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  • 1990-1994  (5)
  • 1975-1979
  • 1920-1924
  • 81.20.-n  (1)
  • Cell wall  (1)
  • Cellulose synthesizing complex  (1)
  • Cerebral fat embolism  (1)
  • Cold-cathode diode  (1)
Datenquelle
Materialart
Erscheinungszeitraum
  • 1990-1994  (5)
  • 1975-1979
  • 1920-1924
Jahr
Schlagwörter
  • 1
    Digitale Medien
    Digitale Medien
    Anomalous photoluminescence and raman scattering behavior in heavily Mg+ ion-implanted InP (1991)
    Springer
    Applied physics 53 (1991), S. 102-108 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 78.55.Cr ; 78.30.Gt ; 81.20.-n
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Mg+ ions were implanted into highly pure InP grown by the liquid encapsulated Czochralski (LEC) method in which the Mg concentration [Mg] was varied between 1×1015 cm−3 and 3×1020 cm–3. Two annealing methods were used: furnace annealing (FA) up to 740° C and flash lamp annealing (rapid thermal annealing, RTA) up to 900° C. For characterization, photoluminescence (PL) spectra were measured between 2K and room temperature together with Raman scattering measurements at room temperature. An emission designated by g, which was attributed to a novel energy state of an isolated acceptor, was found to be produced for a rather low value of [Mg]. In addition, a broad emission denoted by [g−g], which was ascribed to acceptor-acceptor pairs, was observed below bound exciton emissions for moderate values of [Mg]. These features were quite similar to those previously observed in acceptor-doped GaAs when the background concentration of donors is extremely low. Two additional novel emissions located far below the band-to-acceptor emission were also obtained, and each showed a remarkable energy shift towards lower energy with increasing [Mg]. The binding energies of these emissions were estimated from the temperature dependence of PL spectra and the results suggest that they are complex-type radiative recombination centers, presumably donor-acceptor-type centers. A strong broad emission centered near the band-to-acceptor emission was observed for [Mg]=3×1020 cm−3. This observation indicates a formation of a new material between In, P and Mg, which was also attested by the appearance of a new TO-like Raman signal for [Mg] greater than 1×1019 cm−3. A substantial difference of PL and Raman spectra was revealed for the two annealing methods, suggesting that the annealing behaviour of ion-implanted InP should be investigated more extensively in order to establish reliable annealing procedures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00323867
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  • 2
    Digitale Medien
    Digitale Medien
    Magnetic resonance imaging of cerebral fat embolism (1991)
    Springer
    Neuroradiology 33 (1991), S. 72-74 
    Details
    ISSN: 1432-1920
    Schlagwort(e): Magnetic resonance imaging ; Cerebral fat embolism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The cerebral fat embolism is a potentially serious complication of fractures but clinical cases often go undiagnosed. Two cases of clinically diagnosed cerebral fat embolism are reported, and MR images of these patients are described. While brain CT revealed no abnormality, MR imaging showed relative low-intensity areas on T1-weighted images and high-intensity areas on T2-weighted images. In one patient follow-up MR showed nearly complete resolution of the abnormal signal. MR imaging appears to be valuable for detecting the lesions in these patients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00593341
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  • 3
    Digitale Medien
    Digitale Medien
    Role of the microtubule cytoskeleton in alternating changes in cellulose-microfibril orientation in the coenocytic green alga, Chaetomorpha moniligera (1994)
    Springer
    Planta 193 (1994), S. 21-31 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Cell wall ; Cellulose microfibril ; Chaetomorpha ; Cytoskeleton ; Microtubule ; Plasma membrane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The functions of the microtubule (MT) cytoskeleton in changing the orientation of microfibrils (MFs) in the cell walls of the coenocytic green alga Chaetomorpha moniligera Kjellman were investigated by electron microscopy. The cortical MT cytoskeleton in Chaetomorpha was comprised of longitudinally oriented MTs. Cellulose MFs, however, alternately changed their orientation longitudinally and transversely to form crisscross MF textures. Microtubules were parallel to longitudinally oriented MFs but never to those that were transversely oriented. The average density of MTs during the formation of longitudinally oriented MFs was 216 per 50 μm of wall and that of transversely oriented MFs 170/50 μm. To determine exactly the MT-density dependency of each MF orientation, changes in MF orientation were examined by changing MT density after treating and removing amiprophos-methyl (APM). Microtubules were reduced in number by a half (100/50 μm) after 2 h and by 3/4 (50/50 μm) after 3 h of treatment with APM (3 mM). This reduction was caused by the disappearance of alternating MTs. Microtubules retained this density (50/ 50 μm) up to 6 h, and then gradually disappeared within 24 h. Microfibril orientation in the innermost cell wall was transverse after treatment with APM for 2 h but was helicoidal after 6 h. Polymerization of MTs occurred in the longitudinal direction following the removal of APM after treatment for 48 h. Microtubule density rose to about 100/50 μm and 200/50 μm after 6 h and 24 h, respectively. The orientation of MTs changed from helicoidal to transverse and transverse to longitudinal after 6 h and 24 h, respectively. When APM was removed prior to formation of the helicoidal texture, longitudinally oriented MFs appeared within 6 h. There is thus an alternating cycle of formation of longitudinally and transversely oriented MFs within a 12-h period. Formation of transversely oriented MFs as a result of APM treatment started in the middle of a cell as hoops which then extended in the apical and basal directions. Formation of longitudinally oriented MFs as a result of the removal of APM started from the apical end and proceeded toward the base. It follows from these results that: (1) the point of formation of longitudinally oriented MFs differs from that for transversely oriented MFs, (2) MF orientation in each case depends on a separately functioning mechanism, (3) MT density changes rhythmically to trigger a switch for crisscross orientation of MFs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00191602
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  • 4
    Digitale Medien
    Digitale Medien
    Possible involvement of membrane fluidity in helicoidal microfibrillar orientation in the coenocytic green alga,Boergesenia forbesii (1994)
    Springer
    Protoplasma 180 (1994), S. 82-91 
    Details
    ISSN: 1615-6102
    Schlagwort(e): Boergesenia forbesii ; Cellulose synthesizing complex ; Cytoskeleton ; Helicoidal wall ; Membrane fluidity ; Microfibril orientation ; Plasma membrane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Microfibrillar textures and orientation of cellulose microfibrils (MFs) in the coenocytic green alga,Boergesenia forbesii, were investigated by fluorescence and electron microscopy. Newly formed aplanosporic spherical cells inBoergesenia start to form cellulose MFs on their surfaces after 2 h of culture at 25°C. Microfibrillar orientation becomes random, fountain-shaped, and helicoidal after 2, 4, and 5 h, respectively. The fountain orientation of MFs is usually apparent prior to helicoidal MF orientation and thus may be considered to initiate helicoid formation. Microfibrils continue to take on the helicoidal arrangement during the growth ofBoergesenia thallus. The helicoidal orientation of MFs occurs through gradual counterclockwise change in MF deposition by terminal complexes (TCs) viewed from inside the cell. On the dorsal side of curving TC impressions in helicoidal texture formation on a freeze-fractured plasma membrane, the aggregation of intramembranous particles (IMPs) occurs. Membrane flow may thus possibly affect the regulation of helicoidal orientation inBoergesenia. Following treatment with 3 μM amiprophos-methyl (APM) or 1 mM colchicine, cortical microtubules (MTs) completely disappear within 24 h but helicoidal textures formation is not affected. With 15 μM cytochalasin B or 30 μM phalloidin, however, the helicoidal orientation of MFs becomes random. Treatment with CaCl2 (10 mM) causes the helicoidal MF orientation of cells to become random, but co-treatment with N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide (W-7) (100 mM) prevents this effect, though W-7 has no effect on the helicoidal MF formation. It thus follows that MF orientation inBoergesenia possibly involves actin whose action may be regulated by calmodulin.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01379226
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  • 5
    Digitale Medien
    Digitale Medien
    Disk-cathode flash X-ray tube driven by a repetitive two-stage Marx pulser (1993)
    Springer
    Medical & biological engineering & computing 31 (1993), S. S37 
    Details
    ISSN: 1741-0444
    Schlagwort(e): Cold-cathode diode ; Disk cathode ; Flash X-rays ; Photon energy control ; Pulsed X-rays ; Tube current control
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Fundamental studies of a repetitive flash X-ray generator using a diskcathode radiation tube are described. The high-voltage pulser employed a modified two-stage surge-Marx circuit. The two condensers in the pulser were charged from 40 to 60 kV, and the electric charges were discharged to the X-ray tube repetitively to generate flash X-rays. The total capacity during the main discharge was 425 pF, and the maximum output voltage from the pulser was about 1·9 times the charged voltage. The flash X-ray tube of the demountable-diode type and was composed of a rodshaped anode tip made of tungsten, a disk cathode made of graphite and a tube body made of polymethylmethacrylate. The peak tube voltage was primarily determined by the anode-cathode (A-C) space, and the peak tube current was less than 0·5 kA. Thus the maximum photon energy could be easily controlled by varying the A-C space, and the tube current roughly increased according to increases in the charged voltage. The pulse width ranged from 40 to 100 ns, and the X-ray intensity was less than 1·1 μC kg−1 at 0·5 m per pulse. The repetition rate was less than 50 Hz, and the effective focal spot size was equivalent to the anode diameter.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02446648
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