H. M. Davies | Searcharxiv

arXiv2026

HCO$^+$ and the Effect of Mixing in SN 1987A

We present high angular resolution observations of the HCO$^+$ emission in the central ejecta of the supernova remnant SN 1987A using the Atacama Large Millimeter Array (ALMA). We use this to infer the degree and type of mixing required within the ejecta in order to form HCO$^+$. The distribution of the $J=3-2$ HCO$^+$ emission is co-spatial with that of the $J=2-1$ CO emission, with an overlap between their brightest peaks. The correlation between the two molecules is strong and suggests that HCO$^+$ could form from reactions involving CO. We obtain additional observations of the $J=4-3$ HCO$^+$ emission to calculate the mass of HCO$^+$. The estimated HCO$^+$ mass is $3\text{--}9 \times 10^{-6}\,M_{\odot}$. The relatively large fractional abundance of HCO$^+$ with respect to CO ($M_{\mathrm{HCO}^+}/M_{\mathrm{CO}} = 3 \times 10^{-6}\text{--}3 \times 10^{-4}$) suggests that a moderate amount of hydrogen was mixed into the carbon- and oxygen-rich nuclear zones of the ejecta prior to and during the supernova explosion, in addition to large-scale macroscopic mixing.

astro-ph.SR↗

arXiv2017

Are Paralysed Chondrocytes Really Dying?

The aims of the current study were to establish a system of culture for induction of paralysed chondrocytes and to investigate if these cells are really dying. Chondrocytes were isolated from the growth cartilage of fetal equines, centrifuged and cultured as pellets in either 10% fetal calf serum or 10% horse serum for 28 days and processed for light and electron microscopy. Different cell types were counted and expressed as a percentage to the total cell number. Growth kinetics including the pellet weight and thickness and the cellular density were evaluated. After 7 days in culture, paralysed chondrocytes with similar morphology to those described in the rabbit growth cartilage could be identified in pellets in each serum type, however, the proportion of the cells was different. In pellet cultured with 10% fetal calf serum, more than 50% of the cells were paralysed chondrocytes but in 10% horse serum, less than 10% of cells were of paralysed type. At day 14, about 50% of the cells in pellets cultured in either serum type differentiated into hypertrophic dark chondrocytes and the proportion of paralysed cells was markedly decreased. After 21 days in each culture, more than 70% of the cells were hypertrophic dark chondrocytes and no paralysed chondrocytes could be observed. The paralysed chondrocytes may be not dying and they likely to be an immature form of hypertrophic dark chondrocytes. It is better to use the term immature dark chondrocytes instead of paralysed cells. This culture system will be useful for further molecular studies on paralysed chondrocytes and to explore the functions of these cells.

q-bio.TO↗