Intermediate range order in (Fe,Al) silicate network glasses: a neutron diffraction and EPSR modeling investigation

The local structural environment and the spatial distribution of iron and aluminum ions in sodosilicate glasses with composition NaFexAl1-xSi2O6 (x = 1, 0.8, 0.5 and 0) is studied by high-resolution neutron diffraction combined with structural modeling using the Empirical Potential Structure Refinement (EPSR) code. This work gives evidence of differences in the structural behavior of Al3+ and Fe3+, which are both often considered to act as network formers in charge-balanced compositions. The short-range environment and the structural role of the two cations are not composition dependent, and hence the structure of intermediate glasses can then be seen as a mixture of the structures of the two end-members. All Al3+ is 4-coordinated for a distance d[4]Al3+-O=1.76$\pm$0.01{\AA}. The high-resolution neutron data allows deciphering between two populations of Fe. The majority of Fe3+ is 4-coordinated (d[4]Fe3+-O=1.87$\pm$0.01{\AA}) while the remaining Fe3+ and all Fe2+ (~12% of total Fe) are 5-coordinated (d[5]Fe-O=2.01$\pm$0.01{\AA}). Both AlO4 and FeO4 are randomly distributed and connected with the silicate network in which they share corners with SiO4 tetrahedra, in agreement with a network-forming role of those species. On the contrary FeO5 tends to form clusters and to share edges with each other. 5-coordinated Fe is interpreted as network modifier and it turns out that, even if this coordination number is rare in crystals, it is more common in glasses in which they can have a key role on physical properties

FlatSat workshops teaching fundamental electronics skills for CubeSat building

The University of Nottingham (UoN) recently established its own CubeSat programme, with the team commencing design, construction and testing of the first CubeSats in late 2020. However, one major challenge encountered was a common lack of practical applied electronics skills amongst students. This was repeatedly noted by students as a major obstacle to project success in progress reviews for WormSail, our first CubeSat project. Notably, these sorts of skills are also an area of common concern for young workers and employers in the UK Space Sector. This skill gap existed despite the student team coming from a variety of STEM (Science, Technology, Engineering and Math) undergraduate backgrounds, including physics, computer science, and aerospace and mechanical engineering. With insufficient time to recruit students with electronic engineering backgrounds, it proved difficult to find "all-rounders" to join the team with the broad range of skills required for the project. One advantage that several students had however was their experience from informal hobbies involving Arduino and Raspberry Pi (RPi) based microcontroller electronics. These were found to endow highly transferrable skills, with these members providing significant contributions to the team through their skills and teaching. Team members found these so useful, that the “FlatSat” programme was set up to provide electronics teaching resources for new members of the CubeSat team. Sessions within the programme could be planned and delivered by the experienced team members, and hence be targeted to include applicable, referrable, and important skills and knowledge for building CubeSats. Through developing these resources, the team realised it may be beneficial to include this programme in taught modules offered in the Faculty of Engineering, to enhance practical skills for all students enrolled in these modules. This paper is intended to overview the work carried out in developing the FlatSat teaching workshop, and highlight the resources and their benefits to groups including other higher education space module conveners, developing CubeSat teams, School and further education teachers, STEM Outreach Coordinators, and general hobbyists. It is hoped that boosting confidence with such in-demand skills will be of great benefit to learners. We will also review case studies of the first large-scale workshop sessions and outline plans for future developments, particularly taking into consideration the feedback of demonstrators, students, and observers to the workshop

Distribution of Isolated Volcanoes on the Flanks of the East Pacific Rise, 15.3°-20°S

Volcanic constructions, not associated with seamount (or volcano) chains, are abundant on the flanks of the East Pacific Rise (EPR) but are rare along the axial high. The distribution of isolated volcanoes, based on multibeam bathymetric maps, is approximately symmetric about the EPR axis. This symmetry contrasts with the asymmetries in the distribution of volcano chains (more abundant on the west flank), the seafloor subsidence rates (slower on the west flank), and the distribution of plate-motion-parallel gravity lineaments (more prominento nthe west flank). Most of the isolated volcanoes complete their growth within -14 km of the axis on crust younger than 0.2 Ma, while seamount chain volcanoes continue to be active on older crust. Volcanic edifices within 6 km of the ridge axis are primarily found adjacent to axial discontinuities, suggesting a more sporadic magma supply and stronger lithosphere able to support volcanic constructions near axial discontinuities. The volume of isolated near-axis volcanoes correlates with ridge axis cross-sectional area, suggesting a link between the magma budget of the ridge and the eruption of near-axis volcanoes. Within the study area, off-axis volcanic edifices cover at least 6% of the seafloor and contribute more than 0.2% to the volume of the crust. The inferred width of the zone where isolated volcanoes initially form increases with spreading rate for the Mid-Atlantic Ridge (\u3c4 km), northern EPR (\u3c20 km), and southern EPR(\u3c28 km), so that isolated volcanoes form primarily on lithosphere younger than 0.2 Ma (\u3c 4-6 km brittle thickness), independent of spreading rate. This suggests some form of lithospheric control on the eruption of isolated off-axis volcanoes due to brittle thickness, increased normal stresses across cracks impeding dike injection, or thermal stresses within the newly forming lithosphere

Infrared luminosities and aromatic features in the 24 μm flux-limited sample of 5muses

We study a 24 μm selected sample of 330 galaxies observed with the infrared spectrograph for the 5 mJy Unbiased Spitzer Extragalactic Survey. We estimate accurate total infrared luminosities by combining mid-IR spectroscopy and mid-to-far infrared photometry, and by utilizing newempirical spectral templates from Spitzer data. The infrared luminosities of this sample range mostly from 10^9 L_⊙ to 10^(13.5) L_⊙,with 83% in the range 10^(10) L_⊙ < L_(IR) < 10^(12) L_⊙. The redshifts range from 0.008 to 4.27, with a median of 0.144. The equivalent widths of the 6.2 μm aromatic feature have a bimodal distribution, probably related to selection effects. We use the 6.2μm polycyclic aromatic hydrocarbon equivalent width (PAH EW) to classify our objects as starburst (SB)-dominated (44%), SB-AGN composite (22%), and active galactic nucleus (AGN)-dominated (34%). The high EW objects (SB-dominated) tend to have steeper mid-IR to far-IR spectral slopes and lower L_(IR) and redshifts. The low EW objects (AGN-dominated) tend to have less steep spectral slopes and higher L_(IR) and redshifts. This dichotomy leads to a gross correlation between EW and slope, which does not hold within either group. AGN-dominated sources tend to have lower log(L_(PAH7.7 μm)/L_(PAH11.3 μm)) ratios than star-forming galaxies, possibly due to preferential destruction of the smaller aromatics by the AGN. The log(L_(PAH7.7 μm)/L_(PAH11.3 μm)) ratios for star-forming galaxies are lower in our sample than the ratios measured from the nuclear spectra of nearby normal galaxies, most probably indicating a difference in the ionization state or grain size distribution between the nuclear regions and the entire galaxy. Finally, we provide a calibration relating the monochromatic continuum or aromatic feature luminosity to L_(IR) for different types of objects

A map series of the Southern East Pacific Rise and its flanks, 15� S to 19� S

Four large-scale bathymetric maps of the Southern East Pacific Rise and its flanks between 15 S and 19 S display many of the unique features of this superfast spreading environment, including abundant seamounts (the Rano Rahi Field), axial discontinuities, discontinuity migration, and abyssal hill variation. Along with a summary of the regional geology, these maps will provide a valuable reference for other sea-going programs on- and off-axis in this area, include the Mantle ELectromagnetic and Tomography (MELT) experiment

Dynamics of coupled bosonic systems with applications to preheating

Coupled, multi-field models of inflation can provide several attractive features unavailable in the case of a single inflaton field. These models have a rich dynamical structure resulting from the interaction of the fields and their associated fluctuations. We present a formalism to study the nonequilibrium dynamics of coupled scalar fields. This formalism solves the problem of renormalizing interacting models in a transparent way using dimensional regularization. The evolution is generated by a renormalized effective Lagrangian which incorporates the dynamics of the mean fields and their associated fluctuations at one-loop order. We apply our method to two problems of physical interest: (i) a simple two-field model which exemplifies applications to reheating in inflation, and (ii) a supersymmetric hybrid inflation model. This second case is interesting because inflation terminates via a smooth phase transition which gives rise to a spinodal instability in one of the fields. We study the evolution of the zero mode of the fields and the energy density transfer to the fluctuations from the mean fields. We conclude that back reaction effects can be significant over a wide parameter range. In particular for the supersymmetric hybrid model we find that particle production can be suppressed due to these effects.Comment: 23 pages, 16 eps-figures, minor changes in the text, references added, accepted for publication in PR

On the gravitational production of superheavy dark matter

The dark matter in the universe can be in the form of a superheavy matter species (WIMPZILLA). Several mechanisms have been proposed for the production of WIMPZILLA particles during or immediately following the inflationary epoch. Perhaps the most attractive mechanism is through gravitational particle production, where particles are produced simply as a result of the expansion of the universe. In this paper we present a detailed numerical calculation of WIMPZILLA gravitational production in hybrid-inflation models and natural-inflation models. Generalizing these findings, we also explore the dependence of the gravitational production mechanism on various models of inflation. We show that superheavy dark matter production seems to be robust, with Omega_X h^2 ~ (M_X / (10^11 GeV))^2 (T_RH / (10^9 GeV)), so long as M_X < H_I, where M_X is the WIMPZILLA mass, T_RH is the reheat temperature, and H_I is the expansion rate of the universe during inflation.Comment: 26 pages, 7 figures; LaTeX; submitted to Physical Review D; minor typographical error correcte

La santé psychologique et la conciliation travail-famille des infirmières en soins ambulatoires à l’ère de la COVID-19 : résultats d’une enquête

Introduction: The COVID-19 pandemic impacted nurses’ psychological health and work-family balance, including in ambulatory care settings. The results presented in this article are part of a study aiming to describe and contextualize the psychological health and changes in nurses’ follow-up practices in Quebec (Canada) during the COVID-19 pandemic. Objective: Explore and describe factors that influenced ambulatory care nurses’ psychological health and work-family balance during the first wave of the COVID-19 pandemic. Methods: Exploratory mixed data cross-sectional study using the SurveyMonkey platform. We collected data from July 2020 to September 2020. The target population comprised all practicing nurses in Quebec whose clinical activities included the follow-up of ambulatory patients, 200 of whom completed the survey.&nbsp; Results: Multiple linear regression models indicated that anxiety (GAD-7 scores) and depressive symptoms (PHQ-9 scores) were associated with younger age, living alone, worries about transmitting COVID-19, and feeling that one’s work was not coherent with one’s values. Work-family balance was considered more difficult than before the pandemic by 54.5 % of participants. Factors perceived as influencing work-family balance were either related to work conditions (e.g., schedule and time at work, access to work from home, redeployment to another work setting), to family-related responsibilities/tasks or were specific to the pandemic. Discussion and conclusion: Apart from age, the feeling that one’s work was not coherent with their values was the only variable correlated with both GAD-7 and PHQ-9 in multivariate models. Further research should investigate the relationships between sense of coherence, psychological health, and work conditions like schedule flexibility and access to work from home.Introduction : La pandémie a eu des répercussions sur la santé psychologique et la conciliation travail-famille des infirmières, y compris dans les milieux de soins ambulatoires. Les résultats présentés dans cet article font partie d’une étude visant à décrire et contextualiser la santé psychologique et l’évolution des pratiques de suivi infirmier au Québec (Canada) lors de la pandémie de COVID-19. Objectif : Explorer et décrire les facteurs qui ont influencé la santé psychologique et la conciliation travail-famille des infirmières en soins ambulatoires pendant la première vague de la pandémie de COVID-19. Méthodes&nbsp;: Enquête exploratoire avec données mixtes par le biais de la plateforme SurveyMonkey. Les données ont été collectées de juillet 2020 à septembre 2020. La population cible était toutes les infirmières du Québec dont les activités cliniques incluaient le suivi de patients ambulatoires&nbsp;; 200 infirmières ont participé. Résultats : Les modèles de régression ont indiqué que les symptômes anxieux (scores au GAD-7) et dépressifs (scores au PHQ-9) étaient associés à un plus jeune âge, au fait de vivre seul, aux inquiétudes concernant la transmission de la COVID-19 et au sentiment que son travail n’était pas cohérent avec ses valeurs. La conciliation travail-famille était jugée plus difficile qu’avant la pandémie par 54,5 % des participants. Les facteurs perçus comme l’influençant étaient soit liés aux conditions de travail (p. ex., horaire et temps de travail, télétravail, délestage), aux tâches familiales, ou étaient spécifiques à la pandémie. Discussion et conclusion : Outre l’âge, le sentiment que son travail n’était pas cohérent avec ses valeurs était la seule variable corrélée à la fois avec le GAD-7 et le PHQ-9. Les futures recherches devraient s’intéresser à la relation entre le sentiment de cohérence, la santé psychologique et les conditions de travail favorables à la conciliation travail-famille