Cartographic research in EREP programme for small scale mapping

There are no author-identified significant results in this report

A storm on the horizon? 'Twister' and the implications of the blockchain and peer-to-peer social networks for online violent extremism

Twister, developed by Miguel Freitas, is a social network platform centred around micro-blogging, much like Twitter. However, rather than relying on centralised servers owned and maintained by a single firm, Twister users operate a blockchain combined with DHT-like and BitTorrent-like protocols to both make posts and send private messages, and also to receive entries from other users. Twister's raison d'etre is that it offers a social networking platform that cannot be censored and cannot itself censor. The software does not record the IP addresses users use to access the service, nor does it notify other users of an account's online/offline status. Growing adoption of blockchain services means that it is possible that the concept of decentralised social networks could become a norm. It is suggested in this paper that blockchain-based peer-to-peer social networks present challenges to the current counter-extremist practices for content removal and censorship. Whilst there are methods to disrupt usage of blockchain-based peer-to-peer services, these approaches may have the net harm of curtailing bona fide use legal and novel technologies. Given this opportunity cost, non-transitory online violent extremist content may need to be tolerate

Metal-Insulator transitions in the periodic Anderson model

We solve the Periodic Anderson model in the Mott-Hubbard regime, using Dynamical Mean Field Theory. Upon electron doping of the Mott insulator, a metal-insulator transition occurs which is qualitatively similar to that of the single band Hubbard model, namely with a divergent effective mass and a first order character at finite temperatures. Surprisingly, upon hole doping, the metal-insulator transition is not first order and does not show a divergent mass. Thus, the transition scenario of the single band Hubbard model is not generic for the Periodic Anderson model, even in the Mott-Hubbard regime.Comment: 5 pages, 4 figure

Lithium abundance and 6Li/7Li ratio in the active giant HD123351 I. A comparative analysis of 3D and 1D NLTE line-profile fits

Current three-dimensional (3D) hydrodynamical model atmospheres together with NLTE spectrum synthesis, permit to derive reliable atomic and isotopic chemical abundances from high-resolution stellar spectra. Not much is known about the presence of the fragile 6Li isotope in evolved solar-metallicity RGB stars, not to mention its production in magnetically active targets like HD123351. From fits of the observed CFHT spectrum with synthetic line profiles based on 1D and 3D model atmospheres, we seek to estimate the abundance of the 6Li isotope and to place constraints on its origin. We derive A(Li) and the 6Li/7Li isotopic ratio by fitting different synthetic spectra to the Li-line region of a high-resolution CFHT spectrum (R=120 000, S/R=400). The synthetic spectra are computed with four different line lists, using in parallel 3D hydrodynamical CO5BOLD and 1D LHD model atmospheres and treating the line formation of the lithium components in non-LTE (NLTE). We find A(Li)=1.69+/-0.11 dex and 6Li/7Li=8.0+/-4.4 % in 3D-NLTE, using the line list of Mel\'endez et al. (2012), updated with new atomic data for V I, which results in the best fit of the lithium line profile of HD123351. Two other line lists lead to similar results but with inferior fit qualities. Our 2-sigma detection of the 6Li isotope is the result of a careful statistical analysis and the visual inspection of each achieved fit. Since the presence of a significant amount of 6Li in the atmosphere of a cool evolved star is not expected in the framework of standard stellar evolution theory, non-standard, external lithium production mechanisms, possibly related to stellar activity or a recent accretion of rocky material, need to be invoked to explain the detection of 6Li in HD123351.Comment: 16 pages, 11 figures. Accepted for publication in A&

Factors Affecting Seatbelt Use Among the Deaf and Hard-of-Hearing

In the United States, despite the proven significant economic, health, and social benefits of seatbelt use, millions of Americans do not use seatbelts. It is known that some factors, including obesity, reduce the rates of seatbelt use; however, a lack of research exists regarding whether individuals who are deaf or hard-of-hearing (HOH) have different rates of seatbelt use. The purpose of this study was to examine the difference in seatbelt use between deaf or HOH individuals and hearing individuals after adjusting for individual-level factors (BMI, marital status, education, and access to health care). The theoretical foundation for this study was Stokols’ social ecological model for health promotion. This quantitative cross-sectional study was conducted using secondary data from the Behavioral Risk Factor Surveillance System (BRFSS) in 2017. Ordinal logistic regressions was used to address the research questions. The results showed that deaf or HOH individuals, and specifically those who were obese, were less likely to use seatbelts. The findings also showed that having access to health insurance and being married increased the chance of using seatbelts. The impact this study will have on social change is that it will inform car manufacturers of the need to address seatbelt safety reminders for the deaf or HOH, ultimately leading to vehicles equipped with flashing lights and vibrating seats designed to remind the driver and its occupants to buckle up

Insulator-metal-insulator transition and selective spectral weight transfer in a disordered strongly correlated system

We investigate the metal insulator transitions at finite temperature for the Hubbard model with diagonal alloy disorder. We solve the dynamical mean field theory equations with the non crossing approximation and we use the coherent potential approximation to handle disorder. The excitation spectrum is given for various correlation strength $U$ and disorder. Two successive metal insulator transitions are observed at integer filling values as $U$ is increased. An important selective transfer of spectral weight arises upon doping. The strong influence of the temperature on the low energy dynamics is studied in details.Comment: submitted to Phys. Rev.

Critical behavior at Mott-Anderson transition: a TMT-DMFT perspective

We present a detailed analysis of the critical behavior close to the Mott-Anderson transition. Our findings are based on a combination of numerical and analytical results obtained within the framework of Typical-Medium Theory (TMT-DMFT) - the simplest extension of dynamical mean field theory (DMFT) capable of incorporating Anderson localization effects. By making use of previous scaling studies of Anderson impurity models close to the metal-insulator transition, we solve this problem analytically and reveal the dependence of the critical behavior on the particle-hole symmetry. Our main result is that, for sufficiently strong disorder, the Mott-Anderson transition is characterized by a precisely defined two-fluid behavior, in which only a fraction of the electrons undergo a "site selective" Mott localization; the rest become Anderson-localized quasiparticles.Comment: 4+ pages, 4 figures, v2: minor changes, accepted for publication in Phys. Rev. Let

Spin-Hall effect in a [110] quantum well

A self-consistent treatment of the spin-Hall effect requires consideration of the spin-orbit coupling and electron-impurity scattering on equal footing. This is done here for the experimentally relevant case of a [110] GaAs quantum well [Sih {\it et al.}, Nature Physics 1, 31 (2005)]. Working within the framework of the exact linear response formalism we calculate the spin-Hall conductivity including the Dresselhaus linear and cubic terms in the band structure, as well as the electron-impurity scattering and electron-electron interaction to all orders. We show that the spin-Hall conductivity naturally separates into two contributions, skew-scattering and side-jump, and we propose an experiment to distinguish between them.Comment: The connection with the recent experiment on [110] quantum wells is emphasize