Controlling Electron Rebound within Four‐Base π‐Stacks in Z‐DNA by Changing the Sugar Moiety from Deoxy‐ to Ribonucleotide

Charge transfer through DNA is of great interest because of the potential of DNA to be a building block for nanoelectronic sensors and devices. The photochemical reaction of 5‐halouracil has been used for probing charge‐transfer processes along DNA. We previously reported on unique charge transfer following photochemical reaction of 5‐bromouracil within four‐base π‐stacks in Z‐DNA. In this study, we incorporated a guanosine instead of a deoxyguanosine into Z‐DNA, and found that electron transfer occurs in a different mechanism through four‐base π‐stacks.     

Auger Ionization Beats Photo‐Oxidation of Semiconductor Quantum Dots: Extended Stability of Single‐Molecule Photoluminescence

Despite the bright and tuneable photoluminescence (PL) of semiconductor quantum dots (QDs), the PL instability induced by Auger recombination and oxidation poses a major challenge in single‐molecule applications of QDs. The incomplete information about Auger recombination and oxidation is an obstacle in the resolution of this challenge. Here, we report for the first time that Auger‐ionized QDs beat self‐sensitized oxidation and the non‐digitized PL intensity loss. Although high‐intensity photoactivation insistently induces PL blinking, the transient escape of QDs into the ultrafast Auger recombination cycle prevents generation of singlet oxygen (¹O₂) and preserves the PL intensity. By the detection of the NIR phosphorescence of ¹O₂ and evaluation of the photostability of single QDs in aerobic, anaerobic, and ¹O₂ scavenger‐enriched environments, we disclose relations of Auger ionization and ¹O₂‐mediated oxidation to the PL stability of single QDs, which will be useful during the formulation of QD‐based single‐molecule imaging tools and single‐photon devices.     

Synthesis and properties of sulfonated polyimides derived from bis(sulfophenoxy) benzidines

A series of aromatic sulfonated polyimides (SPIs) bearing sulfophenoxy side groups have been successfully synthesized and evaluated as polymer electrolyte membranes for fuel cell applications. The SPIs had high viscosity and gave tough and flexible membranes. The SPI membranes showed anisotropic membrane swelling in water with much larger dimensional change in thickness direction than in plane one. They showed the better proton‐conducting performance even in the lower relative humidity (RH) range than the other SPI membranes, for example, a high proton conductivity of 0.05 S/cm at 50 % RH and 120 °C. They maintained high mechanical strength and conductivity after aging in water at 130 °C for 500 h, showing much better water stability compared with the main‐chain‐type SPI and side‐chain‐type SPI membranes reported so far. In polymer electrolyte fuel cells (PEFCs) operated at 90 °C and 84–30%RH, they showed fairly high cell performances and have high potential for PEFC applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1463–1477, 2009     

Equivalence Between Canonical Gibbs Measures and Stationary Measures for Stochastic Lattice-Gas Model

It is proved that, under appropriate conditions on the jump rate and potential, one- and two-dimensional stochastic lattice-gas models (exclusion process with speed change) have only canonical Gibbs measures as their stationary measures. This extends the previously known result, which treats only a special jump rate and potential.     

Single electron charging of InAs quantum dots characterized by δ-doped channel conductivity

The electron tunneling through single self-assembled InAs dot in split-gate δ-doped channel transistor structure is reported for the first time. In the nearly pinch-off conditions, the channel current was found to manifest itself single-electron tunneling through a self-assembled InAs dot buried in adjacent to the channel. The line shape of the single-electron tunneling current through a single InAs dot is discussed.     

Vocal fold vibration of the canine larynx: Observation from an infraglottic view

The authors studied the vibratory action of the canine vocal fold from the tracheal side utilizing high-speed cinematography. Five excised canine larynges were used, and the lower surface of the vocal fold of three of them were marked with India ink as a tracer of a specific point on the vocal fold. A mucosal prominence, called the mucosal upheaval, appeared between the anterior commissure and the vocal process. Vibration was not seen below the mucosal upheaval. The mucosal wave started to move medially from just above the mucosal upheaval. The mucosal wave then became the free edge (lower lip) and collided with that of the other side at the midline. After collision, the lower lip moved upward to become the upper lip. At the same time, a part of the lower lip reflected laterally. The mucosal wave of the next cycle started from just above the mucosal upheaval during an opening phase. The mucosal upheaval vibrated with a low amplitude and with an earlier phase than the other portion of the vocal fold. The increase in tension of the vocal fold did not change the basic vibratory pattern of the mucosal upheaval, the mucosal wave, or the free edge. However, analysis of the mark before and after the increase in tension revealed that the mucosal upheaval occurred more medially or above when the vocal fold tension increased.     

The absolute cross sections for the quenching of cadmium 5 3P1 and 5 3P0 atoms by carbon monoxide,carbon dioxide and nitric oxide

Absolute cross sections for the quenching of Cd(5 ³P₁ and Cd(5 ³P₀) by carbon monoxide, carbon dioxide and nitric oxide have been determined by a phase-shift method. It was found that carbon monoxide deactivates the Cd³P₁) atoms not only to the ground state, Cd(¹S₀), but also to the metastable state, Cd(³P₀), and that the cross section for the latter process is ten times larger than that for the former one. On the contrary, carbon dioxide quenches Cd(³P₁) atoms to the ¹S₀ state without producing Cd(³P₀) atoms. The quenching efficiency by nitric oxide was considerably large compared with those of carbon mono- and di-oxides. These quenching cross sections were compared with those of other excited metal atom states.