Featured Author

John Hayward

I am a Visiting Research Fellow in Mathematics at the University of South Wales. Before my retirement, I was a senior lecturer at the university, teaching specialist courses in system dynamics, mathematical modelling and agent-based methods. I was awarded a BSc in astrophysics, and a PhD in applied mathematics, from the University of London, and then spent my career as a lecturer in mathematics. My research is in mathematical sociology with applications to the spread of social phenomena, such as ... Read more

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We found 40 items
Author Rank Title Type Views
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#1

Lactase Enzyme Simulation with Data Analysis

by Jon Darkow
sim ⋮ 12,153,830 runs
3149408.5
#2

Enzyme Diversity: Enzymes, Products, and Substrates

by Jon Darkow
sim ⋮ 1,095,188 runs
enzymes substrates products DNA trypsin
1592316.6
#3

Cellular Respiration Accounting Model

by Jon Darkow
The purpose of the model is to understand how glucose is metabolized, and how the energy stored in i ... Read more
The purpose of the model is to understand how glucose is metabolized, and how the energy stored in its chemical bonds is transfered.
sim ⋮ 714,538 runs
cellular respiration aerobic respiration ATP biology
791428.9
#4

Enzyme Diversity

by Jon Darkow
sim ⋮ 477,425 runs
enzyme biology substrate pepsin indicators
727375.06
#5

Photosynthesis Model

by Jon Darkow
sim ⋮ 2,532,833 runs
653119.6
#6

Lactase with Variable Sample Sizes

by Jon Darkow
Arrayed Lactase Model
sim ⋮ 837,027 runs
Lactase array sample size biology
567712.2
#7

Information Processing and Neurophysiology Model

by Jon Darkow
The main dependent variable measured in the model is the membrane potential (millivolts) of two diff ... Read more
The main dependent variable measured in the model is the membrane potential (millivolts) of two different neurons in a series. You will be able to add excitatory and inhibitory neurotransmitters, and compare how these modulate electrical impulses of the two neurons. Additionally, you will be able to compare the effects of three neurotoxins: Tetrodotoxin, botulinum toxin, and sarin nerve gas. While extremely lethal, these toxins are very instructive in understanding neurons because of the specific way the toxins act. Each toxin modifies or inhibits a specific molecule in neurons that help process and transmit information.
sim ⋮ 306,804 runs
infromation processing neurophysiology biology
451861.88
#8

Predator-Prey-LevelA

by Creative Learning Exchange
Level A: Up and Down in the Wild: Predator and Prey This lesson allows students to explore the in ... Read more
Level A: Up and Down in the Wild: Predator and Prey This lesson allows students to explore the interactions of two animal populations (wolves and moose) within an ecosystem. One animal in the simulation is a predator. The other animal is its prey. Their populations rise and fall (oscillate) over time as they interact and impact one another.
sim ⋮ 348,330 runs, 493 downloads
Download Model
ecosystem population predator prey oscillation
411738.9
#9

Lotka-Volterra Predator-Prey Model

by Jon Darkow
Explore my favorite aspect of system dynamics and a historic example. The homeostasis generated by t ... Read more
Explore my favorite aspect of system dynamics and a historic example. The homeostasis generated by the interconnections of a negative feedback loop governs much of life.
sim ⋮ 276,112 runs
negative feedback loop Lotka-Volterra homeostasis predator-prey
364673.78
#10

Population dynamics of white footed mouse

by Jon Darkow
sim ⋮ 1,333,311 runs
340293.88
#11

Growth Factors, Cyclins, and Cancer

by Jon Darkow
Explores the feedback loops that regulate the cell cycle. Model focuses on manipulating stimuli (gro ... Read more
Explores the feedback loops that regulate the cell cycle. Model focuses on manipulating stimuli (growth factors), to stimulate the cell cycle feedback loops.
sim ⋮ 307,171 runs
growth factors cyclins cell cycle cancer
286690.53
#12

COVID-19 Simulator

by isee systems
This simulator looks at the spread of COVID-19 (Coronavirus) through a city. You can implement poli ... Read more
This simulator looks at the spread of COVID-19 (Coronavirus) through a city. You can implement policies, change assumptions about the disease and see the impacts in realtime.
sim ⋮ 122,812 runs
Biology Science Education COVID-19 Coronavirus
273165.03
#13

Evolution of Antibiotic Resistance Simulation

by Jon Darkow
Evolution of Antibiotic Resistance Simulation. This model tracks the accumulation of 40 colonies of ... Read more
Evolution of Antibiotic Resistance Simulation. This model tracks the accumulation of 40 colonies of bacteria. The main purpose of the model is to show that new adaptations are not caused by an environmental factor, like antibiotics. Rather, new adaptations are the selection of available variations. In this model you can increase variations by increasing the UV dose. The UV dose increases the mutation rate with a Monte Carlo function.
sim ⋮ 176,495 runs
Biology Science Ecology Education
190023.9
#14

Lactose Operon: An Inducible System

by Jon Darkow
In this simulation users explore the negative feedback system of the Lactose Operon found in bacteri ... Read more
In this simulation users explore the negative feedback system of the Lactose Operon found in bacteria. Lactose induces the system by inhibiting and inhibitor.
sim ⋮ 145,624 runs
Inhibition negative feedback biology lactose operon
166701.03
#15

Apterous Genetics

by Jon Darkow
Apterous is an allele that results in a fly without wings. Wild-type variants have normally function ... Read more
Apterous is an allele that results in a fly without wings. Wild-type variants have normally functioning wings. The goal of this simulation is to determine the pattern of inheritance for the apterous phenotype. Is apterous dominant or recessive? Sex-linked or autosomal? Complete, incomplete, or codominant?
sim ⋮ 307,464 runs
Genetics
138575.45
#16

Limiting Nutrients in Aquatic Ecosystems

by Jon Darkow
Experiment with a variety of nutrients that are limited by different degrees in four different ecosy ... Read more
Experiment with a variety of nutrients that are limited by different degrees in four different ecosystems.
sim ⋮ 124,572 runs
limiting nutrients ecosystem biology logistic growth
134173.27
#17

Lac Operon with Monod Bump

by Jon Darkow
sim ⋮ 203,762 runs
Lac Operon Gene Regulation mRNA
119811.2
#18

Diffusion of a Spherical Cell

by Jon Darkow
Why are cells small? This model allows users to see how the size of a sphere affects the rate of dif ... Read more
Why are cells small? This model allows users to see how the size of a sphere affects the rate of diffusion.
sim ⋮ 145,404 runs
diffusion surface area volume radius
118786.625
#19

Transformation Simulation

by Jon Darkow
Simulation allows students to test the transformation principle. Two major goals of the experiment a ... Read more
Simulation allows students to test the transformation principle. Two major goals of the experiment are: 1. Allow users to see that supernatant from heat-killed bacteria can transform the genes of another bacterium. 2. What transforms the inheritance of the bacteria is DNA, not RNA or proteins.
sim ⋮ 134,792 runs
transformation DNA biology
107242.625
#20

Water Potential and Osmosis

by Jon Darkow
Factors that affect the flow across a semi-permeable membrane.
sim ⋮ 396,575 runs
103050.13
#21

Evolution and Natural Selection

by Jon Darkow
sim ⋮ 353,030 runs
89985.88
#22

Model 2. Drug Transporters

by Sara Rosenbaum
This simulation shows the location and functioning of the major clinically important drug transporte ... Read more
This simulation shows the location and functioning of the major clinically important drug transporters in the : gastrointestinal membrane; renal tubular membrane; and the membranes of the hepatocyte. Simulations demonstrate their functioning after oral and intravenous doses of a drug substrate
sim ⋮ 54,395 runs
drug transporters efflux uptake drug absorption
88704.31
#23

Cellular Respiration Inquiry

by Jon Darkow
Model of the dynamics of the metabolism of one mole of glucose. Randomness is built into the computa ... Read more
Model of the dynamics of the metabolism of one mole of glucose. Randomness is built into the computations.
sim ⋮ 111,978 runs
metabolism respriation ATP biology
87150.84
#24

Model 1. Introduction to PK and PD

by Sara Rosenbaum
This model allows users to use trial and error to identify appropriate doses of a drug for IV, oral ... Read more
This model allows users to use trial and error to identify appropriate doses of a drug for IV, oral and other extravascular routes of administration
sim ⋮ 77,222 runs
Pharmacokinetics Pharmacodynamics Therapeutic Range
85277.97
#25

Guppy Evolution

by Jon Darkow
sim ⋮ 180,467 runs
evolution biology genes
82181.76
#26

White-Eyed Genetics

by Jon Darkow
White-eyed is an allele that results in a fly white eyes. Wild-type variants have red eyes. The ... Read more
White-eyed is an allele that results in a fly white eyes. Wild-type variants have red eyes. The goal of this simulation is to determine the pattern of inheritance for the white-eyed phenotype. Is yellow body dominant or recessive? Sex-linked or autosomal? Complete, incomplete, or codominant?
sim ⋮ 186,168 runs
Genetics
81288.49
#27

Vacation

by isee systems
Do you ever feel like work is taking over your life? Burnout is generally characterized as a state o ... Read more
Do you ever feel like work is taking over your life? Burnout is generally characterized as a state of mental and physical exhaustion resulting in low productivity and de-personalization and is most likely caused by prolonged stress that does not dissipate. There are many different aspects that affect both the building and dissipation of burnout. This model focuses on workloads and vacations to see how they contribute to both your level of burnout and productivity. Use this model to ask questions about your workload and any benefits you would receive from taking a vacation. What happens when you suddenly have a bigger workload? What happens when work piles up? Does vacation increase or decrease your stress levels?
sim ⋮ 39,302 runs, 898 downloads
Download Model
Vacation burnout stress productivity workload
81228.27
#28

Neurophysiology and Neurotoxicity

by Jon Darkow
The main dependent variable measured in the model is the membrane potential (millivolts) of a motor ... Read more
The main dependent variable measured in the model is the membrane potential (millivolts) of a motor neuron and the muscle fiber it innervates. You will be able to add excitatory and inhibitory neurotransmitters, and compare how neurotransmitters modulate the electrical impulses of the motor neuron and the muscle fiber. Additionally, you will be able to compare the effects of four neurotoxins: Tetrodotoxin, botulinum toxin, sarin nerve gas, and VX. While extremely lethal, these toxins are very instructive in understanding neurons because of the specific way the toxins act. Each toxin modifies or inhibits a specific molecule in neurons that help process and transmit information.
sim ⋮ 46,458 runs
Neurophysiology toxins sarin VX TTX
81203.625
#29

Thyroid Hormone - Negative Feedback

by Jon Darkow
sim ⋮ 79,052 runs
negative feedback thyroid hormone metabolism biology
77148.97
#30

Tesing Unknown Enzymes

by Jon Darkow
sim ⋮ 277,736 runs
enzymes
72169.12
#31

The dynamics of photosynthesis - variable sample size

by Jon Darkow
The dynamics of photosynthesis - variable sample size
sim ⋮ 93,728 runs
photosynthesis sample size biology
65246.996
#32

Oxytocin and Child Birth

by Jon Darkow
sim ⋮ 245,037 runs
63551.94
#33

Zombie Apocalypse

by isee systems
This is our first model in the From Imagination to Simulation series. It is a nod to the Halloween s ... Read more
This is our first model in the From Imagination to Simulation series. It is a nod to the Halloween season and investigates a zombie apocalypse! Our fascination with zombies continually grows with the help of movies, TV shows, and books that give a wide range of zombie possibilities. But what are the dynamics behind a zombie epidemic? This model will specifically look at the spread of a zombie outbreak and examine some of the variables that help and hinder the rate of infection. We hope you will continue to see the benefits and versatility of Systems Thinking and enjoy our new series, From Imagination to Simulation! Continue to ponder those out-of-the-ordinary problems. They may seem unrealistic, but perhaps some of their dynamics may resonate with reality. Check out our zombie apocalypse model to see if there is any chance for human survival!
sim ⋮ 25,644 runs, 910 downloads
Download Model
Systems Thinking zombies epidemic disease susceptible
59389.293
#34

Intravenous Infusion

by Sara Rosenbaum
This model demonstrates the pharmacokinetic characteristics of constant continuous drug administrati ... Read more
This model demonstrates the pharmacokinetic characteristics of constant continuous drug administration.
sim ⋮ 28,904 runs, 95 downloads
Download Model
drug pharmacokinetics intravenous infusion zero order input constant continuous drug administration
55464.195
#35

Photosynthesis Simulation with Variance

by Jon Darkow
sim ⋮ 209,027 runs
54324.8
#36

Evolution of LAP Allele in Mussels

by Jon Darkow
sim ⋮ 85,166 runs
Evolution Natural Selection Cline
53333.094
#37

Oral Absorption

by Sara Rosenbaum
This model is based on first order absoprtion in a 1-compartment model
sim ⋮ 52,999 runs, 153 downloads
Download Model
Drug Absoprtion Bioavailability Bioequivalence
51873.074
#38

College Loans

by isee systems
Each year, the cost of a college education continues to rise and more and more students must turn to ... Read more
Each year, the cost of a college education continues to rise and more and more students must turn to student loans to complete their education. But as graduates leave college to embark on their careers, they face an almost Sisyphean struggle with student debt, forever facing an uphill battle while carrying a heavy burden, only to find they are getting nowhere! Whether you are graduating from college or just entering, we hope this model will enable you to better understand student loans and help plan for your future.
sim ⋮ 27,525 runs, 1,060 downloads
Download Model
Student loans loans college interest repayment
48079.55
#39

Photosynthesis with Variable Sample Sizes

by Jon Darkow
Sample sizes of Photosynthesis stocks in an array
sim ⋮ 181,403 runs, 149 downloads
Download Model
47106.13
#40

Mulitple Bolus Injections Pharmacokinetics

by Sara Rosenbaum
This model shows the typical plasma concentration profile associated with the administration of seve ... Read more
This model shows the typical plasma concentration profile associated with the administration of several doses of a drug over time. It demonstrates the determinants of the fluctuation in the plasma concentrations, the accumulation of the drug over the course of therapy and the resting steady state plasma concentrations.
sim ⋮ 24,869 runs, 79 downloads
Download Model
drug pharmacokinetics multiple doses multiple intravenous bolus injections
40193.246
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Instead of creating bundles, categories, and assemblies one by one, you can upload a single zip file that contains all of your bundle's content. To create your zipped bundle, make a folder with your bundle's name and add subfolders with your categories' names. The folder tree should have the same structure that you want the categories to have in your bundle. Place your assembly .stmx files in the appropriate category folders, then zip your bundle folder and upload it using the Upload Bundle from Zip link above.

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Assemblies are self contained models that demonstrate common ways to connect together building blocks and that can be used as parts of other models. This is analogous to using prefabricated wall and roof pieces to construct a house.

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Sim App (Sim)

An interface that allows users to interact with a model.

Image of a sim

Sim apps allow users to interact with a model using buttons, sliders, knobs, tables, graphs, and storytelling. These interactions help users understand how parts of a system interact.

Interfaces are created by model authors in the Stella desktop software and can be uploaded to the isee Exchange™.

Model

A diagram that represents how elements in a system influence one another.

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Models are mathematical representations of how elements in a system are connected and interact (e.g., ecosystems, organizations, supply chains). When running models on the isee Exchange™, results can be viewed in output devices like graphs and tables.

Models appear in the isee Exchange™ directory when authors upload them from the Stella® desktop software or create them with Stella Online™.

Causal Loop Diagram (CLD)

A map that represents the feedback structure of a system.

Image of a CLD

CLDs are high-level maps that represents the feedback structure of a system and easily communicate the essence of a model. They appear in the isee Exchange™ when authors upload them from the Stella desktop software or create them with Stella Online™.