•Effects of compaction and organic matter on gas and water transport were examined.•Compaction reduced soil gas and water transport properties.•We supposed organic matter blocked pores for gas ...diffusivity and air permeability.•The blocked pores by organic matter yet allowed water to be permeated.
Operation of farm machinery in agricultural fields is the main cause of soil compaction, which may have detrimental effects on soil gas and water transport. However, application of organic matter (OM) reduces the adverse effects of compaction and improves transport properties of soil gases and water. To date, experimental data on the effect of compaction on those transport properties and its relationship to the presence of applied OM remains scarce. The effect of compaction on relative gas diffusivity (Dp/D0)100 and air permeability (ka100) at a soil matric suction of −100cm H2O (soil pF 2.0), and saturated hydraulic conductivity (ks) were investigated using disturbed soil sample taken from 0–15cm layer mixed with rice husk, rice straw, compost, sawdust, and wood bark at a rate of 20% of the soil volume. The common compaction caused by farm machinery in agricultural fields was simulated in the laboratory using a static compression load of 150, 225, and 300kPa. The effect of compaction on total porosity (f) and air content at soil pF 2.0 (ɛ100) was also examined. Compaction reduced f, ɛ100, (Dp/D0)100, ka100, and ks, with the more pronounced significant difference between 150 and 300kPa compactions. The decrease in (Dp/D0)100 was likely attributable to a reduced air content, and the decrease in ka100 and ks was likely attributable to a reduced volume of macropores, as indicated by reduced ɛ100 values. Compared with the control, addition of sawdust and wood bark seemed to have the most positive effect on (Dp/D0)100, ka100, and ks in term of resistance to compaction, while rice straw had the opposite effect. The presence of OM was likely to block the soil pores and increase capillary water in the bottle-neck, leading to lower values of (Dp/D0)100 and ka100 for a given value of ɛ100 (“blockage effect”). These pores blocked by OM, however, seemed to allow the water to flow through the soil matric (“ceramic filter effect”). Further studies on the prolonged application of OM at field scale, taking into account the decomposition process, should be conducted.
Examination of an extensive major and trace element database for about 700 whole rocks from the Ecuadorian Andes reveals series of local trends typified by three volcanoes: Iliniza and Pichincha from ...the Western Cordillera and Tungurahua from the Eastern Cordillera. These local trends are included in a more scattered global trend that reflects typical across-arc chemical variations. The scatter of the global trend is attributed to greater crustal contributions or decreasing melt fractions. Trace element modelling shows that the local trends are consistent with mixing, and not with any fractional crystallization or progressive melting dominated processes. These local trends are extendable to include samples from other Ecuadorian volcanoes, suggesting that mixing processes are dominant throughout the region. Mixing model using trace and major element analyses identifies two end-members: low-silica, basaltic and high-silica, dacitic magmas. It also shows that mixing occurred between magmas after their segregation, rather than earlier mixing between the solid sources prior to melting. As a consequence, there must exist efficient magma-mixing processes that can overcome the obstacles to mixing magmas with contrasting physical properties, and can produce series of hybrid liquids over regional-scale. Model calculations show that estimated silicic end-members are primary magmas and are not co-magmatic derivatives of the corresponding mafic end-members. Lavas of Ecuadorian volcanoes are likely originated from magmas of contrasting origins, such as basaltic magmas generated by fluxed melting of peridotites in the mantle wedge and dacitic, adakite-type magmas originating from the slab or the mafic lower crust.
•We introduced an empirical index of soil macropore volume relative to solid volume.•We introduced an empirical index of macropore continuity for water transport.•Compaction reduced macropore ...continuity in terms of soil air and water transport.•Soil air transport was more sensitive to compaction with organic matter addition.•Soil water transport was less sensitive to compaction with organic matter addition.
Experimental data on the effects of compaction and applied organic matter (OM) on macropore structure indices, more particularly on pore continuity, have yet rarely been documented. In this study, static compaction was simulated in the laboratory at 150, 225, and 300kPa upon rice husk, rice straw, compost, sawdust, and wood bark-mixed soils and control. Measurements of relative gas diffusivity (Dp/D0)100 and air permeability (ka100) were conducted at −100cm H2O soil matric suction after measurement of saturated hydraulic conductivity (ks). Corresponding dry bulk density (ρd), total porosity (f), and air content (ɛ100) values were also determined. Volume of macropores (ϕ≥30μm) and micropores (ϕ<30μm) were expressed as volume of air and water at −100cm H2O soil matric suction, respectively, relative to the volume of soil solid. Specific gas diffusivity (SD100) and specific air permeability (Ska100) were calculated as (Dp/D0)100/ɛ100 and ka100/ɛ100, respectively. Analogous to the SD100 and Ska100, specific hydraulic conductivity (Sks) was defined as ks/ɛ100. The results showed that compaction significantly increased ρd, which was followed by a reduction in f, and the mixed OM resulted in a significantly lower ρd and higher f than the control. The volume of macropores was reduced by compaction whereas the volume of micropores remained unaffected, for which the mixed OM tended to result in a higher volume of macropores than the control. Compaction resulted in more tortuous macropores for gas diffusion (lower SD100) and less continuous macropores for gas convection (lower Ska100) for which a significant difference was more pronounced between the 300 and 150kPa compactions. Compaction also resulted in fewer continuous macropores for water movement as indicated by lower Sks. The mixed OM was likely to result in a lower SD100, but except for rice straw tended to result in a higher Ska100 than the control. In addition, the mixed OM also seemed to result in a higher Sks than the control. Of the OM-mixed soils, the decrease in (Dp/D0)100 and ka100 was more sensitive to compaction (i.e., decrease in ɛ100) than that of the control whereas the decrease in ks acted conversely. Discussion of the measured (Dp/D0)100, ka100, and ks is presented in the companion paper.
To investigate determining factors of happiness during the COVID-19 pandemic.
Observational study.
Large online surveys in Japan before and during the COVID-19 pandemic.
A random sample of 25 482 ...individuals who are representatives of the Japanese population.
Self-reported happiness measured using a 10-point Likert scale, where higher scores indicated higher levels of happiness. We defined participants with ≥8 on the scale as having high levels of happiness.
Among the 25 482 respondents, the median score of self-reported happiness was 7 (IQR 6-8), with 11 418 (45%) reporting high levels of happiness during the pandemic. The multivariable logistic regression model showed that meaning in life, having a spouse, trust in neighbours and female gender were positively associated with happiness (eg, adjusted OR (aOR) for meaning in life 4.17; 95% CI 3.92 to 4.43; p<0.001). Conversely, self-reported poor health, anxiety about future household income, psychiatric diseases except depression and feeling isolated were negatively associated with happiness (eg, aOR for self-reported poor health 0.44; 95% CI 0.39 to 0.48; p<0.001). Using machine-learning methods, we found that meaning in life and social capital (eg, having a spouse and trust in communities) were the strongest positive determinants of happiness, whereas poor health, anxiety about future household income and feeling isolated were important negative determinants of happiness. Among 6965 subjects who responded to questionnaires both before and during the COVID-19 pandemic, there was no systemic difference in the patterns as to determinants of declined happiness during the pandemic.
Using machine-learning methods on data from large online surveys in Japan, we found that interventions that have a positive impact on social capital as well as successful pandemic control and economic stimuli may effectively improve the population-level psychological well-being during the COVID-19 pandemic.
A simple model of a hydrophobic polymer in water is studied. The model polymer, a chain of Lennard-Jones particles with a fixed bond length, is designed in such a way that it undergoes a ...coil-to-globule conformational change near room temperature upon heating in liquid water. At low temperatures (≲270 K), the polymer chain under vacuum takes a globular conformation, whereas in water, it adopts an extended form. At higher temperatures (≳320 K), the polymer has a more compact conformation in water than under vacuum. The same polymer chain in a nonpolar solvent is always extended and shows no sign of a coil-to-globule transformation up to 360 K. The heat-induced collapse of the polymer uniquely observed in water is not attributed to the hydrophobic effect on individual monomers, but it is correlated with the temperature dependence of the potential of mean force between two monomers at contact distance.
Background
Research has suggested optimism is associated with healthy aging and exceptional longevity, but most studies were conducted among non‐Hispanic White populations. We examined associations ...of optimism to longevity across racial and ethnic groups and assessed healthy lifestyle as a possible mediating pathway.
Methods
Participants from the Women's Health Initiative (N = 159,255) completed a validated measure of optimism and provided other demographic and health data at baseline. We evaluated associations of optimism with increments in lifespan using accelerated failure time models, and with likelihood of exceptional longevity (survival to age ≥90) using Poisson regression models. Causal mediation analysis explored whether lifestyle‐related factors mediated optimism‐lifespan associations.
Results
After covariate adjustment, the highest versus lowest optimism quartile was associated with 5.4% (95% confidence interval CI = 4.5, 6.4%) longer lifespan. Within racial and ethnic subgroups, these estimates were 5.1% (95%CI = 4.0, 6.1%) in non‐Hispanic White, 7.6% (95%CI = 3.6, 11.7%) in Black, 5.4% (95%CI = −0.1, 11.2%) in Hispanic/Latina, and 1.5% (95% CI = −5.0, 8.5) in Asian women. A high proportion (53%) of the women achieved exceptional longevity. Participants in the highest versus lowest optimism quartile had greater likelihood of achieving exceptional longevity (e.g., full sample risk ratio = 1.1, 95%CI = 1.1, 1.1). Lifestyle mediated 24% of the optimism‐lifespan association in the full sample, 25% in non‐Hispanic White, 10% in Black, 24% in Hispanic/Latina, and 43% in Asian women.
Conclusions
Higher optimism was associated with longer lifespan and a greater likelihood of achieving exceptional longevity overall and across racial and ethnic groups. The contribution of lifestyle to these associations was modest. Optimism may promote health and longevity in diverse racial and ethnic groups. Future research should investigate these associations in less long‐lived populations.
See related Editorial by Cobert et al. and article by Jeffrey M. Levine in this issue.
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