Estudio de la transferencia de energía, masa y cantidad de movimiento en sistemas fluido-medio poroso

En el Capítulo 1, se presenta una revisión bibliográfica de los diversos temas alrededor de este trabajo, considerando: flujo en cavidades, flujo en medios porosos, convección natural en sistemas con una región, en sistemas con dos regiones y flujo tridimensional. También se revisan trabajos enfocados al estudio de difusión doble y acoplamiento de ecuaciones en ambas regiones. En el Capítulo 2, se establece el sistema físico y las simplificaciones impuestas para el análisis de la convección natural considerando un sistema en tres dimensiones; posteriormente se plantean las ecuaciones de transporte de energía, masa y cantidad de movimiento utilizadas para establecer dos modelos que consideran el transporte en cada una de las regiones. El primer modelo utiliza la ecuación de Darcy con la corrección de Brinkman, mientras que el segundo considera solamente la ecuación de Darcy para la transferencia de cantidad de movimiento en la región porosa, ocasionando que para la condición interregional se requiera la condición semi-empírica de Beavers y Joseph. Al final, se presentan en forma de resumen las ecuaciones que conforman cada uno de los dos modelos tridimensionales. En el Capítulo 3, se presenta el esquema para la solución numérica de las ecuaciones diferenciales parciales (EDP) que conforman los modelos; esto incluye la discretización de las EDP y la descripción del esquema numérico. En el Capítulo 4, se presentan las pruebas realizadas con el modelo computacional, ellas incluyen el análisis del efecto sobre la convección natural de los grupos adimensionales de Rayleigh (Ra) , Darcy (Da) y Lewis (Le). En el Capítulo 5, se presentan las conclusiones y perspectivas relacionadas al estudio presentado en los capítulos 3 y 4. El desarrollo de las condiciones de salto para la transferencia de masa y las ecuaciones promedio utilizadas se presenta en los Apéndices A y B respectivamente, en el Apéndice C se reporta el desarrollo del modelo bidimensional para el proceso de convección natural ocasionada por gradientes simultáneos de masa y temperatura en una cavidad con un fluido y un medio poroso en la parte inferior, finalmente, en el Apéndice D se muestran las formas discretizadas en diferencias finitas para las derivadas involucradas en el modelo computacional. Como aportaciones importantes del trabajo se tienen: • El desarrollo de un modelo que considera los efectos tridimensionales en la formulación vorticidad-vector potencial para el modelado de flujo convectivo en cavidades fluido-medio poroso, considerando la ley de Darcy o la corrección de Brinkman para representar el flujo en el medio poroso. • Los resultados para la formulación tridimensional de los efectos de los números de Rayleigh, Prandtl y Lewis sobre el fenómeno de convección natural. Estos resultados se comparan con los obtenidos mediante un modelo que considera sólo efectos bidimensionales. • El análisis de la ecuación de transferencia de masa (considerando difusión y adsorción) en la frontera entre un fluido homogéneo y un medio poroso, partiendo de las ecuaciones usualmente utilizadas. El desarrollo ha impuesto la condición de continuidad en la frontera para la concentración del soluto y se derivó una condición de salto para el flux que asegura el cumplimiento de la ecuación generalizada para el transporte de masa.El transporte convectivo provocado por gradientes de temperatura y/o concentración frecuentemente se encuentra en problemas de la ingeniería química. En particular, la situación es importante cuando este tipo de transporte se presenta en cavidades, sean cerradas o abiertas. La mayor parte de los estudios de convección natural reportados son para sistemas de una fase o un medio multifásico homogéneo. Sin embargo, muchos de los problemas en ingeniería química se refieren al intercambio de masa, energía y cantidad de movimiento entre un fluido (región I) y un medio poroso (región II). La complejidad de los modelos para este sistema aumenta, debido a que es necesario considerar las ecuaciones de transporte en cada región y las condiciones de frontera que las acoplan. Al respecto, la mayoría de los estudios realizados previamente se refieren a sistemas en los que existe sólo transporte bidimensional. Así, como la mayor parte de los estudios encontrados en la literatura se limitan a sistemas de una sola fase, hay también pocos estudios que se refieren a la validez de las condiciones de frontera que se han usado. De esta manera el desarrollo de modelos para el transporte entre un medio poroso y un fluido, en términos de ecuaciones diferenciales y condiciones de frontera, no es trivial. Motivado en lo anterior, el presente trabajo tiene como objetivo el desarrollo, solución y pruebas numéricas de dos modelos para el proceso de convección natural en una cavidad ocupada parcialmente por un medio poroso en términos de ecuaciones de medio efectivo. En el análisis numérico se imponen gradientes de temperatura y concentración para analizar el efecto sobre los coeficientes de transferencia de los dos modelos mencionados y de la naturaleza bidimensional o tridimensional del transporte. Los objetivos específicos del presente trabajo son: 1. El estudio del fenómeno de convección natural tridimensional en cavidades fluido-medio poroso. 2. El desarrollo de un modelo de difusión doble con transporte bidimensional, y 3. El desarrollo de la condición de salto en la interregión fluido-medio poroso para transferencia de masa. La presentación del trabajo se estructura en cinco capítulos y tres apéndices. A continuación se da una breve descripción de cada uno de ellos

CFD Analysis of Bed Textural Characteristics on TBR Behavior: Kinetics, Scaling-up, Multiscale Analysis and Wall Effects

A simulation of a trickle bed reactor aided by computational fluid dynamics was implemented. With a Eulerian approach, geometrical characteristics were explicitly considered and two simultaneous heterogeneous reactions were included, hydrodesulphurization (HDS) and hydrodenitrogenation (HDN). This was performed in order to achieve the following: (1) attain further insight into a proper scaling‐up procedure to be able to obtain the same hydrodynamics and kinetics behavior in two reactors of different length and diameter scales; (2) develop a multiscale analysis regarding the communication of information between scales through the construction of a porous microstructure model from which the geometrical information of the microscale is captured by the effective transport coefficients (which affect the overall reactor behavior); (3) investigate the effect of operation conditions variations on hydrodynamics and kinetics; (4) and assess the deviations and further differences observed from average to punctual conversion values and the assumptions from kinetic literature models through a preliminary multiscale analysis. The CFD results were validated against experimental pressure drops data as well as HDS and HDN conversions theoretical data. An excellent agreement was found. The model produces a significant improvement in hydrodynamic parameters prediction, achieving 5 times better accuracy in predicting pressure drops and 50% improvement in holdup prediction. The fully coupled model predicts HDS conversion with 96% accuracy and HDN conversion with 94% accuracy. Results suggest that the best way to obtain similar kinetic and hydrodynamic behavior in TBRs with different length and diameter length scales is by equaling the liquid holdup (εγ) or the mass velocities (L‐G)

1,10a-Dihydro-1-aza-10a-boraphenanthrene and 6a,7-Dihydro-7-aza-6a-boratetraphene: Two New Fluorescent BN-PAHs

Previously unknown 1,10a-dihydro-1-aza-10a-boraphenanthreneand 6a,7-dihydro-7-aza-6a-boratetraphene have been efficiently synthesized.Bromination of these BN-PAHs proceeds with complete regioselectivity, resultingin the formation of different substituted derivatives via cross-coupling reactions.These compounds exhibit rather highfluorescence quantum yields (up to?F=0.80)Ministerio de Ciencia e InnovaciónUniversity of AlcaláInstituto de Salud Carlos II

Algunas noticias y novedades del género Genista L. en el SW de Europa

Some news of the genus Genista L. in the Southwest of Europe. Two new hybrids are described in the genus Genista L. (Fabaceae): G. × prestameroi (G. scorpius subsp. scorpius × G. teretifolia Willk.) and G. × aseginolazae (G. carpetana × G. hystrix). Also the known distribution area of G. germanica L. is enlarged in the south west of Europe and it shows a list of the hybrids of this genus known in the Iberian Peninsul

Prevalence, Clinical and Demographic Characteristics of Helicobacter pylori in Patients Undergoing Esophagogastroduodenoscopy in Specialized Health Centers in Two Departments of the Colombian Coffee Growing Axis

Helicobacter pylori is a Gram-negative, microaerophilic bacterium with the ability to survive in extreme acid environments, with pH below 4.0. It is estimated that more than half of the world’s population is infected with this bacterium. Objective: To determine the prevalence, clinical and demographic characteristics of Helicobacter pylori infection in patients undergoing esophagogastroduodenoscopy in two specialized centers of the Coffee Growing Axis in Pereira and Manizales from February to October 2018. Method: Cross-sectional descriptive observational study in which the proportion of positivity to Helicobacter pylori in a period of time was determined. Results: The study included 94 patients; the prevalence of positivity to Helicobacter pylori was 86.1% (81/94), 56 (59.5%) of which were diagnosed by culture and 52 (55.3%) by histology. In the histological study, of the 24 (25.5%) subjects who presented precursor lesions of malignancy, 9 (9.5%) were positive for Helicobacter pylori, while in the 70 subjects (74.5%) without precursor lesions of malignancy, 43 (45.7%) were positive. The significant variables for Helicobacter pylori infection were: Histological response for precursor lesions of malignancy: OR of 0.3808 (95% CI: 0.1408-0.9907) p=0.04 and epigastric pain: OR 0.09489 (95% CI: 0.01928-0.3637) p=0.001. Conclusion: The frequency of Helicobacter pylori infection in the Departments of Risaralda and Caldas is high, and does not discriminate against gender, age, race or origin of the study subjects; Epigastric pain continues to be the most relevant symptom in the diagnosis of Helicobacter pylori infection and the combination of diagnostic tests improves the diagnosis of Helicobacter pylori infection

Prevalence, Clinical and Demographic Characteristics of Helicobacter pylori in Patients Undergoing Esophagogastroduodenoscopy in Specialized Health Centers in Two Departments of the Colombian Coffee Growing Axis

Helicobacter pylori is a Gram-negative, microaerophilic bacterium with the ability to survive in extreme acid environments, with pH below 4.0. It is estimated that more than half of the world’s population is infected with this bacterium. Objective: To determine the prevalence, clinical and demographic characteristics of Helicobacter pylori infection in patients undergoing esophagogastroduodenoscopy in two specialized centers of the Coffee Growing Axis in Pereira and Manizales from February to October 2018. Method: Cross-sectional descriptive observational study in which the proportion of positivity to Helicobacter pylori in a period of time was determined. Results: The study included 94 patients; the prevalence of positivity to Helicobacter pylori was 86.1% (81/94), 56 (59.5%) of which were diagnosed by culture and 52 (55.3%) by histology. In the histological study, of the 24 (25.5%) subjects who presented precursor lesions of malignancy, 9 (9.5%) were positive for Helicobacter pylori, while in the 70 subjects (74.5%) without precursor lesions of malignancy, 43 (45.7%) were positive. The significant variables for Helicobacter pylori infection were: Histological response for precursor lesions of malignancy: OR of 0.3808 (95% CI: 0.1408-0.9907) p=0.04 and epigastric pain: OR 0.09489 (95% CI: 0.01928-0.3637) p=0.001. Conclusion: The frequency of Helicobacter pylori infection in the Departments of Risaralda and Caldas is high, and does not discriminate against gender, age, race or origin of the study subjects; Epigastric pain continues to be the most relevant symptom in the diagnosis of Helicobacter pylori infection and the combination of diagnostic tests improves the diagnosis of Helicobacter pylori infection

Frequency and risk factors of intestinal parasites in pet dogs from Mexicali, Mexico

Parasitic intestinal infections in dogs represent a problem for human health, because a wide variety of these parasites have zoonotic potential. Therefore, proximity to pets puts us at risk. The objective of this study was to determine the frequency and risk factors (age, sex, size, breed, presence of ectoparasites and gastrointestinal disorders) of intestinal parasites in the feces of dogs attending a Veterinary Hospital in the City of Mexicali, Baja California, Mexico. A total of 148 fecal samples were collected from canine patients and analyzed for parasite identification and parasite load. A 12.2% (18/148) of the samples were positive to parasitic intestinal infections. The frequency of specific infections was an 8.1% of Cryptosporidium sp., followed by a 2.7% of Cystoisospora sp., and 1.4% of Toxascaris leonina. A statistical significance was identified between the presence of intestinal parasites and mongrel breed. The predominance of protozoa shows the importance of diagnosis prior to treatment with anthelminthic drugs, since preventive antiparasitic protocols are commonly used, although these particular parasites are out of the spectrum of those drugs. Cryptosporidium spp. have zoonotic potential, particularly in immunocompromised patients, and there are few or no treatment options

Plasma engineering of microstructured piezo – Triboelectric hybrid nanogenerators for wide bandwidth vibration energy harvesting

We introduce herein the advanced application of low-pressure plasma procedures for the development of piezo and triboelectric mode I hybrid nanogenerators. Thus, plasma assisted deposition and functionalization methods are presented as key enabling technologies for the nanoscale design of ZnO polycrystalline shells, the formation of conducting metallic cores in core@shell nanowires, and for the solventless surface modification of polymeric coatings and matrixes. We show how the perfluorinated chains grafting of polydimethylsiloxane (PDMS) provides a reliable approach to increase the hydrophobicity and surface charges at the same time that keeping the PDMS mechanical properties. In this way, we produce efficient Ag/ZnO convoluted piezoelectric nanogenerators supported on flexible substrates and embedded in PDMS compatible with a contact–separation triboelectric architecture. Factors like crystalline texture, ZnO thickness, nanowires aspect ratio, and surface chemical modification of the PDMS are explored to optimize the power output of the nanogenerators aimed for harvesting from low-frequency vibrations. Just by manual triggering, the hybrid device can charge a capacitor to switch on an array of color LEDs. Outstandingly, this simple three-layer architecture allows for harvesting vibration energy in a wide bandwidth, thus, we show the performance characteristics for frequencies between 1 Hz and 50 Hz and demonstrate the successful activation of the system up to ca. 800 Hz.EMERGIA Junta de Andalucía programUniversity of Seville the VI PPIT-USICMS and the CITIUS from the University of Sevill

Ampicillin Plus Ceftriaxone Combined Therapy for Enterococcus faecalis Infective Endocarditis in OPAT

Cardiovascular Infectious Study Group of the Andalusian Society of Infectious Diseases.Ampicillin plus ceftriaxone (AC) is a well-recognized inpatient regimen for Enterococcus faecalis infective endocarditis (IE). In this regimen, ceftriaxone is usually administered 2 g every 2 h (AC12). The administration of AC in outpatient parenteral antibiotic treatment (OPAT) programs is challenging because multiple daily doses are required. AC regimens useful for OPAT programs include once-daily high-dose administration of ceftriaxone (AC24) or AC co-diluted and jointly administered in bolus every 4 h (ACjoined). In this retrospective analysis of prospectively collected cases, we aimed to assess the clinical effectivity and safety of three AC regimens for the treatment of E. faecalis IE. Fifty-nine patients were treated with AC combinations (AC12 n = 32, AC24 n = 17, and ACjoined n = 10). Six relapses occurred in the whole cohort: five (29.4%) treated with AC24 regimen and one (10.0%) with ACjoined. Patients were cured in 30 (93.3%), 16 (94.1%), and eight (80.0%) cases in the AC12, AC24 and ACjoined groups, respectively. Unplanned readmission occurred in eight (25.0%), six (35.3%), and two (20.0%) patients in the AC12, AC24 and ACjoined groups, respectively. The outcome of patients with E. faecalis IE treated with AC in OPAT programs relies on an optimization of the delivery of the combination. AC24 exhibit an unexpected rate of failures, however, ACjoined might be an effective alternative which clinical results should corroborate in further studies.The authors received no financial support for the research, authorship, and/or publication of this article. GVA was supported by the Instituto de Salud Carlos III, cofinanced by the European Development Regional Fund (“A way to achieve Europe”), Subprograma Miguel Servet (grant CP19/00159). HHL was supported by the Instituto de Salud Carlos III, Subprograma Rio Hortega (grant CM19/00152)