Fluid invasion of an unsaturated leaky porous layer

We study the flow and leakage of gravity currents injected into an unsaturated (dry), vertically confined porous layer containing a localized outlet or leakage point in its lower boundary. The leakage is driven by the combination of the gravitational hydrostatic pressure head of the current above the outlet and the pressure build-up from driving fluid downstream of the leakage point. Model solutions illustrate transitions towards one of three long-term regimes of flow, depending on the value of a dimensionless parameter D, which, when positive, represents the ratio of the hydrostatic head above the outlet for which gravity-driven leakage balances the input flux, to the depth of the medium. If D⩽0, the input flux is insufficient to accumulate any fluid above the outlet and fluid migrates directly through the leakage pathway. If 0<D⩽1, some fluid propagates downstream of the outlet but retains a free surface above it. The leakage rate subsequently approaches the input flux asymptotically but much more gradually than if D⩽0. If D>1, the current fills the entire depth of the medium above the outlet. Confinement then fixes gravity-driven leakage at a constant rate but introduces a new force driving leakage in the form of the pressure build-up associated with mobilizing fluid downstream of the outlet. This causes the leakage rate to approach the injection rate faster than would occur in the absence of the confining boundary. This conclusion is in complete contrast to fluid-saturated media, where confinement can potentially reduce long-term leakage by orders of magnitude. Data from a new series of laboratory experiments confirm these predictions

Fluid invasion of an unsaturated leaky porous layer

We study the flow and leakage of gravity currents injected into an unsaturated (dry), vertically confined porous layer containing a localized outlet or leakage point in its lower boundary. The leakage is driven by the combination of the gravitational hydrostatic pressure head of the current above the outlet and the pressure build-up from driving fluid downstream of the leakage point. Model solutions illustrate transitions towards one of three long-term regimes of flow, depending on the value of a dimensionless parameter D, which, when positive, represents the ratio of the hydrostatic head above the outlet for which gravity-driven leakage balances the input flux, to the depth of the medium. If D⩽0, the input flux is insufficient to accumulate any fluid above the outlet and fluid migrates directly through the leakage pathway. If 01, the current fills the entire depth of the medium above the outlet. Confinement then fixes gravity-driven leakage at a constant rate but introduces a new force driving leakage in the form of the pressure build-up associated with mobilizing fluid downstream of the outlet. This causes the leakage rate to approach the injection rate faster than would occur in the absence of the confining boundary. This conclusion is in complete contrast to fluid-saturated media, where confinement can potentially reduce long-term leakage by orders of magnitude. Data from a new series of laboratory experiments confirm these predictions

Computerized cognitive behavioral therapy for anxiety and depression in farming communities: mixed methods feasibility study of participant use and acceptability

Background: Farmers have higher rates of depression than nonfarmers and higher rates of suicide than the general population. Several barriers to help seeking have been identified in farmers, which may be overcome by offering web-based mental health support. Computerized cognitive behavioral therapy (cCBT) is an effective intervention used to prevent and treat mild to moderate depression but has not been evaluated in the farming community. Objective: This study explored the feasibility of delivering a cCBT course tailored to farmers using a mixed methods approach. Methods: Farmers (aged ≥18 years) with no, minimal, or moderately severe depressive symptoms (Patient Health Questionnaire–9 [PHQ-9] score &lt;20) were recruited using web-based and offline advertisements and given access to a cCBT course consisting of 5 core modules and automated and personalized email support. Depression (PHQ-9), anxiety (General Anxiety Disorder–7), and social functioning (Work and Social Adjustment Scale) were measured at baseline and the 8-week follow-up. Wilcoxon signed rank tests assessed changes in scores for all outcome measures over time. Telephone interviews focusing on participant use and satisfaction with the course were analyzed using thematic analysis. Results: Overall, 56 participants were recruited; 27 (48%) through social media. Overall, 62% (35/56) of participants logged into the course. At baseline, almost half of the participants reported experiencing minimal depressive symptoms (25/56, 45%) and mild anxiety (25/56, 45%), and just over half (30/56, 54%) reported mild to moderate functional impairment. Posttreatment data were available for 27% (15/56) of participants (41/56, 73% attrition rate). On average, participants experienced fewer depressive symptoms (P=.38) and less functional impairment (P=.26) at the 8-week follow-up; these results were not statistically significant. Participants experienced significantly fewer symptoms of anxiety at the 8-week follow-up (P=.02). Most participants (13/14, 93%) found the course helpful and easy to access (10/13, 77%) and the email support helpful (12/14, 86%). Qualitative interviews identified heavy workloads and mental health stigma within the farming community as barriers to help seeking. Participants thought that web-based support would be helpful, being convenient and anonymous. There were concerns that older farmers and those with limited internet connections may have difficulty accessing the course. Improvements regarding the layout and content of the course were suggested. Dedicated support from someone with farming knowledge was recommended to improve retention. Conclusions: cCBT may be a convenient way of supporting mental health within farming communities. However, challenges in recruiting and retaining farmers may indicate that cCBT supported only by email may not be an acceptable mode of mental health care delivery for many; however, it was valued by respondents. Involving farming organizations in planning, recruitment, and support may address these issues. Mental health awareness campaigns targeting farming communities may also help reduce stigma and improve recruitment and retention

Roles of Aquaporins in Setaria viridis Stem Development and Sugar Storage

Setaria viridis is a C4 grass used as a model for bioenergy feedstocks. The elongating internodes in developing S. viridis stems grow from an intercalary meristem at the base, and progress acropetally toward fully expanded cells that store sugar. During stem development and maturation, water flow is a driver of cell expansion and sugar delivery. As aquaporin proteins are implicated in regulating water flow, we analyzed elongating and mature internode transcriptomes to identify putative aquaporin encoding genes that had particularly high transcript levels during the distinct stages of internode cell expansion and maturation. We observed that SvPIP2;1 was highly expressed in internode regions undergoing cell expansion, and SvNIP2;2 was highly expressed in mature sugar accumulating regions. Gene co-expression analysis revealed SvNIP2;2 expression was highly correlated with the expression of five putative sugar transporters expressed in the S. viridis internode. To explore the function of the proteins encoded by SvPIP2;1 and SvNIP2;2, we expressed them in Xenopus laevis oocytes and tested their permeability to water. SvPIP2;1 and SvNIP2;2 functioned as water channels in X. laevis oocytes and their permeability was gated by pH. Our results indicate that SvPIP2;1 may function as a water channel in developing stems undergoing cell expansion and SvNIP2;2 is a candidate for retrieving water and possibly a yet to be determined solute from mature internodes. Future research will investigate whether changing the function of these proteins influences stem growth and sugar yield in S. viridis

Roles of aquaporins in Setaria viridis stem development and sugar storage

Setaria viridis is a C4 grass used as a model for bioenergy feedstocks. The elongating internodes in developing S. viridis stems grow from an intercalary meristem at the base, and progress acropetally toward fully expanded cells that store sugar. During stem development and maturation, water flow is a driver of cell expansion and sugar delivery. As aquaporin proteins are implicated in regulating water flow, we analyzed elongating and mature internode transcriptomes to identify putative aquaporin encoding genes that had particularly high transcript levels during the distinct stages of internode cell expansion and maturation. We observed that SvPIP2;1 was highly expressed in internode regions undergoing cell expansion, and SvNIP2;2 was highly expressed in mature sugar accumulating regions. Gene co-expression analysis revealed SvNIP2;2 expression was highly correlated with the expression of five putative sugar transporters expressed in the S. viridis internode. To explore the function of the proteins encoded by SvPIP2;1 and SvNIP2;2, we expressed them in Xenopus laevis oocytes and tested their permeability to water. SvPIP2;1 and SvNIP2;2 functioned as water channels in X. laevis oocytes and their permeability was gated by pH. Our results indicate that SvPIP2;1 may function as a water channel in developing stems undergoing cell expansion and SvNIP2;2 is a candidate for retrieving water and possibly a yet to be determined solute from mature internodes. Future research will investigate whether changing the function of these proteins influences stem growth and sugar yield in S. viridis.Samantha A. McGaughey, Hannah L. Osborn, Lily Chen, Joseph L. Pegler, Stephen D. Tyerman, Robert T. Furbank, Caitlin S. Byrt and Christopher P. L. Gro