Acrylamide production in an ultrafiltration-membrane bioreactor using cells of Brevibacterium imperialis CBS 489-74

Both differential and integral UF-membrane reactors were tested for the bioconversion of acrylonitrile into acrylamide. Use was made of the commercially available flat membrane cell Amicon Mod.52 and the UF-membranes FS81PP, GR81PP, and YM100. The enzymatic reaction was catalyzed by the nitrile hydratase (NHase) present in resting cells of Brevibacterium imperialis CBS 489-74. The system was operated at 4°C and 10°C. Acrylonitrile concentration ranged from 50 to 500 mM. The membrane resistance to chemicals was complete at acrylonitrile and acrylamide concentrations up to 800 mM and 2 M, respectively. No rejection of solute was determined. Membranes totally retained the resting cells and no fouling was observed working with 2 and 16 mg of biocatalyst in stirred systems. Membrane compaction was apparently responsible for roughly 35% flux loss during the first 3–4 h of operation. The laboratory scale membrane bioreactor, continuously operating, allowed to show the dependence of enzyme deactivation on acrylonitrile concentration and process time. Substrate concentration higher than 100 mM were highly detrimental for NHase stability. The acrylamide yield reached in the multi-cycle process operating with 5.6 g/l of resting cells was 93.7% and the product concentration during roughly 450 h of bioconversion attained 8.3% (w/v). Decay of specific membrane flux was 98% of the initial value.     

Transition métal—isolant dans V1−xMnxO2−2xF2x (0 < x ≤ 0, 10)e´tude des proprie´te´s structurales,magne´tiques,ete´lectriques

V_1−xMn_xO_2−2xF_2x samples (0 < x ≤ 0, 10) have been prepared by solid state reaction in sealed platinium tubes. The metal ⇄ insulator transition occurs at a quickly decreasing temperatures as MnF₂ increases. The crystallographic, magnetic, transport properties, and DTA have been determined and discussed.     

圆柱形等离子体对微波散射的数值模拟与实验研究

模拟和实验研究了非均匀圆柱形等离子体及阵列对微波的散射作用。利用有限时域差分(FDTD)方法仿真得到了等离子体柱的密度、碰撞频率对微波传播系数的影响,并利用低气压放电产生的等离子体柱对微波的吸收和散射作用进行了验证。结果表明:电子密度中心高、周围低的非均匀等离子体柱可将微波散射至两个侧向;等离子体频率越大,散射的微波功率越强;增加碰撞频率使等离子体柱的微波散射功率减小、吸收增大。等离子体必须具有合适的密度,才能对微波反射产生较大影响。     

Efficient Resonantly-Pumped Tm:Y2O3 Ceramic Laser

Journal of Russian Laser Research - We present an efficient continuous wave Tm:Y2O3 ceramic laser resonantly pumped by a 1645 nm Er:YAG laser. With an absorbed pump power of 5.9 W, we achieve a...     

Enzymatic electrosynthesis as an emerging electrochemical synthesis platform

Enzymatic electrosynthesis (EES), combining enzymatic catalysis and electrochemical techniques for the production of desired chemicals, has gained prominence because of its use of clean electrical energy inputs and highly specific enzyme biocatalysts and its capability of performing complicated reactions with high yield. In this review, we summarize the most recent state-of-the-art advances in EES and recognize that the research emphasis has shifted from CO₂ reduction to the utilization of N₂ and the synthesis of high-value products. Particular attention is given to the energy sources for powering EES, including direct electrical energy, light energy, and chemical energy obtained from self-powered biosystems. Enzyme-based hybrid systems integrated with microbial or chemical approaches are also presented. Finally, key challenges and future directions of EES are discussed briefly.     

Weighted robust Basis Function for phase unwrapping

This work presents a robust algorithm for phase unwrapping. The proposed algorithm is based on the expansion of the estimated phase through a linear combination of a set of Basis Functions. We present a novel weighted robust functional which is minimised using a two step strategy. This model allows us to reduce the influence of noise and to remove inconsistent pixels in the estimation of the unwrapped phase. The proposed model assumes that the phase is smooth. Under this assumption, experiments demonstrate that if the phase is corrupted by high levels of noise, our model presents a better performance than state of the art algorithms. For low levels of noise, the results are comparable.     

Three New Xanthones from the Fungus Penicillium sp. NH‐7‐1

Three new xanthones, drimiopsins G–I ( 1 – 3 , resp.), and two known congeners, griseoxanthone C ( 4 ) and norlichexanthone ( 5 ), were isolated from a fungal isolate, Penicillium sp. NH‐7‐1. The structures of all compounds were determined on the basis of extensive spectroscopic analyses, as well as by comparison with literature reports, and the structure of compound 1 was further confirmed by single‐crystal X‐ray diffraction.     

双电子传输层结构硫硒化锑太阳电池的界面特性优化

硫硒化锑薄膜太阳电池因其制备方法简单、原材料丰富无毒、光电性质稳定等优点,成为了光伏领域的研究热点.经过近几年的发展,硫硒化锑太阳电池的光电转换效率已经突破10%,极具发展潜力.本文针对硫硒化锑太阳电池中n/i界面引起的载流子复合进行了深入研究.发现硫硒化锑太阳电池的界面特性会受到界面电子迁移能力和能带结构两方面的影响.界面电子迁移率的提高能使电子更有效地传输至电子传输层,实现器件短路电流密度和填充因子的有效提升.在此基础上,引入ZnO/Zn_1-xMg_xO双电子传输层结构能够进一步优化硫硒化锑太阳电池性能.其中,Zn_1-xMg_xO能级位置的改变可以同时调节界面和吸光层的能级分布,在Zn_1-xMg_xO导带能级为-4.2 eV,对应Mg含量为20%时,抑制载流子复合的效果最为明显,硫硒化锑太阳电池也获得了最佳的器件性能.在去除缺陷态的理想情况下,双电子传输层结构硫硒化锑太阳电池在600 nm厚时获得了20.77%的理论光电转换效率,该研究结果为硫硒化锑太阳电池...     

The effect of interaction time and saturation of rock on specific energy in ND:YAG laser perforating

Laser perforating in oil and gas wells is a new scientific approach to the generation of uniform holes at a selected pitch to increasing the permeability of rocks. The influence of laser irradiation time and rock saturation by water and heavy oil on the specific energy, the energy required to remove the unit weight of rock, used during Nd:YAG laser perforating. The results show that an increase in the laser irradiation time increases the depth of the rock hole as well as the specific energy used, with a nonlinear relationship. Here, the estimated equation of rate of penetration as a function of the specific energy (SE) is free from saturation effects. The type of saturation influences the specific energy; the amount of SE required for water saturated samples is more than that required for the heavy oil saturated samples, and heavy oil saturated samples needed more SE than the dry samples.