Personal Health and Community Safety Perceptions and their Association with Meeting Physical Activity Guidelines

Objective: To examine whether Vermonters’ perceptions of physical health, mental health, and community safety are associated with meeting Healthy Vermonters’ (HV) 2020 goals.1,2,3 Data was collected in 2017 and utilized for the present study, completed May 2020. Methods: Predictor variables for logistic regression analysis were the 4,393 respondents’ selfreported 1) physical health, 2) mental health, and 3) community safety for walking. Outcome variables were achievement of the HV 2020 goals for 1) aerobic and muscle-strengthening activity and 2) engagement in leisure-time physical activity (LTPA). Results: The odds of meeting the HV 2020 guidelines for aerobic and muscle strengthening activity for those who ranked their community as “Extremely safe” for walking were higher than for those who ranked their community as “Not at all safe” (OR = 2.48; p = .012). Similarly, the odds of engaging in LTPA were higher for those who ranked their community “Extremely safe” than for those who ranked their community “Not at all safe”. (OR = 1.7; p = .046). Conclusion: Perception of neighborhood safety appears to be significantly related to meeting physical activity goals

Energetics of nanoparticle oxides: interplay between surface energy and polymorphism†

Many oxides tend to form different structures (polymorphs) for small particles. High temperature oxide melt solution calorimetry has been used to measure the enthalpy as a function of polymorphism and surface area for oxides of Al, Ti, and Zr. The results confirm crossovers in polymorph stability at the nanoscale. The energies of internal and external surfaces of zeolitic silicas with open framework structures are an order of magnitude smaller than those of oxides of normal density

Thermodynamics of Pure-Silica Molecular Sieve Synthesis

The thermodynamics of pure-silica molecular sieves (denoted by their structural codes ^*BEA, MFI, MTW, and STF) are investigated by solution calorimetry at 323.15 K using 25% aqueous HF as solvent. The enthalpies of solution are determined for both calcined (silica frameworks) and organic structure-directing agent (SDA) occluded samples (SDAs:  tetraethylammonium (TEA), tetrapropylammonium (TPA), trimethylenebis(N-methyl,N-benzylpiperidinium) (BISPIP), and 2,6-dimethyl-1-aza-spiro[5.4]decane (SPIRO)). These measurements provide data that enable the determination of the following interaction enthalpies between the molecular sieve frameworks and SDAs at 323.15 K: ^*BEA/TEA, −3.1 ± 1.4 kJ/mol SiO_2 (−32 ± 15 kJ/mol SDA); ^*BEA/BISPIP, −5.9 ± 0.7 kJ/mol SiO_2 (−181 ± 21 kJ/mol SDA); MFI/TEA, −1.1 ± 1.4 kJ/mol SiO_2 (−27 ± 33 kJ/mol SDA); MFI/TPA, −3.2 ± 1.4 kJ/mol SiO_2 (−81 ± 34 kJ/mol SDA); MTW/BISPIP, −1.6 ± 1.3 kJ/mol SiO_2 (−124 ± 97 kJ/mol SDA); and STF/SPIRO, −4.9 ± 0.9 kJ/mol SiO_2 (−83 ± 16 kJ/mol SDA). Interaction entropies are estimated, and when used in combination with the measured interaction enthalpies, provide the following Gibbs free energies of interaction between the SDAs and the molecular sieve frameworks: ^*BEA/TEA, −5.4 ± 1.5 kJ/mol SiO_2; MFI/TEA, −2.0 ± 1.4 kJ/mol SiO_2; and MFI/TPA, −4.9 ± 1.4 kJ/mol SiO2. The energetics of the synthesis of molecular sieves (considering all components present in the synthesis mixture) are examined and reveal small differences between various molecular sieve/SDA combinations. Assuming complete transformation of the starting amorphous silica into a molecular sieve, the Gibbs free energy changes for the crystallization are ^*BEA/TEA, −8.5 ± 2.9 kJ/mol SiO_2; MFI/TEA, −4.9 ± 2.8 kJ/mol SiO_2; and MFI/TPA, −8.1 ± 2.8 kJ/mol SiO_2. No single factor (enthalpy, entropy, etc.) dominates the overall Gibbs free energies, and these small energetic differences suggest that kinetic factors are of major importance in molecular sieve preparation

Entropy of Pure-Silica Molecular Sieves

The entropies of a series of pure-silica molecular sieves (structural codes ^*BEA, FAU, MFI, and MTT) are obtained by calorimetric measurements of low-temperature heat capacity. The third-law entropies at 298.15 K are (on the basis of 1 mol of SiO_2):  ^*BEA, 44.91 ± 0.11 J·K^(-1)·mol^(-1); FAU, 44.73 ± 0.11 J·K^(-1)·mol^(-1); MFI, 45.05 ± 0.11 J·K^(-1)·mol^(-1); MTT, 45.69 ± 0.11 J·K^(-1)·mol^(-1); while the corresponding entropies of transition from quartz at 298.15 K are ^*BEA, 3.4 J·K^(-1)·mol^(-1); FAU, 3.2 J·K^(-1)·mol^(-1); MFI, 3.6 J·K^(-1)·mol^(-1); MTT, 4.2 J·K^(-1)·mol^(-1). The entropies span a very narrow range at 3.2−4.2 J·K^(-1)·mol^(-1) above quartz, despite a factor of 2 difference in molar volume. This confirms that there are no significant entropy barriers to transformations between SiO_2 polymorphs. Finally, the Gibbs free energy of transformation with respect to quartz is calculated for eight SiO_2 phases and all are found to be within twice the available thermal energy of each other at 298.15 K

Thermochemistry of Pure-Silica Zeolites

A series of pure-silica molecular sieves (structural codes AST, BEA, CFI, CHA, IFR, ISV, ITE, MEL, MFI, MWW, and STT) is investigated by high-temperature drop solution calorimetry using lead borate solvent at 974 K. The enthalpies of transition from quartz at 298 K (in kJ/mol) are AST, 10.9 ± 1.2; BEA, 9.3 ± 0.8; CFI, 8.8 ± 0.8; CHA, 11.4 ± 1.5; IFR, 10.0 ± 1.2; ISV, 14.4 ± 1.1; ITE, 10.1 ± 1.2; MEL, 8.2 ± 1.3; MFI, 6.8 ± 0.8; MWW, 10.4 ± 1.5; and STT, 9.2 ± 1.2. The range of energies observed is quite narrow at only 6.8−14.4 kJ/mol above that of quartz, and these data are consistent with and extend the earlier findings of Petrovic et al. The enthalpy variations are correlated with the following structural parameters:  framework density, nonbonded distance between Si atoms, and framework loop configurations. A strong linear correlation between enthalpy and framework density is observed, implying that it is the overall packing quality that determines the relative enthalpies of zeolite frameworks. The presence of internal silanol groups is shown to result in a slight (≤2.4 kJ/mol) destabilization of the calcined molecular sieves by comparing calorimetric data for MFI and BEA samples synthesized in hydroxide (containing internal silanol groups) and fluoride (low internal silanol group density) media