Chromatographic formation of a triadic band of lithium in hydrated LTA zeolite: An investigation on lithium isotope separation effects by ion exchange

published online 12 April 2017Lithium concentrations [Li] and isotopic ratios [Li-7]/[Li-6] were measured for effluent fractions from a biphasic zeolite column. The biphasic state was ascribed to a mixture of hydrated Linde Type A (LTA) zeolites, [Li-0.008(NH4)(0.92)]A and [Li-0.33(NH4)(0.67)]A, which were formed by Li ion exchange from hydrated ammonium in the form (NH4)(12)[Al12Si12O48]center dot nH(2)O (NH(4)A). The biphasic Li band of the column was displaced by ion exchange with a solution of NH4NO3. A constant [Li] with a much lower level than the concentration of NHt(4)(_)(+) in the displacer (NH4NO3) was observed for the effluent from a short column. This constant lower level of [Li] was attributable to the biphasic state. On this [Li] plateau of the effluent, the level of [Li-7] shifted higher than the original isotopic composition of the Li feed, whereas Li-6 was concentrated on the biphasic zeolite solid. The accumulation of Li-6 in the zeolite proceeded by a mechanism of differential elution of Li-7 from the biphasic zeolite. For the long column experiment, a significant enrichment of Li-6 in the zeolite was observed, whereby a triadic band of Li was probably formed in the column. Two monophasic and a biphasic state were assigned. The biphasic band was deemed to push the monophasic bands forward, thereby enriching the monophasic bands with Li-7, while Li-6 accumulated at the end of the biphasic band. The trio structure of the Li band and isotopic discrimination in the band were analyzed. (C) 2017 Elsevier Inc. All rights reserved.ArticleMICROPOROUS AND MESOPOROUS MATERIALS. 248:115-121 (2017)journal articl

A Zebrafish Chemical Suppressor Screening Identifies Small Molecule Inhibitors of the Wnt/β-catenin Pathway

SummaryGenetic screening for suppressor mutants has been successfully used to identify important signaling regulators. Using an analogy to genetic suppressor screening, we developed a chemical suppressor screening method to identify inhibitors of the Wnt/β-catenin signaling pathway. We used zebrafish embryos in which chemically induced β-catenin accumulation led to an “eyeless” phenotype and conducted a pilot screening for compounds that restored eye development. This approach allowed us to identify geranylgeranyltransferase inhibitor 286 (GGTI-286), a geranylgeranyltransferase (GGTase) inhibitor. Our follow-up studies showed that GGTI-286 reduces nuclear localization of β-catenin and transcription dependent on β-catenin/T cell factor in mammalian cells. In addition to pharmacological inhibition, GGTase gene knockdown also attenuates the nuclear function of β-catenin. Overall, we validate our chemical suppressor screening as a method for identifying Wnt/β-catenin pathway inhibitors and implicate GGTase as a potential therapeutic target for Wnt-activated cancers

Efficient pH and dissolved CO2 conditions for indoor and outdoor cultures of green alga Parachlorella

Efficient pH and dissolved CO2 conditions for indoor (50–450 mL scale) and outdoor (100–500 L scale) culture of a green alga BX1.5 strain that can produce useful intracellular lipids and extracellular polysaccharides were investigated for the first time in Parachlorella sp. The cultures harvested under 26 different conditions were analysed for pH, dissolved CO2 concentration, and the biomass of extracellular polysaccharides. The BX1.5 strain could thrive in a wide range of initial medium pH ranging from 3 to 11 and produced valuable lipids such as C16:0, C18:2, and C18:3 under indoor and outdoor culture conditions when supplied with 2.0% dissolved CO2. Particularly, the acidic BG11 medium effectively increased the biomass of extracellular polysaccharides during short-term outdoor cultivation. The BG11 liquid medium also led to extracellular polysaccharide production, independent of acidity and alkalinity, proportional to the increase in total sugars derived from cells supplied with high CO2 concentrations. These results suggest Parachlorella as a promising strain for indoor and outdoor cultivation to produce valuable materials

Hybrid anode design of polymer electrolyte membrane water electrolysis cells for ultra-high current density operation with low platinum group metal loading

Reducing platinum group metal (PGM) loading and high current density operation are both essential for minimizing the capital expenditure (CAPEX) of polymer electrolyte membrane (PEM) electrolyzers. Catalyst-integrated porous transport electrodes (PTEs) in which iridium acts as both a catalyst and a conductive coating on porous transport layer (PTL) surfaces, enable the preparation of Pt-coating-free PTLs, but can also result in relatively high activation and ohmic overvoltages. Here, a novel hybrid anode design combining an intermediate catalyst layer and a catalyst-integrated PTE is developed. This hybrid anode demonstrates that Ir on PTL can contribute to the oxygen evolution reaction (OER) and exhibits comparable electrolysis performance to a conventional anode consisting of Pt-coated PTL with the same Ir loadings despite Pt-coating-free on the PTL of the hybrid anode. This novel anode eliminates the need for a Pt coating whilst also enabling ultra-high current density operations up to 20 A cm−2 with a total PGM loading of only around 0.6 mg cm−2 on the anode side. This paper proposes a next-generation anode structure with new functions of PTLs for ultra-high current density operation with low PGM loading to significantly reduce green hydrogen costs

Catalyst-integrated gas diffusion electrodes for polymer electrolyte membrane water electrolysis : porous titanium sheets with nanostructured TiO2 surfaces decorated with Ir electrocatalysts

Novel catalyst-integrated gas diffusion electrodes (GDEs) for polymer electrolyte membrane water electrolysis (PEMWE) cells are presented, in which porous titanium microfiber sheets are etched in NaOH to generate a nanostructured TiO2 surface, followed by arc plasma deposition (APD) of iridium nanoparticles. The porous titanium sheet acts as a gas diffusion layer (GDL); the nanostructured TiO2 surface acts as a catalyst support with large surface area; and the iridium nanoparticles act as the electrocatalyst. The performance of these unique GDEs in PEMWE cells was optimized by etching in different NaOH concentrations to vary the nanostructure of the TiO2; and by varying the Ir loading via the number of APD pulses. The current-voltage characteristics and the durability of the optimized GDEs were comparable to those reported in the literature using conventional Ir-based electrocatalysts, and electrolysis was achieved with current density up to 5 A cm-2. The main advantages of this catalyst-integrated GDE include the very low iridium loading (i.e. around 0.1 mg cm-2, or just one-tenth of the loading typically used in conventional PEMWEs); high electrolysis current density; the fabrication of stacks with fewer components; and the fabrications of thinner stacks. This could ultimately lead to smaller and lower cost PEMWE systems

Ru-core Ir-shell electrocatalysts deposited on a surface-modified Ti-based porous transport layer for polymer electrolyte membrane water electrolysis

Novel Ru-core Ir-shell catalyst-integrated porous transport electrodes (PTEs) for polymer electrolyte membrane water electrolysis (PEMWE) cells are prepared, in which Ru-core Ir-shell catalyst nanostructures are directly deposited onto a porous transport layer (PTL) via arc plasma deposition (APD). The PTL has a nanostructured TiO2 surface prepared via NaOH etching, acting as a catalyst support. The performance and durability of these Ru-core Ir-shell catalysts depend strongly on the ratio of Ir and Ru. The current-voltage (I–V) characteristics of PEMWE cells were improved by applying these core-shell catalysts with a low Ir loading of around 0.1 mg cm−2. The core-shell catalyst-integrated PTEs can operate at current densities of up to 10 A cm−2 without exhibiting limiting current behavior. This unique combination of the core-shell catalyst and the PTE structure enables PEMWE cell operation with low iridium loading and high current density, potentially reducing the cost of green hydrogen

Cold start cycling durability of fuel cell stacks for commercial automotive applications

System durability is crucial for the successful commercialization of polymer electrolyte fuel cells (PEFCs) in fuel cell electric vehicles (FCEVs). Besides conventional electrochemical cycling durability during long-term operation, the effect of operation in cold climates must also be considered. Ice formation during start up in sub-zero conditions may result in damage to the electrocatalyst layer and the polymer electrolyte membrane (PEM). Here, we conduct accelerated cold start cycling tests on prototype fuel cell stacks intended for incorporation into commercial FCEVs. The effect of this on the stack performance is evaluated, the resulting mechanical damage is investigated, and degradation mechanisms are proposed. Overall, only a small voltage drop is observed after the durability tests, only minor damage occurs in the electrocatalyst layer, and no increase in gas crossover is observed. This indicates that these prototype fuel cell stacks successfully meet the cold start durability targets for automotive applications in FCEVs

Accelerated durability testing of fuel cell stacks for commercial automotive applications : a case study

System durability is crucially important for the successful commercialization of fuel cell electric vehicles (FCEVs). Conventional accelerated durability testing protocols employ relatively high voltage to hasten carbon corrosion and/or platinum catalyst degradation. However, high voltages are strictly avoided in commercialized FCEVs such as the Toyota MIRAI to minimize these degradation modes. As such, conventional durability tests are not representative of real-world FCEV driving conditions. Here, modified start-stop and load cycle durability tests are conducted on prototype fuel cell stacks intended for incorporation into commercial FCEVs. Polarization curves are evaluated at beginning of test (BOT) and end of test (EOT), and the degradation mechanisms are elucidated by separating the overvoltages at both 0.2 and 2.2 A cm-2. Using our modified durability protocols with a maximum cell voltage of 0.9 V, the prototype fuel cell stacks easily meet durability targets for automotive applications, corresponding to 15-year operation and 200,000 km driving range. These findings have been applied successfully in the development of new fuel cell systems for FCEVs, in particular the second-generation Toyota MIRAI

Mechanisms of HIV-associated lymphocyte apoptosis: 2010

The inevitable decline of CD4T cells in untreated infection with the Human immunodeficiency virus (HIV) is due in large part to apoptosis, one type of programmed cell death. There is accumulating evidence that the accelerated apoptosis of CD4T cells in HIV infection is multifactorial, with direct viral cytotoxicity, signaling events triggered by viral proteins and aberrant immune activation adding to normal immune defense mechanisms to contribute to this phenomenon. Current antiviral treatment strategies generally lead to reduced apoptosis, but this approach may come at the cost of preserving latent viral reservoirs. It is the purpose of this review to provide an update on the current understanding of the role and mechanisms of accelerated apoptosis of T cells in the immunopathogenesis of HIV infection, and to highlight potential ways in which this seemingly deleterious process could be harnessed to not just control, but treat HIV infection

Mesoporous Carbon Fibers with Tunable Mesoporosity for Electrode Materials in Energy Devices

To improve the properties of mesoporous carbon (MC), used as a catalyst support within electrodes, MC fibers (MCFs) were successfully synthesized by combining organic–organic self-assembly and electrospinning deposition and optimizing heat treatment conditions. The pore structure was controlled by varying the experimental conditions. Among MCFs, MCF-A, which was made in the most acidic condition, resulted in the largest pore diameter (4–5 nm), and the porous structure and carbonization degree were further optimized by adjusting heat treatment conditions. Then, since the fiber structure is expected to have an advantage when MCFs are applied to devices, MCF-A layers were prepared by spray printing. For the resistance to compression, MCF-A layers showed higher resistance (5.5% change in thickness) than the bulk MC layer (12.8% change in thickness). The through-plane resistance was lower when the fiber structure remained more within the thin layer, for example, +8 mΩ for 450 rpm milled MCF-A and +12 mΩ for 800 rpm milled MCF-A against the gas diffusion layer (GDL) 25BC carbon paper without a carbon layer coating. The additional advantages of MCF-A compared with bulk MC demonstrate that MCF-A has the potential to be used as a catalyst support within electrodes in energy devices