Cell-Free Synthesis of Selenoproteins in High Yield and Purity for Selective Protein Tagging

The selenol group of selenocysteine is much more nucleophilic than the thiol group of cysteine. Selenocysteine residues in proteins thus offer reactive points for rapid post-translational modification. Herein, we show that selenoproteins can be expressed in high yield and purity by cell-free protein synthesis by global substitution of cysteine by selenocysteine. Complete alkylation of solvent-exposed selenocysteine residues was achieved in 10 minutes with 4-chloromethylene dipicolinic acid (4Cl-MDPA) under conditions that left cysteine residues unchanged even after overnight incubation. Gd^III−Gd^III distances measured by double electron–electron resonance (DEER) experiments of maltose binding protein (MBP) containing two selenocysteine residues tagged with 4Cl-MDPA-Gd^III were indistinguishable from Gd^III−Gd^III distances measured of MBP containing cysteine reacted with 4Br-MDPA tags.     

Mechanistic study of the effect of Ca–Sn co-doping on the microwave dielectric properties and magnetic properties of YIG

To investigate the crystal structure, electrical properties, and magnetic properties of Ca–Sn co-doped Y_3-xCa_xFe_5-xSn_xO₁₂ (x = 0.00–0.25 in steps of 0.05), solid-state reaction experiments, first principles calculations, and complex crystal bonding theoretical calculations were performed. The relative permittivity (ε_r) is strongly correlated with the average bond ionicity when Ca²⁺ is added. Furthermore, appropriate Sn⁴⁺ substitution significantly lowers the dielectric loss (tanδ_ε) associated with the lattice energy. The right amount of Ca–Sn co-doping can change the saturation magnetization (4πM_S) and improve the microscopic morphology of YIG, lowering the ferromagnetic resonance linewidth (ΔH) of YIG. The optimized microwave dielectric and magnetic properties are as follows: ε_r = 14.7, tanδ_ε = 4.15 × 10^?4, 4πM_S = 1680 G, and ΔH = 53 Oe for Y_2.8Ca_0.2Fe_4.8Sn_0.2O₁₂ sintered for 6 h at 1425 °C. Based on this material, a simple 3D model of a strip-line circulator with an insertion loss of less than 0.3 dB at each port and isolation greater than 20 dB in the 10–12 GHz range was developed, indicating the potential of the material for microwave high-frequency components such as circulators.     

催化共振光散射法测定空气中痕量甲醛的研究

吖啶橙分子聚集体微粒可在513nm波长处出现最大的共振光散射强度(RLS)。在稀硫酸介质中,甲醛能催化溴酸钾氧化吖啶橙的反应,促使其RLS强度减弱。在最佳实验条件下,甲醛质量浓度ρ在0.020～0.25μg/mL的范围内与△I值呈良好的线性关系,线性回归方程为△I=1113.99ρ+49.23,线性相关系数r为0.9986。本法与国标法进行对照,在置信度等于95%时,用Cochran检验,两种方法间不存在显著性差异,方法操作简单、灵敏度高,用于室内外空气中甲醛测定,结果满意。     

Synthesis of mesoporous core-shell structured GdPO_4:Eu@SiO_2@mSiO_2 nanorods for drug delivery and cell imaging applications

Mesoporous GdPO_4:Eu@SiO_2@mSiO_2 core-shell nanorods(NRs) were prepared by a facile two-step method.First,the monodispersed GdPO_4:Eu NRs were obtained on a large scale via a facile precipitation method,then mesoporous silica was wrapped onto their surface through hydrolysis of tetraethylorthosilicate(TEOS).The XRD result indicates that the as-prepared GdPO_4:Eu NRs core has hexagonal phase.The FTIR and the N_2 adsorption/desorption isotherm analysis confirm the successful coating of mesoporous silica.The TEM images show that the obtained GdPO_4:Eu@SiO_2@mSiO_2 NRs exhibit uniform monodisperse core-shell structure with a nanorod core(length of 200 nm;width of 20 nm),and mesoporous silica shell of 15 nm.Under excitation of 274 nm,GdPO_4:Eu@SiO_2@mSiO_2 NRs show strong red luminescence from ~5 D_0→~7 F_J(J=1,2,3 and 4) transitions of Eu~(3+).Furthermore,the GdPO_4:Eu@-SiO_2@mSiO_2 NRs exhibit obvious T_1 enhancement effect due to paramagnetism of Gd~(3+).The drug loading capacity and pH-sensitive releasing behavior of the as-prepared GdPO_4:Eu@SiO_2@mSiO_2 NRs were studied by using doxorubicin(DOX) as model drug.The excellent biocompatibility of GdPO_4:Eu@-SiO_2@mSiO_2 NRs was demonstrated by MTT assay.Taken together,the mesoporous GdPO_4:Eu@-SiO_2@mSiO_2 NRs may be potentially applied in fields of drug delivery and dual-modal imaging.     

Stability enhancement of induction generator–based series compensated wind power plants by alleviating subsynchronous torsional oscillations using BFOA‐optimal controller tuned STATCOM

In this paper, a STATCOM (static synchronous compensator) is used to encounter the potential SSR (subsynchronous resonance) observed by IG (Induction Generator) based series compensated wind farms. The basic controller used for STATCOM control is identical to that of the literature. An idea of a unique meta‐heuristic swarm‐based optimization technique called BFOA (bacterial foraging optimization algorithm) based optimal‐controller is introduced for optimal parameter selection of the basic controller used in the control scheme of the STATCOM. The investigation is carried out with 500 MW IG‐based wind farm exposed to three‐phase LLL‐G fault close to the PCC (point of common coupling) and implemented with MATLAB in both steady and transient states for the three different cases, namely, without STATCOM, with the basic STATCOM controller, and in the presence of the proposed BFOA‐optimal controller‐based STATCOM. In both the states, the observed eigenvalues of the test system, together with the time domain results of the generator rotor dynamics for three distinct cases, reveals the effectiveness of the suggested BFOA‐optimal controller tuned STATCOM in mitigating the potential SSR.     

A brief review of dynamic mechanical metamaterials for mechanical energy manipulation

In the past decades, many mechanical metamaterials with uncommon static properties have been reported. On the other hand, mechanical metamaterials possessing extraordinary dynamic performance, also referred to as acoustic/elastic metamaterials, have gained more and more attractions. Examples include acoustic cloaking metamaterials that can generate an invisible region for acoustic waves, zero-stiffness metamaterials that can isolate vibrating mechanical energy, origami-based metamaterials that can realize the directional transmission of elastic waves and so on. To better understand the mechanisms adopted in dynamic mechanical metamaterials and present a general view about the existing works, we have reviewed some representative works and categorized them based on the ways of how these mechanical metamaterials manipulate the interactions between matters and mechanical energy. To distinguish the different categories of the dynamic mechanical metamaterials, we use a pair of binary numbers to measure the changing states of the magnitude and direction of the energy flow, respectively. A summary of some research works with associated reference numbers is presented in this paper with emphasis on the operating frequency, working bandwidth, and characteristic size of the element.     

Characterisation and in vitro cytotoxicity of toxic and degradation compounds in bamboo shoots (Dendrocalamus Sinicus) during traditional fermentation

Fermentation has been historically applied to reduce bamboo shoot (BS) toxicity. However, the underlying degradation pathway of the toxic compounds remains unknown. In this work, the cytotoxicity of BS against the BRL-3A cells was evaluated, and the changes in chemical constituents were determined to reveal the influence of fermentation on BS. The in vitro toxic evaluation revealed fermentation time was crucial in decreasing the toxicity. The main compounds in fresh and fermented were qualitatively and quantitatively determined and were further targeted isolated and identified. A mathematical model to describe the change rate as a function of fermentation time was formulated. Dynamic profiling revealed that taxiphyllin 1 , p-hydroxybenzaldehyde 2 and methyl-p-hydroxybenzoate 3 decreased and transformed into intermediate compounds (p-hydroxybenzoic acid 4 and p-hydroxybenzyl alcohol 5 ), finally converting into p-hydroxytoluene 6 during fermentation. The results provided basis on the chemical components for practical fermentation and the quality control of BS products.     

基于改进Gauss-Hermite方法的在线多普勒展宽方法研究

温度对核截面的效应对反应堆中子学计算有重要影响，同时也是热工反馈的基础。准确、高效且内存占用较少的蒙特卡罗截面在线温度处理方法是其中的关键。基于多普勒展宽理论及Gauss-Hermite求积组，可使用基准温度下的截面对任意温度进行展宽计算，实现蒙特卡罗粒子输运过程中的在线多普勒展宽。本文针对传统Gauss-Hermite方法存在的问题，对该方法进行了改进，并利用典型压水堆算例进行了验证分析。结果证明，改进算法显著地提高了效率，为在线多普勒展宽方法在多物理耦合中的应用提供了基础。     

频率可调太赫兹回旋振荡管互作用电路的设计与研究

根据动态核极化核磁共振成像技术对回旋振荡管的要求,设计了130 GHz 回旋振荡管的注波互作用电路,基于线性理论对互作用电路进行了研究并选择了合适的工作点,分析了电路的频率调节特性。利用相对论电子回旋脉塞非线性理论对互作用系统进行了模拟和计算,优化了工作参数,计算了磁场及电子注参数对输出功率及效率的影响。最后,用粒子模拟方法进行了模拟并与非线性理论结果进行了比较,两者符合得很好。模拟结果显示,当电压为10 kV、电流为0.3 A、磁场强度由2.34 T 增加到2.41 T 时,输出功率由1310 W 减小到230 W,对应的效率分别为43.6%和7.7%,振荡管的频率可调范围约为2.7 GHz。     

Thermal annealing induced cave in and formation of nanoscale pits in Ag–TiO2 plasmonic nanocomposite thin film

Ag–TiO₂ nanocomposite thin films on silica glass were prepared through thermal evaporation in combination with RF magnetron sputtering. Thermal annealing induced changes in the optical, morphological and structural properties of Ag–TiO₂ nanocomposites were examined using optical absorption, photoluminescence spectroscopy, Raman spectroscopy, FESEM, AFM and XRD. FESEM and AFM studies revealed cave in of the Ag–TiO₂ thin film at various places leading to the formation nanoscale pits upon thermal annealing at 600 °C. The computed average size of pits was found to be 54 nm. Raman studies indicated 600 °C annealing induced transformation of anatase phase of TiO₂ into anatase/rutile mixed phase TiO₂. Optical absorption spectra showed systematic changes due to the effects of mixed phase formation and variation in the plasmonic behavior upon annealing. PL results of the as deposited Ag–TiO₂ thin film showed peaks at 377, 402, 432 and 486 nm. PL studies of Ag–TiO₂ nanocomposites treated at different annealing temperatures revealed changes in defect concentration in TiO₂. The tentative mechanism for the creation of nanoscale pits in Ag–TiO₂ thin film through thermal annealing was proposed.