Spatial considerations for implementing two direct-to-consumer food models in two states

To open new markets, some farmers have adapted direct-to-consumer (DTC) models, such as Community Supported Agriculture (CSA), to reach new settings or audiences. We compared sociodemographic and geospatial contexts to farmers\u27 experience with one of two DTC innovations: a cost-offset CSA for low-income families and food boxes distributed through rural convenience stores. We geocoded addresses of thirteen farms and DTC pickup sites in two U.S. states (Vermont and Washington) and calculated road network distances from pickup to supermarket, farmers\u27 market, and farm. We compiled Census block-level demographic and transportation data, and compared it to postseason interviews to explore the effect of suitability of the pickup location; proximity to food retail; and potential farmer burden. Most pickup areas were heavily car-dependent, with low walkability and few public transportation options. Conventional sources of fresh produce were within six miles of most pickups, but farmers markets were further away. Despite modest profitability, both models were deemed worth pursuing, as they expanded farmers\u27 customer base. Farmers implementing the store-distributed food box were sensitive to market trends and customer needs in choosing pickup location. Farmers seemed more concerned with marketing in convenience store settings, and finding efficient ways to conduct recordkeeping than with delivery distances

Progress in strategies for sequence diversity library creation for directed evolution

Protein engineering has been the most attractive strategy for biologists to redesign enzymes. As the simplest technique of protein engineering, directed evolution has been applied to many fields, such as industry, agriculture and medicine. An experiment of directed evolution comprises mutant libraries creation and screening or selection for enzyme variants with desired properties. Therefore, a successful application of directed evolution depends on whether or not one can generate a quality library and perform effective screening to find the desired properties. Directed evolution is already increasingly used in many laboratories to improve protein stability and activity, alter enzyme substrate specificity, or design new activities. Meanwhile, many more effective novel strategies of mutant library generation and screening or selection have emerged in recent years, and will continue to be developed. Combining computational/rational design with directed evolution has been developed as more available means to redesign enzymes.Keywords: Protein engineering, directed evolution, sequence diversity creation, novel strategy, computational design, rational desig

Route to high-energy density polymeric nitrogen t-N via He−N compounds

Polymeric nitrogen, stabilized by compressing pure molecular nitrogen, has yet to be recovered to ambient conditions, precluding its application as a high-energy density material. Here we suggest a route for synthesis of a tetragonal polymeric nitrogen, denoted t-N, via He-N compounds at high pressures. Using first-principles calculations with structure searching, we predict a class of nitrides with stoichiometry HeN4 that are energetically stable (relative to a mixture of solid He and N2) above 8.5 GPa. At high pressure, HeN4 comprises a polymeric channel-like nitrogen framework filled with linearly arranged helium atoms. The nitrogen framework persists to ambient pressure on decompression after removal of helium, forming pure polymeric nitrogen, t-N. t-N is dynamically and mechanically stable at ambient pressure with an estimated energy density of ~11.31 kJ/g, marking it out as a remarkable high-energy density material. This expands the known polymeric forms of nitrogen and indicates a route to its synthesis

Evaluation of the new capture vapourizer for aerosol mass spectrometers (AMS) through laboratory studies of inorganic species

Aerosol mass spectrometers (AMSs) and Aerosol Chemical Speciation Monitors (ACSMs) commercialized by Aerodyne are widely used to measure the non-refractory species in submicron particles. With the standard vapourizer (SV) that is installed in all commercial instruments to date, the quantification of ambient aerosol mass concentration requires the use of the collection efficiency (CE) to correct for the loss of particles due to bounce. A new capture vapourizer (CV) has been designed to reduce the need for a bounce-related CE correction. Two high-resolution AMS instruments, one with a SV and one with a CV, were operated side by side in the laboratory. Four standard species, NH4NO3, NaNO3, (NH4)2SO4 and NH4Cl, which typically constitute the majority of the mass of ambient submicron inorganic species, are studied. The effect of vapourizer temperature (Tv&thinsp;&sim;&thinsp;200&ndash;800 &deg;C) on the detected fragments, CE and size distributions are investigated. A Tv of 500&ndash;550 &deg;C for the CV is recommended. In the CV, CE was identical (around unity) for more volatile species (e.g. NH4NO3) and comparable to or higher than the SV for less-volatile species (e.g. (NH4)2SO4), demonstrating an improvement in CE for laboratory inorganic species in the CV. The detected relative intensities of fragments of NO3&nbsp;and SO4&nbsp;species observed with the CV are different from those observed with the SV, and are consistent with additional thermal decomposition arising from the increased residence time and multiple collisions. Increased residence times with the CV also lead to broader particle size distribution measurements than with the SV. A method for estimating whether pure species will be detected in AMS sizing mode is proposed. Production of CO2(g) from sampled nitrate on the vapourizer surface, which has been reported for the SV, is negligible for the CV for NH4NO3&nbsp;and comparable to the SV for NaNO3.&thinsp;. We observe an extremely consistent fragmentation for ammonium compared to very large changes for the associated anions. Together with other evidence, this indicates that it is unlikely that a major fraction of inorganic species vapourizes as intact salts in the AMS.</p

Acoustic metamaterial absorbers based on multilayered sonic crystals

Through the use of a layered arrangement, it is shown that lossy sonic crystals can be arranged to create a structure with extreme acoustic properties, namely, an acoustic metamaterial. This artificial structure shows different effective fluids and absorptive properties in different orientations. Theoretical, numerical, and experimental results examining thermoviscous losses in sonic crystals are presented, enabling the fabrication and characterization of an acoustic metamaterial absorber with complex-valued anisotropic inertia. To accurately describe and fabricate such an acoustic metamaterial in a realizable experimental configuration, confining structures are needed which modify the effective properties, due to the thermal and viscous boundary layer effects within the sonic crystal lattice. Theoretical formulations are presented which describe the effects of these confined sonic crystals, both individually and as part of an acoustic metamaterial structure. Experimental demonstrations are also reported using an acoustic impedance tube. The formulations developed can be written with no unknown or empirical coefficients, due to the structured lattice of the sonic crystals and organized layering scheme; and it is shown that higher filling fraction arrangements can be used to provide a large enhancement in the loss factor. (C) 2015 AIP Publishing LLC.This work was supported by the U.S. Office of Naval Research (Award No. N000141210216) and by the Spanish Ministerio de Economia y Competitividad (MINECO) under Contract No. TEC2010-19751.Guild, M.; García Chocano, VM.; Kan, W.; Sánchez-Dehesa Moreno-Cid, J. (2015). Acoustic metamaterial absorbers based on multilayered sonic crystals. Journal of Applied Physics. 117(11):114902-1-114902-14. https://doi.org/10.1063/1.4915346S114902-1114902-1411711Dowling, J. P. (1992). Sonic band structure in fluids with periodic density variations. 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The Journal of the Acoustical Society of America, 129(3), 1173-1183. doi:10.1121/1.3531815García-Chocano, V. M., Cabrera, S., & Sánchez-Dehesa, J. (2012). Broadband sound absorption by lattices of microperforated cylindrical shells. Applied Physics Letters, 101(18), 184101. doi:10.1063/1.4764560Climente, A., Torrent, D., & Sánchez-Dehesa, J. (2012). Omnidirectional broadband acoustic absorber based on metamaterials. Applied Physics Letters, 100(14), 144103. doi:10.1063/1.3701611Allard, J., & Champoux, Y. (1992). New empirical equations for sound propagation in rigid frame fibrous materials. The Journal of the Acoustical Society of America, 91(6), 3346-3353. doi:10.1121/1.402824Johnson, D. L., Koplik, J., & Dashen, R. (1987). Theory of dynamic permeability and tortuosity in fluid-saturated porous media. Journal of Fluid Mechanics, 176(-1), 379. doi:10.1017/s0022112087000727Tarnow, V. (1996). Compressibility of air in fibrous materials. 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The perceived influence of cost-offset community-supported agriculture on food access among low-income families

Objective To examine perspectives on food access among low-income families participating in a cost-offset community-supported agriculture (CO-CSA) programme.Design Farm Fresh Foods for Healthy Kids (F3HK) is a multicentre randomized intervention trial assessing the effect of CO-CSA on dietary intake and quality among children from low-income families. Focus groups were conducted at the end of the first CO-CSA season. Participants were interviewed about programme experiences, framed by five dimensions of food access: Availability, accessibility, affordability, acceptability and accommodation. Transcribed data were coded on these dimensions plus emergent themes.Setting Nine communities in the US states of New York, North Carolina, Washington and Vermont.Subjects Fifty-Three F3HK adults with children.Results CSA models were structured by partner farms. Produce quantity was abundant; however, availability was enhanced for participants who were able to select their own produce items. Flexible CSA pick-up times and locations made produce pick-up more accessible. Despite being affordable to most, payment timing was a barrier for some. Unfamiliar foods and quick spoilage hindered acceptability through challenging meal planning, despite accommodations that included preparation advice.Conclusions Although CO-CSA may facilitate increased access to fruits and vegetables for low-income families, perceptions of positive diet change may be limited by the ability to incorporate share pick-up into regular travel patterns and meal planning. Food waste concerns may be particularly acute for families with constrained resources. Future research should examine whether CO-CSA with flexible logistics and produce self-selection are sustainable for low-income families and CSA farms