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71.
Comparison of particle light scattering and fine particulate matter mass in central California 总被引:2,自引:0,他引:2
Chow JC Watson JG Park K Lowenthal DH Robinson NF Park K Magliano KA 《Journal of the Air & Waste Management Association (1995)》2006,56(4):398-410
Particle light scattering (Bsp) from nephelometers and fine particulate matter (PM2.5) mass determined by filter samplers are compared for summer and winter at 35 locations in and around California's San Joaquin Valley from December 2, 1999 to February 3, 2001. The relationship is described using particle mass scattering efficiency (sigmasp) derived from linear regression of Bsp on PM2.5 that can be applied to estimated PM2.5 from nephelometer data within the 24-hr filter sampling periods and between the every-6th-day sampling frequency. An average of sigmaSp = 4.9 m2/g was found for all of the sites and seasons; however, sigmasp averaged by site type and season provided better PM2.5 estimates. On average, the sigmasp was lower in summer than winter, consistent with lower relative humidities, lower fractions of hygroscopic ammonium nitrate, and higher contributions from fugitive dust. Winter average sigmasp were similar at non-source-dominated sites, ranging from 4.8 m2/g to 5.9 m2/g. The sigmasp was 2.3 m2/g at the roadside, 3.7 m2/g at a dairy farm, and 4.1 m2/g in the Kern County oilfields. Comparison of Bsp from nephelometers with and without a PM2.5 inlet at the Fresno Supersite showed that coarse particles contributed minor amounts to light scattering. This was confirmed by poorer correlations between Bsp and coarse particulate matter measured during a fall sampling period. 相似文献
72.
P. Geoffrey Willis Karen A. Brown Gregory E. Prussia 《Journal of Safety Research》2012,43(5-6):389-396
ProblemResearch on workplace safety has not examined implications for business performance outcomes such as customer satisfaction.MethodIn a U.S. electric utility company, we surveyed 821 employees in 20 work groups, and also had access to archival safety data and the results of a customer satisfaction survey (n = 341).ResultsIn geographically-based work units where there were more employee injuries (based on archival records), customers were less satisfied with the service they received. Safety climate, mediated by safety citizenship behaviors (SCBs), added to the predictive power of the group-level model, but these two constructs exerted their influence independently from actual injuries. In combination, two safety-related predictor paths (injuries and climate/SCB) explained 53% of the variance in customer satisfaction.DiscussionResults offer preliminary evidence that workplace safety influences customer satisfaction, suggesting that there are likely spillover effects between the safety environment and the service environment. Additional research will be needed to assess the specific mechanisms that convert employee injuries into palpable results for customers.Impact on IndustryBetter safety climate and reductions in employee injuries have the potential to offer payoffs in terms of what customers experience. 相似文献
73.
Karen Chan Osilla Rachana Seelam Layla Parast Elizabeth J. D’Amico 《Traffic injury prevention》2019,20(6):563-569
Objective: Risky driving behaviors among adolescents, such as riding with a drinking or impaired driver (RWID) or driving while under the influence (DUI) of alcohol or drugs, are significant public health concerns. Few studies have examined associations of RWID and DUI with future substance use and problems after controlling for baseline substance use. Given that the DUI/RWDD event may be a teachable moment to prevent future consequences (e.g., when injured or arrested), it is important to understand how this risk behavior relates to subsequent use and problems. This study therefore examined characteristics of adolescents who reported DUI and RWID and assessed their risk of future alcohol and marijuana use and consequences 6 months later.Methods: Participants were 668 adolescents aged 12 to 18 (inclusive) recruited at 1 of 4 primary care clinics in Pittsburgh and Los Angeles as part of a larger randomized controlled trial. They completed surveys about their health behaviors at baseline and 6 months after baseline. We examined baseline characteristics of adolescents who reported DUI and RWID and then assessed whether past-year DUI and RWID at baseline were associated with alcohol and marijuana use and consequences 6 months after baseline.Results: Fifty-eight percent of participants were female, 56% were Hispanic, 23% were Black, 14% were White, 7% were multiethnic or other, and the average age was 16 years (SD?=?1.9). At baseline, participants who reported RWID or DUI were more likely to be older, report past-year use of alcohol and marijuana, and more likely to have an alcohol use disorder or cannabis use disorder versus those who did not report RWID or DUI, respectively. At 6-month follow-up and after controlling for baseline demographics and baseline alcohol use, RWID was associated with more frequent drinking episodes in the past 3 months and greater number of drinks in the past month when they drank heavily. DUI at baseline was associated with more frequent heavy drinking episodes and alcohol and marijuana consequences 6 months later.Conclusions: RWID and DUI are significantly associated with greater alcohol and marijuana use over time. This study highlights that teens may be at higher risk for problem substance use in the future even if they ride with someone who is impaired. Prevention and intervention efforts for adolescents need to address both driving under the influence and riding with an impaired driver to prevent downstream consequences. 相似文献
74.
Factors that affect extra-pair mating in birds are likely to vary across the breeding season. Changing densities of active
nests may alter the opportunities for extra-pair mating, and parental duties may alter a male’s opportunity to guard his mate
from extra-pair mating. The latter affects species with multiple broods, where males care for fledglings from first nests
while females initiate second nests. We studied a population of multi-brooded American robins (Turdus migratorius) to assess how seasonal changes in nesting density and changes in mate-guarding opportunity influenced paternity patterns
over successive breeding attempts. Extra-pair paternity (EPP) occurred in 71.9% of broods and accounted for 48.1% of young.
High nesting densities in the study population may explain the high overall rate of EPP, but seasonal variation in breeding
density did not explain patterns of EPP among nests. Contrary to the predictions of the mate-guarding hypothesis, EPP did
not increase in the second nests that followed successful first nests, and the percentage of extra-pair young in second nests
did not decline as the overlap between successive nests increased. The fact that EPP was actually lower when the interval
between clutches was shorter suggests that the sooner the males can assume sole care of first broods and allow their mates
to renest (indicative of superior paternal quality), the more paternity they realize in the next nest. These results suggest
that mate-guarding opportunity does not influence paternity in this population of American robins and that female robins may
allocate paternity based on their assessment of male parental performance at first nests. 相似文献
75.
Effects of restoration and reflooding on soil denitrification in a leveed Midwestern floodplain. 总被引:1,自引:0,他引:1
Cailin H Orr Emily H Stanley Karen A Wilson Jacques C Finlay 《Ecological applications》2007,17(8):2365-2376
River floodplains have the potential to remove nitrate from water through denitrification, the anaerobic microbial conversion of nitrate to nitrogen gas. An important factor in this process is the interaction of river water with floodplain soil; however, many rivers have been disconnected from their historic floodplains by levees. To test the effect of reflooding a degraded floodplain on nitrate removal, we studied changes in soil denitrification rates on the Baraboo River floodplain in Wisconsin, USA, as it underwent restoration. Prior to this study, the site had been leveed, drained, and farmed for more than 50 years. In late fall 2002, the field drainage system was removed, and a gate structure was installed to allow controlled flooding of this site with river water. Soil moisture was extremely variable among zones and months and reflected local weather. Soil organic matter was stable over the study period with differences occurring along the elevation gradient. High soil nitrate concentrations occurred in dry, relatively organic-poor soil samples and, conversely, all samples with high moisture soils characterized by low nitrate. We measured denitrification in static cores and potential denitrification in bulk samples amended with carbon and nitrogen, one year before and two years following the manipulation. Denitrification rates showed high temporal and spatial variability. Static core rates of individual sites ranged widely (from 0.00 to 16.7 microg N2O-N x [kg soil](-1) x h(-1), mean +/- SD = 1.10 +/- 3.02), and denitrification enzyme activity (DEA) rates were similar with a slightly higher mean (from 0.00 to 15.0 microg N2O-N x [kg soil](-1) x h(-1), 1.41 +/- 1.98). Denitrification was not well-correlated with soil nitrate, organic matter content, or moisture levels, the three parameters typically thought to control denitrification. Static core denitrification rates were not significantly different across years, and DEA rates decreased slightly the second year after restoration. These results demonstrate that restored agricultural soil has the potential for denitrification, but that floodplain restoration did not immediately improve this potential. Future floodplain restorations should be designed to test alternative methods of increasing denitrification. 相似文献
76.
The green turtle (Chelonia mydas) nesting population at Tortuguero, Costa Rica, is the largest nesting aggregation in the Atlantic, by at least an order of
magnitude. Previous mitochondrial DNA (mtDNA) surveys based on limited sampling (n = 41) indicated low genetic diversity and low gene flow with other Caribbean nesting colonies. Furthermore, a survey of nuclear
DNA diversity invoked the possibility of substructure within the Tortuguero rookery. To evaluate these characteristics, mtDNA
control region sequences were determined for green turtles nesting at Tortuguero in 2001 (n = 157) and 2002 (n = 235). The increased sample revealed three additional haplotypes; five haplotypes are now known for Tortuguero female green
turtles. Analyses of molecular variance indicated that there was no significant spatial population structure along the 30-km
nesting beach. In addition, no temporal population structure was detected either between the two nesting seasons or within
the nesting season. As a result of the larger sample size and additional haplotypes, estimates of genetic separation among
Caribbean nesting colonies have changed and the concordance of phylogenetic and phylogeographic patterns reported in the past
for green turtles in the Greater Caribbean has weakened. The five haplotypes from Tortuguero represent 36% of the haplotypes
identified in green turtle nesting aggregations in the Greater Caribbean and 17% of the haplotypes known to occur in nesting
or foraging aggregations in the Greater Caribbean. Haplotype diversity (0.16) and nucleotide diversity (0.0034) for the Tortuguero
population are substantially lower than those for the combined rookeries in the Greater Caribbean (0.44 and 0.0078, respectively).
Although comprehensive evaluation of regional genetic diversity requires nuclear DNA data, our study indicates that conserving
genetic diversity in Caribbean green turtles will require careful management of the smaller rookeries in addition to the Tortuguero
rookery. 相似文献
77.
Brian L. Gulson Dino Pisaniello Anthony J. McMichael Karen J. Mizon Michael J. Korsch Colin Luke Rosie Ashbolt David G. Pederson Graham Vimpani Kathryn R. Mahaffey 《Environmental geochemistry and health》1996,18(4):147-163
High-precision lead isotope ratios and lead concentrations have been compared statistically and graphically in women of child-bearing age (n = 77) from two smelter communities and one general urban community to evaluate the relative contributions to blood lead of tissue lead stores and lead from the contemporaneous environment (soil, floor dust, indoor airborne dust, water, food). Blood lead (PbB) contents were generally low (e.g. <10 g dL–1). Statistically significant isotopic differences in blood and environmental samples were observed between the three cities although isotopic differences in blood for individual subjects living in close proximity (200 m radius) was as large as the differences within a city. No single environmental measure dominated the biological isotope profile and in many cases the low levels of blood lead meant that their isotopic profiles could be easily perturbed by relatively small changes of environmental exposure. Apportioning of sources using lead isotopes is possibly not feasible, nor cost effective, when blood lead levels are <5 g dL–1. Interpretations based on statistical analyses of city-wide data do not give the same conclusions as when the houses are considered individually. Aggregating data from multiple subjects in a study such as this obscures potentially useful information. Most of the measures employed in this study, and many other similar studies, are markers of only short-to-medium integration of lead exposure. Serial sampling of blood and longer sampling times, especially for household variables, should provide more meaningful information. 相似文献
78.
Begging and provisioning in broods of asynchronously-hatched yellow-headed blackbird nestlings 总被引:13,自引:0,他引:13
Studies of begging have found a positive relationship between begging level and provisioning level. Studies of unequal nestlings, however, have found that small nestlings generally beg more but are fed less than their larger siblings. We manipulated the begging levels of yellow-headed blackbird (Xanthocephalus xanthocephalus) chicks to investigate how begging benefits individuals in broods of unequal siblings. Food-deprived chicks begged more and were fed more; satiated chicks begged less and were fed less. When we deprived each chick of a brood in turn, large and small chicks generally increased begging and received more provisioning. Small chicks, however, rarely received more food than their larger siblings even when they behged relatively more. Parent yellow-headed blackbirds increase provisioning to hungry begging chicks, but also allocate food based on relative offspring size. 相似文献
79.
Karen S. Oberhauser 《Behavioral ecology and sociobiology》1992,31(5):367-373
Summary Both mass and nitrogen content of ejaculates transferred by male monarch butterflies (Danaus plexippus) varied with male history. Older virgins and males that had waited longer after a previous mating transferred larger ejaculates with more nitrogen. After mating, ejaculates were broken down within the female bursa copulatrix; mass and nitrogen content decreased at constant rates until little material remained. Because the time required for breakdown of large spermatophores is longer than the intermating interval, a significant portion of a male's investment could be used to benefit offspring from other males. 相似文献
80.
The role of different types of detached macrophytes in the food and habitat choice of a surf-zone inhabiting amphipod 总被引:1,自引:0,他引:1
Allorchestes
compressa is the dominant macroinvertebrate species in wrack accumulations on surf zones of south-western Australia. These amphipods
were provided with a choice of macrophyte material representing brown and red algae and seagrass in a series of preference
experiments in the laboratory and field. Feeding experiments showed that A. compressa exhibited a strong preference for particular types of macrophytes (P < 0.01). Amphipods primarily consumed brown algae, with 69–98% of the biomass of Ecklonia radiata and 64% of the biomass of Sargassum sp. lost over the experiments. This study has shown that the amphipod A. compressa exhibits a clear preference for brown algae over red algae and seagrass as food. In terms of habitat preference, tank experiments
using a series of pair-wise comparisons showed that, in the absence of fish predators, A. compressa selected seagrass as its preferred habitat over the other types of wrack (P < 0.001). When satiated or starved, between 68 and 83 and 79 and 98% of amphipods were found in Amphibolis and Posidonia, respectively. In contrast, field-cage experiments revealed that A. compressa preferred either mixed wrack, brown algae or red algae over seagrass as a habitat (P < 0.01). The contrasts between results from the laboratory and field suggest that other factors such as the presence of predators,
water flow and light could influence habitat choice in the surf zone. This study shows that allochthonous material transported
to surf zones from other habitats therefore play different roles in driving secondary production in this shoreline habitat. 相似文献