bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tuning the Polarization Along Linear Polyaromatic Strands for Rationally Inducing Mesomorphism in Lanthanide Nitrate Complexes
Authors: Terazzi Emmanuel , Guénée Laure , Morgantini Pierre‐Yves , Bernardinelli Gérald , Donnio Bertrand , Guillon Daniel , Piguet Claude 
Published: January 2007

AbstractThe opposite orientation of the ester spacers in the rodlike ligands L 4C12 (benzimidazole‐OOC‐phenyl) and L 5C12 (benzimidazole‐COO‐phenyl) drastically changes the electronic structure of the aromatic systems, without affecting their meridional tricoordination to trivalent lanthanides, LnIII, and their thermotropic liquid crystalline (i.e., mesomorphic) behaviors. However, the rich mesomorphism exhibited by the complexes [Ln(L 4C12)(NO3)3] (Ln=La–Lu) vanishes in [Ln(L 5C12)(NO3)3], despite superimposable molecular structures and comparable photophysical properties. Density functional theory (DFT) and time‐dependant DFT calculations performed in the gas phase show that the inversion of the ester spacers has considerable effects on the electronic structure and polarization of the aromatic groups along the strands, which control residual intermolecular interactions responsible for the formation of thermotropic liquid‐crystalline phases. As a rule of thumb, an alternation of electron‐poor and electron‐rich aromatic rings favors intermolecular interactions between the rigid cores and consequently mesomorphism, a situation encountered for L 4C12, L 5C12, [Ln(L 4C12)(NO3)3], but not for [Ln(L 5C12)(NO3)3]. The intercalation of an additional electron‐rich diphenol ring on going from [Ln(L 5C12)(NO3)3] to [Ln(L 6C12)(NO3)3] restores mesomorphism despite an unfavorable orientation of the ester spacers, in agreement with our simple predictive model.
Bond Orders and Atomic Properties of the Highly Deformed Halogenated Fullerenes C60F18 and C60Cl30 Derived from their Charge Densities
Authors: Hübschle Christian B. , Scheins Stephan , Weber Manuela , Luger Peter , Wagner Armin , Koritsánszky Tibor , Troyanov Sergey I. , Boltalina Olga V. , Goldt Il'ya V. 
Published: January 2007

AbstractThe experimental charge densities of the halogenated C60 fullerenes C60F18 and C60Cl30 were determined from high‐resolution X‐ray data sets measured with conventional MoKα radiation at 20 K for C60Cl30 and with synchrotron radiation at 92 K for the fluorine compound. Bond topological and atomic properties were analyzed by using Bader's AIM theory. For the different CC bonds, which vary in lengths between 1.35 and 1.70 Å bond orders n between n=2 and significantly below n=1 were calculated from the bond topological properties at the bond critical points (BCP's). The low bond orders are seen for 5/6 bonds with each contributing carbon carrying a halogen atom. By integration over Bader's zero flux basins in the electron density gradient vector field atomic properties were also obtained. In contrast to free C60, in which all carbon atoms have a uniform volume of 11 Å3 and zero charge, atomic volumes vary roughly between 5 and 10 Å3 in the halogenated compounds. Almost zero atomic charges are also found in the Cl derivative but a charge separation up to ±0.8 e exists between C and F in C60F18 due to the higher fluorine electronegativity, which is also seen in the electrostatic potential for which the electronegativity difference between carbon and fluorine, and the addition to one hemisphere of the fullerene cage leads to a strong potential gradient along the C60F18 molecule. From the summation over all atomic volumes it follows that the halogen addition does not only lead to a dramatic distortion of the C60 cage but also to a significant shrinkage of its volume.
Enantioselective preparative HPLC separation of the HBCD—Stereoisomers from the technical product and their absolute structure elucidation using X‐ray crystallography
Authors: Koeppen Robert , Becker Roland , Emmerling Franziska , Jung Christian , Nehls Irene 
Published: January 2007

Abstract1,2,5,6,9,10‐Hexabromocyclododecane (HBCD) is a widely used flame retardant, which tends to persist in the environment and accumulates in biota. The six stereoisomers (three racemates named α‐, β‐, and γ‐HBCD) of the technical mixture were isolated with high‐performance liquid chromatography (HPLC). Direct separations were performed on a chiral stationary phase containing permethylated β‐cyclodextrin (NUCLEODEX β‐PM column) and the pure enantiomers of α‐, β‐, and γ‐HBCD were physically characterized for the first time. The absolute configurations of all six isomers were determined by anomalous dispersion using single crystal X‐ray crystallography. Optical rotations αD in tetrahydrofuran were +4.2/−4.0 (α‐HBCD), +26.1/−27.5 (β‐HBCD), and +68.0/−66.3 (γ‐HBCD). The sense of rotation could be correlated with the absolute configurations of α‐, β‐, and γ‐HBCD enantiomers and their order of elution on a chiral permethylated β‐cyclodextrin‐bonded stationary phase. The diastereomersα‐, β‐, and γ‐HBCD displayed distinctly different melting points as well as 1H‐, 13C NMR, and IR spectra. Chirality, 2007. © 2007 Wiley‐Liss, Inc.
Neuronal morphology and neuropil structure in the stomatogastric ganglion of the lobster, Homarus americanus
Authors: Bucher Dirk , Johnson Christian D. , Marder Eve 
Published: January 2007

AbstractThe stomatogastric nervous system (STNS) has long been used as a model system for the study of central pattern generation, neuromodulation, and network dynamics. Anatomical studies of the crustacean stomatogastric ganglion (STG) in different species have mostly been restricted to subsets of neurons and/or general structural features. For the first time, we describe the morphology of all STG neurons belonging to the two circuits that produce the well‐described pyloric and gastric rhythms in the lobster, Homarus americanus. Somata sit on the dorsal and lateral surface of the STG and send a single primary neurite into the core of the neuropil, which is mostly made up of larger lower order branches. The perimeter of the neuropil consists mostly of finer higher order branches. Immunohistochemical labeling for synaptic proteins is associated with the small diameter branches. Somata positions are not constant but show preferred locations across individuals. The number of copies is constant for all neuron types except the PY and GM neurons (PY neuron number ranges from 3 to 7, and GM neuron number ranges from 6 to 9). Branch structure is largely nondichotomous, and branches can deviate substantially from cylindrical shape. Diameter changes at branch points can be as large as 20‐fold. Clearly, the morphology of a specific neuron type can be quite variable from animal to animal. J. Comp. Neurol. 501:185–205, 2007. © 2007 Wiley‐Liss, Inc.
Primary visual cortex volume and total neuron number are reduced in schizophrenia
Authors: Dorph‐Petersen Karl‐Anton , Pierri Joseph N. , Wu Qiang , Sampson Allan R. , Lewis David A. 
Published: January 2007

AbstractA number of studies that assessed the visual system in subjects with schizophrenia found impairments in early visual processing. Furthermore, functional imaging studies suggested changes in primary visual cortex activity in subjects with schizophrenia. Interestingly, postmortem studies of subjects with schizophrenia reported an increased density of neurons in the primary visual cortex (Brodmann's area 17, BA17). The observed changes in visual processing may thus be reflected in structural changes in the circuitry of BA17. To characterize the structural changes further we used stereological methods based on unbiased principles of sampling (Cavalieri's principle and the optical fractionator) to estimate the total volume and neuron number of BA17 in postmortem brains from 10 subjects with schizophrenia and 10 matched normal comparison subjects. In addition, we assessed cortical thickness. We found a marked and significant reduction in total neuron number (25%) and volume (22%) of BA17 in the schizophrenia group relative to the normal comparison subjects. In contrast, we found no changes in neuronal density or cortical thickness between the two groups. Subjects with schizophrenia therefore have a smaller cortical area allocated to primary visual perception. This finding suggests the existence of a schizophrenia‐related change in cortical parcellation. J. Comp. Neurol. 501:290–301, 2007. © 2007 Wiley‐Liss, Inc.
Macrophage depletion in the murine olfactory epithelium leads to increased neuronal death and decreased neurogenesis
Authors: Borders Aaron S. , Getchell Marilyn L. , Etscheidt Jordan T. , van Rooijen Nico , Cohen Donald A. , Getchell Thomas V. 
Published: January 2007

AbstractApoptosis of olfactory sensory neurons (OSNs) induced by olfactory bulbectomy (OBX) leads to the activation of resident macrophages within the olfactory epithelium (OE). These macrophages phagocytose degenerating OSNs and secrete chemokines, which recruit additional macrophages into the OE, and cytokines/growth factors, which regulate basal cell proliferation and differentiation and maturation of OSNs. In this study we apply for the first time the use of liposome‐encapsulated clodronate to selectively deplete macrophages during the OSN degeneration/regeneration cycle in order to elucidate the role(s) of macrophages in regulating cellular mechanisms that lead to apoptosis and neurogenesis. Mice were injected intranasally and intravenously with either liposome‐encapsulated clodronate or empty liposomes prior to and after OBX or sham OBX. At 48 hours after surgery the numbers of macrophages in the OE of both sham and OBX clodronate‐treated mice were significantly reduced compared to liposome‐treated controls (38% and 35%, respectively, P < 0.05). The reduction in macrophage numbers was accompanied by significant decreases in OE thickness (22% and 21%, P < 0.05), the number of mOSNs (1.2‐ and 1.9‐fold, P < 0.05), and basal cell proliferation (7.6‐ and 3.8‐fold, P < 0.005) in sham and OBX mice, respectively, compared to liposome‐treated controls. In OBX mice there was also increased immunoreactivity for active caspase‐3 in the OE and olfactory nerves of clodronate‐treated OBX mice compared to liposome‐treated controls. These results indicate that macrophages modulate the OSN population in the normal and target‐ablated murine OE by influencing neuronal survival and basal cell proliferation, resulting in neurogenesis and replacement of mature OSNs. J. Comp. Neurol. 501:206–218, 2007. © 2007 Wiley‐Liss, Inc.
Occipital sulci of the human brain: Variability and probability maps
Authors: Iaria Giuseppe , Petrides Michael 
Published: January 2007

AbstractThe morphological variation of the sulci of the occipital region of the human brain was examined in both the left and the right hemispheres in 40 normal adult human brains on magnetic resonance images. We identified the occipital sulci and marked their corresponding gray matter voxels on the magnetic resonance images, which had been transformed into the Montreal Neurological Institute standard proportional stereotaxic space in order to construct probability maps. In the medial occipital region, the calcarine sulcus was the longest and most constant sulcus. We identified, in the inferior part of the medial occipital lobe, the lingual sulcus and the posterior collateral sulcus, and, in the superior part, the inferior and superior sagittal sulci of the cuneus. On the lateral surface of the occipital lobe, the lateral occipital, the lunate, and the transverse and inferior occipital sulci were identified. The parieto‐occipital fissure and the temporo‐occipital incisure were also identified on the lateral and medial surfaces. Finally, the patterns of the occipital sulci and gyri were examined in 20 post‐mortem human hemispheres fixed in formalin. Probability maps of the occipital sulci were constructed, which provide a quantitative description of the variability of the sulci in standard stereotaxic space and may be used to identify the location of voxels in other magnetic resonance images transformed into the same streotaxic space. These maps are a useful tool in the study of functional activations related to visual processing. J. Comp. Neurol. 501:243–259, 2007. © 2007 Wiley‐Liss, Inc.
Phase‐Selective CVD of Vanadium Oxide Nanostructures
Authors: Mathur S. , Ruegamer T. , Grobelsek I. 
Published: January 2007

AbstractPhase‐selective synthesis of crystalline vanadium oxides is achieved by the CVD of vanadium oxo‐tri‐isopropoxide [VO(OiPr)3]. Preformed V–O and V=O units and their differential thermal stability present in the precursor enabled precise modulation of the vanadium/oxygen stoichiometry in the products of the CVD. No additional oxygen carrier is employed during the deposition processes. Subject to deposition temperature (400–700 °C), different phase compositions (V2O5, V7O13, and VO2) are directly obtained and are investigated regarding structural and electrical properties. Hall measurements on VO2 films show a sharp metal‐to‐semiconductor transition at 78 °C (single crystal, 68 °C) depending on their microstructure formed by an oriented aggregation of individual crystallites.
Flow cytometric immunphenotyping of epithelial cancer cells in effusions—Technical considerations and pitfalls
Authors: Dong Hiep P. , Holth Arild , Berner Aasmund , Davidson Ben , Risberg Björn 
Published: January 2007

AbstractBackground:Data regarding the role of flow cytometry (FCM) in the characterization of malignant effusions are limited to date. In the present study, we optimized the conditions for FCM immunphenotyping of effusions using a four‐color analysis and investigated aspects related to the advantages and limitations of this method in this setting.Methods:FCM analysis optimization for the study of epithelial cells was undertaken using five carcinoma cell lines, and subsequently applied to malignant pleural and peritoneal effusions using antibodies against epithelial and mesothelial markers (Ber‐EP4 and EMA), CD138, and integrin subunits. FCM of frozen versus fresh specimens and the performance of FCM compared to immunhistochemistry were evaluated.Results:FCM optimization was achieved and applied to clinical specimens, with resulting detection of epithelial markers and adhesion molecules on cancer cells. Frozen clinical specimens and cell lines showed reduced CD138 expression compared to fresh specimens, with conservation of the remaining epitopes. FCM generally showed comparable performance to immunhistochemistry.Conclusions:FCM is an effective method for characterization of cancer cells in clinical effusion specimens in both the diagnostic and research setting, and is comparable to immunhistochemistry in terms of sensitivity and specificity, with the additional advantage of providing quantitative data. The majority of epitopes are conserved in frozen cells, but a minority may be lost, suggesting that the thorough testing of each antibody in both conditions is mandatory. © 2007 Clinical Cytometry Society
Syntheses, Properties and Structures of [{(C5Me5)2Nb}2NiTe4] and [(tBuC5H4Nb)2Ni5Te7(Ph2PCH2PPh2)2]: The Quest for Tetratelluronickelate Clusters
Authors: Brandl Martin , Ebner Alexander , Kubicki Marek M. , Mugnier Yves , Wachter Joachim , Vigier‐Juteau Estelle , Zabel Manfred 
Published: January 2007

AbstractThe reaction of [Ni(COD)2] with [Cp*2NbTe2H] (1; Cp* = η‐C5Me5) in the presence of Ph2PCH2PPh2(dppm) in boiling toluene gives black‐violet [(Cp*2Nb)2NiTe4] (3). If [Cp′2NbTe2H] (2; Cp′ =tBuC5H4) is used under similar conditions dark‐brown [(Cp′Nb)2Ni5Te7(dppm)2] (4) is formed. The structures of3and4have been determined crystallographically. Complex3contains a severely distorted NiTe4tetrahedron to which two niobocene groups are coordinated. Density functional analysis of the electronic structure of the NiTe4building block shows that it is best described as an [Ni(η2‐Te2)2]2–fragment. The structure of4reveals the presence of two Ni5and Te5tetragonal pyramids stacked into each other in an opposite way. Six of the Te bridges form two triangular faces, each of which is capped by a Cp′Nb fragment. Additionally, two dppm ligands bridge the long Ni–Ni edges of the Ni4bases. Oxidation of3with [(C5H5)2Fe]BPh4gives paramagnetic [(Cp*2Nb)2NiTe4]BPh4(6), whereas oxidation with [(C5H5)2Fe]PF6proceeds with fluoride transfer to give [Cp*2NbF2]PF6(5). Electrochemical studies of3reveal the existence of the redox couples [3]2+/[3]+/[3]0/[3]–/[3]2–. Density functional calculations carried out on the different oxidation states of3reveal the following main features: the persistent presence of Nb–Ni bonds and the retention of Te–Te bonds in cationic and neutral species and their breaking off in reduced forms. Irrespective of the initial site of electrochemical attack, the Te atoms and Cp rings are principally affected in the final products.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Zinc Thiolate Complexes [ZnLn(SR)]+ with Azamacrocyclic Ligands, Part III: The Influence of the Ligand Ln on the Reactivity of Zinc‐Bound Thiolate
Authors: Notni Johannes , Günther Wolfgang , Anders Ernst 
Published: January 2007

AbstractIn this study, we focus on the structure–reactivity relationship of cationic zinc thiolate complexes with the general formula [Zn(Ln)(SR)]ClO4 (Ln: n‐dentate azamacrocyclic ligand; R = phenylmethyl). The complexes feature macrocyclic ligands with ring sizes varying from 11 to 16 atoms and possess three or four nitrogen donors (three of them containing one tertiary nitrogen). Thiol methylations with methyl iodide have been performed in order to determine the relative reactivities, because this reaction has been used before to investigate zinc thiolate reactivity and therefore allows comparison of our results with literature data. The kinetic behaviour was investigated in nitromethane and dichloromethane and was found to be second order in all cases. The observed rate constants vary in the range of k2 = 2.46–55.28×10–3 M–1 s–1 in nitromethane and k2 = 0.23–7.35×10–3 M–1 s–1 in dichloromethane at 300 K. Furthermore, the structures of all thiolate complexes were optimised at the B3LYP/6‐311+G(d) level of theory. Natural bond orbital (NBO) analyses were performed to obtain information on partial charges of the heteroatoms and energies of a lone pair in a p‐type orbital at the zinc‐bound sulfur. In order to elucidate which parameters determine reactivity, selected structural and electronic parameters were correlated with the experimental rate constants. As a result, we found that the reaction is controlled predominantly by frontier orbital energy in dichloromethane and by charge in nitromethane. However, we observed that electronic reactivity control can be overridden by the degree of steric obstruction of the zinc ion, which directly depends on ring size and configuration of the ring nitrogens. The complex [Zn(cyclen)(SR)]ClO4 (5) can therefore not be included in any of the correlations; steric constraint imposed by the comparably small ring system causes an extraordinarily increased reactivity. In turn, this finding provides a new rationale for the high reactivity reported for the cyclen complex [Zn(cyclen)(OH)]+, which has been used as a model for carbonic anhydrase in previous studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Electrogenerated Chemiluminescence Ethanol Biosensor Based on Carbon Nanotube‐Titania‐Nafion Composite Film
Authors: Choi Han Nim , Yoon Sook Hyun , Lyu Young‐Ku , Lee Won‐Yong 
Published: January 2007

AbstractMesoporous titania‐Nafion composite doped with carbon nanotube (CNT) has been used for the immobilization of tris(2,2′‐bipyridyl)ruthenium(II) (Ru(bpy)32+) and alcohol dehydrogenase on an electrode surface to yield a highly sensitive and stable electrogenerated chemiluminescence (ECL) ethanol biosensor. The presence of CNT in the composite film increases not only the sensitivity of the ECL biosensor but also the long‐term stability of the biosensor. The present biosensor responds linearly to ethanol in the wide concentration ranges from 1.0×10−5 M to 1.0×10−1 M with a detection limit of 5.0×10−6 M (S/N=3). The present ECL ethanol biosensor exhibited higher ECL response compared to that obtained with the ECL biosensor based on the corresponding composite without CNT. The present CNT‐based ECL biosensor showed good long‐term stability with 75% of its initial activity retained after 2 weeks of storage in 50 mM phosphate buffer at pH 7.0.
In Situ Amperometric Detection of Vesicles and Microgel Phases in an Aggregating System: Calcium Alginate
Authors: DeNardis Nadica Ivošević , Žutić Vera , Svetličić Vesna , Urbani Ranieri 
Published: January 2007

AbstractIn situ amperometric characterization of an aggregating system in terms of molecular adsorption and single microparticle interactions at the electrode interface is demonstrated using a model system: alginate/Ca(II) in an aqueous electrolyte solution. Recording of chronoamperometric curves of oxygen reduction at the dropping mercury electrode is designed for detection of dip‐shaped signals of individual gel microparticles. By addition of Ca(II) decrease of alginate adsorption is accompanied by appearance of signals indicating vesicle type association of alginate molecules and microparticles of gel phase. AFM imaging provided evidence of initial stage in calcium alginate gel formation.
Electrocatalysis and Voltammetric Determination of Dopamine at a Calix[4]arene Crown‐4 Ether Modified Glassy Carbon Electrode
Authors: Lai Guo‐Song , Zhang Hai‐Li , Jin Chuan‐Ming 
Published: January 2007

AbstractA sensitive and selective electrochemical method for the determination of dopamine (DA) was developed using a calix[4]arene crown‐4 ether (CACE) film modified glassy carbon electrode (GCE).The modified electrode exhibited good electrocatalytic activity for electrochemical oxidation of DA in the pH 6.00 Britton–Robinson buffer solution, and ascorbic acid (AA) did not interfere with it. The diffusion coefficient (D=2.7×10−5 cm2 s−1), and the kinetic parameter such as the electron transfer coefficient (α=0.54) of DA at the surface of CACE were determined using electrochemical approaches. The catalytic oxidation peak currents showed a linear dependence on the DA concentration and a linear analytical curve was obtained in the range of 2.0×10−5–1.0×10−3 M of DA with a correlation coefficient of 0.9990. The detection limit (S/N=3) was estimated to be 3.4×10−6 M. This method was also examined for the determination of DA in an injection sample. In addition, effects of possible interferences were investigated. The present work shows the potential of the proposed method for the fabrication of a modified electrode, as it can be effectively used for voltammetric detection of DA.
The stability of AGC systems with commensurate delays
Authors: Liu Meizhao , Yang Li , Gan Deqiang , Wang Dexin , Gao Fuying , Chen Yan 
Published: January 2007

AbstractWith communication signal delays, a power system control can actually excite sustained oscillations. This paper proposes a method to analyze the stability of such delayed systems and the like. The stability is estimated using delay margins. The main result is nicely based on a sufficient and necessary condition. Simulation results of the Automatic Generation Control (AGC) system of the real‐world East China Power Grid (ECPG) system are reported to validate the methodology. Copyright © 2007 John Wiley & Sons, Ltd.