Abstract.During the total solar eclipse observed in Europe on August 11, 1999, measurements were made of the amplitude and phase of four VLF transmitters in the frequency range 16-24 kHz. Five receiver sites wcrc set up, and significant variations in phase and amplitude are reported for 17 paths, more than any previously during an eclipse. Distances from transmitter to receiver ranged from 90 to 14,510 kin, although the majority were <2000 kin. Typically, positive amplitude changes were observed throughout the whole eclipse period on path lengths <2000 kin, while negative amplitude changes were observed on paths >10,000 kin. Negative phase changes were observed on most paths, independent of path length. Although there was significant variation from path to path, the typical changes observed were N3 dB and -

[1] Data assimilation processes aim to combine measurement data with background models in an optimal way. In anticipation of the availability of global radio occultation (RO) measurements, a computationally practical data assimilation technique for combining RO data with background ionospheric models has been implemented, and simulations have been conducted to assess the utility of the technique. In simulations where tomographic images provide the truth data and the Parameterized Ionospheric Model (PIM) provides the background, a fourfold decrease in the electron density error at 300 km altitude was achieved. A global assimilation simulation has also been conducted using the International Reference Ionosphere as the truth data. For a constellation of eight RO satellites, a factor of four decrease in the vertical total electron content RMS error has been demonstrated. The same simulation also results in a factor of three decrease in the NmF2 RMS error and a halving of the hmF2 RMS error.

Key Points A solar superstorm will not be catastrophic A UK Space Weather Board should be set up

Purpose To investigate the effects of Merogel coverage on ostial patency in endonasal endoscopic dacryocystorhinostomy (EES-DCR) for primary chronic dacryocystitis (PCD). Methods In all, 260 patients with unilateral PCD were randomized into two groups: the Merogel group and the control group. All patients underwent EES-DCR. The Merogel group received Merogel covering the wound 1-2 mm around the ostium and the control group received no treatment. Patients were followed up for 9 months. The mucosal epithelialization of the wound, the proliferation of fibrosis tissue, and the success rate of ostial patency were compared. Results Our study included 112 patients in the Merogel group and 115 patients in the control group. At the 2-week review, intact mucosal epithelium lined the ostia in 96 Merogel patients compared with 80 control patients (ITT analysis: v 2 ¼ 4.502, P ¼ 0.034). At the 9-month review, scars were present in 18 patients in the Merogel group compared with 39 patients in the control group (ITT analysis: v 2 ¼ 9.909, P ¼ 0.002, ITT analysis). No differences were observed in the granulation formation between the two groups. The success rate of ostial patency reached 94.6% (106/112) in the Merogel group compared with 80% (92/115) in the control group (ITT analysis: v 2 ¼ 4.151, P ¼ 0.042). Conclusion Merogel coverage may enhance the success rate of EES-DCR for PCD by promoting mucosal epithelial healing and preventing excessive scarring.

Spheno-orbital meningiomas are difficult tumours to manage. Surgical resection can reduce the degree of proptosis and stabilise visual function in patients with failing vision, although sustained improvement is difficult to achieve if the tumour behaves in an aggressive manner. The risk of post-operative visual loss is considerable, either due to surgery or tumour progression. Outcomes from surgical decompression may not necessarily be better than the natural history of these tumours.

Abstract. Measurements of Doppler spread, multipath spread, and signal-to-noise ratio have been made on four high-latitude high-frequency (HF) communications paths. The measurement system and analysis techniques are outlined, and an analysis of the data pertinent to the design of robust HF data modems is presented. A summary of the spreads that are exceeded for 5% of time is presented for each path. Doppler spreads range from 2 to 55 Hz, while multipath spreads range from 1 to 11 ms. Physical interpretations of the data are made, and the data are related to the measured performance characteristics of an HF data modem to estimate the modem availability on the paths considered. When there is mode support, availabilities range from 64% to 100% for a signal-to-noise ratio of 0 dB, although the data indicate that the availabilities can generally be increased by optimizing frequency selection.

BackgroundThe management of diabetic patients with refractory macular oedema or patients with no adequate pre-operative view to administer laser treatment provide a challenge to the ophthalmologist. We wished to assess the use, safety and effect of intravitreal triamcinolone injection at the time of cataract surgery in patients with diabetic foveal oedema and sight limiting lens opacities.MethodThis was a longitudinal non-randomised prospective pilot study in 18 eyes (12 patients). All patients had visually significant lens opacities and either persistent diabetic foveal oedema unresponsive to laser treatment-group A, or foveal oedema with no adequate pre-operative view for laser treatment- group B. The cataract surgery was carried out under full aseptic technique using a self-sealing temporal incision and a foldable acrylic lens. Intravitreal triamcinolone was given infratemporally pars plana at the completion of the cataract surgery. The patients were reviewed at day 5, 2 weeks, 2 months and then every 3 months as required. The Wilcoxin matched-pairs test was used to assess the significance of the improvement in visual acuity at 2 months.ResultsTwelve patients with a total of 18 eyes were included in the study. There were 10 patients (15 eyes) in group A and 3 patients (3 eyes) in group B. Preoperatively 16 of the 18 eyes had a visual acuity of 6/24 or worse. Postoperatively 83% of patients had completely dry foveae at 2 weeks. Best-corrected visual acuities at two months review ranged from 6/6 to CF with 9 eyes (50%) achieving 6/12 or better (7 eyes (47%) in group A and 2 eyes (67%) in group B). Three eyes had no recorded improvement in visual acuity, but no eyes had deterioration in acuity. The improvement in visual acuity was significant at p = 0.001. There were no significant sight threatening complications.ConclusionIntravitreal triamcinolone has been shown to lead to an improvement in macular oedema and visual improvement in diabetic patients not undergoing cataract surgery but has not, to our knowledge, been previously used in a study like this one.We suggest that intravitreal injection at the time of cataract surgery could be carried out safely with encouraging visual outcomes in patients with diabetic foveal oedema and cataract.

Severe space weather was identified as a risk to the UK in 2010 as part of a wider review of natural hazards triggered by the societal disruption caused by the eruption of the Eyjafjallajökull volcano in April of that year. To support further risk assessment by government officials, and at their request, we developed a set of reasonable worst‐case scenarios and first published them as a technical report in 2012 (current version published in 2020). Each scenario focused on a space weather environment that could disrupt a particular national infrastructure such as electric power or satellites, thus, enabling officials to explore the resilience of that infrastructure against severe space weather through discussions with relevant experts from other parts of government and with the operators of that infrastructure. This approach also encouraged us to focus on the environmental features that are key to generating adverse impacts. In this paper, we outline the scientific evidence that we have used to develop these scenarios, and the refinements made to them as new evidence emerged. We show how these scenarios are also considered as an ensemble so that government officials can prepare for a severe space weather event, during which many or all of the different scenarios will materialize. Finally, we note that this ensemble also needs to include insights into how public behavior will play out during a severe space weather event and hence the importance of providing robust, evidence‐based information on space weather and its adverse impacts.