Aeration, Phosphorous, and Lime Affect Nitrogen Mineralization in Imperfectly Drained Forest Soils

Unamended, limed, and phosphorus-enriched Caddo, Beauregard, and Wrightsville silt loams (A1 horizon) were incubated for six months at room temperature under two moisture regimes. At field capacity, unamended soils lost 0.7% of organic matter and converted 166 ppm of organic nitrogen to inorganic forms. Ninety-five percent of the converted nitrogen was present as N₄-H or NO₃-N. Limed and phosphorus-treated soils at field capacity lost about 1.0% of organic matter and accumulated 191 to 201 ppm of inorganic nitrogen. Submerged soils lost very little organic matter and accumulated only 24 to 28 ppm of inorganic nitrogen. There was a loss of 35 to 78 ppm of nitrogen from the submerged soils, presumably through denitrification

Rural African American adolescents and factors affecting condom use: a path analysis study

The purpose of this dissertation was to assess factors affecting condom use among rural African American adolescents. Data from the National Longitudinal Study of Adolescent Health was used to conduct the study. Condom use behavior was examined with a sample of 539 sexually active rural African American adolescents ages 15 to 18 years. The Health Belief Model was used to inform the conceptual framework of this study. Several factors that were associated with condom use among adolescents were examined. These factors included perceived susceptibility to HIV/AIDS and other STIs, perceived barriers to protect self from infections, parent-child sex communication, parental attitudes toward sex communication, and condom knowledge. Path analysis using the structural equation modeling framework was used to assess the models. The results revealed that being female was related to condom knowledge, perceived susceptibility, and parent-child sex communication. Parent-child sex communication mediated the relationship between parental attitudes toward sex communication and perceived barriers. Finally, none of the factors were related to condom use. Several implications for future research with this population are provided. First, other individual-level factors and contextual-level factors that were not measured in this study should be assessed. Second, future studies should include the assessment of parent-child sex communication with fathers and other guardians in addition to mothers. Last, future studies should include sexual minority adolescents, as sex communication about protective behaviors may differ for this population of adolescents

Condom Use Self-Efficacy Among Younger Rural Adolescents: The Influence of Parent-Teen Communication, and Knowledge of and Attitudes Toward Condoms

This study examines the role of condom use knowledge and attitudes, and parent-teen communication about sex and relationship quality on reports of condom use self-efficacy among rural, African American youth. Participants were 465 North Carolinian youth (10–14 years). Results indicated that greater condom use self-efficacy was predicted by greater knowledge of condom use (β = .206; p < .001), more favorable attitudes toward condom use (β = −.20; p < .0001) and parent-teen communication about sex (β = .13; p < .05), and actual parent-teen communication about sex and dating (β = .14; p < .05). There was low agreement between parents and youth on measures related to parent-teen communication about sex. Findings call for interventions targeting improvement of condom use knowledge among early adolescents, as well as parent-teen communication about sex. In addition, given the low parent-teen agreement regarding sexual communication, parent-teen sexual communication is an important point of intervention

Trends in source gases

Source gases are defined as those gases that, by their breakdown, introduce into the stratosphere halogen, hydrogen, and nitrogen compounds that are important in stratospheric ozone destruction. Given here is an update of the existing concentration time series for chlorocarbons, nitrous oxide, and methane. Also reviewed is information on halogen containing species and the use of these data for establishing trends. Also reviewed is evidence on trends in trace gases that influence tropospheric chemistry and thus the tropospheric lifetimes of source gases, such as carbon dioxide, carbon monoxide, or nitrogen oxides. Much of the information is given in tabular form

Junior high school students’ use of their afterschool hours in Ghana: The role of household assets

Studies have examined a broad range of factors for how students use their time, but few attempts have been made to explore the nuanced link between different types of asset ownership and students' use of study time, particularly in resource-limited countries. This study uses data from junior high school students in Ghana to examine how students spend their time after school hours, the predictive influence of different types of household assets, and the extent to which these trends and relationships vary by gender. Polynomial quantile regression models were fitted across three quantiles (24th, 53rd, and 76th percentiles) to align with one hour, one and half hours, and two hours of study time. Results show that the average student spends well above the recommended 90 minutes on their schoolwork during afterschool hours, regardless of gender. Multivariate results indicate that owning limited assets tends to have a negative relationship with use of study time, but higher levels tend to be positively related to use of study time. Also, the predictive influence of asset ownership varies by asset type, and higher levels of asset ownership favor girls more than boys. Given this study's realtively small sample size, caution must be exercised in generalizing the study findings to the general population of junior high school students in Ghana. In light of the study's limitations, the finding of varying asset effect may have practical implications for asset development programs designed to enhance the well-being of low-income families

The Role of Social Support and Psychological Well-Being in STEM Performance Trends across Gender and Locality: Evidence from Ghana

This study focuses on trends in STEM performance and inclusiveness. We examine performance trajectories in STEM subjects, the predictive role of social support and psychological well-being of students, and variations across student gender and school locality (rural vs urban). We used three waves of data from 135 junior high school students in Ghana. Multilevel growth curve modeling was used to assess the trajectories and the socio-environmental predictors of STEM performance, and posthoc power calculation was used to confirm the adequacy of the sample size. Results show that overall, students’ STEM performance improves over time. Minimal gender differences exist but depend on the subject area and evolve with time. We observed a nuanced “urban advantage,” with rural students starting well but declining over time. Among various indicators of social support and psychological well-being, teacher support was the strongest positive predictor of STEM performance. The study highlights the need to focus on the structural and cultural impediments to STEM education at the lower levels of education in order not to risk excluding marginalized groups early in the education system. Further, STEM interventions may do well to incorporate long-term measures to sustain girls’ interest, motivation, and efforts in STEM

Ultrahigh-throughput generation and characterization of cellular aggregates in laser-ablated microwells of poly(dimethylsiloxane)

Aggregates of cells, also known as multicellular aggregates (MCAs), have been used as microscale tissues in the fields of cancer biology, regenerative medicine, and developmental biology for many decades. However, small MCAs (fewer than 100 cells per aggregate) have remained challenging to manufacture in large quantities at high uniformity. Forced aggregation into microwells offers a promising solution for forming consistent aggregates, but commercial sources of microwells are expensive, complicated to manufacture, or lack the surface packing densities that would significantly improve MCA production. To address these concerns, we custom-modified a commercial laser cutter to provide complete control over laser ablation and directly generate microwells in a poly(dimethylsiloxane) (PDMS) substrate. We achieved ultra rapid microwell production speeds (>50000 microwells per h) at high areal packing densities (1800 microwells per cm2) and over large surface areas for cell culture (60 cm2). Variation of the PDMS substrate distance from the laser focal plane during ablation allowed for the generation of microwells with a variety of sizes, contours, and aspect ratios. Casting of high-fidelity microneedle masters in polyurethane allowed for non-ablative microwell reproduction through replica molding. MCAs of human bone marrow derived mesenchymal stem cells (hMSCs), murine 344SQ metastatic adenocarcinoma cells, and human C4-2 prostate cancer cells were generated in our system with high uniformity within 24 hours, and computer vision software aided in the ultra-high-throughput analysis of harvested aggregates. Moreover, MCAs maintained invasive capabilities in 3D migration assays. In particular, 344SQ MCAs demonstrated epithelial lumen formation on Matrigel, and underwent EMT and invasion in the presence of TGF-β. We expect this technique to find broad utility in the generation and cultivation of cancer cell aggregates, primary cell aggregates, and embryoid bodies

The Effect of Teach One Reach One (TORO) on Youth Acceptance of Couple Violence

This study evaluated the impact of the Teach One Reach One intervention, a community-based participatory research project designed to address the co-occurrence of adolescent risk behaviors on acceptance of teen dating violence. Data were derived from 331 rural African American youth between 10–14 years of age who participated in caregiver-youth dyads as either: 1) peer lay health advisor dyads, or Ambassadors, 2) caregiver-youth dyads recruited by Ambassadors, or Allies, or 3) comparison dyads. The following study focuses on participating youth only and our results indicated that: 1) Ambassadors and Allies reported less acceptance of couple violence than youth within the comparison group, and 2) less family cohesion, greater family conflict, and greater knowledge of healthy dating behaviors predicted greater acceptance of couple violence. Our findings highlight the efficaciousness of the TORO intervention, which directly engaged participants in prevention efforts through community-based participatory research methods and the use of lay heath advisors