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  • 1995-1999  (2)
  • 1990-1994  (4)
  • 65D07  (4)
  • Colloid  (2)
Materialart
Erscheinungszeitraum
Jahr
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Computing 44 (1990), S. 365-368 
    ISSN: 1436-5057
    Schlagwort(e): 65D07 ; 41A15 ; Positive spline interpolation ; sufficient and necessary existence condition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: 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.
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Computing 44 (1990), S. 245-258 
    ISSN: 1436-5057
    Schlagwort(e): 65D07 ; 41A15 ; Convex or monotone area true splines ; sufficient and necessary existence conditions ; construction of splines with minimal mean curvature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: 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.
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Computing 53 (1994), S. 137-154 
    ISSN: 1436-5057
    Schlagwort(e): 65D05 ; 65D07 ; 41A15 ; Shape preserving interpolation of scattered data ; range restrictions ; Powell-Sabin splines ; minimum norm modification ; thin plate functional
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: 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.
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Computing 47 (1991), S. 87-96 
    ISSN: 1436-5057
    Schlagwort(e): 65D07 ; 41A15 ; 41A63 ; S-convex spline interpolation ; existence conditions ; search procedure for constructingS-convex splines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: 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.
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    ISSN: 1432-1238
    Schlagwort(e): Key words Acute pancreatitis ; Therapy ; Dextran ; Hypertonic ; Colloid ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Objective: Ultrahigh-molecular dextran (500000 Da) has been shown to prevent pancreatic necrosis when given 30 min after induction of pancreatitis. This study should clarify the following: (a) are dextrans still effective after prolongation of the therapy-free interval? (b) what is the impact of the molecular weight of the dextrans? and (c) is their effect influenced by the dextran concentration or by the addition of hypertonic saline? Animals and interventions: Acute pancreatitis was induced in 70 male dextran-tolerant Wistar rats using intraductal bile-salt infusion and intravenous hyperstimulation. After 3 h, animals were assigned to one of seven groups (n=10 per group) receiving either Ringer solution or different dextrans (10%) including 70000 Da (DEX-70), 160000 Da (DEX-160), 300000 Da (DEX-300) or 500000 Da (DEX-500). Additional groups included DEX-70 (6%) and DEX-70 (10%) in combination with hypertonic NaCl (7.5%) (HHS-70). Ringer solution was given at 24 ml/kg and all dextrans at 8 ml/kg. Measurements and results: Trypsinogen activation peptides (TAP) were quantified in ascites and acinar necrosis after death or sacrifice at 9 h. As an index of less pathological trypsinogen activation, the mean TAP levels in ascites were significantly lower in DEX-70 and DEX-160 compared to Ringer controls (p〈0.05, t-test). Furthermore, the amount of acinar necrosis was significantly lower in all dextran groups except the HHS-70 in comparison with Ringer controls (p〈0.01, t-test). Finally, mortality was significantly reduced from 60% in Ringer controls to 10 and 0%, respectively, in the groups treated with DEX-70 and DEX-160 (p〈0.03, Fisher‘s Exact test). There was a similar trend in all other groups except the HHS-70. Conclusions: Despite a therapy-free interval of 3 h, dextrans reduce trypsinogen activation, prevent acinar necrosis, and improve survival in necrotizing rodent pancreatitis. The molecular weight and concentration of dextran are of secondary importance for these beneficial effects.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    ISSN: 1432-1238
    Schlagwort(e): Acute pancreatitis ; Therapy ; Dextran ; Hypertonic ; Colloid ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Objective Ultrahigh-molecular dextran (500 000 DA) has been shown to prevent pancreatic necrosis when given 30 min after induction of pancreatitis. This study should clarify the following: (a) are dextrans still effective after prolongation of the therapy-free interval? (b) what is the impact of the molecular weight of the dextrans? and (c) is their effect influenced by the dextran concentration or by the addition of hypertonic saline? Animals and interventions Acute pancreatitis was induced in 70 male dextran-tolerant Wistar rats using intraductal bile-salt infusion and intravenous hyperstimulation. After 3 h, animals were assigned to one of seven groups (n=10 per group) receiving either Ringer solution or different dextrans (10%) including 70 000 Da (DEX-70), 160 000 Da (DEX-160), 300 000 Da (DEX-300) or 500 000 Da (DEX-500). Additional groups included DEX-70 (6%) and DEX-70 (10%) in combination with hypertonic NaCl (7.5%) (HHS-70). Ringer solution was given at 24 ml/kg and all dextrans at 8 ml/kg. Measurements and results Trypsinogen activation peptides (TAP) were quantified in ascites and acinar necrosis after death or sacrifice at 9 h. As an index of less pathological trypsinogen activation, the mean TAP levels in ascites were significatly lower in DEX-70 and DEX-160 compared to Ringer controls (p〈0.05,t-test). Furthermore, the amount of acinar necrosis was significantly lower in all dextran groups except the HHS-70 in comparison with Ringer controls (p〈0.01,t-test). Finally, mortality was significantly reduced from 60% in Ringer controls to 10 and 0%, respectively, in the groups treated with DEX-70 and DEX-160 (p〈0.03, Fisher's Exact test). There was a similar trend in all other groups except the HHS-70. Conclusions Despite a therapy-free interval of 3 h, dextrans reduce trypsinogen activation, prevent acinar necrosis, and improve survival in necrotizing rodent pancreatitis. The molecular weight and concentration of dextran are of secondary importance for these beneficial effects.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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