bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chalcogeno Morita−Baylis−Hillman Reaction of 2‐(Methylchalcogeno)phenyl Vinyl Ketones with Aldehydes, Ketones, and α‐Dicarbonyl Compounds
Authors: Kinoshita Hironori , Kinoshita Sayaka , Munechika Yukari , Iwamura Tatsunori , Watanabe Shin‐ichi , Kataoka Tadashi 
Published: December 2003

AbstractReactions of 2‐(methylchalcogeno)phenyl vinyl ketones 1 and 4 with aldehydes 5 were conducted in the presence of BF3·Et2O. The reaction was quenched by addition of Et3N and gave the Morita−Baylis−Hillman adducts 6−7 in good yields. When the reaction mixture of 1 with 5a was worked up with saturated aqueous NaHCO3, the sulfonium salt 8a was obtained together with 6. Ketones 10, α‐diketones, and α‐oxo esters 13, which hardly react in the traditional Morita−Baylis−Hillman reaction, similarly reacted with 2‐(methylchalcogeno)phenyl vinyl ketones 1 and 4 to give the Morita−Baylis−Hillman adducts 11−12 and 14−15. Selenochromanones 9 and 16 were obtained together with 7 and 15 from reactions of seleno derivative 4, with 5 and 13 as by‐products. The formation mechanism for the sulfonium salt syn‐trans‐8a is discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Organic Chemistry of Vitamin D Analogues (Deltanoids)
Authors: Posner Gary H. , Kahraman Mehmet 
Published: December 2003

AbstractAn increasing number of synthetic vitamin D analogues (deltanoids) are now being used as sensitive molecular biology probes and also as new drug candidates and new drugs for treatment of various human diseases. The design and stereocontrolled synthesis of such new deltanoids are guided by considering catabolism inhibition and by using large steroidal chirons and small steroid‐derived chirons. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Cover Picture: Synthesis and Water Solubility of Novel Fullerene Bisadduct Derivatives (Eur. J. Org. Chem. 24/2003)
Authors: Bosi Susanna , Feruglio Luigi , Milic Dragana , Prato Maurizio 
Published: December 2003

AbstractThe cover picture shows water‐soluble fullerene derivatives floating in the Trieste bay, Italy, with the magnificent Miramare Castle, built between 1856 and 1860 by Maximilian of Habsburg, in the background. Details of the synthesis and water solubility of novel fullerene bisadduct derivatives are discussed in the article by M. Prato et al. on p. 4741 ff.
Carbon nanotubes as separation carrier in capillary electrophoresis
Authors: Wang Zonghua , Luo Guoan , Chen Jianfang , Xiao Sufang , Wang Yiming 
Published: December 2003

AbstractThe utility and versatility of carboxylic single‐walled carbon nanotubes (c‐SWNT) in capillary electrophoresis (CE) is demonstrated, using as model solutes homologues and structural isomers. In the case of homologues of caffeine and theobromine, distinct changes in the electrophoretic parameters occur at a critical concentration of c‐SWNT in the run buffer. It is suggested that the c‐SWNT of a definite concentration could form a network in the run buffer as a pseudostationary phase on the basis of the unique tubule structure, providing a different separation from sodium dodecyl sulfate (SDS) micelles. In the case of structural isomers of catechol and hydroquinone, differing from the homologues, it is mainly attributable to the functional groups on the c‐SWNT that have an effect on the electrophoretic behaviors by forming intermolecular hydrogen bonding with analytes. Furthermore, aggregated c‐SWNT serve as anticonvective media and minimize solute diffusion contributing to zone broadening. The presence of charged c‐SWNT suppressed the electrodiffusion and decreased the adsorption between capillary wall and solutes, which led to better peak shapes of isomers.
A novel thermogelling matrix for microchannel DNA sequencing based on poly‐N‐alkoxyalkylacrylamide copolymers
Authors: Kan Cheuk‐Wai , Doherty Erin A. S. , Barron Annelise E. 
Published: December 2003

AbstractWe have developed a novel class of thermogelling polymer networks based on poly‐N‐alkoxyalkylacrylamides, and demonstrated their use as DNA sequencing matrices for high‐throughput microchannel electrophoresis in capillary arrays. Polymers and copolymers of N‐ethoxyethylacrylamide (NEEA) and N‐methoxyethylacrylamide (NMEA) were synthesized by aqueous‐phase free‐radical polymerization and characterized by tandem gel permeation chromatography‐multi‐angle laser light scattering. These copolymer matrices exhibit “re‐entrant”‐type volume phase transitions, forming entangled networks with high shear viscosity at low (< 20°C) and high (> 35°C) temperatures, and undergoing a “coil‐to‐globular”, lower critical solution temperature (LCST)‐like phase transition over an intermediate temperature range (20–35°C). Hence, matrix viscosity is relatively low at room temperature (25°C), and increases rapidly above 35°C. The material properties and phase behavior of these thermogelling polymer networks were studied by steady‐shear rheometry. These matrices are easily loaded into capillary arrays at room temperature while existing as viscous fluids, but thermogel above 35°C to form transparent hydrogels via a thermo‐associative phase transition. The extent of the intermediate viscosity drop and the final viscosity increase depends on the composition of the copolymers. DNA sequencing by capillary array electrophoresis with four‐color laser‐induced fluorescence (LIF) detection shows that these thermogelling networks provide enhanced resolution of both small and large DNA sequencing fragments and longer sequencing read lengths, in comparison to appropriate control (closely related, nonthermogelling) polymer networks. In particular, a copolymer comprised of 90% w/w NMEA and 10% w/w NEEA, with a molecular mass of ∼ 2 MDa, delivers around 600 bases at 98.5% base‐calling accuracy in 100 min of electrophoresis.
Modulation of plasma lipid levels affects benzo[a]pyrene‐induced DNA damage in tissues of two hyperlipidemic mouse models
Authors: Curfs Daniëlle M.J. , Beckers Linda , Godschalk Roger W.L. , Gijbels Marion J.J. , van Schooten Frederik J. 
Published: December 2003

AbstractThe role of plasma lipids in the uptake, transportation, and distribution of lipophilic carcinogens like benzo[a]pyrene (B[a]P) remains unclear. Therefore, we studied the effects of dietary‐modulated plasma lipids on B[a]P‐induced DNA damage in several organs of two hyperlipidemic mouse models. Male apolipoprotein E (ApoE)*3‐Leiden (n = 22) and ApoE knockout (ApoE‐KO) mice (n = 20) were fed a high‐fat cholesterol (HFC) diet or low‐fat cholesterol (LFC; standard mouse chow) diet for 3 weeks, after which the animals were exposed to a single oral dose of 5 mg/kg bw B[a]P or vehicle and killed 4 days later. Plasma lipids were determined and DNA adducts were measured in aorta, heart, lung, liver, brain, and stomach. Total cholesterol and low‐density lipoprotein (LDL) cholesterol were increased in all animals on a HFC diet, whereas a decrease of triglycerides was seen only in the ApoE‐KO mice. In ApoE‐KO mice on a normal diet, DNA‐adduct levels were highest in aorta (10.8 ± 1.4 adducts/108 nucleotides), followed by brain (7.8 ± 1.3), lung (3.3 ± 0.7), heart (3.1 ± 0.6), liver (1.5 ± 0.2) and stomach (1.2 ± 0.2). In the ApoE*3‐Leiden mice, adduct levels were equally high in aorta, heart, and lung (4.6 ± 0.7, 5.0 ± 0.5 and 4.6 ± 0.4, respectively), followed by stomach (2.7 ± 0.4), brain (2.3 ± 0.2), and liver (1.7 ± 0.2). In the ApoE‐KO mice, the HFC diet intervention resulted in lower adduct levels in lung (2.1 ± 0.2), heart (1.9 ± 0.2), and brain (2.9 ± 0.5), as compared with the LFC group. In contrast, a nonsignificant increase of adducts was found in aorta (13.1 ± 1.5). A similar but nonsignificant trend was observed in the ApoE*3‐Leiden mice. Multiple regression analysis showed that in aorta, DNA adducts were inversely related to plasma triglycerides (P = 0.004) and were also modulated by the ApoE genotype (P < 0.001). The results of the present study support further investigation into the role of dietary modulation of plasma lipids, ApoE, and polycyclic aromatic hydrocarbon exposure on the formation of DNA adducts in chronic degenerative diseases. Environ. Mol. Mutagen. 42:243–249, 2003. © 2003 Wiley‐Liss, Inc.
Barium chromate is cytotoxic and genotoxic to human lung cells
Authors: Wise Sandra S. , Schuler Julie H.C. , Katsifis Spiros P. , Wise John Pierce 
Published: December 2003

AbstractHexavalent chromium (Cr(VI)) compounds are widely accepted as human lung carcinogens. However, there have been few investigations of the genotoxicity of Cr(VI) in human lung cells. Moreover, our knowledge of the effects of Cr(VI) in human lung cells is further limited because the available data generally focus on the effects of only lead chromate (PbCrO4) and sodium chromate (Na2CrO4). To fully understand these carcinogenic compounds, the genotoxic effects to its target cells need to be evaluated for additional Cr(VI) salts. Accordingly, we investigated the cytotoxicity and clastogenicity of barium chromate (BC) in a human lung cell culture model (WTHBF‐6 cells). We found that BC induced concentration‐dependent cytotoxicity in WTHBF‐6 cells, with relative survival of 88%, 74%, 67%, 12%, 3%, and 0.1% after exposure to 0.01, 0.05, 0.1, 0.5, 1, and 5 μg/cm2 BC, respectively. Similarly, the amount of chromosomal damage also increased with concentration after a 24‐h exposure. Specifically, 0.01, 0.05, 0.1, and 0.5 μg/cm2 BaCrO4 damaged 5%, 9%, 22%, and 49% of metaphase cells, with the total damage reaching 5, 10, 28, and 65 aberrations per 100 metaphases, respectively. Concentrations of 1 and 5 μg/cm2 BC induced a profound cell cycle delay, and no metaphases were observed. The spectrum of damage included chromatid and chromosome‐type lesions consistent with mechanistic events associated with the activation of oncogenes and inactivation of tumor suppressor genes. Overall the data indicate that BC is cytotoxic and genotoxic to human lung cells. Environ. Mol. Mutagen. 42:274–278, 2003. © 2003 Wiley‐Liss, Inc.
Cluster analysis of fMRI data using dendrogram sharpening
Authors: Stanberry Larissa , Nandy Rajesh , Cordes Dietmar 
Published: December 2003

AbstractThe major disadvantage of hierarchical clustering in fMRI data analysis is that an appropriate clustering threshold needs to be specified. Upon grouping data into a hierarchical tree, clusters are identified either by specifying their number or by choosing an appropriate inconsistency coefficient. Since the number of clusters present in the data is not known beforehand, even a slight variation of the inconsistency coefficient can significantly affect the results. To address these limitations, the dendrogram sharpening method, combined with a hierarchical clustering algorithm, is used in this work to identify modality regions, which are, in essence, areas of activation in the human brain during an fMRI experiment. The objective of the algorithm is to remove data from the low‐density regions in order to obtain a clearer representation of the data structure. Once cluster cores are identified, the classification algorithm is run on voxels, set aside during sharpening, attempting to reassign them to the detected groups. When applied to a paced motor paradigm, task‐related activations in the motor cortex are detected. In order to evaluate the performance of the algorithm, the obtained clusters are compared to standard activation maps where the expected hemodynamic response function is specified as a regressor. The obtained patterns of both methods have a high concordance (correlation coefficient = 0.91). Furthermore, the dependence of the clustering results on the sharpening parameters is investigated and recommendations on the appropriate choice of these variables are offered. Hum. Brain Mapping 20:201–219, 2003. © 2003 Wiley‐Liss, Inc.
An empirical comparison of EQ‐5D and SF‐6D in liver transplant patients
Authors: Longworth Louise , Bryan Stirling 
Published: December 2003

AbstractThere remains disagreement about the preferred utility‐based measure of health‐related quality of life for use in constructing quality‐adjusted life years (QALYs). The recent development of a new measure, the SF‐6D, has highlighted this issue. The SF‐6D and EuroQol EQ‐5D measure health‐related utilities on a scale where 0 represents death and 1 represents full health, and both have utility scores generated from random samples of the general UK population. This study explored whether, in a large sample of liver transplant patients, the two instruments provide similar results. The empirical data highlight important variation in the results generated from the use of the two instruments. The data are consistent with a view that the SF‐6D does not describe health states at the lower end of the utility scale but is more sensitive than EQ‐5D in detecting small changes towards the top of the scale. Copyright © 2003 John Wiley & Sons, Ltd.
Classical versus relational approaches to understanding controls on a contract with independent GPs in South Africa
Authors: Palmer Natasha , Mills Anne 
Published: December 2003

AbstractContracts have played a central role in public sector reforms in developed countries over the last decade, and research increasingly highlights their varied nature. In low and middle income countries the use of contracts is encouraged but little attention has been paid to features of the setting that may influence their operation. A qualitative case study was used to examine different dimensions of a contract with private GPs in South Africa. Features of the contract are compared with the notions of classical and relational contracts. Formal aspects of the contract such as design, monitoring and resort to sanctions were found to offer little control over its outcome. The relational rather than classical model of contracting offered a more meaningful framework of analysis, with social and institutional factors found to play an important role. In particular, the individual nature of GP practices highlighted the role played by individual motivation where a contract exercised little formal control. Due to the similarity of factors likely to be present, results are argued to be relevant in many other LMIC settings, and policy‐makers considering contracts for clinical services are advised to consider the possibility of experiencing a similar outcome. Copyright © 2003 John Wiley & Sons, Ltd.
An experiment on simplifying conjoint analysis designs for measuring preferences
Authors: Maddala Tara , Phillips Kathryn A. , Reed Johnson F. 
Published: December 2003

AbstractIn conjoint analysis (CA) studies, choosing between scenarios with multiple health attributes may be demanding for respondents. This study examined whether simplifying the choice task in CA designs, by using a design with more overlap of attribute levels, provides advantages over standard minimal‐overlap methods. Two experimental conditions, minimal and increased‐overlap discrete choice CA designs, were administered to 353 respondents as part of a larger HIV testing preference survey. In the minimal‐overlap survey, all six attribute levels were allowed to vary. In the increased‐overlap survey, an average of two attribute levels were the same between each set of scenarios. We hypothesized that the increased‐overlap design would reduce cognitive burden, while minimally impacting statistical efficiency. We did not find any significant improvement in consistency, willingness to trade, perceived difficulty, fatigue, or efficiency, although several results were in the expected direction. However, evidence suggested that there were differences in stated preferences. The results increase our understanding of how respondents answer CA questions and how to improve future surveys. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of hospital length of stay and discharge destination using hazard functions with unmeasured heterogeneity
Authors: Picone Gabriel , Mark Wilson R. , Chou Shin‐Yi 
Published: December 2003

AbstractThe hospital length‐of‐stay and the discharge destination of a Medicare patient are the outcomes of one decision process involving the interests of the patient, the hospital, and the firms offering covered post‐hospital care. We use a competing risk hazard estimation procedure and adjust for unobserved heterogeneity with a non‐parametric technique to identify significant factors in the decision process. A patient's health and socio‐economic characteristics, the availability of informal care, local market area conditions, and Medicare policies influence length‐of‐stay and discharge destination. The substitution we find between hospital and post‐hospital care and among post‐hospital care alternatives has policy implications for Medicare. Copyright © 2003 John Wiley & Sons, Ltd.
An evaluation of sediment rating curves for estimating suspended sediment concentrations for subsequent flux calculations
Authors: Horowitz Arthur J. 
Published: December 2003

AbstractIn the absence of actual suspended sediment concentration (SSC) measurements, hydrologists have used sediment rating (sediment transport) curves to estimate (predict) SSCs for subsequent flux calculations. Various evaluations of the sediment rating‐curve method were made using data from long‐term, daily sediment‐measuring sites within large (>1 000 000 km2), medium (<1 000 000 to >1000 km2), and small (<1000 km2) river basins in the USA and Europe relative to the estimation of suspended sediment fluxes. The evaluations address such issues as the accuracy of flux estimations for various levels of temporal resolution as well as the impact of sampling frequency on the magnitude of flux estimation errors.The sediment rating‐curve method tends to underpredict high, and overpredict low SSCs. As such, the range of errors associated with concomitant flux estimates for relatively short time‐frames (e.g. daily, weekly) are likely to be substantially larger than those associated with longer time‐frames (e.g. quarterly, annually) because the over‐ and underpredictions do not have sufficient time to balance each other. Hence, when error limits must be kept under ±20%, temporal resolution probably should be limited to quarterly or greater.The evaluations indicate that over periods of 20 or more years, errors of <1% can be achieved using a single sediment rating curve based on data spanning the entire period. However, somewhat better estimates for the entire period, and markedly better annual estimates within the period, can be obtained if individual annual sediment rating curves are used instead. Relatively accurate (errors <±20%) annual suspended sediment fluxes can be obtained from hydrologically based monthly measurements/samples. For 5‐year periods or longer, similar results can be obtained from measurements/samples collected once every 2 months. In either case, hydrologically based sampling, as opposed to calendar‐based sampling is likely to limit the magnitude of flux estimation errors. Published in 2003 John Wiley & Sons, Ltd.
Simulating methane emission from a Chinese rice field as influenced by fertilizer and water level
Authors: Yu Z. , Shangguan X. , Pollard D. , Barron E. J. 
Published: December 2003

AbstractNatural and agricultural wetlands are considered to be the major sources of global atmospheric methane (CH4). A one‐dimensional model was developed to simulate methane emission and used to examine the influence of various physical processes on the rate of methane emission. Three processes involved in the methane emission are implemented in the model: production, reoxidation and transport. Three transport pathways were considered: diffusion across water–air or soil–air interfaces, ebullition and diffusion through plants. These pathways are influenced by soil properties, plant growth, water‐table conditions, temperature and external inputs (e.g. fertilizer). The model was used to examine the seasonal variation of the methane emission at a rice field in Hunan, China, which was observed during a field experiment for consecutive (early and late) rice seasons in 1992. The observed seasonal variations of methane emission, and role of plants in transporting methane to the atmosphere, are captured by the model simulation. Further model applications were conducted to simulate effects of fertilizer and water‐level condition on the methane emission. The results indicate that unfermented organic fertilizer produces a higher methane emission rate than mineral fertilizer. The simulations with treatments of a deep‐water covering and constant moisture reduced the methane emission. The rice field study provides a framework for further development of the model towards simulations based on spatially distributed variables (e.g. water table, soil temperature and vegetation) at a regional scale. Copyright © 2003 John Wiley & Sons, Ltd.
Estimation of snow water equivalent using microwave radiometry over Arctic first‐year sea ice
Authors: Barber D. G. , Iacozza J. , Walker A. E. 
Published: December 2003

AbstractThe magnitude and spatial distribution of snow on sea ice are both integral components of the ocean–sea‐ice–atmosphere system. Although there exists a number of algorithms to estimate the snow water equivalent (SWE) on terrestrial surfaces, to date there is no precise method to estimate SWE on sea ice. Physical snow properties and in situ microwave radiometry at 19, 37 and 85 GHz, V and H polarization were collected for a 10‐day period over 20 first‐year sea ice sites.We present and compare the in situ physical, electrical and microwave emission properties of snow over smooth Arctic first‐year sea ice for 19 of the 20 sites sampled. Physical processes creating the observed vertical patterns in the physical and electrical properties are discussed. An algorithm is then developed from the relationship between the SWE and the brightness temperature measured at 37 GHz (55°) H polarization and the air temperature. The multiple regression between these variables is able to account for over 90% of the variability in the measured SWE. This algorithm is validated with a small in situ data set collected during the 1999 field experiment. We then compare our data against the NASA snow thickness algorithm, designed as part of the NASA Earth Enterprise Program. The results indicated a lack of agreement between the NASA algorithm and the algorithm developed here. This lack of agreement is attributed to differences in scale between the Special Sensor Microwave/Imager and surface radiometers and to differences in the Antarctic versus Arctic snow physical and electrical properties. Copyright © 2003 John Wiley & Sons, Ltd.
Ice‐cover variability on shallow lakes at high latitudes: model simulations and observations
Authors: Duguay Claude R. , Flato Greg M. , Jeffries Martin O. , Ménard Patrick , Morris Kim , Rouse Wayne R. 
Published: December 2003

AbstractA one‐dimensional thermodynamic model for simulating lake‐ice phenology is presented and evaluated. The model can be driven with observed daily or hourly atmospheric forcing of air temperature, relative humidity, wind speed, cloud amount and snowfall. In addition to computing the energy balance components, key model output includes the temperature profile at an arbitrary number of levels within the ice/snow (or the water temperature if there is no ice) and ice thickness (clear ice and snow‐ice) on a daily basis, as well as freeze‐up and break‐up dates. The lake‐ice model is used to simulate ice‐growth processes on shallow lakes in arctic, sub‐arctic, and high‐boreal forest environments. Model output is compared with field and remote sensing observations gathered over several ice seasons. Simulated ice thickness, including snow‐ice formation, compares favourably with field measurements. Ice‐on and ice‐off dates are also well simulated when compared with field and satellite observations, with a mean absolute difference of 2 days. Model simulations and observations illustrate the key role that snow cover plays on the seasonal evolution of ice thickness and the timing of spring break‐up. It is also shown that lake morphometry, depth in particular, is a determinant of ice‐off dates for shallow lakes at high latitudes. Copyright © 2003 John Wiley & Sons, Ltd.