2,235 research outputs found
LIPIcs, Volume 251, ITCS 2023, Complete Volume
LIPIcs, Volume 251, ITCS 2023, Complete Volum
A glassful of graphene: graphene-based materials for drinking water remediation
Modern world suffers from an intense water crisis. Emerging contaminants represent one of the most concerning elements of this issue. Substances, molecules, ions, and microorganisms take part in this vast and variegated class of pollutants, which main characteristic is to be highly resistant to traditional water purification technologies. An intense international research effort is being carried out in order to find new and innovative solutions to this problem, and graphene-based materials are one of the most promising options.
Graphene oxide (GO) is a nanostructured material where domains populated by oxygenated groups alternate with interconnected areas of sp2 hybridized carbon atoms, on the surface of a one-atom thick nanosheets. GO can adsorb a great number of molecules and ions on its surface, thanks to the variety of different interactions that it can express, such as hydrogen bonding, p-p stacking, and electrostatic and hydrophobic interaction. These characteristics, added to the high superficial area, make it an optimal material for the development of innovative materials for drinking water remediation.
The main concern in the use of GO in this field is to avoid secondary contaminations (i.e. GO itself must not become a pollutant). This issue can be faced through the immobilization of GO onto polymeric substrates, thus developing composite materials. The use of micro/ultrafiltration polymeric hollow fibers as substrates allows the design of adsorptive membranes, meaning devices that can perform filtration and adsorption simultaneously.
In this thesis, two strategies for the development of adsorptive membranes were investigated: a core-shell strategy, where hollow fibers are coated with GO, and a coextrusion strategy, where GO is embedded in the polymeric matrix of the fibers. The so-obtained devices were exploited for both fundamental studies (i.e. molecular and ionic behaviour in between GO nanosheets) and real applications (the coextruded material is now at TRL 9)
Development of Small-Angle X-Ray Scattering on a Nanometer and Femtosecond Scale for the Investigation of Laser-Driven Matter
Laser-Plasma-Beschleunigung mittels ultraintensiver Laserstrahlung ist eine vielversprechende Technologie fĂŒr die Entwicklung kompakter Strahlungsquellen. Diese werden in einem breiten Spektrum technischer AnwendungsfĂ€lle genutzt, zum Beispiel zur Krebstherapie, in der Laborastrophysik und fĂŒr die TrĂ€gheitsfusion, weshalb viele interdisziplinĂ€ren Forschungsfelder ein groĂes Interesse an ihrer Entwicklung haben.
Die ersten Machbarkeitsstudien zur Nutzung gepulster Protonenstrahlung zur Tumorbehandlung haben bereits erfreuliche Ergebnisse geliefert. Dennoch lagen die erzielten Parameter des Protonenstrahls weit unter den erwarteten Werten. Die bekannten Faktoren, die diese Performance einschrĂ€nken, wurden fast ausschlieĂlich durch Simulationen identifiziert. Der experimentelle Zugang zur Laser-Plasma-Wechselwirkung ist bisher auf die Auswertung der resultierenden Strahlung und auf makroskopische OberflĂ€cheneffekte beschrĂ€nkt, die mit optischen Messtechniken untersucht werden können. Diese Diagnostiken liefern allerdings keinerlei Informationen ĂŒber die VorgĂ€nge im Inneren des Plasmas, die letztlich die Parameter der beschleunigten Protonen bestimmen. Diese Prozesse werden in ihrer GröĂe und Zeitskala durch die Plasmaoszillation bzw. deren Frequenz und WellenlĂ€nge bestimmt. Das Ziel dieses Forschungsprojekts war es, diese LĂŒcke in der Auflösung bestehender Messmethoden zu schlieĂen und eine Diagnostik zu entwickeln, die in der Lage ist, nanoskopische Plasma-PhĂ€nomene im Inneren der lasergetriebenen Probe zu untersuchen. Dieses Ziel konnten wir durch die EinfĂŒhrung von Röntgenkleinwinkelstreuung (SAXS) in Laserexperimenten an Röntgen-Freie-Elektronen-Lasern (XFELs) erreichen.
In dieser Arbeit erlĂ€utere ich das technische Design und die methodische Auswertung des ersten dedizierten SAXS Experiments, das an der Matter in Extreme Conditions Messstation (auch MEC, Materie unter extremen Bedingungen) der Linac Coherent Light Source (auch LCLS, Linearbeschleuniger als kohĂ€rente Lichtquelle) durchgefĂŒhrt wurde. Dieses Experiment war vorrangig eine Machbarkeitsstudie, die als Basis fĂŒr die weitere Verwendung von SAXS in Laserexperimenten dienen soll. Meine Arbeit wird ausfĂŒhrlich die dafĂŒr nötigen experimentellen Techniken, den Aufbau, die Reinigung des gemessenen Beugungsbilds, das Probendesign und den Auswerteprozess erlĂ€utern.
Um die experimentelle DurchfĂŒhrbarkeit dieser Methode zu testen, nutzten wir SAXS, um die Ausbreitung einer nanostrukturierten Probe in der Zeit kurz vor und wĂ€hrend des Beginns des Laserpulses zu messen. Der Ausbreitungsparameter, den wir so aus den experimentellen Daten gewinnen konnten, liegt im einstelligen Nanometer- und teilweise im Subnanometer-Bereich und stimmte gut mit den Ergebnissen einer Particle In Cell (PIC) Simulation zur frĂŒhen Ausbreitungsphase ĂŒberein. Dies zeigt, dass SAXS in der Lage ist, Plasma Prozesse zu messen, die fĂŒr andere Diagnostiken bisher nicht zugĂ€nglich waren.
AuĂerdem beobachteten wir eine Abweichung der experimentellen Daten von dem von uns entwickelten Modell zur Beschreibung der ungehinderten Ausbreitung des Plasmas ins Vakuum. Dies veranlasste uns zu einer genaueren Untersuchung der Ausbreitung mittels PIC Simulation und tatsĂ€chlich sahen wir darin die Bildung von Plasma-Strömen, die auch in der SAXS-Auswertung qualitativ bestĂ€tigt werden konnten. Die KomplexitĂ€t des Ausbreitungsprozesses, die wir in diesem Forschungsprojekt aufdecken konnten, zeigt, dass weitere Studien dazu durchgefĂŒhrt werden sollten. Wenn wir die Ergebnisse der hier prĂ€sentierten SAXS Modelle nutzen, um unser VerstĂ€ndnis des Effekts von Vorpulsen und IntensitĂ€ts-Plateaus auf die Protonenbeschleunigung mit nanostrukturierten Proben zu verbessern, werden wir zukĂŒnftig in der Lage sein, die damit erzielten Strahlparameter zu verbessern.
Der entwickelte SAXS Aufbau wurde auch an die Gegebenheiten von Experimenten zur Schockwellenverdichtung mittels Hochenergielasern angepasst und angewendet. Es gibt groĂes wissenschaftliches Interesse an der Entmischung von Kohlenwasserstoffen im Zustand warmer dichter Materie (WDM). Viele Laborastrophysikexperimente untersuchen das Innere von Eisriesen wie Uranus und Neptun, insbesondere den Verlauf der Phasentrennung von leichten Elementen wie Kohlenstoff und Wasserstoff, die zu Diamantregen fĂŒhrt.
Bisher war es bei diesen Messungen nicht möglich, nanoskopische DichteĂ€nderungen im Inneren einer dichten Probe unter extremen Bedingungen zu untersuchen. Im Rahmen dieser Forschungsarbeit wurde SAXS als ergĂ€nzende Diagnostik in Hochenergiedichte-Experimenten mit Lasern an Einrichtungen wie an der MEC Messstation und an anderen XFELs etabliert. Ich wendete bekannte SAXS Auswerteroutinen auf den besonderen Fall eines sich von Schuss zu Schuss Ă€ndernden Dichtekontrasts an. Die verschiedenen Komponenten der SAXS Daten wurden mit den Informationen korreliert, die aus anderen Diagnostiken wie Beugung und VISAR gewonnen wurden. So konnte ich durch die Auswertung der Nanodiamant-Komponente eine SchĂ€tzung der DiamantgröĂe und des Diamant-Volumenanteils ableiten, indem ich spezifische Modelle fittete, die auf hydrodynamischen Simulationen basieren.
ZukĂŒnftig möchten wir diese experimentellen Grundlagen auch auf die Untersuchung von FlĂŒssig-FlĂŒssig-Entmischung leichter Elemente im WDM Zustand anwenden. In dieser Arbeit erlĂ€utere ich die von mir entwickelten Auswerteprozesse, die auf weitere Messungen angewendet werden können, sobald deren Messbereich und SensitivitĂ€t so verbessert wurde, dass die Parameter von Interesse bestimmbar sind.
Dieses Projekt half dabei, SAXS als Standarddiagnostik in Forschungseinrichtungen zu etablieren, die XFELs mit Hochleistungslaserexperimenten verbinden. Es bereitet sowohl die technische als auch die methodische Grundlage fĂŒr weitere Experimente.Laser plasma acceleration with ultra-high intensity (UHI) lasers is a promising technology for building compact radiation sources. These hold immense potential for a wide array of applications including cancer therapy, laboratory astrophysics and inertial confinement fusion and there is great interest in their development in many interdisciplinary fields of research.
But while proof of concept experiments using proton pulses for tumor irradiation have delivered encouraging results, the achieved proton beam parameters fell short of the originally expected values. The limiting factors to this performance have mostly been identified in simulation only. Experimental access to the interaction between the drive laser and the dense plasma is so far limited to the analysis of the emitted radiation and the macroscopic surface effects that can be probed by visible light. These diagnostics cannot provide information about the processes in the bulk of the plasma that eventually determine the properties of the accelerated particles. Their spatial and temporal domain is dominated by the plasma oscillation frequency and wavelength. The aim of this project was to bridge this resolution gap with a diagnostic that is capable of investigating nanoscopic plasma features in the bulk of a laser-driven sample on a femtosecond scale. This was achieved by establishing the use of Small Angle X-Ray Scattering (SAXS) at UHI laser experiments at X-Ray Free Electron Lasers.
My thesis will outline the technical design and scientific analysis of the first dedicated SAXS experiment at the Matter in Extreme Conditions (MEC) instrument of the Linac Coherent Light Source. The primary goal of the experiment was proof of concept as a foundation for regular use of SAXS in UHI experiments in the future. I will discuss the experimental procedures, the setup, the cleaning of the diffraction pattern, the target design and the analysis process that were developed for this new diagnostic in detail.
To test the feasibility of this method, we used SAXS to measure the expansion of a nanostructured target in the femtosecond time span before and around the onset of a low intensity drive laser pulse. The expansion parameter that was extracted from the experimental data is in the in the sub- to single nanometer range and was in good agreement with the results of a particle-in-cell (PIC) simulation describing the early expansion phase. This demonstrates that SAXS is capable of measuring plasma processes on scales that were previously unobtainable by other diagnostics.
We also identified a deviation of the experimental data from the simple model that we developed to describe an unobstructed expansion of plasma into vacuum. This lead us to examine the expansion in more detail via PIC simulation and indeed we discovered the formation of plasma jets at a later phase of the plasma expansion in simulation for a grating target. This additional effect was confirmed qualitatively by the SAXS analysis. The complexity of the plasma expansion process for a structured target we found in this project demonstrates the need for further studies. If we use the SAXS models presented here to improve our understanding of the effect of prepulses and pedestals on proton acceleration using nanostructured targets, we can apply this knowledge to the improvement of the proton beam parameters in future developments. %Additionally the technical implementation of SAXS for UHI laser experiments was developed in the framework of this thesis and established as a useful tool for the investigation of other nanoscopic plasma features.
The developed experimental setup for SAXS was also adapted and applied to laser shock compression experiments using high energy drive lasers. There is great research interest in the demixing of hydrocarbons in the Warm Dense Matter (WDM) state. Many laboratory astrophysics experiments investigate the internal structure of ice giants like Uranus and Neptune, specifically the dynamics of the phase separation of light elements like carbon and hydrogen which can result in diamond rain. So far these measurements lacked a diagnostic that is capable of probing nanoscopic density modulations in the bulk of a dense target in an extreme state of matter. SAXS allowed us to gain access to the parameters of the demixing process. In the framework of this project SAXS was established as a complementary diagnostic to the standard setup for high energy density laser experiments at the MEC instrument and at other XFELs.
I applied existing SAXS analysis procedures to the special case of a density contrast that changes on every shot. The different components of the SAXS data were correlated to information from other standard diagnostics including diffraction and VISAR. I was able to quantitatively analyze the component caused by nanodiamonds and retrieved an estimate of the diamond size and volume fraction from fits to custom models that are based on hydrodynamic simulations.
In the future, we would like to extend this experimental basis to the investigation of liquid-liquid demixing of light elements in the WDM state. In this thesis I will discuss the SAXS analysis procedures that I dweveloped so that they can be applied to future measurements, once the experimental range and sensitivity has been improved to retrieve the parameters of interest.
This project helped to establish SAXS as a standard diagnostic at facilities combining XFELs with high power laser experiments. It is supposed to lay both the technical and methodical groundwork for further experiments
Mismarked Flesh: The Interpretability of the Male Body in Julio-Claudian Literature
This dissertation studies the increasing failure of the elite Roman male body to serve, as it had done for centuries, as an easily interpretable sign of social identity. The socio-political shift from Republic to Empire led to general disorientation and a crisis of male elite identity that found expression through depictions of the male body. Through Ovidâs Metamorphoses, Petroniusâ Satyrica, and Senecan drama, I study this preoccupation in light of the Roman socio-historical context and modern theories of bodily identity found in Kristeva, Spillers, and Scarry, among others. I argue that we can trace the frequent scenes of misrecognition and confusion and the preponderance of wounded, marked, and dismembered non-slave bodies to this identity crisis. The mutilated male body in Julio-Claudian literature becomes a nodal point for multiple intersecting anxieties about gender, class, and status in an uncertain world. Chapter One reviews the socio-political context of the early empire and contemporary theories of embodied identity, and surveys the scholarship on embodied masculinity in early imperial literature. Chapter Two shines light on the confusion of bodily signifiers in the disorienting worlds of Ovidâs Metamorphoses and of Augustan Rome, showing through such stories as Actaeon and Pyramus that failure to interpret signs or to act as an interpretable signifier can be disastrous. Chapter Three examines the new vulnerability of elite men in Augustusâ Rome through the mutilated and dehumanized male bodies of the Metamorphoses, including Marsyas and Hippolytus. Chapter Four connects the confusion of bodily signifiers with a larger failure of the body in Petroniusâ Satyrica and in Neronian Rome: whether they do not display legible social identities, fail to perform sexually, or are assaulted, bodies in Petroniusâ novel are problems. Chapter Five connects the abject bodies of Senecaâs Oedipus, Thyestes, and Phaedra to the violence of Neroâs reign, reading them as broken signifiers whose misinterpretation spells disaster for their onlookers. Chapter Six offers concluding thoughts, as well as case studies of Pompeyâs head in Lucanâs Bellum Civile and Herculesâ suffering in the pseudo-Senecan Hercules Oetaeus.Doctor of Philosoph
Modern meat: the next generation of meat from cells
Modern Meat is the first textbook on cultivated meat, with contributions from over 100 experts within the cultivated meat community.
The Sections of Modern Meat comprise 5 broad categories of cultivated meat: Context, Impact, Science, Society, and World.
The 19 chapters of Modern Meat, spread across these 5 sections, provide detailed entries on cultivated meat. They extensively tour a range of topics including the impact of cultivated meat on humans and animals, the bioprocess of cultivated meat production, how cultivated meat may become a food option in Space and on Mars, and how cultivated meat may impact the economy, culture, and tradition of Asia
Exotic Ground States and Dynamics in Constrained Systems
The overarching theme of this thesis is the question of how constraints influence collective behavior.
Constraints are crucial in shaping both static and dynamic properties of systems across diverse areas within condensed matter physics and beyond.
For example, the simple geometric constraint that hard particles cannot overlap at high density leads to slow dynamics and jamming in glass formers.
Constraints also arise effectively at low temperature as a consequence of strong competing interactions in magnetic materials, where they give rise to emergent gauge theories and unconventional magnetic order.
Enforcing constraints artificially in turn can be used to protect otherwise fragile quantum information from external noise.
This thesis in particular contains progress on the realization of different unconventional phases of matter in constrained systems.
The presentation of individual results is organized by the stage of realization of the respective phase.
Novel physical phenomena after conceptualization are often exemplified in simple, heuristic models bearing little resemblance of actual matter, but which are interesting enough to motivate efforts with the final goal of realizing them in some way in the lab.
One form of progress is then to devise refined models, which retain a degree of simplification while still realizing the same physics and improving the degree of realism in some direction.
Finally, direct efforts in realizing either the original models or some refined version in experiment today are mostly two-fold. One route, having grown in importance rapidly during the last two decades, is via the engineering of artificial systems realizing suitable models. The other, more conventional way is to search for realizations of novel phases in materials.
The thesis is divided into three parts, where Part I is devoted to the study of two simple models, while artificial systems and real materials are the subject of Part II and Part III respectively. Below, the content of each part is summarized in more detail.
After a general introduction to entropic ordering and slow dynamics we present a family of models devised as a lattice analog of hard spheres. These are often studied to explore whether low-dimensional analogues of mean-field glass- and jamming transitions exist, but also serve as the canonical model systems for slow dynamics in granular materials more generally.
Arguably the models in this family do not offer a close resemblance of actual granular materials. However, by studying their behavior far from equilibrium, we observe the onset of slow dynamics and a kinetic arrest for which, importantly, we obtain an essentially complete analytical and numerical understanding. Particularly interesting is the fact that this understanding hinges on the (in-)ability to anneal topological defects in the presence of a hardcore constraints, which resonates with some previous proposals for an understanding of the glass transition.
As another example of anomalous dynamics arising in a magnetic system, we also present a detailed study of a two-dimensional fracton spin liquid. The model is an Ising system with an energy function designed to give rise to an emergent higher-rank gauge theory at low energy.
We show explicitly that the number of zero-energy states in the model scales exponentially with the system size, establishing a finite residual entropy.
A purpose-built cluster Monte-Carlo algorithm makes it possible to study the behavior of the model as a function of temperature. We show evidence for a first order transition from a high-temperature paramagnet to a low-temperature phase where correlations match predictions of a higher-rank coulomb phase.
Turning away from heuristic models, the second part of the thesis begins with an introduction to quantum error correction, a scheme where constraints are artificially imposed in a quantum system through measurement and feedback. This is done in order to preserve quantum information in the presence of external noise, and is widely believed to be necessary in order to one day harness the full power of quantum computers.
Given a certain error-correcting code as well as a noise model, a particularly interesting quantity is the threshold of the code, that is the critical amount of external noise below which quantum error correction becomes possible.
For the toric code under independent bit- and phase-flip noise for example, the threshold is well known to map to the paramagnet to ferromagnet transition of the two-dimensional random-bond Ising model along the Nishimori line.
Here, we present the first generalization of this mapping to a family of codes with finite rate, that is a family where the number of encoded logical qubits grows linearly with the number of physical qubits.
In particular, we show that the threshold of hyperbolic surface codes maps to a paramagnet to ferromagnet transition in what we call the 'dual'' random-bond Ising model on regular tessellations of compact hyperbolic manifolds. This model is related to the usual random-bond Ising model by the Kramers-Wannier duality but distinct from it even on self-dual tessellations. As a corollary, we clarify long-standing issues regarding self-duality of the Ising model in hyperbolic space.
The final part of the thesis is devoted to the study of material candidates of quantum spin ice, a three-dimensional quantum spin liquid. The work presented here was done in close collaboration with experiment and focuses on a particular family of materials called dipolar-octupolar pyrochlores.
This family of materials is particularly interesting because they might realize novel exotic quantum states such as octupolar spin liquids, while at the same time being described by a relatively simple model Hamiltonian.
This thesis contains a detailed study of ground state selection in dipolar-octupolar pyrochlore magnets and its signatures as observable in neutron scattering.
First, we present evidence that the two compounds Ce2Zr2O7 and Ce2Sn2O7 despite their similar chemical composition realize an exotic quantum spin liquid state and an ordered state respectively.
Then, we also study the ground-state selection in dipolar-octupolar pyrochlores in a magnetic field. Most importantly, we show that the well-known effective one-dimensional physics -- arising when the field is applied along a certain crystallographic axis -- is expected to be stable at experimentally relevant temperatures.
Finally, we make predictions for neutron scattering in the large-field phase and compare these to measurements on Ce2Zr2O7
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Sonic heritage: listening to the past
History is so often told through objects, images and photographs, but the potential of sounds to reveal place and space is often neglected. Our research project âSonic Palimpsestâ1 explores the potential of sound to evoke impressions and new understandings of the past, to embrace the sonic as a tool to understand what was, in a way that can complement and add to our predominant visual understandings. Our work includes the expansion of the Oral History archives held at Chatham Dockyard to include womenâs voices and experiences, and the creation of sonic works to engage the public with their heritage. Our research highlights the social and cultural value of oral history and field recordings in the transmission of knowledge to both researchers and the public. Together these recordings document how buildings and spaces within the dockyard were used and experienced by those who worked there. We can begin to understand the social and cultural roles of these buildings within the community, both past and present
Maternal transfer and toxicity pathways of hexabromocyclododecane in the fathead minnow (Pimephales promelas)
Hexabromocyclododecane (HBCD) is a persistent organic pollutant (POP) that undergoes maternal transfer and hinders development and growth of early-life stages of fish. However, there is limited understanding of the maternal transfer kinetics and subsequent molecular mechanisms that drive the embryotoxicity of HBCD. The purpose of this study was to (1) characterize the accumulation of dietary HBCD (11.5, 36.4, 106 mg/kg, ww [wet weight]) in adult fathead minnows (FHM) and the subsequent maternal transfer kinetics to eggs, and (2) link transcriptomics responses to apical and physiological effects in larvae exposed through maternal transfer at seven- and 14-days post-fertilization (dpf), respectively. Maternal transfer kinetics displayed similar egg-to-muscle ratios (EMR) in the low and medium treatment groups (1.65 and 1.27, respectively). However, the high treatment group deviated from other treatments with an EMR of 4.2, potentially due to reaching diffusion and/or lipid saturation limits. A positive correlation was observed between egg HBCD concentration and time of exposure. Larvae sampled at 7dpf revealed dysregulation of pathways involved in membrane integrity (inhibition of calcium channel) and metabolic processes (downregulation of amino acid, glucose, and lipid biosynthesis), while the larvae reared for 14 days exhibited a significant decrease in survival at the highest treatment condition. These results indicate that maternal transfer of HBCD is of concern in fish, which may act through indirect mechanisms involving the inhibition of membrane transport leading to disruption in metabolic processes, collectively resulting in energy depletion and subsequently mortality. This study is part of the EcoToxChip project (www.ecotoxchip.ca). The data derived will be used to inform the development of EcoToxChips, which are qPCR arrays that aim to predict apical endpoints of ecological and regulatory relevance for three model species and three native species for eight model chemicals
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