Influence of Sulfur-Containing Diamino Acid Structure on Covalently Crosslinked Copolypeptide Hydrogels.

Biologically occurring non-canonical di-α-amino acids were converted into new di-N-carboxyanhydride (di-NCA) monomers in reasonable yields with high purity. Five different di-NCAs were separately copolymerized with tert-butyl-l-glutamate NCA to obtain covalently crosslinked copolypeptides capable of forming hydrogels with varying crosslinker density. Comparison of hydrogel properties with residue structure revealed that different di-α-amino acids were not equivalent in crosslink formation. Notably, l-cystine was found to produce significantly weaker hydrogels compared to l-homocystine, l-cystathionine, and l-lanthionine, suggesting that l-cystine may be a sub-optimal choice of di-α-amino acid for preparation of copolypeptide networks. The di-α-amino acid crosslinkers also provided different chemical stability, where disulfide crosslinks were readily degraded by reduction, and thioether crosslinks were stable against reduction. This difference in response may provide a means to fine tune the reduction sensitivity of polypeptide biomaterial networks

PARCS: A Safety Net Community-Based Fitness Center for Low-Income Adults

Background: Physical activity (PA) and fitness are critical to maintaining health and avoiding chronic disease. Limited access to fitness facilities in low-income urban areas has been identified as a contributor to low PA participation and poor fitness. Objectives: This research describes community-based fitness centers established for adults living in low-income, urban communities and characterizes a sample of its members. Methods: The community identified a need for physical fitness opportunities to improve residents’ health. Three community high schools were host sites. Resources were combined to renovate and staff facilities, acquire equipment, and refer patients to exercise. The study sample included 170 members older than age 18 who completed demographic, exercise self-efficacy, and quality of life surveys and a fitness evaluation. Neighborhood-level U.S. Census data were obtained for comparison. Results: The community-based fitness centers resulted from university, public school, and hospital partnerships offering safe, accessible, and affordable exercise opportunities. The study sample mean body mass index was 35 + 7.6 kg/m2 (class II obesity), mean age was 50 ± 12.5 years, 66% were Black, 72% were female, 66% completed some college or greater, and 71% had an annual household income of less than $25,000 and supported 2.2 dependents. Participants had moderate confidence for exercise participation and low fitness levels. When compared with census data, participants were representative of their communities. Conclusion: This observational study reveals a need for affordable fitness centers for low-income adults. We demonstrate a model where communities and organizations strategically leverage resources to address disparities in physical fitness and health

Investigating Trends in Atmospheric Compositions of Cool Gas Giant Planets Using Spitzer Secondary Eclipses

We present new 3.6 and 4.5 μm secondary eclipse measurements for five cool (T 1000 K) transiting gas giant planets: HAT-P-15b, HAT-P-17b, HAT-P-18b, HAT-P-26b, and WASP-69b. We detect eclipses in at least one bandpass for all planets except HAT-P-15b. We confirm and refine the orbital eccentricity of HAT-P-17b, which is also the only planet in our sample with a known outer companion. We compare our measured eclipse depths in these two bands, which are sensitive to the relative abundances of methane versus carbon monoxide and carbon dioxide, respectively, to predictions from 1D atmosphere models for each planet. For planets with hydrogen-dominated atmospheres and equilibrium temperatures cooler than ~1000 K, this ratio should vary as a function of both atmospheric metallicity and the carbon-to-oxygen ratio. For HAT-P-26b, our observations are in good agreement with the low atmospheric metallicity inferred from transmission spectroscopy. We find that all four of the planets with detected eclipses are best matched by models with relatively efficient circulation of energy to the nightside. We see no evidence for a solar-system-like correlation between planet mass and atmospheric metallicity, but instead identify a potential (1.9σ) correlation between the inferred CH₄/(CO + CO₂) ratio and stellar metallicity. Our ability to characterize this potential trend is limited by the relatively large uncertainties in the stellar metallicity values. Our observations provide a first look at the brightness of these planets at wavelengths accessible to the James Webb Space Telescope, which will be able to resolve individual CH₄, CO, and CO₂ bands and provide much stronger constraints on their atmospheric compositions

Investigating Trends in Atmospheric Compositions of Cool Gas Giant Planets Using Spitzer Secondary Eclipses

We present new 3.6 and 4.5 μm secondary eclipse measurements for five cool (T 1000 K) transiting gas giant planets: HAT-P-15b, HAT-P-17b, HAT-P-18b, HAT-P-26b, and WASP-69b. We detect eclipses in at least one bandpass for all planets except HAT-P-15b. We confirm and refine the orbital eccentricity of HAT-P-17b, which is also the only planet in our sample with a known outer companion. We compare our measured eclipse depths in these two bands, which are sensitive to the relative abundances of methane versus carbon monoxide and carbon dioxide, respectively, to predictions from 1D atmosphere models for each planet. For planets with hydrogen-dominated atmospheres and equilibrium temperatures cooler than ~1000 K, this ratio should vary as a function of both atmospheric metallicity and the carbon-to-oxygen ratio. For HAT-P-26b, our observations are in good agreement with the low atmospheric metallicity inferred from transmission spectroscopy. We find that all four of the planets with detected eclipses are best matched by models with relatively efficient circulation of energy to the nightside. We see no evidence for a solar-system-like correlation between planet mass and atmospheric metallicity, but instead identify a potential (1.9σ) correlation between the inferred CH₄/(CO + CO₂) ratio and stellar metallicity. Our ability to characterize this potential trend is limited by the relatively large uncertainties in the stellar metallicity values. Our observations provide a first look at the brightness of these planets at wavelengths accessible to the James Webb Space Telescope, which will be able to resolve individual CH₄, CO, and CO₂ bands and provide much stronger constraints on their atmospheric compositions

Stakeholder Influences on the Design of Firms’ Environmental Practices

While prior literature has emphasized that stakeholders can influence a firm's decision to adopt environmental practices that lead to competitive advantage, most scholarship has assumed that stakeholders influence the design of firms' environmental practices similarly. We challenge this notion and suggest that stakeholders affect not only the decision to adopt environmental practices, but also managerial decisions about the design of these practices. We consider the case of firms' strategic decisions about the design of their environmental practices, and in particular their degree of comprehensiveness and visibility. We then develop a classification of four design strategies: movers and shakers, backroom operators, wannabes, and passivists. Using multinomial regression techniques for a sample of more than 1700 firms worldwide, our research shows that while stakeholders exert pressures on firms, managers' perceptions of these pressures vary, and these variations appear to influence the design of their environmental practices. These findings offer important evidence that the scope of stakeholders' influence appears more far reaching (and nuanced) than previously considered. Managers who respond to these influences may therefore be in a better position to satisfy stakeholder expectations, thus enhancing their organization's overall credibility