Using a PBL perspective in continuing education for science and mathematics lower secondary teachers

For years, the need for inquiry- and problem-based learning (PBL) in primary and lower secondary education, within science and mathematics, has been addressed worldwide and requires support from a range of pedagogical sources. One important basis for such support is continuing teacher education. Thepresent research builds upon data froma nationwide qualitative investigation (HesselholtHenneHansen et al., 2019), conducted as part of a feasibility study aimed at initiating a new STEM (science, technology, engineering, mathematics) graduate teacher programme in Denmark, leading to a Master of Science (MSc)in STEM teaching. The investigation identified continuing education needs of science and mathematics teachers and student teachers. We looked into the results of the qualitative portion of the feasibility study and investigated whether and how problem-based learning was being emphasized as comprising desirablecontent areas for continuing teacher education. Data were collected from 35 group interviews with 66 respondents: teachers from public and private schools, and teacher students. The results showed that PBL stands out as a desirable focus area. Other student teachers expressed an interest in including didacticbased topics that are related to PBL, e.g. differentiated teaching, engineering design, technology, and information communication technology [ICT] within STEM education. Furthermore, respondents expressed their desire for collaboration with other subjects (e.g. Danish and social sciences) ininterdisciplinary teaching and, as well, the opportunity to immerse themselvesin academic topics such as education for sustainability, climate education, technology, and including specific experiences with applied science, mathematics and recent research. Without being able to make a quantitative statement, it must also be mentioned that some teachers expressed no need or desire for further education

Formation of nanoscale ferromagnetic MnAs crystallites in low-temperature grown GaAs

3 páginas, 3 figuras, 1 tabla.We report the formation of nanosize ferromagnetic MnAs crystallites imbedded in low-temperature grown GaAs using Mn+ ion implantation and subsequent annealing. The structural and magnetic properties of the crystallites have been characterized by transmission electron microscopy, electron beam induced x-ray fluorescence, and superconducting quantum interference device magnetometry. After an optimized thermal annealing at 750 °C, MnAs crystallites of 50 nm in size are formed. These nanomagnets show room temperature ferromagnetism.This work has been supported by QUEST, an NSF Science and Technology center (Grant No. DMR91.20007). P.J.W. is a postdoctoral fellow of the Deutsche Forschungsgemeinschaft (DFG) J.M.G. is a postdoctoral fellow of the Spanish Ministry of Education and Science.Peer reviewe

Saturation magnetostriction and its low-temperature variation inferred for natural titanomaghemites: implications for internal stress control of coercivity in oceanic basalts

Highly oxidized titanomaghemite in oceanic basalts often carries remanent magnetization of high coercivity (stability), helping preserve the oceanic magnetic anomaly pattern. We study the source of this high coercivity in four oceanic basalts (from ODP sites 238, 572D, 470A and 556) containing highly oxidized titanomaghemite (titanium content parameter x ≈ 0.55 and oxidation parameter z ≈ 0.9 on average). Most of the titanomaghemite is likely in singledomain grains with uniaxial anisotropy because the ratio of saturation remanence J RS to saturation magnetization Js approaches 0.50 (JRS/JS = 0.46 on average). We show that the uniaxial anisotropy is very likely magnetostrictively controlled through internal stresses σi in the titanomaghemite grains. This allows us to use a novel indirect method to estimate the saturation magnetostriction λS of the titanomaghemite. A saturation remanence J RS is given along the axis of a cylindrical sample of each basalt. Then a small compression σ is applied repeatedly along this axis and the reversible change ∆JRS in JRS is measured. Combining equations from single-domain theory for this piezomagnetic effect and for the sample’s coercive force HC gives λS = 1.39HCJS 1/σ ∆JRS/JRS (using cgs units, or with HC in mT, J S in kA m and σ in Pa). This yields four λS estimates (with ca 50 per cent expected error) ranging from 3 × 10−6 to 10 × 10−6 and averaging 6 × 10−6. Theory for the piezomagnetic effect yields four σ i estimates averaging 2 × 108 Pa. This is similar to the internal stress magnitude thought to be responsible for the high coercivity of ball-milled single-domain titanomagnetite (x ≈ 0.6) and natural single-domain haematite. We also show that cooling to 120 ◦K causes HC J S for each oceanic basalt to vary in approximate proportion to (1− T TC)n with n between 1.9 and 2.0 (where T is temperature and T C is Curie point, both in ◦K). This implies that λS of titanomaghemite with x ≈ 0.55 and z ≈ 0.9 also varies in approximate proportion to (1− T TC)n with n near 1.9 or 2.0 on cooling to 120 ◦K (assuming that σ i remains constant on cooling). Our results support the hypothesis that coercivity (magnetic stability) is often magnetostrictively controlled by internal stresses in the highly oxidized titanomaghemites typical of oceanic basalts older than ca 10 Myr.We suggest that this hypothesis can be further tested by more extensive observation of whether cooling to 120 ◦K often causes HC J S of such basalts to vary in approximate proportion to (1 − T TC)n with n near 1.9 or 2.0

Low-temperature alteration and magnetic changes of variably altered pillow basalts

Pillow basalt fragments from the East Pacific Rise, dredged during the Phoenix expedition, often show discoloured rims due to alteration. A suite of nine pillow basalts with such discoloured rims and ranging in age between 200 and 820 ka has been characterized in terms of their Fe–Ti-oxide mineralogy and rock magnetic properties. These large pillow fragments show relatively unaltered grey interiors, surrounded by darker, concentric halos, which vary in thickness as measured from glassy pillow rims and surfaces caused by large cracks penetrating into the original pillow interior. The discoloured zones are characterized by precipitation of abundant secondary minerals, such as Fe 3+ -rich clays that filled vesicle spaces. Fe–Ti oxides in subsamples from discoloured rims and grey interiors have been investigated with electron microscopy and rock magnetic techniques. The subsamples come from traverses that are parallel to the outer glassy pillow rims, allowing us to study the low-temperature alteration effects and rock magnetic properties without having to take variable grain size into account. Not surprisingly, titanomaghemites in discoloured rims are, in a general sense, oxidized to a higher degree ( z typically >0.55) than those in the relatively unaltered grey interior ( z typically 0.6 within 200 000 yr. The difference between the oxidation states of titanomaghemite within the grey pillow interior and the discoloured rims gradually diminishes with increasing age, so that for samples with ages of 800 ka the oxidation state of titanomaghemites in the grey interior approaches that of the discoloured rim. Our study demonstrates that visible discolouration of pillow basalts is not a suitable proxy for z . Because average Ti content can vary from sample to sample, Curie temperatures are also inaccurate proxies for z . If one wants to study possible correlations between z and rock magnetic parameters, the best technique is to determine z for each subsample by using transmission electron microscopy (TEM), electron microprobe, MÖssbauer or similar techniques. In agreement with many (but not all) previous observations on natural samples, we find that bulk coercivity ( H c ) , and high-field susceptibility (Χ hf ) increase, whereas low-field susceptibility (Χ l f ) , natural remanent magnetization intensity and saturation magnetization ( M s ) generally decrease with increasing oxidation state.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73443/1/j.1365-246X.2005.02819.x.pd

Modification of the magnetic mineralogy in basalts due to fluid–rock interactions in a high‐temperature geothermal system (Krafla, Iceland)

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86918/1/j.1365-246X.2011.05029.x.pd

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente

Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector

A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV