150 research outputs found
Helicity conservation by flow across scales in reconnecting vortex links and knots
The conjecture that helicity (or knottedness) is a fundamental conserved quantity has a rich history in fluid mechanics, but the nature of this conservation in the presence of dissipation has proven difficult to resolve. Making use of recent advances, we create vortex knots and links in viscous fluids and simulated superfluids and track their geometry through topology-changing reconnections. We find that the reassociation of vortex lines through a reconnection enables the transfer of helicity from links and knots to helical coils. This process is remarkably efficient, owing to the antiparallel orientation spontaneously adopted by the reconnecting vortices. Using a new method for quantifying the spatial helicity spectrum, we find that the reconnection process can be viewed as transferring helicity between scales, rather than dissipating it. We also infer the presence of geometric deformations that convert helical coils into even smaller scale twist, where it may ultimately be dissipated. Our results suggest that helicity conservation plays an important role in fluids and related fields, even in the presence of dissipation
Time- and Dose-Dependent Induction of HSP70 in Lemna minor Exposed to Different Environmental Stressors
The objective of this study was to examine the influence of different stressors, including cadmium (heavy metal), anthracene (polycyclic aromatic hydrocarbon—PAH) and chloridazon (herbicide), on population growth and biosynthesis of cytoplasmic HSP70 in Lemna minor (duckweed) in short (4 h)- and long (7 days)-term tests. A heat shock response was confirmed in Lemna exposed to high temperature: 35, 37.5, 40, or 42.5°C in short-term (4 h) treatments. The chemicals tested stimulated the biosynthesis of the cytoplasmic HSP70 protein in a concentration-dependent way (0.5–5 μM), higher in fronds exposed to lower doses of stressors. Additionally, production of HSP70 was greater after 4 h of incubation than after 7 days. The results suggest that HSP70 could be applied as a non-specific and sensitive detector of stress induced by different chemicals at concentrations below those that produce the type of response observed in classical cytotoxicity tests, such as growth inhibition
Mining conflicts around the world: Common grounds from an Environmental Justice perspective
Abstract.
This report aims at exploring contemporary mining conflicts in the context of the
sustainable development and environmental justice movement. This is done
based on 24 real case studies from 18 different countries which are described by
local activists and scholars. While 17 of the reported cases focus on conflicts
related to metal mining (e.g. gold, silver, copper, zinc, and lead), four address
uranium mining and one refers to coal mining. As an example of a new frontier in
the industry, a sand mining conflict from India is also reported.
All of these cases are directly chosen and reported, either in factsheet or in-depth
study format, by EJOs, as part of a knowledge sharing activity well-established in
EJOLT between EJOs and the academic community. Although the cases covered
here are all quite unique and diverse in terms of type of conflict and geographical
setting, they all share a common frame of analysis. First, the project and type of
conflict are characterized in a nutshell, with some basic factual background that
describe the companies involved, and the communities and locations affected.
The roots of the conflicts are explored next, as well as relevant socioeconomic,
cultural, health, and ecological impacts and related community claims. Where
relevant, means of resistance are also specified with their influence on the project
and/or the outcome of the conflict.
The report then offers a synthesis of the described mining cases, review their
commonalities, link gained insights with research needs and discuss some policy
recommendations that might follow from this analysis. Despite its limitations,
compiling such a diverse set of mining conflicts that builds on EJO knowledge
promotes mutual learning and collaboration among stakeholders, EJOs and
academia, which is one of the key objectives of EJOLT
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