8,848 research outputs found
Electron Interactions and Transport Between Coupled Quantum Hall Edges
We examine the effects of electron-electron interactions on transport between
edge states in a multilayer integer quantum Hall system. The edge states of
such a system, coupled by interlayer tunneling, form a two-dimensional, chiral
metal at the sample surface. We calculate the temperature-dependent
conductivity and the amplitude of conductance fluctuations in this chiral
metal, treating Coulomb interactions and disorder exactly in the weak-tunneling
limit. We find that the conductivity increases with increasing temperature, as
observed in recent experiments, and we show that the correlation length
characterising conductance fluctuations varies inversely with temperature.Comment: 4 pages, 2 figures, typos corrected, Ref. 17 added, minor changes
made for publicatio
Dynamics of Phononic Dissipation at the Atomic Scale: Dependence on Internal Degrees of Freedom
Dynamics of dissipation of a local phonon distribution to the substrate is a
key issue in friction between sliding surfaces as well as in boundary
lubrication. We consider a model system consisting of an excited nano-particle
which is weakly coupled with a substrate. Using three different methods we
solve the dynamics of energy dissipation for different types of coupling
between the nano-particle and the substrate, where different types of
dimensionality and phonon densities of states were also considered for the
substrate. In this paper, we present our analysis of transient properties of
energy dissipation via phonon discharge in the microscopic level towards the
substrate. Our theoretical analysis can be extended to treat realistic
lubricant molecules or asperities, and also substrates with more complex
densities of states. We found that the decay rate of the nano-particle phonons
increases as the square of the interaction constant in the harmonic
approximation.Comment: 10 pages, 6 figures, submitted to Phys. Rev.
Local spectroscopy and atomic imaging of tunneling current, forces and dissipation on graphite
Theory predicts that the currents in scanning tunneling microscopy (STM) and
the attractive forces measured in atomic force microscopy (AFM) are directly
related. Atomic images obtained in an attractive AFM mode should therefore be
redundant because they should be \emph{similar} to STM. Here, we show that
while the distance dependence of current and force is similar for graphite,
constant-height AFM- and STM images differ substantially depending on distance
and bias voltage. We perform spectroscopy of the tunneling current, the
frequency shift and the damping signal at high-symmetry lattice sites of the
graphite (0001) surface. The dissipation signal is about twice as sensitive to
distance as the frequency shift, explained by the Prandtl-Tomlinson model of
atomic friction.Comment: 4 pages, 4 figures, accepted at Physical Review Letter
Review and synthesis of problems and directions for large scale geographic information system development
Problems and directions for large scale geographic information system development were reviewed and the general problems associated with automated geographic information systems and spatial data handling were addressed
Elevating crop disease resistance with cloned genes
Essentially all plant species exhibit heritable genetic variation for resistance to a variety of plant diseases caused by fungi, bacteria, oomycetes or viruses. Disease losses in crop monocultures are already significant, and would be greater but for applications of disease-controlling agrichemicals. For sustainable intensification of crop production, we argue that disease control should as far as possible be achieved using genetics rather than using costly recurrent chemical sprays. The latter imply CO2 emissions from diesel fuel and potential soil compaction from tractor journeys. Great progress has been made in the past 25 years in our understanding of the molecular basis of plant disease resistance mechanisms, and of how pathogens circumvent them. These insights can inform more sophisticated approaches to elevating disease resistance in crops that help us tip the evolutionary balance in favour of the crop and away from the pathogen. We illustrate this theme with an account of a genetically modified (GM) blight-resistant potato trial in Norwich, using the Rpi-vnt1.1 gene isolated from a wild relative of potato, Solanum venturii, and introduced by GM methods into the potato variety Desiree
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The Psy-Security-Curriculum ensemble: British Values curriculum policy in English schools
Framed as being in response to terrorist attacks and concerns about religious bias in some English schools, ‘British Values’ (BV) curriculum policy forms part of the British Government’s Counter-Terrorism and Security Act, 2015. This includes a Duty on teachers in England to actively promote British Values to deter students from radicalisation. This paper, first, traces the history of Britishness in the curriculum to reveal a prevalence of nationalistic, colonial values. Next, an ensemble of recent policies and speeches focusing on British Values is analysed, using a psycho-political approach informed by anti-colonial scholarship. Finally, we interrogate two key critiques of the British Values curriculum discourse: the universality of British Values globally, and concerns over the securitisation of education. Findings indicate that the constitution of white British supremacist subjectivities operate through curriculum as a defence mechanism against perceived threats to white privilege, by normalising a racialised state-controlled social order. The focus is on ‘British’ values, but the analytic framework and findings have wider global significance
An investigation into CLIL-related sections of EFL coursebooks : issues of CLIL inclusion in the publishing market
The current ELT global coursebook market has embraced CLIL as a weak form of bilingual education and an innovative component to include in General English coursebooks for EFL contexts. In this paper I investigate how CLIL is included in ELT coursebooks aimed at
teenaged learners, available to teachers in Argentina. My study is based on the content analysis of four series which include a section advertised as CLIL-oriented. Results suggest that such sections are characterised by (1) little correlation between featured subject specific content and school curricula in L1, (2) oversimplification of contents, and (3) dominance of reading skills development and lower-order thinking tasks. Through this study, I argue that
CLIL components become superficial supplements rather than a meaningful attempt to promote weak forms of bilingual education
Phage display selected magnetite interacting Adhirons for shape controlled nanoparticle synthesis
Adhirons are robust, well expressing, peptide display scaffold proteins, developed as an effective alternative
to traditional antibody binding proteins for highly specific molecular recognition applications. This paper
reports for the first time the use of these versatile proteins for material binding, and as tools for
controlling material synthesis on the nanoscale. A phage library of Adhirons, each displaying two variable
binding loops, was screened to identify specific proteins able to interact with [100] faces of cubic
magnetite nanoparticles. The selected variable regions display a strong preference for basic residues
such as lysine. Molecular dynamics simulations of amino acid adsorption onto a [100] magnetite surface
provides a rationale for these interactions, with the lowest adsorption energy observed with lysine. These
proteins direct the shape of the forming nanoparticles towards a cubic morphology in room temperature
magnetite precipitation reactions, in stark contrast to the high temperature, harsh reaction conditions
currently used to produce cubic nanoparticles. These effects demonstrate the utility of the selected
Adhirons as novel magnetite mineralization control agents using ambient aqueous conditions. The
approach we outline with artificial protein scaffolds has the potential to develop into a toolkit of novel
additives for wider nanomaterial fabrication
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