bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation, characterization, and properties of poly(thioether ether ketone imide)s from isomeric bis(chlorophthalimide)s
Authors: Wei Haibing , Wu Xueshi , Hu Benlin , Fang Xingzhong 
Published: August 2010

AbstractA series of novel poly(thioether ether ketone imide)s (PTEKIs) bearing the thioether and ketone groups with high molecular weights (Mw: 87,800–150,100 g/mol) were synthesized by aromatic nucleophilic substitution reaction. The polymers were characterized by Fourier transform infrared spectra (FT‐IR), 1H NMR, GPC, and elemental analysis. The composition of the copolymers varied systematically in order to study its relation with polymer properties. Increase in the content of 3‐substituted phthalimide moiety in the polymer backbone improves the solubility in tested solvents, and increases the glass transition temperature (Tg), whereas copolymers with high content of 3‐substituted phthalimide demonstrated to be inferior thermal stability. The PTEKI films also exhibited good optical transparency, including the cutoff wavelengths lower than 400 nm and transmittances higher than 77% at 450 nm. Copyright © 2010 John Wiley & Sons, Ltd.
Comparative study of the optical, electrochemical, electrolumiscent, and photovoltaic properties of dendritic pendants modified poly(p‐phenylene vinylene)s
Authors: Tan Zhanao , Zhang Wenqing , Qian Deping , Zheng Hua , Xiao Shengqiang , Li Yongfang , Tang Rupei , Xi Fu 
Published: August 2010

AbstractIn this study, the optical, electrochemical, electrolumiscent, and photovoltaic properties of a series of poly(p‐phenylene vinylene) (PPV) derivatives bearing different dendritic pendants, poly{2‐[3′,5′‐bis(2″‐ethylhexyloxy)benzyloxy]‐1,4‐phenylenevinylene} (BE‐PPV), poly{2‐[2′,5′‐bis(3″,7″‐dimethyl)octyloxy]‐1,4‐phenylenevinylene} (BD‐PPV), poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene] (MEH‐PPV), poly{2‐[3′,5′‐bis(2″‐ethylhexyloxy)benzyloxy]‐1,4‐phenylenevinylene}‐co‐poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene] (BE‐co‐MEH‐PPV), and poly{2‐[2′,5′‐bis(3″,7″‐dimethyl)octyloxy]‐1,4‐phenylenevinylene}‐co‐poly[2‐methoxy‐5‐(3′,7′‐dimethyloctyloxy)‐1,4‐phenylenevinylene] (BD‐co‐MDMO‐PPV), were investigated. The steric pendants strongly affect the absorption spectra, photoluminescence (PL) sepctra, the onset oxidation/reduction potentials, and further affect the electrolumiscent and photovoltaic properties. Copolymerization can reduce the steric effect and improve the electrolumiscent and photovoltaic properties. The brightness of light‐emitting diodes base on copolymer BE‐co‐MEH‐PPV and BD‐co‐MDMO‐PPV reached 3988 and 3864 cd/m2, respectively, much higher than that based on homopolymer BE‐PPV (523 cd/m2) and BD‐PPV (333 cd/m2), also higher than that based on MEH‐PPV (3788 cd/m2). The power conversion efficiency (PCE) of solar cells based on BE‐co‐MEH‐PPV and BD‐co‐MDMO‐PPV reached 1.41, 0.76%, respectively, much higher than that based on BE‐PPV (0.24%) and BD‐PPV (0.14%). Copyright © 2010 John Wiley & Sons, Ltd.
Simultaneous analysis of diosgenin and sarsasapogenin in Asparagus officinalis byproduct by thin‐layer chromatography
Authors: Wang Liwei , Wang Xiaodong , Yuan Xiaofan , Zhao Bing 
Published: August 2010

AbstractIntroduction – Asparagus officinalis L. has several biological activities including antifungal, antiviral and antitumoral activities due to the steroidal saponins. Normally diosgenin and sarsasapogenin are analysed separately by thin‐layer chromatography or high‐performance liquid chromatography (HPLC‐UV or HPLC‐ELSD), which is time‐consuming and expensive, so we need to find a rapid solution to this problem.Objective – To develop a sensitive, rapid and validated TLC method for simultaneous detection and quantification of diosgenin and sarsasapogenin.Methodology – Samples were prepared by extraction of A. officinalis with 70% aqueous ethanol to get steroidal saponins, and then hydrolysed using 36 mL 2 m hydrochloric acid for 3 h. The hydrolysis product was extracted with chloroform, and then analysed by TLC, the results of which were verified by HPLC and HPLC‐MS.Results – The retention factor (Rf) of diosgenin and sarsasapogenin on TLC plate were 0.49 and 0.6, respectively. After calculation from the regression equation of the standard curve, the contents of diosgenin and sarsasapogenin in the A. officinalis extract were 0.27–0.46 and 0.11–0.32%, respectively.Conclusion – The study showed that thin‐layer chromatography can be applied for the determination of diosgenin and sarsasapogenin in the oldest tissue of A. officinalis, and also can be conducted for screening of sapogenin in other plant or extracts. Copyright © 2010 John Wiley & Sons, Ltd.
Determination and comparative analysis of major iridoids in different parts and cultivation sources of Morinda citrifolia
Authors: Deng Shixin , West Brett J. , Palu 'Afa K. , Jensen C. Jarakae 
Published: August 2010

AbstractIntroduction – Noni is a medicinal plant with a long history of use as a folk remedy in many tropical areas, and is attracting more attention worldwide. A comprehensive study on the major phytochemicals in different plant parts (fruit, leaf, seed, root and flower) and sources is of great value for fully understanding their diverse medicinal benefits.Objective – To quantitatively determine the major iridoid components in different parts of noni plants, and compare iridoids in noni fruits collected from different tropical areas worldwide.Methodology – The optimal chromatographic conditions were achieved on a C18 column with gradient elution using 0.1% formic acid aqueous formic acid and acetonitrile at 235 nm. The selective HPLC method was validated for precision, linearity, limit of detection, limit of quantitation and accuracy.Results – Deacetylasperulosidic acid (DAA) was found to be the major iridoid in noni fruit. In order of predominance, DAA concentrations in different parts of the noni plant were dried noni fruit > fruit juice > seed > flower > leaf > root. The order of predominance for asperulosidic acid (AA) concentration was dried noni fruit > leaf > flower > root > fruit juice > seed. DAA and AA contents of methanolic extracts of noni fruits collected from different tropical regions were 13.8–42.9 and 0.7–8.9 mg/g, respectively, with French Polynesia containing the highest total iridoids and the Dominican Republic containing the lowest.Conclusion – Iridoids DAA and AA are found to be present in leaf, root, seed and flower of noni plants, and were identified as the major components in noni fruit. Given the great variation of iridoid contents in noni fruit grown in different tropical areas worldwide, geographical factors appear to have significant effects on fruit composition. The iridoids in noni fruit were stable at the temperatures used during pasteurisation and, therefore, may be useful marker compounds for identity and quality testing of commercial noni products. Copyright © 2010 John Wiley & Sons, Ltd.
Matrix solid‐phase dispersion with sand in chromatographic analysis of essential oils in herbs
Authors: Dawidowicz Andrzej L. , Wianowska Dorota , Rado Ewelina 
Published: August 2010

AbstractIntroduction – Matrix solid‐phase dispersion (MSPD) is a very simple, cheap and relatively quick sample preparation procedure which involves simultaneous disruption and extraction of various solid and semi‐solid samples due to the direct mechanical blending of the sample with a SPE sorbent, mainly C18. Little is known about MSPD application as a sample preparation method for the analysis of essential oil components in herbs.Objective – To evaluate if C18 sorbent, commonly used in MSPD process, can be substituted with sand in the procedure of essential oil analysis.Methodology – Essential oil extracts were obtained from mint, sage, chamomile, marjoram, savory and oregano using MSPD with C18 sorbent or sand, pressurised liquid extraction and steam distillation. Their qualitative and quantitative compositions ware established by GC‐MS and GC‐FID.Results – The results prove that C18 sorbent can be substituted with sand in the procedure of essential oil analysis in herbs. The recoveries of essential oil components estimated using MSPD/sand are almost equal to those using pressurised liquid extraction.Conclusion – The results presented in the paper reveal that MSPD with sand is suitable for the isolation of essential oil components from herbs. Its extraction efficiency is equivalent to pressurised liquid extraction, recognised as one of the most efficient extraction methods. The cost of MSPD procedure for essential oil analysis can be significantly diminished by substituting C18 with sand. Copyright © 2010 John Wiley & Sons, Ltd.
Systematic characterisation of secondary metabolites from Ixeris sonchifolia by the combined use of HPLC‐TOFMS and HPLC‐ITMS
Authors: Shi Peiying , Zhang Yufeng , Qu Haibin , Fan Xiaohui 
Published: August 2010

AbstractIntroduction – Ixeris sonchifolia (Bunge) Hance, a folk medicine, has been widely used in China for its anti‐inflammatory and haemostatic effects. However, the miscellaneous component composition of this herbal medicine is not well known.Objective – To develop a fast and comprehensive analytical method for the characterisation of various components from I. Sonchifolia, as a tool for the quality control of the herb and its related preparations.Methodology – Ixeris sonchifolia samples were extracted with 60% aqueous methanol, purified by solid‐phase extraction and then analysed by the combinatorial use of HPLC‐TOFMS and HPLC‐ITMS.Results – A total of six sesquiterpene lactones, six phenolic acids and seven flavonoids were identified or tentatively characterised. Five of them were reported for the first time in I. sonchifolia and, in particular, two amino acid‐sesquiterpene lactone conjugates, 11,13‐dihydro‐13‐prolyl‐ixerin Z and 11,13‐dihydro‐13‐prolyl‐ixerin Z1, that were first found in this plant source.Conclusion – A global profile of I. sonchifolia constituents was described, which could be useful for the quality control of this herb and its related preparations. The employed combination of HPLC‐TOFMS and HPLC‐ITMS could also be a promising tool for the analysis of other herbal medicines containing sesquiterpene lactones, phenolic acids or flavonoids. Copyright © 2010 John Wiley & Sons, Ltd.
A comparison of alternative sample preparation procedures for the analysis of swainsonine using LC‐MS/MS
Authors: Gardner Dale R. , Cook Daniel 
Published: August 2010

AbstractIntroduction – Swainsonine, a polyhydroxy indolizidine alkaloid and known glycosidase inhibitor, is found in a number of different plants that cause a lysosomal storage disease known as locoism in the western USA. Most recently swainsonine has been analysed by LC‐MS/MS after sample extraction and preparation from ion‐exchange resins.Objective – To compare previously published sample preparation procedures with several new alternative procedures to provide methods using either commercially available solid‐phase extraction equipment or procedures which significantly reduce sample preparation time.Methodology – A previously reported and validated sample preparation method using ion‐exchange resin was compared with methods using a commercially available solid‐phase extraction cartridge, a solvent partitioning procedure or a single solvent extraction procedure using one of two solvents. Twenty different plant samples of varying swainsonine concentrations were prepared in triplicate and analysed by LC‐MS/MS. The measured concentration of swainsonine was then statistically compared between methods.Results – There were no statistically significant differences found between four of the five different sample preparation methods tested.Conclusion – A commercially available SPE cartridge can be used to replace the previously used ion‐exchange resin for swainsonine analysis. For very rapid analyses the SPE procedure can be eliminated and a simple, single solvent extraction step used for sample preparation. Published in 2010 by John Wiley & Sons, Ltd.
Ethnic differences in participation in prenatal screening for Down syndrome: A register‐based study
Authors: Fransen Mirjam P. , Schoonen Marleen H. M. H. J. D. , Mackenbach Johan P. , Steegers Eric A. P. , de Koning Harry J. , Laudy Jacqueline A. M. , Galjaard Robert‐Jan , Looman Caspar W. N. , Essink‐Bot Marie‐Louise , Wildschut Hajo I. J. 
Published: August 2010

AbstractObjectiveTo assess ethnic differences in participation in prenatal screening for Down syndrome in the Netherlands.MethodsParticipation in prenatal screening was assessed for the period 1 January 2009 to 1 July 2009 in a defined postal code area in the southwest of the Netherlands. Data on ethnic origin, socio‐economic background and age of participants in prenatal screening were obtained from the Medical Diagnostic Centre and the Department of Clinical Genetics. Population data were obtained from Statistics Netherlands. Logistic regression models were used to assess ethnic differences in participation, adjusted for socio‐economic and age differences.ResultsThe overall participation in prenatal screening was 3865 out of 15 093 (26%). Participation was 28% among Dutch women, 15% among those from Turkish ethnic origin, 8% among those from North‐African origin, 15% among those from Aruban/Antillean origin and 26% among women from Surinamese origin.ConclusionsCompared to Dutch women, those from Turkish, North‐African, Aruban/Antillean and other non‐Western ethnic origin were less likely to participate in screening. It was unexpected that women from Surinamese origin equally participated. It should be further investigated to what extent participation and non‐participation in these various ethnic groups was based on informed decision‐making. Copyright © 2010 John Wiley & Sons, Ltd.
Aiming at multidisciplinary consensus: what should be detected in prenatal diagnosis?
Authors: Boormans Elisabeth M. A. , Birnie E. , Knegt Alida C. , Schuring‐Blom G. Heleen , Bonsel Gouke J. , van Lith Jan M. M. 
Published: August 2010

AbstractObjectiveTo determine expert consensus on which chromosomal abnormalities should and should not be detected in prenatal diagnosis, and for which abnormalities disagreement remains after structured discussion.MethodsAn expert panel of 24 prenatal experts (8 clinical cytogeneticists, 8 clinical geneticists and 8 obstetricians) rated 15 chromosomal abnormalities sampled from a nationwide study on rapid aneuploidy detection (RAD). In two individual anonymous rating rounds and one group meeting, the participants rated PRO or AGAINST detection and stated their main argument. The 15 chromosomal abnormalities were described in detail by a stylized vignette containing an obstetrical history, the indication for prenatal diagnosis and the range of possible outcomes of the chromosomal abnormality. Consensus was defined to be present if at least 80% of the experts agreed.ResultsConsensus was reached in 12 out of 15 cases. In ten cases, there was agreement PRO detection and in two cases experts agreed AGAINST detection. At the end of the third round, dissensus remained on three abnormalities.ConclusionExperts largely agreed on detecting chromosomal abnormalities with severe consequences and AGAINST detection in case of irrelevant clinical consequences. For chromosomal abnormalities with mild or uncertain outcomes, dissensus remained. None of the currently available tests corresponds to these demands. Copyright © 2010 John Wiley & Sons, Ltd.
Fundamental losses in solar cells
Authors: Hirst Louise C. , Ekins‐Daukes Nicholas J. 
Published: August 2010

AbstractThis paper considers intrinsic loss processes that lead to fundamental limits in solar cell efficiency. Five intrinsic loss processes are quantified, accounting for all incident solar radiation. An analytical approach is taken to highlight physical mechanisms, obscured in previous numerical studies. It is found that the free energy available per carrier is limited by a Carnot factor resulting from the conversion of thermal energy into entropy free work, a Boltzmann factor arising from the mismatch between absorption and emission angles and also carrier thermalisation. It is shown that in a degenerate band absorber, a free energy advantage is achieved over a discrete energy level absorber due to entropy transfer during carrier cooling. The non‐absorption of photons with energy below the bandgap and photon emission from the device are shown to be current limiting processes. All losses are evaluated using the same approach providing a complete mathematical and graphical description of intrinsic mechanisms leading to limiting efficiency. Intrinsic losses in concentrator cells and spectrum splitting devices are considered and it is shown that dominant intrinsic losses are theoretically avoidable with novel device designs. Copyright © 2010 John Wiley & Sons, Ltd.
High performance wire‐array silicon solar cells
Authors: Gunawan O. , Wang K. , Fallahazad B. , Zhang Y. , Tutuc E. , Guha S. 
Published: August 2010

AbstractNano/micro‐wire silicon solar cells, consisting of wire‐arrays of radial p–n junction structures, are expected to offer performance enhancement at lower costs, using smaller volumes of low carrier lifetime, cheaper silicon. Using inexpensive microsphere‐lithography‐based fabrication that is scalable to large areas, we have demonstrated wire‐array solar cells that outperform the control cell. Key to the design of these cells is the impact of various parameters, such as wire diameter and junction depth, that influences the competing effects of light trapping ability of the wire‐array, quantum efficiency, and series resistance of the resulting device. Using capacitance measurements we can identify two possible types of junction structure in a wire‐array solar cell: radial and planar. We show that the former is the prerequisite for performance‐enhancing wire‐array solar cells. Copyright © 2010 John Wiley & Sons, Ltd.
Variation of the chemical reactivity of Thermus thermophilus HB8 ribosomal proteins as a function of pH
Authors: Running William E. , Reilly James P. 
Published: September 2010

AbstractRibosomes occupy a central position in cellular metabolism, converting stored genetic information into active cellular machinery. Ribosomal proteins modulate both the intrinsic function of the ribosome and its interaction with other cellular complexes, such as chaperonins or the signal recognition particle. Chemical modification of proteins combined with mass spectrometric detection of the extent and position of covalent modifications is a rapid, sensitive method for the study of protein structure and flexibility. By altering the pH of the solution, we have induced non‐denaturing changes in the structure of bacterial ribosomal proteins and detected these conformational changes by covalent labeling. Changes in ribosomal protein modification across a pH range from 6.6 to 8.3 are unique to each protein, and correlate with their structural environment in the ribosome. Lysine residues whose extent of modification increases as a function of increasing pH are on the surface of proteins, but in close proximity either to glutamate and aspartate residues, or to rRNA backbone phosphates. Increasing pH disrupts tertiary and quaternary interactions mediated by hydrogen bonding or ionic interactions, and regions of protein structure whose conformations are sensitive to these changes are of potential importance in modulating the flexibility of the ribosome or its interaction with other cellular complexes.
CH hydrogen bonding: 3. Hammett correlations for phenylacetonitriles and tetrafluorobenzenes with HMPA
Authors: Lorand John P. 
Published: August 2010

AbstractUnderstanding the hydrogen bond, or H‐bond, arguably the strongest known intermolecular attractive force, is of great importance. Models of H‐bonding hold that both electrostatic and covalent components are at work. H‐bonding of CH bonds, and thus presumably other AH bonds, is greatly facilitated by polar substituents. We have found that equilibrium constants, K, for CH H‐bonding in series of phenylacetonitriles and tetrafluorobenzenes with HMPA are closely correlated by the Hammett equation. That is, K values vary as substituents of different polarities are introduced at positions remote from the donor CH bond. This result is consistent with a significant electrostatic component in these examples of H‐bonding. It may, however, also be explained by interaction with the σ* orbital of the CH bond, which is involved in the covalent component of the H‐bond. Theoretical models need to be applied to this and other cases. Copyright © 2010 John Wiley & Sons, Ltd.
Structure development in multistage stretching of PTFE films
Authors: Choi Kyung‐Ju , Spruiell Joseph E. 
Published: September 2010

AbstractThe structure of expanded poly(tetrafluoroethylene) (ePTFE) films that were produced by uniaxial or biaxial stretching of a calendared sheet were studied by wide angle X‐ray diffraction (WAXD), small angle X‐ray scattering, differential scanning calorimetry (DSC), and scanning electron microscopy. The molecular orientation of the stretched films was analyzed by WAXD flat films and pole figures. Biaxial orientation factors were computed to interpret the level of orientation quantitatively. DSC scans showed that oriented samples exhibited two melting peaks, one at the commonly observed temperature in the range 340–345 °C and one around 380 °C. The possible causes of this high‐temperature melting peak and its relation to previously described processes is discussed. The microporous nature of the ePTFE films is also briefly discussed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010
Surface modification and characterization of SEBS films obtained by in situ and ex situ oxidization with potassium permanganate
Authors: Han Xia , Zhou Yuan , Hu Jun , Liu Honglai 
Published: September 2010

AbstractThe surface morphologies and compositions of the asymmetric films of polystyrene‐b‐poly(ethylene‐co‐butylene)‐b‐polystyrene (SEBS) prepared by in situ and ex situ oxidization with the KMnO4 aqueous solution and KMnO4/H2SO4 mixed solution were investigated by using scanning electron microscope, atomic force microscope (AFM), X‐ray photoelectron spectroscopy (XPS) and attenuated total reflectance infrared spectroscopy (ATR‐FTIR). The effect of the oxidization reagents on morphological changes and the influence of in situ and ex situ preparation methods on surface compositions were discussed. Different from the in situ oxidation by degrading the copolymers to form a gradient film, the ex situ oxidation preferentially degraded the uppermost layer of the film. Although both the KMnO4 oxidation and the KMnO4/H2SO4 oxidation gave hierarchical structures, distinctive differences were found that large ridges and smaller granules were fabricated in the former film and the latter produced large and deep ravines and fine sponge‐like morphologies. Additionally, the oxygen concentration and the oxo‐species implanted by these oxidation treatments were characterized and evaluated to provide a quantitative comparison. Oxygen, as well as manganese was found to be implanted in the surface layer of the oxidized film, forming predominantly OC and OCO groups, as well as a small fraction of OH and MnO compounds. Changes in contact angle of water on these films and total surface oxygen content are related but not directly. The hystereses of water contact angle at a value of 119 ± 3° due primarily to surface roughness and at a value of 63 ± 3° due primarily to chemical heterogeneity are led by different oxidation degrees and oxidation methods. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010