ALBERT

Description: Chemical looping combustion (CLC) is a promising technology for CO 2 capture, with inherent CO 2 separation and low energy consumption. In this study, the reactive multiphase model is incorporated into a computational fluid dynamics code to simulate the reactive fluid dynamics in the CLC reactor with a two-fluid model. The solid friction stress is used to account for the interaction of individual particles with their neighbors through sustained contact at high particle concentrations and the kinetic theory of granular flow is used for closure. Gas-solid flow characteristics and chemical reactions in interconnected fluidized beds using a Cu-based oxygen carrier are simulated. The distributions of solid concentration and gas composition are obtained. The predicted gas compositions at the outlet agree with experimental results. The effects of the operating velocity and the temperature on the combustion efficiencies are also shown. The results demonstrate that a higher bed temperature at a lower operating velocity could enhance the CLC performance. The reactive multiphase model is incorporated into the computational fluid dynamics code to simulate the reactive fluid dynamics in a chemical looping combustion (CLC) reactor with a two-fluid model. This model can recognize the complex gas-solid flow behaviors and chemical reactions in the process of a CLC system.

Description: [1]  We present the evolution of dipolarizations in the near-Earth tail during a substorm on 15 March 2009, based on the two-point measurements in the night-side plasma sheet at X ~ – 8.0 R E . The earthward-moving dipolarization, magnetic flux pileup and then tailward-moving dipolarization were observed. For the 30–200 keV electrons, betatron acceleration was the dominant process, which was caused by the much larger gradient of the magnetic field there during the earthward-moving dipolarization or by a local compression of the magnetic field during the magnetic flux pileup and tailward-moving dipolarization. These near-perpendicular distributions for the 30–200 keV electrons are interpreted as produced by a two-step acceleration: Electrons were first accelerated in the dipolarization fronts in the mid-tail or the near-Earth tail and then were further accelerated near the tail current disruption region. For the more than 200 keV electrons, Fermi acceleration was the dominant process, which was caused by the shrinking length of magnetic field line during the tailward-moving dipolarization. The source region of the more than 200 keV electrons may be near the tail current disruption region, but these electrons were accelerated locally. These field-aligned electrons can precipitate into the ionosphere and form the discrete auroral arcs. Two parallel arcs were clearly observed around the substorm onset: one propagated equatorward, another propagated poleward. We suggest that the earthward-moving dipolarization, magnetic flux pileup and then tailward-moving dipolarization near the tail current disruption region can well explain the auroral evolution around the substorm onset.

Description: The kinetic aspects of the gas-liquid-liquid reactive extraction process for the production of hydrogen peroxide were investigated in a batch reactor. It was observed that the gas-liquid reaction rate is strongly affected by mass transfer of oxygen across the liquid film and the reaction can be simplified to pseudo-first order. The extraction rate is governed by both reaction and liquid-liquid mass transfer, and is slightly lower than the reaction rate. In addition, a kinetic model of the reactive extraction process for the production of hydrogen peroxide was developed. Kinetic parameters under different conditions were determined by experiments. The data calculated from the kinetic model match experimental data well under different conditions for hydrogen peroxide production in gas-liquid-liquid reactive extraction. The kinetic aspects of the gas-liquid-liquid reactive extraction process for the production of hydrogen peroxide were investigated. Analysis of the oxidation of 2-ethylanthrahydro-quinone in the gas-liquid-liquid system indicates that the reaction obeys a pseudo-first order kinetic law.

Description: Phospholipase C-η (PLCη) enzymes are a class of phosphatidylinositol 4,5-bisphosphate-hydrolyzing enzymes involved in intracellular signaling. PLCη2 can sense Ca 2+ (stimulated by ∼1 µM free Ca 2+ ) suggesting that it can amplify transient Ca 2+ signals. PLCη enzymes possess an EF-hand domain composed of two EF-loops; a canonical 12-residue loop (EF-loop 1) and a non-canonical 13-residue loop (EF-loop 2). Ca 2+ -binding to synthetic peptides corresponding to EF-loops 1 and 2 of PLCη2 and EF-loop 1 of calmodulin (as a control) was examined by 2D-[ 1 H, 1 H] TOCSY NMR. Both PLCη2 EF-loop peptides bound Ca 2+ in a similar manner to that of the canonical calmodulin EF-loop 1, particularly at their N-terminus. A molecular model of the PLCη2 EF-hand domain, constructed based upon the structure of calmodulin, suggested both EF-loops may participate in Ca 2+ -binding. To determine whether the EF-hand is responsible for Ca 2+ -sensing, inositol phosphate accumulation was measured in COS7 cells transiently expressing wild-type or mutant PLCη2 proteins. Addition of 70 µM monensin (a Na + /H + antiporter that increases intracellular Ca 2+ ) induced a 4 to 7-fold increase in wild-type PLCη2 activity. In permeabilized cells, PLCη2 exhibited a ∼4-fold increase in activity in the presence of 1 µM free Ca 2+ . The D256A (EF-loop1) mutant exhibited a ∼10-fold reduction in Ca 2+ -sensitivity and was not activated by monensin, highlighting the involvement of EF-loop 1 in Ca 2+ -sensing. Involvement of EF-loop 2 was examined using D292A, H296A, Q297A and E304A mutants. Interestingly, the monensin responses and Ca 2+ -sensitivities were largely unaffected by the mutations, indicating that the non-canonical EF-loop 2 is not involved in Ca 2+ -sensing. J. Cell. Biochem. © 2013 Wiley Periodicals, Inc.

Description: The impact of the circulation shift under climate warming on the distribution of precipitation extremes and the associated sensitivity to model resolution are investigated using Community Atmosphere Model CAM3 in an aquaplanet configuration. The response of the probability density function of the precipitation to a uniform SST warming can be interpreted as superimposition of a dynamically induced poleward shift and a thermodynamically induced upward shift toward higher intensities, which give rise to manyfold increase in the frequency of the most extreme categories of the precipitation events at the poleward side of the midlatitude storm track. Coarser resolutions underestimate not only the intensity of the precipitation extremes but also the dynamical contribution to the increase of precipitation extremes. Meanwhile, the thermodynamic contribution to the intensification of the precipitation extremes is substantially less than expected from the Clausius-Clapeyron relation, implicative of significant change in the vertical structure of the precipitation processes.

Description: Abstract Parameterizations of Fractional Vegetation Cover (FVC) in land surface models have important effects on simulations of surface energy budget, especially in arid and semi‐arid regions. This study uses a FVC scheme in which FVC is derived from leaf area index (LAI) and a remotely sensed Clumping Index. The performance of the new scheme (SMFVC) is evaluated against MODIS land surface temperature and in‐situ soil temperature observations, together with two other FVC schemes, a general FVC scheme (CTL) based on land cover map and a climatology based FVC scheme (RSFVC) that uses long term remotely sensed NDVI of MODIS. The three FVC schemes were implemented in the Common Land Model (CoLM) and applied in the Tibetan Plateau using the same forcing data and default parameters. Our results demonstrate that FVC schemes have significant influence on the CoLM performance: (1) the RSFVC and SMFVC schemes significantly reduce the LST biases found in CTL, particularly in grassland and during summer; (2) soil temperature evaluation by in‐situ observations from three networks on the Tibetan Plateau corroborates the LST results; (3) the improvements are mainly related to representing temporal (seasonal) variability and sub‐grid heterogeneity of FVC, which improves surface albedo and surface energy balance. In other words, by including more vegetation characteristics, such as using a clumping index, LSMs may better simulate surface vegetation condition and further better represent the land surface energy budget over the Tibetan Plateau.

Description: The stability of the immobilized lipase from Candida sp. 99–125 during biodiesel production was investigated. The lipase was separately incubated in the presence of various reaction components such as soybean oil, oleic acid methyl ester, n -hexane, water, methanol, and glycerol, or the lipase was stored at 60, 80, 100 and 120 °C. Thereafter the residual lipase activity was determined by methanolysis reaction. The results showed that the lipase was rather stable in the reaction media, except for methanol and glycerol. The stability study performed in a reciprocal shaker indicated that enzyme desorption from the immobilized lipase mainly contributed to the lipase inactivation in the water system. So the methanol and glycerol contents should be controlled more precisely to avoid lipase inactivation, and the immobilization method should be improved with regard to lipase desorption. The stability of immobilized Candida sp. 99–125 lipase was investigated. The lipase shows excellent stability in the biodiesel reaction medium. Methanol and glycerol showed the most negative effects on the lipase stability. Desorption was the main reason leading to lipase inactivation in the water system.

Description: This paper presents a comprehensive modeling investigation of ionospheric and thermospheric variations during a prompt penetration electric field (PPEF) event that took place on 9 November 2004, using the Thermosphere-Ionosphere-Mesosphere Electrodynamic General Circulation Model (TIMEGCM). The simulation results reveal complex latitudinal and longitudinal/local-time variations in vertical ion drift in the middle- and low-latitude regions owing to the competing influences of electric fields and neutral winds. It is found that electric fields are the dominant driver of vertical ion drift at the magnetic equator; at midlatitudes, however, vertical ion drift driven by disturbance meridional winds exceeds that driven by electric fields. The temporal evolution of the UT-latitude electron density profile from the simulation depicts clearly a super-fountain effect caused by the PPEF, including the initial slow-rise of the equatorial F-layer peak height, the split of the F-layer peak density, and the subsequent downward diffusion of the density peaks along magnetic field lines. Correspondingly, low-latitude total electron content (TEC) becomes bifurcated around the magnetic equator. The O/N2 column density ratio, on the other hand, shows very little variations during this PPEF event, excluding composition change as a potential mechanism for the TEC variations. By using realistic, time-dependent, high-latitude electric potential and auroral precipitation patterns to drive the TIMEGCM, the model is able to successfully reproduce the large vertical ion drift of ∼120 m/s over the Jicamarca incoherent radar (IS) in Peru, which is the largest daytime ion drift ever recorded by the radar. The simulation results are validated with several key observations from IS radars, ground GPS-TEC network, and the TIMED-GUVI O/N2 column density ratio. The model-data intercomparison also reveals some deficiencies in the TIMEGCM, particularly the limitations imposed by its upper boundary height as well as the prescribed O+ flux.

Description: Water resources management, in particular flood control, in the Lancang-Mekong River Basin (LMRB) faces two key challenges in the 21st century: climate change and dam construction. A large scale distributed Geomorphology-Based Hydrological Model coupled with a simple reservoir regulation model (GBHM-LMK-SOP) is used to investigate the relative effects of climate change and dam construction on the flood characteristics in the LMRB. Results suggest an increase in both flood magnitude and frequency under climate change, which is more severe in the upstream basin and increases over time. However, stream regulation by dam reduce flood risk consistently throughout this century, with more obvious effects in the upstream basin where larger reservoirs will be located. The flood mitigation effect of dam regulation dominates over the flood intensification effect of climate change before 2060, but the latter emerges more prominently after 2060 and dominates the flood risk especially in the lower basin.