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  • Doppler sonography  (3)
  • Chemistry  (2)
  • 1
    ISSN: 1433-8491
    Keywords: Doppler sonography ; Basilar artery thrombosis ; Doppler-Sonographie ; Basilaristhrombose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei 6380 Doppler-Untersuchungen in den letzten $$3{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$2$}}$$ Jahren wurde in sieben Fällen eine hochgradige Zirkulationsstörung der A. basilaris bzw. beider distaler Vertebralarterien angenommen. Kriterium dafür war, daß die Vertebralarterien entweder beidseits nicht darstellbar waren oder keine diastolische Flußkomponente aufwiesen („externa-a-typische” Pulskurven). Die in sechs Fällen anschließend erfolgte Angiographie bestätigte die Diagnose: Viermal fand sich ein Basilarisverschluß, einmal eine langstreckige Basilarisstenose und einmal ein beidseitiger distaler Vertebralisverschluß. Drei weitere im gleichen Zeitraum angiographisch diagnostizierte Basilarisverschlüsse erfüllten bei der Doppler-sonographischen Erstuntersuchung nicht die oben genannten Kriterien, zwei davon auch nicht bei wiederholter Untersuchung. Die Doppler-Sonographie der Vertebralarterien kann somit als ein wesentliches diagnostisches Hilfsmittel beim Nachweis signifikanter Läsionen auch der distalen A. vertebralis und der A. basilaris gelten.
    Notes: Summary We have investigated 6,380 patients with directional c-w Doppler sonography within the last $$3{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$2$}}$$ years, and have suspected obstruction of the basilar artery or of both distal vertebral arteries in 7 cases. Either bilateral sonographic silence or an absent diastolic flow component of the vertebral arteries were employed as criteria in the sonographic evaluation. Angiography of the vertebro-basilar system, performed in 6 cases, confirmed the diagnoses: basilar artery occlusion was found in 4 patients, 1 patient revealed tight stenosis of the basilar artery in its entire length, and 1 patient exhibited occlusion of both distal vertebral arteries. Three further basilar artery occlusions were detected by means of angiography despite initially negative Doppler sonography within the same period of time; l of those patients, however, met the above criteria for basilar artery occlusion upon sonographic reevaluation on the following day. Thus, we believe that directional c-w Doppler sonography is very useful in the diagnosis of basilar artery obstruction.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 61 (1996), S. 1649-1654 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The kinetics of polycondensation of hydroxyfunctional polydimethylsiloxane has been studied with a simple new inexpensive piece of equipment, i.e., the vibrating needle curemeter. The order of reaction with respect to crosslinker and catalyst concentration has been determined to be unity and 0.24, respectively. The activation energy of the reaction has been found to be zero. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0044-2313
    Keywords: Mono-, di-, and trinuclear tantalum and tantalum | niobium complexes with P4 and P2 ligands ; m̈-η2:1:1-P2 coordination mode ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Niobium and Tantalum Complexes with P2 and P4 LigandsThe photolysis of [Cp″Ta(CO)4] 1 (Cp″ = C5H3tBu2-1,3) and P4 affords Cp″(CO)2Ta(η4-P4) 2, [{Cp″(CO)Ta}2(m̈-η2:2-P2)2] 3 and [Cp3″(CO)3Ta3(P2)2] 4. In a photochemical reaction 2 and [Cp*Nb(CO)4] 5 form [{Cp*(CO)Nb}{Cp″(CO)Ta}(m̈-η2:2-P2)2] 6 and [{Cp*(CO)2Nb} {Cp*Nb}{Cp″(CO)Ta}(m̈3-η2:1:1-P2)2] 7, a compound with the novel m̈3-η2:2:1-P2-coordination mode. The reaction of 2 and [Cp*Co(C2H4)2] 8 leads to [{Cp*Co} {Cp″(CO)Ta}(m̈-η2:2-P2)2] 9, a heteronuclear complex with an „early“ and a „late“ transition metal. Complexes 2, 3, 7 and 9 have been further characterized by X-ray structure analyses.
    Notes: Die Photolyse von [Cp″Ta(CO)4] 1 (Cp″ = C5H3tBu2-1,3) und P4 ergibt [Cp″(CO)2Ta(η4-P4)] 2, [{Cp″(CO)Ta}2(μ-η2:2-P2)2] 3 und [Cp3″(CO)3Ta3(P2)2] 4. 2 reagiert photochemisch mit [Cp*Nb(CO)4] 5 zu [{Cp*(CO)Nb}{Cp″(CO)Ta}(m̈-η2:2-P2)2] 6 und [{Cp*(CO)2Nb}{Cp*Nb} {Cp″(CO)Ta}(m̈3-η2:1:1-P2)2] 7, einer Verbindung mit der neuen m̈3-η2:2:1-P2-Koordinationsvariante. Die Reaktion von 2 und [Cp*Co(C2H4)2] 8 führt zum heteronuklearen Komplex [{Cp*Co} {Cp″(CO)Ta}(m̈-η2:2-P2)2] 9 mit einem „frühen“ und „späten“ Übergangsmetall. Die Komplexe 2, 3, 7 und 9 wurden zusätzlich durch eine Röntgenstrukturanalyse charakterisiert.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1920
    Keywords: Doppler sonography ; Intracranial carotid artery disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have investigated 6,587 patients with directional continuous-wave (c-w) Doppler sonography of the carotid arteries during the last 33 months, and have developed criteria for the diagnosis of a significant increase in peripheral resistance of the internal carotid artery in conjunction with 1,671 retrograde brachial and direct carotid angiograms. We distinguished stenoses proximal (15 cases) and distal (4) to the origin of the ophthalmic artery, supraclinoid internal carotid artery occlusions (8), stenoses (2) and acute occlusions (10) of the middle cerebral artery. Stenoses in the carotid siphon (proximal or distal to the origin of the ophthalmic artery) of at least 60% reduction in lumen diameter showed a reduction of the relative end-diastolic flow velocity (modified Pourcelot's index) of more than 40%; additionally, stenoses proximal to the origin of the ophthalmic artery exhibited a variable alternating flow, or flow reversal, in the supratrochlear artery. Stenoses distal to the origin of the ophthalmic artery rarely revealed the theoretically expected increase in orthograde flow velocity in the supratrochlear artery. Stenoses of the middle cerebral artery consisting of more than atherosclerotic irregularities proved to be an exception. Supraclinoid occlusions of the internal carotid artery were reliably demonstrated by Doppler sonography. However, the majority of acute occlusions of the middle cerebral artery could not be detected by this means, probably due to anastomoses between the anterior and the middle cerebral arteries, which were detected by angiography. Thus, we believe that c-w Doppler sonography is a reliable tool to detect stenoses of the carotid siphon of more than 60% reduction in lumen diameter and supraclinoid carotid artery occlusions. Barriers to the cerebral blood flow located more peripherally cannot be diagnosed reliably with this technique.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1920
    Keywords: Doppler sonography ; basilar artery occlusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have investigated 6,972 patients with directional continuous-wave Doppler sonography within the last three and a half years, and have derived criteria for the sonographic diagnosis of basilar artery occlusion or tight stenosis in conjunction with 1,071 retrograde brachial angiograms. By sonographic patterns, we have suspected obstruction of the basilar artery or of both distal vertebral arteries in nine cases. Either bilateral sonographic silence or the absence of a diastolic flow component of the vertebral arteries served as criteria in the sonographic evaluation. Angiography of the vertebro-basilar system, performed in eight cases, showed near or complete occlusion in the distal vertebrals or in the proximal basilar artery. Degrees of stenosis less than an 80 percent reduction in lumen diameter could not be detected sonographically. Two further basilar artery occlusions were detected by means of angiography despite negative Doppler sonography: one of these patients showed an extensive collateral circulation between the posterior inferior and the superior cerebellar arteries, and one patient had an occlusion only of the middle and rostral thirds of the basilar artery, the proximal third and the anterior inferior cerebellar arteries being widely patent. Thus, we believe that directional CW Doppler sonography is very useful in the diagnosis of near or complete occlusion of both distal vertebral arteries or of the proximal basilar artery.
    Type of Medium: Electronic Resource
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