Repositorio DSpace :: Examinando por Autor "Elsevier"

Examinando por Autor "Elsevier"

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Analysis of the tooth-root stress of external spur gears with high effective contact ratio
(Elsevier, 2024-11-15) Pedrero Moya, José Ignacio; Sánchez Sánchez, Miryam Beatriz; Pleguezuelos González, Miguel; Fuentes Aznar, Alfonso; Elsevier
For spur gears with contact ratio close to 2, the extension of the contact interval resulting from loaded tooth deflections and local contact deformations may result in an effective contact ratio above 2. In these cases, the load is transmitted by at least two tooth-pairs, the maximum load and tooth-root stress decrease, and therefore the calculation methods of the gear rating Standards ISO and AGMA provide very conservative results. In this work, two models are applied to the calculation of the tooth-root stress of load-induced high contact ratio external gears: (i) an analytic model of load sharing, based on the minimum energy method, and (ii) a finite element model, which validates the results obtained from the previous model. Obtained values of the stress are compared with those provided by ISO and AGMA rating methods, which do not account for the stress reduction due to the higher contact ratio. A new modification coefficient is proposed to correct these conservative values, which allows the AGMA and ISO geometry factors to remain as no load-dependent factors and keep their actual calculation methods and significance.
Analytical model of meshing stiffness, load sharing, and transmission error for internal spur gears with profile modification
(Elsevier, 2024-07) Pedrero Moya, José Ignacio; Sánchez Sánchez, Miryam Beatriz; Pleguezuelos González, Miguel; Elsevier
The influence of the teeth geometry on the load distribution, transmission error, and meshing stiffness of internal spur gears is very similar to that of external gears. Therefore, the formulation of the models for strength and dynamic calculations for internal and external gears is also similar. However, the internal gears have usually greater values of the contact ratio, frequently above 1.8, even 1.9. In these cases, the lengthening of the contact interval due to the elastic deflections of the teeth may result in an effective contact ratio greater than 2, with the subsequent changes in the load sharing and transmission error. These changes are not properly described by the theoretical models for high contact ratio spur gears. In this paper, a model of load sharing, quasi-static transmission error, and time-varying meshing stiffness for internal spur gears with profile modification is resented, which has been applied to low contact ratio internal gears which, due to the transmitted load, become high contact ratio internal gears. The influence of the variations of the transmitted load on the load capacity is also studied.
Combined effects of benzophenone-3 and temperature on gene expression and enzymatic activity in the aquatic larvae Chironomus riparius
(Elsevier, 2020) Muñiz González, Ana Belén; Martínez Guitarte, José Luis; Elsevier; https://orcid.org/0000-0002-7722-864X
Climate change and pollution are two of the main environmental problems living organisms currently face. Temperature canmodify a toxicant's effects and the organism's response to it. Globalwarming is expected to increase the temperature of freshwater ecosystems. In thiswork,we analyzed the effect of a mild temperature increase on the acute response of the aquatic larvae Chironomus riparius to the ultraviolet filter benzophenone-3 (BP3). This substance is commonly used in sunscreens and other commercial products and can reach the environment in different ways.We exposed larvae to BP3 at 18.5 or 23 °C for 8 or 24 h and analyzed the acute response at the molecular level. By quantitative real-time polymerase chain reaction (q-PCR), we studied altered messenger RNA (mRNA) levels of genes related to the endocrine system (EcR, InR and Met), detoxification mechanisms (Cyp4d2, Cyp6b7, GST d6, GST o1 and MRP-1) and stress response (Hsp22, Hsp27, Hsp70, HYOU and Gp93). Moreover, enzyme activity was evaluated, with a focus on glutathione-S-transferase (GST), phenoloxidase (PO) and acetylcholinesterase (AChE). Results showed that temperature affected the acute response of this organism by modifying the expression of EcR, Cyp6b7, GST d6, GST o1, MRP-1, Hsp22, Hsp27 and Hsp70 genes. These results suggest that even mild temperature change can affect the response of this organism to BP3 influencing short-term progress of the population. Although longer exposures are required to determine the ability of C. riparius to manage the pollutants in this novel environmental conditions, in order to know the possible mechanisms of detoxification or adaptation that may develop. This research represents a first step in the analysis of multi-stress
Complete multicomponent versus mixture-averaged calculations of a laminar H2/N2 diffusion flame including heattransfer at the burner and Soret effects
(Elsevier, 2025-01-09) Arias Zugasti, Manuel; Naud, Bertrand; Cuoci, Alberto; Elsevier; https://orcid.org/0000-0002-1882-0299
The implementation of full multicomponent treatment of diffusion fluxes in the CFD solver for laminar reacting flows with detailed kinetic mechanisms laminarSMOKE++ is presented. The optimised 1+𝑀 multicomponent formulation (including Fick diffusion and Soret effects) derived from the Kinetic Theory of Gases, with a similar computational cost as mixture-averaged, is considered. Results are presented for a H2/N2 laminar coflow diffusion flame, where either heat transfer at the burner wall is included, either the wall is considered adiabatic. We observe that full multicomponent and mixture-averaged results are very similar when Soret effects are neglected. However, differences are observed when including thermodiffusion. In particular with heat transfer at the wall, large differences are observed whether thermodiffusion is neglected or included. In this case, the mixture-averaged approximation used for the thermal diffusion coefficients leads to significant differences in the results compared to the full multicomponent 1+𝑀 formulation.
An event-based adaptation of the relay feedback experiment for frequency response identification of stable processes
(Elsevier, 2023-04-13) Sánchez Moreno, José; Torre Cubillo, Luis de la; Chacón Sombría, Jesús; Dormido Canto, Sebastián; Elsevier; https://orcid.org/0000-0003-0898-3462
An event-based modification of the classical relay feedback experiment without the inclusion of additional elements (integrator, time delay, . . . ) for identification of the spectrum of stable processes between zero and the phase cross-over frequency is presented. By inserting an event-based sampler in the control loop, the natural behaviour of a classical relay is simulated and the system is forced to work in two modes. The event-based sampler activates the first mode by sending control actions to the process every time the error signal crosses zero; this mode is to discover the approximated value of the cross-over frequency ω180◦ . During the second mode, the event-based sampler sends samples to the process simulating that the error signal crosses zero at ω180◦ /N where N is the number of points to identify in the range 0 ≤ ω ≤ ω180◦ . One advantage of this procedure is that the logic used in an already existing relay feedback experiment to fit a transfer function model or tune a controller could be maintained just replacing the relay block by the event-based sampler block presented in the paper. Simulations and experiments with different processes and in presence of noise demonstrate the effectivity of the procedure.
Ibuprofen as an emerging pollutant on non-target aquatic invertebrates: Effects on Chironomus riparius
(Elsevier, 2020-11-04) Muñiz González, Ana Belén; Elsevier
The concern about pharmaceuticals has been increased over the last decade due to their burgeoning consumption. Ibuprofen has an extensive presence in surface water with risks for the aquatic biota. This study focuses on the effects of ibuprofen at environmental concentrations on the survival, transcriptional level, and enzymatic activity for 24, 96 h on Chironomus riparius. Ibuprofen developed a substantial effect on survival by all the conditions. mRNA levels of EcR, Dronc, and Met (endocrine system), hsp70, hsp24, and hsp27 (stress response), and Proph and Def (immune system) were modified, joined to increased GST and PO activity. The results confirmed alterations on the development of C. riparius, as well as two essential mechanisms, involved in protection against external toxicological challenge. Ibuprofen poses an incipient risk to C. riparius and could at an organismal level by compromising their survival, development, and ability to respond to adverse conditions on the future populations.
Influence of profile modification on the transmission error of spur gears under surface wear
(Elsevier, 2024-01) Sánchez Sánchez, Miryam Beatriz; Pleguezuelos González, Miguel; Pedrero Moya, José Ignacio; Elsevier
The load distribution, transmission error, and time-varying meshing stiffness of spur gears are all influenced by the teeth dimensions and profiles shape. Any modification on the teeth geometry, as a profile relief frequently used to avoid the mesh-in impact, will affect all these parameters and the entire dynamic behavior of the gearset. In addition, due to the friction between contacting surfaces, wear arises at the teeth flanks. This causes the shape of the meshing profiles to change, which will affect the load distribution and the transmission error for the subsequent meshing cycles. And this new load distribution causes a surfaces wear different form that of the previous meshing cycle. Consequently, the wear depth increase is different at any contact point —because the load and sliding velocity are different— and at any meshing cycle as well —because the load distribution changes with the accumulated wear—. And all the above is also influenced by the profile modification the teeth were manufactured with. In this paper, a simple, analytic model of meshing stiffness, load sharing, and transmission error for spur gears with profile modifications including the influence of surfaces wear is presented. The evolution of the transmission error with the number of wear cycles is studied, and the optimal profile modification for minimizing the dynamic load induced by the transmission error is investigated.
Milk fat globule membrane-enriched milk improves episodic memory: A randomized, parallel, double-blind, placebo-controlled trial in older adults
(Elsevier, 2023-12) V. Calvo, María; Loria Kohen , Viviana; Díaz Mardomingo, María del Carmen; García Herranz, Sara; Baliyan, Shishir; Carneiro , João Tomé; Colmenarejo, Gonzalo; Visioli, Francesco; Venero Núñez, César; Fontecha, Javier; Elsevier; https://orcid.org/0000-0002-6785-7661; https://orcid.org/0000-0001-8686-3306; https://orcid.org/0000-0002-3597-9234; https://orcid.org/0000-0002-8249-4547; https://orcid.org/0000-0001-5719-2304
Cognitive decline is one of the most important consequences of aging and pharmacological therapies had been largely unsuccessful. Other strategies include the use of functional foods to reduce the burden of cognitive decline. The MFGM is an important source of polar lipids and glycoproteins that decline in the aging brain. We have developed a milk drink fortified with MFGM (MFGM-M) as a dietary supplement and studied it in a randomized clinical pilot study. Forty-four > 65-year-old healthy or mildly cognitively impaired subjects received MFGM-M or control milk (CM) for 14 weeks, during which they underwent a battery of cognitive tests. Lipidomic analyzes were also performed. The female participants showed improvement in episodic memory, the ability to recall events in our lives. It is conceivable that any intervention should be started before clinical symptoms manifest, as a preventive measure against cognitive decline. Future long-term studies may shed further light on this point
New insights about the toxicity of 2,4-D: Gene expression analysis reveals modulation on several subcellular responses in Chironomus riparius
(Elsevier, 2024-09) da Silva Pinto, Thandy Junio; Martínez Guitarte, José Luis; Amaral Dias, Mariana; Montagner, Cassiana Carolina; Gaeta Espindola, Evaldo Luiz; Muñiz González, Ana Belén; Elsevier
Herbicides are the main class of pesticides applied in crops and are capable of polluting the surrounding freshwater system; thus, understanding their impact on non-target species, whose mechanism of action is not described, helps to elucidate the real risks of these pollutants to the environment. 2,4-dichlorophenoxyacetic acid (2,4-D) is frequently detected in water and, due to its persistence, poses a risk to wildlife. In this way, the present work aimed to describe the implication of exposure to concentrations of 2,4-D already reported in aquatic environments in several physiological mechanisms of C. riparius at molecular and biochemical levels. To achieve this, bioassays were conducted with fourth instar larvae exposed to three concentrations of 2,4-D (0.1, 1.0, and 7.5 μg L 1). Larvae were collected after 24 and 96 h of exposure, and the expression of 42 genes, related to six subcellular mechanisms, was assessed by Real-Time PCR (RT-PCR). Besides, the activity of the enzymes catalase (CAT), glutathione S-transferase (GST), and acetylcholinesterase (AChE) was determined. The main metabolic route altered after exposure to 2,4-D was the endocrine system (mainly related to 20-hydroxyecdysone and juvenile hormone), confirming its endocrine disruptor potential. Four of the eleven stress response genes studied were down-regulated, and later exposure modulated DNA-repair genes suggesting genotoxic capacity. Moreover, only one gene from each detoxification phase was modulated at short exposure to 1.0 μg L 1. The molecular responses were not dose-dependent, and some early responses were not preserved after 96 h, indicating a transient response to the herbicide. Exposure to 2,4-D did not alter the activity of CAT, GST, and AChE enzymes. The responses described in this study reveal new mechanistic pathways of toxicity for 2,4-D in non-target organisms and highlight potential ecological consequences for chironomids in aquatic systems at the edges of agricultural fields.
Simulation and validation of the transmission error, meshing stiffness, and load sharing of planetary spur gear transmissions
(Elsevier, 2024-11-15) Pedrero Moya, José Ignacio; Sánchez Espiga, Javier; Sánchez Sánchez, Miryam Beatriz; Pleguezuelos González, Miguel; Fernández del Rincón, Alfonso; Viadero Rueda, Fernando; Elsevier
Although the load sharing between planets of sequentially phased planetary gear transmissions has been studied in the past, the required solving techniques based on the Finite Element Method result in long time consuming and high computational cost. This limits the possibilities of undertaking extensive studies that take into consideration a high number of cases allowing optimal solutions to be sought or general conclusions drawn. In addition, the determination of the curves of transmission error, time-varying mesh stiffness, and load sharing among tooth pairs in simultaneous contact are also complicated. In this work an analytical model has been developed for the simulation of the time-varying mesh stiffness, quasi-static transmission error, and load sharing ratio between planets and tooth pairs of planetary spur gear transmissions. It is based on similar models for external and internal spur gears previously developed and has been validated by comparison with a hybrid model based on the Finite Element Method and theoreticexperimental correlation.
Systemic administration of a fibroblast growth factor receptor 1 agonist rescues the cognitive deficit in aged socially isolated rats
(Elsevier, 2019-03-29) Pereda Pérez, Inmaculada; Valencia Jiménez, Azucena; Baliyan, Shishir; Núñez, Ángel; Sanz García, Ancor; Rodríguez Fernández, Raquel; Esteban, José Antonio; Venero Núñez, César; Zamora Crespo, Berta; Elsevier; https://orcid.org/0000-0002-8013-4812; https://orcid.org/0000-0002-5024-5108
Social isolation predominantly occurs in elderly people and it is strongly associated with cognitive decline. However, the mechanisms that produce isolation-related cognitive dysfunction during aging remain unclear. Here, we evaluated the cognitive, electrophysiological, and morphological effects of short- (4 weeks) and long-term (12 weeks) social isolation in aged male Wistar rats. Long-term but not short-term social isolation increased the plasma corticosterone levels and impaired spatial memory in the Morris water maze. Moreover, isolated animals displayed dampened hippocampal long-term potentiation in vivo, both in the dentate gyrus (DG) and CA1, as well as a specific reduction in the volume of the stratum oriens and spine density in CA1. Interestingly, social isolation induced a transient increase in hippocampal basic fibroblast growth factor (FGF2), whereas fibroblast growth factor receptor 1 (FGFR1) levels only increased after long-term isolation. Importantly, subchronic systemic administration of FGL, a synthetic peptide that activates FGFR1, rescued spatial memory in long-term isolated rats. These findings provide new insights into the neurobiological mechanisms underlying the detrimental effects on memory of chronic social isolation in the aged.
Towards a comprehensive methodology for ecotoxicological assessment: Prioritizing plant protection products for mixture testing in edge-of-field surface waterbodies
(Elsevier, 2024-11-06) Abrantes, Nelson; Pereira, Joana Luísa; Muñiz González, Ana Belén; Campos, Isabel; Navarro, Irene; de la Torre, Adrián; Martínez, María Ángeles; Osman, Rima; Jurshid, Chrow Ahmed; Harkes, Paula; Lwanga, Esperanza Huerta; Alcón, Francisco; Contreras, Josefa; Baldi, Isabelle; Oficina, Mathilde; Alaoui, Abdallah; Cristo, Florian; Mandrioli, Daniele; Sgargi, Daria; Paskovic, Igor; Policía Pasković, Marija; Glavan, Matjaž; Hofman, Jakub; Norgaard, Trine; Aparicio, Virginia; Silva, Vera; Elsevier; https://orcid.org/0000-0003-0241-2896; https://orcid.org/0000-0001-7975-8954; https://orcid.org/0000-0002-2942-964X; https://orcid.org/0000-0003-0360-7812; https://orcid.org/0000-0002-3927-3183; https://orcid.org/0000-0002-8280-1199; https://orcid.org/0000-0003-3347-9698; https://orcid.org/0000-0003-3227-6805; https://orcid.org/0000-0003-0738-2673; https://orcid.org/0000-0003-0473-1612; https://orcid.org/0000-0001-6156-6516; https://orcid.org/0000-0003-2153-7213; https://orcid.org/0000-0001-8139-1354; https://orcid.org/0000-0002-9511-6588
Pesticide applications in agriculture result in complex mixtures of Plant Protection Products (PPPs) in the environment. The ecotoxicological effects of these mixtures can occur at concentrations considered safe for individual chemicals, indicating potential risks underestimated by current regulatory assessments focused on individual active ingredients. To address this challenge, our study introduces a methodology for identifying priority PPPs for formulating mixtures, enabling further ecotoxicological testing in water and sediment compartments of edge-of-field surface water bodies, targeting pelagic and benthic organisms. This methodology was primarily based on the actual quantification of PPPs present in these compartments from selected case study sites (CSSs) in Europe and Argentina (11 and 4 for water and sediments, respectively). A conceptual framework was developed that discriminates and selects concerning PPPs based on their individual risk quotient and frequency of occurrence in each CSS, drawing upon two EU regulatory risk assessment approaches, i.e., the general approach under REACH for any environmental contaminant of concern– the European Chemicals Agency (ECHA) approach; and that specifically focusing on PPPs– the European Food Safety Authority (EFSA) approach. Irrespective of whether the focus is on water or sediments, the study revealed disparities in PPP rankings depending on the approach used to identify PPPs of concern, with the ECHA approach being more conservative than the EFSA approach. Despite this, the EFSA approach follows a more standardized assessment factor definition strategy, potentially allowing avoidance of risk overestimation, as well as resulting in a more balanced representation of different PPP classes for subsequent mixtures testing. Overall, the methodological development reported herein, along with the inconsistencies found when comparing different regulatory approaches to assess the risk of environmental contaminants, highlight the need for further discussion on the most appropriate directions towards the standardization of the regulatory risk assessment of PPP mixtures.
Unveiling complex responses at the molecular level: Transcriptional alterations by mixtures of bisphenol A, octocrylene, and 2 ′ ethylhexyl 4-(dimethylamino) benzoate on Chironomus riparius
(Elsevier, 2020-12-15) Muñiz González, Ana Belén; Martínez Guitarte, José Luis; Elsevier
Living organisms are exposed to mixtures of pollutants in the wild. Inland aquatic ecosystems contain many compounds from different sources that pollute the water column and the sediment. However, majority of toxicological research is focused on the effects of single exposures to toxicants. Furthermore, studies have been principally oriented toward ecologically relevant effects of intoxication, and lack an analysis of the cellular and molecular mechanisms involved in the response to toxicants. Effects of single, binary, and ternary mixtures of three compounds, bisphenol A, octocrylene, and 2 ′-ethylhexyl 4- (dimethylamino)benzoate, were assessed using a Real-Time PCR array. Forty genes, and additional six reference genes, were included in the array. The genes were selected based on their association with hormone responses, detoxification mechanisms, the stress response, DNA repair, and the immune system. The study was performed on Chironomus riparius, a benthic dipteran with an essential role in the food web. Transcriptional responses were assessed both 24 and 96 h post-exposure, to determinate short- and medium-term cellular responses. Individual fourth instar larvae were exposed to 0.1 and 1 mg/L of each of the toxic compounds and compound mixtures. A weak response was detected at 24 h, which was stronger in larvae exposed to mixtures than to individual toxicants. The response at 96 h was complex and principally involved genes related to the endocrine system, detoxification mechanisms, and the stress response. Furthermore, exposure to mixtures of compounds altered the expression patterns of an increased number of genes than did individual compound exposures, which suggested complex interactions between compounds affected the regulation of transcriptional activity. The results obtained highlight the importance of analyzing the mechanisms involved in the response to mixtures of compounds over extended periods and offer new insights into the basis of the physiological responses to pollution.

Examinando por Autor "Elsevier"

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