Substrate interaction effects on order to disorder transition behavior in block copolymer films

We present an overview of the recent progress on the phase transition in the block copolymer (BCP) films in terms of the interfacial interactions effects of the substrates and the χ (Flory-Huggins segmental interaction parameter) effects between the two blocks. For the BCP films thinner than a critical thickness (L_c) above which the transition is independent of film thickness, the order-to-disorder transition (ODT) increased or decreased with decreasing film thickness depending on the interfacial interaction types. The rapid and slow changes in the ODT were attributed to the relative magnitude of enthalpic contribution to χ between two blocks. Interestingly, a periodic amplification in the block composition for the BCP films suppressed the compositional fluctuation in the film geometry, resulting in the ODT shifts from the bulk ODTs above L_c. This effect of the BCP films was more illustrated by the ODT shift effects depending on the strength of the preferential interactions on the substrates. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Prenylated Flavonoid Glycosides with PCSK9 mRNA Expression Inhibitory Activity from the Aerial Parts of Epimedium koreanum

Phytochemical investigation on the n-BuOH-soluble fraction of the aerial parts of Epimedium koreanum using the PCSK9 mRNA monitoring assay led to the identification of four previously undescribed acylated flavonoid glycosides and 18 known compounds. The structures of new compounds were elucidated by NMR, MS, and other chemical methods. All isolated compounds were tested for their inhibitory activity against PCSK9 mRNA expression in HepG2 cells. Of the isolates, compounds 6, 7, 10, 15, and 17–22 were found to significantly inhibit PCSK9 mRNA expression. In particular, compound 7 was shown to increase LDLR mRNA expression. Thus, compound 7 may potentially increase LDL uptake and lower cholesterol levels in the blood.     

Highly stable,frequency-controlled mode-locked erbium fiber laser comb

A mode-locked Er:fiber laser-based optical frequency comb with high stability in the repetition frequency and carrier-envelope offset (CEO) frequency is realized. The CEO beat signal was detected right after the supercontinuum generation by a compact single-beam f–2f self-referencing interferometer, which does not require further delay compensation. The stabilized repetition frequency has an out-of-loop tracking stability of 1.3×10^-13/ for an integration time τ less than 1000 s, which is limited by the stability of the frequency measurement system. The stabilized CEO frequency has a residual fluctuation of 0.52 mHz measured with a 1 s gate time. This is, to our knowledge, the highest tracking stability realized for fiber laser-based optical frequency comb. PACS 06.30.Ft; 42.60.Lh; 42.55.Wd     

Diffusion mechanism of CO2 in 13X zeolite beads

A systematic study of the diffusion mechanism of CO₂ in commercial 13X zeolite beads is presented. In order to gain a complete understanding of the diffusion process of CO₂, kinetic measurements with a zero length column (ZLC) system and a volumetric apparatus have been carried out. The ZLC experiments were carried out on a single bead of zeolite 13X at 38 °C at a partial pressure of CO₂ of 0.1 bar, conditions representative of post-combustion capture. Experiments with different carrier gases clearly show that the diffusion process is controlled by the transport inside the macropores. Volumetric measurements using a Quantachrome Autosorb system were carried out at different concentrations. These experiments are without a carrier gas and the low pressure measurements show clearly Knudsen diffusion control in both the uptake cell and the bead macropores. At increasing CO₂ concentrations the transport mechanism shifts from Knudsen diffusion in the macropores to a completely heat limited process. Both sets of experiments are consistent with independent measurements of bead void fraction and tortuosity and confirm that under the range of conditions that are typical of a carbon capture process the system is controlled by macropore diffusion mechanisms.     

γ‐Glutamylcysteine‐ and Cysteinylglycine‐Directed Growth of Chiral Gold Nanoparticles and their Crystallographic Analysis

Chiral optical metamaterials with delicate structures are in high demand in various fields because of their strong light–matter interactions. Recently, a scalable strategy for the synthesis of chiral plasmonic nanoparticles (NPs) using amino acids and peptides has been reported. Reported herein, 3D chiral gold NPs were synthesized using dipeptide γ‐Glu‐Cys and Cys‐Gly and analyzed crystallographically. The γ‐Glu‐Cys‐directed NPs present a cube‐like outline with a protruding chiral wing. In comparison, the NPs synthesized with Cys‐Gly exhibited a rhombic dodecahedron‐like outline with curved edges and elliptical cavities on each face. Morphology analysis of intermediates indicated that γ‐Glu‐Cys generated an intermediate concave hexoctahedron morphology, while Cys‐Gly formed a concave rhombic dodecahedron. NPs synthesized with Cys‐Gly are named 432 helicoid V because of their unique morphology and growth pathway.     

Thermal Hysteresis Accompanying Incommensurate-Commensurate Phase Transition in Mixed Crystals (K1-xCsx)2ZnCl4

The mixed crystal (K_1-xCs_x)₂ZnCl₄ with x = 0, 0.001, 0.01, 0.1, and 0.2 with optical quality has been grown by the Czochralski method. Using the Atomic Absorption Spectroscopy (AAS) and Energy Dispersive Spectroscopy (EDS), we determined the amount of Cs ion included in the mixed crystal. By using of DTA and DSC, we observed the change of T_c and T_i. The thermal hysteresis in the dielectric constants show strong dependence on the thermal process and on the amount of impurity which are explained by the influence of the thermal process and impurity, respectively on the creation, annihilation, and growth of discommensuration (DC).     

Sampled-data output voltage regulation for a DC–DC buck converter nonlinear system with actuator and sensor failures

Nonlinear Dynamics - This paper considers the distributed adaptive neural consensus tracking control problem for a class of uncertain nonaffine nonlinear multi-agent systems. By making use of the...