bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of conservation tillage on runoff erosivity and soil erodibility during concentrated flow
Authors: Knapen A. , Poesen J. , Govers G. , De Baets S. 
Published: September 2007

AbstractCrop residues in conservation tillage systems are known to cause both a reduction in the erosive runoff power and an increase in the topsoil erosion resistance. In this study, the relative importance of both mechanisms in reducing soil loss by concentrated flow erosion is examined. Therefore, a method to calculate the effective flow shear stress responsible for soil detachment in the presence of a residue cover is applied. The determination of effective flow shear stress is based on the recalculation of the hydraulic radius for residue treatments. The method was tested in a laboratory flume by comparing soil detachment rates of identical pairs of soil samples that only differ in the presence or absence of crop residues. This shear stress partitioning approach and a soil detachment correction were then applied to a dataset of soil detachment measurements on undisturbed topsoil samples from a no‐till field plot on a loess‐derived soil, sampled during one growing season. Results indicate that only a small fraction (10% on average) of the difference in soil detachment rate between conventional and conservation tillage can be attributed to the dissipation of shear forces on the residues. The remaining decrease in soil detachment during concentrated runoff after a two‐year application of conservation tillage can be explained by the increased dry bulk density and root and crop residue content in the topsoil that reduces soil erodibility. After correcting for the presence of residues, the temporal variability in soil detachment rates (Dr) during concentrated flow for a given flow shear stress (τ) for both treatments can be predicted fairly well (R2 = 0·87) from dry soil bulk density (DBD, representing consolidation effects), soil moisture content (SMC, representing antecedent rainfall conditions), the dry mass of organic material (OM, representing root growth and residue decomposition) and saturated soil shear strength σs, sat using an equation of the form:

This study is the first to show that the effect of conservation tillage on soil detachment rates is a result of soil property modifications affecting soil erodibility, rather than a result of the surface residue decreasing flow erosivity. Copyright © 2007 John Wiley & Sons, Ltd.
Identification of uncertainty in low flow frequency analysis using Bayesian MCMC method
Authors: Lee Kil Seong , Kim Sang Ug 
Published: September 2007

AbstractThis study employs the Bayesian Markov Chain Monte Carlo (MCMC) method with the Metropolis–Hastings algorithm and maximum likelihood estimation (MLE) using a quadratic approximation of the likelihood function for the evaluation of uncertainties in low flow frequency analysis using a two‐parameter Weibull distribution. The two types of prior distributions, a non‐data‐based distribution and a data‐based distribution using regional information collected from neighbouring stations, are used to establish a posterior distribution. Eight case studies using the synthetic data with a sample size of 100, generated from two‐parameter Weibull distribution, are performed to compare with results of analysis using MLE and Bayesian MCMC. Also, Bayesian MCMC and MLE are applied to 36 years of gauged data to validate the efficiency of the developed scheme. These examples illustrate the advantages of Bayesian MCMC and the limitations of MLE based on a quadratic approximation. From the point of view of uncertainty analysis, Bayesian MCMC is more effective than MLE using a quadratic approximation when the sample size is small. In particular, Bayesian MCMC method is more attractive than MLE based on a quadratic approximation because the sample size of low flow at the site of interest is mostly not enough to perform the low flow frequency analysis. Copyright © 2007 John Wiley & Sons, Ltd.
Modelling the impact of afforestation on average annual streamflow in the Loess Plateau, China
Authors: Zhang Xiao Ping , Zhang Lu , McVicar Tim R. , Van Niel Tom G. , Li Ling Tao , Li Rui , Yang QinKe , Wei Liang 
Published: September 2007

AbstractTo prevent severe soil erosion and to ensure sustainable development, the Chinese Central Government mandated in 1999 that forest cover would be significantly increased in the Loess Plateau, China. It is important to assess the subsequent impact on streamflow and its spatial distribution in the region. The water balance model of et al. (2001)Zhang et al. (2001) was used in this study, and the results showed that the model was able to accurately simulate average annual evapotranspiration (ET), but not average annual streamflow when compared with streamflow measurements from 38 hydrologic stations in the coarse sandy hilly catchments (CSHC) in the Loess Plateau. The model was then calibrated using the measured streamflow, and the index of agreement increased from 0·21 to 0·63, the relative error and root mean square error decreased from 42·7 and 17·2 to 18·0% and 7·9 mm, respectively. Hierarchical cluster analysis and stepwise regression were employed to regionalize the optimized model parameter and relate it to the dryness index and forest cover. Once calibrated, the water balance model was used to assess the impacts of two plantation scenarios on streamflow. The two plantation scenarios assume nearly 5·8 and 10·1% of the study area can be planted with trees. It was predicted that streamflow from the region will decrease by 5·5 and 9·2% under the two plantation scenarios. The rate of streamflow reduction decreased from southeast to northwest mainly due to decreasing precipitation. Copyright © 2007 John Wiley & Sons, Ltd.
Estimation of tree water stress from stem and soil water monitoring with time‐domain reflectometry in two small forested basins in Spain
Authors: Hernández‐Santana Virginia , Martínez‐Fernández José , Morán Carlos 
Published: September 2007

AbstractSoil‐tree water relationships were studied using time domain reflectometry (TDR) in two small forested basins in Spain. The stem water content of two Mediterranean Quercus species (Quercus pyrenaica and Quercus rotundifolia) was measured using previously constructed species‐specific equations. To monitor soil moisture, a TDR station network was used in both cases. Sixteen Q. pyrenaica and six Q. rotundifolia individuals were selected to install two TDR probes in their trunks (at 20 and 120 cm above the ground) to monitor stem water content. Stem and soil water contents were measured fortnightly. The stem water content of both species showed a similar temporal trend for the period studied. A spring maximum (0·654 cm3 cm−3 for Q. pyrenaica and 0·568 cm3 cm−3 for Q. rotundifolia) was found to be associated with high transpiration and no soil moisture deficit, and a late‐summer minimum (0·520 cm3 cm−3 for Q. pyrenaica and 0·426 cm3 cm−3 for Q. rotundifolia) was associated with the end of the dry season. This drop in stem water content occurs when the available water in the soil decreases. This seasonal difference presumably reflects water withdrawn from stem storage to support the transpirational demands of the tree. Since plant water stress results in reduced stem water content and since this drop can be measured by TDR, it may be concluded that this technology offers a suitable tool for detecting plant water stress. Copyright © 2007 John Wiley & Sons, Ltd.
Hortonian overland flow from Japanese forest plantations—an aberration, the real thing, or something in between?
Authors: Sidle Roy C. , Hirano Tomonori , Gomi Takashi , Terajima Tomomi 
Published: September 2007

AbstractThere is a growing opinion that poorly managed plantation forests in Japan are contributing to increased storm runoff and erosion. Here we present evidence to the contrary from runoff plots at two scales (hillslope and 0·5 × 2 m plots) for several forest conditions in the Mie and Nariki catchments. Runoff coefficients from small plots in untended hinoki forests were variable but typically higher than from better managed or deciduous forests during small storms at Nariki; at Mie, runoff during small events was highly variable from all small plots but runoff coefficients were similar for hinoki plots with and without understory vegetation, while the deciduous plot had lower runoff coefficients. Storm runoff was less at the hillslope scale than the plot scale in Mie; these results were more evident at sites with better ground cover. During the largest storms at both sites, differences in runoff due to forest condition were not evident regardless of scale. Dynamic soil moisture tension measurements at Nariki indicated that during a large storm, flow in the upper organic‐rich and root‐permeated soil horizons was 3·2 times higher than measured overland runoff from a small hinoki plot with poor ground cover and 8·3 times higher than runoff from a deciduous forest plot. On the basis of field observations during storms, at least a portion of the monitored ‘Hortonian overland flow’ was actually occurring in this near‐surface ‘biomat’. Therefore our field measurements in both small and large plots potentially included biomat flow in addition to short‐lived Hortonian runoff. Because overland flow decreased with increasing scale, rill erosion did not occur on hillslopes. Additionally, runoff coefficients were not significantly different among cover conditions during large storms; thus, the ‘degraded’ forest conditions appear not to greatly enhance peak flows or erosion potential at larger scales, especially when biomat flow is significant. Copyright © 2007 John Wiley & Sons, Ltd.
Theoretical dynamic studies on the reactions of CH3C(O)CH3−nCln (n = 0–3) with the chlorine atom
Authors: Ji Yue‐meng , Zhao Xiao‐lei , Liu Jing‐yao , Wang Ying , Li Ze‐sheng 
Published: September 2007

AbstractThe theoretical investigations were performed on the reaction mechanisms for the title reactions CH3C(O)CH3 + Cl → products (R1), CH3C(O)CH2Cl + Cl → products (R2), CH3C(O)CHCl2 + Cl → products (R3), and CH3C(O)CCl3 + Cl → products (R4) by ab initio direct dynamics approach. Two different reaction channels have been found: abstract of the H atom from methyl (CH3) group or chloromethyl (CH3−nCln) group of chloroacetone and addition of a Cl atom to the carbon atom of the carbonyl group of chloroacetone followed by methyl or chloromethyl eliminations. Because of the higher potential energy barrier, the contribution of addition–elimination reaction pathway to the total rate constants is very small and thus this pathway is insignificant in atmospheric conditions. The rate constants for the H‐abstraction reaction channels are evaluated by using canonical variational transition state theory incorporating with the small‐curvature tunneling correction. Theoretical overall rate constants are in good agreement with the available experimental values and decrease in the order of k1 > k2 > k3 > k4. The results indicate that for halogenated acetones the substitution of halogen atom (F or Cl) leads to the decrease in the CH bond reactivity and more decrease of reactivity is caused by F‐substitution. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008
Accelerating molecular modeling applications with graphics processors
Authors: Stone John E. , Phillips James C. , Freddolino Lydia , Hardy David J. , Trabuco Leonardo G. , Schulten Klaus 
Published: September 2007

AbstractMolecular mechanics simulations offer a computational approach to study the behavior of biomolecules at atomic detail, but such simulations are limited in size and timescale by the available computing resources. State‐of‐the‐art graphics processing units (GPUs) can perform over 500 billion arithmetic operations per second, a tremendous computational resource that can now be utilized for general purpose computing as a result of recent advances in GPU hardware and software architecture. In this article, an overview of recent advances in programmable GPUs is presented, with an emphasis on their application to molecular mechanics simulations and the programming techniques required to obtain optimal performance in these cases. We demonstrate the use of GPUs for the calculation of long‐range electrostatics and nonbonded forces for molecular dynamics simulations, where GPU‐based calculations are typically 10–100 times faster than heavily optimized CPU‐based implementations. The application of GPU acceleration to biomolecular simulation is also demonstrated through the use of GPU‐accelerated Coulomb‐based ion placement and calculation of time‐averaged potentials from molecular dynamics trajectories. A novel approximation to Coulomb potential calculation, the multilevel summation method, is introduced and compared with direct Coulomb summation. In light of the performance obtained for this set of calculations, future applications of graphics processors to molecular dynamics simulations are discussed. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
The role of the EGFR signaling in tumor microenvironment
Authors: De Luca Antonella , Carotenuto Adele , Rachiglio Annamaria , Gallo Marianna , Maiello Monica R. , Aldinucci Donatella , Pinto Antonio , Normanno Nicola 
Published: September 2007

AbstractThe epidermal growth factor receptor (EGFR) family comprehends four different tyrosine kinases (EGFR, ErbB‐2, ErbB‐3, and ErbB‐4) that are activated following binding to epidermal growth factor (EGF)‐like growth factors. It has been long established that the EGFR system is involved in tumorigenesis. These proteins are frequently expressed in human carcinomas and support proliferation and survival of cancer cells. However, activation of the EGFR in non‐malignant cell populations of the neoplastic microenvironment might also play an important role in cancer progression. EGFR signaling regulates in tumor cells the synthesis and secretion of several different angiogenic growth factors, including vascular endothelial growth factor (VEGF), interleukin‐8 (IL‐8), and basic fibroblast growth factor (bFGF). Overexpression of ErbB‐2 also leads to increased expression of angiogenic growth factors, whereas treatment with anti‐EGFR or anti‐ErbB‐2 agents produces a significant reduction of the synthesis of these proteins by cancer cells. EGFR expression and function in tumor‐associated endothelial cells has also been described. Therefore, EGFR signaling might regulate angiogenesis both directly and indirectly. In addition, activation of EGFR is involved in the pathogenesis of bone metastases. Within the bone marrow microenvironment, cancer cells stimulate the synthesis of osteoclastogenic factors by residing stromal cells, a phenomenon that leads to bone destruction. It has been shown that EGFR signaling regulates the ability of bone marrow stromal cells to produce osteoclastogenic factors and to sustain osteoclast activation. Taken together, these findings suggest that the EGFR system is an important mediator, within the tumor microenvironment, of autocrine and paracrine circuits that result in enhanced tumor growth. J. Cell. Physiol. 214: 559–567, 2008. © 2007 Wiley‐Liss, Inc.
Gab2 requires membrane targeting and the met binding motif to promote lamellipodia, cell scatter, and epithelial morphogenesis downstream from the met receptor
Authors: Frigault Melanie M. , Naujokas Monica A. , Park Morag 
Published: September 2007

AbstractGab1 and Gab2 are conserved scaffolding proteins that amplify and integrate signals stimulated by many growth factor receptors including the Met receptor. Gab1 acts to diversify the signal downstream from Met through the recruitment of multiple signaling proteins, and is essential for epithelial morphogenesis. However, whereas Gab1 and Gab2 are both expressed in epithelial cells, Gab2 fails to support a morphogenic response. We demonstrate that Gab1 and Gab2 are divergent in their function whereby Gab1, but not Gab2, promotes lamellipodia formation, and is localized to the membrane of lamellipodia upon Met activation. We have identified activation of ERK1/2 as a requirement for lamellipodia formation. Moreover, activated ERK1/2 are localized to lamellipodia in Gab1 expressing cells but not in cells that overexpress Gab2. By structure–function studies, we identify that enhanced membrane localization conferred through the addition of a myristoylation signal, together with the addition of the direct Met binding motif (MBM) from Gab1, are required to promote lamellipodia and confer a morphogenic signaling response to Gab2. Moreover, the morphogenesis competent myristoylated Gab2MBM promotes localization of activated ERK1/2 to the leading edge of lamellipodia in a similar manner to Gab1. Hence, subcellular localization of the Gab scaffold, as well as the ability of Gab to interact directly with the Met receptor, are both essential components of the morphogenic signaling response which involves lamellipodia formation and the localization of ERK1/2 activation in membrane ruffles. J. Cell. Physiol. 214: 694–705, 2008. © 2007 Wiley‐Liss, Inc.
Functional interleukin‐7/interleukin‐7Rα, and SDF‐1α/CXCR4 are expressed by human periodontal ligament derived mesenchymal stem cells
Authors: Trubiani Oriana , Isgro Antonella , Zini Nicoletta , Antonucci Ivana , Aiuti Fernando , Di Primio Roberto , Nanci Antonio , Caputi Sergio , Paganelli Roberto 
Published: September 2007

AbstractHematopoiesis in the bone marrow (BM) is maintained by specific interactions between both hematopoietic and non‐hematopoietic stromal cells, which are mesenchymal stem cells (MSCs) capable of giving rise to several cell types. The human periodontal ligament (PDL), a tissue of ectomesenchymal origin, has been shown to also be a source of MSCs. We have investigated whether MSCs expanded from the PDL of healthy volunteers express characteristics similar to BM‐derived stem cells using structural, immunocytochemical and molecular approaches. Their ability to support the growth of hematopoietic progenitors was also analyzed. The PDL‐MSCs exhibited a fibroblast‐like morphology and their chromatin was dispersed, indicating active gene transcription. The mesenchymal‐related antigens CD90, CD29, CD166, CD105, and CD44 were homogeneously detected by cytofluorimetric analysis, whereas membrane CXCR4 was expressed only by a minority of cells. The PDL‐MSCs differentiated in vitro into osteogenic and adipogenic cells. Immunolocalization of IL‐7, IL‐7Rα, SDF‐1α, and CXCR4 resulted in a diffuse but specific labeling. RT‐PCR analysis confirmed the expression of the above‐mentioned transcripts. The cells spontaneously produced high levels of IL‐7 and SDF‐1α and were able to support the development and long‐term maintenance of BM precursor cells more efficiently than murine stromal cells and similarly to normal BM human stromal cells. We examined IL‐7 and SDF‐1α secretion pathway during adipogenic and osteogenic differentiation. IL‐7 increased during osteogenic and adipogenic differentiation, while the SDF‐1α secretion was downregulated during osteogenic differentiation but increased during adipogenic induction. Our study provides evidence that in human PDL there is an accessible niche of MSCs showing the features of BM‐derived MSCs. J. Cell. Physiol. 214: 706–713, 2008. © 2007 Wiley‐Liss, Inc.
EGF upregulates Na+/H+ exchanger NHE1 by post‐translational regulation that is important for cervical cancer cell invasiveness
Authors: Chiang Yihan , Chou Cheng‐Yang , Hsu Keng‐Fu , Huang Yu‐Fang , Shen Meng‐Ru 
Published: September 2007

AbstractNa+/H+ exchanger 1 (NHE1) is involved in cell migration but little is known about the signal pathways that regulate NHE1 activity and that are associated with tumor cell invasiveness. This study is to investigate the mechanisms by which epidermal growth factor (EGF) regulates NHE1 expression to promote cervical cancer cell invasiveness and the clinical significance in early‐stage cervical cancer. NHE1 protein was scanty in normal or noncancerous cervical tissues of all surgical specimens examined (n = 92). Tumor tissues clearly expressed NHE1 protein with different amounts. The differential expression level of NHE1 is associated with the clinical outcome. NHE1 protein was also differentially expressed between normal cervical epithelial cells and two cervical cancer cell lines. Cervical cancer cells benefit some enhanced cellular functions from NHE1 abundance, such as cell volume regulation, migration, and invasion. Interestingly, NHE1 colocalized with EGF in cervical cancer tissues. Studies in cell culture systems indicated that EGF‐stimulated NHE1 abundance in a time‐dependent manner by post‐translational regulation. This implies a likely autocrine or paracrine EGF stimulation of NHE1 production in vivo. In addition, the phosphoinositide 3‐kinase pathway is the dominant signal controlling EGF‐stimulated NHE1 abundance. Pharmacological inhibition of NHE1 activity markedly inhibited the basal and EGF‐stimulated cervical cancer cell migration. Image studies and immunoprecipitaion experiments suggest that EGF‐induced NHE1 translocation to the leading‐edge lamellipodia, where NHE1 interacted with actin‐associated protein Ezrin, thereby remodeling cytoskeleton and stimulating cervical cancer cell migration. In conclusion, EGF upregulates NHE1 by post‐translational regulation that is important for cervical cancer cell invasiveness. J. Cell. Physiol. 214: 810–819, 2008. © 2007 Wiley‐Liss, Inc.
Ultraviolet light exposure triggers nuclear accumulation of p21WAF1 and accelerated senescence in human normal and nucleotide excision repair‐deficient fibroblast strains
Authors: Mirzayans Razmik , Scott April , Andrais Bonnie , Pollock Scott , Murray David 
Published: September 2007

AbstractInduction of the p21WAF1 protein (hereafter called p21) following genotoxic stress is known to inhibit proliferating cell nuclear antigen (PCNA)‐dependent DNA repair, downregulate apoptosis, and trigger a sustained growth‐arrested phenotype called accelerated senescence. Studies with immortalized human and murine cell lines have revealed that exposure to ultraviolet light (UVC; 254 nm) results in the degradation of p21 to facilitate DNA repair and promote cell survival, or may lead to apoptotic cell death. The objective of the present study was to determine whether exposure of non‐transformed human fibroblast strains to relatively low fluences of UVC (i.e., fluences typically used in the clonogenic survival assay) might induce sustained nuclear accumulation of p21, leading to accelerated senescence. We have evaluated the responses of normal human fibroblast (NHF) strains and nucleotide excision repair (NER)‐deficient fibroblast strains representing xeroderma pigmentosum (XP) complementation groups A and G and Cockayne syndrome (CS) complementation groups A and B. We report that exposure of NHFs to ≤15 J/m2 of UVC, and NER‐deficient fibroblasts to ≤5 J/m2 of UVC, results in sustained nuclear accumulation of p21 and growth arrest through accelerated senescence. With each fibroblast strain examined, exposure to UVC fluences that resulted in ∼90% loss of clonogenic potential triggered significant (>60%) accelerated senescence, but only marginal (<5%) apoptosis. We conclude that nuclear accumulation of p21 accompanied by accelerated senescence may be an integral component of the response of human fibroblasts to UVC‐induced DNA damage, irrespective of their DNA repair capabilities. J. Cell. Physiol. 215: 55–67, 2008. © 2007 Wiley‐Liss, Inc.