Age hardening and the potential for superplasticity in a fine-grained Al-Mg-Li-Zr alloy

Experiments were conducted to determine the age-hardening characteristics and the mechanical properties of an Al-5.5 pct Mg-2.2 pct Li-0.12 pct Zr alloy processed by equal-channel angular (ECA) pressing to give a very fine grain size of ∼1.2 μm. The results show that peak aging occurs more rapidly when the grain size is very fine, and this effect is interpreted in terms of the higher volume of precipitate-free zones in the fine-grained material. Mechanical testing demonstrates that the ECA-pressed material exhibits high strength and good ductility at room temperature compared to conventional Al alloys containing Li. Elongations of up to ∼550 pct may be achieved at an elevated temperature of 603 K in the ECA-pressed condition, thereby confirming that, in this condition, the alloy may be a suitable candidate material for use in superplastic forming operations.     

Mechanisms of the Cytotoxic Effect of Selenium Nanoparticles in Different Human Cancer Cell Lines

In recent decades, studies on the functional features of Se nanoparticles (SeNP) have gained great popularity due to their high biocompatibility, stability, and pronounced selectivity. A large number of works prove the anticarcinogenic effect of SeNP. In this work, the molecular mechanisms regulating the cytotoxic effects of SeNP, obtained by laser ablation, were studied by the example of four human cancer cell lines: A-172 (glioblastoma), Caco-2, (colorectal adenocarcinoma), DU-145 (prostate carcinoma), MCF-7 (breast adenocarcinoma). It was found that SeNP had different concentration-dependent effects on cancer cells of the four studied human lines. SeNP at concentrations of less than 1 μg/mL had no cytotoxic effect on the studied cancer cells, with the exception of the A-172 cell line, for which 0.5 μg/mL SeNP was the minimum concentration affecting its metabolic activity. It was shown that SeNP concentration-dependently caused cancer cell apoptosis, but not necrosis. In addition, it was found that SeNP enhanced the expression of pro-apoptotic genes in almost all cancer cell lines, with the exception of Caco-2 and activated various pathways of adaptive and pro-apoptotic signaling pathways of UPR. Different effects of SeNP on the expression of ER-resident selenoproteins and selenium-containing glutathione peroxidases and thioredoxin reductases, depending on the cell line, were established. In addition, SeNP triggered Ca²⁺ signals in all investigated cancer cell lines. Different sensitivity of cancer cell lines to SeNP can determine the induction of the process of apoptosis in them through regulation of the Ca²⁺ signaling system, mechanisms of ER stress, and activation of various expression patterns of genes encoding pro-apoptotic proteins.     

Fabrication of High-Resolution Gamma-Ray Metallic Magnetic Calorimeters with Ag:Er Sensor and Thick Electroplated Absorbers

We are developing metallic magnetic calorimeters for high-resolution gamma-ray spectroscopy for non-destructive assay of nuclear materials. Absorbers for these higher-energy photons can require substantial thickness to achieve adequate stopping power. We developed a new absorber fabrication process using dry-film photoresists to electroform cantilevered, thick absorbers. Gamma detectors with these absorbers have an energy resolution of 38 eV FWHM at 60 keV. In this report, we summarize modifications to STARCryo’s “Delta 1000” process for our devices and describe the new absorber fabrication process.     

Inductive System for Reliable Magnesium Level Detection in a Titanium Reduction Reactor

Metallurgical and Materials Transactions B - The determination of the Magnesium level in a Titanium reduction retort by inductive methods is often hampered by the formation of Titanium sponge rings...     

Bulk Nanostructured Metals for Innovative Applications

Nanostructuring of various materials is a key for obtaining extraordinary properties that are very attractive for different structural and functional applications. During the last two decades, the production of bulk nanostructured materials (BNMs) by severe plastic deformation (SPD) techniques has attracted special interest since it offers new opportunities for the fabrication of commercial nanostructured metals and alloys for various specific applications. Very significant progress has been made in this area in recent years, which is evident by the first production of advanced pilot articles from nanostructured metals with new functionality. These aspects of innovations of BNMs processed by SPD are discussed in this overview.     

Assessment of cellular oxygen gradients with a panel of phosphorescent oxygen-sensitive probes

The supply of oxygen (O(2)) to respiring tissue, cells, and mitochondria regulates metabolism, gene expression, and cell fate. Depending on the cell type and mitochondrial function, O(2) gradients between extra- and intracellular compartments may vary and play important physiological roles such as the regulation of activity of prolyl hydroxylases and adaptive responses to hypoxia. Here we present a new methodology for the analysis of localized O(2) gradients in cultures of adherent cells, using three phosphorescent Pt-porphyrin based probes with different localization. One new O(2) probe targeted to the cell membrane was developed and used together with existing MitoXpress and Nano2 probes to monitor mean pericellular (PC), extracellular (EC), and intracellular (IC) O(2) concentrations, respectively. Mouse fibroblasts and neuronal PC12 cells cultured in standard microplates were stained with probes and measured on a commercial time-resolved fluorescence reader in phosphorescence lifetime mode. Respiring cells exposed to various levels of atmospheric O(2) showed differences in oxygenation of their IC, PC, and EC compartments. Experiments with different cell numbers and modulation of respiration activity demonstrated that these gradients are dynamic and regulated by the O(2) diffusion and consumption rate. The new method facilitates the assessment of such gradients.     

大塑性变形纳米结构Al-Mg合金中的形变缺陷和电子辐照效应

为澄清大塑性变形纳米结构Al-Mg合金中形变缺陷形成的本质,采用高分辨透射电子显微镜（HRTEM）研究电子辐照对高压扭转合金中面缺陷形成的影响。结果表明：对已有高密度面缺陷的HRTEM图像,经电子束照射一段时间后,这些面缺陷会完全消失;而在没有缺陷的HRTEM图像区域进行电子辐照,即使电子束的照射提高到足以在该区域击出孔洞,整个过程均未观察到任何晶格缺陷。因此,高压扭转合金中的面缺陷主要来源于极度的塑性变形,而与HRTEM观察过程中的电子辐照效应无关。     

Voltage-controlled double-resonance quartz oscillator using variable-capacitance diode

In this work, we present a variable-frequency quartz crystal oscillator that is able to oscillate at LC resonance under frequency locking of a quartz crystal resonance, with the frequency tuning realized by variable-capacitance diodes. This circuit shows a steep transition between LC oscillation modes to quartz crystal double-resonance, which shows a characteristic change in the oscillation frequency. Control voltage of this diode is precisely adjusted from the low side to higher values and conversely in the vicinity of the oscillation mode transition. The transition of the oscillation modes is experimentally demonstrated and compared with an algebraic analysis.     

Unusual super-ductility at room temperature in an ultrafine-grained aluminum alloy

Processing by severe plastic deformation (SPD) typically increases the strength of metals and alloys drastically by decreasing their grain size into the submicrometer or nanometer range but the ductility of such materials remains typically low. This report describes the first demonstration that it is possible to increase the room temperature ductility of aluminum-based alloys processed by SPD and to attain elongations to failure of >150% while retaining the enhanced strength. This unique combination of properties is due to the occurrence of grain boundary sliding at room temperature. The sliding was obviously achieved by introducing a grain boundary wetting of the aluminum/aluminum grain boundaries.     

Multiscale, Multiphysics Numerical Modeling of Fusion Welding with Experimental Characterization and Validation

Various physical interfacial phenomena occur during the process of welding and influence the final properties of welded structures. As the features of such interfaces depend on physics that resolve at different spatial scales, a multiscale and multiphysics numerical modeling approach is necessary. In a collaborative research project Modeling of Interface Evolution in Advanced Welding, a novel strategy of model linking is employed in a multiscale, multiphysics computational framework for fusion welding. We only directly link numerical models that are on neighboring spatial scales instead of trying to link all submodels directly together through all available spatial scales. This strategy ensures that the numerical models assist one another via smooth data transfer, avoiding the huge difficulty raised by forcing models to attempt communication over many spatial scales. Experimental activities contribute to the modeling work by providing valuable input parameters and validation data. Representative examples of the results of modeling, linking and characterization are presented.