Directly upgrading natural gas is limited by the stability of its primary component, methane, and process economics. Since the 1980s, oxidative coupling of methane (OCM) has shown potential to ...produce ethylene and ethane (C2s). The typical OCM approach catalytically converts methane to C2 products using molecular oxygen, reducing process efficiency. To overcome this, chemical looping OCM converts methane to hydrocarbons via intermediate oxygen carriers rather than gaseous cofed oxidants. The chemical looping approach for OCM has been studied mechanistically for the first time with a Mn–Mg-based catalytic oxygen carrier (COC). The COC delivered stable performance in a fixed bed for 100 cycles for more than 50 h with a 63.2% C2 selectivity and 23.2% yield. These experimental results and original process simulations of an OCM chemical looping system for C2 or liquid fuel production with electricity cogeneration present a direct method for methane utilization.
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► Successful long term (>230h) demonstration of 25-kWth CDCL sub-pilot unit. ► Demonstrated recyclability of oxygen carrier in the sub-pilot unit operation. ► 97% Sub-bituminous coal ...conversion. ► >99% CO2 purity in reducer. ► No needs for solid recirculation device and additional carbon separation unit such as carbon stripper.
The Coal-Direct Chemical Looping (CDCL) process using iron-based oxygen carriers has been developed as a coal conversion process with in situ CO2 capture. The CDCL system cycles oxygen carriers between two reactors, a reducer reactor and a combustor reactor, in order to convert coal for electric power generation. The reducer reactor features a unique design of a gas–solid counter-current moving bed configuration to achieve the reduction of Fe2O3 particles to a mixture of Fe and FeO while converting the coal into CO2 and steam. The combustor reactor is a fluidized bed that oxidizes the reduced particles back to Fe2O3 with air. The oxidation of iron is an exothermic reaction and the heat can be recovered for electricity generation. In the riser, the particles are pneumatically transported back to the reducer. An integrated 25-kWth CDCL sub-pilot plant has been constructed and demonstrated, which is the first integrated chemical looping demonstration unit for the direct conversion of solid fuel with a circulating moving bed system. The design and operation experience of the 25kWth CDCL sub-pilot unit are reported in this paper. Specifically, the design criteria and operation conditions of the CDCL reactor system are first discussed which is followed by the construction of the sub-pilot unit. The tests with metallurgical coke and sub-bituminous coal resulted in 81% and 97% carbon conversions, respectively. Both tests yielded CO2 purity greater than 99%, indicating the complete oxidation of volatile gases in the moving bed reducer. The gas analyses from the combustor outlet demonstrated a proper regeneration of oxygen carriers. A low CO2 concentration in the combustor also confirms that there was no unconverted carbon transfer to the combustor and hence eliminated the need for an additional carbon separation device such as a carbon stripper. The demonstration results from the sub-pilot system substantiate the process concept of the CDCL, which is capable of processing coal continuously with reactor in situ CO2 capture and the cyclic usage of oxygen carriers.
Objective The authors compared the performance of a group of anesthesia providers to closed-loop (Learning Intravenous Resuscitator LIR) management in a simulated hemorrhage scenario using cardiac ...output monitoring. Design A prospective cohort study. Setting In silico simulation. Participants University hospital anesthesiologists and the LIR closed-loop fluid administration system. Interventions Using a patient simulator, a 90-minute simulated hemorrhage protocol was run, which included a 1,200-mL blood loss over 30 minutes. Twenty practicing anesthesiology providers were asked to manage this scenario by providing fluids and vasopressor medication at their discretion. The simulation program was also run 20 times with the LIR closed-loop algorithm managing fluids and an additional 20 times with no intervention. Measurements and Main Results Simulated patient weight, height, heart rate, mean arterial pressure, and cardiac output (CO) were similar at baseline. The mean stroke volume, the mean arterial pressure, CO, and the final CO were higher in the closed-loop group than in the practitioners group, and the coefficient of variance was lower. The closed-loop group received slightly more fluid (2.1 v 1.9 L, p < 0.05) than the anesthesiologist group. Conclusions Despite the roughly similar volumes of fluid given, the closed-loop maintained more stable hemodynamics than the practitioners primarily because the fluid was given earlier in the protocol and CO optimized before the hemorrhage began, whereas practitioners tended to resuscitate well but only after significant hemodynamic change indicated the need. Overall, these data support the potential usefulness of this closed-loop algorithm in clinical settings in which dynamic predictors are not available or applicable.
Sediments from Ocean Drilling Program Site 1165 in the Indian Ocean sector of the Southern Ocean (off Prydz Bay) contain a series of layers that are rich in ice-rafted debris (IRD). Here we present ...evidence that IRD-rich layers at Site 1165 at 7, 4.8, and 3.5
Ma record short-lived, massive discharges of icebergs from Wilkes Land and Adélie Land, more than 1500
kilometers to the east of the depositional site. This distant source of icebergs is clearly defined by the presence of IRD hornblende grains with
40Ar/
39Ar ages of 1200–1100
Ma and 1550–1500
Ma, ages that are not found on the East Antarctic continent in locations closer to Site 1165. This observation requires enormous amounts of detritus-carrying drifting icebergs, most likely in the form of large icebergs. These events probably reflect destabilization, surge, and break-up of ice streams on the Wilkes Land and Adélie Land margins of the East Antarctic Ice Sheet, in the vicinity of the low-lying Aurora and Wilkes Basins. They occurred under warming conditions, but each coast seems to have produced ice-rafting events independently, at different times. The data presented here constitute the first evidence of far-traveled icebergs from specific source areas around the East Antarctic perimeter. Launch of these icebergs may have happened during quite dramatic events, perhaps analogous to “Heinrich Events” in the North Atlantic.
Abstract
Glucocorticoids (GCs) and β
2
-adrenergic receptor (β
2
AR) agonists improve asthma outcomes in most patients. GCs also modulate gene expression in human airway smooth muscle (HASM), thereby ...attenuating airway inflammation and airway hyperresponsiveness that define asthma. Our previous studies showed that the pro-fibrotic cytokine, transforming growth factor- β1 (TGF-β1) increases phosphodiesterase 4D (PDE4D) expression that attenuates agonist-induced levels of intracellular cAMP. Decreased cAMP levels then diminishes β
2
agonist-induced airway relaxation. In the current study, we investigated whether glucocorticoids reverse TGF-β1-effects on β
2
-agonist-induced bronchodilation and modulate
pde4d
gene expression in HASM. Dexamethasone (DEX) reversed TGF-β1 effects on cAMP levels induced by isoproterenol (ISO). TGF-β1 also attenuated G protein-dependent responses to cholera toxin (CTX), a G
αs
stimulator downstream from the β
2
AR receptor. Previously, we demonstrated that TGF-β1 treatment increased β
2
AR phosphorylation to induce hyporesponsiveness to a β
2
agonist. Our current data shows that expression of
grk2/3
, kinases associated with attenuation of β
2
AR function, are not altered with TGF-β1 stimulation. Interestingly, DEX also attenuated TGF-β1-induced
pde4d
gene expression. These data suggest that steroids may be an effective therapy for treatment of asthma patients whose disease is primarily driven by elevated TGF-β1 levels.
The prevalence of nuisance (technical) alarms is the leading cause of alarm fatigue resulting in decreased awareness and a reduction in effective care. The Joint Commission identified in their ...National Patient Safety goals alarm fatigue as a major safety issue. The introduction of noninvasive respiratory volume monitoring (RVM) has implications for effective perioperative respiratory status management. We evaluated this within the Kaiser Permanente health system.
This observational study was conducted at 4 hospitals in the Kaiser Permanente system. Standard data from RVM, pulse oximetry, and capnography were collected postoperatively in the post-anesthesia care unit (PACU) and/or on the general hospital floor. Device-specific alarm types, rates, and respective actions were recorded and analyzed by non-study staff.
RVM was applied to 247 subjects (143 females, body mass index 32.3 ± 8.7 kg/m
, age 60.9 ± 13.9 y) providing 2,321 h. RVM alarms occurred 605 times (0.25 alarms/h); 64% were actionable and addressed, 17% were not addressed, 13% were self-resolved, and only 6% were nuisance. In a subgroup, RVM completed all 127 h of monitoring, whereas oximetry with capnography only completed 51 h with 12.9 alarms/h (73% nuisance). The overall RVM alarm rate was significantly lower than with either pulse oximeters or capnography monitors. We saw a nearly 1,000-fold reduction in nuisance alarms compared to capnography and a 20-50-fold reduction in nuisance alarms compared to pulse oximetry.
Our study indicates that alarm fatigue due to nuisance alarms continues to be a clinical challenge in perioperative settings. Among the 3 common technologies for respiratory function monitoring, RVM had the lowest rate of overall technical alarms and the highest rate of compliance. Furthermore, with early interventions, none of the subjects monitored with RVM suffered any negative outcomes.
Hemodynamic monitoring and optimization improve postoperative outcome during high-risk surgery.However,hemodynamic management practices among Chinese anesthesiologists are largely unknown.This study ...sought to evaluate the current intraoperative hemodynamic management practices for high-risk surgery patients in China.From September 2010 to November 2011,we surveyed anesthesiologists working in the operating rooms of 265 hospitals representing 28 Chinese provinces.All questionnaires were distributed to department chairs of anesthesiology or practicing anesthesiologists.Once completed,the 29-item questionnaires were collected and analyzed.Two hundred and 10 questionnaires from 265 hospitals in China were collected.We found that 91.4%of anesthesiologists monitored invasive arterial pressure,82.9%monitored central venous pressure（CVP）,13.3%monitored cardiac output（CO）,10.5%monitored mixed venous saturation,and less than 2%monitored pulse pressure variation（PPV） or systolic pressure variation（SPV） during high-risk surgery.The majority（88%） of anesthesiologists relied on clinical experience as an indicator for volume expansion and more than 80%relied on blood pressure,CVP and urine output.Anesthesiologists in China do not own enough attention on hemodynamic parameters such as PPV,SPV and CO during fluid management in high-risk surgical patients.The lack of CO monitoring may be attributed largely to the limited access to technologies,the cost of the devices and the lack of education on how to use them.There is a need for improving access to these technologies as well as an opportunity to create guidelines and education for hemodynamic optimization in China.
s
The Nexfin device allows for non-invasive beat-to-beat blood pressure monitoring (BP
NXF
). Perioperative hypotension and hypertension have been shown to be associated with poor clinical outcomes. ...The goal of the present study was to assess the ability of this device to decrease the duration of significant intraoperative hypo- or hypertension compared to standard BP monitoring by cuff (BP
CUFF
). We studied25 patients (ASA I–III) undergoing either abdominal or orthopedic surgery. BP
CUFF
was monitored every 5 min from the introduction of anesthesia, while BP
NXF
was monitored continuously on the opposite arm. When systolic BP
NXF
(SBP
NXF
) decreased or increased more than 20% relative to baseline SBP
NXF
, a standard BP
CUFF
measurement was taken to compare values. In addition, the time interval between the 20% change in SBP
NXF
and the next scheduled standard SBP
CUFF
measurement was recorded for each event. The mean length of surgery was 3.0 ± 0.3 h. Patients presented with 11 ± 4 episodes of hypotension and 12 ± 4 episodes of hypertension during the surgery. If BP
CUFF
had been used, this would have resulted in 21 ± 7 min of hypotension and 20 ± 10 min of hypertension. If hemodynamic changes seen by SBP
NXF
were appropriately treated, an average of 7 ± 1 min/h of hypotension time, 7 ± 2 min/h of hypertension time and 14 ± 3 min per hour of hypo- or hypertension time may have been identified. The Nexfin BP has the potential to decrease the time of hypotension and hypertension compared to conventional intermittent BP
CUFF
monitoring. Therefore, this device has the potential to positively impact clinical outcomes.
This work discusses some fundamental aspects of chemical looping technology for direct solid fuel conversion, with focus on oxygen carrier material development and reactor engineering. Display ...omitted
► A thermodynamics based analysis for selecting oxygen carrier for direct solid fuel CLC is presented. ► CLC reactor design considerations are discussed with respect to critical parameters. ► CLC reactor configurations with respect to gas–solid contact patterns are analyzed and compared. ► Recent advances in solid fueled CLC systems are summarized with respect to their operation mode and performance efficiency.
Direct solid fuel combustion using the concept of chemical looping is a novel approach projected to have higher energy efficiency than conventional and competing technologies in a carbon-constrained scenario. The concept is first discussed by presenting a thermodynamic analysis on oxygen carrier material selection. Iron-based material is considered as a promising candidate, and its salient features in the context of solid fueled chemical looping combustion (CLC) are introduced. The CLC reactor configurations are compared based on the modes of reducer design and operation, which significantly affects the whole system performance. A brief review on recent experimental studies indicates that initial results for the solid fueled CLC technologies are promising. An optimal reducer configuration that provides effective gas–solid contacting pattern, and the need for favorable thermodynamics of the oxygen carrier medium were identified as the important challenges for an eventual chemical looping combustion with solid fuels commercial scale-demonstration.
Developing mechanistic non-animal testing methods based on the adverse outcome pathway (AOP) framework must incorporate molecular and cellular key events associated with target toxicity. Using data ...from an in vitro assay and chemical structures, we aimed to create a hybrid model to predict hepatotoxicants. We first curated a reference dataset of 869 compounds for hepatotoxicity modeling. Then, we profiled them against PubChem for existing in vitro toxicity data. Of the 2560 resulting assays, we selected the mitochondrial membrane potential (MMP) assay, a high-throughput screening (HTS) tool that can test chemical disruptors for mitochondrial function. Machine learning was applied to develop quantitative structure-activity relationship (QSAR) models with 2536 compounds tested in the MMP assay for screening new compounds. The MMP assay results, including QSAR model outputs, yielded hepatotoxicity predictions for reference set compounds with a Correct Classification Ratio (CCR) of 0.59. The predictivity improved by including 37 structural alerts (CCR = 0.8). We validated our model by testing 37 reference set compounds in human HepG2 hepatoma cells, and reliably predicting them for hepatotoxicity (CCR = 0.79). This study introduces a novel AOP modeling strategy that combines public HTS data, computational modeling, and experimental testing to predict chemical hepatotoxicity.
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•The MMP assay was linked to hepatotoxicity and was selected for model development.•QSAR models filled gaps in MMP data for model development.•The inclusion of structural alerts improved model predictivity.•A hybrid AOP framework was employed to predict a key hepatotoxicity mechanism.•Validation in HepG2 hepatoma cells confirmed the reliability of the model.
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