Study of the Pore Formation on CoCrMo Alloys by Selective Laser Melting Manufacturing Process

AbstractCobalt-base alloys are widely used in medical applications as is the hardest known biocompatible alloy along with a high wear and/or corrosion resistance. The manufacturing process used on these alloys strongly influences the features produced, therefore it should be carefully controlled to attain the desired quality. Selective laser melting (SLM) is a novel process proposed for the fabrication of biomedical implants with cobalt alloys. In this technique, density is the most important concern as it has a direct influence on the component performance. Due to its different energy inputs given by its processing parameters, it has the potential to control porosity through them. In this work, SLM experiments were carried out on a CoCrMo alloy to study the formation of pores. The analysis showed that the SLM technique enables the building of high dense samples up to 99%, resulting in a mean of porosity of 5.77% and a pore mean size of 0.759μm2

Leadership Practice in Elementary School Dual Language Programs: A Collective Case Study

Research in effective programming for English language learners has demonstrated the efficacy of dual language education as a model for closing persistent achievement gaps for this growing population of students. With goals of high academic achievement, linguistic proficiency in two languages, and cross-cultural proficiency, dual language education is an enrichment model of education that eschews the deficit thinking often associated with language-minority students. Based on the promise of enriched education for all participants, the number of dual language programs is increasing nationwide. As districts across the United States plan for the implementation of dual language programs, identifying effective leadership practices for sustaining these programs over time is critical to the strategic deployment of human and fiscal resources. This collective case study examines best practices in dual language programs from a leadership perspective, with a focus on transformational and transformative leadership theories. District level policies and practices are discussed as they relate to the support of dual language programs over time. School level leadership practices are examined in the context of best practices in dual language education as they integrate with concepts of transformational and transformative leadership paradigms. Findings indicated that the actions of district leaders were crucial to the sustained implementation of dual language programs, as they supported the work of school leaders in five categories of leadership practice: vision, goals and priorities, high performance expectations, allocation of resources, and collaboration and shared decision making. Without the support of district leadership in these areas, school leaders struggled to recruit and retain qualified teachers, and minimum expectations for program design and implementation were not fulfilled. Written policies were not followed, and consistent, on-going professional development was not provided for dual language teachers or school leaders. Because these essential components were missing, the promise dual language programs hold for increasing student achievement could not be realized

High In-content InGaN layers synthesized by plasma-assisted molecular-beam epitaxy: growth conditions, strain relaxation and In incorporation kinetics

We report the interplay between In incorporation and strain relaxation kinetics in high-In-content InxGa1-xN (x = 0.3) layers grown by plasma-assisted molecular-beam epitaxy. For In mole fractions x = 0.13-0.48, best structural and morphological quality is obtained under In excess conditions, at In accumulation limit, and at a growth temperature where InGaN decomposition is active. Under such conditions, in situ and ex situ analysis of the evolution of the crystalline structure with the growth thickness points to an onset of misfit relaxation after the growth of 40 nm, and a gradual relaxation during more than 200 nm which results in an inhomogeneous strain distribution along the growth axis. This process is associated with a compositional pulling effect, i.e. indium incorporation is partially inhibited in presence of compressive strain, resulting in a compositional gradient with increasing In mole fraction towards the surface

Requirements for Bend Insensitive Fiber in Millimeter-Wave Fronthaul Systems

The impact of fiber bending on mm-wave radio-over-fiber transmission is investigated and the need for bend insensitive fiber for front-haul installation confirmed. A 70m W-band hybrid photonic-wireless link including bend insensitive fiber is demonstrated with BER<10\u3csup\u3e-6\u3c/sup\u3e at 5mm bending radius

Novel Chitinolytic Enzymes with Biological Activity Against Herbivorous Insects

The soil bacteria, Streptomyces albidoflavus, secretes endochitinases and chitobiosidases that are active over a broad range of pH (4-10). Ingestion of this mixture of chitinolytic enzymes significantly reduced the growth and development of Trichoplusia ni and significantly reduced survival of Myzus persicae, Bemisia argentifolii, and Hypothenemus hampei. Perfusion chromatography was used to separate endochitinases from chitobiosidases. The endochitinases had significantly greater biological activity against Bemisia argentifolii than the chitobiosidases. The utility of chitinolytic enzymes as regulators of populations of herbivorous insects is discusse

Spatial epidemiology and adaptive targeted sampling to manage the Chagas disease vector Triatoma dimidiata

Widespread application of insecticide remains the primary form of control for Chagas disease in Central America, despite only temporarily reducing domestic levels of the endemic vector Triatoma dimidiata and having little long-term impact. Recently, an approach emphasizing community feedback and housing improvements has been shown to yield lasting results. However, the additional resources and personnel required by such an intervention likely hinders its widespread adoption. One solution to this problem would be to target only a subset of houses in a community while still eliminating enough infestations to interrupt disease transfer. Here we develop a sequential sampling framework that adapts to information specific to a community as more houses are visited, thereby allowing us to efficiently find homes with domiciliary vectors while minimizing sampling bias. The method fits Bayesian geostatistical models to make spatially informed predictions, while gradually transitioning from prioritizing houses based on prediction uncertainty to targeting houses with a high risk of infestation. A key feature of the method is the use of a single exploration parameter, $\alpha$, to control the rate of transition between these two design targets. In a simulation study using empirical data from five villages in southeastern Guatemala, we test our method using a range of values for $\alpha$, and find it can consistently select fewer homes than random sampling, while still bringing the village infestation rate below a given threshold. We further find that when additional socioeconomic information is available, much larger savings are possible, but that meeting the target infestation rate is less consistent, particularly among the less exploratory strategies. Our results suggest new options for implementing long-term T. dimidiata control