIC wave events detected by Van Allen Probes that are in close conjunction with relativistic electron precipitation observed by POES satellites, the occurrence rate of H+ and He+ band EMIC waves coincident with REP is comparable, suggesting closer examination of the range of ΔL and ΔMLT used to determine coincidence between Van Allen Probes EMIC waves and POES precipitation observation.

Modeling Pc4 Pulsations in Two and a Half Dimensions with Comparisons to Van Allen Probes Observations

Science.gov (United States)

McEachern, Charles A.

Field line resonances---that is, Alfven waves bouncing between the northern and southern foot points of a geomagnetic field line---serve to energize magnetospheric particles through drift-resonant interactions, carry energy from high to low altitude, induce currents in the magnetosphere, and accelerate particles into the atmosphere. Wave structure and polarization significantly impact the execution these roles. The present work showcases a new two and a half dimensional code, Tuna, ideally suited to model FLRs, with the ability to consider large-but-finite azimuthal modenumbers, coupling between the poloidal, toroidal, and compressional modes, and arbitrary harmonic structure. Using Tuna, the interplay between Joule dissipation and poloidal-to-toroidal rotation is considered for both dayside and nightside conditions. An attempt is also made to demystify giant pulsations, a class of FLR knows for its distinctive ground signatures. Numerical results are supplemented by a survey of ˜700 FLRs using data from the Van Allen Probes, the first such survey to characterize each event by both polarization and harmonic. The combination of numerical and observational results suggests an explanation for the disparate distributions observed in poloidal and toroidal FLR events.

Cyclotron Acceleration of Relativistic Electrons through Landau Resonance with Obliquely Propagating Whistler Mode Chorus Emissions

Science.gov (United States)

Omura, Y.; Hsieh, Y. K.; Foster, J. C.; Erickson, P. J.; Kletzing, C.; Baker, D. N.

2017-12-01

A recent test particle simulation of obliquely propagating whistler mode wave-particle interaction [Hsieh and Omura, 2017] shows that the perpendicular wave electric field can play a significant role in trapping and accelerating relativistic electrons through Landau resonance. A further theoretical and numerical investigation verifies that there occurs nonlinear wave trapping of relativistic electrons by the nonlinear Lorentz force of the perpendicular wave magnetic field. An electron moving with a parallel velocity equal to the parallel phase velocity of an obliquely propagating wave basically see a stationary wave phase. Since the electron position is displaced from its gyrocenter by a distance ρ*sin(φ), where ρ is the gyroradius and φ is the gyrophase, the wave phase is modulated with the gyromotion, and the stationary wave fields as seen by the electron are expanded as series of Bessel functions Jn with phase variations n*φ. The J1 components of the wave electric and magnetic fields rotate in the right-hand direction with the gyrofrequency, and they can be in resonance with the electron undergoing the gyromotion, resulting in effective electron acceleration and pitch angle scattering. We have performed a subpacket analysis of chorus waveforms observed by the Van Allen Probes [Foster et al., 2017], and calculated the energy gain by the cyclotron acceleration through Landau resonance. We compare the efficiencies of accelerations by cyclotron and Landau resonances in typical events of rapid electron acceleration observed by the Van Allen Probes.References:[1] Hsieh, Y.-K., and Y. Omura (2017), Nonlinear dynamics of electrons interacting with oblique whistler mode chorus in the magnetosphere, J. Geophys. Res. Space Physics, 122, 675-694, doi:10.1002/2016JA023255.[2] Foster, J. C., P. J. Erickson, Y. Omura, D. N. Baker, C. A. Kletzing, and S. G. Claudepierre (2017), Van Allen Probes observations of prompt MeV radiation belt electron acceleration in nonlinear

NASA's Van Allen Probes RBSP-ECT and NSF's FIREBIRD Data Products and Access to Them: An Insider's Outlook on the Inner and Outer Belts.

Science.gov (United States)

Smith, S. S.; Spence, H. E.; Geoffrey, R.; Klumpar, D. M.

2017-12-01

In this poster, we present a summary of access to data products Radiation Belt Storm Probes - Energetic Particle Composition, and Thermal plasma (RBSP-ECT) suite of NASA's Van Allen Probes mission. The RBSP-ECT science investigation (http://rbsp-ect.sr.unh.edu) measures comprehensively the near-Earth charged particle environment in order to understand the processes that control the acceleration, global distribution, and variability of radiation belt electrons and ions. RBSP-ECT data products derive from the three instrument elements that comprise the suite, which collectively covers the broad energies that define the source and seed populations, the core radiation belts, and also their highest energy ultra-relativistic extensions. These RBSP-ECT instruments include, from lowest to highest energies: the Helium, Oxygen, Proton, and Electron (HOPE) sensor, the Magnetic Electron and Ion Spectrometer (MagEIS), and the Relativistic Electron and Proton Telescope (REPT). We provide a brief overview of their principles of operation, as well as a description of the Level 1-3 data products that the HOPE, MagEIS, and REPT instruments produce, both separately and together. We provide a summary of how to access these RBSP-ECT data products at our Science Operation Center and Science Data Center (http://www.rbsp-ect.lanl.gov/rbsp_ect.php ) as well as caveats for their use. In addition, we also provide a summary of access to the data products from NSF's CubeSat mission called Focused Investigation of Relativistic Electron Burst: Intensity, Range, and Dynamics (FIREBIRD). The dual CubeSat FIREBIRD missions provide data on energetic radiation belt electrons precipitating into the atmosphere at low altitudes, which complements and is contemporary with RBSP-ECT measurements. We provide a similar summary of how to access these data (https://ssel.montana.edu/firebird2.html). Finally, in the spirit of efficiently and effectively promoting and encouraging new collaborations, we present a

Second harmonic poloidal waves observed by Van Allen Probes in the dusk-midnight sector

International Nuclear Information System (INIS)

Min, Kyungguk; Takahashi, Kazue; Ukhorskiy, Aleksandr Y.; Manweiler, Jerry W.; Spence, Harlan E.

2017-01-01

This paper presents observations of ultralow-frequency (ULF) waves from Van Allen Probes. The event that generated the ULF waves occurred 2 days after a minor geomagnetic storm during a geomagnetically quiet time. Narrowband pulsations with a frequency of about 7 mHz with moderate amplitudes were registered in the premidnight sector when Probe A was passing through an enhanced density region near geosynchronous orbit. Probe B, which passed through the region earlier, did not detect the narrowband pulsations but only broadband noise. Despite the single-spacecraft measurements, we were able to determine various wave properties. We find that the observed waves are a second harmonic poloidal mode propagating westward with an azimuthal wave number estimated to be ~100; the magnetic field fluctuations have a finite compressional component due to small but finite plasma beta (~0.1); the energetic proton fluxes in the energy ranging from above 10 keV to about 100 keV exhibit pulsations with the same frequency as the poloidal mode and energy-dependent phase delays relative to the azimuthal component of the electric field, providing evidence for drift-bounce resonance; and the second harmonic poloidal mode may have been excited via the drift-bounce resonance mechanism with free energy fed by the inward radial gradient of ~80 keV protons. Here, we show that the wave active region is where the plume overlaps the outer edge of ring current and suggest that this region can have a wide longitudinal extent near geosynchronous orbit.

EPICS: Allen-Bradley hardware reference manual

International Nuclear Information System (INIS)

Nawrocki, G.

1993-01-01

This manual covers the following hardware: Allen-Bradley 6008 -- SV VMEbus I/O scanner; Allen-Bradley universal I/O chassis 1771-A1B, -A2B, -A3B, and -A4B; Allen-Bradley power supply module 1771-P4S; Allen-Bradley 1771-ASB remote I/O adapter module; Allen-Bradley 1771-IFE analog input module; Allen-Bradley 1771-OFE analog output module; Allen-Bradley 1771-IG(D) TTL input module; Allen-Bradley 1771-OG(d) TTL output; Allen-Bradley 1771-IQ DC selectable input module; Allen-Bradley 1771-OW contact output module; Allen-Bradley 1771-IBD DC (10--30V) input module; Allen-Bradley 1771-OBD DC (10--60V) output module; Allen-Bradley 1771-IXE thermocouple/millivolt input module; and the Allen-Bradley 2705 RediPANEL push button module

Empirical Modeling of the Storm Time Innermost Magnetosphere Using Van Allen Probes and THEMIS Data: Eastward and Banana Currents

Science.gov (United States)

Stephens, G. K.; Sitnov, M. I.; Ukhorskiy, A. Y.; Roelof, E. C.; Tsyganenko, N. A.; Le, G.

2016-01-01

The structure of storm time currents in the inner magnetosphere, including its innermost region inside 4R(sub E), is studied for the first time using a modification of the empirical geomagnetic field model TS07D and new data from Van Allen Probes and Time History of Events and Macroscale Interactions during Substorms missions. It is shown that the model, which uses basis-function expansions instead of ad hoc current modules to approximate the magnetic field, consistently improves its resolution and magnetic field reconstruction with the increase of the number of basis functions and resolves the spatial structure and evolution of the innermost eastward current. This includes a connection between the westward ring current flowing largely at R > or approx. 3R(sub E) and the eastward ring current concentrated at R storm phase. During the main phase, it is complex, with several asymmetries forming banana currents. Near SYM-H minimum, the banana current is strongest, is localized in the evening-midnight sector, and is more structured compared to the main phase. It then weakens during the recovery phase resulting in the equatorial currents to become mostly azimuthally symmetric.

Kolb in de klas: vijf docenten in het hoger onderwijs onderzoeken de waarde van Kolbs leerstijlen voor hun eigen onderwijspraktijk

NARCIS (Netherlands)

Schoonenboom, J.; Van den Heuvel, W.; Leighton, R.; Dols, L.; Visser, W.; Van Steijn, S.

2009-01-01

Deze bundel bevat de resultaten van vijf kortlopende onderzoeken door deelnemers aan de masteropleiding Teaching in Higher Education, allen docenten in het hoger onderwijs, naar de waarde van de leerstijlen van Kolb voor hun eigen lespraktijk. Uit de onderzoeken komt naar voren dat het

The Distribution of Chorus and Plasmaspheric Hiss Waves in the Inner Magnetospahere as Functions of Geomagnetic Activity and Solar Wind Parameters as Observed by The Van Allen Probes.

Science.gov (United States)

Aryan, H.; Sibeck, D. G.; Balikhin, M. A.; Agapitov, O. V.; Kletzing, C.

2015-12-01

The dynamics of the radiation belts is dependent upon the acceleration and loss of radiation belt electrons that is largely determined by the interaction of georesonant wave particles with chorus and plasmaspheric hiss waves. The distribution of these waves in the inner magnetosphere is commonly presented as a function of geomagnetic activity as expressed by the geomagnetic indices (Ae, Kp, and Dst). However, it has been shown that not all geomagnetic storms necessarily increase the flux of energetic electrons at the radiation belts. In fact, almost 20% of all geomagnetic storms cause a decrease in the flux of energetic electrons, while 30% has relatively no effect. Also, the geomagnetic indices are indirect, nonspecific parameters compiled from imperfectly covered ground based measurements that lack time history. This emphasises the need to present wave distributions as a function of both geomagnetic activity and solar wind parameters, such as velocity (V), density (n), and interplanetary magnetic field component (Bz), that are known to be predominantly effective in the control of radiation belt energetic electron fluxes. This study presents the distribution of chorus and plasmaspheric hiss waves in the inner magnetosphere as functions of both geomagnetic activity and solar wind parameters for different L-shell, magnetic local time, and magnetic latitude. This study uses almost three years of data measured by the EMFISIS on board the Van Allen Probes. Initial results indicate that the intensity of chorus and plasmaspheric hiss emissions are not only dependent on the geomagnetic activity but also dependent on solar wind parameters. The largest average wave intensities are observed with equatorial chorus in the region 4

Lower Hybrid Frequency Range Waves Generated by Ion Polarization Drift Due to Electromagnetic Ion Cyclotron Waves: Analysis of an Event Observed by the Van Allen Probe B

Science.gov (United States)

Khazanov, G. V.; Boardsen, S.; Krivorutsky, E. N.; Engebretson, M. J.; Sibeck, D.; Chen, S.; Breneman, A.

2017-01-01

We analyze a wave event that occurred near noon between 07:03 and 07:08 UT on 23 February 2014 detected by the Van Allen Probes B spacecraft, where waves in the lower hybrid frequency range (LHFR) and electromagnetic ion cyclotron (EMIC) waves are observed to be highly correlated, with Pearson correlation coefficient of approximately 0.86. We assume that the correlation is the result of LHFR wave generation by the ions polarization drift in the electric field of the EMIC waves. To check this assumption the drift velocities of electrons and H+, He+, and O+ ions in the measured EMIC wave electric field were modeled. Then the LHFR wave linear instantaneous growth rates for plasma with these changing drift velocities and different plasma compositions were calculated. The time distribution of these growth rates, their frequency distribution, and the frequency dependence of the ratio of the LHFR wave power spectral density (PSD)parallel and perpendicular to the ambient magnetic eld to the total PSD were found. These characteristics of the growth rates were compared with the corresponding characteristics of the observed LHFR activity. Reasonable agreement between these features and the strong correlation between EMIC and LHFR energy densities support the assumption that the LHFR wave generation can be caused by the ions polarization drift in the electric field of an EMIC wave.

Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope

KAUST Repository

Govyadinov, Alexander A.

2017-07-14

Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope.

Science.gov (United States)

Govyadinov, Alexander A; Konečná, Andrea; Chuvilin, Andrey; Vélez, Saül; Dolado, Irene; Nikitin, Alexey Y; Lopatin, Sergei; Casanova, Fèlix; Hueso, Luis E; Aizpurua, Javier; Hillenbrand, Rainer

2017-07-21

Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope

KAUST Repository

Govyadinov, Alexander A.; Konečná , Andrea; Chuvilin, Andrey; Vé lez, Saü l; Dolado, Irene; Nikitin, Alexey Y.; Lopatin, Sergei; Casanova, Fè lix; Hueso, Luis E.; Aizpurua, Javier; Hillenbrand, Rainer

2017-01-01

Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

Wave-Particle Interactions Involving Correlated Electron Bursts and Whistler Chorus in Earth's Radiation Belts

Science.gov (United States)

Echterling, N.; Schriver, D.; Roeder, J. L.; Fennell, J. F.

2017-12-01

During the recovery phase of substorm plasma injections, the Van Allen Probes commonly observe events of quasi-periodic energetic electron bursts correlating with simultaneously detected upper-band, whistler-mode chorus emissions. These electron bursts exhibit narrow ranges of pitch angles (75-80° and 100-105°) and energies (20-40 keV). Electron cyclotron harmonic (ECH) emissions are also commonly detected, but typically do not display correlation with the electron bursts. To examine sources of free energy and the generation of these wave emissions, an observed electron velocity distribution on January 13, 2013 is used as the starting condition for a particle in cell (PIC) simulation. Effects of temperature anisotropy (perpendicular temperature greater than parallel temperature), the presence of a loss cone and a cold electron population on the generation of whistler and ECH waves are examined to understand wave generation and nonlinear interactions with the particle population. These nonlinear interactions produce energy diffusion along with strong pitch angle scattering into the loss cone on the order of milliseconds, which is faster than a typical bounce period of seconds. To examine the quasi-periodic nature of the electron bursts, a loss-cone recycling technique is implemented to model the effects of the periodic emptying of the loss cone and electron injection on the growth of whistler and ECH waves. The results of the simulations are compared to the Van Allen Probe observations to determine electron acceleration, heating and transport in Earth's radiation belts due to wave-particle interactions.

Woody Allen kimpus arhitektuuriga

Index Scriptorium Estoniae

2000-01-01

Woody Allen protesteerib oma uue lühifilmiga kavatsuse vastu ehitada 16-korruseline ärihoone tema New Yorgi kodu lähedale. W. Allen hindab New Yorgi ajaloolisi rajoone, mida näitab ka oma filmides

Design and Development of a Configurable Fault-Tolerant Processor (CFTP) for Space Applications

Science.gov (United States)

2003-06-01

Slot Region BIRA/ IASB Figure 5. Van Allen Belts (After Ref. [20].) 17 The trapped particles in the Van Allen Belts include electrons trapped in...the most sig- nificant role in the failure of electronic equipment in orbit. There exists a wide range of these circuit-crippling events, including...such, the goals of the CFTP project are the most rigorous constraints applied on the design process, and are what will ensure its future role as an

Empirical Modeling of the Storm Time Innermost Magnetosphere Using Van Allen Probes and THEMIS Data: Eastward and Banana Currents

Science.gov (United States)

Stephens, G. K.; Sitnov, M. I.; Ukhorskiy, A. Y.; Roelof, E. C.; Tsyganenko, N. A.; Le, G.

2016-01-01

The structure of storm time currents in the inner magnetosphere, including its innermost region inside 4R(sub E), is studied for the first time using a modification of the empirical geomagnetic field model TS07D and new data from Van Allen Probes and Time History of Events and Macroscale Interactions during Substorms missions. It is shown that the model, which uses basis-function expansions instead of ad hoc current modules to approximate the magnetic field, consistently improves its resolution and magnetic field reconstruction with the increase of the number of basis functions and resolves the spatial structure and evolution of the innermost eastward current. This includes a connection between the westward ring current flowing largely at R > or approx. 3R(sub E) and the eastward ring current concentrated at R banana current' was previously inferred from the pressure distributions based on the energetic neutral atom imaging and first-principles ring current simulations. The morphology of the equatorial currents is dependent on storm phase. During the main phase, it is complex, with several asymmetries forming banana currents. Near SYM-H minimum, the banana current is strongest, is localized in the evening-midnight sector, and is more structured compared to the main phase. It then weakens during the recovery phase resulting in the equatorial currents to become mostly azimuthally symmetric.

Upper limit on the inner radiation belt MeV electron intensity

Science.gov (United States)

Li, X; Selesnick, RS; Baker, DN; Jaynes, AN; Kanekal, SG; Schiller, Q; Blum, L; Fennell, J; Blake, JB

2015-01-01

No instruments in the inner radiation belt are immune from the unforgiving penetration of the highly energetic protons (tens of MeV to GeV). The inner belt proton flux level, however, is relatively stable; thus, for any given instrument, the proton contamination often leads to a certain background noise. Measurements from the Relativistic Electron and Proton Telescope integrated little experiment on board Colorado Student Space Weather Experiment CubeSat, in a low Earth orbit, clearly demonstrate that there exist sub-MeV electrons in the inner belt because their flux level is orders of magnitude higher than the background, while higher-energy electron (>1.6 MeV) measurements cannot be distinguished from the background. Detailed analysis of high-quality measurements from the Relativistic Electron and Proton Telescope on board Van Allen Probes, in a geo-transfer-like orbit, provides, for the first time, quantified upper limits on MeV electron fluxes in various energy ranges in the inner belt. These upper limits are rather different from flux levels in the AE8 and AE9 models, which were developed based on older data sources. For 1.7, 2.5, and 3.3 MeV electrons, the upper limits are about 1 order of magnitude lower than predicted model fluxes. The implication of this difference is profound in that unless there are extreme solar wind conditions, which have not happened yet since the launch of Van Allen Probes, significant enhancements of MeV electrons do not occur in the inner belt even though such enhancements are commonly seen in the outer belt. Key Points Quantified upper limit of MeV electrons in the inner belt Actual MeV electron intensity likely much lower than the upper limit More detailed understanding of relativistic electrons in the magnetosphere PMID:26167446

Quantifying the Precipitation Loss of Radiation Belt Electrons during a Rapid Dropout Event

Science.gov (United States)

Pham, K. H.; Tu, W.; Xiang, Z.

2017-12-01

Relativistic electron flux in the radiation belt can drop by orders of magnitude within the timespan of hours. In this study, we used the drift-diffusion model that includes azimuthal drift and pitch angle diffusion of electrons to simulate low-altitude electron distribution observed by POES/MetOp satellites for rapid radiation belt electron dropout event occurring on May 1, 2013. The event shows fast dropout of MeV energy electrons at L>4 over a few hours, observed by the Van Allen Probes mission. By simulating the electron distributions observed by multiple POES satellites, we resolve the precipitation loss with both high spatial and temporal resolution and a range of energies. We estimate the pitch angle diffusion coefficients as a function of energy, pitch angle, and L-shell, and calculate corresponding electron lifetimes during the event. The simulation results show fast electron precipitation loss at L>4 during the electron dropout, with estimated electron lifetimes on the order of half an hour for MeV energies. The electron loss rate show strong energy dependence with faster loss at higher energies, which suggest that this dropout event is dominated by quick and localized scattering process that prefers higher energy electrons. The estimated pitch angle diffusion rates from the model are then compared with in situ wave measurements from Van Allen Probes to uncover the underlying wave-particle-interaction mechanisms that are responsible for the fast electron precipitation. Comparing the resolved precipitation loss with the observed electron dropouts at high altitudes, our results will suggest the relative role of electron precipitation loss and outward radial diffusion to the radiation belt dropouts during storm and non-storm times, in addition to its energy and L dependence.

Radial transport of high-energy oxygen ions into the deep inner magnetosphere observed by Van Allen Probes

Science.gov (United States)

Mitani, K.; Seki, K.; Keika, K.; Gkioulidou, M.; Lanzerotti, L. J.; Mitchell, D. G.; Kletzing, C.

2017-12-01

It is known that proton is main contributor of the ring current and oxygen ions can make significant contribution during major magnetic storms. Ions are supplied to the ring current by radial transport from the plasma sheet. Convective transport of lower-energy protons and diffusive transport of higher-energy protons were reported to contribute to the storm-time and quiet-time ring current respectively [e.g., Gkioulidou et al., 2016]. However, supply mechanisms of the oxygen ions are not clear. To characterize the supply of oxygen ions to the ring current during magnetic storms, we studied the properties of energetic proton and oxygen ion phase space densities (PSDs) for specific magnetic moment (μ) during the April 23-25, 2013, geomagnetic storm observed by the Van Allen Probes mission. We here report on radial transport of high-energy (μ ≥ 0.5 keV/nT) oxygen ions into the deep inner magnetosphere during the late main phase of the magnetic storm. Since protons show little change during this period, this oxygen radial transport is inferred to cause the development of the late main phase. Enhancement of poloidal magnetic fluctuations is simultaneously observed. We estimated azimuthal mode number ≤5 by using cross wavelet analysis with ground-based observation of IMAGE ground magnetometers. The fluctuations can resonate with drift and bounce motions of the oxygen ions. The results suggest that combination of the drift and drift-bounce resonances is responsible for the radial transport of high-energy oxygen ions into the deep inner magnetosphere. We also report on the radial transport of the high-energy oxygen ions into the deep inner magnetosphere during other magnetic storms.

Allene functionalization via bicyclic methylene aziridines.

Science.gov (United States)

Boralsky, Luke A; Marston, Dagmara; Grigg, R David; Hershberger, John C; Schomaker, Jennifer M

2011-04-15

The oxidative functionalization of olefins is a common method for the formation of vicinal carbon-heteroatom bonds. However, oxidative methods to transform allenes into synthetic motifs containing three contiguous carbon-heteroatom bonds are much less developed. This paper describes the use of bicyclic methylene aziridines (MAs), prepared via intramolecular allene aziridination, as scaffolds for functionalization of all three allene carbons. © 2011 American Chemical Society

Evaluating the Role and Effects of Precipitation on Relativistic Electron Losses during Storms

Science.gov (United States)

Chen, Y.; Fu, X.

2016-12-01

Theoretic studies have suggested that during storm times various waves (e.g., whistler-mode chorus and electromagnetic ion cyclotron waves) can cause significant precipitation of relativistic ( MeV) electrons that are originally trapped inside the outer radiation belt. However, the role of precipitation and its quantitative contribution to the losses of outer-belt electrons remain open questions. In this study, we tackle these questions by systemically examining the latest wave and electron in-situ, simultaneous observations made at different altitudes by Van Allen Probes from near equator, NOAA POES at low Earth orbits near/across electron loss cone, and BARREL under the mesosphere. After calibrating with DEMTER observations, we first confirm and quantify the response of POES MEPED proton channels to MeV electrons. Next, we identify a list of precipitation events from BARREL and POES measurements, examine the temporal adn spatial relation between the two data sets, and estimate the intensities of electron precipitation with ascertained uncertainties. Then, from Van Allen Probes data, we select another list of dropout events during storms. By cross checking the above two lists, we are able to determine the causal relation between precipitation and dropouts through individual case as well as statistical studies so as to quantify the contributions from precipitation. This study mainly focuses on the relatively small L-shells with positive phase space density radial gradient in order to alleviate the impacts from outward radial diffusion and adiabatic effects. Based upon the recent discovery of cross-energy cross-pitch angle coherence, we pay particular attention to the cross-term diffusions which may account for the extra "loss" needed by observed MeV electron dropouts. Results from this observational study will advance our knowledge on the loss mechanism of outer-belt electrons, and thus lay down another stepping stone towards high-fidelity physics-based models for

Nano Electronics on Atomically Controlled van der Waals Quantum Heterostructures

Science.gov (United States)

2018-02-19

AFRL-AFOSR-JP-TR-2018-0012 Nano Electronics on Atomically Controlled van der Waals Quantum Heterostructures PHILIP Kim HARVARD COLLEGE PRESIDENT...21-02-2018 2.  REPORT TYPE      Final 3.  DATES COVERED (From - To)      15 Aug 2015 to 14 Feb 2017 4.  TITLE AND SUBTITLE Nano Electronics on...NOTES 14.  ABSTRACT We report molecular beam epitaxial growth and electronic transport properties of high quality topological insulator Bi2Se3 thin films

Multi-Point Measurements to Characterize Radiation Belt Electron Precipitation Loss

Science.gov (United States)

Blum, L. W.

2017-12-01

Multipoint measurements in the inner magnetosphere allow the spatial and temporal evolution of various particle populations and wave modes to be disentangled. To better characterize and quantify radiation belt precipitation loss, we utilize multi-point measurements both to study precipitating electrons directly as well as the potential drivers of this loss process. Magnetically conjugate CubeSat and balloon measurements are combined to estimate of the temporal and spatial characteristics of dusk-side precipitation features and quantify loss due to these events. To then understand the drivers of precipitation events, and what determines their spatial structure, we utilize measurements from the dual Van Allen Probes to estimate spatial and temporal scales of various wave modes in the inner magnetosphere, and compare these to precipitation characteristics. The structure, timing, and spatial extent of waves are compared to those of MeV electron precipitation during a few individual events to determine when and where EMIC waves cause radiation belt electron precipitation. Magnetically conjugate measurements provide observational support of the theoretical picture of duskside interaction of EMIC waves and MeV electrons leading to radiation belt loss. Finally, understanding the drivers controlling the spatial scales of wave activity in the inner magnetosphere is critical for uncovering the underlying physics behind the wave generation as well as for better predicting where and when waves will be present. Again using multipoint measurements from the Van Allen Probes, we estimate the spatial and temporal extents and evolution of plasma structures and their gradients in the inner magnetosphere, to better understand the drivers of magnetospheric wave characteristic scales. In particular, we focus on EMIC waves and the plasma parameters important for their growth, namely cold plasma density and cool and warm ion density, anisotropy, and composition.

MESSENGER observations of transient bursts of energetic electrons in Mercury's magnetosphere.

Science.gov (United States)

Ho, George C; Krimigis, Stamatios M; Gold, Robert E; Baker, Daniel N; Slavin, James A; Anderson, Brian J; Korth, Haje; Starr, Richard D; Lawrence, David J; McNutt, Ralph L; Solomon, Sean C

2011-09-30

The MESSENGER spacecraft began detecting energetic electrons with energies greater than 30 kilo-electron volts (keV) shortly after its insertion into orbit about Mercury. In contrast, no energetic protons were observed. The energetic electrons arrive as bursts lasting from seconds to hours and are most intense close to the planet, distributed in latitude from the equator to the north pole, and present at most local times. Energies can exceed 200 keV but often exhibit cutoffs near 100 keV. Angular distributions of the electrons about the magnetic field suggest that they do not execute complete drift paths around the planet. This set of characteristics demonstrates that Mercury's weak magnetic field does not support Van Allen-type radiation belts, unlike all other planets in the solar system with internal magnetic fields.

Electronic spectral properties of surfaces and adsorbates and atom-adsorbate van der Waals interactions

International Nuclear Information System (INIS)

Lovric, D.; Gumhalter, B.

1988-01-01

The relevance of van der Waals interactions in the scattering of neutral atoms from adsorbates has been recently confirmed by highly sensitive molecular-beam techniques. The theoretical descriptions of the collision dynamics which followed the experimental studies have necessitated very careful qualitative and quantitative examinations and evaluations of the properties of atom-adsorbate van der Waals interactions for specific systems. In this work we present a microscopic calculation of the strengths and reference-plane positions for van der Waals potentials relevant for scattering of He atoms from CO adsorbed on various metallic substrates. In order to take into account the specificities of the polarization properties of real metals (noble and transition metals) and of chemisorbed CO, we first calculate the spectra of the electronic excitations characteristic of the respective electronic subsystems by using various data sources available and combine them with the existing theoretical models. The reliability of the calculated spectra is then verified in each particular case by universal sum rules which may be established for the electronic excitations of surfaces and adsorbates. The substrate and adsorbate polarization properties which derive from these calculations serve as input data for the evaluation of the strengths and reference-plane positions of van der Waals potentials whose computed values are tabulated for a number of real chemisorption systems. The implications of the obtained results are discussed in regard to the atom-adsorbate scattering cross sections pertinent to molecular-beam scattering experiments

Space Radiation

Energy Technology Data Exchange (ETDEWEB)

Corliss, William R.

1968-01-01

This booklet discusses three kinds of space radiation, cosmic rays, Van Allen Belts, and solar plasma. Cosmic rays are penetrating particles that we cannot see, hear or feel, which come from distant stars. Van Allen Belts, named after their discoverer are great belts of protons and electrons that the earth has captured in its magnetic trap. Solar plasma is a gaseous, electrically neutral mixture of positive and negative ions that the sun spews out from convulsed regions on its surface.

van der Waals forces in density functional theory: Perturbational long-range electron-interaction corrections

International Nuclear Information System (INIS)

Angyan, Janos G.; Gerber, Iann C.; Savin, Andreas; Toulouse, Julien

2005-01-01

Long-range exchange and correlation effects, responsible for the failure of currently used approximate density functionals in describing van der Waals forces, are taken into account explicitly after a separation of the electron-electron interaction in the Hamiltonian into short- and long-range components. We propose a 'range-separated hybrid' functional based on a local density approximation for the short-range exchange-correlation energy, combined with a long-range exact exchange energy. Long-range correlation effects are added by a second-order perturbational treatment. The resulting scheme is general and is particularly well adapted to describe van der Waals complexes, such as rare gas dimers

Direct transformation of silyl enol ethers into functionalized allenes.

Science.gov (United States)

Langer, P; Döring, M; Seyferth, D; Görls, H

2001-02-02

The first elimination reactions of silyl enol ethers to lithiated allenes are reported. These reactions allow a direct transformation of readily available silyl enol ethers into functionalized allenes. The action of three to four equivalents of lithium diisopropylamide (LDA) on silyl enol ethers results in the formation of lithiated allenes by initial allylic lithiation, subsequent elimination of a lithium silanolate, and finally, lithiation of the allene thus formed. Starting with amide-derived silyl imino ethers, lithiated ketenimines are obtained. A variety of reactions of the lithiated allenes with electrophiles (chlorosilanes, trimethylchlorostannane, dimethyl sulfate and ethanol) were carried out. Elimination of silanolate is observed only for substrates that contain the hindered SiMe2tBu or Si(iPr)3 moiety, but not for the SiMe3 group. The reaction of 1,1-dilithio-3,3-diphenylallene with ketones provides a convenient access to novel 1,1-di(hydroxymethyl)allenes which undergo a domino Nazarov-Friedel-Crafts reaction upon treatment with p-toluenesulfonic acid.

The O+ contribution and role on the ring current pressure development for CMEs and CIRs using Van Allen Probes observations

Science.gov (United States)

Mouikis, C.; Bingham, S.; Kistler, L. M.; Farrugia, C. J.; Spence, H. E.; Gkioulidou, M.

2016-12-01

The ring current responds differently to the different solar and interplanetary storm drivers such as coronal mass injections, (CME's), co-rotating interaction regions (CIR's), high-speed streamers and other structures. The resulting changes in the ring current particle pressure change the global magnetic field, which affects the transport of the radiation belts. In order to determine the field changes during a storm, it is necessary to understand the transport, sources and losses of the particles that contribute to the ring current. The source population of the storm time ring current is the night side plasma sheet. We use Van Allen Probes observations to determine the ring current pressure contribution of the convecting plasma sheet H+ and O+ particles in the storm time development of the ring current. We compare storms that are related to different interplanetary drivers, CMEs and CIRs, as observed at different local times. We find that during the storm main phase most of the ring current pressure in the pre-midnight inner magnetosphere is contributed by particles on open drift paths that cause the development of a strong partial ring current that causes most of the main phase Dst drop. These particles can reach as deep as L 2 and their pressure compares to the local magnetic field pressure as deep as L 3. During the recovery phase, if these particles are not lost at the magnetopause, will become trapped and will contribute to the symmetric ring current. However, the largest difference between the CME and CIR ring current responses during the storm main and early recovery phases is caused by how the 15 - 60 keV O+ responds to these drivers.

Modular functionalization of allenes to aminated stereotriads.

Science.gov (United States)

Adams, Christopher S; Boralsky, Luke A; Guzei, Ilia A; Schomaker, Jennifer M

2012-07-04

Nitrogen-containing stereotriads, compounds with three adjacent stereodefined carbons, are commonly found in biologically important molecules. However, the preparation of molecules bearing these motifs can be challenging. Herein, we describe a modular oxidation protocol which converts a substituted allene to a triply functionalized amine of the form C-X/C-N/C-Y. The key step employs a Rh-catalyzed intramolecular conversion of the allene to a strained bicyclic methylene aziridine. This reactive intermediate is further elaborated to the target products, often in one reaction vessel and with effective transfer of the axial chirality of the allene to point chirality in the stereotriad.

Diffusive scattering of electrons by electron holes around injection fronts

Science.gov (United States)

Vasko, I. Y.; Agapitov, O. V.; Mozer, F. S.; Artemyev, A. V.; Krasnoselskikh, V. V.; Bonnell, J. W.

2017-03-01

Van Allen Probes have detected nonlinear electrostatic spikes around injection fronts in the outer radiation belt. These spikes include electron holes (EH), double layers, and more complicated solitary waves. We show that EHs can efficiently scatter electrons due to their substantial transverse electric fields. Although the electron scattering driven by EHs is diffusive, it cannot be evaluated via the standard quasi-linear theory. We derive analytical formulas describing local electron scattering by a single EH and verify them via test particle simulations. We show that the most efficiently scattered are gyroresonant electrons (crossing EH on a time scale comparable to the local electron gyroperiod). We compute bounce-averaged diffusion coefficients and demonstrate their dependence on the EH spatial distribution (latitudinal extent and spatial filling factor) and individual EH parameters (amplitude of electrostatic potential, velocity, and spatial scales). We show that EHs can drive pitch angle scattering of ≲5 keV electrons at rates 10-2-10-4 s-1 and, hence, can contribute to electron losses and conjugated diffuse aurora brightenings. The momentum and pitch angle scattering rates can be comparable, so that EHs can also provide efficient electron heating. The scattering rates driven by EHs at L shells L ˜ 5-8 are comparable to those due to chorus waves and may exceed those due to electron cyclotron harmonics.

Electrons in a Magnetic Field: Special Spin in de Haas-van Alphen effect

International Nuclear Information System (INIS)

Shrivastava, Keshav N

2012-01-01

When the magnetic field is applied in a metal, the electrons behave like a harmonic oscillator. When the field is increased these harmonic oscillator type levels cross the Fermi energy at a particular point resulting into the discontinuities in the population of any particular level at that point. For a large orbital magnetic moment, different from L = 0 and both signs of spin in the total magnetic momentum quantum number, j = l ± s, the discontinuities in the population of the electrons in a particular level become double valued resulting into doubling of oscillations in the magnetization. There is a double valued change in the energy of the electrons when they transfer from the harmonic oscillator type level to the Fermi level. The magnetization depends on the value of j = l ± s so that there is a double valued period in the oscillations. The de Haas-van Alphen effect is usually described for the L = 0 electrons. Hence, we see that the de Haas-van Alphen effect is considerably modified in going from L = 0 to j = l ± s, with both signs in the spin.

The characteristic pitch angle distributions of 1 eV to 600 keV protons near the equator based on Van Allen Probes observations

Science.gov (United States)

Yue, C.; Bortnik, J.; Thorne, R. M.; Ma, Q.; An, X.; Chappell, C. R.; Gerrard, A. J.; Lanzerotti, L. J.; Shi, Q.

2017-12-01

Understanding the source and loss processes of various plasma populations is greatly aided by having accurate knowledge of their pitch angle distributions (PADs). Here, we statistically analyze 1 eV to 600 keV hydrogen (H+) PADs near the geomagnetic equator in the inner magnetosphere based on Van Allen Probes measurements, to comprehensively investigate how the H+ PADs vary with different energies, magnetic local times (MLTs), L-shells, and geomagnetic conditions. Our survey clearly indicates four distinct populations with different PADs: (1) a pancake distribution of the plasmaspheric H+ at low L-shells except for dawn sector; (2) a bi-directional field-aligned distribution of the warm plasma cloak; (3) pancake or isotropic distributions of ring current H+; (4) radiation belt particles show pancake, butterfly and isotropic distributions depending on their energy, MLT and L-shell. Meanwhile, the pancake distribution of ring current H+ moves to lower energies as L-shell increases which is primarily caused by adiabatic transport. Furthermore, energetic H+ (> 10 keV) PADs become more isotropic following the substorm injections, indicating wave-particle interactions. The radiation belt H+ butterfly distributions are identified in a narrow energy range of 100 5), which are less significant during quiet times and extend from dusk to dawn sector through midnight during substorms. The different PADs near the equator provide clues of the underlying physical processes that produce the dynamics of these different populations.

Automatic control model of water filling system with Allen Bradley Micrologix 1400 PLC

Science.gov (United States)

Harahap, R.; Adyatma, AF; Fahmi, F.

2018-02-01

Programmable Logic Controller or PLC today plays an important role in most industrial control systems. PLC usage can be encountered in almost all fields of industry, not only in the manufacturing world but also on many other things such as elevators in office buildings, hotels hospitals, and others. PLC is an electronic control tool that operates in logic that its programming can be modified with relative ease. As with any controller in general, the PLC processes input signals to further discharge output according to the desired program. PLC usage is very broad because of its high reliability, can be reprogrammed or modified with relative ease, and very helpful in the tracking troubleshooting. One type of existing PLC is Allen Bradley PLC. Allen Bradley PLC program is commonly used in various industries. PLC Allen Bradley (AB) has several types, and one of them is the type of Micrologic 1400. In this study we design a system as a comparison with the conventional system. For that to explore the use of a PLC program which will be supported by a simulator tool, including a program to RSLogic 500, how to programming, monitoring via RSView32, and modification. It is expected to understand the application aspect of operation and programming of this specific PLC and its potential. The purpose of this research is to design water filling automation system by using Allen Bradley Micrologic 1400 type 1766-L32BXB PLC, empowering the use of Allen Bradley Micrologic 1400 PLC and to regulate the desired process to obtain efficiency and effectiveness compared with conventional system arrangement using Relay.

Spin polarization of a magnetic electron gas induced by a van Vleck ion

International Nuclear Information System (INIS)

Palermo, L.; Silva, X.A. do

1978-11-01

The mutual polarization of a magnetic electron gas and a van Vleck ion, interacting via exchange, are theoretically investigated using the double-time Green function method. A pair of equations describing the dynamics of the electron gas and the ion are conveniently decoupled and an analytic expression for the electron gas polarization, which depends on the square of the exchange parameter, is obtained. Besides a RKKY-like term, a new term associated to the process of formation of the magnetic moment of the ion appears [pt

Quantifying electronic band interactions in van der Waals materials using angle-resolved reflected-electron spectroscopy.

Science.gov (United States)

Jobst, Johannes; van der Torren, Alexander J H; Krasovskii, Eugene E; Balgley, Jesse; Dean, Cory R; Tromp, Rudolf M; van der Molen, Sense Jan

2016-11-29

High electron mobility is one of graphene's key properties, exploited for applications and fundamental research alike. Highest mobility values are found in heterostructures of graphene and hexagonal boron nitride, which consequently are widely used. However, surprisingly little is known about the interaction between the electronic states of these layered systems. Rather pragmatically, it is assumed that these do not couple significantly. Here we study the unoccupied band structure of graphite, boron nitride and their heterostructures using angle-resolved reflected-electron spectroscopy. We demonstrate that graphene and boron nitride bands do not interact over a wide energy range, despite their very similar dispersions. The method we use can be generally applied to study interactions in van der Waals systems, that is, artificial stacks of layered materials. With this we can quantitatively understand the 'chemistry of layers' by which novel materials are created via electronic coupling between the layers they are composed of.

Electrostatics of electron-hole interactions in van der Waals heterostructures

Science.gov (United States)

Cavalcante, L. S. R.; Chaves, A.; Van Duppen, B.; Peeters, F. M.; Reichman, D. R.

2018-03-01

The role of dielectric screening of electron-hole interaction in van der Waals heterostructures is theoretically investigated. A comparison between models available in the literature for describing these interactions is made and the limitations of these approaches are discussed. A simple numerical solution of Poisson's equation for a stack of dielectric slabs based on a transfer matrix method is developed, enabling the calculation of the electron-hole interaction potential at very low computational cost and with reasonable accuracy. Using different potential models, direct and indirect exciton binding energies in these systems are calculated within Wannier-Mott theory, and a comparison of theoretical results with recent experiments on excitons in two-dimensional materials is discussed.

Diastereoselective Au-Catalyzed Allene Cycloisomerizations to Highly Substituted Cyclopentenes.

Science.gov (United States)

Reeves, Ryan D; Phelps, Alicia M; Raimbach, William A T; Schomaker, Jennifer M

2017-07-07

Site- and regiocontrolled Au-catalyzed allene carbocyclizations furnish highly substituted cyclopentenes in >1:1 dr. Significant substitution on the substrate is tolerated, with potential to install five contiguous stereocenters after alkene functionalization. Major challenges include identifying a Au/Cu catalyst that controls both the relative rates of allene epimerization/cyclization and the facial selectivity in addition of a metal enolate to the allene. Experiments to achieve stereodivergent cyclizations and transform key cyclopentenes into useful synthetic building blocks are described.

Allen Ginsberg kirjutab Ameerikast

Index Scriptorium Estoniae

2003-01-01

Arvustus: Ginsberg, Allen. Ameerika : valik luuletusi 1947-1996 / koostanud ja toimetanud Hasso Krull ; inglise keelest tõlkinud Contra, Lauri Kitsnik, Hasso Krull, Andres Langemets, Margit Langemets, Jürgen Rooste, Tõnu Õnnepalu. Tallinn : Perioodika, 2003

76 FR 36318 - Safety Zone; Waterway Closure, Morgan City-Port Allen Route From Mile Marker 0 to Port Allen Lock

Science.gov (United States)

2011-06-22

... Executive Order 13045, Protection of Children from Environmental Health Risks and Safety Risks. This rule is not an economically significant rule and does not create an environmental risk to health or risk to...-AA00 Safety Zone; Waterway Closure, Morgan City-Port Allen Route From Mile Marker 0 to Port Allen Lock...

Photolysis of allene-ozone mixtures at 647 nm in cryogenic matrices. Part 1. Formation of allene oxide

Science.gov (United States)

Singmaster, Karen A.; Pimentel, George C.

1989-03-01

Matrix studies of the photolytic reaction at 647 nm between allene and ozone were carried out at 12 K. Primary photoproducts include carbon monoxide, acrolein ( cis and trans), cyclopropanone, ketene, ethylene, allene oxide and formaldehyde. In Ar and Kr matrices both acrolein and cyclopropanone are produced in high yields, whereas in Xe matrices cyclopropanone is the major product. Infrared spectra for cyclopropanone and its oxygen-18 and deuterium substitutes are reported. The carbonyl stretch for cyclopropanone is observed at 1815 cm -1 in an Ar matrix. Also reported is the first synthesis of allene oxide. The carbon—carbon double bond stretch is observed at 1823.4 cm -1 and it exhibits a small oxygen-18 shift. The change in product distribution is discussed in terms of heavy atom spin—orbit enhancement of singlet—triplet excitation, so that in xenon reaction takes place on a triplet surface, whereas in argon it occurs on a singlet surface.

33 CFR 80.1440 - Port Allen, Kauai, HI.

Science.gov (United States)

2010-07-01

... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Port Allen, Kauai, HI. 80.1440 Section 80.1440 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Pacific Islands § 80.1440 Port Allen, Kauai, HI. A line drawn from...

Rate Coefficients of the Reaction of OH with Allene and Propyne at High Temperatures

KAUST Repository

Es-sebbar, Et-touhami

2016-09-28

Allene (H2C═C═CH2; a-C3H4) and propyne (CH3C≡CH; p-C3H4) are important species in various chemical environments. In combustion processes, the reactions of hydroxyl radicals with a-C3H4 and p-C3H4 are critical in the overall fuel oxidation system. In this work, rate coefficients of OH radicals with allene (OH + H2C═C═CH2 → products) and propyne (OH + CH3C≡CH → products) were measured behind reflected shock waves over the temperature range of 843–1352 K and pressures near 1.5 atm. Hydroxyl radicals were generated by rapid thermal decomposition of tert-butyl hydroperoxide ((CH3)3–CO–OH), and monitored by narrow line width laser absorption of the well-characterized R1(5) electronic transition of the OH A–X (0,0) electronic system near 306.7 nm. Results show that allene reacts faster with OH radicals than propyne over the temperature range of this study. Measured rate coefficients can be expressed in Arrhenius form as follows: kallene+OH(T) = 8.51(±0.03) × 10–22T3.05 exp(2215(±3)/T), T = 843–1352 K; kpropyne+OH(T) = 1.30(±0.07) × 10–21T3.01 exp(1140(±6)/T), T = 846–1335 K.

Relativistic electron dropout echoes induced by interplanetary shocks

Science.gov (United States)

Schiller, Q.; Kanekal, S. G.; Boyd, A. J.; Baker, D. N.; Blake, J. B.; Spence, H. E.

2017-12-01

Interplanetary shocks that impact Earth's magnetosphere can produce immediate and dramatic responses in the trapped relativistic electron population. One well-studied response is a prompt injection capable of transporting relativistic electrons deep into the magnetosphere and accelerating them to multi-MeV energies. The converse effect, electron dropout echoes, are observations of a sudden dropout of electron fluxes observed after the interplanetary shock arrival. Like the injection echo signatures, dropout echoes can also show clear energy dispersion signals. They are of particular interest because they have only recently been observed and their causal mechanism is not well understood. In the analysis presented here, we show observations of electron drift echo signatures from the Relativistic Electron-Proton Telescope (REPT) and Magnetic Electron and Ion Sensors (MagEIS) onboard NASA's Van Allen Probes mission, which show simultaneous prompt enhancements and dropouts within minutes of the associated with shock impact. We show that the observations associated with both enhancements and dropouts are explained by the inward motion caused by the electric field impulse induced by the interplanetary shock, and either energization to cause the enhancement, or lack of a seed population to cause the dropout.

Recent progress in predicting structural and electronic properties of organic solids with the van der Waals density functional

Energy Technology Data Exchange (ETDEWEB)

Yanagisawa, Susumu, E-mail: shou@sci.u-ryukyu.ac.jp [Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213 (Japan); Okuma, Koji; Inaoka, Takeshi [Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213 (Japan); Hamada, Ikutaro, E-mail: Hamada.Ikutaro@nims.go.jp [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Tsukuba 305-0044 (Japan)

2015-10-01

Highlights: • Review of theoretical studies on organic solids with the density-functional methods. • van der Waals (vdW)-inclusive methods to predict cohesive properties of oligoacenes. • A variant of the vdW density functional describes the structures accurately. • The molecular configuration and conformation crucially affects the band dispersion. - Abstract: We review recent studies on electronic properties of the organic solids with the first-principles electronic structure methods, with the emphasis on the roles of the intermolecular van der Waals (vdW) interaction in electronic properties of the organic semiconductors. After a brief summary of the recent vdW inclusive first-principle theoretical methods, we discuss their performance in predicting cohesive properties of oligoacene crystals as examples of organic crystals. We show that a variant of the van der Waals density functional describes structure and energetics of organic crystals accurately. In addition, we review our recent study on the zinc phthalocyanine crystal and discuss the importance of the intermolecular distance and orientational angle in the band dispersion. Finally, we draw some general conclusions and the future perspectives.

Recent progress in predicting structural and electronic properties of organic solids with the van der Waals density functional

International Nuclear Information System (INIS)

Yanagisawa, Susumu; Okuma, Koji; Inaoka, Takeshi; Hamada, Ikutaro

2015-01-01

Highlights: • Review of theoretical studies on organic solids with the density-functional methods. • van der Waals (vdW)-inclusive methods to predict cohesive properties of oligoacenes. • A variant of the vdW density functional describes the structures accurately. • The molecular configuration and conformation crucially affects the band dispersion. - Abstract: We review recent studies on electronic properties of the organic solids with the first-principles electronic structure methods, with the emphasis on the roles of the intermolecular van der Waals (vdW) interaction in electronic properties of the organic semiconductors. After a brief summary of the recent vdW inclusive first-principle theoretical methods, we discuss their performance in predicting cohesive properties of oligoacene crystals as examples of organic crystals. We show that a variant of the van der Waals density functional describes structure and energetics of organic crystals accurately. In addition, we review our recent study on the zinc phthalocyanine crystal and discuss the importance of the intermolecular distance and orientational angle in the band dispersion. Finally, we draw some general conclusions and the future perspectives.

Chemoselective allene aziridination via Ag(I) catalysis.

Science.gov (United States)

Rigoli, Jared W; Weatherly, Cale D; Vo, Brian T; Neale, Samuel; Meis, Alan R; Schomaker, Jennifer M

2013-01-18

Allene aziridination generates useful bicyclic methylene aziridine scaffolds that can be flexibly transformed into a range of stereochemically complex and densely functionalized amine-containing stereotriads. The scope of this chemistry has been limited by the poor chemoselectivity that often results when typical dinuclear Rh(II) catalysts are employed with homoallenic carbamates. Herein, Ag(I) catalysts that significantly improve the scope and yield of bicyclic methylene aziridines that can be prepared via allene aziridination are described.

The storm time ring current dynamics and response to CMEs and CIRs using Van Allen Probes observations and CIMI simulations

Science.gov (United States)

Mouikis, Christopher; Bingham, Samuel; Kistler, Lynn; Spence, Harlan; Gkioulidou, Matina

2017-04-01

The ring current responds differently to the different solar and interplanetary storm drivers such as coronal mass injections, (CME's), and co-rotating interaction regions (CIR's). Using Van Allen Probes observations, we develop an empirical ring current model of the ring current pressure, the pressure anisotropy and the current density development during the storm phases for both types of storm drivers and for all MLTs inside L 6. Delineating the differences in the ring current development between these two drivers will aid our understanding of the ring current dynamics. We find that during the storm main phase most of the ring current pressure in the pre-midnight inner magnetosphere is contributed by particles on open drift paths that cause the development of a strong partial ring current that causes most of the main phase Dst drop. These particles can reach as deep as L 2 and their pressure compares to the local magnetic field pressure as deep as L 3. During the recovery phase, if these particles are not lost at the magnetopause, will become trapped and will contribute to the symmetric ring current. However, the largest difference between the CME and CIR ring current responses during the storm main and early recovery phases is caused by how the 15 - 60 keV O+ responds to these drivers. This empirical model is compared to the results of CIMI simulations of a CMEs and a CIRs where the model input is comprised of the superposed epoch solar wind conditions of the storms that comprise the empirical model. Different inner magnetosphere boundary conditions are tested in order to match the empirical model results. Comparing the model and simulation results improves our understanding of the ring current dynamics as part of the highly coupled inner magnetosphere system. In addition, within the framework of this empirical model, the prediction of the EMIC wave generation linear theory is tested using the observed plasma parameters and comparing with the observations of

First evidence for correlations between electron fluxes measured by NOAA-POES satellites and large seismic events

International Nuclear Information System (INIS)

Battiston, Roberto; Vitale, Vincenzo

2013-01-01

We present the result for the search of correlations between the precipitation of low energy electrons (E>0.3MeV) trapped within the Van Allen Belts and earthquakes with magnitude above 5 Richter scale. We used the electron data measured by the NOAA POES 15,16,17 and 18 satellites collected during a period of 13 years, corresponding to about 18 thousands M>5 earthquakes registered in the NEIC catalog of the U.S. Geological Survey. We defined Particle Burst (PB) the fluctuations of electrons counting rate having a probability −6 of being a statistical fluctuation. The observed correlation involves about 1.410 −3 of the earthquakes in that period of time. It provides the first statistically convincing evidence for the existence of a detectable coupling mechanism between the lithosphere and the magnetosphere having well defined time characteristics

Interview of David Elliston Allen

OpenAIRE

Allen, David

2009-01-01

Interviewed on 12 April 1983 by Jack Goody and Alan Macfarlane and filmed and edited by Sarah Harrison. Made on old and low quality equipment. An interview of the historian and naturalist David Elliston Allen

Observations Directly Linking Relativistic Electron Microbursts to Whistler Mode Chorus: Van Allen Probes and FIREBIRD II

Czech Academy of Sciences Publication Activity Database

Breneman, A. W.; Crew, A.; Sample, J.; Klumpar, D.; Johnson, A.; Agapitov, O.; Shumko, M.; Turner, D. L.; Santolík, Ondřej; Wygant, J. R.; Cattell, C. A.; Thaller, S. A.; Blake, B.; Spence, H.; Kletzing, C. A.

2017-01-01

Roč. 44, č. 22 (2017), s. 11265-11272 ISSN 0094-8276 R&D Projects: GA ČR GA17-07027S Grant - others:AV ČR(CZ) AP1401 Program:Akademická prémie - Praemium Academiae Institutional support: RVO:68378289 Keywords : VLF-CHORUS * RADIATION BELT * ZONE ELECTRONS * SOURCE REGION * AURORAL-ZONE * GEM STORMS * PRECIPITATION * ASSOCIATION * RESOLUTION * EMISSIONS Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 4.253, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/2017GL075001/epdf

Effects of Drift-Shell Splitting by Chorus Waves on Radiation Belt Electrons

Science.gov (United States)

Chan, A. A.; Zheng, L.; O'Brien, T. P., III; Tu, W.; Cunningham, G.; Elkington, S. R.; Albert, J.

2015-12-01

Drift shell splitting in the radiation belts breaks all three adiabatic invariants of charged particle motion via pitch angle scattering, and produces new diffusion terms that fully populate the diffusion tensor in the Fokker-Planck equation. Based on the stochastic differential equation method, the Radbelt Electron Model (REM) simulation code allows us to solve such a fully three-dimensional Fokker-Planck equation, and to elucidate the sources and transport mechanisms behind the phase space density variations. REM has been used to perform simulations with an empirical initial phase space density followed by a seed electron injection, with a Tsyganenko 1989 magnetic field model, and with chorus wave and ULF wave diffusion models. Our simulation results show that adding drift shell splitting changes the phase space location of the source to smaller L shells, which typically reduces local electron energization (compared to neglecting drift-shell splitting effects). Simulation results with and without drift-shell splitting effects are compared with Van Allen Probe measurements.

Vertical electron transport in van der Waals heterostructures with graphene layers

International Nuclear Information System (INIS)

Ryzhii, V.; Otsuji, T.; Ryzhii, M.; Aleshkin, V. Ya.; Dubinov, A. A.; Mitin, V.; Shur, M. S.

2015-01-01

We propose and analyze an analytical model for the self-consistent description of the vertical electron transport in van der Waals graphene-layer (GL) heterostructures with the GLs separated by the barriers layers. The top and bottom GLs serve as the structure emitter and collector. The vertical electron transport in such structures is associated with the propagation of the electrons thermionically emitted from GLs above the inter-GL barriers. The model under consideration describes the processes of the electron thermionic emission from and the electron capture to GLs. It accounts for the nonuniformity of the self-consistent electric field governed by the Poisson equation which accounts for the variation of the electron population in GLs. The model takes also under consideration the cooling of electrons in the emitter layer due to the Peltier effect. We find the spatial distributions of the electric field and potential with the high-electric-field domain near the emitter GL in the GL heterostructures with different numbers of GLs. Using the obtained spatial distributions of the electric field, we calculate the current-voltage characteristics. We demonstrate that the Peltier cooling of the two-dimensional electron gas in the emitter GL can strongly affect the current-voltage characteristics resulting in their saturation. The obtained results can be important for the optimization of the hot-electron bolometric terahertz detectors and different devices based on GL heterostructures

Woody Allen, serial schlemiel ?

Directory of Open Access Journals (Sweden)

Frédérique Brisset

2011-04-01

Full Text Available Woody Allen a développé au fil des années une persona cinématographique de schlemiel new-yorkais aisément reconnaissable par le spectateur. Elle marque nombre de ses films, qu’il y apparaisse en tant qu’acteur ou y dirige des substituts comédiens comme déclinaisons de lui-même. Si cette figure prototypique est le fondement de la sérialité dans sa filmographie, il est des traits stylistiques qui en portent trace tout au long de son œuvre : la récurrence annuelle de ses réalisations, la signature formelle symbolisée par ses génériques à la typographie singulière, le rythme de ses dialogues ponctués d’interjections et l’usage de l’autocitation sont autant de procédés qui marquent son cinéma d’un sceau très personnel. Ils fonctionnent comme des clins d’œil au spectateur qui reçoit dès lors LE Woody Allen millésimé comme une invitation à retrouver son microcosme. Ainsi la sérialité se pose comme à la fois initiale et conséquentielle de son système filmique, processus de création unique dans le cinéma américain.Woody Allen has long constructed a cinematographic persona of schlemiel New- Yorker that the audience can easily identify. It impacts most of his films, whether he stars in them or directs “substitute” actors to impersonate his character. If this prototypical figure is the basis of seriality in his cinematography, serial stylistic features can also be found all along his career: the annual recurrence of his productions, the formal signature symbolised by the typography of his singular credit titles, his rhythmical interjection-punctuated dialogues and the use of self-quotation imprint a very personal seal upon his movies. They all work as a recognition signals for the audience who thus receive THE Woody Allen vintage as an invitation to re-enter his microcosm. Seriality is then both initial and consequential to his cinematographic system, a unique creative process in American film history.

Using a Neural Network Approach to Find Unusual Butterfly Pitch Angle Distribution Shapes

Science.gov (United States)

Medeiros, C.; Sibeck, D. G.; Souza, V. M. C. E. S.; Vieira, L.; Alves, L. R.; Da Silva, L. A.; Kanekal, S. G.; Baker, D. N.

2017-12-01

A special kind of neural network referred to as a Self-Organizing Map (SOM) was previously adopted to identify, in pitch angle-resolved relativistic electron flux data provided by the REPT instrument onboard the Van Allen Probes, three major types of electron pitch angle distributions (PADs), namely 90o-peaked, butterfly and flattop (Souza et al., 2016), following the classification scheme employed by Gannon et al. (2007). Previous studies show that butterfly distribution can be found in more than one shape. They usually exhibit an intense decrease near 90° pitch angles compared to the peaks usually around 30° and 150°. Sometimes unusual butterfly PAD shapes with peaks near 45° and 135° pitch angles can be observed. These could be correlated with different physical processes that govern the production and loss of energetic particles in the Van Allen radiation belt. A neural network approach allows the distinction of different kinds of butterfly PADs which were not analyzed in detail by Souza et al. (2016). This study uses SOM methodology to find these unusual butterfly PAD shape during the interval between January 1, 2014 and October 1, 2015, during which Van Allen Probes orbit covered all MLT. The spatial and temporal occurrence of these events were investigated as well as their solar wind and magnetospheric drivers.

Space Weather Effects in the Earth's Radiation Belts

Science.gov (United States)

Baker, D. N.; Erickson, P. J.; Fennell, J. F.; Foster, J. C.; Jaynes, A. N.; Verronen, P. T.

2018-02-01

The first major scientific discovery of the Space Age was that the Earth is enshrouded in toroids, or belts, of very high-energy magnetically trapped charged particles. Early observations of the radiation environment clearly indicated that the Van Allen belts could be delineated into an inner zone dominated by high-energy protons and an outer zone dominated by high-energy electrons. The energy distribution, spatial extent and particle species makeup of the Van Allen belts has been subsequently explored by several space missions. Recent observations by the NASA dual-spacecraft Van Allen Probes mission have revealed many novel properties of the radiation belts, especially for electrons at highly relativistic and ultra-relativistic kinetic energies. In this review we summarize the space weather impacts of the radiation belts. We demonstrate that many remarkable features of energetic particle changes are driven by strong solar and solar wind forcings. Recent comprehensive data show broadly and in many ways how high energy particles are accelerated, transported, and lost in the magnetosphere due to interplanetary shock wave interactions, coronal mass ejection impacts, and high-speed solar wind streams. We also discuss how radiation belt particles are intimately tied to other parts of the geospace system through atmosphere, ionosphere, and plasmasphere coupling. The new data have in many ways rewritten the textbooks about the radiation belts as a key space weather threat to human technological systems.

Photochemical generation and 1H NMR detection of alkyl allene oxides in solution

International Nuclear Information System (INIS)

Breen, L.E.; Schepp, N.P.; Tan, C.-H.E.

2005-01-01

Irradiation of substituted 5-alkyl-4,5-epoxyvalerophenones leads to the formation of alkyl allene oxides that, in some cases, are sufficiently long-lived to be detected at room temperature by 1 H NMR spectroscopy. Absolute lifetime measurements show that the size of the alkyl group has a significant influence on the reactivity of the allene oxide, with tert-butyl allene oxide having a lifetime of 24 h in CD 3 CN at room temperature that is considerably longer than the 1.5 h lifetime of the ethyl allene oxide. The allene oxides react rapidly with water to give α-hydroxyketones. The mechanism involves nucleophilic attack to the epoxide carbon to give an enol, which can also be detected as an intermediate by 1 H NMR spectroscopy. (author)

Astronauts Allen and Gemar during extravehicular activity (EVA) training in CCT

Science.gov (United States)

1994-01-01

Astronauts Charles D. (Sam) Gemar, and Andrew M. Allen participate in a training exercise at JSC's Crew Compartment Trainer (CCT), located in the Space Vehicle Mockup Facility. Gemar sits inside the airlock as Allen reviews procedures for EVA.

Mapping lightning discharges on Earth with lightning-generated whistlers wave emission in space and their effects on radiation belt electrons

Science.gov (United States)

Farges, T.; Ripoll, J. F.; Santolik, O.; Kolmasova, I.; Kurth, W. S.; Hospodarsky, G. B.; Kletzing, C.

2017-12-01

It is widely accepted that the slot region of the Van Allen radiation belts is sculpted by the presence of whistler mode waves especially by plasmaspheric hiss emissions. In this work, we investigate the role of lightning-generated whistler waves (LGW), which also contribute to scatter electrons trapped in the plasmaphere but, in general, to a lesser extent due to their low mean amplitude and occurrence rate. Our goal is to revisit the characterization of LGW occurrence in the Earth's atmosphere and in space as well as the computation of LGW effects by looking at a series of particular events, among which intense events, in order to characterize maximal scattering effects. We use multicomponent measurements of whistler mode waves by the Waves instrument of Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) onboard the Van Allen Probes spacecraft as our primary data source. We combine this data set with local measurements of the plasma density. We also use the data of the World Wide Lightning Location Network in order to localize the source of lightning discharges on Earth and their radiated energy, both locally at the footprint of the spacecraft and, globally, along the drift path. We discuss how to relate the signal measured in space with the estimation of the power emitted in the atmosphere and the associated complexity. Using these unique data sets we model the coefficients of quasi-linear pitch angle diffusion and we estimate effects of these waves on radiation belt electrons. We show evidence that lightning generated whistlers can, at least in some cases, influence the radiation belt dynamics.

OLED : de opvolger van LED staat al te trappelen

NARCIS (Netherlands)

Zeiler, W.

2009-01-01

Waren de laatste decennia van de vorige eeuw het ''silicon' tijdperk, nu is het tijdperk van de plastic elektronica aangebroken. De vierde internationale editie van de Plastic Electronics Conference 2008 in Berlijn gaf een recent overzicht van het onderzoek, en waar de wetenschappers mee bezig zijn

Frances Allen Wins Turing Award

Indian Academy of Sciences (India)

Home; Journals; Resonance – Journal of Science Education; Volume 12; Issue 8. Frances Allen Wins Turing Award. Priti Shankar. Article-in-a-Box Volume 12 Issue 8 August 2007 pp ... Author Affiliations. Priti Shankar1. Department of Computer Science and Automation, Indian Institute of Science, Bangalore 560 012, India ...

Magnetic behavior of Van Vleck ions and an electron gas interacting by exchange

International Nuclear Information System (INIS)

Palermo, L.; Silva, X.A. da.

1980-01-01

The magnetic behavior of a model in which Van Vleck ions, under the action of a crystal field, interacting by exchange with an electron gas is investigated. The condition of onset of ferromagnetism and the behavior of the critical temperature, band and ionic magnetizations (and susceptibilities) versus temperature, as a function of the band width, exchange interaction and the crystal field splitting energy parameters are obtained within an approximation equivalent to a molecular field formulation. (Author) [pt

Memory and Nostalgia in Woody Allen’s "Midnight in Paris" (Memoria y nostalgia en "Medianoche en París" de Woody Allen

Directory of Open Access Journals (Sweden)

Peter Eubanks

2015-06-01

Full Text Available Abstract: Woody Allen´s recent "Midnight in Paris" describes a Paris that has as many identities as there are observers to ascribe them. Indeed, there is no one, true Paris that everyone objectively shares; Paris, in Allen´s film, exists only in the phenomenology of the observer’s perception, a perception often marred and made unreliable by an escapist need to withdraw from the present in order to take shelter in a glorified, utopian past. Allen thus criticizes the nostalgic impulse, the "Golden-Age thinking" (as it is called in the film that forces various characters simultaneously to inhabit two worlds, that of a prelapsarian past and that of the fallen present. His protagonist´s journey back and forth between the present and the idealized Roaring Twenties is everyman´s journey, the sometimes surreal voyage between reality and imagination, between the world actually inhabited and the world artificially constructed for oneself. Yet it is when Allen´s protagonist finally discovers nostalgia within his nostalgia, a longing within his longing, that he recognizes the flawed thinking behind his almost mythologized perception of the past, reflecting everyman´s realization that the past is ultimately the expression of our present needs.Resumen: Uno de los films recientes de Woody Allen, "Midnight in Paris", describe un París que tiene tantas identidades como observadores hay a quienes atribuirlos. De hecho, no hay un París auténtico que compartan todos. París, en el film de Allen, solo existe en la fenomenología de la percepción del observador, una percepción con frecuencia dañada/arruinada y realizada poco fidedigna por una necesidad escapista a retirarse del presente para refugiarse en un pasado glorificado, utópico. Así Allen critica el impulso nostálgico, la idea del "pensamiento del siglo de oro" (tal y como viene a ser llamado en el film que obliga a que varios personajes residan en dos mundos al mismo tiempo: el de un mundo

Tuning electronic transport in epitaxial graphene-based van der Waals heterostructures

Science.gov (United States)

Lin, Yu-Chuan; Li, Jun; de La Barrera, Sergio C.; Eichfeld, Sarah M.; Nie, Yifan; Addou, Rafik; Mende, Patrick C.; Wallace, Robert M.; Cho, Kyeongjae; Feenstra, Randall M.; Robinson, Joshua A.

2016-04-01

Two-dimensional tungsten diselenide (WSe2) has been used as a component in atomically thin photovoltaic devices, field effect transistors, and tunneling diodes in tandem with graphene. In some applications it is necessary to achieve efficient charge transport across the interface of layered WSe2-graphene, a semiconductor to semimetal junction with a van der Waals (vdW) gap. In such cases, band alignment engineering is required to ensure a low-resistance, ohmic contact. In this work, we investigate the impact of graphene electronic properties on the transport at the WSe2-graphene interface. Electrical transport measurements reveal a lower resistance between WSe2 and fully hydrogenated epitaxial graphene (EGFH) compared to WSe2 grown on partially hydrogenated epitaxial graphene (EGPH). Using low-energy electron microscopy and reflectivity on these samples, we extract the work function difference between the WSe2 and graphene and employ a charge transfer model to determine the WSe2 carrier density in both cases. The results indicate that WSe2-EGFH displays ohmic behavior at small biases due to a large hole density in the WSe2, whereas WSe2-EGPH forms a Schottky barrier junction.Two-dimensional tungsten diselenide (WSe2) has been used as a component in atomically thin photovoltaic devices, field effect transistors, and tunneling diodes in tandem with graphene. In some applications it is necessary to achieve efficient charge transport across the interface of layered WSe2-graphene, a semiconductor to semimetal junction with a van der Waals (vdW) gap. In such cases, band alignment engineering is required to ensure a low-resistance, ohmic contact. In this work, we investigate the impact of graphene electronic properties on the transport at the WSe2-graphene interface. Electrical transport measurements reveal a lower resistance between WSe2 and fully hydrogenated epitaxial graphene (EGFH) compared to WSe2 grown on partially hydrogenated epitaxial graphene (EGPH). Using low

Eerste inschatting van vrijkomen van plastics als gevolg van slijtage van Mosselzaad-Invagsystemen (MZI's)

NARCIS (Netherlands)

Hartog, E.; Brink, van den A.M.; Kamermans, P.

2014-01-01

IMARES heeft onderzoek uitgevoerd naar het ontstaan en de aanwezigheid van microplastic zwerfvuil afkomstig van mosselzaad invangsystemen (hierna MZI’s genoemd). Deze studie is onderdeel van een opdracht van het ministerie van EL&I, om de ecologische effecten van opschaling van MZI’s in de

Electronic band structure of Two-Dimensional WS2/Graphene van der Waals Heterostructures

Science.gov (United States)

Henck, Hugo; Ben Aziza, Zeineb; Pierucci, Debora; Laourine, Feriel; Reale, Francesco; Palczynski, Pawel; Chaste, Julien; Silly, Mathieu G.; Bertran, François; Le Fèvre, Patrick; Lhuillier, Emmanuel; Wakamura, Taro; Mattevi, Cecilia; Rault, Julien E.; Calandra, Matteo; Ouerghi, Abdelkarim

2018-04-01

Combining single-layer two-dimensional semiconducting transition-metal dichalcogenides (TMDs) with a graphene layer in van der Waals heterostructures offers an intriguing means of controlling the electronic properties through these heterostructures. Here, we report the electronic and structural properties of transferred single-layer W S2 on epitaxial graphene using micro-Raman spectroscopy, angle-resolved photoemission spectroscopy measurements, and density functional theory (DFT) calculations. The results show good electronic properties as well as a well-defined band arising from the strong splitting of the single-layer W S2 valence band at the K points, with a maximum splitting of 0.44 eV. By comparing our DFT results with local and hybrid functionals, we find the top valence band of the experimental heterostructure is close to the calculations for suspended single-layer W S2 . Our results provide an important reference for future studies of electronic properties of W S2 and its applications in valleytronic devices.

X-ray electron density investigation of chemical bonding in van der Waals materials

Science.gov (United States)

Kasai, Hidetaka; Tolborg, Kasper; Sist, Mattia; Zhang, Jiawei; Hathwar, Venkatesha R.; Filsø, Mette Ø.; Cenedese, Simone; Sugimoto, Kunihisa; Overgaard, Jacob; Nishibori, Eiji; Iversen, Bo B.

2018-03-01

Van der Waals (vdW) solids have attracted great attention ever since the discovery of graphene, with the essential feature being the weak chemical bonding across the vdW gap. The nature of these weak interactions is decisive for many extraordinary properties, but it is a strong challenge for current theory to accurately model long-range electron correlations. Here we use synchrotron X-ray diffraction data to precisely determine the electron density in the archetypal vdW solid, TiS2, and compare the results with density functional theory calculations. Quantitative agreement is observed for the chemical bonding description in the covalent TiS2 slabs, but significant differences are identified for the interactions across the gap, with experiment revealing more electron deformation than theory. The present data provide an experimental benchmark for testing theoretical models of weak chemical bonding.

The Mimas ghost revisited - An analysis of the electron flux and electron microsignatures observed in the vicinity of Mimas at Saturn

Science.gov (United States)

Chenette, D. L.; Stone, E. C.

1983-01-01

An analysis of the electron-absorption signature observed by the cosmic-ray system on Voyager 2 near the orbit of Mimas is presented. It is found that these observations cannot be explained as the absorption signature of Mimas. By combining Pioneer 11 and Voyager 2 measurements of the electron flux at Mimas's orbit (L = 3.1), an electron spectrum is found in which most of the flux above about 100 keV is concentrated near 1 to 3 MeV. This spectral form is qualitatively consistent with the bandpass filter model of Van Allen et al. (1980). The expected Mimas absorption signature is calculated from this spectrum neglecting radial diffusion. Since no Mimas absorption signature was observed in the inbound Voyager 2 data, a lower limit on the diffusion coefficient for MeV electrons at L = 3.1 of D greater than 10 to the -8th sq Saturn radii/sec is obtained. With a diffusion coefficient this large, both the Voyager 2 and the Pioneer 11 small-scale electron-absorption-signature observations in Mimas's orbit are enigmatic. Thus the mechanism for producing these signatures is referred to as the Mimas ghost. A cloud of material in orbit with Mimas may account for the observed electron signature if the cloud is at least 1-percent opaque to electrons across a region extending over a few hundred kilometers.

Relativistic electron dynamics produced by azimuthally localized poloidal mode ULF waves: Boomerang-shaped pitch angle evolutions

Science.gov (United States)

Hao, Y.; Zong, Q.; Zhou, X.; Rankin, R.; Chen, X.; Liu, Y.; Fu, S.; Spence, H. E.; Blake, J. B.; Reeves, G. D.

2017-12-01

We present an analysis of "boomerang-shaped" pitch angle evolutions of outer radiation belt relativistic electrons observed by the Van Allen Probes after the passage of an interplanetary shock on June 7th, 2014. The flux at different pitch angles is modulated by Pc5 waves, with equatorially mirroring electrons reaching the satellite first. For 90º pitch angle electrons, the phase change of the flux modulations across energy exceeds 180º, and increasingly tilts with time. Using estimates of the arrival time of particles of different pitch angles at the spacecraft location, a scenario is investigated in which shock-induced ULF waves interact with electrons through the drift resonance mechanism in a localized region westward of the spacecraft. Numerical calculations on particle energy gain with the modified ULF wave field reproduce the observed boomerang stripes and modulations in the electron energy spectrogram. The study of boomerang stripes and their relationship to drift-resonance taking place at a location different from the observation point adds new understanding of the processes controlling the dynamics of the outer radiation belt.

Relativistic electron dynamics produced by azimuthally localized poloidal mode ULF waves: Boomerang-shaped pitch angle evolutions

International Nuclear Information System (INIS)

Hao, Y. X.; Zong, Q.-G.; Zhou, X.-Z.; Rankin, R.; Chen, X. R.

2017-01-01

Here, we present an analysis of “boomerang-shaped” pitch angle evolutions of outer radiation belt relativistic electrons observed by the Van Allen Probes after the passage of an interplanetary shock on 7 June 2014. The flux at different pitch angles is modulated by Pc5 waves, with equatorially mirroring electrons reaching the satellite first. For 90° pitch angle electrons, the phase change of the flux modulations across energy exceeds 180° and increasingly tilts with time. Using estimates of the arrival time of particles of different pitch angles at the spacecraft location, a scenario is investigated in which shock-induced ULF waves interact with electrons through the drift resonance mechanism in a localized region westward of the spacecraft. Numerical calculations on particle energy gain with the modified ULF wavefield reproduce the observed boomerang stripes and modulations in the electron energy spectrogram. The study of boomerang stripes and their relationship to drift resonance taking place at a location different from the observation point adds new understanding of the processes controlling the dynamics of the outer radiation belt.

Global solution branches for a nonlocal Allen-Cahn equation

Science.gov (United States)

Kuto, Kousuke; Mori, Tatsuki; Tsujikawa, Tohru; Yotsutani, Shoji

2018-05-01

We consider the Neumann problem of a 1D stationary Allen-Cahn equation with nonlocal term. Our previous paper [4] obtained a local branch of asymmetric solutions which bifurcates from a point on the branch of odd-symmetric solutions. This paper derives the global behavior of the branch of asymmetric solutions, and moreover, determines the set of all solutions to the nonlocal Allen-Cahn equation. Our proof is based on a level set analysis for an integral map associated with the nonlocal term.

Mechanism of electron attachment to van der Waals clusters: Application to carbon dioxide clusters

International Nuclear Information System (INIS)

Tsukada, M.; Shima, N.; Tsuneyuki, S.; Kageshima, H.; Kondow, T.

1987-01-01

A theory on the attachment of very slow electrons to van der Waals clusters was developed on the basis of the electronic structure theory, and was applied to clarify the mechanism of the collisional electron transfer from a high-Rydberg atom to a CO 2 cluster. The strong coupled electron--phonon model is found to afford a reasonable mechanism of the attachment. The equilibrium geometry of (CO 2 )/sub N/ (2≤N≤13) clusters are determined and their vertical affinity levels are obtained by the DV-X α-transition state method. Using this information, as well as some plausible assumptions on the values of the coupling constants, the attachment cross section σ is evaluated as a function of the energy of the incident electron. The theory predicts the existence of the threshold cluster size for the attachment and a sharp decrease of σ with the energy, which are consistent with the experimental results

The Brosimum allene: a structural revision.

Science.gov (United States)

Hu, Gaojie; Liu, Kai; Williams, Lawrence J

2008-12-04

Insight derived from a synthetic model, calculated (13)C NMR data, and comparison to experimental data indicate that the proposed allenic structure A, originally assigned to an isolate from Brosimum acutifolium Huber, should be revised to B, a natural product and nonallenic substance, mururin C.

Q & A with Ed Tech Leaders: Interview with Michael W. Allen

Science.gov (United States)

Shaughnessy, Michael F.

2014-01-01

Michael W. Allen, the Chairman and CEO of Allen Interactions, is an architect of interactive multimedia learning and is recognized for his many insights, inventions, and presentations. With over 50 years of experience in e-learning, both in academic and corporate settings, he is known for his role in creating Authorware and overseeing the work of…

Physical mechanism causing rapid changes in ultrarelativistic electron pitch angle distributions right after a shock arrival: Evaluation of an electron dropout event

Science.gov (United States)

Zhang, X.-J.; Li, W.; Thorne, R. M.; Angelopoulos, V.; Ma, Q.; Li, J.; Bortnik, J.; Nishimura, Y.; Chen, L.; Baker, D. N.; Reeves, G. D.; Spence, H. E.; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.; Blake, J. B.; Fennell, J. F.

2016-09-01

Three mechanisms have been proposed to explain relativistic electron flux depletions (dropouts) in the Earth's outer radiation belt during storm times: adiabatic expansion of electron drift shells due to a decrease in magnetic field strength, magnetopause shadowing and subsequent outward radial diffusion, and precipitation into the atmosphere (driven by EMIC wave scattering). Which mechanism predominates in causing electron dropouts commonly observed in the outer radiation belt is still debatable. In the present study, we evaluate the physical mechanism that may be primarily responsible for causing the sudden change in relativistic electron pitch angle distributions during a dropout event observed by Van Allen Probes during the main phase of the 27 February 2014 storm. During this event, the phase space density of ultrarelativistic (>1 MeV) electrons was depleted by more than 1 order of magnitude over the entire radial extent of the outer radiation belt (3 pitch angle distribution under a compressed magnetic field topology based on actual solar wind conditions. Although these ultrarelativistic electrons exhibit highly anisotropic (peaked in 90°), energy-dependent pitch angle distributions, which appear to be associated with the typical EMIC wave scattering, comparison of the modeled electron distribution to electron measurements indicates that drift shell splitting is responsible for this rapid change in electron pitch angle distributions. This further indicates that magnetopause loss is the predominant cause of the electron dropout right after the shock arrival.

Sky-distribution of intensity of synchrotron radio emission of relativistic electrons trapped in Earth’s magnetic field

Directory of Open Access Journals (Sweden)

Klimenko V.V.

2017-12-01

Full Text Available This paper presents the calculations of synchrotron radio emission intensity from Van Allen belts with Gaussian space distribution of electron density across L-shells of a dipole magnetic field, and with Maxwell’s relativistic electron energy distribution. The results of these calculations come to a good agreement with measurements of the synchrotron emission intensity of the artificial radiation belt’s electrons during the Starfish nuclear test. We have obtained two-dimensional distributions of radio brightness in azimuth — zenith angle coordinates for an observer on Earth’s surface. The westside and eastside intensity maxima exceed several times the maximum level of emission in the meridian plane. We have also constructed two-dimensional distributions of the radio emission intensity in decibels related to the background galactic radio noise level. Isotropic fluxes of relativistic electrons (Е~1 MeV should be more than 107 cm–2s–1 for the synchrotron emission intensity in the meridian plane to exceed the cosmic noise level by 0.1 dB (riometer sensitivity threshold.

Optically isolated electronic trigger system for experiments on a subnanosecond time scale with a pulsed Van de Graaff electron accelerator

International Nuclear Information System (INIS)

Luthjens, L.H.; Vermeulen, M.J.W.; Hom, M.L.

1980-01-01

An optically isolated electronic trigger system for a pulsed Van de Graaff electron accelerator, producing an external pretrigger pulse 75 ns before arrival of the electron pulse at the target, is described. The total time jitter between trigger signal and electron pulse is 50 ps. The measurement of optical and electrical transients on a subnanosecond time scale with a sequential sampling oscilloscope is demonstrated. The contribution of various parts of the equipment to the total jitter is discussed. Those contributions to the jitter due to the electron transit time fluctuations in the accelerator assuming a constant acceleration voltage gradient and to the shot noise in the photomultiplier detector of the trigger system are calculated to be 5 ps and 12 to 21 ps respectively. Comparison with the experimental results leads to the conclusion that a considerable part of the total jitter may be attributed to acceleration voltage gradient fluctuations, to accelerator vibrations and possibly to density fluctuations in the insulation gas. Possible improvements of the trigger system are discussed. The apparatus is used for pulse radiolysis experiments with subnanosecond time resolution down to 100 ps in combination with subnanosecond time duration electron pulses

Rejuvenating Allen's Arc with the Geometric Mean.

Science.gov (United States)

Phillips, William A.

1994-01-01

Contends that, despite ongoing criticism, Allen's arc elasticity formula remains entrenched in the microeconomics principles curriculum. Reviews the evolution and continuing scrutiny of the formula. Argues that the use of the geometric mean offers pedagogical advantages over the traditional arithmetic mean approach. (CFR)

Isomer-specific combustion chemistry in allene and propyne flames

Energy Technology Data Exchange (ETDEWEB)

Hansen, Nils; Miller, James A. [Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551 (United States); Westmoreland, Phillip R. [Department of Chem. Engineering, University of Massachusetts, Amherst, MA 01003 (United States); Kasper, Tina [Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551 (United States); Department of Chemistry, Bielefeld University, D-33615 Bielefeld (Germany); Kohse-Hoeinghaus, Katharina [Department of Chemistry, Bielefeld University, D-33615 Bielefeld (Germany); Wang, Juan; Cool, Terrill A. [School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853 (United States)

2009-11-15

A combined experimental and modeling study is performed to clarify the isomer-specific combustion chemistry in flames fueled by the C{sub 3}H{sub 4} isomers allene and propyne. To this end, mole fraction profiles of several flame species in stoichiometric allene (propyne)/O{sub 2}/Ar flames are analyzed by means of a chemical kinetic model. The premixed flames are stabilized on a flat-flame burner under a reduced pressure of 25 Torr (=33.3 mbar). Quantitative species profiles are determined by flame-sampling molecular-beam mass spectrometry, and the isomer-specific flame compositions are unraveled by employing photoionization with tunable vacuum-ultraviolet synchrotron radiation. The temperature profiles are measured by OH laser-induced fluorescence. Experimental and modeled mole fraction profiles of selected flame species are discussed with respect to the isomer-specific combustion chemistry in both flames. The emphasis is put on main reaction pathways of fuel consumption, of allene and propyne isomerization, and of isomer-specific formation of C{sub 6} aromatic species. The present model includes the latest theoretical rate coefficients for reactions on a C{sub 3}H{sub 5} potential [J.A. Miller, J.P. Senosiain, S.J. Klippenstein, Y. Georgievskii, J. Phys. Chem. A 112 (2008) 9429-9438] and for the propargyl recombination reactions [Y. Georgievskii, S.J. Klippenstein, J.A. Miller, Phys. Chem. Chem. Phys. 9 (2007) 4259-4268]. Larger peak mole fractions of propargyl, allyl, and benzene are observed in the allene flame than in the propyne flame. In these flames virtually all of the benzene is formed by the propargyl recombination reaction. (author)

Displacement of ethene from the decamethyltitanocene-ethene complex with internal alkynes, substituent-dependent alkyne-to-allene rearrangement, and the electronic transition relevant to the back-bonding interaction.

Science.gov (United States)

Pinkas, Jiří; Gyepes, Róbert; Císařová, Ivana; Kubišta, Jiří; Horáček, Michal; Mach, Karel

2015-04-28

The titanocene-ethene complex [Ti(II)(η(2)-C2H4)(η(5)-C5Me5)2] (1) with simple internal alkynes R(1)C≡CR(2) gives complexes [Ti(II)(η(2)-R(1)C≡CR(2))(η(5)-C5Me5)2] {R(1), R(2): Ph, Ph (3), Ph, Me (4), Me, SiMe3 (5), Ph, SiMe3 (6), t-Bu, SiMe3 (7), and SiMe3, SiMe3 (8). In contrast, alkynes with R(1) = Me and R(2) = t-Bu or i-Pr afford allene complexes [Ti(II)(η(2)-CH2=C=CHR(2))(η(5)-C5Me5)2] (11) and (12), whereas for R(2) = Et a mixture of alkyne complex (13A) and minor allene (13) is obtained. Crystal structures of 4, 6, 7 and 11 have been determined; the latter structure proved the back-bonding interaction of the allene terminal double bond. Only the synthesis of 8 from 1 was inefficient because the equilibrium constant for the reaction [1] + [Me3SiC≡CSiMe3] ⇌ [8] + [C2H4] approached 1. Compound 9 (R(1), R(2): Me), not obtainable from 1, together with compounds 3–6 and 10 (R(1), R(2): Et) were also prepared by alkyne exchange with 8, however this reaction did not take place in attempts to obtain 7. Compounds 1 and 3–9 display the longest-wavelength electronic absorption band in the range 670-940 nm due to the HOMO → LUMO transition. The assignment of the first excitation to be of predominantly a b2 → a1 transition was confirmed by DFT calculations. The calculated first excitation energies for 3–9 followed the order of hypsochromic shifts of the absorption band relative to 8 that were induced by acetylene substituents: Me > Ph ≫ SiMe3. Computational results have also affirmed the back-bonding nature in the alkyne-to-metal coordination.

Crimes e pecados: Woody Allen, Hollywood e o cinema independente

OpenAIRE

Soares, Marcos; Anjos, Ana Paula B.; Fabris, Marcos

2012-01-01

In this essay we propose an analysis of the film Crimes and Misdemeanors (1989) by Woody Allen in an attempt to focus on its reflections both on the American independent movie production in the 80’s as well as on the conditions of possibility of Allen’s career. Este ensaio traz uma análise do filme Crimes e Pecados (1989) do cineasta Woody Allen que enfatiza suas reflexões tanto sobre a situação do cinema independente no final dos anos 80 nos Estados...

Versterking van de loopbaanladder van leraren : wat kunnen we leren van Singapore?

NARCIS (Netherlands)

Elffers, L.

2015-01-01

In de Lerarenagenda 2013-2020 is een aantal doelstellingen geformuleerd ten aanzien van de bevordering van de loopbaan en professionele ontwikkeling van leraren. Enerzijds wordt ingezet op het stimuleren van professionalisering van leraren na hun initiële opleiding, anderzijds op het versterken van

Out-of-plane heat transfer in van der Waals stacks through electron-hyperbolic phonon coupling

Science.gov (United States)

Tielrooij, Klaas-Jan; Hesp, Niels C. H.; Principi, Alessandro; Lundeberg, Mark B.; Pogna, Eva A. A.; Banszerus, Luca; Mics, Zoltán; Massicotte, Mathieu; Schmidt, Peter; Davydovskaya, Diana; Purdie, David G.; Goykhman, Ilya; Soavi, Giancarlo; Lombardo, Antonio; Watanabe, Kenji; Taniguchi, Takashi; Bonn, Mischa; Turchinovich, Dmitry; Stampfer, Christoph; Ferrari, Andrea C.; Cerullo, Giulio; Polini, Marco; Koppens, Frank H. L.

2018-01-01

Van der Waals heterostructures have emerged as promising building blocks that offer access to new physics, novel device functionalities and superior electrical and optoelectronic properties1-7. Applications such as thermal management, photodetection, light emission, data communication, high-speed electronics and light harvesting8-16 require a thorough understanding of (nanoscale) heat flow. Here, using time-resolved photocurrent measurements, we identify an efficient out-of-plane energy transfer channel, where charge carriers in graphene couple to hyperbolic phonon polaritons17-19 in the encapsulating layered material. This hyperbolic cooling is particularly efficient, giving picosecond cooling times for hexagonal BN, where the high-momentum hyperbolic phonon polaritons enable efficient near-field energy transfer. We study this heat transfer mechanism using distinct control knobs to vary carrier density and lattice temperature, and find excellent agreement with theory without any adjustable parameters. These insights may lead to the ability to control heat flow in van der Waals heterostructures.

Electronic charge rearrangement at metal/organic interfaces induced by weak van der Waals interactions

Science.gov (United States)

Ferri, Nicola; Ambrosetti, Alberto; Tkatchenko, Alexandre

2017-07-01

Electronic charge rearrangements at interfaces between organic molecules and solid surfaces play a key role in a wide range of applications in catalysis, light-emitting diodes, single-molecule junctions, molecular sensors and switches, and photovoltaics. It is common to utilize electrostatics and Pauli pushback to control the interface electronic properties, while the ubiquitous van der Waals (vdW) interactions are often considered to have a negligible direct contribution (beyond the obvious structural relaxation). Here, we apply a fully self-consistent Tkatchenko-Scheffler vdW density functional to demonstrate that the weak vdW interactions can induce sizable charge rearrangements at hybrid metal/organic systems (HMOS). The complex vdW correlation potential smears out the interfacial electronic density, thereby reducing the charge transfer in HMOS, changes the interface work functions by up to 0.2 eV, and increases the interface dipole moment by up to 0.3 Debye. Our results suggest that vdW interactions should be considered as an additional control parameter in the design of hybrid interfaces with the desired electronic properties.

Effect of the van der Waals interaction on the electron energy-loss near edge structure theoretical calculation

Energy Technology Data Exchange (ETDEWEB)

Katsukura, Hirotaka; Miyata, Tomohiro; Tomita, Kota; Mizoguchi, Teruyasu, E-mail: teru@iis.u-tokyo.ac.jp

2017-07-15

The effect of the van der Waals (vdW) interaction on the simulation of the electron energy-loss near edge structure (ELNES) by a first-principles band-structure calculation is reported. The effect of the vdW interaction is considered by the Tkatchenko-Scheffler scheme, and the change of the spectrum profile and the energy shift are discussed. We perform calculations on systems in the solid, liquid and gaseous states. The transition energy shifts to lower energy by approximately 0.1 eV in the condensed (solid and liquid) systems by introducing the vdW effect into the calculation, whereas the energy shift in the gaseous models is negligible owing to the long intermolecular distance. We reveal that the vdW interaction exhibits a larger effect on the excited state than the ground state owing to the presence of an excited electron in the unoccupied band. Moreover, the vdW effect is found to depend on the local electron density and the molecular coordination. In addition, this study suggests that the detection of the vdW interactions exhibited within materials is possible by a very stable and high resolution observation. - Highlights: • Effect of van der Waals (vdW) interaction in ELNES calculation is investigated. • The vdW interaction influences more to the excited state owing to the presence of excited electron. • The vdW interaction makes spectral shift to lower energy side by 0.1–0.01 eV. • The vdW interaction is negligible in gaseous materials due to long intermolecular distance.

Diagnostic accuracy of guys Hospital stroke score (allen score) in acute supratentorial thrombotic/haemorrhagic stroke

International Nuclear Information System (INIS)

Zulfiqar, A.; Toori, K. U.; Khan, S. S.; Hamza, M. I. M.; Zaman, S. U.

2006-01-01

A consecutive series of 103 patients, 58% male with mean age of 62 year (range 40-75 years), admitted with supratentorial stroke in our teaching hospital were studied. All patients had Computer Tomography scan brain done after clinical evaluation and application of Allen stroke score. Computer Tomography Scan confirmed thrombotic stroke in 55 (53%) patients and haemorrhagic stroke in 48 (47%) patients. Out of the 55 patients with definitive thrombotic stroke on Computer Tomography Scan, Allen stroke score suggested infarction in 67%, haemorrhage in 6% and remained inconclusive in 27% of cases. In 48 patients with definitive haemorrhagic stroke on Computer Tomography Scan, Allen stroke score suggested haemorrhage in 60%, infarction in 11% and remained inconclusive in 29% of cases. The overall accuracy of Allen stroke score was 66%. (author)

Duurzame inzetbaarheid van ouderen: resultaten van de eerste twee metingen van STREAM

NARCIS (Netherlands)

Heuvel, S. van den; Ybema, J.F; Leijten, F.; Wind, A. de

2013-01-01

In deze notitie richten we ons op voorspellers van duurzame inzetbaarheid, waarbij we gebruik maken van de resultaten van de eerste twee metingen van STREAM en van een interviewstudie bij deelnemers aan STREAM. Meer specifiek gaan we na hoe personen met gezondheidsproblemen toch productief kunnen

Van der Waals epitaxy of functional MoO{sub 2} film on mica for flexible electronics

Energy Technology Data Exchange (ETDEWEB)

Ma, Chun-Hao [Department of Electrical Engineering, National Tsing Hua University, 30013 Hsinchu, Taiwan (China); Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Lin, Jheng-Cyuan [Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China); Liu, Heng-Jui; Do, Thi Hien [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Zhu, Yuan-Min; Zhan, Qian [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Ha, Thai Duy; Juang, Jenh-Yih [Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan (China); He, Qing [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Arenholz, Elke [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Chiu, Po-Wen, E-mail: pwchiu@ee.nthu.edu.tw [Department of Electrical Engineering, National Tsing Hua University, 30013 Hsinchu, Taiwan (China); Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan (China); Chu, Ying-Hao, E-mail: yhc@nctu.edu.tw [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China); Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan (China)

2016-06-20

Flexible electronics have a great potential to impact consumer electronics and with that our daily life. Currently, no direct growth of epitaxial functional oxides on commercially available flexible substrates is possible. In this study, in order to address this challenge, muscovite, a common layered oxide, is used as a flexible substrate that is chemically similar to typical functional oxides. We fabricated epitaxial MoO{sub 2} films on muscovite via pulsed laser deposition technique. A combination of X-ray diffraction and transmission electron microscopy confirms van der Waals epitaxy of the heterostructures. The electrical transport properties of MoO{sub 2} films are similar to those of the bulk. Flexible or free-standing MoO{sub 2} thin film can be obtained and serve as a template to integrate additional functional oxide layers. Our study demonstrates a remarkable concept to create flexible electronics based on functional oxides.

Bepaling van de kwaliteit van reinigingsprocessen.

NARCIS (Netherlands)

Terpstra, P.M.J.

1993-01-01

Ingegaan wordt op de operationalisering van het begrip schoon voor verschillende toepassingen. Daarna worden twee recent ontwikkelde onderzoekmethoden gepresenteerd voor de meting van respectievelijk het reinigingseffect van textiel reinigen en het reinigen van harde vloeroppervlakken en enkele met

Estudo da resistência do tendão do supra-espinal com pontos simples, duplos e Mason Allen Study on the resistance of the supraspinous tendon using simple, matress and mason allen stitches

Directory of Open Access Journals (Sweden)

Roberto Yukio Ikemoto

2010-01-01

Full Text Available OBJETIVO: O objetivo do trabalho foi comparar a resistência entre os pontos simples, duplo e Mason-Allen modificado, utilizados para o reparo do manguito rotador, e verificar se há diferença significativa que justifique a utilização do ponto do tipo Mason-Allen modificado ao invés dos pontos simples ou duplo. MÉTODO: Retiramos tendões do músculo supra-espinal de 15 cadáveres humanos frescos (30 ombros, com a média de idade de 45 anos. Os testes foram realizados na máquina universal de ensaio mecânico Kratos® 500/2000 e os resultados submetidos aos testes estatísticos de t-student, análise de variância (ANOVA, comparação múltipla de Bonferroni e calculadas as correlações de Pearson. Os testes foram realizados ao nível de significância de 5%. RESULTADOS: Não houve diferença significativa com relação à idade, ao tamanho das amostras e deslocamento do tendão. A resistência variou com média de 127,50 N com o ponto simples, 163,95 N com o duplo e com o ponto de Mason-Allen modificado esta foi de 198,45 N. CONCLUSÃO: não existe diferença da resistência no tendão quanto à falha na interface sutura - tendão comparando-se o ponto duplo com o Mason-Allen modificado e os pontos simples e duplo, porém há diferença quando comparados os pontos simples e Mason-Allen modificado.OBJECTIVE: The purpose of this study was to compare the rotator cuff tendon resistance at the interface tendon-suture using three different sorts of stitches (simple, mattress and modified Mason-Allen. METHODS: To do this, 30 rotator cuffs were totally dissected from 15 specimens, which were 45 years old on average. The tests were done using a Kratos® 500/2000 machine and the statistical analyses applied were the Student t-test, ANOVA test, Multiple Bonferroni Comparison, and Pearson's correlation coefficients; all the analyses used a significance level of 5%. RESULTS: No significant difference was observed regarding the age, sample sizes and

Verbeteren van functionele fitheid van brandweermensen

NARCIS (Netherlands)

van Orden, Claudia Y.D.

Posterpresentatie over IAG4-project 'Functional Fitness Monitor', een methodiek voor het verbeteren van functionele fitheid van brandweermensen door een combinatie van meten, presenteren van feedback en coaching. Gepresenteerd op Symposium Healthy Work: Good for Business, gehouden op 29 april 2016

Diastereoselective Synthesis of the Aminocyclitol Core of Jogyamycin via an Allene Aziridination Strategy.

Science.gov (United States)

Gerstner, Nels C; Adams, Christopher S; Grigg, R David; Tretbar, Maik; Rigoli, Jared W; Schomaker, Jennifer M

2016-01-15

Oxidative allene amination provides rapid access to densely functionalized amine-containing stereotriads through highly reactive bicyclic methyleneaziridine intermediates. This strategy has been demonstrated as a viable approach for the construction of the densely functionalized aminocyclitol core of jogyamycin, a natural product with potent antiprotozoal activity. Importantly, the flexibility of oxidative allene amination will enable the syntheses of modified aminocyclitol analogues of the jogyamycin core.

Gold Redox Catalysis through Base-Initiated Diazonium Decomposition toward Alkene, Alkyne, and Allene Activation.

Science.gov (United States)

Dong, Boliang; Peng, Haihui; Motika, Stephen E; Shi, Xiaodong

2017-08-16

The discovery of photoassisted diazonium activation toward gold(I) oxidation greatly extended the scope of gold redox catalysis by avoiding the use of a strong oxidant. Some practical issues that limit the application of this new type of chemistry are the relative low efficiency (long reaction time and low conversion) and the strict reaction condition control that is necessary (degassing and inert reaction environment). Herein, an alternative photofree condition has been developed through Lewis base induced diazonium activation. With this method, an unreactive Au I catalyst was used in combination with Na 2 CO 3 and diazonium salts to produce a Au III intermediate. The efficient activation of various substrates, including alkyne, alkene and allene was achieved, followed by rapid Au III reductive elimination, which yielded the C-C coupling products with good to excellent yields. Relative to the previously reported photoactivation method, our approach offered greater efficiency and versatility through faster reaction rates and broader reaction scope. Challenging substrates such as electron rich/neutral allenes, which could not be activated under the photoinitiation conditions (<5 % yield), could be activated to subsequently yield the desired coupling products in good to excellent yield. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Allene oxide synthase, allene oxide cyclase and jasmonic acid levels in Lotus japonicus nodules.

Directory of Open Access Journals (Sweden)

Anna Zdyb

Full Text Available Jasmonic acid (JA, its derivatives and its precursor cis-12-oxo phytodienoic acid (OPDA form a group of phytohormones, the jasmonates, representing signal molecules involved in plant stress responses, in the defense against pathogens as well as in development. Elevated levels of JA have been shown to play a role in arbuscular mycorrhiza and in the induction of nitrogen-fixing root nodules. In this study, the gene families of two committed enzymes of the JA biosynthetic pathway, allene oxide synthase (AOS and allene oxide cyclase (AOC, were characterized in the determinate nodule-forming model legume Lotus japonicus JA levels were to be analysed in the course of nodulation. Since in all L. japonicus organs examined, JA levels increased upon mechanical disturbance and wounding, an aeroponic culture system was established to allow for a quick harvest, followed by the analysis of JA levels in whole root and shoot systems. Nodulated plants were compared with non-nodulated plants grown on nitrate or ammonium as N source, respectively, over a five week-period. JA levels turned out to be more or less stable independently of the growth conditions. However, L. japonicus nodules formed on aeroponically grown plants often showed patches of cells with reduced bacteroid density, presumably a stress symptom. Immunolocalization using a heterologous antibody showed that the vascular systems of these nodules also seemed to contain less AOC protein than those of nodules of plants grown in perlite/vermiculite. Hence, aeroponically grown L. japonicus plants are likely to be habituated to stress which could have affected JA levels.

Modeling of Jupiter's electron an ion radiation belts

International Nuclear Information System (INIS)

Sicard, Angelica

2004-01-01

In the Fifties, James Van Allen showed the existence of regions of the terrestrial magnetosphere consisted of energetic particles, trapped by the magnetic field: the radiation belts. The radiation belts of the Earth were the subject of many modeling works and are studied since several years at the Departement Environnement Spatial (DESP) of ONERA. In 1998, the DESP decided to adapt the radiation belts model of the Earth, Salammbo, to radiation environment of Jupiter. A first thesis was thus carried out on the subject and a first radiation belts model of electrons of Jupiter was developed [Santos-Costa, 2001]. The aim of this second thesis is to develop a radiation belts model for protons and heavy ions. In order to validate the developed model, the comparisons between Salammbo results and observations are essential. However, the validation is difficult in the case of protons and heavy ions because in-situ measurements of the probes are very few and most of the time contaminated by very energetic electrons. To solve this problem, a very good model of electrons radiation belts is essential to confirm or cancel the contamination of protons and heavy ions measurements. Thus, in parallel to the development of the protons and heavy ions radiation belts model, the electrons models, already existing, has been improved. Then Salammbo results have been compared to the different observations available (in-situ measurements, radio-astronomical observations). The different comparisons show a very good agreement between Salammbo results and observations. (author) [fr

Gold(I)-Catalysed Hydroarylation of 1,3-Disubstituted Allenes with Efficient Axial-to-Point Chirality Transfer.

Science.gov (United States)

Sutherland, Daniel R; Kinsman, Luke; Angiolini, Stuart M; Rosair, Georgina M; Lee, Ai-Lan

2018-05-11

Hydroarylation of enantioenriched 1,3-disubstituted allenes has the potential to proceed with axial-to-point chirality transfer to yield enantioenriched allylated (hetero)aryl compounds. However, the gold-catalysed intermolecular reaction was previously reported to occur with no chirality transfer owing to competing allene racemisation. Herein, we describe the development of the first intermolecular hydroarylations of allenes to proceed with efficient chirality transfer and summarise some of the key criteria for achieving high regio- and stereoselectivity. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Oxidative allene amination for the synthesis of azetidin-3-ones.

Science.gov (United States)

Burke, Eileen G; Schomaker, Jennifer M

2015-10-05

Regioselectivity in the aziridination of silyl-substituted homoallenic sulfamates is readily diverted to the distal double bond of the allene to yield endocyclic bicyclic methyleneaziridines with excellent stereocontrol. Subsequent reaction with electrophilic oxygen sources initiates facile rearrangement to densely functionalized, fused azetidin-3-ones in excellent d.r., effectively transferring the axial chirality of the allene to central chirality in the products. The steric nature of the silyl group dictates which of the two rings of the fused azetidin-3-one will undergo further functionalization, providing an additional element of diversity for the preparation of enantioenriched azetidine scaffolds with potential biological activity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Replacement of two amino acids of 9R-dioxygenase-allene oxide synthase of Aspergillus niger inverts the chirality of the hydroperoxide and the allene oxide.

Science.gov (United States)

Sooman, Linda; Wennman, Anneli; Hamberg, Mats; Hoffmann, Inga; Oliw, Ernst H

2016-02-01

The genome of Aspergillus niger codes for a fusion protein (EHA25900), which can be aligned with ~50% sequence identity to 9S-dioxygenase (DOX)-allene oxide synthase (AOS) of Fusarium oxysporum, homologues of the Fusarium and Colletotrichum complexes and with over 62% sequence identity to homologues of Aspergilli, including (DOX)-9R-AOS of Aspergillus terreus. The aims were to characterize the enzymatic activities of EHA25900 and to identify crucial amino acids for the stereospecificity. Recombinant EHA25900 oxidized 18:2n-6 sequentially to 9R-hydroperoxy-10(E),12(Z)-octadecadienoic acid (9R-HPODE) and to a 9R(10)-allene oxide. 9S- and 9R-DOX-AOS catalyze abstraction of the pro-R hydrogen at C-11, but the direction of oxygen insertion differs. A comparison between twelve 9-DOX domains of 9S- and 9R-DOX-AOS revealed conserved amino acid differences, which could contribute to the chirality of products. The Gly616Ile replacement of 9R-DOX-AOS (A. niger) increased the biosynthesis of 9S-HPODE and the 9S(10)-allene oxide, whereas the Phe627Leu replacement led to biosynthesis of 9S-HPODE and the 9S(10)-allene oxide as main products. The double mutant (Gly616Ile, Phe627Leu) formed over 90% of the 9S stereoisomer of HPODE. 9S-HPODE was formed by antarafacial hydrogen abstraction and oxygen insertion, i.e., the original H-abstraction was retained but the product chirality was altered. We conclude that 9R-DOX-AOS can be altered to 9S-DOX-AOS by replacement of two amino acids (Gly616Ile, Phe627Leu) in the DOX domain. Copyright © 2015 Elsevier B.V. All rights reserved.

Physical mechanism causing rapid changes in ultrarelativistic electron pitch angle distributions right after a shock arrival: Evaluation of an electron dropout event: Drift Shell Splitting on the Dayside

International Nuclear Information System (INIS)

Zhang, X.-J.; University of California, Los Angeles, CA; Li, W.; Boston University, MA; Thorne, R. M.

2016-01-01

Three mechanisms have been proposed to explain relativistic electron flux depletions (dropouts) in the Earth's outer radiation belt during storm times: adiabatic expansion of electron drift shells due to a decrease in magnetic field strength, magnetopause shadowing and subsequent outward radial diffusion, and precipitation into the atmosphere (driven by EMIC wave scattering). Which mechanism predominates in causing electron dropouts commonly observed in the outer radiation belt is still debatable. In the present study, we evaluate the physical mechanism that may be primarily responsible for causing the sudden change in relativistic electron pitch angle distributions during a dropout event observed by Van Allen Probes during the main phase of the 27 February 2014 storm. During this event, the phase space density of ultrarelativistic (>1MeV) electrons was depleted by more than 1 order of magnitude over the entire radial extent of the outer radiation belt (3 < L* < 5) in less than 6 h after the passage of an interplanetary shock. We model the electron pitch angle distribution under a compressed magnetic field topology based on actual solar wind conditions. Although these ultrarelativistic electrons exhibit highly anisotropic (peaked in 90°), energy-dependent pitch angle distributions, which appear to be associated with the typical EMIC wave scattering, comparison of the modeled electron distribution to electron measurements indicates that drift shell splitting is responsible for this rapid change in electron pitch angle distributions. This further indicates that magnetopause loss is the predominant cause of the electron dropout right after the shock arrival.

Allen's astrophysical quantities

CERN Document Server

2000-01-01

This new, fourth, edition of Allen's classic Astrophysical Quantities belongs on every astronomer's bookshelf. It has been thoroughly revised and brought up to date by a team of more than ninety internationally renowned astronomers and astrophysicists. While it follows the basic format of the original, this indispensable reference has grown to more than twice the size of the earlier editions to accommodate the great strides made in astronomy and astrophysics. It includes detailed tables of the most recent data on: - General constants and units - Atoms, molecules, and spectra - Observational astronomy at all wavelengths from radio to gamma-rays, and neutrinos - Planetary astronomy: Earth, planets and satellites, and solar system small bodies - The Sun, normal stars, and stars with special characteristics - Stellar populations - Cataclysmic and symbiotic variables, supernovae - Theoretical stellar evolution - Circumstellar and interstellar material - Star clusters, galaxies, quasars, and active galactic nuclei ...

Characteristics of pitch angle distributions of hundreds of keV electrons in the slot region and inner radiation belt

Science.gov (United States)

Zhao, H.; Li, X.; Blake, J. B.; Fennell, J. F.; Claudepierre, S. G.; Baker, D. N.; Jaynes, A. N.; Malaspina, D. M.

2014-12-01

The pitch angle distribution (PAD) of energetic electrons in the slot region and inner radiation belt received little attention in the past decades due to the lack of quality measurements. Using the state-of-the-art pitch angle-resolved data from the Magnetic Electron Ion Spectrometer instrument onboard the Van Allen Probes, a detailed analysis of hundreds of keV electron PADs below L = 4 is performed, in which the PADs are categorized into three types: normal (flux peaking at 90°), cap (exceedingly peaking narrowly around 90°), and 90° minimum (lower flux at 90°) PADs. By examining the characteristics of the PADs of ˜460 keV electrons for over a year, we find that the 90° minimum PADs are generally present in the inner belt (Lpitch angle scattering of hiss waves. Fitting the normal PADs into sinnα form, the parameter n is much higher below L = 3 than that in the outer belt and relatively constant in the inner belt but changes significantly in the slot region (2 mechanism can hardly explain the formation of 90° minimum PADs at the center of inner belt.

A new Predictive Model for Relativistic Electrons in Outer Radiation Belt

Science.gov (United States)

Chen, Y.

2017-12-01

Relativistic electrons trapped in the Earth's outer radiation belt present a highly hazardous radiation environment for spaceborne electronics. These energetic electrons, with kinetic energies up to several megaelectron-volt (MeV), manifest a highly dynamic and event-specific nature due to the delicate interplay of competing transport, acceleration and loss processes. Therefore, developing a forecasting capability for outer belt MeV electrons has long been a critical and challenging task for the space weather community. Recently, the vital roles of electron resonance with waves (including such as chorus and electromagnetic ion cyclotron) have been widely recognized; however, it is still difficult for current diffusion radiation belt models to reproduce the behavior of MeV electrons during individual geomagnetic storms, mainly because of the large uncertainties existing in input parameters. In this work, we expanded our previous cross-energy cross-pitch-angle coherence study and developed a new predictive model for MeV electrons over a wide range of L-shells inside the outer radiation belt. This new model uses NOAA POES observations from low-Earth-orbits (LEOs) as inputs to provide high-fidelity nowcast (multiple hour prediction) and forecast (> 1 day prediction) of the energization of MeV electrons as well as the evolving MeV electron distributions afterwards during storms. Performance of the predictive model is quantified by long-term in situ data from Van Allen Probes and LANL GEO satellites. This study adds new science significance to an existing LEO space infrastructure, and provides reliable and powerful tools to the whole space community.

Verdeling van oxytetraxycline (afkomstig van versleping) in diervoeders

NARCIS (Netherlands)

Stolker, A.A.M.; Zuidema, T.; Egmond, van H.J.; Jong, de J.; Haelermans, P.J.M.; Hooglugt, J.H.

2012-01-01

De laatste jaren is er een toenemende aandacht voor de mogelijke bijdrage van therapeutisch gebruik van antibiotica in de dierhouderij op de ontwikkeling van antimicrobiële resistentie. Een additionele bron van blootstelling van landbouwhuisdieren aan antibiotica is versleping via diervoeders. In

An Energetic Electron Flux Dropout Due to Magnetopause Shadowing on 1 June 2013

Science.gov (United States)

Kang, Suk-Bin; Fok, Mei-Ching; Komar, Colin; Glocer, Alex; Li, Wen; Buzulukova, Natalia

2018-02-01

We examine the mechanisms responsible for the dropout of energetic electron flux during 31 May to 1 June 2013 using Van Allen Probe (Radiation Belt Storm Probes (RBSP)) electron flux data and simulations with the Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model. During the storm main phase, L-shells at RBSP locations are greater than 8, which are connected to open drift shells. Consequently, diminished electron fluxes were observed over a wide range of energies. The combination of drift shell splitting, magnetopause shadowing, and drift loss all results in butterfly electron pitch angle distributions (PADs) at the nightside. During storm sudden commencement, RBSP observations display electron butterfly PADs over a wide range of energies. However, it is difficult to determine whether there are butterfly PADs during the storm main phase since the maximum observable equatorial pitch angle from RBSP is not larger than 40° during this period. To investigate the causes of the dropout, the CIMI model is used as a global 4-D kinetic inner magnetosphere model. The CIMI model reproduces the dropout with very similar timing and flux levels and PADs along the RBSP trajectory for 593 keV. Furthermore, the CIMI simulation shows butterfly PADs for 593 keV during the storm main phase. Based on comparison of observations and simulations, we suggest that the dropout during this event mainly results from magnetopause shadowing.

de Haas-van Alphen effect investigations of the electronic structure of pure and aluminum-doped MgB2

International Nuclear Information System (INIS)

Carrington, A.; Yelland, E.A.; Fletcher, J.D.; Cooper, J.R.

2007-01-01

Our understanding of the superconducting properties of MgB 2 is strongly linked to our knowledge of its electronic structure. In this paper we review experimental measurements of the Fermi surface parameters of pure and Al-doped MgB 2 using the de Haas-van Alphen (dHvA) effect. In general, the measurements are in excellent agreement with the theoretical predictions of the electronic structure, including the strength of the electron-phonon coupling on each Fermi surface sheet. For the Al doped samples, we are able to measure how the band structure changes with doping. These results are in excellent agreement with calculations based on the virtual crystal approximation. We also review work on the dHvA effect in the superconducting state

A positive correlation between energetic electron butterfly distributions and magnetosonic waves in the radiation belt slot region

International Nuclear Information System (INIS)

Yang, Chang; Su, Z.; Xiao, F.; Zheng, H.

2017-01-01

Energetic (hundreds of keV) electrons in the radiation belt slot region have been found to exhibit the butterfly pitch angle distributions. Resonant interactions with magnetosonic and whistler-mode waves are two potential mechanisms for the formation of these peculiar distributions. Here we perform a statistical study of energetic electron pitch angle distribution characteristics measured by Van Allen Probes in the slot region during a three-year period from May 2013 to May 2016. Our results show that electron butterfly distributions are closely related to magnetosonic waves rather than to whistlermode waves. Both electron butterfly distributions and magnetosonic waves occur more frequently at the geomagnetically active times than at the quiet times. In a statistical sense, more distinct butterfly distributions usually correspond to magnetosonic waves with larger amplitudes and vice versa. The averaged magnetosonic wave amplitude is less than 5 pT in the case of normal and flat-top distributions with a butterfly index BI = 1 but reaches ~ 35–95 pT in the case of distinct butterfly distributions with BI > 1:3. For magnetosonic waves with amplitudes > 50 pT, the occurrence rate of butterfly distribution is above 80%. Our study suggests that energetic electron butterfly distributions in the slot region are primarily caused by magnetosonic waves.

Selectie van Italiaanse werkwoordsvormen op basis van frequentieonderzoek

NARCIS (Netherlands)

Boer, M.G. de

2009-01-01

SAMENVATTING Dit artikel is een vroege recensie (mei 1972) van het LIF, de frequentielijst van IBM Italia uit 1971. De auteur concentreert zich op de verschillen met het project van Juilland, dat als uitgangspunt voor het LIF heeft gefungeerd. Op grond van de gegevens van het LIF is een basislijst

Layer-dependent electronic properties of phosphorene-like materials and phosphorene-based van der Waals heterostructures.

Science.gov (United States)

Huang, Y C; Chen, X; Wang, C; Peng, L; Qian, Q; Wang, S F

2017-06-29

Black phosphorus is a layered semiconducting allotrope of phosphorus with high carrier mobility. Its monolayer form, phosphorene, is an extremely fashionable two-dimensional material which has promising potential in transistors, optoelectronics and electronics. However, phosphorene-like analogues, especially phosphorene-based heterostructures and their layer-controlled electronic properties, are rarely systematically investigated. In this paper, the layer-dependent structural and electronic properties of phosphorene-like materials, i.e., mono- and few-layer MXs (M = Sn, Ge; X = S, Se), are first studied via first-principles calculations, and then the band edge position of these MXs as well as mono- and few-layer phosphorene are aligned. It is revealed that van der Waals heterostructures with a Moiré superstructure formed by mutual coupling among MXs and among MXs and few-layer phosphorene are able to show type-I or type-II characteristics and a I-II or II-I transition can be induced by adjusting the number of layers. Our work is expected to yield a new family of phosphorene-based semiconductor heterostructures with tunable electronic properties through altering the number of layers of the composite.

Thermal electron acceleration by electric field spikes in the outer radiation belt: generation of field-aligned pitch angle distributions

Science.gov (United States)

Vasko, I.; Agapitov, O. V.; Mozer, F.; Artemyev, A.

2015-12-01

Van Allen Probes observations in the outer radiation belt have demonstrated an abundance non-linear electrostatic stucture called Time Domain Structures (TDS). One of the type of TDS is electrostatic electron-acoustic double layers (DL). Observed DLs are frequently accompanied by field-aligned (bi-directional) pitch angle distributions (PAD) of electrons with energies from hundred eVs up to several keV (rarely up to tens of keV). We perform numerical simulations of the DL interaction with thermal electrons making use of the test particle approach. DL parameters assumed in the simulations are adopted from observations. We show that DLs accelerate thermal electrons parallel to the magnetic field via the electrostatic Fermi mechanism, i.e. due to reflections from DL potential humps. Due to this interaction some fraction of electrons is scattered into the loss cone. The electron energy gain is larger for larger DL scalar potential amplitudes and higher propagation velocities. In addition to the Fermi mechanism electrons can be trapped by DLs in their generation region and accelerated due to transport to higher latitudes. Both mechanisms result in formation of field-aligned PADs for electrons with energies comparable to those found in observations. The Fermi mechanism provides field-aligned PADs for <1 keV electrons, while the trapping mechanism extends field-aligned PADs to higher energy electrons.

Functionele aspecten van de gecomputeriseerde lexicografie

African Journals Online (AJOL)

the least possible effort. Keywords: COMPUTERISED LEXICOGRAPHY, ELECTRONIC DICTIONARY, ELEC-. TRONIC PUBLISHING, INFORMATION AND CoMMUNICATION TECHNOLOGY, ON-LINE. ACCESS VIA INTERNET, USER INTERFACE. Samenvatting: Computerisering van de lexicografie heeft er toe geleid dat ...

Spatial and Temporal Extent of Ion Spectral Structures at the Inner Edge of the Plasma Sheet

Science.gov (United States)

Ferradas, C.; Reeves, G. D.; Zhang, J.; Spence, H. E.; Kistler, L. M.; Larsen, B.; Skoug, R. M.; Funsten, H. O.

2017-12-01

Several ion spectral structures are observed near the inner edge of the plasma sheet and constitute the signatures of ion drift and loss in the highly dynamic environment of the inner magnetosphere. Their study helps us understand ion access and losses in this region. Several studies have found that these structures vary with geomagnetic activity, local time, and ion species, but their spatial and temporal extent remain undetermined. We use data from the Helium, Oxygen, Proton, and Electron (HOPE) mass spectrometers onboard the Van Allen Probes to analyze the spectral structures in the energy range of 1- 50 keV. HOPE measurements on both Van Allen Probes spacecraft enable us to resolve the extent of these ion structures in space and time. As the structures respond to changes in the convection electric field on a variety of time scales, the lapping of the two spacecraft on time scales of minutes to hours helps determine their spatial and temporal evolution.

’n Oorsig van die bepaling van die vroeë bakterisidiese aktiwiteit van verskeie antituberkulosemiddels

Directory of Open Access Journals (Sweden)

P. R. Donald

2003-06-01

Full Text Available Die vroeë bakterisidiese aktiwiteit (VBA van ’n antituberkulosemiddel is die daaglikse afname van M tuberculosis in log10 kolonievormende eenhede per ml sputum, tydens die eerste twee dae van behandeling met die middel. Dit weerspieël die vermoë van ’n middel om aktief metaboliserende organismes in tuberkulose-longholtes te dood. Dit is ’n relatief goedkoop metode om in ’n klein groep pasiënte die antituberkulose-aktiwiteit van ’n middel, binne maande, in vivo te evalueer. Hierdie artikel som ons ondervinding op tydens sewe gepubliseerde VBA-studies, en die bronne van variasie in die prosedure word identifiseer. Die pasiënte in hierdie studies was gemiddeld 33 jaar oud, met ’n gemiddelde gewig van 50 kg en 55% het ekstensiewe of massiewe longaantasting gehad. Die hoogste VBA-waardes (0,50-0,66 is gevind in pasiënte wat isoniasied ontvang het, en die laagste waardes (0,05 en 0,09 respektiewelik was gevind in pasiënte wat die aminoglikosiede amikasien en paromomisien, albei in doserings van 15 mg/kg liggaamsgewig, ontvang het. Die algehele variasie in die VBA van 248 pasiënte was 0,0312, en die variasie toegeskryf aan die proses van sputumproduksie en -versameling was 0,0223. Dit blyk dat die verskillende aspekte van sputumproduksie en -versameling, betrokke by die lewering van ’n verteenwoordigende sputummonster, ’n groter bydrae maak tot variasie tydens die prosedure as die laboratoriumaspekte van die tegniek. Die keuring van pasiënte vir insluiting in VBA-studies, en hulle vermoë om saam te werk om ’n verteenwoordigende sputummonster te produseer, is van deurslaggewende belang in die suksesvolle voltooiing van VBA-studies.

Chloroplast DNA haplotype samenstelling van eikenopstanden (categorie "van bekende origine") van de Rassenlijst van Bomen; een aanvullende methode voor identificatie van autochtoniteit

NARCIS (Netherlands)

Buiteveld, J.; Boerwinkel, M.C.; Bovenschen, J.; Kranenborg, K.G.; Vries, de S.M.G.

2005-01-01

Tegenwoordig kan autochtoon materiaal op de Rassenlijst van Bomen geplaatst worden in de categorie `van bekende origine¿ en heeft daardoor een `officiële¿ status. Identificatie van autochtone opstanden blijft echter nog een lastige zaak. Momenteel worden autochtone opstanden geïdentificeerd met de

Neuroinformatics of the Allen Mouse Brain Connectivity Atlas.

Science.gov (United States)

Kuan, Leonard; Li, Yang; Lau, Chris; Feng, David; Bernard, Amy; Sunkin, Susan M; Zeng, Hongkui; Dang, Chinh; Hawrylycz, Michael; Ng, Lydia

2015-02-01

The Allen Mouse Brain Connectivity Atlas is a mesoscale whole brain axonal projection atlas of the C57Bl/6J mouse brain. Anatomical trajectories throughout the brain were mapped into a common 3D space using a standardized platform to generate a comprehensive and quantitative database of inter-areal and cell-type-specific projections. This connectivity atlas has several desirable features, including brain-wide coverage, validated and versatile experimental techniques, a single standardized data format, a quantifiable and integrated neuroinformatics resource, and an open-access public online database (http://connectivity.brain-map.org/). Meaningful informatics data quantification and comparison is key to effective use and interpretation of connectome data. This relies on successful definition of a high fidelity atlas template and framework, mapping precision of raw data sets into the 3D reference framework, accurate signal detection and quantitative connection strength algorithms, and effective presentation in an integrated online application. Here we describe key informatics pipeline steps in the creation of the Allen Mouse Brain Connectivity Atlas and include basic application use cases. Copyright © 2014 Elsevier Inc. All rights reserved.

Biologische effectiviteit van bespuitingen: effecten van druppelgrootte en waterkwaliteit

NARCIS (Netherlands)

Zande, van de J.C.; Schans, van der D.A.; Koster, A.T.J.

2004-01-01

Deze rapportage beschrijft de invloed van watervolume, druppelgrootte en kwaliteit van het tankmengsel op de biologische effectiviteit van bespuitingen. Onder kwaliteit van het tankmengsel wordt in dit verband verstaan: temperatuur, hardheid, pH en zoutgehalte (chloor en ijzerzouten) van de

Photofragment imaging study of the CH2CCH2OH radical intermediate of the OH+allene reaction

International Nuclear Information System (INIS)

Raman, Arjun S.; Justine Bell, M.; Lau, K.-C.; Butler, Laurie J.

2007-01-01

These velocity map imaging experiments characterize the photolytic generation of one of the two radical intermediates formed when OH reacts via an addition mechanism with allene. The CH 2 CCH 2 OH radical intermediate is generated photolytically from the photodissociation of 2-chloro-2-propen-1-ol at 193 nm. Detecting the Cl atoms using [2+1] resonance-enhanced multiphoton ionization evidences an isotropic angular distribution for the Cl+CH 2 CCH 2 OH photofragments, a spin-orbit branching ratio for Cl( 2 P 1/2 ):Cl( 2 P 3/2 ) of 0.28, and a bimodal recoil kinetic energy distribution. Conservation of momentum and energy allows us to determine from this data the internal energy distribution of the nascent CH 2 CCH 2 OH radical cofragment. To assess the possible subsequent decomposition pathways of this highly vibrationally excited radical intermediate, we include electronic structure calculations at the G3//B3LYP level of theory. They predict the isomerization and dissociation transition states en route from the initial CH 2 CCH 2 OH radical intermediate to the three most important product channels for the OH+allene reaction expected from this radical intermediate: formaldehyde+C 2 H 3 , H+acrolein, and ethene+CHO. We also calculate the intermediates and transition states en route from the other radical adduct, formed by addition of the OH to the center carbon of allene, to the ketene+CH 3 product channel. We compare our results to a previous theoretical study of the O+allyl reaction conducted at the CBS-QB3 level of theory, as the two reactions include several common intermediates

Photofragment imaging study of the CH2CCH2OH radical intermediate of the OH +allene reaction

Science.gov (United States)

Raman, Arjun S.; Justine Bell, M.; Lau, Kai-Chung; Butler, Laurie J.

2007-10-01

These velocity map imaging experiments characterize the photolytic generation of one of the two radical intermediates formed when OH reacts via an addition mechanism with allene. The CH2CCH2OH radical intermediate is generated photolytically from the photodissociation of 2-chloro-2-propen-1-ol at 193nm. Detecting the Cl atoms using [2+1] resonance-enhanced multiphoton ionization evidences an isotropic angular distribution for the Cl +CH2CCH2OH photofragments, a spin-orbit branching ratio for Cl(P1/22):Cl(P3/22) of 0.28, and a bimodal recoil kinetic energy distribution. Conservation of momentum and energy allows us to determine from this data the internal energy distribution of the nascent CH2CCH2OH radical cofragment. To assess the possible subsequent decomposition pathways of this highly vibrationally excited radical intermediate, we include electronic structure calculations at the G3//B3LYP level of theory. They predict the isomerization and dissociation transition states en route from the initial CH2CCH2OH radical intermediate to the three most important product channels for the OH +allene reaction expected from this radical intermediate: formaldehyde+C2H3, H +acrolein, and ethene+CHO. We also calculate the intermediates and transition states en route from the other radical adduct, formed by addition of the OH to the center carbon of allene, to the ketene+CH3 product channel. We compare our results to a previous theoretical study of the O +allyl reaction conducted at the CBS-QB3 level of theory, as the two reactions include several common intermediates.

Fluorinated Amine Stereotriads via Allene Amination.

Science.gov (United States)

Liu, Lu; Gerstner, Nels C; Oxtoby, Lucas J; Guzei, Ilia A; Schomaker, Jennifer M

2017-06-16

The incorporation of fluorine into organic scaffolds often improves the bioactivity of pharmaceutically relevant compounds. C-F/C-N/C-O stereotriad motifs are prevalent in antivirals, neuraminidase inhibitors, and modulators of androgen receptors, but are challenging to install. An oxidative allene amination strategy using Selectfluor rapidly delivers triply functionalized triads of the form C-F/C-N/C-O, exhibiting good scope and diastereoselectivity for all syn products. The resulting stereotriads are readily transformed into fluorinated pyrrolidines and protected α-, β-, and γ-amino acids.

On the spatio-temporal and energy-dependent response of riometer absorption to electron precipitation: drift-time and conjunction analyses in realistic electric and magnetic fields

Science.gov (United States)

Kellerman, Adam; Shprits, Yuri; Makarevich, Roman; Donovan, Eric; Zhu, Hui

2017-04-01

Riometers are low-cost passive radiowave instruments located in both northern and southern hemispheres that capable of operating during quiet and disturbed conditions. Many instruments have been operating continuously for multiple solar cycles, making them a useful tool for long-term statistical studies and for real-time analysis and forecasting of space weather. Here we present recent and new analyses of the relationship between the riometer-measured cosmic noise absorption and electron precipitation into the D-region and lower E-region ionosphere. We utilize two techniques: a drift-time analysis in realistic electric and magnetic field models, where a particle is traced from one location to another, and the energy determined by the time delay between similar observations; and a conjunction analysis, where we directly compare precipitated fluxes from THEMIS and Van Allen Probes with the riometer absorption. In both cases we present a statistical analysis of the response of riometer absorption to electron precipitation as a function of MLAT, MLT, and geomagnetic conditions.

Verslag van de voorstudie: Paddenstoelen bedrijf van de toekomst

NARCIS (Netherlands)

Tuijl, van B.A.J.; Bos, A.P.; Sonnenberg, A.S.M.

2013-01-01

Het rapport ‘Paddenstoelenbedrijf van de toekomst’ is het resultaat van een uitgebreid vooronderzoek en geeft de eerste aanzet tot het creëren van gemeenschappelijke visie van de sector op een betere toekomst voor paddenstoelenkwekerijen. Het rapport doet verslag van een reeks interviews en een

Radiation belt electron acceleration during the 17 March 2015 geomagnetic storm: Observations and simulations

International Nuclear Information System (INIS)

Li, W.; Ma, Q.; Thorne, R. M.; Bortnik, J.; Zhang, X.-J.

2016-01-01

Various physical processes are known to cause acceleration, loss, and transport of energetic electrons in the Earth's radiation belts, but their quantitative roles in different time and space need further investigation. During the largest storm over the past decade (17 March 2015), relativistic electrons experienced fairly rapid acceleration up to ~7 MeV within 2 days after an initial substantial dropout, as observed by Van Allen Probes. In the present paper, we evaluate the relative roles of various physical processes during the recovery phase of this large storm using a 3-D diffusion simulation. By quantitatively comparing the observed and simulated electron evolution, we found that chorus plays a critical role in accelerating electrons up to several MeV near the developing peak location and produces characteristic flat-top pitch angle distributions. By only including radial diffusion, the simulation underestimates the observed electron acceleration, while radial diffusion plays an important role in redistributing electrons and potentially accelerates them to even higher energies. Moreover, plasmaspheric hiss is found to provide efficient pitch angle scattering losses for hundreds of keV electrons, while its scattering effect on > 1 MeV electrons is relatively slow. Although an additional loss process is required to fully explain the overestimated electron fluxes at multi-MeV, the combined physical processes of radial diffusion and pitch angle and energy diffusion by chorus and hiss reproduce the observed electron dynamics remarkably well, suggesting that quasi-linear diffusion theory is reasonable to evaluate radiation belt electron dynamics during this big storm.

Samenstelling van de vluchtige olie van Origanum vulgare L. ssp. vulgare gedurende de ontwikkeling van de plant

NARCIS (Netherlands)

Maarse, Henk

1971-01-01

INLEIDING EN DOEL VAN HET ONDERZOEK Vele onderzoekers hebben de laatste jaren de vorming van de verbindingen in vluchtige olien van planten bestudeerd door het bepalen van de verandering in de samenstelling van de vluchtige olie tijdens de groei van de plant. Lemli (68) wees als eerste op de

Onderzoek naar vermindering van de bijvangst van een boomkortuig

NARCIS (Netherlands)

Marlen, van B.; Ybema, M.S.; Duijn, van J.B.

2005-01-01

In het kader van EU-project RECOVERY werden vergelijkende visserij- en selectiviteitsproeven uitgevoerd in 2002 en 2003 aan boord van MS “Tridens” aan 12 m boomkortuigen. De resultaten van een negental vistuigproeven zijn hier gegeven, gericht op het bepalen van het effect van een grote mazen kap

Die Romeinse nastrewing van onsterflikheid deur middel van memoria

Directory of Open Access Journals (Sweden)

D. R. Fouché

1985-05-01

Full Text Available Benewens die omvangryke en nasionale manifestasies van die oorspronklike onsterflikheidsgedagte in die Romeinse gemeenskap, vind ons by die Romein op kleiner skaal in groepe of indiwidueel ’n strewe na onsterflikheid langs die weg van memoria. Soos aangetoon sal word, verskil die pogings van die verskillende groepe radikaal van mekaar, hoewel die strewe en einddoel dieselfde bly, naamlik om deur die daarstelling van memoria op die gebied van woord of daad onsterflikheid te bekom.

Het planetarium van Hartog van Laun

Directory of Open Access Journals (Sweden)

Hans Hooijmaaijers

2009-12-01

Full Text Available The instrument maker Hartog van Laun devised a special table for an orrery, a lunarium and a tellurium. Van Laun made these instruments for educational purposes, but what makes his planetariums so interesting is the great variety and accuracy of demonstrations one can perform with them. In this paper I will deal with Van Laun and his instrument makers business. I will outline the design of the planetarium and some of the firm’s other instruments. Furthermore I will demonstrate that the detailed description of the planetarium made by Professor Jan Hendrik van Swinden boosted the spread of the instrument.

Theory of the Allen method and its practical bearing on pipe discharge measurement

International Nuclear Information System (INIS)

Guizerix, J.; Margrita, R.

1976-01-01

The Allen method for measurement of pipe discharge is based on a general relationship between discharge, instrument section volume and the first moment of the residence time distribution. An original demonstration of this standard chemical engineering relationship is given. The Allen method thus offers a very wide practical application scope. Requirements are limited to knowing the volume of the instrument section and the residence time distribution; the shape of the instrument section is immaterial. The information can be obtained for example by means of a system correlating the instrument section input and output signals [fr

Commentary on Sowcik and Allen: Getting Down to Business

Science.gov (United States)

Murphy, Susan Elaine

2013-01-01

Sowcik and Allen's paper, "Getting Down to Business: A Look at Leadership Education in Business Schools," identifies a number of compelling issues in improving leadership education in business schools and provides a thorough overview of how these efforts could benefit from the considerations present in the National Leadership Educators…

Electronic Properties and Device Applications of van-der-Waals Thin Films

Science.gov (United States)

Renteria, Jacqueline de Dios

Successful exfoliation of graphene and discoveries of its unique electrical and thermal properties have motivated searches for other quasi two-dimensional (2D) materials with interesting properties. The layered van der Waals materials can be cleaved mechanically or exfoliated chemically by breaking the relatively weak bonding between the layers. In this dissertation research I addressed a special group of inorganic van der Waals materials -- layered transition metal dichalcogenides (MX2, where M=Mo, W, Nb, Ta or Ti and X=S, Se or Te). The focus of the investigation was electronic properties of thin films of TaSe2 and MoS2 and their device applications. In the first part of the dissertation, I describe the fabrication and performance of all-metallic three-terminal devices with the TaSe2 thin-film conducting channel. The layers of 2H-TaSe2 were exfoliated mechanically from single crystals grown by the chemical vapor transport method. It was established that devices with nanometer-scale thickness channels exhibited strongly non-linear current-voltage characteristics, unusual optical response, and electrical gating at room temperature. It was found that the drain-source current in thin-film 2H-TaSe2--Ti/Au devices reproducibly shows an abrupt transition from a highly resistive to a conductive state, with the threshold tunable via the gate voltage. Such current-voltage characteristics can be used, in principle, for implementing radiation-hard all-metallic logic circuits. In the second part of the dissertation, I describe the fabrication, electrical testing and measurements of the low-frequency 1/f noise in three-terminal devices with the MoS2 thin-film channel (f is the frequency). Analysis of the experimental data allowed us to distinguish channel and contact noise contributions for both as fabricated and aged devices. The noise characteristics of MoS 2--Ti/Au devices are in agreement with the McWhorter model description. The latter is contrary to what is observed in

‘n Kritiese bespreking van roskam se seining van apartheid as grondslag van die Suid-afrikaanse samelewing

Directory of Open Access Journals (Sweden)

N. van Loggerenberg

1963-03-01

Full Text Available Segregasie is al deur vele ondersoekers histories tot ’n tradisie uit die stigtingsjaar 1652 met die aankoms van Jan van Riebeeck herlei. Roskam sion dit egter as 'n beleid wat veel later aanvaar is. Hy sien dit as beleid wat bepaalde groepe van die bevolking as 'n politieke eenheid, kragtens ’n sosiale hiërargie, van mekaar wil afskei, isoleer. Dit is vir  hom duidelik dat die politieke eenheid van Ordinansie 50 van 1828 nooit werklikheid geword het nie, en die tradisie van blanke heerskappy pas vir liom as heleid beter in die huidige situasic as segregasie. Roskam is dan van oordeel dat ..white supremacy” daarom die juiste en omskrywende betekenis van segregasie is.

Detectie van ziektesymptomen met behulp van fluorescentiebeelden

NARCIS (Netherlands)

Loon, van P.C.C.

2004-01-01

Rapport over de positie van de biologische paddestoelenteelt op intersectoraal en (inter)-regionaal niveau. Het overzicht in tabel- en schemavorm van de stromen grondstoffen en producten verduidelijkt de intersectorale positie van de champignonteelt. Dit kan een aanzet zijn bij het signaleren en

Een revisie van de taxonomie van gifkikkers

NARCIS (Netherlands)

Poelman, E.H.

2007-01-01

Recent kwam het lang verwachte ruim tweehonderdvijftig pagina`s tellende manuscript uit met daarin een revisie van de taxonomie van gifkikkers. De auteurs onder leiding van Taran Grant stellen een nieuwe taxonomie voor, die de familie Dendrobatidae met haar tien algemener geaccepteerde genera

Radiation belt seed population and its association with the relativistic electron dynamics: A statistical study: Radiation Belt Seed Population

International Nuclear Information System (INIS)

Tang, C. L.; Wang, Y. X.; Ni, B.; Zhang, J.-C.

2017-01-01

Using the Van Allen Probes data, we study the radiation belt seed population and it associated with the relativistic electron dynamics during 74 geomagnetic storm events. Based on the flux changes of 1 MeV electrons before and after the storm peak, these storm events are divided into two groups of “non-preconditioned” and “preconditioned”. The statistical study shows that the storm intensity is of significant importance for the distribution of the seed population (336 keV electrons) in the outer radiation belt. However, substorm intensity can also be important to the evolution of the seed population for some geomagnetic storm events. For non-preconditioned storm events, the correlation between the peak fluxes and their L-shell locations of the seed population and relativistic electrons (592 keV, 1.0 MeV, 1.8 MeV, and 2.1 MeV) is consistent with the energy-dependent dynamic processes in the outer radiation belt. For preconditioned storm events, the correlation between the features of the seed population and relativistic electrons is not fully consistent with the energy-dependent processes. It is suggested that the good correlation between the radiation belt seed population and ≤1.0 MeV electrons contributes to the prediction of the evolution of ≤1.0 MeV electrons in the Earth’s outer radiation belt during periods of geomagnetic storms.

De toekomst van flex : een onderzoek van tno naar flexstrategieën van Nederlandse bedrijven

NARCIS (Netherlands)

Verbiest, S.E.; Goudswaard, A.; Wijk, E.B. van

2014-01-01

In 2020 zal het personeelsbestand van organisaties voor 30% uit flexkrachten bestaan. Op dit moment is dat 25%. Dit blijkt uit een onderzoek van TNO onder 900 ondernemingen in opdracht van de ABU (Algemene Bond Uitzendondernemingen). Het blijkt dat met name organisaties die al gebruikmaken van

De trek van kruiden van volgroeid wortelmateriaal : handleiding van A tot Z in beknopte vorm

NARCIS (Netherlands)

Wijk, van C.A.P.

2005-01-01

Deze teelthandleiding richt zich op de trek van vooral dragon, krulpeterselie, rucola en munt, uitgaande van wortelmateriaal dat in de vollegrond wordt geteeld. Deze forcering richt zich zowel op aanbod van kruiden in potjes als de meermalige oogst van het gesneden product in een kas of een

Numerieke simulatie van de blastbelasting op vlucht MH17 van Malaysia Airlines als gevolg van de detonatie van een gevechtslading (U)

NARCIS (Netherlands)

2015-01-01

De Onderzoeksraad voor Veiligheid (OVV) onderzoekt de crash van vlucht MH17 van Malaysia Airlines die plaatsvond op donderdag 17 juli 2014 in de regio Donetsk (Oekraïne). De OVV wil een duidelijk beeld geven van de oorzaak van de crash. Een mogelijke oorzaak is fatale schade aan het vliegtuig als

The effectiveness of the Allen Carr smoking cessation training in companies tested in a quasi-experimental design

NARCIS (Netherlands)

Dijkstra, Arie; Zuidema, Rixt; Vos, Diederick; van Kalken, Marike

2014-01-01

Background: The Allen Carr training (ACt) is a popular one-session smoking cessation group training that is provided by licensed organizations that have the permission to use the Allen Carr method. However, few data are available on the effectiveness of the training. Methods: In a quasi-experimental

Van der Waals Epitaxy of GaSe/Graphene Heterostructure: Electronic and Interfacial Properties.

Science.gov (United States)

Ben Aziza, Zeineb; Henck, Hugo; Pierucci, Debora; Silly, Mathieu G; Lhuillier, Emmanuel; Patriarche, Gilles; Sirotti, Fausto; Eddrief, Mahmoud; Ouerghi, Abdelkarim

2016-10-07

Stacking two-dimensional materials in so-called van der Waals (vdW) heterostructures, like the combination of GaSe and graphene, provides the ability to obtain hybrid systems which are suitable to design optoelectronic devices. Here, we report the structural and electronic properties of the direct growth of multilayered GaSe by Molecular beam Epitaxy (MBE) on graphene. Reflection high-energy electron diffraction (RHEED) images exhibited sharp streaky features indicative of high quality GaSe layer produced via a vdW epitaxy. Micro-Raman spectroscopy showed that, after the vdW hetero-interface formation, the Raman signature of pristine graphene is preserved. However, the GaSe film tuned the charge density of graphene layer by shifting the Dirac point by about 80 meV toward lower binding energies, attesting an electron transfer from graphene to GaSe. Angle-resolved photoemission spectroscopy (ARPES) measurements showed that the maximum of the valence band of few layers of GaSe are located at the Γ point at a binding energy of about -0.73 eV relatively to the Fermi level (p-type doping). From the ARPES measurements, a hole effective mass defined along the ΓM direction and equal to about m*/m0 = -1.1 was determined. By coupling the ARPES data with high resolution X-ray photoemission spectroscopy (HR-XPS) measurements, the Schottky interface barrier height was estimated to be 1.2 eV. These findings allow deeper understanding of the interlayer interactions and the electronic structure of GaSe/graphene vdW heterostructure.

Filosofiese tendense in die wordinggeskiedenis van ons verstaan van die fisiese natuur

Directory of Open Access Journals (Sweden)

D. F. M. Strauss

2006-09-01

Full Text Available Die ontstaan van ’n lang tradisie van natuurwetenskaplike denke is in antieke Griekeland te vind – die bakermat van die Westerse beskawing en die bron van geartikuleerde rasionele besinning. Die vroegste fases van die Griekse kultuur het reeds geboorte geskenk aan ’n teoretiese nadenke oor die heelal. Die Pythagoreërs is veral bekend vir hul klem op die verklaringskrag van getalsverhoudinge. In hul tese dat “alles getal is” het hulle egter slegs rasionale getalle (breuke erken en gevolglik uiteindelik vasgeloop in die ontdekking van irrasionale getalle wat tot die geometrisering van die Griekse wiskunde gelei het en tegelyk die bedding gevorm het van waaruit ’n magtige tradisie van ruimte-metafisika gegroei het wat die hele middeleeuse tydperk omspan het. Die vermeende statiese syn is in die mees ekstreme geval – die skool van Parmenides en die argumente van Zeno teen veelheid en beweging – tot in die uiteindelike antinomiese konsekwensies daarvan deurdink. Dit was egter eers die vroeg-moderne tyd – die voorgangers en nakomelinge van Galilei – wat naas getal en ruimte ’n waardering ontwikkel het vir die verklaringskrag van beweging (vergelyk die klassieke meganistiese wêreldbeeld van die heelal as ’n meganisme van stofdeeltjies in beweging. Maar ook hierdie meganistiese reduksie (waardeur alle fisiese verskynsels herlei is tot die beweging van al of niegelade massapunte sou uiteindelik misluk omdat dit nie van die onomkeerbaarheid van fisiese prosesse rekenskap kon gee nie. Gevolglik beliggaam eers die fisika van die 20ste eeu ’n erkenning van die deurslaggewend-stempelende rol van energie-werking (dus van die fisiese aspek in die aard van stoflike dinge en prosesse. Die artikel word afgesluit met ’n vlugtige verduideliking van die implikasies van die voorafgaande argumentasie vir ’n benadering van die misterie van die bestaan van materie.

Compact two-electron wave function for bond dissociation and Van der Waals interactions: a natural amplitude assessment.

Science.gov (United States)

Giesbertz, Klaas J H; van Leeuwen, Robert

2014-05-14

Electron correlations in molecules can be divided in short range dynamical correlations, long range Van der Waals type interactions, and near degeneracy static correlations. In this work, we analyze for a one-dimensional model of a two-electron system how these three types of correlations can be incorporated in a simple wave function of restricted functional form consisting of an orbital product multiplied by a single correlation function f (r12) depending on the interelectronic distance r12. Since the three types of correlations mentioned lead to different signatures in terms of the natural orbital (NO) amplitudes in two-electron systems, we make an analysis of the wave function in terms of the NO amplitudes for a model system of a diatomic molecule. In our numerical implementation, we fully optimize the orbitals and the correlation function on a spatial grid without restrictions on their functional form. Due to this particular form of the wave function, we can prove that none of the amplitudes vanishes and moreover that it displays a distinct sign pattern and a series of avoided crossings as a function of the bond distance in agreement with the exact solution. This shows that the wave function ansatz correctly incorporates the long range Van der Waals interactions. We further show that the approximate wave function gives an excellent binding curve and is able to describe static correlations. We show that in order to do this the correlation function f (r12) needs to diverge for large r12 at large internuclear distances while for shorter bond distances it increases as a function of r12 to a maximum value after which it decays exponentially. We further give a physical interpretation of this behavior.

Beoordeling van het gedrag van bestrijdingsmiddelen in de verzadigde zone van de bodem

NARCIS (Netherlands)

Linden AMA van der; Beek CGEM van; Boesten JJTI; Leistra M; Meinardi CR; Puijker LM; LBG

1994-01-01

In het MeerJarenPlan-Gewasbescherming van 1991 is de mogelijkheid gegeven om door middel van onderzoek in de verzadigde fase van de bodem aan te tonen dat bestrijdingsmiddelen, die kunnen uitspoelen naar de verzadigde zone, alsnog voor toelating in aanmerking kunnen komen als de

Quantitative Simulation of QARBM Challenge Events During Radiation Belt Enhancements

Science.gov (United States)

Li, W.; Ma, Q.; Thorne, R. M.; Bortnik, J.; Chu, X.

2017-12-01

Various physical processes are known to affect energetic electron dynamics in the Earth's radiation belts, but their quantitative effects at different times and locations in space need further investigation. This presentation focuses on discussing the quantitative roles of various physical processes that affect Earth's radiation belt electron dynamics during radiation belt enhancement challenge events (storm-time vs. non-storm-time) selected by the GEM Quantitative Assessment of Radiation Belt Modeling (QARBM) focus group. We construct realistic global distributions of whistler-mode chorus waves, adopt various versions of radial diffusion models (statistical and event-specific), and use the global evolution of other potentially important plasma waves including plasmaspheric hiss, magnetosonic waves, and electromagnetic ion cyclotron waves from all available multi-satellite measurements. These state-of-the-art wave properties and distributions on a global scale are used to calculate diffusion coefficients, that are then adopted as inputs to simulate the dynamical electron evolution using a 3D diffusion simulation during the storm-time and the non-storm-time acceleration events respectively. We explore the similarities and differences in the dominant physical processes that cause radiation belt electron dynamics during the storm-time and non-storm-time acceleration events. The quantitative role of each physical process is determined by comparing against the Van Allen Probes electron observations at different energies, pitch angles, and L-MLT regions. This quantitative comparison further indicates instances when quasilinear theory is sufficient to explain the observed electron dynamics or when nonlinear interaction is required to reproduce the energetic electron evolution observed by the Van Allen Probes.

Onderzoek naar de effecten van snoezelen op het gedrag van demente verpleeghuisbewoners en de werkbeleving van verzorgenden.

NARCIS (Netherlands)

Weert, J. van; Peter, J.; Dulmen, S. van; Ribbe, M.; Bensing, J.

2004-01-01

Het effect van snoezelen in de 24-uurszorg op de stemming en het gedrag van demente ouderen is nooit eerder onderzocht. Ook is in geen van de eerdere studies het effect onderzocht van snoezelen op de werkbeleving van verzorgenden. Uit onderzoek is bekend dat in verpleeghuizen waar geen

Beoordeling van het gedrag van bestrijdingsmiddelen in de verzadigde zone van de bodem

NARCIS (Netherlands)

Linden, van der A.M.A.; Beek, van C.G.E.M.; Boesten, J.J.T.I.; Leistra, M.; Meinardi, C.R.; Puijker, L.M.

1999-01-01

In het MeerJarenPlan-Gewasbescherming van 1991 is de mogelijkheid gegeven om door middel van onderzoek in de verzadigde fase van de bodem aan te tonen dat bestrijdingsmiddelen, die kunnen uitspoelen naar de verzadigde zone, alsnog voor toelating in aanmerking kunnen komen als de omzettingssnelheid

[A study on Horace N. Allen's medicine and recognition of Korean body].

Science.gov (United States)

Lee, Young Ah

2011-12-31

Je Jung Won was the first modern-style Government hospital built by the Korean King Ko-Jong in April 1885, and it was the medical missionary Horace Newton Allen(1858~1932) who made one of the greatest contributions to the establishment of the hospital. Allen was an American missionary. He graduated from Ohio Wesleyan University with a degree in theology in 1881, and completed one-yearcourse at Miami Medical College. In Korea and America he worked as a physician, a missionary, an American diplomatic minister to Korea and a Korean minister's secretary to America. While acting as a mediator between Korea and America, he knew and recorded the domestic and foreign situation of Korea during Gaehwagi(the civilized and enlightened age). Thus to study him is to understand Korea's Gaehwagi as well as to research American medical missionaries. During his stay in Korea(1884~1905), Allen steadily wrote diaries and letters about Korean politics, diplomacy, society, culture, and medicine. Thus his public/private record through diaries and letters(the quantity of these materials amounts to several thousands) supplements the Korean early modern era's historical record. However, until now these materials have received little scholarly attention from researchers except for a few historians of missionary work between Korea and America, or of Korean modern medicine. I intended to use these materials to suggest a new perspective on the study of Korean Gaehwagi. Allen, along with John W. Heron, who came to Seoul on June 21st 1885, treated about 10,460 Korean patients in the first year of the opening of JeJungWon. They made "the first annual report of the Korean Government Hospital". This report explained how Allen and Heron regarded and treated Korean patients. Allen's diaries, letters and other writings offer a realistic view of how the western people actually recognized the Korean people at that time. As a western doctor, Allen had an ambivalent attitude toward Korean medical concepts

Miks meil on kogu aeg kiire? / David Allen ; interv. Endrik Randoja

Index Scriptorium Estoniae

Allen, David

2006-01-01

Produktiivsuse ekspert vastab küsimustele ettevõetud tegevuste tulemuslikumalt lõpule viimise kohta. Lisa: Aja paremaks kasutamiseks pakub David Allen lisaks veel kolm tõhusat ja lihtsasti rakendatavat põhimõtet

Bepaling van de optredende temperaturen bij tunnelcompostering van geitenmest

NARCIS (Netherlands)

Melse, R.W.; Sauvage, de G.J.; Roest, H.I.J.

2010-01-01

Het doel van het project is om inzicht te krijgen in de composteerbaarheid van geitenmest en het hiermee samenhangende temperatuursverloop . Bepaald dient te worden welke temperaturen tijdens het composteren van geitenmest worden bereikt om op basis daarvan een inschatting te kunnen maken van de

Kleinschalige raffinage van bietenblad : eerste verkenning van de moglijkheden

NARCIS (Netherlands)

Wolf, de P.L.; Visser, de C.L.M.; Keijsers, E.R.P.; Meesters, K.P.H.; Heesakkers, J.W.M.; Aerts, M.

2013-01-01

Doelstelling van de eerste fase van het onderzoek was ‘het verkennen van kleinschalige keten(s) voor de raffinage van bietenblad’, met aandacht voor de technologische en economische haalbaarheid. Deze verkenning vormt de basis voor de volgende fase, waarin kansrijke opties verder worden uitgewerkt

Presence of the vancomycin resistance gene cluster vanC1, vanXYc, and vanT in Enterococcus casseliflavus.

Science.gov (United States)

Hölzel, Christina; Bauer, Johann; Stegherr, Eva-Maria; Schwaiger, Karin

2014-04-01

The three chromosomally located clustered genes vanC1, vanXYc, and vanT confer intrinsic resistance to vancomycin and are used for species identification of Enterococcus gallinarum. In this study, 28 strains belonging to the E. gallinarum/casseliflavus group isolated from cloacal swabs from laying hens were screened for the presence of vanC1. As confirmed by species-specific multiplex PCR, 11 vanC1-positive strains were identified as E. gallinarum. Surprisingly, one yellow pigmented strain, verified as E. casseliflavus by species-specific multiplex PCR, was also vanC1 positive; vanXYc and vanT were additionally detectable in this strain. To our knowledge, this is the first report of vanC1, vanXYc, and vanT in E. casseliflavus. The minimum inhibitory concentration of vancomycin was 4 mg/L. Real-time reverse transcription-PCR revealed that none of the clustered genes was expressed in this strain. Even if the genes seem not to be active, there is a certain risk that they will be transferred to other bacteria where they might be functionally expressed. Therefore, it may be advisable to expand the search for vanC1, vanXYc, and vanT from E. gallinarum to other (enterococcal) species. This study confirms that enterococci live up to their name as being reservoir bacteria and should therefore always be closely monitored.

Scalability of the LEU-Modified Cintichem Process: 3-MeV Van de Graaff and 35-MeV Electron Linear Accelerator Studies

Energy Technology Data Exchange (ETDEWEB)

Rotsch, David A. [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Brossard, Tom [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Roussin, Ethan [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Quigley, Kevin [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Chemerisov, Sergey [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Gromov, Roman [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Jonah, Charles [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Hafenrichter, Lohman [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Tkac, Peter [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Krebs, John [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Vandegrift, George F. [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division

2016-10-31

Molybdenum-99, the mother of Tc-99m, can be produced from fission of U-235 in nuclear reactors and purified from fission products by the Cintichem process, later modified for low-enriched uranium (LEU) targets. The key step in this process is the precipitation of Mo with α-benzoin oxime (ABO). The stability of this complex to radiation has been examined. Molybdenum-ABO was irradiated with 3 MeV electrons produced by a Van de Graaff generator and 35 MeV electrons produced by a 50 MeV/25 kW electron linear accelerator. Dose equivalents of 1.7–31.2 kCi of Mo-99 were administered to freshly prepared Mo-ABO. Irradiated samples of Mo-ABO were processed according to the LEU Modified-Cintichem process. The Van de Graaff data indicated good radiation stability of the Mo-ABO complex up to ~15 kCi dose equivalents of Mo-99 and nearly complete destruction at doses >24 kCi Mo-99. The linear accelerator data indicate that even at 6.2 kCi of Mo-99 equivalence of dose, the sample lost ~20% of Mo-99. The 20% loss of Mo-99 at this low dose may be attributed to thermal decomposition of the product from the heat deposited in the sample during irradiation.

Die gebruik van parallelplaatreologie vir die bepaling van die intrinsieke viskositeit van poli-etileentereftalaat

Directory of Open Access Journals (Sweden)

O. C. Vorster

2005-09-01

Full Text Available Die bepaling van die intrinsieke viskositeit van poli-etileentereftalaat word bemoeilik deur die feit dat daar tans slegs twee metodes in gebruik is. In die eerste metode word die bepaling deur middel van oplossingsviskometrie gedoen, maar die toksisiteit van die oplosmiddel, asook die tydperk wat dit neem om die bepaling te doen, is ’n probleem. Die tweede metode word beperk deur die kompleksiteit en beskikbaarheid van die apparatuur in Suid-Afrika. In hierdie studie word ’n alternatiewe metode, gebaseer op parallelplaatreologie, voorgestel wat albei hierdie probleme oorkom en die resultate sodoende verkry, word vergelyk met dié wat met bestaande metodes verkry is.

Mixed Dimensional Van der Waals Heterostructures for Opto-Electronics.

Science.gov (United States)

Jariwala, Deep

The isolation of a growing number of two-dimensional (2D) materials has inspired worldwide efforts to integrate distinct 2D materials into van der Waals (vdW) heterostructures. While a tremendous amount of research activity has occurred in assembling disparate 2D materials into ``all-2D'' van der Waals heterostructures, this concept is not limited to 2D materials alone. Given that any passivated, dangling bond-free surface will interact with another via vdW forces, the vdW heterostructure concept can be extended to include the integration of 2D materials with non-2D materials that adhere primarily through noncovalent interactions. In the first part of this talk I will present our work on emerging mixed-dimensional (2D + nD, where n is 0, 1 or 3) heterostructure devices performed at Northwestern University. I will present two distinct examples of gate-tunable p-n heterojunctions 1. Single layer n-type MoS2\\ (2D) combined with p-type semiconducting single walled carbon nanotubes (1D) and 2. Single layer MoS2 combined with 0D molecular semiconductor, pentacene. I will present the unique electrical properties, underlying charge transport mechanisms and photocurrent responses in both the above systems using a variety of scanning probe microscopy techniques as well as computational analysis. This work shows that van der Waals interactions are robust across different dimensionalities of materials and can allow fabrication of semiconductor devices with unique geometries and properties unforeseen in bulk semiconductors. Finally, I will briefly discuss our recent work from Caltech on near-unity absorption in atomically-thin photovoltaic devices. This work is supported by the Materials Research Center at Northwestern University, funded by the National Science Foundation (NSF DMR-1121262) and the Resnick Sustainability Institute at Caltech.

Die identifisering van maatstawwe vir die navorsingsprestasie van akademici

Directory of Open Access Journals (Sweden)

H. A. Labuschagne

1990-06-01

Full Text Available Identification of criteria for academic research performance. At South African universities, the achievement of objectives is usually measured in terms of so-called "process criteria" (e.g. pass rates, instead of performance criteria which reflect the quality of academic personnel. Stimulated by the need to identify valid indices of research performance, as a component of academic performance, this study investigated the dimensionality of several criteria, identified from empirical and literature studies. It was found that various valid criteria could be represented by six constructs, viz.: the stature of the researcher as scientist; scientific contributions; enhancement of own profession; community development; participation in research projects; and giving advice to persons or institutions outside the university. Opsomming By Suid-Afrikaanse universiteite word doelwitbereiking gewoonlik aan die hand van sogenaamde "prosesmaat-stawwe" (bv. slaagsyfers in plaas van prestasiemaatstawwe wat die gehalte van akademiese personeel weerspieel, gemeet. Na aanleiding van 'n behoefte aan die identifisering van geldige rigtingwysers vir navorsingsprestasie as 'n komponent van akademiese prestasie, is daar ondersoek ingestel na die dimensionaliteit van verskillende maatstawwe wat vooraf deur middel van empiriese- en literatuurstudies geidentifiseer is. Daar is gevind dat verskeie geldige maatstawwe deur ses konstrukte verteenwoordig word, te wete: die statuur van die navorser as wetenskaplike, wetenskaplike bydraes, uitbouing van eie professie, gemeenskapsontwikkeling, deelname aan navorsingsprojekte en advieslewering aan persone of instellings buite die Universiteit.

Injector for CESAR (2 MeV electron storage ring): 2-beam, 2 MV van de Graaff generator; tank removed.

CERN Multimedia

CERN PhotoLab

1968-01-01

The van de Graaff generator in its tank. For voltage-holding, the tank was filled with pressurized extra-dry nitrogen. 2 beams emanated from 2 separate electron-guns. The left beam, for injection into the CESAR ring, was pulsed at 50 Hz, with currents of up to 1 A for 400 ns. The right beam was sent to a spectrometer line. Its pulselength was also 400 ns, but the pulse current was 12 microA, at a rate variable from 50 kHz to 1 MHz. This allowed stabilization of the top-terminal voltage to an unprecedented stability of +- 100 V, i.e. 6E-5. Although built for a nominal voltage of 2 MV, the operational voltage was limited to 1.75 MV in order to minimize voltage break-down events. CESAR was terminated at the end of 1967 and dismantled in 1968. R.Nettleton (left) and H.Burridge (right) are preparing the van de Graaff for shipment to the University of Swansea.

Arthroscopic modified Mason-Allen technique for large U- or L-shaped rotator cuff tears.

Science.gov (United States)

Jung, Sung-Weon; Kim, Dong-Hee; Kang, Seung-Hoon; Lee, Ji-Heon

2017-07-01

While a conventional single- or double-row repair technique could be applied for repair of C-shaped tears, a different surgical strategy should be considered for repair of U- or L-shaped tears because they typically have complex patterns with anterior, posterior, or both mobile leaves. This study was performed to examine the outcomes of the modified Mason-Allen technique for footprint restoration in the treatment of large U- or L-shaped rotator cuff tears. Thirty-two patients who underwent an arthroscopic modified Mason-Allen technique for large U- or L-shaped rotator cuff tears between January 2012 and December 2013 were included in this study. Margin convergence was first performed to reduce the tear gap and tension, and then, an arthroscopic Mason-Allen technique was performed to restore the rotator cuff footprint in a side-to-end repair fashion. All patients were evaluated preoperatively and for a minimum of 2 years of follow-up with a visual analog scale (VAS) for pain, Constant score, and ultrasonography. There was significant improvement in all VAS and Constant scores compared with the preoperative values (P rotator cuff in our data. Overall satisfactory results were achieved in most patients, with the exception of those with severe fatty degeneration. An arthroscopic modified Mason-Allen technique could be an effective and reliable alternative for patients with large U- or L-shaped rotator cuff tears. Case Series, Therapeutic Level IV.

Ion and electron Van de Graaff accelerators of Kyoto University

International Nuclear Information System (INIS)

Fukuzawa, F.; Imanishi, N.; Tomita, M.; Norisawa, K.; Yoshida, K.; Ohdaira, T.

1990-01-01

Two Van de Graaff accelerators are available at the Uji campus of Kyoto University. One is a 4MV machine, which is used for heavy ion acceleration, while the other is a 2MV machine for electron acceleration. These machines have been modified in various parts and currently used very actively in many fields of investigation. Important modifications of the 4MV machine are: use of a newly developed accelerating tube, addition of a charge-changer before the analyzing magnet, renewal of the charging belt, and development of a microbeam system for PIXE and RBS analysis. An attempt is now being made to accelerate micro-particles using the 2MV machine. The new accelerating tube has bucket type electrodes with large accelerating apertures. By charge-changing the accelerated 1+ ions to higher charge states, 2+, 3+, ..., at the entrance of the analyzing magnet, Ar ions with energies of up to 2.73, 6.21, .... MeV can be deflected to the duct. Scanning microbeam PIXE and RBS are powerful tools for analysis of spatial elemental distribution. Calculations suggest that a beam size of about 3 μm can be attained by using an object aperture of 10μm in diameter and controlling the beam divergence within 10μ rad in both directions. (N.K.)

Invloed van minerale olie op de bestrijding van Phytophthora infestans in pootaardappelen

NARCIS (Netherlands)

Spits, H.G.; Bus, C.B.

2003-01-01

De invloed van toevoeging van olie aan een fungicide op de werking van het fungicide is afhankelijk van het gebruikte fungicide. Gezamenlijk spuiten van olie en Aviso DF, Curzate M en mogelijk ook Acrobat, verhoogt de curatieve werking van deze fungiciden. Gezamenlijk spuiten van olie en Aviso DF,

B. J. van der Merwe . Pentateugtradisies in die prediking van ...

African Journals Online (AJOL)

B. J. van der Merwe . Pentateugtradisies in die prediking van Deuterojesaja. Proefschrift ter verkrijging van de graad van Doctor in de Godgeleerdheid aan de Rijkuniversiteit te Groningen. Uitg. J. B. Wolters, Groningen, Djakarta. 1955. 280 bls.

n Oorsig van die huidige stand van navorsing oor die

African Journals Online (AJOL)

Test

7 Jun 2011 ... Die eerste maal wat dit as deel van die teks van 1 Johannes aangehaal word, is in die. 4de eeu in 'n Latynse teks, Liber Apologeticus (hf 4). Eers aan die einde van die 16de eeu is dit in 'n amptelike Katolieke uitgawe van die Vulgaat ingesluit. Die doel van die Johannesbriewe. Waarom is die Briewe ...

Nanostructure van der Waals interaction between a quantum well and a quantum dot atom

International Nuclear Information System (INIS)

Horing, Norman J Morgenstern

2006-01-01

We examine the van der Waals interaction between mobile plasma electrons in a narrow quantum well nanostructure and a quantum dot atom. This formulation of the van der Waals interaction exhibits it to second order as the correlation energy (self-energy) of the dot-atom electrons mediated by the image potential arising from the dynamic, nonlocal and spatially inhomogeneous polarization of the quantum well plasma electrons. This image potential of the quantum-well plasma is, in turn, determined by the dynamic, nonlocal, inhomogeneous screening function of the quantum well, which involves the space-time matrix inversion of its spatially inhomogeneous, nonlocal and time-dependent dielectric function. The latter matrix inversion is carried out exactly, in closed form, and the van der Waals energy is evaluated in the electrostatic limit to dipole-dipole terms

Relativistic electron flux dropout due to field line curvature during the storm on 1 June 2013

Science.gov (United States)

Kang, S. B.; Fok, M. C. H.; Engebretson, M. J.; Li, W.; Glocer, A.

2017-12-01

Significant electron flux depletion over a wide range of L-shell and energy, referred as a dropout, was observed by Van Allen Probes during the storm main phase on June 1, 2013. During the same period, MeV electron precipitation with isotropic pitch-angle distribution was also observed in the evening sector from POES but no EMIC waves were detected from either space- or ground-based magnetometers. Based on Tsyganenko empirical magnetic field model, magnetic field lines are highly non-dipolar and stretched at the night side in the inner magnetosphere. This condition can break the first adiabatic invariant (conservation of magnetic moment) and generate pitch-angle scattering of relativistic electron to the loss cone. To understand the relative roles of different physical mechanisms on this dropout event, we simulate flux and phase space density of relativistic electrons with event specific plasma wave intensities using the Comprehensive Inner Magnetosphere and Ionosphere (CIMI) model, as a global 4-D inner magnetosphere model. We also employ pitch-angle scattering due to field line curvature in the CIMI model. We re-configure magnetic field every minute and update electric field every 20 seconds to capture radial transport. CIMI-simulation with pitch-angle scattering due to field line curvature shows more depletion of relativistic electron fluxes and better agreement to observation than CIMI-simulation with radial transport only. We conclude that pitch-angle scattering due to field line curvature is one of the dominant processes for the relativistic electron flux dropout.

Detectie van Meloidogyne spp. in grondmonsters - een vergelijking van twee technieken

NARCIS (Netherlands)

Veenhuizen, P.T.M.; Schoemakers, N.; Vos, J.; Versteegen, F.; Landeweert, R.; Karssen, G.

2007-01-01

Hier volgen de samenvattingen van de bijeenkomst van 20 maart 2007 van de KNPV-werkgroep Meloidogyne. 1) Kwantitatieve multiplexdetectie van aaltjes; 2). Meloidogyne chitwoodi en M. fallax: vergelijking visuele beoordeling en Taqman-PCR aan pootaardappelen; 3) Detectie van Meloidogyne spp. in

Stroming en samenstelling van de sprengen en het grondwater van de Veluwe in 1996; een vergelijking met de toestand van 1986

NARCIS (Netherlands)

Meinardi CR; LBG

1999-01-01

Monsters water uit sprengen en grondwater van de Veluwe zijn onderzocht op concentraties van hoofdcomponenten en van microcomponenten (bepalingen door NITG). Onderzoek is gedaan ter bepaling van verblijftijden in de bodem van grondwater en van het water in sprengen. De intrekgebieden van de

Simulation and modeling of whistler-mode wave growth through cyclotron resonance with energetic electrons in the magnetosphere

International Nuclear Information System (INIS)

Carlson, C.R.

1987-01-01

New models and simulations of wave growth experienced by electromagnetic waves propagating through the magnetosphere in the whistler mode are presented. For these waves, which have frequencies below the electron gyro and plasma frequencies, the magnetospheric plasma acts like a natural amplifier often amplifying the waves by ∼ 30 dB. The mechanism for growth is cyclotron resonance between the circularly polarized waves and the gyrating energetic electrons which make up the Van Allen radiation belts. The main emphasis is to simulate single-frequency wave pulses, in the 2-6 kHz range, that have been injected into the magnetosphere, near L ∼ 4, by the Stanford transmitting facility at Siple station, Antarctica. However, the results can also be applied to naturally occurring signals, signals from other transmitters, non-CW signals, and signals in other parts of the magnetosphere not probed by the Siple Station transmitter. Results show the importance of the transient aspects in the wave-growth process. The wave growth established as the wave propagates toward the equator, is given a spatially advancing wave phase structure by the geomagnetic inhomogeneity. Through the feedback of this radiation upon other electrons, conditions are set up that results in the linearly increasing output frequency with time

Ab-initio study of structural and electronic properties of WS2/h-BN van der Waals heterostructure

Science.gov (United States)

Ghasemi majd, Zahra; Amiri, Peiman; Taghizadeh, Seyed Fardin

2018-06-01

First-principle calculations with different exchange-correlation functionals, including LDA, GGA, semi-empirical and ab-initio van der Waals in the forms of vdW-DF2B86R and vdW-DF2 were performed to evaluate the performance of different functionals in describing the bonding mechanism, adsorption energy and interlayer distance of WS2 monolayer on and between h-BN layers. The finding was that the vdW-DF2B86R seems to be the approach best lending itself to this purpose. In order to include the van der Waals (vdW) interactions in our calculations, we used the DFT-D2 and vdW methods, which gave rise to a physical adsorption with no net charge transfer between the WS2 layer and the corresponding substrates. In addition, we investigated the electronic and structural properties of WS2 and h-BN heterolayers, using vdW-DF2B86R functional. Based on density functional theory calculations, WS2 on and between h-BN layers showed a direct band gap at the K-point, which was experimentally observed.

A. VAN SELMS. LUKAS SE SEGSMAN VIR DIE GESKIEDENIS VAN ...

African Journals Online (AJOL)

Test

oordele aan die eerste drie hoofstukke van sy Evangelie, het Lukas onder „van ..... Simon te onderskei van Simon Petrus, hoef ons nie erns te maak nie. .... op hulle beurt vereenselwig met Mosa van Jos. .... i&) Lukas der Arzt. Leipzig, 1906.

Multiple loss processes of relativistic electrons outside the heart of outer radiation belt during a storm sudden commencement

International Nuclear Information System (INIS)

Yu, J.

2015-01-01

By examining the compression-induced changes in the electron phase space density and pitch angle distribution observed by two satellites of Van Allen Probes (RBSP-A/B), we find that the relativistic electrons (>2 MeV) outside the heart of outer radiation belt (L*≥5) undergo multiple losses during a storm sudden commencement. The relativistic electron loss mainly occurs in the field-aligned direction (pitch angle α < 30° or >150°), and the flux decay of the field-aligned electrons is independent of the spatial location variations of the two satellites. However, the relativistic electrons in the pitch angle range of 30°–150° increase (decrease) with the decreasing (increasing) geocentric distance (|ΔL|<0.25) of the RBSP-B (RBSP-A) location, and the electron fluxes in the quasi-perpendicular direction display energy-dispersive oscillations in the Pc5 period range (2–10 min). The relativistic electron loss is confirmed by the decrease of electron phase space density at high-L shell after the magnetospheric compressions, and their loss is associated with the intense plasmaspheric hiss, electromagnetic ion cyclotron (EMIC) waves, relativistic electron precipitation (observed by POES/NOAA satellites at 850 km), and magnetic field fluctuations in the Pc5 band. Finally, the intense EMIC waves and whistler mode hiss jointly cause the rapidly pitch angle scattering loss of the relativistic electrons within 10 h. Moreover, the Pc5 ULF waves also lead to the slowly outward radial diffusion of the relativistic electrons in the high-L region with a negative electron phase space density gradient.

Digitale incunabelen : Over het belang van het archiveren van websites

NARCIS (Netherlands)

Voerman, Gerrit; Keyzer, Andreas; den Hollander, Franciscus

'Het geheugen van Nederland verpulvert'. Zo luidde de noodkreet van ruim twintig grote bibliotheken in het voorjaar van 1998. In een advertentie in enkele landelijke dagbladen vroegen deze bibliotheken om honderden miljoenen guldens voor het restaureren, fotograferen en digitaliseren van boeken en

Digitale incunabelen : Over het belang van het archiveren van websites

NARCIS (Netherlands)

Voerman, Gerrit; Keyzer, Andreas; den Hollander, Franciscus

2000-01-01

'Het geheugen van Nederland verpulvert'. Zo luidde de noodkreet van ruim twintig grote bibliotheken in het voorjaar van 1998. In een advertentie in enkele landelijke dagbladen vroegen deze bibliotheken om honderden miljoenen guldens voor het restaureren, fotograferen en digitaliseren van boeken en

Inclusie door interprofessionele samenwerking. : Resultaten van de proeftuinen van PACT.

NARCIS (Netherlands)

Doornenbal, Jeannette; Fukkink, Ruben; van Yperen, Tom; Balledux, Mariëlle; Spoelstra, Jolanda; Verseveld, Marloes

2017-01-01

Deze rapportage gaat over de resultaten van de PACT-proeftuinen waaraan in opdracht van Het Kinderopvangfonds van 2015 tot 2017 is gewerkt. PACT-proeftuinen zijn innovatieve praktijken waarin door middel van interprofessionele samenwerking tussen de kinderopvang, het basisonderwijs en de zorg wordt

Die opleiding van bedryfsielkundiges aan die universiteit van Fort Hare

Directory of Open Access Journals (Sweden)

W. Botha

1977-11-01

Full Text Available Die Departement Bedryfsielkunde aan die Universiteit van Fort Hare is 'n relatiewe jong departement en het eers in 1965 tot stand gekom. Voor hierdie datum is Bedryfsielkunde as 'n kort kursus deur die departement van suiwer Sielkunde aangebied en een van die destydse dosente, Dr. W. Backer, het die inisiatief geneem om 'n selfstandige departement van Bedryfsielkunde in die Fakulteit van Ekonomiese Wetenskappe op die been te bring.

Het effect van creatief schrijven op het lezen van korte verhalen

NARCIS (Netherlands)

Janssen, T.; van den Bergh, H.

2010-01-01

Schrijven en lezen zijn complementaire vaardigheden, niet alleen bij referentiële teksten, maar ook bij fictionele. Janssen en Van den Bergh doen verslag van een onderzoek naar de invloed van creatief schrijven op het lezen van verhalen. Als leerlingen, voorafgaand aan het lezen van een verhaal, een

Databank van de lithografische opbouw en morfologische ontwikkeling van de uiterwaarden van de Midden-Waal

NARCIS (Netherlands)

Hebinck, K.A.

2008-01-01

In de uiterwaarden zijn de komende decennia veel ingrepen gepland. Een goede kennis van de sedimentatiedynamiek en morfologische ontwikkeling van de uiterwaarden is daarbij een vereiste. Daartoe is een digitale databank (op CD bij dit rapport) opgesteld van de opbouw en geomorfologische ontwikkeling

Electronic structures and enhanced optical properties of blue phosphorene/transition metal dichalcogenides van der Waals heterostructures

Science.gov (United States)

Peng, Qiong; Wang, Zhenyu; Sa, Baisheng; Wu, Bo; Sun, Zhimei

2016-01-01

As a fast emerging topic, van der Waals (vdW) heterostructures have been proposed to modify two-dimensional layered materials with desired properties, thus greatly extending the applications of these materials. In this work, the stacking characteristics, electronic structures, band edge alignments, charge density distributions and optical properties of blue phosphorene/transition metal dichalcogenides (BlueP/TMDs) vdW heterostructures were systematically studied based on vdW corrected density functional theory. Interestingly, the valence band maximum and conduction band minimum are located in different parts of BlueP/MoSe2, BlueP/WS2 and BlueP/WSe2 heterostructures. The MoSe2, WS2 or WSe2 layer can be used as the electron donor and the BlueP layer can be used as the electron acceptor. We further found that the optical properties under visible-light irradiation of BlueP/TMDs vdW heterostructures are significantly improved. In particular, the predicted upper limit energy conversion efficiencies of BlueP/MoS2 and BlueP/MoSe2 heterostructures reach as large as 1.16% and 0.98%, respectively, suggesting their potential applications in efficient thin-film solar cells and optoelectronic devices. PMID:27553787

Electronic structures and enhanced optical properties of blue phosphorene/transition metal dichalcogenides van der Waals heterostructures.

Science.gov (United States)

Peng, Qiong; Wang, Zhenyu; Sa, Baisheng; Wu, Bo; Sun, Zhimei

2016-08-24

As a fast emerging topic, van der Waals (vdW) heterostructures have been proposed to modify two-dimensional layered materials with desired properties, thus greatly extending the applications of these materials. In this work, the stacking characteristics, electronic structures, band edge alignments, charge density distributions and optical properties of blue phosphorene/transition metal dichalcogenides (BlueP/TMDs) vdW heterostructures were systematically studied based on vdW corrected density functional theory. Interestingly, the valence band maximum and conduction band minimum are located in different parts of BlueP/MoSe2, BlueP/WS2 and BlueP/WSe2 heterostructures. The MoSe2, WS2 or WSe2 layer can be used as the electron donor and the BlueP layer can be used as the electron acceptor. We further found that the optical properties under visible-light irradiation of BlueP/TMDs vdW heterostructures are significantly improved. In particular, the predicted upper limit energy conversion efficiencies of BlueP/MoS2 and BlueP/MoSe2 heterostructures reach as large as 1.16% and 0.98%, respectively, suggesting their potential applications in efficient thin-film solar cells and optoelectronic devices.

Fluorescentievingerafdruk van Aardappel, Melganzenvoet en Mais : Eerste resultaten van plantonderscheid met behulp van fluorescentie

NARCIS (Netherlands)

Groot, T.T.; Nieuwenhuizen, A.T.

2012-01-01

Als het spectrum van één “soort” (gewas) vergeleken wordt met de rest (onkruid) neemt het onderscheid van het “gewas” af tot 70%. Het lijkt dus nodig ook de spectra van alle soorten onkruid in het veld te kennen om een goed onderscheid mogelijk te maken. De doelstelling voor deze metingen is een

Proeven van tekstkritiek. Een onderzoek betreffende de tekstgeschiedenis van de Renout van Montalbaen en de Perceval

NARCIS (Netherlands)

Hogenhout-Mulder, Maaike Janna

1984-01-01

In dit proefschrift wordt een poging gedaan de tekstgeschiedenis te achterhalen van twee Middelnederlandse tekstfragmenten: een gedeelte uit de RENOUT VAN MONTALBAEN en een gedeelte uit de PERCEVAL. ... Zie: Twee tekstfragmenten als object van onderzoek

Invoering van algemene vaardigheden: mogelijkheden van een vakoverstijgende aanpak

NARCIS (Netherlands)

Leenders, F.J.

2003-01-01

Centrale vraag: Het onderzoek richtte zich op de implementatie van vakoverstijgend vaardighedenonderwijs in de Tweede Fase van het voortgezet onderwijs. Belangrijkste conclusies: De brochure bevat onder meer een beschrijving van vijf scholen waar op verschillende wijze vaardighedenonderwijs

Double layer -- a particle accelerator in the magnetosphere

Energy Technology Data Exchange (ETDEWEB)

Fu, Xiangrong [Los Alamos National Laboratory

2015-07-16

Slides present the material under the following topics: Introduction (What is a double layer (DL)? Why is it important? Key unsolved problems); Theory -- time-independent solutions of 1D Vlasov--Poisson system; Particle-in-cell simulations (Current-driven DLs); and Electron acceleration by DL (Betatron acceleration). Key problems include the generation mechanism, stability, and electron acceleration. In summary, recent observations by Van Allen Probes show large number of DLs in the outer radiation belt, associated with enhanced flux of relativistic electrons. Simulations show that ion acoustic double layers can be generated by field-aligned currents. Thermal electrons can gain energy via betatron acceleration in a dipole magnetic field.

Resultaten van het Rijkswaterstaat JAMP 2009 monitoringsprogramma van bot (Platichthys flesus L.). Biologische gegevens van bot en milieukritische stoffen in bot

OpenAIRE

Hoek-van Nieuwenhuizen, van, M.; Barneveld, van, E.

2010-01-01

De in dit rapport beschreven werkzaamheden zijn in 2009 door IMARES uitgevoerd op basis van een opdracht van Rijkswaterstaat in het kader van het Joint Assessment and Monitoring Program van de OSPARCOM. De opdracht hield in het verkrijgen van biologische gegevens van bot (visziekten). De benodigde monsters bot werden verzameld door IMARES. Tevens werd materiaal van bot verzameld voor chemisch onderzoek en geanalyseerd.

Optique moderne et post-moderne dans la composition d'images transculturelles dans trois films de Woody Allen

Directory of Open Access Journals (Sweden)

Nadia Fuchs

2010-12-01

Full Text Available Avec le personnage récurrent juif new-yorkais névrosé plus ou moins autobiographique, les films de Woody Allen ont créé, volontairement ou pas, leur propre mythologie et un genre à part entière composé de codes que le spectateur décrypte instantanément. Pourtant, Woody Allen est surtout un cinéaste post-moderne, analysant et déconstruisant les simulacres de son époque. Il est ainsi un passeur d'images retraçant l'histoire des arts modernes des XXe et XXIe siècles et de leurs stratégies énonciatives et réceptives.With the recurrent persona of the neurotic and more or less autobiographical Jewish New Yorker, Woody Allen's films have created, willingly or not, their own mythology and a specific genre made up of codes readily accessible to the spectator. However, Woody Allen is more than anything else a postmodern filmmaker who analyses and deconstructs the simulacra of his time. He is thus a conveyor of images which retrace the history of modern art of the XXth and XXIth centuries, and of their strategies of enunciation and reception.

Direct detection of albedo neutron decay electrons at the inner edge of the radiation belt and experimental determination of neutron density in near-Earth space

Science.gov (United States)

Li, X.; Selesnick, R.; Schiller, Q. A.; Zhang, K.; Zhao, H.; Baker, D. N.; Temerin, M. A.

2017-12-01

The galaxy is filled with cosmic ray particles, mostly protons with kinetic energy above hundreds of mega-electron volts (MeV). Soon after the discovery of Earth's Van Allen radiation belts almost six decades ago, it was recognized that the main source of inner belt protons, with kinetic energies of tens to hundreds of MeV, is Cosmic Ray Albedo Neutron Decay (CRAND). In this process, cosmic rays reaching the upper atmosphere from throughout the galaxy interact with neutral atoms to produce albedo neutrons which, being unstable to 𝛽 decay, are a potential source of geomagnetically trapped protons and electrons. Protons retain most of the neutrons' kinetic energy while the electrons have lower energies, mostly below 1 MeV. The viability of the electron source was, however, uncertain because measurements showed that electron intensity can vary greatly while the neutron decay rate should be almost constant. Recent measurements from the Relativistic Electron and Proton Telescope integrated little experiment (REPTile) onboard the Colorado Student Space Weather Experiment (CSSWE) CubeSat now show that CRAND is the main electron source for the radiation belt near its inner edge, and also contributes to the inner belt elsewhere. Furthermore, measurement of the CRAND electron intensity provides the first experimental determination of the neutron density in near-Earth space, 2x10-9/cm3, confirming earlier theoretical estimates.

Resultaten van het Rijkswaterstaat JAMP 2008 monitoringsprogramma van bot (Platichthys flesus L.). Biologische gegevens van bot en milieukritische stoffen in bot

NARCIS (Netherlands)

Hoek-van Nieuwenhuizen, van M.; Barneveld, van E.

2009-01-01

De in dit rapport beschreven werkzaamheden zijn door Wageningen IMARES uitgevoerd op basis van een opdracht van Rijkswaterstaat in het kader van het Joint Assessment and Monitoring Program van de OSPARCOM. De opdracht hield in het verkrijgen van biologische gegevens van bot. De benodigde monsters

Afbouw van het Wsw-bestand: actualisatie op basis van Wsw-gegevens ultimo 2013

NARCIS (Netherlands)

Berden, C.; Tempelman, C.

2014-01-01

In opdracht van het ministerie van Sociale Zaken en Werkgelegenheid heeft SEO Economisch Onderzoek onderzoek gedaan naar de verdeling van het Participatiebudget over gemeenten. Een onderdeel van dit onderzoek vormde het voorspellen van de afbouw van het huidige zittend bestand in de Wsw op basis van

Resultaten van het Rijkswaterstaat JAMP 2009 monitoringsprogramma van bot (Platichthys flesus L.). Biologische gegevens van bot en milieukritische stoffen in bot

NARCIS (Netherlands)

Hoek-van Nieuwenhuizen, van M.; Barneveld, van E.

2010-01-01

De in dit rapport beschreven werkzaamheden zijn in 2009 door IMARES uitgevoerd op basis van een opdracht van Rijkswaterstaat in het kader van het Joint Assessment and Monitoring Program van de OSPARCOM. De opdracht hield in het verkrijgen van biologische gegevens van bot (visziekten). De benodigde

Die beskerming van biologiese diversiteit deur gebruik te maak van die gevoeligheidsvariasie van spesies vir toksiese stowwe

Directory of Open Access Journals (Sweden)

A. J. Reinecke

2003-09-01

Full Text Available Pogings om algemeen geldende standaarde of maatstawwe vir omgewingskwaliteit op te stel vir die beskerming van Suid-Afrika se ryk biodiversiteit word bemoeilik deur die feit dat spesies baie kan verskil  ten opsigte van hulle gevoeligheid vir toksiese stowwe. Daar kan dus nie sonder meer vanaf een spesie na ’n ander geëkstrapoleer word nie. Deur egter juis gebruik te maak van hierdie variasie in gevoeligheid van spesies, kan die assessering van die risiko wat besoedelingstowwe vir organismes inhou wel op ’n meer wetenskaplike grondslag bedryf word. Hierdie konsep gaan uit van die standpunt dat indien kwaliteitskriteriums opgestel word wat die sensitiefste spesies beskerm, alle ander spesies outomaties beskerm word. Hierdie bydrae fokus op die gebruik van sensitiwiteitsverspreidings van spesies as metode en kyk oorsigtelik en krities na die aard en toepassings van die ekstrapolasiemodelle wat op hierdie verspreidings gebaseer is. Die moontlike aanwending daarvan en die argumente ten gunste daarvan en daarteen word bespreek. Die gevolgtrekking word gemaak dat spesie-sensitiwiteitsverspreidings wel nuttige aanwending kan vind, maar dat  gegewens oor die gevoeligheid van plaaslike spesies  baie skaars is. Hoewel dit reeds bruikbaar is, kan die algemene aanwending daarvan  in Suid-Afrika aansienlik uitgebrei word indien meer navorsing gedoen word om betroubare toksisiteitsgegewens vir verskillende spesies in te win, sodat die model meer verfyn kan word. Daarvoor moet gestandaardiseerde toksisiteitstoetse vir plaaslike spesies eers ontwikkel word.

Gevolgen van hydrocephalus

NARCIS (Netherlands)

Tromp, Cornelis Nicolaas

1984-01-01

Hydrocephalus is een aandoening van het centrale zenuwstelsel die de clinicus vrij lang voor grote problemen ten aanzien van de behandeling heeft qesteld. Door de toepassing van de ventriculo-atriale shunttechniek zijn de behandelingsmogelijkheden van hydrocephalus sterk verbeterd. Deze studie

Activity Regulation by Heteromerization of Arabidopsis Allene Oxide Cyclase Family Members

Czech Academy of Sciences Publication Activity Database

Otto, M.; Naumann, Ch.; Brandt, W.; Wasternack, Claus; Hause, B.

2016-01-01

Roč. 5, č. 1 (2016), č. článku 3. ISSN 2223-7747 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : Activity regulation * Arabidopsis allene oxide cyclase isoforms * Heteromerization Subject RIV: EB - Genetics ; Molecular Biology

Overzicht van de onderzoekresultaten van kroketten, bitterballen en frikandellen van 1986

NARCIS (Netherlands)

Cazemier, G.; Veen, van der N.G.

1987-01-01

In 1986 werden in opdracht van de AID 54 monsters frikandellen en 237 monsters kroketten en bitterballen door het RIKILT onderzocht op de eisen, zoals die zijn vastgelegd in de Kwaliteitsverordening Kroketten, Bitterballen en Frika(n)dellen. In dit verslag zijn de analyseresultaten van deze monsters

Crafoord Symposium on Magnetospheric Physics : Achievements and Prospects

CERN Document Server

Fälthammar, C-G

1990-01-01

This book contains the proceedings of the 1989 Crafoord Symposium organized by the Royal Swedish Academy of Sciences. The scientific field for the Crafoord Prize of 1989 was decided in 1988 by the Academy to be Magnetospheric Physics. On September 27,1989 the Academy awarded the 1989 Crafoord Prize to Professor J. A. Van Allen, Iowa City, USA "for his pioneer work in space research, in particular for the discovery of the high energy charged particles that are trapped in the Earth's magnetic field and form the radiation belts -often called the Van Allen belts - around the Earth". The subject for the Crafoord Symposium, which was held on September 28-29 at the Royal Swedish Academy of Sciences in Stockholm, was Magnetospheric Physics, Achievements and Prospects. Some seventy of the world's leading scientists in magnetospheric physics (see list of participants) were invited to the Symposium. The program contained only invited papers. After the ?resentation of the Crafoord Prize Laureate, Prof. J . A. Van Allen, ...

ʼn Kritiese evaluering van wetgewing wat die gesondheid van ...

African Journals Online (AJOL)

User

gereguleer wat "basiese watervoorsiening" omskryf as "die voorgeskrewe minimum standaard van watervoorsieningsdienste wat nodig is vir die betroubare voorsiening van ʼn toereikende hoeveelheid en gehalte water aan huishoudings, met inbegrip van informele huishoudings, om lewe en persoonlike higiëne te steun".

The Compilation of Electronic Dictionaries for the African Languages

Directory of Open Access Journals (Sweden)

D.J.. Prinsloo

2011-10-01

Full Text Available

Abstract: Lexicographers increasingly acknowledge the enormous potential of electronic dictionaries. The great capacity and speed characteristic of electronic products, combined with enhanced query and data retrieval technology, pave the way to a new generation of dictionaries unimagined in the paper-dictionary era. It is amazing to see how many of the lexicographer's greatest obstacles disappear in the electronic dictionary. This article will, firstly, attempt to give a perspective on typical features of electronic dictionaries. Secondly, electronic-dictionary entries will be designed as a solution to some of the most burning lemmatization problems encountered by lexicographers for African languages in paper dictionaries.

Keywords: ELECTRONIC DICTIONARY, LEXICOGRAPHY, DATA RETRIEVAL, LEMMATIZATION, CD-ROM, ACCESS ROUTE, POP-UP FUNCTIONALITIES, POP-UP SCREENS, EDUTAINMENT, CROSS-REFERENCING, INFORMATION RETRIEVAL, ENCODING, DECODING, AFRICAN LANGUAGES, NAVIGATION BAR.

Opsomming: Die samestelling van elektroniese woordeboeke vir dieAfrikatale. Leksikograwe erken in toenemende mate die enorme moontlikhede van elektroniesewoordeboeke. Die groot vermoë en spoed wat kenmerkend is van elektroniese produkte,tesame met die bykomende tegnologie van soektogte en dataopsporing, berei die weg voor na 'nnuwe generasie woordeboeke wat ondenkbaar was in die era van gedrukte woordeboeke. Dit isverbasend om te sien hoeveel van die leksikograaf se grootste struikelblokke verdwyn in die elektroniesewoordeboek. Hierdie artikel sal eerstens probeer om 'n oorsig te gee oor die kenmerkendeeienskappe van elektroniese woordeboeke. Tweedens sal inskrywings vir die elektroniese woordeboekontwerp word as oplossing vir sommige van die dringendste lemmatiseringsprobleme watleksikograwe van Afrikatale by gedrukte woordeboeke teëkom.

Sleutelwoorde: ELEKTRONIESE WOORDEBOEK, LEKSIKOGRAFIE, DATAOPSPORING,LEMMATISERING, CD-ROM, TOEGANGSROETE

The effect of van der Waal's gap expansions on the surface electronic structure of layered topological insulators

International Nuclear Information System (INIS)

Eremeev, S V; Vergniory, M G; Chulkov, E V; Menshchikova, T V; Shaposhnikov, A A

2012-01-01

On the basis of relativistic ab initio calculations, we show that an expansion of van der Waal's (vdW) spacings in layered topological insulators caused by intercalation of deposited atoms, leads to the simultaneous emergence of parabolic and M-shaped two-dimensional electron gas (2DEG) bands as well as Rashba-splitting of the former states. The expansion of vdW spacings and the emergence of the 2DEG states localized in the (sub)surface region are also accompanied by a relocation of the topological surface state to the lower quintuple layers, that can explain the absence of inter-band scattering found experimentally. (paper)

Cooperative Metal–Ligand Catalyzed Intramolecular Hydroamination and Hydroalkoxylation of Allenes Using a Stable Iron Catalyst

KAUST Repository

El-Sepelgy, Osama

2018-01-18

A new iron-catalyzed chemoselective intramolecular hydroamination and hydroalkoxylation of the readily available α-allenic amines and alcohols to valuable unsaturated 5-membered heterocycles, 2,3-dihydropyrrole and 2,3-dihydrofuran, is reported. Effective selectivity control is achieved by a metal–ligand cooperative activation of the substrates. The mild reaction conditions and the use of low amounts of an air and moisture stable iron catalyst allow for the hydrofunctionalization of a wide range of allenes bearing different functional groups in good yields in the absence of base or any sensitive additives.

Cooperative Metal–Ligand Catalyzed Intramolecular Hydroamination and Hydroalkoxylation of Allenes Using a Stable Iron Catalyst

KAUST Repository

El-Sepelgy, Osama; Brzozowska, Aleksandra; Sklyaruk, Jan; Jang, Yoon Kyung; Zubar, Viktoriia; Rueping, Magnus

2018-01-01

A new iron-catalyzed chemoselective intramolecular hydroamination and hydroalkoxylation of the readily available α-allenic amines and alcohols to valuable unsaturated 5-membered heterocycles, 2,3-dihydropyrrole and 2,3-dihydrofuran, is reported. Effective selectivity control is achieved by a metal–ligand cooperative activation of the substrates. The mild reaction conditions and the use of low amounts of an air and moisture stable iron catalyst allow for the hydrofunctionalization of a wide range of allenes bearing different functional groups in good yields in the absence of base or any sensitive additives.

Karakterisering van het Etimologiewoordeboek van Afrikaans (EWA

Directory of Open Access Journals (Sweden)

Fons Moerdijk

2011-10-01

Full Text Available

Samenvatting: Zesendertig jaar na Afrikaanse etimologieë van Boshoff en Nienaber verscheener in 2003 een nieuw etymologisch woordenboek van het Afrikaans: het Etimologiewoordeboek vanAfrikaans (EWA. Tussen die twee woordenboeken bestaat een wezenlijk verschil. Het werk vanBoshoff en Nienaber is vrijwel alleen toegankelijk voor specialisten en niet specifiek bedoeld vooreen breed publiek. EWA is juist allereerst bestemd voor de leek die zich interesseert voor de oorsprongen de geschiedenis van de eigen taal. Daarnaast biedt het ook de etymoloog en historischtaalkundige een hoop gegevens en inspiratie voor nader onderzoek. Als etymologisch woordenboekbezit EWA een aantal bijzondere, eigen kenmerken. De selectie van de woorden is bepaalddoor het beoogde gebruikerspubliek. Als gevolg daarvan bevat EWA verscheidene typen woordendie in traditionele etymologische woordenboeken doorgaans veronachtzaamd worden, zoals afleidingen,samenstellingen, neologismen en gemeenzame spreektaalwoorden. De artikelstructuurwordt gekenmerkt door een hoge graad van uniformiteit en consistentie. Het accent ligt op dezogenaamde etymologia proxima, de etymologie waarbij men één stap teruggaat en de meestdirecte herkomst van het woord biedt. Voorts is speciale aandacht besteed aan polysemie: nietalleen de herkomst van de dominante betekenis van een woord wordt gegeven, maar ook die vanzijn eventuele andere betekenis(sen. Benoemingsmotieven komen ook veelvuldig aan bod. In eeneventuele tweede druk zouden opvallende verschillen in vorm of betekenis altijd verklaard of inieder geval besproken moeten worden. Dat blijft nu nogal eens achterwege. Ook zou voorafgaandaan zo'n volgende editie meer onderzoek naar woordhistorisch materiaal uit primaire bronnenvoor met name de 17de–19de eeuw verricht moeten worden. Het zou mooi zijn als deze eersteuitgave van EWA de aanleiding tot een dergelijk onderzoek zou vormen.

Sleutelwoorden: BENOEMINGSMOTIEF, ETYMOLOGIA PROXIMA

Kwantificatie van de invloed van regen op de verkeerdoorstroming

NARCIS (Netherlands)

Calvert, S.C.; Van Stralen, W.; Molin, E.J.E.

2013-01-01

Kwantificatie van de invloed van regen op de verkeerdoorstroming Het is bekend dat het weer invloed heeft op het verkeer op snelwegen, en in het bijzonder filevorming. Op de eerste plaats wordt de wegcapaciteit tijdelijk beïnvloed door een verandering in rijgedrag van bestuurders. Ten tweede

Isotope separation by photodissociation of Van der Wall's molecules

International Nuclear Information System (INIS)

Lee, Y.T.

1977-01-01

A method of separating isotopes based on the dissociation of a Van der Waal's complex is described. A beam of molecules of a Van der Waal's complex containing, as one partner of the complex, a molecular species in which an element is present in a plurality of isotopes is subjected to radiation from a source tuned to a frequency which will selectively excite vibrational motion by a vibrational transition or through electronic transition of those complexed molecules of the molecular species which contain a desired isotope. Since the Van der Waal's binding energy is much smaller than the excitational energy of vibrational motion, the thus excited Van der Waal's complex dissociate into molecular components enriched in the desired isotope. The recoil velocity associated with vibrational to translational and rotational relaxation will send the separated molecules away from the beam whereupon the product enriched in the desired isotope can be separated from the constituents of the beam

Hovering and forward flight energetics in Anna's and Allen's hummingbirds.

Science.gov (United States)

Clark, Christopher James; Dudley, Robert

2010-01-01

Aerodynamic theory predicts that the mechanical costs of flight are lowest at intermediate flight speeds; metabolic costs of flight should trend similarly if muscle efficiency is constant. We measured metabolic rates for nine Anna's hummingbirds (Calypte anna) and two male Allen's hummingbirds (Selasphorus sasin) feeding during flight from a free-standing mask over a range of airspeeds. Ten of 11 birds exhibited higher metabolic costs during hovering than during flight at intermediate airspeeds, whereas one individual exhibited comparable costs at hovering and during forward flight up to speeds of approximately 7 m s(-1). Flight costs of all hummingbirds increased at higher airspeeds. Relative to Anna's hummingbirds, Allen's hummingbirds exhibited deeper minima in the power curve, possibly due to higher wing loadings and greater associated costs of induced drag. Although feeding at a mask in an airstream may reduce body drag and, thus, the contributions of parasite power to overall metabolic expenditure, these results suggest that hummingbird power curves are characterized by energetic minima at intermediate speeds relative to hovering costs.

Prozaci asemel GTD ehk getting things done / David Allen ; interv. Endrik Randoja

Index Scriptorium Estoniae

Allen, David

2007-01-01

Konsultant ja koolitaja David Allen oma aja- ja enesejuhtimise meetodist GTD - getting things done. Vt. samas: Väikesed nipid, et tõhusam olla; Milles seisneb Alleni meetod; Kuidas ma oma ülesannet täitsin - logiraamat

Resultaten van het RWS-RIKZ JAMP 2005 monitoringsprogramma van bot (Platichthys flesus L.) : Biologische gegevens van bot en milieukritische stoofen in bot

NARCIS (Netherlands)

Kotterman, M.J.J.

2006-01-01

In opdracht van RWS-RIKZ werden door het RIVO werkzaamheden uitgevoerd in het kader van het Joint Assessment and Monitoring Program van de OSPARCOM. De opdracht hield in het verkrijgen van biologische gegevens van bot. De werkzaamheden bestonden uit het verzamelen van monsters bot waarvan

Efficient scattering of electrons below few keV by Time Domain Structures around injection fronts

Science.gov (United States)

Vasko, I.; Agapitov, O. V.; Mozer, F.; Artemyev, A.; Krasnoselskikh, V.

2016-12-01

Van Allen Probes observations show an abundance of non-linear large-amplitude electrostatic spikes around injection fronts in the outer radiation belt. These spikes referred to as Time Domain Structures (TDS) include electron holes, double layers and more complicated solitary waves. The electron scattering driven by TDS may not be evaluated via the standard quasi-linear theory, since TDS are in principle non-linear plasma modes. In this paper we analyze the scattering of electrons by three-dimensional TDS (with non-negligible perpendicular electric field) around injection fronts. We derive the analytical formulas describing the local scattering by single TDS and show that the most efficiently scattered electrons are those in the first cyclotron resonance (electrons crossing TDS on a time scale comparable with their gyroperiod). The analytical formulas are verified via the test-particle simulation. We compute the bounce-averaged diffusion coefficients and demonstrate their dependence on the TDS spatial distribution, individual TDS parameters and L shell. We show that TDS are able to provide the pitch-angle scattering of <5 keV electrons at rate 10-2-10-4 s-1 and, thus, can be responsible for driving loss of electrons out of injections fronts on a time scale from few minutes to few hours. TDS can be, thus, responsible for driving diffuse aurora precipitations conjugated to injection fronts. We show that the pitch-angle scattering rates driven by TDS are comparable with those due to chorus waves and exceed those due to electron cyclotron harmonics. For injections fronts with no significant wave activity in the frequency range corresponding to chorus waves, TDS can be even dominant mechanism for losses of below few keV electrons.

'Uytnemende Schilder van Antwerpen' : Joos van Cleve: atelier, productie en werkmethoden

NARCIS (Netherlands)

Leeflang, Micha

2007-01-01

Joos van Cleve (ca. 1480-1541) was een van de meest invloedrijke Antwerpse schilders in de eerste helft van dezestiende eeuw. Hij kreeg belangrijke opdrachten voor portretten en altaarstukken van onder anderen de Franse koning Frans I. Micha Leeflang onderzocht met name de materieel-technische

Resultaten van het RWS-RIKZ JAMP 2006 monitoringsprogramma van bot (Platichthys flesus L.). Biologische gegevens van bot en milieukritische stoffen in bot

OpenAIRE

Kotterman, M.J.J.; Barneveld, van, E.

2007-01-01

De in dit rapport beschreven werkzaamheden werden door IMARES uitgevoerd op basis van een opdracht van Rijkswaterstaat- Rijksinstituut voor Kust en Zee (RIKZ) in het kader van het Joint Assessment and Monitoring Program van de OSPARCOM. De opdracht hield in het verkrijgen van biologische gegevens van bot. De benodigde monsters bot werden verzameld door IMARES. Tevens werd materiaal van bot verzameld voor chemisch onderzoek en geanalyseerd.

Toepassing van de basisvrachtbenadering op fosfaat van compost; advies

NARCIS (Netherlands)

Ehlert, P.A.I.

2005-01-01

Bij het vormgeven van het stelsel van gebruiksnormen is een maatschappelijke discussie ontstaan over de aanvoer van fosfaat met grond in compost en zwarte grond. Deze deskstudie gaat in op vragen die hierbij gesteld zijn. Het aandeel grond in compost en zwarte grond en de hoeveelheid fosfaat daarin

"Die beiteltjie" van N.P. van Wyk Louw en

African Journals Online (AJOL)

Tom

belangrike kenmerk van die postmodernisme is, wil ek dit nie tot abso- lute kenmerk verhef nie. Een van die .... oorgang vanaf 'n epistemologiese ingesteldheid tot 'n ontologiese ingesteldheid demonstreer en ..... the neglected and a whole range of phenomena which have been denied a history. Die formulering van die ...

Invioed van de zuurtegraad van varkensurine op de ammoniakemissie

NARCIS (Netherlands)

Eizing, A.; Aarnink, A.J.A.

1996-01-01

Dit rapport beschrijft het effect van een lagere urine-pH op de ammoniakemissie in een varkensstal. Het onderzoek is uitgevoerd in een modelopstelling met de zogenaamde stalsimulator, waarbij de invloed van de urine-pH op de ammoniakemissie werd onderzocht. Hiervoor werd de urine van vleesvarkens op

Ontwerp van een interventie om de groenteconsumptie van jongeren te verhogen

NARCIS (Netherlands)

Gilissen, L.J.W.J.; Meer, van der I.M.; Reinders, M.J.; Sluis, van der A.A.; Woltering, E.J.

2011-01-01

In dit rapport zullen verschillende mogelijke strategieën besproken worden die ingezet kunnen worden om de consumptie van groenten door jongeren te verhogen. De centrale vragen van dit onderzoek zijn: 1) Hoe kunnen groenten in het eetpatroon van jongeren een vaste plek van voldoende omvang krijgen?

Reductie van het kiemgetal van bacteriën op champignons : literatuuroverzicht

NARCIS (Netherlands)

Baars, J.J.P.

2006-01-01

Dit rapport bevat een literatuurstudie waarin een overzicht wordt gegeven van de beschikbare literatuur m.b.t. hoogte van het kiemgetal van bacteriën op champignons en de grondstoffen voor de champignonteelt, aanwezigheid van pathogene bacteriën op champignons die in de retail worden aangeboden en

Het handwerk van de theorie in de praktijk van het Sociaal Werk

Directory of Open Access Journals (Sweden)

Hans Oostrik

2010-06-01

Sociaal werk is een narratieve praktijk. Vanuit een sociaal-constructivistische invalshoek, reflecteert de auteur in dit artikel op de vraag hoe vanuit deze narratieve praktijk tot theoretische handelingsmodellen kan worden gekomen. Drie elementen spelen daarbij een rol, welke door de auteur worden behandeld. Ten eerste zijn dat de vaardigheden van de professional, die bijdragen aan conceptualisering, zoals daar zijn: het signaleren van kwesties, het analyseren en vormen van begrippen en het ontwerpen van conceptuele modellen. Ten tweede kunnen theoretische modellen in de praktijk van het sociaal werk gebruikt worden als instrumenten om die praktijk als het ware te theoretiseren of reflectief te maken. De praktijk wordt met behulp van modellen zoals scenario’s en stappenplannen, verbeterd en verder ontwikkeld. Ten derde bestaat het handwerk van de theorie in het innemen van een theoretische houding of praktische verstandigheid waardoor sociaal werkers beter om kunnen gaan met de complexiteit van hun praktijk.

Effecten van wintergewassen op verliezen en benutting van stikstof bij de teelt van snijmaos; verslag van onderzoek op ROC Aver-Heino tussen voorjaar 1991 en najaar 1994

NARCIS (Netherlands)

Dijk, van W.; Schröder, J.J.; Holte, ten L.; Groot, de W.J.M.

1995-01-01

Tussen 1988 en 1994 is onderzoek verricht naar de effecten van wintergewassen (winterrogge en onderzaai van gras) op de verliezen en benutting van stikstof bij continuteelt van snijmaos op zandgrond. Gemiddeld over de gehele onderzoeksperiode nam zowel rogge als gras 30-40 kg/ha op in de

Gebruik van TaqMan PCR voor het kwantificeren van Fusarium spp. en Microdochium nivale in gewassen en gewasresten van tarwe.

NARCIS (Netherlands)

Köhl, J.; Haas, de B.H.; Kastelein, P.; Burgers, S.L.G.E.; Waalwijk, C.

2005-01-01

Infecties van tarwe door toxigene Fusarium spp. kunnen leiden tot contaminatie van graan met diverse mycotoxines. Voorkoming van mycotoxinebesmetting is uit oogpunt van voedselveiligheid, diergezondheid, maar ook bedrijfseconomisch, vereist. Voor vier Fusariumsoorten is een kwantitatieve detectie

Van die Gasredakteur

African Journals Online (AJOL)

cherish and teach.'1. Die Fakulteit Geneeskunde van die Universiteit van die Oranje-Vrystaat het pragtig gegroei ge- durende die eerste 21 jaar van sy bestaan. Die entoesiasme, doelgerigtheid, harde werk en inisia- tiewe van 'n groot aantal persone was hiervoor verantwoordelik. 'If we see a bit more clearly than they, it is ...

Satellite and Ground Signatures of Kinetic and Inertial Scale ULF Alfven Waves Propagating in Warm Plasma in Earth's Magnetosphere

Science.gov (United States)

Rankin, R.; Sydorenko, D.

2015-12-01

Results from a 3D global numerical model of Alfven wave propagation in a warm multi-species plasma in Earth's magnetosphere are presented. The model uses spherical coordinates, accounts for a non-dipole magnetic field, vertical structure of the ionosphere, and an air gap below the ionosphere. A realistic density model is used. Below the exobase altitude (2000 km) the densities and the temperatures of electrons, ions, and neutrals are obtained from the IRI and MSIS models. Above the exobase, ballistic (originating from the ionosphere and returning to ionosphere) and trapped (bouncing between two reflection points above the ionosphere) electron populations are considered similar to [Pierrard and Stegen (2008), JGR, v.113, A10209]. Plasma parameters at the exobase provided by the IRI are the boundary conditions for the ballistic electrons while the [Carpenter and Anderson (1992), JGR, v.97, p.1097] model of equatorial electron density defines parameters of the trapped electron population. In the simulations that are presented, Alfven waves with frequencies from 1 Hz to 0.01 Hz and finite azimuthal wavenumbers are excited in the magnetosphere and compared with Van Allen Probes data and ground-based observations from the CARISMA array of ground magnetometers. When short perpendicular scale waves reflect form the ionosphere, compressional Alfven waves are observed to propagate across the geomagnetic field in the ionospheric waveguide [e.g., Lysak (1999), JGR, v.104, p.10017]. Signals produced by the waves on the ground are discussed. The wave model is also applied to interpret recent Van Allen Probes observations of kinetic scale ULF waves that are associated with radiation belt electron dynamics and energetic particle injections.

De werking van de hydro- en acetylverbindingen van kinidine en kinine op het hart van Rana esculenta

NARCIS (Netherlands)

Sibie, Johan Dirk

1942-01-01

In hoofdstuk I werd een inleiding gegeven betreffende de geschiedenis van de kina en van het begin der kinacultuur op Java, de chemie der kinaälkaloïden en enkele aspecten der pharmacologische werking van de kinaderivaten. ... Zie: Samenvatting

Introductie van de Chevon : een zoektocht naar de afzet van geitenvlees

NARCIS (Netherlands)

Eleveld, I.; Louis Bolk,

2008-01-01

Het afmesten en afzetten van lammeren op een biologisch bedrijf is geen gemakkelijke weg. Aan de smaak van het vlees zal het niet liggen. De chevon, lammeren met een leeftijd van 5 tot 7 maand, geven vlees met karakter: een vleugje geit! De onbekendheid van het vlees vereist een zorgvuldige

Nucleotide insertion initiated by van der Waals interaction during ...

Indian Academy of Sciences (India)

renormalized van der Waals (vdW) interaction of a stronger type, the ..... can be used to determine the electrostatic dipole–dipole, .... water molecule and a surface oxygen atom. ..... understand proteins electronic interaction.54 Here, we.

De auteursrechtelijke aansprakelijkheid van intermediairs, het kabelpiratenarrest revisited in de tijd van Internet

NARCIS (Netherlands)

Dommering, E.J.; Verkade, D.W.F.; Visser, D.J.G.

1998-01-01

Het kabelpiratenarrest vestigde de auteursrechtelijke aansprakelijkheid van de kabelexploitant voor het verspreiden van gestolen films die clandestien na de uitzendingen van de reguliere omroepen werden uitgezonden met gebruikmaking van de centrale antenne-inrichting van KTA. Zouden wij de

Size effects in van der Waals clusters studied by spin and angle-resolved electron spectroscopy and multi-coincidence ion imaging

International Nuclear Information System (INIS)

Rolles, D; Pesic, Z D; Zhang, H; Bilodeau, R C; Bozek, J D; Berrah, N

2007-01-01

We have studied the valence and inner-shell photoionization of free rare-gas clusters by means of angle and spin resolved photoelectron spectroscopy and momentum resolving electron-multi-ion coincidence spectroscopy. The electron measurements probe the evolution of the photoelectron angular distribution and spin polarization parameters as a function of photon energy and cluster size, and reveal a strong cluster size dependence of the photoelectron angular distributions in certain photon energy regions. In contrast, the spin polarization parameter of the cluster photoelectrons is found to be very close to the atomic value for all covered photon energies and cluster sizes. The ion imaging measurements, which probe the fragmentation dynamics of multiply charged van der Waals clusters, also exhibit a pronounced cluster size dependence

De mislukte missie van mr. Maarten van Naarden als luitenant-stadhouder van Stad en Lande 1541-1557

Directory of Open Access Journals (Sweden)

F. Postma

2005-01-01

Full Text Available Maarten van Naarden’s failed mission  as lieutenant-stadholder of the province of Groningen, 1541-1557In November 1557, Maarten van Naarden resigned from his post as lieutenant-stadholder of the province of Groningen and left the province after staying there for sixteen years. Van Naarden’s resignation was preceded by a number of conflicts with the Groningen town council and the States of the province. However, these conflicts were neither confined to Van Naarden nor the province of Groningen. They had also taken place  in other provinces in the Northeast of the Netherlands. What makes Van Naarden’s clash with the Groningen provincial authorities in the 1550s so important is that it clarifies the principles that were at stake. These principles were less apparent in the conflicts between the representatives of the central government in Friesland, Overijssel and Gelderland. It was a struggle in which Van Naarden tried, as his opponents rightly saw it, to introduce the ‘constitution’ of Utrecht in the town and county of Groningen. In Utrecht, which had been annexed by Charles V in 1528, the autonomy of the province had been reduced to next to nothing. The only authority still resting with the States was the surveillance of the provincial dikes and waterways. All their other areas of authority had been taken over by the provincial court of which Van Naarden had been president between 1537 and 1541. To avoid the same thing happening to them, Van Naarden was ordered to appear before the Groningen States assembly in January 1556. At this meeting, the weakness of his position became crystal clear. None of the members took his side. Because the government lacked the means to keep Van Naarden in office, his withdrawal from Groningen was inevitable. What we see behind the story of Van Naarden more clearly than in the conflicts in the neighbouring provinces is the outline of the absolute state that Van Naarden’s superiors had in mind for the

Effect of the van der Waals interaction on the electron energy-loss near edge structure theoretical calculation.

Science.gov (United States)

Katsukura, Hirotaka; Miyata, Tomohiro; Tomita, Kota; Mizoguchi, Teruyasu

2017-07-01

The effect of the van der Waals (vdW) interaction on the simulation of the electron energy-loss near edge structure (ELNES) by a first-principles band-structure calculation is reported. The effect of the vdW interaction is considered by the Tkatchenko-Scheffler scheme, and the change of the spectrum profile and the energy shift are discussed. We perform calculations on systems in the solid, liquid and gaseous states. The transition energy shifts to lower energy by approximately 0.1eV in the condensed (solid and liquid) systems by introducing the vdW effect into the calculation, whereas the energy shift in the gaseous models is negligible owing to the long intermolecular distance. We reveal that the vdW interaction exhibits a larger effect on the excited state than the ground state owing to the presence of an excited electron in the unoccupied band. Moreover, the vdW effect is found to depend on the local electron density and the molecular coordination. In addition, this study suggests that the detection of the vdW interactions exhibited within materials is possible by a very stable and high resolution observation. Copyright © 2016 Elsevier B.V. All rights reserved.

Electron-phonon superconductivity in YIn3

Science.gov (United States)

Billington, D.; Llewellyn-Jones, T. M.; Maroso, G.; Dugdale, S. B.

2013-08-01

First-principles calculations of the electron-phonon coupling were performed on the cubic intermetallic compound YIn3. The electron-phonon coupling constant was found to be λep = 0.42. Using the Allen-Dynes formula with a Coulomb pseudopotential of μ* = 0.10, a Tc of approximately 0.77 K is obtained which is reasonably consistent with the experimentally observed temperature (between 0.8 and 1.1 K). The results indicate that conventional electron-phonon coupling is capable of producing the superconductivity in this compound.

Vulnerability assessment of a space based weapon platform electronic system exposed to a thermonuclear weapon detonation

Science.gov (United States)

Perez, C. L.; Johnson, J. O.

Rapidly changing world events, the increased number of nations with inter-continental ballistic missile capability, and the proliferation of nuclear weapon technology will increase the number of nuclear threats facing the world today. Monitoring these nation's activities and providing an early warning and/or intercept system via reconnaissance and surveillance satellites and space based weapon platforms is a viable deterrent against a surprise nuclear attack. However, the deployment of satellite and weapon platform assets in space will subject the sensitive electronic equipment to a variety of natural and man-made radiation environments. These include Van Allen Belt protons and electrons; galactic and solar flare protons; and neutrons, gamma rays, and x-rays from intentionally detonated fission and fusion weapons. In this paper, the MASH vl.0 code system is used to estimate the dose to the critical electronics components of an idealized space based weapon platform from neutron and gamma-ray radiation emitted from a thermonuclear weapon detonation in space. Fluence and dose assessments were performed for the platform fully loaded, and in several stages representing limited engagement scenarios. The results indicate vulnerabilities to the Command, Control, and Communication bay instruments from radiation damage for a nuclear weapon detonation for certain source/platform orientations. The distance at which damage occurs will depend on the weapon yield (n,(gamma)/kiloton) and size (kilotons).

DIE ROL VAN DIE TAALWETENSKAP IN DIE ONTWIKKELING VAN ...

African Journals Online (AJOL)

aanslag op die sogenaamde "Intentional Fallacy", heelwat verder. n. Mens sou hier eintlik ook op die invloed van Lacan se toepassing van. De Sacs sure op Freud moet wys, en op Macherey se Theory of Literary. Production. Barthes is naamlik besig om repressie teen te werk, en die teks as produksieproses in stede van ...

'n Voordrag van Adrianus van Seims oor hermeneutiek | Boshoff ...

African Journals Online (AJOL)

A lecture on hermeneutics by Adrianus van Seims This article is the content of a lecture on hermeneutics given by A van Seims. After a few opening words on the introduction to the lecture and its content, the presentation is reproduced in its entirety. Van Seims considers that hermeneutics is concerned not only with ...

"Krakende kaken"; psychiatrische beschouwingen over het syndroom van het pijnlijke, slecht functionerende kaakgewricht (Arthrosis deformans van het kaakgewricht of het syndroom van Costen)

NARCIS (Netherlands)

Schuler, Jacques

1966-01-01

Naar aanleiding van klinische indrukken en mede op grond van literatuurgegevens werd een psychiatrisch onderzoek verricht naar het aandeel van psychogene factoren bij het tot stand komen van kaakgewrichtsklachten. Het klachtencomplex dat van stoornissen in de functie van het kaakgewricht het gevolg

Voedselverspilling, waarden van voedsel in de keten : de mogelijke rol van het groene onderwijs bij het oplossen van een maatschappelijke opgave

OpenAIRE

Waarts, Y.R.; Onwezen, M.C.; Wiersinga, R.C.; Eppink, M.M.; Thoden van Velzen, E.U.; Timmermans, A.J.M.

2009-01-01

Het doel van deze verkenning is om op basis van literatuur en interviews met belangrijkste stakeholders een visie te formuleren over de wijze waarop het groene onderwijs een bijdrage kan leveren aan het verminderen van voedselverliezen binnen alle schakels van de keten inclusief de consument, en aan de nuttige toepassing van reststromen.

die impak van metodologie op die verstaan van die nuwe testament

African Journals Online (AJOL)

voorbeeld eers een maal deur die bril van die vorm- en redaksiekritiek na die Evangelies gekyk het, dink jy vir altyd anders oor hulle tot- standkoming. Inderdaad, nuwe metodes lei tot nuwe perspektiewe! Dit is dan ook waar die fokus van hierdie artikel val: die impak van metodologie op die verstaan van die Nuwe ...

Effectieve bestrijding van varroa

NARCIS (Netherlands)

Cornelissen, B.; Blacquiere, T.; Steen, van der J.J.M.

2010-01-01

De varroa mijtziekte (Varroa destructor) is de belangrijkste bedreiging van de Europese honingbij. Wintersterfte van honingbijen is in de meeste gevallen toe te schrijven aan deze ziekte. Deze brochure van de WUR biedt informatie over de biologie van varroa, de effecten van varroa op honingbijen en

Prediking aan die hand van die metafoor van fiksieskryf

African Journals Online (AJOL)

p1243322

HTS 64(3) 2008 siening van die self en waarheid. In die pre-moderne paradigma kan die dominante metafoor verstaan word aan die hand van 'n spieël wat die lig uit 'n transendente oorsprong weerkaats, terwyl die moderne paradigma uitgedruk word met die metafoor van 'n lamp wat 'n eie, oorspronklike lig binne die self.

’n Etiek van liefde: Die etiese perspektiewe van die Heidelbergse Kategismus

Directory of Open Access Journals (Sweden)

Koos Vorster

2013-06-01

Full Text Available Hierdie artikel behandel die etiese perspektiewe van die Heidelbergse Kategismus – een van die prominente belydenisskrifte in die gereformeerde tradisie. Die etiese relevansie is ingebed in die konfessie se verklaring van die tien gebooie. Die artikel verduidelik dat die etiek van die Heidelbergse Kategismus ten diepste ’n karakteretiek is en dat dit gelowiges oproep tot ’n etiek van liefde. Hierdie liefde sluit in liefde vir die verbondsgemeenskap, die bediening van die Woord, die heiligheid van God en die waardigheid van mense, die gemeenskap van die gelowiges, gesag, die lewe, die huwelik, privaatbesit en arbeid asook waarheid en geregtigheid. As gevolg van die sinekdogeekarakter van die wet is hierdie etiek van liefde vandag baie relevant. This article deals with the ethical relevance of one of the prominent confessions in the reformed tradition, namely the Heidelberg Cathechism. The ethical relevance lies in the confession’s elucidation of the ten commandments and its application to moral conduct. The article explains that the ethics of the Heidelberg Catechism is essentially a virtue ethics calling for an ethics of love. This love should include love for the covenantal communion, ministry of the Word, the holiness of God and the dignity of people, the communion of the saints, authority, life, marriage, private property and labour, and truth and justice. Due to the synecdochical character of the ten commandments this ethics of love is highy relevant in the present times.

Optimaliseren van een biovergister

NARCIS (Netherlands)

van der Bij, Joost; Rademaker, Mark; Visser, Klaas; de Vries, Herman

2014-01-01

Dit rapport beschrijft onderzoek van conversie van biomassa in een Swill-gasser geplaatst bij het Van der Valk restaurant in Cuijk. De Swill-gasser is een biomassa vergister voor restaurant afval. Het onderzoek heeft zich gericht op het optimaliseren van de data acquisitie en op het bepalen van de

Kenmerkend van hierdie afdeling is die tema van ouderdom wat in ...

African Journals Online (AJOL)

8 Apr 2016 ... Kenmerkend van hierdie afdeling is die tema van ouderdom wat in menige van die stories voorkom. Hier is dit die onvermydelike aftakelingsproses van die liggaam (en verstand) wat 'n beduidende invloed op die skrywer het. In verhale soos “Wat 'n lieflike geraas”, “Die ou met die overall”, “Lofredes en ...

Bepaling van enkele neurotransmitters, monoaminen, en metabolieten, met behulp van Continuous Flowapparatuur

NARCIS (Netherlands)

Eigeman L; Schonewille F; Borst M; van der Laan JW

1986-01-01

Bij het onderzoek in de psychofarmacologie kan kennis van de effecten van stoffen op de omzettingssnelheid van neurotransmitters een belangrijk aspect zijn. Met de huidige psychofarmaca lijken vooral de klassieke neurotransmitters zoals de monoaminen, noradrenaline, dopamine en serotonine van

Kansen voor conflictbemiddeling : Verslag van een onderzoek naar de toepassingsmogelijkheden van conflictbemiddeling

NARCIS (Netherlands)

Geveke, Henk; Plant, Ernelies; Thieme, Marianneke; Verberk, Marielle

1998-01-01

In opdracht van het Platform ADR, een klankbordgroep en denktank op het gebied van alternatieve geschilbeslechting, is onderzoek verricht naar de toepasbaarheid van een specifieke vorm van Alternative Dispute Resolution (ADR): conflictbemiddeling (mediation). De onderzoeksopdracht was als volgt: het

Allen Brain Atlas-Driven Visualizations: a web-based gene expression energy visualization tool.

Science.gov (United States)

Zaldivar, Andrew; Krichmar, Jeffrey L

2014-01-01

The Allen Brain Atlas-Driven Visualizations (ABADV) is a publicly accessible web-based tool created to retrieve and visualize expression energy data from the Allen Brain Atlas (ABA) across multiple genes and brain structures. Though the ABA offers their own search engine and software for researchers to view their growing collection of online public data sets, including extensive gene expression and neuroanatomical data from human and mouse brain, many of their tools limit the amount of genes and brain structures researchers can view at once. To complement their work, ABADV generates multiple pie charts, bar charts and heat maps of expression energy values for any given set of genes and brain structures. Such a suite of free and easy-to-understand visualizations allows for easy comparison of gene expression across multiple brain areas. In addition, each visualization links back to the ABA so researchers may view a summary of the experimental detail. ABADV is currently supported on modern web browsers and is compatible with expression energy data from the Allen Mouse Brain Atlas in situ hybridization data. By creating this web application, researchers can immediately obtain and survey numerous amounts of expression energy data from the ABA, which they can then use to supplement their work or perform meta-analysis. In the future, we hope to enable ABADV across multiple data resources.

Allen Brain Atlas-Driven Visualizations: A Web-Based Gene Expression Energy Visualization Tool

Directory of Open Access Journals (Sweden)

Andrew eZaldivar

2014-05-01

Full Text Available The Allen Brain Atlas-Driven Visualizations (ABADV is a publicly accessible web-based tool created to retrieve and visualize expression energy data from the Allen Brain Atlas (ABA across multiple genes and brain structures. Though the ABA offers their own search engine and software for researchers to view their growing collection of online public data sets, including extensive gene expression and neuroanatomical data from human and mouse brain, many of their tools limit the amount of genes and brain structures researchers can view at once. To complement their work, ABADV generates multiple pie charts, bar charts and heat maps of expression energy values for any given set of genes and brain structures. Such a suite of free and easy-to-understand visualizations allows for easy comparison of gene expression across multiple brain areas. In addition, each visualization links back to the ABA so researchers may view a summary of the experimental detail. ABADV is currently supported on modern web browsers and is compatible with expression energy data from the Allen Mouse Brain Atlas in situ hybridization data. By creating this web application, researchers can immediately obtain and survey numerous amounts of expression energy data from the ABA, which they can then use to supplement their work or perform meta-analysis. In the future, we hope to enable ABADV across multiple data resources.

De mislukte missie van mr. Maarten van Naarden als luitenant-stadhouder van Stad en Lande 1541-1557

NARCIS (Netherlands)

Postma, F.

2005-01-01

Maarten van Naarden’s failed mission as lieutenant-stadholder of the province of Groningen, 1541-1557 In November 1557, Maarten van Naarden resigned from his post as lieutenant-stadholder of the province of Groningen and left the province after staying there for sixteen years. Van Naarden’s

Ondersoek na ’n teoretiese onderskraging van boekkuns: Die toepassing van Bakhtin se dialogisme en heteroglossia op geselekteerde voorbeelde van kunstenaarsboeke

Directory of Open Access Journals (Sweden)

David Paton

2012-11-01

Full Text Available Onlangse navorsingsprojekte en konferensies oor boekkuns het gereageer op Johanna Drucker se oproep in 2005 dat noodsaaklike navorsingswerk gedoen moet word om ’n deegliker teoretiese basis vir die terrein van boekkunsproduksie te vestig. Die deelname van kunstenaars en ander praktisyns van boekkuns veroorsaak dat gesprekke en besprekings noodwendig en voorspelbaar neig na die praktyk en weg van die teorie. In die lig van die behoefte aan die bepaling van ’n toepaslike visie waarvolgens die kunsboek meer eksplisiet, ook teoreties, ondersoek kan word, ondersoek hierdie artikel Stéphane Mallarmé en Marcel Broodthaers se Un coup de dés publikasies, Buzz Spector se simplifiserende Marcel Broodthaers, Ulises Carrion se For fans and scholars alike, en Helen Douglas en Telfer Stokes se Real fiction. Hierdie spesifieke voorbeelde, en hulle onderlinge verbande en dialoog met mekaar, word ondersoek vanuit die perspektief van die Russiese filosoof en literêre teoretikus Mikhail Bakhtin se werk oor dialogisme en heteroglossia (‘ander-tongigheid’. Hierdie begrippe demonstreer die dialogiese, multivokale en veeltongige wisselwerking tussen en binne historiese werke as kultuuruitings. Deur die analise toon ek aan dat hierde begrippe toepaslike en funksionele raamwerke uitmaak vir die analise van spesifieke aspekte wat die teenwoordigheid van kunstenaarsboeke aankondig in die wêreld: selfbewustheid en omvattende diskoers wat wederkerend toepaslik is. Ek stel voor dat Bakthin se idees oor dialogisme en heteroglossie gebruik word as die teoretiese begronding van die kunstenaarsboek as ’n dinamiese visuele taal wat in ’n netwerk van ander tekste staan en deel is van die proses van die eindelose herbeskrywing van die wêreld.

Resultaten van het RWS-RIKZ JAMP 2006 monitoringsprogramma van bot (Platichthys flesus L.). Biologische gegevens van bot en milieukritische stoffen in bot

NARCIS (Netherlands)

Kotterman, M.J.J.; Barneveld, van E.

2007-01-01

De in dit rapport beschreven werkzaamheden werden door IMARES uitgevoerd op basis van een opdracht van Rijkswaterstaat- Rijksinstituut voor Kust en Zee (RIKZ) in het kader van het Joint Assessment and Monitoring Program van de OSPARCOM. De opdracht hield in het verkrijgen van biologische gegevens

Voedingpraktyke en behoeftes van hulpbron-arm gemeenskappe deur die oë van laerskoolonderwysers

Directory of Open Access Journals (Sweden)

Ronel Ferreira

2013-02-01

Full Text Available In hierdie artikel bespreek ons die persepsies van onderwysers (n = 45 wat betref die voedingpraktyke van ’n steekproef laerskoolleerders en hul gesinne in ’n hulpbron-arm gemeenskap. Ons fokus spesifiek op die behoeftes, praktyke en verwagtings ten opsigte van die gebruik van voedsel, wat die produksie, keuse en voorbereiding van voedsel impliseer. Ons studie vorm die eerste deel van ’n groter institusionele navorsingprojek. Vir die doel van ons studie het ons deelnemende refleksie en aksie-gebaseerde werkwinkels gehou om data te genereer en tydens die interpretasie van bevindinge op interpretivisme staatgemaak. Hierdie studie beklemtoon die behoeftes van hulpbron-arm en werklose gemeenskapslede wat dikwels genoodsaak is om teen verlaagde pryse voedsel te koop waarvan die kwaliteit nie optimaal is nie. ’n Verskraalde ontbyt, middagete of aandete waarvan die keuse algemeen beperk is tot swart tee, pap en een of twee snye ou brood, bevestig die manifestasies van armoede in hulpbron-arm gemeenskappe. Maaltye is dikwels beperk tot groot hoeveelhede koolhidrate, min groente, ingelegde vis, pap met inkomazi en marog. Hoenderpote en afval vul soms die spyskaart aan. Onderwysers beklemtoon die feit dat gemeenskapslede tipies op skenkings van werkgewers, kerke en kruidenierswinkels staatmaak om hul voedselbegroting aan te vul. Onderwysers fokus verder op die behoeftes aan opleiding vir gemeenskapslede. Na hulle mening moet gemeenskappe ingelig word oor voedselproduksie, groentetuine, die wyses waarop die kwaliteit van grond bepaal kan word, besproeiing en die toepassing van volhoubare wisselbou. Die artikel word afgesluit met uitvoerbare en leersame wenke vir die opleiding van landelike gemeenskappe. Op grond van dié navorsingsbevindinge word ’n intervensieprogram tans ontwikkel, met die doel om dit in die onderskeie deelnemende skole te implementeer ter bevordering van gesonde voedselverwante gedrag en welsyn.

An allene oxide and 12-oxophytodienoic acid are key intermediates in jasmonic acid biosynthesis by Fusarium oxysporum.

Science.gov (United States)

Oliw, Ernst H; Hamberg, Mats

2017-08-01

Fungi can produce jasmonic acid (JA) and its isoleucine conjugate in large quantities, but little is known about the biosynthesis. Plants form JA from 18:3 n -3 by 13 S -lipoxygenase (LOX), allene oxide synthase, and allene oxide cyclase. Shaking cultures of Fusarium oxysporum f. sp. tulipae released over 200 mg of jasmonates per liter. Nitrogen powder of the mycelia expressed 10 R -dioxygenase-epoxy alcohol synthase activities, which was confirmed by comparison with the recombinant enzyme. The 13 S -LOX of F. oxysporum could not be detected in the cell-free preparations. Incubation of mycelia in phosphate buffer with [17,17,18,18,18- 2 H 5 ]18:3 n -3 led to biosynthesis of a [ 2 H 5 ]12-oxo-13-hydroxy-9 Z ,15 Z -octadecadienoic acid (α-ketol), [ 2 H 5 ]12-oxo-10,15 Z -phytodienoic acid (12-OPDA), and [ 2 H 5 ]13-keto- and [ 2 H 5 ]13 S -hydroxyoctadecatrienoic acids. The α-ketol consisted of 90% of the 13 R stereoisomer, suggesting its formation by nonenzymatic hydrolysis of an allene oxide with 13 S configuration. Labeled and unlabeled 12-OPDA were observed following incubation with 0.1 mM [ 2 H 5 ]18:3 n -3 in a ratio from 0.4:1 up to 47:1 by mycelia of liquid cultures of different ages, whereas 10 times higher concentration of [ 2 H 5 ]13 S -hydroperoxyoctadecatrienoic acid was required to detect biosynthesis of [ 2 H 5 ]12-OPDA. The allene oxide is likely formed by a cytochrome P450 or catalase-related hydroperoxidase. We conclude that F. oxysporum , like plants, forms jasmonates with an allene oxide and 12-OPDA as intermediates. Copyright © 2017 by the American Society for Biochemistry and Molecular Biology, Inc.

Beheersing van valse meeldauw in de akkerbouwmatige teelt van peterselie

NARCIS (Netherlands)

Mheen, van der H.J.C.J.; Lamers, J.G.

2009-01-01

In 2007 en 2008 heeft PPO-agv in opdracht van het Productwschap Akkerbouw onderzoek gedaan naar de beheersing van valse meeldauw in de akkerbouwmatige teelt van peterselie. Diverse fungicidentoepassingen zijn in staat om de peterselie (in meer of mindere mate) tegen valse meeldauw te beschermen.

Allen diesel standby sets at Sellafield

International Nuclear Information System (INIS)

Ruff, G.

1982-01-01

As part of the extension and improvement plans for the British Nuclear Fuels Ltd reprocessing facilities at Sellafield, three Allen diesel engines have been installed for essential standby duty. They are 16-cylinder V-form engines with a continuous rating of 2,832 bhp and drive a 2000kW 11,000 volt 3 phase 50Hz salient pole synchronous alternator at 750r/min. They are arranged for running in parallel and with the public electricity mains supply and are also controlled to operate as standby in the event of mains failure. To prevent radioactive contamination from the atmosphere, primary and secondary air filtration has been supplied for each engine. Other operational facilities and safeguards are mentioned and the cooling system described. (U.K.)

Inzicht in het presteren van de executieketen : Ontwikkeling van een monitor voor het meten van Kritieke Prestatie Indicatoren in de Executieketen

NARCIS (Netherlands)

Braak, S.W. van den; Netten, C.P.M.; Witzenburg, R. van

2013-01-01

Dit zijn de voorlopige resultaten van het ontwikkelprojcet Monitor Kritieke Prestatie Indicatoren Executieketen. Het structureel meten van de vastgestelde Kritieke Prestatie Indicatoren (KPI's) behelst het periodiek verzamelen, bewerken en presenteren van grote hoeveelheden data van verschillende

Electronic structure, lattice dynamics, and optical properties of a novel van der Waals semiconductor heterostructure: InGaSe2

Science.gov (United States)

Ibarra-Hernández, Wilfredo; Elsayed, Hannan; Romero, Aldo H.; Bautista-Hernández, Alejandro; Olguín, Daniel; Cantarero, Andrés

2017-07-01

There is a growing interest in the property dependence of transition metal dichalcogenides as a function of the number of layers and formation of heterostructures. Depending on the stacking, doping, edge effects, and interlayer distance, the properties can be modified, which opens the door to novel applications that require a detailed understanding of the atomic mechanisms responsible for those changes. In this work, we analyze the electronic properties and lattice dynamics of a heterostructure constructed by simultaneously stacking InSe layers and GaSe layers bounded by van der Waals forces. We have assumed the same space group of GaSe, P 6 ¯m 2 as it becomes the lower energy configuration for other considered stackings. The structural, vibrational, and optical properties of this layered compound have been calculated using density functional theory. The structure is shown to be energetically, thermally, and elastically stable, which indicates its possible chemical synthesis. A correlation of the theoretical physical properties with respect to its parent compounds is extensively discussed. One of the most interesting properties is the low thermal conductivity, which indicates its potential use in thermolectric applications. Additionally, we discuss the possibility of using electronic gap engineering methods, which can help us to tune the optical emission in a variable range close to that used in the field of biological systems (NIR). Finally, the importance of considering properly van der Waals dispersion in layered materials has been emphasized as included in the exchange correlation functional. As for the presence of atoms with important spin-orbit coupling, relativistic corrections have been included.

Vergelijking van vangsten van een 12 m pulskor met een conventionele wekkerboomkor

NARCIS (Netherlands)

Marlen, van B.; Ybema, M.S.; Kraayenoord, A.; Vries, de M.; Rink, G.J.

2005-01-01

In het kader van de ontwikkeling van een pulskor als alternatief voor de conventionele boomkor met wekkerkettingen werd in nov-dec 2004 en jan 2005 onderzoek uitgevoerd op het visserij-onderzoekingsvaartuig “Tridens” naar de vangstverschillen van beide visserijtechnieken en de overleving van door

Het gebruik van antropometrische gegevens bij het opstellen van normen voor kantoorstoelen

NARCIS (Netherlands)

Groot, M.D. de; Voorbij, A.I.M.; Molenbroek, J.F.M.

2003-01-01

De fysieke belasting van werknemers is bij het invoeren van de personal computer veranderd. De werkplekken zijn zitplekken geworden. Het aantal gebruikers van kantoorstoelen is daarmee enorm toegenomen. Achter een monitor zitten mensen vaak lang achter elkaar in dezelfde houding, wat in weerwil van

Interlayer excitons in a bulk van der Waals semiconductor.

Science.gov (United States)

Arora, Ashish; Drüppel, Matthias; Schmidt, Robert; Deilmann, Thorsten; Schneider, Robert; Molas, Maciej R; Marauhn, Philipp; Michaelis de Vasconcellos, Steffen; Potemski, Marek; Rohlfing, Michael; Bratschitsch, Rudolf

2017-09-21

Bound electron-hole pairs called excitons govern the electronic and optical response of many organic and inorganic semiconductors. Excitons with spatially displaced wave functions of electrons and holes (interlayer excitons) are important for Bose-Einstein condensation, superfluidity, dissipationless current flow, and the light-induced exciton spin Hall effect. Here we report on the discovery of interlayer excitons in a bulk van der Waals semiconductor. They form due to strong localization and spin-valley coupling of charge carriers. By combining high-field magneto-reflectance experiments and ab initio calculations for 2H-MoTe 2 , we explain their salient features: the positive sign of the g-factor and the large diamagnetic shift. Our investigations solve the long-standing puzzle of positive g-factors in transition metal dichalcogenides, and pave the way for studying collective phenomena in these materials at elevated temperatures.Excitons, quasi-particles of bound electron-hole pairs, are at the core of the optoelectronic properties of layered transition metal dichalcogenides. Here, the authors unveil the presence of interlayer excitons in bulk van der Waals semiconductors, arising from strong localization and spin-valley coupling of charge carriers.

De verleidelijkheid van het grote gebaar : Het werk van Dogma

NARCIS (Netherlands)

Teerds, P.J.

2013-01-01

In vier portacabins op het parkeerterrein van de Delftse Faculteit Bouwkunde is nog tot volgende week de tentoonstelling 11+1 projects te zien, een overzichtstentoonstelling van het intrigerende werk van het Brusselse bureau Dogma. Met de tentoonstelling zet de faculteit na de brand in 2008 weer een

De afschaffing van de bezwaarfase bij boetebesluiten van de ACM

NARCIS (Netherlands)

Jans, J.H.; Outhuijse, A.

Per 1 maart 2013 ontstaat door samenvoeging van de NMa, de OPTA en de Consumentenautoriteit, de Autoriteit Consument en Markt. Om de ACM slagvaardig te laten functioneren, wordt voorgesteld het handhavingsinstrumentarium m.b.t. het markttoezicht van de ACM te vereenvoudigen. Eén van de voorstellen

Implementatie van de Surviving Sepsis Campaign bundels : Monitoring van ervaringen

NARCIS (Netherlands)

Lilian Vloet; J. Schouten; N. Stevens; A. Rensen; A. Willems; F. Zeegers

2011-01-01

Sepsis komt vaak voor in ziekenhuizen. Ernstige sepsis is verantwoordelijk voor 10 - 20% van alle Intensive Care (IC) opnames en is de belangrijkste doodsoorzaak op niet-cardiale IC?s. De gemiddelde mortaliteit van volwassenen met ernstige sepsis op de IC is 33% en van volwassenen met septische

Omkering van de bewijslast: knelpunten in de regeling en bij de toepassing van de omkering van de sanctie (deel I)

NARCIS (Netherlands)

Okhuizen, E.C.G.

2013-01-01

De omkering van de bewijslast als processuele sanctie op het niet nakomen van de aangifteplicht en de daaraan verbonden bijkomende verplichtingen lijken niet weg te denken uit ons belastingrecht. De sanctie kwam al voor in de fiscale wetgeving die dateert van vóór de invoering van de Algemene wet

Vervluchtiging van EPTC, tri-allaat en parathion na bespuiting van een kleigrond

NARCIS (Netherlands)

Bor, G.; Berg, van den F.; Smelt, J.H.; Peppel-Groen, van de A.E.; Leistra, M.

1995-01-01

Op tien tijdstippen na de bespuiting van een onbegroeide kleigrond met EPTC, tri-allaat en parathion werden de snelheden van vervluchtiging van deze middelen bepaald met de kapmethode en de theoretisch-profielmethode (TP-methode). De vervluchtiging was het hoogst op de dag van toepassing. In de

Enkele aspecten van de diagnostiek van hypophysaire insufficiëntie bij kinderen

NARCIS (Netherlands)

Israëls, Albertus Leonard Maurits

1960-01-01

In dit proefschrift is een onderzoek beschreven, dat naar de functie van de hypophyse bij kinderen met tekenen van hypophysaire insufficiëntie werd ingesteld. Het onderzoek werd in de kinderkliniek van het Academisch Ziekenhuis te Groningen verricht. In hoofdstuk I is een overzicht van de literatuur

VT-NRK Toepassing bioplastics : verbeteren van de technische eigenschappen van PLA-folies

NARCIS (Netherlands)

Molenveld, K.; Schennink, G.G.J.

2009-01-01

Het doel van dit project, VT-NRK toepassing bioplastics, is het genereren en verspreiden van kennis met betrekking tot het verbeteren van de technische eigenschappen van PLA folies. De kennis is bedoeld voor de bedrijven die binnen de kunststofindustrie aangesloten zijn bij de MJA én folies

Rituele van plesier: Dolf van Coller se Die Bieliebalies

Directory of Open Access Journals (Sweden)

J. van Wyk

1998-04-01

Full Text Available Rituals of pleasure: Dolf van Coller’s Die Bieliebalies This article is an analysis of Dolf van Coller's Die Bieliebalies (1993, read as a hedonist text. It has many points of similarity with what Bakhtin (1984 called grotesque realism, and with Nietzsche’s views as expounded in The birth of tragedy (1956. By comparing Van Caller's text to that of Bakhtin and Nietzsche, a counter-discourse to contemporary moral discourses such as feminism is explored. Van Coller’s use of laughter as a relativising mechanism is very liberating in the context where petty morality intervenes dogmatically in the field of literature and other spheres of life.

Die ontwikkeling van menslike potensiaal in die Republiek van Suid ...

African Journals Online (AJOL)

Erna Kinsey

Dit het dus ook te doen met lewenstandaard, aangesien lewenstandaard `n bepalende faktor is met betrekking tot die optimale ontwikkeling van menslike potensiaal. Ander minder materiële aspekte van menslike potensiaal het te doen met menslike vryheid, waaronder vryheid van spraak, beweging en keuse ter sake is.

Master Illustrator Allen Say Opens Students' Eyes to the Artist's Craft.

Science.gov (United States)

Brehl, Sandy

2002-01-01

Discusses how the author uses Allen Say's picture storybooks to introduce intimidating (even to adults!) artistic language and concepts. Elaborates on several books that she used with her third-grade students. Demonstrates that a meaningful encounter with a skilled artist can change the way students see art in literary experiences and in their…

Katalytisch verbranden van varkensmest

NARCIS (Netherlands)

Hendriks, J.

1995-01-01

Door het verbranden van mest kan het mestvolume worden verkleind. Binnenkort gaat op het Varkensproefbedrijf 'Zuid- en West-Nederland' in Sterksel onderzoek van start om de mogelijkheden van het katalytisch verbranden van varkensmest te bekijken.

Witte vlekken in het bereik van NME? : raamwerk voor het meten van gebruik en de effecten van NME in het primair onderwijs

NARCIS (Netherlands)

Vreke, J.; Langers, F.; Berg, van den A.E.

2011-01-01

In het NME-beleid wordt het geven van NME ingezet als instrument om bij te dragen aan het reduceren van de achteruitgang, in omvang en kwaliteit, van natuur en milieu. Het bereik van NME moet aangeven in hoeverre NME de bevolking heeft bereikt en aan dit doel heeft bijgedragen. Het identificeren van

Produktie van pigmenten

NARCIS (Netherlands)

Etman EJ; Duesmann HB; Eijssen PHM; LAE

1994-01-01

Dit rapport over de produktie van pigmenten is gepubliceerd binnen het Samenwerkingsproject Procesbeschrijvingen Industrie Nederland (SPIN). In het kader van dit project is informatie verzameld over industriele bedrijven of industriele processen ter ondersteuning van het overheidsbeleid op het

Storm-time radiation belt electron dynamics: Repeatability in the outer radiation belt

Science.gov (United States)

Murphy, K. R.; Mann, I. R.; Rae, J.; Watt, C.; Boyd, A. J.; Turner, D. L.; Claudepierre, S. G.; Baker, D. N.; Spence, H. E.; Reeves, G. D.; Blake, J. B.; Fennell, J. F.

2017-12-01

During intervals of enhanced solar wind driving the outer radiation belt becomes extremely dynamic leading to geomagnetic storms. During these storms the flux of energetic electrons can vary by over 4 orders of magnitude. Despite recent advances in understanding the nature of competing storm-time electron loss and acceleration processes the dynamic behavior of the outer radiation belt remains poorly understood; the outer radiation belt can exhibit either no change, an enhancement, or depletion in radiation belt electrons. Using a new analysis of the total radiation belt electron content, calculated from the Van Allen probes phase space density (PSD), we statistically analyze the time-dependent and global response of the outer radiation belt during storms. We demonstrate that by removing adiabatic effects there is a clear and repeatable sequence of events in storm-time radiation belt electron dynamics. Namely, the relativistic (μ=1000 MeV/G) and ultra-relativistic (μ=4000 MeV/G) electron populations can be separated into two phases; an initial phase dominated by loss followed by a second phase dominated by acceleration. At lower energies, the radiation belt seed population of electrons (μ=150 MeV/G) shows no evidence of loss but rather a net enhancement during storms. Further, we investigate the dependence of electron dynamics as a function of the second adiabatic invariant, K. These results demonstrate a global coherency in the dynamics of the source, relativistic and ultra-relativistic electron populations as function of the second adiabatic invariant K. This analysis demonstrates two key aspects of storm-time radiation belt electron dynamics. First, the radiation belt responds repeatably to solar wind driving during geomagnetic storms. Second, the response of the radiation belt is energy dependent, relativistic electrons behaving differently than lower energy seed electrons. These results have important implications in radiation belt research. In particular

Het effect van het bijvoeren van tarwe aan vleeskuikens op de slachtrendementen

NARCIS (Netherlands)

Middelkoop, van J.H.; Harn, van J.

1994-01-01

Tarwe bijvoeren aan vleeskuikens staat momenteel volop in de belangstelling. Redenen hiervoor zijn de lage prijs van de tarwe en het positieve effect dat tarwe kan hebben op de resultaten en gezondheid van de koppel. Door het bijvoeren van tarwe wordt de werking van de spiermaag en de ontwikkeling

St. Teresa van Avila: sentrale figuur in die werk van Cussons en Van Wyk Louw

Directory of Open Access Journals (Sweden)

H. van Vuuren

1989-05-01

Full Text Available A central poem in Van Wyk Louw’s Tristia (1962, is “H. Teresa van Avila flap uit” (literally translated: “Saint Teresa of Avila talks too much/babbles uncontrollably”. This article illustrates how intertextual reading helped to clarify the poem. Teresa of Avila’s The way of perfection (a translation of the Spanish work El Camino de la Perfección, 1573 is the intertext of the Van Wyk Louw poem. In the last section of the article it is shown how the figure of St. Teresa of Avila is central not only to Van Wyk Louw’s Tristia (1962, but also to the oeuvre of Sheila Cussons, which underlines a strong intertextuality between these two Afrikaans oeuvres.

Die gebruik van ’n reologiese tegniek in die bepaling van die verhardingsreaksiekinetika van ’n reaktiewe poliësterpoeierdeklaag

Directory of Open Access Journals (Sweden)

O. C. Vorster

2004-09-01

Full Text Available

Die studie van die verhardingsreaksiekinetika van deklae word bemoeilik deur die aanwesigheid van vlugtige stowwe, pigmente en bypigmente. In hierdie studie word die verhardingsreaksiekinetika van ’n karboksielgetermineerde poliëstertriglisediel-isosianuraat deur middel van parallelplaatspanningsreometrie bepaal. Jeltye is verkry en skaleringseksponente bepaal. ’n Nuwe metode vir die voorspelling van die verloop van die reaksie word voorgestel en vergelyk met resultate verkry deur middel van differensiël skanderingskalorimetrie.

Abstract

The use of a rheological technique in the determination of the curing kinetics of a reactive polyester powder coating

In this article a study of the curing process of carboxyl terminated polyester-triglycidyl isocyanurate systems is reported. A comparison is made between the generally used Differential Scanning Calorimetric methods and rheokinetic methods, using a parallel plate oscillating stress rheometer. Gel times were determined and scaling exponents calculated. A new method for the estimation of the extent of reaction is presented and compared with results obtained by means of differential scanning calorimetry

Handelsstromen van pluimveevlees

NARCIS (Netherlands)

Tacken, G.M.L.; Horne, van P.L.M.

2006-01-01

Dit onderzoek geeft inzicht in de goederenstromen van (rauw) pluimveevlees binnen envooral naar Nederland en de daarmee gepaard gaande zoönoserisico's. Het onderzoek biedtinput voor het nog op te zetten controlebeleid, waarmee handhaving van het beleidsvoornemenom het aanbieden van rauw

Bekalking en toevoegen van nutriënten; evaluatie van de effecten op de vitaliteit van het bos; een veldonderzoek naar boomgroei

NARCIS (Netherlands)

Wolf, R.J.A.M.; Engels, M.E.; Knotters, M.; Schraven, R.; Boertjes, M.

2006-01-01

Dit rapport doet verslag van een deelonderzoek uit de Evaluatie van effectgerichte maatregelen in multifunctionele bossen 2004-2005 en is gericht op de effecten van de maatregelen bemes-ting en bekalking in bossen als overbruggingsmaatregel in het kader van het Overlevingsplan Bos en Natuur (OBN).

Paradiplomacia y desarrollo económico en la región transfronteriza de Reynosa-McAllen

Directory of Open Access Journals (Sweden)

Karla María Nava Aguirre

2018-02-01

Full Text Available La paradiplomacia es un nuevo fenómeno de participación internacional de gobiernos locales y otras entidades no-estatales. La investigación tiene como objetivo analizar la construcción paradiplomática y observar el desarrollo económico en la región transfronteriza Reynosa-McAllen a partir del Tratado de Libre Comercio de América del Norte (TLCAN. Se utilizó la investigación cualitativa con un enfoque descriptivo. Los instrumentos de recolección de información fueron la revisión bibliográfica y la entrevista. Los hallazgos demuestran que las actividades de vinculación entre Reynosa y McAllen, obedecen al trabajo en equipo que se realiza principalmente entre el Gobierno Municipal de Reynosa, Gobierno del Estado de Tamaulipas y la organización McAllen Economic Development Corporation (MEDC, que han incrementado la inversión y empleo generando un desarrollo económico en esta región transfronteriza.

Die berekening van vloeiing in ’n roterende annulus deur die metode van kunsmatige saamdrukbaarheid

Directory of Open Access Journals (Sweden)

H. Grobler

1987-03-01

Full Text Available Die vloeiing van ’n onsaamdrukbare, viskeuse vloeier word ondersoek aan die hand van die numeriese oplossing van die gediskretiseerde Navier-Stokes- en kontinuiteitsbeheervergelykings. In die besonder word vloeiing in ’n annulus bestaande uit twee koaksiale silinders wat elk ten opsigte van die ander kan roteer, en met ’n voorgeskrewe drukval oor die lengte van die silinder, beskou. Die oplossings word bereken deur die toepassing van Chorin se metode van kunsmatige saamdrukbaarheid, waarin die tydonafhanklike beheervergelykings getransformeer word na tydafhanklike hulpvergelykings deur die invoering van ’n kunsmatige toestandsvergelyking. Die oplossing van die hulpvergelykings konvergeer na ’n stasionêre oplossing, wat ooreenstem met die oplossing van die oorspronklike tydonafhanklike beheervergelykings. Die gedrag van die vloeier, wanneer ten voile ontwikkelde laminêre vloeiing bereik word, is met sukses bereken. ’n Eenvoudige model vir die bepaling van ontwikkeling van vloeiing langs die annulus vir enige gegewe invloeisnelheidsprofiel word voorgestel. Die berekende resultate stem ooreen met die resultate wat uit die fisika van die probleem verwag word.

Isotope engineering of van der Waals interactions in hexagonal boron nitride

Science.gov (United States)

Vuong, T. Q. P.; Liu, S.; van der Lee, A.; Cuscó, R.; Artús, L.; Michel, T.; Valvin, P.; Edgar, J. H.; Cassabois, G.; Gil, B.

2018-02-01

Hexagonal boron nitride is a model lamellar compound where weak, non-local van der Waals interactions ensure the vertical stacking of two-dimensional honeycomb lattices made of strongly bound boron and nitrogen atoms. We study the isotope engineering of lamellar compounds by synthesizing hexagonal boron nitride crystals with nearly pure boron isotopes (10B and 11B) compared to those with the natural distribution of boron (20 at% 10B and 80 at% 11B). On the one hand, as with standard semiconductors, both the phonon energy and electronic bandgap varied with the boron isotope mass, the latter due to the quantum effect of zero-point renormalization. On the other hand, temperature-dependent experiments focusing on the shear and breathing motions of adjacent layers revealed the specificity of isotope engineering in a layered material, with a modification of the van der Waals interactions upon isotope purification. The electron density distribution is more diffuse between adjacent layers in 10BN than in 11BN crystals. Our results open perspectives in understanding and controlling van der Waals bonding in layered materials.

Het format van de stad. Een evaluatie van recente Nederlandse stadsgeschiedenissen

Directory of Open Access Journals (Sweden)

P. Kooij

2002-01-01

Full Text Available R. Kunst, Leeuwarden 750-2000. Hoofdstad van Friesland; A. van der Schoor, N. Schadee, Stad in aanwas. Geschiedenis van Rotterdam tot 1813; P. van de Laar, Stad van formaat. Geschiedenis van Rotterdam in de negentiende en twintigste eeuw; R.E. de Bruin, 'Een paradijs vol weelde'. Geschiedenis van de stad Utrecht.The shape of the city. An evaluation of recent historical studies on Dutch townsUrban history in the Netherlands started roundabout 1970. It was initially promoted by mainly economic and social historians who used concepts derived from geography which centred on town and country relations, urban networks, and migration. The spatial factor was considered to be a core feature, also inside the towns and cities. An alternative view, however, argued that a completely introspective urban history, focussing on one city, would result in more integration. This hypothesis has been proved in a number of recent, more or less integral urban histories, commissioned by several independent municipal authorities in individual cities. They show that a combination of internal and external elements offers the best results with regard to integration.

Van de Graaff Irradiation of Materials

Energy Technology Data Exchange (ETDEWEB)

Quigley, Kevin [Argonne National Lab. (ANL), Argonne, IL (United States); Chemerisov, Sergey [Argonne National Lab. (ANL), Argonne, IL (United States); Tkac, Peter [Argonne National Lab. (ANL), Argonne, IL (United States); Vandegrift, George F. [Argonne National Lab. (ANL), Argonne, IL (United States)

2016-10-01

Through irradiations using our 3 MeV Van de Graaf accelerator, Argonne is testing the radiation stability of components of equipment that are being used to dispense molybdenum solutions for use as feeds to ^99mTc generators and in the ^99mTc generators themselves. Components have been irradiated by both a direct electron beam and photons generated from a tungsten convertor.

Psigologiese benadering van pastorale arbeid

Directory of Open Access Journals (Sweden)

D. J. Strümpfer

1969-03-01

Full Text Available In die spreektaal van ons Afrikaanse kerke is ons lief om die bedienaar van die Woord aan te dui as „die predikant”, „die leraar” of „die dominee”. Miskien plaas ons met hierdie semantiese gebruik van terme wat lering en proklamering impliseer, ’n ongelukkige klem op die preekamp. Daarteenoor, het ons semanties miskien iets te leer van die Pinkstersektes wat die benaming „pastoor” verkies, of die Amerikaanse ge­ bruik van die term „the pastor”. Ons is wel lief om te praat van „ons herder en leraar”. Veelal word die herderlike, of pastorale, deel van die taak van die bedienaar van die Woord egter in sy eie gedagtes, asook in die gedagtes van sy gemeentelede, deur die leraarskap op die agtergrond gedwing. Al te dikwels word hy deur gemeentelede beskou as iemand wat op Sondag op die kansel gesien moet word en wat niks met die res van hul lewens te doen het nie. Herstel van die pastoraat sal deel moet wees van die proses om die ontkerstening van die hedendaagse lewe teen te gaan.

Mindfulness voor volwassenen met een licht verstandelijke beperking

NARCIS (Netherlands)

Punt, M.; Helmond, P.E.; Meirmans, M.; Otten, R.; Speckens, A.E.M.

2016-01-01

Mensen met een licht verstandelijke beperking (LVB) hebben veelal te maken met een opeenstapeling van verschillende biologische, psychologische en sociale factoren, waardoor zij vijf tot zes keer meer kans hebben op het ontwikkelen van psychopathologie dan normaal begaafden (Allen, 2008; Buckles,

Verlies van (thuis en haard. Het belang van verliesbegeleiding als onderdeel van de maatschappelijke begeleiding binnen het Vluchtelingenwerk, regio Utrecht

Directory of Open Access Journals (Sweden)

Birgit Hoogenberk

2014-06-01

Full Text Available Loss of home and house. The importance of loss counseling as a part of refugee social supportIn this article it is advocated that it is important that the implementation of loss counseling is part of social support for refugees, also called integrative eclectic working. Social support from VluchtelingenWerk, also known as Refugee Council, is about supporting the client in an effective manner with their personal problems which can hinder their integration. Because the target group of VluchtelingenWerk is a group of people whom have suffered many losses, attention should be brought to this subject. Unfortunately in current work methods there is no room for loss counseling, partly due to the lack of methodological tools. The losses associated with this group have a lot of impact on their daily lives and often are the source of functional limitations. By offering loss counseling and multi-method grief counseling, volunteers and employees are offered tools to make loss more negotiable. In this article different examples will be discussed and the new loss model of Stroebe and Schut will be explained. What will be clarified is the importance of the implementation of loss counseling, for the well-being and the integration process of clients as well as achieving organizational goals.Verlies van (thuis en haard. Het belang van verliesbegeleiding als onderdeel van de maatschappelijke begeleiding binnen het VluchtelingenWerk, regio UtrechtIn dit artikel wordt gepleit voor het implementeren van verliesbegeleiding als onderdeel van de maatschappelijke begeleiding, er is sprake van integratief eclectisch werken. De maatschappelijke begeleiding van het VluchtelingenWerk heeft als taak de cliënt zo goed mogelijk te begeleiden bij persoonlijke problemen die de inburgering kunnen belemmeren. Aangezien de doelgroep van het VluchtelingenWerk bestaat uit mensen die ontzettend veel verliezen hebben geleden dient hier aandacht voor te zijn. Helaas is in de huidige

Spatial and temporal variability of chorus and hiss

Science.gov (United States)

Santolik, O.; Hospodarsky, G. B.; Kurth, W. S.; Kletzing, C.

2017-12-01

Whistler-mode electromagnetic waves, especially natural emissions of chorus and hiss, have been shown to influence the dynamics of the Van Allen radiation belts via quasi-linear or nonlinear wave particle interactions, transferring energy between different electron populations. Average intensities of chorus and hiss emissions have been found to increase with increasing levels of geomagnetic activity but their stochastic variations in individual spacecraft measurements are usually larger these large-scale temporal effects. To separate temporal and spatial variations of wave characteristics, measurements need to be simultaneously carried out in different locations by identical and/or well calibrated instrumentation. We use two-point survey measurements of the Waves instruments of the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) onboard two Van Allen Probes to asses spatial and temporal variability of chorus and hiss. We take advantage of a systematic analysis of this large data set which has been collected during 2012-2017 over a range of separation vectors of the two spacecraft. We specifically address the question whether similar variations occur at different places at the same time. Our results indicate that power variations are dominated by separations in MLT at scales larger than 0.5h.

Economische gevolgen van ontwapening

NARCIS (Netherlands)

Duisenberg, Willem Frederik

1965-01-01

Samenvatting van de gehele studie 4.1. Economie en ontwapening Ontwapening betekent in deze studie de algehele, snelle afschaffing van alle militaire maatregelen in aIle landen. Het negeren van de politieke waarschijnlijkheden die veeleer wijzen op een zeer geleidelijke afschaffing van slechts

Neurotoxische effecten van broomcyclohexaan

NARCIS (Netherlands)

Velsen; F.L.van; Danse; L.H.J.C.; Vries; L.J.de; Liefde; A.de

1984-01-01

Kortdurende toediening (4-7 dagen) van broomcyclohexaan (BCH) veroorzaakt in een dosering van 1200 mg/kg lichaamsgewicht (per maagsonde) necrose van gegranuleerde cellen in de korrellaag van de kleine hersenen. In deze doseringen zijn ook gedragsafwijkingen waargenomen d.m.v. een objectieve

Evaluatie van het gebruik van de iPad in het klaslokaal : Een onderzoek naar het iPadgebruik onder brugklasleerlingen van een Leeuwarder Lyceum

NARCIS (Netherlands)

Klaas Jan Huizing; Chantal Philipsen; Luka Linster

2013-01-01

In november 2012 kregen alle brugklasleerlingen van het Leeuwarder Lyceum een iPad uitgereikt. Dit nieuwe ‘device’ is de aanjager van onderwijsvernieuwingen op het gebied van digitalisering van lesmateriaal. Sowijs volgde de implementatie van de iPad en vroeg zich af: hoe is het iPadgebruik na een

Leven en werken van Geert Reinders. De grondlegger van de immunologie.

NARCIS (Netherlands)

Bruins, Luitje Hendrik

1951-01-01

De levensgeschiedenis van Geert Reinders is het relaas van de vele prestaties, waartoe deze man ondanks een zeer gebrekkige schoolopleiding in staat was. Hij was werkzaam als molenaar, boer, koopman, redger, gemeentesecretaris, secretaris en ontvanger van een groot zijlvest, veeartsenijdeskundige;

Die rol van die blanke werker in die motivering van die swart werker

Directory of Open Access Journals (Sweden)

G. J. Oosthuizen

1980-11-01

Opsomming Die motivering van die Swart werker kan nie in die huidige situasie in isolasie bestudeer word nie, omdat die Blanke werker steeds in die bestuursposisie is en daarom die motivering van die Swart werker kan beïnvloed. Hierdie ondersoek was daarop gerig om die rol van die Blanke werker in die motivering van die Swart werker nader te ondersoek. Die houding en die leierskapsbenadering van die Blanke werker teenoor die Swart werker is gemeet, asook die behoeftes wat volgens die Blanke werker by die Swart werker bestaan, bevredig is, of nie bestaan nie. Die behoeftes van Swart werkers, soos deur hulleself gesien, is ook ondersoek. Ten opsigte van sekere aspekte is beduidende verskille gevind.

De eeuw van de Beeldenstorm

Directory of Open Access Journals (Sweden)

F. Postma

1988-01-01

Full Text Available P. van Boheemen, N.P.J. van der Lof, E. van Meurs, Het boek in Nederland in de 16e eeuw S. Groenveld, Ketters en papen onder Filips II. Het godsdienstig leven in de tweede helft van de zestiende eeuw R. Kistemaker, M. Jonker, De smaak van de elite. Amsterdam in de eeuw van de Beeldenstorm W.Th. Kloek, Kunst voor de Beeldenstorm. Noord-Nederlandse kunst ca 1525-1580, [I], Inleiding, [II, Catalogus] J.R. ter Molen, A.P.E. Ruempol, A.G.A. Dongen, Huisraad van een molenaarsweduwe. Gebruiksvoorwerpen uit een 16e eeuwse boedelinventaris M. de Roever, B. Bakker, Woelige tijden. Amsterdam in de eeuw van de Beeldenstorm I.M. Veldman, Leerrijke reeksen van Maarten van Heemskerck

Benaderingen van over

NARCIS (Netherlands)

Boer, M.G. de

2010-01-01

SAMENVATTING In dit hoofdstuk wordt de relatie tussen de betekenissen van het Nederlandse voorzetsel over en een aantal corpora bestudeerd. Het hoofdstuk begint met een analyse van de voorbeelden uit Uit het leven van Dik Trom (1891); daarna wordt de woordenboekinformatie behandeld en vergeleken

Die effek van intelligensie op die verhouding tussen lokus van kontrole en taakkompleksiteit

Directory of Open Access Journals (Sweden)

F. G. de Kock

1995-06-01

Full Text Available The effect of intelligence on the relationship between locus of control and task complexity. The aim of the study was to establish the effects of intelligence on the relationship between locus of control and task complexity. These constructs were selected by virtue of their importance in the literature, as well as the lack of empirical research regarding the assumed relationship which exists between them. The Human Sciences Research Council's (HSRC General Scholastic Aptitude Test (ASAT was used for measuring intelligence, Duttweiler's Internal Control Index (ICI was used for determining locus of control and the Raven's Advanced Progressive Matrices (APM was used as a criterion for coping with task complexity. These instruments were administered to 292 subjects to determine whether the relationship between locus of control and task complexity was effected when the effect of intelligence was controlled. The results indicated a significant relationship between locus of control and task complexity, however the relationship was no longer significant after the effect of intelligence was controlled. Opsomming Die doel van die studie was om die effek van intelligensie op die verhouding tussen lokus van kontrole en taak-kompleksiteit te ondersoek. Hierdie konstrukte is gekies na aanleiding van hulle belangrikheid in die literatuur asook die leemte in empiric se navorsing rakende die veronderstelde verband wat tussen hulle bestaan. Die Algemene Skolastiese Aanlegtoets (ASAT van die Raad vir Geesteswetenskaplike Navorsing (RGN is gebruik vir die meting van intelligensie, die Internal Control Index (ICI van Duttweiler is gebruik vir die meting van lokus van kontrole en die Advanced Progressive Matrices (APM van Raven is gebruik as maatstaf vir die bantering van taakkompleksiteit. Die genoemde meetinstrumente is op 292 proefpersone toegepas om te bepaal of die verband tussen lokus van kontrole en taakkompleksiteit geaffekteer word wanneer daar vir die effek

Ziekten van het ruggenmerg

NARCIS (Netherlands)

Groen, Robertus; Kuks, Joannes; Snoek, Jozef; Kuks, Jan B.M.; Snoek, Jos W.

2016-01-01

Er zijn vele oorzaken voor een myelopathie. Beschadiging van het myelum kan compleet zijn (zoals in het geval van een complete dwarslaesie), maar is vaker incompleet (zoals bij een incomplete traumatische dwarslaesie en de meeste vormen van myelopathie op basis van niet-traumatische oorzaken). Er

Thermal response in van der Waals heterostructures

KAUST Repository

Gandi, Appala

2016-11-21

We solve numerically the Boltzmann transport equations of the phonons and electrons to understand the thermoelectric response in heterostructures of M2CO2 (M: Ti, Zr, Hf) MXenes with transition metal dichalcogenide monolayers. Low frequency optical phonons are found to occur as a consequence of the van der Waals bonding, contribute significantly to the thermal transport, and compensate for the reduced contributions of the acoustic phonons (increased scattering cross-sections in heterostructures), such that the thermal conductivities turn out to be similar to those of the bare MXenes. Our results indicate that the important superlattice design approach of thermoelectrics (to reduce the thermal conductivity) may be effective for two-dimensional van der Waals materials when used in conjunction with intercalation. © 2016 IOP Publishing Ltd.

Analyse van de vervormingen van de Fusee Ceramique daken van de productiehallen in Dongen : Rapport met bevindingen betreffende de vervormingen van de Fuseedaken van de productiehallen van Coca Cola in Dongen

NARCIS (Netherlands)

Kamerling, M.W.

2014-01-01

In 1962 werden in Dongen bedrijfshallen gemaakt met cilindervormige overkappingen waarin ter besparing van gewicht en cement ceramische elementen, de Fusée's Ceramique, werden gelegd. De schalen worden ondersteund met balken 450*750 mm2 en kolommen 450 * 450 mm2 op een raster van 5,6 m * 20,4 m. Het

Effectiviteit van facultatief aansluitonderwijs wiskunde in de transitie van voortgezet naar hoger onderwijs

NARCIS (Netherlands)

Tempelaar, D.T.; Rienties, B.; Kaper, W.; Giesbers, B.; Gastel, van L.J.; Vrie, van de E.M.; Kooij, van der H.; Cuypers, H.

2011-01-01

Samenvatting Wat is het effect van vrijwillig aansluitonderwijs, zoals het remediërend wiskundeonderwijs dat op veel instellingen voor hoger onderwijs wordt gegeven ter verbetering van de doorstroom? Bepaling van de doelmatigheid van dit onderwijs wordt bemoeilijkt door selectie-effecten die kunnen

De opdeling van Centraal-Afrika, 1875-1885 : een analyse van twee territoriale conflicten

NARCIS (Netherlands)

Foeken, D.W.J.

1992-01-01

Deze studie beschrijft een politiek-historisch proces en vormt een bijdrage aan de systematische studie van internationale territoriale conflicten vanuit het gezichtspunt van de politieke geografie. Tevens worden aspecten van het Europese imperialisme van de late 19e eeuw nader verklaard. De

De economische kracht van de baggerindustrie: clusterstudie met behulp van de 'methode Porter'

NARCIS (Netherlands)

Jacobs, D.; Limpens, I.; Kuijper, J.; Ven, B. van de

1993-01-01

Deze clusterstudie van de Nederlands-Belgische baggerindustrie is uitgevoerd in opdracht van IHC Holland, de belangrijkste bouwer van baggerschepen ter wereld, en de Vereniging Centrale Baggerbedrijf, de branche-organisatie van aannemers in de bagger. De bedoeling is een beter inzicht te krijgen in

Bonding in Mercury-Alkali Molecules: Orbital-driven van der Waals Complexes

Directory of Open Access Journals (Sweden)

Dieter Cremer

2008-06-01

Full Text Available The bonding situation in mercury-alkali diatomics HgA (2Σ+ (A = Li, Na, K, Rb has been investigated employing the relativistic all-electron method Normalized Elimination of the Small Component (NESC, CCSD(T, and augmented VTZ basis sets. Although Hg,A interactions are typical of van der Waals complexes, trends in calculated De values can be explained on the basis of a 3-electron 2-orbital model utilizing calculated ionization potentials and the De values of HgA+(1Σ+ diatomics. HgA molecules are identified as orbital-driven van der Waals complexes. The relevance of results for the understanding of the properties of liquid alkali metal amalgams is discussed.

Maatskaplike aspekte van geriatriese sorg

Directory of Open Access Journals (Sweden)

D. Louw

1979-09-01

Full Text Available Dit is maar enkele dekades gelede dat Westerse gemeenskappe bewus geword het van die besondere behoeftes van die relatief groot en nog steeds groeiende persentasie bejaardes in hulle midde. Nie alleen het die liggaamlike behoeftes van liggaamlike afgetakelde bejaardes die aandag getrek nie maar die gemeenskappe het ook bewus geword van die maatskaplike behoeftes van ouerwordendes in ’n tydperk wat gekenmerk is deur die dramatiese veranderings in die lewenswyses van ons mense — veranderinge wat in baie opsigte ’n negatiewe invloed gehad het op die lewensomstandighede van ’n groot groep bejaardes. Welsynsbeplanners het besef dat hulle in hulle beplanning spesiale voorsiening moes maak vir die lewensbehoeftes van hierdie groep in die gemeenskap en dat hulle in die verband ’n groot agterstand het om in te haal. Geneeshere wat belang begin stel het in die gesondheidsbehoeftes van bejaardes het ook besef dat gevestigde geneeskundige praktyke geensins voldoen aan die spesifieke behoeftes van ’n groot groep bejaardes nie en dat groot aanpassings gemaak moes word met betrekking tot hulle benaderings en metodes van behandeling van hierdie pasiente.

Betekenis van Legionella-soorten voor preventiebeleid van leidingwaterinstallaties

NARCIS (Netherlands)

Versteegh JFM; Brandsema PS; Lodder WJ; de Roda Husman AM; Schalk JAC; van der Aa NGFM; IMG; LZO; EPI

2009-01-01

Het RIVM adviseert om de huidige normstelling voor het preventiebeleid van Legionella te handhaven en niet uitsluitend op Legionella pneumophila te richten. Als andere Legionella-soorten worden aangetroffen kan er ook groei van Legionella pneumophila optreden. Als er dan geen maatregelen worden

Plausibiliteitsdocument STONE 2.0 (Globale verkenning van de plausibiliteit van het model STONE versie 2.0 voor de modellering van uit- en afspoeling van N en P).

NARCIS (Netherlands)

Overbeek, G.B.J.; Beusen, A.H.W.; Boers, P.C.M.; Born, van den G.J.; Groenendijk, P.; Grinsven, van J.J.M.; Kroon, T.; Meer, van der H.G.; Oosterom, H.P.; Puijenbroek, van P.J.T.M.; Roelsma, J.; Roest, C.W.J.; Rötter, R.; Tiktak, A.; Tol, van S.

2002-01-01

STONE is ontwikkeld om landsdekkend voor Nederland de effecten van bemesting en mestbeleid op de emissies van stikstof en fosfaat uit de landbouw naar grond- en oppervlaktewater te verkennen. De nadruk in de hier gerapporteerde plausibiliteitsstudie ligt op vaststelling van de geloofwaardigheid, het

Plausibiliteitsdocument STONE 2.0.Globale verkenning van de plausibiliteit van het model STONE versie 2.0 voor de modellering van uit -en afspoeling van N en P

NARCIS (Netherlands)

Overbeek GBJ; Beusen AHW; Boers PCM; Born GJ van den; Groenendijk P; Grinsven JJM; Kroon T; Meer HG van der; Oosterom HP; Puijenbroek PJTM van; Roelsma J; Roest CJW; Rotter R; Tiktak A; Tol S van; LBG; CIM; LAE; LWD

2002-01-01

STONE is ontwikkeld om landsdekkend voor Nederland de effecten van bemesting en mestbeleid op de emissies van stikstof en fosfaat uit de landbouw naar grond- en oppervlaktewater te verkennen. De nadruk in de hier gerapporteerde plausibiliteitsstudie ligt op vaststelling van de geloofwaardigheid,

Geochemische bodematlas van Nederland

NARCIS (Netherlands)

Mol, G.; Spijker, J.H.; Gaans, van P.; Römkens, P.F.A.M.

2012-01-01

Deze Geochemische bodematlas geeft een uniek overzicht van de chemische samenstelling van de bodem in Nederland. Bodemmonsters van meer dan 350 locaties zijn geanalyseerd op meer dan 40 chemische elementen. De atlas geeft niet alleen informatie over de door de mens beïnvloede toplaag van de bodem,

Evaluatie van bemesting en bekalking in bossen en de ontwikkeling van onbehandelde bossen

NARCIS (Netherlands)

Olsthoorn, A.F.M.; Berg, van den C.A.; Gruijter, de J.J.

2006-01-01

Dit rapport doet verslag van een deelonderzoek uit de Evaluatie van effectgerichte maatregelen in multifunctionele bossen 2004-2005 en is gericht op de effecten van de maatregelen bemesting en bekalking in bossen als overbruggingsmaatregel in het kader van het Overlevingsplan Bos en Natuur (OBN). Na

Die meting van die gelyktydige hantering van teenstrydige en dubbelsinnige inligting as kritieke eienskap in 'n verskeidenheid van Beroepe

Directory of Open Access Journals (Sweden)

W. S. de Villiers

1983-11-01

Min informasie bestaan omtrent die hantering van teenstrydige en dubbelsinnige inligting as kritieke vermoë in vele werksituasies. Met hierdie ondersoek is daar gepoog om die konstruk te omlyn en aan 'n empiriese verifiering te onderwerp. ‘n Meetinstrument (posmandjie is ontwikkel om die hantering van teenstrydige en dubbelsinnige inligting te meet en is saam met ander meetinstrumente ter omlyning van die genoemde konstruk aan twee groepe proefpersone geadministreer. Daar is vasgestel dat hierdie vermoë verband hou met intellektuele vermoëns en sensories kognitiewe oordeel en nie met sekere persoonlikheids- en ander determinante van mens like gedrag nie en dat dit na alle waarskynlikheid dui op die bestaan van 'n afsonderlike werksvermoë of konstruk.

Interlayer excitons in a bulk van der Waals semiconductor

DEFF Research Database (Denmark)

Arora, Ashish; Drueppel, Matthias; Schmidt, Robert

2017-01-01

Bound electron-hole pairs called excitons govern the electronic and optical response of many organic and inorganic semiconductors. Excitons with spatially displaced wave functions of electrons and holes (interlayer excitons) are important for Bose-Einstein condensation, superfluidity......, dissipationless current flow, and the light-induced exciton spin Hall effect. Here we report on the discovery of interlayer excitons in a bulk van der Waals semiconductor. They form due to strong localization and spin-valley coupling of charge carriers. By combining high-field magneto-reflectance experiments...

Een traditie herneemt zich - Over het belang van Aldo van Eyck

NARCIS (Netherlands)

Colenbrander, B.J.F.

1997-01-01

Zo'n zeven, acht jaar geleden veranderde Aldo van Eyck, overigens bij leven en welzijn, van een lijfelijk deelnemer aan de architectuurdiscussie in een historische figuur. Hij werd verguisd en gelauwerd. Met de Rekenkamer in Den Haag echter doet Van Eyck lang vergeten manifesten herleven. Gloort er

Het belang van beschermende factoren in de risicotaxatie van tbs-gestelden

NARCIS (Netherlands)

Nagtegaal, M.H.; Schönberger, H.J.M.

2013-01-01

In dit onderzoek staan de volgende vragen centraal: Is het meenemen van beschermende factoren van toegevoegde waarde voor de risicotaxatie zoals deze plaatsvindt in de tbs-praktijk? Zo ja, op welke manier? Hierbij wordt onder ander het belang van beschermende factoren voor de behandelpraktijk en de

Een geschiedenis van vleesloos eten

NARCIS (Netherlands)

Dagevos, H.

2009-01-01

Recensie van de populaire editie van het proefschrift van Dirk-Jan Verdonk: Het dierloze gerecht: een vegetarische geschiedenis in Nederland. Hierin wordt de geschiedenis van het vegetarisme vanaf de tweede helft van de 19e eeuw tot nu beschreven

Een nieuwe ondersoort van Zosterops montana afkomstig van de Goenoeng Papandajan (West Java)

NARCIS (Netherlands)

Hoogerwerf, A.; Boer, de L.E.

1947-01-01

In zijn laatste revisie van het genus Zosterops (Journ. für Orn., vol. 87, 1939, p. 156-164) geeft Stresemann o.a. een schematische voorstelling van de horizontale en verticale verspreiding binnen deze Archipel van de vier voornaamste groepen van dit geslacht: montana, atricapilla, palpebrosa en

Naar meer bruto nationaal sportgeluk? Verkenning van de rol van sport in geluk

NARCIS (Netherlands)

Dool, R. van den; Breedveld, K.

2017-01-01

Op verzoek van NOC*NSF heeft het Mulier Instituut, met financiële steun van het ministerie van VWS, een verkenning uitgevoerd naar de relatie tussen sport en geluk. NOC*NSF en de Nederlandse sportbonden streven, als onderdeel van het 'transitietraject', ernaar om duidelijker voor het

Gebruik van TaqMan PCR voor het kwantificeren van Fusarium spp. en Microdochium nivale in gewassen en gewasresten van tarwe

NARCIS (Netherlands)

Köhl, J.; Haas, de B.H.; Kastelein, P.; Burgers, S.L.G.E.; Waalwijk, C.

2005-01-01

Samenvattingen van 5 presentaties: 'Heterogenity of Dutch Fusarium oxysporum strains isolated as forma specialis radicis-lycopersici';'Een proteomics benadering om eiwitten te identificeren die door Fusarium oxysporum worden uitgescheiden in xyleemsap van tomaat'; 'Ontwikkeling en implementatie van

Richtlijnen voor selectie en weergave van residugehaltes van bestrijdingsmiddelen

NARCIS (Netherlands)

van den Velde-Koerts T; van Hoeven-Arentzen PH; Ossendorp BC; CSR

2002-01-01

Residubeoordelingen van bestrijdingsmiddelen worden uitgevoerd om wettelijke residulimieten (MRLs = maximum residue limits) vast te leggen. MRLs worden afgeleid uit de resultaten van die residuproeven met bestrijdingsmiddelen die volgens kritisch "Good Agricultural Practice" zijn

Toepassing van optische sensoren (I). Meting van bellengrootteverdeling in luchtige levensmiddelen.

NARCIS (Netherlands)

Bisperink, C.G.J.; Akkerman, J.C.; Prins, A.

1991-01-01

Beschrijving van een methode, ontwikkeld op het laboratorium voor Zuivel en Levensmiddelennatuurkunde van de LU Wageningen in nauwe samenwerking met de TU Delft, waarmee goed en snel de verdeling van de gasfase in de vloeibare fase in de tijd en op verschillende plaatsen in een monster kan worden

van der Waals

Indian Academy of Sciences (India)

University education was beyond reach for van der Waals as he had to work for earning his daily bread ... languages, which was a prerequisite for entering a University those days. van der Waals worked as a school ... take academic examinations at the University yet, van der Waals continued studying at Leiden. University ...

Average and extreme multi-atom Van der Waals interactions: Strong coupling of multi-atom Van der Waals interactions with covalent bonding

Directory of Open Access Journals (Sweden)

Finkelstein Alexei V

2007-07-01

Full Text Available Abstract Background The prediction of ligand binding or protein structure requires very accurate force field potentials – even small errors in force field potentials can make a 'wrong' structure (from the billions possible more stable than the single, 'correct' one. However, despite huge efforts to optimize them, currently-used all-atom force fields are still not able, in a vast majority of cases, even to keep a protein molecule in its native conformation in the course of molecular dynamics simulations or to bring an approximate, homology-based model of protein structure closer to its native conformation. Results A strict analysis shows that a specific coupling of multi-atom Van der Waals interactions with covalent bonding can, in extreme cases, increase (or decrease the interaction energy by about 20–40% at certain angles between the direction of interaction and the covalent bond. It is also shown that on average multi-body effects decrease the total Van der Waals energy in proportion to the square root of the electronic component of dielectric permittivity corresponding to dipole-dipole interactions at small distances, where Van der Waals interactions take place. Conclusion The study shows that currently-ignored multi-atom Van der Waals interactions can, in certain instances, lead to significant energy effects, comparable to those caused by the replacement of atoms (for instance, C by N in conventional pairwise Van der Waals interactions.

Het beslissingsproces van de huisarts bij de keuze van een geneesmiddel

NARCIS (Netherlands)

B. Wierenga (Berend); S.J.T. Jong; A. Mantel

1989-01-01

textabstractHet beslissingsproces van de huisarts bij de keuze van een geneesmiddel, zoals het uit dit empirisch onderzoek naar voren kwam, kan als volgt worden getypeerd. In het merendeel van de gevallen (ca. 90%) beperkt de arts zich tot de informatie die hij al in zijn geheugen heeft. Vaak wordt

Vaststellen reproduceerbaarheid van de nachtactiviteit van de Balb/c/rivm muis over de afgelopen vijf jaar

NARCIS (Netherlands)

Steen BVL; Jansen van ' t Land C; CDL

1999-01-01

Om de inschatting van de mate van ongerief onafhankelijk te maken van ervaring en interpretatie van de persoon die de observatie uitvoert, maken wij in onze studies gebruik van een volledig geautomatiseerde opstelling. Met deze geautomatiseerde opstelling kan de bewegingsactiviteit van

Bereiding van gevriesdroogd cholesterolcalibratie en -controleserum ten behoeve van de Stichting Kwaliteitsbewaking Chemische Analyse ten behoeve van Epidemiologisch Onderzoek (KCA)

NARCIS (Netherlands)

Dreumel; H.J.van; Wikkeling; R.H.; Steentjes; G.M.; Buitenhuis; S.G.; Koedam; J.C.

1986-01-01

In het kader van de samenwerking tussen het RIVM en de Stichting KCA (Kwaliteitsbewaking Chemische Analyse t.b.v. Epidemiologisch Onderzoek) werden drie partijen cholesterolserum bereid. Uitgegaan werd van menselijk serum (Centraal Laboratorium van de Bloedtransfusiedienst). Door uit een deel

De auteursrechtelijke groeipijnen van Google

NARCIS (Netherlands)

Hugenholtz, P.B.

2011-01-01

Het succesverhaal van Google behoort tot de canon van de geschiedenis van onze informatiemaatschappij. In 1998 begonnen in een studentenkamer op de campus van Stanford University, groeide Google in enkele jaren uit tot het orakel van het internet. Zo werd ‘googelen’ de gebruikelijke term voor zoeken

Beoordeling van de gevoeligheid van soorten en habitattypes van Europees belang bij verstoringingrepen

OpenAIRE

Wouters, Jan

2011-01-01

Om ecologische schade te vermijden, moeten activiteiten of plannen met mogelijk schadelijke effecten doorgelicht worden. Het instrument ‘effectenindicator’ licht activiteiten in algemene termen door op mogelijke natuureffecten. De in dit advies weergegeven gevoeligheidstabellen geven de gevoeligheid op van soorten en biotopen voor effecten ten gevolge van menselijke activiteiten. De tabellen bevatten deze gegevens voor de soorten waarvoor gewestelijke instandhoudingsdoelstellingen zijn opgest...

De consequenties van categorieën: een analyse van grensoverschrijdende genre-identiteit in de populaire muziek

NARCIS (Netherlands)

van Venrooij, A.; Schmutz, V.

2013-01-01

Op basis van een analyse van de genreclassificaties door recensenten van 2951 popmuziekalbums worden in dit paper de consequenties onderzocht van het bezitten van een fuzzy of grensoverschrijdende genre-identiteit op het vergaren van commercieel en kritisch succes. De resultaten bevestigen in grote

Advies voor de toepassing van ground-penetrating radar bij de inventarisatie van de grondwaterdynamiek

NARCIS (Netherlands)

Knotters, M.

2001-01-01

Ground-penetrating radar (GPR) biedt mogelijk een nauwkeurig alternatief voor arbeidsintensieve metingen van de grondwaterstand in boorgaten. De GPR-metingen kunnen als hulpinformatie dienen bij geostatistische interpolatie van grondwaterstanden. Op basis van literatuurstudie en verkenning van het

Quantitative mid-infrared spectra of allene and propyne from room to high temperatures

KAUST Repository

Es-sebbar, Et-touhami; Jolly, A.; Benilan, Y.; Farooq, Aamir

2014-01-01

Allene (a-C3H4; CH2CCH2) and propyne (p-C3H4; CH3C2H) have attracted much interest because of their relevance to the photochemistry in astrophysical environments as well as in combustion processes. Both allene and propyne have strong absorption in the infrared region. In the present work, infrared spectra of a-C3H4 and p-C3H4 are measured in the gas phase at temperatures ranging from 296 to 510 K. The spectra are measured over the 580-3400 cm-1 spectral region at resolutions of 0.08 and 0.25 cm-1 using Fourier Transform Infrared spectroscopy. Absolute integrated intensities of the main infrared bands are determined at room temperature and compared with values derived from literature for both molecules. Integrated band intensities are also determined as a function of temperature in various spectral regions.

Quantitative mid-infrared spectra of allene and propyne from room to high temperatures

KAUST Repository

Es-sebbar, Et-touhami

2014-11-01

Allene (a-C3H4; CH2CCH2) and propyne (p-C3H4; CH3C2H) have attracted much interest because of their relevance to the photochemistry in astrophysical environments as well as in combustion processes. Both allene and propyne have strong absorption in the infrared region. In the present work, infrared spectra of a-C3H4 and p-C3H4 are measured in the gas phase at temperatures ranging from 296 to 510 K. The spectra are measured over the 580-3400 cm-1 spectral region at resolutions of 0.08 and 0.25 cm-1 using Fourier Transform Infrared spectroscopy. Absolute integrated intensities of the main infrared bands are determined at room temperature and compared with values derived from literature for both molecules. Integrated band intensities are also determined as a function of temperature in various spectral regions.

Vrouekarakters in enkele prosawerke van C.M. van den Heever

Directory of Open Access Journals (Sweden)

E. Botha

2003-08-01

Full Text Available The role of women in some prose works of C.M. van den Heever Re-reading the C.M. van den Heever “classics” Somer (1935 and Laat vrugte (1939 within the framework of Van den Heever criticism through the years, one becomes aware that central themes in his oeuvre are acted out by women. The beautiful young girl Linda in Somer embodies the sadness of the transcience of beauty and happiness. Through Ouma Willa, Betta and Johanna – three women from three generations in Laat vrugte – the theme of the endurance of the memory of love and passion beyond decay and death is expressed. A cursory examination of other and earlier works by Van den Heever – Op die plaas (1927, Langs die grootpad (1928, Kromburg (1937 and the short story “Leuens” (Lies from Vuurvlieg en sterre (1934 – bears out the observation that women express core meanings in C.M. van den Heever’s prose works.

Tranen van bloed : Het beleg van 's-Hertogenbosch en de oorlog in de Nederlanden, 1629

NARCIS (Netherlands)

Cauwer, de Peter

2008-01-01

Het beleg van 's-Hertogenbosch en de veldtocht van 1629 staat in de Nederlandse geschiedschrijving te boek als een van de meest roemruchte gebeurtenissen van de Tachtigjarige Oorlog. Het beeld en de interpretaties van deze gebeurtenis zijn de afgelopen decennia nauwelijks veranderd. Toch bleven de

Electronic Document Management: A Human Resource Management Case Study

Directory of Open Access Journals (Sweden)

Thomas Groenewald

2004-11-01

Full Text Available This case study serve as exemplar regarding what can go wrong with the implementation of an electronic document management system. Knowledge agility and knowledge as capital, is outlined against the backdrop of the information society and knowledge economy. The importance of electronic document management and control is sketched thereafter. The literature review is concluded with the impact of human resource management on knowledge agility, which includes references to the learning organisation and complexity theory. The intervention methodology, comprising three phases, follows next. The results of the three phases are presented thereafter. Partial success has been achieved with improving the human efficacy of electronic document management, however the client opted to discontinue the system in use. Opsomming Die gevalle studie dien as voorbeeld van wat kan verkeerd loop met die implementering van ’n elektroniese dokumentbestuur sisteem. Teen die agtergrond van die inligtingsgemeenskap en kennishuishouding word kennissoepelheid en kennis as kapitaal bespreek. Die literatuurstudie word afgesluit met die inpak van menslikehulpbronbestuur op kennissoepelheid, wat ook die verwysings na die leerorganisasie en kompleksietydsteorie insluit. Die metodologie van die intervensie, wat uit drie fases bestaan, volg daarna. Die resultate van die drie fases word vervolgens aangebied. Slegs gedeelte welslae is behaal met die verbetering van die menslike doeltreffendheid ten opsigte van elektroniese dokumentbestuur. Die klient besluit egter om nie voort te gaan om die huidige sisteem te gebruik nie.

Onderdeel: Kwaliteit van uitleg, deel uitmakend van het onderzoek naar: Corporate governance in Nederland

NARCIS (Netherlands)

Schutte-Veenstra, J.N.; Boschma, H.E.

2011-01-01

De wijze en mate van naleving en toepasing van de principes en best practices van de nederlandse corporate governance code door de Nederlandse beursgenoteede vennootschappen in ht boekjaar 2010, alsmede de redengeving van eventuele afwijkingen, d.d. 21 september 2011.

Van der Waals stacks of few-layer h-AlN with graphene: an ab initio study of structural, interaction and electronic properties

International Nuclear Information System (INIS)

Dos Santos, Renato B; Mota, F de Brito; Rivelino, R; Kakanakova-Georgieva, A; Gueorguiev, G K

2016-01-01

Graphite-like hexagonal AlN (h-AlN) multilayers have been experimentally manifested and theoretically modeled. The development of any functional electronics applications of h-AlN would most certainly require its integration with other layered materials, particularly graphene. Here, by employing vdW-corrected density functional theory calculations, we investigate structure, interaction energy, and electronic properties of van der Waals stacking sequences of few-layer h-AlN with graphene. We find that the presence of a template such as graphene induces enough interlayer charge separation in h-AlN, favoring a graphite-like stacking formation. We also find that the interface dipole, calculated per unit cell of the stacks, tends to increase with the number of stacked layers of h-AlN and graphene. (paper)

Groei van ongelijkjarige mengingen van grove den en berk op arme zandgronden; resultaten van metingen in 22 opstanden op de Veluwe en de Sallandse Heuvelrug

NARCIS (Netherlands)

Wijdeven, S.M.J.; Oosterbaan, A.; Berg, v.d. C.; Jole, van M.

2000-01-01

Het voorkomen en de groei van berk in ongelijkjarige mengingen van grove den en berk is bepaald op basis van opstandgemiddelden. Er is geen duidelijk verband tussen het voorkomen en de groei van berk en de schermdichtheid van grove den. Actuele groeigegevens zijn noodzakelijk voor een nadere

Die meting van die invloed van organisasiegrootte op bruin werkers se houdings en gedrag

Directory of Open Access Journals (Sweden)

R. van der Bank

1985-11-01

'n Oorsig van die literatuur dui daarop dat bevindinge onkonsekwent is wat betref die invloed van die grootte van organisasies op veranderlikes soos die doeltreffendheid van personeel-keuringstelsels, opleiding, arbeidsomset, werkafwesigheid, werkdoeltreffendheid en so meer. In Wes-Kaapland is tien "groot" fabrieke geselekteer (aantal bruin werkers 300 of meer en vergelyk met 17 "klein" fabrieke (aantal bruin werkers minder as 50. Met behulp van t-toetse is statisties beduidende verskille gevind ten opsigte van die volgende veranderlikes waarvolgens groot organisasies meer gunstig vertoon: 1 meer keuringstegnieke word gebruik; 2 die doeltreffendheid van die keurings-programme is hoër; 3 meer opleidingstegnieke word gebruik; 4 opleidingsprogramme is meer doeltreffend; 5 werkers is meer tevrede; 6 werkers se gemiddelde beroepsaanpassing is beter, en 7 werkers is meer tevrede met hul salarisse of lone. Geen betekenisvolle verskille is egter gevind ten opsigte van arbeidsomset, werkafwesigheid en werkbehoeftes nie.

09 Van Coller 03.pmd

African Journals Online (AJOL)

Owner

29 Jul 2010 ... strangeness, awakening in it a drama whose actors are all those assumptions and operations which make the text the work of another period”. Die spore van Raka: Oor herskrywing en kanonisering. (Deel 2). H.P. van Coller en A. van Jaarsveld. H. P. van Coller is hoof van die Departement. Afrikaans ...

Het dichtwerk van Jan van Foreest (1585-1651)

NARCIS (Netherlands)

Vries, M. de

2007-01-01

The dissertation consists of an edition of Jan van Foreest's Greek poems and the greater part of those written in Latin, provided with translations and a succinct commentary in Dutch. A number of the Latin poems appears in print for the first time ever. Jan van Foreest (1586-1651) studied arts at

Injector for CESAR (2 MeV electron storage ring): 2-beam, 2 MV van de Graaff generator.

CERN Multimedia

CERN PhotoLab

1963-01-01

The van de Graaff generator in its tank. For voltage-holding, the tank was filled with pressurized extra-dry nitrogen. 2 beams emanated from 2 separate electron-guns. The left beam, for injection into the CESAR ring, was pulsed at 50 Hz, with currents of up to 1 A for 400 ns. The right beam was sent to a spectrometer line. Its pulselength was also 400 ns, but the pulse current was 12 microA, at a rate variable from 50 kHz to 1 MHz. This allowed stabilization of the top-terminal voltage to an unprecedented stability of +- 100 V, i.e. 6E-5. Although built for a nominal voltage of 2 MV, the operational voltage was limited to 1.75 MV in order to minimize voltage break-down events.

De miskenning van Theo van Doesburg; zijn bijdrage tot de ontwikkeling van de konkrete poëzie

Directory of Open Access Journals (Sweden)

J. van der Elst

1987-05-01

Full Text Available More literary critics outside Belgium and the Netherlands have written about Theo van Doesburg than from inside these countries. The first important monograph on him appeared in English - Theo van Doesburg - Propagandist and Practitioner of the Avant-Garde, 1909-1923, by Hannah Hedrick. Van Doesburg’s poetry developed in the direction of concrete poetry - the type of poetry in which the spatial, acoustic and visual characteristics of language are maximally utilized towards the creation of the poem. Word as sound and as image is foregrounded in concrete poetry, while the imaging of persons and subjective experience is eliminated as far as possible. The anecdotal or the epic component of the concrete poem is minimal and the language of this sort of poem has been reduced to the minimum. In the spirit of the theory of concrete poetry Van Doesburg advocates the liberation of art from all the commitments imposed upon it. That with which Van Doesburg began was continued by other poets, especially in Germanic literature by poets of the so-called neo-realism.

Effect minerale samenstelling van bodem en plant op de expressie van bladnecrose bij Freesia

NARCIS (Netherlands)

Doorduin, J.C.; Bos, van den A.L.

2003-01-01

Freesiatelers veronderstellen een relatie tussen de voedingstoestand in de grond, de minerale samenstelling van de plant en de expressie van bladnecrose bij freesia. Op verzoek van de Landelijke Freesiacommissie van LTO is een inventarisatie uitgevoerd op ‘gezonde’ en ‘necrose’ bedrijven naar de

Lysine analoga; bereiding en enzymatische hydrolyse van peptide derivaten van lysine en lysine analoga

NARCIS (Netherlands)

Tesser, Godefridus Ignatius

1961-01-01

De synthese van enkele structuuranaloga van lysine wordt beschreven. Aangetoond wordt dat zij lysine in substraten voor trypsine, cathepsine B en papaine kan vervangen. Daar de structuur van de analoga O-(Beta-aminoaethyl)serine en S-(Beta-aminoaethyl) cysteine die van lysine dicht nadert, wordt

Verspreiding en habitats van Bulinus tropicus, tussengasheerslak van die peervormige bot Calicophoron microbothrium, in Suid-Afrika

Directory of Open Access Journals (Sweden)

K. N. de Kock

2002-09-01

Full Text Available Hierdie artikel fokus op die geografiese verspreiding en habitats van Bulinus tropicus, die slaktussengasheer van die peervormige bot, Calicophoron microbothrium. Bulinus tropicus is die varswaterslakspesie met verreweg die wydste geografiese verspreiding, soos gereflekteer deur die vindplekke van die 7 992 monsters wat tans in die databasis van die Nasionale Varswaterslakversameling (NVV van Suid-Afrika op rekord is. Die voorkoms van hierdie spesie is deur versamelaars in ’n totaal van 14 waterliggaamtipes opgeteken, maar die grootste getal monsters is in damme en spruite en in habitats waarvan die water as staande, helder en vars beskryf is, versamel. Die effekgrootte van elke veranderlike is afsonderlik bereken om die rol daarvan in die bepaling van die verspreiding van hierdie spesie vas te stel. Die data in die databasis is verder verwerk en aangepas om ’n geïntegreerde besluitnemingsboom saam te stel. Dit is ’n statistiese model waarvolgens ’n seleksie van veranderlikes gemaak kan word wat maksimaal kan diskrimineer tussen die voorkomsfrekwensie van ’n gegewe spesie en die res van die spesies in die databasis. Die sukses van B. tropicus soos gereflekteer deur sy omvangryke geografiese verspreiding, is waarskynlik toe te skryf aan die omstandigheid dat hierdie spesie grootliks r-geselekteerd is soos onteenseglik in bevolkingsdinamikastudies deur verskeie outeurs bevind is. Daarbenewens beskik die spesie oor’n besondere vermoë om opdroging van ’n habitat vir relatief lang tydperke te kan oorleef. Dit kom egter voor asof sy beperkte verdraagsaamheid ten opsigte van water met ’n relatief lae geleidingsvermoë, moontlik as ’n beperkende faktor vir sy besetting van bepaalde gebiede in Suid-Afrika mag optree. As tussengasheer vir C. microbothrium, wat paramphistomose by vee veroorsaak en soms tot groot verliese kan lei, het die wye verspreiding van B. tropicus in Suid-Afrika egter ook ekonomiese implikasies, veral vir inwoners

Inventarisatie van mogelijke effecten van kribverlaging in de Waal op de beroepsvisserij

NARCIS (Netherlands)

Winter, H.V.

2011-01-01

Om de hoogwaterveiligheid van het rivierengebied te vergroten is het doel van Rijkswaterstaat om eind 2015 ca. 500 kribben in de Waal verlaagd te hebben en daarnaast langsdammen aangelegd te hebben tussen Wamel en Ophemert. In deze korte deskstudie wordt een inventarisatie gemaakt van mogelijke

Beheersing en bestrijding van Botrytis cinerea en van Penicillium in Euphorbia fulgens

NARCIS (Netherlands)

Wubben, J.P.; Hazendonk, A.; Bosker, I.; Slootweg, C.; Hoope, ten M.

2002-01-01

De bloeiwijze van Euphorbia fulgens kent twee belangrijke schimmelbelagers, die problemen in de teelt veroorzaken: Botrytis cinerea en Penicillium. B. cinerea geeft schade in de vorm van smet of pokken, die op de bloemblaadjes verschijnen. Dit zijn kleine donkerbruine/zwarte plekjes van ongeveer 1

Modellering van begrazing in SUMO : verbetering van de vegetatiemodellering in de Natuurplanner

NARCIS (Netherlands)

Wamelink, G.W.W.; Wegman, R.M.A.; Slim, P.A.; Dirksen, J.; Mol-Dijkstra, J.P.; Dobben, van H.F.

2001-01-01

In samenwerking met het RIVM en WU wordt het vegetatievoorspellingsmodel SUMO ontwikkeld. Het model vormt een integraal onderdeel met SMART en wordt onder andere gebruikt in de natuurplanner van het RIVM. Om de modellering van de effecten van begrazing op de vegetatieontwikkeling en successie

Kwaliteitsdocument inzake de bepaling van Cadmium in kunststoffen met behulp van Rontgenflurescentie

NARCIS (Netherlands)

Hoogerbrugge R; van de Wiel HJ; van de Beek ACW; Kliest JJG; IEM

1999-01-01

Bij de handhaving van het besluit Cadmium in Kunststoffen is gebleken, dat de analyse met behulp van Rvntgenfluorescentie (XRF) een snel en goedkoop alternatief zou kunnen zijn voor de op dit moment wettelijk voorgeschreven methoden. In opdracht van de Inspecteur Milieuhygikne is daarom door het

De morbiditeit van astma en COPD in Nederland; een inventariserend onderzoek ten behoeve van de beleidsondersteuning van het Nederlands Astma Fonds

NARCIS (Netherlands)

Smit HA; Beaumont M; CZE

2000-01-01

In opdracht van het Nederlands Astma Fonds is een inventarisatie gemaakt van beschikbare kennis over de morbiditeit van astma en COPD in Nederland. De volgende vraagstellingen werden geformuleerd: Inventarisatie: welke gegevensbronnen zijn beschikbaar, welke gegevens zijn daarin aanwezig? In

’n Evaluering van die welstand onder werknemers van ’n mediesefondsmaatskappy in Suid-Afrika

Directory of Open Access Journals (Sweden)

Lee-Anne Naicker

2015-02-01

Full Text Available Huidige navorsing op die gebied van welstand in die werkplek is gefragmenteer en vereis ’n holistiese, geïntegreerde en stelselmatige begrip van werknemerwelstand sodat gesondheiden welstandsorg doeltreffend bestuur kan word. Die toenemende las van nie-oordraagbare toestande in Suid-Afrika beklemtoon die noodsaaklikheid van voorkomingstrategieë soos welstandprogramme. Die werkomgewing bied ’n ideale plek, aangesien ’n groot deel van die bevolking geteiken word, insluitende diegene wie se lewenstyl verbeter moet word. Hierdie studie is dus daarop gemik om verskeie gesondheid- en welstandkomponente onder werknemers van ’n mediesefondsmaatskappy te evalueer in ’n poging om risikogebiede te identifiseer wat verdere ingryping vereis. Die deelnemers het bestaan uit 140 werknemers van ’n mediesefondsmaatskappy wat ten minste 40 h per week werk. Hulle is onderwerp aan ’n welstandassesseringsbattery bestaande uit antropometrieke, gesondheidverwante en fisieke kapasiteitmetings. Die resultate toon dat ingryping nodig is betreffende alkohol- en dwelmgebruik, dieetgewoontes, hartgesondheid, liggaamsamestelling, spieruithouvermoë, kardiorespiratoriese uithouvermoë en individuele persepsies van die maatskappy. Dié studie het resultate opgelewer wat die bevindings van baie vorige navorsing op hierdie gebied staaf. Die trefwydte van welstandprogramme op die Suid-Afrikaanse bevolking is egter beperk. Die sukses van welstandprogramme wat fisieke aktiwiteit beklemtoon, is goed gedokumenteer in hoë-inkomstelande, met bewys van die ekonomiese voordele en opbrengs op belegging. Gevolglik word daar aangevoer dat die toepassing van welstandprogramme ’n positiewe uitwerking op die Suid-Afrikaanse werkmag sal hê.

Praktijkkennis van leerkrachten als ontwerpers van een ICT rijke leeromgeving

NARCIS (Netherlands)

Boschman, Ferry; McKenney, Susan; Voogt, Joke

2011-01-01

Ormel, B., Pareja, N., & McKenney, S. (2011, 8-10 June). Praktijkkennis van leerkrachten als ontwerpers van een ICT rijke leeromgeving. Presentation at the ORD annual meeting, Maastricht, The Netherlands.

Mogelijkheden tot productie van beertjes

NARCIS (Netherlands)

Scholten, R.; Huiskes, J.

1994-01-01

In opdracht van het Produktschap Vee en Vlees is het project Mogelijkheden tot productie van vleesbeertjes en afzet van vlees en vleesproducten hiervan uitgevoerd. De afzetmogelijkheden voor vlees van beertjes zijn en blijven vooralsnog minimaal

2012, 11/01807, (Vrijstellingsmethode niet van toepassing op Amerikaans deel van bestuurdersbeloning)

NARCIS (Netherlands)

D. Molenaar (Dick)

2012-01-01

textabstractSamenvatting: Belanghebbende is met ingang van 1 februari 2004 werkzaam als CEO bij C en vanaf 31 december 2003 als statutair bestuurder van de Amerikaanse werkmaatschappij van C. Eind 2004 heeft belanghebbende een additioneel belang in C verworven. Het verschil tussen de waarde in het

Van graf tot wieg ; de rol van fintech door de generaties heen

NARCIS (Netherlands)

Vries, A. de; Bakas, A.

2015-01-01

Als financiële dienstverlener moet je rekening houden met mensen van alle leeftijden en uit alle lagen van de bevolking. Van de hulpbehoevende senior tot de nieuwsgierige kleuter. We vroegen 2 experts wat verschillende levensfasen typeert, hoe deze persona’s tegen technologie aankijken en hoe

Isomerization of Internal Alkynes to Iridium(III Allene Complexes via C–H Bond Activation: Expanded Substrate Scope, and Progress towards a Catalytic Methodology

Directory of Open Access Journals (Sweden)

Neha Phadke

2015-11-01

Full Text Available The synthesis of a series of allene complexes (POCOPIr(η2-RC=.=CR’ 1b–4b (POCOP = 2,6-bis(di-tert-butylphosphonitobenzene via isomerization of internal alkynes is reported. We have demonstrated that the application of this methodology is viable for the isomerization of a wide variety of alkyne substrates. Deuterium labeling experiments support our proposed mechanism. The structures of the allene complexes 1b–4b were determined using spectroscopic data analysis. Additionally, the solid-state molecular structure of complex 2b was determined using single crystal X-ray diffraction studies and it confirmed the assignment of an iridium-bound allene isomerization product. The rates of isomerization were measured using NMR techniques over a range of temperatures to allow determination of thermodynamic parameters. Finally, we report a preliminary step towards developing a catalytic methodology; the allene may be liberated from the metal center by exposure of the complex to an atmosphere of carbon monoxide.

De fysica van polymere materialen

NARCIS (Netherlands)

Struik, L.C.E.

1987-01-01

Rede, uitgesproken ter gelegenheid van de aanvaarding van het ambt van buitengewoon hoogleraar in de fysica van polymere materialen aan de Universitelt Twente op donderdag 22 januarì 1987 door Dr.lr. L.C.E. Struik.

Die histologie en ultrastruktuur van die hepatopankreas van die bloukurper Oreochromis mossambicus

Directory of Open Access Journals (Sweden)

M. M. Nel

1990-07-01

Full Text Available Die histologie en ultrastruktuur van die hepatopankreas van die bloukurper Oreochromis mossambicus word beskryf. ’n Dun bindweefselkapsel omring die lewer. Die hepatosietrangskikking vertoon as lobules, met die koorde van hepatosiete wat vanaf ’n sentrale vene uitradieer en met mekaar anastomaseer. Indiwiduele lewerlohules vertoon nie duidelike grense nie, maar enkele duidelike triades word wel in die lewer van O. mossambicus aangetref. Die hepatosiete bevat ’n enkele ronde kern met ’n duidelike nukleolus en die growwe endoplasmiese retikula kom in twee of meer rye om die kerne en teen die selgrense van die hepatosiete voor. Die ander sitoplasmiese organelle kom verspreid in die hepatosietsitoplasma voor. Die eksokriene pankreasselle is om die portale venes gesetel. Die kerne van hierdie selle is rond en is hasaal in die kubies- tot silindervormige selle gelee. ’n Goedontwikkelde growwe endoplasmiese retikulum — vesikulêr, tubulêr en sirkulêr in vorm — en sektretoriese granules wat apikaal in die sel gelee is, kom voor.

Verspreiding van zout bij het terugwinnen van zeezand uit een depot in het Haringvliet

NARCIS (Netherlands)

Kranenburg, C.

1991-01-01

Dit rapport geeft een beknopte analyse van de verdunning en verspreiding van zout vanuit een gepland depot voor ontzilt zeezand in het Haringvliet. Beschouwd zijn de initiële menging van het zout bij terugwinnen van het zand, de verspreiding door stroming en turbulentie bij geopende spuisluis, en de

Van strafbaar tot huwbaar : homorecht wereldwijd (presentatie op Ministerie van Buitenlandse Zaken, Den Haag)

NARCIS (Netherlands)

Waaldijk, C.

2015-01-01

Met de door hem ontwikkelde Global Index on Legal Recognition of Homosexual Orientation (GILRHO) geeft Kees Waaldijk op een schaal van nul tot acht aan, hoe ver een land is met het uit het strafrecht halen van homoseksualiteit, met het verbieden van homodiscriminatie en met het erkennen van

Voorkoming en beheersing van gebreksverschijnselen in de bloembollenteelt : teelt en afbroeiproeven met als doel het voorkomen van ijzergebrek bij tulpen, hyacinten en narcissen van mangaangebrek bij tulpen en van vervroegde afsterving bij lelies

NARCIS (Netherlands)

Dam, van A.M.; Dam, van M.F.N.; Bruin, P.N.A.

2004-01-01

Door veranderingen in de teelten en de aanscherping van het overheidsbeleid t.a.v. het gebruik van met name dierlijke mest kunnen zich bij de teelt van bloembollen verschijnselen voordoen die mogelijk samenhangen met een gebreksituatie. PPO heeft in dit project een aantal van deze verschijnselen

Uw ziekteperceptie is de mijne niet! : DSM-5 over de Somatische Symptoom Aandoening (SSD)

NARCIS (Netherlands)

Drs. Rob Arnoldus

2013-01-01

Worden we met z’n allen steeds gekker? In DSM-5, de nieuwe versie van het handboek van de American Psychiatric Association (APA), maken we kennis met een reeks nieuwe, weinig afgebakende stoornissen. Een daarvan is de Somatische Symptoom Aandoening (SSD). Met dit nieuwe label ligt slodderdiagnostiek

Kosten van allogene stamceltransplantaties

NARCIS (Netherlands)

M. van Agthoven (Michel); M.T. Groot (Martijn); C.A. Uyl-de Groot (Carin)

2001-01-01

textabstractAllogene stamceltransplantatie is een topspecialistische procedure die met succes kan worden ingezet in de behandeling van (hematologische) maligniteiten, met name bij leukemie. Van oudsher worden transplantaten van verwante donoren gebruikt, maar met de mogelijkheden om transplantaten

Contra-expertise op bepalingen van radioactiviteit van afvalwater en ventilatielucht van de kernenergiecentrale Borssele. Periode 2008

NARCIS (Netherlands)

Kwakman PJM; Overwater RMW; LSO

2012-01-01

Dit rapport is eerder vertrouwelijk uitgebracht als briefrapport 610330093. Dit is besproken met de VROM-opdrachtgever en vertegenwoordigers van de betreffende nucleaire installatie: het commentaar op het rapport is verwerkt, voorzien van een Rapport in het Kort, en mag openbaar worden als RIVM

Contra-expertise op bepalingen van radioactiviteit van afvalwater en ventilatielucht van de kernenergiecentrale Borssele. Periode 2009

NARCIS (Netherlands)

Kwakman PJM; Overwater RMW; LSO

2012-01-01

Dit rapport is eerder vertrouwelijk uitgebracht als briefrapport 610330103. Dit is besproken met de VROM-opdrachtgever en vertegenwoordigers van de betreffende nucleaire installatie: het commentaar op het rapport is verwerkt, voorzien van een Rapport in het Kort, en mag openbaar worden als RIVM

Contra-expertise op bepalingen van radioactiviteit van afvalwater en ventilatielucht van de kernenergiecentrale Borssele. Periode 2007

NARCIS (Netherlands)

Kwakman PJM; Overwater RMW; LSO

2012-01-01

Dit rapport is eerder vertrouwelijk uitgebracht als briefrapport 610330076. Dit is besproken met de VROM-opdrachtgever en vertegenwoordigers van de betreffende nucleaire installatie: het commentaar op het rapport is verwerkt, voorzien van een Rapport in het Kort, en mag openbaar worden als RIVM

Resultaten van het RWS-RIKZ JAMP 2003 monitoringsprogramma van bot (Platychthys flesus L.). Biologische gegevens van bot en milieukritische stoffen in bot en mosselen

NARCIS (Netherlands)

Kotterman, M.J.J.

2004-01-01

In opdracht van RWS-RIKZ werden door het RIVO werkzaamheden uitgevoerd in het kader van het Joint Assessment and Monitoring Program van de OSPARCOM. De werkzaamheden bestonden uit het verzamelen van monsters bot waarvan biologische parameters werden bepaald. Tevens werden milieukritische stoffen

Resultaten van het RWS-RIKZ JAMP 2004 monitoringsprogramma van bot (Platichthys flesus L.). Biologische gegevens van bot en milieukritische stoffen in bot en mosselen

NARCIS (Netherlands)

Kotterman, M.J.J.

2005-01-01

In opdracht van RWS-RIKZ werden door het RIVO werkzaamheden uitgevoerd in het kader van het Joint Assessment and Monitoring Program van de OSPARCOM. De werkzaamheden bestonden uit het verzamelen van monsters bot waarvan biologische parameters werden bepaald. Tevens werden milieukritische stoffen

Mathematics and Humor: John Allen Paulos and the Numeracy Crusade

OpenAIRE

Paul H. Grawe

2015-01-01

John Allen Paulos at minimum gave the Numeracy movement a name through his book Innumeracy: Mathematical Illiteracy and Its Consequences. What may not be so obvious was Paulos’ strong interest in the relationship between mathematics and mathematicians on the one hand and humor and stand-up-comedian joke structures on the other. Innumeracy itself could be seen as a typically mathematical Gotcha joke on American culture generally. In this perspective, a Minnesotan acculturated to Minnesota-Nice...

‘Op de wijze van Kavafis’: Die voorbeeld van die digter uit Alexandrië

Directory of Open Access Journals (Sweden)

Phil van Schalkwyk

2014-12-01

Full Text Available Die Griekse digter K.P. Kavafis (1863–1933 word wêreldwyd deur lesers sowel as skrywers besonder hoog geag. Hy het nie net van die grootste twintigste-eeuse skrywers beïnvloed nie,maar is vanweë die buitengewone vertaalbaarheid van sy werk ook betreklik sterk teenwoordig in die letterkunde van meer tale as slegs Grieks en Engels. Vir baie – veral gay lesers, skrywers en kunstenaars – besit Kavafis ’n voorbeeldstatus, ten opsigte van die letterkunde sowel asdie lewe. W.H. Auden het beweer dat dit wat Kavafis onderskei, sy stemtoon is, een wat ’n persoon met ’n unieke perspektief op die wêreld openbaar. Hierdie bydrae, wat deel is van ’nnavorsingsprojek oor idiolektiese skrywersidentiteit, is daarop gerig om die onderskeidende kenmerke van Kavafis se werk, sowel in terme van vorm as inhoud, opnuut te ondersoek. Dit word gedoen binne die raamwerk van die breë kritiese diskoers oor Kavafis en met verwysing na enkele manifestasies/voorbeelde van Nederlandse en Afrikaanse kritiese en kreatieweperspektiewe op sy poësie, met die doel om spesifiek lig te werp op die besondere soortwysheid wat in Kavafis se werk oorgedra word.

Characteristics of Pitch Angle Distributions of 100s Kev Electrons in the Slot Region and Inner Radiation Belt­­­­­­­­

Science.gov (United States)

Zhao, H.; Li, X.; Blake, J. B.; Fennell, J.; Claudepierre, S. G.; Baker, D. N.; Jaynes, A. N.; Malaspina, D.

2014-12-01

The pitch angle distribution (PAD) of energetic electrons in the slot region and inner radiation belt received little attention in the past decades due to the lack of quality measurements. Using the state-of-art pitch-angle-resolved data from the Magnetic Electron Ion Spectrometer (MagEIS) instrument onboard the Van Allen Probes, a detailed analysis of 100s keV electron PADs below L =4 is performed, in which the PADs is categorized into three types: normal (flux peaking at 90°), cap (exceedingly peaking narrowly around 90°) and 90°-minimum (lower flux at 90°) PADs. By examining the characteristics of the PADs of 460 keV electrons for over a year, we find that the 90°-minimum PADs are generally present in the inner belt (Lpitch angle scattering of hiss waves. Fitting the normal PADs into sinnα form, the parameter n is much higher below L=3 than that in the outer belt and relatively constant in the inner belt but changes significantly in the slot region (2mechanism can hardly explain the formation of 90°-minimum PADs at the center of inner belt. These new and compelling observations, made possible by the high-quality measurements of MagEIS, present a challenge for the wave modelers, and future work is still needed to fully understand them.

Stabilisatie en samenstelling van het glycosidenmengsel van Folia digitalis

NARCIS (Netherlands)

Tattje, Derk Hendrik Evert

1952-01-01

Na een korte inleiding wordt een omschrijving van het begrip stabilisatie gegeven en besproken hoe deze stabilisatie, dit is het irreversibel inactiveren van de enzymen, in het algemeen tot stand kan worden gebracht. Tevens wordt nagegaan of ook door verschillende oplosmiddelen reeds bij gewone

Controle van spectrofotometers in ziekenhuislaboratoria

NARCIS (Netherlands)

Ham; W.A.van den; Steentjes; G.M.; Buitenhuis; S.G.; Terlingen; J.B.A.

1985-01-01

In dit rapport worden de resultaten beschreven van een onderzoek dat door twee medewerkers van het Laboratorium voor Klinische Chemie en Hematologie werd ingesteld naar de toestand van 22 fotometers in ziekenhuislaboratoria. Onderzocht werden: - juistheid van de golflengte-instelling - juistheid

Ingredienten voor kwaliteitsborging van modelonderzoek

NARCIS (Netherlands)

Grinsven JJM van; Haan BJ de; Braat LC; MNV; LBG; CIM

1995-01-01

In dit rapport wordt een aanzet gepresenteerd tot harmonisatie van de kwaliteitsborging van modelonderzoek in het RIVM. Het rapport komt voort uit initiatieven van leden van het Intersectoraal Modellen Overleg. Het rapport is in eerste instantie bedoeld voor onderzoekers die modellen

Die meting van sistematiese tydorientasie as 'n sielkundige konstruk van Beroepsgedrag

Directory of Open Access Journals (Sweden)

J. I. De Jager

1985-11-01

Met hierdie navorsing is gepoog om 'n persoonsbeeld van 'n individu met ‘n sistematiese tydoriëntasiestyl saam te stel, en om 'n verfynde instrument vir die meting van sistematiese tydoriëntasie te ontwikkel. Resultate toon dat die vraelys wel 'n bevredigende interne bestendigheid het en ook as ‘n verfynde instrument vir die meting van sistematiese tydoriëntasie beskou kan word.

Well-posedness for one-dimensional anisotropic Cahn-Hilliard and Allen-Cahn systems

Directory of Open Access Journals (Sweden)

Ahmad Makki

2015-01-01

Full Text Available Our aim is to prove the existence and uniqueness of solutions for one-dimensional Cahn-Hilliard and Allen-Cahn type equations based on a modification of the Ginzburg-Landau free energy proposed in [8]. In particular, the free energy contains an additional term called Willmore regularization and takes into account strong anisotropy effects.

Ontwikkeling van een protocol voor de transformatie van iris; introductie van resistentie tegen irismozaik viris (IMMV)

NARCIS (Netherlands)

Langeveld, S.A.; Klerk, de G.J.M.

2004-01-01

Twee iris cultivars, Blue Magic en Blue Sail, werden in weefselkweek gebracht en callus werd geïnduceerd. Dit callus werd genetisch gemodificeerd met virusresistentie via de particle gun procedure die eerder voor lelie was ontwikkeld. Van een van de cultivars, Blue Magic, werden getransformeerde

Effects of island seabird subsidies and invasive species dynamics on the body size and foraging ecology of the Allen Cays Rock Iguana (Cyclura cychlura inornata)

OpenAIRE

Richardson, Kristen Mundie

2015-01-01

Island systems have long been valuable to ecological research as they provide natural experiments for the study of ecosystem processes. We examined Allen, Leaf, U and Flat Rock Reef Cays in the Bahamas to study the effects of seabird driven marine subsidies and invasive mice on island food webs on the body size and foraging ecology of the Allen Cays Rock Iguana (Cyclura cychlura inornata). Iguanas on an island with nesting seabirds (Allen Cay) had 6 times the body mass and 1.7 times the snout...

Plaatsen van beschaafd vertier

Directory of Open Access Journals (Sweden)

James Kennedy

2014-09-01

Full Text Available Plaatsen van beschaafd vertier [Places of civilised amusement] by Jan Hein Furnée, which appeared as a PhD thesis in 2007 and was adapted and extended into a book in 2012, is regarded by historians of the Low Countries as an impressive tour de force. In a stimulating manner Furnée demonstrates with this profound urban history that for the elite of The Hague leisure activities played an important role in acquiring status and maintaining their position. His study is based on extensive and systematic research into a great variety of sources, from census registers, membership lists of clubs and societies to address books. This gives the reader an extraordinarily detailed picture of the changing social relations in the upper echelons of society in The Hague in the latter half of the nineteenth century. The sophisticated use of both qualitative and quantitative methods can serve as a model for other historians in the field of urban history. In a lively fashion Furnée shows that the inhabitants of The Hague grasped at all kinds of pastimes in order to distinguish themselves from others, and when possible to increase their own status through their participation in elegant societies, theatre visits or supporting the proposed zoo: but the book also makes statements about status and class, the history of gender and of politics at the end of the nineteenth century. Plaatsen van beschaafd vertier van Jan Hein Furnée dat in 2007 als proefschrift en in 2012 bewerkt en uitgebreid als boek verscheen, staat onder historici van de Lage Landen bekend als een imponerende tour de force. Op prikkelende wijze laat Furnée in deze diepgravende stadsgeschiedenis zien dat vrijetijdsbesteding voor Haagse elites een belangrijke rol speelde in standsvorming en handhaving van hun positie. Zijn studie is gebaseerd op uitgebreid en systematisch onderzoek van veelsoortige bronnen, van volkstellingsregisters, ledenlijsten van verenigingen en sociëteiten tot adresboeken

Van wie zijn zij? De ambtenaren

NARCIS (Netherlands)

Peters, Jit

2011-01-01

Aan de hand van actuele voorbeelden gaat Jit Peters tijdens zijn afscheidscollege in op de toegenomen macht van ambtenaren. De loyaliteit van de ambtenaar is volgens hem nu te veel gericht op het ondersteunen van de eigen minister. Als tegenwichten van de macht van de ambtenaar staat Peters stil bij

Microbewerking met behulp van lasers

NARCIS (Netherlands)

Ezendam, M.M.M.

1994-01-01

Het bewerken van materialen met behulp van lasers staat momenteel enorm in de belangstelling, en terecht. De ontwikkeling van bestaande en nieuwe typen lasers staat alles behalve stil. Ontwikkelingen bevinden zich met name in het gebied van hogere vermogens, betere bundelkwaliteit en hogere

Thijs van Vugt, Een arbeidersbuurt onder de rook van ‘De Sphinx’. Eeen sociaal-ruimtelijke geschiedenis van het Boschstraatkwartier-Oost te Maastricht, 1829-1904

Directory of Open Access Journals (Sweden)

Christianne Smit

2015-12-01

Full Text Available Thijs van Vugt, Een arbeidersbuurt onder de rook van ‘De Sphinx’. Een sociaal-ruimtelijke geschiedenis van het Boschstraatkwartier-Oost te Maastricht, 1829-1904 (Dissertatie Universiteit van Maastricht 2015; Maaslandse Monografieën 78; Hilversum: Verloren, 2015, 228 pp., isbn 978 90 8704 493 0.

De Smartcard van 2010

NARCIS (Netherlands)

Hartel, Pieter H.; Jacobs, Bart

2001-01-01

Aan de universiteiten van Twente en Nijmegen zijn twee onderzoeksgroepen onder leiding van de auteurs intensief bezig met smartcards. Beide auteurs zijn eerder dit jaar betrokken geweest bij het opstellen van de nieuwe Europese onderzoeksagenda voor smartcards, binnen het zogenaamde zesde kader

Lichtdoorlatendheid van kasdekken onder verschillende omstsndigheden

NARCIS (Netherlands)

Bot, G.P.A.

1984-01-01

Aandacht voor lichtonderschepping; bewolkingsgraad; direkte straling; diffuse straling en gevolgen van veranderingen in kaskonstruktie of materiaaleigenschappen ten aanzien van de lichtdoorlatendheid. Bij vergelijking van de lichttransmissie van diverse kasdekken dient te worden uitgegaan van

Vloeistof-vloeistof verdeling als onderzoekmethode bij de vergelijking van enige rassen van digitalis purpurea L.

NARCIS (Netherlands)

Henning, Gerardus Johannes

1962-01-01

De samenstelling van het glycosidenmengsel van drie rassen van Digitalis purpura L. werd in verschillende groeistadia onderzocht. Door extractie met chloroform van een waterige oplossing der in het gefermenteerde blad voorkomende glycosiden werden deze in twee groepen verdeeld, een in chloroform

Algemene principes van palliatieve zorg

NARCIS (Netherlands)

de Graeff, A; Jobse, A.; Teunissen, SCCM; Verkuijlen, S.; Vissers, K.C.P.; Zylicz, Z; Gilsing, M.

2017-01-01

Palliatieve zorg is een benadering die de kwaliteit van leven verbetert van patiënten (kinderen en volwassenen) en hun naasten die te maken hebben met een levensbedreigende aandoening, door het voorkomen en verlichten van lijden door middel van vroegtijdige signalering en zorgvuldige beoordeling en

Burnout : de stand van zaken

NARCIS (Netherlands)

Taris, T.; Houtman, I.L.D.; Schaufeli, W.

2013-01-01

Dit artikel geeft een overzicht van de stand van zaken in het onderzoek naar burnout. Burnout is een syndroom van extreme vermoeidheid (uitputting), afstand nemen van het werk (distantie) en weinig vertrouwen in het eigen kunnen (verminderde competentie), waarbij de oorzaken voor deze aspecten

Bestrijding van duist in wintertarwe

NARCIS (Netherlands)

Timmer, R.D.

2006-01-01

Duist, en speciaal resistente duist, is één van de grootste problemen in het graantelend gebied het Oldambt. De wintertarwegewassen ondervinden sterke concurrentie van de groeiende duistpopulatie, hetgeen ten koste gaat van de opbrengst. De inzet en kosten van de toegepaste herbiciden nemen toe