47 research outputs found

    The formation of planetary disks and winds: an ultraviolet view

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    Planetary systems are angular momentum reservoirs generated during star formation. This accretion process produces very powerful engines able to drive the optical jets and the molecular outflows. A fraction of the engine energy is released into heating thus the temperature of the engine ranges from the 3000K of the inner disk material to the 10MK in the areas where magnetic reconnection occurs. There are important unsolved problems concerning the nature of the engine, its evolution and the impact of the engine in the chemical evolution of the inner disk. Of special relevance is the understanding of the shear layer between the stellar photosphere and the disk; this layer controls a significant fraction of the magnetic field building up and the subsequent dissipative processes ougth to be studied in the UV. This contribution focus on describing the connections between 1 Myr old suns and the Sun and the requirements for new UV instrumentation to address their evolution during this period. Two types of observations are shown to be needed: monitoring programmes and high resolution imaging down to, at least, milliarsecond scales.Comment: Accepted for publication in Astrophysics and Space Science 9 figure

    Fitorremediación de mercurio presente en aguas residuales provenientes de la industria minera

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    Mining is an industry activity very important but pollutes the environment through exposure to its wastewater containing toxic heavy metals like mercury, which contaminates the water, soil, and the animal and plant wildlife. Therefore, there is a need to minimize or removal this heavy metal from the mine effluents. One eco-friendly and sustainable technology of toxic heavy metal removal is phytoremediation. The objective of this research is to evaluate the performance of the aquatic macrophyte water hyacinth (Eichhornia crassipes) in a constructed wetland with subsurface flow for phytoremediation of a real mining wastewater containing mercury. The study was done in two phases: i) transplant and acclimatization of the plants which lasted 24 days, and ii) phytoremediation of mining effluent about 7 months. The plants responded positively to environment. Moreover, mercury initial concentration for contaminated effluent was 0.325 mg/L. This value is high enough to exceed the permissible limit (0.002 mg/L) stipulated by Colombian legislation for discharge of meaning wastewater into surface water, however, the plants effectively removed up to ï¾ 71% of Hg from the contaminated water. Most of the mercury removal occurred during the first month. It was not possible further Hg reductions to drinking water standards (0.001 mg/L), however, considering the high removal efficiencies of Hg by these aquatic macrophytes, these plants can be recommended for fast removal of mercury in the initial stage of water body remediation.La minería es una actividad industrial muy importante, pero contamina el medio ambiente debido a las descargas de sus aguas residuales conteniendo metales pesados tóxicos como el mercurio, el cual contamina agua, suelo y flora animal y vegetal. Por lo tanto, hay una necesidad de minimizar o remover este metal pesado de los efluentes de las minas. Una tecnología ecológica y sostenible para la eliminación de metales pesados tóxicos es la fitorremediación. El objetivo de esta investigación es evaluar el desempeño del buchón de agua (Eichhornia crassipes) en un humedal de flujo sub-superficial para la fitorremediación de un efluente real contaminado con mercurio. El estudio se realizó en dos fases: i) trasplante y adaptación de las plantas durante 24 días y ii) fitorremediación del efluente durante 7 meses. Las plantas respondieron positivamente al periodo de adaptación. La concentración inicial de mercurio en el efluente fue 0.325 mg/L, este valor supera el límite máximo permisible (0.002 mg/L) establecido por la normatividad colombiana para las descargas de aguas residuales de la industria minera a cuerpos de aguas superficiales, no obstante, las plantas removieron efectivamente hasta un 71% del mercurio presente en el agua residual. La mayor cantidad de Hg se removió en el primer mes, pero no fue posible reducirlo a los niveles estándares establecidos para el agua potable, sin embargo, considerando la alta eficiencia de remoción de esta macrófita acuática, estas plantas pueden ser recomendadas para la remoción de mercurio en una etapa inicial de remediación de un cuerpo de agu

    A method of localizing the spectra of sequences of orthogonal polynomials

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    AbstractOne of the trends in the theory of orthogonal polynomials is to get as much information on their behaviour as possible from the recurrence relation they satisfy. Our intention is to propose a method which in any particular case allows to localize the spectra of polynomial sequences orthogonal either on the real line or on the complex plane

    Experiential Learning and Mentorship in Global Health Leadership Programs: Capturing Lessons from Across the Globe.

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    OBJECTIVES: The changing global landscape of disease and public health crises, such as the current COVID-19 pandemic, call for a new generation of global health leaders. As global health leadership programs evolve, many have incorporated experiential learning and mentoring (ELM) components into their structure. However, there has been incomplete consideration on how ELM activities are deployed, what challenges they face and how programs adapt to meet those challenges. This paper builds on the co-authors' experiences as trainees, trainers, organizers and evaluators of six global health leadership programs to reflect on lessons learned regarding ELM. We also consider ethics, technology, gender, age and framing that influence how ELM activities are developed and implemented. FINDINGS: Despite the diverse origins and funding of these programs, all six are focused on training participants from low- and middle-income countries drawing on a diversity of professions. Each program uses mixed didactic approaches, practice-based placements, competency and skills-driven curricula, and mentorship via various modalities. Main metrics for success include development of trainee networks, acquisition of skills and formation of relationships; programs that included research training had specific research metrics as well. Common challenges the programs face include ensuring clarity of expectations of all participants and mentors; maintaining connection among trainees; meeting the needs of trainee cohorts with different skill sets and starting points; and ensuring trainee cohorts capture age, gender and other forms of diversity. CONCLUSIONS: ELM activities for global health leadership are proving even more critical now as the importance of effective individual leaders in responding to crises becomes evident. Future efforts for ELM in global health leadership should emphasize local adaptation and sustainability. Practice-based learning and established mentoring relationships provide the building blocks for competent leaders to navigate complex dynamics with the flexibility and conscientiousness needed to improve the health of global populations. Key Takeaways: Experiential learning and mentorship activities within global health leadership programs provide the hands-on practice and support that the next generation of global health leaders need to address the health challenges of our times.Six global health leadership programs with experiential learning and mentorship components are showcased to highlight differences and similarities in their approaches and capture a broad picture of achievements that can help inform future programs.Emphasis on inter-professional training, mixed-learning approaches and mentorship modalities were common across programs. Both individual capacity building and development of trainees' professional networks were seen as critical, reflecting the value of inter-personal connections for long-term leadership success.During program design, future programs should recognize the "frame" within which the program will be incorporated and intentionally address diversity-in all its forms-during recruitment as well as consider North-South ethics, leadership roles, hierarchies and transition plans

    Marco de priorización de intervenciones en Agricultura Sostenible Adaptada al Clima (ASAC)

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    长江上游是我国淡水鱼类资源最为丰富的地区之一,已记录鱼类261种;同时,该江段也是我国特有鱼类最为集中的江段,分布特有鱼类112种。这一江段水流湍急,滩潭交错,流态复杂多样。很多鱼类在生理、形态和生活史特征等方面表现出与该江段特殊的栖息地环境相适应的特化。目前长江上游金沙江江段在建的水电站至少有两座(向家坝、洛溪渡),规划建设的还有十余座。这些水电站的建设和运行将极大地改变上游水文环境,对上游鱼类(特别是特有鱼类)产生显著影响

    Climate-smart agriculture investment prioritization framework

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    The CSA Prioritization Framework, developed by CCAFS-CIAT, provides a process for targeting investment towards best-bet CSA options in a given context. The Framework does this by identifying existing and promising CSA practices, assessing the tradeoffs between practices using indicators of CSA and analyzing the costs and benefits of these practices, and identifying possible barriers to adoption. This process aims to contribute to optimized national and sub-national planning, promoting a participatory process for the development of CSA investment portfolios
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