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  • 1
    Electronic Resource
    Electronic Resource
    Effect of acute and prolonged treatment with propranolol on cerebral blood flow and cerebral oxygen metabolism in healthy volunteers (1990)
    Springer
    European journal of clinical pharmacology 39 (1990), S. 295-297 
    Details
    ISSN: 1432-1041
    Keywords: propranolol ; cerebral blood flow ; cerebral oxygen metabolism ; CO2 reactivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of acute and long-term treatment with propranolol on cerebral blood flow (CBF) and the cerebral metabolic rate of oxygen (CMRO2) has been studied in 8 young healthy volunteers. CBF was measured by 133Xe-inhalation and single photon emission computer tomography, and CMRO2 was calculated from the arterio-venous oxygen difference and CBF. Studies were done before and 1 h after i. v. injection of 5 mg propranolol and after three weeks on oral propranolol 80 mg/d for 1 week and 160 mg/d for 2 weeks. Cerebrovascular CO2 reactivity in terms of the A – V oxygen difference was tested on all three occasions during hypercapnia and hyperventilation. CBF, CMRO2 and cerebrovascular CO2 reactivity remained stable both after acute and after 3 weeks of treatment with propranolol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315115
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of ketanserin on cerebral blood flow and cerebrovascular CO2 reactivity in healthy volunteers (1992)
    Springer
    Acta neurochirurgica 119 (1992), S. 7-11 
    Details
    ISSN: 0942-0940
    Keywords: Carbon dioxide ; cerebral blood flow ; cerebral oxygen metabolism ; cerebral vascular reactivity ; ketanserin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of the anti-hypertensive agent ketanserin on the cerebral blood flow (CBF) and the cerebrovascular CO2 reactivity was examined in 10 healthy volunteers. Ketanserin was administered as an intravenous bolus of 10 mg followed by an infusion of 6mg/h. Before administration CBF was measured by single photon emission computerized tomography (SPECT) of inhaled133 Xenon. Then arterial CO2 tension was subsequently decreased by voluntary hyperventilation and increased by breathing an air/CO2 mixture. The relative changes in CBF induced by the changes in arterial CO2 tension were estimated by the cerebral arterio-venous oxygen content difference method. One hour following the start of ketanserin infusion the SPECT measurement and CO2 manipulations were repeated. The CO2 reactivity (expressed as the slope of the regression line of the linear relation between CBF and PaCO2), was unchanged, i.e. 3.2%/0.1 kPa before ketanserin and 4. 1%/0.1 kPa during ketanserin, respectively. Using regression lines from a semi-logarithmic plot the CO2 reactivity was also unchanged 3.4%/0.1 kPa and 3.5%/0.1 kPa, respectively. Ketanserin did not change CBF. The cerebral oxygen metabolism (CMRO2) was decreased 19% one hour after the start of infusion of ketanserin. In conclusion administration of ketanserin in a clinically relevant dose to healthy volunteers does not change the regional CBF not the cerebrovascular CO2 reactivity, but a decrease in CMRO2 was observed. However further studies are needed to clarify whether ketanserin in fact has a depressing effect on CMRO2 or whether the different results are caused by methodological errors or stocastic variation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01541774
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  • 3
    Electronic Resource
    Electronic Resource
    Angiotensin converting enzyme inhibition, CBF autoregulation, and ICP in patients with normal-pressure hydrocephalus (1990)
    Springer
    Acta neurochirurgica 106 (1990), S. 9-12 
    Details
    ISSN: 0942-0940
    Keywords: Intracranial pressure ; cerebral blood flow ; autoregulation ; angiotensin converting enzyme inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Fourteen patients with normal pressure hydrocephalus had the autoregulation of cerebral blood flow (CBF) and intracranial pressure (ICP) investigated. In 8 of the patients the effect of Captopril on ICP and CBF was also investigated. The mean arterial blood pressure (MABP) was 109 mmHg (intra-arterially), and ICP was 11 mmHg (intraventricularly). Changes in global CBF were estimated by the arterio-venous oxygen difference method. The autoregulation of CBF was present in 13 of the patients (p 〈 0.01). The lower limit of CBF autoregulation was 86% of the baseline perfusion pressure. One hour after 50 mg of captopril perorally, MABP was reduced 16 mmHg, and ICP and CBF were unchanged. The autoregulation was maintained and the lower limit was decreased 19 mmHg. Thus patients would be expected to benefit from captopril treatment in hypotensive anaesthesia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01809326
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of nimodipine on ICP and CBF in patients with normal-pressure hydrocephalus (1990)
    Springer
    Acta neurochirurgica 102 (1990), S. 11-13 
    Details
    ISSN: 0942-0940
    Keywords: Intracranial pressure ; cerebral blood flow ; perfusion pressure ; nimodipine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Eight patients with normal-pressure hydrocephalus (NPH) were studied. The resting mean arterial blood pressure (MABP) was 100 (90–125)mmHg and the mean intracranial pressure (ICP) was 11 (5–17)mmHg. ICP and MABP were continuously measured intraventricularly and intra-arterially, respectively. Changes in global cerebral blood flow (CBF) were estimated by the arteriovenous oxygen difference method. Intravenous nimodipine (15 microgram/kg/hour) was given in the first 2 hours and 30 microgram/kg/hour in the next 2 hours. MABP was reduced 23 (4–47)mmHg (p〈0.05). ICP was increased 3 (0–10)mmHg (p 〈 0.05). CBF was unchanged in the group on the whole, but in 4 of patients a major drop in perfusion pressure was seen, and CBF decreased 6, 11, 23 and 34%, respectively. Thus these findings underline the importance of maintaining the perfusion pressure under treatment with nimodipine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01402178
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  • 5
    Electronic Resource
    Electronic Resource
    The acute effect of nimodipine on cerebral blood flow, its CO2 reactivity, and cerebral oxygen metabolism in human volunteers (1991)
    Springer
    Acta neurochirurgica 111 (1991), S. 49-53 
    Details
    ISSN: 0942-0940
    Keywords: Arterial blood pressure ; calcium antagonist ; cerebral blood flow ; cerebral metabolic rate of oxygen ; carbon dioxide reactivity ; nimodipine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study was undertaken in 8 healthy volunteers to examine the effect of a clinically relevant dose of nimodipine (NIM) (15 and 30 microgram/kg/h) on CBF, its CO2 reactivity, and CMRO2. Mean arterial blood pressure (MABP) was measured intra-arterially. Regional CBF was measured by SPECT of inhaled Xenon-133. During the CO2 reactivity tests changes in CBF were estimated by the arterio-venous-oxygen-difference method. Median CBF was 52 ml/ 100 g/min (48–53) with a normal regional distribution, and median baseline MABP was 96 mmHg (92–99). MABP was slightly reduced, by 8 mmHg (7–9), and 9 mmHg (4–11) after infusion of NIM for 2 and 4 hours, respectively. CBF, however, remained constant, although correction for changes in PaCO2, revealed a slight increase after 4 hours (p=0.08). CMRO2 was 3.5 ml/100 g/min (3.2–3.5) and was not changed by the infusion of NIM. At arterial CO2 tensions ranging from 4.0 to 6.5 Kpa the CO2 reactivity was 3.0% CBF/ 0.1 kPa (2.6–3.7) and decreased significantly to 2.6% CBF/0.1 kPa (1.8–3.2) after the infusion of NIM for 3 hours (p=0.02). The median slope of the LnCBFsat/PaCO2 relationship was 1.5 at baseline compared to 1.3 after NIM (p〈0.01). No side effects were observed. The present study shows a decreased CO2 of the cerebral vessels and a maintained coupling of CBF and CMRO2 during the infusion of nimodipine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01402513
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  • 6
    Electronic Resource
    Electronic Resource
    Convexity preserving interpolation with exponential splines (1986)
    Springer
    Computing 36 (1986), S. 335-342 
    Details
    ISSN: 1436-5057
    Keywords: 65D07 ; 41A15 ; 90C20 ; Convexity conditions ; weakly coupled system of inequalities ; numerical algorithms ; quadratic programming ; unconstrained dual program with tridiagonal Hessian
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Während die Aufgabe der konvexen Interpolation im Falle kubischer Splines im allgemeineen nicht lösbar ist, kann jetzt gezeigt werden, daß sie bei Verwendung von Exponentialsplines Lösungen besitzt sofern die vorkommenden Parameter hinreichend roß sind, und es werden konkrete hinreichende und notwendige Lösbarkeitsbedingungen hergeleitet. Da eindeutige Lösbarkeit in der Regel nicht vorliegt, wird eine Auswahlfunktion eingeführt und das entstehende quadratische Optimierungsproblem nach Dualisierung numerisch behandelt.
    Notes: Abstract Sufficient and necessary conditions are derived under which interpolating splines are convex if the data set is in convex position. In order to select one of the interpolants, by means of a well-known objective function a quadratic optimization problem is stated which can be solved effectively by passing to a dual program.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02240208
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  • 7
    Electronic Resource
    Electronic Resource
    Powell-Sabin splines in range restricted interpolation of scattered data (1994)
    Springer
    Computing 53 (1994), S. 137-154 
    Details
    ISSN: 1436-5057
    Keywords: 65D05 ; 65D07 ; 41A15 ; Shape preserving interpolation of scattered data ; range restrictions ; Powell-Sabin splines ; minimum norm modification ; thin plate functional
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Behandelt wird die Interpolation unregelmäßig verteilter Daten durch quadratische Powell-Sabin-Splines, wobei stückweise konstante obere und untere Schranken für die Funktionswerte der Interpolierenden vorgegeben sind. Die hergeleiteten hinreichenden Bedingungen für die Einhaltung der zweiseitigen Schranken ergeben ein lösbares lineares Ungleichungssytem für die Gradienten als Parameter, welches bezüglich der Datenpunkte separiert ist. Die Auswahl von visuell gefälligen Interpolierenden erfolgt durch die Minimierung geeigneter Funktionale.
    Notes: Abstract The construction of range restricted bivariateC 1 interpolants to scattered data is considered. In particular, we deal with quadratic spline interpolation on a Powell-Sabin refinement of a triangulation of the data sites subject to piecewise constant lower and upper bounds on the values of the interpolant. The derived sufficient conditions for the fulfillment of the range restrictions result in a solvable system of linear inequalities for the gradients as parameters, which is separated with respect to the data sites. Since there exists an infinite number of spline interpolants meeting the constraints, the selection of a visually pleasant solution is based on the minimum norm modification of a suitable initial interpolant or on the minimization of the thin plate functional. While the first proposal reduces to the solution of independent local quadratic programs, the second proposal results in a global quadratic optimization problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02252986
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  • 8
    Electronic Resource
    Electronic Resource
    Ratioanl biquadraicC 1-splines inS-convex interpolation (1991)
    Springer
    Computing 47 (1991), S. 87-96 
    Details
    ISSN: 1436-5057
    Keywords: 65D07 ; 41A15 ; 41A63 ; S-convex spline interpolation ; existence conditions ; search procedure for constructingS-convex splines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung In dieser Arbiet wird eine notwendige und hinreichende Bedingung für dieS-Konvexität von rational-biquadratischen Spline interpolierenden auf Rechteckgittern hergeleitet. Da Kriterium kann in Form von linearen Gleichungen und konvexen Ungleichungen formuliert werden, und es wird gezeigt, daß diese im Fall von hinreichend großen Rationalitätsparametern erfüllbar sind, sofer sind die zu interpolierende Datenmenge inS-konvexer Lage befindet.
    Notes: Abstract The purpose of this paper is to give a necessary and sufficient condition for theS-convexity of rational biquadraticC 1-spline interpolants on rectangular grids. The criterion is described in form of linear equalities and convex inequalities, and forS-convex data sets the criterion can be satisfied whenever the rationality parameters are sufficiently large.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02242024
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  • 9
    Electronic Resource
    Electronic Resource
    Shape preserving histopolation using rational quadratic splines (1990)
    Springer
    Computing 44 (1990), S. 245-258 
    Details
    ISSN: 1436-5057
    Keywords: 65D07 ; 41A15 ; Convex or monotone area true splines ; sufficient and necessary existence conditions ; construction of splines with minimal mean curvature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Gegenstand der Arbeit ist die flächentreue Approximation von Histogrammen durch rational-quadratischeC 1-Splines unter Zusatzbedingungen wie Konvexität oder Monotonie. Für derartige Aufgaben werden hinreichende und notwendige Existenzbedingungen in algorithmischer Form angegeben, und es ergibt sich, daß sich diese Bedingungen bei konvexen oder monotonen Histogrammen durch passende Wahl der Rationalitätsparameter stets erfüllen lassen. Da die genannten Aufgaben, sofern überhaupt, im allgemeinen nicht eindeutig lösbar sind, werden Histosplines mit minimaler Gesamtkrümmung ermittelt.
    Notes: Abstract In this paper the area true approximation of histograms by rational quadraticC 1-splines is considered under constraints like convexity or monotonicity. For the existence of convex or monotone histosplines sufficient and necessary conditions are derived, which always can be satisfied by choosing the rationality parameters appropriately. Since the mentioned problems are in general not uniquely solvable histo-splines with minimal mean curvature areconstructed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262220
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  • 10
    Electronic Resource
    Electronic Resource
    A criterion for the positivity of rational cubicC 2-spline interpolants (1990)
    Springer
    Computing 44 (1990), S. 365-368 
    Details
    ISSN: 1436-5057
    Keywords: 65D07 ; 41A15 ; Positive spline interpolation ; sufficient and necessary existence condition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Es wird eine hinreichend und notwendige Bedingung für die Positivität von rational-kubischen Splines angegeben, welche sich leicht überprüfen läßt. Sie ist bei Interpolationsdaten mit positiven Ordinaten durch hinreichend große Rationalitätsparameter stets erfüllbar.
    Notes: Abstract By means of a finite set of inequalities a sufficient and necessary condition for the positivity of rational cubic splines is given which holds true whenever the rationality parameters are sufficiently large.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02241274
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