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991.
The presence of volunteer hardwood species in loblolly pineplantations demands studies on both intra- and inter-specificcompetition in order to build growth and yield models and toguide vegetation management for these stands. This paper, basedon analyses of data collected from a thinning study, reportsan investigation of responses of loblolly pine and hardwoodspecies towards intra- and inter-specific competition. Underhigh levels of overall competition, hardwood species were morecompetitive, both intra- and inter-specifically. Intra-specificcompetition was more effective in reducing hardwood basal areagrowth than inter-specific competition under high levels ofoverall competition. However, under low levels of overall competition,intra- and inter-specific competition were quantitatively similartoward loblolly pine basal area growth. The basal area growthof hardwoods was significantly related to levels of inter-specificcompetition, but not with intra-specific effects under low levelsof overall competition. More than half of the variability inloblolly pine basal area growth under unthinned control andlight thin treatments could be accounted for by competitioneffects. However, only one third of the variability could beexplained for loblolly pine under heavy thin treatment. Forhardwood species, the percentage of growth variation accountedfor by competition was about 45%, and did not change among thethinning treatments. Different resource demands between thetwo categories of tree species and a certain amount of thinningshock were suggested by the modelling results.Copyright 1994,1999 Academic Press Neighbourhood approach, competition index, hardwood, no-interaction model, basal area, reciprocal yield law 相似文献
992.
Electron spin resonance (ESR) spin-label methods were used with 5-doxyl-stearic acid as a probe to investigate membrane fluidity of Chinese hamster ovary (CHO) cells during the cell cycle. A 35 GHz ESR technique was developed to study membrane fluidity of intact cells. This technique requires only about the amount of cells compared to the conventional spin-label techniques. With this technique we observed a cyclic change of membrane fluidity during the cell cycle of CHO cells: cells in mitosis had the highest membrane fluidity, whereas cells in G1 and early S phases had the lowest membrane fluidity. 相似文献
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994.
Wenkui Li Suyi Luo Harold T. Smith Francis L.S. Tse 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2010,878(5-6):583-589
Analyte loss due to non-specific binding, especially container surface adsorption, is not uncommon in the quantitative analysis of urine samples. In developing a sensitive LC–MS/MS method for the determination of a drug candidate, BAF312, in human urine, a simple procedure was outlined for identification, confirmation and prevention of analyte non-specific binding to a container surface and to recover the ‘non-specific loss’ of an analyte, if no transfer has occurred to the original urine samples. Non-specific binding or container surface adsorption can be quickly identified by using freshly spiked urine calibration standards and pre-pooled QC samples during a LC–MS/MS feasibility run. The resulting low recovery of an analyte in urine samples can be prevented through the use of additives, such as the non-ionic surfactant Tween-80, CHAPS and others, to the container prior to urine sample collection. If the urine samples have not been transferred from the bulk container, the ‘non-specific binding’ of an analyte to the container surface can be reversed by the addition of a specified amount of CHAPS, Tween-80 or bovine serum albumin, followed by appropriate mixing. Among the above agents, Tween-80 is the most cost-effective. β-cyclodextrin may be suitable in stabilizing the analyte of interest in urine via pre-treating the matrix with the agent. However, post-addition of β-cyclodextrin to untreated urine samples does not recover the ‘lost’ analyte due to non-specific binding or container surface adsorption. In the case of BAF312, a dynamic range of 0.0200–20.0 ng/ml in human urine was validated with an overall accuracy and precision for QC sample results ranging from ?3.2 to 5.1% (bias) and 3.9 to 10.2% (CV), respectively. Pre- and post-addition of 0.5% (v/v) Tween-80 to the container provided excellent overall analyte recovery and minimal MS signal suppression when a liquid–liquid extraction in combination with an isocratic LC separation was employed. The compound was stable in 0.5% Tween-80 treated human urine QC samples for at least 24 h at room temperature, after three freeze/thaw cycles with storage at ≤?60 °C and for at least 3 months when stored at ≤?60 °C. The current work could serve as a simple example in trouble shooting non-specific binding or container surface adsorption in quantitative analysis of urine samples. 相似文献
995.
Maintaining a stable social organization necessitates that animals recognize their own dominance status relative to the status of other group members. The weakly electric brown ghost knifefish emits a sexually dimorphic sinusoidal electric organ discharge (EOD) for electrolocation. Dominant males discharge at the highest and females at the lowest EOD frequencies (EODFs). Each individual is most sensitive to its own EODF, which can be modulated for communication. To examine how sensitivity and social status influence an individual's response to different cues, we recorded the electrical signals emitted by 10 males and seven females in response to playbacks of sine waves mimicking a wide range of con- and heterospecific EODFs. While all individuals emit small chirps (LoCs) mostly to stimuli around their own EODF, they are more likely to emit rises (gradual nonchirp signals) to frequencies to which they are less sensitive; males similarly emit larger chirps (HiCs) to frequencies more distant from their own, especially to female mimics. Males with ‘dominant’ EODFs are less likely to emit rises, stimuli in the female range elicit more rises from both sexes, and females emit rises to male EOD mimics. Although low-ranking male EOD mimics elicit more LoCs from all males, males with lower-ranking EODFs chirp less at high EOD mimics than males with high-ranking EODFs chirp at low EOD mimics. We conclude that (1) although much of the variation in an individual's response is attributable to its sensitivity, individuals recognize sexual and status cues and have some internal representation of their own social status, and (2) whereas LoCs appear to function in intrasexual aggression, HiCs and rises could be used in both courtship and submissive signalling. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved. 相似文献
996.
Iain MacCallum Dariusz Przybylski Sante Gnerre Joshua Burton Ilya Shlyakhter Andreas Gnirke Joel Malek Kevin McKernan Swati Ranade Terrance P Shea Louise Williams Sarah Young Chad Nusbaum David B Jaffe 《Genome biology》2009,10(10):R103
We demonstrate that genome sequences approaching finished quality can be generated from short paired reads. Using 36 base (fragment) and 26 base (jumping) reads from five microbial genomes of varied GC composition and sizes up to 40 Mb, ALLPATHS2 generated assemblies with long, accurate contigs and scaffolds. Velvet and EULER-SR were less accurate. For example, for Escherichia coli, the fraction of 10-kb stretches that were perfect was 99.8% (ALLPATHS2), 68.7% (Velvet), and 42.1% (EULER-SR). 相似文献
997.
998.
999.
E Garaci C Rinaldi-Garaci V del Gobbo C Favalli M G Santoro B M Jaffe 《Cellular immunology》1981,62(1):8-14
The effect of prostaglandins on the in vivo induction of theta antigen in splenic spontaneous rosette-forming cells derived from adult thymectomized mice was studied. A long-acting synthetic analog of prostaglandin E2, di-M-PGE2, mimicked the effects of thymic hormone and was active when mice were treated with as little as 0.1 μg ip. In addition, indomethacin, a potent inhibitor of prostaglandin biosynthesis, was able to reverse the inductive effects of exogenous thymic hormone and inhibit the expression of theta antigen in normal mice, presumably by interfering with the effect of endogenous thymic factors. Finally, indomethacin also partially suppressed the stimulatory effects of exogenously administered di-M-PGE2, suggesting that this agent is effective, at least in part, because it stimulates endogenous prostaglandin biosynthesis. Possible mechanisms of action for the effects of prostaglandins are presented. 相似文献
1000.