In 1995 the great Hanshin–Awaji earthquake disaster occurred in the Japanese city of Kobe and its vicinity, and more than 6000 people were killed as a result of the collapse of buildings. This was a clear demonstration of how very strong ground motion in the area near a seismic fault can cause severe structural damage beyond that which is usually estimated. It also emphasized the importance of earthquake engineering research in solving such problems as why and how structures collapse in real conditions. In response to this disaster, the National Research Institute for Earth Science and Disaster Prevention (NIED) and the Science and Technology Agency of the Japanese Government (STA) planned to build a three–dimensional, full–scale, earthquake–testing facility as one of the core research facilities for earthquake disaster prevention. It is hoped to be able to carry large–scale structures and to simulate the process of dynamic collapse using three–dimensional, strong earthquake motion. For this purpose, the NIED and the STA began to develop large actuators and related components in 1995 and completed them in 1998. Through this development and testing, the design and manufacturing techniques of a large actuator system were successfully achieved. After that, the NIED and the STA began the design and construction of the new facility in the fiscal year of 1998. The construction work is now in progress in Miki City, near Kobe, Japan. It is scheduled to be completed by the beginning of 2005. In this paper, we summarize the performance and features of this new facility and the results of the technical developments.
{"title":"Construction of a three–dimensional, large–scale shaking table and development of core technology","authors":"N. Ogawa, K. Ohtani, T. Katayama, H. Shibata","doi":"10.1098/rsta.2001.0871","DOIUrl":"https://doi.org/10.1098/rsta.2001.0871","url":null,"abstract":"In 1995 the great Hanshin–Awaji earthquake disaster occurred in the Japanese city of Kobe and its vicinity, and more than 6000 people were killed as a result of the collapse of buildings. This was a clear demonstration of how very strong ground motion in the area near a seismic fault can cause severe structural damage beyond that which is usually estimated. It also emphasized the importance of earthquake engineering research in solving such problems as why and how structures collapse in real conditions. In response to this disaster, the National Research Institute for Earth Science and Disaster Prevention (NIED) and the Science and Technology Agency of the Japanese Government (STA) planned to build a three–dimensional, full–scale, earthquake–testing facility as one of the core research facilities for earthquake disaster prevention. It is hoped to be able to carry large–scale structures and to simulate the process of dynamic collapse using three–dimensional, strong earthquake motion. For this purpose, the NIED and the STA began to develop large actuators and related components in 1995 and completed them in 1998. Through this development and testing, the design and manufacturing techniques of a large actuator system were successfully achieved. After that, the NIED and the STA began the design and construction of the new facility in the fiscal year of 1998. The construction work is now in progress in Miki City, near Kobe, Japan. It is scheduled to be completed by the beginning of 2005. In this paper, we summarize the performance and features of this new facility and the results of the technical developments.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82265555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper reviews the latest developments made at the European Laboratory for Structural Assessment (ELSA) of the Joint Research Centre to extend the spectrum of applications of the pseudo–dynamic (PsD) methodology. After decades of development, a variety of new testing procedures and numerical schemes have been proposed to improve the efficiency and accuracy of the PsD method. Nevertheless, due to the expanded time–scale of the tests with respect to the real seismic events, the conventional PsD method is not appropriate for structures incorporating materials with significant strain–rate sensitivity. Our main objective is to illustrate the advantages of the continuous PsD testing system developed at ELSA and to show its potentiality to test structures fitted with anti–seismic protection devices constructed with strain–rate sensitive materials. Two specific typologies of seismic protection were tested. The first experimental activity aimed to validate the continuous PsD procedure and was conducted on a scaled five–storey frame structure isolated by means of high damping rubber bearings, which had been tested on the shaking table of ISMES (Italy). A second experimental campaign was conducted on a large–scale reinforced–concrete civil building protected by rubber–based energy dissipators.
{"title":"Development and application of large–scale continuous pseudo–dynamic testing techniques","authors":"G. Magonette","doi":"10.1098/rsta.2001.0873","DOIUrl":"https://doi.org/10.1098/rsta.2001.0873","url":null,"abstract":"This paper reviews the latest developments made at the European Laboratory for Structural Assessment (ELSA) of the Joint Research Centre to extend the spectrum of applications of the pseudo–dynamic (PsD) methodology. After decades of development, a variety of new testing procedures and numerical schemes have been proposed to improve the efficiency and accuracy of the PsD method. Nevertheless, due to the expanded time–scale of the tests with respect to the real seismic events, the conventional PsD method is not appropriate for structures incorporating materials with significant strain–rate sensitivity. Our main objective is to illustrate the advantages of the continuous PsD testing system developed at ELSA and to show its potentiality to test structures fitted with anti–seismic protection devices constructed with strain–rate sensitive materials. Two specific typologies of seismic protection were tested. The first experimental activity aimed to validate the continuous PsD procedure and was conducted on a scaled five–storey frame structure isolated by means of high damping rubber bearings, which had been tested on the shaking table of ISMES (Italy). A second experimental campaign was conducted on a large–scale reinforced–concrete civil building protected by rubber–based energy dissipators.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88128424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper introduces and reviews the theme of laboratory testing of structures under dynamic loads. The emphasis is on the simulation of earthquake effects, for which three principle methods are discussed: shaking tables, pseudo–dynamic testing and real–time testing. The latest developments in these areas are discussed in depth in the subsequent papers in this issue. While shaking tables and pseudo–dynamic methods are quite well established, both techniques have undergone significant advances in recent years, including improvements in control to ensure accurate reproduction of dynamic loads, and the construction of very large facilities aimed at eliminating the significant scaling problems. Development of the substructuring method has enabled large–scale pseudo–dynamic tests of parts of structures, coupled to numerical models of the remainder. Attempts are now being made to extend this approach to shaking tables. Recently, considerable efforts have been devoted to methods of testing both at large scale and in real time. Two approaches are discussed: the real–time substructure method, in which a physical test and a numerical model interact in real time; and effective force testing, in which equivalent seismic forces are applied by actuators operating under force control. Both methods have been shown to be feasible, but require further development. Although the techniques described have been developed primarily for seismic testing of structures, there is considerable potential for their application to other load types in the fields of civil and mechanical engineering.
{"title":"Laboratory testing of structures under dynamic loads: an introductory review","authors":"Martin S. Williams, A. Blakeborough","doi":"10.1098/rsta.2001.0860","DOIUrl":"https://doi.org/10.1098/rsta.2001.0860","url":null,"abstract":"This paper introduces and reviews the theme of laboratory testing of structures under dynamic loads. The emphasis is on the simulation of earthquake effects, for which three principle methods are discussed: shaking tables, pseudo–dynamic testing and real–time testing. The latest developments in these areas are discussed in depth in the subsequent papers in this issue. While shaking tables and pseudo–dynamic methods are quite well established, both techniques have undergone significant advances in recent years, including improvements in control to ensure accurate reproduction of dynamic loads, and the construction of very large facilities aimed at eliminating the significant scaling problems. Development of the substructuring method has enabled large–scale pseudo–dynamic tests of parts of structures, coupled to numerical models of the remainder. Attempts are now being made to extend this approach to shaking tables. Recently, considerable efforts have been devoted to methods of testing both at large scale and in real time. Two approaches are discussed: the real–time substructure method, in which a physical test and a numerical model interact in real time; and effective force testing, in which equivalent seismic forces are applied by actuators operating under force control. Both methods have been shown to be feasible, but require further development. Although the techniques described have been developed primarily for seismic testing of structures, there is considerable potential for their application to other load types in the fields of civil and mechanical engineering.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90459406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Four major advantages can be found if a step–by–step integration method is used to solve the momentum equations of motion in performing a pseudo–dynamic test. The first is that less error propagation is shown and the second is that the external momentum–dependent effect of an impulse can be more easily reflected when compared with the use of the force equations of motion. The third is that the rapid changes of dynamic loading can be smoothed out by time integration of the external force and consequently can be easily captured. The fourth advantage is that the detailed variation of resistance within each time–step will be thoroughly taken into account through the time integration of restoring–force and the linearization errors will then be drastically reduced or even eliminated. As a result, more accurate pseudo–dynamic test results can be obtained if the momentum equations of motion are applied. In addition to the four major advantages of using the momentum equations of motion, improved pseudo–dynamic results can be further obtained if a dissipative integration algorithm is employed to perform the step–by–step integration. This is because the favourable numerical dissipation can effectively suppress the spurious growth of high–frequency responses, while the lower modes are integrated very accurately. In this study, the integral form of the γ–function dissipative explicit method is chosen to confirm all the advantages both numerically and experimentally.
{"title":"Application of the momentum equations of motion to pseudo–dynamic testing","authors":"S. Y. Chang","doi":"10.1098/rsta.2001.0874","DOIUrl":"https://doi.org/10.1098/rsta.2001.0874","url":null,"abstract":"Four major advantages can be found if a step–by–step integration method is used to solve the momentum equations of motion in performing a pseudo–dynamic test. The first is that less error propagation is shown and the second is that the external momentum–dependent effect of an impulse can be more easily reflected when compared with the use of the force equations of motion. The third is that the rapid changes of dynamic loading can be smoothed out by time integration of the external force and consequently can be easily captured. The fourth advantage is that the detailed variation of resistance within each time–step will be thoroughly taken into account through the time integration of restoring–force and the linearization errors will then be drastically reduced or even eliminated. As a result, more accurate pseudo–dynamic test results can be obtained if the momentum equations of motion are applied. In addition to the four major advantages of using the momentum equations of motion, improved pseudo–dynamic results can be further obtained if a dissipative integration algorithm is employed to perform the step–by–step integration. This is because the favourable numerical dissipation can effectively suppress the spurious growth of high–frequency responses, while the lower modes are integrated very accurately. In this study, the integral form of the γ–function dissipative explicit method is chosen to confirm all the advantages both numerically and experimentally.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83481420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
William O. George, Bryan F. Jones, Ronald H. Lewis
Compounds of the type ROH are reviewed in terms of hydrogen–bonding interactions with special reference to R = H–, CH3– and C2H5–. The existence of hydrogen bonding in biological, climatic and cosmic processes is briefly described. In linear (open) structures of water and alcohols, the dimers have been the subject of detailed experimental and theoretical study. Cyclic forms of water and alcohols have also received considerable attention. Comparisons of cyclic and linear (open) structures of water and alcohols have led to the concept of cooperativity, by which bonding is strengthened by the formation of a second hydrogen bond within two compounds joined by an existing hydrogen bond. Complexes with other donor and acceptors are reviewed, including the simplest compound of this type, H2O...HF, for which accurate structural and thermodynamic properties have been reported. The transient chirality of the cyclic trimer of water has been recognized for some time and a particularly interesting recent paper measures the right–handed (or clockwise) and left–handed (or anticlockwise) form of the complex of water trimer with indole compounds. This has possible implications for the more recent recognition that methanol and ethanol also exist in chiral forms as cyclic trimers and possibly also as one of the forms of a cyclic tetramer. It is hoped that future work will lead to a better understanding of hydrogen bonding. A particularly important area concerns the dynamic factors controlling the very fast molecular changes that are associated with the central role of hydrogen bonding in the biological and physical processes associated with all forms of life.
从氢键相互作用的角度综述了ROH型化合物，特别参考了R = H -， CH3 -和C2H5 -。简述了氢键在生物、气候和宇宙过程中的存在。在水和醇的线性(开放)结构中，二聚体一直是详细的实验和理论研究的主题。水和醇的循环形式也受到了相当大的关注。对水和醇的环状和线性(开放)结构的比较引出了协同性的概念，即通过在两个化合物中形成由现有氢键连接的第二个氢键来加强键合。综述了与其他供体和受体的配合物，包括该类型最简单的化合物H2O…HF，其精确的结构和热力学性质已被报道。水的环状三聚体的瞬态手性已经被认识了一段时间，最近一篇特别有趣的论文测量了水三聚体与吲哚化合物配合物的右手(或顺时针)和左手(或逆时针)形式。这可能对最近认识到甲醇和乙醇也以环三聚体的手性形式存在，也可能是环四聚体的一种形式。希望未来的工作将导致对氢键的更好理解。一个特别重要的领域涉及控制非常快速的分子变化的动态因素，这些变化与氢键在与所有形式的生命相关的生物和物理过程中的核心作用有关。
{"title":"Water and its homologues: a comparison of hydrogen–bonding phenomena","authors":"William O. George, Bryan F. Jones, Ronald H. Lewis","doi":"10.1098/rsta.2001.0868","DOIUrl":"https://doi.org/10.1098/rsta.2001.0868","url":null,"abstract":"Compounds of the type ROH are reviewed in terms of hydrogen–bonding interactions with special reference to R = H–, CH3– and C2H5–. The existence of hydrogen bonding in biological, climatic and cosmic processes is briefly described. In linear (open) structures of water and alcohols, the dimers have been the subject of detailed experimental and theoretical study. Cyclic forms of water and alcohols have also received considerable attention. Comparisons of cyclic and linear (open) structures of water and alcohols have led to the concept of cooperativity, by which bonding is strengthened by the formation of a second hydrogen bond within two compounds joined by an existing hydrogen bond. Complexes with other donor and acceptors are reviewed, including the simplest compound of this type, H2O...HF, for which accurate structural and thermodynamic properties have been reported. The transient chirality of the cyclic trimer of water has been recognized for some time and a particularly interesting recent paper measures the right–handed (or clockwise) and left–handed (or anticlockwise) form of the complex of water trimer with indole compounds. This has possible implications for the more recent recognition that methanol and ethanol also exist in chiral forms as cyclic trimers and possibly also as one of the forms of a cyclic tetramer. It is hoped that future work will lead to a better understanding of hydrogen bonding. A particularly important area concerns the dynamic factors controlling the very fast molecular changes that are associated with the central role of hydrogen bonding in the biological and physical processes associated with all forms of life.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79832009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
W. Bartczak, J. Kroh, Michal Zapalowski, K. Pernal
The possibilities of trapping an excess electron by potential traps in liquid water and aqueous ionic solutions have been investigated by means of a computer simulation method. The equilibrium configurations of water molecules are generated by the molecular dynamics (MD) method and the molecular configurations are searched for local minima of the potential energy. The analysis of a large set of the minima allows us to obtain an extensive statistical description of the microscopic trapping sites. The estimated concentration of the electron traps in liquid water is ca. 0.5 mol dm–3. The possibility of electron trapping depends very strongly on the lifetime of the potential traps. The simulations yielded the distribution of the trap lifetime with an average of 84 fs. A substantial fraction (20%) of the traps live longer than 100 fs, a small fraction (0.2%) live as long as 1 ps. These values can be compared with experimental measurements of the electron hydration time of the order of 100 fs. The calculations of the localized excess electron in concentrated solutions of LiCl and NaCl have been performed. The MD simulations of the solutions provided an ensemble of configurations of ions and water molecules. The quantum calculations (based on density functional theory, non–local version) of an excess electron in the clusters of ions and water molecules extracted from the MD configurations have been performed for a few hundred cases. It appears that most of the hydrated Li+ cations can trap an excess electron. The histograms of the distribution of energy of the HOMO orbitals and a histogram of the electron excitation spectrum have been constructed.
{"title":"Computer simulation of water and concentrated ionic solutions. Potential fluctuations and electron localization","authors":"W. Bartczak, J. Kroh, Michal Zapalowski, K. Pernal","doi":"10.1098/rsta.2001.0867","DOIUrl":"https://doi.org/10.1098/rsta.2001.0867","url":null,"abstract":"The possibilities of trapping an excess electron by potential traps in liquid water and aqueous ionic solutions have been investigated by means of a computer simulation method. The equilibrium configurations of water molecules are generated by the molecular dynamics (MD) method and the molecular configurations are searched for local minima of the potential energy. The analysis of a large set of the minima allows us to obtain an extensive statistical description of the microscopic trapping sites. The estimated concentration of the electron traps in liquid water is ca. 0.5 mol dm–3. The possibility of electron trapping depends very strongly on the lifetime of the potential traps. The simulations yielded the distribution of the trap lifetime with an average of 84 fs. A substantial fraction (20%) of the traps live longer than 100 fs, a small fraction (0.2%) live as long as 1 ps. These values can be compared with experimental measurements of the electron hydration time of the order of 100 fs. The calculations of the localized excess electron in concentrated solutions of LiCl and NaCl have been performed. The MD simulations of the solutions provided an ensemble of configurations of ions and water molecules. The quantum calculations (based on density functional theory, non–local version) of an excess electron in the clusters of ions and water molecules extracted from the MD configurations have been performed for a few hundred cases. It appears that most of the hydrated Li+ cations can trap an excess electron. The histograms of the distribution of energy of the HOMO orbitals and a histogram of the electron excitation spectrum have been constructed.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79970584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The major topic in this paper is to show how spectroscopy has been used to probe the structure of water and aqueous solutions. The unique nature of the hydrogen bond is stressed, as is the near tetrahedral nature of the bonding. It is because water is bi–bi functional that it is unique. The word ‘anomalous’ is then introduced because water, far more that any other liquid, is seen to be anomalous by thermodynamicists. This means that their equations that describe liquids as being ‘perfect’ are way out for water although they work quite well for related liquids such as methanol.
{"title":"Water structure: unique but not anomalous","authors":"M. Symons","doi":"10.1098/rsta.2001.0869","DOIUrl":"https://doi.org/10.1098/rsta.2001.0869","url":null,"abstract":"The major topic in this paper is to show how spectroscopy has been used to probe the structure of water and aqueous solutions. The unique nature of the hydrogen bond is stressed, as is the near tetrahedral nature of the bonding. It is because water is bi–bi functional that it is unique. The word ‘anomalous’ is then introduced because water, far more that any other liquid, is seen to be anomalous by thermodynamicists. This means that their equations that describe liquids as being ‘perfect’ are way out for water although they work quite well for related liquids such as methanol.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88892526","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Water plays many roles in its interaction with water–soluble proteins through hydrogen bonding, electrostatic shielding and the hydrophobic effect. Water molecules are found on the surface of proteins, in clefts and channels and in cavities buried beneath the surface. We review data on these relating to structure, thermodynamics, dynamics and function. At interfaces, water may play two roles. Firstly, the absence of solvent may contribute to the favourable free energy of binding. Secondly, the presence of solvent may control the level of specificity or contribute to a favourable enthalpy. Finally, we review the role of solvent in unfolding proteins and the relation of protein unfolding/misfolding to disease.
{"title":"The protein–solvent interface: a big splash","authors":"A. Purkiss, S. Skoulakis, J. Goodfellow","doi":"10.1098/rsta.2001.0863","DOIUrl":"https://doi.org/10.1098/rsta.2001.0863","url":null,"abstract":"Water plays many roles in its interaction with water–soluble proteins through hydrogen bonding, electrostatic shielding and the hydrophobic effect. Water molecules are found on the surface of proteins, in clefts and channels and in cavities buried beneath the surface. We review data on these relating to structure, thermodynamics, dynamics and function. At interfaces, water may play two roles. Firstly, the absence of solvent may contribute to the favourable free energy of binding. Secondly, the presence of solvent may control the level of specificity or contribute to a favourable enthalpy. Finally, we review the role of solvent in unfolding proteins and the relation of protein unfolding/misfolding to disease.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73867081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The mobility of simple ions such as alkali–metal and halide ions at room temperature shows two anomalies. Firstly, there are maxima in mobilities as a function of ion size for both positive and negative ions and, secondly, the maximum for negative ions occurs at a larger ionic radius than the maximum for positive ions. Theoretical treatments of this problem are reviewed and it is concluded that a molecular treatment of the system is needed to understand the results. Computer simulation using the simple point charge model (SPC/E) for water reproduced the observations and is used to discuss the application of theories. In particular, the nature of the first solvation shell is correlated with ion mobility. Simulation reveals a further anomaly, namely that if the charge is removed from a large ion, then it moves more slowly. This is interpreted as the result of formation of a solvent cage around the hydrophobic solute. The changes in local structure resulting from changes in charge and size also affect the solvation thermodynamics. Simulations show that the solvation entropy has a double maximum when viewed as a function of charge. The local minimum near zero charge is interpreted as being due to hydrophobic order, and the maxima as the result of structure breaking. This double maximum in the entropy of solvation is a signature of the hydrophobic cage effect. Comparisons are made between ion mobilities in liquid water at ambient and supercritical conditions.
{"title":"Computer simulation studies of the structure and dynamics of ions and non–polar solutes in water","authors":"J. Rasaiah, R. Lynden-Bell","doi":"10.1098/rsta.2001.0865","DOIUrl":"https://doi.org/10.1098/rsta.2001.0865","url":null,"abstract":"The mobility of simple ions such as alkali–metal and halide ions at room temperature shows two anomalies. Firstly, there are maxima in mobilities as a function of ion size for both positive and negative ions and, secondly, the maximum for negative ions occurs at a larger ionic radius than the maximum for positive ions. Theoretical treatments of this problem are reviewed and it is concluded that a molecular treatment of the system is needed to understand the results. Computer simulation using the simple point charge model (SPC/E) for water reproduced the observations and is used to discuss the application of theories. In particular, the nature of the first solvation shell is correlated with ion mobility. Simulation reveals a further anomaly, namely that if the charge is removed from a large ion, then it moves more slowly. This is interpreted as the result of formation of a solvent cage around the hydrophobic solute. The changes in local structure resulting from changes in charge and size also affect the solvation thermodynamics. Simulations show that the solvation entropy has a double maximum when viewed as a function of charge. The local minimum near zero charge is interpreted as being due to hydrophobic order, and the maxima as the result of structure breaking. This double maximum in the entropy of solvation is a signature of the hydrophobic cage effect. Comparisons are made between ion mobilities in liquid water at ambient and supercritical conditions.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79424787","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. W. Neilson, Philip E. Mason, Sandra F. Ramos, Daniel C. Sullivan
The presence of ions and/or apolar species in water provides a rich and varied environment in which many natural processes occur. This review provides results of recent structural studies of aqueous solutions derived from state–of–the–art neutron and X–ray scattering methods. The enhanced resolution provided by methods such as neutron diffraction and isotopic substitution, and anomalous X–ray diffraction, have given scientists new insights into the contrasting hydration structures of a variety of ions and small molecules, and crucially into how these structures might affect the general properties of solutions. The discussion points out common features of ionic hydration within particular series, such as the alkalis, halides and transition metals, and also indicates where significant differences in hydration structure appear.
{"title":"Neutron and X–ray scattering studies of hydration in aqueous solutions","authors":"G. W. Neilson, Philip E. Mason, Sandra F. Ramos, Daniel C. Sullivan","doi":"10.1098/rsta.2001.0866","DOIUrl":"https://doi.org/10.1098/rsta.2001.0866","url":null,"abstract":"The presence of ions and/or apolar species in water provides a rich and varied environment in which many natural processes occur. This review provides results of recent structural studies of aqueous solutions derived from state–of–the–art neutron and X–ray scattering methods. The enhanced resolution provided by methods such as neutron diffraction and isotopic substitution, and anomalous X–ray diffraction, have given scientists new insights into the contrasting hydration structures of a variety of ions and small molecules, and crucially into how these structures might affect the general properties of solutions. The discussion points out common features of ionic hydration within particular series, such as the alkalis, halides and transition metals, and also indicates where significant differences in hydration structure appear.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85236417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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