bluuebunny/crossref_metadata_2025_split huggingface dataset:
13C‐NMR Study of the Ruthenium(II)‐Catalyzed Degradation of Labeled G‐Factor Endoperoxides: Proposal of a Likely Biogenetic Pathway and Evidence for CO2 Release
Authors: André‐Barrès Christiane , Baltas Michel , Massou Stéphane 
Published: March 2006

AbstractG‐factor endoperoxides are natural products acting as phytohormones and contribute to root inhibition and frost resistance in Eucalyptus grandis and other Myrtaceae. Several (Z)‐ and (E)‐configured cyclopentane‐1,3‐dione metabolites of G‐factors have been found in some Eucalyptus extracts. Interestingly, these probable metabolites are identical to the products obtained by RuII‐catalyzed reduction of G‐factors. In the present work, we, thus, studied the mechanism involved in the formation of these compounds by means of in‐depth NMR distribution analysis of two differently 13C‐labeled G3‐factors. The observed CO2 release is underlined, and a comparison with the corresponding FeII‐induced degradation of G‐factor endoperoxides is made. Also, the type of electron transfer proposed in the two processes is discussed and, tentatively, connected to the role of endoperoxides in plants.
Carotid stenting with distal protection in high surgical risk patients: The BEACH trial 30 day results
Authors: White Christopher J. , Iyer Sriram S. , Hopkins L. Nelson , Katzen Barry T. , Russell Mary E. 
Published: March 2006

AbstractBackground: The BEACH trial evaluated the outcomes of carotid artery stent placement with distal emboli protection, using the Carotid Wallstent® and the FilterWire EX®/EZTM, in patients at high surgical risk for carotid endarterectomy (CEA). Methods: We enrolled 747 patients at high surgical risk for CEA due to prespecified anatomical criteria and/or medical comorbidities. The trial included both symptomatic (>50% carotid artery stenosis) as well as asymptomatic (>80% carotid artery stenosis) high surgical risk patients. Three groups of patients were included in the trial. The Roll‐in (R) group (n = 189/747, [25%]) included up to nine patients per site for familiarization of the device and protocol; the Pivotal (P) group (n = 480/747, [65%]) was intended for presentation to the FDA for consideration of device approval; and a Bilateral (B) registry group (n = 78/747, [10%]) was included because of the need to treat patients with bilateral carotid artery disease. In the 480 Pivotal patients, anatomic criteria represented the most frequent high‐risk surgical category for enrollment (58.8%), followed by prior CEA (34.2%), multivessel (≥2) coronary artery disease (21.7%), and contralateral carotid occlusion (18.1%). Results: The technical success rate for stent deployment and FilterWire EX/EZ deployment and retrieval was 98.2%. The mean postprocedure angiographic diameter stenosis in the Pivotal group was reduced to 10.8%, while the overall procedure success rate (<50% residual diameter stenosis) after stent deployment was 98%. The 30 day composite major adverse event (MAE) rate for the entire cohort of 747 patients (i.e. inclusive of all 3 groups) was 5.8% (all death = 1.5%, all stroke = 4.4%, and all myocardial infarction (MI) = 1.0%). In subgroup analysis, there was no significant difference in the MAE rate between the three groups (P = 5.8%, R = 6.9%, B = 2.6%, P = 0.42). Conclusion: The similarity in periprocedural event rates for the Pivotal and Roll‐in groups suggests a flat learning curve for experienced operators using this carotid stent system. The similarity in event rates for the Bilateral group, when compared with the Roll‐in and Pivotal groups, suggests that staged sequential treatment of bilateral stenoses may be performed at the same risk as for unilateral lesions. The 30‐day safety of this stent and distal emboli protection system is encouraging and compares favorably with other carotid stent trials in high surgical risk patients. © 2006 Wiley‐Liss, Inc.
Dehydrodimerization of Isobutene to 2,5‐Dimethyl‐1,5‐Hexadiene over Bismuth‐(III)‐Oxide and Various Additives
Authors: Taubert T. , Scholz P. , Ondruschka B. 
Published: March 2006

AbstractBi2O3 and mixtures with different additives (Cr2O3, MoO3, NH4VO3, SnO2, and V2O5) have been chosen to study the oxidative dehydrodimerization of isobutene. The catalytic performances were investigated by variation of the residence time, isobutene to oxygen molar ratio, and pressure. The best results for 2,5‐dimethyl‐1,5‐hexadiene (DMH) yield (13 %) were achieved with Bi2O3 as the catalyst. The selectivity of DMH reaches values of over 90 %.
Mass Transfer during Solute Extraction from a Droplet with Internal Circulation in the Presence of a Constant Uniform Electric Field
Authors: Elperin T. , Fominykh A. 
Published: March 2006

AbstractMass transfer, under the influence of an constant uniform electric field in a ternary system, comprised of a transformed solute, a liquid dielectric continuous phase, and a stationary dielectric droplet, was considered in this study. The solubilities of the solute in the dispersed and continuous phases have the same order of magnitude, and the resistance to mass transfer in both phases is taken into account. The applied electric field causes Taylor circulation around the droplet, while the droplet deformation under the influence of the electric field is neglected. The problem is solved in the approximations of a thin concentration boundary layer in the dispersed and continuous phases. The bulk of a droplet, beyond the diffusion boundary layer, is completely mixed and the concentration of solute is homogeneous and time‐dependent in the bulk. The system of transient coupled equations of convective diffusion for solute transport in the dispersed and continuous phases with time‐dependent boundary conditions is solved by combining a generalized similarity transformation method with Duhamel's theorem; the solution is obtained in the form of a Volterra integral equation of the second kind. Numerical calculations essentially show an enhancement of the rate of mass transfer for dispersed liquid‐liquid systems, under the influence of an electric field.
MD Simulations of Diffusivities in Methanol‐n‐hexane Mixtures Near the Liquid‐liquid Phase Splitting Region
Authors: Krishna R. , van Baten J. M. 
Published: March 2006

AbstractMolecular Dynamics (MD) simulations have been carried out to determine the self‐diffusivities in binary mixtures of methanol and n‐hexane with varying compositions at four different temperatures of 303.15 K, 307.7 K, 310.7 K, and 313.15 K. The Darken relation was used to determine both the Fick diffusivity and the Maxwell‐Stefan diffusivity. The values of the Fick diffusivity obtained from the simulations are in very good agreement with published experimental data of Clark and Rowley [17]. These diffusivities approach zero near composition regions where liquid‐liquid phase splitting occurs. On the other hand, the Maxwell‐Stefan diffusivity is well‐behaved and appears to be practically insensitive to the complex thermodynamics.
Preparation and Characterization of a Solid Acid Catalyst from Commercial Niobia Hydrate
Authors: Frank B. , Yildiz A. , Habel D. , Schubert H. , Schomäcker R. 
Published: March 2006

AbstractA commercially available niobia hydrate, which is an industrial intermediate in the production of pure niobia, was prepared, characterized, and tested as a solid acid catalyst. The gas phase esterification of acetic acid with ethanol was used as a simple model reaction for the determination of the acidity and the catalytic activity. The kinetic evaluation of the experiments includes an estimation of mass transport limitation as well as a mechanistic study.
A Hybrid Scheme for the Solution of the Bivariate Spatially Distributed Population Balance Equation
Authors: Attarakih M. M. , Bart H.‐J. , Faqir N. M. 
Published: March 2006

AbstractThe advantages of the generalized fixed pivot technique as extended to mass transfer and the quadrature method of moments are hybridized to reduce the bivariate spatially distributed population balance equation describing the coupled hydrodynamics and mass transfer in liquid‐liquid extraction columns. The key idea in the hybridization technique is to use the available moments furnished by the generalized fixed pivot technique to find the abscissa and weights for the Gaussian‐quadrature based approach, in an attempt to evaluate the integrals over unknown droplet densities. To implement the quadrature method of moments efficiently, an explicit form for the abscissas and weights is derived based on the product‐difference algorithm as described by McGraw [1]. The proposed technique is found to reduce the discrete system of partial differential equations from 2 Mx + 1 to Mx + 2, where Mx is the number of pivots or classes. The spatial variable is discretized in a conservative form using a couple of recently published central difference schemes. The numerical predictions of the detailed and reduced models are found to be almost identical, accompanied by a substantial reduction of the CPU time as a characteristic of the hybrid model.
Mechanistic Studies of the Photocatalytic Oxidation of Trichloroethylene with Visible‐Light‐Driven N‐Doped TiO2 Photocatalysts
Authors: Joung Soon‐Kil , Amemiya Takashi , Murabayashi Masayuki , Itoh Kiminori 
Published: March 2006

AbstractVisible‐light‐driven TiO2 photocatalysts doped with nitrogen have been prepared as powders and thin films in a cylindrical tubular furnace under a stream of ammonia gas. The photocatalysts thus obtained were found to have a band‐gap energy of 2.95 eV. Electron spin resonance (ESR) under irradiation with visible light (λ ≥ 430 nm) afforded the increase in intensity in the visible‐light region. The concentration of trapped holes was about fourfold higher than that of trapped electrons. Nitrogen‐doped TiO2 has been used to investigate mechanistically the photocatalytic oxidation of trichloroethylene (TCE) under irradiation with visible light (λ ≥ 420 nm). Cl and O radicals, which contribute significantly to the generation of dichloroacetyl chloride (DCAC) in the photocatalytic oxidation of TCE under UV irradiation, were found to be deactivated under irradiation with visible light. As the main by‐product, only phosgene was detected in the photocatalytic oxidation of TCE under irradiation with visible light. Thus, the reaction mechanism of TCE photooxidation under irradiation with visible light clearly differs markedly from that under UV irradiation. Based on the results of the present study, we propose a new reaction mechanism and adsorbed species for the photocatalytic oxidation of TCE under irradiation with visible light. The energy band for TiO2 by doping with nitrogen may involve an isolated band above the valence band.
Highly Enantioselective Addition of In Situ Prepared Arylzinc to Aldehydes Catalyzed by a Series of Atropisomeric Binaphthyl‐Derived Amino Alcohols
Authors: Lu Gui , Kwong Fuk Yee , Ruan Ji‐Wu , Li Yue‐Ming , Chan Albert S. C. 
Published: March 2006

AbstractThe direct addition of in situ prepared arylzinc to aldehydes with chiral binaphthyl‐derived amino alcohols as catalysts can afford optically active diarylmethanols in high yields and with excellent enantioselectivities (up to 99 % ee, ee=enantiomeric excess). By using a single catalyst, both enantiomers of many pharmaceutically interesting diarylmethanols can be obtained by the proper combination of various arylzinc reagents with different aldehydes; this catalytic system also works well for the phenylation of aliphatic aldehydes to give up to 96 % ee.
Bis(oxazoline) Lewis Acid Catalyzed Aldol Reactions of Pyridine N‐Oxide Aldehydes—Synthesis of Optically Active 2‐(1‐Hydroxyalkyl)pyridine Derivatives: Development, Scope, and Total Synthesis of an Indolizine Alkaloid
Authors: Landa Aitor , Minkkilä Anna , Blay Gonzalo , Jørgensen Karl Anker 
Published: March 2006

AbstractA new, short, and simplified procedure for the synthesis of optically active pyridine derivatives from pro‐chiral pyridine‐N‐oxides is presented. The catalytic and asymmetric Mukaiyama aldol reaction between ketene silyl acetals and 1‐oxypyridine‐2‐carbaldehyde derivatives catalyzed by chiral copper(II)–bis(oxazoline) complexes gave optically active 2‐(hydroxyalkyl)‐ and 2‐(anti‐1,2‐dihydroxyalkyl)pyridine derivatives in good yields and diastereoselectivities, and in excellent enantioselectivities—up to 99 % enantiomeric excess. As a synthetic application of the developed method, a full account for the asymmetric total synthesis of a nonnatural indolizine alkaloid is provided.
Solvent effects on the conformational distribution and optical rotation of γ‐methyl paraconic acids and esters
Authors: Coriani S. , Baranowska A. , Ferrighi L. , Forzato C. , Marchesan D. , Nitti P. , Pitacco G. , Rizzo A. , Ruud K. 
Published: March 2006

AbstractA computational investigation of the optical rotatory power of cis and trans 2‐methyl‐5‐oxo‐tetrahydro‐3‐furancarboxylic acids and the corresponding methyl and ethyl esters is presented. Solvent effects on both the conformational space and the rotatory power are analyzed by comparing results obtained in vacuo with those computed—using the Polarizable Continuum Model—in methanol. A comparison with experimental observations for the optical rotatory power of the title compounds in methanol is also carried out, in a few cases also for several wavelengths. Agreement between theory and experiment is in all cases excellent, in particular when solvent effects are included both in the geometry optimization and in the calculation of the OR, thus confirming the validity of the computational procedure adopted, even for this challenging family of floppy molecules. Chirality, 2006. © 2006 Wiley‐Liss, Inc.
Direct Epimetallation of π‐Bonded Organic Substrates with Titanium(II) Isopropoxide: Intermediacy of Biradical, Oligomeric Titanium(II) Reagents
Authors: Eisch John J. , Gitua John N. , Doetschman David C. 
Published: March 2006

AbstractExtensive EPR experiments show that a titanium‐containing molecular triplet state is formed in solution by the reaction of two equivalents of butyllithium with one equivalent of titanium(IV) isopropoxide. At higher concentrations this product, titanium(II) isopropoxide, admixed with two equivalents of lithium isopropoxide, is accompanied by the formation of a variety of nontitanium‐containing side products. The powder EPR spectrum of the molecular triplet state in frozen solution is consistent with an asymmetric molecular chain of three Ti centers on which the unpaired electron centers are three metal atoms apart. Dilution experiments show that at lower concentrations, where the nontitanium‐containing side products have dissipated, the intensity of the molecular triplet spectrum varies approximately linearly with concentration. Thus there is no evidence that the observed triplet molecule is one component in a series of concentration‐dependent oligomerization steps. The bulky isopropoxy substituents and the coordination of the isopropoxide anions from the LiOiPr present appear to prevent closure of the Ti3 centers into an equilateral triangular diamagnetic structure. This steric hindrance, operative at the terminal diisopropoxytitanium centers and preventing closure to a ring, seems not to be observed with TiCl2·2THF, which is diamagnetic and may thus be expected to exist as an equilateral triangular cluster of three units of TiCl2·2THF, a structural model currently under further investigation. The smaller steric demand of the chloro and THF units would seem to permit octahedral coordination about each Ti center in such an equilateral trigonal array of Ti3 atoms. Chemical reactions carried out individually with diphenylacetylene, cis‐stilbene or cis‐stilbene oxide and titanium(II) diisopropoxide provide stoichiometric and stereochemical evidence that the attacking titanium(II) reagent is in fact the trimeric biradical. The role of the lithium isopropoxide byproduct in fostering the course of the previously reported SET reactions of titanium(II) isopropoxide and in determining the detailed structure of the open‐chain Ti trimer biradical has been explicated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Titanium Complexes of Dialkanolamine Ligands: Synthesis and Structure
Authors: Zaitsev Kirill V. , Karlov Sergey S. , Selina Anastasia A. , Oprunenko Yu. F. , Churakov Andrei V. , Neumüller Bernhard , Howard Judith A. K. , Zaitseva Galina S. 
Published: March 2006

AbstractSynthesis of the title compounds, viz. [RN(CH2CH2O)(CHR1CR2R3O)]Ti(OiPr)2 (13–15) and [RN(CH2CH2O)(CHR1CR2R3O)]2Ti (18–28), by the reaction of one ortwo equivalents of the corresponding dialkanolamines RN(CH2CH2OH)(CHR1CR2R3OH) (1–12) with Ti(OiPr)4 is reported. Other routes to [RN(CH2CH2O)(CHR1CR2R3O)]2Ti, such as the reaction of Ti(CH2Ph)4 with dialkanolamine and the reaction of TiCl4(THF)2 with dialkanolamine/Et3N were also tested. Dimeric titanocane 16, [PhCH2N(CH2CH2O)2Ti(OMe)2]2, was obtained from the reaction of one equivalentof dialkanolamine 3 with CpTi(OMe)3. PhCH2N(CH2CH2O)2Ti(OMenth)2 (17) was prepared from the transalkoxylation reaction of 15 with two equivalents of menthol. The composition and structures of all novel compounds were established by 1H and 13C NMR spectroscopy as well as elemental analysis data. The possible solution structure features of 13–28 are discussed. The single‐crystal X‐ray diffraction study oftitanocane 16 clearly indicates a dimeric structure for this compound in the solid state. According to X‐ray data, compounds [PhCH2N(CH2CH2O)2]2Ti (19), [MeN(CH2CH2O)(CH2CHPhO)]2Ti (20), [MeN(CH2CH2O)(CH2CPh2O)]2Ti (23), erythro‐[MeN(CH2CH2O)(CHPhCHPhO)]2Ti (24), threo‐[MeN(CH2CH2O)(CHPhCHPhO)]2Ti (25), and {MeN(CH2CH2O)[CH(CH2)4CHO]}2Ti (27) possess a monomeric structure with a hexacoordinate titanium atom in the solid state. Among them complexes 19, 20, 23, 25, and 27 are characterized by a cis disposition of the nitrogen atoms in the coordination environment of the Ti atom, while nitrogen atoms in 24 occupy trans positions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Single‐Electron Oxidation of Tungsten Acetylide Complexes [(η5‐C5H5)(CO)(NO)W–C≡C–R]Li
Authors: Ipaktschi Junes , Munz Frank 
Published: March 2006

AbstractThe reaction of a tungsten acetylide complex [(η5‐C5H5)(CO)(NO)W–C≡C–R]Li (1) [1a, R = C6H5; 1b, R = C(CH3)3; 1c, R = Si(CH3)3] with one equivalent of ferrocenium tetrafluoroborate [Cp2Fe][BF4], acting as a one‐electron oxidant in THF at –50 °C, leads to the bimetallic tungsten–alkynyl complexes [(η5‐C5H5)(NO)W–C≡C–R]2 (9) [9a, R = C6H5; 9b, R = C(CH3)3; 9c, R = Si(CH3)3] as pale‐orange crystals. The crystal structure of complex 9a is reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Organic and inorganic di‐cations for capillary silica coating and EOF modulation in CE: Example of application in PEG analysis
Authors: Sebastiano Roberto , Mendieta Martha Elena , Antonioli Paolo , Bossi Alessandra , Righetti Pier Giorgio , Citterio Attilio 
Published: March 2006

AbstractEOF measurements, by using 1,4‐di‐(4‐aza‐1‐azonia‐bicyclo[2.2.2]octane)butane diiodide, barium and strontium tetraborate as silica wall modifiers, are reported and, as an example of application, analysis of PEG (PEG 400–2000) polydisperse preparations in free solution CZE is shown. PEGs have been derivatized with phthalic anhydride so as to form singly or doubly charged derivatives with strong UV absorbance at 214 nm. Whereas separations in plain tetraborate buffer, pH 9.0, without any EOF control, did not lead to good resolution of all‐size oligomers and suffered from long analysis times, excellent resolution of all oligomers up to 40 ethylene oxide (EO) units could be obtained under EOF control. Such EOF modulation was engendered by addition of 1 mM M7C4M7, a doubly charged organic cation able to stick tenaciously to the silica wall. Further modulation of EOF and silica surface modification could be achieved also by addition of inorganic cations, notably those of group II, whereas monovalent cations did not seem to affect much the EOF flux. Among the doubly charged cations investigated, Ca++, Mg++, Sr++ and Ba++, the latter did seem to offer best EOF control and reproducible runs. A judicious blend of M7C4M7 (0.33–1 mM range) with barium (10–20 mM range) allowed baseline resolution of all PEG oligomers investigated up to PEG 2000 and >40 EO units in length. In this last case, best results in terms of reproducibility and separation efficiency of the more heavy homologues were obtained using Li+ salt in small amounts.
Serum protein pattern during cow pregnancy: Acute‐phase proteins increase in the peripartum period
Authors: Cairoli Fausto , Battocchio Massimiliano , Veronesi Maria Cristina , Brambilla Daniela , Conserva Francesca , Eberini Ivano , Wait Robin , Gianazza Elisabetta 
Published: March 2006

AbstractSerum collected in a time‐course mode during the pregnancy of a group of heifers was analyzed by 2‐DE under various experimental conditions to optimize resolution of all protein spots. Changes in the levels of some components were detected during the last phase of pregnancy and early postpartum. These included a decrease of α2‐HS‐glycoprotein, an increase of α1‐antichymotrypsin and, with a much larger and more abrupt variation, of orosomucoid and haptoglobin. These findings associate the weeks preceding calving with an acute‐phase reaction. Analysis of individual animal's sera by 1‐DE demonstrated a higher level of orosomucoid in the sera of cows developing postpartum endometritis during the 2 wk after calving (i.e., in the course of the infection) but a lower level during the 2 wk before calving. This observation could represent an important tool for the prepartum detection of animals prone to develop postpartum endometritis and lead to a more accurate peripartum management of those animals.
Biomarker discovery in breast cancer serum using 2‐D differential gel electrophoresis/ MALDI‐TOF/TOF and data validation by routine clinical assays
Authors: Huang Hong‐Lei , Stasyk Taras , Morandell Sandra , Dieplinger Hans , Falkensammer Gerda , Griesmacher Andrea , Mogg Maurice , Schreiber Martin , Feuerstein Isabel , Huck Christian W. , Stecher Guenther , Bonn Guenther K. , Huber Lukas A. 
Published: March 2006

AbstractIn the present study, we used 2‐D differential gel electrophoresis (2‐D DIGE) and MS to screen biomarker candidates in serum samples obtained from 39 patients with breast cancer and 35 controls. First, we pooled the serum samples matched with age and menopausal status. Then, we depleted the two most abundant proteins albumin and IgG by immunoaffinity chromatography under partly denaturing conditions in order to enrich low‐abundance proteins and proteins with low molecular weight. Concentrated and desalted samples were labeled with three different CyDyes including one internal standard, pooled from all the samples, and separated with 2‐D DIGE in triplicate experiments. Biological variations of the protein expression level were analyzed with DeCyder software and evaluated for reproducibility and statistical significance. The profile of differentially expressed protein spots between patients and controls revealed proapolipoprotein A‐I, transferrin, and hemoglobin as up‐regulated and three spots, apolipoprotein A‐I, apolipoprotein C‐III, and haptoglobin α2 as down‐regulated in patients. Finally, routine clinical immunochemical reactions were used to validate selected candidate biomarkers by quantitative determination of specific proteins in all individual serum samples. The serum level of transferrin correlated well with the 2‐D‐DIGE results. However, the serum levels of apolipoprotein A‐I and haptoglobin could not be detected with the clinical routine diagnostic tests. This demonstrated an advantage 2‐D DIGE still has over other techniques. 2‐D DIGE can distinguish between isoforms of proteins, where the overall immunochemical quantification does fail due to a lack of isoform‐special antibodies.