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  • 11
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 29-30 (Nov. 2007), p. 359-362 
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Changes in crystal phase and electrical properties of oxides composed of Mn, Co, and Niwith the molar ratios of 5:2:1 and 3:3:1 were investigated. Starting oxides were fired from 250°C to800°C, then maintained at prescribed temperatures for 3 h in air. In the 5:2:1 specimen, a monophaseconsisting of a cubic spinel oxide that is important to electrical conductivity was obtained at firingtemperature of 800°C. In the 3:3:1 specimen, the monophase was obtained at temperatures rangingfrom 600°C to 800°C. Electrical resistance decreased exponentially with increasing temperature forall specimens fired at temperatures ranging from 250°C to 800°C, indicating that the oxides haveintrinsic thermistor characteristics with negative temperature coefficient (NTC). The temperaturedependence of the thermistor constant (B value) necessary for practical application was considered tobe related to the existence ratio of cubic spinel-type and ilmenite-type structures and the latticeconstant of the cubic spinel-type structure. The electrical conduction was stabilized by annealing atprescribed temperatures for more than 720 minutes
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Applied mechanics and materials Vol. 1-2 (Sept. 2004), p. 11-16 
    ISSN: 1662-7482
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Compressive stress-strain characteristics of carbon/epoxy laminated composites in the through-thickness direction at strain rates of over 1000/s were evaluated using the standard split Hopkinson pressure bar. Three carbon/epoxy laminated composites (i.e., unidirectional, cross-ply and woven) with almost the same thickness were tested at room temperature. Small solid cylindrical specimens were machined such that the direction of the compression loading was perpendicular to the fiber direction of the laminates. The effects of strain rate and reinforcement geometry on the secant modulus at 1% strain, ultimate compressive strength and strain, and total strain energy to failure were examined in detail
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Applied mechanics and materials Vol. 13-14 (July 2008), p. 195-201 
    ISSN: 1662-7482
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The impact compressive failure behaviour of a unidirectional T700/2521 carbon/epoxycomposite in three principal material directions is investigated in the conventional split Hopkinsonpressure bar. Two different types of specimens with square cross sections are machined from thecomposite in the plane of the laminate. The uniaxial compressive stress-strain curves up to failure atquasi-static and intermediate strain rates are measured on an Instron testing machine. It isdemonstrated that the ultimate compressive strength (or maximum stress) increases slightly, whilethe ultimate compressive strain (or failure strain) decreases marginally with strain rate in the rangeof 10-3 to 103/s in all three directions. Dominant failure mechanisms are found to significantly varywith strain rate and loading directions along three principal material axes
    Type of Medium: Electronic Resource
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  • 14
    ISSN: 0942-0940
    Keywords: Vertebro-basilar junction ; cerebral aneurysm ; 3-D CT angiography ; hypothermia ; cardiopulmonary bypass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This paper highlights two interesting cases of radial clipping of large aneurysms at the vertebro-basilar junction accompanied by a vascular anomaly, consisting of fenestration of the split basilar artery at its origin. Description of the inner and outer surface of the aneurysm were obtained pre-operatively, from analysis by 3D CT and 3D CT endoscopy of the form of the neck, parent vessels of the vertebral arteries on both sides, basilar artery and split basilar artery, as well as other details of branching. The neck exhibited a broad base in both cases. The height of the neck extended to the internal acoustic meatus, and it was possible to expose the circumference of the aneurysmal neck, peripheral basilar artery and both vertebral arteries proximally with an anterior transpetrosal approach. Based on the size of the aneurysm and the site being the anterior surface of the brain stem, clipping (consisting of interruption of the occluded portion and reconstruction of the parent vessels) was performed. In the first case it was achieved protecting the brain by hypothermia and barbiturates under deep hypothermia with extracorporal circulation, and in the second case, a state of circulatory arrest was used. This paper documents the report of two cases along with other cases treated so far.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Acta neurochirurgica 141 (1999), S. 119-126 
    ISSN: 0942-0940
    Keywords: Keywords: Aged patients; craniovertebral junction; disc hernia; surgical approach.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary  The incidence of high cervical disc lesions is extremely rare, and the mechanism of their development is unclear. We report these three cases, and discuss the possible mechanisms. We also describe surgical strategies for these lesions.  The first and second cases were an 82-year-old male and an 84-year-old male with retro-odontoid disc hernia. The third was an 83-year-old female with a herniated disc at C2/C3. To investigate Aetiological mechanisms of these lesions, we examined the findings on cervical images in extension and flexion, and compared the results in a younger than 80-year-old group and an older than 80-year-old group.  The patients underwent surgery via a posterolateral intradural approach. Wide laminectomy and incision of the dentate ligaments enabled access to the ventral space of the upper cervical spinal canal and sufficient decompression. All patients became ambulatory postoperatively without special fixation of the cervical spine. In the younger group, the level mostly loaded during cervical movement was C5/6, however, the levels in the older group were C2/3 and C3/4.  In elderly patients, less mobilization of the middle and/or lower cervical spine due to spondylotic change causes overloading at higher levels resulting in high cervical disc lesions. Retro-odontoid disc lesions can be caused by a herniated disc at C2/C3, which migrates upward. Regarding surgical strategy, the posterolateral intradural approach is less invasive and more advantageous for these lesions.
    Type of Medium: Electronic Resource
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  • 16
    ISSN: 0942-0940
    Keywords: Keywords: Down regulation; nitric oxide; protein kinase C; subarachnoid haemorrhage; vasospasm.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary  We previously showed that a canine basilar artery manifested tonic and potent, protein kinase C (PKC)-dependent contractions when nitric oxide (NO) was inhibited. We also reported a linear correlation between chronological changes in the angiographic severity of vasospasm, enhanced PKC, and attenuated guanosine, 13′,15′-cyclic monophosphate (cGMP) activity in a canine subarachnoid haemorrhage model. The activity of cGMP is an indicator of NO-function. Based on this evidence, we have hypothesized that PKC and NO regulate cerebral vascular tone. We particularly focused on the role of NO in a negative feedback mechanism on PKC activity in the maintenance of vascular tone. To further confirm our hypothesis, we investigated the effect of PKC down-regulation on the tonic vascular contraction induced by NO-inhibition.  Canine basilar artery was used in the experiment. Significant down-regulation of PKC activity in vascular smooth muscle cells was obtained by incubation with 10−5 mole/L of phorbol 12-myristate 13-acetate (PMA) for 24 hours. The tonic and potent contraction induced by NO-inhibition was completely suppressed in the PKC down-regulated artery, even though the artery manifested a significant contraction in high-K+ solutions. These results indicate an obligatory role of PKC activity in tonic contraction when NO is inhibited, and support our previous data. Nitric oxide induces vascular relaxation by inhibiting PKC activity. Subarachnoid haemorrhage impairs this inhibition, resulting in PKC-dependent vascular contraction, such as vasospasm.
    Type of Medium: Electronic Resource
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  • 17
    ISSN: 0942-0940
    Keywords: Keywords: Parkinson's disease; subthalamic nucleus; stereotactic surgery.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary  The neural activity pattern of the subthalmic nucleus (STN) was investigated in five patients with Parkinson's disease who were scheduled for electrode implantation for chronic stimulation of the STN.  The initial target was placed 8 mm or 10 mm lateral to the midline, 3 mm to 4 mm posterior to the midcommissural point, and 5 mm to 6 mm below the intercommissural (AC-PC) line. The STN was identified by semi-microelectrode recordings with a trajectory moving laterally in 2-mm steps. The amplitudes of multi-unit activities were relatively low at depths from 8 mm to 5 mm above and from 1 mm to 4 mm below the target, while those 4 mm to 0 mm above the target were significantly higher than at the other sites (ANOVA, Fisher's test, p〈0.05), with the highest amplitude at 2 mm above the target (91.0±23.3μv, n=15). In the mediolateral direction, amplitudes were relatively higher in the lateral portion, and amplitudes at 14 mm lateral to the midline were significantly higher than at the other sites (ANOVA, Fisher's test, p〈0.05). The target for chronic electrical stimulation was determined to be at the midpoint of the hyperactive STN, i.e., 12 mm lateral to the midline in three patients and 13 mm lateral in two patients. Movement-related neural activity was observed at 5 sites, i.e., 3 sites responded to passive movement of the contralateral wrist and 2 sites to passive knee and/or ankle movement.  In conclusion, our data show that the lateral part of the STN is hyperactive in PD, and recordings of neural activities contributed greatly to identifying the STN and determining the target for chronic stimulation within it.
    Type of Medium: Electronic Resource
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  • 18
    ISSN: 0942-0940
    Keywords: Keywords: Endothelin-1; protein kinase C; subarachnoid haemorrhage; vasospasm.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary  Endothelium plays a role in the regulation of vascular tone. Endothelin is a family of potent vasoconstrictive peptides, and endothelin-1 (ET-1) produced in the endothelium induces a tonic contraction via specific receptor ETa. ET-1 has been postulated as an important factor in the development of vasospasm after subarachnoid haemorrhage (SAH). We have previously shown that protein kinase C (PKC) of the cerebral artery plays a pivotal role in the pathogenesis of vasospasm. The purpose of this study is to clarify the relationship between ET-1 and PKC in the development and maintenance of vasospasm.  Using a “two-haemorrhage” canine model, chronological changes of angiographic progression of vasospasm, PKC activation, and ET-1 level of the basilar artery were assessed. In an isometric tension study with a control artery, the effects of ETa- and ETa/ETb-antagonists on the tonic contraction induced by ET-1 were examined. The effects of ET-1, ET-1 and an ETa-antagonist, and ET-1 and an ETa/ETb-antagonist on PKC activation were also evaluated.  ET-1 level temporarily increased, then decreased to the control level in a later stage of vasospasm. ET-1 induced a tonic contraction and enhancement of PKC activation, but both were inhibited either by an ETa- or an ETa/ETb-antagonist.  These results indicate that ET-1 initiates the development of vasospasm through PKC activation, but does not contribute to prolonged vasospasm.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 91-93 (Jan. 1992), p. 603-608 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 20
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The charge generated in 6H-SiC n+p diodes by gold (Au) ion irradiation at an energy of 12MeV was evaluated using the Transient Ion Beam Induced Current (TIBIC). The signal peak of thetransient current increases, and the fall-time decreases with increasing applied reverse bias. The valueof collected charge experimentally obtained is smaller than the ideal value. The Charge CollectionEfficiency (CCE) of 6H-SiC n+p diodes irradiated with Au ions is approximately 50 % in spite that theCCE of 100 % is obtained in the case of oxygen (O) ion irradiation
    Type of Medium: Electronic Resource
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