 So thank you very much for all of you for coming I got to say I wasn't expecting this many folks to come and You've all just made me much much more nervous than I was This is a rather unique kind of talk for me to give in that There isn't what I would call science And there's no hard data that's in there. That's not the point of this talk I'd like to give you an overview of what I do what I do with my graduate students and Try to help you perhaps get a little bit as excited as we are about the work that we're doing and about these atmospheric Particles that are in the atmosphere. So it turns out that everyone Including my wife hates this title. Come on tantalizing glimpses into the lives. I really couldn't come up with anything better because I Wouldn't say I couldn't say understanding atmospheric aerosols because we know almost nothing about them in spite of all our efforts At one time we considered them to be Systems and stasis they didn't change you form the particles they go in the air and they do whatever they do Well, we realize today that that is not the case They do have real lives and those lives depend on many many factors including the atmospheric conditions But the chemistry which is what we are interested in trying to unravel But first I'll start with just a little quiz All right, so see if you can tell me what these things have in common So this is a beautiful photo that my graduate student Rebecca took from Mount Mansfield looking out This is a nice sunny off September afternoon. I believe in Beijing What has to be a main lighthouse here with the waves breaking okay, and something that I know Joel Goldberg will appreciate a bacon inhaler So what do these things have in common think about it? If we think about what this bacon inhaler does that is that it mists The the fragrance of bacon. I have no idea if it's real. I just found it on the net, but Anybody knows if it's real. Let me know They all form aerosols that is these This these suspensions of fine liquid or solid particles that are dispersed in the gas All right, usually we don't think about it when we're breathing in here, but I mean, I hate to tell you you're breathing probably 10 to 20,000 particles for every milliliter of air that you breathe That's that's a lot of particles, you know, luckily our body can can get rid of them But these particles are everywhere right and as Dwight mentioned they do have health issues And we are involved in that although it's not something that I'll have the time to discuss with you today But if we think about These aerosols and how they might affect the climate which is really It's just our focus again. We build instruments We develop methodologies and we apply to things that interest us but we're by no means atmospheric chemists or global modelers or or Or atmospheric scientists, but if we think about the annual mean particular matter 2.5 So this is what the EPA regulates as part as one as they're one of their air quality standards and This is actually satellite retrieval data that shows the concentration of this fine particulate So these are all particles that are below 2.5 micrometers in diameter You see that there's a these numbers are really not zero They're close to zero, but they're not zero and we really have a global distribution of this fine aerosol and You can pick out some obvious features like of course here. We have the populated regions of China and India The northeastern US you can see the levels of the particulate are quite elevated the EPA limit by the way is a 35 micrograms per thousand liters of air As a 24-hour average, but you can see that as we might expect pollution, right? We have all these very high concentrations of particulate in the atmosphere But maybe what you don't recognize is that in some cases like here in Africa and and the The Amazon rainforest for example, we have still quite elevated concentrations of particulate These are relatively pristine regions and we might ask where those particles come from Which is really going to be the focus of what I'll talk about today Now the EPA regulates the mass of these particulate because that's the easiest thing to measure And it's actually kind of a silly metric to use because there are many coastal regions as you might imagine Because the waves generate these large particles there's lots of mass in those particles and there's a lot of coastal regions that are not in compliance simply because of the of the sea spray But it's difficult to measure any other to quantify any other parameter that we can use as a regulatory metric So these part these particles are in fact globally distributed And if we take a closer look at what the at the some of the physical dimensions of these particles What we really see is that while the EPA regulates from this line down in terms of mass Almost anywhere in the world you will find that particles really exist in three different size ranges and Which rain which size range they exist in really depends largely on how they were formed So if we look over at the course side here, so this is ten to a hundred micrometers That's about the diameter of a human hair not mine necessarily, but of a human hair And these large particles are formed primarily by mechanical processes. So waves breaking Road wear dust being picked up by wind And So these particles as I'll say in a minute we lose them by sedimentation gravity simply pulls them down to the earth To the surface and we lose them and it can do that because these are relatively massive Particles, so we're not really very concerned with these mechanical with aerosols from these mechanical processes Rather particles can be formed in the atmosphere through chemistry All right, that's what gets us excited and these particles are much smaller So you can see there's actually two modes, so this is the so-called nucleation mode So that's the first time that we can measure that particles are formed But that's an instrumental limitation, right? It's not something I'm going to get into but there's actually a fourth mode Which are which is called the eight can mode and particles are even smaller there, but these are formed through through the reaction of organic gases or gases in the atmosphere that react with ozone or some other oxidants in our atmosphere to form New compounds that really don't want to be in the gas phase, right? They're very low volatility So they either condense on themselves making new particles or they can condense on existing particles allowing them to grow if we So we have the we have the the two ways really that we can generate these particles obviously these aren't just building up in our atmosphere There are removal mechanisms. I already mentioned sedimentation for these very small particles here diffusion is actually the primary mechanism of loss So they're so small. They're almost like molecules that they're moving around so quickly They're just by random impact with surfaces. They're lost If we look on the other hand at this range here between point one and one micrometers the so-called accumulation mode This is kind of the the Goldilocks regime because these particles are too small to feel really the pull of gravity They don't settle very well by sedimentation But they're too large to really be lost by diffusion So it turns out that rain out is the only way these particles are lost. They do form clouds and Because they have the lowest removal rate they tend to have the longest atmospheric lifetime So meaning they have more the most time to to create problems in the atmosphere all right to impact atmospheric processes and This is actually one of the challenges with trying to do these analyses is that if you think about it We're spanning about five orders of magnitude in size and to find one method that will allow you to measure across that entire range Is not trivial All right, but let's coming back to the atmosphere then We already saw before that Particles here clearly they reduce the visibility. So even in clean Vermont We We have particles that are getting in the way between us and what we're trying to view So we see this haziness going along. We saw two really good examples of aerosols for For human health if you will that is you know the bacon inhaler and anybody who uses an inhaler for for asthma control For example, so aerosols are a common way for delivering pharmaceuticals What I'm going to concentrate on really is on the impact of aerosols on climate or how they can impact our climate and we're really going to look at We're going to focus in on how the aerosols Change the amount of solar radiation that reaches the Earth's surface the so-called radiative balance As you might imagine particles if they're in the way just as in your line of sight here If they're in the way between the Sun and the Earth's surface, they might scatter radiation back into the atmosphere They might absorb the radiation and then emit it either down or up All right, in either case and they are reducing the amount of sunlight that reaches the Earth's surface And in fact the community has taken to Saying that aerosols tend to be global dimmers Balancing global warming which is a really dangerous thing because they don't balance global warming We know very little about the magnitude of this so-called direct effect So it's a direct interaction of the particles with the sunlight And even though we know we know very little about this effect We know even less about these so-called indirect effects. So again these particles are in the atmosphere There's lots of humidity around they can take on water form clouds And as we can see especially today if we have clouds we have less sunlight reaching your surface again global dimming and for us The unifying factor between these direct and indirect effects is that they're both dependent at least in part on the Chemistry of these particles All right in order for these particles to become cloud droplets. They have to take on water which means they have to be hydrophilic And that's going to depend on the chemistry the wavelengths that are absorbed or scattered depend on the molecules that make up those those particles So if we focus down a little bit here and we look at just the fine mode so again, we're looking at p.m 2.5 and below I can kind of see that Pm 2.5 and below if we were to break it up in this if we were to break this pie into organic So these are particles that contain mainly molecules made up of carbon oxygen nitrogen hydrogen And inorganic particles which you can think of assaults We actually find that between 20 and 90 percent of the mass of these particles is organic in nature Which was a surprise about 15 20 years ago. It was never something that was considered And There's actually this large variability here of 20 to 90 percent for several reasons one Obviously, we're going to have regional differences depending on whether we're measuring above a forest canopy or we're measuring in downtown New York City We're going to have a different distribution of organic and inorganic But there's also uncertainties and our abilities to measure the mass of these particulate And even worse the models that we're using to try and predict what these concentrations are globally Really suffer some major Disadvantages that I'll discuss in a second If we kind of drill in a little bit now and look at just the organic fraction We see that That organic aerosol is actually consists of two classes if you will and these are Defined by how the how the particles are formed that is whether they are emitted directly into the atmosphere so called primary organic particles here and you can see that's a very small portion of it or Whether the particles themselves are formed chemically in the atmosphere and we refer to these as secondary organic particles Secondary because they are formed in the atmosphere as opposed to being directly emitted and if we look at this pie 70 to 90 percent of the mass of the organic fraction Which is 20 to 90 percent of the total fine particulate mass in the atmosphere is secondary in nature So see if you can guess where we focus our work We're really looking at secondary organic aerosols Try to understand their chemistry try to understand how they form how they age and react in the atmosphere And how they interact with how they interact differently with sunlight perhaps based on how they were formed So this To look at it from up on high really and making it as I don't say simple as straightforward as possible Really secondary organic aerosols. They have both Biogenics or natural sources and anthropogenic sources, but by and large the The biogenic sources dominate so all trees all leafy plants grasses they emit a class of compounds called terpenes and these terpenes are very reactive and Red have you got the show-and-tell time So I always tell my students the most dangerous thing we work with is water and any chemicals we use have to smell nice So she's actually passing around if you just waft out on there. There's nothing dangerous about them Honest You just waft them under your except you Jim just waft them under your nose And you can smell two of the compounds that we work with limonene which is emitted predominantly through citrus trees and Hexenol which is a compound that we discovered that is emitted when you mow lawns and both of these are very active and Contribute to atmospheric aerosol. So by and large we focus on the biogenic sources. So these trees They're always emitting these volatile organic compounds or VOCs So these are compounds that want to be in the gas phase They react with Atmospheric oxidants and there's a slew of them But really we focus on ozone for several practical reasons and because it is the primary Occident for this class of compounds So when these VOCs are oxidized you form products you're basically adding oxygen to the molecules And you form products that are lower volatility All right, so they don't want to be in the gas phase as much anymore And if they don't want to be in the gas phase they really have two options They can nucleate or condense Which I mentioned before leads to those very small particles below a hundred nanometers But these volatile semi volatile vapors can also partition Partition is just a fancy way of saying that they spend sort of like the snowbirds half their time in the gas phase And half their time in the particle phase and this partitioning is Very dependent is critically dependent on the phase of the particles on the viscosity of those particles And I'll talk a little bit more about that later But really what what's been guiding our research is this discrepancy here That is we have decent measurements or at least we think we have decent measurements of the mass of secondary organic aerosol in the atmosphere The modelers believe that they have a decent handle on predicting how much so a mass should be out there and Unfortunately the measured so a loading or secondary organic aerosol and by loading. I'm just thinking I'm just trying to Indicate the amount of aerosol mass that's in the atmosphere But the measured amounts are between 10 and 100 times greater than the modeled amounts so there's something missing somewhere and When we brainstorm and try to think about what those things might be Well clearly there's either something missing from the measured values or there's some bad assumptions on the models How can we go about trying to decrease that discrepancy? And really we had three goals to try to do this one We are firm believers that you can't simply look at the chemistry as a bulk property Which is what models do out of necessity Right the computing power simply isn't there to treat every single chemical reaction that's occurring in the atmosphere But people have taken liberties in in extrapolating From these bulk measurements to things like the amount of light that's scattered or the amount of light that's absorbed And we don't think you can do that We think you really need to have a molecular level understanding of what's happening and what's in those particles Obviously there may be some missing soil precursors that aren't being included in the models Okay, that's kind of low-hanging fruit there and finally because this partition is Either is the redistribution of these vapors onto the aerosol It's going to change the amount of aerosol mass that you can have so this partitioning is very important and that partitioning as I said We like to break it up into whether the particles are liquid or solid But really it's a spectrum and I'll talk about that at the very end So the challenge is that we really had the face where that we have very low mass That we're trying to analyze So remember this is the region that we're trying to measure in this is the accumulation mode And if you think that a one micrometer particle has about a picogram 10 to the minus 12 grams of total mass So if it was a pure compound, that's how much mass you'd have to analyze you'd have to measure All right, so that's one trillionth of a gram But if we think that on the other hand that these particles are composed of multiple chemicals It actually turns out that they have hundreds or thousands of different chemicals Now you're taking that one picogram and distributing it over a hundred different compounds or a thousand different compounds So you have even less mass of each compound that you're trying to measure The other thing is as I said these are chemically complex How do we get the chemical information if we want to do molecular level analysis? How do we get that information out and alpha pine in here is one of the predominant terpenes that's emitted So it's become the poster child And aerosol mass spectrometry was something that started to come out while I was working in Italy And that's what got me into the field But there's two ways we can do aerosol mass spectrometry so called hard and it really doesn't It's not important what exactly that means But what we're doing with hard is that we're breaking the molecules So this alpha pine in if we plot a an abundance of a certain molecule Versus the weight of that molecule if I have a pure particle I should see one thing which is the molecular weight of that molecule But when we use traditional or conventional aerosol mass spectrometry that is a very hard hard method of analysis This is what we see So for one compound that we should have seen one signal here We see all of these fragments of that molecule Now we'd have to try and figure out how to how to do this puzzle if you will that is we have all of these pieces How do we put them together? All right, so this is like a five thousand piece puzzle That you're trying to do without having the picture Maybe even after a couple of glasses of wine it becomes a little difficult What we pioneered is this method of Soft ionization that is our goal was to keep all the molecules intact when we did the chemical analysis So this believe it or not is the same particle as this that is alpha pine in that's been reacted with ozone and again the green here is where that compound would be and We see many products many chemical products again each one of these lines is the abundance of a molecule Of that weight which we can then relate to the to the chemical structure if you will So this soft ionization Really simplifies our problem, you know now we've gone to a maybe a 50-piece puzzle You know one of those floor puzzles for the kids and and you'd be doing it while you're drinking your first glass of wine A little more doable. You still don't have the picture. You still don't know what you're supposed to get in the end but the simplicity really helps and This is the only slide I have of our of our instrument even though I'm very proud of it and For lack of any sort of imagination on my part we call it a near infrared laser desorption ionization aerosol mass spectrometer another one of those I don't know how to do short words But this is a so it's a near IR LDI and again we developed it with the express golds of keeping them out keeping the molecules intact so we can do a chemical composition and trying to see those very very low minute amounts of mass that we're trying to measure and Just briefly so here we have our atmospheric aerosol We sample it through something that's called an aerodynamic lens that makes a beam of particles We collect those particles on an aluminum probe Excuse me, and then we fire a near infrared laser. These are very common. They're actually very inexpensive We vaporize and ionize those particle components and Then we do chemical analysis by traditional time of flight mass spectrometry This is actually what the beam what the particle beam looks like so this is the exit of the particle inlet Excuse me, so the particles are moving left to right and counter propagating to that We have a green laser so everywhere those two beams in our Cross you actually get scattered and you see the light so you're really looking at a photograph of those particles and Some pictures not pretty, but this is the one of the instruments that we built This is the green where you see the particle beam is going from left to right And they're not pretty pictures, but hopefully gives you an idea of the the challenge and then the work that went into Developing these and I'm putting putting these systems together mostly by my graduate students. I have to give credit there So we've worked with this for many years now We know it's capable of doing the chemical analysis at the levels we want and with with the Level of softness that we need to keep the molecules intact But that instrument is part of an entire research infrastructure that we were we've been able to put together through the generous contributions of the National Science Foundation and others Where we have the University of Vermont Environmental Chamber or UV mech It's an 8,000 liter chamber and around this chamber we have a whole suite of instruments that we've either developed or their commercial instruments and tried to color code them here for gas phase analysis the LP and the knee and then I'm sorry the LP and the SNPS here these measure physically the size distributions of these aerosols And so on and we can do optical Characterization of these particles as well, but again, I won't talk about that today So as I mentioned, this is what we're trying to decrease this discrepancy between the two and now we have an instrument that allows us to look at the molecular level chemistry going on and one of the first things we applied it to was hey Are there some other precursors out there some other volatile compounds that we've never thought about that could be making particles and The fact that all came about when I was mowing my lawn I mean, we all know that fresh lawn smell, right? You get it from one of those vials but so those are very aromatic compounds when you mow the lawn and All of the terpenes are also very aromatic. That is from a sensory Perspective, so I wondered if all the stuff that I was throwing into the air there all of those volatile compounds could form particulate and Of course after the fact we saw that in fact these compounds here are emitted in great quantities by any kind of leafy plants And their main role is as a response to stress and implant plant or plant Insect signaling so what I did was I took some clippings a few summers ago actually We and Rebecca was waiting with bated breath at the lab. We put the clippings inside the chamber We let them stew for a little bit and then Rebecca started measuring what was in the gas phase and What she found again now each one of these peaks is a different compound that's in the gas phase and She was able to identify these compounds through various methods that we use but of course the question is will they react with ozone to make aerosol and So the next thing to do is to burp in a little bit of ozone and in fact This is what's in the gas phase after we introduce the ozone so you can see some peaks have completely disappeared We completely consumed those those compounds from the gas phase and new ones have shown up meaning we've made different phase Gas phase products, but for us the exciting part was if we look at the amount of aerosol that was formed So here we're looking again at the size distribution of the aerosol that's formed so we have the number of particles on the y-axis and The diameter of those particles on the x-axis and it was lots and lots and lots of particles So we thought this is something that we really need to study and in fact Rebecca just completed her PhD thesis on this project a couple of a couple of weeks ago already and One of my other graduate students shosh will be completing also on this project So it turned out to be a good summer day of mowing the lawn If we take this aerosol now and we want to look at the chemical composition We see things like this So these are two of the compounds that we know is emitted by the leafy plants by the grass clippings We buy the standards we inject them independently inside our chamber and we put in ozone and we measure the chemistry of the particles Again, I want to stress that each one of these lines or peaks is indicative of the abundance of a given type of molecule so we can literally just Add that up and say okay. This has to be made up of carbon oxygen Hydrogen what could it be and looking at that relatively simple mass spectrum? We're able to come up with some chemical mechanisms that tell us the molecular pathway of getting from the gas phase to the particle phase for these compounds and I'll give you a second to study those but They that was a joke Just in case But really did this is important not because of the detail really but because that chemical detail allows us to Determine the type of reaction that's going on if you will so for this particular compound It's an oligomerization reaction meaning we're just adding molecule to a tail of a molecule to a tail of a molecule and so on We're essentially making little bouncy springs Whereas for this molecule just looking at the chemical composition of the particles you can see that they're completely different But here we saw that the the oligomerization was actually shut down So we would not expect these particles to be bouncy all right So Following along with that then we can do the chemical analysis. We can find missing precursors But now we have to figure out. How do we know that? I mean that chemical clue there told us that perhaps One of those SOA sources made one kind of particle bouncy and the other one made non bouncy and Those are the only terms I can use because any scientific terms I use are argued by every reviewer that we have So how do we go about determining how thick these particles are how viscous or how fluid they are All right, so just to give you a little primer on Viscosity right so this is the ability of molecules to flow past each other Here's a scale of some of viscosity based on some known substances going from water olive oil honey all the way up to a glass marble Now you can imagine if these were particles made up of these substances They would behave completely differently in the atmosphere right ozone would would permeate a droplet of water very quickly Throughout the entire droplet it would not do that to a glass marble. It would be limited to the surface Of course we're in Vermont, so I wanted to put the Vermont reference of viscosity there So they have pure Vermont maple syrup between olive oil and honey and as Dwight mentioned I was in Canada I didn't want to forget our friends to the north. So there's the Canadian pure maple syrup a Lot of people didn't get the joke so I was a little worried But anyway the point being that how do we gauge how viscous these particles are so that we know To tell the modelers here's how you should treat these in the models With with regards to partitioning because if you look at liquid particles If you look at liquid particles as I mentioned if a gas is going to react with it that gas is going to quickly diffuse into the Center there's really nothing holding it back and we get what we call bulk chemistry the entire Particle is acting as as one entity if on the other hand We're at the other end of the spectrum like the glass marble then we might have a scenario like this and again solid is in quotes because There's a specific definition for solid and we didn't make specific measurements of viscosity But here you you might expect that the ozone these are little ozone molecules that the ozone is going to be relegated to the surface And we get mainly surface mediated chemistry as opposed to bulk chemistry and here we have slower no diffusion So these are two completely different scenarios now the question is how do we figure out which scenario is at play for any given chemical system and What we did was actually take advantage of the limitation of a The conventional method of making aerosol measurements Which is to accelerate particles towards a filter for example or towards some flat surface and Hopefully they'll splat and they'll stick and then after a week of doing that you wash them off and you do your chemical analysis But one of the big problems that those types of instruments are called cascade impactors That that they have is particle bounce Sometimes when that particle is accelerated towards a plate doesn't go splat goes boing falls off bounces off and moves on and The scientific community tried Not spent a lot of effort trying to reduce that bounce and we actually tried to flip that on its head And I'll show you in a second how we did that so if we have liquid particles that are going into this cascade impactor So we actually have 15 of these impaction stages in turn and the particles are accelerated more and more as you go down So typically we collect large particles on the first so here we have particle diameter We collect large particles on the first stages and we collect small particles at subsequent stages So if we look at the number of particles here as a function of diameter for these liquids Which should splat on every stage We would get a distribution that perhaps looked like this with a hundred nanometers being the peak of that distribution If we did the exact same measurement with solid particles if they all went splat We would see the same kind of distribution So now here a di-octylsubricate is a reference for a liquid particle ammonium sulfate is a reference for a solid particle But that's not what we see So we set up the system so that it either shut down bounce completely or it favored bounce so if something was going to bounce we were going to see it and when we compare the Di-octylsubricate the liquid particles as they're measured with the system to favor bounce Not surprisingly we see the exact same distribution Because there's no way they're going to bounce they're liquid If we do that with ammonium sulfate on the other hand You see that all the particles that should have been counted at these earlier stages as bigger particles are now all being counted as smaller Particles meaning they bounced all the way down So we've tried to maximize this this loss due to bounce and use it as a surrogate for viscosity really is what we're doing and If I show you some real data that we that we took so for example here So from this data we can calculate a bounce factor right which again we relate to the viscosity of the particles So if we inject di-octylsubricate into our UV mech That's these pink pink symbols here the bounce factor is zero just as we expect. We know it's a liquid If on the other hand we inject ammonium sulfate, so these are the open squares We know it's a solid. We know we're gonna get significant bounce and I won't go into why it tails off But that's something that is very interesting to us What was really surprising to us is here. We have a reference for a solid particle This is aerosol that was formed with alpha pining again one of these terpenes After it reacted with ozone and it has a larger bounce factor than our solid reference Which was what makes us think of the super balls right these these polar mirror Polymeric chains That are causing those particles to be really susceptible to bounce So it's giving us some information about about the viscosity of the particles and just to show that we could actually Said these are the lives of these particles that I mean they're living they're changing as a function of time They're changing as a function of humidity and so on and time The green symbols here are oleic acid particles, which we generate So it's a primary organic particle organic aerosol, and we know it's a liquid It's made component in olive oil in a time 45 minutes here. We injected a little bit of ozone and All of a sudden these liquid particles are not entirely liquid anymore. They're actually showing a significant increase in the bounce fraction So this work all came about from some Observations we made with our instrument that we simply could not Interpret unless we assume the particles were solid or at least non-liquid It took us took us a while to convince the community that what that that was the in fact the case So now we have to really start thinking about the viscosity and how it's treated in models We have to start thinking about the specific molecular structure of a compound and how it's going to react To form what types of products will those products take on water? Will they absorb light? This is these are all unknowns again people ask me what it is. I have against modelers. I've got nothing against models They're doing the best they can with the tools they have But unfortunately, we're never going to be able to make accurate predictions unless we start to take some of these factors into account in those models so I started it with how our thinking has changed based on some of the stuff that we've done and Suppose I'll just point out that We found very easily one missing source of so in the atmosphere. There's lots more out there. I Don't know whether anyone will ever make it an inventory of these of these but who knows but for us We like exploratory research. This was something new had never been done So we did it. So these emissions from the green leafy plants are actually called green leaf volatiles It's another class of volatile organic compounds. And that's just one example Importantly so a particles which Conventionally were always thought of to be liquid at atmosphere conditions are not and that's going to change our thinking of The impact during their lifecycle in terms of what they're going to do in the atmosphere and that phase is actually a complex function Of the atmosphere conditions the temperature chemistry time Whether it's a Monday or Tuesday. It's all there It's something that I haven't I had the chance to touch on really but it's that the optical and physical properties of the SOA All right, so I didn't really talk about optical But again, we cannot predict them with conventional methods of analysis Which do not look at the molecular level detail of the chemical composition So we're really These molecular. Yeah, these molecular level analyses are going to require new innovative Instrumentation we still our goal was to do this on a single particle basis. We have not achieved that goal I hope someday we do or someone else does Because that's critical But this molecular level understanding is required in order to adequately adequately model these systems And as I say this is going to require some really innovative technology to achieve Likely not during my professional career, but we'll give it a shot and This is one of my favorite quotes from John Aitken. In fact, they named that smallest mode that I didn't show you after him Where it says we have in this fine dust a most beautiful illustration of how the little things in the world can work great Effects simply by the virtue of their numbers and the key word here is numbers Because this accumulation mode has lots and lots and lots of particles very little mass Therefore it's not regulated. It's difficult to study So of course I have to thank my group. This was a sunny day in Vermont Now these folks are all gone. That's my son who's going to come to UVM next year and These are the rest of the group members So shosh as I mentioned did a lot of the work on the GLVs Rebecca also who just finished she's off to Purdue to pursue a postdoc flying in airplanes making measurements and So on so she's really excited about that And of course I have to thank the funding agencies We do get some funding from NASA But the bulk of our funding is in fact from the National Science Foundation and EPSCOR has helped out tremendously So with that I'm happy to take any questions