Additive manufacturing of bulk refractory fiber within the Ta-Hf-C system for ultra high-temperature reinforced composite materials

This work discusses the production of ultra-high temperature material (UHTM) fibers that can be used to reinforce composite materials in extreme environments. Carbon-fiber-based, carbon-matrix composites are commonly used for many UHTM applications; however within an oxygen containing atmosphere, C-C composites are limited by oxidation well-below their ultimate sublimation temperatures. Hence, research is being carried out to create alternative materials, with very high melting points, but that have greater oxidation resistance. SiC-fiber reinforced composites offer one alternative, but are limited to temperatures below 1870K. Of the 12 binary compounds that have melting points above 3270K, Hafnium Carbide (4170K) and tantalum carbide (4150K) have the highest melting points. The ternary tantalum-hafnium-carbide system, which is derived from hot-isostatically-pressed HfC and TaC powders, has been shown to have a melting point in excess of 4260K. Obviously, these refractory materials are extremely hard to draw/extrude into wires or fibers. In this paper, we demonstrate the first-ever synthesis of Ta-Hf-C compounds in fiber form, where we have used hyperbaric laser chemical vapor deposition (HP-LCVD) to decompose gas-phase precursors. TaC, HfC, and TaxHfyCz fibers were grown from tantalum (V) chloride, hafnium (IV) bromide, and octadecane precursors within a heated glass chamber. Fine-grained and amorphous fibers were grown, depending on the precursor pressures and laser-induced temperatures. Several growth modes were observed, including kinetically-limited and mass-transport limited growth. This additive manufacturing approach holds promise for the bulk fabrication of fine-grained and glassy Ta-Hf-C chopped fiber for UHTM composites, and can be applied to many different material systems. An overview of the HP-LCVD process will be provided, as well as various implementations for producing bulk fiber and microstructures for metal-matrix and ceramic-matrix composites fabrication

Hunting for dark halo substructure using submilliarcsecond-scale observations of macrolensed radio jets

Dark halo substructure may reveal itself through secondary, small-scale gravitational lensing effects on light sources that are macrolensed by a foreground galaxy. Here, we explore the prospects of using Very Long Baseline Interferometry (VLBI) observations of multiply-imaged quasar jets to search for submilliarcsecond-scale image distortions produced by various forms of dark substructures in the 1e3-1e8 Msolar mass range. We present lensing simulations relevant for the angular resolutions attainable with the existing European VLBI Network (EVN), the global VLBI array, and an upcoming observing mode in which the Atacama Large Millimeter Array (ALMA) is connected to the global VLBI array. While observations of this type would not be sensitive to standard cold dark matter subhalos, they can be used to detect more compact forms of halo substructure predicted in alternative structure formation scenarios. By mapping ~5 strongly lensed systems, it should be possible to detect or robustly rule out primordial black holes in the 1e3-1e6 Msolar mass range if they constitute >1% percent of the dark matter in these lenses. Ultracompact minihalos are harder to detect using this technique, but 1e6-1e8 Msolar ultracompact minihalos could in principle be detected if they constitute >10% of the dark matter.Comment: 13 pages, 8 figures; v.2 accepted for publication in MNRA

Original investigatiOn efficacy of a DvD-Based smoking Cessation intervention for african americans

aBstraCt introduction: Previous research suggests that African American smokers may have improved outcomes if interventions are culturally specific. However, few interventions sufficiently address the unique needs of this population in a format with large reach potential. The purpose of this study was to test the efficacy of a newly developed digital video disc (DVD)-based cessation intervention targeting African Americans

Effects of a culturally specific tobacco cessation intervention among African American Quitline enrollees: a randomized controlled trial

Abstract Background African Americans suffer disproportionately from tobacco-related illness and have more difficulty quitting smoking than other racial/ethnic groups. Previous research indicates that African American treatment-seekers are high utilizers of tobacco quitlines, yet cessation rates via quitlines are lower relative to whites. The goal of the present study is to test the effectiveness of adding a culturally specific, video-based, adjunct to standard quitline care. It is hypothesized that the integration of an evidence-based intervention (Pathways to Freedom: Leading the Way to a Smoke-Free Community©; PTF) into quitline services will increase cessation and treatment engagement compared to control conditions, and that effects will be moderated by sociocultural factors (e.g., culturally specific intervention expectancies, acculturation, and ethnic identity). Methods This study is a 3-arm semi-pragmatic randomized controlled trial (RCT). Participants will be 1050 enrollees in the North Carolina State quitline (QuitlineNC) who self-identify as African American. Usual quitline care includes up to 4 proactive quit coaching calls, website access, and two-weeks of nicotine patch therapy. Eligible study participants will be randomized to receive (1) standard quitline services plus PTF (PTF); (2) quitline services plus a standard tobacco cessation DVD (attention control); or (3) quitline services alone (usual care). Assessments will be conducted at baseline, 3 and 6-months post-enrollment. The primary outcome will be biochemically verified 7 day ppa at 6-months. Generalized linear mixed models (GLMMs) and hierarchical logistic regression will be used to assess the effects of treatment group on cessation outcomes and to test potential moderators. Discussion This study will answer questions regarding the implementation and effectiveness of integrating a culturally specific video intervention into a real-world, population-level tobacco intervention. It will also aid our understanding of individual-difference variables that are associated with success. If an incremental benefit is found, this trial will have implications for increasing the responsiveness of tobacco quitlines for African Americans, reducing tobacco cessation disparities, and best practices for improving minority health. In addition, the PTF intervention has the potential for widespread disseminated through quitlines, which are available across the United States. Trial registration Clinicaltrials.gov NCT03064971 . Registered on February 22, 2017.https://deepblue.lib.umich.edu/bitstream/2027.42/140739/1/12889_2017_Article_5015.pd

Toward full integration of quantitative and qualitative methods in case study research: insights from investigating child welfare inequalities

Delineation of the full integration of quantitative and qualitative methods throughout all stages of multisite mixed methods case study projects remains a gap in the methodological literature. This article offers advances to the field of mixed methods by detailing the application and integration of mixed methods throughout all stages of one such project; a study of child welfare inequalities. By offering a critical discussion of site selection and the management of confirmatory, expansionary and discordant data, this article contributes to the limited body of mixed methods exemplars specific to this field. We propose that our mixed methods approach provided distinctive insights into a complex social problem, offering expanded understandings of the relationship between poverty, child abuse, and neglect

Hydrological Partitioning in the Critical Zone: Recent Advances and Opportunities for Developing Transferable Understanding of Water Cycle Dynamics

Hydrology is an integrative discipline linking the broad array of water-related research with physical, ecological, and social sciences. The increasing breadth of hydrological research, often where subdisciplines of hydrology partner with related sciences, reflects the central importance of water to environmental science, while highlighting the fractured nature of the discipline itself. This lack of coordination among hydrologic subdisciplines has hindered the development of hydrologic theory and integrated models capable of predicting hydrologic partitioning across time and space. The recent development of the concept of the critical zone (CZ), an open system extending from the top of the canopy to the base of groundwater, brings together multiple hydrological subdisciplines with related physical and ecological sciences. Observations obtained by CZ researchers provide a diverse range of complementary process and structural data to evaluate both conceptual and numerical models. Consequently, a cross-site focus on ‘‘critical zone hydrology’’ has potential to advance the discipline of hydrology and to facilitate the transition of CZ observatories into a research network with immediate societal relevance. Here we review recent work in catchment hydrology and hydrochemistry, hydrogeology, and ecohydrology that highlights a common knowledge gap in how precipitation is partitioned in the critical zone: ‘‘how is the amount, routing, and residence time of water in the subsurface related to the biogeophysical structure of the CZ?’’ Addressing this question will require coordination among hydrologic subdisciplines and interfacing sciences, and catalyze rapid progress in understanding current CZ structure and predicting how climate and land cover changes will affect hydrologic partitioning

Vocal Interactivity in-and-between Humans, Animals, and Robots

Almost all animals exploit vocal signals for a range of ecologically motivated purposes: detecting predators/prey and marking territory, expressing emotions, establishing social relations, and sharing information. Whether it is a bird raising an alarm, a whale calling to potential partners, a dog responding to human commands, a parent reading a story with a child, or a business-person accessing stock prices using Siri, vocalization provides a valuable communication channel through which behavior may be coordinated and controlled, and information may be distributed and acquired. Indeed, the ubiquity of vocal interaction has led to research across an extremely diverse array of fields, from assessing animal welfare, to understanding the precursors of human language, to developing voice-based human–machine interaction. Opportunities for cross-fertilization between these fields abound; for example, using artificial cognitive agents to investigate contemporary theories of language grounding, using machine learning to analyze different habitats or adding vocal expressivity to the next generation of language-enabled autonomous social agents. However, much of the research is conducted within well-defined disciplinary boundaries, and many fundamental issues remain. This paper attempts to redress the balance by presenting a comparative review of vocal interaction within-and-between humans, animals, and artificial agents (such as robots), and it identifies a rich set of open research questions that may benefit from an interdisciplinary analysis