6,816 research outputs found
Investigating subject-specific writing skills and historical reasoning in historical explanations: a study of 7th- and 8th-grade comprehensive school students in North Rhine-Westphalia, Germany
The purpose of this study was to examine the writing skills of 7th- and 8th-grade students with a high proportion of migration background in North Rhine-Westphalia, Germany. The study was part of the SchriFT project (2017–20), funded by the Federal Ministry of Education and Research. A writing task was given on the topic: Why can we only make assumptions about many past events? As an answer to the task, the students had to write a historical explanation that took into account the epistemological principles of historical reasoning. The students’ writing was analysed using a category system, and their historical knowledge was assessed through a knowledge test. The results showed that the students possess diverse levels of writing skills, with few producing elaborate explanations, and most struggling with the subject-specific language and reasoning skills. The study also highlights the potential for genre-based writing approaches in history education. The results suggest that many students perceive history as an image of the past and have limited understanding of historical reasoning. Further research is needed to investigate the influence of motivation and interest on language learning
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Blending systems thinking approaches for organisational analysis: reviewing child protection in England
This paper concerns the innovative use of a blend of systems thinking ideas in the ‘Munro Review of Child Protection’, a high-profile examination of child protection activities in England, conducted for the Department for Education. We go ‘behind the scenes’ to describe the OR methodologies and processes employed. The circumstances that led to the Review are outlined. Three specific contributions that systems thinking made to the Review are then described. First, the systems-based analysis and visualisation of how a ‘compliance culture’ had grown up. Second the creation of a large, complex systems map of current operations and the effects of past policies on them. Third, how the map gave shape to the range of issues the Review addressed and acted as an organising framework for the systemically coherent set of recommendations made. The paper closes with an outline of the main implementation steps taken so far to create a child protection system with the critically reflective properties of a learning organisation, and methodological reflections on the benefits of systems thinking to support organisational analysis
The Black Hole in the Compact, High-dispersion Galaxy NGC 1271
Located in the Perseus cluster, NGC 1271 is an early-type galaxy with a small
effective radius of 2.2 kpc and a large stellar velocity dispersion of 276 km/s
for its K-band luminosity of 8.9x10^{10} L_sun. We present a mass measurement
for the black hole in this compact, high-dispersion galaxy using observations
from the integral field spectrograph NIFS on the Gemini North telescope
assisted by laser guide star adaptive optics, large-scale integral field unit
observations with PPAK at the Calar Alto Observatory, and Hubble Space
Telescope WFC3 imaging observations. We are able to map out the stellar
kinematics on small spatial scales, within the black hole sphere of influence,
and on large scales that extend out to four times the galaxy's effective
radius. We find that the galaxy is rapidly rotating and exhibits a sharp rise
in the velocity dispersion. Through the use of orbit-based stellar dynamical
models, we determine that the black hole has a mass of (3.0^{+1.0}_{-1.1}) x
10^9 M_sun and the H-band stellar mass-to-light ratio is 1.40^{+0.13}_{-0.11}
M_sun/L_sun (1-sigma uncertainties). NGC 1271 occupies the sparsely-populated
upper end of the black hole mass distribution, but is very different from the
Brightest Cluster Galaxies (BCGs) and giant elliptical galaxies that are
expected to host the most massive black holes. Interestingly, the black hole
mass is an order of magnitude larger than expectations based on the galaxy's
bulge luminosity, but is consistent with the mass predicted using the galaxy's
bulge stellar velocity dispersion. More compact, high-dispersion galaxies need
to be studied using high spatial resolution observations to securely determine
black hole masses, as there could be systematic differences in the black hole
scaling relations between these types of galaxies and the BCGs/giant
ellipticals, thereby implying different pathways for black hole and galaxy
growth.Comment: accepted for publication in Ap
Photoionization models of the CALIFA HII regions. I. Hybrid models
Photoionization models of HII regions require as input a description of the
ionizing SED and of the gas distribution, in terms of ionization parameter U
and chemical abundances (e.g. O/H and N/O). A strong degeneracy exists between
the hardness of the SED and U, which in turn leads to high uncertainties in the
determination of the other parameters, including abundances. One way to resolve
the degeneracy is to fix one of the parameters using additional information.
For each of the ~ 20000 sources of the CALIFA HII regions catalog, a grid of
photoionization models is computed assuming the ionizing SED being described by
the underlying stellar population obtained from spectral synthesis modeling.
The ionizing SED is then defined as the sum of various stellar bursts of
different ages and metallicities. This solves the degeneracy between the shape
of the ionizing SED and U. The nebular metallicity (associated to O/H) is
defined using the classical strong line method O3N2 (which gives to our models
the status of "hybrids"). The remaining free parameters are the abundance ratio
N/O and the ionization parameter U, which are determined by looking for the
model fitting [NII]/Ha and [OIII]/Hb. The models are also selected to fit
[OII]/Hb. This process leads to a set of ~ 3200 models that reproduce
simultaneously the three observations.
We find that the regions associated to young stellar bursts suffer leaking of
the ionizing photons, the proportion of escaping photons having a median of
80\%. The set of photoionization models satisfactorily reproduces the electron
temperature derived from the [OIII]4363/5007 line ratio. We determine new
relations between the ionization parameter U and the [OII]/[OIII] or
[SII]/[SIII] line ratios. New relations between N/O and O/H and between U and
O/H are also determined.
All the models are publicly available on the 3MdB database.Comment: Accepted for publication in A&
The structural and dynamical properties of compact elliptical galaxies
Dedicated photometric and spectroscopic surveys have provided unambiguous
evidence for a strong stellar mass-size evolution of galaxies within the last
10 Gyr. The likely progenitors of today's most massive galaxies are remarkably
small, disky, passive and have already assembled much of their stellar mass at
redshift z=2. An in-depth analysis of these objects, however, is currently not
feasible due to the lack of high-quality, spatially-resolved photometric and
spectroscopic data. In this paper, we present a sample of nearby compact
elliptical galaxies (CEGs), which bear resemblance to the massive and quiescent
galaxy population at earlier times. Hubble Space Telescope (HST) and wide-field
integral field unit (IFU) data have been obtained, and are used to constrain
orbit-based dynamical models and stellar population synthesis (SPS) fits, to
unravel their structural and dynamical properties. We first show that our
galaxies are outliers in the present-day stellar mass-size relation. They are,
however, consistent with the mass-size relation of compact, massive and
quiescent galaxies at redshift z=2. The compact sizes of our nearby galaxies
imply high central stellar mass surface densities, which are also in agreement
with the massive galaxy population at higher redshift, hinting at strong
dissipational processes during their formation. Corroborating evidence for a
largely passive evolution within the last 10 Gyr is provided by their orbital
distribution as well as their stellar populations, which are difficult to
reconcile with a very active (major) merging history. This all supports that we
can use nearby CEGs as local analogues of the high-redshift, massive and
quiescent galaxy population, thus providing additional constraints for models
of galaxy formation and evolution.Comment: 33 pages, 27 figures and 20 tables (with most of the tables provided
as online-only supporting information). Accepted for publication in MNRA
Efficient Parametrization of the Vertex Function, -Scheme, and the (t,t')-Hubbard Model at Van Hove Filling
We propose a new parametrization of the four-point vertex function in the
one-loop one-particle irreducible renormalization group (RG) scheme for
fermions. It is based on a decomposition of the effective two-fermion
interaction into fermion bilinears that interact via exchange bosons. The
numerical computation of the RG flow of the boson propagators reproduces the
leading weak coupling instabilities of the two-dimensional Hubbard model at Van
Hove filling, as they were previously obtained by a temperature RG flow.
Instead of regularizing with temperature, we here use a soft frequency
-regularization that likewise does not artificially suppress
ferromagnetism. Besides being more efficient than previous N-patch schemes,
this parametrization also reduces the ambiguities in introducing boson fields.Comment: 33 pages, 11 figures, references adde
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CD11b/CD18 mediates production of reactive oxygen species by mouse and human macrophages adherent to matrixes containing oxidized LDL
Production of reactive oxygen species (ROS) and other proinflammatory substances by macrophages adherent to matrix proteins that contain or have been modified by oxidized LDL (oxLDL) may play an important role in atherogenesis. In vitro, human macrophages adhere to matrixes containing oxLDL via scavenger receptors and are signaled to produce ROS partly by interactions of the class B scavenger receptor (SR-B) CD36 with ligands on the matrix. In this report, we show that macrophages from mice genetically deficient in SR-A or CD36 adhered equally as well and produced equal amounts of ROS on interaction with matrix-associated oxLDL. In contrast, macrophages from mice genetically deficient in the CD18 chain of β2-integrins produced insignificant amounts of ROS on interaction with oxLDL-containing matrixes, even though they adhered to these matrixes as efficiently as did macrophages from wild-type mice. Antibodies against CD18, CD11b, or EDTA, the last of which chelates divalent cations required for integrin function, had no effect on adhesion of normal mouse or human macrophages to matrixes containing oxLDL but almost completely inhibited ROS production by macrophages adherent to this matrix. Thus, CD11b/CD18 plays an important role in regulating production of ROS by mouse and human macrophages adherent to matrixes containing oxLDL. It may play a hitherto-unsuspected role in regulating macrophage signaling pathways involved in inflammation and atherogenesis
Recommendations for the engineering characterization of single-use bioreactors
Single-use bioreactors have been available for more than 15 years and are nowadays widely accepted for a broad range of applications. However, process engineering data for these bioreactors, including volumetric mass transfer coefficients, mixing times and power inputs, are still limited. Furthermore, these data are often generated using a number of different methods, making comparisons difficult. In addition, the large variety of bioreactor types and their mixing principles (stirred, wave-mixed, orbitally-shaken, etc.) increases the difficulty in comparing the engineering data. In order to facilitate the usage of single-use bioreactors, the DECHEMA Upstream Processing (USP) expert group on ‘Single-use technology in biopharmaceutical manufacturing’ has developed recommendations for the process engineering characterization of single-use bioreactors. The methods are based on procedures that were previously developed for multi-use bioreactors and were tested in universities as well as companies (both from the supplier and user sides) for their robustness. The validated recommendations now include measurements of volumetric mass transfer coefficient, mixing time and power input. These parameters are experimentally determined using the dynamic gassing-out method, the decolorization method or sensor method, and the torque method respectively. The poster gives an overview of the fundamentals and procedures of the methods applied, and current results from the interlaboratory tests. Recent foci include the measurement of carbon dioxide gas-liquid mass transfer and the determination of mechanical stress due to hydrodynamics
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