Comparison of phosphor screen autoradiography and micro-pattern gas detector based autoradiography for the porosity of altered rocks

This study aims to further develop the C-14-PMMA porosity calculation method with a novel autoradiography technique, the Micro-pattern gas detector autoradiography (MPGDA). In this study, the MPGDA is compared with phosphor screen autoradiography (SPA). A set of rock samples from Martinique Island exhibiting a large range of connected porosities was used to validate the MPGDA method. Calculated porosities were found to be in agreement with ones from the SPA and the triple-weight method (TW). The filmless nature of MPGDA as well as straightforward determination of C-14 radioactivity from the source rock makes the porosity calculation less uncertain. The real-time visualization of radioactivity from C-14 beta emissions by MPGDA is a noticeable improvement in comparison to SPA.Peer reviewe

Social network ties before and after retirement : a cohort study

Social networks are associated with individual's health and well-being. Working life offers opportunities to create and maintain social networks, while retirement may change these networks. This study examined how the number of ties in social network changes across the retirement transition. The study population consisted of 2319 participants (84% women, mean age 63.2 years) from the Finnish Retirement and Aging study. Information about social network ties, including the number of ties in the inner, middle and outer circles of the social convoy model, was gathered using annual postal surveys before and after retirement. Three repeat surveys per participant covered the retirement transition and the post-retirement periods. Mean number of network ties was 21.6 before retirement, of which 5.6 were situated in the inner, 6.9 in the middle and 9.1 in the outer circle. The number of ties in the outer circle decreased by 0.67 (95% CI - 0.92, - 0.42) during the retirement transition period, but not during the post-retirement period (0.11, 95% CI - 0.33, 0.12) (interaction period * time, p = 0.006). The pattern of change in these ties did not differ by gender, occupational status, marital status, number of chronic diseases and mental health during the retirement transition period. The number of ties in the inner and middle circles overall did not decrease during these periods. The number of peripheral relationships decreased during the retirement transition but not after that, suggesting that the observed reduction is more likely to be associated with retirement rather than aging.Peer reviewe

Determining Crack Aperture Distribution in Rocks Using the C-14-PMMA Autoradiographic Method : Experiments and Simulations

Because cracks control the global mechanical and transport properties of crystalline rocks, it is of a crucial importance to suitably determine their aperture distribution, which evolves through alteration processes and rock weathering. Due to the high variability of crack networks in rocks, a multiscale approach is needed. The C-14-PMMA (polymethylmethacrylate) method was developed to determine crack apertures using a set of artificial crack samples with different controlled apertures and tilt angles and also using Monte Carlo simulations. The experiments and simulations show the same result: the estimation of apparent aperture w(A) was successful regardless of tilt angle, even if the estimates are less accurate for low tilt angles (Peer reviewe

Weathering of Viama?o granodiorite, south Brazil : Part 2-Initial porosity of un-weathered rock controls porosity development in the critical zone

The development of porosity during rock weathering is a key process controlling nutrients release, water holding capacity available for plants and water flow. Here we used X-ray Computed Tomography (XRCT) and 14C PolyMethylMethAcrylate (PMMA) autoradiography to show how cracks are created and enlarged during initial weathering stages (saprock and saprolite) of granodiorite in southern Brazil (Viama similar to o - RS). The physical evolution is characterized by imaging the pore network, using 14C-PMMA and XRCT methods. Combined with bulk porosity measurements, they highlight the increase in porosity with the degree of weathering (un-weathered rock phi = 1.66 %, saprolite phi = 11.7 %). This increase is related to the joint increase of the density of the cracks (unweathered rock D = 0.28 mm-1, saprolite D = 0.94 mm-1) and of the average opening of the microcracks (unweathered rock w = 2.4 mu m, saprolite w = 3.9 mu m) and macrocracks (un-weathered rock w = 176 mu m, saprolite w = 400 mu m). However, these average crack openings do not account for the variability of the openings that govern the flows, characterized here by specific distribution ranging from the submicrometre to the centimetre scale. The results highlight that the pore network of the un-weathered rock plays a key role in the initial stages or incipient weathering. The density and aperture and cracks increase following the subcritical cracking concept and new pores are formed by chemo-mechanical processes. The presence/absence of initial fractures in the regolith is certainly a key parameter controlling the weathering of different rock types (mafic vs felsic).Peer reviewe

Identification of type III secretion inhibitors for plant disease management

Bacterial plant pathogens are among the most devastating threats to agriculture. To date, there are no effective means to control bacterial plant diseases due to the restrictions in the use of antibiotics in agriculture. A novel strategy under study is the use of chemical compounds that inhibit the expression of key bacterial virulence determinants. The type III secretion system is essential for virulence of many Gram-negative bacteria because it injects into the plant host cells bacterial proteins that interfere with their immune system. Here, we describe the methodology to identify bacterial type III secretion inhibitors, including a series of protocols that combine in planta and in vitro experiments. We use Ralstonia solanacearum as a model because of the number of genetic tools available in this organism and because it causes bacterial wilt, one of the most threatening plant diseases worldwide. The procedures presented can be used to evaluate the effect of different chemical compounds on bacterial growth and virulence

Social relationships as predictors of extended employment beyond the pensionable age: a cohort study

The aim is to examine whether characteristics of social relationships predict extended employment beyond the pensionable age among Finnish public sector workers. The study population consisted of 4014 participants (83% women, age 62.56 ± 1.21) of the Finnish Retirement and Aging Study followed between 2014 and 2019. Extended employment was defined as the difference between actual retirement date and individual age-related pensionable date and classified into three groups: no extension (retired on pensionable age or extended by < 3 months), short extension (3 months–< 1 year), and long extension (≥ 1 year) beyond the pensionable date. Characteristics of social relationships and engagement were assessed 18 months prior to the pensionable date. Social engagement was classified into consumptive social participation, formal social participation, informal social participation, and other social participation. Data were analyzed using multinomial regression analysis. Of total study participants, 17.8% belonged to short- and 16.5% belonged to long-extension group. Adjusted for age, occupational status, self-rated health and depression, and having a working spouse (OR 2.34, 95% CI 1.39–3.95) were associated with long extension of employment beyond the pensionable age when compared to no extension among men. Likewise, among women, living alone (OR 1.60, 95% CI 1.28–2.00), having a working spouse (1.85, 1.39–2.45), and high consumptive (1.32, 1.07–1.65), high formal (1.47, 1.17–1.85), and other social participation (0.79, 0.63–0.98) were associated with long extension. Having a working spouse, living alone, and high consumptive social participation were associated with short extension. Several characteristics of social relationships, such as having a working spouse, living alone, and high frequency of social engagement, predicted an extension of employment beyond the pensionable age