Transverse "resistance overshoot" in a Si/SiGe two-dimensional electron gas in the quantum Hall effect regime

We investigate the peculiarities of the "overshoot" phenomena in the transverse Hall resistance R_{xy} in Si/SiGe. Near the low magnetic field end of the quantum Hall effect plateaus, when the filling factor \nu approaches an integer i, R_{xy} overshoots the normal plateau value h/ie^2. However, if magnetic field B increases further, R_{xy} decreases to its normal value. It is shown that in the investigated sample n-Si/Si_{0.7}Ge_{0.3}, overshoots exist for almost all \nu. Existence of overshoot in R_{xy} observed in different materials and for different \nu, where splitting of the adjacent Landau bands has different character, hints at the common origin of this effect. Comparison of the experimental curves R_{xy}(\nu) for \nu = 3 and \nu = 5 with and without overshoot showed that this effect exist in the whole interval between plateaus, not only in the region where R_{xy} exceeds the normal plateau value.Comment: 3 pages, 5 EPS figure

Access to healthcare for people seeking and refused asylum in Great Britain: a review of evidence

This research report is a review of evidence looking at the barriers people seeking or refused asylum face in trying to access healthcare services in the UK, and what may help them to do so more easily. This report, and the partner report on lived experiences (https://www.equalityhumanrights.com/en/publication-download/lived-experiences-access-healthcare-people-seeking-and-refused-asylum), will be of interest to people who play an important role in delivering healthcare and related support services to people seeking or refused asylum. We have also made recommendations for what changes are needed (https://www.equalityhumanrights.com/en/publication-download/making-sure-people-seeking-and-refused-asylum-can-access-healthcare-what-needs) to make sure that people seeking and refused asylum have full enjoyment of their right to health. This review was carried out by Imperial College London, with primary data provided by Doctors of the World UK

Mercury in Coniferous and Deciduous Upland Forests in Northern New England, USA: Implications of Climate Change

Climatic changes in the northeastern US are expected to cause coniferous stands to transition to deciduous stands over the next hundred years. Mercury (Hg) sequestration in forest soils may change as a result. In order to understand potential effects of such a transition, we studied aboveground vegetation and soils at paired coniferous and deciduous stands on eight mountains in Vermont and New Hampshire, USA

Robust autoresonant excitation in the plasma beat-wave accelerator: a theoretical study

A modified version of the Plasma Beat-Wave Accelerator scheme is introduced and analyzed, which is based on autoresonant phase-locking of the nonlinear Langmuir wave to the slowly chirped beat frequency of the driving lasers via adiabatic passage through resonance. This new scheme is designed to overcome some of the well-known limitations of previous approaches, namely relativistic detuning and nonlinear modulation or other non-uniformity or non-stationarity in the driven Langmuir wave amplitude, and sensitivity to frequency mismatch due to measurement uncertainties and density fluctuations and inhomogeneities

The lived experiences of access to healthcare for people seeking and refused asylum

This research aims to explore the lived experiences of accessing healthcare among people currently seeking asylum and those who have had their claim for asylum refused, as well as the experiences of health service providers working with these communities. It examines the extent to which people are able to exercise their rights to access healthcare. It looks at the differences between those currently in the asylum system and those who have had their claim refused in England, Scotland and Wales. This report, and the partner report providing a review of evidence (https://www.equalityhumanrights.com/en/publication-download/access-healthcare-people-seeking-and-refused-asylum-great-britain-review), will be of interest to people who play an important role in delivering healthcare and related support services to people seeking or refused asylum. We have also made recommendations for what changes are needed (https://www.equalityhumanrights.com/en/publication-download/making-sure-people-seeking-and-refused-asylum-can-access-healthcare-what-needs) to make sure that people seeking and refused asylum have full enjoyment of their right to health. This report was produced in collaboration with Imperial College London and Doctors of the World UK

The horofunction boundary of the Hilbert geometry

We investigate the horofunction boundary of the Hilbert geometry defined on an arbitrary finite-dimensional bounded convex domain D. We determine its set of Busemann points, which are those points that are the limits of `almost-geodesics'. In addition, we show that any sequence of points converging to a point in the horofunction boundary also converges in the usual sense to a point in the Euclidean boundary of D. We prove that all horofunctions are Busemann points if and only if the set of extreme sets of the polar of D is closed in the Painleve-Kuratowski topology.Comment: 24 pages, 2 figures; minor changes, examples adde

Evidence for magnetoplasmon character of the cyclotron resonance response of a two-dimensional electron gas

Experimental results on the absolute magneto-transmission of a series of high density, high mobility GaAs quantum wells are compared with the predictions of a recent magnetoplasmon theory for values of the filling factor above 2. We show that the magnetoplasmon picture can explain the non-linear features observed in the magnetic field evolution of the cyclotron resonance energies and of the absorption oscillator strength. This provides experimental evidence that inter Landau level excitations probed by infrared spectroscopy need to be considered as many body excitations in terms of magnetoplasmons: this is especially true when interpreting the oscillator strengths of the cyclotron transitions

Frohlich mass in GaAs-based structures

The Frohlich interaction is one of the main electron-phonon intrinsic interactions in polar materials originating from the coupling of one itinerant electron with the macroscopic electric field generated by any longitudinal optical (LO) phonon. Infra-red magneto-absorption measurements of doped GaAs quantum wells structures have been carried out in order to test the concept of Frohlich interaction and polaron mass in such systems. These new experimental results lead to question the validity of this concept in a real system.Comment: 4 pages, 3 figure