bluuebunny/crossref_metadata_2025 huggingface dataset:
Different Coordination Modes of the Polyfunctional Ylide Ph3P=C(H)C(O)CH2C(O)OEt: C‐ vs. O,O′‐Bonding in PdII, PtII and AuI Complexes
Authors: Carbó Marta , Falvello Larry R. , Navarro Rafael , Soler Tatiana , Urriolabeitia Esteban P.
Published: April 2004

Treatment of the polyfunctional ylide Ph3P=C(H)C(O)CH2COOEt (1) with the solvated complexes [M(C∧X)(THF)2]ClO4 gave the O,O′ derivatives [M(C∧X)(Ph3PCH2C(O)=C(H)−C(=O)OEt‐κ‐O,O′]ClO4 [M(C∧X) = Pd(C6H4CH2NMe2) (2), Pd(CH2C9H6N) (3), Pd(NC5H4‐2‐C6H4) (4), Pd(NC13H8) (5), Pd[(S)−C6H4C(H)MeNMe2] (6), Pt[o‐CH2C6H4P(o‐tol)2] (7), Pd[o‐CH2C6H4P(o‐tol)2] (8), and Pd(C6F5)(SC4H8) (9)]. During the reaction, one proton of the methylene unit is transferred to the ylidic carbon, which is transformed into a phosphonium group generating the zwitterion [Ph3PCH2C(O)=C(H)−C(=O)OEt], which coordinates to the metal center as an O,O′‐chelating ligand. Treatment of 1 with [AuCl(SC4H8)] or [Au(PPh3)(OCMe2)]ClO4 gave [AuCl{C(H)(PPh3)C(O)CH2COOEt}] (10) or [Au{C(H)(PPh3)C(O)CH2COOEt}(PPh3)]ClO4 (11), in which the ylide is C‐bonded. The X‐ray crystal structures of complexes 2a, 9 and 10 have been determined. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Syntheses, Structures, Bonding and Photoelectron Spectra of “Push‐Pull”‐Substituted P‐[2,6‐Bis(trifluoromethyl)phenyl]‐σ2λ3‐iminophosphanes
Authors: Miqueu Karinne , Sotiropoulos Jean‐Marc , Pfister‐Guillouzo Genevieve , Rudzevich Valentyn L. , Gornitzka Heinz , Lavallo Vincent , Romanenko Vadim D.
Published: April 2004

σ2λ3‐“Push‐pull” iminophosphanes Arf−P=N−R, bearing an electron‐acceptor substituent at phosphorus [Arf = 2,6‐bis(trifluoromethyl)phenyl] and a donor group at nitrogen (R = tBu, NMe2), have been synthesized and characterized by NMR spectroscopy and X‐ray analysis. Density functional calculations [B3LYP/6‐311G(d,p)] have been carried out on different iminophosphanes: HP=NH (1), ArfP=NH (2), ArfP=NSiMe3 (3), ArfP=NtBu (4), HP=NNMe2 (5) and ArfP=NNMe2 (6) in order to determine the electronic effect of the Arf substituent and the influence of the donor group R on the stability of the monomeric species. A comparison of the theoretical results and UV photoelectron spectroscopy data for the iminophosphanes 4 and 6 is presented. Theoretical and experimental data suggest that for all iminophosphanes under investigation the π‐system of the Arf group is almost orthogonal to the πP=N system, preventing any stabilizing interaction between the πP=N and the π*b1(aryl) orbitals previously observed for the ArfPH− anion. Here, the Arf substituent effect is mainly steric. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Tuning the Stoichiometry of Lanthanide Complexes with Calixarenes: Bimetallic Complexes with a Calix[6]arene Bearing Ether‐Amide Pendant Arms
Authors: Ramírez Flor de María , Charbonnière Loïc , Muller Gilles , Bünzli Jean‐Claude G.
Published: April 2004

A de‐tert‐butylated calix[6]arene (A6L6) fitted with six ether‐amide pendant arms was synthesized and characterized in solution. NMR spectroscopic data point to the six phenoxide units adopting an average D6h conformation on the NMR time scale. According to MM3 molecular mechanics, and MOPAC quantum mechanical calculations, A6L6 is a ditopic ligand featuring two nonadentate coordination sites, each built from three pendant arms, and extending in opposite directions with one above, and the other under the main ring. A6L6 reacts with LnIII ions (Ln = La, Eu) in acetonitrile to successively form 1:1 and 2:1 complexes. The isolated EuIII 2:1 complex is luminescent (quantum yield: 2.5% in acetonitrile, upon ligand excitation). In the solid state, the luminescence decay is bi‐exponential, with lifetimes equal to 1.66 and 0.46 ms (upon direct metal excitation), pointing to the presence of two differently coordinated metal ions, one with essentially no bound water molecules, and the other one with two ligated water molecules. According to molecular mechanics calculations, the more stable isomer is indeed asymmetric with two nine‐coordinated metal ions. Both EuIII ions are bound to three bidentate arms, and one monodentate triflate anion, but one metal ion completes its coordination sphere with two phenoxide oxygen atoms, and the other one with two water molecules, consistent with IR spectroscopic and luminescence data. In acetonitrile solution, the two metal ion sites become equivalent, and the relatively long lifetime (1.35 ms) is indicative of a coordination environment free of water molecules. This work demonstrates, that the stoichiometry of lanthanide complexes with calixarenes can be tuned by a suitable choice of the narrow and/or wide rim substituents. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis and Luminescence Properties of New Dinuclear Complexes of Lanthanide(III) Ions
Authors: Patroniak Violetta , Baxter Paul N. W. , Lehn Jean‐Marie , Hnatejko Zbigniew , Kubicki Maciej
Published: April 2004

As a result of coordination of the ligand L, containing two tridentate binding units, to samarium(III), europium(III), terbium(III), and dysprosium(III) ions, new dinuclear architectures containing two ions with coordination number 9 were formed. The structures of the complexes have been assigned on the basis of their solution spectroscopic and microanalytical data, and confirmed by X‐ray crystallography in the case of the europium(III) complex 2. The structural analysis of the dinuclear complex 2 showed the presence of two europium centers [Eu(1) and Eu(2)] and four ligands L. Each europium ion is coordinated by 9 donor atoms with typical Eu−N and Eu−O distances. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis, Crystal Structure and Magnetic Properties of A New Thiazolyl‐Substituted Nitronyl Nitroxide and Its Copper(II) Complexes
Authors: Wang Li‐Ya , Li Li‐Cun , Liao Dai‐Zheng , Jiang Zong‐Hui , Yan Shi‐Ping
Published: April 2004

A new building block for molecule‐based magnetic materials — thiazole‐substituted nitronyl nitroxide NIT2‐thz [1, NIT2‐thz = 4,4,5,5‐tetramethyl‐2‐(2′‐ thiazolyl)imidazolin‐1‐oxyl 3‐oxide] and its copper(II) complexes [Cu(NIT2‐thz)2(N3)2] (2) and [CuCl2(NIT2‐thz)2] (3) — have been synthesized and characterized structurally and magnetically. Compound 1 is found to contain two crystallographically independent molecules; the shortest contact between nitroxide groups is 4.900 Å. Both 2 and 3 are mononuclear complexes, in which the copper(II) centers are hexacoordinate. In complex 2, the copper(II) ion has an elongated octahedral geometry, but complex 3 has a rare compressed‐octahedral coordination sphere. Magnetic susceptibility data for compounds 1−3 have been measured in the range 5−300 K. There are ferromagnetic interactions (J = 10.13 cm−1) between the CuII ions and the radicals of 2, and antiferromagnetic interactions (J = −8.17 cm−1) between the CuII ions and the radicals of 3. The magnetic properties of complexes 2 and 3 are discussed in connection with their crystal structures. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
[Ni(C4H13N3)2]3(Sb3S6)2: The First Structure Containing Isolated Heterocyclic [Sb3S6]3− Anions
Authors: Kiebach Ragnar , Studt Felix , Näther Christian , Bensch Wolfgang
Published: April 2004

The novel thioantimonate(III) compound [Ni(dien)2]3(Sb3S6)2, which was synthesised under solvothermal conditions, contains isolated [Sb3S6]3− anions. In the X‐ray crystal structure, isolated cyclic [Sb3S6]3− anions occupy a boat‐like conformation and two different isomeric [Ni(dien)2]2+ cations are arranged in separate stacks. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
The First Structurally Authenticated Organomercury(1+) Thioether Complexes − Mercury−Carbon Bond Activation Related to the Mechanism of the Bacterial Enzyme Organomercurial Lyase
Authors: Wilhelm Michaela , Deeken Stefan , Berssen Eva , Saak Wolfgang , Lützen Arne , Koch Rainer , Strasdeit Henry
Published: April 2004

The new compounds [MeHg([9]aneS3)](BF4) (1), [MeHg([12]aneS3)](BF4) (2), and [(MeHg)2([14]aneS4)](BF4)2 (3) have been prepared and their crystal structures determined. In 1, the thioether acts as a tridentate ligand [Hg−S 2.611(2)−2.768(2) Å] and thus the metal atom is tetrahedrally coordinated, which is rare in organomercury chemistry. Temperature‐dependent 1H and 13C NMR spectra showed that this coordination is retained in acetonitrile solution. In crystalline 2 and 3, linear‐coordinated HgII occurs with Hg−S bond lengths of 2.441(4) and 2.425(2) Å. [MeHg([9]aneS3)]+ was found to be stable towards ligand substitution by CF3SO3− in dimethyl sulfoxide, whereas the thioether was partly displaced by CF3CO2− and completely by CH3CO2−. Protonolysis by the very strong Brønsted acid CF3SO3H in [D3]nitromethane transformed the methanido ligand into methane. The degree of Hg−C bond cleavage was ca. 25% for the four‐coordinate [MeHg([9]aneS3)]+ after 1 h, whereas no reaction was observed for two‐coordinate [MeHg(SEt2)]+ or MeHgCl under similar conditions even after 24 h. The product Hg2+ was trapped as [Hg([9]aneS3)2]2+, which is a six‐coordinate complex, as shown by a crystal structure analysis of [Hg([9]aneS3)2](BF4)2·2 CH3CN. Quantum chemical calculations [MP2/SDD + SDD ECP Hg, 6‐31+G(d,p) other elements] confirmed that hydrogen transfer activation barriers are significantly lower for “high”‐coordinate (CN > 2) complexes. Hg−C bond activation by the enzyme organomercurial lyase is possibly also based on multiple (cysteinyl) sulfur ligation. We propose a hypothetical reaction mechanism that involves an OH‐containing amino acid side chain or a water molecule simultaneously serving as a proton acceptor (from Cys−SH) and donor (to R− of RHg+). This mechanism is supported by quantum chemical calculations on a model system. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
A New Dichroic, Nitroso‐Bridged Complex of Rhenium: Di‐μ2‐chloro[μ2‐(η2‐N,O)‐N,N‐dimethyl‐4‐nitrosoaniline]bis[tricarbonylrhenium(I)]
Authors: Wilberger Roland , Krinninger Christoph , Piotrowski Holger , Mayer Peter , Lorenz Ingo‐Peter
Published: April 2004

The dimeric μ2‐amino‐phenoxy complexes of rhenium [(CO)3Re(μ2‐O∩NH2)]2 (1) do not react with the C‐nitroso compounds R−C6H4NO [R = NMe2 (2), H (2′)] in the presence of AlCl3 by a condensation reaction to give the desired azo dye complexes [(CO)3Re(μ2‐O∩N=NC6H4R)]2. Instead, they react to give the novel neutral η2‐N,O‐bridged C‐nitroso complexes [{CO)3ReCl}2ONC6H4R] (3, 3′) by means of a substitution reaction. Both complexes yield golden gleaming crystals, and their solutions are deeply blue (3) or violet (3′) due to the broad UV/Vis absorption at λ = 617 (3) and 505 nm (3′). Single crystals of 3, 3′ show nonlinear optical properties, they are dichroic and have a red and blue (3) or violet and green (3′) side. The molecular structures of 3, 3′ have been determined by single‐crystal X‐ray analyses. Both compounds contain two face‐joined octahedra, with two chloro and the NO ligands as bridges. The C‐nitroso groups together with the NC2 moiety of NMe2 (3) lie almost exactly within the symmetry plane of the molecules. Both the N atoms of 3 have a trigonal‐planar geometry. 3 and 3′ are the first single, neutral and dinuclear C‐nitroso complexes with the rare non‐assisted μ‐(η2‐N,O) bridge and only single atoms as additional bridges. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
A New Route to Cationic Half‐Sandwich Ruthenium(II) Complexes with Chiral Cyclopentadienylphosphane Ligands
Authors: Doppiu Angelino , Salzer Albrecht
Published: April 2004

Optically active cyclopentadienyl‐linked phosphane ligands Ln of general formula C5H5CH2CH(R)PR′2 (R = Ph, R′ = Ph, L1; R = Ph, R′ = Cy, L2; R = mesityl, R′ = Ph, L3) and C5H5CH(R)CH2PPh2 (R = Cy, L4; R = Bzl, L5) are synthesised by ring‐opening reactions of 1‐R‐spiro[2.4]hepta‐4,6‐dienes (R = Ph, Cy, mesityl, benzyl), with lithium phosphides LiPR′2 (Ar = Ph, Cy). Reaction of the ligands Ln with [RuH(η5‐C7H11)2][BF4] in acetonitrile at reflux affords the bis(acetonitrile) ruthenium(II) complexes [Ru(η5‐C5H4(C2H3R)PR′2‐κP)(CH3CN)2][BF4], in which the ligands are coordinated to the metal through the cyclopentadienyl and the phosphane moieties forming a chelate, in almost quantitative yields. The complexes are active catalysts in the redox isomerisation of geraniol affording chiral citronellal but with low enantioselectivity. They also catalyze an aldol‐type C−C coupling reaction between 3‐buten‐2‐ol and benzaldehyde affording almost racemic 4‐hydroxy‐3‐methyl‐4‐phenyl‐2‐butanone with good diastereoselectivity (syn/anti ratio up to 77:23). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis, Crystal Structures and Electrical Conductivities of the Ionic Liquid Compounds Butyldimethylimidazolium Tetrafluoroborate, Hexafluorophosphate and Hexafluoroantimonate
Authors: Kölle Philipp , Dronskowski Richard
Published: April 2004

The crystal structures of three very low‐melting ionic liquid (IL) salts containing the 1‐butyl‐2,3‐dimethylimidazolium cation and the fluoro anions BF4−, PF6− and SbF6− are reported. These are considered model compounds for ambient temperature ionic liquids, which are currently being explored as solvents for various types of synthetic reactions. All three compounds adopt significantly different structures in the solid state, highlighting the influence of counterion size in a series comprising a common cation. The crystal structures are discussed with respect to the possible existence of polar and non‐polar domains, which are considered to be involved with the solvation of polar and non‐polar substrates. The melting points of all three compounds are within the range 40−45 °C. A comparative measurement of conductivities of the molten salts in the vicinity of 20−50 °C has been made, including the new IL 1‐allyl‐2,3‐dimethylimidazolium tetrafluoroborate and the widely applied 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIMBF4). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Inclusion Complexes of the Bicyclic Aryl‐Substituted Sulfur‐Nitrogen Compounds Ar−CN5S3 with Fluorocarbon and Hydrocarbon Aromatics
Authors: Knapp Carsten , Lork Enno , Mews Rüdiger , Zibarev Andrey V.
Published: April 2004

Inclusion compounds with a stoichiometry of 2:1 were prepared from 7‐Ar‐1λ4,3λ4,5λ4‐trithia‐2,4,6,8,9‐pentaazabicyclo[3.3.1]nona‐1(9),2,3,5,7‐pentaenes Ar−CN5S3 and hexafluorobenzene (Ar = C6H5, 4‐CH3C6H4, 4‐C6H5C6H4 and 2,6‐F2C6H3) and toluene (Ar = C6F5), by crystallization of the bicycles from the corresponding aromatics. Similar to the pure host compounds, the bicycles in the inclusion compounds form centrosymmetric dimers. The packing of the dimers in the pure host compounds is dominated by the interaction of the substituents at the aryl groups, and in the inclusion compounds by the interaction of the host and guest. The parallel‐displaced arrangement of the aromatic rings of the host and guest is typical of non‐covalent π‐stacking interactions of the arene‐polyfluroarene type. The inability of benzene (in contrast to hexafluorobenzene) to form an inclusion compound with the title bicycle (Ar = C6H5) indicates that inclusion is driven by π‐stacking interactions of the arene‐polyfluoroarene type. Crystallization of the title bicycle (Ar = C6H5) from a 1:1 molar mixture of benzene and hexafluorobenzene gave the same inclusion compound as the crystallization from pure hexafluorobenzene. This can be considered as molecular recognition based on π‐stacking interactions. The compounds prepared provide the first example of aromatic units bearing extremely sterically demanding polyheteroatom bicyclic substituents involved in non‐covalent arene‐polyfluoroarene π‐stacking interactions. Attempts to prepare inclusion compounds with octafluoronaphthalene and decafluorobiphenyl, as well as co‐crystals of para‐tolyl‐ and pentafluorophenyl‐substituted bicycles, failed. The origin of the 2:1 stoichiometry and the lack of inclusion in the case of C12F10 and C10F8 are discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Optimal allocation of tie points in radial distribution systems using a genetic algorithm
Authors: Haghifam M.‐R.
Published: April 2004

For reliability enhancement of radial distribution systems, normally open tie switches are located in feeders. Using tie switches and sectionalizers, the configuration of feeders can be changed in fault conditions for supplying customers from other routes. This is called load restoration in radial distribution systems. In this paper, it is shown that reliability and success of load restoration have a connection with location and number of tie switches. Also, a novel approach for optimal determination of the number and location of tie switches using a genetic algorithm is proposed. In the optimization procedure, load importance using fuzzy membership functions, cost of energy not supplied and cost of tie switches are considered. The effectiveness of the proposed method is shown by simulation results in a radial distribution network.
Habituation to stress and dexamethasone suppression in rats with selective basal forebrain cholinergic lesions
Authors: Helm K.A. , Ziegler D.R. , Gallagher M.
Published: April 2004

Previous studies suggest a role for basal forebrain cholinergic neurons in enhancing the inhibitory influence of the hippocampus and medial prefrontal cortex (mPFC) on glucocorticoid stress responses mediated by the hypothalamic‐pituitary‐adrenocortical (HPA) axis. An inhibitory action of the basal forebrain cholinergic (BFC) system may occur through facilitation of stress‐related information processing and maintenance of glucocorticoid receptor (GR) expression and negative feedback signaling in these target regions. The current study investigated the possibility that BFC input to the hippocampus contributes to habituation of the glucocorticoid response following repeated exposure to a stressor. Cholinergic lesions were made by microinjections of the immunotoxin 192 IgG‐saporin into the medial septum/vertical limb of the diagonal band, and 3 weeks later rats were subjected to six daily sessions of restraint stress. Blood samples taken before, during and after acute stress revealed a significant increase in peak activation and protracted elevation of corticosterone in cholinergic lesioned rats. After 5 days of repeated stress, however, both groups habituated to the stressor, as indicated by similarly low corticosterone profiles throughout both the response and recovery period. Against that habituated background, rats were administered a dexamethasone challenge on day 6, so that feedback status could be examined. Dexamethasone‐induced suppression of endogenous corticosterone before, during, and after stress was significantly attenuated in lesioned rats. The profile of dysfunction in glucocorticoid regulation after selective cholinergic lesions in young animals may be relevant to the adrenocortical hyperactivity and negative feedback deficits seen in conditions such as normal aging and Alzheimer's dementia, in which integrity of the basal forebrain cholinergic system is compromised. © 2004 Wiley‐Liss, Inc.
Hippocampal damage in mouse and human forms of systemic autoimmune disease
Authors: Ballok David A. , Woulfe John , Sur Monalisa , Cyr Michael , Sakic Boris
Published: April 2004

Systemic lupus erythematosus (SLE) is frequently accompanied by neuropsychiatric (NP) and cognitive deficits of unknown etiology. By using autoimmune MRL‐lpr mice as an animal model of NP‐SLE, we examine the relationship between autoimmunity, hippocampal damage, and behavioral dysfunction. Fluoro Jade B (FJB) staining and anti‐ubiquitin (anti‐Ub) immunocytochemistry were used to assess neuronal damage in young (asymptomatic) and aged (diseased) mice, while spontaneous alternation behavior (SAB) was used to estimate the severity of hippocampal dysfunction. The causal relationship between autoimmunity and neuropathology was tested by prolonged administration of the immunosuppressive drug cyclophosphamide (CY). In comparison to congenic MRL +/+ controls, SAB acquisition rates and performance in the “reversal” trial were impaired in diseased MRL‐lpr mice, suggesting limited use of the spatial learning strategy. FJB‐positive neurons and anti‐Ub particles were frequent in the CA3 region. Conversely, CY treatment attenuated the SAB deficit and overall FJB staining. Similarly to mouse brain, the hippocampus from a patient who died from NP‐SLE showed reduced neuronal density in the CA3 region and dentate gyrus, as well as increased FJB positivity in these regions. Gliosis and neuronal loss were observed in the gray matter, and T lymphocytes and stromal calcifications were common in the choroid plexus. Taken together, these results suggest that systemic autoimmunity induces significant hippocampal damage, which may underlie affective and cognitive deficits in NP‐SLE. © 2004 Wiley‐Liss, Inc.
“I have often walked down this street before”: fMRI Studies on the hippocampus and other structures during mental navigation of an old environment
Authors: Rosenbaum R. Shayna , Ziegler Marilyne , Winocur Gordon , Grady Cheryl L. , Moscovitch Morris
Published: April 2004

The role of the hippocampus in recent spatial memory has been well documented in patients with damage to this structure, but there is now evidence that the hippocampus may not be needed for the storage and recovery of a spatial layout that was experienced long before injury. Such preservation may rely, instead, on a network of dissociable, extra‐hippocampal regions implicated in topographical orientation. Using functional magnetic resonance imaging (fMRI), we investigated this hypothesis in healthy individuals with extensive experience navigating in a large‐scale urban environment (downtown Toronto). Participants were scanned as they performed mental navigation tasks that emphasized different types of spatial representations. Tasks included proximity judgments, distance judgments, landmark sequencing, and blocked‐route problem‐solving. The following regions were engaged to varying degrees depending on the processing demands of each task: retrosplenial cortex, believed to be involved in assigning directional significance to locales within a relatively allocentric framework; medial and posterior parietal cortex, concerned with processing space within egocentric coordinates during imagined movement; and regions of prefrontal cortex, present in tasks heavily dependent on working memory. In a second, event‐related experiment, a distinct area of inferotemporal cortex was revealed during identification of familiar landmarks relative to unknown buildings in addition to activation of many of those regions identified in the navigation tasks. This result suggests that familiar landmarks are strongly integrated with the spatial context in which they were experienced. Importantly, right medial temporal lobe activity was observed, its magnitude equivalent across all tasks, though the core of the activated region was in the parahippocampal gyrus, barely touching the hippocampus proper. © 2004 Wiley‐Liss, Inc.
Olfactory learning‐induced increase in spine density along the apical dendrites of CA1 hippocampal neurons
Authors: Knafo Shira , Ariav Gal , Barkai Edi , Libersat Frederic
Published: April 2004

We have previously shown that rule learning of an olfactory discrimination task is accompanied by increased spine density along the apical dendrites of piriform cortex pyramidal neurons. The purpose of the present study was to examine whether such olfactory learning task, in which the hippocampus is actively involved, induces morphological modifications in CA1 pyramidal neurons as well. Rats were trained to discriminate positive cues in pairs of odors for a water reward. Morphological modifications were studied in Golgi‐impregnated neurons with light microscopy, 1 and 3 days after training completion. Spine densities were measured on the proximal region of apical dendrites and on basal dendrites after rule learning. Three days after training completion, the mean spine density on apical dendrites in neurons from trained rats was significantly higher by 20.5% than in neurons from pseudo‐trained and naive animals, which did not differ from each other. By contrast, there was no significant difference in spine density of basal dendrites among the three groups. As length and diameter of spiny dendritic segments did not change after learning, the learning‐related increase in spine density in neurons from trained rats may reflect a net increase in the number of excitatory synapses in the hippocampus following olfactory rule learning. © 2004 Wiley‐Liss, Inc.
Health insurance and savings over the life cycle—a semiparametric smooth coefficient estimation
Authors: Chou Shin‐Yi , Liu Jin‐Tan , Huang Cliff J.
Published: April 2004

Individuals save for future uncertain health care expenses. This is less efficient than pooling health risk through insurance. The provision of comprehensive health insurance may raise welfare by providing the missing market to smooth out consumption through the life cycle. We employ a semiparametric smooth coefficient model to examine the effects of the introduction of the National Health Insurance in Taiwan in 1995 on savings and consumption over the life cycle. The idea is to estimate the coefficients of health insurance which vary with age. Our results suggest that younger households are more sensitive to the risk reductions, and that they demonstrate a greater response in the reduction of their precautionary saving. Copyright © 2004 John Wiley & Sons, Ltd.
Poly(carbonate urethane) and poly(ether urethane) biodegradation: In vivo studies
Authors: Christenson Elizabeth M. , Dadsetan Mahrokh , Wiggins Michael , Anderson James M. , Hiltner Anne
Published: April 2004

Several strategies have been used to increase the biostability of medical‐grade polyurethanes while maintaining biocompatibility and mechanical properties. One approach is to chemically modify or replace the susceptible soft segment. Currently, poly(carbonate urethanes) (PCUs) are being evaluated as a replacement of poly(ether urethanes) (PEUs) in medical devices because of the increased oxidative stability of the polycarbonate soft segment. Preliminary in vivo and in vitro studies have reported improved biostability of PCUs over PEUs. Although several studies have reported evidence of in vitro degradation of these new polyurethanes, there has been no evidence of significant in vivo degradation that validates a degradation mechanism. In this study, the effect of soft segment chemistry on the phase morphology, mechanical properties, and in vivo response of commercial‐grade PEU and PCU elastomers was examined. Results from dynamic mechanical testing and infrared spectroscopy suggested that the phase separation was better in PCU as compared with PEU. In addition, the higher modulus and reduced ultimate elongation of PCU was attributed to the reduced flexibility of the polycarbonate soft segment. Following material characterization, the in vivo biostability and biocompatibility of PEU and PCU were studied using a subcutaneous cage implant protocol. The results from the cage implant study and cell culture experiments indicated that monocytes adhere, differentiate, and fuse to form foreign body giant cells on both polyurethanes. It is now generally accepted that the reactive oxygen species released by these adherent macrophages and foreign body giant cells initiate PEU biodegradation. Attenuated total reflectance–Fourier transform infrared analysis of explanted samples provided evidence of chain scission and crosslinking in both polyurethanes. This indicated that the PCU was also susceptible to biodegradation by agents released from adherent cells. These results reinforce the need to evaluate and understand the biodegradation mechanisms of PCUs. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 407–416, 2004
Differentiation of preosteoblasts is affected by implant surface microtopographies
Authors: Schneider Galen B. , Zaharias Rebecca , Seabold Denise , Keller John , Stanford Clark
Published: April 2004

Osteogenesis involves the recruitment of multipotent mesenchymal cells and the progressive differentiation of these cells into osteoblasts. The transcription factor Runx2 regulates osteoblast differentiation and expression of genes necessary for the development of a mineralized phenotype. The purpose of this study was to determine if preosteoblast cell differentiation associated with Runx2 and osteocalcin gene expression was influenced by implant surface microtopography. Human embryonic palatal mesenchymal cells (HEPM cells) were cultured on grooved or roughened cpTi implant discs. Cell phenotypes were evaluated with epifluorescent microscopy. Real‐time PCR was used for quantitative analysis of Runx2 and osteocalcin gene expression. HEPM cells mineralized when grown on rough and grooved implant surfaces relative to tissue culture plastic. Real‐time PCR showed significant (p < 0.05) increases in Runx2 and osteocalcin gene expression in cells cultured on rough and grooved implant microtopographies. These results suggest that preosteoblast cell differentiation is affected by implant surface microtopographies during osseointegration of dental implants. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 462–468, 2004
Forbidden induced subgraph characterization of cograph contractions
Authors: Zverovich Igor Ed. , Zverovich Inessa I.
Published: April 2004

Let S1, S2,…,St be pairwise disjoint non‐empty stable sets in a graph H. The graph H* is obtained from H by: (i) replacing each Si by a new vertex qi; (ii) joining each qi and qj, 1 ≤ i # j ≤ t, and; (iii) joining qi to all vertices in H – (S1 ∪ S2 ∪ ··· ∪ St) which were adjacent to some vertex of Si. A cograph is a P4‐free graph. A graph G is called a cograph contraction if there exist a cograph H and pairwise disjoint non‐empty stable sets in H for which G ≃ H*. Solving a problem proposed by Le [2], we give a finite forbidden induced subgraph characterization of cograph contractions. © 2004 Wiley Periodicals, Inc. J Graph Theory 46: 217–226, 2004
Anthropogenic changes in the landscape of west Java (Indonesia) during historic times, inferred from a sediment and pollen record from Teluk Banten
Authors: van der Kaars Sander , van den Bergh Gert D.
Published: April 2004

Palynological and charcoal analyses of shallow marine core 98‐28 from the northern coastal area of West Java provide a regional vegetation history during the last few centuries. Reliable chronostratigraphical control is provided by 210Pb analyses and the occurrence of the 1883 Krakatau ash/tsunami layer as a time marker. The results permit the distinction of four successive stages, reflecting increased disturbance and land clearance, with some evidence for the presence of deciduous lowland forests in the Banten area during the early Holocene. The establishment of coconut and pine plantations and the severe loss of biodiversity in the last few decennia are also echoed in the pollen record. The effect of the Krakatau eruption was insignificant compared with human impact on vegetation in the Banten area. Copyright © 2004 John Wiley & Sons, Ltd.
Holocene tephra horizons at Klocka Bog, west‐central Sweden: aspects of reproducibility in subarctic peat deposits
Authors: Bergman Jonas , Wastegård Stefan , Hammarlund Dan , Wohlfarth Barbara , Roberts Stephen J.
Published: April 2004

This paper presents one of the most extensive Holocene tephra records found to date in Scandinavia. Microtephra horizons originating from Icelandic eruptions were recorded in two ca. 2 m thick peat profiles at Klocka Bog in west‐central Sweden. Five of the microtephra horizons were geochemically correlated to the Askja‐1875, Hekla‐3, Kebister, Hekla‐4 and Lairg A tephras respectively. Radiocarbon‐based dating of these tephras broadly agree with previously published ages from Iceland, Sweden, Germany and the British Isles. The identification of the Lairg A tephra demonstrates a more widespread distribution than previously thought, extending the usefulness of Icelandic Holocene tephrochronology further north into west‐central Scandinavia. Long‐lasting snow cover and seasonal wind distribution in the lower stratosphere are suggested as factors that may be responsible for fragmentary tephra deposition patterns in peat deposits of subarctic Scandinavia. Copyright © 2004 John Wiley & Sons, Ltd.
A terrestrial record of Last Interglacial climate preserved by voluminous debris avalanche inundation in Taranaki, New Zealand
Authors: Newnham Rewi , Alloway Brent
Published: April 2004

At Airedale Reef, western North Island, New Zealand, a ca. 4 m thick volcanogenic debris avalanche deposit has facilitated the preservation of an enveloping sequence of peats with interbedded andesitic tephras spanning marine isotope (MIS) 5. The sequence closely overlies a wave‐cut terrace correlated to MIS 5e and, in turn, is overlain by andic beds with tephra interbeds including the Rotoehu and Kawakawa tephras deposited during early MIS 3 and mid‐MIS 2, respectively. Pollen analysis of the organic sequence shows a coherent pattern of fluctuating climate for the Last Interglacial–Last Glacial transition that corresponds with marine isotope stratigraphy and supports the contention that orbital variations were a primary factor in late Quaternary southern mid‐latitude climate change. A five‐stage subdivision of MIS 5 is clearly recognised, with marine isotope substage (MISS) 5b drier than MISS 5d, and the cooling transition from 5a to MIS 4 also may have been comparatively dry and characterised by natural fire, perhaps associated with volcanism. Several other examples of volcanic impact on vegetation and the landscape are evident. The Airedale Reef sequence exhibits strong similarities with fragmentary MIS 5 pollen records preserved elsewhere in New Zealand and enables the proxy record of southern mid‐latitude climatic variability during the Last Interglacial–Glacial cycle to be extended. Copyright © 2004 John Wiley & Sons, Ltd.
A Late‐glacial chironomid record from Hawes Water, northwest England
Authors: Bedford Alan , Jones Richard. T. , Lang Barbara , Brooks Stephen , Marshall Jim D.
Published: April 2004

This paper presents the results of a high‐resolution Late‐glacial chironomid stratigraphy from Hawes Water, a small carbonate lake in northern Lancashire. The samples were from a core taken from the terrestrialised margin of the present lake, which represents an intermediate depth between the true littoral and the profundal. The chironomid assemblage showed a high degree of sensitivity to both broad‐scale and short‐term temperature changes. Comparison with an existing proxy temperature record (δ18O) for the site confirmed the presence of four temperature inversions within the Late‐glacial Interstadial. A mean July air temperature inference model, derived from acid, soft‐water lakes in Norway and Svalbard, was applied to the data. Despite the absence of carbonate lakes within the Norwegian training set, there was a close similarity between trends in estimated July air temperature and the δ18O trace, with a particularly strong correspondence in the periods of clay deposition. This suggests that this model is highly robust. The inferred maximum Interstadial temperature was 13.4°C, dropping initially to 7.5°C in the Loch Lomond Stadial. Temperatures reach a maximum of nearly 10°C in this period, cool for a short period before rising rapidly to 13.2°C at the start of the Holocene. These temperatures are similar to but slightly higher than those estimated for Whitrig Bog, southeast Scotland, and lower than those inferred from coleopteran‐based models for sites in South Wales. Copyright © 2004 John Wiley & Sons, Ltd.
Small‐scale faulting, topographic steps and seismic ruptures in the Alhambra (Granada, southeast Spain
Authors: Azañón J. M. , Azor A. , Booth‐Rea G. , Torcal F.
Published: April 2004

The Alhambra (14th century AD) in Granada (southeast Spain) is built at the summit of a Pliocene to Lower Pleistocene conglomeratic formation. Tens of small‐scale normal faults crop out along the northern hillslope of the Alhambra, which have a N130–N150°E strike, dipping 65–75° mostly to the southwest. These are closely spaced faults (approximately 5–30 m) with centimetre to several metre displacements. Several topographic steps in this area coincide with hectometre‐ to kilometre‐scale faults with the same kinematics as the small‐scale ones. Some of these faults appear to be active and related to the present seismicity detected in this region, and associated with the cracks and other damage observed in the Alhambra. Several focal mechanisms calculated in this study are in accordance with the dominant NW–SE orientated normal faults. We interpret that the topographic steps of these faults are a consequence of repeated earthquakes during the past 800 ka. The last large earthquake of approximately 5.1 magnitude in this area occurred in 1431, destroying the Alixares Palace, the Arabian fence and part of the Alhambra wall. We consider the seismic risk associated with these faults to be moderate, as the displacement is partitioned into several hectometre‐ to kilometre‐scale faults. Copyright © 2004 John Wiley & Sons, Ltd.
Climatic change recorded by stable isotopes and trace elements in a British Holocene tufa
Authors: Garnett E. R. , Andrews J. E. , Preece R. C. , Dennis P. F.
Published: April 2004

Combined stable isotope (δ18O and δ13C) and trace element (Mg, Sr) geochemistry from bulk tufa calcite and ostracod shell calcite from an early Holocene British tufa reveal clear records of Holocene palaeoclimatic change. Variation in δ18O is caused principally by change in the isotopic composition of Holocene rainfall (recharge), itself caused mainly by change in air temperature. The δ13C variability through much of the deposit reflects increasing influence of soil‐zone CO2, owing to progressive woodland soil development. Bulk tufa Mg/Ca and Sr/Ca are controlled by their concentrations in the spring water. Importantly, Mg/Ca ratios are not related to δ18O values and thus show no temperature dependence. First‐order sympathetic relationships between δ13C values and Mg/Ca and Sr/Ca are controlled by aquifer processes (residence times, CO2 degassing and calcite dissolution/reprecipitation) and probably record intensity of palaeorainfall (recharge) effects. Stable isotope records from ostracod shells show evidence of vital effects relative to bulk tufa data. The ostracod isotopic records are markedly ‘spiky’ because the ostracods record ‘snapshots’ of relatively short duration (years), whereas the bulk tufa samples record averages of longer time periods, probably decades.

The δ18O record appears to show early Holocene warming, a thermal maximum at ca. 8900 cal. yr BP and the global 8200 yr BP cold event. Combined δ13C, Mg/Ca and Sr/Ca data suggest that early Holocene warming was accompanied by decreasing rainfall intensity. The Mg/Ca data suggest that the 8200 yr BP cold event was also dry. Warmer and wetter conditions were re‐established after the 8200 yr BP cold event until the top of the preserved tufa sequence at ca. 7100 cal. yr BP. Copyright © 2004 John Wiley & Sons, Ltd.
Kinetics of the gas‐phase reaction of CF3OC(O)H with OH radicals at 242–328 K
Authors: Chen L. , Kutsuna S. , Tokuhashi K. , Sekiya A.
Published: April 2004

The rate constants, k1, of the reaction of CF3OC(O)H with OH radicals were measured by using a Fourier transform infrared spectroscopic technique in an 11.5‐dm3 reaction chamber at 242–328 K. OH radicals were produced by UV photolysis of an O3–H2O–He mixture at an initial pressure of 200 Torr. Ozone was continuously introduced into the reaction chamber during UV irradiation. With CF3OCH3 as a reference compound, k1 at 298 K was (1.65 ± 0.13) × 10−14 cm3 molecule−1 s−1. The temperature dependence of k1 was determined as (2.33 ± 0.42) × 10−12 exp[−(1480 ± 60)/T] cm3 molecule−1 s−1; possible systematic uncertainty could add an additional 20% to the k1 values. The atmospheric lifetime of CF3OC(O)H with respect to reaction with OH radicals was calculated to be 3.6 years. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 337–344 2004
Experimental study of fuel decomposition and hydrocarbon growth processes for practical fuel components in nonpremixed flames: MTBE and related alkyl ethers
Authors: McEnally Charles S. , Pfefferle Lisa D.
Published: April 2004

Fuel decomposition and hydrocarbon growth processes of methyl tert‐butyl ether (MTBE) and related alkyl ethers have been studied experimentally in soot‐producing nonpremixed flames. Temperature, C1–C12 hydrocarbons, and major species were measured in coflowing methane/air flames whose fuel was separately doped with 5000 ppm of MTBE, n‐butyl methyl ether (NBME), sec‐butyl methyl ether (SBME), ethyl tert‐butyl ether (ETBE), and tert‐amyl methyl ether (TAME; =1,1‐dimethylpropyl methyl ether). The consumption rates of the dopants, several simple kinetic calculations, and the dependence of the observed products on fuel composition indicate that the dominant decomposition process was unimolecular dissociation, not H‐atom abstraction. The dominant dissociations were four‐center elimination of alcohols for the doubly branched ethers (MTBE, ETBE, and TAME) and CO fission for the linear ether (NBME), while four‐center elimination and CO fission were comparably important for the singly branched ether (SBME). These dissociations produced alkenes which further reacted to produce alkadienes/alkynes, alkenynes, acetylenic compounds, and aromatics. The dependence of the maximum benzene mole fractions on fuel composition was consistent with benzene formation through reactions of highly‐unsaturated C3 and/or C4 hydrocarbons (C3H3, n‐C4H3, C4H4, n‐C4H5, etc.). © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 345–358, 2004
Peptide/Protein Hybrid Materials: Enhanced Control of Structure and Improved Performance through Conjugation of Biological and Synthetic Polymers
Authors: Vandermeulen Guido W. M. , Klok Harm‐Anton
Published: April 2004

Summary: The conjugation of peptides/proteins and synthetic polymers is a useful strategy to overcome some of the limitations related to the use of the individual components. This review will highlight two aspects: enhanced structural control at the nanometer level and improved performance, in particular with respect to biomedical applications. In the former case, peptide sequences are mainly used to mediate self‐assembly of synthetic polymers. In the latter case, conjugation of an appropriate synthetic polymer to a pharmaceutically active peptide/protein can, for example, prevent premature enzymatic degradation and enhance blood circulation times, which is therapeutically advantageous.

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Monitoring of the Gelation Process on a Radical Chain Cross‐Linking Reaction Based onN‐Vinylcaprolactam by Using Dynamic Light Scattering
Authors: Boyko Volodymyr , Richter Sven
Published: April 2004

Summary:The sol‐gel transition of radical chain cross‐linking copolymerization system [N‐vinylcaprolactam (monomer)/3,3′‐(ethane‐1,1‐diyl)bis(1‐vinyl‐2‐pyrrolidone) (cross‐linker)] has been studied using in situ by time‐resolved dynamic light scattering (DLS). A critical dynamical behavior was observed near the sol‐gel transition, which is characterized by the presence of power‐law spectra over three decades in the time‐intensity correlation functiong2(t) − 1 ∼ t−μ. It was found, that the critical exponentμis dependent on the amount of the cross‐linker: higher the amount of the cross‐linker, higher is the value of the exponentμ. The occurrence of speckle patterns in the scattered intensity profile and of a power law behavior in the time‐intensity correlation function appeared at the same time. At the lowest concentration of 0.25% cross‐linker, no power law was observed. The estimated values forμwere in the range of 0.39 ≤ μ ≤ 0.577. It can be concluded, that the amount of branching in the critical gel determines the value ofμ.

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Photoreversible Chain Extension of Poly(ethylene glycol)
Authors: Trenor Scott R. , Long Timothy E. , Love Brian J.
Published: April 2004

Summary: Coumarin containing poly(ethylene glycol) monols and diols were prepared in a telechelic fashion using quantitative end group esterification. The coumarin modified poly(ethylene glycol) monols and diols were solution cast into films (1 to 15 μm) and chain extended via the dimerization of the coumarin derivatives with UVA (>300 nm) light irradiation. The coumarin‐modified PEG diol doubled in molecular weight, and the molecular weight distribution increased from 1.17 to 2.75 upon exposure to 110 J · cm−2 of UVA light. The chain extended poly(ethylene glycol)s were subsequently converted to their original molecular weight via the photocleavage reaction of the coumarin dimer at 254 nm with less than 2 J · cm−2. The photoreversible chain length modulation was monitored utilizing GPC, DSC and UV‐Vis spectroscopy.

Molecular weight modulation of COU‐PEG‐COU.

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Molecular weight modulation of COU‐PEG‐COU.
Evidence of Intramolecular Cyclization in Copolymerization of Ethylene with 1,3‐Butadiene: Thermal Properties of the Resulting Copolymers
Authors: Monteil Vincent , Spitz Roger , Barbotin Fanny , Boisson Christophe
Published: April 2004

Summary: Ethylene and butadiene were copolymerized with a silylene‐bridged bis(fluorenyl) complex {[Me2Si(C13H8)2]NdCl} (1) in combination with various alkylating agents (BuLi/AlH(iBu)2, (Bu)MgCl, Mg(Bu)(Oct)). Copolymers have a unique microstructure since they contain 1,2‐cyclohexane rings and unsaturations along the polymer chain. An intramolecular mechanism was proposed for the formation of six‐membered rings. The influence of these cyclic structures on thermal properties of the copolymers has been investigated.

Proposed mechanism for formation of 1,2‐cyclohexane rings.

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Proposed mechanism for formation of 1,2‐cyclohexane rings.
Lattice embeddings and array noncomputable degrees
Authors: Walk Stephen M.
Published: April 2004

We focus on a particular class of computably enumerable (c. e.) degrees, the array noncomputable degrees defined by Downey, Jockusch, and Stob, to answer questions related to lattice embeddings and definability in the partial ordering (ℜ︁, ≤) of c. e. degrees under Turing reducibility. We demonstrate that the latticeM5 cannot be embedded into the c. e. degrees below every array noncomputable degree, or even below every nonlow array noncomputable degree. As Downey and Shore have proved that M5 can be embedded below every nonlow2 degree, our result is the best possible in terms of array noncomputable degrees and jump classes. Further, this result shows that the array noncomputable degrees are definably different from the nonlow2 degrees. We note also that there are embeddings of M5 in which all five degrees are array noncomputable, and in which the bottom degree is the computable degree 0 but the other four are array noncomputable. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Boolean algebras of definable sets in weakly o‐minimal theories
Authors: Leonesi Stefano , Toffalori Carlo
Published: April 2004

We consider the sets definable in the countable models of a weakly o‐minimal theory T of totally ordered structures. We investigate under which conditions their Boolean algebras are isomorphic (hence T is p‐ω‐categorical), in other words when each of these definable sets admits, if infinite, an infinite coinfinite definable subset. We show that this is true if and only if T has no infinite definable discrete (convex) subset. We examine the same problem among arbitrary theories of mere linear orders. Finally we prove that, within expansions of Boolean lattices, every weakly o‐minimal theory is p‐ω‐categorical. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An infinitary variant of Metric Temporal Logic over dense time domains
Authors: Baratella Stefano , Masini Andrea
Published: April 2004

We introduce a complete and cut‐free proof system for a sufficiently expressive fragment of Metric Temporal Logic over dense time domains in which a schema of induction is provable. So doing we extend results previously obtained by Montagna et al. to unbounded temporal operators. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)