Sample records for computational chemistry experimental

  1. Transuranic Computational Chemistry. (United States)

    Kaltsoyannis, Nikolas


    Recent developments in the chemistry of the transuranic elements are surveyed, with particular emphasis on computational contributions. Examples are drawn from molecular coordination and organometallic chemistry, and from the study of extended solid systems. The role of the metal valence orbitals in covalent bonding is a particular focus, especially the consequences of the stabilization of the 5f orbitals as the actinide series is traversed. The fledgling chemistry of transuranic elements in the +II oxidation state is highlighted. Throughout, the symbiotic interplay of experimental and computational studies is emphasized; the extraordinary challenges of experimental transuranic chemistry afford computational chemistry a particularly valuable role at the frontier of the periodic table. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Exercises in Computational Chemistry

    DEFF Research Database (Denmark)

    Spanget-Larsen, Jens


    A selection of HyperChem© PC-exercises in computational chemistry. Answers to most questions are appended (Roskilde University 2014-16).......A selection of HyperChem© PC-exercises in computational chemistry. Answers to most questions are appended (Roskilde University 2014-16)....

  3. Computational quantum chemistry website

    International Nuclear Information System (INIS)


    This report contains the contents of a web page related to research on the development of quantum chemistry methods for computational thermochemistry and the application of quantum chemistry methods to problems in material chemistry and chemical sciences. Research programs highlighted include: Gaussian-2 theory; Density functional theory; Molecular sieve materials; Diamond thin-film growth from buckyball precursors; Electronic structure calculations on lithium polymer electrolytes; Long-distance electronic coupling in donor/acceptor molecules; and Computational studies of NOx reactions in radioactive waste storage

  4. Using Computers in Chemistry. (United States)

    Pankuch, Brian


    Describes the use of two interactive computer programs in a college chemistry course. The first is a commercially-available simulation program (for Apple microcomputers with game paddles) which demonstrates gas laws. The second is a teacher-developed molecular bonding simulation program. (JN)

  5. Computational Chemistry Comparison and Benchmark Database (United States)

    SRD 101 NIST Computational Chemistry Comparison and Benchmark Database (Web, free access)   The NIST Computational Chemistry Comparison and Benchmark Database is a collection of experimental and ab initio thermochemical properties for a selected set of molecules. The goals are to provide a benchmark set of molecules for the evaluation of ab initio computational methods and allow the comparison between different ab initio computational methods for the prediction of thermochemical properties.

  6. Corrosion chemistry closing comments: opportunities in corrosion science facilitated by operando experimental characterization combined with multi-scale computational modelling. (United States)

    Scully, John R


    Recent advances in characterization tools, computational capabilities, and theories have created opportunities for advancement in understanding of solid-fluid interfaces at the nanoscale in corroding metallic systems. The Faraday Discussion on Corrosion Chemistry in 2015 highlighted some of the current needs, gaps and opportunities in corrosion science. Themes were organized into several hierarchical categories that provide an organizational framework for corrosion. Opportunities to develop fundamental physical and chemical data which will enable further progress in thermodynamic and kinetic modelling of corrosion were discussed. These will enable new and better understanding of unit processes that govern corrosion at the nanoscale. Additional topics discussed included scales, films and oxides, fluid-surface and molecular-surface interactions, selected topics in corrosion science and engineering as well as corrosion control. Corrosion science and engineering topics included complex alloy dissolution, local corrosion, and modelling of specific corrosion processes that are made up of collections of temporally and spatially varying unit processes such as oxidation, ion transport, and competitive adsorption. Corrosion control and mitigation topics covered some new insights on coatings and inhibitors. Further advances in operando or in situ experimental characterization strategies at the nanoscale combined with computational modelling will enhance progress in the field, especially if coupling across length and time scales can be achieved incorporating the various phenomena encountered in corrosion. Readers are encouraged to not only to use this ad hoc organizational scheme to guide their immersion into the current opportunities in corrosion chemistry, but also to find value in the information presented in their own ways.

  7. Scaffolding a Complex Task of Experimental Design in Chemistry with a Computer Environment (United States)

    Girault, Isabelle; d'Ham, Cédric


    When solving a scientific problem through experimentation, students may have the responsibility to design the experiment. When students work in a conventional condition, with paper and pencil, the designed procedures stay at a very general level. There is a need for additional scaffolds to help the students perform this complex task. We propose a…

  8. Recent development in computational actinide chemistry

    International Nuclear Information System (INIS)

    Li Jun


    Ever since the Manhattan project in World War II, actinide chemistry has been essential for nuclear science and technology. Yet scientists still seek the ability to interpret and predict chemical and physical properties of actinide compounds and materials using first-principle theory and computational modeling. Actinide compounds are challenging to computational chemistry because of their complicated electron correlation effects and relativistic effects, including spin-orbit coupling effects. There have been significant developments in theoretical studies on actinide compounds in the past several years. The theoretical capabilities coupled with new experimental characterization techniques now offer a powerful combination for unraveling the complexities of actinide chemistry. In this talk, we will provide an overview of our own research in this field, with particular emphasis on applications of relativistic density functional and ab initio quantum chemical methods to the geometries, electronic structures, spectroscopy and excited-state properties of small actinide molecules such as CUO and UO 2 and some large actinide compounds relevant to separation and environment science. The performance of various density functional approaches and wavefunction theory-based electron correlation methods will be compared. The results of computational modeling on the vibrational, electronic, and NMR spectra of actinide compounds will be briefly discussed as well [1-4]. We will show that progress in relativistic quantum chemistry, computer hardware and computational chemistry software has enabled computational actinide chemistry to emerge as a powerful and predictive tool for research in actinide chemistry. (authors)

  9. Relativistic quantum chemistry on quantum computers

    DEFF Research Database (Denmark)

    Veis, L.; Visnak, J.; Fleig, T.


    The past few years have witnessed a remarkable interest in the application of quantum computing for solving problems in quantum chemistry more efficiently than classical computers allow. Very recently, proof-of-principle experimental realizations have been reported. However, so far only...... the nonrelativistic regime (i.e., the Schrodinger equation) has been explored, while it is well known that relativistic effects can be very important in chemistry. We present a quantum algorithm for relativistic computations of molecular energies. We show how to efficiently solve the eigenproblem of the Dirac......-Coulomb Hamiltonian on a quantum computer and demonstrate the functionality of the proposed procedure by numerical simulations of computations of the spin-orbit splitting in the SbH molecule. Finally, we propose quantum circuits with three qubits and nine or ten controlled-NOT (CNOT) gates, which implement a proof...

  10. A DFT-Based Computational-Experimental Methodology for Synthetic Chemistry: Example of Application to the Catalytic Opening of Epoxides by Titanocene. (United States)

    Jaraíz, Martín; Enríquez, Lourdes; Pinacho, Ruth; Rubio, José E; Lesarri, Alberto; López-Pérez, José L


    A novel DFT-based Reaction Kinetics (DFT-RK) simulation approach, employed in combination with real-time data from reaction monitoring instrumentation (like UV-vis, FTIR, Raman, and 2D NMR benchtop spectrometers), is shown to provide a detailed methodology for the analysis and design of complex synthetic chemistry schemes. As an example, it is applied to the opening of epoxides by titanocene in THF, a catalytic system with abundant experimental data available. Through a DFT-RK analysis of real-time IR data, we have developed a comprehensive mechanistic model that opens new perspectives to understand previous experiments. Although derived specifically from the opening of epoxides, the prediction capabilities of the model, built on elementary reactions, together with its practical side (reaction kinetics simulations of real experimental conditions) make it a useful simulation tool for the design of new experiments, as well as for the conception and development of improved versions of the reagents. From the perspective of the methodology employed, because both the computational (DFT-RK) and the experimental (spectroscopic data) components can follow the time evolution of several species simultaneously, it is expected to provide a helpful tool for the study of complex systems in synthetic chemistry.

  11. Handbook of computational quantum chemistry

    CERN Document Server

    Cook, David B


    Quantum chemistry forms the basis of molecular modeling, a tool widely used to obtain important chemical information and visual images of molecular systems. Recent advances in computing have resulted in considerable developments in molecular modeling, and these developments have led to significant achievements in the design and synthesis of drugs and catalysts. This comprehensive text provides upper-level undergraduates and graduate students with an introduction to the implementation of quantum ideas in molecular modeling, exploring practical applications alongside theoretical explanations.Wri

  12. Deep learning for computational chemistry. (United States)

    Goh, Garrett B; Hodas, Nathan O; Vishnu, Abhinav


    The rise and fall of artificial neural networks is well documented in the scientific literature of both computer science and computational chemistry. Yet almost two decades later, we are now seeing a resurgence of interest in deep learning, a machine learning algorithm based on multilayer neural networks. Within the last few years, we have seen the transformative impact of deep learning in many domains, particularly in speech recognition and computer vision, to the extent that the majority of expert practitioners in those field are now regularly eschewing prior established models in favor of deep learning models. In this review, we provide an introductory overview into the theory of deep neural networks and their unique properties that distinguish them from traditional machine learning algorithms used in cheminformatics. By providing an overview of the variety of emerging applications of deep neural networks, we highlight its ubiquity and broad applicability to a wide range of challenges in the field, including quantitative structure activity relationship, virtual screening, protein structure prediction, quantum chemistry, materials design, and property prediction. In reviewing the performance of deep neural networks, we observed a consistent outperformance against non-neural networks state-of-the-art models across disparate research topics, and deep neural network-based models often exceeded the "glass ceiling" expectations of their respective tasks. Coupled with the maturity of GPU-accelerated computing for training deep neural networks and the exponential growth of chemical data on which to train these networks on, we anticipate that deep learning algorithms will be a valuable tool for computational chemistry. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  13. Refresher Course in Experimental Chemistry

    Indian Academy of Sciences (India)


    The Course will consist of stimulating experiments in different branches of chemistry covering diverse topics such as chemical kinetics, electrochemistry, spectrophotometry, polymer chemistry, advanced synthesis in inorganic and organic chemistry and molecular modelling. The focus of this. Course is to acquaint the ...

  14. Deep learning for computational chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Goh, Garrett B. [Advanced Computing, Mathematics, and Data Division, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland Washington 99354; Hodas, Nathan O. [Advanced Computing, Mathematics, and Data Division, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland Washington 99354; Vishnu, Abhinav [Advanced Computing, Mathematics, and Data Division, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland Washington 99354


    The rise and fall of artificial neural networks is well documented in the scientific literature of both the fields of computer science and computational chemistry. Yet almost two decades later, we are now seeing a resurgence of interest in deep learning, a machine learning algorithm based on “deep” neural networks. Within the last few years, we have seen the transformative impact of deep learning the computer science domain, notably in speech recognition and computer vision, to the extent that the majority of practitioners in those field are now regularly eschewing prior established models in favor of deep learning models. In this review, we provide an introductory overview into the theory of deep neural networks and their unique properties as compared to traditional machine learning algorithms used in cheminformatics. By providing an overview of the variety of emerging applications of deep neural networks, we highlight its ubiquity and broad applicability to a wide range of challenges in the field, including QSAR, virtual screening, protein structure modeling, QM calculations, materials synthesis and property prediction. In reviewing the performance of deep neural networks, we observed a consistent outperformance against non neural networks state-of-the-art models across disparate research topics, and deep neural network based models often exceeded the “glass ceiling” expectations of their respective tasks. Coupled with the maturity of GPU-accelerated computing for training deep neural networks and the exponential growth of chemical data on which to train these networks on, we anticipate that deep learning algorithms will be a useful tool and may grow into a pivotal role for various challenges in the computational chemistry field.

  15. Minicomputer and computations in chemistry

    Energy Technology Data Exchange (ETDEWEB)


    The introduction of multiple-precision hardware and longer word lengths has given the minicomputer a much more general potential for chemistry applications. It was the purpose of this workshop to address this potential, particularly as it is related to computations. The workshop brought together persons with minicomputer experience and those who are considering how the minicomputer might enhance their research activities. The workshop sessions were arranged in sequence to address the following questions: (1) Is the general purpose minicomputer an appropriate tool to meet the computational requirements of a chemistry research laboratory. (2) What are the procedures for wisely designing a minicomputer configuration. (3) What special-purpose hardware is available to enhance the speed of a minicomputer. (4) How does one select the appropriate minicomputer and ensure that it can accomplish the tasks for which is was designed. (5) How can one network minicomputers for more efficient and flexible operation. (6) Can one do really large-scale computations on a minicomputer and what modifications are necessary to convert existing programs and algorithms. (7) How can the minicomputer be used to access the maxicomputers at the NRCC. (8) How are computers likely to evolve in the future. (9) What should be the role of the NRCC in relation to minicomputers. This report of the workshop consists mainly of edited transcripts of introductory remarks. These were augmented by relevant bibliographies as an alternative to transcription of the entire workshop. There was no attempt in the workshop to give final answers to the questions that were raised, since the answers are determined in large part by each particular minicomputer environment.

  16. Refresher Course in Experimental Chemistry

    Indian Academy of Sciences (India)


    diverse topics such as chemical kinetics, electrochemistry, spectrophotometry, polymer chemistry, advanced synthesis in inorganic and organic chemistry and molecular modelling. The focus of this. Course is to acquaint the participants with novel avenues of sensitizing the students at the undergraduate level about the ...

  17. Experimentally calibrated computational chemistry of tryptophan hydroxylase: Trans influence, hydrogen-bonding, and 18-electron rule govern O-2-activation

    DEFF Research Database (Denmark)

    Haahr, Lærke Tvedebrink; Kepp, Kasper Planeta; Boesen, Jane


    with the experimental value (0.25 mm/s) which we propose as the structure of the hydroxylating intermediate, with the tryptophan substrate well located for further reaction 3.5 Å from the ferryl group. Based on the optimized transition states, the activation barriers for the two paths (glu and his) are similar, so...... a two-state scenario involving Ohis and Pglu is possible. A structure of the activated deoxy state which is high-spin implies that the valence electron count has been lowered from 18 to 16 (glutamate becomes bidentate), giving a “green light” that invites O2-binding. Our mechanism of oxygen activation...

  18. Atomic-Scale Design of Iron Fischer-Tropsch Catalysts; A Combined Computational Chemistry, Experimental, and Microkinetic Modeling Approach

    Energy Technology Data Exchange (ETDEWEB)

    Manos Mavrikakis; James Dumesic; Rahul Nabar; Calvin Bartholonew; Hu Zou; Uchenna Paul


    This work focuses on (1) searching/summarizing published Fischer-Tropsch synthesis (FTS) mechanistic and kinetic studies of FTS reactions on iron catalysts; (2) preparation and characterization of unsupported iron catalysts with/without potassium/platinum promoters; (3) measurement of H{sub 2} and CO adsorption/dissociation kinetics on iron catalysts using transient methods; (3) analysis of the transient rate data to calculate kinetic parameters of early elementary steps in FTS; (4) construction of a microkinetic model of FTS on iron, and (5) validation of the model from collection of steady-state rate data for FTS on iron catalysts. Three unsupported iron catalysts and three alumina-supported iron catalysts were prepared by non-aqueous-evaporative deposition (NED) or aqueous impregnation (AI) and characterized by chemisorption, BET, temperature-programmed reduction (TPR), extent-of-reduction, XRD, and TEM methods. These catalysts, covering a wide range of dispersions and metal loadings, are well-reduced and relatively thermally stable up to 500-600 C in H{sub 2} and thus ideal for kinetic and mechanistic studies. Kinetic parameters for CO adsorption, CO dissociation, and surface carbon hydrogenation on these catalysts were determined from temperature-programmed desorption (TPD) of CO and temperature programmed surface hydrogenation (TPSR), temperature-programmed hydrogenation (TPH), and isothermal, transient hydrogenation (ITH). A microkinetic model was constructed for the early steps in FTS on polycrystalline iron from the kinetic parameters of elementary steps determined experimentally in this work and from literature values. Steady-state rate data were collected in a Berty reactor and used for validation of the microkinetic model. These rate data were fitted to 'smart' Langmuir-Hinshelwood rate expressions derived from a sequence of elementary steps and using a combination of fitted steady-state parameters and parameters specified from the transient

  19. Atomic-Scale Design of Iron Fischer-Tropsch Catalysts: A Combined Computational Chemistry, Experimental, and Microkinetic Modeling Approach

    Energy Technology Data Exchange (ETDEWEB)

    Manos Mavrikakis; James A. Dumesic; Amit A. Gokhale; Rahul P. Nabar; Calvin H. Bartholomew; Hu Zou; Brian Critchfield


    rate-determining steps. In the coming year, studies will focus on quantitative determination of the rates of kinetically-relevant elementary steps on Fe catalysts with/without K and Pt promoters and at various levels of Al{sub 2}O{sub 3} support, providing a database for understanding (1) effects of promoter and support on elementary kinetic parameters and (2) for validation of computational models that incorporate effects of surface structure and promoters. Kinetic parameters will be incorporated into a microkinetics model, enabling prediction of rate without invoking assumptions, e.g. of a rate-determining step or a most-abundant surface intermediate. Calculations using periodic, self-consistent Density Functional Theory (DFT) methods were performed on two model surfaces: (1) Fe(110) with 1/4 ML subsurface carbon, and (2) Fe(110) with 1/4 ML Pt adatoms. Reaction networks for FTS on these systems were characterized in full detail by evaluating the thermodynamics and kinetics of each elementary step. We discovered that subsurface C stabilizes all the reactive intermediates, in contrast to Pt, which destabilizes most of them. A comparative study of the reactivities of the modified-Fe surfaces against pure Fe is expected to yield a more comprehensive understanding of promotion mechanisms for FTS on Fe.

  20. Superheavy Elements Challenge Experimental and Theoretical Chemistry

    CERN Document Server

    Zvára, I


    When reflecting on the story of superheavy elements, the an experimenter, acknowledges the role, which the predictions of nuclear and chemical theories have played in ongoing studies. Today, the problems of major interest for experimental chemistry are the studies of elements 112 and 114 including their chemical identification. Advanced quantum chemistry calculations of atoms and molecules would be of much help. First experiments with element 112 evidence that the metal is much more volatile and inert than mercury.

  1. computational chemistry capacity building in an underprivileged ...

    African Journals Online (AJOL)


    ABSTRACT. Computational chemistry is a fast developing branch of modern chemistry, focusing on the study of molecules to enable better understanding of the properties of substances. Its applications comprise a variety of fields, from drug design to the design of compounds with desired properties. (e.g., catalysts with ...

  2. Computational Chemistry Capacity Building in an Underprivileged ...

    African Journals Online (AJOL)

    Computational chemistry is a fast developing branch of modern chemistry, focusing on the study of molecules to enable better understanding of the properties of substances. Its applications comprise a variety of fields, from drug design to the design of compounds with desired properties (e.g., catalysts with specific actions) ...

  3. Disciplines, models, and computers: the path to computational quantum chemistry. (United States)

    Lenhard, Johannes


    Many disciplines and scientific fields have undergone a computational turn in the past several decades. This paper analyzes this sort of turn by investigating the case of computational quantum chemistry. The main claim is that the transformation from quantum to computational quantum chemistry involved changes in three dimensions. First, on the side of instrumentation, small computers and a networked infrastructure took over the lead from centralized mainframe architecture. Second, a new conception of computational modeling became feasible and assumed a crucial role. And third, the field of computa- tional quantum chemistry became organized in a market-like fashion and this market is much bigger than the number of quantum theory experts. These claims will be substantiated by an investigation of the so-called density functional theory (DFT), the arguably pivotal theory in the turn to computational quantum chemistry around 1990.

  4. Experimental interstellar organic chemistry - Preliminary findings (United States)

    Khare, B. N.; Sagan, C.


    Review of the results of some explicit experimental simulation of interstellar organic chemistry consisting in low-temperature high-vacuum UV irradiation of condensed simple gases known or suspected to be present in the interstellar medium. The results include the finding that acetonitrile may be present in the interstellar medium. The implication of this and other findings are discussed.

  5. Integration of Computational Chemistry into the Undergraduate Organic Chemistry Laboratory Curriculum (United States)

    Esselman, Brian J.; Hill, Nicholas J.


    Advances in software and hardware have promoted the use of computational chemistry in all branches of chemical research to probe important chemical concepts and to support experimentation. Consequently, it has become imperative that students in the modern undergraduate curriculum become adept at performing simple calculations using computational…

  6. Medicinal electrochemistry: integration of electrochemistry, medicinal chemistry and computational chemistry. (United States)

    Almeida, M O; Maltarollo, V G; de Toledo, R A; Shim, H; Santos, M C; Honorio, K M


    Over the last centuries, there were many important discoveries in medicine that were crucial for gaining a better understanding of several physiological processes. Molecular modelling techniques are powerful tools that have been successfully used to analyse and interface medicinal chemistry studies with electrochemical experimental results. This special combination can help to comprehend medicinal chemistry problems, such as predicting biological activity and understanding drug action mechanisms. Electrochemistry has provided better comprehension of biological reactions and, as a result of many technological improvements, the combination of electrochemical techniques and biosensors has become an appealing choice for pharmaceutical and biomedical analyses. Therefore, this review will briefly outline the present scope and future advances related to the integration of electrochemical and medicinal chemistry approaches based on various applications from recent studies.

  7. Experimental DNA computing

    NARCIS (Netherlands)

    Henkel, Christiaan


    Because of their information storing and processing capabilities, nucleic acids are interesting building blocks for molecular scale computers. Potential applications of such DNA computers range from massively parallel computation to computational gene therapy. In this thesis, several implementations

  8. Simulating chemistry using quantum computers. (United States)

    Kassal, Ivan; Whitfield, James D; Perdomo-Ortiz, Alejandro; Yung, Man-Hong; Aspuru-Guzik, Alán


    The difficulty of simulating quantum systems, well known to quantum chemists, prompted the idea of quantum computation. One can avoid the steep scaling associated with the exact simulation of increasingly large quantum systems on conventional computers, by mapping the quantum system to another, more controllable one. In this review, we discuss to what extent the ideas in quantum computation, now a well-established field, have been applied to chemical problems. We describe algorithms that achieve significant advantages for the electronic-structure problem, the simulation of chemical dynamics, protein folding, and other tasks. Although theory is still ahead of experiment, we outline recent advances that have led to the first chemical calculations on small quantum information processors.

  9. Relativistic quantum chemistry on quantum computers

    Czech Academy of Sciences Publication Activity Database

    Veis, Libor; Višňák, Jakub; Fleig, T.; Knecht, S.; Saue, T.; Visscher, L.; Pittner, Jiří


    Roč. 85, č. 3 (2012), 030304 ISSN 1050-2947 R&D Projects: GA ČR GA203/08/0626 Institutional support: RVO:61388955 Keywords : simulation * algorithm * computation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.042, year: 2012

  10. Quantum chemistry simulation on quantum computers: theories and experiments. (United States)

    Lu, Dawei; Xu, Boruo; Xu, Nanyang; Li, Zhaokai; Chen, Hongwei; Peng, Xinhua; Xu, Ruixue; Du, Jiangfeng


    It has been claimed that quantum computers can mimic quantum systems efficiently in the polynomial scale. Traditionally, those simulations are carried out numerically on classical computers, which are inevitably confronted with the exponential growth of required resources, with the increasing size of quantum systems. Quantum computers avoid this problem, and thus provide a possible solution for large quantum systems. In this paper, we first discuss the ideas of quantum simulation, the background of quantum simulators, their categories, and the development in both theories and experiments. We then present a brief introduction to quantum chemistry evaluated via classical computers followed by typical procedures of quantum simulation towards quantum chemistry. Reviewed are not only theoretical proposals but also proof-of-principle experimental implementations, via a small quantum computer, which include the evaluation of the static molecular eigenenergy and the simulation of chemical reaction dynamics. Although the experimental development is still behind the theory, we give prospects and suggestions for future experiments. We anticipate that in the near future quantum simulation will become a powerful tool for quantum chemistry over classical computations.

  11. Computers in Chemistry Teaching: A Bibliography and Index of CAL Packages. (United States)

    Rushby, N. J.

    This resource document lists 36 books, papers, and reports dealing with various uses of computers in chemistry instruction; and describes several computer program packages available for use in teaching undergraduate, experimental laboratory, physical, and nuclear and X-ray chemistry, including biochemistry. Each program package is presented by…

  12. Experimental design in chemistry: A tutorial. (United States)

    Leardi, Riccardo


    In this tutorial the main concepts and applications of experimental design in chemistry will be explained. Unfortunately, nowadays experimental design is not as known and applied as it should be, and many papers can be found in which the "optimization" of a procedure is performed one variable at a time. Goal of this paper is to show the real advantages in terms of reduced experimental effort and of increased quality of information that can be obtained if this approach is followed. To do that, three real examples will be shown. Rather than on the mathematical aspects, this paper will focus on the mental attitude required by experimental design. The readers being interested to deepen their knowledge of the mathematical and algorithmical part can find very good books and tutorials in the references [G.E.P. Box, W.G. Hunter, J.S. Hunter, Statistics for Experimenters: An Introduction to Design, Data Analysis, and Model Building, John Wiley & Sons, New York, 1978; R. Brereton, Chemometrics: Data Analysis for the Laboratory and Chemical Plant, John Wiley & Sons, New York, 1978; R. Carlson, J.E. Carlson, Design and Optimization in Organic Synthesis: Second Revised and Enlarged Edition, in: Data Handling in Science and Technology, vol. 24, Elsevier, Amsterdam, 2005; J.A. Cornell, Experiments with Mixtures: Designs, Models and the Analysis of Mixture Data, in: Series in Probability and Statistics, John Wiley & Sons, New York, 1991; R.E. Bruns, I.S. Scarminio, B. de Barros Neto, Statistical Design-Chemometrics, in: Data Handling in Science and Technology, vol. 25, Elsevier, Amsterdam, 2006; D.C. Montgomery, Design and Analysis of Experiments, 7th edition, John Wiley & Sons, Inc., 2009; T. Lundstedt, E. Seifert, L. Abramo, B. Thelin, A. Nyström, J. Pettersen, R. Bergman, Chemolab 42 (1998) 3; Y. Vander Heyden, LC-GC Europe 19 (9) (2006) 469].

  13. Exploratory Experimentation and Computation

    Energy Technology Data Exchange (ETDEWEB)

    Bailey, David H.; Borwein, Jonathan M.


    We believe the mathematical research community is facing a great challenge to re-evaluate the role of proof in light of recent developments. On one hand, the growing power of current computer systems, of modern mathematical computing packages, and of the growing capacity to data-mine on the Internet, has provided marvelous resources to the research mathematician. On the other hand, the enormous complexity of many modern capstone results such as the Poincare conjecture, Fermat's last theorem, and the classification of finite simple groups has raised questions as to how we can better ensure the integrity of modern mathematics. Yet as the need and prospects for inductive mathematics blossom, the requirement to ensure the role of proof is properly founded remains undiminished.

  14. Integrating Computational Chemistry into a Course in Classical Thermodynamics (United States)

    Martini, Sheridan R.; Hartzell, Cynthia J.


    Computational chemistry is commonly addressed in the quantum mechanics course of undergraduate physical chemistry curricula. Since quantum mechanics traditionally follows the thermodynamics course, there is a lack of curricula relating computational chemistry to thermodynamics. A method integrating molecular modeling software into a semester long…

  15. Virtually going green: The role of quantum computational chemistry in reducing pollution and toxicity in chemistry (United States)

    Stevens, Jonathan


    Continuing advances in computational chemistry has permitted quantum mechanical calculation to assist in research in green chemistry and to contribute to the greening of chemical practice. Presented here are recent examples illustrating the contribution of computational quantum chemistry to green chemistry, including the possibility of using computation as a green alternative to experiments, but also illustrating contributions to greener catalysis and the search for greener solvents. Examples of applications of computation to ambitious projects for green synthetic chemistry using carbon dioxide are also presented.

  16. Experimental Mathematics and Computational Statistics

    Energy Technology Data Exchange (ETDEWEB)

    Bailey, David H.; Borwein, Jonathan M.


    The field of statistics has long been noted for techniques to detect patterns and regularities in numerical data. In this article we explore connections between statistics and the emerging field of 'experimental mathematics'. These includes both applications of experimental mathematics in statistics, as well as statistical methods applied to computational mathematics.

  17. Effects of Computer Based Learning on Students' Attitudes and Achievements towards Analytical Chemistry (United States)

    Akcay, Husamettin; Durmaz, Asli; Tuysuz, Cengiz; Feyzioglu, Burak


    The aim of this study was to compare the effects of computer-based learning and traditional method on students' attitudes and achievement towards analytical chemistry. Students from Chemistry Education Department at Dokuz Eylul University (D.E.U) were selected randomly and divided into three groups; two experimental (Eg-1 and Eg-2) and a control…

  18. Computational chemistry at the petascale: Are we there yet?

    International Nuclear Information System (INIS)

    Apra, E; Harrison, R J; Shelton, W A; Tipparaju, V; Vazquez-Mayagoitia, A


    We have run computational chemistry calculations approaching the Petascale level of performance (∼ 0.5 PFlops). We used the Coupled Cluster CCSD(T) module of the computational chemistry code NWChem to evaluate accurate energetics of water clusters on a 1.4 PFlops Cray XT5 computer.

  19. JACOB: An Enterprise Framework for Computational Chemistry (United States)

    Waller, Mark P; Dresselhaus, Thomas; Yang, Jack


    Here, we present just a collection of beans (JACOB): an integrated batch-based framework designed for the rapid development of computational chemistry applications. The framework expedites developer productivity by handling the generic infrastructure tier, and can be easily extended by user-specific scientific code. Paradigms from enterprise software engineering were rigorously applied to create a scalable, testable, secure, and robust framework. A centralized web application is used to configure and control the operation of the framework. The application-programming interface provides a set of generic tools for processing large-scale noninteractive jobs (e.g., systematic studies), or for coordinating systems integration (e.g., complex workflows). The code for the JACOB framework is open sourced and is available at: © 2013 Wiley Periodicals, Inc. PMID:23553271

  20. Analysis of irradiated biogenic amines by computational chemistry and spectroscopy

    International Nuclear Information System (INIS)

    Oliveira, Jorge L.S.P.; Borges Junior, Itamar; Cardozo, Monique; Souza, Stefania P.; Lima, Antonio L.S.; Lima, Keila S.C.


    Biogenic Amines (B A) are nitrogenous compounds able to cause food poisoning. In this work, we studied the tyramine, one of the most common BA present in foods by combining experimental measured IR (Infrared) and GC/MS (Gas Chromatograph / Mass Spectrometry) spectra and computational quantum chemistry. Density Functional Theory (DFT) and the Deformed Atoms in Molecules (DMA) method was used to compute the partition the electronic densities in a chemically-intuitive way and electrostatic potentials of molecule to identify the acid and basic sites. Trading pattern was irradiated using a Cs 137 radiator, and each sample was identified by IR and GC/MS. Calculated and experimental IR spectra were compared. We observed that ionizing gamma irradiation was very effective in decreasing the population of standard amine, resulting in fragments that could be rationalized through the quantum chemistry calculations. In particular, we could locate the acid and basic sites of both molecules and identify possible sites of structural weaknesses, which allowed to propose mechanistic schemes for the breaking of chemical bonds by the irradiation. Moreover, from this work we hope it will be also possible to properly choose the dose of gamma irradiation which should be provided to eliminate each type of contamination. (author)

  1. Computational materials chemistry for carbon capture using porous materials

    International Nuclear Information System (INIS)

    Sharma, Abhishek; Malani, Ateeque; Huang, Runhong; Babarao, Ravichandar


    Control over carbon dioxide (CO 2 ) release is extremely important to decrease its hazardous effects on the environment such as global warming, ocean acidification, etc. For CO 2 capture and storage at industrial point sources, nanoporous materials offer an energetically viable and economically feasible approach compared to chemisorption in amines. There is a growing need to design and synthesize new nanoporous materials with enhanced capability for carbon capture. Computational materials chemistry offers tools to screen and design cost-effective materials for CO 2 separation and storage, and it is less time consuming compared to trial and error experimental synthesis. It also provides a guide to synthesize new materials with better properties for real world applications. In this review, we briefly highlight the various carbon capture technologies and the need of computational materials design for carbon capture. This review discusses the commonly used computational chemistry-based simulation methods for structural characterization and prediction of thermodynamic properties of adsorbed gases in porous materials. Finally, simulation studies reported on various potential porous materials, such as zeolites, porous carbon, metal organic frameworks (MOFs) and covalent organic frameworks (COFs), for CO 2 capture are discussed. (topical review)

  2. Computational materials chemistry for carbon capture using porous materials (United States)

    Sharma, Abhishek; Huang, Runhong; Malani, Ateeque; Babarao, Ravichandar


    Control over carbon dioxide (CO2) release is extremely important to decrease its hazardous effects on the environment such as global warming, ocean acidification, etc. For CO2 capture and storage at industrial point sources, nanoporous materials offer an energetically viable and economically feasible approach compared to chemisorption in amines. There is a growing need to design and synthesize new nanoporous materials with enhanced capability for carbon capture. Computational materials chemistry offers tools to screen and design cost-effective materials for CO2 separation and storage, and it is less time consuming compared to trial and error experimental synthesis. It also provides a guide to synthesize new materials with better properties for real world applications. In this review, we briefly highlight the various carbon capture technologies and the need of computational materials design for carbon capture. This review discusses the commonly used computational chemistry-based simulation methods for structural characterization and prediction of thermodynamic properties of adsorbed gases in porous materials. Finally, simulation studies reported on various potential porous materials, such as zeolites, porous carbon, metal organic frameworks (MOFs) and covalent organic frameworks (COFs), for CO2 capture are discussed.

  3. Computational chemistry and metal-based radiopharmaceuticals

    International Nuclear Information System (INIS)

    Neves, M.; Fausto, R.


    Computer-assisted techniques have found extensive use in the design of organic pharmaceuticals but have not been widely applied on metal complexes, particularly on radiopharmaceuticals. Some examples of computer generated structures of complexes of In, Ga and Tc with N, S, O and P donor ligands are referred. Besides parameters directly related with molecular geometries, molecular properties of the predicted structures, as ionic charges or dipole moments, are considered to be related with biodistribution studies. The structure of a series of oxo neutral Tc-biguanide complexes are predicted by molecular mechanics calculations, and their interactions with water molecules or peptide chains correlated with experimental data of partition coefficients and percentage of human protein binding. The results stress the interest of using molecular modelling to predict molecular properties of metal-based radiopharmaceuticals, which can be successfully correlated with results of in vitro studies. (author)

  4. What influences on demonstration experimental work in chemistry classroom?


    Logar, Ana; Ferk Savec, Vesna


    Teachers and researchers agree that experimental work has a crucial role in teaching and learning of science. The article presents results of a qualitative investigation dealing with factors that influence on the efficiency of primary school students` experimental work in chemistry classroom. The sample consisted of 9 chemistry teachers and 141 randomly selected primary school students (age 13-14 years). Based on the research results a model for effective planning and integration of students`...

  5. Computer simulation and experimental self-assembly of irradiated glycine amino acid under magnetic fields: Its possible significance in prebiotic chemistry. (United States)

    Heredia, Alejandro; Colín-García, María; Puig, Teresa Pi I; Alba-Aldave, Leticia; Meléndez, Adriana; Cruz-Castañeda, Jorge A; Basiuk, Vladimir A; Ramos-Bernal, Sergio; Mendoza, Alicia Negrón


    Ionizing radiation may have played a relevant role in chemical reactions for prebiotic biomolecule formation on ancient Earth. Environmental conditions such as the presence of water and magnetic fields were possibly relevant in the formation of organic compounds such as amino acids. ATR-FTIR, Raman, EPR and X-ray spectroscopies provide valuable information about molecular organization of different glycine polymorphs under static magnetic fields. γ-glycine polymorph formation increases in irradiated samples interacting with static magnetic fields. The increase in γ-glycine polymorph agrees with the computer simulations. The AM1 semi-empirical simulations show a change in the catalyst behavior and dipole moment values in α and γ-glycine interaction with the static magnetic field. The simulated crystal lattice energy in α-glycine is also affected by the free radicals under the magnetic field, which decreases its stability. Therefore, solid α and γ-glycine containing free radicals under static magnetic fields might have affected the prebiotic scenario on ancient Earth by causing the oligomerization of glycine in prebiotic reactions. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Experimental quantum computing without entanglement. (United States)

    Lanyon, B P; Barbieri, M; Almeida, M P; White, A G


    Deterministic quantum computation with one pure qubit (DQC1) is an efficient model of computation that uses highly mixed states. Unlike pure-state models, its power is not derived from the generation of a large amount of entanglement. Instead it has been proposed that other nonclassical correlations are responsible for the computational speedup, and that these can be captured by the quantum discord. In this Letter we implement DQC1 in an all-optical architecture, and experimentally observe the generated correlations. We find no entanglement, but large amounts of quantum discord-except in three cases where an efficient classical simulation is always possible. Our results show that even fully separable, highly mixed, states can contain intrinsically quantum mechanical correlations and that these could offer a valuable resource for quantum information technologies.

  7. Experimental interstellar organic chemistry: Preliminary findings (United States)

    Khare, B. N.; Sagan, C.


    In a simulation of interstellar organic chemistry in dense interstellar clouds or on grain surfaces, formaldehyde, water vapor, ammonia and ethane are deposited on a quartz cold finger and ultraviolet-irradiated in high vacuum at 77K. The HCHO photolytic pathway which produces an aldehyde radical and a superthermal hydrogen atom initiates solid phase chain reactions leading to a range of new compounds, including methanol, ethanol, acetaldehyde, acetonitrile, acetone, methyl formate, and possibly formic acid. Higher nitriles are anticipated. Genetic relations among these interstellar organic molecules (e.g., the Cannizzaro and Tischenko reactions) must exist. Some of them, rather than being synthesized from smaller molecules, may be degradation products of larger organic molecules, such as hexamethylene tetramine, which are candidate consitituents of the interstellar grains. The experiments reported here may also be relevant to cometary chemistry.

  8. Integrating medicinal chemistry, organic/combinatorial chemistry, and computational chemistry for the discovery of selective estrogen receptor modulators with Forecaster, a novel platform for drug discovery. (United States)

    Therrien, Eric; Englebienne, Pablo; Arrowsmith, Andrew G; Mendoza-Sanchez, Rodrigo; Corbeil, Christopher R; Weill, Nathanael; Campagna-Slater, Valérie; Moitessier, Nicolas


    As part of a large medicinal chemistry program, we wish to develop novel selective estrogen receptor modulators (SERMs) as potential breast cancer treatments using a combination of experimental and computational approaches. However, one of the remaining difficulties nowadays is to fully integrate computational (i.e., virtual, theoretical) and medicinal (i.e., experimental, intuitive) chemistry to take advantage of the full potential of both. For this purpose, we have developed a Web-based platform, Forecaster, and a number of programs (e.g., Prepare, React, Select) with the aim of combining computational chemistry and medicinal chemistry expertise to facilitate drug discovery and development and more specifically to integrate synthesis into computer-aided drug design. In our quest for potent SERMs, this platform was used to build virtual combinatorial libraries, filter and extract a highly diverse library from the NCI database, and dock them to the estrogen receptor (ER), with all of these steps being fully automated by computational chemists for use by medicinal chemists. As a result, virtual screening of a diverse library seeded with active compounds followed by a search for analogs yielded an enrichment factor of 129, with 98% of the seeded active compounds recovered, while the screening of a designed virtual combinatorial library including known actives yielded an area under the receiver operating characteristic (AU-ROC) of 0.78. The lead optimization proved less successful, further demonstrating the challenge to simulate structure activity relationship studies.

  9. Computational chemistry meets cultural heritage: challenges and perspectives. (United States)

    Fantacci, Simona; Amat, Anna; Sgamellotti, Antonio


    Chemistry is central to addressing topics of interest in the cultural heritage field, offering particular insight into the nature and composition of the original materials, the degradation processes that have occurred over the years, and the attendant physical and chemical changes. On the one hand, the chemical characterization of the constituting materials allows researchers to unravel the rich information enclosed in a work of art, providing insight into the manufacturing techniques and revealing aspects of artistic, chronological, historical, and sociocultural significance. On the other hand, despite the recognized contribution of computational chemistry in many branches of materials science, this tool has only recently been applied to cultural heritage, largely because of the inherent complexity of art materials. In this Account, we present a brief overview of the available computational methods, classified on the basis of accuracy level and dimension of the system to be simulated. Among the discussed methodologies, density functional theory (DFT) and time-dependent DFT represent a good compromise between accuracy and computational cost, allowing researchers to model the structural, electronic, and spectroscopic properties of complex extended systems in condensed phase. We then discuss the results of recent research devoted to the computer simulation of prototypical systems in cultural heritage, namely, indigo and Maya Blue, weld and weld lake, and the pigment minium (red lead). These studies provide insight into the basic interactions underlying the materials properties and, in some cases, permit the assignment of the material composition. We discuss properties of interest in the cultural heritage field, ranging from structural geometries and acid-base properties to IR-Raman vibrational spectra and UV-vis absorption-emission spectra (including excited-state deactivation pathways). We particularly highlight how computational chemistry applications in cultural

  10. Thole's interacting polarizability model in computational chemistry practice

    NARCIS (Netherlands)

    deVries, AH; vanDuijnen, PT; Zijlstra, RWJ; Swart, M

    Thole's interacting polarizability model to calculate molecular polarizabilities from interacting atomic polarizabilities is reviewed and its major applications in computational chemistry are illustrated. The applications include prediction of molecular polarizabilities, use in classical expressions

  11. Exploiting Locality in Quantum Computation for Quantum Chemistry. (United States)

    McClean, Jarrod R; Babbush, Ryan; Love, Peter J; Aspuru-Guzik, Alán


    Accurate prediction of chemical and material properties from first-principles quantum chemistry is a challenging task on traditional computers. Recent developments in quantum computation offer a route toward highly accurate solutions with polynomial cost; however, this solution still carries a large overhead. In this Perspective, we aim to bring together known results about the locality of physical interactions from quantum chemistry with ideas from quantum computation. We show that the utilization of spatial locality combined with the Bravyi-Kitaev transformation offers an improvement in the scaling of known quantum algorithms for quantum chemistry and provides numerical examples to help illustrate this point. We combine these developments to improve the outlook for the future of quantum chemistry on quantum computers.

  12. Recent advances in the computational chemistry of soft porous crystals. (United States)

    Fraux, Guillaume; Coudert, François-Xavier


    Here we highlight recent progress in the field of computational chemistry of nanoporous materials, focusing on methods and studies that address the extraordinary dynamic nature of these systems: the high flexibility of their frameworks, the large-scale structural changes upon external physical or chemical stimulation, and the presence of defects and disorder. The wide variety of behavior demonstrated in soft porous crystals, including the topical class of metal-organic frameworks, opens new challenges for computational chemistry methods at all scales.

  13. Cuby: An Integrative Framework for Computational Chemistry

    Czech Academy of Sciences Publication Activity Database

    Řezáč, Jan


    Roč. 37, č. 13 (2016), s. 1230-1237 ISSN 0192-8651 R&D Projects: GA ČR GP13-01214P Institutional support: RVO:61388963 Keywords : software framework * workflow automation * QM/MM * datasets * Ruby Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.229, year: 2016

  14. The chemistry of transactinide elements. Experimental achievements and perspectives

    International Nuclear Information System (INIS)

    Schaedel, M.


    The chemistry of transactinides and superheavy elements has reached element 108. Preparations are under way to leap to element 112 and beyond. This development, its current status and future perspectives are reviewed from an experimental point of view. The atom-at-a-time situation of transactinide chemistry is briefly outlines. Experimental techniques and important results enlightening the chemical properties of elements 104 through 108 are presented in an exemplary way with emphasis on the aqueous chemistry of the lighter ones. From the results of these experiments it is justified to place these elements in the Periodic Table of the Elements into groups 4 through 8, respectively. However, strongly due to the influence of relativistic effects, it is no longer possible to deduce detailed chemical properties of these superheavy elements from this position. Perspectives for future research programs are given. (author)

  15. Computational Chemistry in the Pharmaceutical Industry: From Childhood to Adolescence. (United States)

    Hillisch, Alexander; Heinrich, Nikolaus; Wild, Hanno


    Computational chemistry within the pharmaceutical industry has grown into a field that proactively contributes to many aspects of drug design, including target selection and lead identification and optimization. While methodological advancements have been key to this development, organizational developments have been crucial to our success as well. In particular, the interaction between computational and medicinal chemistry and the integration of computational chemistry into the entire drug discovery process have been invaluable. Over the past ten years we have shaped and developed a highly efficient computational chemistry group for small-molecule drug discovery at Bayer HealthCare that has significantly impacted the clinical development pipeline. In this article we describe the setup and tasks of the computational group and discuss external collaborations. We explain what we have found to be the most valuable and productive methods and discuss future directions for computational chemistry method development. We share this information with the hope of igniting interesting discussions around this topic. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. From transistor to trapped-ion computers for quantum chemistry. (United States)

    Yung, M-H; Casanova, J; Mezzacapo, A; McClean, J; Lamata, L; Aspuru-Guzik, A; Solano, E


    Over the last few decades, quantum chemistry has progressed through the development of computational methods based on modern digital computers. However, these methods can hardly fulfill the exponentially-growing resource requirements when applied to large quantum systems. As pointed out by Feynman, this restriction is intrinsic to all computational models based on classical physics. Recently, the rapid advancement of trapped-ion technologies has opened new possibilities for quantum control and quantum simulations. Here, we present an efficient toolkit that exploits both the internal and motional degrees of freedom of trapped ions for solving problems in quantum chemistry, including molecular electronic structure, molecular dynamics, and vibronic coupling. We focus on applications that go beyond the capacity of classical computers, but may be realizable on state-of-the-art trapped-ion systems. These results allow us to envision a new paradigm of quantum chemistry that shifts from the current transistor to a near-future trapped-ion-based technology.

  17. Experimental and Theoretical Studies of Atmosphereic Inorganic Chlorine Chemistry (United States)

    Sander, Stanley P.; Friedl, Randall R.


    Over the last five years substantial progress has been made in defining the realm of new chlorine chemistry in the polar stratosphere. Application of existing experimental techniques to potentially important chlorine-containing compounds has yielded quantitative kinetic and spectroscopic data as well as qualitative mechanistic insights into the relevant reactions.

  18. Computer-Assisted Instruction in Undergraduate Organic Chemistry: Design, Application, and Evaluation. Technical Report 10. (United States)

    Culp, George

    The computer-assisted instruction (CAI) program in undergraduate organic chemistry at the University of Texas was evaluated by an experimental design in 1969 and found to be successful. This report discusses in detail the formation of the design, its application, and the method of evaluation. The program itself included 15 teaching modules that…

  19. Computational and experimental study of laminar flames

    Energy Technology Data Exchange (ETDEWEB)

    Smooke, Mitchell [Yale Univ., New Haven, CT (United States)


    During the past three years, our research has centered on an investigation of the effects of complex chemistry and detailed transport on the structure and extinction of hydrocarbon flames in coflowing axisymmetric configurations. We have pursued both computational and experimental aspects of the research in parallel on both steady-state and time-dependent systems. The computational work has focused on the application of accurate and efficient numerical methods for the solution of the steady-state and time-dependent boundary value problems describing the various reacting systems. Detailed experimental measurements were performed on axisymmetric coflow flames using two-dimensional imaging techniques. Previously, spontaneous Raman scattering, chemiluminescence, and laser-induced fluorescence were used to measure the temperature, major and minor species profiles. Particle image velocimetry (PIV) has been used to investigate velocity distributions and for calibration of time-varying flames. Laser-induced incandescence (LII) with an extinction calibration was used to determine soot volume fractions, while soot surface temperatures were measured with three-color optical pyrometry using a color digital camera. A blackbody calibration of the camera allows for determination of soot volume fraction as well, which can be compared with the LII measurements. More recently, we have concentrated on a detailed characterization of soot using a variety of techniques including time-resolved LII (TiRe-LII) for soot primary particles sizes, multi-angle light scattering (MALS) for soot radius of gyration, and spectrally-resolved line of sight attenuation (spec-LOSA). Combining the information from all of these soot measurements can be used to determine the soot optical properties, which are observed to vary significantly depending on spatial location and fuel dilution. Our goal has been to obtain a more fundamental understanding of the important fluid dynamic and chemical interactions in

  20. Towards quantum chemistry on a quantum computer. (United States)

    Lanyon, B P; Whitfield, J D; Gillett, G G; Goggin, M E; Almeida, M P; Kassal, I; Biamonte, J D; Mohseni, M; Powell, B J; Barbieri, M; Aspuru-Guzik, A; White, A G


    Exact first-principles calculations of molecular properties are currently intractable because their computational cost grows exponentially with both the number of atoms and basis set size. A solution is to move to a radically different model of computing by building a quantum computer, which is a device that uses quantum systems themselves to store and process data. Here we report the application of the latest photonic quantum computer technology to calculate properties of the smallest molecular system: the hydrogen molecule in a minimal basis. We calculate the complete energy spectrum to 20 bits of precision and discuss how the technique can be expanded to solve large-scale chemical problems that lie beyond the reach of modern supercomputers. These results represent an early practical step toward a powerful tool with a broad range of quantum-chemical applications.

  1. Chemistry computations for irradiated hot air

    International Nuclear Information System (INIS)

    Sutherland, C.D.; Zinn, J.


    A description is given of a computational model of chemical kinetics in air at temperatures between 300 and 4000 0 K, with and without imposed fluxes of ionizing radiation and uv radiation, at pressures up to 10 atmospheres. Included are 1360 chemical reactions, involving 71 H, C, N, and O-containing chemical species. The reaction set is complete in the sense of including a reverse reaction for every reaction and including the dominant destruction reactions for each species produced. Photochemical reaction rates are computed in terms of a prescribed intensity and spectral distribution of radiant flux. Reactions of the metastable species O( 1 D), N( 2 D), O 2 ( 1 Δg), and O 2 ( 1 Σ + /sub g/) are included explicitly, but all other quantum state populations are assumed to be in thermodynamic equilibrium. Results of several sets of model computations are described. These include: computations of rates of equilibration of systems subjected to abrupt temperature changes at a pressure of 1 atmosphere; computations of relaxation of systems subjected to impulsive sources of ionizing radiation at P = 1 atmosphere and 0.01 atm, with and without superimposed sources of optical-uv radiation; and computations of the approach to steady state in systems subjected to steady sources of ionizing radiation, for pressures between 10 -3 atm and 10 atm. For computing concentrations of electrons, ions, NO, NO 2 , O, N, and O 3 , an abbreviated lumped-parameter reaction set was constructed with 31 reactions, designed to be incorporated in a fluid-dynamics code. Rate coefficients were calibrated against results from the 1360-reaction code for temperatures between 300 and 4000 0 K and pressures between 10 -3 and 10 atm

  2. Virtual drug discovery: beyond computational chemistry? (United States)

    Gilardoni, Francois; Arvanites, Anthony C


    This editorial looks at how a fully integrated structure that performs all aspects in the drug discovery process, under one company, is slowly disappearing. The steps in the drug discovery paradigm have been slowly increasing toward virtuality or outsourcing at various phases of product development in a company's candidate pipeline. Each step in the process, such as target identification and validation and medicinal chemistry, can be managed by scientific teams within a 'virtual' company. Pharmaceutical companies to biotechnology start-ups have been quick in adopting this new research and development business strategy in order to gain flexibility, access the best technologies and technical expertise, and decrease product developmental costs. In today's financial climate, the term virtual drug discovery has an organizational meaning. It represents the next evolutionary step in outsourcing drug development.

  3. Computational chemistry reviews of current trends v.4

    CERN Document Server


    This volume presents a balanced blend of methodological and applied contributions. It supplements well the first three volumes of the series, revealing results of current research in computational chemistry. It also reviews the topographical features of several molecular scalar fields. A brief discussion of topographical concepts is followed by examples of their application to several branches of chemistry.The size of a basis set applied in a calculation determines the amount of computer resources necessary for a particular task. The details of a common strategy - the ab initio model potential

  4. Computational Chemistry of Cyclopentane Low Temperature Oxidation

    KAUST Repository

    El Rachidi, Mariam


    Cycloalkanes are significant constituents of conventional fossil fuels, but little is known concerning their combustion chemistry and kinetics, particularly at low temperatures. This study investigates the pressure dependent kinetics of several reactions occurring during low-temperature cyclopentane combustion using theoretical chemical kinetics. The reaction pathways of the cyclopentyl + O2 adduct is traced to alkylhydroperoxide, cyclic ether, β-scission and HO2 elimination products. The calculations are carried out at the UCCSD(T)-F12b/cc-pVTZ-F12//M06-2X/6-311++G(d,p) level of theory. The barrierless entrance channel is treated using variable-reaction-coordinate transition state theory (VRC-TST) at the CASPT2(7e,6o) level of theory, including basis set, geometry relaxation and ZPE corrections. 1-D time-dependent multiwell master equation analysis is used to determine pressure-and temperature-dependent rate parameters of all investigated reactions. Tunneling corrections are included using Eckart barriers. Comparison with cyclohexane is used to elucidate the effect of ring size on the low temperature reactivity of naphthenes. The rate coefficients reported herein are suitable for use in cyclopentane and methylcyclopentane combustion models, even below ~900 K, where ignition is particularly sensitive to these pressure-dependent values.

  5. 40 CFR 158.270 - Experimental use permit data requirements for residue chemistry. (United States)


    ... requirements for residue chemistry. 158.270 Section 158.270 Protection of Environment ENVIRONMENTAL PROTECTION... Experimental use permit data requirements for residue chemistry. All residue chemistry data, as described in... section 408(r) is sought. Residue chemistry data are not required for an experimental use permit issued on...

  6. Experimental and Analytical Studies of Solar System Chemistry (United States)

    Burnett, Donald S.


    The cosmochemistry research funded by this grant resulted in the publications given in the attached Publication List. The research focused in three areas: (1) Experimental studies of trace element partitioning. (2) Studies of the minor element chemistry and O isotopic compositions of MgAlO4 spinels from Ca-Al-Rich Inclusions in carbonaceous chondrite meteorites, and (3) The abundances and chemical fractionations of Th and U in chondritic meteorites.

  7. Computations for a condenser. Experimental results

    International Nuclear Information System (INIS)

    Walden, Jean.


    Computations for condensers are presented with experimental results. The computations are concerned with the steam flux at the condenser input, and inside the tube bundle. Experimental results are given for the flux inside the condenser sleeve and the flow passing through the tube bundle [fr

  8. Investigating the Effectiveness of Computer Simulations for Chemistry Learning (United States)

    Plass, Jan L.; Milne, Catherine; Homer, Bruce D.; Schwartz, Ruth N.; Hayward, Elizabeth O.; Jordan, Trace; Verkuilen, Jay; Ng, Florrie; Wang, Yan; Barrientos, Juan


    Are well-designed computer simulations an effective tool to support student understanding of complex concepts in chemistry when integrated into high school science classrooms? We investigated scaling up the use of a sequence of simulations of kinetic molecular theory and associated topics of diffusion, gas laws, and phase change, which we designed…

  9. Applied Computational Chemistry for the Blind and Visually Impaired (United States)

    Wedler, Henry B.; Cohen, Sarah R.; Davis, Rebecca L.; Harrison, Jason G.; Siebert, Matthew R.; Willenbring, Dan; Hamann, Christian S.; Shaw, Jared T.; Tantillo, Dean J.


    We describe accommodations that we have made to our applied computational-theoretical chemistry laboratory to provide access for blind and visually impaired students interested in independent investigation of structure-function relationships. Our approach utilizes tactile drawings, molecular model kits, existing software, Bash and Perl scripts…

  10. [Animal experimentation, computer simulation and surgical research]. (United States)

    Carpentier, Alain


    We live in a digital world In medicine, computers are providing new tools for data collection, imaging, and treatment. During research and development of complex technologies and devices such as artificial hearts, computer simulation can provide more reliable information than experimentation on large animals. In these specific settings, animal experimentation should serve more to validate computer models of complex devices than to demonstrate their reliability.

  11. Adaptive chemistry computations of reacting flow

    International Nuclear Information System (INIS)

    Ortega, J M; Najm, H N; Ray, J; Valorani, M; Goussis, D A; Frenklach, M


    We present a new tabulation strategy for the numerical integration of chemical reacting flow processes on the basis of a non-stiff system of equations. Both the tabulation and the identification of the non-stiff system are adaptive and are based on the Computational Singular Perturbation (CSP) method. The tabulation strategy is implemented in order to store and reuse the CSP quantities required for the construction of the non-stiff model. In this paper we describe a particular feature of this algorithm, the 'homogeneous correction', that allows for an accurate and efficient identification of the manifold on which the solution moves according to the slow time scales. The improved efficiency in constructing the slow model and simulating the system dynamics along the manifold during run-time calculations is demonstrated

  12. Interactive Computer Visualization in the Introductory Chemistry Curriculum (United States)

    Bragin, Victoria M.


    related applications such as one on VSEPR. Computer-fitting of smooth curves to experimental data was a new experience for many students. In the second semester general chemistry course, students determined the equivalence points from the first derivative of a curve fit to their experimental measurements. Points of inflection, maxima, minima, and other mathematical parameters now had a real meaning in terms of observable properties of the physical systems being studied, and many students voiced satisfaction in applying what they had learned in mathematics classes to analyzing data collected in the science laboratory. A commercial spreadsheet with a scripting language is used for data analysis. Students enter their experimental data and calculated results. The script indicates if their result is correct within reasonable limits of error but does not perform the calculations for them. Most students opt to use this application even though it is not required. A bulletin board system (ChemistryBBS) with a graphical user interface has been created in which students post questions on course material and other students or faculty post answers or suggestions. ChemistryBBS encourages participation by those who do not speak up in class as well as by those whose spoken English is imperfect. Students use e-mail to hand in homework and laboratory reports. They particularly enjoy the ease with which graphics can be incorporated into text documents, and many students produce professional looking reports. Other courseware in various stages of development include Dimensions (dimensional analysis), MindYourSigFigs (use of significant figures in measurements), What'sInAName (inorganic nomenclature), PeriodicTable (an interactive handbook of periodic properties of the elements), RedoxReactions, ElectrochemicalCells, and Carbon-13NMR. A commercial application that captures screen images and sound is used to develop custom lesson modules adapted to the learning styles of individual students and

  13. Computational Tools To Model Halogen Bonds in Medicinal Chemistry. (United States)

    Ford, Melissa Coates; Ho, P Shing


    The use of halogens in therapeutics dates back to the earliest days of medicine when seaweed was used as a source of iodine to treat goiters. The incorporation of halogens to improve the potency of drugs is now fairly standard in medicinal chemistry. In the past decade, halogens have been recognized as direct participants in defining the affinity of inhibitors through a noncovalent interaction called the halogen bond or X-bond. Incorporating X-bonding into structure-based drug design requires computational models for the anisotropic distribution of charge and the nonspherical shape of halogens, which lead to their highly directional geometries and stabilizing energies. We review here current successes and challenges in developing computational methods to introduce X-bonding into lead compound discovery and optimization during drug development. This fast-growing field will push further development of more accurate and efficient computational tools to accelerate the exploitation of halogens in medicinal chemistry.

  14. Analytical chemistry measurements quality control program using computer applications

    International Nuclear Information System (INIS)

    Clark, J.P.; Huff, G.A.


    An Analytical Chemistry Measurements Quality Control Program assures the reliability of analytical measurements performed at the Barnwell Nuclear Fuel Plant. The program includes training, methods quality control, replicate samples and measurements, mass measurements, interlaboratory sample exchanges, and standards preparation. This program has been designed to meet the requirements of 10CFR70.57. Portions of the program have been automated by using a PDP 11/35 computer system to provide features which are not readily available in manual systems. These include such items as realtime measurement control, computer calculated bias and precision estimates, various surveillance applications, and evaluation of measurement system variables. The efficiency of the computer system has been demonstrated in gathering and assimilating the results of over 1100 quality control samples during a recent cold chemical checkout campaign. These data were used to determine equations for predicting measurements reliability estimates; to evaluate measurement performance of the analysts, equipment, and measurement period; and to provide directions for chemistry methods modifications and additional training requirements. A procedure of replicate sampling and measuring provides random error estimates. The analytical chemistry measurement quality control activities during the campaign represented about 10% of the total analytical chemistry effort

  15. Simulation and experimentation of PSCAR chemistry for complex structures (United States)

    Carcasi, Michael; Nagahara, Seiji; Shiraishi, Gosuke; Iseki, Tomohiro; Minekawa, Yukie; Yoshihara, Kosuke; Nakagawa, Hisashi; Naruoka, Takehiko; Nagai, Tomoki; Oshima, Akihiro; Tagawa, Seiichi


    Extreme ultraviolet lithography (EUVL, λ = 13.5 nm) continues to be one of the most important candidates for future technology nodes. For the insertion of EUV lithography into device mass production, higher sensitivity of EUV resists is helpful for better cost of ownership of the EUV tool and light source. However, obtaining low sensitivity (S), high resolution (R), and low line edge roughness (L) simultaneously is very difficult. Many previous experiments by lithographers proved the existence of this "RLS trade-off"1-2. This paper furthers the work related to Photosensitized Chemically Amplified ResistTM (PSCAR)TM**, a chemistry which is trying to break the "RLS tradeoff" relationship. This chemistry was introduced as a new chemically amplified lithographic concept and is accomplished in an in-line track tool with secondary exposure module connected to EUV exposure tool. PSCAR is a modified CAR which contains a photosensitizer precursor (PP) in addition to other standard CAR components such as a protected polymer, a photo acid generator (PAG) and a quencher. In the PSCAR process, an improved chemical gradient can be realized by dual acid quenching steps with the help of increased quencher concentration. The addition of the PP, as well as other material optimization, offers more degrees of freedom for getting high sensitivity and low LER, but also makes the system more complicated. Thus coupling simulation and experimentation is the most rational approach to optimizing the overall process and for understanding complicated 2-D structures. In this paper, we will provide additional background into the simulation of PSCAR chemistry, explore the effects of PSCAR chemistry on chemical contrast of complex structures (e.g. T structures, slot contacts, I/D bias for L/S), and explore the sensitivity enhancement levels capable while improving or maintaining lithographic performance. Finally, we will explore modifications of PSCAR chemistry on performance.

  16. From transistor to trapped-ion computers for quantum chemistry (United States)

    Yung, M.-H.; Casanova, J.; Mezzacapo, A.; McClean, J.; Lamata, L.; Aspuru-Guzik, A.; Solano, E.


    Over the last few decades, quantum chemistry has progressed through the development of computational methods based on modern digital computers. However, these methods can hardly fulfill the exponentially-growing resource requirements when applied to large quantum systems. As pointed out by Feynman, this restriction is intrinsic to all computational models based on classical physics. Recently, the rapid advancement of trapped-ion technologies has opened new possibilities for quantum control and quantum simulations. Here, we present an efficient toolkit that exploits both the internal and motional degrees of freedom of trapped ions for solving problems in quantum chemistry, including molecular electronic structure, molecular dynamics, and vibronic coupling. We focus on applications that go beyond the capacity of classical computers, but may be realizable on state-of-the-art trapped-ion systems. These results allow us to envision a new paradigm of quantum chemistry that shifts from the current transistor to a near-future trapped-ion-based technology. PMID:24395054

  17. The computer library of experimental neutron data

    International Nuclear Information System (INIS)

    Bychkov, V.M.; Manokhin, V.N.; Surgutanov, V.V.


    The paper describes the computer library of experimental neutron data at the Obninsk Nuclear Data Centre. The format of the library (EXFOR) and the system of programmes for supplying the library are briefly described. (author)

  18. Experimental studies in high temperature aqueous chemistry at Oak Ridge National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Mesmer, R.E.; Palmer, D.A.; Simonson, J.M.; Holmes, H.F.; Ho, P.C.; Wesolowski, D.J.; Gruszkiewicz, M.S.


    Experimental research is conducted and models developed in a long- standing program at Oak Ridge on aqueous chemistry at high temperatures of broad classes of electrolytes emphasizing thermodynamics of reaction equilibria and excess thermodynamic properties of electrolytes. Experimental methods, their capabilities, data analysis, and results are summarized. Relevance of the work to problems in power plants, natural and industrial processes as well as basic solution chemistry and geochemistry are given. Progress in potentiometry, electrical conductivity, flow calorimetry, and isopiestic research is described. Future in this field demands greater precision in measurements and significant gains in our understanding of the solvation phenomena especially in the vicinity and beyond the critical point for water. The communities who do research on scattering, spectroscopy, and computer simulations can help guide these efforts through studies at extreme conditions.

  19. Computational Exploration of Molecular Scaffolds in Medicinal Chemistry. (United States)

    Hu, Ye; Stumpfe, Dagmar; Bajorath, Jürgen


    The scaffold concept is widely applied in medicinal chemistry. Scaffolds are mostly used to represent core structures of bioactive compounds. Although the scaffold concept has limitations and is often viewed differently from a chemical and computational perspective, it has provided a basis for systematic investigations of molecular cores and building blocks, going far beyond the consideration of individual compound series. Over the past 2 decades, alternative scaffold definitions and organization schemes have been introduced and scaffolds have been studied in a variety of ways and increasingly on a large scale. Major applications of the scaffold concept include the generation of molecular hierarchies, structural classification, association of scaffolds with biological activities, and activity prediction. This contribution discusses computational approaches for scaffold generation and analysis, with emphasis on recent developments impacting medicinal chemistry. A variety of scaffold-based studies are discussed, and a perspective on scaffold methods is provided.

  20. Experimental and computational benchmark tests

    International Nuclear Information System (INIS)

    Gilliam, D.M.; Briesmeister, J.F.


    A program involving principally NIST, LANL, and ORNL has been in progress for about four years now to establish a series of benchmark measurements and calculations related to the moderation and leakage of 252 Cf neutrons from a source surrounded by spherical aqueous moderators of various thicknesses and compositions. The motivation for these studies comes from problems in criticality calculations concerning arrays of multiplying components, where the leakage from one component acts as a source for the other components. This talk compares experimental and calculated values for the fission rates of four nuclides - 235 U, 239 Pu, 238 U, and 237 Np - in the leakage spectrum from moderator spheres of diameters 76.2 mm, 101.6 mm, and 127.0 mm, with either pure water or enriched B-10 solutions as the moderator. Very detailed Monte Carlo calculations were done with the MCNP code, using a open-quotes light waterclose quotes S(α,β) scattering kernel

  1. 40 CFR 158.210 - Experimental use permit data requirements for product chemistry. (United States)


    ... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Experimental use permit data requirements for product chemistry. 158.210 Section 158.210 Protection of Environment ENVIRONMENTAL PROTECTION... Experimental use permit data requirements for product chemistry. All product chemistry data, as described in...

  2. Computationally efficient implementation of combustion chemistry in parallel PDF calculations

    International Nuclear Information System (INIS)

    Lu Liuyan; Lantz, Steven R.; Ren Zhuyin; Pope, Stephen B.


    In parallel calculations of combustion processes with realistic chemistry, the serial in situ adaptive tabulation (ISAT) algorithm [S.B. Pope, Computationally efficient implementation of combustion chemistry using in situ adaptive tabulation, Combustion Theory and Modelling, 1 (1997) 41-63; L. Lu, S.B. Pope, An improved algorithm for in situ adaptive tabulation, Journal of Computational Physics 228 (2009) 361-386] substantially speeds up the chemistry calculations on each processor. To improve the parallel efficiency of large ensembles of such calculations in parallel computations, in this work, the ISAT algorithm is extended to the multi-processor environment, with the aim of minimizing the wall clock time required for the whole ensemble. Parallel ISAT strategies are developed by combining the existing serial ISAT algorithm with different distribution strategies, namely purely local processing (PLP), uniformly random distribution (URAN), and preferential distribution (PREF). The distribution strategies enable the queued load redistribution of chemistry calculations among processors using message passing. They are implemented in the software x2f m pi, which is a Fortran 95 library for facilitating many parallel evaluations of a general vector function. The relative performance of the parallel ISAT strategies is investigated in different computational regimes via the PDF calculations of multiple partially stirred reactors burning methane/air mixtures. The results show that the performance of ISAT with a fixed distribution strategy strongly depends on certain computational regimes, based on how much memory is available and how much overlap exists between tabulated information on different processors. No one fixed strategy consistently achieves good performance in all the regimes. Therefore, an adaptive distribution strategy, which blends PLP, URAN and PREF, is devised and implemented. It yields consistently good performance in all regimes. In the adaptive parallel

  3. Computationally efficient implementation of combustion chemistry in parallel PDF calculations (United States)

    Lu, Liuyan; Lantz, Steven R.; Ren, Zhuyin; Pope, Stephen B.


    In parallel calculations of combustion processes with realistic chemistry, the serial in situ adaptive tabulation (ISAT) algorithm [S.B. Pope, Computationally efficient implementation of combustion chemistry using in situ adaptive tabulation, Combustion Theory and Modelling, 1 (1997) 41-63; L. Lu, S.B. Pope, An improved algorithm for in situ adaptive tabulation, Journal of Computational Physics 228 (2009) 361-386] substantially speeds up the chemistry calculations on each processor. To improve the parallel efficiency of large ensembles of such calculations in parallel computations, in this work, the ISAT algorithm is extended to the multi-processor environment, with the aim of minimizing the wall clock time required for the whole ensemble. Parallel ISAT strategies are developed by combining the existing serial ISAT algorithm with different distribution strategies, namely purely local processing (PLP), uniformly random distribution (URAN), and preferential distribution (PREF). The distribution strategies enable the queued load redistribution of chemistry calculations among processors using message passing. They are implemented in the software x2f_mpi, which is a Fortran 95 library for facilitating many parallel evaluations of a general vector function. The relative performance of the parallel ISAT strategies is investigated in different computational regimes via the PDF calculations of multiple partially stirred reactors burning methane/air mixtures. The results show that the performance of ISAT with a fixed distribution strategy strongly depends on certain computational regimes, based on how much memory is available and how much overlap exists between tabulated information on different processors. No one fixed strategy consistently achieves good performance in all the regimes. Therefore, an adaptive distribution strategy, which blends PLP, URAN and PREF, is devised and implemented. It yields consistently good performance in all regimes. In the adaptive parallel

  4. Methods and experimental techniques in computer engineering

    CERN Document Server

    Schiaffonati, Viola


    Computing and science reveal a synergic relationship. On the one hand, it is widely evident that computing plays an important role in the scientific endeavor. On the other hand, the role of scientific method in computing is getting increasingly important, especially in providing ways to experimentally evaluate the properties of complex computing systems. This book critically presents these issues from a unitary conceptual and methodological perspective by addressing specific case studies at the intersection between computing and science. The book originates from, and collects the experience of, a course for PhD students in Information Engineering held at the Politecnico di Milano. Following the structure of the course, the book features contributions from some researchers who are working at the intersection between computing and science.

  5. Tensegrity structures - Computational and experimental tensegrity mechanics (United States)

    Kuhl, Detlef; Lim, Yi Chung; Long, David S.


    The present paper deals with tensegrity structures. We review the definition of tensegrity structures, and describe both experimental and computational form finding methods. Also described are the numerical methods for the simulation of prestress induced stiffness, and the static and dynamic structural analyses. Furthermore, we present laboratory models and measurement methods for identifying the realized geometry and prestress state. Finally, computationally and experimentally obtained geometries and prestress states are compared, a representative realization of a real world tensegrity tower is shown and the modeling of biological cells as tensegrity structures is adressed.

  6. The performance of low-cost commercial cloud computing as an alternative in computational chemistry. (United States)

    Thackston, Russell; Fortenberry, Ryan C


    The growth of commercial cloud computing (CCC) as a viable means of computational infrastructure is largely unexplored for the purposes of quantum chemistry. In this work, the PSI4 suite of computational chemistry programs is installed on five different types of Amazon World Services CCC platforms. The performance for a set of electronically excited state single-point energies is compared between these CCC platforms and typical, "in-house" physical machines. Further considerations are made for the number of cores or virtual CPUs (vCPUs, for the CCC platforms), but no considerations are made for full parallelization of the program (even though parallelization of the BLAS library is implemented), complete high-performance computing cluster utilization, or steal time. Even with this most pessimistic view of the computations, CCC resources are shown to be more cost effective for significant numbers of typical quantum chemistry computations. Large numbers of large computations are still best utilized by more traditional means, but smaller-scale research may be more effectively undertaken through CCC services. © 2015 Wiley Periodicals, Inc.

  7. The defect chemistry of nitrogen in oxides: A review of experimental and theoretical studies

    International Nuclear Information System (INIS)

    Polfus, Jonathan M.; Norby, Truls; Haugsrud, Reidar


    Incorporation of nitrogen into oxides has in recent years received increased attention as a variable for tuning their functional properties. A vast number of reports have been devoted to improving the photocatalytic properties of TiO 2 , p-type charge carrier concentration in ZnO and the ionic transport properties of ZrO 2 by nitrogen doping. In comparison, the fundamentals of the nitrogen related defect chemistry for a wider range of oxides have been less focused upon. In the present contribution, we review experimental and computational investigations of the nitrogen related defect chemistry of insulating and semiconducting oxides. The interaction between nitrogen and protons is important and emphasized. Specifically, the stability of nitrogen defects such as N O / , NH O × and (NH 2 ) O • is evaluated under various conditions and their atomistic and electronic structure is presented. A final discussion is devoted to the role of nitrogen with respect to transport properties and photocatalytic activity of oxides. - Graphical abstract: Experimental and theoretical investigations of the nitrogen related defect chemistry of a range of wide band gap oxides is reviewed. The interaction between nitrogen dopants and protons is emphasized and described through the atomistic and electronic structure as well as defect chemical processes involving NH and NH 2 defects. Consequently, the physical properties of oxides containing such species are discussed with respect to e.g., diffusion and photocatalytic properties. Highlights: ► Experimental and theoretical investigations of the nitrogen and hydrogen related defect chemistry of wide band gap oxides is reviewed. ► The interaction between nitrogen dopants and protons is important and emphasized. ► Diffusion and photocatalytic properties of N-doped oxides are discussed.

  8. Faster quantum chemistry simulation on fault-tolerant quantum computers

    International Nuclear Information System (INIS)

    Cody Jones, N; McMahon, Peter L; Yamamoto, Yoshihisa; Whitfield, James D; Yung, Man-Hong; Aspuru-Guzik, Alán; Van Meter, Rodney


    Quantum computers can in principle simulate quantum physics exponentially faster than their classical counterparts, but some technical hurdles remain. We propose methods which substantially improve the performance of a particular form of simulation, ab initio quantum chemistry, on fault-tolerant quantum computers; these methods generalize readily to other quantum simulation problems. Quantum teleportation plays a key role in these improvements and is used extensively as a computing resource. To improve execution time, we examine techniques for constructing arbitrary gates which perform substantially faster than circuits based on the conventional Solovay–Kitaev algorithm (Dawson and Nielsen 2006 Quantum Inform. Comput. 6 81). For a given approximation error ϵ, arbitrary single-qubit gates can be produced fault-tolerantly and using a restricted set of gates in time which is O(log ϵ) or O(log log ϵ); with sufficient parallel preparation of ancillas, constant average depth is possible using a method we call programmable ancilla rotations. Moreover, we construct and analyze efficient implementations of first- and second-quantized simulation algorithms using the fault-tolerant arbitrary gates and other techniques, such as implementing various subroutines in constant time. A specific example we analyze is the ground-state energy calculation for lithium hydride. (paper)

  9. GRID computing for experimental high energy physics

    International Nuclear Information System (INIS)

    Moloney, G.R.; Martin, L.; Seviour, E.; Taylor, G.N.; Moorhead, G.F.


    Full text: The Large Hadron Collider (LHC), to be completed at the CERN laboratory in 2006, will generate 11 petabytes of data per year. The processing of this large data stream requires a large, distributed computing infrastructure. A recent innovation in high performance distributed computing, the GRID, has been identified as an important tool in data analysis for the LHC. GRID computing has actual and potential application in many fields which require computationally intensive analysis of large, shared data sets. The Australian experimental High Energy Physics community has formed partnerships with the High Performance Computing community to establish a GRID node at the University of Melbourne. Through Australian membership of the ATLAS experiment at the LHC, Australian researchers have an opportunity to be involved in the European DataGRID project. This presentation will include an introduction to the GRID, and it's application to experimental High Energy Physics. We will present the results of our studies, including participation in the first LHC data challenge

  10. Opportunities and challenges of high-performance computing in chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Guest, M.F.; Kendall, R.A.; Nichols, J.A. [eds.] [and others


    The field of high-performance computing is developing at an extremely rapid pace. Massively parallel computers offering orders of magnitude increase in performance are under development by all the major computer vendors. Many sites now have production facilities that include massively parallel hardware. Molecular modeling methodologies (both quantum and classical) are also advancing at a brisk pace. The transition of molecular modeling software to a massively parallel computing environment offers many exciting opportunities, such as the accurate treatment of larger, more complex molecular systems in routine fashion, and a viable, cost-effective route to study physical, biological, and chemical `grand challenge` problems that are impractical on traditional vector supercomputers. This will have a broad effect on all areas of basic chemical science at academic research institutions and chemical, petroleum, and pharmaceutical industries in the United States, as well as chemical waste and environmental remediation processes. But, this transition also poses significant challenges: architectural issues (SIMD, MIMD, local memory, global memory, etc.) remain poorly understood and software development tools (compilers, debuggers, performance monitors, etc.) are not well developed. In addition, researchers that understand and wish to pursue the benefits offered by massively parallel computing are often hindered by lack of expertise, hardware, and/or information at their site. A conference and workshop organized to focus on these issues was held at the National Institute of Health, Bethesda, Maryland (February 1993). This report is the culmination of the organized workshop. The main conclusion: a drastic acceleration in the present rate of progress is required for the chemistry community to be positioned to exploit fully the emerging class of Teraflop computers, even allowing for the significant work to date by the community in developing software for parallel architectures.

  11. Computer system for Monte Carlo experimentation

    International Nuclear Information System (INIS)

    Grier, D.A.


    A new computer system for Monte Carlo Experimentation is presented. The new system speeds and simplifies the process of coding and preparing a Monte Carlo Experiment; it also encourages the proper design of Monte Carlo Experiments, and the careful analysis of the experimental results. A new functional language is the core of this system. Monte Carlo Experiments, and their experimental designs, are programmed in this new language; those programs are compiled into Fortran output. The Fortran output is then compiled and executed. The experimental results are analyzed with a standard statistics package such as Si, Isp, or Minitab or with a user-supplied program. Both the experimental results and the experimental design may be directly loaded into the workspace of those packages. The new functional language frees programmers from many of the details of programming an experiment. Experimental designs such as factorial, fractional factorial, or latin square are easily described by the control structures and expressions of the language. Specific mathematical modes are generated by the routines of the language

  12. Experimental and Computational Characterization of Combustion Phenomena (United States)


    example, in low-pressure diamond-synthesis environments, the hydrogen atom plays a significant role in determining the growth rate and quality of...CFDC) known as UNICORN . Excellent agreement between experimental and computational data has been achieved, as documented in Figure 1. Three...14] R. J. Santoro, T. T. Yeh, J. J. Horvath, and H. G. Semerjian, “The Transport and Growth of Soot Particles in Laminar Diffusion Flames

  13. Human brain mapping: Experimental and computational approaches

    Energy Technology Data Exchange (ETDEWEB)

    Wood, C.C.; George, J.S.; Schmidt, D.M.; Aine, C.J. [Los Alamos National Lab., NM (US); Sanders, J. [Albuquerque VA Medical Center, NM (US); Belliveau, J. [Massachusetts General Hospital, Boston, MA (US)


    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). This program developed project combined Los Alamos' and collaborators' strengths in noninvasive brain imaging and high performance computing to develop potential contributions to the multi-agency Human Brain Project led by the National Institute of Mental Health. The experimental component of the project emphasized the optimization of spatial and temporal resolution of functional brain imaging by combining: (a) structural MRI measurements of brain anatomy; (b) functional MRI measurements of blood flow and oxygenation; and (c) MEG measurements of time-resolved neuronal population currents. The computational component of the project emphasized development of a high-resolution 3-D volumetric model of the brain based on anatomical MRI, in which structural and functional information from multiple imaging modalities can be integrated into a single computational framework for modeling, visualization, and database representation.

  14. Theoretical Hammett Plot for the Gas-Phase Ionization of Benzoic Acid versus Phenol: A Computational Chemistry Lab Exercise (United States)

    Ziegler, Blake E.


    Computational chemistry undergraduate laboratory courses are now part of the chemistry curriculum at many universities. However, there remains a lack of computational chemistry exercises available to instructors. This exercise is presented for students to develop skills using computational chemistry software while supplementing their knowledge of…

  15. Computational Materials Science and Chemistry: Accelerating Discovery and Innovation through Simulation-Based Engineering and Science

    Energy Technology Data Exchange (ETDEWEB)

    Crabtree, George [Argonne National Lab. (ANL), Argonne, IL (United States); Glotzer, Sharon [University of Michigan; McCurdy, Bill [University of California Davis; Roberto, Jim [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)


    abating, has enabled the development of computer simulations and models of unprecedented fidelity. We are at the threshold of a new era where the integrated synthesis, characterization, and modeling of complex materials and chemical processes will transform our ability to understand and design new materials and chemistries with predictive power. In turn, this predictive capability will transform technological innovation by accelerating the development and deployment of new materials and processes in products and manufacturing. Harnessing the potential of computational science and engineering for the discovery and development of materials and chemical processes is essential to maintaining leadership in these foundational fields that underpin energy technologies and industrial competitiveness. Capitalizing on the opportunities presented by simulation-based engineering and science in materials and chemistry will require an integration of experimental capabilities with theoretical and computational modeling; the development of a robust and sustainable infrastructure to support the development and deployment of advanced computational models; and the assembly of a community of scientists and engineers to implement this integration and infrastructure. This community must extend to industry, where incorporating predictive materials science and chemistry into design tools can accelerate the product development cycle and drive economic competitiveness. The confluence of new theories, new materials synthesis capabilities, and new computer platforms has created an unprecedented opportunity to implement a "materials-by-design" paradigm with wide-ranging benefits in technological innovation and scientific discovery. The Workshop on Computational Materials Science and Chemistry for Innovation was convened in Bethesda, Maryland, on July 26-27, 2010. Sponsored by the Department of Energy (DOE) Offices of Advanced Scientific Computing Research and Basic Energy Sciences, the workshop

  16. Pharmacokinetic study with computational tools in the medicinal chemistry course

    Directory of Open Access Journals (Sweden)

    Monique Araújo de Brito


    Full Text Available To improve the teaching-learning process in the Medicinal Chemistry course, new strategies have been incorporated into practical classes of this fundamental discipline of the pharmaceutical curriculum. Many changes and improvements have been made in the area of medicinal chemistry so far, and students should be prepared for these new approaches with the use of technological resources in this field. Practical activities using computational techniques have been directed to the evaluation of chemical and physicochemical properties that affect the pharmacokinetics of drugs. Their objectives were to allow students to know these tools, to learn how to access them, to search for the structures of drugs and to analyze results. To the best of our knowledge, this is the first study in Brazil to demonstrate the use of computational practices in teaching pharmacokinetics. Practical classes using Osiris and Molinspiration were attractive to students, who developed the activities easily and acquired better theoretical knowledge.Para melhorar o processo ensino-aprendizagem no curso de Química Medicinal novas estratégias estão sendo incorporadas às aulas práticas desta disciplina fundamental do currículo farmacêutico. Muitas mudanças e melhorias vêm marcando a área de química medicinal e por isso é importante que os alunos sejam colocados nestas novas abordagens na área, com a utilização de recursos tecnológicos. As atividades práticas foram direcionadas para a avaliação dos dados químicos e físico-químicos de fármacos que influenciam as propriedades farmacocinéticas com o auxílio de técnicas computacionais. Os objetivos foram permitir aos alunos conhecer essas ferramentas, saber como acessá-las, procurar as estruturas de fármacos e analisar os resultados. Este é o primeiro estudo publicado no Brasil que apresenta aula prática computacional sobre o tema farmacocinética. As aulas práticas utilizando os servidores Osiris e

  17. Computational organic chemistry: bridging theory and experiment in establishing the mechanisms of chemical reactions. (United States)

    Cheng, Gui-Juan; Zhang, Xinhao; Chung, Lung Wa; Xu, Liping; Wu, Yun-Dong


    Understanding the mechanisms of chemical reactions, especially catalysis, has been an important and active area of computational organic chemistry, and close collaborations between experimentalists and theorists represent a growing trend. This Perspective provides examples of such productive collaborations. The understanding of various reaction mechanisms and the insight gained from these studies are emphasized. The applications of various experimental techniques in elucidation of reaction details as well as the development of various computational techniques to meet the demand of emerging synthetic methods, e.g., C-H activation, organocatalysis, and single electron transfer, are presented along with some conventional developments of mechanistic aspects. Examples of applications are selected to demonstrate the advantages and limitations of these techniques. Some challenges in the mechanistic studies and predictions of reactions are also analyzed.

  18. Promoting Intrinsic and Extrinsic Motivation among Chemistry Students Using Computer-Assisted Instruction (United States)

    Gambari, Isiaka A.; Gbodi, Bimpe E.; Olakanmi, Eyitao U.; Abalaka, Eneojo N.


    The role of computer-assisted instruction in promoting intrinsic and extrinsic motivation among Nigerian secondary school chemistry students was investigated in this study. The study employed two modes of computer-assisted instruction (computer simulation instruction and computer tutorial instructional packages) and two levels of gender (male and…

  19. Quantum Mechanical Calculations in Collaborations with Experimental Chemistry: The Theoretical Organic Chemistry Perspective (United States)

    Nguyen, Quynh Nhu Ngoc

    synthesized peptides, dynamic simulations were used to sample a large conformational space, generating diverse conformer libraries. Quantum mechanical calculations were then used to determine the relative energies between the conformers, and to compute theoretical NMR data, which were then compared to the experimental values, to determine the best match conformers. Hydropersulfides are commonly found among many mammalian systems, and has recently gained more interest due to their greater nucleophilicity and reducing capacity compared to the related thiols. A series of quantum mechanical calculations were performed for small sulfur-containing molecules in order to help understand these biological compounds. First part of this chapter explores the basics of chemical properties and reactivity of hydropersulfides. The later sections further discuss the redox component of RSSH in generation of the radical RSS, which was found to be unreactive in the presence of O 2 and NO. Modeling the formation of these natural products in the absence of the enzymes has many of its own limitation, but understanding the inherent reactivity of the substrates could be beneficial to future enzymatic studies. Density functional theory calculations of mechanism of caryolene featured one mechanism with a base-catalyzed deprotonation/reprotonation sequence, while the other higher-energy mechanism involved intramolecular proton transfer and a secondary carbocation minimum. This result suggested the role of the enzyme in helping to avoid the secondary carbocation. Both pathways bypassed the concerted suprafacial/suprafacial [2+2] cycloadditions, which were not in violation of orbital symmetry due to their asynchronicity. Quantum mechanical calculations were used to determine theoretical 1H and 13C chemical shifts, which were then compared to the experimental NMR data to assign relative configurations for isohirsut-1-ene, isohirsut-4-ene, and tsukubadiene, which were previously isolated from engineered

  20. Computer network for experimental research using ISDN

    International Nuclear Information System (INIS)

    Ida, Katsumi; Nakanishi, Hideya


    This report describes the development of a computer network that uses the Integrated Service Digital Network (ISDN) for real-time analysis of experimental plasma physics and nuclear fusion research. Communication speed, 64/128kbps (INS64) or 1.5Mbps (INS1500) per connection, is independent of how busy the network is. When INS-1500 is used, the communication speed, which is proportional to the public telephone connection fee, can be dynamically varied from 64kbps to 1472kbps (depending on how much data are being transferred using the Bandwidth-on-Demand (BOD) function in the ISDN Router. On-demand dial-up and time-out disconnection reduce the public telephone connection fee by 10%-97%. (author)


    In the last decade three new techniques scanning probe microscopy (SPM), virtual reality (YR) and computational chemistry ave emerged with the combined capability of a priori predicting the chemically reactivity of environmental surfaces. Computational chemistry provides the cap...

  2. An experimental unification of reservoir computing methods. (United States)

    Verstraeten, D; Schrauwen, B; D'Haene, M; Stroobandt, D


    Three different uses of a recurrent neural network (RNN) as a reservoir that is not trained but instead read out by a simple external classification layer have been described in the literature: Liquid State Machines (LSMs), Echo State Networks (ESNs) and the Backpropagation Decorrelation (BPDC) learning rule. Individual descriptions of these techniques exist, but a overview is still lacking. Here, we present a series of experimental results that compares all three implementations, and draw conclusions about the relation between a broad range of reservoir parameters and network dynamics, memory, node complexity and performance on a variety of benchmark tests with different characteristics. Next, we introduce a new measure for the reservoir dynamics based on Lyapunov exponents. Unlike previous measures in the literature, this measure is dependent on the dynamics of the reservoir in response to the inputs, and in the cases we tried, it indicates an optimal value for the global scaling of the weight matrix, irrespective of the standard measures. We also describe the Reservoir Computing Toolbox that was used for these experiments, which implements all the types of Reservoir Computing and allows the easy simulation of a wide range of reservoir topologies for a number of benchmarks.

  3. Using Computational Chemistry Activities to Promote Learning and Retention in a Secondary School General Chemistry Setting (United States)

    Ochterski, Joseph W.


    This article describes the results of using state-of-the-art, research-quality software as a learning tool in a general chemistry secondary school classroom setting. I present three activities designed to introduce fundamental chemical concepts regarding molecular shape and atomic orbitals to students with little background in chemistry, such as…

  4. Experimental studies of lithium-based surface chemistry for fusion plasma-facing materials applications

    International Nuclear Information System (INIS)

    Allain, J.P.; Rokusek, D.L.; Harilal, S.S.; Nieto-Perez, M.; Skinner, C.H.; Kugel, H.W.; Heim, B.; Kaita, R.; Majeski, R.


    Lithium has enhanced the operational performance of fusion devices such as: TFTR, CDX-U, FTU, T-11 M, and NSTX. Lithium in the solid and liquid state has been studied extensively in laboratory experiments including its erosion and hydrogen-retaining properties. Reductions in physical sputtering up to 40-60% have been measured for deuterated solid and liquid lithium surfaces. Computational modeling indicates that up to a 1:1 deuterium volumetric retention in lithium is possible. This paper presents the results of systematic in situ laboratory experimental studies on the surface chemistry evolution of ATJ graphite under lithium deposition. Results are compared to post-mortem analysis of similar lithium surface coatings on graphite exposed to deuterium discharge plasmas in NSTX. Lithium coatings on plasma-facing components in NSTX have shown substantial reduction of hydrogenic recycling. Questions remain on the role lithium surface chemistry on a graphite substrate has on particle sputtering (physical and chemical) as well as hydrogen isotope recycling. This is particularly due to the lack of in situ measurements of plasma-surface interactions in tokamaks such as NSTX. Results suggest that the lithium bonding state on ATJ graphite is lithium peroxide and with sufficient exposure to ambient air conditions, lithium carbonate is generated. Correlation between both results is used to assess the role of lithium chemistry on the state of lithium bonding and implications on hydrogen pumping and lithium sputtering. In addition, reduction of factors between 10 and 30 reduction in physical sputtering from lithiated graphite compared to pure lithium or carbon is also measured.

  5. Computational carbohydrate chemistry: what theoretical methods can tell us (United States)

    Woods, Robert J.


    Computational methods have had a long history of application to carbohydrate systems and their development in this regard is discussed. The conformational analysis of carbohydrates differs in several ways from that of other biomolecules. Many glycans appear to exhibit numerous conformations coexisting in solution at room temperature and a conformational analysis of a carbohydrate must address both spatial and temporal properties. When solution nuclear magnetic resonance data are used for comparison, the simulation must give rise to ensemble-averaged properties. In contrast, when comparing to experimental data obtained from crystal structures a simulation of a crystal lattice, rather than of an isolated molecule, is appropriate. Molecular dynamics simulations are well suited for such condensed phase modeling. Interactions between carbohydrates and other biological macromolecules are also amenable to computational approaches. Having obtained a three-dimensional structure of the receptor protein, it is possible to model with accuracy the conformation of the carbohydrate in the complex. An example of the application of free energy perturbation simulations to the prediction of carbohydrate-protein binding energies is presented. PMID:9579797

  6. The Use of Computer-Based Instruction in Undergraduate Organic Chemistry. (United States)

    Culp, George H.

    Thirty-two computer-based lesson modules in organic chemistry were developed at the University of Texas (Austin) over an 18-month period and evaluated in varying classroom situations for three semesters starting in the Fall of 1972. The modules were designed as supplements to the traditional organic chemistry course of the University. As such,…

  7. Developing computational model-based diagnostics to analyse clinical chemistry data

    NARCIS (Netherlands)

    Schalkwijk, D.B. van; Bochove, K. van; Ommen, B. van; Freidig, A.P.; Someren, E.P. van; Greef, J. van der; Graaf, A.A. de


    This article provides methodological and technical considerations to researchers starting to develop computational model-based diagnostics using clinical chemistry data.These models are of increasing importance, since novel metabolomics and proteomics measuring technologies are able to produce large

  8. E.C.C.C.1 Computational Chemistry: F.E.C.S. Conference. Proceedings

    International Nuclear Information System (INIS)

    These proceedings represent the papers presented at the First European Conference on Computational Chemistry held in Nancy, France. The papers presented fall into three groups:1. Methods and applications of quantum molecular modeling, 2. Classical molecular modeling, 3. Methods and applications in the treatment of chemical information. The papers represent a fair and balanced survey of the present trends of European research in computational chemistry. There were 237 papers presented and 10 have been abstracted for the Energy Science and Technology database

  9. Chemometrics in analytical chemistry-part I: history, experimental design and data analysis tools. (United States)

    Brereton, Richard G; Jansen, Jeroen; Lopes, João; Marini, Federico; Pomerantsev, Alexey; Rodionova, Oxana; Roger, Jean Michel; Walczak, Beata; Tauler, Romà


    Chemometrics has achieved major recognition and progress in the analytical chemistry field. In the first part of this tutorial, major achievements and contributions of chemometrics to some of the more important stages of the analytical process, like experimental design, sampling, and data analysis (including data pretreatment and fusion), are summarised. The tutorial is intended to give a general updated overview of the chemometrics field to further contribute to its dissemination and promotion in analytical chemistry.

  10. Improve Outcomes Study subjects Chemistry Teaching and Learning Strategies through independent study with the help of computer-based media (United States)

    Sugiharti, Gulmah


    This study aims to see the improvement of student learning outcomes by independent learning using computer-based learning media in the course of STBM (Teaching and Learning Strategy) Chemistry. Population in this research all student of class of 2014 which take subject STBM Chemistry as many as 4 class. While the sample is taken by purposive as many as 2 classes, each 32 students, as control class and expriment class. The instrument used is the test of learning outcomes in the form of multiple choice with the number of questions as many as 20 questions that have been declared valid, and reliable. Data analysis techniques used one-sided t test and improved learning outcomes using a normalized gain test. Based on the learning result data, the average of normalized gain values for the experimental class is 0,530 and for the control class is 0,224. The result of the experimental student learning result is 53% and the control class is 22,4%. Hypothesis testing results obtained t count> ttable is 9.02> 1.6723 at the level of significance α = 0.05 and db = 58. This means that the acceptance of Ha is the use of computer-based learning media (CAI Computer) can improve student learning outcomes in the course Learning Teaching Strategy (STBM) Chemistry academic year 2017/2018.




  12. Computer information resources of inorganic chemistry and materials science

    Energy Technology Data Exchange (ETDEWEB)

    Kiselyova, N N; Dudarev, V A; Zemskov, V S [A.A.Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, Moscow (Russian Federation)


    Information systems used in inorganic chemistry and materials science are considered. The following basic trends in the development of modern information systems in these areas are highlighted: access to information via the Internet, merging of documental and factual databases, involvement of experts in the evaluation of the data reliability, supplementing databases with information analysis tools on the properties of inorganic substances and materials.

  13. The Application of Computational Chemistry to Problems in Mass Spectrometry (United States)

    Quantum chemistry is capable of calculating a wide range of electronic and thermodynamic properties of interest to a chemist or physicist. Calculations can be used both to predict the results of future experiments and to aid in the interpretation of existing results. This paper w...

  14. Experimental and computational studies of nanofluids (United States)

    Vajjha, Ravikanth S.

    The goals of this dissertation were (i) to experimentally investigate the fluid dynamic and heat transfer performance of nanofluids in a circular tube, (ii) to study the influence of temperature and particle volumetric concentration of nanofluids on thermophysical properties, heat transfer and pumping power, (iii) to measure the rheological properties of various nanofluids and (iv) to investigate using a computational fluid dynamic (CFD) technique the performance of nanofluids in the flat tube of a radiator. Nanofluids are a new class of fluids prepared by dispersing nanoparticles with average sizes of less than 100 nm in traditional heat transfer fluids such as water, oil, ethylene glycol and propylene glycol. In cold regions of the world, the choice of base fluid for heat transfer applications is an ethylene glycol or propylene glycol mixed with water in different proportions. In the present research, a 60% ethylene glycol (EG) or propylene glycol (PG) and 40% water (W) by mass fluid mixture (60:40 EG/W or 60:40 PG/W) was used as a base fluid, which provides freeze protection to a very low level of temperature. Experiments were conducted to measure the convective heat transfer coefficient and pressure loss of nanofluids flowing in a circular tube in the fully developed turbulent regime. The experimental measurements were carried out for aluminum oxide (Al2O3), copper oxide (CuO) and silicon dioxide (SiO2) nanoparticles dispersed in 60:40 EG/W base fluid. Experiments revealed that the heat transfer coefficient of nanofluids showed an increase with the particle volumetric concentration. Pressure loss was also observed to increase with the nanoparticle volumetric concentration. New correlations for the Nusselt number and the friction factor were developed. The effects of temperature and particle volumetric concentration on different thermophysical properties (e.g. viscosity, thermal conductivity, specific heat and density) and subsequently on the Prandtl number

  15. Model for diffusion and porewater chemistry in compacted bentonite. Experimental arrangements and preliminary results of the porewater chemistry studies

    International Nuclear Information System (INIS)

    Muurinen, A.; Lehikoinen, J.


    This report describes the progress of the experimental research on the porewater chemistry in bentonite. The research is part of the project Microstructural and chemical parameters of bentonite as determinants of waste isolation efficiency within the Nuclear Fission Safety Program organized by The Commission of the European Communities. The study was started by a literature overview on the properties of bentonite, porewater-sampling methods and obtained results. On the basis of the literature study, porewater extraction by squeezing seemed the most promising method for further development. The apparatus developed in this study consists of a pressing apparatus, which is used to create the necessary long-term compression, and of the compaction cell where porewater is separated from bentonite and collected in a syringe. The constant log-term force is maintained by a strong spring. An experimental study of solution-bentonite interactions was initiated. The parameters varied are the bentonite density, bentonite-water ratio, composition of the solutions, and the composition of bentonite. The report presents the experimental arrangements, the preliminary results for studying the evolution of water chemistry and the results of pre-modelling. (orig.) (27 refs.)

  16. Chemistry aspects of the Heva and Vercors experimental programmes

    International Nuclear Information System (INIS)

    Leveque, J.P.; Andre, B.; Ducros, G.; Le Marois, G.; Lhiaubet, G.


    The HEVA and VERCORS experimental programmes have been carried out of characterise some of the fission products (release rate coefficient, aerosol sizing, chemical species) emitted by nuclear fuel irradiated to approximately 30 GWd/tU and heated up to 2300 K (HEVA) and higher temperatures (VERCORS). Various test parameters were based on those expected in the course of a severe reactor accident. Eight test were performed during the now completed HEVA programme and four tests have been performed in the VERCORS studies. The chemical species recovered in the experimental loop are described with particular emphasis placed on the volatile fission products (caesium, iodine, tellurium), oxides (mainly molybdenum), and the components of the neutron absorbing control rods (silver, indium and cadmium). (authors)

  17. Understanding organometallic reaction mechanisms and catalysis experimental and computational tools computational and experimental tools

    CERN Document Server

    Ananikov, Valentin P


    Exploring and highlighting the new horizons in the studies of reaction mechanisms that open joint application of experimental studies and theoretical calculations is the goal of this book. The latest insights and developments in the mechanistic studies of organometallic reactions and catalytic processes are presented and reviewed. The book adopts a unique approach, exemplifying how to use experiments, spectroscopy measurements, and computational methods to reveal reaction pathways and molecular structures of catalysts, rather than concentrating solely on one discipline. The result is a deeper

  18. FOREWORD: Third Nordic Symposium on Computer Simulation in Physics, Chemistry, Biology and Mathematics (United States)

    Kaski, K.; Salomaa, M.


    These are Proceedings of the Third Nordic Symposium on Computer Simulation in Physics, Chemistry, Biology, and Mathematics, held August 25-26, 1989, at Lahti (Finland). The Symposium belongs to an annual series of Meetings, the first one of which was arranged in 1987 at Lund (Sweden) and the second one in 1988 at Kolle-Kolle near Copenhagen (Denmark). Although these Symposia have thus far been essentially Nordic events, their international character has increased significantly; the trend is vividly reflected through contributions in the present Topical Issue. The interdisciplinary nature of Computational Science is central to the activity; this fundamental aspect is also responsible, in an essential way, for its rapidly increasing impact. Crucially important to a wide spectrum of superficially disparate fields is the common need for extensive - and often quite demanding - computational modelling. For such theoretical models, no closed-form (analytical) solutions are available or they would be extremely difficult to find; hence one must rather resort to the Art of performing computational investigations. Among the unifying features in the computational research are the methods of simulation employed; methods which frequently are quite closely related with each other even for faculties of science that are quite unrelated. Computer simulation in Natural Sciences is presently apprehended as a discipline on its own right, occupying a broad region somewhere between the experimental and theoretical methods, but also partially overlapping with and complementing them. - Whichever its proper definition may be, the computational approach serves as a novel and an extremely versatile tool with which one can equally well perform "pure" experimental modelling and conduct "computational theory". Computational studies that have earlier been made possible only through supercomputers have opened unexpected, as well as exciting, novel frontiers equally in mathematics (e.g., fractals

  19. Using Free Computational Resources to Illustrate the Drug Design Process in an Undergraduate Medicinal Chemistry Course (United States)

    Rodrigues, Ricardo P.; Andrade, Saulo F.; Mantoani, Susimaire P.; Eifler-Lima, Vera L.; Silva, Vinicius B.; Kawano, Daniel F.


    Advances in, and dissemination of, computer technologies in the field of drug research now enable the use of molecular modeling tools to teach important concepts of drug design to chemistry and pharmacy students. A series of computer laboratories is described to introduce undergraduate students to commonly adopted "in silico" drug design…

  20. Parallel Computation Chemistry Using Constraints: Final Report, LDRD 97-0301, Case 3504140000

    Energy Technology Data Exchange (ETDEWEB)

    Todd D. Plantenga


    Computer modeling to estimate material properties, design chem/bio sensors, and evaluate protein-protein interactions all require solving force field equations for molecular structures that contain tens of thousands of covalently connected atoms. Potential energy minimization is a key step in the calculation, but stiff covalent bonding forces make optimization difficult and expensive. This two-year LDRD developed two classes of advanced minimization algorithms that were specialized for chemistry applications and distributed computing machines. The project led to two successful algorithms that were implemented in three Sandia computational chemistry codes to support various users.

  1. Transforming the Organic Chemistry Lab Experience: Design, Implementation, and Evaluation of Reformed Experimental Activities--REActivities (United States)

    Collison, Christina G.; Kim, Thomas; Cody, Jeremy; Anderson, Jason; Edelbach, Brian; Marmor, William; Kipsang, Rodgers; Ayotte, Charles; Saviola, Daniel; Niziol, Justin


    Reformed experimental activities (REActivities) are an innovative approach to the delivery of the traditional material in an undergraduate organic chemistry laboratory. A description of the design and implementation of REActivities at both a four- and two-year institution is discussed. The results obtained using a reformed teaching observational…

  2. Effects of watershed experiments on water chemistry at the Marcell Experimental Forest. Chapter 14. (United States)

    Stephen D. Sebestyen; Elon S. Verry


    The Marcell Experimental Forest (MEF) was established during the 1960s to study the hydrology and ecology of lowland watersheds where upland mineral soils drain to central peatlands (Boelter and Verry 1977). The effects of seven large-scale manipulations on water chemistry have been studied on the MEF watersheds and the data now span up to four decades. In this chapter...

  3. CHEMEX; Understanding and Solving Problems in Chemistry. A Computer-Assisted Instruction Program for General Chemistry. (United States)

    Lower, Stephen K.

    A brief overview of CHEMEX--a problem-solving, tutorial style computer-assisted instructional course--is provided and sample problems are offered. In CHEMEX, students receive problems in advance and attempt to solve them before moving through the computer program, which assists them in overcoming difficulties and serves as a review mechanism.…

  4. Cyclopentane combustion chemistry. Part I: Mechanism development and computational kinetics

    KAUST Repository

    Rachidi, Mariam El


    Cycloalkanes are significant constituents of conventional fossil fuels, in which they are one of the main contributors to soot formation, but also significantly influence the ignition characteristics below ∼900K. This paper discusses the development of a detailed high- and low-temperature oxidation mechanism for cyclopentane, which is an important archetypical cycloalkane. The differences between cyclic and non-cyclic alkane chemistry, and thus the inapplicability of acyclic alkane analogies, required the detailed theoretical investigation of the kinetics of important cyclopentane oxidation reactions as part of the mechanism development. The cyclopentyl+O reaction was investigated at the UCCSD(T)-F12a/cc-pVTZ-F12//M06-2X/6-311++G(d,p) level of theory in a time-dependent master equation framework. Comparisons with analogous cyclohexane or non-cyclic alkane reactions are presented. Our study suggests that beyond accurate quantum chemistry the inclusion of pressure dependence and especially that of formally direct kinetics is crucial even at pressures relevant for practical application.

  5. Experimental comparison of two quantum computing architectures. (United States)

    Linke, Norbert M; Maslov, Dmitri; Roetteler, Martin; Debnath, Shantanu; Figgatt, Caroline; Landsman, Kevin A; Wright, Kenneth; Monroe, Christopher


    We run a selection of algorithms on two state-of-the-art 5-qubit quantum computers that are based on different technology platforms. One is a publicly accessible superconducting transmon device (www. with limited connectivity, and the other is a fully connected trapped-ion system. Even though the two systems have different native quantum interactions, both can be programed in a way that is blind to the underlying hardware, thus allowing a comparison of identical quantum algorithms between different physical systems. We show that quantum algorithms and circuits that use more connectivity clearly benefit from a better-connected system of qubits. Although the quantum systems here are not yet large enough to eclipse classical computers, this experiment exposes critical factors of scaling quantum computers, such as qubit connectivity and gate expressivity. In addition, the results suggest that codesigning particular quantum applications with the hardware itself will be paramount in successfully using quantum computers in the future.

  6. Green Cloud Computing: An Experimental Validation

    International Nuclear Information System (INIS)

    Monteiro, Rogerio Castellar; Dantas, M A R; Rodriguez y Rodriguez, Martius Vicente


    Cloud configurations can be computational environment with interesting cost efficiency for several organizations sizes. However, the indiscriminate action of buying servers and network devices may not represent a correspondent performance number. In the academic and commercial literature, some researches highlight that these environments are idle for long periods. Therefore, energy management is an essential approach in any organization, because energy bills can causes remarkable negative impacts to these organizations in term of costs. In this paper, we present a research work that is characterized by an analysis of energy consumption in a private cloud computing environment, considering both computational resources and network devices. This study was motivated by a real case of a large organization. Therefore, the first part of the study we considered empirical experiments. In a second moment we used the GreenCloud simulator which was utilized to foresee some different configurations. The research reached a successful and differentiated goal in presenting key issues from computational resources and network, related to the energy consumption for real private cloud

  7. Combustion chemistry of alcohols: Experimental and modeled structure of a premixed 2-methylbutanol flame

    KAUST Repository

    Lucassen, Arnas


    This paper presents a detailed investigation of 2-methylbutanol combustion chemistry in low-pressure premixed flames. This chemistry is of particular interest to study because this compound is potentially a lignocellulosic-based, next-generation biofuel. The detailed chemical structure of a stoichiometric low-pressure (25 Torr) flame was determined using flame-sampling molecular-beam mass spectrometry. A total of 55 species were identified and subsequently quantitative mole fraction profiles as function of distance from the burner surface were determined. In an independent effort, a detailed flame chemistry model for 2-methylbutanol was assembled based on recent knowledge gained from combustion chemistry studies for butanol isomers ([Sarathy et al. Combust. Flame 159 (6) (2012) 2028-2055]) and iso-pentanol (3-methylbutanol) [Sarathy et al. Combust. Flame 160 (12) (2013) 2712-2728]. Experimentally determined and modeled mole fraction profiles were compared to demonstrate the model\\'s capabilities. Examples of individual mole fraction profiles are discussed together with the most significant fuel consumption pathways to highlight the combustion chemistry of 2-methylbutanol. Discrepancies between experimental and modeling results are used to suggest areas where improvement of the kinetic model would be needed. © 2014.

  8. Chemistry

    International Nuclear Information System (INIS)

    Gomez G, H.


    A brief description about the development and activities executed in chemistry, in the Instituto de Asuntos Nucleares, during the last years is presented. The plans and feasibility of nuclear techniques in Colombia are also described

  9. Experimental and computational study of thaumasite structure

    Energy Technology Data Exchange (ETDEWEB)

    Scholtzová, Eva, E-mail: [Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 36 Bratislava (Slovakia); Kucková, Lenka; Kožíšek, Jozef [Department of Physical Chemistry, Institute of Physical Chemistry and Chemical Physics, Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, Radlinského 9, 812 37 Bratislava (Slovakia); Pálková, Helena [Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 36 Bratislava (Slovakia); Tunega, Daniel [Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 36 Bratislava (Slovakia); Institute for Soil Science, University of Natural Resources and Life Sciences, Peter-Jordanstrasse 82, A-1190 Wien (Austria)


    The structure of thaumasite has been studied experimentally by means of a single crystal X-ray diffraction and FTIR methods, and theoretically using density functional theory (DFT) method. Very good agreement was achieved between calculated and experimental structural parameters. In addition, calculations offered the refinement of the positions of the hydrogen atoms. The detailed analysis of the hydrogen bonds existing in the thaumasite structure has been performed. Several types of hydrogen bonds have been classified. The water molecules coordinating Ca{sup 2+} cation act as proton donors in moderate O-H···O hydrogen bonds formed with CO₃⁻²and SO₄⁻² anions. The multiple O-H···O hydrogen bonds exist among water molecules themselves. Finally, relatively weak hydrogen bonds form water molecules with the OH groups from the coordination sphere of the Si(OH)₆⁻² anion. Further, calculated vibrational spectrum allowed complete assignment of all vibrational modes which are not available from the experimental spectrum that has a complex structure with overlapped bands, especially below 1500 cm⁻¹. Highlights: • The thaumasite structure was studied experimentally and using DFT method. • We used DFT method for the refinement of the positions of hydrogen atoms. • A detailed analysis of the hydrogen bonds was done. • A complete assignment of all bands to particular types of vibrations was done.

  10. Computer-based, Jeopardy™-like game in general chemistry for engineering majors (United States)

    Ling, S. S.; Saffre, F.; Kadadha, M.; Gater, D. L.; Isakovic, A. F.


    We report on the design of Jeopardy™-like computer game for enhancement of learning of general chemistry for engineering majors. While we examine several parameters of student achievement and attitude, our primary concern is addressing the motivation of students, which tends to be low in a traditionally run chemistry lectures. The effect of the game-playing is tested by comparing paper-based game quiz, which constitutes a control group, and computer-based game quiz, constituting a treatment group. Computer-based game quizzes are Java™-based applications that students run once a week in the second part of the last lecture of the week. Overall effectiveness of the semester-long program is measured through pretest-postest conceptual testing of general chemistry. The objective of this research is to determine to what extent this ``gamification'' of the course delivery and course evaluation processes may be beneficial to the undergraduates' learning of science in general, and chemistry in particular. We present data addressing gender-specific difference in performance, as well as background (pre-college) level of general science and chemistry preparation. We outline the plan how to extend such approach to general physics courses and to modern science driven electives, and we offer live, in-lectures examples of our computer gaming experience. We acknowledge support from Khalifa University, Abu Dhabi

  11. Combinatorial computational chemistry approach for materials design: applications in deNOx catalysis, Fischer-Tropsch synthesis, lanthanoid complex, and lithium ion secondary battery. (United States)

    Koyama, Michihisa; Tsuboi, Hideyuki; Endou, Akira; Takaba, Hiromitsu; Kubo, Momoji; Del Carpio, Carlos A; Miyamoto, Akira


    Computational chemistry can provide fundamental knowledge regarding various aspects of materials. While its impact in scientific research is greatly increasing, its contributions to industrially important issues are far from satisfactory. In order to realize industrial innovation by computational chemistry, a new concept "combinatorial computational chemistry" has been proposed by introducing the concept of combinatorial chemistry to computational chemistry. This combinatorial computational chemistry approach enables theoretical high-throughput screening for materials design. In this manuscript, we review the successful applications of combinatorial computational chemistry to deNO(x) catalysts, Fischer-Tropsch catalysts, lanthanoid complex catalysts, and cathodes of the lithium ion secondary battery.

  12. Using computer simulations to improve concept formation in chemistry

    African Journals Online (AJOL)

    The goal of this research project was to investigate whether computer simulations used as a visually-supporting teaching strategy, can improve concept formation with regard to molecules and chemical bonding, as found in water. Both the qualitative and quantitative evaluation of responses supported the positive outcome ...

  13. Phase behavior of multicomponent membranes: Experimental and computational techniques

    DEFF Research Database (Denmark)

    Bagatolli, Luis; Kumar, P.B. Sunil


    membranes. Current increase in interest in the domain formation in multicomponent membranes also stems from the experiments demonstrating liquid ordered-liquid disordered coexistence in mixtures of lipids and cholesterol and the success of several computational models in predicting their behavior....... This review includes basic foundations on membrane model systems and experimental approaches applied in the membrane research area, stressing on recent advances in the experimental and computational techniques....

  14. A Fresh Math Perspective Opens New Possibilities for Computational Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Vu, Linda; Govind, Niranjan; Yang, Chao


    By reformulating the TDDFT problem as a matrix function approximation, making use of a special transformation and taking advantage of the underlying symmetry with respect to a non-Euclidean metric, Yang and his colleagues were able to apply the Lanczos algorithm and a Kernal Polynomial Method (KPM) to approximate the absorption spectrum of several molecules. Both of these algorithms require relatively low-memory compared to non-symmetrical alternatives, which is the key to the computational savings.

  15. Drug repurposing: translational pharmacology, chemistry, computers and the clinic. (United States)

    Issa, Naiem T; Byers, Stephen W; Dakshanamurthy, Sivanesan


    The process of discovering a pharmacological compound that elicits a desired clinical effect with minimal side effects is a challenge. Prior to the advent of high-performance computing and large-scale screening technologies, drug discovery was largely a serendipitous endeavor, as in the case of thalidomide for erythema nodosum leprosum or cancer drugs in general derived from flora located in far-reaching geographic locations. More recently, de novo drug discovery has become a more rationalized process where drug-target-effect hypotheses are formulated on the basis of already known compounds/protein targets and their structures. Although this approach is hypothesis-driven, the actual success has been very low, contributing to the soaring costs of research and development as well as the diminished pharmaceutical pipeline in the United States. In this review, we discuss the evolution in computational pharmacology as the next generation of successful drug discovery and implementation in the clinic where high-performance computing (HPC) is used to generate and validate drug-target-effect hypotheses completely in silico. The use of HPC would decrease development time and errors while increasing productivity prior to in vitro, animal and human testing. We highlight approaches in chemoinformatics, bioinformatics as well as network biopharmacology to illustrate potential avenues from which to design clinically efficacious drugs. We further discuss the implications of combining these approaches into an integrative methodology for high-accuracy computational predictions within the context of drug repositioning for the efficient streamlining of currently approved drugs back into clinical trials for possible new indications.

  16. Chemistry

    International Nuclear Information System (INIS)

    Ferris, L.M.


    The chemical research and development efforts related to the design and ultimate operation of molten-salt breeder reactor systems are concentrated on fuel- and coolant-salt chemistry, including the development of analytical methods for use in these systems. The chemistry of tellurium in fuel salt is being studied to help elucidate the role of this element in the intergranular cracking of Hastelloy N. Studies were continued of the effect of oxygen-containing species on the equilibrium between dissolved UF 3 and dissolved UF 4 , and, in some cases, between the dissolved uranium fluorides and graphite, and the UC 2 . Several aspects of coolant-salt chemistry are under investigation. Hydroxy and oxy compounds that could be formed in molten NaBF 4 are being synthesized and characterized. Studies of the chemistry of chromium (III) compounds in fluoroborate melts were continued as part of a systematic investigation of the corrosion of structural alloys by coolant salt. An in-line voltammetric method for determining U 4+ /U 3+ ratios in fuel salt was tested in a forced-convection loop over a six-month period. (LK)

  17. The Dirac equation in quantum chemistry: Strategies to overcome the current computational problems

    NARCIS (Netherlands)

    Visscher, L.


    A perspective on the use of the relativistic Dirac equation in quantum chemistry is given. It is demonstrated that many of the computational problems that plague the current implementations of the different electronic structure methods can be overcome by utilizing the locality of the small component

  18. Computational Modeling of the Optical Rotation of Amino Acids: An "in Silico" Experiment for Physical Chemistry (United States)

    Simpson, Scott; Autschbach, Jochen; Zurek, Eva


    A computational experiment that investigates the optical activity of the amino acid valine has been developed for an upper-level undergraduate physical chemistry laboratory course. Hybrid density functional theory calculations were carried out for valine to confirm the rule that adding a strong acid to a solution of an amino acid in the l…

  19. Students' Cognitive Focus during a Chemistry Laboratory Exercise: Effects of a Computer-Simulated Prelab (United States)

    Winberg, T. Mikael; Berg, C. Anders R.


    To enhance the learning outcomes achieved by students, learners undertook a computer-simulated activity based on an acid-base titration prior to a university-level chemistry laboratory activity. Students were categorized with respect to their attitudes toward learning. During the laboratory exercise, questions that students asked their assistant…

  20. Exploring Interactive and Dynamic Simulations Using a Computer Algebra System in an Advanced Placement Chemistry Course (United States)

    Matsumoto, Paul S.


    The article describes the use of Mathematica, a computer algebra system (CAS), in a high school chemistry course. Mathematica was used to generate a graph, where a slider controls the value of parameter(s) in the equation; thus, students can visualize the effect of the parameter(s) on the behavior of the system. Also, Mathematica can show the…

  1. A Computer Algebra Approach to Solving Chemical Equilibria in General Chemistry (United States)

    Kalainoff, Melinda; Lachance, Russ; Riegner, Dawn; Biaglow, Andrew


    In this article, we report on a semester-long study of the incorporation into our general chemistry course, of advanced algebraic and computer algebra techniques for solving chemical equilibrium problems. The method presented here is an alternative to the commonly used concentration table method for describing chemical equilibria in general…

  2. Column chromatography with almecega resin: a project for experimental organic chemistry

    International Nuclear Information System (INIS)

    Vieira Junior, Gerardo Magela; Carvalho, Adonias Almeida; Gonzaga, Wellington de Abreu; Chaves, Mariana H.


    The use of natural products to demonstrate the silica gel column chromatography technique is proposed in the present article. It describes the separation of the triterpenes α- and β-amirin from the diol breine and maniladiol, obtained from almecega resin (Protium heptaphyllum March.). The experiment uses an accessible material, was accomplished in 4 h, and can be applied with success an the experimental course of organic chemistry for undergraduate students. (author)

  3. Experimental Realization of High-Efficiency Counterfactual Computation. (United States)

    Kong, Fei; Ju, Chenyong; Huang, Pu; Wang, Pengfei; Kong, Xi; Shi, Fazhan; Jiang, Liang; Du, Jiangfeng


    Counterfactual computation (CFC) exemplifies the fascinating quantum process by which the result of a computation may be learned without actually running the computer. In previous experimental studies, the counterfactual efficiency is limited to below 50%. Here we report an experimental realization of the generalized CFC protocol, in which the counterfactual efficiency can break the 50% limit and even approach unity in principle. The experiment is performed with the spins of a negatively charged nitrogen-vacancy color center in diamond. Taking advantage of the quantum Zeno effect, the computer can remain in the not-running subspace due to the frequent projection by the environment, while the computation result can be revealed by final detection. The counterfactual efficiency up to 85% has been demonstrated in our experiment, which opens the possibility of many exciting applications of CFC, such as high-efficiency quantum integration and imaging.

  4. Experimental Realization of High-Efficiency Counterfactual Computation (United States)

    Kong, Fei; Ju, Chenyong; Huang, Pu; Wang, Pengfei; Kong, Xi; Shi, Fazhan; Jiang, Liang; Du, Jiangfeng


    Counterfactual computation (CFC) exemplifies the fascinating quantum process by which the result of a computation may be learned without actually running the computer. In previous experimental studies, the counterfactual efficiency is limited to below 50%. Here we report an experimental realization of the generalized CFC protocol, in which the counterfactual efficiency can break the 50% limit and even approach unity in principle. The experiment is performed with the spins of a negatively charged nitrogen-vacancy color center in diamond. Taking advantage of the quantum Zeno effect, the computer can remain in the not-running subspace due to the frequent projection by the environment, while the computation result can be revealed by final detection. The counterfactual efficiency up to 85% has been demonstrated in our experiment, which opens the possibility of many exciting applications of CFC, such as high-efficiency quantum integration and imaging.

  5. Students' Hands-on Experimental Work vs Lecture Demonstration in Teaching Elementary School Chemistry. (United States)

    Logar, Ana; Ferk-Savec, Vesna


    Science educators have suggested many benefits that accrue from engaging students in experimental activities, therefore, experimental work has a long and distinctive role in chemistry curriculum since. The presented empirical study focuses on the valuation of effectiveness of different forms of experimental work - students' hands-on experimental work vs teacher's lecture demonstration - from the viewpoint of the quality of content knowledge acquisition and knowledge retention in teaching primary school chemistry. 106 primary school students (age 14-15 years) participated in the study. The data was collected via pre- and post- test protocol and two delayed post tests. Additionally 16 students selected from the sample were interviewed. The results indicate that students' content knowledge gained through teacher's demonstration of experiment is better and better knowledge retention takes place in comparison to students' knowledge gained through students' hands-on experimental work. However, most of the inteviewed students stated that they prefered conducting of experiments by themselves in comparison to observation of teacher's demonstration.

  6. Effects of a test taking strategy on postsecondary computer assisted chemistry assessments (United States)

    Manco, Sharon Ann

    Metacognitive test taking strategies have proven advantageous in improving content-based test scores in a wide variety of disciplines and age/grade levels using traditional paper-and-pencil tests. However, despite the increase in computer assisted assessment (CAA), little research has examined whether these test taking strategies are effective for computer assisted tests. Research was conducted to determine if learning a proven test taking strategy would improve the online quiz scores of six university students in an introductory chemistry course intended for science, technology, engineering and math majors. Participants completed six to ten chemistry quizzes prior to intervention---learning the test taking strategy---and four to eight chemistry quizzes after intervention. Results indicated that, while students learned the strategy, it had little effect on their online chemistry quiz scores. Additionally, at the end of the semester, participants completed a satisfaction survey indicating general satisfaction with having learned the test taking strategy and generalization to other courses and types of tests. Furthermore, results suggest that adaptations to the on-line delivery method of the quizzes and to the test taking strategies may improve the robustness of the effect. Due to the increased use of computer assisted assessment, additional research is warranted to determine appropriate test taking strategies for online tests.

  7. CO 2 sorption on substituted carbon materials . Computational chemistry studies (United States)

    Gauden, P. A.; Wiśniewski, M.


    Theoretical study of sorption of CO 2 on the 4-ring graphene ("unmodified" or N-, O-, and OH-substituted) structures possessing one completely unsaturated edge zigzag site is reported using the DFT (B3LYP/6-31G(d,p)) method. Lactone and heterocyclic complexes (due to thermodynamic favourability) are taken into account. The analysis of theoretical results shows that the enthalpy of reaction strongly depends on the chemical nature, i.e. the position of the doping of atom(s) is crucial. All substitutions do not change or decrease the enthalpy in comparison with the "unmodified" graphene sheet. The well-known theoretical reactivity indices (ionization potential, electron affinity, global softness, and HOMO-LUMO gaps) are calculated for the studied adsorbents in order to explain the above-mentioned tendencies. Finally, the effect of the presence of heteroatoms on the enthalpy of reaction (Δ H298) for all CO 2-heteroatom-doping adsorbent complexes is shown. Thus, carbon dioxide molecules adsorb on the edge plane surface of N-, O-, OH-containing carbon surfaces similarly or much less favourably in comparison with the "unmodified" adsorbents. This confirms some experimental observations.

  8. Pedagogical and Epistemological Contributions in Texts of Experimentation in the Chemistry Teaching

    Directory of Open Access Journals (Sweden)

    Fábio Peres Gonçalves


    Full Text Available We have investigated the characteristics of the discourses about purposes of the experiments published in the section “Experimentação no Ensino de Química” of Química Nova na Escola magazine. From a pedagogical and epistemological approach, the goal of the data analysis was to rethink the methodological aspects of experimentation in fundamental and high school Chemistry classes, and to raise questions relevant to teacher formation. Some aspects are pointed out, such as: relation between experimental activity and motivation; the need for a reflection on epistemological nature of the experimentation in teaching; the importance of a dialogical context for learning; material conditions for the development of experimental activities; and characteristics of the contents taught through experiments.

  9. The use of computer-aided learning in chemistry laboratory instruction (United States)

    Allred, Brian Robert Tracy

    This research involves developing and implementing computer software for chemistry laboratory instruction. The specific goal is to design the software and investigate whether it can be used to introduce concepts and laboratory procedures without a lecture format. This would allow students to conduct an experiment even though they may not have been introduced to the chemical concept in their lecture course. This would also allow for another type of interaction for those students who respond more positively to a visual approach to instruction. The first module developed was devoted to using computer software to help introduce students to the concepts related to thin-layer chromatography and setting up and running an experiment. This was achieved through the use of digitized pictures and digitized video clips along with written information. A review quiz was used to help reinforce the learned information. The second module was devoted to the concept of the "dry lab". This module presented students with relevant information regarding the chemical concepts and then showed them the outcome of mixing solutions. By these observations, they were to determine the composition of unknown solutions based on provided descriptions and comparison with their written observations. The third piece of the software designed was a computer game. This program followed the first two modules in providing information the students were to learn. The difference here, though, was incorporating a game scenario for students to use to help reinforce the learning. Students were then assessed to see how much information they retained after playing the game. In each of the three cases, a control group exposed to the traditional lecture format was used. Their results were compared to the experimental group using the computer modules. Based upon the findings, it can be concluded that using technology to aid in the instructional process is definitely of benefit and students were more successful in

  10. Linking Experimental Characterization and Computational Modeling in Microstructural Evolution

    Energy Technology Data Exchange (ETDEWEB)

    Demirel, Melik Cumhar [Univ. of Pittsburgh, PA (United States)


    It is known that by controlling microstructural development, desirable properties of materials can be achieved. The main objective of our research is to understand and control interface dominated material properties, and finally, to verify experimental results with computer simulations. In order to accomplish this objective, we studied the grain growth in detail with experimental techniques and computational simulations. We obtained 5170-grain data from an Aluminum-film (120μm thick) with a columnar grain structure from the Electron Backscattered Diffraction (EBSD) measurements. Experimentally obtained starting microstructure and grain boundary properties are input for the three-dimensional grain growth simulation. In the computational model, minimization of the interface energy is the driving force for the grain boundary motion. The computed evolved microstructure is compared with the final experimental microstructure, after annealing at 550 ºC. Two different measures were introduced as methods of comparing experimental and computed microstructures. Modeling with anisotropic mobility explains a significant amount of mismatch between experiment and isotropic modeling. We have shown that isotropic modeling has very little predictive value. Microstructural evolution in columnar Aluminum foils can be correctly modeled with anisotropic parameters. We observed a strong similarity between grain growth experiments and anisotropic three-dimensional simulations.

  11. Linking Experimental Characterization and Computational Modeling in Microstructural Evolution

    Energy Technology Data Exchange (ETDEWEB)

    Demirel, Melik Cumhur [Univ. of California, Berkeley, CA (United States)


    It is known that by controlling microstructural development, desirable properties of materials can be achieved. The main objective of our research is to understand and control interface dominated material properties, and finally, to verify experimental results with computer simulations. In order to accomplish this objective, we studied the grain growth in detail with experimental techniques and computational simulations. We obtained 5170-grain data from an Aluminum-film (120μm thick) with a columnar grain structure from the Electron Backscattered Diffraction (EBSD) measurements. Experimentally obtained starting microstructure and grain boundary properties are input for the three-dimensional grain growth simulation. In the computational model, minimization of the interface energy is the driving force for the grain boundary motion. The computed evolved microstructure is compared with the final experimental microstructure, after annealing at 550 ºC. Two different measures were introduced as methods of comparing experimental and computed microstructures. Modeling with anisotropic mobility explains a significant amount of mismatch between experiment and isotropic modeling. We have shown that isotropic modeling has very little predictive value. Microstructural evolution in columnar Aluminum foils can be correctly modeled with anisotropic parameters. We observed a strong similarity

  12. Development of the experimental evaluation method for crevice chemistry in steam generators

    Energy Technology Data Exchange (ETDEWEB)

    Rhee, In Hyoung [Soonchunghyang Univ., Cheonan (Korea); Hwang, Il Soon; Lee, Na Young; Kim, Ji Hyun; Lim, Jung Yeon; Bahn, Chi Bum; Oh, Young Jin; Han, Byung Chan; Oh, Si Hyoung [Seoul National Univ., Seoul (Korea)


    Steam generator tube degradation problems is very sensitive to water chemistry. But even if the secondary water chemistry is well controlled, it is needed. Tubesheet crevice has three boiling regimes with depth: liquid penetration and discharge(or wet) region, liquid drop scattering(or dry and wet) region, and dryout region. This results showed a good agreement with earlier works. High temperature, high pressure tubesheet crevice simulation system was constructed. As {delta}T increased, the temperature gradient in crevice and time constant for concentration increased. When the experimental results were compared with MULTEQ calculation results, a similar behavior was shown, packed crevice have longer time constant for Na concentration and showed heavier concentration that open crevice. The verification experiment for Molar Ratio Control and advanced Molar Ration Control test were conducted. To check the applicability of boric acid as pH neutralizer another experiment was conducted. 40 refs., 102 figs., 3 tabs. (Author)

  13. Experimental high energy physics and modern computer architectures

    International Nuclear Information System (INIS)

    Hoek, J.


    The paper examines how experimental High Energy Physics can use modern computer architectures efficiently. In this connection parallel and vector architectures are investigated, and the types available at the moment for general use are discussed. A separate section briefly describes some architectures that are either a combination of both, or exemplify other architectures. In an appendix some directions in which computing seems to be developing in the USA are mentioned. (author)

  14. Structure-based library design: molecular modelling merges with combinatorial chemistry. (United States)

    Böhm, H J; Stahl, M


    Recent advances in both computational and experimental techniques now allow a very fruitful interplay of computational and combinatorial chemistry in the structure-based design of combinatorial libraries.

  15. 1st International Conference on Computational and Experimental Biomedical Sciences

    CERN Document Server

    Jorge, RM


    This book contains the full papers presented at ICCEBS 2013 – the 1st International Conference on Computational and Experimental Biomedical Sciences, which was organized in Azores, in October 2013. The included papers present and discuss new trends in those fields, using several methods and techniques, including active shape models, constitutive models, isogeometric elements, genetic algorithms, level sets, material models, neural networks, optimization, and the finite element method, in order to address more efficiently different and timely applications involving biofluids, computer simulation, computational biomechanics, image based diagnosis, image processing and analysis, image segmentation, image registration, scaffolds, simulation, and surgical planning. The main audience for this book consists of researchers, Ph.D students, and graduate students with multidisciplinary interests related to the areas of artificial intelligence, bioengineering, biology, biomechanics, computational fluid dynamics, comput...

  16. Effect of Computer-Based Blended Learning Strategy on Secondary School Chemistry Students� Retention in Individualised and Collaborative Learning Settings in Minna, Nigeria


    M.S. Suleiman; B.M. Salaudeen; O.C. Falode


    This study investigated effects of Computer-based blended learning strategy on Secondary School Chemistry students retention in individualised and collaborative learning settings in Minna, Niger State, Nigeria. The study adopted a quazi-experimental design and three research questions and three null hypotheses were formulated to guide the study. Multi-staged sampling procedure was used to select a total of 120 (71 female & 49 male) students from three co-educational schools within the study a...

  17. User's guide for vectorized code EQUIL for calculating equilibrium chemistry on Control Data STAR-100 computer (United States)

    Kumar, A.; Graves, R. A., Jr.; Weilmuenster, K. J.


    A vectorized code, EQUIL, was developed for calculating the equilibrium chemistry of a reacting gas mixture on the Control Data STAR-100 computer. The code provides species mole fractions, mass fractions, and thermodynamic and transport properties of the mixture for given temperature, pressure, and elemental mass fractions. The code is set up for the electrons H, He, C, O, N system of elements. In all, 24 chemical species are included.

  18. Development of tight-binding, chemical-reaction-dynamics simulator for combinatorial computational chemistry

    International Nuclear Information System (INIS)

    Kubo, Momoji; Ando, Minako; Sakahara, Satoshi; Jung, Changho; Seki, Kotaro; Kusagaya, Tomonori; Endou, Akira; Takami, Seiichi; Imamura, Akira; Miyamoto, Akira


    Recently, we have proposed a new concept called 'combinatorial computational chemistry' to realize a theoretical, high-throughput screening of catalysts and materials. We have already applied our combinatorial, computational-chemistry approach, mainly based on static first-principles calculations, to various catalysts and materials systems and its applicability to the catalysts and materials design was strongly confirmed. In order to realize more effective and efficient combinatorial, computational-chemistry screening, a high-speed, chemical-reaction-dynamics simulator based on quantum-chemical, molecular-dynamics method is essential. However, to the best of our knowledge, there is no chemical-reaction-dynamics simulator, which has an enough high-speed ability to perform a high-throughput screening. In the present study, we have succeeded in the development of a chemical-reaction-dynamics simulator based on our original, tight-binding, quantum-chemical, molecular-dynamics method, which is more than 5000 times faster than the regular first-principles, molecular-dynamics method. Moreover, its applicability and effectiveness to the atomistic clarification of the methanol-synthesis dynamics at reaction temperature were demonstrated

  19. The quark gluon plasma: Lattice computations put to experimental test

    Indian Academy of Sciences (India)

    journal of. November 2003 physics pp. 877–888. The quark gluon plasma: Lattice computations put to experimental test. SOURENDU GUPTA. Department of Theoretical Physics, Tata Institute ... lattice gauge theory is the only theoretical tool of direct relevance to experiments currently ... In this talk I will concentrate on other.

  20. Biobetters From an Integrated Computational/Experimental Approach

    Directory of Open Access Journals (Sweden)

    Serdar Kuyucak


    Full Text Available Biobetters are new drugs designed from existing peptide or protein-based therapeutics by improving their properties such as affinity and selectivity for the target epitope, and stability against degradation. Computational methods can play a key role in such design problems—by predicting the changes that are most likely to succeed, they can drastically reduce the number of experiments to be performed. Here we discuss the computational and experimental methods commonly used in drug design problems, focusing on the inverse relationship between the two, namely, the more accurate the computational predictions means the less experimental effort is needed for testing. Examples discussed include efforts to design selective analogs from toxin peptides targeting ion channels for treatment of autoimmune diseases and monoclonal antibodies which are the fastest growing class of therapeutic agents particularly for cancers and autoimmune diseases.

  1. Computational Design and Experimental Validation of New Thermal Barrier Systems

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Shengmin; Yang, Shizhong; Khosravi, Ebrahim


    This project (10/01/2010-9/30/2013), “Computational Design and Experimental Validation of New Thermal Barrier Systems”, originates from Louisiana State University (LSU) Mechanical Engineering Department and Southern University (SU) Department of Computer Science. This project will directly support the technical goals specified in DEFOA- 0000248, Topic Area 3: Turbine Materials, by addressing key technologies needed to enable the development of advanced turbines and turbine-based systems that will operate safely and efficiently using coal-derived synthesis gases. We will develop and implement novel molecular dynamics method to improve the efficiency of simulation on novel TBC materials; perform high performance computing (HPC) on complex TBC structures to screen the most promising TBC compositions; perform material characterizations and oxidation/corrosion tests; and demonstrate our new thermal barrier coating (TBC) systems experimentally under integrated gasification combined cycle (IGCC) environments. The durability of the coating will be examined using the proposed Durability Test Rig.

  2. Introduction to Computational Chemistry: Teaching Hu¨ckel Molecular Orbital Theory Using an Excel Workbook for Matrix Diagonalization (United States)

    Litofsky, Joshua; Viswanathan, Rama


    Matrix diagonalization, the key technique at the heart of modern computational chemistry for the numerical solution of the Schrödinger equation, can be easily introduced in the physical chemistry curriculum in a pedagogical context using simple Hückel molecular orbital theory for p bonding in molecules. We present details and results of…

  3. Research and Teaching: Computational Methods in General Chemistry--Perceptions of Programming, Prior Experience, and Student Outcomes (United States)

    Wheeler, Lindsay B.; Chiu, Jennie L.; Grisham, Charles M.


    This article explores how integrating computational tools into a general chemistry laboratory course can influence student perceptions of programming and investigates relationships among student perceptions, prior experience, and student outcomes.

  4. Managing the computational chemistry big data problem: the ioChem-BD platform. (United States)

    Álvarez-Moreno, M; de Graaf, C; López, N; Maseras, F; Poblet, J M; Bo, C


    We present the ioChem-BD platform ( ) as a multiheaded tool aimed to manage large volumes of quantum chemistry results from a diverse group of already common simulation packages. The platform has an extensible structure. The key modules managing the main tasks are to (i) upload of output files from common computational chemistry packages, (ii) extract meaningful data from the results, and (iii) generate output summaries in user-friendly formats. A heavy use of the Chemical Mark-up Language (CML) is made in the intermediate files used by ioChem-BD. From them and using XSL techniques, we manipulate and transform such chemical data sets to fulfill researchers' needs in the form of HTML5 reports, supporting information, and other research media.

  5. Combining experimental and computational studies to understand and predict reactivities of relevance to homogeneous catalysis. (United States)

    Tsang, Althea S-K; Sanhueza, Italo A; Schoenebeck, Franziska


    This article showcases three major uses of computational chemistry in reactivity studies: the application after, in combination with, and before experiment. Following a brief introduction of suitable computational tools, challenges and opportunities in the implementation of computational chemistry in reactivity studies are discussed, exemplified with selected case studies from our and other laboratories. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Computational design and experimental validation of new thermal barrier systems

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Shengmin [Louisiana State Univ., Baton Rouge, LA (United States)


    The focus of this project is on the development of a reliable and efficient ab initio based computational high temperature material design method which can be used to assist the Thermal Barrier Coating (TBC) bond-coat and top-coat design. Experimental evaluations on the new TBCs are conducted to confirm the new TBCs’ properties. Southern University is the subcontractor on this project with a focus on the computational simulation method development. We have performed ab initio density functional theory (DFT) method and molecular dynamics simulation on screening the top coats and bond coats for gas turbine thermal barrier coating design and validation applications. For experimental validations, our focus is on the hot corrosion performance of different TBC systems. For example, for one of the top coatings studied, we examined the thermal stability of TaZr2.75O8 and confirmed it’s hot corrosion performance.

  7. Statistical Methodologies to Integrate Experimental and Computational Research (United States)

    Parker, P. A.; Johnson, R. T.; Montgomery, D. C.


    Development of advanced algorithms for simulating engine flow paths requires the integration of fundamental experiments with the validation of enhanced mathematical models. In this paper, we provide an overview of statistical methods to strategically and efficiently conduct experiments and computational model refinement. Moreover, the integration of experimental and computational research efforts is emphasized. With a statistical engineering perspective, scientific and engineering expertise is combined with statistical sciences to gain deeper insights into experimental phenomenon and code development performance; supporting the overall research objectives. The particular statistical methods discussed are design of experiments, response surface methodology, and uncertainty analysis and planning. Their application is illustrated with a coaxial free jet experiment and a turbulence model refinement investigation. Our goal is to provide an overview, focusing on concepts rather than practice, to demonstrate the benefits of using statistical methods in research and development, thereby encouraging their broader and more systematic application.

  8. Optimizing qubit resources for quantum chemistry simulations in second quantization on a quantum computer

    International Nuclear Information System (INIS)

    Moll, Nikolaj; Fuhrer, Andreas; Staar, Peter; Tavernelli, Ivano


    Quantum chemistry simulations on a quantum computer suffer from the overhead needed for encoding the Fermionic problem in a system of qubits. By exploiting the block diagonality of a Fermionic Hamiltonian, we show that the number of required qubits can be reduced while the number of terms in the Hamiltonian will increase. All operations for this reduction can be performed in operator space. The scheme is conceived as a pre-computational step that would be performed prior to the actual quantum simulation. We apply this scheme to reduce the number of qubits necessary to simulate both the Hamiltonian of the two-site Fermi–Hubbard model and the hydrogen molecule. Both quantum systems can then be simulated with a two-qubit quantum computer. Despite the increase in the number of Hamiltonian terms, the scheme still remains a useful tool to reduce the dimensionality of specific quantum systems for quantum simulators with a limited number of resources. (paper)

  9. Experimental and modelling studies of the near-field chemistry for Nirex repository concepts

    International Nuclear Information System (INIS)

    Atkinson, A.; Ewart, F.T.; Pugh, S.Y.R.; Rees, J.H.; Sharland, S.M.; Tasker, P.W.; Wilkins, J.D.


    A research programme is described which is designed to investigate the chemical conditions in the near field of a concrete based repository and the behaviour of the radiologically important nuclides under these conditions. The chemical conditions are determined by the corrosion of the iron components of the repository and by the soluble components of the concrete. Both of these have been investigated experimentally and models developed which have been validated by further experiment. The effect of these reactions on the repository pH and Eh, and how these develop in time and space have been modelled using a coupled chemical equilibrium and transport code. The solubility of the important nuclides are being studied experimentally under these conditions, and under sensible variations. These data have been used to refine the thermodynamic data base used for the geochemical code PHREEQE. The sorption behaviour of plutonium and americium, under the same conditions, have been studied; the sorption coefficients were found to be large and independent of the concrete formulation, particle size and solid liquid ratio. Recent experimental results from sorption/exchange experiments with lead and 14-carbon are also reported. The programme has also investigated experimentally the possible perturbation of the repository chemistry by microbial action and by natural and added organic material. A final set of experiments combine all the repository components and the waste in a long term equilibration experiment. (author)

  10. An Open Environment to Support the Development of Computational Chemistry Solutions (United States)

    Bejarano, Bernardo Palacios; Ruiz, Irene Luque; Gómez-Nieto, Miguel Ángel


    In this paper we present an open software environment devoted to support the investigations in computational chemistry. The software, named CoChiSE (Computational Chimica Software Environment) is fully developed in Java using Eclipse as IDE; in this way, the system is integrated by different perspectives oriented to solve different aspects of the computational chemistry research. CoChiSE is able to manage large chemical databases, maintaining information about molecules and properties as well; this information can be exported and imported to/from the most popular standard file formats. The system also allows the user to perform the calculation of different type of isomorphism and molecular similarity. Besides, CoChiSE incorporates a perspective in charge of the calculation of molecular descriptors, considering more than four hundred descriptors of different categories. All the information and system perspectives are integrated in the same environment, so a huge amount of information is managed by the user. The characteristics of the developed system permit the easy integration of either user, proprietary and free software.

  11. Experimental study on iodine chemistry (EXSI) - Containment experiments with methyl iodide

    Energy Technology Data Exchange (ETDEWEB)

    Holm, J.; Glaenneskog, H.; Ekberg, C. (Chalmers Univ. of Technology (Sweden)); Kaerkelae, T.; Auvinen, A. (VTT Technical Research Centre of Finland (Finland))


    An experimental study on radiolytic decomposition of methyl iodide was conducted in co-operation between VTT and Chalmers University of Technology as a part of the NKS-R programs. The behaviour of iodine during a severe accident has been studied in several experimental programs, ranging from the large-scale PHEBUS FP tests and intermediate-scale ThAI tests to numerous separate effect studies. In year 2008 the NROI project, a Nordic collaboration studying iodine chemistry in the containment was started. During 2009, oxidation of iodine, especially organic iodine, was studied within the NROI project. The chemistry of organic iodine in the gas phase is still one of the greatest remaining uncertainties concerning iodine behaviour during a severe accident. During the first year of the NROI project the oxidation of elemental iodine, I2, with ozone and UV-light was investigated. In this study organic iodide, in this case methyl iodide, was investigated in similar conditions as in the NROI-1 project. The experimental facility applied in this study is based on the sampling system built at VTT for the ISTP project CHIP conducted by IRSN. The experimental facility and the measuring technology are sophisticated and unique in the area of nuclear research as well as in the field of aerosol science. Experimental results showed that the methyl iodide concentration in the facility was reduced with increasing temperature and increasing UVC intensity. Similar behaviour occurred when ozone was present in the system. Formed organic gas species during the decomposition of methyl iodide was mainly formaldehyde and methanol. Instant and extensive particle formation occurred when methyl iodide was transported through a UVC radiation field and/or when ozone was present. The size of the formed primary particles was about 10 nm and the size of secondary particles was between 50-150 nm. From the SEM-EDX analyses of the particles, the conclusion was drawn that these were some kind of iodine

  12. Playing with the Soccer Ball-an Experimental Introduction to Fullerene Chemistry (United States)

    Hildebrand, Achim; Hilgers, Uwe; Blume, Rudiger; Wiechoczek, Dagmar


    The "molecule of the year 1991", C60 buckminsterfullerene, has found its way to experimental chemistry courses in high schools and universities. For the first time a selection of simple experiments with C60 on high-school and university level are presented: the bromination with Winkler's solution, hydroxylation with an alkaline permanganate solution, cycloadditions of dichlorcarbene and cyclopentadiene and the formation of a molecular complex with o-dimethoxybenzene. They are easy to carry out due to the high reactivity of C60. The experiments demonstrate some chemical properties of this new form of carbon. C60 reacts like a giant alkene with electron acceptor properties. To stress this fact, one should compare C60 with other alkenes and aromatic compounds. The characteristic color change of the C60 solutions during the reactions make them easy to observe, even without spectroscopic methods.

  13. Inserção do conceito de economia atômica no programa de uma disciplina de química orgânica experimental Inclusion of atom economy concept in an experimental organic chemistry undergraduate course

    Directory of Open Access Journals (Sweden)

    Leila Maria Oliveira Coelho Merat


    Full Text Available In this paper, the atom economy concepts are applied in a series of experiments during an experimental organic chemistry class, to implement "green chemistry" in an undergraduate course.

  14. Computational Design and Experimental Validation of New Thermal Barrier Systems

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Shengmin; Yang, Shizhong; Khosravi, Ebrahim


    This project (10/01/2010-9/30/2013), “Computational Design and Experimental Validation of New Thermal Barrier Systems”, originates from Louisiana State University (LSU) Mechanical Engineering Department and Southern University (SU) Department of Computer Science. This proposal will directly support the technical goals specified in DE-FOA-0000248, Topic Area 3: Turbine Materials, by addressing key technologies needed to enable the development of advanced turbines and turbine-based systems that will operate safely and efficiently using coal-derived synthesis gases. We will develop novel molecular dynamics method to improve the efficiency of simulation on novel TBC materials; we will perform high performance computing (HPC) on complex TBC structures to screen the most promising TBC compositions; we will perform material characterizations and oxidation/corrosion tests; and we will demonstrate our new Thermal barrier coating (TBC) systems experimentally under Integrated gasification combined cycle (IGCC) environments. The durability of the coating will be examined using the proposed High Temperature/High Pressure Durability Test Rig under real syngas product compositions.

  15. Distributed computing testbed for a remote experimental environment

    International Nuclear Information System (INIS)

    Butner, D.N.; Casper, T.A.; Howard, B.C.; Henline, P.A.; Davis, S.L.; Barnes, D.


    Collaboration is increasing as physics research becomes concentrated on a few large, expensive facilities, particularly in magnetic fusion energy research, with national and international participation. These facilities are designed for steady state operation and interactive, real-time experimentation. We are developing tools to provide for the establishment of geographically distant centers for interactive operations; such centers would allow scientists to participate in experiments from their home institutions. A testbed is being developed for a Remote Experimental Environment (REE), a ''Collaboratory.'' The testbed will be used to evaluate the ability of a remotely located group of scientists to conduct research on the DIII-D Tokamak at General Atomics. The REE will serve as a testing environment for advanced control and collaboration concepts applicable to future experiments. Process-to-process communications over high speed wide area networks provide real-time synchronization and exchange of data among multiple computer networks, while the ability to conduct research is enhanced by adding audio/video communication capabilities. The Open Software Foundation's Distributed Computing Environment is being used to test concepts in distributed control, security, naming, remote procedure calls and distributed file access using the Distributed File Services. We are exploring the technology and sociology of remotely participating in the operation of a large scale experimental facility

  16. Thermodynamics of natural selection III: Landauer's principle in computation and chemistry. (United States)

    Smith, Eric


    This is the third in a series of three papers devoted to energy flow and entropy changes in chemical and biological processes, and their relations to the thermodynamics of computation. The previous two papers have developed reversible chemical transformations as idealizations for studying physiology and natural selection, and derived bounds from the second law of thermodynamics, between information gain in an ensemble and the chemical work required to produce it. This paper concerns the explicit mapping of chemistry to computation, and particularly the Landauer decomposition of irreversible computations, in which reversible logical operations generating no heat are separated from heat-generating erasure steps which are logically irreversible but thermodynamically reversible. The Landauer arrangement of computation is shown to produce the same entropy-flow diagram as that of the chemical Carnot cycles used in the second paper of the series to idealize physiological cycles. The specific application of computation to data compression and error-correcting encoding also makes possible a Landauer analysis of the somewhat different problem of optimal molecular recognition, which has been considered as an information theory problem. It is shown here that bounds on maximum sequence discrimination from the enthalpy of complex formation, although derived from the same logical model as the Shannon theorem for channel capacity, arise from exactly the opposite model for erasure.

  17. Recent progress in orbital-free density functional theory (recent advances in computational chemistry)

    CERN Document Server

    Wesolowski, Tomasz A


    This is a comprehensive overview of state-of-the-art computational methods based on orbital-free formulation of density functional theory completed by the most recent developments concerning the exact properties, approximations, and interpretations of the relevant quantities in density functional theory. The book is a compilation of contributions stemming from a series of workshops which had been taking place since 2002. It not only chronicles many of the latest developments but also summarises some of the more significant ones. The chapters are mainly reviews of sub-domains but also include original research. Readership: Graduate students, academics and researchers in computational chemistry. Atomic & molecular physicists, theoretical physicists, theoretical chemists, physical chemists and chemical physicists.

  18. Intermolecular Forces in Introductory Chemistry Studied by Gas Chromatography, Computer Models, and Viscometry (United States)

    Wedvik, Jonathan C.; McManaman, Charity; Anderson, Janet S.; Carroll, Mary K.


    An experiment on intermolecular forces for first-term introductory college chemistry is presented. The experiment integrates traditional viscometry-based measurements with modern chromatographic analysis and use of computer-based molecular models. Students performing gas chromatographic (GC) analyses of mixtures of n-alkanes and samples that simulate crime scene evidence discover that liquid mixtures can be separated rapidly into their components based upon intermolecular forces. Each group of students is given a liquid sample that simulates one collected at an arson scene, and the group is required to determine the identity of the accelerant. Students also examine computer models to better visualize how molecular structure affects intermolecular forces: London forces, dipole-dipole interactions, and hydrogen bonding. The relative viscosities of organic liquids are also measured to relate physical properties to intermolecular forces.

  19. Predicting Complex Organic Mixture Atmospheric Chemistry Using Computer-Generated Reaction Models (United States)

    Klein, M. T.; Broadbelt, L. J.; Mazurek, M. A.


    New measurement and chemical characterization technologies now offer unprecedented capabilities for detecting and describing atmospheric organic matter at the molecular level. As a result, very detailed and extensive chemical inventories are produced routinely in atmospheric field measurements of organic compounds found in the vapor and condensed phases (particles, cloud and fog droplets). Hundreds of organic compounds can constitute the complex chemical mixtures observed for these types of samples, exhibiting a wide spectrum of physical properties such as molecular weight, polarity, pH, and chemical reactivity. The central challenge is describing chemically the complex organic aerosol mixture in a useable fashion that can be linked to predictive models. However, the great compositional complexity of organic aerosols engenders a need for the modeling of the reaction chemistry of these compounds in atmospheric chemical models. On a mechanistic level, atmospheric reactions of organic compounds can involve a network of a very large number of chemical species and reactions. Deriving such large molecular kinetic models by hand is a tedious and time-consuming process. However, such models are usually built upon a few basic chemical principles tempered with the model builder's observations, experience, and intuition that can be summarized as a set of rules. This suggests that given an algorithmic framework, computers (information technology) may be used to apply these chemical principles and rules, thereby building a kinetic model. The framework for this model building process has been developed by means of graph theory. A molecule, which is a set of atoms connected by bonds, may be conceptualized as a set of vertices connected by edges, or to be more precise, a graph. The bond breaking and forming for a reaction can be represented compactly in the form of a matrix operator formally called the "reaction matrix". The addition of the reaction matrix operator to the reduced

  20. Chemical Equilibrium, Unit 2: Le Chatelier's Principle. A Computer-Enriched Module for Introductory Chemistry. Student's Guide and Teacher's Guide. (United States)

    Jameson, A. Keith

    Presented are the teacher's guide and student materials for one of a series of self-instructional, computer-based learning modules for an introductory, undergraduate chemistry course. The student manual for this unit on Le Chatelier's principle includes objectives, prerequisites, pretest, instructions for executing the computer program, and…

  1. The Importance of Computer Based Active Learning for Basic Chemistry in Vocational High Schools

    Directory of Open Access Journals (Sweden)

    Tuğçe GÜNTER


    Full Text Available Chemistry is a very comprehensive discipline that researches atoms; molecules; the structure of matter in the form of element or compound; combinations, and physical and chemical properties of matter; macroscopic and microscopic transformations of matters; the energy and entropy released or absorbed in the course of these transformations; the structures and functions of carbohydrates, lipids, proteins, enzymes, vitamins and minerals in the body. This discipline includes numerous reactions at the macroscopic, microscopic and particulate levels, abstract concepts, three-dimensional structure of molecules, mathematics, and graphics. It is important for students to be trained as scientists to internalize -with meaningful learning - chemistry having much abstract concepts. Especially for students in associate degree programs in Vocational High Schools, taking this integrated course will provide them to be more creative in their future professional work; to cope with and overcome analytical problems; to be self-learners; to fill the gaps concerning chemical analysis originated from secondary education; and to gain critical thinking and self-evaluation skills regarding chemical problems. In the age of developing science and technology, “Computer-Based Active Learning Method” emerged with the introduction of multi-media into education and training. In this context, students will learn difficult and complex mathematical operations and graphics interpretations more meaningfully with computer-based simulations and analogies.

  2. Computational and Experimental Methods to Decipher the Epigenetic Code

    Directory of Open Access Journals (Sweden)

    Stefano ede Pretis


    Full Text Available A multi-layered set of epigenetic marks, including post-translational modifications of histones and methylation of DNA, is finely tuned to define the epigenetic state of chromatin in any given cell type under specific conditions. Recently, the knowledge about the combinations of epigenetic marks occurring in the genome of different cell types under various conditions is rapidly increasing. Computational methods were developed for the identification of these states, unraveling the combinatorial nature of epigenetic marks and their association to genomic functional elements and transcriptional states. Nevertheless, the precise rules defining the interplay between all these marks remain poorly characterized. In this perspective we review the current state of this research field, illustrating the power and the limitations of current approaches. Finally, we sketch future avenues of research illustrating how the adoption of specific experimental designs coupled with available experimental approaches could be critical for a significant progress in this area.

  3. Experimental and Computational Investigations of Flow past Spinning Cylinders (United States)

    Carlucci, Pasquale; Mehmedagic, Igbal; Buckley, Liam; Carlucci, Donald; Thangam, Siva


    Experiments are performed in a low speed subsonic wind tunnel to analyze flow past spinning cylinders. The sting-mounted cylinders are oriented such that their axis of rotation is aligned with the mean flow. Data from spinning cylinders with both rear-mounted and fore-mounted stings are presented for a Reynolds numbers of up to 260000 and rotation numbers of up to 1.2 (based on cylinder diameter). Computations are performed using a two-equation turbulence model that is capable of capturing the effects of swirl and curvature. The model performance was validated with benchmark experimental flows and implemented for analyzing the flow configuration used in the experimental study. The results are analyzed and the predictive capability of the model is discussed. Funded in part by U. S. Army, ARDEC.

  4. Experimental and computational study of transonic flow about swept wings (United States)

    Bertelrud, A.; Bergmann, M. Y.; Coakley, T. J.


    An experimental investigation of NACA 0010 and 10% circular arc wing models, swept at 45 deg, spanning a channel, and at zero angle of attack is described. Measurements include chordwise and spanwise surface pressure distributions and oil-flow patterns for a range of transonic Mach numbers and Reynolds numbers. Calculations using a new three-dimensional Navier-Stokes code and a two-equation turbulence model are included for the circular-arc wing flow. Reasonable agreement between measurements and computations is obtained.

  5. Mathematical Chemistry


    Trinajstić, Nenad; Gutman, Ivan


    A brief description is given of the historical development of mathematics and chemistry. A path leading to the meeting of these two sciences is described. An attempt is made to define mathematical chemistry, and journals containing the term mathematical chemistry in their titles are noted. In conclusion, the statement is made that although chemistry is an experimental science aimed at preparing new compounds and materials, mathematics is very useful in chemistry, among other things, to produc...

  6. Controlled experimental aquarium system for multi-stressor investigation: carbonate chemistry, oxygen saturation, and temperature (United States)

    Bockmon, E. E.; Frieder, C. A.; Navarro, M. O.; White-Kershek, L. A.; Dickson, A. G.


    As the field of ocean acidification has grown, researchers have increasingly turned to laboratory experiments to understand the impacts of increased CO2 on marine organisms. However, other changes such as ocean warming and deoxygenation are occurring concurrently with the increasing CO2 concentrations, complicating the anthropogenic impact on organisms. This experimental aquarium design allows for independent regulation of CO2 concentration, O2 levels, and temperature in a controlled environment to study the impacts of multiple stressors. The system has the flexibility for a wide range of treatment chemistry, seawater volumes, and study organisms. Control of the seawater chemistry is achieved by equilibration of a chosen gas mixture with seawater using a Liqui-Cel® membrane contactor. Included as examples, two experiments performed using the system have shown control of CO2 between approximately 500-1400 μatm and O2 from 80-240 μmol kg-1. Temperature has been maintained to 0.5 °C or better in the range of 10-17 °C. On a weeklong timescale, control results in variability in pH of less than 0.007 pH units and in oxygen concentration less than 3.5 μmol kg-1. Longer experiments, over a month, have been completed with reasonable but lessened control, still better than 0.08 pH units and 13 μmol kg-1 O2. The ability to study the impacts of multiple stressors in the laboratory simultaneously, as well as independently, will be an important part of understanding the response of marine organisms to a high-CO2 world.

  7. Experimental and computational evidence of halogen bonds involving astatine (United States)

    Guo, Ning; Maurice, Rémi; Teze, David; Graton, Jérôme; Champion, Julie; Montavon, Gilles; Galland, Nicolas


    The importance of halogen bonds—highly directional interactions between an electron-deficient σ-hole moiety in a halogenated compound and an acceptor such as a Lewis base—is being increasingly recognized in a wide variety of fields from biomedicinal chemistry to materials science. The heaviest halogens are known to form stronger halogen bonds, implying that if this trend continues down the periodic table, astatine should exhibit the highest halogen-bond donating ability. This may be mitigated, however, by the relativistic effects undergone by heavy elements, as illustrated by the metallic character of astatine. Here, the occurrence of halogen-bonding interactions involving astatine is experimentally evidenced. The complexation constants of astatine monoiodide with a series of organic ligands in cyclohexane solution were derived from distribution coefficient measurements and supported by relativistic quantum mechanical calculations. Taken together, the results show that astatine indeed behaves as a halogen-bond donor—a stronger one than iodine—owing to its much more electrophilic σ-hole.


    Energy Technology Data Exchange (ETDEWEB)

    Paul Lam; Dimitri Gidaspow


    The objective if this study was to develop a predictive experimentally verified computational fluid dynamics (CFD) model for gas-liquid-solid flow. A three dimensional transient computer code for the coupled Navier-Stokes equations for each phase was developed. The principal input into the model is the viscosity of the particulate phase which was determined from a measurement of the random kinetic energy of the 800 micron glass beads and a Brookfield viscometer. The computed time averaged particle velocities and concentrations agree with PIV measurements of velocities and concentrations, obtained using a combination of gamma-ray and X-ray densitometers, in a slurry bubble column, operated in the bubbly-coalesced fluidization regime with continuous flow of water. Both the experiment and the simulation show a down-flow of particles in the center of the column and up-flow near the walls and nearly uniform particle concentration. Normal and shear Reynolds stresses were constructed from the computed instantaneous particle velocities. The PIV measurement and the simulation produced instantaneous particle velocities. The PIV measurement and the simulation produced similar nearly flat horizontal profiles of turbulent kinetic energy of particles. This phase of the work was presented at the Chemical Reaction Engineering VIII: Computational Fluid Dynamics, August 6-11, 2000 in Quebec City, Canada. To understand turbulence in risers, measurements were done in the IIT riser with 530 micron glass beads using a PIV technique. The results together with simulations will be presented at the annual meeting of AIChE in November 2000.

  9. Extraction of pigments from seeds of Bixa orellana L.: an alternative for experimental courses in organic chemistry

    International Nuclear Information System (INIS)

    Costa, Charllyton Luis S. da; Chaves, Mariana H.


    This paper describes methodologies for the extraction and characterization by TLC, UV-VIS, IR and NMR of bixin from Bixa orellana L. (urucum) seeds. Based on the results, the extraction with NaOH 5% is the fastest, uses low cost materials, requires two to four laboratory hours and is a useful alternative for an experimental Organic Chemistry discipline. (author)

  10. Open Experimentation on Phenomena of Chemical Reactions via the Learning Company Approach in Early Secondary Chemistry Education (United States)

    Beck, Katharina; Witteck, Torsten; Eilks, Ingo


    Presented is a case study on the implementation of open and inquiry-type experimentation in early German secondary chemistry education. The teaching strategy discussed follows the learning company approach. Originally adopted from vocational education, the learning company method is used to redirect lab-oriented classroom practice towards a more…

  11. Modeling methods for merging computational and experimental aerodynamic pressure data (United States)

    Haderlie, Jacob C.

    This research describes a process to model surface pressure data sets as a function of wing geometry from computational and wind tunnel sources and then merge them into a single predicted value. The described merging process will enable engineers to integrate these data sets with the goal of utilizing the advantages of each data source while overcoming the limitations of both; this provides a single, combined data set to support analysis and design. The main challenge with this process is accurately representing each data source everywhere on the wing. Additionally, this effort demonstrates methods to model wind tunnel pressure data as a function of angle of attack as an initial step towards a merging process that uses both location on the wing and flow conditions (e.g., angle of attack, flow velocity or Reynold's number) as independent variables. This surrogate model of pressure as a function of angle of attack can be useful for engineers that need to predict the location of zero-order discontinuities, e.g., flow separation or normal shocks. Because, to the author's best knowledge, there is no published, well-established merging method for aerodynamic pressure data (here, the coefficient of pressure Cp), this work identifies promising modeling and merging methods, and then makes a critical comparison of these methods. Surrogate models represent the pressure data for both data sets. Cubic B-spline surrogate models represent the computational simulation results. Machine learning and multi-fidelity surrogate models represent the experimental data. This research compares three surrogates for the experimental data (sequential--a.k.a. online--Gaussian processes, batch Gaussian processes, and multi-fidelity additive corrector) on the merits of accuracy and computational cost. The Gaussian process (GP) methods employ cubic B-spline CFD surrogates as a model basis function to build a surrogate model of the WT data, and this usage of the CFD surrogate in building the WT

  12. User's Guide to Handlens - A Computer Program that Calculates the Chemistry of Minerals in Mixtures (United States)

    Eberl, D.D.


    HandLens is a computer program, written in Excel macro language, that calculates the chemistry of minerals in mineral mixtures (for example, in rocks, soils and sediments) for related samples from inputs of quantitative mineralogy and chemistry. For best results, the related samples should contain minerals having the same chemical compositions; that is, the samples should differ only in the proportions of minerals present. This manual describes how to use the program, discusses the theory behind its operation, and presents test results of the program's accuracy. Required input for HandLens includes quantitative mineralogical data, obtained, for example, by RockJock analysis of X-ray diffraction (XRD) patterns, and quantitative chemical data, obtained, for example, by X-ray florescence (XRF) analysis of the same samples. Other quantitative data, such as sample depth, temperature, surface area, also can be entered. The minerals present in the samples are selected from a list, and the program is started. The results of the calculation include: (1) a table of linear coefficients of determination (r2's) which relate pairs of input data (for example, Si versus quartz weight percents); (2) a utility for plotting all input data, either as pairs of variables, or as sums of up to eight variables; (3) a table that presents the calculated chemical formulae for minerals in the samples; (4) a table that lists the calculated concentrations of major, minor, and trace elements in the various minerals; and (5) a table that presents chemical formulae for the minerals that have been corrected for possible systematic errors in the mineralogical and/or chemical analyses. In addition, the program contains a method for testing the assumption of constant chemistry of the minerals within a sample set.

  13. Web-based computational chemistry education with CHARMMing II: Coarse-grained protein folding.

    Directory of Open Access Journals (Sweden)

    Frank C Pickard


    Full Text Available A lesson utilizing a coarse-grained (CG Gō-like model has been implemented into the CHARMM INterface and Graphics (CHARMMing web portal ( to the Chemistry at HARvard Macromolecular Mechanics (CHARMM molecular simulation package. While widely used to model various biophysical processes, such as protein folding and aggregation, CG models can also serve as an educational tool because they can provide qualitative descriptions of complex biophysical phenomena for a relatively cheap computational cost. As a proof of concept, this lesson demonstrates the construction of a CG model of a small globular protein, its simulation via Langevin dynamics, and the analysis of the resulting data. This lesson makes connections between modern molecular simulation techniques and topics commonly presented in an advanced undergraduate lecture on physical chemistry. It culminates in a straightforward analysis of a short dynamics trajectory of a small fast folding globular protein; we briefly describe the thermodynamic properties that can be calculated from this analysis. The assumptions inherent in the model and the data analysis are laid out in a clear, concise manner, and the techniques used are consistent with those employed by specialists in the field of CG modeling. One of the major tasks in building the Gō-like model is determining the relative strength of the nonbonded interactions between coarse-grained sites. New functionality has been added to CHARMMing to facilitate this process. The implementation of these features into CHARMMing helps automate many of the tedious aspects of constructing a CG Gō model. The CG model builder and its accompanying lesson should be a valuable tool to chemistry students, teachers, and modelers in the field.

  14. Collision induced dissociation study of azobenzene and its derivatives: computational and experimental results (United States)

    Rezaee, Mohammadreza; Compton, Robert


    Experimental and computational investigation have been performed in order to study the bond dissociation energy of azobenzene and its derivatives using collision induced dissociation method as well as other energy and structural characteristics. The results have been verified by comparing with results obtained from computational quantum chemistry. We used different density functional methods as well as the Möller-Plesset perturbation theory and the coupled cluster methods to explore geometric, electronic and the spectral properties of the sample molecules. Geometries were calculated and optimized using the 6-311 + + G(2d,2p) basis set and the B3LYP level of theory and these optimized structures have been subjected to the frequency calculations to obtain thermochemical properties by means of different density functional, Möller-Plesset, and coupled cluster theories to obtain a high accuracy estimation of the bond dissociation energy value. The results from experiments and the results obtained from computational thermochemistry are in close agreement. Physics and Astronomy Department

  15. Computational Flame Diagnostics for Direct Numerical Simulations with Detailed Chemistry of Transportation Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Tianfeng [Univ. of Connecticut, Storrs, CT (United States)


    The goal of the proposed research is to create computational flame diagnostics (CFLD) that are rigorous numerical algorithms for systematic detection of critical flame features, such as ignition, extinction, and premixed and non-premixed flamelets, and to understand the underlying physicochemical processes controlling limit flame phenomena, flame stabilization, turbulence-chemistry interactions and pollutant emissions etc. The goal has been accomplished through an integrated effort on mechanism reduction, direct numerical simulations (DNS) of flames at engine conditions and a variety of turbulent flames with transport fuels, computational diagnostics, turbulence modeling, and DNS data mining and data reduction. The computational diagnostics are primarily based on the chemical explosive mode analysis (CEMA) and a recently developed bifurcation analysis using datasets from first-principle simulations of 0-D reactors, 1-D laminar flames, and 2-D and 3-D DNS (collaboration with J.H. Chen and S. Som at Argonne, and C.S. Yoo at UNIST). Non-stiff reduced mechanisms for transportation fuels amenable for 3-D DNS are developed through graph-based methods and timescale analysis. The flame structures, stabilization mechanisms, local ignition and extinction etc., and the rate controlling chemical processes are unambiguously identified through CFLD. CEMA is further employed to segment complex turbulent flames based on the critical flame features, such as premixed reaction fronts, and to enable zone-adaptive turbulent combustion modeling.

  16. Computer-controlled radiochemical synthesis: a chemistry process control unit for the automated production of radiochemicals

    Energy Technology Data Exchange (ETDEWEB)

    Padgett, H.C.; Schmidt, D.G.; Luxen, A.; Bida, G.T.; Satyamurthy, N.; Barrio, J.R. (California Univ., Los Angeles, CA (USA). Dept. of Radiology)


    A computer-controlled general purpose chemistry process control unit (CPCU) suitable for the automated production of radiochemicals has been developed. This valve-and-tubing synthesis system can be user programmed to accommodate a variety of chemical processes. In a practical demonstration of its utility, the CPCU has been configured and programmed to synthesize 2-deoxy-2-(/sup 18/F)fluoro-D-glucose (2-(/sup 18/F)FDG) using aqueous (/sup 18/F)fluoride ion. The unit has been similarly configured and programmed to synthesize 2-deoxy-2-(/sup 18/F)fluoro-D-mannose (48% EOB), 3-(2'-(/sup 18/F)fluoroethyl)spiperone (29% EOB), and (/sup 18/F)fluoroacetate (66% EOB) from aqueous (/sup 18/F)-fluoride ion, and 2-(/sup 18/F)FDG from gaseous acetyl hypo(/sup 18/F)fluorite (20% EOB). (author).

  17. Benchmark studies of computer prediction techniques for equilibrium chemistry and radionuclide transport in groundwater flow

    International Nuclear Information System (INIS)

    Broyd, T.W.


    A brief review of two recent benchmark exercises is presented. These were separately concerned with the equilibrium chemistry of groundwater and the geosphere migration of radionuclides, and involved the use of a total of 19 computer codes by 11 organisations in Europe and Canada. A similar methodology was followed for each exercise, in that series of hypothetical test cases were used to explore the limits of each code's application, and so provide an overview of current modelling potential. Aspects of the user-friendliness of individual codes were also considered. The benchmark studies have benefited participating organisations by providing a means of verifying current codes, and have provided problem data sets by which future models may be compared. (author)

  18. Computer-Generated Experimental Designs for Irregular-Shaped Regions

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Nam K.; Piepel, Gregory F.


    This paper focuses on the construction of computer-generated designs on irregularly-shaped, constrained regions. Overviews of the Fedorov exchange algorithm (FEA) and other exchange algorithms for the construction of D-optimal designs are given. A faster implementation of the FEA is presented, which is referred to as fast-FEA (denoted FFEA). The FFEA was applied to construct D-optimal designs for several published examples with constrained experimental regions. Designs resulting from the FFEA are more D-efficient than published designs, and provide benchmarks for future comparisons of design construction algorithms. The construction of G-optimal designs for constrained regions is also discussed and illustrated with a published example.

  19. QSPIN: A High Level Java API for Quantum Computing Experimentation (United States)

    Barth, Tim


    QSPIN is a high level Java language API for experimentation in QC models used in the calculation of Ising spin glass ground states and related quadratic unconstrained binary optimization (QUBO) problems. The Java API is intended to facilitate research in advanced QC algorithms such as hybrid quantum-classical solvers, automatic selection of constraint and optimization parameters, and techniques for the correction and mitigation of model and solution errors. QSPIN includes high level solver objects tailored to the D-Wave quantum annealing architecture that implement hybrid quantum-classical algorithms [Booth et al.] for solving large problems on small quantum devices, elimination of variables via roof duality, and classical computing optimization methods such as GPU accelerated simulated annealing and tabu search for comparison. A test suite of documented NP-complete applications ranging from graph coloring, covering, and partitioning to integer programming and scheduling are provided to demonstrate current capabilities.

  20. Introduction to Naval Hydrodynamics using Advanced Computational and Experimental Tools (United States)

    Buchholz, James; Carrica, Pablo; Russell, Jae-Eun; Pontarelli, Matthew; Krebill, Austin; Berdon, Randall


    An undergraduate certificate program in naval hydrodynamics has been recently established at the University of Iowa. Despite several decades of graduate research in this area, this is the first formal introduction to naval hydrodynamics for University of Iowa undergraduate students. Central to the curriculum are two new courses that emphasize open-ended projects conducted in a novel laboratory/learning community that exposes students to advanced tools in computational and experimental fluid mechanics, respectively. Learning is pursued in a loosely-structured environment in which students work in small groups to conduct simulations and experiments relating to resistance, propulsion, and seakeeping using a revised version of the naval hydrodynamics research flow solver, REX, and a small towing tank. Survey responses indicate that the curriculum and course format has strongly increased student interest in naval hydrodynamics and effectively facilitated depth of student learning. This work was supported by the Office of Naval Research under Award Number N00014-15-1-2448.

  1. Dynamics of microtubules: highlights of recent computational and experimental investigations (United States)

    Barsegov, Valeri; Ross, Jennifer L.; Dima, Ruxandra I.


    Microtubules are found in most eukaryotic cells, with homologs in eubacteria and archea, and they have functional roles in mitosis, cell motility, intracellular transport, and the maintenance of cell shape. Numerous efforts have been expended over the last two decades to characterize the interactions between microtubules and the wide variety of microtubule associated proteins that control their dynamic behavior in cells resulting in microtubules being assembled and disassembled where and when they are required by the cell. We present the main findings regarding microtubule polymerization and depolymerization and review recent work about the molecular motors that modulate microtubule dynamics by inducing either microtubule depolymerization or severing. We also discuss the main experimental and computational approaches used to quantify the thermodynamics and mechanics of microtubule filaments.

  2. Helicopter fuselage drag - combined computational fluid dynamics and experimental studies (United States)

    Batrakov, A.; Kusyumov, A.; Mikhailov, S.; Pakhov, V.; Sungatullin, A.; Valeev, M.; Zherekhov, V.; Barakos, G.


    In this paper, wind tunnel experiments are combined with Computational Fluid Dynamics (CFD) aiming to analyze the aerodynamics of realistic fuselage configurations. A development model of the ANSAT aircraft and an early model of the AKTAI light helicopter were employed. Both models were tested at the subsonic wind tunnel of KNRTU-KAI for a range of Reynolds numbers and pitch and yaw angles. The force balance measurements were complemented by particle image velocimetry (PIV) investigations for the cases where the experimental force measurements showed substantial unsteadiness. The CFD results were found to be in fair agreement with the test data and revealed some flow separation at the rear of the fuselages. Once confidence on the CFD method was established, further modifications were introduced to the ANSAT-like fuselage model to demonstrate drag reduction via small shape changes.

  3. Semantics guide infants' vowel learning: Computational and experimental evidence. (United States)

    Ter Schure, S M M; Junge, C M M; Boersma, P P G


    In their first year, infants' perceptual abilities zoom in on only those speech sound contrasts that are relevant for their language. Infants' lexicons do not yet contain sufficient minimal pairs to explain this phonetic categorization process. Therefore, researchers suggested a bottom-up learning mechanism: infants create categories aligned with the frequency distributions of sounds in their input. Recent evidence shows that this bottom-up mechanism may be complemented by the semantic context in which speech sounds occur, such as simultaneously present objects. To test this hypothesis, we investigated whether discrimination of a non-native vowel contrast improves when sounds from the contrast were paired consistently or randomly with two distinct visually presented objects, while the distribution of speech tokens suggested a single broad category. This was assessed in two ways: computationally, namely in a neural network simulation, and experimentally, namely in a group of 8-month-old infants. The neural network, trained with a large set of sound-meaning pairs, revealed that two categories emerge only if sounds are consistently paired with objects. A group of 49 real 8-month-old infants did not immediately show sensitivity to the pairing condition; a later test at 18 months with some of the same infants, however, showed that this sensitivity at 8 months interacted with their vocabulary size at 18 months. This interaction can be explained by the idea that infants with larger future vocabularies are more positively influenced by consistent training (and/or more negatively influenced by inconsistent training) than infants with smaller future vocabularies. This suggests that consistent pairing with distinct visual objects can help infants to discriminate speech sounds even when the auditory information does not signal a distinction. Together our results give computational as well as experimental support for the idea that semantic context plays a role in disambiguating

  4. Experimental and computational studies on a gasifier based stove

    International Nuclear Information System (INIS)

    Varunkumar, S.; Rajan, N.K.S.; Mukunda, H.S.


    Highlights: ► A simple method to calculate the fraction of HHC was devised. ► η g for stove is same as that of a downdraft gasifier. ► Gas from stove contains 5.5% of CH 4 equivalent of HHC. ► Effect of vessel size on utilization efficiency brought out clearly. ► Contribution of radiative heat transfer from char bed to efficiency is 6%. - Abstract: The work reported here is concerned with a detailed thermochemical evaluation of the flaming mode behaviour of a gasifier based stove. Determination of the gas composition over the fuel bed, surface and gas temperatures in the gasification process constitute principal experimental features. A simple atomic balance for the gasification reaction combined with the gas composition from the experiments is used to determine the CH 4 equivalent of higher hydrocarbons and the gasification efficiency (η g ). The components of utilization efficiency, namely, gasification–combustion and heat transfer are explored. Reactive flow computational studies using the measured gas composition over the fuel bed are used to simulate the thermochemical flow field and heat transfer to the vessel; hither-to-ignored vessel size effects in the extraction of heat from the stove are established clearly. The overall flaming mode efficiency of the stove is 50–54%; the convective and radiative components of heat transfer are established to be 45–47 and 5–7% respectively. The efficiency estimates from reacting computational fluid dynamics (RCFD) compare well with experiments.

  5. Experimental demonstration of reservoir computing on a silicon photonics chip (United States)

    Vandoorne, Kristof; Mechet, Pauline; van Vaerenbergh, Thomas; Fiers, Martin; Morthier, Geert; Verstraeten, David; Schrauwen, Benjamin; Dambre, Joni; Bienstman, Peter


    In today’s age, companies employ machine learning to extract information from large quantities of data. One of those techniques, reservoir computing (RC), is a decade old and has achieved state-of-the-art performance for processing sequential data. Dedicated hardware realizations of RC could enable speed gains and power savings. Here we propose the first integrated passive silicon photonics reservoir. We demonstrate experimentally and through simulations that, thanks to the RC paradigm, this generic chip can be used to perform arbitrary Boolean logic operations with memory as well as 5-bit header recognition up to 12.5 Gbit s-1, without power consumption in the reservoir. It can also perform isolated spoken digit recognition. Our realization exploits optical phase for computing. It is scalable to larger networks and much higher bitrates, up to speeds >100 Gbit s-1. These results pave the way for the application of integrated photonic RC for a wide range of applications.

  6. Mutations that Cause Human Disease: A Computational/Experimental Approach

    Energy Technology Data Exchange (ETDEWEB)

    Beernink, P; Barsky, D; Pesavento, B


    can be used to understand how an amino acid change affects the protein. The experimental methods that provide the most detailed structural information on proteins are X-ray crystallography and NMR spectroscopy. However, these methods are labor intensive and currently cannot be carried out on a genomic scale. Nonetheless, Structural Genomics projects are being pursued by more than a dozen groups and consortia worldwide and as a result the number of experimentally determined structures is rising exponentially. Based on the expectation that protein structures will continue to be determined at an ever-increasing rate, reliable structure prediction schemes will become increasingly valuable, leading to information on protein function and disease for many different proteins. Given known genetic variability and experimentally determined protein structures, can we accurately predict the effects of single amino acid substitutions? An objective assessment of this question would involve comparing predicted and experimentally determined structures, which thus far has not been rigorously performed. The completed research leveraged existing expertise at LLNL in computational and structural biology, as well as significant computing resources, to address this question.

  7. Multi-scale multi-physics computational chemistry simulation based on ultra-accelerated quantum chemical molecular dynamics method for structural materials in boiling water reactor

    International Nuclear Information System (INIS)

    Miyamoto, Akira; Sato, Etsuko; Sato, Ryo; Inaba, Kenji; Hatakeyama, Nozomu


    In collaboration with experimental experts we have reported in the present conference (Hatakeyama, N. et al., “Experiment-integrated multi-scale, multi-physics computational chemistry simulation applied to corrosion behaviour of BWR structural materials”) the results of multi-scale multi-physics computational chemistry simulations applied to the corrosion behaviour of BWR structural materials. In macro-scale, a macroscopic simulator of anode polarization curve was developed to solve the spatially one-dimensional electrochemical equations on the material surface in continuum level in order to understand the corrosion behaviour of typical BWR structural material, SUS304. The experimental anode polarization behaviours of each pure metal were reproduced by fitting all the rates of electrochemical reactions and then the anode polarization curve of SUS304 was calculated by using the same parameters and found to reproduce the experimental behaviour successfully. In meso-scale, a kinetic Monte Carlo (KMC) simulator was applied to an actual-time simulation of the morphological corrosion behaviour under the influence of an applied voltage. In micro-scale, an ultra-accelerated quantum chemical molecular dynamics (UA-QCMD) code was applied to various metallic oxide surfaces of Fe 2 O 3 , Fe 3 O 4 , Cr 2 O 3 modelled as same as water molecules and dissolved metallic ions on the surfaces, then the dissolution and segregation behaviours were successfully simulated dynamically by using UA-QCMD. In this paper we describe details of the multi-scale, multi-physics computational chemistry method especially the UA-QCMD method. This method is approximately 10,000,000 times faster than conventional first-principles molecular dynamics methods based on density-functional theory (DFT), and the accuracy was also validated for various metals and metal oxides compared with DFT results. To assure multi-scale multi-physics computational chemistry simulation based on the UA-QCMD method for

  8. Planning Committee for a National Resource for Computation in Chemistry. Final report, October 1, 1974--June 30, 1977

    International Nuclear Information System (INIS)


    The Planning Committee for a National Resource for Computation in Chemistry (NRCC) was charged with the responsibility of formulating recommendations regarding organizational structure for an NRCC including the composition, size, and responsibilities of its policy board, the relationship of such a board to the operating structure of the NRCC, to federal funding agencies, and to user groups; desirable priorities, growth rates, and levels of operations for the first several years; and facilities, access and site requirements for such a Resource. By means of site visits, questionnaires, and a workshop, the Committee sought advice from a wide range of potential users and organizations interested in chemical computation. Chemical kinetics, crystallography, macromolecular science, nonnumerical methods, physical organic chemistry, quantum chemistry, and statistical mechanics are covered

  9. Planning Committee for a National Resource for Computation in Chemistry. Final report, October 1, 1974--June 30, 1977

    Energy Technology Data Exchange (ETDEWEB)

    Bigeleisen, Jacob; Berne, Bruce J.; Coton, F. Albert; Scheraga, Harold A.; Simmons, Howard E.; Snyder, Lawrence C.; Wiberg, Kenneth B.; Wipke, W. Todd


    The Planning Committee for a National Resource for Computation in Chemistry (NRCC) was charged with the responsibility of formulating recommendations regarding organizational structure for an NRCC including the composition, size, and responsibilities of its policy board, the relationship of such a board to the operating structure of the NRCC, to federal funding agencies, and to user groups; desirable priorities, growth rates, and levels of operations for the first several years; and facilities, access and site requirements for such a Resource. By means of site visits, questionnaires, and a workshop, the Committee sought advice from a wide range of potential users and organizations interested in chemical computation. Chemical kinetics, crystallography, macromolecular science, nonnumerical methods, physical organic chemistry, quantum chemistry, and statistical mechanics are covered.

  10. Computationally efficient implementation of combustion chemistry using in situ adaptive tabulation (United States)

    Pope, S. B.


    A computational technique is described and demonstrated that can decrease by three orders of magnitude the computer time required to treat detailed chemistry in reactive flow calculations. The method is based on the in situ adaptive tabulation (ISAT) of the accessed region of the composition space - the adaptation being to control the tabulation errors. Test calculations are performed for non-premixed methane - air combustion in a statistically-homogeneous turbulent reactor, using a kinetic mechanism with 16 species and 41 reactions. The results show excellent control of the tabulation errors with respect to a specified error tolerance; and a speed-up factor of about 1000 is obtained compared to the direct approach of numerically integrating the reaction equations. In the context of PDF methods, the ISAT technique makes feasible the use of detailed kinetic mechanisms in calculations of turbulent combustion. The technique can also be used with reduced mechanisms, and in other approaches for calculating reactive flows (e.g. finite difference methods).


    Energy Technology Data Exchange (ETDEWEB)

    Paul C.K. Lam; Isaac K. Gamwo; Dimitri Gidaspow


    The objective of this study was to develop a predictive experimentally verified computational fluid dynamics (CFD) model for gas-liquid-solid flow. A three dimensional transient computer code for the coupled Navier-Stokes equations for each phase was developed and is appended in this report. The principal input into the model is the viscosity of the particulate phase which was determined from a measurement of the random kinetic energy of the 800 micron glass beads and a Brookfield viscometer. The details are presented in the attached paper titled ''CFD Simulation of Flow and Turbulence in a Slurry Bubble Column''. This phase of the work is in press in a referred journal (AIChE Journal, 2002) and was presented at the Fourth International Conference on Multiphase Flow (ICMF 2001) in New Orleans, May 27-June 1, 2001 (Paper No. 909). The computed time averaged particle velocities and concentrations agree with Particle Image Velocimetry (PIV) measurements of velocities and concentrations, obtained using a combination of gamma-ray and X-ray densitometers, in a slurry bubble column, operated in the bubbly-coalesced fluidization regime with continuous flow of water. Both the experiment and the simulation show a down-flow of particles in the center of the column and up-flow near the walls and nearly uniform particle concentration. Normal and shear Reynolds stresses were constructed from the computed instantaneous particle velocities. The PIV measurement and the simulation produced instantaneous particle velocities. The PIV measurement and the simulation produced similar nearly flat horizontal profiles of turbulent kinetic energy of particles. To better understand turbulence we studied fluidization in a liquid-solid bed. This work was also presented at the Fourth International Conference on Multiphase Flow (ICMF 2001, Paper No. 910). To understand turbulence in risers, measurements were done in the IIT riser with 530 micron glass beads using a PIV

  12. Solutions, Unit 5: Colligative Properties of Solutions. A Computer-Enriched Module for Introductory Chemistry. Student's Guide and Teacher's Guide. (United States)

    Bader, Morris

    Presented are the teacher's guide and student manual for one of a series of self-instructional, computer-based learning modules for an introductory, undergraduate chemistry course. The student manual for this unit on the colligative properties of solutions includes objectives, prerequisites, pretest, discussion, and 20 problem sets. Included in…

  13. Introductory Molecular Orbital Theory: An Honors General Chemistry Computational Lab as Implemented Using Three-Dimensional Modeling Software (United States)

    Ruddick, Kristie R.; Parrill, Abby L.; Petersen, Richard L.


    In this study, a computational molecular orbital theory experiment was implemented in a first-semester honors general chemistry course. Students used the GAMESS (General Atomic and Molecular Electronic Structure System) quantum mechanical software (as implemented in ChemBio3D) to optimize the geometry for various small molecules. Extended Huckel…


    In this chapter we review the literature on scanning probe microscopy (SPM), virtual reality (VR), and computational chemistry and our earlier work dealing with modeling lignin, lignin-carbohydrate complexes (LCC), humic substances (HSs) and non-bonded organo-mineral interactions...

  15. Computação em química teórica: informações técnicas Computation in theoretical chemistry: technical informations

    Directory of Open Access Journals (Sweden)

    Nelson Henrique Morgon


    Full Text Available The purpose of this work is to demonstrate the usefulness of low cost high performance computers. It is presented technics and software packages used by computational chemists. Access to high-performance computing power remains crucial for many computational quantum chemistry. So, this work introduces the concept of PC cluster, an economical computing plataform.

  16. Experimental study on iodine chemistry (EXSI) - Containment experiments with methyl iodide

    Energy Technology Data Exchange (ETDEWEB)

    Holm, J.; Ekberg, C. (Chalmers Univ. of Technology, Goeteborg (Sweden)); Kaerkelae, T.; Auvinen, A. (VTT, Espoo (Finland)); Glaenneskog, H. (Vattenfall Power Consultant, Goeteborg (Sweden))


    An experimental study on radiolytic decomposition of methyl iodide was conducted in co-operation between VTT and Chalmers University of Technology as a part of the NKS-R programs. In year 2008 the NROI project, a Nordic collaboration studying iodine chemistry in the containment, was started. During year 2008 (NROI-1) the radiolytic oxidation of elemental iodine was investigated and during 2009 (NROI-2), the radiolytic oxidation of organic iodine was studied. This project (NROI-3) is a continuation of the investigation of the oxidation of organic iodine. The project has been divided into two parts. 1. The aims of the first part were to investigate the effect of ozone and UV-radiation, in dry and humid conditions, on methyl iodide. 2. The second project was about gamma radiation (approx20 kGy/h) and methyl iodide in dry and humid conditions. 1. Experimental results showed that the methyl iodide concentration in the facility was reduced with increasing temperature and increasing UV-radiation intensity. Similar behaviour occurred when ozone was present in the system. Formed organic gas species during the decomposition of methyl iodide was mainly formaldehyde and methanol. The particle formation was instant and extensive when methyl iodide was exposed to ozone and/or radiation at all temperatures. The size of the formed primary particles was about 10 nm and the size of secondary particles was between 50-200 nm. From the SEM-EDX analyses of the particles, the conclusion was drawn that these were some kind of iodine oxides (I{sub xO{sub y}). However, the correct speciation of the formed particles was difficult to obtain because the particles melted and fused together under the electron beam. 2. The results from this sub-project are more inconsistent and hard to interpret. The particle formation was significant lesser than corresponding experiments when ozone/UV-radiation was used instead of gamma radiation. The transport of gaseous methyl iodide through the facility was

  17. Positronium chemistry

    CERN Document Server

    Green, James


    Positronium Chemistry focuses on the methodologies, reactions, processes, and transformations involved in positronium chemistry. The publication first offers information on positrons and positronium and experimental methods, including mesonic atoms, angular correlation measurements, annihilation spectra, and statistical errors in delayed coincidence measurements. The text then ponders on positrons in gases and solids. The manuscript takes a look at the theoretical chemistry of positronium and positronium chemistry in gases. Topics include quenching, annihilation spectrum, delayed coincidence

  18. Improving Students' Understanding of Molecular Structure through Broad-Based Use of Computer Models in the Undergraduate Organic Chemistry Lecture (United States)

    Springer, Michael T.


    Several articles suggest how to incorporate computer models into the organic chemistry laboratory, but relatively few papers discuss how to incorporate these models broadly into the organic chemistry lecture. Previous research has suggested that "manipulating" physical or computer models enhances student understanding; this study…

  19. NWFSC OA facility water chemistry - Ocean acidification species exposure experimental facility (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — We have developed a unique facility for conducting high-quality experiments on marine organisms in seawater with controlled carbon chemistry conditions. The...

  20. Computational Optimization of a Natural Laminar Flow Experimental Wing Glove (United States)

    Hartshom, Fletcher


    Computational optimization of a natural laminar flow experimental wing glove that is mounted on a business jet is presented and discussed. The process of designing a laminar flow wing glove starts with creating a two-dimensional optimized airfoil and then lofting it into a three-dimensional wing glove section. The airfoil design process does not consider the three dimensional flow effects such as cross flow due wing sweep as well as engine and body interference. Therefore, once an initial glove geometry is created from the airfoil, the three dimensional wing glove has to be optimized to ensure that the desired extent of laminar flow is maintained over the entire glove. TRANAIR, a non-linear full potential solver with a coupled boundary layer code was used as the main tool in the design and optimization process of the three-dimensional glove shape. The optimization process uses the Class-Shape-Transformation method to perturb the geometry with geometric constraints that allow for a 2-in clearance from the main wing. The three-dimensional glove shape was optimized with the objective of having a spanwise uniform pressure distribution that matches the optimized two-dimensional pressure distribution as closely as possible. Results show that with the appropriate inputs, the optimizer is able to match the two dimensional pressure distributions practically across the entire span of the wing glove. This allows for the experiment to have a much higher probability of having a large extent of natural laminar flow in flight.

  1. Experimental and computational prediction of glass transition temperature of drugs. (United States)

    Alzghoul, Ahmad; Alhalaweh, Amjad; Mahlin, Denny; Bergström, Christel A S


    Glass transition temperature (Tg) is an important inherent property of an amorphous solid material which is usually determined experimentally. In this study, the relation between Tg and melting temperature (Tm) was evaluated using a data set of 71 structurally diverse druglike compounds. Further, in silico models for prediction of Tg were developed based on calculated molecular descriptors and linear (multilinear regression, partial least-squares, principal component regression) and nonlinear (neural network, support vector regression) modeling techniques. The models based on Tm predicted Tg with an RMSE of 19.5 K for the test set. Among the five computational models developed herein the support vector regression gave the best result with RMSE of 18.7 K for the test set using only four chemical descriptors. Hence, two different models that predict Tg of drug-like molecules with high accuracy were developed. If Tm is available, a simple linear regression can be used to predict Tg. However, the results also suggest that support vector regression and calculated molecular descriptors can predict Tg with equal accuracy, already before compound synthesis.

  2. Computational and Experimental Investigations of Flow past Spinning Cylinders (United States)

    Mehmedagic, Igbal; Buckley, Liam; Carlucci, Pasquale; Carlucci, Donald; Aljalis, Elias; Thangam, Siva; Stevens-Ardec Collaboration


    An anisotropic two-equation Reynolds-stress model is developed by considering the modifications to the energy spectrum and through invariance based scaling. In this approach the effect of rotation is used to modify the energy spectrum, while the influence of swirl is modeled based on scaling laws. The resulting generalized model is validated for benchmark turbulent flows with swirl and curvature. The time-averaged equations of motion and energy are solved using the modeled form of transport equations for the turbulence kinetic energy and the scalar form of turbulence dissipation with an efficient finite-volume algorithm. Computations for flow past an axially rotating cylinder with a free-spinning base are performed along with experiments for a range of spin rates and free stream flow conditions. A subsonic wind tunnel with a forward-sting mounted spinning cylinder is used for experiments. The experimental results of Carlucci & Thangam (2001) are used to benchmark flow over spinning cylinders. The data is extended to munitions spinning in the wake of other munitions and applications involving the design of projectiles are discussed. This work was funded in part by U. S. Army ARDEC.

  3. Experimental validation of a computer simulation of radiographic film

    Energy Technology Data Exchange (ETDEWEB)

    Goncalves, Elicardo A. de S., E-mail: [Instituto Federal do Rio de Janeiro (IFRJ), Paracambi, RJ (Brazil). Laboratorio de Instrumentacao e Simulacao Computacional Cientificas Aplicadas; Azeredo, Raphaela, E-mail: [Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, RJ (Brazil). Instituto de Fisica Armando Dias Tavares. Programa de Pos-Graduacao em Fisica; Assis, Joaquim T., E-mail: [Universidade do Estado do Rio de Janeiro (UERJ), Nova Friburgo, RJ (Brazil). Instituto Politecnico; Anjos, Marcelino J. dos; Oliveira, Davi F.; Oliveira, Luis F. de, E-mail:, E-mail:, E-mail: [Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, RJ (Brazil). Instituto de Fisica Armando Dias Tavares. Departamento de Fisica Aplicada e Termodinamica


    In radiographic films, the behavior of characteristic curve is very important for the image quality. Digitization/visualization are always performed by light transmission and the characteristic curve is known as a behavior of optical density in function of exposure. In a first approach, in a Monte-Carlo computer simulation trying to build a Hurter-Driffield curve by a stochastic model, the results showed the same known shape, but some behaviors, like the influence of silver grain size, are not expected. A real H and D curve was build exposing films, developing and measuring the optical density. When comparing model results with a real curve, trying to fit them and estimating some parameters, a difference in high exposure region shows a divergence between the models and the experimental data. Since the optical density is a function of metallic silver generated by chemical development, direct proportion was considered, but the results suggests a limitation in this proportion. In fact, when the optical density was changed by another way to measure silver concentration, like x-ray fluorescence, the new results agree with the models. Therefore, overexposed films can contain areas with different silver concentrations but it can't be seen due to the fact that optical density measurement is limited. Mapping the silver concentration in the film area can be a solution to reveal these dark images, and x-ray fluorescence has shown to be the best way to perform this new way to digitize films. (author)

  4. Magnetic circular dichroism of chlorofullerenes: Experimental and computational study

    Czech Academy of Sciences Publication Activity Database

    Štěpánek, Petr; Straka, Michal; Šebestík, Jaroslav; Bouř, Petr


    Roč. 647, Mar (2016), s. 117-121 ISSN 0009-2614 R&D Projects: GA ČR GA13-03978S; GA ČR(CZ) GA14-03564S Institutional support: RVO:61388963 Keywords : chlorofullerenes * magnetic circular dichroism * density functional theory Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.815, year: 2016

  5. Web-based computational chemistry education with CHARMMing III: Reduction potentials of electron transfer proteins.

    Directory of Open Access Journals (Sweden)

    B Scott Perrin


    Full Text Available A module for fast determination of reduction potentials, E°, of redox-active proteins has been implemented in the CHARMM INterface and Graphics (CHARMMing web portal ( The free energy of reduction, which is proportional to E°, is composed of an intrinsic contribution due to the redox site and an environmental contribution due to the protein and solvent. Here, the intrinsic contribution is selected from a library of pre-calculated density functional theory values for each type of redox site and redox couple, while the environmental contribution is calculated from a crystal structure of the protein using Poisson-Boltzmann continuum electrostatics. An accompanying lesson demonstrates a calculation of E°. In this lesson, an ionizable residue in a [4Fe-4S]-protein that causes a pH-dependent E° is identified, and the E° of a mutant that would test the identification is predicted. This demonstration is valuable to both computational chemistry students and researchers interested in predicting sequence determinants of E° for mutagenesis.

  6. Recent developments in computer vision-based analytical chemistry: A tutorial review. (United States)

    Capitán-Vallvey, Luis Fermín; López-Ruiz, Nuria; Martínez-Olmos, Antonio; Erenas, Miguel M; Palma, Alberto J


    Chemical analysis based on colour changes recorded with imaging devices is gaining increasing interest. This is due to its several significant advantages, such as simplicity of use, and the fact that it is easily combinable with portable and widely distributed imaging devices, resulting in friendly analytical procedures in many areas that demand out-of-lab applications for in situ and real-time monitoring. This tutorial review covers computer vision-based analytical (CVAC) procedures and systems from 2005 to 2015, a period of time when 87.5% of the papers on this topic were published. The background regarding colour spaces and recent analytical system architectures of interest in analytical chemistry is presented in the form of a tutorial. Moreover, issues regarding images, such as the influence of illuminants, and the most relevant techniques for processing and analysing digital images are addressed. Some of the most relevant applications are then detailed, highlighting their main characteristics. Finally, our opinion about future perspectives is discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Chemistry for Kids: Generating Carbon Dioxide in Elementary School Chemistry and Using a Computer To Write about It. (United States)

    Schlenker, Richard M.; Yoshida, Sarah

    This material describes an activity using vinegar and baking soda to generate carbon dioxide, and writing a report using the Appleworks word processing program for grades 3 to 8 students. Time requirement, relevant process skills, vocabulary, mathematics skills, computer skills, and materials are listed. Activity procedures including class…

  8. Quantum-Enhanced Cyber Security: Experimental Computation on Quantum-Encrypted Data (United States)


    AFRL-AFOSR-UK-TR-2017-0020 Quantum -Enhanced Cyber Security: Experimental Computation on Quantum -Encrypted Data Philip Walther UNIVERSITT WIEN Final...REPORT TYPE Final 3. DATES COVERED (From - To) 15 Oct 2015 to 31 Dec 2016 4. TITLE AND SUBTITLE Quantum -Enhanced Cyber Security: Experimental Computation ...project developed methods and technologies are necessary prerequisites for performing experimental quantum computations with quantum -encrypted data. Even

  9. Computational and experimental study of copper–gold nitride formation

    International Nuclear Information System (INIS)

    Ponce-Cázares, I.; Soto, G.; Moreno-Armenta, Ma. Guadalupe; De la Cruz, W.


    Highlights: • The new Cu 3 Au-nitride compound was successfully grown by the sputtering method. • This material is Cu 3 Au 0.5 N with cubic system (Pm3m space group), where the gold randomly occupies half of the 1a Wyckoff sites. • The material was a pseudo-gap conductor with conductance as good as a heavily-doped semiconductor at room temperature. - Abstract: This work investigates the formation of a Cu 3 Au-nitride alloy using experimental and computational methods. For this purpose, we prepared a custom-made Cu–Au target and then hit it with argon ions in the presence of molecular nitrogen that produced a film on Corning glass. This film was analyzed using spectroscopic and diffraction techniques. The four-point-probe method and Tauc plots were applied to determine the electrical and optical properties of this thin film. Using first principle calculations a structural model was constructed that validated our observations. The crystalline system that we used was cubic (Pm3m space group) with half the sites filled with Au randomly. The composition was close to Cu 3 Au 0.5 N. In agreement with the electrical measurements and calculations, the Cu 3 Au 0.5 N band structure was highly affected by the Au incorporation since the electrical resistance and carrier density were in the 10 −3 Ω cm and 10 22 cm −3 ranges, respectively, and the optical gap decreased 0.61 eV with respect to the Cu 3 N. The material was a pseudo-gap conductor with conductance as good as a heavily-doped semiconductor at room temperature; this should give it great potential for use in the optoelectronics industry

  10. Computational and experimental study of copper–gold nitride formation

    Energy Technology Data Exchange (ETDEWEB)

    Ponce-Cázares, I., E-mail: [Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Carretera Tijuana-Ensenada No. 3918, A. Postal 360, 22860 Ensenada, B.C. (Mexico); Soto, G., E-mail: [Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, Km. 107 Carretera Tijuana-Ensenada, C.P. 22860 Ensenada, B.C. (Mexico); Moreno-Armenta, Ma. Guadalupe, E-mail: [Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, Km. 107 Carretera Tijuana-Ensenada, C.P. 22860 Ensenada, B.C. (Mexico); De la Cruz, W., E-mail: [Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, Km. 107 Carretera Tijuana-Ensenada, C.P. 22860 Ensenada, B.C. (Mexico)


    Highlights: • The new Cu{sub 3}Au-nitride compound was successfully grown by the sputtering method. • This material is Cu{sub 3}Au{sub 0.5}N with cubic system (Pm3m space group), where the gold randomly occupies half of the 1a Wyckoff sites. • The material was a pseudo-gap conductor with conductance as good as a heavily-doped semiconductor at room temperature. - Abstract: This work investigates the formation of a Cu{sub 3}Au-nitride alloy using experimental and computational methods. For this purpose, we prepared a custom-made Cu–Au target and then hit it with argon ions in the presence of molecular nitrogen that produced a film on Corning glass. This film was analyzed using spectroscopic and diffraction techniques. The four-point-probe method and Tauc plots were applied to determine the electrical and optical properties of this thin film. Using first principle calculations a structural model was constructed that validated our observations. The crystalline system that we used was cubic (Pm3m space group) with half the sites filled with Au randomly. The composition was close to Cu{sub 3}Au{sub 0.5}N. In agreement with the electrical measurements and calculations, the Cu{sub 3}Au{sub 0.5}N band structure was highly affected by the Au incorporation since the electrical resistance and carrier density were in the 10{sup −3} Ω cm and 10{sup 22} cm{sup −3} ranges, respectively, and the optical gap decreased 0.61 eV with respect to the Cu{sub 3}N. The material was a pseudo-gap conductor with conductance as good as a heavily-doped semiconductor at room temperature; this should give it great potential for use in the optoelectronics industry.

  11. The use of domestic microwave oven in experimental classes of organic chemistry: salicylaldehyde nitration

    International Nuclear Information System (INIS)

    Teixeira, Eurides Francisco; Santos, Ana Paula Bernardo dos; Bastos, Renato Saldanha; Pinto, Angelo C.


    The use of microwave in chemistry has known benefits over conventional heating methods, e.g. reduced reaction times, chemical yield improvement and the possibility if reducing or eliminating the use of organic solvents. We describe herein a procedure for the nitration of salicylaldehyde in water using a domestic microwave oven, which can be used as an experiment in the undergraduate chemistry laboratory. The experiment involves safe and rapid preparation and identification of the position isomers by thin layer chromatography and 1 H NMR, or by their melting points. (author)

  12. Fully Automated Quantum-Chemistry-Based Computation of Spin-Spin-Coupled Nuclear Magnetic Resonance Spectra. (United States)

    Grimme, Stefan; Bannwarth, Christoph; Dohm, Sebastian; Hansen, Andreas; Pisarek, Jana; Pracht, Philipp; Seibert, Jakob; Neese, Frank


    We present a composite procedure for the quantum-chemical computation of spin-spin-coupled 1 H NMR spectra for general, flexible molecules in solution that is based on four main steps, namely conformer/rotamer ensemble (CRE) generation by the fast tight-binding method GFN-xTB and a newly developed search algorithm, computation of the relative free energies and NMR parameters, and solving the spin Hamiltonian. In this way the NMR-specific nuclear permutation problem is solved, and the correct spin symmetries are obtained. Energies, shielding constants, and spin-spin couplings are computed at state-of-the-art DFT levels with continuum solvation. A few (in)organic and transition-metal complexes are presented, and very good, unprecedented agreement between the theoretical and experimental spectra was achieved. The approach is routinely applicable to systems with up to 100-150 atoms and may open new avenues for the detailed (conformational) structure elucidation of, for example, natural products or drug molecules. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  13. Synthesis, Reduction Chemistry, and Spectroscopic and Computational Studies of Isomeric Quinolinecarboxaldehyde Triosmium Clusters

    Czech Academy of Sciences Publication Activity Database

    Rosenberg, E.; Rokhsana, D.; Nervi, C.; Gobetto, R.; Milone, L.; Viale, A.; Fiedler, Jan; Botavina, M. A.


    Roč. 23, - (2004), s. 215-223 ISSN 0276-7333 R&D Projects: GA ČR GA203/03/0821; GA MŠk OC D15.10 Institutional research plan: CEZ:AV0Z4040901 Keywords : organometallic chemistry * radical-anions * density Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.196, year: 2004

  14. Minimum Learning Essentials: Science. Chemistry, Earth Science, Biology, Physics, General Science. Experimental Edition 0/4. (United States)

    New York City Board of Education, Brooklyn, NY. Div. of Curriculum and Instruction.

    This guide presents the "minimum teaching essentials" published by the New York City Board of Education, for science education in grades 9-12. Covered are: biology, physics, earth science, and chemistry. Work study skills for all subjects are given with content areas, performance objectives, and suggested classroom activities. (APM)

  15. The Development and Assessment of an Experimental Teacher Training Program for Beginning Graduate Assistants in Chemistry. (United States)

    Murphy, Michael D.

    In this study a training program for new teaching assistants in freshman chemistry was developed and assessed. All new assistants in the Freshman Division were assigned by a stratified random technique to either the control or treatment group, with the latter receiving inservice training in the skills of teaching recitation classes. This training…

  16. Energy-resolved computed tomography: first experimental results

    International Nuclear Information System (INIS)

    Shikhaliev, Polad M


    First experimental results with energy-resolved computed tomography (CT) are reported. The contrast-to-noise ratio (CNR) in CT has been improved with x-ray energy weighting for the first time. Further, x-ray energy weighting improved the CNR in material decomposition CT when applied to CT projections prior to dual-energy subtraction. The existing CT systems use an energy (charge) integrating x-ray detector that provides a signal proportional to the energy of the x-ray photon. Thus, the x-ray photons with lower energies are scored less than those with higher energies. This underestimates contribution of lower energy photons that would provide higher contrast. The highest CNR can be achieved if the x-ray photons are scored by a factor that would increase as the x-ray energy decreases. This could be performed by detecting each x-ray photon separately and measuring its energy. The energy selective CT data could then be saved, and any weighting factor could be applied digitally to a detected x-ray photon. The CT system includes a photon counting detector with linear arrays of pixels made from cadmium zinc telluride (CZT) semiconductor. A cylindrical phantom with 10.2 cm diameter made from tissue-equivalent material was used for CT imaging. The phantom included contrast elements representing calcifications, iodine, adipose and glandular tissue. The x-ray tube voltage was 120 kVp. The energy selective CT data were acquired, and used to generate energy-weighted and material-selective CT images. The energy-weighted and material decomposition CT images were generated using a single CT scan at a fixed x-ray tube voltage. For material decomposition the x-ray spectrum was digitally spilt into low- and high-energy parts and dual-energy subtraction was applied. The x-ray energy weighting resulted in CNR improvement of calcifications and iodine by a factor of 1.40 and 1.63, respectively, as compared to conventional charge integrating CT. The x-ray energy weighting was also applied

  17. Experimental study on controls on fluid chemistry and permeability evolution during serpentinization reactions (United States)

    Farough, A.; Moore, D. E.; Lockner, D. A.; Lowell, R. P.


    Serpentinization plays a key role in hydrothermal processes and structural deformation at slow and ultraslow mid-ocean ridges, where it is commonly associated with the formation of oceanic core complexes and detachment faults. Many details of how serpentinization reactions progress at small scales and the links between the reactions and changes in permeability and stresses are poorly understood. To advance our understanding of the evolution of permeability and fluid chemistry accompanying serpentinization reactions and provide a framework for developing more realistic models at a larger scale, we performed a series of high-temperature permeability experiments on fractured solid ultramafic rock samples that reasonably simulate serpentinization in natural settings. Experimental conditions were 260°C, 50 MPa confining pressure, and 20×2 MPa pore pressure. Ultramafic rock types containing different proportions of olivine and pyroxene were tested, to investigate the effect of mineral assemblage on fluid-rock interaction and permeability. Samples were cylindrical cores of 18 mm diameter and 23 mm length that were split axially to form a well-mated tensile fracture, jacketed in a 0.5 mm thick teflon liner and inserted into a 0.4 mm thick annealed silver jacket. A 7.5 mm thick layer of the same rock, crushed and sieved (0.18-1.0 mm size range) was placed on the inlet side of the sample to produce a coarse-grained gouge. The gouge layer provided a heated fluid reservoir with which the deionized water, used as pore fluid, could equilibrate before entering the fracture. Routinely, about 1 cm3 of water was pumped through the sample each day and collected (without dropping sample pore pressure) for chemical analysis. Pore fluid flow was in one direction and the pore pressure change and flow rate were recorded to determine permeability. In most samples, the initial fracture permeability at 260°C was between 10-15 and 10-18 m2, and decreased by about 3 orders of magnitude in

  18. Characterization of sodium stibogluconate by online liquid separation cell technology monitored by ICPMS and ESMS and computational chemistry

    DEFF Research Database (Denmark)

    Hansen, Helle Rusz; Hansen, Claus; Kepp, Kasper Planeta


    High-performance liquid chromatography (HPLC), mass spectrometry (MS), and computational chemistry has been applied to resolve the composition and structure of the Sb species present in dilutions of Pentostam, a first-line treatment drug against Leishmania parasites. Using HPLC-inductively coupled...... functional theory was used to study the structure of the 1:1 Sb-gluconate complex with three or four solvent molecules bound. By computing the structures and the free energies of the various possible isomers in aqueous solvation models, the most likely structures of the species were deduced. Importantly, 6...

  19. Real-World Experimentation Comparing Time-Sharing and Batch Processing in Teaching Computer Science, (United States)

    effectiveness of time-sharing and batch processing in teaching computer science . The experimental design was centered on direct, ’real world’ comparison...ALGOL). The experimental sample involved all introductory computer science courses with a total population of 415 cadets. The results generally

  20. A computational chemistry investigation of the mechanism of the water-assisted decomposition of trichloroethylene oxide. (United States)

    Huang, Jinqing; Yeung, Chi Shun; Ma, Jiani; Gayner, Emma R; Phillips, David Lee


    Trichloroethylene oxide is a downstream product in the oxidative metabolism of trichloroethylene (TCE) and it may be involved in cytochrome P450 inactivation, protein function destruction, and nucleic acid base alkalization. To explore the hydrolysis mechanism of the decomposition of TCE oxide, an investigation using Second-order Møller-Plesset perturbation theory in conjunction with density functional theory has been conducted to analyze the effect of the water solvation shell on probable reaction steps. The decomposition of TCE oxide is accelerated by coordinated water molecules (up to seven), which reveals that water molecules can help to solvate the TCE oxide molecule and activate the release of the Cl(-) leaving group. After the opening of the epoxide ring, several pathways are proposed to account for the dehalogenation step along with the formation of CO as well as three carboxylic acids (formic acid, glyoxylic acid, and dichloroacetic acid). The predominant pathways were examined by comparing the computed activation energies for the formation of the products to each other for the possible reaction steps examined in this work. After rationally analyzing the computational results, the ring-opening reaction has been identified as the rate-determining step. The rate constant estimated for the TCE oxide decomposition from the calculations performed here was found to be reasonably consistent with previous experimental observations reported in the literature.

  1. Experimental Blind Quantum Computing for a Classical Client. (United States)

    Huang, He-Liang; Zhao, Qi; Ma, Xiongfeng; Liu, Chang; Su, Zu-En; Wang, Xi-Lin; Li, Li; Liu, Nai-Le; Sanders, Barry C; Lu, Chao-Yang; Pan, Jian-Wei


    To date, blind quantum computing demonstrations require clients to have weak quantum devices. Here we implement a proof-of-principle experiment for completely classical clients. Via classically interacting with two quantum servers that share entanglement, the client accomplishes the task of having the number 15 factorized by servers who are denied information about the computation itself. This concealment is accompanied by a verification protocol that tests servers' honesty and correctness. Our demonstration shows the feasibility of completely classical clients and thus is a key milestone towards secure cloud quantum computing.

  2. Experimental quantum computing to solve systems of linear equations. (United States)

    Cai, X-D; Weedbrook, C; Su, Z-E; Chen, M-C; Gu, Mile; Zhu, M-J; Li, Li; Liu, Nai-Le; Lu, Chao-Yang; Pan, Jian-Wei


    Solving linear systems of equations is ubiquitous in all areas of science and engineering. With rapidly growing data sets, such a task can be intractable for classical computers, as the best known classical algorithms require a time proportional to the number of variables N. A recently proposed quantum algorithm shows that quantum computers could solve linear systems in a time scale of order log(N), giving an exponential speedup over classical computers. Here we realize the simplest instance of this algorithm, solving 2×2 linear equations for various input vectors on a quantum computer. We use four quantum bits and four controlled logic gates to implement every subroutine required, demonstrating the working principle of this algorithm.

  3. The computer as crucible an introduction to experimental mathematics

    CERN Document Server

    Borwein, Jonathan


    Keith Devlin and Jonathan Borwein, two well-known mathematicians with expertise in different mathematical specialties but with a common interest in experimentation in mathematics, have joined forces to create this introduction to experimental mathematics. They cover a variety of topics and examples to give the reader a good sense of the current state of play in the rapidly growing new field of experimental mathematics. The writing is clear and the explanations are enhanced by relevant historical facts and stories of mathematicians and their encounters with the field over time.

  4. Dicopper(II) metallacyclophanes as multifunctional magnetic devices: a joint experimental and computational study. (United States)

    Castellano, María; Ruiz-García, Rafael; Cano, Joan; Ferrando-Soria, Jesús; Pardo, Emilio; Fortea-Pérez, Francisco R; Stiriba, Salah-Eddine; Julve, Miguel; Lloret, Francesc


    Metallosupramolecular complexes constitute an important advance in the emerging fields of molecular spintronics and quantum computation and a useful platform in the development of active components of spintronic circuits and quantum computers for applications in information processing and storage. The external control of chemical reactivity (electro- and photochemical) and physical properties (electronic and magnetic) in metallosupramolecular complexes is a current challenge in supramolecular coordination chemistry, which lies at the interface of several other supramolecular disciplines, including electro-, photo-, and magnetochemistry. The specific control of current flow or spin delocalization through a molecular assembly in response to one or many input signals leads to the concept of developing a molecule-based spintronics that can be viewed as a potential alternative to the classical molecule-based electronics. A great variety of factors can influence over these electronically or magnetically coupled, metallosupramolecular complexes in a reversible manner, electronic or photonic external stimuli being the most promising ones. The response ability of the metal centers and/or the organic bridging ligands to the application of an electric field or light irradiation, together with the geometrical features that allow the precise positioning in space of substituent groups, make these metal-organic systems particularly suitable to build highly integrated molecular spintronic circuits. In this Account, we describe the chemistry and physics of dinuclear copper(II) metallacyclophanes with oxamato-containing dinucleating ligands featuring redox- and photoactive aromatic spacers. Our recent works on dicopper(II) metallacyclophanes and earlier ones on related organic cyclophanes are now compared in a critical manner. Special focus is placed on the ligand design as well as in the combination of experimental and computational methods to demonstrate the multifunctionality

  5. Designing a Scalable Fault Tolerance Model for High Performance Computational Chemistry: A Case Study with Coupled Cluster Perturbative Triples. (United States)

    van Dam, Hubertus J J; Vishnu, Abhinav; de Jong, Wibe A


    In the past couple of decades, the massive computational power provided by the most modern supercomputers has resulted in simulation of higher-order computational chemistry methods, previously considered intractable. As the system sizes continue to increase, the computational chemistry domain continues to escalate this trend using parallel computing with programming models such as Message Passing Interface (MPI) and Partitioned Global Address Space (PGAS) programming models such as Global Arrays. The ever increasing scale of these supercomputers comes at a cost of reduced Mean Time Between Failures (MTBF), currently on the order of days and projected to be on the order of hours for upcoming extreme scale systems. While traditional disk-based check pointing methods are ubiquitous for storing intermediate solutions, they suffer from high overhead of writing and recovering from checkpoints. In practice, checkpointing itself often brings the system down. Clearly, methods beyond checkpointing are imperative to handling the aggravating issue of reducing MTBF. In this paper, we address this challenge by designing and implementing an efficient fault tolerant version of the Coupled Cluster (CC) method with NWChem, using in-memory data redundancy. We present the challenges associated with our design, including an efficient data storage model, maintenance of at least one consistent data copy, and the recovery process. Our performance evaluation without faults shows that the current design exhibits a small overhead. In the presence of a simulated fault, the proposed design incurs negligible overhead in comparison to the state of the art implementation without faults.

  6. Development of antibacterial conjugates using sulfamethoxazole with monocyclic terpenes: A systematic medicinal chemistry based computational approach. (United States)

    Swain, Shasank S; Paidesetty, Sudhir K; Padhy, Rabindra N


    To develop 6 conjugate agents of the moribund antibiotic sulfamethoxazole (SMZ) joined to 6 individual monoterpenes, followed by protocols of medicinal chemistry as potent antibacterials, against multidrug resistant (MDR) human gruesome pathogenic bacteria. Antibacterial activities of the proposed conjugates were ascertained by the 'prediction of activity spectra of substances' (PASS) program. Drug-likeness parameters and toxicity profiles of conjugates were standardized with the Lipinski rule of five, using cheminformatic tools, Molsoft, molinspiration, OSIRIS and ProTox. Antibacterial activities of individual chemicals and conjugates were examined by targeting the bacterial folic acid biosynthesis enzyme, dihydropteroate synthases (DHPSs) of bacteria, Bacillus anthracis, Escherichia coli, Staphylococcus aureus, Streptococcus pneumoniae and Mycobacterium tuberculosis, with 3D structures of DHPSs from protein data bank. According to the PASS program, biological spectral values of conjugate-2, conjugate-5 and conjugate-6 were ascertained effective with 'probably active' or 'Pa' value > 0.5, for anti-infective and antituberculosic activities. Using molecular docking against 5 cited bacterial DHPSs, effective docking scores of 6 monoterpenes in the specified decreasing order (kcal/mol): -9.72 (eugenol against B. anthracis), -9.61 (eugenol against S. pneumoniae), -9. 42 (safrol, against B. anthracis), -9.39 (thymol, against M. tuberculosis), -9.34 (myristicin, against S. pneumoniae) and -9.29 (thymol, against B. anthracis); whereas the lowest docking score of SMZ was -8.46kcal/mol against S. aureus DHPS. Similarly, effective docking scores of conjugates were as specified (kcal/mol.): -10.80 (conjugate-4 consisting SMZ+safrol, against M. tuberculosis), -10.78 (conjugate-5 consisting SMZ+thymol, against M. tuberculosis), -10.60 (conjugate-5 against B. anthracis), -10.26 (conjugate-2 consisting SMZ+ eugenol, against M. tuberculosis), -10.25 (conjugate-5, against S

  7. Experimental and theoretical investigation of stratospheric ozone depletion in the northern hemisphere caused by heterogeneous chemistry (United States)

    Storvold, Rune

    Stratospheric ozone is of crucial importance for life on Earth. This thin layer protects us from the ultraviolet solar radiation and also works as a greenhouse gas that helps maintaining our climate. Large changes in thickness and vertical distribution of the ozone abundance may have detrimental effects on life on Earth. But even small changes could have considerable impact on UV irradiance, bio-production and cancer rates. During the last decade record low spring time vertical column amounts of stratospheric ozone have been observed over Northern Europe. However, this decrease is not as severe as the depletion observed over Antarctica and at mid-latitudes in the Southern Hemisphere. The discovery of the spring time stratospheric ozone depletion first in Antarctica and later in the Arctic has triggered international research efforts on stratospheric ozone chemistry and the possible effects of human activities on the ozone layer. Ground-based differential optical absorption spectroscopy measurements of NO2 and ozone have been performed over Fairbanks (65°N) and Ny-Ålesund (79°N) during the 1994-95 season. In this work we present improvements to ground based differential optical spectroscopy measurements by improving dark current corrections and spectral fitting of spectrographic photo diode array detector measurements. We have also improved the retrieval of vertical column amounts from diffuse light measurements by improving the corrections for seasonal changes in absorber air mass. This is particularly important at high latitudes. We used these data together with local weather and ozone sounding data, and with trace gas and aerosol data measured by other ground based instruments and by instruments deployed on satellites. This comprehensive dataset was used to investigate the performance of two current state of the art chemical transport models with and without the presence of heterogeneous chemistry. These are the University of Cambridge SLIMCAT model and the

  8. Experimentation With Computer-Assisted Indexing: American Documentation, Volume 20 (United States)

    Hines, Theodore C.; And Others


    The procedures used to produce the index to volume 20 (1969) of American Documentation are described to demonstrate a system for computer-assisted indexing and bibliographic production developed at the Columbia University School of Library Science. The system is demonstrated to be economic in comparison to currently used manual methods. (Author/MF)

  9. Computational Time Reversal for NDT Applications Using Experimental Data

    NARCIS (Netherlands)

    Lopatin, Craig; Rabinovich, Daniel; Givoli, D.; Turkel, Eli


    A model-based non destructive testing (NDT) method is proposed for damage identification in elastic structures, incorporating computational time reversal (TR) analysis. Identification is performed by advancing elastic wave signals, measured at discrete sensor locations, backward in time. In

  10. P300-based brain computer interface experimental setup

    NARCIS (Netherlands)

    Arboleda, C.; Garcia Cossio, E.; Posada, A.; Torres, R.


    A Brain-Computer interface (BCI) is a communication system that enables the generation of a control signal from brain signals such as sensorymotor rhythms and evoked potentials; therefore, it constitutes a novel communication option for people with severe motor disabilities (such as Amyotrophic

  11. Heats of formation of phosphorus compounds determined by current methods of computational quantum chemistry (United States)

    Haworth, Naomi L.; Bacskay, George B.


    The heats of formation of a range of phosphorus containing molecules (P2, P4, PH, PH2, PH3, P2H2, P2H4, PO, PO2, PO3, P2O, P2O2, HPO, HPOH, H2POH, H3PO, HOPO, and HOPO2) have been determined by high level quantum chemical calculations. The equilibrium geometries and vibrational frequencies were computed via density functional theory, utilizing the B3LYP/6-31G(2df,p) functional and basis set. Atomization energies were obtained by the application of ab initio coupled cluster theory with single and double excitations from (spin)-restricted Hartree-Fock reference states with perturbative correction for triples [CCSD(T)], in conjunction with cc-pVnZ basis sets (n=T, Q, 5) which include an extra d function on the phosphorus atoms and diffuse functions on the oxygens, as recommended by Bauschlicher [J. Phys. Chem. A 103, 11126 (1999)]. The valence correlated atomization energies were extrapolated to the complete basis limit and corrected for core-valence (CV) correlation and scalar relativistic effects, as well as for basis set superposition errors (BSSE) in the CV terms. This methodology is effectively the same as the one adopted by Bauschlicher in his study of PO, PO2, PO3, HPO, HOPO, and HOPO2. Consequently, for these molecules the results of this work closely match Bauschlicher's computed values. The theoretical heats of formation, whose accuracy is estimated as ranging from ±1.0 to ±2.5 kcal mol-1, are consistent with the available experimental data. The current set of theoretical data represent a convenient benchmark, against which the results of other computational procedures, such as G3, G3X, and G3X2, can be compared. Despite the fact that G3X2 [which is an approximation to the quadratic CI procedure QCISD(T,Full)/G3Xlarge] is a formally higher level theory than G3X, the heats of formation obtained by these two methods are found to be of comparable accuracy. Both reproduce the benchmark heats of formation on the average to within ±2 kcal mol-1 and, for these

  12. Understanding the hydrolysis mechanism of ethyl acetate catalyzed by an aqueous molybdocene: a computational chemistry investigation. (United States)

    Tílvez, Elkin; Cárdenas-Jirón, Gloria I; Menéndez, María I; López, Ramón


    A thoroughly mechanistic investigation on the [Cp2Mo(OH)(OH2)](+)-catalyzed hydrolysis of ethyl acetate has been performed using density functional theory methodology together with continuum and discrete-continuum solvation models. The use of explicit water molecules in the PCM-B3LYP/aug-cc-pVTZ (aug-cc-pVTZ-PP for Mo)//PCM-B3LYP/aug-cc-pVDZ (aug-cc-pVDZ-PP for Mo) computations is crucial to show that the intramolecular hydroxo ligand attack is the preferred mechanism in agreement with experimental suggestions. Besides, the most stable intermediate located along this mechanism is analogous to that experimentally reported for the norbornenyl acetate hydrolysis catalyzed by molybdocenes. The three most relevant steps are the formation and cleavage of the tetrahedral intermediate immediately formed after the hydroxo ligand attack and the acetic acid formation, with the second one being the rate-determining step with a Gibbs energy barrier of 36.7 kcal/mol. Among several functionals checked, B3LYP-D3 and M06 give the best agreement with experiment as the rate-determining Gibbs energy barrier obtained only differs 0.2 and 0.7 kcal/mol, respectively, from that derived from the experimental kinetic constant measured at 296.15 K. In both cases, the acetic acid elimination becomes now the rate-determining step of the overall process as it is 0.4 kcal/mol less stable than the tetrahedral intermediate cleavage. Apart from clarifying the identity of the cyclic intermediate and discarding the tetrahedral intermediate formation as the rate-determining step for the mechanism of the acetyl acetate hydrolysis catalyzed by molybdocenes, the small difference in the Gibbs energy barrier found between the acetic acid formation and the tetrahedral intermediate cleavage also uncovers that the rate-determining step could change when studying the reactivity of carboxylic esters other than ethyl acetate substrate specific toward molybdocenes or other transition metal complexes. Therefore

  13. Effects of Combined Hands-on Laboratory and Computer Modeling on Student Learning of Gas Laws: A Quasi-Experimental Study (United States)

    Liu, Xiufeng


    Based on current theories of chemistry learning, this study intends to test a hypothesis that computer modeling enhanced hands-on chemistry laboratories are more effective than hands-on laboratories or computer modeling laboratories alone in facilitating high school students' understanding of chemistry concepts. Thirty-three high school chemistry…

  14. Experimental and Computational Techniques in Soft Condensed Matter Physics (United States)

    Olafsen, Jeffrey


    1. Microscopy of soft materials Eric R. Weeks; 2. Computational methods to study jammed Systems Carl F. Schrek and Corey S. O'Hern; 3. Soft random solids: particulate gels, compressed emulsions and hybrid materials Anthony D. Dinsmore; 4. Langmuir monolayers Michael Dennin; 5. Computer modeling of granular rheology Leonardo E. Silbert; 6. Rheological and microrheological measurements of soft condensed matter John R. de Bruyn and Felix K. Oppong; 7. Particle-based measurement techniques for soft matter Nicholas T. Ouellette; 8. Cellular automata models of granular flow G. William Baxter; 9. Photoelastic materials Brian Utter; 10. Image acquisition and analysis in soft condensed matter Jeffrey S. Olafsen; 11. Structure and patterns in bacterial colonies Nicholas C. Darnton.

  15. Experimental magic state distillation for fault-tolerant quantum computing. (United States)

    Souza, Alexandre M; Zhang, Jingfu; Ryan, Colm A; Laflamme, Raymond


    Any physical quantum device for quantum information processing (QIP) is subject to errors in implementation. In order to be reliable and efficient, quantum computers will need error-correcting or error-avoiding methods. Fault-tolerance achieved through quantum error correction will be an integral part of quantum computers. Of the many methods that have been discovered to implement it, a highly successful approach has been to use transversal gates and specific initial states. A critical element for its implementation is the availability of high-fidelity initial states, such as |0〉 and the 'magic state'. Here, we report an experiment, performed in a nuclear magnetic resonance (NMR) quantum processor, showing sufficient quantum control to improve the fidelity of imperfect initial magic states by distilling five of them into one with higher fidelity.

  16. Chemical Structure Identification in Metabolomics: Computational Modeling of Experimental Features

    Directory of Open Access Journals (Sweden)

    Lochana C Menikarachchi


    Full Text Available The identification of compounds in complex mixtures remains challenging despite recent advances in analytical techniques. At present, no single method can detect and quantify the vast array of compounds that might be of potential interest in metabolomics studies. High performance liquid chromatography/mass spectrometry (HPLC/MS is often considered the analytical method of choice for analysis of biofluids. The positive identification of an unknown involves matching at least two orthogonal HPLC/MS measurements (exact mass, retention index, drift time etc. against an authentic standard. However, due to the limited availability of authentic standards, an alternative approach involves matching known and measured features of the unknown compound with computationally predicted features for a set of candidate compounds downloaded from a chemical database. Computationally predicted features include retention index, ECOM50 (energy required to decompose 50% of a selected precursor ion in a collision induced dissociation cell, drift time, whether the unknown compound is biological or synthetic and a collision induced dissociation (CID spectrum. Computational predictions are used to filter the initial “bin” of candidate compounds. The final output is a ranked list of candidates that best match the known and measured features. In this mini review, we discuss cheminformatics methods underlying this database search-filter identification approach.

  17. Central Computer Science Concepts to Research-Based Teacher Training in Computer Science: An Experimental Study (United States)

    Zendler, Andreas; Klaudt, Dieter


    The significance of computer science for economics and society is undisputed. In particular, computer science is acknowledged to play a key role in schools (e.g., by opening multiple career paths). The provision of effective computer science education in schools is dependent on teachers who are able to properly represent the discipline and whose…

  18. Computational and experimental model of transdermal iontophorethic drug delivery system. (United States)

    Filipovic, Nenad; Saveljic, Igor; Rac, Vladislav; Graells, Beatriz Olalde; Bijelic, Goran


    The concept of iontophoresis is often applied to increase the transdermal transport of drugs and other bioactive agents into the skin or other tissues. It is a non-invasive drug delivery method which involves electromigration and electroosmosis in addition to diffusion and is shown to be a viable alternative to conventional administration routs such as oral, hypodermic and intravenous injection. In this study we investigated, experimentally and numerically, in vitro drug delivery of dexamethasone sodium phosphate to porcine skin. Different current densities, delivery durations and drug loads were investigated experimentally and introduced as boundary conditions for numerical simulations. Nernst-Planck equation was used for calculation of active substance flux through equivalent model of homogeneous hydrogel and skin layers. The obtained numerical results were in good agreement with experimental observations. A comprehensive in-silico platform, which includes appropriate numerical tools for fitting, could contribute to iontophoretic drug-delivery devices design and correct dosage and drug clearance profiles as well as to perform much faster in-silico experiments to better determine parameters and performance criteria of iontophoretic drug delivery. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Evaluation of computer-based learning material for food chemistry education

    NARCIS (Netherlands)

    Diederen, J.; Gruppen, H.; Hartog, R.J.M.; Voragen, A.G.J.


    Digital exercises were designed and developed for food chemistry education. During the design process, design requirements were described for such exercises. The exercises were evaluated in three case studies, firstly to determine whether the exercises satisfy the design requirements with respect to

  20. Quantum Chemistry beyond Born–Oppenheimer Approximation on a Quantum Computer: A Simulated Phase Estimation Study

    Czech Academy of Sciences Publication Activity Database

    Veis, Libor; Višňák, Jakub; Nishizawa, H.; Nakai, H.; Pittner, Jiří


    Roč. 116, č. 18 (2016), s. 1328-1336 ISSN 0020-7608 R&D Projects: GA ČR GA203/08/0626 Institutional support: RVO:61388955 Keywords : Born-Oppenheimer approximation * nuclear orbital plus molecular orbital method * phase estimation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.920, year: 2016

  1. Experimental study on iodine chemistry (EXSI) - Containment experiments with elemental iodine

    Energy Technology Data Exchange (ETDEWEB)

    Kaerkelae, T.; Auvinen, A. (VTT Technical Research Centre of Finland (Finland)); Holm, J.; Ekberg, C. (Chalmers Univ. of Technology (Sweden)); Glaenneskog, H. (Vattenfall Power Consultant (Sweden))


    The behaviour of iodine during a severe accident has been studied in several experimental programs, ranging from the large-scale PHEBUS FP tests and intermediate-scale ThAI tests to numerous separate effect studies. Oxidation of iodine in gas phase has been one of the greatest remaining uncertainties in iodine behaviour during a severe accident. In this study the possible formation of iodine oxide aerosol due to radiolytic oxidation of gaseous iodine is experimentally tested and the reaction products are analysed. The experimental facility applied in this study is based on the sampling system built at VTT for ISTP program project CHIP conducted IRSN. The experimental facility and the measuring technology are sophisticated and unique in the area of nuclear research as well as in the field of aerosol science. The results from the experiments show an extensive particle formation when ozone and gaseous iodine react with each other. The formed particles were collected on filters, while gaseous iodine was trapped into bubbles. The particles were iodine oxides and the size of particles was approximately 100 nm. The transport of gaseous iodine through the facility decreased when both gaseous iodine and ozone were fed together into facility. Experimental study on radiolytic oxidation of iodine was conducted in co-operation between VTT and Chalmers University of Technology as a part of the NKS-R programs. (author)

  2. Experimental and computing strategies in advanced material characterization problems

    Energy Technology Data Exchange (ETDEWEB)

    Bolzon, G. [Department of Civil and Environmental Engineering, Politecnico di Milano, piazza Leonardo da Vinci 32, 20133 Milano, Italy (Italy)


    The mechanical characterization of materials relies more and more often on sophisticated experimental methods that permit to acquire a large amount of data and, contemporarily, to reduce the invasiveness of the tests. This evolution accompanies the growing demand of non-destructive diagnostic tools that assess the safety level of components in use in structures and infrastructures, for instance in the strategic energy sector. Advanced material systems and properties that are not amenable to traditional techniques, for instance thin layered structures and their adhesion on the relevant substrates, can be also characterized by means of combined experimental-numerical tools elaborating data acquired by full-field measurement techniques. In this context, parameter identification procedures involve the repeated simulation of the laboratory or in situ tests by sophisticated and usually expensive non-linear analyses while, in some situation, reliable and accurate results would be required in real time. The effectiveness and the filtering capabilities of reduced models based on decomposition and interpolation techniques can be profitably used to meet these conflicting requirements. This communication intends to summarize some results recently achieved in this field by the author and her co-workers. The aim is to foster further interaction between engineering and mathematical communities.

  3. Many Body Methods from Chemistry to Physics: Novel Computational Techniques for Materials-Specific Modelling: A Computational Materials Science and Chemistry Network

    Energy Technology Data Exchange (ETDEWEB)

    Millis, Andrew [Columbia Univ., New York, NY (United States). Dept. of Physics


    Understanding the behavior of interacting electrons in molecules and solids so that one can predict new superconductors, catalysts, light harvesters, energy and battery materials and optimize existing ones is the ``quantum many-body problem’’. This is one of the scientific grand challenges of the 21st century. A complete solution to the problem has been proven to be exponentially hard, meaning that straightforward numerical approaches fail. New insights and new methods are needed to provide accurate yet feasible approximate solutions. This CMSCN project brought together chemists and physicists to combine insights from the two disciplines to develop innovative new approaches. Outcomes included the Density Matrix Embedding method, a new, computationally inexpensive and extremely accurate approach that may enable first principles treatment of superconducting and magnetic properties of strongly correlated materials, new techniques for existing methods including an Adaptively Truncated Hilbert Space approach that will vastly expand the capabilities of the dynamical mean field method, a self-energy embedding theory and a new memory-function based approach to the calculations of the behavior of driven systems. The methods developed under this project are now being applied to improve our understanding of superconductivity, to calculate novel topological properties of materials and to characterize and improve the properties of nanoscale devices.

  4. Experimental determination of the segregation process using computer tomography

    Directory of Open Access Journals (Sweden)

    Konstantin Beckmann


    Full Text Available Modelling methods such as DEM and CFD are increasingly used for developing high efficient combine cleaning systems. For this purpose it is necessary to verify the complex segregation and separation processes in the combine cleaning system. One way is to determine the segregation and separation function using 3D computer tomography (CT. This method makes it possible to visualize and analyse the movement behaviour of the components of the mixture during the segregation and separation process as well as the derivation of descriptive process parameters. A mechanically excited miniature test rig was designed and built at the company CLAAS Selbstfahrende Erntemaschinen GmbH to achieve this aim. The investigations were carried out at the Fraunhofer Institute for Integrated Circuits IIS. Through the evaluation of the recorded images the segregation process is described visually. A more detailed analysis enabled the development of segregation and separation function based on the different densities of grain and material other than grain.

  5. Pore water chemistry of domestic bentonite for the buffer of a repository: analysis of experimental data

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae Owan; Cho, Won Jin; Chun, Kwan Sik; Kang, Chul Hyung


    Experiments were conducted using synthetic ground water and domestic bentonite. Upon reaction of the bentonite and ground water, ionic concentration, ph and Eh nearly reached a steady-state within a few days. The pore water chemistry was dominated mainly by the mineralogical composition of bentonite. Analytic results showed that sodium, sulfate, and carbonate were major ions, and their concentrations increased to about 4-5 times those of original ground water. The ph increased from 8.1 to 8.9, and the Eh were between 365 mV and 375 mV. The concentration of most dissolved ions increased with increasing bentonite-to-ground water ratio. On the contrary, the ph and Eh were little affected by bentonite-to-ground water ratio. The dependence of ionic concentration upon temperature had different trends with different ions. Little change in the ph occurred up to 80 dg C, and decreased beyond the value of temperature. The Eh rather increased beyond 80 dg C on contrary to ph. (Author). 21 refs., 4 tabs., 18 figs.

  6. Computational and Experimental Approaches to Cancer Biomarker Discovery

    DEFF Research Database (Denmark)

    Krzystanek, Marcin

    at least two fundamental mechanisms responsible for DNA aberrations present in a given tumor: 1) active mutational processes caused either by endogenous or exogenous factors, for example chemical agents such as tobacco smoke or cancer cytotoxics, or by active enzymatic processes such as APOBEC related...... with a purely biological, experimental approach where the effects of treatment with cytotoxic agents or defects in DNA repair mechanisms can be individually quantified and turned into mutational signatures.In the second part of the thesis I present work towards identification and improvement of the current...... are expected.This work, together with manifold of efforts being done all over the world, is hopefully a step towards implementation of personalized medicine and better treatments for cancer patients. ...

  7. Heavy enzymes--experimental and computational insights in enzyme dynamics. (United States)

    Swiderek, Katarzyna; Ruiz-Pernía, J Javier; Moliner, Vicent; Tuñón, Iñaki


    The role of protein motions in the chemical step of enzyme-catalyzed reactions is the subject of an open debate in the scientific literature. The systematic use of isotopically substituted enzymes has been revealed as a useful tool to quantify the role of these motions. According to the Born-Oppenheimer approximation, changing the mass of the protein does not change the forces acting on the system but alters the frequencies of the protein motions, which in turn can affect the rate constant. Experimental and theoretical studies carried out in this field are presented in this article and discussed in the framework of Transition State Theory. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. Computer modelling of the plasma chemistry and plasma-based growth mechanisms for nanostructured materials

    International Nuclear Information System (INIS)

    In this review paper, an overview is given of different modelling efforts for plasmas used for the formation and growth of nanostructured materials. This includes both the plasma chemistry, providing information on the precursors for nanostructure formation, as well as the growth processes itself. We limit ourselves to carbon (and silicon) nanostructures. Examples of the plasma modelling comprise nanoparticle formation in silane and hydrocarbon plasmas, as well as the plasma chemistry giving rise to carbon nanostructure formation, such as (ultra)nanocrystalline diamond ((U)NCD) and carbon nanotubes (CNTs). The second part of the paper deals with the simulation of the (plasma-based) growth mechanisms of the same carbon nanostructures, i.e. (U)NCD and CNTs, both by mechanistic modelling and detailed atomistic simulations.

  9. Experimental and computational development of a natural breast phantom for dosimetry studies

    International Nuclear Information System (INIS)

    Nogueira, Luciana B.; Campos, Tarcisio P.R.


    This paper describes the experimental and computational development of a natural breast phantom, anthropomorphic and anthropometric for studies in dosimetry of brachytherapy and teletherapy of breast. The natural breast phantom developed corresponding to fibroadipose breasts of women aged 30 to 50 years, presenting radiographically medium density. The experimental breast phantom was constituted of three tissue-equivalents (TE's): glandular TE, adipose TE and skin TE. These TE's were developed according to chemical composition of human breast and present radiological response to exposure. Completed the construction of experimental breast phantom this was mounted on a thorax phantom previously developed by the research group NRI/UFMG. Then the computational breast phantom was constructed by performing a computed tomography (CT) by axial slices of the chest phantom. Through the images generated by CT a computational model of voxels of the thorax phantom was developed by SISCODES computational program, being the computational breast phantom represented by the same TE's of the experimental breast phantom. The images generated by CT allowed evaluating the radiological equivalence of the tissues. The breast phantom is being used in studies of experimental dosimetry both in brachytherapy as in teletherapy of breast. Dosimetry studies by MCNP-5 code using the computational model of the phantom breast are in progress. (author)

  10. Primary water chemistry optimization for extended fuel cycle operation. Results of the 'Duo experimentation' after three cycles

    International Nuclear Information System (INIS)

    Viricel, L.; Andrieu, C.; Segura, J.C.; Rocher, A.; Thomazet, J.; Clinard, M.H.; Dacquait, F.


    The primary coolant conditioning in French nuclear power plants is essentially based on the boron-lithium coordinated chemistry, with a target pH of 7.2 at 300 C and a maximum lithium concentration of 2.2 mg/kg. In 1996, EDF 1300 MWe units began operating 18-month fuel cycles, increasing boron concentrations at the beginning of the cycles. Since today the maximum lithium concentration in normal operation is 2.2 mg/kg, extended cycle operation results in a decrease in the pH at the beginning of the cycles, which may possibly lead to deposits in RCS, and particularly on the fuel cladding, and increased dose rates. It has to be noted that today, the fuel assemblies maximum burnup is set at 52 GWd/tU. One solution is to adjust the pH by increasing the lithium content at the beginning of the cycles, which is easy to implement and does not require any modification on the units. Hence, EDF is testing a ''modified'' chemistry regime in the > during 4 fuel cycles, with a maximum authorized lithium content of 3.5 mg/kg at the beginning of the cycles in the Cattenom 2 pilot unit. The Golfech 1 reference unit implements a standard boron-lithium coordination pH 300 7.2. The major goal of the experimentation is to assess the impact of elevated lithium concentrations at the beginning of the cycles on fuel cladding oxide behavior, mass transport and dose rates. This paper presents the results of the first three cycles of the Duo experimentation. (author)

  11. Computing the carbonate chemistry of the coral calcifying medium and its response to ocean acidification. (United States)

    Raybaud, Virginie; Tambutté, Sylvie; Ferrier-Pagès, Christine; Reynaud, Stéphanie; Venn, Alexander A; Tambutté, Éric; Nival, Paul; Allemand, Denis


    Critical to determining vulnerability or resilience of reef corals to Ocean Acidification (OA) is a clearer understanding of the extent to which corals can control carbonate chemistry in their Extracellular Calcifying Medium (ECM) where the CaCO 3 skeleton is produced. Here, we employ a mathematical framework to calculate ECM aragonite saturation state (Ω arag.(ECM) ) and carbonate system ion concentration using measurements of calcification rate, seawater characteristics (temperature, salinity and pH) and ECM pH (pH (ECM) ). Our calculations of ECM carbonate chemistry at current-day seawater pH, indicate that Ω arag.(ECM) ranges from ∼10 to 38 (mean 20.41), i.e. about 5 to 6-fold higher than seawater. Accordingly, Dissolved Inorganic Carbon (DIC) and Total Alkalinity (TA) were calculated to be around 3 times higher in the ECM than in seawater. We also assessed the effects of acidification on ECM chemical properties of the coral Stylophora pistillata. At reduced seawater pH our calculations indicate that Ω arag.(ECM) remains almost constant. DIC (ECM) and TA (ECM) gradually increase as seawater pH declines, reaching values about 5 to 6-fold higher than in seawater, respectively for DIC and TA. We propose that these ECM characteristics buffer the effect of acidification and explain why certain corals continue to produce CaCO 3 even when seawater chemistry is less favourable. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Effect of Computer-Based Video Games on Children: An Experimental Study (United States)

    Chuang, Tsung-Yen; Chen, Wei-Fan


    This experimental study investigated whether computer-based video games facilitate children's cognitive learning. In comparison to traditional computer-assisted instruction (CAI), this study explored the impact of the varied types of instructional delivery strategies on children's learning achievement. One major research null hypothesis was…

  13. An Experimental Study into the use of computers for teaching of ...

    African Journals Online (AJOL)

    This study was an experimental study which sought to establish how English language teachers used computers for teaching composition writing at Prince Edward High School in Harare. The findings of the study show that computers were rarely used in the teaching of composition despite the observation that the school ...

  14. Experimental physical chemistry: a proposal to address phase equilibria in three-component systems


    Reiznautt, Quelen Bulow; Girelli, Bruna; Santa Catharina, Vinícius Millan; Samios, Dimitrios; Garcia, Irene Teresinha Santos


    On undergraduate courses, practical classes represent periods in which students can verify the concepts presented in theoretical classes. Conversely, the teaching internship in graduate programs allows these students to incorporate pedagogical practices into their experience, predominantly involving observation and reproduction of methods adopted by supervisors. We propose internship teaching as a period for reflection on our pedagogical practice and present a methodology for an experimental ...

  15. Computations for the 1:5 model of the THTR pressure vessel compared with experimental results

    International Nuclear Information System (INIS)

    Stangenberg, F.


    In this report experimental results measured at the 1:5-model of the prestressed concrete pressure vessel of the THTR-nuclear power station Schmehausen in 1971, are compared with the results of axis-symmetrical computations. Linear-elastic computations were performed as well as approximate computations for overload pressures taking into consideration the influences of the load history (prestressing, temperature, creep) and the effects of the steel components. (orig.) [de

  16. Experimental and computational studies of electromagnetic cloaking at microwaves (United States)

    Wang, Xiaohui

    An invisibility cloak is a device that can hide the target by enclosing it from the incident radiation. This intriguing device has attracted a lot of attention since it was first implemented at a microwave frequency in 2006. However, the problems of existing cloak designs prevent them from being widely applied in practice. In this dissertation, we try to remove or alleviate the three constraints for practical applications imposed by loosy cloaking media, high implementation complexity, and small size of hidden objects compared to the incident wavelength. To facilitate cloaking design and experimental characterization, several devices and relevant techniques for measuring the complex permittivity of dielectric materials at microwave frequencies are developed. In particular, a unique parallel plate waveguide chamber has been set up to automatically map the electromagnetic (EM) field distribution for wave propagation through the resonator arrays and cloaking structures. The total scattering cross section of the cloaking structures was derived based on the measured scattering field by using this apparatus. To overcome the adverse effects of lossy cloaking media, microwave cloaks composed of identical dielectric resonators made of low loss ceramic materials are designed and implemented. The effective permeability dispersion was provided by tailoring dielectric resonator filling fractions. The cloak performances had been verified by full-wave simulation of true multi-resonator structures and experimental measurements of the fabricated prototypes. With the aim to reduce the implementation complexity caused by metamaterials employment for cloaking, we proposed to design 2-D cylindrical cloaks and 3-D spherical cloaks by using multi-layer ordinary dielectric material (epsilon r>1) coating. Genetic algorithm was employed to optimize the dielectric profiles of the cloaking shells to provide the minimum scattering cross sections of the cloaked targets. The designed cloaks can

  17. Advanced Computational and Experimental Techniques for Nacelle Liner Performance Evaluation (United States)

    Gerhold, Carl H.; Jones, Michael G.; Brown, Martha C.; Nark, Douglas


    The Curved Duct Test Rig (CDTR) has been developed to investigate sound propagation through a duct of size comparable to the aft bypass duct of typical aircraft engines. The axial dimension of the bypass duct is often curved and this geometric characteristic is captured in the CDTR. The semiannular bypass duct is simulated by a rectangular test section in which the height corresponds to the circumferential dimension and the width corresponds to the radial dimension. The liner samples are perforate over honeycomb core and are installed on the side walls of the test section. The top and bottom surfaces of the test section are acoustically rigid to simulate a hard wall bifurcation or pylon. A unique feature of the CDTR is the control system that generates sound incident on the liner test section in specific modes. Uniform air flow, at ambient temperature and flow speed Mach 0.275, is introduced through the duct. Experiments to investigate configuration effects such as curvature along the flow path on the acoustic performance of a sample liner are performed in the CDTR and reported in this paper. Combinations of treated and acoustically rigid side walls are investigated. The scattering of modes of the incident wave, both by the curvature and by the asymmetry of wall treatment, is demonstrated in the experimental results. The effect that mode scattering has on total acoustic effectiveness of the liner treatment is also shown. Comparisons of measured liner attenuation with numerical results predicted by an analytic model based on the parabolic approximation to the convected Helmholtz equation are reported. The spectra of attenuation produced by the analytic model are similar to experimental results for both walls treated, straight and curved flow path, with plane wave and higher order modes incident. The numerical model is used to define the optimized resistance and reactance of a liner that significantly improves liner attenuation in the frequency range 1900-2400 Hz. A

  18. UV absorbers for cellulosic apparels: A computational and experimental study (United States)

    Sahar, Anum; Ali, Shaukat; Hussain, Tanveer; Irfan, Muhammad; Eliasson, Bertil; Iqbal, Javed


    Two triazine based Ultra Violet (UV) absorbers Sulfuric acid mono-(2-{4-[4-chloro-6-(4-{4-chloro-6-[4-(2-sulfooxy-ethanesulfonyl)-phenylamino]-[1,3,5] triazin-2-ylamino-phenylamino)-[1,3,5]triazin-2-ylamino]-benzenesulfonyl}-ethyl) ester (1a) and 4-{4-chloro-6-[4-(2-sulfooxy-ethanesulfonyl)-phenylamino]-[1,3,5] triazin-2-ylamino}-2-[4-chloro-6-(2-sulfooxy-ethanesulfonyl)-[1,3,5]triazin-2-ylamino]-benzenesulfonic acid (2a) with different substituents were designed computationally. The influence of different substituents on the electrochemical properties and UV spectra of the absorbers was investigated. The presence of electron deficient unit in 1a to the molecular core significantly reduces the LUMO levels and energy gap. The designed absorbers were synthesized via condensation reaction and characterized by UV-Vis, FT-IR, MS studies. The performance of synthesized compounds as UV absorbers and their fastness properties were assessed by finishing the cotton fabric through exhaust method at different concentration and results appeared in good range.

  19. Modelling the spatial shape of nondiffracting beams: Experimental generation of Frozen Waves via computer generated holograms


    Vieira, Tárcio A.; Zamboni-Rached, Michel; Gesualdi, Marcos R. R.


    In this paper we implement experimentally the spatial shape modelling of nondiffracting optical beams via computer generated holograms. The results reported here are the experimental confirmation of the so called Frozen Wave method, developed few years ago. Optical beams of this type can possess potential applications in optical tweezers, medicine, atom guiding, remote sensing, etc..

  20. Experimental and computational thermochemical study of 3-hydroxypropanenitrile

    International Nuclear Information System (INIS)

    Roux, Maria Victoria; Notario, Rafael; Velez, Ederley; Temprado, Manuel; Guerrero, Andres; Verevkin, Sergey P.; Quijano, Jairo; Gaviria, Jair


    This paper reports the values of the standard (p 0 = 0.1 MPa) molar enthalpy of formation in the gas phase, at T = 298.15 K, for 3-hydroxypropanenitrile derived from the respective enthalpy of combustion in oxygen, measured by static bomb combustion calorimetry and the standard molar enthalpy of vaporization, at T = 298.15 K, determined using the transference (transpiration) method in a saturated N 2 stream, the value of the gas-phase enthalpy of formation being Δ f H m 0 (g)=-(91.2±1.4)kJ.mol -1 . Furthermore, we have performed high-level ab initio molecular orbital calculations at the G3 level. Four different conformations corresponding to local minima of the potential energy surface have been found for 3-hydroxypropanenitrile. The optimised molecular and electronic structure of the most stable conformer of 3-hydroxypropanenitrile shows a gauche arrangement with a weak intramolecular hydrogen bond from OH hydrogen to the π-bond charge cloud of the nitrile group. The calculated values for the enthalpy of formation of the most stable conformer using atomization and isodesmic bond separation reactions, -94.7 and -95.0 kJ . mol -1 , respectively, are in very good agreement with the experimental value

  1. Computational and Experimental Insight Into Single-Molecule Piezoelectric Materials (United States)

    Marvin, Christopher Wayne

    Piezoelectric materials allow for the harvesting of ambient waste energy from the environment. Producing lightweight, highly responsive materials is a challenge for this type of material, requiring polymer, foam, or bio-inspired materials. In this dissertation, I explore the origin of the piezoelectric effect in single molecules through density functional theory (DFT), analyze the piezoresponse of bio-inspired peptidic materials through the use of atomic and piezoresponse force microscopy (AFM and PFM), and develop a novel class of materials combining flexible polyurethane foams and non-piezoelectric, polar dopants. For the DFT calculations, functional group, regiochemical, and heteroatom derivatives of [6]helicene were examined for their influence on the piezoelectric response. An aza[6]helicene derivative was found to have a piezoelectric response (108 pm/V) comparable to ceramics such as lead zirconium titanate (200+ pm/V). These computed materials have the possibility to compete with current field-leading piezomaterials such as lead zirconium titanate (PZT), zinc oxide (ZnO), and polyvinylidene difluoride (PVDF) and its derivatives. The use of AFM/PFM allows for the demonstration of the piezoelectric effect of the selfassembled monolayer (SAM) peptidic systems. Through PFM, the influence that the helicity and sequence of the peptide has on the overall response of the molecule can be analyzed. Finally, development of a novel class of piezoelectrics, the foam-based materials, expands the current understanding of the qualities required for a piezoelectric material from ceramic and rigid materials to more flexible, organic materials. Through the exploration of these novel types of piezoelectric materials, new design rules and figures of merit have been developed.

  2. Experimental pain leads to reorganisation of trapezius electromyography during computer work with active and passive pauses

    DEFF Research Database (Denmark)

    Samani, Afshin; Holtermann, Andreas; Søgaard, Karen


    The aim of this laboratory study was to investigate acute effects of experimental muscle pain on spatial electromyographic (EMG) activity of the trapezius muscle during computer work with active and passive pauses. Twelve healthy male subjects performed four sessions of computer work for 2 min...... in one day, with passive (relax) and active (30% maximum voluntary contraction of shoulder elevation) pauses given every 40 s without and with presence of experimental pain. Surface EMG signals were recorded from four parts of the trapezius. The centroid of exposure variation analysis along the time axis...... was lower during computer work with active pauses when compared with passive one in all muscle parts (P

  3. Instrumentation, computer software and experimental techniques used in low-frequency internal friction studies at WNRE

    International Nuclear Information System (INIS)

    Sprugmann, K.W.; Ritchie, I.G.


    A detailed and comprehensive account of the equipment, computer programs and experimental methods developed at the Whiteshell Nuclear Research Estalbishment for the study of low-frequency internal friction is presented. Part 1 describes the mechanical apparatus, electronic instrumentation and computer software, while Part II describes in detail the laboratory techniques and various types of experiments performed together with data reduction and analysis. Experimental procedures for the study of internal friction as a function of temperature, strain amplitude or time are described. Computer control of these experiments using the free-decay technique is outlined. In addition, a pendulum constant-amplitude drive system is described. (auth)

  4. Experimental research of the impact of the dosing of chemical reagents on the dynamic behavior of regulation system of cycle chemistry (United States)

    Yegoshina, O. V.; Bolshakova, N. A.


    Organization of reliable chemical control for maintaining cycle chemistry is one of the most important problems to be solved at the present time the design and operation of thermal power plants. To maintain optimal parameters of cycle chemistry are used automated chemical control system and regulation system of dosing chemical reagents. Reliability and stability analyzer readings largely determine the reliability of the water cycle chemistry. Now the most common reagents are ammonia, alkali and film-forming amines. In this paper are presented the results of studies of the impact of concentration and composition of chemical reagents for readings stability of automatic analyzers and transients time of control systems for cycles chemistry. Research of the impact of chemical reagents on the dynamic behavior of regulation system for cycle chemistry was conducted at the experimental facility of the Department of thermal power stations of the Moscow Engineering Institute. This experimental facility is model of the work of regulation system for cycle chemistry close to the actual conditions on the energy facilities CHP. Analysis of results of the impact of chemical reagent on the dynamic behavior of ammonia and film forming amines dosing systems showed that the film-forming amines dosing system is more inertia. This emphasizes the transition process of the system, in which a half times longer dosing of ammonia. Results of the study can be used to improve the monitoring systems of water chemical treatment.

  5. Physical chemistry and the environment

    International Nuclear Information System (INIS)

    Dunning, T.H. Jr.; Garrett, B.C.; Kolb, C.E. Jr.; Shaw, R.W.; Choppin, G.R.; Wagner, A.F.


    From the ozone hole and the greenhouse effect to plastics recycling and hazardous waste disposal, society faces a number of issues, the solutions to which require an unprecedented understanding of the properties of molecules. We are coming to realize that the environment is a coupled set of chemical systems, its dynamics determining the welfare of the biosphere and of humans in particular. These chemical systems are governed by fundamental molecular interactions, and they present chemists with an unparalleled challenge. The application of current concepts of molecular behavior and of up-to-date experimental and computational techniques can provide us with insights into the environment that are needed to mitigate past damage, to anticipate the impact of current human activity, and to avoid future insults to the environment. Environmental chemistry encompasses a number of separate, yet interlocking, areas of research. In all of these areas progress is limited by an inadequate understanding of the underlying chemical processes involved. Participation of all chemical approaches -- experimental, theoretical and computational -- and of all disciplines of chemistry -- organic, inorganic, physical, analytical and biochemistry -- will be required to provide the necessary fundamental understanding. The Symposium on ''Physical Chemistry and the Environment'' was designed to bring the many exciting and challenging physical chemistry problems involved in environmental chemistry to the attention of a larger segment of the physical chemistry community

  6. Computational modeling of RNA 3D structures, with the aid of experimental restraints (United States)

    Magnus, Marcin; Matelska, Dorota; Łach, Grzegorz; Chojnowski, Grzegorz; Boniecki, Michal J; Purta, Elzbieta; Dawson, Wayne; Dunin-Horkawicz, Stanislaw; Bujnicki, Janusz M


    In addition to mRNAs whose primary function is transmission of genetic information from DNA to proteins, numerous other classes of RNA molecules exist, which are involved in a variety of functions, such as catalyzing biochemical reactions or performing regulatory roles. In analogy to proteins, the function of RNAs depends on their structure and dynamics, which are largely determined by the ribonucleotide sequence. Experimental determination of high-resolution RNA structures is both laborious and difficult, and therefore, the majority of known RNAs remain structurally uncharacterized. To address this problem, computational structure prediction methods were developed that simulate either the physical process of RNA structure formation (“Greek science” approach) or utilize information derived from known structures of other RNA molecules (“Babylonian science” approach). All computational methods suffer from various limitations that make them generally unreliable for structure prediction of long RNA sequences. However, in many cases, the limitations of computational and experimental methods can be overcome by combining these two complementary approaches with each other. In this work, we review computational approaches for RNA structure prediction, with emphasis on implementations (particular programs) that can utilize restraints derived from experimental analyses. We also list experimental approaches, whose results can be relatively easily used by computational methods. Finally, we describe case studies where computational and experimental analyses were successfully combined to determine RNA structures that would remain out of reach for each of these approaches applied separately. PMID:24785264

  7. "Named Small but Doing Great": An Investigation of Small-Scale Chemistry Experimentation for Effective Undergraduate Practical Work (United States)

    Tesfamariam, Gebrekidan Mebrahtu; Lykknes, Annette; Kvittingen, Lise


    In theory, practical work is an established part of university-level chemistry courses. However, mainly due to budget constraints, large class size, time constraints and inadequate teacher preparations, practical activities are frequently left out from chemistry classroom instruction in most developing countries. Small-scale chemistry (SSC)…

  8. Streamwater Chemistry and Nutrient Export During Five Years of Bark Beetle Infestation of Subalpine Watersheds at the Fraser Experimental Forest (United States)

    Rhoades, C.; Elder, K.; Hubbard, R.; Porth, L.


    Forested watersheds of western North America are currently undergoing rapid and extensive canopy mortality caused by a variety of insect species. The mountain pine bark beetle (Dendroctonus ponderosae) began to attack lodgepole pine (Pinus contorta) at the USFS Fraser Experimental Forest in central Colorado in 2002. By 2007, bark beetles had killed 78% of the overstory pine in Fraser research watersheds on average. The hydrologic, climatic, biogeochemical and vegetation records at the Fraser Experimental Forest provide a unique opportunity to quantify the impacts of this widespread, but poorly understood forest disturbance relative to a multi-decade pre-disturbance period. Here we compare seasonal streamwater chemistry and annual nutrient export for the five years since the bark beetle outbreak began with the pre- attack record. Patterns in post-outbreak streamwater biogeochemistry are compared to changes is species composition and proportional loss of overstory basal area for four basins. The influence of the outbreak will depend upon an aggregate of short (i.e. halted overstory water and nutrient use) and longer-term (i.e. altered canopy interception, windthrow, and understory growth) processes, so the hydrologic and biogeochemical implications of current beetle activity will not be fully realized for decades.

  9. Experimental evidence for the involvement of dinuclear alkynylcopper(I) complexes in alkyne-azide chemistry. (United States)

    Buckley, Benjamin R; Dann, Sandra E; Heaney, Harry


    Dinuclear alkynylcopper(I) ladderane complexes are prepared by a robust and simple protocol involving the reduction of Cu(2)(OH)(3)OAc or Cu(OAc)(2) by easily oxidised alcohols in the presence of terminal alkynes; they function as efficient catalysts in copper-catalysed alkyne-azide cycloaddition reactions as predicted by the Ahlquist-Fokin calculations. The same copper(I) catalysts are formed during reactions by using the Sharpless-Fokin protocol. The experimental results also provide evidence that sodium ascorbate functions as a base to deprotonate terminal alkynes and additionally give a convincing alternative explanation for the fact that the Cu(I)-catalysed reactions of certain 1,3-diazides with phenylacetylene give bis(triazoles) as the major products. The same dinuclear alkynylcopper(I) complexes also function as catalysts in cycloaddition reactions of azides with 1-iodoalkynes.

  10. Comprehensive Mechanisms for Combustion Chemistry: An Experimental and Numerical Study with Emphasis on Applied Sensitivity Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Dryer, Frederick L.


    This project was an integrated experimental/numerical effort to study pyrolysis and oxidation reactions and mechanisms for small-molecule hydrocarbon structures under conditions representative of combustion environments. The experimental aspects of the work were conducted in large-diameter flow reactors, at 0.3 to 18 atm pressure, 500 to 1100 K temperature, and 10-2 to 2 seconds reaction time. Experiments were also conducted to determine reference laminar flame speeds using a premixed laminar stagnation flame experiment and particle image velocimetry, as well as pressurized bomb experiments. Flow reactor data for oxidation experiments include: (1)adiabatic/isothermal species time-histories of a reaction under fixed initial pressure, temperature, and composition; to determine the species present after a fixed reaction time, initial pressure; (2)species distributions with varying initial reaction temperature; (3)perturbations of a well-defined reaction systems (e.g. CO/H2/O2 or H2/O2)by the addition of small amounts of an additive species. Radical scavenging techniques are applied to determine unimolecular decomposition rates from pyrolysis experiments. Laminar flame speed measurements are determined as a function of equivalence ratio, dilution, and unburned gas temperature at 1 atm pressure. Hierarchical, comprehensive mechanistic construction methods were applied to develop detailed kinetic mechanisms which describe the measurements and literature kinetic data. Modeling using well-defined and validated mechanisms for the CO/H2/Oxidant systems and perturbations of oxidation experiments by small amounts of additives were also used to derive absolute reaction rates and to investigate the compatibility of published elementary kinetic and thermochemical information. Numerical tools were developed and applied to assess the importance of individual elementary reactions to the predictive performance of the

  11. Electron tunneling in chemistry

    International Nuclear Information System (INIS)

    Zamaraev, K.I.; Khajrutdinov, R.F.; Zhdanov, V.P.; Molin, Yu.N.


    Results of experimental and theoretical investigations are outlined systematically on electron tunnelling in chemical reactions. Mechanism of electron transport to great distances is shown to be characteristic to chemical compounds of a wide range. The function of tunnel reactions is discussed for various fields of chemistry, including radiation chemistry, electrochemistry, chemistry of solids, chemistry of surface and catalysis

  12. miRNA and cancer; computational and experimental approaches. (United States)

    Tutar, Yusuf


    Human genome sequencing was started to solve four letter algorithm of the genome to understand the complex nature of human metabolism. However, after completion of Human Genome Project many scientists realized that sequence information alone was not sufficient to solve the biochemical mechanism of the organism through classical approaches. Non-coding parts of the genome produce small conserved ribonucleic acids, miRNAs to control cellular and physiological processes [1, 2]. This breakthrough discovery directed researches to examine role of miRNA in cancer since miRNAs are involved in the development, cell differentiation, and regulation of cell cycle [3]. The first paper of the special issue provides general information of miRNA in cancer research. This thematic issue presents two computational approaches for miRNA identification and their role in cancer. The first one comes from Dr. Wang and his presented work predicts cancer-related miRNAs by using expression profiles in tumor tissues. The work relies on R-squared method to investigate miRNA-mRNA regulatory relationship between miRNAs and mRNAs from different tissues and predicts miRNAs associated with colon, prostate, pancreatic, lung, breast, bladder, and kidney cancer. The second paper by Allmer et al. examines miRNA-gene regulatory networks and their implications in cancer. Their work provides complex network of expression regulation and miRNAs' role in personalized medicine. miRNAs regulate tumor progression and metastasis by interacting with target genes in the cells. Exosomal shuttle small RNAs mediate cell to cell communication and regulate cancer metastasis. The regulation via heterotypic signals in the microenvironment was explained by Dr. Liang and Dr. Yu groups. The rest of the issue highlights the roles of miRNAs on multiple myeloma, non-small cell lung cancer, urological malignancies, myeloid leukemia, and laryngeal squamous cell carcinoma. Proliferation of bone marrow of malignant plasma cells

  13. Technical Note: Controlled experimental aquarium system for multi-stressor investigation of carbonate chemistry, oxygen saturation, and temperature

    Directory of Open Access Journals (Sweden)

    E. E. Bockmon


    Full Text Available As the field of ocean acidification has grown, researchers have increasingly turned to laboratory experiments to understand the impacts of increased CO2 on marine organisms. However, other changes such as ocean warming and deoxygenation are occurring concurrently with the increasing CO2 concentrations, complicating the understanding of the impacts of anthropogenic changes on organisms. This experimental aquarium design allows for independent regulation of CO2 concentration, O2 levels, and temperature in a controlled environment to study the impacts of multiple stressors. The system has the flexibility for a wide range of treatment chemistry, seawater volumes, and study organisms. Control of the seawater chemistry is achieved by equilibration of a chosen gas mixture with seawater using a Liqui-Cel® membrane contactor. Included as examples, two experiments performed using the system have shown control of CO2 at values between approximately 500 and 1400 μatm and O2 at values from 80 to 240 μmol kg−1. Temperature has been maintained to 0.5 °C or better in the range of 10–17 °C. On a weeklong timescale, the system has achieved variability in pH of less than 0.007 pH units and in oxygen concentration of less than 3.5 μmol kg−1. Longer experiments, over a month in duration, have been completed with control to better than 0.08 pH units and 13 μmol kg−1 O2. The ability to study the impacts of multiple stressors in the laboratory simultaneously, as well as independently, will be an important part of understanding the response of marine organisms to a high-CO2 world.

  14. Technical Note: Controlled experimental aquarium system for multi-stressor investigation of carbonate chemistry, oxygen saturation, and temperature (United States)

    Bockmon, E. E.; Frieder, C. A.; Navarro, M. O.; White-Kershek, L. A.; Dickson, A. G.


    As the field of ocean acidification has grown, researchers have increasingly turned to laboratory experiments to understand the impacts of increased CO2 on marine organisms. However, other changes such as ocean warming and deoxygenation are occurring concurrently with the increasing CO2 concentrations, complicating the understanding of the impacts of anthropogenic changes on organisms. This experimental aquarium design allows for independent regulation of CO2 concentration, O2 levels, and temperature in a controlled environment to study the impacts of multiple stressors. The system has the flexibility for a wide range of treatment chemistry, seawater volumes, and study organisms. Control of the seawater chemistry is achieved by equilibration of a chosen gas mixture with seawater using a Liqui-Cel® membrane contactor. Included as examples, two experiments performed using the system have shown control of CO2 at values between approximately 500 and 1400 μatm and O2 at values from 80 to 240 μmol kg-1. Temperature has been maintained to 0.5 °C or better in the range of 10-17 °C. On a weeklong timescale, the system has achieved variability in pH of less than 0.007 pH units and in oxygen concentration of less than 3.5 μmol kg-1. Longer experiments, over a month in duration, have been completed with control to better than 0.08 pH units and 13 μmol kg-1 O2. The ability to study the impacts of multiple stressors in the laboratory simultaneously, as well as independently, will be an important part of understanding the response of marine organisms to a high-CO2 world.

  15. Modeling and experimental validation of CO heterogeneous chemistry and electrochemistry in solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Yurkiv, Vitaly


    In the present work experimental and numerical modeling studies of the heterogeneously catalyzed and electrochemical oxidation of CO at Nickel/yttria-stabilized zirconia (YSZ) solid oxide fuel cell (SOFC) anode systems were performed to evaluate elementary charge-transfer reaction mechanisms taking place at the three-phase boundary of CO/CO{sub 2} gas-phase, Ni electrode, and YSZ electrolyte. Temperature-programmed desorption and reaction experiments along with density functional theory calculations were performed to determine adsorption/desorption and surface diffusion kinetics as well as thermodynamic data for the CO/CO{sub 2}/Ni and CO/CO{sub 2}/YSZ systems. Based on these data elementary reaction based models with four different charge transfer mechanisms for the electrochemical CO oxidation were developed and applied in numerical simulations of literature experimental electrochemical data such as polarization curves and impedance spectra. Comparison between simulation and experiment demonstrated that only one of the four charge transfer mechanisms can consistently reproduce the electrochemical data over a wide range of operating temperatures and CO/CO{sub 2} gas compositions. (orig.) [German] In der vorliegenden Arbeit wurden experimentelle und numerische Untersuchungen zur heterogen katalysierten und elektrochemischen Oxidation von CO an Anodensystemen (bestehend aus Nickel und yttriumdotiertem Zirkoniumdioxid, YSZ) von Festoxidbrennstoffzellen (engl. Solid Oxide Fuel Cells, SOFCs) ausgefuehrt, um den mikroskopischen Mechanismus der an der CO/CO{sub 2}-Gasphase/Ni-Elektrode/YSZ-Elektrolyt- Dreiphasen-Grenzflaeche ablaufenden Ladungsuebertragungsreaktion aufzuklaeren. Temperaturprogrammierte Desorptionsmessungen (TPD) und Temperaturprogrammierte Reaktionsmessungen (TPR) sowie Dichtefunktionaltheorierechnungen wurden ausgefuehrt, um adsorptions-, desorptions- und reaktionskinetische sowie thermodynamische Daten fuer die CO/CO{sub 2}/Ni- und CO/CO{sub 2}/YSZ

  16. Characterizing the ozone formation potential of agricultural sources in California's San Joaquin Valley: A computational and experimental approach (United States)

    Howard, Cody Jerome

    The global pattern of expanding urban centers and increasing agricultural intensity is leading to more frequent interactions between air pollution emissions from urban and agricultural sources. The confluence of these emissions that traditionally have been separated by hundreds of kilometers is creating new air quality challenges in numerous regions across the United States. An area of particular interest is California's San Joaquin Valley (SJV), which has an agricultural output higher than many countries, a rapidly expanding human population, and ozone concentrations that are already higher than many dense urban areas. New regulations in the SJV restrict emissions of reactive organic gases (ROG) from animal sources in an attempt to meet Federal and State ozone standards designed to protect human health. A transportable "smog" chamber was developed and tested to directly measure the ozone formation potential of a variety of agricultural emissions in representative urban and rural atmospheres. After validation of the experimental procedure, four animal types were examined: beef cattle, dairy cattle, swine, and poultry, as well as six commonly used animal feeds: cereal silage (wheat grain and oat grain), alfalfa silage, corn silage, high moisture ground corn, almond shells, almond hulls, and total mixed ration. The emitted ROG composition was also measured so that the theoretical incremental reactivity could be calculated for a variety of atmospheres and directly compared with the measured ozone formation potential (OFP) under the experimental conditions. A computational model was created based on a modified form of the Caltech Atmospheric Chemistry Mechanism and validated against experimental results. After validation, the computational model was used to predict OFP across a range of NOx and ROG concentrations. The ROG OFP measurements combined with adjusted agricultural ROG emissions inventory estimates were used to predict the actual ozone production in the SJV

  17. Analytical chemistry

    International Nuclear Information System (INIS)

    Choi, Jae Seong


    This book is comprised of nineteen chapters, which describes introduction of analytical chemistry, experimental error and statistics, chemistry equilibrium and solubility, gravimetric analysis with mechanism of precipitation, range and calculation of the result, volume analysis on general principle, sedimentation method on types and titration curve, acid base balance, acid base titration curve, complex and firing reaction, introduction of chemical electro analysis, acid-base titration curve, electrode and potentiometry, electrolysis and conductometry, voltammetry and polarographic spectrophotometry, atomic spectrometry, solvent extraction, chromatograph and experiments.

  18. Integrated experimental and computational approach to laser machining of structural bone. (United States)

    Dahotre, Narendra B; Santhanakrishnan, Soundarapandian; Joshi, Sameehan S; Khan, Riaz J K; Fick, Daniel P; Robertson, William B; Sheh, Raymond K; Ironside, Charlie N


    This study describes the fundamentals of laser-bone interaction during bone machining through an integrated experimental-computational approach. Two groups of laser machining parameters identified the effects of process thermodynamics and kinetics on machining attributes at micro to macro. A continuous wave Yb-fiber Nd:YAG laser (wavelength 1070 nm) with fluences in the range of 3.18 J/mm 2 -8.48 J/mm 2 in combination of laser power (300 W-700 W) and machining speed (110 mm/s-250 mm/s) were considered for machining trials. The machining attributes were evaluated through scanning electron microscopy observations and compared with finite element based multiphysics-multicomponent computational model predicted values. For both groups of laser machining parameters, experimentally evaluated and computationally predicted depths and widths increased with increased laser energy input and computationally predicted widths remained higher than experimentally measured widths whereas computationally predicted depths were slightly higher than experimentally measured depths and reversed this trend for the laser fluence >6 J/mm 2 . While in both groups, the machining rate increased with increased laser fluence, experimentally derived machining rate remained lower than the computationally predicted values for the laser fluences lower than ∼4.75 J/mm 2 for one group and ∼5.8 J/mm 2 for other group and reversed in this trend thereafter. The integrated experimental-computational approach identified the physical processes affecting machining attributes. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

  19. Long-term water chemistry database, Little River Experimental Watershed, southeast Coastal Plain, United States (United States)

    Feyereisen, G. W.; Lowrance, R.; Strickland, T. C.; Sheridan, J. M.; Hubbard, R. K.; Bosch, D. D.


    A water quality sampling program was initiated in 1974 by the U.S. Department of Agriculture Agricultural Research Service on the 334 km2 Little River Experimental Watershed (LREW) near Tifton in south Georgia to monitor the effects of changing land use and agricultural practices over time and to support development of simulation models capable of predicting future impacts of agricultural land use and management changes. Stream samples were taken on a weekly or more frequent basis and were analyzed for chloride, ammonium nitrogen, nitrate plus nitrite nitrogen, total kjeldahl nitrogen, total phosphorus, and dissolved molybdate reactive phosphorus. Monitoring began in 1974 on the entire watershed and four nested subwatersheds, ranging in size from 16.7 to 114.9 km2, and continues until present. Partial records of 7, 10, and 19 years exist for three additional subwatersheds. Suspended solids data are available for all eight subwatersheds for 1974-1978 and 1979-1981, three subwatersheds for 1982-1986, and all eight subwatersheds again beginning in the year 2000. The concentration and associated load data are being published on the LREW database anonymous ftp site (

  20. Pretreatment chemistry for dual media filtration: model simulations and experimental studies. (United States)

    Shin, J Y; O'Melia, C R


    Laboratory dual media filtration experiments were conducted (a) in direct filtration mode using model raw water moderate in turbidity and low in DOC, and (b) in conventional filtration mode treating water moderate in turbidity and high in DOC. Model simulations of filter performance for the removal of particles provided hypotheses for the experimental studies of dual media filtration. An increase in alum dose in direct filtration mode, while improving filter performance, also showed some disadvantages, including rapid development of head loss. Suboptimal dose in direct filtration significantly impaired the filter performance. In conventional mode, the effect of alum dose on the filter performance, while obvious, was not as dramatic as in direct filtration. Ripening indicated by particle counts occurred earlier than by turbidity and breakthrough of particle counts started earlier than breakthrough of turbidity, suggesting that turbidity can be used as a more conservative monitor of filter performance during the ripening period to minimise the risk of passage of small particles, while particle counts can be considered a more sensitive indicator of deteriorating filter performance during the breakthrough period. The lower sand layer served as a multiple barrier for particle when the performance of the anthracite layer was not effective.

  1. Effect of Peer-Led Team Learning (PLTL) on Student Achievement, Attitude, and Self-Concept in College General Chemistry in Randomized and Quasi Experimental Designs (United States)

    Chan, Julia Y. K.; Bauer, Christopher F.


    This study investigated exam achievement and affective characteristics of students in general chemistry in a fully-randomized experimental design, contrasting Peer-Led Team Learning (PLTL) participation with a control group balanced for time-on-task and study activity. This study population included two independent first-semester courses with…

  2. Matched molecular pair-based data sets for computer-aided medicinal chemistry (United States)

    Bajorath, Jürgen


    Matched molecular pairs (MMPs) are widely used in medicinal chemistry to study changes in compound properties including biological activity, which are associated with well-defined structural modifications. Herein we describe up-to-date versions of three MMP-based data sets that have originated from in-house research projects. These data sets include activity cliffs, structure-activity relationship (SAR) transfer series, and second generation MMPs based upon retrosynthetic rules. The data sets have in common that they have been derived from compounds included in the ChEMBL database (release 17) for which high-confidence activity data are available. Thus, the activity data associated with MMP-based activity cliffs, SAR transfer series, and retrosynthetic MMPs cover the entire spectrum of current pharmaceutical targets. Our data sets are made freely available to the scientific community. PMID:24627802

  3. Chemistry of burning the forest floor during the FROSTFIRE experimental burn, interior Alaska, 1999 (United States)

    Harden, J.W.; Neff, J.C.; Sandberg, D.V.; Turetsky, M.R.; Ottmar, R.; Gleixner, G.; Fries, T.L.; Manies, K.L.


    Wildfires represent one of the most common disturbances in boreal regions, and have the potential to reduce C, N, and Hg stocks in soils while contributing to atmospheric emissions. Organic soil layers of the forest floor were sampled before and after the FROSTFIRE experimental burn in interior Alaska, and were analyzed for bulk density, major and trace elements, and organic compounds. Concentrations of carbon, nutrients, and several major and trace elements were significantly altered by the burn. Emissions of C, N, and Hg, estimated from chemical mass balance equations using Fe, Al, and Si as stable constituents, indicated that 500 to 900 g C and up to 0 to 4 ?? 10-4 g Hg/M2 were lost from the site. Calculations of nitrogen loss range from -4 to +6 g/m2 but were highly variable (standard deviation 19), with some samples showing increased N concentrations post-burn potentially from canopy ash. Noncombustible major nutrients such as Ca and K also were inherited from canopy ash. Thermogravimetry indicates a loss of thermally labile C and increase of lignin-like C in char and ash relative to unburned counterparts. Overall, atmospheric impacts of boreal fires include large emissions of C, N and Hg that vary greatly as a function of severe fire weather and its access to deep organic layers rich in C, N, and Hg. In terrestrial systems, burning rearranges the vertical distribution of nutrients in fuels and soils, the proximity of nutrients and permafrost to surface biota, and the chemical composition of soil including its nutrient and organic constituents, all of which impact C cycling. Copyright 2004 by the American Geophysical Union.

  4. A computational chemistry study on friction of h-MoS(2). Part I. Mechanism of single sheet lubrication. (United States)

    Onodera, Tasuku; Morita, Yusuke; Suzuki, Ai; Koyama, Michihisa; Tsuboi, Hideyuki; Hatakeyama, Nozomu; Endou, Akira; Takaba, Hiromitsu; Kubo, Momoji; Dassenoy, Fabrice; Minfray, Clotilde; Joly-Pottuz, Lucile; Martin, Jean-Michel; Miyamoto, Akira


    In this work, we theoretically investigated the friction mechanism of hexagonal MoS(2) (a well-known lamellar compound) using a computational chemistry method. First, we determined several parameters for molecular dynamics simulations via accurate quantum chemistry calculations and MoS(2) and MoS(2-x)O(x) structures were successfully reproduced. We also show that the simulated Raman spectrum and peak shift on X-ray diffraction patterns were in good agreement with those of experiment. The atomic interactions between MoS(2) sheets were studied by using a hybrid quantum chemical/classical molecular dynamics method. We found that the predominant interaction between two sulfur layers in different MoS(2) sheets was Coulombic repulsion, which directly affects the MoS(2) lubrication. MoS(2) sheets adsorbed on a nascent iron substrate reduced friction further due to much larger Coulombic repulsive interactions. Friction for the oxygen-containing MoS(2) sheets was influenced by not only the Coulomb repulsive interaction but also the atomic-scale roughness of the MoS(2)/MoS(2) sliding interface.

  5. Visually impaired researchers get their hands on quantum chemistry: application to a computational study on the isomerization of a sterol (United States)

    Lounnas, Valère; Wedler, Henry B.; Newman, Timothy; Schaftenaar, Gijs; Harrison, Jason G.; Nepomuceno, Gabriella; Pemberton, Ryan; Tantillo, Dean J.; Vriend, Gert


    In molecular sciences, articles tend to revolve around 2D representations of 3D molecules, and sighted scientists often resort to 3D virtual reality software to study these molecules in detail. Blind and visually impaired (BVI) molecular scientists have access to a series of audio devices that can help them read the text in articles and work with computers. Reading articles published in this journal, though, is nearly impossible for them because they need to generate mental 3D images of molecules, but the article-reading software cannot do that for them. We have previously designed AsteriX, a web server that fully automatically decomposes articles, detects 2D plots of low molecular weight molecules, removes meta data and annotations from these plots, and converts them into 3D atomic coordinates. AsteriX-BVI goes one step further and converts the 3D representation into a 3D printable, haptic-enhanced format that includes Braille annotations. These Braille-annotated physical 3D models allow BVI scientists to generate a complete mental model of the molecule. AsteriX-BVI uses Molden to convert the meta data of quantum chemistry experiments into BVI friendly formats so that the entire line of scientific information that sighted people take for granted—from published articles, via printed results of computational chemistry experiments, to 3D models—is now available to BVI scientists too. The possibilities offered by AsteriX-BVI are illustrated by a project on the isomerization of a sterol, executed by the blind co-author of this article (HBW).

  6. Methods and experimental coefficients used in the computation of reactor shielding

    International Nuclear Information System (INIS)

    Bourgeois, J.; Lafore, P.; Millot, J.P.; Rastoin, J.; Vathaire, F. de


    1. The concept of an effective removal cross section has been developed in order more easily to compute reactor shielding thicknesses. We have built an experimental facility for the purpose of measuring effective removal cross sections, the value of which had not been published at that time. The first part of this paper describes the device or facility used, the computation method applied, and the results obtained. 2. Starting from this concept, we endeavored to define a removal cross section as a function of energy. This enabled us to use the method for computations bearing on the attenuation of fast neutrons of any spectrum. An experimental verification was carried out for the case of fission neutrons filtered by a substantial thickness of graphite. 3. Finally, we outline a computation method enabling us to determine the sources of captured gamma rays by the age theory and we give an example of the application in a composite shield. (author) [fr

  7. The Variation Theorem Applied to H-2+: A Simple Quantum Chemistry Computer Project (United States)

    Robiette, Alan G.


    Describes a student project which requires limited knowledge of Fortran and only minimal computing resources. The results illustrate such important principles of quantum mechanics as the variation theorem and the virial theorem. Presents sample calculations and the subprogram for energy calculations. (GS)

  8. Computer techniques for experimental work in GDR nuclear power plants with WWER

    International Nuclear Information System (INIS)

    Stemmler, G.


    Nuclear power plant units with WWER are being increasingly equipped with high-performance, programmable process control computers. There are, however, essential reasons for further advancing the development of computer-aided measuring systems, in particular for experimental work. A special structure of such systems, which is based on the division into relatively rigid data registration and primary handling and into further processing by advanced programming language, has proved useful in the GDR. (author)

  9. Experimental and Computational Study of Ductile Fracture in Small Punch Tests

    Directory of Open Access Journals (Sweden)

    Betül Gülçimen Çakan


    Full Text Available A unified experimental-computational study on ductile fracture initiation and propagation during small punch testing is presented. Tests are carried out at room temperature with unnotched disks of different thicknesses where large-scale yielding prevails. In thinner specimens, the fracture occurs with severe necking under membrane tension, whereas for thicker ones a through thickness shearing mode prevails changing the crack orientation relative to the loading direction. Computational studies involve finite element simulations using a shear modified Gurson-Tvergaard-Needleman porous plasticity model with an integral-type nonlocal formulation. The predicted punch load-displacement curves and deformed profiles are in good agreement with the experimental results.

  10. XI International conference Problems of solvation and complex formation in solutions, and VI Conference of young scientists Theoretical and experimental chemistry of liquid-phase systems (Krestovsky readings). Summary of reports

    International Nuclear Information System (INIS)


    The collection contains materials of plenary, sectional and poster sessions, presented at the XI International conference Problems of solvation and complex formation in solutions, and VI Conference of young scientists Theoretical and experimental chemistry of liquid-phase systems (Krestovsky readings). Theoretical questions and new experimental methods of chemistry of solutions, structure and dynamics of molecular and ion-molecular systems in solution and at the phase boundary; modern aspects of applied chemistry of solutions are discussed [ru

  11. Discovery and development of anticancer agents from marine sponges: perspectives based on a chemistry-experimental therapeutics collaborative program. (United States)

    Valeriote, Frederick A; Tenney, Karen; Media, Joseph; Pietraszkiewicz, Halina; Edelstein, Matthew; Johnson, Tyler A; Amagata, Taro; Crews, Phillip


    A collaborative program was initiated in 1990 between the natural product chemistry laboratory of Dr. Phillip Crews at the University of California Santa Cruz and the experimental therapeutics laboratory of Dr. Fred Valeriote at the Henry Ford Hospital in Detroit. The program focused on the discovery and development of anticancer drugs from sponge extracts. A novel in vitro disk diffusion, solid tumor selective assay was used to examine 2,036 extracts from 683 individual sponges. The bioassay-directed fractionation discovery component led to the identification of active pure compounds from many of these sponges. In most cases, pure compound was prepared in sufficient quantities to both chemically identify the active compound(s) as well as pursue one or more of the biological development components. The latter included IC50, clonogenic survival-concentration exposure, maximum tolerated dose, pharmacokinetics and therapeutic assessment studies. Solid tumor selective compounds included fascaplysin and 10-bromofascaplysin (Fascaplysinopsis), neoamphimedine, 5-methoxyneoamphimedine and alpkinidine (Xestospongia), makaluvamine C and makaluvamine H (Zyzzya), psymberin (Psammocinia and Ircinia), and ethylplakortide Z and ethyldidehydroplakortide Z (Plakortis). These compounds or analogs thereof continue to have therapeutic potential.

  12. Impact of the spectral and spatial properties of natural light on indoor gas-phase chemistry: Experimental and modeling study. (United States)

    Blocquet, M; Guo, F; Mendez, M; Ward, M; Coudert, S; Batut, S; Hecquet, C; Blond, N; Fittschen, C; Schoemaecker, C


    The characteristics of indoor light (intensity, spectral, spatial distribution) originating from outdoors have been studied using experimental and modeling tools. They are influenced by many parameters such as building location, meteorological conditions, and the type of window. They have a direct impact on indoor air quality through a change in chemical processes by varying the photolysis rates of indoor pollutants. Transmittances of different windows have been measured and exhibit different wavelength cutoffs, thus influencing the potential of different species to be photolysed. The spectral distribution of light entering indoors through the windows was measured under different conditions and was found to be weakly dependent on the time of day for indirect cloudy, direct sunshine, partly cloudy conditions contrary to the light intensity, in agreement with calculations of the transmittance as a function of the zenithal angle and the calculated outdoor spectral distribution. The same conclusion can be drawn concerning the position within the room. The impact of these light characteristics on the indoor chemistry has been studied using the INCA-Indoor model by considering the variation in the photolysis rates of key indoor species. Depending on the conditions, photolysis processes can lead to a significant production of radicals and secondary species. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  13. Experimental realization of Deutsch's algorithm in a one-way quantum computer. (United States)

    Tame, M S; Prevedel, R; Paternostro, M; Böhi, P; Kim, M S; Zeilinger, A


    We report the first experimental demonstration of an all-optical one-way implementation of Deutsch's quantum algorithm on a four-qubit cluster state. All the possible configurations of a balanced or constant function acting on a two-qubit register are realized within the measurement-based model for quantum computation. The experimental results are in excellent agreement with the theoretical model, therefore demonstrating the successful performance of the algorithm.

  14. Express: a Web-based technology to support human and computational experimentation. (United States)

    Yule, Peter; Cooper, Richard P


    Experimental cognitive psychology has been greatly assisted by the development of general computer-based experiment presentation packages. Typically, however, such packages provide little support for running participants on different computers. It is left to the experimenter to ensure that group sizes are balanced between conditions and to merge data gathered on different computers once the experiment is complete. Equivalent issues arise in the evaluation of parameterized computational models, where it is frequently necessary to test a model's behavior over a range of parameter values (which amount to between-subjects factors) and where such testing can be speeded up significantly by the use of multiple processors. This article describes Express, a Web-based technology for coordinating "clients" participants or computational models) and collating client data. The technology provides an experiment design editor, client coordination facilities (e.g., automated randomized assignment of clients to groups so that group sizes are balanced), general data collation and tabulation facilities, a range of basic statistical functions (which are constrained by the specified experimental design), and facilities to export data to standard statistical packages (such as SPSS). We report case studies demonstrating the utility of Express in both human and computational experiments. Express may be freely downloaded from the Express Web site (

  15. Calibration of uncertain inputs to computer models using experimentally measured quantities and the BMARS emulator

    International Nuclear Information System (INIS)

    Stripling, H.F.; McClarren, R.G.; Kuranz, C.C.; Grosskopf, M.J.; Rutter, E.; Torralva, B.R.


    We present a method for calibrating the uncertain inputs to a computer model using available experimental data. The goal of the procedure is to produce posterior distributions of the uncertain inputs such that when samples from the posteriors are used as inputs to future model runs, the model is more likely to replicate (or predict) the experimental response. The calibration is performed by sampling the space of the uncertain inputs, using the computer model (or, more likely, an emulator for the computer model) to assign weights to the samples, and applying the weights to produce the posterior distributions and generate predictions of new experiments within confidence bounds. The method is similar to the Markov chain Monte Carlo (MCMC) calibration methods with independent sampling with the exception that we generate samples beforehand and replace the candidate acceptance routine with a weighting scheme. We apply our method to the calibration of a Hyades 2D model of laser energy deposition in beryllium. We employ a Bayesian Multivariate Adaptive Regression Splines (BMARS) emulator as a surrogate for Hyades 2D. We treat a range of uncertainties in our system, including uncertainties in the experimental inputs, experimental measurement error, and systematic experimental timing errors. The results of the calibration are posterior distributions that both agree with intuition and improve the accuracy and decrease the uncertainty in experimental predictions. (author)

  16. Validation of thermohydraulic codes by comparison of experimental results with computer simulations

    International Nuclear Information System (INIS)

    Madeira, A.A.; Galetti, M.R.S.; Pontedeiro, A.C.


    The results obtained by simulation of three cases from CANON depressurization experience, using the TRAC-PF1 computer code, version 7.6, implanted in the VAX-11/750 computer of Brazilian CNEN, are presented. The CANON experience was chosen as first standard problem in thermo-hydraulic to be discussed at ENFIR for comparing results from different computer codes with results obtained experimentally. The ability of TRAC-PF1 code to prevent the depressurization phase of a loss of primary collant accident in pressurized water reactors is evaluated. (M.C.K.) [pt

  17. Computational Fluid Dynamics Modelling and Experimental Study on a Single Silica Gel Type B

    Directory of Open Access Journals (Sweden)

    John White


    Full Text Available The application of computational fluid dynamics (CFDs in the area of porous media and adsorption cooling system is becoming more practical due to the significant improvement in computer power. The results from previous studies have shown that CFD can be useful tool for predicting the water vapour flow pattern, temperature, heat transfer and flow velocity and adsorption rate. This paper investigates the effect of silica gel granular size on the water adsorption rate using computational fluid dynamics and gravimetric experimental (TGA method.

  18. Contributions of computational chemistry and biophysical techniques to fragment-based drug discovery. (United States)

    Gozalbes, Rafael; Carbajo, Rodrigo J; Pineda-Lucena, Antonio


    In the last decade, fragment-based drug discovery (FBDD) has evolved from a novel approach in the search of new hits to a valuable alternative to the high-throughput screening (HTS) campaigns of many pharmaceutical companies. The increasing relevance of FBDD in the drug discovery universe has been concomitant with an implementation of the biophysical techniques used for the detection of weak inhibitors, e.g. NMR, X-ray crystallography or surface plasmon resonance (SPR). At the same time, computational approaches have also been progressively incorporated into the FBDD process and nowadays several computational tools are available. These stretch from the filtering of huge chemical databases in order to build fragment-focused libraries comprising compounds with adequate physicochemical properties, to more evolved models based on different in silico methods such as docking, pharmacophore modelling, QSAR and virtual screening. In this paper we will review the parallel evolution and complementarities of biophysical techniques and computational methods, providing some representative examples of drug discovery success stories by using FBDD.

  19. Química orgânica experimental: integração de teoria, experimento e análise Experimental organic Chemistry: integration of theory, experiment and analysis


    Lothar W. Bieber


    A new approach for teaching in basic experimental organic chemistry is presented. Experimental work goes on parallel to theoretical lectures leading to an immediate application of theoretical concepts transmitted therein. One day/week is dedicated exclusively to the organic laboratory. Reactions are proposed as problems to be solved; the student has to deduce the structure of the product on the basis of his observations, the analytical data and his mechanistical knowledge. 70 different experi...


    Directory of Open Access Journals (Sweden)

    I. A. Khorunzhii


    Full Text Available A cooling system for powerful semi-conductor device (power -1 kW consisting of a pin-type radiator and a body is considered in the paper. Cooling is carried out by forced convection of a coolant. Calculated values of temperatures on the radiator surface and experimentally measured values of temperatures in the same surface points have been compared in the paper. It has been shown that the difference between calculated and experimentally measured temperatures does not exceed 0,1-0,2 °C and it is comparable with experimental error value. The given results confirm correctness of a computer model.

  1. Experimental and computational approaches to evaluate the environmental mitigation effect in narrow spaces by noble metal chemical addition (NMCA)

    International Nuclear Information System (INIS)

    Shimizu, Ryosuke; Ota, Nobuyuki; Nagase, Makoto; Aizawa, Motohiro; Ishida, Kazushige; Wada, Yoichi


    The environmental mitigation effect of NMCA in a narrow space was evaluated by experimental and computational approaches. In the experiment at 8 MPa and 553K, T-tube whose branched line had a narrow space was prepared, and the Zr electrodes were set in the branched line at certain intervals, which were 1, 3, 5, 7, 9, 11, 15 and 29 cm from the opening section of the branched line. Electrochemical corrosion potential (ECP) at the tip of the branched narrow space varied in response to the water chemistry in the main line which was at right angle with the branched line. Computational fluid dynamics (CFD) analysis reproduced the experimental results. It was also confirmed by CFD analysis that the ingress of water from the main line into the narrow space was accelerated by cavity flow and thermal convection. By CFD analysis in a thermal sleeve of actual plant condition, which had a narrow space, the concentration of dissolved oxygen at a tip of the thermal sleeve reached at 250 ppb within 300 sec, which was the same concentration of the main line. Noble metal deposition on the surface of the thermal sleeve was evaluated by mass transfer model. Noble metal deposition was the largest near the opening section of the branched line, and gradually decreased toward the tip section. In light of the consumption of dissolved oxygen in the branched line, noble metal deposition in the thermal sleeve was sufficient to reduce the ECP. It was expected that NMCA could mitigate the corrosion environment in the thermal sleeve. (author)

  2. Video Analysis of Projectile Motion Using Tablet Computers as Experimental Tools (United States)

    Klein, P.; Gröber, S.; Kuhn, J.; Müller, A.


    Tablet computers were used as experimental tools to record and analyse the motion of a ball thrown vertically from a moving skateboard. Special applications plotted the measurement data component by component, allowing a simple determination of initial conditions and "g" in order to explore the underlying laws of motion. This experiment…

  3. Experimental and Computer Modelling Studies of Metastability of Amorphous Silicon Based Solar Cells

    NARCIS (Netherlands)

    Munyeme, Geoffrey


    We present a combination of experimental and computer modelling studies of the light induced degradation in the performance of amorphous silicon based single junction solar cells. Of particular interest in this study is the degradation kinetics of different types of amorphous silicon single junction

  4. Characteristic thermal-hydraulic problems in NHRs: Overview of experimental investigations and computer codes

    International Nuclear Information System (INIS)

    Falikov, A.A.; Vakhrushev, V.V.; Kuul, V.S.; Samoilov, O.B.; Tarasov, G.I.


    The paper briefly reviews the specific thermal-hydraulic problems for AST-type NHRs, the experimental investigations that have been carried out in the RF, and the design procedures and computer codes used for AST-500 thermohydraulic characteristics and safety validation. (author). 13 refs, 10 figs, 1 tab

  5. Mechanism of the Hydrosilylation Reaction of Alkenes at Porous Silicon: Experimental and Computational Deuterium Labeling Studies

    NARCIS (Netherlands)

    Smet, de L.C.P.M.; Zuilhof, H.; Sudhölter, E.J.R.; Lie, L.H.; Houlton, A.; Horrocks, B.R.


    The mechanism of the formation of Si-C bonded monolayers on silicon by reaction of 1-alkenes with hydrogen-terminated porous silicon surfaces has been studied by both experimental and computational means. We propose that monolayer formation occurs via the same radical chain process as at

  6. Computational Material Modeling of Hydrated Cement Paste Calcium Silicate Hydrate (C-S-H) Chemistry Structure - Influence of Magnesium Exchange on Mechanical Stiffness: C-S-H Jennite (United States)


    hydrated cement paste constituent - calcium silicate hydrate (C-S-H) based on its material chemistry structure are studied following a molecular dynamics...2015 Approved for public release; distribution is unlimited. Computational Material Modeling of Hydrated Cement Paste Calcium Silicate Hydrate (C-S-H...1601 East Market Street Greensboro, NC 27411 -0001 ABSTRACT Computational Material Modeling of Hydrated Cement Paste Calcium Silicate Hydrate (C-S-H

  7. A Case for Soft Error Detection and Correction in Computational Chemistry. (United States)

    van Dam, Hubertus J J; Vishnu, Abhinav; de Jong, Wibe A


    High performance computing platforms are expected to deliver 10(18) floating operations per second by the year 2022 through the deployment of millions of cores. Even if every core is highly reliable the sheer number of them will mean that the mean time between failures will become so short that most application runs will suffer at least one fault. In particular soft errors caused by intermittent incorrect behavior of the hardware are a concern as they lead to silent data corruption. In this paper we investigate the impact of soft errors on optimization algorithms using Hartree-Fock as a particular example. Optimization algorithms iteratively reduce the error in the initial guess to reach the intended solution. Therefore they may intuitively appear to be resilient to soft errors. Our results show that this is true for soft errors of small magnitudes but not for large errors. We suggest error detection and correction mechanisms for different classes of data structures. The results obtained with these mechanisms indicate that we can correct more than 95% of the soft errors at moderate increases in the computational cost.

  8. Direction and Integration of Experimental Ground Test Capabilities and Computational Methods (United States)

    Dunn, Steven C.


    This paper groups and summarizes the salient points and findings from two AIAA conference panels targeted at defining the direction, with associated key issues and recommendations, for the integration of experimental ground testing and computational methods. Each panel session utilized rapporteurs to capture comments from both the panel members and the audience. Additionally, a virtual panel of several experts were consulted between the two sessions and their comments were also captured. The information is organized into three time-based groupings, as well as by subject area. These panel sessions were designed to provide guidance to both researchers/developers and experimental/computational service providers in defining the future of ground testing, which will be inextricably integrated with the advancement of computational tools.

  9. Identifying controlling variables for math computation fluency through experimental analysis: the interaction of stimulus control and reinforcing consequences. (United States)

    Hofstadter-Duke, Kristi L; Daly, Edward J


    This study investigated a method for conducting experimental analyses of academic responding. In the experimental analyses, academic responding (math computation), rather than problem behavior, was reinforced across conditions. Two separate experimental analyses (one with fluent math computation problems and one with non-fluent math computation problems) were conducted with three elementary school children using identical contingencies while math computation rate was measured. Results indicate that the experimental analysis with non-fluent problems produced undifferentiated responding across participants; however, differentiated responding was achieved for all participants in the experimental analysis with fluent problems. A subsequent comparison of the single-most effective condition from the experimental analyses replicated the findings with novel computation problems. Results are discussed in terms of the critical role of stimulus control in identifying controlling consequences for academic deficits, and recommendations for future research refining and extending experimental analysis to academic responding are made. © The Author(s) 2014.

  10. Charge-assisted triel bonding interactions in solid state chemistry: A combined computational and crystallographic study (United States)

    Bauzá, Antonio; García-Llinás, Xavier; Frontera, Antonio


    A combined energetic and geometric study of a series of triel bond complexes involving haloborane salts has been carried out at the M06-2X/def2-QZVPD level of theory. We have used 1-(dihaloboranyl)pyridin-1-ium compounds Py+BX2 (X = Cl, Br and I) as triel bond donors and Cl-, Br-, HCO2-, BF4- and ClO4- as electron donor moieties. In addition we have used Bader's theory of 'atoms in molecules' to further characterize the noncovalent interactions described herein. Finally, several examples were retrieved from the CSD (Cambridge Structural Database) in order to provide experimental support to the results presented in this work.

  11. Experimental validation of numerical simulations: a comparison of computational fluid dynamics and the oil film method. (United States)

    Stoiber, M; Grasl, C; Pirker, S; Huber, L; Gittler, P; Schima, H


    Today Computational Fluid Dynamics (CFD) is used for simulating flow in many applications. The quality of the results, however, depends on various factors, like grid quality, boundary conditions and the computational model of the fluid. For this reason, it is important to validate the performed computation with experimental results. In this work, a comparison of numerical simulation with the oil film method was performed for two cardiovascular applications. The investigations were conducted at various geometries, such as a bended cannula tubing, an impeller of a magnetically levitated rotary blood pump and tips of inflow cannulas. The oil film for the experimental validation was composed of black oil color and varnish. In the numerical simulation, color abrasion was displayed with a special post-processing tool by means of wall-attached pathlines. With the proper choice of numerical parameters, the computer simulations and the oil film method demonstrated good correlation. Improper generation of the simulation grid did lead to divergent results between the numerical simulation and the experiment. For the pump impeller as well as for the inflow cannulas, the calculation and the experiment showed similar flow patterns with backflow and stall zones. The oil film method represents a fast and simple approach to help validate numerical simulations of fluid flow. The experimentally generated near wall flow patterns can be easily compared with the solution of the CFD analysis.

  12. Investigation of anticancer properties of caffeinated complexes via computational chemistry methods (United States)

    Sayin, Koray; Üngördü, Ayhan


    Computational investigations were performed for 1,3,7-trimethylpurine-2,6-dione, 3,7-dimethylpurine-2,6-dione, their Ru(II) and Os(III) complexes. B3LYP/6-311 ++G(d,p)(LANL2DZ) level was used in numerical calculations. Geometric parameters, IR spectrum, 1H-, 13C and 15N NMR spectrum were examined in detail. Additionally, contour diagram of frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP) maps, MEP contour and some quantum chemical descriptors were used in the determination of reactivity rankings and active sites. The electron density on the surface was similar to each other in studied complexes. Quantum chemical descriptors were investigated and the anticancer activity of complexes were more than cisplatin and their ligands. Additionally, molecular docking calculations were performed in water between related complexes and a protein (ID: 3WZE). The most interact complex was found as Os complex. The interaction energy was calculated as 342.9 kJ/mol.

  13. Emerging experimental and computational technologies for purpose designed engineering of photosynthetic prokaryotes

    KAUST Repository

    Lindblad, Peter


    With recent advances in synthetic molecular tools to be used in photosynthetic prokaryotes, like cyanobacteria, it is possible to custom design and construct microbial cells for specific metabolic functions. This cross-disciplinary area of research has emerged within the interfaces of advanced genetic engineering, computational science, and molecular biotechnology. We have initiated the development of a genetic toolbox, using a synthetic biology approach, to custom design, engineer and construct cyanobacteria for selected function and metabolism. One major bottleneck is a controlled transcription and translation of introduced genetic constructs. An additional major issue is genetic stability. I will present and discuss recent progress in our development of genetic tools for advanced cyanobacterial biotechnology. Progress on understanding the electron pathways in native and engineered cyanobacterial enzymes and heterologous expression of non-native enymzes in cyanobacterial cells will be highlighted. Finally, I will discuss our attempts to merge synthetic biology with synthetic chemistry to explore fundamantal questions of protein design and function.

  14. Computational chemistry approach for the early detection of drug-induced idiosyncratic liver toxicity. (United States)

    Cruz-Monteagudo, Maykel; Cordeiro, M Natália D S; Borges, Fernanda


    Idiosyncratic drug toxicity (IDT), considered as a toxic host-dependent event, with an apparent lack of dose response relationship, is usually not predictable from early phases of clinical trials, representing a particularly confounding complication in drug development. Albeit a rare event (usually approach proposed in the present study, can play an important role in addressing IDT in early drug discovery. We report for the first time a systematic evaluation of classification models to predict idiosyncratic hepatotoxicity based on linear discriminant analysis (LDA), artificial neural networks (ANN), and machine learning algorithms (OneR) in conjunction with a 3D molecular structure representation and feature selection methods. These modeling techniques (LDA, feature selection to prevent over-fitting and multicollinearity, ANN to capture nonlinear relationships in the data, as well as the simple OneR classifier) were found to produce QSTR models with satisfactory internal cross-validation statistics and predictivity on an external subset of chemicals. More specifically, the models reached values of accuracy/sensitivity/specificity over 84%/78%/90%, respectively in the training series along with predictivity values ranging from ca. 78 to 86% of correctly classified drugs. An LDA-based desirability analysis was carried out in order to select the levels of the predictor variables needed to trigger the more desirable drug, i.e. the drug with lower potential for idiosyncratic hepatotoxicity. Finally, two external test sets were used to evaluate the ability of the models in discriminating toxic from nontoxic structurally and pharmacologically related drugs and the ability of the best model (LDA) in detecting potential idiosyncratic hepatotoxic drugs, respectively. The computational approach proposed here can be considered as a useful tool in early IDT prognosis.

  15. Experimental assessment of computer codes used for safety analysis of integral reactors

    Energy Technology Data Exchange (ETDEWEB)

    Falkov, A.A.; Kuul, V.S.; Samoilov, O.B. [OKB Mechanical Engineering, Nizhny Novgorod (Russian Federation)


    Peculiarities of integral reactor thermohydraulics in accidents are associated with presence of noncondensable gas in built-in pressurizer, absence of pumped ECCS, use of guard vessel for LOCAs localisation and passive RHRS through in-reactor HX`s. These features defined the main trends in experimental investigations and verification efforts for computer codes applied. The paper reviews briefly the performed experimental investigation of thermohydraulics of AST-500, VPBER600-type integral reactors. The characteristic of UROVEN/MB-3 code for LOCAs analysis in integral reactors and results of its verification are given. The assessment of RELAP5/mod3 applicability for accident analysis in integral reactor is presented.

  16. Computational and experimental studies of reassociating RNA/DNA hybrids containing split functionalities. (United States)

    Afonin, Kirill A; Bindewald, Eckart; Kireeva, Maria; Shapiro, Bruce A


    Recently, we developed a novel technique based on RNA/DNA hybrid reassociation that allows conditional activation of different split functionalities inside diseased cells and in vivo. We further expanded this idea to permit simultaneous activation of multiple different functions in a fully controllable fashion. In this chapter, we discuss some novel computational approaches and experimental techniques aimed at the characterization, design, and production of reassociating RNA/DNA hybrids containing split functionalities. We also briefly describe several experimental techniques that can be used to test these hybrids in vitro and in vivo. 2015 Published by Elsevier Inc.

  17. A computer program to evaluate the experimental data in instrumental multielement neutron activation analysis

    International Nuclear Information System (INIS)

    Greim, L.; Motamedi, K.; Niedergesaess, R.


    A computer code evaluating experimental data of neutron activation analysis (NAA) for determination of atomic abundancies is described. The experimental data are, beside a probe designation, the probe weight, irradiation parameters and a Ge(Li)-pulse-height-spectrum from the activity measurement. The organisation of the necessary nuclear data, comprising all methods of activation in reactor-irradiations, is given. Furthermore the automatic evaluation of spectra, the designation of the resulting peaks to nuclei and the calculation of atomic abundancies are described. The complete evaluation of a spectrum with many lines, e.g. 100 lines of 20 nuclei, takes less than 1 minute machine-time on the TR 440 computer. (orig.) [de

  18. Experimental validation of convection-diffusion discretisation scheme employed for computational modelling of biological mass transport

    Directory of Open Access Journals (Sweden)

    Ku David N


    Full Text Available Abstract Background The finite volume solver Fluent (Lebanon, NH, USA is a computational fluid dynamics software employed to analyse biological mass-transport in the vasculature. A principal consideration for computational modelling of blood-side mass-transport is convection-diffusion discretisation scheme selection. Due to numerous discretisation schemes available when developing a mass-transport numerical model, the results obtained should either be validated against benchmark theoretical solutions or experimentally obtained results. Methods An idealised aneurysm model was selected for the experimental and computational mass-transport analysis of species concentration due to its well-defined recirculation region within the aneurysmal sac, allowing species concentration to vary slowly with time. The experimental results were obtained from fluid samples extracted from a glass aneurysm model, using the direct spectrophometric concentration measurement technique. The computational analysis was conducted using the four convection-diffusion discretisation schemes available to the Fluent user, including the First-Order Upwind, the Power Law, the Second-Order Upwind and the Quadratic Upstream Interpolation for Convective Kinetics (QUICK schemes. The fluid has a diffusivity of 3.125 × 10-10 m2/s in water, resulting in a Peclet number of 2,560,000, indicating strongly convection-dominated flow. Results The discretisation scheme applied to the solution of the convection-diffusion equation, for blood-side mass-transport within the vasculature, has a significant influence on the resultant species concentration field. The First-Order Upwind and the Power Law schemes produce similar results. The Second-Order Upwind and QUICK schemes also correlate well but differ considerably from the concentration contour plots of the First-Order Upwind and Power Law schemes. The computational results were then compared to the experimental findings. An average error of 140

  19. Experimental validation of convection-diffusion discretisation scheme employed for computational modelling of biological mass transport. (United States)

    Carroll, Gráinne T; Devereux, Paul D; Ku, David N; McGloughlin, Timothy M; Walsh, Michael T


    The finite volume solver Fluent (Lebanon, NH, USA) is a computational fluid dynamics software employed to analyse biological mass-transport in the vasculature. A principal consideration for computational modelling of blood-side mass-transport is convection-diffusion discretisation scheme selection. Due to numerous discretisation schemes available when developing a mass-transport numerical model, the results obtained should either be validated against benchmark theoretical solutions or experimentally obtained results. An idealised aneurysm model was selected for the experimental and computational mass-transport analysis of species concentration due to its well-defined recirculation region within the aneurysmal sac, allowing species concentration to vary slowly with time. The experimental results were obtained from fluid samples extracted from a glass aneurysm model, using the direct spectrophometric concentration measurement technique. The computational analysis was conducted using the four convection-diffusion discretisation schemes available to the Fluent user, including the First-Order Upwind, the Power Law, the Second-Order Upwind and the Quadratic Upstream Interpolation for Convective Kinetics (QUICK) schemes. The fluid has a diffusivity of 3.125 x 10-10 m2/s in water, resulting in a Peclet number of 2,560,000, indicating strongly convection-dominated flow. The discretisation scheme applied to the solution of the convection-diffusion equation, for blood-side mass-transport within the vasculature, has a significant influence on the resultant species concentration field. The First-Order Upwind and the Power Law schemes produce similar results. The Second-Order Upwind and QUICK schemes also correlate well but differ considerably from the concentration contour plots of the First-Order Upwind and Power Law schemes. The computational results were then compared to the experimental findings. An average error of 140% and 116% was demonstrated between the experimental

  20. Preliminary experimentally-validated forced and mixed convection computational simulations of the Rotatable Buoyancy Tunnel

    International Nuclear Information System (INIS)

    Clifford, Corey E.; Kimber, Mark L.


    Although computational fluid dynamics (CFD) has not been directly utilized to perform safety analyses of nuclear reactors in the United States, several vendors are considering adopting commercial numerical packages for current and future projects. To ensure the accuracy of these computational models, it is imperative to validate the assumptions and approximations built into commercial CFD codes against physical data from flows analogous to those in modern nuclear reactors. To this end, researchers at Utah State University (USU) have constructed the Rotatable Buoyancy Tunnel (RoBuT) test facility, which is designed to provide flow and thermal validation data for CFD simulations of forced and mixed convection scenarios. In order to evaluate the ability of current CFD codes to capture the complex physics associated with these types of flows, a computational model of the RoBuT test facility is created using the ANSYS Fluent commercial CFD code. The numerical RoBuT model is analyzed at identical conditions to several experimental trials undertaken at USU. Each experiment is reconstructed numerically and evaluated with the second-order Reynolds stress model (RSM). Two different thermal boundary conditions at the heated surface of the RoBuT test section are investigated: constant temperature (isothermal) and constant surface heat flux (isoflux). Additionally, the fluid velocity at the inlet of the test section is varied in an effort to modify the relative importance of natural convection heat transfer from the heated wall of the RoBuT. Mean velocity, both in the streamwise and transverse directions, as well as components of the Reynolds stress tensor at three points downstream of the RoBuT test section inlet are compared to results obtained from experimental trials. Early computational results obtained from this research initiative are in good agreement with experimental data obtained from the RoBuT facility and both the experimental data and numerical method can be used

  1. Modeling an Excitable Biosynthetic Tissue with Inherent Variability for Paired Computational-Experimental Studies.

    Directory of Open Access Journals (Sweden)

    Tanmay A Gokhale


    Full Text Available To understand how excitable tissues give rise to arrhythmias, it is crucially necessary to understand the electrical dynamics of cells in the context of their environment. Multicellular monolayer cultures have proven useful for investigating arrhythmias and other conduction anomalies, and because of their relatively simple structure, these constructs lend themselves to paired computational studies that often help elucidate mechanisms of the observed behavior. However, tissue cultures of cardiomyocyte monolayers currently require the use of neonatal cells with ionic properties that change rapidly during development and have thus been poorly characterized and modeled to date. Recently, Kirkton and Bursac demonstrated the ability to create biosynthetic excitable tissues from genetically engineered and immortalized HEK293 cells with well-characterized electrical properties and the ability to propagate action potentials. In this study, we developed and validated a computational model of these excitable HEK293 cells (called "Ex293" cells using existing electrophysiological data and a genetic search algorithm. In order to reproduce not only the mean but also the variability of experimental observations, we examined what sources of variation were required in the computational model. Random cell-to-cell and inter-monolayer variation in both ionic conductances and tissue conductivity was necessary to explain the experimentally observed variability in action potential shape and macroscopic conduction, and the spatial organization of cell-to-cell conductance variation was found to not impact macroscopic behavior; the resulting model accurately reproduces both normal and drug-modified conduction behavior. The development of a computational Ex293 cell and tissue model provides a novel framework to perform paired computational-experimental studies to study normal and abnormal conduction in multidimensional excitable tissue, and the methodology of modeling

  2. A ferrofluid based energy harvester: Computational modeling, analysis, and experimental validation (United States)

    Liu, Qi; Alazemi, Saad F.; Daqaq, Mohammed F.; Li, Gang


    A computational model is described and implemented in this work to analyze the performance of a ferrofluid based electromagnetic energy harvester. The energy harvester converts ambient vibratory energy into an electromotive force through a sloshing motion of a ferrofluid. The computational model solves the coupled Maxwell's equations and Navier-Stokes equations for the dynamic behavior of the magnetic field and fluid motion. The model is validated against experimental results for eight different configurations of the system. The validated model is then employed to study the underlying mechanisms that determine the electromotive force of the energy harvester. Furthermore, computational analysis is performed to test the effect of several modeling aspects, such as three-dimensional effect, surface tension, and type of the ferrofluid-magnetic field coupling on the accuracy of the model prediction.

  3. Computational and experimental study on supersonic film cooling for liquid rocket nozzle applications

    Directory of Open Access Journals (Sweden)

    Vijayakumar Vishnu


    Full Text Available An experimental and computational investigation of supersonic film cooling (SFC was conducted on a subscale model of a rocket engine nozzle. A computational model of a convergent-divergent nozzle was generated, incorporating a secondary injection module for film cooling in the divergent section. Computational Fluid Dynamic (CFD simulations were run on the model and different injection configurations were analyzed. The CFD simulations also analyzed the parameters that influence film cooling effectiveness. Subsequent to the CFD analysis and literature survey an angled injection configuration was found to be more effective, therefore the hardware was fabricated for the same. The fabricated nozzle was later fixed to an Air-Kerosene combustor and numerous sets of experiments were conducted in order to ascertain the effect on film cooling on the nozzle wall. The film coolant employed was gaseous Nitrogen. The results showed substantial cooling along the walls and a considerable reduction in heat transfer from the combustion gas to the wall of the nozzle. Finally the computational model was validated using the experimental results. There was fairly good agreement between the predicted nozzle wall temperature and the value obtained through experiments.

  4. Combined computational and experimental approach to improve the assessment of mitral regurgitation by echocardiography. (United States)

    Sonntag, Simon J; Li, Wei; Becker, Michael; Kaestner, Wiebke; Büsen, Martin R; Marx, Nikolaus; Merhof, Dorit; Steinseifer, Ulrich


    Mitral regurgitation (MR) is one of the most frequent valvular heart diseases. To assess MR severity, color Doppler imaging (CDI) is the clinical standard. However, inadequate reliability, poor reproducibility and heavy user-dependence are known limitations. A novel approach combining computational and experimental methods is currently under development aiming to improve the quantification. A flow chamber for a circulatory flow loop was developed. Three different orifices were used to mimic variations of MR. The flow field was recorded simultaneously by a 2D Doppler ultrasound transducer and Particle Image Velocimetry (PIV). Computational Fluid Dynamics (CFD) simulations were conducted using the same geometry and boundary conditions. The resulting computed velocity field was used to simulate synthetic Doppler signals. Comparison between PIV and CFD shows a high level of agreement. The simulated CDI exhibits the same characteristics as the recorded color Doppler images. The feasibility of the proposed combination of experimental and computational methods for the investigation of MR is shown and the numerical methods are successfully validated against the experiments. Furthermore, it is discussed how the approach can be used in the long run as a platform to improve the assessment of MR quantification.

  5. Survey of engineering computational methods and experimental programs for estimating supersonic missile aerodynamic characteristics (United States)

    Sawyer, W. C.; Allen, J. M.; Hernandez, G.; Dillenius, M. F. E.; Hemsch, M. J.


    This paper presents a survey of engineering computational methods and experimental programs used for estimating the aerodynamic characteristics of missile configurations. Emphasis is placed on those methods which are suitable for preliminary design of conventional and advanced concepts. An analysis of the technical approaches of the various methods is made in order to assess their suitability to estimate longitudinal and/or lateral-directional characteristics for different classes of missile configurations. Some comparisons between the predicted characteristics and experimental data are presented. These comparisons are made for a large variation in flow conditions and model attitude parameters. The paper also presents known experimental research programs developed for the specific purpose of validating analytical methods and extending the capability of data-base programs.

  6. Redox Chemistry of Bis(pyrrolyl)pyridine Chromium and Molybdenum Complexes: An Experimental and Density Functional Theoretical Study. (United States)

    Gowda, Anitha S; Petersen, Jeffrey L; Milsmann, Carsten


    The three- and four-membered redox series [Cr( Me PDP) 2 ] z (z = 1-, 2-, 3-) and [Mo( Me PDP) 2 ] z (z = 0, 1-, 2-, 3-) were synthesized to study the redox properties of the pincer ligand Me PDP 2- (H 2 Me PDP = 2,6-bis(5-methyl-3-phenyl-1H-pyrrol-2-yl)pyridine). The monoanionic complexes were characterized by X-ray crystallography, UV/vis/NIR spectroscopy, and magnetic susceptibility measurements. Experimental and density functional theory (DFT) studies are consistent with closed-shell Me PDP 2- ligands and +III oxidation states (d 3 , S = 3/2) for the central metal ions. Cyclic voltammetry established multiple reversible redox processes for [M( Me PDP) 2 ] 1- (M = Cr, Mo), which were further investigated via chemical oxidation and reduction. For molybdenum, one-electron oxidation yielded Mo( Me PDP) 2 which was characterized by X-ray crystallography, UV/vis/NIR, and magnetic susceptibility measurements. The experimental and computational data indicate metal-centered oxidation to a Mo IV complex (d 2 , S = 1) with two Me PDP 2- ligands. In contrast, one- and two-electron reductions were found to be ligand centered resulting in the formation of Me PDP •3- radicals, in which the unpaired electron is predominantly located on the central pyridine ring of the ligand. The presence of ligand radicals was established experimentally by observation of ligand-to-ligand intervalence charge transfer (LLIVCT) bands in the UV/vis/NIR spectra of the dianionic and trianionic complexes and further supported by broken-symmetry DFT calculations. X-ray crystallographic analyses of the one-electron-reduced species [M( Me PDP) 2 ] 2- (S = 1, M = Cr, Mo) established structural indicators for pincer reduction and showed localization of the radical on one of the two pincer ligands. The two-electron-reduced, trianionic complexes (S = 1/2) were characterized by UV/vis/NIR spectroscopy, magnetic susceptibility measurements, and EPR spectroscopy. The electronic structures of the reduced


    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhe-Chen; Cole, Callie A.; Bierbaum, Veronica M. [Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309 (United States); Snow, Theodore P., E-mail: [Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States)


    Studies of interstellar chemistry have grown in number and complexity by both observations and laboratory measurements, and nitrogen-containing aromatics have been implicated as important interstellar molecules. In this paper, the gas-phase collision induced dissociation (CID) processes of protonated pyridazine (1,2-diazine), pyrimidine (1,3-diazine), and pyrazine (1,4-diazine) cations (C{sub 4}H{sub 5}N{sub 2} {sup +}) are investigated in detail both experimentally and theoretically. The major neutral loss for all three CID processes is HCN, leading to the formation of C{sub 3}H{sub 4}N{sup +} isomers; our density functional theory (DFT) calculations support and elucidate our experimental results. The formation of C{sub 3}H{sub 4}N{sup +} isomers from the reaction of abundant interstellar acrylonitrile (CH{sub 2}CHCN) and H{sup +}is also studied employing DFT calculations. Our results lead to a novel mechanism for interstellar protonated diazine formation from the consecutive reactions of CH{sub 2}CHCN+ H{sup +} + HCN. Moreover, our results motivate the continuing search for interstellar C{sub 3}H{sub 4}N{sup +} isomers as well as polycyclic aromatic N-containing hydrocarbons (PANHs)

  8. A detailed experimental study of a DNA computer with two endonucleases. (United States)

    Sakowski, Sebastian; Krasiński, Tadeusz; Sarnik, Joanna; Blasiak, Janusz; Waldmajer, Jacek; Poplawski, Tomasz


    Great advances in biotechnology have allowed the construction of a computer from DNA. One of the proposed solutions is a biomolecular finite automaton, a simple two-state DNA computer without memory, which was presented by Ehud Shapiro's group at the Weizmann Institute of Science. The main problem with this computer, in which biomolecules carry out logical operations, is its complexity - increasing the number of states of biomolecular automata. In this study, we constructed (in laboratory conditions) a six-state DNA computer that uses two endonucleases (e.g. AcuI and BbvI) and a ligase. We have presented a detailed experimental verification of its feasibility. We described the effect of the number of states, the length of input data, and the nondeterminism on the computing process. We also tested different automata (with three, four, and six states) running on various accepted input words of different lengths such as ab, aab, aaab, ababa, and of an unaccepted word ba. Moreover, this article presents the reaction optimization and the methods of eliminating certain biochemical problems occurring in the implementation of a biomolecular DNA automaton based on two endonucleases.

  9. A novel computational framework for deducing muscle synergies from experimental joint moments

    Directory of Open Access Journals (Sweden)

    Anantharaman eGopalakrishnan


    Full Text Available Prior experimental studies have hypothesized the existence of a ‘muscle synergy’ based control scheme for producing limb movements and locomotion in vertebrates. Such synergies have been suggested to consist of fixed muscle grouping schemes with the co-activation of all muscles in a synergy resulting in limb movement. Quantitative representations of these groupings (termed muscle weightings and their control signals (termed synergy controls have traditionally been derived by the factorization of experimentally measured EMG. This study presents a novel approach for deducing these weightings and controls from inverse dynamic joint moments that are computed from an alternative set of experimental measurements – movement kinematics and kinetics. This technique was applied to joint moments for healthy human walking at 0.7 and 1.7 m/s, and two sets of ‘simulated’ synergies were computed based on two different criteria (1 synergies were required to minimize errors between experimental and simulated joint moments in a musculoskeletal model (pure-synergy solution (2 along with minimizing joint moment errors, synergies also minimized muscle activation levels (optimal-synergy solution. On comparing the two solutions, it was observed that the introduction of optimality requirements (optimal-synergy to a control strategy solely aimed at reproducing the joint moments (pure-synergy did not necessitate major changes in the muscle grouping within synergies or the temporal profiles of synergy control signals. Synergies from both the simulated solutions exhibited many similarities to EMG derived synergies from a previously published study, thus implying that the analysis of the two different types of experimental data reveals similar, underlying synergy structures.

  10. Supersonic Retro-Propulsion Experimental Design for Computational Fluid Dynamics Model Validation (United States)

    Berry, Scott A.; Laws, Christopher T.; Kleb, W. L.; Rhode, Matthew N.; Spells, Courtney; McCrea, Andrew C.; Truble, Kerry A.; Schauerhamer, Daniel G.; Oberkampf, William L.


    The development of supersonic retro-propulsion, an enabling technology for heavy payload exploration missions to Mars, is the primary focus for the present paper. A new experimental model, intended to provide computational fluid dynamics model validation data, was recently designed for the Langley Research Center Unitary Plan Wind Tunnel Test Section 2. Pre-test computations were instrumental for sizing and refining the model, over the Mach number range of 2.4 to 4.6, such that tunnel blockage and internal flow separation issues would be minimized. A 5-in diameter 70-deg sphere-cone forebody, which accommodates up to four 4:1 area ratio nozzles, followed by a 10-in long cylindrical aftbody was developed for this study based on the computational results. The model was designed to allow for a large number of surface pressure measurements on the forebody and aftbody. Supplemental data included high-speed Schlieren video and internal pressures and temperatures. The run matrix was developed to allow for the quantification of various sources of experimental uncertainty, such as random errors due to run-to-run variations and bias errors due to flow field or model misalignments. Some preliminary results and observations from the test are presented, although detailed analyses of the data and uncertainties are still on going.

  11. Review of the Experimental Background and Implementation of Computational Models of the Ocular Lens Microcirculation. (United States)

    Wu, Ho-Ting D; Donaldson, Paul J; Vaghefi, Ehsan


    Our sense of vision is critically dependent on the clarity of the crystalline lens. The most common cause of transparency loss in the lens is age-related nuclear cataract, which is due to accumulative oxidative damage to this tissue. Since the ocular lens is an avascular tissue, it has to maintain its physiological homeostasis and antioxidant levels using a system of water microcirculation. This system has been experimentally imaged in animal lenses using different modalities. Based on these data, computational models have been developed to predict the properties of this system in human lenses and its changes due to aging. Although successful in predicting many aspects of lens fluid dynamics, at least in animal models, these in-silica models still need further improvement to become more accurate and representative of human ocular lens. We have been working on gathering experimental data and simultaneously developing computational models of lens microcirculation for the past decade. This review chronologically looks at the development of data-driven computational foundations of lens microcirculation model, its current state, and future advancement directions. A comprehensive model of lens fluid dynamics is essential to understand the physiological optics of this tissue and ultimately the underlying mechanisms of cataract onset and progression.

  12. Experimental and computer thermodynamics evaluations of an Al-Si-Coating on a quenchable steel

    International Nuclear Information System (INIS)

    Trindade, Vicente Braz


    High-strength steels are commonly used in the automobile industry in order to reduce the weight of the vehicles. However, a technical difficulty appears due to the need of hot stamping of the components, which leads to oxidation. Therefore, the application of a coating on the substrate to avoid high-temperature oxidation is used. In this work, experimental analysis and computer thermodynamic calculation were used to describe the phase transformations within an Al-Si coating on a quenchable high strength steel. The Al-Si coating was deposited by hot dipping and its characterization was done using SEM and XRD techniques. Computer thermodynamics calculations were done using the commercial software FactSage using the Calphad methodology. It demonstrated a good relationship between the experimental results and the computer calculations of phase stabilities for the as-deposited condition and after diffusion experiment at 920 deg C for 7 minutes, which simulates the thermal cycle of hot stamping of the quenchable steel used. (author)

  13. Investigation and experimental validation of the contribution of optical interconnects in the SYMPHONIE massively parallel computer

    International Nuclear Information System (INIS)

    Scheer, Patrick


    Progress in microelectronics lead to electronic circuits which are increasingly integrated, with an operating frequency and an inputs/outputs count larger than the ones supported by printed circuit board and back-plane technologies. As a result, distributed systems with several boards cannot fully exploit the performance of integrated circuits. In synchronous parallel computers, the situation is worsen since the overall system performances rely on the efficiency of electrical interconnects between the integrated circuits which include the processing elements (PE). The study of a real parallel computer named SYMPHONIE shows for instance that the system operating frequency is far smaller than the capabilities of the microelectronics technology used for the PE implementation. Optical interconnections may cancel these limitations by providing more efficient connections between the PE. Especially, free-space optical interconnections based on vertical-cavity surface-emitting lasers (VCSEL), micro-lens and PIN photodiodes are compatible with the required features of the PE communications. Zero bias modulation of VCSEL with CMOS-compatible digital signals is studied and experimentally demonstrated. A model of the propagation of truncated gaussian beams through micro-lenses is developed. It is then used to optimise the geometry of the detection areas. A dedicated mechanical system is also proposed and implemented for integrating free-space optical interconnects in a standard electronic environment, representative of the one of parallel computer systems. A specially designed demonstrator provides the experimental validation of the above physical concepts. (author) [fr

  14. Experimental and computer thermodynamics evaluations of an Al-Si-Coating on a quenchable steel

    Directory of Open Access Journals (Sweden)

    Vicente Braz Trindade

    Full Text Available Abstract High-strength steels are commonly used in the automobile industry in order to reduce the weight of the vehicles. However, a technical difficulty appears due to the need of hot stamping of the components, which leads to oxidation. Therefore, the application of a coating on the substrate to avoid high-temperature oxidation is used. In this work, experimental analysis and computer thermodynamic calculation were used to describe the phase transformations within an Al-Si coating on a quenchable high strength steel. The Al-Si coating was deposited by hot dipping and its characterization was done using SEM and XRD techniques. Computer thermodynamics calculations were done using the commercial software FactSage using the Calphad methodology. It demonstrated a good relationship between the experimental results and the computer calculations of phase stabilities for the as-deposited condition and after diffusion experiment at 920ºC for 7 minutes, which simulates the thermal cycle of hot stamping of the quenchable steel used.

  15. Computational and experimental approaches for development of methotrexate nanosuspensions by bottom-up nanoprecipitation. (United States)

    Dos Santos, Aline Martins; Carvalho, Flávia Chiva; Teixeira, Deiver Alessandro; Azevedo, David Lima; de Barros, Wander Miguel; Gremião, Maria Palmira Daflon


    Development of nanosuspensions offers a promising tool for formulations involving poorly water-soluble drugs. In this study, methotrexate (MTX) nanosuspensions were prepared using a bottom-up process based on acid-base neutralization reactions. Computational studies were performed to determine structural and electronic properties for isolated molecules and molecular clusters in order to evaluate the mechanism of MTX nanoparticle formation. Computational results indicated that the clusters in zwitterionic and cationic states presented larger dimensions and higher energies of interaction between MTX molecules, which favored aggregation. In contrast, the clusters in the anionic state exhibited lower energies of interaction, indicating aggregation was less likely to occur. Experimental results indicated that the higher the HCl proportion during drug precipitation, the greater the particle size, resulting in micrometric particles (2874-7308nm) (cationic and zwitterionic forms). However, MTX nanoparticles ranging in size from 132 to 186nm were formed using the lowest HCl proportion during drug precipitation (anionic form). In vitro release profiles indicated that the drug release rate from nanosuspension was increased (approximately 2.6 times) over that of the raw material. Overall, computational modeling and experimental analysis were complementary and assisted in the rational design of the nanosuspension based on acid-base reactions. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Experimental and computational study on thermoelectric generators using thermosyphons with phase change as heat exchangers

    International Nuclear Information System (INIS)

    Araiz, M.; Martínez, A.; Astrain, D.; Aranguren, P.


    Highlights: • Thermosyphon with phase change heat exchanger computational model. • Construction and experimentation of a prototype. • ±9% of maximum deviation from experimental values of the main outputs. • Influence of the auxiliary equipment on the net power generation. - Abstract: An important issue in thermoelectric generators is the thermal design of the heat exchangers since it can improve their performance by increasing the heat absorbed or dissipated by the thermoelectric modules. Due to its several advantages, compared to conventional dissipation systems, a thermosyphon heat exchanger with phase change is proposed to be placed on the cold side of thermoelectric generators. Some of these advantages are: high heat-transfer rates; absence of moving parts and lack of auxiliary consumption (because fans or pumps are not required); and the fact that these systems are wickless. A computational model is developed to design and predict the behaviour of this heat exchangers. Furthermore, a prototype has been built and tested in order to demonstrate its performance and validate the computational model. The model predicts the thermal resistance of the heat exchanger with a relative error in the interval [−8.09; 7.83] in the 95% of the cases. Finally, the use of thermosyphons with phase change in thermoelectric generators has been studied in a waste-heat recovery application, stating that including them on the cold side of the generators improves the net thermoelectric production by 36% compared to that obtained with finned dissipators under forced convection.

  17. Experimental and computer thermodynamics evaluations of an Al-Si-Coating on a quenchable steel

    Energy Technology Data Exchange (ETDEWEB)

    Trindade, Vicente Braz, E-mail: [Universidade Federal de Ouro Preto (UFOP), Ouro Preto, MG (Brazil). Escola de Minas. Departamento de Engenharia Metalurgica e de Materiais; Christ, Hans-Juergen, E-mail: [University of Siegen (Germany)


    High-strength steels are commonly used in the automobile industry in order to reduce the weight of the vehicles. However, a technical difficulty appears due to the need of hot stamping of the components, which leads to oxidation. Therefore, the application of a coating on the substrate to avoid high-temperature oxidation is used. In this work, experimental analysis and computer thermodynamic calculation were used to describe the phase transformations within an Al-Si coating on a quenchable high strength steel. The Al-Si coating was deposited by hot dipping and its characterization was done using SEM and XRD techniques. Computer thermodynamics calculations were done using the commercial software FactSage using the Calphad methodology. It demonstrated a good relationship between the experimental results and the computer calculations of phase stabilities for the as-deposited condition and after diffusion experiment at 920 deg C for 7 minutes, which simulates the thermal cycle of hot stamping of the quenchable steel used. (author)

  18. Experimental and computational studies of two-dimensional compressible vortex-shock interaction (United States)

    Kao, Chun-Teh

    The problem of two-dimensional compressible vortex-shock interaction is studied both experimentally and numerically. On the experimental side, a strong compressible vortex and a shock wave are produced in the open test section of a shock tube. The shock wave of strength M ≈ 1.2 then collides with the vortex that possesses a density drop at the vortex center exceeding 60% of the free stream value. Shadowgraphs and schlieren pictures of the event are taken in a sequence of experiments with progressive time delays. The pictures show that the shock profile is significantly modified by the interaction, with substantial distortion, disconnection, and a local nonlinear focusing structure. In the computational work, both the Euler equations and the Navier-Stokes equations are solved to simulate the problem. Two flux-splitting techniques are employed: (1) first-order-accurate Modified Steger-Warming method and (2) second-order-accurate variable-extrapolation method satisfying the total-variation-diminishing (TVD) condition. Based on the numerical data, the respective behaviors of the vortex, the shock wave, and the secondary wave generated during the interaction are analyzed. The simulation also reveals that the focal region of the distorted shock structure is bounded by a Mach stem and two slipstreams, in which local intensified pressure, density, and temperature peaks occur. It is found that the local intensification of fluid properties and the secondary wave possess essentially nonlinear characteristics at their early stages. The computational results agree well, qualitatively, with the experimental observations.

  19. Experimental realization of nondestructive discrimination of Bell states using a five-qubit quantum computer (United States)

    Sisodia, Mitali; Shukla, Abhishek; Pathak, Anirban


    A scheme for distributed quantum measurement that allows nondestructive or indirect Bell measurement was proposed by Gupta et al [1]. In the present work, Gupta et al.'s scheme is experimentally realized using the five-qubit super-conductivity-based quantum computer, which has been recently placed in cloud by IBM Corporation. The experiment confirmed that the Bell state can be constructed and measured in a nondestructive manner with a reasonably high fidelity. A comparison of the outcomes of this study and the results obtained earlier in an NMR-based experiment (Samal et al. (2010) [10]) has also been performed. The study indicates that to make a scalable SQUID-based quantum computer, errors introduced by the gates (in the present technology) have to be reduced considerably.

  20. A distributed computing environment with support for constraint-based task scheduling and scientific experimentation

    Energy Technology Data Exchange (ETDEWEB)

    Ahrens, J.P.; Shapiro, L.G.; Tanimoto, S.L. [Univ. of Washington, Seattle, WA (United States). Dept. of Computer Science and Engineering


    This paper describes a computing environment which supports computer-based scientific research work. Key features include support for automatic distributed scheduling and execution and computer-based scientific experimentation. A new flexible and extensible scheduling technique that is responsive to a user`s scheduling constraints, such as the ordering of program results and the specification of task assignments and processor utilization levels, is presented. An easy-to-use constraint language for specifying scheduling constraints, based on the relational database query language SQL, is described along with a search-based algorithm for fulfilling these constraints. A set of performance studies show that the environment can schedule and execute program graphs on a network of workstations as the user requests. A method for automatically generating computer-based scientific experiments is described. Experiments provide a concise method of specifying a large collection of parameterized program executions. The environment achieved significant speedups when executing experiments; for a large collection of scientific experiments an average speedup of 3.4 on an average of 5.5 scheduled processors was obtained.

  1. Integration of computational modeling and experimental techniques to design fuel surrogates

    DEFF Research Database (Denmark)

    Choudhury, H.A.; Intikhab, S.; Kalakul, Sawitree


    Virtual Process-Product Design Laboratory (VPPD-Lab) are applied onto the defined compositions of the surrogate gasoline. The aim is to primarily verify the defined composition of gasoline by means of VPPD-Lab. ρ, η and RVP are calculated with more accuracy and constraints such as distillation curve...... and flash point on the blend design are also considered. A post-design experiment-based verification step is proposed to further improve and fine-tune the “best” selected gasoline blends following the computation work. Here, advanced experimental techniques are used to measure the RVP, ρ, η, RON...... and distillation temperatures. The experimental results are compared with the model predictions as well as the extended calculations in VPPD-Lab....

  2. Experimental and computational fluid dynamics studies of mixing of complex oral health products (United States)

    Cortada-Garcia, Marti; Migliozzi, Simona; Weheliye, Weheliye Hashi; Dore, Valentina; Mazzei, Luca; Angeli, Panagiota; ThAMes Multiphase Team


    Highly viscous non-Newtonian fluids are largely used in the manufacturing of specialized oral care products. Mixing often takes place in mechanically stirred vessels where the flow fields and mixing times depend on the geometric configuration and the fluid physical properties. In this research, we study the mixing performance of complex non-Newtonian fluids using Computational Fluid Dynamics models and validate them against experimental laser-based optical techniques. To this aim, we developed a scaled-down version of an industrial mixer. As test fluids, we used mixtures of glycerol and a Carbomer gel. The viscosities of the mixtures against shear rate at different temperatures and phase ratios were measured and found to be well described by the Carreau model. The numerical results were compared against experimental measurements of velocity fields from Particle Image Velocimetry (PIV) and concentration profiles from Planar Laser Induced Fluorescence (PLIF).

  3. A computer program for processing experimental Compton profile of solids and liquids

    International Nuclear Information System (INIS)

    Das, G.P.


    A computer program COMPRO has been developed for processing experimental Compton profile data of solids and liquids generated by inelastic gamma ray scattering using a solid state detector and a multichannel analyser. It also calculates the fourier transform of the profile yielding the one electron autocorrelation function in position space. The theory behind the method of calculation is outlined and the various data processing steps needed to be applied on the raw experimental data have been discussed in detail. A flow chart of the program is given and the various subroutines of the program, method of feeding the input data and the method of presenting the final result are briefly described. The procedure is illustrated by measurement on a polycrystalline sample of manganese. The actual listing of the program along with the test run input data and the test run output data is also given. (M.G.B.)

  4. Experimental quadrotor flight performance using computationally efficient and recursively feasible linear model predictive control (United States)

    Jaffery, Mujtaba H.; Shead, Leo; Forshaw, Jason L.; Lappas, Vaios J.


    A new linear model predictive control (MPC) algorithm in a state-space framework is presented based on the fusion of two past MPC control laws: steady-state optimal MPC (SSOMPC) and Laguerre optimal MPC (LOMPC). The new controller, SSLOMPC, is demonstrated to have improved feasibility, tracking performance and computation time than its predecessors. This is verified in both simulation and practical experimentation on a quadrotor unmanned air vehicle in an indoor motion-capture testbed. The performance of the control law is experimentally compared with proportional-integral-derivative (PID) and linear quadratic regulator (LQR) controllers in an unconstrained square manoeuvre. The use of soft control output and hard control input constraints is also examined in single and dual constrained manoeuvres.

  5. Educational Game Design. Bridging the gab between computer based learning and experimental learning environments

    DEFF Research Database (Denmark)

    Andersen, Kristine


    with a prototype of a MOO storyline. The aim of the MOO storyline is to challenge the potential of dialogue, user involvement, and learning responsibility and to use the children?s natural curiosity and motivation for game playing, especially when digital games involves other children. The paper proposes a model......, based on the narrative approach for experimental learning subjects, relying on ideas from Csikszentmihalyis notion of flow (Csikszentmihalyi, 1991), storyline-pedagogy (Meldgaard, 1994) and ideas from Howard Gardner (Gardner, 1991). The model forms the basis for educational games to be used in home......Considering the rapidly growing amount of digital educational materials only few of them bridge the gab between experimental learning environments and computer based learning environments (Gardner, 1991). Observations from two cases in primary school and lower secondary school in the subject...

  6. Experimental and Computational Analysis of Water-Droplet Formation and Ejection Process Using Hollow Microneedle (United States)

    Kato, Norihisa; Oka, Ryotaro; Sakai, Takahiro; Shibata, Takayuki; Kawashima, Takahiro; Nagai, Moeto; Mineta, Takashi; Makino, Eiji


    In this paper, we present the possibility of liquid delivery using fabricated hollow silicon dioxide microneedles of approximately 2 µm in diameter. As a fundamental study, the water-droplet formation and ejection process was examined via dynamic observations during water ejection tests and computational fluid dynamics (CFD) analysis. The experimental results indicated that fluid flow in a microneedle follows the Hagen-Poiseuille law, i.e., the flow rate is approximately directly proportional to the fourth power of the inner diameter. Moreover, the ejection pressure and maximum droplet curvature obtained using the proposed microfluid ejection model were in good agreement with the experimental results. The resulting ejection pressure is equal to the theoretical pressure difference of a spherical droplet, which is determined using the Young-Laplace equation. The maximum curvature of a droplet formed at the tip of a microneedle can be estimated on the basis of the contact angle theory expressed by the Young equation.

  7. FLICA III. A digital computer program for thermal-hydraulic analysis of reactors and experimental loops

    International Nuclear Information System (INIS)

    Plas, Roger.


    This computer program describes the flow and heat transfer in steady and transient state in two-phase flows. It is the present stage of the evolution about FLICA, FLICA II and FLICA II B codes which have been used and developed at CEA for the thermal-hydraulic analysis of reactors and experimental loops with heating rod bundles. In the mathematical model all the significant terms of the fundamental hydrodynamic equations are taken into account with the approximations of turbulent viscosity and conductivity. The two-phase flow is calculated by the homogeneous model with slip. In the flow direction an implicit resolution scheme is available, which make possible to study partial or total flow blockage, with upstream and downstream effects. A special model represents the helical wire effects in out-of pile experimental rod bundles [fr

  8. Experimental realization of quantum cheque using a five-qubit quantum computer (United States)

    Behera, Bikash K.; Banerjee, Anindita; Panigrahi, Prasanta K.


    Quantum cheques could be a forgery-free way to make transaction in a quantum networked banking system with perfect security against any no-signalling adversary. Here, we demonstrate the implementation of quantum cheque, proposed by Moulick and Panigrahi (Quantum Inf Process 15:2475-2486, 2016), using the five-qubit IBM quantum computer. Appropriate single qubit, CNOT and Fredkin gates are used in an optimized configuration. The accuracy of implementation is checked and verified through quantum state tomography by comparing results from the theoretical and experimental density matrices.

  9. Sensitivity Measurement of Transmission Computer Tomography: thePreliminary Experimental Study

    International Nuclear Information System (INIS)

    Widodo, Chomsin-S; Sudjatmoko; Kusminarto; Agung-BS Utomo; Suparta, Gede B


    This paper reports result of preliminary experimental study onmeasurement method for sensitivity of a computed tomography (CT) scanner. ACT scanner has been build at the Department of Physics, FMIPA UGM and itsperformance based on its sensitivity was measured. The result showed that themeasurement method for sensitivity confirmed this method may be developedfurther as a measurement standard. Although the CT scanner developed has anumber of shortcoming, the analytical results from the sensitivitymeasurement suggest a number of reparations and improvements for the systemso that improved reconstructed CT images can be obtained. (author)

  10. Wake and higher order mode computations for the CMS experimental chamber at the LHC

    CERN Document Server

    Wanzenberg, R


    Wakefields and trapped Higher Order Modes (HOMs) in the CMS experimental chamber at the LHC are investigated using a geometrical model which closely reflects the presently installed vacuum chamber. The basic rf-parameters of the HOMs including the frequency, loss parameter, and the Q-value are provided. To cover also transient effects the short range wakefields and the total loss parameter has been calculated, too. Most numerical calculations are performed with the computer code MAFIA. The calculations of the Modes are complemented with an analysis of the multi-bunch instabilities due to the longitudinal and dipole modes in the CMS vacuum chamber.

  11. Experimental realization of an entanglement access network and secure multi-party computation (United States)

    Chang, Xiuying; Deng, Donglin; Yuan, Xinxing; Hou, Panyu; Huang, Yuanyuan; Duan, Luming; Department of Physics, University of Michigan Collaboration; Center for Quantum Information in Tsinghua University Team


    To construct a quantum network with many end users, it is critical to have a cost-efficient way to distribute entanglement over different network ends. We demonstrate an entanglement access network, where the expensive resource, the entangled photon source at the telecom wavelength and the core communication channel, is shared by many end users. Using this cost-efficient entanglement access network, we report experimental demonstration of a secure multiparty computation protocol, the privacy-preserving secure sum problem, based on the network quantum cryptography.

  12. Adsorptive desulfurization with CPO-27/MOF-74: an experimental and computational investigation. (United States)

    Van de Voorde, Ben; Hezinová, Markéta; Lannoeye, Jeroen; Vandekerkhove, Annelies; Marszalek, Bartosz; Gil, Barbara; Beurroies, Isabelle; Nachtigall, Petr; De Vos, Dirk


    By combining experimental adsorption isotherms, microcalorimetric data, infrared spectroscopy and quantum chemical calculations the adsorption behaviour of the CPO-27/MOF-74 series (Ni, Co, Mg, Cu, and Zn) in the desulfurization of fuels is evaluated. The results show a clear influence of the metal ion on the adsorption capacity and affinity for S-heterocyclic compounds, with CPO-27(Ni) being the best performing material both in terms of capacity and affinity. The microcalorimetric data and infrared spectroscopy confirm the high affinity of CPO-27(Ni) for thiophene and similar compounds, while the computational data reveal that the origin of this outstanding adsorption performance is the strong sulfur-metal interaction.


    Directory of Open Access Journals (Sweden)

    A. Ya. Kaplan


    Full Text Available Technology brain-computer interface (BCI allow saperson to learn how to control external devices via thevoluntary regulation of own EEG directly from the brain without the involvement in the process of nerves and muscles. At the beginning the main goal of BCI was to replace or restore motor function to people disabled by neuromuscular disorders. Currently, the task of designing the BCI increased significantly, more capturing different aspects of life a healthy person. This article discusses the theoretical, experimental and technological base of BCI development and systematized critical fields of real implementation of these technologies.

  14. Magnetical and optical properties of nanodiamonds can be tuned by particles surface chemistry: theoretical and experimental study

    Czech Academy of Sciences Publication Activity Database

    Kratochvílová, Irena; Šebera, Jakub; Ashcheulov, Petr; Golan, Martin; Ledvina, Miroslav; Mičová, Júlia; Mravec, F.; Kovalenko, A.; Zverev, D.; Yavkin, B.; Orlinskii, S.; Záliš, Stanislav; Fišerová, Anna; Richter, Jan; Šefc, L.; Turánek, J.


    Roč. 118, č. 43 (2014), s. 25245-25252 ISSN 1932-7447 R&D Projects: GA TA ČR TA01011165; GA ČR(CZ) GA14-10279S Institutional support: RVO:68378271 ; RVO:61388971 ; RVO:61388963 ; RVO:61388955 Keywords : nanodiamond particles * NV luminescent centers * surface functionalization * DFT Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.772, year: 2014

  15. Experimental realization of a one-way quantum computer algorithm solving Simon's problem. (United States)

    Tame, M S; Bell, B A; Di Franco, C; Wadsworth, W J; Rarity, J G


    We report an experimental demonstration of a one-way implementation of a quantum algorithm solving Simon's problem-a black-box period-finding problem that has an exponential gap between the classical and quantum runtime. Using an all-optical setup and modifying the bases of single-qubit measurements on a five-qubit cluster state, key representative functions of the logical two-qubit version's black box can be queried and solved. To the best of our knowledge, this work represents the first experimental realization of the quantum algorithm solving Simon's problem. The experimental results are in excellent agreement with the theoretical model, demonstrating the successful performance of the algorithm. With a view to scaling up to larger numbers of qubits, we analyze the resource requirements for an n-qubit version. This work helps highlight how one-way quantum computing provides a practical route to experimentally investigating the quantum-classical gap in the query complexity model.

  16. Computational and experimental study of the effect of mass transfer on liquid jet break-up (United States)

    Schetz, J. A.; Situ, M.


    A computational method has been developed to predict the effect of mass transfer on liquid jet break-up in coaxial, low velocity gas streams. Two conditions, both with and without the effect of mass transfer on the jet break-up, are calculated, and compared with experimental results and the classical linear theory. Methanol and water were used as the injectants. The numerical solution can predict the instantaneous shape of the jet surface and the break-up time, and it is very close to the experimental results. The numerical solutions and the experimental results both indicate that the wave number of the maximum instability is about 6.9, higher than 4.51 which was predicted by Rayleigh's linear theory. The experimental results and numerical solution show that the growth of the amplitude of the trough is faster than the growth of the amplitude of the crest, especially for a rapidly vaporizing jet. The numerical solutions show that for the small rates of evaporation, the effect of the mass transfer on the interface has a stabilizing effect near the wave number for maximum instability. Inversely, it has a destabilizing effect far from the wave number for maximum instability. For rapid evaporation, the effect of the mass transfer always has a destabilizing effect and decreases the break-up time of the jet.

  17. UV-photoelectron spectroscopy of BN indoles: experimental and computational electronic structure analysis. (United States)

    Chrostowska, Anna; Xu, Senmiao; Mazière, Audrey; Boknevitz, Katherine; Li, Bo; Abbey, Eric R; Dargelos, Alain; Graciaa, Alain; Liu, Shih-Yuan


    We present a comprehensive electronic structure analysis of two BN isosteres of indole using a combined UV-photoelectron spectroscopy (UV-PES)/computational chemistry approach. Gas-phase He I photoelectron spectra of external BN indole I and fused BN indole II have been recorded, assessed by density functional theory calculations, and compared with natural indole. The first ionization energies of these indoles are natural indole (7.9 eV), external BN indole I (7.9 eV), and fused BN indole II (8.05 eV). The computationally determined molecular dipole moments are in the order: natural indole (2.177 D) > fused BN indole II (1.512 D) > external BN indole I (0.543 D). The λmax in the UV-vis absorption spectra are in the order: fused BN indole II (292 nm) > external BN indole I (282 nm) > natural indole (270 nm). The observed relative electrophilic aromatic substitution reactivity of the investigated indoles with dimethyliminium chloride as the electrophile is as follows: fused BN indole II > natural indole > external BN indole I, and this trend correlates with the π-orbital coefficient at the 3-position. Nucleus-independent chemical shifts calculations show that the introduction of boron into an aromatic 6π-electron system leads to a reduction in aromaticity, presumably due to a stronger bond localization. Trends and conclusions from BN isosteres of simple monocyclic aromatic systems such as benzene and toluene are not necessarily translated to the bicyclic indole core. Thus, electronic structure consequences resulting from BN/CC isosterism will need to be evaluated individually from system to system.

  18. Computational and experimental studies of solids in the ammonia-water system (United States)

    Fortes, Andrew

    This thesis reports the results of first-principles computational studies of thirteen crystalline structures in the H2O-NH3 system. This includes eight low- and high-pressure polymorphs of pure water ice, two polymorphs of solid ammonia, and three low-pressure stoichiometric ammonia hydrates. These simulations have been used to determine the athermal equation of state (EoS) of each phase. Where empirical data was lacking, experiments have been undertaken. Hence, this thesis also reports the results of time-of-flight neutron scattering studies of deuterated ammonia dihydrate powders down to 4 K, and up to a maximum pressure of 8.6 GPa. In addition, I have developed a flexible and accurate planetary model that can be used to calculate the triaxial shape and gravitational field of any object, regardless of size or composition, given an assumed mineralogical constitution and provided the EoS of said minerals are known. The EoS parameters found in this work have therefore been used to model the structure and thermal evolution of icy moons orbiting Saturn in anticipation of the Cassini spacecraft arriving at Saturn in mid-2004. Models of Rhea, Saturn's second largest moon, suggest that its volatile component is likely to contain >3 weight percent ammonia, but that one is unlikely to be able to constrain the bulk chemistry of the ice mantle from Cassini flyby data.

  19. Experimental studies and modelling of cation interactions with solid materials: application to the MIMICC project. (Multidimensional Instrumented Module for Investigations on chemistry-transport Coupled Codes)

    International Nuclear Information System (INIS)

    Hardin, Emmanuelle


    The study of cation interactions with solid materials is useful in order to define the chemistry interaction component of the MIMICC project (Multidimensional Instrumented Module for Investigations on chemistry-transport Coupled Codes). This project will validate the chemistry-transport coupled codes. Database have to be supplied on the cesium or ytterbium interactions with solid materials in suspension. The solid materials are: a strong cation exchange resin, a natural sand which presents small impurities, and a zirconium phosphate. The cation exchange resin is useful to check that the surface complexation theory can be applied on a pure cation exchanger. The sand is a natural material, and its isotherms will be interpreted using pure oxide-cation system data, such as pure silica-cation data. Then the study on the zirconium phosphate salt is interesting because of the increasing complexity in the processes (dissolution, sorption and co-precipitation). These data will enable to approach natural systems, constituted by several complex solids which can interfere on each other. These data can also be used for chemistry-transport coupled codes. Potentiometric titration, sorption isotherms, sorption kinetics, cation surface saturation curves are made, in order to obtain the different parameters relevant to the cation sorption at the solid surface, for each solid-electrolyte-cation system. The influence of different parameters such as ionic strength, pH, and electrolyte is estimated. All the experimental curves are fitted with FITEQL code based on the surface complexation theory using the constant capacitance model, in order to give a mechanistic interpretation of the ion retention phenomenon at the solid surface. The speciation curves of all systems are plotted, using the FITEQL code too. Systems with an increasing complexity are studied: dissolution, sorption and coprecipitation coexist in the cation-salt systems. Then the data obtained on each single solid, considered

  20. Artificial soils from alluvial tin mining wastes in Malaysia--a study of soil chemistry following experimental treatments and the impact of mycorrhizal treatment on growth and foliar chemistry. (United States)

    Tompkins, David S; Bakar, Baki B; Hill, Steve J


    For decades Malaysia was the world's largest producer of Sn, but now the vast open cast mining operations have left a legacy of some 100,000 ha of what is effectively wasteland, covered with a mosaic of tailings and lagoons. Few plants naturally recolonise these areas. The demand for such land for both urban expansion and agricultural use has presented an urgent need for better characterisation. This study reports on the formation of artificial soils from alluvial Sn mining waste with a focus on the effects of experimental treatments on soil chemistry. Soil organic matter, clay, and pH were manipulated in a controlled environment. Adding both clay tailings and peat enhanced the cation exchange capacity of sand tailings but also reduced the pH. The addition of peat reduced the extractable levels of some elements but increased the availability of Ca and Mg, thus proving beneficial. The use of clay tailings increased the levels of macro and micronutrients but also released Al, As, La, Pb and U. Additionally, the effects of soil mix and mycorrhizal treatments on growth and foliar chemistry were studied. Two plant species were selected: Panicum milicaeum and Pueraria phaseoloides. Different growth patterns were observed with respect to the additions of peat and clay. The results for mycorrhizal treatment (live inoculum or sterile carrier medium) are more complex, but both resulted in improved growth. The use of mycorrhizal fungi could greatly enhance rehabilitation efforts on sand tailings.

  1. Comparison of Experimental Surface and Flow Field Measurements to Computational Results of the Juncture Flow Model (United States)

    Roozeboom, Nettie H.; Lee, Henry C.; Simurda, Laura J.; Zilliac, Gregory G.; Pulliam, Thomas H.


    Wing-body juncture flow fields on commercial aircraft configurations are challenging to compute accurately. The NASA Advanced Air Vehicle Program's juncture flow committee is designing an experiment to provide data to improve Computational Fluid Dynamics (CFD) modeling in the juncture flow region. Preliminary design of the model was done using CFD, yet CFD tends to over-predict the separation in the juncture flow region. Risk reduction wind tunnel tests were requisitioned by the committee to obtain a better understanding of the flow characteristics of the designed models. NASA Ames Research Center's Fluid Mechanics Lab performed one of the risk reduction tests. The results of one case, accompanied by CFD simulations, are presented in this paper. Experimental results suggest the wall mounted wind tunnel model produces a thicker boundary layer on the fuselage than the CFD predictions, resulting in a larger wing horseshoe vortex suppressing the side of body separation in the juncture flow region. Compared to experimental results, CFD predicts a thinner boundary layer on the fuselage generates a weaker wing horseshoe vortex resulting in a larger side of body separation.

  2. Integration of experimental and computational methods for identifying geometric, thermal and diffusive properties of biomaterials (United States)

    Weres, Jerzy; Kujawa, Sebastian; Olek, Wiesław; Czajkowski, Łukasz


    Knowledge of physical properties of biomaterials is important in understanding and designing agri-food and wood processing industries. In the study presented in this paper computational methods were developed and combined with experiments to enhance identification of agri-food and forest product properties, and to predict heat and water transport in such products. They were based on the finite element model of heat and water transport and supplemented with experimental data. Algorithms were proposed for image processing, geometry meshing, and inverse/direct finite element modelling. The resulting software system was composed of integrated subsystems for 3D geometry data acquisition and mesh generation, for 3D geometry modelling and visualization, and for inverse/direct problem computations for the heat and water transport processes. Auxiliary packages were developed to assess performance, accuracy and unification of data access. The software was validated by identifying selected properties and using the estimated values to predict the examined processes, and then comparing predictions to experimental data. The geometry, thermal conductivity, specific heat, coefficient of water diffusion, equilibrium water content and convective heat and water transfer coefficients in the boundary layer were analysed. The estimated values, used as an input for simulation of the examined processes, enabled reduction in the uncertainty associated with predictions.

  3. Experimental and computational analysis of pressure response in a multiphase flow loop (United States)

    Morshed, Munzarin; Amin, Al; Rahman, Mohammad Azizur; Imtiaz, Syed


    The characteristics of multiphase fluid flow in pipes are useful to understand fluid mechanics encountered in the oil and gas industries. In the present day oil and gas exploration is successively inducing subsea operation in the deep sea and arctic condition. During the transport of petroleum products, understanding the fluid dynamics inside the pipe network is important for flow assurance. In this case the information regarding static and dynamic pressure response, pressure loss, optimum flow rate, pipe diameter etc. are the important parameter for flow assurance. The principal aim of this research is to represents computational analysis and experimental analysis of multi-phase (L/G) in a pipe network. This computational study considers a two-phase fluid flow through a horizontal flow loop with at different Reynolds number in order to determine the pressure distribution, frictional pressure loss profiles by volume of fluid (VOF) method. However, numerical simulations are validated with the experimental data. The experiment is conducted in 76.20 mm ID transparent circular pipe using water and air in the flow loop. Static pressure transducers are used to measure local pressure response in multiphase pipeline.

  4. Vortex-Concept for Radioactivity Release Prevention at NPP: Development of Computational Model of Lab-Scale Experimental Setup

    Energy Technology Data Exchange (ETDEWEB)

    Ullah, Sana; Sung, Yim Man; Park, Jin Soo; Sung Hyung Jin [KAERI, Daejeon (Korea, Republic of)


    The experimental validation of the vortex-like air curtain concept and use of an appropriate CFD modelling approach for analyzing the problem becomes crucial. A lab-scale experimental setup is designed to validate the proposed concept and CFD modeling approach as a part of validation process. In this study, a computational model of this lab-scale experiment setup is developed using open source CFD code OpenFOAM. The computational results will be compared with experimental data for validation purposes in future, when experimental data is available. 1) A computation model of a lab-scale experimental setup, designed to validate the concept of artificial vortex-like airflow generation for application to radioactivity dispersion prevention in the event of severe accident, was developed. 2) The mesh sensitivity study was performed and a mesh of about 2 million cells was found to be sufficient for this setup.

  5. A green analytical chemistry approach for lipid extraction: computation methods in the selection of green solvents as alternative to hexane. (United States)

    Cascant, Mari Merce; Breil, Cassandra; Garrigues, Salvador; de la Guardia, Miguel; Fabiano-Tixier, Anne Silvie; Chemat, Farid


    There is a great interest in finding alternatives and green solvents in extraction processes to replace petroleum based solvents. In order to investigate these possibilities, computational methods, as Hansen solubility parameters (HSP) and conductor-like screening model for real solvent (COSMO-RS), were used in this work to predict the solvation power of a series of solvents in salmon fish lipids. Additionally, experimental studies were used to evaluate the performance in lipids extraction using 2-methyltetrahydrofurane, cyclopentyl methyl ether, dimethyl carbonate, isopropanol, ethanol, ethyl acetate, p-cymene and d-limonene compared with hexane. Lipid classes of extracts were obtained by using high performance thin-layer chromatography (HPTLC), whereas gas chromatography with a flame ionization detector (GC/FID) technique was employed to obtain fatty acid profiles. Some differences between theoretical and experimental results were observed, especially regarding the behavior of p-cymene and d-limonene, which separate from the predicted capability. Results obtained from HPTLC indicated that p-cymene and d-limonene extract triglycerides (TAGs) and diglycerides (DAGs) at levels of 73 and 19%, respectively, whereas the other studied extracts contain between 75 and 76% of TAGs and between 16 and 17% of DAGs. Fatty acid profiles, obtained by using GC-FID, indicated that saturated fatty acids (SFAs) between 19.5 and 19.9% of extracted oil, monounsaturated fatty acids (MUFAs) in the range between 43.5 and 44.9%, and PUFAs between 31.2 and 34.6% were extracted. p-Cymene and limonene extracts contained lower percentages than the other studied solvents of some PUFAs due probably to the fact that these unsaturated fatty acids are more susceptible to oxidative degradation than MUFAs. Ethyl acetate has been found to be the best alternative solvent to hexane for the extraction of salmon oil lipids. Graphical Abstract ᅟ.

  6. A Computing Environment to Support Repeatable Scientific Big Data Experimentation of World-Wide Scientific Literature

    Energy Technology Data Exchange (ETDEWEB)

    Schlicher, Bob G [ORNL; Kulesz, James J [ORNL; Abercrombie, Robert K [ORNL; Kruse, Kara L [ORNL


    A principal tenant of the scientific method is that experiments must be repeatable and relies on ceteris paribus (i.e., all other things being equal). As a scientific community, involved in data sciences, we must investigate ways to establish an environment where experiments can be repeated. We can no longer allude to where the data comes from, we must add rigor to the data collection and management process from which our analysis is conducted. This paper describes a computing environment to support repeatable scientific big data experimentation of world-wide scientific literature, and recommends a system that is housed at the Oak Ridge National Laboratory in order to provide value to investigators from government agencies, academic institutions, and industry entities. The described computing environment also adheres to the recently instituted digital data management plan mandated by multiple US government agencies, which involves all stages of the digital data life cycle including capture, analysis, sharing, and preservation. It particularly focuses on the sharing and preservation of digital research data. The details of this computing environment are explained within the context of cloud services by the three layer classification of Software as a Service , Platform as a Service , and Infrastructure as a Service .

  7. Flow pattern visualization in a mimic anaerobic digester: experimental and computational studies. (United States)

    Vesvikar, M S; Varma, R; Karim, K; Al-Dahhan, M


    Advanced non-invasive experiments like computer automated radioactive particle tracking and computed tomography along with computational fluid dynamics (CFD) simulations were performed in mimic anaerobic digesters to visualize their flow pattern and obtain hydrodynamic parameters. The mixing in the digester was provided by sparging gas at three different flow rates. The simulation results in terms of overall flow pattern, location of circulation cells and stagnant regions, trends of liquid velocity profiles, and volume of dead zones agree reasonably well with the experimental data. CFD simulations were also performed on different digester configurations. The effects of changing draft tube size, clearance, and shape of the tank bottoms were calculated to evaluate the effect of digester design on its flow pattern. Changing the draft tube clearance and height had no influence on the flow pattern or dead regions volume. However increasing the draft tube diameter or incorporating a conical bottom design helped in reducing the volume of the dead zones as compared to a flat bottom digester. The simulations showed that the gas flow rate sparged by a single point (0.5 cm diameter) sparger does not have appreciable effect on the flow pattern of the digesters.

  8. Experimental and computational studies of thermal mixing in next generation nuclear reactors (United States)

    Landfried, Douglas Tyler

    The Very High Temperature Reactor (VHTR) is a proposed next generation nuclear power plant. The VHTR utilizes helium as a coolant in the primary loop of the reactor. Helium traveling through the reactor mixes below the reactor in a region known as the lower plenum. In this region there exists large temperature and velocity gradients due to non-uniform heat generation in the reactor core. Due to these large gradients, concern should be given to reducing thermal striping in the lower plenum. Thermal striping is the phenomena by which temperature fluctuations in the fluid and transferred to and attenuated by surrounding structures. Thermal striping is a known cause of long term material failure. To better understand and predict thermal striping in the lower plenum two separate bodies of work have been conducted. First, an experimental facility capable of predictably recreating some aspects of flow in the lower plenum is designed according to scaling analysis of the VHTR. Namely the facility reproduces jets issuing into a crossflow past a tube bundle. Secondly, extensive studies investigate the mixing of a non-isothermal parallel round triple-jet at two jet-to-jet spacings was conducted. Experimental results were validation with an open source computational fluid dynamics package, OpenFOAMRTM. Additional care is given to understanding the implementation of the realizable k-a and Launder Gibson RSM turbulence Models in OpenFOAMRTM. In order to measure velocity and temperature in the triple-jet experiment a detailed investigation of temperature compensated hotwire anemometry is carried out with special concern being given to quantify the error with the measurements. Finally qualitative comparisons of trends in the experimental results and the computational results is conducted. A new and unexpected physical behavior was observed in the center jet as it appeared to spread unexpectedly for close spacings (S/Djet = 1.41).

  9. Experimental measurement and computational fluid dynamics simulation of mixing in a stirred tank: a review

    Directory of Open Access Journals (Sweden)

    K. Kiriamiti


    Full Text Available Stirred tanks are typically used in many reactions. The quality of mixing generated by the impellers can be determined using either experimental and simulation methods, or both methods. The experimental techniques have evolved from traditional approaches, such as the application of hot-wire anemometry, to more modern ones like laser Doppler velocimetry (LDV. Similarly, computational fluid dynamics (CFD simulation techniques have attracted a lot of attention in recent years in the study of the hydrodynamics in stirred tanks, compared to the empirical modelling approach. Studies have shown that the LDV technique can provide very detailed information on the spatio-temporal variations in a tank, but the method is costly. For this reason, CFD simulation techniques may be employed to provide such data at a lower cost. In recent years, both integrated experimental and CFD approaches have been used to determine flow field and to design various systems. Both CFD and LDV data reveal the existence of flow maldistribution caused by system design features, and these in turn show that the configurations that have, over the years, been regarded as standard may not provide the optimal operating conditions with regards to the system homogeneity and power consumption. The current trends in CFD studies point towards an increasing application of more refined grids, such as in large eddy simulation, to capture turbulent structures at microscales. This trend will further improve the quality of the simulation results for processes such as precipitation, in which micromixing and reaction kinetics are important.

  10. Nanosecond electrical explosion of thin aluminum wire in vacuum: experimental and computational investigations

    International Nuclear Information System (INIS)

    Cochrane, Kyle Robert; Struve, Kenneth William; Rosenthal, Stephen Edgar; McDaniel, Dillon Heirman; Sarkisov, Gennady Sergeevich; Deeney, Christopher


    The experimental and computational investigations of nanosecond electrical explosion of thin Al wire in vacuum are presented. We have demonstrated that increasing the current rate leads to increased energy deposited before voltage collapse. Laser shadowgrams of the overheated Al core exhibit axial stratification with a ∼100 (micro)m period. The experimental evidence for synchronization of the wire expansion and light emission with voltage collapse is presented. Two-wavelength interferometry shows an expanding Al core in a low-ionized gas condition with increasing ionization toward the periphery. Hydrocarbons are indicated in optical spectra and their influence on breakdown physics is discussed. The radial velocity of low-density plasma reaches a value of ∼100 km/s. The possibility of an overcritical phase transition due to high pressure is discussed. 1D MHD simulation shows good agreement with experimental data. MHD simulation demonstrates separation of the exploding wire into a high-density cold core and a low-density hot corona as well as fast rejection of the current from the wire core to the corona during voltage collapse. Important features of the dynamics for wire core and corona follow from the MHD simulation and are discussed.

  11. Comparison of Computational and Experimental Microphone Array Results for an 18%-Scale Aircraft Model (United States)

    Lockard, David P.; Humphreys, William M.; Khorrami, Mehdi R.; Fares, Ehab; Casalino, Damiano; Ravetta, Patricio A.


    An 18%-scale, semi-span model is used as a platform for examining the efficacy of microphone array processing using synthetic data from numerical simulations. Two hybrid RANS/LES codes coupled with Ffowcs Williams-Hawkings solvers are used to calculate 97 microphone signals at the locations of an array employed in the NASA LaRC 14x22 tunnel. Conventional, DAMAS, and CLEAN-SC array processing is applied in an identical fashion to the experimental and computational results for three different configurations involving deploying and retracting the main landing gear and a part span flap. Despite the short time records of the numerical signals, the beamform maps are able to isolate the noise sources, and the appearance of the DAMAS synthetic array maps is generally better than those from the experimental data. The experimental CLEAN-SC maps are similar in quality to those from the simulations indicating that CLEAN-SC may have less sensitivity to background noise. The spectrum obtained from DAMAS processing of synthetic array data is nearly identical to the spectrum of the center microphone of the array, indicating that for this problem array processing of synthetic data does not improve spectral comparisons with experiment. However, the beamform maps do provide an additional means of comparison that can reveal differences that cannot be ascertained from spectra alone.

  12. Adsorption of bentazon on CAT and CARBOPAL activated carbon: Experimental and computational study (United States)

    Spaltro, Agustín; Simonetti, Sandra; Torrellas, Silvia Alvarez; Rodriguez, Juan Garcia; Ruiz, Danila; Juan, Alfredo; Allegretti, Patricia


    Removal of the bentazon by adsorption on two different types of activated carbon was investigated under various experimental conditions.Kinetics of adsorption is followed and the adsorption isotherms of the pesticide are determined. The effects of the changes in pH, ionic strength and temperature are analyzed. Computational simulation was employed to analyze the geometry and the energy of pesticide absorption on activated carbon. Concentration of bentazon decreases while increase all the variables, from the same initial concentration. Experimental data for equilibrium was analyzed by three models: Langmuir, Freundlich and Guggenheim-Anderson-de Boer isotherms. Pseudo-first and pseudo-second-order kinetics are tested with the experimental data, and pseudo-second-order kinetics was the best for the adsorption of bentazon by CAT and CARBOPAL with coefficients of correlation R2 = 0.9996 and R2 = 0.9993, respectively. The results indicated that both CAT and CARBOPAL are very effective for the adsorption of bentazon from aqueous solutions, but CAT carbon has the greater capacity.

  13. Computational-experimental approach to drug-target interaction mapping: A case study on kinase inhibitors.

    Directory of Open Access Journals (Sweden)

    Anna Cichonska


    Full Text Available Due to relatively high costs and labor required for experimental profiling of the full target space of chemical compounds, various machine learning models have been proposed as cost-effective means to advance this process in terms of predicting the most potent compound-target interactions for subsequent verification. However, most of the model predictions lack direct experimental validation in the laboratory, making their practical benefits for drug discovery or repurposing applications largely unknown. Here, we therefore introduce and carefully test a systematic computational-experimental framework for the prediction and pre-clinical verification of drug-target interactions using a well-established kernel-based regression algorithm as the prediction model. To evaluate its performance, we first predicted unmeasured binding affinities in a large-scale kinase inhibitor profiling study, and then experimentally tested 100 compound-kinase pairs. The relatively high correlation of 0.77 (p < 0.0001 between the predicted and measured bioactivities supports the potential of the model for filling the experimental gaps in existing compound-target interaction maps. Further, we subjected the model to a more challenging task of predicting target interactions for such a new candidate drug compound that lacks prior binding profile information. As a specific case study, we used tivozanib, an investigational VEGF receptor inhibitor with currently unknown off-target profile. Among 7 kinases with high predicted affinity, we experimentally validated 4 new off-targets of tivozanib, namely the Src-family kinases FRK and FYN A, the non-receptor tyrosine kinase ABL1, and the serine/threonine kinase SLK. Our sub-sequent experimental validation protocol effectively avoids any possible information leakage between the training and validation data, and therefore enables rigorous model validation for practical applications. These results demonstrate that the kernel

  14. An Iminosemiquinone-Coordinated Oxidovanadium(V) Complex: A Combined Experimental and Computational Study

    Czech Academy of Sciences Publication Activity Database

    Sarkar, P.; Mondal, M. K.; Sarmah, Amrit; Maity, S.; Mukherjee, C.


    Roč. 56, č. 14 (2017), s. 8068-8077 ISSN 0020-1669 Institutional support: RVO:61388963 Keywords : transition metal complexes * induced electron transfer * non-innocent ligands Subject RIV: CA - Inorganic Chemistry OBOR OECD: Inorganic and nuclear chemistry Impact factor: 4.857, year: 2016

  15. Theoretical chemistry

    International Nuclear Information System (INIS)



    Work in theoretical chemistry was organized under the following topics: scattering theory and dynamics (elastic scattering of the rare gas hydrides, inelastic scattering in Li + H 2 , statistical theory for bimolecular collisions, model study of dissociative scattering, comparative study of elastic scattering computational methods), studies of atmospheric diatomic and triatomic species, structure and spectra of diatomic molecules, the evaluation of van der Waals forces, potential energy surfaces and structure and dynamics, calculation of molecular polarizabilities, and development of theoretical techniques and computing systems. Spectroscopic parameters are tabulated for NO 2 , N 2 O, H 2 O + , VH, and NH. Self-consistent-field wave functions were computed for He 2 in two-center and three-center bases. Rare gas hydride intermolecular potentials are shown. (9 figures, 14 tables) (U.S.)

  16. Experimental and computational investigation of flow of pebbles in a pebble bed nuclear reactor (United States)

    Khane, Vaibhav B.

    The Pebble Bed Reactor (PBR) is a 4th generation nuclear reactor which is conceptually similar to moving bed reactors used in the chemical and petrochemical industries. In a PBR core, nuclear fuel in the form of pebbles moves slowly under the influence of gravity. Due to the dynamic nature of the core, a thorough understanding about slow and dense granular flow of pebbles is required from both a reactor safety and performance evaluation point of view. In this dissertation, a new integrated experimental and computational study of granular flow in a PBR has been performed. Continuous pebble re-circulation experimental set-up, mimicking flow of pebbles in a PBR, is designed and developed. Experimental investigation of the flow of pebbles in a mimicked test reactor was carried out for the first time using non-invasive radioactive particle tracking (RPT) and residence time distribution (RTD) techniques to measure the pebble trajectory, velocity, overall/zonal residence times, flow patterns etc. The tracer trajectory length and overall/zonal residence time is found to increase with change in pebble's initial seeding position from the center towards the wall of the test reactor. Overall and zonal average velocities of pebbles are found to decrease from the center towards the wall. Discrete element method (DEM) based simulations of test reactor geometry were also carried out using commercial code EDEM(TM) and simulation results were validated using the obtained benchmark experimental data. In addition, EDEM(TM) based parametric sensitivity study of interaction properties was carried out which suggests that static friction characteristics play an important role from a packed/pebble beds structural characterization point of view. To make the RPT technique viable for practical applications and to enhance its accuracy, a novel and dynamic technique for RPT calibration was designed and developed. Preliminary feasibility results suggest that it can be implemented as a non

  17. Calculating buoy response for a wave energy converter—A comparison of two computational methods and experimental results

    Directory of Open Access Journals (Sweden)

    Linnea Sjökvist


    Full Text Available When designing a wave power plant, reliable and fast simulation tools are required. Computational fluid dynamics (CFD software provides high accuracy but with a very high computational cost, and in operational, moderate sea states, linear potential flow theories may be sufficient to model the hydrodynamics. In this paper, a model is built in COMSOL Multiphysics to solve for the hydrodynamic parameters of a point-absorbing wave energy device. The results are compared with a linear model where the hydrodynamical parameters are computed using WAMIT, and to experimental results from the Lysekil research site. The agreement with experimental data is good for both numerical models.

  18. Experimental Plan to Verify the YPCP Model: "Yukawa Pico Chemistry and Physics" Implications in the CF-Lenr Field


    Dufour, Jacques; Dufour, Xavier; Murat, Denis; Foos, Jacques


    In the CF-LERN field (Cold Fusion and Low Energy Nuclear reactions) many experimental results are available: unexplained energy production, presence of unusual patterns of classical fusion reaction products, isotopic composition variations, sporadic emission of nuclear radiations. These effects are not always observed, for similar experimental conditions. Should a fundamental reason exist for these effects to occur, funding would be justified, to make them repeatable and more intense (this st...

  19. Catalyst-Controlled and Tunable, Chemoselective Silver-Catalyzed Intermolecular Nitrene Transfer: Experimental and Computational Studies. (United States)

    Dolan, Nicholas S; Scamp, Ryan J; Yang, Tzuhsiung; Berry, John F; Schomaker, Jennifer M


    The development of new catalysts for selective nitrene transfer is a continuing area of interest. In particular, the ability to control the chemoselectivity of intermolecular reactions in the presence of multiple reactive sites has been a long-standing challenge in the field. In this paper, we demonstrate examples of silver-catalyzed, nondirected, intermolecular nitrene transfer reactions that are both chemoselective and flexible for aziridination or C-H insertion, depending on the choice of ligand. Experimental probes present a puzzling picture of the mechanistic details of the pathways mediated by [( t Bu 3 tpy)AgOTf] 2 and (tpa)AgOTf. Computational studies elucidate these subtleties and provide guidance for the future development of new catalysts exhibiting improved tunability in group transfer reactions.

  20. The experimental nuclear reaction data (EXFOR): Extended computer database and Web retrieval system (United States)

    Zerkin, V. V.; Pritychenko, B.


    The EXchange FORmat (EXFOR) experimental nuclear reaction database and the associated Web interface provide access to the wealth of low- and intermediate-energy nuclear reaction physics data. This resource is based on numerical data sets and bibliographical information of ∼22,000 experiments since the beginning of nuclear science. The principles of the computer database organization, its extended contents and Web applications development are described. New capabilities for the data sets uploads, renormalization, covariance matrix, and inverse reaction calculations are presented. The EXFOR database, updated monthly, provides an essential support for nuclear data evaluation, application development, and research activities. It is publicly available at the websites of the International Atomic Energy Agency Nuclear Data Section,, the U.S. National Nuclear Data Center,, and the mirror sites in China, India and Russian Federation.

  1. Experimental, computational and theoretical studies of δ′ phase coarsening in Al–Li alloys

    International Nuclear Information System (INIS)

    Pletcher, B.A.; Wang, K.G.; Glicksman, M.E.


    Experimental characterization of microstructure evolution in three binary Al–Li alloys provides critical tests of both diffusion screening theory and multiparticle diffusion simulations, which predict late-stage phase-coarsening kinetics. Particle size distributions, growth kinetics and maximum particle sizes obtained using quantitative, centered dark-field transmission electron microscopy are compared quantitatively with theoretical and computational predictions. We also demonstrate the dependence on δ′ precipitate volume fraction of the rate constant for coarsening and the microstructure’s maximum particle size, both of which remained undetermined for this alloy system for nearly a half century. Our experiments show quantitatively that the diffusion-screening theoretical description of phase coarsening yields reasonable kinetic predictions, and that useful simulations of microstructure evolution are obtained via multiparticle diffusion. The tested theory and simulation method will provide useful tools for future design of two-phase alloys for elevated temperature applications.

  2. Experimental and computational validation of BDTPS using a heterogeneous boron phantom

    CERN Document Server

    Daquino, G G; Mazzini, M; Moss, R L; Muzi, L


    The idea to couple the treatment planning system (TPS) to the information on the real boron distribution in the patient acquired by positron emission tomography (PET) is the main added value of the new methodology set-up at DIMNP (Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione) of University of Pisa, in collaboration with the JRC (Joint Research Centre) at Petten (NL). This methodology has been implemented in a new TPS, called Boron Distribution Treatment Planning System (BDTPS), which takes into account the actual boron distribution in the patient's organ, as opposed to other TPSs used in BNCT that assume an ideal uniform boron distribution. BDTPS is based on the Monte Carlo technique and has been experimentally validated comparing the computed main parameters (thermal neutron flux, boron dose, etc.) to those measured during the irradiation of an ad hoc designed phantom (HEterogeneous BOron phanto M, HEBOM). The results are also in good agreement with those obtained by the standard TPS SER...

  3. Specialized, multi-user computer facility for the high-speed, interactive processing of experimental data

    International Nuclear Information System (INIS)

    Maples, C.C.


    A proposal has been made at LBL to develop a specialized computer facility specifically designed to deal with the problems associated with the reduction and analysis of experimental data. Such a facility would provide a highly interactive, graphics-oriented, multi-user environment capable of handling relatively large data bases for each user. By conceptually separating the general problem of data analysis into two parts, cyclic batch calculations and real-time interaction, a multilevel, parallel processing framework may be used to achieve high-speed data processing. In principle such a system should be able to process a mag tape equivalent of data through typical transformations and correlations in under 30 s. The throughput for such a facility, for five users simultaneously reducing data, is estimated to be 2 to 3 times greater than is possible, for example, on a CDC7600. 3 figures

  4. Improving Wind Turbine Drivetrain Reliability Using a Combined Experimental, Computational, and Analytical Approach

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Y.; van Dam, J.; Bergua, R.; Jove, J.; Campbell, J.


    Nontorque loads induced by the wind turbine rotor overhang weight and aerodynamic forces can greatly affect drivetrain loads and responses. If not addressed properly, these loads can result in a decrease in gearbox component life. This work uses analytical modeling, computational modeling, and experimental data to evaluate a unique drivetrain design that minimizes the effects of nontorque loads on gearbox reliability: the Pure Torque(R) drivetrain developed by Alstom. The drivetrain has a hub-support configuration that transmits nontorque loads directly into the tower rather than through the gearbox as in other design approaches. An analytical model of Alstom's Pure Torque drivetrain provides insight into the relationships among turbine component weights, aerodynamic forces, and the resulting drivetrain loads. Main shaft bending loads are orders of magnitude lower than the rated torque and are hardly affected by wind conditions and turbine operations.

  5. Taylor Flow in Microchannels: A Review of Experimental and Computational Work

    Directory of Open Access Journals (Sweden)

    R. Gupta


    Full Text Available Over the past few decades an enormous interest in two-phase flow in microchannels has developed because of their application in a wide range of new technologies, ranging from lab-on-a-chip devices used in medical and pharmaceutical applications to micro-structured process equipment used in many modern chemical plants. Taylor flow, in which gas bubbles are surrounded by a liquid film and separated by liquid plugs, is the most common flow regime encountered in such applications. This review introduces the important attributes of two phase flow in microchannels and then focuses on the Taylor flow regime. The existing knowledge from both experimental and computational studies is presented. Finally, perspectives for future work are suggested.

  6. Structures of discoidal high density lipoproteins: a combined computational-experimental approach. (United States)

    Gu, Feifei; Jones, Martin K; Chen, Jianguo; Patterson, James C; Catte, Andrea; Jerome, W Gray; Li, Ling; Segrest, Jere P


    Conversion of discoidal phospholipid (PL)-rich high density lipoprotein (HDL) to spheroidal cholesteryl ester-rich HDL is a central step in reverse cholesterol transport. A detailed understanding of this process and the atheroprotective role of apolipoprotein A-I (apoA-I) requires knowledge of the structure and dynamics of these various particles. This study, combining computation with experimentation, illuminates structural features of apoA-I allowing it to incorporate varying amounts of PL. Molecular dynamics simulated annealing of PL-rich HDL models containing unesterified cholesterol results in double belt structures with the same general saddle-shaped conformation of both our previous molecular dynamics simulations at 310 K and the x-ray structure of lipid-free apoA-I. Conversion from a discoidal to a saddle-shaped particle involves loss of helicity and formation of loops in opposing antiparallel parts of the double belt. During surface expansion caused by the temperature-jump step, the curved palmitoyloleoylphosphatidylcholine bilayer surfaces approach planarity. Relaxation back into saddle-shaped structures after cool down and equilibration further supports the saddle-shaped particle model. Our kinetic analyses of reconstituted particles demonstrate that PL-rich particles exist in discrete sizes corresponding to local energetic minima. Agreement of experimental and computational determinations of particle size/shape and apoA-I helicity provide additional support for the saddle-shaped particle model. Truncation experiments combined with simulations suggest that the N-terminal proline-rich domain of apoA-I influences the stability of PL-rich HDL particles. We propose that apoA-I incorporates increasing PL in the form of minimal surface bilayers through the incremental unwinding of an initially twisted saddle-shaped apoA-I double belt structure.

  7. Nanotube dispersion and polymer conformational confinement in a nanocomposite fiber: a joint computational experimental study. (United States)

    Meng, Jiangsha; Zhang, Yiying; Cranford, Steven W; Minus, Marilyn L


    A combination of computational and experimental methods was implemented to understand and confirm that conformational changes of a polymer [specifically polyacrylonitrile (PAN)] vary with the dispersion quality and confinement between single-wall carbon nanotubes (SWNT) in the composite fibers. A shear-flow gel-spinning approach was utilized to produce PAN-based composite fibers with high concentration (i.e., loading of 10 wt %) of SWNT. Dispersion qualities of SWNT ranging from low to high were identified in the fibers, and their effects on the structural morphologies and mechanical properties of the composites were examined. These results show that, as the SWNT dispersion quality in terms of distribution in the fiber and exfoliation increases, PAN conformations were confined to the extended-chain form. Full atomistic computational results show that the surface interaction energy between isolated PAN and SWNT was not preferred, leading to the self-agglomeration of PAN. However, confinement of the polymer chains between SWNT bundles or individual tubes (i.e., molecular crowding) resulted in large increases in the PAN-SWNT interaction energy. In other words, the crowding of polymer chains by the SWNT at high concentrations can promote extended-chain conformational development during fiber spinning. This was also evidenced experimentally by the observance of significantly improved PAN orientation and crystallization in the composite. Ultimately this work provides fundamental insight toward the specific structural changes capable at the polymer/nanotube interface which are important toward improvement of the effective contribution of the SWNT to the mechanical performance of the composite.

  8. Computational and experimental investigations into the conformations of cyclic tetra-α/β-peptides. (United States)

    Oakley, Mark T; Oheix, Emmanuel; Peacock, Anna F A; Johnston, Roy L


    We present a combined computational and experimental study of the energy landscapes of cyclic tetra-α/β-peptides. We have performed discrete path sampling calculations on a series of cyclic tetra-α/β-peptides to obtain the relative free energies and barriers to interconversion of their conformers. The most stable conformers of cyclo-[(β-Ala-Gly)2] contain all-trans peptide groups. The relative energies of the cis isomers and the cis-trans barriers are lower than in acyclic peptides but not as low as in the highly strained cyclic α-peptides. For cyclic tetra-α/β-peptides containing a single proline residue, of the type cyclo-[β-Ala-Xaa-β-Ala-Pro], the energy landscapes show that the most stable isomers containing cis and trans β-Ala-Pro have similar free energies and are separated by barriers of approximately 15 kcal mol(-1). We show that the underlying energy landscapes of cyclo-[β-Ala-Lys-β-Ala-Pro] and cyclo-[β-Ala-Ala-β-Ala-Pro] are similar, allowing the substitution of the flexible side chain of Lys with Ala to reduce the computational demand of our calculations. However, the steric bulk of the Val side chain in cyclo-[β-Ala-Val-β-Ala-Pro] affects the conformations of the ring, leading to significant differences between its energy landscape and that of cyclo-[β-Ala-Ala-β-Ala-Pro]. We have synthesized the cyclic peptide cyclo-[β-Ala-Lys-β-Ala-Pro], and NMR spectroscopy shows the presence of conformers that interconvert slowly on the NMR time scale at temperatures up to 80 °C. Calculated circular dichroism (CD) spectra for the proposed major isomer of cyclo-[β-Ala-Ala-β-Ala-Pro] are in good agreement with the experimental spectra of cyclo-[β-Ala-Lys-β-Ala-Pro], suggesting that the Ala cyclic tetrapeptide is a viable model for the Lys analogue.

  9. An Experimental study on a Method of Computing Minimum flow rate

    International Nuclear Information System (INIS)

    Cho, Yeon Sik; Kim, Tae Hyun; Kim, Chang Hyun


    Many pump reliability problems in the Nuclear Power Plants (NPPs) are being attributed to the operation of the pump at flow rates well below its best efficiency point(BEP). Generally, the manufacturer and the user try to avert such problems by specifying a minimum flow, below which the pump should not be operated. Pump minimum flow usually involves two considerations. The first consideration is normally termed the 'thermal minimum flow', which is that flow required to prevent the fluid inside the pump from reaching saturation conditions. The other consideration is often referred to as 'mechanical minimum flow', which is that flow required to prevent mechanical damage. However, the criteria for specifying such a minimum flow are not clearly understood by all parties concerned. Also various factor and information for computing minimum flow are not easily available as considering for the pump manufacturer' proprietary. The objective of this study is to obtain experimental data for computing minimum flow rate and to understand the pump performances due to low flow operation. A test loop consisted of the pump to be used in NPPs, water tank, flow rate measurements and piping system with flow control devices was established for this study

  10. Experimental and Computational Sonic Boom Assessment of Lockheed-Martin N+2 Low Boom Models (United States)

    Cliff, Susan E.; Durston, Donald A.; Elmiligui, Alaa A.; Walker, Eric L.; Carter, Melissa B.


    Flight at speeds greater than the speed of sound is not permitted over land, primarily because of the noise and structural damage caused by sonic boom pressure waves of supersonic aircraft. Mitigation of sonic boom is a key focus area of the High Speed Project under NASA's Fundamental Aeronautics Program. The project is focusing on technologies to enable future civilian aircraft to fly efficiently with reduced sonic boom, engine and aircraft noise, and emissions. A major objective of the project is to improve both computational and experimental capabilities for design of low-boom, high-efficiency aircraft. NASA and industry partners are developing improved wind tunnel testing techniques and new pressure instrumentation to measure the weak sonic boom pressure signatures of modern vehicle concepts. In parallel, computational methods are being developed to provide rapid design and analysis of supersonic aircraft with improved meshing techniques that provide efficient, robust, and accurate on- and off-body pressures at several body lengths from vehicles with very low sonic boom overpressures. The maturity of these critical parallel efforts is necessary before low-boom flight can be demonstrated and commercial supersonic flight can be realized.

  11. Fluorine as a hydrogen-bond acceptor: experimental evidence and computational calculations. (United States)

    Dalvit, Claudio; Invernizzi, Christian; Vulpetti, Anna


    Hydrogen-bonding interactions play an important role in many chemical and biological systems. Fluorine acting as a hydrogen-bond acceptor in intermolecular and intramolecular interactions has been the subject of many controversial discussions and there are different opinions about it. Recently, we have proposed a correlation between the propensity of fluorine to be involved in hydrogen bonds and its (19)F NMR chemical shift. We now provide additional experimental and computational evidence for this correlation. The strength of hydrogen-bond complexes involving the fluorine moieties CH2F, CHF2, and CF3 was measured and characterized in simple systems by using established and novel NMR methods and compared to the known hydrogen-bond complex formed between acetophenone and p-fluorophenol. Implications of these results for (19)F NMR screening are analyzed in detail. Computed values of the molecular electrostatic potential at the different fluorine atoms and the analysis of the electron density topology at bond critical points correlate well with the NMR results. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Experimental and computational studies of active flow control on a model truck-trailer

    Directory of Open Access Journals (Sweden)

    Jahanmiri Mohsen


    Full Text Available Active flow control is probably the most challenging research area in vehicle aerodynamics. Being able to manipulate a flow field in order to achieve desired results beneficial to engineering is the only way to meet today’s demands for competitive and efficient solutions in the automotive industry. The current work studies the flow control on a semi detailed model truck by using detached-eddy simulations and wind tunnel experiments aiming at reducing the aerodynamic drag. This study combines both passive and active flow control applied on the rear end of the trailer. An indigenous fluidic actuator (loudspeaker in cavity with slots is used as a synthetic jet in the experiment. Both experiments and computations demonstrate that the active flow control works successfully and results in flow reattachment to the flaps. The numerical simulations show that the drag coefficient, CD decreased by 3.9% when AFC was activated compared to the baseline case without flaps. The corresponding decrease when AFC was deactivated (with flaps was only 0.7%. The experimental results show a decrease of CD by 3.1% for the case with activated AFC compared to the baseline case. When AFC was deactivated the corresponding decrease in CD was 1.8%. A detailed flow analysis made in computations and experiments is used to explain these results.

  13. Computational and experimental identification of mirtrons in Drosophila melanogaster and Caenorhabditis elegans (United States)

    Chung, Wei-Jen; Agius, Phaedra; Westholm, Jakub O.; Chen, Michael; Okamura, Katsutomo; Robine, Nicolas; Leslie, Christina S.; Lai, Eric C.


    Mirtrons are intronic hairpin substrates of the dicing machinery that generate functional microRNAs. In this study, we describe experimental assays that defined the essential requirements for entry of introns into the mirtron pathway. These data informed a bioinformatic screen that effectively identified functional mirtrons from the Drosophila melanogaster transcriptome. These included 17 known and six confident novel mirtrons among the top 51 candidates, and additional candidates had limited read evidence in available small RNA data. Our computational model also proved effective on Caenorhabditis elegans, for which the identification of 14 cloned mirtrons among the top 22 candidates more than tripled the number of validated mirtrons in this species. A few low-scoring introns generated mirtron-like read patterns from atypical RNA structures, but their paucity suggests that relatively few such loci were not captured by our model. Unexpectedly, we uncovered examples of clustered mirtrons in both fly and worm genomes, including a <8-kb region in C. elegans harboring eight distinct mirtrons. Altogether, we demonstrate that discovery of functional mirtrons, unlike canonical miRNAs, is amenable to computational methods independent of evolutionary constraint. PMID:21177960

  14. [Structural mechanism of immune evasion of HIV-1 gp120 by genomic, computational, and experimental science]. (United States)

    Yokoyama, Masaru


    The third variable region (V3) of the human immunodeficiency virus type 1 (HIV-1) envelope gp120 subunit participates in determination of viral infection co-receptor tropism and host humoral immune responses. Positive charge of the V3 plays a key role in determining viral co-receptor tropism. In our previous papers, we showed a key role of the V3's net positive charge in the immunological escape and co-receptor tropism evolution in vivo. On the other hand, the several papers suggested that trimeric gp120s are protected from immune system by occlusion on the oligomer, by mutational variation, by carbohydrate masking and by conformational masking. If we can reveal the mechanism of neutralization escape, we expect that we will regulate the neutralization of HIV-1. In this review, we will overview the structural mechanism of neutralization escape of HIV-1 gp120 examined by computational science. The computational sciences for virology can provide more valuable information in combination with genomic and experimental science.

  15. Self-Assembled Binary Nanoscale Systems: Multioutput Model with LFER-Covariance Perturbation Theory and an Experimental-Computational Study of NaGDC-DDAB Micelles. (United States)

    Messina, Paula V; Besada-Porto, Jose Miguel; González-Díaz, Humberto; Ruso, Juan M


    Studies of the self-aggregation of binary systems are of both theoretical and practical importance. They provide an opportunity to investigate the influence of the molecular structure of the hydrophobe on the nonideality of mixing. On the other hand, linear free energy relationship (LFER) models, such as Hansch's equations, may be used to predict the properties of chemical compounds such as drugs or surfactants. However, the task becomes more difficult once we want to predict simultaneaously the effect over multiple output properties of binary systems of perturbations under multiple input experimental boundary conditions (b(j)). As a consequence, we need computational chemistry or chemoinformatics models that may help us to predict different properties of the autoaggregation process of mixed surfactants under multiple conditions. In this work, we have developed the first model that combines perturbation theory (PT) and LFER ideas. The model uses as input covariance PT operators (CPTOs). CPTOs are calculated as the difference between covariance ΔCov((i)μ(k)) functions before and after multiple perturbations in the binary system. In turn, covariances calculated as the product of two Box-Jenkins operators (BJO) operators. BJOs are used to measure the deviation of the structure of different chemical compounds from a set of molecules measured under a given subset of experimental conditions. The best CPT-LFER model found predicted the effects of 25,000 perturbations over 9 different properties of binary systems. We also reported experimental studies of different experimental properties of the binary system formed by sodium glycodeoxycholate and didodecyldimethylammonium bromide (NaGDC-DDAB). Last, we used our CPT-LFER model to carry out a 1000 data point simulation of the properties of the NaGDC-DDAB system under different conditions not studied experimentally.

  16. Receiver operating characteristic curve evaluation on computed radiography: an experimental study

    International Nuclear Information System (INIS)

    Yu Zixi; Wang Changyuan; Xu Yue; Xie Jindong; Zhang Menglong; Wang Jian


    Objective: To get the maximum information from computed radiography (CR) output images by changing post-processing parameters. Methods: Six experimental photos of polypropylene balls of 2.0 mm in diameter were taken by means of one time X-ray exposing on an imaging plate (IP) with different post-processing parameters including rotation amount (GA), gray gradation type (GT), rotation center (GC), shifting amount (GS), frequency rank (RN), frequency type (RT), and degree of enhancement (RE). 6 photos were viewed by three students and one radiologist on a 6000 lx illuminance viewbox. Receiver operating characteristic (ROC) curves were made by means of 5-value-differentiation method. Results: The largest mean area value (Az) below ROC curves of a low contrast experimental photo with post-processing parameters GA=1.0, GT=A, GC=1.6, GS=0.3, RN=4.0, RT=R and RE=3.0 was 0.96, and the maximum information was obtained. The smallest mean area value (Az) was 0.78 with changed post-processing parameters GA=0.8, GS=-0.2 and RE=0.5 while other parameters were not changed. The minimum information was obtained from this photo. Conclusion: In order to get the maximum information from a CR output image, the post-processing parameters should be suitably selected

  17. Computational simulations of frictional losses in pipe networks confirmed in experimental apparatusses designed by honors students (United States)

    Pohlman, Nicholas A.; Hynes, Eric; Kutz, April


    Lectures in introductory fluid mechanics at NIU are a combination of students with standard enrollment and students seeking honors credit for an enriching experience. Most honors students dread the additional homework problems or an extra paper assigned by the instructor. During the past three years, honors students of my class have instead collaborated to design wet-lab experiments for their peers to predict variable volume flow rates of open reservoirs driven by gravity. Rather than learn extra, the honors students learn the Bernoulli head-loss equation earlier to design appropriate systems for an experimental wet lab. Prior designs incorporated minor loss features such as sudden contraction or multiple unions and valves. The honors students from Spring 2015 expanded the repertoire of available options by developing large scale set-ups with multiple pipe networks that could be combined together to test the flexibility of the student team's computational programs. The engagement of bridging the theory with practice was appreciated by all of the students such that multiple teams were able to predict performance within 4% accuracy. The challenges, schedules, and cost estimates of incorporating the experimental lab into an introductory fluid mechanics course will be reported.

  18. Computational and experimental study of nanoporous membranes for water desalination and decontamination.

    Energy Technology Data Exchange (ETDEWEB)

    Hickner, Michael A. (Penn State University, University Park, PA); Chinn, Douglas Alan (Sandia National Laboratories, Albuquerque, NM); Adalsteinsson, Helgi; Long, Kevin R. (Texas Tech University, Lubbock, TX); Kent, Michael Stuart (Sandia National Laboratories, Albuquerque, NM); Debusschere, Bert J.; Zendejas, Frank J.; Tran, Huu M.; Najm, Habib N.; Simmons, Blake Alexander


    Fundamentals of ion transport in nanopores were studied through a joint experimental and computational effort. The study evaluated both nanoporous polymer membranes and track-etched nanoporous polycarbonate membranes. The track-etched membranes provide a geometrically well characterized platform, while the polymer membranes are more closely related to ion exchange systems currently deployed in RO and ED applications. The experimental effort explored transport properties of the different membrane materials. Poly(aniline) membranes showed that flux could be controlled by templating with molecules of defined size. Track-etched polycarbonate membranes were modified using oxygen plasma treatments, UV-ozone exposure, and UV-ozone with thermal grafting, providing an avenue to functionalized membranes, increased wettability, and improved surface characteristic lifetimes. The modeling effort resulted in a novel multiphysics multiscale simulation model for field-driven transport in nanopores. This model was applied to a parametric study of the effects of pore charge and field strength on ion transport and charge exclusion in a nanopore representative of a track-etched polycarbonate membrane. The goal of this research was to uncover the factors that control the flux of ions through a nanoporous material and to develop tools and capabilities for further studies. Continuation studies will build toward more specific applications, such as polymers with attached sulfonate groups, and complex modeling methods and geometries.

  19. Recent advances in protein-protein interaction prediction: experimental and computational methods. (United States)

    Jessulat, Matthew; Pitre, Sylvain; Gui, Yuan; Hooshyar, Mohsen; Omidi, Katayoun; Samanfar, Bahram; Tan, Le Hoa; Alamgir, Md; Green, James; Dehne, Frank; Golshani, Ashkan


    Proteins within the cell act as part of complex networks, which allow pathways and processes to function. Therefore, understanding how proteins interact is a significant area of current research. This review aims to present an overview of key experimental techniques (yeast two-hybrid, tandem affinity purification and protein microarrays) used to discover protein-protein interactions (PPIs), as well as to briefly discuss certain computational methods for predicting protein interactions based on gene localization, phylogenetic information, 3D structural modeling or primary protein sequence data. Due to the large-scale applicability of primary sequence-based methods, the authors have chosen to focus on this strategy for our review. There is an emphasis on a recent algorithm called Protein Interaction Prediction Engine (PIPE) that can predict global PPIs. The readers will discover recent advances both in the practical determination of protein interaction and the strategies that are available to attempt to anticipate interactions without the time and costs of experimental work. Global PPI maps can help understand the biology of complex diseases and facilitate the identification of novel drug target sites. This study describes different techniques used for PPI prediction that we believe will significantly impact the development of the field in a new future. We expect to see a growing number of similar techniques capable of large-scale PPI predictions.

  20. Binding of the neuroleptic drug, gabapentin, to bovine serum albumin: Insights from experimental and computational studies

    Energy Technology Data Exchange (ETDEWEB)

    Jalali, Fahimeh, E-mail: [Department of Chemistry, Razi University, 67346 Kermanshah (Iran, Islamic Republic of); Dorraji, Parisa S. [Department of Chemistry, Razi University, 67346 Kermanshah (Iran, Islamic Republic of); Mahdiuni, Hamid [Department of Biology, Razi University, 67346 Kermanshah (Iran, Islamic Republic of)


    The interaction between antiepileptic drug, gabapentin (GP), and bovin serum albumin (BSA) was studied by spectroscopic and computational methods. The native fluorescence of BSA was quenched by GP. Stern–Volmer quenching constant was calculated at different temperatures which suggested a static mechanism. The association constant (K{sub a}) was calculated from fluorescence quenching studies, which increased with temperature rising. GP competed well with warfarine for hydrophobic subdomain IIA (Sudlow's site I) on the protein. Enthalpy and entropy changes during the interaction of GP with BSA were obtained using van't Hoff plot, which showed an entropy-driven process and involvement of hydrophobic forces (ΔH>0 and ΔS>0). Synchronous fluorescence measurements of BSA solution in the presence of GP showed a considerable blue shift when Δλ=15 nm, therefore, GP interacts with tyrosine-rich sites on BSA. Optimized docked model of BSA–GP mixture confirmed the experimental results. -- Highlights: • Interaction of gabapentin and bovine serum albumin (BSA) is investigated by spectroscopic techniques. • Gabapentin can quench the fluorescence of BSA through a static quenching procedure. • The binding of gabapentin to BSA is driven mainly by hydrophobic interactions. • Subdomain IIA (Sudlow's site I) of BSA is found to be the main binding site for gabapentin. • Molecular docking modeling confirmed the experimental results.

  1. Experimental and computational evaluation of neutrals in the Alcator C-Mod edge pedestal (United States)

    Hughes, J. W.; Mossessian, D.; Labombard, B.; Terry, J.


    Pedestal-forming edge transport barriers (ETBs) in tokamak plasmas and the physics governing them are linked to the enhancement of confinement obtained in H-mode plasmas. Studies on Alcator C-Mod employ experimental measurements and simple 1-D transport models in order to better understand ETB physics. We examine the influences of ionization and charge exchange on the pedestals in electron density and temperature. Routine measurements from edge Thomson scattering (ETS) give pedestal scalings with global plasma parameters, while individual ETS profiles are combined with scanning Langmuir probe data and optical D_α emissivity measurements to give atomic density profiles and the associated radial distribution of the ionization source rate. From H-mode profiles of these quantities a well in effective plasma diffusivity is calculated, and is shown to systematically vary as the confinement regime is varied from ELM-free to EDA. Experimental work is supplemented with modeling and computation of edge neutral transport via KN1D, a kinetic solver for atomic and molecular distribution functions in slab geometry. The level of agreement between experiment and model is encouraging.

  2. Investigation of mixed mode - I/II fracture problems - Part 1: computational and experimental analyses

    Directory of Open Access Journals (Sweden)

    O. Demir


    Full Text Available In this study, to investigate and understand the nature of fracture behavior properly under in-plane mixed mode (Mode-I/II loading, three-dimensional fracture analyses and experiments of compact tension shear (CTS specimen are performed under different mixed mode loading conditions. Al 7075-T651 aluminum machined from rolled plates in the L-T rolling direction (crack plane is perpendicular to the rolling direction is used in this study. Results from finite element analyses and fracture loads, crack deflection angles obtained from the experiments are presented. To simulate the real conditions in the experiments, contacts are defined between the contact surfaces of the loading devices, specimen and loading pins. Modeling, meshing and the solution of the problem involving the whole assembly, i.e., loading devices, pins and the specimen, with contact mechanics are performed using ANSYSTM. Then, CTS specimen is analyzed separately using a submodeling approach, in which three-dimensional enriched finite elements are used in FRAC3D solver to calculate the resulting stress intensity factors along the crack front. Having performed the detailed computational and experimental studies on the CTS specimen, a new specimen type together with its loading device is also proposed that has smaller dimensions compared to the regular CTS specimen. Experimental results for the new specimen are also presented.

  3. Crown-ether functionalized carbon nanotubes for purification of lithium compounds: computational and experimental study

    International Nuclear Information System (INIS)

    Singha Deb, A.K.; Arora, S.K.; Joshi, J.M.; Ali, Sk. M.; Shenoy, K.T.; Goyal, Aiana


    Lithium compounds finds several applications in nuclear science and technology, viz, lithium fluoride/hydroxide/alloys are used as dosimetric materials in luminescence devices, molten-salt breeder reactor, international thermonuclear experimental reactor, single crystal based neutron detectors etc. The lithium compounds should be in a proper state of purity; especially it should not contain other alkali metal cations which can downgrade the performance. Hence, there is a need to develop a process for purification of the lithium salt to achieve the desired quality. Therefore an attempt has been made to develop advanced nanomaterials for purification of the lithium salts. In this work, benzo-15-crown-5(B15C5) functionalized carbon nanotubes (CNTs), owing to the good adsorption properties of CNT and alkali metal encapsulation behaviour of B15C5, were showed to bind preferentially with sodium and potassium ions compared to lithium ions. DFT based computation calculations have shown that the free energy of complexation of Na + and K + by B15C5-CNT is higher than that of Li + , implying that B15C5-CNT selectively binds Na + and K + . The experimental batch solid-liquid extraction has also revealed the same trend as in the calculations. The crown-ethers functionalized CNTs have the potentiality for use in purifying lithium compounds. (author)

  4. Verification of SACI-2 computer code comparing with experimental results of BIBLIS-A and LOOP-7 computer code

    International Nuclear Information System (INIS)

    Soares, P.A.; Sirimarco, L.F.


    SACI-2 is a computer code created to study the dynamic behaviour of a PWR nuclear power plant. To evaluate the quality of its results, SACI-2 was used to recalculate commissioning tests done in BIBLIS-A nuclear power plant and to calculate postulated transients for Angra-2 reactor. The results of SACI-2 computer code from BIBLIS-A showed as much good agreement as those calculated with the KWU Loop 7 computer code for Angra-2. (E.G.) [pt

  5. VX hydrolysis by human serum paraoxonase 1: a comparison of experimental and computational results.

    Directory of Open Access Journals (Sweden)

    Matthew W Peterson

    Full Text Available Human Serum paraoxonase 1 (HuPON1 is an enzyme that has been shown to hydrolyze a variety of chemicals including the nerve agent VX. While wildtype HuPON1 does not exhibit sufficient activity against VX to be used as an in vivo countermeasure, it has been suggested that increasing HuPON1's organophosphorous hydrolase activity by one or two orders of magnitude would make the enzyme suitable for this purpose. The binding interaction between HuPON1 and VX has recently been modeled, but the mechanism for VX hydrolysis is still unknown. In this study, we created a transition state model for VX hydrolysis (VX(ts in water using quantum mechanical/molecular mechanical simulations, and docked the transition state model to 22 experimentally characterized HuPON1 variants using AutoDock Vina. The HuPON1-VX(ts complexes were grouped by reaction mechanism using a novel clustering procedure. The average Vina interaction energies for different clusters were compared to the experimentally determined activities of HuPON1 variants to determine which computational procedures best predict how well HuPON1 variants will hydrolyze VX. The analysis showed that only conformations which have the attacking hydroxyl group of VX(ts coordinated by the sidechain oxygen of D269 have a significant correlation with experimental results. The results from this study can be used for further characterization of how HuPON1 hydrolyzes VX and design of HuPON1 variants with increased activity against VX.

  6. Computational and experimental analysis of short peptide motifs for enzyme inhibition.

    Directory of Open Access Journals (Sweden)

    Jinglin Fu

    Full Text Available The metabolism of living systems involves many enzymes that play key roles as catalysts and are essential to biological function. Searching ligands with the ability to modulate enzyme activities is central to diagnosis and therapeutics. Peptides represent a promising class of potential enzyme modulators due to the large chemical diversity, and well-established methods for library synthesis. Peptides and their derivatives are found to play critical roles in modulating enzymes and mediating cellular uptakes, which are increasingly valuable in therapeutics. We present a methodology that uses molecular dynamics (MD and point-variant screening to identify short peptide motifs that are critical for inhibiting β-galactosidase (β-Gal. MD was used to simulate the conformations of peptides and to suggest short motifs that were most populated in simulated conformations. The function of the simulated motifs was further validated by the experimental point-variant screening as critical segments for inhibiting the enzyme. Based on the validated motifs, we eventually identified a 7-mer short peptide for inhibiting an enzyme with low μM IC50. The advantage of our methodology is the relatively simplified simulation that is informative enough to identify the critical sequence of a peptide inhibitor, with a precision comparable to truncation and alanine scanning experiments. Our combined experimental and computational approach does not rely on a detailed understanding of mechanistic and structural details. The MD simulation suggests the populated motifs that are consistent with the results of the experimental alanine and truncation scanning. This approach appears to be applicable to both natural and artificial peptides. With more discovered short motifs in the future, they could be exploited for modulating biocatalysis, and developing new medicine.

  7. Experimental and Computational Sonic Boom Assessment of Boeing N+2 Low Boom Models (United States)

    Durston, Donald A.; Elmiligui, Alaa; Cliff, Susan E.; Winski, Courtney S.; Carter, Melissa B.; Walker, Eric L.


    Near-field pressure signatures were measured and computational predictions made for several sonic boom models representing Boeing's Quiet Experimental Validation Concept (QEVC) supersonic transport, as well as three axisymmetric calibration models. Boeing developed the QEVC under a NASA Research Announcement (NRA) contract for Experimental Systems Validations for N+2 Supersonic Commercial Transport Aircraft, which was led by the NASA High Speed Project under the Fundamental Aeronautics Program. The concept was designed to address environmental and performance goals given in the NRA, specifically for low sonic boom loudness levels and high cruise efficiency, for an aircraft anticipated to enter service in the 2020 timeframe. Wind tunnel tests were conducted on the aircraft and calibration models during Phases I and II of the NRA contract from 2011 to 2013 in the NASA Ames 9- by 7-Foot and NASA Glenn 8- by 6-Foot Supersonic Wind Tunnels. Sonic boom pressure signatures were acquired primarily at Mach 1.6 and 1.8, and force and moment data were acquired from Mach 0.8 to 1.8. The sonic boom test data were obtained using a 2-in. flat-top pressure rail and a 14-in. round-top tapered "reflection factor 1" (RF1) pressure rail. Both rails capture an entire pressure signature in one data point, and successive signatures at varying positions along or above the rail were used to improve data quality through spatial averaging. The sonic boom data obtained by the rails were validated with high-fidelity numerical simulations of off-body pressures using the CFD codes USM3D, Cart3D, and OVERFLOW. The test results from the RF1 rail showed good agreement between the computational and experimental data when a variety of testing techniques including spatial averaging of a series of pressure signatures were employed, however, reflections off the 2-in. flat-top rail caused distortions in the signatures that did not agree with the CFD predictions. The 9 x 7 and 8 x 6 wind tunnels generally

  8. Mathematical Modeling of Complex Reaction Systems for Computer-Aided Control and its Illustration on Atmospheric Chemistry (United States)

    Amiryan, A.


    Modeling of sequential process has its own importance in Atmospheric Chemistry. Numerical calculations which allow to predict separate stages and components of chemical reaction make possible the reaction management, such is the new and perspective direction in chemical researches. Chemical processes basically pass multiple simple stages where various atoms and radicals participate. The complex chain of chemical reactionary systems complicates their research and the research is impossible without new methods of mathematical simulation and high technologies which allow not only to explain results of experiments but also to predict dynamics of processes. A new program package is suggested for solving research problems of chemical kinetics. The program is tested on different illustrative examples on Atmospheric Chemistry and installed in various scientific and educational institutions.

  9. Fuel treatment effects on soil chemistry and foliar physiology of three coniferous species at the Teakettle Experimental Forest, California, USA (United States)

    Rakesh Minocha; Swathi A. Turlapati; Stephanie Long; Malcolm. North


    A full factorial design crossing overstory (O) and understory (U) thinning and prescribed burning (B) was started at Teakettle Experimental Forest, California, in 2001 with the aim of achieving shifts in species composition to favor fire-resistant pines over fir. The goal of the present study was to evaluate the use of metabolic changes as early indicators for...

  10. Development of an Interdisciplinary Experimental Series for the Laboratory Courses of Cell and Molecular Biology and Advance Inorganic Chemistry (United States)

    Smith, Montserrat Rabago; McAllister, Robert; Newkirk, Kiera; Basing, Alexander; Wang, Lihua


    An interdisciplinary approach to education has become more important in the development of science and technology, which requires universities to have graduates with broad knowledge and skills and to apply these skills in solving real-world problems. An interdisciplinary experimental series has been developed for the laboratories in cell and…

  11. Stepwise adsorption of phenanthrene at the fly ash-water interface as affected by solution chemistry: experimental and modeling studies. (United States)

    An, Chunjiang; Huang, Guohe


    Fly ash (FA) is predominantly generated from coal-fired power plants. Contamination during disposal of FA can cause significant environmental problems. Knowledge about the interaction of FA and hydrophobic organic pollutants in the environment is very limited. This study investigated the adsorption of phenanthrene at the interface of FA and water. The performance of phenanthrene adsorption on FA and the effects of various aqueous chemistry conditions were evaluated. The adsorption isotherms exhibited an increasing trend in the adsorbed amounts of phenanthrene, while a stepwise pattern was apparent. A stepwise multisite Langmuir model was developed to simulate the stepwise adsorption process. The adsorption of phenanthrene onto FA was noted to be spontaneous at all temperatures. The thermodynamic results indicated that the adsorption was an exothermic process. The adsorption capacity gradually decreased as pH increased from 4 to 8; however, this trend became less significant when pH was changed from 8 to 10. The binding affinity of phenanthrene to FA increased after the addition of humic acid (HA). The pH variation was also responsible for the changes of phenanthrene adsorption on FA in the presence of HA. High ionic strength corresponded to low mobility of phenanthrene in the FA-water system. Results of this study can help reveal the migration patterns of organic contaminants in the FA-water system and facilitate environmental risk assessment at FA disposal sites.

  12. Efficient Discovery of Novel Multicomponent Mixtures for Hydrogen Storage: A Combined Computational/Experimental Approach

    Energy Technology Data Exchange (ETDEWEB)

    Wolverton, Christopher [Northwestern Univ., Evanston, IL (United States). Dept. of Materials Science and Engineering; Ozolins, Vidvuds [Univ. of California, Los Angeles, CA (United States). Dept. of Materials Science and Engineering; Kung, Harold H. [Northwestern Univ., Evanston, IL (United States). Dept. of Chemical and Biological Engineering; Yang, Jun [Ford Scientific Research Lab., Dearborn, MI (United States); Hwang, Sonjong [California Inst. of Technology (CalTech), Pasadena, CA (United States). Dept. of Chemistry and Chemical Engineering; Shore, Sheldon [The Ohio State Univ., Columbus, OH (United States). Dept. of Chemistry and Biochemistry


    The objective of the proposed program is to discover novel mixed hydrides for hydrogen storage, which enable the DOE 2010 system-level goals. Our goal is to find a material that desorbs 8.5 wt.% H2 or more at temperatures below 85°C. The research program will combine first-principles calculations of reaction thermodynamics and kinetics with material and catalyst synthesis, testing, and characterization. We will combine materials from distinct categories (e.g., chemical and complex hydrides) to form novel multicomponent reactions. Systems to be studied include mixtures of complex hydrides and chemical hydrides [e.g. LiNH2+NH3BH3] and nitrogen-hydrogen based borohydrides [e.g. Al(BH4)3(NH3)3]. The 2010 and 2015 FreedomCAR/DOE targets for hydrogen storage systems are very challenging, and cannot be met with existing materials. The vast majority of the work to date has delineated materials into various classes, e.g., complex and metal hydrides, chemical hydrides, and sorbents. However, very recent studies indicate that mixtures of storage materials, particularly mixtures between various classes, hold promise to achieve technological attributes that materials within an individual class cannot reach. Our project involves a systematic, rational approach to designing novel multicomponent mixtures of materials with fast hydrogenation/dehydrogenation kinetics and favorable thermodynamics using a combination of state-of-the-art scientific computing and experimentation. We will use the accurate predictive power of first-principles modeling to understand the thermodynamic and microscopic kinetic processes involved in hydrogen release and uptake and to design new material/catalyst systems with improved properties. Detailed characterization and atomic-scale catalysis experiments will elucidate the effect of dopants and nanoscale catalysts in achieving fast kinetics and reversibility. And

  13. Rapid Computer Aided Ligand Design and Screening of Precious Metal Extractants from TRUEX Raffinate with Experimental Validation

    Energy Technology Data Exchange (ETDEWEB)

    Clark, Aurora Sue [Washington State Univ., Pullman, WA (United States); Wall, Nathalie [Washington State Univ., Pullman, WA (United States); Benny, Paul [Washington State Univ., Pullman, WA (United States)


    through the design of a software program that uses state-of-the-art computational combinatorial chemistry, and is developed and validated with experimental data acquisition; the resulting tool allows for rapid design and screening of new ligands for the extraction of precious metals from SNF. This document describes the software that has been produced, ligands that have been designed, and fundamental new understandings of the extraction process of Rh(III) as a function of solution phase conditions (pH, nature of acid, etc.).

  14. Rapid Computer Aided Ligand Design and Screening of Precious Metal Extractants from TRUEX Raffinate with Experimental Validation

    International Nuclear Information System (INIS)

    Clark, Aurora Sue; Wall, Nathalie; Benny, Paul


    design of a software program that uses state-of-the-art computational combinatorial chemistry, and is developed and validated with experimental data acquisition; the resulting tool allows for rapid design and screening of new ligands for the extraction of precious metals from SNF. This document describes the software that has been produced, ligands that have been designed, and fundamental new understandings of the extraction process of Rh(III) as a function of solution phase conditions (pH, nature of acid, etc.).

  15. Comparative experimental and modeling study of the low- to moderate-temperature oxidation chemistry of 2,5-dimethylfuran, 2-methylfuran, and furan

    KAUST Repository

    Tran, Luc-Sy


    The reaction chemistry of furanic fuels, proposed as next-generation bio-derived fuels, has been a target of recent studies. However, quantitative intermediate species profiles at low- to moderate-temperature (LMT) conditions remain scarce. The present paper reports the first systematic full speciation dataset in the temperature range 730–1170 K for three furanic fuels, 2,5-dimethylfuran (DMF), 2-methylfuran (MF), and furan, measured for different equivalence ratios under near-identical LMT conditions in a flow reactor at 1 bar. More than 35 species including reactants, intermediate species, and products were analyzed using electron ionization (EI) molecular-beam mass spectrometry (MBMS). These experimental results provided motivation to extend a previous single joint mechanism for the three furanic fuels, developed for the high-temperature regime in low-pressure premixed flames, to include the LMT oxidation chemistry. A decisive difference of the present mechanism versus all previously reported models is a more complete description of fuel radical reactions for LMT oxidation, obtained from theoretical calculations of thermodynamic properties and rate constants. The experimentally observed differences in fuel conversion behavior and species distribution between the three fuels have been compared to model predictions using the newly extended mechanism. The dependence of fuel conversion on equivalence ratio decreases significantly from DMF to furan, a behavior consistent with the different number of lateral methyl groups in the fuel structure. All three furanic fuels, especially DMF, produce several highly toxic oxygenated species including acrolein, methyl vinyl ketone, furfural, and phenol. These toxic species were found to be products of the primary reactions of these fuels, and these undesirable trends could be explained satisfactorily by the present model, pointing to some caution with regard to the potential emission spectra under LMT conditions.

  16. Fourth Indo-US Workshop on Mathematical Chemistry Held in Pune, Maharastra, India on 8-12 January 2005 (United States)


    experimental and computational data in chemistry Lech P, Schulz, Adam Mickiewicz University, Department of Chemistry, Grunwaldzka 6, 60-780 Poznajh, Schulz Lech Sem Daniel Adam Mickiewicz University Marquette University Poland USA Isch

  17. Computational Design of Creep-Resistant Alloys and Experimental Validation in Ferritic Superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Liaw, Peter


    A new class of ferritic superalloys containing B2-type zones inside parent L21-type precipitates in a disordered solid-solution matrix, also known as a hierarchical-precipitate strengthened ferritic alloy (HPSFA), has been developed for high-temperature structural applications in fossil-energy power plants. These alloys were designed by the addition of the Ti element into a previously-studied NiAl-strengthened ferritic alloy (denoted as FBB8 in this study). In the present research, systematic investigations, including advanced experimental techniques, first-principles calculations, and numerical simulations, have been integrated and conducted to characterize the complex microstructures and excellent creep resistance of HPSFAs. The experimental techniques include transmission-electron microscopy, scanningtransmission- electron microscopy, neutron diffraction, and atom-probe tomography, which provide detailed microstructural information of HPSFAs. Systematic tension/compression creep tests revealed that HPSFAs exhibit the superior creep resistance, compared with the FBB8 and conventional ferritic steels (i.e., the creep rates of HPSFAs are about 4 orders of magnitude slower than the FBB8 and conventional ferritic steels.) First-principles calculations include interfacial free energies, anti-phase boundary (APB) free energies, elastic constants, and impurity diffusivities in Fe. Combined with kinetic Monte- Carlo simulations of interdiffusion coefficients, and the integration of computational thermodynamics and kinetics, these calculations provide great understanding of thermodynamic and mechanical properties of HPSFAs. In addition to the systematic experimental approach and first-principles calculations, a series of numerical tools and algorithms, which assist in the optimization of creep properties of ferritic superalloys, are utilized and developed. These numerical simulation results are compared with the available experimental data and previous first

  18. Lubrication Chemistry Viewed from DFT-Based Concepts and Electronic Structural Principles

    Directory of Open Access Journals (Sweden)

    Jin Yuansheng


    Full Text Available Abstract: Fundamental molecular issues in lubrication chemistry were reviewed under categories of solution chemistry, contact chemistry and tribochemistry. By introducing the Density Functional Theory(DFT-derived chemical reactivity parameters (chemical potential, electronegativity, hardness, softness and Fukui function and related electronic structural principles (electronegativity equalization principle, hard-soft acid-base principle, and maximum hardness principle, their relevancy to lubrication chemistry was explored. It was suggested that DFT, theoretical, conceptual and computational, represents a useful enabling tool to understand lubrication chemistry issues prior to experimentation and the approach may form a key step in the rational design of lubrication chemistry via computational methods. It can also be optimistically anticipated that these considerations will gestate unique DFT-based strategies to understand sophisticated tribology themes, such as origin of friction, essence of wear, adhesion in MEMS/NEMS, chemical mechanical polishing in wafer manufacturing, stress corrosion, chemical control of friction and wear, and construction of designer tribochemical systems.

  19. Bad chemistry


    Petsko, Gregory A


    General chemistry courses haven't changed significantly in forty years. Because most basic chemistry students are premedical students, medical schools have enormous influence and could help us start all over again to create undergraduate chemistry education that works.

  20. Enthalpy of formation of the cyclohexadienyl radical and the C-H bond enthalpy of 1,4-cyclohexadiene: an experimental and computational re-evaluation. (United States)

    Gao, Yide; DeYonker, Nathan J; Garrett, E Chauncey; Wilson, Angela K; Cundari, Thomas R; Marshall, Paul


    A quantitative understanding of the thermochemistry of cyclohexadienyl radical and 1,4-cyclohexadiene is beneficial for diverse areas of chemistry. Given the interest in these two species, it is surprising that more detailed thermodynamic data concerning the homolytic C-H bond enthalpies of such entities have not been forthcoming. We thus undertook an experimental and computational evaluation of (a) the enthalpy of formation of cyclohexadienyl radical (C(6)H(7)), (b) the homolytic C-H bond enthalpy of 1,4-cyclohexadiene (C(6)H(8)), and (c) the enthalpy of the addition of a hydrogen atom to benzene. Using laser photolysis experiments coupled with highly accurate ab initio quantum mechanical techniques, a newly recommended enthalpy of formation for C(6)H(7) is determined to be 208.0 +/- 3.9 kJ mol(-1), leading to a homolytic bond dissociation enthalpy of 321.7 +/- 2.9 kJ mol(-1), almost 9 kJ mol(-1) higher than previously determined enthalpies that used less certain experimental values for the C(6)H(7) enthalpy of formation.

  1. Experimental and computational study of dielectric barrier discharges for environmental applications (United States)

    Aerts, Robby

    Air pollution has become a major global concern which affects all inhabitants of our precious earth. Nowadays it is fact that our climate is changing and the sea level is rising. Moreover, we are facing an energy crisis because all our fossil fuel resources will sooner or later be running empty. It is clear that drastic measures are needed to keep our planet as it is today for generations to come. One of these measures is the 20-20-20 targets imposed by the European Commission, which stimulates the research for environmental energy applications. In this PhD dissertation two environmental applications of plasma technology are investigated. The first one is the abatement of flue gases, and more specifically the destruction of volatile organic compounds (VOCs). The second one is the conversion of CO2 into valuable chemicals. Both of these applications suffer from a large energy cost under classical (thermodynamic) conditions, due to the chemical stability of these molecules. Plasma technology is quite promising to overcome these thermodynamic barriers. Plasmas allow reactions at different time-scales with different species, such as electrons, ions, radicals, molecules and excited species, creating new chemical pathways. Indeed, in a plasma the applied electrical energy is directly transferred to the electrons, which activate the gas by ionization, excitation and dissociation, hence creating reactive species (ions, excited species, radicals), that can further easily undergo other chemical reactions. Especially gas discharges, which are low temperature plasmas, show promising results in the destruction of pollutants at mild conditions. A common type of gas discharge is the dielectric barrier discharge (DBD) which has been successfully scaled up for industrial ozone generation and is widely investigated in the field of environmental applications. The complexity of DBDs creates difficulties for experimental diagnostics and therefore numerical studies can help to improve

  2. Microstructure and defect chemistry of yttrium aluminium garnet ceramics

    International Nuclear Information System (INIS)

    Schuh, L.H.


    This thesis describes basic aspects concerning the defect chemistry and the microstructure of yttrium aluminium garnet ceramics. The work consists of three parts: a literature study, an experimental part and a section giving computer simulation data of defects. (author). 320 refs.; 68 figs.; 72 schemes; 32 tabs

  3. Probing the Mutational Interplay between Primary and Promiscuous Protein Functions: A Computational-Experimental Approach (United States)

    Garcia-Seisdedos, Hector; Ibarra-Molero, Beatriz; Sanchez-Ruiz, Jose M.


    Protein promiscuity is of considerable interest due its role in adaptive metabolic plasticity, its fundamental connection with molecular evolution and also because of its biotechnological applications. Current views on the relation between primary and promiscuous protein activities stem largely from laboratory evolution experiments aimed at increasing promiscuous activity levels. Here, on the other hand, we attempt to assess the main features of the simultaneous modulation of the primary and promiscuous functions during the course of natural evolution. The computational/experimental approach we propose for this task involves the following steps: a function-targeted, statistical coupling analysis of evolutionary data is used to determine a set of positions likely linked to the recruitment of a promiscuous activity for a new function; a combinatorial library of mutations on this set of positions is prepared and screened for both, the primary and the promiscuous activities; a partial-least-squares reconstruction of the full combinatorial space is carried out; finally, an approximation to the Pareto set of variants with optimal primary/promiscuous activities is derived. Application of the approach to the emergence of folding catalysis in thioredoxin scaffolds reveals an unanticipated scenario: diverse patterns of primary/promiscuous activity modulation are possible, including a moderate (but likely significant in a biological context) simultaneous enhancement of both activities. We show that this scenario can be most simply explained on the basis of the conformational diversity hypothesis, although alternative interpretations cannot be ruled out. Overall, the results reported may help clarify the mechanisms of the evolution of new functions. From a different viewpoint, the partial-least-squares-reconstruction/Pareto-set-prediction approach we have introduced provides the computational basis for an efficient directed-evolution protocol aimed at the simultaneous

  4. Phantom-based experimental validation of computational fluid dynamics simulations on cerebral aneurysms. (United States)

    Sun, Qi; Groth, Alexandra; Bertram, Matthias; Waechter, Irina; Bruijns, Tom; Hermans, Roel; Aach, Til


    Recently, image-based computational fluid dynamics (CFD) simulation has been applied to investigate the hemodynamics inside human cerebral aneurysms. The knowledge of the computed three-dimensional flow fields is used for clinical risk assessment and treatment decision making. However, the reliability of the application specific CFD results has not been thoroughly validated yet. In this work, by exploiting a phantom aneurysm model, the authors therefore aim to prove the reliability of the CFD results obtained from simulations with sufficiently accurate input boundary conditions. To confirm the correlation between the CFD results and the reality, virtual angiograms are generated by the simulation pipeline and are quantitatively compared to the experimentally acquired angiograms. In addition, a parametric study has been carried out to systematically investigate the influence of the input parameters associated with the current measuring techniques on the flow patterns. Qualitative and quantitative evaluations demonstrate good agreement between the simulated and the real flow dynamics. Discrepancies of less than 15% are found for the relative root mean square errors of time intensity curve comparisons from each selected characteristic position. The investigated input parameters show different influences on the simulation results, indicating the desired accuracy in the measurements. This study provides a comprehensive validation method of CFD simulation for reproducing the real flow field in the cerebral aneurysm phantom under well controlled conditions. The reliability of the CFD is well confirmed. Through the parametric study, it is possible to assess the degree of validity of the associated CFD model based on the parameter values and their estimated accuracy range.

  5. Interaction of anthraquinone anti-cancer drugs with DNA:Experimental and computational quantum chemical study (United States)

    Al-Otaibi, Jamelah S.; Teesdale Spittle, Paul; El Gogary, Tarek M.


    Anthraquinones form the basis of several anticancer drugs. Anthraquinones anticancer drugs carry out their cytotoxic activities through their interaction with DNA, and inhibition of topoisomerase II activity. Anthraquinones (AQ4 and AQ4H) were synthesized and studied along with 1,4-DAAQ by computational and experimental tools. The purpose of this study is to shade more light on mechanism of interaction between anthraquinone DNA affinic agents and different types of DNA. This study will lead to gain of information useful for drug design and development. Molecular structures were optimized using DFT B3LYP/6-31 + G(d). Depending on intramolecular hydrogen bonding interactions two conformers of AQ4 were detected and computed as 25.667 kcal/mol apart. Molecular reactivity of the anthraquinone compounds was explored using global and condensed descriptors (electrophilicity and Fukui functions). Molecular docking studies for the inhibition of CDK2 and DNA binding were carried out to explore the anti cancer potency of these drugs. NMR and UV-VIS electronic absorption spectra of anthraquinones/DNA were investigated at the physiological pH. The interaction of the three anthraquinones (AQ4, AQ4H and 1,4-DAAQ) were studied with three DNA (calf thymus DNA, (Poly[dA].Poly[dT]) and (Poly[dG].Poly[dC]). NMR study shows a qualitative pattern of drug/DNA interaction in terms of band shift and broadening. UV-VIS electronic absorption spectra were employed to measure the affinity constants of drug/DNA binding using Scatchard analysis.

  6. Experimental design of membrane sensor for selective determination of phenazopyridine hydrochloride based on computational calculations

    Energy Technology Data Exchange (ETDEWEB)

    Attia, Khalid A.M.; El-Abasawi, Nasr M.; Abdel-Azim, Ahmed H., E-mail:


    Computational study has been done electronically and geometrically to select the most suitable ionophore to design a novel sensitive and selective electrochemical sensor for phenazopyridine hydrochloride (PAP). This study has revealed that sodium tetraphenylbarate (NaTPB) fits better with PAP than potassium tetrakis (KTClPB). The sensor design is based on the ion pair of PAP with NaTPB using dioctyl phthalate as a plasticizer. Under optimum conditions, the proposed sensor shows the slope of 59.5 mV per concentration decade in the concentration range of 1.0 × 10{sup −2}–1.0 × 10{sup −5} M with detection limit 8.5 × 10{sup −6} M. The sensor exhibits a very good selectivity for PAP with respect to a large number of interfering species as inorganic cations and sugars. The sensor enables track of determining PAP in the presence of its oxidative degradation product 2, 3, 6-Triaminopyridine, which is also its toxic metabolite. The proposed sensor has been successfully applied for the selective determination of PAP in pharmaceutical formulation. Also, the obtained results have been statistically compared to a reported electrochemical method indicating no significant difference between the investigated method and the reported one with respect to accuracy and precision. - Highlights: • Novel use of ISE for selective determination of phenazopyridine hydrochloride. • Investigating the degradation pathway of phenazopyridine with enough confirmation scan. • To avoid time-consuming and experimental trials, computational studies have been applied. • The proposed sensor shows high selectivity, reasonable detection limit and fast response.

  7. Experimental design of membrane sensor for selective determination of phenazopyridine hydrochloride based on computational calculations

    International Nuclear Information System (INIS)

    Attia, Khalid A.M.; El-Abasawi, Nasr M.; Abdel-Azim, Ahmed H.


    Computational study has been done electronically and geometrically to select the most suitable ionophore to design a novel sensitive and selective electrochemical sensor for phenazopyridine hydrochloride (PAP). This study has revealed that sodium tetraphenylbarate (NaTPB) fits better with PAP than potassium tetrakis (KTClPB). The sensor design is based on the ion pair of PAP with NaTPB using dioctyl phthalate as a plasticizer. Under optimum conditions, the proposed sensor shows the slope of 59.5 mV per concentration decade in the concentration range of 1.0 × 10 −2 –1.0 × 10 −5 M with detection limit 8.5 × 10 −6 M. The sensor exhibits a very good selectivity for PAP with respect to a large number of interfering species as inorganic cations and sugars. The sensor enables track of determining PAP in the presence of its oxidative degradation product 2, 3, 6-Triaminopyridine, which is also its toxic metabolite. The proposed sensor has been successfully applied for the selective determination of PAP in pharmaceutical formulation. Also, the obtained results have been statistically compared to a reported electrochemical method indicating no significant difference between the investigated method and the reported one with respect to accuracy and precision. - Highlights: • Novel use of ISE for selective determination of phenazopyridine hydrochloride. • Investigating the degradation pathway of phenazopyridine with enough confirmation scan. • To avoid time-consuming and experimental trials, computational studies have been applied. • The proposed sensor shows high selectivity, reasonable detection limit and fast response.

  8. Evaluation of medical countermeasures against organophosphorus compounds: the value of experimental data and computer simulations. (United States)

    Worek, Franz; Aurbek, Nadine; Herkert, Nadja M; John, Harald; Eddleston, Michael; Eyer, Peter; Thiermann, Horst


    Despite extensive research for more than six decades on medical countermeasures against poisoning by organophosphorus compounds (OP) the treatment options are meagre. The presently established acetylcholinesterase (AChE) reactivators (oximes), e.g. obidoxime and pralidoxime, are insufficient against a number of nerve agents and there is ongoing debate on the benefit of oxime treatment in human OP pesticide poisoning. Up to now, the therapeutic efficacy of oximes was mostly evaluated in animal models but substantial species differences prevent direct extrapolation of animal data to humans. Hence, it was considered essential to establish relevant experimental in vitro models for the investigation of oximes as antidotes and to develop computer models for the simulation of oxime efficacy in different scenarios of OP poisoning. Kinetic studies on the various interactions between erythrocyte AChE from various species, structurally different OP and different oximes provided a basis for the initial assessment of the ability of oximes to reactivate inhibited AChE. In the present study, in vitro enzyme-kinetic and pharmacokinetic data from a minipig model of dimethoate poisoning and oxime treatment were used to calculate dynamic changes of AChE activities. It could be shown that there is a close agreement between calculated and in vivo AChE activities. Moreover, computer simulations provided insight into the potential and limitations of oxime treatment. In the end, such data may be a versatile tool for the ongoing discussion of the pros and cons of oxime treatment in human OP pesticide poisoning. Copyright (c) 2009 Elsevier Ireland Ltd. All rights reserved.

  9. Evaporation of freely suspended single droplets: experimental, theoretical and computational simulations

    International Nuclear Information System (INIS)

    Hołyst, R; Litniewski, M; Jakubczyk, D; Kolwas, K; Kolwas, M; Kowalski, K; Migacz, S; Palesa, S; Zientara, M


    Evaporation is ubiquitous in nature. This process influences the climate, the formation of clouds, transpiration in plants, the survival of arctic organisms, the efficiency of car engines, the structure of dried materials and many other phenomena. Recent experiments discovered two novel mechanisms accompanying evaporation: temperature discontinuity at the liquid–vapour interface during evaporation and equilibration of pressures in the whole system during evaporation. None of these effects has been predicted previously by existing theories despite the fact that after 130 years of investigation the theory of evaporation was believed to be mature. These two effects call for reanalysis of existing experimental data and such is the goal of this review. In this article we analyse the experimental and the computational simulation data on the droplet evaporation of several different systems: water into its own vapour, water into the air, diethylene glycol into nitrogen and argon into its own vapour. We show that the temperature discontinuity at the liquid–vapour interface discovered by Fang and Ward (1999 Phys. Rev. E 59 417–28) is a rule rather than an exception. We show in computer simulations for a single-component system (argon) that this discontinuity is due to the constraint of momentum/pressure equilibrium during evaporation. For high vapour pressure the temperature is continuous across the liquid–vapour interface, while for small vapour pressures the temperature is discontinuous. The temperature jump at the interface is inversely proportional to the vapour density close to the interface. We have also found that all analysed data are described by the following equation: da/dt = P 1 /(a + P 2 ), where a is the radius of the evaporating droplet, t is time and P 1 and P 2 are two parameters. P 1 = −λΔT/(q eff ρ L ), where λ is the thermal conductivity coefficient in the vapour at the interface, ΔT is the temperature difference between the liquid droplet

  10. Ion beam nanopatterning of III-V semiconductors: consistency of experimental and simulation trends within a chemistry-driven theory. (United States)

    El-Atwani, O; Norris, S A; Ludwig, K; Gonderman, S; Allain, J P


    Several proposed mechanisms and theoretical models exist concerning nanostructure evolution on III-V semiconductors (particularly GaSb) via ion beam irradiation. However, making quantitative contact between experiment on the one hand and model-parameter dependent predictions from different theories on the other is usually difficult. In this study, we take a different approach and provide an experimental investigation with a range of targets (GaSb, GaAs, GaP) and ion species (Ne, Ar, Kr, Xe) to determine new parametric trends regarding nanostructure evolution. Concurrently, atomistic simulations using binary collision approximation over the same ion/target combinations were performed to determine parametric trends on several quantities related to existing model. A comparison of experimental and numerical trends reveals that the two are broadly consistent under the assumption that instabilities are driven by chemical instability based on phase separation. Furthermore, the atomistic simulations and a survey of material thermodynamic properties suggest that a plausible microscopic mechanism for this process is an ion-enhanced mobility associated with energy deposition by collision cascades.

  11. Analog series-based scaffolds: computational design and exploration of a new type of molecular scaffolds for medicinal chemistry (United States)

    Dimova, Dilyana; Stumpfe, Dagmar; Hu, Ye; Bajorath, Jürgen


    Aim: Computational design of and systematic search for a new type of molecular scaffolds termed analog series-based scaffolds. Materials & methods: From currently available bioactive compounds, analog series were systematically extracted, key compounds identified and new scaffolds isolated from them. Results: Using our computational approach, more than 12,000 scaffolds were extracted from bioactive compounds. Conclusion: A new scaffold definition is introduced and a computational methodology developed to systematically identify such scaffolds, yielding a large freely available scaffold knowledge base. PMID:28116132

  12. Experimental and computational investigation of the tip clearance flow in a transonic axial compressor rotor

    Energy Technology Data Exchange (ETDEWEB)

    Suder, K.L. [NASA-Lewis Research Center, Cleveland, OH (United States); Celestina, M.L. [Sverdrup Technology Inc., Cleveland, OH (United States). Lewis Research Center Group


    Experimental and computational techniques are used to investigate tip clearance flows in a transonic axial compressor rotor at design and part-speed conditions. Laser anemometer data acquired in the endwall region are presented for operating conditions near peak efficiency and near stall at 100 percent design speed and at near peak efficiency at 60 percent design speed. The role of the passage shock/leakage vortex interaction at design speed, the radial influence of the tip clearance flow extends to 20 times the physical tip clearance height. At part speed, in the absence of the shock, the radial extent is only five times the tip clearance height. Both measurements and analysis indicate that under part-speed operating conditions a second vortex, which does not originate from the tip leakage flow, forms in the end-wall region within the blade passage and exits the passage near midpitch. Mixing of the leakage vortex with the primary flow downstream of the rotor at both design and part-speed conditions is also discussed.

  13. Experimental and Computational Investigation of the Tip Clearance Flow in a Transonic Axial Compressor Rotor (United States)

    Suder, Kenneth L.; Celestina, Mark L.


    Experimental and computational techniques are used to investigate tip clearance flows in a transonic axial compressor rotor at design and part speed conditions. Laser anemometer data acquired in the endwall region are presented for operating conditions near peak efficiency and near stall at 100% design speed and at near peak efficiency at 60% design speed. The role of the passage shock/leakage vortex interaction in generating endwall blockage is discussed. As a result of the shock/vortex interaction at design speed, the radial influence of the tip clearance flow extends to 20 times the physical tip clearance height. At part speed, in the absence of the shock, the radial extent is only 5 times the tip clearance height. Both measurements and analysis indicate that under part-speed operating conditions a second vortex, which does not originate from the tip leakage flow, forms in the endwall region within the blade passage and exits the passage near midpitch. Mixing of the leakage vortex with primary flow downstream of the rotor at both design and part speed conditions is also discussed.

  14. An experimental platform for triaxial high-pressure/high-temperature testing of rocks using computed tomography (United States)

    Glatz, Guenther; Lapene, Alexandre; Castanier, Louis M.; Kovscek, Anthony R.


    A conventional high-pressure/high-temperature experimental apparatus for combined geomechanical and flow-through testing of rocks is not X-ray compatible. Additionally, current X-ray transparent systems for computed tomography (CT) of cm-sized samples are limited to design temperatures below 180 °C. We describe a novel, high-temperature (>400 °C), high-pressure (>2000 psi/>13.8 MPa confining, >10 000 psi/>68.9 MPa vertical load) triaxial core holder suitable for X-ray CT scanning. The new triaxial system permits time-lapse imaging to capture the role of effective stress on fluid distribution and porous medium mechanics. System capabilities are demonstrated using ultimate compressive strength (UCS) tests of Castlegate sandstone. In this case, flooding the porous medium with a radio-opaque gas such as krypton before and after the UCS test improves the discrimination of rock features such as fractures. The results of high-temperature tests are also presented. A Uintah Basin sample of immature oil shale is heated from room temperature to 459 °C under uniaxial compression. The sample contains kerogen that pyrolyzes as temperature rises, releasing hydrocarbons. Imaging reveals the formation of stress bands as well as the evolution and connectivity of the fracture network within the sample as a function of time.

  15. Angiographic and artefact-free computed tomography imaging of experimental aneurysms embolised with hydrogel filaments

    Energy Technology Data Exchange (ETDEWEB)

    McCoy, Mark R. [Paracelsus Medical University, Department of Radiology and Magnetic Resonance Tomography, Christian Doppler Clinic, Salzburg (Austria); Cruise, Gregory M. [MicroVention Terumo, Aliso Viejo, CA (United States); Killer, Monika [Paracelsus Medical University, Department of Neurology/Neuroscience Institute, Christian Doppler Clinic, Salzburg (Austria)


    We compared experimental rabbit carotid bifurcation aneurysms embolised with platinum coils or hydrogel filaments by using digital subtraction angiography (DSA) and computed tomography angiography (CTA). Embolisation was performed using platinum coils (n = 2), hydrogel filaments loaded with iodine (n = 3) and hydrogel filaments loaded with barium sulphate (n = 3). In one case, a stent was deployed in the parent vessel to determine the effect of hydrogel filaments on stent visualisation. DSA evaluations occurred immediately post-treatment. CTA evaluations occurred at 0-13 weeks post-treatment. The DSA and CTA images were evaluated for the lack of artefacts and the visibilities of the embolic mass, individual coils and residual flow in the aneurysm sac and neck. The DSA results were largely concordant among the three groups. The embolic masses were readily evident with some individual coils being distinguished. In the aneurysms embolised with hydrogel filaments, visualisation of the individual coils, residual flow and stent with minor or no artefacts was possible using CTA. On the other hand, the beam hardening artefacts precluded analysis of aneurysms embolised with platinum coils. CTA-compatible embolic devices could have wide applications in diverse locations throughout the vasculature, particularly in combination with stents or stent grafts. (orig.)

  16. Gypsum plasterboards enhanced with phase change materials: A fire safety assessment using experimental and computational techniques

    Directory of Open Access Journals (Sweden)

    Kolaitis Dionysios I.


    Full Text Available Phase Change Materials (PCM can be used for thermal energy storage, aiming to enhance building energy efficiency. Recently, gypsum plasterboards with incorporated paraffin-based PCM blends have become commercially available. In the high temperature environment developed during a fire, the paraffins, which exhibit relatively low boiling points, may evaporate and, escaping through the gypsum plasterboard's porous structure, emerge to the fire region, where they may ignite, thus adversely affecting the fire resistance characteristics of the building. Aiming to assess the fire safety behaviour of such building materials, an extensive experimental and computational analysis is performed. The fire behaviour and the main thermo-physical physical properties of PCM-enhanced gypsum plasterboards are investigated, using a variety of standard tests and devices (Scanning Electron Microscopy, Thermo Gravimetric Analysis, Cone Calorimeter. The obtained results are used to develop a dedicated numerical model, which is implemented in a CFD code. CFD simulations are validated using measurements obtained in a cone calorimeter. In addition, the CFD code is used to simulate an ISO 9705 room exposed to fire conditions, demonstrating that PCM addition may indeed adversely affect the fire safety of a gypsum plasterboard clad building.

  17. 3-Phenylpyridinium hydrogen squarate: Experimental and computational study of a nonlinear optical material (United States)

    Korkmaz, Ufuk; Bulut, Ahmet; Bulut, İclal


    The detailed investigation of an organic nonlinear optical (NLO) squarate salt of 3-phenylpyridinium hydrogen squarate (1), C11H10N+·C4HO4-, was reported in this study. The XRD data indicates that the crystal structure of the title compound is in the triclinic P-1 space group. In the asymmetric unit, the 3-phenylpyridine molecule is protonated by one hydrogen atom donation of squaric acid molecule, forming the salt (1). The X-ray analysis shows that the crystal packing has hydrogen bonding ring pattern of D22 (10) (α-dimer) through Nsbnd H···O interactions. The structural and vibrational properties of the compound were also studied by computational methods of ab initio at DFT/B3LYP/6-31++G(d,p) (2) and HF/6-31++G(d,p) (3) levels of theory. The calculation results on the basis of two models for both the optimized molecular structure and vibrational properties for the 1 are presented and compared with the experimental results. Non-linear optical properties (NLO) of the title compound together with the molecular electrostatic potential (MEP), electronic absorption spectrum, frontier molecular orbitals (FMOs) and conformational flexibility were also studied at the 2 level and the results were reported. In order to evaluate the suitability for NLO applications thermal analysis (TG, DTA and DTG) data of 1 were also obtained.

  18. An experimental/computational approach for examining unconfined cohesive powder flow. (United States)

    Faqih, AbdulMobeen; Chaudhuri, Bodhisattwa; Alexander, Albert W; Davies, Clive; Muzzio, Fernando J; Silvina Tomassone, M


    This paper describes a new method to quantitatively measure the flow characteristics of unconfined cohesive powders in a rotating drum. Cohesion plays an important role, affecting flow properties/characteristics, mixing rates, and segregation tendencies. The method relies on measuring the change in center of mass of the powder bed as it avalanches in the vessel, using a load cell that is sampled continuously. Filtering and analysis of the signal is done using Fast-Fourier transform into the frequency domain, where noise is eliminated using signal processing methods. The filtered data is transformed back to the time domain by using an inverse Fast-Fourier transform to give quantitative information on the powder flow characteristics. In order to understand the nature of the forces controlling powder flow behavior, a computational model was developed to estimate the relationship between inter-particle cohesive strength and experimental measurements. A "flow index" generated by the method correlates well with the degree of bed expansion (dynamic dilation) of the cohesive powders. The flow index also predicts the dynamics of flow through hoppers. As the flow index increases it becomes increasingly difficult for the powder to flow through the hoppers.

  19. Molecular interactions in the betaine monohydrate-polyol deep eutectic solvents: Experimental and computational studies (United States)

    Zahrina, Ida; Mulia, Kamarza; Yanuar, Arry; Nasikin, Mohammad


    DES (deep eutectic solvents) are a new class of ionic liquids that have excellent properties. The strength of interaction between molecules in the DES affects their properties and applications. In this work, the strength of molecular interactions between components in the betaine monohydrate salt and polyol (glycerol or/and propylene glycol) eutectic mixtures was studied by experimental and computational studies. The melting point and fusion enthalpy of the mixtures were measured using STA (Simultaneous Thermal Analyzer). The nature and strength of intermolecular interactions were observed by FT-IR and NMR spectroscopy. The molecular dynamics simulation was used to determine the number of H-bonds, percent occupancy, and radial distribution functions in the eutectic mixtures. The interaction between betaine monohydrate and polyol is following order: betaine monohydrate-glycerol-propylene glycol > betaine monohydrate-glycerol > betaine monohydrate-propylene glycol, where the latter is the eutectic mixture with the lowest stability, strength and extent of the hydrogen bonding interactions between component molecules. The presence of intra-molecular hydrogen bonding interactions, the inter-molecular hydrogen bonding interactions between betaine molecule and polyol, and also interactions between polyol and H2O of betaine monohydrate in the eutectic mixtures.

  20. Mathematical Modeling, Computation, and Experimental Imaging of Thin-Layer Objects by Magnetic Resonance Imaging

    Directory of Open Access Journals (Sweden)

    Ivan Frollo


    Full Text Available Imaging of thin layers using magnetic resonance imaging (MRI methods belongs to the special procedures that serve for imaging of weak magnetic materials (weak ferromagnetic, diamagnetic, or paramagnetic. The objective of the paper is to present mathematical models appropriate for magnetic field calculations in the vicinity of thin organic or inorganic materials with defined magnetic susceptibility. Computation is similar to the double layer theory. Thin plane layers in their vicinity create a deformation of the neighboring magnetic field. Calculations with results in the form of analytic functions were derived for rectangular, circular, and general shaped samples. For experimental verification, an MRI 0.2 Tesla esaote Opera imager was used. For experiments, a homogeneous parallelepiped block (reference medium—a container filled with doped water—was used. The resultant images correspond to the magnetic field variations in the vicinity of the samples. For data detection, classical gradient-echo (GRE imaging methods, susceptible to magnetic field inhomogeneities, were used. Experiments proved that the proposed method was effective for thin organic and soft magnetic materials testing using magnetic resonance imaging methods.

  1. Experimental and computational analysis of Doppler cooling and the magneto-optic trap. (United States)

    Cowan, J. A., Jr.; Cline, R. A.


    Cold, dense clouds of cesium atoms have been produced in an undergraduate research lab using Doppler cooling and a vapor cell magneto-optic trap (MOT). Measurements of temperature, density, and filling of a MOT will be reported. In conjunction with this experiment, Windows-based software has been developed to simulate laser cooling and trapping. The program graphically depicts the position and velocity of a variable number of atoms in two dimensions as they are cooled and trapped. The algorithm accounts for absorption, spontaneous and stimulated emission, Doppler and Zeeman shifts, and radiation trapping. The user can adjust time step, atom velocity, laser intensity and detuning, and magnetic field gradient. The program can demonstrate optical molasses, a MOT, and a dark MOT. Simulations can be recorded and played back in the same graphical environment, along with movies from the actual experiment. The simulation is a useful educational tool for explaining and investigating Doppler cooling and the magneto-optic trap. The program allows anyone to obtain computational results and compare them with published experimental results. A beta version of Cool Simulation is downloadable off the World Wide Web.

  2. Experimental, Theoretical and Computational Studies of Plasma-Based Concepts for Future High Energy Accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Chan [Univ. of California, Los Angeles, CA (United States); Mori, W. [Univ. of California, Los Angeles, CA (United States)


    This is the final report on the DOE grant number DE-FG02-92ER40727 titled, “Experimental, Theoretical and Computational Studies of Plasma-Based Concepts for Future High Energy Accelerators.” During this grant period the UCLA program on Advanced Plasma Based Accelerators, headed by Professor C. Joshi has made many key scientific advances and trained a generation of students, many of whom have stayed in this research field and even started research programs of their own. In this final report however, we will focus on the last three years of the grant and report on the scientific progress made in each of the four tasks listed under this grant. Four tasks are focused on: Plasma Wakefield Accelerator Research at FACET, SLAC National Accelerator Laboratory, In House Research at UCLA’s Neptune and 20 TW Laser Laboratories, Laser-Wakefield Acceleration (LWFA) in Self Guided Regime: Experiments at the Callisto Laser at LLNL, and Theory and Simulations. Major scientific results have been obtained in each of the four tasks described in this report. These have led to publications in the prestigious scientific journals, graduation and continued training of high quality Ph.D. level students and have kept the U.S. at the forefront of plasma-based accelerators research field.

  3. Computational tools for experimental determination and theoretical prediction of protein structure

    Energy Technology Data Exchange (ETDEWEB)

    O`Donoghue, S.; Rost, B.


    This tutorial was one of eight tutorials selected to be presented at the Third International Conference on Intelligent Systems for Molecular Biology which was held in the United Kingdom from July 16 to 19, 1995. The authors intend to review the state of the art in the experimental determination of protein 3D structure (focus on nuclear magnetic resonance), and in the theoretical prediction of protein function and of protein structure in 1D, 2D and 3D from sequence. All the atomic resolution structures determined so far have been derived from either X-ray crystallography (the majority so far) or Nuclear Magnetic Resonance (NMR) Spectroscopy (becoming increasingly more important). The authors briefly describe the physical methods behind both of these techniques; the major computational methods involved will be covered in some detail. They highlight parallels and differences between the methods, and also the current limitations. Special emphasis will be given to techniques which have application to ab initio structure prediction. Large scale sequencing techniques increase the gap between the number of known proteins sequences and that of known protein structures. They describe the scope and principles of methods that contribute successfully to closing that gap. Emphasis will be given on the specification of adequate testing procedures to validate such methods.

  4. Synthesis and characterization of sulfolane-based amino alcohols: A combined experimental and computational study (United States)

    Palchykov, Vitalii A.; Zarovnaya, Iryna S.; Tretiakov, Serhii V.; Reshetnyak, Alyona V.; Omelchenko, Iryna V.; Shishkin, Oleg V.; Okovytyy, Sergiy I.


    Aminolysis of 3,4-epoxysulfolane in aqueous media leads to a very complex mixture of products with unresolved stereochemistry. Herein, we report a detailed theoretical and experimental mechanistic investigation of this reaction along with extensive spectroscopic characterization of the resulting amino alcohols, using 1D and 2D NMR techniques (1H, 13C, NOE, NOESY, COSY, HSQC, HMBC) as well as XRD analysis. In addition to simple amines such as ammonia and benzylamine, our study also employed the more sterically hindered endo-bicyclo[2.2.1]hept-5-en-2-ylmethanamine. The mechanism of the aminolysis of 3,4-epoxysulfolane by aqueous ammonia was studied in more detail using quantum chemical calculations at the M06-2X/6-31++G** level of theory. The computational results led us to conclude that the most probable way of initial epoxide transformation is base-catalyzed rearrangement to a corresponding allylic alcohol. Subsequent formation of vicinal amino alcohols and diols proceeds via addition of ammonia or hydroxy-anions to activated double Cdbnd C bond with some preference of a cis-attack. Detailed analytical data obtained in the course of our work will be useful for the stereochemical identification of new sulfolane derivatives.

  5. Computer-mediated communication and interpersonal attraction: an experimental test of two explanatory hypotheses. (United States)

    Antheunis, Marjolijn L; Valkenburg, Patti M; Peter, Jochen


    The aims of this study were (a) to investigate the influence of computer-mediated communication (CMC) on interpersonal attraction and (b) to examine two underlying processes in the CMC-interpersonal attraction relationship. We identified two variables that may mediate the influence of CMC on interpersonal attraction: self-disclosure and direct questioning. Focusing on these potential mediating variables, we tested two explanatory hypotheses: the CMC-induced direct questioning hypothesis and the CMC-induced self-disclosure hypothesis. Eighty-one cross-sex dyads were randomly assigned to one of three experimental conditions: text-only CMC, visual CMC, and face-to-face communication. We did not find a direct effect of CMC on interpersonal attraction. However, we did find two positive indirect effects of text-only CMC on interpersonal attraction: text-only CMC stimulated both self-disclosure and direct questioning, both of which in turn enhanced interpersonal attraction. Results are discussed in light of uncertainty reduction theory and CMC theories.

  6. Thermal Hydraulic Computational Fluid Dynamics Simulations and Experimental Investigation of Deformed Fuel Assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Mays, Brian [AREVA Federal Services, Lynchburg, VA (United States); Jackson, R. Brian [TerraPower, Bellevue, WA (United States)


    The project, Toward a Longer Life Core: Thermal Hydraulic CFD Simulations and Experimental Investigation of Deformed Fuel Assemblies, DOE Project code DE-NE0008321, was a verification and validation project for flow and heat transfer through wire wrapped simulated liquid metal fuel assemblies that included both experiments and computational fluid dynamics simulations of those experiments. This project was a two year collaboration between AREVA, TerraPower, Argonne National Laboratory and Texas A&M University. Experiments were performed by AREVA and Texas A&M University. Numerical simulations of these experiments were performed by TerraPower and Argonne National Lab. Project management was performed by AREVA Federal Services. The first of a kind project resulted in the production of both local point temperature measurements and local flow mixing experiment data paired with numerical simulation benchmarking of the experiments. The project experiments included the largest wire-wrapped pin assembly Mass Index of Refraction (MIR) experiment in the world, the first known wire-wrapped assembly experiment with deformed duct geometries and the largest numerical simulations ever produced for wire-wrapped bundles.


    Directory of Open Access Journals (Sweden)

    S.C. Yim


    Full Text Available A diverse series of research projects have taken place or are underway at the NEES Tsunami Research Facility at Oregon State University. Projects range from the simulation of the processes and effects of tsunamis generated by sub-aerial and submarine landslides (NEESR, Georgia Tech., model comparisons of tsunami wave effects on bottom profiles and scouring (NEESR, Princeton University, model comparisons of wave induced motions on rigid and free bodies (Shared-Use, Cornell, numerical model simulations and testing of breaking waves and inundation over topography (NEESR, TAMU, structural testing and development of standards for tsunami engineering and design (NEESR, University of Hawaii, and wave loads on coastal bridge structures (non-NEES, to upgrading the two-dimensional wave generator of the Large Wave Flume. A NEESR payload project (Colorado State University was undertaken that seeks to improve the understanding of the stresses from wave loading and run-up on residential structures. Advanced computational tools for coupling fluid-structure interaction including turbulence, contact and impact are being developed to assist with the design of experiments and complement parametric studies. These projects will contribute towards understanding the physical processes that occur during earthquake generated tsunamis including structural stress, debris flow and scour, inundation and overland flow, and landslide generated tsunamis. Analytical and numerical model development and comparisons with the experimental results give engineers additional predictive tools to assist in the development of robust structures as well as identification of hazard zones and formulation of hazard plans.

  8. Experimental and Computational Studies on Non-Covalent Imprinted Microspheres as Recognition System for Nicotinamide Molecules

    Directory of Open Access Journals (Sweden)

    Giuseppe Vasapollo


    Full Text Available Molecularly imprinted microspheres obtained by precipitation polymerization using nicotinamide (nia as template have been prepared and characterised by SEM. How various experimental parameters can affect microsphere morphology, reaction yield and re-binding capacity have been evaluated. Pre-polymerization interactions between template and functional monomer in chloroform and MeCN have been studied by 1H-NMR. The results suggest that the interaction between nia and methacrylic acid (MAA is mainly based on hydrogen-bonding between amide protons and MAA. Computational density functional theory (DFT studies on MAA-nia complexes have been also performed to better understand hydrogen-bonding interactions. The imprinted activity of the microspheres, synthesized in chloroform or acetonitrile (MeCN, has been evaluated by spectrophotometric analysis of nia solutions when chloroform or MeCN are used as incubation solvents. The results suggest that MeCN interferes with hydrogen bonding between template and MAA during either the polymerization step or re-binding process as also observed from theoretical results. Finally, the selectivity towards selected nia analogues has been also confirmed.

  9. Strength and Reliability of Wood for the Components of Low-cost Wind Turbines: Computational and Experimental Analysis and Applications

    DEFF Research Database (Denmark)

    Mishnaevsky, Leon; Freere, Peter; Sharma, Ranjan


    This paper reports the latest results of the comprehensive program of experimental and computational analysis of strength and reliability of wooden parts of low cost wind turbines. The possibilities of prediction of strength and reliability of different types of wood are studied in the series...... of experiments and computational investigations. Low cost testing machines have been designed, and employed for the systematic analysis of different sorts of Nepali wood, to be used for the wind turbine construction. At the same time, computational micromechanical models of deformation and strength of wood...

  10. Computational and Experimental Evaluations of a Novel Thermo-Brachytherapy Seed for Treatment of Solid Tumors (United States)

    Warrell, Gregory R.

    Hyperthermia has long been known as a radiation therapy sensitizer of high potential; however successful delivery of this modality and integrating it with radiation have often proved technically difficult. We present the dual-modality thermobrachytherapy (TB) seed, based on the ubiquitous low dose-rate (LDR) brachytherapy permanent implant, as a simple and effective combination of hyperthermia and radiation therapy. Heat is generated from a ferromagnetic or ferrimagnetic core within the seed, which produces Joule heating by eddy currents. A strategically-selected Curie temperature provides thermal self-regulation. In order to obtain a uniform and sufficiently high temperature distribution, additional hyperthermia-only (HT-only) seeds are proposed to be used in vacant spots within the needles used to implant the TB seeds; this permits a high seed density without the use of additional needles. Experimental and computational studies were done both to optimize the design of the TB and HT-only seeds and to quantitatively assess their ability to heat and irradiate defined, patient-specific targets. Experiments were performed with seed-sized ferromagnetic samples in tissue-mimicking phantoms heated by an industrial induction heater. The magnetic and thermal properties of the seeds were studied computationally in the finite element analysis (FEA) solver COMSOL Multiphysics, modelling realistic patient-specific seed distributions. These distributions were derived from LDR permanent prostate implants previously conducted at our institution; various modifications of the seeds' design were studied. The calculated temperature distributions were analyzed by generating temperature-volume histograms, which were used to quantify coverage and temperature homogeneity for a range of blood perfusion rates, as well as for a range of seed Curie temperatures and thermal power production rates. The impact of the interseed attenuation and scatter (ISA) effect on radiation dose distributions

  11. Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen: Systematic Computational and Experimental Study. Phase I (United States)

    Thibeault, Sheila A.; Fay, Catharine C.; Lowther, Sharon E.; Earle, Kevin D.; Sauti, Godfrey; Kang, Jin Ho; Park, Cheol; McMullen, Amelia M.


    The key objectives of this study are to investigate, both computationally and experimentally, which forms, compositions, and layerings of hydrogen, boron, and nitrogen containing materials will offer the greatest shielding in the most structurally robust combination against galactic cosmic radiation (GCR), secondary neutrons, and solar energetic particles (SEP). The objectives and expected significance of this research are to develop a space radiation shielding materials system that has high efficacy for shielding radiation and that also has high strength for load bearing primary structures. Such a materials system does not yet exist. The boron nitride nanotube (BNNT) can theoretically be processed into structural BNNT and used for load bearing structures. Furthermore, the BNNT can be incorporated into high hydrogen polymers and the combination used as matrix reinforcement for structural composites. BNNT's molecular structure is attractive for hydrogen storage and hydrogenation. There are two methods or techniques for introducing hydrogen into BNNT: (1) hydrogen storage in BNNT, and (2) hydrogenation of BNNT (hydrogenated BNNT). In the hydrogen storage method, nanotubes are favored to store hydrogen over particles and sheets because they have much larger surface areas and higher hydrogen binding energy. The carbon nanotube (CNT) and BNNT have been studied as potentially outstanding hydrogen storage materials since 1997. Our study of hydrogen storage in BNNT - as a function of temperature, pressure, and hydrogen gas concentration - will be performed with a hydrogen storage chamber equipped with a hydrogen generator. The second method of introducing hydrogen into BNNT is hydrogenation of BNNT, where hydrogen is covalently bonded onto boron, nitrogen, or both. Hydrogenation of BN and BNNT has been studied theoretically. Hyper-hydrogenated BNNT has been theoretically predicted with hydrogen coverage up to 100% of the individual atoms. This is a higher hydrogen content

  12. Containment Sodium Chemistry Models in MELCOR.

    Energy Technology Data Exchange (ETDEWEB)

    Louie, David [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Humphries, Larry L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Denman, Matthew R [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)


    To meet regulatory needs for sodium fast reactors’ future development, including licensing requirements, Sandia National Laboratories is modernizing MELCOR, a severe accident analysis computer code developed for the U.S. Nuclear Regulatory Commission (NRC). Specifically, Sandia is modernizing MELCOR to include the capability to model sodium reactors. However, Sandia’s modernization effort primarily focuses on the containment response aspects of the sodium reactor accidents. Sandia began modernizing MELCOR in 2013 to allow a sodium coolant, rather than water, for conventional light water reactors. In the past three years, Sandia has been implementing the sodium chemistry containment models in CONTAIN-LMR, a legacy NRC code, into MELCOR. These chemistry models include spray fire, pool fire and atmosphere chemistry models. Only the first two chemistry models have been implemented though it is intended to implement all these models into MELCOR. A new package called “NAC” has been created to manage the sodium chemistry model more efficiently. In 2017 Sandia began validating the implemented models in MELCOR by simulating available experiments. The CONTAIN-LMR sodium models include sodium atmosphere chemistry and sodium-concrete interaction models. This paper presents sodium property models, the implemented models, implementation issues, and a path towards validation against existing experimental data.

  13. Experimental acute rumen acidosis in sheep: consequences on clinical, rumen, and gastrointestinal permeability conditions and blood chemistry. (United States)

    Minuti, A; Ahmed, S; Trevisi, E; Piccioli-Cappelli, F; Bertoni, G; Jahan, N; Bani, P


    Acute acidosis was induced in sheep, and gastrointestinal permeability was assessed by using lactulose as a permeability marker. Metabolism was evaluated by monitoring blood metabolites. Four rams (72.5 ± 4.6 kg BW) were used in a 2 × 2 changeover design experiment. The experimental period lasted 96 h from -24 to 72 h. After 24 h of fasting (from -24 to 0 h) for both controls and acidosis-induced rams (ACID), 0.5 kg of wheat flour was orally dosed at 0 and 12 h of the experimental period to ACID, while the basal diet (grass hay, ad libitum) was restored to control. At 24 h, a lactulose solution (30 g of lactulose in 200 mL of water) was orally administered. Blood samples were collected at -24, 0, 24, 48, and 72 h of the experimental periods for the analysis of metabolic profiles and during the 10 h after lactulose dosage to monitor lactulose changes in blood. In addition, rumen and fecal samples were collected at 24 h of the experimental period. The acidotic challenge markedly reduced (P < 0.01) rumen pH and VFA but increased rumen d- and l-lactic acid (P < 0.01). Concurrently, a decrease of fecal pH and VFA occurred in ACID (P < 0.01), together with an abrupt increase (P < 0.01) of lactate and fecal alkaline phosphatase. Blood lactulose was significantly increased in ACID peaking 2 h after lactulose dosage. Blood glucose, β-hydroxybutyrate, Ca, K, Mg, and alkaline phosphatase showed a significant reduction (P < 0.05) at 24 h, whereas urea and NEFA declined (P < 0.05) from 48 to 72 h. A strong inflammatory acute phase response with oxidative stress in ACID group was observed from 24 to 72 h; higher values of haptoglobin (P < 0.01) were measured from 24 to 72 h and of ceruloplasmin from 48 (P < 0.05) to 72 h (P < 0.01). Among the negative acute phase reactants, plasma albumin, cholesterol, paraoxonase, and Zn concentration also decreased (P < 0.05) in ACID at different time points between 24 and 72 h after acidotic challenge start. A rise (P < 0.05) of reactive

  14. Immuno-chemistry of hydroxyl radical modified GAD-65: A possible role in experimental and human diabetes mellitus. (United States)

    Moinuddin; Ansari, Nadeem A; Shahab, Uzma; Habeeb, Safia; Ahmad, Saheem


    The repertoire of known auto-antigens is limited to a very small proportion of all human proteins, and the reason why only some proteins become auto-antigens is unclear. The 65 kDa isoform of the enzyme glutamic acid decarboxylase (GAD-65) is a major auto-antigen in type I diabetes, and in various neurological diseases. Most patients with type I diabetes (70-80%) have auto-antibodies against GAD-65, which often appear years before clinical onset of the autoimmune diabetes. Thus, the aim of the study is to focus on the immunogenicity of GAD65 and its reactive oxygen species (ROS) conformer in STZ-induced diabetic rats and on human diabetic patients. In the present study, GAD-65 was modified by hydroxyl radical following Fenton's reaction. The modifications in the structure of the GAD-65 are supported by UV-vis and fluorescence spectral studies. Immunogenicity of both native and hydroxyl radical modified GAD-65 (ROS-GAD-65) was studied in experimental rabbits and was confirmed by inducing type I diabetes in experimental male albino rats using streptozotocin (45 mg/kg). We found that ROS-GAD-65 was a better immunogen as compared to the native GAD-65. A considerable high binding to ROS-GAD-65 was observed as compared to native GAD-65 in both the serum antibodies from diabetes animal models and as well as in the serum samples of type I diabetes. Hydrogen peroxide under the exposure of UV light produces hydroxyl radical (·OH) which is most potent oxidant, and could cause protein damage (GAD-65) to the extent of generating neo-epitopes on the molecule, thus making it immunogenic. © 2015 International Union of Biochemistry and Molecular Biology.

  15. Cellular burning in lean premixed turbulent hydrogen-air flames: Coupling experimental and computational analysis at the laboratory scale (United States)

    Day, M. S.; Bell, J. B.; Cheng, R. K.; Tachibana, S.; Beckner, V. E.; Lijewski, M. J.


    One strategy for reducing US dependence on petroleum is to develop new combustion technologies for burning the fuel-lean mixtures of hydrogen or hydrogen-rich syngas fuels obtained from the gasification of coal and biomass. Fuel-flexible combustion systems based on lean premixed combustion have the potential for dramatically reducing pollutant emissions in transportation systems, heat and stationary power generation. However, lean premixed flames are highly susceptible to fluid-dynamical combustion instabilities making robust and reliable systems difficult to design. Low swirl burners are emerging as an important technology for meeting design requirements in terms of both reliability and emissions for next generation combustion devices. In this paper, we present simulations of a lean, premixed hydrogen flame stabilized on a laboratory-scale low swirl burner. The simulations use detailed chemistry and transport without incorporating explicit models for turbulence or turbulence/chemistry interaction. Here we discuss the overall structure of the flame and compare with experimental data. We also use the simulation data to elucidate the characteristics of the turbulent flame interaction and how this impacts the analysis of experimental measurements.

  16. Experimental determination and computational interpretation of biophysical properties of lipid bilayers enriched by cholesteryl hemisuccinate

    Czech Academy of Sciences Publication Activity Database

    Kulig, W.; Jurkiewicz, Piotr; Olžyńska, Agnieszka; Tynkkynen, J.; Javanainen, M.; Manna, M.; Rog, T.; Hof, Martin; Vattulainen, I.; Jungwirth, Pavel


    Roč. 1848, č. 2 (2015), s. 422-432 ISSN 0005-2736 R&D Projects: GA ČR GBP208/12/G016 Institutional support: RVO:61388955 ; RVO:61388963 Keywords : Time-dependent fluorescence shift * Molecular dynamics simulations * Cholesterol -mimicking detergents Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.687, year: 2015

  17. Stability of polycation-DNA complexes: comparison of computer model and experimental data

    Czech Academy of Sciences Publication Activity Database

    Dybal, Jiří; Huml, Karel; Kabeláč, Martin; Reschel, Tomáš; Ulbrich, Karel


    Roč. 11, č. 1 (2004), s. 3-6 ISSN 1211-5894 R&D Projects: GA AV ČR KSK4055109 Institutional research plan: CEZ:AV0Z4050913 Keywords : polycation-DNA complexes * gene delivery * quantum mechanical calculations Subject RIV: CC - Organic Chemistry

  18. Spectroscopic Properties of Anisole at the Air-Ice Interface: A Combined Experimental-Computational Approach

    Czech Academy of Sciences Publication Activity Database

    Malongwe, J. K.; Nachtigallová, Dana; Corrochano, P.; Klán, P.


    Roč. 32, č. 23 (2016), s. 5755-5764 ISSN 0743-7463 R&D Projects: GA ČR(CZ) GA15-12386S Institutional support: RVO:61388963 Keywords : polycyclic aromatic hydrocarbons * absorption spectra * aqueous solutions Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.833, year: 2016

  19. Computed and experimental chemical shift parameters for rigid and flexible YAF peptides in the solid state

    Czech Academy of Sciences Publication Activity Database

    Pawlak, T.; Trzeciak-Karlikowska, K.; Czernek, Jiří; Ciesielski, W.; Potrzebowski, M. J.


    Roč. 116, č. 6 (2012), s. 1974-1983 ISSN 1520-6106 R&D Projects: GA MŠk 2B08021 Institutional research plan: CEZ:AV0Z40500505 Keywords : NMR * CST * DFT Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.607, year: 2012

  20. Characterization of the Cu+ sites in MFI zeolites: combined computational and experimental study

    Czech Academy of Sciences Publication Activity Database

    Bludský, Ota; Nachtigall, Petr; Čičmanec, P.; Knotek, P.; Bulánek, R.


    Roč. 100, - (2005), 385-389 ISSN 0920-5861 R&D Projects: GA MŠk(CZ) LN00A032 Institutional research plan: CEZ:AV0Z40550506 Keywords : ZSM-5 zeolite * carbon-monoxide Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.365, year: 2005

  1. Advanced fuel chemistry for advanced engines.

    Energy Technology Data Exchange (ETDEWEB)

    Taatjes, Craig A.; Jusinski, Leonard E.; Zador, Judit; Fernandes, Ravi X.; Miller, James A.


    Autoignition chemistry is central to predictive modeling of many advanced engine designs that combine high efficiency and low inherent pollutant emissions. This chemistry, and especially its pressure dependence, is poorly known for fuels derived from heavy petroleum and for biofuels, both of which are becoming increasingly prominent in the nation's fuel stream. We have investigated the pressure dependence of key ignition reactions for a series of molecules representative of non-traditional and alternative fuels. These investigations combined experimental characterization of hydroxyl radical production in well-controlled photolytically initiated oxidation and a hybrid modeling strategy that linked detailed quantum chemistry and computational kinetics of critical reactions with rate-equation models of the global chemical system. Comprehensive mechanisms for autoignition generally ignore the pressure dependence of branching fractions in the important alkyl + O{sub 2} reaction systems; however we have demonstrated that pressure-dependent 'formally direct' pathways persist at in-cylinder pressures.

  2. Synthesis of radiolabelled aryl azides from diazonium salts: experimental and computational results permit the identification of the preferred mechanism. (United States)

    Joshi, Sameer M; de Cózar, Abel; Gómez-Vallejo, Vanessa; Koziorowski, Jacek; Llop, Jordi; Cossío, Fernando P


    Experimental and computational studies on the formation of aryl azides from the corresponding diazonium salts support a stepwise mechanism via acyclic zwitterionic intermediates. The low energy barriers associated with both transition structures are compatible with very fast and efficient processes, thus making this method suitable for the chemical synthesis of radiolabelled aryl azides.

  3. Experimental and computational analysis of micromotions of an uncemented femoral knee implant using elastic and plastic bone material models

    NARCIS (Netherlands)

    Berahmani, Sanaz; Janssen, Dennis; Verdonschot, Nico


    It is essential to calculate micromotions at the bone-implant interface of an uncemented femoral total knee replacement (TKR) using a reliable computational model. In the current study, experimental measurements of micromotions were compared with predicted micromotions by Finite Element Analysis

  4. Irrigant flow in the root canal: experimental validation of an unsteady computational fluid dynamics model using high-speed imaging

    NARCIS (Netherlands)

    Boutsioukis, C.; Verhaagen, B.; Versluis, M.; Kastrinakis, E.; van der Sluis, L.W.M.


    Aim  To compare the results of a Computational Fluid Dynamics (CFD) simulation of the irrigant flow within a prepared root canal, during final irrigation with a syringe and a needle, with experimental high-speed visualizations and theoretical calculations of an identical geometry and to evaluate the

  5. Irrigant flow in the root canal: experimental validation of an unsteady Computational Fluid Dynamics model using high-speed imaging

    NARCIS (Netherlands)

    Boutsioukis, C.; Boutsioukis, C.; Verhaagen, B.; Versluis, Michel; Kastrinakis, E.; van der Sluis, L.W.M.


    Aim  To compare the results of a Computational Fluid Dynamics (CFD) simulation of the irrigant flow within a prepared root canal, during final irrigation with a syringe and a needle, with experimental high-speed visualizations and theoretical calculations of an identical geometry and to evaluate the

  6. Complex chemistry

    International Nuclear Information System (INIS)

    Kim, Bong Gon; Kim, Jae Sang; Kim, Jin Eun; Lee, Boo Yeon


    This book introduces complex chemistry with ten chapters, which include development of complex chemistry on history coordination theory and Warner's coordination theory and new development of complex chemistry, nomenclature on complex with conception and define, chemical formula on coordination compound, symbol of stereochemistry, stereo structure and isomerism, electron structure and bond theory on complex, structure of complex like NMR and XAFS, balance and reaction on solution, an organo-metallic chemistry, biology inorganic chemistry, material chemistry of complex, design of complex and calculation chemistry.

  7. An experimental and theoretical vibrational study of interaction of adenine and thymine with artificial seawaters: A prebiotic chemistry experiment. (United States)

    Anizelli, Pedro R; Baú, João P T; Nabeshima, Henrique S; da Costa, Marcello F; de Santana, Henrique; Zaia, Dimas A M


    Nucleic acid bases play important roles in living beings. Thus, their interaction with salts the prebiotic Earth could be an important issue for the understanding of origin of life. In this study, the effect of pH and artificial seawaters on the structure of adenine and thymine was studied via parallel determinations using FT-IR, Raman spectroscopy and theoretical calculations. Thymine and adenine lyophilized in solutions at basic and acidic conditions showed characteristic bands of the enol-imino tautomer due to the deprotonation and the hydrochloride form due to protonation, respectively. The interaction of thymine and adenine with different seawaters representative of different geological periods on Earth was also studied. In the case of thymine a strong interaction with Sr(2+) promoted changes in the Raman and infrared spectra. For adenine changes in infrared and Raman spectra were observed in the presence of salts from all seawaters tested. The experimental results were compared to theoretical calculations, which showed structural changes due to the presence of ions Na(+), Mg(2+), Ca(2+) and Sr(2+) of artificial seawaters. For thymine the bands arising from C4=C5 and C6=O stretching were shifted to lower values, and for adenine, a new band at 1310cm(-1) was observed. The reactivity of adenine and thymine was studied by comparing changes in nucleophilicity and energy of the HOMO orbital. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Direct Observation of Cr3+ 3d States in Ruby: Toward Experimental Mechanistic Evidence of Metal Chemistry. (United States)

    Hunault, Myrtille O J Y; Harada, Yoshihisa; Miyawaki, Jun; Wang, Jian; Meijerink, Andries; de Groot, Frank M F; van Schooneveld, Matti M


    The role of transition metals in chemical reactions is often derived from probing the metal 3d states. However, the relation between metal site geometry and 3d electronic states, arising from multielectronic effects, makes the spectral data interpretation and modeling of these optical excited states a challenge. Here we show, using the well-known case of red ruby, that unique insights into the density of transition metal 3d excited states can be gained with 2p3d resonant inelastic X-ray scattering (RIXS). We compare the experimental determination of the 3d excited states of Cr 3+ impurities in Al 2 O 3 with 190 meV resolution 2p3d RIXS to optical absorption spectroscopy and to simulations. Using the crystal field multiplet theory, we calculate jointly for the first time the Cr 3+ multielectronic states, RIXS, and optical spectra based on a unique set of parameters. We demonstrate that (i) anisotropic 3d multielectronic interactions causes different scaling of Slater integrals, and (ii) a previously not observed doublet excited state exists around 3.35 eV. These results allow to discuss the influence of interferences in the RIXS intermediate state, of core-hole lifetime broadenings, and of selection rules on the RIXS intensities. Finally, our results demonstrate that using an intermediate excitation energy between L 3 and L 2 edges allows measurement of the density of 3d excited states as a fingerprint of the metal local structure. This opens up a new direction to pump-before-destroy investigations of transition metal complex structures and reaction mechanisms.

  9. Experimental and computational investigation of graphene/SAMs/n-Si Schottky diodes (United States)

    Aydin, H.; Bacaksiz, C.; Yagmurcukardes, N.; Karakaya, C.; Mermer, O.; Can, M.; Senger, R. T.; Sahin, H.; Selamet, Y.


    We have investigated the effect of two different self-assembled monolayers (SAMs) on electrical characteristics of bilayer graphene (BLG)/n-Si Schottky diodes. Novel 4″bis(diphenylamino)-1, 1‧:3″-terphenyl-5‧ carboxylic acids (TPA) and 4,4-di-9H-carbazol-9-yl-1,1‧:3‧1‧-terphenyl-5‧ carboxylic acid (CAR) aromatic SAMs have been used to modify n-Si surfaces. Cyclic voltammetry (CV) and Kelvin probe force microscopy (KPFM) results have been evaluated to verify the modification of n-Si surface. The current-voltage (I-V) characteristics of bare and SAMs modified devices show rectification behaviour verifying a Schottky junction at the interface. The ideality factors (n) from ln(I)-V dependences were determined as 2.13, 1.96 and 2.07 for BLG/n-Si, BLG/TPA/n-Si and BLG/CAR/n-Si Schottky diodes, respectively. In addition, Schottky barrier height (SBH) and series resistance (Rs) of SAMs modified diodes were decreased compared to bare diode due to the formation of a compatible interface between graphene and Si as well as π-π interaction between aromatic SAMs and graphene. The CAR-based device exhibits better diode characteristic compared to the TPA-based device. Computational simulations show that the BLG/CAR system exhibits smaller energy-level-differences than the BLG/TPA, which supports the experimental findings of a lower Schottky barrier and series resistance in BLG/CAR diode.

  10. 2-Pyridinium propanol hydrogen squarate: Experimental and computational study of a nonlinear optical material (United States)

    Korkmaz, Ufuk; Bulut, Ahmet


    The experimental and theoretical investigation of a novel organic nonlinear optical (NLO) squarate salt of 2-pyridinium propanol hydrogen squarate (1), C8H12ON+ ·C4HO4-, were reported in this study. The crystal structure of the title compound was found to crystallize in the triclinic P-1 space group. In the asymmetric unit each squaric acid molecules have donated one H atom to the pyridines N1 and N2 atoms of a 2-pyridine propanol molecule, forming the salt (1). The X-ray analysis clearly indicated that the crystal packing has shown the hydrogen bonding ring pattern of D22 (10) (α-dimer) through Nsbnd H⋯O interactions. The structural and vibrational properties of the compound were also studied by computational methods of ab initio performed on the compound at DFT/B3LYP/6-31++G(d,p) (2) and HF/6-31++G(d,p) (3) level of theory. The calculation results on the basis of two models for both the optimized molecular structure and vibrational properties for the 1 are presented and compared with the X-ray analysis result. The molecular electrostatic potential (MEP), electronic absorption spectra, frontier molecular orbitals (FMOs), conformational flexibility and non-linear optical properties (NLO) of the title compound were also studied at the 2 level and the results are reported. In order to evaluate the suitability for NLO applications thermal analysis (TG, DTA and DTG) data of 1 were also obtained.

  11. Experimental and computational studies of poly-L-lactic acid for cardiovascular applications: recent progress (United States)

    Naseem, Raasti; Zhao, Liguo; Liu, Yang; Silberschmidt, Vadim V.


    Stents are commonly used in medical procedures to alleviate the symptoms of coronary heart disease, a prevalent modern society disease. These structures are employed to maintain vessel patency and restore blood flow. Traditionally stents are made of metals such as stainless steel or cobalt chromium; however, these scaffolds have known disadvantages. An emergence of transient scaffolds is gaining popularity, with the structure engaged for a required period whilst healing of the diseased arterial wall occurs. Polymers dominate a medical device sector, with incorporation in sutures, scaffolds and screws. Thanks to their good mechanical and biological properties and their ability to degrade naturally. Polylactic acid is an extremely versatile polymer, with its properties easily tailored to applications. Its dominance in the stenting field increases continually, with the first polymer scaffold gaining FDA approval in 2016. Still some challenges with PLLA bioresorbable materials remain, especially with regard to understanding their mechanical response, assessment of its changes with degradation and comparison of their performance with that of metallic drug-eluting stent. Currently, there is still a lack of works on evaluating both the pre-degradation properties and degradation performance of these scaffolds. Additionally, there are no established material models incorporating non-linear viscoelastic behaviour of PLLA and its evolution with in-service degradation. Assessing these features through experimental analysis accompanied by analytical and numerical studies will provide powerful tools for design and optimisation of these structures endorsing their broader use in stenting. This overview assesses the recent studies investigating mechanical and computational performance of poly(l-lactic) acid and its use in stenting applications.

  12. Electronic nature of zwitterionic alkali metal methanides, silanides and germanides - a combined experimental and computational approach. (United States)

    Li, H; Aquino, A J A; Cordes, D B; Hase, W L; Krempner, C


    Zwitterionic group 14 complexes of the alkali metals of formula [C(SiMe 2 OCH 2 CH 2 OMe) 3 M], (M- 1 ), [Si(SiMe 2 OCH 2 CH 2 OMe) 3 M], (M- 2 ), [Ge(SiMe 2 OCH 2 CH 2 OMe) 3 M], (M- 3 ), where M = Li, Na or K, have been prepared, structurally characterized and their electronic nature was investigated by computational methods. Zwitterions M- 2 and M- 3 were synthesized via reactions of [Si(SiMe 2 OCH 2 CH 2 OMe) 4 ] ( 2 ) and [Ge(SiMe 2 OCH 2 CH 2 OMe) 4 ] ( 3 ) with MOBu t (M = Li, Na or K), resp., in almost quantitative yields, while M- 1 were prepared from deprotonation of [HC(SiMe 2 OCH 2 CH 2 OMe) 3 ] ( 1 ) with LiBu t , NaCH 2 Ph and KCH 2 Ph, resp. X-ray crystallographic studies and DFT calculations in the gas-phase, including calculations of the NPA charges confirm the zwitterionic nature of these compounds, with the alkali metal cations being rigidly locked and charge separated from the anion by the internal OCH 2 CH 2 OMe donor groups. Natural bond orbital (NBO) analysis and the second order perturbation theory analysis of the NBOs reveal significant hyperconjugative interactions in M- 1 -M- 3 , primarily between the lone pair and the antibonding Si-O orbitals, the extent of which decreases in the order M- 1 > M- 2 > M- 3 . The experimental basicities and the calculated gas-phase basicities of M- 1 -M- 3 reveal the zwitterionic alkali metal methanides M- 1 to be significantly stronger bases than the analogous silanides M- 2 and germanium M- 3 .

  13. Spectroscopic Properties of Naphthalene on the Surface of Ice Grains Revisited: A Combined Experimental Computational Approach

    Czech Academy of Sciences Publication Activity Database

    Krausko, J.; Malongwe, J. K.; Bičanová, G.; Klán, P.; Nachtigallová, Dana; Heger, D.


    Roč. 119, č. 32 (2015), s. 8565-8578 ISSN 1089-5639 R&D Projects: GA ČR(CZ) GA15-12386S Grant - others:GA MŠk(CZ) LO1214; GA MŠk(CZ) LM2011028 Institutional support: RVO:61388963 Keywords : polycyclic aromatic hydrocarbons * frozen aqueous solutions * molecular dynamics Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.883, year: 2015

  14. Química orgânica experimental: integração de teoria, experimento e análise Experimental organic Chemistry: integration of theory, experiment and analysis

    Directory of Open Access Journals (Sweden)

    Lothar W. Bieber


    Full Text Available A new approach for teaching in basic experimental organic chemistry is presented. Experimental work goes on parallel to theoretical lectures leading to an immediate application of theoretical concepts transmitted therein. One day/week is dedicated exclusively to the organic laboratory. Reactions are proposed as problems to be solved; the student has to deduce the structure of the product on the basis of his observations, the analytical data and his mechanistical knowledge. 70 different experiments, divided in 7 thematical chapters, are presented. All experiments require the analysis and discussion of 1H and 13C NMR, IR and UV spectra. Additional questions about each reaction have to be answered by the student in his written report. Laboratory safety is garanteed by the exclusion or substitution of hazardous and toxic reagents. Microscale preparations are adopted in most cases to lower the cost of materials and the amount of waste. Recycling of many reaction products as starting materials in other experiments reduces the need for commercial reagents and allows the execution of longer reaction sequences. Only unexpensive standard laboratory equipment and simple glassware are required. All experiments include instructions for the save treatment or disposal of chemical waste.

  15. Irrigant flow in the root canal: experimental validation of an unsteady Computational Fluid Dynamics model using high-speed imaging. (United States)

    Boutsioukis, C; Verhaagen, B; Versluis, M; Kastrinakis, E; van der Sluis, L W M


    To compare the results of a Computational Fluid Dynamics (CFD) simulation of the irrigant flow within a prepared root canal, during final irrigation with a syringe and a needle, with experimental high-speed visualizations and theoretical calculations of an identical geometry and to evaluate the effect of off-centre positioning of the needle inside the root canal. A CFD model was created to simulate irrigant flow from a side-vented needle inside a prepared root canal. Calculations were carried out for four different positions of the needle inside a prepared root canal. An identical root canal model was made from poly-dimethyl-siloxane (PDMS). High-speed imaging of the flow seeded with particles and Particle Image Velocimetry (PIV) were combined to obtain the velocity field inside the root canal experimentally. Computational, theoretical and experimental results were compared to assess the validity of the computational model. Comparison between CFD computations and experiments revealed good agreement in the velocity magnitude and vortex location and size. Small lateral displacements of the needle inside the canal had a limited effect on the flow field. High-speed imaging experiments together with PIV of the flow inside a simulated root canal showed a good agreement with the CFD model, even though the flow was unsteady. Therefore, the CFD model is able to predict reliably the flow in similar domains.

  16. Verification and validation of predictive computer programs describing the near and far-field chemistry of radioactive waste disposal systems

    International Nuclear Information System (INIS)

    Read, D.; Broyd, T.W.


    This paper provides an introduction to CHEMVAL, an international project concerned with establishing the applicability of chemical speciation and coupled transport models to the simulation of realistic waste disposal situations. The project aims to validate computer-based models quantitatively by comparison with laboratory and field experiments. Verification of the various computer programs employed by research organisations within the European Community is ensured through close inter-laboratory collaboration. The compilation and review of thermodynamic data forms an essential aspect of this work and has led to the production of an internally consistent standard CHEMVAL database. The sensitivity of results to variation in fundamental constants is being monitored at each stage of the project and, where feasible, complementary laboratory studies are used to improve the data set. Currently, thirteen organisations from five countries are participating in CHEMVAL which forms part of the Commission of European Communities' MIRAGE 2 programme of research. (orig.)

  17. Results of water chemistry control in the in-pile ''Callisto'' loop (an experimental PWR rig installed in the BR2 reactor)

    International Nuclear Information System (INIS)

    Weber, M.; Benoit, P.; Dekeyser, J.; Verwimp, A.


    Since June 1992, a new experimental facility, called CALLISTO, is being irradiated in the BR2 materials testing reactor at Mol, Belgium. The main objective of the present test campaign is to study the behaviour of advanced fuel to high burn-up rates in a realistic PWR environment. Three in-pile sections, containing each 9 fuel rods, are loaded inside the reactor vessel and are connected to a common out-of-pile pressurized water circulation loop (ref.1). The later is branched-off into a purification circuit (feed-bleed concept) and further equipped with safety and auxiliary systems. To cope with the test programme, the equipments are designed so that the guidelines of a PWR primary water chemistry can be followed (ref.2). Real steady-state conditions cannot be observed because the typical BR2 cycle (3 weeks running/3 weeks shut-down) is much shorter and because the rig is cooled down during each reactor shut-down. The purpose of this poster is to provide results of chemical parameters recorded during the cycling behaviour of the CALLISTO primary water. (authors). 4 figs., 1 tab., 2 refs

  18. Teacher Conceptions and Approaches Associated with an Immersive Instructional Implementation of Computer-Based Models and Assessment in a Secondary Chemistry Classroom (United States)

    Waight, Noemi; Liu, Xiufeng; Gregorius, Roberto Ma.; Smith, Erica; Park, Mihwa


    This paper reports on a case study of an immersive and integrated multi-instructional approach (namely computer-based model introduction and connection with content; facilitation of individual student exploration guided by exploratory worksheet; use of associated differentiated labs and use of model-based assessments) in the implementation of coupled computer-based models and assessment in a high-school chemistry classroom. Data collection included in-depth teacher interviews, classroom observations, student interviews and researcher notes. Teacher conceptions highlighted the role of models as tools; the benefits of abstract portrayal via visualizations; appropriate enactment of model implementation; concerns with student learning and issues with time. The case study revealed numerous challenges reconciling macro, submicro and symbolic phenomena with the NetLogo model. Nonetheless, the effort exhibited by the teacher provided a platform to support the evolution of practice over time. Students' reactions reflected a continuum of confusion and benefits which were directly related to their background knowledge and experiences with instructional modes. The findings have implications for the role of teacher knowledge of models, the modeling process and pedagogical content knowledge; the continuum of student knowledge as novice users and the role of visual literacy in model decoding, comprehension and translation.

  19. Incorporation of Uncertainty Analysis in Experimental/Computational Fluid Dynamics Validations

    National Research Council Canada - National Science Library

    Coleman, Hugh


    A quantitative approach to verification and validation of simulations was developed which properly takes into account the uncertainties in experimental data and the uncertainties in the simulation result...

  20. Energy Research and Development Administration Ad Hoc Computer Networking Group: experimental program

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, I.


    The Ad Hoc Computer Networking Group was established to investigate the potential advantages and costs of newer forms of remote resource sharing and computer networking. The areas of research and investigation that are within the scope of the ERDA CNG are described. (GHT)