Della Robbia blue glaze: micro‐Raman temperature study and X‐ray fluorescence spectroscopy characterization

Micro‐Raman temperature study and X‐ray fluorescence (XRF) spectroscopy were used for characterization of the blue glaze on Saint John the Baptist—majolica terracotta relief attributed to Andrea Della Robbia and Saint John the Baptist with Cross—majolica terracotta statue attributed to Giovanni Della Robbia. Both objects are on permanent exhibition in the John and Mable Ringling Museum of Art in Sarasota, FL. This study proves that the detection of the 548 cm⁻¹ Raman band alone cannot serve as evidence for presence of lazurite crystallites in the pigment in the glaze. It was established that the famous Della Robbia blue is due to the combined effect of Co Ni Cu Zn atoms and S₃⁻ ions embedded in a lead silicate matrix. It is proposed that the Della Robbia family used Co‐containing sulfide ores as a source for manufacturing their blue pigments. Copyright © 2009 John Wiley & Sons, Ltd.     

Micro‐Raman mapping on polished cross sections: a tool to define the penetration depth of conservation treatment on cultural heritage

Nowadays, in order to preserve the surfaces of works of art, several organic and inorganic substances are used. To evaluate the penetration depth and the distribution of these substances inside the materials, it is essential to define the effectiveness of a conservative treatment. Owing to the ambiguous results obtained with the current analytical techniques, the achievement of this aim is critical. This study shows how micro‐Raman mapping on polished cross section is an effective tool capable of investigating the inner portions of the materials. A set of painted plasters has been treated with ammonium oxalate solutions, an inorganic substance widely used for conservation works of carbonatic materials. The micro‐Raman mapping of the lines of the newly formed calcium oxalate allowed correlation of the penetration depth and the distribution of the product inside the specimens with different conditions of treatment. Moreover, a good agreement between micro‐Raman spectroscopy and microscopic techniques has been obtained. Copyright © 2010 John Wiley & Sons, Ltd.     

A Priori Feedback Estimates for Multiscale Reaction-Diffusion Systems

We study the approximation of a multiscale reaction–diffusion system posed on both macroscopic and microscopic space scales. The coupling between the scales is done through micro–macro flux conditions. Our target system has a typical structure for reaction–diffusion flow problems in media with distributed microstructures (also called, double porosity materials). Besides ensuring basic estimates for the convergence of two-scale semi-discrete Galerkin approximations, we provide a set of a priori feedback estimates and a local feedback error estimator that help in designing a distributed-high-errors strategy to allow for a computationally e?cient zooming in and out from microscopic structures. The error control on the feedback estimates relies on two-scale-energy, regularity, and interpolation estimates as well as on a fine bookeeping of the sources responsible with the propagation of the (multiscale) approximation errors. The working technique based on a priori feedback estimates is in principle applicable to a large class of systems of PDEs with dual structure admitting strong solutions.     

Estimation of N Absorption and Secretion by Digesta Exchange between 15N Labelled and Unlabelled Pigs

Abstract

Three female pigs (LW～30 kg) were fitted with re-entrant cannulas in the duodenum and the ileum and with bladder catheters. Animal No. 1 was labelled by continuous infusion of [¹⁵N]leucine via a catheter into the vena jugularis. After reaching a steady state in the level of endogenous N (4–5 d after beginning of the infusion) the digesta of the labelled animal No. 1 and the two unlabelled animals were exchanged in a 3 day experiment. During this time the course of transit rates of digesta, digesta N and ¹⁵N through duodenum and ileum as well as the proportion of endogenous N: exogenous N were estimated. Using these data it was possible to calculate the secretion and absorption rates of endogenous and exogenous N in the three segments of the digestive tract: mouth-duodenum, duodenum-ileum, ileum-anus and in addition the reabsorption (intestinal recycling) of the endogenous N during its passage through the gut could be computed.     

微纳光纤布拉格光栅折射率传感特性研究

利用光纤布拉格光栅方程和光纤基模有效折射率随纤芯半径和环境折射率的函数关系, 建立了微纳光纤布拉格光栅(MNFBG)反射波长随环境折射率变化的数学模型, 给出了波长灵敏度函数, 并指出MNFBG反射波长的变化规律决定于有效折射率随纤芯半径和环境折射率变化的关系. 详细探究了有效折射率及其灵敏度的变化规律, 结果表明: 有效折射率随纤芯半径和环境折射率的减小而非线性减小, 其对环境折射率变化的灵敏度随环境折射率的增大而非线性增加, 而且随纤芯半径减小, 有效折射率的灵敏度、线性度以及线性响应范围均呈递增规律. 通过对纤芯半径为0.5 μm的MNFBG在1.20–1.30和1.33–1.43 环境折射率范围内的波长响应关系拟合, 分别获得了477.33 nm/RIU和856.30 nm/RIU的波长灵敏度以及99.58 %和99.7%的高线性度, 论证了分析结论以及折射率区间划分测量方案的正确性, 为MNFBG折射率传感器的设计、优化以及应用提供了参考依据. 关键词： 微纳光纤 光纤布拉格光栅 折射率传感 数值模拟     

Crystallization Fouling in Experimental Micro Heat Exchangers—Optical and Thermal Investigations

The intention of this work is the basic investigations of the fouling behavior in micro heat exchangers. Therefore fouling experiments with calcium carbonate (CaCO₃) in an experimental micro heat exchanger were carried out and observed with a digital microscope. The investigations included local temperature measurements confirmed by computational fluid dynamics simulation as well as optical visualization of the fouling process inside the microchannels. The detected fouling resistances R _f were in the range of 10^?5–10^?4 m₂ K W^?1. Cleaning in place was possible and also optically observed.     

Study of carrier concentration profiles in Al‐implanted Ge by micro‐Raman spectroscopy under different excitation wavelengths

The distribution profile of Al implanted in crystalline Ge has been investigated by micro‐Raman spectroscopy. Using different excitation laser lines, corresponding to different optical penetration depths, the Al concentration at different depths beneath the sample surface has been studied. We have found a strong correlation between the intensity of the Al–Ge Raman peak at ~370 cm⁻¹, which is due to the local vibrational mode of substitutional Al atoms, and the carrier concentration profile, obtained by the spreading resistance profiling analysis. A similar connection has been also observed for both shape and position of the Ge–Ge Raman peak at ~300 cm⁻¹. According to these experimental findings, we propose here a fast and nondestructive method, based on micro‐Raman spectroscopy under different excitation wavelengths, to estimate the carrier concentration profiles in Al‐implanted Ge. Copyright © 2013 John Wiley & Sons, Ltd.     

微构件材料力学性能测试方法

随着MEMS的商业化进程,微构件材料力学性能的研究成为越来越重要的一个课题。微小试件的制备、安装、夹持、微驱动、高分辨率的载荷和位移测量等技术问题都是对微构件材料力学性能测试的很大挑战,很多传统的测试方法和装置已经不再适用了。近十几年,国内外学者发展了一些微构件材料力学性能的研究方法,来测量微构件的弹性模量、屈服强度、断裂强度、残余应力和疲劳强度等。本文从实验系统的集成度出发,将这些测试方法大致分为片外测试和片上测试两类。本文对单轴拉伸法、纳米压痕法、鼓膜法、微梁弯曲法和衬底曲率法等典型的片外测试方法和一些典型的片上测试方法进行了介绍,并比较了各自的优缺点。     

稀有原人参二醇型皂苷的人肠道菌群生物转化

利用高分离度液相色谱-四极杆飞行时间质谱(RRLC-Q-TOF MS)和超高效液相色谱-三重四极杆质谱(UPLC-QQQ MS)定性定量分析了稀有原人参二醇型皂苷Rd, F₂, Rg₃, CK和Rh₂在离体人肠道菌群中的生物转化过程. 并将上述二醇型皂苷与人肠道菌群在体外厌氧, 37 ℃下共温孵育, 采用电喷雾质谱在负离子模式进行检测, 鉴定代谢产物, 监测其含量变化, 拟合代谢路径. 结果表明, 人参皂苷Rd主要被代谢为F₂, Rg₃, CK, Rh₂和PPD; 人参皂苷F₂主要被代谢为CK和PPD; 人参皂苷Rg₃主要被代谢为Rh₂和PPD; 人参皂苷CK和Rh₂主要被代谢为PPD. 在离体条件下, 人参皂苷Rd, F₂和Rg₃会被肠道菌群完全转化为其代谢产物, 而人参皂苷CK和Rh₂则不能被肠道菌群完全转化为其代谢产物. 原人参二醇型皂苷在人肠道菌群中的主要转化为脱糖基反应, 单糖苷和苷元是稀有原人参二醇型皂苷在人体内发挥药效的物质基础.     

侧链PEG基聚合物的制备及其催化酯化反应性能

聚乙二醇单(乙烯基苄基)醚(PEG-VBE)和聚乙二醇二(乙烯基苄基)醚(PEG-DVBE)是重要的可聚合聚乙二醇衍生物,可用于催化剂载体及功能高分子的合成。本文以氢氧化钾为碱,乙烯基苄基氯(VBC)与乙二醇、一缩二乙二醇、二缩三乙二醇、PEG400、PEG600和PEG1500反应,高效合成了一系列乙烯基苄基聚乙二醇衍生物,乙烯基苄基氯的转化率可达96%以上,PEG-VBE的分离收率为32 ~ 93%。乙烯基衍生物在过硫酸钾引发下聚合得到水溶性高分子,产物经1H NMR、ESI-HRMS及FT-IR分析表征。以制备的水溶性PEG基聚合物为微反应器,研究了苯甲酸与甲醇的酯化反应,PEG基聚合物与硫酸的体系对酯化反应具有很好地催化活性。在优化的条件下,苯甲酸的转化率可达99%以上,催化体系循环5次后,催化活性几乎没有下降