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  • 1
    Electronic Resource
    Electronic Resource
    Design and manufacture of a 10-T superconducting wiggler magnet at TERAS : Proceedings of the 5th international conference on synchrotron radiation instrumentation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1960-1963 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The 10-T wiggler is an iron-cored superconducting wiggler destined for Electrotechnical Laboratory's 800-MeV electron storage ring to enhance the available radiation. The design and manufacturing contract for this magnet was started in April 1990 and was preceded by a feasibility study. The major features of the magnet are described in the article. Also, the effect of the superconducting wiggler with high magnetic field on the stored electron beam has been simulated. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145770
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  • 2
    Electronic Resource
    Electronic Resource
    Single bunch injection system of the storage ring NIJI-IV for free electron laser use (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2796-2800 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The system of single bunch injection (SBI) for the storage ring NIJI-IV was completed. The system was used for the injection of the short pulse beams from an electron gun into only one of the 16 rf buckets in the ring. On a compact storage ring, the multipulse beams in one pulse train can be stored into only one of many bunches by one injection. The optimum number of the grid pulse in one pulse train was determined to improve the storage efficiency and the storage current by one injection. The keeping time of the bump orbit was calculated by using the transfer matrices. The optimum pulse number obtained by the calculation is 2. In the SBI system, the number of grid pulses in one pulse train can be selected by the gate circuit. A snap off diode and a clip line are used to generate 2 ns grid pulses. The measured grid pulse was shorter than the longitudinal space 5.5 ns of the rf bucket with voltage of −80 V. The EIMAC Y-646B cathode-grid assembly is used as the electron source. It is expected that the injection system provides a higher peak current and easier free electron laser use operation in comparison with the rf-knockout system. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145557
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of hydrogen on structural relaxation and defect evolution in amorphous silicon (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3126-3128 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogenation effects on the structural relaxation and defect evolution in amorphous silicon (a-Si) prepared by ion implantation and evaporation have been investigated using Raman scattering spectroscopy and positron lifetime measurements. Bond angle deviation Δθ in nonhydrogenated a-Si was significantly reduced due to 300 °C annealing in atomic hydrogen atmosphere. This indicates that the reduction in Δθ of hydrogenated amorphous silicon (a-Si:H) is not only due to relaxation during the deposition process of a-Si:H films as proposed by Jackson et al. [Philos. Mag. B 64, 611 (1991)] but also due to posthydrogenation of nonhydrogenated a-Si. It was also found that agglomeration of vacancy-type defects in evaporated a-Si during 450 °C annealing is enhanced after posthydrogenation, while no remarkable enhancement can be seen in a-Si prepared by ion implantation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115799
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  • 4
    Electronic Resource
    Electronic Resource
    The mechanism of mental scanning in foveal vision (1978)
    Springer
    Biological cybernetics 30 (1978), S. 147-155 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract In order to perceive a visual pattern which includes several elemental pictures, the perceiver must allot his cognitive resources to suitably selected parts of the pattern and scan them in sequence. Even when the visual field is small and eye-movement is not required, such scanning is found. We called it ‘mental scanning’ and performed psychological experiments to investigate the mechanism. The tasks were to discern whether the elemental pictures in a pattern are all the same (SP) or not (DP). The per cents correct of the task were measured for various exposure durations. We defined the threshold as the exposure duration at which 75% correct answers were obtained. Our main findings are as follows. The threshold for SP is proportional to the number of picture elements, while the threshold for DP is constant. It appears that two modes of mental scanning exist. One is serial processing for SP, and the other is parallel processing for DP. We proposed a two-layered neural network model having the following characteristics. 1) Information is transmitted as two types of signals through two separate channels; one is the transient signals to the Y layer and the other is the sustained signals slowly conducted to the X layer. 2) Interactions among neurons in the Y layer are lateral inhibitory, while those in the X layer are self-excitatory and lateralinhibitory. 3) Every neuron in the Y layer sends inhibitory signals to every neuron in the X layer except one with the same receptive field. Under these conditions, the dynamics of neurons in the X layer is represented by a set of certain equations. From phase plane analysis and numerical integration, the model appears to have an ability to account for various experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00337143
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  • 5
    Electronic Resource
    Electronic Resource
    Biological oscillators can be stopped—Topological study of a phase response curve (1978)
    Springer
    Biological cybernetics 30 (1978), S. 241-248 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Many biological oscillators are stable against noise and perturbation (e.g. circadian rhythms, biochemical oscillators, pacemaker neurons, bursting neurons and neural networks with periodic outputs). The experiment of phase shifts resulting from discrete perturbation of stable biological rhythms was developed by Perkel and coworkers (Perkel et al., 1964). By these methods, they could get important insights into the entrainment behaviors of biological rhythms. Phase response curves, which are measured in these experiments, can be classified into two types. The one is the curve with one mapping degree (Type 1), and the other is that with zero mapping degree (Type 0) (Winfree, 1970). We define the phase response curve mathematically, and explain the difference between these two types by the homotopy theory. Moreover, we prove that, if a Type 0 curve is obtained at a certain magnitude of perturbation, there exists at least one lower magnitude for which the phase response curve cannot be measured. Some applications of these theoretical results are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00361045
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  • 6
    Electronic Resource
    Electronic Resource
    Synergism and antagonism of neurons caused by an electrical synapse (1979)
    Springer
    Biological cybernetics 34 (1979), S. 81-89 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract To investigate the role of electrical junctions in the nervous system, a model system consisting of two nearly identical neurons electrotonically coupled is studied. We assume that each neuron discharges a train of impulses or bursts either spontaneously or under constant stimulus via chemical synapses. It is known that not only an electric current but also chemical substances whose molecular weight is about 1000 can pass through the junction of an electrical synapse (gap junction). So, our model system is regarded as a set of non-linear oscillators coupled by diffusion, and it may be described by a system of ordinary differential equations. Neurons are excited constantly when they are stimulated by an electric current above the threshold level. Therefore, we expect Hopf bifurcation to occur at the critical magnitude of a stimulating electric current in the system of differential equations which describes the dynamics of a single neuron. Studying our model system according to the theory of Hopf bifurcation, we found regions of diffusion constants of the electrical junction which give two kinds of periodic solutions. One is the solution where two neurons oscillate in phase synchrony. The other is where two neurons oscillate 180° out of phase. In the case where one neuron is described by the BVP model, the following was found by computer simulation. When the initial difference between the phase of two neurons is small, the two neurons come to oscillate synchronously. If the initial difference is large, however, the two come to be excited alternately. The physiological implications of these results are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365472
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of brefeldin A on the Golgi apparatus, the nuclear envelope, and the endoplasmic reticulum in a green alga,Scenedesmus acutus (1998)
    Springer
    Protoplasma 201 (1998), S. 202-212 
    Details
    ISSN: 1615-6102
    Keywords: Brefeldin A ; Endoplasmic reticulum ; Golgi apparatus ; Scenedesmus ; Vesicle transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of brefeldin A (BFA) on the structure of the Golgi apparatus, the nuclear envelope, and the endoplasmic reticulum (ER), and on the thiamine pyrophosphatase (TPPase) activity in these organelles were examined in a green alga,Scenedesmus acutus, to obtain evidence for the existence of a retrograde transport from the Golgi apparatus to the ER via the nuclear envelope. InScenedesmus, Golgi bodies are situated close to the nuclear envelope throughout the cell cycle and receive the transition vesicles not directly from the ER, but from the nuclear envelope. BFA induced the disassembly of Golgi bodies and an increase in the ER cisternae at the trans-side of decomposed Golgi bodies in interphase cells and multinuclear cells before septum formation. The accumulated ER cisternae connected to the nuclear envelope at one part. TPPase activity was detected in all cisternae of Golgi bodies, but not in the nuclear envelope or the ER in nontreated cells. On the contrary, in BFA-treated cells, TPPase activity was detected in the nuclear envelope and the ER in addition to the decomposed Golgi bodies. When septum-forming cells were treated with BFA, the disassembly of Golgi bodies was less than that in interphase cells, and TPPase activity was detected in the Golgi cisternae but not in the nuclear envelope or the ER. These results suggest mat BFA blocks the anterograde transport from the nuclear envelope to the Golgi bodies but does not block the retrograde transport from the Golgi bodies to the nuclear envelope in interphase and multinuclear cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01287416
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  • 8
    Electronic Resource
    Electronic Resource
    Theophylline induces apoptosis of the IL-3 activated eosinophils of patients with bronchial asthma (1999)
    Springer
    Apoptosis 4 (1999), S. 461-468 
    Details
    ISSN: 1573-675X
    Keywords: Apoptosis ; caspase-3 ; eosinophil ; interleukin-3 ; poly(ADP-ribose) polymerase ; theophylline.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In bronchial asthma, eosinophils are upregulated and their survival is suggested to be prolonged by the action of some cytokines such as Interleukin (IL)-3, IL-5 and granulocyte-macrophage colony-stimulating factor (GM-CSF). We find here that the survival of eosinophils in the peripheral blood of patients with asthma is correlated with the serum levels of IL-3 but not of IL-5 and GM-CSF. Interestingly, theophylline is revealed to induce apoptosis of the prolonged survival eosinophils by IL-3, as judged by morphological changes and nucleosomal DNA fragmentation. During the apoptosis, caspase-3 in eosinophils stimulated by IL-3 is activated by theophylline. The substrate of caspase-3, poly (ADP-ribose) polymerase (PARP), is cleaved in the eosinophils after theophylline treatment. These results suggest that theophylline is able to induce apoptosis of the IL-3 activated eosinophils in patients with bronchial asthma, and that its clinical effectiveness may be due to the reduction of inflammatory cells in the airway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009656527168
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  • 9
    Electronic Resource
    Electronic Resource
    Positron/positronium annihilation in nanocrystalline silicon thin films (1996)
    Springer
    Journal of radioanalytical and nuclear chemistry 211 (1996), S. 31-38 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Positron and positronium annihilation investigations were applied to nanocrystalline silicon (nc-Si) thin films, for the first time. The nc-Si thin films with average grain diameters of 3–5 nm show intense blue luminescence at room temperature. The nanometer-sized Si crystallites formed in amorphous Si (a-Si) matrix give rise to this luminescence. Very highS-parameters up to 0.62 were observed in the as-grown a-Si thin film suggesting positronium formation in the a-Si layer. The average lifetime of the positrons in the a-Si was determined to be about 520 ps. TheS-parameters dropped significantly to 0.53 by crystallization of the thin film at 800 °C for 10 seconds, which was almost the same to the value observed in bulk Si (100) substrate. Further crystallization from 60 seconds to 1 hour showed smaller change in theS-parameters than that from the a-Si to 10 seconds. The large change in theS-parameters due to the annealing might be caused by the formation of Si nanocrystallites in a-Si matrix suggesting that positron is a sensitive probe for structural investigations of the nc-Si materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02036252
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  • 10
    Electronic Resource
    Electronic Resource
    Slow positron study on dielectric-coated mirror for free-electron-laser experiments (1996)
    Springer
    Journal of radioanalytical and nuclear chemistry 211 (1996), S. 47-52 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A positron lifetime study has been done on dielectric multilayer cavity mirrors for free-electron-laser experiments by the use of a variable-energy pulsed positron beam. A long-lived ortho-positronium component has been observed at low positron energy region, corresponding to the depth of the top amorphous SiO2 layer. The intensity of the positronium component correlates with the degradation and restoration of the mirrors. We discuss the relation between the positronium intensity and degradation mechanism of the mirrors. The present studies revealed that the slow positron lifetime technique is highly sensitive to the properties of the mirrors and is useful for the evaluation of the mirrors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02036254
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