Structural and electrical characterization of hybrid metal-polypyrrole nanowires

We present here the synthesis and structural characterization of hybrid Au-polypyrrole-Au and Pt- polypyrrole-Au nanowires together with a study of their electrical properties from room-temperature down to very low temperature. A careful characterization of the metal-polymer interfaces by trans- mission electron microscopy revealed that the structure and mechanical strength of bottom and upper interfaces are very different. Variable temperature electrical transport measurements were performed on both multiple nanowires - contained within the polycarbonate template - and single nanowires. Our data show that the three-dimensional Mott variable-range-hopping model provides a complete framework for the understanding of transport in PPy nanowires, including non-linear current-voltage characteristics and magnetotransport at low temperatures.Comment: Phys. Rev. B Vol. 76 Issue 11 (2007

2D Rutherford-Like Scattering in Ballistic Nanodevices

Ballistic injection in a nanodevice is a complex process where electrons can either be transmitted or reflected, thereby introducing deviations from the otherwise quantized conductance. In this context, quantum rings (QRs) appear as model geometries: in a semiclassical view, most electrons bounce against the central QR antidot, which strongly reduces injection efficiency. Thanks to an analogy with Rutherford scattering, we show that a local partial depletion of the QR close to the edge of the antidot can counter-intuitively ease ballistic electron injection. On the contrary, local charge accumulation can focus the semi-classical trajectories on the hard-wall potential and strongly enhance reflection back to the lead. Scanning gate experiments on a ballistic QR, and simulations of the conductance of the same device are consistent, and agree to show that the effect is directly proportional to the ratio between the strength of the perturbation and the Fermi energy. Our observation surprisingly fits the simple Rutherford formalism in two-dimensions in the classical limit

Socio-Technical Challenges of Large Scale CI

In 2007 the National Science Foundation awarded a grant to the University of Michigan, School of Information to evaluate the George E. Brown Jr. Network for Earthquake Engineering and Simulation (NEES). The objective of the evaluation is to understand how NEES is working in its first years of operation. Although NEES is a huge technological undertaking, this evaluation uses qualitative and quantitative data collection methods to consider the social and organizational aspects of NEES as well. It is a formative evaluation intended to provide guidance for the second phase of the NEES operation and to inform current cyberinfrastructure (CI) initiatives that are underway. As a precursor to the current CI initiatives, NEES is not merely an innovation in how to do EE research, but an innovation in how to do research generally. NEES has shown that useful CI can be developed on a large scale to serve a scientific and engineering research community. Its capabilities have encouraged researchers to propose and conduct more innovative experimental research that spans disciplines and research methods. As an early initiative with few examples to draw upon, NEES has also shown that developing CI on such a scale can be a difficult process that does not always go as planned. This study reports the successes and challenges NEES has experienced in the context of five major findings.National Science Foundationhttp://deepblue.lib.umich.edu/bitstream/2027.42/61845/1/Unrealized_Potential_The_Socio-Technical_Challenges_of_a_Large_Scale_CI_Initiative_Feb_2009.pd

Data reuse and sensemaking among novice social scientists

We know little about the data reuse practices of novice data users. Yet large scale data reuse over the long term depends in part on uptake from early career researchers. This paper examines 22 novice social science researchers and how they make sense of social science data. Novices are particularly interested in understanding how data: 1) are transformed from qualitative to quantitative data, 2) capture concepts not well‐established in the literature, and 3) can be matched and merged across multiple datasets. We discuss how novice data users make sense of data in these three circumstances. We find that novices seek to understand the data producer's rationale for methodological procedures and measurement choices, which is broadly similar to researchers in other scientific communities. However we also find that they not only reflect on whether they can trust the data producers' decisions, but also seek guidance from members of their disciplinary community. Specifically, novice social science researchers are heavily influenced by more experienced social science researchers when it comes to discovering, evaluating, and justifying their reuse of other's data.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96429/1/14504901068_ftp.pd