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91.
S. Archibald A. Nickless N. Govender R. J. Scholes V. Lehsten 《Global Ecology and Biogeography》2010,19(6):794-809
Aim This study investigates inter‐annual variability in burnt area in southern Africa and the extent to which climate is responsible for this variation. We compare data from long‐term field sites across the region with remotely sensed burnt area data to test whether it is possible to develop a general model. Location Africa south of the equator. Methods Linear mixed effects models were used to determine the effect of rainfall, seasonality and fire weather in driving variation in fire extent between years, and to test whether the effect of these variables changes across the subcontinent and in areas more and less impacted by human activities. Results A simple model including rainfall and seasonality explained 40% of the variance in burnt area between years across 10 different protected areas on the subcontinent, but this model, when applied regionally, indicated that climate had less impact on year‐to‐year variation in burnt area than would be expected. It was possible to demonstrate that the relative importance of rainfall and seasonality changed as one moved from dry to wetter systems, but most noticeable was the reduction in climatically driven variability of fire outside protected areas. Inter‐annual variability is associated with the occurrence of large fires, and large fires are only found in areas with low human impact. Main conclusions This research gives the first data‐driven analysis of fire–climate interactions in southern Africa. The regional analysis shows that human impact on fire regimes is substantial and acts to limit the effect of climate in driving variation between years. This is in contrast to patterns in protected areas, where variation in accumulated rainfall and the length of the dry season influence the annual area burnt. Global models which assume strong links between fire and climate need to be re‐assessed in systems with high human impact. 相似文献
92.
K van Oers A W Santure I De Cauwer N EM van Bers R PMA Crooijmans B C Sheldon M E Visser J Slate M AM Groenen 《Heredity》2014,112(3):307-316
Linking variation in quantitative traits to variation in the genome is an important, but
challenging task in the study of life-history evolution. Linkage maps provide a valuable
tool for the unravelling of such trait−gene associations. Moreover, they give
insight into recombination landscapes and between-species karyotype evolution. Here we
used genotype data, generated from a 10k single-nucleotide polymorphism (SNP) chip, of
over 2000 individuals to produce high-density linkage maps of the great tit (Parus
major), a passerine bird that serves as a model species for ecological and
evolutionary questions. We created independent maps from two distinct populations: a
captive F2-cross from The Netherlands (NL) and a wild population from the United Kingdom
(UK). The two maps contained 6554 SNPs in 32 linkage groups, spanning 2010 cM and
1917 cM for the NL and UK populations, respectively, and were similar in size and
marker order. Subtle levels of heterochiasmy within and between chromosomes were
remarkably consistent between the populations, suggesting that the local departures from
sex-equal recombination rates have evolved. This key and surprising result would have been
impossible to detect if only one population was mapped. A comparison with zebra finch
Taeniopygia guttata, chicken Gallus gallus and the green anole lizard
Anolis carolinensis genomes provided further insight into the evolution of
avian karyotypes. 相似文献
93.
Summary The arrangement of chromosome arms in metaphases and anaphases has been studied inVicia faba root meristem cells. During metaphase, the long chromosome arms are aligned parallel to the spindle axis. As a consequence, at the onset of anaphase, one chromatid can move straight ahead to the spindle pole whereas the other has to invert its orientation. Specially in narrow cells it has been observed frequently that some chromatids move in a reverse orientation to the pole, i.e., they move telomere-first instead of centromere-first. This behaviour results in a chromatid which protrudes beyond the main group of late anaphase or telophase chromatids. It is dicussed that the most likely explanation for the phenomenon is that in narrow cells chromatid behaviour is influenced by steric hindrance by the tightly packed surrounding chromatids and microtubules. When there is insufficient room, some chromatids are unable to make the required U-turn. Under such conditions the kinetochore of a non-inverted chromatid pulls the chromatid in a reverse orientation to the pole. An alternative explanation, i.e., protruding chromatids being the result of a neocentric activity at the telomere end of a reverse-directed chromatid or the lateral associations of spindle microtubules, failed to find support by electron microscopical studies. 相似文献
94.
A procedure is presented which is suitable for the qualitative and quantitative analysis of the betaine homarine in aqueous tissue extracts. After preliminary purification of the extract by gel permeation chromatography on Sephadex G-25, quantitative analysis of the homarine content is performed by high pressure liquid chromatography on a 1-m column of Corasil II. 相似文献
95.
96.
97.
The accumulation of cadmium, zinc and copper by the marine gastropod molluscs Patella vulgata and Patella intermedia has been studied by gel permeation chromatography of water-soluble extracts of environmentally contaminated shellfish.A major proportion of the water-soluble cadmium and copper in these molluscs is associated with a protein of molecular weight 10 800 daltons. Evidence is presented supporting the similarity of this protein with mammalian metallothionein. This protein contained only a small proportion of the zinc found in the samples. 相似文献
98.
99.
Marieke Biegstraaten Ivo N van Schaik Wouter Wieling Frits A Wijburg Carla EM Hollak 《BMC neurology》2010,10(1):38
Background
Fabry patients have symptoms and signs compatible with autonomic dysfunction. These symptoms and signs are considered to be due to impairment of the peripheral nervous system, but findings indicative of autonomic neuropathy in other diseases, such as orthostatic intolerance and male sexual dysfunction, are infrequently reported in Fabry disease. The aim of our study was to investigate autonomic symptoms and cardiovascular autonomic function in a large cohort of male and female Fabry patients. 相似文献100.
Dutch rabbits were acutely exposed to electromagnetic pulsed (EMP) fields (pulse duration 0.4μs, field strengths of 1–2 kV/cm and pulse repetition rates in the range of 10 to 38 Hz) for periods of up to two hours. The dependent variables investigated were pentobarbital-induced sleeping time and serum chemistry (including serum triglycerides, creatine phosphokinase (CPK) isoenzymes, and sodium and potassium). Core temperature measured immediately pre-exposure and postexposure revealed no exposure-related alterations. Over the range of field strengths and pulse durations investigated no consistent, statistically significant alterations were found in the end-points investigated. 相似文献