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排序方式: 共有276条查询结果,搜索用时 15 毫秒
1.
Alf Hornborg 《Ethnos》2013,78(1):21-32
Animistic or ‘relational’ ontologies encountered in non-Western (i.e. premodern) settings pose a challenge to Western (i.e. modern) knowledge production, as they violate fundamentalassumptions of Cartesian science. Naturalscientists who have tried seriously to incorporate subject-subject relations into their intellectual practice (e.g. Uexküll, Bateson) have inexorably been relegated to the margins. Surrounded by philosophers and sociologists of science (e.g. Latour) announcing the end of Cartesian objectivism, however,late modern or ‘post-modern’ anthropologists discussing animistic understandings of nature will be excused for taking them more seriously than their predecessors. It is incumbent on them to analytically sort out what epistemological options there are, and to ask why pre-modern, modern, and post-modern people will tend to deal with culture/nature or subject/object hybridity in such different ways. Animism, fetishism, and objectivism can be understood as alternative responses to universal semiotic anxieties about where or how to draw boundaries between persons and things. 相似文献
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Seafloor integrity is threatened by disturbances owing to human activities. The capacity of the system to recover from disturbances, as well as maintain resilience and function, depends on dispersal. In soft-sediment systems, dispersal continues after larval settlement, but there are very few measurements of how far the post-settlers disperse in nature. Spatial scales of post-settlement dispersal are, however, likely to be similar to pelagic larval dispersal because of continued, frequent, small-scale dispersal over longer periods. The consequences of this dispersal may be more important for the maintenance of biodiversity and metacommunity dynamics than is pelagic larval dispersal, because of the greater size and competency of the dispersers. We argue that an increased empirical understanding of post-settlement dispersal processes is key for predicting how benthic communities will respond to local disturbances and shrinking regional species pools, with implications for monitoring, managing and conserving biodiversity. 相似文献
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Ralf Watzlawick Elisabeth E. Kenngott Francesca Diane M. Liu Jan M. Schwab Alf Hamann 《PloS one》2015,10(9)
Rapid activation of the innate immune system is critical for an efficient host response to invading pathogens. However, the inflammatory reaction has to be strictly controlled to minimize harmful immunopathology. A number of mediators including the cytokine interleukin-27 (IL-27) appear to be responsible for limitation and resolution of inflammation. Despite increasing knowledge of its suppressive effects on T cells, the influence on neutrophils and macrophages is poorly understood. To determine the role of IL-27 in innate immune responses we analysed the effect of IL-27 in a T cell independent model of zymosan-induced peritonitis. Early administration of recombinant IL-27 strongly reduced the number of neutrophils recruited to the peritoneal cavity after zymosan application as well as the neutrophil frequency in the blood. Simultaneously, IL-27 reduced the release of neutrophils from the bone marrow upon inflammation. Although cytokine levels were not affected by IL-27 treatment, the levels of the chemokines KC, MCP-1 and MIP-1α in the peritoneal fluid were strongly decreased. These findings demonstrate that IL-27 is able to control mobilisation and recruitment of neutrophils into the peritoneal cavity and identify a novel mechanism to limit inflammation caused by innate immune cells. 相似文献
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Sebastian Valanko Jani Heino Mats Westerbom Markku Viitasalo Alf Norkko 《Ecology and evolution》2015,5(22):5203-5215
The majority of studies in metacommunity ecology have focused on systems other than marine benthic ecosystems, thereby providing an impetus to broaden the focus of metacommunity research to comprise marine systems. These systems are more open than many other systems and may thus exhibit relatively less discrete patterns in community structure across space. Metacommunity structure of soft‐sediment benthic invertebrates was examined using a fine‐grained (285 sites) data set collected during one summer across a large spatial extent (1700 km2). We applied the elements of metacommunity structure (EMS) approach, allowing multiple hypothesis of variation in community structure to be tested. We demonstrated several patterns associated with environmental variation and associated processes that could simultaneously assemble species to occur at the sites. A quasi‐Clementsian pattern was observed frequently, suggesting interdependent ecological relationships among species or similar response to an underlying environmental gradient across sites. A quasi‐nested clumped species loss pattern was also observed, which suggests nested habitat specialization. Species richness declined with depth (from 0.5 to 44.8 m). We argue that sensitive species may survive in shallower water, which are more stable with regard to oxygen conditions and present greater habitat complexity, in contrast to deeper waters, which may experience periodic disturbance due to hypoxia. Future studies should better integrate disturbance in terms of temporal dynamics and dispersal rates in the EMS approach. We highlight that shallow water sites may act as sources of recruitment to deeper water sites that are relatively more prone to periodic disturbances due to hypoxia. However, these shallow sites are not currently monitored and should be better prioritized in future conservation strategies in marine systems. 相似文献
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The two components of soil respiration, autotrophic respiration (from roots, mycorrhizal hyphae and associated microbes) and heterotrophic respiration (from decomposers), was separated in a root trenching experiment in a Norway spruce forest. In June 2003, cylinders (29.7 cm diameter) were inserted to 50 cm soil depth and respiration was measured both outside (control) and inside the trenched areas. The potential problems associated with the trenching treatment, increased decomposition of roots and ectomycorrhizal mycelia and changed soil moisture conditions, were handled by empirical modelling. The model was calibrated with respiration, moisture and temperature data of 2004 from the trenched plots as a training set. We estimate that over the first 5 months after the trenching, 45% of respiration from the trenched plots was an artefact of the treatment. Of this, 29% was a water difference effect and 16% resulted from root and mycelia decomposition. Autotrophic and heterotrophic respiration contributed to about 50% each of total soil respiration in the control plots averaged over the two growing seasons. We show that the potential problems with the trenching, decomposing roots and mycelia and soil moisture effects, can be handled by a modelling approach, which is an alternative to the sequential root harvesting technique. 相似文献
7.
Vivi Andasari Alf Gerisch Georgios Lolas Andrew P. South Mark A. J. Chaplain 《Journal of mathematical biology》2011,63(1):141-171
The ability of cancer cells to break out of tissue compartments and invade locally gives solid tumours a defining deadly characteristic.
One of the first steps of invasion is the remodelling of the surrounding tissue or extracellular matrix (ECM) and a major
part of this process is the over-expression of proteolytic enzymes, such as the urokinase-type plasminogen activator (uPA)
and matrix metalloproteinases (MMPs), by the cancer cells to break down ECM proteins. Degradation of the matrix enables the
cancer cells to migrate through the tissue and subsequently to spread to secondary sites in the body, a process known as metastasis.
In this paper we undertake an analysis of a mathematical model of cancer cell invasion of tissue, or ECM, which focuses on
the role of the urokinase plasminogen activation system. The model consists of a system of five reaction-diffusion-taxis partial
differential equations describing the interactions between cancer cells, uPA, uPA inhibitors, plasmin and the host tissue.
Cancer cells react chemotactically and haptotactically to the spatio-temporal effects of the uPA system. The results obtained
from computational simulations carried out on the model equations produce dynamic heterogeneous spatio-temporal solutions
and using linear stability analysis we show that this is caused by a taxis-driven instability of a spatially homogeneous steady-state.
Finally we consider the biological implications of the model results, draw parallels with clinical samples and laboratory
based models of cancer cell invasion using three-dimensional invasion assay, and go on to discuss future development of the
model. 相似文献
8.
Fabio Attorre Marco Alfò Michele De Sanctis Fabio Francesconi Roberto Valenti Marcello Vitale Franco Bruno 《应用植被学》2011,14(2):242-255
Question: What is the effect of climate change on tree species abundance and distribution in the Italian peninsula? Location: Italian peninsula. Methods: Regression tree analysis, Random Forest, generalized additive model and geostatistical methods were compared to identify the best model for quantifying the effect of climate change on tree species distribution and abundance. Future potential species distribution, richness, local colonization, local extinction and species turnover were modelled according to two scenarios (A2 and B1) for 2050 and 2080. Results: Robust Random Forest proved to be the best statistical model to predict the potential distribution of tree species abundance. Climate change could lead to a shift in tree species distribution towards higher altitudes and a reduction of forest cover. Pinus sylvestris and Tilia cordata may be considered at risk of local extinction, while the other species could find potential suitable areas at the cost of a rearrangement of forest community composition and increasing competition. Conclusions: Geographical and topographical regional characteristics can have a noticeable influence on the impact of predicted climate change on forest ecosystems within the Mediterranean basin. It would be highly beneficial to create a standardized and harmonized European forest inventory in order to evaluate, at high resolution, the effect of climate change on forest ecosystems, identify regional differences and develop specific adaptive management strategies and plans. 相似文献
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