518 research outputs found
Modelo de transferencia de calor para concentradores solares con flujo bifásico
In this work, a dynamic mathematical model of heat transfer through the absorber tube of a Fresnel solar concentrator type, which uses water as working fluid, is developed. The water is considered to change phase as it flows through the absorber tube, giving rise to a monophasic region and a biphasic region. The model is validated with experimental data, published in the literature, and the thermal efficiency is analyzed as a function of the solar resource in this concentrator.En este trabajo se desarrolla un modelo matemático dinámico de la transferencia de calor a través del tubo absorbedor de un concentrador solar Fresnel, que emplea como fluido de trabajo agua. Se considera que el agua cambia de fase a medida que fluye a través del tubo absorbedor, dando lugar a una región monofásica y una región bifásica. El modelo es validado con datos experimentales, publicados en la literatura, y se analiza la eficiencia térmica en función del recurso solar en este concentrador
Efecto térmico de las azoteas verdes en la Ciudad de México, Yucatán y Coahuila
In this work, a mathematical heat transfer model is presented to evaluate the thermal effect of the implementation of extensive green roofs for the rehabilitation of poorly insulated buildings subjected to the climatic conditions of Mexico City, Yucatan and Coahuila. The model, which requires a few amounts of input data, is solved numerically and implemented in Python. The results show that the implementation of a green roof contributes to decrease the amplitude of internal temperature oscillation of the building, decreases the average indoor temperature and reduces the consumption of electrical energy for air conditioning. En este trabajo, se presenta un modelo matemático de transferencia de calor para evaluar el efecto térmico de la implementación de azoteas verdes extensivas para la rehabilitación de edificaciones mal aisladas sometidas a las condiciones climáticas de la Ciudad de México, Yucatán y Coahuila. El modelo, que requiere pocos datos de entrada, es resuelto numéricamente e implementado en Python. Los resultados muestran que la implementación de una azotea verde contribuye a disminuir la amplitud de oscilación en la temperatura interna de la edificación, disminuye la temperatura media interior, y reduce el consumo de energía eléctrica destinada al acondicionamiento de aire
Factores de riesgo asociados a enfermedades cardiovasculares en la población adulta en cuatro estratos socioeconómicos del municipio de Guatemala
Describir el comportamiento epidemiológico de los factores de riesgo asociados a enfermedades cardiovasculares crónicas no transmisibles en población adulta de cuatro
estratos socioeconómicos del municipio de Guatemala.
Estudio de tipo descriptivo, transversal, con muestreo no probabilístico por conveniencia, en cuatro sectores cartográficos, 223 viviendas. Los datos se recolectaron por medio de una encuesta con base al cuestionario del método progresivo (STEPS) modificado. La prevalencia de factores de riesgo modificables asociados a enfermedad cardiovascular en población adulta de cuatro Estratos socioeconómicos del municipio de Guatemala fue de: consumo de cigarrillos (15%), consumo nocivo de alcohol (26%), sedentarismo (83%), obesidad central (47% y el consumo excesivo de sal (36%). La prevalencia de factores de riesgo no modificables asociados a enfermedad cardiovascular en población adulta, en 4 estratos socioeconómicos del municipio de Guatemala fue de: grupo etario femenino con mayor riesgo cardiovascular (36%), antecedente de diabetes mellitus (11%),antecedente de hipertensión arterial (35%) y antecedente de dislipidemia (17%). El comportamiento epidemiológico de los factores de riesgo asociado a enfermedad cardiovascular varía entre los estratos
socioeconómico; de los factores de riesgo modificable el más prevalente en los cuatro estratos fue el sedentarismo; de los factores de riesgo no modificables el más prevalente en los cuatro estratos fue el antecedente personal de diabetes mellitus; el sedentarismo es el factor de riesgo más prevalente en las mujeres de cuatro estratos socioeconómicos y el consumo nocivo de alcohol es el factor de riesgo más prevalente en los hombres de los cuatro estratos socioeconómicos
Ética profesional en educación superior : finalidades, estrategias y desafíos de la formación
Todo proyecto educativo que no responde a su época se expone a problemas de legitimidad y al duro escrutinio y sanción de los usuarios. Las instituciones de educación superior no son la excepción de esta premisa clásica, incluso más validada por eldinamismos, la versatilidad y ojo crítico en el mundo contemporáneo. La ética se ha convertido en el baremo principal para someter a juicio a las instituciones y a las personas que ahí actuan, como a las finalidades que se pretenden en sus acciones. En esta perspectiva, debe examinarse la función de las instituciones de educación superior.Este libro es el esfuerzo colectivo por acercarnos a esa problemática, en especial a las finalidades, estrategias y relaciones en juego para cumplir la tarea de la formación y sus nexos inevitables con la ética profesional
1er. Coloquio de educación para el diseño en la sociedad 5.0
Las memorias del 1er. Coloquio de Educación para el Diseño en la Sociedad 5.0 debenser entendidas como un esfuerzo colectivo de la comunidad de académicos de la División de Ciencias y Artes para el Diseño, que pone de manifiesto los retos y oportunidades que enfrenta la educación en diseño en un contexto de cambio acelerado y rompimiento de paradigmas.El evento se realizó el pasado mes de mayo de 2018 y se recibieron más de 50 ponencias por parte de las profesoras y profesores de la División.Las experiencias y/o propuestas innovadoras en cuanto a procesos de enseñanza y aprendizaje que presentan los autores en cada uno de sus textos son una invitación a reflexionar sobre nuestra situación actual en la materia, y emprender acciones en la División para continuar brindando una educación de calidad en diseño a nuestras alumnas, alumnos y la sociedad.Adicionalmente, se organizaron tres conferencias magistrales sobre la situación actual de la educación en Diseño y de las Instituciones de Educación Superior, impartidas por el Mtro. Luis Sarale, profesor de la Universidad Nacional de Cuyo en Mendoza (Argentina), y Presidente en su momento, de la Red de Carreras de Diseño en Universidades Públicas Latinoamericanas (DISUR), el Dr. Romualdo López Zárate, Rector de la Unidad Azcapotzalco, así como del Mtro. Luis Antonio Rivera Díaz, Jefe de Departamento de Teoría y Procesos del Diseño de la División de la Ciencias de la Comunicación y Diseño, en la Unidad Cuajimalpa de nuestra institución.La publicación de estas memorias son un esfuerzo divisional, organizado desde la Coordinación de Docencia Divisional y la Coordinación de Tecnologías del Aprendizaje, del Conocimiento y la Comunicación, para contribuir a los objetivos planteados en el documento ACCIONES:Agenda CyAD2021, en particular al eje de Innovación Educativa. Es necesario impulsar a todos los niveles de la División espacios de discusión orientados a reflexionar sobre el presente y futuro en la educación del diseñador, que contribuya a mejorar la calidad de la docencia y favorezca al fortalecimiento de los procesos de enseñanza y aprendizaje.Finalmente, extiendo un amplio reconocimiento a todos los miembros de la División que hicieron posible este evento, así como a todos los ponentes y participantes por compartir su conocimiento para que la División sea cada día mejor
Evolving trends in the management of acute appendicitis during COVID-19 waves. The ACIE appy II study
Background: In 2020, ACIE Appy study showed that COVID-19 pandemic heavily affected the management of patients with acute appendicitis (AA) worldwide, with an increased rate of non-operative management (NOM) strategies and a trend toward open surgery due to concern of virus transmission by laparoscopy and controversial recommendations on this issue. The aim of this study was to survey again the same group of surgeons to assess if any difference in management attitudes of AA had occurred in the later stages of the outbreak.
Methods: From August 15 to September 30, 2021, an online questionnaire was sent to all 709 participants of the ACIE Appy study. The questionnaire included questions on personal protective equipment (PPE), local policies and screening for SARS-CoV-2 infection, NOM, surgical approach and disease presentations in 2021. The results were compared with the results from the previous study.
Results: A total of 476 answers were collected (response rate 67.1%). Screening policies were significatively improved with most patients screened regardless of symptoms (89.5% vs. 37.4%) with PCR and antigenic test as the preferred test (74.1% vs. 26.3%). More patients tested positive before surgery and commercial systems were the preferred ones to filter smoke plumes during laparoscopy. Laparoscopic appendicectomy was the first option in the treatment of AA, with a declined use of NOM.
Conclusion: Management of AA has improved in the last waves of pandemic. Increased evidence regarding SARS-COV-2 infection along with a timely healthcare systems response has been translated into tailored attitudes and a better care for patients with AA worldwide
Multidifferential study of identified charged hadron distributions in -tagged jets in proton-proton collisions at 13 TeV
Jet fragmentation functions are measured for the first time in proton-proton
collisions for charged pions, kaons, and protons within jets recoiling against
a boson. The charged-hadron distributions are studied longitudinally and
transversely to the jet direction for jets with transverse momentum 20 GeV and in the pseudorapidity range . The
data sample was collected with the LHCb experiment at a center-of-mass energy
of 13 TeV, corresponding to an integrated luminosity of 1.64 fb. Triple
differential distributions as a function of the hadron longitudinal momentum
fraction, hadron transverse momentum, and jet transverse momentum are also
measured for the first time. This helps constrain transverse-momentum-dependent
fragmentation functions. Differences in the shapes and magnitudes of the
measured distributions for the different hadron species provide insights into
the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb
public pages
Study of the decay
The decay is studied
in proton-proton collisions at a center-of-mass energy of TeV
using data corresponding to an integrated luminosity of 5
collected by the LHCb experiment. In the system, the
state observed at the BaBar and Belle experiments is
resolved into two narrower states, and ,
whose masses and widths are measured to be where the first uncertainties are statistical and the second
systematic. The results are consistent with a previous LHCb measurement using a
prompt sample. Evidence of a new
state is found with a local significance of , whose mass and width
are measured to be and , respectively. In addition, evidence of a new decay mode
is found with a significance of
. The relative branching fraction of with respect to the
decay is measured to be , where the first
uncertainty is statistical, the second systematic and the third originates from
the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb
public pages
Measurement of the ratios of branching fractions and
The ratios of branching fractions
and are measured, assuming isospin symmetry, using a
sample of proton-proton collision data corresponding to 3.0 fb of
integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The
tau lepton is identified in the decay mode
. The measured values are
and
, where the first uncertainty is
statistical and the second is systematic. The correlation between these
measurements is . Results are consistent with the current average
of these quantities and are at a combined 1.9 standard deviations from the
predictions based on lepton flavor universality in the Standard Model.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb
public pages
Hotspots of biogeochemical activity linked to aridity and plant traits across global drylands
14 páginas.- 4 figuras.- 67 referencias.- The online version contains supplementary material available at https://doi.org/10.1038/s41477-024-01670-7Perennial plants create productive and biodiverse hotspots, known as fertile islands, beneath their canopies. These hotspots largely determine the structure and functioning of drylands worldwide. Despite their ubiquity, the factors controlling fertile islands under conditions of contrasting grazing by livestock, the most prevalent land use in drylands, remain virtually unknown. Here we evaluated the relative importance of grazing pressure and herbivore type, climate and plant functional traits on 24 soil physical and chemical attributes that represent proxies of key ecosystem services related to decomposition, soil fertility, and soil and water conservation. To do this, we conducted a standardized global survey of 288 plots at 88 sites in 25 countries worldwide. We show that aridity and plant traits are the major factors associated with the magnitude of plant effects on fertile islands in grazed drylands worldwide. Grazing pressure had little influence on the capacity of plants to support fertile islands. Taller and wider shrubs and grasses supported stronger island effects. Stable and functional soils tended to be linked to species-rich sites with taller plants. Together, our findings dispel the notion that grazing pressure or herbivore type are linked to the formation or intensification of fertile islands in drylands. Rather, our study suggests that changes in aridity, and processes that alter island identity and therefore plant traits, will have marked effects on how perennial plants support and maintain the functioning of drylands in a more arid and grazed world.This research was supported by the European Research Council (ERC grant 647038 (BIODESERT) awarded to F.T.M.) and Generalitat Valenciana (CIDEGENT/2018/041). D.J.E. was supported by the Hermon Slade Foundation (HSF21040). J. Ding was supported by the National Natural Science Foundation of China Project (41991232) and the Fundamental Research Funds for the Central Universities of China. M.D.-B. acknowledges support from TED2021-130908B-C41/AEI/10.13039/501100011033/Unión Europea Next Generation EU/PRTR and the Spanish Ministry of Science and Innovation for the I + D + i project PID2020-115813RA-I00 funded by MCIN/AEI/10.13039/501100011033. O.S. was supported by US National Science Foundation (Grants DEB 1754106, 20-25166), and Y.L.B.-P. by a Marie Sklodowska-Curie Actions Individual Fellowship (MSCA-1018 IF) within the European Program Horizon 2020 (DRYFUN Project 656035). K.G. and N.B. acknowledge support from the German Federal Ministry of Education and Research (BMBF) SPACES projects OPTIMASS (FKZ: 01LL1302A) and ORYCS (FKZ: FKZ01LL1804A). B.B. was supported by the Taylor Family-Asia Foundation Endowed Chair in Ecology and Conservation Biology, and M. Bowker by funding from the School of Forestry, Northern Arizona University. C.B. acknowledges funding from the National Natural Science Foundation of China (41971131). D.B. acknowledges support from the Hungarian Research, Development and Innovation Office (NKFI KKP 144096), and A. Fajardo support from ANID PIA/BASAL FB 210006 and the Millennium Science Initiative Program NCN2021-050. M.F. and H.E. received funding from Ferdowsi University of Mashhad (grant 39843). A.N. and M.K. acknowledge support from FCT (CEECIND/02453/2018/CP1534/CT0001, SFRH/BD/130274/2017, PTDC/ASP-SIL/7743/2020, UIDB/00329/2020), EEA (10/CALL#5), AdaptForGrazing (PRR-C05-i03-I-000035) and LTsER Montado platform (LTER_EU_PT_001) grants. O.V. acknowledges support from the Hungarian Research, Development and Innovation Office (NKFI KKP 144096). L.W. was supported by the US National Science Foundation (EAR 1554894). Y.Z. and X.Z. were supported by the National Natural Science Foundation of China (U2003214). H.S. is supported by a María Zambrano fellowship funded by the Ministry of Universities and European Union-Next Generation plan. The use of any trade, firm or product names does not imply endorsement by any agency, institution or government. Finally, we thank the many people who assisted with field work and the landowners, corporations and national bodies that allowed us access to their land.Peer reviewe
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