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Artificial Neural Networks (ANNs) have emerged as a powerful tool in combustion simulations to replace memory-intensive tabulation of integrated chemical kinetics. Complex reaction mechanisms, however, present a challenge for standard ANN approaches as modeling multiple species typically suffers from inaccurate predictions on minor species. This paper presents a novel ANN approach which can be applied on complex reaction mechanisms in tabular data form, and only involves training a single ANN for a complete reaction mechanism. The approach incorporates a network architecture that automatically conserves mass and employs a particular loss weighting based on species depletion. Both modifications are used to improve the overall ANN performance and individual prediction accuracies, especially for minor species mass fractions. To validate its effectiveness, the approach is compared to standard ANNs in terms of performance and ANN complexity. Four distinct reaction mechanisms (H2, C7H16, C12H26, OME34) are used as a test cases, and results demonstrate that considerable improvements can be achieved by applying both modifications.

Oxymethylene dimethyl ethers (OMEx), having a chemical formula of CH3O-(CH2O)x-CH3 where x varies from 1 to 5, have been widely considered as a promising fuel to partially replace diesel in CI engines in terms of reducing soot emissions. This work is focused on developing a reduced primary reference fuel (PRF)-OMEx chemical mechanism to better describe the combustion and emission characteristics of gasoline/diesel blends with OMEx. The novelty of this work lies in the fact that the OMEx part of the mechanism is represented not only by OME3 as done in most studies found in literature, but also with other OME chain lengths that is, OME2-4 which are considered to be optimum and better represent the commercial OMEx blends. For this purpose, a detailed OMEx mechanism is reduced by applying different reduction techniques considering a wide range of operating conditions including pressure, temperatures, equivalence ratios and fuel compositions. The result is merged with an already validated PRF mechanism to form a reduced PRF-OMEx mechanism consisting of 213 species and 840 reactions. The newly formed mechanism is validated against a wide set of experimental data including ignition delay times, laminar flame speeds and species concentration profiles. Furthermore, a rigorous set of numerical simulations for various diesel-OMEx blends in a compression ignition engine are carried out at two different operating points to validate the developed mechanism. Simulation results highlight that the developed mechanism not only replicates the experimental behavior in terms of in-cylinder pressure and heat release rate but exhibits a better combustion phasing closer to experimental data when compared with other mechanisms where only OME3 is utilized to represent OMEx. Overall, the developed PRF-OMEx mechanism proves to be realistic and suitable for application in engine combustion simulations involving gasoline/diesel and OMEx blends. [ABSTRACT FROM AUTHOR]

The solution to the dilemma of carbon footprint of internal combustion engines and pollutant emissions is necessary for the survival of this technology. In this context, alternative fuels have shown great potential in terms of achieving cleaner combustion and compliance with ever increasing pollutant emissions regulations. This work is focused on the study of two promising alternative fuels as Hydrotreated vegetable oil (HVO), which is a biofuel and Dimethoxymethane also termed as OME1, which is an e-fuel. A comprehensive numerical approach has been followed to study these fuels. Primarily a compact reaction mechanism having 121 species and 678 reactions has been developed which can be utilized to perform 3D CFD simulations of blends of these fuels. Secondly, a detailed numerical investigation including combustion and emissions analysis has been carried out. Results show that the developed mechanism is able to offer predictions, which match the experimental behavior observed in various combustion parameters and thus can be utilized for compression ignition engine applications involving these promising fuels. In addition, the numerical analysis also highlights that a reduction of 50% and 37% in terms soot and NOx emissions respectively can be achieved by addition of 30% OME1 in the blend containing HVO, suggesting that these blends can be utilized in unmodified CI engines to break the soot-NOx tradeoff without significantly penalizing the energy loss. [ABSTRACT FROM AUTHOR]

Abstract Background Histone H2B deubiquitination is performed by numerous deubiquitinases in eukaryotic cells including Ubp8, the catalytic subunit of the tetrameric deubiquitination module (DUBm: Ubp8; Sus1; Sgf11; Sgf73) of the Spt-Ada-Gcn5 acetyltransferase (SAGA). Ubp8 is linked to the rest of SAGA through Sgf73 and is activated by the adaptors Sus1 and Sgf11. It is unknown if DUBm/Ubp8 might also work in a SAGA-independent manner. Results Here we report that a tetrameric DUBm is assembled independently of the SAGA–CORE components SPT7, ADA1 and SPT20. In the absence of SPT7, i.e., independent of the SAGA complex, Ubp8 and Sus1 are poorly recruited to SAGA-dependent genes and to chromatin. Notably, cells lacking Spt7 or Ada1, but not Spt20, show lower levels of nuclear Ubp8 than wild-type cells, suggesting a possible role for SAGA–CORE subunits in Ubp8 localization. Last, deletion of SPT7 leads to defects in Ubp8 deubiquitinase activity in in vivo and in vitro assays. Conclusions Collectively, our studies show that the DUBm tetrameric structure can form without a complete intact SAGA–CORE complex and that it includes full-length Sgf73. However, subunits of this SAGA–CORE influence DUBm association with chromatin, its localization and its activity.

Abstract Background Gametes are highly differentiated cells specialized to carry and protect the parental genetic information. During male germ cell maturation, histone proteins undergo distinct changes that result in a highly compacted chromatin organization. Technical difficulties exclude comprehensive analysis of precise histone mutations during mammalian spermatogenesis. The model organism Saccharomyces cerevisiae possesses a differentiation pathway termed sporulation which exhibits striking similarities to mammalian spermatogenesis. This study took advantage of this yeast pathway to first perform systematic mutational and proteomics screens on histones, revealing amino acid residues which are essential for the formation of spores. Methods A systematic mutational screen has been performed on the histones H2A and H2B, generating ~ 250 mutants using two genetic backgrounds and assessing their ability to form spores. In addition, histones were purified at key stages of sporulation and post-translational modifications analyzed by mass spectrometry. Results The mutation of 75 H2A H2B residues affected sporulation, many of which were localized to the nucleosome lateral surface. The use of different genetic backgrounds confirmed the importance of many of the residues, as 48% of yeast histone mutants exhibited impaired formation of spores in both genetic backgrounds. Extensive proteomic analysis identified 67 unique post-translational modifications during sporulation, 27 of which were previously unreported in yeast. Furthermore, 33 modifications are located on residues that were found to be essential for efficient sporulation in our genetic mutation screens. The quantitative analysis of these modifications revealed a massive deacetylation of all core histones during the pre-meiotic phase and a close interplay between H4 acetylation and methylation during yeast sporulation. Methylation of H2BK37 was also identified as a new histone marker of meiosis and the mouse paralog, H2BK34, was also enriched for methylation during meiosis in the testes, establishing conservation during mammalian spermatogenesis. Conclusion Our results demonstrate that a combination of genetic and proteomic approaches applied to yeast sporulation can reveal new aspects of chromatin signaling pathways during mammalian spermatogenesis.

Objective: To explore whether there is a possible problem regarding indoor radon concentration surpassing the new European Directive 2013/59/Euratom threshold in Spanish workplaces. We also aim to find out whether radon concentration might be associated with certain characteristics of workplaces. Method: We performed a cross-sectional study to measure indoor radon concentrations in Spanish workplaces including five different sectors (education, public administration, the health sector, the tourist sector and the private sector). To be measured, the workplace should be occupied permanently by at least one worker. Alpha-track type radon detectors were placed for at least three months and read at the Galician Radon Laboratory at the University of Santiago de Compostela. A descriptive analysis was performed on radon distribution by sector, building characteristics and number of workers affected. Results: We faced enormous difficulties in finding volunteers for this study. Galicia and Madrid had the highest number of measurements. Of a total of 248 measurements, 27% had concentrations above 300 Bq/m3. Median radon concentration was 251 Bq/m3 in Galicia, followed by Madrid, with 61.5 Bq/m3. Forty-six percent of the workplaces measured in Galicia had radon concentrations higher than 300 Bq/m3 followed by 10.6% in Madrid. Nineteen percent of all workers were exposed to more than 300 Bq/m3 and 6.3% were exposed to radon concentrations higher than 500 Bq/m3. Conclusion: Indoor radon exposure might be a relevant problem in Spanish workplaces and the number of affected workers could be high. The prevalence of workers exposed to high radon concentrations probably depends on the geographical area. Resumen: Objetivo: Explorar si podría existir un problema en cuanto a la concentración de radón en los puestos de trabajo en España por superación del umbral propuesto por la nueva Directiva Europea 2013/59/Euratom. También se pretende conocer si la concentración de radón puede estar asociada a las características de los puestos de trabajo. Método: Estudio transversal en seis regiones y diferentes sectores (educación, administración pública, sanitario, turístico y privado). El puesto de trabajo medido debía ser ocupado de manera permanente por al menos un trabajador. Los detectores de radón de tipo alfa-track estuvieron colocados al menos 3 meses y fueron revelados en el Laboratorio de Radón de Galicia, de la Universidad de Santiago de Compostela. Se realizó un análisis descriptivo de la concentración de radón por sector, por características de los edificios y por número de trabajadores afectados. Resultados: Hubo dificultades para encontrar voluntarios para este estudio. Galicia y Madrid tuvieron el mayor número de mediciones. Se midieron 248 lugares de trabajo, con el 27% por encima de los 300 Bq/m3. La concentración mediana fue de 251 Bq/m3 en Galicia, seguida de Madrid con 61,5 Bq/m3. El 46% de los puestos de trabajo en Galicia tenían concentraciones mayores de 300 Bq/m3, y el 10,6% en Madrid. El 19% de los trabajadores estuvieron expuestos a más de 300 Bq/m3 y el 6,3% a más de 500 Bq/m3. Conclusión: La exposición a radón podría ser un problema de salud relevante en los lugares de trabajo en España. El número de trabajadores expuestos parece elevado. La prevalencia de trabajadores afectados depende del área geográfica. Keywords: Radon, Lung cancer, Cross-sectional studies, Workplace, Spain, Palabras clave: Radón, Cáncer de pulmón, Estudio transversal, Lugar de trabajo, España

This work describes an experimental installation for the investigation of the combustion and injection processes. This installation is based on a two-stroke direct injection diesel engine with a total displacement of 3 L and a cylinder head equipped with three quartz windows. The windows are optical accesses that allow studying the process of injection, the atomization and evaporation of the fuel jet in an inert atmosphere (nitrogen), and the combustion process in a reactive atmosphere (ambient air). Additionally, the application of a two-color pyrometry technique to measure soot formation in this facility is presented. A methodological study is carried out regarding the influence of the dynamic range of the detectors and the wavelengths used. Maps of KL2C, flame temperature, and error probability are presented. The use of cameras with high dynamic range provides better results since the system seems to be less sensitive to measurement noise, and fewer points are obtained with a non-physical solution. Moreover, an appropriate combination of interference filters can improve the reliability of the solution. The greater the difference between the wavelengths of both interference filters, the fewer points with a non-physical solution, which improves the reliability of results.

The combustion process of the Engine Combustion Network (ECN) Spray A and Spray D is studied over a wide range of ambient temperatures from 750 K to 900 K. With nominal diameters of 89.4 μm for the Spray A and 190.3 μm for the Spray D, these n-dodecane sprays are representative for light- and heavy-duty compression ignition engine applications, respectively. Computational Fluid Dynamics calculations are carried out using a Lagrangian parcel Eulerian fluid approach in a Reynolds averaged Navier–Stokes framework. For the Spray D reference condition, two sub-grid flame structure assumptions and the effect of turbulence chemistry interaction (TCI) on autoignition and flame structure at quasi-steady state are assessed in the context of a well-mixed and an Unsteady Flamelet Progress Variable (UFPV) combustion model. After that, UFPV approach is used to evaluate combustion behavior for the different ambient temperature conditions. Reference condition results show that both well-mixed and flamelet assumptions lead to a similar autoignition sequence. In terms of ignition delay time, TCI plays an important role, within the UFPV model, in reproducing the experimental trend observed for the increase in nozzle diameter. In terms of lift-off length, the well-mixed model is observed to predict a longer value compared to the flamelet-based sub-grid assumption. Lastly, the analysis of the autoignition sequence and flame structure at quasi-steady state is also extended over the whole range of ambient temperature conditions.