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51.
Falk D Hildebolt C Smith K Morwood MJ Sutikna T Brown P Jatmiko Saptomo EW Brunsden B Prior F 《Science (New York, N.Y.)》2005,308(5719):242-245
The brain of Homo floresiensis was assessed by comparing a virtual endocast from the type specimen (LB1) with endocasts from great apes, Homo erectus, Homo sapiens, a human pygmy, a human microcephalic, specimen number Sts 5 (Australopithecus africanus), and specimen number WT 17000 (Paranthropus aethiopicus). Morphometric, allometric, and shape data indicate that LB1 is not a microcephalic or pygmy. LB1's brain/body size ratio scales like that of an australopithecine, but its endocast shape resembles that of Homo erectus. LB1 has derived frontal and temporal lobes and a lunate sulcus in a derived position, which are consistent with capabilities for higher cognitive processing. 相似文献
52.
Carpenter BK 《Science (New York, N.Y.)》2011,332(6035):1269-1270
53.
Ferguson AD McKeever BM Xu S Wisniewski D Miller DK Yamin TT Spencer RH Chu L Ujjainwalla F Cunningham BR Evans JF Becker JW 《Science (New York, N.Y.)》2007,317(5837):510-512
Leukotrienes are proinflammatory products of arachidonic acid oxidation by 5-lipoxygenase that have been shown to be involved in respiratory and cardiovascular diseases. The integral membrane protein FLAP is essential for leukotriene biosynthesis. We describe the x-ray crystal structures of human FLAP in complex with two leukotriene biosynthesis inhibitors at 4.0 and 4.2 angstrom resolution, respectively. The structures show that inhibitors bind in membrane-embedded pockets of FLAP, which suggests how these inhibitors prevent arachidonic acid from binding to FLAP and subsequently being transferred to 5-lipoxygenase, thereby preventing leukotriene biosynthesis. This structural information provides a platform for the development of therapeutics for respiratory and cardiovascular diseases. 相似文献
54.
Soundscape ecology is being proposed as a new synthesis that leverages two important fields of study: landscape ecology and
acoustic ecology. These fields have had a rich history. Running “in parallel” for over three decades now, soundscape ecology
has the potential to unite these two (among other) fields in ways that provide new perspectives on the acoustics of landscapes.
Each of us was involved in the “birth” of these two fields. We each reflect here on the rich history of landscape ecology
and acoustic ecology and provide some thoughts on the future of soundscape ecology as a new perspective. 相似文献
55.
Adequate K, Mg and Ca supply is important to develop well-structured and functional cell walls and membranes in fruit, and insufficient levels or imbalances of these minerals are known to be involved in various postharvest disorders. Microclimatic variation exists in the ‘Nules Clementine’ mandarin tree canopy and results in lower photosynthetically active radiation (PAR) levels and temperature as well as a higher humidity inside the tree canopy. The aim of this experiment was to determine the impact of this variation in microclimate on accumulation patterns of K, Ca and Mg in the flavedo of the fruit rind during stages II and III of fruit development. Fruit mass, dimensions, rind colour development and mineral composition of the flavedo were measured to describe the condition of fruit borne on the outside and inside of the tree's canopy. The data revealed that canopy position influenced mineral nutrient accumulation patterns in the flavedo. Outside fruit flavedo accumulated significantly higher concentrations of Ca and Mg in all three seasons (2005–2007). In contrast, inside fruit flavedo (shaded fruit) accumulated significantly higher levels of K compared with outside fruit flavedo. The accumulation of K and Ca differed from that of kiwifruit and apple in that Ca concentration increased and K decreased towards maturity. These results suggest that xylem, as in citrus leaves, is the main vasculature supply conduit to the citrus fruit flavedo for mineral nutrients. The reduction of transpiration potential by lower temperatures and higher humidity inside the canopy could be responsible for the reduced accumulation of Ca and Mg. The high K concentration of inside fruit flavedo is suggested to be a stress response, due to the low light levels, to maintain osmotic potential in the shaded rind tissue, and this imbalance could possibly lead to a reduction in rind condition, which manifests through rind breakdown symptom development. 相似文献
56.
Grimalt S Thompson D Chartrand D McFarlane J Helson B Lyons B Meating J Scarr T 《Pest management science》2011,67(10):1277-1284
BACKGROUND: Azadirachtins are natural insecticides derived from the neem tree. The emerald ash borer (EAB) is an exotic invasive insect pest that infests various ash tree species and has the potential for significant economic, aesthetic and ecological impacts throughout North America. The initial translocation and foliar residue dynamics of azadirachtins were examined following direct injection into white and green ash trees growing in urban scenarios as a potential control for EAB. RESULTS: Substantial concentrations of azadirachtins A and B [mean maxima > 0.98 mg kg?1 fresh weight (f.w.)] were observed within 2 days of injecting a specifically designed formulation of azadirachtins. Foliar residues declined exponentially through time, with half‐life estimates ranging from 5.1 to 12.3 days. At the time of leaf senescence, foliar residue levels approximated 0.01 mg kg?1 f.w., strongly mitigating the potential effects of non‐target biota in soil or aquatic compartments. CONCLUSION: The magnitude and duration of exposures observed in this field study were considered to be above the thresholds required for biological effectiveness against both larval and adult life stages of EAB. Results support the use of azadirachtins as an environmentally acceptable systemic insecticide for control of EAB and protection of high‐value ash trees in urban environments. Copyright © 2011 Society of Chemical Industry 相似文献
57.
M. B. Barry J. L. Pham B. Courtois C. Billot N. Ahmadi 《Genetic Resources and Crop Evolution》2007,54(8):1675-1690
Rice genetic diversity partitioning between farms, varieties and, within-variety diversity, were analysed in two villages
of Maritime Guinea with contrasted agroecological conditions. One thousand and two hundred individual plants belonging to
45 accessions collected in eight farms were genotyped using 10 SSR markers. The molecular variance was evenly shared between
and within accessions, while the farm effect was almost nil. Local varieties had a multi-line genetic structure. The number
of multilocus genotypes was proportional to the utilisation rate of the variety in the village. The F
ST values between different accessions of each variety were significant which indicated low genetic consistency in the variety
names. This varietal structure could mainly be explained by the migration phenomenon and the high varietal turnover. Compared
to allelic diversity, multilocus genotypic diversity seemed to be the most suitable indicator of the quantitative distribution
of diversity at different management scales (accession, farm and village). The within- and between-farm F
ST values were in the same order of magnitude. The within-farm diversity was not farm-specific but quantitatively high, i.e.
up to 50% of the total genotypic diversity of a given village. Given the relative importance of the within-variety diversity,
the in situ approach stands out as the most effective solution. As farms do not host specific diversity the in situ approach
could be implemented by working with a small number of farms. 相似文献
58.
Castillo UF Wilkins AL Lauren DR Smith BL Alonso-Amelot M 《Journal of agricultural and food chemistry》2003,51(9):2559-2564
Fractionation of an extract of Pteridium caudatum L. Maxon. (syn P. aquilinum L. Kuhn var. caudatum) which had earlier yielded the illudane-type sesquiterpene glucosides, ptaquiloside (1a), isoptaquiloside (1b), and caudatoside (1c) afforded a mixture containing 1a and two minor components. Preparative HPLC afforded ptaquiloside Z (1d) and a new pteroside glucoside (pteroside A2) (3e), which was identified using a combination of mass spectral and one- and two-dimensional NMR analyses. The (1)H and (13)C NMR and mass spectrometric characterization of caudatodienone (2b), an unstable dienone derived from the degradation of caudatoside (1c) in pyridine solution, and the GC-MS characterization of some pterosin-type degradation products produced by reacting this solution with cosolvents is also reported. 相似文献
59.
Direct estimates of extinction risk are frequently unavailable, so surrogate indicators are used in threatened species categorizations, but there is inadequate information on which best predict vulnerability. We compared the ability of 16 frequently-used factors to predict extinction risk for 45 vertebrate taxa. Median times to extinction were estimated using taxon-specific stochastic population models. Population size (N) and trend were clearly the best correlates of extinction risk in our data set. Stepwise multiple regression with additive and interaction terms identified N, N × trend, plus taxonomic level, number of sub-populations × N × trend, number of offspring (O) and N × O as predictors, and explained 70% of the variation. Trend was important in large, but not in small populations. Population size is the most important data to collect for threatened species and with trend should be the major focus in endangered species categorization and state of the environment reporting. 相似文献
60.
Cheryl Waldner Sylvia Checkley Barry Blakley Colleen Pollock Becky Mitchell 《Journal of veterinary diagnostic investigation》2002,14(6):481-486
Lead poisoning is commonly diagnosed in cattle. In this study, 3 groups of cattle from different herds accidentally exposed to discarded lead batteries on pasture were intensively studied to determine the extent and severity of exposure. The losses from acute death due to lead toxicity were substantial in all the 3 study groups at 12%, 17%, and 4%. Blood samples were taken from all cattle around the time of the first diagnosis and then later in 2 of the 3 herds to monitor the change in lead concentrations over time. Asymptomatic lead toxicosis was observed in these herds. In these 3 groups, between 4% and 12% of asymptomatic cattle had blood lead concentrations consistent with acute lead poisoning (> 0.35 ppm), and between 7% and 40% of these asymptomatic animals were in the high-normal range (0.1-0.35 ppm). Because of the consistently high number of asymptomatic cattle with elevated lead levels, all cattle potentially exposed to a lead source should be tested before sale or slaughter to minimize the entry of lead into the food chain. The blood lead concentrations, which were monitored for months after the initial diagnosis, decreased slowly after the cattle were removed from the lead source. The prolonged retention of lead may be due to continued release and absorption of lead from metal particles in the reticulum or rumen. The mean reduction in the lead level was 0.046 ppm (95% CI, 0.017-0.075 ppm) every 30 days for these 2 herds. Using a single-component exponential model, the half-life of lead in the animals retested from Herds 1 and 2 was highly variable. The median half-life was 63 days (interquartile range, 34-107 days). One out of 8 pregnant heifers with high blood levels had a stillborn calf. There were no abortions or calf mortalities in this group. Blood samples were'collected from the calves around the time of birth. The concentrations of lead in the blood of the calves exposed in utero were low (0.010-0.095 ppm). 相似文献