The Comet Interceptor Mission

Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA's F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum Δ V capability of 600  ms - 1 . Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes - B1, provided by the Japanese space agency, JAXA, and B2 - that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission's science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule.

A Perovskite-Graphene Device for X-ray Detection

This study examines a perovskite-based graphene field effect transistor (P-GFET) device for X-ray detection. The device architecture consisted of a commercially available GFET-S20 chip, produced by Graphenea, with a layer of methylammonium lead iodide (MAPbI3) perovskite spin coated onto the top of it. This device was exposed to the field of a molybdenum target X-ray tube with beam settings between 20-60 kVp (X-ray tube voltage) and 30-300 uA (X-ray tube current). Dose measurements were taken with an ion-chamber and thermo-luminescent dosimeters and used to determine the sensitivity of the device as a function of the X-ray tube voltage and current, as well as source-drain voltage. The X-ray tube was also simulated in this work with GEANT4 and MCNP to determine the dose rate and power incident on the device during irradiation. These simulations were then used to determine the responsivity as a function of the X-ray tube voltage and current, as well as the source-drain voltage. Overall, a strong positive correlation between sensitivity and source-drain voltage was found. Conversely, the sensitivity was found to decrease - roughly exponentially - as a function of both the X-ray tube current and energy. Similar trends were seen with responsivity. We report the models used for the study as well as address the feasibility of the device as a low-energy (< 70 keV) X-ray photon detector.

Macular injuries secondary to handheld lasers in a paediatric population-clinical characteristics and indicators of visual impact

BACKGROUND/OBJECTIVES

Aim to identify incidence and prevalence of laser-induced retinal injuries in the Northern Ireland paediatric population and to determine negative clinical and OCT indicators in relation to visual acuity.

SUBJECTS/METHODS

A retrospective analysis was conducted of retinal injuries secondary to handheld laser pens over a 6-year time period with presenting and final visual acuity (VA), laser source and circumstances of the injury recorded. Fundus photographs and OCT images for each case were also collated.

RESULTS

Sixty-five patients (74 eyes) were identified of which 72% were male and mean age was 11.6 years. 40% of patients were symptomatic. Mean presenting VA was 0.16 LogMAR. VA was ≤0.30 LogMAR in 20 eyes (27%) at presentation. Features which impacted VA to a significant level were foveolar location, diffuse morphology, ELM and BM/RPE/IDZ disruption and ORH presence on presenting OCT images. ORHs or ELM disruption resulted in a significant risk ratio of 3.5 (p = 0.002) and 3.4 (p = <0.001) respectively. Mean presenting VA was demonstrated to improve during follow-up from 0.36 to 0.22 LogMAR (n = 20, p = 0.03). When VA was ≤0.30 LogMAR at presentation, mean presenting VA improved from 0.56 to 0.29 LogMAR (p < 0.01) with 58% of eyes improving to a VA of better than 0.30 LogMAR.

CONCLUSIONS

The overall visual loss from macular laser injuries was low and we have identified features on retinal imaging that significantly impact presenting VA. When VA is affected following macular laser injury there is evidence of recovery with >50% of those presenting with VA ≤ 0.30 LogMAR improving to better than 0.30 LogMAR.

Presumed ocular tuberculosis in the United Kingdom: a British Ophthalmological Surveillance Unit (BOSU) study

Introduction

Ocular tuberculosis (TB) is an extrapulmonary manifestation of mycobacterium infection that most commonly presents as uveitis. This is the first prospective incidence study of presumed ocular tuberculosis performed in the United Kingdom (UK).

Method

New cases of ocular tuberculosis presenting to hospitals in the UK were prospectively ascertained between October 2016 and November 2017 with the aid of the British Ophthalmological Surveillance Unit (BOSU). Initial presentation data and 1-year follow-up data was collected using questionnaires.

Results

Forty-eight patients were recruited giving an overall incidence for ocular TB of 0.73 per million population per annum. The origin of birth for 71% of the patients was a non-UK country and 87.5% had their initial diagnosis of TB made by an ophthalmologist. The most common first line treatment was isoniazid, rifampicin, ethambutol and pyrazinamide which 71% of patients were treated with 60% of patients were commenced on a reducing course of oral steroids. At 1-year follow-up, 29 patients (83%) had complete resolution of active clinical signs. Mean best corrected visual acuity (BCVA) at presentation was +0.41 LogMAR(SD = 0.62), compared to +0.31 LogMAR (SD = 0.56) at 12-month follow-up.

Discussion

It is increasingly the responsibility of the ophthalmologist to diagnose ocular TB and although it remains a rare condition, consensus on diagnostic criteria and treatment is required. Increasing recognition and accessibility to gamma-interferon testing should enable earlier detection. Treatment with quadruple ATT treatment regimens for at least 6 months shows good clinical outcomes. However, it is still unclear whether steroid use is beneficial. Further large studies with longer follow-up would be warranted to answer these questions.

Torpedo maculopathy: disease spectrum and associated choroidal neovascularisation in a paediatric population

PURPOSE

Torpedo maculopathy is a rare lesion of the retinal pigment epithelium. This study set out to look at these lesions in the paediatric population and determine the spectrum and features of the disease.

METHODS

The paediatric ophthalmology database was used to identify eight children with torpedo maculopathy between 2012 and 2017. Fundal images and optical coherence tomography (OCT) was used to analyse the cases.

RESULTS

Eight patients with torpedo maculopathy were identified, making the prevalence approximately 2 per 100,000 population under 16 years old. The OCT images were classified using the previously described subtypes: Type 1 in patients 5 and 6 and Type 2 in patients 1, 2, 3, 4 and 8. The average age of presentation of Type 1 and Type 2 lesions was 8 and 7 years old respectively. We also report patient 8, who is the youngest reported case of choroidal neovascular membrane associated with torpedo maculopathy. Good anatomical response to a single injection of anti-Vegf was shown.

CONCLUSIONS

This study is the first case series of torpedo maculopathy in the paediatric population. Contrary to previous reports of two distinct types of lesion on OCT representing different stages of the same disease, our case series indicates that Type 1 and Type 2 lesions are in fact different phenotypic entities both of which can occur at a young age. We also present the associated risk of choroidal neovascular membrane formation which is an important consideration for long term follow-up.

A clinical study of Aicardi syndrome in Northern Ireland: the spectrum of ophthalmic findings

PurposeAicardi syndrome is a rare disorder, affecting ~1 in 100 000 live births. Chorioretinal lacunae feature alongside agenesis of the corpus callosum and spasms in flexion to make up a diagnostic triad. Recently ophthalmic findings such as microphthalmia and optic disc anomalies have been recognised in association with Aicardi syndrome. This population study aims to determine the presence of ocular findings and identifies some novel associations in these patients.MethodsA retrospective review of charts for seven patients with Aicardi syndrome was carried out.ResultsThe incidence of Aicardi syndrome in Northern Ireland was found to be 1 in 110 000 live births. Four patients who had microphthalmus also had iris abnormalities; two patients with bilateral microphthalmus had partial aniridia and two patients with unilateral microphthalmus had iris coloboma in the same eye. Optic disc abnormalities were found in 11 eyes of six patients. Two patients were found to have areas of fibrovascular proliferation with a thickened white ridge and avascular zone beyond. Both of these patients developed retinal detachments.ConclusionsOur review of patients with Aicardi syndrome in Northern Ireland has revealed some novel clinical findings, including aniridia in two cases. We also found a higher than previously reported rate of excavated disc anomalies of 50% in our cohort. We found two cases of peripheral retinal dysplasia, which has not been previously reported. This finding was associated with microphthalmus and severe optic disc abnormalities, and we feel this warrants early EUA to enable early treatment and hopefully result in better visual prognosis.

Late asthmatic reactions provoked by intradermal injection of T-cell peptide epitopes are not associated with bronchial mucosal infiltration of eosinophils or T(H)2-type cells or with elevated concentrations of histamine or eicosanoids in bronchoalveolar fluid

BACKGROUND

Isolated late asthmatic reactions can be provoked by intradermal challenge of allergen-derived T-cell peptide epitopes.

OBJECTIVE

The purpose of this study was to determine whether the isolated LAR is associated with the local accumulation of inflammatory cells, the expression of T(H)2 cytokines, and the production of pharmacologic mediators.

METHODS

A randomized, placebo-controlled, crossover study design was used. The investigation involved bronchial and skin biopsies and bronchoalveolar lavage (BAL) fluids from 8 cat-allergic subjects who developed significant late asthmatic reactions 6 hours after intradermal injection of Fel d 1 chain 1-derived peptides (FC1Ps).

RESULTS

Immunostaining of bronchial biopsy specimens showed no changes in the numbers of eosinophils, neutrophils, basophils, mast cells, CD3(+), CD4(+) or CD8(+) T cells, CD25(+) cells or macrophages, or cells mRNA(+) for IL-4, IL-5, or IL-13 when the FC1P day was compared with the diluent control day. There were also no significant differences in eosinophil numbers, either in BAL fluids or in peripheral blood after FC1P challenge. Furthermore, there were no significant alterations in the concentrations of histamine, histamine-releasing factors, or eicosanoids (LTC(4)/D(4)/E(4), PGD(2), PGE(2), TXB(2), PGF(2alpha)) in BAL fluids. FC1Ps induced a significant (P <.05) elevation in CD8(+) cells in the skin and an unexpected decrease in IL-5 in BAL fluids (P =.043).

CONCLUSION

Part of the asthma process might involve T cell-dependent airway narrowing with no requirement for IgE, mast cells, or infiltrating inflammatory cells.

Mechanisms of T cell peptide epitope-dependent late asthmatic reactions

Short peptide sequences corresponding to T cell epitopes have been identified in the major cat allergen Fel d 1. In order to directly activate allergen-specific T cells in cat-allergic asthmatic individuals, peptides were administered by intradermal injection. Subsequently, a proportion of subjects experienced a delayed reduction of airway calibre manifested as a decrease in FEV(1). Changes in lung function occurred approximately 3 h after peptide injection, peaked at 6 h and resembled an isolated late asthmatic reaction (LAR). Using molecular tissue typing techniques, it was determined that many of the individuals experiencing isolated LAR expressed particular HLA-DR molecules. These molecules were shown in subsequent experiments to bind individual peptides within the preparation and thus to activate T cells in a major histocompatibility complex (MHC)-restricted fashion. The precise mechanisms whereby MHC-restricted activation of allergen-specific T cells gives rise to bronchoconstriction are currently under investigation.