bluuebunny/crossref_metadata_2025_split huggingface dataset:
Octyl‐Decorated Fréchet‐Type Dendrons: A General Motif for Visualisation of Static and Dynamic Behaviour Using Scanning Tunnelling Microscopy?
Authors: Merz Leo , Güntherodt H.‐J. , Scherer Lukas J. , Constable Edwin C. , Housecroft Catherine E. , Neuburger Markus , Hermann B. A. 
Published: February 2005

AbstractA detailed STM study of monolayers of 3,5‐bis[(3,5‐bisoctyloxyphenyl)methyloxy]benzaldehyde and 3,5‐bis[(3,5‐bisoctyloxyphenyl)methyloxy]benzyl alcohol adsorbed on graphite is presented. Very highly resolved scanning tunnelling microscopy images are observed at room temperature in air allowing the analysis of the conformation of the adsorbed molecules. These long‐chain alkyl‐decorated Fréchet‐type dendrons are a powerful assembly motif and initially form a pattern based on trimeric units, assembled into hexagonal host structures with a pseudo‐unit cell of seven molecules, one of which remains highly mobile. Over time, the supramolecular ordering changes from a trimeric into a dimeric pattern. The chirality arising from the adsorption onto a surface of the dendrons is discussed.
N‐Fused Pentaphyrins and Their Rhodium Complexes: Oxidation‐Induced Rhodium Rearrangement
Authors: Mori Shigeki , Shin Ji‐Young , Shimizu Soji , Ishikawa Fumiaki , Furuta Hiroyuki , Osuka Atsuhiro 
Published: February 2005

Abstractmeso‐Aryl‐substituted pentaphyrins were isolated in the modified Rothemund–Lindsey porphyrin synthesis as a 22‐π‐electron N‐fused pentaphyrin ([22]NFP5) and a 24‐π‐electron N‐fused pentaphyrin ([24]NFP5), which were reversibly interconvertible by means of two‐electron reduction with NaBH4 or two‐electron oxidation with dichlorodicyanobenzoquinone (DDQ). Judging from 1H NMR data, [22]NFP5 is aromatic and possesses a diatropic ring current, while [24]NFP5 exhibits partial anti‐aromatic character. Metalation of [22]NFP5 1 with a rhodium(I) salt led to isolation of rhodium complexes 9 and 10, whose structures were unambiguously characterized by X‐ray diffraction analyses and were assigned as conjugated 24‐π and 22‐π electronic systems, respectively. In the rhodium(I) metalation of 1, the complex 9 was a major product at 20 °C, but the complex 10 became preferential at 55 °C. Upon treatment with DDQ, compound 9 was converted to 10 with an unprecedented rearrangement of the rhodium atom.
Bile acid derivatives as enantiodifferentiating host molecules in inclusion processes
Authors: Bortolini Olga , Fantin Giancarlo , Fogagnolo Marco 
Published: February 2005

AbstractA review on the use of bile acids as hosts for molecular recognition and enantioresolution is presented. The optical resolution of different classes of organic derivatives, i.e., lactones, aliphatic alcohols, sulfoxides, epoxides, ketones, cyclic amides, cyclic carbonates, and sulfites, may be obtained by host–guest enantioselective inclusion complexation. The salient aspects of the enclathration process, including X‐ray diffraction results, are discussed. Chirality 17:121–130, 2005. © 2005 Wiley‐Liss, Inc.
On the Low‐Lying Excited States of sym‐Triazine‐Based Herbicides
Authors: Oliva Josep M. , Azenha M. Emilia D. G. , Burrows Hugh D. , Coimbra Rita , Seixas de Melo J. Serxio , Canle L. Moisés , Fernández M. Isabel , Santaballa J. Arturo , Serrano‐Andrés Luis 
Published: February 2005

AbstractWe report a joint computational and luminescence study on the low‐lying excited states of sym‐triazines, namely, 1,3,5‐triazine (1) and the ubiquitous herbicides atrazine [6‐chloro‐N2‐ethyl‐N4‐isopropyl‐1,3,5‐triazine‐2,4‐diamine (2)] and ametryn [6‐methylthio‐N2‐ethyl‐N4‐isopropyl‐1,3,5‐triazine‐2,4‐diamine (3)]. Geometrical structures, energetics, and transition and state properties of 1 and 2 were computed at the TD‐DFT, CASSCF, and CASPT2 levels of theory. The fluorescence and phosphorescence emission spectra, lifetimes, and fluorescence quantum yields were measured for the three compounds, and from these, the energies of the lowest excited states and their corresponding radiative rates were determined. The predictions from CASPT2 calculations are in good agreement with the experimental results obtained from the luminescence studies and allow the interpretation of different absorption and emission features.
Phase Separation of LaI3 inside Single‐Walled Carbon Nanotubes
Authors: Friedrichs Steffi , Falke Uwe , Green Malcolm L. H. 
Published: February 2005

AbstractSimple binary solids can be found to adopt unprecedented structures when confined into nanometre‐sized cavities, such as the inner cylindrical bore of single‐walled carbon nanotubes (SWNT). In the case of the discussed LaIx@SWNT encapsulation composite, the LaI2 “crystal” fragment adopts the structure of bulk LaI3, with one third of the iodine positions unoccupied. A complete characterisation of the encapsulation composite was achieved using an enhanced digital restoration approach of high‐resolution transmission electron microscopy (HRTEM) images. The resulting complex exit surface wave provides information about the precise structural data of both filling material and host SWNT, establishing the SWNT's chirality and thus enabling a prediction of the composite's overall electron‐transport properties.
Probing the N(5)H Bond of the Isoalloxazine Moiety of Flavin Radicals by X‐ and W‐Band Pulsed Electron–Nuclear Double Resonance
Authors: Weber Stefan , Kay Christopher W. M. , Bacher Adelbert , Richter Gerald , Bittl Robert 
Published: February 2005

AbstractAn X‐ (9.7 GHz) and W‐band (94 GHz) pulsed electron–nuclear double resonance (ENDOR) study of the flavin cofactor of Escherichia coli DNA photolyase in its neutral radical form is presented. Through proton and deuteron ENDOR measurements at T=80 K, we detect and characterize the full anisotropy of the hyperfine coupling (hfc) tensor of the proton or deuteron bound to N(5) of the isoalloxazine ring. Scaling of the anisotropic proton hfc components by multiplication with the quotient of the magnetogyric ratio of a deuteron and a proton, χD/χH, reveals subtle differences compared to the respective deuteron couplings obtained by 95‐GHz deuterium ENDOR spectroscopy on an H→D buffer‐exchanged sample. These differences can be attributed to the different lengths of N(5)H and N(5)D bonds arising from the different masses of protons and deuterons. From the R−3 dependence of the dipolar hyperfine splitting, we estimated that the N(5)D bond is about 2.5 % shorter than the respective N(5)H bond. That such subtle bond‐length differences can be resolved by pulsed ENDOR spectroscopy suggests that this method may be favorably used to probe the geometry of hydrogen bonds between the H(5) of the paramagnetic flavin and the protein backbone. Such information is only obtained with difficulty by other types of spectroscopy.
Geometry Optimization and Conformational Analysis of (C60)N Clusters Using a Dynamic Lattice‐Searching Method
Authors: Cheng Longjiu , Cai Wensheng , Shao Xueguang 
Published: February 2005

AbstractA newly developed unbiased global optimization method, named dynamic lattice searching (DLS), is used to locate putative global minima for all (C60)N clusters with Girifalco potential up to N=150. A simple greedy strategy is adopted for the basic frame, so DLS has a very high convergence speed and may converge at various configurations. As most structures are packed by basic tetrahedra, some sequences are defined by both configurations and the size of the basic tetrahedra. A sequence‐based conformational analysis is carried out with the defined sequences by counting the hit number over 10 000 independent DLS runs for all the cases up to N=150. It was found that the hit rate of a sequence is related to the size of the basic tetrahedra. Use of this method proved that the Leary tetrahedral sequence is dominant in a certain range of cluster sizes, although the sequence has no potential energy advantage. The calculation results are also consistent with those of annealing experiments at high temperature, both in magic numbers and height of the peaks in the mass spectrum.
A DFT Study of the Adsorption and Dissociation of CO on Fe(100): Influence of Surface Coverage on the Nature of Accessible Adsorption States
Authors: Bromfield Tracy C. , Curulla Ferré Daniel , Niemantsverdriet J. W. 
Published: February 2005

AbstractIn the present article, we report adsorption energies, structures, and vibrational frequencies of CO on Fe(100) for several adsorption states and at three surface coverages. We have performed a full analysis of the vibrational frequencies of CO, thus determining what structures are stable adsorption states and characterizing the transition‐state structure for CO dissociation. We have calculated the activation energy of dissociation of CO at 0.25 ML (ML=monolayers) as well as at 0.5 ML; we have studied the dissociation at 0.5 ML to quantify the destabilization effect on the CO(α3) molecules when a neighboring CO molecule dissociates. In addition, it is shown that the number and nature of likely adsorption states is coverage dependent. Evidence is presented that shows that the CO molecule adsorbs on Fe(100) at fourfold hollow sites with the molecular axis tilted away from the surface normal by 51.0°. The adsorption energy of the CO molecule is −2.54 eV and the CO stretching frequency is 1156 cm−1. This adsorption state corresponds to the α3 molecular desorption state reported in temperature programmed desorption (TPD) experiments. However, the activation energy of dissociation of CO(α3) molecules at 0.25 ML is only 1.11 eV (≈25.60 kcal mol−1) and the gain in energy is −1.17 eV; thus, the dissociation of CO is largely favored at low coverages. The activation energy of dissociation of CO at 0.5 ML is 1.18 eV (≈27.21 kcal mol−1), very similar to that calculated at 0.25 ML. However, the dissociation reaction at 0.5 ML is slightly endothermic, with a total change in energy of 0.10 eV. Consequently, molecular adsorption is stabilized with respect to CO dissociation when the CO coverage is increased from 0.25 to 0.5 ML.
Effect of DEM data resolution on SWAT output uncertainty
Authors: Chaubey I. , Cotter A. S. , Costello T. A. , Soerens T. S. 
Published: February 2005

AbstractThis paper describes the effect of DEM data resolution on predictions from the SWAT model. Measured hydrologic, meteorological, watershed characteristics and water quality data from Moores Creek watershed (near Lincoln, AR, USA) were used in the simulation. The effect of input data resolution was evaluated by running seven scenarios at increasing DEM grid sizes (30 × 30 m, 100 × 100 m, 150 × 150 m, 200 × 200 m, 300 × 300 m, 500 × 500 m, 1000 × 1000 m). The model was calibrated on an annual basis for flow, NO3‐N and total P using 30 × 30 m DEM data. The predicted output at the calibrated scale was used to evaluate output accuracy for the remaining input resolutions. Results of this study showed that DEM resolution affects the watershed delineation, stream network and sub‐basin classification in the SWAT model. A decrease in DEM resolution resulted in decreased stream flow and NO3‐N load predictions. However, model predicted total P did not always decrease with DEM resolution. Results of this study indicate that the choice of input DEM resolution depends on the watershed response of interest. Minimum DEM data resolution ranged from 100 to 200 m to achieve less than 10% error in SWAT output for flow, NO3‐N and TP predictions. Copyright © 2005 John Wiley & Sons, Ltd.
An analysis of high‐flow sediment event data for evaluating model performance
Authors: Benaman J. , Shoemaker C. A. 
Published: February 2005

AbstractA methodology for utilizing high‐flow event data in model evaluation is presented. The methodology was applied to the Soil and Water Assessment Tool, version 2000 (SWAT) for the Cannonsville watershed, a rural, hilly watershed in northeastern USA, with a substantial winter snow pack. Thirty‐five high‐flow events that contained intensive total suspended solid sampling were selected in order to evaluate SWAT strengths and limitations. A comparison of calibrated model results to total sediment load data over 34 of the 35 events shows that the model underestimated the observed load by 29% (observed = 61 414 MT, predicted = 43 491 MT). In general, high sediment loading events (over 2000 metric tons) were underestimated. Most winter events were underestimated, likely due to limitations in SWAT for simulating erosion caused by snowmelt. In general, the model fit measured TSS concentrations better in the late summer/early fall than in other seasons. In addition, the model does not model erosion caused by flood waters eroding the flood plain. Additional analysis was performed for nine high‐flow events during the validation, but little conclusion could be drawn from so few events. The methodology can be used to evaluate the relative performance of the model's simulation of different processes and seasons (e.g., summer runoff events versus winter snowmelt events), provide guidance for expanding the model, and focus future calibration efforts towards controlling equations and/or parameters. Copyright © 2005 John Wiley & Sons, Ltd.
Modelling the hydrology of a catchment using a distributed and a semi‐distributed model
Authors: El‐Nasr Ahmed Abu , Arnold Jeffrey G. , Feyen Jan , Berlamont Jean 
Published: February 2005

AbstractVarious hydrological models exist that describe the phases in the hydrologic cycle either in an empirical, semi‐mechanistic or fully mechanistic way. The way and level of detail for the different processes of the hydrologic cycle that needs to be described depends on the objective, the application and the availability of data. In this study the performance of two different models, the fully distributed MIKE SHE model and the semi‐distributed SWAT model, was assessed. The aim of the comparative study was to examine if both models are equally able to describe the different phases in the hydrologic cycle of a catchment, given the availability of hydrologic data in the catchment. For the comparison, historic data of the Jeker river basin, situated in the loamy belt region of Belgium, was used. The size of the catchment is 465 km2. The landscape is rolling, the dominant land use is farmland, and the soils vary from sandy‐loam to clay‐loam. The daily data of a continuous period of 6 years were used for the calibration and validation of both models. The results were obtained by comparing the performance of the two models using a qualitative (graphical) and quantitative (statistical) assessment, such as graphical representation of the observed and simulated river discharge, performance indices, the hydrograph maxima, the baseflow minima, the total accumulated volumes and the extreme value distribution of river flow data. The analysis revealed that both models are able to simulate the hydrology of the catchment in an acceptable way. The calibration results of the two tested models, although they differ in concept and spatial distribution, are quite similar. However, the MIKE SHE model predicts slightly better the overall variation of the river flow. Copyright © 2005 John Wiley & Sons, Ltd.
SWAT2000: current capabilities and research opportunities in applied watershed modelling
Authors: Arnold J. G. , Fohrer N. 
Published: February 2005

AbstractSWAT (Soil and Water Assessment Tool) is a conceptual, continuous time model that was developed in the early 1990s to assist water resource managers in assessing the impact of management and climate on water supplies and non‐point source pollution in watersheds and large river basins. SWAT is the continuation of over 30 years of model development within the US Department of Agriculture's Agricultural Research Service and was developed to ‘scale up’ past field‐scale models to large river basins. Model components include weather, hydrology, erosion/sedimentation, plant growth, nutrients, pesticides, agricultural management, stream routing and pond/reservoir routing. The latest version, SWAT2000, has several significant enhancements that include: bacteria transport routines; urban routines; Green and Ampt infiltration equation; improved weather generator; ability to read in daily solar radiation, relative humidity, wind speed and potential ET; Muskingum channel routing; and modified dormancy calculations for tropical areas. A complete set of model documentation for equations and algorithms, a user manual describing model inputs and outputs, and an ArcView interface manual are now complete for SWAT2000. The model has been recoded into Fortran 90 with a complete data dictionary, dynamic allocation of arrays and modular subroutines. Current research is focusing on bacteria, riparian zones, pothole topography, forest growth, channel downcutting and widening, and input uncertainty analysis.The model SWAT is meanwhile used in many countries all over the world. Recent developments in European Environmental Policy, such as the adoption of the European Water Framework directive in December 2000, demand tools for integrative river basin management. The model SWAT is applicable for this purpose. It is a flexible model that can be used under a wide range of different environmental conditions, as this special issue will show. The papers compiled here are the result of the first International SWAT Conference held in August 2001 in Rauischholzhausen, Germany. More than 50 participants from 14 countries discussed their modelling experiences with the model development team from the USA. Nineteen selected papers with issues reaching from the newest developments, the evaluation of river basin management, interdisciplinary approaches for river basin management, the impact of land use change, methodical aspects and models derived from SWAT are published in this special issue. Copyright © 2005 John Wiley & Sons, Ltd.
Effect of GIS data quality on small watershed stream flow and sediment simulations
Authors: Di Luzio Mauro , Arnold Jeffrey G. , Srinivasan Raghavan 
Published: February 2005

AbstractSimulations of total runoff and fine sediment yield in Goodwin Creek watershed, which covers 21·3 km2 in Mississippi, were carried out using a hydrological model‐GIS system. The system includes the recently released Soil and Water Assessment Tool (SWAT) model version 2000 and AVSWAT version 1·0, the supporting interface with ArcView GIS. Among the required GIS input, some are commonly available in the United States with multiple options and characteristics. In our study, two available digital elevation models, three land use–land cover maps and two soil maps were grouped in all possible ways to obtain 12 applied input combinations.The objective of this study was to assess the impact of GIS input variation on the uncalibrated water runoff and sediment yield outputs and compare them with the respective observed data. The implicated issues are significant wherever multiple choices of GIS input are available. In the United States, agencies are developing TMDL (total maximum daily load) programmes at the watershed scale and are also using supporting tools along with the available GIS data. In addition, the involved water quality appraisals often include assessment of limited size watersheds, i.e. draining into a specific stream segment. This watershed, operated by the United States Department of Agriculture, Agriculture Research Service, is highly instrumented, thereby representing a severe test and a primary verification of the new system.The GIS data had a varying impact on model results. DEM choice was critical for a realistic definition of the watershed and subwatershed boundaries and topographic input, and consequently simulated outputs. Land use–land cover maps had a significant effect on both runoff and sediment yield prediction. Soil maps showed a limited influence on model results.While evidences and basic justifications of the results are provided, further investigations are needed to determine the influence of the input GIS data distribution on watersheds with various sizes, geomorphological and spatial settings. Copyright © 2005 John Wiley & Sons, Ltd.
Automatic model calibration
Authors: Eckhardt Klaus , Fohrer Nicola , Frede Hans‐Georg 
Published: February 2005

AbstractModel calibration allows reducing parameter uncertainty and, therefore, uncertainty in simulation results. In the present study, automatic model calibration with the shuffled complex evolution algorithm is demonstrated using the example of the distributed conceptual model SWAT‐G, a derivative of the Soil and Water Assessment Tool (SWAT). The special challenge in calibrating SWAT is that it describes many physical processes and therefore is highly parameterized. Moreover, as SWAT or SWAT‐G, respectively, is a distributed model, the parameters may take on different values in different spatial subunits of a catchment model. A strategy of imposing constraints on the parameters to limit the number of independently calibrated values is outlined and applied to the model of a mesoscale low mountain range catchment. Copyright © 2005 John Wiley & Sons, Ltd.
Estimating shallow groundwater recharge in the headwaters of the Liverpool Plains using SWAT
Authors: Sun H. , Cornish P. S. 
Published: February 2005

AbstractA physically based catchment model (SWAT) was used for recharge estimation in the headwaters of the Liverpool Plains in NSW, Australia. The study used water balance modelling at the catchment scale to derive parameters for long‐term recharge estimation. The derived parameters were further assessed at a subcatchment scale. Modelling results suggest that recharge occurs only in wet years, and is dominated by a few significant years or periods. The results were matched by independently observed bore data across the study area in the past 30 years. The study suggests that variations in recharge can be primarily explained by the climatic factor rather than land‐use changes. The study estimated less recharge than previous studies where point scale modelling results have been scaled up to the catchment scale. It suggests that a catchment‐based approach is needed for recharge estimation at the catchment scale. The study indicates that the current model may overestimate runoff on cracking vertosols under dry conditions where improvement is likely needed. The need for long‐term runoff and bore monitoring data to confidently establish the relationships among water balance/recharge estimation and groundwater level variation is discussed. SWAT provides an alternative to point scale modelling for evaluating recharge and its response to changes in land use and land management. Copyright © 2005 John Wiley & Sons, Ltd.