873 research outputs found
What do students know and understand about the Holocaust? Evidence from English secondary schools
This research report has been written under the auspices
of the University College London (UCL) Centre for
Holocaust Education. The Centre is part of the UCL
Institute of Education – currently the world’s leading
university for education – and is comprised of a team
of researchers and educators from a variety of different
disciplinary fields. The Centre works in partnership with
the Pears Foundation who, together with the Department
for Education, have co-funded its operation since it was
first established in 2008.
A centrally important principle of all activity based at
the UCL Centre for Holocaust Education is that, wherever
possible, classroom practice should be informed by
academic scholarship and relevant empirical research.
In 2009, Centre staff published an extensive national
study of secondary school teachers’ experience of
and attitudes towards teaching about the Holocaust
(Pettigrew et al. 2009). This new report builds on that
earlier work by critically examining English school
students’ knowledge and understanding of this history.
In both cases, research findings have been – and will
continue to be – used to develop an innovative and
ground-breaking programme of continuing professional
development (CPD) for teachers and educational
resources that are uniquely responsive to clearly identified
classroom needs. The UCL Centre for Holocaust
Education is the only institution of its kind, both within
the United Kingdom and internationally, where pioneering
empirical research is placed at the heart of work to
support teachers and their students encountering this
profoundly important yet complex and challenging
subject in schools.
The Centre offers a wide-ranging educational
programme appropriate to teachers at all stages of their
careers through a carefully constructed ‘pathway of
professional development’. This provides opportunities
for individuals to progressively deepen their knowledge
and improve their practice. It offers a national programme
of Initial Teacher Education in Holocaust education and a
variety of in-depth and subject-specific CPD. In addition,
the Centre also offers online distance learning facilities,
including a fully accredited taught Masters-level module
The Holocaust in the Curriculum. Through its Beacon
School programme, Centre staff work intensively
with up to 20 schools across England each year in order
to recognise and further develop exemplary
whole-school approaches and effective pedagogy.
All of the courses and classroom materials developed
by the UCL Centre for Holocaust Education are available
free of charge to teachers working in England’s statefunded
secondary schools. Further information can be
found at www.ioe.ac.uk/holocaust
Perfectly-absorbing photoconductive metasurfaces for THz applications
Ultrafast switching of photoconductivity is essential for many terahertz (THz) technologies, however this process is inefficient. Recently developed concepts of all-dielectric metasurfaces can improve efficiency of ultrafast switches, overcoming material limitations, reducing the thickness of the photoconductive region and lowering optical power requirements for THz devices. We will consider two types of perfectly absorbing metasurfaces compatible with the photoconductive switch architecture and discuss performance of THz detectors with integrated metasurfaces. We will show that optical power level required for optimum operation for these THz detectors is more than one order of magnitude lower in comparison to devices without metasurfaces
Perfect absorption in GaAs metasurfaces near the bandgap edge
Perfect optical absorption occurs in a metasurface that supports two degenerate and critically-coupled modes of opposite symmetry. The challenge in designing a perfectly absorbing metasurface for a desired wavelength and material stems from the fact that satisfying these conditions requires multi-dimensional optimization often with parameters affecting optical resonances in non-trivial ways. This problem comes to the fore in semiconductor metasurfaces operating near the bandgap wavelength, where intrinsic material absorption varies significantly. Here we devise and demonstrate a systematic process by which one can achieve perfect absorption in GaAs metasurfaces for a desired wavelength at different levels of intrinsic material absorption, eliminating the need for trial and error in the design process. Using this method, we show that perfect absorption can be achieved not only at wavelengths where GaAs exhibits high absorption, but also at wavelengths near the bandgap edge. In this region, absorption is enhanced by over one order of magnitude compared a layer of unstructured GaAs of the same thickness
Sensitivity and Noise in THz Photoconductive Metasurface Detectors
Photoconductive antenna THz detectors based on highly absorbing LT-GaAs metasurfaces enable high sensitivity and high signal-to-noise ratio (> 106) at optical gate powers as low as 5 μW. By investigating the dependence of detector performance on optical gate power, we compare several metasurface detectors with standard PCAs and develop a general model for quantifying the sensitivity and optimal gate power for detector operation. We also show that the LT-GaAs metasurface can even enhance sub bandgap absorption, enabling the use of these detectors in telecom wavelength systems
Gel chromatographic characterization of immunoreactive adrenocorticotropin in patients with ACTH hypersecretion
We investigated the molecular size of circulating immunoreactive ACTH by gel chromatography in patients with ACTH hypersecretion due to various disorders of the hypothalamic-pituitary-adrenal axis. 4 patients with Addison's disease, 2 with Nelson's syndrome, 4 with Cushing's disease, 6 with the ectopic ACTH syndrome (2 bronchial carcinoma, 1 medullary carcinoma, 1 metastatic islett cell carcinoma, 1 benign bronchial carcinoid and 1 patient with occult ectopic Cushing's syndrome) and 1 patient with hypersecretion of ACTH from a clinically nonfunctioning pituitary adenoma were studied. Analysis of the molecular size of immunoreactive ACTH was performed by gel chromatography on a Sephadex G-75 column (superfine, 100×1.5 cm) equilibrated with 1% formic acid. 2 ml fractions were collected and evaporated to dryness. The ACTH content of the recovered samples was determined by RIA. In Addison's disease, Nelson's syndrome and Cushing's disease the plasma showed a single peak of ACTH immunoreactivity at the expected position of 1–39 ACTH. In the ectopic ACTH syndrome the plasma of 4 patients revealed at chromatography at least one other peak eluting between the void volume and 1–39 ACTH suggestive of a high molecular weight form of ACTH whereas plasma of 2 patients showed only a single ACTH peak at the position of labeled 1–39 ACTH. The patient with a clinically non-functioning pituitary adenoma revealed a gel filtration pattern similar to the patients with ectopic ACTH syndrom and secretion of high molecular weight ACTH. We conclude that secretion of high molecular weight forms of ACTH is not a unique feature of the ectopic ACTH syndrome. It may therefore not serve as a marker of the ectopic Cushing's syndrome in the differential diagnosis of the ACTH dependent Cushing's syndrome. Vice versa, lack of high molecular weight ACTH does not exclude an ectopic source of ACTH secretion as cause of Cushing's syndrome
Nonlinear Terahertz Generation in Semiconductor Metasurfaces
We demonstrate ultra-thin semiconductor metasurfaces for generation of THz pulses. By investigating the dependence of the THz amplitude and phase on excitation field polarization and crystal orientation, we deduce that the underlying THz emission mechanism in metasurfaces differs from bulk semiconductor wafers with second order nonlinearity playing a dominant role. The metasurface enables control of the THz phase and can therefore be used to spatially structure the THz emitted field. We use this effect to design and demonstrate a metasurface which simultaneously emits and focusses THz pulses
Terahertz Generation from GaAs Metasurfaces: Role of Surface Nonlinearity
We show that a GaAs metasurface can generate THz radiation with comparable efficiency to a bulk GaAs crystal. We attribute the enhanced generation to second order nonlinearity with the surface making a strong contribution
Weather in stellar atmosphere: the dynamics of mercury clouds in alpha Andromedae
The formation of long-lasting structures at the surfaces of stars is commonly
ascribed to the action of strong magnetic fields. This paradigm is supported by
observations of evolving cool spots in the Sun and active late-type stars, and
stationary chemical spots in the early-type magnetic stars. However, results of
our seven-year monitoring of mercury spots in non-magnetic early-type star
alpha Andromedae show that the picture of magnetically-driven structure
formation is fundamentally incomplete. Using an indirect stellar surface
mapping technique, we construct a series of 2-D images of starspots and
discover a secular evolution of the mercury cloud cover in this star. This
remarkable structure formation process, observed for the first time in any
star, is plausibly attributed to a non-equilibrium, dynamical evolution of the
heavy-element clouds created by atomic diffusion and may have the same
underlying physics as the weather patterns on terrestrial and giant planets.Comment: 10 pages, 2 figures; to be published in Nature Physic
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