Reaction mechanisms in the six-nucleon system with the multi-configuration resonating-group method

The properties of the six-nucleon system are examined with a multi-configuration resonating-group method consisting of thed+ configuration, thep+⁵He andn+⁵Li configurations, and deuteron pseudo-inelastic configurations. The main purpose is to study the reaction mechanisms in this system. The results obtained are quite satisfactory, with the calculatedd+ total reaction cross sections equal to around 90% of the empirically determined values. The one-nucleon transfer process turns out to be significantly more important than the deuteron direct-breakup process; however, the latter process must still be properly taken into consideration, since it does contribute to about one third of thed+ total reaction cross section. The process of one-nucleon transfer is shown to occur mainly in the peripheral region, while the process of deuteron direct-kreakup is found to take place predominantly in the interior region of the compound nucleus. The convergence property with respect to the number of deuteron pseudo-inelastic configurations has also been investigated. Here it is found that, with the dominant configurations included, the number of such configurations required can be rather small, which is an important finding because it greatly simplifies the computational aspects of multi-configuration resonating-group calculations.     

Effect of Electrode Pattern on the Column Structure and Yield Stress of Electrorheological Fluids

For electrorheological (ER) suspensions, the aggregate structures of particles were observed in electric fields by the use of transparent cells with different electrode patterns. Although the suspension is dispersed to noninteracting particles without electric fields, many aggregates are formed on the electrode surface in electric fields. Since the dipole–dipole interactions cause chain structures of particles and equilibrium conformations of chains are always aligned with electric field, the aggregates indicate the presence of columns spanning the electrode gap. The particle concentration in columns which are developed between parallel-plate electrodes is about 22 vol %. In striped electrodes, the particles construct striped aggregates along the electrodes and no particles remain in the insulating region. The particle concentration in striped aggregates is about 35 vol %. The nonuniformity of electric field is responsible for the high particle concentration. The increase in particle concentration of column lead to the high yield stress of electrified suspension. Therefore, the ER performance of suspension as an overall response can be improved by the electrode design.     

Intermolecular-medium and intramolecular-weak hydrogen bonding chains in the crystals of chiral trifluoromethylated amino alcohols

A structural feature of hydrogen bonding chains found in the crystals of trifluoromethylated amino alcohols is reported. Hydrogen bondings of 3-(N,N-dialkylamino)-1,1,1-trifluoro-2-propanols construct chiral spiral hydrogen bonding chains. Lone pairs on the nitrogen atoms of the amino alcohols participate in two hydrogen bondings. Detailed structural analysis of the hydrogen bonds of the 3-(N,N-dimethylamino)-1,1,1-trifluoro-2-propanol suggested that the chain built up with alternating intermolecular-medium and intramolecular-weak hydrogen bonds. The medium intermolecular hydrogen bond, which transfers a proton from the hydroxy group to the amino nitrogen, would make a tentative zwitterionic form of the molecule. Then, electrostatic attraction between the charges in the zwitterion centers induced a weak intramolecular hydrogen bond.     

Evolution and characterization of fluorite-like nano-SrBi2Nb2O9 phase in the SrO-Bi2O3-Nb2O5-Li2B4O7 glass system

Transparent glasses of various compositions in the system (100−x)Li₂B₄O₇−x(SrO-Bi₂O₃-Nb₂O₅) (where x=10, 20, 30, 40, 50 and 60, in molar ratio) were fabricated via splat quenching technique. The glassy nature of the as-quenched samples was established by differential thermal analyses. X-ray powder diffraction (XRD) and transmission electron microscopic studies confirmed the amorphous nature of the as-quenched and crystallinity in the heat-treated samples. Fluorite phase formation prior to the perovskite SrBi₂Nb₂O₉ phase was analyzed by both the XRD and high-resolution transmission electron microscopy. Dielectric and the optical properties (transmission, optical band gap and Urbach energy) of these samples have been found to be compositional dependent. Refractive index was measured and compared with the values predicted by Wemple-Didomemenico and Gladstone-Dale relations. The glass nanocomposites comprising nanometer-sized crystallites of fluorite phase were found to be nonlinear optic active.     

NMR Study of Vulcanized Rubber

It is shown that NMR-linewidth measurements are useful to obtain information about the cross-linkage density and the average distance between the cross-links in vulcanized rubber. Inhomogeneous structure of the rubber phase in carbon-filled rubber is evidenced and the thickness of the rubber layer on carbon is evaluated at 50 Å.     

Room-Temperature Phosphorescence from a Series of 3-Pyridylcarbazole Derivatives

Exploration of pure metal-free organic molecules that exhibit strong room-temperature phosphorescence (RTP) is an emerging research topic. In this regard, unveiling the design principles for an efficient RTP molecule is an essential, but challenging, task. A small molecule is an ideal platform to precisely understand the fundamental role of each functional component because the parent molecule can be easily derivatized. Here, the RTP behaviors of a series of 3-pyridylcarbazole derivatives are presented. Experimental studies in combination with theoretical calculations reveal the crucial role of the n orbital on the central pyridine ring in the dramatic enhancement of the intersystem crossing between the charge-transfer-excited singlet state and the locally excited triplet states. Single-crystal X-ray crystallographic studies apparently indicate that both the pyridine ring and fluorine atom contribute to the enhancement of the RTP because of the restricted motion owing to weak C−H⋅⋅⋅N and H⋅⋅⋅F hydrogen-bonding interactions. The single crystal of the fluorine-substituted derivative shows an ultra-long phosphorescent lifetime (τ_P) of 1.1 s and a phosphorescence quantum yield (Φ_P) of 1.2 %, whereas the bromine-substituted derivative exhibits τ_P of 0.15 s with a Φ_P of 7.9 %. We believe that this work provides a fundamental and universal guideline for the generation of pure organic molecules exhibiting strong RTP.     

Arylpyrrolyldiketone Boron Complexes Exhibiting Various Anion‐Binding Modes Based on Dynamic Conformation Changes

Arylpyrrolyldiketone boron complexes as anion‐responsive π‐electronic molecules were synthesized by Claisen condensations of acetylpyrrole and corresponding aryl esters. The synthesized π‐electronic molecules exhibited anion‐binding behavior with various binding modes including pyrrole‐inverted and non‐inverted [1+1]‐type anion complexes as well as [2+1]‐type complexes owing to the presence of only a single pyrrole ring. Furthermore, solid‐state ion‐pairing assemblies, comprising receptor–anion complexes and countercations, were constructed based on fairly planar [2+1]‐type complexes.     

Synthesis and Reactions of 1-Phenylbenzo[b]thiophenium Salts

1-Phenylbenzo[b]thiophenium salts are prepared and reacted under thermal and photochemical conditions. The chemical behaviors are discussed.     

Stereodivergent Synthesis and Stereochemical Reassignment of the C79–C104 Fragment of Symbiodinolide

We have synthesized eight possible diastereoisomers 3 a – h of the C79–C97 fragment of symbiodinolide ( 1 ) in a stereodivergent manner by utilizing a dithiane addition to the aldehyde as a key step. Comparison of the ¹³C NMR chemical shifts of the natural product 1 and the synthetic products 3 a – h indicated that the relative stereostructure of this fragment in symbiodinolide ( 1 ) is that represented in 3 a or f . We have stereodivergently synthesized eight possible diastereoisomers of the C94–C104 fragment 4 a – h , and we have compared their ¹³C NMR chemical shifts with those of the natural product, which established the relative stereochemistry of this fragment to be that described in diastereoisomers 4 a or e . By combining the stereostructural outcomes of the C79–C97 and C94–C104 fragments, we have proposed four candidate compounds of the C79–C104 fragment 2 a – d . We also synthesized diastereoisomers 2 a and b ( 2 a in the preceding article; Chem. Eur. J. 2015 , DOI: 10.1002/chem.201503880) by a Julia–Kocienski olefination and diastereoisomers 2 c and d by a Wittig reaction. By comparing the ¹³C NMR chemical shifts of natural symbiodinolide ( 1 ) with those of the synthetic products 2 a – d , we have reassigned the stereostructure of the C79–C104 fragment of natural product 1 to be that depicted in diastereoisomer 2 b .