Elemental analysis of valvular and atherosclerotic calcification

Aim. To analyze the topographic patterns of valvular and atherosclerotic calcification growth.Methods. Dysfunctional aortic valves (n = 18) and atherosclerotic plaques (n = 20) were fixed in formalin, postfixed in 1% osmium tetroxide, consecutively stained by 2% osmium tetroxide and 2% uranyl acetate, and embedded into epoxy resin (Epon) with the further grinding and polishing ofthe samples. Upon the counterstaining by lead citrate and sputter coating with carbon, samples were visualized by backscattered scanning electron microscopy. Elemental analysis was conducted via energy-dispersive X-ray spectroscopy. Measurement of Ca/P ratio within the mineral deposits was carried out employing a pool table principle (i.e., in the center of the deposit, in the near and far circumferences (clockwise), and in control regions around the mineral deposit). Topographic patterns of calcifications were modeled using the correlation analysis. Results. Significant correlation was revealed between the Ca/P ratio in the deposit center and in the near and far circumferences of deposit in both in valvular (r = 0,35-0,78 - near circumference; r = 0,63-0,69 - far circumference) and atherosclerotic mineral deposits (r = 0,37-0,56 - near circumference; r = 0,48-0,63 - far circumference), suggesting the hierarchical growth of cardiovascular calcification around the initial nucleation sites.Conclusion. Valvular and atherosclerotic calcifications development is concentric.

Prediction of Grain Formation and Defects during Solidification in Single Crystal Superalloy Castings

Numerical simulation and prediction of grain formation and defects, including the stray grain and high angle orientation deviation during directional solidification process of a single crystal superalloy hollow turbine blade are experimentally conducted by means of commercial software ProCAST and backscattering scanning electron microscope. The results show that the initial nucleation amount at the beginning section of the starter block is 104 of magnitude, and the number of grains decreases gradually with the competitive growth, and the number is about 100 at the spiral of the selector. And the orientation distribution of grains is close to <001> direction, with the orientation deviation between 10° and 15°. Moreover, with the increase of withdrawal rate, the curvature of isoline of liquidus of single crystal blade increases, and the tendency to form stray grains defects increases. The grain with a large deviation from orientation blocks the growth of other grains at the first rotating transition site of the selector, and then gradually grows and solidifies to form the final blade.

Establishment of H3K9me3-dependent heterochromatin during embryogenesis in Drosophila miranda

Heterochromatin is a key architectural feature of eukaryotic genomes crucial for silencing of repetitive elements. During Drosophila embryonic cellularization, heterochromatin rapidly appears over repetitive sequences but the molecular details of how heterochromatin is established are poorly understood. Here, we map the genome-wide distribution of H3K9me3-dependent heterochromatin in individual embryos of Drosophila miranda at precisely-staged developmental time points. We find that canonical H3K9me3 enrichment is established prior to cellularization, and matures into stable and broad heterochromatin domains through development. Intriguingly, initial nucleation sites of H3K9me3 enrichment appear as early as embryonic stage3 over transposable elements (TE) and progressively broaden, consistent with spreading to neighboring nucleosomes. The earliest nucleation sites are limited to specific regions of a small number of recently active retrotransposon families and often appear over promoter and 5' regions of LTR retrotransposons, while late nucleation develops broadly across the entirety of most TEs. Interestingly, early nucleating TEs are strongly associated with abundant maternal piRNAs and show early zygotic transcription. These results support a model of piRNA-associated co-transcriptional silencing while also suggesting additional mechanisms for site-restricted H3K9me3 nucleation at TEs in pre-cellular Drosophila embryos.

Inherently Area-Selective Atomic Layer Deposition of Manganese Oxide through Electronegativity-Induced Adsorption

Manganese oxide (MnOx) shows great potential in the areas of nano-electronics, magnetic devices and so on. Since the characteristics of precise thickness control at the atomic level and self-align lateral patterning, area-selective deposition (ASD) of the MnOx films can be used in some key steps of nanomanufacturing. In this work, MnOx films are deposited on Pt, Cu and SiO2 substrates using Mn(EtCp)2 and H2O over a temperature range of 80–215 °C. Inherently area-selective atomic layer deposition (ALD) of MnOx is successfully achieved on metal/SiO2 patterns. The selectivity improves with increasing deposition temperature within the ALD window. Moreover, it is demonstrated that with the decrease of electronegativity differences between M (M = Si, Cu and Pt) and O, the chemisorption energy barrier decreases, which affects the initial nucleation rate. The inherent ASD aroused by the electronegativity differences shows a possible method for further development and prediction of ASD processes.

Protein nanofibril design via manipulation of hydrogen bonds

The process of amyloid nanofibril formation has broad implications including the generation of the strongest natural materials, namely silk fibers, and their major contribution to the progression of many degenerative diseases. The key question that remains unanswered is whether the amyloidogenic nature, which includes the characteristic H-bonded β-sheet structure and physical characteristics of protein assemblies, can be modified via controlled intervention of the molecular interactions. Here we show that tailored changes in molecular interactions, specifically in the H-bonded network, do not affect the nature of amyloidogenic fibrillation, and even have minimal effect on the initial nucleation events of self-assembly. However, they do trigger changes in networks at a higher hierarchical level, namely enhanced 2D packaging which is rationalized by the 3D hierarchy of β-sheet assembly, leading to variations in fibril morphology, structural composition and, remarkably, nanomechanical properties. These results pave the way to a better understanding of the role of molecular interactions in sculpting the structural and physical properties of protein supramolecular constructs.