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  • 1
    ISSN: 1433-0350
    Keywords: Key words Callosotomy ; Corpus callosum ; Lennox-Gastaut syndrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  From September 1989 to August 1996, we performed anterior corpus callosotomy in 83 patients. Unfortunately, 9 patients were lost to follow-up. Among the remaining 74 patients, 59 had Lennox-Gastaut syndrome (evolved from infantile spasms in 22), 9 had complex partial seizures with or without secondary generalized seizures, 1 had multifocal independent epileptogenic foci (MISF) syndrome, 3 had hemiconvulsion-hemiplegia-epilepsy (HHE), and 2 had infantile spasms. All cases were followed up for at least 2 years after surgery. The highest rate of significant improvement (more than 50% reduction in seizure frequency) was noted in the patients with generalized tonic-clonic seizures, 82.1% of whom experienced significant improvement, followed by those with generalized tonic seizures (76.7%), atonic seizures (72.7%), myoclonic seizures (64.9%), atypical absences (58.6%), and complex partial seizure with or without secondary generalization (61.5%). Complete freedom from seizures was noted in 14 cases (18.9%). One patient had the anterior half of his right palm amputated following radial artery thrombosis complicated by insertion of an arterial line during anesthesia. Otherwise, there were no major postoperative complications except for brief mutism and multifocal jerks in some patients during the 1st postoperative week. Thus, we conclude that corpus callosotomy is a safe alternative treatment for all kinds of medically intractable seizures, especially generalized epilepsy.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 3879-3882 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: To obtain fast time response plasma properties, electron density and electron temperature, with a Langmuir probe, the applied probe voltage has to be swept at high frequency. Due to the RC characteristics of coaxial cables, an induced noise of a square-wave form will appear when a sawtooth voltage is applied to the probe. Such a noise is very annoying and difficult to remove, particularly when the probe signal is weak. This paper discusses a noise reduction method using a dual-cable circuit. One of the cables is active and the other is a dummy. Both of them are of equal length and are laid parallel to each other. The active cable carries the applied probe voltage and the probe current signal. The dummy one is not connected to the probe. After being carefully tuned, the induced noises from both cables are nearly identical and therefore can be effectively eliminated with the use of a differential amplifier. A clean I–V characteristic curve can thus be obtained. This greatly improves the accuracy and the time resolution of the values of ne and Te. © 1995 American Institute of Physics.
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  • 3
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The energy distributions of ions and electrons in the scrape-off layer of TEXT are measured with a bidirectional retarding field analyzer (RFA). The probe provides simultaneous measurements parallel and antiparallel to the plasma current. Large asymmetries in this direction in the flux and temperature that were found with the RFA appear partly due to differences in the connection lengths Lc. The measurements from the analyzer are compared with the results of a simple edge model to infer the edge particle diffusion coefficient. While the measurements are consistent with the model for longer connection lengths (∼10 m in TEXT-U), the agreement deteriorates for shorter Lc. © 1995 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1542-1551 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Janus is a multiple-function edge probe used to diagnose the Alcator C limiter shadow plasma whose components include two sets of identical diagnostics, each set facing a different direction. Included within each set of diagnostics are a retarding-field energy analyzer (RFEA), Langmuir probe, and calorimeter. Janus is constructed to make measurements both parallel and antiparallel to a magnetic field. It can withstand high heat fluxes and can be scanned perpendicular to the magnetic field in the limiter shadow. The RFEA can alternatively sample both the ion and electron parallel energy distribution functions during a tokamak discharge. From the Langmuir probe, one can infer electron temperature, density, and the plasma floating potential. The calorimeter independently detects the total parallel heat flux incident on an electrically floating plate. Together these three diagnostics enable detailed, localized edge plasma studies on Alcator C. This paper presents the design considerations for each of the diagnostics along with a brief summary of the analysis techniques. Some experimental results obtained using Janus will also be presented.
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  • 5
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The resonance fluorescence of neutral hydrogen illuminated by Hα radiation has been used as a technique for the spatially and temporally resolved density measurements of neutral hydrogen in high temperature plasmas, such as in the tokamak and magnetic mirror plasma fusion devices. The fluorescence signal, usually very weak and buried in the background of stray laser light and Hα emission, is very difficult to extract and its measurements are inaccurate. This paper discusses the improvement of the signal extraction using two optical path laser-induced fluorescence (LIF) methods. One optical path carries the fluorescence signal and the background (the stray laser light and Hα emission), whereas the other path carries only the background signal. By combining these two signals, a clean fluorescence signal can be isolated by subtracting out the background using a differential amplifier. The measurement is obtained instantaneously from these two signals which are taken simultaneously in one pulse rather than being extracted from two separate spectra taken in two sequential pulses (double pulses). This method, therefore, makes a significant improvement on the double pulse technique in terms of the accuracy of the measurement and the time resolution. Using this LIF technique the measurement of the neutral density profile in the exhaust of a tandem mirror plasma propulsion device is obtained and presented. © 1995 American Institute of Physics.
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  • 6
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: For the purpose of measuring the plasma momentum flux in a plasma system, a highly sensitive and precision balance has been developed. It can measure a force, an impulse, or thrust as low as 0.1 mN free of mechanical noise, electrical and magnetic pickups. The double pendulum system consists of two parallel conducting plates. One or both of the plates can be suspended by needles. The needle suspended plate (or plates) can swing freely with negligible friction because of the sharp points of the needles. When one of the plates is impacted by an impulse it will swing relatively to the fixed plate or other movable plate. The capacitance between the plates changes as a result of such a motion. The change of capacitance as a function of time is recorded as an oscillating voltage signal. The amplitude of such a voltage signal is proportional to the impacting force or impulse. The proportional factor can be calibrated. The forces can thus be read out from the recorded value of the voltage. The equation of motion for the pendulum system has been solved analytically. The circuit equation for the electronic measurement system has been formulated and solved numerically. Using this balance the thrust at the exhaust of a Tandem Mirror plasma thruster has been measured. The analytical solution of the overall characteristics agrees greatly with the measurement. © 1995 American Institute of Physics.
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  • 7
    ISSN: 0040-4039
    Keywords: Cyclopropyl Carbocyclic Nucleosides ; Enantiomeric synthesis
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Tetrahedron 50 (1994), S. 11363-11368 
    ISSN: 0040-4020
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
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  • 9
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A retarding energy analyzer, JANUS [A. S. Wan, T. F. Yang, B. Lipschultz, and B. LeBonbard, Rev. Sci. Instrum. 57, 1542 (1986)], has been developed at MIT which has the capability of measuring the local electron temperature, ion temperature, and sheath potential in the scrape-off layer of a plasma. This offers a useful tool in the study of material development for the divertor target to be considered for ITER. The radial profile of sheath potential (φw) on tungsten surfaces has been measured in the boundary layer of Alcator C plasma using this analyzer. Simultaneous measurement of the electron temperature (Te) and ion temperature (Ti) profiles were also made. The retarding grids of the JANUS analyzer were made of fine screens, which made it difficult to determine the absolute values of the ion and electron current. A new analyzer under development replaces the screen with slits, making determination of the absolute currents, ne, and ni easier. This analyzer will be calibrated and tested on a compact tandem mirror machine, the PPEX, that is currently operational at MIT. This work was supported by U.S. DOE contract No. DE-AC02-78ET51053, AFOSR, and NASA/JPL.
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