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801.
INTRODUCTION: The study reported here was designed to test the ability of the theory of planned behavior to mediate the effect of parental supervision on adolescents' intentions to violate driving rules. METHOD: A representative sample of 1,654 adolescents completed questionnaires during individual and anonymous interviews carried out at their schools. RESULTS: Results showed that age, gender, prior risky driving-behavior, and parental supervision significantly predict intentions to violate driving rules. Attitude and the subjective norm partially mediate the effect of age, prior behavior, and parental supervision. Perceived behavioral control does not predict intention and is not predicted by other variables. IMPACT: The results suggest that social cognitive variables partially mediate the effect of parenting practices such as supervision. 相似文献
802.
火灾下钢框架结构热-力耦合模拟与性能分析 总被引:1,自引:0,他引:1
基于"自然火灾安全概念"(NFSC)的基本思想,提出了火灾下钢结构热-力耦合模拟方法。利用ANSYS的参数化设计语言,建立了ANSYS软件与OZone火灾分析软件的数据接口,实现了火灾分析软件与大型有限元软件的耦合运用。基于火灾模拟软件OZone的分析结果,利用APDL语言,对钢框架结构进行了真实火灾场景下的热-力耦合模拟。研究表明:钢框架结构在真实火灾场景下,受非均匀变热流影响,结构内部将产生热应力梯度和应力牵移现象;同时钢框架中钢梁固接时,火灾初期变形较小,当达到某个关键时间点后将开始大的变形破坏,其主要原因是钢框架内部产生塑性铰,即钢梁由固接变为铰接,释放了对钢梁的约束。 相似文献
803.
基于人体皮肤热模型的热防护服评价方法研究 总被引:1,自引:0,他引:1
在热防护服热防护性能测试装置基础上,用自行研制的新型耐高温模拟皮肤传感器代替铜片热流计测量通过应急热防护服装面料的热流量,将热流量作为热波皮肤模型边界条件,得到人体皮肤表层下80μm处的温度值,从而得到一定条件下人体真实皮肤达到二级烧伤所需时间,用其评价热防护服用织物的热防护性能,并将热波皮肤模型(TWMBT)的测试值与Pennes模型以及铜片热流计的测试结果进行分析比较。采用热波皮肤模型分析织物层下的"皮肤"防热时间更接近实际皮肤达到二级烧伤时间值,可较为精确的量化织物热防护性能,为应急救援热防护服装的热设计提供理论依据。 相似文献
804.
Myrmecophily provides various examples of how social structures can be overcome to exploit vast and well-protected resources.
Ant nest beetles (Paussinae) are particularly well suited for ecological and evolutionary considerations in the context of
association with ants because life habits within the subfamily range from free-living and predatory in basal taxa to obligatory
myrmecophily in derived Paussini. Adult Paussini are accepted in the ant society, although parasitising the colony by preying
on ant brood. Host species mainly belong to the ant families Myrmicinae and Formicinae, but at least several paussine genera
are not host-specific. Morphological adaptations, such as special glands and associated tufts of hair (trichomes), characterise
Paussini as typical myrmecophiles and lead to two different strategical types of body shape: while certain Paussini rely on
the protective type with less exposed extremities, other genera access ant colonies using glandular secretions and trichomes
(symphile type). We compare these adaptations with other taxonomic groups of insects by joining contemporary research and
early sources and discuss the possibility of an attracting or appeasing effect of the secretion. Species that are ignored
by their host ants might use chemical mimicry instead. Furthermore, vibrational signals may contribute to ant–beetle communication,
and chemical signals have proven to play a role in host finding. The powerful defense chemistry of paussines as “bombardier
beetles” is not used in contact with host ants. We attempt to trace the evolution of myrmecophily in paussines by reviewing
important aspects of the association between paussine beetles and ants, i.e. morphological and potential chemical adaptations,
life cycle, host specificity, alimentation, parasitism and sound production.
相似文献
Stefanie F. GeiselhardtEmail: |
805.
Sasakawa K 《Die Naturwissenschaften》2007,94(5):384-391
The morphological characteristics of sperm and reproductive organs may offer clues as to how reproductive systems have evolved.
In this paper, the morphologies of the sperm and male reproductive organs of carabid beetles in the tribe Pterostichini (Coleoptera:
Carabidae) are described, and the morphological associations among characters are examined. All species form sperm bundles
in which the head of the sperm was embedded in a rod-shaped structure, i.e., spermatodesm. The spermatodesm shape (left-handed
spiral, right-handed spiral, or without conspicuous spiral structure) and the condition of the sperm on the spermatodesm surface
(with the tail free-moving or forming a thin, sheetlike structure) vary among species. In all species, the spiral directions
of the convoluted seminal vesicles and vasa deferentia are the same on both sides of the body; that is, they show an asymmetric
structure. The species in which the sperm bundle and the seminal vesicles both have a spiral structure could be classified
into two types, with significant differences in sperm-bundle length between the two types. The species with a sperm-bundle
spiral and seminal-vesicle spiral of almost the same diameter have longer sperm bundles than the species with a sperm-bundle
spiral and seminal-vesicle tube of almost the same diameter. In the former type, the spiral directions of the sperm bundles
and seminal vesicles are inevitably the same, whereas they differ in some species with the later type. Therefore, increased
sperm bundle length appears to have been facilitated by the concordance of the sperm bundle’s coiling direction with the coiling
direction of the seminal vesicle. 相似文献
806.
The existence of sex is one of the major unsolved problems in biology. We use computer simulations to model conditions in
which sex may first become established. We develop an individual-based population model and show that a hypothetical facultative
sex gene can fix, provided that the initial cost is low. It is demonstrated that the equilibrium fitness in the population
increases with increasing population size and decreasing mutation rate. The probability of the establishment of the sex gene
is found not to be directly related to the fitness difference between the asexual and sexual populations. This change in fitness
on changing the parameters of the model is investigated. 相似文献
807.
嫩江水体溶解氧变化规律的混沌研究 总被引:1,自引:0,他引:1
针对目前溶解氧研究主要是从生物、化学等方面开展,而对溶解氧自身变化规律的研究很少的特点,以嫩江干流浏园水文站测得的溶解氧质量浓度序列为例,首先进行相空间重构,应用自相关函数法确定出延迟时间、伪邻近点法确定出嵌入维数;然后应用主分量分析(PCA)方法对序列进行分析,表明该序列不是噪声序列而可能是混沌序列,通过计算Kolmogorov熵得出溶解氧质量浓度序列具有混沌特性的结论;最后应用基于关联度的局域加权线性回归预测法对该序列进行了混沌预测研究,得到了比较理想的预测结果,这为应用混沌理论进行溶解氧变化规律的研究提供了依据. 相似文献
808.
平朔安太堡矿区复垦地土壤微生物与土壤性质关系的研究 总被引:8,自引:0,他引:8
调查安太堡大型露天矿区西排土场植被恢复与土壤微生物的关系.结果表明,土壤中微生物量与土壤中的水分、速效磷、土壤有机质、有效性氮和海拔高度有明显的关系.麦地、林地、草地的土壤中呈现出:细菌》放线菌》固氮菌》霉菌;撂荒地呈现为:细菌》放线菌》霉菌》固氮菌;裸地呈现出:细菌》放线菌》霉菌.细菌、放线菌和霉菌呈现麦地最高,裸地最低,固氮菌为林地高于其他样地.在撂荒地和裸地中,细菌占微生物总量的一半以上.麦地、林地、草地、撂荒地中的各种菌、速效磷、土壤有机质、有效性氮含量明显高于裸地中的含量.微生物总量和样地的海拔、样地土壤的含水率有明显的关系,土壤中的含水量直接影响微生物总量.微生物总量与速效磷含量和有机质含量成正比,有机质含量与有效性氮含量成正比.细菌与海拔呈极显著负相关,与其他几种养分指标呈极显著正相关,放线菌与海拔和速效磷呈极显著相关,与其他指标相关性不显著,固氮菌与几种养分指标相关性均不显著.按全国土壤养分划分标准,安太堡大型露天矿区复垦地等级不高,还需要用科学的方法加快复垦区土壤的恢复. 相似文献
809.
810.