Resolution of type IV singularities in quantum cosmology

We discuss the fate of classical type IV singularities in quantum cosmology. The framework is Wheeler-DeWitt quantization applied to homogeneous and isotropic universes with a perfect fluid described by a generalized Chaplygin gas. Such a fluid can be dynamically realized by a scalar field. We treat the cases of a standard scalar field with positive kinetic energy and of a scalar field with negative energy (phantom field). We first present the classical solutions. We then discuss in detail the Wheeler-DeWitt equation for these models. We are able to give analytic solutions for a special case and to draw conclusions for the general case. Adopting the criterion that singularities are avoided if the wave function vanishes in the region of the classical singularity, we find that type IV singularities are avoided only for particular solutions of the Wheeler-DeWitt equation. We compare this result with earlier results found for other types of singularities.Comment: 10 pages, 4 figures, clarifications include

Pre-inflation from the multiverse: Can it solve the quadrupole problem in the cosmic microwave background?

We analyze a quantized toy model of a universe undergoing eternal inflation using a quantum-field-theoretical formulation of the Wheeler-DeWitt equation. This so-called third quantization method leads to the picture that the eternally inflating universe is converted to a multiverse in which sub-universes are created and exhibit a distinctive phase in their evolution before reaching an asymptotic de Sitter phase. From the perspective of one of these sub-universes, we can thus analyze the pre-inflationary phase that arises naturally. Assuming that our observable universe is represented by one of those sub-universes, we calculate how this pre-inflationary phase influences the power spectrum of the cosmic microwave background (CMB) anisotropies and analyze whether it can explain the observed discrepancy of the power spectrum on large scales, i.e. the quadrupole issue in the CMB. While the answer to this question is negative in the specific model analyzed here, we point out a possible resolution of this issue.Comment: 15 pages, 9 figures. Correction of typos, one figure added. Accepted for publication in European Physical Journal

What if? - Exploring the Multiverse through Euclidean wormholes

We present Euclidean wormhole solutions describing possible bridges within the multiverse. The study is carried out in the framework of the third quantization. The matter content is modelled through a scalar field which supports the existence of a whole collection of universes. The instanton solutions describe Euclidean solutions that connect baby universes with asymptotically de Sitter universes. We compute the tunnelling probability of these processes. Considering the current bounds on the energy scale of inflation and assuming that all the baby universes are nucleated with the same probability, we draw some conclusions about what are the universes more likely to tunnel and therefore undergo a standard inflationary era.Comment: 12 pages, 5 figures. Explanations improved. Version accepted in EPJ

The Intersection of Culturally Responsive Pedagogy and Engineering Design in Secondary STEM

The instructional practices of the engineering design process and culturally responsive pedagogy have each garnered national attention and multiple decades of research. Findings from the respective literature bases call for educators and policymakers to integrate these two pedagogical approaches into K-12 classroom instruction. Scholars have argued that this integration would improve student engagement and academic achievement. There is a significant amount of research that supports the positive student outcomes associated with each approach, yet there remains a dearth of literature that addresses the integration of these two practices into the science and mathematics content areas. The movement around educational reform is rooted in teachers serving as learners; however, understanding how teachers learn and respond to reform is largely overlooked. The present research sought to examine the way in which teachers perceive and define integrated pedagogical approaches upon implementation. The authors utilized a comparative case study design to represent experiences of five secondary math and science teachers enrolled in graduate-level coursework and professional development on culturally responsive pedagogy and the engineering design process. Findings suggest that teachers’ self-reported pedagogical beliefs acted synergistically between the two pedagogical approaches. Subsequently, participating teachers expressed a strong preference towards the enactment of an integrated pedagogy of a culturally responsive engineering design process. The present research offers valuable recommendations for teacher educators, professional development providers, policymakers, and researchers who wish to integrate culturally responsive pedagogy and the engineering design process in math or science K-12 classrooms. The significance of this research underscores the importance of empowering teachers with professional development, around implementation of novel pedagogical approaches, to both shape and inform their beliefs and practices

Enhancing Engineering Identity Among Boys of Color

Black and Brown men continue to be underrepresented in engineering. One explanation for the dearth of Black and Latino men in engineering is that engineering (and STEM) identity often is not inclusive of People of Color. As a result, Black and Brown boys may be less likely to become interested in STEM subjects. The purpose of this study, then, was to investigate how the components of one afterschool engineering program tap into engineering identity formation among fourth- and fifth-grade Black and Brown boys. Leveraging research on the STEM and engineering identity, we argue that the program and its key components play both constructive and protective roles. This study comprises a case study of an afterschool engineering program completing its third year of implementation at three elementary schools. Over four semesters, we recruited approximately 60 students from the three schools and 21 mentors to participate in the study. We collected data via one-on-one interviews, focus groups, and observations. We found that engineering design activities are constructive, offering the young Black and Brown boys opportunities to engage with the work of engineers. The mentors played constructive roles by recognizing the students’ engineering work. The mentors also played a protective role, buffering against identity interference and cultivating a sense of belonging. We conclude by discussing how the findings contribute to existing research on engineering identity and making recommendations for practice

Energization and Start-up of Modular Three-stage Solid State Transformers

Workshop on Control and Modeling for Power Electronics, COMPEL (9th, 2028, Padua

Risk of infection associated with Janus Kinase (JAK) inhibitors and biological therapies in inflammatory intestinal disease and rheumatoid arthritis. Prevention strategies

Patients with certain immune-mediated inflammatory diseases, such as rheumatoid arthritis (RA) and inflammatory bowel disease (IBD), have an increased risk of severe infectious diseases than the general population, which are mainly associated with the immunosuppressive treatments that they receive. These treatments act on the immune system through different mechanisms, causing different degrees of immunosuppression and a variable risk depending on whether the pathogen is a virus, bacteria or fungus. This article reviews the most relevant literature on the subject, which was selected and discussed by a panel of experts. The aim of this article is to review the risk of infections in patients with IBD and RA, and the potential preventive measures. (C) 2021 The Author(s). Published by Elsevier Espana, S.L.U

Diseño del sistema de agua potable en las comunidades El Cristal y El Guineo en Ciudad Darío, departamento de Matagalpa, 2021

El propósito de este estudio fue realizar el diseño de un sistema de agua potable, que prestara un servicio eficiente y continuo durante su periodo de diseño de 20 años, para abastecer a 1086 habitantes en el año 2041, con la finalidad de mejorar las condiciones de vida de los pobladores de las comunidades