bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cationic Triple‐Decker Complexes with a Bridging 4‐Borataborepine Ligand: Synthesis, Structure, and Bonding
Authors: Mutseneck Elena V. , Wadepohl Hubert , Kudinov Alexander R. , Siebert Walter 
Published: June 2008

AbstractCationic 30 VE triple‐decker complexes [Cp*Ru(μ‐η7:η7‐C5B2Me6H)ML]+[ML = Co(C4Me4) (3a), RuCp* (4a), Rh(cod) (7a), and Ir(cod) (8a)] with a bridging hexamethyl‐4‐borataborepine ligand were obtained by electrophilic stacking of the sandwich compound Cp*Ru(η7‐C5B2Me6H) (2a) with [ML]+complex fragments. The reaction of the phenyl‐substituted derivative Cp*Ru(η7‐7‐PhC5B2Me5H) (2b) with [(C4Me4)Co(MeCN)3]+selectively affords the triple‐decker complex [Cp*Ru(μ‐η7:η7‐7‐PhC5B2Me5H)Co(C4Me4)]+(3b), whereas a similar reaction with [Cp*RuCl]4/TlBF4produces a 1:3 mixture of cations, the triple‐decker [Cp*Ru(μ‐η7:η7‐7‐PhC5B2Me5H)RuCp*]+(4b) and the arene‐coordinated [Cp*Ru(μ‐η6:η7‐7‐PhC5B2Me5H)RuCp*]+(5). Stacking of Cp*Ru(η7‐7‐PhCH2C5B2Me5H) (2c) with [CpRu(MeCN)3]+selectively gives the triple‐decker complex [Cp*Ru(μ‐η7:η7‐7‐PhCH2C5B2Me5H)RuCp]+(6c). The dinuclear cations3–8were isolated as deep‐colored air‐stable salts with [BF4]–or [PF6]–anions in moderate to high yields. Structures of3bPF6,4aBF4,7aBF4, and8aBF4were confirmed by X‐ray diffraction studies. Energy decomposition analysis of complexes CpRu(ring) and [CpRu(ring)RuCp]+(ring = Cp, C5BH6, C5B2H7) revealed that the insertion of BH units makes the bonding between [ring]–and [RuCp]+more covalent. According to Mulliken population analysis, weakening of π‐donation and strengthening of δ‐back donation occur in the same order. The electrostatic character of the bond and the contribution of σ‐donation to the covalent bonding are higher in the case of bifacially bonded rings. The boron‐containing triple‐decker complexes are considerably more stable than the cyclopentadienyl analog. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Polymer‐Mediated Growth of Highly Crystalline Nano‐ and Micro‐Sized LiNi0.5Mn1.5O4 Spinels
Authors: Arrebola José Carlos , Caballero Alvaro , Hernán Lourdes , Morales Julián 
Published: June 2008

AbstractThe use of polymers containing oxygen‐based functional groups [polyethylene glycol (PEG), poly(methyl methacrylate) (PMMA)] has been studied to synthesize highly crystalline nanometric LiNi0.5Mn1.5O4 spinel. Polyvinylidene fluoride (PVDF), which was also tested, failed in the spinel synthesis. Mechanical activation of hydrated salts in the presence of oxalic acid and the polymer, followed by heating at 800 °C for a few minutes, is sufficient to obtain pseudopolyhedral particles ranging from 60–80 nm in size. X‐ray broadening analysis and the electron micrographs of the microstructure reveal that the polymer has an improved particle crystallinity. Calcining at 400 °C tailors the particle shape towards a nanorod‐like morphology due to the nonionic surfactant properties of PEG. The ability of the functional groups of these polymers to bind to metal ions brings them closer and therefore shortens the diffusion paths followed to adopt the spinel structure. At high temperature, the particles adopt a well‐defined pseudopolyhedral morphology with a smooth texture and a lower microstrain content than that obtained in the absence of polymer. The results of the electrochemical tests show that the polymer‐assisted nanoparticles exhibit improved reversible capacity and better cycling properties as electrode materials in lithium cells. The improved crystallinity of the particles is the key factor in this respect, particularly when the cells are operated at low rates.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Characterization and chemometric study of crude and refined oils from table olive by‐products
Authors: Ruiz‐Méndez M. Victoria , López‐López Antonio , Garrido‐Fernández Antonio 
Published: June 2008

AbstractTable olive processing produces defective fruits and the conditioning operations give rise to solid by‐products which are processed to obtain oil. In this study, the most relevant characteristics of crude oils extracted from table olive by‐products were high average acidity values (4.5%, green olives; 8.1%, ripe olives), ECN42 values of 0.34 (green olives) and 0.10 (ripe olives), while 2‐mono‐palmitin averaged 0.92%. The overall content of sterols was 2257 mg/kg (green olives) and 1746 mg/kg (ripe olives), while the concentration of cholesterol was 36 mg/kg (green olives) and 19 mg/kg (ripe olives). The effect of refining was mainly reflected by a decrease in acidity and sterols. Although most characteristics were in agreement with the established regulation for olive oil, the overall trans fatty acid content, the low apparent β‐sitosterol content, and the relatively high cholesterol content prevented their inclusion into classes of crude or refined lampante or pomace olive oils, not even into the vegetable oil category. Therefore, the oils analyzed should be considered for non‐edible purposes. The physicochemical characteristics used for chemometric discrimination permitted discrimination among types of oils (crude, 100%; physically refined, 90%; chemically refined, 100%), elaboration styles (green and ripe olives, 100%) and cultivars (Gordal, Manzanilla, Hojiblanca and Cacereña, 100%), with the sterol composition being the most useful parameter for discrimination.
Imino‐Diels–Alder Reactions of 1‐Aryl‐3‐(trialkylsiloxy)‐1,3‐butadienes in Solution and the Solid Phase
Authors: Caballero Esther , Figueroa Javier , Puebla Pilar , Peláez Rafael , Tomé Fernando , Medarde Manuel 
Published: June 2008

AbstractImino‐Diels–Alder reactions between 1‐aryl‐ or 1‐heteroaryl‐3‐(trialkylsiloxy)‐1,3‐butadienes and imines derived from ethyl glyoxylate have been studied. When an achiral imine was used, the diastereoselectivity depended on the nature of the aryl or heteroaryl system; diastereoselectivities > 90 % were observed with methoxyphenyl or indolyl substituents, but were much lower for nitro substituents. High diastereoselectivities were also achieved if a chiral imine derived from methylbenzylamine was used as the dienophile. Solid‐supported imine dienophiles yielded the N‐deprotected cycloadducts by direct cleavage from the resin with no diastereoselectivity. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Synthesis of New Polycyclic γ‐ and δ‐Lactones upon Activation of, and Nucleophilic Additions to, Diazines: Influence of the Activating Agents
Authors: Garduno‐Alva A. , Xu Y. , Gualo‐Soberanes N. , Lopez‐Cortes J. , Rudler H. , Parlier A. , Ortega‐Alfaro M. C. , Alvarez‐Toledano C. , Toscano R. A. 
Published: June 2008

AbstractThe reaction of bis(trimethylsilyl)ketene acetals 2 with N‐heterocycles containing either one or two nitrogen atoms in the presence of triflic anhydride has been examined and the structures of the resulting products compared with those obtained by using methyl chloroformate as the activating agent. Whereas pyridine, pyrazine, quinoxaline and pyrimidine led to the same type of fused δ‐ or γ‐lactones 4, 6, 8, 10 and 11 as with methyl chloroformate, the behaviour of pyridazine appeared to be peculiar. In the presence of methyl chloroformate, this heterocycle led to δ‐lactones 16 via stable dihydropyridazines, with triflic anhydride, the direct formation of γ‐lactones 20 was observed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Use of Allenylphosphonates as New Substrates for Phosphane‐Catalyzed [3+2] and [4+2] Annulations
Authors: Panossian Armen , Fleury‐Brégeot Nicolas , Marinetti Angela 
Published: June 2008

AbstractThe suitability of allenylphosphonates as substrates in phosphane‐catalyzed annulation reactions has been investigated. Despite their lower reactivity relative to allenyl esters, allenylphosphonates overall display the anticipated behavior: pyrrolines, tetrahydropyridines, and cyclopentenes bearing phosphoryl functions were obtained from imines, α,β‐unsaturated esters, and enones in Bu3P‐ or iBu3P‐promoted reactions. Enantioselective variants of these cyclization reactions afforded enantiomeric excesses of up to 90 % when phosphepine A2 was used as the chiral catalyst. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
2H‐Pyrrole Derivatives from an Aza‐Nazarov Reaction Cascade Involving Indole as the Neutral Leaving Group
Authors: Ghavtadze Nugzar , Fröhlich Roland , Würthwein Ernst‐Ulrich 
Published: June 2008

AbstractTrifluoromethyl‐substituted N‐indolinyl‐1‐aza‐1,4‐dien‐3‐ones 4, which are accessible in good yields from indolinylimino esters 6 in a two‐step procedure, undergo a novel type of aza‐Nazarov cyclization if treated with strong acids to give the hitherto unknown 3‐hydroxy‐5H‐pyrrole derivatives 8a–p. The solvent‐free polyphosphoric acid/acyl anhydride system as the acidic reaction medium is especially efficient and requires only short reaction times. According to quantum chemical calculations the key step in the reaction cascade is the cleavage of the N–N bond of the hydrazone fragment of a protonated N‐(indolin‐1‐yl)‐1‐aza‐1,4‐dien‐3‐one intermediate such as 10. This intermediate releases 3H‐indole as an unusual, but very efficient neutral leaving group. Several 1‐aza‐1,4‐dien‐3‐ones 4 and some 3‐hydroxy‐5H‐pyrrole derivatives 8 were characterized by X‐ray diffraction.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Separation of α‐, β‐, γ‐, δ‐tocopherols and α‐tocopherol acetate on a pentaerythritol diacrylate monostearate‐ethylene dimethacrylate monolith by capillary electrochromatography
Authors: Chaisuwan Patcharin , Nacapricha Duangjai , Wilairat Prapin , Jiang Zhengjin , Smith Norman W. 
Published: June 2008

AbstractThis work reports the first use of a monolith with method development for the separation of tocopherol (TOH) compounds by CEC with UV detection. A pentaerythritol diacrylate monostearate‐ethylene dimethacrylate (PEDAS‐EDMA) monolithic column has been investigated for an optimised condition to separate α‐, β‐, γ‐ and δ‐TOHs, and α‐tocopherol acetate (TAc). The PEDAS‐EDMA monolith showed a remarkably good selectivity for separation of the TOH isomers including the β‐ and γ‐isomers which are not easily separated by standard C8 or C18 particle‐packed columns. Retention studies indicated that an RP mechanism was involved in the separation on the PEDAS‐EDMA column, but polar interactions with the underlying ester and hydroxyl groups enhanced the separation of the problematic β‐ and γ‐isomers. Separation of all the compounds was achieved within 25 min using 3:10:87 v/v/v 100 mM Tris buffer (pH 9.3)/methanol/ACN as the mobile phase. The method was successfully applied to a pharmaceutical sample with recoveries from 93 to 99%. Intraday and interday precisions (%RSD) for peak area and retention time were less than 2.3. LODs for all four TOHs and TAc were below 1 ppm.
Analysis of disulphide linkages in bovine κ‐casein oligomers using two‐dimensional electrophoresis
Authors: Holland John W. , Deeth Hilton C. , Alewood Paul F. 
Published: June 2008

AbstractDisulphide bonds play an important role in protein structure and function. Bovine κ‐casein (κ‐csn), an important glycoprotein in milk, contains two cysteines that can form disulphide bonds. On 2‐D gels run under nonreducing conditions the κ‐csn in milk presented a complex pattern of monomers and disulphide‐linked oligomers. Trains of spots corresponding to monomers to hexamers were observed as a result of the participation of different glycoforms and phosphoforms in oligomer formation. The dimers and trimers ran as doublets on the gel and analysis of the disulphide‐linked peptides released from them after in‐gel tryptic digestion showed they were the result of different disulphide linkages. The linkages were confirmed by MSMS. When milks with electrophoretically distinct genetic variants of κ‐csn were mixed and run on 2‐D gels, they retained their distinct patterns indicating that disulphide exchange reactions or disulphide ‘scrambling’ was not occurring during 2‐D analysis. The patterns observed represent the native distribution of κ‐csn in milk at harvest. The role and significance of the disulphide bonding of κ‐csn are discussed.
Microfluidic electroporation for selective release of intracellular molecules at the single‐cell level
Authors: Bao Ning , Wang Jun , Lu Chang 
Published: June 2008

AbstractAnalysis of intracellular materials at the single‐cell level presents opportunities for probing the heterogeneity of a cell population. Lysis by electroporation has been gaining popularity as a rapid method for disruption of the cell membrane and release of intracellular contents. In this report, we selectively released specific intracellular molecules for interrogation at the single‐cell level by tuning the parameters of electroporation. We examined the release of a small molecule, calcein (MW˜600), and a 72‐kDa protein kinase, Syk, tagged by enhanced green fluorescent protein (EGFP) from chicken B cells during electroporation at the single‐cell level. We studied the effects of the field intensity and the field duration on the release of the two molecules. We found that calcein in general was released at lower field intensities and shorter durations than did SykEGFP. By tuning the electrical parameters, we were able to deplete calcein from the cells before SykEGFP started to release. This approach potentially provides a high‐throughput alternative for probing different intracellular molecules at the single‐cell level compared to chemical cytometry by eliminating complete disruption of the cell membrane.
Study of protein binding and micellar partition of highly hydrophobic molecules in a single system using capillary electrophoresis
Authors: Liu Shufang , Wang Hailin , Song Maoyong , Yin Junfa , Jiang Guibin 
Published: June 2008

AbstractThe measurement of protein binding of highly hydrophobic molecules is challenging due to poor solubility and strong adsorption, and further complicated by the competition of lipophilic partition in biological systems. Here, an attempt is presented to simultaneously simulate protein binding and lipophilic partition of hydrophobic molecules in a single system using CE. In this system, the incorporated biocompatible micelles also facilitate the protein binding study of hydrophobic molecules by enhancing their solubility (27 to 104times) and eliminating the problematic adsorption. An equation is derived to describe the competition of protein binding and lipophilic partition and to estimate the protein binding constants in nonmicellar aqueous solution. Five polycyclic aromatic hydrocarbons (PAHs) and HSA were used as model hydrophobic compounds and protein, respectively. The study of the competition between lipophilic partition and protein binding reveals that the binding of the PAHs to HSA is governed by hydrophobic interactions and such binding (except naphthalene) can be eliminated by the lipophilic partition in the nonionic surfactant Tween‐20. The developed method may be extended to evaluate the interactions of various macromolecules (receptors, enzymes, proteins, and DNA/RNA) and hydrophobic molecules.
Confinement effects on the morphology of photopatterned porous polymer monoliths for capillary and microchip electrophoresis of proteins
Authors: He Mei , Zeng Yong , Sun Xuejun , Harrison D. Jed 
Published: June 2008

AbstractWe find that the morphology of porous polymer monoliths photopatterned within capillaries and microchannels is substantially influenced by the dimensions of confinement. Porous polymer monoliths were prepared by UV‐initiated free‐radical polymerization using either the hydrophilic or hydrophobic monomers 2‐hydroxyethyl methacrylate or butyl methacrylate, cross‐linker ethylene dimethacrylate and different porogenic solvents to produce bulk pore diameters between 3.2 and 0.4 µm. The extent of deformation from the bulk porous structure under confinement strongly depends on the ratio of characteristic length of the confined space to the monolith pore size. The effects are similar in cylindrical capillaries and D‐shaped microfluidic channels. Bulk‐like porosity is observed for a confinement dimension to pore size ratio >10, and significant deviation is observed for a ratio <5. At the extreme limit of deformation a smooth polymer layer ˜300 nm thick is formed on the surface of the capillary or microchannel. Surface tension or wetting also plays a role, with greater wetting enhancing deformation of the bulk structure. The films created by extreme deformation provide a rapid and effective strategy to create robust wall coatings, with the ability to photograft various surface chemistries onto the coating. This approach is demonstrated through cationic films used for electroosmotic flow control and neutral hydrophilic coatings for electrophoresis of proteins.
Isoelectric focusing in an ordered micropillar array
Authors: Dauriac Virginie , Descroix Stéphanie , Chen Yong , Peltre Gabriel , Sénéchal Hélène 
Published: June 2008

AbstractAn original micropillar array dedicated to electrophoretic separations has been developed. It consists of a rectangular zone of PDMS micropillars protruding on a PDMS block. This area has been chosen to mimic a diluted gel structure and remains uncovered to keep the ability to perform an immunoblot after the protein separation for further applications in the field of allergy diagnosis. The micropillar array geometry has been optimized by evaluating the influence of pillar shape, pillar size and interpillar distance on evaporation and IEF separation. The separation conditions namely electrolyte composition, temperature and sample loading have been studied. Finally a protein mixture with pI ranging from 4.7 to 10.6 has been successfully separated within this microdevice by IEF without decreasing the resolving power obtained with conventional minigel. The micropillar array developed for electrophoretic separations leads to much shorter analysis times and can be reused several times while gels are disposable.
Flow resistance in steep mountain streams
Authors: Reid Donald E. , Hickin Edward J. 
Published: June 2008

AbstractResistance to flow at low to moderate stream discharge was examined in five small (12–77 km2 drainage area) tributaries of Chilliwack River, British Columbia, more than half of which exhibit planar bed morphology. The resulting data set is composed of eight to 12 individual estimates of the total resistance to flow at 61 cross sections located in 13 separate reaches of five tributaries to the main river. This new data set includes 625 individual estimates of resistance to flow at low to moderate river stage. Resistance to flow in these conditions is high, highly variable and strongly dependent on stage. The Darcy–Weisbach resistance factor (ff) varies over six orders of magnitude (0·29–12 700) and Manning's n varies over three orders of magnitude (0·047–7·95). Despite this extreme range, both power equations at the individual cross sections and Keulegan equations for reach‐averaged values describe the hydraulic relations well. Roughness is divided into grain and form (considered as all non‐grain sources) components. Form roughness is the dominant component, accounting for about 90% of the total roughness of the system (i.e., form roughness is on average 8.6 times as great as grain roughness). Of the various quantitative and qualitative form‐roughness indicators observed, only the sorting coefficient (σ = D84/D50) correlates well with form roughness. Copyright © 2008 John Wiley & Sons, Ltd.
Spatial analysis of stream power using GIS: SLk anomaly maps
Authors: Pérez‐Peña J. V. , Azañón J. M. , Azor A. , Delgado J. , González‐Lodeiro F. 
Published: June 2008

AbstractThe stream length‐gradient index (SL) shows the variation in stream power along river reaches. This index is very sensitive to changes in channel slope, thus allowing the evaluation of recent tectonic activity and/or rock resistance. Nevertheless, the comparison of SL values from rivers of different length is biased due to the manner in which the index is formulated, thus making correlations of SL anomalies along different rivers difficult. Therefore, when undertaking a comparison of SL values of rivers of different lengths, a normalization factor must be used. The graded river gradient (K) has already been used in some studies to normalize the SL index. In this work, we explore the relationships between the graded river gradient (K), the SL index and the stream power, proposing the use of a re‐named SLk index, which enables the comparison of variable‐length rivers, as well as the drawing of SLk anomaly maps. We present here a GIS‐based procedure to generate SLk maps and to identify SLk anomalies. In order to verify the advantages of this methodology, we compared an SLk map of the NE border of the Granada basin with both simple river profile–knickpoint identification and with an SL map. The results show that the SLk map supplies good results with defined anomalies and suitably reflects the main tectonic and lithological features of the study area. Copyright © 2008 John Wiley & Sons, Ltd.
Channel degradation and slope adjustment in steep streams controlled through bed sills
Authors: Martín‐Vide J. P. , Andreatta A. 
Published: June 2008

AbstractGeneral, parallel and rotational degradation and the effect of bed sills are investigated with the aid of historical field data and laboratory experiments. The case under consideration is a system of two tributaries and a main river in northeast Spain, characterized by its short length, steepness and ephemeral nature. The comparison of bed profiles since 1962 revealed an incision greater than 5·5 m. The main causes of degradation are thought to be channelization (width reduction) and urban growth. The equilibrium slopes with and without sills were obtained in 111 live‐bed flume tests. It is demonstrated that the bed slope is milder with sills than without sills under the same flow and sediment rates. The equations for the calculation of equilibrium slopes, scaled to prototype, are applied to the case‐study, with good agreement. Copyright © 2008 John Wiley and Sons, Ltd.
Effects of terrain smoothing on topographic shielding correction factors for cosmogenic nuclide‐derived estimates of basin‐averaged denudation rates
Authors: Norton Kevin P. , Vanacker Veerle 
Published: June 2008

AbstractEstimation of spatially averaged denudation rates from cosmogenic nuclide concentrations in sediments depends on the surface production rates, the scaling methods of cosmic ray intensities, and the correction algorithms for skyline, snow and vegetation shielding used to calculate terrestrial cosmogenic nuclide production. While the calculation of surface nuclide production and application of latitude, altitude and palaeointensity scaling algorithms are subjects of active research, the importance of additional correction for shielding by topographic obstructions, snow and vegetation is the subject of ongoing debate. The derivation of an additional correction factor for skyline shielding for large areas is still problematic. One important issue that has yet to be addressed is the effect of the accuracy and resolution of terrain representation by a digital elevation model (DEM) on topographic shielding correction factors. Topographic metrics scale with the resolution of the elevation data, and terrain smoothing has a potentially large effect on the correction of terrestrial cosmogenic nuclide production rates for skyline shielding. For rough, high‐relief landscapes, the effect of terrain smoothing can easily exceed analytical errors, and should be taken into account. Here we demonstrate the effect of terrain smoothing on topographic shielding correction factors for various topographic settings, and introduce an empirical model for the estimation of topographic shielding factors based on landscape metrics. Copyright © 2008 John Wiley and Sons, Ltd.