2,169 research outputs found

    Plate Tectonics Initiation on Earth-Like Planets: Insights From Numerical and Theoretical Analysis of Convection-Induced Lithospheric Failure

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    Plate tectonics is central to many aspects of the geology and evolution of terrestrial planets, yet it is only observed on the Earth while all other known planets are covered with a stagnant lithosphere. Plate motions on the Earth are mostly driven by the pull of subducting slabs, therefore understanding the initiation of subduction is crucial to understanding plate tectonics initiation. On a one-plate planet which lacks the forces due to plate motions, some other mechanisms will have to cause the first episode of subduction to mobilize the surface. Sublithospheric convection has been proposed as a possible mechanism that induce stresses in the lithosphere. The question is whether these stresses can initiate subduction. We develop scaling laws for the criterion of lithospheric failure from single-cell steady-state convection, which has more controlled flow and thus easier to analyze. We show that these scaling laws are applicable to time-dependent convection. We also investigate the time-dependent behavior of convection to understand the factors controlling the timing of lithospheric failure. We find that the variation in timing not only systematically depends on the physical parameters of the convecting mantle; for convective systems with the same set of parameters, small variations in initial conditions result in different structures of the lithosphere. This changes the stresses in the lithosphere and gives rise to different times of lithospheric failure. This study suggests that it is important to address the question of when plate tectonics can initiate on a planet, in addition to finding favorable conditions for lithospheric failure. We extrapolate the scaling laws to planetary conditions to assess the feasibility of plate tectonics for terrestrial planets, and estimate whether plate tectonics can happen in reasonable planetary lifetimes

    Beyond Passive Learning: Utilizing Active Learning Tools for Engagement, Reflection, and Creation

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    The twenty-first-century student frequently engages with mobile environments to fulfill his or her information needs. Reports from the Pew Research Center (Duggan, 2015) indicate an increasing trend in the use of mobile social media platforms in the US adult population. According to the report, Social Media Usage: 2005–2015 (2015), 65 percent of American adults use social networking sites, and young adults (ages 18–29) reported the highest social media usage for all age groups, at 90 percent. Among the young adult age group, social media usage in 2005 was reported to be 12 percent (Perrin, 2015). This sharp 650 percent rise illustrates the increasingly networked environment inhabited by young adults. In an effort to engage students in the online environment they frequent, educators at the University of Massachusetts Boston utilized iPads to integrate mobile technology into library instruction and other teaching initiatives. This chapter will discuss activities that integrate iPads into library instruction and highlight the use of research guides, web-based polling, gaming pedagogy, online surveys, and other web-based applications for academic research that participants directly engage with, reflect upon, and use to create information in transformative ways

    Quantitative evaluation of the educational programmes on students’ awareness of social responsibility

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    As discrimination and hazardous working conditions have been constituting social costs in the Hong Kong economy, legislative progress in enforcing equal opportunity, safety and health at work becomes obvious with the enactment of discrimination ordinances and the Occupational Safety and Health Ordinance in 1997. Educational programmes were being conducted for students to realise such social responsibility soon after they graduate. The evaluation of the educational programmes is based on the empirical data collected after the delivery of educational packages

    TOX3 mutations in breast cancer

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    TOX3 maps to 16q12, a region commonly lost in breast cancers and recently implicated in the risk of developing breast cancer. However, not much is known of the role of TOX3 itself in breast cancer biology. This is the first study to determine the importance of TOX3 mutations in breast cancers. We screened TOX3 for mutations in 133 breast tumours and identified four mutations (three missense, one in-frame deletion of 30 base pairs) in six primary tumours, corresponding to an overall mutation frequency of 4.5%. One potentially deleterious missense mutation in exon 3 (Leu129Phe) was identified in one tumour (genomic DNA and cDNA). Whilst copy number changes of 16q12 are common in breast cancer, our data show that mutations of TOX3 are present at low frequency in tumours. Our results support that TOX3 should be further investigated to elucidate its role in breast cancer biology.Breast Cancer Research Foundation grant; University of Cambridge; Cancer Research UK; Hutchison Whampoa Limited; NIHR Cambridge Biomedical Research Centre; Marie Curie Career Integration Grant; Cancer Research UK [16942]; National Institute for Health Research [NF-SI-0611-10154

    Interleukin-2 Production by Dendritic Cells and its Immuno-Regulatory Functions

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    Dendritic cells (DCs) are uniquely potent antigen presenting cells that acquire microbial products and prime adaptive immune responses against pathogens. Furthermore, DCs also play a key role in induction and maintenance of tolerance. Although numerous studies have assessed the diverse functions of DCs, many unanswered questions remain regarding the molecular mechanisms that DCs use to achieve immunoregulation. While not widely regarded as a significant provider of T-cell growth factors, DCs have previously been identified as a potential source of IL-2 cytokine. Recent research indicates that microbes are the most effective stimuli to trigger IL-2 production in DCs by activating the calcineurin/NFAT signaling pathway. Herein we describe recent insights into the production and function of IL-2 cytokine and IL-2 receptor in DCs early after stimulation through pattern recognition receptors. These findings clarify how DCs fine-tune effector and regulatory responses by modulating IL-2 production in both tolerance and immunity

    Pediatric Patients with Intravascular Devices: Polymicrobial Bloodstream Infections and Risk Factors

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    A retrospective study was conducted, including 61 patients with long-term intravascular devices (IVDs) admitted to the Childrens Hospital Los Angeles with diverse underlying diseases, different types of catheters, and culture-proven catheter-related bloodstream infections (BSIs). Within these patients, 125 catheter-related BSIs occurred, and the incidence of monomicrobial and polymicrobial BSIs was evaluated. Risk factors for polymicrobial BSIs were determined. Forty-two BSIs contained more than one pathogen. These polymicrobial BSIs were observed more often in younger patients (<4.1 years versus ≥4.1 years) and less in patients using venous implanted ports. No other associations were found between the occurrences of polymicrobial BSIs and underlying diseases, other types of catheters, host defense status, parenteral nutrition, recurrences, or catheter removal. Patients with long-term IVDs at a younger age have a higher risk of developing a polymicrobial BSI. Future prospective studies should address the issue of polymicrobial infection in IVDs in more detail

    Building on the Past - Looking to the Future. Part 2: A Focus on Expanding Horizons

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    The history of space endeavors stretches far from the first liquid-fueled rocket created by the father of modern rocketry, Robert Goddard, in 1926 and will certainly extend far beyond the construction of the International Space Station (ISS) scheduled to be complete with the addition of the Permanent Multipurpose Module on STS-133/ULF5. National Aeronautics and Space Administration (NASA) and the ISS International Partners (IPs) will be the unrelenting venue used to satisfy the curiosities of man as we seek an understanding of space through various experiments (also referred to as payloads) conducted in microgravity. The NASA Payload Safety Review Panel (PSRP) continues to serve as the lead for the review and assessment of payload hardware to assure facility and crew safety. This is the second in a series of papers and presentations that illustrate challenges and lessons learned in the areas of communication, safety requirements, and processes which have been vital to the PSRP

    Building on the Past - Looking to the Future: A Focus on Payload Safety

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    The history of the space industry stretches far and above lunar landings to the construction of the International Space Station. For years, humans have sought to understand the nature of the universe. As society grows in knowledge and curiosity of space, the focus of maintaining the safety of the crew and vehicle habitability is of utmost importance to the National Aeronautics and Space Administration (NASA) community. Through the years, Payload Safety has developed not only as a Panel, but also as part of the NASA community, striving to enhance the efficiency and understanding of how business should be conducted as more International Partners become involved. This is the first in a series of papers and presentations in what is hoped to be an annual update that provides continuous challenges and lessons learned in the areas of communication, safety requirements and processes and other areas which have been vital to the Payload Safety Review Panel (PSRP)
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