Unsymmetric 1,3,4-oxa(thia)diazoles of quinoxaline–naphthalene conjugates

Two new series of unsymmetric 1,3,4-oxa(thia)diazoles 1a,b containing both quinoxaline and naphthalene moieties were prepared and their mesomorphic properties were investigated. The mesomorphic behavior of compounds 1a,b and 2 was studied by DSC analysis and polarized optical microscopy. All compounds 1a and 2 exhibited hexagonal columnar phases (Col_h), which were also confirmed by powder XRD diffractometer. N_cell and R_ar values equal to 5.23 and 22.73 Å² within a slice of 9.0 Å thick were also obtained for 1a (n=16), indicating that a more disc-like structure constructed by two molecules lying side-by-side was correlated in Col_h phases. In contrast, all compounds 1b were not mesogenic, and the lack of mesomorphic properties in 1b might be due to their unfavorable conformations. The PL spectra of all compounds 1a,b showed one intense peak at λ_max=509–512 nm, and these photoluminescent emissions originated from quinoxaline moiety.     

Study of Thin Polymeric Film Deposited by the PECVD Process for use at 193 nm

A plasma enhanced chemical vapor deposition (PECVD) reactor was used to deposit thin polymeric films with high absorption at 193 nm. The reactor is suitable to deposit uniform and pinhole free thin polymeric films with conformality over 95%. Conformal films with thickness as low as 200 Å have been deposited on silicon, glass, and quartz substrates, as well as silicon oxide, silicon nitrate, and aluminum films. Deposited films had variations in thickness of 3 to 5% over an area of 8 inches in diameter. Thin films deposited on silicon substrates under varying levels of RF power were scanned using the AFM technique. The measurements show increasing surface roughness of the scanned samples as the RF power increases.     

Catenar bimetallomesogens derived from quinoxaline–salicylaldimine conjugates

The preparation, characterization, and mesomorphic properties of two series of tridentate N-salicylidene-2-hydroxyanilines and their metal complexes were described. The crystal and molecular structure of bis[2-hydroxy-4-propyloxy-N-(2-hydroxy-3,4-dipropyloxybenzylidene) aniline]copper(II) were determined by means of X-ray analysis. It crystallizes in the monoclinic space group P2(1)/n and a Z=4. The geometry at Cu²⁺ ions is square pyramidal with a THF solvent molecule coordinated. The core structure was nearly flat, and the intramolecular Cu–Cu atoms were separated by ca. 3.0163(6) Å. All compounds 2a formed smectic C phases, and copper complexes 1a–Cu were not mesogenic. In contrast, compound 2e and complexes 1b–Cu, 1d–Cu, 1e–Cu, and 1e–Pd exhibited columnar phases. The lack of mesomorphism in 1e–Zn was attributed to a preferred tetrahedral over square planar geometry. A N_cell equal to 2.44–2.92, calculated from powder XRD data within a 9.0 Å thick indicated that an induced structure correlated by two catenar-shaped molecules was formed in Col_h phases.     

Comparison of Antioxidant and Anticancer Properties of Soft Coral-Derived Sinularin and Dihydrosinularin

Marine natural products are abundant resources for antioxidants, but the antioxidant property of the soft corals-derived sinularin and dihydrosinularin were unknown. This study aimed to assess antioxidant potential and antiproliferation effects of above compounds on cancer cells, and to investigate the possible relationships between them. Results show that sinularin and dihydrosinularin promptly reacted with 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS), and hydroxyl (^•OH), demonstrating a general radical scavenger activity. Sinularin and dihydrosinularin also show an induction for Fe⁺³-reduction and Fe⁺²-chelating capacity which both strengthen their antioxidant activities. Importantly, sinularin shows higher antioxidant properties than dihydrosinularin. Moreover, 24 h ATP assays show that sinularin leads to higher antiproliferation of breast, lung, and liver cancer cells than dihydrosinularin. Therefore, the differential antioxidant properties of sinularin and dihydrosinularin may contribute to their differential anti-proliferation of different cancer cells.     

Kapitza conductance of Bi/sapphire interface studied by depth- and time-resolved X-ray diffraction

We present Kapitza conductance measurements of the bismuth/sapphire interface using depth- and time-resolved X-ray diffraction, for Bi film thicknesses ranging from 65 to 284 nm. Our measurements provide complementary information about heat transport in the films; we directly observe the thinnest film to be uniformly heated within 1 ns, whereas the thickest film sustains a large near-surface temperature gradient for several ns. The deduced Kapitza conductance is 1950 W/cm²/K. This value is close to the theoretical prediction using the radiation limit.     

New SmCG phases in a hydrogen-bonded bent-core liquid crystal featuring a branched siloxane terminal group

In this study, we synthesized three analogous bent-core molecules, a hydrogen-bonded complex and a covalent-bonded compound with branched siloxane units (H-SiO and C-SiO, respectively) and a hydrogen-bonded complex with an alkyl unit (H-Alk), and investigated the effects of the hydrogen bonding and branched siloxane terminal units on their mesomorphic properties. The covalent-bonded compound C-SiO and the hydrogen-bonded complex H-Alk exhibited typical SmCP phases; in contrast, the hydrogen-bonded complex H-SiO exhibited a series of general tilt smectic (SmCG) phases with highly ordered layer structures (i.e., SmC?G(2)P(F)-USmCG(2)P(A)-SmCG(2)P(F)-SmCGP(F) upon cooling). During the SmCG-type phase transition process, a 2D-modulated ribbon structure transferred into highly ordered layers via undulated layers, as the hydrogen-bonding strength increased with reduced temperatures. As the SmCG domains were aligned under dc electric fields, a gradual decrease in the leaning angle from ca. 60° to 50° (while the tilt angle kept at ca. 31°) could be determined by in situ wide-angle X-ray scattering (WAXS). Combined with Fourier transform infrared and Raman spectroscopic data, our results suggest that the change in the leaning angle was governed by the competition of the hydrogen bonds and microsegregation of siloxane units within the bilayer structure of the hydrogen-bonded complex H-SiO. In addition, the ferroelectric-(antiferroelectric)-ferroelectric transitions proven by the switching current responses in the SmCG-type phases of H-SiO reveal that the polar switching occurred through collective rotations around the long axis of H-SiO. Therefore, novel SmCG phases with a series of highly ordered 2D-structures were induced by the effects of the hydrogen bonding and branched terminal siloxane unit in the bent-core hydrogen-bonded LC complex H-SiO.     

Microscopic modeling and control logic for incident-responsive automatic vehicle movements in single-automated-lane highway systems

Automatic response to lane-blocking incidents is a critical issue in the field of automated highway systems (AHS). Accordingly, this paper presents a microscopic vehicular control methodology for automatic-control (AC) vehicular movements in response to lane-blocking incidents in the AHS environment. The embedded traffic control logic is based on the basic safety requirements for automatic-control lane traffic maneuvers responding to lane-blocking incidents in the single-automated-lane AHS environment. Accordingly, respective automated vehicular control models are proposed to deal with AC vehicles moving in three corresponding sequential phases, i.e., (1) AC platoon approaching the incident site from the blocked lane, (2) mandatory lane changing and mixed car following in the adjacent lane, and (3) AC platoon reforming downstream from the incident site in the blocked automated lane. Using a microscopic simulation model which embeds these proposed models, preliminary tests are conducted to investigate the relative performance of the proposed method in various traffic flow and control scenarios. The resulting numerical results, including simplified sensitivity analyses, indicate that the proposed microscopic traffic control logic permits regulating automatic-control vehicular movements in response to the effects of lane-blocking incidents on traffic flows either in control-free lanes or in the automatic-control lanes. Implications of the results and some findings are discussed for further research.     

Adsorption and nucleation on smooth surfaces

The nucleation and growth of condensate nuclei on smooth surfaces, e.g., an immiscible liquid or a smooth solid, can occur both by the direct addition of molecules from the vapor and from those adsorbed on the substrate. We show how to generalize nucleation theory to allow for the simultaneous occurrence of both mechanisms. The vapor-condensate-substrate interfacial forces, the contact angle, the critical supersaturation, and the coefficient in the adsorption isotherm are different ways of expressing the affinity between vapor molecules and the substrate surface. The critical supersaturations for nucleation on the surface of an immiscible liquid and nucleation on the surface of a perfectly smooth solid are predicted in terms of these parameters and the relationships among them. For most values of these parameters we find that adsorbed molecules are usually far more important to the nucleation process than those in the vapor phase.