Energy Sciences

Chronic groundwater overdraft threatens agricultural sustainability in California's Central Valley. Diverting flood flows onto farmland for groundwater recharge offers an opportunity to help address this challenge. We studied the infiltration rate of floodwater diverted from the Kings River at a turnout upstream of the James Weir onto adjoining cropland; and calculated how much land would be necessary to capture the available floodwater, how much recharge of groundwater might be achieved, and the costs. The 1,000-acre pilot study included fields growing tomatoes, wine grapes, alfalfa and pistachios. Flood flows diverted onto vineyards infiltrated at an average rate of 2.5 inches per day under sustained flooding. At that relatively high infiltration rate, 10 acres are needed to capture one CFS of diverted flood flow. We considered these findings in the context of regional expansion. Based upon a 30-year record of Kings Basin surplus flood flows, we estimate 30,000 acres operated for on-farm flood recharge would have had the capacity to capture 80% of available flood flows and potentially offset overdraft rates in the Kings Basin. Costs of on-farm flood capture for this study were estimated at $36 per acre-foot, less than the cost for surface water storage and dedicated recharge basins.

Field research and grower interviews were used to evaluate the potential of minimum tillage for California rice systems. We found that by tilling only in the fall (instead of both the fall and spring), rice farmers can control herbicide-resistant weeds when combined with a stale rice seedbed, which entails spring flooding to germinate weeds followed by a glyphosate application to kill them. Our results indicated that yield potentials are comparable between water-seeded minimum- and conventional-till systems. We also found that rice growers can reduce fuel costs and plant early. However, minimum tillage may require more nitrogen fertilizer to achieve these yields.

[No abstract]

New gene editing technologies give us the potential ability to bring back extinct species, help control the spread of invasive ones, and genetically modify those that spread diseases. They allows us to not only influence the evolutionary path of entire species, but entire ecosystems as well. Furthermore, gene editing has the potential to help us live healthier and longer lives. We have moved past rudimentary macroscopic methods of DNA manipulation and can now remove individual genes from a strand of DNA. However, due to the complexity of this technology, and given that there are few who can use it to its full effect, people have largely failed to respond to its development, particularly regulators. It is not within the scope of this paper to explore the full implications of these various emerging technologies, so instead I will focus on CRISPR, a specific new gene editing complex first used in 2012, and the major developments that have taken place since then.

In this study, the structure and transport properties of two polymorphs, nanoparticles and nanorods, of the iron(II) triazole [Fe(Htrz)₂(trz)](BF₄) spin crossover complex were compared. Conductive atomic force microscopy was used to map the electrical conductivity of individual nanoparticles and nanorods. The [Fe(Htrz)₂(trz)](BF₄) nanorods showed significantly higher conductivity compared to nanoparticles. This difference in electrical conductivity is partially associated to the different Fe-N bond lengths in each of the polymorphs, with an inverse relationship between Fe-N bond length and conductivity. Transport measurements were done on the nanorods for both high spin (at 380 K) and low spin (at 320 K) states under dark and illuminated conditions. The conductance is highest for the low spin state under dark conditions. In illumination, the conductance change is much diminished.

The sodium (Na) superionic conductor is a key component that could revolutionize the energy density and safety of conventional Na-ion batteries. However, existing Na superionic conductors are primarily based on a single-anion framework, each presenting inherent advantages and disadvantages. Here we introduce a family of amorphous Na-ion conductors (Na₂O₂-MCl_y, M = Hf, Zr and Ta) based on the dual-anion framework of oxychloride. Benefiting from a dual-anion chemistry and with the resulting distinctive structures, Na₂O₂-MCl_y electrolytes exhibit room-temperature ionic conductivities up to 2.0 mS cm^-1, wide electrochemical stability windows and desirable mechanical properties. All-solid-state Na-ion batteries incorporating amorphous Na₂O₂-HfCl₄ electrolyte and a Na_0.85Mn_0.5Ni_0.4Fe_0.1O₂ cathode exhibit a superior rate capability and long-term cycle stability, with 78% capacity retention after 700 cycles under 0.2 C (1C = 120 mA g^-1) at room temperature. The discoveries in this work could trigger a new wave of enthusiasm for exploring new superionic conductors beyond those based on a single-anion framework.

The distribution of counterions and dopants within electrically doped semicrystalline conjugated polymers, such as poly(3-hexylthiophene-2,5-diyl) (P3HT), plays a pivotal role in charge transport. The distribution of counterions in doped films of P3HT with controlled crystallinity was examined using polarized resonant soft X-ray scattering (P-RSoXS). The changes in scattering of doped P3HT films containing trifluoromethanesulfonimide (TFSI-) and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ•-) as counterions to the charge carriers revealed distinct differences in their nanostructure. The scattering anisotropy of P-RSoXS from doped blends of P3HT was examined as a function of the soft X-ray absorption edge and found to vary systematically with the composition of crystalline and amorphous domains and by the identity of the counterion. A computational methodology was developed and used to simulate the soft X-ray scattering as a function of morphology and molecular orientation of the counterions. Modeling of the P-RSoXS at N and F K-edges was consistent with a structure where the conjugated plane of F4TCNQ•- aligns perpendicularly to that of the P3HT backbone in ordered domains. In contrast, TFSI- was distributed more uniformly between domains with no significant molecular alignment. The approach developed here demonstrates the capabilities of P-RSoXS in identifying orientation, structural, and compositional distributions within doped conjugated polymers using a computational workflow that is broadly extendable to other soft matter systems.