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  • 1
    Electronic Resource
    Electronic Resource
    Functional organisation of corticonuclear pathways to motoneurones of lower facial muscles in man (1994)
    Springer
    Experimental brain research 101 (1994), S. 465-472 
    Details
    ISSN: 1432-1106
    Keywords: Magnetic stimulation ; Single motor units ; Lower facial muscles ; Corticobulbar connexions ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract EMG responses were recorded from lower facial muscles (depressor labii inferioris or depressor anguli oris) of 12 normal subjects after magnetic stimulation of the motor cortex. Using a figure-of-eight stimulating coil, the largest responses were obtained from points around 8–10 cm lateral to the vertex. Usually they were bilateral and had the same latency (11–12 ms) on both sides of the face. Patients with complete Bell's palsy had no response in muscles on the same side as the lesion, indicating that the ipsilateral component to cortical stimulation was not the result of recrossing in the periphery of nerve fibres from the contralateral side. Single-unit studies showed that cortical stimulation produced two phases of motoneuronal facilitation: a short-latency (central motor delay from contralateral cortex to the intracranial portion of the facial nerve, 7.6 ms), short-duration (1– to 2-ms duration peak in the post-stimulus time histogram) input, which was more commonly evoked by contralateral than ipsilateral stimulation; and a longer latency (central delay 〉 15 ms), long-duration input evoked equally well from either hemisphere. The former may represent activity in a predominantly contralateral oligosynaptic corticobulbar pathway; the latter, a polysynaptic indirect (e.g. co-rticotegmento-nuclear) bilateral pathway to lower facial muscles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227339
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  • 2
    Electronic Resource
    Electronic Resource
    Lack of interaction between ramipril and simvastatin (1994)
    Springer
    European journal of clinical pharmacology 47 (1994), S. 373-375 
    Details
    ISSN: 1432-1041
    Keywords: ACE-inhibitors ; Simvastatin ; ramipril ; lipid lowering drugs ; drug interaction ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Twenty two healthy males participated in a randomised, placebo-controlled, double blind, cross-over study to investigate the influence of simvastatin on the pharmacokinetics of ramipril and its active metabolite (ramiprilat), and on the ACE-inhibiting effect of ramiprilat. During two study periods, each of 7 days, subjects received daily either simvastatin 20 mg at 19.00 h or placebo; ramipril (5 mg) was given on Day 5 of each of the periods. Plasma concentrations of ramipril and ramiprilat and ACE-activity were measured in sequential blood specimens, and ramipril and ramiprilat concentrations were measured in urine. Blood and urine collections for pharmacokinetic and pharmacodynamic assessment were made up to 72 h after the dose of ramipril. The mean AUC of ramipril for ramipril+placebo (R+P) and ramipril+simvastatin (R+S) was 22.2 and 21.3 ng.h.ml−, respectively; for ramiprilat the corresponding figures were 61.3 and 57.6 ng.h.ml−. The urinary excretion of ramipril+metabolites for (R+P) and (R+S) was 25.2 and 24.1% of dose. The maximum percentage inhibition of ACE-activity for (R+P) was 94.6%, and for (R+S) it was 94.1%. It is concluded that concomitant administration of simvastatin and ramipril has no clinically relevant effect on the pharmacokinetics or ACE-inhibition of the latter drug and its metabolites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00191171
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  • 3
    Electronic Resource
    Electronic Resource
    Percutaneous needle trephination. Experience in 200 cases (1994)
    Springer
    Acta neurochirurgica 127 (1994), S. 232-235 
    Details
    ISSN: 0942-0940
    Keywords: Percutaneous needle trephination ; ventriculostomy ; complication ; technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary For many years percutaneous needle and classic burr-hole trephination with insertion of plastic catheters for external ventricular drainage are in use. The shortcomings of the conventional puncture needles were compensated for by the development of a modified instrument in recent years. In this prospective study we tried to define advantages and disadvantages of percutaneous ventriculostomy with this modified needle in a large number of patients. We treated and followed a total number of 200 patients with external ventricular drainage for various reasons (42% obstructive hydrocephalus, 27% haematocephalus, 11% malresorptive hydrocephalus, 11% elevated ICP and 9% infections). The ventriculostomy is performed — after percutaneous trepheication with a 1.5 mm drill and 1.2 mm needle under the local aesthesia as a bedside procedure. The modified blunt needle is provided with markings and a set screw which allows insertion to a prefixed depth and a sharp guide which is withdrawn after penetration of the dura. It is then bent rostrally and fixed by a plaster cast. The mean duration of drainage was 9 days (1–30 days). Mean operating time for the whole procedure including fixation and connection to the drainage system was 20 minutes. Overall complication rate was 13% (N=26). Two intracerebral haemorrhages (1%) occurred, of which one was caused by overdrainage. Five (3%) infections in primarily not infectious cases (N=182) were seen. Only one case of infection occurred without loosing of the needle on day 17. In 19 patients (10%) the needles had loosened. Fifteen times this complication was repaired in time and no infection occurred. The overall complication rate (13%) and the needle related risk of bleeding (0.5%) seem average. The true risk of infection with correct handling (0.5%) is very low despite the very long average duration of drainage. The main risk lies in the markedly high danger of loosening (10%), which entails a disproportionally high demand for nursing care. Nevertheless, we regard percutaneous needle trephination as the ventriculostomy method of choice because of its better practicability and low infection rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01808772
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  • 4
    Electronic Resource
    Electronic Resource
    Neuroactive Steroids Modulate GABAA Receptors in Peptidergic Nerve Terminals (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neuroendocrinology 6 (1994), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Neuroactive steroid modulation of GABAA receptors was investigated in the peptidergic nerve terminals of the posterior pituitary using patch clamp techniques. In common with GABAA receptors in cell bodies, the nerve terminal GABAA receptor was potentiated by the synthetic steroid alphaxalone and by physiological concentrations of the progesterone metabolite allopregnanolone. Both of these agents enhanced Cl− currents elicited by GABA. Estradiol-17β had a weak inhibitory effect on GABA responses of nerve terminals, but only at high concentrations. The potentiating action was manifest as an increase in the probability of channel opening, with no effect on the rate of desensitization of the GABAA receptor. Neuroactive steroids enhanced GABA-gated Cl∼ channel activity in cell-free membrane patches, thus demonstrating a membrane delimited response. These results indicated that with regard to allosteric modulation by neuroactive steroids, the nerve terminal GABAA receptor is similar to the GABAA receptors of nerve cell bodies and endocrine cells. Neuroactive steroids are thus capable of altering the chemosensitivity of nerve terminal membranes by enhancing GABA inhibition at this location. The neuroactive steroid sensitivity of nerve terminal GABAA receptors provides a pathway by which gonadal steroid derivatives could regulate peptide secretion from neurosecretory neurons. Such a pathway could participate in the coordination of neuropeptide secretion during complex neuroendocrine functions. With specific regard to the neurohypophysis, neuroactive steroid-induced changes in the sensitivity of nerve terminal GABAA receptors could play a role in the initiation of oxytocin secretion during the transition between pregnancy and parturition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2826.1994.tb00616.x
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  • 5
    Electronic Resource
    Electronic Resource
    Application of microwave detection of the Shubnikov–de Haas effect in two-dimensional systems (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7533-7542 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microwave detection of the Shubnikov–de Haas (SdH) effect as a contact-free characterization technique for different types of two-dimensional semiconductor structures is explored in the low magnetic field region. The detection technique and the data analysis are described. The character and relevance of the single-particle relaxation time that can be detected by this technique are distinguished from the usual transport scattering time. The measured values of the carrier concentration and single-particle relaxation time agree with electrical measurements, while the problem of making contacts on the structure is avoided. Uncertainties in the analysis for the single-particle relaxation time are discussed. Cyclotron resonance, optically detected cyclotron resonance, and magneto-photoluminescence are applied as other contact-free techniques on the same samples. The results and suitability of these techniques are compared with the microwave detection of the SdH effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354001
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  • 6
    Electronic Resource
    Electronic Resource
    Excitonic line broadening in bulk grown Cd1−xZnxTe (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4523-4526 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cd1−xZnxTe crystals grown by the traveling heater method have been investigated by low-temperature photoluminescence. The excitonic energy gap as a function of the alloy composition was determined over the complete range of x=0 to x=1. The composition dependent broadening of the neutral acceptor bound exciton (A 0X) line was determined. Theoretical calculations, where the A 0X exciton is treated within the pseudodonor model and the conduction/valence band offset between CdTe and ZnTe is taken into account, give close agreement with the experiment for x≤0.77. Evidence for clustering of Zn atoms is found for x≥0.77.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350798
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  • 7
    Electronic Resource
    Electronic Resource
    Electrical, magnetic circular dichroism and Raman spectroscopic investigations on the EK2 double acceptor (78/203 meV) in GaAs (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1454-1462 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical and optical properties of liquid encapsulated Czochralski grown, Ga-rich (melt composed of 55% Ga and 45% As), p-type GaAs were studied by the Hall effect, capacitance-voltage measurements, magnetic circular dichroism, optically detected electron spin resonance, deep level transient spectroscopy (DLTS), and Raman spectroscopy. Two levels with ionization energies of 78 and 203 meV above the valence band edge were examined and fitted to the singly and doubly charged ground states of a double acceptor which is designated an EK2 center. The Raman scattering cross sections for electronic excitations were determined from the defect concentrations measured by DLTS. The EK2 center is electrically passivated via a remote microwave hydrogen plasma technique. It can be reactivated by heat treatments with an activation energy of Ea=1.4 eV. The concentrations of the two levels were equal to each other in four as-grown samples, in samples following passivation, and at all stages during the subsequent reactivation. The observations are inconsistent with previous suggestions that the levels are due to two separate defects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347287
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  • 8
    Electronic Resource
    Electronic Resource
    EL2 and anion antisite defects in plastically deformed GaAs (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3381-3385 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on optical absorption its magnetic circular dichroism (MCD), optically detected electron spin-resonance (ODESR), and electron nuclear double-resonance (ODENDOR) investigations of plastically deformed semi-insulating GaAs. By plastic deformation arsenic antisite defects are created which show a similar ODESR pattern as EL2 defects present in the material prior to deformation. EL2 and the new antisite defects can be distinguished by their different spectral dependence of the MCD. The new antisite defect formation starts at 2% deformation and is investigated as a function of the degree of deformation; additional EL2 defects are not created. With ODENDOR it is shown that the atomistic structure of the EL2 defects changes in the deformed GaAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346341
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  • 9
    Electronic Resource
    Electronic Resource
    On the time scale and time course of protein conformational changes (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 7253-7259 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Proteins change their global conformation very slowly compared to the time scales of most localized internal motion. The relationship between these slow and fast processes was investigated with the aid of a stochastic model recently applied to a related problem of protein folding [Zwanzig et al., Proc. Natl. Acad. Sci. 89, 20 (1992)]. In the present study a change in conformation was treated as a bond rotational isomerization that may only occur when several other gating bonds simultaneously assume permissive orientations. The requirement of correct orientation of these gating bonds is analogous to the alignment of the tumblers in a lock. For a range of reasonable choices of parameters, this model generated realistic time scales for protein conformational changes. Although the transition time depended on the value of an energy bias against the permissive position of a gating bond, the model could still generate reasonable transition times in the absence of an energy bias. For a wide range of parameters chosen to give typical experimental rates for biological transitions, the model predicted conformational changes with simple exponential kinetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465418
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  • 10
    Electronic Resource
    Electronic Resource
    Carrier-modulated, microwave-detected Shubnikov–de Haas oscillations in two-dimensional systems (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2725-2727 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It was recently shown that Shubnikov–de Haas (SdH) oscillations observed in conventional resistance measurements can be dramatically enhanced by light-induced carrier modulation [S. E. Schacham, E. J. Haugland, and S. A. Alterovitz, Appl. Phys. Lett. 61, 551 (1992)]. Here we report on a similar observation in the case of contact-free, microwave-detected SdH oscillations. In the original version of this nondestructive technique [P. Omling, B. Meyer, and P. Emanuelsson, Appl. Phys. Lett. 58, 931 (1991)], magnetic-field modulation was applied in order to enhance the sensitivity. If, instead, the carrier concentration is modulated by illumination, we show that a similar enhancement in the sensitivity of the signal is obtained. We demonstrate that very simple microwave equipment can be used for the measurements, and that the accessible magnetic-field region can be extended, allowing for contact-free transport investigations in the high magnetic-field region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109245
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