Semisynthesis and characterization of versatile azide intermediates using sodium alginate and its homopolymeric derivatives as starting material.

Alginate, a polyuronic biopolymer composed of mannuronic and guluronic acid units, contain hydroxyl and carboxyl groups as targeting modification sites to obtain structures with new and/or improved biological properties. The copper-catalyzed azide-alkyne cycloaddition (CuAAC) is a versatile click reaction for polymer functionalization, but it typically requires a "pre-click" modification to introduce azide or alkyne groups. Here, we described a straightforward chemical path to selectively modify alginate carboxyl groups producing versatile azido derivatives through N-acylation using 3-azydopropylamine. The resulting azide-functionalized polysaccharides underwent click chemistry to yield amino derivatives, confirmed by NMR and FTIR analyses. The 1H NMR spectrum reveals a characteristic triazole group signal at 8.15 ppm. The absence of the azide FTIR band for all amino derivatives, previously observed for the N-acylation products, indicated reaction success. Antibacterial and antioxidant assessments revealed that the initial polysaccharide lacks E. coli inhibition, while the click chemistry-derived amine products exhibit growth inhibition at 5.0 mg/mL. Lower molecular weight derivatives demonstrate superior DPPH scavenging ability, particularly amino-derivatives (24-33 % at 1.2 mg/mL). This innovative chemical pathway offers a promising strategy for developing polysaccharide structures with enhanced properties, demonstrating potential applications in various fields.

Selenide [Se(-II)] Immobilization in Anoxic, Fe(II)-Rich Environments: Coprecipitation and Behavior during Phase Transformations.

The radionuclide selenium-79 (Se-79) is predicted to be a key contributor to the long-term radiologic hazards associated with geological high-level waste (HLW) repositories; hence its release is of pertinent concern in the safety assessment of repositories. However, interactions of reduced Se species with aqueous Fe(II) species and solid phases arising from the corrosion of a steel overpack could play a role in mitigating its migration to the surrounding environment. In this study, we examined the immobilization mechanisms of Se(-II) during its interaction with aqueous Fe(II) and freshly precipitated Fe(OH)2 at circumneutral and alkaline conditions, respectively, its response to changes in pH, and its behavior during aging at 90 °C. Using microscopic and spectroscopic techniques, we observed ß-FeSe precipitation, regardless of whether Se(-II) reacts with aqueous species or solid phases, and that modifying the pH following initial immobilization did not remobilize Se(-II). These observations indicate that Se(-II) migration beyond the overpack can be effectively and rapidly retarded via interactions with Fe(II) species arising from overpack corrosion. Thermodynamic calculations, however, showed that iron selenides became metastable at alkaline conditions and will dissolve in the long term. Aging experiments at 90 °C showed that Se(-II) can be completely retained via the crystallization of ferroselite at circumneutral conditions, while it will be largely remobilized at alkaline conditions. Our results show that Se(-II) mobility can be significantly influenced by its interactions with the corrosion products of the steel overpack and that these behaviors will have to be considered in repository safety assessments.

Comparison of two arbitrary cast transfer systems with a kinematic facebow for mounting a maxillary cast on a semiadjustable articulator.

STATEMENT OF PROBLEM: The Kois Dento-Facial Analyzer (KDFA) is used by clinicians to mount maxillary casts and to evaluate and treat patients. Limited information is available for understanding whether the KDFA should be considered as an alternative to an arbitrary facebow. PURPOSE: The purpose of this clinical study was to evaluate and compare maxillary casts mounted by using the KDFA with casts mounted by using the Panadent Pana-Mount Facebow (PMF) and a kinematic axis (KA) facebow. MATERIAL AND METHODS: Fifteen participants were enrolled in the study. Three maxillary impressions were made of each study participant. One cast from each study participant was mounted on an articulator by means of the KDFA, PMF, and KA. A standardized photograph of each mounting was made, and the condylar center-incisor distance and the occlusal and incisal plane angles were measured. A randomized complete block design analysis of variance (RCBD) (α=.05) and post hoc tests (Tukey-Kramer HSD) were used to evaluate the occlusal and incisal plane angles and the condylar center-incisor distance. RESULTS: Compared with the occlusal plane angle (OPA), the KDFA mounted the maxillary cast at an angle that was statistically lower than those of PMF and KA (P<.001). The KDFA and the PMF condylar center-incisor distances were both significantly greater than that of KA (P=.01). No differences were found between the incisal plane angle (IPA) on maxillary casts mounted with the KDFA, KA, or PMF (P=.16). CONCLUSIONS: The KDFA and PMF mounted the maxillary casts in a position that was farther from the axis when compared with the KA mounted casts. The KDFA resulted in a lower articulator OPA compared with both PMF and KA. No difference was found between the IPAs of the KDFA, PMF, and KA.

Quantifying Proximity, Confinement, and Interventions in Disease Outbreaks: A Decision Support Framework for Air-Transported Pathogens.

The inability to communicate how infectious diseases are transmitted in human environments has triggered avoidance of interactions during the COVID-19 pandemic. We define a metric, Effective ReBreathed Volume (ERBV), that encapsulates how infectious pathogens, including SARS-CoV-2, transport in air. ERBV separates environmental transport from other factors in the chain of infection, allowing quantitative comparisons among situations. Particle size affects transport, removal onto surfaces, and elimination by mitigation measures, so ERBV is presented for a range of exhaled particle diameters: 1, 10, and 100 µm. Pathogen transport depends on both proximity and confinement. If interpersonal distancing of 2 m is maintained, then confinement, not proximity, dominates rebreathing after 10-15 min in enclosed spaces for all but 100 µm particles. We analyze strategies to reduce this confinement effect. Ventilation and filtration reduce person-to-person transport of 1 µm particles (ERBV1) by 13-85% in residential and office situations. Deposition to surfaces competes with intentional removal for 10 and 100 µm particles, so the same interventions reduce ERBV10 by only 3-50%, and ERBV100 is unaffected. Prior knowledge of size-dependent ERBV would help identify transmission modes and effective interventions. This framework supports mitigation decisions in emerging situations, even before other infectious parameters are known.

Radon and moisture impacts from interventions integrated with housing energy retrofits.

Energy retrofits can reduce air exchange, raising the concern of whether indoor radon and moisture levels could increase. This pre/post-intervention study explored whether simple radon interventions implemented in conjunction with energy retrofits can prevent increases in radon and moisture levels. Treatment homes (n = 98) were matched with control (no energy retrofits or radon intervention) homes (n = 12). Control homes were matched by geographic location and foundation type. t-tests were used to determine whether post-energy retrofit radon and moisture level changes in treatment homes significantly differed from those in control homes. The radon interventions succeeded in preventing statistically significant increases in first floor radon using arithmetic (p = 0.749) and geometric means (p = 0.120). In basements, arithmetic (p = 0.060) and geometric (p = 0.092) mean radon levels statistically significantly increased, consistent with previous studies which found that basement radon levels may increase even if first floor levels remain unchanged. Changes in infiltration were related to changes in radon (p = 0.057 in basements; p = 0.066 on first floors). Only 58% of the change in infiltration was due to air sealing, with the rest due to weather changes. There was no statistically significant association between air sealing itself and radon levels on the first floor (p = 0.664). Moisture levels also did not significantly increase.

Unburned Methane Emissions from Residential Natural Gas Appliances.

Methane, the primary component of natural gas (NG), is a potent greenhouse gas. NG is a common fuel for residential appliances because of low cost, high energy density, and relatively clean combustion. NG exhaust contains some unburned methane due to inevitable incomplete combustion. A field campaign measuring methane concentrations in exhaust from residential NG appliances was conducted in Boston and Indianapolis to determine their contribution to overall emissions. NG space heating, water heating, and cooking appliances were measured in 100 homes. Appliance exhaust typically exhibits a brief methane concentration spike during ignition and extinguishment and relatively low concentrations during steady-state operation. Exceptions to this pattern include ovens, suboptimal stove burners, and tankless water heaters, which either have a different operating pattern or nontrivial steady-state concentrations. Findings were combined with appliance usage and prevalence assumptions to estimate total emissions. Annually, ∼30 [97.5% CI: 19-160] Gg of methane emissions can be attributed to U.S. residential NG appliances, corresponding to ∼830 [530-4500] Gg carbon dioxide equivalent (CO2e100). This accounts for ∼0.1% [0.08-0.7%] of U.S. anthropogenic methane emissions (which account for ∼10% of total U.S. greenhouse gas emissions) and corresponds to an emission factor of 0.38 g/kg of NG consumed (0.038% [0.024%-0.21%]).

Mechanisms of Se(IV) Co-precipitation with Ferrihydrite at Acidic and Alkaline Conditions and Its Behavior during Aging.

Understanding the form of Se(IV) co-precipitated with ferrihydrite and its subsequent behavior during phase transformation is critical to predicting its long-term fate in a range of natural and engineered settings. In this work, Se(IV)-ferrihydrite co-precipitates formed at different pH were characterized with chemical extraction, transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS) to determine how Se(IV) is associated with ferrihydrite. Results show that despite efficient removal, the mode and stability of Se(IV) retention in the co-precipitates varied with pH. At pH 5, Se(IV) was removed dominantly as a ferric selenite-like phase intimately associated with ferrihydrite, while at pH 10, it was mostly present as a surface species on ferrihydrite. Similarly, the behavior of Se(IV) and the extent of its retention during phase transformation varied with pH. At pH 5, Se(IV) remained completely associated with the solid phase despite the phase change, whereas it was partially released back into solution at pH 10. Regardless of this difference in behavior, TEM and XAS results show that Se(IV) was retained within the crystalline post-aging products and possibly occluded in nanopore and defect structures. These results demonstrate a potential long-term immobilization pathway for Se(IV) even after phase transformation. This work presents one of the first direct insights on Se(IV) co-precipitation and its behavior in response to iron phase transformations.