Evolution and characterization of fluorite-like nano-SrBi2Nb2O9 phase in the SrO-Bi2O3-Nb2O5-Li2B4O7 glass system

Transparent glasses of various compositions in the system (100−x)Li₂B₄O₇−x(SrO-Bi₂O₃-Nb₂O₅) (where x=10, 20, 30, 40, 50 and 60, in molar ratio) were fabricated via splat quenching technique. The glassy nature of the as-quenched samples was established by differential thermal analyses. X-ray powder diffraction (XRD) and transmission electron microscopic studies confirmed the amorphous nature of the as-quenched and crystallinity in the heat-treated samples. Fluorite phase formation prior to the perovskite SrBi₂Nb₂O₉ phase was analyzed by both the XRD and high-resolution transmission electron microscopy. Dielectric and the optical properties (transmission, optical band gap and Urbach energy) of these samples have been found to be compositional dependent. Refractive index was measured and compared with the values predicted by Wemple-Didomemenico and Gladstone-Dale relations. The glass nanocomposites comprising nanometer-sized crystallites of fluorite phase were found to be nonlinear optic active.     

Micromechanisms of failure in short-fiber-reinforced high-impact polystyrene under tensile loading

Injection-molded, short-glass-fiber-reinforced high-impact polystyrene was investigated under uniaxial tension with special attention to the effects of fiber and rubber concentration on fracture behavior. According to a fracture morphology study performed by polarized optical and scanning electron microscopy, crazes were consecutively initiated from rubber-styrene composite particles and from fiber ends. The rubber particles exhibited an intra-particle failure mode which resulted from the failure manner of the matrix becoming of a more brittle character with increasing fiber fraction. Fibers were surrounded by neigh boring growing crazes. Failure at the fiber-matrix interfaces proceeded with an increase in the number of crazes. With increasing concentration of the fibers, crazing at rubber particles appeared to be suppressed and crazing occurred more preferentially at the fiber ends, which accelerated a macroscopic fracture.Dedicated to Prof. H. H. Kausch on the occasion of his 60th birthday.     

Polymer‐Assisted Solution‐Phase Synthesis and Neurite‐Outgrowth‐Promoting Activity of 15‐Deoxy‐Δ12,14‐PGJ2 Derivatives

An efficient solution‐phase synthesis of rac‐15‐deoxy‐Δ^12,14‐PGJ₂ (15dPGJ₂) derivatives that contain variable α and ω chains based on a polymer‐assisted strategy and their neurite‐outgrowth‐promoting activity are described. The strategy for the synthesis of PGJ₂ derivatives involves the use of a vinyl iodide bearing cyclopentenone as a key intermediate, which undergoes Suzuki–Miyaura coupling and subsequent Lewis acid catalyzed aldol condensation for incorporation of the ω and α chains, respectively. For easy access to the PGJ₂ derivatives, a polymer‐supported catalyst and scavengers were adapted for use in these four diverse steps, in which workup and purification can be performed by simple filtration of the solid‐supported reagents. By using this methodology, we succeeded in the synthesis of 16 PGJ₂ derivatives with four alkyl boranes and four aldehydes. The neurite‐outgrowth‐promoting activity of the 16 synthetic compounds in PC12 cells revealed that the side‐chains play a major role in modulating their biological activity. The carboxylic acid on the α chain improved the biological activity, although it was not absolutely required. Furthermore, a PGJ₂ derivative with a phenyl moiety on the ω chain was found to exhibit an activity comparable to that of natural 15dPGJ₂.     

Hydrogen bonding in macrocyclic receptor systems

Abstract

The interactions of macrocyclic polyethers with alkali and alkaline earth cations have been well studied and much about their chemistry is now well understood. Less well examined or comprehended are hydrogen bond interactions. A combination of ion selective electrode binding constant determination techniques and fast atom bombardment mass spectrometry are brought to bear on this problem. It is found that all-oxygen crown ethers and their derivatives exhibit quite different complexation behaviour with ammonium salts than do their various azacrown counterparts.     

Catalytic enantioselective synthesis of atropisomeric 2-aryl-4-quinolinone derivatives with an N–C chiral axis

In the presence of an (R)-MOP-Pd₂(dba)₃ catalyst, the reaction of ortho-tert-butylaniline with 2-bromophenyl arylethynyl ketone proceeded via a tandem amination (1,4-addition of aniline to an ynone and subsequent intramolecular Buchwald–Hartwig amination) to afford axially chiral N-(2-tert-butylphenyl)-2-aryl-4-quinolinone derivatives with moderate enantioselectivity (up to 72% ee).     

Development of a stable isotope dilution UPLC‐MS/MS method for quantification of dexmedetomidine in a small amount of human plasma

Dexmedetomidine (Dex) is a selective central α2‐agonist with anesthetic properties and has been used in clinical practice for sedation in the intensive care unit (ICU) after operations. In this study, an analytical assay for the determination of Dex in a small amount of plasma was developed for the application to pediatric ICU trials. The quantification of Dex was constructed using the original stable isotope Dex‐d₃ for electrospray ionization‐tandem mass spectrometry (ESI‐MS/MS) in the selected reaction monitoring mode. A rapid ultra‐performance liquid chromatography technique was adopted using ESI‐MS/MS with a runtime of 3 min. Efficacious concentration levels (50 pg/mL to 5 ng/mL) could be evaluated using a very small amount of plasma (10 μL) from patients. The lower limit of the quantification was 5 pg/mL in the plasma (100 µL). For sample preparation, a solid‐phase extraction was used along with the OASIS‐HLB cartridge type. Recovery values ranged from 98.8 to 100.3% for the intra‐ [relative standard deviation (RSD), 0.9–1.3%] and inter‐ (RSD, 0.9–1.5%) day assays. A stable test had recovery values that ranged from 97.8 to 99.7% with an RSD of 1.0–1.9% for the process/wet extract, bench‐top, freeze–thaw and long‐term tests. This method was used to measure the Dex levels in plasma from pediatric ICU patients. In the clinical ICU trial, the small amount of blood (approximate plasma volume, 200 μL) remaining from blood gas analysis was reused and targeted for the clinical analysis of Dex in plasma. Copyright © 2013 John Wiley & Sons, Ltd.     

Application and analysis of a DSC-Raman spectroscopy for indium and poly(lactic acid)

Simultaneous measurement system of DSC-Raman spectroscopy and its analysis method are developed. The developed method was applied to the melting of Indium and the optimum laser irradiation condition was determined. The obtained result of the heat flow is similar to the modulated DSC and the precise melting temperature and the heat of fusion can be obtained from the analyzed DSC. DSC-Raman spectroscopy is also applied to PLLA. Analyzed data indicate the existence of the recrystallization behavior in addition to T _g and T _m. Corresponding to these transitions, Raman peak shifts, intensities, and widths varied. From those results, it is proved that DSC-Raman spectroscopy is useful for the analysis of thermal property of the polymer in connection with the polymer structure.     

Uric acid quantification in fingernail of gout patients and healthy volunteers using HPLC‐UV

The presence of elevated uric acid (UA) levels is a sign of gout, that is, hyperuricemia. In this study the monitoring of the UA levels in less‐invasive biological samples, such as the human fingernail, is suggested for the diagnosis and therapy of gout. Twenty‐six healthy volunteers (HV) and 22 gout patients (GP) were studied. The UA was extracted from human fingernail samples, then separated on an Inertsil ODS‐3 column (250 × 4.6 mm i.d., 4.0 μm, GL Sciences) by isocratic elution using methanol–74 mm phosphate buffer (pH 2.2) 2:98 (v/v). A UV detector was used to monitor the samples at 284 nm. Using the developed method, different UA concentrations were found in the GP and HV. When comparing the concentrations from GP with those from HV, a statistically significant correlation was observed between the UA (p < 0.01). In this study, the UA was confirmed as a potential biomarker for the diagnosis and therapy of gout. We have developed a novel sensitive, and simple method for the determination of UA in the fingernails of GP and HV. The human fingernail may serve as a noninvasive biosample for the diagnosis of gout. Copyright © 2016 John Wiley & Sons, Ltd.     

Determination of l‐tryptophan and l‐kynurenine derivatized with (R)‐4‐(3‐isothiocyanatopyrrolidin‐1‐yl)‐7‐(N,N‐dimethylaminosulfonyl)‐2,1,3‐benzoxadiazole by LC‐MS/MS on a triazole‐bonded column and their quantification in human serum

The concentrations of l ‐tryptophan (Trp) and the metabolite l ‐kynurenine (KYN) can be used to evaluate the in‐vivo activity of indoleamine 2,3‐dioxygenase (IDO) and tryptophan 2,3‐dioxygenase (TDO). As such, a novel method involving derivatization of l ‐Trp and l ‐KYN with (R)‐4‐(3‐isothiocyanatopyrrolidin‐1‐yl)‐7‐(N,N‐dimethylaminosulfonyl)‐2,1,3‐benzoxadiazole (DBD‐PyNCS) and separation by high‐performance liquid chromatography (HPLC) with tandem mass spectrometric (MS/MS) detection on a triazole‐bonded column (Cosmosil HILIC®) was developed to determine their concentrations. The optimized mobile phase, CH₃CN/10 mm ammonium formate in H₂O (pH 5.0) (90:10, v/v) eluted isocratically, resulted in satisfactory separation and MS/MS detection of the analytes. The detection limits of l ‐Trp and l ‐KYN were approximately 50 and 4.0 pm , respectively. The column temperature affected the retention behaviour of the Trp and KYN derivatives, with increased column temperatures leading to increased capacity factors; positive enthalpy changes were revealed by van't Hoff plot analyses. Using the proposed LC‐MS/MS method, l ‐Trp and l ‐KYN were successfully determined in 10 μL human serum using 1‐methyl‐l ‐Trp as an internal standard. The precision and recovery of l ‐Trp were in the ranges 2.85–9.29 and 95.8–113%, respectively, while those of l ‐KYN were 2.51–16.0 and 80.8–98.2%, respectively. The proposed LC‐MS/MS method will be useful for evaluating the in vivo activity of IDO or TDO. Copyright © 2016 John Wiley & Sons, Ltd.