ABSTRACT
Water use efficiency (WUE) is an effective index to study the coupling of land carbon and water cycle. The Qinghai-Tibet Plateau is the most important ecological security barrier in China. Understanding the characteristics and mechanism of WUE is important for the carbon cycle and water resources rational utilization in the plateau. Based on MODIS data of gross primary productivity (GPP) and evapotranspiration (ET), we analyzed the spatial-temporal variations of WUE over the Qinghai-Tibet Plateau and the effects of climate factors. The results showed that WUE in the Qinghai-Tibet Plateau had an upward trend under the combined action of GPP and ET during 2001-2020. The southeast and northeast of the Plateau had the highest WUE value, while the central part had the lowest WUE value. WUE of grassland, marsh and alpine vegetation showed an increasing trend, while that of shrub land, broadleaved forest and coniferous forest showed a decreasing trend. There was a significant positive correlation between WUE and annual air temperature, and the sensitivity increased with the increases of air temperature. The relationship between WUE and annual precipitation was non-linear. When precipitation was less than 700 mm, the sensitivity of WUE to precipitation decreased with the increases of precipitation. When precipitation was more than 700 mm, the sensitivity of precipitation increased with the increases of precipitation. However, WUE was negatively correlated with precipitation in more than 75% of regions, and was affected by precipitation in a larger area. In the future, warm and humid climate would lead to a decrease in WUE.
Subject(s)
Ecosystem , Water , China , Climate Change , TibetABSTRACT
We have previously reported that sulfated cyclodextrins inhibit the invasion of Plasmodium merozoites by interacting with receptors present on the surface of erythrocytes. The observation that tetrazolium salts formed stable complexes with the inhibitory sulfated cyclodextrins suggested that tetrazolium salts might have anti-Plasmodium activity as well. Evaluation of commercially available tetrazolium salts indicated that some were active in the low nanomolar range and showed specificity in their inhibition of Plasmodium. Synthesis of a further 54 structures allowed us to determine that activity results from an aromatic component attached to the tetrazolium carbon atom (R1) and its size is not critical to the activity of the compound. Nitro modifications of active compounds are poorly tolerated, however, the presence of halogen atoms on aromatic groups attached to the nitrogen atoms of the tetrazolium ring (R2 and R3) has little effect on activity. Methoxy groups are tolerated on R2 and R3 components; however, they are disruptive on the R1 component. The overall results suggest that the R1 component is interacting with a specific hydrophobic environment and the R2 and R3 components are less constrained. The activity of these compounds in several human and mouse Plasmodium cultures suggests that the compounds interact with a component of the parasite that is both essential and conserved.
Subject(s)
Antiprotozoal Agents/chemistry , Plasmodium/drug effects , Tetrazolium Salts/pharmacology , Animals , Cells, Cultured , Humans , Hydrophobic and Hydrophilic Interactions , Mice , Structure-Activity Relationship , Tetrazolium Salts/chemistryABSTRACT
Benzotriazole, 2,5-dimethoxytetrahydrofuran, and (S)-phenylglycinol in one step gave 80% of (3S, 5R,7aR)-5-(benzotriazol-1-yl)-3-phenyl-[2,1-b]oxazolopyrrolidine (6), whose crystal structure was confirmed by X-ray crystallography. Novel chiral pyrrolidine synthon 6 reacts with organosilicon (allyltrimethylsilanes and vinyloxytrimethylsilanes), organophosphorus, organozinc, and Grignard reagents to afford chiral 2-substituted and 2,5-disubstituted pyrrolidines.
ABSTRACT
N,N-Bis[(benzotriazol-1-yl)methyl]benzylamines and N,N-bis[(benzotriazol-1-yl)methyl](p-N',N'-dimethylphenyl)amine on reaction with allyltrimethylsilanes yielded substituted piperidines. Other N,N-bis[(benzotriazol-1-yl)methyl]anilines (unsubstituted and p-CH(3), OCH(3), Cl) gave julolidines (2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij] quinoline).
