Predictive microstructural evolution via localized strain dependence measurements using correlated precession diffraction and In situ TEM

Although significant advances have been made in elucidating atomic-scale mechanisms that control properties of polycrystalline materials for a wide range of applications, the need for predictive understanding of material response based on crystal orientation information still exists. In this discussion, a combined approach to understanding strain-driven microstructural evolution processes using in situ transmission electron microscopy (TEM) and precession diffraction is described. Specifically, TEM-based Nanomegas DIGISTAR/ASTAR orientation mapping and precession diffraction techniques in conjunction with in situ TEM heating, strain, and irradiation will be discussed. Case studies of the advantages and drawbacks of TEM-based orientation imaging and precession diffraction during in situ TEM exploration of the stability of irradiated nanocrystalline BCC metals and strain-based twin evolution in FCC metals will be highlighted, and compared to SEM-based EBSD strain measurement techniques. The results presented will help provide a connection of the role of localized strain in developing stable materials for extreme applications

Ranking of production and management risks of digital resources in digital libraries by means of Shanon Entropy and Fuzzy TOPSIS Techniques

Purpose: The present research has been done with a view to evaluation and ranking of production and management of digital resources in the supply chain of digital libraries. Methodology: The present research is essentially an applied one and the method employed, has been descriptive survey based on Shanon Entropy and Fuzzy TOPSIS methods. Findings: According to our findings, the risks of “Collection development strategy of digital resources” with highest rate of Proximity Coefficient(PC)=%731 stand in the first place and then the other ones in order include: risks of “Management strategy of digital resources at libraries” with PC=%7186, “The high cost of technological changes of information carriers and storage formats” with PC=711 and “Competence of library software in detecting repetitious copies” with PC=%651. Conclusion: 26 risks for production and management of digital resources in the supply chain of digital libraries have been identified and amidst production and management risks of digital resources in the supply chain of digital libraries the risk of” Collection development strategy of digital resources” stands in the first place

Hemato-immunological, serum metabolite and enzymatic stress response alterations in exposed rainbow trout (Oncorhynchus mykiss) to nanosilver

The aim of present study was to investigate the effects of sub-lethal concentrations of silver nanoparticles (AgNP) on hematological parameters, differential tests of white blood cells, serum metabolite parameters, serum enzymes activity and serum ions in rainbow trout, Oncorhynchus mykiss. Healthy rainbow trout, were exposed to sub-lethal concentrations (0, 1.5 and 2.5 ppm) of nanosilver for 14 days. RBC, WBC and Hct levels were significantly (P<0.05) increased in exposed groups. Within the white blood cells, only neutrophils showed a significant increase at 7 and 14 days post exposure (P<0.05). Serum triglyceride, total serum protein, albumin and globulin levels were decreased (P<0.05) in exposed fish, however, cholesterol levels increased in the 2.5 ppm group at 7 days after exposure (P<0.05). Cortisol and glucose increased significantly at 7 and 14 days of exposure in both concentrations of AgNPs (P<0.05). Decreases in serum ions level were observed, although reduction in chloride ions occurred earlier and more severe than other measured parameters (P<0.05). Elevation in serum ALP, LDH, ALT and AST enzymes were observed during the experiment (P<0.05), although SOD and CAT activity were significantly decreased in exposed groups (P<0.05). The results revealed that AgNP can affect the hematological, serum metabolite and enzymatic parameters of O. mykiss, as well as AgNP exposure induce a general oxidative stress response in O. mykiss

Magnetic properties of Co2C and Co3C nanoparticles and their assemblies

Nano-composite material consisting of Co2C and Co3C nanoparticles has recently been shown to exhibit unusually large coercivities and energy products. Experimental studies that can delineate the properties of individual phases have been undertaken and provide information on how the coercivities and the energy product change with the size and composition of the nanoparticles. The studies indicate that while both phases are magnetic, the Co3C has higher magnetization and coercivity compared to Co2C. Through first principles electronic structure studies using a GGA+U functional, we provide insight on the role of C intercalation on enhancing the magnetic anisotropy of the individual phases

Mapping Structural Heterogeneity at the Nanoscale with Scanning Nano-structure Electron Microscopy (SNEM)

Here we explore the use of scanning electron diffraction coupled with electron atomic pair distribution function analysis (ePDF) to understand the local order as a function of position in a complex multicomponent system, a hot rolled, Ni-encapsulated, Zr$_{65}$Cu$_{17.5}$Ni$_{10}$Al$_{7.5}$ bulk metallic glass (BMG), with a spatial resolution of 3 nm. We show that it is possible to gain insight into the chemistry and chemical clustering/ordering tendency in different regions of the sample, including in the vicinity of nano-scale crystallites that are identified from virtual dark field images and in heavily deformed regions at the edge of the BMG. In addition to simpler analysis, unsupervised machine learning was used to extract partial PDFs from the material, modeled as a quasi-binary alloy, and map them in space. These maps allowed key insights not only into the local average composition, as validated by EELS, but also a unique insight into chemical short-range ordering tendencies in different regions of the sample during formation. The experiments are straightforward and rapid and, unlike spectroscopic measurements, don't require energy filters on the instrument. We spatially map different quantities of interest (QoI's), defined as scalars that can be computed directly from positions and widths of ePDF peaks or parameters refined from fits to the patterns. We developed a flexible and rapid data reduction and analysis software framework that allows experimenters to rapidly explore images of the sample on the basis of different QoI's. The power and flexibility of this approach are explored and described in detail. Because of the fact that we are getting spatially resolved images of the nanoscale structure obtained from ePDFs we call this approach scanning nano-structure electron microscopy (SNEM), and we believe that it will be powerful and useful extension of current 4D-STEM methods

Quantum paramagnetism in a non-Kramers rare-earth oxide: Monoclinic Pr2Ti2O7\rm Pr_2Ti_2O_7

Little is so far known about the magnetism of the $\rm A_2B_2O_7$ monoclinic layered perovskites that replace the spin-ice supporting pyrochlore structure for $r_A/r_B>1.78$. We show that high quality monoclinic Pr$_2$Ti$_2$O$_7$ single crystals with a three-dimensional network of non-Kramers Pr$^{3+}$ ions that interact through edge-sharing super-exchange interactions, form a singlet ground state quantum paramagnet that does not undergo any magnetic phase transitions down to at least 1.8 K. The chemical phase stability, structure, and magnetic properties of the layered perovskite Pr$_2$Ti$_2$O$_7$ were investigated using x-ray diffraction, transmission electron microscopy, and magnetization measurements. Synthesis of polycrystalline samples with the nominal compositions of Pr$_2$Ti$_{2+x}$O$_7$ ($-0.16 \leq x \leq 0.16$) showed that deviations from the Pr$_2$Ti$_2$O$_7$ stoichiometry lead to secondary phases of related, structures including the perovskite phase Pr$_{2/3}$TiO$_3$ and the orthorhombic phases Pr$_4$Ti$_9$O$_{24}$ and Pr$_2$TiO$_5$. No indications of site disordering (stuffing and anti-stuffing) or vacancy defects were observed in the Pr$_2$Ti$_2$O$_7$ majority phase. A procedure for growth of high-structural-quality, stoichiometric single crystals of Pr$_2$Ti$_2$O$_7$ by the traveling solvent floating zone (TSFZ) method is reported. Thermo-magnetic measurements of single-crystalline Pr$_2$Ti$_2$O$_7$ reveal an isolated singlet ground state that we associate with the low symmetry crystal electric field environments that split the $2J+1=9$-fold degenerate spin-orbital multiplets of the four differently coordinated Pr$^{3+}$ ions into 36 isolated singlets resulting in an anisotropic temperature independent van-Vleck susceptibility at low $T$. A small isotropic Curie term is associated with 0.96(2)\% non-interacting Pr$^{4+}$ impurities.Comment: 18 pages, 7 figures, 6 table

High Throughput Discovery of Lightweight Corrosion-Resistant Compositionally Complex Alloys

Compositionally complex alloys hold the promise of simultaneously attaining superior combinations of properties such as corrosion resistance, light-weighting, and strength. Achieving this goal is a challenge due in part to a large number of possible compositions and structures in the vast alloy design space. High throughput methods offer a path forward, but a strong connection between the synthesis of a given composition and structure with its properties has not been fully realized to date. Here we present the rapid identification of light weight highly corrosion-resistant alloys based on combinations of Al and Cr in a Cantor-like base alloy (Al-Co-Cr-Fe-Ni). Previously unstudied alloy stoichiometries were identified using a combination of high throughput experimental screening coupled with key metallurgical and electrochemical corrosion tests, identifying alloys with excellent passivation behavior. Importantly, the electrochemical impedance modulus of the exposure-modified, air-formed film at the corrosion potential was found as an accurate non-destructive predictor of corrosion and passivation characteristics. Multi-element EXAFS analyses connected more ordered type chemical short range order in the Ni-Al 1st nn shell to poorer corrosion. This report underscores the utility of high throughput exploration of compositionally complex alloys for the identification and rapid screening of vast stoichiometric space

Potential Molecular Mechanisms of Bisphenol A in Obesity Development

Bisphenol A (BPA), an endocrine disruptor, is associated with metabolic disorders. However, several studies have suggested that exposure to BPA can cause obesity. It has recently got more attention from scientists as a risk factor for obesity due to its ability to mimic natural estrogens and bind to their receptors. Nonetheless, the molecular mechanism underpinning the environmental etiology of metabolic disorders has not been not fully clarified. In this regard, BPA exposure directly disrupts endocrine regulation, neuroimmune and signaling pathways, and gut microbes, resulting in obesity. In addition, epidemiological studies have revealed a significant relationship between BPA exposure and the development of obesity, although conflicting results have been reported. Therefore, this review summarized the possible role and molecular mechanisms associated with BPA exposure that may lead to obesity based on in vivo and in vivo studies