The processes controlling the morphology of dendrites have been of great interest to a wide range of communities, since they are examples of an out-of-equilibrium pattern forming system, there is a ...clear connection with battery failure processes, and their morphology sets the properties of many metallic alloys. We determine the three-dimensional morphology of free growing metallic dendrites using a novel X-ray tomographic technique that improves the temporal resolution by more than an order of magnitude compared to conventional techniques. These measurements show that the growth morphology of metallic dendrites is surprisingly different from that seen in model systems, the morphology is not self-similar with distance back from the tip, and that this morphology can have an unexpectedly strong influence on solute segregation in castings. These experiments also provide benchmark data that can be used to validate simulations of free dendritic growth.
Macrophages exhibit diverse phenotypes and functions; they are also a major cell type infiltrating chronically rejected allografts. The exact phenotypes and roles of macrophages in chronic graft loss ...remain poorly defined. In the present study, we used a mouse heart transplant model to examine macrophages in chronic allograft rejection. We found that treatment of C57BL/6 mice with CTLA4 immunoglobulin fusion protein (CTLA4‐Ig) prevented acute rejection of a Balb/c heart allograft but allowed chronic rejection to develop over time, characterized by prominent neointima formation in the graft. There was extensive macrophage infiltration in the chronically rejected allografts, and the graft‐infiltrating macrophages expressed markers associated with M2 cells but not M1 cells. In an in vitro system in which macrophages were polarized into either M1 or M2 cells, we screened phenotypic differences between M1 and M2 cells and identified purinergic receptor P2X7 (P2x7r), an adenosine triphosphate (ATP)–gated ion channel protein that was preferentially expressed by M2 cells. We further showed that blocking the P2x7r using oxidized ATP (oATP) inhibited M2 induction in a dose‐dependent fashion in vitro. Moreover, treatment of C57BL/6 recipients with the P2x7r antagonist oATP, in addition to CTLA4‐Ig treatment, inhibited graft‐infiltrating M2 cells, prevented transplant vasculopathy, and induced long‐term heart allografts survival. These findings highlight the importance of the P2x7r–M2 axis in chronic rejection and establish P2x7r as a potential therapeutic target in suppression of chronic rejection.
The authors demonstrate an association between chronic heart allograft rejection and preferential enrichment of M2 macrophages in grafts that express the purinergic receptor P2X7, and demonstrate a therapeutic potential for a P2X7 receptor antagonist. See the editorial from Baldwin and Morelli on page 2510.
This contribution outlines Synchrotron-based X-ray micro-tomography and its potential use in structural geology and rock mechanics. The paper complements several recent reviews of X-ray ...microtomography. We summarize the general approach to data acquisition, post-processing as well as analysis and thereby aim to provide an entry point for the interested reader. The paper includes tables listing relevant beamlines, a list of all available imaging techniques, and available free and commercial software packages for data visualization and quantification. We highlight potential applications in a review of relevant literature including time-resolved experiments and digital rock physics. The paper concludes with a report on ongoing developments and upgrades at synchrotron facilities to frame the future possibilities for imaging sub-second processes in centimetre-sized samples.
•This paper gives an overview on Synchrotron radiation based microtomography.•Image acquisition, processing and quantification are outlined.•Review of applications in hard rock geology, rock mechanics and porous media research.
Elastic mechanical properties of 316 L stainless steel samples fabricated using laser powder bed fusion were studied non-destructively through resonant ultrasound spectroscopy. Samples in five ...different conditions were obtained by varying the laser power from 103 W (the highest density condition) to 68 W (the lowest density condition) at constant laser speed, producing samples with a volume energy density in the 24.5–16.5 J/mm3 range and volumetric porosity in the 0.1–10% range. The observed elastic mechanical properties are discussed taking into consideration the bulk texture developed and quantitative pore characteristics studied using high-energy high-resolution synchrotron X-ray diffraction and X-ray computed micro-tomography, respectively. Furthermore, empirical exponential relationships are provided to express the functional dependence of Young's and shear moduli with porosity.
Nuclear security is one of the defining challenges of our time. Nuclear threats range from deliberate dispersal of radioactive material to contaminate the vital infrastructure to diversion and ...smuggling of special nuclear material for clandestine nuclear programs and nuclear terrorism, respectively. There is an associated need to develop and sustain nuclear forensics capabilities, which can be aided by good understanding of complex processes that occur in plasmas containing nuclear materials. The area of nuclear safety has seen a resurgence of public interest, and there is a concomitant need to safely store used nuclear fuel and to detect structural material failure in nuclear power systems, especially in innovative reactor designs envisioned for future adoption. Laser-produced plasmas are complicated extreme environments that can generate intense and rich, highly specific signatures of nuclear and radiological materials, which can then be explored for applications. They include interdiction and rapid detection of nuclear materials, including their isotopic composition, detection over long distances, laboratory simulation of weapons effects, monitoring the condition of structural materials in dry cask storage containers, and novel instrumentation for nuclear power systems. We present a compilation of recent representative examples of the application of laser spectroscopy, and laser-induced breakdown spectroscopy in particular, to nuclear safety and security problems. A case is made that spectroscopic techniques based on laser-produced plasmas offer complementary, and sometimes unique, capabilities that motivate continued exploration of their efficient production and broader understanding of the signatures they produce.
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•Spatiotemporal analysis of laser-induced plasma reveals the uranium plasma chemistry.•Ultrafast laser filamentation is effective for remote uranium elemental and isotope detection.•LIBS may be used for monitoring of fuel integrity in nuclear reactors.•LIBS is capable of detection of trace chlorine concentrations in dry cask storage systems.
ABSTRACT
Fluorosis can induce oxidative stress through leading to reactive oxygen species (ROS) generation. Selenium (Se) can eliminate ROS by direct and indirect manners. In this study, therefore, ...we investigated the possible protective effects of sodium selenite (SS) and selenomethionine (Se-Met) on fluorine (F)-induced oxidative stress in broilers. A total of 720 1-day-old Lingnan Yellow broilers were allotted to 4 groups (6 replicates of 30 birds each group) and fed with basal diet (control group), 800 mg/kg F (high F group), 800 mg/kg F+0.15 mg Se/kg as SS (SS group), or Se-Met (Se-Met group), respectively. The experiment lasted 50 d. High F group significantly decreased (P < 0.05) the average daily gain (ADG) and feed efficiency (FE) in comparison with control group. The contents of ROS, malondialdehyde, 8-hydroxydeoxyguanosine, protein carbonyl, and cysteinyl aspartate specific proteinases 3 in serum, liver, and kidney were higher (P < 0.05) in high F group than those in control group. Compared with control group, the decreased (P < 0.05) activities of glutathione peroxidase (GSH-Px) and cytoplasmic thioredoxin reductase (TrxR1) as well as contents of selenoprotein P (SelP), total protein (TP), and B-cell lymphoma-2 in serum and tissues were observed in high F group. Moreover, the pathological lesions of liver and kidney in high F group were more than those in control group. However, supplementation with SS and Se-Met could improve ADG and FE, increase SelP and TP concentrations, elevate GSH-Px and TrxR1 activities, minimize the changes of oxidative stress and apoptosis parameters as well as ultrastructure of liver and kidney, whereas the effects of Se-Met were better than those of SS. The results indicated that excess F could result in growth inhibition of broilers through inducing oxidative stress and subsequently caused oxidative damage to biological macromolecules and soft tissues as well as apoptosis, whereas dietary SS and Se-Met supplementation could antagonize high F induced growth retardation by inhibiting oxidative stress and a mechanism of apoptosis regulation and the impact was more with Se-Met.
Cardiac lipotoxicity, characterized by increased uptake, oxidation, and accumulation of lipid intermediates, contributes to cardiac dysfunction in obesity and diabetes mellitus. However, mechanisms ...linking lipid overload and mitochondrial dysfunction are incompletely understood.
To elucidate the mechanisms for mitochondrial adaptations to lipid overload in postnatal hearts in vivo.
Using a transgenic mouse model of cardiac lipotoxicity overexpressing ACSL1 (long-chain acyl-CoA synthetase 1) in cardiomyocytes, we show that modestly increased myocardial fatty acid uptake leads to mitochondrial structural remodeling with significant reduction in minimum diameter. This is associated with increased palmitoyl-carnitine oxidation and increased reactive oxygen species (ROS) generation in isolated mitochondria. Mitochondrial morphological changes and elevated ROS generation are also observed in palmitate-treated neonatal rat ventricular cardiomyocytes. Palmitate exposure to neonatal rat ventricular cardiomyocytes initially activates mitochondrial respiration, coupled with increased mitochondrial polarization and ATP synthesis. However, long-term exposure to palmitate (>8 hours) enhances ROS generation, which is accompanied by loss of the mitochondrial reticulum and a pattern suggesting increased mitochondrial fission. Mechanistically, lipid-induced changes in mitochondrial redox status increased mitochondrial fission by increased ubiquitination of AKAP121 (A-kinase anchor protein 121) leading to reduced phosphorylation of DRP1 (dynamin-related protein 1) at Ser637 and altered proteolytic processing of OPA1 (optic atrophy 1). Scavenging mitochondrial ROS restored mitochondrial morphology in vivo and in vitro.
Our results reveal a molecular mechanism by which lipid overload-induced mitochondrial ROS generation causes mitochondrial dysfunction by inducing post-translational modifications of mitochondrial proteins that regulate mitochondrial dynamics. These findings provide a novel mechanism for mitochondrial dysfunction in lipotoxic cardiomyopathy.
The property of biomaterials to control the sequential release of growth factors has been widely concerned in the field of bone repair and regeneration. Double-factor sustained-release scaffolds have ...good biocompatibility and bioactivity. O‑Carboxymethyl chitosan microspheres (O-CMCS) has antimicrobial activity, biodegradability, biocompatibility and film formation. This study developed scaffolds materials with microspheres with a purpose of forming a controlled slow release secondary structure. O-CMCS were used as drug carrier to construct the compound sustained-release system with rhBMP-2 and VEGF double factors release. The O-CMCS were loaded with rhBMP-2 and the hydroxyapatite collagen (HC) scaffolds were loaded with VEGF to prepare the scaffolds. These were double factors composite sustained-release system scaffolds. The biocompatibility of the sustained-release system was evaluated by in vitro and in vivo experiments. HC composite scaffolds were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction detection (XRD), in vitro sustained release test, in vitro cell culture and in vivo animal experiments. The results showed that rhBMP-2/VEGF in HC composite scaffolds (HCBV) successfully achieved the sequential release of the double factors, which could benefit bone regeneration.
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