bluuebunny/crossref_metadata_2025_split huggingface dataset:
Toward Diels−Alder Reactions on a Solid Support Using Polymer Bound N‐Substituted 3‐Hydroxy‐4,4‐dimethyl‐2‐pyrrolidinone Acrylate Derivatives
Authors: Akkari Rhalid , Calmès Monique , Martinez Jean 
Published: May 2004

AbstractSeveral N‐substituted 3‐hydroxy‐4,4‐dimethyl‐2‐pyrrolidinone acrylate derivatives, selected to allow their attachment to a polymer, have been prepared and tested as dienophiles in the Diels−Alder reaction. The experiments, performed under TiCl4 catalysis in solution or the solid phase with isoprene and cyclopentadiene as dienes, pointed out the difficulties associated with some of these compounds that failed to give the corresponding cycloadduct. 13C NMR studies provided some evidence regarding the nature of the interactions between the acrylate compounds and TiCl4. It appears that the outcome of the reaction is dependent on the acrylate structure and that the 4‐(3‐hydroxy‐4,4‐dimethyl‐2‐oxopyrrolidin‐1‐yl)benzoic acid acrylate derivatives are highly efficient to give the cycloadduct in good yield and with high regio‐ or endoselectivity in both solution and solid‐phase reaction conditions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Interaction of Dihydropyridines and Nucleophiles with Carbene Complexes of Chromium: Diastereo‐ and Enantioselective Synthesis of Polycyclic Butenolides
Authors: Rudler Henri , Parlier Andrée , Certal Victor , Lastennet Gabriel , Audouin Max , Vaissermann Jacqueline 
Published: May 2004

AbstractThe interaction ofN‐methyldihydropyridine with carbene complexes of chromium promotes their spontaneous homologation upon addition of a hydride to the carbene carbon and an insertion of CO. This is followed in the case of complexes tethered to a triple bond by cascade insertions of the triple bond and of a CO ligand giving finally butenolides. The scope of the reaction has been established with its limitations, together with the stereochemical outcome, which is discussed. [5.5], [5.6], [5.7] bicyclic and tricyclic systems have been synthesised together with chiral butenolides starting from chiral carbene complexes. Most of the new structures have been assessed by X‐ray crystallography. This transformation was first extended to dihydronicotinamides, to chiral dihydropyridines such as dihydronicotines which led to the butenolides in an enantioselective way, and to other sources of hydrides. Second, a series of nucleophiles such as alkoxides, alkyllithium and alkylmagnesium compounds led also to polycyclic, substituted butenolides. Moreover, the final lactone enolates could be trapped with oxygen and gave unsaturated lactonols. The key point in all of these reactions is the formation of tetrahedral intermediates upon interaction of the nucleophiles with the carbene carbon. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
2‐Oxopiperazine Scaffolds by [3+2] Cycloaddition Reactions with a Polymer‐Supported Cyclic Nitrone
Authors: Wierschem Frank , Rück‐Braun Karola 
Published: May 2004

AbstractIsoxazolidines and 1,3‐aminoalcohols with a piperazin‐2‐one skeleton were readily prepared on a solid support through [3+2] cycloaddition and subsequent N−O‐bond cleavage, starting from a polymer‐supported cyclic nitrone. Libraries of functionalized 1,3‐aminoalcohols and their derivatives were obtained by automated amine acylation and Mitsunobu reactions on a solid support. The key to success is the oxidation of the immobilized cyclic secondary amine precursor to the nitrone on a solid support and the reductive N−O‐bond cleavage of the isoxazolidines, employing Mo(CO)6. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
“Aha!” effects in a guessing riddle task: An event‐related potential study
Authors: Mai Xiao‐Qin , Luo Jing , Wu Jian‐Hui , Luo Yue‐Jia 
Published: May 2004

AbstractInsight problem solving has been the topic of much investigation. It is believed widely that insight critically contains the process of breaking one's mental set. Recent functional magnetic resonance imaging (fMRI) research on puzzle solving showed that insight was associated with activities in anterior cingulate cortex (ACC) and other areas (Luo and Niki [2003]: Hippocampus 13:274–281). We proposed ACC might mediate processes of breaking one's mental set, given its well‐known role in cognitive conflict. In the present research, high‐density event‐related potentials (ERPs) were recorded to examine the electrophysiologic correlates of insight problem solving. One hundred twenty interesting Chinese riddles (half difficult and half easy) were adopted as materials. For each trial, subjects were either given an easy puzzle followed by a keyword that was consistent with the subject's initial thinking (“No‐aha answer”), or a difficult puzzle followed by a keyword that was consistent with an unusual interpretation, so that it broke the subject's initial mental set (“Aha answer”). Results from 14 subjects showed that Aha answers elicited a more negative ERP deflection than did No‐aha answers in the time window from 250–500 msec after onset of the answer. The ERP difference wave (Aha minus No‐aha answer) showed the maximum amplitude over the central site (Cz) with a peak latency of 380 msec (N380). Voltage and current density maps of the difference wave showed strong activity and current density in the frontocentral region. Dipole analysis localized the generator of the N380 in the ACC. N380 therefore probably reflects an “Aha!” effect, and the ACC generator may be involved in the breaking of mental set. Hum. Brain Mapp. 22:261–270, 2004. © 2004 Wiley‐Liss, Inc.
Cross‐modal temporal order memory for auditory digits and visual locations: An fMRI study
Authors: Zhang Daren , Zhang Xiaochu , Sun Xiwen , Li Zhihao , Wang Zhaoxin , He Sheng , Hu Xiaoping 
Published: May 2004

AbstractA function of working memory is to remember the temporal sequence of events, often occurring across different sensory modalities. To study the neural correlates of this function, we conducted an event‐related functional magnetic resonance imaging (fMRI) experiment with a cross‐modal memory task. Subjects were required to recall auditory digits and visual locations either in mixed order (cross‐modality) or in separate order (within‐modality). To identify the brain regions involved in the memory of cross‐modal temporal order, we compared the blood oxygenation level‐dependent (BOLD) response between the mixed and the separate order tasks. As a control, cortical areas sensitive to the memory load were mapped by comparing the 10‐item condition with the 6‐item condition in the separate order task. Results show that the bilateral prefrontal, right premotor, temporo‐parietal junction (TPJ) and left superior parietal cortices had significantly more activation in the mixed task than in the separate task. Some of these areas were also sensitive to the memory load, whereas the right prefrontal cortex and TPJ were relatively more sensitive to the cross‐modal order but not the memory load. Our study provides potential neural correlates for the episodic buffer, a key component of working memory as proposed previously [Baddeley. Trends Cogn Sci 2000;4:417–423]. Hum. Brain Mapping 22:280–289, 2004. © 2004 Wiley‐Liss, Inc.
Lingual abscess: diagnosis and treatment
Authors: Balatsouras Dimitrios G. , Eliopoulos Panayotis N. , Kaberos Antonis C. 
Published: May 2004

AbstractBackground.Lingual abscesses are very rare, and as a result, the individual surgeon usually lacks experience in the diagnosis and therapy of this entity. We present four cases of abscesses of the tongue diagnosed and treated during the past 2 years.Methods.The medical records, films, and charts of four patients with lingual abscess were retrospectively reviewed. The clinical presentation, radiographic features, treatment, and outcome of the cases were examined.Results.Diagnosis was obtained by clinical examination and CT. In all cases, we avoided incision and drainage and preferred draining the abscess and aspirating pus with a large‐bore needle through the inferior surface of the tongue. All patients responded remarkably well and did not have any recurrence.Conclusions.Lingual abscesses are rare conditions. In contrast to the approach in cases of most deep neck space infections, a more conservative therapeutic approach by needle‐aspiration is effective and has the advantages of not exacerbating the edema of the tongue and of avoiding airway compromise. © 2004 Wiley Periodicals, Inc. Head Neck 26: 550–554, 2004
Pediatric submandibular triangle masses: a fifteen‐year experience
Authors: Hockstein Neil G. , Samadi Daniel S. , Gendron Kristin , Carpentieri David , Wetmore Ralph F. 
Published: May 2004

AbstractBackground.The purpose of this study was to evaluate the surgical results of pediatric submandibular triangle masses, with specific attention to neoplastic processes.Methods.We retrospectively reviewed the medical records of 105 patients aged 6 months to 21 years who underwent surgery in the submandibular triangle at a major pediatric tertiary care hospital from 1987 to 2001.Results.One hundred five patients who underwent surgery in the submandibular triangle were included in the study. Twenty patients had neoplastic processes, six of which were of primary salivary origin (two mucoepidermoid carcinomas and four pleomorphic adenomas). Twenty‐four patients underwent excision of inflamed or infected lymph nodes, and 23 patients underwent excision of inflamed or infected submandibular glands. Thirty‐eight patients were included who underwent surgery for sialorrhea or to gain access for another surgical procedure. Complications included tumor recurrence, transient and permanent marginal mandibular nerve weakness, ranula, postoperative fluid collection, and cellulitis. Duration of follow‐up ranged from no follow‐up to 11 years.Conclusion.Surgical excision of submandibular triangle masses is uncommon. We present our experience with these lesions, with a discussion of diagnosis, surgical indications, and surgical complications. © 2004 Wiley Periodicals, Inc. Head Neck 26: 675–680, 2004
Significance of particle interaction to the modelling of cohesive sediment transport in rivers
Authors: Bungartz Heinz , Wanner Susanne C. 
Published: May 2004

AbstractAggregation processes of fine sediments have rarely been integrated in numerical simulations of cohesive sediment transport in riverine systems. These processes, however, can significantly alter the hydrodynamic characteristics of suspended particulate matter (SPM), modifying the particle settling velocity, which is one of the most important parameters in modelling suspended sediment dynamics. The present paper presents data from field measurements and an approach to integrate particle aggregation in a hydrodynamic sediment transport model. The aggregation term used represents the interaction of multiple sediment classes (fractions) with corresponding multiple deposition behaviour. The k–ε–turbulence model was used to calculate the coefficient of vertical turbulent mixing needed for the two‐dimensional vertical‐plane simulations. The model has been applied to transport and deposition of tracer particles and natural SPM in a lake‐outlet lowland river (Spree River, Germany). The results of simulations were evaluated by comparison with field data obtained for two levels of river discharge. Experimental data for both discharge levels showed that under the prevailing uniform hydraulic conditions along the river reach, the settling velocity distribution did not change significantly downstream, whereas the amount of SPM declined. It was also shown that higher flow velocities (higher fluid shear) resulted in higher proportions of fast settling SPM fractions. We conclude that in accordance with the respective prevailing turbulence structures, typical aggregation mechanisms occur that continuously generate similar distribution patterns, including particles that settle toward the river bed and thus mainly contribute to the observed decline in the total SPM concentration. In order to determine time‐scales of aggregation and related mass fluxes between the settling velocity fractions, results of model simulations were fitted to experimental data for total SPM concentration and of settling velocity frequency distributions. The comparison with simulations for the case of non‐interacting fractions clearly demonstrated the practical significance of particle interaction for a more realistic modelling of cohesive sediment and contaminant transport. Copyright © 2004 John Wiley & Sons, Ltd.
Multiple objective evaluation of a simple phosphorus transfer model
Authors: Smith Russell M. S. , Wheater Howard S. 
Published: May 2004

AbstractA simple phosphorus (P) transfer model of the Welland catchment, UK, is evaluated against multiple objective functions using a Monte Carlo approach that combines calibration, identifiability, sensitivity and uncertainty analysis. The model is based on simple conceptual rainfall‐runoff and river routing components, combined with estimates of the daily non‐point source load derived from annual landuse‐based export coefficients, disaggregated as a function of the runoff. The model has limited data requirements, consistent with data availability, and is parsimoneous with respect to the number of parameters identified through inverse modelling. The best performing parameter sets capture the main aspects of the observed flow and total P (TP) concentrations and provide a suitable basis for a decision‐support tool. However, a trade‐off is evident between matching the observed flow peaks, flow recessions and TP concentrations simultaneously, highlighting some limitations of the model structure and/or calibration data. Model analysis indicates that daily non‐point source load cannot be described as a function of near‐surface runoff and land use alone, but that other influences, including seasonality, are important. However, further model development to improve performance is likely to introduce additional complexity (in terms of parameter numbers), and hence additional problems of parameter identifiability and output uncertainty, which in turn raises issues of the information content of the available data. Copyright © 2004 John Wiley & Sons, Ltd.
Hydrological modelling of a small watershed using generated rainfall in the soil and water assessment tool model
Authors: Tripathi M. P. , Panda R. K. , Raghuwanshi N. S. , Singh R. 
Published: May 2004

AbstractAn adequately tested soil and water assessment tool (SWAT) model was applied to the runoff and sediment yield of a small agricultural watershed in eastern India using generated rainfall. The capability of the model for generating rainfall was evaluated for a period of 18 years (1981–1998). The watershed and subwatershed boundaries, drainage networks, slope, soil series and texture maps were generated using a geographical information system (GIS). A supervised classification method was used for land‐use/cover classification from satellite imageries.Model simulated monthly rainfall for the period of 18 years was compared with observations. Simulated monthly rainfall, runoff and sediment yield values for the monsoon season of 8 years (1991–1998) were also compared with their observed values. In general monthly average rainfall predicted by the model was in close agreement with the observed monthly average values. Also, simulated monthly average values of surface runoff and sediment yield using generated rainfall compared well with observed values during the monsoon season of the years 1991–1998. Results of this study revealed that the SWAT model can generate monthly average rainfall satisfactorily and thereby can produce monthly average values of surface runoff and sediment yield close to the observed values. Therefore, it can be concluded that the SWAT model could be used for developing a multiple year management plan for the critical erosion prone areas of a small watershed. Copyright © 2004 John Wiley & Sons, Ltd.
Effects of the catchment runoff coefficient on the performance of TOPMODEL in rainfall–runoff modelling
Authors: Xiong Lihua , Guo Shenglian 
Published: May 2004

AbstractEffects of the catchment runoff coefficient on the performance of TOPMODEL in simulating catchment rainfall–runoff relationships are investigated in this paper, with an aim to improve TOPMODEL's simulation efficiency in catchments with a low runoff coefficient. Application of TOPMODEL in the semi‐arid Yihe catchment, with an area of 2623 km2 in the Yellow River basin of China, produced a Nash–Sutcliffe model efficiency of about 80%. To investigate how the catchment runoff coefficient affects the performance of TOPMODEL, the whole observed discharge series of the Yihe catchment is multiplied with a larger‐than‐unity scale factor to obtain an amplified discharge series. Then TOPMODEL is used to simulate the amplified discharge series given the original rainfall and evaporation data. For a set of different scale factors, TOPMODEL efficiency is plotted against the corresponding catchment runoff coefficient and it is found that the efficiency of TOPMODEL increases with the increasing catchment runoff coefficient before reaching a peak (e.g. about 90%); after the peak, however, the efficiency of TOPMODEL decreases with the increasing catchment runoff coefficient. Based on this finding, an approach called the discharge amplification method is proposed to enhance the simulation efficiency of TOPMODEL in rainfall–runoff modelling in catchments with a low runoff coefficient. Copyright © 2004 John Wiley & Sons, Ltd.
Modelling artificial channel and land‐use changes and their impact on floods and sediment yield to the Ishikari basin
Authors: Wongsa Sanit , Shimizu Yasuyuki 
Published: May 2004

AbstractThe potential for flooding and sediment transport is greatly affected by river channel form and changes in land use. Therefore the modelling of channel morphology prior to canalization and of land‐use change is important with respect to the prediction of floods and sediment yield and their consequences. A combination of land‐use transformation maps and soil properties shows certain decision rules for the conversion of forest into arable or vice versa. The model proposed, from this study, was used to simulate possible past and/or future channel and land‐use patterns. Subsequently, the outcome of this simulation was used to assess the risk of flooding, sediment transport and soil‐erosion under different conditions. In this study, channel morphology prior to canalization and land‐use change in the Ishikari basin, Hokkaido, Japan, were analysed by comparing three scenarios using a physical based channel and slope model. The results indicate that pre‐canalization channel morphology has a significant impact on flood peak, but no significant effect on sediment yield. In contrast, land‐use change has a significant effect on soil eroded from hillslopes, but no significant effect on flooding for Ishikari basin. This study also illustrates the challenges that a simple model, such as a physical based channel and slope model, can simulate large‐scale river basin processes using fewer hydrological data resources. Copyright © 2004 John Wiley & Sons, Ltd.
Wetland nitrogen dynamics in an Adirondack forested watershed
Authors: McHale Michael R. , Cirmo Christopher P. , Mitchell Myron J. , McDonnell Jeffrey J. 
Published: May 2004

AbstractWetlands often form the transition zone between upland soils and watershed streams, however, stream–wetland interactions and hydrobiogeochemical processes are poorly understood. We measured changes in stream nitrogen (N) through one riparian wetland and one beaver meadow in the Archer Creek watershed in the Adirondack Mountains of New York State, USA from 1 March to 31 July 1996. In the riparian wetland we also measured changes in groundwater N. Groundwater N changed significantly from tension lysimeters at the edge of the peatland to piezometer nests within the peatland. Mean N concentrations at the peatland perimeter were 1·5, 0·5 and 18·6 µmol L−1 for NH4+, NO3− and DON (dissolved organic nitrogen), respectively, whereas peatland groundwater N concentration was 56·9, 1·5 and 31·6 µmol L−1 for NH4+, NO3− and DON, respectively. The mean concentrations of stream water N species at the inlet to the wetlands were 1·5, 10·1 and 16·9 µmol L−1 for NH4+, NO3− and DON, respectively and 1·6, 28·1 and 8·4 µmol L−1 at the wetland outlet. Although groundwater total dissolved N (TDN) concentrations changed more than stream water TDN through the wetlands, hydrological cross‐sections for the peatland showed that wetland groundwater contributed minimally to stream flow during the study period. Therefore, surface water N chemistry was affected more by in‐stream N transformations than by groundwater N transformations because the in‐stream changes, although small, affected a much greater volume of water.Stream water N input–output budgets indicated that the riparian peatland retained 0·16 mol N ha−1 day−1 of total dissolved N and the beaver meadow retained 0·26 mol N ha−1 day−1 during the study period. Nitrate dominated surface water TDN flux from the wetlands during the spring whereas DON dominated during the summer. This study demonstrates that although groundwater N changed significantly in the riparian peatland, those changes were not reflected in the stream. Consequently, although in‐stream changes of N concentrations were less marked than those in groundwater, they had a greater effect on stream water chemistry—because wetland groundwater contributed minimally to stream flow. Copyright © 2004 John Wiley & Sons, Ltd.
Investigating landfill‐impacted groundwater seepage into headwater streams using stable carbon isotopes
Authors: Atekwana E. A. , Krishnamurthy R. V. 
Published: May 2004

AbstractThe impact of landfill contaminated groundwater along a reach of a small stream adjacent to a municipal landfill was investigated using stable carbon isotopes as a tracer. Groundwater below the stream channel, groundwater seeping into the stream, groundwater from the stream banks and stream water were sampled and analysed for dissolved inorganic carbon (DIC) and the isotope ratio of DIC (δ13CDIC). Representative samples of groundwater seeping into the stream were collected using a device (a ‘seepage well’) specifically designed for collecting samples of groundwater seeping into shallow streams with soft sediments. The DIC and δ13CDIC of water samples ranged from 52 to 205 mg C/L and −16·9 to +5·7‰ relative to VPDB standard, respectively. Groundwater from the stream bank adjacent to the landfill and some samples of groundwater below the stream channel and seepage into the stream showed evidence of δ13C enriched DIC (δ13CDIC = −2·3 to +5·7‰), which we attribute to landfill impact. Stream water and groundwater from the stream bank opposite the landfill did not show evidence of landfill carbon (δ13CDIC = −10·0 to −16·9‰). A simple mixing model using DIC and δ13CDIC showed that groundwater below the stream and groundwater seeping into the stream could be described as a mixture of groundwater with a landfill carbon signature and uncontaminated groundwater. This study suggests that the hyporheic zone at the stream–groundwater interface probably was impacted by landfill contaminated groundwater and may have significant ecological implications for this ecotone. Copyright © 2004 John Wiley & Sons, Ltd.