Effect of in‐office bleaching with 35% hydrogen peroxide with and without addition of calcium on the enamel surface

This study aimed to evaluate effectiveness and effects of bleaching with 35% hydrogen peroxide with and without calcium on color, micromorphology, and the replacement of calcium and phosphate on the enamel surface. Thirty bovine enamel blocks (5.0 × 5.0 mm) were placed into the following groups: G1: artificial saliva (control); G2: 35% hydrogen peroxide gel without calcium (Whiteness HP Maxx–FGM); and G3: 35% hydrogen peroxide gel with calcium (Whiteness HP Blue–FGM). Three color measurements were performed with a spectrophotometer: untreated (baseline), after performing staining, and after application of bleaching agents. Calcium deposition on the enamel was evaluated before and after the application of bleaching agents using energy‐dispersive X‐ray spectrometry. The enamel surface micromorphology was observed under scanning electron microscopy. The pH of each product was measured. The data were subjected to one‐factor analysis of variance (ANOVA), and any differences were analyzed using Tukey's test (P < 0.05). G3 showed greater variation in total color after the experiment than G2 and G1; there was no significant difference in calcium or phosphorus concentration before and after the experimental procedures; morphological changes were observed only in G2 and G3; and the pH values of the Whiteness HP Maxx and Whiteness HP Blue bleaching agents were 5.77 and 7.79, respectively. The 35% hydrogen peroxide with calcium showed greater bleaching potential, but the addition of calcium had no effect in terms of reducing morphological changes or increasing the calcium concentration on the enamel surface. Microsc. Res. Tech. 78:975–981, 2015. © 2015 Wiley Periodicals, Inc.     

Identification of the three-dimensional gel microstructure from transmission electron micrographs

Mass transport in gels depends crucially on local properties of the gel network. We propose a method for identifying the three‐dimensional (3D) gel microstructure from statistical information in transmission electron micrographs. The gel strand network is modelled as a random graph with nodes and edges (branches). The distribution of edge length, the number of edges at nodes and the angles between edges at a node are estimated from transmission electron micrographs by image analysis methods. The 3D network is simulated by Markov chain Monte Carlo, with a probability function based on the statistical information found from the micrographs. The micrographs are projections of stained gel strands in slices, and we derive a formula for estimating the thickness of the stained gel slice based on the total projected gel strand length and the number of times that gel strands enter or exit the slice.     

多层次信息融合在铁谱图像磨粒识别中的应用

针对铁谱图像磨粒识别中异类信息综合利用率较低的问题,提出多层次信息融合的铁谱图像磨粒识别方法。首先,在铁谱图像二值化分割的基础上进行二值滤波,结合彩色铁谱图的R、G、B三分量,实现铁谱图像的彩色滤波。其次,以实际采集的磨粒图像样本为例,提取滤波后二值图像的形态特征,以及滤波后彩色图像的颜色特征;在特征层利用PCA对异类特征进行维数约简,并结合SVM和k-fold交叉验证,实现形态特征和颜色特征的特征层融合;在决策层将异类特征的SVM概率输出结果作为D-S证据理论的基本概率分配函数,实现形态特征和颜色特征的决策层融合。通过与形态学滤波结果对比,验证了本文提出滤波方法的优越性;其次,不同层次的信息融合结果表明,与单独使用颜色特征和形态特征相比,异类信息融合后可实现优势互补,有效提高故障磨粒的识别准确率。     

Determination of a homogeneity factor for composite materials by a microstructural image analysis method

The physical properties of particle‐reinforced composite materials are highly affected by the distribution of particles within a matrix material. In this study, a microstructural image analysis method with a new distribution index for quantifying the degree of distribution in composite materials was developed. The free‐path spacing between particles was measured to calculate the distribution (D) index based on the coefficient of variation. The proposed method was applied to six digitally created reference patterns as representative binary composite microstructures and three actual ceramic‐matrix composites, respectively. It is found that the D index increased from 0.00 to 0.67 depending on the degree of distribution or homogeneity level based on the reference patterns. The homogeneity levels for the binary composites are then classified from a perfect (maximum) to very low level (minimum) based on increasing D index values, where a high D index presents a poorer distribution. The results obtained for reference patterns and metal silicide‐refractory oxide composite microstructures indicate that the proposed method is a useful tool to quantify the degree of distribution with high accuracy, and can be efficiently used for different types of composite microstructures.     

Correlation between gas molecular weight, heating value and sonic speed under variable compositions of natural gas

A simulation study of likely uncertainties in molecular weight and heating value of the gas mixture as predicted from measured or calculated sonic speed. The sonic speed, molecular weight and heating value of natural gas were studied as a function of random fluctuation of the gas fractions. A method of sonic speed prediction was developed and used for over 50,000 computer-simulated variants of component concentrations in four- and five-component mixtures. Comparison of the obtained and the reference data on binary (methane–ethane) and multicomponent (Gulf Coast) gas mixtures under standard pressure and moderate temperatures indicates predictability of sonic speed on the basis of the binary virial coefficients, sonic speeds and heat capacities of the pure components. The results for two natural gas mixtures — with and without nonflammable components — are reported. Bivariate distribution and covariance elliptic zone plots are presented for three pairs of dependences of practical interest: molecular weight–sonic speed, heating value–sonic speed and heating value–molecular weight. The correlation coefficients, covariance, and regression equations are given for each pair of variance and mixture.     

非接触式高压静电场微胶囊制备方法

为制备脂肪干细胞微胶囊,设计并研制基于高压静电成囊原理的非接触式微囊发生装置。以海藻酸钠在氯化钙溶液中成囊的方法制备细胞微胶囊,并分析电场电压、推进速度、电极距离和针头型号等参数对所制微囊粒径的影响。采用非接触式微囊发生器能制备出表面光滑、形状规则、大小均匀的微胶囊。用该装置制备出微囊化脂肪干细胞,经过一周培养,细胞在微胶囊中存活良好,增殖明显。     

应用形态学top-hat变换的支票方形印鉴自适应分割

为了准确分割支票中的方形印鉴图像,为印鉴真伪自动识别提供无失真的二值待验图像和预留图像,提出一种基于top-hat变换的自适应形态学分割算法.根据支票印鉴的色彩信息和拓扑结构特点得到方形印鉴的灰度图像,将印鉴灰度图像分成4个子区域,以便准确分割印鉴中具有不同笔划结构和背景均匀度的印鉴成份.对每个子区域中的字符和印框分别做top-hat变换增强图像细节后,再用Otsu方法二值化.由于top-hat变换中所用结构元素的尺寸对分割结果有很大影响,本文根据每个子区域中印框和字符的结构特点分别迭代地计算适用于它们的最佳尺寸结构元素.分割了350枚不同支票方形印鉴,分割准确率为99.43%.结果表明,该方法可以准确地分割笔划复杂且分布密集的方形支票印鉴图像,有效地减少分割结果中容易出现的笔划粘结和残缺失真,降低了对原始印鉴图像的质量要求.     

基于网格纵横局部二值模式的三维人脸识别

提出一种基于网格纵横局部二值模式的三维人脸识别方法。为了充分体现人脸表面的细节差异,有效表示出由表情引起的局部形状变化,本文首先在人脸网格表面的半刚性区域内检测关键点集,并且由关键点确定中心面片,由中心面片及其周围有序环确定关键点邻域;其次将网格上中心面片及其周围有序环看成一个整体,从纵向(相邻环上对应面片之间)和横向(同一环上相邻标号面片之间)分别提取网格纵向局部二值模式描述符和网格横向局部二值模式描述符;然后对这两者进行特征融合得到网格纵横局部二值模式描述符;最后利用LC-KSVD2字典学习算法在Bosphorus数据库和FRGC v2.0数据库上完成识别实验。在Bosphorus数据库上各表情的平均Rank-1识别率为97.6%,在FRGC v2.0数据库上的Rank-1识别率为97.9%,该实验结果充分表明本文所提算法具有较高的识别精度,并且对表情变化具有一定的鲁棒性。     

Structural diversity of sphingomyelin microdomains

In cells plasma membrane, sphingomyelin (SM) plays a key role in the formation of a category of lipid microdomains enriched in cholesterol (Chl) often referred to as rafts. Atomic force microscopy (AFM) was used to analyze the mesoscopic topography of enriched SM microdomains in supported bilayers made of SM/dioleoylphosphatidylcholine (SM/DOPC) and SM/palmitoyl-oleoyl-phosphatidylcholine (SM/POPC) equimolar mixtures, in buffer, at room temperature. Gel–fluid phase separation occurs in both SM/DOPC and SM/POPC bilayers. The gel phase SM-enriched microdomains adopt a variety of size, shape and mesoscopic structure, from homogeneous flat domains of a few hundreds of nanometer in diameter to domains of several micrometers made of closely packed globular structures. Gel–gel phase separation in SM domains is also observed which gives rise to different structures for the diunsaturated and the mixed-saturated PC species. These differences could also extend to the interactions with Chl. This suggests that studies on rafts formation commonly performed using SM/DOPC mixture as a model should also include the physiologically more relevant POPC species.     

Correlating motif analysis and morphological filters for surface texture analysis

In contrast to the mean-line based evaluation system, motif analysis and morphological filters are two techniques oriented to the characterization of functional properties of surfaces. The motif combination procedure is consistent with the functionality of the morphological closing filter that insignificant peaks on the profile are suppressed. By linking the functionality of the structuring elements with motif combination criterions, morphological envelopes are computed efficiently. Reversely the morphological closing filter coupled with horizontal line-segment structuring elements with lengths equivalent to the motif limits for roughness and waviness provides an alternative for motif analysis. The proposed morphological method has a sound mathematical basis and is stable. An example of applying the empirical motif method (ISO 12085) and the morphological method is demonstrated. The motif parameters resulted from two methods reveal that they coincide with each other. Thus two distinct function oriented methods for surface texture evaluation are technically correlated by mutual exploitation.     

基于形态成分分析的轴承复合故障诊断

独立分量分析(ICA)已被广泛运用于线性混合模型的盲源分离问题,但却有2个重要的限制:信源统计独立和信源非高斯分布。形态成分分析是最新提出的一种基于稀疏表示的信号和图像分解(分离)方法。介绍了形态成分分析的基本原理,进行了仿真说明,并应用该方法对设置了3种故障的轴承进行故障诊断,最终发现了故障特征,成功判别出了轴承的3种故障,验证了该方法在轴承故障诊断中的有效性。     

High resolution transmission soft X-ray microscopy of deterioration products developed in large concrete dams

In concrete structures, the reaction of certain siliceous aggregates with the highly alkaline concrete pore solution produces an alkali-silicate gel that can absorb water and expand. This reaction can lead to expansion, cracking, increased permeability, and decreased strength of the concrete. Massive concrete structures, such as dams, are particularly susceptible to the damage caused by the alkali-silica reaction because of the availability of water and because massive gravity dams usually do not contain steel reinforcement to restrain the expansion. Both the cement hydration products and alkali-silica reaction products are extremely sensitive to humidity. Consequently, characterization techniques that require high vacuum or drying, as many existing techniques do, are not particularly appropriate for the study of the alkali-silica reaction because artefacts are introduced. Environmental scanning electron micrographs and scanning electron micrographs with energy dispersive X-ray analysis results demonstrate the effect of drying on the morphology and chemical composition of the alkali-silicate reaction gel. Thus, the impetus for this research was the need to observe and characterize the alkali-silica reaction and its gel product on a microscopic level in a wet environment (i.e. without introducing artefacts due to drying). Only soft X-ray transmission microscopy provides the required high spatial resolution needed to observe the reaction process in situ. The alkali-silica reaction can be observed over time, in a wet condition, and at normal pressures, features unavailable with most other high resolution techniques. Soft X-rays also reveal information on the internal structure of the sample. The purpose of this paper is to present research, obtained using transmission soft X-ray microscopy, on the effect of concrete pore solution cations, namely sodium and calcium, on the product formed as a result of alkali attack. Alkali-silicate reaction (ASR) gel was obtained from the FURNAS Dam in Minas Gerais, Brazil. Images of the ASR gel in sodium hydroxide indicated dissolution and repolymerization of the silicate into a less dense form, demonstrating the expansive nature of the gel when exposed to alkalis. In the calcium hydroxide solution, ASR gel, silica fume, and chemical grade silica gel each reacted with the calcium ions in solution to produce a calcium silicate hydrate precursor with a lathlike, branching morphology. The distinctive spherulitic microstructure formed during this reaction was identified as the ‘sheaf of wheat’ morphology, previously described in the literature. In addition, the development of the sheaf of wheat morphology was documented over time. These results suggest that of the cations studied in this investigation, it is the alkalis in concrete pore solution that produce the expansive ASR gel, while reaction with calcium ions does not result in expansion or damage to the concrete structure. More broadly, these results demonstrate the advantage of transmission soft X-ray microscopy for the study of the alkali-silica reaction, indicating the value of this technique for further studies in concrete technology.     

Imaging of mouse experimental melanoma in vivo and ex vivo by combination of confocal and nonlinear microscopy

We investigated possibilities of the combination of the one- and two-photon excitation microscopy for examination of the experimental melanoma tissue in vivo, in mice under general anesthesia, and ex vivo on freshly harvested specimens. Our aim was to obtain sufficiently informative images of unstained tumor tissues and their modifications after hyperthermia treatment. The mouse experimental melanoma structure was studied and compared with normal tissue from the same animal by using confocal and nonlinear microscopy techniques based on (i) one-photon excitation (1PE) fluorescence, (ii) 1PE reflectance, (iii) second harmonic generation imaging, and (iv) two-photon excitation autofluorescence. We checked different spectral conditions and other settings of image acquisition, as well as combinations of the above imaging modalities, to fully exploit the potential of these techniques in the evaluation of treated and untreated cancer tissue morphology. Our approach enabled to reveal the collagen fiber network in relation with the other tissues, and to identify invasive tumor cells. It also proved to be useful for the examination of interrelationships between functional and morphological aspects based on optical properties of the tissues, especially in studies of changes between the tumor and control tissue, as well as changes induced by physical treatments, e.g., delivery of microwave hyperthermia treatment. These differences were also evaluated quantitatively, when we found out that the maximum Euler–Poincaré characteristic reflects well the melanoma morphological structure. The results showed that the proposed investigative approach could be suitable also for a direct evaluation of tissue modifications induced by clinical interventions. Microsc. Res. Tech., 2009. © 2009 Wiley-Liss, Inc.     

基于支持向量机和小波分解的气体识别研究

提出将支持向量机应用到气体种类识别的研究中，并建立小波分解提取特征量和支持向量机识别气体种类的气体定性分析模型。通过小波分解提取半导体气体传感器在温度调制下的动态响应特性的特征量，分别使用不同核函数和不同结构的支持向量机建立判断特征量与气体种类的模型。实验结果说明使用支持向量机进行气体成分定性识别的效果优于同结构的神经网络，且对支持向量机自身结构的选择不敏感，适合于对多组分气体定性分析研究。建立的模型在分辨力为13ppm（对CO）和15ppm（对Hz）的条件下，对单一氢气、一氧化碳及其混合气体的识别率可达98％，适合于工程应用。     

生物凝胶微孔挤出胀大的有限元模拟与三维打印成形

由于挤出胀大现象的存在,在室温条件下通过三维打印技术(Three-dimensional printing,3DP)成形的凝胶组织工程支架与输入的目标支架原始模型相比,内部微观孔隙结构精度与孔隙率明显降低。针对这一问题,采用流体计算软件Polyflow对明胶-海藻酸钠共混体系交联形成的生物凝胶材料在挤出成形过程中通过喷头直径过渡段时流线的收缩与离开喷头后的挤出胀大现象进行有限元模拟,着重分析凝胶黏度与供料压力对挤出胀大的影响规律,并通过试验验证模拟的合理性。提出将挤出胀大引起的尺寸变形误差引入支架模型的设计过程。通过数值模拟与试验结果的对比,合理调整模型中纤维间距,利用得到的最佳工艺参数进行凝胶组织工程支架的三维打印成形。结果表明,支架内部的微观孔隙结构精度和孔隙率与理想支架要求近似吻合。通过对生物凝胶挤出胀大的模拟分析,可为凝胶组织工程支架的精确打印成形提供理论依据和技术指导。     

基于特征贡献率的机械故障分类方法

为提高往复压缩机、航空发动机等复杂机械故障分类的准确率,依据特征参数对不同故障的敏感度存在差异的特性,提出一种狄利克雷过程混合模型(Dirichlet process mixture model,简称DPMM)与贝叶斯推断贡献(Bayesian inference contribution,简称BIC)相结合的分析方法。采用DPMM方法自学习机械振动信号高维特征的统计分布模型,并依据BIC理论计算得到各特征参数对模型的贡献率,通过对比观测数据与各类故障数据特征贡献率间的差异实现故障分类。试验结果表明,该方法的平均分类准确率比基于高斯混合模型(Gaussian mixture model,简称GMM)的故障诊断方法的平均分类准确率提高19.29%,比基于Relief算法的故障诊断方法的平均分类准确率提高32.71%,且该方法的时效性高,泛化性能强,能够更有效地进行复杂机械故障分类。     

The nacre protein perlucin nucleates growth of calcium carbonate crystals

Atomic force microscopy (AFM) in aqueous solution was used to investigate native nacre of the marine snail Haliotis laevigata on the microscopic scale and the interaction of purified nacre proteins with calcium carbonate crystals on the nanoscopic scale. These investigations were controlled by scanning electron microscopy (SEM), light microscopy (LM) and biochemical methods. For investigations with AFM and SEM, nacre was cleaved parallel to the aragonite tablets in this biogenic polymer/mineral composite. Multilamellar organic sheets consisting of a core of chitin with layers of proteins attached on both sides lay between the aragonite layers consisting of confluent aragonite tablets. Cleavage appeared to occur between the aragonite tablet layer and the protein layer. AFM images revealed a honeycomb‐like structure to the organic material with a diameter of the ‘honeycombs’ equalling that of the aragonite tablets. The walls of the structures consisted of filaments, which were suggested to be collagen. The flat regions of the honeycomb‐like structures exhibited a hole with a diameter of more than 100 nm. When incubated in saturated calcium carbonate solution, aragonite needles with perfect vertical orientation grew on the proteinacous surface. After treatment with proteinase K, no growth of orientated aragonite needles was detected. Direct AFM measurements on dissolving and growing calcite crystals revealed a surface structure with straight steps the number of which decreased with crystal growth. When the purified nacre protein perlucin was added to the growth solution (a super‐saturated calcium carbonate solution) new layers were nucleated and the number of steps increased. Anion exchange chromatography of the water‐soluble proteins revealed a mixture of about 10 different proteins. When this mixture was dialysed against saturated calcium carbonate solution and sodium chloride, calcium carbonate crystals precipitated together with perlucin leaving the other proteins in the supernatant. Thus perlucin was shown to be a protein able to nucleate calcium carbonate layers on calcite surfaces, and in the presence of sodium chloride, is incorporated as an intracrystalline protein into calcium carbonate crystals.     

．NETFramework中二进制与XML序列化方法的比较

研究了二进制序列化和XML序列化在．NET平台下所表现的不同性能，分析了二进制序列化和XML序列化的不同特点；通过实例比较了二进制序列化和XML序列化的效率，研究了导致二者间性能不同的原因并提出了合理的优化方案。