bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of model complexity and space–time resolution on the prediction of long‐term soil salinity dynamics, western San Joaquin Valley, California
Authors: Schoups G. , Hopmans J. W. , Tanji K. K. 
Published: April 2006

AbstractThe numerical simulation of long‐term large‐scale (field to regional) variably saturated subsurface flow and transport remains a computational challenge, even with today's computing power. Therefore, it is appropriate to develop and use simplified models that focus on the main processes operating at the pertinent time and space scales, as long as the error introduced by the simpler model is small relative to the uncertainties associated with the spatial and temporal variation of boundary conditions and parameter values. This study investigates the effects of various model simplifications on the prediction of long‐term soil salinity and salt transport in irrigated soils. Average root‐zone salinity and cumulative annual drainage salt load were predicted for a 10‐year period using a one‐dimensional numerical flow and transport model (i.e. UNSATCHEM) that accounts for solute advection, dispersion and diffusion, and complex salt chemistry. The model uses daily values for rainfall, irrigation, and potential evapotranspiration rates. Model simulations consist of benchmark scenarios for different hypothetical cases that include shallow and deep water tables, different leaching fractions and soil gypsum content, and shallow groundwater salinity, with and without soil chemical reactions. These hypothetical benchmark simulations are compared with the results of various model simplifications that considered (i) annual average boundary conditions, (ii) coarser spatial discretization, and (iii) reducing the complexity of the salt‐soil reaction system. Based on the 10‐year simulation results, we conclude that salt transport modelling does not require daily boundary conditions, a fine spatial resolution, or complex salt chemistry. Instead, if the focus is on long‐term salinity, then a simplified modelling approach can be used, using annually averaged boundary conditions, a coarse spatial discretization, and inclusion of soil chemistry that only accounts for cation exchange and gypsum dissolution–precipitation. We also demonstrate that prediction errors due to these model simplifications may be small, when compared with effects of parameter uncertainty on model predictions. The proposed model simplifications lead to larger time steps and reduced computer simulation times by a factor of 1000. Copyright © 2006 John Wiley & Sons, Ltd.
Influence of flow rate and organic carbon content on benzene transport in a sandy soil
Authors: Kim Song‐Bae , Ha Heon‐Cheol , Choi Nag‐Choul , Kim Dong‐Ju 
Published: April 2006

AbstractThe influence of organic carbon content at various flow rates on the transport of aqueous benzene in a sandy soil was investigated. Column experiments were conducted for a sandy soil with different carbon contents (0%, 0·5%, and 2% by weight) and flow rates (0·25, 0·625, and 1·25 ml min−1) to observe breakthrough curves of KCl and benzene using a step application. Three types of convection–dispersion transport model (equilibrium, reversible two‐site, and reversible–irreversible sorption) were used to determine the appropriate model that best described the observed benzene transport. The modelling results revealed that the reversible–irreversible transport model was suitable for describing the transport and sorption behaviour of benzene in the sandy soil studied. Retardation and irreversible sorption coefficients increased with increasing carbon content, since the increment of carbon content resulted in the enhancement of sorption capacity for benzene. With increasing flow rate, decreased retardation of aqueous benzene was observed due to less reaction time; however, the model parameter for irreversible sorption increased unrealistically. This was attributed to the interference of velocity change on the irreversible sorption coefficient during parameter estimation. In order to avoid this problem, we introduced a Damköhler number (Da1), which took into account the velocity changes in estimating the irreversible sorption coefficient. A reasonable relationship was then found between Da1 and flow rate, which showed a decrease of Da1 with the increase in flow rate. Copyright © 2006 John Wiley & Sons, Ltd.
When does bedload transport begin in steep boulder‐bed streams?
Authors: Aristide Lenzi Mario , Mao Luca , Comiti Francesco 
Published: April 2006

AbstractThe paper presents the results of field measurements of critical conditions for bedload motion conducted in the Rio Cordon, a steep boulder‐bed stream in the Italian Alps, under conditions of high Reynolds numbers and low relative submergence poorly explored before. Two methods have been used to determine threshold of motion: the displacement of marked clasts and the flow competence approach, which uses the largest grain size diameter transported by each flood event.The high values of $\tau_{\rm {c}i}^{*}$ confirm the great relevance of non‐bedload effective shear stresses in step–pool streams given by the additional form drag associated with this morphology. Relative submergence effects on the dimensionless critical shear stress $\tau_{\rm {c}i}^{*}$ have been quantified by considering the relative submergence ratio Rh/D84, and the major effect of relative size on the mobility of each particle in steep, widely graded bed mixtures has been evaluated. Finally, the dimensionless critical unit discharge $q_{\rm {c}i}^{*}$ has also been adopted in the regression equations as the critical hydraulic parameter, because it may represent an easier parameter to use than the critical shear stress for steep, rough mountain rivers. Copyright © 2006 John Wiley & Sons, Ltd.
Peptide nucleic acid (PNA) — a review
Authors: Shakeel Shabih , Karim Sajjad , Ali Arif 
Published: April 2006

AbstractPeptide nucleic acid (PNA) is a nucleobase oligomer in which the entire backbone has been replaced by a backbone composed of N‐(2‐aminoethyl)glycine units. In other words, PNA can be regarded as DNA with a neutral peptide backbone instead of a negatively charged sugar–phosphate backbone. It is chemically stable and resistant to hydrolytic (enzymatic) cleavage and thus not expected to be degraded inside a living cell, although its transportation within the cell is difficult. PNA is capable of recognising specific sequences of DNA and RNA obeying the Watson–Crick hydrogen bonding scheme, and the hybrid complexes exhibit extraordinary thermal stability and unique ionic strength effects. It may also recognise duplex homopurine sequences of DNA to which it binds by strand invasion, forming a stable PNA/DNA/PNA triplex with a looped‐out DNA strand. PNA exhibits superior hybridisation characteristics and improved chemical and enzymatic stability relative to nucleic acids, which is why PNA finds major applications in the diagnostic and pharmaceutical fields. Studies indicate that PNA is capable of inhibiting transcription as well as translation, so it can be used as a new tool for antigene and antisense therapy. Owing to its superior properties, PNA could replace DNA as a probe for many investigation purposes. This paper reviews the synthesis of PNA, its important properties making it a new hot tool in the market and its major applications. Copyright © 2006 Society of Chemical Industry
Characterization of the fracture behavior of polyethylene using measured cohesive curves. III. Structure–property relationships
Authors: Ting S.K.M. , Williams J.G. , Ivankovic A. 
Published: April 2006

AbstractIn part I of this article, the deformation and failure mechanisms of different polyethylene grades formed under different rate and constraint conditions were identified. This study attempts to develop a microstructural understanding of the long term behavior of polyethylene by linking it to the measured fracture properties. Examination of the influence of the microstructural properties, particularly the effect of the chain structure and their interrelated nature on the crack growth resistance forms a basis of discussion. The study performed here should provide pipe manufacturers a valuable understanding of the crack growth behavior of polyethylene. POLYM. ENG. SCI., 46:792–798, 2006. © 2006 Society of Plastics Engineers
Effects of ball milling dispersion of nano‐SiOx particles on impact strength and crystallization behavior of nano‐SiOx–poly(phenylene sulfide) nanocomposites
Authors: Lu Dan , Pan Shiwei 
Published: April 2006

AbstractBall milling and mixing with strong shear force and strike force were applied to get fine dispersion of nano‐SiOx particles in poly(phenylene sulfide) (PPS) powder. Nano‐SiOx/PPS composites were manufactured by intensive compounding with 3 wt% nano‐SiOx particles. Effects of the ball milling dispersion on crystal behavior and impact strength of nano‐SiOx/PPS nanocomposites were studied. Physical mechanisms of ball milling dispersion were investigated. Evaluations based on both WAXD and DSC indicates that crystallization behavior of nano‐SiOx/heat‐treated PPS (HT‐PPS) nanocomposites was influenced by the ball milling process. Their crystallinity was 25% less while Izod impact strength was 89% better than those of as‐received neat PPS. Increased kinetic energy via ball milling by external work makes nano‐SiOx able to overcome the attraction from itself to prevent agglomeration. Interfacial bonding of two phases between nano‐SiOx and PPS was enhanced by crosslinking in HT‐PPS and reduction in surface tension of interface during ball milling. The bonds allow SiOx to dissipate energy and thus improve PPS impact strength from the addition of nano‐SiOx. POLYM. ENG. SCI., 46:820–825, 2006. © 2006 Society of Plastics Engineers
Influence of processing aids on the uniaxial extensional behavior of metallocene polyethylenes
Authors: Vogel R. , Brünig H. , Häußler L. , Hatzikiriakos S.G. 
Published: April 2006

AbstractIt has been reported in the literature that boron nitride powders with hexagonal crystal structure in combination with fluoroelastomers at small concentrations (typically 500–1000 ppm) can be used as suitable processing aids in melt extrusion processes to overcome flow instabilities such as sharkskin and gross melt fracture. They essentially act as energy dissipaters and suppress the unbound increase of extensional stresses, which are responsible for triggering gross melt fracture. This paper reports on the mechanism by which the presence of a small amount of boron nitride changes the behavior of metallocene polyethylenes in uniaxial elongation. Samples modified with different processing aids were tested in solid and molten state using uniaxial elongation and other rheological tests. The stress–strain behavior is described by the BDEW (Ball–Doi–Edwards–Warner; Ball et al., Polymer, 22, 1010, (1981)) network theory. This theory predicts a reduction of the entanglement density (number of “slip‐links”) in the presence of boron nitride particles that explains the decrease in extensional stresses. Thus, it can be argued that the presence of boron nitride particles dissipates the release of elastic energy at lower extensional stress levels due to the decrease in the entanglement density, thus preventing catastrophic failures such as gross melt fracture. POLYM. ENG. SCI., 46:735–742, 2006. © 2006 Society of Plastics Engineers
Nanostructures and nanocrystalline composite materials—synthesis, stability and phase transformations
Authors: Wilde Gerhard 
Published: April 2006

AbstractNanostructured materials offer particular promise for new and potentially very useful products since they can have very different and often superior properties that crucially depend on the atomistic details of interior or exterior interfaces. The nanostructures may be used in a wide range of contexts, most of these are ones in which ensembles of nanostructures are assembled into complex, functional arrangements. As nanostructured materials are structures that are far from the thermodynamic equilibrium and since they have short transport pathways, fast diffusion and rapid transformation kinetics often lead to coarsening and to the deterioration of the microstructure and the associated properties. Ensuring the stability of the nanoscale structures, e.g. by utilizing a composite approach, is therefore a key issue. This approach, however, imposes additional constraints on processing‐related issues as well as on the stability of phases and phase mixtures, and also on the phase transformations within the nanoscale structural units because of the size confinement and the presence of internal heterophase interfaces. While the entire field is far too vast to be addressed in a single overview, an attempt will be made to highlight recent developments concerning advanced synthesis options and phase stability and phase transformation issues of inorganic nanocrystalline composite materials. These issues are to be considered generally for nanostructured systems, i.e. for systems that are characterized by a large specific interface area. Copyright © 2006 John Wiley & Sons, Ltd.
Effects of intermolecular interactions on the controlled assembly of organic monolayers: an STM study
Authors: Yang Yanlian , Deng Ke , Zeng Qingdao , Wang Chen 
Published: April 2006

AbstractRepresentative types of intermolecular interactions were seen to affect self‐assembled molecular architectures, as studied by scanning tunneling microscopy (STM) under ambient conditions. As an example, the ππ interaction is attributed to the formation of chiral domains consisting of 4‐octadecylnitrobenzene (ONB). It is further demonstrated that the ONB assembly can serve as a buffer layer to immobilize coronene molecules on large areas of two‐dimensional close‐packed assemblies. Assemblies of 1,4‐dicarboxylic benzoic acid (DBA) and 4,4′‐bipyridine (Bpy) are associated with two different hydrogen‐bonded, two‐dimensional supramolecular networks. The results of theoretical calculations using density functional theory (DFT) are in qualitative agreement with the observed STM images. Copyright © 2006 John Wiley & Sons, Ltd.
Multistable features of boronized interstitial‐pentamers on Si(113) surfaces
Authors: Zhang Zhaohui , Liu Zhenghui , Sumitomo Koji , Zhu Xing 
Published: April 2006

AbstractOn Si(113) surfaces there exists a peculiar type of reconstructing blocks called pentamers, which are stabilized by self‐interstitial atoms at the subsurface. Here, we demonstrate that such interstitial‐pentamers (IP) can be boronized with different numbers of B atoms and therefore behave as differently stable blocks. The multistable features of the blocks are presented by images of scanning tunneling microscopy and investigated by ab initio calculations, which revealed the surface energy as a function of the number of B atoms in an IP and a minimum of the surface energy for three B atoms in each block. Copyright © 2006 John Wiley & Sons, Ltd.
Measuring the extent of linkage disequilibrium in commercial pig populations
Authors: Harmegnies N. , Farnir F. , Davin F. , Buys N. , Georges M. , Coppieters W. 
Published: April 2006

SummaryTo evaluate the extent of linkage disequilibrium in domestic pigs, we genotyped 33 and 44 unrelated individuals from two commercial populations for 29 and five microsatellite markers located on chromosomes 15 and 2 respectively. A high proportion of marker pairs up to 40 cM apart exhibited significant linkage disequilibrium in both populations. Pair‐wise r2 values averaged between 0.15 and 0.50 (depending on chromosome and population) for markers <1 cM apart and declined to values of 0.05 for more distant syntenic markers. Our results suggest that both populations underwent a bottleneck approximately 20 generations ago, which reduced the effective population size from thousands to <200 animals.
Validation of the European Prognostic Index for younger adult patients with acute myeloid leukaemia in first relapse
Authors: Giles Francis , Verstovsek Srdan , Garcia‐Manero Guillermo , Thomas Deborah , Ravandi Farhad , Wierda William , Ferrajoli Alessandra , Kornblau Steve , Jabbour Elias , Shan Jianqin , O'Brien Susan , Albitar Maher , Kantarjian Hagop 
Published: April 2006

SummaryIn order to validate the European Prognostic Index (EPI) for patients 60 years with acute myeloid leukaemia in first relapse, a cohort of 599 such patients, treated between 1980 and 2004 at the MD Anderson Cancer Center, were assessed using this prognostic index. Three risk groups were defined: favourable, 76 patients (13%) [Overall survival (OS), 64% at 1 year, 22% at 5 years]; intermediate, 137 patients (23%) (OS, 38% at 1 year, 12% at 5 years); and poor, 386 patients (64%) (OS, 17% at 1 year 6% at 5 years). The EPI is reproducible and useful.
The‘Lightspeed’preparation technique evaluated by Swiss clinicians after attending continuing education courses
Authors: BARBAKOW F. , LUTZ F. 
Published: April 2006

SummaryThis survey evaluated acceptance of the Lightspeed canal preparation (LS) technique by Swiss practitioners. The technique was introduced to Switzerland inJune 1994and 10 other continuing education (CE) courses were held at the Zurich Dental School by July 1995. Acceptance was assessed by posting questionnaires to the CE course attendees. Of the 305 questionnaires posted, 177 (58%) were returned. Of the CE participants 80% had used the technique with 60% finding the method easier and 43% finding it quicker than their usual preparation techniques. Of the respondents 58% used the technique on all tooth types and 76% of the LS users had fractured an instrument at least once. Amongst others, fractures were caused by too much pressure (25%), incorrect insertion angles (17%) and by a complicated root morphology (15%). Fractures occurred high up on the instrument shaft (74%) and near the tip (7%). Working lengths were claimed by 62% to be easier to maintain by LS than their usual preparation techniques. Among the respondents 52% obturated LS prepared canals more easily and quickly compared with their usual preparation techniques. Only 10% of LS users would not recommend the technique, but those who would suggested that proper tuition was necessary to minimize the risk of instrument fracture. The LS technique was positively assessed by clinicians who attended the CE courses in Switzerland where endodontics is not accepted as a speciality
The sequence of sediment behaviour during wave‐induced liquefaction
Authors: MUTLU SUMER B. , HATIPOGLU FIGEN , FREDSØE JØRGEN , KAAN SUMER S. 
Published: April 2006

AbstractThis paper presents the results of an experimental investigation of the complete sequence of sediment behaviour beneath progressive waves. The sediment was silty with d50 = 0.060 mm. Two kinds of measurements were carried out: pore‐water pressure measurements (across the sediment depth), and water‐surface elevation measurements. The process of liquefaction/compaction was videotaped from the side simultaneously with the pressure and water‐surface elevation measurements. The video records were then analysed to measure: (i) the time development of the mudline, (ii) the time development of liquefaction and compaction fronts in the sediment and (iii) the characteristics of the orbital motion of the liquefied sediment including the motion of the interface between the water body and the sediment. The ranges of the various quantities in the tests were: wave height, H = 9–17 cm, wave period, T = 1.6 sec, water depth = 42 cm, and the Shields parameter = 0.34–0.59. The experiments reveal that, with the introduction of waves, excess pore pressure builds up, which is followed by liquefaction during which internal waves are experienced at the interface of the water body and the liquefied sediment, the sequence of processes known from a previous investigation. This sequence of processes is followed by dissipation of the accumulated excess pore pressure and compaction of the sediment which is followed by the formation of bed ripples. The present results regarding the dissipation and compaction appear to be in agreement with recent centrifuge wave‐tank experiments. As for the final stage of the sequence of processes (formation of ripples), the ripple steepness (normalized with the angle of repose) for sediment with liquefaction history is found to be the same as that in sediment with no liquefaction history.
Postoperative sleep disturbance in pediatric patients using patient‐controlled devices (PCA)
Authors: KELLY J.J. , DONATH SUSAN , JAMSEN KRIS , CHALKIADIS G.A. 
Published: April 2006

SummaryBackground : Sleep disturbance has not been well quantified in pediatric postoperative management, yet has broad implications in pain management as well as upon the physical and psychological well‐being of the young patient admitted for surgery. We aimed to describe sleep disturbance in this population using patient‐controlled analgesia (PCA) and then identify the predictors of disturbed sleep.Methods : A retrospective audit and analysis of sleep disturbance in postoperative pediatric patients using PCA devices were performed in a postoperative surgical ward population of a major tertiary referral center. PCA presses were used as a proxy measure of sleep. The description of the sleep disturbance included an unadjusted and adjusted analysis of the proposed predictors of sleep disturbance: age, sex, nature of presentation, operation type, PCA opioid type, presence of background infusion, postoperative night number, and adjuvant medication. All data were entered into an access database developed for the audit and analyzed using stata 8.0.Results : The first 126 children prescribed PCA devices in the year 2004 were audited. One‐third of patients in the population prescribed PCA experienced sleep disturbance. Observed predictors of sleep disturbance include older children (OR: 0.86, P = 0.001) and those receiving a background infusion (OR: 0.19, P = 0.002).Other predictors were not significant.Conclusions : Sleep disruption is common in children‐prescribed PCA opioid analgesia. Older children and those receiving a background infusion were observed to experience less sleep. Other proposed predictors were not found to be reliable. Further investigation into the predictors of disturbed sleep in the postoperative patient is warranted.