具有变时滞和马尔可夫切换的随机递归神经网络的弱收敛(英文)

本文研究了具有变时滞和马尔可夫切换的随机递归神经网络的弱收敛,通过运用Lyapunov函数、随机分析技巧和推广了的Halanay不等式,得到了上述模型为弱收敛的充分性条件,并且我们揭示了对上述递归神经网络模型所确定的segment过程的转移概率的极限分布是此模型的解过程的唯一的遍历不变概率测度.此外,我们还给出了例子和数值模拟来说明我们结论的正确性.     

Self-calibration method for cerium-doped lanthanum bromide scintillator detector in the 0.1–2.0 MeV energy range

In recent years, the cerium-doped lanthanum bromide, LaBr₃ (Ce = 5 %) detector is increasingly playing an important role in radiation measurements because of its higher energy resolution (~3 % at 662 keV), faster luminescence decay time (~35 ns) and higher detection efficiency compared to 7.65 cm × 7.65 cm NaI(Tl) detector. Intrinsic spectra between 1,800 and 3,000 keV derived from internal radioactivity within LaBr₃(Ce) scintillators have been investigated in some literatures, and these results are confirmed by the experiments in this work. In this paper, a new method for LaBr₃(Ce) detector energy calibration from 100 to 2,000 keV is proposed using the intrinsic spectra (self-calibration) instead of the standard gamma sources. Proof-of-concept experiment results show that self-calibration can guarantee energy accuracy of better than 0.815 % and can be applied outside the laboratory. The stability and applicability of this method are also investigated systematically.     

Transformations of iodine species inside elliptical channels of AlPO4‐11 crystals at low temperature: a Raman study

Raman spectra of iodine species confined in one‐dimensional elliptical channels of AlPO₄‐11 (AEL) crystals have been studied from room temperature down to −196 °C. As temperature decreases, thermal fluctuations of individual iodine molecules confined in AEL channels are slowed down and they prefer to rotate to channel axis direction, which increases the population of iodine molecules along channel axis (i.e., lying molecules and chains). Such temperature‐driven orientation transformation of iodine molecules is found to be reversible upon heating up to room temperature. The experimental observations are in good agreement with our theoretical simulations by molecular dynamics on low density iodine‐filled AEL crystals. We thus provide a new way to modulate the orientation of iodine molecules in nanochannels, which may have implications in low‐temperature‐sensitive nanoscale devices. Copyright © 2015 John Wiley & Sons, Ltd.     

Elastic-inertial separation of microparticle in a gradually contracted microchannel

Separation of microparticle in viscoelastic fluid is highly required in the field of biology and clinical medicine. For instance, the separation of the target cell from blood is an important prerequisite step for the drug screening and design. The microfluidic device is an efficient way to achieve the separation of the microparticle in the viscoelastic fluid. However, the existing microfluidic methods often have some limitations, including the requirement of the long channel length, the labeling process, and the low throughput. In this work, based on the elastic-inertial effect in the viscoelastic fluid, a new separation method is proposed where a gradually contracted microchannel is designed to efficiently adjust the forces exerted on the particle, eventually achieving the high-efficiency separation of different sized particles in a short channel length and at a high throughput. In addition, the separation of WBCs and RBCs is also validated in the present device. The effect of the flow rate, the fluid property, and the channel geometry on the particle separation is systematically investigated by the experiment. With the advantage of small footprint, simple structure, high throughput, and high efficiency, the present microfluidic device could be utilized in the biological and clinical fields, such as the cell analysis and disease diagnosis.     

溶剂热合成可调控氧空位的Bi2MoO6纳米晶及其光催化氧化制喹啉和抗生素降解

近年来,半导体光催化在环境净化和有机合成领域的研究引起了广泛的重视.其中,在有机合成领域中,光催化技术已经应用在醇类、环己烷以及芳香族化合物的选择性氧化研究.而另一类具有特殊结构的有机物——N-杂环芳烃,在药物化学和材料科学中具有重要意义.而传统用于合成N-杂化芳烃的脱氢催化氧化反应通常需要高温高压的苛刻环境,传统方法通常还需要使用贵金属催化剂,这也增加了N-杂化芳烃的合成成本;另外,如果合成是均相催化过程,则催化剂难以实现回收利用.因此,开发室温常压条件下的非贵金属多相光催化技术具有巨大的应用前景.本文以能够被可见光驱动的钼酸铋半导体为催化剂,利用氧缺陷策略来提升钼酸铋的光催化氧化性能.不同于传统氧缺陷制备方法(氢气还原热处理、离子掺杂等),本文采用一种低成本的乙二醛辅助溶剂热的方法合成具有可调控的含氧空位Bi₂MoO₆催化剂(OVBMO).通过X射线粉末衍射(XRD)、扫描电镜、透射电镜、紫外可见漫反射吸收光谱、氮气物理吸附脱附、X射线光电子能谱(XPS)、电子自旋共振光谱、光致发光光谱及电化学测试等技术对制备的OVBMO材料进行了物理化学性质及能带研究.XPS,XRD,Raman和FT-IR结果表明,氧空位存在于[Bi₂O₂]²⁺和MoO₆八面体的层间.紫外可见漫反射结果表明,随着氧空位的引入,Bi₂MoO₆的光吸收范围扩大,带隙变窄.结合莫特肖特基和VBXPS分析获得OVBMO的能带位置,发现氧空位的存在不仅会导致禁带中出现缺陷带能级,还会导致价带顶位置上移,促进光生空穴的迁移.PL和电化学结果表明,氧空位的存在使得载流子浓度、载流子的分离能力与界面电荷迁移能力都有较大提升,这是因为氧空位引入的缺陷能级可以浅势捕获电子,抑制光催化剂中的电子与空穴的复合,改变化学反应的速率.同时,氧空位有助于捕获分子氧,分子氧与捕获的光生电子发生反应,产生更多的超氧自由基(·O₂)和空穴(h⁺),从而极大地提升光催化剂的氧化性能.因此,OVBMO在1,2,3,4-四氢喹啉脱氢氧化产生喹啉及系列抗生素(环丙沙星、四环素、盐酸土霉素)的降解反应中,表现出较好的光催化氧化性能.结合多种表征分析,本文还进一步阐明了OVBMO催化剂将1,2,3,4-四氢喹啉脱氢氧化为喹啉的自由基参与的多相催化反应机理.     

Continuous Porous Aromatic Framework Membranes with Modifiable Sites for Optimized Gas Separation

Continuous microporous membranes are widely studied for gas separation, due to their low energy premium and strong molecular specificity. Porous aromatic frameworks (PAFs) with their exceptional stability and structural flexibility are suited to a wide range of separations. Main-stream PAF-based membranes are usually prepared with polymeric matrices, but their discrete entities and boundary defects weaken their selectivity and permeability. The synthesis of continuous PAF membranes is still a major challenge because PAFs are insoluble. Herein, we successfully synthesized a continuous PAF membrane for gas separation. Both pore size and chemistry of the PAF membrane were modified by ion-exchange, resulting in good selectivity and permeance for the gas mixtures H₂/N₂ and CO₂/N₂. The membrane with Br^? as a counter ion in the framework exhibited a H₂/N₂ selectivity of 72.7 with a H₂ permeance of 51844 gas permeation units (GPU). When the counter ions were replaced by BF₄^?, the membrane showed a CO₂ permeance of 23058 GPU, and an optimized CO₂/N₂ selectivity of 60.0. Our results show that continuous PAF membranes with modifiable pores are promising for various gas separation situations.     

基于微流控热泳的生物传感技术※

复杂生命体系中关键分子及微纳生物粒子的高灵敏、高特异检测, 对理解多层次多尺度生物学过程、阐明疾病发生发展机制和探索新型生物标志物等具有重要意义. 微流控生物传感器整合了微流控技术和生物传感技术的诸多优势, 在微量生物样本精准测量方面取得了显著进展. 近年来, 微流控热泳生物传感技术(Thermomicrofluidic biosensing)利用物质在局域温度梯度场中的热泳定向迁移现象, 并结合均相生物传感及信号放大新策略, 实现了复杂样本中生物分子及微纳生物粒子的快速、高灵敏、原位检测. 重点阐述了以热泳为核心的微流控传感技术, 包括微量热泳、热泳-对流耦合、热泳-扩散泳耦合以及热泳-电泳耦合等方法, 总结了不同传感方法的原理、特点及其在生物分子(蛋白、核酸等)与微纳生物粒子(细胞外囊泡、病毒、细胞等)检测中的应用, 并探讨了微流控热泳技术在生物医学检测领域中面临的挑战与未来发展方向.     

Controllable fabrication of ZnO nanorods@cellulose membrane with self-cleaning and passive radiative cooling properties for building energy-saving applications

Cellulose - The energy consumption for building cooling occupies non-ignorable part of global energy consumption, causing the increasing aggravation of energy crisis and environmental...     

液相色谱-四极杆/飞行时间质谱法分析29种芬太尼类物质及其碎裂机理北大核心CSCD

芬太尼类物质品种繁多,自我国整类列管后,整类检测是该领域的重点和难点。该文详细研究了29种化合物的二级质谱碎片离子碎裂机理,总结出芬太尼类物质的碎裂规律和特点,为芬太尼物质的整类筛查检测提供参考。建立了分析29种芬太尼类物质的一级和二级质谱库的定性方法,建立了液相色谱-四极杆/飞行时间质谱(LC-QTOF-MS)检测29种芬太尼类物质的定量方法。药品和白色粉末类、蛋白质和乳饮料类样品经乙腈提取,含糖固体或粉末类、饮用水类、果蔬饮料类、保健饮料类、茶饮料类、酒类样品经10%乙腈水溶液提取,提取液经涡旋、离心和过膜后,采用Kinetex C18色谱柱(100 mm×2.1 mm,2.6μm)分离,以乙腈和0.08%甲酸水溶液为流动相进行梯度洗脱,采用四极杆/飞行时间质谱,在正离子模式下,外标法定量检测。结果表明,29种芬太尼类物质在1~20μg/L范围内线性关系良好,相关系数均大于0.995,检出限(LOQ)均为0.01 mg/kg,定量限(LOQ)均为0.05 mg/kg,在降糖药、露露、葡萄糖粉、珍露保健饮料和巧克力样品中3个加标水平平均回收率为85.2%~112.9%,相对标准偏差(RSD)为1.9%~19.8%(n=6)。该方法操作简单,耗时短,灵敏度高,稳定性好,检测品种覆盖范围广,适用于药品类、含糖固体或粉末类、饮料类、饮用水类和酒类等样品中29芬太尼类物质的定性和定量检测。     

Plasmonic photoelectrochemical reactions on noble metal electrodes of nanostructures

Plasmonic noble metal nanostructures have been targeted due to their strong surface plasmon resonance at photoelectrochemical interfaces. Recently, it has been concluded that, the plasmonic noble metal nanostructures on photoexcitation permit the transfer of effective hot carriers (hot electron/hole pair) to nearby adsorbed molecules where, the transformed hot carriers can efficiently decrease the activation barrier of a reaction. In this review, our recent achievements in the plasmon-mediated chemical reactions of organic molecules such as para-aminothiophenol, substituted para-aminothiophenol and para-nitrothiophenol at nanostructures modified noble metal electrodes using surface enhanced Raman spectroscopy, electrochemical methods, and theoretical calculations will be discussed.