Waching daily Oct 3 2017

thank you very much for coming and thank you for the invitations and it's my

honor to be here and give it this distinguished lecture series in both

Institute so I was really impressed in the past two days the visit here and

this exciting research going on as well as the facilities and people here thing

is that very impressive in many aspect originally when I was invited to give a

talk that I didn't give a talk title so until quite recently but then I found

that somebody put in my talk title ready and the title that they're listed here

that as well you can find the poster is actually the title that I

didn't give I don't know somebody actually assigned to me but then I reassigned

my talk title as a bit more, some of the research that related to my research

but then actually the reason that I just bring it back here is in past two days

that my experience here I start to realize that a lot of things in this

title is pretty much a generic title that also related with something going

on this research center that whether I want kind of make a little pitch on

to the my research which is a two dimensional systems tied with this

quantum frontier and that a nano scale so we'll see the how it goes alright so

as Holger said that the main topic I want to discuss is about the particular class

of material there I've been working on it's called a two dimensional material

or the van der waals materials system and it's material that we've been known

for quite a long time nature provides us a lot of so-called delated materials

graphite is a good example in this material that the chemical bond is a

within atomic layer but between the layer there is no real chemical bonding

it's just the weak van der waals which holds all them together because of this weak

van der Waals force nature the worst first thing you can realize that many of

the this material that simply can cleave

quite well using scotch tape that peoples in about 12 years ago

demonstrate you can break the graphite down to a single layer of the atomic

layer of graphite while you hold the graphene and that is possible simply

because the material is is stable because all the chemical bond is within

the layer it turns out that's only the beginning and soon we start to realize

there are all other type of the so-called layered materials or we can

call the van der waals materials that you can increase we take this material down

to one atomic layer or in other word you can also grow this material using

CVD and be in various different type of synthesized method you can grow this

material stabilized down to one atomic layer such that you can effectively

create a two dimensional material system and that has been quite exciting first

of all the material comes with the various different flavor graphite that i

mentioned that turn into the graphene but if you just go above this at the time below

the periodic table there is solisten domains and all this if the number four

families can generate something like graphene like the structures they can be

stabilized down to one atomic layer and they tend to usually shows the

interesting electronic properties so-called semi-metal or zero gap

semiconductor all durán materials in modern terms but also some of the

material becomes an insulator boron nitride that I'm going to discuss is a

good example or some of the materials especially transition metal dark or

denied which consists of the transition metal with charcoal gene atoms such as

sulfur selenium and tellurium those kind of materials often

demonstrate as a semiconductor pure anti or sometime we become superconductor if

you just use an item for example or some materials becomes the strange matter

such as charges wave system and the list actually grows every day and we've been

just enjoying to see in past five or ten years that what kind of materials we can

create in the two dimensional limits and one can study a lot of their interest in

electronic property in this the in a sense quantum limits of this

2 dimensional system now one another advantage e we can see is in this that

captured in cartoon that which was a listened by the way physics today last

year it's kind of following tom not only you can study them as a down to one atomic

layer limits such that you can understand their interest in quantum

physics in principle you can stack them together this is relatively easy in part

because again it's a big van der Waals force when you just put them together

you don't have to worry about their lattice mismatch and just commend your

abilities they simply just kind of put them together and because of a diverse

interaction they just can hold them together and yet there is no real

chemical bond so they just kind of exist a data stack system so this ability

allows us to the following things not only you just kind of work on single

layer system you can just bring it back and stack them together to put some of

the these complicated structures either in plane or even out of plane

no plane but even the same plane even further because as I said this material

comes with a various different flavor you can think about this is a unit that

just displays some of the interesting functionalities right so if you just

choose by just interesting design like as if the you just block the kind of

fact it's a Lego block in principle you can stack this Pandarus materials to try

to come up with quasi three-dimensional structures with some of them interesting

the functionality basically this idea of a Hector structuring of this functioning

system actually bring us a quite exciting new moments such that we can

probably study this material down to atomic length scale and look at this the

how the quantum mechanics plays all but on the top of that one can actually

build distant into this some of the functional devices

we're not even individual layer see that that the properties that if appearing in

the interface actually exceed that they are expectations coming from the silicon

individual materials right it's not only just kind of science fiction's but

indeed in past five years people have been

moving on to demonstrate some of the devices starting from the simple field

effect transistors or interconnect or biosensors the tunneling device memories

LEDs and now kind of more of this electronic and optoelectronic devices

based on this combination of 2d materials and even just try to build up

this flexible devices there are least actually growing up and a lot of the in

tech interest to use this material as some of the application has been come

around in quite recent years I'm not going to discuss about the detail about

the application simply because I'm not good at this kind of real applications

but at least I want to kind of address a part that what kind of the capability

that we've been stuck kind of developing and moreover what type of the

interesting the physical property we start to see especially electronic and

electro optical properties that might be used for some of the realizing

conventional device I would say but even further beyond this conventional device

where the quantum mechanics plays quite important role the method that we've

been using is a rather simple things it's basically what I call the van der waals

reverse a hetero structure this method has been developed out of the

collaboration that I had at Columbia University a few years ago especially

together with the Jim horns group at the mechanical engineering but this can be

easily generalized quite a bit so of course you can get this deep materials

using various synthesis method including the hetero structures such as MB MOCVD

is a method that people try but even before that if you are not worrying

about the scaling about the idea following idea works quite well so I

told you that we can cleave this material down to single atomic layer on

the surface say silicon oxide surface or something and then you can prepare the

polymer tapes or polymer the membrane specially designed such that it may not

lived a lot of residues and we can control the origins and then you start

with pick up some of van der waals system you want to start with typically boron

nitride is a good system because it's a good engineer and then you bring down

this boron nitride on to the another the single layer system in this particular

case the graphene and you just kind of change

the temperature of the substrate controlling the adhesions between the

silicon oxide this material and mature to the boron nitrite you can

controllably pick up this much yours say from the silicon oxide and attach to in

boron nitrite right and then you can start to repeat this process and over

and over again and other materials in this cases you can pick up the boron

nitride again or other the layer the materials and then in the end of the day

you have the distal stacks of the materially different compositions in

there now it depends on the sequences you have the different type of things

but the important part is if you just do it in really controllable way as you see

in this cross sectional TEM image here is a graphene encapsulated in the boron

nitride important part is that this interface especially this hetero

interface between graphene and boron nitride is the extremely clean there is

no single atomic defects you can see in this cross sectional TM images all this

a dot and impurities basically squeezed out from this vanderbass interface such

that you have atomically shaft interfaces possible not only you can get

this mb type of the screen interface in principle you can just kind of cut this

these texts at a very careful manner and expose certain atomic layer that you want

to make the contact and there has been some method that developed that you can

selectively contact the the layers that you want in this particular graphene is

contact with this gold and make the extremely good contact so today you can

make this a device that based on this the quantum Etro stretch structures

where individual atomic layer can be contact right so that's very important

part so in a sense you can mimic that semiconductor heterostructures people

having made have been synthesized using mb technique but here there's a poor

man's mb technique but nevertheless it works rather beautifully

especially in the graphene now we can make this type of devices such a clean

limit the electron mean prepared measured in this type of the system is

basically exceeding several tens of micron in fact that electron mean free

path is set by the sides of sample we can get a list in the low-temperature

means that we can make extrema clean interface between graphene and boron

nitride this type of the clean sample immediately allows us to do a lot of

exciting physics this is a good example that once you apply this strong magnetic

field you start to see that your transport shows this quantizing effect

what you call often the quantum hall effect but it's not only quantum hall

effect it turns out there is an interesting interaction between the

graphene and boron nitride what you call the more apparent forms and give us the

super lattice which actually quantized the graphene band even further and

create this all these kind of complicated structures I'm not going to

discuss anything in detail here on this one because it's Arabella's static

subject but nevertheless this problem actually gives us exciting these new

physics that how this the commander ational in combination lattice

structures in fact with a magnetic field to create this a fractal like the energy

spectrum in the system and this type of the experiment is our only possible that

when you have the extremely clean sample that available in the extreme quantum

condition so this is a good example that what you can do when we have the

clean sample but this is the beginning it's not only graphene but you can make

this all this hetero structure in various semiconductors and the other

system in this particular example we have the boron nitride encapsulated

sorry graphene and moldy disulfide is encapsulated in between boron nitride

make hetro structures that graphene onto the moldy disulfide I serve I didn't make

the good contact between them so graphite in this fuel a of the graphene

server is a good content on moly disulfide and nevertheless moldy

disulfide is encapsulated in this boron nitride

give us a really good channel and entire these structures can be work as a

transistors and their mobility is quite good something like easily ten thousands

under the magnetic field issues are gained quantum oscillations so you start

to see that this example actually extended beyond the graphene one can

make this come interesting these quantum devices as well not only just kind of

this magnetic field and road temperature quantum device but you can also make

this some of this known the other quantum device a beyond the CMOS here is

another good example in this particular example we have sorry about these small

characters but here is a bit tungsten di cilinide

p-type semiconductor and another tungsten dicilinide but in between that

we insert a very thin layer of the boron nitride as a tunneling layer right again

this made made out of this successive stacking and then you can clearly see

that between this two layer because it's a Saltine boron nitride is a tunnelling

device now this type of the tunnelling device is what we can make we the so

called the quantum well resonance tunneling device that out of

semiconductor heterostructures big different see here is we have the gate

from top and bottom such that we can control this band alignment between

these two materials right in the net when you measure tunnelling current

through this device the tunnelling current at the fixed the gate voltage for

example shows increasing tunnelling the current as a bias voltage and there is a

peaks and there's tips and going up again so this peak appears in the terms

of the bias is what I call this the negative differential resistance in a

sense there is a negative slope in here is they actually indications of this

resonance tunnelling between this so 2 dimensional system so has been

demonstrated again they say many of the discs on these quantum hectro

structures as a key diode is a good example but important part is those kind

of this this signature of the resonance tunnelling peaks can be movable by the

gate voltage we apply in the system showing that we have the control

complete controllability in those kinda hetero structures and we can build up

this type of interesting devices as well so not only this type of the electronic

device it turns out you can also turn this in the electron opto electronic

devices in this particular example that we have P PI by n type semiconductor

with them together again very similar fashions and you can see that this is

the thinnest PN diode that you can make either P or n Junction is only one atom

thick materials but exciting part is when you just bias this one is that kind

of illuminating the light like this the LED light enemy emitting diode and that

the spectrum can be tunable by the gate voltage again simply because we can tune

this parallel alignment right or if you want you can use these are these photo

sensors if you shine the lights and measured

you get the photocurrent actually is different it's a kind of you can view as

world thinnest a photovoltaic for photovoltaic diode but variously this

type of the device operation can be done in the extreme that when you make that

this sample is extremely thin right so this is kind of good starting point that

what kind of the application we can just kinda launch you on this extremely 2D

limit of the system now I know that up to here that is a good demonstration

but probably a lot of the my physics colleagues may not be too happy to see

this well this is electric engineering again may I know that you can just make

it thin but what we can learn from here now exciting part of the this two

dimensional system and the hetero structure is actually allows us some

things go beyond that what I just kind of showed you at the example of the

conventional electronic devices we've been known right so let me show you a

few example that I am pretty much excited about the opportunities it's by

far its ongoing project but nevertheless was you will see that some play but what

we are excited about just kind of using this type of to this system so you've

been heard about especially in this institute that you've been a lot heard

about a lot of this mijorana fermions and quantum computing based on

the mijorana fermions and mijorana particles and so on right so I don't have to explain

or a lot of these things but in 1930s this Ettore Majorana the Italian

physicist come up with this intriguing solution of the drug equations which is

brand new equations to describe that's the electrode the relativistic quantum

mechanical particles and that defined the solutions that quite unique

solutions such that it's a the self antiparticle as a solution it turns out

this majorana is a formal solution one of the foremost solution of the di-equations

but it's a weird innocence its particle is its own antiparticle

especially if you just think about in terms of electrons it's basically half

electron it's a half electron or half a whole like and they always comes as kind

of pair right what has been just realizing what a rather recent a year is

if you just realize this majorana particle pairs and especially if they

isolate pairs and if you just can just kind of play around because they're

inherently entangled between these two majorana particles and they are

rather robust because it's partially protected one may be able to use this as

the elements that realize a robust quantum computing and out of this idea

of the past five years that in the condensed matter system there's a

massive search of the material platform to realize this my own on a particles to

be used as a quantum computing right and there are many example that I don't want

to go through but some of the example that a lot of commonalities a you need

some sort of spin orbit coupling or just kind of something that

twisting the band structures around and important ingredient is you have to

interface with a superconductor to proximatize and realizes 1/2 or 1/2

electron type of system there are quite a progress in this field in the

condensed matter field and just realizing one of the materials many

topological insulator it turns out this all the two-dimensional like and that's

kind of good interesting point but the other part interesting part is and you

can just also work on the non conventional superconductors such as the

P wave superconductors and quality particles all the vortices in this the P

wave soup can often consider as a mariner particles the problem here that

is there's another easy way that we can realize those kinds of system in the

reliable way the one example I want to share in that this a two-dimensional

world there are many things that kinda touch upon this so to demand rate system

is at the last part it turns out there's a way that you cannot approximatize

the higher states of the quantum Hall state so quantum anomalous so here whole

states and try to realize this robust be the

topologically unique particles in there how it works basically we need to know

that how to approximatize you are the quantum or say to be the superconductor

and that has been really difficult task in conventional semiconductor system

part of the reason is when you just apply the magnetic field the magnetic

field basically compete with the superconductivity and furthermore in

typical semiconductor under the magnetic field is a very difficult to make a good omi

contact to do just a quantum or measurement with the superconductor

which is usually reflected in materials here comes that kind of interesting new

directions I told you about the graphene and this is a single layer and a high

quality treatment system under the magnetic field we know that it developed

a nice quantum or effect but even further because it is the geoweb

semiconductor nevertheless once you put down the superconductor there is a good

way you can engineers a fairly highly transparent or highly effective

superconducting in there so it turns out graphene can be really good candidate

one can realize both superconductivity proximitizations as well as the

quantum hall effective indeed this experiment so we made this very narrow

the finger like the electrode onto the graphene channel and apply the magnetic

field under the magnetic field once the Landau level forms and everything is

quantized it turns out the transporter is only carried by these edges states

and simply measuring the edges state the potentials one know that how the

quantization is happening so basically we just did very similar experiments

like the typical quantum or measurement except that one of the electrode is

replaced by this niobium nitrite which is known to be type 2 superconductors

where the HST 2 is a large enough such that when you have the quantum Hall

effect still the superconductivity can be

reached preserved in our experiment we found that that this sample actually

did show that nice quantum Hall effect down to say few Tesla

nicely developed all this Venn diagram with all nice quantum Plateau

but not only that when you just carefully measure the chemical

potentials of the edge states we realize the interesting part some part of the

chemical potential image in the circuit only to the negative and that's very

weird moment because we just applied only the positive voltages

0 to positive voltage in these circuits but at some point of the circuit you

start to pick up negative voltages classically or semi classically it

cannot be explained and the way that it happen is when this edge states carry

the electron and hit the superconductor across the superconductor basically this

electron into the whore out of this interesting

procedure what we call the and reprocess right and from there that the electron

turn into the hole leaving the Cooper pair behind and we start to be able to

read this negative voltages in the circuit and this fact that we just read

this negative voltage tells us that there is electron and hole conversion is

happening in this system and in terms of this more complicated world this is what

you call the and reprocess or especially cross and due process and it happens

when you have the really thin superconductor where the electron is allowed

to turn into the whore across this very thin superconductor thinner than the

soup canoed clearance length which means that if you just make the discipline

electrode thicker and thicker basically we start quickly lose the signal

negative signal and this length scale tells us about how much actually the

superconducting currency in this system so it has been nicely done right I mean you

may say that all right so I can see this one but why this is a relator is so

called a majorana particle up to here this is basically description nice

description of the experiment of this 80's and 90's idea right

what have that we have this recent tweak is there is a new way that we can just

view this problem so I'm just kind of showing you that that device but let me

just zoom in there what is the device to look like right follow moment let's

forget about this is a superconductor right and then quantum edge state

comes in if there is no graphene underneath indeed we just make the

trench out of it that the quantum edge state will turn around and coming

like this right so across the distant trench that we had the one quantum

edge states to run this way and the other one is opposite way this is basically

counter-propagating States and then we feel that state in between the state

with the superconductor which can couple that these are two different edge States

can't prepare any agitates through the superconducting the superconducting

interactions basically this is a basic ingredient of the any majorana physics any

majorana on a particle is that you want create in the previous the material

platform works in very similar way that you have the counter-propagating states

topologically protected right but then you just couple them with a superconductor

approximatize them at the end of the day

basically at the end of those can approximatizations you just gapped out

those kind of the counter propogating United States at the end of the diskette

are two state you actually expect is that they localized majorana and that's

case basically more than view and this is not my idea my saying that all this

theorist actually worked it out this type of things a couple with the

counter-propagating states that this is what is the expectation interpretation

of the our cross and the reflection therefore is basically there's a

resonance state that through that this majorana that we have the resonance

transport through that edge state which actually turn into the cross and the

reflections why this is exciting basically this is a way that now we can

start to see that how we can engineer the majorana states and then how to

manipulate them in some sense rather than we started with the one majorana

I can demonstrate it we can just have the descend we can make there another

fingers and then indeed you can ask what if that I start can turn on the

interaction between these two majorana or maybe I can just try any layer were

created and this is basically the basic ingredient we can just present

not only you can create a majorana particle we can start to the

interactions as you see here this is a extremely preliminary data we just start

to make these things that we at least know that from the cross annual fraction

they exist of the majorana and we started to pick up the idea that we can

create them we can manipulate them very preliminary data but promising there is

indeed when you just measure the Josephson coupling between these two

through the majorana we start to see that whenever we change in this quantum

Hall plateau we start to see that this Josephson critical current changes

with same steps that we expected from this be the superconducting gap indicating

that these two states are closer linked together and hope that just give us the

promise or hope that that we start we must be able to manipulate them some more

efficiently so at this point is actually preliminary data but already I give you

some flavor that just combining that advantage we have in this treatment

system such that we can create this clean system we can also make the

contact proximate idea superconductors I give you some flavor that what kind of

non-conventional device we can create it right

as you see in the title that I mentioned also this not only electronic device but

we can just go for the opto electronic devices so let me just kind of dwell

on this now optic side well I'm not this really optics guy I know that

I'm in danger that they're in this Institute I'm talking about optics but

let me just try to do that anyway so in my simple mind that the important object

we have to discuss in when we just discuss of the optics are the optical

properties of the electronic property in semiconductor its accidents which is

basically one can create in this field band with cap the system of semiconductor

shined in the light and we know the photon can create the electron hole pair

as the excitation right well this electron hole can Coulomb contact

each other and they can form the bound state so what that's what we call the

excitons and this bound state shows a lot of the interesting properties like the

lewd read bud excitons is a good example but absorption properties and all a lot

of the optical properties governed by the exciton now unfortunately this

exciton is a rather short-lived because it said it's not the ground state it's a

transient States so depends on the system exciton lifetime can be something

like even less than Pico seconds something like the microseconds depends

on the all these the mechanism how the exciton is a recombine there right but you

can ask the following questions where external as a composite particle they

must have if you're I just streetlight the pollen particle should have the same

symmetry what is their symmetry where it's pair of the electron and hole which

is both of the pheromone is called a spin of the 1/2 so exciton must have the

integer spin which means that we know that this is supposed to be bozon

composite bozon so idea is well if the exciton is bozan if I pump there a lot

of exciton then in principle they can condense down into the Depot giants and

condensation and form some of the macroscopic quantum states maybe that

can be called that one can use something only the problem is exciton is a rather

short lift so the first thing you have to do to move in that direction is it just

to try to create a long-lived exciton one part we can do is you

and just walk on this semiconductor quantum well this is something that

Professor Na Young Kim has been working on for a long time right you just create

this quantum well and then nice thing about this quantum well especially in the

double quantum well is you can create the exciton in the one over those as

well but also you can apply the electric field and you can kill this quantum well

and such that that now the valence band bottom and the conduction band top of

the conduction band bottom and the valence band the top getting close each

other such that exciton can be now addressed in the even this ground state

in principle all close to ground state right and this idea of the creating this

spatially indirect external indirect internal has been around and people actually

using this type of the spatially indirect excitons or maybe put this excitons

into this cavities to create extra proton in Y or whatever way that

there isn't some demonstration you can create this the collection of the exciton

and there is a signatures that this exciton start forms at least some

collective states such as spontaneous coherence actually start up here's some

of the example that recently demonstrated in this semiconductor

hetero structures but nevertheless external majorana today is

still another ground state such that it can be only changing and only exists in

the pumped the system non equilibrium states so whether this you can call this

extern condensation or not that's a lot of the debates in the system now there

is a way that though one can make that this exciton as a ground state and

there's a possibility then you can condense them and it's going back to

again quantum well system so idea idea is following imagine that i have the two

quantum well system then just one top and bottom each other and apply the magnetic

field in there right if i just feel this then then there's a Landau level forms

nicely Landau level formed but let's imagine that instead of that I make that

these two landau completely full completely empty

whether you expect quantized Hall effect appears what if that I just partially

filled this landau level and partially filled on landau level is kind of bad metal

I'm the nothing special things happen it's just kind of poor metal right but

nevertheless if you just put this to partially fill landau level very close

to each other and then I just kind of deliberately put this the density of the

each of the layer each of the layers partially filled but it's complementary

partially fill means that if I just put them together their full rundown level

and in this particular case especially when the lathe delay is close by then

you naturally expected that electron in the top start to see that electron in

the bottom layer and of course the exchange interactions or Pauli exclusion

exclusion principle tells us they don't want to sit in the same space they just

kind of want to experience such that you want me to this public

scrutiny exclusion principle works which means that as the put the layers close

by they it's a self-organized such that they just avoid each other right now if

you just look at this system from the top they look like something like this

right if you just project lead out it's completely full landau right as

if they behave like completely full landau level so that's basically idea behind

of these things that you have the partially filled to landau levels

together and put them together and then you just form this completely full landau

level why this is a related with exciton if you just go back to this

picture basically here's the electron directly related hole and electron

directly relate the hole such that you start to see that this exciton sub pair is

actually formed in this picture right but as a whole this is a full landau

level which means that there as a whole they actually we store back the quantum

Hall effect as if these two layers behavior one layer right and this

beautiful arguments actually work it out already in the garden arsenide and from

the 90s that Jim and Jane Stein's group at Caltech is basically the pioneer under

this view demonstrated when you have this two

quantum or layers together is that kind of talk to each other and form this

quantum mechanically quieren states can be detected by just carefully measuring

the transport for example now again you have the two layer that you send the

current in the top layer and just measure the voltage in the bottom layer

and define the resistance this is not the director resistance this is what we

call the drag resistance and they start to see that drug resistance is

quantizer and if this two layers doesn't talk to each other there is no reason

they a connected each other but in this picture basically because of this

quantum mechanical process they are connected and they do see that that

there is a direct resistance appears and this direct resistance is also quantized

and that has been strong evidence that even in this these two layers just kind

of talking together and make this exciton turn and not only make the exciton

they actually condensate it into the quantum mechanical system showing this a

quantized direct resistance so this has been beautifully done in in past 20

years and well demonstrate it now of course in the two dimensional electron

system such as graphene boron nitride all of these things as as long as your

layer is clean you can repeat this one into the graphene right well here is it

devices so we have the two graphene layers separate by the boron nitride

with the top and bottom gates and or each of the layers got contact as I

mentioned that this can be done and then you just kind of well the real device

images like this and then when you apply the magnetic field and measure their

direct resistance and indeed we do see that like the what in gallium arsenide

we did see that drag resistance is quantized right so quantum or effect

appears in one layer to the other layers is kind of connected although

electrically they are separated out right so two partially filled band

Landau levels shows a drag quantum quantization indicating indeed that we

are seeing the condensed magnetic exciton in the system right well on the

top of that since we have this more capability on to the tuning the density

the gallium arsenide that people did seem a high field landau level but in this

case we see that those effector into the many different Landau level for example

and two half fill landau level to the full landau level we do see again that is

similar drag effect is showing that we can also created exciton condensation in

various places of the difference between different Landau level but perhaps the

very different things that we cannot see in the gallium arsenide but clearly see

in the in this particular system is following case I told you that in the

magnetic external condensation is a very close some the excellent

condensation except that as a whole layer it is still quantum effects such

that we have this the agitated we exist right but in principle that we can make

this rather than this coupling between electron Landau level to another

electron landau level in different layer what if I just using the gate that

turned this on at bottom layer of the graphene into the whole system right so

I have the electron landau over to the whole Landau level and ask the same

thing now in this particular case it is a real

hole and there is a really electron and still it kind of this is a real extra

forms right but the important idea there is especially if you just put the same

amount of these landau level feeling so half fill landau level hald fill landau

level and there are edge States or they're adjusting the the edge estate is

counter productive directions meaning that this becomes on exciton but via

insulator without any edge States it's very close to the real exciton

condensation we are creating if you just can put the electron and hole togethers

and make these things indeed they all experiment I showed you we can just

choose now electron in the whole side so especially this is the filling fraction

of the top layer filling friction the bottom layer along this line basically

we populate half full landau level top and half full landau a heavier electron

Landau level top have failed hole under level in bottom right what is the

feature we are seeing is all these would be drug resistance and drag conductance

we imagine goes to zero basically it becomes really good insulator and if you

just can simply make a two terminal resistance call together

it turns out your conductance actually drop to zero when when you have the half full

Landau levels together and this will is rather weird situation so I know that

this is esoteric but let me just kind of explain that something really

simple half full landau level I told you is a

bad metal right so I have the electron half filled landau level bad metal the

electron have a whore half full landau level which is bad metal right so you have the bad

metal but it's still metal conductor what if we you just put them together you make the

parallel plates and you just kind of measure them

together what is your expectation classically okay it's a poor conductor

another poor conductor it is probably still poor conductor but slightly a

better conductor right what I'm saying here is if I just add a two conductor

together but suddenly it becomes insulator although it's parallel connected

and why is that because it's an electron and hole coupled together when I just try

to send the current electron is flowing in that way if he did strongly couple

holes are flowing the same way it canceled the current right so that's why

it becomes an insulator another way to say that is now the carrier that here is

basically electron hole pair it's a neutral object they cannot carry the

current anymore right so this is basically clear demonstration but

something really happened when we have that really just accident condensed

excellent condensation here there will be more of the exciting part is the

other way that you can view that is now I send the current in the bottom layer

but simply that imagining the voltage in top layer I'm sorry that I'm just as mad at

the bias the voltage on to the table to send the current on the top but if

I just make this short in the bottom layer what happen is in the bottom layer

there is no voltage source but then you start to see the current is flowing

another way to say that is where exciton is here if the exciton is a dragged by

this the bias voltage in the top basically that if the hole is flowing

there electron is flowing there in other columns the flow in there amount of

current I'm getting here should be same as amount current there indeed if you

measure in this situation or cross here that where action is condensating

exactly we getting this the dragging current is the same as a driving current

it's what we call the politic the drag right and this is another indication

indeed we have the condensed X in this system right now we can just do a ribbon

no more things I don't want kind of do it on this one or a bit more but you can

actually carefully look at this how this exciton condensation is happening in

different magnetic field and different temperatures and in all of them

indication let me just skip this one because it's a but the okay so I will do

it here that then you start see that there's interesting the phase

diagram I can draw that how the extent is conversating as a function of

magnetic field and temperature I don't want to go into too much of detail but

once we see these things we just realize this is not only just to what we are

seeing the experiment but has been discussed in long time in exciton

condensation communities it's basically that phase diagram you expect see when

you have the excitons in electron hole of course if the temperature becomes high

and high exciton becomes unbinding and then becomes the electron hole plasma or if

you just put a more and more exciton in there there's so-called emal

transitions happen in other word that basically screaming between the charge

carrier increases such that you start to lose a full on binding energy that the

electron hole the exciton system turn into the electron hole liquid just kind

of binding States right and all of the system as you go down to low temperature

they can condense of course in if you have the exciton, the exciton is boson it

condensed into the bose-einstein condensation if you have the electron

hole plasma that condensed as a superconducting state BCS turns out that

in the low temperature there is sure to be some BC to the BCS crossover happens

and the other is what is the expectation indeed what we measure into the day of

our system is very under Louis when we just measured we are seeing the very

similar things happening when you look at this a gap that out of there

measurement we are seeing that this conversation gap or transition

temperature shows a nice dome shapes and that kind of eject the crossover what we

expect to see in the BCM bcs so indeed the system that we discrete

out of this magnetic sense really follow through the what we what we supposed to

see in this section state however as i mentioned that i want to talk about

optic optical states but you already start to see that is this guy is already

digress of the his convenient the pace pace of the graphene not to mention

about any of the properties right and this is nice the demonstration makes and

conversation but only appears in the strong magnetic field right how about

the real excitons to of these systems we are dealing with actually is a good

system

in principle that we can discuss about that some part of the reason is in 2D

semiconductor TMDC it has a decent gap and because of his safety atomic

limits when you shine the lights they form the excitons but they'd have the

very strong binding energies simply because electron hole pair you created

all of the field aligned going out of the materials without screening and their

chrome interaction becomes very strong so it turns out experimentally you find

that half electron of this half electron both of these exciton binding energies

because if they have the strong binding energy in principle you can also attach

this exciton with a charged particle create so-called a trion or positive

negative charge at trion states they can be also stabilized and this type of the

beautiful idea has been tested out already in the three dimension electron

system by the many other groups here is at Antonio Heinz group and Xiao Dong Xu's

group they all demonstrated indeed exciton do exist in two dimensional system they

are very robust and strongly bound and you can create a lot of different type

of optical species and make the interesting quadrants and interesting on

other parties strong in a spin orbit coupling in the system made these valleys

gas spin split which means that using the light you can also control the spin

state of the particles or excitons in the system so we know that this is a

very exciting system can you actually couple this with electronic device

indeed it's a relatively straightforward right you just make this a transistor I

just so to show that before right and then you just put the gate as if it is

fill that effective transistors rather then you just measure transport you can

just measure the optical spectrum and see how you look like under there all

these kind of different electronic conditions so here it's a good example

here is that we have a transistor made of the tungsten di cell and

monolayers we have top and bottom gates as you see the Y and the source and

drain and we can just act or to study about their transport properties but we

can also study their optical properties as a function of a gate using the gate

we can control the electric field edge where as a charge density and this

particular diagram I am showing you there is a photo luminescent

data as a function of the density we can change in the system if you just apply

the same polarity of the voltage onto the gate we can change the density

without applying the electric field or we just apply the different polarity on

top and bottom gate we can change the electric field without changing the

density and what you see here is their spectrum the bright the red is basically

peak and blue is a deep and there are the peaks appears in the optical

spectrum we can assign following to the previous work this is exciton this is a

negatively charged trion on this is positively charged trions as a function of

the density extreme quickly dies off outside of the gap region their energy

has shifted as you change the density because they are screening property got

changes so we start to see that a spectrum got changes but important part

is this exciton we create or try on we create in two dimensional system as a

function of the electric field in the vertical directions there instead

intensity got modulated but what you see in that the energy position is that just

constant right and this tells us whatever dipole moment of this the

species accidents or Trion you create if this type of moment is they should be in

plane such that it's orthogonal to the electric field we applied in the

vertical direction another way to say that is truly two-dimensional object we

can create optically created and potentially we can also electrically

manipulate it right while this the two-dimensional system we

create is a completely the two-dimensional electron default this

system one can create this the rather semi three-dimensional system by hetero

structuring I told you that we can create the PN junctions by just kind

changing different type of materials in this particular case I'm only thyself I

sell and I tungsten Dyson and I put them together it's a type 2 band alignment we

can create this the structures I showed you before that this behave like PN

diode we can create the photoluminescence and we can get we can

get the electro luminescence and photo currents out of it we actually put a

little bit more efforts in here we can put complete control top and bottom

gates each of the electrode each of the layer and if each of the

electro need to be gated to make the homie contact but in the end of the day

we have the device by the way this is kind of heroic efforts of the couple of

students and making this type of device takes us sometimes to build in the

working device but nevertheless once you make the device you get beautiful

optical spectrum here I'm showing you out again photo luminescent curve so

this one is that when we have the tungsten disseminate along this is where

the molten dicelonide and I are on a low temperature the peak width is about

Mille level 4 almost a radiative a lifetime they're limited but the

interesting part is interlay exciton when you have that this part of this the

transitions we do see that the peak appears in heterostructure area

indicating that indeed now we have this intellects and forms and that's

important kind of beginning point right I told you that interlay exciton can be

long-lived in principle because now electron holes are separated right and

over the on the top of that because of this band alignment is not the

three-dimensional structures by just again we can control this band alignment

which means that this energy scale got changed indeed that's a case when we

actually show this intellect some peak changes with the gate voltages again as

you change the density we see the intellects and the energy got slowly

slightly changes but outside the gap we quickly lose the intelligence so

intellection only appears when thermal level is within the gap but important

part is unlike this is a two dimensional system in disappeared junctions in the

atomic Alateen PN Junction as you change the electric field by controlling the

gate inter exciton and energy is linearly

changing just kinda linear structure meaning that dipole moment is now

out of plane and just looking at this the magnitude of linear shift we know

that this is a completely interlay excitons we just created now I told you

interlayer exciton can be long-lived indeed if you just look at the external lifetime

external lifetime is a reasonably long it's something like 200 nanoseconds the

half micron half microseconds more importantly energy you just change

Gate voltage as you just apply the electric field along the exciton direction

such that you start to pull this excitons away you start to get this electron and

whole wave functions overlap and less and less and you expect a lifetime

becomes a longer and longer and that's precisely what you see as you apply the

electric field lifetime becomes longer because you pull

this exciton ends up right and such a long leave the exciton is already forcing

gradient we need to create the exciton condensation right the first thing that

you start to see is this because exciton is a long leave that when you just create the

exciton they can start can diffuse out the sample rather fast right in this 10

micron size of sample you just kind of shine the laser there about this spot

and then you start to see that the exciton can be picked up or across the

sample even further you can actually look at this how the exciton get diffuse

out by just just posting this exciton and you can get this exciton actually diffuse

out to rather fast and just the time dependence this extra measurement we can

start to get this in the numbers it turns out diffusion constant of exciton is a

three centimeter square wall centromere seconds which actually correspond this

the the mobility of the carrier do we measure in the system so we know that it

works more important part is that this in homogeneity that tells us the exciton

we create can be also trapped in some part of sample due to the imaginary

and the density inside of trap can be controlled by descending the current

through the desist one of the layer so this starts tells us that in principle

using the current in one of the layer we may be able to drive this exciton in the

system this is very analogous to the magnetics and I showed you right when I

send the currently one of the layer that I said get the perfect drags in to the

other current unfortunately we are not in yet get that

new range of the measure but clearly the optical spectrum start

tells us that sending the current in one of the layer

apparently affected systems in the way that excellent distribution is

something's it's a very kind of important part are we in the exciton

condensation regime I think let me just skip this one

I think we probably not we don't have the really good evidence yet but at

least we are getting it there how do we know if you just pumped in the exciton

with the high density the exciton and it's that blue shift and that's because exciton and

exciton and interactions and this blue shift actually give us a sense that what is

exciton density we can create in this system without heating the system it

turns out exciton and ends to be creating about 10 to the 10 10 to the 11th

they're centimeters we don't know that yet that what is the density that exciton

can be created but if we just rely on the mean field type of the theory

calculations already here okay so this is a BKT line where the exciton conducts

BC condensation is happening so we is about here right I did it and then you

see the temperature is something like this we measure this is a 4 Kelvin so in

terms of this density we are not really far from this mean field of the line of

the exciton condensation we hope that once we just create a little more

careful experiment especially direct type over the experiment we should be

able to really pick up this quantitative quantitative analysis of this exciton

condensation features so this is another example I think at this point it is just

the demonstrations of that at least we start to see the very first step that

what we are looking for that just can be on the convention of the electron device

such as the photodiode or the photovoltaic device and here is

another example that once you create the so kinda exciton condensation in

principle you can create exciton and condensation even a really elaborate

temperature as long as you you just make the long-lived excitons in the in this

system and that's kind of another hole that maybe it there is a way that we can

create this quantum electrical optical devices based on this type of and there was

hetero structures technology got evolved not only you just

kind of create the excitons but you can create this excitons and they can one can

mode they modulate the exciton and the various positions and some things I don't have

the real time is going through and just kind of create this at the some of the

localized excitons and trials by just the look at the engineering the

important part is important message that I want to deliver in some sense as a

summary is this the new opportunity that we are just received just arise from

this availability of the various different type of materials combined

with this the mesoscopic experimental technique subtle ways to give us some of

the exciting the the the new quantum physics especially new many-body quantum

physics startup here in this type of system now the next level question is is

there a way that we can tame this type of new physical phenomena into the kind

of device going beyond of the CMOS type of applications so that's basically next

many years of the answer that we have to work on finally I should probably thank

my group first that they just kind of make the oldest the various part of the

presentation is possible but also not only is within my group there are strong

collaborations both the superconducting inside optic side and theory side that

most of the my local collaborators as well as they might collaborate in the

Japan who provide high quality of this boron nitride crystal thank you very

much

For more infomation >> Philip Kim - Materials in 2-dimension and beyond: platform for novel electronics and optoelectronics - Duration: 54:31.

-------------------------------------------

Jury reaches verdict for teen accused of killing Manzano High School student - Duration: 1:51.

For more infomation >> Jury reaches verdict for teen accused of killing Manzano High School student - Duration: 1:51.

-------------------------------------------

Free indicators , Forex factory news feed (for ctrader user ) - Duration: 1:28.

input parameter

if you don't want to see detail about actual,forecast previous

This fill volatility news >= 1,2,3,4

Change color of Text details

This number fill 0 is today , -1 yesterday , +1 tomorrow

If you want to see all news fill no and Yes is show only symbol relation with chart

For more infomation >> Free indicators , Forex factory news feed (for ctrader user ) - Duration: 1:28.

-------------------------------------------

How to Make High Speed Spinning Top for a long time - Duration: 5:01.

Watching Now How to Make High Speed Spinning Top

Please Subscribe Our Channel

For more infomation >> How to Make High Speed Spinning Top for a long time - Duration: 5:01.

-------------------------------------------

Twiyubake members sending their thanks to WD for healthcards - Duration: 0:58.

My name is Martha,

From Twiyubake cooperative,

I am so much thankful to World Dance for having paid for our health insurance,

Before getting your support, we would fall sick and stay at home without going to hospital,

but because of your support, we are able to go to hospital on time, we thank you so much World Dance,

we deeply thank you and pray for your blessings from God

My name is Seraphine Uwamahoro,

I am very thankful for World Dance for their contribution toward our health insurance

I used to get sick and could not go to hospital to be treated,

and it was the same case from my children too,,

but this time ,even when i am pregnant i go to hospital to be treated quickly,

And i pay very less money

where I was asked to pay around 50,000 francs, this time with health insurance i pay around 2,000 only.

I thank you so much and i pray that God continues to help you,

For more infomation >> Twiyubake members sending their thanks to WD for healthcards - Duration: 0:58.

-------------------------------------------

Divyanka Tripathi and Vivek Dahiya GO CRAZY WITH FANS - Shopping for DIWALI 2017 - Duration: 1:30.

Divyanka Tripathi and Vivek Dahiya GO CRAZY WITH FANS - Shopping for DIWALI 2017

For more infomation >> Divyanka Tripathi and Vivek Dahiya GO CRAZY WITH FANS - Shopping for DIWALI 2017 - Duration: 1:30.

-------------------------------------------

Trusted Care and Respect for People at 354th MDG - Duration: 1:46.

For more infomation >> Trusted Care and Respect for People at 354th MDG - Duration: 1:46.

-------------------------------------------

Pleas for Gun Control After the Las Vegas Massacre - Duration: 4:14.

Pleas for Gun Control After the Las Vegas Massacre

  To the Editor: Perhaps the saddest fact about the horrifying mass shooting in Las Vegas on Sunday night is that it won't be the last.

These mass killings will continue until there is the political will to enact effective gun control measures.

If the heartbreaking massacre of 20 6- and 7-year-olds at an elementary school in Newtown, Conn., nearly five years ago couldn't bring about that change in culture, I doubt the latest tragedy in Las Vegas will either.

SILVER, SAN FRANCISCO To the Editor: Listening to the recordings of the massacre in Las Vegas, we hear the sickening continuation of the ammunition rounds coming from the weapons of one man.

This kind of terrorism is brought to you by the National Rifle Association and all those who support the idea of semiautomatic weapons being in the hands of practically anyone.

More weapons and more dangerous weapons are killing us, not protecting us. The death rate from gun violence in the United States is on average 25 times higher than in high-income nations with sensible gun control laws.

Making more dangerous weapons available to more people increases our danger. No number of weapons, including semiautomatic weapons, in the hands of the tragic victims in Las Vegas would have saved their lives.

HIRZEL, DENVER To the Editor: President Trump's tweet, offering "warmest condolences and sympathies to the victims and families of the terrible Las Vegas shooting," says nothing about the proliferation of guns in our country.

    We have a president who is quick to tweet leaders of other countries about what they are not doing to protect their citizens from terrorism, but notice how he says nothing about how our leaders should be taking steps to prevent homegrown terrorism in our country.

  That would mean having a face-to-face debate with the National Rifle Association, and this president will never do that. Shame on him! STUART GLAZERFORT LAUDERDALE, FLA.

To the Editor: As a psychiatrist, I have been repeatedly dismayed at the press coverage awarded to mass murderers.

An example is your article, published within hours of the Las Vegas shootings on Sunday night, about the gunman ("Who Is Stephen Paddock, the Las Vegas Shooting Suspect?," nytimes.com, Oct.

Mass murderers are highly unstable individuals, some of whom are looking to be famous (or infamous), and that desire should not be rewarded, even posthumously. It also encourages other, like-minded people to use similar means to achieve the same goal.

Many of these individuals suffer from some kind of severe mental illness.

Media coverage of this stigmatizes others with related diagnoses, most of whom suffer greatly but rarely become dangerous enough even to harm an individual person, much less carry out a mass murder.

They are much more likely to hurt or kill themselves. I encourage you to be the first to prohibit publication of these profiles.

For more infomation >> Pleas for Gun Control After the Las Vegas Massacre - Duration: 4:14.

-------------------------------------------

Power for the people who need crossovers | 2018 Audi SQ5 First Drive - Duration: 9:42.

Power for the people who need crossovers | 2018 Audi SQ5 First Drive

The 2018 Audi SQ5 is pretty simple. Its the sporty version of the redesigned Q5. Its for the enthusiast. The buyers skew male, and Audi pitches it as the solution for when an S4 doesnt meet your needs.

Its a 354-horsepower purple pill for the Dad whos resigned himself to driving a crossover-but still wants to have some fun. The SQ5 is simple, but its also very important.

The Q5 is Audis best-seller, and a sportier sibling makes the entire family look good. The midsize crossover segment is big business, and the performance industry is hot.

Archrivals Mercedes, BMW, and Porsche have formidable entries. A few years ago a hotted-up crossover was a nice thing for an automaker to develop–a bonus addition to the lineup.

The SQ5 definitely feels like the right vehicle at the right time. Cruising around Vancouver Island outside Victoria, the stately capital city of British Columbia, were having heck of a good time.

The crossover, based on a platform shared with the larger Q7, feels nimble and eager. Breaking free from early morning traffic, we find the Trans-Canada Highway, cue up Dynamic mode, and take off.

Dynamic mode adds heft to the steering, lowers the vehicle 0. 6 inches from Auto mode, and deepens the exhaust note. Its low, growly, and sounds surprisingly good.

The 30-liter TFSI engine has plenty of punch. You know it from the S4 and S5.

Like those cars, the SQ5 now ditches the supercharger for turbo power. It was a mildly controversial move as the blown motors in the S4 and S5 gave those cars true muscle-car character.

Weve made our peace, and turbos just seem like the natural move for the SQ5. Audi is quick to point out the wide torque curve–you get 369 pound-feet sooner than with the supercharger, and output is 23 more pound-feet than before.

The horsepower remains the same, though it maxes out slightly sooner in the band. Audi says the turbo, mounted in the middle of the engines V, makes the SQ5 more responsive, and with all of the low-end torque, we agree.

It certainly feels capable as we open it up, finding gaps in traffic, side-stepping tree haulers and deftly out-maneuvering slow-moving motorists.

We find a rhythm on the Pacific Rim Highway, smoothly tackling the curves, pulling the paddles for quick downshifts from the eight-speed automatic Tiptronic transmission, and aggressively accelerating before giving way to common sense. Its a beautiful drive.

Spring is taking hold in British Columbia, the daylight is streaming through the expansive sunroof, and were soaking in the sights as we pass waterfalls, rock formations, and a stream called Cats Ear Creek.

The mountains, some already sprouting green trees, and some topped with snow, beckon us forward. It rained briefly earlier in the day and fleeting thoughts of the Quattro all-wheel-drive systems capability crept into our consciousness.

Equipped with the optional S Sport package ($3,000), the system gets a rear differential that can split torque between the rear wheels or send most of the output to one wheel, if conditions require.

The sport package also adds red brake calipers and the adaptive air suspension, which offers 3. 9 inches of height flexibility. Ride high in the Lift/Off-Road setting or drop all the way down in Dynamic.

Or let Auto figure it out for you. Changing modes is easy in the SQ5, just as you would in any Audi with driver select.

There are two buttons to the lower right of the flat-bottomed steering wheel. The cabin is a mix of analogue and digital features, which strikes the right chord with us.

The Virtual Cockpit offers a full-color interface in front of the driver. Setting the navigation using the MMI wheel is easy and the system shepherds us along the Canadian roads without fuss.

Its the centerpiece of a sporty yet austere cabin. Our test SQ5 has dark surfaces broken up by silver and carbon-fiber trim. Theres also black leather, white stitching, and Alcantara. They work together, and its a good look.

The Nappa leather seats with diamond stitching offer a lot of support and provide an excellent view of the road.

The second row has a decent amount of leg- and headroom for an adult of average height and build, and the hatch has plenty of space for luggage and other carry-on items.

As Anthony Garbis, SQ5 product manager put it, Its really the right balance of performance and functionality. The exterior is busier than some Audi fans are used to.

Theres a strong shoulder line running from the LED headlights all the way back. The fenders have slight curves, and the silhouette is like a big yet graceful hatch.

The SQ5 is separated from the rest of the Q5 herd with a platinum gray single frame grille, different bumpers, a rear roof spoiler, and aluminum optic mirrors. Twenty-inch wheels are standard and the 21s offer a touch of bling.

One complaint: Theres a rear design element that looks like a diffuser with fake exhausts, which we think is unnecessary and overwrought.

Despite the fact its an expensive luxury vehicle with a high level of performance, the SQ5 attracts few stares during our time rolling around Vancouver Island.

Its nice to have a crossover capable of hitting 60 mph in 5. 1 seconds – and no ones the wiser. Do you need that exhilaration?.

Thats the $12,800 question, which is the difference between the Q5, which starts at $42,475, and the SQ5, which begins at $55,275. Our tester came in at $65,800.

Youre really paying for the engine, which offers a 102-hp burst over the Q5s still-punchy turbo four. Factor in all the extra standard equipment on the S variant and it seems like the reasonable play if you have the means.

But these siblings arent competing with each other. The Q5 is Audis bread-and-butter crossover making up one-quarter of its sales this year, and the market is demanding more and more of these vehicles.

Though the SQ5 only made up 10-15 percent of the last-generation Q5 sales, it was a crucial slice. It made this grocery-getter just a bit cooler, while reminding Audis rivals that it can inject racing DNA into anything.

A sporty SUV is a simple notion, but for Audi the SQ5 is a vitally important vehicle. Soccer Dads wont be disappointed.

For more infomation >> Power for the people who need crossovers | 2018 Audi SQ5 First Drive - Duration: 9:42.

-------------------------------------------

How To Free Phone Memory For Video Production Using Dropbox - 1 Minute Moment #91 - Duration: 1:59.

I'm sorry didn't see you there... because my cat just did this really cute thing and

when I whipped out my phone to go and shoot it

there was no memory left so now I'm gonna have to delete loads of stuff.

Dropbox I should be using Dropbox? That's just for file... Okay tell me more

In this week's one-minute moment we're going to look at how and why you should

use Dropbox on your phone when you're planning a video shoot. I've one minute

let me set my timer.

Now if you're like me you've thought of Dropbox as just a file

sharing app it's great if you want to share a big old document you've created

with other people that you're collaborating with, but since Social

Media Marketing World in 2017 I have been using Dropbox for video and the

reason is, it doesn't matter what phone you've got if you shoot loads of video

it's gonna fill up the memory really quickly. So if you're planning on

shooting a lot of video you need to get it off your phone and save it somewhere

in the cloud for use later on. Make sure you've got the app on your computer

before you leave and you've got an account then download the app on your

phone. Once you've shot your video you can go into the app click the plus

button upload your video into Dropbox and once it's uploaded, make sure they

have uploaded before you delete them from your camera roll but there it is

they're done they're sitting in your Dropbox loads of space on your phone but

what if I want to use those videos what if I want to edit them on my phone while

I'm there and they're all in my Dropbox now. You just go into the Dropbox, click

on the file and you can save it back into your camera roll. I honestly don't

know what I ever did before I had Dropbox, give it a go and let me know how

you get on

For more infomation >> How To Free Phone Memory For Video Production Using Dropbox - 1 Minute Moment #91 - Duration: 1:59.

-------------------------------------------

In wake of gun violence, GOP calls for prayer & unity, victims call for change - Duration: 1:51.

There's a time and place for a political debate but now is the time to unite as a country.

What is clear now is that this is a moment for national mourning.

You truly hope that in a moment like this, we can move beyond politics.

It's really a time, we find what divides us to put aside.

A man named Caleb Keeter.

He's the guitarist of the Josh Abbott band who was on stage in Las Vegas just before

the attack.

Keeter, a self-described proponent of the second amendment.

He now says in a tweet I can't express how wrong I was.

Enough is enough.

We need gun control.

We need it right now.

This is a club that nobody wants to be in.

Please can we do something with the assault weapons so that we can stop this club from

ever getting any new members.

I beg all of you please.

Politicians from the local level to the state level to the national level, they sidestep

the issue.

They kick the can down the road.

This can't happen anymore.

It says my name is Natalie Barden and I wanted to tell the president that only police officers

and the military should get guns.

If people want to do it as a sport than they could go to shooting range and the guns would

not be able to leave there.

For more infomation >> In wake of gun violence, GOP calls for prayer & unity, victims call for change - Duration: 1:51.

-------------------------------------------

Reverse clutches:Bevel gear clutch for changing rotation direction 2-Tutorial Video||Design engineer - Duration: 1:02:29.

For more infomation >> Reverse clutches:Bevel gear clutch for changing rotation direction 2-Tutorial Video||Design engineer - Duration: 1:02:29.

-------------------------------------------

Lamp/ Wall Light/ Decorative Lamp / Wall Hanging Light for Office & Shop Wholesale Market - Duration: 8:57.

For more infomation >> Lamp/ Wall Light/ Decorative Lamp / Wall Hanging Light for Office & Shop Wholesale Market - Duration: 8:57.

-------------------------------------------

Welcome to Mary Gates Hall: Advocates for Equal Access - Duration: 5:38.

[music]

>>Dan: Hi I'm Dan Comden.

I'm manager of the Access Technology Center.

And in this space in the basement of Mary Gates Hall,

we provide consulting services for accessible design

of web pages and online applications.

We also do accommodations for students, faculty and staff who have disabilities

who need some help using computing technology.

We've got a showroom behind me that has all kinds of technology

that can help people with various disabilities have access to computers.

Also located in the basement is the Disability Resources for Students office.

They provide academic accommodations for students with disabilities.

They provide accessible academic materials in alternate digital format,

they provide for extended exam times

and they actually have a testing center that's located here as well –

very active during finals and mid-terms.

This is the counseling part of Disability Resources for Students

where the counselors who meet with individual students

to discuss accommodations are located.

And in here we have Jon McGough,

who's the associate director of Disability Resources for Students.

Hi Jon!

>>Jon: Hey Dan!

We work with over 2,000 students a year

ensuring that they have equal access to university programs and classes.

In DRS, we work with students in every program across the university.

That's undergraduate students, graduate students,

students in professional programs like medicine or law.

In working with our counseling staff, our counseling staff works to ensure

that the students can access the classroom.

That means that lectures are accessible to them.

This could include sign language interpreters or closed-captioned videos.

We worked to ensure that their books are accessible to them.

This could be textbooks in Braille or audio or many other digital formats.

We work to ensure that clinical experiences and field trips are also accessible.

>>Krista: These accommodations are designed to level the playing field,

not to give preferential access.

Leveling the playing field means that a student with a disability

has the same right to succeed or fail as any other student.

>>Jon: One important thing to keep in mind is

that the term disability is really broad under the law.

Many people may hear the term disability and think of individuals

who are blind, low vision, or in a wheelchair.

That actually makes up probably less than 10%

of the students our office works with.

Common diagnoses that students have in working with our office

can be things like anxiety or depression,

attention deficit disorder, chronic health conditions.

>> Dan: Here we have the D Center, the disability and deaf culture center.

This is a student-run organization that provides a space

for students to hang out, study or meet.

>>Lesley: My name is Lesley Ellis.

I'm the adviser here at the D Center.

>> Lesley to student: Hey, how's it going with the website?

>> Student: Um, well, good.

>> Lesley: We feel really strongly there should be a center for disabled students

to come together and be able to share space,

to maybe unwind from the day, maybe take a break between classes.

>> Lesley to student: Are you applying for new jobs now?

>> Dan: The transition from the K-12 system into higher education

can be a bit of a shock for some students.

They come from a very supportive environment to an environment that is supportive but

requires that the student really be their own best advocate.

They have to seek out the services.

So it's really nice to have these different units

co-located in the same building.

>> Lesley: See you soon!