Comparative study of mechanical properties of 316L stainless steel between traditional production methods and selective laser melting

Additive manufacturing, also known as 3D printing, is a technology which has recently seen expanding use, as well as expansion of the materials and methods able to be used. This thesis looks at the comparison of mechanical properties of 316L stainless steel manufactured by both traditional methods and selective laser melting found by tensile testing. The traditional method used here involved cold rolled 316L steel being machined to the desired part geometry. Selective laser melting used additive manufacturing to produce the parts from powdered 316L stainless steel, doing so in two different build orientations, flat and on edge with regards to the build plate. Solid test specimens, as well as specimens containing a circular stress concentration in the center of the parts, were manufactured and tensile tested. The tensile tests of the specimens were used to find the mechanical properties of the material; including yield strength, ultimate tensile strength (UTS), and Young’s modulus of elasticity; where statistical analyses were performed to determine if the different manufacturing processes caused significant differences in the mechanical properties of the material. These analysis consisting of f-tests, to test for variance, and t-test, testing for significant difference of means. Through this study it was found that there were statistically significant differences existing between the mechanical properties of selective laser melting, and its orientations, and cold roll forming of production of parts. Even with a statistical difference, it was found that the results were reasonably close between flat oriented SLM parts and purchased parts. So it can be concluded that, with regards to strength, SLM methods produce parts similar to traditional production methods

Creating deletion strains to study the role of the argonaute and dicer genes in RNA interference in Cryptococcus neoformans

Cryptococcus neoformans is a spherical, encapsulated, basidiomycetous yeast and the causative agent of cryptococcosis, a form of meningitis that affects the central nervous system of immunocompromised individuals (immunocompromised means patients with compromised immune systems). Since the 1980’s and the emergence of the AIDS epidemic, much study has been concentrated on this fungus because cryptococcosis is 100% fatal in untreated patients. Even with treatment, the condition does not always decrease in severity, and no major advancements in antifungal drugs have been made in a decade. Recently, Cryptococcus has been shown to possess the necessary machinery for RNA interference (RNAi). RNAi is a method of post-transcriptional gene silencing that may increase cryptococcal survival within mammalian hosts by controlling gene expression at various stages of the life cycle through heterochromatin and euchromatin rearrangement. RNAi was first described in Caenorhabditis elegans in 1998 by Andrew Fire and his colleagues, and is best studied in Drosophila melanogaster. The pathway includes argonaute and dicer proteins that aid in highly specific degradation of mRNA in vivo. To date, no organism has been shown to utilize RNAi as a factor for virulence, nor should it be thought of as such; however, this pathway may indeed play a role in the formation of certain virulence factors for Cryptococcus, including the transcription of heat stress response genes required for thermotolerance, oxidative stress response genes such as those required for melanin and mannitol biosynthesis, as well as the formation of the polysaccharide capsule. Two separate, yet equally effective methods were used in order to create deletion constructs of the AGO1 and AGO2 genes. Overlap PCR and traditional cloning methods were employed. While overlap PCR was optimized, molecular cloning techniques were also used to create the complementation constructs for the above genes. Through overlap PCR, this study resulted in the creation of deletion constructs for the AGO1 and AGO2 genes, which are thought to play a role in RNAi. This study also resulted in the creation of a complementation construct for the ago1 deletion. These constructs can be biolistically inserted into C. neoformans to produce the corresponding deletion strains. Once these strains are produced, future experiments will include many phenotypic studies between them and other known strains, as well as an eventual murine virulence study

Detection, diversity, and activity on anaerobic ammonium oxidizing bacteria (Anammox) in the Cape Fear River Estuary

Anammox is a new pathway in the nitrogen cycle, in which NH4+ oxidiation is coupled to NO2- reduction to produce N2. Anammox was first discovered in a wastewater treatment plant in 1995, and the process was attributed to bacteria that branch deeply in the bacterial genus Planctomycetes. Since this initial finding, anammox bacteria have been detected in anoxic marine sediments, oxygen minimum zones of the oceanic water column, estuaries, arctic sea ice, and even a freshwater lake. Activity measurements have further revealed that these bacteria can contribute significantly to the nitrogen removal process. This chemolithotrophic process is a new loop in the biogeochemical nitrogen cycle that was previously unknown. Prior to the discovery of anammox, denitrification was considered to be the only process responsible for nitrogen removal via N2 gas production. Little is known about the genetics, ecology, and physiology of this organism. Therefore, this study was an attempt to gain better understanding in the community structure of anammox bacteria and their activity related to environmental parameters such as, ammonium, nitrate, and salinity levels. The Cape Fear River Estuary was chosen as the study site. A combination of molecular tools and stable isotope probing technique was employed to study anammox bacteria in the Cape Fear River Estuary. Anammox bacteria were identified at all three sampling sites, and each site had distinct community structure. Salinity and ammonium levels were positively correlated with diversity. Although, no correlation could be established between environmental parameters and activity levels, there did seem to be a link between community structure and activity levels

Metaliteracy in Practice [book review]

Metaliteracy is a reframing of information literacy that “emphasizes the metacognitive dimension of learning and the active roles we play as producers of original and repurposed information” (p. xvi). Editors Trudi Jacobson (Head of the Information Literacy Department, University Libraries, University at Albany SUNY) and Thomas Mackey (Vice-Provost for Academic Programs, SUNY Empire State College) coined the term in a 2011 article and further explored it in their 2014 book Metaliteracy: Reinventing Information Literacy to Empower Learners. Metaliteracy has recently gained recognition in the field of information literacy, primarily through its influence on the Association of College and Research Libraries Framework for Information Literacy for Higher Education. A foreword by Allison Head (from Project Information Literacy) and a preface by the editors situate this book at the intersection of metaliteracy, the Framework, and teaching practice, briefly explaining the theoretical terrain in which the practical applications described in the case studies exist

Peer-Model Attributes and Children's Achievement Behaviors

In two experiments, we investigated how attributed of peer models influenced achievement behaviors among children who had experienced difficulties learning mathematical skills in school. In Experiment 1, children (M = 10.6 years) observed either a same- or opposite-sex peer model demonstrating rapid (mastery model) or gradual (coping model) acquisition of fraction skills. Observing a coping model led to higher self-efficacy, skill, and training performance. In Experiment 2, children (M = 10.9 years) observed either one or three same-sex peer models demonstrating mastery or coping behaviors while solving fractions. Children in the single-coping model, multiple-coping-model, and multiple-mastery-model conditions demonstrated higher self-efficacy, skill, and training performance, compared with subjects who observed a single mastery model. In both studies, children who observed coping models judged themselves more similar in competence to the models than did subjects who observed mastery models

Social-self interaction and achievement behavior

This article describes a dynamic model of achievement in which social influences are internalized and used self-regulatively by learners. The conceptual focus is social cognitive theory with emphasis on triadic reciprocality and phases of self-regulatory development. Social (instructional) factors, self (personal) influences, and achievement outcomes (behaviors) reciprocally interact during learning; the direction and strength of reciprocal influence will vary due to level of skill acquisition and phase of self-regulatory development. Research is summarized on social modeling, self-verbalization, and goals with progress feedback; each involves social transmittal of skills and strategies and a means for learner internalization. The social cognitive perspective is contrasted with other theoretical views that highlight the role of the social environment in learning. This article concludes with suggestions for future research

Polite responses to polite requests

Indirect requests vary in politeness, for example, Can you tell me where Jordan Hall is? is more polite than Shouldn't you tell me where Jordan Hall is? By one theory, the more the literal meaning of a request implies personal benefits for the listener, within reason, the more polite is the request. This prediction was confirmed in Experiment I. Responses to indirect requests also vary in politeness. For Can you tell me where Jordan Hall is?, the response Yes, I can — it's up the street is more polite than It's up the street. By an extension of that theory, the more attentive the responder is to all of the requester's meaning, the more polite is the response. This prediction was confirmed in Experiments 2, 3 and 4. From this evidence, we argued that people ordinarily compute both the literal and the indirect meanings of indirect requests. They must if they are to recognize when the speaker is and isn't being polite, and if they are to respond politely, impolitely, or even neutrally

Reward Contingencies and the Development of Children's Skills and Self-Efficacy

This experiment tested the hypothesis that rewards offered for performance attainments during competency development promote children's arithmetic skills and percepts of self-efficacy. Children received didactic instruction in division operations and were offered rewards contingent on their actual performance, rewards for simply participating, or no rewards. Results showed that performance-contingent rewards led to the highest levels of division skill and self-efficacy, as well as the most rapid problem solving during the training program. In contrast, offering rewards for participation resulted in no benefits compared with offering no rewards. The findings suggest caution in how rewards are distributed in educational contexts

Inherent Details of Self-Regulated Learning Include Student Perceptions

Winne' s (1995) thoughtful and proactive article stressed the role of metacognitive processes in self-regulated learning. Although metacognition and forms of knowledge are important, they provide an incomplete picture of the processes involved in self-regulation. Theoretical and empirical evidence support the inclusion of student perceptions and motivational processes as integral components of self-regulation. Research incorporating the operation of student knowledge and perceptions will make a significant contribution to the self-regulation literature and have important implications for instruction

Modeled Importance of Task Strategies and Achievement Beliefs: Effect on Self-Efficacy and Skill Development

This experiment explored how modeling the importance of task strategy use and positive achievement beliefs affected self-efficacy and skill acquisition. Students deficient in division skills participated in a training program that included instruction and practice opportunities. In the context of instruction, students observed a model demonstrate division solution strategies. For one group the model emphasized the importance of using task strategies, for a second group the model emphasized the importance of positive achievement beliefs. Students in a third group received modeled importance of task strategy use and positive achievement beliefs. Modeling the importance of using task strategies enhanced students' motivation and skill development, but emphasizing both task strategy use and achievement beliefs led to the highest self-efficacy. Implications for teaching are discussed