基于芯片实验室技术的表面增强光谱学在分析科学中的应用

集成具有一序列微流控操作单元的芯片实验室技术,在微流控通道内铺陈金属纳米粒子(尤其是金、银以及铜纳米粒子)作为衬底,泵入多通道微纳升分析物,用于联用表面增强光谱在痕量、实时、原位、过程反应等检测中具有重要的意义。这种联用检测技术集成了芯片实验室和表面光谱两种技术的优点：芯片实验室技术集成流程式分步操作,实现筛选取样,分段、实时反应检测,减小样品量,稳定测试环境等优势以及表面增强光谱的光谱响应快,灵敏性和选择性强、原位检测等优点。借助于Drude模型以及适当的边界条件,外电场引发金属颗粒价电子的局域等离子振荡,并推导了产生共振的局域表面等离子增强以及受激感应偶极子振荡产生表面拉曼增强的物理电磁增强机制。综述了芯片实验室表面局域等离子检测在生物、医药、食品安全等方面的应用,检测通道的增加促使检测效率有较大的提高,同时检测限能力获得较大的突破。综述了芯片实验室技术结合表面增强拉曼光谱公共安全、生物医学、电化学和生物传感器等领域的应用, 表面增强拉曼光谱的高度灵敏性以及指纹性应用于痕量检测。根据芯片实验室技术在研究开发和应用已经获得不断的进展,结合3D打印技术,精准控制多通道结构尺寸,更好地满足设计的需求。表面等离子增强光谱以及表面增强拉曼光谱等表面光谱检测技术在应用上日趋成熟,获得突破传统显微镜的光学极限的分辨能力。这种联用技术在实际定性或者半定量痕量分析检测应用中具有光明的前景。     

风湿性关节炎动物模型中血啉甲醚荧光强度的同步检测研究

光动力疗法的疗效依赖于治疗过程中靶组织中光敏剂的含量或浓度 ,而药物在组织中的分布特性是受动物机体调控的 ,因此 ,同一个体不同组织对光敏剂吸收的时间特性需要同时进行检测才能排除个体之间的差异。建立了一套空间三通道激光诱导荧光同步检测装置 ,并用该装置研究了活体大耳白兔风湿性关节炎模型滑膜、软骨和皮肤对血啉甲醚吸收的时间特性。研究结果表明 ,炎性滑膜组织对血啉甲醚的吸收量远大于软骨和皮肤 ,这一差别在静脉给药即刻就很明显 ,在静脉给药后 2 0min内 ,滑膜中的光敏剂药物含量约为软骨和皮肤中的 6倍。因此 ,对于借助血啉甲醚 ,用光动力疗法治疗风湿性关节炎并采用体外照射治疗方案时 ,从注药即刻开始 ,前 2 0min左右进行光照治疗可能是较好的选择。     

在激光大气传输中利用SBS阈值效应实现小面积信标的研究

 在理论上建立起将受激布里渊散射（SBS）与激光大气传输过程相结合的激光补偿传输的数学模型,并进行了数值模拟，提出并证明了利用SBS阈值效应可以将相位共轭光会聚到目标上一个小面积上，从而在目标上主动获得小面积信标光斑。利用SBS实现激光大气补偿传输（传输距离250m）的实验研究,证实了上述理论预期。     

Carbon nanotubes supported Pt-Ni catalysts and their properties for the liquid phase hydrogenation of cinnamaldehyde to hydrocinnamaldehyde

The Pt-Ni catalysts supported on CNTs have been prepared by wet impregnation and the selective hydrogenation of cinnamaldehyde (CMA) to the corresponding hydrocinnamaldehyde (HCMA) over the catalysts has been studied in ethanol at different reaction conditions. The results show that Pt-0.34 wt% Ni/CNTs catalyst exhibits the highest activity and selectivity at a reaction temperature of 70 °C under a pressure of around 2.0 MPa, and 98.6% for the conversion of CMA and 88.2% for the selectivity of CMA to HCMA, respectively. The selective hydrogenation for the CC bond in CMA would be improved as increasing the reaction temperature, and the hydrogenation for the CO bond in CMA is enhanced as increasing the H₂ pressure. In addition, these catalysts have also been characterized using TEM-EDS, XPS, H₂-TPR and H₂-TPD techniques. The results show that Pt particles are dispersed more homogeneously on the outer surface of the nanotubes, while the strong interaction between Pt and Ni would improve the increasing of activated hydrogen number because of the hydrogen spillover from reduced Pt⁰ onto CNTs and increase the catalytic activity and selectivity of CMA to HCMA.     

Selective hydrogenation of cinnamaldehyde to cinnamyl alcohol with carbon nanotubes supported Pt-Co catalysts

The Pt-Co catalysts supported on carbon nanotubes (CNTs) have been prepared by wet impregnation and the selective hydrogenation of cinnamaldehyde (CMA) to the corresponding cinnamyl alcohol (CMO) over the catalysts has been studied in ethanol at different reaction conditions. The results show that Pt-0.17 wt%Co/CNTs catalyst exhibits the highest activity and selectivity at a reaction temperature of 60 °C under a pressure of around 2.5 MPa, and 92.4% for the conversion of CMA and 93.6% for the selectivity of CMA to CMO, respectively. The selective hydrogenation for the CO double bond in CMA would be improved as increasing the H₂ pressure, and the selective hydrogenation for the CC double bond in CMA is enhanced as increasing the reaction temperature. In addition, these catalysts have also been characterized using transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), H₂-temperature programmed reduction (H₂-TPR) and H₂-temperature programmed desorption (H₂-TPD) techniques. The results show that Pt particles are dispersed more homogeneously on the outer surface of the nanotubes, while the strong interaction between Pt and Co would improve the increasing of activated hydrogen number because of the hydrogen spillover from reduced Pt⁰ onto CNTs and increase the catalytic activity and selectivity of CMA to CMO.     

Intrinsically smooth discretisation of Connolly's solvent-excluded molecular surface

The switching/Gaussia (SWIG) algorithm for intrinsically smooth discretisation of the van der Waals cavity surface, for use in implicit solvation modelling, is extended here to the case of the solvent-excluded surface (SES), also known as the Connolly surface or sometimes the molecular surface. In conjunction with a polarisable continuum model (PCM), SES-SWIG discretisation affords continuum electrostatics that vary smoothly with respect to the nuclear coordinates, with a solvation energy that is analytically differentiable with respect to those coordinates. If the SES is the desired cavity construction, then the PCM + SES-SWIG method represents an efficient, boundary-element alternative to three-dimensional, finite-difference solution of Poisson's equation. The algorithm introduced here allows the SES to be constructed and discretised quickly and easily, and its analytically differentiable form paves the way for derivation of analytic gradients.     

SES微波脉冲压缩系统瞬态特性的模拟研究

 通过MATLAB编程,实现了储能切换（stored energy switch）方式产生高功率微波脉冲瞬态响应过程的模拟。程序可用于研究微波压缩系统的功率增益、储能转换效率及脉宽压缩比等主要指标与系统开关耦合腔的固有品质因数、输入与输出耦合系数的关系;并可用于对工作频率失谐、“开关”导通前的泄漏及“开关”启动时间的影响等进行分析,输出瞬态响应过程图像。     

基于连续时间无规行走模型研究反常扩散

基于连续时间无规行走(CTRW)理论，数值研究了布朗粒子的欠扩散、正常扩散和超扩散三种扩散行为.解决了CTRW模型的跳跃步长和等待时间分布函数的可实现化问题，对Metropolis抽样方法进行了改进以适用于周期势.探讨了布朗马达依靠闪烁棘轮和摇摆棘轮整流反常扩散所获得的定向速度，结果显示，闪烁布朗马达定向流极大值出现在超扩散条件下；摇摆布朗马达定向流最大值出现在弹道扩散条件下.     

基于连续时间无规行走模型研究反常扩散

基于连续时间无规行走(CTRW)理论,数值研究了布朗粒子的欠扩散、正常扩散和超扩散三种扩散行为.解决了CTRW模型的跳跃步长和等待时间分布函数的可实现化问题,对Metropolis抽样方法进行了改进以适用于周期势.探讨了布朗马达依靠闪烁棘轮和摇摆棘轮整流反常扩散所获得的定向速度,结果显示,闪烁布朗马达定向流极大值出现在超扩散条件下;摇摆布朗马达定向流最大值出现在弹道扩散条件下. 关键词： 无规行走 反常扩散 Metropolis抽样 棘轮势     

蒸气压缩式制冷装置仿真的基本理论和热点问题

针对蒸气压缩式制冷装置仿真的基本理论进行了总结。将稳态仿真方法归纳为四种 :连续替代 (SS)方法、牛顿 -辛普生 (NR)方法、顺序模块 (SM)方法以及联立方程解 (SES)方法。动态仿真研究在总量上还较少 ,从中难以归纳出普遍适用的方法。模型的数值健壮性、模型的通用性以及大型机组的仿真是目前的热点问题。     

Determination of thermal wave reflection coefficient to better estimate defect depth using pulsed thermography

Thermography is a promising method for detecting subsurface defects, but accurate measurement of defect depth is still a big challenge because thermographic signals are typically corrupted by imaging noise and affected by 3D heat conduction. Existing methods based on numerical models are susceptible to signal noise and methods based on analytical models require rigorous assumptions that usually cannot be satisfied in practical applications. This paper presents a new method to improve the measurement accuracy of subsurface defect depth through determining the thermal wave reflection coefficient directly from observed data that is usually assumed to be pre-known. This target is achieved through introducing a new heat transfer model that includes multiple physical parameters to better describe the observed thermal behaviour in pulsed thermographic inspection. Numerical simulations are used to evaluate the performance of the proposed method against four selected state-of-the-art methods. Results show that the accuracy of depth measurement has been improved up to 10% when noise level is high and thermal wave reflection coefficients is low. The feasibility of the proposed method in real data is also validated through a case study on characterising flat-bottom holes in carbon fibre reinforced polymer (CFRP) laminates which has a wide application in various sectors of industry.     

Numerical Analysis of Electromagnetic Fields in Multiscale Model

Modeling technique for electromagnetic fields excited by antennas is an important topic in computational electromagnetics, which is concerned with the numerical solution of Maxwell's equations. In this paper, a novel hybrid technique that combines method of moments(MoM) with finite-difference time-domain(FDTD) method is presented to handle the problem. This approach employed Huygen's principle to realize the hybridization of the two classical numerical algorithms. For wideband electromagnetic data, the interpolation scheme is used in the MoM based on the dyadic Green's function. On the other hand, with the help of equivalence principle, the scattered electric and magnetic fields on the Huygen's surface calculated by MoM are taken as the sources for FDTD. Therefore, the electromagnetic fields in the environment can be obtained by employing finite-difference time-domain method. Finally, numerical results show the validity of the proposed technique by analyzing two canonical samples.     

镥的激光共振电离同位素选择性研究

本文在速率方程基础上通过数值模拟方法 ,对镥的激光共振电离通道 :5d6s2 2 D3 /2 (5 73.6 5 5nm)→5d6s6 p4F3 /2 (6 4 2 .5 18nm)→ 6s6 p2 4P1/2 (6 4 3.5 4 8nm)→Autoionizationstate的激光诱导同位素选择性进行了研究。在实际实验条件下用这一方法计算得到的激光波长对激光诱导同位素选择性的关系与实验结果相符合。探讨了在偏振激光作用的情况下各种激光参数 (波长、带宽和激光强度 )对激光诱导同位素选择性的影响 ,并提出了在一定实验条件下激光共振电离质谱计较为准确地测定同位素比值的方法。这一理论方法 ,同样适用于研究其它元素的激光共振电离同位素选择性和选择激光同位素分离电离通道     

Possible relationship between Seismic Electric Signals (SES) lead time and earthquake stress drop

Stress drop values for fourteen large earthquakes with M(W)> or =5.4 which occurred in Greece during the period 1983-2007 are available. All these earthquakes were preceded by Seismic Electric Signals (SES). An attempt has been made to investigate possible correlation between their stress drop values and the corresponding SES lead times. For the stress drop, we considered the Brune stress drop, Deltasigma(B), estimated from far field body wave displacement source spectra and Deltasigma(SB) derived from the strong motion acceleration response spectra. The results show a relation may exist between Brune stress drop, Deltasigma(B), and lead time which implies that earthquakes with higher stress drop values are preceded by SES with shorter lead time.     

磁化铁氧体覆盖二维导体目标FDTD分析的移位算子方法

采用移位算子方法把时域有限差分法推广应用于二维磁各向异性色散介质—磁化铁氧体中.证明了电磁波横向入射二维轴向磁化铁氧体目标情形下,电磁波可按目标的轴向分解为横电波(TE波)和横磁波(TM波),且TE波的散射特性与铁氧体介质无关,而TM波的散射特性与介质电磁参量密切相关,同时对其物理原因进行了分析.通过采用移位算子方法处理磁化铁氧体频域本构关系,得到该情形下目标电磁散射的移位算子时域有限差的迭代计算公式,同时解决了电磁波在各向异性和频率色散介质中传播的问题.计算了轴向磁化铁氧体涂敷VonKarman型导体柱的TM波双站雷达散射截面,分析了铁氧体参量对目标双站雷达散射截面的影响.结果表明:恰当地选择铁氧体参量能有效地减少目标的雷达散射截面,本文时谐因子取exp〔jωt〕.     

时域磁场积分方程时间步进算法稳定性研究

从时域磁场积分方程时间步进算法出发,结合范数概念,从理论上推导得到了感应电流稳定的充分条件. 满足该条件,可以保证任何形式的入射波入射时,计算结果都后时稳定. 同时通过推导得到了表征感应电流递推关系的因子,该因子的大小可以表征感应电流收敛性的相对好坏. 最后通过数值算例验证了感应电流稳定的充分条件, 以及利用本文推导的感应电流递推因子表征感应电流后时稳定性的准确性. 关键词： 时域磁场积分方程 时间步进算法 后时不稳定性     

粗糙面重构问题的混合算法研究

基于Desanto的谱表示法,采用数值和近似算法相结合的混合算法对一维粗糙面的重构问题进行了研究.对于正问题,采用数值算法——矩量法(MOM)得到一维粗糙面的相关散射数据,对于逆问题,考虑不同粗糙度的粗糙面,分别采用两种近似算法——微扰近似(SPA)、基尔霍夫近似(KA)与矩量法的混合算法,对粗糙面轮廓进行了重构;数值结果以高斯粗糙面为例,给出了混合算法对不同粗糙度粗糙面的重构算例,并进行了数据比较和分析. 关键词： 粗糙面重构 矩量法 微扰近似 基尔霍夫近似     

THz-waves channeling in a monolithic saddle-coil for Dynamic Nuclear Polarization enhanced NMR

A saddle coil manufactured by electric discharge machining (EDM) from a solid piece of copper has recently been realized at EPFL for Dynamic Nuclear Polarization enhanced Nuclear Magnetic Resonance experiments (DNP-NMR) at 9.4 T. The corresponding electromagnetic behavior of radio-frequency (400 MHz) and THz (263 GHz) waves were studied by numerical simulation in various measurement configurations. Moreover, we present an experimental method by which the results of the THz-wave numerical modeling are validated. On the basis of the good agreement between numerical and experimental results, we conducted by numerical simulation a systematic analysis on the influence of the coil geometry and of the sample properties on the THz-wave field, which is crucial in view of the optimization of DNP-NMR in solids.     

Pd-Sn双金属催化剂催化1, 3-丁二烯加氢反应的仲氢诱导极化研究

本文首先利用等体积共浸渍法合成了一系列Pd/Sn比（原子比）不同的Pd₁-Sn_x/Al₂O₃双金属催化剂,然后通过多相催化仲氢诱导极化（PHIP）技术研究了Pd-Sn/Al₂O₃双金属催化剂上1, 3-丁二烯选择性加氢反应.结果发现催化剂的Pd/Sn比会影响1, 3-丁二烯反应活性和丁烯选择性：随着Pd/Sn比的下降,反应中1, 3-丁二烯转化率降低,丁烯选择性提高.利用PASADENA（parahydrogen and synthesis allow for dramatically enhanced nuclear alignment）技术,发现Pd/Sn比的变化影响了1-丁烯与2-丁烯之间的异构化过程：随着Pd/Sn比的下降,1-丁烯异构化率降低,这是由于Sn组分含量的提高减少了表面暴露的Pd组分,使得催化剂反应活性降低;Sn组分含量的提高同时导致了Pd电子密度的上升,使得选择性还原产物丁烯更易脱附,阻止其进一步加氢生成丁烷,并抑制了1-丁烯异构化反应过程.