The razorback sucker ( Xyrauchen texanus ) is a large, long-lived catostomid fish endemic to the Colorado River drainage of western North America, endangered because of recruitment failure. Efforts to preserve the species have emphasized artificial propagation and reintroduction. Given the importance of maintaining genetic diversity in such a program, we examined mitochondrial DNA diversity in a source population (Lake Mohave, Arizona-Nevada) and three hatchery-produced year classes (1987, 1989, 1990). The source contained considerable variation, indicated by high haplotype diversity ( ĥ = 0.97) and a large number of unique haplotypes (17 in 25 individuals). Diversity also was high in the 1987 ( ĥ = 0.89, 6 haplotypes in 10 individuals) and 1989 hatchery-produced year classes ( ĥ = 0.91, 7 in 11), but significantly lower in the 1990 year class ( ĥ = 0.71, 4 in 10). Low diversity in the last class was likely because of differences among females in fecundity, viability of progeny, or both. Because natural populations have collapsed throughout the species' range, we must identify methods that preserve the most diversity. We examined three potential alternatives: standard hatchery propagation, natural spawning in predator-free environments, and protective custody of larvae collected from the lake with reintroduction after growth to a size likely to survive. The last is the preferred alternative and should be pursued as the most cost-effective option for preserving genetic diversity in the razorback sucker. 相似文献
Objective: The objective of this study was to describe demographic and injury characteristics of hospitalized injured patients involved in e-bike and motorized scooter accidents at a national level in Israel divided by different road user groups: riders and pedestrians.
Methods: This was a retrospective study based on data from the National Trauma Registry, between January 1, 2013, and December 31, 2015. All hospitalized casualties due to the involvement of an e-bike or motorized scooter were included. The type of hospitalized road user was further categorized and described by different variables.
Results: During the study period, the Israel Trauma Registry identified 795 hospitalized patients due to an e-bike or motorized scooter accident, with a dramatic 6-fold increase from 2013 to 2015. Although the majority of the injured patients were riders, 8% were pedestrians. Among the total casualties, 33% were children aged 0–14 years and among pedestrians 42% were children and 33% were seniors (ages 60+). Five persons died in hospital, 3 riders and 2 pedestrians.
Conclusions: E-bike and motorized scooter riders represent the majority of patients hospitalized due to related traffic incident. This finding questions the social and economic advantages of electric-powered 2-wheeled vehicles. 相似文献
A comprehensive review of online, official, and scientific literature was carried out in 2012–13 to develop a framework of disaster social media. This framework can be used to facilitate the creation of disaster social media tools, the formulation of disaster social media implementation processes, and the scientific study of disaster social media effects. Disaster social media users in the framework include communities, government, individuals, organisations, and media outlets. Fifteen distinct disaster social media uses were identified, ranging from preparing and receiving disaster preparedness information and warnings and signalling and detecting disasters prior to an event to (re)connecting community members following a disaster. The framework illustrates that a variety of entities may utilise and produce disaster social media content. Consequently, disaster social media use can be conceptualised as occurring at a number of levels, even within the same disaster. Suggestions are provided on how the proposed framework can inform future disaster social media development and research. 相似文献
A literature search and survey of Virginia, USA, campgrounds with RV pump-out stations were used to determine whether boat
holding-tank deodorant chemicals would have deleterious effects on marina septic systems or package treatment plants. Laboratory
studies reported in the literature indicate that these chemical additives could affect septic system function in three ways:
(1) active ingredients in the additives can impair sewage degradation in septic tanks, causing sludge buildup and overflow
of solids into the drainfield, (2) additive chemicals might enter the drainfield and, in high enough concentrations, reduce
the drainfield's ability to degrade waste, or (3) toxic additive chemicals might migrate from the drainfield to ground or
surface water. Laboratory studies also show that some ingredients added to holding tanks interfere with functioning of activated
sludge treatment process. Experience in the field and in other laboratory studies suggests that factors such as dilution of
treated waste with untreated waste and the characteristics of the sewage to be treated can reduce the possibility of damage
to septic and activated sludge systems. The campground owners surveyed indicated that they have few problems with their septic
systems in spite of the presence of chemical additives in the RV waste. However, most of them practice good septic system
maintenance and have devised other means of ensuring that their systems function efficiently. In addition, the survey indicates
that most Virginia campgrounds get only seasonal use (as would marinas in Virginia), allowing their systems to recover between
peak seasons. 相似文献