Aluminum. II. Derivation of C v0from C p and comparison to C v0 calculated from anharmonic models

The specific heat at constant pressure, C _p, of aluminum measured by Ditmars, Plint, and Shukla has been reduced to the volume V ₀ appropriate for 0 K employing the Murnaghan equation. The C _v0 thus obtained is compared with the theoretical C _v0 calculated in the harmonic and the lowest-order anharmonic approximation from three different pseudopotentials (Harrison, Ashcroft, and Dagens-Rasolt-Taylor) as well as a phenomenological Morse potential. The higher-order ( ⁴) anharmonic contributions are calculated from the same nearest-neighbor Morse potential as in the lowest-order anharmonic theory. The role of the vacancy and the higher-order anharmonic contributions to C _v0 has been examined and we conclude that the ⁴ contributions to C _v0 are much smaller than the vacancy contribution. After removal of the vacancy contribution, the reduced C _v0 is found to be in excellent agreement with the Ashcroft and Harrison pseudopotentials as well as the Morse potential including the ² and ⁴ contributions to C _v0.     

Photovoltaic effect and carrier transport mechanisms in Hg1-Mnxtdiodes

Hg_1-xMn_xTe semiconducting semimagnetic alloy has been examined in the context of its possible applications in infrared detectors. For analysis of detector properties the intrinsic carrier concentration has been calculated as a function of temperature and crystal composition. The starting material was In-doped Hg_1-xMn_xTe grown by the modified Bridgman method. The as-grown crystals with manganese content of 12-19% were p-type with carrier concentration and mobility of 100 cm²/ Vs at 77 K. An-type layer was formed on the surface by the annealing process in saturated Hg-vapour at 270-320° for 2 hrs. Capacitance-voltage curves have C^-3 dependence on applied voltage indicating that the junction is linearly graded. From standard electrical measurements and spectral characteristics the main detector parameters were determined and compared to those of Hg_1-xCd_xTe devices. The influence of material properties on detector parameters was analyzed. In order to estimate the carrier transport mechanisms, differential resistivities and current-voltage curves were measured over a wide range of temperaturesi.e. 25 to 300 K. From the temperature dependence of the R₀A product, it was established that at high temperatures (150-300 K) the carrier transport is dominated by a recombination-generation mechanism. In low temperature region the excess current at forward bias is probably attributed to carrier tunneling via energy states distributed randomly within the forbidden gap. At reverse bias the leakage surface or volume currents dominate in the carrier transport.     

Accurate Receptor-Ligand Binding Free Energies from Fast QM Conformational Chemical Space Sampling

Small molecule receptor-binding is dominated by weak, non-covalent interactions such as van-der-Waals hydrogen bonding or electrostatics. Calculating these non-covalent ligand-receptor interactions is a challenge to computational means in terms of accuracy and efficacy since the ligand may bind in a number of thermally accessible conformations. The conformational rotamer ensemble sampling tool (CREST) uses an iterative scheme to efficiently sample the conformational space and calculates energies using the semi-empirical ‘Geometry, Frequency, Noncovalent, eXtended Tight Binding’ (GFN2-xTB) method. This combined approach is applied to blind predictions of the modes and free energies of binding for a set of 10 drug molecule ligands to the cucurbit[n]urils CB[8] receptor from the recent ‘Statistical Assessment of the Modeling of Proteins and Ligands’ (SAMPL) challenge including morphine, hydromorphine, cocaine, fentanyl, and ketamine. For each system, the conformational space was sufficiently sampled for the free ligand and the ligand-receptor complexes using the quantum chemical Hamiltonian. A multitude of structures makes up the final conformer-rotamer ensemble, for which then free energies of binding are calculated. For those large and complex molecules, the results are in good agreement with experimental values with a mean error of 3 kcal/mol. The GFN2-xTB energies of binding are validated by advanced density functional theory calculations and found to be in good agreement. The efficacy of the automated QM sampling workflow allows the extension towards other complex molecular interaction scenarios.     

高水头泄水建筑物侧墙掺气减蚀特性研究

工程中通常采用强迫掺气减蚀措施,防止泄水建筑物在高速水流作用下发生空蚀破坏,但在保护过流面底板的同时,忽视了对其侧墙的保护。为了减免位于高流速区域和低压区域侧墙发生空化空蚀,消除侧墙清水区,采用理论分析和物理模型试验研究方法,对龙抬头明流泄洪洞下游边墙掺气减蚀进行了研究,提出了在反弧末端加折流器（突扩）和突跌掺气方式。结果表明,采用突扩和突跌的掺气方式后,侧墙水流的出射角增大,侧空腔畅通,并直接和底空腔相连,有助于掺气坎后水舌的全断面的掺气,对侧墙和底板皆起到了很好的保护作用。     

Simulation study on the gasification process of Ningdong coal with iron-based oxygen carrier

Chemical looping gasification (CLG) of Ningdong coal by using Fe₂O₃ as the oxygen carriers (OCs) was studied, and the gasification characteristics were obtained. A computation fluid dynamics (CFD) model based on Eulerian‐-Lagrangian multiphase framework was established, and a numerical simulation the coal chemical looping gasification processes in fuel reactor (FR) was investigated. In addition, the heterogeneous reactions, homogeneous reactions and Fe₂O₃ oxygen carriers' reduction reactions were considered in the gasification process. The characteristics of gas flow and gasification in the FR were analyzed and it was found that the experiment results were consistent with the simulation values. The results show that when the O/C mole rate was 0.5:1, the gasification temperature was 900 ℃ and the water vapor volume flow rate was 2.2 ml·min^-1, the mole fraction of syngas reached a maximum value of the experimental result and simulation value were 71.5% and 70.2%, respectively. When the O/C mole rate was 0.5:1, the gasification temperature was 900 ℃, and the water vapor volume flow was 1.8 ml·min^-1; the gasification efficiency reached the maximum value was 62.2%, and the maximum carbon conversion rate was 84.0%.     

Deciphering the Binding Interactions between Acinetobacter baumannii ACP and β-ketoacyl ACP Synthase III to Improve Antibiotic Targeting Using NMR Spectroscopy

Fatty acid synthesis is essential for bacterial viability. Thus, fatty acid synthases (FASs) represent effective targets for antibiotics. Nevertheless, multidrug-resistant bacteria, including the human opportunistic bacteria, Acinetobacter baumannii, are emerging threats. Meanwhile, the FAS pathway of A. baumannii is relatively unexplored. Considering that acyl carrier protein (ACP) has an important role in the delivery of fatty acyl intermediates to other FAS enzymes, we elucidated the solution structure of A. baumannii ACP (AbACP) and, using NMR spectroscopy, investigated its interactions with β-ketoacyl ACP synthase III (AbKAS III), which initiates fatty acid elongation. The results show that AbACP comprises four helices, while Ca²⁺ reduces the electrostatic repulsion between acid residues, and the unconserved F47 plays a key role in thermal stability. Moreover, AbACP exhibits flexibility near the hydrophobic cavity entrance from D59 to T65, as well as in the α₁α₂ loop region. Further, F29 and A69 participate in slow exchanges, which may be related to shuttling of the growing acyl chain. Additionally, electrostatic interactions occur between the α₂ and α₃-helix of ACP and AbKAS III, while the hydrophobic interactions through the ACP α₂-helix are seemingly important. Our study provides insights for development of potent antibiotics capable of inhibiting A. baumannii FAS protein–protein interactions.     

Preparation of Iron Filler-Based Photocomposites and Application in 3D Printing

The introduction of metallic fillers to polymers via the photopolymerization approach can endow the composite materials with some unique properties, but the relevant research is still scarce due to the issue of light penetration and inner filter effect. Herein, for the first time the fabrication of photocomposites based on fine iron powder (i.e., a typical kind of metallic filler) is reported in this work. The free radical polymerization of two different acrylate monomers, poly(ethylene glycol) diacrylate and trimethylolpropane triacrylate, is performed in the presence of iron filler under mild conditions (i.e., light emitting diode (LED)@405 nm irradiation at room temperature under air). And the real-time Fourier transform infrared spectroscopy reveals remarkable photopolymerization kinetics of acrylates with high final conversions and fast polymerization rates despite the increasing contents of iron filler in the composites. Interestingly, the 3D printing technique is applied to the iron filler-based composites to produce tridimensional patterns with excellent spatial resolution. This work not only paves the way for the investigation of photocomposites based on metallic fillers through photochemical methods, but also broadens the potential application prospects.     

铈基SCR脱硝催化剂研究进展

近年来铈（Ce）基脱硝催化剂成为低温脱硝领域的研究热点,按载体类型可分为金属氧化物催化剂、二氧化钛载体催化剂、分子筛载体催化剂、活性炭及氧化铝载体催化剂等。按催化剂种类分别介绍了掺杂改性、制备工艺、反应条件等对催化剂性能的影响,并阐述了可能的原因机理。目前,铈基催化剂大多处于实验室阶段,工业化应用尚存在问题,尤其作为低温脱硝催化剂,活性中心堵塞问题更加突出,并且催化剂成本较高。未来可从催化剂制备工艺入手解决催化剂成型问题,以实现工业应用。同时探讨催化剂中毒机理,进一步提升其抗中毒能力。另外,寻求适宜的材料与铈掺杂组合,达到高效脱硝和经济效益最大化。     

NiFeAlO4载氧体制备及煤化学链燃烧反应特性

铁基载氧体是一种具有工业应用前景的载氧体,但存在氧利用率低、在高温下易烧结等问题。虽可通过制备双金属复合载氧体或添加惰性组分改进其性能,但均存在一定缺陷。若将活性组分和惰性材料融入到一个晶体结构制备尖晶石结构载氧体,则可实现利用双金属协同作用提高载氧体活性的同时,利用Al3+提高载氧体的稳定性。采用共沉淀法和溶胶凝胶法制备了具有尖晶石结构的NiFeAlO₄载氧体,考察了制备方法、载氧体与煤质量比对NiFeAlO₄载氧体化学链燃烧特性和循环稳定性的影响,并分析了载氧体对煤转化过程的作用。结果表明,溶胶凝胶法制备的NiFeAlO₄载氧体具有更好的反应性,载氧体与煤质量比为20∶1时,碳转化率为86.7%,远高于煤单独热解时的碳转化率(34%),此时CO₂体积分数为93.6%。对反应前后NiFeAlO₄载氧体晶相结构和形貌进行分析,表明循环过程中经“还原-氧化”后生成的NiO和载氧体颗粒团聚是导致载氧体活性下降的主要原因。相较于载热作用,NiFeAlO₄载氧体在煤化学链燃烧中主要起供氧作用,其不仅会促进挥发分向煤气的转化,且NiFeAlO₄载氧体与焦炭之间也存在固-固反应,利于更多CO₂的生成。