Trophic Ecology during the Ontogenetic Development of the Pelagic Thresher Shark Alopias pelagicus in Baja California Sur, Mexico

The trophic ecology of the Pelagic Thresher shark (Alopias pelagicus) was evaluated based on chemical ecology using stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in the vertebrae and muscles. Individuals were caught between August 2013 and October 2019 on both the coasts of Baja California Sur, Mexico. In Bahía Tortugas, the mean vertebrae (n = 35) values were 12.72 ± 1.06‰ (δ15N) and −14.79 ± 0.61‰ (δ13C), while in muscles (n = 32) these values were 16.63 ± 0.76‰ (δ15N) and −17.18 ± 0.39‰ (δ13C). In Santa Rosalía, the mean vertebrae (n = 125) isotopic values were 14.4 ± 1.59‰ (δ15N) and −14.18 ± 0.51‰ (δ13C), while in muscles (n = 43), these values were 18.08 ± 0.96‰ (δ15N) and −16.43 ± 0.34‰ (δ13C). These results show higher δ15N values in Santa Rosalía as an effect of baseline isotopic differences between the two regions, whereas the δ13C values were lower in Bahía Tortugas, suggesting offshore ecological behavior (p 0.05), suggesting a high overlap between their isotopic niches. Therefore, Alopias pelagicus uses the same ecological niche throughout its life, and there is consistency between sexes. The mean trophic position for both tissues and regions was 4.5, which corresponds to a tertiary predator, without any differences between stages or sex. Due to their higher energetic needs, juveniles and females showed the greatest isotopic niche amplitude; thus, their ecological niche is the widest.Instituto Politécnico Nacional, Project SIP-IPN 2022057

Influence of Formate Concentration on the Rheology and Thermal Degradation of Xanthan Gum

Xanthan gum solutions have gained increasing interest for their use as environmentally friendly chemicals in the oil industry. Xanthan is compatible with most concentrate brines used for controlling formation damage and fluid loss. Particularly, formate brines reinforce the ordered structure of the biopolymer in solution, gel strength, and the specific gravity of the resulting fluid. In this paper, we studied the effect of thermal aging on the rheological behavior of xanthan solutions as a function of the concentration in potassium formate. Ionic strength below a threshold concentration does not prevent the degradation of the structure of xanthan after being submitted to aging at 165 °C. Aged solutions show an important loss of strength in their mechanical properties, lower pH, and higher content in furfural and hydroxymethylfurfural. Highly concentrated formate brines are necessary to maintain the strength of the rheological properties after exposure to high-temperature environmentsThis research was funded by the EU-FEDER Program, grant numbers P18-RT-4684 and CTQ-2017-89792-

Oil-in-Oil emulsions of stearic acid dispersed in silicone oil with enhanced energy storage capability for heat transfer fluids

Non-aqueous phase change emulsions are very unknown and promising multifunctional fluids consisting of phase change materials dispersed in carrier fluids, both being oily phases. The oil-in-oil phase change emulsions allow the possibility of using the same medium for latent heat storage and transport under more extreme pressure and temperature conditions. In this paper, stable emulsions composed of stearic acid with a melting point of 68–71 °C dispersed in silicone oil have been developed. Stearic acid-in-silicone oil emulsion samples with different phase concentrations were evaluated by analysing their thermophysical properties, viscous and viscoelastic behaviour and microstructure. Emulsion properties below the melting point of the phase change material were greatly influenced by the concentration of the disperse phase. Thus, as the temperature lowered, a well-developed three-dimensional network of stearic acid crystalline structures interconnected with each other was formed. Furthermore, emulsion physicochemical and thermal stabilities were examined and proved under several mechanical–thermal cycles, withstanding more than 100 cycles in the calorimeter. The results indicate that stearic acid-in-silicone oil emulsions are an attractive candidate for energy storage applications with a phase change enthalpy in emulsions with the 10 wt% of phase change material of 22.32 J/g.Non-aqueous phase change emulsions are very unknown and promising multifunctional fluids consisting of phase change materials dispersed in carrier fluids, both being oily phases. The oil-in-oil phase change emulsions allow the possibility of using the same medium for latent heat storage and transport under more extreme pressure and temperature conditions. In this paper, stable emulsions composed of stearic acid with a melting point of 68–71 C dispersed in silicone oil have been developed. Stearic acid-in-silicone oil emulsion samples with different phase concentrations were evaluated by analysing their thermophysical properties, viscous and viscoelastic behaviour and microstructure. Emulsion properties below the melting point of the phase change material were greatly influenced by the concentration of the disperse phase. Thus, as the temperature lowered, a well-developed three- dimensional network of stearic acid crystalline structures interconnected with each other was formed. Furthermore, emulsion physicochemical and thermal stabilities were examined and proved under several mechanical–thermal cycles, withstanding more than 100 cycles in the calorimeter. The results indicate that stearic acid-in-silicone oil emulsions are an attractive candidate for energy storage applications with a phase change enthalpy in emulsions with the 10 wt% of phase change material of 22.32 J/g

Form-stable bitumen/paraffin-wax/polymer binders for energy-efficient building applications

Novel form-stable bitumen/paraffin-wax/polymer binders were successfully manufactured to be applied as energy-efficient building materials with advanced thermal energy storage and thermoregulation features. These roofing materials are composed of bitumen (B), styrene butadiene styrene copolymer (SBS), and paraffin wax (PW) as phase change material (PCM) for thermal energy storage applications. Systems with a fixed weight ratio B/SBS = 7.33 and PW concentration ranging from 0 to 70 wt% were prepared. Then, thermal stability, microstructure, rheological properties, technological and leakproof performance tests were performed on these binders to assess the optimal compositions. After that, a comprehensive thermal energy storage characterization was conducted on the selected prototypes and, finally, the temperature regulation performance was studied by using simulated solar irradiation. All materials show excellent thermal stability no matter PW concentration used, whereas the rheological properties improve as PW content in blends increases. However, softening temperature requirements, specified by ASTM D8051, limited PW concentration to 30 wt%. Interestingly, no liquid PW leakage from bituminous matrix was found for such a concentration, which has a high heat storage capacity (ca. 60 J/g) and suitable thermal properties (e.g. thermal conductivity and specific heat capacity). As a result, material exhibits a complex solar and thermal behaviour that yields a Latent Heat Thermoregulation Index (LHTI) value greater than for other efficient energy building materials.This work is part of the project TED2021-131284B-I00 funded by MCIN/AEI/10.13039/501100011033 (Spanish Ministry of Science and Innovation) and European Union Next Generation EU/PRTR; and the Cátedra Fundación CEPSA through the project “BituFoil” of the edition 2023. Clara Delgado-Sánchez also acknowledges financial support from Junta de Andalucía through post-doctoral Grant No. DC 01228 (PAIDI 2020), co-funded by the EU Fondo Social Europeo (FSE). Funding for open access charge: Universidad de Huelva / CBUA.Departamento de Ingeniería Química, Química Física y Ciencias de los Materiale

Bio and waste-based binders with hybrid rubberized-thermoplastic characteristics for roofing

Non-bituminous binders with sustainable characteristics have been developed as potential roofing materials. A vegetable colophony rosin ester, waste cooking oil, waste crumb rubber and a blend of recycled high-density polyethylene (HDPE) and polypropylene (PP) have been used for binder formulations. Rheological, calorimetric and technological characterizations have been performed to assess the compatibility among binder components and optimal compositions. Additionally, thermal conductivity, heat capacity and solar radiation tests have been performed on selected non-bituminous and bitumen-based binders. Solar radiation experimental set-up has been simulated by Computational Fluid Dynamics (CFD) in order to get a deeper insight into heat transmission mechanisms involved. A binder formulation composed of 40 wt% maleic-modified rosin ester, 32 wt % waste oil, 20 wt% crumb rubber and 8 wt% recycled HDPE/PP blend has shown suitable mechanical properties and solar behaviour for roofing materials. The use of recycled thermoplastics and elastomers imparts material with a hybrid character, showing enhanced flexibility and softening points, respectively, at low and high inservice temperatures. Its solar behaviour is comparable to that of the modified bitumen, with a similar heat absorption from Sun (about 30 %) but lower heat storage capacity at ambient temperature.This work is co-funded by FEDER European Programme (80 %) and Junta de Andalucía (Consejería de Economía, Conocimiento, Empresas y Universidades/Agencia-IDEA) and of project TED2021-131284 B–I00 funded by MCIN/AEI/10.13039/501100011033 (Spanish Ministry of Science and Innovation) and European Union NextGenerationEU/PRTR. Clara Delgado-Sánchez also acknowledges financial support from Junta de Andalucía through post-doctoral Grant No. DC 01228 (PAIDI 2020), co-funded by the EU Fondo Social Europeo (FSE).Departamento de Ingeniería Química, Química Física y Ciencias de los Materiale

Non-bituminous binders formulated with bio-based and recycled materials for energy-efficient roofing applications

Non-bituminous binders have been designed as potential roofing materials with sustainable characteristics. To that end, three bio-based rosin esters (R), a waste cooking oil (O) and a recycled polyethylene from greenhouse agriculture (LDPEr) have been used in their formulations. A comprehensive rheological, microstructural, calorimetric, and technological characterization have been performed on binary (polymer/oil or rosin/oil) and ternary (polymer/rosin/oil) blends, allowing the compatibility among binder compounds to be studied. Additionally, thermal conductivity and solar radiation tests have been conducted on a selected non-bituminous binder and compared with a reference polymer modified bitumen. The formulation composed of 61.0% phenolic-modified rosin, 30.5% oil and 8.5% LDPEr has shown suitable mechanical properties for roofing materials, and has exhibited enhanced energy efficiency derived from its light yellowish to brownish color. Under the experimental radiant flux conditions, surface temperature of the non-bituminous binder was 8 °C lower than that of the black bitumen. Moreover, conduction heat transfer through this roofing material was about 14% lower than that conducted through a bitumen-based membrane with the same thickness. Accordingly, developed binders are expected to behave as reflective building materials aiming to reduce the heat island effects and save energy.This work is part of GreenAsphalt project (ref. 802C1800001), cofunded by FEDER European Programme (80%) and Junta de Andalucía (Consejería de Economía, Conocimiento, Empresas y Unversidades/ Agencia-IDEA), and has been also co-funded by FEDER/Junta de Andalucía-Consejería de Economía y Conocimiento/Project UHU- 1256916. Clara Delgado-S´anchez also acknowledges financial support from Junta de Andalucía through post-doctoral Grant No. DC 01228 (PAIDI 2020), co-funded by the EU Fondo Social Europeo (FSE). Funding for open access charge: Universidad de Huelva / CBUA

Rheological aspects of solid-to-liquid phase transitions in paraffin wax/bitumen blends for thermal energy storage applications

This paper correlates the evolution of the rheological and thermal properties with microstructure during the phase change of a blend of bitumen with a selected paraffin wax, having a melting point centred around 60 ◦C, for the development of bituminous based membranes for thermal energy storage applications. For this purpose, temperature sweep tests within the linear viscoelastic range, stationary state flow curves, Differential Scanning Calorimetry (DSC), polarised optical microscopy observations and solar irradiation tests were performed. The reported rheological results clearly point out a gel-like behaviour for both paraffin and paraffin/bitumen blend that is preserved almost up to the end of the phase change interval. This is consequence of the development of a network of interconnected crystals of paraffin wax which progressively disappear as temperature increases. Interestingly, a weak gel structure is kept even at low crystallinity levels since only a few junctions among structures are necessary to build a spanning network. Finally, the large degree of crystallinity of paraffin wax retained in the bitumen/paraffin wax is behind its thermoregulation ability, as was corroborated by solar irradiation tests. Therefore, results indicated the great potential of these formulations for thermal energy storage and related applications.Grant TED2021-131284B-I00 funded by MCIN/AEI/ 10.13039/501100011033 (Spain) and grant PID2020-116905RB-I00 funded by MCIN/AEI/10.13039/501100011033 (Spain) and European Union “NextGenerationEU”/PRTR. Clara Delgado and Adrián Tenorio also acknowledge financial support from Junta de Andalucía (Spain) through post-doctoral Grants DC 01228 (co-funded by the European Union Fondo Social Europeo (FSE)) and POSTDOC_21_00644, respectively, Funding for open access charge: Universidad de Huelva / CBUA and the Cátedra Fundación CEPSA.Departamento de Ingeniería Química, Química Física y Ciencias de los Materiale

Acute effect of moderate-intensity exercise on spirometric variables in broncodilated asthmatic subjects. A pilot study

Background: Exercise-Induced Bronchospasm (BIE) occurs in 70 % to 80 % of asthmatics and its occurrence is more frequent at the end of a session of physical exercise, mainly of vigorous intensity. Objective: To evaluate the acute effect of moderateintensity physical exercise on spirometric variables in asthmatic subjects. Methodology: A before-and-after type quasi-experimental design. Ten subjects were included (mean age = 23 ± 4 years), which were divided into two groups: five asthmatic subjects and five healthy subjects. Both groups performed 10 min of warm-up, 20 min of treadmill exercise at an intensity of 60 % of the Heart Rate Reserve, and a final cool-down of 5 minutes. Lung function was assessed before and 15 minutes after exercise. Results: There were statistically significant differences between groups (with asthma = 6 % vs. without asthma = -1 %, p = 0.03) in the pre-post-exercise changes of the ratio of the forced expiratory volume in one second and the forced vital capacity (FEV1/FVC). The multivariate analysis showed that post-exercise FVC in subjects with asthma was significantly lower than in subjects without asthma, after adjusting for the baseline assessment and total body mass. Conclusion: Moderate-intensity exercise on a treadmill did not shows clinically significant differences on the changes pre-post exercise of the studied spirometric variables, since the changes on FEV1 or FVC did not exceed 10 % having as reference the baseline evaluation

A Mathcad‐based educational experience to address the design of nonisothermal plug flow reactors

Mathcad is a simple-to-use and intuitive mathematical software that helps students to minimize the mathematical difficulties involved in solving engineering problems. The design of nonisothermal plug flow reactors (PFR) is a fundamental issue within the field of chemical reaction engineering; however, its teaching–learning process is hindered by students' mathematical difficulties in solving ordinary differential equations. In this paper, the software Mathcad was conveniently integrated into an educational experience through the resolution of two real case studies. In the first one, a simple liquid-phase reaction is considered in a PFR working at different operating conditions, whereas the second case evaluates a PFR taking place multiple reactions (parallel reactions) with a heat exchanger attached. The assessment of this experience, which was held into two 5-h Mathcad workshops, revealed that Mathcad made the design of non-isothermal PFR more appealing, facilitated the understanding of the design process, and brought another dimension to the way the students perform complex calculations