Effect of temporal resolution on the estimation of left ventricular function by cardiac MR imaging

The aim of this study was to investigate the effect of temporal resolution on the estimation of left ventricular (LV) function by cardiac magnetic resonance (MR) imaging using a steady-state free precession (SSFP) sequence. Left ventricular function was assessed by cine MR imaging using a segmented SSFP sequence in 10 healthy volunteers. Views per segment (VPS) were set at 8 and 20, resulting in high and low true temporal resolution, respectively. Irrespective of VPS, images were reconstructed at 40 cardiac phases, providing high apparent temporal resolution. Data were analyzed using 40, 20 and 10 phases to simulate different apparent temporal resolutions. Increasing the cardiac phases used for analysis slightly decreased mean end-systolic volume (ESV) and slightly increased mean ejection fraction (EF). No substantial difference in estimates of end-diastolic volume (EDV) was found between VPSs of 8 and 20. Imaging with a VPS of 20 yielded a larger ESV and smaller EF than imaging with a VPS of 8 when 40 phases were used. In conclusion, low true temporal resolution causes overestimation of ESV and underestimation of EF. Improvement of apparent temporal resolution mildly reduces but does not eliminate the errors caused by low true temporal resolution.     

High Refractive-Index Microspheres as Optical Cavity Structure

Microspheres of refractive index of n_D > 2.0 have been investigated. The organic-inorganic hybrid microspheres of n_D = 1.72 were prepared by the vibrating orifice technique using titanium-tetra-n-butoxide (TTBu) and diphenyldimethoxysilane (DPhDMS). For lasing demonstration, Eu³⁺-doped microspheres were prepared using europium (III) thenoyltrifluoroacetonate [Eu(TTFA)₃] as the dopant. The particles have good spherical shape, smooth surface and high optical transparency. The diameters of the particles could be controlled to within 0.1 m. Subsequent heating of the microspheres at 550°C under oxygen atmosphere resulted in an increase in the refractive index up to n_D = 2.6 with retention of the spherical shape. Resonant emission was confirmed from Eu^{3 +}-doped microspheres after heating at 400–550°C, by pumping with the 514.5 nm line of a CW- Ar⁺laser.     

Molecular optical gating devices based on polymer nanosheets assemblies

We describe here a polymer nanosheet assembly that serves as a molecular photoswitching and optical exclusive OR (EXOR) logic gate. Separate polymer nanosheets (monolayers) containing phenanthrene, anthracene, and dinitrobenzene chromophore were prepared by the Langmuir-Blodgett technique (LB films). A bilayer-couple, consisting of phenanthrene (sensitizer) monolayer and dinitrobenzene (acceptor) monolayer, and the other couple, of anthracene monolayer and dinitrobenzene monolayer, were confirmed to function as a photodiode showing current rectification on light irradiation. The two photodiodes are connected as each photocurrent direction becomes opposite. In the polymer photodiode array (LB films), anodic photocurrent was observed when the anthracene was selectively excited. On the other hand, cathodic photocurrent was observed by selective excitation of the phenanthrene. Moreover, the output photocurrent displayed a very small value when the phenanthrene and anthracene were excited simultaneously. The performance is discussed for this gate's application to an optical EXOR logic gate.     

Ni-catalyzed, ZnCl(2)-assisted domino coupling of enones, alkynes, and alkenes

A Ni(0)/ZnCl(2) system effectively promotes the coupling of enones and alkene-tethered alkynes. In the reaction with 1,6-enynes, the oxidative cyclization of Ni(0) species on enones across the alkyne part followed by ZnCl(2)-promoted cleavage generates alkenylnickel intermediates. Subsequent migratory insertion of the tethered alkene occurs with 5-exo-cyclization. When the resulting sigma-alkylnickel intermediates have beta-hydrogen atoms, the reaction terminates by beta-hydrogen elimination to provide cyclopentane derivatives. On the other hand, a sigma-alkylnickel intermediate that does not have beta-hydrogen atoms undergoes the insertion of a second alkene unit to cause a domino effect via a three-fold C-C bond formation process with and without the cleavage of one C-C bond.     

O-selectivity and utility of phosphorylation mediated by phosphite triester intermediates in the N-unprotected phosphoramidite method

Previously, O-selective phosphorylation on polymer supports in the N-unprotected phosphoramidite method could not be carried out because the amino groups of dA and dC have high reactivity toward tervalent phosphorus(III)-type phosphitylating reagents. In this paper, we developed a new coupling strategy named the "activated phosphite method" in which the phosphitylation is mediated by phosphite triester intermediates 1. Application of 1-hydroxybenzotriazole as the promoter to the solid-phase synthesis resulted in excellent O-selectivity of more than 99.7%. This O-selectivity was explained by the frontier molecular orbital interactions between the reactive intermediates and the nucleophiles such as the amino or hydroxyl groups of nucleosides. Furthermore, longer oligonucleotides were synthesized not only by a manual operation but also by a DNA synthesizer. The utility of our new method was demonstrated by the successful synthesis of a base-labile modified oligodeoxyribonucleotide having 4-N-acetyldeoxycytidine residues. Finally, DNA 20-mers containing dA or dC could be synthesized in good yields by use of a combined reagent of 6-trifluoromethyl-1-hydroxybenzotriazole and benzimidazolium triflate.     

Ruthenium-catalyzed hydrogenation of alkynylstannanes with migration of the stannyl group

Molecular hydrogen adds to aliphatic and aromatic alkynylstannanes in the presence of a ruthenium catalyst, pushing the stannyl group to the adjacent carbon atom to give alpha-substituted vinylstannanes. This is the first achievement of hydrogenation of alkynylstannanes, which is applicable also to the deuteration affording precursors for an important class of deuterium-labeled compounds.     

Photochemical ligation of DNA conjugates through anthracene cyclodimer formation and its fidelity to the template sequences

Anthracene readily forms photoadducts, anthracene dimers, and this photodimerization reaction has been well characterized. In general, however, the reaction requires close proximity and certain spatial alignment of both reaction partners. DNA could provide an ideal scaffold for accelerating the photocyclic addition. We synthesized a number of anthracene-DNA conjugates. The sequences of the conjugates, 5'AntODNn and 3'AntODNn (the length of methylene linkers: n = 3 or 6), were designed to bind adjacent sequences of the template with the anthracene units directed such that they stacked with each other. The conjugates were only dimerized in the presence of the template by light irradiation. The efficiency was affected by one-base displacement in the template sequence.     

Controllable photoinduced optical attenuation in a single-mode optical fiber by irradiation of a femtosecond pulse laser

Novel optical attenuation fibers were fabricated by the irradiation of a focused infrared femtosecond pulsed laser onto the core of a silica glass single-mode optical fiber. Optical attenuation at a wavelength of 1.55 microm proportionally increased with increasing numbers of irradiation points and was controllable under laser irradiation conditions. The single-mode property of the waveguide and the mode-field diameter of the optical fiber were maintained after irradiation of the femtosecond laser. It is suggested that the attenuation results from optical scattering at photoinduced spots formed inside the fiber core.