211 research outputs found
Validation of the 3-under-2 principle of cell wall growth in Gram-positive bacteria by simulation of a simple coarse-grained model
The aim of this work is to propose a first coarse-grained model of Bacillus
subtilis cell wall, handling explicitly the existence of multiple layers of
peptidoglycans. In this first work, we aim at the validation of the recently
proposed "three under two" principle.Comment: Revised introduction, results unchange
Control of a wind turbine equipped with a variable rotor resistance
In this thesis the control of a wind turbine equipped with an induction generator with variable rotor resistances was investigated. Analysis, modelling and control of the induction generator system was conducted. In particular the focus was put on the reduction of torque fluctuations, in order to reduce the stresses in the gearbox and in the mechanical structure as well as reducing the flicker emission. Different controlling methods were studied in order to find an appropriate choice. Finally, the induction machine with the variable rotor resistance controller was compared with the same induction machine without controller for the wind application, in order to study the improvement of implementing the controller. The first thing to be emphasized is that by utilising the controller the flicker contribution can be reduced between 35%‐60% compared to the uncontrolled system. It was also found that the reduction of the flicker contributions was strongly related with the turbulence intensity in the wind. The reduction in the flicker emission was stronger for more turbulent winds. Furthermore, a reduction in the magnitude of the electrical torque components for the frequencies above 1Hz was found. Those high‐frequency components are the ones that more contribute to the mechanical stresses in the gearbox and structure of the turbine, this means that by utilising the controller there will be less tear and wear on the mechanical parts of the turbine. _____________________________________________________En este proyecto final de carrera se ha investigado el control de una turbina de viento equipada con un generador de inducción, que a su vez está equipado con resistencias del rotor variables. En el mismo, el análisis, modelado y control del generador de inducción ha sido llevado a cabo. En particular, el mayor interés del proyecto se puso en la reducción de las fluctuaciones del par generado por el generador de inducción, para así reducir el estrés mecánico tanto en la caja de cambios como en la estructura mecánica, así como reducir las fluctuaciones en la potencia entregada a la red.
Diferentes métodos de control fueron estudiados para encontrar la elección más adecuada. Una vez seleccionado el método de control que se iba a emplear, Se compararon los resultados obtenidos con la maquina de inducción donde se había implementado el controlador de las resistencias variables, con la misma máquina de inducción sin el controlador. Esta comparación se realizó para estudiar la mejora que se obtenía al utilizar el controlador.Ingeniería Industria
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Propelling Children’s Empathy and Friendship
Schools play a crucial role in creating supportive and safe environments, and positive feelings are key in fostering such environments. Schools as Learning Communities, based on the dialogic participation of the whole community, are improving social cohesion. However, the underlying processes leading to such transformations remain underexplored. This article suggests that successful educational actions (SEAs) implemented in a school as a learning community, analyzed in this case study, promote positive feelings such as friendship and empathy, contributing to a safe and supportive environment. The purpose of this study was to analyze how SEAs generate friendship and empathy and their impact in the environment in a school as a learning community in Spain. To that end, the methods used were interviews with 18 students and 10 teachers, and reviews of two documentary films featuring the school. Results suggest that SEAs generate friendship and empathy among many children by promoting mutual support and sharing narratives in such dialogic settings. In addition, developing friendship and empathy contributes to reducing violent behaviors and promoting more inclusive attitudes among many students. This study concludes by providing insights on how SEAs can contribute to safe and supportive environments through fostering friendship and empathy.</jats:p
The scope of presentation of non-financial information in financial statements of farms – the example of crop production
The aim of the article is to indicate areas of non-financial information disclosures in financial statements of entities engaged in agricultural activity in the light of economic practices and regulatory requirements. An attempt was made to identify and classify the scope of non-financial information disclosures. To achieve the purpose of the article, a review of legal regulations was carried out. In the period 20152017, individual in-depth interviews were conducted with chief accountants (30 persons) and owners (150 persons) of farm businesses that keep accounts in accordance with the Accounting Act, located in Wielkopolskie Province. The topic of the interviews was the reporting of non-financial information in the integrated report of farms. The research has enabled the identification of demand for non-financial information, which so far have not been presented in the reports. It was found that the integrated financial reporting does not take full account of agricultural activity. Presentation of the results of this activity requires a detailed clarification
Artistas y fotógrafos catalanes en Ecuador (1860-1939)
La presencia de migrantes catalanes en el Ecuador en el siglo pasado, si bien no fue numerosa, fue importante y trascendente en la vida social, económica, política y cultural del país. El objetivo de la presente investigación es explicar la trayectoria y principales obras de los artistas y fotógrafos catalanes en el primer tercio del siglo XX. Es una investigación de corte cualitativo y de carácter histórico, en la que se utilizó el método biográfico narrativo porque se analizó varias obras de artistas catalanes en el Ecuador y su influencia en el contexto en el
que estos estuvieron inmersos. La técnica bibliográfica fue la empleada durante la investigación y dos son las preguntas científicas que la guiaron: ¿Cuál es la trayectoria de los artistas catalanes en el Ecuador? ¿Cuáles fueron las obras relevantes desarrolladas en el Ecuador por los artistas catalanes? La investigación concluye la presencia de diez artistas y fotógrafos catalanes destacados en el pais entre 1900 y 1939, quienes jugaron roles importantes en la definición del arte ecuatoriano contemporáneo
Shigella MreB promotes polar IcsA positioning for actin tail formation.
Pathogenic Shigella bacteria are a paradigm to address key issues of cell and infection biology. Polar localisation of the Shigella autotransporter protein IcsA is essential for actin tail formation, which is necessary for the bacterium to travel from cell-to-cell; yet how proteins are targeted to the bacterial cell pole is poorly understood. The bacterial actin homologue MreB has been extensively studied in broth culture using model organisms including Escherichia coli, Bacillus subtilis and Caulobacter crescentus, but has never been visualised in rod-shaped pathogenic bacteria during infection of host cells. Here, using single-cell analysis of intracellular Shigella, we discover that MreB accumulates at the cell pole of bacteria forming actin tails, where it colocalises with IcsA. Pharmacological inhibition of host cell actin polymerisation and genetic deletion of IcsA is used to show, respectively, that localisation of MreB to the cell poles precedes actin tail formation and polar localisation of IcsA. Finally, by exploiting the MreB inhibitors A22 and MP265, we demonstrate that MreB polymerisation can support actin tail formation. We conclude that Shigella MreB promotes polar IcsA positioning for actin tail formation, and suggest that understanding the bacterial cytoskeleton during host-pathogen interactions can inspire development of new therapeutic regimes for infection control.This article has an associated First Person interview with the first author of the paper
No radiographic sacroiliitis progression was observed in patients with early spondyloarthritis at 6 years: results of the Esperanza multicentric prospective cohort
Objective: To estimate the 6-year radiographic progression of sacroiliitis in patients with early spondyloarthritis (SpA). Patients and methods: Sacroiliac joint (SIJ) radiographs (baseline and 6 years) of 94 patients with recent-onset SpA from the Esperanza cohort were scored, blindly and in a random order, by nine readers. The modified New York criteria were used to define the presence of sacroiliitis. As the gold standard for radiographic (r) sacroiliitis, the categorical opinion of at least five readers was used. Progression was defined as the shift from non-radiographic (nr) to r-sacroiliitis. Results: In the 94 SIJ radiographs (baseline and 6 years), 78/94 (83%) pairs of radiographs had not changed from baseline to 6 years. Sacroiliitis was present in 20 patients at baseline (21.3%) and in 18 (19.2%) patients at 6 years; 11 patients had sacroiliitis at both the baseline and final visits; 9 patients changed from baseline r-sacroiliitis to nr-sacroiliitis at 6 years, and 7 changed from baseline nr-sacroiliitis to r-sacroiliitis at 6 years. The mean continuous change score (range: -8 to +8) was 2.80 at baseline and 2.55 at 6 years (mean net progression of -0.25). The reliability of the readers was fair (mean inter-reader kappa of 0.375 (0.146-0.652) and mean agreement of 73.7% (58.7-90%)). Conclusion: In the early SpA Esperanza cohort, progression from nr-axSpA to r-axSpA over 6 years was not observed, although the SIJ radiographs scoring has limitations to detect low levels of radiographic progression
Matrix tablets based on a novel poly (magnesium acrylate) hydrogel for the treatment of inflammatory bowel diseases
The objective of this work was to evaluate the potential use of a new polymer (PAMgA) in the development sustained release matrix tablets for the treatment of bowel inflammatory diseases. For this purpose, budesonide, a highly lipophilic compound, was used as model drug. Tablets with two reticulation grades of PAMgA (PAMgA 5 and 40) and with 9 mg of budesonide were developed and characterized. All the studies were carried out using biorelevant media (FaSSGF and FaSSIF). Swelling and erosion of PAMgA tablets was influenced by the reticulation grade of the polymer and the biorelevant media assayed, being water uptake higher for PAMgA 40 tablets in intestinal fluid, whereas PAMgA 5 showed more intense erosion in this biorelevant medium. Budesonide was released slowly from PAMgA tablets, both in gastric and intestinal environment, following Super case II transport kinetics (relaxation-controlled delivery), with a lag time of around 1–2 h. When the dissolution medium was changed sequentially throughout the trial, 75% of the budesonide dose was released in a sustained manner between 4 and 20 h of testing from PAMgA tablets, showing a more controlled budesonide release than Entocort® and Budenofalk® (commercially available sustained release formulations of budesonide). In conclusion, PAMgA polymer allows controlling the release of highly lipophilic drugs as budesonide, being an useful excipient for the development of sustained release matrix tablets
Controlled Release of Highly Hydrophilic Drugs from Novel Poly(Magnesium Acrylate) Matrix Tablets
The potential of a new poly(magnesium acrylate) hydrogel (PAMgA) as a pharmaceutical excipient for the elaboration of matrix tablets for the extended release of highly hydrophilic drugs was evaluated. The polymer was synthetized with two di_erent crosslinking degrees that were characterized by FTIR and DSC. Their acute oral toxicity was determined in a mouse model, showing no toxicity at doses up to 10 g/kg. Matrix tablets were prepared using metformin hydrochloride as a model drug and the mechanisms involved in drug release (swelling and/or erosion) were investigated using biorrelevant media. This new hydrogel e_ectively controlled the release of small and highly hydrophilic molecules as metformin, when formulated in matrix tablets for oral administration.
The rate of metformin release from PAMgA matrices was mainly controlled by its di_usion through the gel layer (Fickian di_usion). The swelling capacity and the erosion of the matrix tablets influenced the metformin release rate, that was slower at pH 6.8, where polymer swelling is more intensive, than in gastric medium, where matrix erosion is slightly more rapid. The crosslinking degree of the polymer significantly influenced its swelling capacity in acid pH, where swelling is moderate, but not in intestinal fluid, where swelling is more intense
Septins Recognize and Entrap Dividing Bacterial Cells for Delivery to Lysosomes.
The cytoskeleton occupies a central role in cellular immunity by promoting bacterial sensing and antibacterial functions. Septins are cytoskeletal proteins implicated in various cellular processes, including cell division. Septins also assemble into cage-like structures that entrap cytosolic Shigella, yet how septins recognize bacteria is poorly understood. Here, we discover that septins are recruited to regions of micron-scale membrane curvature upon invasion and division by a variety of bacterial species. Cardiolipin, a curvature-specific phospholipid, promotes septin recruitment to highly curved membranes of Shigella, and bacterial mutants lacking cardiolipin exhibit less septin cage entrapment. Chemically inhibiting cell separation to prolong membrane curvature or reducing Shigella cell growth respectively increases and decreases septin cage formation. Once formed, septin cages inhibit Shigella cell division upon recruitment of autophagic and lysosomal machinery. Thus, recognition of dividing bacterial cells by the septin cytoskeleton is a powerful mechanism to restrict the proliferation of intracellular bacterial pathogens
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