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Rheology and gel point of the enzymatic hydrolysis of urea in the presence of urease
R. Serrato-Millán,L. Medina-Torres,F. Calderas,B.L. España-Sánchez,M. Estevez,A.R. Hernandez-Martínez,M. Cruz-Soto,I.C. Sánchez,R. Gómez-García,I. Sánchez-Betancourt,M.C. Velasquillo-Martínez,G. Luna- 한국유변학회 2017 Korea-Australia rheology journal Vol.29 No.1
This study reports on the rheology of the gelation kinetics of raw chitosan (CTS) solutions (2% w/v) produced by enzymatic hydrolysis of urea at different urea concentrations (40, 50, 60, 80, and 100 mM) in the presence of urease at 1 U/mL. Viscoelastic parameters and pH values were evaluated during gelation process and the rheological properties of CTS hydrogels produced were monitored after 24 h at 37°C to simulate human body temperatures. pH measurements suggest that above some critical urea concentration (50 mM) the time required (tgel) to reach the critical pH gelation shows no dependence on urea concentration (tgel was ca. 70 minutes). Above 50 mM of urea concentration, CTS hydrogels exhibit an elastic modulus G' higher than the viscous modulus G'' with no frequency dependence characteristic of a gel behavior. Gelation kinetics analyzed by rheology suggest that the G' (i.e., structure) development depends on urea concentration during solution neutralization.
Seismic assessment of steel structures through a cumulative damage
R. Perera,S. Gómez,E. Alarcón 국제구조공학회 2001 Steel and Composite Structures, An International J Vol.1 No.3
In the present work a constitutive model is developed which permits the assessment of the structural performance through a criterion based on cumulative damage. For it, a damage index is defined and is evaluated through the application of the Miner’s rule in low-cycle fatigue. However, the damage index is not considered as a posteriori variable since is incorporated explicitly as an internal variable in the constitutive equations which produces a direct coupling between the damage and the structural mechanical behaviour allowing the possibility of considering as a whole different coupled phenomena. For the elaboration of this damage model, the concepts of the mechanics of continuum medium are applied on lumped dissipative models in order to obtain a coupled simplified model. As a result an elastoplastic model coupled with damage and fatigue damage is obtained.
Álvarez-Ríos Gonzalo D.,Casas Alejandro,Pérez-Volkow Lucía,Figueredo-Urbina Carmen J.,de Dios Páramo-Gómez Juan,Vallejo Mariana 한국식품연구원 2022 Journal of Ethnic Foods Vol.9 No.-
Pulque is a fermented beverage prepared with the sap of agave species, consumed since pre-Hispanic times in Mexico. In the sixteenth century, spaces called pulquerías were established for the sale and consumption of pulque. The demand for pulque became so high that there were more than 1500 pulquerías in Mexico City early twentieth century, but due to socio-cultural factors, the popularity of pulque plummeted. Currently, there are few pulquerías in Mexico City, and these are the main spaces for the consumption of this beverage in the metropolis. The pulque sold in pulquerías comes from eight localities, largely from Nanacamilpa, Tlaxcala. People working in pulquerías have deep knowledge and specific practices to keep pulque in good conditions and to prepare it in a wide spectrum of flavors by mixing the fermented beverage with fruits, vegetables or seeds. We recorded 69 types of pulque mixtures. Pulquerías allow the economic maintenance of working families in urban and rural contexts, are spaces of socialization, and identity and help the conservation of an ancient traditional beverage.
Load Rating of Highway Bridges by Proof-loading
Joan R. Casas,Juan D. Gómez 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.3
Aging and lack of maintenance are a matter of increasing concern for most bridges that are part of the road and railway systems of the European Union. Many of these bridges are very old and without documentation and as a consequence load rating by analytical tools is not possible. This paper explains how a possible way to assess their capacity is by means of a so-called “proof load test”. The work was developed as part of the Project ARCHES (Assessment and Rehabilitation of Central European Highway Structures)funded by the VI Framework Program of the European Union. A methodology of proof load testing for existing highway bridges is proposed and applied to the traffic conditions of several European Countries. The final objective is to provide guidance on the appropriate target proof load to be used based in very simple parameters of the bridge as span-length and percentage of heavy traffic.
Salvatore Rudilosso,José Ríos,Alejandro Rodríguez,Meritxell Gomis,Víctor Vera,Manuel Gómez-Choco,Arturo Renú,Núria Matos,Laura Llull,Francisco Purroy,Sergio Amaro,Mikel Terceño,Víctor Obach,Joaquim Se 대한뇌졸중학회 2021 Journal of stroke Vol.23 No.3
Background and Purpose In real-world practice, the benefit of mechanical thrombectomy (MT) is uncertain in stroke patients with very favorable or poor prognostic profiles at baseline. We studied the effectiveness of MT versus medical treatment stratifying by different baseline prognostic factors. Methods Retrospective analysis of 2,588 patients with an ischemic stroke due to large vessel occlusion nested in the population-based registry of stroke code activations in Catalonia from January 2017 to June 2019. The effect of MT on good functional outcome (modified Rankin Score ≤2) and survival at 3 months was studied using inverse probability of treatment weighting (IPTW) analysis in three pre-defined baseline prognostic groups: poor (if pre-stroke disability, age >85 years, National Institutes of Health Stroke Scale [NIHSS] >25, time from onset >6 hours, Alberta Stroke Program Early CT Score <6, proximal vertebrobasilar occlusion, supratherapeutic international normalized ratio >3), good (if NIHSS <6 or distal occlusion, in the absence of poor prognostic factors), or reference (not meeting other groups’ criteria). Results Patients receiving MT (n=1,996, 77%) were younger, had less pre-stroke disability, and received systemic thrombolysis less frequently. These differences were balanced after the IPTW stratified by prognosis. MT was associated with good functional outcome in the reference (odds ratio [OR], 2.9; 95% confidence interval [CI], 2.0 to 4.4), and especially in the poor baseline prognostic stratum (OR, 3.9; 95% CI, 2.6 to 5.9), but not in the good prognostic stratum. MT was associated with survival only in the poor prognostic stratum (OR, 2.6; 95% CI, 2.0 to 3.3). Conclusions Despite their worse overall outcomes, the impact of thrombectomy over medical management was more substantial in patients with poorer baseline prognostic factors than patients with good prognostic factors.
Verónica García-Villamar,Laura G. Hernández-Aragón,Jesús R. Chávez-Ríos,Arturo Ortega,Margarita Martínez-Gómez,Francisco Castelán 대한배뇨장애요실금학회 2018 International Neurourology Journal Vol.22 No.S2
Purpose: To evaluate the expression of glial cell line-derived neurotrophic factor (GDNF) and its receptor, GDNF family receptor alpha subunit 1 (GFRα-1) in the pelvic (middle third) vagina and, particularly, in the paravaginal ganglia of nulliparous and primiparous rabbits. Methods: Chinchilla-breed female rabbits were used. Primiparas were killed on postpartum day 3 and nulliparas upon reaching a similar age. The vaginal tracts were processed for histological analyses or frozen for Western blot assays. We measured the ganglionic area, the Abercrombie-corrected number of paravaginal neurons, the cross-sectional area of the neuronal somata, and the number of satellite glial cells (SGCs) per neuron. The relative expression of both GDNF and GFRα-1 were assessed by Western blotting, and the immunostaining was semiquantitated. Unpaired two-tailed Student t -test or Wilcoxon test was used to identify statistically significant differences (P≤0.05) between the groups. Results: Our findings demonstrated that the ganglionic area, neuronal soma size, Abercrombie-corrected number of neurons, and number of SGCs per neuron were similar in nulliparas and primiparas. The relative expression of both GDNF and GFRα- 1 was similar. Immunostaining for both GDNF and GFRα-1 was observed in several vaginal layers, and no differences were detected regarding GDNF and GFRα-1 immunostaining between the 2 groups. In the paravaginal ganglia, the expression of GDNF was increased in neurons, while that of GFRα-1 was augmented in the SGCs of primiparous rabbits. Conclusions: The present findings suggest an ongoing regenerative process related to the recovery of neuronal soma size in the paravaginal ganglia, in which GDNF and GFRα-1 could be involved in cross-talk between neurons and SGCs.
Enhanced CO2 capture by cupuassu shell-derived activated carbon with high microporous volume
Cruz Orlando F.,Campello-Gómez Ignacio,Casco Mirian E.,Serafin Jarosław,Silvestre-Albero Joaquín,Martínez-Escandell Manuel,Hotza Dachamir,Rambo Carlos R. 한국탄소학회 2023 Carbon Letters Vol.33 No.3
Here, we report the preparation of microporous-activated carbons from a Brazilian natural lignocellulosic agricultural waste, cupuassu shell, by pyrolysis at 500 ºC and KOH activation under different experimental conditions and their subsequent application as adsorbent for CO2 capture. The effect of the KOH:precursor ratio (wt/wt%) and the activation temperature on the porous texture of activated carbons have been studied. The values of specific surface area ranged from 1132 to 2486 m2/g, and the overall micropore volume ranged from 0.73 to 1.02 cm3/g. Carbons activated with 2:1 ratio of KOH and activation temperature of 700 ºC presented a CO2 adsorption at 1 bar of 7.8 and 4.4 mmol/g at 0 °C and 25 ºC, respectively. The isosteric heat of adsorption, Qst , was calculated for all samples by applying the Clausius–Clapeyron approach to CO2 adsorption isotherms at both temperatures. The values of CO2 adsorption capacities are among the highest reported in the literature, especially for activated carbons produced from biomass.
Prototype of a Computer Vision-Based CubeSat Detection System for Laser Communications
I. Medina,J. J. Hernández-Gómez,C. R. Torres-San Miguel,L. Santiago,C. Couder-Castañeda 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.3
Up to now, CubeSat nano-satellites have strong limitations in communication data rates (∼100 ∼100 kbps) and bandwidth due to the strictness of CubeSat standard. However, if they could be endowed with optical communications (data rates up to 1 Gbps in optimal state), CubeSat applications would exponentially increase. Nonetheless, laser communications face some important drawbacks as the development of a very strict and accurate tracking mechanism. This work proposes an on-board fine pointing system to locate an optical ground station beacon using an embedded system complying with the restrictive CubeSat standard. Such on-board fine pointing system works based on computer vision. The experimental prototype is implemented in Matlab/Simulink, within a Raspberry Pi 3B. The main outcome is the usage of off-the-shelf components (COTS), obtaining an efficient tracking with low power consumption in very noisy and reflective environments. The developed system proves to be fast, stable and strong. It also satisfies the strict size and power consumption restrictions of CubeSat standard.