Reversal of gulf stream circulation in a vertically vibrated triangular fluidized bed

Vibrated fluidized beds are a process intensification technique consisting in introducing vibratory kinetic energy in a fluidized bed (1). In this work we assess experimentally the effect of vibration on the gulf-stream circulation pattern of particles in a fluidized bed that is of triangular shape. The bed has 0.206 m span and 0.01 m thickness. The base of the bed is composed of two inclined walls, each one forming an angle of 45º with the horizontal. Air was injected through the inclined bed walls to fluidize the bed (see Figure 1a). This gas injection, together with vibration, can make the dynamics of this bed different to that found in a spouted fluidized bed (2). The bed is filled with ballotini particles with a mean diameter of 1.15 mm up to the top of the inclined walls. The bed vessel is made of antistatic PMMA to allow optical access with a high-speed camera. The bed was mounted on an electrodynamic shaker which produces the vibration. A high speed camera is used to record the motion of particles. The particle velocity was obtained via Particle Image Velocimetry (PIV). As a function of vibration amplitude and frequency, we observe several circulation patterns when the fluidization velocity is just below and above the minimum fluidization velocity. Noticeably, for zero gas velocity, particles ascend close to the side walls descend in the center of the bed. By injecting fluidization gas, the circulation pattern of the bed could be reversed (i.e. particles descending near the side walls ascend in the center of the bed) for certain conditions. For example, reversal of the gulf stream circulation of particles appeared in the triangular bed for gas superficial velocities higher than the minimum fluidization velocity and sufficiently high values of the vibration strength. This phenomenon is illustrated in Figure 1b in which, for the same vibrating conditions, the injection of gas superficial velocity through the walls reverses the gulf stream motion of particles in the bed. REFERENCES R. Gupta, A.S. Mujumdar, Hydrodynamic of vibrated fluidized bed, Can. J. Chem. Eng., 58:332-338, 1980. Vinayak S. Sutkar, Niels G. Deen, J.A.M. Kuipers, Spout fluidized beds: Recent advances in experimental and numerical studies, Chem. Eng. Sci., 86:124:136, 2013. Please click Additional Files below to see the full abstract

Influencia del mucílago de cactus y extracto de algas pardas marinas en la resistencia a compresión y durabilidad del hormigón

This paper presents the mechanical performance and durability of concrete with water/cement (w/c) ratios of 0.30 and 0.60 containing cactus mucilage and brown marine seaweed extract solutions (at 0.5° Brix concentrations). Cylindrical specimens (100 mm x 200 mm) were cast and moist-cured for 0 and 28 days. Compressive strength, rapid chloride permeability, and chloride diffusion tests were conducted to evaluate all of the concrete mixes at the ages of 60 and 120 days. In addition, accelerated carbonation tests were carried out on specimens at the age of 180 days by exposure to 23 °C, 60% RH and at 4.4% CO2 for 120 days. The compressive strength results showed that only one concrete mix with admixtures increased in strength compared to the control. Regarding the rapid chloride permeability, chloride diffusion and carbonation, the results indicated that the durability of concretes containing organic additions was enhanced compared to the control.Este trabajo presenta el comportamiento mecánico y de durabilidad de concretos con relaciones agua/cemento de 0.30 y 0.60, conteniendo soluciones de mucílago de nopal y extracto de algas marinas cafés (0.5 °Brix de concentración). Especímenes cilíndricos (100 mm x 200 mm) fueron elaborados y curados en húmedo por 0 y 28 días. Se evaluó la resistencia a la compresión, permeabilidad rápida y difusión de cloruros a los 60 y 120 días de edad. Adicionalmente, se realizaron pruebas de carbonatación acelerada en especímenes con 180 días de edad, expuestos a 23 °C, 60% HR y 4.4% de CO2 por 120 días. Los resultados de resistencia a la compresión muestran que únicamente una mezcla de concreto con adición orgánica incrementó su resistencia con respecto al control. Con respecto a la permeabilidad rápida a cloruros, difusión de cloruros y carbonatación, los resultados indican que la durabilidad de los concretos que contenían adiciones orgánicas fue mejorada con respecto al control

Segregation of equal-sized particles of different densities in a vertically vibrated fluidized bed

Many operations in the chemical and energy-conversion industries rely on the fluidization of heterogeneous materials. During fluidization, particles of different densities can segregate, even if they are of the same size. Segregation is typically an undesired phenomenon, especially in fluidized bed reactors (1). Thus, an understanding of segregation on a fundamental level is paramount to identify effective measures to control it. One approach to control segregation could be the vibration of the bed vessel. However, there is very little literature available concerning the effect of vibration on density-induced segregation dynamics (2). Thus, this work studies the influence of vibration on density-induced segregation dynamics in a gas fluidized bed. Experiments were carried out in a pseudo-2D bed of 0.2 m width, 0.5 m height and 0.01 m thickness. The bed was filled with black, ballotini spheres (density 2500 kg/m3) mixed with heavier, white, ceramic particles (density 4100 kg/m3 and 6000 kg/m3). All particles have an average diameter of 1.1 mm. The bed was fluidized by air and vibrated by an electrodynamic shaker. High-speed images were recorded through the transparent front wall of the bed. Digital Image Analysis (DIA) was used to characterize the rate and extent of particle mixing with time (see Figure 1). At the start of the experiments the particles were mixed. The results obtained indicate that both the vibration strength and the gas velocity have an important effect on both the rate and the maximum degree of segregation of particles. We observed that particles become segregated for fluidization velocities greater than the minimum fluidization velocity of the denser particles. Adding vertical vibration to this system tended to enhance density-induced segregation. Interestingly, we found that, for sufficiently high vibration strengths, the degree of segregation decreased with vibration. These results indicate that by a judicious choice of the vibration strength and the fluidization velocity density-induced segregation can be controlled. REFERENCES W-C. Yang, Handbook of fluidization and fluid-particle systems, CRC Press, 2003. L. Sun, F. Zhao, Q. Zhang, D. Li, H. Lu, Numerical simulation of particle segregation in vibration fluidized bed, Chem. Eng. Technol., 37(12):2109-2115, 2014. Please click Additional Files below to see the full abstract

Near-infrared spectroscopy in NGC 7538

The characterisation of the stellar population toward young high-mass star-forming regions allows to constrain fundamental cluster properties like distance and age. These are essential when using high-mass clusters as probes to conduct Galactic studies. NGC 7538 is a star-forming region with an embedded stellar population only unearthed in the near-infrared. We present the first near-infrared spectro-photometric study of the candidate high-mass stellar content in NGC 7538. We obtained H and K spectra of 21 sources with both the multi-object and long-slit modes of LIRIS at the WHT, and complement these data with sub-arcsecond JHKs photometry of the region using the imaging mode of the same instrument. We find a wide variety of objects within the studied stellar population of NGC 7538. Our results discriminate between a stellar population associated to the HII region, but not contained within its extent, and several pockets of more recent star formation. We report the detection of CO bandhead emission toward several sources as well as other features indicative of a young stellar nature. We infer a spectro-photometric distance of 2.7+-0.5 kpc, an age spread in the range 0.5-2.2 Myr and a total mass ~1.7x10^3 Msun for the older population.Comment: 11 pages, 8 figures, 1 table, accepted by A&

Evaluación de calidad de agua en un sistema ribereño utilizado para riego agrícola de subsistencia

En la evaluación del impacto de la contaminación en el ambiente, existen diversas herramientas y técnicas que se aplican para conocer la calidad ambiental de los recursos naturales. El objetivo de este trabajo fue evaluar la calidad del agua en un sistema ribereño en San Luis Potosí, México asociado al impacto del uso agrícola, urbano e industrial. Fueron establecidos cinco puntos de muestreo asociado a diversos usos y descargas residuales en donde se evaluaron 28 muestras durante cuatro días de muestro. Estas fueron distribuidas a los 20, 40, 60, 80, 100 y 120 minutos del trayecto determinando con un medidor multiparámetro los sólidos disueltos totales (SDT), temperatura (T), conductividad eléctrica (CE), pH y oxígeno disuelto (OD). El resultado más destacado de las 28 muestras diarias y del total de 112 que los promedios oxígeno disuelto indican condición hipoxia que indica la desaparición de organismos y especies sensibles, concluyendo que el área ribereña requiere un constante monitoreo y diversificación de parámetros para evaluar su condición para actividades agrícolas.In the assessment of the impact of pollution on the environment, there are various tools and techniques that are applied to know the environmental quality of natural resources. The objective of this work was to evaluate water quality in a river system in San Luis Potosí, Mexico associated with the impact of agricultural, urban and industrial use. Five sampling points associated to various uses and residual discharges were established where 28 samples were evaluated during four days of sampling. The total dissolved solids (SDT), temperature (T), electrical conductivity (CE), pH and dissolved oxygen (OD) were distributed at 20, 40, 60, 80, 100 and 120 minutes of the path. The most outstanding result of the 28 daily samples and the total of 112 that dissolved oxygen averages indicate hypoxia condition indicating the disappearance of sensitive organisms and species, concluding that the riparian area requires constant monitoring and diversification of parameters to evaluate agricultural activities.Fil: Alcalá Jáuregui, J. A. Universidad Autónoma de San Luis Potosí. Facultad de AgronomíaFil: Acosta Doporto Geiler, A. Instituto Tecnológico Superior de los Ríos de Balancan (México)Fil: Rodríguez Ortiz, J.C. Universidad Autónoma de San Luis Potosí. Facultad de AgronomíaFil: Hernández Montoya, A. Universidad Autónoma de San Luis Potosí. Facultad de AgronomíaFil: Martínez Carretero, Eduardo. Consejo Nacional de Investigaciones Científicas y TécnicasFil: Filippini, Maria Flavia. Universidad Nacional de Cuyo. Facultad de Ciencias AgrariasFil: Díaz Flores, P. E. Universidad Autónoma de San Luis Potosí. Facultad de AgronomíaFil: Lara Mireles, J. L. Universidad Autónoma de San Luis Potosí. Facultad de Agronomí

Feminist Pedagogy in the STEM Research Laboratory: an Intersectional Approach

The research laboratory is a crucial and indispensable classroom for STEM education. It is where we practice science as a craft and test the ideas that awaken our curiosity, allowing us to create knowledge. It is also a space where challenges await and struggles are imminent. Thus, supporting mentees through their traineeship in a research lab requires an intersectional approach and lens to provide equitable mentorship and guidance. The concept of intersectionality, initially devised by Black feminist professor Kimberlé W. Crenshaw, can be employed to generate practices and frameworks that democratize laboratory culture and provide trainees with a space in which they shape the laboratory culture while helping them recognize their positionality. This critical commentary provides insights and experiences when incorporating feminist frameworks to sustain equitable working environments in the research lab setting, specifically in leading a research group composed predominantly of Puerto Rican women

Childhood leukemias in Mexico: towards implementing CAR-T cell therapy programs

Leukemias are the most common type of pediatric cancer around the world. Prognosis has improved during the last decades, and many patients are cured with conventional treatment as chemotherapy; however, many patients still present with a refractory disease requiring additional treatments, including hematopoietic stem cell transplantation. Immunotherapy with monoclonal antibodies or cellular therapy is a promising strategy for treating refractory or relapsed hematological malignancies. Particularly, CAR-T cells have shown clinical efficacy in clinical trials, and different products are now commercially approved by regulatory agencies in the USA and Europe. Many challenges still need to be solved to improve and optimize the potential of these therapies worldwide. Global access to cell therapy is a significant concern, and different strategies are being explored in the middle- and low-income countries. In Mexico, leukemias represent around 50% of total cancer diagnosed in pediatric patients, and the rate of relapsed or refractory disease is higher than reported in other countries, a multi-factorial problem. Although significant progress has been made during the last decades in leukemia diagnosis and treatment, making new therapies available to Mexican patients is a priority, and cell and gene therapies are on the horizon. Efforts are ongoing to make CAR-T cell therapy accessible for patients in Mexico. This article summarizes a general landscape of childhood leukemias in Mexico, and we give a perspective about the current strategies, advances, and challenges ahead to make gene and cell therapies for leukemia clinically available

BROMATOLOGICAL ANALYSIS OF ANNATTO (Bixa orellana L.) SEEDS

The objective of this study was to carry out a bromatological and physicochemical analysis of local annatto seeds and a commercial pasteObjective: to carry out a bromatological and physicochemical analysis of local annatto seeds and a commercialpaste.Materials and Methods: local annatto seeds to which a physicochemical analysis was carried out whereash, humidity (weight difference), dry matter, proteins were determined. ADF and NDF, fat, and in addition,bromatological analysis was carried out on the samples and the commercial pasta.Results: sample M3 (dark heart-shaped annatto without filaments) presented the highest values. The bixincontent was recorded with 4.09% in sample M2 (heart-shaped red annatto without filaments) and thecommercial paste was the lowest with 0.56%.Limitations and Implications of the study: the importance of performing the bromatological and physicalchemicalanalysis of annatto seeds of local genotypes determined which of the local samples and the commercialpaste are the ones that contain the greatest amount of bixin.Findings and Conclusions: Sample M3 (dark heart-shaped annatto without filaments) presented the highestvalues. The highest bixin content was found in the smooth heart-red variety and the lowest value in thecommercial pasta