[1] In the northern prairie region of North America, numerous seasonal wetlands and ephemeral ponds form as snowmelt water is trapped in small topographical depressions. A detailed hydrogeological investigation is combined with electrical resistivity imaging (ERI) to evaluate the roles of the wetlands and ponds on depression-focused groundwater recharge at the St. Denis National Wildlife Area in Saskatchewan, Canada. The analysis of groundwater samples indicated two distinct geochemical zones: a zone of salt leaching under Wetland 109 and zones of salt accumulation under the adjacent uplands. Two intermediate zones were identified as partially leached or mixed leached-unleached and premodern or mixed saline-nonsaline water. The resistivity images of the areas around 109 were classified using the correlation between ERI-derived electrical conductivity (EC) and the groundwater EC. The ERI data clearly showed that depression-focused recharge occurs under all depressions regardless of size. Leaching is observed to the depth of a regional intertill aquifer, indicating that depression-focused recharge contributes to the regional groundwater system. The ERI data also revealed the complex pattern of salt distribution that could not have been recognized by hydrogeological observations alone. The complex distribution of salts appears to be caused by interaction between wetlands and variations in topography.
Microribonucleic acids (miRNAs) are small, noncoding RNAs that play important regulatory roles by downregulating target transcripts in a sequence-specific manner. The miRBase Registry (Release 8.2) lists 732 miRNAs from flowering plant species, with the majority identified from Arabidopsis, rice and poplar where genome sequence is available. In the absence of genomic sequence and on the basis that sequences of many miRNAs are conserved amongst divergent plant species, we analysed approximately 120,000 Malus domestica cv. Royal Gala expressed sequence tags (ESTs) and identified ten distinct sequences that could be classified into seven conserved plant miRNA families (miR156, miR159, miR162, miR167, miR172, miR393 and miR398). Secondary structure predictions showed these sequences have the characteristic fold-back structures of precursor miRNAs, and northern analysis validated the presence of these miRNA families within Royal Gala tissues.
Particle image velocity measurements were applied on thermally driven convection at low Rayleigh numbers. In a model experiment using a water column heated from bottom and cooled from above, the velocity field was studied at different vertical temperature gradients. In the testing facility with high aspect ratio (about 19) representing a 1-m-long column with 5 cm diameter, occurrence of free convection was verified for destabilizing temperature gradients of 0.1-2 K/m. The PIV results revealed that significant flow exists already at low vertical temperature gradients. The velocity of the stable large-scale circulations increased linearly with temperature gradient (\1 K/m) from 8 9 10 -5 to 1 9 10 -3 m/s. At higher temperature gradients (1-2 K/m), a transition from quasistationary into time-dependent flow was observed, where convection cells changed position, number, and form temporarily. The motivation of this research was to gain more insight into density-driven convection in boreholes and groundwater monitoring wells.
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