Microscopic Structural Features Research Articles

First-Principles Assisted Prediction of the Nonlinear Optical Behavior of Mg3B7O13Cl Crystal

In order to explore new nonlinear optical (NLO) crystals with superior performance, it is greatly desirable to understand the intrinsic relationship between the microscopic structural features and macroscopic optical properties of crystals. In this paper, the electronic structures and optical properties of Mg3B7O13Cl (MBOC), which contains B7O13 functional building blocks, were investigated to understand the structure — optical property relationship by first-principles calculation. Our calculated results show that the large band gap and the moderate second-harmonic generation (SHG) coefficient of MBOC (8.43 eV and d32 = 0.41 pm/V) are comparable to those of KBe2BO3F2 (8.64 eV and d11 = 0.46 pm/V). The origin of the large band gap and the moderate SHG response of MBOC were explained by combining electronic structure analysis and the SHG density method.

Microscopic Structural Features and Properties of Single Fibers from Different Morphological Parts of the Windmill Palm

The chemical, morphological, physical, and thermal properties of raw materials and single fibers extracted from different morphological parts of windmill palm were examined and comprehensively characterized after an alkali treatment. Leaf sheathes (LS) with the highest cellulose content (52.26%) achieved the most efficient extraction of fibers. Single fibers extracted from the vascular bundles of the windmill palm raw material had a slender shape with a tapering and sealing terminus, with each single fiber possessing a lumen in its cross-section. These windmill palm fibers displayed similar chemical compositions, but they exhibited significant differences in morphological parameters. Leaf blade fibers (LBFs) had the longest length (1240 μm ± 470 μm) and highest aspect ratio (121.39), which presented excellent potential as a reinforced fiber. After the alkali treatment, almost all of the hemicelluloses and lignin were removed, which resulted in increased crystallinity of extracted fibers. Thermogravimetric analysis confirmed LS stability up to 319 °C, which was higher than that of other materials from windmill palm.

Recent progresses on numerical investigations of microscopic structure of strong shock waves in fluid

Shock wave appears widely in various complex systems and plays an important role in the fundamental research and engineering applications. Much effort has been devoted to getting insight into the microscopic structure and dynamic features on the shock front and obtaining the shock hugoniot of materials. The scope of this review would be limited to strong shock waves in fluid, considering that materials behave as fluid under strong impact loading. The development of methods used to study shock waves has been reviewed and the applicable conditions and features of these method has been summarized. The microscopic structures, non-equilibrium effects and dynamic processes on the shock front have been discussed, which have reference value for the modeling of shock wave in complex system.

ПАТОМОРФОЛОГИЧЕСКИЕ ИЗМЕНЕНИЯ В ЩИТОВИДНОЙ ЖЕЛЕЗЕ ПРИ ДИФФУЗНОМ ТОКСИЧЕСКОМ ЗОБЕ

Objective: To study the main pathomorphological and morphometric structural rearrangements of thyroid tissue (TT) formations in toxic diffuse goiter (TDG). Methods: By the methods of anatomical preparation and histological sections, macro and microscopic structural features of the thyroid gland were studied in 22 patients with TDG; both sexes aged 36 to 60 years, operated in the Department of General Surgery, State Clinical Hospital № 5, named by Academician K.T. Tadjiev Results: An analysis of the degree of progression of pathomorphological changes in the tissue and the follicular structure of the thyroid gland revealed a dependence on the duration and severity of the disease. The results of a quantitative study showed that the average diameter of the follicles, as compared with the norm (70.8±1.19 μm), became larger (80.8±1.26 μm). The height of the follicular epithelium for this pathology was 15.16±0.22 μm, with a norm of 10.06±0.09 μm (p<0.01). This led to a change in the Brown index, i.e. the more this index was, the lower the functional activity of the organ. Conclusion: The characteristic morphological signs of thyroid disease in TDG are lymphoplasmacytic infiltration of the stroma of the gland, activation of folliculogenesis and hyperplasia of the thyroid epithelium, which can lead to the development of functional thyroid disorders. Keywords: Thyroid gland, toxic diffuse goiter, pathomorphology.

Staying connected: structural integration at the intervertebral disc-vertebra interface of human lumbar spines.

To investigate the microscopic fibrous integration between the intervertebral disc, cartilage endplates and vertebral endplates in human lumbar spines of varying degrees of degeneration using differential interference contrast (DIC) optics. Weakness at these junctions is considered to be an important factor in the aetiology of disc herniations. Magnetic resonance images (MRIs) of cadaveric lumbar spines were graded for degeneration and motion segments from a range of degenerative grades isolated and bisected sagittally. Following fixation and decalcification, these were cut into segments containing anterior or posterior annulus fibrosus or nucleus pulposus. The segments were cryo-sectioned and sections visualised using both standard light and DIC microscopy. Detachment at the interface between the disc and vertebrae increased with greater degenerative grade (from 1.9% in Grade I to 28% in Grade V), especially at the boundary between the cartilage and vertebral endplates. DIC microscopy revealed the fibrous organisation at the IVD-cartilage endplate interface with structural features, such as annular lamellae branching and nodal insertions in the nucleus pulposus region; these have been previously observed in ovine spines, but were less uniform in humans. Structural integrity of the IVD and cartilage endplate was also lost with increasing degeneration. This preliminary study shows that microscopic structural features may act to maintain attachment between the IVD and CEP in the human spine. Loss of structural integrity in this region may destabilise the spine, possibly altering the mechanical environment of the cells in the disc and so potentially contribute to the aetiopathogenesis of IVD degeneration.

Макро-микроскопические структурные характеристики собственных желез двенадцатиперстной кишки у людей разного возраста

Макро-микроскопические структурные характеристики собственных желез двенадцатиперстной кишки у людей разного возраста

Engineering meniscus structure and function via multi-layered mesenchymal stem cell-seeded nanofibrous scaffolds

Despite advances in tissue engineering for the knee meniscus, it remains a challenge to match the complex macroscopic and microscopic structural features of native tissue, including the circumferentially and radially aligned collagen bundles essential for mechanical function. To mimic this structural hierarchy, this study developed multi-lamellar mesenchymal stem cell (MSC)-seeded nanofibrous constructs. Bovine MSCs were seeded onto nanofibrous scaffolds comprised of poly(ε-caprolactone) with fibers aligned in a single direction (0° or 90° to the scaffold long axis) or circumferentially aligned (C). Multi-layer groups (0°/0°/0°, 90°/90°/90°, 0°/90°/0°, 90°/0°/90°, and C/C/C) were created and cultured for a total of 6 weeks under conditions favoring fibrocartilaginous tissue formation. Tensile testing showed that 0° and C single layer constructs had stiffness values several fold higher than 90° constructs. For multi-layer groups, the stiffness of 0°/0°/0° constructs was higher than all other groups, while 90°/90°/90° constructs had the lowest values. Data for collagen content showed a general positive interactive effect for multi-layers relative to single layer constructs, while a positive interaction for stiffness was found only for the C/C/C group. Collagen content and cell infiltration occurred independent of scaffold alignment, and newly formed collagenous matrix followed the scaffold fiber direction. Structural hierarchies within multi-lamellar constructs dictated biomechanical properties, and only the C/C/C constructs with non-orthogonal alignment within layers featured positive mechanical reinforcement as a consequence of the layered construction. These multi-layer constructs may serve as functional substitutes for the meniscus as well as test beds to understand the complex mechanical principles that enable meniscus function.

Scanning multishot irradiations on a large-area glass substrate for Xe-Arc flash lamp crystallization of amorphous silicon thin-film

Applying an in-line Xe-arc flash lamp annealing (FLA) process for the fabrication of low-temperature polycrystalline silicon (LTPS) on a large-scale glass substrate, this study investigates the effects of scanning multishot irradiations on the thermo-mechanical deformation of the substrate and the microscopic phase-change of the amorphous silicon (a-Si) thin-film. A glass substrate with thin-film structures was preheated at 650 °C, exposed to sequential multiple flashes, and thus heated rapidly far beyond the glass softening temperature to achieve crystallization of a-Si. Temperature variations in the substrate were predicted by one-dimensional heat conduction model with radiation absorption, and the structural deformations were simulated through a FEM code and compared to the experimental observations. The maximum temperatures arisen in the substrate during the second or subsequent flash irradiations were substantially lower than that during the first irradiation owing to reduced absorptions of flash energies. These absorption reductions were resulted from phase-changes of silicon from amorphous to polycrystalline. Those temperatures, however, were still sufficiently high to cause a significant thermal warpage, resulting in the bathtub shape of the substrate. The critical mechanisms for the warpage were the structural shrinkage and the gravitational sagging. In addition, the microscopic structural characteristics of the LTPS fabricated by the scanning multishot FLA process were explored through optical and Raman spectroscopies, and transmission electron microscopy.

Development of nonlinear optical materials promoted by density functional theory simulations

Nonlinear optical (NLO) crystals are very important optoelectronic functional materials and their developments have significantly contributed to the progress of laser science and technology for decades. In order to explore new NLO crystals with superior performances, it is greatly desirable to understand the intrinsic relationship between the macroscopic optical properties and microscopic structural features in crystals. In this paper, the applications of density functional theory (DFT) method to the elucidation of the structure-property relationship and to the exploration on novel NLO materials in the ultraviolet and infrared spectrum regions are reviewed. The great success in the linear and NLO property predictions has been achieved using the first-principles computational simulations, and the mechanism understanding obtained by various analysis tools can give substantial guidance to the search and design of new NLO crystals.

Microscopic Structure Analysis in Disordered Materials using Anomalous X-ray Scattering

Abstract Although X-ray diffraction is still mainly used to determine crystal structures, the demand for an understanding of the atomic arrangement in disordered matter has progressively become more important over the past decades. However, apart from simple model systems, it is still a challenging task to unravel the microscopic ordering of the atoms in amorphous multi-component materials, although this knowledge becomes increasingly important in modern materials science, in which the physical properties are often related to the microscopic ordering of the different chemical species of the substance. This article reports about the combination of Anomalous X-ray Scattering (AXS) with Reverse Monte Carlo Computer simulation (RMC) as a proper tool to precisely determine the microscopic structural characteristics in such systems with high reliability. The basic principles of the method will be illustrated and some examples of modern materials will be given to proof the applicability and the capability of this method.

Reconstruction of multiphase microstructure based on statistical descriptors

The microscopic structural features of porous media directly affect their macroscopic properties (e.g., mechanical, electromagnetic, capillary, and transport properties). As for sandstone, the distributions of the clay and the pore in three-dimensional (3D) space have important effects on its electrical conductivity and transport property. In this paper, the experiment of the two-dimensional (2D) and 3D reconstructions of multiphase microstructure (pore, grain, and clay) based on 2D images was carried out. In the reconstruction procedure of simulated annealing for multiphase microstructure, three independent two-point correlation functions and two lineal-path functions are chosen as the morphological information descriptors. Another important morphological descriptor of microstructure is the two-point cluster function, which is used to validate the reconstruction results. From the result of the 2D reconstruction, it is found that the 2D generation is similar with the original 2D image in morphological information and their correlation functions match very well, which illustrate that the presented method has the ability to generate the 2D microstructure from the original 2D image for multiphase microstructure. In the case of 3D reconstruction, the two-point correlation functions and lineal-path functions of the 3D generation are in excellent agreement with that of the original 2D image, and comparison of the two-point cluster functions from the slices of the 3D generation with the original image reflects the similarity and the variability of the slices in real sandstone, which illustrate that the presented methodology is effective and proper for the reconstruction of 3D microstructure based on the 2D image.

Effects of Feed Rate and pH Value on the Physical and Electrochemical Properties of LiNi<sub>0.4</sub>Co<sub>0.2</sub>Mn<sub>0.4</sub>O<sub>2</sub> Cathode Material for Lithiumion Battery

The layered LiNi0.4Co0.2Mn0.4O2was synthesized by co-precipitation method using carbonate sodium as precipitant. The microscopic structural features and morphologies of as-prepared cathode materials were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). And then, the charge-discharge measurements were carried out to determine the electrochemical properties in a voltage range of 2.5-4.6 V. The results show that the pH value in the process of co-precipitation reaction plays a greater part on the electrochemical properties than feed rate does. The cathode materials prepared at higher pH value illustrate better electrochemical properties in the voltage range of 2.5-4.6 V, which can be attributed to a less cation mixing in the cathode material as well as the smaller primary particles and the smaller second particles.

Application of Conventional and Constant-Rate Mercury Injection on Microscopic Pore Structure Research

Microscopic pore structure features for cores in different formations are studied by conventional mercury method and constant-rate mercury method. With constant-rate mercury injection data, distribution curve feature of pore parameters are related with permeability, which including body radius, throat radius and aspect ratio distribution curve; the statistics parameters (skewness, standard deviation and kurtosis) for above three pore features are also analyzed and related to macroscopic parameters, including permeability and porosity. With conventional mercury injection data, major factors affecting reservoir producing in microscopic pore are screened with statistics methods, normalization Pc-curves are made by J function method including withdrawal curves, and compared on different permeability and formations; relationship between microscopic pore structures features and reservoir producing is analyzed, which need further research. Key words : Conventional mercury injection; Constant-rate mercury injection; Producing state; Statistics method

Gelatin-based biomaterial engineering with anhydride-containing oligomeric cross-linkers.

Chemically cross-linked gelatin hydrogels are versatile cell-adhesive hydrogel materials that have been established for a variety of biomedical applications. The most prominent cross-linker is glutaraldehyde, which, however, has been described to cause compatibility problems and loss of microscopic but relevant structural features. A recently developed oligomeric cross-linker that contains anhydride functionalities was evaluated as cross-linker for the fabrication of gelatin-based hydrogels and microparticles. In a fast curing reaction, hydrogels composed of gelatin and oligomeric cross-linker were fabricated with good conversion over a wide concentration range of constituents and with cross-linkers of different anhydride contents. Hydrogel properties, such as dry weight and mechanics, could be controlled by hydrogel composition and rheological properties correlated to elastic moduli from 1 to 10 kPa. The gels were shown to be cytocompatible and promoted cell adhesion. In soft formulations, cells migrated into the hydrogel bulk. Gelatin microparticles prepared by a standard water-in-oil emulsion technique were also treated with the novel oligomers, and cross-linking degrees matching those obtained with glutaraldehyde were obtained. At the same time, fewer interparticular cross-links were observed. Fluorescein-derivatized cross-linkers yielded labeled microparticles in a concentration-dependent manner. The oligomeric cross-linkers are presented as an efficient and possibly more functional and compatible alternative to glutaraldehyde. The engineered hydrogel materials hold potential for various biomedical applications.

Chemical regulation of signaling pathways to programmed necrosis

Necroptosis is an active and well-orchestrated necrosis, distinctive from apoptosis in microscopic structure, and biochemical and molecular features. Unlike apoptosis-undergoing cells, which are removed by macrophage or neighboring cells, necrotic cell death releases danger signals and provokes inflammation, and further a severe damage to neighbor tissue. A regulated necrosis, termed as necroptosis or programmed necrosis, is emerging as a new paradigm of cell death that can be activated when apoptotic machinery is genetically or pathogenically defective. It plays biological significances in pathogenesis of a variety of inflammatory diseases as well as in a beneficial innate immune defense mechanism. This review highlights the identification of hits against necroptosis, and comprehensive approaches to discovery of small molecules that regulate necroptotic cell death. Also, the signaling molecular mechanism of necroptosis and future clinical uses of necroptosis inhibitor will be described in brief.

Synthesis and characterization of LiNi1/3Co1/3Mn1/3O2 cathode material for rechargeable lithium batteries by polyacrylic acid-assisted sol–gel method

Nanocrystalline LiNi1/3Co1/3Mn1/3O2 cathode materials are synthesized by sol–gel method using polyacrylic acid as a chelating agent. The effects of the calcination temperature and calcination time on the structure, morphology, and electrochemical performances of the LiNi1/3Co1/3Mn1/3O2 electrode materials are investigated by X-ray diffraction, scanning electron microscopy and charge–discharge cycling test, respectively. All experiments show that the microscopic structural features and the morphology properties are deeply related with the electrochemical performance. The results show that the nanocrystalline LiNi1/3Co1/3Mn1/3O2 with a particle size of 80 nm sintered at 700 °C for 2 h presents good α-NaFeO2 layer structure and the best electrochemical performance. When it is discharged between 4.4 and 2.8 V at 20 mAg−1, the initial specific capacity of the LiNi1/3Co1/3Mn1/3O2 obtained at 700 °C for 2 h is 169.2 mAhg−1. The investigated electrode materials retain 151 mAhg−1 after 30 cycles when cycled at 20 mAg−1.

Cement lines and interlamellar areas in compact bone as strain amplifiers – Contributors to elasticity, fracture toughness and mechanotransduction

Bone is multi-scale hierarchical composite material making the prediction of fragility, as well as pinning it to a certain cause, complicated. For proper mechanical simulation and reflection of bone properties in models, microscopic structural features of bone tissue need to be included. This study sets out to gain a mechanistic insight into the role of various microstructural features of bone tissue in particular cement lines and interlamellar areas. Further the hypothesis that compliant interlamellar areas and cement lines within osteonal bone act as strain amplifiers was explored. To this end, a series of experimentally-based micromechanical finite element models of bovine osteonal bone were developed. Different levels of detail for the bone microstructure were considered and combined with the results of physical three-point bending tests and an analytical composite model of a single osteon. The objective was to examine local and global effects of interface structures. The geometrical and microstructural characteristics of the bone samples were derived from microscopy imaging. Parametric finite element studies were conducted to determine optimal values of the elastic modulus of interstitial bone and interlamellar areas. The average isotropic elastic modulus of interfaces suggested in this study is 88.5MPa. Based on the modelling results, it is shown that interfaces are areas of accumulated strain in bone and are likely to act as potential paths for crack propagation. The strain amplification capability of interface structures in the order of 10 predicted by the models suggests a new explanation for the levels of strain required in bone homoeostasis for maintenance and adaptation.

Leaf dimorphism of <i>Microgramma squamulosa</i> (Polypodiaceae): a qualitative and quantitative analysis focusing on adaptations to epiphytism

The epiphytic fern Microgramma squamulosa occurs in the Neotropics and shows dimorphic sterile and fertile leaves. The present study aimed to describe and compare qualitatively and quantitatively macroscopic and microscopic structural characteristics of the dimorphic leaves of M. squamulosa, to point more precisely those characteristics which may contribute to epiphytic adaptations. In June 2009, six isolated host trees covered by M squamulosa were selected close to the edge of a semi-deciduous seasonal forest fragment in the municipality of Novo Hamburgo, State of Rio Grande do Sul, Brazil. Macroscopic and microscopic analyzes were performed from 192 samples for each leaf type, and permanent and semi-permanent slides were prepared. Sections were observed under light microscopy using image capture software to produce illustrations and scales, as well as to perform quantitative analyses. Fertile and sterile leaves had no qualitative structural differences, being hypostomatous and presenting uniseriate epidermis, homogeneous chlorenchyma, amphicribal vascular bundle, and hypodermis. The presence of hypodermal tissue and the occurrence of stomata at the abaxial face are typical characteristics ofxeromorphic leaves. Sterile leaves showed significantly larger areas (14.80cm2), higher sclerophylly index (0.13g/cm2) and higher stomatal density (27.75stomata/mm2) than fertile leaves. The higher sclerophylly index and the higher stomatal density observed in sterile leaves are features that make these leaves more xeromorphic, enhancing their efficiency to deal with limited water availability in the epiphytic environment, compared to fertile leaves.

Molecular dynamics study of pair interactions, interfacial microstructure, and nanomorphology of C60/MEH-PPV hybrids

Atomistic molecular dynamics (AMD) simulations are utilized to simultaneously explore the detailed pair interactions, interfacial microstructure, and nanoscale (phase-separated) morphology of a series of thermally annealed C60-MEH-PPV (monomer and oligomer) (poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene)) hybrids. The present study provides essential details for understanding fundamental particle interactions that regulate the microscopic (structural and morphological) features of a standard polymer-fullerene material, paving the way to the eventual goal of capturing the photovoltaic physics of similar hybrid systems widely viewed as a potential alternative to the conventional (inorganic) semiconducting materials. Specifically, we show that two dominant interfacial pair C60-MEH-PPV-mer configurations—denoted as “face-on” or “side-on” motif—can thus be identified. These two motifs seem to be rather universal, and are shown to be dictated by many-body energetic forces in a condensed phase, as they display clear independence on the effects of system temperature, blending ratio, and chain connectivity. Importantly, the pair configurations (which should embed precise information on separation distance and mutual alignment) so unraveled provide an unambiguous first step toward resolving quantum-mechanic properties relevant to the photovoltaic performance of a hybrid material. Although the simulation length scale is limited for one to unequivocally reveal bulk phase behavior, the results on nanoscale phase morphologies are in accord with recent experimental trends regarding the effects of polymer molecular weight and blending ratio. Future outlooks of utilizing the established molecular system for predicting light adsorption and interfacial charge behavior are remarked.

High Frequency Oscillatory Ventilation Versus Conventional Ventilation in a Newborn Piglet Model with Acute Lung Injury

High frequency oscillatory ventilation (HFOV) is considered a protective strategy for human lungs. This study was designed to define microscopic structural features of lung injury following HFOV with a high lung volume strategy in newborn piglets with acute lung injury. After acute lung injury with saline lavage, newborn piglets were randomly assigned to 5 study groups (6 in each group): control (no mechanical ventilation), conventional mechanical ventilation for 24 hours, conventional ventilation for 48 hours, HFOV for 24 hours, and HFOV for 48 hours. The right upper lung tissue was divided into the gravitation-dependent and gravitation-nondependent regions after the completion of mechanical ventilation. Under light microscopy, the numbers of polymorphonuclear leukocytes (PMNLs), alveolar macrophages, red blood cells, and hyaline membrane/alveolar edema were assessed in all lung tissues. Oxygenation index was continuously monitored. Our results showed that the degree of histopathologic lung damage in the gravitation-dependent region was greater than that in the gravitation-nondependent region. Compared with the control group, PMNLs, red blood cells and hyaline membrane/alveolar edemas were significantly increased and alveolar macrophages were significantly decreased in lung tissues of conventional ventilation and HFOV piglets. In HFOV with high lung volume strategy piglets, lung tissues had significantly fewer PMNLs, red blood cells, and hyaline membrane/alveolar edemas, and oxygenation was improved significantly, compared to those of the conventional ventilation piglets. Histopathologic lung damage in newborn piglets with lung injury was more severe in the gravitation-dependent region than in the gravitation-nondependent region. HFOV with high lung volume strategy reduced pulmonary PMNL infiltration, hemorrhage, alveolar edema, and hyaline membrane formation with improved oxygenation.