Adaptive Systems Lecture 2: Natural Systems part 1

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Adaptive SystemsLecture 2 Natural Systems
(part 1)

• Dr Giovanna Di Marzo Serugendo
• Department of Computer Science
• and Information Systems
• Birkbeck College, University of London
• Email dimarzo_at_dcs.bbk.ac.uk
• Web Page http//www.dcs.bbk.ac.uk/dimarzo

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Lecture 1 Review

• Concepts
• Self-Organisation
• Emergent Phenomena
• Decentralised Control
• Adaptation
• Dynamic Change
• Complexity

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Lecture 2 Overview (Part 1)

• Non-living systems
• Pattern formation
• Living systems
• Pattern formation
• Animals
• Plants
• Collective behaviour
• Micro-organisms (cells)
• Animals Social Behaviour
• Swarms
• Part 2 Human Social Behaviour (Lecture 3)
• Human Social networks
• Markets

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Non-Living Systems

• Pattern Formation
• Bénard convection cells
• Snowflakes
• Glass cracks
• Sand dune ripples
• Mud cracks

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Bénard Convection Cells

• Experiment
• Henri Bénard, French physicist 1900
• Liquid (oil) with initial temperature
• Same temperature at top and bottom planes
• Liquid is in a stable state (is at equilibrium)
• Heat applied from below
• Temperature of bottom plane
• increases progressively
• Bottom layer less dense rise
• Top layer more dense sink
• Permanent flow of energy occurs within the liquid
• Convection   transfer of heat by currents
  within a fluid (flow)

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Bénard Convection Cells

• Emergent phenomena
• Regular cellular pattern of hexagonal convection
  cells appear
• Caused by
• Random motion of heated cells
• Random perturbation gives rise to upward or
  downard motion
• Bifurcation point
• Physical forces amplify the motion (positive
  feedback)
• Non-deterministic arrangement of cells
• Reproducing the experiment does not produce the
  same arrangement of cells
• Sensitivity to initial conditions
• Small perturbations produce large variations in
  system behaviour

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Bénard Convection Cells
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Bénard Convection Cells
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Bénard Convection Cells

• German artist
• Volkhart Stuerzbecher
• Does not use computers, but is inspired by same
  self-organising principles
• http//www.stuerzbecher.de/website.php
• http//www.stuerzbecher.de/img/konvektion_256.wmv

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Snowflakes

• Snowflakes
• Snow crystals made of ice
• Snowflake one or more snow crystals stuck
  together
• Ice crystal material in which molecules are
  arranged as a hexagonal lattice (crystal lattice)
• http//www.its.caltech.edu/atomic/snowcrystals/

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Snowflakes

• Snowflakes Complex Shapes

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Snowflakes

• Snowflakes Formation
• Snow crystal formed by
• Water vapor condensed directly into ice
• Snowflakes patterns arise as snow crystal grow
• Growth depends on temperature and humidity
• Snowflakes growing
• http//www.its.caltech.edu/atomic/snowcrystal
  s/movies/movies.htm

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Snowflakes

• Snowflakes Formation Faceting and Branching
• Beginnig
• molecules water condense on a dust particule
• Snowflakes faceting
• Hexagonal ice crystal leads to hexagonal
  snowflakes shapes
• When crystal is small
• growing occurs on each facet
• hexagonal prism

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Snowflakes

• Snowflakes Formation Faceting and Branching
• Snowflakes branching
• When crystal grows
• Corners of hexagon stick out further in the air
• Corners of hexagon grow a bit faster
• Because of different temperature at the corners
• Water molecules reach them quicker
• Branching instability (positive feedback)
• Branches appear
• Many different temperatures experienced by the
  falling snowflake
• growth and complexity in branches/arms
• Symmetrical shape
• Occurs when each branch is under the same
  conditions (temperature and humidity)

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Living Systems

• Pattern Formation
• Animals
• Zebra stripes
• Giraffe coat patterns
• Vermiculated rabbitfish
• Cone shells
• Plants
• Morel
• Leafs

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Stripes Formation

• Regular pattern
• Animal Stripes (2D)
• Porous Structures (3D)
• Created during (embryonic) growth
• Model Reaction-Diffusion Model /
  Activator-Inhibitor Model
• Two interacting substances with different
  diffusion rates can generate stable patterns
• Necessary condition for pattern formation
• local autocatalysis (short range activation of a
  process)
• long range inhibition (prevention of a process)
• Interactions generate regions in which a certain
  process (e.g. pigment formation) is turned on or
  off
• http//www.mbl.edu/CASSLS/scott_camazine.htm
• http//www.eb.mpg.de/dept4/meinhardt/periodic.html

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Leafs Formation

• Leafs
• Leafs usually grow along spirals
• Golden angle 1370
• Initiation of a new leaf is inhibited by
  existing leaves  
• new leaf can be initiated only at a certain
  distance from the last formed leaf
• Model
• Activator-inhibitor (with two inhibitors)
• Activator of new leaf
• Two inhibitors one rapid and one slow
• New leaf when concentrations of both inhibitors
  become low enough
• Simulation
• http//www.eb.mpg.de/dept4/meinhardt/phyllo.htmlA
  nchor-Phyllotaxis-36190

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Immune System

• Aim
• To provide responses to attacks from outside the
  body
• Antigen
• Any substance that elicits an immune response
  (e.g. virus, bacteria)
• Self/Non-Self recognition
• Each cell has a marker (self)
• Cells without marker (non-self) are considered
  antigen
• Immune system attacks antigen

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Immune System

• Characteristics
• Antigen-specific
• Systemic (throughout the body)
• Memory
• next attack recognised quicker
• level of response higher
• Dysfunctions
• Autoimmune disease
• System attacks self cells
• Allergies
• System attacks innocuous substances (allergen)

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Immune System

• Agents of Immune System
• Lymphocites (white blood cells)
• Organs of lymphatic system bone marrow, thymus
  gland, spleen
• Lymph colorless fluid transported by lymphatic
  vessels
• Lymphocites (B and T cells)
• Cells transported by blood and lymphatic vessels
  across the whole body
• Cells exchanged between blood and lymphatic
  vessels
• Foreign organisms enter body through lymph nodes

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Immune System
http//www.niaid.nih.gov/final/immun/immun.htm
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Immune System

• B cells (Bone)
• Produced by bone marrow / enter blood system
• Wait for antigen (in blood cells)
• Activation of B cells requires help of T cells
  when encounter antigen
• B cells replicate and release antibodies
• Antibodies circulate in the blood vessels for
  additional antigens to mark
• B cells antibodies mark the antigen for
  destruction by other immune system cells
• T cells (Thymus)
• Produced by bone marrow / initialised in thymus
  enter lymphatic vessels
• Coordinate immune response destroy infected
  body cells
• T cells replicate and create memory cells (for
  subsequent attacks)

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Immune System
T
B cells recognise Antigen T cell activates B
cell B cell replicates B cells generate
Antibodies (AB)
B and T cells circulate into body Antigen enters
body
T
B
B
T
B
B
AB marks Antigen as non-self T cells destroy
Antigen
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Immune System

• Innate immunity
• Cells of immune system bind to specific antigen
• Pattern-recognition receptors
• Passed from generation to generation
• Evolution
• Acquired Immunity
• Characteristics
• Distributed
• No centralized control
• Uses learning and memory
• Tolerant of self
• http//uhaweb.hartford.edu/BUGL/immune.htm
• http//www.cancer.gov/cancertopics/understandingca
  ncer/immunesystem

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Social Behaviour

• Swarms
• Social insects
• Ants pheromone trails
• Termites mounds
• Wasps and Bees
• Fishes
• Birds

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Social Insects ants

• Ants pheromone trails
• Ants find source of food (recruiter)
• Ant marks the trail
• Going back to the nest and during subsequent
  visit to food
• Marker is a chemical volatile substance
  pheromone
• Produced by special glands
• Lifetime 30 min - 60 min
• Path is marked with a certain frequency (e.g.
  each 4 cm)
• Strength of pheromone depends on frequency of
  deposited pheromone
• Frequency depends on orientation of path wrt nest

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Social Insects ants

• Ants follow the trail (recruit)
• Follow the stronger of two pheromone trails
• Stronger more concentrated / higher frequency
• Sense trail with antenna
• U-turn
• Trail pheromone concentration decreases
• Trail in  bad  orientation wrt nest

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Social Insects ants

• http//mute-net.sourceforge.net/howAnts.shtml

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Social insects Ants Foraging

• Ants Trails Formation
• Two branches bridge
• Same length
• One branch is preferred because of random
  pheromone fluctuations (slightly more)
• Amplification of initial fluctuations
• Different lengths
• Shortest path is chosen (emergent pattern)
• More pheromone on shortest branch
• Deposited by ants that choose the shortest branch
  (go and return)
• Ants go back to take shortest path (u-turn)

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Social Insects Ants Tasks

• Other ants tasks
• Foraging
• Nest maintenance
• Cleaning, removing dead bodies, nursery
• Division of labour

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Social Insects Termites Mounds

• Termite mounds construction
• Initial step
• Termites drop soil pellets at random around
  their queen
• Random fluctuations produce greater
  concentrations of pellets at some place
• Termites tend to reinforce this concentration
• Positive feedback
• Pheromones involved
• Cement (in pellets), trail, queen pheromone
• Distance among pilars
• Negative feedback
• Pheromone template diffused by queen
• Nest has shape of queen

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Social Insects Termites Mounds

• Size
• Diameters up to 30 m
• Height up to 15 m
• Highly sophisticated structures
• Air-conditioning
• Nursery sections
• Galleries
• http//www.labyrinth.net.au/dewart/pictures.htm

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Social Insects Termites Mounds