bluuebunny/crossref_metadata_2025 huggingface dataset:
Catalytic Ethylene Polymerisation in Carbon Dioxide as a Reaction Medium with Soluble Nickel(II) Catalysts
Authors: Bastero Amaia , Franciò Giancarlo , Leitner Walter , Mecking Stefan
Published: June 2006

A series of neutral NiII–salicylaldiminato complexes substituted with perfluorooctyl‐ and trifluoromethyl groups, [Ni{κ2‐N,O‐6‐C(H)NAr‐2,4‐R′2C6H2O}(Me)(pyridine)] (6 a: Ar=2,6‐{4‐(F17C8)C6H4}2C6H3, R′=I; 6 b: Ar=2,6‐{4‐(F3C)C6H4}2C6H3, R′=I; 6 c: Ar=2,6‐{3,5‐(F3C)2C6H3}2C6H3, R′=3,5‐(F3C)2C6H3; 6 d: Ar=2,6‐{4‐(F17C8)C6H4}2C6H3, R′=3,5‐(F3C)2C6H3; 6 e: Ar=2,6‐{3,5‐(F3C)2C6H3}2C6H3, R′=I) were studied as catalyst precursors for ethylene polymerisation in supercritical CO2. Catalyst precursors 6 a and 6 c, which are soluble in scCO2, afford the highest polymer yields, corresponding to 2×103 turnovers. Semicrystalline polyethylene (Mn typically 104 g mol−1) is obtained with variable degrees of branching (11 to 24 branches per 1000 carbon atoms, predominantly Me branches) and crystallinities (54 to 21 %), depending on the substitution pattern of the catalyst.
Specific Vectorial Immobilization of Oligonucleotide‐Modified Yeast Cytochrome c on Carbon Nanotubes
Authors: Heering Hendrik A. , Williams Keith A. , de Vries Simon , Dekker Cees
Published: June 2006

Iso‐1‐cytochrome c from the yeast Saccharomyces cerevisiae (YCC) contains a surface cysteine residue, Cys102, that is located opposite to the lysine‐rich side containing the exposed heme edge, which is the docking site for enzymes. Site‐specific vectorial immobilization of YCC via Cys102 on single‐walled carbon nanotubes (SWNT) thus provides a selective interface between nanoscopic electronic devices and complex enzymes. We have achieved this by modification of Cys102 with an oligonucleotide (dT18). Atomic force microscopy, fluorescence imaging, and cyclic voltammetry show the specific adsorption of YCC, modified with dT18, on the SWNT sidewall with retention of its native properties. Pretreatment of the SWNT with Triton‐X405 blocks the nonspecific binding of untreated YCC but does not interfere with binding of the oligonucleotide‐modified YCC.
Surface Composition of Materials Used as Catalysts for Methanol Steam Reforming: A Theoretical Study
Authors: Lim Kok Hwa , Moskaleva Lyudmila V. , Rösch Notker
Published: June 2006

PdZn (1:1) alloy is assumed to be the active component of a promising catalyst for methanol steam reforming. Using density functional calculations on periodic supercell slab models, followed by atomistic thermodynamics modeling, we study the chemical composition of the surfaces PdZn(111) and, as a reference, Cu(111) in contact with water and hydrogen at conditions relevant to methanol steam reforming. For the two surfaces, we determine similar maximum adsorption energies for the dissociative adsorption of H2, O2, and the molecular adsorption of H2O. These reactions are calculated to be exothermic by about −40, −320, and −20 kJ mol−1, respectively. Using a thermodynamic analysis based on theoretically predicted adsorption energies and vibrational frequencies, we determine the most favorable surface compositions for given pressure windows. However, surface energy plots alone cannot provide quantitative information on individual coverages in a system of coupled adsorption reactions. To overcome this limitation, we employ a kinetic model, from which equilibrium surface coverages of H, O, OH, and H2O are derived. We also discuss the sensitivity of our results and the ensuing conclusions with regard to the model surfaces employed and the inaccuracies of our computational method. Our kinetic model predicts surfaces of both materials, PdZn and Cu, to be essentially adsorbate‐free already from very low values of the partial pressure of H2. The model surfaces PdZn(111) and Cu(111) are predicted to be free of water‐related adsorbates for a partial H2 pressure greater than 10−8 and 10−5 atm, respectively.
Prediction of upper aerodigestive tract cancer by slide‐based cytometry
Authors: Gerstner Andreas O. H. , Thiele Alexander , Tárnok Attila , Tannapfel Andrea , Weber Anette , Bootz Friedrich
Published: June 2006

Aim:

To evaluate slide‐based cytometry in screening for and following up of carcinoma of the upper aerodigestive tract using swabs for a minimal‐invasive approach.

Methods:

Laser scanning cytometry (LSC) was used for multiparametric analysis of cells stained for cytokeratin and DNA to determine the DNA‐index (DI) of the tumor cells. Histograms with 0.95 < DI < 1.05 and 1.9 < DI < 2.1 were defined as DNA euploid and any other DI as DNA aneuploid. After subsequent HE‐staining, single cells were relocalized in order to document morphology. Conventional cytology was also performed on a subset of the slides. Routine histopathology of parallel biopsies served as gold standard in all cases.

Results:

115 swabs from 109 patients were obtained from the entire upper aerodigestive tract. 16 swabs were classified as insufficient for LSC. In the remaining 99 specimens, 1 benign lesion was misclassified as malignant, while 61 of the 75 malignant lesions were correctly identified. This corresponds to predictive values of 98.4% and 62.2% for the detection of malignant and benign samples by LSC.

Conclusion:

This pilot study demonstrates the validity of LSC screening for the identification of tumor malignancy in the upper aerodigestive tract from swab collected cytological material. © 2005 International Society for Analytical Cytology
A Route to Multi‐Clusters Containing Half‐Sandwich Rh and Ir Complexes of Chelating 1,2‐Dicarba‐closo‐dodecaborane(12)‐1,2‐dithiolate Ligands
Authors: Wang Jian‐Qiang , Ren Chun‐Xia , Jin Guo‐Xin
Published: June 2006

Reaction of the 16‐electron half‐sandwich rhodium and iridium complexes [Cp*M{S2C2(B10H10)}] [M = Rh (1a), Ir (1b)] with multidentate ligands (L) such as 5,10,15,20‐tetra(4‐pyridyl)porphyrin) (H2TPyP), 2,4,6‐tri(4‐pyridyl)‐1,3,5‐triazine (tpt), and 4,4′‐azopyridine, gave the corresponding multi‐cluster complexes [Cp*MS2C2(B10H10)]n(L) [M = Rh, Ir; n = 4, L = H2TPyP (2); 3, L = tpt (3); 2, L = 4,4′‐azopyridine (4), N,N′‐bis(4‐pyridinylmethylene)biphenyl‐4,4′‐diamine (5), pyrazine, (6), 2,5‐di(4‐pyridyl)‐1,3,4‐oxadiazole (7), 1,2‐di(4‐pyridyl)ethylene) (8), diisonicotinic acid 1,4‐phenylene diester (9), 4,4′‐bipyridine (10)]. The X‐ray structure of 2a reveals that an H2TPyP unit bridges four [Cp*RhS2C2(B10H10)] fragments to form a tetranuclear [Cp*RhS2C2(B10H10)]4(H2TPyP) complex and the [Cp*RhS2C2(B10H10)] units adopt a tail‐to‐tail contact mode, rather than a head‐to‐tail mode, in spite of the large steric repulsion between the two carborane ligands. In complex 3a, three [Cp*RhS2C2(B10H10)] units are symmetrically arranged around the periphery of one tpt core, thus forming a “bowl‐shaped” structure. In 4a, 5a, 6a, 8b, and 9b, two [Cp*RhS2C2(B10H10)] fragments take a trans conformation around the linear or pseudo‐linear pyridyl‐based ligand core, while in 7a they are in a cis conformation. All new complexes 2–10 were characterized by 1H and 11B NMR spectroscopy, and X‐ray structural analyses are reported for complexes 2a, 3a, 4a, 5a, 6a, 7a, 8b, and 9b. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Cationic Brønsted Acids for the Preparation of SnIV Salts: Synthesis and Characterisation of [Ph3Sn(OEt2)][H2N{B(C6F5)3}2],[Sn(NMe2)3(HNMe2)2][B(C6F5)4] and [Me3Sn(HNMe2)2][B(C6F5)4]
Authors: Sarazin Yann , Coles Simon J. , Hughes David L. , Hursthouse Michael B. , Bochmann Manfred
Published: June 2006

Ph3SnN(SiMe3)2 (1) was prepared in good yields by reaction of [{NaN(SiMe3)2}2·THF] (2) with Ph3SnF. Treatment of 1 with [H(OEt2)2][H2N{B(C6F5)3}2] (4) in dichloromethane afforded the stannylium cation [Ph3Sn(OEt2)][H2N{B(C6F5)3}2] (5), which was characterised by 1H, 13C{1H}, 11B, 19F and 119Sn NMR spectroscopy. The reaction of Sn(NMe2)4 with [Ph2MeNH][B(C6F5)4] (3) gave the amidotin(IV) compound [Sn(NMe2)3(HNMe2)2][B(C6F5)4] (6) which proved very stable towards ligand substitution and resisted treatment with Et2O, THF, TMEDA and pyrazine. Two new Brønsted acid salts [H(NMe2H)2][B(C6F5)4] (7) and [(C4H4N2)H·OEt2][H2N{B(C6F5)3}2] (8) were synthesised. The reaction of 7 with Sn(NMe2)4 in Et2O allowed the preparation of 6 in a much improved yield (83 %). The treatment of 7 with Me3SnN(SiMe3)2 in Et2O yielded [Me3Sn(HNMe2)2][B(C6F5)4] (9) nearly quantitatively. Compounds 1, 2, 6, 8 and 9 were characterised by single‐crystal X‐ray diffraction analyses; 6 is the first example of a structurally characterised amidotin(IV)cation.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Novel Catalytic Tandem Isomerisation/Cyclisation Reaction of α‐Methallyloxy Carboxylic Acids
Authors: Chaminade Xavier , Coulombel Lydie , Olivero Sandra , Dunach Elisabet
Published: June 2006

A new tandem isomerisation/cyclisation of α‐methallyloxy carboxylic acids leading to substituted 1,3‐dioxolan‐4‐ones in 60–70 % yields was catalysed by Cu(OTf)2 or Al(OTf)3. Extension to the synthesis of oxathiolanones and oxathianones is also described. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Highly Enantio‐ and Diastereoselective One‐Pot Reactions in Aqueous Media: Combined Asymmetric Rh‐Catalyzed Conjugate Addition/Metal‐Mediated Allylation
Authors: Källström Sara , Jagt Richard B. C. , Sillanpää Reijo , Feringa Ben L. , Minnaard Adriaan J. , Leino Reko
Published: June 2006

1,3‐Disubstituted, enantiopure cyclohexanols have been prepared in very high diastereoselectivities and good yields by a concise one‐pot method combining the enantioselective rhodium‐catalyzed conjugate addition of arylboronic acids with indium‐mediated allylation into a highly efficient one‐pot reaction in aqueous media. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
One‐Pot Synthesis of (±)‐Crispine A and Its C‐Ring‐Substituted Analogs
Authors: Meyer Nino , Opatz Till
Published: June 2006

A straightforward access to crispine A and C‐ring‐substituted analogs by 1,4‐addition of a deprotonated α‐amino nitrile to α,β‐unsaturated carbonyl compounds is described. If the reduction step is omitted, substituted 5,6‐dihydropyrrolo[2,1‐a]isoquinolines can be obtained. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Amperometric Glucose Biosensor Based on Rhodium Dioxide‐Modified Carbon Ink
Authors: Kotzian Petr , Brázdilová Petra , Řezková Soňa , Kalcher Kurt , Vytřas Karel
Published: June 2006

An amperometric method for the determination of glucose using a screen printed carbon electrode is reported. The electrode material was bulk modified with rhodium dioxide and the enzyme glucose oxidase immobilized in a Nafion‐film on the electrode surface and investigated for its ability to serve as a detector of glucose in flow injection analysis. The sensor exhibited a linear increase of the amperometric signal with the concentration of glucose in the range of 1–250 mg L−1 with a detection limit (evaluated as 3σ) of 0.2 mg L−1 under optimized flow rate of 0.4 mL min−1 in 0.1 M phosphate buffer (pH 7.5) carrier. At the potential applied (−0.2 V vs. Ag/AgCl), interferences from redox species present in the sample matrix were negligible. The biosensor reported here retained its activity for more than 40 injections or 4 months of storage at 6 °C. The RSD was determined as 1.8% for a glucose concentration of 25 mg L−1 (n=5) with a typical response time of about 28 s.
Anodic Stripping Voltammetric Determination of Aurothiomalate in Urine Using a Screen‐Printed Carbon Electrode
Authors: Bergamini Márcio F. , Boldrin Zanoni Maria Valnice
Published: June 2006

This work describes an electroanalytical method for determining gold(I) thiomalate, aurothiomalate, widely used for treatment of reumatoid arthiritis, using a screen‐printed carbon electrode (SPCE). Aurothiomalate (AuTM) was determined indirectly at the same electrode by accumulating it first at −1.5 V vs. printed carbon. At this potential in the adsorbed state, the AuTM is reduced to Au(0), which is then oxidized at two steps at −0.22 V and +0.54 V on SPCE. Using optimized conditions of 60 s deposition time, −1.5 V (vs. printed carbon) accumulation potential, 100 mV s−1 scan rate, linear calibration graphs can be obtained by monitoring the peak at +0.54 V for AuTM in HCl 0.1 mol L−1 from 1.43×10−6 to 1.55×10−4 mol L−1. A limit of detection obtained was 6.50×10−7 mol L−1, and the relative standard deviation from five measurements of 3.0×10−5 mol L−1 AuTM is 4.5%. The method was successfully applied for AuTM determination in human urine sample.
Peptide Modified Electrodes as Electrochemical Metal Ion Sensors
Authors: Chow Edith , Gooding J. Justin
Published: June 2006

Sensors for the detection of metal ions are of considerable importance for enabling the monitoring of environmental samples for metal ion contamination directly in the field. This review outlines the use of peptides and amino acids as the recognition element of electrochemical sensors for metal ion detection. Initially the complexation of metals by peptides is discussed followed by the immobilization of peptides on electrode surfaces. Subsequently, the application of peptide modified electrodes for detecting metals is reviewed and finally challenges and future prospects are outlined.
Large‐scale Pyrosequencing of synthetic DNA: A comparison with results from Sanger dideoxy sequencing
Authors: Gharizadeh Baback , Herman Zelek S. , Eason Robert G. , Jejelowo Olufisayo , Pourmand Nader
Published: June 2006

Pyrosequencing is a relatively recent method for sequencing short stretches of DNA. Because both Pyrosequencing and Sanger dideoxy sequencing were recently used to characterize and validate DNA molecular barcodes in a large yeast gene‐deletion project, a meta‐analysis of those data allow an excellent and timely opportunity for evaluating Pyrosequencing against the current gold standard, Sanger dideoxy sequencing. Starting with yeast genomic DNA, parallel PCR amplification methods were used to prepared 4747 short barcode‐containing constructs from 6000 Saccharomyces cerevisiae gene‐deletion strains. Pyrosequencing was optimized for average read lengths of 25–30 bases, which included in each case a 20‐mer barcode sequence. Results were compared with sequence data obtained by the standard Sanger dideoxy chain termination method. In most cases, sequences obtained by Pyrosequencing and Sanger dideoxy sequencing were of comparable accuracy, and the overall rate of failure was similar. The DNA in the barcodes is derived from synthetic oligonucleotide sequences that were inserted into yeast‐deletion‐strain genomic DNA by homologous recombination and represents the most significant amount of DNA from a synthetic source that has been sequenced to date. Although more automation and quality control measures are needed, Pyrosequencing was shown to be a fast and convenient method for determining short stretches of DNA sequence.
Perphenylcarbamoylated β‐cyclodextrin bonded‐silica particles as chiral stationary phase for enantioseparation by pressure‐assisted capillary electrochromatography
Authors: Lin Bo , Shi Zhi‐Guo , Zhang Hui‐Juan , Ng Siu‐Choon , Feng Yu‐Qi
Published: June 2006

Perphenylcarbamoylated β‐cyclodextrin bonded‐silica particles (5 μm) were packed into 75‐μm fused‐silica capillaries, and used for the enantiomer separation of neutral and basic solutes by pressure‐assisted capillary electrochromatography. Triethylammonium acetate and phosphate buffer were employed as the BGEs. A cathodic EOF was observed with these two BGEs. Seven chiral analytes were successfully resolved into their enantiomers under optimized conditions, and five of them could be baseline‐separated within 12 min due to their high electrophoretic mobility. Better results were achieved with phosphate buffer as the BGE. The effects of organic content and pH on the enantioseparation were also investigated.
Synaptophysin protein and mRNA expression in the human hippocampal formation from birth to old age
Authors: Eastwood Sharon L. , Weickert Cyndi Shannon , Webster Maree J. , Herman Mary M. , Kleinman Joel E. , Harrison Paul J.
Published: June 2006

In the human neocortex, progressive synaptogenesis in early postnatal life is followed by a decline in synaptic density, then stability from adolescence until middle age. No comparable data are available in the hippocampus. In this study, the integral synaptic vesicle protein synaptophysin, measured immunoautoradiographically, was used as an index of synaptic terminal abundance in the hippocampal formation of 37 subjects from 5 weeks to 86 yr old, divided into 4 age groups (10 infants, 15 adolescents/young adults, 6 adults, and 6 elderly). In all hippocampal subfields, synaptophysin was lowest in infancy, but did not differ significantly between the older age groups, except in dentate gyrus (DG) where the rise was delayed until adulthood. A similar developmental profile was found in the rat hippocampus. We also measured synaptophysin mRNA in the human subjects and found no age‐related changes, except in parahippocampal gyrus wherein the mRNA declined from infancy to adolescence, and again in old age. The synaptophysin protein data demonstrate a significant presynaptic component to human postnatal hippocampal development. In so far as synaptophysin abundance reflects synaptic density, the findings support an increase in hippocampal and parahippocampal synapse formation during early childhood, but provide no evidence for adolescent synaptic pruning. The mRNA data indicate that the maturational increases in synaptophysin protein are either translational rather than transcriptional in origin, or else are secondary to mRNA increases in neurons, the cell bodies of which lie outside the hippocampal formation. Published 2006 Wiley‐Liss, Inc.
A relook at NEH‐4 curve number data and antecedent moisture condition criteria
Authors: Mishra Surendra Kumar , Singh Vijay P.
Published: June 2006

This paper investigates the variation of the popular curve number (CN) values given in the National Engineering Hand Book–Section 4 (NEH‐4) of the Soil Conservation Service (SCS) with antecedent moisture condition (AMC) and soil type. Using the volumetric concept, involving soil, water, and air, a significant condensation of the NEH‐4 tables is achieved. This leads to a procedure for determination of CN for gauged as well as ungauged watersheds. The rainfall‐runoff events derived from daily data of four Indian watersheds exhibited a power relation between the potential maximum retention or CN and the 5‐day antecedent rainfall amount. Including this power relation, the SCS‐CN method was modified. This modification also eliminates the problem of sudden jumps from one AMC level to the other. The runoff values predicted using the modified method and the existing method utilizing the NEH‐4 AMC criteria yielded similar results. Copyright © 2006 John Wiley & Sons, Ltd.
Multiple modes of storm runoff generation in a North Carolina coastal plain watershed
Authors: Slattery Michael C. , Gares Paul A. , Phillips Jonathan D.
Published: June 2006

The results of field measurements conducted in a small (19·37 ha) agricultural watershed on the North Carolina coastal plain during the summer of 1996 are presented. The objective of the study was to develop a more complete understanding of basin response in the region with respect to stormflow generation and, in particular, to identify the processes that determine storm runoff and the conditions under which such processes occur. Twenty‐four storm events were monitored, including two tropical storm systems and two hurricanes. The data demonstrate considerable spatial and temporal heterogeneity in runoff generation within the watershed. Surface flowpaths, in the form of Hortonian overland flow and saturation overland flow, were found to be the dominant runoff processes during the storm events measured. The hillslope flowpaths had the same response time as the basin streamflow, but significantly shorter time of rise and lag times. The importance of Hortonian flow in a basin with sandy, permeable soils, as well as the rapid stormflow response in a low‐relief area with a humid climate, was contrary to expectations. This, coupled with the contingency of runoff response, suggests that it may be difficult to generalize about runoff generation mechanisms in broad terms, and that a synoptic approach may be more appropriate. Copyright © 2006 John Wiley & Sons, Ltd.
Complementary aspects of linear flood routing modelling and flood frequency analysis
Authors: Strupczewski Witold G. , Singh Vijay P. , Weglarczyk Stanislaw , Kochanek Krzysztof , Mitosek Henryk T.
Published: June 2006

Similarity and differences between linear flood routing modelling (LFRM) and flood frequency analysis (FFA) techniques are presented. The moment matching used in LFRM to approximate the impulse response function (IRF) was applied in FFA to derive the asymptotic bias caused by the false distribution assumption. Proceeding in this way, other estimation methods were used as approximation methods in FFA to derive the asymptotic bias. Using simulation experiments, the above investigation was extended to evaluate the sampling bias. As a feedback, the maximum likelihood method (MLM) can be used for approximating linear channel response (LCR) by the IRFs of conceptual models.

Impulse responses of the convective diffusion and kinematic diffusion models were applied and developed as FFA models. Based on kinematic diffusion LFRM, the equivalence of estimation problems of discrete‐continuous distribution and single‐censored sample are shown both for the method of moments (MOM) and the MLM. Hence, the applicability of MOM is extended for the case of censored samples.

Owing to the complexity and non‐linearity of hydrological systems and resulting processes, the use of simple models is often questionable. The rationale of simple models is discussed. The problems of model choice and overparameterization are common in mathematical modelling and FF modelling. Some results for the use of simple models in the stationary FFA are presented. The problems of model discrimination are then discussed.

Finally, a conjunction of linear stochastic processes and LFRM is presented. The influence of river courses on stochastic properties of the runoff process is shown by combining Gaussian input with the LCR of the simplified Saint Venant model. It is shown that, from the classification of the ways of their development, both LFRM and FFA can benefit. Copyright © 2006 John Wiley & Sons, Ltd.
Artificial extracellular matrix proteins contain heparin‐binding and RGD‐containing domains to improve osteoblast‐like cell attachment and growth
Authors: Wu Suh‐Chin , Yu Jung‐Chuan , Hsu Shan‐hui , Chen David Chanhen
Published: June 2006

Through the recombinant DNA technology, it is possible to create artificial extracellular matrix (aECM) proteins with domains chosen to modulate cellular behaviors. In this study, we constructed three aECM proteins containing both heparin‐binding and RGD‐containing domains (387RGDS, Tri‐FN10, and TNC‐FN3) produced in Escherichia coli. Promotion of MG‐63 cell attachment and growth in two‐dimensional (2D) cultures (tissue culture plate, polycaprolactone membrane) and 3D cultures (Cytodex 1 and Plastic Plus microcarriers) were demonstrated on these three aECM protein‐coated surfaces. These three aECM proteins improved MG‐63 cell attachment and growth in the order TNC‐FN3 > Tri‐FN10 > 387RGDS in both 2D and 3D cultures. This study is the first report of the construction of aECM proteins that contain both heparin‐binding and RGD‐containing domains used in osteoblast tissue engineering applications. © 2006 Wiley Periodicals, Inc. Inc. J Biomed Mater Res, 2006
A DFT study on the relative affinity for oxygen of the α and β subunits of hemoglobin
Authors: Maréchal Jean‐Didier , Maseras Feliu , Lledós Agustí , Mouawad Liliane , Perahia David
Published: June 2006

DFT calculations are carried out on computational models of the active center of the α and β subunits of hemoglobin in both its oxygenated (R) and deoxygenated (T) states. The computational models are defined by the full heme group, including all porphyrin substituents, and the four amino acids closer to it. The role of the protein environment is introduced by freezing the position of the α carbon atom of each of the four amino acids to the positions they have in the available PDB structures. Oxygen affinity is then evaluated by computing the energy difference between the optimized structures of the oxygenated and deoxygenated forms of each model. The results indicate a higher affinity of the α subunits over the β ones. Analysis of the computed structures points out to the strength of the hydrogen bond between the distal histidine and the oxygen molecule as a key factor in discriminating the different systems. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1446–1453, 2006
Metal–thiolate bonds in bioinorganic chemistry
Authors: Solomon Edward I. , Gorelsky Serge I. , Dey Abhishek
Published: June 2006

Metal–thiolate active sites play major roles in bioinorganic chemistry. The MSthiolate bonds can be very covalent, and involve different orbital interactions. Spectroscopic features of these active sites (intense, low‐energy charge transfer transitions) reflect the high covalency of the MSthiolate bonds. The energy of the metal–thiolate bond is fairly insensitive to its ionic/covalent and π/σ nature as increasing MS covalency reduces the charge distribution, hence the ionic term, and these contributions can compensate. Thus, trends observed in stability constants (i.e., the Irving–Williams series) mostly reflect the dominantly ionic contribution to bonding of the innocent ligand being replaced by the thiolate. Due to high effective nuclear charges of the CuII and FeIII ions, the cupric– and ferric–thiolate bonds are very covalent, with the former having strong π and the latter having more σ character. For the blue copper site, the high π covalency couples the metal ion into the protein for rapid directional long range electron transfer. For rubredoxins, because the redox active molecular orbital is π in nature, electron transfer tends to be more localized in the vicinity of the active site. Although the energy of hydrogen bonding of the protein environment to the thiolate ligands tends to be fairly small, H‐bonding can significantly affect the covalency of the metal–thiolate bond and contribute to redox tuning by the protein environment. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1415–1428, 2006
Variation in Activation Energy of the Glass Transition for Polymers of Different Dynamic Fragility
Authors: Vyazovkin Sergey , Sbirrazzuoli Nicolas , Dranca Ion
Published: June 2006

Summary: Variations of the effective activation energy E of glass transitions have been determined by applying an isoconversional method to DSC data on the glass transition in PVC, PBMA, PVP, and PEN. A variability parameter ΔE has been introduced to characterize the rate of decrease in E with increasing temperature. By using the present data and our previous results for PS, PET, and B2O3, it has been found that ΔE correlates with the values of dynamic fragility, increasing with the latter in approximately exponential fashion.

Correlation of the variability parameter with the dynamic fragility.

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Correlation of the variability parameter with the dynamic fragility.
Non‐Isothermal Crystallization of Hyperbranched Poly(ε‐caprolactone)s and Their Linear Counterpart
Authors: Choi Jeongsoo , Chun Sang‐Wook , Kwak Seung‐Yeop
Published: June 2006

Summary: Three hyperbranched poly(ε‐caprolactone)s were prepared with the architectural variation in the length of linear backbone segments consisting of 5, 10, and 20 ε‐caprolactone units (accordingly given the names HPCL–5, –10, and –20, respectively) and in the number of branching points as characterized by 1H NMR end group analyses. The non‐isothermal crystallizations of HPCLs and LPCL were performed using DSC at various cooling rates and the kinetic study was further performed by using both Ozawa and Kissinger methods. All the kinetic parameters such as the cooling functions and the apparent activation energy of crystallization indicated that HPCLs with longer linear segments and fewer number of branching points showed faster crystallization rates, whereas LPCL exhibited an intermediate rate between HPCL–10 and HPCL–20, i.e., HPCL–5 < HPCL–10 < LPCL < HPCL–20. The decrease in the crystallization rate is attributed to the presence of heterogeneous branching points in HPCLs with shorter segments, which hinders the regular chain packing to crystallize. In addition, the faster crystallization of HPCL–20 compared to LPCL was associated with the higher cooperative chain mobility in the melt.

Schematic illustrations for HPCL and LPCL.

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Schematic illustrations for HPCL and LPCL.
Synthesis of Silicone‐Methacrylate Copolymers by ATRP Using a Nickel‐Based Supported Catalyst
Authors: Duquesne Emmanuel , Habimana Jean , Degée Philippe , Dubois Philippe
Published: June 2006

Summary: A nickel (II) bromide catalyst immobilized onto crosslinked diphenylphosphinopolystyrene (PS‐PPh3/NiBr2) was used for the synthesis of silicone‐methacrylate copolymers by atom transfer radical polymerization (ATRP) of various methacrylate monomers using ω‐bromide silicone chains as macroinitiator. The polymerization proved to be very well‐controlled when a sufficient amount of soluble ligand, i.e., triphenylphosphine (PPh3), was added to the polymerization medium. Under these conditions, this technique efficiently led to the production of different copolymers with controlled compositions and molecular weights as well as narrow polydispersity indices ($\overline M _{\rm w} /\overline M _{\rm n}$ < 1.5). The recovered copolymers proved to be almost free of catalyst residues. Indeed, inductively coupled plasma (ICP) analysis revealed a metal content lower than 100 ppm, representing only a few percent of the initial metal content in the polymerization medium.

Synthesis of PDMS block copolymer in toluene catalyzed by PS‐PPh3/NiBr2 in the presence of soluble PPh3 at 90 °C.

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Synthesis of PDMS block copolymer in toluene catalyzed by PS‐PPh3/NiBr2 in the presence of soluble PPh3 at 90 °C.
Comparison of Polyamide‐6 Nanocomposites Based on Pristine and Organic Montmorillonite Obtained via Anionic Ring‐Opening Polymerization
Authors: Liu Andong , Xie Tingxiu , Yang Guisheng
Published: June 2006

Summary: Exfoliated Na+‐MMT/polyamide‐6 and intercalated organic MMT/polyamide‐6 nanocomposites were prepared using sodium montmorillonite with water dispersion and organic MMT with acetone dispersion via anionic ring‐opening polymerization, respectively. The effects of Na+‐MMT and OMMT on the polyamide‐6 were compared. Analysis shows that incorporation of exfoliated Na+‐MMT obviously improved mechanical properties, thermal stability, crystalline rate and favored formation of a γ‐crystalline form of matrix, but intercalated OMMT has no obvious effect on it. Nanoscale dispersing Na+‐MMT dramatically elevated the viscosity of matrix comparing with pure polyamide‐6. FTIR analysis indicates that the exfoliated Na+‐MMT improved the stability of hydrogen bonding comparing with the OMMT treated by alkylammonium salt modifier, which is different from previous studies. It is believed that hydrogen bonding between Na+‐MMT and polyamide‐6 plays a pivotal role.

FTIR spectra of the NH stretching region of (a) PA, (b) PAM and (c) PAO.

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FTIR spectra of the NH stretching region of (a) PA, (b) PAM and (c) PAO.
A Robust Proton NMR Method to Investigate Hard/Soft Ratios, Crystallinity, and Component Mobility in Polymers
Authors: Maus Andreas , Hertlein Christopher , Saalwächter Kay
Published: June 2006

Summary: An improved proton NMR method for the real‐time measurement of the hard/soft ratio or the crystallinity, and the mobile‐fraction dynamics, in phase‐separated or semicrystalline polymers is presented. It avoids some difficulties associated with earlier approaches and can be applied on high‐ as well as inexpensive low‐field instrumentation. A pulsed mixed magic‐sandwich echo is shown to provide near‐quantitative refocusing of the rigid contribution to the initial part of the free induction decay. This essentially removes the need to account for signal loss during the receiver dead time, and the method should thus be useful for a variety of applications where the magnetization distribution over differently mobile fractions is to be determined. The overall decay of the mobile signal of a semicrystalline polymer was found to exhibit a significant field dependence, such that the apparent transverse relaxation function of the amorphous part is in a real‐time experiment best characterized by a subsequent Carr–Purcell–Meiboom–Gill pulse train. It is demonstrated to be mainly influenced by mobility, while instrumental effects play a minor role. The mobility of the amorphous fraction depends not only on the overall crystallinity, but also on the crystallization conditions, thus on the nanometer‐scale morphology.

Isothermal crystallization of sPP monitored on a 20 MHz low‐field proton NMR spectrometer using the MSE‐CPMG experiment.

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Isothermal crystallization of sPP monitored on a 20 MHz low‐field proton NMR spectrometer using the MSE‐CPMG experiment.
Goal hierarchies as antecedents of market structure
Authors: Paulssen Marcel , Bagozzi Richard P.
Published: June 2006

Current models of market structure are descriptive in nature and lack theoretical grounding in consumer behavior. Such grounding is especially needed in the specification of marketing strategies. A self‐regulatory model of consumer consideration‐set formation will be employed as a basis of market structure in this article. The authors propose and show that consumers regulate their behavior according to goals at different levels of their goal hierarchies, which in turn determine brand consideration. Differences in the salience of goals at different hierarchical levels lead to differences in the composition of consideration sets. It is precisely these individual differences in brand consideration that determine the structure of a market. The analysis of consumers' goal hierarchies therefore answers, in part, the question of why a market has a certain structure. Hypotheses on brand consideration and the role of system‐ and principle‐level goals are tested on a sample of 1,018 consumers of automobiles. © 2006 Wiley Periodicals, Inc.
Marketplace and personal space: Investigating the differential effects of attachment style across relationship contexts
Authors: Thomson Matthew , Johnson Allison R.
Published: June 2006

An individual's tendencies in purely personal relationships seem to lead to related tendencies in consumer relationships. The following article presents a study that illustrates how individual differences in personal relationship attachment style can be used to predict the likely success of consumer relationships. In addition, it illustrates how the success of consumption versus nonconsumption relationships can be explained by the effect of attachment style on the individual's perception of qualities of the relationship. © 2006 Wiley Periodicals, Inc.
A Novel Highly Resilient Nanocomposite Hydrogel with Low Hysteresis and Ultrahigh Elongation
Authors: Zhu Meifang , Liu Yang , Sun Bin , Zhang Wei , Liu Xiaoli , Yu Hao , Zhang Yu , Kuckling Dirk , Adler Hans‐Juergen P.
Published: June 2006

Summary: A series of high clay content Laponite XLS/polyacrylamide (PAAm) nanocomposite hydrogels (S‐M gels) with excellent resilience, low elastic hysteresis, and ultrahigh elongation, have been successfully synthesized. Based on our results, it is concluded that the mechanical properties of nanocomposite hydrogels probably depend to a great extent on the hydrophilicity and flexibility of the macromolecules. Moreover, it is found that the transparency during the in‐situ polymerization of S‐M gels does not change, which is quite different from clay/poly(N‐isopropylacrylamide) nanocomposite hydrogels.

Formation of nanocomposite hydrogels using Clay‐S by in‐situ polymerization.

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Formation of nanocomposite hydrogels using Clay‐S by in‐situ polymerization.
Heat‐treated BMP‐2 depots release BMP‐2 in its bioactive form
Authors: Winkler L. , Müller R. , Wiemann M.
Published: June 2006

Small depots of locally fixed bone morphogenetic protein‐2 (BMP‐2), which were dried onto biocompatible carriers and afterwards heat‐treated, induce a local differentiation of contacting osteoblastic cells. Here we investigate whether such depots may act via a release of bioactive BMP‐2. For in vivo experiments we employed a modified gap‐healing approach using dump bell‐shaped implants made from titanium plasma‐sprayed Ti‐6Al‐4V, which were coated with BMP‐2 at only one side. Four weeks after implantation into the cancellous bone of the lateral femur condylus of adult sheep we observed a polar formation of new trabecular bone close to the side where BMP‐2 had been immobilized. We also tested whether BMP‐2 depots stimulate remote cells under cell culture conditions and found that alkaline phosphatase (ALP) of MC3T3‐E1 cells was induced over a distance of several millimetres. Experiments show that BMP‐2 at least in part desorbs from air‐dried and heat‐treated BMP‐2 depots in its bioactive form. Local depots of BMP‐2 may therefore allow to improve bone formation next to metal implants at predefined sites.
A Triphasic Theory for Growth in Biological Tissue – Basics and Applications
Authors: Ricken T. , Schwarz A. , Bluhm J.
Published: June 2006

A triphasic model (solid, interstices filled with water containing nutrients) is proposed for the phenomenological description of transversely isotropic saturated biological tissues including the phenomena of growth. This is done within the framework of a macro‐mechanical description based on the Theory of Porous Media (TPM). Thereby, the constitutive equation of growth is determined by the state of stress and the local proportion of nutrients responsible for the mass exchange. The transversely isotropic behavior of the solid influences both the stress response and the internal fluid permeability, which is considered using an invariant formulation of the Helmholtz free energy and transversely isotropic permeability functions. After presenting the developed framework of the calculation concept including the representation of the governing weak formulations of the equations for large deformations, some representative numerical examples are examined.
Bone repair and regeneration: possibilities
Authors: Vallet‐Regí M.
Published: June 2006

The most significant demand for biomaterials has emerged as a consequence of the need to provide clinical treatment to a large number of patients. The key factors and driving forces are the increase in life expectancy and the aim to provide a minimum quality of life to an aging population. In particular, said increase in life expectancy has increased considerably the number of patients with osteoporosis. If we take also into account the continuous increase in the number of motor vehicles, with its associated social penalty in terms of traffic accidents, the incidence of bone pathologies is increasing at an alarming rate in recent years. The search for potential solutions in this field produces a large demand for materials suitable for bone repair or replacement. Calcium phosphates, bio‐glasses, bio‐glass ceramics and ordered silica mesoporous materials, among other types of materials, will be reviewed and studied from the point of view of their potential applications as replacement materials in bone repair and regeneration, as potential substrates in tissue engineering, and also as drug delivery systems. The ability of functionalising the material surfaces with various molecules of different nature and shape will allow to actuate selectively on the biological environment. An overview on the present achievements, but also on the ‘missing links’ will be presented.
Study on the influence of plasma spray processes and spray parameters on the structure and crystallinity of hydroxylapatite coatings
Authors: Zhao L. , Bobzin K. , Ernst F. , Zwick J. , Lugscheider E.
Published: June 2006

Hydroxylapatite (HA) is one of the most important materials for human hard tissue implants. Until now, HA coatings are widely deposited on implants using atmospheric plasma spraying (APS). Due to the decomposition of HA and formation of amorphous phase during spraying, the crystallinity of APS coatings is usually below 70 %, although coarser spray powders such as one with a size distribution of –150 +45 μm are used. In this study a finer HA powder –80 +50 μm was sprayed using both a conventional APS process and the new “microplasma spraying” (MPS) process. The coatings were characterized in terms of their microstructure and crystallinity. It was found that the spray parameters influenced strongly the coating structure and phase composition. Despite the smaller particles, the HA content of APS coatings could be increased from 27 % to 72 % only by changing the spray parameters. Higher HA contents up to over 85 % could be obtained by microplasma spraying. It was found that textured coatings could form under certain conditions during both spray processes.
X‐ray powder diffraction data of synthetic β‐Tricalcium Phosphate
Authors: Ermrich M. , Peters F.
Published: June 2006

The production of synthetic Tricalcium Phosphate (β‐TCP, Ca3(PO4)2) allows to exclude all disadvantages of biological based ceramics. Moreover the sintered pure‐phase material ensures a high reproducibility without any organic residues or foreign matters. The material was characterized by X‐ray powder diffraction. Using the well‐known structure, the trigonal cell parameters were refined using the information of the Powder Diffraction File PDF #9‐169 to ([1], space group R‐3c, #167, hexagonal setting) : a = b = 10.4183(5) Å, c = 37.346(2) Å, γ = 120°, V = 3510.5(5) Å3; Z = 21, Dx = 3.081 g/cm3. These values represent the lowest lattice parameters for this structure, because of its lowest possible Mg‐ content.
Bioceramic Granulates for use in 3D Printing: Process Engineering Aspects
Authors: Irsen St. H. , Leukers B. , Höckling Chr. , Tille C. , Seitz H.
Published: June 2006

For the fabrication of patient individual bone replacement scaffolds using rapid prototyping (RP) technology, materials with properties adapted to the 3D printing process are needed. First of all the granulate properties of the building material have to match certain specifications concerning particle size and morphology. To fulfil these demands in laboratory scale a commercial fluidized bed granulator was modified to match the specific needs. The changes were tested spraying a sample granulate for the fabrication of synthetic bone grafts. This granulate could successfully be processed in the 3D printer.
A porous media model describing the inhomogeneous behaviour of the human intervertebral disc
Authors: Ehlers W. , Karajan N. , Markert B.
Published: June 2006

Due to the remarkable number of patients suffering from low back pain, a higher research interest is initiated regarding modern numerical simulation techniques. Herein, the Finite Element Method (FEM) in combination with an elaborated model has the potential to be the best choice aiding the design of new intervertebral disc (IVD) implants.

As one of the most vulnerable parts of the human spine, the (IVD) belongs to the class of soft avascular cartilaginous tissues consisting of mostly ionized water (interstitial fluid) and collagen of type I and II embedded in an extracellular meshwork of charged protein compounds. More precisely, the type I collagen is organized in fiber bundles building a fiber‐reinforced ring, the anulus fibrosus (AF), which encloses a highly charged gelatinous core, the nucleus pulposus (NP).

The purpose of this contribution is to utilize the established Theory of Porous Media (TPM) as a continuum‐mechanical framework for the modelling of the IVD. In this context, the TPM is perfectly suitable for the description of multi‐component continua with internal interactions and is proven to yield stable implementations within the mixed Finite Element Method (FEM). Following this, one succeeds in describing the electro‐chemomechanical couplings between the constituents as well as the viscoelastic and anisotropic properties of the extracellular matrix. Moreover, the fiber vectors, which represent the aligned collagen in a continuum‐mechanical sense, as well as the location‐dependent material parameters must be inhomogeneously distributed over the discretized IVD.
Biomaterial structure in deep‐sea bamboo coral (Anthozoa: Gorgonacea: Isididae): perspectives for the development of bone implants and templates for tissue engineering
Authors: Ehrlich H. , Etnoyer P. , Litvinov S. D. , Olennikova M.M. , Domaschke H. , Hanke T. , Born R. , Meissner H. , Worch H.
Published: June 2006

Natural structural biomaterials of marine origin including mollusc shells, sponges and corals not only provide an abundant source of novel bone and cartilage replacements but also inspire investigations to develop nano‐sized biomimetic composites. This study presents a characterisation of the ultrastructure of the deep‐sea Bamboo coral (Anthozoa: Gorgonacea: Isididae) and the nanostructure of some interstitial surfaces with respect to biomineralization phenomena. The skeletons of the corals examined exhibit jointed axes of large bony calcareous structures alternated with smaller proteinaceous nodes of gorgonin, giving the skeletal remains of the organism a digitated appearance, like terrestrial bamboo. To test the hypothesis that bamboo coral internodes exhibit bone‐like mechanical and biochemical properties, structural and biochemical analyses of these natural biomineral composites and separation of proteinaceous components was performed. Due to its high potential for colonization with both human osteoblasts and osteoclasts, the organic matrix, composed of an acidic fibrillar protein framework, proved to be a very successful model for possible applications in tissue engineering. The material properties of the calcareous internodes correlate well with the material property charts for materials used in orthopedic surgery, though denser and stronger than bone. Results of the present study also clearly indicate the quinonproteinaceous nature of the gorgonin. On the basis of the high biomimetic potential of the results obtained, the use of Isididae corals as “living bone implants” as well as their biotechnological aquacultural cultivation seems to be promising for the near future.
Trout Ea4‐ or human Eb‐peptide of pro‐IGF‐I disrupts heart, red blood cell, and vasculature development in zebrafish embryos
Authors: Chun Chang Zoon , Tsai H.J. , Chen Thomas T.
Published: June 2006

E‐peptide of the pro‐insulin‐like growth factor (pro‐IGF)‐I is produced by proteolytic cleavage of the pro‐hormone in post‐translational processing. Introduction of a transgene encoding a secreted form of rtEa4‐ or hEb‐peptide into newly fertilized zebrafish (Danio rerio) eggs by electroporation or microinjection resulted in embryos with abnormal cardiovascular features and reduced red blood cells and vasculature. Two different phenocopies of heart developmental defects were observed: (i) Group I embryos exhibited heart development arrested at the heart muscle stage and (ii) group II embryos exhibited heart development arrested at the heart tube stage. Both groups of embryos also exhibited reduction of red blood cells and vasculature. The mRNA levels of genes essential for heart development (GATA 5 and NKX2.5), hematopoiesis (GATA 1 and GATA 2), and vasculogenesis (VEGF) in normal and defective embryos were determined by quantitative real‐time RT‐PCR at 36 hr post‐fertilization (hpf). Significant reduction of GATA 5, NKX2.5, GATA 1, GATA 2, and VEGF mRNA levels was observed in both groups of defective embryos. These results suggest that overexpression of rtEa4 or hEb transgene in zebrafish embryos disrupts heart development, hematopoiesis, and vasculogenesis by reducing the levels of GATA 5, NKX2.5, GATA 1, GATA 2, and VEGF mRNA. Mol. Reprod. Dev. 1112–1121, 2006. © 2006 Wiley‐Liss, Inc.