The Fuglede-Putnam theorem and a generalization of Barría's lemma

Let and be bounded linear operators, and let be a partial isometry on a Hilbert space. Suppose that (1) , (2) , (3) and (4) . Then we have .

     

Two-photon absorption properties of azulenyl compounds having a conjugated ketone backbone

Two-photon absorption (TPA) properties of newly synthesized conjugated ketone derivatives that include nonalternant azulenyl moieties in the pi-conjugation system, alpha,alpha'-bis(1-azulenylidene)cyclopentanone (1Az), alpha,alpha'-bis(2-azulenylidene)cyclopentanone (2Az), and alpha,alpha'-bis(6-azulenylidene)cyclopentanone (6Az) are reported. TPA spectra of these azulenyl compounds were measured using the open-aperture Z-scan method with a femtosecond laser. The TPA cross section at the peak position (sigma(2)peak) of 1Az was found to be the largest among the three azulenyl compounds, which is almost 7 times larger than that of the alpha,alpha'-bis(1-naphthylidene)cyclopentanone (1Nph), an alternant isomer of 1Az with the same number of pi-electrons. The small detuning energies of the azulenyl compounds compared to those of 1Nph were responsible for the large TPA cross sections. We report that a compound having an azulenyl moiety can be a promising TPA material.     

Photo-responsive gel droplet as a nano- or pico-litre container comprising a supramolecular hydrogel

Photo-responsive gel droplets having nano- or pico-L volume that showed photo-induced gel-sol transition were successfully developed, for which the inter-droplet mass transport and the subsequent enzymatic reactions in the interior of the gel droplets were photo-triggered.     

Fabrication of Porous Polyimide Membrane with Through-Hole via Multiple Solvent Displacement Method

Porous polyimide (PI) membranes are widely used in separation processes because of their excellent thermal and mechanical properties. However, the applications of porous PI membranes are limited in the nanofiltration range. In this study, porous PI membranes with through-holes have been successfully fabricated by the novel multiple solvent displacement method. This new method requires only a porous polyamic acid (PAA) membrane, which was prepared by immersing PAA film in N-methylpyrrolidoneebk; (NMP) prior to immersing it in a mixed solvent consisting of NMP and a poor solvent, followed by immersion only in poor solvent. The pore size, morphology, porosity, and air permeability demonstrated that the fabricated PI membranes had a uniformly porous structure with through-holes over their surface. This new method enabled control of pore size (3–11 μm) by selecting a suitable poor solvent. This multiple solvent displacement method is highly versatile and promising for the fabrication of porous PI membranes.     

Multi-Directional Mechanofluorochromism of Acetyl Pyrenes and Pyrenyl Ynones

A series of acetyl pyrenes and pyrenyl ynones with and without tert-butyl groups showed distinct mechanofluorochromism (MFC). Four pairs of polymorphic solids were found out of six compounds and interestingly, each of them showed hypsochromic, bathochromic or off-to-on MFC. The MFC properties were rationalized by categorizing the packing schemes into herringbone, sandwich, beta and gamma motifs depending on the relative contributions of C⋅⋅⋅C (or π-π) against C⋅⋅⋅H contacts. The bulky tert-butyl and trimethylsilyl groups served not only to reduce the number of aggregation patterns but also to prohibit the complete back reactions in solid state. Our results suggest that the simple pyrene derivatives may be promising candidates for a novel group of mechanically-sensitive materials.     

The amounts of hydroxyl radicals generated by titanium dioxide and 3.5% hydrogen peroxide under 405-nm diode laser irradiation

A new bleaching agent consisting of a titanium dioxide photocatalyst and 3.5% hydrogen peroxide has recently been developed for in-office bleaching and has proven to react well with irradiated light around a wavelength of 400 nm. This study was conducted to evaluate the efficacy of dental bleaching with a 405-nm diode laser irradiation on titanium dioxide and 3.5% hydrogen peroxide by measuring the generation of hydroxyl radicals. The amount of hydroxyl radicals generated from a titanium dioxide and 3.5% hydrogen peroxide irradiated by a 405-nm diode laser were measured using electron spin resonance spin-trapping techniques. The irradiation conditions of the laser were a spot size of 1 mm, output powers of 100, 200, 400 mW, and 600 mW, and irradiation times of 10, 20, 30, and 60 s. Nonirradiated samples were used as controls. DMPO-OH adduct spectra and DMPO-O ₂ ^? adduct spectra were observed when the bleaching agent was irradiated by laser light. The amount of hydroxyl radicals generated changed in accordance with adjustments in the irradiation power and irradiation time. In the nonirradiated controls, hydroxyl radicals were generated in far smaller amounts. The 405-nm diode laser is effective in inducing the generation of hydroxyl radicals and shows promise as a bleaching light source for use in combination with bleaching agents composed of titanium dioxide and low concentrations of hydrogen peroxide.     

A quinoline-polyamine conjugate as a fluorescent chemosensor for quantitative detection of Zn(II) in water

A simple ligand (L1), a diethylenetriamine bearing two end quinoline fragments, was synthesized. Without metal cations, L1 shows no fluorescence at pH 2-13; however, Zn²⁺ addition creates strong fluorescence at pH 5-12. The emission intensity exhibits linear and stoichiometrical response to the Zn²⁺ amount. No remarkable emission enhancement was, however, observed for other cations.     

Liquid-crystalline physical gels

Liquid-crystalline (LC) physical gels are a new class of dynamically functional materials consisting of liquid crystals and fibrous aggregates of molecules that are called "gelators". Liquid-crystalline physical gels, which are macroscopically soft solids, exhibit induced or enhanced electro-optical, photochemical, electronic properties due to the combination of two components that form phase-separated structures. In this tutorial review, we describe the materials design and structure-property relationships of the LC physical gels. The introduction of self-assembled fibers into nematic liquid crystals leads to faster responses in twisted nematic (TN) mode and high contrast switching in light scattering mode. Furthermore, the LC physical gels can be exploited as a new type of materials for electro-optical memory. This function is achieved by the control of reversible aggregation processes of gelators under electric fields in nematic liquid crystals. Electronic properties such as hole mobilities are improved by the introduction of fibrous aggregates into triphenylene-based columnar liquid crystals. The incorporation of photochromic azobenzenes or electroactive tetrathiafulvalenes into the chemical structures of gelators leads to the preparation of ordered functional materials.     

Conformation and position of membrane-bound amphotericin B deduced from NMR in SDS micelles

Amphotericin B (AmB) is known to self-assemble to form an ion channel across lipid bilayer membranes. To gain insight into the conformation of AmB in lipidic environments, AmB in SDS micelles was subjected to high-resolution NMR and CD measurements, and the NMR-derived conformation thus obtained was refined by molecular mechanics calculations. These results indicate that AmB in SDS micelles is conformationally fixed particularly for the macrolide moiety. Paramagnetic relaxation experiments with the use of Mn2+ reveal that AmB is shallowly embedded in the micelle with the polyhydroxyl chain being close to the water interface and the side of polyene portion facing to the micelle interior. CD measurements demonstrate that AmB is in a monomeric form in SDS micelles. The structure of AmB in the micelles obtained in the present study may reproduce the initial stage of membrane interaction of AmB prior to the assembly formation in biomembranes.     

Efficient conversion of tomatidine into neuritogenic pregnane derivative

Moderate acetylation of tomatidine with anhydrous acetic acid and pyridine for 20 h at r.t., followed by pseudomerization in ice-water, gave a delta(20(22))-pseudo compound, which was then subjected to ozonolysis to provide a pregnane derivative in a total 54% yield showing neuritogenic and NGF-enhancing activities.