Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An NPZ Model with State-Dependent Delay due to Size-Structure in
  Juvenile Zooplankton   The study of planktonic ecosystems is important as they make up the bottom
trophic levels of aquatic food webs. We study a closed
Nutrient-Phytoplankton-Zooplankton (NPZ) model that includes size structure in
the juvenile zooplankton. The closed nature of the system allows the
formulation of a conservation law of biomass that governs the system. The model
consists of a system of nonlinear ordinary differential equation coupled to a
partial differential equation. We are able to transform this system into a
system of delay differential equations where the delay is of threshold type and
is state-dependent. The system of delay differential equations can be further
transformed into one with fixed delay. Using the different forms of the model
we perform a qualitative analysis of the solutions, which includes studying
existence and uniqueness, positivity and boundedness, local and global
stability, and conditions for extinction. Key parameters that are explored are
the total biomass in the system and the maturity level at which the juvenile
zooplankton reach maturity. Numerical simulations are also performed to verify
our analytical results.

3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
24
The categories of this paper are: dg-ga
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph
9
The categories of this paper are: nlin
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci