排序方式: 共有63条查询结果,搜索用时 842 毫秒
51.
Net Ecosystem Exchanges of Carbon, Water, and Energy in Young and Old-growth Douglas-Fir Forests 总被引:1,自引:1,他引:0
Jiquan Chen Kyaw Tha Paw U Susan L. Ustin Thomas H. Suchanek Barbara J. Bond Kimberley D. Brosofske Matthias Falk 《Ecosystems》2004,7(5):534-544
To be able to estimate the cumulative carbon budget at broader scales, it is essential to understand net ecosystem exchanges (NEE) of carbon and water in various ages and types of ecosystems. Using eddy-covariance (EC) in Douglas-fir dominated forests in the Wind River Valley, Washington, USA, we measured NEE of carbon, water, and energy from July through September in a 40-year-old stand (40YR) in 1998, a 20-year-old stand (20YR) in 1999, and a 450-year-old stand (450YR) during both years. All three stands were net carbon sinks during the dry, warm summers, with mean net daily accumulation of –0.30 g C m–2 d–1, –2.76 g C m–2 d–1, and –0.38 g C m–2 d–1, respectively, in the 20YR, 40YR, and 450YR (average of 1998, 1999) stands; but for individual years, the 450YR stand was a carbon source in 1998 (0.51 g C m–2 d–1) and a sink in 1999 (–1.26 g C m–2 d–1). The interannual differences for the summer months were apparent for cumulative carbon exchange at the 450YR stand, which had 46.9 g C m–2 loss in 1998 and 115.9 g C m–2 gain in 1999. As predicted, the 40YR stand assimilated the most carbon and lost the least amount of water to the atmosphere through evapotranspiration. 相似文献
52.
Kralova Lesna I Suchanek P Kovar J Stavek P Poledne R 《Journal of lipid research》2008,49(11):2414-2418
Dietary intervention is the first and usually successful approach in the treatment of high LDL cholesterol (LDL-C) concentration, but it is frequently accompanied by a decrease in HDL concentration. We studied 14 male volunteers on two different diets, high saturated fatty acid (SFA) and high PUFA, in a crossover design to test whether a decrease in HDL can affect reverse cholesterol transport from relabeled macrophages. A significant decrease of LDL-C (in mmol/l) after a PUFA diet compared with an SFA diet from 3.15 +/- 0.65 to 2.80 +/- 0.56 (P < 0.01) was accompanied by a significant decrease of HDL cholesterol (HDL-C) (in mmol/l) from 1.21 +/- 0.30 to 1.10 +/- 0.32 (P < 0.05). These changes did not affect cholesterol efflux (CHE) from macrophages (9.74 +/- 1.46% vs. 9.53 +/- 1.41%). There was no correlation between individual changes of HDL-C and changes of CHE. It is concluded that the decrease of HDL-C after successful dietary intervention of LDL-C is not accompanied by a decrease of CHE. 相似文献
53.
O'Neil SV Wang Y Laufersweiler MC Oppong KA Soper DL Wos JA Ellis CD Baize MW Bosch GK Fancher AN Lu W Suchanek MK Wang RL De B Demuth TP 《Bioorganic & medicinal chemistry letters》2005,15(24):5434-5438
Two novel 8,6-fused bicyclic peptidomimetic ring systems were synthesized utilizing olefin metathesis as the key reaction for the formation of the eight-membered ring. Both peptidomimetic scaffolds were further elaborated into potent ICE inhibitors, with numerous compounds exhibiting caspase-1 IC50s less than 10 nM. 相似文献
54.
55.
56.
Sebastian Görn Bernd Dobner Axinia Suchanek Klaus Fischer 《Biodiversity and Conservation》2014,23(2):309-326
Fens and concomitantly the associated species assemblages have undergone dramatic declines in recent decades. Given that many remaining or restored fens are currently lying fallow, an important question is which management regime, if any, is most effective in preserving fen biodiversity. Against this background we here investigate the effects of five management regimes (intensive grassland, moist meadows, summer harvested sites, winter harvested sites, fallows) on three insect taxa (butterflies, grasshoppers, carabid beetles) in riverine fens in north-eastern Germany. Butterflies and grasshoppers showed highest species numbers, diversity and numbers of threatened species on moist meadows and were detrimentally affected by high vegetation. In contrast, ground dwelling carabid beetles were less strongly affected by different management regimes, but responded very sensitive to drainage. Winter harvested sites and fallows seemed to be particularly beneficial to carabid beetles. Overall, drained, intensive grassland was not suitable for preserving fen-specific communities, while extensively managed moist meadows harboured overall the highest numbers of threatened species. We conclude that in terms of management maintaining high water tables is most important. Furthermore, some management seems necessary to maintain stands with lower vegetation turf for associated species. However, care is needed to also maintain fallows and to consider the specific demands of some highly endangered, management-sensitive species. 相似文献
57.
Soper DL Sheville JX O'Neil SV Wang Y Laufersweiler MC Oppong KA Wos JA Ellis CD Baize MW Chen JJ Fancher AN Lu W Suchanek MK Wang RL Schwecke WP Cruze CA Buchalova M Belkin M Wireko F Ritter A De B Wang D Demuth TP 《Bioorganic & medicinal chemistry》2006,14(23):7880-7892
An 8,5-fused bicyclic peptidomimetic ring system generated by a stereoselective ring metathesis reaction was elaborated into potent inhibitors of interleukin-1beta converting enzyme (ICE, caspase-1). Multiple compounds were found that exhibited ICE IC50 values < 10 nM and were selective over caspase-3 and caspase-8. These active analogs generally possessed good activity (IC50 values < 100 nM) in a whole cell assay measuring IL-1beta production. Pharmacokinetic analysis of the ethyl acetal prodrug form of a selected active lead revealed a compound with a reasonable plasma half-life (1.1 h) and good oral bioavailability (30%). 相似文献
58.
Sabat M Vanrens JC Brugel TA Maier J Laufersweiler MJ Golebiowski A De B Easwaran V Hsieh LC Rosegen J Berberich S Suchanek E Janusz MJ 《Bioorganic & medicinal chemistry letters》2006,16(16):4257-4261
This communication details the synthesis, biological activity, and proposed binding mode of a novel class of tri-cyclic derivatives of 1,2-dihydro-pyrimido[4,5-c]pyridazines 1 and 2. The most potent analogs disclosed showed low nanomolar activity for the inhibition of Lck kinase. 相似文献
59.
Silke Walter Axinia Doering Maryse Letiembre Yang Liu Wenlin Hao Ricarda Diem Christian Bernreuther Markus Glatzel Britta Engelhardt Klaus Fassbender 《Cellular physiology and biochemistry》2006,17(3-4):167-172
Innate immune receptors are crucial for defense against microorganisms. Recently, a cross-talk between innate and adaptive immunity has been considered. Here, we provide first evidence for a role of the key innate immune receptor, LPS receptor (CD14) in pathophysiology of experimental autoimmune encephalomyelitis, the animal model of multiple sclerosis. Indicating a functional importance in vivo, we show that CD14 deficiency increased clinical symptoms in active experimental autoimmune encephalomyelitis. Consistent with these observations, CD14 deficient mice exhibited a markedly enhanced infiltration of monocytes and neutrophils in brain and spinal cord. Moreover, we observed an increased immunoreactivity of CD14 in biopsy and post mortem brain tissues of multiple sclerosis patients compared to age-matched controls. Thus, the key innate immune receptor, CD14, may be of pathophysiological relevance in experimental autoimmune encephalomyelitis and multiple sclerosis. 相似文献
60.