bluuebunny/crossref_metadata_2025_split huggingface dataset:
η6:η6 Coordination of Tetraphenylborate to Ytterbium(II): A New Class of Lanthanoid ansa‐Metallocenes
Authors: Deacon Glen B. , Forsyth Craig M. , Junk Peter C. 
Published: March 2005

AbstractThe ytterbium(II) complexes [Yb(tBu2pz)(THF)BPh4] (2) (tBu2pzH = 3,5‐di‐tert‐butylpyrazole) and [Yb{N(SiMe3)2}‐BPh4] (3) were synthesised by reaction of [Yb{N(SiMe3)2}‐(THF)BPh4] (1) with tBu2pzH or by in situ desolvation of the THF complex 1. X‐ray analysis of 2 and 3 reveals η6:η6 binding of chelating BPh4– to ytterbium in both cases, generating true metallocene structures. Complex 3 is distinguished by a very short Yb–N bond and an agostic Yb–Me interaction, both indicative of a highly Lewis acidic metal centre. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
The Formation of 1‐Aryl‐Substituted Naphthalenes by an Unusual Cyclization of Arylethynes Catalyzed by Ruthenium and Rhodium Porphyrins
Authors: Elakkari Elfituri , Floris Barbara , Galloni Pierluca , Tagliatesta Pietro 
Published: March 2005

AbstractThe dimerization of arylethynes to give 1‐aryl‐substituted naphthalenes through catalysis by rhodium and ruthenium porphyrins has been investigated. When performed at temperatures above 130 °C, this reaction affords a mixture of triarylbenzenes and 1‐aryl‐substituted naphthalenes. The yields of naphthalene derivatives range from low to high, depending on the temperature and the phenyl substituents. The concentrations of the initial compounds affect the selectivity of the reaction: the dimerization/trimerization ratios in 1,2‐dichlorobenzene increase as concentration decreases. The reaction mechanism is determined by the peculiar structure of the catalyst ligand and involves the formation of a vinylidene intermediate of the metalloporphyrins. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Coarse sediment transport in mountain streams in Colorado and Wyoming, USA
Authors: Ryan Sandra E. , Porth Laurie S. , Troendle C. A. 
Published: March 2005

AbstractSince the early 1990s, US Forest Service researchers have made thousands of bedload measurements in steep, coarse‐grained channels in Colorado and Wyoming, USA. In this paper we use data from 19 of those sites to characterize patterns and rates of coarse sediment transport for a range of channel types and sizes, including step–pool, plane‐bed, pool–riffle, and near‐braided channels. This effort builds upon previous work where we applied a piecewise regression model to (1) relate flow to rates of bedload transport and (2) define phases of transport in coarse‐grained channels. Earlier, the model was tested using bedload data from eight sites on the Fraser Experimental Forest near Fraser, Colorado. The analysis showed good application to those data and to data from four supplementary channels to which the procedure was applied. The earlier results were, however, derived from data collected at sites that, for the most part, have quite similar geology and runoff regimes. In this paper we evaluate further the application of piecewise regression to data from channels with a wider range of geomorphic conditions. The results corroborate with those from the earlier work in that there is a relatively narrow range of discharges at which a substantial change in the nature of bedload transport occurs. The transition from primarily low rates of sand transport (phase I) to higher rates of sand and coarse gravel transport (phase II) occurs, on average, at about 80 per cent of the bankfull (1·5‐year return interval) discharge. A comparison of grain sizes moved during the two phases showed that coarse gravel is rarely trapped in the samplers during phase I transport. Moreover, the movement and capture of the D16 to D25 grain size of the bed surface seems to correspond with the onset of phase II transport, particularly in systems with largely static channel surfaces. However, while there were many similarities in observed patterns of bedload transport at the 19 studied sites, each had its own ‘bedload signal’ in that the rate and size of materials transported largely reflected the nature of flow and sediment particular to that system. Published in 2005 by John Wiley & Sons, Ltd.
Rock moisture measurements: techniques, results, and implications for weathering
Authors: Sass Oliver 
Published: March 2005

AbstractRock moisture is an important factor for the intensity and distribution of frost weathering processes. However, quantitative measurements are scarce, which is partly due to the lack of reliable measurement techniques. This paper presents five different techniques for obtaining rock moisture data. While collecting rock pieces and two‐dimensional geoelectric measurements allow determination of the spatial moisture distribution, the temporal variability can be derived from conductivity and time domain reflectometry records. Computer simulations, using rock properties and climatic records as input data, render it possible to clarify the important aspects that are responsible for the moisture distribution. It proved to be advisable to use several methods to check and validate the results.The results, obtained in study areas in the Bavarian Alps, make it clear that direct rainfall is the main source of rock moisture. The influence of snow is limited to the immediate vicinity of the snow fields and is not equally pronounced at different times and positions. Rock moisture levels are higher in summer than they are in winter, since in winter less water is supplied in liquid form. Northerly exposed rockwalls are generally more moist than those exposed in a southerly direction, which is due to the different insolation as well as to the wind direction during rainfall. In every position the rock is, on average, wetter on the inside than it is on the surface. This means that shallow frost cycles, as typical for south‐exposed sites, are not affecting weathering, since they take place at a depth level that is mostly dried out.Numerous spatial and temporal patterns of rockfall found in the same study areas can be explained through variations in rock moisture. Thus, the moisture content of the rock is considered to be one of the major controlling factors of the frost‐shattering rate. Copyright © 2005 John Wiley & Sons, Ltd.
Modelling of wetting and drying of shallow water using artificial porosity
Authors: van't Hof B. , Vollebregt E. A. H. 
Published: March 2005

AbstractA new method for wetting and drying in two‐dimensional shallow water flow models is proposed. The method is closely related to the artificial porosity method used by different authors in Boussinesq‐type models, but is further extended for use in a semi‐implicit (ADI‐type) time integration scheme. The method is implemented in the simulation model WAQUA using general boundary fitted coordinates and is applied to realistic schematization for a portion of the river Meuse in the Netherlands.A large advantage of the artificial porosity method over traditionally used methods on the basis of ‘screens’ is a strongly reduced sensitivity of model results. Instead of blocking all water transport in grid points where the water level becomes small, as in screen‐based methods, the flow is gradually closed off. Small changes in parameters such as the initial conditions or bottom topography therefore no longer lead to large changes in the model results. Copyright © 2005 John Wiley & Sons, Ltd.
New nuclear functions of the glycolytic protein, glyceraldehyde‐3‐phosphate dehydrogenase, in mammalian cells
Authors: Sirover Michael A. 
Published: March 2005

AbstractRecent studies establish that the glycolytic protein, glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH), is not simply a classical metabolic protein involved in energy production. Instead, it is a multifunctional protein with defined functions in numerous subcellular processes. New investigations establish a primary role for GAPDH in a variety of critical nuclear pathways apart from its already recognized role in apoptosis. These new roles include its requirement for transcriptional control of histone gene expression, its essential function in nuclear membrane fusion, its necessity for the recognition of fraudulently incorporated nucleotides in DNA, and its mandatory participation in the maintenance of telomere structure. Each of these new functions requires GAPDH association into a series of multienzyme complexes. Although other proteins in those complexes are variable, GAPDH remains the single constant protein in each structure. To undertake these new functions, GAPDH is recruited to the nucleus in S phase or its intracellular distribution is regulated as a function of drug exposure. Other investigations relate a substantial role for nuclear GAPDH in hyperglycemic stress and the development of metabolic syndrome. Considerations of future directions as well as the role of GAPDH post‐translational modification as a basis for its multifunctional activities is suggested. © 2005 Wiley‐Liss, Inc.
Functional interactions of HPK1 with adaptor proteins
Authors: Boomer Jonathan S. , Tan Tse‐Hua 
Published: March 2005

AbstractHematopoietic progenitor kinase 1 (HPK1 or MAP4K1) is a hematopoietic‐specific mammalian STE20‐like protein serine/threonine kinase, comprised of a STE20‐like kinase domain in its N‐terminus, four proline‐rich motifs, a caspase cleavage site, and a distal C‐terminal Citron homology domain. HPK1 is involved in many cellular signaling cascades that include MAPK signaling, antigen receptor signaling, apoptosis, growth factor signaling, and cytokine signaling. HPK1 binds many adaptor proteins including members of the Grb2 family, Nck family, Crk family, SLP‐76 family, and actin‐binding adaptors like HIP‐55. HPK1 tyrosine phosphorylation and kinase activation depend on the presence of adaptor proteins. Adaptor proteins are required not only for linking HPK1 to cell surface receptors like the EGFR, but also for downstream gene transcription like NFAT, AP‐1 and IL‐2. The HPK1 association with Crk, CrkL, and HIP‐55 mediate HPK1‐dependent c‐Jun N‐terminal kinase (JNK) activation, while the association of HPK1 with SLP‐76, Gads, CrkL, Grb2, and Grap affect T‐ and B‐cell dependent gene transcription. Interestingly, HPK1 has been implicated in both increasing and decreasing NFAT, AP‐1, and IL‐2 gene transcription in T‐cells where adaptor proteins play a key role. Lastly, HPK1 will phosphorylate Crk and CrkL, in vitro, which presents a novel possibility for the regulation of adaptor proteins and downstream signaling events. © 2005 Wiley‐Liss, Inc.
Fast apoptosis and erythroid differentiation induced by imatinib mesylate in JURL‐MK1 cells
Authors: Kuželová Kateřina , Grebeňová Dana , Marinov Iuri , Hrkal Zbyněk 
Published: March 2005

AbstractWe compare the effects of Imatinib mesylate (Glivec®) on chronic myeloid leukemia derived cell lines K562 and JURL‐MK1. In both cell lines, the cell cycle arrests in G1/G0 phase within 24 h after the addition of 1 μM Imatinib. This is followed by a decrease of Ki‐67 expression and the induction of apoptosis. In JURL‐MK1 cells, the apoptosis is faster in comparison with K562 cells: the caspase‐3 activity reaches the peak value (20 to 30 fold of the control) after about 40 h and the apoptosis proceeds to its culmination point, the DNA fragmentation, within 48 h following 1 μM Imatinib addition. Unlike K562 cells, JURL‐MK1 cells possess a probably functional p53 protein inducible by TPA (tetradecanoyl phorbol acetate) or UV‐B irradiation. However, no increase in p53 expression was observed in Imatinib‐treated JURL‐MK1 cells indicating that the difference in the apoptosis rate between the two cell lines is not due to the lack of p53 in K562 cells. Imatinib also triggers erythroid differentiation both in JURL‐MK1 and K562 cells. Glycophorin A expression occurred simultaneously with the apoptosis, even at the single cell level. In K562 cells, but not in JURL‐MK1 cells, the differentiation process involved increased hemoglobin synthesis. However, during spontaneous evolution of JURL‐MK1 cells in culture, the effects produced by Imatinib progressively changed from the fast apoptosis to the more complete erythroid differentiation. We suggest that the apoptosis and the erythroid differentiation are parallel effects of Imatinib and their relative contributions, kinetics and completeness are related to the differentiation stage of the treated cells. © 2005 Wiley‐Liss, Inc.
Protein interactions with model chromatographic stationary phases constructed using self‐assembled monolayers
Authors: Barrett David A. , Power Gillian M. , Hussain Maruf A. , Pitfield Ian D. , Shaw P. Nicholas , Davies Martyn C. 
Published: March 2005

AbstractModel surfaces representative of chromatographic stationary phases were developed by immobilising an homologous series (C2–C18) of n‐alkylthiols, mixed monolayers of C4/C18 and thioalkanes with alcohol, carboxylic acid, amino and sulphonic acid terminal groups onto a flat, silver‐coated glass surface using self‐assembled monolayer (SAM) chemistry. The processes of adsorption and desorption of serum albumins onto the monolayer surfaces was monitored in real‐time using surface plasmon resonance (SPR). Alkyl‐terminated SAMs all showed a strong adsorption of bovine serum albumin which was largely independent of alkyl chain length, the ratio of mixed C4/C18 SAMs or the solution pH/ionic strength. The adsorption of human serum albumin to carboxylic and amine terminated SAMs was shown to be predominantly via non‐electrostatic interactions (hydrophobic or hydrogen bonding). However, sulphonic acid terminated SAMs showed almost exclusively electrostatic interactions with human serum albumin. This preliminary work using self‐assembled monolayer chemistry confirms the usefulness of well characterised SAMs surfaces for investigating protein adsorption and desorption onto/from model chromatography surfaces and gives some guidance for selecting appropriate functionalities to develop better surfaces for chromatography and electrophoresis.
Characterisation of poly(N‐isopropylacrylamide) by asymmetrical flow field‐flow fractionation, dynamic light scattering, and size exclusion chromatography
Authors: Yohannes Gebrenegus , Shan Jun , Jussila Matti , Nuopponen Markus , Tenhu Heikki , Riekkola Marja‐Liisa 
Published: March 2005

AbstractAsymmetrical flow field‐flow fractionation (AsFlFFF) was used to determine the hydrodynamic particle sizes, molar masses, and phase transition behaviour of various poly(N‐isopropylacrylamide) (PNIPAM) samples synthesised by reversible addition–fragmentation chain transfer (RAFT) and conventional free radical polymerisation processes. The results were compared with corresponding data obtained by dynamic light scattering (DLS) and size exclusion chromatography (SEC). Agreement between the three methods was good except at higher molar masses, where the molar mass averages obtained by SEC were much lower than those obtained by AsFlFFF and light scattering. The aggregation of the polymers, which are thermally sensitive, was studied by DLS and AsFlFFF at various temperatures. In deionised water there was an abrupt change in the particle size due to phase separation at ≈32–35°C. The critical temperatures determined by AsFlFFF were 3–5°C higher than those obtained by DLS.
Preparation and evaluation of a doubly tethered chiral stationary phase based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid
Authors: Hyun Myung Ho , Kim Do Hun , Cho Yoon Jae , Jin Jong Sung 
Published: March 2005

AbstractA new doubly tethered chiral stationary phase (CSP) was prepared to enhance CSP stability as well as to take advantage of the tertiary amide linkage by bonding (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid to bis(3‐aminopropyl)silica gel. The new CSP was quite effective in the resolution of α‐amino acids, β‐amino acids, amino alcohols, and amines and the chromatographic resolution behaviors of the new CSP were exactly consistent with those of the corresponding singly tethered CSP containing N—CH3 tertiary amide linkage. Direct comparison between the stabilities of the new CSP and the corresponding singly tethered CSP containing N—CH3 tertiary amide linkage under harsh chromatographic conditions reveals that the new CSP is more stable than the latter.
Polyacrylonitrile Enzyme Ultrafiltration and Polyamide Enzyme Microfiltration Membranes Prepared by Diffusion and Convection
Authors: Dayal Rajeshwar , Godjevargova Tzonka 
Published: March 2005

AbstractSummary: Glucose oxidase (GOD) and catalase (CAT) were covalently immobilized onto three types of polyacrylonitrile (PAN 1, PAN 2, and PAN 3) ultrafiltration (UF) membranes with different pore sizes and one type of polyamide (PA) microfiltration (MF) membrane by the bifunctional reagent, glutaraldehyde. The initial membranes were pre‐modified to generate active amide groups in the PAN membranes and active amino groups in the PA membranes. The PAN 3 membrane contained the highest amount of active groups, and the membrane PA the lowest. The modified membranes were enzyme‐loaded by diffusion and convection (UF). The effect of membrane pore size and immobilization methods on enzymatic activity and bound protein were studied. The most effective immobilized system was prepared by diffusion using a PAN 3 membrane as a carrier (bound protein: 0.055 mg/cm2, relative activity: 87.6%). This membrane had the highest pore size of all the PAN membranes. Despite the highest pore size of PA membrane, the enzyme PA membranes prepared by diffusion showed the lowest amount of bound protein (0.03 mg/cm2) and the lowest relative activity (35.38%). This correlates with the lowest amount of active groups found in these membranes. The relative activity was higher for all the enzyme systems loaded by diffusion. The systems prepared by convection of the enzyme solution contained higher amounts of enzymes (0.035–0.13 mg/cm2 protein), which led to internal substrate diffusion resistance and a decrease in the GOD relative activity (21.55–68.5%) in these systems. The kinetic parameters (Vmax and Km) and the glucose conversion of the immobilized systems prepared by diffusion were also studied.Relative activity of GOD in immobilized GOD plus CAT membranes prepared by different methods of enzyme loading: diffusion and convection (UF). The bars represent the difference between relative activities of immobilized GOD prepared by two methods for all the membranes. The enzyme activity was determined under static (a) and dynamic (b) conditions; 1 M glucose, pH 5.8, and 28 °C.magnified imageRelative activity of GOD in immobilized GOD plus CAT membranes prepared by different methods of enzyme loading: diffusion and convection (UF). The bars represent the difference between relative activities of immobilized GOD prepared by two methods for all the membranes. The enzyme activity was determined under static (a) and dynamic (b) conditions; 1 M glucose, pH 5.8, and 28 °C.
Adsorption Kinetics and Thermodynamics of Acid Dyes on a Carboxymethylated Chitosan‐Conjugated Magnetic Nano‐Adsorbent
Authors: Chang Yang‐Chuang , Chen Dong‐Hwang 
Published: March 2005

AbstractSummary: The monodisperse chitosan‐conjugated Fe3O4 nanoparticles with a mean diameter of 13.5 nm were fabricated by the carboxymethylation of chitosan and its covalent binding onto Fe3O4 nanoparticles via carbodiimide activation. The carboxymethylated chitosan (CMCH)‐conjugated Fe3O4 nanoparticles with about 4.92 wt.‐% of CMCH had an isoelectric point of 5.95 and were shown to be quite efficient as anionic magnetic nano‐adsorbent for the removal of acid dyes. Both the adsorption capacities of crocein orange G (AO12) and acid green 25 (AG25), as the model compounds, decreased with increasing pH, and the decreasing effect was more significant for AO12. On the contrary, the increase in the ionic strength decreased the adsorption capacity of AG25 but did not affect, obviously, the adsorption capacity of AO12. By the addition of NaCl and NaOH, both AO12 and AG25 could desorb and their different desorption behavior could be attributed to the combined effect of pH and ionic strength. From the adsorption kinetics and thermodynamics studies, it was found that both the adsorption processes of AO12 and AG25 obeyed the pseudo‐second‐order kinetic model, Langmuir isotherm, and might be surface reaction‐controlled. Furthermore, the time required to reach the equilibrium for each one was significantly shorter than those using the micro‐sized adsorbents due to the large available surface area. Also, based on the weight of chitosan, the maximum adsorption capacities were 1 883 and 1 471 mg · g−1 for AO12 and AG25, respectively, much higher than the reported data. Thus, the anionic magnetic nano‐adsorbent could not only be magnetically manipulated but also possessed the advantages of fast adsorption rate and high adsorption capacity. This could be useful in the fields of separation and magnetic carriers.Acid dyes adsorption onto the CMCH‐conjugated Fe3O4 nanoparticles.magnified imageAcid dyes adsorption onto the CMCH‐conjugated Fe3O4 nanoparticles.
Polymer Thermoplastic Proton Conductors Based on PPO and PS Ionomer Blends
Authors: Cánovas María José , Acosta José Luis , Linares Amelia 
Published: March 2005

AbstractSummary: Two new proton‐conducting ionomers types were obtained based on poly(2,6‐dimethyl‐1,4‐phenylene) oxide (PPO) and polystyrene (PS) with different ionic group contents. They were characterized by means of infrared spectroscopy (FT‐IR), differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA) and X‐ray photoelectron spectroscopy (XPS). From PPO and PS ionomers, binary blends of different compositions were prepared, the blend compatibility of the samples being assessed by means of DSC and DMA. Conducting properties of these materials were studied by means of complex impedance spectroscopy. In addition, water and methanol crossover through the different samples was measured, the results being compared with Nafion. The high conductivity and the low methanol permeability of some systems make them a valid alternative for application in fuel cells.Variation of the interaction parameter, χ12, for PPO‐SH III/PS‐SH III blends.magnified imageVariation of the interaction parameter, χ12, for PPO‐SH III/PS‐SH III blends.
Eosinophilic perimyositis as the presenting feature of a monoclonal T‐cell expansion
Authors: Dunand Murielle , Lobrinus Johannes A. , Spertini Olivier , Kuntzer Thierry 
Published: March 2005

AbstractA 51‐year‐old physically active man was investigated for exertional myalgias and muscle stiffness. On examination he had mild proximal muscle weakness of the upper extremities and retraction of the digit flexors. Blood eosinophilia was present, but serum creatine kinase (CK) levels and an electromyographic study were normal. A skin–fascia–muscle biopsy of the calf revealed a macrophagic and CD4+T‐cell infiltration of the perimysium, and a T‐cell expansion was observed in blood, bone marrow, and muscle. A diagnosis of eosinophilic perimyositis was made, and prednisone and azathioprine were administrated with a good clinical response. This case highlights the differential diagnosis of blood eosinophilia with muscle disorders, and underscores that eosinophilic perimyositis may be the expression of a T‐cell monoclonal expansion. Although the pathogenesis behind the T‐cell expansion is unclear but probably inflammatory, we suggest regular follow‐up to allow early treatment of any T‐cell lymphoproliferative malignancy that may develop. Muscle Nerve, 2005