Enhancement of pionic modes in the quasielastic region

We report an evidence for the precursor phenomena of the pion condensation, which is found in the enhancement of the spin longitudinal cross sections ID _q of the quasielastic ¹²C, $^{40} Ca(\vec p, \vec n)$ , reactions at the incident energy 494 and 346 MeV around the momentum transfer q ≈ q _c , the critical momentum of the pion condensation. We utilized the distorted wave impulse approximation incorporated with the continuum random phase approximation. We adjusted the Landau-Migdal parameters, g′ _NN and g′ _NΔ, and obtained g′ _NN ≈ 0.6–0.7 and g′ _N Δ ≈ 0.3–0.4, which are consistent with those obtained from the energy of the Gamov-Teller giant resonance and the quenching factor of the Gamov-Teller sum rule.     

Command surfaces 12 [1]. Factors affecting in-plane photoregulation of liquid crystal alignment by surface azobenzenes on a silica substrate

In-plane alignment of nematic liquid crystals was regulated by polarized-light-irradiation of a cell assembled with a silica plate, the surface of which was modified by attaching 4-hexyl-4'-hexyloxyazobenzene at its o-position through surface silylation. The photoisomerizability of the chemisorbed azo-chromophore was affected by their surface density and the nature of photoinactive co-modifiers. The efficiency of the photoregulation of liquid crystal alignment was optimized by two-dimensional dilution of the chromophore with ethyltriethoxysilane (ETS) or 3-aminopropyltriethoxysilane (ATS). As a result, favourable procedure was to modify a silica surface with a crude azo-silylating reagent contaminated by ATS. The rate of the photoinduced reorientation of liquid crystals was followed by monitoring the alteration of the alignment direction of a dichroic dye dissolving in a mesophasic layer upon exposure to linearly polarized light. Exposure energy for the in-plane reorientation of a liquid crystal was about 100mJcm^-2 of 445 nm light at elevated temperatures close to T_NI. The effect of positional isomerism on the photoregulation was determined with the use of 4-cyano-4'-hexyloxyazobenzene as a commander molecule. It was confirmed that the photoalignment efficiency was markedly enhanced by attaching the chromophore at the ortho- or meta-position. The exposure energy for the reorientation of a liquid crystal was reduced by linking the p-cyanoazobenzene at the meta-position so that the reorientation was complete with an exposure energy of 20mJcm^-2.     

Synthesis and properties of new chiral dopants containing a δ-lactone ring for practical ferroelectric liquid crystal mixtures

A series of new optically active δ-lactones were synthesized as chiral dopants for ferroelectric liquid crystals (FLCs). The response time of an FLC mixture containing 4 mol% (S)-2,2-dimethyl-5-[2-fluoro-4-(5-n-octylpyrimidin-2-yl)-phenoxy[methyl-δ-valerolactone was 25 μs at 25°C. (0-90 per cent change in light transmission, 10 V μm^-1). The synthesis and properties of these materials as practical chiral dopants are reported.     

Tripod self-assembled monolayer on Au(111) prepared by reaction of hydroxyl-terminated alkylthiols with SiCl4

Infrared reflection spectroscopy (IRS), single wavelength ellipsometry, and density functional theory were used to elucidate the structure of a molecular tripod self-assembled monolayer (SAM) on polycrystalline gold{111} substrates. The tripod SAM was formed by the reaction of SiCl4 with a densely packed monolayer of 2-mercaptoethanol, 6-mercaptohexanol, and 16-mercaptohexadecanol under inert atmosphere. After reaction with SiCl4, IRS spectra show an intense absorption at approximately 1112 cm(-1) that is attributed to Si-O-C asymmetric stretching vibration of a molecular tripod structure. Harmonic vibrational frequencies computed at the B3LYP/6-311+g** level of theory for the mercaptoethanol tripod SAM closely match the experimental IRS spectra, giving further support for the tripod structure. When rinsed with methanol or water, the Si-Cl-terminated SAM becomes capped with Si-OMe or Si-OH. The silanol-terminated tripod SAM is expected to find use in the preparation of thin zeolite and silica films on gold substrates.     

Hilbert-Speiser number fields for a prime p inside the p-cyclotomic field

Let p be a prime number. We say that a number field F satisfies the condition when for any cyclic extension N/F of degree p, the ring of p-integers of N has a normal integral basis over . It is known that F=Q satisfies for any p. It is also known that when p?19, any subfield F of Q(ζp) satisfies . In this paper, we prove that when p?23, an imaginary subfield F of Q(ζp) satisfies if and only if and p=43, 67 or 163 (under GRH). For a real subfield F of Q(ζp) with F≠Q, we give a corresponding but weaker assertion to the effect that it quite rarely satisfies .     

Note on Bernoulli numbers associated to some Dirichlet character of prime conductor

We fix an integer \({n \geq 1}\) and a divisor m of n such that n/m is odd. Let p be a prime number of the form \({p=2n\ell+1}\) for some odd prime number \({\ell}\) with \({\ell \nmid m}\). Let \({S=pB_{1,2m\ell}}\) be the p times of the generalised Bernoulli number associated to an odd Dirichlet character of conductor p and order \({2m\ell}\), which is an algebraic integer of the \({2m\ell}\)th cyclotomic field. It is known that \({S \neq 0}\). More strongly, we show that when \({\ell}\) is sufficiently large, the trace of \({\zeta^{-1}S}\) to the \({2m}\)th cyclotomic field does not vanish for any\({\ell}\)th root \({\zeta}\) of unity. We also show a related result on indivisibility of relative class numbers.     

Low-frequency vibrations specific for conformers of 1-aminoindan studied by UV-UV hole-burning spectroscopy

The UV-UV hole-burning spectra of the jet-cooled 1-aminoindan were measured for the first time. Complicated spectral features observed in the laser-induced fluorescence excitation spectrum due to two conformers, R and B, were firmly separated. On the basis of fluorescence measurements and B3LYP/cc-pVTZ calculations, low-frequency ring twisting and ring puckering modes were assigned. These modes are coupled in the S1 state due to the Duschinsky rotation. The Duschinsky matrix was calculated from the normal modes predicted by quantum chemical calculations. The coupling between the twisting and puckering modes for conformer B is stronger than that for conformer R. The twisting mode was observed at 0+99 cm(-1) in the S1 state for conformer B, while not for conformer R. The Franck-Condon activity of the twisting mode substantially differs between the two conformers. The transition to the twisting level for conformer B would be allowed by the Duschinsky rotation. The fluorescence lifetime of conformer vibronic levels was also measured and differed for each conformer.     

Surface-assisted photoalignment of discotic liquid crystals by nonpolarized light irradiation of photo-cross-linkable polymer thin films

In this article, we describe the surface-assisted photoalignment of discotic liquid crystals (DLCs) on thin films of photo-cross-linkable polymers with cinnamoyl moieties as the side chains. Oblique irradiation of the polymer thin films with nonpolarized UV light at 313 nm brought about inclined orientation of the cinnamoyl residues as a result of their direction-selective photoisomerization and photodimerization. The DLC molecules on the photoirradiated polymer films were aligned in a tilted hybrid manner. This means that the DLC directors are continuously altered from the substrate to the DLC film surface so as to minimize the elastic free energy. Interestingly, we found that the tilted direction of aligned DLC molecules is clearly influenced by the chemical structures of the cinnamate-containing polymers. When a poly(vinyl cinnamate) thin film was obliquely exposed to nonpolarized UV light, the DLCs were inclined to the direction opposite to the UV light propagation. In a keen contrast, the thin film of poly(methacrylate)s tethering cinnamoyl groups, which was obliquely exposed to nonpolarized UV light in advance, provided the tilting DLC direction in parallel with the light propagation. The results were supported by tilted orientation of calamitic (rod-shaped) liquid crystal on the obliquely irradiated polymer films. Such photoalignment behavior of the DLCs can be rationalized by anchoring balance between intermolecular interaction of the DLC molecules with the photodimers of polymer films and those with the remaining E-isomers of cinnamoyl side chains at the film interface. The present technique of DLC photoalignment opens promising ways not only to understand anisotropic physical properties of DLCs, but also to design and fabricate novel nanodevices for photonics and electronics applications.     

Multicolor fluorescence of a styrylquinoline dye tuned by metal cations

A styrylquinoline dye with a dipicolylamine (DPA) moiety (1) has been synthesized. The dye 1 in acetonitrile demonstrates multicolor fluorescence upon addition of different metal cations. Compound 1 shows a green fluorescence without cations. Coordination of 1 with Cd(2+) shows a blue emission, while with Hg(2+) and Pb(2+) exhibits yellow and orange emissions, respectively. The different fluorescence spectra are due to the change in intramolecular charge transfer (ICT) properties of 1 upon coordination with different cations. The DPA and quinoline moieties of 1 behave as the electron donor and acceptor units, respectively, and both units act as the coordination site for metal cations. Cd(2+) coordinates with the DPA unit. This reduces the donor ability of the unit and decreases the energy level of HOMO. This results in an increase in HOMO-LUMO gap and blue shifts the emission. Hg(2+) or Pb(2+) coordinate with both DPA and quinoline units. The coordination with the quinoline unit decreases the energy level of LUMO. This results in a decrease in HOMO-LUMO gap and red shifts the emission. Addition of two different metal cations successfully creates intermediate colors; in particular, the addition of Cd(2+) and Pb(2+) at once creates a bright white fluorescence.