Order reduction and bifurcation analysis of a flexible rotor system supported by a full circular journal bearing

Nonlinear Dynamics - Journal bearing has been widely used in the wide range of rotating machineries to support large loads and to add significant damping to the system. Conventionally, its fluid...     

Facile synthesis of ortho‐Phenylene‐based conjugated polymers through transformation of cross‐conjugated poly(2,3‐diaryl[2]dendralene)s and their optical properties

We studied the facile synthesis of ortho‐phenylene‐based conjugated polymers through transformation of cross‐conjugated polymers having [2]dendralene moiety, poly(2,3‐diaryl[2]dendralene)s ( P1 s), and demonstrated the sequential synthesis of (Z)‐alkene‐ and ortho‐arylene‐containing conjugated polymers from P1 s. P1 s were transformed into cyclohexa‐1,4‐diene‐containing conjugated polymers ( P2 s) through a Diels–Alder reaction. Aromatization of the cyclohexa‐1,4‐diene skeleton was achieved by using 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone to give the ortho‐phenylene‐containing conjugated polymers ( P3 s). The ultraviolet–visible and fluorescence spectra of the cross‐conjugated polymers P1 s, and the conjugated polymers P2 s and P3 s indicated that the π–π interactions between the arylene moieties in P2 s were stronger than those in P1 s and P3 s. The synthetic method for P2 s and P3 s offers an effective synthesis of various types of (Z)‐alkene‐ and ortho‐arylene‐containing conjugated polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 827–832     

Highly efficient asymmetric conjugate addition of 5-benzylfurfurals to nitroalkenes using a thiourea organocatalyst

The asymmetric direct bisvinylogous conjugate addition of 5-benzylfurfural derivatives to nitroalkenes using a thiourea organocatalyst resulted in a corresponding ε-regioselective addition products in high yields and up to 95% enantiomeric excess.     

A Stable N‐Hetero‐Rh‐Metallacyclic Silylene

A cyclic (amino)metal‐substituted dicoordinated silylene derivative has been synthesized and fully characterized. Of particular interest is that the N‐hetero‐Rh^I‐metallacyclic silylene exhibits a distorted tetrahedral geometry around the rhodium atom and a considerably shortened Si?Rh bond (2.138 Å) compared to classical Si?Rh single bonds (ca. 2.30–2.35 Å). A theoretical investigation reveals that the geometrical deviation around the rhodium center from the classical square‐planar to a tetrahedral geometry increases the π‐donating and σ‐accepting character of the rhodium atom, thereby efficiently stabilizing the silylene moiety.     

High performance n-type organic field-effect transistors based on pi-electronic systems with trifluoromethylphenyl groups

Novel pi-electron systems with trifluoromethylphenyl groups and/or a thiazolothiazole unit were developed as n-type semiconductors for OFETs. They showed excellent n-type performances with high electron mobilities. The trifluoromethylphenyl group was found to be very effective in inducing n-type behavior. The thiazolothiazole unit was favorable for forming stacking structures leading to efficient intermolecular pi-pi interactions.     

Quantum dots-ionic liquid hybrids: efficient extraction of cationic CdTe nanocrystals into an ionic liquid

Water soluble CdTe nanocrystals covered with cationic thiol derivatives are efficiently transferred into a hydrophobic ionic liquid, in which they show enhanced photoluminescence.     

Can dark matter annihilation dominate the extragalactic gamma-ray background?

Annihilating dark matter (DM) has been discussed as a possible source of gamma rays from the galactic center and as a contribution to the extragalactic gamma-ray background. Assuming universality of the density profile of DM halos, we show that it is quite unlikely that DM annihilation is a main constituent of extragalactic gamma-ray background, without exceeding the observed gamma-ray flux from the galactic center. This argument becomes stronger when we include enhancement of the density profiles by supermassive black holes or baryon cooling. The presence of a substructure may loosen the constraint, but only if a very large cross section as well as the rather flat profile are realized.     

Coherence and superconductivity in coupled one-dimensional chains: a case study of YBa2Cu3Oy

We report the infrared (IR) response of Cu-O chains in the high-T(c) superconductor YBa(2)Cu(3)O(y) over the doping range spanning y=6.28-6.75. We find evidence for a power law scaling at mid-IR frequencies consistent with predictions for Tomonaga-Luttinger liquid, thus supporting the notion of one-dimensional transport in the chains. We analyze the role of coupling to the CuO2 planes in establishing metallicity and superconductivity in disordered chain fragments.     

Investigation of methyl tert-butyl ether levels in river-, ground-, and sewage-waters analyzed using a purge-and-trap interfaced to a gas chromatograph-mass spectrometer

River water collected from 27 sites in 21 rivers, groundwater from 66 sites in 34 cities, and 2 sewage plants in the Niigata Prefecture, Japan (total 301 samples) were analyzed for methyl tert-butyl ether (MTBE) using an improved purge-and-trap-GC-MS method. The amount of MTBE found in water samples from the 27 river sites ranged from 0.003 to 5.3 microg l(-1). MTBE was found in all 27 sites during winter but it was found at only 9 sites and 14 sites, respectively, during the summer. MTBE was found most frequently (in 21 sites) at levels ranging from 0.003 to 0.009 microg l(-1) during February. The highest levels of MTBE were always found in the samples collected from the same site. The amount of MTBE found in sewage water samples ranged from <0.003 to 0.025 microgl(-1). No significant differences were observed between the amounts of MTBE recovered from inflow and outflow waters. Relatively high levels (0.02-0.034 microg l(-1) ) of MTBE were found in January at two sites, which were located on the upper course of the Shinano River. MTBE levels ranged from 0.004 to 0.035 microgl(-l) and from 0.005 to 0.041 microgl(-1) at the mouths of the Shinano River and Agano River, respectively. The levels of MTBE in groundwater collected from 66 sites in 34 cities in Niigata Prefecture ranged from <0.003 to 5.9 microg l(-1).