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The paper presents an overview of the current research and achievements of the DEISA project, with a focus on the general concept of the infrastructure, the operational model, application projects and science communities, the DEISA Extreme Computing Initiative, user and application support, operations and technology, services, collaborations and interoperability, and the use of standards and policies. The paper concludes with a discussion about the long-term sustainability of the DEISA infrastructure.

Summary In Autumn 2013, we—an international team of climate scientists, computer scientists, eScience researchers, and e-Infrastructure specialists—participated in the enlighten your research global competition, organized to showcase advanced lightpath technologies in support of state-of-the-art research questions. As one of the winning entries, our enlighten your research global team embarked on a very ambitious project to run an extremely high resolution climate model on a collection of supercomputers distributed over two continents and connected using an advanced 10 G lightpath networking infrastructure. Although good progress was made, we were not able to perform all desired experiments due to a varying combination of technical problems, configuration issues, policy limitations and lack of (budget for) human resources to solve these issues. In this paper, we describe our goals, the technical and non-technical barriers, we encountered and provide recommendations on how these barriers can be removed so future project of this kind may succeed. Copyright © 2016 John Wiley & Sons, Ltd.

The rapid acquisition of mutations conferring resistance to particular drugs remains a significant cause of anti-HIV treatment failure. Informatics based techniques give resistance scores to individual mutations which can be combined additively to assess the resistance levels of complete sequences. It is likely however, that the full picture is more complicated, with non-linear epistatic effects between combinations of mutations playing an important role in determining the level of viral resistance [1, 2]. Molecular dynamics is one simulation technique which offers the ability to derive quantitative (as well as qualitative) insight into the interplay of resistance-causing mutations. The dynamics of sequence specific models can be simulated and the free energy change associated with the drug binding calculated. The free energy change (or binding affinity) is the thermodynamic quantity which determines how tightly a drug will bind to its target. Hence, comparing values for mutant and wildtype systems allows the level of resistance of a particular sequence to be estimated. Validating such an approach is computationally demanding and the management of large numbers of simulations is a considerable administrative challenge. Here we present the use of tools based on the Simple API for Grid Applications (SAGA) to tackle this computational problem. This allows us to utilise high-end infrastructure, such as TeraGrid/XD, to provide extreme scales of throughput for highperformance simulations. This paper presents initial results and experience of using the TeraGrid in conjunction with DEISA, the European analogue of the US TeraGrid. High-throughput (high-performance) calculations are one of the few classes of computational problems that can easily exploit the computational power of widely distributed computing resources, thereby amassing more computational power than any of the individual resources could offer. In addition to the resource utilization rationale the need for cross-Grid capabilities in this case arises from shared and complementary scientific and technical skills found in this intercontinental collaboration.

De-Haas-van Alphen (DHVA) frequencies corresponding to the neck orbits of a majority-spin Fermi surface have been observed over a wide range of orientations in the ferromagnetic FCC alloy Co0.92Fe0.08. Self-consistent band-structure calculations can largely explain the experimental results, albeit that the predicted neck diameter is 20% too small.

The Fermi surface of Nb/sub 3/Sn has been derived from an APW band calculation. de Haas-van Alphen (dHvA) oscillations have been observed in Nb/sub 3/Sn and V/sub 3/Si which give a consistent FS description. Using single crystals of high resistance ratio's and magntic fields up to 400 kOe, dHvA oscillations have been seen in the normal state for both specimens. New features of the Fermi surface include osculated ellipsoidal structure around M and a large cubical structure around LAMBDA.

In molecular orbital calculations a linear combination of Slater-type atomic orbitals is frequently used as a trial wavefunction. To determine hyperfine energies, certain matrix elements, involving the electron orbitals and the hyperfine interaction operator, are required. In the paper explicit expressions are reported, which are valid for Slater-type orbitals with principal quantum number n = 3, and s- or p-type angular dependence. The expressions allow for a fast computation of the integrals. In Rechnungen mit molekularen Orbitals werden haufig lineare Kombinationen atomarer Orbitals vom Slater-Typ als Wellenfunktion angewandt. Zur Berechnung der Hyperfeinenergie braucht man bestimmte Matrixelemente, die sich aus den Elektronenorbitals und aus dem Hyper feinwechselwirkungsoperator zusammensetzen. In diesem Bericht werden explizite Formeln gegeben, die igre Gultigkeit haben fur Orbitale vom Slater-Typ mit Hauptquantenzahl n =3, und s-oder p-Typ-Winkelabhangigkeit. Die Formeln ermoglichen eine schnelle Berechnung dieser Integrale.

Calculations are carried out for the positive divacancy in silicon using the extended Huckel theory. These are non-iterative calculations in the molecular unit cell approach for various sizes of the unit cell and for various points in the Brillouin zone. The effects of two symmetry-allowed distortion modes of the six nearest-neighbour atoms of the divacancy are investigated. The parameters for stable Jahn-Teller distortion are determined by minimizing the extended-Huckel-theory energy. A second minimum with slightly higher energy is a saddle point with respect to distortions corresponding to other Jahn-Teller configurations. The energy barrier for reorientation between these configurations is obtained. From the wavefunction of the unpaired electron the hyperfine interaction with 29Si nuclei in the two nearest-neighbour shells are calculated. For suitable distortions the results compare favourably with existing experimental data. A large discrepancy is found between the distortion parameters for minimum energy and for optimum match of the hyperfine constants. Nicht-iterative Rechnungen werden fur die positive Doppelleerstelle in Silizium mit Hilfe der erweiterten Huckel-Theorie ausgefuhrt. Es handelt sich hier um Rechnungen nach dem Verfahren der molekularen Einheitszelle fur verschiedene Grose der Einheitszelle und fur verschiedene Punkte in der Brillouin-Zone. Die sechs nachsten Nachbaratome der Doppelleerstelle werden systematisch in zwei von der Symmetrie erlaubten Verzerrungsmoden versetzt. Die Gleichgewichtslagen fur Jahn-Teller-Relaxation werden bestimmt durch Minimalisierung der EHT-Energie. Ein zweites Minimum mit einer nur urn wenig hoheren Energie ist ein Sattelpunkt bezuglich der Verzerrungen, die mit den ubrigen Jahn-Teller-Orientierungen zusammenhangen. Die Energiebarriere fur Reorientierung zwischen unterschiedlichen Orientierungen wird ermittelt. Die Wellenfunktionskoeffizicnten ermoglichen die Berechnung der Hyperfeinwechselwirkung zwischen dem ungepaarten Defektelektron und 29Si-Kernen in den zwei Schalen der nachsten Nachbarn. Fur geeignete Werte der Verzerrungsparameter existiert eine vernunftige Ubereinstimmung mit zur Verfugung stehenden experimentellen Ergebnissen. Die Verzerrungskombinationen fur minimale Energie und fur das beste Resultat der Hyperfeinkonstanten weisen lider einen grosen Unterschied auf.

A simple mathematical model of a double-sucrose-gap voltage-clamp setup is presented. The model is used to calculate the difference between an assumed current-voltage relationship of a preparation, and the one measured by the double-sucrose-gap technique, taking into account the cable-like structure of the preparation. It is demonstrated that the abovementioned difference may be important for the early peak current, as well as for the late outward current. It is concluded that quantitative results obtained bythe double- sucrose-gap technique should be considered with care.

The de Haas-van Alphen (DHVA) effect has been investigated in Pd and Pd-Ni alloys in magnetic fields extending to 40 T. With increasing Ni content, the incipient ferromagnetism gives rise to an unusual behaviour which is dominated by a field dependence of the Stoner factor.

de Haas-van Alphen frequencies in the (100) and (110) planes of Nb3Sn have been measured with a typical accuracy of 1%. Several frequency branches have been found between 100 and 1000 T. Effective masses corresponding to some of the orbits at symmetry directions have been estimated from the experiments. A pronounced anisotropy ( approximately 10%) in the upper critical field was observed. The magnitude of the critical field was found to be sample dependent. The DHVA data are interpreted using self-consistent new ASW band-structure calculations which include tetragonal distortion of the unit cell.

de Haas-van Alphen (dHvA) oscillations have been observed in ${\mathrm{Nb}}_{3}$Sn in the (110) plane and in ${\mathrm{V}}_{3}$Si at two orientations using single crystals of high resistance ratio and magnetic fields in excess of ${H}_{c2}$. The dHvA frequency data for ${\mathrm{Nb}}_{3}$Sn can be interpreted as a series of nested ellipsoids centered at $M$, as suggested by a recent high-precision calculation of the ${\mathrm{Nb}}_{3}$Sn Fermi surface.