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A new covalently-bonded, silica-based stationary phase, using as the chiral selector the 1-(3-aminopropyl) derivative of (+)-(5R,8S,10R)-terguride, has been developed to resolve optically active isomers by HPLC. Good resolution of structurally related racemic ergot alkaloids were obtained using water-methanol mixtures as the eluent. Analysis of the influence of the type and concentration of the organic modifier, and the pH of the buffer in the mobile phase allowed the enantioseparation of these compounds to be optimized. Determination of the optical purity of a lisuride-containig drug is reported. © 1994 Wiley-Liss, Inc. 相似文献
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C. David Pauza Peter Emau Maria S. Salvato Parul Trivedi Debra MacKenzie Miroslav Malkovsky Hideo Uno Kevin T. Schultz 《Journal of medical primatology》1993,22(2-3):154-161
Intrarectal inoculation of rhesus monkeys with low doses of SIVmac led to a prolonged clinical and virological latency that was not observed for high intrarectal doses or for intravenous inoculation. Animals infected intrarectally with low virus doses remained negative for serum antibody responses to SIV for at least one year even though they readily transferred SIV to naive recipients via transfusion of whole blood. 相似文献
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Filamentous algae in eutrophic carp ponds in South Bohemia (Central Europe) were studied from 1988 to 1990. High biomass (490 g DW m-2) was attained by Cladophora fracta (O. F. Müll. ex Vahl) Kütz. after two months of growth. This marked growth depleted inorganic carbon in the water, but did not decrease the concentration of tissue nutrients. Laboratory measurements of final pH indicate that all the filamentous algae studied, except for Tribonema, are very efficient HCO3
- users. An extremely high pH of 11.6 and oxygen concentration of 32 mg l-1 were measured in the algal mats. High pH resulted in CaCO3 precipitation, visible as white incrustations on algal filaments. The amount of precipitated CaCO3 reached 134 kg ha-1. After reaching peak biomass, 90% of the Cladophora decomposed over the next 95 days.The highest net photosynthetic rate in C. fracta was measured between pH range 8.5–10.0 and oxygen concentrations of 7–12 mg l-1. Optimum temperature for photosynthesis was between 17–22°C. 相似文献
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Factors influencing the regeneration capacity of oilseed rape and cauliflower in transformation experiments 总被引:2,自引:0,他引:2
The efficiency ofAgrobacterium-based transformation technique in oilseed rape and cauliflower was influenced by cultivar specificity, donor plant age and explant type. Marked differences in demands for plant hormone contents in the regeneration medium were recorded already among different types of nontransformed explants. The highest regeneration capacity was recorded with stem and leaf segments isolated from one-month-old aseptically grown plants. The regeneration was markedly species-dependent. Regeneration of transformed plants from stem segments and thin layers isolated from field-grown oilseed rape plants (at the most 2% of regenerating explants) and from oilseed rape hypocotyls (0.8% of regenerating explants) and cauliflower (1.2% of explant regenerated transformed shoots) was achieved after disarmedAgrobacterium treatment. Hypersensitive reaction of explants could be prevented by using prolongedin vitro precultivation and delayed application of the selective agent. 相似文献
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Jan Tumajer Krešimir Begović Vojtěch Čada Michal Jenicek Jelena Lange Jiří Mašek Ryszard J. Kaczka Miloš Rydval Miroslav Svoboda Lukáš Vlček Václav Treml 《Global Change Biology》2023,29(2):462-476
Radial tree growth is sensitive to environmental conditions, making observed growth increments an important indicator of climate change effects on forest growth. However, unprecedented climate variability could lead to non-stationarity, that is, a decoupling of tree growth responses from climate over time, potentially inducing biases in climate reconstructions and forest growth projections. Little is known about whether and to what extent environmental conditions, species, and model type and resolution affect the occurrence and magnitude of non-stationarity. To systematically assess potential drivers of non-stationarity, we compiled tree-ring width chronologies of two conifer species, Picea abies and Pinus sylvestris, distributed across cold, dry, and mixed climates. We analyzed 147 sites across the Europe including the distribution margins of these species as well as moderate sites. We calibrated four numerical models (linear vs. non-linear, daily vs. monthly resolution) to simulate growth chronologies based on temperature and soil moisture data. Climate–growth models were tested in independent verification periods to quantify their non-stationarity, which was assessed based on bootstrapped transfer function stability tests. The degree of non-stationarity varied between species, site climatic conditions, and models. Chronologies of P. sylvestris showed stronger non-stationarity compared with Picea abies stands with a high degree of stationarity. Sites with mixed climatic signals were most affected by non-stationarity compared with sites sampled at cold and dry species distribution margins. Moreover, linear models with daily resolution exhibited greater non-stationarity compared with monthly-resolved non-linear models. We conclude that non-stationarity in climate–growth responses is a multifactorial phenomenon driven by the interaction of site climatic conditions, tree species, and methodological features of the modeling approach. Given the existence of multiple drivers and the frequent occurrence of non-stationarity, we recommend that temporal non-stationarity rather than stationarity should be considered as the baseline model of climate–growth response for temperate forests. 相似文献
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Krešimir Begović Jonathan S. Schurman Marek Svitok Jakob Pavlin Thomas Langbehn Kristyna Svobodová Martin Mikoláš Pavel Janda Michal Synek William Marchand Lucie Vitková Daniel Kozák Ondrej Vostarek Vojtech Čada Radek Bače Miroslav Svoboda 《Global Change Biology》2023,29(1):143-164
In a world of accelerating changes in environmental conditions driving tree growth, tradeoffs between tree growth rate and longevity could curtail the abundance of large old trees (LOTs), with potentially dire consequences for biodiversity and carbon storage. However, the influence of tree-level tradeoffs on forest structure at landscape scales will also depend on disturbances, which shape tree size and age distribution, and on whether LOTs can benefit from improved growing conditions due to climate warming. We analyzed temporal and spatial variation in radial growth patterns from ~5000 Norway spruce (Picea abies [L.] H. Karst) live and dead trees from the Western Carpathian primary spruce forest stands. We applied mixed-linear modeling to quantify the importance of LOT growth histories and stand dynamics (i.e., competition and disturbance factors) on lifespan. Finally, we assessed regional synchronization in radial growth variability over the 20th century, and modeled the effects of stand dynamics and climate on LOTs recent growth trends. Tree age varied considerably among forest stands, implying an important role of disturbance as an age constraint. Slow juvenile growth and longer period of suppressed growth prolonged tree lifespan, while increasing disturbance severity and shorter time since last disturbance decreased it. The highest age was not achieved only by trees with continuous slow growth, but those with slow juvenile growth followed by subsequent growth releases. Growth trend analysis demonstrated an increase in absolute growth rates in response to climate warming, with late summer temperatures driving the recent growth trend. Contrary to our expectation that LOTs would eventually exhibit declining growth rates, the oldest LOTs (>400 years) continuously increase growth throughout their lives, indicating a high phenotypic plasticity of LOTs for increasing biomass, and a strong carbon sink role of primary spruce forests under rising temperatures, intensifying droughts, and increasing bark beetle outbreaks. 相似文献
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