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141.
Wannapa Chumeka Varaporn Tanrattanakul Jean-François Pilard Pamela Pasetto 《Journal of Polymers and the Environment》2013,21(2):450-460
Natural rubber grafted with poly(vinyl acetate) copolymer (NR-g-PVAc) was synthesized by emulsion polymerization. Three graft copolymers were prepared with different PVAc contents: 1 % (G1), 5 % (G5) and 12 % (G12). Poly(lactic acid) (PLA) was melt blended with natural rubber (NR) and/or NR-g-PVAc in a twin screw extruder. The blends contained 10–20 wt% rubber. The notched Izod impact strength and tensile properties were determined from the compression molded specimens. The effect of NR mastication on the mechanical properties of the PLA/NR/NR-g-PVAc blend was evaluated. Characterization by DMTA and DSC showed an enhancement in miscibility of the PLA/NR-g-PVAc blend. The temperature of the maximum tan δ of the PLA decreased with increasing PVAc content in the graft copolymer, i.e., from 71 °C (pure PLA) to 63 °C (the blend containing 10 % G12). The increase in miscibility brought about a reduction in the rubber particle diameter. These changes were attributed to the enhancement of toughness and ductility of PLA after blending with NR-g-PVAc. Therefore, NR-g-PVAc could be used as a toughening agent of PLA and as a compatibilizer of the PLA/NR blend. NR mastication was an efficient method for increasing the toughness and ductility of the blends which depended on the blend composition and the number of mastications. 相似文献
142.
Perfluoroalkyl chemicals (PFCs) have been used as surfactants and stain repellants in a variety of consumer products for more than 50 years and there is growing concern regarding their persistence and toxicity. Human exposure to these chemicals is essentially universal in North America and researchers have linked them to a variety of health problems ranging from higher rates of cancer, to developmental and reproductive problems, and higher cholesterol levels. Major exposure pathways are food and water ingestion, dust ingestion via hand to mouth transfer. In an effort to assess residential exposure, the Wisconsin Department of Health Services tested vacuum cleaner contents from thirty-nine homes for 16 perflouroalkyl chemicals. PFOS, PFOA, PFHxS, PFHpA and PFNA were found in all of the vacuum dust samples and dust from eight homes contained all 16 PFCs included in our analysis. The most commonly detected compounds were perfluorooctanesulfonate (PFOS), perfluorohexanesulfonate (PFHxS) and perfluorooctanoic acid (PFOA) which together made up 70% of the total PFC residues in dust from these homes. Summed PFC concentrations in these dust samples ranged from 70 to 2513 ng/g (median 280 ng/g). Our investigation suggests that these chemicals may be ubiquitous contaminants in US homes. 相似文献
143.
Ralph I. Larsen Thomas R. McCurdy Pamela M. Johnson Walter W. Heck 《Journal of the Air & Waste Management Association (1995)》2013,63(12):1497-1503
Soybean percent crop reduction was estimated as a function of ambient O3 concentrations for each of 80 agricultural sites in the National Aerometric Data Bank (NADB) for each available year of data for years 1981-1985. Fourteen O3 concentration statistics were calculated for each of the resulting 320 site-years of data. The two statistics that correlated best with estimated crop reduction were an effective mean O3 concentration (1 percent of variance unexplained) and an arithmetic mean O3 concentration (4 percent unexplained). The worst correlation of the 14 was for the statistic used in the present O3 National Ambient Air Quality Standard (NAAQS), the second highest daily maximum 1-h O3 concentration (42 percent unexplained). The number of site-years for estimated percent soybean yield reductions was plotted versus increasing O3 concentrations for each of the 14 O3 statistics. A maximum crop reduction line was drawn on each plot. These lines were used to estimate (and list) potential ambient O3 standards for each of the 14 statistics that would limit soybean crop reduction at agricultural. NADB sites to 5, 10, 15, or 20 percent. 相似文献
144.
The role of self‐regulation in the relationship between abusive supervision and job tension
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Trait and state self‐regulation both have critical influences on workplace behavior, but their influences are thought to operate quite differently. We draw from social exchange and ego depletion theories to investigate the relationship between trait and state self‐regulation, as well as how they differentially affect the relationship between subordinates' perceptions of abusive supervision and job tension. Specifically, we examine (a) how the interaction between abusive supervision and trait self‐regulation affects job tension and (b) how state self‐regulation mediates the relationship between abusive supervision and job tension. Using 3 studies that include an experiment (n = 81) and 2 field studies with cross‐sectional (n = 157) and time‐separated (n = 109) data, we demonstrate that the interaction between abusive supervision and trait self‐regulation increases experienced job tension for subordinates who report higher levels of abusive supervision and trait self‐regulation than others. Also, we provide evidence that abusive supervision is indirectly associated with job tension through state self‐regulation. This study's findings have important implications for abusive supervision and self‐regulation research, as well as social exchange and ego depletion theories, because we extend our understanding of how trait and state self‐regulation affect cognitive responses associated with abusive supervision. 相似文献
145.
Glenn EP Hucklebridge K Hinojosa-Huerta O Nagler PL Pitt J 《Environmental management》2008,41(3):322-335
Arid zone rivers have highly variable flow rates, and flood control projects are needed to protect adjacent property from
flood damage. On the other hand, riparian corridors provide important wildlife habitat, especially for birds, and riparian
vegetation is adapted to the natural variability in flows on these rivers. While environmental and flood control goals might
appear to be at odds, we show that both goals can be accommodated in the Limitrophe Region (the shared border between the
United States and Mexico) on the Lower Colorado River. In 1999, the International Boundary and Water Commission proposed a
routine maintenance project to clear vegetation and create a pilot channel within the Limitrophe Region to improve flow capacity
and delineate the border. In 2000, however, Minute 306 to the international water treaty was adopted, which calls for consideration
of environmental effects of IBWC actions. We conducted vegetation and bird surveys within the Limitrophe and found that this
river segment is unusually rich in native cottonwood and willow trees, marsh habitat, and resident and migratory birds compared
to flow-regulated segments of river. A flood-frequency analysis showed that the existing levee system can easily contain a
100 year flood even if vegetation is not removed, and the existing braided channel system has greater carrying capacity than
the proposed pilot channel. 相似文献
146.
Polybrominated diphenyl ethers (PBDE) in serum: findings from a US cohort of consumers of sport-caught fish 总被引:2,自引:0,他引:2
Polybrominated diphenyl ethers (PBDEs) have been used as flame retardants in foams, fabrics and plastics, and are common contaminants of household air and dust and bioaccumulate in wildlife, and are detectable in human tissues and in fish and animal food products. In the Great Lakes Basin sport fish consumption has been demonstrated to be an important source of PCB and DDE exposure. PBDEs are present in the same sport fish but prior to our study the contribution to human PBDE body burdens from Great Lakes sport fish consumption had not been investigated. This study was designed to assess PBDE, PCB and 1,1-bis(4-chlorophenyl)-2,2-dichloroethene (DDE) serum concentrations in an existing cohort of 508 frequent and infrequent consumers of sport-caught fish living in five Great Lake states. BDE congeners 47 and 99 were identified in the majority of blood samples, 98% and 62% respectively. summation operatorPBDE levels were positively associated with age, hours spent outdoors, DDE, summation operatorPCB, years of sportfish consumption, and catfish and shellfish intake, and negatively associated with income and recent weight loss. Other dietary components collected were not predictive of measured summation operatorPBDE levels. In multivariate models, summation operatorPBDE levels were positively associated with age, years consuming sport fish, shellfish meals, and computer use and negatively associated with recent weight loss. Having summation operatorPBDE levels in the highest quintile was independently associated with older age, male gender, consumption of catfish and shellfish, computer use and spending less time indoors. summation operatorPCB and DDE were strongly associated suggesting common exposure routes. The association between summation operatorPBDE and summation operatorPCB or DDE was much weaker and modeling suggested more diverse PBDE sources with few identified multi-contaminant-shared exposure routes. In our cohort Great Lakes sport fish consumption does not contribute strongly to PBDE exposure. 相似文献
147.
Victoria Reyes-García lvaro Fernndez-Llamazares Yildiz Aumeeruddy-Thomas Petra Benyei Rainer W. Bussmann Sara K. Diamond David García-del-Amo Sara Guadilla-Sez Natalia Hanazaki Nicolas Kosoy Margarita Lavides Ana C. Luz Pamela McElwee Vicky J. Meretsky Teresa Newberry Zsolt Molnr Isabel Ruiz-Malln Matthieu Salpeteur Felice S. Wyndham Francisco Zorondo-Rodriguez Eduardo S. Brondizio 《Ambio》2022,51(1):84
The Convention on Biological Diversity is defining the goals that will frame future global biodiversity policy in a context of rapid biodiversity decline and under pressure to make transformative change. Drawing on the work of Indigenous and non-Indigenous scholars, we argue that transformative change requires the foregrounding of Indigenous peoples’ and local communities’ rights and agency in biodiversity policy. We support this argument with four key points. First, Indigenous peoples and local communities hold knowledge essential for setting realistic and effective biodiversity targets that simultaneously improve local livelihoods. Second, Indigenous peoples’ conceptualizations of nature sustain and manifest CBD’s 2050 vision of “Living in harmony with nature.” Third, Indigenous peoples’ and local communities’ participation in biodiversity policy contributes to the recognition of human and Indigenous peoples’ rights. And fourth, engagement in biodiversity policy is essential for Indigenous peoples and local communities to be able to exercise their recognized rights to territories and resources. 相似文献
148.
Thomas J. SmithIII Ginger Tiling Pamela S. Leasure 《Journal of Coastal Conservation》2007,11(1):67-74
The wetlands surrounding Tampa Bay, Florida were extensively ditched for mosquito control in the 1950s. Spoil from ditch construction
was placed adjacent to the wetlands ditches creating mound-like features (spoil-mounds). These mounds represent a loss of
14% of the wetland area in Tampa Bay. Spoil mounds interfere with tidal flow and are locations for non-native plants to colonize
(e.g., Schinus terebinthifolius). Removal of the spoil mounds to eliminate exotic plants, restore native vegetation, and re-establish natural hydrology is
a restoration priority for environmental managers. Hydro-leveling, a new technique, was tested in a mangrove forest restoration
project in 2004. Hydro-leveling uses a high pressure stream of water to wash sediment from the spoil mound into the adjacent
wetland and ditch. To assess the effectiveness of this technique, we conducted vegetation surveys in areas that were hydro-leveled
and in non-hydro-leveled areas 3 years post-project. Adult Schinus were reduced but not eliminated from hydro-leveled mounds. Schinus seedlings however were absent from hydro-leveled sites. Colonization by native species was sparse. Mangrove seedlings were
essentially absent (≈2 m−2) from the centers of hydro-leveled mounds and were in low density on their edges (17 m−2) in comparison to surrounding mangrove forests (105 m−2). Hydro-leveling resulted in mortality of mangroves adjacent to the mounds being leveled. This was probably caused by burial
of pneumatophores during the hydro-leveling process. For hydro-leveling to be a useful and successful restoration technique
several requirements must be met. Spoil mounds must be lowered to the level of the surrounding wetlands. Spoil must be distributed
further into the adjacent wetland to prevent burial of nearby native vegetation. Finally, native species may need to be planted
on hydro-leveled areas to speed up the re-vegetation process. 相似文献
149.
Eric F. Lambin Pamela Cashman Aaron Moody Bruce H. Parkhurst Mary H. Pax Crystal Barker Schaaf 《Journal of environmental management》1993,38(4)
The main objective is to review the current status of research related to the monitoring of agricultural production in the Sahel (west Africa). The Sahel suffers from frequent shortages of food. It is therefore important to have a tool to monitor environmental variables, and thus crop production, during the agricultural season. Satellite remote sensing can contribute significantly to such a system by collecting information on crops and on environmental variables at a sub-continental geographical scale and with a high temporal frequency. One part of the problem is to estimate crop acreage. The technique of area-sampling frame has to adapted to the Sahelian landscape, which is dominated by traditional farming systems. The second part is to estimate crop yields. Three main approaches exist: statistical, semi-deterministic or deterministic. The use of vegetation indices is discussed as well as techniques to derive biophysical variables from remotely-sensed data. Finally, the integration of these remote-sensing techniques with crop-growth models is discussed and some research needs are identified. It is argued that the quantitative assessment of agricultural production in the Sahel should be based on the integration of remotely-sensed data with semi-deterministic agrometeorological models. This approach will allow a regionalization of the production estimates. 相似文献
150.