Development of Kabila rocket: A radioisotope heated thermionic plasma rocket engine

AbstractA new type of plasma rocket engine, the Kabila rocket, using a radioisotope heated thermionic heating chamber instead of a conventional combustion chamber or catalyst bed is introduced and it achieves specific impulses similar to the ones of conventional solid and bipropellant rockets. Curium-244 is chosen as a radioisotope heat source and a thermal reductive layer is also used to obtain precise thermionic emissions. The self-sufficiency principle is applied by simultaneously heating up the emitting material with the radioisotope decay heat and by powering the different valves of the plasma rocket engine with the same radioisotope decay heat using a radioisotope thermoelectric generator. This rocket engine is then benchmarked against a 1N hydrazine thruster configuration operated on one of the Pleiades-HR-1 constellation spacecraft. A maximal specific impulse and power saving of respectively 529s and 32% are achieved with helium as propellant. Its advantages are its power saving capability, high specific impulses and simultaneous ease of storage and restart. It can however be extremely voluminous and potentially hazardous. The Kabila rocket is found to bring great benefits to the existing spacecraft and further research should optimize its geometric characteristics and investigate the physical principals of its operation

Vertical Fiscal Imbalance and Local Fiscal Discipline: Empirical Evidence from China

Using a nationwide city-level panel dataset for China for the years 1999-2009, this paper examines the effects of vertical fiscal imbalances (VFI) on local fiscal discipline, and explicitly explores the institutional conditions under which these effects may take place. We find that higher VFI levels induce fiscal indiscipline by reducing tax effort of local governments. We exploit the unique Chinese fiscal institution of assigning taxing power for local taxes and shared taxes to two separate authorities (i.e., the local tax bureau and the central tax bureau, respectively) in several ways. We show that local governments respond to the presence of the VFI by lowering their tax effort on local taxes, but do not do so for shared taxes. In addition, we show that the (in)disciplining effect of the VFI is not present for extra-budgetary revenues, which reflects the institutional fact that extra-budgetary revenues are not considered for the determination of central fiscal transfers to local governments, thus creating no incentive for local governments to respond in this are

Effect of solvent quality and chain density on normal and frictional forces between electrostatically anchored thermoresponsive diblock copolymer layers

Equilibration in adsorbing polymer systems can be very slow, leading to different physical properties at a given condition depending on the pathway that was used to reach this state. Here we explore this phenomenon using a diblock copolymer consisting of a cationic anchor block and a thermoresponsive block of poly(2-isopropyl-2-oxazoline), PIPOZ. We find that at a given temperature different polymer chain densities at the silica surface are achieved depending on the previous temperature history. We explore how this affects surface and friction forces between such layers using the atomic force microscope colloidal probe technique. The surface forces are purely repulsive at temperaturesPeer reviewe

Role of dimensional crossover on spin-orbit torque efficiency in magnetic insulator thin films

Magnetic insulators (MIs) attract tremendous interest for spintronic applications due to low Gilbert damping and absence of Ohmic loss. Magnetic order of MIs can be manipulated and even switched by spin-orbit torques (SOTs) generated through spin Hall effect and Rashba-Edelstein effect in heavy metal/MI bilayers. SOTs on MIs are more intriguing than magnetic metals since SOTs cannot be transferred to MIs through direct injection of electron spins. Understanding of SOTs on MIs remains elusive, especially how SOTs scale with the film thickness. Here, we observe the critical role of dimensionality on the SOT efficiency by systematically studying the MI layer thickness dependent SOT efficiency in tungsten/thulium iron garnet (W/TmIG) bilayers. We first show that the TmIG thin film evolves from two-dimensional to three-dimensional magnetic phase transitions as the thickness increases, due to the suppression of long-wavelength thermal fluctuation. Then, we report the significant enhancement of the measured SOT efficiency as the thickness increases. We attribute this effect to the increase of the magnetic moment density in concert with the suppression of thermal fluctuations. At last, we demonstrate the current-induced SOT switching in the W/TmIG bilayers with a TmIG thickness up to 15 nm. The switching current density is comparable with those of heavy metal/ferromagnetic metal cases. Our findings shed light on the understanding of SOTs in MIs, which is important for the future development of ultrathin MI-based low-power spintronics

Lubrication synergy: Mixture of hyaluronan and dipalmitoylphosphatidylcholine (DPPC) vesicles

AbstractPhospholipids and hyaluronan have been implied to fulfil important roles in synovial joint lubrication. Since both components are present in synovial fluid, self-assembly structures formed by them should also be present. We demonstrate by small angle X-ray scattering that hyaluronan associates with the outer shell of dipalmitoylphophatidylcholine (DPPC) vesicles in bulk solution. Further, we follow adsorption to silica from mixed hyaluronan/DPPC vesicle solution by Quartz Crystal Microbalance with Dissipation measurements. Atomic Force Microscope imaging visualises the adsorbed layer structure consisting of non-homogeneous phospholipid bilayer with hyaluronan/DPPC aggregates on top. The presence of these aggregates generates a long-range repulsive surface force as two such surfaces are brought together. However, the aggregates are easily deformed, partly rearranged into multilayer structures and partly removed from between the surfaces under high loads. These layers offer very low friction coefficient (<0.01), high load bearing capacity (≈23MPa), and self-healing ability. Surface bound DPPC/hyaluronan aggregates provide a means for accumulation of lubricating DPPC molecules on sliding surfaces

Visible-light-driven coproduction of diesel precursors and hydrogen from lignocellulose-derived methylfurans

Photocatalytic hydrogen production from biomass is a promising alternative to water splitting thanks to the oxidation half-reaction being more facile and its ability to simultaneously produce solar fuels and value-added chemicals. Here, we demonstrate the coproduction of H2 and diesel fuel precursors from lignocellulose-derived methylfurans via acceptorless dehydrogenative C 12C coupling, using a Ru-doped ZnIn2S4 catalyst and driven by visible light. With this chemistry, up to 1.04\u2009g\u2009gcatalyst 121\u2009h 121 of diesel fuel precursors (~41% of which are precursors of branched-chain alkanes) are produced with selectivity higher than 96%, together with 6.0\u2009mmol\u2009gcatalyst 121\u2009h 121 of H2. Subsequent hydrodeoxygenation reactions yield the desired diesel fuels comprising straight- and branched-chain alkanes. We suggest that Ru dopants, substituted in the position of indium ions in the ZnIn2S4 matrix, improve charge separation efficiency, thereby accelerating C 12H activation for the coproduction of H2 and diesel fuel precursors

Photo-generated dinuclear {Eu(II)}2 active sites for selective CO2 reduction in a photosensitizing metal-organic framework

利用太阳光驱动CO2还原不仅可降低大气中CO2浓度，而且可以生成重要的化工原料，是缓解气候变暖和开发新能源的理想途径之一。然而如何制备高效光催化剂将CO2高选择性地转化为高附加值的化学产品极具挑战性。课题组巧妙地将具有催化活性的稀土簇合物与光敏配体组装在一起，合成了具有大孔结构的稀土Eu-Ru(phen)3-MOF催化剂，实现了可见光驱动的CO2到甲酸盐的高效选择性转化。研究表明，该材料光催化生成甲酸盐的反应速率可达到321.9 μmol h−1 mmolMOF−1，这是至今为止报道的光催化还原CO2转化为甲酸盐活性最高的MOFs催化剂。 该项研究工作由博士生闫志浩完成，博士生杜明浩参与部分表征工作；中国科学院大连化学物理研究所金盛烨研究员、刘俊学博士在瞬态光谱表征中给予了支持；我校化学化工学院汪骋教授在数据分析过程中给予大量帮助；理论计算由浙江工业大学庄桂林副教授完成。【Abstract】Photocatalytic reduction of CO2 is a promising approach to achieve solar-to-chemical energy conversion. However, traditional catalysts usually suffer from low efficiency, poor stability, and selectivity. Here we demonstrate that a large porous and stable metal-organic framework featuring dinuclear Eu(Ⅲ)2 clusters as connecting nodes and Ru(phen)3 -derived ligands as linkers is constructed to catalyze visible-light-driven CO2 reduction. Photo-excitation of the metalloligands initiates electron injection into the nodes to generate dinuclear {Eu(Ⅱ)} 2 active sites, which can selectively reduce CO2 to formate in a two-electron process with a remarkable rate of 321.9μmolh −1 mmol MOF −1 . The electron transfer from Ru metalloligands to Eu(Ⅲ)2 catalytic centers are studied via transient absorption and theoretical calculations, shedding light on the photocatalytic mechanism. This work highlights opportunities in photo- generation of highly active lanthanide clusters stabilized in MOFs, which not only enables efficient photocatalysis but also facilitates mechanistic investigation of photo-driven charge separation processes.We are grateful for the financial support from the 973 project (Grant 2014CB845601) of the Ministry of Science and Technology of China, the National Natural Science Foundation of China (Grants no. 21422106, 21673184, 21431005, 21721001, and 21390391) and the Fok Ying Tong Education Foundation (151013). We thank Dr. Wen-Ming Qin and the staffs from the BL17B beamline of National Center for Protein Sciences Shanghai at Shanghai Synchrotron Radiation Facility for assistance during data collection; we also thank Miss Ying-Zi Han for helpful measurement on ESI-MS. We also gratefully acknowledge Mr Xuefu Hu for helpful measurement on time-resolved PL and Miss Rong Chen for her assistance on CV measurement and analysis. 研究工作得到科技部（项目批准号：2014CB845601）、国家自然科学基金委（项目批准号：21422106、21673184、21431005、21721001、21390391）、教育部霍英东基金会青年教师基金（项目批准号：151013）等资助