Feasibility Study of Jet-Ejector Refrigeration Systems as a Mechanism for Harnessing Low-Grade Thermal Energy from Different Sources

[ES] Los sistemas de refrigeración por eyección activados por calor de origen renovable o fuentes de calor residual tienen el potencial de alcanzar ahorros energéticos significativos al sustituir o asistir a los sistemas de refrigeración tradicionales. Su campo de aplicabilidad es muy amplio y el presente trabajo se ha centrado en un estudio detallado de dos aplicaciones con gran potencial siguiendo un enfoque computacional: (i) generación de aire acondicionado activado por energía solar térmica y (ii) refrigeración de la admisión de un motor de combustión reutilizando la energía térmica disponible en la línea de escape de este. Las actividades de investigación han estado dirigidas a mitigar dos de los principales puntos débiles que caracterizan a los ciclos de refrigeración por eyección: su eficiencia relativamente baja y la incapacidad mostrada por la configuración base del ciclo de eyección para operar de forma robusta en condiciones de operación alejadas de las de diseño. La primera cuestión ha sido abordada principalmente diseñando geometrías de eyector altamente optimizadas usando técnicas de mecánica de fluidos computacional y optimizando la integración del eyector en el conjunto del sistema de refrigeración. La segunda cuestión se ha abordado caracterizando el comportamiento del sistema en condiciones de diseño y fuera de diseño. Se han propuesto dos estrategias avanzadas para hacer frente a la caída de prestaciones que sufre el sistema al operar en condiciones fuera de diseño, como son la utilización de eyectores de geometría ajustable o la implementación de tanques de almacenamiento térmico. La respuesta del sistema se ha analizado en condiciones fuera de diseño con dos aproximaciones temporales complementarias. Los modelos estacionarios se han usado para optimizar las diferentes arquitecturas de eyector y la operación global del sistema en ciertas condiciones de operación representativas, mientras que el análisis transitorio representa un enfoque más realista y tiene en cuenta la naturaleza impredecible e inestable de la climatología. El estudio se ha concluido con un análisis termoeconómico, el cual ha sido útil para discernir si los diseños altamente optimizados son competitivos al ser comparados con las soluciones de refrigeración que se encuentran actualmente consolidadas en el mercado. La principal conclusión del análisis en condiciones estáticas para la aplicación termosolar es que la transformación de potencia térmica a potencia de refrigeración puede alcanzar un rendimiento del 37.7%, mientras que el rendimiento global del sistema alcanza el 20.1% con diseños altamente optimizados de eyector para unas condiciones de evaporación y condensación de 13°C y 40°C, respectivamente. En condiciones dinámicas, la implementación de la geometría variable mejora en torno a un 40% el rendimiento del sistema de refrigeración, además de incrementar su operatividad. El tanque de almacenamiento térmico juega un papel relevante en este aspecto y, para una envergadura de colector parabólico de 7.1 m, un consumo nominal de 13.3 kW de potencia térmica del tanque ha resultado ser una solución de compromiso para mantener en equilibrio los principales indicadores de prestaciones. El análisis termoeconómico de la arquitectura más prometedora sugiere que el ahorro de coste operativo está lejos de poder compensar la elevada inversión inicial en equipamiento (16.905€ para una capacidad de refrigeración aproximada de 5.6 kW), destacando la dificultad del sistema para competir con las soluciones de refrigeración actualmente consolidadas en el mercado y resaltando la necesidad de considerar soluciones híbridas. La principal conclusión de la aplicación en motor de combustión es que la reducción de temperaturas en la línea de admisión por debajo de 4°C es factible, produciendo mejoras en el rendimiento volumétrico de en torno al 11%, no obstante, el sistema muestra vulnerabilidades al operar en puntos de motor diferentes al de diseño.[CA] Els sistemes de refrigeració per ejecció activats per calor d'origen renovable o fonts de calor residual tenen el potencial d'assolir estalvis energètics significatius al substituir o assistir als sistemes de refrigeració tradicionals. El seu camp d'aplicabilitat es ampli i el present treball s'ha centrat en un estudi detallat de dos aplicacions amb gran potencial seguint un enfocament computacional: (i) generació d'aire condicionat activat per energia solar tèrmica i (ii) refrigeració de l'admissió d'un motor de combustió reutilitzant l'energia tèrmica disponible en la línia d'escapament d'aquest. Les activitats d'investigació han estat dirigides a mitigar dos dels principals punts dèbils que caracteritzen als cicles de refrigeració per ejecció: la seua eficiència relativament baixa i la incapacitat mostrada per la configuració base del cicle d'ejecció per a operar de forma robusta en condicions d'operació allunyades de les de disseny. La primera qüestió ha sigut abordada principalment dissenyant geometries d'ejector altament optimitzades usant tècniques de mecànica de fluids computacional i optimitzant la integració de l'ejector en el conjunt del sistema de refrigeració. La segona qüestió s'ha abordat caracteritzant el comportament del sistema en condicions de disseny i fora de disseny. S'han proposat dos estratègies avançades per a fer front a la caiguda de prestacions que pateix el sistema quan opera en condicions fora de disseny, com són la utilització d'ejectors de geometria ajustable o la implementació de tancs de emmagatzemament tèrmic. La resposta del sistema s'ha analitzat en condicions fora de disseny amb dos aproximacions temporals complementàries. Els models estacionaris s'han usat per a optimitzar les diferents arquitectures d'ejector i l'operació global del sistema en certes condicions d'operació representatives, mentre que l'anàlisi transitori representa un enfocament més realista i té en compte la natura impredictible i inestable dels canvis en les condiciones climàtiques. L'estudi s'ha conclòs amb un anàlisi termoeconòmic, el qual ha sigut útil per a discernir si els dissenys altament optimitzats són competitius quan es comparen amb les solucions de refrigeració que es troben actualment consolidades al mercat. La principal conclusió de l'anàlisi en condicions estàtiques per a l'aplicació termosolar és que la transformació de potència tèrmica a potència de refrigeració pot arribar a un rendiment del 37.7%, mentre que el rendiment global del sistema arriba al 20.1 % amb dissenys altament optimitzats d'ejector per a unes condicions d'evaporació i condensació de 13°C i 40°C, respectivament. En condicions dinàmiques, la implementació de la geometria variable millora al voltant d'un 40% el rendiment del sistema de refrigeració, a més d'incrementar la seua capacitat de romandre en funcionament. El tanc d'emmagatzemament tèrmic juga un paper rellevant en aquest aspecte i, per a una llargària de col·lector parabòlic de 7.1 m, un consum nominal de 13.3 kW de potencia tèrmica del tanc ha resultat ser una solució de compromís per a mantenir en equilibri els principals indicadors de prestacions. L'anàlisi termoeconòmic de l'arquitectura més prometedora suggereix que l'estalvi de cost operatiu està lluny de poder compensar l'elevada inversió inicial en equipament (16.905€ per a una capacitat de refrigeració aproximada de 5.6 kW), posant de manifest la dificultat del sistema per a competir amb les solucions de refrigeració actualment consolidades al mercat i ressaltant la necessitat de considerar solucions híbrides. La principal conclusió de l'aplicació en motor de combustió és que la reducció de temperatures a la línia d'admissió per baix de 4°C és factible, produint millores en el rendiment volumètric de al voltant de l'11%, no obstant això, el sistema mostra vulnerabilitats a l'hora d'operar en punts de motor diferents al de disseny.[EN] Jet-ejector refrigeration systems powered by renewable heat or waste heat sources have the potential to achieve significant primary energy savings when substituting or aiding traditional refrigeration systems. Their field of applicability is vast and the present work has been focused on a detailed study of two applications with great potential following a computational approach: (i) air-conditioning generation powered by solar thermal energy and (ii) internal combustion engine intake air refrigeration powered by its exhaust line waste heat. The research efforts have been directed towards mitigating the negative effect of two of the main weak points of jet-ejector refrigeration systems: their relatively low efficiency and the incapacity of the baseline configuration to operate robustly away from the design conditions. The first issue has been addressed mainly by designing highly optimized jet-ejector geometries using computational fluid dynamics techniques and optimizing the jet-ejector integration in the overall system. The second one has been addressed by carrying out complete characterizations of the refrigeration system response in design and off-design conditions. Advanced strategies to face the refrigeration system performance decay away from design conditions have been proposed, like the utilization of adjustable jet-ejector architectures or the implementation of hot thermal storage tanks. The system response has been analyzed in off-design conditions with two complementary temporal schemes. The steady-state models have been used to optimize the jet-ejector architectures and the overall system operation for representative operating scenarios, while the transient analysis represents a more realistic approach and accounts for changes in climatic conditions, which have an unpredictable and unstable nature. The study has been concluded with a thermoeconomic analysis, which has been useful to discern if the highly optimized designs are competitive when compared to existing refrigeration solutions consolidated in the market. The main conclusions of the steady-state analysis for the solar application are that the transformation from thermal power to refrigeration power can achieve an efficiency of 37.7%, while the global efficiency achieves 20.1% when highly optimized jet-ejectors are used for an evaporating and condensing conditions of 13°C and 40°C, respectively. In dynamic conditions, the implantation of an adjustable jet-ejector brings improvements in refrigeration system efficiency of around 40%, besides improving its capacity to remain in operation. The thermal storage system plays a relevant role in this sense and, for a fixed parabolic trough collector span of 7.1 m, a nominal thermal power consumption of 13.3 kW represents a trade-off between the performance indicators subject to analysis. The thermoeconomic assessment of the most promising system architecture suggests that the operating cost savings are far from compensating for the capital expenditures (16,905€ for a refrigeration capacity of approximately 5.6 kW), evidencing the difficulties of the system to compete against refrigeration solutions currently consolidated in the market and outlining the interest in hybrid solutions. The main conclusion of the automotive application is that it is feasible to achieve in the engine intake line temperatures below 4°C, bringing improvements in volumetric engine efficiency of around 11%. Nevertheless, the system shows vulnerabilities when operating in engine operating points different from the design one.My most sincere acknowledgment to the whole CMT-Motores Térmicos team for giving me the opportunity of being part of it and the grant program Subvenciones para la contrataci ́on de personal investigador predoctoral for doctoral studies (reference ACIF/2018/124), awarded by Generalitat Valenciana, Conselleria de Innovación, Universidades, Ciencia y Sociedad Digital and the European Union for funding this project.Ponce Mora, A. (2022). Feasibility Study of Jet-Ejector Refrigeration Systems as a Mechanism for Harnessing Low-Grade Thermal Energy from Different Sources [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/18171

Numerical Optimization of an Ejector for Waste Heat Recovery Used to Cool Down the Intake Air in an Internal Combustion Engine

[EN] In the present paper, a numerical investigation of a jet-ejector is carried out using a real gas model of R1234yf. The prototype under investigation works with specific operating conditions of a jet-ejector refrigeration system intended for waste heat recovery in an internal combustion engine (ICE). In the first instance, the geometry optimization involving nozzle exit diameter, mixing chamber diameter, and nozzle exit position (NXP) is performed. Once the optimum geometry has been obtained, the jet-ejector prototype is tested with different operating pressure ratios to determine its off-design performance. The flow structure in relevant cases has been examined with an emphasis on critical and subcritical modes. The flow phenomena occurring during expansion, entrainment, and mixing processes are discussed so performance degradation can be directly related to physical processes. The analysis has been completed fitting simulated points to critical and subcritical planar surfaces. The results in terms of goodness of fit are satisfactory so the jet-ejector performance in off-design operating conditions can be reflected through simple mathematic models. When the overall cycle is assessed by using previous computational fluid dynamics (CFD) maps, it is observed that the achievable cooling drops significantly when an ambient temperature of 31 degrees C is exceeded.The authors want to acknowledge the institution "Conselleria d'Educacio, Investigacio, Cultura i Esport de la Generalitat Valenciana" and its grant program "Subvenciones para la contratacion de personal investigador de caracter predoctoral" for doctoral studies (ACIF/2018/124).Galindo, J.; Gil, A.; Dolz, V.; Ponce-Mora, A. (2020). Numerical Optimization of an Ejector for Waste Heat Recovery Used to Cool Down the Intake Air in an Internal Combustion Engine. Journal of Thermal Science and Engineering Applications. 12(5):1-13. https://doi.org/10.1115/1.4046906S113125Varga, S., Oliveira, A. C., & Diaconu, B. 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An experimental and theoretical study of a jet-pump refrigeration system designed using a new two-dimensional model for the entrainment region of the ejector. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 227(4), 486-497. doi:10.1177/0957650913477092Zhu, Y., & Jiang, P. (2014). Experimental and analytical studies on the shock wave length in convergent and convergent–divergent nozzle ejectors. Energy Conversion and Management, 88, 907-914. doi:10.1016/j.enconman.2014.09.023Zhu, Y., & Jiang, P. (2014). Experimental and numerical investigation of the effect of shock wave characteristics on the ejector performance. International Journal of Refrigeration, 40, 31-42. doi:10.1016/j.ijrefrig.2013.11.008Sargolzaei, J., Pirzadi Jahromi, M. R., & Saljoughi, E. (2010). Triple-Choking Model for Ejector. Journal of Thermal Science and Engineering Applications, 2(2). doi:10.1115/1.4002752Armstead, J. R., & Miers, S. A. (2013). Review of Waste Heat Recovery Mechanisms for Internal Combustion Engines. Journal of Thermal Science and Engineering Applications, 6(1). doi:10.1115/1.4024882Luján, J. M., Climent, H., Dolz, V., Moratal, A., Borges-Alejo, J., & Soukeur, Z. (2016). Potential of exhaust heat recovery for intake charge heating in a diesel engine transient operation at cold conditions. Applied Thermal Engineering, 105, 501-508. doi:10.1016/j.applthermaleng.2016.03.028Aghaali, H., & Ångström, H.-E. (2015). A review of turbocompounding as a waste heat recovery system for internal combustion engines. Renewable and Sustainable Energy Reviews, 49, 813-824. doi:10.1016/j.rser.2015.04.144Hsiao, Y. Y., Chang, W. C., & Chen, S. L. (2010). A mathematic model of thermoelectric module with applications on waste heat recovery from automobile engine. Energy, 35(3), 1447-1454. doi:10.1016/j.energy.2009.11.030In, B. D., & Lee, K. H. (2015). A study of a thermoelectric generator applied to a diesel engine. 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Preliminary analysis of organic Rankine cycles to improve vehicle efficiency. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 228(10), 1142-1153. doi:10.1177/0954407014528904Zegenhagen, M. T., & Ziegler, F. (2015). Feasibility analysis of an exhaust gas waste heat driven jet-ejector cooling system for charge air cooling of turbocharged gasoline engines. Applied Energy, 160, 221-230. doi:10.1016/j.apenergy.2015.09.057Novella, R., Dolz, V., Martín, J., & Royo-Pascual, L. (2017). Thermodynamic analysis of an absorption refrigeration system used to cool down the intake air in an Internal Combustion Engine. Applied Thermal Engineering, 111, 257-270. doi:10.1016/j.applthermaleng.2016.09.084Galindo, J., Dolz, V., Tiseira, A., & Ponce-Mora, A. (2019). Thermodynamic analysis and optimization of a jet ejector refrigeration cycle used to cool down the intake air in an IC engine. 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Flow structure of a steam ejector influenced by operating pressures and geometries. International Journal of Thermal Sciences, 46(8), 823-833. doi:10.1016/j.ijthermalsci.2006.10.012Bartosiewicz, Y., Aidoun, Z., Desevaux, P., & Mercadier, Y. (2005). Numerical and experimental investigations on supersonic ejectors. International Journal of Heat and Fluid Flow, 26(1), 56-70. doi:10.1016/j.ijheatfluidflow.2004.07.003Mazzelli, F., Little, A. B., Garimella, S., & Bartosiewicz, Y. (2015). Computational and experimental analysis of supersonic air ejector: Turbulence modeling and assessment of 3D effects. International Journal of Heat and Fluid Flow, 56, 305-316. doi:10.1016/j.ijheatfluidflow.2015.08.003Mazzelli, F., & Milazzo, A. (2015). Performance analysis of a supersonic ejector cycle working with R245fa. International Journal of Refrigeration, 49, 79-92. doi:10.1016/j.ijrefrig.2014.09.020Croquer, S., Poncet, S., & Aidoun, Z. (2016). 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T., & Ziegler, F. (2015). A one-dimensional model of a jet-ejector in critical double choking operation with R134a as a refrigerant including real gas effects. International Journal of Refrigeration, 55, 72-84. doi:10.1016/j.ijrefrig.2015.03.013Besagni, G., Mereu, R., Chiesa, P., & Inzoli, F. (2015). An Integrated Lumped Parameter-CFD approach for off-design ejector performance evaluation. Energy Conversion and Management, 105, 697-715. doi:10.1016/j.enconman.2015.08.029Gagan, J., Smierciew, K., Butrymowicz, D., & Karwacki, J. (2014). Comparative study of turbulence models in application to gas ejectors. International Journal of Thermal Sciences, 78, 9-15. doi:10.1016/j.ijthermalsci.2013.11.009Hakkaki-Fard, A., Aidoun, Z., & Ouzzane, M. (2015). A computational methodology for ejector design and performance maximisation. Energy Conversion and Management, 105, 1291-1302. doi:10.1016/j.enconman.2015.08.070Besagni, G., & Inzoli, F. (2017). 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Optimization of the thermal storage system in a solar-driven refrigeration system equipped with an adjustable jet-ejector

[EN] The present paper shows a numerical research about the influence of different thermal storage capacities and thermal power consumption strategies in a solar-driven air-conditioning system operating with refrigerant R1234yf. The computational model is fed with hourly climatic data (solar irradiance and ambient temperature) of the typical meteorological year of a Mediterranean location. A special focus is put on the dynamic response of the refrigeration system, the solar collector, and the sensible heat storage tank. Since the refrigeration needs are nearly synchronized with the sunny hours, small tank volumes are the most convenient architecture to achieve a rapid heating-up after tank discharges. For a parabolic trough collector span of 7.1 m, 13.3 kW of thermal power consumption represents a reasonable trade-off between the main performance indicators, mainly, the refrigeration capacity, COPth (thermal coefficient of performance) and the system's capability to operate properly ensuring an adequate thermal level in the heat reservoir.Authors want to acknowledge to the institution Conselleria dInnovacio, Universitats, Ciencia i Societat Digital de la Generalitat Valenciana for the public aid granted in the research project AICO/2021/124) .Luján, JM.; Galindo, J.; Dolz, V.; Ponce-Mora, A. (2022). Optimization of the thermal storage system in a solar-driven refrigeration system equipped with an adjustable jet-ejector. Journal of Energy Storage. 45:1-12. https://doi.org/10.1016/j.est.2021.1034951124

Advanced exergy analysis of a jet ejector refrigeration cycle used to cool down the intake air in an internal combustion engine

[EN] This paper describes a jet ejection cycle coupled to a 1.5 L diesel engine to reduce the intake air temperature using the waste heat of the exhaust gases. This cycle is evaluated by means of conventional and advanced exergy analysis. The conventional analysis allows to determine the origin and magnitude of the irreversibilities, whereas the advanced analysis sheds light on the mutual interdependencies between components and the real improvement potential considering technological limitations. From the conventional exergy analysis it is inferred that more than a half of exergy destruction is due to generator followed by ejector (one third part) and condenser. However, the advanced exergy analysis suggests that the ejector plays a prominent role because the avoidable endogenous part corresponds to 42% of total exergy destruction in that component whereas the avoidable part of exergy destruction in the generator is mostly exogenous (83%). Hence, exergy destruction could be significantly reduced if improvement efforts are focused on the ejector instead of other components like the generator.Authors want to acknowledge to the institution 'Conselleria d'Educacio, Investigacio, Cultura i Esport de la Generalitat Valenciana' and its grant program `Subvenciones para la contratacion de personal investigador de caracter predoctoral' for doctoral studies (ACIF/2018/124).Galindo, J.; Dolz, V.; Pla Moreno, B.; Ponce-Mora, A. (2020). Advanced exergy analysis of a jet ejector refrigeration cycle used to cool down the intake air in an internal combustion engine. International Journal of Exergy. 32(4):388-411. https://doi.org/10.1504/IJEX.2020.108948S38841132

Gasometría arterial en pacientes con sepsis y choque séptico atendidos en el Hospital Dr. Napoleón Dávila Córdova

Arterial blood gases were determined as a prognostic indicator in patients with sepsis treated in the Intensive Care Unit (ICU) at the Dr. Napoleón Dávila Córdova Hospital in Cantón Chone-Manabí during the period January to June 2021. An observational, descriptive, retrospective, cross-sectional, descriptive study was carrying out, the results of which were taken from the Hospital's database in the ICT area. The sample consisted of 28 patients who underwent arterial blood gas analysis during their stay in the ICU. The mean age of the patients was 49 years with an age range of 22-91 years and there were more women than men admitted to the ICU for sepsis. Predominated the patients with unspecified severe sepsis, relative to the number of patients diagnosed with septic shock and ICU stay was longer in patients with septic shock. More than half of the patients presented lactic acidosis, which corresponded to a gasometrical diagnosis of metabolic acidosis, in some cases decompensated and in others partially compensated. More than half of the patients managed to normalize their blood gas values upon discharge from the ICU.La sepsis se define como una respuesta inmunitaria desbalanceada frente a una infección que da lugar a una disfunción orgánica e insuficiencia cardiorrespiratoria que acelera el riesgo de sufrir complicaciones metabólicas. La gasometría arterial en el paciente con sepsis es fundamental para establecer diagnóstico, tratamiento y pronóstico. En este trabajo se caracterizaron los resultados de gasometría arterial incluyendo lactato en los pacientes con sepsis y choque séptico, atendidos en la Unidad de Cuidados Intensivos (UCI) del Hospital Dr. Napoleón Dávila Córdova del cantón Chone, Manabí durante el periodo enero-junio de 2021. Se realizó un estudio observacional, descriptivo, de carácter retrospectivo y de corte transversal de los datos de los 28 pacientes que se atendieron en la UCI en el periodo de estudio, a través de la revisión de la base de datos del hospital. La edad promedio fue de 50 años y hubo más mujeres que hombres. Predominaron los pacientes con sepsis sin foco identificado y la estadía en UCI fue mayor en los pacientes con choque séptico. Más de la mitad de los pacientes presentaron acidosis láctica lo cual correspondió con diagnóstico gasométrico de acidosis metabólica en algunos casos descompensada y en otros parcialmente compensada. Más de la mitad de los pacientes lograron normalizar sus valores de gasometría al egreso de UCI

Lifestyle in undergraduate students and demographically matched controls during the covid-19 pandemic in Spain

Few studies have used a multidimensional approach to describe lifestyle changes among undergraduate students during the COVID-19 pandemic or have included controls. This study aimed to evaluate lifestyle behaviors and mental health of undergraduate students and compare them with an age and sex-matched control group. A cross-sectional web survey using snowball sampling was conducted several months after the beginning of COVID-19 pandemic in Spain. A sample of 221 students was recruited. The main outcome was the total SMILE-C score. Students showed a better SMILE-C score than controls (79.8 +- 8.1 vs. 77.2 +- 8.3; p < 0.001), although these differences disappeared after controlling for covariates. While groups did not differ in the screenings of depression and alcohol abuse, students reported lower rates of anxiety (28.5% vs. 37.1%; p = 0.042). A lower number of cohabitants, poorer self-perceived health and positive screening for depression and anxiety, or for depression only were independently associated (p < 0.05) with unhealthier lifestyles in both groups. History of mental illness and financial difficulties were predictors of unhealthier lifestyles for students, whereas totally/moderate changes in substance abuse and stress management (p < 0.05) were predictors for the members of the control group. Several months after the pandemic, undergraduate students and other young adults had similar lifestyles

Lifestyle in Undergraduate Students and Demographically Matched Controls during the COVID-19 Pandemic in Spain

Few studies have used a multidimensional approach to describe lifestyle changes among undergraduate students during the COVID-19 pandemic or have included controls. This study aimed to evaluate lifestyle behaviors and mental health of undergraduate students and compare them with an age and sex-matched control group. A cross-sectional web survey using snowball sampling was conducted several months after the beginning of COVID-19 pandemic in Spain. A sample of 221 students was recruited. The main outcome was the total SMILE-C score. Students showed a better SMILE-C score than controls (79.8 + 8.1 vs. 77.2 + 8.3; p < 0.001), although these differences disappeared after controlling for covariates. While groups did not differ in the screenings of depression and alcohol abuse, students reported lower rates of anxiety (28.5% vs. 37.1%; p = 0.042). A lower number of cohabitants, poorer self-perceived health and positive screening for depression and anxiety, or for depression only were independently associated (p < 0.05) with unhealthier lifestyles in both groups. History of mental illness and financial difficulties were predictors of unhealthier lifestyles for students, whereas totally/moderate changes in substance abuse and stress management (p < 0.05) were predictors for the members of the control group. Several months after the pandemic, undergraduate students and other young adults had similar lifestyles

Awake Craniotomy and Brain Mapping for Brain Tumor Resection in Pediatric Patients

Brain tumor resection in pediatric patients constitutes a real challenge. In order to improve survival and to preserve neurological function, we will further on describe our experience with awake craniotomy and functional mapping for brain tumor resection in pediatric patients. Although our experience with this technique was relatively short, we did not observe complications, and a gross total resection was successfully achieved in all cases. In the postoperative period we did not find any new deficiency in our patients. We observed functional recovery - motor and sensitive aphasia, motor strength improvement in hemiplegic patients, and recovery of neurodevelopmental milestones during follow-up. In our experience, the use of awake craniotomy and brain mapping for brain tumor resection in pediatric patients is truly safe and reliable

Carbon-sensitive pedotransfer functions for plant available water

Currently accepted pedotransfer functions show negligible effect of management-induced changes to soil organic carbon (SOC) on plant available water holding capacity (θAWHC), while some studies show the ability to substantially increase θAWHC through management. The Soil Health Institute\u27s North America Project to Evaluate Soil Health Measurements measured water content at field capacity using intact soil cores across 124 long-term research sites that contained increases in SOC as a result of management treatments such as reduced tillage and cover cropping. Pedotransfer functions were created for volumetric water content at field capacity (θFC) and permanent wilting point (θPWP). New pedotransfer functions had predictions of θAWHC that were similarly accurate compared with Saxton and Rawls when tested on samples from the National Soil Characterization database. Further, the new pedotransfer functions showed substantial effects of soil calcareousness and SOC on θAWHC. For an increase in SOC of 10 g kg–1 (1%) in noncalcareous soils, an average increase in θAWHC of 3.0 mm 100 mm–1 soil (0.03 m3 m–3) on average across all soil texture classes was found. This SOC related increase in θAWHC is about double previous estimates. Calcareous soils had an increase in θAWHC of 1.2 mm 100 mm–1 soil associated with a 10 g kg–1 increase in SOC, across all soil texture classes. New equations can aid in quantifying benefits of soil management practices that increase SOC and can be used to model the effect of changes in management on drought resilience

Linking soil microbial community structure to potential carbon mineralization: A continental scale assessment of reduced tillage

Potential carbon mineralization (Cmin) is a commonly used indicator of soil health, with greater Cmin values interpreted as healthier soil. While Cmin values are typically greater in agricultural soils managed with minimal physical disturbance, the mechanisms driving the increases remain poorly understood. This study assessed bacterial and archaeal community structure and potential microbial drivers of Cmin in soils maintained under various degrees of physical disturbance. Potential carbon mineralization, 16S rRNA sequences, and soil characterization data were collected as part of the North American Project to Evaluate Soil Health Measurements (NAPESHM). Results showed that type of cropping system, intensity of physical disturbance, and soil pH influenced microbial sensitivity to physical disturbance. Furthermore, 28% of amplicon sequence variants (ASVs), which were important in modeling Cmin, were enriched under soils managed with minimal physical disturbance. Sequences identified as enriched under minimal disturbance and important for modeling Cmin, were linked to organisms which could produce extracellular polymeric substances and contained metabolic strategies suited for tolerating environmental stressors. Understanding how physical disturbance shapes microbial communities across climates and inherent soil properties and drives changes in Cmin provides the context necessary to evaluate management impacts on standardized measures of soil microbial activity