Accelerating cosmologies from spacelike branes

We point out that the recently proposed model of a flat four-dimensional universe with accelerated expansion in string or M theory is a special case of time-dependent solutions that the author found under the name of spacelike (S) branes. We also show that similar accelerating models can be obtained from S branes if the internal space is chosen to be hyperbolic or flat spaces.     

Ab initio calculations of structures and interaction energies of toluene dimers including CCSD(T) level electron correlation correction

The intermolecular interaction energy of the toluene dimer has been calculated with the ARS-F model (a model chemistry for the evaluation of intermolecular interaction energy between ARomatic Systems using Feller's method), which was formerly called as the AIMI model III. The CCSD(T) (coupled cluster calculations with single and double substitutions with noniterative triple excitations) interaction energy at the basis set limit has been estimated from the second-order Moller-Plesset perturbation interaction energy at the basis set limit obtained by Feller's method and the CCSD(T) correction term obtained using a medium-size basis set. The cross (C(2)) dimer has the largest (most negative) interaction energy (-4.08 kcal/mol). The antiparallel (C(2h)) and parallel (C(S)) dimers (-3.77 and -3.41 kcal/mol, respectively) are slightly less stable. The dispersion interaction is found to be the major source of attraction in the toluene dimer. The dispersion interaction mainly determines the relative stability of the stacked three dimers. The electrostatic interaction of the stacked three dimers is repulsive. Although the T-shaped and slipped-parallel benzene dimers are nearly isoenergetic, the stacked toluene dimers are substantially more stable than the T-shaped toluene dimer (-2.62 kcal/mol). The large dispersion interaction in the stacked toluene dimers is the cause of their enhanced stability.     

Giant optical activity in quasi-two-dimensional planar nanostructures

We examine the spectral dependence in the visible frequency range of the polarization rotation of two-dimensional gratings consisting of chiral gold nanostructures with subwavelength features. The gratings, which do not diffract, are shown to exhibit giant specific rotation (approximately 10(4) degrees/mm) of polarization in direct transmission at normal incidence. The rotation is the same for light incident on the front and back sides of the sample. Such reciprocity indicates three dimensionality of the structure arising from the asymmetry of light-plasmon coupling at the air-metal and substrate-metal interfaces. The structures thus enable polarization control with quasi-two-dimensional planar objects. However, in contradiction with recently suggested interpretation of experiments on larger scale but otherwise similar structures, the observed polarization phenomena violate neither reciprocity nor time-reversal symmetry.     

Mirror symmetry and

We show that counting functions of covers of are equal to sums of integrals associated to certain `Feynman' graphs. This is an analogue of the mirror symmetry for elliptic curves.

     

Liquid crystalline nanosheet colloids with controlled particle size obtained by exfoliating single crystal of layered niobate k(4)nb(6)o(17)

Colloidally dispersed niobate nanosheets with the thickness of 1.8 nm and controlled mean lateral sizes of 0.15-7.8 mum were prepared and their liquid crystallinity was examined. The nanosheet colloids with different lateral sizes were obtained by exfoliation of single crystals of layered niobate K4Nb6O17 and subsequent ultrasonication. Naked-eye and microscope observations of the nanosheet colloids between crossed polarizers revealed liquid crystallinity of the sols characterized by birefringence as functions of the lateral sizes and concentration of the nanosheets. The nanosheet colloids with smaller lateral sizes (0.15-1.9 mum) varied from isotropic to biphasic (isotropic + liquid crystalline), and finally to fully liquid crystalline states as the colloid concentration increased. The phase transition concentrations (from isotropic to biphasic and biphasic to liquid crystalline) decreased with increasing aspect ratio (lateral-to-thickness ratio) of the nanosheets, almost in accordance with the prediction by Onsager theory, indicating that the liquid crystallinity is explained basically by excluded-volume effect between the nanosheets. On the other hand, the colloids with larger lateral sizes (6.2 and 7.8 mum) stably kept liquid crystalline state even at very low concentration (5.1 x 10-6 in volume fraction), which was much lower than that expected from the theory.     

Creation of magnetic cerasomes through electroless plating and their manipulation using external magnetic fields

Magnetic cerasome, an artificial cell membrane having ultrathin magnetic metal layers on the surface, was prepared through electroless plating of magnetic metal alloy onto an organic–inorganic vesicular nanohybrid “cerasome.” Morphological and functional characteristics of the magnetic cerasome were evaluated using various physical measurements: scanning and transmission electron microscopies, energy-dispersive X-ray spectroscopy, electron tomography, and vibrating sample magnetometry. The results proved that high morphological stability of the cerasome was important for constructing the magnetic lipid vesicle and that insertion of an alkylated metal ligand into the cerasome was essential to the magnetic metal alloy deposition on the cerasome surface. Fluorescence microscopic observations revealed that the magnetic cerasomes were collected reversibly on the slide glass surface and manipulated depending on external motion of a magnet. The potential use of the magnetic cerasomes as a novel vesicular nanohybrid is also described in this report.