36,718 research outputs found

    Kinetic model for ye’elimite polimorphs formation during clinkering production of CSA cement

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    The calcium sulfoaluminate, orthorhombic (OY) and pseudo- cubic (CY) ye’elimite polymorphs, were synthesized by solid state reaction from SiO2, Al2O3, Fe2O3, CaCO3, Na2CO3, CaSO4·2H2O in specific oxide relationships. Thermal gravimetric analysis (TGA) was made before sintering the raw mixes in an electrical furnace. Laboratory X-Ray Powder Diffraction (LXRPD) and Rietveld quantitative phase analysis (RQPA) and amorphous and crystalline non-quantified (ACn) quantification were made on each sample. Kinetic were analyzed isothermally between 1150 °C and 1300 °C. The kinetic model who best fitted each OY and CY polymorph was the geometrical and diffusional model proposed by Jander (D3 model). The activation energy, Ea (kJ/mol), values obtained for OY and CY were 420 and 275 respectively. The activation energy is lower in CY due to the presence of minor elements that reduce the sintering temperature. The frequency factor or compensation factor A is higher for OY than CY, meaning the need for a higher collision frequency. As founded by previous authors, the coexistence of both polymorphs must be considered into the kinetic study as a fundamental condition of these results. For this reason, this research proposes the inclusion of αmodified. OY always is present at the reaction beginning. But as higher the temperature and reaction time, in the presence of some minor elements, CY appears mainly at lower temperatures regarding OY, it means requiring lesser energy. Knowing the kinetic model proposed by this work would allow a better control or tailor of the ratio OY/CY, to produce CSA with different performances.The stay at University of Malaga of A. Berrio was partially funded by Spanish Junta de Andalucía [UMA18-FEDERJA-095] research project, which is cofounded by ERDF

    Obstructive sleep apneas naturally occur in mice during REM sleep and are more prevalent in a mouse model of Down syndrome

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    Study Objectives. The use of mouse models in sleep apnea research is limited by the belief that central (CSA) but not obstructive sleep apneas (OSA) occur in rodents. With this study we wanted to develop a protocol to look for the presence of OSAs in wild-type mice and, then, to apply it to a mouse model of Down Syndrome (DS), a human pathology characterized by a high incidence of OSAs. Methods. Nine C57Bl/6J wild-type mice were implanted with electrodes for electroencephalography (EEG), neck electromyography (nEMG), diaphragmatic activity (DIA) and then placed in a whole-body-plethysmographic (WBP) chamber for 8h during the resting (light) phase to simultaneously record sleep and breathing activity. The concomitant analysis of WBP and DIA signals allowed the discrimination between CSA and OSA. The same protocol was then applied to 12 Ts65Dn mice (a validated model of DS) and 14 euploid controls. Results. OSAs represented about half of the apneic events recorded during rapid-eye-movement sleep (REMS) in each experimental group while almost only CSAs were found during non-REMS. Ts65Dn mice had similar rate of apneic events than euploid controls but a significantly higher occurrence of OSAs during REMS. Conclusions. We demonstrated for the first time that mice physiologically exhibit both CSAs and OSAs and that the latter are more prevalent in the Ts65Dn mouse model of DS. These findings indicate that mice can be used as a valid tool to accelerate the comprehension of the pathophysiology of all kind of sleep apnea and for the development of new therapeutical approaches to contrast these respiratory disorders

    Charge sharing energy correction in CdTe sensors using machine learning and its application in SPECT imaging

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    Small-pixel CdTe/CZT detectors based multi-Isotope hyperspectral SPECT imaging systems suffering serious degradation of energy performance and detection efficiency due to the incomplete charge collection. The charge sharing events collected by more than one pixel usually lose energy which is relevant to the collected energy ratio. When the interaction of photon is closer to the metal contact gap between metal contacts and loss more energy, the collected energy ratio by several pixels is more evenly distributed. In this thesis, a multi-pixel charge sharing energy reconstruction method based on Fully Connected Neural Network (FCNN) was developed and can flexibly reconstruct multi-pixel charge sharing events energy. The proposed FCNN charge sharing correction algorithm could enhance the spectral performance of the small-pixel CdTe semiconductor detectors by reconstructing bi-pixel, triple-pixel, and quad-pixel charge sharing events. Compared to the traditional charge-sharing discrimination (CSD) method, the correction of the charge-sharing events could increase the sensitivity of SPECT system with higher detection efficiency. In this study, we will compare the pure energy reconstruction and combination reconstruction energy reconstruction method implying bi-pixel, tri-pixel, and quad-pixel events and the results of traditional charge sharing addition (CSA) and charge sharing discrimination (CSD) methods. The machine learning method shows significant flexibility in multi-pixel charge sharing energy reconstruction and potential in sub-pixel SPECT imaging. Our future work is planned to investigate the application of FCNN on position estimation for increasing of the spatial resolution of the SPECT system.U of I OnlyAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD syste

    Early Results from GLASS-JWST. XIX: A High Density of Bright Galaxies at z≈10z\approx10 in the Abell 2744 Region

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    We report the detection of a high density of redshift z≈10z\approx 10 galaxies behind the foreground cluster Abell 2744, selected from imaging data obtained recently with NIRCam onboard {\it JWST} by three programs -- GLASS-JWST, UNCOVER, and DDT\#2756. To ensure robust estimates of the lensing magnification μ\mu, we use an improved version of our model that exploits the first epoch of NIRCam images and newly obtained MUSE spectra, and avoids regions with μ>5\mu>5 where the uncertainty may be higher. We detect seven bright z≈10z\approx 10 galaxies with demagnified rest-frame −22≲MUV≲−19-22 \lesssim M_{\rm UV}\lesssim -19 mag, over an area of ∼37\sim37 sq. arcmin. Taking into account photometric incompleteness and the effects of lensing on luminosity and cosmological volume, we find that the density of z≈10z\approx 10 galaxies in the field is about 10×10\times (3×3\times) larger than the average at MUV≈−21 (−20)M_{UV}\approx -21~ (-20) mag reported so far. The density is even higher when considering only the GLASS-JWST data, which are the deepest and the least affected by magnification and incompleteness. The GLASS-JWST field contains 5 out of 7 galaxies, distributed along an apparent filamentary structure of 2 Mpc in projected length, and includes a close pair of candidates with MUV<−20M_{\rm UV}< -20 mag having a projected separation of only 16 kpc. These findings suggest the presence of a z≈10z\approx 10 overdensity in the field. In addition to providing excellent targets for efficient spectroscopic follow-up observations, our study confirms the high density of bright galaxies observed in early {\it JWST} observations, but calls for multiple surveys along independent lines of sight to achieve an unbiased estimate of their average density and a first estimate of their clustering.Comment: Accepted for publication in ApJL, 13 pages, 4 figure

    Cosmology with one galaxy? -- The ASTRID model and robustness

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    Recent work has pointed out the potential existence of a tight relation between the cosmological parameter Ωm\Omega_{\rm m}, at fixed Ωb\Omega_{\rm b}, and the properties of individual galaxies in state-of-the-art cosmological hydrodynamic simulations. In this paper, we investigate whether such a relation also holds for galaxies from simulations run with a different code that made use of a distinct subgrid physics: Astrid. We find that also in this case, neural networks are able to infer the value of Ωm\Omega_{\rm m} with a ∼10%\sim10\% precision from the properties of individual galaxies while accounting for astrophysics uncertainties as modeled in CAMELS. This tight relationship is present at all considered redshifts, z≤3z\leq3, and the stellar mass, the stellar metallicity, and the maximum circular velocity are among the most important galaxy properties behind the relation. In order to use this method with real galaxies, one needs to quantify its robustness: the accuracy of the model when tested on galaxies generated by codes different from the one used for training. We quantify the robustness of the models by testing them on galaxies from four different codes: IllustrisTNG, SIMBA, Astrid, and Magneticum. We show that the models perform well on a large fraction of the galaxies, but fail dramatically on a small fraction of them. Removing these outliers significantly improves the accuracy of the models across simulation codes.Comment: 16 pages, 12 figure


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    Este artigo aborda a reformulação curricular do ensino médio na rede estadual de educação do Rio de Janeiro, que funcionou como laboratório das matrizes curriculares defendidas pela classe empresarial, no momento que precedeu a recente contrarreforma da educação básica, iniciada no âmbito nacional em 2016. Através da pesquisa documental, analisa os elementos de atualização e refuncionalização ideológica, materializados na ênfase conferida às competências socioemocionais e ao empreendedorismo juvenil na legislação e nos documentos normativos de políticas públicas educacionais. Palavras-chave: Contrarreforma do ensino médio; Juventude; Empreendedorism

    Multilevel governance and control of the Covid-19 pandemic in the Democratic Republic of Congo: Learning from the four first waves

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    The COVID-19 pandemic continues to impose a heavy burden on people around the world. The Democratic Republic of the Congo (DRC) has also been affected. The objective of this study was to explore national policy responses to the COVID-19 pandemic in the DRC and drivers of the response, and to generate lessons for strengthening health systems’ resilience and public health capacity to respond to health security threats. This was a case study with data collected through a literature review and in-depth interviews with key informants. Data analysis was carried out manually using thematic content analysis translated into a logical and descriptive summary of the results. The management of the response to the COVID-19 pandemic reflected multilevel governance. It implied a centralized command and a decentralized implementation. The centralized command at the national level mostly involved state actors organized into ad hoc structures. The decentralized implementation involved state actors at the provincial and peripheral level including two other ad hoc structures. Non-state actors were involved at both levels

    Enhancing Access and Adoption of Improved Seed for Food Security of Ethiopia (A Review)

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    Increasing agricultural productivity is central to accelerate economic growth and improving the wellbeing of both rural and urban people in Ethiopia. Agriculture, particularly crop production, has a greater effect on both the rural and the urban poor who spend more than a half of their incomes on food. Therefore, generation and transfer of improved technologies are critical prerequisites for agricultural development particularly for an agrarian based economy such as of Ethiopian. Seed, especially that of improved varieties, are among the most important productive inputs which can take the lion`s share from other agricultural inputs in affecting productivity, livelihood and assuring food security in Ethiopia. The direct contribution of quality seed alone to the total production is estimated at 15 –20% depending upon the crop and it can be further raised up to 45% with efficient management of the other inputs. Despite the importance of improved seed in increasing crop productivity, their availability on the required amount, quality and time is still limited in Ethiopia. The unavailability of quality seed at the right place and time coupled with the poor promotion system is one key factor accounting for the limited use of improved seed, which further contributing to low crop productivity. Therefore, in order to access quality seed at the required time and amount to the farmers and increase the adoption of improved seed, there is a need to have a robust seed system which can strictly control seed outlets and a strong seed-related extension program. The present paper reviews about enhancing access and adoption of improved seeds for better food security in Ethiopia. Keywords: Adoption, food security, improved seed, seed access DOI: 10.7176/DCS/13-3-02 Publication date:March 31st 202
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