The effects of N and P supply on invertebrate foodwebs: an experimental test of ecological stoichiometry in detritus-based ecosystems

In the last several decades, ecological stoichiometry has emerged as a promising framework for predicting how shifts in the relative availability of N and P influence biological processes from cellular to ecosystem scales. However, explicit tests of ecological stoichiometry theory from ecosystem scale experiments remain rare. In this dissertation, I present the results of a three year experiment where five detritus-based headwater streams were continuously fertilized with N and P at different concentrations, creating a range of molar N:P ratios (from 2:1 to 128:1), for two years following one year of pre-nutrient enrichment monitoring. Nutrient enrichment of the five detritus-based streams resulted in significant shifts in the N and P content of leaf detritus, which is the primary food resource for the invertebrate communities. Patterns of invertebrate productivity among the five streams were closely related to the N:P ratio of leaf detritus, providing strong evidence of food web P-limitation. In addition to effects on overall productivity, nutrient enrichment resulted in shifts in the taxonomic composition of the resident invertebrate community, which were largely driven by increased biomass of a few common detritivores. Nutrient enrichment also had significant effects on organic matter flows within the detrital food webs, as flows of all detrital resources to consumers increased following nutrient enrichment. Increased organic matter flows were necessary to support higher rates of invertebrate production following enrichment and were significantly related to the N:P ratio of leaf detritus, which accounted for ~2/3 of total organic matter flows. Furthermore, invertebrates consumed a greater proportion of the total mass of leaf litter lost from these systems annually following enrichment, a pattern that was once again driven by the N:P ratio of leaf litter. The results of this study provide compelling support for ecological stoichiometry as a framework for predicting consequences of altered N and P dynamics. Our ability to predict how ecosystems respond to shifting N and P availability remains an important challenge in contemporary ecological research given the globally pervasive nature of anthropogenic impacts on biogeochemical N and P cycles. (Published By University of Alabama Libraries

Grandparent caregivers: factors contributing to their experience of life satisfaction

Globally, the number of grandparents providing primary, custodial, or co-parenting for biological and legal grandchildren has grown progressively. Often time examination of grandparent caregiving occurs through the lens of burden and deleterious familial, psychological, and medical outcomes. The present cross-sectional research study is a preliminarily exploration of factors that promote grandparent experience of positive life satisfaction. Bivariate research findings supported an association between grandparent caregivers’ experience of positive life satisfaction and reported resources (rs(94) = .51; p =.000), choice to parent (rs(94) = .26; p =.006), and spirituality (rs(94) = .214; p =.019. Because life satisfaction scores were reversed, the outcome indicated higher life satisfaction is associated with higher reported resources, choice to parent, spirituality, and parental stress. Social support (r(94) = .093; p =.375) and parental stress (r(94) = .181; p =.081) did not demonstrate significant relationships. Multiple Regression Analysis (MRA) found reported resources (β = .45) and choice to parent (β = .21) were the strongest predictors of grandparent caregivers’ positive life satisfaction (F(2, 91) = 26.54, p < .001). However, MRA with caregiver satisfaction interaction terms did not contribute significantly to the model (F(2, 91) = 26.54, p < .001). Study findings evidenced grandparent caregivers experienced positive life satisfaction when they engage in spiritual practices; perceive reduced stress, choice in parenting, adequate personal, social, and familial resources to meet life demands. Implications for social work practice, policy, and research are offered that build on grandparent caregivers’ adaptability, capabilities, and strengths rather than deficits. (Published By University of Alabama Libraries

Barriers to exercise/physical activity for adolescents in rural west Alabama

Regular physical activity (PA) in childhood and adolescence improves strength and endurance, helps build healthy bones and muscles, helps control weight, reduces anxiety and stress, increases self-esteem, and may improve blood pressure and cholesterol levels. The American College of Sports Medicine (ACSM) shows PA trends among adolescents (defined as 13 – 18 yrs.) decrease such that the majority of adolescents are not participating in sufficient activity to meet recommended guidelines. Cardiovascular Disease (CVD) risk factors that are present in adolescence have a tendency to track into adulthood. Youth who are overweight tend to have a higher prevalence of CVD risk factors than their normal weight peers. Rural adolescents may not be engaging in PA as often as their urban counterparts due to barriers of their rural lifestyle. Many rural communities are characterized by vast distances, low socioeconomic status, transportation challenges, and low public funding levels for facilities, programs, and other public amenities. Rural residency, especially in the southern U.S. has been associated with low levels of PA. The rural population is very unique in that they have specific barriers to PA. These may be social, financial, transportation, personal (i.e. lack of time, resources, caregiver responsibilities) or environmental factors (i.e., transportation, inadequate programs, lack of facilities). The purpose of this study was to extend previous findings by surveying a large sample of rural Alabama adolescents regarding barriers to PA and surveying parents and school administrators in this regard as well. Also, this study evaluated the effect that age, race/ethnicity, gender, and SES have on barriers to PA. This study did indeed demonstrate several demographic differences concerning barriers to PA. Additionally, it demonstrated several differences between students, parents, and administrators regarding perceived barriers to PA. Finally, this study provided additional data concerning common barriers to PA reported in the literature. Gender and SES differences were found to be the two covariates that were barriers to exercise and PA in rural West Alabama adolescents. (Published By University of Alabama Libraries

Expert testimony and substance-themed mitigation in capital case sentencing

The present study explored how jurors utilize biopsychosocial variables during the sentencing phase of a capital trial.  According to literature, certain mitigating factors, like substance abuse, cause a "backfire effect."  This means that contrary to the defense's intentions, jurors considered the information more aggravating than mitigating.  Previous studies of biopsychosocial mitigation have neglected the impact of expert testimony on juror decision-making.  Ideally, an expert imparts knowledge so jurors are more informed in their sentencing choice.  However, such testimony may exacerbate the “backfire effect” by underscoring unfavorable qualities of the defendant. Hypotheses anticipated participants (mock jurors) exposed to expert testimony regarding a defendant’s substance abuse would be more likely to choose the death penalty. Further, it was anticipated this effect would be greater for mock jurors displaying problematic drinking patterns. Results revealed a significant main effect of expert testimony such that mock jurors exposed to testimony were significantly less likely to choose the death penalty, regardless of whether the defendant abused substances. Upon further investigation, the significant effect of expert testimony only held true for college student participants. These results highlight the importance of a two-step process of data analysis in juror decision-making studies using college student samples. Specifically, significant effects should be confirmed within a more venire-representative sample before drawing conclusions. Uncovered data also shed more light on the influence of expert testimony during capital cases, as well as the juror characteristics associated with different sentencing decisions for a defendant displaying mental health problems. In addition, data suggested substance-themed mitigation is not necessarily deleterious for the defense. Effective expert testimony may provide a buffer against the backfire effect, especially for jurors with higher levels of achieved education. (Published By University of Alabama Libraries

Understanding the effect of residual stresses and deformation on the fatigue behavior of permanent fasteners

In this work, the complex relationship between deformation history and mechanical performance of self-pierce riveted (SPR) joints is elucidated. This study focuses on understanding how the material deformation that occurs during the riveting process impacts the quasi-static and fatigue behavior of the joint. Experimental results show that fatigue crack initiation in SPR joints can occur away from the rivet. Numerical simulations predicted the deformation of the riveted aluminum-alloy joint, revealing a strong correlation between residual contact pressure due to the riveting process and fretting induced fatigue crack initiation. Furthermore, the number of cycles to failure was calculated by applying linear elastic fracture mechanics approach, which correlated to the experimental fatigue results and further supported the hypothesis that the deformation induced by the riveting process altered the failure mode under high cycle fatigue. Since residual contact stresses were evaluated and correlated to fretting, a more in-depth analysis was performed. To aid in understanding the role of deformation in the riveting process, residual stresses originating from elastic strains within a magnesium-to-aluminum SPR joint were evaluated using neutron diffraction and X-Ray diffraction (XRD) measurements. Furthermore, micro hardness mapping was performed in order to quantify the plastic deformation on a cross-section of the SPR joint. The experimental characterization of the stress and strain state of the SPR joint were then compared to finite element simulations showing good agreement. After validation, the macro lap-shear mechanical response of the SPR joint was simulated and compared with experimental results. In particular, SPR simulations were carried out in order to assess the effect of including the residual stresses and plastic strains in the modeling approach. The simulation results reveal that the inclusion of plastic strains is the main driving force for strength and joint stiffness under quasi-static lap-shear loading, while the residual stresses have a negligible effect. Also, the role of residual stresses and plastic strains was investigated on cyclic loading. Results show that including the deformation history captured in the process simulation changes the prediction of the location of crack initiation, resulting in an estimated number of cycles to failure that differs by a factor of two in the high cycle regime. (Published By University of Alabama Libraries

Solution structure determination for the CYS74 to ALA74 mutant of the catalytic domain of Zoocin A

Zoocin A is a Zn-metallopeptidase secreted by Streptococcus zooepidemicus strain 4881. It has strong inhibitory activity against Streptococcus mutans and thus can serve as a potential treatment for dental caries. The solution NMR structure of the Cys74 to Ala74 mutant of the recombinant catalytic domain (rCAT C74A) of zoocin A has been determined. The structure of rCAT C74A, together with the structure of recombinant target recognition domain (rTRD) of zoocin A, completes a three dimensional view of zoocin A. While the structure of rCAT C74A resembles those of lysostaphin and lytM, the substrate binding groove is wider and no tyrosine residue was observed in the active site. The wider binding groove of rCAT C74A may account for its substrate specificity for D-alanyl-L-alanine peptides, and the absence of a tyrosyl residue or spatially and structurally equivalent hydrogen bond donor in the active site indicates that rCAT C74A may adopt a catalytic mechanism different in some details from that of lytM, and the catalytic mechanism of M23 endopeptidases may have divergent aspects. (Published By University of Alabama Libraries

Minimal supersymmetric b-l and left-right models

We propose a simple gauged U(1)B−L extension of the minimal supersymmetric Standard Model (MSSM), where R-parity is conserved as usual in the MSSM. The global B−L (baryon minus lepton number) symmetry in the MSSM is gauged and three MSSM gauge-singlet chiral multiplets with a unit B −L charge are introduced, ensuring the model free from gauge and gravitational anomalies. We assign an odd R-parity for two of the new chiral multiplets The scalar component of the R-parity even superfield plays the role of a Higgs field to beak the U (1)BL symmetry through its negative mass squared which is radiatively generated by the renormalization group running of soft supersymmetry (SUSY) breaking parameters. Because of our novel R-parity assignment, three light neutrinos are Dirac particles with one massless state. Since R-parity is conserved, the lightest superpartner (LSP) neutralino is a prime candidate of the cosmological dark matter. In particular, the B − L gauge boson (Z ), once discovered at the Large Hadron Collider, will be a novel probe of the Dirac nature of the light neutrinos since its invisible decay processes include the final states with one massless (left-handed) neutrino and two Dirac neutrinos, in sharp contrast with the conventional B − L extension of the SM or MSSM, where the right-handed neutrinos are heavy Majorana particles and decay to the SM leptons. We generalize a variation to the SUSY Left-Right symmetric model based on the gauge group SU (3)c × SU (2)L × SU (2)R × U (1)BL . The charge conjugate SU (2)L singlets are put into SU (2)R doublets, mirroring the former. We only introduce a second Higgs bidoublet to produce realistic fermion mass matrices. We calculate renormalization group evolutions of soft SUSY parameters at the one-loop level down to low energy. We find that an SU (2)R slepton doublet acquires a negative mass squared at low energies, so that the breaking of SU (2)R × U (1)BL → U (1)Y is realized by a non-zero vacuum expectation value of a right-handed sneutrino. Small neutrino masses are produced through neutrino mixings with gauginos. Mass limits on the SU (2)R × U (1)BL sector are obtained by direct search results at the LHC as well as lepton-gaugino mixing bounds from the LEP precision data. (Published By University of Alabama Libraries

Dynamic capabilities “now we see them” in the airline industry

The study of dynamic capabilities is one of the dominant research streams in strategic management. This dissertation contributes to the dynamic capabilities literature by theorizing and testing key questions regarding the relationship between dynamic capabilities and firm performance. Specific questions to be resolved include: 1) how does the performance of dynamic capabilities affect how firms adapt and co-evolve with the environment, 2) what is the interplay of two different kinds of dynamic capabilities operating simultaneously in the same context, and 3) what role does environmental dynamism and munificence play in the relationship between capability development and fitness in asset intensive industries. These questions are examined in the context of the airline industry where I identify two main capabilities that act as dynamic capabilities, namely, Resource Planning Capability (RPC) and Alliance Management Capability (AMC). First, I propose that there is a positive relationship between the two main capabilities (RPC and AMC) and sustained performance. Secondly, I propose alliance orientation will precede the development of an alliance capability. Third, I propose the interaction effect of AMC and RPC is positively associated with sustained performance. Finally, I propose that the positive relationship between each of these capabilities and sustained performance is moderated by environmental dynamism and environmental munificence such that the relationships is weaker, or stronger, at different levels of dynamism and munificence. I test hypotheses using longitudinal panel data on a sample of 132 firms in the airline industry. The analysis was performed using econometric estimators: a stochastic frontier estimator to test technical fitness of capabilities and random effect estimator to test the effect on dependent variable sustained performance. The results show that the two capabilities (RPC and AMC) have a positive effect on sustained performance. Interestingly, the two moderators appear to have differing effects on the two capabilities. Environmental dynamism appear to strengthen RPC and weakens AMC. Conversely, environmental munificence strengthen AMC and weakens RPC. (Published By University of Alabama Libraries

The development and implementation of academic optimism and parent involvement: a case study

The development and implementation of academic optimism and parent involvement were studied. The purpose of this study was to fill in the gaps in the literature regarding how academic optimism and parent involvement is formed in secondary schools, specifically middle school, and examine the connection between teacher academic optimism, parent trust, and parent involvement in one middle school in Northeast Alabama. The participants in the study included teachers currently employed at the school and parents of currently enrolled seventh and eighth grade students in the school. The Teacher Academic Optimism Scale (Fahy, Wu, & Hoy, 2010), the Parent Trust in Schools Scale (Forsyth & Adams, 2004), and the Parental Involvement Scale along with teacher and parent focus group interviews were utilized to collect data. Through a qualitative method of research, the researcher conducted an analysis of the data. The surveys were used to determine levels of academic optimism among teachers in the school, parent trust, and parental involvement in the school. Survey results revealed that even though teacher academic optimism in the school was average and parent involvement was somewhat low, parent trust was high. Focus group interviews were used to collect data on teacher and parent perceptions of academic optimism, parent trust, and parent involvement. From these data, three important themes emerged: the importance of communication and trust, the importance of supportive environments, and the importance of relationships. The findings in this study determined that there is a connection between academic optimism and parent involvement. It also offers implications for development and implementation of academic optimism and parent involvement in a middle school. (Published By University of Alabama Libraries

An exploratory study of the use of classroom blogs to improve student writing

Today’s adolescents experience constant interaction with technology, which brings about new literacies. These literacies become part of school curriculums and ultimately, the future of adolescents. This study explored the use of a microblogging tool through Edmodo to determine if the students’ writing changed. The study framed the writing assignments using the Inside Writing Frame theory as a platform for creating the microblogs and grading rubric. This qualitative case study examined six microblog work samples from six eighth grade students. The writing was analyzed to determine how the students’ writing changed while using the microblog tool. Additionally, this study sought to gain knowledge of how adolescents viewed their experience with writing using the microblog tool. After all data were collected and analyzed, eight codes emerged. Those eight codes are: explore, investigating, gathering data, brainstorm, organizing, defining, redefining, connecting and citing. The participants began with strengths in brainstorming, organizing, defining, redefining and gathering data. From the start of the research, areas of weakness in writing surfaced with exploring, investigating, citing, and connecting. Through the duration of using the microblogs, the participants showed growth in each of those weak areas. Therefore, participants experienced a positive change in their writing through the use of microblogging with Edmodo. In addition to coding the writing samples, the researcher also used a focus group to examine the participants’ experience with using the microblog as a tool for writing. The participants indicated a positive outlook with using the microblog as a tool for writing; they expressed how the tool should be expanded to other subjects. Overall, the results showed a positive effect on the participants’ writing while using microblogs both from the coding of samples and from the focus group responses. (Published By University of Alabama Libraries