08:03:18 Welcome everybody to the first official discussion of the film's 21 program, so this week. Our topic will be on non equilibrium equilibrium and only equilibrium fluctuations of fluids membranes and solid shells. 08:03:33 So I hope you already watch the pre recorded talks by Petaluma Oscar for focused on the fluctuations on food membranes, and by David Nelson focused on fluctuations of solid membranes, and both were discussing the equilibrium aspects, and you know on Thursday, 08:03:50 we're going to discuss also the non equilibrium aspects, and the discussion chair for today's session is Alex Levine, will moderate the whole discussion. 08:04:01 But first, just a few before I give the floor to Alex just a few logistical notes. 08:04:08 So you know like whenever you're not speaking, please mute yourself so that we don't have any background noise, and then to coordinate the discussion. 08:04:17 So you know if you would like to speak, you know like, please raise your hands on zoom. So typically you know like you will find like the depending on which version you have the newer versions, the race can option is fine, among reactions so if you go 08:04:31 towards the bottom of your zoom, you can click on reactions, and then you have like an option to raise hand right and then if you raise hand and we'll see see these on the list of participants that your hand is up, so you know, please don't raise your 08:04:44 physical hand on there too many windows so we cannot really monitor that. Right. And then, in addition to, you know, raising hands in the past we've seen the results of has been like a lot of very nice activities in the zoom chat so you know you're welcome 08:05:00 to also you know post questions directly in the zoom chat and we'll try to monitor that and maybe will, you know, bring this up to the whole community. 08:05:15 And then, just for sure so we realized that, you know, all these, you know, interesting comments and references that appear in the chat should not go to waste. 08:05:18 So at the end of the session will save them, and we'll post them on slack and also on the Google Drive, so that you know like you will have access to the relevant comments and differences. 08:05:30 And then, when and when you get. 08:05:33 So we you know like when we asked you to speak, you know like, when, then please unmute yourself and you know just raise your questions, comments, and then if you wish, like you know like if it helps to you know make the point more clearly you're also 08:05:49 welcome to share your screen and you know like show the relevant, you know, images, movies, and so on. 08:05:56 And then afterwards as we said the discussions will be also post a video recordings of these discussions wants to be posted on the Kp website. And as I mentioned yesterday, you know, please keep in mind that we should all respect the KGB Code of Conduct 08:06:11 so you know we're Welcome to you know get into, you know scientific disagreements and heated discussions, but you know, please, you know, make sure that we treat everybody with respect, and so on. 08:06:23 So with this I'll give the floor. Back to Alex. 08:06:27 Oh, thank you, Andre, first of all, good morning to everyone at least Good morning, Allah, California time. 08:06:47 There's been a great deal of activity on slack with a number of questions, and I thought to get the ball rolling. 08:06:57 I would start by bringing up at least a few of those questions. If you feel that your question on slack wasn't brought up appropriately, please feel free to jump in, I'm going to try to summarize longer questions as a shorter piece, but if I summarize 08:07:15 them in appropriately please feel free to correct me as we go. 08:07:20 And as another point of organization I understand that we have, trying to have a free willing discussion that encompasses two different talks is are both Patty and David here by the way. 08:07:35 Yes, yes. Great. So what I was hoping to do was to switch back and forth between questions directed at David and questions directed at petty edit try to sort of make this a more organic whole, and hopefully we can draw connections between the talks as 08:07:54 we go. So I think you've heard plenty for me, one of the first questions came from Marcus the SIR know who not only asks a question but tells us that he feels squeamish about the series expansion that David did on slide for the key point if you remember 08:08:13 is that he's doing a conservative expansion, and the correction term is proportional to the fog of uncommon number squared. And we've already heard that that's a big number and big squared is worse. 08:08:26 So, Marcus is asking should I be concerned about that and will higher order terms in this picture but if series, be even more. 08:08:45 You should be able to. Ok. 08:08:48 I will try it. 08:08:52 So, this is the slide or the squeamish inducing slide, don't Are you seeing it, Alex No. Yes sir, you know, then works. So that's it that's a very good point that that's exactly what I was trying to convey here in fact, There are a number of examples 08:09:13 in different areas of physics, where we have diverging perturbations series. This is one of the most dramatic that I know. 08:09:25 Indeed, this little fireman graph here is getting very big with the top of uncommon number as was pointed out, This one's even bigger. 08:09:36 And there are more divergences further out in the series, and a very powerful method that sometimes solves this problem which was eventually used here is the normalization group. 08:09:51 And what you do is you take these integrals over wave vector and you break them into momentum shells and the contribution from each shell is finite and easy to handle. 08:10:03 In perturbation theory and then you iterate. This process. And that has turned out to be a very useful technique here. And that ultimately led to the 08:10:20 next slide, which I'm not sure it'll come up but in any event. It's the result of this free normalization group calculation that produces the scale dependent elastic constants, it's it You shouldn't be surprised. 08:10:37 It is very unusual. And it's a, I believe a key to understanding these elastic. 08:10:45 That's I hopefully hopefully that's helpful. 08:10:48 Even while we're on this slide and on the subject, or the slide there What are a couple of questions in the slack that I think were resolved that maybe you'd like to weigh in. 08:11:01 Okay. String tensor has a nonlinear term, which would be you you are you order u squared not order f squared, and comments we're just we're pointing out that this is irrelevant in the RG sense, and that was where the slack left it. 08:11:17 Do you want to comment anymore on that or is that a satisfactory answer. 08:11:23 I think it's a good answer. I think it's the one Andre gave, I've tried to start started to answer the many interesting slack questions so people won't want to look there for more detail. 08:11:34 I think that's a good answer and a fancy way to say it in the context of this view normalization perspective is that it's an irrelevant variable as you are screen as you sent out the degrees of freedom of those in you are less than less important. 08:11:54 But that's not true, of those flexible photons which have many interesting manifestations I hope I explained, one or two of them but they also by the way have important inputs for the electron degrees of freedom in graphene, which have important quantum 08:12:19 mechanical aspects, which coupled to these flexible phones so they do play an important role in a very broad variety of problems where this and share my thoughts. 08:12:30 Well thank you for elaborating for us. 08:12:33 Let's turn that over to a question for Petya. 08:12:40 And it seems. Let's see what one of the, one of the earlier questions was from printer Sharma, if I butchered your first name in particular, I apologize. 08:12:56 But the question, well, which I hopefully I will not put your is essentially the question of if a fluctuation analysis on these giant uni similar vessels, typically uses surface tension as a fit parameter, how can I understand that when I should believe 08:13:22 from basic thermodynamics that the that the Gulf should be surface tension free. So pettier, are you. 08:13:32 discusses this issue about you know like he's the tension is zero or infinity. And I think it all boils down to the fact that physical sort of closed by layers, and it is the excess area that is prescribed and the tension adjust to to enforce this area 08:13:41 It's a good question and I think probably the physicist in the community and the group can answer it much better. I will just take a shot of it because physicals, I mean there's this great paper from Seifert on the concept of effective tension, and he 08:13:54 constraint. 08:13:57 And this is all I could tell and I would, I would ask actually the, you know, the people like Tom powers or, you know, who Akrotiri oh you could actually theorist and have worked a lot more on lippy buyers way, if my, my interpretation is misleading. 08:14:12 Thank you. let's see. So does that satisfactorily answer the question to Sharma is ok I guess well, please raise your hand. I should have the participant list open my, my mistake here. 08:14:29 I go satisfactory. Thank you. Thank you. I'm sorry to keep trying to navigate a million boxes here so I'm a little. 08:14:36 I'm working on it. 08:14:37 Alright so along similar lines patio, there was a question, or at least related lines by Eric do frame, who asked, why is membrane viscosity more important at long wavelengths or small mode number. 08:14:54 I guess the the nature of the question is can you give us a physical interpretation as to why I should expect that trend. 08:15:02 My intuitive understanding, and I guess explanation attempt of explanation will be the wavelength has to see the curvature. So, the longer the wavelength, the more you know comparable to the radius of the medical, the more you know then it will be, you 08:15:16 know, aware of the curvature and the effect is important. The. If you have shorter wavelength, then then they don't see the curvature they behave like as if the membrane is vocally planar. 08:15:27 That's why the long way blanks they correspond to lower wave, wave modes and that's why the lowest mo wave Mozart, the most affected. 08:15:36 Thank you, Eric had a second part to his question which was lambda m vanishes for flat surfaces just as a reminder lambda m is a ratio of what I call the saffman del broke length, the membrane viscosity over the surrounding fluid viscosity, divided by 08:15:58 the radius of curvature of the of this circular of. gov. 08:16:04 He asks if lambda, clearly vanishes for flat surfaces are goes to infinity. Does that mean that the membrane viscosity will never matter for a flat membrane. 08:16:15 My Becky said, you know what we've been doing what we what was presented is the linear analysis so it's the linear dynamics, the moment you go to non linear dynamics and you start accounting for quadratic corrections to the evolution equations. 08:16:30 I mean, then the curvature will, I mean, the interface will start curving and the effects of the membrane because they will enter. I haven't done this quadratic theory. 08:16:40 So, this is just the guest. 08:16:54 As long as you have another link scale and the problem then the South Middelburg length can make its appearance again so if you don't have a radius of curvature. You could also instead talk about the mobility of a finite size the object in the membrane, 08:16:59 It just to put my own two cents in. 08:16:59 which of course saffman new generated in effect related to the saffman don't break links. And I guess Mr Gilbert can do it as well. 08:17:08 So those are all I think valid points. Let me switch back to a question, well, keeping the theme. Eric do frame has a question for David, he asks, Can you comment further on the collapse of a GOV using your the essentially fluctuation and Deuce collapse 08:17:33 theory that you've presented. Can you say anything about the experimental implications of that so I guess maybe the. I'm paraphrasing but maybe the right way to say it is what should the experimental is be looking for. 08:17:48 You're muted. 08:17:53 You did is the most common phrase in the last year. 08:17:58 Unfortunately, I'd like to share the screen Let me try that question. 08:18:04 And let me see if I can get out of this. 08:18:09 My seems to be freezing up a bit. 08:18:14 But I can say, Well, hopefully, you know the phrases itself, is that 08:18:22 there, you can make a variety of systems with across polymerization or longer and longer lifted by layer tails. 08:18:36 And by various devices get closer and closer to a freezing transition to the freezing transition that transition could be first daughter, and then you'll have something to share modulus and some of the things that are of event that I talked about in the, 08:18:56 in my presentation will come into play. 08:19:01 Andre and I did an estimate of the follow von Karman number for some of these preliminary isms that Dave laces group. 08:19:11 In fact, studies. And I think that five of uncommon number comes out to be something like 10 to the eighth or attempt to the ninth. 08:19:25 And I think Eric put in numbers in the slack. I think that there are approximately right so when you get out, you have cross glamorization or just ordinary to the melting. 08:19:36 You'll have to deal with the non linearity with a vengeance. There's no sense in which you can really ignore them on scales longer than this thermal length, and I forget what era got maybe it was some fraction of a micron something like that. 08:19:58 In any event, giant, you know, Union remember vessels, really should display some of these phenomena such as collapse. 08:20:07 If you can control the sheer modulus by the degree of cross polymerization or the to the sheer viscosity, then that, that's a parameter that you could look at to try to control the collapse. 08:20:20 you could look and see if it's reversible. 08:20:23 These things turn into raisins, as I as I showed, and that's been seen in more recent experiments and the weights lab by Anderson Sean. 08:20:35 And I think there's a fascinating. 08:20:38 physics there, possibly influenced by disorder. 08:20:45 The last thing I'll say is that you know that line we're watching films, which are half a little bit by layer, so to speak, can undergo a second order defect mediated freezing transition. 08:21:00 And if that happens, the viscosity. 08:21:05 actually divergence continuously to infinity. 08:21:09 And so, under those circumstances, you could have actually a very nice control parameter, perhaps to look at some of these effects fact let's see if I'll just close by attempting another screen share if this fails. 08:21:33 Just shut up. 08:21:43 Let me go here and try this and Alex Are you seeing a picture of glimmers of it working. Yeah, good. So this, this is a kind of polymers zone factory. 08:21:53 And this this little film razon factory produces lots and lots of these things, and they come out they wrinkle up like raisins, but as far as I know, no one's really studied and carefully creation of a reason at the North Pole. 08:22:10 In this. I think it's a diabolical polymer double layer. 08:22:17 It suggests the transition is first order. 08:22:20 However, if there were a continuous transition and so the right lifted by layer, there might well be one a couple installers transition, the viscosity supposed to do this the TV viscosity that patches so beautifully explained to us, so you can get in 08:22:33 a regime like this, whether it's planar as Alex said, or spherical. There's going to be interesting consequences and perhaps an interesting control parameter, and I will stop there. 08:22:46 Thank you, David. Now we have some hands up by the way I didn't mean for all questions to be coming through slack. So, let's open the floor I the first hand I saw was Mark Bowe UK. 08:22:58 So please go ahead mark. 08:23:01 I just wanted to come back to the earlier question that picked up on said about the surface tension. So it depends completely on the thermodynamic ensemble you're in. 08:23:17 If you're a couple to a reservoir so that things can come in and out in the functional derivative with respect to the area must vanish and that's the surface tension as you get into micro motion and so on. 08:23:25 Then the functional derivative with respect to the area must vanish and that's the surface tension as you get into micro motion and so on. If it's not, then you have an effective surface tension which you can try to tune, that's a that's just to comment. 08:23:34 That's an excellent point and certainly true. 08:23:37 Let's see also Andre and since he's the organizer of this thing his hand will always be counted immediately. 08:23:48 And I think I just wanted to follow up on as we were discussing potential experimental realizations of these like collapsing shells. So just want to mention that last year we did a study with Robin boon smart, in the context of viral cap sits. 08:24:03 And, interestingly, what we find that some of the large party or bacterial pages are in regimes where they were expected to be unstable. And then like, in order to cope with that they are self assemble these capsules are self assembled on scaffolds which 08:24:18 tried to you know suppress this collapse. And then after the capsules are fully assembled then they also go mature undergo maturation process, which makes them that much deeper and then will suppress this collapse I just thought like that I would mention 08:24:31 this since we're already discussing this topic. 08:24:35 Thank you. Thank you, Andre mean that I saw that paper especially because it comes from the guy down the hall from me as well. 08:24:42 But is it possible that these things that we could like make a list of, when we discussed when we mentioned papers, is there a way to sort of post the reference somewhere so people want to find it, they can. 08:24:56 Yeah, I will put the reference to this paper in the chat, and then then you know we'll see the chat down the slack. So, that's perfect. Thank you. the next hand I see up is from Daniel mottos. 08:25:11 Daniel Are you there. Yes, my yeah I'm here. Just my son just froze. There's a question for for David, Thank you for your dog. And I have a question about how much you can model with elastic theory in the graphing. 08:25:30 If you have such as such a thing graphene later, without introducing quantum collections for example. 08:25:38 I mean, maybe it's just really a question, but I don't know how much we can actually model in the graph and using elastic feeling. 08:25:47 Okay, I don't I don't think it's a silly question at all. There are no silly questions in my experience, maybe some silly answers. But, yes, there are regimes, where we need quantum mechanics to understand graphene. 08:26:03 And they needed to understand the graphene electrons and look at the analog of a fairly surface. It's a fairy energy is very large compared to say room temperature and so they're quantum mechanics, certainly play an important role. 08:26:22 As far as the photons of graphene I'm talking about freestanding graphene not not glued to a substrate. 08:26:32 There is a straightforward criteria that you can investigate to see when we have to quantifies the phone on energies, both in plane or out of plane, flexible photons. 08:26:47 And at the room temperature at which the McEwen experiments on graphene ribbons we're done. 08:26:54 You don't need to worry about it. 08:26:57 You can treat the phone on both lecture on in plain classically. 08:27:01 But if you were to go to zero temperature and you can do this in a vacuum perhaps with freestanding graphene ribbons, then you would have to do, you know, careful. 08:27:22 One calculation that I don't think has been done is just to take a hemisphere of graphene or something like it and see whether the zero point energy of photons structural photons it's enough to collapse it at zero temperature. 08:27:38 I don't know the answer to that question. 08:27:42 Thank you, David. Let's see, he. I'm glad we have a number of hands up and I hope we get to the mall. The first one I saw was from a mere who Sean bahrami. 08:27:56 Please, go right ahead. 08:27:58 Thanks. 08:27:59 My question goes to a TL. So thanks for the talk. 08:28:04 In one of your conclusive slides before and you ask a question that either. This, this cause of the effect could be integrated into the bending rigidity, because it's somehow controlling the the fluctuation of spectrum. 08:28:24 But my question is that, if it does, wouldn't many other things. Do the same like if you assume this active ion channels or pumps that Patricia was talking about, and everything else like psycho skeleton filaments somehow sort of control or change fluctuation 08:28:48 spectrum of the membrane. And I think, wouldn't it pose a question that we are somehow we cannot incorporate something intrinsically not equilibrium, like viscosity to something equilibrium like. 08:29:06 And if I may, can I ask the second question or. 08:29:11 So, so the second one is that. 08:29:17 I mean, if so viscosity is to my understanding, a non equilibrium fluid like property in the membrane with he can also have can, this is the question indeed can be also have like sheer electricity in the membrane. 08:29:35 Similar like to a solid shell and viscosity in the limit. 08:29:41 If you increase it at the other end of the spectrum, somehow, show similar behavior like you approach a sort of paper sheet for instance. Thank you. 08:29:55 Thanks for great questions. 08:29:59 I'll start from the second one with the effect of the share in the city. There was also question on slack about it. 08:30:06 So it's all about models and okay you know like what do we include in the model and of course the model can be expanded to include, you know, share, you know, share, solid the last expresses. 08:30:21 The question is for lifted by layers. 08:30:24 Do they ever behave as solid the last six and this is also another question that I posed you know when do you know do we think of lifted by layers is a non Newtonian, and then what time scale. 08:30:34 So is there a frequency beyond which we have to consider the, you know, this elastic, you know, solid elastic responsive the by layer. 08:30:45 My motivation of the project was the, you know, physical seeing the fluid state and that's why that's the only thing that we incorporated in the model, but the sheer necessity can be included. 08:30:59 And that's in the works. And the question is can we see these behaviors and experiments. and if we see. Then we are going to incorporate. 08:31:07 There was, let me see remember all the questions so you asked about incorporating active activity in the membrane. 08:31:15 I will leave the people who actually do modeling of active membranes to respond to this question so I have only discussed passive membranes. And then the final thing was the question about the normalizing the bending rigidity. 08:31:31 Correct me if I understood because a long question so what is the effect of memory viscosity on the flex the bending rigidity. 08:31:38 Correct. 08:31:41 Yeah. Yeah. So, 08:31:45 yeah, I mean, if this viscosity effect to be somehow incorporated into an extension to the bending rigidity, as it comes from the fluctuation of spectrum. 08:31:59 Then, my might do anything else, like the active act of the old ion channels, and I'm very this, I mean, you might say that this is a slight deviation. 08:32:13 Then where is the limit that we can say we depart from this reflecting everything in bending rigidity, rather than continue. 08:32:23 Yeah. So Ben you can do 30 minutes of elastic property and member of his cost is a distributive property so the memory of his calls the only affects time correlations and Time, time responses. 08:32:35 So, my point in the slide was that if you measure bending rigidity from time correlations, then you have to account for the fact of the matter and discuss the however if you're measuring the bending digitally from, you know, means square displacements, 08:32:49 then you're, you know, then the membrane because he does not enter the picture. 08:32:55 I hope this answers the question. 08:32:58 Yes, thanks, um, the next hand up, is, as far as I can tell is Buddha Priya Chakrabarti Hey Bhutto long time baseless. Yeah. 08:33:10 So I have a question for in stillness see whether you can see no, not very. 08:33:21 Not that it's a very pleasant side but anyway. Okay, so I had a question for for David which is, I really liked the, The dramatic shell collapse. 08:33:31 The question is, when we are looking at this shell collapse, there is inside a fluid, and as far as I could see in the analysis the income possibility of the fluid was not taken into account, does that play a role in the nonlinear defamation of this Shin, 08:33:48 presumably the volume conservation constraints that you need to put in, or something. Yeah, thanks little, nice, nice to see you and I. Nice to see you today. 08:34:04 I hope you're well and I hope you're vaccinated and it's a tough year for all of us. 08:34:05 It's a great question. The collapses that I've thought about with my collaborators will often be glimmer isms for example, where there's water on the inside and water on the outside, and our assumption is that water can diffuse through lifted by layer 08:34:23 on the time scale of the collapse. 08:34:27 So, the, we don't indeed if that were the case, that they couldn't get through. 08:34:35 Then we'll have an incompatibility constraint. 08:34:39 But we're assuming that the water can slide through the the two leaves. And then, I think we're okay. Although I do have a small comment about whether these giant you melt in a matter of articles or tense, or not, or tense or not, depending on their construction. 08:34:59 If there's no liquid reservoir around, and they encapsulate larger stuff like straight proteins, for example, then they'll be an asthmatic pressure. If the Protein Concentration inside is different than the Protein Concentration outside, and there. 08:35:18 Something analogous to what you're asking about could play a role they will become tense. If the proteins can easily get from the inside to the outside. 08:35:28 Thank you very much. Thank you. Thank you. Thank you. We have another question from Alex clots, one of my colleagues from down the road. 08:35:36 I. 08:35:40 There's a for David and people feel created with David. 08:35:43 So the way I think about these sort of flat versus crumbled membrane phases is you look at how the various like let's say principal eigenvectors of scale with the molecular weight or whatever. 08:35:58 Yeah, I'm a physicist. 08:36:00 So my question is, when the thing is globally curved like what do you look for if the, there's no smallest eigenvector or there's nothing out of plane that is different from in plane to look for these phases and experimenters simulation. 08:36:16 Yeah, that's an interesting question. What is the generalization of the moment of inertia tensor, I missed your call earlier. 08:36:30 What's up. 08:36:32 Okay, so So I think if you go locally. 08:36:37 You can certainly mimic, how we would handle sheets. 08:36:44 That's the you know as you know probably the same way that we would treat a linear polymer chain with various eigenvalues and so forth. 08:36:54 For a spherical and cylindrical objects. I think you can get make some progress and almost replace those eigenvalues, by looking at the fractal dimension of the object, as it gets bigger, how does it scale with radius of the cylinder and the length of 08:37:14 the cylinder, for example, and even if there are thermal wrinkles superimposed. 08:37:23 You can ask whether that scaling is going to be linear or quadratic in the radio, radio sphere or the diameter of a cylinder. 08:37:36 And then, if it's locally flat. In that sense, you can then be the normal fluctuations. So that's the only way I know how to attack that problem. 08:37:48 Even though there is a very straightforward way to do it with moment of attention inertia answers for approximately flat sheet so thank you for that question. 08:38:00 Thank you. And our next question is from trip Bhatia out there you are. 08:38:14 I'm having trouble hearing me. 08:38:19 Okay, maybe I can just type it. 08:38:23 Oh no, now you're coming through to me anyway. 08:38:26 Please go ahead. We'll try and if not we'll type, we'll see how it goes. 08:38:35 PAGE 11 so this is about the talk by 08:38:39 about measuring. 08:38:42 It's about this capacity by measuring using the production information method. 08:38:47 So my question is that, in the slide, 11, the term which contains the tension and slide. 08:38:57 Number six, which contains the tension, are the same, or are the different and how they are different and what are the values like i is the same tension I, because when we apply the electric. 08:39:11 It's not the same, then we don't have the. 08:39:16 I think the short answer is, these are different potentials, so the. 08:39:23 If I understood correctly the question character was referring to the, the relaxation frequencies in all these are their workstation frequencies or somebody that even fluctuations and in that case the tension is the equilibrium tension. 08:39:36 And in the electric deformation mattered, the tension is dependent upon you know it depends on the deformation so as the fluctuations being aren't detention Also Rises So one has to include this through there for example the healthy nation. 08:39:54 Does this answer the question. 08:39:56 Yes. 08:39:59 Let's see if 08:40:05 the order of magnitude, like about the tensions. 08:40:09 Uh, well maybe we can talk later so you know the tension comes from, you know, it's a fitting parameter and it also can be measured potentially independently from, pretty simple fluctuation analysis, we are fixing the whole curve that information and 08:40:25 relaxation and we have the because it is independently determined from the initial slop, and then you use the maximum deformation to figure out the tension and then you can use the whole curve to figure out both the tension and the bending rigid. 08:40:42 But that's becoming too technical, let's talk about it after the meeting after the discussion. Okay. It would be great if you guys could have a discussion. 08:40:52 Um, let's see, I let's have another question from a hand. After that I would like to use my oh so temporary and minimal authority to fold in a slack question that I like. 08:41:05 But first, we have Rana Ashkar. 08:41:11 Um, hi, um, my question is directed to that to first thank you so much for this wonderful talk, there was obviously a lot of food for thought. 08:41:23 I'm, I'm very curious about applying your new model to interpret our data but I believe. Much of this was kind of stimulated by some of the recent results that we've gotten on your PC cholesterol membranes where we saw a change in the pending rigidity 08:41:38 using Spinnaker and and the more that wasn't absurd before. 08:41:43 So I have a couple of questions, and I'm happy to ask one or two now and then discuss later or ask my questions in a different status, but I do want to give other people the opportunity to also contribute and ask but I think the most like the two most 08:41:58 pressing questions that I have the following. 08:42:02 So you kind of give this really beautiful 08:42:07 kind of connection between curvature, and bending rigidity and the importance of this call city. 08:42:14 Taking it, taking it into account when you have curvature. 08:42:17 I'm wondering whether you've also looked into how this can come into play when you're also working with animated extremity experiments. And those are experiments that are done on slack membranes, these are just stuck. 08:42:32 My second question is, um, so you know that it's been Echo, we can do experiments with different contrast by simply changing the isotope labeling of our limits. 08:42:46 And right now the way that we think about it is that if we're using for created live events we're mostly sensitive to bending or rigidity or bending fluctuations and producing kind of feel deflated little bits were more sensitive to thickness fluctuations 08:43:01 which are a closer connection to viscosity. 08:43:17 So my question is related to some recent observations that we have where we were looking into membranes, which also had proteins or peptides in them. And we saw very little difference when we did the measurements on the difference so when we're looking 08:43:23 looking maybe offending fluctuations, but dramatic differences when you look into thickness fluctuations so if the differences that we're seeing at the related the viscosity are also kind of incorporated in the bending fluctuations that we're imagining 08:43:38 with spin echo. I'm finding a hard time kind of become silent, these two different observations. And I'm wondering if you have any insights into that. 08:43:53 So I'm by no means expert in uterus been echo and I don't know anything about anymore so I will, you know plead the fifth and maybe we can discuss later. 08:44:04 a paper in 2011 on deciphered langur in the effect and modification on the zoom and Quranic theory, and then we did it but then it went you know it was hibernating until your data came out and then you know we've been actually working simultaneously on 08:44:26 looking at Jesus, and their time correlations and trying to understand their relaxation dynamics and the membrane viscosity I would say that the effect is important to life wisdoms, I don't see the effect is important when you work with stacks and. 08:44:43 And as I said, I don't know much about Nami so I cannot tell the disease a completely different interpretation. 08:44:52 And what was the other question about the protein, the you know the labeling. 08:44:58 And when we do measurements with peptides and membranes, we don't see much of a difference when we're measuring whatever is called the bending fluctuation signal but we see a dramatic difference when we're measuring thickness fluctuations which are more 08:45:11 than more data to discuss this is this is the way that we kind of can understand the model. Um, so, if you think about depends on the how many petabytes you have. 08:45:22 So from my perspective as a mechanics person, I would think of this is a, you know, like a suspension so you have these particles that are dispersed in the fluid and anytime you have the systems the viscosity should kind of effectively go up, but again, 08:45:37 you know my perspective is continuum, you're looking at very, you know scales that are, you know, can we think about the membrane is a continuum anymore So, and by their sickness fluctuations are tricky. 08:45:49 You have shared is causing relational viscosity so there's too many things blaming, but great questions, so I'm, you know, we're learning along the way. 08:45:59 Yeah, I think we should follow up on the discussion later it will be really nice to kind of combined few days with different experiments and most to kind of associate these different parameters and kind of measure them more reliably. 08:46:11 Thank you. Thanks. Thank you, um, as promised, I wanted to fold in one more slack question at least at least one more at this point. 08:46:21 JOHN Nagle asks David Nelson, about the, well, I'll quote here supposing that phone ons in your model, take you away from 2d ice, presumably, the icing criticality john Would you like to ask, just ask the question yourself I think I saw you in one of 08:46:41 the many little lock boxes at one point. 08:46:44 Yes. Okay. 08:46:46 Sorry I don't need to repeat what you said then this goes way back there to critical phenomena and I was fascinated by David's comment that the there's a new universality class and I was just proven him to see how that would work so I mean, would it be 08:47:01 a continued with the critical indices change. 08:47:06 Gradually as you increase the coupling parameter, or AND and OR would there be a. So the question is how do you get back to, to the pure Isaac model with this coupling parameter goes to zero. 08:47:22 Okay. And then the question is, would there be a, a critical region where the new indices would show up but would that region shrink. as you reduce the, the coupling parameter. 08:47:38 So I think David answered those questions on the, on the chat but go ahead David you can say it again. 08:47:47 I'll say it briefly but thanks nice to see john. 08:47:51 So yeah, he's what john is one of the few people that probably remember those ancient days of critical phenomena. 08:48:03 I don't know are you seeing slides, Alex, I am. Yeah, okay. So, the question is summarized year, maybe. 08:48:18 And so, lots and lots of complicated equations here. But the question the crucial question is, is this coupling g important or not. 08:48:26 And we can get back to those two things. 08:48:43 We can show I think rather convincingly in two dimensions from known results about flexible photons. 08:48:47 When she goes to zero, or W, if you like W is the same as portion, G, and, but if we put in a little bit of W john. 08:48:58 2d on sagor easy models that this coupling constant will get bigger and bigger. It's the coupling constant that causes this anomalous thermal expansion. 08:49:04 And so I would expect a crossover to a new if there is a new, new universality class as this argument suggests, I would suggest the crossover to these new exponents, which have the same value of gamma over new as onsite profound, but we think a different 08:49:26 value, perhaps of alpha renew. 08:49:31 Oh, thank you. I thought that was. 08:49:37 I was just gonna say thanks I know part of this was in the slack I thought it was interesting and worth, maybe bringing up in front of live audiences, as it work back to some of the live questions from the live group here. 08:49:52 Luis Binya has a question and thank you for your patience. 08:49:59 Thank you. So these are question for David and actually I brought it up in the slack so it's going to be more or less the same. 08:50:08 There it is. So, when you have like crumpling paper. Of course the 08:50:17 elastic. 08:50:19 elastic model and so on change. In the case of graphene. We know that there are a lot of reports on the surface of freestanding graphene. So, I would like to know whether they can be taken into account in the any calculation, for instance, one of the 08:50:39 things that you presented, you have these impurities that are placed regularly us on call them impurities and but still keep it there, you may have some kind of the state, that this really want to graphene. 08:51:09 Yeah, thanks for the question and Andre may want to chime in and I'm pleased to say that I'm going to practicing his last name, it's cash Merrill, and I'll get it eventually. 08:51:11 Andre. 08:51:13 So, yes. So if there are frozen ripples, for whatever reason, some sort of charge density wave induced out of plane defamation. They could be by similar techniques to what we developed for these regular arrays of impurities, as you call, call them as 08:51:37 far as I know. No one's done that. 08:51:41 Andre Do you have any comments. 08:51:46 Yeah, like I mean, so you know like piano the sun and the earth because you can publish some papers where they were looking at this, both thermal fluctuations plus impurities with David, we also have one period paper back in 2014, when you had like static 08:51:59 ripples like without quench the effects of just static peoples plus them of fluctuations. And basically the finding that we found is that whether the weather the, you know, randomization of elastic coins is dominated, either by static reports or thermal 08:52:15 fluctuations comes down to a very simple quantity, where I basically like if you measure the emphasis of height fluctuations, use the term of fluctuations and if you compare this to the amplitude of static reports, so you know like if the capital five 08:52:32 locations with the thermal footage is larger than the thermal effect dominates, but the the impact of static report is larger than they dominate the mechanical response. 08:52:39 So that's like a very simple answer but you know like definitely one can do this like more rigorously similar to put in chat. The link to our paper with David from 2014 and I was gonna put like more recent like a very long review paper about getting to 08:52:58 the southern Europe Sikorsky where they have also come at least in the context of different. 08:53:04 It's just to comment on that briefly, a student of mine john Kearns and I just published a paper looking at the localization of flexible photons from geometric look from key metric quench disorder. 08:53:21 So essentially, if you take a tin foil sheet and you pound it down onto a relief map of the Rocky Mountains, you can ask then what happens to the vibrational modes of such a sheet and in fact you can show that they are localized in two dimensions is the 08:53:37 is the lower critical dimensions, so in fact you get logarithms and things but that is NPR. Now, very interesting. Can you post that in the slack. 08:53:49 So yeah soon as I figure out how to do those things I will definitely do that. 08:53:54 We have more questions here. Oh, in fact, Andre has a question. Your hand is up anyway Andre so. 08:54:02 Thanks Alex yeah that was actually a question that I wanted to pose both to Petra and David, and it actually goes I also brought up in slack by Carlos, so you know like some of these materials that you know that we can study are also the Scholastic there, 08:54:17 you know neither fine solid but they can be something in between. So has anybody tried to attempt to, you know, investigate these fluctuation spectrum of me scholastic materials. 08:54:28 Were you know in some, you know, in some skills, it could be head like fluid in some schools like solid. 08:54:36 Go ahead patch a great question. So I can answer the physical side of the you know the fluctuations of a quality psycho bicycle as planar, I think, Alex moving did affect the, the planar membrane which cheerless diversity way show that the bending and 08:55:00 She was this the can be entered in the model actually these are 2005 paper by Rochelle on the fluctuations of a composite bicycle. So the problem is down the question is, is it relevant to real systems. 08:55:05 sheer motor decoupled when you are on the sphere, of course the curvature matters. 08:55:13 Can we see lippy by layers or any by their membranes behaving as the Scholastic materials and that's what I posted also in countless posted, you know, add a timescale or any frequency at which you know the by layer started behaving as start showing solid 08:55:29 elastic response. 08:55:32 We see this in experiment. Yeah, so, so, so, Andre, my, my answer is similar, but just to mention that, not quite the same problem but i think you know this field. 08:55:47 These condensates that the membrane was condensates in cells. 08:55:53 There's a paper by Frankie liqueur and Tony Hyman, that looks at a kind of Maxwell approximation to the disco elasticity of those condensates which seemed to gradually gel over time. 08:56:07 So that's a that's a such a three dimensional aging problem. 08:56:13 but I suspect there's something interesting in two dimensions as well. 08:56:19 With the fiscal elastic sheets, but I don't know that anyone's worked on. 08:56:24 The fiscal elastic sheets, but I don't know that anyone's worked on. Um, there's been a little bit of work on the fiscal elastic shells and sheets Tiana Kuru Bova. And I actually talked to you on a worked with Tom powers later as a postdoc, but she did 08:56:53 very nice work pet to you mentioned the flat sheet calculation that I did. And then fortunately Tatiana was younger and stronger and did the full spherical disco Elastic Membrane with not only this goal is this city but also permeation, so you can change 08:57:00 the permeation mode and change the the Scholastic response of the membrane shear modulus and look at how you change the fluctuation spectrum of the sphere that way. 08:57:12 The, she did I think was a nice calculation, but I feel a little bit embarrassed plugging it, so I will shut up. 08:57:20 That's very interesting. 08:57:23 Yeah, so, oh I see john. But I think the only hand I see up at the moment is john please go ahead again. Okay. 08:57:34 So I wanted to turn back to the neutron spin Echo, and patches. 08:57:41 Talk. 08:57:41 And I think actually would be if I could share the screen I want to show one of patches slides. 08:57:48 Can I do that, I think you can. Let's find out. 08:57:52 All right. 08:57:57 Okay so this slide is essentially reviewing. I think pet. 08:58:23 from your work, you know really only applies to flat violators. 08:58:28 The second layer of the analysis Seifert Langer and also Watson and brown came up with this formula, which is an amusing formula because the viscosity, does it, it's disappeared from this formula in the NFC regime, it's quite amusing. 08:58:48 So what you have is to km that's essentially the area compressor ability module list. The D here is the Neutral Plane distance. 08:58:58 This is what NFC actually measures and this is the traditional equilibrium, bending modules that those of us who do equilibrium experiments I've always been focused on. 08:59:10 So, so this is the second layer of analysis. The third layer that in as he people have used the guy was group, Rhonda Ashkar and Kelly and so forth. 08:59:25 And have replaced case of a by the formula, the well known formula which has been kicked around for a long time, relating case of a to Kappa. Okay. And that formula. 08:59:41 Typically people use polymer brush for that formula I haven't put that formula down here, that by the way is where Rhonda and I disagree, quite strongly for the cholesterol study. 08:59:57 So, but the issue here is, I believe that Petya is really attacking this whole procedure of NFC. Bye. 09:00:09 Bye. And of course, Ronnie Granick is involved now in this and they've shown that this formula no longer applies. So this whole edifice that we've had analyzing NFC for the last 10 years. 09:00:26 Looks like it's going to crumble. 09:00:30 And that's extremely interesting and very product provocative. I'm not sure if we're going to solve this problem in this workshop, but it's it's certainly a revolutionary thing. 09:00:42 So, That's my discussion comment, let pet you follow up on that. 09:00:51 Well these are very strong words, and it was no my intention to attack any see interpretation of data, it's just the whole thing started as a you know side effect of my work on do this and trying to hunt down membrane discuss the effects with God. 09:01:07 And then realizing that going at smaller scales that life was on the effect would be stronger. 09:01:23 If I really hope that a more careful look at the NSC data will, you know, show you know the light and, you know, which scaling is the correct one in which analysis correct one this is just the beginning of, you know, just exploration and let's see where 09:01:31 it goes. That's all I can say right now. 09:01:35 Well, but it's it's a different theory with considerably different consequences for NFC analysis. 09:01:42 Correct. So then the theories there The result is there. And, which we just have to talk to the work with the experimentalists to see how the theory compares with the experiments. 09:01:56 My understanding is that experiments are very noisy and difficult to do me as a being a theorist you know I think it's perfect. You know, power loss and perfect data, and it's hard to distinguish a power law of two thirds versus one half, the data is 09:02:11 noisy. But, I will leave this to the experimenters if people see the other problem of course is that, that the, the only have essentially one decade of time data. 09:02:24 And you showed in one of your last slides I don't know if I can get to it quickly through here but one of your last slides you showed the problem. The usual problem of doing power law analysis. 09:02:38 Yeah. 09:02:39 And, you know, that's just, let's see where did it go here. 09:02:48 So I would just mention that we're working on the problem in the context of TVs and polyamorous, which are much more viscous or the effect will be more pronounced. 09:02:57 And I hope I will be able to share with you results sooner than than later. Yeah, so this is the power lawyer, but I did have a question here on this disfigure. 09:03:08 Where is the NSC time regime. 09:03:12 Ah, so it's, is it nanoseconds. So let's see. 09:03:19 Oh I scaled everything with the bending timescale. 09:03:26 Another question, which, which happened to us to do the scaling. 09:03:31 So there are lots of question I realized this yeah we can talk later. Maybe we could have like a discussion group separate on the. 09:03:40 These effects. 09:03:41 Yeah that's right I if I understand correctly gathered town has this thing where you can have little separate meetings so I don't mean I'll get it to work but I'll stop, I'll stop sharing them. 09:03:55 Well thank you john. 09:03:57 I see Michael Schindler has his hand up but if I can just pause for a second, Michael. 09:04:04 Mark Bullock wanted to pose a question to the gallery at some point and this seems like sort of a reasonable spot an hour in Mark, you want to step in for us. 09:04:16 Yeah, I have a question for the experts about an old problem, I thought about when David talked about water going through physical membranes and so on. 09:04:29 The, the old problem is that the diffusion constant for water going through, and by layers like a factor of 10 higher than you would expect from going through a hydrophobic by layer, and people like David David I had this seemingly crazy theory that it 09:04:57 like a proton chain like Newton's cradle. So I wonder how that is developed Does anyone know more about this recent years. I just don't know. 09:05:00 Well, I think that the day Redeemer was more interested in protons at that point. 09:05:05 But the permeability of bulk water I don't think is particularly a mystery I think that it's it's considerably, the diffusion coefficient for the permeability of bowl of water going through the membrane is is pretty much what you would expect for a hydro 09:05:24 for hydrocarbon slab. 09:05:26 But maybe rich faster might have more to say about that. 09:05:35 But you do have protons right. 09:05:50 I see so we do have a rich, maybe rich you would like, I'm sorry, Michael I promised we would go straight to you, rich if you can hold your question for a minute. 09:06:03 So, thank you very much. 09:06:05 Can you hear me. 09:06:06 Yeah. 09:06:09 So, as, as the other side the first like to thank you for for these nice talks and I would have a question for David medicine. 09:06:18 When you showed. 09:06:22 I think on page three of your presentation is implied theory of the phone column, separate from common questions. 09:06:40 Had the displacement fields and to talk to the relative to the nearest one. And I wonder what would happen at this point, if you took the true nonlinear strain. 09:06:49 I mean, you have nonlinear chance, coming from the height field. 09:06:57 But if I remember correctly the Gnostic theory. 09:07:03 Already the variables train which is difference of the metric, and so on, is already normal India. 09:07:13 Inflate displacements. 09:07:17 So I was wondering whether adding this and this second, lovely narrative with not recommend and I wreck your lives. Your 09:07:29 divergences yeah okay so thanks. 09:07:34 I, the iPad, it's a similar to an answer I gave earlier. Yes, it's another non linearity. 09:07:44 You can put it in, but it doesn't change the problems or the infrared singularities associated with the factual. 09:07:59 Well, they, they are not couple in a way that 09:08:04 dampens out their, their fluctuation. So, as I said earlier, it's a, it seems to be a long wavelength irrelevant to the physics, compared to the non linearity, they did keep. 09:08:17 So, and I think football environment, also drop them in 1904 for for similar reasons so even at t zero, there are less important. 09:08:29 With the short answer, in a sense, is there already are derivatives of in playing phone lines in the problem. 09:08:38 And they, they are more important than the square of those in plain derivatives that I think you're asking about how to find structural term. 09:08:50 It has nothing. It only modifies this very soft, bending virginity term. And so it has to be taken more seriously. 09:08:59 I that's all I can say at the moment I've 09:09:07 already tried to put them in already. I know that these trans actually can play a role but to measure elastic 10 slots, so the rest of modular line to get them right. 09:09:21 You need these terms. So, certainly for some applications you would need them. But for the long wavelength phenomena like height fluctuations are the running coupling constants of the bed entity. 09:09:37 I don't think they they play a role. 09:09:43 Okay, thank you. 09:09:45 Is there a couple of hands that came up, Richard please go right ahead. Sure, of this regards the diffusion constant of water. 09:10:01 simulations. 09:10:02 The advantage of models are up 09:10:14 underestimate the what are the future concepts by about a factor of five. 09:10:23 Compared to the experimental the numbers I was, I was comparing against a from a from john angle 09:10:42 is for a bunch of violators of. 09:10:48 The reason for that is because, because the, the partition coefficient 09:11:05 a hydrocarbon, it's about one kilocalories per mole. 09:11:17 water into a, 09:11:17 To lie, which leads to about this this fact reply. 09:11:19 When, when we look at a polarized one model. The agreement is a lot better. 09:11:30 The diffusion constants. And as you go through the by layer vary by about a factor of five as well, no relationship to the 09:11:46 polarized ability. So, We think once we have a good, but I apologize my model. 09:12:02 These are not from a protons going through this is the 09:12:11 watermark, I guess I had a question for 09:12:16 David Nelson on that. 09:12:19 On that point. He said that he looked at the at the at the permeability of water. When you having the bicycle collapse. 09:12:36 I believe that that basically collapse is a lower temperature. Where, where, where the bicycle isn't apparently I shall fail phase 09:12:50 in which case you, you have a facets and sort of dislocation points. 09:12:57 So 09:13:01 I'm wondering if the ability of the water to sort of quickly leave the vessel is not the regular permeability as in you know through a flat file air, but rather through a dislocation. 09:13:16 I think that's a very excellent suggestion, if in the collapse that Andre and I studied gets more prominent and higher temperatures, rather than lower temperatures it's a stronger effect due to the entropic shrinkage in a closed spherical shell, if it 09:13:39 holds together, and you think about the collapse though. I think your point is well taken. If it's if it's a locally crystal and, and maybe you call it a gel transition or whatever but if it's locally crystal and I would say not just dislocations but 09:13:54 grain boundaries, would be like right, very important. 09:13:59 And I wouldn't be surprised if water preferentially escaped, or enter the bicycle. 09:14:06 In the more disorderly regions of the grain boundaries. In that case. 09:14:11 Thank you. Um, let's see. So tomorrow had Cz has his hand up and then Andre I see you and will come to you next. 09:14:20 Okay, so come on please go right ahead. Well thank you so much. Yeah, so I think this question is staring back to the slide question, and I just wanted to discuss and it's a more general question that why do we see a discrepancy in the viscosity data 09:14:35 between simulations and experiments. So for example like the deal PC, but you can spin echo and with data for their formation method we see this call studies and like 10 to four minus eight passport seconds per meter. 09:14:48 But the simulation is like 10s upon minus 10, like you're the two orders of magnitude difference. And when you look at manual monitors for a similar kind of a liquid like Neo PC it's like four orders of magnitude, even higher. 09:15:03 So, I wanted to have a discussion, maybe we can have a reconsideration that's why do we see such big differences. 09:15:12 Some more general questions or anyone can start a conversation on that. 09:15:21 That's my question to I when I started in the field I discovered that there is this wide range of values reported for viscosity. 09:15:31 There is quite a bit of information now on slack. So, I think ed is in the audience, and there was. So now, maybe, maybe you can comment on the simulations, I, I, at this point, I don't have a good explanation of the discrepancies. 09:15:48 One thing I also point is a question is like universities assume that to the viscosity is equal to the 3d viscosity, multiplied by the thickness of the membrane and the question is this always the case. 09:16:03 You know, to me, right, that's definitely not the case near in two dimensional freezing transition to the viscosity can independently go to infinity, while the 3d viscosity remains finite. 09:16:16 Okay. 09:16:17 We also well we might Denon measured the viscosity of linear model layers. 09:16:25 And if you took your reasonable guess about the height of the one layer and the viscosity of the oily chains, you don't get the right answer either there. 09:16:36 For what it's worth. 09:16:39 So, it seems that that's in a mean dimensionally it has to be sort of right but it doesn't seem to work quantitatively from what I've seen, 09:16:51 but I think you know please Edward Go right ahead. 09:16:55 Yeah, I mean I, unfortunately, I don't really have an answer either at yet, but we're certainly very interested and kind of related to what Alex just said rich pointed out to me some years ago and kind of this is partly what piqued my interest in this 09:17:09 subject that you know you make a thin slab of hex a decade, it's about 100 times less viscous than a membrane and if you use a 16 carbon Allah static alcohol it's still like a factor of 10 lower. 09:17:25 Okay, why we don't know. 09:17:29 We thought that, and I'll talk more about this in my talk we you know we thought initially that we had issues with the force field that would be fixed by inclusion of longer range. 09:17:39 Leonard Jones interactions and perhaps polarized ability but those don't seem to buy us another factor of 10 or so, which leaves us with only one kind of vague answer that, maybe as a starting point, certainly not an ending point and that's that are simulations 09:17:57 Our simulations are measuring viscosity is on much shorter link scales. Then basically all of the experiments and so maybe we're not in the hydrodynamic limit yet. 09:18:11 Sounds like a fair point. 09:18:15 Um. Any other comments from the group 09:18:20 dog for a second. Sure, go ahead. 09:18:24 So it's related to also better stalking. This session on what's the value of the member of the society and the previous questions. 09:18:35 If you can actually incorporate member of the society into the building models. So, obviously the right way. I mean, everything I'm going to say is obvious. 09:18:47 Okay. 09:18:49 So, obviously the right way to measure, because something's by Columbia measurements like if you measuring the fluctuation spectrum in equilibrium. 09:19:02 But because this has been an issue, practical issues and long time ago with Anton Zimmerman we suggested that if they use our expression for the obsession of the dynamic such a factor. 09:19:21 You could deduce the value of others from it and it's it would be more likely, but obviously that relied on assuming that member of the society is negligible. 09:19:34 The signature should have been that you see a stretch exponential of searching it's put into thirds. If you have a clean exponent like this then you can say, okay, else which is correct. 09:19:57 hydrodynamic interaction is correct. Through the solvent and then you can you use the known solvent viscosity you get the right. 09:20:02 Any models. 09:20:02 Now, the question is how, how will you measure these exponential, or if you're doing experiments flickering spectroscopy with Govt. You should measure. 09:20:17 msc is of the two the two thirds or power spectra omega to the minus five thirds and again if you measure the clean exponent, then you can, you have a reliable bending models. 09:20:27 But unfortunately, I mean maybe I should be blamed. I mean, Because. 09:20:35 So, when, when a theory or a calculation is used widely and you never question it. 09:20:43 Here's some of the problem. And apparently, if you go to very small physicals in the 10s of nanometers. 09:20:53 Then, even if the member of the society is not very high. 09:20:57 This factor lambda m aphasia is important. 09:21:02 And then the signature should be that you have to the one half in the MSC or what we believe it is such an exponent to one half for the natural spiritual relaxation. 09:21:19 And if you measure this slim, in a clean way like one half you distinguish from two thirds, you can say that you have a true measurement of the member of the society, which is distinguishable from the bending models, I mean, the both of them come in, 09:21:40 but a, it's a dynamic of a gym that you have a signature of of ours like if you like me in the polymer language so I was like dynamics because it's the local friction I mean that the relaxation of remote few is going like to to the fore and not YouTube. 09:22:01 Like is it would be only solving viscosity. 09:22:07 So, I don't know if I'm making talking to the point, what I'm saying. Also that you cannot incorporate simply bending in the dynamical measurement. If you have a good measurement you cannot incorporate simply the blending mode, a member of the society 09:22:26 into the battery models because you will you will stay with the two thirds. 09:22:33 Searching exponent. So the question is, how, how would you measure things, and hopefully with some kind of a collaboration between the increasing number of people will get to the bottom of it. 09:22:48 That's the only thing I can see right now. Well thank you, Ronnie I would like to continue this discussion a bit more on the topic, but I promise we'll first Andrea, do you want to jump in on this or did you want to switch gears here are the different 09:23:04 questions so if anybody else wants to comment. 09:23:09 Okay, um, I maybe want to make a nice question so motivated by the talks, but this is more probably a question for all the simulators here about like what can simulation do that happened a bunch of papers by people pointing out that it's very difficult, 09:23:27 very very strong finance is effects and simulations for about anything that involves hydrodynamic is the hundred and me kernels so long range, but even if you ignore all of that. 09:23:38 I think one of the problems of simulations is in particular one precise numbers, is that virtually any, any force fields that we have mostly been optimized to get the equilibrium right, and to get the dynamics right is yet another matter. 09:23:52 The extent to which I know about this is very limited and I encourage the more hardcore simulators to chime in, but we want really hardcore numbers, it's probably much harder to get dynamical numbers right in simulations tend to get equilibrium numbers 09:24:05 right in simulations, maybe rich wants to comment on that, or someone else. 09:24:14 I mean, I think, I think we know that and that's why we're trying so hard to measure viscosity and simulations as accurately as possible. 09:24:21 Because until we do you know we're not entirely we can't say for sure. 09:24:25 But of course we also need to know whether we're comparing to the right experimental number you know because if you measure rotational diffusion of small chromophores you get a different number if you measure, you know, use a shearing method you get a 09:24:46 Right. But what I'm saying is you might get a different number of Have you measured charm or the measured in Ember and so when you actually compared to him. 09:24:54 Oh, there's only one limit for 09:24:58 course. 09:25:02 There's a look in the mix of simulations of proteins, were originally divert ram tries to get results, Nick liberating structures. 09:25:11 But it turns out to be not that difficult to get the dynamics right especially if you have better experimental data you parameters this. 09:25:19 I think your lip it's relatively simple. There's no reason why optimistic simulations, shouldn't get the dynamics rights, based on the force fields. 09:25:27 And if you make the first feel better, rich improvements will make it a little bit better or changes a little bit, but I don't think there's a fundamental reason within the finite size limits, which I think are more important than just city, which I think 09:25:39 you said another issue, it's difficult to avoid, and where you couldn't get the interactions right at least. So let's talk about this water diffusion coefficient being off by a factor of five, that's basically one kcal barrier in the PMF of partitioning 09:25:53 that you can change if you want to, if you have two parameters for that. That's basically what people did in protein simulations. They fiddled with the barriers for rotations in an individual's from within was now initially not very good data, but now 09:26:07 you can easily calculate them from quantum mechanics and you can easily measure them. And Mr. 09:26:13 So I don't think there's a fundamental reason where to mystic forces can't get to the net make strides but I just think a more fundamental problem for comparing two experiments, is for interpretation of many of the experiments at pointed out, but the 09:26:25 fact that we are typically using very boundaries and finite sizes, there's no real solution obviously for that I think is is Brian Kelly Are you here listening by serving his head up, I'm around Yeah. 09:26:38 Yeah, so I, I did make the claim that I don't think that the effect of viscosity as as as strongly to dependent on the periodic boundary conditions as the diffusion coefficient is that it's not as affected by the same order of singularity in this. 09:26:58 You know in the hydrodynamic, but that's something I haven't sat down and really computed I think it's worth thinking about a little bit more. 09:27:06 My, my, sort of side question I raised this on the slack. 09:27:10 But I think there's this question of whether or not we are comparing to really comparable things in that all of the continuum interpretations of the experimental data are usually done with this relatively simplified geometry, like a you know a perfect 09:27:28 sphere or a perfect flat membrane. And I wonder to what extent the roughness of the membrane leads to local hydro dynamic changes that then would normalize the effective viscosity that you measure at large distances. 09:27:42 And I don't have a sensible way to compute that myself. but it seems 09:27:49 like something that, you know, you know, Alex will be in or David Nelson might be interested in I know there has been some work on this a little bit in the past by, by Tom Lewinsky, but there. 09:28:04 It seems like something that hasn't been systematically addressed to see if we could get this factor of 10, because it seems like a very tough question. 09:28:14 Yeah, David, would you like to weigh in on that. 09:28:30 You're still muted. 09:28:32 I always said was I yield to your superior knowledge Alex sorry. 09:28:38 Well, boy, I've waited years to hear that. Okay. 09:28:42 Look, so yeah I guess I sadly I don't have a great deal of superior knowledge in this case the only point I would perhaps want to make is that how you measure the viscosity does depend on what you think you're measuring depends on the curvature of the 09:29:15 surface, Tony Densmore did some really nice experiments about the motion of particles and a Pickering emotion on this oil drop, and there the curvature, essentially because the saffman del brick length introduces a link scale, the particle size, and the 09:29:17 curvature get to compete with that and complicated ways. So if you think you're measuring the mobility of a particle to back out viscosity, you might be sadly mistaken because the curvature plays a big role in that. 09:29:30 I have no great wisdom beyond that point. 09:29:33 And, which I could add off the wall suggestion that there's something, as you know, perhaps two dimensional hydrogen dynamics breaks down into the long wavelength, and stuff like that, long time tails and so forth short, maybe there's some interplay between 09:29:56 curvature and just long time tales. 09:30:00 Were Scotty will be scaled dependent. 09:30:03 Yeah, I'll be it in a much more week fashion than the quantities I talked about. 09:30:10 Yeah that's that goes back to your work from. I can't remember the year 70 something. Seven Bridges millennium. 09:30:20 Yeah, so maybe it's best not to dwell on exactly how it goes. 09:30:24 Yeah, that's a very good point where in two dimensions you end up with a scale dependent viscosity as you shared. Um, let's see. Oh, I'm Andre I apologize I was about to get to you for a long time now. 09:30:39 So, oh no no worries, no worries that was a good discussion. So I want to switch gears and as David about his fluctuating pocket membranes, right. 09:30:49 So, you know like when you show these nn deterministic like interactions between these deletion defects, presumably, these are like short range interactions can you try to vary the spacing between these defects in simulations. 09:31:03 Well, we should maybe I should let Abby plumber respond. She certainly looked at that question and low, low, low temperatures and zero temperature and, maybe, Paul Chanukah wants to chime in, why don't we let them try to answer that. 09:31:19 I yeah I can start and pause and feel free to jump in, but we we wrote a zero temperature paper where puckers were separated by for a lot of space things. 09:31:30 And every one of the two to the end configurations was meta stable. In that case, which made simulate it was all then when Paul started taking find a temperature effects into account that made it really hard for things to a calibrated any sort of time 09:31:57 We can do so because there's so few degrees of freedom when they're just separated by two lot of spaces we can actually use a discrete framework to really nail down that these are anti for magnetic interactions and there's a sense in which it really does 09:31:59 so we move them closer together to 02, and then in that case, things things came out a lot more cleanly and the interactions were a lot stronger and actually we have. 09:32:12 behave like an Isaac model, I think. Do I remember correctly that you sometimes see go off in the right direction for the separation with the right distance, you can get federal magnetic interactions as well. 09:32:21 Yeah, we, we saw that with the triangular lattice I don't think we ever found a direction like that for the square lattice, but there was, if you if you went along in the zero and directional triangular lattice, things were, you know, weird and different 09:32:36 and they had some fair magnetic behavior that we never we never really understood. We never came up with a good way to understand why that was so different than both the continuum limit and this end direction that seemed to be a little more independent 09:32:49 of these lattice effects. 09:32:53 As my, my answer I don't know Paul's Welcome to here yeah I guess I can add a little bit more I think there is another thing that I be also found at zero temperature is the interaction also matters. 09:33:07 Basically the strength of this, the ratio between the young whitelist and banning literally so that also attract so when you go to find a temperature as Abby mentioned that once you go to when they are the distance at the far Actually, it's really hard 09:33:23 to relax, especially when we try and when we're looking at the relaxation time of this stagger mechanization So, yeah, that's exactly. So So speaking of slaps. 09:33:35 Speaking of puckers. 09:33:38 Mark Bullock and one of his students have some interesting stuff where you get a flat, that puckers would just be a good time mark or somebody to show a slide on that. 09:33:49 Oh yeah. 09:33:50 Yes, sure. So my student Jeff our chin, he's here and he prepared to fly to Cal, and he shot, and explain it. 09:34:01 I'm sure if I can. 09:34:06 If I can share my screen here. 09:34:10 You should be able to share the screen, like just find the share screen button. Yes, the green thing at the bottom. 09:34:20 Right, okay. 09:34:25 Yeah, that's I guess I was just I was just talking about this one on this, so basically on. 09:34:32 There is a quick advertisement detail car. 09:34:36 So we start we started out with triangle or Latisse, and the energy has the stretching part in the pending part. 09:34:45 But I guess the most important thing that we do is thought this lot is is not freestanding. 09:34:53 We actually quote unquote clamp, two columns on the left edge. 09:34:58 So the two columns define an XY plane. 09:35:04 No, no. Okay, so we also defined aspect ratio, with divided by length. 09:35:17 And what then we turn on find that temperature and excitement within the dynamics. 09:35:17 Well, what we see is that depending on parameter chosen the finite temperature that system connected that we call the horizontal phase where it. The system fluctuates about x y point. 09:35:48 And what we notice is that the correct way to think about this system is to use the thermal lies membrane us the reference that. 09:35:49 But it can also exit that's a what we call the toe to face, where the membrane fluctuates about a plane that is tilted with respect to x y point. 09:35:58 And I guess this was important. So she had to I understand correctly, you can fluctuate both above and below the mid Yes Yes, that is correct. 09:36:07 All right, thank you. 09:36:08 Yep. 09:36:10 And in fact the tunnel, or wall, for lack of a better word, let me use tunnel from up and down and find that time, what we realized is that well though the most. 09:36:23 For us, the most important aspect for the thermal mass membrane is. It has a smaller area, as David pointed out, also in his talk. 09:36:33 So for example if I use this crumpled paper model for thermal membrane the zero temperature with his w not and the final temperature with SW prime and W Primus smaller by W not by some amount that is already present it to my knowledge in this in this 09:36:52 reference right here. 09:36:56 So the role of our clamping it starts with respect to the thermal eyes, membrane. It stretches out the left edge from a with w not a W. Two w not. 09:37:11 And I will actually encourage people to play with this in their, in their free time and that is. 09:37:20 And you can do this with a rubber band and you can do this or with a wrinkled paper. 09:37:25 That is when you stretch out vertically the upper and lower and upper and lower edge on the left edge. 09:37:35 What do you see is that, actually, this this left edge becomes curved it curves felt like a belly. 09:37:56 And that's why, you will see a curved profile on the left. 09:37:59 And the intuition is kind of is this like the takeaway from this is that on the right side, you're not pulling it this free on the left side you're pulling it So in a sense, you're kind of like, spreading out of paper fan. 09:38:02 But this current profile is not allowed by our clan because the clan fixes this SB strict. 09:38:10 So what that means is that you have to push in the belly. 09:38:15 And you have to pull on the upper and lower edge to keep that edge strict. 09:38:23 And it's pushing in the middle is competitive, stress, which can lead to buckling, and this direction. 09:38:38 In, in practice, we doubled the system to calculate in plane stress from the flap from flat place. And that does agree with that intuition that I just explained the stress in x direction sigma x x is impressive. 09:38:53 In the middle here in the belly of that 09:38:58 and and it's 10 sell on the upper and lower edge. 09:39:04 Yeah, that's, that's more or less to take away the rest is just detail. 09:39:10 Yeah, that the experimental is David Nelson did a, an experiment on a wall without exercise that latex you pull it vertically on the wall and it goes seems to go right or left which is zero temperature analog on this that probably some elastic instability. 09:39:32 David and I talked about for some time. So we your thing, if I take a rubber sheet, and I glue it on one side to the wall and then I pull. That's the experiment. 09:39:43 Yes, Yes, yes. 09:39:58 Great still practice sounds. 09:40:00 Yeah. Right, right, right, right. 09:40:02 Well, I, I think it's probably beyond my experimental capabilities, but it does sound like an interesting problem to try very cheap. 09:40:16 Oh, we have Andre with another with his hand up please go ahead Andre. 09:40:21 Yeah, I just wanted to. Since there are no cans race I wanted to bring up another question from slack. And I can also comment on this you know like Carlos asked about, you know, like what happens to these fluctuating solid sheets are, you know, like it's 09:40:23 Well cheap is in my wheelhouse. 09:40:35 an interface, right, you know, like say like a fluid interface or they're sitting on a substrate power the affected. So I just want to comment that everything that David Nelson talked about his talk was full of 3d suspended sheets right that they're not 09:40:49 in contact with anything else right so as soon as they're trapped in the air, let's say, at some you know fluidly interface, you don't have to worry about the surface that engine, right, and that way long wavelength, these tangible actually suppress the 09:41:03 the normalization and we'll stop right sooner like a short length skills, you will have thermal effects but the long length about long wavelength, the surface tension dominates and completely suppresses these fluctuations and it stops are normalization 09:41:17 of elastic consonants. And this effect is even more pronounced. If you actually have like a sheet that sitting on a substrate, because then you have like you know wonder boss interactions or some other you know like spring like interactions that suppress 09:41:32 things even more strongly with the wavelength, right, because you know like when you surface tension will go as a q squared, whereas if something's going on the substrate will go eschewed to the, you know like, it's constant independent of you. 09:41:47 Right, so, so this impression will be even more pronounced right so I just wanted to mention this but Carlos, you know you can comment. 09:41:53 Great. Carlos Please go ahead. 09:41:57 You're muted. 09:41:59 Yeah. 09:42:01 Since the spirit of this meeting is to compare really food membranes and solid seen sheets I was trying to understand this particular point with respect to that include membranes we know the answer right you still keep some scaling structure at length 09:42:16 scales which are smaller that link skill that is determined by basically the confinement potential and above it of course the combined with potential kills everything. 09:42:27 So, for this effect you're on the flex flex role for news this is quite the same you're saying you still keep style dependent phenomenology below that link scale but then that long wavelength that skilled. 09:42:41 That's why guys like scale, which is fixed by potential. 09:42:46 Exactly. Exactly. Okay, all right, that that landscape, everything behaves just like for a few days suspend the cheats but beyond that then potential of okay so phenomenal logical it is quite like the fleet members as well. 09:42:58 Okay, thank you. 09:43:00 All right, um, maybe to bring things back to pet to talk and also to fold in another slack question. 09:43:09 Hiroshi Gucci asked Wilson said nice just to broaden the subject. 09:43:23 Comment on the effect of membrane viscosity for red blood cells are lip zones or more generally for by layer systems. 09:43:27 So for instance, I guess, red with red blood cells you have a spectrum elastic network also going on so it's not quite the same problem of course but 09:43:40 can you repeat the question so Hiroshi asked about the comparison of essentially, if my interpretation was that he's asking you to speculate on the role of membrane viscosity more ov and systems, including our VCs and zones and other things. 09:43:59 Okay, got it. Yeah, I remember his question. 09:44:00 So this is going back to my previous life of working on physicals in flow as a model of red blood cells. And so we did actually include the effect of the membrane viscosity and it shows as an effectively, you know, a CPU effectively increase their because 09:44:18 the contrast between the interior and the exterior of the physical and therefore promotes things like transition to tumbling that it's observed with red blood cells and so on. 09:44:29 And I mean it's it's not been measured directly in the, like, how important is for, for red blood cells but it's, you know, the model exists but I guess I would say it's the viscosity of the matter because the blood with red blood cells is not as important 09:44:48 as the viscosity contrast between the interior and the exterior and the effect of the elastic, the spectrum network. 09:44:59 And my answer to get a little bit easier, because we haven't discussed it, but okay. All right, so you can do the same experiment. 09:45:10 Correct. Good question. Yeah, then you can measure. 09:45:15 You can measure angle. 09:45:17 And then you can shift to maybe squishy. 09:45:21 Okay, this is a great suggestion for an experiment to see the effect of the membrane viscosity, by doing experiments with God is in, let's say share flow and measure the inclination anger which is directly related to them, because the contrast and the 09:45:41 goes. Thank you. When you have to figure out how to do that experiment. 09:45:44 Thanks. All right, let's see where there are a couple of hands up. 09:45:49 Marcus, sir no put in the chat something about me and two point micro reality, I will. Yes, Marcus I did that because there was a period in my life where if it had to point microbiology possible I had to do the calculation. 09:46:05 But let's not talk about that. 09:46:07 I think the first hand they saw up was john Nagel, if that's correct. Please go ahead. JOHN again. 09:46:18 Did I get it wrong john. 09:46:22 I might have unmute myself so that was it. 09:46:26 Since red blood cells came up. 09:46:30 I wasn't expecting to say anything about this but the the bending modulus of red blood cells is very much, very complicated subject and it's because of course there's a complex membrane and spectrum spectrum sight of skeleton, plus the plasma membrane. 09:46:48 And I'm just wanting to mention that the numbers for the bending modulus go all the way from something like five kt up to 100 k t, then the literature, and that's an interesting question to sort out. 09:47:02 I'm collaborating right now actually with the people doing the experiments or Michael Ryan stat or at McMaster and his student, Sebastian Hibbert, and they've used my method of X ray scattering implement implemented for their particular instrument, and 09:47:21 they're finding bending modules on the low skip low end of the thing. However, they've done it with by stripping off the spectrum Saito skeleton. So, because it's a complex membrane to begin with, it makes sense to try to you know look at each part by 09:47:38 itself. And so the plasma membrane seems to have a very low bending modulus, but the whole thing. 09:47:47 If you look at, Evan Evans experiments were going way back to the 80s. He has this bending modules in the order of 40 KT. So there's an interesting story there which we're just we're just coming to grips with now and it hasn't been hasn't been published 09:48:04 yet. 09:48:10 So john just you probably know this but to the extent that the spectrum hasn't share modulus, it will come on a scale dependent things that I was talking about. 09:48:15 And so for get rid of the psycho skeleton we don't have to worry about the sheer modulates. Exactly. Yeah. So I think that we've got so you know by by trying to. 09:48:25 This is the reductionist approach of course the science. We're taking it into pieces. And I think we might have something interesting to say about the this issue which has been, you know, looking at the literature, it's really quite complicated and confusing. 09:48:41 Yes, I think that's a fair point, and Gabrielle Popescu and I made some measurements about a decade ago he made measurements I tinkered. 09:48:52 And also ended up on the low side both for the area stretching modulus and for the bending modulus. 09:48:59 Our contention at the time was that because he was using essentially the flicker of the red blood cells to back out these measurements and sort of a micro reality since you get a lower number but if you actually start making large deformations there's 09:49:21 strong strain Stephanie. So if you automatically swell the RBC for instance, then the numbers go up. So we're very, we're very much aware of your papers of course I forgotten that you were sort of a middle author. 09:49:28 I hadn't made the connection that fescue has several papers and the numbers in the two different papers, disagree by quite a lot which is really amusing so we should have a private conversation about what happened back then. 09:49:42 Yeah, so the numbers changed when we, when I stepped in and we did the basically we analyze the data a different way. But that we can talk let's probably best for an offline discussion, right. 09:49:54 So, I don't let's see we have a number of hands of Richard has been very patient I apologize Richard please go right ahead. Yeah, hi. 09:50:09 Man, this is a point on whether or not. We've been we've been trying to look at look at like dynamic properties from simulations mean we're like restricted to ones are relatively short length, and a timescale, but will be a week but but but but when we 09:50:24 we validate the force field we asked you look at the future Dawson's of lk ins which we get right. And one interesting one that we looked at was I'm going to share my screen. 09:50:41 I think you should see a liquid wobble now so early in my career. I learned a Michael Brown's. 09:50:52 This is not Frank rounds, a 09:50:59 frequency dependent relaxation times on for dp BC, and it turns out it is a very characteristic one nanosecond relaxation done, which comes from liquid liquid wobble, which I've sketched on this slide here, it's the emotion associated with the D perpendicular. 09:51:21 So with simulations now we can nail that down and a parallel and get the frequency dependence. Now, I want to make a comment about the viscosity, briefly, so this is probably going down to a lens scale that's much smaller than you want to think about, 09:51:39 but But actually, when you look at the ad for a cylinder this size. 09:51:46 What's the viscosity that you need to get this one nanosecond relaxation time. It's almost exactly the viscosity, 09:51:57 but 09:52:05 have a need a hexagon decade, which is which is this temperature it's about, about a two sentence squat. So in other words that the very local level, a membrane has been as costly, which is like a Andy arcane. 09:52:19 And then, there have been neutron scattering experiments, I believe, aware, where we look at wobble in a cage. 09:52:32 And those results are also very consistent with with this very low viscosity. 09:52:38 So, I realized that's getting too way too small. But the fact is that viscosity does seem to have this lens scale associated with it. 09:52:47 So let me stop my sharing and stop my talking. 09:52:52 Thank you Richard, and while you were talking a few hands went up, Mark, would you like to comment or ask a new question. 09:53:00 Yes, I just wanted to comment on the red blood cell which Pete new people are tackling which is great, is an additional complication which is that the decide to scousers dynamically coupled to the liquid by layer, these are these anchor and molecules 09:53:17 which are like nodes. So, you have the two universality classes of membranes the fluid and the last one which are very, very, very different opposite in their long wavelength by the and then they're dynamically coupled to each other on quite rapid timescales 09:53:34 so this is a nightmare for for theorists and and experimental a second. 09:53:44 Excellent. 09:53:44 All right, well on that cheery note of nightmare. Let's, uh, Kili Maury would like the way and. Yes, thanks for the question to David the last one or, so it's concerning the. 09:54:00 I had the question to David the last one or, so it's concerning the. So the boundary conditions in this theory of flexor of finance, because. So the point is that these correlations grow with distance so one would expect, very strong sensitivity in some 09:54:12 sense and. 09:54:14 So, for example will fund can imagine some experiment on graphene then there is maybe some substrate with a hole in the middle and this membrane placed there, or something like that and so one would be tempted to put a uniform tension in a first approximation 09:54:31 to make things easier, theoretically, but my question is how this boundary conditions can affect the physics. 09:54:45 David you're muted again. 09:54:52 Very good question, and I am on simulations that I still had a periodic boundary conditions and we were very careful to relax the dimensions of the square to eliminate that tension and, but I think that person who would bet better able to answer if he's 09:55:14 still in the audience is Sheriff Shankar. 09:55:16 Do you want to try to answer the question about boundary conditions 09:55:24 may not be in the audience which case I will, I can attempt to do it. 09:55:38 So yeah, if you have graphene stretched across the whole with anchoring around the rim of the whole. It's sort of freestanding doesn't have the substrate to pull it down or something but it has anchoring around the whole. 09:55:47 And in general, you'll get attention you can either be a positive tension or a negative tension. 09:55:54 If you take such a system, and then very the temperature. 09:56:00 You can use the temperature to tune that tension through zero. 09:56:05 And then you'll get something which can flop, and be freestanding rather like a unit level or vessel that's no longer tense. So you can certainly do that. 09:56:19 You can also look at a cantilever, which is only like a diving board geometry which is only attached at one end and then there's no problem with tension. 09:56:32 And what I was hoping that survives can comment on and I, there's a paper which I can share in the chat perhaps that he and I wrote, is that it turns out that when you have things stretched across the whole, and it's a constant area ensemble. 09:56:50 There are subtle differences but quite striking ones in the long wavelength physics. 09:56:57 As you anticipated by saying that we have these scale dependent quantities so it's very sensitive to boundary conditions and constant area ensemble is not the same as a constant tension ensemble. 09:57:12 Normally these ensembles are expected to be the same and the thermodynamic limit. Before the system which has this exclusive sensitive with the boundary conditions in that that's no longer true, but we think we figured out what happens with least with 09:57:27 a circular hole, and I'll put a paper in the chat. 09:57:31 Thank you, David. 09:57:35 Yeah, it's also not a uniform tension, it's more like, I think more like a boundary layer because it's free it's the tension is confined some sense around the boundary depending on your aspect ratio, depending on new geometrical parameters and so on. 09:57:36 Mark ur backup. 09:57:55 And it does depend on the ensemble as David was saying, but I would, in general, I don't think it can be modeled as a uniform tension, and in the top problem that detail talked about we can molecular dynamics simulations which my student dawned on one 09:58:14 originally did to see this phenomenal you can map out the stream field, and you get a parabolic like shape because the crescent moon, so that it has to be taking the counter. 09:58:28 It's not uniform. 09:58:32 All right. Thank you, Mark. Let's see, um, Andre how draconian are we about time visits, I mean, typically 10 o'clock. Yeah, we're coming to the toolbox you know we should probably be respectful of other people's time because they may have other meetings. 09:58:48 But I just want to say that you know this was like a very wonderful discussion, you know, thank you all for participating. And you know, we hope that it will not stop here but it will continue on slack so you know please take advantage of slack and again 09:59:02 at a time to you know continue this discussion to organize other like smaller, you know groups, as we saw there were like some odd some potential interest in forming these, so we definitely hope that all the platforms that will provide it will promote 09:59:15 this discussion, because that's the whole point of the Kp programs as Mark, can attest, right. 09:59:23 Yeah, so let me just say thank you to all the participants and can we especially think the two speakers David and pat TF for their filmed presentations or whatever we're calling those asynchronous ones. 09:59:38 All right, well with that I believe we are ending this discussion session, and have a great day everyone. 09:59:49 Thank you. Thank you. Thank you. 09:59:51 Good, thanks. 09:59:54 Bye. Bye. bye.