9,909 research outputs found
Existence of positive solutions of a superlinear boundary value problem with indefinite weight
We deal with the existence of positive solutions for a two-point boundary
value problem associated with the nonlinear second order equation
. The weight is allowed to change its sign. We assume
that the function is
continuous, and satisfies suitable growth conditions, so as the case
, with , is covered. In particular we suppose that is
large near infinity, but we do not require that is non-negative in a
neighborhood of zero. Using a topological approach based on the Leray-Schauder
degree we obtain a result of existence of at least a positive solution that
improves previous existence theorems.Comment: 12 pages, 4 PNG figure
Microstability analysis of pellet fuelled discharges in MAST
Reactor grade plasmas are likely to be fuelled by pellet injection. This
technique transiently perturbs the profiles, driving the density profile hollow
and flattening the edge temperature profile. After the pellet perturbation, the
density and temperature profiles relax towards their quasi-steady-state shape.
Microinstabilities influence plasma confinement and will play a role in
determining the evolution of the profiles in pellet fuelled plasmas. In this
paper we present the microstability analysis of pellet fuelled H-mode MAST
plasmas. Taking advantage of the unique capabilities of the MAST Thomson
scattering system and the possibility of synchronizing the eight lasers with
the pellet injection, we were able to measure the evolution of the post-pellet
electron density and temperature profiles with high temporal and spatial
resolution. These profiles, together with ion temperature profiles measured
using a charge exchange diagnostic, were used to produce equilibria suitable
for microstability analysis of the equilibrium changes induced by pellet
injection. This analysis, carried out using the local gyrokinetic code GS2,
reveals that the microstability properties are extremely sensitive to the rapid
and large transient excursions of the density and temperature profiles, which
also change collisionality and beta e significantly in the region most strongly
affected by the pellet ablation.Comment: 21 pages, 10 figures. This is an author-created, un-copyedited
version of an article submitted for publication in Plasma Physics and
Controlled Fusion. IOP Publishing Ltd is not responsible for any errors or
omissions in this version of the manuscript or any version derived from i
Statistical models of mixtures with a biaxial nematic phase
We consider a simple Maier-Saupe statistical model with the inclusion of
disorder degrees of freedom to mimic the phase diagram of a mixture of rod-like
and disc-like molecules. A quenched distribution of shapes leads to the
existence of a stable biaxial nematic phase, in qualitative agreement with
experimental findings for some ternary lyotropic liquid mixtures. An annealed
distribution, however, which is more adequate to liquid mixtures, precludes the
stability of this biaxial phase. We then use a two-temperature formalism, and
assume a separation of relaxation times, to show that a partial degree of
annealing is already sufficient to stabilize a biaxial nematic structure.Comment: 11 pages, 2 figure
Information and telecommunications project for a digital city: a brazilian case study
Making information and telecommunications available is a permanent challenge for cities concerned to their social, urban and local planning and development, focused on life quality of their citizens and on the effectiveness of public management. Such a challenge requires the involvement of everyone in the city. The objective is to describe the information and telecommunications project from the planning of a digital city carried out in Vinhedo-SP, Brazil. It was built as a telecommunications infrastructure of the kind of "open access metropolitan area networks" which enables the integration of citizens in a single telecommunications environment. The research methodology was emphasized by a case study which turned to be a research-action, comprising the municipal administration and its local units. The results achieved describe, by means of a methodology, the phases, sub-phases, activities, approval points and resulting products, and formalize their respective challenges and difficulties. The contributions have to do with the practical feasibility of the project and execution of its methodology. The conclusion reiterates the importance of the project, collectively implemented and accepted, as a tool to help the management of cities, in the implementation of Strategic Digital City Projects, in the decisions of public administration managers, and in the quality of life of their citizens3119811
Uso do extrato de folhas do cartucho de milho como estimulante à ovoposição de doru luteipes (Dermaptera, forficulidae).
Fermion Helicity Flip Induced by Torsion Field
We show that in theories of gravitation with torsion the helicity of fermion
particles is not conserved and we calculate the probability of spin flip, which
is related to the anti-symmetric part of affine connection. Some cosmological
consequences are discussed.Comment: 6 pages, to appear in Europhysics Letter
Using soft systems methodology to fight against info-exclusion: The experience of a Brazilian University
The aim of this paper is to apply a systemic methodology to analyse the concept of info-inclusion which can guide strategic actions of institutions within civil society and within several levels of government. The paper provides a plan of action that, integrated with other tools, aims at fighting the technological and social gap. We apply Soft System Methodology (SSM), because it provides a holistic approach to info-exclusion. SSM is often used to analyse and resolve problems in complex social studies such as info-exclusion. An info-exclusion reduction project, developed by a university in the country region of Sao Paulo will be provided as a case study. This project is one of the several Brazilian initiatives to solve the problem of limited access to information technology tools. We start by contextualising info-exclusion in Brazil and follow with a review of SSM. We then introduce the concept of info-inclusion and apply SSM to it. We end with a discussion of the results obtained and with some suggestions for action and possible improvements. © Springer Science+Business Media, LLC 2006
Online and offline representations of biocultural diversity: A political ecology perspective on nature-based tourism and indigenous communities in the Brazilian Pantanal
The concept of biocultural diversity is confronted with contemporary changes that impact
on local communities, such as globalization and digital transformations. Engaging the conceptual
flexibility of ‘biocultural diversity’, we studied nature-based tourism at the intersection of indigenous
communities and the digital realm. We employed a political ecology perspective to examine online
and offline representations of biocultural diversity in the Brazilian Pantanal, one of the biggest
wetlands in the world, and home to groups of peoples known as the Pantaneiros. Data from
interviews with 48 stakeholders in the tourist sector were structured along three ‘myths’—the
Uncivilised, Unrestrained, and Unchanged—for which we have also constructed counter narratives.
Each myth denoted the primacy of biodiversity, and ignored broader dimensions of the Pantanal
as a bioculturally diverse landscape. The relationships of the Pantaneiros with their environment
were found to be intricate and had clear repercussions for tourism, but ironically, reference to the
Pantaneiro culture in nature-based tourism was superficial. Moreover, thriving on the myths, this
form of tourism perpetuates skewed power structures and social inequalities. Lower-class Pantaneiros
likely suffer most from this. We recommend stakeholder engagement with a biocultural design that
facilitates the integration of other-than-biodiversity values, and that thereby promotes sustainability
of the entire social-ecological system
Antioxidant activity of thymbra capitata essential oil in meat-treated oil
Several synthetic antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and tertiary butyl hydroquinone (TBHQ), have been used to preserve meat. Nevertheless they are considered toxic and to have carcinogenic effects. Natural products, such as those present in essential oils, have been the target of studies as alternative antioxidants, showing promising results. In addition, these natural compounds have the advantage of having consumer's acceptance. Thymbra capitata is a perennial, herbaceous shrub commonly used as a spicy herb. The essential oils isolated from this plant showed antimicrobial and antioxidant activities. The main goal of the present work was to evaluate the capacity of T. capitata oil to prevent lipid oxidation in bovine meat. Different concentrations of essential oil (0, 50, 75 and 100 mg/5 g of meat) were used in two types of bovine meat samples purchased in the local market. The protein content of both types of meat samples was 21%, and lipid content ranged from 9% to 15%. After covering with the oil, the two types of meat samples were stored at -17 degrees C, for one month. After 1 day, 15 days and 30 days, meat samples were taken and cooked at 85 degrees C for 90 min. The samples were then submitted to the TBARS modified method, for antioxidant activity evaluation. The essential oil was able to prevent meat oxidation even after one month of storage and showed a dose-dependent activity
- …