Microscópio alternativo para produção em série para trabalhos práticos com estudantes do ensino fundamental

The teaching of life sciences in elementary school faces a major problem: the lack of materials for laboratory practice. This lack of equipment results in many cases in the transformation of the class into theoretical information routines, discouraging the student to care for nature. The sense of admiration that should be worked with at this level of education is now neglected and the trainee is enchanted with technology and not dedicated to caring for nature. Taking the student to a set of activities that return his taste for nature, especially with the use of alternative microscopy was the objective of the present work. Using alternative materials, especially magnifying glasses from various equipment, three alternative microscopes were assembled, which were tested and worked with teachers of a school to verify their potential use in class. The assembled equipment proved to be efficient for microscopic studies, especially to arouse the student's interest in the subject, with the possibility of even having his own equipment at home and continuing to develop a sense of charm for nature. The increase achieved was 300 times. Possible activity kits were assembled, which are presented in the form of routine work with a microscopy laboratory. The evaluation of the equipment allows the possibility of working disciplines such as biology, chemistry, physics and mathematics in an interdisciplinary manner.O ensino de ciências biológicas no ensino fundamental esbarra num grande problema: a falta de materiais para a prática de laboratório. Esta inexistência de equipamentos resulta em muitos casos na transformação da aula em rotinas de informações teóricas, desestimulando o estudante para o cuidado com a natureza. O sentido de admiração, que deveria ser trabalhado com este nível do ensino passa a ser deixado de lado e o formando acaba por se encantar com a tecnologia e não se dedica ao cuidado com a natureza. Levar o estudante a um conjunto de atividades que lhe devolvam o gosto pela natureza, em especial com o uso de microscopia alternativa foi objetivo do presente trabalho. Com o uso de materiais alternativos, em especial lentes de aumento de equipamentos diversos, foram montados três microscópios alternativos, os quais foram testados e trabalhados com professores de uma escola para verificar o seu uso potencial em classe. Os equipamentos montados se mostraram eficientes para estudos microscópicos, em especial para despertar no aluno o interesse pelo tema, com a possibilidade até dele ter seu próprio equipamento em casa e continuar amadurecendo o desenvolvimento de um sentido de encanto pela natureza. O aumento conseguido foi de 300 vezes. Foram montados kits de atividades possíveis, as quais são apresentadas na forma de rotina de trabalho com laboratório de microscopia. A avaliação do equipamento permite a possibilidade de trabalhar disciplinas como biologia, química, física e matemática de maneira interdisciplinar

Processos de Ensino e Aprendizagem de Biologia no Ensino Remoto Emergencial: Possibilidades de Inovação Pedagógica?

All over the world people are witnessing a new form of social behavior, in this sense, the work strategies and, mainly, the teaching work has been affected. Faced with this scenario, education, in a time of facing COVID-19, comes to understand technology even more as an instrument of solution, adaptation, but also of inequalities. In this context, remote teaching came to replace face-to-face classes, while the pandemic situation lasts. Legislations were modified, ordinances were created, so that teachers could continue with teaching. This work sought to map the elements of innovation in pedagogical practices, carried out by different teachers, during the remote period, which aim to ensure the teaching and learning processes in Biology. To operationalize this study, Grounded Theory was used. The results indicate that, in the view of the research participants, remote teaching is harmful to the teaching and learning processes in Biology, being pointed out as aggravating spatio-temporal, technological and socio-emotional factors. Thus, the data point to remote teaching as a way to meet the need for school contact, but which does not provide significant learning and innovative teaching and learning spaces-times, since pedagogical practices for teaching Biology are not promoting student protagonism, nor guaranteeing the right to learn for students.    Keywords: Meaningful learning. Remote teaching emergency. Pedagogical innovation. Grounded theory. No mundo, todas pessoas estão presenciando uma nova forma de comportamento social, nesse sentido, as estratégias de trabalho e, principalmente, o trabalho docente foi afetado. Frente a este cenário, a educação, em época de enfrentamento à COVID-19, passa a entender ainda mais a tecnologia como um instrumento de solução, adaptação, mas também de desigualdades.  Assim, o ensino remoto veio para substituir as aulas presenciais, enquanto durar a situação de pandemia. Legislações foram modificadas, portarias foram criadas, para que os professores prosseguissem com o ensino. Este trabalho buscou mapear os elementos de inovação nas práticas pedagógicas, executadas por diferentes professoras, durante o período remoto, que se propõem a assegurar os processos de ensino e aprendizagem de conteúdos na área de Biologia. Para operacionalizar este estudo utilizou-se da Teoria Fundamentada nos Dados. Os resultados apontam que, na visão dos participantes da pesquisa, o ensino remoto é prejudicial aos processos de ensino e aprendizagem em Biologia, sendo apontados como agravantes fatores espaço-temporais, tecnológicos e socioemocionais. Deste modo, os dados apontam o ensino remoto como uma forma de suprir a necessidade de contato escolar, mas que não proporciona aprendizagens significativas e espaços-tempos de ensino e aprendizagem inovadores, visto que as práticas pedagógicas para o ensino de Biologia não estão promovendo o protagonismo estudantil, tampouco garantindo o direito à aprendizagem dos estudantes.  Palavras-chave: Aprendizagem significativa. Ensino remoto emergencial. Inovação pedagógica. Teoria fundamentada nos dados

Emission of single and few electrons in XENON1T and limits on light dark matter

Delayed single- and few-electron emissions plague dual-phase time projection chambers, limiting their potential to search for light-mass dark matter. This paper examines the origins of these events in the XENON1T experiment. Characterization of the intensity of delayed electron backgrounds shows that the resulting emissions are correlated, in time and position, with high-energy events and can effectively be vetoed. In this work we extend previous S2-only analyses down to a single electron. From this analysis, after removing the correlated backgrounds, we observe rates <30 events/(electron×kg×day) in the region of interest spanning 1 to 5 electrons. We derive 90% confidence upper limits for dark matter-electron scattering, first direct limits on the electric dipole, magnetic dipole, and anapole interactions, and bosonic dark matter models, where we exclude new parameter space for dark photons and solar dark photons

Application and modeling of an online distillation method to reduce krypton and argon in XENON1T

A novel online distillation technique was developed for the XENON1T dark matter experiment to reduce intrinsic background components more volatile than xenon, such as krypton or argon, while the detector was operating. The method is based on a continuous purification of the gaseous volume of the detector system using the XENON1T cryogenic distillation column. A krypton-in-xenon concentration of (360±60)ppq was achieved. It is the lowest concentration measured in the fiducial volume of an operating dark matter detector to date. A model was developed and fit to the data to describe the krypton evolution in the liquid and gas volumes of the detector system for several operation modes over the time span of 550 days, including the commissioning and science runs of XENON1T. The online distillation was also successfully applied to remove 37Ar after its injection for a low energy calibration in XENON1T. This makes the usage of 37Ar as a regular calibration source possible in the future. The online distillation can be applied to next-generation LXe TPC experiments to remove krypton prior to, or during, any science run. The model developed here allows further optimization of the distillation strategy for future large scale detectors

Double-weak decays of 124Xe and 136Xe in the XENON1T and XENONnT experiments

We present results on the search for two-neutrino double-electron capture (2νECEC) of 124Xe and neutrinoless double-β decay (0νββ) of 136Xe in XENON1T. We consider captures from the K shell up to the N shell in the 2νECEC signal model and measure a total half-life of T2νECEC1/2=(1.1±0.2stat±0.1sys)×1022yr with a 0.87kgyr isotope exposure. The statistical significance of the signal is 7.0σ. We use XENON1T data with 36.16kgyr of 136Xe exposure to search for 0νββ. We find no evidence of a signal and set a lower limit on the half-life of T0νββ1/2>1.2×1024yrat90%CL. This is the best result from a dark matter detector without an enriched target to date. We also report projections on the sensitivity of XENONnT to 0νββ. Assuming a 275kgyr 136Xe exposure, the expected sensitivity is T0νββ1/2>2.1×1025yrat90%CL, corresponding to an effective Majorana mass range of ⟨mββ⟩<(0.19–0.59)eV/c2

Search for New Physics in Electronic Recoil Data from XENONnT

We report on a blinded analysis of low-energy electronic-recoil data from the first science run of the XENONnT dark matter experiment. Novel subsystems and the increased 5.9 tonne liquid xenon target reduced the background in the (1, 30) keV search region to (15.8±1.3) events/(tonne×year×keV), the lowest ever achieved in a dark matter detector and ∼5 times lower than in XENON1T. With an exposure of 1.16 tonne-years, we observe no excess above background and set stringent new limits on solar axions, an enhanced neutrino magnetic moment, and bosonic dark matter

Search for Two-Neutrino Double Electron Capture of 124^{124}Xe with XENON100

Two-neutrino double electron capture is a rare nuclear decay where two electrons are simultaneously captured from the atomic shell. For $^{124}$Xe this process has not yet been observed and its detection would provide a new reference for nuclear matrix element calculations. We have conducted a search for two-neutrino double electron capture from the K-shell of $^{124}$Xe using 7636 kg$\cdot$d of data from the XENON100 dark matter detector. Using a Bayesian analysis we observed no significant excess above background, leading to a lower 90 % credibility limit on the half-life $T_{1/2}>6.5\times10^{20}$ yr. We also evaluated the sensitivity of the XENON1T experiment, which is currently being commissioned, and find a sensitivity of $T_{1/2}>6.1\times10^{22}$ yr after an exposure of 2 t$\cdot$yr.Comment: 6 pages, 4 figure

Removing krypton from xenon by cryogenic distillation to the ppq level

The XENON1T experiment aims for the direct detection of dark matter in a cryostat filled with 3.3 tons of liquid xenon. In order to achieve the desired sensitivity, the background induced by radioactive decays inside the detector has to be sufficiently low. One major contributor is the $\beta$-emitter $^{85}$Kr which is an intrinsic contamination of the xenon. For the XENON1T experiment a concentration of natural krypton in xenon $\rm{^{nat}}$Kr/Xe < 200 ppq (parts per quadrillion, 1 ppq = 10$^{-15}$ mol/mol) is required. In this work, the design of a novel cryogenic distillation column using the common McCabe-Thiele approach is described. The system demonstrated a krypton reduction factor of 6.4$\cdot$10$^5$ with thermodynamic stability at process speeds above 3 kg/h. The resulting concentration of $\rm{^{nat}}$Kr/Xe < 26 ppq is the lowest ever achieved, almost one order of magnitude below the requirements for XENON1T and even sufficient for future dark matter experiments using liquid xenon, such as XENONnT and DARWIN

Search for Two-Neutrino Double Electron Capture of ¹²⁴Xe with XENON100

Two-neutrino double electron capture is a rare nuclear decay where two electrons are simultaneously captured from the atomic shell. For $^{124}$Xe this process has not yet been observed and its detection would provide a new reference for nuclear matrix element calculations. We have conducted a search for two-neutrino double electron capture from the K-shell of $^{124}$Xe using 7636 kg$\cdot$d of data from the XENON100 dark matter detector. Using a Bayesian analysis we observed no significant excess above background, leading to a lower 90 % credibility limit on the half-life $T_{1/2}>6.5\times10^{20}$ yr. We also evaluated the sensitivity of the XENON1T experiment, which is currently being commissioned, and find a sensitivity of $T_{1/2}>6.1\times10^{22}$ yr after an exposure of 2 t$\cdot$yr

Solar Neutrino Detection Sensitivity in DARWIN via Electron Scattering

We detail the sensitivity of the proposed liquid xenon DARWIN observatory to solar neutrinos via elastic electron scattering. We find that DARWIN will have the potential to measure the fluxes of five solar neutrino components: pp, 7Be, 13N, 15O and pep. The precision of the 13N, 15O and pep components is hindered by the double-beta decay of 136Xe and, thus, would benefit from a depleted target. A high-statistics observation of pp neutrinos would allow us to infer the values of the electroweak mixing angle, sin2θw, and the electron-type neutrino survival probability, Pee, in the electron recoil energy region from a few keV up to 200 keV for the first time, with relative precision of 5% and 4%, respectively, with 10 live years of data and a 30 tonne fiducial volume. An observation of pp and 7Be neutrinos would constrain the neutrino-inferred solar luminosity down to 0.2%. A combination of all flux measurements would distinguish between the high- (GS98) and low-metallicity (AGS09) solar models with 2.1–2.5σ significance, independent of external measurements from other experiments or a measurement of 8B neutrinos through coherent elastic neutrino-nucleus scattering in DARWIN. Finally, we demonstrate that with a depleted target DARWIN may be sensitive to the neutrino capture process of 131Xe