Ultrashort Sintering and Near Net Shaping of Zr-Based AMZ4 Bulk Metallic Glass

The GeniCore Upgraded Field Assisted Sintering Technology U-FAST was applied to the sintering of a commercial Zr-based bulk metallic glass powder AMZ4. The XRD, SEM and DSC analysis of the sintered compacts showed the benefit of the U-FAST method as an enabler for the production of fully amorphous samples with 100% relative density when sintering at 420 °C/480 s (693 K/480 s) and 440 °C/ 60 s (713 K/480 s). The hardness values for fully amorphous samples, over HV1 519, surpass cast materials and 1625 MPa compressive strengths are comparable to commercial cast products. The advantage of the U-FAST technology in this work is attributed to the high heating and cooling rates inherent to ultra-short pulses, which allow to maintain metastable structures and achieve better temperature control during the process. Increasing sintering temperature and time led to the crystallization of the materials. The geometry and material of the dies and punch determine the thermal inertia and pressure distribution inside the compacts, thus affecting the properties of the near net shape NNS compacts made using the U-FAST device.

Anion substitution and influence of sulfur on the crystal structures, phase transitions, and electronic properties of mixed TiO2/TiS2 compounds

Recent studies of TiO2/TiS2 nanostructures with various morphologies have been reported, usually showing improved properties with applications from electronics and catalysis to solar cells and medicine. However, there is a limited number of studies on the crystal structures of TiO2/TiS2 compounds with corresponding properties. In this research, relevant crystal structures of TiO1–x S x (x = 0, 0.25, 0.5, 0.75 and 1) solid solutions were investigated using an ab initio method. For each composition, crystal structures adopting anatase, rutile and CdI2 structure type were calculated on LDA-PZ and GGA-PBE levels of theory. Novel phase transitions and predicted structures are presented, and apart from several interesting metastable structures, a very interesting pressure-induced phase transition is found in the TiOS compound. Furthermore, electronic properties were studied through the dependence of semiconducting properties on dopant concentration. The first description of the electronic properties of the mixed TiO1–x S x compounds in crystal form has been presented, followed by a detailed study of the structure–property relationship, which will possibly have numerous industrial and technological applications.

Adsorption of Carbon Dioxide, Methane, and Nitrogen on Zn(dcpa) Metal-Organic Framework

Adsorption-based processes using metal-organic frameworks (MOFs) are a promising option for carbon dioxide (CO2) capture from flue gases and biogas upgrading to biomethane. Here, the adsorption of CO2, methane (CH4), and nitrogen (N2) on Zn(dcpa) MOF (dcpa (2,6-dichlorophenylacetate)) is reported. The characterization of the MOF by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), and N2 physisorption at 77 K shows that it is stable up to 650 K, and confirms previous observations suggesting framework flexibility upon exposure to guest molecules. The adsorption equilibrium isotherms of the pure components (CO2, CH4, and N2), measured at 273–323 K, and up to 35 bar, are Langmuirian, except for that of CO2 at 273 K, which exhibits a stepwise shape with hysteresis. The latter is accurately interpreted in terms of the osmotic thermodynamic theory, with further refinement by assuming that the free energy difference between the two metastable structures of Zn(dcpa) is a normally distributed variable due to the existence of different crystal sizes and defects in a real sample. The ideal selectivities of the equimolar mixtures of CO2/N2 and CO2/CH4 at 1 bar and 303 K are 12.8 and 2.9, respectively, which are large enough for Zn(dcpa) to be usable in pressure swing adsorption.

Introduction to Colloidal and Microfluidic Nematic Microstructures

In this brief review, we give an introduction to selected colloidal and microfluidic nematic microstructures, as enabled by the inherent anisotropy and microscopic orientational ordering in complex liquid crystalline materials. We give a brief overview of the mesoscopic theory, for equilibrium and dynamics, of nematic fluids, that provides the framework for understanding, characterization, and even prediction of such microstructures, with particular comment also on the role of topology and topological defects. Three types of nematic microstructures are highlighted: stable or metastable structures in nematic colloids based on spherical colloidal particles, stationary nematic microfluidic structures, and ferromagnetic liquid crystal structures based on magnetic colloidal particles. Finally, this paper is in honor of Noel A. Clark, as one of the world pioneers that helped to shape this field of complex and functional soft matter, contributing at different levels to works of various groups worldwide, including ours.

Layering transitions and metastable structures of cholesteric liquid crystals in cylindrical confinement

Our study of cholesteric lyotropic chromonic liquid crystals in cylindrical confinement reveals the topological aspects of cholesteric liquid crystals. The double-twist configurations we observe exhibit discontinuous layering transitions, domain formation, metastability, and chiral point defects as the concentration of chiral dopant is varied. We demonstrate that these distinct layer states can be distinguished by chiral topological invariants. We show that changes in the layer structure give rise to a chiral soliton similar to a toron, comprising a metastable pair of chiral point defects. Through the applicability of the invariants we describe to general systems, our work has broad relevance to the study of chiral materials.

Targeting G-quadruplexes in the rhinovirus genome by Pyridostatin inhibits uncoating 3 and highlights a critical role for sodium ions.

The ~ 2.4 µm long rhinovirus ss(+)RNA genome consists of roughly 7,200 nucleotides. It is tightly folded to fit into the ~ 22 nm diameter void in the protein capsid. In addition to previously predicted secondary structural elements in the RNA, using the QGRS mapper, we revealed the presence of multiple quadruplex forming G-rich sequences (QGRS) in the RV-A, B, and C clades, with four of them being exquisitely conserved. The biophysical analyses of ribooligonucleotides corresponding to selected QGRS demonstrate G-quadruplex (GQ) formation in each instance and resulted in discovering another example of an unconventional, two-layer zero-nucleotide loop RNA GQ stable at physiological conditions. By exploiting the temperature-dependent viral breathing to allow diffusion of small compounds into the virion, we demonstrate that the GQ-binding compounds PhenDC3 and pyridostatin (PDS) uniquely interfere with viral uncoating. Remarkably, this inhibition was entirely prevented in the presence of K+ but not Na+, despite the higher GQ stabilising effect of K+. Based on virus thermostability studies combined with ultrastructural imaging of isolated viral RNA, we propose a mechanism where Na+ keeps the encapsidated genome loose, allowing its penetration by PDS to promote the transition of QGRS sequestered in alternative metastable structures into GQs. The resulting conformational change then materialises in a severely compromised RNA release from the proteinaceous shell. Targeting extracellularly circulating RVs with GQ-stabilisers might thus become a novel way of combating the common cold.

Targeting G-quadruplexes in the rhinovirus genome by Pyridostatin inhibits uncoating and highlights a critical role for sodium ions.

The ~ 2.4 µm long rhinovirus ss(+)RNA genome consists of roughly 7,200 nucleotides. It is tightly folded to fit into the ~ 22 nm diameter void in the protein capsid. In addition to previously predicted secondary structural elements in the RNA, using the QGRS mapper, we revealed the presence of multiple quadruplex forming G-rich sequences (QGRS) in the RV-A, B, and C clades, with four of them being exquisitely conserved. The biophysical analyses of ribooligonucleotides corresponding to selected QGRS demonstrate G-quadruplex (GQ) formation in each instance and resulted in discovering another example of an unconventional, two-layer zero-nucleotide loop RNA GQ stable at physiological conditions. By exploiting the temperature-dependent viral breathing to allow diffusion of small compounds into the virion, we demonstrate that the GQ-binding compounds PhenDC3 and pyridostatin (PDS) uniquely interfere with viral uncoating. Remarkably, this inhibition was entirely prevented in the presence of K+ but not Na+, despite the higher GQ stabilising effect of K+. Based on virus thermostability studies combined with ultrastructural imaging of isolated viral RNA, we propose a mechanism where Na+ keeps the encapsidated genome loose, allowing its penetration by PDS to promote the transition of QGRS sequestered in alternative metastable structures into GQs. The resulting conformational change then materialises in a severely compromised RNA release from the proteinaceous shell. Targeting extracellularly circulating RVs with GQ-stabilisers might thus become a novel way of combating the common cold.