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.

We study the effect of strain on the magnetic properties and magnetization configurations in nanogranular Fe_xGe1-xfilms (x=0.53±0.05) with and without B20 FeGe nanocrystals surrounded by an amorphous structure. Relaxed films on amorphous silicon nitride membranes reveal a disordered skyrmion phase while films near and on top of a rigid substrate favor ferromagnetism and an anisotropic hybridization of Fedlevels and spin-polarized Gespband states. The weakly coupled topological states emerge at room temperature and become more abundant at cryogenic temperatures without showing indications of pinning at defects or confinement to individual grains. These results demonstrate the possibility to control magnetic exchange and topological magnetism by strain and inform magnetoelasticity-mediated voltage control of topological phases in amorphous quantum materials.

A high-nuclearity {Ni₁₈} complex (1) with a unique 'flying saucer' motif has been prepared from the organic chelate, α-methyl-2-pyridine-methanol (mpmH), in conjunction with bridging azido (N₃ ^-) and peroxido (O₂ ^2-) ligands. Magnetic susceptibility measurements revealed the presence of both ferro- and antiferromagnetic exchange interactions between the metal centres in 1, and the stabilization of spin states with appreciable S values at two different temperature regimes. The end-on bridging azido and alkoxido groups are in all likelihood the ferromagnetic mediators, while the η³:η³:μ₆-bridging peroxides most likely promote the antiparallel alignment of the metals' spin vectors, yielding an overall non-zero spin ground state for the centrosymmetric compound 1. Furthermore, the {Ni₁₈} nanosized cluster behaves as a single-molecule magnet, exhibiting magnetic hysteresis at low temperatures and two relaxation processes at 15 K and 1.3 K, a very rare phenomenon in polynuclear magnetic 3d-metal clusters.