Segregated and alternately stacked donor/acceptor nanodomains in tubular morphology tailored with zinc porphyrin-C60 amphiphilic dyads: clear geometrical effects on photoconduction

Amphiphilic zinc porphyrin (P(Zn); electron donor, D)-fullerene (C(60); electron acceptor, A) dyads 2 and 3, bearing an identical hydrophilic wedge with triethylene glycol chains but different linkers between the P(Zn) and C(60) units, self-assemble into nanotubes with essentially different dimensional and geometrical features from one another. The nanotube from dyad 2 with an ester linker consists of a bilayer wall formed with coaxially segregated D and A nanodomains along the tube axis (coaxial D-A heterojunction), thereby displaying explicit photoconductivity with ambipolar carrier transport properties. In contrast, the nanotube from dyad 3 with a rigid arylacetylene linker consists of a monolayer wall with an alternate geometry of D/A stacking, resulting in poor photoconducting outputs. Such a geometrical difference also significantly affects the photovoltaic properties.     

On transversality with deficiency and a conjecture of Sard

Let be a map between manifolds and a manifold. In this paper, by using the Sard theorem, we study the topological properties of the space of maps which satisfy a certain transversality condition with respect to in a weak sense. As an application, by considering the case where is a point, we obtain some new results about the topological properties of , where is the set of points of where the rank of the differential of is less than or equal to . In particular, we show a result about the topological dimension of , which is closely related to a conjecture of Sard concerning the Hausdorff measure of .

     

Separation by a codimension-1 map with a normal crossing point

Letf:M ^n–1N ⁿ be an immersion with normal crossings of a closed orientable (n–1)-manifold into an orientablen-manifold. We show, under a certain homological condition, that iff has a multiple point of multiplicitym, then the number of connected components ofN–f(M) is greater than or equal tom+1, generalizing results of Biasi and Romero Fuster (Illinois J. Math. 36 (1992), 500–504) and Biasi, Motta and Saeki (Topology Appl. 52 (1993), 81–87). In fact, this result holds more generally for every codimension-1 continuous map with a normal crossing point of multiplicitym. We also give various geometrical applications of this theorem, among which is an application to the topology of generic space curves.     

Simplifying stable mappings into the plane from a global viewpoint

Let be a stable map of an -dimensional manifold into the plane. The main purpose of this paper is to define a global surgery operation on which simplifies the configuration of the critical value set and which does not change the diffeomorphism type of the source manifold . For this purpose, we also study the quotient space of , which is the space of the connected components of the fibers of , and we completely determine its local structure for arbitrary dimension of the source manifold . This is a completion of the result of Kushner, Levine and Porto for dimension 3 and that of Furuya for orientable manifolds of dimension 4. We also pay special attention to dimension 4 and obtain a simplification theorem for stable maps whose regular fiber is a torus or a 2-sphere, which is a refinement of a result of Kobayashi.

     

(2H)2-2C type superstructure of TiS1.62, determined by high-resolution electron microscopy

A superstructure of TiS_1.62 is determined by 100 kV high-resolution electron microscopy, in which the arrangement of metal vacancies is obtained from structure images. The crystal has monoclinic symmetry (pseudo-hexagonal) with lattice parameters a = 11.9, b = 6.85, c = 11.5Å, β = 90°. The space group is considered as $\text{F2}\text{m}$. Metal vacancies are confined to every second metal layer and ordered within the partly filled metal layer, resulting in formation of a (2H)₂2C type of superstructure. The ordered metal vacancy layers are arranged in 2C-type stacking sequence along the c axis, while sulfur atoms are arranged in 2H-type stacking sequence along the c axis.     

Behavior of vanadium dioxide single crystals synthesized under the various oxygen partial pressures at 1500 K

The effects of nonstoichiometry upon the behavior of vanadium dioxide single crystals in the vicinity of the semiconductor/metal transition temperature (T_c) were experimentally investigated. According to the electrical and thermal measurements, more stoichiometric vanadium dioxide exhibited the less electrical conductivity gap, the larger thermal and electrical hysteresis, and the lower transition temperature than the increased nonstoichiometric one near transition. Infrared absorptions and X-ray observations indicated the local and overall lattice distortion in the nonstoichiometric crystal due to the existence of V⁵⁺ ions. Furthermore, an intermediate phase between the low-temperature monoclinic and the high-temperature tetragonal phases was found in the nonstoichiometric VO₂. On the other hand, no evidence for this intermediate phase was found in the stoichiometric one. Finally, some comparisons and discussions of our present data with the previously published ones were made.     

Electronegative oligothiophenes fully annelated with hexafluorocyclopentene: synthesis, properties, and intrinsic electron mobility

Synthesis of hexafluorocyclopenta[c]thiophene-repeated oligothiophenes up to 6-mer has been accomplished. The photophysical and electrochemical properties of these oligomers unambiguously exemplify marked electronegative character without disrupting the effective conjugation. The combination of time-resolved microwave conductivity and transient optical spectroscopy measurements of the 6-mer revealed the intrinsic electron mobility to be as high as 2.0 x 10(-1) cm(2) V(-1) s(-1).