Numerical simulation on the adaptation of forms in trabecular bone to mechanical disuse and basic multi-cellular unit activation threshold at menopause

The objective of this paper is to identify the effects of mechanical disuse and basic multi-cellular unit （BMU） activation threshold on the form of trabecular bone during menopause. A bone adaptation model with mechanical- biological factors at BMU level was integrated with finite element analysis to simulate the changes of trabecular bone structure during menopause. Mechanical disuse and changes in the BMU activation threshold were applied to the model for the period from 4 years before to 4 years after menopause. The changes in bone volume fraction, trabecular thickness and fractal dimension of the trabecular structures were used to quantify the changes of trabecular bone in three different cases associated with mechanical disuse and BMU activation threshold. It was found that the changes in the simulated bone volume fraction were highly correlated and consistent with clinical data, and that the trabecular thickness reduced signi-ficantly during menopause and was highly linearly correlated with the bone volume fraction, and that the change trend of fractal dimension of the simulated trabecular structure was in correspondence with clinical observations. The numerical simulation in this paper may help to better understand the relationship between the bone morphology and the mecha-nical, as well as biological environment; and can provide a quantitative computational model and methodology for the numerical simulation of the bone structural morphological changes caused by the mechanical environment, and/or the biological environment.     

基于长光程技术的痕量海水营养盐自动分析仪的设计与测试

海水中可溶性的营养盐浓度是海洋监测的常规项目之一;大洋水体中的营养盐含量很低,使用传统的分光光度计难于定量测量。文章基于液芯波导长光程技术,设计了高灵敏度的痕量海水营养盐光谱分析仪。分析仪以1.02 nm的光谱分辨率实现350～900 nm光谱范围的水样吸光度连续光谱测量,并由嵌入式PC104微机自动实现了水样采集、吸光度测量和数据分析的功能。针对亚硝酸盐的测试实验结果表明,仪器检出限达到nmol·L-1的量级,比传统分光光度计的检测限提高了三个量级,且显色反应时间可缩短到3 min,能适用于大洋水体中营养盐的现场痕量分析。     

新型波长解调技术在干涉型光纤传感器输出解调中的应用

提出了一种改进型边缘滤波波长解调技术,解决干涉型或谐振型光纤传感器输出的干涉谱波长的快速解调问题。该波长解调技术基于啁啾光栅和长周期光栅的光谱特点,以啁啾光栅作为矩形滤波器,提取传感器输出干涉谱的一个干涉峰;以长周期作为边缘滤波器,将干涉峰的波长信息转化为光强信息进行检测。该波长解调技术波长解调范围为传感器输出干涉谱的一个自由光谱范围(FSR),解调速度快,克服了当前波长解调技术中存在的测量范围与测量速度难以同时提高的问题,同时还具有系统成本低 ,体积小,能够灵活多路扩展的特点。详细介绍了解调系统的工作原理以及系统结构,并将其实际应用于一种干涉型光纤电流传感器输出干涉谱的波长解调中。通过实验证明电流传感器工作在工频及脉冲电流(脉冲宽度25 μs)情况下,该解调系统对传感器输出干涉谱具有准确、快速的解调效果。该研究对推进干涉或谐振型光纤传感器的实际工程化水平的提高具有重要意义。     

α、ω-双香豆素长链化合物激基缔合物的研究

通过α、ω－双香豆素长链化合物详细研究了香豆素激基缔合物的荧光行办，通过吸收光谱、荧光光谱和激发光谱，考察了香豆素激基缔合物的发光位置与激发波长，借助单光子技术确定了形成的是分子内的激基缔合物，通过1HNMR谱研究了不同双香豆素长链化合物的构象分布，揭示了在水溶液中由于疏水相互作用促进了长链化合物分子内激基缔合物的形成．     

Upper bounds on correlation decay for one-dimensional long-range spin-glass models

Some recent results on one-dimensional spin-glass models with polynomially decreasing interactions are described.     

Microstructure dependent dynamic fracture analyses of trabecular bone based on nascent bone atomistic simulations

Trabecular bone fracture is closely related to the trabecular architecture, microdamage accumulation, and bone tissue properties. Primary constituents of trabecular tissue are hydroxyapatite (HA) mineralized type-I collagen fibers. In this research, dynamic fracture in two dimensional (2-D) micrographs of ovine (sheep) trabecular bone is modeled using the mesoscale cohesive finite element method (CFEM). The bone tissue fracture properties are obtained based on the atomistic strength analyses of a type-I collagen + HA interfacial arrangement using molecular dynamics (MD). Analyses show that the presented framework is capable of analyzing the architecture dependent fracture in 2-D micrographs of trabecular bone.     

Comparison between a white-light interferometer and a tactile formtester for the measurement of long inner cylindrical surfaces

Shape measurements of engineering surfaces are an interesting and important application for white-light interferometry (WLI). Due to some factors such as: (a) the high-processing speed, (b) the ability to measure a huge quantity of points of the evaluated surface, and (c) the non-contacting nature; WLI has become a valuable tool for practical applications. This paper shows the achieved comparison between a modified white-light interferometer and an established measurement system, namely a formtester with a tactile spherical stylus sensor, which is the most commonly used instrument in the industry. Furthermore, this paper shows that the combination between the modified white-light interferometer and an adequate measurement and processing strategy has enabled to obtain a good agreement between optical and tactile measurements of long inner cylindrical surfaces. A cloud of points (COP) measured with the modified white-light interferometer has presented a standard deviation of about 0.3 μm when it was compared with formtester measurement of the same parts.     

High Sensitive Long Period Fiber Grating Sensor for Detection of Nitrite

A high sensitive long period fiber grating(LPFG) sensor for the detection of nitrite is proposed, which is realized by coating multiple poly(sodium 4-styrensulfonate)(PSS) and poly(diallyldimethylammonium) chloride (PDDA) layers on the fiber grating surface. The sensitivity of this LPFG sensor is maximum when the number of assembled layers is 70. Under this condition, a nitrite concentration of 3×10-3 mol/L, which is lower than the National Food Additive Standard, 4.2×10-3 mol/L, can be distinguished. The s...     

Detection of water in jet fuel using layer-by-layer thin film coated long period grating sensor

The quantitative measurement of jet fuel additives in the field is of interest to the Air Force. The “smart nozzle” project was designed as a state-of-the-art diagnostics package attached to a single-point refueling nozzle for assessing key fuel properties as the fuel is dispensed. The objective of the work was to show proof of concept that a layer-by-layer thin film and long period grating fibers could be used to detect the presence of water in jet fuel. The data for the nafion/PDMA film and a long period grating fiber is a combination capable of quantitative measurement of water in kerosene. The average response (spectral loss wavelength shift) to the kerosene sample ranged from −6.0 for 15 ppm to −126.5 for 60 ppm water. The average calculated value for the check standard was 21.71 and ranged from 21.25 to 22.00 with a true value of 22.5 ppm water. Potential interferences were observed and are judged to be insignificant in real samples.     

Towards high peak capacity separations in normal pressure nanoflow liquid chromatography using meter long packed capillary columns

Single shot proteomics is a promising approach to high throughput proteomics analysis. In this strategy, long capillary columns are needed to perform long and shallow gradients to achieve high peak capacity and good peak width for informative mass spectrometric detection. Herein, we report that meter long capillary columns, packed with 5 μm particulate material, can be facilely fabricated based on single particle fritting technology. The long columns could reliably generate high peak capacities of 800 in 10 h long gradients for protein digest separations. The operation was within the pressure range (40 MPa) of the most widely used normal pressure nanoLC systems. Due to the excellent life time (>100 injections) and inter-column performance consistency, the meter long capillary columns reported here should be of practical usefulness in single shot proteomics without the need for ultra-high pressure instrumentation.