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971.
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974.
Although the contribution of community members to functional diversity is a key question of conservation ecology, its measurement and interpretation are rather problematic. In this paper, we suggest a novel method for decomposing functional diversity. To do this we consider functional units (i.e. species or a group of species with identical traits) as the functional building blocks of communities. Then we propose the use of a recently developed measure of functional diversity (called modified functional attribute diversity or MFAD) and suggest additive decomposition of MFAD into functional values contributed by the functional units. We point out that functional values are related to changes in MFAD if the functional unit is removed from the community. This property of decomposition allows the quantification of the contribution of community members to functional diversity. By studying artificial and actual communities we compare the performance of our new method with other recently developed contribution measures, which are based on dendrograms and ordinations. Both theoretical considerations and analyses of artificial and actual data sets suggest that the proposed method of calculating functional values expresses more explicitly the contribution of community members to functional diversity and hereby can be used as a simple, yet efficient method for searching for functional keystones in ecological communities or for quantifying the contribution of community members to functional diversity. 相似文献
975.
We construct a tractable model to describe the rate at which a knotted polymer is ejected from a spherical capsid via a small pore. Knots are too large to fit through the pore and must reptate to the end of the polymer for ejection to occur. The reptation of knots is described by symmetric exclusion on the line, with the internal capsid pressure represented by an additional biased particle that drives knots to the end of the chain. We compute the exact ejection speed for a finite number of knots L and find that it scales as 1/L. We establish a mapping to the solvable zero-range process. We also construct a continuum theory for many knots that matches the exact discrete theory for large L. 相似文献
976.
Zdenka Gasparova Pavol Janega Nada Pronayova Tibor Liptaj 《Central European Journal of Biology》2012,7(5):810-816
Background
Studies of the middle-aged hippocampus may clarify the early mechanisms of aging and may lead to timely initiation of treatment for age-related cognitive impairments. 相似文献977.
Effects of habitat fragmentation on carabids in forest patches 总被引:12,自引:0,他引:12
978.
Ensuring recovery of intact RNA from rat pancreas 总被引:1,自引:0,他引:1
Santokh S. Gill Rémy A. Aubin Claudia A. Bura Ivan H. A. Curran Tibor I. Matula 《Molecular biotechnology》1996,6(3):359-362
The isolation of intact RNA from rat pancreas is compromised by autolysis and by the presence of endogenous ribonucleases.
In order to ameliorate recovery we systematically investigated available RNA extraction methods and paid particular attention
to the influence of frozen storage and ribonuclease inhibition strategies on overall yield and quality of RNA. Modifications
to the basic procedure of Chomczynski and Sacchi (1987) are described which allow, reproducibly, to obtain rat pancreatic
RNA suitable for Northern blot hybridization, RT-PCR, and differential display analysis. 相似文献
979.
Exenatide, a synthetic peptide originally isolated from salivary secretions of Heloderma suspectum, like other subcutaneously injected peptides, can cause antibody formation. Despite that antibody formation has been observed in some patients, results from previous clinical trials have not shown safety and efficacy concerns in exenatide-naïve patients. The objective of this multicenter, open-label study was to investigate the response of anti-exenatide antibody formation and the incidence of immune-related and hypersensitivity reactions after exenatide re-exposure. Fifty-eight patients (57% male; 59 ± 10 years; weight 85 ± 19 kg; HbA1c 8.1 ± 0.9%; duration of diabetes 10 ± 5 years) were enrolled. At study initiation, 98.3% of patients were taking 1 or more antidiabetes drugs, including oral medication and various types of insulin. Treatment-emergent adverse events (TEAEs) at any time during the study were observed in 40 and 47% of patients with positive and negative treatment-emergent antibodies, respectively. Immune-related AEs were observed in 6 patients (4 were antibody positive). These AEs had not been reported in their previous exposure to exenatide. Re-exposure to exenatide did not result in increased hypersensitivity reactions. Overall, 72% of patients had a baseline to endpoint reduction in HbA1c (range −0.1 to −2.8%), and 87% of antibody negative versus 62% of antibody positive patients had an HbA1c endpoint reduction. The study design and the patients’ baseline characteristics, including diabetes treatment at study initiation, are confounding factors limiting clinical conclusions on exenatide's glycemic effect in this patient population. The study results indicate that anti-exenatide antibody formation did not increase the incidence of TEAEs in patients re-exposed to exenatide. 相似文献
980.
Helena Morais Cristina Ramos Esther Forgcs Tibor Cserhti Jos Oliviera 《Journal of biochemical and biophysical methods》2002,50(2-3):99-109
The activity of manganese-dependent and manganese-independent peroxidases produced by Pleurotus ostreatus in culture media composed of agro-residues was measured by visible spectrophotometry. The overall enzyme activity and its selectivity were separated by using spectral mapping technique followed by nonlinear mapping. The relationships between the parameters of enzyme production and the composition of culture media and fermentation time was assessed by stepwise regression analysis. Calculations proved that the addition of extract of straw to the culture media significantly decreased the overall production of both enzymes, whereas the selectivity of enzyme production was influenced by amount of potato extract and the concentration of total sugar in the culture media. Enzyme activity depended quadratically on the fermentation time. 相似文献