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Vibration of gas-solid fluidized beds is often used to enable fluidization of cohesive particles; however, it has also been shown to reduce the minimum fluidization velocity (Umf). Here, we show via experiments that vibration can reduce both Umf and the minimum bubbling velocity (Umb) in Geldart Group B and D particles. We observe that Umf is reduced more than Umb, thereby creating a densely packed, bubble-free fluidization state when the superficial gas velocity is in between Umf and Umb. Umf and Umb decrease with increasing vibration frequency and amplitude and the results for Umf and Umb across a variety of vibration conditions could be plotted along a single curve when plotted versus vibration strength, i.e. the ratio of peak vibration acceleration to gravitational acceleration. Changes in Umf and Umb due to vibration are not affected significantly by changing particle density, but in a non-monotonic way by changing particle diameter.

Major challenges in developing implanted neural stimulation devices are the invasiveness, complexity, and cost of the implantation procedure. Here, we report an injectable, nanofibrous 2D flexible hydrogel sheet-based neural stimulation device that can be non-invasively implanted via syringe injection for optoelectrical and biochemical dual stimulation of neuron. Specifically, methacrylated gelatin (GelMA)/alginate hydrogel nanofibers were mechanically reinforced with a poly(lactide-co-ε-caprolactone) (PLCL) core by coaxial electrospinning. The lubricant hydrogel shell enabled not only injectability, but also facile incorporation of functional nanomaterials and bioactives. The nanofibers loaded with photocatatlytic g-C 3N 4/GO nanoparticles were capable of stimulating neural cells via blue light, with a significant 36.3 % enhancement in neurite extension. Meanwhile, the nerve growth factor (NGF) loaded nanofibers supported a sustained release of NGF with well-maintained function to biochemically stimulate neural differentiation. We have demonstrated the capability of an injectable, hydrogel nanofibrous, neural stimulation system to support neural stimulation both optoelectrically and biochemically, which represents crucial early steps in a larger effort to create a minimally invasive system for neural stimulation.

In order to reach the goals of the United Nations Framework Convention on Climate Change, a stepwise reduction of energy related greenhouse gas emissions as well as an increase in the share of renewable energies is necessary. For a successful realization of these changes in energy supply, an integrated view of multiple energy sectors is necessary. The coupling of different energy sectors is seen as an option to achieve the climate goals in a cost-effective way. In this paper, a methodical approach for multi-modal energy system planning and technology impact evaluation is presented. A key feature of the model is a coupled consideration of the sectors electricity, heat, fuel and mobility. The modeling framework enables system planners to optimally plan future investments in a detailed transition pathway of the energy system of a country, considering politically defined climate goals. Based on these calculations, in-depth analyses of energy markets as well as electrical transmission and distribution grids can be performed using the presented optimization models. Energy demands, conversion and storage technologies in households, the Commerce, Trade and Services (CTS) area and the industry are modeled employing a bottom-up modeling approach. The results for the optimal planning of the German energy system until 2050 show that the combination of an increased share of renewable energies and the direct electrification of heat and mobility sectors together with the use of synthetic fuels are the main drivers to achieve the climate goals in a cost-efficient way.

Rapid magnetic resonance imaging is used to investigate the volume, shape and rise velocity of single isolated bubbles injected into incipiently fluidized beds as well as the particle velocity field surrounding these bubbles. The volume of gas injected and particle size are varied to investigate their effects on bubble behavior. Image processing is used to quantify data into plots which can be compared directly with predictions from analytical and numerical models. Results show that more injected gas leaks into the interstitial flow in beds of large particles than beds of small particles because of the higher permeability to gas flow. Bubbles develop from a taller shape with a large wake angle into a wider shape with a smaller wake angle as they develop from a spherical shape to a spherical cap shape as they rise. Bubble rise velocities for fully formed bubbles are consistent with correlations in the literature.

A thermal lattice Boltzmann method has been applied to simulate gas-solid heat transfer in a random assembly of spheres using an immersed moving boundary approach. The numerical data was correlated to propose an expression for the Nusselt number as a function of the Reynolds number and solid volume fraction over a wide range of solid volume fractions ( ϕ = [ 0 , 0.5 ] ) for Reynolds numbers up to 100. It is hoped that the new Nusselt number correlation for gas-solid systems improves the accuracy of Euler-Euler and Euler-Lagrangian simulations of gas-solid heat transfer in packed and fluidized beds.

Chemical Engineering Science, 198, ISSN:0009-2509

We report an experimental evaluation of NH3 oxidation over three types of oxygen carrier materials under conditions relevant for chemical-looping combustion. The active metal and the oxidation state of the oxygen carrier is crucial to NO formation from NH3. Although, the carriers tested were equally efficient in terms of CO oxidation they differed from 0 to 6000 ppm of NO in the off-gas. The nickel based carrier produced the lowest amounts of NO and the manganese based the most. The sensitivity to the oxidation state also differed between the materials. The results stress that NO formation should be consider in the choice of oxygen carrier material as well as in the design of chemical looping-combustion systems.

RNA polymerase (Pol) III is specialized to transcribe short, abundant RNAs, for which it terminates transcription on poly-thymine (dT) stretches on the non-template (NT) strand. When Pol III reaches the termination signal, it pauses and forms the pre-termination complex (PTC). Here, we report cryo-EM structures of the yeast Pol III PTC and complementary functional states at 2.7-3.9 Å resolution. Pol III recognizes the poly-dT termination signal with subunit C128 that forms a hydrogen-bond network with the NT-strand and, thereby, induces pausing. Mutating key interacting residues interferes with transcription termination in vitro, impairs yeast growth, and causes global termination defects in vivo confirming our structural results. Additional cryo-EM analysis reveals that C53-C37, a Pol III subcomplex and key termination factor, participates indirectly in Pol III termination. We propose a mechanistic model of Pol III transcription termination and rationalize why Pol III, unlike Pol I and Pol II, terminates on poly-dT signals.

The catalytic hydrogenation of CO2 to methanol depends significantly on the structures of metal-oxide interfaces. We show that doping a high-valency metal, viz. tungsten, to CeO2 could render improved catalytic activity for the hydrogenation of CO2 on a Cu/CeW0.25Ox catalyst, whilst making it more selective towards methanol than the undoped Cu/CeO2. We experimentally investigated and elucidated the structural-functional relationship of the Cu/CeO2 interface for CO2 hydrogenation. The promotional effects are attributed to the irreversible reduction of Ce4+ to Ce3+ by W-doping, the suppression of the formation of redox-active oxygen vacancies on CeO2, and the activation of the formate pathway for CO2 hydrogenation. This catalyst design strategy differs fundamentally from those commonly used for CeO2-supported catalysts, in which oxygen vacancies with high redox activity are considered desirable., Applied Catalysis B: Environmental, 306, ISSN:1873-3883, ISSN:0926-3373

Rapid magnetic resonance imaging was used to take snapshots of solids volume fraction and particle velocity fields in an incipiently fluidized bed with single bubbles injected under both dry and wet conditions. Under wet conditions, cohesive liquid bridges formed between particles, altering the flow such that bubbles became flatter as compared to dry cases, and in some cases, the bubbles split or disintegrated entirely. The alteration in bubble behavior can be attributed to liquid bridging causing an increased heterogeneity in the roof of the bubble, which decreases the drag force on particles in the roof such that the gas flow through the roof can no longer support the weight of the particles in the roof. Quantification of the change in bubble behavior shows that increasing liquid loading has a much stronger effect on bubble behavior than increasing liquid viscosity, and liquid bridging affects small bubbles more than large bubbles.

Innovative Solutions for Energy Transitions / Edited by Jinyue Yan, Hong-xing Yang, Hailong Li, Xi Chen 10th International Conference on Applied Energy, ICAE2018, Hong Kong, Hong Kong, 22 Aug 2018 - 25 Aug 2018; Amsterdam [u.a.] : Elsevier, Energy Procedia 158, 3482-3487 (2018). doi:10.1016/j.egypro.2019.01.923, Published by Elsevier, Amsterdam [u.a.]

The accurate prediction of the drag force exerted by a fluid on assemblies of particles is critical to simulate key characteristics of gas-solid systems such as the bed expansion in fluidized beds. To this end, a lattice Boltzmann method has been applied to compute the drag force acting on assemblies of cubes for a wide range of Reynolds numbers, Re V = 0 - 200 , and solid volume fractions, ϕ = 0.1 - 0.45 . The numerical data was used to propose a new drag force correlation for assemblies of cubes as a function of the Reynolds number and solid volume fraction. The new drag force correlation is expected to improve the accuracy of Euler-Euler and Euler-Lagrangian simulations of cubic particles.

The development of bifunctional CaO/CuO matrix composites with both high and stable reactivity is a research priority and key for the development of calcium looping integrated with chemical looping combustion (CaL-CLC), a new CO2 capture technology that eliminates the requirement for pure O2 for the regeneration of CaO-based sorbents. In this work, a simple but effective approach was first used, i.e., solution combustion synthesis (SCS), to produce various nanostructured CaO/CuO matrix composites with homogenous elemental distributions. All CaO/CuO matrix composites possessed increased CO2 uptake in the form of self-activation and excellent cyclically stable O2 carrying capacity over as many as 40 reaction cycles. For instance, the final carbonation conversion of CaO-CuO-1-800-30 was 51.3%, approximately 52.7% higher than that of the original material (33.6%). Here, the self-activation phenomenon have been observed for the first time in contrast to the rapid decay in CO2 uptake capacity previously reported, due mainly to the increase of both specific surface area and pore volume. In-situ X-ray diffraction (in-situ XRD) analysis revealed that no side reactions occurred between CaO/CaCO3 and CuO/Cu during the overall process. All of these results make CaO/CuO matrix composites an attractive candidate for CaL-CLC.

Graphical abstract, Highlights • Gold rush in cryo-EM structure determination of challenging transcription complexes. • Initiation complexes of all eukaryotic RNA polymerases have been solved by cryo-EM. • Cryo-EM structures of chromatin modifiers become available at increasing pace., Direct electron detector technology combined with improved imaging processing procedures has dramatically increased the resolution that can be obtained by single-particle cryo-electron microscopy and cryo-electron tomography. These developments — often referred to as the `resolution revolution’ in cryo-EM — have had a profound impact on the structural biology of transcription as they allow the determination of atomic or near-atomic resolution structures of very large, flexible and often transient transcription complexes that in many cases had resisted crystal structure determination for decades. In this review, we will discuss recent advances and breakthroughs in the structural biology of transcription complexes enabled by the revolution in cryo-electron microscopy with particular focus on eukaryotic RNA polymerases and their pre-initiation complexes, but also chromatin remodelers and epigenetic regulators.

Calcium (or carbonate) looping (CaL) is a high-temperature process to capture CO2 from industrial installation using CaO-based materials as the sorbent. A large number of natural and synthetic CaO-based sorbents for CO2 capture have been developed and investigated in the laboratory by cycling the material between a low-temperature carbonation stage and a high-temperature calcination stage. We demonstrate the importance of the exact experimental protocol chosen to transition from the carbonation to the calcination step by varying the CO2 concentration and the heating rate while keeping the conditions during the actual carbonation (650 °C, 15 vol.% CO2) and calcination (950 °C, 80 vol.% CO2) stages constant. The experiments were performed in a thermogravimetric analyser, the equipment most frequently used in investigations of the cyclic CO2 uptake, using a natural limestone as the sorbent. Our results show that the reaction conditions under which the CaCO3 is decomposed to CaO determines the cyclic performance of the sorbent, whereas the effect of the CO2 concentration during the set calcination stage (which usually begins after most of the CaCO3 has been converted to CaO) appears to be insignificant. Higher heating rates facilitate a higher cyclic CO2 uptake because the carbonate phase, known to be prone to sintering, is exposed to higher temperatures for a shorter time. The reaction conditions during the transition period crucially affect the CO2 uptake determined in laboratory tests and hence need to be reported in full detail, yet this is currently hardly the case. Otherwise it is unclear whether differences in the CO2 uptake of different CO2 sorbents are due to modifications of the material or variations in the testing protocol.

Ethylene is an essential building block in the petrochemical industry and it is almost exclusively produced via ethane steam cracking, a well-established albeit highly energy and carbon dioxide intensive process. The oxidative dehydrogenation of ethane is a promising alternative to steam cracking reactions due to its exothermic nature, which decreases the overall energy requirements and carbon footprint. The need of a capital intensive air separation unit for producing oxygen limits its potential for industrial application. The current study investigates an alternative route, i.e. the production of oxygen via chemical looping, where oxygen is released in-situ by suitable oxygen carriers. The chemical looping oxidative dehydrogenation, supported by original experimental data, and the steam cracking processes are simulated with ASPEN Plus®. A comprehensive analysis of the energy requirements and an economic assessment are carried out for both processes. Compared with state-of-the-art ethane steam cracking, the proposed process provides ~28% energy savings per tonnes of ethylene produced and ~21% reduction in the resulting ethylene price. Sensitivity analysis show that the economy of the chemical looping oxidative dehydrogenation process is strongly sensitive to the feedstock price., Renewable and Sustainable Energy Reviews, 149, ISSN:1364-0321

The majority of non-protein-coding RNAs present in eukaryotic cells comprises rRNAs, tRNAs and U6 snRNA that are involved in protein biosynthesis and are synthesized by DNA-dependent-RNA polymerase I and III. The transcription cycle (initiation, elongation and termination) has similar principles in all three nuclear RNA polymerases with specific features that are reflected back in their structures. Recently, owing to the 'resolution revolution' in electron cryo-microscopy, there has been a significant advancement in the understanding of these molecular machines. Here, we highlight the structure-function adaptation in specificity and activity of these molecular machines and present parallels and distinctions between their transcription mechanisms.

Circularized oligonucleotides, or coligos, were previously found to serve as RNA polymerase III (Pol III) templates in vitro and in human tissue culture cells. Here we randomized the 12-nucleotide larger loop (L-loop) of a well characterized coligo and found unexpectedly that in vitro transcription by FLAG-Pol III was not significantly affected. This observation allowed us to test the variable of coligo L-loop size separately from the variable of its sequence. Transcription efficiency increased with L-loop size from 3 to 12 nucleotides of randomized sequence, and the smallest loop forced initiation to move into the stem region. To test further the need for any specific sequence we compared seven nucleotide L-loops composed of random, abasic and abasic-acyclic nucleotides, and all supported transcription by Pol III. Transcription of a series of coligos containing twelve contiguous randomized nucleotides placed at different locations within the coligo structure provided further evidence that the stem-loop junction structure is important for precise initiation. Nearly the same transcript pattern was formed in vitro by Pol III from yeast and human cells. Overall, these experiments support structure, rather than L-loop sequence, as the major determinant of coligo transcription initiation by Pol III.

International audience; Our previous work demonstrated the fabrication of the NiO nanoparticle-nanographitic flake composite through a direct current (DC) electrophoretic deposition (EPD) process. The composite was used as a catalyst layer having a low onset voltage in ethanol electro-oxidation. This paper presents a new catalyst material fabricated through pulsed EPD, which permitted to acquire a higher efficiency of ethanol electro-oxidation when compared to the catalyst layer fabricated by the DC EPD. The reason behind the enhancement of the performances of the catalyst layers fabricated using the pulsed EPD is the selective deposition of low-weight NiO nanoparticles on nanographitic flakes causing a reduction in the deposition of agglomerated NiO nanoparticles and therefore an enhancement in the efficiency of the ethanol electro-oxidation.

Titanium dioxide (TiO2) (nano)particles are produced in large quantities and their potential impacts on ecosystems warrants investigations into their fate after disposal. TiO2 particles released into wastewater are retained by wastewater treatment plants and accumulate in digested sludge, which is increasingly incinerated in industrialized countries. Therefore, we investigated the changes of the Ti-speciation during incineration of as-received sludge and of sludge spiked with anatase (d=20–50 nm) or rutile (d=200–400 nm) using X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM). In the as-received sludge, rutile and anatase were the dominant Ti bearing minerals and both remained unaffected by the anaerobic treatment. During incineration, Ti reacts with hematite to members of the hematite-ilmenite solid solution series (Hem-Ilm). Up to 80% of the Ti spiked as anatase transformed into Hem-Ilm, a distorted 6-fold coordinated Ti (Ti(IV)sulfate) and rutile during incineration. Up to 30% and 60% of rutile transformed into Hem-Ilm and Ti(IV)sulfate represented phases in fly and bottom ash, respectively. Fe and Ti were spatially correlated in ash derived from as-received and anatase spiked sludge, whereas only a thin layer of the spiked rutile reacted with Fe, in line with XAS data. This study highlights the transient nature of nano-Ti species during sewage sludge incineration.

Previous reports, albeit being partially contradictory, have indicated that the alloying of Ni with inexpensive transition metals, e.g. Co or Fe can affect the activity and stability of Ni-based catalysts under dry reforming conditions. In this work we critically assess the catalytic performance of Ni-based bi-metallic catalysts derived via the reduction of perovskite precursors, i.e. LaNi 0.8 M 0.2 O 3 (M = Ni, Co and Fe). In-situ XRD and energy dispersive X-ray spectroscopy techniques were employed to probe metal–metal and metal–support interactions and phase transformations under reactive conditions. Ni–Co was found to be the most active catalyst, whereas Ni–Fe showed no activity. We observed that the addition of Co increases the rate of La 2 O 2 CO 3 formation, which in turn enhances the removal of carbonaceous deposits from neighbouring active sites, thus, leading to a catalyst with an increased stability and activity. The poor activity of Ni–Fe was explained by the encapsulation of active Ni particle by LaFeO 3 .

Monte Carlo particle tracking methods used to model particle motion in inclined rotating cylinders with bulk flow have been reported in the literature. This paper reports some analytic results for the mean squared deviation of axial position in the following special case: the particles are in the rolling mode; the bed surface is flat, with no axial variation of bed depth; the avalanche is instantaneous and of negligible thickness; collisional axial dispersion is ignored; fill = 0.5. Fill = 0.5 means that in every half-rotation of the cylinder every particle will have participated in one and only one avalanche; this simplification allows analytic results to be obtained. The calculations are carried out by relating the number densities of tracer particles in successive cycles of avalanching. In the case of well-mixed avalanches, the model is also developed using a random walk approach. The results confirm predictions obtained from discrete element modelling and Monte Carlo particle tracking simulations, which indicate that the mean squared deviation of axial position can oscillate with time for short enough times.

Chemical looping can provide attractive alternative process routes in which solid oxygen carriers function as lattice oxygen transfer agents, for example for the partial oxidation of methane. We report on the development of a perovskite-based oxygen carrier (La0.85Sr0.15Fe0.95Al0.05O3-δ) that enables the complete conversion of CH4 to a synthesis gas (a mixture of H2 and CO, selectivity > 99 %) through donation of its lattice oxygen (up to 9 wt%) at temperatures > 900 °C. The thermodynamic properties of the oxygen carrier permit its lattice oxygen to be replenished with CO2 or H2O, of which > 94 % is converted into CO or H2, respectively. The potential of this compositionally and structurally flexible oxygen carrier is demonstrated in a continuous experiment lasting more than 45 days (∼ 4050 redox cycles), in which all CH4 (reductant) and all CO2 (oxidant) is converted into a synthesis gas without CO2 contamination., Applied Catalysis B: Environmental, 278, ISSN:1873-3883, ISSN:0926-3373

The thermal lattice Boltzmann method using an immersed moving boundary condition was employed to calculate the particle-to-fluid heat transfer in an assembly of super-quadric cubes. The simulations were performed for Reynolds numbers 1–100 (based on the volume equivalent diameter) and solid volume fractions ϕ = 0.1–0.45. The simulation results show that the Nusselt numbers for assemblies of super-quadric cubes are larger than those for assemblies of spheres, in particular for high solid volume fractions. A relationship between the average Nusselt number and the drag force (Chen & Muller, 2018) for assemblies of cubes was developed. It was found that the average drag force acting on cubes increases faster with increasing solid volume fraction than the average Nusselt number. Defining the Reynolds number and the Nusselt number using the hydraulic diameter of the packing system ( R e h ) and the Sauter diameter of the cube, respectively, the Nusselt number correlation of Chen & Muller (2019), that was proposed for assemblies of spheres, can be applied for assemblies of non-spherical particles. We also demonstrate that the proposed Nusselt number correlation predicts well the heat transfer between a gas and ellipsoidal or cylindrical particles.

Real-time magnetic resonance imaging was used to study the different flow regimes which occur in a fluidized bed containing a gas injection system. The gas flow rates through the main distributor and a central orifice were varied independently. We identified six different regimes of bubbling and jetting behavior: (1) freely bubbling, (2) permanent jet, (3) spouting, (4) pulsating jet, (5) pulsating jet with bubble collapse and (6) pulsating jet and freely bubbling. While regimes (1–4) have been described previously in the literature, regimes (5) and (6) are described here for the first time. To construct a regime map, the Froude number (Fr) and the ratio of the superficial gas velocity to the minimum fluidization velocity (U/Umf) were used to describe the system. We observed that bubbles formed predominantly, when U/Umf > 1. Further, we propose an empirical model that predicts the length of jets in the permanent jet regime as a function of Fr and background gas flow as l jet d or = 0.12 Fr 0.38 1 + U bg U mf 0.81 . The proposed model is in good agreement with tomographic measurements in smaller 3D systems reported in the literature, indicating that the non-dimensionalized description of jet length using a Fr number is valid throughout a large range of system diameters. Moreover, the bubble breakoff frequency of the pulsating jet regime was assessed by Fourier analysis, demonstrating that the frequency increases with increasing Fr before plateauing.

Trithorax histone methyltransferase Ash1/ASH1L is tightly regulated because it activates developmental gene transcription and counteracts Polycomb silencing. In this issue of Structure, Lee et al. (2019) and Hou et al. (2019) report the crystal structure of ASH1L bound to its activator MRG15 and suggest a mechanism that releases ASH1L auto-inhibition.

Transcription factors (TFs) are thought to function with partners to achieve specificity and precise quantitative outputs. In the developing heart, heterotypic TF interactions, such as between the T-box TF TBX5 and the homeodomain TF NKX2-5, have been proposed as a mechanism for human congenital heart defects. We report extensive and complex interdependent genomic occupancy of TBX5, NKX2-5, and the zinc finger TF GATA4, coordinately controlling cardiac gene expression, differentiation, and morphogenesis. Interdependent binding serves not only to co-regulate gene expression, but also to prevent TFs from distributing to ectopic loci and activate lineage-inappropriate genes. We define preferential motif arrangements for TBX5 and NKX2-5 cooperative binding sites, supported at the atomic level by their co-crystal structure bound to DNA, revealing direct interaction between the two factors, and induced DNA bending. Complex interdependent binding mechanisms reveal tightly regulated TF genomic distribution and define a combinatorial logic for heterotypic TF regulation of differentiation.

This study reports the technical performance of an advanced configuration of the calcium looping (Ca-looping) process, called Ca-Cu looping, for the reduction of CO2 emissions from a subcritical CFB power plant with a net output of 250 MWe. In this new process concept, the thermal power requirement in the calciner is satisfied using a chemical looping combustion cycle. Thus, the power consumption associated with the air separation unit that is required in the conventional Ca-looping process scheme can be eliminated. The reference power plant has also been modified to integrate oxy-combustion, Ca-looping and amine scrubbing technologies for comparison. The fully integrated process flowsheets have been simulated using Honeywell's UniSim Design Suit R400. For a more accurate prediction of the CO2 capture efficiency in the carbonator of the Ca-Cu looping process, the experimentally obtained cyclic activity of a novel copper-functionalised, calcium-based composite sorbent has been implemented yielding a rigorous carbonator model. The process simulations also include a comprehensive analysis of the CO2 compression and purification unit as well as a heat exchanger network optimized using pinch analysis for the recovery of excess heat from the high temperature gas and solid streams available in the Ca-looping and Ca-Cu looping processes. Compared to the energy penalty of 10.5 percentage points for a conventional amine scrubbing configuration, the Ca-Cu looping process evaluated in this study achieves the same overall CO2 capture efficiency with a significantly reduced energy penalty of 3.5 percentage points; the lowest value for all CO2 capture architectures assessed here. (C) 2015 Elsevier Ltd. All rights reserved.

A fundamental understanding of the underlying physics of granular (particulate) systems is not only of academic interest, but is also highly relevant for industrial applications. Nowadays computational techniques, e.g. the discrete element method (DEM), are frequently applied as a tool to probe the behaviour of granular systems. The DEM is a particularly attractive modelling technique since it can provide both macroscopic and microscopic ‘measurements’ in granular systems and allows particles of non-spherical shape to be modelled. This ability is important since there is a common understanding that particle shape has a strong influence on the dynamics of these systems. Here, we critically review recent developments in DEM to model particles of non-spherical shape. The first section of the review is concerned with advances in the formulation and implementation of non-spherical particle models, including shape representation, algorithms for the efficient detection of contacts and the determination of contact parameters. In the second part, we review the main findings obtained from numerical ‘measurements’ in granular systems containing non-spherical particles using the DEM. The systems covered in this review include the packing of particles, particle flow (e.g. plane shear flow, the discharge of particles from hoppers and particle motion in vibrated beds and rotating cylinders) and two-phase particle flows such as gas–solid fluidized beds and pneumatic conveying. We conclude with an outlook highlighting the future research needed to further advance this promising modelling technique.

The lattice Boltzmann method has been used to compute the drag force acting on assemblies of approximately cubic particles constructed from eight spheres for a wide range of Reynolds numbers. Based on the simulation data we propose a new drag force correlation for assemblies of approximately cubic particles. We have compared the drag force obtained with that predicted by the correlation proposed by Beetstra et al. (2007) , originally proposed for spheres, by considering either the drag acting on individual spheres or the drag acting on an approximately cubic particle composed of eight spheres. The comparisons showed that Beetstra׳s correlation cannot predict the system well. The correlation proposed in this paper enables Euler–Euler and Euler–Lagrangian simulations of approximately cubic particles, allowing the influence of the solid volume fraction in these models to be assessed.

SummaryThe small, highly conserved Kti11 alias Dph3 protein encoded by the Kluyveromyces lactis killer toxin insensitive gene KTI11/DPH3 is involved in the diphthamide modification of eukaryotic elongation factor 2 and, together with Kti13, in Elongator-dependent tRNA wobble base modifications, thereby affecting the speed and accuracy of protein biosynthesis through two distinct mechanisms. We have solved the crystal structures of Saccharomyces cerevisiae Kti13 and the Kti11/Kti13 heterodimer at 2.4 and 2.9 Å resolution, respectively, and validated interacting residues through mutational analysis in vitro and in vivo. We show that metal coordination by Kti11 and its heterodimerization with Kti13 are essential for both translational control mechanisms. Our structural and functional analyses identify Kti13 as an additional component of the diphthamide modification pathway and provide insight into the molecular mechanisms that allow the Kti11/Kti13 heterodimer to coregulate two consecutive steps in ribosomal protein synthesis.

In this work we introduce a boundary condition for thermal lattice Boltzmann simulations that contain a Dirichlet boundary condition by bouncing back the non-equilibrium distribution of the energy distribution function. To this end the thermal lattice Boltzmann equation is modified by introducing an additional collision term that takes into account the thermal diffusivity and local solid volume fraction of a lattice (partially) covered by the solid phase. Asymptotic analysis of the boundary condition confirms that it is of second order accuracy. The method is validated using (i) an analytical solution for the Nusselt number correlation of a single sphere in an unbounded stationary fluid and (ii) direct numerical simulations of the heat transfer between a fluid and individual particles.

We report the synthesis of CaO-based, ZrO2-stabilized CO2 sorbents using a sol–gel technique. In addition, the influence of different synthesis parameters, i.e. the calcium precursor, the condensation time and the ratio of Ca2+ to Zr4+ on the morphology and the CO2 uptake of the materials was evaluated. The morphology and the chemical composition of the materials were characterized using X-ray diffraction, N2 physisorption and scanning electron microscopy whereas the CO2 uptake of the materials was determined using a thermogravimetric analyzer and a packed bed reactor. After 90 cycles of the repeated calcination and carbonation reactions, the CO2 uptake of the best sorbent was 0.34 g CO2/g sorbent exceeding the performance of the reference limestone by 160%. The favorable CO2 capture characteristics of the synthetic CO2 sorbent were attributed to the formation of a finely dispersed, high Tammann temperature calcium zirconate framework, which minimized thermal sintering.

Chemical looping with oxygen uncoupling (CLOU) is a novel combustion technology that utilizes the decomposition reaction of an oxygen storage material to combust solid (hydro-)carbonaceous fuels. CuO is an ideal candidate for CLOU owing to its high oxygen uncoupling capacity (∼10 wt.%) and its ability to release oxygen at temperatures relevant for chemical looping combustion (CLC), i.e. 850–1000 °C. Here, we investigate the feasibility of Cu-rich, Al2O3 or MgAl2O4-stabilized oxygen carriers containing 70–90 wt.% CuO for the CLOU process. Al2O3- and MgAl2O4-stabilized oxygen carriers were synthesized using a co-precipitation technique and calcined either at 800 °C or 1000 °C. The CLOU performance of the oxygen carriers was evaluated at 950 °C in a fluidized bed reactor using a N2 atmosphere for the decomposition reaction and a mixture of 10.5 vol.% O2 and 89.5 vol.% N2 for the re-oxidation reaction. It was found that the calcination temperature and the surface area had no significant influence on the oxygen carrying capacity of the synthesized oxygen carriers. The oxygen uncoupling capacity of Al2O3-stabilized oxygen carriers was substantially below the theoretically expected values due to the formation of the mixed oxides CuAl2O4 and CuAlO2. Based on thermo-gravimetric measurements, a reaction pathway for the oxygen release and re-oxidation reactions of Al2O3-stabilized CuO was proposed. On the other hand, no interaction between MgAl2O4 and the active phase, i.e. CuO was observed. As a consequence, MgAl2O4-stabilized oxygen carriers possessed a high oxygen uncoupling capacity very close to the theoretical values. Owing to its stable and high oxygen release capacity, MgAl2O4-supported oxygen carriers containing 80 wt.% CuO were identified as a promising material for CLOU.

The hysteresis in the jet–spout transition in packed beds was systematically investigated using magnetic resonance imaging (MRI) and pressure measurements. Specifically, the hysteresis in the jet height as a function of the orifice velocity was studied as a function of particle type, bed dimension and fill level. In order to compare the hysteresis of different experimental configurations, a hysteresis coefficient h = ( U sf − U ms ) / U sf was introduced. It was observed that an increase in the fill level or the bed dimensions resulted in higher values of h. It was also found that the hysteresis is most pronounced for non-spherical particles, whereas no hysteresis was observed for the most spherical particles when placed in the smallest bed. In addition, pressure measurements were used to explore the relationship between the pressure drop and the jet height.

We report on the development of a bifunctional catalyst (Pt) - oxygen carrier (Fe2O3) that integrates the dry reforming of methane (DRM) into the chemical looping-based production of hydrogen. The material exhibits a high and stable methane conversion (˜ 80%) and hydrogen yield (10.8 mmol/g catalyst-oxygen carrier) with only a small quantity of impurities (CO, CO2

Rapid magnetic resonance imaging (MRI) was used to visualize and quantify the interaction of two bubbles injected into an incipiently fluidized bed. The particle size, bubble sizes and the vertical and horizontal separations between bubbles were varied to understand their effects on bubble behavior. Image analysis quantified the size, shape and position of the bubbles over time. Bubbles were found to either (a) coalesce, (b) influence one another without coalescing or (c) have a collapse of a lower bubble due to influence from the upper bubble. In all cases, the lower bubbles were much more influenced in their rise by the upper bubbles than vice-versa, as lower bubbles accelerated toward the wakes of upper bubbles. Upper bubbles developed spherical cap shapes, while lower bubbles elongated vertically elongated as they rose. The experimental data provided here will serve as excellent benchmarks to challenge the assumptions made in computational and theoretical models.

Summary Ubiquitin C-terminal hydrolase deubiquitinase BAP1 is an essential tumor suppressor involved in cell growth control, DNA damage response, and transcriptional regulation. As part of the Polycomb repression machinery, BAP1 is activated by the deubiquitinase adaptor domain of ASXL1 mediating gene repression by cleaving ubiquitin (Ub) from histone H2A in nucleosomes. The molecular mechanism of BAP1 activation by ASXL1 remains elusive, as no structures are available for either BAP1 or ASXL1. Here, we present the crystal structure of the BAP1 ortholog from Drosophila melanogaster, named Calypso, bound to its activator, ASX, homolog of ASXL1. Based on comparative structural and functional analysis, we propose a model for Ub binding by Calypso/ASX, uncover decisive structural elements responsible for ASX-mediated Calypso activation, and characterize the interaction with ubiquitinated nucleosomes. Our results give molecular insight into Calypso function and its regulation by ASX and provide the opportunity for the rational design of mechanism-based therapeutics to treat human BAP1/ASXL1-related tumors.

The evaluation of research beyond scientific impact is increasingly required, but has not yet been widely applied. One reason is that data necessary for the evaluation of the societal impact of science are often not available in sufficient quantities or suitable form. This paper describes first results from a research project that develops improved documentation to serve evaluation beyond scientific impact. Firstly, we refer to the need to do this, and to the specific challenges for data assessment in this area. Secondly, we describe the concept for documenting achievements of research beyond scientific impact with a research information system that integrates the relevant parts of research proposals and reports. This enables data to be provided without causing additional effort for scientists, and makes them usable for scientists, research funding agencies and research institutions for different purposes, including evaluation. Compatibility of the system with interoperability standards (e.g. CERIF) is also taken into account. The concept is currently being developed and tested from the user perspectives of scientists, research funding agencies and evaluators.

Hydrogen production from natural gas, combined with advanced CO2 capture technologies, such as iron-based chemical looping (CL), is considered in the present work. The processes are compared to the conventional base case, i.e. hydrogen production via natural gas steam reforming (SR) without CO2 capture. The processes are simulated using commercial software (ChemCAD) and evaluated from a technical point of view considering important key performance indicators such as hydrogen thermal output, net electric power, carbon capture rate and specific CO2 emissions. The environmental evaluation is performed using Life Cycle Analysis (LCA) with the following system boundaries considered: i) hydrogen production from natural gas coupled to CO2 capture technologies based on CL, ii) upstream processes such as: extraction and processing of natural gas, ilmenite and catalyst production and iii) downstream processes such as: H2 and CO2 compression, transport and storage. The LCA assessment was carried out using the GaBi6 software. Different environmental impact categories, following here the CML 2001 impact assessment method, were calculated and used to determine the most suitable technology. Sensitivity analyses of the CO2 compression, transport and storage stages were performed in order to examine their effect on the environmental impact categories. ISSN:1876-6102

International audience; Chromosome region maintenance 1/exportin1/Xpo1 (CRM1) associates with the GTPase Ran to mediate the nuclear export of proteins bearing a leucine-rich nuclear export signal (NES). CRM1 consists of helical hairpin HEAT repeats and a C-terminal helical extension (C-extension) that inhibits the binding of NES-bearing cargos. We report the crystal structure and small-angle X-ray scattering analysis of a human CRM1 mutant with enhanced NES-binding activity due to deletion of the C-extension. We show that loss of the C-extension leads to a repositioning of CRM1's C-terminal repeats and to a more extended overall conformation. Normal mode analysis predicts reduced rigidity for the deletion mutant, consistent with an observed decrease in thermal stability. Point mutations that destabilize the C-extension shift CRM1 to the more extended conformation, reduce thermal stability, and enhance NES-binding activity. These findings suggest that an important mechanism by which the C-extension regulates CRM1's cargo-binding affinity is by modulating the conformation and flexibility of its HEAT repeats.

Co-precipitation was employed to synthesize Ca-based, Al 2 O 3 -stabilized sorbents for CO 2 capture. The chemical composition and morphology of the sorbents were characterized using scanning electron microscopy, X-ray diffraction and N 2 adsorption analysis. The cyclic CO 2 uptake of the materials synthesized was studied in a thermo-gravimetric analyzer and compared to limestone. It was found that the calcium precursor and precipitation agent strongly influenced the chemical composition and morphology of the precipitated sorbents and, in turn, their cyclic CO 2 uptake capabilities. The sorbent which was synthesized using Ca(NO 3 ) 2 as the calcium precursor, and precipitated with (NH 4 ) 2 CO 3 at pH 9.7 showed the best cyclic CO 2 uptake capability, viz. 0.36 g CO 2 /g sorbent after 30 cycles of calcination and carbonation, a value which compares favorably to the CO 2 uptake of limestone of 0.20 g CO 2 /g sorbent.

12 p.-5 fig.-2 tab., Saccharomyces cerevisiae τ55, a subunit of the RNA polymerase III-specific general transcription factor TFIIIC, comprises an N-terminal histidine phosphatase domain (τ55-HPD) whose catalytic activity and cellular function is poorly understood. We solved the crystal structures of τ55-HPD and its closely related paralogue Huf and used in silico docking methods to identify phosphoserine- and phosphotyrosine-containing peptides as possible substrates that were subsequently validated using in vitro phosphatase assays. A comparative phosphoproteomic study identified additional phosphopeptides as possible targets that show the involvement of these two phosphatases in the regulation of a variety of cellular functions. Our results identify τ55-HPD and Huf as bona fide protein phosphatases, characterize their substrate specificities, and provide a small set of regulated phosphosite targets in vivo.

The eukaryotic Elongator complex was initially identified in yeast as a RNA polymerase II (Pol II) associated transcription elongation factor, although there is accumulating evidence that its main cellular function is the specific modification of uridines at the wobble base position of tRNAs. Elongator complex is built up by six highly conserved subunits and was shown to be involved in a variety of different cellular activities. Here, we summarize structural and functional information on individual Elongator subunits or subcomplexes. On the basis of homology models of the Elp1, Elp2 and Elp3 subunits and the crystal structure of the Elp456 subcomplex, the role of each subunit in Elongator complex assembly and catalytic activity is discussed.

Discrete element method simulations of super-quadric shaped particles have been performed by describing the particles using either a continuous function representation (CFR) or as an array of discrete points (discrete function representation, DFR). For the DFR, techniques of uniform discretization and adaptive discretization were proposed for spherical and non-spherical particles, respectively. The concept of a ‘contact candidate list’ was put forward to speed up the stage of contact detection. For the CFR, a numerical approach was described to determine the contact point between colliding particles. Points generated through the DFR were used to make the initial guess for the numerical, Newton–Raphson based iterations. The proposed algorithms were employed to model hoppers, horizontal rotating cylinders and vibrated beds. By analyzing the dynamics of these systems the number of discrete points required accurately to describe particles using the DFR was determined. The efficiencies of the DFR and the CFR were measured based on the system of a horizontal rotating cylinder. The characteristics of both modeling approaches in granular simulations were highlighted.

A lattice Boltzmann method is used to model gas-solid reactions where the composition of both the gas and solid phase changes with time, while the boundary between phases remains fixed. The flow of the bulk gas phase is treated using a multiple relaxation time MRT D3Q19 model; the dilute reactant is treated as a passive scalar using a single relaxation time BGK D3Q7 model with distinct inter- and intraparticle diffusivities. A first-order reaction is incorporated by modifying the method of Sullivan et al. [13] to include the conversion of a solid reactant. The detailed computational model is able to capture the multiscale physics encountered in reactor systems. Specifically, the model reproduced steady state analytical solutions for the reaction of a porous catalyst sphere (pore scale) and empirical solutions for mass transfer to the surface of a sphere at Re=10 (particle scale). Excellent quantitative agreement between the model and experiments for the transient reduction of a single, porous sphere of Fe"2O"3 to Fe"3O"4 in CO at 1023K and 10^5Pa is demonstrated. Model solutions for the reduction of a packed bed of Fe"2O"3 (reactor scale) at identical conditions approached those of experiments after 25 s, but required prohibitively long processor times. The presented lattice Boltzmann model resolved successfully mass transport at the pore, particle and reactor scales and highlights the relevance of LB methods for modelling convection, diffusion and reaction physics.