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The effect of stepwise arterial hypotension on blood flow and oxidative metabolism of the brain (1974)

Hoyer, S. ; Hamer, J. ; Alberti, E. ; [et al.]

Springer

Pflügers Archiv 351 (1974), S. 161-172

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ISSN: 1432-2013

Keywords: Arterial Hypotension ; Cerebral Blood Flow ; Oxidative Metabolism ; Non-hypoxic Lactacidosis

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Summary With the Kety-Schmidt-technique in ten dogs anaesthetized with 0.5% halothane, blood flow and oxidative metabolism of the brain were studied during stepwise lowering of CPP due to arterial hypotension at 71 and 41 torr. CBF remained constant (65.6 and 64.1 ml/100 g min) when CPP dropped from 98 to 71 torr, but at a CPP of 41 torr CBF fell to 32.2 ml/100 g min, i. e. to about 50% of the resting value. The CMR-oxygen did not change (4.20 and 4.38 ml/100 g min) when CPP was reduced from about 100 to about 70 torr, but decreased to 2.90 ml/100 g min, i. e. about 70% of the resting value in deep arterial hypotension. The uptake of glucose changed from 4.62 to 6.19 mg/100 g min as well as the output of CO2 and lactate (from 4.64 to 6.57 ml/100 g min and from 0.33 to 1.62 mg/100 g min) when CPP was decreased to 71 torr. It could be demonstrated that at this CPP range the oxidative metabolism was unchanged. It was assumed that the increased uptake of glucose was only to form lactate, and that this non-hypoxic lactate production was responsible for the elevated CO2 release. At a CPP range of 41 torr the metabolic rates of glucose and CO2 decreased to 3.33 mg/100 g min and to 3.37 ml/100 g min, respectively, while the output of lactate remained relatively high (1.14 mg/100 g min). These findings support the assumption that at a CPP range of 41 torr the oxidative metabolism of the brain becomes insufficient. All findings demonstrate close interactions between cerebral flow blood and oxidative brain metabolism in arterial hypotension. In deep arterial hypotension respiratory acidosis has an effect on CBF. The increase of CBF is accompanied by an improvement of CMR-oxygen but not of CMR-glucose. Although CMR-lactate is reduced, the lactate/glucose index remains high.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00587434

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The fracture toughness of polypropylene containing poly(ethylene terephthalate) fibers (1981)

Hamer, J. W. ; Woodhams, R. T.

Stamford, Conn. [u.a.] : Wiley-Blackwell

Polymer Engineering and Science 21 (1981), S. 603-611

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ISSN: 0032-3888

Keywords: Chemistry ; Chemical Engineering

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 fracture toughness of polypropylene was increased tenfold by the addition of 30 volume percent of chopped poly(ethylene terephthalate) rovings without any appreciable sacrifice in strength or modulus. The resulting fracture toughness was independent of temperature to -40°C. For maximum effectiveness the rovings must be integrated so that the component filaments cannot disperse during the processing and injection molding stages. The three different methods employed to measure fracture toughness showed good correlation with each other and confirmed the general utility of the Izod test (with slight modification) as a measure of fracture energy. The increased toughness was attributed almost entirely to frictional energy losses during fiber pullout. Polyester fibers can be useful additives for increasing the fracture toughness of brittle resins where processing temperatures do not preclude their use.

Additional Material: 13 Ill.