Fourier analysis of vertebral shape change due to growth and selection for large and small body size

Summary Fourier analysis of videodigitised outlines of mouse vertebrae from two stocks, a pseudo-longitudinal series of mice aged 25–60 days and one selected for large or small body size over many generations shows that the shape changes due to normal growth are not similar to those produced by selection for body size.     

Magnetic resonance microscopy: in vivo sectioning of a developing insect

Summary The utility of magnetic resonance imaging vis-a-vis insect morphology and development was investigated. MRI is a noninvasive technique that distinguishes between tissues based on proton content and proton environment. At present a resolution of 100 m is achievable. The technique avoids fixation artifacts and allows the detection of motion within the organism.     

浑善达克沙漠化防治重点生态系统功能区防风固沙功能动态特征分析

浑善达克沙漠化防治重点生态系统功能区是位于内蒙古地区维护国家北方生态安全屏障的重要区域.本文基于气象、遥感数据,运用RWEQ(Revised Wind Erosion Equation)模型,定量分析了1990—2015年浑善达克防风固沙功能区生态系统结构与防风固沙功能的时空变化特征,揭示了生态系统结构变化对防风固沙服务功能的影响.结果表明:26年间各生态系统间转换强烈,以草地生态系统转出为主,2005年之前主要向农田生态系统和荒漠生态系统转变,2005年以后得益于生态建设工程的实施和禁牧封育等措施,主要向草地、森林生态系统转变.研究区以微度和轻度土壤侵蚀为主,风蚀情况整体好转.农田生态退耕、荒漠化程度减轻、草地质量提高等生态系统转换有益于提升防风固沙功能.同时,也揭示了该功能区内生态退耕对防风固沙服务功能的影响,两者呈显著负相关.     

Light is a dominant mouse mutation resulting in premature cell death.

Light is a dominant mutant allele of the mouse brown locus which results in hairs pigmented only at their tips. The phenotype is due to premature melanocyte death. We have sequenced the tyrosinase-related protein-1 cDNA encoded at this locus from Light mice and found that it contains a single base alteration from wild-type, causing an Arg to Cys change in the protein. To further elucidate the mutant phenotype, we studied the expression of melanocyte specific genes in the skin of Light mice. We have demonstrated premature melanocyte death, but only in pigmented mice, indicating that the cell death is mediated through the inherent cytotoxicity of pigment production.     

语言自主性学习理论评述

人本主义心理学认为学习者具有发展潜能的能力和动力，研究者应促进其个性发展和潜能发挥；社会认知学派通过所构建的研究框架确定学习自主性程度，采用五个维度描述自主学习状态，认为自主学习能力习得是将外部学习技能内化为个人能力的过程；信息加工理论指出完整意义上的自主学习过程经历四个阶段，还构建了自主学习内在机制；元认知理论认为循序渐进的发展过程直接影响自主性学习能力的发展。对各理论学派教育哲学理念进行全面梳理，利于研究者借鉴其成果，从而提出本土化之理论。     

Estimating root biomass and distribution after fire in a Great Basin woodland using cores and pits

Quantifying root biomass is critical to an estimation and understanding of ecosystem net primary production, biomass partitioning, and belowground competition. We compared 2 methods for determining root biomass: a new soil-coring technique and traditional excavation of quantitative pits. We conducted the study in an existing Joint Fire Sciences demonstration area in the central Great Basin. This area is representative of a shrub (sagebrush) ecosystem exhibiting tree (pinyon and juniper) encroachment. The demonstration area had a prescribed burn implemented 4 years prior to our study, and we sampled both control and burned plots. The samples were stratified across 3 microsites (interspace, under shrub, and under tree) and 4 soil depths (0–8, 8–23, 23–38, and 38–52 cm) to determine the effects of plant life form and burning on root biomass. We found that estimates of total root biomass were similar between quantitative pits and our soil cores. However, cores tended to show a more even distribution of root biomass across all microsites and depths than did pits. Overall, results indicated that root biomass differs significantly among microsites and soil depths and that the amount of root biomass at a given depth differs among microsites. Burning reduced root biomass in our study by 23% and altered the spatial distribution of root mass.     

Mycorrhization of ponderosa pine in a second-growth Sierra Nevada forest

Ectomycorrhizal colonization and rooting characteristics were quantified in a mature ponderosa pine ( Pinus ponderosa Dougl. ex Laws.) stand in the western Sierra Nevada. Root length totaled 3835.9 m · m –2 of forest floor surface area, with 96% consisting of the fine-root fraction. Total root dry weight and volume were 2230.4 g · m –2 and 5807.4 cm 3 · m –2 of forest floor area, respectively, with 69% of the former and 75% of the latter accounted for by the coarse fraction. Fine roots were most prevalent in the upper 15 cm of the mineral soil profile, and their abundance declined with increasing depth. Coarse roots were most abundant at a depth of 15–30 cm. Ectomycorrhizal counts totaled 26,814 · m –2 of forest floor area, and an overwhelming preponderance was associated with the fine-root fraction. More than three-quarters of mychorrhizae resided in the upper 15 cm of mineral soil, with an overall trend of declining numbers with increasing depth. Roots and mycorrhizae were exceedingly scarce at a depth of 45–60 cm, and neither was found in the organic soil layer above the mineral profile. A necessary step in understanding the ecophysiological role of mycorrhizae in mature forests is to quantify their abundance in such settings, and the results of this study contribute such information for ponderosa pine.     

Characterizing a first occurrence of bison deposits in southeastern Nevada

Late Holocene bison bones eroding from the badlands topography of Cathedral Gorge State Park in southeastern Nevada have been identified as the remains of Bison and date between approximately 400 and 850 years old. The bones were originally thought to be turn-of-the-century cattle and then early bison, so park personnel had need to solve this interpretive problem. A multidisciplinary team sought information on archaeology, geomorphology, paleontology, and paleoenvironment to document the 1st established occurrence of bison in this part of Nevada and to develop a hypothesis explaining their demise.     

Feeding by the Great Basin spadefoot toad ( Spea intermontana ) (Anura: Pelobatidae)

The present study analyzed the stomach contents of 65 Great Basin spadefoot toads, Spea intermontana (Cope), collected in an area of irrigation runoff in south central Washington State. Toads were collected by pitfall trapping. Traps were maintained for 1 year beginning in April 2002. Toads consumed at least 56 different arthropod taxa belonging to the orders Coleoptera, Diptera, Hemiptera, Hymenoptera, Lepidoptera, Neuroptera, Orthoptera, Trichoptera, Collembola, and Araneae. Ants and darkling beetles were among the most common prey. Feeding appeared to be very generalized with the toads accepting almost anything they could capture and subdue.