Simulation of liquid water beakthrough in a nano-tomography reconstruction of a carbon paper gas diffusion layer

This study reports the feasibility of newly simulating liquid water intrusion into the porous gas diffusion layer (GDL) of a polymer electrolyte fuel cell (PEFC) using X-ray nano-tomography and two-phase lattice Boltzmann (LB) simulation. A digital 3D model of the GDL is reconstructed using X-ray nanotomography while two-phase porous flow is simulated at two different levels of surface wettability by applying a newly-developed numerical LB model. The results show liquid infiltration in a hydrophobic GDL is comparatively lower (pore saturation of 0.11 to 0.90) than that for a hydrophilic GDL (pore saturation of 0.36 to 0.96) over the liquid intrusion range of 1 kPa . 100 kPa. Visualisation of simulated results in three dimensions reveal dissimilar liquid infiltration characteristics for the two levels of wettability considered, yet also reveal a general breakthrough of liquid water at a pressure of 10 kPa due to specific structural features of the GDL

Multiscale modeling of single-phase multicomponent transport in the cathode gas diffusion layer of a polymer electrolyte fuel cell

This research reports a feasibility study into multiscale polymer electrolyte fuel cell (PEFC) modeling through the simulation of macroscopic flow in the multilayered cell via one-dimensional (1D) electrochemical modeling, and the simulation of microscopic flow in the cathode gas diffusion layer (GDL) via three-dimensional (3D) single-phase multicomponent lattice Boltzmann (SPMC-LB) modeling. The heterogeneous porous geometry of the carbon-paper GDL is digitally reconstructed for the SPMC-LB model using X-ray computer microtomography. Boundary conditions at the channel and catalyst layer interfaces for the SPMC-LB simulations such as specie partial pressures and through-plane flowrates are determined using the validated 1D electrochemical model, which is based on the general transport equation (GTE) and volume-averaged structural properties of the GDL. The calculated pressure profiles from the two models are cross-validated to verify the SPMC-LB technique. The simulations reveal a maximum difference of 2.4% between the thickness-averaged pressures calculated by the two techniques, which is attributable to the actual heterogeneity of the porous GDL structure

Flipped learning, flipped satisfaction, getting the right balance

This paper explores students' perceptions of their learning outcomes, engagement, and satisfaction with a technology-facilitated flipped approach in a third-year core subject at an Australian university during 2014. In this pilot study, findings reveal that students preferred the flipped approach to the traditional face-to-face delivery and reported increased engagement, satisfaction, and learning outcomes as a result of both the flipped classroom approach and the use of digital technologies in the delivery of the unit. However, students did report frustration and less satisfaction generally with the flipped model in the initial stages of the semester. The implications are that students may require extra support in the initial stages of delivery of a flipped class to assist them to understand and take up the challenge of the approach, thereby maximising student engagement and satisfaction earlier in the semester

An x-ray tomography based lattice Boltzmann simulation study on gas diffusion layers of polymer electrolyte fuel cells

This work reports a feasibility study into the combined full morphological reconstruction of fuel cell structures using X-ray computed micro- and nanotomography and lattice Boltzmann modeling to simulate fluid flow at pore scale in porous materials. This work provides a description of how the two techniques have been adapted to simulate gas movement through a carbon paper gas diffusion layer (GDL). The validation work demonstrates that the difference between the simulated and measured absolute permeability of air is 3%. The current study elucidates the potential to enable improvements in GDL design, material composition, and cell design to be realized through a greater understanding of the nano- and microscale transport processes occurring within the polymer electrolyte fuel cell

Description of <i>NLRP7</i> mutations with methylation and expression profiling of imprinted loci.

<p>(A) Confirmation of recessive <i>NLRP7</i> mutations in female patients and heterozygous status in the RHM samples. The asterisk (*) on the electropherogram highlights the position of the mutation. For patient 3 the position of the deletion is shown. (B) Circular heat map of the 616 Infinium array probes mapping to 36 ubiquitously imprinted DMRs. The inner circle represents the methylation values of androgenetic HMs, the middle circles normal placental biopsies and the outer circle the RHMs associated with maternal-effect <i>NLRP7</i> mutations. (C) Confirmation of the methylation profile of the <i>NLRP7</i> mutated RHMs at the <i>NAP1L5</i>, <i>PEG10</i>, <i>RB1</i>, <i>L3MBTL1</i> and <i>H19</i> DMRs by bisulphite PCR and subcloning. Each circle represents a single CpG dinucleotide on a DNA strand, a methylated cytosine (●) or an unmethylated cytosine (○). For clarity, only the first 10 CpG dinucleotides from each amplicon are shown with the letters in the parentheses indicating SNP genotype. (D) Allelic expression analysis of imprinted genes <i>NAP1L5</i>, <i>HYMAI</i>, <i>PEG10</i> and <i>PEG3</i> in control placenta samples (PL) and <i>NLRP7</i>-mutated moles (RHM).</p

Identification of additional placenta-specific imprinted DMRs in RHM samples.

<p>(A) A heatmap for the β_mean of the Infinium probes with a methylation difference (>20%, minimum 3 consecutive probes) in RHMs associated with maternal effect <i>NLRP7</i> mutations compared to control placental biopsies. (B) Schematic representation of the methylation-sensitive <i>Hpa</i>II genotyping assay. (C) Methylation profiles as determined by methylation-sensitive genotyping and (D) bisulfite PCR and subcloning on placenta and somatic tissue DNA samples at the <i>SCIN</i>, <i>ST8AIA1</i> and <i>CABIN1</i> promoters. Note that the samples used for methylation-sensitive genotyping and bisulphite PCR maybe different to highlight that methylation is not associated with genotype but parental origin.</p

Methylation and expression analyses of placenta-specific DMRs in RHM samples.

<p>(A) Circular heatmap of the 153 Infinium array probes mapping to the 18 known placenta-specific imprinted DMRs. The inner circles represent the methylation values of androgenetic HMs, the middle circles normal placental biopsies and the outer circle the RHMs associated with maternal-effect <i>NLRP7</i> mutations. (B) Confirmation of the methylation profile at the maternally methylated <i>GLIS3</i>, <i>DNMT1</i> and <i>MCCC1</i> DMRs by bisulphite PCR and subcloning. Each circle represents a single CpG dinucleotide on a DNA strand, a methylated cytosine (●) or an unmethylated cytosine (○). For clarity, only the first 10 CpG dinucleotides from each amplicon are shown with the letters in the parentheses indicating SNP genotype. (C) Allelic expression analysis of imprinted genes <i>MCCC1</i>, <i>LIN28B</i> and <i>GLIS3</i> in control placenta samples (PL) and <i>NLRP7</i>-mutated moles (RHM). (D) Quantitative RT-PCR for <i>H19</i>, <i>DNMT1</i> and <i>AGBL3</i> in RHM samples. The boxplot show the median expression (whiskers 5–95% percentile) determined for 15 control placenta samples with the values of RHMs highlighted.</p