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Statistical evaluation of fluoride contamination in groundwater resources of Santiago del Estero province, Argentina

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Geoscience Frontiers 2020年第6期11卷 2197-2205页

作者： K.rondano Gómez C.E.López pasquali G.paniagua González p.Fernández Hernando r.M.Garcinuño Martínez Departamento de Ciencias Básicas Facultad de Ciencias ForestalesUniversidad Nacional de Santiago Del EsteroArgentina Departamento de Ciencias Analíticas Facultad de CienciasUniversidad Nacional de Educación a DistanciaSpain Departamento de Química Analítica Facultad de Agronomía y AgroindustriasUniversidad Nacional de Santiago Del EsteroArgentina

This study investigates the suitability of statistical techniques for evaluating the fluoride content and the groundwater quality from robles Department(rD)and Banda Department(BD)in Santiago del Estero(Argentina).For the original statistical study,evaluation of nine parameters(fluoride,pH,conductivity,atmospheric and water temperature,total dissolved solids,chloride,hardness,and alkalinity)of 110 collected underground water samples from 23 dispersed rural areas was *** samples were obtained by sampling taken from wells at different *** levels were determined by a standard colorimetric method in two seasonal periods,the dry(from April to September)and rainy(from October to March)*** analytical results obtained for physicochemical parameters such as pH,total dissolved solids(TDS),and temperature does not reveal any notable difference between the rainy and dry seasons *** both seasons,the atmospheric temperature average was 22℃.With respect to fluoride content,approximately 50%of the analysed groundwater samples exceeded the limit established by current legislation(1.0 mg/L),obtaining concentration levels in the range of 0.01-2.80 mg/*** study demonstrates the usefulness of the univariate statistical method(quartiles calculation,interquartile range IQr),multivariate principal component analysis(pCA),and cluster analysis to establish a better understanding of the state of the contamination of the waters in the region studied.

关键词： Source water protection Santiago del Estero Multivariate statistical analysis Fluoride Spectrophotometry

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Comparison of reduced point charge models of proteins: Molecular Dynamics simulations of Ubiquitin

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Science China Chemistry 2014年第10期57卷 1340-1354页

作者： LEHErTE Laurence VErCAUTErEN Daniel p. Unité de Chimie physique Théorique et Structurale Laboratoire de Physico-Chimie Informatique Namur MEdicine & Drug Innovation Center (NAMEDIC) Department of Chemistry University of Namur Rue de Bruxelles 61 B-5000 Namur Belgium

reduced point charge models of amino acids are used to model Ubiquitin （pDB： 1UBQ）. They are designed （i） from local ex- tremum positions in charge density （CD） distribution functions built from the poisson equation applied to smoothed molecular electrostatic potential functions, or （ii） from local maximum positions in promolecular electron density distribution （ED） func- tions. Charge values are fitted versus all-atom Amber99 molecular electrostatic potentials. The program GrOMACS is used to generate molecular dynamics trajectories of the protein, under various implementation schemes, solvation, and temperature conditions. point charges that are not located on atoms are considered as virtual sites with a null mass and radius. The results illustrate that secondary structure is best preserved with the CD-based model at low temperatures and in vacuum. This indi- cates that local potential energy wells are consistent with the all-atom model. However, at room temperature, the structure is best conserved when point charges are forced to be located on atoms, due to a better description of the Coulomb l-4 energy terms. The ED-based model, generated at a lower resolution, led to the largest discrepancies versus the all-atom case. The CD-based model allows the formation of protein-water H-bonds with geometrical properties similar to the all-atom ones. Con- trarily, intra-molecular H-bonds are not well described. Structural, thermodynamical, and dynamical properties of proteins modelled with reduced point charge models are also significantly affected by the choice of the solvent force field.

关键词： molecular electrostatic potential electron density smoothing of molecular fields critical points point charge model protein Ubiquitin

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polymer flooding: Current status and future directions

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petroleum Science 2023年第2期20卷 910-921页

作者： r.S.Seright Dongmei Wang New Mexico Institute of Mining and Technology SocorroNMUSA University of North Dakota Grand ForksNDUSA

This review presents our perspective on the factors that have brought polymer flooding to its current state. Insights are provided on why HpAM is the dominant polymer used as well as what is needed to make alternative polymers and mobility-control methods viable. Explanation is given for why large polymer banks are needed for polymer flooding, and design of the injected polymer viscosity is detailed for cases with/without crossflow. The role of fractures and horizontal wells are discussed for improving injectivity and extending polymer flooding to recover oils with viscosities as high as 10,000 cp. Operational improvements are described to minimize mechanical and oxidative stability to allow HpAM polymers to be viable to 70 °C and ATBS polymers to 120 °C. Key factors affecting polymer retention are summarized. The paper points out unresolved issues and future directions for polymer flooding.

关键词： polymer flooding reservoir sweep improvement

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Microsoft Excel 5应用开发技术精解 1

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1995年

作者：埃里克·韦尔斯（Eric wells）王华译

489 p. : 图 ; 26 cm 附软盘一张

ISBN: (纸本)7302020574

489 p. : 图 ; 26 cm 附软盘一张

关键词：电子表格系统窗口软件

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On selection and scaling of ground motions for analysis of seismically isolated structures

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Earthquake Engineering and Engineering Vibration 2016年第4期15卷 633-648页

作者： Deepak r. pant Manika Maharjan Department of Civil Engineering University of Toronto Toronto ON M5S 1A4 Canada Atkins Limited The Wells Church Street Epsom KT17 4PE United Kingdom

A broader consensus on the number of ground motions to be used and the method of scaling to be adopted for nonlinear response history analysis （rHA） of structures is yet to be reached. Therefore, in this study, the effects of selection and scaling of ground motions on the response of seismically isolated structures, which are routinely designed using nonlinear rHA, are investigated. For this purpose, isolation systems with a range of properties subjected to bidirectional excitation are considered. Benchmark response of the isolation systems is established using large sets of unscaled ground motions systematically categorized into pulse-like, non-pulse-like, and mixed set of motions. Different subsets of seven to 14 ground motions are selected from these large sets using （a） random selection and （b） selection based on the best match of the shape of the response spectrum of ground motions to the target spectrum. Consequences of weighted scaling （also commonly referred to as amplitude scaling or linear scaling） as well as spectral matching are investigated. The ground motion selection and scaling procedures are evaluated from the viewpoint of their accuracy, efficiency, and consistency in predicting the benchmark response. It is confirmed that seven time histories are sufficient for a reliable prediction of isolation system displacement demands, for all ground motion subsets, selection and scaling procedures, and isolation systems considered. If ground motions are selected based on their best match to the shape of the target response spectrum （which should be preferred over randomly selected motions）, weighted scaling should be used if pulse-like motions are considered, either of weighted scaling or spectral matching can be used if non-pulse-like motions are considered, and an average of responses from weighted-scaled and spectrum-matched ground motions should be used for a mixed set of motions. On the other hand, the importance of randomly selected motions in represen

关键词： bidirectional excitation seismic isolation selection and scaling spectral matching weighted scaling

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Temperature dependence of excitonic transition in ZnSe/ZnCdSe quantum wells

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Optoelectronics Letters 2005年第3期 10-13页

作者： GUO Zi-zheng~(1,2**), LIANG Xi-xia~1, and BAN Shi-liang~11.Department of physics,Inner Mongolia University,Hohhot 010021,p.r.China2.Department of physics,Inner Mongolia Normal University,Hohhot 010022,p.r.China

A theoretical calculation for the temperature dependence of the excitonic transition in ZnSe/ZnCdSe quantum wells is performed. The exciton binding energy is calculated with a variational technique by considering the temperature-dependence parameters. Our results show that the exciton binding energy reduces linearly with temperature increasing. We find that the strain due to lattice mismatch and differential thermal expansion decreases with the temperature increasing.

关键词： ZnSe CdSe Temperature dependence of excitonic transition in ZnSe/ZnCdSe quantum wells

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振动能磨矿及其在金选矿中的应用

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国外黄金参考 1991年第7期 11-16页

作者： wells,JA 许鹏秋

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Expiratory Upper Airway Obstruction Caused by the Soft palate during Bag-Mask Ventilation

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Open Journal of Anesthesiology 2012年第2期2卷 38-43页

作者： Charles W. Buffington Cynthia M. Q. wells ryan J. Soose Departments of Anesthesiology and Otolaryngology University of Pittsburgh Pittsburgh USA Departments of Anesthesiology and Otolaryngology University of Pittsburgh Pittsburgh USA.

Introduction: Expiratory upper airway obstruction during bag-mask ventilation is not well characterized. Methods: An audit was done to assess expiratory obstruction in 90 adult surgical patients undergoing bag-mask ventilation during the induction of general anaesthesia. results: Clinicians experienced difficulty delivering gas to the lungs when the head was neutral in 52 of 90 patients (58%;inspiratory obstruction) but this problem was corrected by head tilt and chin lift in all but 2 patients. Clinicians experienced difficulty recovering gas from the lungs when the mouth was held closed under the mask in 30 of the remaining 88 patients (34%;expiratory obstruction). This problem persisted despite head tilt and chin lift in all but one patient but was uniformly corrected by opening the mouth. Inspection of the soft palate revealed that it was lying on the posterior pharyngeal wall in 27 of 30 patients with expiratory obstruction and that the retropalatal space was patent in 55 of 58 patients without expiratory obstruction (χ2, p predictors of expiratory upper airway obstruction included advanced age, large tongue, and large uvula. Conclusion: Expiratory airway obstruction should be suspected in all cases of difficult mask ventilation that cannot be corrected by head tilt and chin lift. Simply allowing the mouth to open between positive pressure breaths will permit gas to exit the lungs.

关键词： Expiration Soft palate Mask Ventilation

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Fast and Sensitive Chiral Analysis of Amphetamines and Cathinones in Equine Urine and plasma Using Liquid Chromatography Tandem Mass Spectrometry

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American Journal of Analytical Chemistry 2015年第13期6卷 995-1003页

作者： Caroline C. Wang petra Hartmann-Fischbach Tim r. Krueger Alisha Lester Aaron Simonson Terry L. wells Max O. Wolk Nick J. Hidlay Industrial Laboratories Wheat Ridge USA

A simple, rapid, sensitive and reproducible method for enantiomer analysis of methamphetamine, amphetamine, cathinone and methcathinone was developed and validated. The compounds were extracted from equine plasma and urine using a fast liquid-liquid extraction procedure. Only one milliliter plasma and one hundred microliter urine sample is needed for analysis. The extraction procedure had good recovery (>70%) and the matrix effect was negligible. Enantiomer differentiation and confirmation were achieved using liquid chromatography with chiral stationary phase and mass spectrometry detection. The method demonstrated excellent reproducibility with intra-day and inter-day precision of lower than 5%. The lower limits of detection for all of the compounds studied here were at low pg/mL level for both plasma and urine. This is the first report of the analysis of four chiral compounds in equine plasma and urine. routine application was demonstrated for (S)- and (r)-enantiomer differentiation.

关键词： Amphetamines and Cathinones Equine plasma and Urine Chiral Analysis Liquid Chromatography Tandem Mass Spectrometry

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如何有效改善外商投资环境

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财经 2002年第22期 36-37页

作者： LouisT.wells 哈佛大学工商管理研究生院国际管理系

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