bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Nanocrystalline Iron Oxide Particles in the Iron(III) Acetate/Alcohol/Acetic Acid System
Authors: Gotić Marijan , Musić Svetozar 
Published: January 2008

AbstractNanosized iron oxide particles were synthesised without the addition of water by autoclaving iron(III) acetate/alcohol and iron(III) acetate/acetic acid/alcohol solutions at 180 °C for different time periods. Magnetite was formed in iron(III) acetate/ethanol, whereas hematite was formed in the iron(III) acetate/acetic acid/ethanol system. The average crystallite sizes of 11.1 and 22.6 nm and the stoichiometry of Fe2.89O4 were found for the nanosized magnetite particles. The primary magnetite particles aggregated into regular spheres 5 to 10 μm in size, which can be explained by the specific character of the small, reactive and polar molecules of ethanol. In the iron(III) acetate/octanol system, a mixture of magnetite and hematite was obtained. The average crystallite size of magnetite was up to 22 nm and that of hematite was up to 46.7 nm. In the iron(III) acetate/acetic acid/ethanol system, nanosized hematite particles were exclusively formed. 13C NMR spectroscopy revealed the presence of ethyl acetate ester in the supernatants. The formation of ester in the iron(III) acetate/ethanol system was explained by the catalytic oxidation of ethanol in the presence of acetate groups bonded to iron. Thus, in the oxidative dehydrogenation of ethanol into ethyl acetate, coordinated Fe3+ served as an electron acceptor that was reduced to Fe2+, and exclusively magnetite was formed. With the addition of acetic acid to the iron(III) acetate/ethanol system, the free acetic acid directly participated in an esterification reaction with ethanol. Water molecules generated in situ in this esterification reaction hydrolysed iron(III) acetate, and thus hematite was formed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Effects of Precipitation, SolGel Synthesis Conditions, and Drying Methods on the Properties of Nano‐TiO2 for Photocatalysis Applications
Authors: Junin Chabaiporn , Thanachayanont Chanchana , Euvananont Chanipat , Inpor Kroekchai , Limthongkul Pimpa 
Published: January 2008

AbstractA comparative study of TiO2 powders prepared by precipitation and sol–gel methods was conducted. Titanium tetrachloride and titanium tetraisopropoxide were used as the starting materials for the precipitation and sol–gel processes, respectively. The effects of the two different drying methods, freeze drying and normal drying at 100 °C, of the precipitates on the properties of the prepared TiO2 powders were also investigated. The effects of the synthesis methods on phase, surface area, crystallite size, and photodegradation of methylene blue were studied by XRD, SEM, TEM, BET, and UV/Vis techniques. It was found that the major phase of the synthesized TiO2 was anatase, but small amounts of the brookite phase (<10 %) were found in some samples. The synthesized anatase TiO2 with no pretreatment was found to be stable up to 600 °C for the samples prepared by the precipitation method, whereas a small amount of rutile was detected for the sample prepared by the sol–gel method when heated to 600 °C. Effects of the different processing methods on phase, particle size, surface area, and photocatalytic activity were not highly pronounced. However, the calcination temperature was found to have a strong influences on the properties. As the calcination temperature increased, the size of the crystallite and the percent degradation of methylene blue were found to increase, whereas the surface area was found to decrease. These results indicate the degree of crystallinity has a greater effect on the photocatalytic activity than the surface area for nano‐TiO2 synthesized by these methods.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Dynamic Behaviour of the [(Triphos)Rh(η1:η2‐P4RR′)]n+ Complexes [Triphos = MeC(CH2PPh2)3; R = H, Alkyl, Aryl; R′ = Lone Pair, H, Me; n = 0, 1]: NMR and Computational Studies
Authors: Barbaro Pierluigi , Caporali Maria , Ienco Andrea , Mealli Carlo , Peruzzini Maurizio , Vizza Francesco 
Published: January 2008

AbstractSolution multinuclear and multidimensional NMR analyses of the [(triphos)Rh(η1:η2‐P4RR′)]n+ complex cations [triphos = MeC(CH2PPh2)3; R = H, Me, Ph; R′ = lone pair, H, Me; n = 0, 1] confirm the same primary structure determined by X‐rays in the solid state. In addition, 2D 1H NOESY and 31P{1H} exchange NMR spectroscopy show that these complexes are nonrigid on the NMR time‐scale over the 253–318 K temperature range. A dynamic process that involves the terminal phosphane groups of the triphos ligand is displayed by each compound. The NMR spectroscopic data indicate a slow scrambling motion in which the P4R unit tumbles with respect to the (triphos)Rh moiety. DFT calculations outline a possible turnstile mechanism involving the threefold and twofold rotors into which the complex is subdivided. The process goes through a transition state in which the axial and equatorial dispositions of the PRR′ and P=P donating groups of the P4RR′ ligand are inverted with respect to the ground state. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Synthesis, Electrochemical and Optical Properties of RuII–Diphenylphenanthroline–Ethynylpyrenephenanthroline Systems
Authors: Goze Christine , Sabatini Cristiana , Barbieri Andrea , Barigelletti Francesco , Ziessel Raymond 
Published: January 2008

AbstractThe synthesis, electrochemical and optical spectroscopic properties of a RuII–diphenylphenanthroline complex decorated with ethynylpyrene (EP) appendages, 1, and those of its parent bromo‐substituted complex, 2, are reported; complex 1 is [Ru(dpp)2(phen–EP2)](PF6)2 and 2 is [Ru(dpp)2(phen–Br2)](PF6)2, where dpp is 4,7‐diphenyl‐1,10‐phenanthroline, phen–EP is 5,6‐(1‐ethynylpyrene)‐1,10‐phenanthroline and phen–Br2 is 5,6‐dibromo‐1,10‐phenanthroline. In CH3CN solvent, both bromo‐ and EP‐substituted complexes are redox active and metal‐centred and ligand‐centred processes are assigned with reference to the analogous steps for [Ru(phen)3]2+ and to steps for the EP appendages. The complexes exhibit strong absorption bands in the near‐UV and visible regions due to ligand‐centred (LC) and metal‐to‐ligand charge‐transfer (MLCT) transition, respectively. For 1, the lowest‐lying absorption band is slightly redshifted due to better delocalisation at the phen–EP ligand. At room temperature and in O2‐free solvent, complex 1 appeared to be practically nonluminescent, whereas 2 exhibited intense 3MLCT emission; quantum yields of fem = 9 × 10–4 and 6.1 × 10–2 were found for 1 and 2, respectively and λexc = 462 nm in both cases. The lowest‐lying excited states of 1 were assigned as 3LC states, which were localised on the EP moiety. These states are nonluminescent, which thus explains the weak room‐temperature luminescence for this complex. At 77 K, 2 is emissive, as expected for 3MLCT levels; however, a moderately intense 3MLCT emission was also observed for 1 at this temperature. For the latter case, this outcome is tentatively explained in terms of local trapping of 3MLCT states at the 4,7‐diphenylphenanthroline ligands free of EP appendages.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Microwave‐Assisted Hydrothermal Synthesis of Structurally and Morphologically Controlled Sodium Niobates by Using Niobic Acid as a Precursor
Authors: Paula Amauri J. , Zaghete Maria A. , Longo Elson , Varela José A. 
Published: January 2008

AbstractThere are many advantages to using a microwave as a source of heat in hydrothermal reactions. Because it is a quick and homogeneous way to crystallize ceramic powders, it was used in this work for the production of antiferroelectric sodium niobate (NaNbO3) in a cubic‐like form and its intermediary phase, disodium diniobate hydrate (Na2Nb2O6.H2O), with a fiber morphology. The syntheses were carried out by treating niobic acid (Nb2O5·nH2O) with NaOH. By changing the reaction time and the concentration of the reactants, particles with different structures and different morphologies could be obtained. The structural evolution of the products of this reaction was elucidated on the basis of the arrangement of the NbO6 octahedral units. Conclusive results were obtained with morphological and structural characterizations through XRD, TEM, MEV, and NMR and Raman spectroscopy. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Synthesis of Polyprenylated Benzoylphloroglucinols by Regioselective Prenylation of Phloroglucinol in an Aqueous Medium
Authors: Raikar Sanjay B. , Nuhant Philippe , Delpech Bernard , Marazano Christian 
Published: January 2008

AbstractRegioselective tri‐C‐prenylation of phloroglucinol, leading to a compound with gem‐disubstitution, has been achieved with prenyl bromide in the presence of potassium hydroxide in an aqueous medium. Geranyl‐ and isolavandulylphloroglucinol, obtained by ortho‐lithiation, were diprenylated under the same conditions. C‐Benzoylation of the trialkylated derivatives using benzoyl cyanide in the presence of triethylamine afforded two natural products, grandone and kolanone, and an isomer of weddellianone A. Attemped electrophilic cyclization reactions, aimed at a biomimetic synthesis of polycyclic polyprenylated acylphloroglucinols (PPAPs), are also reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Intermolecular and Intramolecular Pauson–Khand Reactions of Functionalized Allenes
Authors: González‐Gómez Álvaro , Añorbe Loreto , Poblador Amalia , Domínguez Gema , Pérez‐Castells Javier 
Published: January 2008

AbstractPauson–Khand reactions of functionalized allenes with different alkynes give cyclopentenones with generally high regio‐ and stereoselectivities. The allenes react through their external double bonds, giving cyclopentenones with exocyclic double bond at their β positions and predominantly with E stereochemistry. Some intramolecular reactions with allenynes connected through aromatic rings are described. These give the corresponding heterocycles with moderate to good yields.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Synthesis of Indene and Naphthalene Derivatives by a Palladium‐Catalyzed Domino Carbopalladation/Cyclization/Coupling Process
Authors: Guo Li‐Na , Duan Xin‐Hua , Hu Jie , Bi Hai‐Peng , Liu Xue‐Yuan , Liang Yong‐Min 
Published: January 2008

AbstractHighly substituted indene and naphthalene derivatives have been readily prepared in good‐to‐high yields by a palladium‐catalyzed domino reaction. This domino reaction involves a Heck carbopalladation/cyclization/coupling process. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Nucleophilic Substitution at C, Si and P: How Solvation Affects the Shape of Reaction Profiles (Eur. J. Org. Chem. 4/2008)
Authors: van Bochove Marc A. , Bickelhaupt F. Matthias 
Published: January 2008

AbstractThe cover picture shows that solvation smoothes reaction profiles not only for SN2 reactions at carbon but also for SN2 reactions at silicon, tricoordinate phosphorus and tetracoordinate phosphorus. Thus, the characteristic double‐well, single‐well and triple‐well structures on the gas‐phase potential energy surfaces (PES) disappear, which results, in all cases, in a unimodal reaction profile in solution. Details are discussed in the article by M. A. van Bochove and F. M. Bickelhaupt on p. 649 ff. We thank Dr. Marcello Luppi for the design of the cover picture.
Crosslinked hyaluronic acid dermal fillers: A comparison of rheological properties
Authors: Falcone Samuel J. , Berg Richard A. 
Published: January 2008

AbstractTemporary dermal fillers composed of crosslinked hyaluronic acid (XLHA) are space filling gels that are readily available in the United States and Europe. Several families of dermal fillers based on XLHA are now available and here we compare the physical and rheological properties of these fillers to the clinical effectiveness. The XLHA fillers are prepared with different crosslinkers, using HA isolated from different sources, have different particle sizes, and differ substantially in rheological properties. For these fillers, the magnitude of the complex viscosity, |η*|, varies by a factor of 20, the magnitude of the complex rigidity modulus, |G*|, and the magnitude of the complex compliance, |J*| vary by a factor of 10, the percent elasticity varies from 58% to 89.9%, and the tan δ varies from 0.11 to 0.70. The available clinical data cannot be correlated with either the oscillatory dynamic or steady flow rotational rheological properties of the various fillers. However, the clinical data appear to correlate strongly with the total concentration of XLHA in the products and to a lesser extent with percent elasticity. Hence, our data suggest the following correlation: dermal filler persistence = [polymer] × [% elasticity] and the clinical persistence of a dermal filler composed of XLHA is dominated by the mass and elasticity of the material implanted. This work predicts that the development of future XLHA dermal filler formulations should focus on increasing the polymer concentration and elasticity to improve the clinical persistence. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Histological and biomechanical properties of regenerated articular cartilage using chondrogenic bone marrow stromal cells with a PLGA scaffold in vivo
Authors: Han Seung Hwan , Kim Yun Hee , Park Min Sung , Kim In Ae , Shin Jung Woog , Yang Woo Ick , Jee Kyoung Soo , Park Ki Dong , Ryu Gyu Ha , Lee Jin Woo 
Published: January 2008

AbstractThe properties of regenerated cartilage using bone marrow‐derived mesenchymal stem cells (MSCs) and poly lactic‐co‐glycolic acid (PLGA) scaffold composites pretreated with TGF‐β3 were investigated and compared to the non‐TGF‐β3 treated MSCs/PLGA composites in a rabbit model. We prepared MSCs/PLGA scaffold composites and pretreated it with TGF‐β3 for 3 weeks prior to transplantation. Then, composites were transplanted to the osteochondral defect in the rabbit knee. After 12 weeks of transplantation, 10 of the 12 rabbits in which TGF‐β3 pretreated MSCs/PLGA scaffold composites were transplanted showed cartilaginous regeneration. In gross morphology, regenerated cartilage showed smooth, flush, and transparent features. In indentation test, this had about 80% of Young's modulus of normal articular cartilage. Histological examination demonstrated hyaline like cartilage structures with glycosaminoglycan and type II collagen expression. Histological scores were not statistically different to the normal articular cartilage. These results showed improvement of cartilage regeneration compared to the non‐TGF‐β3 pretreated MSCs/PLGA scaffold composite transplanted group. Thus, we have successfully regenerated improved hyaline‐like cartilage and determined the feasibility of treating damaged articular cartilage using MSCs/PLGA scaffold composite pretreated with TGF‐β3. Also, we suggest this treatment modality as another concept of cartilage tissue engineering. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Evaluation of the biocompatibility of calcium phosphate cement/PLGA microparticle composites
Authors: Link Dennis P. , van den Dolder Juliette , van den Beucken Jeroen J. J. P. , Cuijpers Vincent M. , Wolke Joop G. C. , Mikos Antonios G. , Jansen John A. 
Published: January 2008

AbstractIn this study, the biocompatibility of a calcium phosphate (CaP) cement incorporating poly (D,L‐lactic‐co‐glycolic acid) (PLGA) microparticles was evaluated in a subcutaneous implantation model in rats. Short‐term biocompatibility was assessed using pure CaP discs and CaP discs incorporating PLGA microparticles (20% w/w) with and without preincubation in water. Long‐term biocompatibility was assessed using CaP discs incorporating varying amounts (5, 10, or 20% w/w) and diameter sizes (small, 0–50 μm; medium, 51–100 μm, or large, 101–200 μm) of PLGA microparticles. The short‐term biocompatibility results showed a mild tissue response for all implant formulations, irrespective of disc preincubation, during the early implantation periods up to 12 days. Quantitative histological evaluation revealed that the different implant formulations induced the formation of similar fibrous tissue capsules and interfaces. The results concerning long‐term biocompatibility showed that all implants were surrounded by a thin connective tissue capsule (<10 layers of fibroblasts). Additionally, no significant differences in capsule and interface scores were observed between the different implant formulations. The implants containing 20% PLGA with medium‐ and large‐sized microparticles showed fibrous tissue ingrowth throughout the implants, indicating PLGA degradation and interconnectivity of the pores. The results demonstrate that CaP/PLGA composites evoke a minimal inflammatory response. The implants containing 20% PLGA with medium‐ and large‐sized microparticles showed fibrous tissue ingrowth after 12‐ and 24‐weeks indicating PLGA degradation and interconnectivity of the pores. Therefore, CaP/PLGA composites can be regarded as biocompatible biomaterials with potential for bone tissue engineering and advantageous possibilities of the microparticles regarding material porosity. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Linear and ultrafast optical spectroscopy in the regime of the quantum Hall effect
Authors: Broocks K.‐B. , Su B. , Schröter P. , Heyn Ch. , Heitmann D. , Wegscheider W. , Apalkov V. M. , Chakraborty T. , Perakis I. E. , Schüller C. 
Published: January 2008

AbstractWe review our optical experiments on two‐dimensional electron systems (2DES) of different mobilities, realized in modulation‐doped GaAs–AlGaAs single quantum wells, in quantizing magnetic fields. The carrier densities of the 2DESs could be tuned in a quite broad range between about 1 × 1010 cm–2 and 2 × 1011 cm–2 via gate electrodes. In photoluminescence (PL) and absorption experiments on 2DES with moderate mobility, at very low electron densities, we have observed the formation of negatively charged excitons. In these experiments, we could identify a dark triplet exciton, which is observable at temperatures below 1 K and for electron filling factors v < 1/3 i.e., in the fractional quantum Hall regime, only. In experiments where we have increased the density of the 2DES so that a uniform 2DES starts to form, we have found a strong energetic anomaly of the charged excitons in the vicinity of filling factor 1/3. The anomaly could be explained by a model, assuming that at very low temperatures localized charged excitons and a uniform Laughlin liquid coexist. Furthermore, we report on ultrafast optical experiments at the v = 1 quantum Hall state of a high‐mobility 2DES in a GaAs–AlGaAs single quantum well. By spectrally‐resolved four‐wave‐mixing experiments, we have investigated the coherent dynamics of photo‐excited electron–hole pairs and found extraordinarily long decoherence times for electrons, excited into the upper spin level, around v = 1 We attribute the observed faster decay of the dephasing time for v < 1 as compared to v > 1 presumably to the coherent coupling of the spin levels via spin waves. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Separately contacted edge states at high imbalance in the integer and fractional quantum Hall effect regime
Authors: Deviatov E. V. , Lorke A. 
Published: January 2008

AbstractThis review presents experimental results on the inter‐edge‐state transport in the quantum Hall effect, mostly obtained in the regime of high imbalance. The application of a special geometry makes it possible to perform I –V spectroscopy between individual edge channels in both the integer and the fractional regime. This makes it possible to study in detail a number of physical effects such as the creation of topological defects in the integer quantum Hall effect and neutral collective modes excitation in fractional regime. While many of the experimental findings are well explained within established theories of the quantum Hall effects, a number of observations give new insight into the local structure at the sample edge, which can serve as a starting point for further theoretical studies. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Laughlin's function on a cylinder: plasma analogy and representation as a quantum polymer
Authors: Jansen Sabine , Lieb Elliott H. , Seiler Ruedi 
Published: January 2008

AbstractWe investigate Laughlin's fractional quantum Hall effect wave function in the cylinder geometry of Laughlin's integer quantum Hall effect argument, at filling factor 1/3. We show that the plasma analogy leads to a periodic density, and that the wave function admits a representation as a “quantum polymer”, reminiscent of the quantum dimer model by Rokhsar and Kivelson. We explain how the representation can be exploited to compute the normalization and one‐particle density in the limit of infinitely many particles. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Associations between peer victimization, self‐reported depression and social phobia among adolescents: The role of comorbidity
Authors: Ranta Klaus , Kaltiala‐Heino Riittakerttu , Pelkonen Mirjami , Marttunen Mauri 
Published: January 2008

AbstractAssociations of peer victimization with adolescent depression and social phobia (SP), while controlling for comorbidity between them, have not been sufficiently explored in earlier research. A total of 3156 Finnish adolescents aged 15–16 years participated in a survey study. Self‐reported peer victimization, as well as self‐reported depression (Beck Depression Inventory), SP (Social Phobia Inventory), and selected background variables were assessed. Frequency of overt and covert peer victimization was examined among four groups: (1) adolescents with depression non‐comorbid with SP (DEP), (2) those with SP non‐comorbid with depression (SP), (3) those with both SP and depression (SP+DEP), and (4) controls, with neither. A logistic regression analysis controlling for confounding familial (family moving, parental unemployment), and psychopathology (delinquency, aggressiveness, general anxiety) covariates was conducted to confirm the associations between peer victimization and the four groups. Among boys the comorbid SP+DEP group reported the highest rates of both overt and covert victimization, these being significantly higher than among both DEP and SP groups. Among girls covert victimization was again most frequent in the SP+DEP group, but overt victimization was not more frequent in the comorbid group than it was in the DEP and SP groups. In the logistic regression analysis depression without SP did not maintain an independent association with either type of victimization. Instead, SP without depression with ORs from 2.8 to 4.3, and SP comorbid with depression, with ORs between 3.2 and 11.4 had independent associations with peer victimization. In conclusion, overt and covert peer victimization seem to be associated with SP, rather than depression, among adolescents.