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

Backbone motif.

<p>Full MGSTR network is decomposed into a backbone motif (a) which provides the major biological functions and a remaining motif (b) which makes the system more stable.</p

Perturbation of deleting interaction.

<p>The distribution of relative changes () under the perturbation of deleting 21 interaction arrows from the MGSTR network and random networks. The majority of values are small, which indicates that most perturbations will not alter the size of the biggest attractor significantly.</p

The most probable time sequence of the network state that corresponding to the biological pathway, which is indicated by blue arrows in Fig. 2.

<p>The most probable time sequence of the network state that corresponding to the biological pathway, which is indicated by blue arrows in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0057009#pone-0057009-g002" target="_blank">Fig. 2</a>.</p

Attractor size distribution of random networks.

<p>Calculated from 1000 random networks with the same number of nodes and the same number of lines as our MGSTR network.</p

Minimal lines for every nodes of the MGSTR network.

<p>They are obtained by using process-based approach as described in <b>Methods</b>.</p

Dynamic trajectories.

<p>Dynamic trajectories of the regulatory network with 256 initial states in state space. All states converge towards fixed point attractors. Each green circle corresponds to one specific network state, and the largest circle corresponds to the S phase. Arrows between the network states indicate the dynamic flow from one state to its subsequent state, and the size of flow is indicated by the thickness of arrows.</p

Mammalian cancer cell network during G1/s transition (MGSTR network).

<p>The 8-node network is constructed on the basis of previous experimental results <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0057009#pone.0057009-Ho1" target="_blank">[17]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0057009#pone.0057009-Coller1" target="_blank">[22]</a>. The circular nodes represent oncogene, the octagon nodes represent tumor suppressors, and the quadrilateral nodes represent oncogenes or tumor suppressors. Green arrow represents active interactions, and the blue (or black) hammerheads represent inhibitory interactions.</p

Perturbation of adding interactions.

<p>The distribution of relative changes () under the perturbation of adding 86 interaction arrows into our MGSTR network. The majority of values are small, which indicates that most perturbations will not alter the size of the biggest attractor significantly.</p

Perturbation of switching interactions.

<p>The distribution of relative changes () under the perturbation of switching 16 interaction arrows in the MGSTR network. Most of values are small, whereas about 25 of values are located at the interval of 0.91.0.</p