基于机器视觉的软体纤维丝集束智能计数系统

设计了一种基于机器视觉的可以对软体纤维丝集束实现自动计数的检测系统。系统采用自制半球形LED光源照明,对软体纤维丝集束切片,经显微光学系统放大,再由电荷耦合器件(Charge coupled device,CCD)采集放大图像至计算机,通过图像处理系统计算出集束中软体纤维丝数量,并与标准值比较,自动给出是否合格的判别结果。并提出了一种图像处理方法,该方法首先采用基于区域熵值最大的原则将不同光强照射下获取的源图像进行融合,再对融合后的图像利用自组织特征映射(Self organization feature map,SOFM)神经网络求取分割阈值,然后使用求取的分割阈值作为测度指导源图像实现二值化融合,最后采用基于统计量的边界分离和计数方法实现纤维丝集束的计数。实验证明,该系统检测误差不大于1%,重复测量标准差不超过0.07,实现了对软体纤维丝集束的智能计数。     

Effects of pepsin hydrolysis on the soy β‐conglycinin aggregates formed by heat treatment at different pH

The effects of pepsin hydrolysis on the β‐conglycinin aggregates formed by heat treatment at different pH were investigated. Results showed that fibrils were still observed, whereas the random aggregates were easily to be digested in the simulated gastric fluid. Electrophoresis and molecular weight analysis indicated that large aggregates still existed after pepsin treatment for fibrils. Hydrolysis resulted in changes in the apparent viscosity (ηapp) of 6% fibril solutions. The ηapp at the shear rate range (0–30 s^?1) increased in the order of fibrils < fibrils with pepsin for 60 min < fibrils with pepsin for 30 min. Smaller peptide/fibril fragments were generated, and additional aggregates were reformed during the hydrolysis process, as evidenced by thioflavin T and atomic force microscopy images. The native β‐conglycinin hydrolysates comprised a mixture of polypeptides enriched in about 47 kDa. These findings would provide valuable information about effects of enzymatic hydrolysis on plant oligometric globulin aggregates.     

Biomechanics of fibrous proteins of the extracellular matrix studied by Brillouin scattering

Brillouin light scattering (BLS) spectroscopy is a technique that is able to detect thermally excited phonons within a material. The speed of propagation of these phonons can be determined from the magnitude of the Brillouin frequency shift between incident and scattered light, thereby providing a measure of the mechanical properties of the material in the gigahertz range. The mechanical properties of the extracellular matrices of biological tissues and their constituent biopolymers are important for normal tissue function and disturbances in these properties are widely implicated in disease. BLS offers the prospect of measuring mechanical properties on a microscopic scale in living tissues, thereby providing insights into structure–function relationships under normal and pathological conditions. In this study, we investigated BLS in collagen and elastin—the fibrous proteins of the extracellular matrix (ECM). Measurements were made on type I collagen in rat tail tendon, type II collagen in articular cartilage and nuchal ligament elastin. The dependence of the BLS spectrum on fibre orientation was investigated in a backscattering geometry using a reflective substrate. Two peaks, a bulk mode arising from phonon propagation along a quasi-radial direction to the fibre axis and a mode parallel to the surface, depending on sample orientation relative to the fibre axis, could be distinguished. The latter peak was fitted to a model of wave propagation through a hexagonally symmetric elastic solid, and the five components of the elasticity tensor were combined to give axial and transverse Young''s, shear and bulk moduli of the fibres. These were 10.2, 8.3, 3.2 and 10.9 GPa, and 6.1, 5.3, 1.9 and 8 GPa for dehydrated type I collagen and elastin, respectively. The former values are close to those previously reported. A microfocused BLS approach was also applied providing selection of single fibres. The moduli of collagen and elastin are much higher than those measured at lower frequency using macroscopic strains, and the difference between them is much less. We therefore believe, like previous investigators, that molecular-scale viscoelastic effects are responsible for the frequency dependence of the fibre biomechanics. Combining BLS with larger-scale mechanical testing methods therefore should, in the future, provide a means of following the evolution of mechanical properties in the formation of the complex structures found in the ECM.     

用液晶高分子微纤自增强的原位复合材料

刚性棒状的主链型热致液晶聚合物(TLCP)能自组织形成液晶畴,具有各向异性和优异的物理性质。将其加入到热塑性聚合物(TP)中,可明显改善体系的加工特性,并能"原位"生成高长径比、高模量和高强度的微纤,形成自增强的原位复合材料。本文作者简述了原位复合材料的加工流变学和微观结构形态;详细讨论了TLCP/TP原位复合材料的化学组成、物理性质(特别是相容性),和加工成型参数等因素对TLCP微纤的"原位"生成及其性能的影响;重点阐述了TLCP/TP共混体系的增容技术。文中作者首次提出了在加工过程中引入电场协助微纤原位生成,制备高性能原位复合材料的新概念。     

Polarization confocal microscopy and Congo Red fluorescence: a simple and rapid method to determine the mean cellulose fibril orientation in plants

The mean or net preferential orientation of cellulose fibrils in plant cell walls is detected with polarization confocal laser scanning microscopy using the fluorescence dichroism of Congo Red. Single cells, arrays of cells in a tissue, or the epidermis of whole organs can be assayed in vivo . Aerial parts require an extra pectinase treatment because of the cuticle, which is impermeable to aqueous solutions. Peeling off the epidermis can be an elegant alternative, especially for leaves. With this method the net preferential fibril orientation can be related to the symmetry axis of the cell in quantitative terms. Data issuing from this approach are useful in current research on plant biomechanics.     

Effect of strain history on craze microstructure

Crazes formed under a constant tensile strain in polystyrene (PS) have a dense network of fibrils with an extension ratio $\text{λ ? 4}$, but a midrib of higher λ forms by drawing fibrils from the craze-matrix interface in the high stress region just behind the craze tip. Stepwise increases in tensile strain during craze growth should thus produce layers of fibrils of different λ, which can be revealed by transmission electron microscopy (TEM) of crazes in stepwise strained PS films. When the time interval between strain increments of 0.5–1% is one minute, TEM images show ‘ridges’ of lower λ fibrils, corresponding to the position of the craze-matrix interface at the time of the strain increments. The ridges appear to be the analogue of the bulge remaining on a macroscopic fibre which has been allowed to stress age by stress relaxation before resuming drawing and imply that rapid stress ageing must occur near rthe craze-matrix interface so that more material is drawn into the craze in preference to increasing the λ of the existing fibrils.     

Rational Structure-Based Design of Fluorescent Probes for Amyloid Folds

Amyloid fibrils are pathological hallmarks of various human diseases, including Parkinson's, Alzheimer's, amyotrophic lateral sclerosis (ALS or motor neurone disease), and prion diseases. Treatment of the amyloid diseases are hindered, among other factors, by timely detection and therefore, early detection of the amyloid fibrils would be beneficial for treatment against these disorders. Here, a small molecular fluorescent probe is reported that selectively recognize the fibrillar form of amyloid beta(1–42), α-synuclein, and HET-s(218–289) protein over their monomeric conformation. The rational design of the reporters relies on the well-known cross-β-sheet repetition motif, the key structural feature of amyloids.     

牛肉肌纤维间距与嫩化效果关系的研究

以秦川牛肉(背最长肌)为原料,将牛肉切分成5×5×5cm3的肉块,分别用不同浓度磷酸氢二钠溶液(0.2%、0.4%、0.6%、0.8%、1.0%)、焦磷酸钠溶液(0.2%、0.4%、0.6%、0.8%、1.0%)、三聚磷酸钠溶液(0.2%、0.4%、0.6%、0.8%、1.0%)浸渍,4℃放置3d,对各种处理液中肉样作剪切力测定,并对处理的最佳效果肉样作石蜡切片,测定肌纤维间距.结果表明:0.8%三聚磷酸钠、0.8%磷酸氢二钠、0.8%焦磷酸钠对牛肉的嫩化效果显著(P<0.05),0.8%三聚磷酸钠、0.8%磷酸氢二钠对牛肉的嫩化效果无显著差异(P>0.05),0.8%焦磷酸钠与0.8%三聚磷酸钠、0.8%磷酸氢二钠对牛肉的嫩化效果差异显著(P<0.05),这与以肌纤维间距作为嫩化指标测定结果一致,表明肌纤维间距可作为肉的嫩化指标.     

Alpha Synuclein only Forms Fibrils In Vitro when Larger than its Critical Size of 70 Monomers

The aggregation of α-synuclein into small soluble aggregates and then fibrils is important in the development and spreading of aggregates through the brain in Parkinson's disease. Fibrillar aggregates can grow by monomer addition and then break into fragments that could spread into neighboring cells. The rate constants for fibril elongation and fragmentation have been measured but it is not known how large an aggregate needs to be before fibril formation is thermodynamically favorable. This critical size is an important parameter controlling at what stage in an aggregation reaction fibrils can form and replicate. We determined this value to be approximately 70 monomers using super-resolution and atomic force microscopy imaging of individual α-synuclein aggregates formed in solution over long time periods. This represents the minimum size for a stable α-synuclein fibril and we hypothesis the formation of aggregates of this size in a cell represents a tipping point at which rapid replication occurs.