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991.
992.
In this paper we describe the use of punched feature cards in a general practice for 18 months. Its advantages are the low cost, speed of information retrieval, visible statistics, computer compatibility, accuracy, confidentiality, flexibility, and simplicity of setting up and collection of information. The system encourages the doctor to ask questions about his practice, and could readily be adopted in other practices. 相似文献
993.
Divergence time estimates of mammals from molecular clocks and fossils: Relevance of new fossil finds from India 总被引:1,自引:0,他引:1
G. V. R. Prasad 《Journal of biosciences》2009,34(5):649-659
This paper presents a brief review of recent advances in the classification of mammals at higher levels using fossils and
molecular clocks. It also discusses latest fossil discoveries from the Cretaceous — Eocene (66–55 m.y.) rocks of India and
their relevance to our current understanding of placental mammal origins and diversifications. 相似文献
994.
995.
The Capricorn silvereye (Zosterops lateralis chlorocephalus) is ideally suited to investigating the genetic basis of body size evolution. We have isolated and characterized a set of microsatellite markers for this species. Seven out of 11 loci were polymorphic. The number of alleles detected ranged from two to five and observed heterozygosities between 0.12 and 0.67. One locus, ZL49, was found to be sex‐linked. This moderate level of diversity is consistent with that expected in an isolated, island population. 相似文献
996.
M A Kersten M J Arninkhof H J Op den Camp L J Van Griensven C van der Drift 《Biochimica et biophysica acta》1999,1428(2-3):260-272
Mycelium of Agaricus bisporus took up methylamine (MA), glutamate, glutamine and arginine by high-affinity transport systems following Michaelis-Menten kinetics. The activities of these systems were influenced by the nitrogen source used for mycelial growth. Moreover, MA, glutamate and glutamine uptakes were derepressed by nitrogen starvation, whereas arginine uptake was repressed. The two ammonium-specific transport systems with different affinities and capacities were inhibited by NH(+)(4), with a K(i) of 3.7 microM for the high-velocity system. The K(m) values for glutamate, glutamine and arginine transport were 124, 151 and 32 microM, respectively. Inhibition of arginine uptake by lysine and histidine showed that they are competitive inhibitors. MA, glutamate and glutamine uptake was inversely proportional to the intracellular NH(+)(4) concentration. Moreover, increase of the intracellular NH(+)(4) level caused by PPT (DL-phosphinotricin) resulted in an immediate cessation of MA, glutamine and glutamate uptake. It seems that the intracellular NH(+)(4) concentration regulates its own influx by feedback-inhibition of the uptake system and probably also its efflux which becomes apparent when mycelium is grown on protein. Addition of extracellular NH(+)(4) did not inhibit glutamine uptake, suggesting that NH(+)(4) and glutamine are equally preferred nitrogen sources. The physiological importance of these uptake systems for the utilization of nitrogen compounds by A. bisporus is discussed. 相似文献
997.
998.
D. L. Grekov 《Plasma Physics Reports》2001,27(12):1011-1016
A possible way to affect the influxes of heavy impurities into the plasma of a stellarator with poloidal slits in the vacuum wall (e.g., the W7-AS stellarator) by RF heating of the impurities is discussed. It is shown that the influxes can be reversed in direction by applying a relatively low RF power. The design features of the W7-AS stellarator are such that there is no need to place additional antennas inside the vacuum chamber. 相似文献
999.
1000.
Flash-induced absorption changes at 820 nm were studied as a function of redox potential in Tris-extracted Photosystem II oxygen-evolving particles and Triton subchloroplast fraction II particles. The rereduction kinetics of P-680+ in both preparations showed biphasic recovery phases with half-times of 42 and 625 microseconds at pH 4.5. The magnitude of the 42 microseconds phase of P-680+ rereduction was strongly dependent on the redox potential of the medium. This absorption transient, attributed to electron donation from D1 (the secondary electron donor in oxygen-inhibited chloroplasts), titrated as a single redox component with a midpoint potential of +240 +/- 35 mV. The experimentally determined midpoint potential was found to be independent of pH over the tested range 4.5-6.0. In contrast, the magnitude of the 625 microseconds phase of P-680+ rereduction was independent of redox potential between +350 and +100 mV. These results are interpreted in terms of a model in which an alternate electron donor with Em approximately equal to 240 mV, termed D0, serves as a rapid donor (t 1/2 less than or equal to 2 microseconds) to P-680+ in Tris-extracted and Triton-treated Photosystem-II preparations. According to this model, the slower electron donor, D1, is functional only when D0 becomes oxidized. 相似文献