We evaluated the relationship between play behavior and motor development in juvenile Beldings ground squirrels (Spermophilus beldingi). We observed the social play behavior of juvenile S. beldingi during their primary play period and conducted motor skills tests at the beginning and end of the play period. We also placed different-sized boxes in juveniles natal areas during the play period and observed box climbing behavior to assess the difficulty of non-social play tasks undertaken by juveniles. Rates of social play were greater in heavy compared to light individuals, supporting the idea that juveniles must selectively allocate available energy among competing demands such as growth and play behavior. Juveniles played almost exclusively with littermates; however, they did not play at equal rates with all partners. Rather, they tended to have one preferred partner and to devote significantly less time to playing with each additional partner, indicating that stability and familiarity are important in social play interactions. Motor skill levels at the end of the play period were greater among juveniles who played with many compared to few partners, suggesting that exposure to a variety of play interactions helps facilitate motor development. Improvement in motor skills was greater among juveniles who played at high compared to low rates, had several compared to few male play partners, and engaged in several compared to few play bouts with male partners, suggesting that elements of play with male partners prominently influence motor development. The partner with whom males played at the highest rate tended to be male, and rates of social play were highest in male biased litters, raising the possibility that improvement in motor proficiency arising from play with males may be especially important for young males. The size of experimental boxes that juveniles climbed increased during the play period, supporting the idea that individuals choose play tasks that pose the greatest challenge.Communicated by T. Czeschlik 相似文献
Objective: We conducted a cohort study of recent wartime veterans to determine the postservice mortality risk due to motor vehicle accidents (MVAs).
Methods: Veterans were identified from the Defense Manpower Data Center records. Deployment to te Iraq or Afghanistan war zone was determined from the Contingency Tracking System. Vital status of 317,581 deployed and 964,493 nondeployed veterans was followed from their discharge dates between 2001 to 2007 until earlier of date of death or December 31, 2009. Underlying causes of death were obtained from the National Death Index Plus.
Results: Based on 9,353 deaths (deployed, 1,650; nondeployed, 7,703), of which 779 were MVA deaths as drivers (166; 613), both cohorts had 25 to 24% lower mortality risk from all causes but had 44 to 45% higher risk of MVA deaths relative to the U.S. general population. The higher MVA mortality risk was not associated with deployment to the war zone. After controlling for age, sex, race, marital status, branch of service, and rank, the risk for deployed veterans was comparable to that of nondeployed veterans (hazard ratio = 0.91; 95% confidence interval, 0.77–1.09).
Conclusions: Veterans exhibit significantly higher risk of MVA deaths compared to the U.S. general population. However, deployment to the Iraq or Afghanistan war was not associated with the excess risk. 相似文献
Ants inhabit diverse terrestrial biomes from the Sahara Desert to the Arctic tundra. One factor contributing to the ants’
successful colonization of diverse geographical regions is their ability to manipulate objects when excavating nests, capturing,
transporting and rendering prey or grooming, feeding and transporting helpless brood. This paper is the first to report the
form and function of opposable spines on the foretarsi of queens and workers used during fine motor and gross motor object
manipulation in the fire ant, Solenopsis invicta. In conjunction with their mandibles, queens and workers used their foretarsi to grasp and rotate eggs, push or pull thread-like
objects out of their way or push excavated soil pellets behind them for disposal by other workers. Opposable spines were found
on the foretarsi of workers from seven of eight other ant species suggesting that they might be a common feature in the Formicidae. 相似文献
Air samples were collected in Izmir, Turkey at two (suburban and urban) sites during three sampling programs in 2002 and 2004
to determine the ambient concentrations of several monoaromatic, chlorinated and oxygenated volatile organic compounds (VOCs).
Samples were analyzed for 60 VOCs using gas chromatography/mass spectrometry and 28 compounds were detected in most samples.
On the average, urban air VOC concentrations were about four times higher than those measured at the suburban site. Toluene
(40.6%) was the most abundant compound in suburban site and was followed by benzene (7.4%), o,m-xylene (6.5%), and 1,2-dichloroethane
(5.1%). In urban site, toluene (30.5%), p-xylene (14.9%), o,m-xylene (11.4%), and ethyl benzene (7.2%) were the dominating
compounds in summer. In winter, toluene (31.1%), benzene (23.9%), 1,2-dichloroethane (9.5%), and o,m-xylene (8.2%) were the
most abundant compounds. Receptor modeling (positive matrix factorization) has been performed to estimate the contribution
of specific source types to ambient concentrations. Six source factors (gasoline vehicle exhaust, diesel vehicle exhaust+residential
heating, paint production/application, degreasing, dry cleaning, and an undefined source) were extracted from the samples
collected in the urban site. Three source factors (gasoline vehicle exhaust, diesel vehicle exhaust, and paint production/application)
were identified for the suburban site. 相似文献
The 24-h average coarse (PM10) and fine (PM2.5) fraction of airborne particulate matter (PM) samples were collected for winter, summer and monsoon seasons during November 2008-April 2009 at an busy roadside in Chennai city, India. Results showed that the 24-h average ambient PM10 and PM2.5 concentrations were significantly higher in winter and monsoon seasons than in summer season. The 24-h average PM10 concentration of weekdays was significantly higher (12-30%) than weekends of winter and monsoon seasons. On weekends, the PM2.5 concentration was found to slightly higher (4-15%) in monsoon and summer seasons. The chemical composition of PM10 and PM2.5 masses showed a high concentration in winter followed by monsoon and summer seasons.The U.S.EPA-PMF (positive matrix factorization) version 3 was applied to identify the source contribution of ambient PM10 and PM2.5 concentrations at the study area. Results indicated that marine aerosol (40.4% in PM10 and 21.5% in PM2.5) and secondary PM (22.9% in PM10 and 42.1% in PM2.5) were found to be the major source contributors at the study site followed by the motor vehicles (16% in PM10 and 6% in PM2.5), biomass burning (0.7% in PM10 and 14% in PM2.5), tire and brake wear (4.1% in PM10 and 5.4% in PM2.5), soil (3.4% in PM10 and 4.3% in PM2.5) and other sources (12.7% in PM10 and 6.8% in PM2.5). 相似文献
In 2006 Texas raised the daytime speed limit for passenger vehicles on segments of I-10 and I-20 from 75 to 80 mph. Methods: Traffic speeds were measured before and 3, 12, and 16 months after the limit was changed. Results: During the 16-month period following the speed limit increase, mean speeds of passenger vehicles on I-20 increased by 9 mph relative to the comparison road, where no speed limit change occurred and traffic speeds declined. On I-10 mean speeds increased by 4 mph relative to the comparison road. Limiting the analysis to the month before the speed limit change and 1 year later, the proportion of drivers exceeding 80 mph was 18 times higher on I-20 and 2 times higher on I-10. Discussion: The smaller speed increases on I-10 may be related to its proximity to the U.S. border with Mexico. Highly visible border patrol activity coincided with posting of the higher speed limit. Long-term monitoring in other states suggests that traffic speeds in Texas are likely to continue to increase. Impact on Industry: The present study adds to the wealth of evidence that increased speed limits lead to increased travel speeds. The primary countermeasures to reduce the risk of speed-related crashes include highly visible police traffic enforcement and the use of speed cameras accompanied by publicity. 相似文献
Studies have shown that older drivers have high death rates and lower rates of involvement in crashes that kill others; but most studies have not considered drivers' responsibility for their crashes, and many have considered only one particular measure of risk.
Method
This study examines risks that drivers of various ages pose to themselves and to others on per-driver, per-trip, and per-mile bases, taking responsibility for crashes into account, using United States fatal crash data from 1999 through 2003 and travel estimates from 2001.
Results
Relative to other age groups, drivers aged 85 and older face the highest risk of their own death, whereas teens pose the greatest risk to passengers, occupants of other vehicles, and non-motorists.
Discussion
The oldest drivers pose more risk to other road users than middle-aged drivers do; the degree of their excess risk depends strongly upon how risk is measured.
Impact on industry
These results demonstrate the importance of keeping clear the meaning and implications of various risk measures. 相似文献
Motor vehicles emit a cocktail of pollutants; however, little is known about the effects of these pollutants on bryophytes located in roadside habitats. Six bryophyte species were transplanted to either a woodland or a moorland site adjacent to a motorway, and were monitored over seven months from autumn through to spring. All species showed an increase in one or more of the following near the motorway: growth, membrane leakage, chlorophyll concentration, and nitrogen concentration. The strongest effects were observed in the first 50-100 m from the motorway: this was consistent with the nitrogen dioxide pollution profile, which decreased to background levels at a distance of 100-125 m. It is hypothesised that motor vehicle pollution was responsible for the effects observed, and that nitrogen oxides had a key influence. The observed effects may lead to changes in vegetation composition with significant implications for nature conservation and management of roadside sites. 相似文献