Great pleasure to interview
with her this week.

And.

He just joined.

He was pretty Cornell University graduate.

Thank you Richard thanks actually so
Pleasure to be here.

Very happy to be here and joining John at
Georgia Tech I'm thrilled to be here and

working with a lot of students and our
faculty and the from the parliaments so I.

Be working mostly on kind of thing I mix
but originally I mean most most of my area

of work a complex system some part
information so that's just mostly

systems that depend on dynamics that
is composed by different elements and

every element has a similar they now mix
mostly Aussie lottery they now mix but

when you couple together then he
generates new dynamics new new new.

Complexities kind of marriage so
wonderful.

Yet there's still can you hear me or
you know you can do.

This is there is there are these
one work in better or.

OK You know I can go a little
hard I mean just I just finished

a class we did hundred twenty students
he said like my voice also kind

of gets a little tired from the from
the things that they will not work better

all right go back go back to the end.

All right so
that when I was a little bit too loud and.

All right so this is basically a chemical
reaction when you have a chemical reaction

you always see that you mix things and
it goes into one direction and

then that's that's it but
this is kind of like one special kind of.

Reaction that blows through
the complex systems.

Area.

So let me see if I can remember
the quantities of this me

do.

So.

We're going to change color yellow.

They changed all blue.

There.

But that it will.

Be changed to there's
something about the blue and

I was going to be your slate in between
the different colors between yellow and

blue this kind of like
Harry Potter writing like.

Focus pocus or
whatever they say they go so

this is a system that is basically says
call the the bricks Roger reaction it's

typical system of a reaction
diffusion style so

it's going to like you imagine
just when you have the predator

prey you have a predator you have a prey
the prey starts to grow in numbers and

then the predators start growing
in numbers until they catch up and

then the prey will then the too much too
much predator so the praise number starts

to the crease and then eventually then
the the predator start to decrease and

again so then there's a solution between
the two so you can see like the Predator

will be there the blue and
the prey will be the yellow and

then you just basically a silly thing and
between the two of them so these discount

of oscillations you see them out well
this will go for a few more minutes but.

So what you see that basically these are
solutions when it happen in space they for

patterns and patterns we see
them in nature and everywhere so

from a from pattern seeing in structures
to but they're seen in ninety miles.

And these patterns actually.

Related to these kind of questions or
reaction diffusion equations and

they're recently there but
in the last thirty years some someone

actually developed these
a mouse who has stripes butt.

Actually the stripes the moving time so
that actually the the the color

in the in the in the hair grows and then
you recycles and in recent works again so

there you have actually one of
these patterns propagation time so

you have these actually these very nice
mice that partners just generate and

but propagate so this is like
the mouse in time in thirty days

it has a way that actually propagates
in another one generally So

this is one of the main solutions to these
kind of problems these equations these

are questions they have for OK So
this is questions they have.

Solutions which are steady state solutions
but also have wave solutions and then in

space they have actually more complicated
solutions like even spiral waves.

So most of my might make my
research using complex systems but

it's mostly focused two to two
they don't use a credit card that

they now mix from normal to have normal
dynamics so what I want to do is to

give you a first then just so
you know where I'm going with the talk and

motivation of the other problem of what
we try to study the UK they now mix with

some information about how their functions
to your memory how the heart works.

Then I'll talk about the complex question
there are they now means that you get into

these into the system.

And then I go some example some
stability seem to the nth really and and

we talk about the need of supercomputing
performance when you try to

solve these kind of
problems numerically so

as Richard said our region I am
a physicist some theoretical physicist but

over the years I've been became
a level playing around to become a.

Experimental physiologies than
a little bit of computer scientist so

in the lab we do a little bit of all
the different kinds of experiments from

experiments in hearts through to
the theory and into the simulations to

try to compare between the two and
unlearn between the experiments and

simulations and back by going forward so.

One of the motivations study kind of
the dynamics is well how this is actually

living because of that there in the world
rats number one industrialized countries.

You can see that the number of
people dying of heart disease.

It's as much as the next
the cost of their together.

So ranks number one in
the street as country so

say one in five people die in front of
some part of that it hardly sees in

the United States because
a bigger economy can impact.

The mission before one third of the total
deaths are due to higher this is

as a physicist also this is a very
nice system also and not only

interesting because of the of the of the
human impact and the economic impact but

also it is the system that is the next
act that will see them and there's so

much broad range of the states and you
can find and there's so much well known

is wide open so there's a lot of research
that can be done to understand and

to our and to analyse the heart
from a physics point of view.

So the hardest just to remind you see
is the system that has four chambers so

the opera chamber is the gates here
which are receiving chambers and

the bottom two chambers
are the ventricles the so

the powerhouse they basically they
contract and the so they send this in

the blood to oxygenate to the to the to
the Longs and the oxygen into the one from

the left ventricle to the to the rest
of the other body to be oxygenated.

So the way it works is you have an
electrical activity actually that's this

and it works through or through through
our through an electrical wave which is

probably use that and the Sinatra not
you progress through the year three and

then you propose to the bench of course
and that and that electrical wave actually

makes a contraction so you have.

So this is a movie of an open open chest
heart so then you can see actually you

have electrical activity on the extra make
some contracting goes to the ventricle of

Mexican trucks so you have use is
the answer then the ventricle the IT and

the ventricle and the contraction
is due to an electrical signal

he said I took a signal is formed because
this cells are basically integrated like

a ceiling they're sort of our first
approximation they're sitting there soon.

Of about one hundred microns one hundred
fifty microns by ten and there so

they have a membrane so these membrane
doesn't allow the flux of ions

there basically say hydrophobic
membrane and there's inside and

outside there distributions of
concentrations of fire and different so

there is in the outside of this system
there so you might potassium you side

there's this there's a cloud soon
discussing the same in say the cell so

there's at the front of us
considerations between the center and

outside the only way they can go these
signs can go through is through.

Proteins that go along the membrane and

form channels so these channels actually
there can be close but they can open and

close a function of time and it's function
of voltage and the open and close in and

only way so when you try to create
a model for the electrical activity

you have to account for all the different
in channels that exist in the cell so

that it actually turns out to be a lot of
them so it is and the Nalini are a few

of the system comes into precisely
the beginning the time of the opening and

close so when you're right on
a question of for a complex mother

of an ironic mother you had to write all
these there are nearly every time for

these for these processes.

So just let me show you just a quick.

Caricature of how this works so this is
you have a little cell in this is a cell

so you're looking at these are the
boundary so this is basically the membrane

you have there in the channels you have
concentration of sodium outside mostly but

that's human side and
you have bit of consumer.

With equal inside that that has some
culture so in general the he she said rest

and the systems address sorry and
there is some difference in charge because

of the concentration so it's a difference
in voltage between the east side and

they are sort of about minus
eighty million votes so

this is the rest they discovered minus
eighty million votes you can if you

excite that a little bit doings in through
the overcurrent then you're going to work.

Really opened.

The southern China up in first.

And then the second influx of sodium so

that the prices that the shoes we got
from minus eighty becomes to twenty.

And then and then they saw the I'm
actually crosses very quickly so

this is one of the future sort problems
of where they're going I mean it is that

some of this is there some of the the
sodium is very fast so there's a timescale

of sorting which is in the in the OR
There are two to three milliseconds and

then the time of scale for the calcium and
the and the potassium to open and

close it's about two hundred milliseconds
so then there's a different time

scales that that actually become very
important and becomes a problem when you

try to do simulations because you have
to have a very stiff solution here and

then you have a more relaxed time
later on that you have to account for.

So.

So that before questions you can do to
solve this well as you can go from a very

simplified model that has to buy
also one for the voltage and one for

the number of I am trying also to a little
bit more phenomenology godmother which for

a question turns out to be that we find
out that it's going to take the minimal

model that reproduce a lot of the
physiology you see with four equations but

still it's an idealized system so if you
want to go more complex there are mothers

there that have a twenty five differential
equations for the for the in China US and

there are some others when half
are like eighty sixty seven variables

like this is one of the human mothers
that came out like five years ago

has sixteen variables hundred thirteen
equations so this is just for

one single cell that you have to count.

So of course there's you can see the page
just initial conditions you see it's one

for each right kind of becomes a lever
too complicated to to work with.

Can you hear me.

Anything anyway so the.

So this is just resting up so.

So when you you have to connect
the cells to the whole system so

the cells they connect actually.

A sheets.

Full of sheets and then these sheets also
connect together to form the volume.

So all these all these three
questions they just sell for

a single cell they have to connect them
they connect actually the if you simply so

you have to have basically the here
is the information of the currents

they're connected if you see
you have a capacitance and

you have the side on the outside
of the system so you have and

this resistors between the two so
you have actually what is called Me So

you have a domain for
the set of interstellar medium for

the extracellular medium and they're
connected by the capacitance of the other

membrane and all the unique
channels of the of the system.

So that's in one the into the then
you have to have basically.

To the mission and
measure of resistance and

when you get to three The world
becomes more complicated.

So the question of when you put it
spatially then you have to solve.

Reaction if you can equations so use the
the the diffusion and you have a term for

the fusion inside itself and outside
the cell these term here these this is

a matrix that has information of
the of the direction of the five or

six you not is the five percent actually
inaugurated so propagation these is

three times faster along the fire
along the axis than across so

there's a natural ice and
I saw a drop in the system.

So this and I sort of piecing through
that into these into the stand source.

This term here is basically the current
that our counts for all the use that exist

in the cell capacitance in the cell and
then basically you have some

other conditions that the flux when
there are conditions in the system.

So so the main problem is
basically that the fusion part is

that these Matrix part here and
the complicated number of it.

Questions that you have for the only part.

Was a couple together then the selector
collectivity the association that

we saw from the experiments for
example some cells here and

there is going to produce because of
the fusion of propagating wave so

this wave as we mentioned before
it has a very fast upstroke So

it's that we get waves and they way
they suffer his weight on the back so so

you just you have to be very well
resolved on the front so it's about.

So you have to be about two to three
milliseconds on the on the time scale for

the OPs right of the of
the action potential This is

called actually an action for tension so
is the electrical activity in time is

called an action potential so it's a very
fast stop rice and then a slower the K.

of about two hundred milliseconds
the same mission before.

Now this electrical activity that
actually produces a contraction so

electrical activity once that way passes
he releases calcium you say the cell and

the calcium then actually makes
the the binding between the Miocene and

the acting so they got away passes
the cult soon gets outside of the cell

from the rest equalization site and makes
the the binding between the Miocene and

the acting and makes the contraction.

So that's basically the how the contract
use an electrical way then then produces

the consumer nomics and then produces
a contraction saw in you want to sort

the whole system complete you
have the electrical part of the.

Part and you also have to account for the
contraction so you have a passive stress

and at the stress and ahead the side the
pressure the past history of the sun in.

The.
Formation tensor that changes in time so

then what basically the psychology is that
then that you fusion term is going to

be a function of time and because he would
more complicated then because you had

to solve also then of course
only question everything step.

So was have an electrical wave that
actually what happens you have

a contraction wave following.

And he says so that the.

There the problem is to solve the
electrical part which he was the questions

there actually Fischer the questions that
I wrote here so if you do that by domain

parts you have to solve a persona question
there and then if you have the contraction

you have sort of another persona question
there too so that takes a lot of time you

can also assume that just
the the the the external the from

the internal to the external medium
the just as a lot of medium is grounded so

then you can actually get a good
read of some of the conditions and

just simulate without bein just a reaction
the fusion equation alone without the.

Without the.

The person equation.

So let me just tell you a little bit
more about the why we want to study this

before we go more in
the complex of the modeling.

These waves that propagate through
the heart actually turns out that

that is not just in the only solution as I
was mentioning you have troubling ways but

actually you can also
produce a spiral waves and

spiral which is a solution of the system
and they actually appear in the hearts so

on one spot away appears in the heart
of the they have a characteristic that

they have a frequency faster than
the frequency of the natural pacemaker So

when a spot away appears then it drives
the heart and a much faster frequency and

that's basically makes the hard
contract much faster and

this far away center in general they're
not very stable they destabilize

they form a lot of spiral waste which
is then very fast moving everywhere but

out of face so then the heart
is not contracting anymore so

this kind of color we enter and
I read me us.

So also saying origin or you have a way
that propagates through the tissue

you can generate this bar wave this is
from experiment I'll show you how do your

pain those expire waves so when you have
a spiral wave in the in the ventricles

the hard disk contracting very fast and
what is called technique are you having

to protect the when the spar with
actually the starlight is very quickly so

you ended up with a lot of waves and
becomes chaotic motion and

then that becomes when you have
been too close relation and

the only way you can terminate is with
a shock you have to give a big strong.

So then everybody gets excited
all the sales and then and

then you terminate the comics I review.

So let me just show you a couple of
examples off the thank you Carlia So

then we see this is a hard thing it
invented I think you can if you can see

the hype has been contracting faster
the simulation on the on the right it's

actually you can see the spot where you
actually see is driving the contractions

she makes a contract much faster.

This is when the spot we've been
basically breaks then you go right away

into into into the relation so this is the
case we have all these spy ways here and

the hard things just varying
it's not really contracting.

And then.

As I mentioned at the beginning the heart
is composed of four or four chambers so

the atrium the ventricle they're actually
disconnected electrically they're only

connected to a passage so
you can actually have them.

There really you can have it in just on
the ventricles or just in the year three

so when it happens in the year three or
it just makes that rhythm of the ventricle

very irregular so you can have a
relationship you can see the year there's

right here he has the spot of waves you
know like in the simulation here and

then the contraction of the ventricle
becomes irregular and that's that's not.

Going by right away over the sea of these
seas but he said increases the risk of

stroke and contributes to the winner
of that of heart failure.

So these are how the this part always
actually receiving the heart so

there are many mechanisms but one of them
is actually because these these waves they

are they have what is called a Character
series call a refractory period so

once you excited a cell.

You can excite the cell again but
you have to wait there's so

many one time a little amount of time
that you have to wait before you can

excite the cell again so
the simplest way to do

just imagine this is using the knowledge
of the toilet so the toilet.

You can flush the toilet once and all the
water goes away but you cannot you cannot

flush it again right away you have to wait
certain amount of time before you you can

flush so the same way so when you have
when you come out weighed and you come up

with much wood beat or an expectation
some what happens if it happens too late

then you have that wave the primitive beat
happens and then the tissues excitable so

then he will create another wave so
let me repeat it again so

you have a way you have a premature beat
the tissues excitable if you can excite so

then produces a wave now if
the excited stimulus is too soon when

I was talking about this reference there
is the period so you cannot excite So

you excite and that is the expectation
that US So you have and you need

us now in between this time in between
what is called the winner of the window so

there is the time in which part of
that issue will be refractory and

part of the issue would be excitable so
in that case actually would waive

the activation would propagating one way
but he will block in another way and

the police are facing Laurie and
the producers basically spar away so

here you have their way was
propagating one direction but

it was blocking the other one so
then the way front and

the way back they're going to meet at
some point which is the facing Larry and

that produces to control
the thing spiral waves.

So it's all about the timing when you
initiate one of the spiral waves and

then there are many of these.

But even just the pure dynamic of spiral
ways when we think of a spiral we think

a spot away with or like an R.Q.
medium spiral way with a simpler core.

But it turns out I mean you can actually
the earlier say really the analysis of

these equations so you can find that there
is a frequency but there are other your

values then it can appear so
these values actually can grow and

as they grow they they can become larger
comparable or larger than their original

frequency so then that's when you have
actually you can generate when you have

two frequencies there is not frequency and
another frequency that are solved and

you in the rough with the cyclo That's
right if you screw the territory so

in fact actually in some of the models
you can change the parliament.

If you can change the what is called
the excitability of the system and

because from simpler it
becomes two it can produce.

Change to Sequoia so you can have six.

You can have it be cyclo That's right
there is and then one more more disappear

I mean so this is the case when when is
growing the second frequency when the two

frequencies are the same when the original
gross larger than the when the second

frequency large grows larger than the
original one and then one more frequency

start hearing then you have more high
premium there trajectories and then after

you go to end up with a linear quarter
you carry when actually the action to.

The traitor of the spark wave sexually
more linear when spot always appear in

the heart there are actually more of these
type of spiral waves they have more linear

core more than the sequel or
core us as the tissue becomes the skin

make that means that there's less oxygen
because the tissues are being profuse

because there's no actually the heart
is not contracting as well so the heart

itself the same get enough oxygen so then
you get these are you getting two more.

Which is more skimming less oxygen so less
excitable you in the top in these regions.

So the way we actually in
the lab we can we can we saw

this explain these
experimentally these waves.

We use fast cameras and we use so
these surface cameras we can put a.

Bath where we can the tissue of
our lives and we can keep it.

Profuse we need to put out.

A way to be so like these waves so

in order to be so
light is waves what we use is.

A couple of the front.

That you can.

Put inside the tissue these guys
are getting to the membrane and

they upswell and the characteristic
of these that is that they have so

light that one frequency which are around
five hundred the A nanometers and

a meter on six hundred so the and
the mission and the source.

Is nearly a function of the voltage so
this is very nice because one of the men.

The dice gets into the membrane you excite
with about five hundred with a light of

five hundred you put half a filter and

then you record only these this is this
despite of the frequency and any shift on

the frequency will give your signal
which is proportional to the voltage.

So it's a very small frequency so
you cannot really see I mean Chief so

you cannot really see it with
the right eye but in the computers and

you can you can actually use what I said
So this is for example the right ventricle

is profuse So here we keep it for
a few so it skips a life.

Then we put the the die we look
in it with a five hundred so

this is how it looks when you mean it
with a light which is around five hundred

then you put the filter and
this is how it looks with the filter so

you now can see that the sure
they got six was profuse and

this part is the one that he
gives you the the emission and

changes in that emission
corresponds to the voltage.

So this is an action potential like the
simulation I was showing at the beginning

so this is an actual position measure in
the cell directly using what is called

microelectronic orally so you actually
measuring the voltage directly from inside

and outside the cell the only problem is
you can get really good recordings you can

get very good accurate in time but it's
only locally so you can only do once or

two or mean up to four or
five in a certain profile ration so

you only get good information in time but
not in space but

when using the optical system then you
can get the signal a function of light

everywhere in space are the surface on the
on the this is the surface of the fish so

there is actually the signal from
the optical mapping you can put a color so

you can use what I said when you win when
you analyze the data so in general we

use black for that issue that is at
rest of ninety eight minus eighty eighty

eighty five eighty volts it becomes yellow
when you say about twenty million watts.

And and this is then this is a view
of our of of a heart from a.

Heart So
this is the right its we are these.

Is the left the right ventricle So we're
going to see here this is the Sinatra not

here so this is actually how you see the
electrical activity so you see the USA not

producing the way the Course through the
ventricle I mean through the if you're.

The say for the ventricle this is
a venture called that is profuse and

we have actually we can see the electrical
activity propagating through

the through the tissue.

So these are just the first solution that
I talk about that it is a plane wave

propagation of the waves you can actually
use right there that's what is going to

be doing now in the lab in Georgia Tech
we're going to cost truck the system with

multiple cameras so we can then get out of
the sort of station of all the waves from

from a panoramic point of view so
we have done a little bit of the work so

a little bit so but just with one camera
so we can reconstruct the heart and

then we can see so this is a rabbit heart
so we can reconstruct the heart and

then put the electrical
activity in one with a nice and

then we can have electrical
activity from all the surfaces.

Everywhere.

So I was talking about the spiral is that
you're coming in the simulations you

can have in the spine where you
squeeze you can walk or in tissue and

you can have in the leaner Courtrai there
is twenty in in tissue you can also have

these problems that for
all you know courts rectory.

And then well these far waves which
correspond spar with in simulations that

we can do or
you can you can have a circular core.

Or you can have a very complicated
The name is when when they go from a from

a once for
a week into multiple spinal waves.

So basically what maybe is that we can
be sort icing and we can we can see that

there exist despite waves in the heart
this is the heart from a from a from a pig

and you can see this part ways can
appear there are some simulation and

then they actually respond with a settled
before they're not very stable after some

time they become unstable and
then produce the security numbers.

Now when you.

We're going to right now so far we have
been talking about spot waste like into

the missions but they hardly
sexuality the mission and system so

when you go from front to the two three
the then you start to see the color right

when you have a surface you have X. and Y.
in there how color for the voltage so

in three these kind of hard to do it so
what we do is that then at every every

part of the of cube in tissue there's
actually going to be a spiral wave but

as you go through that there
there where you can be so

like the electrical activity is by
following the tip of this bar wave as you

go from from from front to the to three D.
you become somewhat fixed line so

these vortex lines you can try then to
to follow if you if you calculate the.

Curvature of these or ticks filaments then
you understand what is happening around

the electrical activity around the system.

So this is these are these four ticks line
structures they're actually similar to

if you're against or what they're spouts
just in ideally but of course it's

a different kind of wave right this is
a phase wave that that has a different

change it doesn't have the this one as
as you move along the the the radius Any

change the velocity here is a different
story right but it isn't going to have

what this film is that go from front from
one side to another side of the tissue but

it can be also these they can
to apology they can close so

you can have actually rings the supporting
strings so you can have these.

Different different apologise of.

Spiral which in three D..

One thing that actually makes the next
even harder they're the study of the heart

and also the simulations is as I was
mentioning you have the the elongated and

the beginning I was mentioning
the the Linus' sheets and

then these sheets actually as
they go from inside to outside

they rotate at one hundred
eighty degrees so there's

a rotation of then I saw therapy on the
ventricles So this is actually diffusion.

They're sorry messages from from from
a ventricle going on the on the why

the actions of these for
example here you can see there the.

This is the left ventricle
the right ventricle there and

this is a view from from the top So this
is the the right the reference you call

the right when to call and this is
the other the other the other axis so

you can see actually here you can see that
there is the direction of the fibers and

when you reconstruct these you can
actually cause very complicated but

the idea is that as you go from it
because into in the Caribbean there

is from the outside to the inside
this dish it's actually four hundred

eighty degree rotation because
they follow actually so

it's a very complicated structure they
follow their six actually turns out that

that these these distribution is
such a They're sick and these cones.

Just basically get the ventricles are
formed by these columns with their six and

as you go then from the inside to
the outside that's when you see these two

hundred eighty degree rotation of
the fivers So that's something you have to

include into the diffusion term that I was
talking at the beginning that accounts for

the for the for
the complex propagation in a tissue and

that affects also the dynamics
of the spider waves so

the scrotal waves because now they are in
a not you know much in your system they're

going to be stylized by the by
the by the fusion of the system.

So and also there's the polity too so

you can have a vortex ring can appear and
disappear.

Can appear and then if you have the right
face to confuse with an original ring

you can have an original.

Text that actually elongates and
then pinch yourself and ends up with or

without one for
ticks line and one one ring.

So then the complexity
of the system because.

You can start with.

So this is the sort of station of
a simulation where you see the.

Right to see I guess
the cellular the dark but

I'll show you a lot of simulation
later on so you can see that.

Top on the bottom you started with that
we feel I mean that we're straight.

But we time is going to our
stubbornness because of this.

These are Titian and I sort of peak and
he's going to grow into into multiple our.

Boards extremes of what
it's lines through.

So there's a simulation on
the on a on when to call.

So you can see how the volution of these
vortex race because very complicated so

you can see the the in the surface and
then inside you can see just the solace of

orthodox lights that become
a little bit complicated so

these are the things that we're trying to
understand from the experimental point

of view in the simulation point of view
but then doing the simulations actually is

very cost the fish I mean it's very
complicated not only because of the.

Fusion that I was saying if
you do simulations in the year

three that your structure your
source are very complicated

it's very regular He has also
parts that have different.

The different kind of teeth these so
you how they can the tensor changes so so

we can look at the end changes
the the the diffusion So

you defects how you do
the simulations through.

And in showing these.

So this is actually you just so these are
the two chambers of the year of human and

the human.

You're showing that is very complicated
and you can hear again in a scene

eventually you can have spider
waves represented to flutter or

when he they sell ice and beef or multiple
spider waves that becomes relation.

So OK so now let's go back to
the problem of the computer science of.

One of the problems of these of these
simulations so so far over the last.

The first actually the first
car that mother was

by Denise noble in one nine hundred
sixty two around one hundred sixty two

then another one was developed in
one nine hundred seventy seven and

then from there they have been growing and
more the my.

More information has been become available
over the I in China seen the cells so

they've been a lot of mothers being
developed around almost one hundred by now

and it can be depending on how complex
they are go from us the same from two to

sixty seven there's one now that
has like nine hundred ninety eight

from you see is the.

And The ago.

So so the problem is where are we
show these these these these.

These.
These are these questions basically So

this is equations with all
the other variables here so

you have different mothers I was saying so
there are different mothers there are only

different mothers with different details
of the of the of their own channels but

different mothers with
different types of cells of

from human from right
from Mouse from rabbit so

there are about five mothers of humans
who call our mothers right now.

One of the most mothers that is use
a lot this is use a rat Well mouse and

right because there's a lot of sperm is
from us and RAT this actually said very

simple model very simple action but they
show you can see just goes up and down but

just the the number of buyers that you
need to use to describe this mother

is twenty six so if you want to do
a simulation of a sprout a waiver or

just a reentry in this mother of two
hundred or two hundred cells times twenty

six miles already a million so you have
a million of these every time step

that model when you go to a mother like
the human mother of your thought which is

sixty seven variables then you know two
hundred by two hundred the main which is

actually quite small you need already
like almost two and a half million.

Or these every time step and
you have to solve and

the problem also the other this is
the time stamp you have to use because of

a summation at the beginning the influx
is very fast this happens within.

A couple of seconds so they the.

Litigation time step has to
be around point zero one.

Or something.

Many of the methods you
can go to point to five.

The number for these Purcell then
the penny on the mother they're using

that can go between four and
about one hundred now.

So and the number of such simulated So

we assume that every cell is about two
hundred microns that does the the research

in the space that you need to in order
to have a result front and a world for

a way that propagates so
simulation in a four by four centimeters

using our four burials we already four
million or these equations you know mother

that is very used by a lot of researchers
which has twenty nine of these then

you have to solve one second of simulation
into the use already one time so

the eleven or these you had to solve.

For one second a simulation
Now if you go to really

then you have to solve twenty
three million of these.

So it becomes really really that's
why now we need to do some high

performance computing for
for these kind of of.

Of methods now some of the solve we
use actually some Cartesian meshes.

From the physics point of view
we we don't like much finer

elements we like more Finally Frances so
I generally like more of course the finer

differences I mean find elements we
know we know more Finally Francis So

we try to where we find out the physicists
and and then we had developed a couple of

methods to to handle irregular boundaries
because as a heart is a complicated system

so we develop a method that is called
a face feel so you see sexually Burra

from from a physics for the need to really
grow so this sort of if you creation so

you sort of if you cation you have a front
of of liquid than a front of solid that

is growing on the liquid and in order to
solve these equations you use what is

called a face field which is
you're in the system one of.

The system you're starting university
into into into an equation that.

We've all seen time that actually
has an interface of sea run one and

a very fast transition
between the boundary so

what we do is that then we can we can use
this kind of method to implement it into

the into the real into the diffusion
equation part so we embed that.

This field into the into the equation and

then it turns out you can do some some a
synthetic some an analytic senators other

you can actually recall for when the front
becomes very sharp you can recover

the the boundary conditions of zero flux.

So we have done that.

We many are just actually just using to
the heat equation you can use that method

and actually reproduce that other boundary
so this is for example this is the face

here you say everywhere but then it's
just embedded into the structure and

then at the boundaries you can see for the
heat equation you can see that there is

actually see a flux right I mean this
is normal to this to the scene and

the nice thing about
this method is actually.

If you're not there's these Actually
they're pretty on the pond there is so

we're using actually in this case
a spectral method using first first we're

transforms so in general you cannot
use fussier transforms in before

before these metals in Iraq boundaries so
by using these these in Mayer's.

Method of face feel you can use periodic
band there is in the system but

looking for actually inside the structure
in there you're looking for

you can actually force this year flux when
there are conditions and and he works.

Another method that we can used in order
to try to isolate the simulations is to

use that if you measure refinement So
in that case you

use a larger whenever you have
the time the you have the action but

a shot so
they are in the plot of the action but

they said you know how to describe ties
to space that much but on the front and

a little bit on the way back you have
to this time so the way when you have

the front do this with ice more there and
as the front propagates you can just as.

With a cell on the front so that saves
time and that's that's very efficient but

and this is another another for example
one probably is going to generate So

you have use the more the more
the space in the fronts and

in the backs but but when you have a lot
of spiral ways when you have studying

chaos where you have a lot of waves then
this these metal doesn't become very

efficient because you have a lot of fronts
so then the time it goes to to go between

between resolving the short and the large
scales then becomes counterproductive so

what if there is out there then this is
them sexually the alpha probably station

because he said the fusion program you
know parallax is really really good so so

these mother is just using the Hundred
the model as a center sample So

you see the number of processors so

it actually is far less is really
really nice you saw mostly near.

So now with the use of G.P.U.

we started to our to use and and it turns
out there is very nice because you can

not sure do some some of
the simulations almost in real time and

I mean you know there's stuff you need to
go now to the super computers wait for

the Q. and then bring back the data you
can run it on the on the on the G.P.U. So

this is this is a resource from for
the from models from the two burials

This is number of R.'s two four eight
nineteen and a human mother of sixty seven

versus the the time it takes
would occur in relation

to real time so if you have a mother
with two for a viable she's actually

close to real time it's one second of
simulation is very close to one second so

you see it actually as it happens as
you go to more complex models but

we can tell you a bit more as the series
is a is not as before that you have to

wait hours or days it's all within minutes
but still what we want to need to do

is is is to do a few more of
dates one of things to try to

include other methods right now is
just only using implicit all or so.

We want to go to market Vance methods
to speed up these these these three

these simulations now one of the things
that we've been playing are all around you

is also using G.P.S. but actually we
use it over the web with H.T.M.L. so

with a new version of H.T.M.L. five
there's actually a way to do right now to

get directions to get access
to the graphic cards.

So so you can actually call
them are using Web G.L.

which is a cross browser from technology
that just basically uses Javascript

sure there's.

An Open G.L. to do to the graphics so
and then that way you can actually write

these basically H.T.M.L. code that
when you connect you download it you

can price in your machine and then runs so
the nice thing is that these becomes is is

independent of the platform you
see in the pendant of the system.

But it has no need to start libraries or

compilers like if you were
using up in C.L. or without.

Each machine an operating system
independent can run directly over you or

your computer so you just have to download
connect and bring it and run it and

you can interact with it directly by
because he has it goes through Javascript

you can you can change parameters and
on the web page and then he will change

the parameters on the fly However there
are some cons of course it only works

on Google Chrome and must see opera
doesn't work on Internet Explorer.

The Because morsel of
security we sense the.

Claiming that he has some problem so
Internet Explorer is for

the sin they haven't or allowed it to
get so even more complicated to code.

Because you see the share the language and
Open G.L..

And so far it's on your single position so
and also you cannot save the data you

can in principle you can process
into into into a into a into.

ASCII and put it on another way of and
then download it from there but I mean but

right direct access to
writing is not possible.

But in a way but
he said I see it's just us us also for

just to just to get
an idea of programs and

mothers is actually very interesting
this is so this is for example using.

This is a to our own mother so

right now is running on my computer
on the on the graphics card so

my computer which is not very fast
is not very but still is running a.

Series running one thousand
five twelve by five twelve

times through the wire was
every every time step and

then you can interact with
here you can you can actually.

Interact directly with the model and
you can change parameters.

To me just.

Let me show you another.

Another mother here so this is also
to my own mother but this one.

I want to go now which.

Let me just change the parameters.

Changing the parameters.

So so now one of the dynamics that we see
as physicists is actually sometimes these

models they have what is called Peer
doubling bifurcation so you can

produce outer Nance which is Saturn as
means this is a it's a cycle when you go

from wrong to short or long to short and
that's one of the mechanisms that actually

has been found to be probably making
incorrect issue so in this mother for

example you have a very nice pair away
there we can change the parameter and

we're going to go to the region where
it's there producing the entrance so

you can see it actually puts a thing so.

And then we can produce in
the break up at some point.

So this is one we can use one of the
mechanisms that is known to produce a real

mess and we can we can study it in Priest
with he said very simple moral body but

in principle in real life.

In real time we can actually change
parameters and study some of the nomics.

Again there are more and
more complex models like this one this is

this is the first Actually this is
a forerunner of a model of the novel one

of these actually
the first mother that was.

Made.

For their tissue nine hundred sixty two
but it was so complicate I mean back then

it was four burials but it's a complicated
mother enough that he was not known if you

produce a spot where he was believed
that he could produce spider waste but

he was until one thousand
nine hundred ninety two

when when the first simulation was
being able to do of this model and

he was a supercomputer and
he was he was done very low.

Resolution So actually this pile of
waste were appealing to the lattice so

it was very square.

But but his mother actually now it
can be solving in just in a laptop so

this actually picture so that the
simulation of the first simulation of that

model you can see that he
was very on the resolve but

he was I mean it was a big step but
back then in the.

Let me just show you some.

There's a simulation in three D.
So this is actually a three D.

simulation running in.

In.

In the computer here so you can rotate
you can see the different angles and

they said again because so they are this
structure of this of the system this far

away all regionally was straight but
it's going to start developing I think.

And he's going to.

Do well in a dual Foster computer you'll
see right in the end game developing much

faster but he just basically
you'll see that it will grow and

become multiple multiple waves.

So.

So basically that's there's a step were
I mean where we are at the moment with

some of the simulations that we do in

some of the applications that we have gone
through through the study of the sim.

And then applied to the experiments you
see actually we use some of the computer

simulations first to try to
study a method to relate so we

study some methods to control the tissue
using up horse number of pulses with low

energy still one big shock the study where
the product properties in America and

how to enhance these these
mechanisms were the sweet spots and

we ended up to decrease
that even the simulation

to the freeway later read yes
we ten percent of the energy.

So I don't have time to show
you the whole study but but

it actually was published in circulation
in Nature last year and we demonstrated

actually then from the computers we took
it to the experiments and we actually did.

Experiments where we actually switch
successfully to the free will if you see

these methods and use only ten percent
of the energy compared to the relation.

So well basically that's.

My collaborator says my wife at least I
would Cherry was on a lot of the numerical

simulations if any the need of
help me a lot with a Web G.L.

Stefan Luther whose work on the on
the optical mapping system you know.

With me and some of the experiments
Robert Gilmore Q So

if you see Elegies the near satanically
source a physicist so our students and

I like to think some N.S.F.
and in H. as well as

a European Grant most of the formation
that I have some of the movie sent and

our plates are in our website which
is if you're to our hearts or.

So one of the things that used to
finish in that I like to work on

sometimes the source of
Utah reality motherly so so

we have this is this little museum that it
is very all now because it's written in

via e-mail but we want to change
it now in the shop in jail and

another other options we want to
convert these twenty two into make.

More.

So now you can actually.

We're trying to import that into our and
maybe even doing an i Phone so on so

that's why we like to have some some
students of you to help us through

to advance all these studies and
all these they nomics anyway so

I leave it in the background and
open for questions.

Thank

you.

So right so well in a simulation you need
to have your frocks when they're condition

so the solutions to be normal basically
accounts for conservation of charge so

so you need to you're off
rocks on the boundaries so

the problem is then if you have any
regrets I mean if you use it with finite

differences then you have everything you
have I'd rather you have their cases and

when you have staircases then you
cannot use get ghosts' else because

then we'll be over this over and over.

The solution will not be unique so
then these method actually uses.

An embedded value with
a very sharp front and

when you as the front goes to zero then.

In forces to be this your flux.

The question regarding the experiments or

the.

Yeah so so.

Two ways of analyzing a problem so

from the physics point of view we want
to always do this very cold call how we.

No friction write the simplest
mother possible and

then start growing up from the point of
view they something they believe that you

have to have all the information possible
to to to to to describe the system so

as time goes by the more people discover
more and more are specialized currents and

more the tale so as you know
there was believe there was for

example just one potassium current and
then from there.

And then there's the US fast and
in a certain time during the but

then the action potential and
then they discover they're actually two so

then they have to generate
that the they devalue for

those because in time if you if you're
going to create drugs that prevent certain

I read me as some of the drugs may affect
only one one type of fine channels and all

the others so that's as you want to make
sure that you have all the information so

when you block one eye on channel
you block the correct one and

not the wrong one or you can see what
he will affect will be another once.

So that's.

One of the

reasons.

Not so that we actually tried
to go between experiments and

simulations both ways so
so we tried to do.

Inform the theory from experiments to try
to develop the NOMIC any Simic Spanish and

of certain phenomena we seen tissue and
then from and

then the other way around we we use
the experiments to then try to.

To make them others more accurate and
and then so

you can make a prediction better sort so
we will both goes in both directions.