Temperatures of quiescent prominences measured from hydrogen Paschen and CaII IR lines

During 12 to 17 September 1983 a number of prominences were observed with the McMatch solar telescope of National Solar Observatories, using the Fourier transform spectrometer with a InSb detector (Brault 1979). The present study refers to three prominences observed 13 and 14 September. Prominence A: Large quiescent prominence at S28 E90 Prominence B. Stable prominence in weakly enhanced magnetic region at about NO8 E90 Prominence C: Quiescent prominence at N30 E90. Spectra were obtained at a total of 15 different locations in the three prominences in the wavelength range lambda, lambda 7740 to 14,000 Angstroms. The observed differences between T sub exc and T sub kin are hardly significant. Researchers conclude that the two methods for temperature determination when applied to optically thin lines give reasonably consistent results, i.e., the population of the excited levels of hydrogen is collisionally controlled. The well known increase in T and V towards the edge of equiescent prominences (Hirayama 1964) is not corroborated by the present data. One explanation for this could be that prominence A is atypical. The optical thickness of prominence emission lines tends to increase from center to edges as demonstrated by the case of He I lambda 10830 angstroms. If line opacity plays a significant role in earlier center to edge determinations of T and V, a smaller variation would be expected from measurements in optically thin lines, such as in the present case

On the Verdet constant and Faraday rotation for graphene-like materials

We present a rigorous and rather self-contained analysis of the Verdet constant in graphene- like materials. We apply the gauge-invariant magnetic perturbation theory to a nearest- neighbour tight-binding model and obtain a relatively simple and exactly computable formula for the Verdet constant, at all temperatures and all frequencies of sufficiently large absolute value. Moreover, for the standard nearest neighbour tight-binding model of graphene we show that the transverse component of the conductivity tensor has an asymptotic Taylor expansion in the external magnetic field where all the coefficients of even powers are zero.Comment: 23 pages, 4 figures, revised versio

2019 Veteran\u27s Day

I am honored to join you all on Veteran’s Day. I hope you’ve deduced by my uniform, and my being here that I am in the military, and a veteran myself. I am married to a veteran and I am the child of veterans. This day is near and dear to my heart, and dare I say it’s a bit of a family tradition

An agentic perspective on teachers’ enactment of professional digital competence

Understanding digital competence in teaching is challenging because technology and teachers’ workdays are moving targets. Previous research suggests using professional digital competence (PDC) as an approach for better understanding how teachers develop a deep understanding of technology, learning processes and subjects. Accordingly, inspired by a short-term design-based research methodology, a project was conceived to have a group of teachers and teacher educators collaborate on developing digital teaching environments using Microsoft Class Teams and OneNote Class Notebook at a lower secondary school in Norway. To investigate the outcomes, this paper adopts an agentic socio-cultural perspective to examine how the teachers enacted digital teaching environments to develop PDC. The results show that the teachers employed negotiation strategies and used different material and immaterial resources in their local school contexts to enact digital teaching environments. The study suggests adding new research to two emerging and relevant research streams—teachers’ digital competence and Microsoft Class Teams and the OneNote Class Notebook—by emphasising a strong human-centric agency approach and that teachers’ digital competence can be made visible through acts of collaboration.publishedVersio

Optical Hall conductivity in bulk and nanostructured graphene beyond the Dirac approximation

We present a perturbative method for calculating the optical Hall conductivity in a tight-binding framework based on the Kubo formalism. The method involves diagonalization only of the Hamiltonian in absence of the magnetic field, and thus avoids the computational problems usually arising due to the huge magnetic unit cells required to maintain translational invariance in presence of a Peierls phase. A recipe for applying the method to numerical calculations of the magneto-optical response is presented. We apply the formalism to the case of ordinary and gapped graphene in a next-nearest neighbour tight-binding model as well as graphene antidot lattices. In both case, we find unique signatures in the Hall response, that are not captured in continuum (Dirac) approximations. These include a non-zero optical Hall conductivity even when the chemical potential is at the Dirac point energy. Numerical results suggest that this effect should be measurable in experiments.Comment: 7 pages, 4 figures, accepted in Physical Review

Propagating slow magnetoacoustic waves in coronal loops observed by Hinode/EIS

We present the first Hinode/EIS observations of 5 min quasi-periodic oscillations detected in a transition-region line (He II) and five coronal lines (Fe X, Fe XII, Fe XIII, Fe XIV, and Fe XV) at the footpoint of a coronal loop. The oscillations exist throughout the whole observation, characterized by a series of wave packets with nearly constant period, typically persisting for 4-6 cycles with a lifetime of 20-30 min. There is an approximate in-phase relation between Doppler shift and intensity oscillations. This provides evidence for slow magnetoacoustic waves propagating upwards from the transition region into the corona. We find that the oscillations detected in the five coronal lines are highly correlated, and the amplitude decreases with increasing temperature. The amplitude of Doppler shift oscillations decrease by a factor of about 3, while that of relative intensity decreases by a factor of about 4 from Fe X to Fe XV. These oscillations may be caused by the leakage of the photospheric p-modes through the chromosphere and transition region into the corona, which has been suggested as the source for intensity oscillations previously observed by TRACE. The temperature dependence of the oscillation amplitudes can be explained by damping of the waves traveling along the loop with multithread structure near the footpoint. Thus, this property may have potential value for coronal seismology in diagnostic of temperature structure in a coronal loop.Comment: 13 pages, 11 color figures, 4 tables, Astrophys.J, May 2009 - v696 issue, (in press

An integrated network approach identifies the isobutanol response network of Escherichia coli

Isobutanol has emerged as a potential biofuel due to recent metabolic engineering efforts. Here we used gene expression and transcription network connectivity data, genetic knockouts, and network component analysis (NCA) to map the initial isobutanol response network of Escherichia coli under aerobic conditions. NCA revealed profound perturbations to respiration. Further investigation showed ArcA as an important mediator of this response. Quinone/quinol malfunction was postulated to activate ArcA, Fur, and PhoB in this study. In support of this hypothesis, quinone-linked ArcA and Fur target expressions were significantly less perturbed by isobutanol under fermentative growth whereas quinol-linked PhoB target expressions remained activated, and isobutanol impeded growth on glycerol, which requires quinones, more than on glucose. In addition, ethanol, n-butanol, and isobutanol response networks were compared. n-Butanol and isobutanol responses were qualitatively similar, whereas ethanol had notable induction differences of pspABCDE and ndh, whose gene products manage proton motive force. The network described here could aid design and comprehension of alcohol tolerance, whereas the approach provides a general framework to characterize complex phenomena at the systems level

Il punto di vista degli insegnanti sul miglioramento delle competenze digitali professionali partecipando a TeachMeet

This study examines teachers’ experiences in fostering professional digital competence (PDC) by participating in TeachMeet. TeachMeet are bottom-up professional development events where teachers meet to share pedagogical ideas about teaching and learning using digital technology. The study also examines how this participation may nurture teachers’ transformative digital agency as competent digital practitioners. The study employs qualitative methods, drawing on data from open-ended questionnaire answers (n=36) and five in-depth interviews. Thematic analysis is performed by taking an inductive approach to identify themes and drawing on the Norwegian PDC Framework for Teachers as the analytical lens. The findings reveal that the teachers consider participation in TeachMeet useful for the development of their PDC and participation may nurture teachers’ transformative digital agency. These findings have implications for facilitating teachers’ continuing professional development by focussing not only on their pedagogical and technological competencies but also their agentic capacities.publishedVersio

EUV Sunspot Plumes Observed with SOHO

Bright EUV sunspot plumes have been observed in five out of nine sunspot regions with the Coronal Diagnostic Spectrometer -- CDS on SOHO. In the other four regions the brightest line emissions may appear inside the sunspot but are mainly concentrated in small regions outside the sunspot areas. These results are in contrast to those obtained during the Solar Maximum Mission, but are compatible with the Skylab mission results. The present observations show that sunspot plumes are formed in the upper part of the transition region, occur both in magnetic unipolar-- and bipolar regions, and may extend from the umbra into the penumbra.Comment: 8 pages, 3 figures, to be published in ApJ Letter

Goals à la carte : selective translation of the Sustainable Development Goals in strategic municipal planning in Norway

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