Platinum/Apatite Water-Gas Shift Catalysts

Water-gas shift (WGS) micro and membrane reactors are interesting components for compact H₂ production and purification devices, but they require catalysts with very high activity for optimum efficiency to minimize catalyst bed thickness and mass transfer limitations. On the other hand, activation of H₂O is known to be more challenging than CO in this reaction. Catalysts comprising ca. 2 nm large Pt particles on hydrophilic apatites are found to have very high WGS activity, with specific reaction rates exceeding those of a highly active Pt/CeO₂ catalyst by up to 50% at 573 K. These apatite-supported catalysts exhibit stable CO conversions at 673 K without showing any CH₄ formation tendencies up to 723 K. WGS activity increases with Ca/P ratio in the apatite, leveling off around Ca/P ≈ 1.75, and formate has been identified as the main reaction intermediate. The outstanding WGS performance is attributed to the superior activation of H₂O on these ionic oxides due to coordination of H₂O to Lewis acidic Ca²⁺ ions and H bonding to basic O atoms of PO₄^3– units. This renders H₂O molecules highly polarized and thus reactive on apatite surfaces with the ensuing formate-like intermediates being well stabilized through bonding to multiple Ca²⁺ ions, as well. Thus, apatites provide an intriguing alternative to increasingly expensive rare-earth oxides in high-performance noble-metal WGS catalysts not only for micro and membrane reactors

Structural and Permeation Kinetic Correlations in PdCuAg Membranes

Addition of Ag is a promising way to enhance the H₂ permeability of sulfur-tolerant PdCu membranes for cleanup of coal-derived hydrogen. We investigated a series of PdCuAg membranes with at least 70 atom % Pd to elucidate the interdependence between alloy structure and H₂ permeability. Membranes were prepared via sequential electroless plating of Pd, Ag, and Cu onto ceramic microfiltration membranes and subsequent alloying at elevated temperatures. Alloy formation was complicated by a wide miscibility gap in the PdCuAg phase diagram at the practically feasible operation temperatures. X-ray diffraction showed that the lattice constants of the fully alloyed ternary alloys obey Vegard’s law closely. In general, H₂ permeation rates increased with increasing Ag and decreasing Cu content of the membranes in the investigated temperature range. Detailed examination of the permeation kinetics revealed compensation between activation energy and pre-exponential factor of the corresponding H₂ permeation laws. The origin of this effect is discussed. Further analysis showed that the activation energy for H₂ permeation decreases overall with increasing lattice constant of the ternary alloy. The combination of these correlations results in a structure–function relationship that will facilitate rational design of PdCuAg membranes

Transcriptome analysis revealed the possible regulatory pathways initiating female geese broodiness within the hypothalamic-pituitary-gonadal axis

<div><p>Geese have the strongest tendency toward broodiness among all poultry. The mechanisms initiating broodiness within the goose hypothalamic-pituitary-gonadal axis (HPGA) are still unclear. Here, we reported the transcriptome differences between laying and initial nesting within the HPGA tissues of geese. We constructed a unigene database based on HPGA tissues and identified 128,148 unigenes, 100% of which have been annotated. By using Digital Gene Expression (DGE) sequencing, we screened 19, 110, 289, and 211 differentially expressed genes (DEGs) in the hypothalamus, pituitary gland, stroma ovarii, and follicles, respectively, between laying and nesting geese. Expression changes of hypocretin (HCRT) and pro-opiomelanocortin (POMC) in the hypothalamus of nesting geese may cause appetite reduction, which is possibly the first step and a prerequisite to initiate broodiness. In addition to prolactin (PRL), follicle-stimulating hormone (FSH) and luteinizing hormone (LH), genes including oxytocin-neurophysin (OXT), chordin-like protein 1 (CHRDL1) and growth hormone (GH), expressed in the pituitary gland, are new candidate molecules that may be involved in broodiness in geese. Heme oxygenase 1 (HMOX1) in the pituitary gland, the proto-oncogene c-Fos (FOS), heat shock protein 90-alpha (HSP90AA), and cyclin-dependent kinase 1 (CDK1) in the ovary that may consolidate and transduce signals regulating the HPGA during broodiness in geese.</p></div

Hierarchical clusters of DEGs.

<p>A, Clustering of the DEGs listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0191213#pone.0191213.t004" target="_blank">Table 4</a>. B, Clustering of groups based on gene expression patterns among groups.</p

Validation of the sequencing data by qRT-PCR.

<p>A-D, Validation of results for the hypothalamus, the pituitary gland, the stroma ovarii and the walls of follicles (diameter range 8–10 mm), respectively. E, The correlation coefficient between qRT-PCR and DEG data was analyzed based on all validated genes. The genes were selected randomly from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0191213#pone.0191213.s008" target="_blank">S3</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0191213#pone.0191213.s011" target="_blank">S6</a> Tables, and the primers designed for qRT-PCR are listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0191213#pone.0191213.s006" target="_blank">S1 Table</a>. For both the qRT-PCR and DEG results, the fold changes were calculated based on the expression levels in laying and nesting group and were then converted to log₂(Fold change).</p

The DEGs of interest that enriched in HPGA-related tissues.

<p>The DEGs of interest that enriched in HPGA-related tissues.</p

Quality analyses of DEG Library.

<p>Quality analyses of DEG Library.</p

Regulatory processes within the HPGA that may take part in initiating broodiness in geese.

<p>Regulatory processes within the HPGA that may take part in initiating broodiness in geese.</p

Quality analyses of transcriptome sequencing quality.

<p>Quality analyses of transcriptome sequencing quality.</p

The entire experimental design and inclusion criteria for the groups of geese.

<p>A, The entire experimental design and sequencing procedure. L_Hy, L_Pitu, L_Ov and L_ThB, respectively, mean hypothalamus, pituitary gland, stroma ovarii and walls of follicles with a diameter range of 8–10 mm from laying geese. N_Hy, N_Pitu, N_Ov and N_ThB refer to the corresponding tissues from geese at the beginning of nesting. B, The standards for dividing geese into initial laying and nesting basing on the status of hierarchical follicles status (before the anatomical observation, the geese were distinguished first by their nesting behaviors, such as nesting, foraging times and fluffy feathers).</p