The effect of eddy distribution on momentum and heat transfer near the wall in turbulent pipe flow

A study was conducted to determine the effect of eddy distribution on momentum and heat transfer near the wall in turbulent pipe flow. The buffer zone was of particular interest in that it is perhaps the most complicated and least understood region in the turbulent flow field. Six eddy diffusivity relationships are directly compared on their ability to predict mean velocity and temperature distributions in turbulent air flow through a cylindrical, smooth-walled pipe with uniform heat transfer. Turbulent flow theory and the development of the eddy diffusivity relationships are briefly reviewed. Velocity and temperature distributions derived from the eddy diffusivity relationships are compared to experimental data for fully-developed pipe flow in turbulent air at a Prandtl number of 0.73 and Reynolds numbers ranging from 8100 to 25 000

THE U.S. DAIRY INDUSTRY

Agribusiness,

Epidermal growth factor (EGF)-like repeats of human tenascin-C as ligands for EGF receptor.

Signaling through growth factor receptors controls such diverse cell functions as proliferation, migration, and differentiation. A critical question has been how the activation of these receptors is regulated. Most, if not all, of the known ligands for these receptors are soluble factors. However, as matrix components are highly tissue-specific and change during development and pathology, it has been suggested that select growth factor receptors might be stimulated by binding to matrix components. Herein, we describe a new class of ligand for the epidermal growth factor (EGF) receptor (EGFR) found within the EGF-like repeats of tenascin-C, an antiadhesive matrix component present during organogenesis, development, and wound repair. Select EGF-like repeats of tenascin-C elicited mitogenesis and EGFR autophosphorylation in an EGFR-dependent manner. Micromolar concentrations of EGF-like repeats induced EGFR autophosphorylation and activated extracellular signal-regulated, mitogen-activated protein kinase to levels comparable to those induced by subsaturating levels of known EGFR ligands. EGFR-dependent adhesion was noted when the ligands were tethered to inert beads, simulating the physiologically relevant presentation of tenascin-C as hexabrachion, and suggesting an increase in avidity similar to that seen for integrin ligands upon surface binding. Specific binding to EGFR was further established by immunofluorescence detection of EGF-like repeats bound to cells and cross-linking of EGFR with the repeats. Both of these interactions were abolished upon competition by EGF and enhanced by dimerization of the EGF-like repeat. Such low affinity behavior would be expected for a matrix-tethered ligand; i.e., a ligand which acts from the matrix, presented continuously to cell surface EGF receptors, because it can neither diffuse away nor be internalized and degraded. These data identify a new class of insoluble growth factor ligands and a novel mode of activation for growth factor receptors

ORDINARY AND GENERALIZED STOCHASTIC DOMINANCE: A PRIMER

Research Methods/ Statistical Methods,

The Human Transformation of Rapa Nui (Easter Island, Pacific Ocean)

Rapa Nui (Easter Island) has become widely known as a case study of human-induced environmental catastrophe resulting in cultural collapse. The island\u27s alleged ecocide is offered as a cautionary tale of our own environmental recklessness. The actual archaeological and historical record for the island reveals that while biodiversity loss unfolded, the ancient Polynesians persisted and succeeded. Demographic collapse came with epidemics of Old World diseases introduced by European visitors. In this paper, we outline the process of prehistoric landscape transformation that took place on Rapa Nui. This process includes the role of humans using fire to remove forest and convert to land for agricultural use as well as the impact of introduced rats (Rattus exulans) as agents that depressed recruitment of native vegetation and contributed to the island\u27s deforestation. For humans, the transformation of the landscape improved productivity. Burning of palms and other trees provided a short-term addition of nutrients to poor soils. Rock mulch and agricultural enclosures solved problems of cultivation and mitigated risk in an uncertain environment. The environmental transformation of Rapa Nui, while a tragedy in terms of biodiversity, was a success for a sustainable Polynesian subsistence economy

U.S. Government Raises the Bar on Deemed Exports and Continues Other Trade Restrictions

Este proyecto de investigación contiene un diseño de un proceso de Gestión de Seguridad y Salud Ocupacional basado en la ISO 45001, propuesto para las MYPES productoras de palta Hass, con el objetivo de disminuir los riesgos presentes en sus actividades, lo cual es un problema relevante debido a los accidentes y enfermedades comunes que presentan. El primer capítulo está compuesto por un estado del arte en base a artículos científicos que se encuentran en un periodo de 5 años antes, además, cuenta con un marco teórico con temas relacionados a las MYPES en el Perú, asociatividad, gestión por procesos, productividad, y seguridad y salud ocupacional. En el segundo capítulo, se efectúa un diagnóstico de la situación actual de las MYPES productoras de palta hass, en donde se identificaron distintos problemas que originan una baja productividad en la producción de la palta hass. En el tercer capítulo, se plantea un diseño de un sistema de gestión de seguridad y salud ocupacional basada en la gestión por procesos, con la finalidad de fomentar una cultura de preventiva, la cual reduce los riesgos y mejora la productividad en el sector agrícola de palta Hass. En el capítulo cuatro, se presenta la validación tanto de los expertos como de los agricultores, con la finalidad de obtener recomendaciones y poder mejorar el diseño del proceso que se propone. Por último, en el capítulo 5 se presenta las conclusiones, recomendaciones y las futuras líneas de investigación acerca del modelo propuesto.This research project contains a design of an Occupational Health and Safety Management process based on ISO 45001, proposed for the MYPES producing Hass avocado, with the objective of reducing the risks present in their activities, which is a relevant problem due to the accidents and common diseases they present. The first chapter is composed of a state of the art based on scientific articles that are found in a period of 5 years before, in addition, it has a theoretical framework with issues related to MYPES in Peru, associativity, process management, productivity , and occupational health and safety. In the second chapter, a diagnosis is made of the current situation of the MYPES producing hass avocado, where different problems were identified that cause low productivity in the production of hass avocado. In the third chapter, a design of an occupational health and safety management system based on process management is proposed, in order to foster a culture of prevention, which reduces risks and improves productivity in the agricultural sector of Hass avocado. In the fourth chapter, the validation of both experts and farmers is presented, in order to obtain recommendations and to improve the design of the proposed process. Finally, chapter 5 presents the conclusions, recommendations and future lines of research on the proposed model.Tesi

A Comparison of Risk Evaluation in Emergency Medical Services Helicopter Operation Regulations

This study represents a comparison of Helicopter Emergency Medical Services (HEMS) operations, between US Federal Aviation Regulations (FARs), and European Joint Aviation Regulations Operations Specifications. Presently, US regulations allow HEMS operators to conduct work under FAR Part 135, Commercial Aviation Operations, or under FAR Part 91, General Aviation Operations. This allows HEMS operators to accept a greater level of risk by substituting lower minimum procedural standards under FAR Part 91 than under FAR Part 135, and may be partly culpable for a higher rate of fatal crashes in HEMS operations conducted under FAR Part 91. In stark contrast, explicit criteria and minimum operating considerations are stated in the European regulations. The Federal Aviation Administration (FAA) has been slow to take a similar clear and firm regulatory stance as that of its European counterpart regarding the human factors involved in the risk assessment of HEMS operations. Providing clearly defined steps to analyze and mitigate unnecessary threats, developing optimum performance guidelines, as well as minimum acceptable operational standards would benefit not only the US HEMS industry but also the patients and public it serves by reducing exposure to preventable dangers

Bringing NASA Technology Down to Earth

Whether putting rovers on Mars or sustaining life in extreme conditions, NASA develops technologies to solve some of the most difficult challenges ever faced. Through its Technology Transfer Program, the agency makes the innovations behind space exploration available to industry, academia, and the general public. This paper describes the primary mechanisms through which NASA disseminates technology to solve real-life problems; illustrates recent program accomplishments; and provides examples of spinoff success stories currently impacting everyday life