Anisotropic optical properties of Fe/GaAs(001) nanolayers from first principles

We investigate the anisotropy of the optical properties of thin Fe films on GaAs(001) from first-principles calculations. Both intrinsic and magnetization-induced anisotropy are covered by studying the system in the presence of spin-orbit coupling and external magnetic fields. We use the linearized augmented plane wave method, as implemented in the WIEN2k density functional theory code, to show that the $C_{2v}$ symmetric anisotropy of the spin-orbit coupling fields at the Fe/GaAs(001) interface manifests itself in the corresponding anisotropy of the optical conductivity and the polar magneto-optical Kerr effect. While their magnetization-induced anisotropy is negligible, the intrinsic anisotropy of the optical properties is significant and reflects the underlying $C_{2v}$ symmetry of the Fe/GaAs(001) interface. This suggests that the effects of anisotropic spin-orbit coupling fields in experimentally relevant Fe/GaAs(001) slabs can be studied by purely optical means.Comment: 8 pages, 11 figure

Optical conductivity of hydrogenated graphene from first principles

We investigate the effect of hydrogen coverage on the optical conductivity of single-side hydrogenated graphene from first principles calculations. To account for different degrees of uniform hydrogen coverage we calculate the complex optical conductivity for graphene supercells of various sizes, each containing a single additional hydrogen atom. We use the linearized augmented plane wave (LAPW) method, as implemented in the WIEN2k density functional theory code, to show that the hydrogen coverage strongly influences the complex optical conductivity and thus the optical properties, such as absorption, of hydrogenated graphene. We find that the optical conductivity of graphene in the infrared, visible, and ultraviolet range has different characteristic features depending on the degree of hydrogen coverage. This opens up new possibilities to tailor the optical properties of graphene by reversible hydrogenation, and to determine the hydrogen coverage of hydrogenated graphene samples in the experiment by contact-free optical absorption measurements.Comment: 8 pages, 7 figure

SCoT: a Python toolbox for EEG source connectivity

Analysis of brain connectivity has become an important research tool in neuroscience. Connectivity can be estimated between cortical sources reconstructed from the electroencephalogram (EEG). Such analysis often relies on trial averaging to obtain reliable results. However, some applications such as brain-computer interfaces (BCIs) require single-trial estimation methods. In this paper, we present SCoT—a source connectivity toolbox for Python. This toolbox implements routines for blind source decomposition and connectivity estimation with the MVARICA approach. Additionally, a novel extension called CSPVARICA is available for labeled data. SCoT estimates connectivity from various spectral measures relying on vector autoregressive (VAR) models. Optionally, these VAR models can be regularized to facilitate ill posed applications such as single-trial fitting. We demonstrate basic usage of SCoT on motor imagery (MI) data. Furthermore, we show simulation results of utilizing SCoT for feature extraction in a BCI application. These results indicate that CSPVARICA and correct regularization can significantly improve MI classification. While SCoT was mainly designed for application in BCIs, it contains useful tools for other areas of neuroscience. SCoT is a software package that (1) brings combined source decomposition and connectivtiy estimation to the open Python platform, and (2) offers tools for single-trial connectivity estimation. The source code is released under the MIT license and is available online at github.com/SCoT-dev/SCoT

Hydrophobic lung surfactant proteins B and C remain associated with surface film during dynamic cyclic area changes

AbstractThe biophysical activity of lung surfactant depends, to a large extent, on the presence of the hydrophobic surfactant proteins B (SP-B) and C (SP-C). The role of these proteins in lipid adsorption and lipid squeeze-out under dynamic conditions simulating breathing is not yet clear. Therefore, the aim of this study was to investigate the interaction of spread hydrophobic surfactant proteins with phospholipids in a captive-bubble surfactometer during rapid cyclic area changes (6 cycles/min). We found that SP-B and SP-C facilitated the rapid transport of lipids into the air–water interface in a concentration-dependent manner (threshold concentration ≥0.05:0.5 mol% SP-B/SP-C). Successive rapid cyclic area changes did not affect the concentration-dependent lipid adsorption process, suggesting that SP-B and SP-C remained associated with the surface film

Spin-orbit coupling in fluorinated graphene

We report on theoretical investigations of the spin-orbit coupling effects in fluorinated graphene. First-principles density functional calculations are performed for the dense and dilute adatom coverage limits. The dense limit is represented by the single-side semifluorinated graphene, which is a metal with spin-orbit splittings of about 10 meV. To simulate the effects of a single adatom, we also calculate the electronic structure of a $10 \times 10$ supercell, with one fluorine atom in the top position. Since this dilute limit is useful to study spin transport and spin relaxation, we also introduce a realistic effective hopping Hamiltonian, based on symmetry considerations, which describes the supercell bands around the Fermi level. We provide the Hamiltonian parameters which are best fits to the first-principles data. We demonstrate that, unlike for the case of hydrogen adatoms, fluorine's own spin-orbit coupling is the principal cause of the giant induced local spin-orbit coupling in graphene. The $sp^3$ hybridization induced transfer of spin-orbit coupling from graphene's $\sigma$ bonds, important for hydrogenated graphene, contributes much less. Furthermore, the magnitude of the induced spin-orbit coupling due to fluorine adatoms is about $1000$ times more than that of pristine graphene, and 10 times more than that of hydrogenated graphene. Also unlike hydrogen, the fluorine adatom is not a narrow resonant scatterer at the Dirac point. The resonant peak in the density of states of fluorinated graphene in the dilute limit lies 260 meV below the Dirac point. The peak is rather broad, about 300 meV, making the fluorine adatom only a weakly resonant scatterer.Comment: 11 pages, 14 figure

In Pursuit of an Easy to Use Brain Computer Interface for Domestic Use in a Population with Brain Injury

This paper presents original research investigating a sensor based, ambient assisted smart home platform, within the framework of a brain computer interface (BackHome). This multimodal system integrates home-based sensors, mobile monitoring, with communication tools, web browsing, smart home control and cognitive rehabilitation. The target population are people living at home with acquired brain injury. This research engaged with the target population and those without brain injury, who provided a control for system testing. Aligned with our ethical governance a strong user centric ethos was foundational to participant engagement. Participant experience included three individual sessions to complete a pre-set protocol with supervision. Evaluation methodology included observations, time logging, completion of protocol and usability questionnaires. Results confirmed the average accuracy score for the people without brain injury was 82.6% (±4.7), performing best with the cognitive rehabilitation. Target end users recorded an average accuracy score of 76% (±11.5) with the speller logging the highest accuracy score. Additional outcomes included the need to refine the aesthetic appearance, as well as improving the reliability and responsiveness of the BCI. The findings outline the importance of engaging with end users to design and develop marketable BCI products for use in a domestic environment. DOI: 10.17762/ijritcc2321-8169.150610

Towards a versatile and multidimensional framework to analyse regional governance

Regional governance has received growing attention, not only from researchers, but also from politicians and practitioners of regional development. The understanding and usage of the concept, however, are highly heterogeneous: sometimes regional governance is described or explained in terms of its characteristics, processes and impacts, while at other times, it is framed as a tool for regional development. This article develops a definition and framework for a systematic assessment of various regional governance forms. For this purpose, it draws on material from a three-round Delphi survey among practitioners and researchers who are experts of regional governance. On this basis, a consolidated definition of regional governance is proposed as ‘the vertical and horizontal coordination of regional transformation processes beyond administrative boundaries by state and non-state actors’. Furthermore, the framework identifies five dimensions of regional governance: (a) participation, (b) bindingness, (c) formalisation, (d) regional autonomy and (e) power relations. These dimensions are disaggregated into a total of 21 indicators to systematically describe and analyse different regional governance forms., Regional governance has received growing attention, not only from researchers, but also from politicians and practitioners of regional development. The understanding and usage of the concept, however, are highly heterogeneous: sometimes regional governance is described or explained in terms of its characteristics, processes and impacts, while at other times, it is framed as a tool for regional development. This article develops a definition and framework for a systematic assessment of various regional governance forms. For this purpose, it draws on material from a three-round Delphi survey among practitioners and researchers who are experts of regional governance. On this basis, a consolidated definition of regional governance is proposed as ‘the vertical and horizontal coordination of regional transformation processes beyond administrative boundaries by state and non-state actors’. Furthermore, the framework identifies five dimensions of regional governance: (a) participation, (b) bindingness, (c) formalisation, (d) regional autonomy and (e) power relations. These dimensions are disaggregated into a total of 21 indicators to systematically describe and analyse different regional governance forms