Synthesis of a conformationally locked version of puromycin amino nucleoside

[reaction: see text] A conformationally locked carbocyclic version of puromycin amino nucleoside was synthesized via Mitsunobu coupling of a 3-azido-substituted carbocyclic moiety with 6-chloropurine without interference from the azido group reacting with triphenylphosphine. The requisite 3-azido-substituted carbocyclic pseudosugar was prepared by a double inversion of configuration at C3' (nucleoside numbering) involving a nucleophilic displacement with azide.     

Some New Features in the Pseudoscalar Meson and Vector Meson Photoproductions

We investigate the role of the t-channel meson exchange in various photoproduction processes to discuss features of the respective production mechanism. For the less model-dependent analysis we work with the t-channel meson pole reggeized in the Born approximation amplitude. With the meson–baryon coupling constants chosen consistently with symmetry prediction we show that the Reggeized pole model could reproduce the experimental data to a good degree in the lower energy region. Numerical consequences show the significance of the tensor meson exchange in the γ p → K ⁺Λ, the dominance of the pseudoscalar meson exchange in the πΔ (and KΣ*) processes, and the sizable role of the vector-meson magnetic moment in the charged ρ (and K*) photoproductions, respectively. These new features from the present analyses could provide a useful guide for future study of the N* resonances in the low energy region.     

Recent approaches for clickable poly(2-oxazoline)-based functional stimuli-responsive polymers and related applications

Abstract

Poly(2-oxazoline)s (POxs) are well-known thermo-responsive polymers that exhibit reversible hydrophilic–hydrophobic phase transitions at the lower critical solution temperature (LCST). Using living cationic ring-opening polymerisation, various functional groups can be introduced into POxs. Several clickable POxs with propargyl or azide end groups have been designed and subsequently reacted with various functional groups to prepare multifunctional POxs that respond to stimuli such as temperature, pH, chemicals and light. In this article, we briefly review recent approaches for clickable POx-based functional stimuli-responsive polymers and related applications.     

A fast automatic calibration system for a sound level meter in an anechoic room

A fast automatic calibration system for a sound level meter in an anechoic environment has been developed. The precise and fast generation of the constant frequency-independent acoustic pressure field and reduction of digital voltmeter readout to sound pressure level were achieved by a newly designed software algorithm, assuming the system linearity. The performance test justified the assumed linearity, and showed that the searching speed was sufficiently fast within the small error limit.     

Preparation and Characterization of Electroactive Anion‐Exchange Acrylic Polymer–Gold Composites

The characteristics and performance of an ionic polymer–metal composite (IPMC), prepared with an anion‐exchange acrylic copolymer, was examined. The acrylic copolymer was synthesized by the radical copolymerization of fluoroalkyl methacrylate and 2‐(dimethyl amino)ethyl methacrylate(AMA). Effects of the AMA repeating unit's content in the copolymer and effects of the anion type present on the actuation of the IPMC were observed. The optimal content of 19.4 wt% AMA in the IPMC copolymer yielded the best actuation. The actuation also improved according to the type of anion present in the composite, in the following order: Br^???4 ^?.     

EPR and photoluminescence properties of green light emitting LaAl11O18:Mn phosphors

The LaAl₁₁O₁₈:Mn²⁺ powder phosphor has been prepared using a self-propagating synthesis. Formation and homogeneity of the LaAl₁₁O₁₈:Mn²⁺ phosphor has been verified by X-ray diffraction and energy dispersive X-ray analysis respectively. The EPR spectra of Mn²⁺ ions exhibit resonance signals with effective g values at g≈4.8 and g≈1.978. The signal at g≈1.978 exhibits six-line hyperfine structure and is due to Mn²⁺ ions in an environment close to tetrahedral symmetry, whereas the resonance at g≈4.8 is attributed to the rhombic surroundings of the Mn²⁺ ions. It is observed that the number of spins participating in resonance for g≈1.978 increases with decreasing temperature obeying the Boltzmann law. Upon 451 nm excitation, the photoluminescence spectrum exhibits a green emission peak at 514 nm due to ⁴T₁ (G)→⁶A₁ (S) transition of Mn²⁺ ions. The crystal field parameter Dq and Racah inter-electronic repulsion parameters B and C have been evaluated from the excitation spectrum.     

The preparation of highly ordered TiO2 nanotube arrays by an anodization method and their applications

The tubular-shaped nanostructure of TiO(2) is very interesting, and highly ordered arrays of TiO(2) nanotubes (TNTs) can be easily fabricated by anodization of the Ti substrate in specific electrolytes. Here in this feature article, we review synthesis methods for various TNTs including normal, alloy, and architectural forms such as bamboos, lace, and flowers. Specific nanosize architectures such as bamboo and lace types can be regulated by alternating voltage and further anodizing. In order to extend light response of TNTs to visible solar spectra, various dopings of specific elements have been discussed. The normal and modified TNTs are suggested for applications such as dye sensitized solar cells, water splitting, photocatalytic degradation of pollutants, CO(2) reduction, sensors, energy storage devices including Li ion batteries and supercapacitors, and other applications such as flexible substrate and biomaterials.     

Highly interconnected ordered mesoporous carbon-carbon nanotube nanocomposites: Pt-free, highly efficient, and durable counter electrodes for dye-sensitized solar cells

We report the preparation of highly interconnected ordered mesoporous carbon-carbon nanotube nanocomposites which show Pt-like dye-sensitized solar cell (DSSC) efficiency and remarkable long-term durability as DSSC counter electrodes.     

Synthesis,characterisation, luminescence and defect centres in solution combustion synthesised CaZrO3:Tb3+ phosphor

Tb³⁺ doped CaZrO₃ has been prepared by an easy solution combustion synthesis method. The combustion derived powder was investigated by X-ray diffraction, Fourier-transform infrared spectrometry and scanning electron microscopy techniques. A room temperature photoluminescence study showed that the phosphors can be efficiently excited by 251 nm light with a weak emission in the blue and orange region and a strong emission in green light region. CaZrO₃:Tb³⁺ exhibits three thermoluminescence (TL) glow peaks at 126 °C, 200 °C and 480 °C. Electron Spin Resonance (ESR) studies were carried out to study the defect centres induced in the phosphor by gamma irradiation and also to identify the centres responsible for the TL peaks. The room temperature ESR spectrum of irradiated phosphor appears to be a superposition of two distinct centres. One of the centres (centre I) with principal g-value 2.0233 is identified as an O^? ion. Centre II with an axial symmetric g-tensor with principal values g_=1.9986 and g_?=2.0023 is assigned to an F⁺ centre (singly ionised oxygen vacancy). An additional defect centre is observed during thermal annealing experiments and this centre (assigned to F⁺ centre) seems to originate from an F centre (oxygen vacancy with two electrons). The F centre and also the F⁺ centre appear to correlate with the observed high temperature TL peak in CaZrO₃:Tb³⁺ phosphor.