Competition of mixing and segregation in rotating cylinders

Using discrete element methods, we study numerically the dynamics of the size segregation process of binary particle mixtures in three-dimensional rotating drums, operated in the continuous flow regime. Particle rotations are included and we focus on different volume filling fractions of the drum to study the interplay between the competing phenomena of mixing and segregation. It is found that segregation is best for a more than half-filled drum due to the non-zero width of the fluidized layer. For different particle size ratios, it is found that radial segregation occurs for any arbitrary small particle size difference and the final amount of segregation shows a linear dependence on the size ratio of the two particle species. To quantify the interplay between segregation and mixing, we investigate the dynamics of the center of mass positions for each particle component. Starting with initially separated particle groups we find that no mixing of the component is necessary in order to obtain a radially segregated core.Comment: 9 pages, 12 figures (EPIC/EEPIC & EPS, macros included), submitted to Physics of Fluid

Coaxial multi-mode cavities for fundamental SRF research in an unprecedented parameter space

Recent developments in superconducting radio-frequency (SRF) research have focused primarily on high frequency elliptical cavities for electron accelerators. Advances have been made in both reducing RF surface resistance and pushing the readily achievable accelerating gradient by using novel SRF cavity treatments including surface processing, custom heat treatments, and flux expulsion. Despite the global demand for SRF based hadron accelerators, the advancement of TEM mode cavities has lagged behind. To address this, two purpose-built research cavities, one quarter-wave and one half-wave resonator, have been designed and built to allow characterization of TEM-mode cavities with standard and novel surface treatments. The cavities are intended as the TEM mode equivalent to the 1.3GHz single cell cavity, which is the essential tool for high frequency cavity research. Given their coaxial structure, the cavities allow testing at the fundamental mode and higher harmonics, giving unique insight into the role of RF frequency on fundamental loss mechanisms from intrinsic and extrinsic sources. In this paper, the cavities and testing infrastructure are described and the first performance measurements of both cavities are presented

The z-spectrum from human blood at 7T

Chemical Exchange Saturation Transfer (CEST) has been used to assess healthy and pathological tissue in both animals and humans. However, the CEST signal from blood has not been fully assessed. This paper presents the CEST and nuclear Overhauser enhancement (NOE) signals detected in human blood measured via z-spectrum analysis. We assessed the effects of blood oxygenation levels, haematocrit, cell structure and pH upon the z-spectrum in ex vivo human blood for different saturation powers at 7T. The data were analysed using Lorentzian difference (LD) model fitting and AREX (to compensate for changes in T1), which have been successfully used to study CEST effects in vivo. Full Bloch-McConnell fitting was also performed to provide an initial estimate of exchange rates and transverse relaxation rates of the various pools. CEST and NOE signals were observed at 3.5 ppm, -1.7ppm and -3.5 ppm and were found to originate primarily from the red blood cells (RBCs), although the amide proton transfer (APT) CEST effect, and NOEs showed no dependence upon oxygenation levels. Upon lysing, the APT and NOE signals fell significantly. Different pH levels in blood resulted in changes in both the APT and NOE (at -3.5ppm), which suggests that this NOE signal is in part an exchange relayed process. These results will be important for assessing in vivo z-spectra

Organización y resultados de la plataforma de diálogo

“Cali Come Mejor” es un proyecto dirigido a promover políticas locales y/o regionales que contribuyan eficazmente a reducir las desigualdades, a mejorar el acceso y la disponibilidad a una alimentación saludable para la población vulnerable de Cali y fortalecer los vínculos con pequeños productores del Valle. El desarrollo del proyecto se encuentra estructurado en dos etapas fundamentales, la primera etapa (marzo-diciembre 2015) buscó analizar el sistema alimentario de Cali a través una revisión y recolección de los datos disponibles (canales de distribución, consumo de alimentos, mercados formales e informales, actores etc.); el proceso de finalización de esta primera fase consistió en la realización de una plataforma de diálogo donde participaron actores del sector público, privado y de la sociedad civil identificados a lo largo del estudio (ver anexo 1 y 2, lista de invitados y lista de participantes) . Este dialogo tuvo como objetivo compartir y socializar ideas y propuestas a favor de un sistema alimentario sostenible para Cali, tanto para la zona urbana como la rural. Su realización busco llegar a un consenso sobre los resultados del estudio y a generar algunas propuestas para optimizar el funcionamiento del sistema alimentario de Cali. Esta primera fase del proyecto, llevada a cabo desde marzo 2015, es condicional al desarrollo y toma de decisiones en la segunda etapa, a realizarse en el 2016. De esta manera, en el presente documento se encontraran los resultados del primer taller de la Plataforma de diálogo “Cali Come Mejor”, así como la descripción del proceso de desarrollo