Attitudes of South Australian psychiatrists towards attention deficit hyperactivity disorder in adults.

OBJECTIVE: A lack of access to psychiatric services for adult ADHD is a recognised issue in South Australia and nationally. This study aims to explore the practices of local psychiatrists and their attitudes towards adult ADHD, with a view to determining any barriers influencing accessibility to treatment. METHODS: We developed an online survey to examine the aims of the study. Free text boxes were included to obtain qualitative data. Quantitative data were tallied and presented as percentages. Qualitative data (free text responses) were analysed thematically. RESULTS: 73 out of 322 psychiatrists responded (22.7%). The greatest barrier to seeing adult ADHD was the fear of being inundated with cases (68.5%), followed by lack of experience managing ADHD (32.9%), and potential drug-seeking behaviour of patients (31.5%). Two overarching qualitative themes were identified: practical barriers and attitudinal barriers. CONCLUSION: ADHD service provision is complex and relates to many systemic factors such as public versus private, funding, and service organisation. More psychiatrists need to become involved in treating ADHD so that the work is more widely spread. Increased training in ADHD is also needed to increase confidence in managing the condition.

All-fibre heterogeneously-integrated frequency comb generation using silicon core fibre.

Originally developed for metrology, optical frequency combs are becoming increasingly pervasive in a wider range of research topics including optical communications, spectroscopy, and radio or microwave signal processing. However, application demands in these fields can be more challenging as they require compact sources with a high tolerance to temperature variations that are capable of delivering flat comb spectra, high power per tone, narrow linewidth and high optical signal-to-noise ratio. This work reports the generation of a flat, high power frequency comb in the telecom band using a 17 mm fully-integrated silicon core fibre as a parametric mixer. Our all-fibre, cavity-free source combines the material benefits of planar waveguide structures with the advantageous properties of fibre platforms to achieve a 30 nm bandwidth comb source containing 143 tones with <3 kHz linewidth, 12 dB flatness, and >30 dB OSNR over the entire spectral region.

Phase noise of electro-optic dual frequency combs.

Dual frequency combs are emerging as new tools for spectroscopy and signal processing. The relative phase noise of the tone pairs determines the performance (e.g., signal-to-noise ratio) of the detected spectral components. Although previous research has shown that the signal quality generally degrades with an increase in frequency difference between tone pairs, the scaling of the relative phase noise of dual frequency comb systems has not been fully characterized. In this Letter, we model and characterize the phase noise of a coherent electro-optic dual frequency comb system. Our results show that at high offset frequencies, the phase noise is an incoherent sum of the timing phase noise of the two combs, multiplied by line number. At low offset frequencies, however, the phase noise scales more slowly due to the coherence of the common frequency reference.

Noise and distortion analysis of dual frequency comb photonic RF channelizers.

Dual frequency combs are emerging as highly effective channelizers for radio frequency (RF) signal processing, showing versatile capabilities in various applications including Fourier signal mapping, analog-to-digital conversion and sub-sampling of sparse wideband signals. Although previous research has considered the impact of comb power and harmonic distortions in individual systems, a rigorous and comprehensive performance analysis is lacking, particularly regarding the impact of phase noise. This is especially important considering that phase noise power increases quadratically with comb line number. In this paper, we develop a theoretical model of a dual frequency comb channelizer and evaluate the signal to noise ratio limits and design challenges when deploying such systems in a high bandwidth signal processing context. We show that the performance of these dual comb based signal processors is limited by the relative phase noise between the two optical frequency combs, which to our knowledge has not been considered in previous literature. Our simulations verify the theoretical model and examine the stochastic noise contributions and harmonic distortion, followed by a broader discussion of the performance limits of dual frequency comb channelizers, which demonstrate the importance of minimizing the relative phase noise between the two frequency combs to achieve high signal-to-noise ratio signal processing.