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711.
Graeme Shannon Maria Thaker Abi Tamim Vanak Bruce R. Page Rina Grant Rob Slotow 《Ecosystems》2011,14(8):1372-1381
Elephant and fire are considered to be among the most important agents that can modify the African savanna ecosystem. Although
the synergistic relationship between these two key ecological drivers is well documented, it has proved much more difficult
to establish the relative effects they have on savanna vegetation structure at a fine-scale over time. In this study, we explore
the comparative impacts of fire and elephant on 2,522 individually identified large trees (≥5 m in height) in the Kruger National
Park, South Africa. Data were collected from 21 transects first surveyed in April 2006 and resurveyed in November 2008, to
determine the relative importance of past damage by these agents on subsequent impacts and mortality. The occurrence of fire
or elephant damage in 2006 affected the amount of tree volume subsequently removed by both these agents; elephant removed
more tree volume from previously burned trees and the impact of subsequent fire was higher on previously burned or elephant-utilized
trees than on undamaged trees. Mortality was also affected by an interaction between previous and recent damage, as the probability
of mortality was highest for trees that suffered from fire or elephant utilization after being pushed over. Subsequent fire
damage, but not elephant utilization, on debarked trees also increased the probability of mortality. Mortality was twice (4.6%
per annum) that of trees progressing into the ≥5 m height class, suggesting an overall decline in large tree density during
the 30-month study period. The responses of large trees were species and landscape-specific in terms of sensitivity to elephant
and fire impacts, as well as for levels of mortality and progression into the ≥5 m height class. These results emphasize the
need for fine-scale site-specific knowledge for effective landscape level understanding of savanna dynamics. 相似文献
712.
Nafiu Amidu William KBA Owiredu Eric Woode Otchere Addai-Mensah Lawrence Quaye Abass Alhassan Edmond A Tagoe 《Reproductive biology and endocrinology : RB&E》2010,8(1):106
Background
Sexuality is a complex phenomenon that is being influenced by psychological as well as physiological factors. Its dysfunction includes desire, arousal, orgasmic and sex pain disorders. The present study aimed to assess the incidence of sexual dysfunction (SD) and related risk factors in a cohort of Ghanaian women. 相似文献713.
714.
715.
Gifty A. Blankson Daniel S. Pilch Angela A. Liu Leroy F. Liu Joseph E. Rice Edmond J. LaVoie 《Bioorganic & medicinal chemistry》2013,21(15):4511-4520
A series of macrocyclic biphenyl tetraoxazoles was synthesized. The latter stages of the synthetic approach allowed for the addition of varied N-protected α-amino acids, which were subsequently deprotected and condensed to provide the desired macrocycles. Improved yields could be realized in the macrocyclization step of their synthesis relative to other macrocyclic G-quadruplex stabilizers. These 24-membered macrocycles were evaluated for their ability to stabilize G-quadruplex DNA and for their relative cytotoxicity against human tumor cells. These biphenyl tetraoxazoles were not strong ligands for G-quadruplex DNA relative to other macrocyclic polyoxazoles. This reduced stabilizing potential did correlate with their comparatively lower cytotoxic activity as observed in the human tumor cell lines, RPMI 8402 and KB3-1. These studies provide useful insights into the conformational requirements for the development of selective and more potent G-quadruplex ligands. 相似文献
716.
Ahmed Khalil Chambaz Edmond M. Issinger Olaf-George 《Molecular and cellular biochemistry》1999,196(1-2):1-2
Molecular and Cellular Biochemistry - 相似文献
717.
Using satellite telemetry to define spatial population structure in polar bears in the Norwegian and western Russian Arctic 总被引:2,自引:0,他引:2
718.
A theory of mass isotopomer analysis based on the well-known principle of isotope dilution mass spectrometry is reviewed. An algorithm for the determination of isotope incorporation into a metabolic substrate from a labeled precursor using mass isotopomer analysis is presented. The steps include the determination of the contribution of the derivatization reagent to the observed spectrum of the derivatized substrate and the correction of contribution from 13C natural abundance using multiple linear regression analysis. Examples of the application of this theory to determine the spectrum of the trimethylsilyl derivative of the 'pure unlabeled' or mononuclidic cholesterol, and the calculation of mass isotopomer distribution in cholesterol due to tracer incorporation using this 'pure unlabeled' spectrum, are also provided. 相似文献