bluuebunny/crossref_metadata_2025_split huggingface dataset:
Permeation properties of hydrogen and water vapor through porous silica membranes at high temperatures
Authors: Tsuru Toshinori , Igi Ryousuke , Kanezashi Masakoto , Yoshioka Tomohisa , Fujisaki Shinji , iwamoto Yuji 
Published: May 2010

AbstractSilica and cobalt‐doped silica membranes that showed a high permeance of 1.8 × 10−7 mol m−2 s−1 Pa−1 and a H2/N2 permeance ratio of ∼730, with excellent hydrothermal stability under steam pressure of 300 kPa, were successfully prepared. The permeation mechanism of gas molecules, focusing particularly on hydrogen and water vapor, was investigated in the 300–500°C range and is discussed based on the activation energy of permeation and the selectivity of gaseous molecules. The activation energy of H2 permeation correlated well with the permeance ratio of He/H2 for porous silica membranes prepared by sol–gel processing, chemical vapor deposition (CVD), and vitreous glasses, indicating that similar amorphous silica network structures were formed. The permeance ratios of H2/H2O were found to range from 5 to 40, that is, hydrogen (kinetic diameter: 0.289 nm) was always more permeable than water (0.265 nm). © 2010 American Institute of Chemical Engineers AIChE J, 2011
Mixing in tangentially crossing microchannels
Authors: Lee Denz , Chen Yu Tzu 
Published: May 2010

AbstractIn this study, we have demonstrated that effective mixing can be achieved in simple and regular crossing channels. The dynamical processes combining split‐and‐recombine and chaotic mixing elements of stretching and folding were discussed. In channels with simple turns (up/down/right/left), flow could be stretched; on the other hand, tangential crossings could yield folding. Theoretically, repeating stretching and folding then result in the increase of interfacial area and decrease of striation thickness which facilitate the eventual mixing by diffusion. Practically, the structural sequence of turning and/or crossing affects the performance of the mixing. Three types of micromixers were studied, and the simulated performance was favorably compared with the published data. Experiments were carried out to qualitatively demonstrate the typical performance in the mixers. © 2010 American Institute of Chemical Engineers AIChE J, 2011
Remote actuation of hydrogel nanocomposites: Heating analysis, modeling, and simulations
Authors: Satarkar Nitin S. , Meenach Samantha A. , Anderson Kimberly W. , Hilt J. Zach 
Published: May 2010

AbstractRecently, there has been increasing interest in remote heating of polymer nanocomposites for applications such as actuators, microfluidic valves, drug delivery devices, and hyperthermia treatment of cancer. In this study, magnetic hydrogel nanocomposites of poly(ethylene glycol) (PEG) with varying amounts of iron oxide nanoparticle loadings were synthesized. The nanocomposites were remotely heated using an alternating magnetic field (AMF) at three different AMF amplitudes, and the resultant temperatures were recorded. The rate of the temperature rise and the steady state temperatures were analyzed with a heat transfer model, and a correlation of heat generation per unit mass with the nanoparticle loadings was established for different AMF amplitudes. The temperature rise data of a PEG system with different swelling properties were found to be accurately predicted by the model. Furthermore, the correlations were used to simulate the temperatures of the nanocomposite and the surrounding tissue for potential hyperthermia cancer treatment applications. © 2010 American Institute of Chemical Engineers AIChE J, 2011
Synthesis of PVC‐TEPA‐supported proline derivative and its catalytic behavior in the direct asymmetric aldol reaction
Authors: Zou Jun , Zhao Wenshan , Li Runtao , Zhang Hefeng , Cui Yuanchen 
Published: May 2010

AbstractPVC‐TEPA‐supported L‐proline catalyst has been synthesized and characterized by IR. It is developed as an efficient catalyst for the direct asymmetric aldol reaction of unmodified ketones with various aldehydes in the presence of water at 0°C. The corresponding aldol products were obtained with high yields (up to 94%) and good enantioselectivities (up to 97% ee) on optimized conditions. Recycling investigations have shown that this material can be reused without loss of catalytic activity and stereoselectivity for at least 15 cycles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Synthesis of polyundecamethylene 2,6‐naphthalamide as semiaromatic polyamide‐containing naphthalene ring
Authors: Yang Shaohui , Fu Peng , Liu Minying , Wang Yudong , Zhao Qingxiang 
Published: May 2010

AbstractA novel engineering plastic polyundecamethylene 2,6‐naphthalamide (PA11N) was prepared via a reaction of 2,6‐naphthalene dicarboxylic acid and 1,11‐undecanediamine through a three‐step procedure. The structure of synthesized PA11N was characterized by elemental analysis, Fourier transform infrared spectroscopy, and proton nuclear magnetic resonance (1H‐NMR). The thermal behaviors were determined by differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. The solubility, water‐absorbing capacity, and mechanical properties of PA11N have also been investigated. Melting temperature (Tm), glass transition temperature (Tg), and decomposition temperature (Td) of PA11N are 294, 139, and 493°C, respectively. The results show that the heat resistance and mechanical properties of PA11N are near to those of polynonamethylene terephthalamide, and PA11N is a promising heat‐resistant and processable engineering plastic. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Flame retarded epoxy resins by adding layered silicate in combination with the conventional protection‐layer‐building flame retardants melamine borate and ammonium polyphosphate
Authors: Schartel B. , Weiß A. , Mohr F. , Kleemeier M. , Hartwig A. , Braun U. 
Published: May 2010

AbstractThe pyrolysis and flammability of phosphonium‐modified layered silicate epoxy resin nanocomposites (EP/LS) were evaluated when LS was combined with two flame retardants, melamine borate (MB) and ammonium polyphosphate (APP), that also act via a surface protection layer. Thermogravimetry (TG), TG coupled with Fourier Transform Spectroscopy (TG‐FTIR), oxygen index (LOI), UL 94 burning chamber (UL 94) and cone calorimeter were used. The glassy coating because of 10 wt % MB during combustion showed effects in the cone calorimeter test similar to nanodispersed LS, and somewhat better flame retardancy in flammability tests, such as LOI and UL 94. Adding APP to EP resulted in intumescent systems. The fire retardancy was particularly convincing when 15 wt % APP was used, especially for low external heat flux, and thus, also in flammability tests like LOI and UL 94. V0 classification is achieved when 15 wt % APP is used in EP. The flame retardancy efficiency of the protection layers formed does not increase linearly with the MB and APP concentrations used. The combination of LS with MB or APP shows antagonism; thus the performance of the combination of LS with MB or APP, respectively, was disappointing. No optimization of the carbonaceous‐inorganic surface layer occurred for LS‐MB. Combining LS with APP inhibited the intumescence, most probably through an increase in viscosity clearly above the value needed for intumescent behavior. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Scopus's source normalized impact per paper (SNIP) versus a journal impact factor based on fractional counting of citations
Authors: Leydesdorff Loet , Opthof Tobias 
Published: May 2010

AbstractImpact factors (and similar measures such as the Scimago Journal Rankings) suffer from two problems: (a) citation behavior varies among fields of science and, therefore, leads to systematic differences, and (b) there are no statistics to inform us whether differences are significant. The recently introduced “source normalized impact per paper” indicator of Scopus tries to remedy the first of these two problems, but a number of normalization decisions are involved, which makes it impossible to test for significance. Using fractional counting of citations—based on the assumption that impact is proportionate to the number of references in the citing documents—citations can be contextualized at the paper level and aggregated impacts of sets can be tested for their significance. It can be shown that the weighted impact of Annals of Mathematics (0.247) is not so much lower than that of Molecular Cell (0.386) despite a five‐f old difference between their impact factors (2.793 and 13.156, respectively).
Asymmetric Catalytic Aziridination of Cyclic Enones
Authors: De Vincentiis Francesco , Bencivenni Giorgio , Pesciaioli Fabio , Mazzanti Andrea , Bartoli Giuseppe , Galzerano Patrizia , Melchiorre Paolo 
Published: May 2010

AbstractThe first catalytic method for the asymmetric aziridination of cyclic enones is described. The presented organocatalytic strategy is based on the use of an easily available organocatalyst that is able to convert a wide range of cyclic enones into the desired aziridines with very high enantiomeric purity and good chemical yield. Such a method may very well open up new opportunities to stereoselectively prepare complex chiral molecules that possess an indane moiety, a framework that is found in a large number of bioactive and pharmaceutically important molecules
Intramolecular Scrambling of Aryl Groups in Organopalladium Complexes [ArPd(PPh3)2]+: From Solution to the Gas Phase, Back Again, and In‐Between
Authors: Agrawal Divya , Zins Emilie‐Laure , Schröder Detlef 
Published: May 2010

AbstractGas‐phase experiments are used to probe the intramolecular scrambling of aryl groups between palladium and phosphorus in organopalladium complexes, [ArPd(PPh3)2]+, generated by means of electrospray ionization (ESI). To this aim, ESI mass spectrometry, including tandem mass spectrometric experiments, were carried out on deuterated, non‐deuterated, and substituted [ArPd(PPh3)2]+ complexes. The fragment ions obtained from the deuterated parent ions clearly show the occurrence of intramolecular scrambling between the aryl group bound to palladium and the phenyl groups of the phosphine in the gas phase. Fragmentation pathways, supported by a statistical model, are proposed to explain these migrations and the implications for the condensed‐phase chemistry are probed experimentally by using ESI mass spectrometry.
N‐isopropylacrylamide‐based thermoresponsive polyelectrolyte multilayer films for human mesenchymal stem cell expansion
Authors: Liao Tianqing , Moussallem Maroun D. , Kim Junho , Schlenoff Joseph B. , Ma Teng 
Published: May 2010

AbstractHuman mesenchymal stem cells (hMSCs) are colony‐forming unit fibroblasts (CFU‐F) derived from adult bone marrow and have significant potential for many cell‐based tissue‐engineering applications. Their therapeutic potential, however, is restricted by their diminishing plasticity as they are expanded in culture. In this study, we used N‐isopropylacrylamide (NIPAM)‐based thermoresponsive polyelectrolyte multilayer (N‐PEMU) films as culture substrates to support hMSC expansion and evaluated their effects on cell properties. The N‐PEMU films were made via layer‐by‐layer adsorption of thermoresponsive monomers copolymerized with charged monomers, positively charged allylamine hydrochloride (PAH), or negatively charged styrene sulfonic acid (PSS) and compared to fetal bovine serum (FBS) coated surfaces. Surface charges were shown to alter the extracellular matrix (ECM) structure and subsequently regulate hMSC responses including adhesion, proliferation, integrin expression, detachment, and colony forming ability. The positively charged thermal responsive surfaces improved cell adhesion and growth in a range comparable to control surfaces while maintaining significantly higher CFU‐F forming ability. Immunostaining and Western blot results indicate that the improved cell adhesion and growth on the positively charged surfaces resulted from the elevated adhesion of ECM proteins such as fibronectin on the positively charge surfaces. These results demonstrate that the layer‐by‐layer approach is an efficient way to form PNIPAM‐based thermal responsive surfaces for hMSC growth and removal without enzymatic treatment. The results also show that surface charge regulates ECM adhesion, which in turn influences not only cell adhesion but also CFU‐forming ability and their multi‐lineage differentiation potential. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010
A new approach to outdoor illumination estimation based on statistical analysis for augmented reality
Authors: Liu Yanli , Qin Xueying , Xing Guanyu , Peng Qunsheng 
Published: May 2010

AbstractIllumination consistency plays an important role in realistic rendering of virtual characters which are integrated into a live video of real scene. This paper proposes a novel method for estimating the illumination conditions of outdoor videos captured by a fixed viewpoint. We first derive an analytical model which relates the statistics of an image to the lighting parameters of the scene adhering to the basic illumination model. Exploiting this model, we then develop a framework to estimate the lighting conditions of live videos. In order to apply the above approach to scenes containing dynamic objects such as intrusive pedestrians and swaying trees, we enforce two constraints, namely spatial and temporal illumination coherence, to refine the solution. Our approach requires no geometric information of the scenes and is sufficient for real‐time performance. Experiments show that with the lighting parameters recovered by our method, virtual characters can be seamlessly integrated into the live video. Copyright © 2010 John Wiley & Sons, Ltd.
Evolved Diversification of a Modular Natural Product Pathway: Apratoxins F and G, Two Cytotoxic Cyclic Depsipeptides from a Palmyra Collection ofLyngbya bouillonii
Authors: Tidgewell Kevin , Engene Niclas , Byrum Tara , Media Joseph , Doi Takayuki , Valeriote Fred A. , Gerwick William H. 
Published: May 2010

AbstractA collection ofLyngbya bouilloniifrom Palmyra Atoll in the Central Pacific, a site several thousand kilometers distant from all previous collections of this chemically prolific species of cyanobacterium, was found to contain two new cancer cell cytotoxins of the apratoxin family. The structures of the new compounds, apratoxins F and G, were determined by 1D and 2D NMR techniques in combination with mass spectrometric methods. Stereochemistry was explored by using chromatographic analyses of the hydrolytically released fragments in combination with NMR and optical rotation comparisons with known members of the apratoxin family. Apratoxins F and G add fresh insights into the SAR of this family because they incorporate anN‐methyl alanine residue at a position where all prior apratoxins have possessed a proline unit, yet they retain high potency as cytotoxins to H‐460 cancer cells with IC50values of 2 and 14 nM, respectively. Additional assays using zone inhibition of cancer cells and clonogenic cells give a comparison of the activities of apratoxin F to apratoxin A. Additionally, the clonogenic studies in combination with maximum tolerated dose (MTD) studies provided insights as to dosing schedules that should be used for in vivo studies, and preliminary in vivo evaluation validated the predicted in vivo efficacy for apratoxin A. These new apratoxins are illustrative of a mechanism (the modification of an NRPS adenylation domain specificity pocket) for evolving a biosynthetic pathway so as to diversify the suite of expressed secondary metabolites.
Sum of ranking differences for method discrimination and its validation: comparison of ranks with random numbers
Authors: Héberger Károly , Kollár‐Hunek Klára 
Published: May 2010

AbstractThis paper describes the theoretical background, algorithm and validation of a recently developed novel method of ranking based on the sum of ranking differences [TrAC Trends Anal. Chem. 2010; 29: 101–109]. The ranking is intended to compare models, methods, analytical techniques, panel members, etc. and it is entirely general. First, the objects to be ranked are arranged in the rows and the variables (for example model results) in the columns of an input matrix. Then, the results of each model for each object are ranked in the order of increasing magnitude. The difference between the rank of the model results and the rank of the known, reference or standard results is then computed. (If the golden standard ranking is known the rank differences can be completed easily.) In the end, the absolute values of the differences are summed together for all models to be compared. The sum of ranking differences (SRD) arranges the models in a unique and unambiguous way. The closer the SRD value to zero (i.e. the closer the ranking to the golden standard), the better is the model. The proximity of SRD values shows similarity of the models, whereas large variation will imply dissimilarity. Generally, the average can be accepted as the golden standard in the absence of known or reference results, even if bias is also present in the model results in addition to random error. Validation of the SRD method can be carried out by using simulated random numbers for comparison (permutation test). A recursive algorithm calculates the discrete distribution for a small number of objects (n < 14), whereas the normal distribution is used as a reasonable approximation if the number of objects is large. The theoretical distribution is visualized for random numbers and can be used to identify SRD values for models that are far from being random. The ranking and validation procedures are called Sum of Ranking differences (SRD) and Comparison of Ranks by Random Numbers (CRNN), respectively. Copyright © 2010 John Wiley & Sons, Ltd.
A Reusable DNA Single‐Walled Carbon‐Nanotube‐Based Fluorescent Sensor for Highly Sensitive and Selective Detection of Ag+ and Cysteine in Aqueous Solutions
Authors: Zhao Chao , Qu Konggang , Song Yujun , Xu Can , Ren Jinsong , Qu Xiaogang 
Published: May 2010

AbstractHere we report a reusable DNA single‐walled carbon nanotube (SWNT)‐based fluorescent sensor for highly sensitive and selective detection of Ag+ and cysteine (Cys) in aqueous solution. SWNTs can effectively quench the fluorescence of dye‐labeled single‐stranded DNA due to their strong π–π stacking interactions. However, upon incubation with Ag+, Ag+ can induce stable duplex formation mediated by C–Ag+–C (C=cytosine) coordination chemistry, which has been further confirmed by DNA melting studies. This weakens the interactions between DNA and SWNTs, and thus activates the sensor fluorescence. On the other hand, because Cys is a strong Ag+ binder, it can remove Ag+ from C–Ag+–C base pairs and deactivates the sensor fluorescence by rewrapping the dye‐labeled oligonucleotides around the SWNT. In this way, the fluorescence signal‐on and signal‐off of a DNA/SWNT sensor can be used to detect aqueous Ag+ and Cys, respectively. This sensing platform exhibits high sensitivity and selectivity toward Ag+ and Cys versus other metal ions and the other 19 natural amino acids, with a limit of detection of 1 nM for Ag+ and 9.5 nM for Cys. Based on these results, we have constructed a reusable fluorescent sensor by using the covalent‐linked SWNT–DNA conjugates according to the same sensing mechanism. There is no report on the use of SWNT–DNA assays for the detection of Ag+ and Cys. This assay is simple, effective, and reusable, and can in principle be used to detect other metal ions by substituting C–C base pairs with other native or artificial bases that selectively bind to other metal ions.
Organocatalyzed Cyclopropanation of α‐Substituted α,β‐Unsaturated Aldehydes: Enantioselective Synthesis of Cyclopropanes Bearing a Chiral Quaternary Center
Authors: Terrasson Vincent , van der Lee Arie , Marcia de Figueiredo Renata , Campagne Jean Marc 
Published: May 2010

AbstractAn enantioselective cyclopropanation of α‐substituted α,β‐unsaturated aldehydes with bromomalonate has been successfully developed through a domino Michael/α‐alkylation strategy. The method allows the efficient formation of cyclopropanes bearing a quaternary carbon stereocenter at the α‐position of the aldehydes by using iminium/enamine catalysis and gives a nice extension on the organocatalytic cyclopropanation of bromomalonate and α,β‐unsaturated aldehydes previously reported by other groups. Very good yields (up to 81 %) and enantioselectivities (up to 97 % ee) have been obtained. The optically active cyclopropane derivatives are of high synthetic interest as useful targets for further elaboration into more complex structures.
Influence of Process Parameters on the Reaction Kinetics of the Chromium‐Catalyzed Trimerization of Ethylene
Authors: Wöhl Anina , Müller Wolfgang , Peitz Stephan , Peulecke Normen , Aluri Bhaskar R. , Müller Bernd H. , Heller Detlef , Rosenthal Uwe , Al‐Hazmi Mohammed H. , Mosa Fuad M. 
Published: May 2010

AbstractIn this paper we report the results of an extensive experimental kinetic study carried out on the novel ethylene trimerization catalyst system, comprising the chromium source [CrCl3(thf)3] (thf=tetrahydrofuran), a Ph2P‐N(iPr)‐P(Ph)‐N(iPr)H (PNPNH) ligand (Ph=phenyl, iPr=isopropyl), and triethylaluminum (AlEt3) as activator. It could be shown that the initial activity shows a first‐order dependency on the ethylene concentration. Also, a first‐order dependency was found for the catalyst concentration. The initial activity follows a typical Arrhenius behavior with an experimentally determined activation energy of 52.6 kJ mol−1. At elevated temperatures (ca. 80 °C), a significant deactivation was observed, which can be tentatively traced back to a ligand rearrangement in the presence of AlEt3. After a fast initial phase, a pronounced ‘kink’ in the ethylene‐uptake curve is observed, followed by a slow, almost linear, further increase of the total ethylene consumption. The catalyst composition, in particular the ligand/chromium and the cocatalyst/chromium molar ratio, has a strong impact on the catalytic performance of the trimerization of ethylene.
ChemInform Abstract: N‐Hydroxyphthalimide‐Catalyzed Radical Addition of 1,3‐Dioxolanes and Molecular Oxygen to Alkenes under Ambient Conditions: A New Route to β‐Oxycarbonyl Compounds.
Authors: Hirano Kazutaka , Iwahama Takahiro , Sakaguchi Satoshi , Ishii Yasutaka 
Published: May 2010

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Synthesis of New Pyridoquinoxalines, Thienopyridoquinoxalines and Pyrimidothienopyridoquinoxalines.
Authors: Moustafa O. S. , Badr M. Z. A. , Kamel E. M. 
Published: May 2010

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Radical Cyclizations of Methylenecyclopropyl Azetidinones — Synthesis of Novel Tricyclic β‐Lactams.
Authors: Penfold David J. , Pike Kurt , Genge Anthony , Anson Mike , Kitteringham John , Kilburn Jeremy D. 
Published: May 2010

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.