Strategies for diagnosing electrical status epilepticus during slow-wave sleep (ESES) vary among interpreting neurologists. Our aim was to evaluate if the spike-wave index (SWI) for the first 100 ...seconds of sleep is reflective of the SWI when compared with a conventional method.
We reviewed EEGs from 2005 to 2011 that were considered diagnostic of ESES based on unspecified methods. The SWI for the first nonrapid eye movement sleep cycle (long method) was calculated by two neurophysiologists. Two different neurophysiologists calculated SWI for the first 100 seconds of sleep (short method). For the purposes of this study, ESES was defined as an SWI of >85%. The two SWI scores were compared.
Fourteen EEGs were reviewed. Despite being considered by the initial interpreter as diagnostic of ESES, only 4 of the studies had an SWI of >85% based on each of the methods. For a diagnosis of ESES, the sensitivity of the short method is 80% and the specificity is 89%. Wilcoxon signed rank test was used to compare the long and short methods. A P value of 0.70 indicates no significant difference between the methods. Additionally, the Spearman correlation coefficient is 0.553 (P = 0.04), indicating moderate correlation between the methods.
The SWI for the first 100 seconds of nonrapid eye movement sleep is predictive of the SWI for the entire first sleep cycle with a good sensitivity and specificity in our cohort. This suggests an alternative method for diagnosing ESES, which is comparable to analysis of a full night of sleep.
Isobutene is an important intermediate in the pyrolysis and oxidation of higher-order branched alkanes, and it is also a component of commercial gasolines. To better understand its combustion ...characteristics, a series of ignition delay time (IDT) and laminar flame speed (LFS) measurements have been performed. In addition, flow reactor speciation data recorded for the pyrolysis and oxidation of isobutene is also reported. Predictions of an updated kinetic model described herein are compared with each of these data sets, as well as with existing jet-stirred reactor (JSR) species measurements.
IDTs of isobutene oxidation were measured in four different shock tubes and in two rapid compression machines (RCMs) under conditions of relevance to practical combustors. The combination of shock tube and RCM data greatly expands the range of available validation data for isobutene oxidation models to pressures of 50atm and temperatures in the range 666–1715K. Isobutene flame speeds were measured experimentally at 1atm and at unburned gas temperatures of 298–398K over a wide range of equivalence ratios. For the flame speed results, there was good agreement between different facilities and the current model in the fuel-rich region. Ab initio chemical kinetics calculations were carried out to calculate rate constants for important reactions such as H-atom abstraction by hydroxyl and hydroperoxyl radicals and the decomposition of 2-methylallyl radicals.
A comprehensive chemical kinetic mechanism has been developed to describe the combustion of isobutene and is validated by comparison to the presently considered experimental measurements. Important reactions, highlighted via flux and sensitivity analyses, include: (a) hydrogen atom abstraction from isobutene by hydroxyl and hydroperoxyl radicals, and molecular oxygen; (b) radical–radical recombination reactions, including 2-methylallyl radical self-recombination, the recombination of 2-methylallyl radicals with hydroperoxyl radicals; and the recombination of 2-methylallyl radicals with methyl radicals; (c) addition reactions, including hydrogen atom and hydroxyl radical addition to isobutene; and (d) 2-methylallyl radical decomposition reactions. The current mechanism accurately predicts the IDT and LFS measurements presented in this study, as well as the JSR and flow reactor speciation data already available in the literature.
The differences in low-temperature chemistry between alkanes and alkenes are also highlighted in this work. In normal alkanes, the fuel radical Ṙ adds to molecular oxygen forming alkylperoxyl (RȮ2) radicals followed by isomerization and chain branching reactions which promote low-temperature fuel reactivity. However, in alkenes, because of the relatively shallow well (∼20kcalmol–1) for RȮ2 formation compared to ∼35kcalmol–1 in alkanes, the Ṙ+O2 ⇌ RȮ2 equilibrium lies more to the left favoring Ṙ+O2 rather than RȮ2 radical stabilization. Based on this work, and related studies of allylic systems, it is apparent that reactivity for alkene components at very low temperatures (<800K) emanates from hydroxyl radical addition followed by addition of molecular oxygen to radical. At intermediate temperatures (800–1300K), alkene reactivity is controlled by hydrogen abstraction by molecular oxygen and the reactions between resonantly stabilized radicals and hydroperoxyl radicals which results in chain branching. At higher temperatures (>1300K), the reactivity is mainly governed by the competition between hydrogen abstractions by molecular oxygen and ȮH radicals.
•Tilt-induced syncope is associated with changes in several quantitative EEG (QEEG) parameters.•QEEG changes include a shift in power from higher to lower frequency ranges.•Laterality of QEEG changes ...is not different from a probability of 0.5.
To characterize the quantitative electroencephalographic (QEEG) patterns associated with tilt-induced syncope in youth.
Several QEEG parameters were analyzed. Data were calculated for peak or nadir changes with syncope for amplitude-EEG, fast Fourier transform (FFT) power in several frequency ranges, 8–13 Hz/1–4 Hz frequency ratio, and FFT edge.
Changes in QEEG parameters were present among all patients with tilt-induced syncope (n = 76). These changes included increases in the low frequency FFT power (1–4 Hz range), decreases in the power ratio (8–13 Hz/1–4 Hz) and decreases in the FFT edge (95%, 1–18 Hz). All patients had suppression of EEG amplitudes that closely followed loss of consciousness. Asymmetry indices demonstrated cerebral hemisphere lateralization at multiple periods during the evolution of syncope, but the side of lateralization did not differ from 0.5 probability.
QEEG parameters can be used to characterize EEG changes associated with tilt-induced, neurally-mediated syncope.
QEEG may serve as a useful tool for the study of syncope neurophysiology, and the modeling of changes with syncope may improve our understanding of other neurologic disorders caused by defects in cerebral perfusion.
A major global research and development effort is underway to commercialize carbon capture and storage (CCS) as a method to mitigate climate change. Recent studies have shown the potential to couple ...CCS with geothermal energy extraction using supercritical CO2 (ScCO2) as the working fluid. In a geothermal reservoir, the working fluid produces electricity as a byproduct of the CCS process by mining heat out of a reservoir as it is circulated between injector and producer wells. While ScCO2 has lower heat capacity than water, its lower viscosity more than compensates by providing for greater fluid mobility. Furthermore, CO2 exhibits high expansivity and compressibility, which can both help reduce parasitic loads in fluid cycling. Given the high capital costs for developing the deep well infrastructure for geologic storage of CO2, the potential to simultaneously produce geothermal energy is an attractive method to offset some of the costs and added energy requirements for separating and transporting the waste CO2 stream.
We present here the preliminary design and reservoir engineering associated with the development of direct-fired turbomachinery for pilot-scale deployment at the SECARB Cranfield Phase III CO2 Storage Project, in Cranfield, Mississippi, U.S.A. The pilot-scale deployment leverages the prior investment in the Cranfield Phase III research site, providing the first ever opportunity to acquire combined CO2 storage/geothermal energy extraction data necessary to address the uncertainties involved in this novel technique. At the SECARB Cranfield Site, our target reservoir, the Tuscaloosa Formation, lies at a depth of 3.0km, and an initial temperature of 127°C. A CO2 injector well and two existing observation wells are ideally suited for establishing a CO2 thermosiphon and monitoring the thermal and pressure evolution of the well-pair on a timescale that can help validate coupled models. It is hoped that this initial demonstration on a pre-commercial scale can accelerate commercialization of combined CCS/geothermal energy extraction by removing uncertainties in system modeling.
To develop a training program enabling paramedics to use sedation and paralytic medications to facilitate endotracheal intubation in patients who otherwise could not be successfully intubated.
...Paramedics underwent a training program consisting of six hours of didactic education, two four-hour mannequin labs, one four-hour animal intubation lab, and operating room experience. Rapid-sequence intubation (RSI) runs were reviewed for appropriateness in patient selection and medication use. Non-RSI runs were reviewed to determine whether appropriate patients were being missed. Intubation success rates continue to be followed. Long-term quality assurance includes monthly run reviews, periodic quizzes, and unannounced on-site practical tests.
101 patients have been intubated using RSI, including medical, trauma, pediatric, and adult cases. Of all patients receiving RSI drugs, 100 of 101 were successfully intubated. There were no undetected esophageal intubations. Paramedics were able to demonstrate proper patient selection and appropriately administer RSI medications. The use of sheep labs was a critical component of this training because it permitted multiple intubations in a live model possessing an airway quite similar to that of the human. The gum elastic bougie was felt to be critical in the intubation of three patients.
This RSI training model can serve as a template for other agencies seeking to implement RSI. Limitations of this model include the availability of live animal labs and the expense of conducting the training. Intense medical director involvement has been key to the success of this prehospital RSI program.
Objective. To develop a training program enabling paramedics to use sedation and paralytic medications to facilitate endotracheal intubation in patients who otherwise could not be successfully ...intubated. Methods. Paramedics underwent a training program consisting of six hours of didactic education, two four-hour mannequin labs, one four-hour animal intubation lab, and operating room experience. Rapid-sequence intubation (RSI) runs were reviewed for appropriateness in patient selection and medication use. Non-RSI runs were reviewed to determine whether appropriate patients were being missed. Intubation success rates continue to be followed. Long-term quality assurance includes monthly run reviews, periodic quizzes, and unannounced on-site practical tests. Results. 101 patients have been intubated using RSI, including medical, trauma, pediatric, and adult cases. Of all patients receiving RSI drugs, 100 of 101 were successfully intubated. There were no undetected esophageal intubations. Paramedics were able to demonstrate proper patient selection and appropriately administer RSI medications. The use of sheep labs was a critical component of this training because it permitted multiple intubations in a live model possessing an airway quite similar to that of the human. The gum elastic bougie was felt to be critical in the intubation of three patients. Conclusion. This RSI training model can serve as a template for other agencies seeking to implement RSI. Limitations of this model include the availability of live animal labs and the expense of conducting the training. Intense medical director involvement has been key to the success of this prehospital RSI program.
The recent increase in the use of methanol and methyl tertiary-butyl ether (MTBE) in the automotive fuel industry has generated great interest in the chemical kinetics of their oxidation. Pre-flame ...reactions in spark-ignition engines are controlling factors in the autoignition properties and unburned hydrocarbon emissions of these fuels. To gain a more detailed understanding of these processes, data are collected in well-defined experiments operating in an appropriate pressure and temperature range and used to develop and validate detailed chemical kinetic models of the oxidation reactions. The oxidation chemistry of methanol has been studied experimentally in a variable pressure flow reactor, over a pressure range from 1 to 20 atmospheres, a temperature range of 752 to 1043 K, and an equivalence ratio range of 0.4 to 2.6. Stable species measurements indicate that nearly all the methanol is consumed directly through formaldehyde, with little contribution from a methane path. No C$\sb2$ hydrocarbon products were detectable. Two species were detected in the present study that were not measured in previous methanol experiments, formic acid and 1,2-ethanediol. A detailed chemical kinetic model has been constructed that accurately reproduces the methanol experiments. Sensitivity and reaction path analyses allow the identification of important kinetic pathways and rate constants. Application of the model to static reactor, shock tube and flame speed experiments allows extension of its range of validity beyond that possible with a single experiment. The hydroperoxyl radical, through its effect on radical branching and termination, is a central feature of methanol oxidation, even at shock tube and flame conditions. The oxidation and pyrolysis chemistry of isobutene, the primary intermediate in MTBE oxidation, has been studied at high temperatures and atmospheric pressure. A detailed chemical kinetic model demonstrates the effectiveness of isobutene as a radical trap, converting hydrogen and hydroxyl radicals to unreactive species. This model, combined with a set of reactions describing MTBE consumption, also reproduces earlier atmospheric pressure flow reactor experiments on MTBE oxidation. The two dominant consumption paths of MTBE, molecular elimination and H-atom abstraction, both produce isobutene. The anti-knock qualities of MTBE are derived from the chemical inhibition of the isobutene intermediate species.
Tipping elements in the Earth's climate system Lenton, Timothy M; Held, Hermann; Kriegler, Elmar ...
Proceedings of the National Academy of Sciences - PNAS,
02/2008, Letnik:
105, Številka:
6
Journal Article
Recenzirano
Odprti dostop
The term "tipping point" commonly refers to a critical threshold at which a tiny perturbation can qualitatively alter the state or development of a system. Here we introduce the term "tipping ...element" to describe large-scale components of the Earth system that may pass a tipping point. We critically evaluate potential policy-relevant tipping elements in the climate system under anthropogenic forcing, drawing on the pertinent literature and a recent international workshop to compile a short list, and we assess where their tipping points lie. An expert elicitation is used to help rank their sensitivity to global warming and the uncertainty about the underlying physical mechanisms. Then we explain how, in principle, early warning systems could be established to detect the proximity of some tipping points.
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