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971.
The selective catalytic reduction (SCR) rate of NO with N-containing reducing agents can be enhanced considerably by converting
part of NO into NO2. The enhanced reaction rate is more pronounced even at lower temperatures by using an equimolar mixture of NO and NO2 (fast SCR reaction). The oxidation characteristics of NO over catalyst Pt/TiO2 have been determined in a fixed bed reactor (8 mm-ID) with different concentrations of oxygen, nitric oxide and nitrogen
dioxide in the presence of 8% water. The conversion of NO to NO2 increases with increasing oxygen (O2) concentration from 3 to 12%, but it levels off at higher O2 concentrations. The NO conversion to NO2 decreases with increasing NO concentration and it also decreases by an addition of NO2 in the feed stream. Therefore, the oxidation of NO over Pt/TiO2 catalyst could be auto-inhibited by the reaction product of NO2. The effects of CO and SO2 on NO oxidation characteristics have also been determined. In fact, the presence of SO2 significantly suppresses oxidation of NO but due to the less stability of sulfate on anatase structure in TiO2, it becomes less significant. On the other hand, the presence of CO increases NO oxidation significantly due to the auto-inhibition
effect by CO. Moreover, the effect of SO2/CO on NO oxidation has also been determined and it was observed that NO oxidation decreases with the increase in SO2/CO ratio. 相似文献
972.
Gabi N. Waite Stéphane J. P. Egot-Lemaire Walter X. Balcavage 《The Environmentalist》2011,31(2):107-113
Over the past decades, strong evidence has accumulated that low-frequency electromagnetic fields (EMFs) can be useful in treating
human pathologies, such as bone fractures, soft tissue illnesses, and pain. Common strategies for the design of commercial
therapeutic devices are to generate EMFs that simulate body endogenous EMFs, or EMFs that resonate with a particular biological
process, such as the natural motions of ions. We recently came across a biologically active commercial EMF signal that seems
to be different. The signal is generated by summing the fundamental frequencies and harmonics of several periodic base signals
which remain proprietary to the company. When first examined in the time domain, the signal resembled electronic noise; however,
when critically analyzed, the signal is not identical with noise. Rather, it is a highly complex waveform exhibiting a very
wide range of values for the time derivative of the magnetic field density (dB/dt) and a beat frequency in the Extremely Low-Frequency
range. In this paper, we speculate on the mechanism of action of this and similar signals. We consider it less likely that
cells, or cell components, act like filters to extract and couple with individual signals that make up the complex EMF signal.
Consequently, we favor the possibility that with the signal discussed here cells respond to the very complex signal and that
the biological response can be modified by the presence of a beat in the signal, in this case a low-frequency beat. More generally,
this would suggest the hypothesis that biological processes can be regulated by noise-like signals and that the effects of
a noisy signal can be modified by the presence of signal repetition patterns, such as beats. Given the very small energy that
signals like these can transduce into a biological system, biological effects can be expected only when the molecular processes
involved are poised so that the available energy leads to molecular reactions that achieve the activation state for the reaction. 相似文献
973.
Marko S. Markov 《The Environmentalist》2011,31(2):89-96
Natural and man-made magnetic and electromagnetic fields are important factors in the contemporary life. The paper discusses
the role of environmental magnetic and electromagnetic fields in origin and evolution of life. A brief review of the characteristics
of Earth magnetic field, Earth magnetosphere, and their role as a shield for cosmic radiation follows. The role of endogenous
and exogenous magnetic fields is discussed in respect of the clarification of the potential hazard and benefit of electromagnetic
fields. The second part of the paper discusses the mechanisms of detection and response to exogenous electromagnetic fields,
as well as threshold versus window hypothesis for mechanisms of interactions. Finally, the necessity of accurate dosimetry
at the target site and the importance of relevant research and clinical protocols in studying biological responses are pointed
out. 相似文献
974.
975.
Throughout the world there is a general consensus among environmentalists that there should be an increase in the amount of
marine area that should be reserved in marine protected areas (MPAs). In fact, the 1998 Philippines Fishery Code indicates
a need for designation of at least 15% of municipal waters for fish refuges or sanctuaries. Such an increase in area would
take productive fishing areas away from fishing communities that can ill-afford the loss. The larger the protected area, there
will be a greater number of people impacted. This article examines the relationship between factors that influence the success
of Community Based MPA (CBMPA) performance in the Visayas, Philippines and their significance in efforts to increase the size
of protected areas. 相似文献
976.
Cetacean-focused tourism in Taiwan has grown rapidly since 1997. This development, measured in terms of both number of tour
boats and visitors, has resulted in many resource management challenges stemming from the absence of regulation and scientific
data. To fill this void in empirical evidence, we used 464 sighting records from 2002 to 2005 to model the impact of cetacean-focused
tourism. Cox proportional hazard analysis indicated cetacean avoidance responses to cetacean watching boats were strongly
associated with pod size, mother–calf pairs, and cetacean-vessel distances. Mother–calf pairs abandoned their avoidance tactic
by 55% compared to noncalf groups when tour boats approached. Second, the hazard ratio of abundance was 0.996, suggesting
that the odds of encountering avoidance responses by the cetaceans decreased by 42% for every 100-member increase in the cetacean
pod size. Last, distances maintained by boats from the cetaceans was positively related to avoidance responses (i.e., less
avoidance behavior with closer interaction). Based on our findings, we have the following recommendations: (a) limit vessels
from approaching mothers with calves, (b) limit vessels from approaching small groups of cetaceans, (c) reduced avoidance
behavior to boat traffic may be a red flag for potential long-term disturbance, and (d) apply the “precautionary principle”
based on the best scientific information available in cetacean-based tourism in Taiwan. These recommendations will help contribute
to the sustainable development of cetacean-focused tourism in Taiwan. 相似文献
977.
This article examines one MPA—the Gulf of Mannar National Park and Biosphere Reserve—located in southern India, and four types
of social conflict that have surrounded its establishment. Taking the strength of wellbeing aspirations as point of departure,
we focus on two themes: the implications of MPA embeddedness in wider societal systems, and the consequences of natural and
social variety for governance. We conclude first of all that conflict resolution depends on MPA authorities’ willingness to
engage with the interferences that emerge from outside the MPA area. Secondly, we point out the varying wellbeing aspirations
of the population and the need to develop governance partnerships. The latter are argued to contribute to more balanced decision
making, as well as to a greater appreciation among the target population of the ‘fairness’ of MPA policy. 相似文献
978.
Marine Protected Dramas: The Flaws of the Brazilian National System of Marine Protected Areas 总被引:1,自引:0,他引:1
Leopoldo C. Gerhardinger Eduardo A. S. Godoy Peter J. S. Jones Gilberto Sales Beatrice P. Ferreira 《Environmental management》2011,47(4):630-643
This article discusses the current problems and issues associated with the implementation of a National System of Marine Protected
Areas in Brazil. MPA managers and higher governmental level authorities were interviewed about their perceptions of the implementation
of a national MPA strategy and the recent changes in the institutional arrangement of government marine conservation agencies.
Interviewees’ narratives were generally pessimistic and the National System was perceived as weak, with few recognizable marine
conservation outcomes on the ground. The following major flaws were identified: poor inter-institutional coordination of coastal
and ocean governance; institutional crisis faced by the national government marine conservation agency; poor management within
individual MPAs; problems with regional networks of marine protected areas; an overly bureaucratic management and administrative
system; financial shortages creating structural problems and a disconnect between MPA policy and its delivery. Furthermore,
a lack of professional motivation and a pessimistic atmosphere was encountered during many interviews, a malaise which we
believe affects how the entire system is able to respond to crises. Our findings highlight the need for a better understanding
of the role of ‘leadership’ in the performance of socio-ecological systems (such as MPA networks), more effective official
evaluation mechanisms, more localized audits of (and reforms if necessary to) Brazil’s federal biodiversity conservation agency
(ICMBio), and the need for political measures to promote state leadership and support. Continuing to focus on the designation
of more MPAs whilst not fully addressing these issues will achieve little beyond fulfilling, on paper, Brazil’s international
marine biodiversity commitments. 相似文献
979.
The Fate of Priority Areas for Conservation in Protected Areas: A Fine-Scale Markov Chain Approach 总被引:1,自引:0,他引:1
Park managers in alpine areas must deal with the increase in forest coverage that has been observed in most European mountain
areas, where traditional farming and agricultural practices have been abandoned. The aim of this study is to develop a fine-scale
model of a broad area to support the managers of Paneveggio Nature Park (Italy) in conservation planning by focusing on the
fate of priority areas for conservation in the next 50–100 years. GIS analyses were performed to assess the afforestation
dynamic over time using two historical maps (from 1859 and 1936) and a series of aerial photographs and ortho-photos (taken
from 1954 to 2006) covering a time span of 150 years. The results show an increase in the forest surface area of about 35%.
Additionally, the forest became progressively more compact and less fragmented, with a consequent loss of ecotones and open
habitats that are important for biodiversity. Markov chain-cellular automata models were used to project future changes, evaluating
the effects on a habitat scale. Simulations show that some habitats defined as priority by the EU Habitat Directive will be
compromised by the forest expansion by 2050 and suffer a consistent loss by 2100. This protocol, applied to other areas, can
be used for designing long-term management measures with a focus on habitats where conservation status is at risk. 相似文献
980.
Rosenfeld J Hogan D Palm D Lundquist H Nilsson C Beechie TJ 《Environmental management》2011,47(1):28-39
Sediment size and supply exert a dominant control on channel structure. We review the role of sediment supply in channel structure,
and how regional differences in sediment supply and landuse affect stream restoration priorities. We show how stream restoration
goals are best understood within a common fluvial geomorphology framework defined by sediment supply, storage, and transport.
Landuse impacts in geologically young landscapes with high sediment yields (e.g., coastal British Columbia) typically result
in loss of instream wood and accelerated sediment inputs from bank erosion, logging roads, hillslopes and gullies. In contrast,
northern Sweden and Finland are landscapes with naturally low sediment yields caused by low relief, resistant bedrock, and
abundant mainstem lakes that act as sediment traps. Landuse impacts involved extensive channel narrowing, removal of obstructions,
and bank armouring with boulders to facilitate timber floating, thereby reducing sediment supply from bank erosion while increasing
export through higher channel velocities. These contrasting landuse impacts have pushed stream channels in opposite directions
(aggradation versus degradation) within a phase-space defined by sediment transport and supply. Restoration in coastal British
Columbia has focused on reducing sediment supply (through bank and hillslope stabilization) and restoring wood inputs. In
contrast, restoration in northern Fennoscandia (Sweden and Finland) has focused on channel widening and removal of bank-armouring
boulders to increase sediment supply and retention. These contrasting restoration priorities illustrate the consequences of
divergent regional landuse impacts on sediment supply, and the utility of planning restoration activities within a mechanistic
sediment supply-transport framework. 相似文献