Abstract
The Weyl semimetal (WSM), which hosts pairs of Weyl points and accompanying Berry curvature in momentum space near Fermi level, is expected to exhibit novel electromagnetic phenomena. ...Although the large optical/electronic responses such as nonlinear optical effects and intrinsic anomalous Hall effect (AHE) have recently been demonstrated indeed, the conclusive evidence for their topological origins has remained elusive. Here, we report the gigantic magneto-optical (MO) response arising from the topological electronic structure with intense Berry curvature in magnetic WSM Co
3
Sn
2
S
2
. The low-energy MO spectroscopy and the first-principles calculation reveal that the interband transitions on the nodal rings connected to the Weyl points show the resonance of the optical Hall conductivity and give rise to the giant intrinsic AHE in dc limit. The terahertz Faraday and infrared Kerr rotations are found to be remarkably enhanced by these resonances with topological electronic structures, demonstrating the novel low-energy optical response inherent to the magnetic WSM.
Californian strawberry growers have been relying on methyl bromide for several decades. Notwithstanding the substantial dependence on this broad-spectrum biocide, a phase out was planned due to its ...ozone layer depleting character. With the aim to meet sustainability issues facing the emerging organic strawberry producers and reinforce the interaction among local actors, a research network was developed through 2004–2020.
In this paper we investigated the factors affecting the creation and dissemination of knowledge within the above-mentioned multi-year network. Embeddedness in agro-food networks is the framework that we chose, while from an empirical point of view we analyzed a case study with many available datasets.
We observed a progressive build-up of trust among people throughout the sixteen years. The shared activities and the already established relationship provided the base of this strong networking. Furthermore, innovative methods emerging from network activities provided critical information and management approaches for expanding organic production in the region.
Relational embeddedness explains the observed performance, whereas a complementary role seems to be played by the structural aspect of the same framework at the regional level.
The facilitation function by a university within a participatory method, the unique role of advisors along with the connection to the industry contributed to the reinforcement of the network allowing new ways of stable multi-year co-operation.
Alternatives to soil fumigation are needed for soilborne disease control. The aim of this study was to test anaerobic soil disinfestation (ASD) as an alternative to soil fumigation for control of ...critical soilborne pathogens in Californian strawberry production. Controlled environment experiments were conducted at 25 and 15 °C to test different materials as carbon sources for ASD using soil inoculated with Verticillium dahliae. Field trials were conducted in three locations comparing ASD with 20 Mg ha−1 rice bran (RB) against fumigated and untreated controls, steam, mustard seed meal and fish emulsion. In ASD‐treated soils, temperature and extent of anaerobic conditions were critical for control of V. dahliae, but multiple carbon inputs reduced inoculum by 80–100%. In field trials, ASD with RB provided control of a number of pathogens, and in three of four trials produced marketable fruit yields equivalent to fumigation. Little weed control benefit from ASD was found. ASD with RB also induced changes in the soil microbiome that persisted through the growing season. When equivalent yields were obtained, net returns above harvest and treatment costs with ASD RB were 92–96% of those with bed fumigation based on average prices over the previous 5 years. ASD can be a viable alternative for control of some soilborne pathogens. Growers are adopting ASD in California strawberry production, but research to determine optimal soil temperatures, anaerobicity thresholds and carbon sources for effective control of specific pathogens is needed.
Anaerobic soil disinfestation (ASD), a biological alternative to soil fumigation, has been shown to control a wide range of soil-borne pathogens and nematodes in numerous crop production systems ...across Japan, The Netherlands and the US. A brief review of the status to the science behind ASD and its application for commercial settings is discussed for each country. Future work needs to focus on how to optimize the technique (in terms of carbon source used, temperature and degree of anaerobiosis attained) to control specific sets of pathogens, and to better which mechanism(s) are responsible for disease control in different situations. The role of observed microbial community shifts as a result of ASD in immediate disease control and long term disease suppression needs to be more fully explored. Further reductions in the costs of ASD compared to fumigant use will help increase adoption of the technique which is currently limited by cost and uncertainty about its effectiveness at controlling different pathogens across a range of environments.
Quantum state transfer from a single photon to a single electron following selection rules can only occur for a spin-resolved light-hole excitation in GaAs quantum dots; however, these phenomena have ...yet to be experimentally realized. Here, we report on single-shot readout of a single electron spin via the Zeeman-resolved light-hole excitation using an optical spin blockade method in a GaAs quantum dot and a Pauli spin blockade method in a double GaAs quantum dot. The observed photoexcitation probability strongly depends on the photon polarization, an indication of angular momentum transfer from a single photon to an electron. Our demonstration will open a pathway to further investigation of fundamental quantum physics and applications of quantum networking technology.
Anaerobic soil disinfestation (ASD), a biological alternative to soil fumigation, can control soilborne pathogens and nematodes in numerous crop production systems. To optimize ASD for California ...strawberries, a series of field and pot experiments have been conducted since 2003. Overall, ASD treatment was shown to be consistently effective at suppressing Verticillium dahlia and obtaining comparable yield with fumigant control in coastal California when 20 t ha-1 of rice bran (RB) was pre-plant incorporated and at least 75 mm of irrigation was applied in sandy-loam to clay-loam soils. However, due to economic and high nitrogen application issues associated with use of 20 t ha-1 RB, there is interest in examining alternative C sources used in ASD. In the 2012-2013 season, we conducted non-replicated demonstration trials at 4 local farms in which sugarcane molasses (Mol) 20 t ha-1 alone or in combination with RB (Mol 10 t ha-1 + RB 10 t ha-1) were tested. Although Mol has advantages over RB in terms of ease of application and lower N content, the anaerobic condition created by Mol did not last long and split applications were needed. Further, cumulative marketable fruit yield from Mol 20 t ha-1 plots were as low as 70% of fumigated controls, whereas RB 20 t ha-1 and Mol 10 t ha-1 + RB 10 t ha-1 plots had similar yields as the control. Lack of effectiveness in Mol-based ASD may be related to uneven distribution of Mol across the bed profile and low soil temperatures at trial sites. We also evaluated the potential for eliminating pre-plant fertilizer application when using RB-based ASD at one site. Pre-plant fertilizer increased fruit yield only ~5%, suggesting a possibility of reducing pre-plant fertilizer at ASD fields. Future studies should examine other C-sources including summer cover crops combined with a low rate of RB or Mol in ASD.
Organic strawberry/vegetable producers in coastal California face soilborne disease, nutrient, and weed management challenges. In conventional systems, stringent regulations and air quality concerns ...make the sustainability of fumigant-dependent systems uncertain. To evaluate efficacy of anaerobic soil disinfestation (ASD), mustard cake (MC) application and broccoli residue incorporation, we initiated trials at an organic farm (Org) and a conventional farm (Conv) with crop rotation (broccoli (Brassica oleracea L. italic) – strawberries (Fragaria ananassa), cauliflower (Brassica oleracea L. botrytis) – strawberries, or fallow – strawberries) as main plot in June 2011. Sub plots (ASD, MC, ASD+MC, untreated control (UTC), and fumigant (Pic-Clor 60. Conv only)) were applied prior to strawberry in October 2011. Cover crop and lettuce (Lactuca sativa) were grown after strawberries at Org only. Marketable fruit yield, weed density, and disease level were monitored during the strawberry season and soil inorganic N dynamics for the entire period. ASD+MC and ASD produced similar fruit yields as fumigant at the Conv site. ASD+MC produced greater fruit yield than UTC and MC at both sites and ASD at the Org site. ASD and ASD+MC produced high inorganic N in the soil 2 to 3 months after application at both sites. This caused salt damage on strawberry during early growth especially at Conv which may have reduced fruit yields in both treatments. Verticillium dahlia population in soil at strawberry transplanting was less than 1 microsclerotia/g soil at both sites. However, V. dahlia infection on strawberry plants at the end of the harvest season in Org was reduced by ASD and ASD+MC suggesting that the mechanisms of yield increase by ASD involved disease suppression. Weed suppression by ASD and MC was limited. The effect of broccoli rotation in V. dahliae and weed suppression was also limited and no synergistic effect of broccoli rotation with ASD and MC was observed.
The California organic agriculture industry has grown in size and consumer acceptance despite a very limited scientific research base. The Organic Research Network Project, funded by USDA-Organic ...Agriculture Research and Extension Initiative (USDA-OREI) program in 2004 (S.R. Gliessman, P.I.), was designed to 1) strengthen an existing organic research and extension network to support organic vegetable and strawberry producers in the region; and 2) develop integrated fertility and pest management strategies in order to minimize negative impacts of agriculture on surrounding natural ecosystems and improve the economic viability of organic farming. The project participants included multidisciplinary researchers, extension personnel, organic growers, a land owner, and three NGOs. Ten studies on fertility management, soil-borne disease management, arthropod pest management, weed management, and economic analysis in organic strawberry and vegetable production were conducted. Three core growers played a crucial role in designing, implementing, and evaluating on-farm trials. To evaluate the impact of the project, we conducted pre- and post-project assessments. At the end of the project, 15 of the 18 participants said it had met or exceeded their expectations and the remaining 3 said that most of their expectations were met. Participants were motivated by a desire to build community, increase opportunities to collaborate, improve linkages between farmers and researchers, and improve access to and exchange of information. Participating growers appreciated the many opportunities for interaction with researchers, felt the project provided useful information, and reported that it had either reinforced or changed practices used on their farms. Extension personnel commented on the successful collaborations, improved knowledge of organic production, and the impact it had on growers in the area. This project contributed to the “Organic Strawberry Production Manual” (Koike et al., 2012). The Organic Research Network is further expanding with new funding from the USDA-OREI program in 2011 (C. Shennan, P.I.).
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