bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Concentration of Some Lanthanide(III) Complexes of 1,7‐Bis(carboxymethyl)‐1,4,7,10‐tetraazacyclododecane on Bis(p‐nitrophenyl)phosphate Hydrolysis
Authors: Chang C. Allen , Wu Bo Hong , Hsiao Chih‐Hsiang 
Published: February 2009

AbstractA detailed study of the effects of the concentration of some lanthanide(III) complexes [LnDO2A+; DO2A = 1,7‐bis(carboxymethyl)‐1,4,7,10‐tetraazacyclododecane] on the hydrolysis of the phosphodiester bond of the compound BNPP [sodium bis(4‐nitrophenyl)phosphate] is reported at 25 °C and pH 7.90 (Ln = Eu), 9.35 (Ln = Eu), and 9.90 (Ln = Eu, Er and Yb). The reaction is found to be first order with respect to BNPP concentration at pH 7.90 and 9.35 and to increase to 1.78 ± 0.09, 1.64 ± 0.07, and 1.63 ± 0.09 with respect to [EuDO2A+] concentration at pH 7.90, 9.35, and 9.90, respectively, thereby indicating that dinuclear species are involved in the reactions. Similar observations were found for the other two LnDO2A+ complexes at pH 9.90 [1.63 ± 0.11 (Er) and 1.49 ± 0.09 (Yb)]. The kobs data obtained by the initial rate method could be fitted to a monomer‐dimer reaction model for all LnDO2A+ complexes at pH 7.90, 9.35, and 9.90 in the [LnDO2A+] concentration range 1.0–20.0 mM. The dinuclear species, namely the mono‐hydroxo‐bridged complexes [Ln2(DO2A)2(μ‐OH)(OH)(H2O)n = 1–3] and the di‐hydroxo‐bridged complexes [Ln2(DO2A)2(μ‐OH)2(H2O)n = 0–2] are found to be more reactive, with reactivities in the order Eu > Yb > Er. The overall formation constants for [Ln2(DO2A)2(μ‐OH)2(H2O)n]‐BNPP are around 104 M–1. The EuDO2A+‐promoted BNPP hydrolysis rates are similar to, or up to two orders of magnitude faster than, most of those reported for other lanthanide and transition‐metal complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
A Versatile Synthesis of 5′‐Functionalized Nucleosides Through Regioselective Enzymatic Hydrolysis of Their Peracetylated Precursors
Authors: Bavaro Teodora , Rocchietti Silvia , Ubiali Daniela , Filice Marco , Terreni Marco , Pregnolato Massimo 
Published: February 2009

AbstractWe describe a chemo‐enzymatic synthesis of modified nucleosides through lipase‐catalyzed hydrolysis of their peracetylated precursors. It was found from screening of a large number of substrates that these enzymes' regioselectivities were affected by the sugar and the nucleobase structures. By selecting the best enzyme for each substrate in terms of activity and regioselectivity, we prepared a small library of differently monodeprotected purine and pyrimidine nucleosides useful as intermediates for the synthesis of high‐value nucleosides and mononucleotides. By this approach, the chemo‐enzymatic preparation of doxifluridine (14) anduridine 5′‐monophosphate (5′‐UMP,15) from peracetylated uridine1was carried out. Elimination of many of the processing stages associated with existing methods was achieved, and higher yields and products of increased purity were generated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Fluorescent Switches Based on Photochromic Compounds
Authors: Cusido Janet , Deniz Erhan , Raymo Françisco M. 
Published: February 2009

AbstractThe photochemical transformations associated with photochromic compounds can be exploited to switch the emission of complementary fluorophores under the influence of optical stimulations. Specifically, fluorescent and photochromic components can be integrated within the same molecular or supramolecular assembly and the significant changes in thestereoelectronic properties associated with the photoinduced interconversion of one component can be designed to modulate the emission intensity and/or wavelength of the other. In particular, the modifications in absorption properties, conjugation, dipole moment, redox potentials and shape of a photochrome can all be transduced effectively into reversible alterations of the emissive behavior of a fluorophore. Furthermore, some of these ingenious mechanisms for fluorescence modulation can be extended from relatively small molecular and supramolecular assemblies to large macromolecular, nanostructured and biomolecular constructs. In fact, a diversity of chemical systems with photoswitchable luminescence have already emerged on the basis of these operating principles and choice of functional components. Ultimately, these fundamental studies on the photochemical and photophysical signature of multicomponent assemblies might well lead to a new generation of photonic materials with unique properties for possible applications in biomedical imaging and sensing as well as in information processing and storage.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Domino or Single‐Step Tsuji–Trost/Heck Reactions and Their Application in the Synthesis of 3‐Benzazepines and Azepino[4,5‐b]indole Ring Systems
Authors: Stewart Scott G. , Heath Charles H. , Ghisalberti Emilio L. 
Published: February 2009

AbstractA series of methods for palladium‐mediated single‐step and domino Tsuji–Trost/Heck reactions are described. These methods are applied to the synthesis of both 3‐benzazepines and azepino[4,5‐b]indoles in the category of complex 6‐7‐6 and 6‐5‐7 ring heterocycles. In addition, a domino Heck/Heck sequence of reactions that produces the azepinobenzindolizine tetracyclic ring system fromN‐diallylated precursors is described. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Screening the Structural Space of Bicyclo‐DNA: Synthesis and Thermal Melting Properties of bc4,3‐DNA (Eur. J. Org. Chem. 8/2009)
Authors: Stauffiger Andrea , Leumann Christian J. 
Published: February 2009

AbstractThe cover picture shows two low‐energy conformations of monomeric units of [4.3.0]bicyclo‐DNA, a conformationally restricted DNA analogue. In an energy‐minimized double helix containing a fully modified strand paired against its complementary DNA, the [4.3.0]bicyclo‐DNA sugar arranges in such a way that O(5′) adopts a pseudoaxial orientation. In the article by A. Stauffiger and C. J. Leumann on p. 1153 ff the synthesis of the modified DNA building block, the X‐ray structure of the monomeric unit as well as thermal melting properties of oligonucleotides are discussed. The authors would like to thank Michael Eggli for his help in designing the cover picture.
Highly Selective and Sensitive Tin(II) Membrane Electrode Based on a New Synthesized Schiff's Base
Authors: Hosseini Morteza , Bagheri Sadeghi Hayedeh , Rahimi Mohammad , Salavati‐Niasari Masoud , Dehghan Abkenar Shiva , Alizadeh Kamal , Reza Ganjali Mohammad 
Published: February 2009

AbstractStudies on complex formation of tris(3‐(2‐hydroxybenzophenone)propyl)amine (THPA) with a number of metal ions in acetonitrile solution revealed the occurrence of a selective 1 : 1 complexation of the proposed ligand with Sn2+ ion. Consequently, THPA was used as a suitable neutral ionophore for the preparation of a polymeric membrane‐selective electrode. The electrode exhibits a Nernstian behavior with a slope of 29.4±0.3 mV per decade and a detection limit of 2.0×10−7 M. It also showed a good selectivity for Sn2+ ions in comparison with some of group A and B metal ions over a wide concentration range of 5.0×10−7–1.0×10−1 M. Improved selectivity was achieved compared to the best selectivity recently reported by other authors for tin(II). The electrode was successfully applied to the determination of Sn2+ ion in waste water and various canned products.
Fabrication and Characterization of Carbon Nanotube‐Hydroxyapatite Nanocomposite: Application to Anodic Stripping Voltammetric Determination of Cadmium
Authors: Pan Dawei , Wang Yuane , Chen Zhaopeng , Yin Tanji , Qin Wei 
Published: February 2009

AbstractA novel chemically modified electrode for stripping determination of cadmium is presented in this paper, based on carbon nanotube‐hydroxyapatite (CNT‐HAP) nanocomposite, which can be prepared by an easy and effective one‐step sonication. The newly synthesized nanocomposite was characterized with FTIR, TEM, and electrochemical methods. Due to the combination of the strong absorption ability of HAP and excellent electroanalytical properties of CNTs, the GC/CNT‐HAP electrode has been successfully used for determination of Cd2+ by anodic stripping voltammetry with a linear range of 20 nM–3 μM. The sensitivity and detection limit are 25.6 μA/μM and 4 nM, respectively. The practical application of the proposed electrode has been carried out for the determination of trace levels of Cd2+ in real water samples.
Lead Sensor Using Gold Nanostructured Screen‐Printed Carbon Electrodes as Transducers
Authors: Martínez‐Paredes Graciela , González‐García María Begoña , Costa‐García Agustín 
Published: February 2009

AbstractGold nanostructured screen‐printed carbon electrodes are demonstrated to be suitable transducers for the determination of lead using square‐wave voltammetry. Reproducible gold nanostructures have been obtained by direct electrochemical deposition. A calibration plot from 2.5 to 250 μg/L was obtained in acidic solutions of Pb(II) with a reproducibility of 4% (n=10). The detection limit was 0.09 μg/L of lead. The method is then applied to perform a blood lead analysis by adjusting square‐wave parameters in capillary or venous blood with a minimum sample pretreatment and excellent accuracy and reproducibility.
Fe(CN)$\rm{ {_{6}^{4-}}}$‐Doped‐Glutaraldehyde‐Cross‐Linked Poly‐L‐Lysine Film Electrode. Part 1: Electrochemical Characterization and Its Electrocatalytic Activity Towards Oxidation of Ascorbic Acid
Authors: Wu Yu‐Ching , Thangamuthu R. , Chen Shen‐Ming 
Published: February 2009

AbstractThe present work describes preparation, characterization, and electrocatalytic behavior of a hexacyanoferrate‐doped‐glutaraldehyde‐cross‐linked poly‐L‐lysine (PLL‐GA‐Fe(CN)$\rm{ {_{6}^{4-}})}$film modified glassy carbon electrode. The modified electrode has been successfully prepared by electrostatically binding negatively charged Fe(CN)$\rm{ {_{6}^{4-}}}$mediator into cross‐linked poly‐L‐lysine cationic film. The dependence of the peak current of the modified electrode in pure supporting electrolyte (pH 6.8 phosphate buffer solution; PBS) shows that the charge transport in the film is fast and relatively unimpeded at lower scan rates. Cyclic voltammetry and rotating disk electrode (RDE) techniques are used to investigate the electrocatalytic activity of modified electrode towards oxidation of ascorbic acid. The rate constant (k), of catalytic reaction between electrogenerated Fe(CN)$\rm{ {_{6}^{3-}}}$ions and ascorbic acid, obtained from RDE analysis was found to be 5.53×105 cm3mol−1s−1. Finally, the PLL‐GA‐Fe(CN)$\rm{ {_{6}^{4-}}}$film electrodes are successfully used for the individual estimation of ascorbic acid in the concentration range of physiological interest.
Polyaniline Film Based Amperometric pH Sensor Using A Novel Electrochemical Measurement System
Authors: Gao Wei , Song Junfeng 
Published: February 2009

AbstractA polyaniline based amperometric pH sensor has been developed using a novel electrochemical measurement system. A polyaniline film (PANI) coated pencil graphite electrode (PGE) is connected in series between the working and counter electrodes of a potentiostat, and immersed in the solution together with a reference electrode. When an external potential is applied, the resulting current varies with the solution pH, which provides the basis for the amperoemtric pH sensor. Equations describing the measurement principle are presented. Based on pH dependent emeraldine salt–emeraldine base transition of PANI film, the pH sensor exhibits high stability, accuracy, selectivity, sensitivity and a short time.
Electrodeposition of TiO2 Nanoparticles on Multiwalled Carbon Nanotube Arrays for Hydrogen Peroxide Sensing
Authors: Jiang Liao‐Chuan , Zhang Wei‐De 
Published: February 2009

AbstractIn this work, an amperometric H2O2 sensor based on TiO2/MWCNTs electrode is reported. TiO2 nanoparticles were synthesized on vertically aligned multiwalled carbon nanotube (MWCNT) arrays by electrodeposition. The morphology of the TiO2/MWCNTs was characterized by scanning electron microscopy (SEM). The electrochemical performance of the TiO2/MWCNTs electrode for detection of H2O2 was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry. The TiO2/MWCNTs electrode displays high electrocatalytic activity towards oxidation of H2O2 in 0.1 M phosphate buffer solution (PBS, pH 7.4). At an applied potential of +0.40 V, the TiO2/MWCNTs electrode exhibits a linear dependence (R=0.998) in the H2O2 concentration up to 15.0×10−3 M with a sensitivity of 13.4 μA mM−1 and detection limit of 4.0×10−7 M with signal/noise=3. The optimal response time is less than 5 s with addition of 1 mM H2O2. The TiO2/MWCNTs electrode presents stable, high sensitivity and also exhibits fast amperometric response to the detection of H2O2, which is promising for the development of H2O2 sensor.
Determination of Total Phenols in Foods by Boron Doped Diamond Electrode
Authors: Dejmkova Hana , Scampicchio Matteo , Zima Jiri , Barek Jiri , Mannino Saverio 
Published: February 2009

AbstractA robust electrochemical method to measure the total phenol content in food samples is presented. Under optimal condition, BDD electrode showed excellent performance to detect the oxidation of several phenols and does not present the drawback due to electrode fouling. The analytical method used to perform such measurement has been optimized and successfully applied in different food samples. The results obtained were compared with the standard Folin–Ciocalteau method.
Electrochemical Characterization of Epigallocatechin Gallate Using Square‐Wave Voltammetry
Authors: Novak Ivana , Šeruga Marijan , Komorsky‐Lovrić Šebojka 
Published: February 2009

AbstractElectrochemical oxidation of (−)‐epigallocatechin gallate (EGCG), the main monomer flavanol found in green tea, has been investigated over a wide pH range at a glassy‐carbon electrode using square‐wave voltammetry (SWV). Square‐wave voltammograms of (−)‐epigallocatechin (EGC) and gallic acid have been studied as well. The I–E profile of EGCG, i.e. the oxidation potentials and the current responses of the first and the second peak, is pH dependent. The oxidation of EGCG is a quasireversible process over the studied pH range, which was also confirmed by the non‐linear relationship between the peak currents and squre root of frequency. The best SWV responses for EGCG were obtained at pH 2.0, frequency of 100 Hz, step of 2 mV and amplitude of 50 mV. Under these conditions, linear responses for EGCG were obtained for concentrations from 1×10−7 M to 1×10−6 M, and calculated LOD and LOQ for the first oxidation peak were 6.59×10−8 M and 2.19×10−7 M, respectively. The proposed electroanalytical procedure was applied for the determination of EGCG content in green tea. Developed SWV methodology represents a potential analytical tool in determination of catechins in tea samples.
Hemoglobin‐Titanate Composite Based Biosensor for the Amperometric Determination of Hydrogen Peroxide in Acidic Medium
Authors: Wu Yihua , Gao Qiuming , Shi Linpu , Gao Lu 
Published: February 2009

AbstractA hemoglobin‐titanate composite based biosensor was chosen for determination of H2O2 in an acidic medium. CV results of the Hb‐titanate modified pyrolytic graphite electrode showed a pair of well‐defined, quasi‐reversible redox peaks centered at −246 mV (vs. Ag/AgCl) in a pH 5.0 HAc‐NaAc buffer solution. The modified electrode exhibited good electrocatalytic response for monitoring H2O2 and had a large linear detection range from 20 μM to 3.2 mM with a detection limit of 8 μM (S/N=3) and a sensitivity of 29.7 mA M−1 cm−2 in the pH 5.0 solution. The biosensor also possessed good long term storage stability.
A New Indirect Electroanalytical Method to Monitor the Contamination of Natural Waters with 4‐Nitrophenol Using Multiwall Carbon Nanotubes
Authors: Moraes Fernando Cruz , Tanimoto Sonia Tomie , Salazar‐Banda Giancarlo Richard , Machado Sergio Antonio Spinola , Mascaro Lucia Helena 
Published: February 2009

AbstractThe electrochemical detection of the hazardous pollutant 4‐nitrophenol (4‐NP) at low potentials, in order to avoid matrix interferences, is an important research challenge. This study describes the development, electrochemical characterization and utilization of a multiwall carbon nanotube (MWCNT) film electrode for the quantitative determination of 4‐NP in natural water. Electrochemical impedance spectroscopy measurements showed that the modified surface exhibits a decrease of ca. 13 times in the charge transfer resistance when compared with a bare glassy carbon (GC) surface. Voltammetric experiments showed the possibility to oxidize a hydroxylamine layer (produced by the electrochemical reduction of 4‐NP on the GC/MWNCT surface) in a potential region which is approximately 700 mV less positive than that needed to oxidize 4‐NP, thus minimizing the interference of matrix components. The limit of detection for 4‐NP obtained using square‐wave voltammetry (0.12 μmol L−1) was lower than the value advised by EPA. A natural water sample from a dam located in São Carlos (Brazil) was spiked with 4‐NP and analyzed by the standard addition method using the GC/MWCNT electrode, without any further purification step. The recovery procedure yielded a value of 96.5% for such sample, thus confirming the suitability of the developed method to determine 4‐NP in natural water samples. The electrochemical determination was compared with that obtained by HPLC with UV‐vis detection.
Cox processes for estimating temporal variation in disease risk
Authors: Paez Marina Silva , Diggle Peter J. 
Published: February 2009

AbstractWe propose a class of Cox processes as models for the times of occurrence of cases of a disease, and develop associated methods of Bayesian inference for parameter estimation and for prediction of the temporal variation in disease risk. The data may consist of either incidence times of individual cases or counts of the numbers of incident cases in disjoint time‐intervals. We explore the consequences of working with different levels of temporal aggregation of the data. We use a simulated example to demonstrate the feasibility of our methodology, which we then apply to data giving daily counts of incident cases of gastrointestinal infections in the county of Hampshire, UK. Copyright © 2009 John Wiley & Sons, Ltd.
A substructure shaking table test for reproduction of earthquake responses of high‐rise buildings
Authors: Ji Xiaodong , Kajiwara Kouichi , Nagae Takuya , Enokida Ryuta , Nakashima Masayoshi 
Published: February 2009

AbstractWhen subjected to long‐period ground motions, high‐rise buildings' upper floors undergo large responses. Furniture and nonstructural components are susceptible to significant damage in such events. This paper proposes a full‐scale substructure shaking table test to reproduce large floor responses of high‐rise buildings. The response at the top floor of a virtual 30‐story building model subjected to a synthesized long‐period ground motion is taken as a target wave for reproduction. Since a shaking table has difficulties in directly reproducing such large responses due to various capacity limitations, a rubber‐and‐mass system is proposed to amplify the table motion. To achieve an accurate reproduction of the floor responses, a control algorithm called the open‐loop inverse dynamics compensation via simulation (IDCS) algorithm is used to generate a special input wave for the shaking table. To implement the IDCS algorithm, the model matching method and the H∞ method are adopted to construct the controller. A numerical example is presented to illustrate the open‐loop IDCS algorithm and compare the performance of different methods of controller design. A series of full‐scale substructure shaking table tests are conducted in E‐Defense to verify the effectiveness of the proposed method and examine the seismic behavior of furniture. The test results demonstrate that the rubber‐and‐mass system is capable of amplifying the table motion by a factor of about 3.5 for the maximum velocity and displacement, and the substructure shaking table test can reproduce the large floor responses for a few minutes. Copyright © 2009 John Wiley & Sons, Ltd.
Performance analysis of optically preamplified DC‐coupled burst mode receivers
Authors: Zuo T. J. , Ma R. , Phillips A. J. , Sujecki S. 
Published: February 2009

AbstractBit error rate and threshold acquisition penalty evaluation is performed for an optically preamplified DC‐coupled burst mode receiver using a moment generating function (MGF) description of the signal plus noise. The threshold itself is a random variable and is also described using an appropriate MGF. Chernoff bound (CB), modified Chernoff bound (MCB) and the saddle‐point approximation (SPA) techniques make use of the MGF to provide the performance analyses. This represents the first time that these widely used approaches to receiver performance evaluation have been applied to an optically preamplified burst mode receiver and it is shown that they give threshold acquisition penalty results in good agreement with a prior existing approach, whilst having the facility to incorporate arbitrary receiver filtering, receiver thermal noise and non‐ideal extinction ratio. A traditional Gaussian approximation (GA) is also calculated and comparison shows that it is clearly less accurate (it exceeds the upper bounds provided by CB and MCB) in the realistic cases examined. It is deduced, in common with the equivalent continuous mode analysis, that the MCB is the most sensible approach. Copyright © 2009 John Wiley & Sons, Ltd.
Prion protein and its ligand stress inducible protein 1 regulate astrocyte development
Authors: Arantes Camila , Nomizo Regina , Lopes Marilene H. , Hajj Glaucia N. M. , Lima Flavia R. S. , Martins Vilma R. 
Published: February 2009

AbstractPrion protein (PrPC) interaction with stress inducible protein 1 (STI1) mediates neuronal survival and differentiation. However, the function of PrPC in astrocytes has not been approached. In this study, we show that STI1 prevents cell death in wild‐type astrocytes in a protein kinase A‐dependent manner, whereas PrPC‐null astrocytes were not affected by STI1 treatment. At embryonic day 17, cultured astrocytes and brain extracts derived from PrPC‐null mice showed a reduced expression of glial fibrillary acidic protein (GFAP) and increased vimentin and nestin expression when compared with wild‐type, suggesting a slower rate of astrocyte maturation in PrPC‐null animals. Furthermore, PrPC‐null astrocytes treated with STI1 did not differentiate from a flat to a process‐bearing morphology, as did wild‐type astrocytes. Remarkably, STI1 inhibited proliferation of both wild‐type and PrPC‐null astrocytes in a protein kinase C‐dependent manner. Taken together, our data show that PrPC and STI1 are essential to astrocyte development and act through distinct signaling pathways. © 2009 Wiley‐Liss, Inc.