论CSS定位机制及其应用

CSS是Web标准的主要组成部分,用来设置元素的表现样式。本文从盒子模型入手,总结了CSS的三种定位机制,并举例说明他们的应用。

Influence of vegetation type and topographic position on volumetric soil water content dynamics and similarity among surface and deep soil layers

Clarifying the mechanisms governing volumetric soil water content(VSWC)dynamics in soil profiles is essential,as it can help to elucidate soil water transport processes and improve the prediction accuracy of soil hydrological processes.Using Spearman's rank correlation and wavelet coherence analysis methods,similarity in soil profile VSWC dynamics and factors governing VSWC soil profile dynamics in upslopes and downslopes under three vegetation types(evergreen forest[EG],secondary deciduous forest mixed with shrubs[SDFS],and deforested pasture[DP])at different time scales(hourly,daily,weekly,and monthly)and in different seasons were analyzed.The results revealed significant similarity in the VSWC of different soil depths(P<0.01),with the similarity decreasing in accordance with the increment in soil depth.Greater VSWC similarity was found in EG than SDFS and DP sites and in upslope than downslope areas at both forest sites.The average significant coherence area(SCA)of VSWC similarity among surface and deep soil layers varied with the time scale,which was in the order of monthly(58.6%)>weekly(42.8%)>daily(21.8%).The effects of soil properties(e.g.,texture,saturated hydraulic conductivity),rainfall,and potential evapotranspiration(ET_(p))on VSWC similarity were related to the time scale and season in which VSWC monitoring took place.Soil properties had apparent effects on VSWC similarity at longer time scales(i.e.,monthly),with a high SCA.In contrast,the effects of rainfall and ET_(p) on VSWC similarity were concentrated at weekly and daily scales,with a relatively low SCA.Rainfall and ET_(p) dominated VSWC dynamics in the summer and fall,respectively.These results imply the use of measured VSWC at one soil depth to predict the VSWC at other soil depths was a reliable method.While the in-fluence of time scale effects and seasonal variations on prediction accuracy of VSWC should be considered.

Subcellular chemical imaging of structurally similar acridine drugs by near-field laser desorption/laser postionization mass spectrometry

Insights into the pharmacologic effect on cellular processes and the potential toxicological effects are vital to new drug development and evaluation,yet research on these subjects remains a great challenge due to the lack of information regarding the spatiotemporal distribution of drugs and metabolites within a single cell.Mass spectrometry imaging(MSI)has proven to be a label-free and high-throughput approach for visualizing drug distribution in spatial and temporal domains.However,single-cell drug imaging has been limited so far by detection sensitivity and microscale lateral resolution.Herein,we report near-field laser desorption/laser postionization mass spectrometry(NDPI-MS)for single-cell imaging of two structurally similar drugs,proflavine and ethacridine,and subcellular distributions of proflavine at different drug concentrations were investigated.The NDPI-MS imaging results indicate that proflavine was accumulated in lysosomes,which was verified by laser scanning confocal microscopy(LSCM).Additionally,a distinguished subcellular distribution pattern of ethacridine from proflavine could be visualized,highlighting the complexity of the interaction between the drugs and biological environment even though these two drugs possess similar structures.Taken together,the present results demonstrate the great potential of the integrated single-cell MSI platform for characterizing the drug distribution and its phenotype changes within individual cells,expediting the identification and evaluation of newly developed drugs.