A comparison of exact and approximate adjoint sensitivities in fluorescence tomography

Many approaches to fluorescence tomography utilize some form of regularized nonlinear least-squares algorithm for data inversion, thus requiring repeated computation of the Jacobian sensitivity matrix relating changes in observable quantities, such as emission fluence, to changes in underlying optical parameters, such as fluorescence absorption. An exact adjoint formulation of these sensitivities comprises three terms, reflecting the individual contributions of 1) sensitivities of diffusion and decay coefficients at the emission wavelength, 2) sensitivities of diffusion and decay coefficients at the excitation wavelength, and 3) sensitivity of the emission source term. Simplifying linearity assumptions are computationally attractive in that they cause the first and second terms to drop out of the formulation. The relative importance of the three terms is thus explored in order to determine the extent to which these approximations introduce error. Computational experiments show that, while the third term of the sensitivity matrix has the largest magnitude, the second term becomes increasingly significant as target fluorophore concentration or volume increases. Image reconstructions from experimental data confirm that neglecting the second term results in overestimation of sensitivities and consequently overestimation of the value and volume of the fluorescent target, whereas contributions of the first term are so low that they are probably not worth the additional computational costs.     

Comparison of entropy and complexity measures for the assessment of depth of sedation

Entropy and complexity of the electroencephalogram (EEG) have recently been proposed as measures of depth of anesthesia and sedation. Using surrogate data of predefined spectrum and probability distribution we show that the various algorithms used for the calculation of entropy and complexity actually measure different properties of the signal. The tested methods, Shannon entropy (ShEn), spectral entropy, approximate entropy (ApEn), Lempel-Ziv complexity (LZC), and Higuchi fractal dimension (HFD) are then applied to the EEG signal recorded during sedation in the intensive care unit (ICU). It is shown that the applied measures behave in a different manner when compared to clinical depth of sedation score--the Ramsay score. ShEn tends to increase while the other tested measures decrease with deepening sedation. ApEn, LZC, and HFD are highly sensitive to the presence of high-frequency components in the EEG signal.     

利用高能电子预电离的大气压脉冲CO2激光器

描述了一种通过将高能电子注入激光器内使气体预电离的大气压脉沖CO2激光器。这些电子是从对激光器周围进行高压（120仟伏）辉光放电得出的。经预电离后,可将300焦耳的能量传递给一次放电的1.7立升气体而没发生击穿,而不管气体中是否含有氦。在CO2、N2和He按 3:3:4比例混合时获得了最高输出能量(20焦耳）。     

下一代互联网的基础:全光格形骨干网

当前,互联网上迅速增长的数据业务量对骨干网络的传输和处理能力提出了严峻的挑战。如果单从传输容量来看,通过采用密集波分复用（DWDM）点到点系统就应当可以满足传输方面的需求,DWDM系统能够使每根光纤上的数据传输速率达到每秒十几甚至是上百吉比特。然而,对网络节点（如IP路由器、电路交换机等）的处理能力的需求不断增长,这对系统的可扩展性和成本是一个严重的挑战。此外,在一个国家的骨干网络中,由于网络节点之间的再生器的数量很大,所以传统的点到点WDM系统的安装和运营成本都非常高。和传统的技术方案相比,一个全光…     

盲人使用的激光手杖制成

美帝无线电公司已研制出一种实验型“探路手杖”。此手杖系以脉冲激光束引导盲人绕过障碍物。嵌于手杖中的两只激光器不断发射红外光束,并不断从手杖前的两点（3呎和6呎)反射回杖中安装的两个光电管中。     

An ensemble-based system for microaneurysm detection and diabetic retinopathy grading

Reliable microaneurysm detection in digital fundus images is still an open issue in medical image processing. We propose an ensemble-based framework to improve microaneurysm detection. Unlike the well-known approach of considering the output of multiple classifiers, we propose a combination of internal components of microaneurysm detectors, namely preprocessing methods and candidate extractors. We have evaluated our approach for microaneurysm detection in an online competition, where this algorithm is currently ranked as first, and also on two other databases. Since microaneurysm detection is decisive in diabetic retinopathy (DR) grading, we also tested the proposed method for this task on the publicly available Messidor database, where a promising AUC 0.90 ± 0.01 is achieved in a "DR/non-DR"-type classification based on the presence or absence of the microaneurysms.     

Status and Trends in Advanced SOI Devices and Materials

提供了一种用于安德鲁反射测量样品制备新方法.该方法采用聚焦粒子束刻蚀和磁控溅射,可以获得可控的、干净的、无应力的纳米接触用于自旋极化探测.所制备的样品中,磁性和非磁性材料样品的反射谱都表现出复杂的峰和谷结构,这些结构可能源于与界面相关的零偏压反常以及与激发态相关的准离子相互作用.对另一个Co40Fe40B20合金样品采用简单的钕针尖压针方法进行了对比性测量,反射谱中没有观察到谷结构,但谱结构出现较明显的热扩展,这种热扩展可能来源于界面处的非弹性输运.所有的反射谱目前还不能由现有的理论给出令人满意的解释.利用点接触反射方法获得可靠的自旋极化信息还有赖于接触界面特征的进一步分析.而一个更切合实际的、更完善的理论成为迫切的需要.     

TeO_2高分辨率声光射电频谱仪(AOS)

声光射电频谱分析是借助于高分辨率的声光器件将射电信号进行光学模拟的过程。扩束的激光被声光器件偏转后,经傅里叶变换透镜,将在其后焦平面上形成射电频谱的空间分布。利用光电二极管阵列PDA进行光电探测,然后由计算机处理后即可得到射电信号的频谱结构。在PDA的阵元数、间距和傅氏透镜的焦距确定后,其分辨率主要决定于器件的窗口函数。分辨率的提高将使旁瓣明显加大,两者是互相制约的一对参数。必须仔细调整高斯光束的截断     

通过实验表征、计算机辅助结构解析和原子模拟对切尔西土壤腐植酸进行三维结构模拟

本文描述了一个用于开发腐植酸(HAs)三维结构模型的完整的实验和计算框架。这种方法结合了实验表征、计算机辅助结构解析(CASE)和原子模拟,生成与HAs的分析数据和热力学/结构特性相一致的所有三维结构模型或这些模型的代表性样本。从元素分析、漫反射傅里叶变换红外光谱、一维/二维¹H和¹³C溶液核磁共振光谱和电喷雾电离四极杆飞行时间质谱(ESI QqTOF MS)中获得的结构数据,结合CASE程序SIGNATURE,生成了切尔西土壤腐植酸(HA)所有的三维结构模型。这些模型随后被用作初始三维结构,进行恒温恒压分子动力学模拟,以估算其体密度和Hildebrand溶解度参数。只有少数模型异构体显示出的分子组成和体热力学性质与实验数据一致。这些模型异构体的等摩尔混合物的模拟¹³C核磁共振光谱与切尔西土壤HA的实测光谱相比有较好的一致性。