Browsing by Subject "Hydrogen"

Now showing 1 - 5 of 5
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    Human SLC4A11 Is a Novel NH3/H+ Co-transporter
    (American Society for Biochemistry and Molecular Biology, 2015-07-03) Zhang, Wenlin; Ogando, Diego G.; Bonanno, Joseph A.; Obukhov, Alexander G.; Department of Cellular & Integrative Physiology, IU School of Medicine
    SLC4A11 has been proposed to be an electrogenic membrane transporter, permeable to Na(+), H(+) (OH(-)), bicarbonate, borate, and NH4 (+). Recent studies indicate, however, that neither bicarbonate or borate is a substrate. Here, we examined potential NH4 (+), Na(+), and H(+) contributions to electrogenic ion transport through SLC4A11 stably expressed in Na(+)/H(+) exchanger-deficient PS120 fibroblasts. Inward currents observed during exposure to NH4Cl were determined by the [NH3]o, not [NH4 (+)]o, and current amplitudes varied with the [H(+)] gradient. These currents were relatively unaffected by removal of Na(+), K(+), or Cl(-) from the bath but could be reduced by inclusion of NH4Cl in the pipette solution. Bath pH changes alone did not generate significant currents through SLC4A11, except immediately following exposure to NH4Cl. Reversal potential shifts in response to changing [NH3]o and pHo suggested an NH3/H(+)-coupled transport mode for SLC4A11. Proton flux through SLC4A11 in the absence of ammonia was relatively small, suggesting that ammonia transport is of more physiological relevance. Methylammonia produced currents similar to NH3 but with reduced amplitude. Estimated stoichiometry of SLC4A11 transport was 1:2 (NH3/H(+)). NH3-dependent currents were insensitive to 10 μM ethyl-isopropyl amiloride or 100 μM 4,4'- diisothiocyanatostilbene-2,2'-disulfonic acid. We propose that SLC4A11 is an NH3/2H(+) co-transporter exhibiting unique characteristics.
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    Long Duration Solid-State Hydrogen Storage From ISRU Materials
    (IAF, 2020) Schubert, Peter J.; Electrical and Computer Engineering, School of Engineering and Technology
    Hydrogen storage is vital for use in fuel cells and nuclear thermal rockets (NTR), both of which benefit from low-energy reservoirs available for long durations. A novel method of solid-state storage using catalytically-modified porous silicon can be fabricated entirely from materials found on the moon and in asteroids, requiring only a fixed quantity of re-usable reagents to be brought from earth. Consumables include silicon, aluminum, iron, and water, all of which can be extracted from suitable regolith ore bodies. An aluminum pressure vessel containing granular porous silicon particles is recharged by hydrogen pressures of 0.8 MPa. Once charged the hydrogen storage subsystem can be maintained at any temperature from 0 to 373 K for an indefinite period, suitable for lunar nights or months-long trips to main belt asteroids. Discharge is facilitated by heating above 393 K, provided by IR, resistive, or metal foam heat conductors embedded in the particulate bed. Systems-level volumetric and gravimetric storage metrics are 39 g/l and 5.8 percent w/w, respectively, comparable to cryogenic hydrogen storage in size and mass. The embodied energy in storing the hydrogen is very small, less than 2 percent of the embodied chemical energy, which makes it more efficient than cryogenic at 40 percent. Silicon and aluminum can be extracted from regolith using isotopic separation by charge/mass ratio. Iron and nickel are harvested from lunar regolith by electromagnets, and used as the catalyst to mediate between gaseous hydrogen and monatomic surface adsorbed hydrogen. Deposition is accomplished via carbonyl gases, which require a quantity of CO, which is recovered after each use. Making the silicon porous requires hydrofluoric acid (HF), which will need to be supplied from earth. The hydrofluorosilicic acid byproduct can be heated to decompose into HF vapor and silicon dioxide. The HF is condensed and re-used, and the silicon dioxide is a waste byproduct which can be formed into quartz objects such as portals and glassware. A lunar factory with a mass of 30 MT can produce complete hydrogen storage vessels, assuming that electronic control can be provided by the remainder of the power system. Being granular the size and shape of such vessels are essentially unlimited. One example is two-meter thick shell sections for a deep space crew cabin for radiation protection. The hydrogen therein could be withdrawn as a back-up supply of fuel, or for a final Hohman transfer burn just before refueling.
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    Photoinduced C(sp3)-H Chalcogenation of Amide Derivatives and Ethers via Ligand-to-Metal Charge-Transfer
    (American Chemical Society, 2022) Niu, Ben; Sachidanandan, Krishnakumar; Cooke, Maria Victoria; Casey, Taylor E.; Laulhé, Sébastien; Chemistry and Chemical Biology, School of Science
    A photoinduced, iron(III) chloride-catalyzed C-H activation of N-methyl amides and ethers leads to the formation of C-S and C-Se bonds via a ligand-to-metal charge transfer (LMCT) process. This methodology converts secondary and tertiary amides, sulfonamides, and carbamates into the corresponding amido-N,S-acetal derivatives in good yields. Mechanistic work revealed that this transformation proceeds through a hydrogen atom transfer (HAT) involving chlorine radical intermediates.
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    Review—Combining Experimental and Engineering Aspects of Catalyst Design for Photoelectrochemical Water Splitting
    (IOP, 2022) Sharma, Chhavi; D., Pooja; Thakur, Anupma; Negi, Y. S.; Engineering Technology, Purdue School of Engineering and Technology
    Hydrogen is one of the cleanest, most favourable, and most practical energy transferors. However, its efficient generation, storage and transportation are still a challenge. There are various routes available toward greener hydrogen. Solar-driven splitting is considered a cleaner method with no harmful emission and viability of up-scaling. Various semiconductors were studied for photo-electrochemical catalysis to improve overall efficiency of the system (i.e. Solar-to-Hydrogen (STH)). The insistence of framing this article is to offer an intense evaluation of scientific and technical aspects of available designing strategies' for photocatalysts and recent fruitful advancements towards product development. This review might act as a handbook for budding researchers and provide a cutting-edge towards innovative & efficient catalyst designing strategy to improve efficiency for working scientists.
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    Ultra-safe nuclear thermal rockets using lunar-derived fuel
    (Elsevier, 2021-09-01) Schubert, Peter J.; Marrs, Ian; Daniel, Ebin; Conaway, Adam; Bhaskaran, Amal; Electrical and Computer Engineering, School of Engineering and Technology
    Rocket launch failure rate is slightly higher than five percent. Concerned citizens are likely to protest against private-sector launches involving fission reactors. Yet, fission reactors can power long-duration lunar operations for science, observation, and in situ resource utilization. Furthermore, fission reactors are needed for rapid transport around the solar system, especially considering natural radiation doses for crews visiting Mars or an asteroid. A novel approach is to create nuclear fuel on the Moon. In this way, a rocket launched from the earth with no radioactive material can be fueled in outer space, avoiding the risks of spreading uranium across Earth's biosphere. A solution is to harvest fertile thorium on the lunar surface, then transmute it into fissile uranium using the gamma ray fog which pervades the deep sky. It is only at lunar orbit, at the very edge of cislunar space, that the Earth-launched machine becomes a nuclear thermal rocket (NTR). Thorium is not abundant, but can be concentrated by mechanical methods because of its very high specific density relative to the bulk of lunar regolith. Thorium dioxide (ThO2) has an extremely high melting point, such that skull crucible heating can be used to separate it from supernatant magma. When filled into a graphite-lined beryllium container (brought from Earth) and set out on the lunar surface, high-energy gamma rays will liberate neutrons from the Be. After moderation by the graphite, these thermal neutrons are captured by the thorium nucleus, which is transmuted into protactinium (Pa91). This element can be extracted using the THOREX process, and will then decay naturally into U-233 within two or three lunar days. The uranium is oxidized and packed into fuel pellets, ready to be inserted into a non-radioactive machine, which now becomes an NTR. Additionally, hydrogen can be extracted from deposits in permanently-shadowed regions on the Moon, providing reaction mass for the NTR. A novel method of solid-state hydrogen storage, which can be entirely fabricated using in situ resources, can deliver said hydrogen to the fission reactor to provide high and efficient propulsive thrust. These combined operations lead to an ultra-safe (for the Earth) means for private sector, commercial transport and power generation throughout the Solar System. With the hydrogen storage material used as radiation shielding for crewed spacecraft, and greatly-reduced transit times relative to chemical rocketry, this innovative approach could fundamentally transform how humans work, play, and explore in outer space.