bluuebunny/crossref_metadata_2025 huggingface dataset:
Fragmentation of Carbohydrate Anomeric Alkoxyl Radicals: New Synthesis of Chiral 1‐Fluoro‐1‐halo‐1‐iodoalditols
Authors: Francisco Cosme G. , González Concepción C. , Kennedy Alan R. , Paz Nieves R. , Suárez Ernesto
Published: June 2008

A new general methodology for the synthesis of 1,1,1‐trihaloalditols by starting from 1,5‐anhydro‐2‐deoxy‐hex‐1‐enitol derivatives (glycals) is described. The halogens are introduced sequentially in each of the three different steps of the process. The fluorine is introduced in the first step by electrophilic fluorination of the starting glycal; next, hydroxyhalogenation of the resulting vinyl fluoride allows the addition of any halogen (F, Cl, Br or I) at will, and finally, an iodine atom is inserted through an alkoxyl radical fragmentation reaction. This methodology allows the preparation of diverse types of 1,1,1‐trihalogenated compounds (RCF2I, RCFI2, RCFClI and RCFBrI) under mild conditions compatible with sensitive substituents. In some cases, the diastereomeric mixtures generated from RCFClI and RCFBrI can be chromatographically separated, and their configuration determined by X‐ray crystallographic analysis. The synthetic usefulness of these compounds has been preliminarily assessed by examining the reactivity of the fluorinated radical generated by rupture of the CI bond.
Intramolecular Charge Transfer of Carotene‐porphyrin‐fullerene Triad: Sequential or Superexchange Cechanism
Authors: SUN Yu , CHEN Yue‐Hui , LI Yuan‐Zuo , LI Yong‐Qing , MA Feng‐Cai
Published: June 2008

As an excellent artificial photosynthetic reaction center, the carotene (C)‐porphyrin (P)‐fullerene (F) triad was extensively investigated experimentally. To reveal the mechanism of the intramolecular charge transfer (ICT) on the mimic of photosynthetic solar energy conversion (such as singlet energy transfer between pigments, and photoinduced electron transfer from excited singlet states to give long‐lived charge‐separated states), the ICT mechanisms of C‐P‐F triad on the exciton were theoretically studied with quantum chemical methods as well as the 2D and 3D real space analysis approaches. The results of quantum chemical methods reveal that the excited states are the ICT states, since the densities of HOMO are localized in the carotene or porphyrin unit, and the densities of LUMO are localized in the fullerene unit. Furthermore, the excited states should be the intramolecular superexchange charge transfer (ISCT) states for the orbital transition from the HOMO whose densities are localized in the carotene to the LUMO whose densities are localized in the fullerene unit. The 3D charge difference densities can clearly show that some excited states are ISCT excited states, since the electron and hole are resident in the fullerene and carotene units, respectively. From the results of the electron‐hole coherence of the 2D transition density matrix, not only 3D results are supported, but also the delocalization size on the exciton can be observed. These phenomena were further interpreted with non‐linear optical effect. The large changes of the linear and non‐linear polarizabilities on the exciton result in the charge separate states, and if their changes are large enough, the ICT mechanism can become the ISCT on the exciton.
Interaction of N′‐(1‐Carboxyethylidene)salicylhydrazide with Bovine Serum Albumin
Authors: ZHANG Ye‐Zhong , DAI Jie , LIU Cheng , ZHANG Xiao‐Ping , DING Xin‐Liang , LIU Yi
Published: June 2008

Under the simulated physiological condition of an animal body, the interaction between N′‐(1‐carboxyethylidene)salicylhydrazide (CESH) and bovine serum albumin (BSA) was investigated by fluorescence spectra, UV‐Vis absorption spectra and circular dichroism (CD) spectra. The experiment results showed that the fluorescence of BSA was strongly quenched by CESH because of the formation of a CESH‐BSA complex, indicating a static quenching mechanism in the binding process. The modified Stern‐Volmer quenching constants (Ka) were 11.23×104, 7.103×104, 4.934×104 and 2.495×104 L·mol−1 at 292, 298, 304 and 310 K, respectively. The thermodynamic parameters ΔG, ΔH and ΔS at the four temperatures were calculated according to van't Hoff equation and the results indicated that hydrogen bonds and van der Waals force played major roles in stabilizing the CESH‐BSA complex. The distance r=4.26 nm between the donor BSA and acceptor CESH was obtained according to F?rster's non‐radiative energy transfer theory. The synchronous fluorescence spectral results indicated that the hydrophobicity of tyrosine residue increased while the microenvironment around tryptophan residue had no change. The CD and three‐dimensional fluorescence spectral results showed that in the presence of CESH, the α‐helix content of BSA decreased and the microenvironment and conformation of BSA changed.
Reduction of NO2 in Flue Gas by CO and Propylene over CuO‐CeO2/SiO2 in the Presence of O2
Authors: LU Mo‐Hong , LI Ming‐Shi , SHAN Yu‐Hua , SESHAN K. , LEFFERTS Leon
Published: June 2008

Catalytic reduction of NO2 with CO and/or propylene in the presence of NO and excess oxygen, a model mixture for flue gas, was studied over a series of CuO‐CeO2/SiO2 catalysts between 120–260 °C. The effect of HCl, an impurity in flue gas, on the activity of the catalysts was evaluated. It was found that a binary oxide catalyst, 2% CuO‐8% CeO2/SiO2, was active for the reduction of NO2 by CO and/or propylene. CO was effective for selective reduction of NO2 in the presence of NO and O2 in a temperature window between 160–200 °C while propylene was effective at temperature higher than 200 °C. In the presence of HCl, the activity of the catalyst for reduction of NO2 with CO was irreversibly deactivated. However, the activity for reduction of NO2 with propylene was not influenced by HCl.
Novel Flower‐Like Ag‐SiO2‐MgO‐Al2O3 Material: Preparation, Characterization and Catalytic Application in Methanol Dehydrogenation
Authors: LI Jing‐Xia , REN Li‐Ping , DAI Wei‐Lin , CAO Yong , FAN Kang‐Nian
Published: June 2008

Catalytic direct dehydrogenation of methanol to formaldehyde was carried out over Ag‐SiO2‐MgO‐Al2O3 catalysts prepared by sol‐gel method. The optimal preparation mass fractions were determined as 8.3% MgO, 16.5% Al2O3 and 20% silver loading. Using this optimum catalyst, excellent activity and selectivity were obtained. The conversion of methanol and the selectivity to formaldehyde both reached 100%, which were much higher than other previously reported silver supported catalysts. Based on combined characterizations, such as X‐ray diffraction (XRD), scanning electronic microscopy (SEM), diffuse reflectance ultraviolet‐visible spectroscopy (UV‐Vis, DRS), nitrogen adsorption at low temperature, temperature programmed desorption of ammonia (NH3‐TPD), desorption of CO2 (CO2‐TPD), etc., the correlation of the catalytic performance to the structural properties of the Ag‐SiO2‐ MgO‐Al2O3 catalyst was discussed in detail. This perfect catalytic performance in the direct dehydrogenation of methanol to formaldehyde without any side‐products is attributed to its unique flower‐like structure with a surface area less than 1 m2/g, and the strong interactions between neutralized support and the nano‐sized Ag particles as active centers.
Kinetics of the Oxidation of D‐Glucose and Cellobiose by Acidic Solution of N‐Bromoacetamide Using Transition Metal Complex Species, [RuCl3(H2O)2OH] −, as Catalyst
Authors: SINGH Ashok Kumar , SRIVASTAVA Jaya , SRIVATAVA Shalini , RAHMANI Shahla
Published: June 2008

The kinetics of Ru(III)‐catalyzed and Hg(II)‐co‐catalyzed oxidation of D‐glucose (Glc) and cellobiose (Cel) by N‐bromoacetamide (NBA) in the presence of perchloric acid at 40 °C have been investigated. The reactions exhibit the first order kinetics with respect to NBA, but tend towards the zeroth order to higher NBA. The reactions are the first order with respect to Ru(III) and are fractional positive order with respect to [reducing sugar]. Positive effect of Cl− and Hg(OAc)2 on the rate of reaction is also evident in the oxidation of both reducing sugars. A negative effect of variation of H+ and acetamide was observed whereas the ionic strength (µ) of the medium had no influence on the oxidation rate. The rate of reaction decreased with the increase in dielectric constant and this enabled the computation of dAB, the size of the activated complex. Various activation parameters have been evaluated and suitable explanation for the formation of the most reactive activated complex has been given. The main products of the oxidation are the corresponding arabinonic acid and formic acid. HOBr and [RuCl3(H2O)2OH]− were postulated as the reactive species of oxidant and catalyst respectively. A common mechanism, consistent with the kinetic data and supported by the observed effect of ionic strength, dielectric constant and multiple regression analysis, has been proposed. Formation of complex species such as [RuCl3·S·(H2O)OH]− and RuCl3·S·OHgBr·OH during the course of reaction was fully supported by kinetic and spectral evidences.
Interaction of Antitumor Drug Aclacinomycin‐A with DNA and Its Specific Sequence Site
Authors: CHENG Gui‐Fang , ZHANG Fan , TAN Xue‐Lian , HE Pin‐Gang , FANG Yu‐Zhi
Published: June 2008

Through UV and fluorescence spectrophotometries, the interaction of aclacinomycin‐A (ACM‐A) with DNA and its specific sequence have been investigated with the aid of circular dichroism spectrophotometry and differential pulse voltammetry method. The results demonstrated that ACM‐A was capable of intercalating DNA double helix, the π‐π electronic overlapping between π‐electrons of ACM‐A and base pair of DNA stabilized the ACM‐A‐DNA adduct, and through electrostatic interaction, the trisaccharide interacted with the minor groove of DNA owing to an amino group at C(3′). Electrochemical and spectroelectrochemical studies revealed that the original form of ACM‐A had higher affinity for DNA than the reduction form in which the trisaccharide group at C(7) was lost. According to the results obtained in this paper, ACM‐A showed preference for AT base pairs of the deoxyribonucleic acid duplex, and it was apt to interact with cytosine and thymine rather than the adenine of oligonucleotide.
Synthesis and Optical Properties of 2,13‐Dibenzothiazol‐2′‐yldibenzo[b,k]‐18‐crown‐6
Authors: HUANG Zhi‐Bin , KIM Sung‐Hong , SHI Da‐Qing , KANG Tai‐Jong , CHANG Seung‐Hyun
Published: June 2008

A new crown ether of 2,13‐dibenzothiazol‐2′‐yldibenzo[b,k]‐18‐crown‐6 was synthesized from 2,13‐diformyl‐ dibenzo[b,k]‐18‐crown‐6 with 2‐aminothiophenol. The binding behavior and the optical properties of the crown ether were examined through UV‐visible spectroscopy and fluorescence spectroscopy. When complexed with Na+, K+, Rb+ and Cs+ ions, it led to intramolecular charge transfer and caused the changes of the fluorescence spectra. The protonation of the crown ether was also studied.
Synthesis of 14‐{[(Un)substituted phenyl] or alkyl}‐14H‐dibenzo[a,j]xanthenes Using Yb(OTf)3 as an Efficient Catalyst under Solvent‐free Conditions
Authors: WANG Li‐Min , SUI Yuan‐Yuan , ZHANG Liang
Published: June 2008

A series of 14‐{[(Un)substituted phenyl] or alkyl}‐14H‐dibenzo[a,j]xanthenes were prepared under solvent‐free conditions by Yb(OTf)3 catalyzed condensation reactions of β‐naphthol with various aldehydes. The process presented here is operationally simple, environmentally benign and has good to excellent yields. Furthermore, the catalyst can be recovered conveniently and reused efficiently.
Substituent Effect on the C–NO2 and N–NO2 Bond Dissociation Energies of Nitroaromatic Molecules
Authors: FANG, Ming Ming , LI Zhe , FU Yao
Published: June 2008

Six density function theory methods (B3LYP, B3P86, MPWB1K1, MPWPW91, PBEPBE, TPSS1KCIS3) were used to calculate bond dissociation enthalpies of nitro compounds, where the B3P86 method was found to give the most accurate predictions. Using the B3P86 method meta‐ and para‐substituted nitroaromatics were systematically studied for the first time. The remote substituent effects, Hammett relationships, and the origin of the substituent effects were discussed on the basis of the calculated results. Both meta‐ and para‐substituted nitromethyl‐benzenes showed significant substituent effects and a fair correlation against substituent constants σp+ The ground state effects were found to play the major role in determining the overall substituent effects. Meanwhile, nitroamino‐ benzenes showed irregular substituent effects and a poorer Hammett correlation, where both ground and radical state effects contributed to the overall substituent effects.
Design, Synthesis and Antitumor Activity of Asymmetric Bis(s‐triazole Schiff‐base)s Bearing Functionalized Side‐Chain
Authors: HU Guo‐Qiang , HOU Li‐Li , XIE Song‐Qiang , HUANG Wen‐Long
Published: June 2008

1‐Amino‐2‐pyrid‐3‐yl‐5‐(2‐benzoylethylthio)‐s‐triazole (1) was condensed with 1‐amino‐3‐mercapto‐5‐ [(un)substituted phenyl]‐s‐triazoles and subsequently substituted with chloroacetic acid to afford bis‐s‐triazole sulfanylacetic acid mono‐Schiff bases (3a–3e), which were condensed with 9‐formylanthracene to produce asymmetric bis(s‐triazole Schiff base) sulfanylacetic acids (4a–4e). The structures of new synthesized compounds were characterized by elemental analysis and spectral data, and their in vitro antitumor activity against L1210, CHO and HL60 cell lines was evaluted via the respective IC50 values by methylthiazole trazolium (MTT) assay.
Evaluation of Solvent Accessibility Epitopes for Different Dehydrogenase Inhibitors
Authors: Ludwig Christian , Michiels Paulus J. A. , Lodi Alessia , Ride John , Bunce Chris , Günther Ulrich L.
Published: June 2008

Knowledge about the orientation of ligands or inhibitors bound to a protein is vital for the development of new drugs. It was recently shown that solvent accessibility epitopes for protein ligands can be mapped by transferring magnetization from water molecules to the ligand to derive the ligand orientation. This is based on the fact that NMR signals of ligands arising from magnetization transferred from solvent molecules via the protein have a different sign from those arising from direct magnetization transfer from bulk water. Herein we critically evaluate the applicability of solvent accessibility mapping to derive binding orientations for ligands of two dehydrogenases (AKR1C3 and HSD17β1) with very different binding pockets, including complexes in which the ligand is buried more deeply inside the protein. We also evaluate the possibility of using co‐solvents, such as DMSO, for magnetization transfer.
Nanodroplet Cluster Formation in Ionic Liquid Microemulsions
Authors: Gao Yanan , Voigt Andreas , Hilfert Liane , Sundmacher Kai
Published: June 2008

A common ionic liquid (IL), 1‐butyl‐3‐methylimidazolium tetrafluoroborate (bmimBF4), is used as polar solvent to induce the formation of a reverse bmimBF4‐in‐toluene IL microemulsion with the aid of the nonionic surfactant Triton X‐100. The swelling process of the microemulsion droplets by increasing bmimBF4 content is detected by dynamic light scattering (DLS), conductivity, UV/Vis spectroscopy, and freeze‐fracture transmission electron microscopy (FF–TEM). The results show that the microemulsion droplets initially formed are enlarged by the addition of bmimBF4. However, successive addition of bmimBF4 lead to the appearance of large‐sized microemulsion droplet clusters (200–400 nm). NMR spectroscopic analysis reveal that the special structures and properties of bmimBF4 and Triton X‐100 together with the polar nature of toluene contribute to the formation of such self‐assemblies. These unique self‐assembled structures of IL‐based microemulsion droplet clusters may have some unusual and unique properties with a number of interesting possibilities for potential applications.
Novel Technique for Direct Measurement of the Plasma Diffusion Coefficient in Magnetized Plasma
Authors: Brotánková J. , Martines E. , Adámek J. , Stöckel J. , Popa G. , Costin C. , Ionita C. , Schrittwieser R. , Van Oost G.
Published: June 2008

The diffusion coefficient in the edge plasma of fusion devices is measured by a new technique. The method is based on studying the decay of the plasma fluctuation spectrum inside the so‐called “Ball‐pen probe”: a small ceramic tube having its mouth flush with a magnetic surface and a movable electrode inside the tube. When the electrode protrudes from the tube, the measured signal shows the floating potential fluctuations of the plasma or the ion saturation current outside the tube. Retracting the electrode into the tube, the power spectrum of the signal displays an exponential decay that is different for different frequencies. Assuming a mainly diffusive behaviour of the plasma inside the tube, the spectrum decay length can be used to derive the value of the diffusion coefficient. The measurements were performed at several radial positions in the CASTOR edge region for three different values of Btor. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study of Sheath Dynamics in Multicomponent Plasma
Authors: Černý P. , Novák S. , Hrach R. , Bruna P.
Published: June 2008

A one‐dimensional self‐consistent particle model for a low‐pressure discharge in an electronegative gas near the cylindrical electrode was developed. The model is based on a deterministic particle‐in‐cell technique with scattering events treated stochastically. The data for the simulation were taken from the simplified model of oxygen‐argon plasma based on a macroscopic kinetic approach. The purpose of the present work was to clarify the role of both electron and individual ions mobilities in the low‐temperature plasma on the dynamics of sheath formation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of Highly Energetic Electrons on Probe Measurements in A Hot Cathode Arc Discharge Plasma
Authors: Ezumi N.
Published: June 2008

Influences of highly energetic electrons on probe measurements has been investigated in a vacuum arc discharge plasma. Double and triple probe measurements clearly show these probe method is very sensitive for the small amount of hot electron component. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Measurements of EEDF in Helium Flowwing Afterglow at Pressures 500 – 2000 PA
Authors: Korolov I. , Plašil R. , Kotrík T. , Dohnal P. , Novotný O. , Glosík J.
Published: June 2008

For measurements of recombination rate coefficients of slowly recombining ions with rate coefficients below 10–7cm3s–1 in Flowing Afterglow Langmuir Probe (FALP) experiment the plasma decay time has to be long and this requires buffer gas (helium) pressures in range 500 – 2000 Pa. Application of Langmuir probe for measurements of electron energy distribution function, EEDF (f (ε)), at these pressures is not trivial. The Druyvestein formula for calculating f (ε) from the second derivative of the electron current to the probe (I″e) cannot be used. More complex analyses of measured probe characteristic are required to obtain reliable EEDF. To characterize the extent of the required corrections, the probe characteristics in well‐defined flowing afterglow plasma were measured and two different methods were used to obtain EEDF. In the first method, the first and second derivative of probe characteristics were used to obtain EEDF [1]. In the second method, numerical correction was calculated [2] and applied to values obtained from Druyvesteyn formula. By comparison of obtained EEDF with Maxwell distribution we determine a region of electron energies where advanced analysis is necessary. It was found that in a helium afterglow at 250 K, with pressure 600 – 2000 Pa, where plasma is nearly Maxwellian with T e ∼ 250 – 600 K, the correction is necessary for electron energies ε ≤ 3.5 kBTe. At higher electron energies correction is negligible and is not necessary. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ion‐Conducting Probes for Low Temperature Plasmas
Authors: Meiss S. A. , Rohnke M. , Rettig F. , Moos R. , Janek J.
Published: June 2008

Probes interacting with a low temperature plasma are typically built of electron conducting materials, mostly metals. We apply yttria‐stabilized zirconia (YSZ) which is oxygen ion conducting at elevated temperatures and which is a typical solid electrolyte with high ionic and negligible electronic conductivity. The processes at the plasma|YSZ interface are discussed and first results of measurements with ion‐conducting single‐ and double‐probes in oxygen containing radio frequency plasmas are presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Emissive Probe Diagnostics in Low Temperature Plasma – Effect of Space Charge and Variations of Electron Saturation Current
Authors: Marek A. , Jílek M. , Picková I. , Kudrna P. , Tichý M. , Schrittwieser R. , Ionita C.
Published: June 2008

We report a study of electron saturation current variations at varying probe heating that were found to be closely related to probe wire contamination. The study was performed in three types of low temperature argon plasma – the weakly magnetized plasma of a cylindrical magnetron, the non‐magnetized plasma of a double plasma machine and a hollow cathode plasma jet, showing different trends. In the present work the effect of overestimation of the plasma potential by a strongly emitting probe is discussed and experimental data are compared with a theoretical model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study of Electronegative Ar/O2 Discharge by Means of Langmuir Probe
Authors: Straňák V. , Blažek J. , Wrehde S. , Adámek P. , Hubička Z. , Tichý M. , Špatenka P. , Hippler R.
Published: June 2008

The paper presents systematic Langmuir probe diagnostic of a dc discharge in Ar/O2 mixture with low fraction of O2, burning in a sputtering planar magnetron. Electron density, electron temperature and plasma potential are investigated in dependence upon experimental conditions like pressure, rate of oxygen, incoming power, and on balanced or unbalanced mode of magnetron. A new method of determining negative‐ion density from the current‐voltage characteristic is proposed. This method is based on comparison of the characteristic measured in electronegative plasma (e.g. Ar/O2) with a reference characteristic scanned in an electropositive counterpart (Ar), existing in similar conditions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of Langmuir Probe in Recombination Dominated Afterglow Plasma
Authors: Korolov I. , Kotrík T. , Plašil R. , Varju J. , Hejduk M. , Glosík J.
Published: June 2008

New advanced data analysis method for calculation of recombination rate coefficients from the decay of electron density during the afterglow (along the flow tube) in a Flowing Afterglow Langmuir Probe (FALP) experiment is presented. The method is advantageous for measurements of recombination rate coefficients of slowly recombining ions in conditions where formation of the studied ions is slow, decaying plasma contains several types of ions and the ion formation and recombination proceed simultaneously. The new method is demonstrated on the analysis of the data obtained from plasma decay in He/Kr/H2 and He/Kr/D2 gas mixtures. In a limit for [Kr]/[D2] ≫ 1, the recombination rate coefficients for KrD+ ions α (KrD+, 250 K) = 1 × 108cm3s–1 was obtained. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical Probe Diagnostics of the Hollow Cathode Plasma Jet System for Deposition of TiOx Thin Films
Authors: Virostko P. , Hubička Z. , Čada M. , Adámek P. , Kment Š. , Tichý M. , Jastrabík L.
Published: June 2008

Measurements of positive ion flux to a negatively biased substrate for deposition of TiOx thin films by the hollow cathode plasma jet system are presented. Different methods of obtaining the bias of substrate and measuring the resulting ion flux were used for different bias frequencies. Pulsed DC bias, middle frequency 500 kHz bias, and pulse‐modulated 13.56 MHz RF bias were compared. The measurements were performed for different bias and discharge conditions. Time‐resolved Langmuir probe technique was simultaneously used to observe the basic plasma properties during the ion flux measurements. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis and Characterization of Benzannelated Thienyl Oligomers
Authors: Amaladass Pitchamuthu , Clement J. Arul , Mohanakrishnan Arasambattu K.
Published: June 2008

An array of 1,3‐diarylbenzo[c]thiophenes have been synthesized by the ring‐opening of lactones followed by thionation using Lawesson's reagent with concurrent intramolecular cyclization. Photophysical studies of the various benzo[c]thiophene analogues are presented. The results of a cyclic voltammetric investigation of the benzo[c]thiophenes are also reported.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
The use of cationic surfactants and ionic liquids in the detection of microbial contamination by capillary electrophoresis
Authors: Bao Ye , Lantz Andrew W. , Crank Jeffrey A. , Huang Junmin , Armstrong Daniel W.
Published: June 2008

A rapid test of whether a laboratory sample contains any microorganisms is important and necessary for many areas of science and technology. Currently, most of the standard procedures for the detection of aerobic bacteria, anaerobic bacteria and fungi, require the preparation of microbial cultures in respective growth media, which are dramatically slow. Different approaches providing fast analysis such as CE are becoming more desired. To compensate for the natural electrophoretic heterogeneity of microbes, various buffer additives were examined to stack all bacteria and fungi in a sample plug into a single peak. This peak was removed from the molecular contaminants in the sample to prevent false positives. Both cationic surfactants and ionic liquids (IL) were investigated as run buffer additives and they are both widely applicable to different species of bacteria and fungi. Given that high concentrations of surfactants can potentially lyse cells, dicationic IL offer attractive auxiliary buffer additives for use in CE‐based sterility tests. The analysis can be completed in 10 min, thus providing a great advantage over traditional direct inoculation methods that require several weeks to complete.
High‐sensitivity capillary electrophoresis for speciation of organomercury in biological samples using hollow fiber‐based liquid‐liquid‐liquid microextraction combined with on‐line preconcentration by large‐volume sample stacking
Authors: Li Pingjing , Duan Jiankun , Hu Bin
Published: June 2008

A hollow fiber‐based liquid‐liquid‐liquid microextraction (HF‐LLLME) combined with on‐line large‐volume sample stacking (LVSS) has been developed for the speciation of organomercury in biological samples by CE with UV detection. Separation was achieved in less than 11 min with an electrolyte consisting of 35 mM sodium tetraborate at pH 9.1. In LVSS, a reverse electrode polarity‐stacking mode (REPSM) was applied as on‐line preconcentration strategy. In HF‐LLLME, the analytes were extracted from 12 mL volume of sample solution (pH adjusted to 3.0) into bromobenzene impregnated in the pores of the hollow fiber, and into an acceptor solution of L‐cysteine (15 μL, 0.02% w/v) inside the hollow fiber. Under the optimized conditions, concentration factors of 2610–4580 were achieved and LODs in the range of 0.03–0.14 μg/L were feasible. The linearity was found to be over two orders of magnitude with correlation coefficient of 0.9991–0.9996. The developed method has been validated using a certified reference material (DORM‐2, dogfish muscle), and the determined values coincided very well with the certified values. The method was also applied to the speciation of organomercury in three kinds of fish samples and human hair samples.
Performance of a damage‐protected beam–column subassembly utilizing external HF2V energy dissipation devices
Authors: Rodgers Geoffrey W. , Solberg Kevin M. , Chase J. Geoffrey , Mander John B. , Bradley Brendon A. , Dhakal Rajesh P. , Li Luoman
Published: June 2008

Ductile‐jointed connections, which generally require some form of supplementary energy dissipation to alleviate displacement response, typically employ mild steel energy dissipation devices. These devices run the risk of low‐cycle fatigue, are effective only for peak cycles that exceed prior displacements, are prone to buckling, and may require replacement following an earthquake. This study presents an experimental investigation employing an alternative to mild steel: a high force‐to‐volume (HF2V) class of damper‐based energy dissipation devices. Tests are performed on a near full‐scale beam–column joint subassembly utilizing externally mounted compact HF2V devices. Two configurations are considered: an exterior joint with two seismic beams and one gravity beam framing into a central column, and a corner joint with only one seismic beam and one gravity beam framing into a column. Quasi‐static tests are performed to column drifts up to 4%. The experiments validate the efficacy of the HF2V device concept, demonstrating good hysteretic energy dissipation, and minimal residual device force, allowing ready re‐centring of the joint. The devices dissipate energy consistently on every cycle without the deterioration observed in the yielding steel bar type of devices. The effectiveness of the HF2V devices on structural hysteretic behavior is noted to be sensitive to the relative stiffness of the anchoring elements, indicating that better efficiency would be obtained in an embedded design. Copyright © 2008 John Wiley & Sons, Ltd.
Human catalytic antibody Se‐scFv‐B3 with high glutathione peroxidase activity
Authors: Huo Rui , Wei Jingyan , Xu Junjie , Lv Shaowu , Zheng Qingchuan , Yan Fei , Su Jiaming , Fan Jia , Li Jieshuai , Duan Yujing , Yu Yang , Jin Fenghai , Sun Weiguo , Shi Yi , Cong Dengli , Li Wei , Yan Ganglin , Luo Guimin
Published: June 2008

In order to generate catalytic antibodies with glutathione peroxidase (GPX) activity, we prepared GSH‐S‐2,4‐dinitrophenyl t‐butyl ester (GSH‐S‐DNPBu) as target antigen. Three clones (A11, B3, and D5) that bound specifically to the antigen were selected from the phage display antibody library (human synthetic VH + VL single‐chain Fv fragment (scFv) library). Analysis of PCR products using gel electrophoresis and sequencing showed that only clone B3 beared intact scFv‐encoding gene, which was cloned into the expression vector pPELB and expressed as soluble form (scFv‐B3) in Escherichia coli Rosetta. The scFv‐B3 was purified by Ni2+‐immobilized metal affinity chromatography (IMAC). The yield of purified proteins was about 2.0–3.0 mg of proteins from 1 L culture. After the active site serines of scFv‐B3 were converted into selenocysteines (Secs) with the chemical modification method, we obtained the human catalytic antibody (Se‐scFv‐B3) with GPX activity of 1288 U/µmol. Copyright © 2008 John Wiley & Sons, Ltd.
Nutritional supplements cross‐contaminated and faked with doping substances
Authors: Geyer Hans , Parr Maria Kristina , Koehler Karsten , Mareck Ute , Schänzer Wilhelm , Thevis Mario
Published: June 2008

Since 1999 several groups have analyzed nutritional supplements with mass spectrometric methods (GC/MS, LC/MS/MS) for contaminations and adulterations with doping substances.

These investigations showed that nutritional supplements contained prohibited stimulants as ephedrines, caffeine, methylenedioxymetamphetamie and sibutramine, which were not declared on the labels. An international study performed in 2001 and 2002 on 634 nutritional supplements that were purchased in 13 different countries showed that about 15% of the nonhormonal nutritional supplements were contaminated with anabolic‐androgenic steroids (mainly prohormones). Since 2002, also products intentionally faked with high amounts of ‘classic’ anabolic steroids such as metandienone, stanozolol, boldenone, dehydrochloromethyl‐testosterone, oxandrolone etc. have been detected on the nutritional supplement market. These anabolic steroids were not declared on the labels either. The sources of these anabolic steroids are probably Chinese pharmaceutical companies, which sell bulk material of anabolic steroids. In 2005 vitamin C, multivitamin and magnesium tablets were confiscated, which contained cross‐contaminations of stanozolol and metandienone. Since 2002 new ‘designer’ steroids such as prostanozol, methasterone, androstatrienedione etc. have been offered on the nutritional supplement market. In the near future also cross‐contaminations with these steroids are expected. Recently a nutritional supplement for weight loss was found to contain the β2‐agonist clenbuterol. The application of such nutritional supplements is connected with a high risk of inadvertent doping cases and a health risk. For the detection of new ‘designer’ steroids in nutritional supplements, mass spectrometric strategies (GC/MS, LC/MS/MS) are presented. Copyright © 2008 John Wiley & Sons, Ltd.
Mass spectrometric determination of gonadotrophin‐releasing hormone (GnRH) in human urine for doping control purposes by means of LC–ESI‐MS/MS
Authors: Thomas Andreas , Geyer Hans , Kamber Matthias , Schänzer Wilhelm , Thevis Mario
Published: June 2008

The decapeptide gonadotrophin‐releasing hormone (GnRH) is endogenously produced in the hypothalamus and secreted into the microcirculation between hypothalamus and pituitary gland. Here, the bioactive hormone is responsible for the release of luteinizing hormone (LH) and follicle‐stimulating hormone (FSH) into the systemic circulation. Because an intermittent application of exogenous GnRH in young males increases the testosterone plasma level by stimulation of the Leydig cells, the potential misuse of the administered substance offers a reasonable relevancy for doping controls and is prohibited in accordance to the list of banned substances of the World Anti‐Doping Agency (WADA).

The presented method provides a mass spectrometric approach to determine the nondegraded hormone in regular doping control samples by utilizing a sample preparation procedure with solid phase extraction, immunoaffinity purification and a subsequent separation by liquid chromatography with ESI‐MS/MS detection. For liquid chromatography/mass spectrometry two alternative instrumental equipments were tested: the first consisted of an Agilent 1100 liquid chromatograph coupled to an Applied Biosystem Q Trap 4000 mass spectrometer, the second equipment was assembled by a Waters Aquity nano‐UPLC coupled to a Thermo LTQ Orbitrap high resolution/high accuracy mass spectrometer.

In urine specimens provided from healthy volunteers GnRH was not detected in accordance to the recent literature, but in postadministration samples urinary concentrations between 20 to 100 pg/ml of the intact peptide were determined. The method offered good validation results considering the parameter specificity, linearity (5–300 pg/ml), limit of detection (LOD, approx. 5 pg/ml), precision (inter/intraday, < 20%) and accuracy (105%) using Des‐pGlu1‐GnRH as internal standard to control each sample preparation step. Copyright © 2008 John Wiley & Sons, Ltd.
Spectroscopic studies of the corrosion of model iron electrodes in carbonate and phosphate buffer solutions
Authors: Larroumet Damien , Greenfield David , Akid Robert , Yarwood Jack
Published: June 2008

We have extended our unenhanced (non‐SERS) Raman spectroscopic investigations to include a study of the corrosion of an iron electrode in carbonate and phosphate buffer solutions. The measurements have been supported by electrochemical investigations (via cyclic voltammetry), enabling oxidation and reduction reactions to be systematically followed at variable applied potentials.

In a carbonate buffer (pH = 9.4) the surface oxidation led to the formation of a ‘green rust’ (a hydrated hydroxy‐carbonate), followed by the α‐ and β‐forms of FeOOH and an underlying magnetite layer formed on the cathodic (reduction) cycle.

In a phosphate buffer (pH = 7.7) the surface was passivated by hydrated phosphates of iron [identified as FePO4 · xH2O and Fe3(PO4)2·8H2O]. The formation of oxides (Fe2O3 and Fe3O4) were inferred from voltammetry, but spectral identification was more difficult because of broad, ill‐defined spectra.

Despite the challenges of using unenhanced Raman spectroscopy, we believe that the effort was worthwhile, the reactions identified being more likely to be relevant to real electrochemical environments. Copyright © 2008 John Wiley & Sons, Ltd.
Raman spectroscopic study of the tellurite mineral: poughite Fe23+SO4(TeO3)2·3H2O—a multi‐anion mineral
Authors: Frost Ray L. , Keeffe Eloise C.
Published: June 2008

Poughite Fe23+SO4(TeO3)2·3H2O, a multi‐anion mineral containing both tellurite and sulfate units has been studied by Raman spectroscopy. Raman bands at 655 cm−1 is attributed to (TeO3)2− stretching bands. The intense sharp Raman band at 1026 cm−1 is assigned to the ν1(SO4)2− symmetric stretching mode, while the bands at 1078, 1152 and 1187 cm−1 are assigned to the ν3(SO4)2− antisymmetric stretching mode. The spectral region 100 to 600 cm−1 displays the bands, which are attributable to the (SO4)2− and (TeO3)2− bending modes. Some evidence from very low intensity Raman bands in the 2800–3600 cm−1 region provides evidence of proton‐tellurite anion interactions. Hydrogen bond distances have been calculated. Copyright © 2008 John Wiley & Sons, Ltd.
Disorder‐induced symmetry lowering in Ba(Y1/2Nb1/2)O3 ceramics probed by Raman spectroscopy
Authors: Dias Anderson , Sá Rodrigo G. , Moreira Roberto L.
Published: June 2008

This work investigates the evolution of the crystal structure of microwave‐hydrothermal synthesized Ba(Y1/2Nb1/2)O3 powders as a function of firing temperature by Raman spectroscopy. The samples were produced at 200 °C and fired at temperatures ranging from 600 to 1600 °C. Raman spectra were obtained at room temperature for all samples and the results showed that materials fired at 1600 °C exhibited tetragonal (I4/m or $C_{4h}^{5}$) structure, whereas those fired at lower temperatures exhibited the triclinic (P1 or Ci1) structure. The results were compared with those observed for ceramics obtained by conventional solid‐state methods. It is believed that the lowering of the symmetry verified in materials fired below 1600 °C is a consequence of the local disorder of Y+3 and Nb+5 ions in octahedral sites. Copyright © 2008 John Wiley & Sons, Ltd.
Semicrystalline Lysine Functionalized Precision Polyolefins
Authors: Leonard James K. , Hopkins Timothy E. , Chaffin Kim , Wagener Kenneth B.
Published: June 2008

A family of semicrystalline polymers with the amino acid lysine regularly and atactically attached along a polyethylene backbone has been prepared via metathesis polymerization. The lysine branches are placed precisely on every 21st carbon of the polyethylene backbone giving these polymers a perfectly known architecture. Attachment of the amino acid is varied either by using a succinic acid spacer or directionally through its C‐ or N‐terminus. Changes in physical and spectral properties are discussed as a direct consequence of the nature of the amino acid connection and structure. The crystallinity of these polymers is studied by differential scanning calorimetry (DSC) and wide angle X‐ray scattering (WAXS), where it has become clear that the crystalline unit cell resembles that of the pure monomer. Long range order was absent as shown by small angle X‐ray scattering (SAXS). Complete deprotection of the amine branch of the lysine moiety of one polymer is discussed both in terms of procedure and its subsequent effect on the material's crystallinity.

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High Molecular Weight Poly(ε‐caprolactone) by Initiation with Triphenyl Bismuth
Authors: Kricheldorf Hans R. , Behnken Gesa , Schwarz Gert , Brockaert Josè A.
Published: June 2008

Ring‐opening polymerizations of ε‐caprolactone (εCL) were conducted in bulk at 120 °C with triphenyl bismuth, Ph3Bi, as an initiator or catalyst. Variation of the monomer–initiator ratio (M/I) allowed for a variation of the molecular weight, but not an accurate control. With an M/I ratio of 1 000:1 and ultra‐dry εCL, a number average molecular weight (corrected $\overline M _{\rm n}$) of 285 kDa was obtained corresponding to a degree of polymerization around 2 500. Addition of tetra(ethylene glycol) resulted in incorporation of this coinitiator and allowed for a better control of the molecular weight. Time–conversion curves revealed a long induction period followed by a conspicuous acceleration upon addition of a coinitiator (tetraethylene glycol). Model experiments demonstrated that Ph3Bi is unstable at 120 °C in the presence of water, oxygen, or alcohols and slowly a precipitate is formed which mainly consists of (PhBiO)x. Ph2BiOR groups formed by side reactions seem to be the true initiators.

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Contrast Inversion in TEM Studies of Poly(ferrocenylsilane)‐block‐Poly(dimethylsiloxane) Diblock Copolymers
Authors: Wang Yishan , Coombs Neil , Manners Ian , Winnik Mitchell A.
Published: June 2008

This paper describes an unusual contrast inversion phenomenon in TEM imaging of PFS‐b‐PDMS block copolymer bulk samples. It is clearly observed especially in samples that show a lamellar morphology that the contrast inversion is accompanied by a contraction of the PDMS domains and an expansion of the Fe‐rich domains. The location of the iron‐ and silicon‐rich domains was monitored by EDX analysis. We infer that the contrast inversion was caused by electron beam radiation‐induced damage to, and possible cross‐linking of, PDMS chains. A simple way to selectively deposit metal on electron beam patterned polymer film was demonstrated.

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Iron(III)‐Mediated ATRP of Methyl Methacrylate Using Activators Generated by Electron Transfer
Authors: Zhang Lifen , Cheng Zhenping , Tang Fan , Li Qiang , Zhu Xiulin
Published: June 2008

A novel procedure, atom‐transfer radical polymerization using activators generated by electron transfer (AGET ATRP) mediated by iron catalyst, was developed, using an oxidatively stable FeCl3/triphenylphosphine as a catalyst complex, ascorbic acid as a reducing agent, and methyl methacrylate as a monomer. The polymerization can be conducted successfully in the presence of a limited amount of air and shows the features of “living”/controlled free‐radical polymerizations such as number‐average molecular weights increasing linearly with monomer conversion and narrow molecular weight distributions. The living feature of the obtained polymer was further verified by a chain extension experiment.

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PBA–PMMA 3‐Arm Star Block Copolymer Thermoplastic Elastomers
Authors: Dufour Bruno , Koynov Kaloian , Pakula Tadeusz , Matyjaszewski Krzysztof
Published: June 2008

A series of well‐defined poly(methyl methacrylate)‐block‐poly(butyl acrylate) 3‐arm star block copolymers have been synthesized by ATRP. The incorporation of polar hard segment of PMMA was made possible with the aid of halogen exchange technique. Phase‐separated morphology of cylindrical PMMA domains hexagonally arranged in the pBA matrix was observed by small angle X‐ray scattering in all studied materials. The mechanical and thermal properties of the PBA–PMMA 3‐arm star block copolymers have been thoroughly characterized and their thermoplastic elastomer behavior was studied. It was found that the tensile properties of these materials are comparable with those of their linear ABA type block copolymer counterparts with similar compositions.

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Phase Transition Behavior and Molecular Orientation of Oligo(9,9′‐dioctylfluorene‐alt‐bithiophene)
Authors: Li Na , Zhang Xiaojie , Geng Yanhou , Su Zhaohui
Published: June 2008

A novel conjugated oligomer, oligo(9,9′‐dioctylfluorene‐alt‐bithiophene) (OF8T2), was found to exhibit a unique phase transition between crystalline and liquid‐crystalline states, and a liquid‐crystalline glass was easily generated, offering better TFT device performance. In thin films, upon annealing the OF8T2 molecules oriented preferentially with their planes of conjugation being normal to the substrate, and both film thickness and annealing temperature were critical to the film morphology and the molecular orientation. When the OF8T2 film was deposited on a rubbed polyimide surface and annealed, the molecules aligned their long axes along the rubbing direction.

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Macromol. Chem. Phys. 13/2008
Authors: Berti Corrado , Celli Annamaria , Marchese Paola , Marianucci Elisabetta , Barbiroli Giancarlo , Di Credico Francesco
Published: June 2008

Cover: The properties of poly(butylene 1,4‐cyclohexanedicarboxylate) can be easily modulated by controlling the cis/trans ratio of the cycloaliphatic unit, as can be seen in the cover picture. The crystalline phase perfection increases with an increasing trans percentage. The mechanical relaxations at low temperatures, which improve the impact properties, depend on the cis/trans ratio. Further details can be found in the article by C. Berti, A. Celli, P. Marchese,* E. Marianucci, G. Barbiroli, and F. Di Credico on page 1333.
Polymer Foams Stabilized by Particles Adsorbed at the Air/Polymer Interface
Authors: Thareja Prachi , Ising Brian P. , Kingston Samuel J. , Velankar Sachin S.
Published: June 2008

In aqueous systems, partially hydrophobic particles are known to stabilize foams even in the absence of any added surfactant. This paper shows that the same principle can be applied to polymeric systems: particles that are partially wetted by a polymer melt can stabilize a foam of that polymer. The foam stability is attributable to the adsorption of the particles at the air/polymer interface. Remarkably, stable foams are realized even from polymers that are liquid at room temperature, and hence are otherwise unfoamable. The implications of this result to practical foaming operations are discussed.

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General decay of energy for a viscoelastic equation with nonlinear damping
Authors: Han Xiaosen , Wang Mingxin
Published: June 2008

In this paper we are concerned with a nonlinear viscoelastic equation with nonlinear damping. The general uniform decay of the energy is obtained. Copyright © 2008 John Wiley & Sons, Ltd.
The modified FitzHugh–Nagumo system as an oscillator
Authors: Rabinovitch A. , Friedman M.
Published: June 2008

The use of the modified FitzHugh–Nagumo system is extended to the limit cycle regime. Ranges of parameters for which such oscillatory behavior prevails are calculated and properties of phase space and individual pulses are obtained. Copyright © 2008 John Wiley & Sons, Ltd.
Regularization of the non‐stationary Schrödinger operator
Authors: Cerejeiras Paula , Vieira Nelson
Published: June 2008

In this paper we prove a Lp‐decomposition where one of the components is the kernel of a first‐order differential operator that factorizes the non‐stationary Schrödinger operator −Δ−i∂t. Copyright © 2008 John Wiley & Sons, Ltd.
Global nonexistence of solutions with positive initial energy for a class of wave equations
Authors: Liu Wenjun , Wang Mingxin
Published: June 2008

In this study, we consider a class of wave equations with strong damping and source terms associated with initial and Dirichlet boundary conditions. We establish a blow up result for certain solutions with nonpositive initial energy as well as positive initial energy. This further improves the results by Yang (Math. Meth. Appl. Sci. 2002; 25:825–833) and Messaudi and Houari (Math. Meth. Appl. Sci. 2004; 27: 1687–1696). Copyright © 2008 John Wiley & Sons, Ltd.