Resonant tunnelling diode based high speed optoelectronic transmitters

Resonant tunneling diode (RTD) integration with photo detector (PD) from epi-layer design shows great potential for combining terahertz (THz) RTD electronic source with high speed optical modulation. With an optimized layer structure, the RTD-PD presented in the paper shows high stationary responsivity of 5 A/W at 1310 nm wavelength. High power microwave/mm-wave RTD-PD optoelectronic oscillators are proposed. The circuitry employs two RTD-PD devices in parallel. The oscillation frequencies range from 20-44 GHz with maximum attainable power about 1 mW at 34/37/44GHz.European Commission [645369

Spinal and Supraspinal Motor Control Predictors of Rate of Torque Development

During explosive movements and potentially injurious situations, the ability to rapidly generate torque is critical. Previous research has suggested that different phases of rate of torque development (RTD) are differentiately controlled. However, the extent to which supraspinal and spinal mechanisms predict RTD at different time intervals is unknown. RTD of the plantarflexors across various phases of contraction (i.e., 0–25, 0–50, 0–100, 0–150, 0–200, and 0–250 ms) was measured in 37 participants. The following predictor variables were also measured: (a) gain of the resting soleus H-reflex recruitment curve; (b) gain of the resting homonymous post-activation depression recruitment curve; (c) gain of the GABAergic presynaptic inhibition recruitment curve; (d) the level of postsynaptic recurrent inhibition at rest; (e) level of supraspinal drive assessed by measuring V waves; and (f) the gain of the resting soleus M wave. Stepwise regression analyses were used to determine which variables significantly predicted allometrically scaled RTD. The analyses indicated that supraspinal drive was the dominant predictor of RTD across all phases. Additionally, recurrent inhibition predicted RTD in all of the time intervals except 0–150 ms. These results demonstrate the importance of supraspinal drive and recurrent inhibition to RTD

Two-phase RTD-CMOS pipelined circuits

MOnostable-BIstable Logic Element (MOBILE) networks can be operated in a gate-level pipelined fashion (nanopipeline) allowing high through output. Resonant tunneling diode (RTD)-based MOBILE nanopipelined circuits have been reported using different clock schemes including a four-phase strategy and a single-phase clock scheme. In particular, significant power advantages of single-phase RTD-CMOS MOBILE circuits over pure CMOS have been shown. This letter compares the RTD-CMOS realizations using a single clock and a novel two-phase clock solution. Significant superior robustness and performance in terms of power and area are obtained for the two-phase implementations

Loading Effect of W-band Resonant Tunneling Diode Oscillator by Using Load-Pull Measurement

Resonant tunneling diode (RTD) is the fastest solid-state electronic device with the highest reported frequency at 1.92 THz [1]. RTD-based THz sources have many promising applications such as ultrafast wireless communications, THz imaging, etc. To date, the main limitation of RTD technology is the low output power. Many efforts had been made to increase the power level by such as optimizing the layer structure [2], employing more devices in an array [3], matching impedance by displacing the device in circuit [3], etc. Here we report the loading effect by using E/H impedance tuner. We found that the maximum power is over 20dB higher than the worst impedance matching and the frequency shift is within 14% range of the central frequency. The load-pull measurement provides a convenient way to investigate the power/frequency variation versus the impedance change. Further work will benefit from the measurement results to design corresponding impedance matching network. The power level of RTD oscillator will be increased

Investigation into the integration of a resonant tunnelling diode and an optical communications laser: model and experiment

A resonant tunnelling diode has been monolithically integrated with an optical communications laser [the resonant tunnelling diode (RTD-LD)] to form a simple optoelectronic integrated circuit (OEIC) that is a novel bistable device suitable for an optical communications system. The RTD-LD was based on a ridge-waveguide laser structure and was fabricated from an InAlGaAs-InP epi-wafer grown by molecular beam epitaxy; it emitted at around 1500 nm. Voltage controlled optical-electrical switching and bistability were observed during the characterisation of the RTD-LD - useful features for a fibre-optic communications laser. Optical and electrical simulations of the RTD-LD were carried out using the circuit simulation tool PSPICE. In addition, a discrete component version of the RTD-LD was constructed which exhibited optical power oscillations, and along with the results of the simulations, gave insight into the operating principles of the monolithically integrated RTD-LD

Early diffusion evidence of retrograde transsynaptic degeneration in the human visual system

We investigated whether diffusion tensor imaging (DTI) indices of white matter integrity would offer early markers of retrograde transsynaptic degeneration (RTD) in the visual system after stroke Objective: We investigated whether diffusion tensor imaging (DTI) indices of white matter integrity would offer early markers of retrograde transsynaptic degeneration (RTD) in the visual system after stroke. Methods: We performed a prospective longitudinal analysis of the sensitivity of DTI markers of optic tract health in 12 patients with postsynaptic visual pathway stroke, 12 stroke controls, and 28 healthy controls. We examined group differences in (1) optic tract fractional anisotropy (FA-asymmetry), (2) perimetric measures of visual impairment, and (3) the relationship between FA-asymmetry and perimetric assessment. Results: FA-asymmetry was higher in patients with visual pathway lesions than in control groups. These differences were evident 3 months from the time of injury and did not change significantly at 12 months. Perimetric measures showed evidence of impairment in participants with visual pathway stroke but not in control groups. A significant association was observed between FA-asymmetry and perimetric measures at 3 months, which persisted at 12 months. Conclusions: DTI markers of RTD are apparent 3 months from the time of injury. This represents the earliest noninvasive evidence of RTD in any species. Furthermore, these measures associate with measures of visual impairment. DTI measures offer a reproducible, noninvasive, and sensitive method of investigating RTD and its role in visual impairment

Exploring Research through Design in Animal-Computer Interaction

This paper explores Research through Design (RtD) as a potential methodology for developing new interactive experiences for animals. We present an example study from an on-going project and examine whether RtD offers an appropriate framework for developing knowledge in the context of Animal-Computer Interaction, as well as considering how best to document such work. We discuss the design journey we undertook to develop interactive systems for captive elephants and the extent to which RtD has enabled us to explore concept development and documentation of research. As a result of our explorations, we propose that particular aspects of RtD can help ACI researchers gain fresh perspectives on the design of technology-enabled devices for non-human animals. We argue that these methods of working can support the investigation of particular and complex situations where no idiomatic interactions yet exist, where collaborative practice is desirable and where the designed objects themselves offer a conceptual window for future research and development

Residence time distribution of gas flows in microreactors: Measurement and model comparison

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.The optimization of microreactor designs for applications in chemical process engineering usually requires knowledge of the residence time distribution (RTD). The applicability of established models to microstructured reactors is currently under debate (Bošković et al. 2008, Günther et al. 2004, Stief et al. 2008). This work provides new experimental data on the residence time distributions of gas flows through different types of microstructured reactors and analyses the data with established RTD models. By this, the dispersion model was found to describe the RTD behavior of gas flow for a majority of the microstructured devices tested. The model could therefore be used to predict the RTD of those reactors.German Federal Ministry of Economics and Technology (IGF Project 15495