 the during each talk. Okay, so being that said, the first speaker of today is Ali Rajapur. The title of his talk is going to be Heat Transfer at the Solid Liquid Interface. So Ali, whenever you want to start, go ahead. Thank you, Oriel. So let me share my screen, my entire screen and screen number two. Can you hear, can you see my desktop? Nope. Okay, now we can. Okay. Perfect. And the laser, it is very important to see the laser. I would like to remind everyone to mute your microphones, of course, Ali. Yeah. Okay. Hi, everyone. Again, let me introduce myself again. My name is Ali Rajapur. I hope you enjoy this workshop today. My affiliation is from IKIU, which is a university in Qazmin and also from IPM, which is an institute in fundamental science in Tehran. In my group, the focus of my group is working on thermal transport in nanostructures. And our approach is more computational using molecular dynamics simulation, lattice dynamics to study the phononic properties of materials, and finite element method, finite volume method as a continuum approach, and also density functional theory and Boltzmann transport equation and Monte Carlo and so on. In this presentation, the main focus of my talk is on the heat transfer at the interface between solid and liquid. When we have two different objects, even if they are in complete contact, we see a thermal resistance at the interface. This resistance at nano-scale may be greater than the thermal resistance of each body. Of course, this resistance is different from the resistance due to incomplete contact, and of course, its value is much less than the thermal resistance due to insufficient physical contact. But this resistance becomes important at the nano-scale, and we call it interfacial thermal resistance or conductance, its reverse value, or another name is kapitza resistance. So I will focus on the application of this resistance in fluidic systems. Considering the application, one is the treatment of cancer with the help of photothermal therapy. A cancer tissue could be destroyed by laser heating, and in this regard, gold nanoparticles are used to better heat the tissues and to transfer heat to the environment, which could be considered generally as water. In this process, the interfacial thermal resistance between gold and water could be a bottleneck. Therefore, reducing this resistance can lead to a reduction of the required laser pop. Another application is- Ali, I had a question for you. What's the local temperature that you need to to heal these cancer tumors? Plus 10 to the body temperature, 10 or 20. That's it. Yeah, yeah. Okay. And the laser power is at the order of a nanowatts or something like that. Yeah. So people have studied what happens with a mouse if you put a laser, because this should be also dangerous, no? Yeah. Yeah. I mean, it should be concentrant on the specific tissue. So we use a gold nanoparticle to locally hit the tissue, if I understand your question. Yes. Now, I'm worried by the poor mouse that take this light, which can burn the skin or create the secondary effects in the organs of the tumor. Yeah. Yeah. Okay. And yeah. Another application is nanofluids. To define a nanofluid, it is a fluid that contains nanoparticles. Since the thermal conductivity of this nanofluid is higher than the base fluid, which can be generally water, it can be applicable in many industrial applications, like car radiators, leading to a reduction in radiator size because we use a fluid with higher thermal conductivity, so we can reduce the size of the radiator and thus a reduction in fuel consumption. And in these fluids and the thermal resistance between nanoparticles, here is a silver nanoparticle, for example. So the thermal resistance between the nanoparticle and the surrounding fluid is very important to engineer the properties of the liquid. About ongoing projects in these applications, I would like to talk about the water shells around the nanoparticle. As we know, a shell of water is formed around the particle in the water, which has different properties from the bulk water. This layer, because of the solid liquid interaction, this layer has higher thermal conductivity, higher density, and also higher viscosity. Also, this layer is very thin. It can be important at the nanoskill. This project is being implemented in collaboration with Sami Marabia from Leon, ILM, and also Ali, and two of my post-doctorals researchers, Fatemeh and Reza. We have also investigated... Ali, just a question and a comment. You mentioned a viscosity. I mean, as far as I know, it's rather difficult to come up with estimates of, let's say, local estimates of viscosity. So for example, in these models that you use, how do you treat the viscosity as it goes from bulk to the surface? Is it constant? Does it change? The viscosity of this layer is 10 times greater than the viscosity of the bulk. The thermal conductivity is 50% larger than the bulk. How do you know that it's 10 times larger than the viscosity? We measured by molecular dynamic simulation. Actually, in experiments, it is very difficult to measure the local viscosity of each shell. It's almost impossible to have the viscosity distribution by experimental devices. But by molecular dynamics, there are several methods. One is green cubo formalism. We divided the... You've done it? Yeah, we divided the... Okay, okay. And you were able to make it work? Yeah. Impressive. Yeah, yeah, yeah. Okay, all right. Now, that's good. Thanks. Another project is to investigate the cooling of amino acids in water and calculated the relaxation time for different types of hydrophilic and hydrophobic amino acids. We have a phone that, at a given mass, as you see, the hydrophilic amino acids cool faster than the hydrophobic amino acids. And we studied the interfacial thermal resistance between different amino acids, 19 amino acids, and water and calculated the distribution of the cooling time of each amino acid. And this guy is Haider, who did the project. He's not an amino acid, but he's a combination of many amino acids. Sorry, I think there was a question. Yeah. Sorry, I don't see the chat or... So please let me know if there's any questions. I had a question in the previous slide. In that you mentioned that the thermal conductivity, the local thermal conductivity is 50% higher than the work. So shouldn't it depend on the surface properties of the nanoparticle also? Of course. What is the local thermal conductivity? Just on the density of the water? The local thermal conductivity, what is the value you mean? No, no. What does it depend on? Does it just depend on the density of the water? No, no, no. It depends on many parameters. For example, on the solid fluid interaction or the surface of the... I mean, if there are some surfactants on the surface, it depends, of course, on the surface of the nanoparticle. But the most influential parameter is the solid-liquid interaction. I mean, the strange of the interaction. And for different liquids, it is different, the enhancement of the thermal conductivity. So 50% greater local thermal conductivity is for one type of nanoparticle? Yeah, 50% for water case. For other case, it could be different, if I understand. Also for some kind of nanoparticle? Of course. If you replace, for example, here is a silver nanoparticle. If you replace the silver with gold or with silica or any other material, you get different values of enhancement. But the range should be, I mean, between 20% or to 100%. Thank you very much. We have another question from Meira. Go ahead, Meira. Yeah, can you hear me? Yeah. So, Adi, you mentioned that where you have the more... When you have a higher water density, you also, you have seen a higher thermal conductivity. Mm-hmm. And I missed that part. So what did you explain for the reason? For the reason. Yeah. Yeah. And the reason could be, I mean, the structure of water around the nanoparticle is more solid-like behavior because it is under interaction of a strong interaction of the solid. So if we plot the, for example, a radial distribution function or see the structure of the molecules around nanoparticles, they are more structured than other molecules, water molecules. So this strong interaction leads to a higher density and also a higher thermal conductivity and also higher viscosity. Okay. And have you seen this, the same effect with different types of nanoparticles or? Yeah. Yeah. Gold. We examine for gold, silver, simple Lenard-Jones interaction solids, alumina, yeah, different kinds of materials. Okay. Thank you very much. You're welcome. Okay. Another project that we are collaborating with Edgar is an idea that we got from a very interesting recent paper. In this nature paper, they created a Carnot cycle using an optically trapped particle. And this nice simulation is an attempt by Said to find out more about how heat is distributed around the oscillating particle. And as you see in this nice paper, we see an ideal cycle, zero entropy variation. And we try to, this is an experiment done by Raoul and his group who is present here and he can explain more about the experiment. But we are focusing on the simulation. So we oscillate the particle by noise, by random force. And you see the temperature distribution around a particle. So this project is ongoing and we are working on to have a smooth temperature distribution. And there are some technical computational things that we should do to have better simulation. Okay. Yeah. Question? Yes, I had a question. Yes, please. Yeah. For a small number of molecules, in fact, in your simulation, how did you measure temperature? It should have a lot of, I mean, uncertainty. Is that right? Yeah. This is a good question. So we had to increase the the size of the simulation and also getting average on many time steps. Yeah, to have a good, less on statistical uncertainty. Ali, we have three minutes left. Okay. And this is my last slide. And the last project that I talked about is a simulation of the reverse heat transfer. It has recently been shown by a statistical thermodynamics that the heat can be transferred from a cold source to a hot source by creating non-Gosian noise in the cold bath. And in this simulation, we have created a two completely isolated heat source. So the baths are isolated. And the only connection between two particles is a spring between two particles. And we try to create a series of non-Gosian noises to see in the simulation environment what has been suggested by statistical thermodynamics. And this reverse heat transfer can also be created by Maxwell's demon through opening and closing a gate to allow only the particles with the highest kinetic energy to pass from the cold bath to the hot source. And we are working on this project and any idea to help to the reverse heat is appreciated. So the summary of my talk was on liquid layering around the nanoparticle. Heat transfer from amino acids to the water, temperature distribution around an optical litra particle and reverse heat transfer, which means energy flow from the cold to the hot system induced by non-Gosian thermal fluctuations. And thanks for your attention. Thanks a lot, Ali. It was a very, very interesting talk. Thank you. I give you an applause in the name of everyone.