Effects of a thermal inversion experiment on STEM students learning and application of damped harmonic motion

There are diverse teaching methodologies to promote both collaborative and individual work in undergraduate physics courses. However, few educational studies seek to understand how students learn and apply new knowledge through open-ended activities that require mathematical modeling and experimentation focused on environmental problems. In this work, we propose a novel home experiment to simulate the dynamics of a particulate under temperature inversion and model it as damped harmonic motion. Twenty six first year students enrolled in STEM majors answered six qualitative questions after designing and developing the experiment. These questions helped analyze the students epistemological beliefs about their learning process of physics topics and its applications. Results showed that this type of open-ended experiments could facilitate the students understanding of physics phenomena. In addition, this experiment showed that it could help physics professors to promote students epistemological development by giving their students the opportunity to search for different sources of knowledge and becoming self-learners instead of looking at the professor as the epistemological authority. At the end, students described this activity as a positive experience that helped them realize alternative ways to apply physics topics in different contexts of their environment.Comment: 23 pages, 5 figure

A label free disposable device for rapid isolation of rare tumor cells from blood by ultrasounds

The use of blood samples as liquid biopsy is a label-free method for cancer diagnosis that offers benefits over traditional invasive biopsy techniques. Cell sorting by acoustic waves offers a means to separate rare cells from blood samples based on their physical properties in a label-free, contactless and biocompatible manner. Herein, we describe a flow-through separation approach that provides an efficient separation of tumor cells (TCs) from white blood cells (WBCs) in a microfluidic device, "THINUS-Chip" (Thin-Ultrasonic-Separator-Chip), actuated by ultrasounds. We introduce for the first time the concept of plate acoustic waves (PAW) applied to acoustophoresis as a new strategy. It lies in the geometrical chip design: different to other microseparators based on either bulk acoustic waves (BAW) or surface waves (SAW, SSAW and tSAW), it allows the use of polymeric materials without restrictions in the frequency of work. We demonstrate its ability to perform high-throughput isolation of TCs from WBCs, allowing a recovery rate of 84%±8% of TCs with a purity higher than 80% and combined viability of 85% at a flow rate of 80 µL/min (4.8 mL/h). The THINUS-Chip performs cell fractionation with low-cost manufacturing processes, opening the door to possible easy printing fabrication

Dielectric spectroscopy and application of mixing models describing dielectric dispersion in clay minerals and clayey soils

The number of sensors, ground-based and remote, exploiting the relationship between soil dielectric response and soil water content continues to grow. Empirical expressions for this relationship generally work well in coarse-textured soils but can break down for high-surface area and intricate materials such as clayey soils. Dielectric mixing models are helpful for exploring mechanisms and developing new understanding of the dielectric response in porous media that do not conform to a simple empirical approach, such as clayey soils. Here, we explore the dielectric response of clay minerals and clayey soils using the mixing model approach in the frequency domain. Our modeling focuses on the use of mixing models to explore geometrical effects. New spectroscopic data are presented for clay minerals (talc, kaolinite, illite and montmorillonite) and soils dominated by these clay minerals in the 1 MHz–6 GHz bandwidth. We also present a new typology for the way water is held in soils that we hope will act as a framework for furthering discussion on sensor design. We found that the frequency-domain response can be mostly accounted for by adjusting model structural parameters, which needs to be conducted to describe the Maxwell–Wagner (MW) relaxation effects. The work supports the importance of accounting for soil structural properties to understand and predict soil dielectric response and ultimately to find models that can describe the dielectric–water content relationship in fine-textured soils measured with sensors.The authors wish to thank Sally Logsdon for supplying the soils from USDA

Proyecto LIFE Ammonia Trapping: planta piloto para la captura de amoniaco del purín

Las emisiones de amoniaco son uno de los contaminantes más importantes generados en las actividades agrícolas y ganaderas, estos sectores son los responsables de más del 93% de las emisiones de amoniaco en la UE. Dichas emisiones causan problemas medioambientales y de salud, por lo que la Unión Europea trata de reducirlas desde el año 2010 con la Directiva NEC 2001/81/CE sobre techos de emisiones, la cual ha sido revisada a través de la Directiva 2016/2284/EU. El proyecto Life Ammonia Trapping tiene como principal objetivo reducir las emisiones de amoniaco de granjas porcinas y avícolas, a través de la aplicación de una nueva tecnología de membranas permeables a los gases. En este trabajo se presentan resultados del primer estudio a escala piloto con la tecnología de membranas permeables a los gases, llevado a cabo en una granja porcina. De acuerdo con estos datos se ha conseguido una recuperación de amoníaco del 66,2% en el prototipo estudiado

Eliminación de arsénico en aguas subterráneas: diseño tecnológico para su aplicación en zonas rurales

En el marco de un proyecto general dirigido al tratamiento de aguas subterráneas para consumo, conteniendo valores de arsénico superiores a los establecidos por la OMS (10 μg L-1), se ha abordado, el diseño de una tecnología de procesamiento de aguas para ser instalada en zonas rurales y peri-urbanas, carentes de aguas de red. Se ha logrado la construcción de equipos de tratamiento de tipo discontinuo, de simple construcción y facilidad operativa, en base a las condiciones locales, particularmente, las condiciones fisicoquímicas de las aguas. Se emplea como adsorbente mineral de arcilla rico en hierro, de bajo costo y abundante en la provincia de Buenos Aires. El proceso, que permite trabajar con volúmenes de entre 2000 y 4000 L de agua/ etapa, se basa en el empleo de adsorbentes minerales de bajo costo y amplia distribución en la provincia de Buenos Aires. Se instalaron hasta el presente tres plantas en escuelas de zonas rurales de la Provincia de Buenos Aires, y está en etapa de construcción una planta en la Escuela Inchausti, perteneciente a la UNLP, sita en la localidad de 25 de Mayo, asegurando la provisión de agua en los establecimientos educativos y poblaciones cercanas. En esta comunicación se reportan datos técnicos relativos al funcionamiento y parámetros operacionales de las plantas. El primer prototipo instalado lleva más de 2 años de uso continuo sin recambio de la carga de adsorbente; ha procesado 400 mil litros de agua cuya concentración original de As, del orden de las 200 μg L-1, llega a valores de 10 μg L-1.A technological design for water processing for rural and peri-urban areas with no drinking water was created as part of a general project aimed at treating groundwater containing arsenic values higher than those established by the WHO (10 μg L-1) for consumption. The construction of treatment equipments (batch type) is simple and operatively easy. The adsorbent is a low-cost, Fe-rich and clay mineral that is abundant in Buenos Aires Province. Local conditions of water, particularly physicochemical properties, have been taken into account to adapt the process which operates with volumes from 2000 to 4000 L of water/stage. Three plants have been installed in schools of rural areas of Buenos Aires Province. A new plant is being constructed in Inchausti School of the UNLP located in 25 de Mayo city. The equipments provide water in educational buildings and nearby populations. Some technical data about the process are reported in this communication. It is necessary to mention that the first prototype, which was installed two years ago, has been continuously used without having replaced the adsorbent so far. It has processed 400000 L of water whose original concentration of arsenic was around 200 μg L-1 that now reaches values lower than 10 μg L-1

Mindfulness-based program for anxiety and depression treatment in healthcare professionals: A pilot randomized controlled trial

In primary health care, the work environment can cause high levels of anxiety and depression, triggering relevant expert and individual change. Mindfulness-Based Stress Reduction (MBSR) programs reduce signs of anxiety and depression. The purpose of this sub-analysis of the total project, was to equate the effectiveness of the standard MBSR curriculum with the abbreviated version in minimizing anxiety and depression. This randomized controlled clinical trial enrolled 112 mentors and resident specialists from Family and Community Medicine and Nurses (FCMN), distributed across six teaching units (TU) of the Spanish National Health System (SNHS). Experimental group participants received a MBRS training (abbreviated/standard). Depression and anxiety levels were measured with the Goldberg Anxiety and Depression Scale (GADS) at three different time periods during the analysis: before (pre-test) and after (post-test) participation, as well as 3 months after the completion of intervention. Taking into account the pre-test scores as the covariate, an adjusted analysis of covariance (ANCOVA) showed significant depletion in anxiety and depression in general (F (2.91) = 4.488; p = 0.014; ¿2 = 0.090) and depression in particular (F (2, 91) = 6.653; p = 0.002; ¿2 = 0.128 at the post-test visit, maintaining their effects for 3 months (F (2.79) = 3.031; p = 0.050; ¿2 = 0.071—F (2.79) = 2.874; p = 0.049; ¿2 = 0.068, respectively), which is associated with the use of a standard training program. The abbreviated training program did not have a significant effect on the level of anxiety and depression. The standard MBSR training program had a positive effect on anxiety and depression and promotes long-lasting effects in tutors and resident practitioners. New research is needed to demonstrate the effectiveness of abbreviated versions of training programs. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Desarrollo de recubrimientos comestibles con aditivos alimentarios antifúngicos para el control de Penicilliun spp. y la conservación de mandarina ‘Orri’

Recubrimientos comestibles compuestos a base de goma arábiga (AG), hidroxipropilmetilcelulosa (HPMC) o almidón de patata (S) en combinación con cera de abeja (BW), gliceril monoestearato (GME) o cera de carnauba (CW) fueron formulados con dos aditivos alimentarios o sales GRAS (‘generally recognized as safe’) con propiedades antifúngicas: benzoato de sodio (SB, 2% p/p) o sorbato de potasio (PS, 2% p/p). Los efectos de los recubrimientos sobre la calidad de mandarinas ‘Orri’ se evaluaron tras un almacenamiento a 20 ºC de 14 días. Posteriormente, se evaluó la actividad curativa de los recubrimientos seleccionados en el control de las podredumbres verde y azul, causadas respectivamente por Penicillium digitatum y P. italicum, en mandarinas inoculadas artificialmente 24 h antes e incubadas a 20 ºC durante 7 días. Las emulsiones a base de AG con BW y CW mostraron valores bajos de viscosidad (4,54-26,34 mPa·s), pero aumentaron la pérdida de peso (WL) de las mandarinas. Las formulaciones a base de HPMC-BW y HPMC-CW fueron estables, con valores de viscosidad de 18 mPa·s, pero aportaron poco brillo. El recubrimiento a base de S-GME, con viscosidad de 58,91 mPa·s, redujo significativamente la WL sin afectar negativamente la apariencia de la fruta. La adición de PS a los recubrimientos aumentó significativamente la WL del fruto. El recubrimiento S-GME con 2% SB fue el más efectivo para controlar las podredumbres causadas por Penicillium spp. y redujo la incidencia y la severidad de las enfermedades en un 40 y 35%, respectivamente. Además, redujo también la WL de las mandarinas durante el almacenamiento a 20 ºC, lo que demuestra su potencial para la conservación de la mandarina ‘Orri’ en poscosecha

A suppressed contribution of low mass galaxies to reionization due to supernova feedback

Motivated by recent observations of the star formation rate density function out to z~7, we describe a simple model for the star formation rate density function at high redshift based on the extended Press-Schechter formalism. This model postulates a starburst following each major merger, lasting for a time t_SF and converting at most f_star of galactic gas into stars. We include a simple physical prescription for supernovae feedback that suppresses star formation in low mass galaxies. Constraining t_SF and f_star to describe the observed star formation rate density at high redshifts, we find that individual starbursts were terminated after a time t_SF~10^7 years. This is comparable to the main-sequence lifetimes of supernova progenitors, indicating that high redshift starbursts are quenched once supernovae feedback had time to develop. High redshift galaxies convert ~10% of their mass into stars for galaxies with star formation rates above ~1 solar mass per year, but a smaller fraction for lower luminosity galaxies. Our best fit model successfully predicts the observed relation between star formation rate and stellar mass at z>~4, while our deduced relation between stellar mass and halo mass is also consistent with data on the dwarf satellites of the Milky Way. We find that supernovae feedback lowers the efficiency of star formation in the lowest mass galaxies and makes their contribution to reionization small. As a result, photo-ionization feedback on low mass galaxy formation does not significantly affect the reionization history. Using a semi-analytic model for the reionization history, we infer that approximately half of the ionizing photons needed to complete reionization have already been observed in star-forming galaxies.Comment: 16 pages, 10 figures. Submitted to MNRA

Stellar populations of galaxies in the ALHAMBRA survey up to z∼1z \sim 1. I. MUFFIT: A Multi-Filter Fitting code for stellar population diagnostics

We present MUFFIT, a new generic code optimized to retrieve the main stellar population parameters of galaxies in photometric multi-filter surveys, and we check its reliability and feasibility with real galaxy data from the ALHAMBRA survey. Making use of an error-weighted $\chi^2$-test, we compare the multi-filter fluxes of galaxies with the synthetic photometry of mixtures of two single stellar populations at different redshifts and extinctions, to provide through a Monte Carlo method the most likely range of stellar population parameters (mainly ages and metallicities), extinctions, redshifts, and stellar masses. To improve the diagnostic reliability, MUFFIT identifies and removes from the analysis those bands that are significantly affected by emission lines. We highlight that the retrieved age-metallicity locus for a sample of $z \le 0.22$ early-type galaxies in ALHAMBRA at different stellar mass bins are in very good agreement with the ones from SDSS spectroscopic diagnostics. Moreover, a one-to-one comparison between the redshifts, ages, metallicities, and stellar masses derived spectroscopically for SDSS and by MUFFIT for ALHAMBRA reveals good qualitative agreements in all the parameters. In addition, and using as input the results from photometric-redshift codes, MUFFIT improves the photometric-redshift accuracy by $\sim 10$-$20\%$, and it also detects nebular emissions in galaxies, providing physical information about their strengths. Our results show the potential of multi-filter galaxy data to conduct reliable stellar population studies with the appropiate analysis techniques, as MUFFIT.Comment: 31 pages, 18 figures, accepted for publication in A&