Nonconventional Ca(OH) ₂ treatment of bamboo for the reinforcement of cement composites

This study compares the structural and morphological changes in Guadua angustifolia Kunth (GAK) fiber prepared in three different ways (chips, barkless and crushed) when non-conventional alkaline treatment is applied. Moreover, it shows the improvement of mechanical properties of cement composites reinforced with these treated fibers. The three different preparations of Guadua were treated with a saturated solution of calcium hydroxide (5%) at 125 °C and 1.25 kPa for 3 h to remove non-cellulosic compounds. Then, their chemical, morphological, and structural properties were examined. The fibers exhibiting the higher delignification rate were selected to prepare cement composite boards, whose mechanical properties were successively compared with those of composites reinforced with untreated G. angustifolia fibers. The water/cement ratios of the cement mixed with the Ca(OH)2-treated and the untreated fibers were, respectively, around 0.3 and 0.25. The flexural strength and toughness of the two composites were evaluated after 7, 28, and 90 days of curing. The calcium hydroxide treatment showed higher efficiency in removing non-cellulosic materials when performed on crushed bamboo; moreover, the mechanical properties of the composites reinforced with the treated fibers were higher than those mixed with the untreated ones. After 90 days of curing, the flexural strength increased by around 40% and the toughness became three times higher (p < 0.05). The mechanical improvement by the Ca(OH)2 treatment of G. angustifolia fibers demonstrates its potential for the fabrication of cement composites

Obtención de las propiedades del concreto celular para su aplicación en el análisis sísmico de edificios de muros de ductilidad limitada

El objeto de estudio de la presente investigación es el concreto celular, el cual viene siendo cada vez más investigado a nivel nacional. Dadas las ventajas que otorga sus propiedades térmicas y acústicas se pretende dar como alternativa al concreto convencional usado en la construcción de edificios con Muros de Ductilidad Limitada. Para el desarrollo de la siguiente investigación primero se realizará un diseño de mezclas del concreto celular que cumpla los requerimientos necesarios señalados en las normas ACI 211 y ACI 253. La obtención de los valores de las propiedades mecánicas reales del concreto se obtuvo mediante ensayos de laboratorio, estos ensayos se realizarán cumpliendo los requerimientos de las siguientes normas: NTP 339.034 Resistencia a la compresión del concreto, f´c=15.27 Mpa - ASTM C469 Módulo de elasticidad del concreto, E =16834.7 Mpa - ASTM C469M-14 Coeficiente de Poisson, v = 0.2631 -AASHTO T-336 Obtención del coeficiente de expansión térmica del concreto CTE = 9.23 µ/ºC-NTP 339.078 Resistencia a la flexión del concreto, Mr = 3.088 Mpa Luego de la obtención de los resultados de los ensayos estos se usarán como datos de entrada para hacer el análisis sísmico de un edificio con muros de ductilidad limitada con el objetivo que cumpla los requerimientos de la norma sismo resistente peruana E-030 2018 la cual indica que las derivas máximas para edificios con muros de ductilidad limitada es 0.5%Tesi

Mineral status and interrelationship in soil, forage, and blood serum of horses in the rainy and dry seasons

The feeding and nutrition of livestock becomes less of an empirical endeavor when the information necessary to scientifically balance diets is available [1]. Equine performance is influenced by genetic, nutritional, health, and management factors. Thus, optimal nutrition is essential for a foal to achieve maximal performance. Likewise, nutrition is fundamental for husbandry purposes as several reproductive problems due to nutritional deficiencies have been identified [2].The objective was to evaluate the content of P, Ca, Mg, K, Na, Cu, Fe, Zn, Se, and Mn in soil, forage, and serum of horses in several production units (PU) during rainy and dry seasons and predict their concentration in serum from their content in soil and forage. Soil and pastures were sampled in the dry (November–December) and in rainy seasons (June–July), and blood samples were collected from the jugular vein of 76 horses in both seasons at four PU. The experimental design was a completely random design within a 4 2 (PU season) factorial arrangement of treatments. Concentration of minerals in soil differed (P < .05) among PU, and contents of P, Ca, Mg, and K were low; Zn and Fe were high; and Cu and Mn were adequate. Mineral concentrations in forage differed among PU and season, and among PU within season (interaction P <.05). Contents of Ca, Mg, Na, Zn, and Cu were low; Fe was high; and P, K, Se, and Mn adequate. The mineral concentration in equine blood serum differed (P <.05) among PU and season. Overall, there were deficiencies of P, Ca, Mg, Na, Cu, and Se, but adequate amounts of K, Zn, and Fe. There are imbalances of minerals in soil and forages which effected their concentration inequine blood

Age-dependent defective TGF-beta1 signaling in patients undergoing coronary artery bypass grafting

Background: Transforming growth factor beta (TGF-beta 1) is a pleiotropic cytokine, which is deregulated in atherosclerosis; however the role of age in this process is unknown. We aimed to assess whether TGF-beta 1 signaling is affected by age. Methods: Vascular smooth muscle cells (VSMC) were obtained from patients undergoing abdominal surgery. Levels of TGF-beta 1 were measured by ELISA in sera from 169 patients undergoing coronary artery bypass grafting (CABG). The p27 expression was determined by Western blot from internal mammary arteries (IMA) obtained from CABG patients (n = 13). In VSMC from these patients undergoing abdominal surgery, secretion of TGF-beta 1 was determined by ELISA of cell-conditioned media. Results: In VSMC from aged patients we observed a lower TGF-beta 1 secretion, measured as TGF-beta 1 concentration in cell conditioned medium (p < 0.001). This effect was correlated to an age-dependent decrease of p27 expression in IMA from aged CABG patients. In a similar manner, there was an age-dependent decrease of serum TGF-beta 1 levels in CABG patients (p = 0.0195). Conclusions: VSMC from aged patients showed a higher degree of cellular senescence and it was associated to a lower TGF-beta 1 secretion and signaling.S

EXPRESIÓN ORAL Y ESCRITA

GUÍA DIDÁCTICA / PLANEACIÓN DIDÁCTICA (NMS

LITERATURA

GUÍA DIDÁCTICA / PLANEACIÓN DIDÁCTICA (NMS

Risk factors associated with mortality in severely ill COVID-19 patients: cohort study

Background: Patients diagnosed with COVID-19 who require intensive care unit (ICU) demand multidisciplinary care, which is decisive for their intervention and prognosis. The objective of this study was to identify the risk factors for mortality in critically ill COVID-19 patients in Bogota, Colombia.  Methods: This was a retrospective descriptive study (from March 2020 to February 2021) which included critically ill COVID-19 patients admitted to the ICU. Electronic medical records were reviewed, and demographic and clinical data were collected. A logistic regression model was performed. Mortality was considered as the dependent variable, and the clinical and demographic variables as explanatory factors.  Results: We included 562 patients with an overall mortality of 42%, associated comorbidities such as diabetes mellitus (51%), grade 2 obesity (75%), and age over 65 years (51%). The logistic regression model showed that patients over 65 years of age [odds ratio (OR): 3.23 (2.28 - 4.59)]; diabetes mellitus [OR: 1.68 (1.16 - 2.44)], and grade 2 obesity [OR: 3.5 (1.31 - 9.77)] were risk factors for mortality in COVID-19 patients at the ICU.  Conclusion: This study reported that age over 65 years, diabetes mellitus, and grade 2 obesity were risk factors for death in critically ill COVID-19 patients.

Mechanosensitive ACKR4 scavenges CCR7 chemokines to facilitate T cell de-adhesion and passive transport by flow in inflamed afferent lymphatics.

T cell migration via afferent lymphatics to draining lymph nodes (dLNs) depends on expression of CCR7 in T cells and CCL21 in the lymphatic vasculature. Once T cells have entered lymphatic capillaries, they slowly migrate into contracting collecting vessels. Here, lymph flow picks up, inducing T cell detachment and rapid transport to the dLNs. We find that the atypical chemokine receptor 4 (ACKR4), which binds and internalizes CCL19 and CCL21, is induced by lymph flow in endothelial cells lining lymphatic collectors, enabling them to scavenge these chemokines. In the absence of ACKR4, migration of T cells to dLNs in TPA-induced inflammation is significantly reduced. While entry into capillaries is not impaired, T cells accumulate in the ACKR4-deficient dermal collecting vessel segments. Overall, our findings identify an ACKR4-mediated mechanism by which lymphatic collectors facilitate the detachment of lymph-borne T cells in inflammation and their transition from crawling to free-flow toward the dLNs

Biofunctionalization of hydrogel-based scaffolds for vascular tissue regeneration

Congenital and acquired tissular losses due to disease or trauma are a major world health problem. Regenerative therapy aims to fix damaged tissues by directing the natural capacity of a host organism to use biofunctionalized artificial tissue scaffolds. These three-dimensional (3D) scaffolds can be customized with cells and/or bioactive molecules to induce cellular homing and angiogenesis, essential to ensure successful tissue regeneration. Hydrogels (HGs) scaffolds are networks of hydrophilic homopolymers, copolymers, and/or macromers with chemical and biological activities that enhance their cell colonization. The use of HGs in regenerative medicine has shown to be advantageous since HGs can be prepared under clinical-grade conditions and tailored to the specific needs of the replaced tissue. They can be made to emulate native extracellular matrices (ECMs) including physical, mechanical, and chemical cues and resilience properties. These customized HGs can reproduce the natural hygroscopic capacity of the original tissue which improves cellular anchoring, nutrition, and waste disposal. They can enable host molecular and cellular modification conducive to a natural cellular microenvironment, modifying the properties of the scaffold, and improving chemotaxis, cell adhesion, migration, proliferation, differentiation, and angiogenesis; HGs can be created and biofunctionalized with linked growth factors and synthetic peptides tailored to positively influence scaffold colonization and functional biocompatibility. This review aims to collect the most relevant information regarding biofunctionalization of HGs used for vascular tissue regeneration, their biological effects, and their clinical implications. While most biofunctionalized HGs are still under investigation, some of them have been studied in vitro, ex vivo, and in vivo with promising results. In this regard, in vivo studies have shown that biofunctionalized scaffolds with peptides such as chitosan hydrogel with LL-37 promotes angiogenesis and healing of pressure ulcers. Also, the GHK tripeptide is widely used in trials focused on guided tissue remodeling