Complex refractive index of normal and malignant human colorectal tissue in the visible and near‐infrared

A multi‐wavelength prism coupling refractometer is utilized to measure the angular reflectance of freshly excised human intestinal tissue specimens. Based on reflectance data, the real and imaginary part of the refractive index is calculated via Fresnel analysis for three visible (blue, green, red) and two near‐infrared (963 nm and 1551 nm) wavelengths. Averaged values of the complex refractive index and corresponding Cauchy dispersion fits are given for the mucosa, submucosa and serosa layers of the colorectal wall at the normal state. The refractive constants of tumorous and normal mucosa are then cross‐compared for the indicative cases of one patient diagnosed with a benign polyp and three patients diagnosed with adenocarcinomas of different phenotype. Significant index contrast exists between the normal and diseased states, indicating the potential use of refractive index as a marker of colorectal dysplasia.

     

Modeling of Nonlinear Chemical Reaction Systems and Two-Parameter Stochastic Resonance

The idea of stochastic resonance (SR) is extended to two-parameter dynamical systems based on the Oregonator model of the Belousov-Zhabotinsky (BZ) reaction. The first case presents the photosensitivity of the reaction, and light flux and a flow rate are the two control parameters. The second case presents the effect of temperature on the oscillatory behaviors, and temperature and a flow rate are the control parameters. Stochastic resonance is demonstrated in the first case in which a signal and noise are applied to the different inputs, respectively. The scenario and novel aspects of SR in two-parameter systems are discussed, and the possibility of the analogous SR in biological systems is also pointed out.     

甘油生物歧化非线性动力系统的平衡点及其稳定性分析

针对甘油生物歧化为1,3-丙二醇过程的酶催化动力系统,利用符号化实根隔离法求解系统的平衡点,验证了系统的多稳态现象,利用微分方程稳定性理论,分析了平衡点的稳定性,并结合数值结果讨论了系统的多态现象．本文的结果可为微生物发酵甘油生产1,3-丙二醇的实验优化参数设计提供参考．     

具Holling第Ⅱ类功能性反应的捕食者--食饵系统的定性分析

考虑捕食者无密度制约,食饵具有非线性密度制约的第二类Holling功能性反应捕食者－食饵系统。对该系统给出了完整的定性分析,证明了该系统至多有一个极限环,存在极限环的充要条件是平衡点不稳定。     

基于功能性近红外光谱技术的双人同步交互测量研究

多人同步交互式记录是认知神经科学的一种新的研究范式,它可以揭示两个或多个个体的大脑间在社交情境下神经活动的耦合。这一目标仅靠单个大脑活动的记录与测量是无法实现的。功能性近红外光谱成像在进行多人同步交互记录研究中有独特的优势。该方面的研究已经涵盖了社会认知神经科学的多个领域。本研究使用近红外光谱成像对社交情境下自我表露的双人大脑前额皮层的活动进行交互式测量,并使用小波相关来分析双人大脑互动时的神经同步性。研究结果表明在进行社交对话时,被试对的大脑间左侧额中回、右侧眶额皮层和右侧额下回下部的活动同步性显著增强。共情能力与社交情境下脑间同步性的强度呈正相关,这种关系主要体现在右侧额下回。本研究支持了采用近红外光谱成像技术研究多人同步交互记录大脑间神经耦合的可行性和有效性。     

生物数学中的反应扩散系统的同伦映射方法

本文研究了一类非线性捕食-被捕食反应扩散系统,利用同伦映射理论,得到了初边值问题解的近似表示式。     

Characterization of blood coagulation dynamics and oxygenation in ex‐vivo retinal vessels by fluorescence hyperspectral imaging

Blood coagulation mechanisms forming a blood clot and preventing hemorrhage have been extensively studied in the last decades. Knowing the mechanisms behind becomes very important particularly in the case of blood vessel diseases. Real‐time and accurate diagnostics accompanied by the therapy are particularly needed, for example, in diseases related to retinal vasculature. In our study, we employ for the first time fluorescence hyperspectral imaging (fHSI) combined with the spectral analysis algorithm concept to assess physical as well as functional information of blood coagulation in real‐time. By laser‐induced local disruption of retinal vessels to mimic blood leaking and subsequent coagulation and a proper fitting algorithm, we were able to reveal and quantify the extent of local blood coagulation through direct identification of the change of oxyhemoglobin concentration within few minutes. We confirmed and illuminated the spatio‐temporal evolution of the essential role of erythrocytes in the coagulation cascade as the suppliers of oxygenated hemoglobin. By additional optical tweezers force manipulation, we showed immediate aggregation of erythrocytes at the coagulation site. The presented fluorescence‐based imaging concept could become a valuable tool in various blood coagulation diagnostics as well as theranostic systems if coupled with the laser therapy.     

Optical Saturable Absorption in Gold Nanoparticles

In this work, we present the experimental study of the nonlinear absorption of gold nanospheres and nanorods in aqueous suspension, using picosecond white-light supercontinuum open-aperture Z-scan. We demonstrate a saturable absorption effect in all particle suspensions at low-pulse energy. In the high-pulse energy regime, the apparent reverse-saturable absorption, observed in gold nanorods, was determined to be induced by photodegradation. Using the Lorentzian deconvolution method for the absorption spectra, we explain the variations on nonlinear optical effects and prove that saturable absorption only occurs within the plasmonic bands.