Dispersion insensitive, high-speed optical clock recovery based on a mode-locked laser diode

An investigation into the effects of varying levels of chromatic dispersion on a mode- locked laser diode optical clock recovery process is presented. Results demonstrate that this technique is invariant to input dispersion varying between +75 ps/nm

Chromatic dispersion monitoring for high-speed WDM systems using two-photon absorption in a semiconductor microcavity

This paper presents a theoretical and experimental investigation into the use of a two-photon absorption (TPA) photodetector for use in chromatic dispersion (CD) monitoring in high-speed, WDM network. In order to overcome the inefficiency associated with the nonlinear optical-to-electrical TPA process, a microcavity structure is employed. An interesting feature of such a solution is the fact that the microcavity enhances only a narrow wavelength range determined by device design and angle at which the signal enters the device. Thus, a single device can be used to monitor a number of different wavelength channels without the need for additional external filters. When using a nonlinear photodetector, the photocurrent generated for Gaussian pulses is inversely related to the pulsewidth. However, when using a microcavity structure, the cavity bandwidth also needs to be considered, as does the shape of the optical pulses incident on the device. Simulation results are presented for a variety of cavity bandwidths, pulse shapes and durations, and spacing between adjacent wavelength channels. These results are verified experimental using a microcavity with a bandwidth of 260 GHz (2.1 nm) at normal incident angle, with the incident signal comprising of two wavelength channels separated by 1.25 THz (10 nm), each operating at an aggregate data rate of 160 Gb/s. The results demonstrate the applicability of the presented technique to monitor accumulated dispersion fluctuations in a range of 3 ps/nm for 160 Gb/s RZ data channel

All-optical pulse processing for advanced photonic communication system

This paper investigates the use of a two-photon absorption photodetector for high speed processing of ultrashort optical pulses in advanced photonic communication systems. Specifically the paper describes how the two-photon absorption photodetector maybe employed for chromatic dispersion monitoring in high-speed, wavelength division multiplexed networks, and also for reducing multiple access interference noise in an optical code division multiplexed system

Zero-dimensional methylammonium iodo bismuthate solar cells and synergistic interactions with silicon nanocrystals

This work was supported by EPSRC (EP/K022237/1 and EP/M024938/1) and by the New Energy and Industrial Technology Development Organization (NEDO).Organometal trihalide perovskite solar cells have attracted monumental attention in recent years. Today's best devices, based on a three-dimensional perovskite structure of corner-sharing PbI6 octahedra, are unstable, toxic, and display hysteresis in current-voltage measurements. We present zero-dimensional organic-inorganic hybrid solar cells based on methylammonium iodo bismuthate (CH3NH3)3(Bi2I9) (MABI) comprising a Bi2I9 bioctahedra and observe very low hysteresis for scan rates in the broad range of 150 mV s-1 to 1500 mV s-1 without any interfacial layer engineering. We confirm good stability for devices produced and stored in open air without humidity control. The MABI structure can also accommodate silicon nanocrystals, leading to an enhancement in the short-circuit current. Through the material MABI, we demonstrate a promising alternative to the organometal trihalide perovskite class and present a model material for future composite third-generation photovoltaics.PostprintPeer reviewe

A comparison of CT-body composition measurements in non-cancer and cancer patients from a single UK centre

Objectives: Establish the prevalence of low skeletal muscle index and density in our population, by comparing age and sex matched cohorts of patients with and without cancer, using standardized methodology for CT-Body composition (CT-BC). Methods: A retrospective analysis of prospectively collected data. Patients admitted to our institution between 17th March 2020 - 1st May 2020, with confirmed coronavirus disease and imaging suitable for CT-BC (n=52), were age and sex matched with patients undergoing resection for colorectal cancer (n=52). Results: 104 patients were included in the final analysis. 43% (n=45) were male, 77% (n=80) were aged 65 years or older, 50% (n=50) were overweight (BMI ≥25) and 53% (n=55) were systemically inflamed (mGPS ≥1). The prevalence of a low SMI (56% vs. 65%) and low SMD (83% vs. 67%) was similar between cohorts. A low SMI and SMD were both associated with age (p<0.05 and p<0.01, respectively) on univariate analysis. On multivariate analysis, a low SMD was independently associated with age (OR 2.38 (1.34-4.22), p=0.003) and mGPS (OR 2.10 (1.20-3.68), p=0.01). Conclusions: In conclusion, the prevalence of a low SMI and low SMD was similar in non-cancer and cancer cohorts in our institution

Carrier extraction from metallic perovskite oxide nanoparticles

This work was supported by EPSRC (EP/K022237/1, EP/M024938/1 and EP/R023638/1), the EPSRC Supergen SuperSolar Hub, the Department for Employment and Learning (DEL) of Northern Ireland Studentship, and by the New Energy and Industrial Technology Development Organization (NEDO).We observe the extraction of carriers excited between two types of bands in the perovskite oxide, Sr-deficient strontium niobate (Sr0.9NbO3). Sr0.9NbO3 exhibits metallic behaviour and high conductivity, whilst also displaying broad absorption across the ultraviolet, visible, and near-infrared spectral regions, making it an attractive material for solar energy conversion. Furthermore, the optoelectronic properties of strontium niobate can easily be tuned by varying the Sr fraction or through doping. Sr-deficient strontium niobate exhibits a split conduction band, which enables two types of optical transitions: intraband and interband. However, whether such carriers can be extracted from an unusual material as such remains unproven. In this report, we have overcome the immense challenge of photocarrier extraction by fabricating an extremely thin absorber layer of Sr0.9NbO3 nanoparticles. These findings open up great opportunities to harvest a very broad solar spectral absorption range with reduced recombination losses.Publisher PDFPeer reviewe

Event-related fMRI responses in the human frontal eye fields in a randomized pro- and antisaccade task

We examined whether the frontal eye fields (FEF) are involved in the suppression of reflexive saccades. Simultaneous recording of horizontal eye movements and functional magnetic resonance imaging enabled us to perform a randomized pro- and antisaccade task and to sort blood oxygenation level dependent (BOLD) time series on the basis of task performance. Saccadic reaction time distributions were comparable across tasks indicating a similar effort in preprocessing of the saccades. Furthermore, we found similar BOLD activation in FEF during both correctly performed pro- and antisaccades. Frontal eye field activation started prior to target presentation and saccade generation. While we observed only few erroneous antisaccades, these were associated with a decrease in BOLD activity prior to target presentation, and increased BOLD activity after target presentation relative to correctly performed antisaccades. These findings are consistent with a role of the FEF in the suppression of reflexive saccades. The increase in activity after target presentation for antisaccade errors can only be indirectly linked to such a role but may also reflect activity related to the generation of a correction saccade. Frontal eye field BOLD activity may further represent general arousal, preparatory set, shortterm memory, or salience-map related activity

Television news and the symbolic criminalisation of young people

This is an Author's Accepted Manuscript of an article published in Journalism Studies, 9(1), 75 - 90, 2008, copyright Taylor & Francis, available online at: http://www.tandfonline.com/10.1080/14616700701768105.This essay combines quantitative and qualitative analysis of six UK television news programmes. It seeks to analyse the representation of young people within broadcast news provision at a time when media representations, political discourse and policy making generally appear to be invoking young people as something of a folk devil or a locus for moral panics. The quantitative analysis examines the frequency with which young people appear as main actors across a range of different subjects and analyses the role of young people as news sources. It finds a strong correlation between young people and violent crime. A qualitative analysis of four “special reports” or backgrounders on channel Five's Five News explores the representation of young people in more detail, paying attention to contradictions and tensions in the reports, the role of statistics in crime reporting, the role of victims of crime and the tensions between conflicting news frames.Arts and Humanities Research Counci

Sustaining entrepreneurial business: a complexity perspective on processes that produce emergent practice

This article examines the management practices in an entrepreneurial small firm which sustain the business. Using a longitudinal qualitative case study, four general processes are identified (experimentation, reflexivity, organising and sensing), that together provide a mechanism to sustain the enterprise. The analysis draws on concepts from entrepreneurship and complexity science. We suggest that an entrepreneur’s awareness of the role of these parallel processes will facilitate their approaches to sustaining and developing enterprises. We also suggest that these processes operate in parallel at multiple levels, including the self, the business and inter-firm networks. This finding contributes to a general theory of entrepreneurship. A number of areas for further research are discussed arising from this result