bluuebunny/crossref_metadata_2025_split huggingface dataset:
Postfunctionalization of polyoxanorbornene via sequential Michael addition and radical thiol‐ene click reactions
Authors: Durmaz Hakan , Butun Muge , Hizal Gurkan , Tunca Umit 
Published: May 2012

AbstractWe demonstrated the successful postfunctionalization of poly(oxanorbornene imide) (PONB) with two types of double bonds using sequential orthogonal reactions, nucleophilic thiol‐ene coupling via Michael addition and radical thiol‐ene click reactions. First, the synthesis of PONB with side chain acrylate groups is carried out via ring‐opening metathesis polymerization and nitroxide radical coupling reaction, respectively. Subsequently, the resulting polymer having two different orthogonal functionalities, main chain vinyl and side chain acrylate, is selectively modified via two sequential thiol‐ene click reactions, nucleophilic thiol‐ene coupling via Michael addition and photoinduced radical thiol‐ene. The orthogonal reactivity of two diverse double bonds, vinyl and acrylate functionalities, for the abovementioned consecutive thiol‐ene click reactions was first demonstrated on the model compound. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Formation of a crosslinked POSS network by an unusual hydrosilylation: Thermo‐oxidative stabilization of the α‐cristobalite phase in its amorphous regions
Authors: Kolel‐Veetil Manoj K. , Fears Kenan P. , Qadri Syed B. , Klug Christopher A. , Keller Teddy M. 
Published: May 2012

AbstractA semicrystalline inorganic–organic hybrid crosslinked network containing polyhedral oligomeric silsesquioxane (POSS) cores was constructed by the unusual hydrosilylation of the terminal vinyl groups of an internal acetylene‐containing silane linker by a POSS monomer. Products from the thermal treatments of this network in either argon or air at 250, 550, and 1000 °C, respectively, were characterized by Fourier transform infrared, Solid‐state 13C and 29Si magic angle spinning NMR, X‐ray diffraction and XPS analyses. The highly symmetrically functionalized POSS silica clusters, in the fluorite silica phase, in the network were found to remain unchanged on thermal treatment possibly due to the shielding of the silica core by the functionalities and a cancellation of thermal stresses on the silica core. Stabilization of the metastable α‐cristobalite phase, which is typically formed on cooling by a β‐ to α‐transition of the β‐cristobalite phase formed above 1400 °C, was observed in the amorphous regions in the network sample treated only to 1000 °C in air. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Phospha‐Michael addition to enone‐containing triglyceride derivatives as an efficient route to flame retardant renewable thermosets
Authors: Moreno Maryluz , Lligadas Gerard , Ronda Joan C. , Galià Marina , Cádiz Virginia 
Published: May 2012

AbstractA novel phosphorus‐containing vegetable oil (PETR) was prepared through phospha‐Michael addition of a diphenyl phosphine oxide to the enone derivative of high‐oleic sunflower oil (ETR). The reaction was investigated using the enone derivative of methyl oleate under conventional thermal heating and microwave irradiation. The kinetic study showed a great enhancement of reaction rate for the microwave‐initiated addition. The crosslinking of ETR with diaminodiphenylmethane (DDM) via aza‐Michael addition was also investigated under microwave irradiation, showing a noticeable acceleration of the curing. The new phosphorus‐containing triglyceride was crosslinked with DDM to obtain phosphorus‐containing vegetable oil‐based thermosets of different phosphorus contents. Limiting oxygen index values from 26.4 to 35.0 for the final materials were obtained, demonstrating that the flame retardant properties of vegetable oil‐based thermosets can be improved by adding covalently bonded phosphorus to the polymer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
In situ formation of Sn(IV) catalyst with increased activity in ε‐caprolactone and L‐lactide polymerization using stannous(II) 2‐ethylhexanoate
Authors: Chen Hsuan‐Ying , Fang Hsin‐Jou , Chen Yen‐Jen , Hsu Sodio C. N. , Lai Yi‐Chun , Ou Hsiu‐Wei , Peng Wei‐Te , Chang Ya‐Ju , Tsou Yu‐Chi , Wu Ting‐Yi , Chung Hsuan , Chen Yun , Huang Ta Chou , Wu Bo Sheng 
Published: May 2012

AbstractRing‐opening polymerization (ROP) of ε‐caprolactone and L‐lactide (LA) was studied using stannous(II) 2‐ethylhexanoate (Sn(Oct)2) with N,N‐dimethylformamide‐dimethyl acetal (DMF‐DMA). DMF‐DMA showed a tenfold improvement in catalytic activity over that of Sn(Oct)2 under the same conditions. It also enhanced the capability to control molecular weight in the synthesis of small molecular weight polymers of polycaprolactone and polylactide (PLA). The high molecular weight polymerization demonstrated a strong capability to control molecular weight for the polymerization of LA: a molecular weight of PLA exceeding 400,000 was obtained at very low catalytic loadings. The individual polymerization rates of other tin reagents with DMF‐DMA also clearly increased. Applying this methodology could drastically reduce the time and cost required for the fabrication of these products to increase the competitive advantage of manufacturers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Fabrication and proton conductivity of sulfonated silica composites prepared by postoxidization of mercaptomethoxysilane
Authors: Yasumoto Kazuhiro , Norisuye Tomohisa , Teranishi Yusuke , Tran‐Cong‐Miyata Qui , Nomura Shigeki 
Published: May 2012

AbstractSol–gel derived organic–inorganic hybrids containing phosphotungstic acid (PWA) have been prepared previously to obtain proton conductive membranes. However, leaking of PWA was a serious problem to achieve the higher proton conductivity. In this study, polyelectrolyte membranes functionalized with sulfonic acid groups were fabricated by the sol–gel method. Proton conductivity measurements were performed on an impedance analyzer at 80°C/95% RH. The functionalized polyelectrolyte membranes exhibited the proton conductivity σ ∼ 0.9 (S/cm) which was much higher than the previously reported hybrids containing PWA. Although the hybrids exhibited fairly high proton conductivity irrespective to the catalysts used, that under the low relative humidity strongly depends on the catalysts. Among the hybrids prepared in this study, the membrane synthesized with HCl showed outstanding proton conductive properties even at the low humidity thanks to the proton transport channel formed by the swelling of ionic clusters. This fact was confirmed by measuring the ion exchange capacity, water uptake, swelling rate, Fourier transform infrared spectroscopy, atomic force microscopy, and thermogravimetric analysis. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Novel approaches to flexible visible transparent hybrid films for ultraviolet protection
Authors: Calvo Mauricio E. , Castro Smirnov José R. , Míguez Hernán 
Published: May 2012

AbstractHerein, we present an overview of the most recent achievements and innovations regarding the development of flexible visible transparent films for selective ultraviolet (UV) shielding, with focus on those based on hybrid inorganic–organic materials. The main synthetic paths used nowadays to ensure a high degree of protection are reviewed. Polymers containing organic UV absorbing molecules, hybrid mixtures of polymers and nanoparticles, and the recently introduced series of structures displaying structural color, are identified as the three main types of materials used for this purpose. The use of biocompatible and flexible films to achieve spectrally selective UV protection can find applications in a wide diversity of fields such as photo‐treatment of skin diseases, food and beverage packing, and storage of cosmetics. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
Martensitic structure and magnetic domain transformation in melt‐spun Ni–Mn–Ga ferromagnetic ribbons
Authors: Chen Fenghua , Zhang Mingang , Chai Yuesheng , Gong Changwei 
Published: May 2012

AbstractNi53Mn23.8Ga23.2 ribbons were fabricated by melt‐spinning and subsequent high vacuum annealing process. The structure and magnetic properties of the as‐spun and annealed ribbons were investigated by X‐ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimeter (DSC), and vibrating sample magnetometer. All the samples exhibit an orthorhombic structure of a seven‐layered modulation at room temperature. The martensitic and its reverse transformation were clearly observed on all the samples. With increasing annealing temperature, the saturation magnetization increases while the coercivity decreases. It was found that the transformation becomes drastic in the sample annealed at 1073 K. In addition, an in situ observation on the evolution of magnetic domain patterns with temperature was carried out by means of magnetic force microscopy (MFM).
Strain–polarisation coupling and elastic constant determined from polarisation and strain curves in order–disorder uniaxial ferroelectrics
Authors: Gałązka Mirosław , Zieliński Piotr 
Published: May 2012

AbstractA practical method is developed to determine the strain dependence of the pseudospin–pseudospin interaction parameters in discrete models of the continuous order–disorder improper ferroelastic phase transitions from experimental data on the primary order parameter (polarisation). The temperature dependence of the mechanical strain can be then deduced from the spontaneous polarisation data only. It is also shown that the dependence of the elastic constant on the temperature can be obtained from the polarisation and the strain data. The temperature dependences of the coupling constant and the elastic constant between the molecular dipoles of the methylammonium ions in the uniaxial ferroelectrics (CH3NH3)5Bi2Cl11(MAPCB) and (CH3NH3)5Bi2Br11(MAPBB) are determined and shown to be at the origin of the particular shape of the polarisation and the strain curves.
Progress in growth, fabrication, and characterization of semiconductor photonic crystal nanocavities [Phys. Status Solidi B 248, No. 4, 892–896 (2011)]
Authors: Richards B. C. , Hendrickson J. , Olitzky J. D. , Gibson R. , Gehl M. , Kieu K. , Polynkin P. , Khitrova G. , Gibbs H. M. , Khankhoje U. K. , Homyk A. , Scherer A. , Kim J.‐Y. , Lee Y.‐H. 
Published: May 2012

AbstractAn error was made in the calculation of the photonic crystal mode volume. Fixing this error increases our mode volume by a factor of 2 and makes our claim of highest Q/V invalid.
Investigation of absolute and relative response for three different liquid chromatography/tandem mass spectrometry systems; the impact of ionization and detection saturation
Authors: Nilsson Lars B. , Skansen Patrik 
Published: May 2012

RATIONALEThe investigations in this article were triggered by two observations in the laboratory; for some liquid chromatography/tandem mass spectrometry (LC/MS/MS) systems it was possible to obtain linear calibration curves for extreme concentration ranges and for some systems seemingly linear calibration curves gave good accuracy at low concentrations only when using a quadratic regression function.METHODSThe absolute and relative responses were tested for three different LC/MS/MS systems by injecting solutions of a model compound and a stable isotope labeled internal standard. The analyte concentration range for the solutions was 0.00391 to 500 μM (128 000×), giving overload of the chromatographic column at the highest concentrations. The stable isotope labeled internal standard concentration was 0.667 μM in all samples.RESULTSThe absolute response per concentration unit decreased rapidly as higher concentrations were injected. The relative response, the ratio for the analyte peak area to the internal standard peak area, per concentration unit was calculated. For system 1, the ionization process was found to limit the response and the relative response per concentration unit was constant. For systems 2 and 3, the ion detection process was the limiting factor resulting in decreasing relative response at increasing concentrations.CONCLUSIONSFor systems behaving like system 1, simple linear regression can be used for any concentration range while, for systems behaving like systems 2 and 3, non‐linear regression is recommended for all concentration ranges. Another consequence is that the ionization capacity limited systems will be insensitive to matrix ion suppression when an ideal internal standard is used while the detection capacity limited systems are at risk of giving erroneous results at high concentrations if the matrix ion suppression varies for different samples in a run. Copyright © 2012 John Wiley & Sons, Ltd.
A simplified method for busulfan monitoring using dried blood spot in combination with liquid chromatography/tandem mass spectrometry
Authors: Ansari Marc , Uppugunduri Chakradhara Rao S. , Déglon Julien , Théorêt Yves , Versace François , Gumy‐Pause Fabienne , Ozsahin Hulya , Dayer Pierre , Desmeules Jules , Daali Youssef 
Published: May 2012

RATIONALEBusulfan (Bu) is an important component of the myeloablative conditioning regimen prior to hematopoietic stem cell transplantation (HSCT) especially in children. Intravenously administered Bu exhibits a therapeutic window phenomenon requiring therapeutic drug monitoring. Analytical methods developed for Bu routine monitoring were aimed at using low volumes of biological fluids and development of simple procedures to facilitate the dosage adjustment. In this report, we describe a simple, rapid method for Bu measurement using dried blood spots (DBS) from only 5 μL of whole blood.METHODSBu extracted from DBS with methanol was measured by high‐performance liquid chromatography with electrospray ionization and tandem mass spectrometry in multiple reaction monitoring mode using D8‐Bu as an internal standard. The method was in‐house validated evaluating trueness, repeatability, within‐laboratory reproducibility, specificity and the lower limit of quantification (LLOQ).RESULTSThe method was linear in the calibration range of 100–2000 ng mL–1 (r2 >0.99) encompassing the therapeutic concentrations of Bu. A good trueness (<14%), precision (<10%), and recovery (100%) were observed during validation of the method with quality controls of 300, 600 and 1400 ng mL–1. The LLOQ was determined as 50 ng mL–1 and no matrix or carryover effects were observed. The validated method was applied to measure Bu levels in four children receiving infusion of Bu prior to HSCT. A good correlation was observed between the Bu levels measured by DBS and dried plasma spot (DPS) (r2 = 0.96) and between DPS and the GC/MS method (r2 = 0.92). Bu was found to be stable in DBS up to 6 h at room temperature and for 24 h at 4°C.CONCLUSIONSThe new DBS method facilitates earlier dosage adjustment during Bu therapy by its specific and simple procedure using 5 μL of whole blood. Copyright © 2012 John Wiley & Sons, Ltd.
Active capillary plasma source for ambient mass spectrometry
Authors: Nudnova Maryia M. , Zhu Liang , Zenobi Renato 
Published: May 2012

RATIONALEImaging mass spectrometry with high spatial resolution has become a rapidly developing area of mass spectrometric research. Many scientific and industrial problems deal with mass spectrometric analysis at ambient pressures. This requires efficient transport and ionization of small amounts of substance.METHODSAn active sampling capillary based on a dielectric barrier discharge was constructed for ambient mass spectrometry. The capillary serves as an ionization source as well as an atmospheric interface of the mass spectrometer. The analyzed samples are transported through the sampling capillary due to the pressure difference between the atmospheric environment and the vacuum in the mass spectrometer. Ionization of the transported samples is provided by a low‐temperature dielectric barrier discharge. This active capillary was shown to work in a robust fashion for ionizing both gas‐phase and laser‐ablated solid‐phase samples.RESULTSThe geometry of the electrodes was found to play a crucial role in ionization efficiency. The capillary was optimized in order to perform surface analysis of solid samples. Sensitivity tests were carried out to characterize different active capillary constructions. The sensitivity of the constructed active capillary was 0.1 ppb (relative concentration of a gaseous sample in ambient air). The active capillary was able to detect samples evaporated from a solid surface. With the active capillary source, it was possible to detect anthracene traces evaporated from a surface located 3 cm from the capillary inlet.CONCLUSIONSA plasma‐based active capillary ionization source was constructed. This concept of an active sample inlet should broaden the range of applications of ambient mass spectrometry. Copyright © 2012 John Wiley & Sons, Ltd.
Isomerization of cannabidiol and Δ9‐tetrahydrocannabinol during positive electrospray ionization. In‐source hydrogen/deuterium exchange experiments by flow injection hybrid quadrupole‐time‐of‐flight mass spectrometry
Authors: Broecker Sebastian , Pragst Fritz 
Published: May 2012

RATIONALELiquid chromatography/tandem mass spectrometry (LC/MS/MS) is frequently used for analysis of cannabinoids in drug abuse control. Despite differences in structure, the isomers Δ9‐tetrahydrocannabinol (THC) and cannabidiol (CBD) provide identical fragment spectra after positive electrospray ionization (ESI). For elucidation of the reason, hydrogen/deuterium (H/D) exchange experiments were performed.METHODSSolutions of THC and CBD in D2O/acetonitrile (50:50, v/v) were flow‐injected into acetonitrile as the mobile phase and measured by hybrid quadrupole‐time‐of‐flight mass spectrometry (FI‐QTOF‐MS) in targeted MS/MS mode. The MS and collision‐induced dissociation (CID) spectra at 10, 20 and 40 eV were interpreted with respect to number and position of exchanged hydrogen atoms. For comparison the same measurements were preformed in H2O, after addition of 0.5% formic acid and with negative ESI.RESULTSDepending on injected volume and position in the response curve, up to 7 or 8 hydrogen atoms were exchanged by deuterium in THC or CBD. Positive ESI CID spectra were available for precursors with up to 4 exchanged D‐atoms and showed that besides the OH groups also an H/D exchange at carbon atoms of the non‐aromatic part of the molecules occurred for both THC and CBD. After negative ESI, no H/D exchange in addition to the OH groups and different CID spectra of both substances was found.CONCLUSIONSInjection of the investigated substances in D2O and measurement by FI‐QTOF‐MS proved to be an efficient way to perform H/D exchange experiments. The results were interpreted as an acid‐catalyzed in‐source equilibration between THC and CBD leading to the same precursor ions and to an H/D exchange in the methyl groups under the increased acidic conditions in the positive ESI droplets. Therefore, in positive LC/ESI‐MS/MS, peak identification by CID spectra or by abundance ratio of multiple reaction monitoring (MRM) transitions is not sufficient for unambiguous discrimination between THC and CBD and must be supported by retention time or other experimental evidence. Copyright © 2012 John Wiley & Sons, Ltd.
Analysis of plasma nucleotides in rat by micellar electrokinetic capillary chromatography/electrospray ionization mass spectrometry
Authors: Bhowmik Salil Kumar , Jung Byung Hwa 
Published: May 2012

RATIONALEThe aim of this study was to establish a simultaneous quantitative analysis method of nine endogenous nucleotides in rat plasma using micellar electrokinetic capillary chromatography/electrospray ionization mass spectrometry (MEKC/ESI‐MS).METHODSTo select the optimum conditions for separation of the nucleotides, various pH, concentrations of running buffers and surfactants were tested. Ammonium acetate (20 mM) containing the surfactant dodecyltrimethylammonium bromide (2 mM, pH 3.5) was selected as the micellar running buffer. The plasma samples were prepared by precipitating the proteins with 2 mM EDTA in 60% ethanol. The samples were analyzed using capillary electrophoresis (CE)/MS and selected ion monitoring (SIM) mode with positive ionization. CE was performed using a silica capillary column in reversed polarity mode.RESULTSThe limits of detection (LODs) and limits of quantification (LOQs) of the nucleotides ranged from 0.05–5 and 2.0–20 μM, respectively. The calibration curves were linear (R2 >0.99) for all analytes, and the accuracy and precision were within ±15%. The developed method was applied to the analysis of nucleotides in rat plasma that was collected after oral administration of acetaminophen (1000 mg/kg/day) to evaluate the changes in plasma nucleotide levels under hepatotoxic conditions.CONCLUSIONSDecreased level of GTP and increased level of cytosine nucleotides were found to be associated with liver toxicity, which led to the conclusion that liver toxicity is closely related to changes in nucleotide levels in plasma. Copyright © 2012 John Wiley & Sons, Ltd.
Electrochemistry/liquid chromatography/mass spectrometry to demonstrate irreversible binding of the skin allergen p‐phenylenediamine to proteins
Authors: Jahn Sandra , Faber Helene , Zazzeroni Raniero , Karst Uwe 
Published: May 2012

RATIONALEpara‐Phenylenediamine (PPD) is a potent and well‐known allergen, which is commonly used in hair or fur dyes and can cause severe allergic contact dermatitis. In this work, the skin‐sensitizing potential of PPD with respect to the conjugation of proteins was evaluated using an approach without animal testing.METHODSElectrochemistry (EC) coupled offline to liquid chromatography (LC) and electrospray ionization mass spectrometry (ESI‐MS) was employed to convert the pre‐hapten PPD into its reactive hapten analogs. A previous study had already shown that this purely instrumental method is suitable for accelerating and simulating the various oxidation processes, which PPD may undergo, and that the emerging products are prone to react with soft thiol groups of small nucleophiles like glutathione and cysteine.RESULTSThis investigation was extended by successfully demonstrating adduct formation between EC‐generated PPD oxidation products and the three proteins β‐lactoglobulin A (β‐LGA), human serum albumin and human hemoglobin. A tryptic digest of modified β‐LGA provided evidence for irreversible protein binding of monomeric PPD, a PPD dimer and the PPD trimer known as Bandrowski's Base. It was shown that the main oxidation product p‐phenylene quinone diimine, and the reactive oligomerized species, primarily attack the free thiol function of proteins rather than other nucleophilic amino acid residues.CONCLUSIONSThe pre‐hapten PPD was efficiently activated upon EC oxidation and the resulting species were further reacted with different proteins leading to diverse hapten‐protein complexes. Thereby, problems related to the complex matrix present in conventional in vitro or in vivo methods could effectively be avoided. Copyright © 2012 John Wiley & Sons, Ltd.