A. Priyadarshi | Searcharxiv

arXiv2023

Mathematical Modelling of Hypothalamus-Pituitary-Adrenal Axis Dynamics: A Review, a Novel Approach, and Future

A novel mathematical model for the hypothalamic pituitary adrenal (HPA) axis is proposed to comprehend the oscillations observed in hormone concentration and potential dysfunction within the HPA axis in stressful situation. This model integrates impact of hippocampal receptors on the secretion of corticotropin-releasing hormone (CRH), an additional signaling pathway involving Arginine Vasopressin (AVP) for the production and secretion of adrenocorticotropic hormone (ACTH), the inclusion of a daylight-related function for modeling circadian rhythms, and a short negative feedback loop from the pituitary to the hypothalamus in a minimal mechanistic model of the HPA axis. This expansion allows us to estimate model parameters that led to a significant reduction in the mean absolute percent error, thereby enhancing the model's predictive accuracy with a demonstration of a strong fit to the validation dataset. Through sensitivity and correlation analyses, our study shows the parameters that exert the most significant influence on the dynamics of cortisol within the system. This study reveals intricate interdependencies within the model and among the various components of the HPA axis. Despite current advancements in the model to comprehend the dynamics of the HPA Axis, these models are still lacking in addressing major factors such as the impact of genetic and epigenetics, the role of the amygdala in processing and transmitting stress signals, and other minor impacting factors.

math.DS↗

arXiv2023

TransitFit: combined multi-instrument exoplanet transit fitting for JWST, HST and ground-based transmission spectroscopy studies

We present TransitFit, a package designed to fit exoplanetary transit light-curves. TransitFit offers multi-epoch, multi-wavelength fitting of multi-telescope transit data. TransitFit allows per-telescope detrending to be performed simultaneously with transit parameter fitting, including custom detrending. Host limb darkening can be fitted using prior conditioning from stellar atmosphere models. We demonstrate TransitFit in a number of contexts. We model multi-telescope broadband optical data from the ground-based SPEARNET survey of the low-density hot-Neptune WASP-127b and compare results to a previously published higher spectral resolution GTC/OSIRIS transmission spectrum. Using TransitFit, we fit 26 transit epochs by TESS to recover improved ephemeris of the hot-Jupiter WASP-91b and a transit depth determined to a precision of 111 ppm. We use TransitFit to conduct an investigation into the contested presence of TTV signatures in WASP-126b using 180 transits observed by TESS, concluding that there is no statistically significant evidence for such signatures from observations spanning 27 TESS sectors. We fit HST observations of WASP-43b, demonstrating how TransitFit can use custom detrending algorithms to remove complex baseline systematics. Lastly, we present a transmission spectrum of the atmosphere of WASP-96b constructed from simultaneous fitting of JWST NIRISS Early Release Observations and archive HST WFC3 transit data. The transmission spectrum shows generally good correspondence between spectral features present in both datasets, despite very different detrending requirements.

astro-ph.EP↗