1,738 research outputs found
Microscopic and Macroscopic Signatures of Antiferromagnetic Domain Walls
Magnetotransport measurements on small single crystals of Cr, the elemental
antiferromagnet, reveal the hysteretic thermodynamics of the domain structure.
The temperature dependence of the transport coefficients is directly correlated
with the real-space evolution of the domain configuration as recorded by x-ray
microprobe imaging, revealing the effect of antiferromagnetic domain walls on
electron transport. A single antiferromagnetic domain wall interface resistance
is deduced to be of order at a
temperature of 100 K.Comment: 3 color figure
Mercury removal in wastewater by iron oxide nanoparticles
Mercury is one of the persistent pollutants in wastewater; it is becoming a severe environmental and public health problem, this is why nowadays its removal is an obligation. Iron oxide nanoparticles are receiving much attention due to their properties, such as: great biocompatibility, ease of separation, high relation of surface-area to volume, surface modifiability, reusability, excellent magnetic properties and relative low cost. In this experiment, Fe3O4 and γ-Fe2O3 nanoparticles were synthesized using iron salts and NaOH as precipitation agents, and Aloe Vera as stabilizing agent; then these nanoparticles were characterized by three different measurements: first, using a Zetasizer Nano ZS for their size estimation, secondly UV-visible spectroscopy which showed the existence of resonance of plasmon at λmax∼360 nm, and lastly by Scanning Electron Microscopy (SEM) to determine nanoparticles form. The results of this characterization showed that the obtained Iron oxides nanoparticles have a narrow size distribution (∼100nm). Mercury removal of 70% approximately was confirmed by atomic absorption spectroscopy measurements
Seeking for toroidal event horizons from initially stationary BH configurations
We construct and evolve non-rotating vacuum initial data with a ring
singularity, based on a simple extension of the standard Brill-Lindquist
multiple black-hole initial data, and search for event horizons with spatial
slices that are toroidal when the ring radius is sufficiently large. While
evolutions of the ring singularity are not numerically feasible for large
radii, we find some evidence, based on configurations of multiple BHs arranged
in a ring, that this configuration leads to singular limit where the horizon
width has zero size, possibly indicating the presence of a naked singularity,
when the radius of the ring is sufficiently large. This is in agreement with
previous studies that have found that there is no apparent horizon surrounding
the ring singularity when the ring's radius is larger than about twice its
mass.Comment: 24 pages, 14 figure
Caracterización de la planeación y el control de la producción en las mipymes del sector manufacturero en la ciudad Neiva
El estudio realizado en las Mipymes de Neiva para la caracterización de la Planificación y el control de la producción, los cuales se constituyen en pilar fundamental para alcanzar los niveles de competitividad regional se basó en los estudios de tiempos y movimientos, capacidad de producción, eficiencia de cada centro de producción y del total de la planta, nivel de utilización de cada centro, y del total de la planta, registros de ventas de los últimos cinco años y la técnica del pronóstico para encontrar el tamaño de las ventas a futuro. Para la planeación a corto plazo se estudiaron los siguientes aspectos: Plan Maestro de Producción, evaluación de los diferentes planes, capacidad necesaria de cada lote de producción, diagramas de ruta para sus productos, registros de carga de cada operación, lista de materiales para cada producto, registro para identificar cuando pedir y registro de inventarios. El estudio arroja como resultado que las pequeñas empresas y las microempresas, carecen de sistemas de planeación y control y que los registros históricos necesarios para adelantar dichas labores son incipientes, con baja utilización de mano de obra calificada y poca intervención de profesionales en los procesos de gestión empresarial
Improving Mechanical Properties and Reaction to Fire of EVA/LLDPE Blends for Cable Applications with Melamine Triazine and Bentonite Clay
The high flame-retardant loading required for ethylene-vinyl acetate copolymer blends with polyethylene (EVA-PE) employed for insulation and sheathing of electric cables represents a significant limitation in processability and final mechanical properties. In this work, melamine triazine (TRZ) and modified bentonite clay have been investigated in combination with aluminum trihydroxide (ATH) for the production of EVA-PE composites with excellent fire safety and improved mechanical properties. Optimized formulations with only 120 parts per hundred resin (phr) of ATH can achieve self-extinguishing behavior according to the UL94 classification (V0 rating), as well as reduced combustion kinetics and smoke production. Mechanical property evaluation shows reduced stiffness and improved elongation at break with respect to commonly employed EVA-PE/ATH composites. The reduction in filler content also provides improved processability and cost reductions. The results presented here allow for a viable and halogen-free strategy for the preparation of high performing EVA-PE composites
Community-Based Climate Change Adaptation Action Plans to Support Climate-Resilient Development in the Eastern African Highlands
Smallholder farmers in the Eastern African Highlands depend on rain-fed agriculture for their livelihoods. Climate adaptation and sustainable development goals must be targeted in an integrated way to better match farmers’ realities and address local priorities and vulnerabilities in these areas. To support climate-resilient development in the Eastern African Highlands, 224 local stakeholders were engaged in the development of community-based climate change adaptation action plans for the Jimma Highlands in Ethiopia, Taita Hills in Kenya and Mount Kilimanjaro in Tanzania. Participatory methods, high-resolution climate projections and the United Nations Development Programme’s (UNDP’s) guidelines were used in the design of these climate action plans with specific objectives to: 1) engage stakeholders to increase understanding of climate change impacts, adaptation options and their potential trade-offs, 2) build their capacities to design climate change adaptation projects, 3) empower stakeholders to identify existing vulnerabilities and enhance climate resilience and 4) strengthen networks to facilitate information access and sharing. Increased risk of water stress and reduction of agricultural productivity were the most frequently identified climate-change-induced problems in the three areas. The developed action plans target the underlying causes of these problems and describe sector-specific responses, activities, critical barriers and opportunities and support the National Adaptation Programmes of Action.Peer reviewe
Essential nonlinearities in hearing
Our hearing organ, the cochlea, evidently poises itself at a Hopf bifurcation
to maximize tuning and amplification. We show that in this condition several
effects are expected to be generic: compression of the dynamic range,
infinitely shrap tuning at zero input, and generation of combination tones.
These effects are "essentially" nonlinear in that they become more marked the
smaller the forcing: there is no audible sound soft enough not to evoke them.
All the well-documented nonlinear aspects of hearing therefore appear to be
consequences of the same underlying mechanism.Comment: 4 pages, 3 figure
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