Electrostatics in Periodic Slab Geometries I

We propose a new method to sum up electrostatic interactions in 2D slab geometries. It consists of a combination of two recently proposed methods, the 3D Ewald variant of Yeh and Berkowitz, J. Chem. Phys. 111 (1999) 3155, and the purely 2D method MMM2D by Arnold and Holm, to appear in Chem. Phys. Lett. 2002. The basic idea involves two steps. First we use a three dimensional summation method whose summation order is changed to sum up the interactions in a slab-wise fashion. Second we subtract the unwanted interactions with the replicated layers analytically. The resulting method has full control over the introduced errors. The time to evaluate the layer correction term scales linearly with the number of charges, so that the full method scales like an ordinary 3D Ewald method, with an almost linear scaling in a mesh based implementation. In this paper we will introduce the basic ideas, derive the layer correction term and numerically verify our analytical results.Comment: 10 pages, 7 figure

Electrostatics in Periodic Slab Geometries II

In a previous paper a method was developed to subtract the interactions due to periodically replicated charges (or other long-range entities) in one spatial dimension. The method constitutes a generalized "electrostatic layer correction" (ELC) which adapts any standard 3D summation method to slab-like conditions. Here the implementation of the layer correction is considered in detail for the standard Ewald (EW3DLC) and the PPPM mesh Ewald (PPPMLC) methods. In particular this method offers a strong control on the accuracy and an improved computational complexity of O(N log N) for mesh-based implementations. We derive anisotropic Ewald error formulas and give some fundamental guidelines for optimization. A demonstration of the accuracy, error formulas and computation times for typical systems is also presented.Comment: 14 pages, 7 figure

Bridging the Disconnect

New York City is facing a youth unemployment crisis, but the city's youth workforce development programs reach only a fraction of those in need of help and are too often misaligned to the developmental needs of young New Yorkers

The production and diffusion of policy knowledge

"The published works of the International Food Policy Research Institute (IFPRI) represent the most immediate and tangible measure of the new policy-related knowledge attributable to the institute, its staff, and research partners. This study provides a quantitative assessment of the number, nature, form, and use of IFPRI's published products since 1979 and compares and contrasts that with the publication performance of several similar agencies, including the economics and social sciences programs of the Centro Internacional de Mejoramiento de Maíz y Trigo (CIMMYT) and the International Rice Research Institute (IRRI) respectively, the Australian Bureau of Agricultural and Resource Economics (ABARE), the Bangladesh Institute for Development Studies (BIDS), and the now defunct Stanford University Food Research Institute (SFRI). Overall, IFPRI's circulated output is extensive, published not only in a broad portfolio of leading scholarly journals, but also in a wide range of books, technical reports, and extension documents. The amount of published output has tended to increase throughout IFPRI's history, and it continues to do so. Going beyond counting and classifying IFPRI's published record, we report the results of a bibliometric assessment of IFPRI and the comparison institutes for the period 1981–96 using the publication and citation performance details recorded in the Institute for Scientific Information's (ISI) Science Citation Index and Social Science Citation Index data bases. Citations to published literature are not indicative of an impact on policy or the economy generally but on further research and analysis. An analysis of coauthorship patterns provides an indication of impact too (more directly through the conduct of joint research), as well as indications of the way the research is carried out. Our analysis reveals the role IFPRI plays as a knowledge intermediary between the scholarly community and policy clienteles, but that a high proportion of its research collaborations leading to formal publications (and especially publications in the leading journals covered in ISI's data bases) involve researchers in advanced agencies. This partly reflects the limited capacity to perform food policy research in many developing countries — itself a reflection of local priorities for education and limited, long-term international support to increase scientific capacity in developing countries — and also underscores the role IFPRI could, and arguably should, play in redressing this state of affairs." Authors' AbstractInternational Food Policy Research Institute History ,Research institutes Evaluation ,Communication in learning and scholarship ,Bibliometrics ,Information science Statistical methods ,Knowledge management ,International Food Policy Research Institute Communications systems Evaluation ,Food policy Research ,

Modelling and trading the Greek stock market with gene expression and genetic programing algorithms

This paper presents an application of the gene expression programming (GEP) and integrated genetic programming (GP) algorithms to the modelling of ASE 20 Greek index. GEP and GP are robust evolutionary algorithms that evolve computer programs in the form of mathematical expressions, decision trees or logical expressions. The results indicate that GEP and GP produce significant trading performance when applied to ASE 20 and outperform the well-known existing methods. The trading performance of the derived models is further enhanced by applying a leverage filter

Web information systems: A study of maintenance, change and flexibility

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Information Systems (IS’s) have provided organisations with huge efficiency gains and benefits over the years; however an outstanding problem that is yet to be successfully tackled is that of the troublesome maintenance phase. Consuming vast resources and thwarting business progression in a competitive global market place, system maintenance has been recognised as one of the key areas where IS is failing organisations. Organisations are too often faced with the dilemma of either replacement or the continual upkeep of an unwieldy system. The ability for IS’s to be able to adapt to exogenous influences is even more acute today than at any time in the past. This is due to IS’s namely, Web Information Systems (WIS’s) increasingly and continually having to accommodate the needs of organisations to interconnect with a plethora of additional systems as well as supporting evolving business models. The richness of the interconnectivity, functionalities and services WIS’s now offer are shaping social, cultural and economic behaviour on a truly global scale, making the maintenance of such systems and evermore pertinent issue. The growth and proliferation of WIS’s shows no sign of abating which leads to the conclusion that what some have termed as the ‘maintenance iceberg’ should not be ignored. The quandary that commercial organisations face is typically driven by two key aspects; firstly, systems are built on the cultural premise of using fixed requirements, with not enough thought or attention being paid to systems abilities to deviate from these requirements. Secondly, systems do not generally cope well with adapting to unpredictable change arising from outside of the organisations environment. Over the recent past, different paradigms, approaches and methods have attempted to make software development more predictable, controllable and adaptable, however, the benefits of such measures in relation to the maintenance dilemma have been limited. The concept of flexible systems that are able to cope with such change in an efficient manner is currently an objective that few can claim to have realised successfully. The primary focus of the thesis was to examine WIS post-development change in order to empirically substantiate and understand the nature of the maintenance phase. This was done with the intention to determine exactly ‘where’ and ‘how’ flexibility could be targeted to address these changes. This study uses an emergent analytical approach to identify and catalogue the nature of change occurring within WIS maintenance. However, the research framework design underwent a significant revision as the initial results indicated that a greater emphasis and refocus was required to achieve the research objective. To study WIS’s in an appropriate and detailed context, a single case study was conducted in a web development software house. In total the case study approach was used to collect empirical evidence from four projects that investigated post-development change requests in order to identify areas of the system susceptible to change. The maintenance phases of three WIS projects were considered in-depth, resulting in the collection of over four hundred change requests. The fourth project served as a validation case. The results are presented and the findings are used to identify key trends and characteristics that depict WIS maintenance change. The analytical information derived from the change requests is consolidated and shown diagrammatically for the key areas of change using profile models developed in this thesis. Based on the results, the thesis concludes and contributes to the ongoing debate that there is a discernable difference when considering WIS maintenance change compared to that of traditional IS maintenance. The detailed characteristics displayed in the profile models are then used to map specific flexibility criteria that ultimately are required to facilitate change. This is achieved using the Flexibility Matrix of Change (FMoC) tool which was developed within the remit of this research. This tool is a qualitative measurement scheme that aligns WIS maintenance changes to a reciprocal flexibility attribute. Thus, the wider aim of this thesis is to also expand the awareness of flexibility and its importance as a key component of the WIS lifecycle

General Zoology Laboratory Manual

This lab manual for General Zoology was created under a Round Twelve ALG Textbook Transformation Grant. The manual contains six individual labs to be completed within a laboratory, along with a collection project to be completed outdoors with an instructor. Topics include: Classification and Evolution The Planaria Project Introduction to Invertebrates Introduction to Chordates Vertebrates Continued Mammalogyhttps://oer.galileo.usg.edu/biology-textbooks/1017/thumbnail.jp