Nanoscale mapping of residual stresses in Al 2024 alloys using correlative and multimodal scanning transmission electron microscopy.

A methodology for the mapping of residual stresses in metal alloys has been developed by analyzing an isotropic and homogeneous Al2024 alloy with scanning transmission electron microscopy (STEM), combined with diffraction (4DSTEM) and electron energy loss spectroscopy (STEM-EELS) techniques of TEM. The investigations on the alloy's microstructure and elemental distributions were also carried out with conventional dark-field STEM (DFSTEM) and X-ray energy dispersive (EDS) techniques, respectively. Using the STEM-EELS technique, the Young's modulus (YM) is mapped in the (001) plane of the Al alloy in the same regions where the residual strain maps are generated in [1‾ 00] and [010] directions by using 4DSTEM technique. The YM vs. residual strain plot for the Al 2024 alloy revealed that the value of YM decreased by about ∼ 7 % after the tensile residual strain reached 0.02 %. Whereas such a decrease in YM happens after the compressively residual strain reaches -0.015 %. The residual stress maps were also obtained in accordance with the Hooke's law i.e., by multiplying YM map with the corresponding residual strain maps.

Evolution of Oxygen Vacancy Sites in Ceria-Based High-Entropy Oxides and Their Role in N2 Activation.

In this work, a relatively new class of materials, rare earth (RE) based high entropy oxides (HEO) are discussed in terms of the evolution of the oxygen vacant sites (Ov) content in their structure as the composition changes from binary to HEO using both experimental and computational tools; the composition of HEO under focus is the CeLaPrSmGdO due to the importance of ceria-related (fluorite) materials to catalysis. To unveil key features of quinary HEO structure, ceria-based binary CePrO and CeLaO compositions as well as SiO2, the latter as representative nonreducible oxide, were used and compared as supports for Ru (6 wt % loading). The role of the Ov in the HEO is highlighted for the ammonia production with particular emphasis on the N2 dissociation step (N2(ads) → Nads) over a HEO; the latter step is considered the rate controlling one in the ammonia production. Density functional theory (DFT) calculations and 18O2 transient isotopic experiments were used to probe the energy of formation, the population, and the easiness of formation for the Ov at 650 and 800 °C, whereas Synchrotron EXAFS, Raman, EPR, and XPS probed the Ce-O chemical environment at different length scales. In particular, it was found that the particular HEO composition eases the Ov formation in bulk, in medium (Raman), and in short (localized) order (EPR); more Ov population was found on the surface of the HEO compared to the binary reference oxide (CePrO). Additionally, HEO gives rise to smaller and less sharp faceted Ru particles, yet in stronger interaction with the HEO support and abundance of Ru-O-Ce entities (Raman and XPS). Ammonia production reaction at 400 °C and in the 10-50 bar range was performed over Ru/HEO, Ru/CePrO, Ru/CeLaO, and Ru/SiO2 catalysts; the Ru/HEO had superior performance at 10 bar compared to the rest of catalysts. The best performing Ru/HEO catalyst was activated under different temperatures (650 vs 800 °C) so to adjust the Ov population with the lower temperature maintaining better performance for the catalyst. DFT calculations showed that the HEO active site for N adsorption involves the Ov site adjacent to the adsorption event.

Growth and characterization of germanium telluride nanowires via vapor-liquid-solid mechanism.

Phase-change materials (PCMs), which can transition reversibly between crystalline and amorphous phases, have shown great promise for next-generation memory devices due to their nonvolatility, rapid switching periods, and random-access capability. Several groups have investigated phase-change nanowires for memory applications in recent years. The ability to regulate the scale of nanostructures remains one of the most significant obstacles in nanoscience. Herein, we describe the growth and characterization of germanium telluride (GeTe) nanowires, which are essential for phase-change memory devices. GeTe nanowires were produced by combining thermal evaporation and vapor-liquid-solid (VLS) techniques, using 8 nm Au nanoparticles as the metal catalyst. The influence of various growth parameters, including inert gas flow rate, working pressure, growth temperature, growth duration, and growth substrate, was examined. Ar gas flow rate of 30 sccm and working pressure of 75 Torr produced the narrowest GeTe nanowires horizontally grown on a Si substrate. Using scanning electron microscopy, the dimensions, and morphology of GeTe nanowires were analyzed. Transmission electron microscopy and energy-dispersive x-ray spectroscopy were utilized to conduct structural and chemical analyses. Using a SiO2/Si substrate produced GeTe nanowires that were thicker and lengthier. The current-voltage characteristics of GeTe nanowires were investigated, confirming the amorphous nature of GeTe nanowires using conductive atomic force microscopy. In addition, the effects of the VLS mechanism and the Gibbs-Thomson effect were analyzed, which enables the optimization of nanowires for numerous applications, such as memory and reservoir computing.

Inflammatory markers and control of type 2 diabetes mellitus.

BACKGROUND: Subclinical inflammation and presence of almost all indicators of systemic inflammation are found in type 2 diabetic patients. Such a systemic and subclinical inflammatory process can be characterized by elevated circulating levels of inflammatory markers. AIM: To study the state of subclinical inflammation in patients with type 2 diabetes mellitus and establish a correlation between glycemic control and inflammatory markers. METHODS: This research included 90 subjects divided into 2 groups; Group A: 70 patients with type 2 diabetes and Group B: 20 Age and sex matched people as the control group. All patients were clinically examined, had laboratory investigations including; fasting and 2 h postprandial blood sugar, HbA1c, serum ferritin., high sensitivity C-reactive protein hs-CRP, kidney functions tests, liver function tests, complete blood count and erythrocyte sedimentation rate and antinuclear antibody. RESULTS: The estimated levels of ESR, FBS, serum ferritin, hs-CRP and HbA1c in T2DM were 10.69 ±â€¯3.05, 186.01 ±â€¯92.21, 6005.2 ±â€¯2639.83, 155.75 ±â€¯73.95, 7.5 ±â€¯3.23, respectively. In a similar way, in control subject, the estimated levels for respective parameters were 12.4 ±â€¯3.41, 83.25 ±â€¯6.25, 45.088 ±â€¯39.35, 19.97 ±â€¯18.51, 4.555 ±â€¯0.58, respectively. Mean values of all parameters, except ESR, were found to be significantly augmented in T2DM subjects when compared to control group. There is significant positive correlation between HbA1c and hs-CRP (r=0.761, p < 0.001). Moreover, serum ferritin has shown significant positive correlation with HbA1c (r = 0.853, p < 0.001). CONCLUSION: Strong correlation between inflammation and glycemic control in patient with type 2 diabetes mellitus suggests that inflammation plays an important role in the pathogenesis of diabetes.