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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.
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.
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.
Oil is the world’s primary source of non-renewable energy, and it has also contaminated ocean coastlines due to spills. It is therefore important to have remediation treatments that are both effective, and ecologically not harmful. Current in situ bioremediation methods consist primarily of biostimulation, through addition of nutrients, and bioaugmentation, the addition of hydrocarbon degrading microorganisms. The purpose of this article is to discuss successful and unsuccessful remediation through the use of biostimulation, bioaugmentation, or a combination of both. As microbial treatments are capable of enhancing coastal oil remediation in temperate and tropical settings, the success of a particular remediation approach will be determined based on the type and amount of oil, type of soil and/or sediment, microbial inoculants and the often changing physical, chemical and biological environmental conditions. Environmental factors and limitations will be discussed as to why certain bioremediation events were successful while others were not.  相似文献   
975.
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   
976.
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   
977.
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   
978.
Major Forest Types and the Evolution of Sustainable Forestry in China   总被引:1,自引:0,他引:1  
Dai L  Wang Y  Su D  Zhou L  Yu D  Lewis BJ  Qi L 《Environmental management》2011,48(6):1066-1078
In this article, we introduce China’s major forest types and discuss the historical development of forest management in China, including actions taken over the last decade toward achieving SMF. Major challenges are identified, and a strategy for SFM implementation in China is presented. China’s forests consist of a wide variety of types with distinctive distributional patterns shaped by complex topography and multiple climate regimes. How to manage this wide array of forest resources has challenged forest managers and policy-makers since the founding of the country. Excessive exploitation of China's forest resources from the 1950s to the late 1990s contributed to environmental problems and calamities, such as floods, soil erosion, and desertification. At the start of the new millennium, the Chinese government decided to shift its emphasis from timber production towards the achievement of sustainable forest management (SFM). With a series of endeavors such as the implementation of the “Six Key Forestry Projects” and the reform of forest tenure policies, and the adoption of a classification system for China's forests, a beginning has been made at reversing the trend of environmental degradation that occurred throughout the latter half of the last century. At the same time, huge challenges remain to be tackled for the development of forestry in China.  相似文献   
979.
We demonstrate the use of an expert-assisted spatial model to examine geographic factors influencing the poaching risk of a rare plant (American ginseng, Panax quinquefolius L.) in Shenandoah National Park, Virginia, USA. Following principles of the analytic hierarchy process (AHP), we identified a hierarchy of 11 geographic factors deemed important to poaching risk and requested law enforcement personnel of the National Park Service to rank those factors in a series of pair-wise comparisons. We used those comparisons to determine statistical weightings of each factor and combined them into a spatial model predicting poaching risk. We tested the model using 69 locations of previous poaching incidents recorded by law enforcement personnel. These locations occurred more frequently in areas predicted by the model to have a higher risk of poaching than random locations. The results of our study can be used to evaluate resource protection strategies and to target law enforcement activities.  相似文献   
980.
Recently Prévot-Julliard and colleagues presented a concept paper on biological conservation strategies using exotic species as a case study. They emphasized the difficulty of integrating conservation into a broad picture that accounts for public perception as well as scientific knowledge. We support this general call for better integration of society in conservation research, but we believe that the original framework might misguide conservation practices if wrongly interpreted. Our objective is to complement their paper and correct a few misleading points, by showing that (1) for regions of high endemicity “reservation” may be the best conservation practice, and does not prevent public participation, (2) aiming for broad societal agreement is valuable, but in some cases risky, and always complex, and (3) calling a harmful invasive species harmful shouldn’t be an issue. The Australian context provides us with many cases of the labeling of exotic species as harmful or not, using inputs from scientists, industry, and the public. Integration of social and scientific points of view can only improve conservation on the ground if it allows managers to use the ecological, economic and social impacts of exotic species to prioritize conservation actions in an operative way.  相似文献   
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