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- Lenfeldt, Niklas, et al.
(författare)
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Cerebrospinal fluid pulse pressure method: a possible substitute for the examination of B waves
- 2004
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Ingår i: Journal of Neurosurgery. - : American Association of Neurological Surgeons. - 0022-3085 .- 1933-0693. ; 101:6, s. 944-950
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Tidskriftsartikel (refereegranskat)abstract
- Object. The appearance of numerous B waves during intracranial pressure (ICP) registration in patients with idiopathic adult hydrocephalus syndrome (IAHS) is considered to predict good outcome after shunt surgery. The aim of this study was to describe which physical parameters of the cerebrospinal fluid (CSF) system B-waves reflect and to find a method that could replace long-term B-wave analysis.Methods. Ten patients with IAHS were subjected to long-term registration of ICP and a lumbar constant-pressure infusion test. The B-wave presence, CSF outflow resistance (Rout), and relative pulse pressure coefficient (RPPC) were assessed using computerized analysis. The RPPC was introduced as a parameter reflecting the joint effect of elastance and pulsatory volume changes on ICP and was determined by relating ICP pulse amplitudes to mean ICP.Conclusions. The B-wave presence on ICP registration correlates strongly with RPPC (r = 0.91, p < 0.001, 10 patients) but not with CSF Rout. This correlation indicates that B waves—like RPPC—primarily reflect the ability of the CSF system to reallocate and store liquid rather than absorb it. The RPPC-assessing lumbar short-term CSF pulse pressure method could replace the intracranial long-term B-wave analysis.
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- Tunestål, Per, et al.
(författare)
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Hydrogen Addition For Improved Lean Burn Capability of Slow and Fast Burning Natural Gas Combustion Chambers
- 2002
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Ingår i: SAE Special Publications. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0099-5908. ; 2002:1725, s. 21-32
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Konferensbidrag (refereegranskat)abstract
- One way to extend the lean-burn limit of a natural gas engine is by addition of hydrogen to the primary fuel. This paper presents measurements made on a one-cylinder, 1.6- liter natural gas engine. Two combustion chambers, one slow and one fast burning, were tested with various amounts of hydrogen (0, 5, 10 and 15%-vol) added to natural gas. Three operating points were investigated for each combustion chamber and each hydrogen content level; idle, part load (5 bar IMEP) and 13 bar IMEP (simulated turbocharging). Air/fuel ratio was varied between stoichiometric and the lean limit. For each operating point, a range of ignition timings were tested to find maximum brake torque (MBT) and/or knock. Heat-release rate calculations were made in order to assess the influence of hydrogen addition on burn rate. Addition of hydrogen showed an increase in burn rate for both combustion chambers, resulting in more stable combustion close to the lean limit. This effect was most pronounced for lean operation with the slow combustion chamber.
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