bluuebunny/crossref_metadata_2025_split huggingface dataset:
Climatic oscillations in central Italy during the Last Glacial–Holocene transition: the record from Lake Accesa
Authors: Magny Michel , de Beaulieu Jacques‐Louis , Drescher‐Schneider Ruth , Vannière Boris , Walter‐Simonnet Anne‐Véronique , Millet Laurent , Bossuet Gilles , Peyron Odile 
Published: March 2006

AbstractThis paper presents an event stratigraphy based on data documenting the history of vegetation cover, lake‐level changes and fire frequency, as well as volcanic eruptions, over the Last Glacial–early Holocene transition from a terrestrial sediment sequence recovered at Lake Accesa in Tuscany (north‐central Italy). On the basis of an age–depth model inferred from 13 radiocarbon dates and six tephra horizons, the Oldest Dryas–Bølling warming event was dated to ca. 14 560 cal. yr BP and the Younger Dryas event to ca. 12 700–11 650 cal. yr BP. Four sub‐millennial scale cooling phases were recognised from pollen data at ca. 14 300–14 200, 13 900–13 700, 13 400–13 100 and 11 350–11 150 cal. yr BP. The last three may be Mediterranean equivalents to the Older Dryas (GI‐1d), Intra‐Allerød (GI‐1b) and Preboreal Oscillation (PBO) cooling events defined from the GRIP ice‐core and indicate strong climatic linkages between the North Atlantic and Mediterranean areas during the last Termination. The first may correspond to Intra‐Bølling cold oscillations registered by various palaeoclimatic records in the North Atlantic region. The lake‐level record shows that the sub‐millennial scale climatic oscillations which punctuated the last deglaciation were associated in central Italy with different successive patterns of hydrological changes from the Bølling warming to the 8.2 ka cold reversal. Copyright © 2006 John Wiley & Sons, Ltd.
Double‐Hydrophilic Polymer Brushes: Synthesis and Application for Crystallization Modification of Calcium Carbonate
Authors: He Lihong , Zhang Yanhong , Ren Lixia , Chen Yongming , Wei Hao , Wang Dujin 
Published: March 2006

AbstractSummary: A water‐soluble diblock copolymer composed of poly(ethylene glycol) (PEG) and a cylindrical poly(acrylic acid) (PAA) brush is reported. It is prepared by a ‘grafting from’ approach using stepwise atom transfer radical polymerization combined with group transformation. Uniform molecular brushes, PEG113‐b‐P(MA‐g‐PAA26)169, are thus prepared as indicated by atom force microscopy analysis. This PAA densely grafted polymer is used to induce the crystallization of calcium carbonate in aqueous solution. Different experimental conditions, fast mixing reactions and static diffusion methods, are applied to explore the effect of polymer brushes on the crystallization, which is characterized by scanning electron microscopy, X‐ray diffraction, and thermogravimetric analysis.AFM image of the polymer brushes on mica and an SEM image of CaCO3 particles prepared in its presence.magnified imageAFM image of the polymer brushes on mica and an SEM image of CaCO3 particles prepared in its presence.
Some Properties of Nanomaterials prepared through the Encapsulation within Polymer Fibrils of 1‐D Filaments of a Self‐assembled Bicopper Complex
Authors: Guenet Jean‐Michel , Poux Sandrine , Thierry Annette 
Published: March 2006

AbstractSummary: A new type of nanomaterial prepared from ternary systems polymer/bicopper organic complex/solvent is presented. Each binary system displays differing types of behaviour: The polymer solutions produce thermoreversible gels while the bicopper organic complex forms randomly‐dispersed, self‐assembled threads in organic solvents The nanomaterial results from the encapsulation of the bicopper complex threads into the polymer fibrils through heterogeneous nucleation. The magnetic behaviour and the rheological properties of these materials will be briefly outlined and discussed.
Molecular Recognition and Catalysis: from Macrocyclic Receptors to Molecularly Imprinted Metal Complexes
Authors: Karakhanov Edward A. , Karapetyan Lyusyen M. , Kardasheva Yulia S. , Maksimov Anton L. , Runova Elena A. , Skorkin Vitaliy A. , Terenina Maria V. 
Published: March 2006

AbstractSummary: The results of studying a number of reactions catalyzed by several types of soluble macromolecular catalytic systems capable of selectively binding organic substrates, namely, modified cyclodextrins, calixarenes and dendrimers are presented. The use of modified cyclodextrins as components of a catalytic system in the phenol and benzene hydroxylation by hydrogen peroxide allows one both to increase the catalytic activity and to change significantly the chemical selectivity. Phosphorilated calixarene – Rh catalytic systems was found to be catalytically active in hydroformylation of linear alkenes C7–C12. The results of experiments on the oxidation of C7–C16 alkenes show that, when the ligand is the dendrimer molecule, the fraction of forming methyl ketones substantially increases for the substrates C7–C9. For the higher alkenes, this effect is not observed.
Solid Polymer Electrolytes Studied by NMR Spectroscopy and DFT Calculations
Authors: Spěváček Jiří , Brus Jiří , Dybal Jiří 
Published: March 2006

AbstractSummary: Results obtained recently on polymer electrolytes poly(ethylene oxide) (PEO)/LiCF3SO3 and poly(2‐ethyl‐2‐oxazoline) (POZ)/AgCF3SO3 by a combination of solid‐state 13C and 1H NMR spectroscopy and DFT quantum‐chemical calculations are discussed. Essentially the same local structure was found for the amorphous and crystalline phases of semicrystalline PEO/LiCF3SO3 polymer electrolyte. The amorphous POZ/AgCF3SO3 complex has a defined stoichiometry with two POZ monomeric units per one AgCF3SO3. A close contact between the metal salt and polymer was determined for both investigated systems from the Lee‐Goldburg cross‐polarization 1H → 13C dynamics.
Polymeric Quasi‐one‐dimensional Platinum Compounds
Authors: Bremi Juliane , Fontana Margherita , Caseri Walter , Smith Paul 
Published: March 2006

AbstractSummary: Magnus' green salt, [Pt(NH3)4][PtCl4], is a quasi‐one‐dimensional inorganic semiconductor containing linear arrays of platinum atoms. Its use in materials science is limited since it does not melt prior to decomposition and is largely insoluble in water and organic solvents which makes processing difficult. We have remedied this deficiency by substitution of coordinated ammonia or chloride by monodentate or bidentate ligands, including optically active aminoalkanes, resulting in soluble compounds. Depending on the ligands, the polymeric supramolecular structure in the solid state persisted in solution or decayed to ion pairs. In the solid state, the ligands markedly influenced the Pt‐Pt distances, which on their part directed optical and electrical properties. Thus, high chiral anisotropy factors, cryochromic behavior, or (anisotropic) electric semiconductivity were found. A number of derivatives were processed to oriented films and fibers. Some complexes exhibited the color and electric characteristics of Magnus' green salt and thus can be regarded as soluble equivalents of Magnus' green salt. Oriented films of such a compound were applied as active semiconducting layer in field‐effect transistors (FET). The corresponding devices showed remarkable stability towards air and water which was superior to that of unprotected field‐effect transistors based on typical organic polymers.
Optical Properties of M(II) Schiff‐base Complexes Dispersed in Ethylene based Polymers
Authors: Boccia Massimiliano , Liuzzo Vincenzo , Pucci Andrea , Narducci Piero , Ruggeri Giacomo 
Published: March 2006

AbstractSummary: Several salicylaldiminate M(II) complexes of Nickel, Copper and Cobalt have been prepared and mixed with ethylene based polymers in order to prepare new composite materials with interesting morphological and optical properties by profiting of the presence of alkyl chains and push‐pull substituents connected to the ligand structure. The phase dispersion behaviour of the binary films has been studied by scanning electron microscopy (SEM) and x‐ray microanalysis, whereas the optical properties of the composite samples have been evaluated by UV‐vis and fluorescence spectroscopy. The results in absorption have been analysed in terms of the anisotropy induced by the mechanical orientation of the polymer matrix and by the role of the metal centre according to the different strength of the complexes transition dipole moment. The luminescence behaviour have been discussed in terms of potential developments aimed at preparing polymeric supported Schiff base ligands for metal ions sensor applications.
Silica Polyamine Composites: New Supramolecular Materials for Cation and Anion Recovery and Remediation
Authors: Hughes Mark , Miranda Paul , Nielsen Dan , Rosenberg Edward , Gobetto Roberto , Viale Alessandra , Burton Sarah 
Published: March 2006

AbstractSummary: The surface coverage of amorphous silica gels used in the synthesis of silica polyamine composites has been investigated by 29Si NMR. By diluting the polyamine anchor silane, chloropropyl trichlorosilane, with methyl trichlorosilane it was found that surface coverage could be markedly improved for a range of amine polymers after grafting to the silica surface. The commensurate decrease in the number of anchor points and increase in the number of free amines results in an increase in metal capacity and/or an improvement in capture kinetics. Solid state CPMAS‐13C NMR has been employed to investigate the structure and metal ion binding of a series of these composite materials. It is reported that the highly branched polymer, poly(ethyleneimine) (PEI) exhibits much broader 13C NMR resonances than the linear polymers poly(allylamine) (PAA) and poly(vinylamine) (PVA). These results are understood in terms of the low energy conformations calculated from molecular modeling studies. Three new applications of the technology are also presented: 1) separation of lanthanides as a group from ferric ion and all other divalent ions; 2) a multi step process for recovering and concentrating the valuable metals in acid mine drainage; 3) a process for removing low level arsenic and selenium in the presence of sulfate using immobilized cations on the composite materials.
Synthesis and Photophysical Properties of Some PEG Substitued Titanyl Phthalocyanine Derivatives
Authors: Kang Hyo‐Jin , Kang Eun‐Hee , Park Sang‐Wook , Lee Jae‐Wook , Lee Jin‐ Kook 
Published: March 2006

AbstractSummary: Polyethylene glycol substituted titanyl phthalocyanine was prepared in two steps starting from phthalonitrile and characterized by FT‐IR, UV‐vis spectrophotometry, and fluorescence spectrophotometry. The titanyl phthocyanine derivatives (TiOPcs) showed high solubility in common organic solvents, such as, CH3Cl and DMF. These compounds decreased in absorbance intensity with increase of molecular weight of polyethylene glycol at maxima wavelength of visible range. The fluorescence spectra showed a fluorescence emission near 690 nm with a quantum yield of 0.05–0.32 (λex = 625 nm).
Ultrafiltration of Polymer‐Metal Complexes for Metal Ion Removal from Wastewaters
Authors: Molinari Raffaele , Argurio Pietro , Poerio Teresa 
Published: March 2006

AbstractSummary: A case‐study using macromolecular metal complexes is described. The results of a process named Polymer Assisted Ultrafiltration (PAUF) for ion removal from various types of waters is reported. The water soluble polymers such as polyetilenimine (PEI), polyacrylic acid (PAA), polyacrylic acid sodium salt (PAASS) and poly(dimethylamine–co–epichlorohydrin–co–ethylenediamine) (PDEHED) as chelating agents, the Cu2+ as model ion and five ultrafiltration membranes have been used. The complexing agents were previously tested to establish the binding capacity and the best operating conditions for the process. Among the tested polymers the PEI appeared the most interesting one because its binding mechanism does not involve a counter ion release. It was tested in the simulation of wastewaters treatment containing the Cu2+ ion chelated with citric acid; this is a problem of interest in the recycling of water from soil washing operations. The polyethylenimine quantitatively bound the copper‐citrate chelate at pH 5.5 and the three component complex was separated by UF membranes producing a permeate with very low metal concentration. The polymer regeneration was carried out with good results by operating with the diafiltration method. The copper ion present in the diafiltration permeate in a form chelated with citric acid was recovered by oxidising the citrate in a membrane photoreactor. The positive results of the described case‐study show that Macromolecule‐Metal Complexes play a key role for running effectively and selectively the PAUF process for removing metal ions from various type of waters.
Effects of Nanocrystalline Porous TiO2 Films on Interface Adsorption of Phthalocyanines and Polymer Electrolytes in Dye‐Sensitized Solar Cells
Authors: Lee Hyun‐Jeong , Kim Woo‐Seok , Park Sung‐Hae , Shin Won Suk , Jin Sung‐Ho , Lee Jin‐Kook , Han Sang‐Min , Jung Ki‐Suck , Kim Mi‐Ra 
Published: March 2006

AbstractSummary: We have synthesized three kinds of titanylphthalocyanines with different crystal structures (TiOPcs; PcT2000R, PcT3000R, and PcT1100S) and analyzed their crystal structure by X‐ray Diffraction (XRD), Fourier transfer IR (FT‐IR) spectroscopy, and Transmission Electron Microscope (TEM). From experimental results, we have confirmed that PcT2000R was estimated to be alpha‐form; PcT3000R was beta‐form, and PcT1100S was gamma‐form. Quasi‐solid state dye‐sensitized solar cell (DSSC) devices were prepared with a polymer electrolyte using TiOPcs as a co‐adsorbent. The DSSC device using TiOPc has higher power conversion efficiency than without TiOPc, due to decrease of electron transfer distance by the interface adsorption between TiO2 film and polymer electrolyte. Also, we have studied the effects of the crystal structures of TiOPcs on the property of polymer electrolyte and the performance of the DSSC device. The best result on power conversion efficiency was 7.13% in DSSC device using PcT3000R having its highest stability. The open‐circuit voltage (Voc) was 0.69 V, the short‐circuit current density (Jsc) was 20.02 mA/cm2, and the Fill Factor (FF) was 0.52. the addition of TiOPc as co‐adsorbent is useful for improve to the performances of DSSC devices such as Voc, Jsc, and power conversion efficiency.
Anion Influence in Metallocene‐based Olefin Polymerisation Catalysts
Authors: Wilson Polly A. , Hannant Mark H. , Wright Joseph A. , Cannon Roderick D. , Bochmann Manfred 
Published: March 2006

AbstractThe effects of perfluoroarylborate anions on the activities of metallocene‐based propylene polymerisation catalysts on the one hand, and on the cationic polymerisation of isobutylene to butyl rubber are summarised. In both systems the anions follow the same activity sequence, [CN{B(C6F5)3}2]−  > [H2N{B(C6F5)3{2]−] ≈ [B(C6F5)4]− > [MeB(C6F5)3]−. In an effort to maximise the delocalisation of negative charge over large volumes, new anions based on the very bulky borane B(C6F4‐2‐C6F5)3 (PBB) with longer linking groups have been prepared, e.g [N(CN‐PBB)2]−. The van der Waals volumes of representative anions and cations are reported. The influence of anions on the structure of catalytically active species is demonstrated using (SBI)Zr(CH2SiMe3)(µ‐Me)B(C6F5)3 and [(SBI)Zr(CH2SiMe3)+ · · · B(C6F5)] as examples. The alkyl ligand in the latter is stabilised by agostic bonding, which relegates the anion into the outer coordination sphere. The differences in ion pair structure profoundly influence the nature of chain termination in 1‐hexene polymerisations: whereas the MeB(C6F5) catalyst gives a mixture of vinylene and vinylidene terminations, with the latter predominanting at higher temperatures and conversions, the B(C6F5) system terminates exclusively after 2,1‐misinsertion to give vinylene‐terminated poly(1‐hexene).
Coordination Homopolymerization of ω–undecenyl Poly(styrene‐block‐isoprene) Macromonomers in the Presence of CGC‐Ti/MAO Complexes
Authors: Catarí Edgar , Peruch Frédéric , Isel François , Lutz Pierre Joseph 
Published: March 2006

AbstractThis paper deals with the coordination homopolymerization of ω–undecenyl poly(styrene‐block‐isoprene) macromonomers. The synthesis of the macromonomers made use of an anionic living poly(styrene‐block‐isoprene) copolymer which is deactivated at low temperature by 11‐bromo‐1‐undecene. The ability of these macromonomers to get involved in coordination homopolymerization in the presence of selected titanium catalysts was discussed. Special emphasis was given to the influence of polymerization temperature, macromonomer molar mass and concentration on the yield of homopolymerization and average degree of polymerization (DPn). In the presence of the CGC‐Ti/MAO catalyst, macromonomer conversion, determined by SEC, was between 35 to 52 wt.‐%, and DPn was between 5 to 14 depending upon the experimental conditions. However, as revealed by SEC/LS, the resulting comb‐shaped polymers (PE‐graft‐(PI‐block‐PS), are characterized by sharp molar distributions. Increasing macromonomer molar mass, led to only a slight decrease of DPn whereas conversion increased moderately. Other titanium catalysts such as CpTiCl3/MAO and Cp*TiCl3/MAO only caused macromonomer dimerization.
PP/PMMA Block Copolymers by Combination of ATRP and Metallocene Catalysis
Authors: Dix Albrecht , Ptacek Saija , Poser Sven , Arnold Manfred 
Published: March 2006

AbstractPP‐b‐PMMA has been synthesized by a combination of metallocene catalysis and the controlled radical polymerization technique ATRP. Cp2ZrCl2/MAO and (Me4Cp)SiMe2(N‐tert‐Bu)TiCl2/MAO were used for the synthesis of atactic polypropylene. By a series of chemical modifications pp macroinitiators for the ATRP polymerization of MMA were synthesized. The PP‐b‐PMMA with polydispersities from 1.8–2.8 and an Mn ranging from 8 to 26 kg/mol was characterized by 1H‐NMR,SEC and DSC.
Polymerization of Polar Monomers Using Cyclopentadienyl Complexes of the Alkaline Earth Metals
Authors: Steffens Alexandra , Schumann Herbert 
Published: March 2006

AbstractTetramethylcyclopentadienyl complexes of magnesium, calcium and strontium are efficient catalysts at −78 °C for the solution polymerization of polar monomers such as alkyl methacrylates in the presence of only small amounts of triethylaluminium as cocatalyst. The molecular mass of the resulting polymers is predictable on the monomer/catalyst ratio. The polymerization reaction follows a first order kinetics with respect to the initial catalyst concentration. Block‐copolymers are easily available by sequential dosage of the monomer. A living polymerization mechanism is proposed involving activation of the catalyst by alkylation and subsequent insertion of coordinated monomers.
Activation of Metallacyclopropenes, five‐membered Metallacyclocumulenes and Metallacyclopentynes of Zirconium with iBu2AlH
Authors: Burlakov Vladimir V. , Bach Marc A. , Klahn Marcus , Arndt Perdita , Baumann Wolfgang , Spannenberg Anke , Rosenthal Uwe 
Published: March 2006

AbstractThe recently described reaction products of zirconacyclopropenes Cp′2Zr(η2‐Me3SiC2SiMe3) and five‐membered zirconacyclocumulenes (zirconacyclopenta‐2,3,4‐trienes) Cp*2Zr(η4‐1,2,3,4‐RC4R), Cp* = η5‐pentamethylcyclopentadienyl, R = Me, Me3Si and Ph, with i‐Bu2AlH are active catalysts in the polymerization of ethylene and in the ring opening polymerization of ε‐caprolactone. Here we describe the different activity of these complexes after thermal activation or if additional i‐Bu2AlH together with water are added. These results are compared to those which were obtained with the complexes Cp2Zr(η4‐1,2,3,4‐H2C4H2), rac‐(EBTHI)ZrF2, rac‐(EBTHI)ZrCl2, [rac‐(EBTHI)Zr(H)(µ‐H)]2 and rac (EBTHI)Zr(F)CH2‐CH2(2‐Py) after activation with i‐Bu2AlH together with water.
19F NMR Investigations of the Reaction of B(C6F5)3 with Different Tri(alkyl)aluminum Compounds
Authors: Janiak Christoph , Lassahn Paul‐Gerhard 
Published: March 2006

AbstractTris(pentafluorophenyl)borane, B(C6F5)3 reacts with triethylaluminum, AlEt3 to a mixture of Al(C6F5)3−nEtn and Al2(C6F5)6−nEtn compounds depending on the B/Al ratio. From excess borane to excess AlEt3 the species Al(C6F5)3 → Al(C6F5)2Et $\mathbin{\lower.3ex\hbox{$\buildrel\textstyle\leftarrow\over{\smash{\rightarrow}\vphantom{_{\vbox to.5ex{\vss}}}}$}}$ Al2(C6F5)4Et2 → Al2(C6F5)3Et3 → Al2(C6F5)2Et4 → Al2(C6F5)Et5 are formed and differentiated by their para‐F signal in 19F NMR. The reaction between B(C6F5)3 and the higher aluminum alkyls, tri(iso‐butyl)aluminum and tri(n‐hexyl)aluminum AlR3 (R = i‐Bu, n‐C6H13) is slower and requires AlR3 excess to shift the C6F5 $\leftrightarrow$ R exchange equilibria to almost complete formation of Al(C6F5)R2 and BR3. At equimolar ratio the equilibrium lies on the side of the unchanged borane together with its boranate [B(C6F5)3R]− anion. For tri(n‐octyl)aluminum even at large Al(n‐C8H17)3 excess no C6F5 $\leftrightarrow$ alkyl exchange can be observed, but boranate anions form.
Diffusion‐weighted imaging in Huntington's disease
Authors: Seppi Klaus , Schocke Michael F.H. , Mair Katherina J. , Esterhammer Regina , Weirich‐Schwaiger Helga , Utermann Barbara , Egger Karl , Brenneis Christian , Granata Roberta , Boesch Sylvia , Poewe Werner , Wenning Gregor K. 
Published: March 2006

AbstractHuntington's disease (HD) is an autosomal dominant progressive neurodegenerative disorder that results from an expanded trinucleotide (CAG) repeat on the huntingtin gene. Neurodegeneration in HD affects most prominently the basal ganglia. Therefore, diffusivity was obtained in the basal ganglia and thalamus of 29 patients with early HD and 27 healthy volunteers by means of the trace of the diffusion tensor (Trace(D)). Putaminal, caudate, pallidal, and thalamic Trace(D) values were increased in patients with HD compared with controls. Increased diffusivity in the putamen and caudate nucleus correlated with global functional impairment, CAG repeat length, as well as bicaudate ratio. Diffusion‐weighted imaging appears to be a promising surrogate marker for disease severity in HD. Sensitivity to change remains to be established longitudinally. © 2006 Movement Disorder Society
Analysis and equivalent circuit of aperture‐coupled cavity‐fed microstrip patch antenna
Authors: Kim Jeong Phill 
Published: March 2006

AbstractA simple but accurate equivalent circuit of an aperture‐coupled cavity‐fed microstrip patch antenna is developed. It consists of ideal transformers, admittance elements, and transmission lines, and the related circuit‐element values are computed by applying the reciprocity theorem and complex power concept with the spectral‐domain immittance approach. The antenna input impedance calculated from network theory is compared with the measured data, and their good agreement validates the simplicity and accuracy of the proposed equivalent‐circuit model. Based on the proposed theory, the effect of structural parameters on the antenna characteristics is also examined. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 843–846, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21493