Carbon Nanotube Based Sensor for Simultaneous Determination of Acetaminophen and Ascorbic Acid Exploiting Multiple Response Optimization and Measures in the Presence of Surfactant

A simple procedure for the simultaneous determination of acetaminophen (AC) and ascorbic acid (AA) by differential pulse voltammetry (DPV) using a carbon nanotube paste electrode exploiting measures in cetylpyridinium bromide (CPB) medium is described. Under the best instrumental parameters of DPV, optimized by means of factorial design, the calibration plots in the range 100.0–700.0 µmol L^?1 (r=0.993) and 39.4–146.3 µmol L^?1 (r=0.995) with limits of detection of 7.1 and 2.1 µmol L^?1, were achieved for AA and AC, respectively. The developed method was successfully applied for the AC and AA determination in pharmaceutical formulations, whose accuracy was attested by comparison with HPLC method.     

ESR study of Mn2+ in GeTe and GeTeSi glasses

The electron spin resonance spectra of Mn²⁺ ions have been studied in Ge_xTe_100?x with x = 15, 17.5 and 20, and Ge_20?xTe₈₀Si_x with 0 ?x? 20. All samples are found to exhibit six hyperfine lines centered at g = 4.3 with hyperfine interaction constant A = 56 × 10^?4cm^?1. The g = 4.3 line is interpreted as being caused by Mn²⁺ ions incorporated in the amorphous network and surrounded by four Te atoms in an arrangement of orthorhombic symmetry. Some of the samples of GeTe show a g = 2.0 line. This line also appears after heat treatment in air at temperatures above the glass transition temperature. It is concluded that the g = 2.0 line is caused by Mn²⁺ ions in phase separated microcrystalline or concentrated regions of MnO in the glass.     

Palladium-Catalyzed Difunctionalization of 1,3-Diene with Amine and Disilane under a Mild Re-oxidation System

A highly regioselective and stereoselective difunctionalization reaction of 1,3-diene with amine and disilane to form C−N and C−Si bonds via a one-step Pd/Cu/O₂ system is disclosed. The difunctionalization reaction affords allylic silanes, including the allylic amine moiety, in up to 92 % yield in the absence of any acid, base, or external ligand. The developed synthetic methodology can be scaled to 100 g in high yield with high Z-selectivity, which demonstrates the feasibility of the reaction for industrial applications.     

Formation of the CuII–Phenoxyl Radical by Reaction of O2 with a CuII–Phenolate Complex via the CuI–Phenoxyl Radical

Reaction of Cu(ClO₄)₂ ⋅ 6 H₂O with a tripodal 2N2O ligand, H₂Me₂NL, having a p-(dimethylamino)phenol moiety, in CH₂Cl₂/MeOH (1:1 v/v) under basic conditions under an inert gas atmosphere gave [Cu(Me₂NL)(H₂O)] ( 1 ). The same reaction carried out under aerobic conditions gave [Cu(Me₂NL)(MeOH)]ClO₄ ( 2 ), which could be obtained also from the isolated complex 1 by reaction with O₂ in CH₂Cl₂/MeOH. The X-ray crystal structures of 1 and 2 revealed similar square-pyramidal structures, but 2 showed the (dimethylamino)phenoxyl radical features. Complex 1 exhibits characteristic Cu^II EPR signals of the d ground state in CH₂Cl₂/MeOH at 77 K, whereas 2 is EPR-silent. The EPR and X-ray absorption fine structure (XAFS) results suggest that 2 is assigned to the Cu^II–(dimethylamino)phenoxyl radical. However, complex 1 showed different features in the absence of MeOH. The EPR spectrum of the CH₂Cl₂ solution of 1 exhibits distortion from the d ground state and a temperature-dependent equilibrium between the Cu^II–(dimethylamino)phenolate and the Cu^I–(dimethylamino)phenoxyl radical. From these results, Cu^II–phenoxyl radical complex 2 is concluded to be formed by the reaction of 1 with O₂ via the Cu^I–phenoxyl radical species.     

Optical techniques for active integratedantenna circuits

This paper reviews some of the recent efforts in the area of microwave–optical interactions applied to active integrated antennas and arrays. Two optical–microwave techniques and examples of their application are presented. First, antenna remoting via optical means is discussed. Second, optical control of microwave devices in active antenna circuits is demonstrated.     

Specific thermosensitive volume change of biopolymer gels derived from propylated poly(γ-glutamate)s

Thermosensitive biopolymers with an amphipathic structure were synthesized through the propyl esterification of the carboxyl groups of poly(γ-glutamic acid) (γ-PGA). The clouding temperature on heating was controlled by the addition of different amounts of NaCl and by the degree of esterification. The clearing temperature on cooling was independent of the aqueous milieu, presumably because of the strong multiple hydrogen bonds between the polymer chains formed in the collapsed state. The hydrogel of γ-PGA propylate crosslinked by a chemical reaction with hexamethylene diisocyanate also showed pH-responsive and thermoresponsive shrinking, but the volume recovery was incomplete during the cooling process. A Fourier transform infrared/attenuated total reflection study showed that the incomplete volume recovery might be associated with the amide hydrogen bonding being strengthened by the chemical crosslinkage. The addition of urea made the volume change complete. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4492–4501, 2004     

Site-specific valence-band X-ray photoelectron spectra of a SrTiO3 single-crystal by X-ray standing wave technique

Site-specific valence-band X-ray photoelectron spectra of SrTiO₃ (111) were successfully obtained by using X-ray standing wave technique. Contributions of the Ti and SrO₃ derived states to the valence-band spectra were clearly separated. The spectra provided not only site-specific but also bulk-sensitive information on the SrTiO₃ crystal because of the use of a high-energy synchrotron X-ray source (hν=4750 eV) for photoelectron excitation with the large escape depth. The electronic structures calculated by the DV-Xα method using a (Sr₈Ti₂₇O₁₀₈)⁹²⁻ cluster model well reproduced the observed structures in the valence-band spectra. The partial density of states of both Ti and Sr ions in SrTiO₃ were mainly distributed over the bottom of the valence-band to produce the covalent bonding with O ions.     

Vitamin D and bone: — How does vitamin D regulate bone formation and resorption? —

Vitamin D was discovered as an anti-rachitic agent, but even at present, there is no direct evidence to support the concept that vitamin D directly stimulates osteoblastic bone formation and mineralization. It appears to be paradoxical, but vitamin D functions in the process of osteoclastic bone resorption. Osteoclasts, the only cells responsible for bone resorption, develop from hematopoietic cells of the monocyte-macrophage lineage. In 1992, we hypothesized that a membrane-bound factor, designated as “osteoclast differentiation factor (ODF)”, is expressed on the plasma membrane of osteoblasts/stromal cells in response to osteotropic factors including the active form of vitamin D₃, 1α,25-dihydroxyvitamin D₃ [1α,25(OH)₂D₃]. Recently, four research groups including ours independently identified three key molecules (RANKL, RANK, and OPG) responsible for osteoclastogenesis. A long-sought-after ligand, ODF, was identical to RANKL. RANKL was a member of the membrane-associated TNF ligand family, which induced differentiation of spleen cells (osteoclast progenitors) into osteoclasts in the presence of M-CSF. RANK, a member of the TNF receptor family, was a signaling receptor essential for the RANKL-mediated osteoclastogenesis. OPG, a secreted member of the TNF receptor family, was a decoy receptor for RANKL. The discovery of RANKL, RANK and OPG opens a new era in the study of bone biology and the therapy of several metabolic bone diseases such as osteoporosis, rheumatoid arthritis, and periodontal diseases.