Events: Centre: Physics Centre events at Chalmers University of TechnologyFri, 04 Dec 2020 09:25:10 +0100 Rodriguez Palomo, Materials Science<p>Online via Zoom.</p><p>​Title of thesis: &quot;Study of the flow-induced structure and anisotropy in lyotropic liquid crystals for hierarchical composites&quot; Follow the presentation online​ Passcode: 401980</p><h2 class="chalmersElement-H2">Abstract:</h2> <div><span style="background-color:initial">Controlling the micro and nanostructure of materials is highly beneficial in order to tailor their physical properties. Extrusion-based 3D printing is a promising tool to produce hierarchical structures with controlled architecture. Combining additive manufacturing and self-assembled materials, complex structures with high anisotropy can be created. Lyotropic liquid crystals offer a wide variety of structures and compositions, in which hexagonal and </span><span style="background-color:initial">lamellar phases are very interesting options. Far from the idealistic concepts of 3D printing and extrusion, the variability of the different systems, physical properties of the inks and environmental conditions play a fundamental role in the appearance of imperfections, undesired nanostructures and the limitation in the maximum effective alignment achieved. <br /><br />To understand the mechanisms that induce alignment in liquid crystalline phases and produce secondary effects and imperfections, a combination of different methods was utilized. Using small-angle X-ray scattering as the main characterization tool, the nanostructure of the liquid crystals as well as the anisotropy was measured. The use of imaging techniques adds an extra dimension which brings a broader view of the self-assembled structure. Microfluidic channels were used to study the mechanisms of alignment in the confined space offered by the nozzle walls and the high pressures applied in the printing process. The confined flow in the printing nozzle has different properties and constraints compared to the open flow that the extruded filament encounters in the printing platform, which was studied by in-situ 3D printing in the X-ray beam. By complementary rheological characterization, a more detailed analysis understanding of the flow behaviour was achieved and birefringence microscopy opened up the possibilities of a time-resolved study of the anisotropy in the filament. The results demonstrated the role of the shear stress in liquid crystals in confined flow, highlighting both the effect it has on the anisotropy as well as on morphological transitions in the self-assembled structures. The performed experiments also reflect on the possible causes of misalignment such as stress release and try to find the optimal parameters in the nozzle design which lead to the best alignment in terms of homogeneity in the strand and maximizing the orientation. <br /><br />Finally, the results also show the importance of time and environmental conditions during 3D printing, which may affect the final structure and orientation prior the fixation of the nanostructure.​</span></div> Högberg, Physics and Astronomi<p>Online via Zoom</p><p>​ Title of thesis:  Non-heating Floquet systemsAnalysis of energy absorption in (1+1)D CFTs with a square wave drive, using asine-k-square deformation​ Follow the presentationen online​ Passcode: 6cAcgy​</p><h2 class="chalmersElement-H2">​Abstract:</h2> <div><span style="background-color:initial">I</span><span style="background-color:initial">n the last decade there has been immense progress in experimentally realizing periodically driven, so-called Floquet systems, that exhibit topological features. However, there is an expectation that most Floquet systems heat up with time, absorbing energy from the drive, and thus evolve towards a featureless state in which all local correlations are fully random. </span></div> <div><span class="text-normal page-content"><div> </div> <div><br />In this thesis it is shown that it is theoretically possible to have a Floquet system which do not heat up, giving that any existing local correlations could be infinitely long lived. In other words, this shows that interesting physical phenomenon, such as a non-trivial topological phase, could in principal be present in a Floquet system for infinitely long times. The Floquet model which exhibits this non-heating phase is that of a square-wave drive where the Hamiltonian of the system jumps between an arbitrarily chosen CFT and a sine-square deformation of the same CFT. This model was first proposed in 2018 by Wen and Wu in Ref.[1]. We present in this thesis a generalization of the Floquet system proposed by Wen and Wu – we still use the same square wave drive but now with what we call a sine-k-square deformation, hence a deformation of higher harmonics. With this generalization we also find the interesting property of a non-heating phase for certain values of the driving parameters.<br /><br />Furthermore, we find that the value of k in the sine-k-squared deformation that we propose has some rather important implications for which driving parameter values we can have in a non-heating phase: The region of the driving parameter values which gives the non-heating phase shrinks with growing k and furthermore, a repetitive feature shown when plotting the regions of parameter values increase in intensity with growing k.</div></span></div> Hogstrand and Johan Rogestedt<p>Online via Zoom</p><p>​ Title of thesis: Non-invasive lactate estimation - An investigation of a spectroscopic approach​Master program: Systems, Control and Mechatronics Follow the presentation  online​</p><h2 class="chalmersElement-H2">​Abstract:</h2> <div><span style="background-color:initial">To monitor the accumulation of lactate in the blood during physical activity is a key concept for athletes in all endurance sports. This thesis has attempted to identify and develop a method which does not need any blood to estimate lactate, i.e. a non-invasive method. In particular, transmission of light through a fingertip and the absorption thereof has been related to lactate concentration. A concept based on this idea has been developed, ranging from an initial theoretical and clinical study to system development and infield validation of a constructed device. The results indicate some promising wavelength regions, however highlights the difficulty to overcome noise and signal attenuation. The developed system performs lactate estimation with a RMSE of 1.63 for lactate concentrations of 1-9 mmol/L using support vector regression. In conclusion, the thesis has developed a complete framework for non-invasive lactate estimation. The performance, however, is unsatisfactory relative conventional, invasive, lactate meters. Many areas of future development have been suggested, building on the developed concept.</span><span style="background-color:initial">​</span></div> webinar: Combining 2D and 1D nanomaterials towards smart electronics for wireless applications<p>Online</p><p>​George Deligeorgis, Foundation for Research &amp; Technology Hellas, Crete, Greece​ Join on Zoom: Password: 2d-tech141</p>​​Abstract:<div>TBA <span style="background-color:initial">[WP Energy]​</span></div> <div><span style="background-color:initial"><br /></span></div> Entekhabi<p>Online via Zoom</p><p>​Title of thesis: Astrochemical Modeling of Infrared Dark Clouds Follow the presentation online​</p><strong>​</strong><strong>​<br />A​bstract:</strong> To be announced interactions in van der Waals heterostructures<p>online</p><p>Welcome to a Quantum Materials seminar with Prof. Dr. Jaroslav Fabian, Universität Regensburg, Regensburg, Germany The seminar will be virtual on Zoom ZOOM link: Password: 846031​  ​</p><p class="chalmersElement-P"><strong>​</strong><span lang="EN-US"><strong>Abstract</strong></span></p> <p class="chalmersElement-P"><span lang="EN-US">Two dimensional materials offer unprecedented opportunities for spintronics research. The main advantages of van der Waals heterostructures are (i) the possibility to control the spin properties of electrons electrically very efficiently by gating, and (ii) tailoring the spin properties---spin-orbit and exchange couplings---by the proximity effect. In this talk, I will present the current understanding of the spin-orbit coupling in graphene-based heterostructures, and introduce some new ideas how to turn the spin-orbit coupling on and off, and even how to swap spin-orbit and exchange interactions in ex-so-tic</span><span lang="EN-US"><br /> <span>heterostructu</span><span></span><span></span><span>res which comprise strong spin-orbit as well as ferromagnetic layers [1]. Finally, I will discuss ramifications of the spin proximity effects on topological transport in graphene [2]. </span><br /> <span> </span><br /> </span><span>[1] K Zollner et al, Phys. Rev. Lett. 125, 196402 (2020)</span><span><br /> <span>[2] P. Högl et al, Phys. </span></span><span lang="EN-US">Rev. Lett. 124, 136403 (2020)</span></p> <p class="chalmersElement-P"> </p> Jones, Physics<p>Online via Zoom</p><p>​Title of thesis: &quot;Mass transport via thermoplasmonics</p><h2 class="chalmersElement-H2">Abstract:</h2> <div><div>Losses are a ubiquitous feature of our universe. They are encoded in the fundamental laws of thermodynamics. In our everyday lives, we experience these losses as friction, air resistance, etc. Generally speaking, losses are the effects that occur in any physical process that cause a decrease in efficiency and result in the generation of heat. </div> <div><br /></div> <div>Plasmonics is no different. </div> <div><span style="background-color:initial">Plasmonics is the study of how light interacts with metallic nanostructures (e.g. gold nanoparticles). Small gold structures can act as optical antennas and allow scientists to probe nanoscopic environments. However, because of losses, these nanoantennas can also generate a significant amount of heat. </span><br /></div> <div><br /></div> <div>Thermoplasmonics concerns itself with studying the effects of heat generated by plasmonic interactions. Historically this heat generation has often been viewed as an unwelcome side-effect, and thus it is imperative to study these processes to understand ways to design systems to mitigate heat generation. However, there are also new and exciting ways that these losses can be utilized for entirely new purposes. </div> <div><br /></div> <div>This thesis explores both the detrimental and beneficial aspects of thermoplasmonics. In particular, the adverse effects of thermally enhanced Brownian motion and thermophoretic depletion are examined in the context of conventional plasmonic systems. Additionally, the use of thermally nucleated bubbles is explored as a potential means of efficient mass transport in microfluidic systems. </div></div> Andersson, Physics<p>Online via Zoom</p><p>​ Title of doctoral thesis:  &quot;Dynamic structure discovery and ion transport in liquid battery electrolytes</p><h2 class="chalmersElement-H2">Abstract:</h2> <div><div><strong>The secret life of battery electrolytes</strong></div> <div><span style="background-color:initial">Lithium-ion batteries have conquered the world via cell phones and laptops and are now en route to disrupt transport and large-scale energy storage, thereby accelerating a green transition.</span><br /></div> <div><br /></div> <div>Lithium-ion batteries are not perfect, though. The electrolytes transporting ions between the electrodes contain flammable, unstable, and toxic ingredients. They are unfortunately hard to modify without performance losses. Safer, greener and stronger batteries are therefore in need of new electrolyte concepts.</div> <div><br /></div> <div>One such candidate is highly concentrated electrolytes, which consist of the same kind of ingredients as today's electrolytes: a salt of lithium ions and negative ions dissolved in a solvent. Compared to today's electrolytes the salt content is much higher, making the electrolyte more stable and opening up a larger design space.</div> <div><br /></div> <div>Highly concentrated electrolytes and other promising concepts are harder to understand on the molecular scale, which however is necessary for guiding further research and development. To advance the understanding of electrolytes in general I have developed methods and the software CHAMPION to find out which atoms move together and study their behaviour in great detail. The methods are here applied to a number of quite different battery electrolytes, and the methods can likely also be used for completely different materials. The work has also resulted in a pending patent and in the founding of the start-up Compular AB of which I am a co-founder.<span style="background-color:initial">​</span></div></div>,-MC2.aspx,-MC2.aspxDocent lecture - Giulia Ferrini, MC2<p>Online</p><p>​Title: Continuous-Variable Quantum Computing: Fundamental Resources for Quantum Advantage and Experimental Prospects</p>​<span>​The docent lecture will be held online: <a href=""></a><br />To be admitted, please enter the letters: <strong>Giulia</strong><br />As you enter the meeting, please make sure that your username reflects your actual full name for easy recognition.<span style="display:inline-block"></span></span>