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  • 1
    Electronic Resource
    Electronic Resource
    Induction of a plasmodial stage of Physarum without plasmalemma invaginations (1979)
    Springer
    Cell & tissue research 197 (1979), S. 463-477 
    Details
    ISSN: 1432-0878
    Keywords: Cytoplasmic actomyosin ; Plasmalemma ; Caffeine ; Physarum polycephalum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Experimentally generated protoplasmic drops of Physarum show time-dependent differentiation processes, i.e. regeneration of plasmalemma, actomyosin fibrillogenesis and regeneration of the plasmalemma invagination system. According to Hatano (1970), caffeine treatment of drops results in a pinching off process of small translucent droplets in which specific effects of Ca++ on protoplasmic streaming phenomena were demonstrated. The light and electron microscopic investigation of the original drop reveal that the time-dependent differentiation processes, e.g. actomyosin fibrillogenesis, are not inhibited by caffeine. However, caffeine hinders the regeneration of the plasmalemma invaginations in the original drop (up to a drop age of 30–40 min). The experimental advantage of this stage of Physarum with full vitality, but without plasmalemma invaginations is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233571
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of caffeine and D2O on persistence and de novo generation of intrinsic oscillatory contraction automaticity in Physarum (1979)
    Springer
    Cell & tissue research 197 (1979), S. 479-499 
    Details
    ISSN: 1432-0878
    Keywords: Cytoplasmic actomyosin ; Plasmalemma ; Excitation-contraction coupling ; Ion pumps ; Physarum polycephalum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The present investigation was performed in an attempt to contribute to answering the question whether the plasmalemma of the plasmodial stage of Physarum represents the site of a trigger mechanism for the oscillating contraction activity of cytoplasmic actomyosin. The effects of the following substances on persistence of tensiometrically measured longitudinal and radial activities of Physarum veins and on de novo generation of activities in experimentally generated drops were studied: caffeine, theophylline, acetylcholinium chloride, procaine, physostigminium salicylate, iso-ompa, nifedipin, sodium nitroprusside, potassium thiocyanate, D2O; as well as the effects of ions such as La+++ and high outer concentrations of Na+ and K+. Some of the substances were applied simultaneously for comparison externally (by bathing solutions) and internally (by injection). The experimental data speak against the existence of electrogenic rhythmical Ca++, Na+ or K+ pumps across the plasmalemma which could have a triggering function for the oscillation. The contraction activities of the cytoplasmic actomyosin seem to represent a spontaneous endogeneous oscillation which can be modulated via the plasmalemma during chemotaxis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233572
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  • 3
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    Dust Impact Signals on the Wind Spacecraft (2016)
    Wiley
    Details
    Publication Date: 2016-01-08
    Description: We analyze waveforms recorded by the Time Domain Sampler (TDS) of the Waves experiment on Wind which are similar to impulsive waveforms observed by the SWaves experiment on STEREO. These have been interpreted as dust impacts by Meyer-Vernet et al. and M.L.Kaiser and K. Goetz, and extensively analyzed by Zaslavsky et al. The mechanism for coupling the emission to the antennas to produce an electrical signal is still not well understood, however. One suggested mechanism for coupling of the impact to the antenna is that the spacecraft body changes potential with respect to the surrounding plasma but the antennas do not (the body mechanism). Another class of mechanisms, with several forms, is that the charge of the emitted cloud interacts with the antennas. The Wind data show that both are operating. The time domain shapes of the dust pulses are highly variable but we have little understanding of what provides these shapes. One feature of the STEREO data has been interpreted as impacts from high velocity nanoparticles entrained by the solar wind. We have not found evidence for fast nanodust in the Wind data. An appreciable fraction of the impacts observed on Wind is consistent with interstellar dust. The impact rates do not follow a Poisson distribution, expected for random independent events, and this is interpreted as bunching. We have not succeeded in relating this bunching to known meteor showers, and they do not repeat from one year to the next. The data suggest bunching by fields in the heliosphere.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    The “Best Catalyst” for Water Oxidation Depends on the Oxidation Method Employed: A Case Study of Manganese Oxides (2015)
    American Chemical Society (ACS)
    Details
    Publication Date: 2015-06-26
    Description: Journal of the American Chemical Society DOI: 10.1021/jacs.5b05093
    Print ISSN: 0002-7863
    Electronic ISSN: 1520-5126
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society (ACS)
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  • 5
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    Large-amplitude transmitter-associated and lightning-associated whistler waves in the Earth's inner plasmasphere at L 〈 2 (2011)
    Wiley
    Details
    Publication Date: 2011-06-16
    Description: We report observations of very large amplitude whistler mode waves in the Earth's nightside inner radiation belt enabled by the STEREO Time Domain Sampler. Amplitudes range from 30–110 mV/m (zero-peak), 2 to 3 orders of magnitude larger than previously observed in this region. Measurements from the peak electric field detector (TDSMax) indicate that these large-amplitude waves are prevalent throughout the plasmasphere. A detailed examination of high time resolution electric field waveforms is undertaken on a subset of these whistlers at L 〈 2, associated with pump waves from lightning flashes and the naval transmitter NPM in Hawaii, that become unstable after propagation through the ionosphere and grow to large amplitudes. Many of the waveforms undergo periodic polarization reversals near the lower hybrid and NPM naval transmitter frequencies. The reversals may be related to finite plasma temperature and gradients in density induced by ion cyclotron heating of the plasma at 200 Hz, the modulation frequency of the continuous-mode NPM naval transmitter signal. Test particle simulations using the amplitudes and durations of the waves observed herein suggest that they can interact strongly with high-energy (〉100 keV) electrons on a time scale of
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    Electromagnetic waves and electron anisotropies downstream of supercritical interplanetary shocks (2013)
    Wiley
    Details
    Publication Date: 2013-02-01
    Description: [1]  We present waveform observations of electromagnetic lower hybrid and whistler waves with f ci  ≪ f 〈 f ce downstream of four supercritical interplanetary shocks using the Wind search coil magnetometer. The whistler waves were observed to have a weak positive correlation between δ B and normalized heat flux magnitude and an inverse correlation with T eh /T ec . All were observed simultaneous with electron distributions satisfying the whistler heat flux instability threshold and most with T ⊥  h /T ∥  h  〉 1.01. Thus, the whistler mode waves appear to be driven by a heat flux instability and cause perpendicular heating of the halo electrons. The lower hybrid waves show a much weaker correlation between δ B and normalized heat flux magnitude and are often observed near magnetic field gradients. A third type of event shows fluctuations consistent with a mixture of both lower hybrid and whistler mode waves. These results suggest that whistler waves may indeed be regulating the electron heat flux and the halo temperature anisotropy, which is important for theories and simulations of electron distribution evolution from the Sun to the Earth.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    STEREO database of interplanetary Langmuir electric waveforms (2016)
    Wiley
    Details
    Publication Date: 2016-01-15
    Description: This paper describes a database of electric waveforms that is available at the Centre de Données de la Physique des Plasmas (CDPP, http://cdpp.eu/ ). This database is specifically dedicated to waveforms of Langmuir/Z-mode waves. These waves occur in numerous kinetic processes involving electrons in space plasmas. Statistical analysis from a large data set of such waves is then of interest e.g. to study the relaxation of high velocity electron beams generated at interplanetary shock fronts, in current sheets and magnetic reconnection region, the transfer of energy between high and low frequencies, the generation of electromagnetic waves etc.The Langmuir waveforms were recorded by the Time Domain Sampler (TDS) of the WAVES radio instrument onboard of the STEREO mission. In this paper, we detail the criteria used to identify the Langmuir/Z-mode waves among the whole set of waveforms of the STEREO spacecraft. A database covering the November 2006 - August 2014 period is provided. It includes electric waveforms expressed in the normalized frame with B and V s w the local magnetic field and solar wind velocity vectors, and the local magnetic field in the variance frame, in an interval of ±1.5min around the time of the Langmuir event. Quicklooks are also provided that display the three components of the electric waveforms together with the spectrum of E ∥ , together with the magnitude and components of the magnetic field in the 3min interval, in the variance frame. Finally, the distribution of the Langmuir/Z-mode waves peak amplitude is also analyzed.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
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    Observations of electromagnetic whistler precursors at supercritical interplanetary shocks (2012)
    Wiley
    Details
    Publication Date: 2012-04-25
    Description: We present observations of electromagnetic precursor waves, identified as whistler mode waves, at supercritical interplanetary shocks using the Wind search coil magnetometer. The precursors propagate obliquely with respect to the local magnetic field, shock normal vector, solar wind velocity, and they are not phase standing structures. All are right-hand polarized with respect to the magnetic field (spacecraft frame), and all but one are right-hand polarized with respect to the shock normal vector in the normal incidence frame. They have rest frame frequencies fci 〈 f ≪ fce and wave numbers 0.02 ≲ kρce ≲ 5.0. Particle distributions show signatures of specularly reflected gyrating ions, which may be a source of free energy for the observed modes. In one event, we simultaneously observe perpendicular ion heating and parallel electron acceleration, consistent with wave heating/acceleration due to these waves. Although the precursors can have δB/Bo as large as 2, fluxgate magnetometer measurements show relatively laminar shock transitions in three of the four events.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    Explaining polarization reversals in STEREO wave data (2012)
    Wiley
    Details
    Publication Date: 2012-04-25
    Description: Recently, Breneman et al. (2011) reported observations of large amplitude lightning and transmitter whistler mode waves from two STEREO passes through the inner radiation belt (L 
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
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    The properties of large amplitude whistler mode waves in the magnetosphere: Propagation and relationship with geomagnetic activity (2011)
    Wiley
    Details
    Publication Date: 2011-09-09
    Description: We present results of a study of the characteristics of very large amplitude whistler mode waves inside the terrestrial magnetosphere at radial distances of less than 15 RE using waveform capture data from the Wind spacecraft. We observed 247 whistler mode waves with at least one electric field component (105/247 had ≥80 mV/m peak-to-peak amplitudes) and 66 whistler mode waves with at least one search coil magnetic field component (38/66 had ≥0.8 nT peak-to-peak amplitudes). Wave vectors determined from events with three magnetic field components indicate that 30/46 propagate within 20° of the ambient magnetic field, though some are more oblique (up to ∼50°). No relationship was observed between wave normal angle and GSM latitude. 162/247 of the large amplitude whistler mode waves were observed during magnetically active periods (AE 〉 200 nT). 217 out of 247 total whistler mode waves examined were observed inside the radiation belts. We present a waveform capture with the largest whistler wave magnetic field amplitude ($\gtrsim$8 nT peak-to-peak) ever reported in the radiation belts. The estimated Poynting flux magnitude associated with this wave is $\gtrsim$300 μW/m2, roughly four orders of magnitude above estimates from previous satellite measurements. Such large Poynting flux values are consistent with rapid energization of electrons.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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