3,884 research outputs found
Associations In Protected Areas: Restrictions And Possibilities In The Experience Of Tourist Guides In Catimbau, Pernambuco
The aim of the current study is to analyze the organizational dynamics established by the Association of Tourist Guides and for the Development of Catimbau National Park (AGTURC - Associação de Guias do Turismo e do Desenvolvimento do Parque Nacional do Catimbau) as a way to structure the tourist activity in the park, which is located in Pernambuco State. This perspective is set in discussions about the changes the countryside has faced due to new territorial dynamics that have resulted from the idea of environmental conservation and enhancement of the country area, and the consequent implementation of protected natural areas. The abandonment by the public power, the poor logistics infrastructure of the association, in addition to the bad management of scarce resources in the herein presented case, among other reasons, have favored internal disputes over visitors among the AGTURC members, thus motivating, for instance, the noncompliance with the agreements defined by the group. These aspects reveal the tourism-related difficulties and tensions experienced in Brazilian Conservation Units.19216918
Educación pandémica, una oportunidad para redescubrir la filosofía y su enseñanza
The pandemic is an opportunity to rethink philosophy and its teaching, where it should not only be the presentation of biographies of philosophers and summaries of their thought and doctrine, but also a series of contents and a teaching-learning process that lead to critical thinking, to a living philosophy that is understood as wonder
Microstructure modelling of hot deformation of Al–1%Mg alloy
This study presents the application of the finite elementmethod and intelligent systems techniques to the
prediction of microstructural mapping for aluminium alloys. Here, the material within each finite element
is defined using a hybrid model. The hybrid model is based on neuro-fuzzy and physically based components
and it has been combined with the finite element technique. The model simulates the evolution of
the internal state variables (i.e. dislocation density, subgrain size and subgrain boundary misorientation)
and their effect on the recrystallisation behaviour of the stock. This paper presents the theory behind
the model development, the integration between the numerical techniques, and the application of the
technique to a hot rolling operation using aluminium, 1 wt% magnesium alloy. Furthermore, experimental
data from plane strain compression (PSC) tests and rolling are used to validate the modelling outcome.
The results show that the recrystallisation kinetics agree well with the experimental results for different
annealing times. This hybrid approach has proved to be more accurate than conventional methods using empirical equations
Dynamical Breakdown of Symmetry in a (2+1) Dimensional Model Containing the Chern-Simons Field
We study the vacuum stability of a model of massless scalar and fermionic
fields minimally coupled to a Chern-Simons field. The classical Lagrangian only
involves dimensionless parameters, and the model can be thought as a (2+1)
dimensional analog of the Coleman-Weinberg model. By calculating the effective
potential, we show that dynamical symmetry breakdown occurs in the two-loop
approximation. The vacuum becomes asymmetric and mass generation, for the boson
and fermion fields takes place. Renormalization group arguments are used to
clarify some aspects of the solution.Comment: Minor modifications in the text and figure
Sources and distributions of branched and isoprenoid tetraether lipids on the Amazon shelf and fan: Implications for the use of GDGT-based proxies in marine sediments
Branched glycerol dialkyl glycerol tetraethers (brGDGTs) in river fan sediments have been used successfully to reconstruct mean annual air temperature (MAAT) and soil pH of the Congo River drainage basin. However, in a previous study of Amazon deep-sea fan sediments the reconstructed MAATs were ca. 10 °C colder than the actual MAAT of the Amazon basin. In this study we investigated this apparent offset, by comparing the concentrations and distributions of brGDGTs in Amazon River suspended particulate matter (SPM) and sediments to those in marine SPM and surface sediments. The riverine brGDGT input was evident from the elevated brGDGT concentrations in marine SPM and surface sediments close to the river mouth. The distributions of brGDGTs in marine SPM and sediments varied widely, but generally showed a higher relative abundance of methylated and cyclic brGDGTs than those in the river. Since this difference in brGDGT distribution was also found in intact polar lipid (IPL)-derived brGDGTs, which were more recently produced, the change in the marine brGDGT distribution was most likely due to marine in situ production. Consequently, the MAATs calculated based on the methylation of branched tetraethers (MBT) and the cyclisation of branched tetraethers (CBT) were lower and the CBT-derived pH values were higher than those of the Amazon basin. However, SPM and sediments from stations close to the river mouth still showed MBT/CBT values that were similar to those of the river. Therefore, we recommend caution when applying the MBT/CBT proxy, it should only be used in sediment cores that were under high river influence. The influence of riverine derived isoprenoid GDGT (isoGDGT) on the isoGDGT-based TEX86 temperature proxy was also examined in marine SPM and sediments. An input of riverine isoGDGTs from the Amazon River was apparent, but its influence on the marine TEX86 was minor since the TEX86 of SPM in the Amazon River was similar to that in the marine SPM and sediments
Glauber dynamics in a single-chain magnet: From theory to real systems
The Glauber dynamics is studied in a single-chain magnet. As predicted, a
single relaxation mode of the magnetization is found. Above 2.7 K, the
thermally activated relaxation time is mainly governed by the effect of
magnetic correlations and the energy barrier experienced by each magnetic unit.
This result is in perfect agreement with independent thermodynamical
measurements. Below 2.7 K, a crossover towards a relaxation regime is observed
that is interpreted as the manifestation of finite-size effects. The
temperature dependences of the relaxation time and of the magnetic
susceptibility reveal the importance of the boundary conditions.Comment: Submitted to PRL 10 May 2003. Submitted to PRB 12 December 2003;
published 15 April 200
Low rank perturbations and the spectral statistics of pseudointegrable billiards
We present an efficient method to solve Schr\"odinger's equation for
perturbations of low rank. In particular, the method allows to calculate the
level counting function with very little numerical effort. To illustrate the
power of the method, we calculate the number variance for two pseudointegrable
quantum billiards: the barrier billiard and the right triangle billiard
(smallest angle ). In this way, we obtain precise estimates for the
level compressibility in the semiclassical (high energy) limit. In both cases,
our results confirm recent theoretical predictions, based on periodic orbit
summation.Comment: 4 page
Measuring in decays
We develop a method to measure the CKM angle without hadronic
uncertainties from the analysis of and K^\pm \D0bar
followed by singly Cabibbo-suppressed decays to non CP-eigenstates, such as
. This method utilizes the interference between and decays, and we point out several attractive features of
it. All the modes that need to be measured for this method are accessible in
the present data.Comment: 8 page
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