氧化石墨烯插层聚β-羟基丁酸酯复合材料的结晶形态与宏观性能

由微生物直接合成的聚β-羟基丁酸酯（PHB）可实现从原料合成到加工成型和回收降解的全周期生态循环, 在生物医用和包装材料等领域有着重要的应用前景. 受制于PHB自身成核能力差导致的球晶尺寸偏大等不利结晶形态特点, 其制品存在抗冲韧性差、 延展率低和易蠕变等缺陷. 本文提出了水相加工和受限成型相结合的制备方法, 将氧化石墨烯（GO）纳米片在水溶液中充分剥离后, 直接包覆于亚微米级PHB微颗粒表面形成PHB@GO复合物, 然后在压力场下受限成型获得GO插层PHB纳米复合材料. 研究结果表明, 即使在极低GO添加量（质量分数0.1%）下, PHB的等温和非等温结晶能力都有显著提高, 并获得晶核密度高且晶体尺寸均一的结晶形态. 插层GO纳米片还促使复合材料发生了脆-韧转变, 使其拉伸强度和延展性均成倍提高, 同时显著增强了动态热力学性能、 抗蠕变性能和热学性能.     

二氧化碳电还原制草酸研究进展

近年来, 二氧化碳过量排放所引发的全球变暖等气候问题引起了全世界的广泛关注, 碳减排已成为人类社会可持续发展面临的共同挑战. 利用电化学方法将二氧化碳转化为高附加值化学品是实现碳减排和二氧化碳高附加值利用的理想途径之一, 但仍面临能耗高、 二氧化碳转化率低、 产物选择性差和难分离等问题. 本文以电还原二氧化碳制草酸为例, 从反应机理、 催化剂、 电解液、 催化电极及反应器等方面介绍该反应的研究进展, 对当前二氧化碳电还原制草酸存在的关键问题进行了分析, 并对其未来研究方向进行了展望.     

基于高分辨质谱的甲基化心磷脂高通量分析方法的建立和应用

该文基于心磷脂标准品的甲基化反应,建立了高灵敏度高通量分析甲基化心磷脂的液相色谱 - 高分辨质谱方法。由于甲基化后的心磷脂具有特征性的碎片,因此建立了包含780个分子特征片段的模拟数据库用于脂质鉴定。衍生化后,CL（14∶0/14∶0/14∶0/14∶0）信号提高了10倍,定量下限（LOQ）达到10 ng/mL。将该方法应用于小鼠衰老过程中心磷脂的调控研究,通过Tracefinder本地二级数据库共鉴定了43个心磷脂分子,其中21个心磷脂在衰老的大脑中有差异变化。结果发现：含有FA（20∶4）、FA（22∶6）长链多不饱和脂肪酸的心磷脂在衰老过程中呈下降趋势。高分辨质谱平台为甲基化的心磷脂分析提供了一种高通量筛选方法,对于低丰度心磷脂的检测具有很大潜力。     

钙钛矿光伏电池的非辐射复合损耗及调控策略

基于金属卤化物的钙钛矿光伏电池(PSCs)具有较大的光吸收系数、长的载流子扩散距离以及较低的制备成本等优势,在过去十几年来得到了研究者的广泛关注,目前最高光电转换效率(PCE)已经达到25.5%。然而,由于载流子运输过程中存在各类非辐射复合损耗,器件的PCE仍然低于肖克利-奎伊瑟理论极限。本文围绕PSCs的结构与工作原理,着重综述了器件工作过程中常见的非辐射复合方式,具体包括缺陷辅助复合、界面诱导复合、俄歇复合和带尾复合等,这些复合方式作为影响器件效率与工作稳定性的重要因素,受到研究者的广泛关注。结合最新的研究进展,从减小钙钛矿晶体缺陷、钝化晶界缺陷、钝化表面缺陷、优化能级结构等四个方面总结概括了降低非辐射复合的常用措施和策略。最后,对PSCs的非辐射复合调控前景进行了展望。     

A No-washing Point-of-Care Electrochemical Biosensor Based on CuS Nanoparticles for Rapid and Sensitive Detection of Neuron-specific Enolase

Electrochemical biosensors have made outstanding achievements in recent years. However, the single pursuit of sensitivity and accuracy sometimes cannot meet the detection requirements and achieve high-efficiency measurements. Therefore, no-washing biosensors have more practical advantages. In this work, a disposable point-of-care (POC) electrochemical biosensor was designed for the sensitive and fast detection of neuron-specific enolase (NSE). Fe₃O₄ and CuS nanoparticles were used as the substrate material for capturing Ab₁ and the signal probe for labeling Ab₂ respectively. The disposable syringe filter was introduced into the determination procedure for simple sample separation, which easily realized no-washing detection. Due to the syringe filters with 200 nm pore diameter could only allow the small nanoparticles of CuS−Ab₂ pass through, the large-sized immunocomplex of Fe₃O₄−Ab₁/NSE/CuS−Ab₂ were blocked on the membrane. The uncombined CuS−Ab₂ particles were pushed out from the syringe and would occur electron transfer between Cu²⁺ and Cu⁺ to generate a current signal detected by the Au electrode. Under optimal conditions, the no-washing biosensor shows a wide linear concentration range (100 fg mL⁻¹∼50 ng mL⁻¹) with the limit of detection of 33 fg mL⁻¹ (S/N=3). Additionally, the biosensor exhibited excellent selectivity, storage stability and reproducibility. The outstanding advantages of the no-washing biosensor make it more suitable for POC testing.     

磁共振T2WI、DWI对直肠癌新辅助治疗疗效的评估价值

本研究探讨磁共振成像T2WI、弥散加权成像(DWI)在直肠癌新辅助治疗疗效的评估价值。选取直肠癌患者92例,给予新辅助治疗,比较治疗前后T2WI、DWI参数变化。治疗无效患者治疗后肿瘤绝对信号值(SIT)明显高于治疗有效患者(P<0.05),而肿瘤绝对信号值减低率(SITRR)、治疗后肿瘤相对信号值(SIT/M)、肿瘤相对信号值减低率(SIT/MRR)明显低于治疗有效患者(P<0.05);治疗无效患者治疗后表观扩散系数(ADC)值、ADC变化值明显低于治疗有效患者(P<0.05);治疗后SIT、SITRR、SIT/MRR预测治疗有效的ROC曲线下面积分别为0.671、0.950和0.879(P<0.05);治疗后ADC值、ADC变化值预测治疗有效的ROC曲线下面积分别为0.717和0.977(P<0.05)。磁共振T2WI图像参数、ADC在预测直肠癌新辅助治疗疗效中有较高的应用价值。     

右$c$-群逆及其应用

研究了由右$c$-正则元确定的一类新的群逆,将之称为右$c$-群逆.证明了每个右$c$-群可逆元都是群可逆的,并通过反例说明了群可逆元未必是右$c$-群可逆的.给出了右$c$-群可逆元是群可逆元的条件,并对右$c$-群可逆元的强clean分解进行了研究.作为应用,从右$c$-群逆的角度对abelian环和直接有限环给出了一些新刻画.     

块状高温超导体俘获磁通密度实验测试方法

块状单畴高温超导体的重要特性参数之一"俘获磁通密度"决定了单畴超导体能够冻结住的最大磁通俘获场,实际用户在设计装置时必须了解这些参数.然而,这些数值强烈地依赖于测试方法.随着国内块状单畴超导体的研究、生产、应用的不断发展,市场规模的不断扩大以及国际贸易的开展,迫切需要建立一个与国际接轨的测试标准,统一材料提供方与用户之间对单畴块材性能的表征过程.经国家标准化管理委员会批准,2013年全国超导标准化技术委员会将IEC 61788-9国际标准《SUPERCONDUCTIVITY-Measurements for bulk high temperature superconductors-Trapped flux density of large grain bulk oxide superconductors》(《超导电性:块状高温超导体的测量—大晶粒氧化物超导体的俘获磁通密度》)转化为国家标准,本文主要介绍有关"标准"的转化实施过程.     

涡发生器结构对翼型绕流场的影响

为了研究涡发生器在风力机叶片上的应用,以进一步提高风力机气动效率,本文采用CFD数值模拟方法,分析涡发生器几何形状对其绕流场和翼型边界层特性的影响.涡发生器几何形状为同样高度的矩形、梯形和三角形。翼型为风力机专用翼型DU97-W-300。首先对数值模拟结果与实验值进行了对比,验证了数值方法的可信性。然后详细讨论了各种涡发生器所产生的集中涡涡量、翼型边界层特性、以及绕流场等沿流向的发展演变。总体上看,三角形涡发生器较适合用于风力机翼型的流动控制。     

Synchrotron study of metal localization in Typha latifolia L. root sections

Understanding mechanisms that control plant root metal assimilation in soil is critical to the sustainable management of metal‐contaminated land. With the assistance of the synchrotron X‐ray fluorescence technique, this study investigated possible mechanisms that control the localization of Fe, Cu, Mn, Pb and Zn in the root tissues of Typha latifolia L. collected from a contaminated wetland. Metal localizations especially in the case of Fe and Pb in the dermal tissue and the vascular bundles were different. Cluster analysis was performed to divide the dermal tissue into iron‐plaque‐enriched dermal tissue and regular dermal tissue based on the spatial distribution of Pb and Fe. Factor analysis showed that Cu and Zn were closely correlated to each other in the dermal tissues. The association of Cu, Zn and Mn with Fe was strong in both regular dermal tissue and iron‐plaque‐enriched dermal tissue, while significant (p < 0.05) correlation of Fe with Pb was only observed in tissues enriched with iron plaque. In the vascular bundles, Zn, Mn and Cu showed strong association, suggesting that the localization of these three elements was controlled by a similar mechanism. Iron plaque in the peripheral dermal tissues acted as a barrier for Pb and a buffer for Zn, Cu and Mn. The Casparian strip regulated the transportation of metals from dermal tissues to the vascular bundles. The results suggested that the mechanisms controlling metal localization in root tissues varied with both tissue types and metals.