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  • Chemistry  (10)
  • Arterial blood pressure  (1)
  • Chemical Engineering  (1)
  • General Chemistry  (1)
  • Haemodynamic monitoring  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 15 (1971), S. 3117-3125 
    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: Early transition, early turbulence, and drag reduction were detected in flowing solutions of high molecular weight poly(ethylene oxide) condensates. Progressive addition of salt (magnesium sulfate) increased the onset point characterizing deviations from Newtonian flow for 1 ppm Polyox Coagulant solutions and eliminated early transition in the 10 ppm WSR-35 solutions. No further drag reduction was observed when the salt molarity reached the 0.65 level. In the Coagulant solutions the onset wall shear stress characterizing the flow deviation was an inverse function of the intrinsic viscosity of the polymer in the salt solution.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    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 frictional drag reduction of high molecular weight poly(ethylene oxide) and polystyrene solutions under turbulent flow conditions has been studied as a function of temperature, solvent power, and solvent viscosity. A rotating-disc apparatus was used to make the drag reduction measurements. For aqueous poly(ethylene oxide) solutions, at concentrations well above that needed to produce maximum drag reduction, all drag reduction data reduced to a common curve when per cent drag reduction was plotted against the Reynolds number for the flow. However, for poly(ethylene oxide) solutions below this optimum concentration, the drag reduction-versus-Reynolds number curves showed decreasing drag reduction with increasing temperature. The data are explained primarily in terms of the inverse temperature solubility characteristics of poly(ethylene oxide) in water. The per cent drag reduction of polystyrene in nonaqueous liquids was found to be greater in good solvents than in poor ones. It was also found that increases in solvent viscosity and decreases in temperature increased the per cent drag reduction. The results are discussed in relation to the current drag reduction theories and are shown to be in opposition to Virk's theory. It is concluded from the data that drag reduction is very likely a function of a relaxation time phenomenon involving the polymer molecules and the flow system. The results also emphasize the importance of considering solvent power, viscosity, and temperature in the design of an efficient drag reduction system.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 15 (1971), S. 1515-1519 
    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 flow of dilute drag reducing polymer solutions through capillary tubes into a region of slightly greater tube diameter is characterized by almost complete recovery of the fluid. It is conjectured that the polymer molecules react to prevent the loss of kinetic energy by minimizing the formation of eddies resulting from the expansion.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    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: Turbulent drag reduction data were obtained at Re = 9000 in a 0.62-cm-I.D. pipe for five Polyox compounds covering a wide range of molecular weights. The concentration dependence of drag reduction was shown to obey an improved form of Virk's drag reduction equation, which was previously applied only to flows in capillary tubes. The efficiency of the drag-reducing polymer additives on a unit concentration basis at infinite dilution was determined by using a characteristic parameter, DRm/[c], for each compound. A linear relationship was found to exist between this parameter and polymer molecular weight. The polymer degradation data were analyzed through use of a variable related to the dissipated energy in the wall region. The polymer molecular weight was found to decrease as a hyperbolic function of the dissipated energy function. By examining the change of molecular weight with respect to this function, a degradation index characteristic of the entire Polyox polymer family was established. This index may be of general application and provide a method by which the shear stability of various species of drag-reducing polymers may be meaningfully compared.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 22 (1978), S. 419-427 
    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 mechanical behavior of urea-formaldehyde foam was studied to evaluate its potential for energy absorption applications. The apparent elastic modulus (Ef) as a function of foam density was obtained from force-deformation tests. The values of energy absorption capacity were derived from a numerical integration technique. Poisson's ratio (v) was determined by a method of uniaxial compression of cylindrical samples. An increase in foam density results in an increase in the apparent elastic modulus of the material and therefore in its energy absorption capacity. Poisson's ratio is independent of the foam density. The mechanical properties' values obtained can be incorporated in various analyses for predicting desired characteristics for energy absorption applications.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1238
    Keywords: Key words Fluid resuscitation ; Haemodynamic monitoring ; Stroke distance ; Doppler ultrasound ; Hypovolaemic shock ; Severe sepsis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objectives: To assess the feasibility of constructing left ventricular response curves non-invasively during the fluid resuscitation of critically ill patients in the emergency department (ED) using a portable suprasternal Doppler ultrasound (PSSDU) device.¶Design: Prospective case series.¶Setting: Emergency department, Catholic University of Leuven, Belgium. Patients: Shocked patients in the ED were diagnosed by predefined criteria. Only those thought to require standardised intravenous colloid challenges were observed i. e., sequential boluses of 3.5 ml/kg/10 min titrated against changes in stroke distance (Doppler surrogate for left ventricular stroke volume).¶Results: A total of 50 shocked patients were studied. Stroke distance was measurable in 45 patients. 35 patients were fluid responders in terms of stroke distance. Group mean stroke distance increased during resuscitation (8.6 ± 4.1 cm to 19.5 ± 4.6 cm, P 〈 0.001) and then reached a plateau value (19.6 ± 4.6 cm, P = 0.488). No response to fluid was seen in nine patients of which eight had severe sepsis. Alternative therapeutic approaches increased stroke distance for all of these patients. Evidence for right ventricular dysfunction was found as a cause for fluid non-response in the majority of patients with sepsis.¶Conclusions: Previous experimental work has shown that changes in central blood flow can be derived using the PSSDU device. This clinical feasibility study suggests that the PSSDU can help tailor haemodynamic therapy for an individual patient and give an early indication of treatment failure in the ED.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-2013
    Keywords: Arterial blood pressure ; Baroreceptors ; Haemorrhage ; Shivering ; Thermoregulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 1. Shivering in the barbitone-anaesthetised cat exposed to a lowered ambient temperature was reduced by transient haemorrhagic or drug induced hypotension such that there was a positive correlation between mean arterial blood pressure and the intensity of shivering. 2. Shivering which had been reduced by haemorrhage could be restored by the reinfusion of blood, centripetal stimulation of a buffer nerve or by the intravenous administration of methoxamine. 3. The intensity of shivering was increased by the intravenous injection of methoxamine and by stimulation of a buffer nerve, although the latter response was attenuated by intact buffer nerves. 4. There was a marked variation in the importance of the different buffer nerves in maintaining shivering. 5. Shivering was abolished by deafferentation of the baroreceptors and although it could be restored by electrical stimulation of a buffer nerve methoxamine was then without effect. 6. A prolonged period (90–120 min) of hypotension (50–60 mm Hg) impaired the ability to shiver even after the hypovolaemia and hypotension had been corrected.
    Type of Medium: Electronic Resource
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  • 8
    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: Turbulent friction reduction by high molecular weight poly(ethylene oxide) polymers has been examined in a series of salt solutions ranging from pure water to nearly theta solvent conditions. The effects of polymer homology and solvent character have been successfully analyzed under these conditions and relationships are proposed for the observed effects. The reduction in turbulent friction (drag reduction) has been catalogued through evaluation of the polymer intrinsic concentration - an index of drag reduction effectiveness. Plots of the reciprocal of the polymer intrinsic concentration versus salt molarity are approximately linear and are similar to the plots of intrinsic viscosity versus molarity reported by other workers. An attempt is made to graphically and numerically combine these results. The suggestion is advanced that those solvent properties which bring about decided conformational changes in these polymer molecules (as indexed by intrinsic viscosity effects) also affect, in an apparently analogous fashion, the turbulent friction reduction efficiencies of these molecules. The decreases in turbulent friction reduction resulting from the increasingly collapsed state of the polymer coil suggest the possibility of correlating friction reduction with changes in the polymer expansion factor α. On the basis of the limited data available, the suggestion is also made that drag reduction studies might best be made under theta solvent conditions where different polymer families might be more meaningfully compared in the absence of solvent effects.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 18 (1974), S. 1261-1264 
    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
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1434-193X
    Keywords: TMM ; Diyl trapping reaction ; DNA cleavage ; Atom transfer ; Diradical-induced vinylcyclopropane fragmentation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The diyl trapping reaction has been applied as the key step in the assembly of a variety of ring systems. An overview of the various modes of reactivity of the trimethylenemethane (TMM) diyl is presented, detailing both the mechanistic features affecting selectivity as well as several applications directed towards the synthesis of a variety of natural products. Also highlighted are two new areas of focus, atom transfer and diyl-induced vinylcyclopropane ring opening.
    Type of Medium: Electronic Resource
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