bluuebunny/crossref_metadata_2025 huggingface dataset:
Engrailed‐2 negatively regulates the onset of perinatal Purkinje cell differentiation
Authors: Jankowski Jakob , Holst Martin I. , Liebig Christian , Oberdick John , Baader Stephan L.
Published: March 2004

The transcription factor Engrailed‐2 is expressed in cerebellar Purkinje cells (PCs) throughout embryonic development but is downregulated in PCs after birth. Since the onset of PC differentiation coincides with this change of gene expression, we asked whether downregulation of Engrailed‐2 is necessary for proper timing of PC differentiation. To investigate this, we used an L7En‐2 transgenic mouse model in which Engrailed‐2 expression in PCs is maintained beyond the day of birth. In these L7En‐2 mice the onset of parvalbumin expression was delayed in all PCs by about 3 days; the spatial expression pattern, however, remained comparable to wildtype cerebella. Furthermore, parvalbumin expression resembled the known pattern of normal PC maturation, suggesting a direct link between parvalbumin expression and PC differentiation. Consistent with a delay of PC differentiation, we found that PCs of L7En‐2 cerebella displayed a reduced tendency to align in the typical monolayer. The average size of L7En‐2 PCs was reduced and the dendritic arbor developed more slowly than in wildtype PCs. In contrast, major morphological features of PCs were comparable in L7En‐2 and wildtype cerebella after postnatal day 11. In addition, we observed a transient reduction of PC survival in organotypic slice cultures of L7En‐2 cerebella in comparison with wildtype slice cultures. Since PC survival parallels PC differentiation in vitro, we propose that the observed delay in PC differentiation upon Engrailed‐2 overexpression is an intrinsic property of Engrailed‐2 activity, and that downregulation of Engrailed‐2 in wildtype PCs around the day of birth is critical for the timing of distinct steps of PC differentiation. J. Comp. Neurol. 472:87–99, 2004. © 2004 Wiley‐Liss, Inc.
The postnatal developmental expression pattern of urocortin in the rat olivocerebellar system
Authors: Swinny Jerome D. , Kalicharan Dharamdajal , Brouwer Nieske , Biber Knut , Shi Fuxin , Gramsbergen Albert , van der Want Johannes J.L.
Published: March 2004

Urocortin belongs to the family of corticotropin‐releasing factor (CRF)‐like peptides, which play an important role in sensorimotor coordination. CRF induces locomotor activity, and urocortin has an inhibitory effect. Here, we document the regional and subcellular localization of urocortin in the developing rat cerebellum to compare it with CRF. During the first postnatal week, urocortin immunoreactivity (UCN‐ir), within the white matter and cerebellar cortex, was strongest in vermal lobules I, II, IX, and X, closely followed by lobules IV, V, and VIII; lobules VI and VII showed the weakest labeling. Cortical immunoreactivity was in the form of puncta that encircled Purkinje cell somata. By postnatal day (PD) 12, UCN‐ir had increased appreciably in all lobules. In Purkinje cells, labeling was spread throughout their somata and proximal dendrites. By PD 15, labeling in lobules I–IV appeared to wane, yet still prevailed in the central and posterior lobules. This anterior‐to‐posterior gradient persisted through to adulthood. The study shows that urocortin and CRF have similar regional distribution profiles during development, suggesting synergistic roles within the vestibulocerebellum. The onset of the adult distributional pattern of urocortin at the stage when rats are capable of fluent walking patterns further strengthens the correlation between CRF‐like peptides and postural control. An important difference between urocortin and CRF is the localization of urocortin, and not CRF, within Purkinje cells, implying that urocortin probably has an additional role in modulating the signals emanating from the cerebellar cortex to the deep cerebellar nuclei. J. Comp. Neurol. 472:40–51, 2004. © 2004 Wiley‐Liss, Inc.
Abnormal c‐fos‐like immunoreactivity in the superior colliculus and other subcortical visual centers of pigmented royal college of surgeons rats
Authors: Lu Bin , Coffey Peter , Wang Shaomei , Ferrari Renata , Lund Raymond
Published: March 2004

Neurons in the central nervous system often show a transient up‐regulation of expression of the immediate early gene c‐fos when presented with precise novel stimuli. In normal rats, neurons in most subcortical visual centers show low levels of fos‐like immunoreactivity (FLI) expression, but there is a substantial and transient increase in FLI expression if the animal is exposed to a flashing light. This is especially evident in the superior colliculus (SC). We have examined here FLI expression in the subcortical visual centers of the Royal College of Surgeons rat, focusing specifically on the SC. In this animal, as a result of a genetic defect, there is early loss of rod photoreceptors over the first few months of life, along with slower disappearance of cones. Although light stimulation showed that FLI expression was very similar to that seen in normal rats, the basal levels of FLI expression under dark‐maintained conditions were much higher than normal, even exceeding the levels seen after visual stimulation. In the SC, the elevation of FLI expression was already evident by 6 weeks of age and reached a plateau by 17 weeks. Other subcortical visual centers also showed elevated basal levels of FLI expression, although in general the increases were less dramatic than the increase in the SC. The elevated FLI expression in dark‐maintained condition seen in the SC was abolished by contralateral optic nerve section. It was also severely diminished by subretinal cell transplantation at 3 weeks of age with the objective of limiting photoreceptor loss over part of the retina. These results suggest that the elevated basal FLI expression is a retina‐driven event. Although it correlates with the loss of rod photoreceptors, it is unlikely to reflect reduced photoreceptor drive but rather some form of bursting activity generated in the inner retina, as a result of circuit reorganization or receptor up‐regulation. J. Comp. Neurol. 472:100–112, 2004. © 2004 Wiley‐Liss, Inc.
Infrared Cavity Ringdown Spectroscopy of Jet‐Cooled Polycyclic Aromatic Hydrocarbons
Authors: Huneycutt Alex J. , Casaes Raphael N. , McCall Benjamin J. , Chung Chao‐Yu , Lee Yuan‐Pern , Saykally Richard J.
Published: March 2004

Infrared absorption spectra of the CH stretching region were observed for naphthalene, anthracene, phenanthrene, pyrene, and perylene using a heated, supersonic, slit‐jet source and cavity ringdown spectroscopy. Band positions and intensities recorded with 0.2‐cm−1 resolution were compared with previous gas‐phase and argon matrix isolation experiments, as well as theoretical calculations. The largest matrix shift in the absorption maximum (‐7.4 cm−1) was observed for anthracene, with all others shifted by 3.0 cm−1 or less. Spectral features in the supersonic jet spectrum were generally narrower than those observed in the Ar matrix, with the largest matrix broadening found for the perylene (80 % increase). Low number densities observed for the larger polycyclic aromatic hydrocarbons (PAHs) suggest that the lower vapor pressure of PAHs with catacondensed four‐membered rings and with five‐membered rings other than perylene will not be detectable using our current configuration.
Supported Membranes with Well‐Defined Polymer Tethers—Incorporation of Cell Receptors
Authors: Purrucker Oliver , Förtig Anton , Jordan Rainer , Tanaka Motomu
Published: March 2004

We report the design of supported lipid membranes attached to the surface by tailored lipopolymer tethers. A series of well‐defined lipopolymers were synthesized by means of living cationic polymerization of 2‐methyl‐2‐oxazolines. The polymers were equipped with a silane coupling group on the proximal, and lipid anchors on the distal chain ends. The length of the intermediate hydrophilic polymer tether was varied (n=14, 18, 33) to change the distance between the membrane and the substrate. Supported membranes have been prepared in two‐steps. First, a suitable lipopolymer/lipid mixture was deposited by Langmuir–Blodgett transfer, and annealed to establish the covalent coupling to the surface. On the dry lipopolymer/lipid monolayer, the upper leaflet was deposited by vesicle fusion. Optimization of both preparation steps resulted in the formation of stable and defect‐free membranes. Impacts of the spacer length and the lipopolymer fraction upon the lateral diffusivity of the lipids were systematically compared by fluorescence recovery after photobleaching (FRAP). First experiments on the incorporation of a large transmembrane cell receptor (integrin αIIbβ3) into the polymer‐tethered membrane suggested that the length of the polymer tether plays a crucial role in distribution of the proteins on the surface.
Formation of Light‐Emitting Ag2 and Ag3 Species in the Course of Condensation of Ag Atoms with Ar
Authors: Schulze Wilfried , Rabin Irene , Ertl Gerhard
Published: March 2004

Fluorescent clusters: The agglomeration of Ag clusters resulting from the codeposition of Ag and Ar atoms onto a cold substrate is accompanied by light emission from deexcitation of intermediately formed electronically excited Ag2* and Ag3* species. The yield of chemiluminescence was investigated as a function of the deposition rates of Ag and Ar. The relative concentrations of Ag, Ag2, Ag3, and Ag8 species were monitored by means of their fluorescence spectra, and it is concluded that the light‐emitting species are created by aggregation of Agn clusters with n>8.
Tunnelling Motion of HF Between the Two Oxygen Lone Pairs in the Dimethyl Ether–Hydrogen Fluoride Complex: A Pure Rotational Study
Authors: Ottaviani Paolo , Caminati Walther , Velino Biagio , Blanco Susana , Lesarri Alberto , López Juan C. , Alonso José L.
Published: March 2004

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

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

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

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

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

The photochemical and photophysical behavior of two dendrimers consisting of a benzophenone core and branches that contain dimethoxybenzene units has been investigated. Such dendrimers can undergo a variety of photochemical and photophysical processes, namely: 1) quenching of the fluorescence and phosphorescence of the dimethoxybenzene units by energy transfer to the benzophenone core (antenna effect), 2) direct and sensitized phosphorescence (and delayed fluorescence) of the benzophenone core, 3) hydrogen abstraction by the triplet excited state of the benzophenone core from solvent molecules, 4) intramolecular hydrogen abstraction by the triplet excited state of the benzophenone core from the dendrimer branches, 5) quenching of the phosphorescence and hydrogen abstraction reaction of the benzophenone core by energy transfer to terbium ions and dioxygen; 6) conversion of the UV light absorbed by the dendrimer branches into visible (Tb3+) or near infrared (O2) emission via the sequence of processes 1) and 5). The results obtained emphasize the great potential of suitably designed dendrimers for a multiple use of light signals.
Nanopatterns and Nanostructures at Interfaces, Mulhouse, 12–15 October 2003
Authors: Leggett Graham J.
Published: March 2004

Getting down to nano. This conference on nanotechnology was attended by eminent physical chemists and state‐of‐the‐art work was presented on topics such as self‐assembly, supramolecular chemistry, surface organisation, surface patterning, optical techniques and lithography. Although a real nanotechnology may still be a long way off, there are many exciting developments across a broad spectrum of interfacial physical chemistry and many opportunities to push forward the boundaries of science.
Promotion of crystal growth rate in aqueous solution by direct contact with gas corona discharge
Authors: Maeda Kouji , Sano Noriaki , Sonoda Akira , Fukui Keisuke
Published: March 2004

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

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

TlBiTe2 and TlBiSe2 ‐ that are ternary analogs of the IV‐VI semiconductors ‐, although they crystallize in the same space group R$ \bar 3 $m (D53d), exhibit different behaviour during heating. The observed phase transformation depends on Se content (x) in the system TlBi(Te1‐xSex)2 and the transformation disappears by increasing Se content after a certain value (x = 0.25). This dependence is examined through the analysis of the DSC non‐isothermal measurements and an attempt for the explanation of the observed behaviour is undertaken through the consideration of off‐center atoms. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of SHG candidate crystals in barium aluminum (gallium) borates
Authors: Miyazaki A. , Kimura H. , Maiwa K. , Nakamura H. , Kannan C. V.
Published: March 2004

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

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

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

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

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

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

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

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

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

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

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

A comparative evaluation of the utility of the various modes of stripping chronopotentiometry (SCP) for trace metal speciation analysis is presented in the broad context of stripping voltammetric techniques. The remarkable fundamental advantages of depletive SCP at scanned deposition potential (SSCP) are highlighted, and the rigorous underpinning theory is described. The distinctive features of SSCP include: i) an effective getting around part of the Nernstian extension of the reoxidation process, leading to ii) greater resolution than conventional stripping voltammetries; iii) a certain insensitivity to electrochemical irreversibility, especially at a microelectrode; iv) in principle, freedom from induced metal ion adsorption interferences; v) no requirement for excess ligand during stripping; and vi) ability to provide a certain measure of any chemical heterogeneity in the metal speciation that is easily distinguishable from effects of electrochemical irreversibility.
An Extended Method for the Practical Evaluation of the Standard Rate Constant from Cyclic Voltammetric Data
Authors: Lavagnini Irma , Antiochia Riccarda , Magno Franco
Published: March 2004

The Nicholson's treatment for the evaluation of the heterogeneous standard rate constant k0 of electron transfer from cyclic voltammetric (CV) data is combined with the Klingler and Kochi method suitable to totally irreversible systems in order to use very large ΔEp x n values, where n is the number of electrons involved in a simple electron‐transfer process O+n e−⇌R. An empirical relationship between the dimensionless parameter Ψ=k0 [πDnvF/(RT)]−1/2 and ΔEp x n which practically replaces the Nicholson's working curve up to about 200 mV is reported.
The Influence of Doping Levels and Surface Termination on the Electrochemistry of Polycrystalline Diamond
Authors: Latto Matthew N. , Pastor‐Moreno Gustavo , Riley D. Jason
Published: March 2004

The influence of surface chemistry and boron doping density on the redox chemistry of Fe(CN)$\rm{ {_{6}^{3-/4-}}}$ at CVD polycrystalline diamond electrodes is considered. It is demonstrated that for this couple both the doping density and the surface chemistry are important in determining the rate of charge transfer at the electrode/electrolyte interface. For hydrogen terminated CVD diamond metallic electrochemical behavior is always observed, even at boron doping densities as low as 7×1018 cm−3. In contrast, the electrochemical behavior of oxygen terminated CVD diamond varies with doping density, a metallic response being observed at high doping density and semiconductor behavior at low doping density. It is shown that the results attained may be explained by a surface state mediated charge transfer mechanism, thus demonstrating the importance of controlling surface chemistry in electroanalytical applications of diamond.
Electrochemical Determination of Sulfide at High Temperatures via Its Electrochemically Initiated Reaction with Diethyl‐p‐phenylenediamine in Dimethylformamide
Authors: Wildgoose Gregory G. , Giovanelli Debora , Klymenko Oleksiy V. , Lawrence Nathan S. , Jiang Li , Jones Timothy G. J. , Compton Richard G.
Published: March 2004

The electrochemical oxidation of DEPD proceeds via an ECrevECE mechanism in dimethylformamide. It has been investigated at elevated temperatures up to 130 °C at both micro and macro platinum and glassy carbon electrodes. Kinetic and thermodynamic parameters for the reaction process have been calculated for each temperature. Further, the voltammetric response of DEPD shows enhanced limiting currents in the presence of sulfide. The analytical utility of the approach has been investigated with linear range from 50 to 850 μM sulfide concentration observed and a corresponding limit of detection of 20 μM achievable at temperatures of 70 °C.
Voltammetry in Undiluted Acetic Acid. In Situ Determination of Water
Authors: Bak Elzbieta , Michalkiewicz Slawomir , Stojek Zbigniew
Published: March 2004

Water present in undiluted acetic acid can be monitored in situ with Pt and Au microelectrodes using differential pulse and square‐wave voltammetries. Both reduction and oxidation peaks can be obtained. The best quantitative analytical results were obtained for the anodic peak, the Pt microelectrode, and differential pulse voltammetry. The anodic water peak is located at +1.55 V vs. the quasi reference Pt electrode. The voltammetric peak obtained at Pt electrode is apparently not a diffusional one, however, the calibration plot obtained by employing this peak is linear over a wide concentration range, up to 4 mol dm−3. The detection limit has been estimated as 2.3 mM or 0.0043 v/v%. The developed method may be particularly useful, since the Karl Fischer method can not be used to determine water in glacial acetic acid due to the estrification reaction of acetic acid with methanol. A voltammetric wave of undiluted acetic acid could not be obtained in the positive and negative ranges of potential.
Anodic Stripping Voltammetry: An AFM Study of Some Problems and Limitations
Authors: Hyde Michael E. , Banks Craig E. , Compton Richard G.
Published: March 2004

The use of anodic stripping voltammetry for quantitative analytical measurements using solid electrodes is addressed in the light of generic limitations arising from i) electrode heterogeneity, ii) electrode morphology, iii) inhibited electrodeposition, and iv) incomplete stripping of deposited metal in the anodic sweep. It is shown, using direct imaging of electrode surfaces via AFM and optical microscopy, that each of the preceding factors may produce significant deviations from ideal electrode behavior. The use of atomic force microscopy to fully characterize any developed ASV procedures is strongly recommended. To ensure reproducible and accurate stripping voltammetry, steps should be taken to minimize the effects discussed.
Detecting DNA Damage with a Silver Solid Amalgam Electrode
Authors: Kuchariková Katerina , Novotny Ladislav , Yosypchuk Bogdan , Fojta Miroslav
Published: March 2004

Mercury electrodes modified with supercoiled (sc) DNA have been used as highly sensitive tools for the detection of DNA strand breaks or as sensors for DNA cleaving substances. In this paper we show that silver solid amalgam electrode (AgSAE), in connection with alternating current voltammetry, provides similar information about DNA damage as the hanging mercury drop electrode. The AgSAE can be used for the detection of enzymatic or chemical DNA cleavage in solution or at the electrode surface. AgSAE modified with scDNA can be utilized as a sensor for DNA nicking substances.
Hydrogen Peroxide Detection at Electrochemically and Sol‐Gel Derived Ir Oxide Films
Authors: Elzanowska Hanna , Abu‐Irhayem Erfan , Skrzynecka Beata , Birss Viola I.
Published: March 2004

Ir oxide (IrOx) films, formed electrochemically on bulk Ir metal (Ir/IrOx) and also on sol‐gel (SG) derived non‐silica based nanoparticulate Ir, have been studied as material useful for the detection of hydrogen peroxide, with possible application as a glucose biosensor. H2O2 reduction and oxidation on Ir/IrOx and SG‐derived IrOx films, deposited on various substrates such as Pt, Ir and GC, have been compared to the H2O2 behavior at the bare substrate. It was found that H2O2 reduction proceeds on the underlying electrode substrate, while H2O2 oxidation is independent of the nature of the substrate, therefore occurring via the IrOx film. The reactivity of IrOx towards H2O2 oxidation is similar to that seen at Pt, although IrOx has the additional advantages of excellent stability, insensitivity to common interfering substances, biocompatibility and a linear range of detection, up to at least 12 mM H2O2. At micromolar concentrations of H2O2, a second mode of detection, involving the catalyzed growth of IrOx films at Ir substrates, can be employed. These two methods of H2O2 analysis (oxidation/reduction and enhanced IrOx growth) can also be employed for glucose detection using IrOx‐based glucose biosensors.
Novel Cesium‐Selective Electrodes Based on Lipophilic 1,3‐Bisbridged Cofacial‐calix[6]crowns
Authors: Jeon Seungwon , Yeo Heekyoung , Lee Hyo Kyoung , Ko Seung Whan , Nam Kye Chun
Published: March 2004

Five bisbridged calix[6]crowns have been investigated as Cs+ionophore in PVC membrane electrodes. As ionophores, three 1,3‐bisbridged calix[6]crown‐4‐ethers(I–III), 1,3‐bisbridged calix[6]crown‐5‐ether(IV), and 1,3‐bisbridged calix[6]crown‐6‐ether(V) have been evaluated. The membranes all give good Nernstian response in the concentration range from 1×10−7to 1×10−1 M of cesium ion. The best detection limits (−loga=7.08–7.36) are obtained for electrode membranes containing 1,3‐bisbridged cofacial‐calix[6]crown‐4‐ethers(I‐III), and the values are the lowest compared with those reported previously. The highest selectivity coefficients [$\rm{ {\rm p}K_{{\rm Cs}^ + ,{\rm j}}^{{\rm pot}} = 5.53({\rm Cs/Na}),}$3.74(Cs/K), 2.63(Cs/Rb)] are obtained for the membrane of 1,3‐bisbridged calix[6]crown‐4‐ether(II), and these values are also the highest compared with previous reports for Cs+‐ISEs. The highest selectivity towards cesium ion is attributed to the geometrically cofacial positions of two crown‐ethers in calix[6]crowns in order to provide the complex of cesium ion and eight oxygens of cofacial crowns.
Chemical composition of essential oil of Cinnamomum tamala Nees et Eberm. leaves
Authors: Mir Showkat R. , Ali Mohammed , Kapoor Reni
Published: March 2004

A hydrodistilled oil obtained from the leaves of Cinnamomum tamala Nees et Eberm., grown in India, was analysed by capillary GC and GC–MS. The leaf volatile oil contained 40 constituents, of which a high proportion were monoterpenes (65.6%). The predominant monoterpenes were trans‐sabinene hydrate (29.8%), (Z)‐β‐ocimene (17.9%), myrcene (4.6%), α‐pinene (3.1%) and β‐sabinene (2.3%). Among 21 sesquiterpenes (32.9%), the major ones were germacrene A (11.3%) and α‐gurjunene (4.7%). Copyright © 2004 John Wiley & Sons, Ltd.
Composition and antibacterial activity of the essential oil of six Stachys species from Serbia
Authors: Grujic‐Jovanovic Slavica , Skaltsa Helen D. , Marin Petar , Sokovic Marina
Published: March 2004

The essential oils of Stachys scardica, S. ofﬁcinalis, S. germanica, S. sylvatica, S. plumosa and S. recta were analysed by GC–MS. From more than 100 identiﬁed constituents of the oils, the sequiterpene hydrocarbons were the major components of all samples except that of S. plumosa, which was rich in monoterpene hydrocarbons. Furthermore, the oils were tested against three Gram‐positive and three Gram‐negative bacteria. The essential oil of S. ofﬁcinalis proved to be the most active. Copyright © 2004 John Wiley & Sons, Ltd.
Essential oil constituents of aerial parts of Artemisia scoparia Waldst. & Kit.
Authors: Kapoor Reni , Ali Mohammed , Mir Showkat R. , Raﬁullah M. R. M.
Published: March 2004

Hydrodistilled oil obtained from the aerial parts of Artemisia scoparia Waldst. & Kit. was analysed by capillary GC and GC–MS. The volatile oil of the 10–15 cm high herb was composed mainly of eight monoterpenes (ca. 68.5%), and the predominant constituents were β‐myrcene (24.4%), γ‐terpinene (18.3%), neral (12.5%) and cis‐p‐mentha‐2‐en‐1‐ol (5.1%). Among seven sesquiterpenes (6.9%) present in the oil, the prominent one was β‐caryophyllene (3.4%). p‐Cymene (17.4%) and p‐cymene‐8‐ol were the characterized aromatic compounds in the volatile oil. Three aliphatic constituents, identiﬁed as n‐octane, n‐heptadecane and n‐eicosane, occurred in trace amounts. Copyright © 2004 John Wiley & Sons, Ltd.
Olfactory study on optically active citronellyl derivatives
Authors: Yamamoto Takeshi , Shimada Akemi , Ohmoto Tatsuya , Matsuda Hiroyuki , Ogura Miharu , Kanisawa Tsuneyoshi
Published: March 2004

Odour threshold concentrations, determined in agueous‐ethanol solution, and odour qualities are reported for 18 enantiomeric and diastereomeric pairs of citronellyl derivatives [13 linear monoterpene compounds and ﬁve monocyclic α‐damascone and α‐ionone‐related compounds (trans‐2,2,6‐trimethylcyclohexyl derivatives)] (98%ee). Fairly large differences in both odour strength and odour qualities were found between the monocyclic diastereomeric pairs. In four of the ﬁve cyclic compounds, the (1R, 6S)‐form was found to be stronger and more sensorily active than the antipode. On the other hand, the linear enantiomeric pairs showed only small differences in both odour strength (half of them showed the same threshold values) and odour character. However, all the (3S)‐forms showed milder, cleaner and a much preferable top note than the (3R)‐forms except for citronellyl nitrile and the diester (citronellyl ethyl oxalate), whose (3R)‐form showed a characteristic ﬂoral musk odour, although the (3S)‐form showed a rose ﬂoral odour. Copyright © 2004 John Wiley & Sons, Ltd.
Composition of the essential oil from ﬂowerheads of Chrysanthemum coronarium L. (Asteraceae) growing wild in Southern Italy
Authors: Senatore Felice , Rigano Daniela , De Fusco Raffaele , Bruno Maurizio
Published: March 2004

The essential oils from the aerial parts of Chrysanthemum coronarium L. (Asteraceae) growing wild in two different localities of Southern Italy, Lascari (L) and Palinuro (P), were obtained by hydrodistillation in a 0.13–0.16% yield. The oils were analysed by GC and GC–MS; 68 constituents, amounting to 89.0% of the oil (L), and 43 constituents, amounting to 91.6% of the oil (P), were identiﬁed. The trans‐spiroketal–enol ether 2‐(2,4‐hexadiynylidene)‐1,6‐dioxaspiro[4,4]non‐3‐ene (trans‐tonghaosu) with chrysanthenyl and lyratyl esters and camphor were the main components of the oils. Copyright © 2004 John Wiley & Sons, Ltd.
Essential oil composition of Cephalophora aromatica cultivated in Iran
Authors: Seﬁdkon F. , Omidbaigi R.
Published: March 2004

Hydrodistilled volatile oil from the ﬂowers of Cephalophora aromatica Schrad. (cultivated in Iran) was analysed by a combination of GC and GC–MS. Twenty‐nine components were identiﬁed. The main constituents of the essential oil were 2‐ethyl hexanoic acid (27.0%), n‐undecane (14.1%), decane (11.4%) and geranyl tiglate (7.9%). Copyright © 2004 John Wiley & Sons, Ltd.
Analysis of the volatile constituents of Nepeta macrosiphon Boiss. grown in Iran
Authors: Javidnia K. , Miri R. , Jafari A. , Rezai H.
Published: March 2004

Composition of the volatile oil of Nepeta macrosiphon Boiss. (Lamiaceae) was investigated by GLC and GC–MS. Seventy‐three components, representing 96.9% of the total oil, were characterized. The main components of the oil were spathulenol (28.8%), α‐cadinol (13.6%), bicyclogermacrene (10.1%), β‐caryophyllene (9.6%) and linalool (5.6%). Nepetalactone isomers were not present in the essential oil of N. macrosiphon. Copyright © 2004 John Wiley & Sons, Ltd.
Essential oils and fragrance compounds: bioactivity and mechanisms of action
Authors: Lahlou Mouhssen
Published: March 2004

Many studies on essential oils and fragrance compounds are performed and then published without any biological testing whatsoever. In addition, the mechanisms of action of such compounds can remain unknown for years in many cases. The present paper gives more comprehensive knowledge on the actions of essential oils and fragrance compounds; in addition, the bioactivity of chiral, isomer and chemotype compounds is discussed. Copyright © 2004 John Wiley & Sons, Ltd.
Volatile constituents of different organs of Psoralea bituminosa L.
Authors: Bertoli Alessandra , Menichini Francesco , Noccioli Cecilia , Morelli Ivano , Pistelli Luisa
Published: March 2004

The essential oil and SPME samples of the leaves, ﬂowers and seeds of Psoralea bituminosa L. were analysed by GC and GC–MS. We have investigated also the presence of monoterpene or aliphatic alcohol glucosides. The essential oils showed both qualitative and quantitative differences. The main constituents of the leaf and the ﬂower essential oils were caryophyllene (23% and 18%, respectively), β‐farnesene (15% and 6%, respectively), and germacrene D (24% and 18%, respectively). Signiﬁcant amounts (7%) of the same compounds were also directed in the seed essential oil, but tricyclene (11%) and α‐pinene (50%) were the most important constituents of this oil. The volatile fractions of remaining leaf aqueous extracts after treatment with β‐glucosidase revealed qualitative differences in comparison with the composition of the corresponding essential oils, and high levels of 3‐hexen‐1‐ol (37%) and 1‐octen‐3‐ol (27%) were observed. The SPME analysis of the fresh leaves, ﬂowers and seeds of P. bituminosa conﬁrmed the qualitative composition of the volatile oils, even if we detected signiﬁcative differences in the percentage ratio between monoterpenes and sesquiterpenes in comparison with the oils, where sesquiterpenes were the main components. In fact the variation of the monoterpenes, tricyclene, α‐pinene and camphene between the leaf oil and the corresponding headspace sample was remarkable: tricyclene increased from 0.1% to 8%, α‐pinene from 0.1% to 16% and camphene from 0.3% to 10% in the SPME samples. Copyright © 2004 John Wiley & Sons, Ltd.