The photometric observation of the quasi-simultaneous mutual eclipse and occultation between Europa and Ganymede on 22 August 2021

Mutual events (MEs) are eclipses and occultations among planetary natural satellites. Most of the time, eclipses and occultations occur separately. However, the same satellite pair will exhibit an eclipse and an occultation quasi-simultaneously under particular orbital configurations. This kind of rare event is termed as a quasi-simultaneous mutual event (QSME). During the 2021 campaign of mutual events of jovian satellites, we observed a QSME between Europa and Ganymede. The present study aims to describe and study the event in detail. We observed the QSME with a CCD camera attached to a 300-mm telescope at the Hong Kong Space Museum Sai Kung iObservatory. We obtained the combined flux of Europa and Ganymede from aperture photometry. A geometric model was developed to explain the light curve observed. Our results are compared with theoretical predictions (O-C). We found that our simple geometric model can explain the QSME fairly accurately, and the QSME light curve is a superposition of the light curves of an eclipse and an occultation. Notably, the observed flux drops are within 2.6% of the theoretical predictions. The size of the event central time O-Cs ranges from -14.4 to 43.2 s. Both O-Cs of flux drop and timing are comparable to other studies adopting more complicated models. Given the event rarity, model simplicity and accuracy, we encourage more observations and analysis on QSMEs to improve Solar System ephemerides.Comment: 23 pages, 5 appendixes, 16 figures, 7 table

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Clinical and manometric evaluations of anorectal function in patients after transanal endorectal pull-through operation for Hirschsprung's disease: A multicentre study

© 2015 College of Surgeons of Hong Kong. Aim: Transanal endorectal pull-through (TEPT) operation is one the most popular operations for Hirschsprung's disease. This aim of the present study was to evaluate its outcome by clinical and manometric assessments. Patients and Methods: This study was a multicentred study involving all three paediatric surgical centres under the Hospital Authority in Hong Kong. All patients, over the age of 3years, who had undergone primary TEPT operation for more than 1year, were included in the present study. Clinical evaluation with bowel function score (BFS) and anorectomanometry were carried out. A BFS >18 and sphincter resting pressure between 30mmHg and 60mmHg were considered normal. Those with concomitant anorectal/neurological anomaly or who could not cooperate were excluded. Results: A total of 37 patients were enrolled in this study. The median age was 60months (range: 36-144months), and the median age at the time of operation was 3months (range: 0.5-60months). With respect to functional outcomes, six patients (16.2 per cent) suffered from constipation, but more than two-thirds of patients had satisfactory stool consistency, as well as frequency. Sixteen patients (43.2 per cent) had no report of any soiling. For the BFS, 26 patients had a BFS above 18, with the median value being 16 (range: 7-20). Manometric assessment revealed that 27 patients (72.9 per cent) had sphincteric resting pressure within the normal value, and the median value was 45mmHg (range: 14-79mmHg). Rectoanal inhibitory reflex was present in six patients (16.2 per cent), and the median value for the volume of air to elicit the first anal sensation was 41mL (range: 18-126mL). Using univariate analysis, long segment disease was identified as a risk factor for developing soiling of more than two times per week [relative risk (RR): 1.87, 95 per cent confidence interval (CI):1.03-2.22, P=0.05], whereas the creation of stoma (RR: 1.69, 95 per cent CI: 1.41-2.14, P=0.04) and occurrence of postoperative enterocolitis (RR: 1.58, 95 per cent CI: 1.36-1.0, P=0.04) were risk factors for abnormal bowel function score. There was no significant risk factor identified for abnormal manometric results. Lastly, patients with abnormal sphincter resting pressure detected in the anorectomanometry study were also more likely to have an abnormal BFS. Conclusion: Most patients have satisfactory clinical and manometric outcomes after primary TEPT operation. Anorectomanometry findings can predict clinical outcomes. Patients with long segment disease, development of enterocolitis and stoma creation before operation will need more attention, as they are prone to develop abnormal bowel function. Early interventions, such as manometric assessment and proper bowel management, are recommended in order to correct bowel dysfunction, as well enabling patients to have a better quality of life.Link_to_subscribed_fulltex