bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of galactic model parameters with the Sloan Digital Sky Survey and the metallicity distribution in two fields in the anti‐centre direction of the Galaxy
Authors: Ak S. , Bilir S. , Karaali S. , Buser R.
Published: February 2007

We estimated the galactic model parameters from the Sloan Digital Sky Survey (SDSS) data reduced for two fields in the anti‐centre direction of the Galaxy, l = 180°, and symmetric relative to the galactic plane, b = +45° (north field) and b = –45° (south field). The large size of each field, 60 deg2, and the faint limiting apparent magnitude, g0 = 22, give us the chance to determine reliable parameters for three components, thin and thick discs and halo, in the north and south hemispheres of the Galaxy, except the scale lengths for two discs which are adopted from Jurić et al. (2005). Metallicities were evaluated by a recent calibration for SDSS, and absolute magnitudes of stars with 4 < M (g) ≤ 8 were derived as a function of (g – r)0 colour and metallicity. A χ2 method was employed to fit the analytical density laws to the observational‐based space densities with the addition constraint of producing local densities consistent with those derived from Hipparcos. Conspicuous differences could not be detected between the corresponding galactic model parameters for the thin disc of north and south fields, and our results are consistent with the ones in the literature. The same case is valid for the halo, especially the axis ratios for two fields are exactly equal, κ = 0.45, and close to the one of Jurić et al. (2005). However, we revealed differences between the scale heights and local space densities for the thick disc of the north and south fields. The metallicity distribution for unevolved G type stars with 5 < M (g) ≤ 6 shows three substructures relative to the distance from the galactic plane: for z * < 3 kpc, the metallicity gradient for two fields is d[M/H]/dz ∼ –0.20(±0.02) dex kpc–1, consistent with the formation scenario of the thin disc. For 5 < z * < 10 kpc, d[M/H]/dz ∼ –0.03(±0.001) dex kpc–1 for two fields, confirming that the metallicity gradient for the halo component is close to zero. However, the tendency of the metallicity for stars with 3 < z * < 5 kpc, corresponding to the transition region from thick disc to halo is different. For the north field d[M/H]/dz = –0.36(±0.12) dex kpc–1, whereas it is half of this value for the south field, d[M/H]/dz = –0.18(±0.01) dex kpc–1. The origin of this conflict is probably due to the different structure of the thick disc in opposite latitudes of the Galaxy. When we combine these substructures, however, we find a smooth metallicity gradient for two fields, –0.30(±0.04) dex kpc–1. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Holmberg effect of Luminous Red Galaxy (LRG) pairs of the SDSS Data Release 4 (SDSS4)
Authors: Deng X.‐F. , Zou S.‐Y. , He J.‐Z. , Jiang P. , He C.‐G. , Luo C.‐H.
Published: February 2007

We investigate the Holmberg effect of Luminous Red Galaxy (LRG) pairs of the SDSS Data Release 4 (SDSS4). It is found that the Holmberg effect of LRG pairs has no statistical significance. According to types of the two components in each pair, we divide the isolated LRG pair sample into three subsamples: the early+early subsample, the late+late subsample and the early+late subsample. Further analyses show that all LRG pair subsamples do not exhibit statistically significant Holmberg effect. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of calcium on microbial reduction of solid phase uranium(VI)
Authors: Liu Chongxuan , Jeon Byong‐Hun , Zachara John M. , Wang Zheming
Published: February 2007

The effect of calcium on the dissolution and microbial reduction of a representative solid phase uranyl [U(VI)], sodium boltwoodite (NaUO2SiO3OH · 1.5H2O), was investigated to evaluate the rate‐limiting step of microbial reduction of the solid phase U(VI). Microbial reduction experiments were performed in a culture of a dissimilatory metal‐reducing bacterium (DMRB), Shewanella oneidensis strain MR‐1, in a bicarbonate medium with lactate as electron donor at pH 6.8 buffered with PIPES. Calcium increased the rate of Na‐boltwoodite dissolution and U(VI) bioavailability by increasing its solubility through the formation of a ternary aqueous calcium‐uranyl‐carbonate species. The ternary species, however, decreased the rates of microbial reduction of aqueous U(VI). Laser‐induced fluorescence spectroscopy (LIFS) and transmission electron microscopy (TEM) collectively revealed that microbial reduction of solid phase U(VI) was a sequentially coupled process of Na‐boltwoodite dissolution, U(VI) aqueous speciation, and microbial reduction of dissolved U(VI) to U(IV) that accumulated on bacterial surfaces/periplasm. Under studied experimental conditions, the overall rate of microbial reduction of solid phase U(VI) was limited by U(VI) dissolution reactions in solutions without calcium and limited by microbial reduction in solutions with calcium. Generally, the overall rate of microbial reduction of solid phase U(VI) was determined by the coupling of solid phase U(VI) dissolution, U(VI) aqueous speciation, and microbial reduction of dissolved U(VI) that were all affected by calcium. Biotechnol. Bioneg. 2007;97: 1415–1422. © 2007 Wiley Periodicals, Inc.
Application of chromatographic theory for process characterization towards validation of an ion‐exchange operation
Authors: Kaltenbrunner O. , Giaverini O. , Woehle D. , Asenjo J.A.
Published: February 2007

The behavior of ion‐exchange chromatography is well understood with respect to changes in ionic strength, pH, resin ligand density, bed height, elution flow rate, and gradient slope. Their relative importance for any specific chromatographic situation varies. When a chromatographic operation utilized to purify a human therapeutic protein is prepared for validation before commercial production, numerous tests have to be performed to establish the relative importance of each operating parameter to define its future role and importance in the framework of in‐process controls. This prioritization process is usually performed using a purely empirical approach. In this work, we demonstrate the application of a rational approach based on chromatographic theory to prioritize operating parameters. Both methodologies, empirical and rational, were performed to evaluate a specific ion‐exchange chromatography operation for the preparative separation of closely related protein species. We show that the application of the rational approach has the potential to accelerate the evaluation and significantly reduce the amount of analytical testing needed. Biotechnol. Bioeng. 2007; 98: 201–210. © 2007 Wiley Periodicals, Inc.
The role of the surgeon in whether patients with lymph node‐positive colon cancer see a medical oncologist
Authors: Luo Ruili , Giordano Sharon H. , Zhang Dong D. , Freeman Jean , Goodwin James S.
Published: February 2007

BACKGROUND.

Chemotherapy improves survival for patients with stage III colon cancer, but some older patients with lymph node‐positive colon cancer do not see a medical oncologist and, thus, do not receive adjuvant chemotherapy.

METHODS.

To evaluate the role of the surgeon in determining referrals to medical oncology among patients with stage III colon cancer, the authors conducted a retrospective cohort study of 6158 patients aged ≥66 years who were diagnosed with stage III colon cancer from 1992 through 1999 by using the Surveillance, Epidemiology, and End Results‐Medicare linked database. Multilevel analysis was used to simultaneously model variations in patients' seeing a medical oncologist at the patient and surgeon levels.

RESULTS.

Twenty‐one percent of the total variance in seeing a medical oncologist was attributable to the surgeon after adjusting for available patient, tumor, and surgeon characteristics. The individual surgeon characteristics that significantly predicted whether the patient saw a medical oncologist were year since graduation (≤10 years vs >20 years; hazard ratio [HR], 1.60; 95% confidence interval [95% CI], 1.19–2.16), practicing in a teaching hospital (yes vs. no: HR; 1.30; 95% CI, 1.07–1.58), and volume of patients with colon cancer (<30 patients vs ≥121 patients; HR, 0.66; 95% CI, 0.46–0.94). Surgeon sex, race, board certification, and type of practice were not independent predictors of medical oncology referral.

CONCLUSIONS.

Surgeons accounted for approximately 20% of the variation in patients seeing a medical oncologist. Interventions at the level of the surgeon may be appropriate to improve the care of patients with colon cancer. Cancer 2007 © 2007 American Cancer Society.
Kinetic Isotope Effects in Complex Reaction Networks: Formic Acid Electro‐Oxidation
Authors: Chen Yan‐Xia , Heinen Martin , Jusys Zenonas , Behm Rolf Jürgen
Published: February 2007

The determination of kinetic isotope effects (KIEs) for different reaction pathways and steps in a complex reaction network, where KIEs may affect the overall reaction in various different ways including dominant and minority pathways or the buildup of a reaction‐inhibiting adlayer, is demonstrated for formic acid electro‐oxidation on a Pt film electrode by quantitative electrochemical in situ IR spectroscopic measurements under controlled mass‐transport conditions. The ability to separate effects resulting from different contributions—which is not possible using purely electrochemical kinetic measurements—allows conclusions on the nature of the rate‐limiting steps and their transition state in the individual reaction pathways. The potential‐independent values of ≈1.9 for the KIE of formic acid dehydration (COad formation) in the indirect pathway and ≈3 for the COad coverage‐normalized KIE of formic acid oxidation to CO2 (direct pathway) indicate that 1) CH bond breaking is rate‐limiting in both reaction steps, 2) the transition states for these reactions are different, and 3) the configurations of the transition states involve rather strong bonds to the transferred D/H species, either in the initial or in the final state, for the direct pathway and—even more pronounced—for formic acid dehydration (COad formation).
Synthesis of SrMnO3 powders with different morphologies by hydrothermal method
Authors: Zhu Jing‐Sen , Liu Jing‐Bing , Wang Hao , Zhu Man‐Kang , Yan Hui
Published: February 2007

By using two different reagents as the starting materials, SrMnO3 crystallines with two different morphologies rhombus‐like and rod‐like, have been directly synthesized by hydrothermal conditions. The effects of the hydrothermal parameters on the quality of the SrMnO3 samples were given for the fist time. And a preparative mechanism for the formation of different morphologies using different reagents during the hydrothermal reaction has been discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Properties of solution grown PbI2 layers embedded in PVA
Authors: Ponpon J. P. , Amann M.
Published: February 2007

Polycrystalline lead iodide layers with crystallites in the micrometer range have been prepared using a solution growth method from water and polyvinyl alcohol. Structural, electrical and optical measurements have been performed to characterize these layers and compare their properties to those of polycrystalline films prepared by solution growth in pure water. Most of these properties are very similar. The main difference comes from the photoresponse: that of films prepared with PVA remains high but presents an unusual behaviour with temperature. This has been related to the presence of a trapping/recombination energy level in the band gap. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Applications of Microplasmas and Microreactor Technology
Authors: Kogelschatz U.
Published: February 2007

During the last decade a number of microcavity plasma devices have been developed. Examples are microhollow cathode (MHC) discharges and cathode boundary layer (CBL) discharges proposed by Schoenbach, capillary plasma electrode (CPE) discharges proposed by Kunhardt and Becker, and micro‐structured electrode arrays (MSEs) introduced by Gericke and Penache. Arrays of microplasmas based on silicon, ceramic, or metal/polymer structures were investigated by Eden, Frame, Park and coworkers. A breakthrough in the life expectancy of such devices was achieved when all metal electrodes were covered by dielectrics, thus combining dielectric‐barrier discharge technology with microcavity plasma devices.

The advantage of this technology is that large numbers of miniature atmospheric‐pressure non‐equilibrium discharges can be operated in parallel. Applications include emitters for visible and UV radiation, photodetectors, sensors, decontamination, surface modification, etching, film deposition, generation of nanoparticles. Operated in different gas mixtures many of these devices proved to be efficient emitters of ultraviolet excimer radiation. If a small gas flow is fed through these microplasmas applications for plasmachemical synthesis and pollution control become feasible. Novel applications are expected from the combination of microreactor technology with non‐equilibrium plasma chemistry. Doping or coating of the dielectric surfaces results in additional catalytic effects. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recent Progress in Dielectric Barrier Discharges for Aerodynamic Flow Control
Authors: Font G. I. , Morgan W. L.
Published: February 2007

Plasma actuators are electrical devices that use an atmospheric pressure dielectric barrier discharge for flow control. They have been employed successfully to promote boundary layer attachment. Simulations have been carried out of a plasma actuator using Direct‐Simulation‐Monte‐Carlo and Particle‐in‐Cell methods. This work summarizes some recent results including: 1) the method by which force is imparted by the actuator to the neutral flow, 2) the effect of electronegative gasses, such as oxygen, and 3) the effects on the neutral flow of the plasma force. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
RF Capillary Jet ‐ a Tool for Localized Surface Treatment
Authors: Foest R. , Kindel E. , Lange H. , Ohl A. , Stieber M. , Weltmann K.‐D.
Published: February 2007

The UV/VUV spectrum of a non‐thermal capillary plasma jet operating with Ar at ambient atmosphere and the temperature load of a substrate exposed to the jet have been measured. The VUV radiation is assigned to N, H, and O atomic lines along with an Ar*2 excimer continuum. The absolute radiance (115‐200 nm) of the source has been determined. Maximum values of 880 μW/mm2sr are obtained. Substrate temperatures range between 35 °C for low powers and high gas flow conditions and 95 °C for high powers and reduced gas flow. The plasma source (13.56, 27.12 or 40.78 MHz) can be operated in Ar and in N2. The further addition of a low percentage of silicon containing reactive admixtures has been demonstrated for thin film deposition. Several further applications related to surface modification have been successfully applied. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Prestin–prestin and prestin–GLUT5 interactions in HEK293T cells
Authors: Wu Xudong , Currall Benjamin , Yamashita Tetsuji , Parker Lisan L. , Hallworth Richard , Zuo Jian
Published: February 2007

The remarkable hearing sensitivity and frequency selectivity in mammals is attributed to cochlear amplifier in the outer hair cells (OHCs). Prestin, a membrane protein in the lateral wall of OHC plasma membrane, is required for OHC electromotility and cochlear amplifier. In addition, GLUT5, a fructose transporter, is reported to be abundant in the plasma membrane of the OHC lateral wall and has been originally proposed as the OHC motor protein. Here we provide evidence of interactions between prestin/prestin and prestin/GLUT5 in transiently transfected HEK293T cells. We used a combination of techniques: (1) membrane colocalization by confocal microscopy, (2) fluorescence resonance energy transfer (FRET) by fluorescence activated cell sorting (FACS), (3) FRET by acceptor photobleaching, (4) FRET by fluorescence lifetime imaging (FRET–FLIM), and (5) coimmunoprecipitation. Our results suggest that homomeric and heteromeric prestin interactions occur in native OHCs to facilitate its electromotile function and that GLUT5 interacts with prestin for its elusive function. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007
Increased natural cytotoxicity receptor expression and relevant IL‐10 production in NK cells from chronically infected viremic HCV patients
Authors: De Maria Andrea , Fogli Manuela , Mazza Stefania , Basso Monica , Picciotto Antonio , Costa Paola , Congia Sonia , Mingari Maria Cristina , Moretta Lorenzo
Published: February 2007

Hepatitis C virus (HCV) readily establishes high‐level lifelong persistent infection in the majority of immunocompetent adults with failure of HCV‐specific CD8+ CTL to clear viral replication. Virus‐induced conditioning of innate immune responses is a possible mechanism that may contribute to the impairment of virus‐specific CD8+ CTL responses. Here, we analyzed whether triggering of NK cell receptor expression and function is affected during chronic viremic HCV infection. Flow cytometric analysis of purified resting peripheral NK cells showed no evidence of NK cell activation, while analysis of natural cytotoxicity receptors (NCR) showed that NK cells from HCV‐infected patients had selective increased expression of NKp30 and NKp46. NK cells had corresponding conserved cytotoxic activity against all targets with the exception of HepG2 hepatoma cells. Freshly separated NK cells from HCV patients showed significant production of IL‐10 and normal concentrations of IFN‐γ upon cell‐mediated triggering. Thus, increased expression of NKp30 during HCV infection with increased IL‐10 production could contribute, once NK cells localize in the liver, to a NK‐DC crosstalk leading to skewing of subsequent adaptive immune responses and lack of virus control.
Functional and biophysical characterization of an HLA‐A*6801‐restricted HIV‐specific T cell receptor
Authors: Gostick Emma , Cole David K. , Hutchinson Sarah L. , Wooldridge Linda , Tafuro Sabrina , Laugel Bruno , Lissina Anna , Oxenius Annette , Boulter Jonathan M. , Price David A. , Sewell Andrew K.
Published: February 2007

HLA‐A*6801 exhibits several unusual features. First, it is known to bind weakly to CD8 due to the presence of an A245V substitution in the α3 domain. Second, it is able to accommodate unusually long peptides as a result of peptide ‘kinking’ in the binding groove. Third, CD8+ cytotoxic T lymphocytes that recognise HLA‐A*6801‐restricted antigens can tolerate substantial changes in the peptide sequence without apparent loss of recognition. In addition, it has been suggested that HLA‐A68‐restricted TCR might bind with higher affinity than other TCR due to their selection in the presence of a decreased contribution from CD8. Here we (1) examine monoclonal T cell recognition of an HLA‐A*6801‐restricted HIV‐1 Tat‐derived 11‐amino acid peptide (ITKGLGISYGR) and natural variant sequences thereof; (2) measure the affinity and kinetics of a TCR/pHLA‐A68 interaction biophysically for the first time, showing that equilibrium binding occurs within the range previously determined for non‐HLA‐A68‐restricted TCR (KD approx. 7 μM); and (3) show that “normalization” of the non‐canonical HLA‐A*6801 CD8‐binding domain enhances recognition of agonist peptides without inducing non‐specific activation. This latter effect may provide a fundamental new mechanism with which to enhance T cell immunity to specific antigens.
Immunoregulatory role of Jα281 T cells in aged mice developing lupus‐like nephritis
Authors: Sireci Guido , Russo Domenica , Dieli Francesco , Porcelli Steven A. , Taniguchi Masaru , La Manna Marco Pio , Di Liberto Diana , Scarpa Francesco , Salerno Alfredo
Published: February 2007

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the emergence of autoreactive T cells. Humans and mice with SLE have reduced numbers of CD1d‐restricted invariant natural killer T (iNKT) cells, suggesting a key role for these cells in its immunopathogenesis. This subset uses an invariant TCR constituted by Vα14Jα281 chains paired with some Vβ domains. The regulatory role for iNKT cells in non‐autoimmune mice was suggested by our previous results showing that aged Jα281 knockout (KO) mice produce anti‐dsDNA. Here we show that old Jα281 KO mice have proteinuria and antibodies against dsDNA and cardiolipin. Histological analysis of Jα281 KO mice revealed glomeruli damage and deposition of C3c and IgG, mainly of the IgG3 subclass. In spleens of aged Jα281 KO mice there is an increase of activated marginal zone B cells. The evolution of lesions may depend on the age‐associated increase of autoantibodies production, preferentially IgG3, mainly secreted by marginal zone B cells. Our results provide the first evidence of a lupus‐like syndrome in non‐autoimmune mice, supporting an age‐related immunoregulatory role of Jα281+ cells, probably associated with the activation of marginal zone B cells.
Immunoregulatory and antimicrobial activities of myeloid cells
Authors: Bogdan Christian
Published: February 2007

180 scientists recently met at the 20th Annual meeting of the European Macrophage and Dendritic Cell Society to discuss the interaction between interferons, myeloid cells, TLR, killing mechanisms and microbial pathogens.
Acetylide Addition to Bridging Vinyliminium Ligands in Dinuclear Complexes
Authors: Busetto Luigi , Marchetti Fabio , Zacchini Stefano , Zanotti Valerio
Published: February 2007

The (vinyliminium)diiron complexes [Fe2{μ‐η1:η3‐Cγ(R′)=Cβ(R′)Cα=N(Me)(R)}(μ‐CO)(CO)(Cp)2][SO3CF3] [R = Xyl, R′ = Me (1a); R = Xyl, R′ = Et (1b); R = R′ = Me (1c); R = Me, R′ = Et (1d); R = CH2Ph, R′ = Me (1e); Xyl = 2,6‐Me2C6H3] undergo regio‐ and stereoselective addition by lithium acetylides. Addition of LiC≡CR″ (R″ = Tol, Ph, SiMe3; Tol = 4‐MeC6H4) to trans‐1a occurs at the Cβ atom of the vinyliminium ligand and results in the formation of the bis(alkylidene) complexes cis‐[Fe2{μ‐η1:η2‐C(Me)C(Me)(C≡CR″)CN(Me)(Xyl)}(μ‐CO)(CO)(Cp)2] [R″ = Tol (2a), Ph (2b), SiMe3 (2c)]. The molecular structure of 2a has been determined by X‐ray diffraction. Similarly, the diruthenium complex [Ru2{μ‐η1:η3‐C(Me)=C(Me)C=N(Me)(Xyl)}(μ‐CO)(CO)(Cp)2][SO3CF3] (3) reacts with LiC≡CTol to give the bis(alkylidene) compound[Ru2{μ‐η1:η2‐C(Me)C(Me)(C≡CTol)CN(Me)(Xyl)}(μ‐CO)(CO)(Cp)2] (4). Conversely, 1c and 1d undergo acetylide attack at the Cα atom of the vinyliminium ligand to yield the allylidenecomplexes [Fe2{μ‐η1:η3‐C(R′)C(R′)C(C≡CR″)N(Me)2}(μ‐CO)(CO)(Cp)2] [R′ = Me, R″ = Tol (5a); R′ = Me, R″ = Ph (5b); R′ = Me, R″ = SiMe3 (5c); R′ = Me, R″ = nBu (5d); R′ = Me, R″ = C(Me)=CH2 (5e); R′ = Me, R″ = H (5f); R′ = Et, R″ = Tol (5g); R′ = Et, R″ = Ph (5h); R′ = Et, R″ = SiMe3 (5i); R′ = Et, R″ = C(Me)=CH2 (5j)]. Analogously, the reaction of 1e with LiC≡CPh affords [Fe2{μ‐η1:η3‐C(Me)C(Me)C(C≡CPh)N(Me)(CH2Ph)}(μ‐CO)(CO)(Cp)2] (6). The molecular structure of 5h has been determined by X‐ray diffraction. Finally, 1b, in both its cis and trans forms, undergoes acetylide attack at the Cα atom of the vinyliminium ligand to give the complexes[Fe2{μ‐η1:η3‐C(Et)C(Et)C(C≡CR″)N(Me)(Xyl)}(μ‐CO)(CO)(Cp)2] [R″ = SiMe3 (7a), H (7b)]. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Metal Complexes Incorporating Monoanionic Bisoxazolinate Ligands: Synthesis, Structures, Reactivity and Applications in Asymmetric Catalysis
Authors: Dagorne Samuel , Bellemin‐Laponnaz Stéphane , Maisse‐François Aline
Published: February 2007

The present contribution reviews the synthesis, structures, reactivity and applications in asymmetric catalysis of metal complexes containing monoanionic bisoxazolinate ligands. The anionic and bidentate bisoxazolinate ligand, which may be seen as a nitrogenated version of the acetylacetonate unit and may also be closely related to the diketiminate bidentate ligand, appears to exhibit a rich and versatile coordination chemistry with various metal centers. These excellent coordination properties, combined with the ready accessibility of chiral bisoxazolinate ligands in an enantiomerically pure form, has opened the way to various applications in asymmetric catalysis involving this class of bidentate ligands. Thus, the use of chiral bisoxazolinate ligands in asymmetric catalysis constitutes a central part of this review. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
RuCl2(dmso)4 Catalyzes the Solvent‐Free Indirect Friedländer Synthesis of Polysubstituted Quinolines from Alcohols
Authors: Martínez Ricardo , Ramón Diego J. , Yus Miguel
Published: February 2007

The first synthesis of polysubstituted quinoline derivatives from aromatic or aliphatic alcohols with RuCl2(dmso)4 as catalyst under solvent‐free conditions is described. The reaction involves the in situ oxidation of alcohols to the corresponding carbonyl compounds through a hydrogen‐transfer, followed by a Friedländer annulation process. The whole process is a mild, efficient, selective, and high‐yielding single‐step procedure. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Preparation and Electrochemical Study of Modified Carbon Ceramic Electrode with 5‐(4‐Dimethyl amino benzelyden)‐rhodanin for the Determination of Silver
Authors: Majidi M. R. , Asadpour‐Zeynali K. , Hosseini S.‐A.
Published: February 2007

The carbon ceramic technique is a new, simple and reliable way for the preparation of modified electrodes. The carbon ceramic conduct in the presence of graphite powder was recently proposed as a versatile way to obtain tailored electrode materials. In the present study, 5‐(4‐dimethyl amino benzelyden)‐rhodanin (RNSH) was used as a reagent in the preparation of modified carbon ceramic electrode. This electrode was used in the determination of trace amounts of silver by differential pulse anodic stripping voltammetry (DPASV) technique. The best results were obtained under the following optimized conditions: 10 min accumulation, +0.8 V potential accumulation, 50 mV pulse amplitude, 50 mV s−1 scan rate. Applying in the DPASV method at 0.1 M McIlvaine buffer with pH 5.0, linearity was achieved from 10−13 to 10−7 M with limit of detection 4.5×10−14 M. The proposed method was applied to determination of silver in human hair.
Development and Application of Oxysilane Sol–Gel Electrochemical Glucose Biosensors Based on Cobalt Hexacyanoferrate Modified Carbon Film Electrodes
Authors: Florescu Monica , Barsan Madalina , Pauliukaite Rasa , Brett Christopher M. A.
Published: February 2007

The evaluation and characterization of a new glucose oxidase (GOx) electrochemical enzyme biosensors on a carbon film electrode support and using two types of sol–gel precursor mixture for enzyme immobilization was carried out in order to be employed as a short‐time‐use or as a disposable sensor. Carbon film electrodes were modified with films of CoHCF mediator by potential cycling. The sol–gel was prepared using a combination of 3‐glycidoxypropyltrimethoxysilane (GOPMOS) with methyltrimethoxysilane (MTMOS) or tetraethoxysilane (TEOS).
Semicontinuous Monitoring of Cadmium and Lead with a Screen‐Printed Sensor Modified by a Membrane
Authors: Betelu Stéphanie , Parat Corinne , Petrucciani Nathalie , Castetbon Alain , Authier Laurent , Potin‐Gautier Martine
Published: February 2007

The analytical performances of the developed sensor were evaluated in laboratory for the semicontinuous monitoring of Cd and Pb in water samples at μg L−1 level. The effects of oxygen, pH, and stirring on the voltammetric response of these metals were investigated. The O2 removal did not allow to improve the peak current. In return, stirring appeared indispensable to avoid the impoverishment of metals in the diffusion layer. The necessity to control the pH and the solution evolution in laboratory experiments was also clearly established. The semicontinuous monitoring of Cd and Pb was then performed for 42 h in tap water and demonstrated that sensor is a promised tool for semicontinuous environmental analyses.
Photoelectrocatalytic Oxidation of NADH with Electropolymerized Toluidine Blue O
Authors: Dilgin Yusuf , Gorton Lo , Nisli Gurel
Published: February 2007

A poly(Toluidine Blue O) (poly‐TBO) modified electrode was successfully prepared by repeated sweeping the applied potential from −0.6 to +0.8 V (vs. SCE) on a glassy carbon electrode (GCE) in borate buffer solution at pH 9.1 containing 0.1 M NaNO3 and 0.4 mM Toluidine Blue O (TBO). The poly‐TBO modified GCE shows electrocatalytic activity toward NADH oxidation in phosphate buffer solution at pH 7.0, with an overpotential of ca. 350 mV lower than that at the bare electrode. The photoelectrocatalytic oxidation of NADH at this electrode was also successfully investigated by using cyclic voltammetry and amperometry at constant potential. When the modified electrode surface was irradiated with a 250 W halogen lamp, a photoelectrocatalytic effect was observed for NADH oxidation and the current was increased about 2.2 times. The applied potential was selected at +100 mV for amperometric and photoamperometric detection of NADH. A linear calibration graph for NADH was obtained in the range between 1.0×10−5 and 1.0×10−3 M and between 5.0×10−6 and 1.0×10−3 M for amperometric and photoamperometric studies, respectively. The effect of some interfering compounds, such as ascorbic acid and dopamine on the electrocatalytic and photoelectrocatalytic oxidation of NADH was tested.
Voltammetric Determination of Metamitron with an Electrogenerated Molecularly Imprinted Polymer Microsensor
Authors: Gómez‐Caballero Alberto , Unceta Nora , Goicolea M. Aranzazu , Barrio Ramón J.
Published: February 2007

A molecularly imprinted polymer microsensor was synthesized onto the surface of a carbon fiber microelectrode (CFME) by cyclic voltammetry between −0.1 V and +1.35 V at a scan rate of 50 mV s−1. The monomers aniline and o‐phenylenediamine (o‐PD) were electrocopolymerized in the presence of the template (metamitron) in an aqueous medium of 0.1 M H2SO4. In order to obtain a sensor with the highest number of imprinted sites as possible, different experiments related to the polymerization process were carried out. The response of the synthesized microsensor was linear to the metamitron in the range between 10−6 and 10−4 with sensitivity of 0.143 nA μM−1 with good repeatability (<9% RSD). Employing these experimental conditions, the microsensor was able to distinguish the metamitron from other closely related triazines like metribuzin or isomethiozin.
Resolution of Overlapped Reduction Signals in Short Hetero‐oligonucleotides by Elimination Voltammetry
Authors: Mikelova Radka , Trnkova Libuse , Jelen Frantisek , Adam Vojtech , Kizek Rene
Published: February 2007

The resolution of overlapped reduction voltammetric signals of adenine (A) and cytosine (C) residues in short synthetic hetero‐oligodeoxynucleotides (ODNs) with different sequences of A and C, but with the same ratio (A/C=1/2), was carried out by elimination voltammetry with linear scan (EVLS). The EVLS, as a mathematical transformation of voltammetric total currents measured at different scan rates, is capable to yield very sensitive resolution of potentially closed signals, which cannot be separated by common electrochemical methods. The best resolution of A and C signals was observed when the EVLS function eliminating the charging and kinetic currents (Ic, Ik) and conserving the diffusion current (Id) was combined with adsorption stripping technique (AdS). The resulting peak‐counterpeak signal made it possible not only to separate the responses of A and C residues, but also to follow the dynamics of adsorption processes on mercury electrode surfaces. Together with the effect of the accumulation time on peak‐counterpeak signal, the effect of pH and temperature on this signal was studied. The relation between elimination signals and the structure changes of ODNs was discussed.
Amperometric Biosensors Based on Choline Oxidase Entrapped in Polyacrylamide Microgels
Authors: Sánchez‐Paniagua López M. , Hervás Pérez J. P. , López‐Cabarcos E. , López‐Ruiz B.
Published: February 2007

A choline amperometric biosensor has been designed using as biological component choline oxidase (ChOx) entrapped in polyacrylamide microgels. The working electrode was prepared by holding the enzyme loaded microgels on a platinum electrode by a dialysis membrane. It was found that the optimum microgel cross‐linking required to retain ChOx and to allow the diffusion of choline was 7.0%. The response of the biosensor was optimized in relation to pH, temperature and working potential and the following optimal values were obtained: pH 9.0, temperature range between 20 and 30 °C, and potential +0.6 V. Under optimal conditions the sensitivity for choline was 17.45 mA M−1 cm−2, the detection limit 8 μM, and the response linear range from 2×10−5 M to 2×10−4 M. This biosensor has been also used as a nicotine detector due to the inhibition of the catalytic activity of choline oxidase by this compound. Moreover, the simultaneous entrapment of a second enzyme, acetylcholinesterase (AChE), in the microgels makes the biosensor sensible to acetylcholine.
Open tubular CE for in vitro oxidation studies of human very‐low‐density lipoprotein particles
Authors: Ruiz‐Jiménez José , Kuldvee Ruth , Chen Jie , Öörni Katariina , Kovanen Petri , Riekkola Marja‐Liisa
Published: February 2007

Human very‐low‐density lipoprotein (VLDL) particles were immobilised on the inner wall of electrochromatographic fused‐silica capillaries, and the applicability of these capillary columns in oxidation studies was investigated. Capillaries coated with radiolabelled VLDL particles showed a coating efficiency of 97%, and allowed estimation of the amount of VLDL present in a capillary. Radioactivity measurements and atomic force microscopy with tapping mode confirmed the presence of VLDL particles as a monolayer. The pI determined for the VLDL was 4.7–4.8 varying with the human source. The effects of VLDL concentration, coating time and pH on the coating stability were clarified, and the stability was examined in terms of the repeatability of EOF and retention factors of selected steroids. The repeatability of run‐to‐run and the coating‐to‐coating reproducibility ranged from 2.6 to 4.9% and 3.2 to 6.6%, respectively. The lifetime of a coating was at least 7 days or 84 consecutive runs. The in situ copper‐mediated VLDL oxidation carried out in the capillary with optimised VLDL coating showed that, during the oxidation of VLDL particles, the negative charges of the particles are increased, leading to enhanced EOF mobilities. Several oxidation parameters, including copper sulfate concentration, amount of EDTA needed to stop the reaction, pH and the oxidation procedure, were examined. Effect of the oxidation process on the stability of the coating in one capillary, and in five different capillaries ranged between 0.4–4.1% and 0.8–6.6%, respectively. The in situ oxidation of VLDL particles was compared with that of low‐density lipoproteins.
Problems in the determination of plastic and liquid limits of remoulded soils using a drop‐cone penetrometer
Authors: Davidson Donald A.
Published: February 2007

This short communication describes difficulties of sample preparation associated with the determination of plastic and liquid limits using a drop‐cone penetrometer. Problems of sample packing, soil moisture distribution and degree of remoulding are identified. These problems are particularly relevant in influencing liquid limit values whilst the effects on plastic limits are less marked. It is concluded that if the need is for the quick determination of liquid and plastic limits for general classification purposes, then the traditional Casagrande and thread methods are adequate. If these limits require to be measured with greater precision using the drop‐cone technique, then careful consideration must be given to sample preparation.
The measurement of watertable levels in structured clay soils by means of open auger holes
Authors: Armstrong Adrian C.
Published: February 2007

In structured clay soils, water levels in open auger holes (dipwells) respond to water movement through macropores and may mask the existence of drier zones either at depth or within peds. Variability between replicated dipwells expresses the small scale variation in the soil, and statements about soil water regimes should be made in statistical terms. Suitably replicated dipwells give sufficiently precise measurements of mean watertable position for studies of soil water regimes.
Vertical soil water movement in a tropical rainforest catchment in northeast queensland
Authors: Bonell M. , Cassells D. S. , Gilmour D. A.
Published: February 2007

In a tropical rainforest catchment, shallow piezometers respond almost instantaneously to rainfall, but the dominant ground water recharge mechanisms are not well understood. To improve understanding, the downward movement of soil water on a runoff plot was traced using tritiated water injected at 0·20 m below the surface which marks the lower boundary of active subsurface storm flow. The tritium pulse was translated slowly down the profile, apparently dominated by interstitial piston flow on the lines described by Zimmermann's theoretical model. This recharge mechanism accounted for about 35 per cent of rainfall or 50 per cent of throughfall. The pulse's advance may have also been delayed by the upward movement of soil water indicated by the distribution of hydraulic potential under different hydrological conditions. The result was an increase in soil water transit time particularly below 1·0 m. There was also evidence in the tracer profiles for rapid by‐pass flow but the volumes concerned could not be quantified in this experiment.
Flandrian relative sea level changes in the Ythan Valley, Northeast Scotland
Authors: Smith D. E. , Cullingford R. A. , Brooks C. L.
Published: February 2007

Relict Flandrian estuarine deposits in the Ythan valley are confined to an area in the lower valley around the present estuary. They rest upon a discontinuous layer of peat over an irregular surface of sand and gravel, and consist for the most part of a grey silty clay, or carse deposit, which forms terraces or small areas of carseland. At the seaward end of the estuary the grey silty clay contains a layer of grey, micaceous, silty fine sand, which tapers into the basal peat, whilst in places the surface of the grey silty clay is covered by peat and/or blown sand. The vegetational context and age of these deposits have been determined at Waterside, near the mouth of the present estuary. Here, the grey silty clay accumulated as the result of a marine transgression which began in the early Flandrian, and culminated between about 6189·95 and some time prior to 4000·80 radiocarbon years B.P. The carseland surface produced by this phase of accumulation is the highest Flandrian estuarine surface in the valley, at about 4·5 m O.D., and is correlated with the Main Postglacial Shoreline elsewhere in eastern Scotland. Withdrawal of the sea from this level may have been interrupted by the formation of a lower carseland surface before present levels were reached, though this is far from certain. The grey, micaceous, silty fine sand layer is dated at approximately 6850·140 radiocarbon years B.P., and is correlated with similar layers that may have been deposited following a storm surge. The paper concludes with some considerations on the age and distribution of the Main Postglacial Shoreline in eastern Scotland.
Rates of cave and landform development in the Yorkshire Dales from speleothem age data
Authors: Gascoyne Melvyn , Ford Derek C. , Schwarcz Henry P.
Published: February 2007

Uranium‐series ages have been obtained for 87 speleothems collected from nine major cave systems in the Craven district of northern England. Large systems such as Ease Gill Caverns, the West Kingsdale caves, and Gaping Gill‐Ingleborough Cave, which contain relict high‐level tunnels, are found to be older than 350,000 years (the limit of the 230Th/234U dating method). There is little evidence to indicate a significant enlargement of these passages since this time. Estimates of the age of Victoria Cave from 234U/238U isotopic ratios suggest that the cave has been fully relict for more than 500,000 years. Ages of in situ speleothems immediately adjacent to local base level cave streams show that mean maximum downcutting rates in limestone channels are about 2 to 5 cm 1000 yr. These rates are significantly lower than those obtained from direct measurements on limestone bedrock in stream channels but are comparable to areal denudation rates based on solute budgets. Using the present elevation of caves with respect to adjacent valley floor levels, mean maximum valley entrenchment rates are found to range between 5 cm/ky and < 20cm/ky, which corresponds to 6 m to < 24 m of lowering per glacial/interglacial cycle. These rates suggest that upper beds of the limestone were incised to form the Yorkshire Dales between 1 and 2 million years ago.

The results indicate that the erosional effects of individual glaciations are not as severe as previously proposed in the literature.
The formation of deep topsoils in Orkney
Authors: Davidson Donald A. , Simpson Ian A.
Published: February 2007

The Soil Survey for Scotland, in their mapping of the soils in Orkney, identified a deep top phase of the Bilbster Series. This soil is distinguished by having a topsoil usually in excess of 75 cm and it occurs almost exclusively on the Mainland of Orkney, especially in the west round Marwick and Skaill Bays. An anthropogenic origin to this soil is proposed and the present study is designed to investigate the particular processes of formation which have led to the increase in soil depth. Results from transect and grid surveys indicate how the soil is thickest adjacent to old farms. The historical literature suggests a wide range of possible inputs from seaweed and calcareous sand to turves after they had been used as bedding for cattle. Analytical results support the last process as the dominant one and an accumulation rate of c.1 mm/yr is proposed.
Refinement of a technique for determining rock mass strength for geomorphological purposes
Authors: Moon B. P.
Published: February 2007

Use of a field technique recently devised by Selby for the measurement of rock mass strength has resulted in the understanding of the relationship between rock mass strength and slope form. It is suggested that the accuracy of rock mass strength assessments may be enhanced by further subdividing the rating scales for intact rock strength and the spacing of partings. The relationship between rock mass strength and gradient is reformulated using southern African data, and statistically based confidence limits for identifying strength equilibrium slopes are proposed.
Gas‐induced erosion features in the North Sea
Authors: Hovland Martin
Published: February 2007

Pockmarks are prominent features on the seafloor at two main regions of the North Sea, the South Fladen area and the Norwegian Trench.

The pockmarks vary in size from 5 m across to about 150 m and in depth from 1 m to about 20 m. Some of the features consist of several very small ‘unit‐pockmarks’. These are probably gas‐induced erosion features and found only in soft, finegrained, marine and glaciomarine sediments. They are probably caused by shallow‐ or deep‐seated gas (or fluid) release through the seabed, whereby the finest particles are thrown into suspension and redistributed by nearbottom currents.

On the North Sea Plateau a small pockmarked area has recently been found. A close relationship exists here between mobile gas in the upper sediments, faulting in the soft sediments and the morphology of the seabed.

Other morphological features in the North Sea such as ‘coast parallel depressions’ and ‘elongated depressions’ or terraces are also interpreted here as gas‐induced erosion products. This applies, yet again, to the ‘mottled seabed’ features, which appear as patches of high reflectivity on side scan sonar records from the North Sea Plateau; they correspond to shallow seabed depressions on the deep towed boomer records. Judging from reported observations from several shallow seas world wide volatile transport through the seabed is probably quite common and several morphological features are undoubtably induced by this process. Several erosion features of similar origin are probably common, also, in deep ocean basins.
A test of petrological control in the development of bornhardts and koppies on the Matopos Batholith, Zimbabwe
Authors: Pye K. , Goudie A. S. , Thomas D. S. G.
Published: February 2007

This paper investigates the reasons for the presence of both domed inselbergs (bornhardts) and boulder inselbergs (koppies) on the Matopos Batholith, Zimbabwe. XRF and microprobe analyses of rock samples from 16 bornhardts and 24 koppies have shown no significant chemical or mineralogical differences which might indicate greater weathering resistance of the bornhardts. Many bornhardts are located on massive bodies of slowly‐cooled porphyritic granite which were emplaced at a relatively late stage in the evolution of the batholith. The surrounding rocks are less porphyritic and appear to have been foliated during deformation associated with emplacement of the later bodies. The entire batholith has been affected by post‐emplacement tectonism which has created three major fracture systems. The morphological differences between bornhardts and koppies in this area are therefore considered to reflect differences in jointing which arise both from the primary igneous emplacement process and from tectonic deformation.
Abrupt variation in channel width along part of the River Severn, near Shrewsbury, Shropshire, England
Authors: Dury G. H.
Published: February 2007

The River Severn, near Shrewsbury, Shropshire, England, is formed by the union of the uppermost Severn with the Vyrnwy; both of these major headstreams drain from the Welsh upland. That part of the trunk Severn here under consideration has been under investigation for some years as exemplifying Osage‐type underfitness. In the course of the investigation, a census was made of width between banktops on two reaches, and of water surface width on one of these reaches: the difference between the two types of width gives the value of a third type, the width of batter. All three width types produce Poisson distributions of frequency. Width, particularly width between banktops, varies rapidly in the downstream direction. In view of the observed Poisson distributions, transform rather than arithmetic values have been used in difference‐of‐means tests applied to variation along the channel: cube root transforms are the type selected. Although there is little to choose, on the study reaches, between arithmetic means and Poisson modes, the results obtained do suggest a query about the selection of the most appropriate width values, for instance for the purposes of channel morphology. All types of width are found to vary along the channel far more rapidly than would be expected from mere randomness. Variation in bank strength appears to account for about half the variation in width between banktops. The results obtained for batter width could be applied in the design of a sampling programme designed to identify local difference in bank strength.