In situ Detection of Cobaloxime Intermediates During Photocatalysis Using Hollow-Core Photonic Crystal Fiber Microreactors.

Hollow-core photonic crystal fibers (HC-PCFs) provide a novel approach for in situ UV/Vis spectroscopy with enhanced detection sensitivity. Here, we demonstrate that longer optical path lengths than afforded by conventional cuvette-based UV/Vis spectroscopy can be used to detect and identify the CoI and CoII states in hydrogen-evolving cobaloxime catalysts, with spectral identification aided by comparison with DFT-simulated spectra. Our findings show that there are two types of signals observed for these molecular catalysts; a transient signal and a steady-state signal, with the former being assigned to the CoI state and the latter being assigned to the CoII state. These observations lend support to a unimolecular pathway, rather than a bimolecular pathway, for hydrogen evolution. This study highlights the utility of fiber-based microreactors for understanding these and a much wider range of homogeneous photocatalytic systems in the future.

Postgraduate medical education quality metrics panels can be enhanced by including learner outcomes.

Postgraduate medical education (PME) quality assurance at Health Education England (HEE) currently relies upon survey data. As no one metric can reflect all aspects of training, and each has its limitations, additional metrics should be explored. At HEE (West Midlands), we explored the use of learner outcomes, speciality examination pass rates and Annual Review of Competence Progression (ARCP) outcomes, as quality metrics. Feedback received from our local Quality Forum of 40 senior educators frames the discussion through this paper. Overall, learner outcomes are useful quality metrics that add to survey data to provide a more comprehensive picture of PME quality. However, the utility of ARCP outcomes as quality metrics is currently limited by concerns regarding variations in ARCP practice between regions. To address these concerns, ARCPs need the same processes, rigour, scrutiny and investment as other high-stakes assessments. This will improve the reliability and validity of the ARCP as an assessment and improve the usefulness of ARCP outcomes as quality metrics. Research is required to determine the optimal combination of metrics to use in PME quality assurance and to appraise the validity and reliability of the ARCP as an assessment.

Modal analysis of structured light with spatial light modulators: a practical tutorial.

A quantitative analysis of optical fields is essential, particularly when the light is structured in some desired manner, or when there is perhaps an undesired structure that must be corrected for. A ubiquitous procedure in the optical community is that of optical mode projections-a modal analysis of light-for the unveiling of amplitude and phase information of a light field. When correctly performed, all the salient features of the field can be deduced with high fidelity, including its orbital angular momentum, vectorial properties, wavefront, and Poynting vector. Here, we present a practical tutorial on how to perform an efficient and effective optical modal decomposition, with emphasis on holographic approaches using spatial light modulators, highlighting the care required at each step of the process.

Single-step shaping of the orbital angular momentum spectrum of light.

Control of orbital angular momentum (OAM) in optical fields has seen tremendous growth of late, with a myriad of tools existing for their creation and detection. What has been lacking is the ability to arbitrarily modify the OAM spectrum of a superposition in amplitude and phase, especially if a priori knowledge of the initial OAM spectrum is absent. Motivated by a quasi-mapping that exists between the position and OAM of Laguerre-Gaussian modes, we propose an approach for a single-step modulation of a field's OAM spectrum. We outline the concept and implement it through the use of binary ring apertures encoded on spatial light modulators. We show that complete control of the OAM spectrum is achievable in a single step, fostering applications in classical and quantum information processing that utilise the OAM basis.

How perfect are perfect vortex beams?

Perfect (optical) vortex (PV) beams are fields whose radial profile is mooted to be independent of orbital angular momentum (OAM). To date, the best experimental approximation of these modes is obtained from passing Bessel-Gaussian beams through a Fourier lens. However, the OAM-dependent width of these quasi-PVs is not precisely known and is often understated. We address this here by deriving and experimentally confirming an explicit analytic expression for the second moment radius of quasi-PVs. We show that this width scales in proportion to ℓ in the best case, the same as most "regular" vortex modes, albeit with a much smaller proportionality constant. This Letter will be of interest to the large community who seek to use such structured light fields in various applications, including optical trapping, tweezing, and communications.

Ultrasonography of occipital arteries to diagnose giant cell arteritis: a case series and literature review.

We describe four cases of giant cell arteritis (GCA) that presented with occipital headache in the last 6 months. Typical ultrasound features of GCA were found in the occipital arteries which helped to confirm the diagnosis. One patient had already suffered significant visual loss by the time the diagnosis was made, reflecting the similarity in prognosis to the more typical GCA patients. These cases prompted a review of the literature to evaluate the evidence regarding the use of occipital artery ultrasonography in the investigation of GCA. We searched PubMed, Google Scholar and Web of Science and identified 17 papers but only four of these were relevant studies. The studies available show that typical features of GCA can be detected in the occipital arteries using ultrasonography. They also suggest that ultrasonography can detect changes in the occipital arteries when temporal arteries are not involved. However, occipital artery abnormalities were less common than temporal artery abnormalities in GCA. We advocate maintaining a high index of suspicion for GCA in patients presenting with atypical features, such as occipital headache. Ultrasonography has a vital role to play in the diagnosis of these patients. We recommend priority imaging of the affected area to facilitate prompt and accurate diagnosis of GCA, especially when atypical vessels are involved.