The devolution of urban food waste governance: Case study of food rescue in Los Angeles

In Los Angeles (LA), food waste is at record levels. This has negative outcomes for food insecurity, land use, and methane production associated with climate change. To overcome these challenges, a range of government, private, and civil society organizations (CSOs) have developed programs to reduce food waste. With the decentralization, privatization, and devolution of food waste policies to local actors, CSOs have emerged as key institutions in the governance of food waste in many contexts. However, it is unclear whether CSOs have the capacity to reduce food waste and food insecurity, empower communities, or promote social change. To this end, this paper critically analyzes a local food rescue CSO as a case study in order to understand the challenges associated with food waste governance in LA and the roles that CSOs play in food waste reduction. Through an analysis of interview and participant observation data in LA’s food system, this paper examines the ways that food waste is produced, regulated, and reused by institutions in LA. Findings illustrate that although local CSOs have expanded their food waste reduction programs, the impact of their operations may be limited. In addition, while CSOs rescue some food, they operate in conjunction with food waste surpluses and the overabundance of food, and do little to reduce the root cause of food waste or food insecurity. Although the structural causes of food waste are arguably beyond the scope of some CSOs to change, data in this paper suggest that some CSOs may contribute indirectly to neoliberal governance when they romanticize the power of local communities, depoliticize food issues, and focus on individual personal responsibility. For these reasons, this research suggests that food waste may only be reduced significantly with more government regulation of the institutions which produce food waste, namely food businesses and households.     

Simultaneous sulfonation and reduction of graphene oxide as highly efficient supports for metal nanocatalysts

The sulfonated reduced graphene oxide (S-rGO) as supports and size-controlled Pt nanoparticles (NPs) for proton exchange membrane fuel cell (PEMFC) catalysts was investigated. The S-rGO was fabricated by a lyophilization-assisted method from a liquid mixture of GO and (NH₄)₂SO₄ with a subsequent thermal treatment in inert gas. Sulfonic acid groups were grafted on GO and a reduction of GO was achieved simultaneously. Transmission electron microscope (TEM) results showed a uniform deposition of Pt NPs on S-rGO (Pt/S-rGO) with a narrow particle size distribution ranging from 2 to 5 nm in diameter. A higher catalytic activity of this novel Pt/S-rGO catalyst was revealed in comparison with that of Pt/GO, Pt/rGO and conventional Pt/C catalysts by cyclic voltammetry and oxygen reduction reaction measurements due to an enhanced triphase boundary. Significantly, the Pt/S-rGO catalyst also presented an excellent electrochemical stability. This new catalyst thus holds a great potential application in PEMFCs in terms of enhanced activity and durability.     

Thermoplastic polymer impregnation of cellulose nanofibre networks: Morphology,mechanical and optical properties

Biobased nanocomposite sheets of cellulose nanofibres (CNF) and cellulose acetate butyrate (CAB) were prepared using resin impregnation. Porous nanofibre networks together with a low viscosity thermoplastic resin were the key elements in the processing. SEM images of the network before the impregnation showed high porosity and after the impregnation indicated impregnated fibre network. A significant improvement in the visible light transmittance was observed for the nanocomposite compared to the nanofibre network, which is explained on the filling of the pores with a transparent matrix. The tensile tests showed an increase of 364% and 145% for stiffness and strength respectively for nanocomposites with 60 wt.% CNF when compared to CAB. Dynamic mechanical properties showed a good interaction between the CAB and cellulose nanofibres. These results show that CAB impregnated cellulose nanofibre networks are promising biocomposite that could be used in applications where transparency and good mechanical properties are of interest.     

Dialectics of nature: Temporal and spatial regulation in material sciences

The cooperative interaction distance measure has been proposed as a novel law pertaining to dialectics of nature,and has been extensively carried out in the design of functional nanomaterials.However,the temporal and spatial dimensions are akin to yin and yang,and thus temporal regulation needs to be accounted for when implementing the above-mentioned principle.Here,we summarize recent advances in temporally and spatially regulated materials and devices.We showcase the temporal regulation of organic semiconductors for organic photovoltaics (OPVs) using the example of exciton lifetime manipulation.As an example of spatial regulation,we consider the distribution of charge carriers in core-shell quantum dot (QD) nanocrystals for modulating their optical properties.Long exciton lifetime can in principle increase the exciton diffussion length,which is desiable for high-efficiency large-area OPV devices.Spatially regulated QDs are highly valuable emitters for light-emitting applications.We aim to show that cooperative spatio-temporal regulation of nanomaterils is of vital importance to the development of functional devices.     

基于全流程模拟的催化裂化装置多目标优化

应用流程模拟软件Petro SIM对催化裂化装置进行了全流程模拟,采用平均影响因子法从15个独立可调的变量中筛选出7个影响产品分布的主要优化变量,以各产品质量指标为约束,建立了液化石油气和汽油产量最大化的双目标优化模型,应用多目标列队竞争算法对该优化模型求解,所得Pareto最优解集揭示了液化石油气、汽油和柴油产量的分布规律. 根据市场对不同产品需求的变化,确定了5种优化操作方案,调整催化裂化装置的多产品方案.     

Reduction of acrylamide formation by selected agents in fried potato crisps on industrial scale

Great interest and rapid research efforts on acrylamide in foods followed an announcement in April 2002 by the Swedish National Food Authority and the University of Stockholm. Reduction of acrylamide in high-temperature processing foods, including selection of the raw material and variation of processing parameters, etc. were extensive reported. In this research, effect of some agents on acrylamide formation was investigated. A glucose-asparagines reaction model system was used to test the effect of ferulic acid, catechin, CaCl₂, NaHSO₃, and l-cysteine on inhibition of acrylamide formation and three efficient inhibitors, NaHSO₃, CaCl₂ and l-cysteine were screened. The results showed that immersing of the fresh potato chips using different concentration of the agents greatly inhibited acrylamide formation in fried potato crisps, and the efficiency increased as their concentrations increased; among them, l-cysteine is the most efficient agent but CaCl₂ is most potential. Effects of these food additives on the texture of fried potato crisps were also studied. It was found that l-cysteine showed little effect on the texture of the crisps and CaCl₂ is regarded as the suitable choice because of its low price and the acceptable mouth feel of fried crisps treated by CaCl₂, although it increased the brittleness. Moreover, the application of CaCl₂ in industrial production of fried potato crisps was also studied. In the blanching process (deactivation process of enzymes at 85 °C), a computerized electrical conductivity detector was used to keep the concentration of CaCl₂ at constant and the result showed that immersion of potato slices in CaCl₂ solution at 5 g/L reduced acrylamide formation by more than 85% in fried crisps.Industrial relevanceThis research presents a technology to inhibit acrylamide formation in fried potato chips by immersion of fresh potato chips with some food additives. The approach suggested that cysteine and calcium chloride significantly decreased the content of acrylamide in fried potato chips and their concentrations could be kept constant by using a conductor as a detector.     

Computational screening of metal-organic frameworks with open copper sites for hydrogen purification

With the increasing demand for environmental protection worldwide, metal-organic frameworks (MOFs) have been pivotal in the clean energy domain. Due to the high surface areas, large porosities and structural tunability, they are promising for the adsorption separation of H₂/CH₄ mixtures. High-throughput computational screening was adopted to identify the optimal adsorbents for hydrogen purification from 502 MOFs with open copper sites. Firstly, the adsorption performance of H₂/CH₄ mixture in 440 MOFs, which exhibit non-zero surface area and over -3.8 Å largest cavity diameter (LCD), was calculated using grand canonical Monte Carlo (GCMC) simulations at 300 K and various pressures. Secondly, we identified the top 9 high-performance MOFs by evaluating the ranking of candidate adsorbent performance according to a combination metric of adsorption performance score (APS, the product of adsorption capacity of CH₄ and selectivity of CH₄ over H₂) and percent regenerability (R%). PCN-39 and MOF-505 exhibit high APS of 101 mol kg⁻¹ and 67.9 mol kg⁻¹, respectively, promising for hydrogen purification. Subsequently, the breakthrough curves of H₂/CH₄ mixture through the fixed bed packed with some optimal MOFs were predicted to evaluate their effects in practical hydrogen purification. UMODEH08 or UMOBEF04 exhibits the long dimensionless residence time over 30 of CH₄ for the H₂/CH₄ separation. Finally, we also explored the behaviors of the radial distribution functions (RDF) and adsorption equilibrium configurations to further demonstrate how the selected MOFs differentiate CH₄ from H₂. The investigation on all these observations at molecular level will pave the way for the development of new materials for clean energy applications.     

胜利原油活性组分对原油-甜菜碱溶液体系油-水界面张力的影响

采用传统的柱色谱四组分分离方法（SARA）将胜利孤岛原油分离得到沥青质、饱和分、芳香分和胶质,采用碱醇液法萃取原油得到酸性组分。测定了正构烷烃、煤油以及原油活性组分模拟油与2种不同疏水结构的甜菜碱溶液组成的体系的油 水界面张力。结果表明,在原油活性组分模拟油 甜菜碱溶液体系中,直链甜菜碱由于疏水基团较小,与原油活性组分尤其是酸性组分和胶质发生正协同效应的混合吸附,使油 水界面上表面活性剂分子的含量增加,界面膜的排布更紧密,导致油 水界面张力降低;支链甜菜碱由于具有较大尺寸的疏水基团,煤油中少量的活性物质即可将油 水界面张力降至超低(<10-3 mN/m),而原油活性组分的加入,则使界面上表面活性剂分子的排布被破坏,削弱了界面膜原有的紧密性,导致油 水界面张力大幅度升高。     

Hydrothermal synthesis of submicrometer crystals of boehmite

The effect of solvents, mechanically ground gibbsites and amorphous hydrated alumina gels on the formation of well-crystallized and submicrometer-sized crystals of boehmite was studied. Nearly monodispersed boehmite particles of 0.2–0.3 μm with a parallelogram shape were hydrothermally synthesized from ball-milled gibbsite in water at 200°C for 6 h. The 100 nm-sized crystals of boehmite were prepared from amorphous hydrated alumina gels at 255°C for 24 h.