Patterned Irradiation of YBa_2Cu_3O_(7-x) Thin Films

We present a new experiment on YBa_2Cu_3O_{7-x} (YBCO) thin films using spatially resolved heavy ion irradiation. Structures consisting of a periodic array of strong and weak pinning channels were created with the help of metal masks. The channels formed an angle of +/-45 Deg with respect to the symmetry axis of the photolithographically patterned structures. Investigations of the anisotropic transport properties of these structures were performed. We found striking resemblance to guided vortex motion as it was observed in YBCO single crystals containing an array of unidirected twin boundaries. The use of two additional test bridges allowed to determine in parallel the resistivities of the irradiated and unirradiated parts as well as the respective current-voltage characteristics. These measurements provided the input parameters for a numerical simulation of the potential distribution of the Hall patterning. In contrast to the unidirected twin boundaries in our experiment both strong and weak pinning regions are spatially extended. The interfaces between unirradiated and irradiated regions therefore form a Bose-glass contact. The experimentally observed magnetic field dependence of the transverse voltage vanishes faster than expected from the numerical simulation and we interpret this as a hydrodynamical interaction between a Bose-glass phase and a vortex liquid.Comment: 7 pages, 8 Eps figures included. Submitted to PR

TPACKing for the Student Learning Centre digital strategy

Providing academic support for a diverse tertiary population requires the inclusion of a digital approach. However, in order to develop a digital strategy, there is a need to provide an allencompassing reflection on how to integrate technology. This paper aims to report on Auckland University of Technology (AUT) Student Learning Centre (SLC) current progress in the digital space, while providing direction to its future development. This paper combines technological knowledge with content and pedagogical knowledge to design SLC’s future developments. It also provides an analysis of current SLC digital presence developments and addresses possible future directions. Recommendations reinforce the need for an overall learning strategy, and address the affordances of Web 2.0 for this project. These recommendations and reflections are important for setting the foundations for a pedagogically solid digital development

Biovolume determination of phytoplankton guilds in transitional water ecosystems of Mediterranean Ecoregion

1 - Conceptually, morphometric measurements of phytoplankton guilds seem to have major advantages as descriptors of the ecological status of transitional water ecosystems (TW) with respect to classical taxonomic descriptors. However, at present, standardized or common methodologies for the use of morphometric descriptors do not exist. 2 - This paper aims to provide a starting point for the activation of standardized methods for the determination of morphometric descriptors of phytoplankton as a quality element in TW in accordance with the new directive of WFD 2000/60/EU. 3 - Phytoplankton biovolume is one of the most studied morphometric descriptors. It can be estimated by associating the algae with similar geometric forms and determining the volume of these by measuring the linear dimensions required for its calculation under the microscope. However, the lack of a standardized set of geometric forms and equations for calculating biovolume causes difficulties and produces data that are not comparable. 4 - A set of geometric models is suggested here for calculating the cell biovolumes of 201 phytoplankton genera found in transitional water ecosystems of Mediterranean Ecoregion. The equations were designed to minimize the effort of microscopic measurements. The main methodological problems, and the similarities and differences between our own and previously published proposals are discussed

Spin orbit coupling at the level of a single electron

We utilize electron counting techniques to distinguish a spin conserving fast tunneling process and a slower process involving spin flips in AlGaAs/GaAs-based double quantum dots. By studying the dependence of the rates on the interdot tunnel coupling of the two dots, we find that as many as 4% of the tunneling events occur with a spin flip related to spin-orbit coupling in GaAs. Our measurement has a fidelity of 99 % in terms of resolving whether a tunneling event occurred with a spin flip or not

High Frequency Quantum Admittance and Noise Measurement with an On-chip Resonant Circuit

By coupling a quantum detector, a superconductor-insulator-superconductor junction, to a Josephson junction \textit{via} a resonant circuit we probe the high frequency properties, namely the ac complex admittance and the current fluctuations of the Josephson junction at the resonant frequencies. The admittance components show frequency dependent singularities related to the superconducting density of state while the noise exhibits a strong frequency dependence, consistent with theoretical predictions. The circuit also allows to probe separately the emission and absorption noise in the quantum regime of the superconducting resonant circuit at equilibrium. At low temperature the resonant circuit exhibits only absorption noise related to zero point fluctuations, whereas at higher temperature emission noise is also present.Comment: 15 pages, 15 figure

Probabilistic Timed Automata with Clock-Dependent Probabilities

Probabilistic timed automata are classical timed automata extended with discrete probability distributions over edges. We introduce clock-dependent probabilistic timed automata, a variant of probabilistic timed automata in which transition probabilities can depend linearly on clock values. Clock-dependent probabilistic timed automata allow the modelling of a continuous relationship between time passage and the likelihood of system events. We show that the problem of deciding whether the maximum probability of reaching a certain location is above a threshold is undecidable for clock-dependent probabilistic timed automata. On the other hand, we show that the maximum and minimum probability of reaching a certain location in clock-dependent probabilistic timed automata can be approximated using a region-graph-based approach.Comment: Full version of a paper published at RP 201

Phytoplankton composition in the coastal Magnetic Island lagoon, Western Pacific Ocean (Australia)

1 - Coastal lagoons have traditionally been considered as transitional systems between continental and marine domains. The phytoplankton plays a key role in these aquatic environments, forming the base of the food web and having a substantial function in nutrient dynamics and in the carbon biogeochemical cycle.2 - Due to their short life cycle, planktonic algae respond quickly to environmental changes and they are thus a valuable indicator of water quality. It is essential to investigate the development of phytoplankton populations to understand the biological functioning and to detect changes in aquatic systems.3 - Phytoplankton studies in the Australian estuaries and lagoons are relatively scarce. This study has provided a broad perspective and preliminary information on taxonomic structure of phytoplankton guilds for the Magnetic Island Lagoon (Queensland, Australia). This work may provide valuable information of interest to later ecological studies.4 - In the whole sampling a total of 143 taxa were identified. In terms of species richness, diatoms (Bacillariophyceae, Coscinodiscophyceae, Fragilariophyceae) and dinoflagellates (Dinophyceae) were the most important groups. In taxonomic terms, diatoms were the major contributor to the phytoplankton composition (~ 70%) whereas Dinophyceae were moderately abundant (~23%). Diatoms are a very important component in estuarine and shallow coastal wetlands and they are increasingly being utilized as indicators of environmental change

Shift of the surface-barrier part of the irreversibility line due to columnar defects in Bi_2Sr_2CaCu_2O_8 thin films

We report the results of studying the influence of the uranium-ion irradiation of the Bi_2Sr_2CaCu_2O_8 thin films on the high-temperature part (close to critical temperature) of their irreversibility line. We studied irreversible properties of the films by measuring the hysteresis of nonresonant microwave absorption. The results have revealed the shift of irreversibility line towards low temperatures and magnetic fields. The effect is most significant for the films irradiated with large doses, more than 1T. This fact is in good agreement with the theoretical prediction by Koshelev and Vinokur of suppression of surface barrier by columnar defects.Comment: LaTeX2e, 9 pages with 3 figures, to be published in Physica

Whole-ecosystem experimental manipulations of tropical forests.

Tropical forests are highly diverse systems involving extraordinary numbers of interactions between species, with each species responding in a different way to the abiotic environment. Understanding how these systems function and predicting how they respond to anthropogenic global change is extremely challenging. We argue for the necessity of 'whole-ecosystem' experimental manipulations, in which the entire ecosystem is targeted, either to reveal the functioning of the system in its natural state or to understand responses to anthropogenic impacts. We survey the current range of whole-ecosystem manipulations, which include those targeting weather and climate, nutrients, biotic interactions, human impacts, and habitat restoration. Finally we describe the unique challenges and opportunities presented by such projects and suggest directions for future experiments.This review was initiated during a symposium on ‘The effects of large scale manipulations of tropical forests on arthropod assemblages’ at the INTECOL 2013 congress, London 18–23 August 2013. T.M.F. is funded by the Australian Research Council (DP140101541), T.M.F. and R.M.E. by Yayasan Sime Darby, TMF and Y.B. by the project Biodiversity of Forest Ecosystems (CZ.1.07/2.3.00/20.0064) co-financed by the European Social Fund and the state budget of the Czech Republic, and T.M.F. Y.B. and V.N. by the Czech Science Foundation (GACR 14-32302S, 14-36098G, 14-04258S respectively). Y.B. is also supported by the Sistema Nacional de Investigacio´n of Panama. E.C.T. is supported by funds from PT SMART Research Institute and the Isaac Newton Trust, Cambridge. R.M.E. is supported by European Research Council Project number 281986. We are grateful to Maureen Fayle, Andrew Hector, Jan Leps, Scott Miller, Kalsum M. Yusah, Paul Craze, and two anonymous reviewers for advice during the drafting of the manuscript, and Jennifer Balch for additional information regarding her burning experiments.This is the final published version. It first appeared at http://www.cell.com/trends/ecology-evolution/abstract/S0169-5347%2815%2900069-5