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  • Articles  (533)
  • Articles: DFG German National Licenses  (533)
  • Life and Medical Sciences  (533)
  • 1995-1999  (316)
  • 1985-1989  (217)
  • Physics  (533)
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  • Articles  (533)
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  • Articles: DFG German National Licenses  (533)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 17 (1996), S. 33-36 
    ISSN: 0197-8462
    Keywords: static magnetic field ; poly-L-lysine ; Raman spectroscopy ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: We have explored the mechanism of coupling of an approximately 50 mT static magnetic field with the α helices of poly-L-lysine. Structural changes in poly-L-lysine were determined by Raman spectroscopy. Our testable hypothesis is that static magnetic fields of this magnitude can couple with the α-helical segments of the polypeptide, and, as a result, the structure of the polypeptide is significantly altered. Our model further suggests that a static magnetic field can promote protein unfolding and can prevent refolding. © 1996 Wiley-Liss, Inc.
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  • 2
    ISSN: 0197-8462
    Keywords: AC/DC magnetic fields ; IPR ; proton ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: PC-12 cells primed with nerve growth factor (NGF) were exposed to sinusoidal extremely-low-frequency (ELF) magnetic fields (MFs) selected to test the predictions of the ion parametric resonance (IPR) model under resonance conditions for a single ion (hydrogen). We examined the field effects on the neurite outgrowth (NO) induced by NGF using three different combinations of flux densities of the parallel components of the AC MF (Bac) and the static MF (Bdc). The first test examined the NO response in cells exposed to 45 Hz at a Bdc of 2.96 μT with resonant conditions for H+ according to the model. The Bac values ranged from 0.29 to 4.11 μT root-mean-square (rms). In the second test, the MF effects at off-resonance conditions (i.e., no biologically significant ion at resonance) were examined using the frequency of 45 Hz with a Bdc of 1.97 μT and covering a Bac range between 0.79 and 2.05 μT rms. In the third test, the AC frequency was changed to 30 Hz with the subsequent change in Bdc to 1.97 μT to tune for H+ as in the first test. The Bac values ranged from 0.79 to 2.05 μT rms. After a 23 h incubation and exposure to the MF in the presence of NGF (5 ng/ml), the NO was analyzed using a stereoscopic microscope. The results showed that the NGF stimulation of neurite outgrowth (NSNO) was affected by MF combinations over most of the Bac exposure range generally consistent with the predictions of the IPR model. However, for a distinct range of Bac where the IPR model predicted maximal ionic influence, the observed pattern of NSNO contrasted sharply with those predictions. The symmetry of this response suggests that values of Bac within this distinct range may trigger alternate or additional cellular mechanisms that lead to an apparent lack of response to the MF stimulus. © 1996 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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  • 3
    ISSN: 0197-8462
    Keywords: cohort ; electrolysis ; pot room ; sick leave ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: This is a study of the relationship between occupational exposure to magnetic fields in pot rooms and occurrence of sick leave caused by musculoskeletal disorders. The average exposure to static magnetic fields was 8 mT in the pot rooms. Ripple fields were recorded as well. A cohort of 342 exposed workers and 222 unexposed workers from the same electrolysis plant was retrospectively followed for 5 years. The reference group had a type of work similar to the exposed group except for the exposure to magnetic fields. The occurrence of sick leave and the diagnoses causing the sick leave were obtained from the Occupational Health Care Unit: these data were stored in their computer files. The data were complete. No relationship between the occurrence of sick leave caused by musculoskeletal disorders and exposure to magnetic fields was found. This was the case for both the annual number of periods of sick leave and the total number of days with sick leave. The results must be interpreted with caution due to limitations in the design and available data. Also, static magnetic fields constituted the major exposure, and the results may be different when related to work in other types of magnetic-field exposure. © 1996 Wiley-Liss, Inc.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 17 (1996), S. 21-32 
    ISSN: 0197-8462
    Keywords: blood flow ; static magnetic field ; magnetohydrodynamic interactions ; finite element analysis ; sinuatrial node ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The flow of blood in the presence of a magnetic field gives rise to induced voltages in the major arteries of the central circulatory system. Under certain simplifying conditions, such as the assumption that the length of major arteries (e.g., the aorta) is infinite and that the vessel walls are not electrically conductive, the distribution of induced voltages and currents within these blood vessels can be calculated with reasonable precision. However, the propagation of magnetically induced voltages and currents from the aorta into neighboring tissue structures such as the sinuatrial node of the heart has not been previously determined by any experimental or theoretical technique. In the analysis presented in this paper, a solution of the complete Navier-Stokes equation was obtained by the finite element technique for blood flow through the ascending and descending aortic vessels in the presence of a uniform static magnetic field. Spatial distributions of the magnetically induced voltage and current were obtained for the aortic vessel and surrounding tissues under the assumption that the wall of the aorta is electrically conductive. Results are presented for the calculated values of magnetically induced voltages and current densities in the aorta and surrounding tissue structures, including the sinuatrial node, and for their field-strength dependence. In addition, an analysis is presented of magnetohydrodynamic interactions that lead to a small reduction of blood volume flow at high field levels above approximately 10 tesla (T). Quantitative results are presented on the offsetting effects of oppositely directed blood flows in the ascending and descending aortic segments, and a quantitative estimate is made of the effects of assuming an infinite vs. a finite length of the aortic vessel in calculating the magnetically induced voltage and current density distribution in tissue. © 1996 Wiley-Liss, Inc.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 17 (1996), S. 44-47 
    ISSN: 0197-8462
    Keywords: regeneration ; rat sciatic nerve ; microsurgical suture ; millimeter wave radiation ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The effect of low-intensity millimeter wave electromagnetic radiation (MWR) on regeneration of the rat sciatic nerve after transection and microsurgical reapproximation was examined. Rats were exposed to 54 GHz MWR at a power density of 4 mW/cm2. It was found that MWR treatment of the femoral skin in the area of suture accelerated the regeneration of nerve fibers. At the twentieth postoperative day, the MWR-treated animals had a 32% increase in the regeneration distance compared to the control animals. The conduction velocity showed a 26% increase in the MWR-treated animals. © 1996 Wiley-Liss, Inc.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 17 (1996) 
    ISSN: 0197-8462
    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 17 (1996), S. 48-57 
    ISSN: 0197-8462
    Keywords: ELF fields ; modeling ; induced current ; induced electric field ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Calculations of the current density and electric field distributions induced in cell cultures by an applied low-frequency magnetic field have assumed that the medium is uniform. This paper calculates these distributions for a more realistic, inhomogeneous, anisotropic model in which the cells are regarded as conducting squares surrounded by insulating membranes. Separate parameters are used to specify the resistivities of the cell interior, the cell membrane parallel to its surface, the cell membrane perpendicular to its surface, and the intercellular junction parallel to the membrane. The presence of gap junctions connecting the interiors of adjacent cells is also considered. For vertical applied magnetic fields, the induced currents and field distributions may deviate considerably from the homogeneous medium model if there is sufficiently tight binding of the cells to each other. The presence of gap junctions can produce relatively large transmembrane electric fields or intracellular current densities. These considerations are generally less important for horizontal applied fields. A simple microscopic model of the cell surface is also discussed. © 1996 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 17 (1996), S. 1-2 
    ISSN: 0197-8462
    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 17 (1996), S. 58-70 
    ISSN: 0197-8462
    Keywords: ion parametric resonance ; AC/DC magnetic fields ; excitation and deexcitation mechanisms ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: This paper presents a further development of the mechanism for the detection of weak magnetic fields proposed by [Lednev (1991): Bioelectromagnetics 12:71-75]. The fraction of excited oscillator states of an unhydrated ion is studied in a dynamic model driven by the predicted (time-varying) transition probability in the presence of thermal noise and an unspecified excitation mechanism. The main results of Lednev are confirmed. In addition, I conclude that ultraharmonic and ultrasubharmonic resonances may also be observed, provided that the response time of the dynamic system is similar to the period of the oscillating magnetic field. I discuss the time scales involved in the mechanism and present theoretical constraints on these parameters. The crucial requirement for the theory's applicability is that the lifetime of the excited states of the affected ion oscillator exceeds the period of the applied magnetic field. Numerical solutions of the dynamic system are given and are shown to correspond well to theoretical expectations. The main discrepancy between the theories of Lednev and of Blanchard and Blackman [Blanchard and Blackman (1994): Bioelectromagnetics 15:217-238] appears to be due to an inconsistency in the latter paper. The general problem of robust analysis of experimental data is discussed, and I suggest a test of compliance with the Lednev model that is independent of all parameters except for the ratio of oscillating and static field strength (B1/B0) for many resonance conditions and experimental models. © 1996 Wiley-Liss, Inc.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 17 (1996), S. 85-88 
    ISSN: 0197-8462
    Keywords: brain tumor ; coagulation ; bleeding ; hemostasis ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Implantable microwave coagulation was used to perform resection on 62 patients that had intracranial meningiomas. When 20-60 W microwave power was applied for 15 s, the temperature at the center of the tumor tissue was 43-63°C; 30 mm from the center, the temperature was under 40°C. Histological changes in the center of the tumor showed coagulative necrosis, diminished nuclei, and obliterated blood vessels. The changes at 10-20 mm from the center of the tumor showed coagulative necrosis and degeneration and, 30-50 mm from the center of the tumor, showed normal cell morphology after microwave coagulation. The thermal field in brain tumor has an effective diameter of about 40 mm. No side effects on the normal brain tissues were observed. The amount of blood loss during the operation was minimal while the meningioma was coagulated, especially when the meningioma was located at the skull base or in the parasagittal or cerebral convexity region. After microwave coagulation, the entire tumor could easily be removed. Among the 62 surgically treated cases, gross total tumor excision was 85%. No postoperative complications occurred after microwave coagulation, and there was no operative mortality in the series. We believe that this new technique has the advantage of simplicity, less blood loss, and smooth postoperative procedures. Hemostatic effects during the operation are satisfactory, and blood transfusion can be reduced by 50-60%. © 1996 Wiley-Liss, Inc.
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