数字散斑相关测量中亚象素位移搜索的曲面拟合研究

本文介绍一种在散斑相关测量技术中进行亚象素位移搜索的新方法.用对相关系数作曲面拟合的方法来进行亚象素位移搜索,不但可以减少相关分析的运算量从而提高测量分析的速度,而且可以提高测量精度.     

一般1×N的MMI成像位置和相位关系

根据多模干涉器(MMI)的自映像原理,讨论了一般1×N多模干涉器件的成像位置和相位关系,并用导模传输法验证了分析结果,一般的成像位置和相对相位关系同原像的初始位置密切相关.     

Bioactive Potential: A Pharmacognostic Definition through the Screening of Four Hypericum Species from the Canary Islands

In this work, we propose a general methodology to assess the bioactive potential (BP) of extracts in the quest of vegetable-based drugs. To exemplify the method, we studied the anticancer potential (AP) of four endemic species of genus Hypericum (Hypericum canariense L, Hypericum glandulosum Aiton, Hypericum grandifolium Choisy and Hypericum reflexum L.f) from the Canary Islands. Microextracts were obtained from the aerial parts of these species and were tested against six human tumor cell lines, A549 (non-small-cell lung), HBL-100 (breast), HeLa (cervix), SW1573 (non-small-cell lung), T-47D (breast) and WiDr (colon). The methanol–water microextracts were evaluated further for cell migration, autophagy and cell death. The most promising bioactive polar microextracts were analyzed by UHPLC–DAD–MS. The extraction yield, the bioactivity evaluation and the chemical profiling by LC–MS suggested that H. grandifolium was the species with the highest AP. Label-free live-cell imaging studies on HeLa cells exposed to the methanol–water microextract of H. grandifolium enabled observing cell death and several apoptotic hallmarks. Overall, this study allows us to select Hypericum grandifolium Choisy as a source of new chemical entities with a potential interest for cancer treatment.     

神经网络反演算法在超声测量单向复合纤维材料特性中的应用

提出了一种神经网络反演算法,用于超声测量单向复合纤维材料的参数。算法基于Chistoffel方程,将单向复合纤维材料视作六角对称晶体,通过测量纤维样品中的声速,可以反演出五个独立的弹性系数C₁₁,C₁₂,C₁₃,C₃₃和C₄₄。反演方法则利用了神经网络反复学习不断用较好样例更新的训练样本集,克服了由于学习样例数目有限而使神经网络在预测过程中所产生的误差,提高了计算精度。并将该方法用于单向复合材料S2/DET85的弹性系数的实验测量和反演,所得声速与实验测量值吻合较好。该方法实现了超声测量单向复合纤维材料特性的自动递进反演过程。     

Optimization of supercritical fluid extraction of geniposidic acid from plantain seeds using response surface methodology

The process parameters of supercritical CO₂ (SCCO₂) plus modifer for the extraction of geniposidic acid from plantain seeds were studied using a Box–Behnken design. The effects of independent variables, that is, ethanol concentration (0–70%, ethanol:water, v/v), extraction pressure (10–30 MPa), and temperature (50–80°C) on the yield of geniposidic acid were evaluated. Results indicated that the data could be well fitted to a second-order polynomial model. The effects of ethanol concentration and temperature, as well as the interaction between ethanol concentration and temperature were significant (p < 0.05). The yield (8.9 mg/g) of modified SCCO₂ extraction at optimal conditions was compared with that obtained by Soxhlet extraction or ultrasound assisted extraction.     

烟道气国际比对中低浓度一氧化碳的精确测量

研究了烟道气体中低浓度一氧化碳(CO)的精确分析方法.结果显示,使用非色散红外光谱法的重复性明显优于气相色谱法,但烟道气中高浓度二氧化碳( CO2)的存在会影响光谱法对CO的精确测量,因此测量样品时采用含有CO2成分的标准气体作为标准.由不确定度评定结果及比对样品重复性测量结果可知,本方法精确度高.通过参加国际计量局物...     

A new rhodamine-based dual chemosensor for Al and Cu

A new rhodamine B derivative bearing a hydrazone group has been designed and prepared. The synthesized colorimetric and fluorescent molecular chemosensor can be used as a dual probe, selectively detecting Al³⁺ and Cu²⁺ in acetonitrile solution by monitoring changes in the absorption and fluorescence spectral patterns. The results show that Al³⁺ ions can induce a greater fluorescence enhancement, while the addition of Cu²⁺ ions induces a strong UV–vis absorption enhancement with weak fluorescence. The limits of detection of Cu²⁺ and Al³⁺ were estimated to be 2.9 × 10⁻⁷ M and 8.3 × 10⁻⁹ M, respectively.     

Three dimensional finite element analysis for Rayleight-Benard convection in rectangular enclosures

The pattern of Rayleigh-Benard convection of air in a rectangular box heated-from-below is studied by numerically solving the three-dimensional time-dependent Navier-Stokes equations under the Boussinesq approximation. Slightly supercritical Rayleigh number was adopted to track the evolutions of flow structure as a function of enclosure's aspect ratio (A=L/H). The flow will asymptotically evolve to different patterns, among which, two possible types of flow pattern are found. One consists of the pair of straight vortex rolls and the other appears as closed vortex rings. The transition between the flow patterns indicates that there exists a flow bifurcation with the variation of container's aspect ratio. In addition, both steady and oscillatory flows have been observed, corresponding to the pair of straight vortex rolls and the vortex ring, respectively. The complexity of flow structure tends to increase with the increasing aspect ratio of the rectangular enclosure. The project supported by the National Natural Science Foundation of China (19889210), the National Distinguished Young Fund (10125210), the Hundred Talents Program of CAS, and the Training Program for the Trans-Century Outstanding Young of MOE     

Creating an Amyloid ‘Kaleidoscope’ Using Short Iodinated Peptides

Amyloid fibrils formed by peptides with different sequences exhibit diversified morphologies, material properties and activities, making them valuable for developing functional bionanomaterials. However, the molecular understanding underlying the structural diversity of peptide fibrillar assembly at atomic level is still lacking. In this study, by using cryogenic electron microscopy, we first revealed the structural basis underlying the highly reversible assembly of ¹GFGGNDNFG⁹ (referred to as hnRAC1) peptide fibril. Furthermore, by installing iodine at different sites of hnRAC1, we generated a collection of peptide fibrils with distinct thermostability. By determining the atomic structures of the iodinated fibrils, we discovered that iodination at different sites of the peptide facilitates the formation of diverse halogen bonds and triggers the assembly of entirely different structures of iodinated fibrils. Finally, based on this structural knowledge, we designed an iodinated peptide that assembles into new atomic structures of fibrils, exhibiting superior thermostability, that aligned with our design. Our work provides an in-depth understanding of the atomic-level processes underlying the formation of diverse peptide fibril structures, and paves the way for creating an amyloid “kaleidoscope” by employing various modifications and peptide sequences to fine-tune the atomic structure and properties of fibrillar nanostructures.     

Geometrically Compelled Silicon(II)/Silicon(IV) Donor–Acceptor Interaction Enables the Enamination of Nitriles

Discovering new bonding scenarios and subsequently exploring the reactivity contribute substantially to advance the main group element chemistry. Herein, we report on the isolation and characterization of an intriguing class of the hydrido-benzosiloles 2 – 4 . These compounds exhibit a side arm of the amidinatosilylenyl group, featuring unidirectional silicon(II)/silicon(IV) donor-acceptor interaction on account of the geometric constraint. Furthermore, the reactions involving 2 – 4 with nitriles yield the tricyclic compounds that edge-fused of the Si-heteroimidazolidine-CN₂Si₂, silole-C₄Si, and phenyl-C₆-rings ( 5 – 13 ). These compounds are manifesting a unique reaction that the silicon(II)/silicon(IV) interaction enables the enamination of the α-H-bearing nitriles. The reaction mechanism involved in H-shift under oxidative addition at silylene followed by hydrosilylation of a ketenimine intermediate was revealed by density function theory (DFT) calculations.