bluuebunny/crossref_metadata_2025_split huggingface dataset:
“One‐pot” preparation of basic amino acid–silica hybrid monolithic column for capillary electrochromatography
Authors: Xu Hongrui , Xu Zhendong , Yang Limin , Wang Qiuquan 
Published: July 2011

AbstractA novel “one‐pot” strategy was developed for the preparation of amino acid (AA)–silica hybrid monolithic column. The basic AA (L‐Arginine, L‐Lysine and L‐Histidine) was covalently incorporated into the silica hybrid skeleton via the epoxy ring‐opening reaction between the amine group and the glycidyl moiety in γ‐glycidoxypropyltrimethoxysilane (GPTMS), which was confirmed by elemental analysis and FT‐IR studies, while the basic AA was also found to catalyze the polycondensation of tetramethoxysilane and GPTMS. The average mesopore and macropore sizes of the prepared basic AA–silica hybrid monolithic columns were 3.86 nm and 1.71 μm for the L‐Lysine–silica hybrid monolith, 5.38 nm and 4.24 μm for the L‐Arginine–silica hybrid monolith, and 6.38 nm and 1.24 μm for the L‐Histidine–silica hybrid monolith. The hybrid monolith afforded a zwitterionic stationary phase for CEC, the direction and magnitude of EOF can be controlled by the pH of the mobile phase used. Besides an electrophoretic mechanism, the monoliths behave in a typical hydrophilic interaction with the analytes when ACN percentage in the mobile phase is over 40%. Four polar compounds (toluene, DMF, formamide and thiourea) were tested on the three AA–silica hybrid monolithic columns, and the best separation efficiency was observed in the L‐Lysine–silica hybrid monolithic column, its theoretical plate height was down to 5.7 μm for thiourea when 20 mM HCOOH‐HCOONH4 containing 20% ACN (pH 4.1) was used as a running buffer. The corresponding theoretical plate number for toluene, DMF, formamide and thiourea were 123 385, 103 620, 121 845 and 105 345 plates/m, respectively. Effective separation of phenols and peptides on the L‐Lysine–silica hybrid monolithic column was achieved using CEC. We believe that this strategy paves a way for the easy preparation of various functional silica hybrid monolithic columns, aiming at different separation purposes.
Correlation between structure, retention and activity of cholic acid derived cis–trans isomeric bis‐steroidal tetraoxanes
Authors: Šegan Sandra , Andrić Filip , Radoičić Aleksandra , Opsenica Dejan , Šolaja Bogdan , Zlatović Mario , Milojković‐Opsenica Dušanka 
Published: July 2011

AbstractBoth quantitative structure–retention (QSRR) and quantitative structure–activity relationship (QSAR) studies have been performed to correlate the molecular characteristics of seven pairs of cis–trans isomeric bis‐steroidal tetraoxanes with their reversed‐phase thin‐layer chromatography (RPTLC) retention as well as with their antiproliferative activity. 2D and 3D molecular descriptors as whole molecule representations together with retention parameters as well as with biological activity data were subjected to the multivariate statistical analysis (principal component analysis – PCA and hierarchical cluster analysis – HCA) in order to determine the most influential factors governing the retention and activity against human cervix carcinoma (HeLa) and human malignant melanoma (Fem‐X) cell lines. Both QSRR and QSAR models were built by means of the partial least‐squares (PLS) statistical method. It was found that hydrogen bond donating (HBD), hydrogen bond accepting (HBAcc), hydrophilic surface percentage (%HS) and hydrophilic–lipophilic balance (HLB) exhibit the strongest influence on retention. The most prominent factors affecting antiproliferative activity of the investigated substances are those relating to the size and shape of a molecule such as: connectivity indices, refractivity (Ref), surface area (SA), molecular volume and weight, polarizability (Pol) and those regarding the ability of hydrogen bonding (HB).
New method for determination of (E)‐resveratrol in wine based on microextraction using packed sorbent and ultra‐performance liquid chromatography
Authors: Gonçalves João , Câmara José S. 
Published: July 2011

AbstractAn ultra‐fast and improved analytical methodology based on microextraction by packed sorbent (MEPS) combined with ultra‐performance LC (UPLC) was developed and validated for determination of (E)‐resveratrol in wines. Important factors affecting the performance of MEPS such as the type of sorbent material (C2, C8, C18, SIL, and M1), number of extraction cycles, and sample volume were studied. The optimal conditions of MEPS extraction were obtained using C8 sorbent and small sample volumes (50–250 μL) in one extraction cycle (extract–discard) and in a short time period (about 3 min for the entire sample preparation step). (E)‐Resveratrol was eluted by 1×250 μL of the mixture containing 95% methanol and 5% water, and the separation was carried out on a high‐strength silica HSS T3 analytical column (100 mm×2.1 mm, 1.8 μm particle size) using a binary mobile phase composed of aqueous 0.1% formic acid (eluent A) and methanol (eluent B) in the gradient elution mode (10 min of total analysis). The method was fully validated in terms of linearity, detection (LOD) and quantification (LOQ) limits, extraction yield, accuracy, and inter/intra‐day precision, using a Madeira wine sample (ET) spiked with (E)‐resveratrol at concentration levels ranging from 5 to 60 μg/mL. Validation experiments revealed very good recovery rate of 95±5.8% RSD, good linearity with r2 values >0.999 within the established concentration range, excellent repeatability (0.52%), and reproducibility (1.67%) values (expressed as RSD), thus demonstrating the robustness and accuracy of the MEPSC8/UPLC‐photodiode array (PDA) method. The LOD of the method was 0.21 μg/mL, whereas the LOQ was 0.68 μg/mL. The validated methodology was applied to 30 commercial wines (24 red wines and six white wines) from different grape varieties, vintages, and regions. On the basis of the analytical validation, the MEPSC8/UPLC‐PDA methodology shows to be an improved, sensitive, and ultra‐fast approach for determination of (E)‐resveratrol in wines with high resolving power within 6 min.
FARMERS' KNOWLEDGE AND PERCEPTION OF AGRICULTURAL WETLAND MANAGEMENT IN RWANDA
Authors: Nabahungu N. L. , Visser S. M. 
Published: July 2011

ABSTRACTMost of Rwanda's wetlands are being reclaimed under government schemes with the aim of growing rice as the main crop. In the present study, information on farmers' knowledge and perceptions of agricultural wetland management was collected in Cyabayaga and Rugeramigozi wetlands. The two wetlands were selected as representatives for typical reclaimed wetland agriculture in Rwanda. They provide contrasts in both environmental and social terms. Three tools were used to investigate farmers' knowledge and perception of agricultural wetland management: (i) household survey; (ii) focus group discussions; and (iii) transect walk. The major constraints identified by farmers in the two wetlands were water shortage and lack of availability of improved seeds and high prices of fertilisers. The primary benefits from wetlands for farmers are income generation in Cyabayaga and food security in Rugeramigozi. The most commonly reported concern about the wetlands in the Cyabayaga and Rugerameragozi was that they are a source of malaria. Rice is an important crop in both wetlands, whereas farmers in Cyabahaga wish to continue cultivating rice, Rugeramigozi farmers prefer to grow rice only after it has been tested for its adaptability. Farmers have sufficient knowledge on the causes and the potential solutions to overcome most constraints. They know that soil suitability is closely related to relief. They classify soils by a number of criteria and choose crops accordingly. Any programme designed to address wetland management in the region will have to take account of farmers' knowledge and adopt a holistic view of wetland management. Copyright © 2011 John Wiley & Sons, Ltd.
Robust satisfactory fault‐tolerant control of continuous‐time interval systems with time‐varying state and input delays
Authors: Zhang Dengfeng , Lu Baochun , Wang Hong , Wang Zhiquan 
Published: July 2011

SUMMARYWith the performance constraints on exponential stability, H∞ norm of disturbance attenuation and upper bound of quadratic cost performance, the satisfactory and passive fault‐tolerant control problem is investigated for a class of interval systems with time‐varying input and state delays in the case of possible actuator faults. The bounded‐varying dynamics of actuator faults is described by interval matrix, which is more general and can be dealt with by the interval system theory. The delay‐dependent satisfactory fault‐tolerant controller design is developed based on multi‐objective optimization strategy. The results are derived in the forms of linear matrix inequalities, which is convenient to be solved in practice. Simulative example is presented to illustrate the effectiveness and necessity of the proposed fault‐tolerant control strategy. Copyright © 2011 John Wiley & Sons, Ltd.
Two‐dimensional Hydrophilic Interaction/Reversed‐phase Liquid Chromatography for the Preparative Separation of Polar and Non‐polar Taxanes
Authors: Rezadoost Hassan , Ghassempour Alireza 
Published: July 2011

ABSTRACTIntroductionPaclitaxel (Taxol®) is one of the best‐known compounds of natural origin that has been used in the pharmaceutical industry. It is derived from taxanes extracted from different parts of yew trees (Taxaceae), cell cultures and taxane‐producing endophytic fungi. Previous work reported a semi‐preparative HPLC for the extraction of Paclitaxel (a non‐polar taxane) from Taxus baccata L. and cell culture. In other work, 10‐deacetylbaccatin III (a polar taxane) was separated from this medium at a preparative scale.ObjectiveTo introduce a novel on‐line two‐dimensional heart‐cut liquid chromatography using hydrophilic interaction/reversed‐phase chromatography for preparative separation of polar and non‐polar taxanes.MethodologyTo achieve this goal the system was developed from analytical to a larger preparative scale. In the first dimension of a semi‐preparative column, taxanes were separated from polar compounds using a CN column, and in the second dimension the fraction containing taxanes was transferred to a C18‐column.ResultsUsing this method polar and non‐polar taxanes could be separated at analytical and semi‐preparative scales.ConclusionCombination of hydrophilic and reversed‐phase chromatography in two‐dimensional liquid chromatography (2D‐LC) systems is a useful method for the separation of compounds with a large polarity range such as taxanes. Copyright © 2011 John Wiley & Sons, Ltd.
Qualitative and Quantitative Evaluation of Phenolic Compounds in Iris dichotoma Pall
Authors: Wei Yuling , Shu Pan , Hong Junli , Qin Minjian 
Published: July 2011

ABSTRACTIntroductionThe rhizome of Iris dichotoma Pall., a traditional Chinese herbal medicine that contains (iso) flavonoids as the main bioactive compound, has been used to treat several disorders such as inflammation, throat disorders, asthma and coughs. However, there is a lack of suitable methods for its qualitative and quantitative analysis as well as quality control.ObjectivesTo establish an HPLC method for the simultaneous determination of phenolic constituents, the identification of characteristic metabolites in the rhizomes of I. dichotoma and to compare their contents in samples from different areas of China.MethodologyHPLC coupled with diode‐array detection (DAD) and electrospray ionisation multistage mass spectrometry (ESI‐MSn), and principal component analysis (PCA) were used for the qualitative and quantitative analysis of phenolic compounds in I. dichotoma samples.ResultsTwenty characteristic compounds were identified or tentatively characterised. A quantitative HPLC‐UV method allowing the simultaneous quantification of 10 phenolic compounds was optimised and validated in terms of linearity, precision, accuracy, and limits of detection and quantification.ConclusionThe methodology developed proved to be effective for the identification and quantification of phenolic compounds in the rhizomes of I. dichotoma. Samples were classified into three groups according to their geographical origin based on their phenolic composition using principal component analysis. Copyright © 2011 John Wiley & Sons, Ltd.
Simultaneous Determination of Plant Growth Regulators 1‐Naphthylacetic Acid and 2‐Naphthoxyacetic Acid in Fruit and Vegetable Samples by Room Temperature Phosphorescence
Authors: Murillo Pulgarín José A. , García Bermejo Luisa F. , Sánchez‐Ferrer Robles Ignacio , Becedas Rodríguez Sonia 
Published: July 2011

Introduction1‐Naphthylacetic and 2‐naphthoxyacetic acids belong to the synthetic branch of auxins. Auxins have attracted considerable interest as a subject of study by virtue of their biological and physiological significance. Their broad use as plant growth regulators has raised the need for simple, rapid, sensitive and selective analytical methods for their determination in real samples.ObjectiveThe primary aim of this work was to develop an analytical method for the simultaneous determination of 1‐naphthylacetic acid and 2‐naphthoxyacetic acid in commercial technical formulations, tomato and various fruit types (apple, strawberry, orange and plum) by room temperature phosphorescence.MethodologyFiltrated solutions of aqueous slurries from ecological fruit and tomato samples are acidified and then extracted with dichloromethane. Once the solvent is evaporated, the dried residue is dissolved in sodium dodecyl sulphate (a micellar agent), and supplied with thallium (I) nitrate as an external heavy atom source and sodium sulphite as deoxygenation agent to enhance the ensuing phosphorescence.ResultsThe broad‐band overlapping spectra for the two analytes were resolved by first‐ and second‐derivative phosphorescence spectrometry. Zero‐crossing measurements at 488.5 nm in the first‐derivative spectrum and 469.5 nm in the second derivative spectrum exhibited a linear dependence on the 2‐naphthoxyacetic acid and 1‐naphthylacetic acid concentration, respectively. The detection limits as determined in accordance with the error propagation theory were 11.5 ng/mL for 1‐naphthylacetic acid and 15.6 ng/mL for 2‐naphthoxyacetic acid.ConclusionThe proposed method affords the determination of 1‐naphthylacetic acid and 2‐naphthoxyacetic acid in real samples with near‐quantitative recoveries from agricultural products. Copyright © 2011 John Wiley & Sons, Ltd.
Comparison of combined, stepwise sequential, contingent, and integrated screening in 7292 high‐risk pregnant women
Authors: Guanciali‐Franchi Paolo , Iezzi Irene , Palka Chiara , Matarrelli Barbara , Morizio Elisena , Calabrese Giuseppe , Benn Peter 
Published: July 2011

AbstractObjectiveTo compare the efficacy of combined, stepwise sequential, and contingent screening versus the integrated test in detecting fetal aneuploidies.Study designFirst trimester combined test, sequential second trimester, and contingent risks were retrospectively calculated for 7292 unselected pregnant women with singleton pregnancies who had received integrated screening. The first trimester testing was based on nuchal translucency, pregnancy‐associated plasma protein‐A, and free‐beta‐human chorionic gonadotrophin (free β‐hCG) and the second trimester tests were alpha‐fetoprotein, hCG, and unconjugated estriol. A second trimester risk of 1:250 defined a positive result for all protocols with the contingent protocol based on additional second trimester testing for those with risks between 1:30 and 1:1200.ResultsAmong the population submitted for the integrated test, the detection rate was 19/21 (90%) for Down syndrome (DS) and 6/6 (100%) for Edwards syndrome (ES) and the DS false‐positive rate (FPR) was 247/7271 (3.4%). Provision of the first trimester combined test alone would have resulted in a 17/21 (81%) detection rate for DS, that of 4/6 (67%) for ES and a DS FPR of 292/7271 (4.0%). The sequential and contingent approaches had the same final detection rates as the integrated test but potentially allowed a high proportion of the affected pregnancies to be detected in the first trimester. The lowest net DS FPR was seen with the contingent approach (2.6%) and using this protocol only 12.7% of women would have required second trimester testing.ConclusionsIntegrated, sequential, and contingent screenings are all more efficacious than the combined test. Overall, the contingent approach was the most efficient with a high‐detection rate, the lowest FPR, and the least amount of testing. Copyright © 2011 John Wiley & Sons, Ltd.
Nanostructured hybrid polymer networks from in situ self‐assembly of RAFT‐synthesized POSS‐based block copolymers
Authors: Deng Yuanming , Bernard Julien , Alcouffe Pierre , Galy Jocelyne , Dai Lizong , Gérard Jean‐François 
Published: July 2011

AbstractA series of well‐defined hybrid block copolymers PMACyPOSS‐b‐PMMA and PMAiBuPOSS‐b‐PMMA exhibiting high POSS weight contents have been synthesized by RAFT polymerization and further studied as modifiers for epoxy thermosets based on diglycidyl ether of bisphenol A. The hybrid block copolymers self‐assembled within the epoxy precursors into micelles possessing an inorganic core and a PMMA corona. Thanks to the presence of the PMMA blocks that remain miscible until the end of the reaction, curing of the resulting blends afforded nanostructured hybrid organic/inorganic networks with well‐dispersed inorganic‐rich nanodomains with diameters on the order of 20 nm. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Kinetic study of semifluorinated arylene vinylene ether polymers
Authors: Buquoi John Q. , Smith Dennis W. , Iacono Scott T. 
Published: July 2011

AbstractFluorinated arylene vinylene ether (FAVE) polymers were prepared from the base‐promoted addition of commercial 2,2‐bis(4‐hydroxyphenyl)hexafluoropropane (6F bisphenol A) to aryl trifluorovinyl ether (TFVE), 2,2′‐bis(4‐trifluorovinyloxybiphenyl)‐1,1,1,3,3,3‐hexafluoropropane. The step‐growth polymerization kinetics by using stoichiometric NaH and catalytic Cs2CO3 were investigated by monitoring the 19F NMR signals of the aryl TFVEs. The nth order kinetic model was used to determine rate constants over a series of programmed temperatures. Polymerization using stoichiometric NaH resulted in second‐order kinetics with an activation energy of 59 kJ/mol. This model kinetic study provided insight into the mechanistic pathways of the FAVE polymer system that has recently shown a lot of interest in many areas of materials science. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Thermal and ion transport properties of hydrophilic and hydrophobic polymerized styrenic imidazolium ionic liquids
Authors: Weber Ryan L. , Ye Yuesheng , Banik Steven M. , Elabd Yossef A. , Hickner Michael A. , Mahanthappa Mahesh K. 
Published: July 2011

AbstractPolymerized ionic liquids (PILs) are a platform for fundamental studies of structure‐property relationships in single ion conductors, with potential applications in energy storage and conversion. The synthesis, thermal properties, and ionic conductivities of homologous, narrow dispersity styrenic PILs are described. Hydrophilic poly(4‐vinylbenzyl alkylimidazolium chloride) (PVBn(alkyl)ImCl) homopolymers with constant average degrees of polymerization were synthesized by post‐synthetic functionalization of a poly(4‐vinylbenzyl chloride) (Mn = 15.9 kg/mol, Mw/Mn = 1.34) master batch with N‐alkylimidazoles (alkyl = CH3 (Me), C4H9 (Bu), and C6H13 (Hex)). The chloride counterions of PVBnHexImCl were exhaustively metathesized with BF, PF, and bis(trifluoromethanesulfonyl)imide (TFSI−) to yield a series of hydrophobic PILs. Thermogravimetric analyses indicate that PVBn(alkyl)ImCl homopolymers are unstable above 220 °C, whereas the hydrophobic PILs remain stable up to 290 °C. The glass transition temperatures (Tg) decrease with both increasing alkyl side‐chain length and increasing counterion size, exemplified by Tg = 9 °C for PVBnHexImTFSI. Hydrophilic PILs exhibit high ionic conductivities (as high as ∼0.10 S cm−1) that depend on the relative humidity, water uptake, and the PIL side chain length. The hydrophobic PILs exhibit lower conductivities (up to ∼5 × 10−4 S cm−1) that depend predominantly on the polymer Tg, however, counterion size and symmetry also contribute. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1287–1296, 2011
Prediction and Comparison of Shelf Life of Solid Rocket Propellants Using Arrhenius and Berthelot Equations
Authors: Shekhar Himanshu 
Published: July 2011

AbstractThe Arrhenius equation and the Berthelot equation for the prediction of shelf life of composite propellant formulations are compared. The elongation has a measurable variation with time and is taken as the fastest degrading parameter for HTPB/AP/Al based composite solid rocket propellants. An HTPB based aluminized composite propellant with 85 % solid loading and an initial elongation of 63.24 % is prepared. It is kept at an elevated temperature of 60 °C to achieve a higher rate of degradation for a prolonged time period (1 year). The elongation is monitored at regular intervals using JANNAF class C dog bone specimen in uni‐axial tensile mode. A reduction of the elongation to less than 50 % is taken as the end‐of‐shelf life of the propellant. The shelf life of the propellant is calculated to be 1.2 years at 60 °C. For the extrapolation of the shelf life at 60 °C to the shelf life at 27 °C, the results of both the Arrhenius equation and the Berthelot equation are compared. The activation energy (E) in the Arrhenius equation is obtained as 72.8 kJ mol−1 and the 10 °C reaction rate rise factor (γ10) is found to be 2.4. This comparison is independent of the propellant formulation and other researchers have reported a similar range of values for these parameters. The shelf life of this propellant formulation at 27 °C is conservatively predicted to be 20 years using both equations. In addition to estimation of shelf life by both equations using elongation as control parameter, this paper gives scaling curves, which are valid universally for predicting shelf life at 27 °C from data of shelf life at 60 °C. The use of scaling curves is independent of properties, propellant formulation and degradation mechanism considered for analysis.