Scaling properties of universal tetramers

We evidence the existence of a universal correlation between the binding energies of successive four-boson bound states (tetramers), for large two-body scattering lengths (a), related to an additional scale not constrained by three-body Efimov physics. Relevant to ultracold atom experiments, the atom-trimer relaxation peaks for |a|→∞ when the ratio between the tetramer and trimer energies is ?4.6 and a new tetramer is formed. The new scale is also revealed for a < 0 by the prediction of a correlation between the positions of two successive peaks in the four-atom recombination process.     

壁面附近火焰OH自由基行为的PLIF研究

利用OH-PLIF测试技术在狭缝燃烧器上考察了不同壁面条件对平行平板间甲烷/空气预混火焰壁面附近处OH浓度分布的影响.实验结果表明,随着壁面间距的减小,狭缝火焰出现不稳定传播现象,不同壁面温度下不稳定传播现象不同.壁面附近OH浓度越高,熄火间距越小.壁面附近的OH浓度是决定熄火间距的关键因素,而火焰的OH浓度峰值只表示...     

Constraints on two-neutron separation energy in the Borromean C nucleus

The recently extracted matter radius of carbon isotope ²²C allows us to estimate the mean-square distance of a halo neutron with respect to the center-of-mass of this nucleus. By considering this information, we suggest an energy region for an experimental investigation of the unbound ²¹C virtual state. Our analysis, in a renormalized zero-ranged three-body model, also indicates that the two-neutron separation energy in ²²C is expected to be found below ∼0.4 MeV$\sim 0.4\text{MeV}$, where the ²²C is approximated by a Borromean configuration with a pointlike ²⁰C and two s-wave halo neutrons. A virtual-state energy of ²¹C close to zero, would make the ²²C, within Borromean nuclei configurations, the most promising candidate to present an excited bound Efimov state or a continuum three-body resonance.     

Internal cooling efficiency of a junction diode

The three thermal rate equations were built newly up at both ends and at the junction of a p–n diode, in order to derive analytically the temperature difference ΔT (between a junction and both ends) and the internal cooling efficiency η defined newly for a homojunction diode. The maxima ΔT and η of a diode were derived analytically as a function of V _j within the short-length approximation and calculated numerically as a function of V _j or V _bi, where V _j is a voltage across the junction and V _bi is a built-in voltage at the junction. As a result, ΔT increases abruptly with an increase of V _j below V _j=0.050 V or of V _bi below V _bi=0.10 V, while above their values, it increases slowly with an increase of V _j or V _bi to saturate a certain value. For example, ΔT was estimated as 14.6 K for Hg_0.8Cd_0.2Te diode with V _bi=0.36 V. η has a local maximum of 63% at V _j≈0.01 V or at V _bi≈0.03 V, while above their respective values, it decreases abruptly with an increase of V _j or V _bi and falls to 4.4% at V _bi=0.80 V which is equivalent to that of a diode emitting a laser for fiber optical communication. However, the greater enhancements in ΔT and η of a diode are required to apply the internal cooling system to a laser-emitting diode which needs the exact control of temperature. These results should be useful for the application of the internal cooling system to the double heterojunction diode used in the optical communication.     

Syntheses of (±)-9-epi-hederacine A and (±)-9-epi-hederacine B

Racemic syntheses of 9-epi-hederacine A and 9-epi-hederacine B have been achieved. Key transformations include a transannular hemiaminal formation for construction of the azabicyclo[3.2.1]octane core fused to a cyclopentane ring.     

A novel samarium(II)-mediated tandem spirocyclization onto an aromatic ring

We report a samarium(II)-mediated tandem spirocyclization reaction to provide dispiro[4.2.4.2]tetradecadiene and dispiro[4.2.5.2]pentadecadiene skeletons. The reaction was achieved by intramolecular addition of a ketyl radical onto an aromatic ring bearing an electrophilic moiety followed by reductive capture of the spirohexadienyl radical intermediate with SmI₂ in the presence of HMPA.     

Stepwise neutral-ionic phase transitions in a covalently bonded donor/acceptor chain compound

Neutral (N)-ionic (I) transitions in organic donor (D)/acceptor (A) charge-transfer complexes are intriguing because a 'reservoir of functions' is available. For systematically controlling N-I transitions, tuning the ionization potential of D and the electron affinity of A is extremely important. However, the effect of Coulomb interactions, which likely causes a number of charge-gap states at once in a system bringing about stepwise transitions, is a long-standing mystery. Here, we show definite evidence for stepwise N-I transitions caused by contributions from anisotropic interchain Coulomb interactions in a metal-complex-based covalently bonded DA chain compound, [Ru(2)(2,3,5,6-F(4)PhCO(2))(4)(DMDCNQI)]·2(p-xylene) (1; 2,3,5,6-F(4)PhCO(2)(-) = 2,3,5,6-tetrafluorobenzoate; DMDCNQI = 2,5-dimethyl-N,N'-dicyanoquinonediimine), where the [Ru(2)(II,II)(2,3,5,6-F(4)PhCO(2))(4)] moiety has a paddlewheel diruthenium(II,II) motif with a Ru-Ru bond. An intermediate-temperature phase involving self-organized N and I chains was observed in the temperature range between 210 K (= T(2)) and 270 K (= T(1)) with N phase at T > T(1) and I phase at T < T(2). Accompanying the charge transitions, the spin-ground states as well as the ferrimagnetic ordering in the I phase vary. The stepwise feature of the N-I transition with a highly sensitive magnetic response should bring about new dynamical functionalities associated with charge, spin, and lattice.     

Microwave-assisted organic functionalization of silica surfaces: Effect of selectively heating silylating agents

Microwave (MW)-assisted (2.45 GHz) organic functionalization of silica surfaces was investigated using (3-chloropropyl)dimethylsilanes with alkoxy, allyl, or aryl leaving groups in heptane or toluene at 80 °C. ²⁹Si and ¹³C CP/MAS spectroscopy confirmed the 3-chloropropyldimethylsilyl moiety was covalently grafted onto silica for all the samples. The effect of MW irradiation on the loading amount strongly depended on the leaving group as well as the solvent; using methoxysilane and p-anisylsilane in heptane caused a distinct acceleration. The correlation with the dielectric loss factors of the silylating agents suggested that the MW acceleration effect resulted from selectively heating the strongly MW-absorbing silylating agent. For the grafting reaction in toluene, the MW effect was not observed possibly because toluene masked the selective heating effect of the silylating agent.     

In vitro gene delivery mediated by lactosylated dendrimer (generation 3, G3)/��-cyclodextrin conjugates into hepatocytes

The purpose of this study is to evaluate in vitro gene delivery efficiency of polyamidoamine (PAMAM) starburst dendrimer (generation 3, G3) conjugates with ??-cyclodextrin (??-CDE (G3)) bearing lactose (Lac-??-CDE) with various degrees of substitution of the lactose moiety (DSL) as a novel hepatocyte-selective carrier. Lac-??-CDE (G3, DSL 1.2) was found to have much higher gene transfer activity than ??-CDE (G3), Lac-??-CDE (G2, DSL 2.6) and Lac-??-CDEs (G3, DSL 2.6, 4.1 and 6.1) in HepG2 cells, which are dependent on the expression of cell-surface asialoglycoprotein receptor (ASGP-R). Lac-??-CDE (G3, DSL 1.2) provided negligible cytotoxicity up to a charge ratio of 100 (carrier/pDNA) in HepG2 cells. These results suggest the potential use of Lac-??-CDE (G3, DSL 1.2) as a non-viral vector for gene delivery toward hepatocytes.     

Flame structure and flame spread rate over a solid fuel in partially premixed atmospheres

We have investigated the downward flame spread over a thin solid fuel. Hydrogen, methane, or propane, included in the gaseous product of pyrolysis reaction, is added in the ambient air. The fuel concentration is kept below the lean flammability limit to observe the partially premixing effect. Both experimental and numerical studies have been conducted. Results show that, in partially premixed atmospheres, both blue flame and luminous flame regions are enlarged, and the flame spread rate is increased. Based on the flame index, a so-called triple flame is observed. The heat release rate ahead of the original diffusion flame is increased by adding the fuel, and its profile is moved upstream. Here, we focus on the heat input by adding the fuel in the opposed air, which could be a direct factor to intensify the combustion reaction. The dependence of the flame spread rate on the heat input is almost the same for methane and propane/air mixtures, but larger effect is observed for hydrogen/air mixture. Since the deficient reactant in lean mixture is fuel, the larger effect of hydrogen could be explained based on the Lewis number consideration. That is, the combustion is surely intensified for all cases, but this effect is larger for lean hydrogen/air mixture (Le < 1), because more fuel diffuses toward the lean premixed flame ahead of the original diffusion flame. Resultantly, the pyrolysis reaction is promoted to support the higher flame spread rate.