Vapor Selectivity of a Natural Photonic Crystal to Binary and Tertiary Mixtures Containing Chemical Warfare Agent Simulants.

Vapor sensing via light reflected from photonic crystals has been increasingly studied as a means to rapidly identify analytes, though few studies have characterized vapor mixtures or chemical warfare agent simulants via this technique. In this work, light reflected from the natural photonic crystals found within the wing scales of the Morpho didius butterfly was analyzed after exposure to binary and tertiary mixtures containing dimethyl methylphosphonate, a nerve agent simulant, and dichloropentane, a mustard gas simulant. Distinguishable spectra were generated with concentrations tested as low as 30 ppm and 60 ppm for dimethyl methylphosphonate and dichloropentane, respectively. Individual vapors, as well as mixtures, yielded unique responses over a range of concentrations, though the response of binary and tertiary mixtures was not always found to be additive. Thus, while selective and sensitive to vapor mixtures containing chemical warfare agent simulants, this technique presents challenges to identifying these simulants at a sensitivity level appropriate for their toxicity.

Fresh for Less: Cross-Sector Collaboration for Funding, Implementation, and Evaluation of a Local Initiative to Improve Equitable Healthy Food Access.

INTRODUCTION: This study describes the cross-sector collaboration, dynamic implementation/evaluation, and implications of Fresh for Less (FFL); an equity-focused, multi-strategy healthy food access promotion program that has been implemented since 2017 in underserved communities in Austin, Texas through farmstands, mobile markets, and Healthy Corner Stores. METHODS: Annual evaluation has consisted of repeat cross-sectional quantitative surveys, qualitative customer/staff interviews, audits and cost-effective analyses. RESULTS: Farmstand/mobile market customers reported increased fresh produce consumption and high satisfaction. During COVID-19, mobile markets quickly pivoted to delivery, filling a huge need for safe and affordable grocery delivery. Healthy Corner Stores were not as successful, and this strategy was adapted and reintroduced in 2021. Audits show increased produce provision over time and that mobile markets offered increasingly competitive pricing. DISCUSSION: Fresh for Less demonstrates how cross-sector collaborators can work together to ensure that a program designed to improve equitable food access can be resilient, sustainable, and successful.

Additive Combination of Spectra Reflected from Porous Silicon and Carbon/Porous Silicon Rugate Filters to Improve Vapor Selectivity.

Selectivity remains a challenge for rapid optical vapor sensing via light reflected from porous silicon photonic crystals. This work highlights a method to increase optical vapor selectivity of porous silicon rugate filters by analyzing additive spectra from two rugate filter substrates with different functionalities, an oxidized and carbonized surface. Individually, both porous silicon rugate filters demonstrated sensitivity but not selectivity toward the vapor analytes. However, differences in peak shift trends between the two substrates suggested differences in vapor affinities for the surfaces. By adding the two spectra, improvements to selectivity relative to the individual surfaces were observed even at low vapor pressures and for analytes of similar polarity, refractive index, and concentration. These results are expected to contribute toward optical vapor selectivity improvements in one-dimensional porous silicon photonic crystals.