bluuebunny/crossref_metadata_2025_split huggingface dataset:
Supported Membranes with Well‐Defined Polymer Tethers—Incorporation of Cell Receptors
Authors: Purrucker Oliver , Förtig Anton , Jordan Rainer , Tanaka Motomu 
Published: March 2004

AbstractWe report the design of supported lipid membranes attached to the surface by tailored lipopolymer tethers. A series of well‐defined lipopolymers were synthesized by means of living cationic polymerization of 2‐methyl‐2‐oxazolines. The polymers were equipped with a silane coupling group on the proximal, and lipid anchors on the distal chain ends. The length of the intermediate hydrophilic polymer tether was varied (n=14, 18, 33) to change the distance between the membrane and the substrate. Supported membranes have been prepared in two‐steps. First, a suitable lipopolymer/lipid mixture was deposited by Langmuir–Blodgett transfer, and annealed to establish the covalent coupling to the surface. On the dry lipopolymer/lipid monolayer, the upper leaflet was deposited by vesicle fusion. Optimization of both preparation steps resulted in the formation of stable and defect‐free membranes. Impacts of the spacer length and the lipopolymer fraction upon the lateral diffusivity of the lipids were systematically compared by fluorescence recovery after photobleaching (FRAP). First experiments on the incorporation of a large transmembrane cell receptor (integrin αIIbβ3) into the polymer‐tethered membrane suggested that the length of the polymer tether plays a crucial role in distribution of the proteins on the surface.
Tunnelling Motion of HF Between the Two Oxygen Lone Pairs in the Dimethyl Ether–Hydrogen Fluoride Complex: A Pure Rotational Study
Authors: Ottaviani Paolo , Caminati Walther , Velino Biagio , Blanco Susana , Lesarri Alberto , López Juan C. , Alonso José L. 
Published: March 2004

AbstractThe rotational spectrum of the dimethyl ether–hydrogen fluoride complex was assigned by millimetre‐wave free‐jet absorption spectroscopy. Fine details of the spectrum were resolved by FT microwave molecular‐beam spectroscopy. The HF group acts as a proton donor and tunnels at a rate of 44178.2(7) MHz between the two oxygen lone pairs, which corresponds to an inversion barrier of 0.17(1) kcal mol−1. The barrier to internal rotation of the two methyl groups is about 25 % lower relative to the isolated ether.
Microarray‐Based in vitro Evaluation of DNA Oligomer Libraries Designed in silico
Authors: Feldkamp Udo , Wacker Ron , Schroeder Hendrik , Banzhaf Wolfgang , Niemeyer Christof M. 
Published: March 2004

AbstractWe report on the microarray‐based in vitro evaluation of two libraries of DNA oligonucleotide sequences, designed in silico for applications in supramolecular self‐assembly, such as DNA computing and DNA‐based nanosciences. In this first study which is devoted to the comparison of sequence motif properties theoretically predicted with their performance in real‐life, the DNA‐directed immobilization (DDI) of proteins was used as an example of DNA‐based self‐assembly. Since DDI technologies, DNA computing, and DNA nanoconstruction essentially depend on similar prerequisites, in particular, large and uniform hybridization efficiencies combined with low nonspecific cross‐reactivity between individual sequences, we anticipate that the microarray approach demonstrated here will enable rapid evaluation of other DNA sequence libraries.
Can One Assess the π Character of a C–C Bond with the Help of the NMR Spin–Spin Coupling Constants?
Authors: Cremer Dieter , Kraka Elfi , Wu Anan , Lüttke Wolfgang 
Published: March 2004

AbstractMeasured one‐bond spin–spin coupling constants (SSCC) 1J(CC) can be used to describe the nature of the C–C bond, provided one is able to separate the various coupling mechanisms leading to 1J(CC). The Fermi‐contact (FC) term probes the first‐order density at the positions of the coupling nuclei, whereas the noncontact terms (the paramagnetic spin orbit (PSO) and the spin–dipole (SD) terms) probe the π character of the C–C bond (the diamagnetic spin orbit (DSO) term can mostly be neglected). A model is tested, in which the value of the FC(CC) term is estimated with the help of measured SSCCs 1J(CH). The difference between the measured J(CC) and the estimated FC(CC) values, Δ(CC)=PSO(CC)+SD(CC)+DSO(CC), provides a semiquantitative measure of the π character of a C–C multiple bond. The applicability and limitations of this approach are discussed by partitioning the four Ramsey terms of the SSCC 1J(CC) into one‐ and two‐orbital contributions. The FC, PSO, and SD terms of 1J(CC) are explained and analyzed with regard to their relationship to other C–C bond properties. It is shown that empirical relationships between measured SSCCs and the s character of a bond need reconsideration.
Computer Simulation of Long Side‐Chain Substituted Poly(phenylene vinylene) Polymers
Authors: Yang Hsiao‐Ching , Hua Chih‐Yu , Kuo Ming‐Yu , Huang Qiang , Chen Cheng‐Lung 
Published: March 2004

AbstractA molecular dynamics (MD) simulation was employed to investigate structure features and segment orientation of four poly(phenylene vinylene) (PPV) derivatives with long, flexible side chains at room temperature. In the simulations, the main chains of the polymers were found to be semirigid and exhibit a tendency to coil into ellipsoidal helices or form zigzag conformations of limited regularity. The simulations show that continuous quasi‐coplanar segments along the backbone are in a range of ≈2–4 repeat units. The ordered orientation and coupling distance of interchain aromatic rings can be correlated with optical properties of materials. A simplified quantum‐mechanical method was developed to investigate optical properties based on MD trajectories. The method was tested to simulate the absorption spectra of four PPV derivatives. The absorption maxima of the calculated spectra are in reasonable agreement with experimental data. This work implies that long‐range electron transfer along the backbones of these polymers may not occur, but may be mediated by interchain interactions.
Issues in the Synthesis of Crystalline Molecular Sieves: Towards the Crystallization of Low Framework‐Density Structures
Authors: Corma Avelino , Davis Mark E. 
Published: March 2004

AbstractFundamental and practical interest in crystalline, microporous, molecular sieves is largely a direct consequence of the fact that their bulk properties can be manipulated through variations in atomic structure. This correspondence between the macroscale and the atomic scale is due to the uniformity of these crystalline materials. Control of the atomic structure therefore is of extreme importance, and is the thesis of this Review. Synthesis mechanisms and the parameters that can direct the crystal assembly pathway and the ultimate product formed are discussed and rationalized.
Designing Systems for a Multiple Use of Light Signals
Authors: Bergamini Giacomo , Ceroni Paola , Balzani Vincenzo , Vögtle Fritz , Lee Sang‐Kyu 
Published: March 2004

AbstractThe photochemical and photophysical behavior of two dendrimers consisting of a benzophenone core and branches that contain dimethoxybenzene units has been investigated. Such dendrimers can undergo a variety of photochemical and photophysical processes, namely: 1) quenching of the fluorescence and phosphorescence of the dimethoxybenzene units by energy transfer to the benzophenone core (antenna effect), 2) direct and sensitized phosphorescence (and delayed fluorescence) of the benzophenone core, 3) hydrogen abstraction by the triplet excited state of the benzophenone core from solvent molecules, 4) intramolecular hydrogen abstraction by the triplet excited state of the benzophenone core from the dendrimer branches, 5) quenching of the phosphorescence and hydrogen abstraction reaction of the benzophenone core by energy transfer to terbium ions and dioxygen; 6) conversion of the UV light absorbed by the dendrimer branches into visible (Tb3+) or near infrared (O2) emission via the sequence of processes 1) and 5). The results obtained emphasize the great potential of suitably designed dendrimers for a multiple use of light signals.
Promotion of crystal growth rate in aqueous solution by direct contact with gas corona discharge
Authors: Maeda Kouji , Sano Noriaki , Sonoda Akira , Fukui Keisuke 
Published: March 2004

AbstractA new technique to promote crystal growth in aqueous solution using gas plasma is proposed. In this method, short‐lived radical species produced in solution which is contacted with gas corona discharge play a role to increase chemical potential of inorganic solute. In an experimental examination, single crystal of KDP was grown in a supersaturated solution which receives oxygen ions and radicals from adjacent corona discharge in air. KDP crystal has two unique growth faces (100) and (101), and the growth rates of both faces were increased considerably by generating the corona discharge. The both growth rates with and without corona discharge were well converged by one function based on chemical potential supersaturation. This result revealed that the solution in contact with gas corona discharge has a larger capacity of chemical potential than that without the discharge. Short‐lived species induced by gas corona discharge are considered to be anti‐solvents to cause this effect. The crystal growth process proposed here is considered to be an excellent method in terms of low impurity inclusion because such short‐lived species do not remain in the final crystal products and solution. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of trivalent ions doped PbWO4 crystals and their scintillation properties
Authors: Yang C. H. , Li J. L. , Wang B. 
Published: March 2004

AbstractUndoped and series of trivalent ions(including La, Y, Gd and Tb) doped PWO crystals were grown from 5N raw materials by using Czochralski technique. Trivalent ions doping improved the transmittance, fast components of luminescence and radiation damage resistance for compensating structure defects. Corresponding, the fraction of light yield at shorter collecting time was increased. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase transformation in the system TlBi(Te1‐xSex)2
Authors: Chrissafis K. , Vinga E. S. , Ozer M. , Paraskevopoulos K. M. , Polychroniadis E. K. 
Published: March 2004

AbstractTlBiTe2 and TlBiSe2 ‐ that are ternary analogs of the IV‐VI semiconductors ‐, although they crystallize in the same space group R$ \bar 3 $m (D53d), exhibit different behaviour during heating. The observed phase transformation depends on Se content (x) in the system TlBi(Te1‐xSex)2 and the transformation disappears by increasing Se content after a certain value (x = 0.25). This dependence is examined through the analysis of the DSC non‐isothermal measurements and an attempt for the explanation of the observed behaviour is undertaken through the consideration of off‐center atoms. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of SHG candidate crystals in barium aluminum (gallium) borates
Authors: Miyazaki A. , Kimura H. , Maiwa K. , Nakamura H. , Kannan C. V. 
Published: March 2004

AbstractCrystals listed in the JCPDS card in BaO‐B2O3‐Al2O3 and BaO‐B2O3‐Ga2O3 systems were synthesized by means of a solid‐state reaction method and a liquid‐state reaction method. Synthesized crystals were characterized from a viewpoint of Second Harmonic Generation (SHG) and crystal growth possibility. Ba5Al4B12O29 and Ba5Ga4B12O29 are promising new candidate crystals from the viewpoint of SHG activity and congruent melting behavior. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystal structure of 17α‐acetoxyprogesterone, C23H32O4
Authors: Rajnikant  , Dinesh  , Anshu  , Mousmi  
Published: March 2004

AbstractThe crystal structure of the title compound (C23H32O4) has been determined by X‐ray diffraction methods. It crystallizes in the orthorhombic space group P212121 with cell parameters: a = 10.86(1), b = 11.95(2), c = 15.65(5) Å and Z = 4. The structure has been refined to an R‐value of 0.045 for 1610 observed reflections. Ring A exists in sofa conformation, Ring B adopts a distorted chair conformation while as Ring C assumes a chair conformation. The five membered ring D adopts a half‐chair conformation. The crystal structure is stabilized by intra‐ and intermolecular C‐H…O interactions. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystal structure of cis‐dichloro(2,2′‐dipyridylamine)‐platinum(II)
Authors: Li Dacheng , Liu Daojie 
Published: March 2004

AbstractDichloro(2,2′‐dipyridylamine)platinum(II) has been prepared and studied by single‐crystal X‐ray diffraction methods at 293(2) K. The mononuclear complex has a square‐planar geometry. The platinum atom is coordinated by two chloride and two nitrogen atom of pyridyl groups in a cis fashion. The NH group is not coordinated, but involves in intermolecular hydrogen bonding interaction. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystal structure of N‐(3,4‐dichlorophenyl)‐N′‐hydroxy‐2‐oxo‐2‐phenylacetamidine
Authors: Hökelek T. , Taş M. , Batį H. 
Published: March 2004

AbstractThe title compound (C14H10N2O2Cl2) crystallizes in the monoclinic space group P21/a with a=10.042(1) Å, b=10.317(1) Å, c=13.877(2) Å, β=97.36(2)°, V=1425.8(3) Å3, Z=4, Dx=1.44 g.cm‐3. The structure was solved by direct methods and refined by full‐matrix least‐squares method (R = 0.0457). The title molecule consists of 3,4‐dichlorophenylamino and 2‐phenyl‐1,2‐ethanedione‐1‐oxime groups. The intermolecular O‐H…N and N‐H…O hydrogen bonds [O…N 2.760(6) and 3.087(5) Å] are highly effective in forming the polymeric chains. The oxime group has an E configuration. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystal structures and spectroscopic characterization of chiral and racemic 4‐phenyl‐1,3‐oxazolidin‐2‐one
Authors: Kitoh S. , Senda H. , Kunimoto K.‐K. , Maeda S. , Kuwae A. , Hanai K. 
Published: March 2004

AbstractCrystal structures of (R)‐ and (rac)‐4‐phenyl‐1,3‐oxazolidin‐2‐one (4‐POO) have been determined by X‐ray diffraction and characterized by the solid state 13C NMR and IR spectra. Molecular geometries and intermolecular interactions in (R)‐ and (rac)‐4‐POO crystals are very similar to each other; 4‐POO molecules are linked via the N‐H…O intermolecular hydrogen bonds to form the chained structure. Chemical shifts of the solid state 13C NMR spectra are very similar to each other, whereas the 1H spin‐lattice relaxation times (T1H) value for (R)‐4‐POO is five times as large as that for (rac)‐4‐POO, reflecting the more restricted mobility of the (R)‐4‐POO chain. Although both crystals contain an unique molecule in the asymmetric unit, a doublet feature is observed for the C=O stretching mode in the IR spectra of (R)‐ and (rac)‐4‐POO crystals. The frequency gap of the C=O bands are correlated with the strength of the dipole‐dipole interactions between the neighboring C=O groups. © 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
Discrete Fourier Transform Analysis of Chronoamperometric Currents Obtained Under Ultrasound
Authors: E Lihai , Zhou Ding 
Published: March 2004

AbstractA discrete Fourier transform (DFT) technique was used to analyze chronoamperometric currents at a Pt microdisk electrode (Ø=15 μm) in an electrolyte containing [Fe(CN)6]3−/[Fe(CN)6]4− under ultrasound at a frequency of 26.3 kHz and the powers of 0–50 W. The currents were measured by a high‐speed data acquisition card. Considering the effects of acoustic vibrations and cavitations on the limiting currents, a microdisk electrode and a high frequency sampling (10 MHz) were used to collect the current signals to restrain the deviation of average from sampling period in other methods. The results show that the amplitudes at 0 Hz and 26.3 kHz are related to the decay of ultrasound at constant power output when the separation between sono‐horn and electrode increases, and also related to the reactant concentration at the same ultrasonic conditions. The frequency signals are always shown in frequency spectrum despite different ultrasonic conditions. The amplitudes reflect the intensity of ultrasound and the concentration of reactant in solution, so they can be called specific frequencies. This method can be used to analyze quantitatively the effects of ultrasound on electrochemical reaction, determine the reactant concentration and measure the distribution of ultrasonic intensity in a solution.
Radial Electrochemical Flow Cell for On‐Line Coupling with Mass Spectrometry: Theory and Electrooxidation of Dimethylaminomethyl Ferrocene
Authors: Modestov Alexander D. , Gun Jenny , Mudrov Andrei , Lev Ovadia 
Published: March 2004

AbstractA new, radial, miniature, three‐electrode flow cell is introduced. The cell's configuration is most suitable for on‐line electrochemistry – mass spectrometry since it is characterized by low resistive losses, high conversion efficiency, and isolation of the counter electrode reaction by‐products from the product stream reaching the MS. A mathematical model describing convection diffusion in the radial cell is developed. Cell's performance can be predicted over a wide parametric range by a simple mathematical expression which converges to the Levich equation under low conversion conditions. The performance of the cell is demonstrated by studies of dimethylaminomethyl ferrocene (DMAMF) oxidation which is a simple single electron charge transfer reaction and allows validation of the mathematical model. The theoretical predictions of the model were in agreement with the results of on‐line electrochemistry – mass spectrometry studies of DMAMF.
All‐Solid‐State Chloride Sensors with Poly(3‐Octylthiopene) Matrix and Trihexadecylmethylammonium Chlorides as an Ion Exchanger Salt
Authors: Sjöberg‐Eerola Pia , Bobacka Johan , Sokalski Tomasz , Mieczkowski Jozef , Ivaska Ari , Lewenstam Andrzej 
Published: March 2004

AbstractAll‐solid‐state chloride sensors were prepared by incorporation of trihexadecyl‐methylammonium chloride (THMACl) as an ion‐exchanger salt into a conjugated polymer membrane, poly(3‐octylthiophene) (POT). The influence of additional membrane components, such as a lipophilic anion, (potassium tetrakis[3,5‐bis(trifluoromethyl)phenyl] borate), poly(vinyl chloride) (PVC) or a plasticizer, (2‐nitrophenyl octyl ether) were studied. The membrane components were dissolved in chloroform except for PVC, which was dissolved in tetrahydrofuran (THF). The membrane solution was deposited on glassy carbon (GC) by solution casting resulting in all‐solid‐state chloride sensors. The sensor characteristics were determined potentiometrically and with impedance spectroscopy. The addition of plasticizer was found to be crucial in obtaining a well functioning Cl−‐ISE based on POT and THMACl.
Kinetic Analysis of a Two‐Phase EC Mechanism with Concomitant Lateral Processes
Authors: Fernández Mariana Adela , Yudi Lidia Mabel , Baruzzi Ana María 
Published: March 2004

AbstractElectrochemical transfer of azo dye fast red TR across the water/1,2 – dichloroethane (DCE) interface followed by the coupling reaction with 1‐naphthylamine in the organic phase is studied. Pseudo first order rate constants of this reaction were obtained by fitting the experimental Ip−/Ip+ ratio under different experimental conditions with the theoretical values reported by Nicholson and Shain. The occurrence of lateral processes is demonstrated (partition of the azo dye non assisted by potential and electrochemical transfer of the protons generated in the coupling reaction), which constrains the accurate determination of the kinetic parameters.
Remote Stripping Analysis of Lead and Copper by a Mercury‐Coated Platinum Microelectrode
Authors: Baldo M. Antonietta , Daniele Salvatore , Ciani Ilenia , Bragato Carlo , Wang Joseph 
Published: March 2004

AbstractThe performance of a remote stripping sensor based on mercury microelectrodes (MM‐RS) for the in situ detection of trace metals in aquatic systems, was investigated. The submersible device employed here consists of a single mercury‐coated platinum disk microelectrode assembled in a two‐electrode cell configuration, and connected remotely by a 30 m long shielded cable. First, the MM‐RS device is characterized in Ru(NH3)$\rm{ {_{6}^{3+}}}$ and Pb2+ synthetic aqueous solutions by applying cyclic voltammetry and anodic stripping voltammetry (ASV), respectively. The results obtained show that the small electrode dimensions and the related low currents involved, the long remote connection cable or the use of a two‐electrode system do not cause noise effects or uncompensated resistance problems in the measurements. Using square‐wave voltammetry in the stripping step, linear calibration graphs for Pb2+ ions over the concentration range 1×10−9−5×10−7 M were obtained, and a detection limit, DL, of 0.15 nM was found. The relative standard deviation (RSD), at 5×10−8 M Pb2+ level, was within 5%. The effect of humic acid and of sodium dodecylsulfate surfactants on the stripping responses was also investigated. The performance of the submersible MM‐RS system was tested for the in situ monitoring of the labile fraction of lead and copper on a site of the Lagoon of Venice. In situ Pb2+ and Cu2+ concentrations were monitored for about 8 hours, by leaving the sensor immersed in the lagoon waters (2 m depth) and recording the response every hour. Under these field conditions, reliable in situ data for the labile fraction of these metal ions with a satisfactory precision, the RSD being within 7 and 9 % for lead and copper, respectively, were obtained.
Electrocatalytic Sensor for the Determination of Chemical Oxygen Demand Using a Lead Dioxide Modified Electrode
Authors: Ai Shiyun , Gao Mengnan , Yang Ya , Li Jiaqing , Jin Litong 
Published: March 2004

AbstractAn amperometric method that makes use of a nano‐PbO2 modified electrode as an electrocatalytic sensor for the determination of chemical oxygen demand (COD) is described. The sensor signal was observed as a result of the detection of the oxidation current due to electrocatalytic oxidation of organic compounds in the sample solution. This sensor responded linearly to the CODCr of standard samples in the range of 5–3 000 ppm and the detection limit was 2.5 ppm. When using the sensor to determine real samples, it displays short analysis time, simplicity and no sample pretreatment. The sensor was stable for over 20 days in real wastewater samples and has successfully been applied to the determination of COD in real wastewater samples.
Depletive Stripping Chronopotentiometry: A Major Step Forward in Electrochemical Stripping Techniques for Metal Ion Speciation Analysis
Authors: Town Raewyn M. , van Leeuwen Herman P. 
Published: March 2004

AbstractA comparative evaluation of the utility of the various modes of stripping chronopotentiometry (SCP) for trace metal speciation analysis is presented in the broad context of stripping voltammetric techniques. The remarkable fundamental advantages of depletive SCP at scanned deposition potential (SSCP) are highlighted, and the rigorous underpinning theory is described. The distinctive features of SSCP include: i) an effective getting around part of the Nernstian extension of the reoxidation process, leading to ii) greater resolution than conventional stripping voltammetries; iii) a certain insensitivity to electrochemical irreversibility, especially at a microelectrode; iv) in principle, freedom from induced metal ion adsorption interferences; v) no requirement for excess ligand during stripping; and vi) ability to provide a certain measure of any chemical heterogeneity in the metal speciation that is easily distinguishable from effects of electrochemical irreversibility.