bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Copper(II) Complexes as Efficient Catalysts for Olefin Aziridination: The Effect of Ligand Steric Hindrance on Reactivity
Authors: Dhanalakshmi Thirumanasekaran , Suresh Eringathodi , Stoeckli‐Evans Helen , Palaniandavar Mallayan 
Published: September 2006

AbstractThree new copper(II) complexes derived from the tridentate N3 ligands 4‐methyl‐1‐(pyrid‐2‐ylmethyl)‐1,4‐diazacycloheptane (L1), 1‐(quinol‐2‐ylmethyl)‐1,4‐diazacycloheptane (L2), and 4‐methyl‐1‐(quinol‐2‐ylmethyl)‐1,4‐diazacycloheptane (L3) have been prepared and examined as copper catalysts for olefin aziridination. In the X‐ray crystal structures of the complexes [Cu(L2)Cl2] (2) and [Cu(L3)Cl2] (3) copper(II) adopts a trigonal‐bipyramidal distorted square‐based pyramidal geometry (TBDSBP) as seen from the values of the trigonality index τ (0.08 for 2 and 0.48 for 3). The enhanced trigonal distortion in 3 is due to the presence of an N‐Me group, the lone pair orbital of which is not oriented exactly along the d orbital of copper(II). While [Cu(L1)(H2O)](ClO4)2 (1) assumes a tetragonal geometry in solution, complexes 2 and 3 adopt a distorted tetragonal geometry, as revealed by UV/Vis and EPR spectral studies. The complexes undergo quasi‐reversible CuII/CuI redox behavior in methanol solution. The ability of the complexes to mediate nitrene transfer from PhINTs to olefins to form N‐tosylaziridines has been studied. The complexes are found to be efficient catalysts (in 5 mol‐% amounts) for the aziridination of the reactive olefin styrene, with yields varying from 80 to 90 % (with respect to PhINTs). They exhibit significant catalytic nitrene transfer reactivity (yields of 30 to 60 %) also towards the less reactive olefins cyclohexene and cyclooctene. A remarkable observation is the significantly accelerated rate of aziridination by 3, which is ascribed to the steric crowding around copper(II) imposed by the bulky quinolyl and N‐Me groups of the tridentate ligand L3.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
A High‐Temperature Multinuclear NMR Study of Na3AlF6–FeO andNa3AlF6–Fe2O3 Melts
Authors: Šimko František , Rakhmatullin Aydar , Boča Miroslav , Daněk Vladimír , Bessada Catherine 
Published: September 2006

AbstractIn the Hall–Héroult process for the industrial production of aluminum, iron oxide impurities are known to lower the current efficiency as well as the metal quality. Iron can be present in the di‐ or trivalent form. The nature of dissolved FeIII and FeII species and the reactions taking place in cryolitic melts have been investigated by high‐temperature NMR spectroscopy. The evolution of 27Al, 23Na, and 19F NMR chemical shifts are reported in the Na3AlF6–FeO and Na3AlF6–Fe2O3 systems for different iron oxide contents. They express the formation of oxofluoroaluminate species. For the Na3AlF6–FeO system, the 19F signal appears only after 14 minutes at 1020 °C. The line position is shifted with heating time. This evolution is associated with a narrowing of the 27Al signal due to a decrease in the content of paramagnetic compounds in the sample. This effect is probably caused by the evaporation of an FeII compound, as already mentioned in the literature. For the Na3AlF6–Fe2O3 system we have never observed the 19F NMR spectra over the full heating time (ca. 30 min). This could be due to the influence of paramagnetic FeIII nuclei, probably in FeF63– species present in the melt. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
SnCl4‐Mediated Reactions of Cyclopropyl Alkyl Ketones with α‐Keto Esters
Authors: Yang Yong‐Hua , Shi Min 
Published: September 2006

AbstractThis paper reports the full details of Lewis acid SnCl4‐mediated reactions of cyclopropyl alkyl ketones with α‐keto esters under mild conditions. In general, it was found that four products were formed in the SnCl4‐mediated reactions of cyclopropyl alkyl ketones. However, by controlling the aldol reaction process, the corresponding spiro‐γ‐lactone products can be exclusively obtained in moderate to good yields with good stereoselectivities via the sequential nucleophilic ring‐opening reaction of cyclopropane by H2O, aldol type reaction and subsequent cyclic transesterification mediated by the Lewis acid. The mechanism was further confirmed by introducing a substituent at the other α‐position of the cyclopropyl alkyl ketone to produce two or three other products without the formation of spiro‐γ‐lactone products under the same reaction conditions. In summary, SnCl4‐mediated reactions of cyclopropyl alkyl ketones with α‐keto esters afforded a new general method for the synthesis of spiro‐γ‐lactones in moderate to good yields with good stereoselectivities. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Simultaneous separation of nitrofuran antibiotics and their metabolites by using micellar electrokinetic capillary chromatography
Authors: Wickramanayake Priyanga U. , Tran Tin C. , Hughes Jeff G. , Macka Mirek , Simpson Nigel , Marriott Philip J. 
Published: September 2006

AbstractMixtures comprising nitrofuran antibiotics (NFA) and nitrofuran metabolites (NFM) were resolved for the first time by using MEKC. Sodium deoxycholate (SDC) was chosen as the micelle‐forming surfactant. Optimization of separation conditions was achieved by using a central composite experimental design (CCD) approach. Experimental parameters such as concentration ratio of borate to phosphate in the buffer, pH of the running electrolyte and voltage were investigated. The effect of concentration of the surfactant on resolution was significant. Under optimal conditions of 80 mM SDC, pH 9.0, (20 mM borate + 20 mM phosphate) and 16 kV, the resolution between eight consecutive peak pairs ranged from 1.9 to 11.8. Due to the absence of a UV‐active chromophore in the metabolites, they were derivatized with 2‐nitrobenzaldehyde (2‐NBA). In order to mimic a proposed extraction procedure for the analysis of both NFA and/or derivatized NFM in a sample, aqueous samples (prederivatized with 2‐NBA) were extracted by using C18 SPE cartridges. After washing with H2O, the cartridges were eluted with a small portion of organic solvent with weak elution characteristics to remove excess 2‐NBA (hexane was chosen). Target analytes were then recovered with ACN. Excellent reproducibility of migration time (tmig) was achieved for all analytes using the developed MECC approach, with absolute tmig <1% RSD and tmig ratio <0.2% RSD, and peak area ratio was 4% RSD. The LOD for each compound, calculated by extrapolating to an S/N of 3, were found to be 0.19–2.0 μg/mL.
Application of capillary zone electrophoresis with large‐volume sample stacking to the sensitive determination of sulfonamides in meat and ground water
Authors: Soto‐Chinchilla Jorge J. , García‐Campaña Ana M. , Gámiz‐Gracia Laura , Cruces‐Blanco Carmen 
Published: September 2006

AbstractA CZE method with UV‐Vis detection has been established and validated for the determination of nine sulfonamides: sulfapyridine, sulfamethazine, sulfamerazine, sulfamether, sulfadiazine, sulfadimethoxine, sulfamethoxazole, sulfachlorpyridazine, and sulfamethizole. Optimum separation was obtained on a 64.5 cm×75 μm bubble cell capillary using a buffer containing 45 mM sodium phosphate and 10% methanol at pH 7.3, with temperature and voltage of 27°C and 25 kV, respectively. p‐Aminobenzoic acid was used as an internal standard . Taking into account the lack of sensitivity of the UV‐Vis detection, the application of an on‐line preconcentration methodology, such as large‐volume sample stacking with polarity switching has been proposed. This procedure combined with a solvent extraction/SPE method applied for off‐line preconcentration and cleanup provides a significant improvement in the LODs, ranging from 2.59 to 22.95 μg/L for the studied compounds; the quantification of these residues being possible below the levels established by EU legislation in animal food products, such as meat. Satisfactory recoveries were also obtained in the analysis of these compounds in ground water.
Discontinuous native protein gel electrophoresis
Authors: Niepmann Michael , Zheng Junfeng 
Published: September 2006

AbstractAnalysis of the oligomeric state of a native protein usually requires analytical ultracentrifugation or repeated gel filtration to calculate the protein's size. We have developed a discontinuous native protein gel electrophoresis system that allows the separation of even basic proteins according to their size, oligomeric state, and shape. This gel system combines the addition of negative charges to the proteins by Serva Blue G with a discontinuous buffer system and gradient gels. As in SDS‐PAGE, chloride constitutes the high mobility anion in the gel and anode buffer. However, for sample focusing this system employs histidine instead of glycine as the slow dipolar ion following from the cathode buffer to improve migration of basic proteins. In addition, proteins run into gel pores corresponding to their size and shape in the gradient gel. Using this gel system, we show that the polypyrimidine tract‐binding protein (PTB) is a monomer.
Kinetic study of paracetamol on prolidase activity in erythrocytes by capillary electrophoresis with Ru(bpy)32+ electrochemiluminescence detection
Authors: Yuan Jipei , Wei Hui , Jin Wenrui , Yang Xiurong , Wang Erkang 
Published: September 2006

AbstractWe explored the CE with (bpy) 2+3 electrochemiluminescence detection for the kinetic study of drug–enzyme interaction. Effects of four nonsteroidal anti‐inflammatory drugs including aspirin, paracetamol, sodium salicylate and phenacetin on prolidase (PLD) activity in erythrocytes were investigated. Aspirin enhanced PLD activity whereas the other three had inhibiting effects. This may reveal their different effects on the collagen biosynthesis and catabolism that influence tumor invasiveness. Kinetic study of paracetamol on PLD showed that the value of Michaelis constant Km for PLD was 1.23 mM. The mechanism of PLD inhibition by paracetamol is noncompetitive inhibition, and the inhibitor constant Ki value obtained in our research was 9.73×103 μg/L.
A Retrospective lyrical analysis of songs written by adolescents with anorexia nervosa
Authors: McFerran Katrina , Baker Felicity , Patton George C. , Sawyer Susan M. 
Published: September 2006

AbstractSong‐writing plays a central role in music therapy with adolescents. A retrospective lyrical analysis of songs written by adolescents with anorexia nervosa was undertaken in order to identify common themes solicited through song‐writing interventions. Fifteen participants contributed 17 songs, from which 368 lyrical units were identified. A modified content analysis approach was used with each lyrical unit being categorised to one of six themes determined from the literature and clinical experience. The theme of ‘identity’ was used most frequently (28%), with the sub‐theme of ‘exploring new behaviours, positive self‐talk’ being addressed most often (12.5% of total). The dominance of the developmentally important theme of ‘identity’ may reflect the relationship between adolescents, music and identity or may be related to the way in which anorexia nervosa has been theorised to assist the adolescent in managing challenges to the emerging sense of self. Copyright © 2006 John Wiley & Sons, Ltd and Eating Disorders Association.
Persistent alluvial fanhead trenching resulting from large, infrequent sediment inputs
Authors: Davies Timothy R. H. , Korup Oliver 
Published: September 2006

AbstractWe present laboratory and field evidence that in mountainous catchment‐fan systems persistent alluvial fanhead aggradation and trenching may result from infrequent, large sediment inputs. We suggest that the river‐fan systems along the fault‐bounded range front of the western Southern Alps, New Zealand, are likely to be in a dynamic equilibrium on ≥103‐yr timescales, superimposed on which their fanheads undergo long‐term cumulative episodic aggradation. These fanheads are active only in rare events, do not take part in the usual behaviour of the catchment‐fan system and require much longer to exhibit dynamic equilibrium than the rest of the fan. These findings (1) increase our knowledge of the effects of extreme events on alluvial fan morphodynamics in humid climates, (2) question the general applicability of inferring past climatic or tectonic regimes from alluvial‐fan morphology and stratigraphy and (3) provide a conceptual basis for hazard zonation on alluvial fans. Copyright © 2006 John Wiley & Sons, Ltd.
Validation of WEPS for soil and PM10 loss from agricultural fields within the Columbia Plateau of the United States
Authors: Feng G. , Sharratt B. 
Published: September 2006

AbstractWind erosion from agricultural fields contributes to poor air quality within the Columbia Plateau of the United States. Erosion from fields managed in a conventional winter wheat–summer fallow rotation was monitored during the fallow period near Washtucna, WA, in 2003 and 2004. Loss of soil and PM10 (particulates ≤10 µm in diameter) was measured during six high wind events (sustained wind speed at 3 m height >6·4 m s−1). Soil loss associated with suspension, saltation and creep as well as PM10 emission was used to validate the Wind Erosion Prediction System (WEPS) erosion submodel. Input parameters for WEPS simulations were measured before each high wind event. The erosion submodel produced no erosion for half of the observed events and over‐predicted total soil loss by 200–700 kg ha−1 for the remaining events. The model appears to over‐predict total soil loss as a result of overestimating creep, saltation and suspension. The model both over‐predicted and under‐predicted PM10 loss. High values for the index of agreement (d > 0·5) suggest that the performance of the model is acceptable for the conditions of this study. While the performance of the model is acceptable, improvements can be made in modeling efficiency by better specifying the static threshold friction velocity or coefficients that govern emissions, abrasion and breakage of silt loams on the Columbia Plateau. Copyright © 2006 John Wiley & Sons, Ltd.
A Sinc‐collocation method with boundary treatment for the Stokes equations
Authors: Li Chen , Wu Xionghua 
Published: September 2006

AbstractIn Stokes equations the velocity u and the pressure p are coupled together by the imcompressibility condition div u=0 which makes the equations difficult to solve numerically. In this paper, a method named Sinc‐collocation method with boundary treatment (SCMBT) is applied to the Stokes equations. The numerical results show that our method is of high accuracy, of good convergence with little computational effort. Copyright © 2006 John Wiley & Sons, Ltd.
Error assessment of lattice Boltzmann equation method for variable viscosity flows
Authors: Chao Jianghui , Mei Renwei , Shyy Wei 
Published: September 2006

AbstractIn lattice Boltzmann simulations, variable viscosity can complicate the truncation error analysis and create additional interaction between the truncation error and the boundary condition error. In order to address this issue, two boundary conditions for the lattice Boltzmann equation (LBE) simulations are used, including an exact, but narrowly applicable scheme previously proposed by Noble et al. (Phys. Fluids 1995; 7(1):203–209) and the popular bounce‐back‐on‐link scheme. Using a 2‐D laminar channel flow with a specified variable viscosity as a test case, it is shown that the boundary treatment error does not have a significant interaction with the truncation error associated with variable viscosity. The truncation error behaviour of the LBE for flows with variable viscosity is further investigated through a comparison between the LBE solution and the Navier–Stokes solution, showing that in the presence of strong variable viscosity the truncation error behaviour of the LBE solution is consistent with that of the Navier–Stokes solution, indicating that the LBE model closely matches the Navier–Stokes model for fluid flows with large viscosity variation. Copyright © 2006 John Wiley & Sons, Ltd.
Modelling of wind wave‐induced bottom processes during the slack water periods in Tampa Bay, Florida
Authors: Shi John Z. , Luther Mark E. , Meyers Stephen 
Published: September 2006

AbstractEstuarine process‐oriented modelling studies were undertaken to understand bottom boundary layer processes in Tampa Bay, Florida. A stationary shallow water wave model, SWAN, was applied to predict wind wave‐induced rms bottom orbital currents in Tampa Bay on a 70 × 100 curvilinear grid. Simulations were performed by using two idealized wind forcing (i.e. northeasterly winds of 10 and 20 m s−1) and high‐resolution bathymetry. Calculations of bed load and total load of fine sand were made by using the transport formulas of Van Rijn (J. Hydraulic Eng.1984;110:1431–1456) and Engelund–Hansen (A Monograph on Sediment Transport in Alluvial Streams. Copenhagen Technical Press: 1972), respectively. Simulations of wind wave induced currents reveal that they are important for fine sand transport along the shallow margins of the Tampa Bay. Modelled bottom orbital currents ranged from 0.05 to 0.39 m s−1. Total loads of fine sand ranged from 2.26×10−10to 1.05×10−5kg m−1s−1for northeasterly winds of 10 m s−1and from 2.46×10−5to 3.21×10−5kg m−1s−1for northeasterly winds of 20 m s−1. Wind wave‐induced bottom resuspension is an important process affecting water quality in Tampa Bay. Copyright © 2006 John Wiley & Sons, Ltd.
Statins induce differentiation and cell death in neurons and astroglia
Authors: März Pia , Otten Uwe , Miserez André R. 
Published: September 2006

AbstractStatins are potent inhibitors of the hydroxy‐methyl‐glutaryl‐coenzyme A reductase, the rate limiting enzyme for cholesterol biosynthesis. Experimental and clinical studies with statins suggest that they have beneficial effects on neurodegenerative disorders. Thus, it was of interest to characterize the direct effects of statins on CNS neurons and glial cells. We have treated defined cultures of neurons and astrocytes of newborn rats with two lipophilic statins, atorvastatin and simvastatin, and analyzed their effects on morphology and survival. Treatment of astrocytes with statins induced a time‐ and dose‐dependent stellation, followed by apoptosis. Similarly, statins elicited programmed cell death of cerebellar granule neurons but with a higher sensitivity. Analysis of different signaling cascades revealed that statins fail to influence classical pathways such as Akt or MAP kinases, known to be activated in CNS cells. In addition, astrocyte stellation triggered by statins resembled dibutryl‐cyclic AMP (db‐cAMP) induced morphological differentiation. However, in contrast to db‐cAMP, statins induced upregulation of low‐density lipoprotein receptors, without affecting GFAP expression, indicating separate underlying mechanisms. Analysis of the cholesterol biosynthetic pathway revealed that lack of mevalonate and of its downstream metabolites, mainly geranylgeranyl‐pyrophosphate (GGPP), is responsible for the statin‐induced apoptosis of neurons and astrocytes. Moreover, astrocytic stellation triggered by statins was inhibited by mevalonate and GGPP. Interestingly, neuronal cell death was significantly reduced in astrocyte/neuron co‐cultures treated with statins. We postulate that under these conditions signals provided by astrocytes, e.g., isoprenoids play a key role in neuronal survival. © 2006 Wiley‐Liss, Inc.
Health care funding levels and patient outcomes: a national study
Authors: Byrne Margaret M. , Pietz Kenneth , Woodard LeChauncy , Petersen Laura A. 
Published: September 2006

AbstractBackground: Health care funding levels differ significantly across geographic regions, but there is little correlation between regional funding levels and outcomes of elderly Medicare beneficiaries. Our goal was to determine whether this relationship holds true in a non‐Medicare population cared for in a large integrated health care system with a capitated budget allocation system.Methods: We explored the association between health care funding and risk‐adjusted mortality in the 22 Veterans Affairs (VA) geographic Networks over a six‐year time period. Allocations to Networks were adjusted for illness burden using Diagnostic Cost Groups. To test the association between funding and risk‐adjusted three‐year mortality, we ran logistic regressions with single‐year patient cohorts, as well as hierarchical regressions on a six year longitudinal data set, clustering on VA Network.Results: A $1000 increase in funding per unit of patient illness burden was associated with a 2–8% reduction in three‐year mortality in cross sectional regressions. However, in longitudinal hierarchical regressions clustering on Network, the significant effect of funding level was eliminated.Conclusions: When longitudinal data are used, the significant cross sectional effect of funding levels on mortality disappear. Thus, the factors driving differences in mortality are Network effects, although part of the Network effect may be due to past levels of funding. Our results provide a caution for cross sectional examinations of the association between regional health care funding levels and health outcomes. Copyright © 2006 John Wiley & Sons, Ltd.
Incremental distributed modelling investigation in a small agricultural catchment: 1. Overland flow with comparison with the unit hydrograph model
Authors: Taskinen Antti , Bruen Michael 
Published: September 2006

AbstractA distributed overland flow model is presented and the test results compared with those of the unit hydrograph (UH) model. Infiltration excess in the overland model was calculated using both a modified Green and Ampt (G–A) method and a more complicated method that keeps track of the soil moisture content. The two‐dimensional partial differential flow equations with kinematic flow approximation were solved using both backward‐central explicit and implicit finite‐difference schemes. Moreover, a baseflow component was added to the flow model. Each part of the model was built by replacing a process by a parallel process or by adding a completely new component. When the model was developed and validated in small agricultural fields in southern Finland, comparisons were made between corresponding processes and the significance of added components were estimated in order to find out whether increased model complexity improves the model performance. Apart from the basic model, all the other distributed models outperformed the UH approach. The implicit scheme was clearly more accurate than the explicit scheme, and the baseflow component improved the results significantly. There was no major difference between the performances of the infiltration models, but the G–A method was more stable and much faster. The approaches that were best in the calibration were also the best in the verification. The full distributed model provides a potential method for running water‐quality models and testing their different processes. Copyright © 2006 John Wiley & Sons, Ltd.