Structure–Function Relationship of Retinal Ganglion Cells in Multiple Sclerosis

The retinal ganglion cells (RGC) may be considered an easily accessible pathophysiological site of degenerative processes in neurological diseases, such as the RGC damage detectable in multiple sclerosis (MS) patients with (HON) and without a history of optic neuritis (NON). We aimed to assess and interrelate RGC functional and structural damage in different retinal layers and retinal sites. We included 12 NON patients, 11 HON patients and 14 healthy controls for cross-sectional multifocal pattern electroretinography (mfPERG) and optical coherence tomography (OCT) measurements. Amplitude and peak times of the mfPERG were assessed. Macula and disc OCT scans were acquired to determine macular retinal layer and peripapillary retinal nerve fiber layer (pRNFL) thickness. In both HON and NON patients the foveal N2 amplitude of the mfPERG was reduced compared to controls. The parafoveal P1 peak time was significantly reduced in HON only. For OCT, parafoveal (pfGCL) and perifoveal (pGCL) ganglion cell layer thicknesses were decreased in HON vs. controls, while pRNFL in the papillomacular bundle sector (PMB) showed reductions in both NON and HON. As the mfPERG derived N2 originates from RGC axons, these findings suggest foveal axonal dysfunction not only in HON, but also in NON patients.     

Development of surface reconstruction algorithms for optical interferometric measurement

Optical interferometry is a powerful tool for measuring and characterizing areal surface topography in precision manufacturing. A variety of instruments based on optical interferometry have been developed to meet the measurement needs in various applications, but the existing techniques are simply not enough to meet the ever-increasing requirements in terms of accuracy, speed, robustness, and dynamic range, especially in on-line or on-machine conditions. This paper provides an in-depth perspective of surface topography reconstruction for optical interferometric measurements. Principles, configurations, and applications of typical optical interferometers with different capabilities and limitations are presented. Theoretical background and recent advances of fringe analysis algorithms, including coherence peak sensing and phase-shifting algorithm, are summarized. The new developments in measurement accuracy and repeatability, noise resistance, self-calibration ability, and computational efficiency are discussed. This paper also presents the new challenges that optical interferometry techniques are facing in surface topography measurement. To address these challenges, advanced techniques in image stitching, on-machine measurement, intelligent sampling, parallel computing, and deep learning are explored to improve the functional performance of optical interferometry in future manufacturing metrology.     

Clinical significance of contact lens related changes of ocular surface tissue observed on optical coherence images

PurposeTo investigate the relationship between the real contact lens imprint into the conjunctival tissue, observed by optical coherence tomography (OCT) and conjunctival staining and contact lens wearing comfort.Methods17 participants (mean age = 26.6 SD ± 3.6 years; 7 females) were fitted with three different contact lenses base curves of the same silicone hydrogel custom lens type (Visell 50; Hecht Contactlinsen, Au, Germany) in a randomised order. One lens was optimally fitted according to the manufacturer's recommendation, one fitted 0.4 mm flatter and one fitted 0.4 mm steeper. After 4 h of lens wear the contact lens edge in the area of the conjunctiva was imaged nasally and temporally using OCT (Optovue iVue SD-OCT). To correct the artefact due to optical distortion with OCT, the imprint of all worn lenses was measured on a glass plate afterwards. Conjunctival staining in the limbal region after 4 h of lens wear was classified using the CCLRU Grading Scale. Comfort scoring was based on visual analog scales from 0 (very poor) to 100 (excellent).ResultsThe mean conjunctival imprint of all contact lens edges was 32.0 ± 8.1 μm before and 7.3 ± 6.5 μm after distortion correction of the OCT images. The distortion corrected conjunctival imprint with the 0.4 mm steeper lens (11.5 ± 6.2 μm) was statistically significantly greater compared to the optimally fitted lens (6.5 ± 5.9 μm) (One-way ANOVA followed Tukey-test; p = 0.017) and greater compared to the 0.4 mm flatter lens (3.9 ± 5.3 μm) (p < 0.001). There was no statistically significant difference between the optimally fitted lens and the 0.4 mm flatter lens (p = 0.209). The nasally measured imprint (11.4 ± 9.0 μm) was significantly greater than the temporally measured (3.3 ± 7.6 μm) (p < 0.001). There was no statistically significant correlation between the amount of conjunctival imprint and the graded conjunctival staining (p = 0.346) or the wearer’s comfort (p = 0.735).ConclusionsContact lens edges imaged by OCT exhibited displacement artefacts. The observed conjunctival imprints are a combination of real conjunctival compression and artefacts. A deeper imprint of the contact lens into the conjunctiva caused by a steeper base curve was not related to clinically significant staining or changes in comfort after 4 h of lens wear. The observed differences between nasal and temporal imprint are likely to be caused by variations of conjunctival thickness and the shape of the underlying sclera.     

Unraveling the film-formation kinetics of interfacial polymerization via low coherence interferometry

Interfacial polymerization (IP) is one of the most important methods for fabricating thin film composite (TFC) membranes. Understanding the film-formation mechanisms is of great value for developing membranes with enhanced performance. This work proposed a novel method to in situ characterize the film-formation kinetics via low coherence interferometry (LCI). The polyamide film formed at the liquid–substrate interface was scanned in real time; the polymerization induced significant variations in the optical properties around the reaction zone. After mitigating the effects of the perturbed interface, the surface-averaged intensity profiles provide a solid basis for analyzing the film-formation kinetics at various depths. In particular, the effects of the monomer concentrations were investigated to reveal the asymmetric growth and development of irregular substructures. All the characterization results confirm that the LCI-based characterization is a powerful tool for studying the structural evolution of the IP layer and thereby providing deeper insights for optimizing TFC membranes.     

网络化雷达现状及技术发展趋势

随着新的作战对象和作战样式的出现,以及作战环境更加复杂,仅依靠单个雷达节点的能力已经越来越难以满足新的作战需求。文中针对网络化雷达这一新体制雷达开展研究,通过分析国外网络化雷达系统发展现状、趋势及关键技术,总结对我国网络化雷达技术发展的经验启示,为我国网络化雷达系统发展提供技术参考。     

改型Wollaston棱镜干涉光谱仪的调制度研究

改型Wollaston棱镜(MWP)无需中继,可构建微型傅里叶变换光谱仪。回顾了MWP的基本原理,从调制度定义出发,计算得到准单色光源的复相干度,找到调制度的影响因素——扩展视场、剪切结构、焦面探测等。建立一般的干涉定域分析模型后,由像点逆光路追迹给出MWP的厚度计算公式,代入调制度约束参数得到不同参量的误差容限。通过FRED记录不同视场扩展情况的灰度与辐照度,结果显示,调制度为0.9时,视场与理论估算值1.24°基本相符;不同剪切量的灰度与辐照度变化特性表明,结构角会使定域垂直系统光轴的入射角发生变化,与晶轴倾角共同影响双折射率差;2.5和8μm像元探测采样表现出调制度差异,描述了定域深度或离焦的影响。以准单色光源、复相干度表示调制度,可将不同影响因素统一至约束参数中,相关变量误差容限可作为MWP-FTS的设计依据。     

基于Copula函数的郑州市夏季双重城市热岛及其影响因素关系分析

城市热环境变化影响城市小区域气候，探究影响因子与其作用机制，可有效减缓城市热岛现象。利用郑州市1960～2017年长序列数据，从相对热岛（RHI）和绝对热岛（AHI）两个层面探究驱动因子降雨（R）、蒸发（E）、建成区面积(B_BUA)、城镇化率(U_UR)的影响关系，利用交叉小波和小波相干探究热岛与降雨的雨热关系，采用Copula函数计算影响因子在不同取值条件下与热岛的遭遇概率。结果表明，相对热岛-相对降雨在短中周期、绝对热岛-降雨在短周期上均呈负相关关系，雨热关系不同步，且绝对热岛-降雨的关系最为显著；影响因子B_BUA、U_UR取值越大，R取值越小，则与RHI、AHI的遭遇概率越大；不同影响因子在不同评价层面，敏感性强弱不同，E在不同层面的反馈机制也不同，可见选取合适评价分析层面，有利于准确量化影响程度。     

类噪声环境下基于滑动相干谱的强迫振荡检测方法研究

电力系统中时刻存在负荷投切等环境激励,使得系统响应表现为类似噪声的小幅波动。如果强迫功率振荡的幅值较小,很容易淹没在类噪声信号中。本文推导了类噪声环境下电力系统强迫功率振荡解析表达式,从数学角度阐释了类噪声环境下强迫振荡的机理特性。在深入分析类噪声环境下小幅强迫振荡频谱特征的基础上,提出了基于滑动相干谱法(SCM)的小幅强迫功率振荡检测方法。首先采集得到两组发电机有功功率类噪声响应数据,计算得到对应的自功率谱密度和互功率谱密度,从而计算得到两组数据的幅值平方相干函数值,进而通过对所得幅值平方相干函数值的量化比较,检测出淹没在类噪声信号中的小幅强迫功率振荡。IEEE 4机2区域系统和16机68节点系统验证了所提检测方法的可行性及有效性。     

Removing noises caused by motion artefacts in microcirculation maps of human skin in vivo

This paper presents a zero‐padding and cross‐correlation technique‐based correlation mapping optical coherence tomography (ZPCC‐cmOCT) to reconstruct microcirculation maps of human skin in vivo, which can remove the background decorrelation noise caused by motion artefacts. In conventional correlation mapping optical coherence tomography method, the correlation degree of static tissue may be lowered by the motion artefacts due to cardiac and respiratory motion, resulting in background decorrelation noise in microcirculation maps. In zero‐padding and cross‐correlation technique‐based correlation mapping optical coherence tomography method, structural images are first obtained by performing Fourier transform on zero‐padded interference fringes, and then cross‐correlation‐based image registration is utilized to align local areas in two adjacent structural images. Finally, correlation mapping optical coherence tomography method is performed to generate microcirculation maps. Both phantom experiments and in vivo experiments were implemented and the results demonstrate that the proposed method is capable of providing microcirculation maps with the background decorrelation noise removed.     

二维频域光学相干层析系统研究

针对时域光学相干层析成像系统的成像速度较慢的问题,采用VC++与Matlab混合编程技术开发了二维频域光学相干层析成像系统,实现了对被测样品进行内部快速成像;搭建二维频域光学相干层析成像系统代替一维频域光学相干层析成像系统;利用计算机驱动面阵CCD相机对干涉信号进行采集得到干涉信号;采用计算机驱动NI卡对压电陶瓷(PZT)移相器进行相移控制以达到频域光学相干层析成像系统对移相的需求,利用计算机驱动线性电动移动平台实现检测样品进行横向扫描以达到对样品进行三维成像。研究结果表明,该系统集成度高,开发的软件功能齐全、界面友好、便于维护和升级;该二维系统相比一维光学相干层析成像系统而言减少了一维的扫描采集次数,大大提高了成像速度。