Immunoglobulin G4 (IgG4)-related disease is a systemic fibroinflammatory disease capable of affecting virtually any organ. Although the pancreas and hepatobiliary system are commonly affected, ...involvement of the tubular gut is unusual. The pancreatic manifestations of this disease (autoimmune pancreatitis) often mimic pancreatic carcinoma, whereas the hepatobiliary manifestations are mistaken for cholangiocarcinoma or primary sclerosing cholangitis. The characteristic histologic features include a dense lymphoplasmacytic infiltrate, storiform-type fibrosis, and obliterative phlebitis. An increase in IgG4(+) plasma cells and an IgG4 to IgG ratio of more than 40% are considered obligatory components of the diagnostic algorithm.
To review the challenges associated with the diagnosis of IgG4-related disease of the gastrointestinal tract.
A review of pertinent literature, along with the author's personal experience, based on institutional and consultation materials.
The complete spectrum of histologic changes is seldom captured in a biopsy specimen, and thus, the histopathology findings are best interpreted within the overall clinical context. Increased IgG4(+) plasma cells are identified in a variety of benign and malignant diseases of the gastrointestinal tract.
A family of 2D coordination polymers were successfully synthesized through “bottom-up” techniques using Ni2+, Cu2+, Co2+, and hexaaminobenzene. Liquid–liquid and air–liquid interfacial reactions were ...used to realize thick (∼1–2 μm) and thin (<10 nm) stacked layers of nanosheet, respectively. Atomic-force microscopy and scanning electron microscopy both revealed the smooth and flat nature of the nanosheets. Selected area diffraction was used to elucidate the hexagonal crystal structure of the framework. Electronic devices were fabricated on thin samples of the Ni analogue and they were found to be mildly conducting and also showed back gate dependent conductance.
A simple snap-fit and vacuum brazing method has been developed to fabricate three dimensional space filling octet-truss lattice structures from Ti–6Al–4V alloy sheets. Using strut lengths of 7–25mm ...resulted in a relative density of the lattices ranging from 2% to 16%. The lattice elastic stiffness constants and strengths have been characterized under through-thickness compression and in-plane shear as a function of their relative density, and are shown to be well predicted by previously proposed micromechanical models adapted to account for the increased nodal mass and strut separations of the snap-fit lattice design. The Ti–6Al–4V octet-truss lattices exhibit excellent mechanical properties compared to other cellular material – cell topology combinations, and appear to be promising candidates for high temperature applications where a robust mechanical performance is required.
Non linear constitutive models for lattice materials Vigliotti, Andrea; Deshpande, Vikram S.; Pasini, Damiano
Journal of the mechanics and physics of solids,
March 2014, 2014-03-00, 20140301, Letnik:
64
Journal Article
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We use a computational homogenisation approach to derive a non linear constitutive model for lattice materials. A representative volume element (RVE) of the lattice is modelled by means of discrete ...structural elements, and macroscopic stress–strain relationships are numerically evaluated after applying appropriate periodic boundary conditions to the RVE. The influence of the choice of the RVE on the predictions of the model is discussed. The model has been used for the analysis of the hexagonal and the triangulated lattices subjected to large strains. The fidelity of the model has been demonstrated by analysing a plate with a central hole under prescribed in plane compressive and tensile loads, and then comparing the results from the discrete and the homogenised models.
Contact guidance, the widely-known phenomenon of cell alignment, is an essential step in the organization of adherent cells. This guidance is known to occur by, amongst other things, anisotropic ...features in the environment including elastic heterogeneity. To understand the origins of this guidance we employed a novel statistical thermodynamics framework, which recognises the non-thermal fluctuations in the cellular response, for modelling the response of the cells seeded on substrates with alternating soft and stiff stripes. Consistent with observations, the modelling framework predicts the existence of three regimes of cell guidance: (i) in regime I for stripe widths much larger than the cell size guidance is primarily entropic; (ii) for stripe widths on the order of the cell size in regime II guidance is biochemically mediated and accompanied by changes to the cell morphology while (iii) in regime III for stripe widths much less than the cell size there is no guidance as cells cannot sense the substrate heterogeneity. Guidance in regimes I and II is due to “molli-avoidance” with cells primarily residing on the stiff stripes. While the molli-avoidance tendency is not lost with decreasing density of collagen coating the substrate, the reduced focal adhesion formation with decreasing collagen density tends to inhibit contact guidance. Our results provide clear physical insights into the interplay between cell mechano-sensitivity and substrate elastic heterogeneity that ultimately leads to the contact guidance of cells in heterogeneous tissues.
Cellular morphology and organization play a crucial role in the micro-architecture of tissues and dictates their biological and mechanical functioning. Despite the importance of cellular organization in all facets of tissue biology, the fundamental question of how a cell organizes itself in an anisotropic environment is still poorly understood. We employ a novel statistical thermodynamics framework which recognises the non-thermal fluctuations in the cellular response to investigate cell guidance on substrates with alternating soft and stiff stripes. The propensity of cells to primarily reside on stiff stripes results in strong guidance when the period of the stripes is larger than the cell size. For smaller stripe periods, cells sense a homogeneous substrate and guidance is lost.
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The integration of materials and architectural features at multiple length scales into structural mechanics has shifted the paradigm of structural design toward optimally engineered structures, which ...resulted in, for example, the Eiffel Tower. This structural revolution paved the way for the development of computational design approaches used in modern-day construction. Similar principles are now being applied to the design and manufacture of architected materials with a suite of properties determined a priori and attained through multiscale approaches. These new material classes potentially offer breakthrough advances in almost every branch of technology: from ultra-lightweight and damage-tolerant structural materials to safe and efficient energy storage, biomedical devices, biochemical, and micromechanical sensors and actuators, nanophotonic devices, and textiles. When reduced to the microscale, such materials embody the characteristics of both the constituent material, which brings the effects of its microstructure and ensuing properties at the relevant characteristic length scales, as well as the structure, which is driven by architected design. This issue gives an overview of the current state of the art of this new class of materials.
Cell-cell interaction dictates cell morphology and organization, which play a crucial role in the micro-architecture of tissues that guides their biological and mechanical functioning. Here, we ...investigate the effect of cell density on the responses of cells seeded on flat substrates using a novel statistical thermodynamics framework. The framework recognizes the existence of nonthermal fluctuations in cellular response and thereby naturally captures entropic interactions between cells in monolayers. In line with observations, the model predicts that cell area and elongation decrease with increasing cell seeding density—both are a direct outcome of the fluctuating nature of the cellular response that gives rise to enhanced cell-cell interactions with increasing cell crowding. The modeling framework also predicts the increase in cell alignment with increasing cell density: this cellular ordering is also due to enhanced entropic interactions and is akin to nematic ordering in liquid crystals. Our simulations provide physical insights that suggest that entropic cell-cell interactions play a crucial role in governing the responses of cell monolayers.
Recently the hybrid organic-inorganic trihalide perovskites have shown remarkable performance as active layers in photovoltaic and other optoelectronic devices. However, their spin characteristic ...properties have not been fully studied, although due to the relatively large spin-orbit coupling these materials may show great promise for spintronic applications. Here we demonstrate spin-polarized carrier injection into methylammonium lead bromide films from metallic ferromagnetic electrodes in two spintronic-based devices: a 'spin light emitting diode' that results in circularly polarized electroluminescence emission; and a 'vertical spin valve' that shows giant magnetoresistance. In addition, we also apply a magnetic field perpendicular to the injected spins orientation for measuring the 'Hanle effect', from which we obtain a relatively long spin lifetime for the electrically injected carriers. Our measurements initiate the field of hybrid perovskites spin-related optoelectronic applications.
The ability of cells to orient in response to mechanical stimuli is essential to embryonic development, cell migration, mechanotransduction, and other critical physiologic functions in a range of ...organs. Endothelial cells, fibroblasts, mesenchymal stem cells, and osteoblasts all orient perpendicular to an applied cyclic stretch when plated on stretchable elastic substrates, suggesting a common underlying mechanism. However, many of these same cells orient parallel to stretch in vivo and in 3D culture, and a compelling explanation for the different orientation responses in 2D and 3D has remained elusive. Here, we conducted a series of experiments designed specifically to test the hypothesis that differences in strains transverse to the primary loading direction give rise to the different alignment patterns observed in 2D and 3D cyclic stretch experiments (“strain avoidance”). We found that, in static or low-frequency stretch conditions, cell alignment in fibroblast-populated collagen gels correlated with the presence or absence of a restraining boundary condition rather than with compaction strains. Cyclic stretch could induce perpendicular alignment in 3D culture but only at frequencies an order of magnitude greater than reported to induce perpendicular alignment in 2D. We modified a published model of stress fiber dynamics and were able to reproduce our experimental findings across all conditions tested as well as published data from 2D cyclic stretch experiments. These experimental and model results suggest an explanation for the apparently contradictory alignment responses of cells subjected to cyclic stretch on 2D membranes and in 3D gels.
A dilute system of electrons interacting through long-range Coulomb forces has been predicted to form a periodic solid known as a Wigner crystal. To date, this state has been observed directly only ...in two-dimensional systems. Here, using low-temperature single-electron transport spectroscopy, we show that the hole gas in low-disorder semiconducting carbon nanotubes forms a one-dimensional Wigner crystal. In an axial magnetic field, we observe three distinct regimes of spin and isospin polarization as carrier density is varied. We explain these regimes in terms of a Wigner crystal picture based on a gapped Luttinger liquid model, with the carriers represented by spatially localized solitons. Our observations could enable greater control over the behaviour of the spatially separated system of carriers. Such control, combined with the inherently long coherence times of carriers in carbon nanotubes, could prove useful in the development of solid-state quantum computing. PUBLICATION ABSTRACT
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