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
Include in results:
#1

Lactase Enzyme Simulation with Data Analysis

sim12,097,807 runs
3143617
#2

Enzyme Diversity: Enzymes, Products, and Substrates

sim1,087,247 runs
enzymes substrates products DNA trypsin
1580778.2
#3

Cellular Respiration Accounting Model

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.
sim709,643 runs
cellular respiration aerobic respiration ATP biology
786056.25
#4

Enzyme Diversity

sim472,632 runs
enzyme biology substrate pepsin indicators
721451.6
#5

Photosynthesis Model

sim2,505,782 runs
649844.1
#6

Lactase with Variable Sample Sizes

Arrayed Lactase Model
sim831,922 runs
Lactase array sample size biology
566136.3
#7

Information Processing and Neurophysiology Model

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.
sim306,214 runs
infromation processing neurophysiology biology
451332.6
#8

Predator-Prey-LevelA

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.
sim343,565 runs, 488 downloads
Download Model
ecosystem population predator prey oscillation
406159.7
#9

Lotka-Volterra Predator-Prey Model

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.
sim273,153 runs
negative feedback loop Lotka-Volterra homeostasis predator-prey
362038.38
#10

Population dynamics of white footed mouse

sim1,291,412 runs
332792.6
#11

Growth Factors, Cyclins, and Cancer

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.
sim306,984 runs
growth factors cyclins cell cycle cancer
286587.84
#12

COVID-19 Simulator

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.
sim121,827 runs
Biology Science Education COVID-19 Coronavirus
272743.47
#13

Evolution of Antibiotic Resistance Simulation

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.
sim174,325 runs
Biology Science Ecology Education
188122.52
#14

Lactose Operon: An Inducible System

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.
sim144,662 runs
Inhibition negative feedback biology lactose operon
166057.44
#15

Apterous Genetics

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?
sim305,442 runs
Genetics
137744.03
#16

Limiting Nutrients in Aquatic Ecosystems

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.
sim119,148 runs
limiting nutrients ecosystem biology logistic growth
128583.46
#17

Lac Operon with Monod Bump

sim201,720 runs
Lac Operon Gene Regulation mRNA
119077.84
#18

Diffusion of a Spherical Cell

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.
sim145,381 runs
diffusion surface area volume radius
118765.38
#19

Transformation Simulation

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.
sim132,464 runs
transformation DNA biology
106582.51
#20

Water Potential and Osmosis

Factors that affect the flow across a semi-permeable membrane.
sim396,167 runs
102975.51
#21

Evolution and Natural Selection

sim344,978 runs
89380.6
#22

Model 2. Drug Transporters

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
sim54,312 runs
drug transporters efflux uptake drug absorption
88704.31
#23

Cellular Respiration Inquiry

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.
sim111,299 runs
metabolism respriation ATP biology
87103.1
#24

Model 1. Introduction to PK and PD

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
sim77,160 runs
Pharmacokinetics Pharmacodynamics Therapeutic Range
85277.97
#25

Neurophysiology and Neurotoxicity

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.
sim46,458 runs
Neurophysiology toxins sarin VX TTX
81203.625
#26

Guppy Evolution

sim176,783 runs
evolution biology genes
81122.38
#27

White-Eyed Genetics

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?
sim184,334 runs
Genetics
80697.16
#28

Vacation

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?
sim38,482 runs, 894 downloads
Download Model
Vacation burnout stress productivity workload
79629.84
#29

Thyroid Hormone - Negative Feedback

sim78,573 runs
negative feedback thyroid hormone metabolism biology
76347.125
#30

Tesing Unknown Enzymes

sim277,252 runs
enzymes
72070.32
#31

The dynamics of photosynthesis - variable sample size

The dynamics of photosynthesis - variable sample size
sim93,717 runs
photosynthesis sample size biology
65246.996
#32

Oxytocin and Child Birth

sim244,438 runs
63368.64
#33

Zombie Apocalypse

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!
sim25,267 runs, 908 downloads
Download Model
Systems Thinking zombies epidemic disease susceptible
58547.555
#34

Intravenous Infusion

This model demonstrates the pharmacokinetic characteristics of constant continuous drug administrati ... Read more
This model demonstrates the pharmacokinetic characteristics of constant continuous drug administration.
sim28,419 runs, 95 downloads
Download Model
drug pharmacokinetics intravenous infusion zero order input constant continuous drug administration
55464.195
#35

Photosynthesis Simulation with Variance

sim208,998 runs
54324.28
#36

Evolution of LAP Allele in Mussels

sim85,051 runs
Evolution Natural Selection Cline
53279.83
#37

Oral Absorption

This model is based on first order absoprtion in a 1-compartment model
sim52,439 runs, 153 downloads
Download Model
Drug Absoprtion Bioavailability Bioequivalence
51873.074
#38

College Loans

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.
sim27,380 runs, 1,055 downloads
Download Model
Student loans loans college interest repayment
47828.785
#39

Photosynthesis with Variable Sample Sizes

Sample sizes of Photosynthesis stocks in an array
sim179,289 runs, 144 downloads
Download Model
46637.09
#40

Mulitple Bolus Injections Pharmacokinetics

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.
sim23,806 runs, 79 downloads
Download Model
drug pharmacokinetics multiple doses multiple intravenous bolus injections
40193.246
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Uploading a Bundle from Zip

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.

Assemblies, Bundles, and Categories

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.

Bundles are groups of assemblies with a common use or theme. For example, a Health Care bundle might contain a variety of assemblies that aid in creating health care models. When you download assemblies from the isee Exchange™, you download an entire bundle, rather than individual assemblies.

Categories are subgroups of assemblies within a bundle. For example, a Health Care bundle might contain a Funding category for assemblies related to the management of hospital funds. All assemblies must be assigned to a category—they cannot be assigned to the root of a bundle.

Assemblies, bundles, and categories can be created and uploaded to the isee Exchange™ via the options on the Manage My Assemblies page. To learn more, visit our help pages, or take our assemblies tutorial.

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.

Image of a model

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™.