Fatigue Life Predictions of Additively Manufactured Components for Satelite Structures

The fatigue life properties of Additive Manufactured (AM) components are limited due to the defects naturally generated from the AM Process. For limited design life problems the finite fatigue life El-Haddad model linked defect size, applied stress, and design life. This paper developed a method to predict the smallest defect of interest for a given load case and the lowest failure generating stress for a given defect size. Experimental testing validated the method steps. The model was adjusted to demonstrate the space utility based on a 12U CubeSat chassis. Applying the design life and expected load, the finite fatigue life El-Haddad model predicted the minimum defect size for two configurations of the 12U CubeSat. The minimum defect size defined the Non-Destructive Evaluation (NDE) criteria for component certification. Combining the worst case potential defect size with the design life, the finite fatigue life El-Haddad model defined a minimum stress to generate failure. Linking the minimum stress value to the CubeSat Finite Element Model (FEM) predicted every location on the structure that could potentially fail due to the formation of AM defects. This second aspect defined the required inspection region to certify the structure for the given load case and design life

Characterization of Archaeal Community in Contaminated and Uncontaminated Surface Stream Sediments

Archaeal communities from mercury and uranium-contaminated freshwater stream sediments were characterized and compared to archaeal communities present in an uncontaminated stream located in the vicinity of Oak Ridge, TN, USA. The distribution of the Archaea was determined by pyrosequencing analysis of the V4 region of 16S rRNA amplified from 12 streambed surface sediments. Crenarchaeota comprised 76% of the 1,670 archaeal sequences and the remaining 24% were from Euryarchaeota. Phylogenetic analysis further classified the Crenarchaeota as a Freshwater Group, Miscellaneous Crenarchaeota group, Group I3, Rice Cluster VI and IV, Marine Group I and Marine Benthic Group B; and the Euryarchaeota into Methanomicrobiales, Methanosarcinales, Methanobacteriales, Rice Cluster III, Marine Benthic Group D, Deep Sea Hydrothermal Vent Euryarchaeota 1 and Eury 5. All groups were previously described. Both hydrogen- and acetate-dependent methanogens were found in all samples. Most of the groups (with 60% of the sequences) described in this study were not similar to any cultivated isolates, making it difficult to discern their function in the freshwater microbial community. A significant decrease in the number of sequences, as well as in the diversity of archaeal communities was found in the contaminated sites. The Marine Group I, including the ammonia oxidizer Nitrosopumilus maritimus, was the dominant group in both mercury and uranium/nitrate-contaminated sites. The uranium-contaminated site also contained a high concentration of nitrate, thus Marine Group I may play a role in nitrogen cycle

Influencia de la alimentación y el estilo de vida en el estrés oxidativo

Dado que no existen en nuestra región estudios sobre estrés oxidativo en humanos y su relación con el consumo de alimentos, comparando grupos omnívoros, ovo lacto vegetarianos y vegetarianos estrictos, se ha realizando el presente trabajo de investigación aplicada

From Duty to Right: The Role of Public Education in the Transition to Aging Societies

This paper argues that the introduction of compulsory schooling in early industrialization promoted the growth process that eventually led to a vicious cycle of population aging and negative pressure on education policy. In the early phases of industrialization, public education was undesirable for the young poor who relied on child labor. Compulsory schooling therefore discouraged childbirth, while the accompanying industrialization stimulated their demand for education. The subsequent rise in the share of the old population, however, limited government resources for education, placing heavier financial burdens on the young. This induced further fertility decline and population aging, and the resulting cycle may have delayed the growth of advanced economies in the last few decades