Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Existence and stability analysis of solutions for a ultradian
  glucocorticoid rhythmicity and acute stress model   The hypothalamic pituitary adrenal (HPA) axis responds to physical and mental
challenge to maintain homeostasis in part by controlling the body's cortisol
level. Dysregulation of the HPA axis is implicated in numerous stress-related
diseases. For a structured model of the HPA axis that includes the
glucocorticoid receptor but does not take into account the system response
delay, we analyze linear and non-linear stability of stationary solutions. For
a second mathematical model that describes the mechanism of the HPA axis
self-regulatory activities and takes into account a delay of system response,
we prove existence of periodic solutions under certain assumptions on ranges of
parameter values and analyze stability of these solutions with respect to the
time delay value.

35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
27
The categories of this paper are: comp-gas
14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
3
The categories of this paper are: physics
4
The categories of this paper are: cond-mat
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
24
The categories of this paper are: dg-ga
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
6
The categories of this paper are: astro-ph