A numerical study on the effects of gas channel wettability in PEM fuel cells

The wettability of channel walls and gas diffusion layer has a great influence on the water management of fuel cells. In this paper, a numerical study has been carried out to examine the effect of the wall and gas diffusion layer wettability on gas channels. The investigation employed a three dimensional numerical simulation using the volume-of-fluid (VOF) method to simulate the air-water flow in a straight micro-channel representing a gas channel in a PEM fuel cell. Nine combinations of wall and GDL wettabilities were investigated. Different wettability combinations were found to give different water behaviour. For fixed wall wettability, the pattern of the analysed parameters was changing between uniform cyclic, random cyclic and continuous. In addition, it was found that changing the GDL wettability has a greater impact on the analysed parameter compared to changing the wall wettability

Estimation of Shatavarin IV and Sarsasapogenin from the roots of <i>Asparagus racemosus</i> Wild using validated HPLC-ELSD method optimized using QbD approach

The plant Asparagus racemosus Wild is mentioned in Ayurveda and used commercially alone or as an ingredient of many poly-herbal formulations indicated as a tonic and to improve the functioning of the reproductive system. Shatavarin type of saponin glycosides present in the roots were found to be responsible for the activity. An analytical method was developed using HPLC equipped with an evaporating light scattering detector (ELSD) to estimate Shatavarin-IV and a non-sugar moiety of this glycoside Sarsasapogenin from the dried roots of Asparagus racemosus. Chromatographic separation was achieved using PhenomenexTM (C18, 250 × 4.6 mm, id: 5 μm) column using an isocratic mobile phase comprising of methanol: water (95:05, %v/v) at a flow rate of 0.8 mL/min. The failure modes were identified and studied for their impact on Critical Method Attributes, and further, the chromatographic parameters were optimized using the design of the experiment approach. The developed method was found to be linear in the concentration range of 90–300 ng/mL for Shatavarin-IV and 150–500 ng/mL for Sarsasapogenin. The validation studies confirmed the precision, accuracy, and robustness of the developed analytical method. The plant material was found to contain 0.23 ± 0.01% w/w Shatavarin-IV and 1.48 ± 0.03% w/w Sarsasapogenin on a dried weight basis when estimated using the developed method.</p

The experiment.

<p>(a) Confocal laser scanning micrograph of a spreading double lipid bilayer membrane(DLBM), top view. (b) Schematic drawing of the DLBM in (a), side view. DLBM consists of a distal (upper, red color) bilayer and the proximal (lower, blue color) bilayer. The spreading edge of the double bilayer performs a 'tank-tread' motion. (c) Micrograph of a ruptured membrane. (d) Schematic drawing showing a rupture in the distal membrane. Upon rupturing, the lipid material migrates towards the edges onto the substrate.</p

The peridynamic model.

<p>(a) A small, randomly selected region in the distal membrane is represented as a collection of particles (small circles). Each particle represents a collection of lipid molecules, and is located at the center of a circular neighborhood (N_x). The motion of an arbitrary particle x (in yellow) at the center of N_x is influenced by the motion of every particle in N_x via bonds. If no forces apply to the membrane, the particles in N_x are considered to be in an undeformed state. The close-up shows vector ξ, representing the distance between bonded particles x and x’, where T is the force vector state that existed prior to the bond being broken. (b) As tension increases, the particles move apart from each other and the corresponding bonds stretch. At some critical value of stretch, the distance between the center particle (yellow dot) and some number of neighboring particles becomes too large, leading to broken bonds and disconnected particles (x', white dots). This corresponds to the rupture (pore) formation among membrane lipids.</p

Fractal dimension analysis of ruptures in actual membranes and simulations.

<p>(a-c) Binary images showing the contour of the fractal ruptures in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0165947#pone.0165947.g003" target="_blank">Fig 3O and 3R</a> (G = 5) and 4l (G = 7.5). (c) Plots showing the fractal dimension (D) of rupture patterns in (a),(b) and (c). The slope of the red line shows the fractal dimension of the pattern in panel a, D = 1.63, the pattern in panel (b), D = 1.70, and the pattern in c, D = 1.56. The circular rim forming around the expanding membrane in the simulations has been removed manually with image processing software. All fractal dimensions have been calculated by using the reticular cell counting (box counting) method. The plots show the relation between the number of occupied boxes (y-axes) and the box size. The fractals in biological membranes (not shown) feature D values around 1.7[<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0165947#pone.0165947.ref001" target="_blank">1</a>]). The analysis from the simulations show that both slope and D are similar to the experimental values.</p

Transition in rupture morphology with increasing shear moduli.

<p>(a-l) The peridynamic simulations of the lipid membrane which is shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0165947#pone.0165947.g003" target="_blank">Fig 3</a> (j-l), but with gradually increased shear modulus. (a-d) The ruptures become rugged where G = 1 MPa. (e-h) The straight edges of the ruptures become more pronounced where G = 2.5 MPa and branches start to appear. (i-l) The ruptures appear as elongated finely branched structures where G = 7.5 MPa. These structures typically evolve into fractals(l). The color bar in (d) applies to all simulations shown in Fig 4, and is identical to the one in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0165947#pone.0165947.g003" target="_blank">Fig 3</a>. The number of pinning points in all simulations in this figure is 16, and the positions of the pinning sites are identical to the ones in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0165947#pone.0165947.g003" target="_blank">Fig 3J</a> and p (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0165947#pone.0165947.s004" target="_blank">S2 Movie</a>). The ratio of the diameter of the expanded membrane to the initial diameter (D/D₀) is shown below each snapshot of the simulations.</p

Floral and fractal biomembrane ruptures and corresponding peridynamic model simulations.

<p>(a-c) Confocal micrographs of a floral rupture occurring in the distal bilayer of a DLBM. Yellow arrow heads indicate threads of lipids between two layers, which are the pinned regions. (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0165947#pone.0165947.s003" target="_blank">S1 Movie</a>) (d-f) Peridynamic simulations showing floral ruptures (G = 0 MPa). The ruptures nucleate at the pre-determined locations of pinned (fixed) particles, and then merge into one large floral pore. The pinning points (n = 6) are marked with red circles in (d). Black arrow heads show threads of points remain between two layers which correspond to the pinned regions, similar to (c). (g-i) Confocal micrographs showing small circular pores opening and progressing in the distal bilayer. (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0165947#pone.0165947.s004" target="_blank">S2 Movie</a>) (j-l) Peridynamic simulations showing circular pores opening over time. Shear modulus G is 0 MPa as in (a-f), with the number of pinning points increased (n = 17). (m-o) Confocal micrographs of fractal ruptures occurring in the distal bilayer. (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0165947#pone.0165947.s005" target="_blank">S3 Movie</a>) (p-r) Peridynamic simulations showing fractal ruptures (G = 5 MPa). The number and location of pinning points are the same as in (g-l). The color bar in f applies to all simulations in Fig 3 and shows the amount of material point damage (%) where 100% damage corresponds to a complete breaking of all bonds associated with the material point. The scale bar in (e) applies to all simulations in Fig 3. The ratio of the diameter of the expanded membrane to the initial diameter (D/D₀) is shown below each snapshot of the simulations.</p

Additional file 1: of Human pathogens associated with the blacklegged tick Ixodes scapularis: a systematic review

Search strategy example using Ovid MEDLINE(R) In-Process & Other Non-Indexed Citations and Ovid MEDLINE(R) 1 January 1995 to 20 April 2015. (DOCX 26 kb