Formation of Hierarchical Lamellae‐in‐Lamella Nanostructures from Polymer Blends Via Controlled Nonequilibrium Freezing

The creation of hierarchical nanostructures in polymeric materials has been intensively studied due to the great potential to tailor their physicochemical properties. Although much success has been achieved over the past decades in block copolymers, hierarchical structure engineering in polymer blends remains a great challenge. Here, the formation of hierarchical lamellae‐in‐lamella nanostructures from polymer blends via controlled nonequilibrium freezing is reported. Polymer blends are first dissolved in molten hexamethylbenzene (HMB) to form a homogeneous melt. When cooled to below its melting temperature, the HMB is crystallized and depleted, and the polymers are directionally solidified. This process is rapid enough that phase separation of the polymer blends is kinetically trapped at the nanoscale level. Then, the polymer blend epitaxially crystallizes onto the HMB inside the nanophase, resulting in the hierarchical lamellae‐in‐lamella structure. This structure is stable under ambient conditions and tunable depending on the annealing temperature and blending ratio.

     

Plasma-Induced Synthesis of CuO Nanofibers and ZnO Nanoflowers in Water

Fiber-shaped cupric oxide (CuO) nanoparticles and flower-shaped ZnO nanoparticles were facilely synthesized by plasma-induced technique directly from copper and zinc electrode pair in water, respectively. The phase composition, morphologies and optical property of nanoparticles have been investigated by energy dispersive X-ray analysis, X-ray powder diffraction, transmission electron microscopy and UV–vis. The in situ analysis by an optical emission spectroscopy clarified the formation mechanism. Plasma was generated from the discharge between a metal electrode pair in water by a pulse direct current power. CuO and ZnO nanoparticles were synthesized via almost the same formation mechanism, which were prepared via the rapid energetic radicals’ bombardment to electrodes’ surface, atom vapour diffusion, plasma expansion, solution medium condensation, and in situ oxygen reaction and further growth. This novel plasma-induced technique will become a potential application in nanomaterials synthesis.     

Involvement of Proton Transfer for Carbon Dioxide Reduction Coupled with Extracellular Electron Uptake in Shewanella oneidensis MR‐1

Microbial biosynthesis of hydrocarbon from CO₂ reduction driven by electron uptake process from the cathodic electrode has gained intensive attention in terms of potential industrial application. However, a lack of a model system for detailed studies on the mechanism of the CO₂ reduction hinders the improvement in efficiency for microbial electrosynthesis. Here, we examined the mechanism of microbial CO₂ reduction at the cathode by a well‐described microbe for extracellular electron uptake, Shewanella oneidensis MR‐1, capable of reducing gaseous CO₂ to produce formic acid. Using whole‐cell electrochemical assay, we observed stable cathodic current production at ?0.65 V vs Ag/AgCl KCl sat. associated with the introduction of CO₂. The observed cathodic current was enhanced by the addition of 4 μM riboflavin, which specifically accelerates the electron uptake process of MR‐1 by the interaction to its outer‐membrane c‐type cytochromes. The significant impact of an uncoupler agent and a mutant strain of MR‐1 lacking sole F‐type ATPase suggested the importance of proton import to the cytoplasm for the cathodic CO₂ reduction. The present data suggest that MR‐1 potentially serves as a model system for microbial electrosynthesis from CO₂.     

Essential independent sets and Hamiltonian cycles

An independent set S of a graph G is said to be essential if S has a pair of vertices distance two apart in G. We prove that if every essential independent set S of order k ≥ 2 in a k-connected graph of order p satisfies max {deg v:v ϵ S} ≥ ½ p, then g is hamiltonian. This generalizes the result of Fan (J. Combinatorial Theory B 37 (1984), 221–227). If we consider the essential independent sets of order k + 1 instead of k in the assumption of the above statement, we can no longer assure the existence a hamiltonian cycle. However, we can still give a lower bound to the length of a longest cycle. © 1996 John Wiley & Sons, Inc.     

High-Affinity Ratiometric Fluorescence Probe Based on 6-Amino-2,2′-Bipyridine Scaffold for Endogenous Zn2+ and Its Application to Living Cells

Zinc is an essential trace element involved in many biological activities; however, its functions are not fully understood. To elucidate the role of endogenous labile Zn²⁺, we developed a novel ratiometric fluorescence probe, 5-(4-methoxyphenyl)-4-(methylsulfanyl)-[2,2′-bipyridin]-6-amine (6 (rBpyZ)) based on the 6-amino-2,2′-bipyridine scaffold, which acts as both the chelating agent for Zn²⁺ and the fluorescent moiety. The methoxy group acted as an electron donor, enabling the intramolecular charge transfer state of 6 (rBpyZ), and a ratiometric fluorescence response consisting of a decrease at the emission wavelength of 438 nm and a corresponding increase at the emission wavelength of 465 nm was observed. The ratiometric probe 6 (rBpyZ) exhibited a nanomolar-level dissociation constant (K_d = 0.77 nM), a large Stokes shift (139 nm), and an excellent detection limit (0.10 nM) under physiological conditions. Moreover, fluorescence imaging using A549 human lung adenocarcinoma cells revealed that 6 (rBpyZ) had good cell membrane permeability and could clearly visualize endogenous labile Zn²⁺. These results suggest that the ratiometric fluorescence probe 6 (rBpyZ) has considerable potential as a valuable tool for understanding the role of Zn²⁺ in living systems.     

Second-order Coriolis resonance between ν2 and ν5 of CH3F by microwave spectroscopy

The J = 1 ← 0 and J = 2 ← 1 transitions and the l-doubling transitions of J = 2 – 6 of ¹²CH₃F in the ν₂ and ν₅ states were analyzed by taking into account the Coriolis interaction between the two modes. The molecular constants which are derived are: ν₅ - ν₂, 252 412 ± 112; $\text{B}{}_5{}^1$, 25 611.60 ± 0.40; A_ζ5, ?38 772 ± 116; $\text{B}{}_2{}^1$, 25 432.52 ± 0.33; D, 21 838.4 ± 8.2; $\text{q}{}_5{}^1$, 39.58 ± 0.30 MHz; in addition to a few other minor constants. The present result is completely consistent with the recent Raman data of Escribano, Mills, and Brodersen, J. Mol. Spectrosc.61, 249 (1976). Molecular constants in the ν₃ and ν₆ states have also been obtained: B₃, 25 197.570 ± 0.020; B₆, 25 418.917 ± 0.047; A_ζ6ηJ, ?0.562 ± 0.030; |q₆|, 8.70 ± 0.13 MHz. Errors are 2.5 times the standard deviations.     

Doppler-limited dye laser excitation spectroscopy of HCCl

The cw dye laser excitation spectrum of the $\text{A}\text{?}{}^1\text{A″(050) ←}\text{X}\text{?}{}^1\text{A′(000)}$ vibronic band of HCCl was observed between 16 539 and 16 656 cm^?1 with the Doppler-limited resolution, 0.03 cm^?1. The HCCl molecule was generated by the reaction of discharged CF₄ with CH₃Cl. The observed spectra were assigned to c-type transitions with ΔK_a = ±1 and also to axis-switching transitions with ΔK_a = 0 or ?2, but all with K′_a = 0, both for HC³⁵Cl and HC³⁷Cl. A rotational analysis yielded the rotational constants and quartic centrifugal distortion constants for the ground vibronic state and the band origin. A weak vibronic band, about one-third as intense as the main band, was found at about 57 cm^?1 to the violet of the main band for both isotopic species, and was ascribed to a transition from the ground vibronic state to a vibrational level, possibly (041), of the à state. The rotational levels of HC³⁵Cl in the à state showed a large perturbation; the J′ = 8, 9, and 10 levels were found to be split into two components. A normal coordinate analysis was carried out to calculate the centrifugal distortion constants and the inertia defect, which were in fair agreement with the observed values. The molecular structure of HCCl in the ground vibronic state was recalculated from the rotational constants of the two isotopic species combined with the 0.75B₀ + 0.25C₀ value previously reported for DC³⁵Cl.     

Energetics and electronic structures of encapsulated C60 in a carbon nanotube

We report total-energy electronic structure calculations that provide energetics of encapsulation of C60 in the carbon nanotube and electronic structures of the resulting carbon peapods. We find that the encapsulating process is exothermic for the (10,10) nanotube, whereas the processes are endothermic for the (8,8) and (9,9) nanotubes, indicative that the minimum radius of the nanotube for the encapsulation is 6.4 A. We also find that the C(60)@(10,10) is a metal with multicarriers each of which distributes either along the nanotube or on the C60 chain. This unusual feature is due to the nearly free electron state that is inherent to hierarchical solids with sufficient space inside.     

Family of symplectic implicit Runge-Kutta formulae

A family of formulae for the sympletic IRK method is investigated. Specifically, focus is given to general solutions for formula parameters of IRK under the symplectic and the order conditions. Examples of such formulae are constructed for up to three stages.     

Long Pulse Operation of the THz Gyrotron with a Pulse Magnet

Long pulse operation up to 1 msec of a high frequency gyrotron with a pulse magnet has been successfully carried out in a frequency range including 1 THz. In the experiments, the timing of an electron beam pulse injection is adjusted at the top of the magnetic field pulse, where the variation of field intensity is negligible. The operation cavity modes seem to be TE_{1, 12} and TE_4,12 at the second harmonics. The corresponding frequencies are 903 GHz and 1,013 GHz, respectively. Additionally several features of radiation measurement results of the gyrotron are described and brief considerations are presented.