Observations of the Crab Nebula with MACE (Major Atmospheric Cherenkov Experiment)

The Major Atmospheric Cherenkov Experiment (MACE) is a large size (21m) Imaging Atmospheric Cherenkov Telescope (IACT) installed at an altitude of 4270m above sea level at Hanle, Ladakh in northern India. Here we report the detection of Very High Energy (VHE) gamma-ray emission from Crab Nebula above 80 GeV. We analysed ~15 hours of data collected at low zenith angle between November 2022 and February 2023. The energy spectrum is well described by a log-parabola function with a flux of ~(3.46 +/- 0.26stat) x 10-10 TeV-1 cm-2 s-1, at 400 GeV with spectral index of 2.09 +/- 0.06stat and a curvature parameter of 0.08 +/- 0.07stat. The gamma-rays are detected in an energy range spanning from 80 GeV to ~5 TeV. The energy resolution improves from ~34% at an analysis energy threshold of 80 GeV to ~21% above 1 TeV. The daily light curve and the spectral energy distribution obtained for the Crab Nebula is in agreement with previous measurements, considering statistical and systematic uncertainties.Comment: Accepted for publication in Astroparticle Physic

Morgagni Hernia With Down syndrome: A Rare Association - Case Report and Review of Literature

Morgagni hernia is a rare diaphragmatic hernia accounting for only 2% of the congenital diaphragmatic defects. A case of Morgagni hernia was diagnosed radiologically in a 12-months-old male with Down syndrome, with recurrent respiratory distress and chest deformity. The 2-dimensional echocardiography was normal. The diagnosis of Morgagni hernia was confirmed by barium studies. The patient underwent a corrective surgery at 18 months of age following which his symptoms subsided. Literature review revealed only 18 cases of Morgagni hernia with Down syndrome reported till date, with age of presentation varying from neonatal age group to 12 years of age. The mode of presentations varied from asymptomatic detection to severe respiratory distress. The possible mechanism of association and its clinical implication has been discussed. The case emphasises a need for diaphragmatic hernia to be looked for as a possible cause of respiratory distress in Down syndrome

Architecture of polyglutamine-containing fibrils from time-resolved fluorescence decay

The disease risk and age of onset of Huntington disease (HD) and nine other repeat disorders strongly depend on the expansion of CAG repeats encoding consecutive polyglutamines (polyQ) in the corresponding disease protein. PolyQ length-dependent misfolding and aggregation are the hallmarks of CAG pathologies. Despite intense effort, the overall structure of these aggregates remains poorly understood. Here, we used sensitive time-dependent fluorescent decay measurements to assess the architecture of mature fibrils of huntingtin (Htt) exon 1 implicated in HD pathology. Varying the position of the fluorescent labels in the Htt monomer with expanded 51Q (Htt51Q) and using structural models of putative fibril structures, we generated distance distributions between donors and acceptors covering all possible distances between the monomers or monomer dimensions within the polyQ amyloid fibril. Using Monte Carlo simulations, we systematically scanned all possible monomer conformations that fit the experimentally measured decay times. Monomers with four-stranded 51Q stretches organized into five-layered β-sheets with alternating N termini of the monomers perpendicular to the fibril axis gave the best fit to our data. Alternatively, the core structure of the polyQ fibrils might also be a zipper layer with antiparallel four-stranded stretches as this structure showed the next best fit. All other remaining arrangements are clearly excluded by the data. Furthermore, the assessed dimensions of the polyQ stretch of each monomer provide structural evidence for the observed polyQ length threshold in HD pathology. Our approach can be used to validate the effect of pharmacological substances that inhibit or alter amyloid growth and structure