156 research outputs found
Fragmentation Experiment and Model for Falling Mercury Drops
The experiment consists of counting and measuring the size of the many
fragments observed after the fall of a mercury drop on the floor. The size
distribution follows a power-law for large enough fragments. We address the
question of a possible crossover to a second, different power-law for small
enough fragments. Two series of experiments were performed. The first uses a
traditional film photographic camera, and the picture is later treated on a
computer in order to count the fragments and classify them according to their
sizes. The second uses a modern digital camera. The first approach has the
advantage of a better resolution for small fragment sizes. The second, although
with a poorer size resolution, is more reliable concerning the counting of all
fragments up to its resolution limit. Both together clearly indicate the real
existence of the quoted crossover.
The model treats the system microscopically during the tiny time interval
when the initial drop collides with the floor. The drop is modelled by a
connected cluster of Ising spins pointing up (mercury) surrounded by Ising
spins pointing down (air). The Ising coupling which tends to keep the spins
segregated represents the surface tension. Initially the cluster carries an
extra energy equally shared among all its spins, corresponding to the coherent
kinetic energy due to the fall. Each spin which touches the floor loses its
extra energy transformed into a thermal, incoherent energy represented by a
temperature used then to follow the dynamics through Monte Carlo simulations.
Whenever a small piece becomes disconnected from the big cluster, it is
considered a fragment, and counted. The results also indicate the existence of
the quoted crossover in the fragment-size distribution.Comment: 6 pages, 3 figure
Estimating the global conservation status of more than 15,000 Amazonian tree species
Estimates of extinction risk for Amazonian plant and animal species are rare and not often incorporated into land-use policy and conservation planning. We overlay spatial distribution models with historical and projected deforestation to show that at least 36% and up to 57% of all Amazonian tree species are likely to qualify as globally threatened under International Union for Conservation of Nature (IUCN) Red List criteria. If confirmed, these results would increase the number of threatened plant species on Earth by 22%. We show that the trends observed in Amazonia apply to trees throughout the tropics, and we predict thatmost of the world’s >40,000 tropical tree species now qualify as globally threatened. A gap analysis suggests that existing Amazonian protected areas and indigenous territories will protect viable populations of most threatened species if these areas suffer no further degradation, highlighting the key roles that protected areas, indigenous peoples, and improved governance can play in preventing large-scale extinctions in the tropics in this century
School organizational culture: The peak of research in the context of neoliberal policies
Inscrita numa matriz teórica multirreferencial, a problemática da cultura organizacional tem sido objecto de múltiplos desenvolvimentos conceptuais e diversificadas apropriações políticas e ideológicas. No campo da educação e no contexto mais específico das organizações escolares, as abordagens culturais e simbólicas sofreram algumas inflexões teóricas apenas compreensíveis quando contextualizadas no quadro mais global das políticas internacionais de cariz neoliberal e neoconservador. Neste trabalho, procura-se reflectir criticamente sobre a forma como a problemática da cultura organizacional em contexto escolar passa a ser (re)perspectivada numa altura em que se expandem alguns objectivos e valores políticos associados às ideologias da modernização e da racionalização. Num segundo momento, tomando como ponto de partida a análise de um vasto número de investigações integradas em quatro bases de dados electrónicas de âmbito internacional, debatemos as principais tendências teóricas, conceptuais e metodológicas deste campo de estudo, fazendo sobressair o lugar e o estatuto da escola enquanto contexto privilegiado de investigação, designadamente nos domínios crítico-reflexivos.Within a multi-referential theoretical framework, the issue of organizational culture has been a subject for multiple conceptual developments and different ideological and political appropriations. In the field of education and in the specific context of school organizations, the cultural and symbolic approaches were subjected to some theoretical inflections. These can only be understood in the global framework of international policies of neoliberal and neoconservative nature. First, this paper critically discusses how the issue of organizational culture in school context was put in perspectives at a time when some political-ideological objectives and values were associated to modernization and rationalization ideologies. Based on the analysis of a great number of researches included in four electronic databases with an international scope, it then discusses the main theoretical, conceptual and methodological trends of this field of study, stressing the place and statute of school as a privileged research context, namely in the reflexive and critical domain.info:eu-repo/semantics/publishedVersio
Implementação e otimização de projeto para certificação do MDL em estação de tratamento de águas residuárias
Ocotea Aubl. (Lauraceae) no Núcleo Curucutu, Parque Estadual da Serra do Mar, São Paulo, SP, Brasil
A subfamília Faboideae (Fabaceae Lindl.) no Parque Estadual do Guartelá, Paraná, Brasil
Resource partitioning and ecomorphological variation in two syntopic species of Lebiasinidae (Characiformes) in an Amazonian stream
Detecção de Aethalion reticulatum (L., 1767) (Hemiptera: Aethalionidae) em alfavaca-cravo (Ocimum gratissimum L.) e observações sobre sua ocorrência
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