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101.
Toshihide Hirao Masashi Murakami Jiro Iwamoto Hino Takafumi Hiroyuki Oguma 《Ecological Research》2008,23(1):189-196
The effect of disturbance on local communities may operate within the context of the spatial landscape. We examined the scale-dependent
effects of windthrow disturbance caused by a large typhoon on three arthropod communities in a temperate forest of Japan.
Canopy arthropods were collected by beating foliage, forest-floor arthropods were collected by sweeping the vegetation, and
flying arthropods were collected in Malaise traps. To assess the “functional spatial scale” at which arthropods responded
to tree-fall disturbance, the gap rate was quantified at different spatial scales by sequentially enlarging the radius of
a circular landscape sector in 10-m increments from 10 to 500 m. We then analyzed the responses of order richness and abundance
to the gap rate for each arthropod community. The spatial scale of the significant best-fitting model, which was selected
from the models fitted to the gap rate at stepwise spatial scales, was regarded as the arthropod-specific functional spatial
scale. Arthropod order richness was not dependent on the gap rate. In contrast, arthropod order abundance depended significantly
on the gap rate in many orders, but varied in the response direction and functional spatial scale. These order-specific, scale-dependent
responses to tree-fall gaps could complicate interactions among organisms, leading to complex community organization. An understanding
of the spatial processes that link the use of space by organisms with the spatial scale at which ecological processes are
experienced is required to elucidate the responses of populations, communities, and biotic interactions to disturbances in
a spatial landscape context. 相似文献
102.
S. Kumar Sunil Kumar S. P. Negi J. K. Kanwar 《In vitro cellular & developmental biology. Plant》2008,44(6):474-479
Callus cultures derived from leaf segments of chrysanthemum cultivar ‘Snow Ball’ which was susceptible to Septoria obesa were successfully used for in vitro selection for resistance to this pathogenic fungus. Resistant cell lines were selected by culturing callus on growth medium
containing various concentrations of S. obesa filtrate. Resistant calluses obtained after two cycles (30 d each cycle) of selection were used for plant regeneration. About
30% of the plants regenerated from the resistant calluses and 70–80% of the plants raised from cuttings had acquired considerable
resistance against the pathogen in the field. No phenotypic variation was observed in the selected regenerates. 相似文献
103.
Vertical ionization energies (VIEs) of medazepam, nordazepam and their molecular subunits have been calculated using the electron
propagator method in the P3/CEP-31G* approximation. Vertical electron affinities (VEAs) have been obtained with a ∆SCF procedure
at the DFT-B3LYP/6-31+G* level of theory. Excellent correlations have been achieved between IEcalc and IEexp, allowing reliable assignment of the ionization processes. Our proposed assignment differs in many instances from that previously
reported in the literature. The electronic structure of the frontier Dyson orbitals shows that the IE and EA values of the
benzodiazepines can be modulated by substitution at the benzene rings. Hardness values, evaluated as (IE − EA)/2, follow the
trend of the experimental singlet transition energies. Medazepam is a less hard (i.e., less stable) compound than nordazepam. 相似文献
104.
Background
Plant lipoxygenases (LOXs) have been proposed to form biologically active compounds both during normal developmental stages such as germination or growth as well as during responses to environmental stress such as wounding or pathogen attack. In our previous study, we found that enzyme activity of endogenous 9-LOX in Nicotiana benthamiana was highly induced by agroinfiltration using a tobacco mosaic virus (TMV) based vector system. 相似文献105.
Background
Since the first well-known electrocardiogram (ECG) delineator based on Wavelet Transform (WT) presented by Li et al. in 1995, a significant research effort has been devoted to the exploitation of this promising method. Its ability to reliably delineate the major waveform components (mono- or bi-phasic P wave, QRS, and mono- or bi-phasic T wave) would make it a suitable candidate for efficient online processing of ambulatory ECG signals. Unfortunately, previous implementations of this method adopt non-linear operators such as root mean square (RMS) or floating point algebra, which are computationally demanding. 相似文献106.
Recent studies suggest that evergreen plants may maintain their photosynthetic capacity through the winter. Since mild winters
are predicted to be more frequent in the future, the metabolic activity of plants is also likely to increase. The aim of the
present study was to assess how various environmental factors, such as temperature, photoperiod and preceding frost, affect
the recovery of photosynthesis during a mild spell in winter. The recovery of photosynthesis was studied in a series of growth
chamber experiments where the overwintering of lingonberry (Vaccinium vitis-idaea) was interrupted by an intermittent warm spell of 1 week during different phases of winter. Rapid activation was observed
in all the experiments during the first 3–4 days. No obvious effects of the phase of winter or photoperiod on the recovery
of photosynthesis were observed, but a severe freezing treatment prior to the warm spell retarded the recovery significantly.
Once recovered, however, lingonberry was able to maintain high rates of photosynthesis even at near-freezing temperatures,
which prevail in their natural sub-nivean environment. The apparent quantum yield of photosynthesis remained high through
the winter for lingonberry. This may prove advantageous for evergreen dwarf shrubs which overwinter in dim environments under
snow. 相似文献
107.
HUMAN serum contains several protease inhibitors, one of which is identified as α1-globulin (α1-antitrypsin) and another as α2-macroglobulin. Serum also contains inhibitors against the activation of plasminogen, which may differ from the protease inhibitors. Thus, inhibition of plasminogen activation by urokinase is selectively increased during the last trimester of pregnancy1,2. Likewise, increased inhibition of streptokinase-activated human euglobulin or of a tissue plasminogen activator was noticed in some groups of patients with thrombotic disease3,4. This observation is of particular interest because the tissue activator, which is present in venous endothelium5, is believed to assist in the removal of fibrinous deposits caused by tissue injury6. 相似文献
108.
Inhibition of RNA Polymerase by Streptolydigin 总被引:23,自引:0,他引:23
GIOVANNI CASSANI RICHARD R. BURGESS HOWARD M. GOODMAN LAWRENCE GOLD 《Nature: New biology》1971,230(15):197-200
109.
S C Pan 《Experimental parasitology》1978,45(2):274-286
Established cultures of human skin-muscle cells were used for determining the parasite—host cell relationship of Trypanosoma cruzi amastigotes (12–16 passages) cultured in a cell-free medium (F-69) at 37 C. The medium used for this experiment was tissue culture fluid M-199 enriched with 10% fetal bovine serum and relatively high concentrations of ATP, ADP and AMP. Amastigotes entered skin-muscle cells incubated at 32 or 35 C, multiplied and completed their intracellular life cycle in about 7 days. At 35 C, 23.6% of cells became infected in 7 days and at 32 C, 43.6% were infected in 5 days. The higher infection rate of cultured cells at 32 C was probably due to more frequent and prolonged cell-parasite contact, as amastigotes multiplied in the tissue culture medium and remained viable for a longer period at the lower temperature. As a control, epimastigotes were used to infect skinmuscle cells. Epimastigotes transformed into metacyclic trypomastigotes before entering host cells, multiplied, and completed the intracellular life cycle. We conclude that the amastigotes cultured in F-69 at 37 C are biologically similar to intracellular amastigotes from the vertebrate host, in that both can multiply and complete the life cycle intracellulary. 相似文献
110.