Microscopic Cellular Structures Research Articles

Sex and mental health are related to subcortical brain microstructure

Some mental health problems such as depression and anxiety are more common in females, while others such as autism and attention deficit/hyperactivity (AD/H) are more common in males. However, the neurobiological origins of these sex differences are poorly understood. Animal studies have shown substantial sex differences in neuronal and glial cell structure, while human brain imaging studies have shown only small differences, which largely reflect overall body and brain size. Advanced diffusion MRI techniques can be used to examine intracellular, extracellular, and free water signal contributions and provide unique insights into microscopic cellular structure. However, the extent to which sex differences exist in these metrics of subcortical gray matter structures implicated in psychiatric disorders is not known. Here, we show large sex-related differences in microstructure in subcortical regions, including the hippocampus, thalamus, and nucleus accumbens in a large sample of young adults. Unlike conventional T1-weighted structural imaging, large sex differences remained after adjustment for age and brain volume. Further, diffusion metrics in the thalamus and amygdala were associated with depression, anxiety, AD/H, and antisocial personality problems. Diffusion MRI may provide mechanistic insights into the origin of sex differences in behavior and mental health over the life course and help to bridge the gap between findings from experimental, epidemiological, and clinical mental health research.

Design Strategies towards the Optimization of 3D Additive Manufactured Lattice Structures

Additive manufacturing (AM) techniques are based on the process of joining materials, layer upon layer, differently from subtractive manufacturing methods. The design for AM allows for the creation of complex shapes as well as for the improvement of the performance of critical components in several fields, spanning from aerospace and automotive to biomedical applications. On the other hand, unlike man-made high load-bearing capacity devices, which are usually dense solids, nature uses mesoscopic or microscopic cellular structures as a fundamental support for the design. The increasing applications of AM in industrial production have led to product reimagination from a novel standpoint, enabling the fabrication of advanced lattice structures using polymer-based materials. Over the past few years, many efforts have been made to develop strategies for finding the design which is best suited to the requirements. In the current research, specific design scenarios were explored, the aim being to develop novel lattice structures for energy absorption, using an AM technique (i.e., fused deposition modelling) and a modified Acrylonitrile Styrene Acrylate (ASA)-based material. The fabricated structures were preliminarily analysed by means of compression tests.

Penetration and distribution efficacy of chemotherapeutic drugs in biological tissues: A computational investigation

Many chemotherapeutic drugs, developed so far, show significant anticancer activities during the clinical trials; however, their treatment efficacy is limited in practice. The limited efficacy is attributed to the inadequate knowledge of interplay between a drug and the physicochemical properties of tissues. This study employs the finite volume heterogeneous multiscale method to study the penetration and distribution efficacy of chemotherapeutic agents such as, fluorouracil, carmustine, cisplatin, methotrexate, doxorubicin, and paclitaxel. The physical properties of these drugs are incorporated in the model to provide physiological scenario. The effects of fluid flow, drug elimination, and microscopic cellular structures are analysed on penetration and distribution of these chemotherapeutic drugs. It is observed that carmustine penetrates deeper into the tissue, followed by paclitaxel, methotrexate, fluorouracil, doxorubicin, whereas cisplatin penetrates least. In order to explain advection–diffusion–reaction processes, a novel dimensionless number KT=Ka/Th2 is introduced, where Ka and Th are Karlovitz and Thiele modulus numbers, respectively. This number may be defined as the ratio of time-scale of reaction rate with the cumulative time-scale of advection and diffusion processes. As the model involves several parameters, the global sensitivity analysis is also performed to determine the sensitivity of uncertainties in the input parameters to the model output.

The Kinematics of Scale Deflection in the Course of Multi-Step Seed Extraction from European Larch Cones (Larix decidua Mill.) Taking into Account Their Cellular Structure.

The objective of the study was to elucidate the kinematics of cone opening in the European larch (Larix decidua Mill.) during a four-step seed extraction process and to determine optimum process time on that basis. Each step lasted 8 h with 10 min of water immersion between the steps. The study also described the microscopic cellular structure of scales in cones with a moisture content of 5% and 20%, as well as evaluated changes in cell wall thickness. The obtained results were compared with the structural investigations of scales conducted using scanning electron microscopy (SEM) of characteristic sites on the inner and outer sides of the scales. The greatest increment in the scale opening angle was noted on the first day of the process (34°) and in scales from the middle cone segment (39°). In scales with a moisture content of 5% and 20%, the greatest changes in cell wall thickness were recorded for large cells (57%). The inner and outer structure of scales differed in terms of the presence and size of cells depending on the moisture content of the cones (5%, 10%, or 20%). The study demonstrated that the moisture content of cones was the crucial determinant of the cellular structure and opening of scales in larch cones. The scale opening angle increased with decreasing moisture content but did not differ significantly for various segments of cones or various hours of the consecutive days of the process. This finding may lead to reducing the seed extraction time for larch cones. The internal and external structure of scales differed depending on moisture content, which also determined the size and wall thickness of cells.

Systematic construction of gapped nonliquid states

This paper use 2+1D topological orders, or domain walls between 3+1D topological orders, to construct the microscopic cellular structure of a 3+1D gapped non-liquid state by glueing those 2+1D topological orders, or domain walls, together. The author further shows that this construction could produce gapped non-liquid states with fractal-like excitations.

Design and additive manufacturing of closed cells from supportless lattice structure

In nature, mesoscopic or microscopic cellular structures like trabecular bone, wood, shell, and sea urchin, can have high load-carrying capacity. These cellular structures with diverse shapes, forms and designs can be mainly classified into open and closed cell cellular structures. It is difficult to replicate these natural complex lattice structures with traditional manufacturing, but additive manufacturing (AM) technology development has allowed engineers and scientists to mimic these natural structures. Fabricating close cell lattice structures is still considered difficult due to the support structure within the lattices. This paper evaluates a novel way of fabricating a close cell lattice structure with a material extrusion process. The design eliminates the need for support structures and the subsequent post-processing required to remove them. A shell-shaped close cell lattice structure bio-mimicking a sea urchin shape was introduced for the load-bearing structure application. The mechanical properties of the proposed structure, including stiffness, deformation behavior and energy absorption, were compared with those of benchmarked honeycomb and open cell sea urchin (SU) lattice structures of the same density. SU lattice structures and honeycomb periodic lattice structures with varied sizes but the same morphology and fixed density were designed and printed in polylactic acid material (PLA). Their physical characteristics, deformation behavior, and compressive properties were investigated experimentally and via finite element analysis. The effect of the unit cell size on mechanical properties was studied and discussed, and the rankings of better performances were drawn. A possible application of the closed cell is for fabricating the load bearing structure; it can also be encapsulated within a fluid to impart strength and damping characteristics.

3D Printing of Ultralight Biomimetic Hierarchical Graphene Materials with Exceptional Stiffness and Resilience.

Biological materials with hierarchical architectures (e.g., a macroscopic hollow structure and a microscopic cellular structure) offer unique inspiration for designing and manufacturing advanced biomimetic materials with outstanding mechanical performance and low density. Most conventional biomimetic materials only benefit from bioinspired architecture at a single length scale (e.g., microscopic material structure), which largely limits the mechanical performance of the resulting materials. There exists great potential to maxime the mechanical performance of biomimetic materials by leveraging a bioinspired hierarchical structure. An ink-based three-dimensional (3D) printing strategy to manufacture an ultralight biomimetic hierarchical graphene material (BHGMs) with exceptionally high stiffness and resilience is demonstrated. By simultaneously engineering 3D-printed macroscopic hollow structures and constructing an ice-crystal-induced cellular microstructure, BHGMs can achieve ultrahigh elasticity and stability at compressive strains up to 95%. Multiscale finite element analyses indicate that the hierarchical structures of BHGMs effectively reduce the macroscopic strain and transform the microscopic compressive deformation into the rotation and bending of the interconnected graphene flakes. This 3D printing strategy demonstrates the great potential that exists for the assembly of other functional materials into hierarchical cellular structures for various applications where high stiffness and resilience at low density are simultaneously required.

Self-aligned and hierarchically porous graphene-polyurethane foams for acoustic wave absorption

Manipulating the morphology of three-dimensional (3D) cellular structures in both macroscale and microscale is very important in designing a sound absorbing material effective in a broad frequency bandwidth. However, it is extremely difficult to synthesize the hierarchical porous structures having nano- and micro-pores in a self-assembled or controlled manner. Herein, we report an efficient strategy to fabricate the self-aligned and hierarchically porous graphene-polyurethane foams as a sound absorbing material via electrostatic repulsion mechanism of graphene oxide and potassium hydroxide activation. Two unique microscopic cellular structures are designed by controlling the morphology of graphene layers inside the polyurethane backbone using spontaneous self-alignment and stochastic disruptive methods, respectively. The obtained heterogeneous graphene microstructure network provides enhanced mechanically load-bearing ability and significantly improves the sound energy attenuation performance over 312% compared to pristine sound absorber depending on the existence of ordered or disordered graphene lattices, resulting in an efficient pathway for rapidly decaying out acoustic wave energy.

Pronounced energy absorption capacity of cellular bulk metallic glasses

Cellular bulk metallic glasses (BMGs) with macroscopic cellular structures were designed and fabricated. The cellular BMGs exhibited remarkable energy absorption capacity as compared with reported BMG foams and honeycombs. The enhanced energy absorption capability is attributed to the large plastic bending of the struts, the blunting of the cracks, and the large plastic deformation at the nodes. This work shows that, in cellular BMGs, the macroscopic cellular structures are more efficient in dissipating mechanical energy than microscopic cellular structures, opening a window for developing energy absorption devices using BMGs.

An Iterative Method for Problems with Multiscale Conductivity

A model with its conductivity varying highly across a very thin layer will be considered. It is related to a stable phantom model, which is invented to generate a certain apparent conductivity inside a region surrounded by a thin cylinder with holes. The thin cylinder is an insulator and both inside and outside the thin cylinderare filled with the same saline. The injected current can enter only through the holes adopted to the thin cylinder. The model has a high contrast of conductivity discontinuity across the thin cylinder and the thickness of the layer and the size of holes are very small compared to the domain of the model problem. Numerical methods for such a model require a very fine mesh near the thin layer to resolve the conductivity discontinuity. In this work, an efficient numerical method for such a model problem is proposed by employing a uniform mesh, which need not resolve the conductivity discontinuity. The discrete problem is then solved by an iterative method, where the solution is improved by solving a simple discrete problem with a uniform conductivity. At each iteration, the right-hand side is updated by integrating the previous iterate over the thin cylinder. This process results in a certain smoothing effect on microscopic structures and our discrete model can provide a more practical tool for simulating the apparent conductivity. The convergence of the iterative method is analyzed regarding the contrast in the conductivity and the relative thickness of the layer. In numerical experiments, solutions of our method are compared to reference solutions obtained from COMSOL, where very fine meshes are used to resolve the conductivity discontinuity in the model. Errors of the voltage in L2 norm follow O(h) asymptotically and the current density matches quitewell those from the reference solution for a sufficiently small mesh size h. The experimental results present a promising feature of our approach for simulating the apparent conductivity related to changes in microscopic cellular structures.

Effects of Osmotic Agents on Colour, Textural, Structural, Thermal, and Sensory Properties of Apple Slices

Effects of various osmotic agents (i.e., glucose, fructose, sucrose, maltose, sorbitol, and honey) were evaluated in terms of moisture loss and solid gain besides objective measurements of colour, texture, glass transition temperature; subjective sensory profile; and scanning electron microscopic cellular structure of osmotically dehydrated apple slices. Significantly (p < 0.05) higher solid gains were observed in the samples dipped in glucose and fructose solutions, whereas maltose-treated samples showed higher water loss. The glass transition temperatures varied from −68.4 to −45.6°C, minimum in the case of glucose and maximum in maltose-treated ones. The sucrose- and maltose-treated samples had significantly (p < 0.05) higher L* showing restricted browning. The a* value was maximum and minimum in the case of sucrose- and fructose-treated samples, respectively. Hardness was found to be significantly (p < 0.05) higher (20.104 N) in sucrose-treated samples, while it was at a minimum (4.441 N) in sorbitol-treated ones. The scanning electron microscope studies revealed that cellular structure was retained in sucrose-treated samples, while the damage was observed to be more in the glucose- and fructose-treated ones. The sensory attributes of the osmo-dehydrated samples were found to be better in the case of sucrose-treated samples. The type of humectant, in terms of molecular size, significantly influences the mass transfer process that could be optimized to make the process versatile to meet the requirements of processors and consumers.

Diffusion Tensor MR Imaging

AbstractThis unit reviews the physical principles and methodologies involved in diffusion‐weighted imaging (DWI) and diffusion tensor imaging (DTI) for clinical applications. Diffusion‐sensitive MRI noninvasively provides insight into processes and microscopic cellular structures that alter molecular water mobility. Formalism to extend the Bloch equation to include effects of random translational motion through field gradients is reviewed. Definition of key acquisition parameters is also reviewed along with common methods to calculate and display tissue diffusion properties in a variety of image formats. Characterization of potential directional‐dependence of diffusion (i.e., anisotropy), such as that which exists in white matter, requires DTI. Diffusion tensor formalism and measurement techniques then reduce the diffusion tensor into standard anisotropy quantities that are summarized along with commonly used methods to depict directional information in an image format.

Cell-by-Cell Construction of Living Tissue

ABSTRACTThis paper outlines investigations into a potentially revolutionary approach to tissue engineering. Tissue is a complex three-dimensional structure that contains many different biomaterials such as cells, proteins, and extracellular matrix molecules that are ordered in a very precise way to serve specific functions. In order to replicate such complex structure, it is necessary to have a tool that could deposit all these materials in an accurate and controlled fashion. Most methods to fabricate living three-dimensional structures involve techniques to engineer biocompatible and biodegradable scaffolding, which is then seeded with living cells to form tissue. This scaffolding gives the tissue needed support, but the resulting tissue inherently has no microscopic cellular structure because cells are injected into the scaffolding where they adhere at random. We have developed a novel technique that actually engineers tissue, not scaffolding, that includes the mesoscopic cellular structure inherent in naturaltissues. This approach uses a laser-based rapid prototyping system known as matrix assisted pulsed laser evaporation direct write (MAPLE DW) to construct living tissue cell-by-cell. This manuscript details our efforts to rapidly and reproducibly fabricate complex 2D and 3D tissue structures with MAPLE-DW by placing different cells and biomaterials accurately and adherently on the mesoscopic scale

In vitro study of the developing inner ear.

<h3>Introduction</h3> The purpose of this presentation is to describe a tissue culture technique which makes possible the microscopic study and photography of the differentiating cells of the inner ear in the living state. The first successful attempt at cultivating the chick embryo otocyst in vitro was by Fell¹in 1928. A plasma clot formed in a watch glass was used as the culture medium. Lawrence and Merchant²in 1953 and Friedmann³in 1956 reported their studies using similar methods. In all 3 cases, cultures were fixed, sectioned, and stained in order to study the microscopic cellular structure in later stages of differentiation. This was made necessary by the thickness of the preparation due to the rapid outgrowth of opaque tissues, which obscured the ectodermal structures. The morphology of tissues is inevitably changed by the conventional methods of preparing tissues by histologic technique; the cells often shrink to