The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Akira Ogawa - One of the best experts on this subject based on the ideXlab platform.
-
transient hyperemia immediately after Rapid Decompression of chronic subdural hematoma
Neurosurgery, 2000Co-Authors: Kuniaki Ogasawara, Takashi Yoshimoto, Keiji Koshu, Akira OgawaAbstract:OBJECTIVE: Intracerebral hemorrhage occurring after removal of a chronic subdural hematoma (CSH) is a rare but usually devastating postoperative complication. In patients with CSH, we determined cerebral blood flow immediately after surgical Decompression to clarify the pathogenic mechanism of this complication. METHODS: In 22 patients with unilateral CSH, a catheter was inserted into the hematoma cavity through a single burr hole without leakage of the contents. Cerebral blood flow was measured using single-photon emission computed tomography 1 day before surgery, immediately after Rapid Decompression by opening the catheter, and 3 days after surgery. RESULTS: Single-photon emission computed tomography imaging immediately after Decompression demonstrated areas of hyperemia in nine patients (41%). In all nine patients, hyperemia was observed in the cortex beneath the CSH, and it disappeared on the 3rd postoperative day. The patients with hyperemia were significantly older than those without hyperemia. Other variables, including preoperative cerebral blood flow, intrahematoma pressure before Decompression, and mean arterial blood pressure during Decompression had no significant effect on the occurrence of hyperemia. CONCLUSION: In elderly patients, Rapid Decompression of CSH frequently results in transient hyperemia in the cerebral cortex beneath the hematoma.
-
Transient hyperemia immediately after Rapid Decompression of chronic subdural hematoma.
Neurosurgery, 1999Co-Authors: Kuniaki Ogasawara, Takashi Yoshimoto, Keiji Koshu, Akira OgawaAbstract:Intracerebral hemorrhage occurring after removal of a chronic subdural hematoma (CSH) is a rare but usually devastating postoperative complication. In patients with CSH, we determined cerebral blood flow immediately after surgical Decompression to clarify the pathogenic mechanism of this complication. In 22 patients with unilateral CSH, a catheter was inserted into the hematoma cavity through a single burr hole without leakage of the contents. Cerebral blood flow was measured using single-photon emission computed tomography 1 day before surgery, immediately after Rapid Decompression by opening the catheter, and 3 days after surgery. Single-photon emission computed tomography imaging immediately after Decompression demonstrated areas of hyperemia in nine patients (41%). In all nine patients, hyperemia was observed in the cortex beneath the CSH, and it disappeared on the 3rd postoperative day. The patients with hyperemia were significantly older than those without hyperemia. Other variables, including preoperative cerebral blood flow, intrahematoma pressure before Decompression, and mean arterial blood pressure during Decompression had no significant effect on the occurrence of hyperemia. In elderly patients, Rapid Decompression of CSH frequently results in transient hyperemia in the cerebral cortex beneath the hematoma.
Kuniaki Ogasawara - One of the best experts on this subject based on the ideXlab platform.
-
transient hyperemia immediately after Rapid Decompression of chronic subdural hematoma
Neurosurgery, 2000Co-Authors: Kuniaki Ogasawara, Takashi Yoshimoto, Keiji Koshu, Akira OgawaAbstract:OBJECTIVE: Intracerebral hemorrhage occurring after removal of a chronic subdural hematoma (CSH) is a rare but usually devastating postoperative complication. In patients with CSH, we determined cerebral blood flow immediately after surgical Decompression to clarify the pathogenic mechanism of this complication. METHODS: In 22 patients with unilateral CSH, a catheter was inserted into the hematoma cavity through a single burr hole without leakage of the contents. Cerebral blood flow was measured using single-photon emission computed tomography 1 day before surgery, immediately after Rapid Decompression by opening the catheter, and 3 days after surgery. RESULTS: Single-photon emission computed tomography imaging immediately after Decompression demonstrated areas of hyperemia in nine patients (41%). In all nine patients, hyperemia was observed in the cortex beneath the CSH, and it disappeared on the 3rd postoperative day. The patients with hyperemia were significantly older than those without hyperemia. Other variables, including preoperative cerebral blood flow, intrahematoma pressure before Decompression, and mean arterial blood pressure during Decompression had no significant effect on the occurrence of hyperemia. CONCLUSION: In elderly patients, Rapid Decompression of CSH frequently results in transient hyperemia in the cerebral cortex beneath the hematoma.
-
Transient hyperemia immediately after Rapid Decompression of chronic subdural hematoma.
Neurosurgery, 1999Co-Authors: Kuniaki Ogasawara, Takashi Yoshimoto, Keiji Koshu, Akira OgawaAbstract:Intracerebral hemorrhage occurring after removal of a chronic subdural hematoma (CSH) is a rare but usually devastating postoperative complication. In patients with CSH, we determined cerebral blood flow immediately after surgical Decompression to clarify the pathogenic mechanism of this complication. In 22 patients with unilateral CSH, a catheter was inserted into the hematoma cavity through a single burr hole without leakage of the contents. Cerebral blood flow was measured using single-photon emission computed tomography 1 day before surgery, immediately after Rapid Decompression by opening the catheter, and 3 days after surgery. Single-photon emission computed tomography imaging immediately after Decompression demonstrated areas of hyperemia in nine patients (41%). In all nine patients, hyperemia was observed in the cortex beneath the CSH, and it disappeared on the 3rd postoperative day. The patients with hyperemia were significantly older than those without hyperemia. Other variables, including preoperative cerebral blood flow, intrahematoma pressure before Decompression, and mean arterial blood pressure during Decompression had no significant effect on the occurrence of hyperemia. In elderly patients, Rapid Decompression of CSH frequently results in transient hyperemia in the cerebral cortex beneath the hematoma.
Alison H. Colotelo - One of the best experts on this subject based on the ideXlab platform.
-
empirical investigation into the applicability of surrogacy for juvenile salmonids oncorrhynchus spp exposed to hydropower induced Rapid Decompression
Ecological Indicators, 2021Co-Authors: Bernardo Beirao, Brett D. Pflugrath, Ryan A. Harnish, Samuel F Harding, Marshall C Richmond, Alison H. ColoteloAbstract:Abstract Surrogacy, whereby the response of a representative species subjected to a stressor is applied to one or more species, is commonly used without validation in conservation research and applications. The objective of this study was to empirically evaluate the appropriateness of using morphologically and phylogenetically similar species as surrogates for laboratory experiments that develop dose–response relationships for Rapid Decompression. In this study, juvenile kokanee, rainbow trout, and Chinook salmon were evaluated for injuries after exposure to Rapid Decompression that simulated pressure time-histories that are representative of hydropower turbine passage. Dose-response relationships, which modeled probability of mortal injury as a function of Rapid Decompression, were constructed for each species and compared to determine if differences existed between species across the range of Rapid Decompression. The surrogacy potential of these three species was also evaluated by incorporating the dose–response curves into the Biological Performance Assessment (BioPA) tool to predict the probability of adverse passage as a function of mortal injury and LRP exposure probabilities during three common operation scenarios of a computational fluid dynamics modeled Kaplan turbine (lower 1% generation limit, peak generation, and upper 1% generation limit). Although dose–response curves differed among species, the differences occurred at more extreme Decompression values which had a low probability of occurring under the three Kaplan turbine operation scenarios tested using the BioPA tool. Therefore, the three species had similar BioPA scores for adverse passage probabilities, indicating they could act as surrogates for one another under certain (i.e., low LRP) passage conditions.
-
The Susceptibility of Juvenile American Shad to Rapid Decompression and Fluid Shear Exposure Associated with Simulated Hydroturbine Passage
Water, 2020Co-Authors: Brett D. Pflugrath, Ryan A. Harnish, Briana Rhode, Kristin Engbrecht, Bernardo Beirao, Robert P. Mueller, Erin L. Mccann, John R. Stephenson, Alison H. ColoteloAbstract:Throughout many areas of their native range, American shad (Alosa sapidissima) and other Alosine populations are in decline. Though several conditions have influenced these declines, hydropower facilities have had significant negative effects on American shad populations. Hydropower facilities expose ocean-migrating American shad to physical stressors during passage through hydropower facilities, including strike, Rapid Decompression, and fluid shear. In this laboratory-based study, juvenile American shad were exposed separately to Rapid Decompression and fluid shear to determine their susceptibility to these stressors and develop dose–response models. These dose–response relationships can help guide the development and/or operation of hydropower turbines and facilities to reduce the negative effects to American shad. Relative to other species, juvenile American shad have a high susceptibility to both Rapid Decompression and fluid shear. Reducing or preventing exposure to these stressors at hydropower facilities may be a potential method to assist in the effort to restore American shad populations.
-
pathways of barotrauma in juvenile salmonids exposed to simulated hydroturbine passage boyle s law vs henry s law
Fisheries Research, 2012Co-Authors: Richard S. Brown, Thomas J. Carlson, Brett D. Pflugrath, Alison H. Colotelo, Colin J Brauner, Daniel Z Deng, Adam G SeaburgAbstract:Abstract On their seaward migration, juvenile salmonids commonly pass hydroelectric dams. Fish passing by the turbine blade may experience Rapid Decompression, the severity of which can be highly variable and may result in a number of barotraumas. The mechanisms of these injuries can be due to expansion of existing bubbles or gases coming out of solution; governed by Boyle's law and Henry's law, respectively. This paper combines re-analysis of published data with new experiments to gain a better understanding of the mechanisms of injury and mortality for fish experiencing Rapid Decompression associated with hydroturbine passage. From these data it appears that the majority of Decompression related injuries are due to the expansion of existing bubbles in the fish, particularly the expansion and rupture of the swim bladder. This information is particularly useful for fisheries managers and turbine manufacturers, demonstrating that reducing the rate of swim bladder ruptures by reducing the frequency of occurrence and severity of Rapid Decompression during hydroturbine passage could reduce the rates of injury and mortality for hydroturbine passed juvenile salmonids.
-
Pathways of Barotrauma in Juvenile Salmonids Exposed to Simulated Hydroturbine Passage: Boyle’s Law vs. Henry’s Law
Fisheries Research, 2012Co-Authors: Richard S. Brown, Thomas J. Carlson, Brett D. Pflugrath, Alison H. Colotelo, Colin J Brauner, Z. Daniel Deng, Adam G SeaburgAbstract:Abstract On their seaward migration, juvenile salmonids commonly pass hydroelectric dams. Fish passing by the turbine blade may experience Rapid Decompression, the severity of which can be highly variable and may result in a number of barotraumas. The mechanisms of these injuries can be due to expansion of existing bubbles or gases coming out of solution; governed by Boyle's law and Henry's law, respectively. This paper combines re-analysis of published data with new experiments to gain a better understanding of the mechanisms of injury and mortality for fish experiencing Rapid Decompression associated with hydroturbine passage. From these data it appears that the majority of Decompression related injuries are due to the expansion of existing bubbles in the fish, particularly the expansion and rupture of the swim bladder. This information is particularly useful for fisheries managers and turbine manufacturers, demonstrating that reducing the rate of swim bladder ruptures by reducing the frequency of occurrence and severity of Rapid Decompression during hydroturbine passage could reduce the rates of injury and mortality for hydroturbine passed juvenile salmonids.
Donald B Dingwell - One of the best experts on this subject based on the ideXlab platform.
-
Analysis of source characteristics of experimental gas burst and fragmentation explosions generated by Rapid Decompression of volcanic rocks
Journal of Geophysical Research, 2015Co-Authors: A. Arciniega-ceballos, M. A. Alatorre-ibarguengoitia, Bettina Scheu, Donald B DingwellAbstract:Gas burst and fragmentation explosions induced by Rapid Decompression of volcanic rocks in a high-pressure autoclave have been analyzed. We performed experiments from 4 to 20 MPa on (1) loose pyroclasts and (2) pumice from recent eruptions of Popocatepetl volcano. Our aim is to characterize the source mechanism distinguishing the physical processes that operate in the conduit which determine the dynamics of explosive volcanoes. For this aim we have analyzed experimentally the parameters that indicate the state and behavior of the conduit (i.e., Decompression time, fragmentation threshold and speed, forces, and the partitioning of energy), using microseismic monitoring, the Decompression time curves, and the sample rheological properties. The initial available potential energy in the system and its partitioning into different types of energies are correlated in space and time with specific stages of the explosive phenomenon. Such correlations, taken together with the energy distribution, enable the distinction of the individual physical processes involved and their causal sequence and relationships. Our observations suggest that in volcanic conduits with regular explosive activity, a source mechanism may operate whereby a causal sequence of processes results in a system that undergoes both Rapid and stable transitions. Such behavior may persist over long periods of time.
-
Revealing the process of fragmentation from high-speed video analysis of Rapid Decompression of magma.
2010Co-Authors: Bettina Scheu, Andrew C. Fowler, Mark J. Mcguiness, William T. Lee, Donald B DingwellAbstract:It is the fragmentation of magma which distinguishes explosive volcanic eruptions from the more quiet effusive form of volcanic activity. Hence the conditions leading to magma fragmentation as well as the fragmentation process itself are key points in order to better our understanding of the dynamics of volcanic eruptions. Better understanding of eruption dynamics will lead in return to improved hazard mitigation. So far, various models have been proposed for magma fragmentation, based on the investigation of deposits of explosive eruptions, theoretical constraints and laboratory experiments. The latter have been performed on a broad variety of natural magma and varying analogue materials, pointing out important correlations between magma properties and fragmentation behavior but also posed new questions. We performed Rapid Decompression experiments of vesicular natural magma and monitored the fragmentation process with high-speed video recordings of the experiments and three pressure transducers along the sample. The coarse fraction of the generated pyroclasts was recovered and analyzed. The high-speed video recording allowed for the first time to scrutinize not only the result of fragmentation, but the fragmentation process itself for natural samples.
-
Permeability and degassing of dome lavas undergoing Rapid Decompression: An experimental determination
Bulletin of Volcanology, 2005Co-Authors: Sebastian Mueller, Bettina Scheu, Oliver Spieler, Oleg Melnik, Donald B DingwellAbstract:The gas permeability of volcanic rocks may influence various eruptive processes. The transition from a quiescent degassing dome to rock failure (fragmentation) may, for example, be controlled by the rock’s permeability, in as much as it affects the speed by which a gas overpressure in vesicles is reduced in response to Decompression. Using a modified shock-tube-based fragmentation bomb (Alidibirov and Dingwell 1996a , b ; Spieler et al. 2003a ), we have measured unsteady-state permeability at a high initial pressure differential. Following sudden Decompression above the rock cylinder, pressurized gas flows through the sample. Two pressure transducers record the pressure signals above and below the sample. A transient 1D filtration code has been developed to calculate permeability using the experimental decay curve of the lower pressure transducer. Additionally an analytical steady-state method to achieve permeability is presented as an alternative to swiftly predict the sample permeability in a sufficiently precise manner. Over 100 permeability measurements have been performed on samples covering a wide range of porosity. The results show a general positive relationship between porosity and permeability with a high data scatter. Our preferred interpretation of the results is a combination of two different, but overlapping effects. We propose that at low porosities, gas escape occurs predominantly through microcracks or elongated micropores and therefore could be described by simplified forms of Kozeny–Carman relations (Carman 1956 ) and fracture flow models. At higher porosities, the influence of vesicles becomes progressively stronger as they form an increasingly connected network. Therefore, a model based on the percolation theory of fully penetrable spheres is used, as a first approximation, to describe the permeability-porosity trend. In the data acquired to date it is evident, that in addition to the porosity control, the sample’s bubble size, shape and distribution strongly influence the permeability. This leads to a range of permeability values up to 2.5 orders of magnitude at a given porosity.
-
Three fragmentation mechanisms for highly viscous magma under Rapid Decompression
Journal of Volcanology and Geothermal Research, 2000Co-Authors: Mikhail Alidibirov, Donald B DingwellAbstract:Abstract Analysis of the behavior of viscous magma under short-term tensile stresses demonstrates that the strain rates anticipated in the eruptive stages of collapse-related events may be high enough under certain circumstances to provide fragmentation of the melt by brittle failure. Mechanisms of fragmentation of a highly viscous vesicular magma by the propagation of an unloading wave, by layer-by-layer vesicle bursting (“fragmentation wave” propagation) and by Rapid filtration gas flow are outlined. Fragmentation scenarios involving possible combinations of the three fragmentation mechanisms are evaluated for two models of magma (with isolated and with connected pores). Experimental results for magma fragmentation under high Decompression rates appear to support such mechanisms. These mechanisms of highly viscous magma fragmentation by Rapid Decompression probably have their greatest application in cases of explosive disintegration of lava domes and cryptodomes caused by collapse events.
-
Fragmentation of foamed silicic melts: an experimental study
Earth and Planetary Science Letters, 2000Co-Authors: Caroline Martel, Donald B Dingwell, Oliver Spieler, Michel Pichavant, Max WilkeAbstract:We present the first experimental investigation of the fragmentation behavior of two-phase (melt+gas) rhyolitic systems under Rapid Decompression. Two-phase samples have been generated by foaming water-oversaturated rhyolitic melts up to 900°C and up to 18 MPa prior to Rapid Decompression in a fragmentation bomb. The fragmented particles or experimental pyroclasts were recovered for analysis. Several features of naturally foamed pumices have been reproduced, including the generation of both isotropic and tube pumices. We focus here on the fragmentation behavior. Fragmentation occurred through a layer-by-layer process, in the brittle regime of melt response. We investigated the influence of the magnitude of the Decompression (4 to 18 MPa), the porosity (0 to 85 vol%) and the pore morphology (tube versus isotropic) on the fragment size distribution. Less vesicular samples (porosity50 vol%) yield coarser fragments when decompressed below 15 MPa and finer fragments when decompressed above 15 MPa. Increasing Decompression of the vesicular samples results in a decrease in fragment size of 0.2 Φ unit/MPa. The presence of tubes instead of isotropic pores in vesicular samples generates finer fragments under Decompression. Implications for dome eruptions are discussed.
Brett D. Pflugrath - One of the best experts on this subject based on the ideXlab platform.
-
empirical investigation into the applicability of surrogacy for juvenile salmonids oncorrhynchus spp exposed to hydropower induced Rapid Decompression
Ecological Indicators, 2021Co-Authors: Bernardo Beirao, Brett D. Pflugrath, Ryan A. Harnish, Samuel F Harding, Marshall C Richmond, Alison H. ColoteloAbstract:Abstract Surrogacy, whereby the response of a representative species subjected to a stressor is applied to one or more species, is commonly used without validation in conservation research and applications. The objective of this study was to empirically evaluate the appropriateness of using morphologically and phylogenetically similar species as surrogates for laboratory experiments that develop dose–response relationships for Rapid Decompression. In this study, juvenile kokanee, rainbow trout, and Chinook salmon were evaluated for injuries after exposure to Rapid Decompression that simulated pressure time-histories that are representative of hydropower turbine passage. Dose-response relationships, which modeled probability of mortal injury as a function of Rapid Decompression, were constructed for each species and compared to determine if differences existed between species across the range of Rapid Decompression. The surrogacy potential of these three species was also evaluated by incorporating the dose–response curves into the Biological Performance Assessment (BioPA) tool to predict the probability of adverse passage as a function of mortal injury and LRP exposure probabilities during three common operation scenarios of a computational fluid dynamics modeled Kaplan turbine (lower 1% generation limit, peak generation, and upper 1% generation limit). Although dose–response curves differed among species, the differences occurred at more extreme Decompression values which had a low probability of occurring under the three Kaplan turbine operation scenarios tested using the BioPA tool. Therefore, the three species had similar BioPA scores for adverse passage probabilities, indicating they could act as surrogates for one another under certain (i.e., low LRP) passage conditions.
-
The Susceptibility of Juvenile American Shad to Rapid Decompression and Fluid Shear Exposure Associated with Simulated Hydroturbine Passage
Water, 2020Co-Authors: Brett D. Pflugrath, Ryan A. Harnish, Briana Rhode, Kristin Engbrecht, Bernardo Beirao, Robert P. Mueller, Erin L. Mccann, John R. Stephenson, Alison H. ColoteloAbstract:Throughout many areas of their native range, American shad (Alosa sapidissima) and other Alosine populations are in decline. Though several conditions have influenced these declines, hydropower facilities have had significant negative effects on American shad populations. Hydropower facilities expose ocean-migrating American shad to physical stressors during passage through hydropower facilities, including strike, Rapid Decompression, and fluid shear. In this laboratory-based study, juvenile American shad were exposed separately to Rapid Decompression and fluid shear to determine their susceptibility to these stressors and develop dose–response models. These dose–response relationships can help guide the development and/or operation of hydropower turbines and facilities to reduce the negative effects to American shad. Relative to other species, juvenile American shad have a high susceptibility to both Rapid Decompression and fluid shear. Reducing or preventing exposure to these stressors at hydropower facilities may be a potential method to assist in the effort to restore American shad populations.
-
How low can they go when going with the flow? Tolerance of egg and larval fishes to Rapid Decompression
Biology open, 2016Co-Authors: Craig A. Boys, Richard S. Brown, Brett D. Pflugrath, Wayne Robinson, Brett Miller, Lee J. Baumgartner, Anna Navarro, Zhiqun DengAbstract:Egg and larval fish that drift downstream are likely to encounter river infrastructure and consequently Rapid Decompression, which may result in significant injury. Pressure-related injury (or barotrauma) has been shown in juvenile fishes when pressure falls sufficiently below that at which the fish has acclimated. There is a presumption that eggs and larvae may be at least as, if not more, susceptible to barotrauma injury because they are far less-developed and more fragile than juveniles, but studies to date report inconsistent results and none have considered the relationship between pressure change and barotrauma over a sufficiently broad range of pressure changes to enable tolerances to be properly determined. To address this, we exposed eggs and larvae of three physoclistic species to Rapid Decompression in a barometric chamber over a broad range of discrete pressure changes. Eggs, but not larvae, were unaffected by all levels of Decompression tested. At exposure pressures below ∼40 kPa, or ∼40% of surface pressure, swim bladder deflation occurred in all species and internal haemorrhage was observed in one species. None of these injuries killed the fish within 24 h, but subsequent mortality cannot be excluded. Consequently, if larval drift is expected where river infrastructure is present, adopting design or operational features which maintain exposure pressures at 40% or more of the pressure to which drifting larvae are acclimated may afford greater protection for resident fishes.
-
pathways of barotrauma in juvenile salmonids exposed to simulated hydroturbine passage boyle s law vs henry s law
Fisheries Research, 2012Co-Authors: Richard S. Brown, Thomas J. Carlson, Brett D. Pflugrath, Alison H. Colotelo, Colin J Brauner, Daniel Z Deng, Adam G SeaburgAbstract:Abstract On their seaward migration, juvenile salmonids commonly pass hydroelectric dams. Fish passing by the turbine blade may experience Rapid Decompression, the severity of which can be highly variable and may result in a number of barotraumas. The mechanisms of these injuries can be due to expansion of existing bubbles or gases coming out of solution; governed by Boyle's law and Henry's law, respectively. This paper combines re-analysis of published data with new experiments to gain a better understanding of the mechanisms of injury and mortality for fish experiencing Rapid Decompression associated with hydroturbine passage. From these data it appears that the majority of Decompression related injuries are due to the expansion of existing bubbles in the fish, particularly the expansion and rupture of the swim bladder. This information is particularly useful for fisheries managers and turbine manufacturers, demonstrating that reducing the rate of swim bladder ruptures by reducing the frequency of occurrence and severity of Rapid Decompression during hydroturbine passage could reduce the rates of injury and mortality for hydroturbine passed juvenile salmonids.
-
Pathways of Barotrauma in Juvenile Salmonids Exposed to Simulated Hydroturbine Passage: Boyle’s Law vs. Henry’s Law
Fisheries Research, 2012Co-Authors: Richard S. Brown, Thomas J. Carlson, Brett D. Pflugrath, Alison H. Colotelo, Colin J Brauner, Z. Daniel Deng, Adam G SeaburgAbstract:Abstract On their seaward migration, juvenile salmonids commonly pass hydroelectric dams. Fish passing by the turbine blade may experience Rapid Decompression, the severity of which can be highly variable and may result in a number of barotraumas. The mechanisms of these injuries can be due to expansion of existing bubbles or gases coming out of solution; governed by Boyle's law and Henry's law, respectively. This paper combines re-analysis of published data with new experiments to gain a better understanding of the mechanisms of injury and mortality for fish experiencing Rapid Decompression associated with hydroturbine passage. From these data it appears that the majority of Decompression related injuries are due to the expansion of existing bubbles in the fish, particularly the expansion and rupture of the swim bladder. This information is particularly useful for fisheries managers and turbine manufacturers, demonstrating that reducing the rate of swim bladder ruptures by reducing the frequency of occurrence and severity of Rapid Decompression during hydroturbine passage could reduce the rates of injury and mortality for hydroturbine passed juvenile salmonids.
