8,998 research outputs found
Empowering Rural Citizen Journalism Via Web 2.0 Technologies
Once acquainted with the modern information and communication tools made available with the advent of the Internet, five Brazilian rural communities participating in a pilot project to develop a self-sustaining telecenter model, engaged in citizen journalism using inexpensive digital video cameras. Community members used Web 2.0 collaborative tools to post short videos on the telecenter portal. The 95 video blogs published between September 2006 and May 2008 recorded various aspects of community life,including religious celebrations,oral history arts and crafts traditions,folklore,and envirnmental concerns. This study evaluates the impact of video blogging in these communities
Effective Spin Couplings in the Mott Insulator of the Honeycomb Lattice Hubbard Model
Motivated by the recent discovery of a spin liquid phase for the Hubbard
model on the honeycomb lattice at half-filling, we apply both perturbative and
non-perturbative techniques to derive effective spin Hamiltonians describing
the low-energy physics of the Mott-insulating phase of the system. Exact
diagonalizations of the so-derived models on small clusters are performed, in
order to assess the quality of the effective low-energy theory in the
spin-liquid regime. We show that six-spin interactions on the elementary loop
of the honeycomb lattice are the dominant sub-leading effective couplings. A
minimal spin model is shown to reproduce most of the energetic properties of
the Hubbard model on the honeycomb lattice in its spin-liquid phase.
Surprisingly, a more elaborate effective low-energy spin model obtained by a
systematic graph expansion rather disagrees beyond a certain point with the
numerical results for the Hubbard model at intermediate couplings.Comment: 20 pages, 10 figure
Quantum Critical Scaling of Fidelity Susceptibility
The behavior of the ground-state fidelity susceptibility in the vicinity of a
quantum critical point is investigated. We derive scaling relations describing
its singular behavior in the quantum critical regime. Unlike it has been found
in previous studies, these relations are solely expressed in terms of
conventional critical exponents. We also describe in detail a quantum Monte
Carlo scheme that allows for the evaluation of the fidelity susceptibility for
a large class of many-body systems and apply it in the study of the quantum
phase transition for the transverse-field Ising model on the square lattice.
Finite size analysis applied to the so obtained numerical results confirm the
validity of our scaling relations. Furthermore, we analyze the properties of a
closely related quantity, the ground-state energy's second derivative, that can
be numerically evaluated in a particularly efficient way. The usefulness of
both quantities as alternative indicators of quantum criticality is examined.Comment: 13 pages, 7 figures. Published versio
Phase separation versus supersolid behavior in frustrated antiferromagnets
We investigate the competition between spin-supersolidity and phase
separation in a frustrated spin-half model of weakly coupled dimers. We start
by considering systems of hard-core bosons on the square lattice, onto which
the low-energy physics of the herein investigated spin model can be mapped, and
devise a criterion for gauging the interplay between supersolid order and
domain wall formation based on strong coupling arguments. Effective bosonic
models for the spin model are derived via the contractor renormalization (CORE)
algorithm and we propose to combine a self-consistent cluster mean-field
solution with our criterion for the occurrence of phase separation to derive
the phase diagram as a function of frustration and magnetic field. In the limit
of strong frustration, the model is shown to be unstable toward phase
separation, in contradiction with recently published results. However, a region
of stable supersolidity is identified for intermediate frustration, in a
parameter range not investigated so far and of possible experimental relevance.Comment: 8 pages, 7 figures. Published versio
On invariants of almost symplectic connections
We study the irreducible decomposition under Sp(2n, R) of the space of
torsion tensors of almost symplectic connections. Then a description of all
symplectic quadratic invariants of torsion-like tensors is given. When applied
to a manifold M with an almost symplectic structure, these instruments give
preliminary insight for finding a preferred linear almost symplectic connection
on M . We rediscover Ph. Tondeur's Theorem on almost symplectic connections.
Properties of torsion of the vectorial kind are deduced
X, Y and Z States
Many new states in the charmonium mass region were recently discovered by
BaBar, Belle, CLEO-c, CDF, D0, BESIII, LHCb and CMS Collaborations. We use the
QCD Sum Rule approach to study the possible structure of some of these states.Comment: Contribution for the proceedings of the "XII Quark Confinement and
the Hadron Spectrum - CONF12" conferenc
Exportação de nutrientes pelas videiras cvs. Itália e Benitaka cultivads no Vale do São Francisco.
Shotguns vs Lasers: Identifying barriers and facilitators to scaling-up plant molecular farming for high-value health products.
Plant molecular farming (PMF) is a convenient and cost-effective way to produce high-value recombinant proteins that can be used in the production of a range of health products, from pharmaceutical therapeutics to cosmetic products. New plant breeding techniques (NPBTs) provide a means to enhance PMF systems more quickly and with greater precision than ever before. However, the feasibility, regulatory standing and social acceptability of both PMF and NPBTs are in question. This paper explores the perceptions of key stakeholders on two European Union (EU) Horizon 2020 programmes-Pharma-Factory and Newcotiana-towards the barriers and facilitators of PMF and NPBTs in Europe. One-on-one qualitative interviews were undertaken with N = 20 individuals involved in one or both of the two projects at 16 institutions in seven countries (Belgium, France, Germany, Italy, Israel, Spain and the UK). The findings indicate that the current EU regulatory environment and the perception of the public towards biotechnology are seen as the main barriers to scaling-up PMF and NPBTs. Competition from existing systems and the lack of plant-specific regulations likewise present challenges for PMF developing beyond its current niche. However, respondents felt that the communication of the benefits and purpose of NPBT PMF could provide a platform for improving the social acceptance of genetic modification. The importance of the media in this process was highlighted. This article also uses the multi-level perspective to explore the ways in which NPBTs are being legitimated by interested parties and the systemic factors that have shaped and are continuing to shape the development of PMF in Europe
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