A comprehensive CFD (Computational Fluid Dynamics) model using the MP-PIC (Multiphase Particle-In-Cell) method was developed to simulate a pilot-scale (6 tons/day, 1 MW th) dual fluidized-bed biomass ...gasification system. In this model the particulate phase was described with the blended acceleration model. The momentum, mass, and energy transport equations were integrated with the kinetics of heterogeneous biomass and char reactions and homogeneous gas-phase reactions to predict the particle circulation, producer gas composition, and reactor temperature. The simulation results were compared with experimental data from the pilot-scale gasification system to validate the model at different operating conditions. Parametric studies were conducted to investigate the impact of gasifier temperature, steam to biomass ratio (S/B), and air supply to the combustor on the producer gas composition. The studies showed that increasing gasifier temperature and steam to biomass ratio (S/B) promoted syngas (CO + H2) production and increased hydrogen content in producer gas. The effect of air supply was minor, because for the dual fluidized-bed system air was not directly involved in biomass gasification.
•CFD modeling of dual fluidized-bed biomass gasification.•The particle circulation in the dual fluidized-bed system.•The gas species distribution in the dual fluidized-bed system.•The Effect of gasifier temperature, steam to biomass ratio, and air supply to the combustor.
Ni-Fe-Mg catalyst showed much higher tar conversion activity in producer gas mixture as compared with Ni-K-Mg reference catalyst.
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•The elemental composition of Ni-Fe-Mg catalysts were ...optimized to achieve high tar conversion activity in producer gas.•Catalytic tar decomposition activity was nearly 100% with almost no deactivation for at least 48 h.•MgO was found as the best promoter as compared with other alkaline earth promoters like CaO, BaO and SrO.•The role of Fe seems to have improved the coke resistance of the Ni catalyst by forming FeNi3 alloy.•This catalyst was superior as compared with standard Ni-K-Mg based reference catalyst.
A Ni-Fe-Mg material, supported on a ceramic substrate, suitable for application in a gasifier or reforming reactor was evaluated as a catalyst for tar decomposition via steam reforming. Experiments were conducted in a laboratory-scale fixed-bed reactor using simulated producer gas containing toluene and ethylene as tar surrogates. The catalyst was prepared by wet-impregnation and characterized by analytical techniques to include: BET, XRD, TPR, and SEM. The elemental composition of Ni, Fe, and MgO was optimized for maximum activity and stability. The optimized catalyst composition contained Ni, Fe, and MgO in the ratio 45:21:34 by weight. The observed catalyst activity was superior in comparison to other alkaline earth metal promoters: CaO, SrO, and BaO as well as a reference catalyst, Ni-K-MgO, in the temperature range between 600 and 800 °C. Time on stream with the optimized composition showed sustained tar (toluene + ethylene) conversion of near 100% at 750 °C for at least 48 h, indicating no coke formation. The coke formation affinity of Ni was reduced by the presence of the FeNi3 alloy. The enhanced performance with MgO is attributed to the strong adsorption of H2O forming Mg(OH)2 species facilitated on the oxide ion vacancy site of MgO acting as oxygen exchange site.
The solids circulation is crucial for sustaining biomass gasification within dual fluidized-bed gasification systems, because the heat utilization between the gasifier and combustor is mainly ...implemented through the circulation of bed material. In this work, a three-dimensional model was established to simulate the hydrodynamics of a dual fluidized-bed gasification system. The purpose of this work was to find effective ways to improve the solids circulation. In this CFD (computational fluid dynamics) model, the MP-PIC (multiphase particle-in-cell) method was applied to simulate the gas-solid flows in the dual fluidized-bed system. This model simulated the hydrodynamics of the bubbling fluidized-bed gasifier, chute, pneumatic-riser combustor, cyclone separator, and loop-seal in the dual fluidized-bed system. Studies of grid resolution and numerical parcel were conducted to examine the model accuracy. A series of case studies were implemented to investigate the impact of operating parameters on the solids circulation rate, such as particle diameter, solid inventory, steam supply to gasifier, and air supplies to combustor.
•The solids circulation of a dual fluidized-bed system is investigated in a CFD model.•Particle diameter has the strongest impact on the solids circulation.•The impact of the 1st and 2nd air supplies on the solids circulation is significant.•The increments of steam and solid inventory can enhance the solids circulation.
•CFD simulation of biomass gasification in a dual fluidized-bed.•The CFD model predicts the gas composition and the reactor temperature distribution.•The CFD model has been validated by experimental ...data.•The effects of the particle size distribution and drag models have been investigated.
A three-dimensional CFD model was developed to simulate the full-loop of a dual fluidized-bed biomass gasification system consisting of a gasifier, a combustor, a cyclone separator, and a loop-seal. This full-loop simulation includes the chemical kinetic modeling of biomass drying and pyrolysis, heterogeneous char reactions, and homogeneous gas-phase reactions. In the model, the gas phase is described using Large Eddy Simulation (LES) and the particle phase is described with the Multiphase Particle-In-Cell (MP-PIC) method. The simulation was performed using the GPU-accelerated computing and the simulation results were compared with the gas composition and temperature measurements from a pilot-scale biomass gasification power plant (1MWth, 6tonsbiomass/day). The independence of the accuracy of the model on mesh resolution and computational particle number was determined. The impacts of the particle size distributions (PSD) and drag models on the reactive flows were also investigated.
Rod and cone photoreceptors support vision across large light intensity ranges. Rods, active under dim illumination, are thought to saturate at higher (photopic) irradiances. The extent of rod ...saturation is not well defined; some studies report rod activity well into the photopic range. Using electrophysiological recordings from retina and dorsal lateral geniculate nucleus of cone-deficient and visually intact mice, we describe stimulus and physiological factors that influence photopic rod-driven responses. We find that rod contrast sensitivity is initially strongly reduced at high irradiances, but progressively recovers to allow responses to moderate contrast stimuli. Surprisingly, rods recover faster at higher light levels. A model of rod phototransduction suggests that phototransduction gain adjustments and bleaching adaptation underlie rod recovery. Consistently, exogenous chromophore reduces rod responses at bright background. Thus, bleaching adaptation renders mouse rods responsive to modest contrast at any irradiance. Paradoxically, raising irradiance across the photopic range increases the robustness of rod responses.
To our knowledge, the Oral Ponesimod Versus Teriflunomide In Relapsing Multiple Sclerosis (OPTIMUM) trial is the first phase 3 study comparing 2 oral disease-modifying therapies for relapsing ...multiple sclerosis (RMS).
To compare the efficacy of ponesimod, a selective sphingosine-1-phosphate receptor 1 (S1P1) modulator with teriflunomide, a pyrimidine synthesis inhibitor, approved for the treatment of patients with RMS.
This multicenter, double-blind, active-comparator, superiority randomized clinical trial enrolled patients from April 27, 2015, to May 16, 2019, who were aged 18 to 55 years and had been diagnosed with multiple sclerosis per 2010 McDonald criteria, with a relapsing course from the onset, Expanded Disability Status Scale (EDSS) scores of 0 to 5.5, and recent clinical or magnetic resonance imaging disease activity.
Patients were randomized (1:1) to 20 mg of ponesimod or 14 mg of teriflunomide once daily and the placebo for 108 weeks, with a 14-day gradual up-titration of ponesimod starting at 2 mg to mitigate first-dose cardiac effects of S1P1 modulators and a follow-up period of 30 days.
The primary end point was the annualized relapse rate. The secondary end points were the changes in symptom domain of Fatigue Symptom and Impact Questionnaire-Relapsing Multiple Sclerosis (FSIQ-RMS) at week 108, the number of combined unique active lesions per year on magnetic resonance imaging, and time to 12-week and 24-week confirmed disability accumulation. Safety and tolerability were assessed. Exploratory end points included the percentage change in brain volume and no evidence of disease activity (NEDA-3 and NEDA-4) status.
For 1133 patients (567 receiving ponesimod and 566 receiving teriflunomide; median range, 37.0 18-55 years; 735 women 64.9%), the relative rate reduction for ponesimod vs teriflunomide in the annualized relapse rate was 30.5% (0.202 vs 0.290; P < .001); the mean difference in FSIQ-RMS, -3.57 (-0.01 vs 3.56; P < .001); the relative risk reduction in combined unique active lesions per year, 56% (1.405 vs 3.164; P < .001); and the reduction in time to 12-week and 24-week confirmed disability accumulation risk estimates, 17% (10.1% vs 12.4%; P = .29) and 16% (8.1% vs 9.9; P = .37), respectively. Brain volume loss at week 108 was lower by 0.34% (-0.91% vs -1.25%; P < .001); the odds ratio for NEDA-3 achievement was 1.70 (25.0% vs 16.4%; P < .001). Incidence of treatment-emergent adverse events (502 of 565 88.8% vs 499 of 566 88.2%) and serious treatment-emergent adverse events (49 8.7% vs 46 8.1%) was similar for both groups. Treatment discontinuations because of adverse events was more common in the ponesimod group (49 of 565 8.7% vs 34 of 566 6.0%).
In this study, ponesimod was superior to teriflunomide on annualized relapse rate reduction, fatigue, magnetic resonance imaging activity, brain volume loss, and no evidence of disease activity status, but not confirmed disability accumulation. The safety profile was in line with the previous safety observations with ponesimod and the known profile of other S1P receptor modulators.
ClinicalTrials.gov Identifier: NCT02425644.
Members of the genus Tetrasphaera are considered to be putative polyphosphate accumulating organisms (PAOs) in enhanced biological phosphorus removal (EBPR) from wastewater. Although abundant in ...Danish full-scale wastewater EBPR plants, how similar their ecophysiology is to 'Candidatus Accumulibacter phosphatis' is unclear, although they may occupy different ecological niches in EBPR communities. The genomes of four Tetrasphaera isolates (T. australiensis, T. japonica, T. elongata and T. jenkinsii) were sequenced and annotated, and the data used to construct metabolic models. These models incorporate central aspects of carbon and phosphorus metabolism critical to understanding their behavior under the alternating anaerobic/aerobic conditions encountered in EBPR systems. Key features of these metabolic pathways were investigated in pure cultures, although poor growth limited their analyses to T. japonica and T. elongata. Based on the models, we propose that under anaerobic conditions the Tetrasphaera-related PAOs take up glucose and ferment this to succinate and other components. They also synthesize glycogen as a storage polymer, using energy generated from the degradation of stored polyphosphate and substrate fermentation. During the aerobic phase, the stored glycogen is catabolized to provide energy for growth and to replenish the intracellular polyphosphate reserves needed for subsequent anaerobic metabolism. They are also able to denitrify. This physiology is markedly different to that displayed by 'Candidatus Accumulibacter phosphatis', and reveals Tetrasphaera populations to be unusual and physiologically versatile PAOs carrying out denitrification, fermentation and polyphosphate accumulation.
Drug resistance is a challenge for the global control of tuberculosis. We examined mortality in patients with tuberculosis from high-burden countries, according to concordance or discordance of ...results from drug susceptibility testing done locally and in a reference laboratory.
This multicentre cohort study was done in Côte d'Ivoire, Democratic Republic of the Congo, Kenya, Nigeria, South Africa, Peru, and Thailand. We collected Mycobacterium tuberculosis isolates and clinical data from adult patients aged 16 years or older. Patients were stratified by HIV status and tuberculosis drug resistance. Molecular or phenotypic drug susceptibility testing was done locally and at the Swiss National Center for Mycobacteria, Zurich, Switzerland. We examined mortality during treatment according to drug susceptibility test results and treatment adequacy in multivariable logistic regression models adjusting for sex, age, sputum microscopy, and HIV status.
We obtained M tuberculosis isolates from 871 patients diagnosed between 2013 and 2016. After exclusion of 237 patients, 634 patients with tuberculosis were included in this analysis; the median age was 33·2 years (IQR 26·9–42·5), 239 (38%) were women, 272 (43%) were HIV-positive, and 69 (11%) patients died. Based on the reference laboratory drug susceptibility test, 394 (62%) strains were pan-susceptible, 45 (7%) monoresistant, 163 (26%) multidrug-resistant (MDR), and 30 (5%) had pre-extensively or extensively drug resistant (pre-XDR or XDR) tuberculosis. Results of reference and local laboratories were concordant for 513 (81%) of 634 patients and discordant for 121 (19%) of 634. Overall, sensitivity to detect any resistance was 90·8% (95% CI 86·5–94·2) and specificity 84·3% (80·3–87·7). Mortality ranged from 6% (20 of 336) in patients with pan-susceptible tuberculosis treated according to WHO guidelines to 57% (eight of 14) in patients with resistant strains who were under-treated. In logistic regression models, compared with concordant drug susceptibility test results, the adjusted odds ratio of death was 7·33 (95% CI 2·70–19·95) for patients with discordant results potentially leading to under-treatment.
Inaccurate drug susceptibility testing by comparison with a reference standard leads to under-treatment of drug-resistant tuberculosis and increased mortality. Rapid molecular drug susceptibility test of first-line and second-line drugs at diagnosis is required to improve outcomes in patients with MDR tuberculosis and pre-XDR or XDR tuberculosis.
National Institutes of Allergy and Infectious Diseases, Swiss National Science Foundation, Swiss National Center for Mycobacteria.
How complex networks of activators and repressors lead to exquisitely specific cell-type determination during development is poorly understood. In the
Drosophila eye, expression patterns of ...Rhodopsins define at least eight functionally distinct though related subtypes of photoreceptors. Here, we describe a role for the transcription factor gene
defective proventriculus (
dve) as a critical node in the network regulating Rhodopsin expression.
dve is a shared component of two opposing, interlocked feedforward loops (FFLs). Orthodenticle and Dve interact in an incoherent FFL to repress Rhodopsin expression throughout the eye. In R7 and R8 photoreceptors, a coherent FFL relieves repression by Dve while activating Rhodopsin expression. Therefore, this network uses repression to restrict and combinatorial activation to induce cell-type-specific expression. Furthermore, Dve levels are finely tuned to yield cell-type- and region-specific repression or activation outcomes. This interlocked FFL motif may be a general mechanism to control terminal cell-fate specification.
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► Dve is a key transcription factor in the network regulating Rhodopsins in the fly eye ► Dve is a shared component of two opposing, interlocked feedforward loops (FFLs) ► An incoherent FFL represses expression of Rhodopsins in outer photoreceptors ► A coherent FFL relieves Dve repression and activates Rhodopsins in inner photoreceptors
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