Modelling of an intersubband quantum confined Stark effect in Ge quantum wells for mid-infrared photonics

: In this work we theoretically investigate quantum confined Stark effect of intersubband transitions in asymmetric Ge/SiGe quantum wells for intensity modulation in the mid-infrared. Our calculations show that extinction ratios up to 1 dB and modulation speeds of several tens of GHz could be obtained in 100 µm long waveguides

A Generalized Diffusion Tensor for Fully Anisotropic Diffusion of Energetic Particles in the Heliospheric Magnetic Field

The spatial diffusion of cosmic rays in turbulent magnetic fields can, in the most general case, be fully anisotropic, i.e. one has to distinguish three diffusion axes in a local, field-aligned frame. We reexamine the transformation for the diffusion tensor from this local to a global frame, in which the Parker transport equation for energetic particles is usually formulated and solved. Particularly, we generalize the transformation formulas to allow for an explicit choice of two principal local perpendicular diffusion axes. This generalization includes the 'traditional' diffusion tensor in the special case of isotropic perpendicular diffusion. For the local frame, we motivate the choice of the Frenet-Serret trihedron which is related to the intrinsic magnetic field geometry. We directly compare the old and the new tensor elements for two heliospheric magnetic field configurations, namely the hybrid Fisk and the Parker field. Subsequently, we examine the significance of the different formulations for the diffusion tensor in a standard 3D model for the modulation of galactic protons. For this we utilize a numerical code to evaluate a system of stochastic differential equations equivalent to the Parker transport equation and present the resulting modulated spectra. The computed differential fluxes based on the new tensor formulation deviate from those obtained with the 'traditional' one (only valid for isotropic perpendicular diffusion) by up to 60% for energies below a few hundred MeV depending on heliocentric distance.Comment: 8 pages, 6 figures, accepted in Ap

Assessing the invertebrate fauna trajectories in remediation sites of Winstone Aggregates Hunua quarry in Auckland

This study monitored the invertebrates in restoration plantings in the Winstone Aggregates Hunua Quarry. This was to assess the re-establishment of invertebrates in the restoration planting sites and compare them with unplanted control and mature sites. This study follows on from a baseline study carried out in 2014-2015 measuring the restoration trajectory of invertebrates in the Winstone Aggregate Hunua quarry site. A range of entomological monitoring techniques were used and found that dung beetles, millipedes, foliage moths, leaf litter moths and some mite species increased in numbers from the control sites through to the mature sites, while ants, rove beetles, grass moths, some carabid beetles, and worms showed a downwards trend from the mature sites to the control sites. Further monitoring of invertebrates in the restoration area should be carried out

Five rules of thumb for post-ELSI interdisciplinary collaborations

In this paper we identify five rules of thumb for interdisciplinary collaboration across the natural and social sciences. We link these to efforts to move away from the ‘ethical, legal and social issues’ framework of interdisciplinarity and towards a post-ELSI collaborative space. It is in trying to open up such a space that we identify the need for: collaborative experimentation, taking risks, collaborative reflexivity, opening-up discussions of unshared goals and neighbourliness

Low-Power consumption Franz-Keldysh effect plasmonic modulator

In this paper we report on a low energy consumption CMOS-compatible plasmonic modulator based on Franz-Keldysh effect in germanium on silicon. We performed integrated electro-optical simulations in order to optimize the main characteristics of the modulator. A 3.3 dB extinction ratio for a 30 µm long modulator is demonstrated under 3 V bias voltage at an operation wavelength of 1647 nm. The estimated energy consumption is as low as 20 fJ/bit

Taking roles in interdisciplinary collaborations: Reflections on working in post-ELSI spaces in the UK synthetic biology community

Based on criticism of the “ethical, legal and social implications” (ELSI) paradigm, researchers in science and technology studies (STS) have begun to create and move into “post-ELSI” spaces. In this paper, we pool our experiences of working towards collaborative practices with colleagues in engineering and science disciplines in the f eld of synthetic biology. We identify a number of dif erent roles that we have taken, been assumed to take, or have had foisted upon us as we have sought to develop postELSI practices. We argue that the post-ELSI situation is characterised by the demands placed on STS researchers and other social scientists to f uctuate between roles as contexts shift in terms of power relations, af ective tenor, and across space and over time. This leads us to posit four orientations for post-ELSI collaborative practices that could help establish more fruitful negotiations around these roles

Making Sense of Family Deaths in Urban Senegal: Diversities, Contexts, and Comparisons

Despite calls for cross-cultural research, Minority world perspectives still dominate death and bereavement studies, emphasizing individualized emotions and neglecting contextual diversities. In research concerned with contemporary African societies, on the other hand, death and loss are generally subsumed within concerns about AIDS or poverty, with little attention paid to the emotional and personal significance of a death. Here, we draw on interactionist sociology to present major themes from a qualitative study of family deaths in urban Senegal, theoretically framed through the duality of meanings-in-context. Such themes included family and community as support and motivation; religious beliefs and practices as frameworks for solace and (regulatory) meaning; and material circumstances as these are intrinsically bound up with emotions. Although we identify the experience of (embodied, emotional) pain as a common response across Minority and Majority worlds, we also explore significant divergencies, varying according to localized contexts and broader power dynamics

QPSK Modulation in the O-Band Using a Single Dual-Drive Mach Zehnder Silicon Modulator

[EN] Keeping up with bandwidth requirements in next generation short- and long-reach optical communication systems will require migrating from simple modulation formats such as on-off keying to more advanced formats such as quaternary phase-shift keying (QPSK). In this paper, we report the first demonstration of QPSK signal generation in the O-band using a silicon dual-drive Mach-Zehnder modulator (DD-MZM). The performance of the silicon DD-MZM is assessed at 20 Gb/s and compared against a similar DD-MZM based on LiNbO3, showing a limited implementation power penalty of only 1.5 dB.This work was supported in part by the European project Plat4m (FP7-2012-318178); European project Cosmicc (H2020-ICT-27-2015- 688516); French Industry Ministry Nano2017 program.Pérez-Galacho, D.; Bramerie, L.; Baudot, C.; Chaibi, M.; Messaoudène, S.; Vulliet, N.; Vivien, L.... (2018). QPSK Modulation in the O-Band Using a Single Dual-Drive Mach Zehnder Silicon Modulator. Journal of Lightwave Technology. 36(18):3935-3940. https://doi.org/10.1109/JLT.2018.2851370S39353940361