bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aquapalladium Complex: A Stable and Convenient Catalyst for the Intermolecular Hydroamination of Alkynes
Authors: Shimada Tomohiro , Bajracharya Gan B. , Yamamoto Yoshinori 
Published: December 2004

AbstractThe intermolecular hydroamination of alkynes proceeds very smoothly in the presence of a catalytic amount of the aquapalladium complex [Pd(dppe)(H2O)2](TfO)2. This reaction most probably proceeds through the formation of an equilibrium between the hydroxopalladium and the amidopalladium complexes, and subsequent aminopalladation of alkynes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
The Structures and Thermodynamics of Complexes between Water‐Soluble Calix[4]arenes and Dipyridinium Ions
Authors: Liu Yu , Guo Dong‐Sheng , Yang En‐Cui , Zhang Heng‐Yi , Zhao Yan‐Li 
Published: December 2004

AbstractThree crystalline complexes were prepared by the inclusion complexation of p‐sulfonatothiacalix[4]arene (TCAS) and p‐sulfonatocalix[4]arene (CAS) with 2,2′‐dipyridinium (2‐DPD; (complexes 1 and 2, respectively), and TCAS with 4,4′‐dipyridinium (4‐DPD; complex 3). The crystal structures show that the calixarenes in 1 and 2 maintain their original cone conformation, with shallow inclusion of 2‐DPD, and assemble themselves into bi‐layer arrangements. However, the cone shape of TCAS in 3 is disrupted by 4‐DPD to assume the so‐called 1,2‐alternate conformation in the solid state, which is similar to the 1,3‐alternate case of CAS stabilized by 4‐DPD (4). The thermodynamics of this inclusion complexation were further investigated by microcalorimetric titration in aqueous solution. The obtained results indicated that the molecular binding ability and selectivity of TCAS/CAS with DPDs is entirely controlled by enthalpy gains accompanied by a smaller negative entropic change; these are discussed from the viewpoint of electrostatic, hydrogen‐bonding, π‐stacking, and van der Waals interactions, size/shape‐fit, and a desolvation effect between host and guest. The molecular selectivity for the inclusion complexation of 2‐DPD with CAS was found to be nine times greater than that of 4‐DPD with CAS. Combining the present crystal structures and thermodynamic parameters revealed that the position of the nitrogen atoms in the DPDs is the crucial factor for controlling the binding modes, molecular selectivity, conformational features, and assembly behavior of the host upon complexation with TCAS/CAS. This will help us to design large molecular assemblies possessing highly supramolecular architectures based on calixarenes by controlling exactly the guest molecules. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
On the Mechanism of the Reductive Metallation of Asymmetrically Substituted Silyl Chlorides
Authors: Oestreich Martin , Auer Gertrud , Keller Manfred 
Published: December 2004

AbstractAn investigation of the stereochemical course of the reductive metallation of silyl chlorides with silicon‐centred chirality has revealed two major events which are detrimental to stereoselection during silyl anion formation: (1) chloride‐induced racemisation of silyl chlorides and (2) nonstereoselective formal dimerisation during metallation providing the corresponding disilane. In control experiments, the stereochemical course of these processes has been independently verified for the reductive metallation of the enantioenriched cyclic silyl chloride (SiS)‐7a(R = H,er⩾ 88:12). A screening of several related derivatives of (SiS)‐7aled to the sterically encumbered silyl chloride (SiR)‐7c(R =iPr,er⩾ 94:6) which displays some unique features. This structural modification prevents racemisation by lithium chloride (T< −40 °C) as well as dimerisation (T< −100 °C) thus allowing for the first generation of an asymmetrically substituted silyl anion (SiS)‐8c(er= 74:26) by reductive metallation of a silyl chloride with silicon‐centred chirality. Moreover, the enantiospecificity of the preparation of (SiR)‐7cby chlorination [(SiS)‐9c→ (SiR)‐7c] and its reduction with aluminium hydrides [(SiR)‐7c→ (SiR)‐9c] have been unambiguously determined by X‐ray crystallography as retention (⩾99%) and inversion (⩾99%), respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Ring‐Closing Metathesis Dimerizations of Enynes and Deprotections of Propargyl Ethers Mediated by Carbene Ruthenium Complexes
Authors: Hahn Dong‐Woo , Byun Dong‐Min , Tae Jinsung 
Published: December 2004

AbstractThe ring‐forming dimerizations of enynes were catalyzed by the first‐generation carbene ruthenium complex, and the effects of the catalysts and ethylene gas were studied. The deprotection of propargyl ethers by the carbene ruthenium complexes is the first to be reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
A Simple Route to a Pyridinyl[2.2]paracyclophane
Authors: Hopf Henning , Aly Ashraf A. , Swaminathan Vijay Narayanan , Ernst Ludger , Dix Ina , Jones Peter G. 
Published: December 2004

Abstract4‐Acetyl[2.2]paracyclophane (1) is converted into the nitrone 2 by treatment with N‐methylhydroxylamine·hydrochloride. When 2 is reacted with (E)‐1,2‐dibenzoylethene (4) the pyridinyl[2.2]paracyclophane 13 is formed in a novel condensation reaction. The structures of 2 and 13, and the mechanism of formation of the latter are discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
On‐Line Monolithic Enzyme Reactor Fabricated by Sol‐Gel Process for Elimination of Ascorbic Acid While Monitoring Dopamine
Authors: Chen Zilin , Hayashi Katsuyoshi , Iwasaki Yuzuru , Kurita Ryoji , Niwa Osamu , Sunaawa Kenji 
Published: December 2004

AbstractCatecholamine, a well‐known neurotransmitter, is released to restore heart function after the occurrence of cardiac ischemia. Endogenous ascorbic acid interferes considerably with the monitoring of neurotransmitters such as catecholamine and glutamate. In this work we have successfully developed a nanoliter volume monolithic enzyme reactor and integrated it with a carbon film electrode for monitoring dopamine in order to scavenge such electroactive interferents as ascorbic acid. A monolithic silica support prepared by the sol‐gel process has a large through‐pore structure and a nanoporous surface. The low back pressure resulting from the large though‐pore structure makes it possible to immobilize the enzyme and introduce fluid into the flow monitoring system by using a microsyringe pump. Ascorbate oxidase (AOx) was immobilized on the nanoporous surface of a monolithic matrix by physical adsorption and used for converting the ascorbic acid into its electrochemically inert form, dehydroascorbic acid, while monitoring dopamine. We showed that more than 99.8% of 100 μM of ascorbic acid could be converted to its oxidized form in the monolithic enzyme reactor. We succeeded in monitoring dopamine at a concentration of less than 100 nM in the presence of 50 μM of ascorbic acid. Therefore, this work demonstrated that a monolithic silica support offers excellent potential in regards to realizing a highly selective enzymatic reactor for biosensors.
Computational Electrochemistry: A Model to Studying Ohmic Distortion of Voltammetry in Multiple Working Electrode, Microfluidic Devices, an Adaptive FEM Approach
Authors: Henley Iain , Fisher Adrian 
Published: December 2004

AbstractCharacteristics of mass transport and potential distribution applicable to microfluidic electrochemical flow cell devices has been modelled using the finite element method. A flexible, automatic grid generation algorithm has been combined with an a‐posteriori error indication technique presented by Nann and Heinze to allow irregular cell geometries to be modelled. The code has been applied to the problem of steady state generator – detector linear sweep voltammetry in a channel flow cell showing the effects of IR drop on the voltammetric response of each electrode.
Preparation of Thallium Hexacyanoferrate Film and Mixed‐Film Modified Electrodes with Cobalt(II) Hexacyanoferrate
Authors: Chen Shen‐Ming , Peng Kuo‐Tzu , Lin Kuo‐Chiang 
Published: December 2004

AbstractThallium hexacyanoferrate films have been prepared from various aqueous electrolyte solutions using consecutive cyclic voltammetry. The cyclic voltammograms recorded the direct deposition of thallium hexacyanoferrate films from the mixing of Tl3+ and [Fe(CN)6]3− ions from solutions of seven cations: Li+, Na+, K+, Rb+, Cs+, H+, and Tl+. An electrochemical quartz crystal microbalance (EQCM) and cyclic voltammetry were used to study the in situ growth of the thallium hexacyanoferrate films. The thallium hexacyanoferrate film shows a single redox couple with a formal potential between +0.6 V and +1.2 V, and shows a cation effect (H+, Li+, Na+, K+, Rb+, Cs+, and Tl+). A mixed film and a two‐layered modified electrodes composed of a thallium hexacyanoferrate film with cobalt(II) hexacyanoferrate film were prepared.
Simultaneous Determination of Hydroquinone and Catechol at a Glassy Carbon Electrode Modified with Multiwall Carbon Nanotubes
Authors: Qi Honglan , Zhang Chengxiao 
Published: December 2004

AbstractA simply and high selectively electrochemical method for simultaneous determination of hydroquinone and catechol has been developed at a glassy carbon electrode modified with multiwall carbon nanotubes (MWNT). It was found that the oxidation peak separation of hydroquinone and catechol and the oxidation currents of hydroquinone and catechol greatly increase at MWNT modified electrode in 0.20 M acetate buffer solution (pH 4.5). The oxidation peaks of hydroquinone and catechol merge into a large peak of 302 mV (vs. Ag/AgCl, 3 M NaCl) at bare glassy carbon electrode. The two corresponding well‐defined oxidation peaks of hydroquinone in the presence of catechol at MWNT modified electrode occur at 264 mV and 162 mV, respectively. Under the optimized condition, the oxidation peak current of hydroquinone is linear over a range from 1.0×10−6 M to 1.0×10−4 M hydroquinone in the presence of 1.0×10−4 M catechol with the detection limit of 7.5×10−7 M and the oxidation peak current of catechol is linear over a range from 6.0×10−7 M to 1.0×10−4 M catechol in the presence of 1.0×10−4 M hydroquinone with the detection limit of 2.0×10−7 M. The proposed method has been applied to simultaneous determination of hydroquinone and catechol in a water sample with simplicity and high selectivity.
Highly‐Sensitive Determination of 6‐Mercaptopurine and Its Metabolites by Electrochemical Reductive Desorption Measurements
Authors: Sato Yukari , Ishikawa Yayoi , Matsuura Hiroaki , Uosaki Kohei , Mizutani Fumio , Niwa Osamu 
Published: December 2004

AbstractThe electrochemical detection of 6‐mercaputopurine (6‐MP), which is one of the most well‐known drugs of antimetabolites, and its analogues was studied. The presented method is based on chemisorption (accumulation)/desorption processes of drugs onto/from the Au electrode surface. Using this method, we succeeded in detecting 6‐MP even in very diluted solution (concentration of 6‐MP: 1×10−8 M). The lower detection limit of 6‐MP was considerably improved compared with the previous HPLC studies by using our proposed system. Desorptive potentials of 6‐MP‐metabolites and its analogues were different from those of 6‐MP. This provides the possibility of simultaneous detection of 6‐MP and its typical metabolites.
Catastrophic precipitation‐triggered lahar at Casita volcano, Nicaragua: occurrence, bulking and transformation
Authors: Scott Kevin M. , Vallance James W. , Kerle Norman , Luis Macías Jose , Strauch Wilfried , Devoli Graziella 
Published: December 2004

AbstractA catastrophic lahar began on 30 October 1998, as hurricane precipitation triggered a small ﬂank collapse of Casita volcano, a complex and probably dormant stratovolcano. The initial rockslide‐debris avalanche evolved on the ﬂank to yield a watery debris ﬂood with a sediment concentration less than 60 per cent by volume at the base of the volcano. Within 2·5 km, however, the watery ﬂow entrained (bulked) enough sediment to transform entirely to a debris ﬂow. The debris ﬂow, 6 km downstream and 1·2 km wide and 3 to 6 m deep, killed 2500 people, nearly the entire populations of the communities of El Porvenir and Rolando Rodriguez. These ‘new towns’ were developed in a prehistoric lahar pathway: at least three ﬂows of similar size since 8330 14C years bp are documented by stratigraphy in the same 30‐degree sector. Travel time between perception of the ﬂow and destruction of the towns was only 2·5–3·0 minutes. The evolution of the ﬂow wave occurred with hydraulic continuity and without pause or any extraordinary addition of water.The precipitation trigger of the Casita lahar emphasizes the need, in volcano hazard assessments, for including the potential for non‐eruption‐related collapse lahars with the more predictable potential of their syneruption analogues. The ﬂow behaviour emphasizes that volcano collapses can yield not only volcanic debris avalanches with restricted runouts, but also mobile lahars that enlarge by bulking as they ﬂow. Volumes and hence inundation areas of collapse‐runout lahars can increase greatly beyond their sources: the volume of the Casita lahar bulked to at least 2·6 times the contributing volume of the ﬂank collapse and 4·2 times that of the debris ﬂood. At least 78 per cent of the debris ﬂow matrix (sediment < −1·0Φ; 2 mm) was entrained during ﬂow. Copyright © 2004 John Wiley & Sons, Ltd.
Studies on essential oils, Part 42: chemical, antifungal, antioxidant and sprout suppressant studies on ginger essential oil and its oleoresin
Authors: Singh Gurdip , Maurya Sumitra , Catalan C. , de Lampasona M. P. 
Published: December 2004

AbstractGC–MS analysis of fresh rhizome essential oil of Zingiber ofﬁcinale showed the presence of 69 components, accounting for 96.93% of the total oil. The major component was α‐zingiberene (28.62%) followed by camphene (9.32%), ar‐curcumene (9.09%) and β‐phellandrene (7.97%). Analysis of the oleoresin showed the presence of 34 components, accounting for 88.63% of the total oleoresin. The major components were trans‐6‐shogaol (26.23%), trans‐10‐shogaol (13.0%), α‐zingiberene (9.66%) and 10‐gingerdione (6.80%). Moreover, the essential oil was found to be 100% antifungal against Fusarium oxysporum, whereas the oleoresin was 100% antifungal against Aspergillus niger. The latter expressed better antioxidant activity in sunﬂower oil as compared to the essential oil and synthetic antioxidants (BHA and BHT). Copyright © 2004 John Wiley & Sons, Ltd.
Volatile constituents and antioxidant activity of essential oils from Lippia multiﬂora Mold. growing in Gabon
Authors: Agnaniet Huguette , Makani Thomas , Akagah Aristide , Menut Chantal , Bessière Jean Marie 
Published: December 2004

AbstractThe leaf essential oils from two samples of Lippia multiﬂora (Verbenaceae) collected in two localities of Gabon were obtained by hydrodistillation and analysed by GC and GC‐MS. The oils differed completely in their chemical composition: the former was characterized by a high amount of ipsdienone (54.6%), (Z)‐ and (E)‐ocimenones (20.3%); (E)‐β‐farnesene (7.4%) and β‐caryophyllene (4.6%) were the main components of the sesquiterpenoid fraction; the latter consisted mainly of thymol (41.9%), thymyl acetate (21.2%), p‐cymene (9.8%) and carvacrol (7.2%), which allows differenciation between two chemotypes. The antioxidant and antiradical activities of both samples were evaluated comparatively to those of reference compounds (BHT, thymol and carvacrol). An interesting antioxidant activity was found for the second chemotype as expected on the basis of its phenolic compounds content. Copyright © 2004 John Wiley & Sons, Ltd.
Essential oil composition from some plant parts of Conyza bonariensis (L.) Cronquist
Authors: Barbosa Luiz C. A. , Paula Vanderlúcia F. , Azevedo Anelisa S. , Silva Eldo A. M. , Nascimento Evandro A. 
Published: December 2004

AbstractThe essential oils from the roots, leaves, stems and inﬂorescences of Conyza bonariensis L. were investigated. A total of 17 constituents were identiﬁed by GC‐MS, including monoterpenes, acetylenes, sesquiterpenes and diterpenes. The major constituents were matricaria methyl ester (roots, 74.4%), limonene (leaves, 29.6%), manool (stems, 25.3%) and carvone (inﬂorescences, 21.1%). Copyright © 2004 John Wiley & Sons, Ltd.
Chemical composition and antimicrobial activity of the essential oil of Acinos arvensis (Lam.) Dandy from Serbia
Authors: Jovanovic Tatjana , Kitic Dusanka , Palic Radosav , Stojanovic Gordana , Ristic Mihailo 
Published: December 2004

AbstractThe hydrodistilled essential oil of Acinos arvensis (Lam.) Dandy was analysed by GC and GC/MS. Thirty constituents representing 83.8% of the oil were identiﬁed, of which germacrene D (47.0%) was the major component. Furthermore, β‐bourbonene (7.7%), caryophyllene oxide (3.2%) and β‐caryophyllene (3.0%) were noted as additional signiﬁcant constituents. The antimicrobial activity of the oil was screened against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumoniae. All the microorganisms, except for Pseudomonas aeruginosa, were found to be susceptible to the oil. Copyright © 2004 John Wiley & Sons, Ltd.
Composition and antimicrobial activity of the essential oil of Achillea falcata L. (Asteraceae)
Authors: Senatore Felice , Napolitano Francesco , Apostolides Arnold Nelly , Bruno Maurizio , Herz Werner 
Published: December 2004

AbstractThe composition of the essential oil from aerial parts of Achillea falcata L. (Asteraceae) growing wild in Lebanon was analysed by GC and GC–MS; 58 compounds, representing 94.4% of the oil, were identiﬁed. Isomers of the cyclobutane ethanol, 1‐methyl‐2‐(1‐methylethenyl), grandisol (21.4%) and fragranol (16.8%) were the main components of the oil. Also abundant were artemisia ketone (5.2%), terpinen‐4‐ol (4.5%) and 1,8‐cineole (4.0%). The essential oil shows inhibitory activity mainly against Gram‐positive bacteria. Copyright © 2004 John Wiley & Sons, Ltd.
The chemical composition of essential oils of Silphium perfoliatum L.
Authors: Kowalski R. , Wolski T. 
Published: December 2004

AbstractThe content and chemical composition of essential oil of leaves, inﬂorescences and rhizomes of Silphium perfoliatum L. were studied in this paper. The mean content of oil in leaves amounted to 0.19% v/w per dry matter; inﬂorescences contained 0.27% v/w of oil per dry matter, while the rhizomes contained 0.41% v/w. Qualitative and quantitative analysis of distilled oils were carried out using the GC and GC–MS technique. The chemical composition of the essential oils obtained from inﬂorescences and leaves is quite similar, although in the inﬂorescence oil the dominant constituent is the bicyclic monoterpene α‐pinene (16.0–20.9%), and in the leaf oil the prevailing components are the bicyclic sesquiterpene caryophyllene oxide (8.5–34.7%) and the monocyclic sesquiterpene germacrene D (6.4–24.3%). In the rhizome oil from Silphium perfoliatum L., the dominating compounds are the tricyclic sesquiterpenes 7‐β‐H‐silphiperfol‐5‐ene (5.7–14.9%), isocomene (2.8–14.4%), modhephene (2.3–9.9%), 7‐a‐H‐silphiperfol‐5‐ene (1.2–9.7%), which considerably differentiates this oil from those obtained from the leaves and inﬂorescences. Copyright © 2004 John Wiley & Sons, Ltd.
Essential oil composition of Hyssopus ofﬁcinalis L. subsp. angustifolius (Bieb.) Arcangeli from Turkey
Authors: Özer Hakan , Şahin Fikrettin , Kılıç Hamdullah , Güllüce Medine 
Published: December 2004

AbstractThe oil obtained by hydrodistillation from the aerial parts of Hyssopus ofﬁcinalis L. subsp. angustifolius (Bieb.) Arcangeli from Turkey was analysed by GC–MS. Thirty‐four components were characterized, representing 91.0% of the total components detected. The major constituents were identiﬁed as pinocarvone (36.3%), pinocamphone (19.6%), β‐pinene (10.6%), 1,8‐cineole (7.2%) and isopinocamphone (5.3%). Copyright © 2005 John Wiley & Sons, Ltd.
Aromatic plants of tropical central Africa. Part L. Volatile components of Clerodendrum buchholzii Gürke from Cameroon
Authors: Nyegue M. A. , Belinga‐Ndoye C. F. , Amvam Zollo P. H. , Agnaniet H. , Menut C. , Bessière J. M. 
Published: December 2004

AbstractThe chemical composition of the essential oil obtained by hydrodistillation of fresh leaves of Clerodendrum buchholzii Gürke grown in Cameroon was investigated by GC–FID and GC–MS. The major compounds were benzaldehyde (96%) and octen‐3‐ol, which were also determined by the AEDA method as the key odourants of this sample. Copyright © 2004 John Wiley & Sons, Ltd.
Novel regions of chromosomal amplification at 6p21, 5p13, and 12q14 in gastric cancer identified by array comparative genomic hybridization
Authors: Gorringe Kylie L. , Boussioutas Alex , Bowtell David D. L. 
Published: December 2004

AbstractGastric cancer (GC) frequently displays changes in DNA copy number, but few studies have precisely correlated specific genetic alterations with changes in gene expression. We undertook both array comparative genomic hybridization (aCGH) and expression analyses of 20 primary GCs using a cDNA microarray with more than 9,300 genes. Diverse clinical and histopathologic tumor subtypes, including signet‐ring tumors and tumors at the gastroesophageal junction, were analyzed. All tumors showed changes in gene copy number, with the majority showing multiple changes. Regions of gain and loss were generally consistent with previous cytogenetic reports; however, the use of aCGH greatly increased the resolution of measured genomic change. By comparing gene expression and high‐resolution measurement of gene copy number directly, we were able to identify several regions of high‐level gain associated with substantially increased gene expression that have not been defined previously in GC. Novel candidate oncogenes included dual‐specificity tyrosine‐(Y)‐phosphorylation‐regulated kinase 2 (DYRK2) and protein tyrosine kinase 7 (PTK7). © 2004 Wiley‐Liss, Inc.
High‐resolution chromosome arm 5p array CGH analysis of small cell lung carcinoma cell lines
Authors: Coe Bradley P. , Henderson Laura‐Jane , Garnis Cathie , Tsao Ming‐Sound , Gazdar Adi F. , Minna John , Lam Stephen , MacAulay Calum , Lam Wan L. 
Published: December 2004

AbstractGenomic amplification of regions on chromosome arm 5p has been observed frequently in small cell lung cancer (SCLC), implying the presence of multiple oncogenes on this arm. Although conventional comparative genomic hybridization (CGH) detects gross chromosomal copy number changes, gene discovery requires a higher‐resolution approach in order to identify regions of alteration precisely. To identify candidate genes on this chromosome arm, we developed a high‐resolution, 10‐clone‐per‐megabase bacterial artificial chromosome CGH array for 5p and examined a panel of 15 SCLC cell lines. Utilization of this CGH array has allowed the fine‐mapping of breakpoints to regions as small as 200 kb in a single experiment. In addition to reporting our observations of aberrations at the well‐characterized SKP2 and TERT loci, we describe the identification of microdeletions that have escaped detection by conventional screens and the identification TRIO and ANKH as novel putative oncogenes. © 2004 Wiley‐Liss, Inc.