The influence of electron-beam treatment on the structure of a TiNi powder alloy obtained by calcium-hydride reduction

The study of the influence of electron-beam treatment on the structural features of a TiNi powder alloy obtained by calcium-hydride reduction is carried out. It is found that electron-beam treatment leads to homogenization of the phase and chemical composition of the surface layer of the TiNi powder alloy, smoothing of the surface relief of TiNi powder particles, and the healing of the defects on their surface. It is shown by energy dispersive X-ray spectral microanalysis that the concentration of Ti in the surface layer increases. This is due to recrystallization of this layer containing Ti2Ni particles during its remelting under the influence of the high energy density of the electron beam during treatmen

Perovskite nanowire lasers on low-refractive-index conductive substrate for high-Q and low-threshold operation

Over the last five years, inorganic lead halide perovskite nanowires have emerged as prospective candidates to supersede standard semiconductor analogs in advanced photonic designs and optoelectronic devices. In particular, CsPbX3 (X = Cl, Br, I) perovskite materials have great advantages over conventional semiconductors such as defect tolerance, highly efficient luminescence, and the ability to form regularly shaped nano- and microcavities from solution via fast crystallization. However, on the way of electrically pumped lasing, the perovskite nanowires grown on transparent conductive substrates usually suffer from strong undesirable light leakage increasing their threshold of lasing. Here, we report on the integration of CsPbBr3 nanowires with nanostructured indium tin oxide substrates possessing near-unity effective refractive index and high conductivity by using a simple wet chemical approach. Surface passivation of the substrates is found out to govern the regularity of the perovskite resonators’ shape. The nanowires show room-temperature lasing with ultrahigh quality factors (up to 7860) which are up to four times higher than that of similar structures on a flat indium tin oxide layer, resulting in more than twofold reduction of the lasing threshold for the nanostructured substrate. Numerical modeling of eigenmodes of the nanowires confirms the key role of low-refractive-index substrate for improved light confinement in the Fabry–Pérot cavity which results in superior laser performance

Rebuilding C₆₀: Chlorination-Promoted Transformations of the Buckminsterfullerene into Pentagon-Fused C₆₀ Derivatives

In recent years, many higher fullerenes that obey the isolated pentagon rule (IPR) were found capable of rearranging into molecules with adjacent pentagons and even with heptagons via chlorination-promoted skeletal transformations. However, the key fullerene, buckminsterfullerene <i>I</i>_<i>h</i>-C₆₀, long seemed insusceptible to such rearrangements. Now we demonstrate that buckminsterfullerene yet can be transformed by chlorination with SbCl₅ at 420–440 °C and report X-ray structures for the thus-obtained library of non-IPR derivatives. The most remarkable of them are non-IPR C₆₀Cl₂₄ and C₆₀Cl₂₀ with fundamentally rearranged carbon skeletons featuring, respectively, four and five fused pentagon pairs (FPPs). Further high-temperature trifluoromethylation of the chlorinated mixture afforded additional non-IPR derivatives C₆₀(CF₃)₁₀ and C₆₀(CF₃)₁₄, both with two FPPs, and a nonclassical C₆₀(CF₃)₁₅F with a heptagon, two FPPs, and a fully fused pentagon triple. We discuss the general features of the addition patterns in the new non-IPR compounds and probable pathways of their formation via successive Stone–Wales rearrangements

Kinetics of Thermal Denaturation and Aggregation of Bovine Serum Albumin

<div><p>Thermal aggregation of bovine serum albumin (BSA) has been studied using dynamic light scattering, asymmetric flow field-flow fractionation and analytical ultracentrifugation. The studies were carried out at fixed temperatures (60°C, 65°C, 70°C and 80°C) in 0.1 M phosphate buffer, pH 7.0, at BSA concentration of 1 mg/ml. Thermal denaturation of the protein was studied by differential scanning calorimetry. Analysis of the experimental data shows that at 65°C the stage of protein unfolding and individual stages of protein aggregation are markedly separated in time. This circumstance allowed us to propose the following mechanism of thermal aggregation of BSA. Protein unfolding results in the formation of two forms of the non-native protein with different propensity to aggregation. One of the forms (highly reactive unfolded form, U_hr) is characterized by a high rate of aggregation. Aggregation of U_hr leads to the formation of primary aggregates with the hydrodynamic radius (<i>R</i>_h,1) of 10.3 nm. The second form (low reactive unfolded form, U_lr) participates in the aggregation process by its attachment to the primary aggregates produced by the U_hr form and possesses ability for self-aggregation with formation of stable small-sized aggregates (A_st). At complete exhaustion of U_lr, secondary aggregates with the hydrodynamic radius (<i>R</i>_h,2) of 12.8 nm are formed. At 60°C the rates of unfolding and aggregation are commensurate, at 70°C the rates of formation of the primary and secondary aggregates are commensurate, at 80°C the registration of the initial stages of aggregation is complicated by formation of large-sized aggregates.</p></div

Fractograms of BSA (1 mg/ml) preheated at 65°C.

<p>The heating times were the following: (1) 0, (2) 5, (3) 15, (4) 90 and (5) 600 min. AF4 conditions: 23°C, axial (detector) flow 1 ml/min, focus flow 5 ml/min, cross flow 5 ml/min for 10 min and then linear decay to 0.1 ml/min within 20 min plus 8 min at 0 ml/min.</p

Dependences of the hydrodynamic radius (<i>R</i>_h) on the portion of the denatured protein (γ_den) for aggregation of BSA at (A) 60°C, (B) 65°C, (C) 70°C and (D) 80°C.

<p>The values of γ_den were calculated from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0153495#pone.0153495.e007" target="_blank">Eq 4</a>. For each temperature parameters <i>B</i>, <i>k</i>_1,den and <i>k</i>_2,den indicated in corresponding panels of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0153495#pone.0153495.g002" target="_blank">Fig 2</a> were used. The <i>R</i>_h <i>vs</i> γ_den plots at 65°C and 70°C (panels B and C) were used for determination of the hydrodynamic radius of the primary aggregates (<i>R</i>_h,1).</p