Fluorescent Diarylethene Photoswitches—A Universal Tool for Super‐Resolution Microscopy in Nanostructured Materials

Super‐resolution fluorescence microscopy allows for unprecedented in situ visualization of biological structures, but its application to materials science has so far been comparatively limited. One of the main reasons is the lack of powerful dyes that allow for labeling and photoswitching in materials science systems. In this study it is shown that appropriate substitution of diarylethenes bearing a fluorescent closed and dark open form paves the way for imaging nanostructured materials with three of the most popular super‐resolution fluorescence microscopy methods that are based on different concepts to achieve imaging beyond the diffraction limit of light. The key to obtain optimal resolution lies in a proper control over the photochemistry of the photoswitches and its adaption to the system to be imaged. It is hoped that the present work will provide researchers with a guide to choose the best photoswitch derivative for super‐resolution microscopy in materials science, just like the correct choice of a Swiss Army Knife's tool is essential to fulfill a given task.     

Comparative study on the densification process of different titanium powders

In the powder metallurgy of titanium and titanium alloys, titanium powders produced through hydrogenation/dehydrogenation (HDH) approach and titanium hydride powder are extensively used. The choice of initial powder greatly influences the properties and performance of as-sintered materials. In the present study, comparative experiments were performed on two powders of various sizes to elucidate the peculiarities of their densification process and the characteristics (as-sintered density, impurity content, and tensile properties) of the processed materials. As expected, the sintering performance of both powder-type compacts were greatly affected by the specific surface and contact areas, so finer powders and higher compaction pressures were used to achieve higher densities upon sintering. However, the systematic results clearly indicated the advantage of using titanium hydride powder as a starting material in titanium powder metallurgy. At equal size, compaction, and sintering parameters, materials processed from titanium hydride powder had higher density and lower impurity content, thereby providing better balance of tensile properties compared with materials processed from HDH titanium powder. This advantage is explained by the higher relative density of green compacts made of brittle titanium hydride powder and by the higher sintering ability of such compacts activated by powder-released hydrogen.     

Wavefront sensor based on the Talbot effect with the precorrected holographic grating

A holographic wavefront sensor based on the Talbot effect is proposed. Optical wavefronts are measured by sampling the light amplitude distribution with a two-dimensional (2D) precorrected holographic grating. The factors that allow changing an angular measurement range and a spatial resolution of the sensor are discussed. A comparative analysis with the Shack-Hartmann sensor is illustrated with some experimental results.     

Analytical reasoning task reveals limits of social learning in networks

Social learning—by observing and copying others—is a highly successful cultural mechanism for adaptation, outperforming individual information acquisition and experience. Here, we investigate social learning in the context of the uniquely human capacity for reflective, analytical reasoning. A hallmark of the human mind is its ability to engage analytical reasoning, and suppress false associative intuitions. Through a set of laboratory-based network experiments, we find that social learning fails to propagate this cognitive strategy. When people make false intuitive conclusions and are exposed to the analytic output of their peers, they recognize and adopt this correct output. But they fail to engage analytical reasoning in similar subsequent tasks. Thus, humans exhibit an ‘unreflective copying bias’, which limits their social learning to the output, rather than the process, of their peers’ reasoning—even when doing so requires minimal effort and no technical skill. In contrast to much recent work on observation-based social learning, which emphasizes the propagation of successful behaviour through copying, our findings identify a limit on the power of social networks in situations that require analytical reasoning.     

Segregation Development in Multiple Melt Vacuum Arc Remelting

A numerical model of the vacuum arc remelting (VAR) process was used to study multistage VAR processes. The studies of low and high power 3XVAR confirmed the results of the single stage process studies for Ti-10-2-3: (1) high arc power results in strong electromagnetically driven flow and undesirably high macrosegregation; (2) low arc power does not generate significant Lorentz forces and the flow is dominated by weaker buoyancy forces, which cause less segregation; and (3) even short-lived changes in process conditions during the run may result in a switch of the flow regime in low power cases from buoyancy driven to electromagnetically driven. The switch of flow regime results in an increase in macrosegregation levels and a change in the pattern of solute redistribution. The most significant finding in the studies of 3XVAR processing of Ti-10-2-3 is the small effect of the electrode composition distribution on ingot segregation development. In both low and high power VAR cases, macrosegregation levels and patterns in the final ingots were similar to those demonstrated assuming a uniform electrode for that final case. However, for low power cases, nonuniformities in the electrode composition may strongly affect the final ingot macrosegregation. The nonuniformity in the composition of the electrode results in the formation of additional buoyancy forces within the liquid pool, which can cause a switch from buoyancy driven flow to the undesirable electromagnetically driven flow regime and a drastic change in segregation development. This article is based on a presentation given at the International Symposium on Liquid Metal Processing and Casting (LMPC 2007), which occurred in September 2007 in Nancy, France.     

Determining optimum carob powder adsorbtion for cleaning wastewater: intelligent optimization with electro-search algorithm

Wireless Networks - In this study, effective and fast removal efficiency of carob powder (as an absorbent material from liquid phase) was investigated by focusing on the dangerous paint methylene...     

Fine equiaxed β grains and superior tensile property in Ti-6Al-4V alloy deposited by coaxial electron beam wire feeding additive manufacturing

Coarse columnar β grains result in anisotropic mechanical properties in Ti alloys deposited by additive manufacturing. This study reports that Ti-6Al-4V alloy fabricated by coaxial electron beam wire feeding additive manufacturing presents a weak anisotropy, high strength and ductility. The superior tensile property arises from a microstructure with fine equiaxed β grains (EGβ), discontinuous grain boundary α phase and short intragranular α lamellae. A large region of fine EGβ arises from a special combination of the temperature gradient and solidification rate, and attractive α morphology is caused by solid phase transformations during interpass thermal cycling and post heat treatments.