Microscopic Units Research Articles

Pharmacognostic investigations of Achyranthes aspera Linn

Aims & objective: Some pharmacognostical investigations were carried out on the leaves, stems and roots of Achyranthes aspera Linn to record parameters for identifying and differentiating various species of Achyranthes. Methods: The research specimens were authenticated and preserved both in fresh and dry forms. The leaves and stems were morphologically screened followed by anatomical studies with the aid of Labphot 2 microscopic units. Powder microscopy and micrometric studies, including leaf constants, were performed using suitable tools and reagents under different magnifications. Important observations and results: The leaves were petiolate and opposite, decussate, elliptic-obovate, acute apex with decurrent base, abaxial surfaces which turned blackish on storage, and had irritant smell with a slightly bitter taste. The vein islets were squarish and polygonal. Covering and glandular trichomes; anisocytic and anomocytic stomata were evident. Anomalous secondary growth of xylem and phloem in stem and roots; Vessels were helical, spiral and pitted; rosette shaped calcium oxalate crystals were also evident.

The rationale for using microscopic units of a donor matrix in cartilage defect repair

The efficacy of existing articular cartilage defect repair strategies are limited. Native cartilage tissue forms via a series of exquisitely orchestrated morphogenic events spanning through gestation into early childhood. However, defect repair must be achieved in a non-ideal microenvironment over an accelerated time-frame compatible with the normal life of an adult patient. Scaffolds formed from decellularized tissues are commonly utilized to enable the rapid and accurate repair of tissues such as skin, bladder and heart valves. The intact extracellular matrix remaining following the decellularization of these relatively low-matrix-density tissues is able to rapidly and accurately guide host cell repopulation. By contrast, the extraordinary density of cartilage matrix limits both the initial decellularization of donor material as well as its subsequent repopulation. Repopulation of donor cartilage matrix is generally limited to the periphery, with repopulation of lacunae deeper within the matrix mass being highly inefficient. Herein, we review the relevant literature and discuss the trend toward the use of decellularized donor cartilage matrix of microscopic dimensions. We show that 2-µm microparticles of donor matrix are rapidly integrate with articular chondrocytes, forming a robust cartilage-like composites with enhanced chondrogenic gene expression. Strategies for the clinical application of donor matrix microparticles in cartilage defect repair are discussed.

Study on the phase transitions of ferroelectric systems by Weiss's molecular field theory with an external field

The descriptions of the paramagnetic-ferromagnetic and paraelectric-ferroelectric phase transitions (PTs) by Weiss's molecular field theory (WMFT) are quite successful, and the WMFT is also a theoretical basis of initial analysis of the PTs of structural disorder and complex compositional systems because of its mean-field characteristic. However, there is not any study on the PT behaviors of the WMFT with external field, and only the case of two orientational states of molecules for ferroelectric systems has been investigated by the WMFT. Although the descriptions of the above two kinds of PTs by the WMFT are quite similar, the exact ones and the corresponding results are different more or less due to the difference in microscopic unit between the magnetization and polarization In this work, the exact descriptions of the ferroelectric systems with arbitrary orientational states of molecules by the WMFT are provided, including the temperature dependences of the spontaneous polarization, the internal energy, the specific heat and the static polarizability, and then the evolutions of the PTs with an external field are studied. The obtained results are as follows. 1) Without the external field, the PTs of the systems are of the second order, and the transition temperatures and spontaneous polarizations decrease, which are different from those of the ferromagnetic systems, but the internal energy, the specific heat and the polarizability increase with the increase of the orientational states. 2) The external field drives the second order PT to a diffusive one, and diffusive temperature range becomes wider as the field is increases. The results mentioned above would benefit the deep studies of ferroelectric PT, especially the diffusive one.

Image Processing in an Automated Live Cell Imaging System

In vitro embryo production and selection is a key step of infertility treatment. Time-lapse technology was introduced in embryology in order to increase the efficiency of embryo selection. This paper describes the image processing algorithms used to detect embryos and the accommodating microwells in an automated time-lapse imaging system specialized for this purpose. The system consists of compact digital inverted microscope units, microwell culture dishes and a controller, and includes software for controlling the time-lapse cycles and managing the visualization of the observed cells/tissues. The purpose of the described algorithms is to identify the regions of interest on the photos: the well detection algorithm detects the microwells of the applied culture dish holding the embryos, the embryo detection algorithm locates the embryos within the microwells. The algorithms proved to be robust during test runs and were integrated to the software system, which allows providing views for the users automatically that show only the relevant regions of the images taken by the microscope units.

Microstructure and finite element analysis of 3D five-directional braided composites

Microstructure of 3D five-directional braided composites determines its mechanical properties. Microscopic evidence of the microstructure reveals that the cross-sections of the axial yarn are variable along its central axial due to the lateral compression from the adjacent braiding yarns. On the basis of microscopic observations, a dense but non-intersecting geometry internal unit cell model of 3D five-directional braided composites is established. By using the unti-cell model, a 3D mesomechanical FEA is proposed to predict the effective elastic properties of 3D five-directional braided composites. Compared with existing model, present model is more effective to calculate the mechanical properties of 3D five-directional braided composites with more than 50% fiber volume fraction.

Peripheral Nerve: From the Microscopic Functional Unit of the Axon to the Biomechanically Loaded Macroscopic Structure

Peripheral nerves are composed of motor and sensory axons, associated ensheathing Schwann cells, and organized layers of connective tissues that are in continuity with the tissues of the central nervous system. Nerve fiber anatomy facilitates conduction of electrical impulses to convey information over a distance, and the length of these polarized cells necessitates regulated axonal transport of organelles and structural proteins for normal cell function. Nerve connective tissues serve a protective function as the limb is subjected to the stresses of myriad limb positions and postures. Thus, the tissues are uniquely arranged to control the local nerve fiber environment and modulate physical stresses. In this brief review, we describe the microscopic anatomy and physiology of peripheral nerve and the biomechanical properties that enable nerve to withstand the physical stresses of everyday life.

Finite Time Corrections in KPZ Growth Models

We consider some models in the Kardar-Parisi-Zhang universality class, namely the polynuclear growth model and the totally/partially asymmetric simple exclusion process. For these models, in the limit of large time t, universality of fluctuations has been previously obtained. In this paper we consider the convergence to the limiting distributions and determine the (non-universal) first order corrections, which turn out to be a non-random shift of order t^{-1/3} (of order 1 in microscopic units). Subtracting this deterministic correction, the convergence is then of order t^{-2/3}. We also determine the strength of asymmetry in the exclusion process for which the shift is zero. Finally, we discuss to what extend the discreteness of the model has an effect on the fitting functions.

Thermal stability of carbon nanotubes probed by anchored tungsten nanoparticles

The thermal stability of multiwalled carbon nanotubes (CNTs) was studied in high vacuum using tungsten nanoparticles as miniaturized thermal probes. The particles were placed on CNTs inside a high-resolution transmission electron microscope equipped with a scanning tunneling microscope unit. The setup allowed manipulating individual nanoparticles and heating individual CNTs by applying current to them. CNTs were found to withstand high temperatures, up to the melting point of 60-nm-diameter W particles (∼3400 K). The dynamics of W particles on a hot CNT, including particle crystallization, quasimelting, melting, sublimation and intradiffusion, were observed in real time and recorded as a video. Graphite layers reel off CNTs when melted or premelted W particles revolve along the tube axis.

A modular designed ultra-high-vacuum spin-polarized scanning tunneling microscope with controllable magnetic fields for investigating epitaxial thin films

A room-temperature ultra-high-vacuum scanning tunneling microscope for in situ scanning freshly grown epitaxial films has been developed. The core unit of the microscope, which consists of critical components including scanner and approach motors, is modular designed. This enables easy adaptation of the same microscope units to new growth systems with different sample-transfer geometries. Furthermore the core unit is designed to be fully compatible with cryogenic temperatures and high magnetic field operations. A double-stage spring suspension system with eddy current damping has been implemented to achieve ≤5 pm z stability in a noisy environment and in the presence of an interconnected growth chamber. Both tips and samples can be quickly exchanged in situ; also a tunable external magnetic field can be introduced using a transferable permanent magnet shuttle. This allows spin-polarized tunneling with magnetically coated tips. The performance of this microscope is demonstrated by atomic-resolution imaging of surface reconstructions on wide band-gap GaN surfaces and spin-resolved experiments on antiferromagnetic Mn(3)N(2)(010) surfaces.

Optimization of microscope unit for studying fluorescence emitters under high-vacuum and ambient gas conditions: Optical properties for various ionic liquids as a refractive index matching medium

We briefly introduce our microscope unit with an immersion objective and ionic liquid used as a refractive index matching medium, and describe its application to single molecular spectroscopy under high-vacuum and various ambient gas conditions. In this article, we particularly focus our attention on studies toward optimizing the microscope unit. For this purpose, the refractive index and background fluorescence, absorption spectrum for various ionic liquids wre investigated. We also measured the images of the beam spot of excitation laser at focal point by using an immersion objective and various ionic liquids. We found that some have more suitable characteristics than before.

Opposing Actions of Extracellular Signal-regulated Kinase (ERK) and Signal Transducer and Activator of Transcription 3 (STAT3) in Regulating Microtubule Stabilization during Cardiac Hypertrophy

Excessive proliferation and stabilization of the microtubule (MT) array in cardiac myocytes can accompany pathological cardiac hypertrophy, but the molecular control of these changes remains poorly characterized. In this study, we examined MT stabilization in two independent murine models of heart failure and revealed increases in the levels of post-translationally modified stable MTs, which were closely associated with STAT3 activation. To explore the molecular signaling events contributing to control of the cardiac MT network, we stimulated cardiac myocytes with an α-adrenergic agonist phenylephrine (PE), and observed increased tubulin content without changes in detyrosinated (glu-tubulin) stable MTs. In contrast, the hypertrophic interleukin-6 (IL6) family cytokines increased both the glu-tubulin content and glu-MT density. When we examined a role for ERK in regulating cardiac MTs, we showed that the MEK/ERK-inhibitor U0126 increased glu-MT density in either control cardiac myocytes or following exposure to hypertrophic agents. Conversely, expression of an activated MEK1 mutant reduced glu-tubulin levels. Thus, ERK signaling antagonizes stabilization of the cardiac MT array. In contrast, inhibiting either JAK2 with AG490, or STAT3 signaling with Stattic or siRNA knockdown, blocked cytokine-stimulated increases in glu-MT density. Furthermore, the expression of a constitutively active STAT3 mutant triggered increased glu-MT density in the absence of hypertrophic stimulation. Thus, STAT3 activation contributes substantially to cytokine-stimulated glu-MT changes. Taken together, our results highlight the opposing actions of STAT3 and ERK pathways in the regulation of MT changes associated with cardiac myocyte hypertrophy.

A multiscale method for analysis of heterogeneous thin slabs with irreducible three dimensional microstructures

A multiscale method is presented for analysis of thin slab structures in which the microstructures can not be reduced to two-dimensional plane stress models and thus three dimensional treatment of microstructures is necessary. This method is based on the classical asymptotic expansion multiscale approach but with consideration of the special geometric characteristics of the slab structures. This is achieved via a special form of multiscale asymptotic expansion of displacement field. The expanded three dimensional displacement field only exhibits in-plane periodicity and the thickness dimension is in the global scale. Consequently by employing the multiscale asymptotic expansion approach the global macroscopic structural problem and the local microscopic unit cell problem are rationally set up. It is noted that the unit cell is subjected to the in-plane periodic boundary conditions as well as the traction free conditions on the out of plane surfaces of the unit cell. The variational formulation and finite element implementation of the unit cell problem are discussed in details. Thereafter the in-plane material response is systematically characterized via homogenization analysis of the proposed special unit cell problem for different microstructures and the reasoning of the present method is justified. Moreover the present multiscale analysis procedure is illustrated through a plane stress beam example.

Hysteresis in kinking nonlinear elastic solids and the Preisach-Mayergoyz model

Herein we show that the stress-induced, dislocation-based, elastic hysteric loops of kinking nonlinear elastic solids---polycrystalline cobalt, $10\text{ }\text{vol}\text{ }\mathrm{%}$ porous ${\text{Ti}}_{2}\text{AlC}$, and fully dense ${\text{Ti}}_{3}{\text{SiC}}_{2}$---obey the scalar Preisach-Mayergoyz phenomenological model because they exhibit wiping out and congruency, two necessary and sufficient tenets of the model. We also demonstrate the power of the model in predicting the response of these materials to complex stress histories, as well as, determining the distributions of the threshold and friction stresses associated with the incipient kink bands---the fundamental microscopic units responsible for kinking nonlinear elasticity.

The ecosystem dynamics of the garden

Gardens have always been seen as places stimulating well-being and pleasure. This feature emerges from the dynamics of these peculiar ecosystems. In the present paper these dynamics are analyzed in the framework of recent approaches to self-organization. The role of the different components of a garden is examined. From the most ancient times the garden has been considered a privileged place for achieving emotional and physical well-being and pleasure. This result emerges by a skilful combination of ingredients, whose main components are water, rocks, plants and architectural design. This combi- nation induces in the humans staying in the garden a strong enhancement of many inner capabilities, including the most hidden or less utilized ones. We could say that humans visit gardens in order to discover hidden parts of themselves, to feel well and to be in harmony with nature. An intriguing connection has been discovered in ancient times between gardens and healing places. For instance the famous Asclepeion, the sanctuary of Asklepios at Epidaurus, in Greece, was built around a network of pathways that exhibit in a sequence symbols, shapes, places able to induce healing and transformation processes. The aim of the present article is to analyze these properties of gardens in the frame of some con- cepts introduced by the holistic approaches of modern science, such as thermodynamics of irreversible processes (TIP) and quantum field theory (QFT). These approaches are discussed in other articles of the present issue of the journal (1-4). SOME FEATURES OF THE DYNAMICS OF LIFE 2 The main achievement of the holistic approaches to biology is that life emerges from a process of self-organization. This conclusion is the result of a long chain of achievements that starts from the vitalistic tradition whose main exponent at beginning of last century has been Driesch (5, 6). Further steps have been accomplished by Gurwitsch (7) with the discovery of mitogenetic radiation, Piccardi (8, 9) with the recognition of the fundamental role of water and ambient electromagnetic (e.m.) background in the dynamics of life. Tentative synthesis have been formulated along the last century by Bauer (10), Szent-Gyorgyi (11, 12), Prigogine (13) and Froehlich (14, 15). The following formulation emerges at the end of this chain: living matter comes out from a process of self-organization, absent in non-living matter, centred around water. Let us summarize the properties of liquid water as emerging from the QFT approach (16). Liquid water is a mixture of two interspersed phases, one coherent, where all microscopic units oscillate in unison between two configurations of the molecule electron cloud, the other, noncoherent, made up of noncorrelated molecules behaving as a dense gas. In bulk water there is a continuous crossover of molecules between the two phases. However, near a hydrophilic surface the coherence domains get stabilized by the interaction between molecules and wall, so that the coherent fraction is allowed to develop a long-lasting dynamics. The coherent phase of liquid water has the peculiar property that the oscillation of the electron clouds occurs between a ground state where all electrons are tightly

Spatial Pattern of Health Clubs in Beijing at Various Scales

The research target is the health club,which is a special type of the recreation space in a city. Based on GIS and geostatistical software,using point pattern identification and ESDA(exploratory spatial data analysis) methods,the paper analyzes the spatial pattern characteristics of health clubs in Beijing. The nearest neighbor indicator (NNI) and quadrat analysis results indicate that the health clubs cluster together evidently at a whole region scale. But if we observe the pattern in the units separated by the roads or district,it presents different spatial patterns,varying from clustering to random,even dispersing. The analyzing results of health clubs based on the 5 scale cell units from 1 km to 5 km grids make further explanation that its spatial pattern are influenced evidently by the units' scale. At any scales the density and NNI of health club samples have evident spatial diversification. From the Moran's I statistics and Moran Scatterplot Map we also find the evident spatial autocor-relation of the units. The 2 km and 3 km unit scales are the best scales for finding the microscopic spatial pat-tern and diversification. So the whole region scale is not the only or the best scale for spatial pattern research of recreation spaces especially for the health clubs. In some microscopic units the spatial pattern will be more evident and the research results will even be opposite to that at the whole region scale. The pattern description based on more statistical units at various scales may discover the points' distributional characteristics and the patterns more easily. The spatial pattern research of health club points in units at various scales provides a new way of describing spatial patterns of recreation space points. And the effects of such a way are also demonstrated in this paper.

Real-Time In Situ HRTEM-Resolved Resistance Switching of Ag2S Nanoscale Ionic Conductor

The switching behaviors of ionic/electronic mixed conductor-based solid electrolyte nonvolatile memories have been attributed to repetitive formation and breakage of the conductive pathways inside a solid electrolyte. However, direct evidence of such pathway existence and their formations has never been provided. Herein, we reproduced the switching behavior of a Ag/Ag(2)S/W sandwich structure inside a high-resolution transmission electron microscope equipped with a scanning tunneling microscope unit. The on/off current ratio of 5 orders of magnitude was documented. The in situ formation and breakage of a nanoscale conductive channel were ultimately verified in real time and under atomic resolution. We found that a conducting Ag(2)S argentite phase and a Ag nanocrystal together formed the ionic and electronic conductive channel. The preferential atomic sites for Ag nanocrystal growth within the argentite phase were finally clarified.

Modeling of Dynamically Loaded Open-Cell Metallic Foams: Yielding, Collapse, and Strain Rate Effects

Open-cell metallic foams exhibit properties desirable in engineering applications requiring mitigation of the adverse effects resulting from impact loading; however, the history dependent dynamic response of these cellular materials has not been clearly elucidated. This article contributes an approach for modeling the response of dynamically loaded open-cell metallic foams from ligament level to unit cell level to specimen level. The effective response captures the localized chaotic collapse phenomena through ligament reorientation at cell level while maintaining the history of plastic deformation at ligament level. First, the phenomenological elastoplastic constitutive behavior of the ligaments composing the unit cell is modeled. Then, using the constitutive ligament model, the effective unit cell response is obtained from a micromechanical model that enforces the principle of minimum action on a representative 3D unit cell. Finally, the macroscopic specimen response is predicted utilizing a finite element analysis program, which obtains the response at every Gauss point in the mesh from the microscopic unit cell model. The current communication focuses on the ability of the model to capture the yielding and collapse behaviors, as well as the strain rate effects, observed during impact loading of metallic foams.

Pharmacognostic Investigation of the Leaves and Stems of Viburnum erubescens Wall.ex DC

Purpose: Some pharmacognostical investigations were carried out on the leaves and stems of Viburnum erubescens Wall.ex DC to record parameters for identifying and differentiating various species of Viburnum. Methods: The research specimens were authenticated and preserved both in fresh and dry forms. The leaves and stems were morphologically screened followed by anatomical studies with the aid of Labphot 2 microscopic units. Powder microscopy and micrometric studies, including leaf constants, were performed using suitable tools and reagents under different magnifications. Physicochemical parameters such as alcohol and aqueous extractive values, ash values, crude fibre content for stem, and fluorescence properties were also determined. The specimens were subjected to successive extraction processes by Soxhlet method using solvents of increasing polarity. Qualitative chemical screening tests with suitable reagents were also undertaken. Results: The leaves were petiolate and opposite, acuminate apex with unequal base, abaxial surfaces which turned blackish on storage, and had irritant smell with a slightly bitter taste. The vein islets were squarish and polygonal. Trichomes and club-shaped glandular trichomes were evident. The barks were hard and brittle with abundant fissures. The periderm was four-layered followed by homogenous parenchyma. The phloem region appeared with sclerenchyma elements; libriform fibres and tanniferous cells were also evident. The presence of phytosterols, triterpenoids, glycosides (saponins) and phenolic compounds (flavonoids and procyanidins) was positive for both the leaf and the stem. Conclusion: The findings of this study could be useful in identifying Viburnum species, both in whole and powder form. Also, the parameters derived from this study may be useful in differentiating this species from the rest of its relatives.

Time-Correlated Single-Photon Counting System with a Modified Objective Unit for Studying Fluorescence Emitters under High-Vacuum and Ambient Gas Conditions

In this study, we introduce a modified microscope unit for studying fluorescence emitters under high-vacuum and ambient gas conditions. The modified microscope unit has an immersion objective and uses an ionic liquid as a refractive index matching medium. In our optical geometry, the immersion objective and ionic liquid are placed in high vacuum and ambient gas. The optical properties of single colloidal quantum dots (CdSe/ZnS) in a poly(methyl methacrylate) (PMMA) matrix placed in ambient air, high vacuum, and ambient nitrogen gas with an appropriate pressure are studied.

Universal divergenceless scaling between structural relaxation and caged dynamics in glass-forming systems

On approaching the glass transition, the microscopic kinetic unit spends increasing time rattling in the cage of the first neighbors, whereas its average escape time, the structural relaxation time tau(alpha), increases from a few picoseconds up to thousands of seconds. A thorough study of the correlation between tau(alpha) and the rattling amplitude, expressed by the Debye-Waller factor, was carried out. Molecular-dynamics simulations of both a model polymer system and a binary mixture were performed by varying the temperature, the density rho, the potential and the polymer length to consider the structural relaxation as well as both the rotational and the translation diffusion. The present simulations, together with MD studies on other glassformers, evidence the scaling between the structural relaxation and the caged dynamics. An analytic model of the master curve is developed in terms of two characteristic length scales a(2) (1/2) and sigma(a(2) ) (1/2), pertaining to the distance to be covered by the kinetic unit to reach a transition state. The model does not imply tau(alpha) divergences. The comparison with the experiments supports the numerical evidence over a range of relaxation times as wide as about eighteen orders of magnitude. A comparison with other scaling and correlation procedures is presented. In particular, the density scaling of the length scales a(2) (1/2), sigma(a(2) ) (1/2) proportional to rho(-1/3) is shown to be not supported by the present simulations. The study suggests that the equilibrium and the moderately supercooled states of the glassformers possess key information on the huge slowing-down of their relaxation close to the glass transition. The latter, according to the present simulations, exhibits features consistent with the Lindemann melting criterion and the free-volume model.