Adsorption characteristics in a layered bed packed with activated carbon and zeolite 5A were studied experimentally and theoretically through the breakthrough experiments of binary (H 2 / CO, H 2 /CH 4 , H 2 /CO 2 ), ternary (H 2 /CH 4 /CO), and five-component (H 2 /CH 4 /CO/N 2 /CO 2 ) systems. The effects of adsorption pressure, feed flow rate, and carbon-to-zeolite ratio on the breakthrough curve in a layered bed were observed. Breakthrough curves in all of the mixtures showed tailing due to temperature variance in the bed by the heat of adsorption. In the layered bed, each mixture showed the specific characteristics of concentration and temperature wave fronts in each layer. Although the amount of impurity in a ternary mixture is larger than that in a binary mixture, the breakthrough time and elongation depending on the adsorption pressure and flow rate showed an intermediate value between the results of the H 2 /CO and H 2 /CH 4 mixtures, and the tailing was not much different from those in these binary systems. Also, the roll-up phenomenon of CO breakthrough curves occurred because of the breakthrough of CH 4 . Also, because the wave propagation velocity was changed in the layer interface, the concentration wave fronts could become crossover in layered bed. The breakthrough behavior of the major impurities (CH 4 and CO) in the five-component system was very similar to the results for the ternary system with the same carbon-to-zeolite ratio, and the most weakly adsorbed impurity (N 2 ) was the leading wave front in all cases. As a result, in the breakthrough study, the most weakly adsorbed impurity in the mixture should be included in the design of the optimum layered bed for the PSA process.

BackgroundZinc finger homeodomain proteins (ZHD) constitute a plant-specific transcription factor family with a conserved DNA binding homeodomain and a zinc finger motif. Members of the ZHD protein family play important roles in plant growth, development, and stress responses. Genome-wide characterization of ZHD genes has been carried out in several model plants, including Arabidopsis thaliana and Oryza sativa, but not yet in tomato (Solanum lycopersicum).ResultsIn this study, we performed the first comprehensive genome-wide characterization and expression profiling of the ZHD gene family in tomato (Solanum lycopersicum). We identified 22 SlZHD genes and classified them into six subfamilies based on phylogeny. The SlZHD genes were generally conserved in each subfamily, with minor variations in gene structure and motif distribution. The 22 SlZHD genes were distributed on six of the 12 tomato chromosomes, with segmental duplication detected in four genes. Analysis of Ka/Ks ratios revealed that the duplicated genes are under negative or purifying selection. Comprehensive expression analysis revealed that the SlZHD genes are widely expressed in various tissues, with most genes preferentially expressed in flower buds compared to other tissues. Moreover, many of the genes are responsive to abiotic stress and phytohormone treatment.ConclusionSystematic analysis revealed structural diversity among tomato ZHD proteins, which indicates the possibility for diverse roles of SlZHD genes in different developmental stages as well as in response to abiotic stresses. Our expression analysis of SlZHD genes in various tissues/organs and under various abiotic stress and phytohormone treatments sheds light on their functional divergence. Our findings represent a valuable resource for further analysis to explore the biological functions of tomato ZHD genes.Electronic supplementary materialThe online version of this article (10.1186/s12864-017-4082-y) contains supplementary material, which is available to authorized users.

The actin depolymerizing factor (ADF) proteins have growth, development, defense-related and growth regulatory functions in plants. The present study used genome-wide analysis to investigate ADF family genes in tomato. Eleven tomato ADF genes were identified and differential expression patterns were found in different organs. SlADF6 was preferentially expressed in roots, suggesting its function in root development. SlADF1, SlADF3 and SlADF10 were predominately expressed in the flowers compared to the other organs and specifically in the stamen compared to other flower parts, indicating their potential roles in pollen development. The comparatively higher expression of SlADF3 and SlADF11 at early fruit developmental stages might implicate them in determining final fruit size. SlADF5 and SlADF8 had relatively higher levels of expression five days after the breaker stage of fruit development, suggesting their possible role in fruit ripening. Notably, six genes were induced by cold and heat, seven by drought, five by NaCl, and four each by abscisic acid (ABA), jasmonic acid (JA) and wounding treatments. The differential expression patterns of the SlADF genes under different types of stresses suggested their function in stress tolerance in tomato plants. Our results will be helpful for the functional characterization of ADF genes during organ and fruit development of tomato under different stresses.

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