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The meshless Diffuse Approximate Method (DAM) is for the first time formulated and applied to simulate the compressible Newtonian flow of an ideal gas in an axisymmetric tube with varying cross-sections. The problem is structured by coupled partial differential equations for conservation of mass, momentum and energy, and the equation of state closure. These equations are solved in primitive variables and strong form. DAM is formulated on irregular node arrangement by using the second and third-order polynomial shape functions and Gaussian weights, leading to weighted least squares approximation on overlapping local subdomains. Pressure-velocity coupling is performed by the Pressure Implicit with Splitting of Operators (PISO) scheme. The solution of the represented novel application of DAM is verified by matching the meshless results with the fine-mesh finite -volume method results. The characteristics of meshless DAM for this kind of problem are systematically assessed by a detailed investigation of the varying node density, shape function order, Gaussian weight's shape, and the number of nodes in a local subdomain. The sensitivity study of DAM parameters shows that for the tested problems, the most suitable values of the Gaussian weight function and the number of nodes in a local subdomain are 5.0 and 13, respectively. Third-order convergence rate with better results is observed while using third-order polynomial shape functions.

In this letter, triangular-cavity bandpass filters are investigated in stackable multilayer technologies in order to achieve highly compact designs with reduced fabrication complexity. The triangular-shaped cavities are first introduced in the form of singlets and then expanded on as a novel method for achieving a quasi-triplet filter response, where the filter's input and output irises are utilized as resonating means for two additional passband poles. Exploitation of this advanced singlet scheme exemplifies innovative use of resonant irises for achieving highly compact filters that can be manufactured with simple multilayer fabrication steps for use in future terahertz applications. QC 20221214

Chemical looping combustion (CLC) enables efficient combustion of hydrocarbon fuels while also producing a gas stream with high CO2 concentrations, suitable for carbon capture and storage (CCS). CLC of biomass in combination with CCS results in efficient removal of carbon dioxide from the atmosphere, i.e., negative emissions. However, biomass and waste-derived fuels can contain significant fractions of aggressive ash precursors, which can affect the operability and functionality of oxygen carriers. In this paper, the fate of common ash elements will be investigated thermodynamically in a system utilizing iron-based oxygen carriers: ilmenite and iron oxide. Multiphase, multicomponent equilibrium calculations were performed using databases from FACT and a user-defined database, with a specific focus on alkali (K and Na) and heavy metals (Cu, Zn, and Pb). A detailed and comprehensive comparison with available literature data from experimental investigations was performed, and compounds not available in the databases were identified. Due to a lack of thermodynamic data in the literature, thermodynamic properties for four compounds, K0.85Fe0.85Ti0.15O2, K0.4Fe0.4Ti0.6O2, KTi8O16, and KTi8O16.5, were obtained from first-principles calculations. The fate of ash elements is studied for CLC of three biomass and waste-derived solid fuels under relevant CLC conditions: 950 °C in the fuel reactor and 1050 °C in the air reactor. Results show that the choice of the oxygen carriers largely influences the behavior of the ash elements. Compared to CLC with iron oxide, ilmenite is more beneficial with respect to high-temperature corrosion since less potassium is released into the gas phase since the titanium content in ilmenite immobilizes both potassium and calcium. For both oxygen carriers, the most corrosive compounds are expected to leave with the gas in the fuel reactor, keeping the air reactor free from chlorides. It was found that the compound KTi8O16 is stable in reducing conditions and low potassium concentrations. This is in conformity with previous experimental data, where this phase has been identified in the interior of ilmenite particles used in oxygen carrier aided combustion of wood chips. This article is part of the 2022 Pioneers in Energy Research: Anders Lyngfelt special issue.

Adhesive pili assembled through the chaperone–usher pathway are hair-like appendages that mediate host tissue colonization and biofilm formation of Gram-negative bacteria1–3. Archaic chaperone–usher pathway pili, the most diverse and widespread chaperone–usher pathway adhesins, are promising vaccine and drug targets owing to their prevalence in the most troublesome multidrug-resistant pathogens1,4,5. However, their architecture and assembly–secretion process remain unknown. Here, we present the cryo-electron microscopy structure of the prototypical archaic Csu pilus that mediates biofilm formation of Acinetobacter baumannii—a notorious multidrug-resistant nosocomial pathogen. In contrast to the thick helical tubes of the classical type 1 and P pili, archaic pili assemble into an ultrathin zigzag architecture secured by an elegant clinch mechanism. The molecular clinch provides the pilus with high mechanical stability as well as superelasticity, a property observed for the first time, to our knowledge, in biomolecules, while enabling a more economical and faster pilus production. Furthermore, we demonstrate that clinch formation at the cell surface drives pilus secretion through the outer membrane. These findings suggest that clinch-formation inhibitors might represent a new strategy to fight multidrug-resistant bacterial infections.

X-ray detectors based on dual-site-doped perovskite single crystals exhibit excellent sensitivity of 2.6 x 10(4) mu C Gy(air)(-1) cm(-2) under a low field of 1 V cm(-1). The detectable dose rate is as low as 7.09 nGy(air) s(-1). The operational stability is beyond half a year. Although three-dimensional metal halide perovskite (ABX(3)) single crystals are promising next-generation materials for radiation detection, state-of-the-art perovskite X-ray detectors include methylammonium as A-site cations, limiting the operational stability. Previous efforts to improve the stability using formamidinium-caesium-alloyed A-site cations usually sacrifice the detection performance because of high trap densities. Here we successfully solve this trade-off between stability and detection performance by synergistic composition engineering, where we include A-site alloys to decrease the trap density and B-site dopants to release the microstrain induced by A-site alloying. As such, we develop high-performance perovskite X-ray detectors with excellent stability. Our X-ray detectors exhibit high sensitivity of (2.6 +/- 0.1) x 10(4) mu C Gy(air)(-1) cm(-2) under 1 V cm(-1) and ultralow limit of detection of 7.09 nGy(air) s(-1). In addition, they feature long-term operational stability over half a year and impressive thermal stability up to 125 degrees C. We further demonstrate the promise of our perovskite X-ray detectors for low-bias portable applications with high-quality X-ray imaging and monitoring prototypes. Funding Agencies|National Natural Science Foundation of China [62004182, 61875072, 51863013, 61874052]; Key Research and Development Projects of Jilin Science and Technology Department [20200401044GX]; Excellent Young Foundation of Jiangxi Province [20192BCB23009]; Knut and Alice Wallenberg Foundation [KAW 2019.0082]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University ((faculty grant SFO-Mat-LiU) [2009-00971]

Conjugation is used by bacteria to propagate antimicrobial resistance (AMR) in the environment. Central to this process are widespread conjugative F-pili that establish the connection between donor and recipient cells, thereby facilitating the spread of IncF plasmids among enteropathogenic bacteria. Here, we show that the F-pilus is highly flexible but robust at the same time, properties that increase its resistance to thermochemical and mechanical stresses. By a combination of biophysical and molecular dynamics methods, we establish that the presence of phosphatidylglycerol molecules in the F-pilus contributes to the structural stability of the polymer. Moreover, this structural stability is important for successful delivery of DNA during conjugation and facilitates rapid formation of biofilms in harsh environmental conditions. Thus, our work highlights the importance of F-pilus structural adaptations for the efficient spread of AMR genes in a bacterial population and for the formation of biofilms that protect against the action of antibiotics.

Radiative cooling forms an emerging direction in which objects are passively cooled via thermal radiation to cold space. Cooling materials should provide high thermal emissivity (infrared absorptance) and low solar absorptance, making cellulose an ideal and sustainable candidate. Broadband solar-reflective or transparent coolers are not the only systems of interest, but also more pleasingly looking colored systems. However, solutions based on wavelength-selective absorption generate not only color but also heat and thereby counteract the cooling function. Intended as coatings for solar cells, we demonstrate a transreflective cellulose material with minimal solar absorption that generates color by wavelength-selective reflection, while it transmits other parts of the solar spectrum. Our solution takes advantage of the ability of cellulose nanocrystals to self-assemble into helical periodic structures, providing nonabsorptive films with structurally colored reflection. Application of violet-blue, green, and red cellulose films on silicon substrates reduced the temperature by up to 9 degrees C under solar illumination, as result of a combination of radiative cooling and reduced solar absorption due to the wavelength-selective reflection by the colored coating. The present work establishes self-assembled cellulose nanocrystal photonic films as a scalable photonic platform for colored radiative cooling. Funding Agencies|Knut and Alice Wallenberg foundation; Linkoping University; Wallenberg Wood Science Center; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; Swedish Foundation for Strategic Research; Wenner-Gren Foundations; Olle Engkvist Foundation [194-0679]; Swedish Research Council

Plasmonic nanometasurfaces/nanostructures possess strong electromagnetic field enhancement caused by resonant oscillations of free electrons, and has been extensively applied in biosensing, nanophotonic and photocatalysis. However, fabrication of uniform nanostructured metasurfaces by conventional methods is complicated and costly, which mitigates a wide-spread use of this technique in ubiquitous applications. Here, we present a facile and scalable method to fabricate an active nanotrench plasmonic gold substrate. The surface comprises sub-10 nm plasmonic nanogaps and their formation is assisted by a pre-fabrication of nano-imprinted polymer nano-well arrays. The plasmonic metasurface is optimized to maximize the density of the nano-trenches by tuning the substrate material, imprinting procedure and film deposition. We show that the surface Raman enhancement due to plasmonic resonances correlates well with trench density and reach a meritorious enhancement factor of EF > 105 over large surfaces. We further show that the electric field strength at the nanotrench features are well explained by finite element method simulations using COMSOL Multiphysics. The plasmonic substrate is transparent in the visible spectrum and conductive. In combination with a scalable bottom-up fabrication the plasmonic metasurface opens up for a wider use of the sensitive and reliable SERS substrate in applications such as portable sensing devices and for future internet of things.

The observed magnetic field of the Sun is believed to originate from a "dynamo-effect" in its convective surface layer. However, there is no natural 11-year timescale in such models. We show that this major magnetic solar cycle naturally may arise through magnetic "chaos- control" of the inherently chaotic solar dynamo, mainly due to Jupiter.

Adhesion pili assembled by the chaperone-usher pathway are superelastic helical filaments on the surface of bacteria, optimized for attachment to target cells. Here, we investigate the biophysical function and structural interactions that stabilize P pili from uropathogenic bacteria. Using optical tweezers, we measure P pilus subunit-subunit interaction dynamics and show that pilus compliance is contour-length dependent. Atomic details of subunit-subunit interactions of pili under tension are shown using steered molecular dynamics (sMD) simulations. sMD results also indicate that the N-terminal “staple” region of P pili, which provides interactions with pilins that are four and five subunits away, significantly stabilizes the helical filament structure. These data are consistent with previous structural data, and suggest that more layer-to-layer interactions could compensate for the lack of a staple in type 1 pili. This study informs our understanding of essential structural and dynamic features of adhesion pili, supporting the hypothesis that the function of pili is critically dependent on their structure and biophysical properties.

The paper has two parts, in the first part, we apply the localisation technique to the Rozansky-Witten theory on compact HyperK\"ahler targets. We do so via first reformulating the theory as some supersymmetric sigma-model. We obtain the exact formula for the partition function with Wilson loops on $S^1\times\Sigma_g$ and the lens spaces, the results match with earlier computations using Feynman diagrams on K3. The second part is motivated by a very curious preprint \cite{Gukov:2020lqm}, where the equivariant index formula for the dimension of the Hilbert space the theory is interpreted as a kind of Verlinde formula. In this interpretation, the fixed points of the target HyperK\"ahler geometry correspond to certain 'states'. In the second half of the paper we extend the formalism of part one to incorporate equivariance on the target geometry. For certain non-compact hyperK\"ahler geometry, we can apply the tilting theory to the derived category of coherent sheaves, whose objects label the Wilson loops, allowing us to pick a 'basis' for the latter. We can then compute the fusion products in this basis and we show that the objects that have diagonal fusion rules are intimately related to the fixed points of the geometry. Using these objects as basis to compute the dimension of the Hilbert space leads back to the Verlinde formula, thus answering the question that motivated the paper., Comment: 60 pages

Bacterial adhesion pili are key virulence factors that mediate host-pathogen interactions in diverse epithelial environments. Deploying a multimodal approach, we probed the structural basis underpinning the biophysical properties of pili originating from enterotoxigenic (ETEC) and uropathogenic (UPEC) bacteria. Using cryo-electron microscopy we solved the structures of three vaccine target pili from ETEC bacteria, CFA/I, CS17, and CS20. Pairing these and previous pilus structures with force spectroscopy and steered molecular dynamics simulations, we find a strong correlation between subunit-subunit interaction energies and the force required for pilus unwinding, irrespective of genetic similarity. Pili integrate three structural solutions for stabilizing their assemblies: layer-to-layer interactions, N-terminal interactions to distant subunits, and extended loop interactions from adjacent subunits. Tuning of these structural solutions alters the biophysical properties of pili and promotes the superelastic behaviour that is essential for sustained bacterial attachment.

Sub-ms 3D tracking of individual molecules in living cells is an important goal for microscopy since it will enable measurements at the scale of diffusion limited macromolecular interactions. Here, we present a 3D tracking principle based on the true excitation point spread function and cross-entropy minimization for position localization of moving fluorescent reporters that approaches the relevant regime. When tested on beads moved on a stage, we reached 67nm lateral and 109nm axial precision with a time resolution of 0.84 ms at a photon count rate of 60kHz, coming close to the theoretical and simulated predictions. A critical step in the implementation was a new method for microsecond 3D PSF positioning that combines 3D holographic beam shaping and electro-optical deflection. For the analysis of tracking data, a new point estimator for diffusion was derived and evaluated by a detailed simulation of the 3D tracking principle applied to a fictive reaction-diffusion process in an E. coli-like geometry. Finally, we successfully applied these methods to track the Trigger Factor protein in living bacterial cells. Overall our results show that it is possible to reach sub-millisecond live-cell single molecule tracking, but that it is still hard to resolve state transitions based on diffusivity at this time scale.

Background Clostridioides difficile is a spore forming bacterial species and the major causative agent of nosocomial gastrointestinal infections. C. difficile spores are highly resilient to disinfection methods and to prevent infection, common cleaning protocols use sodium hypochlorite solutions to decontaminate hospital surfaces and equipment. However, there is a balance between minimising the use of harmful chemicals to the environment and patients as well as the need to eliminate spores, which can have varying resistance properties between strains. In this work, we employ TEM imaging and Raman spectroscopy to analyse changes in spore physiology in response to sodium hypochlorite. We characterize different C. difficile clinical isolates and assess the chemical’s impact on spores’ biochemical composition. Changes in the biochemical composition can, in turn, change spores’ vibrational spectroscopic fingerprints, which can impact the possibility of detecting spores in a hospital using Raman based methods. Results We found that the isolates show significantly different susceptibility to hypochlorite, with the R20291 strain, in particular, showing less than 1 log reduction in viability for a 0.5% hypochlorite treatment, far below typically reported values for C. difficile. While TEM and Raman spectra analysis of hypochlorite-treated spores revealed that some hypochlorite-exposed spores remained intact and not distinguishable from controls, most spores showed structural changes. These changes were prominent in B. thuringiensis spores than C. difficile spores. Conclusion This study highlights the ability of certain C. difficile spores to survive practical disinfection exposure and the related changes in spore Raman spectra that can be seen after exposure. These findings are important to consider when designing practical disinfection protocols and vibrational-based detection methods to avoid a false-positive response when screening decontaminated areas. Graphical Abstract

We consider the partition function for Euclidean $SU(N)$ super Yang-Mills on a squashed seven-sphere. We show that the localization locus of the partition function has instanton membrane solutions wrapping the six "fixed" three-spheres on the $\mathbb{S}^7$. The ADHM variables of these instantons are fields living on the membrane world volume. We compute their contribution by localizing the resulting three-dimensional supersymmetric field theory. In the round-sphere limit the individual instanton contributions are singular, but the singularities cancel when adding the contributions of all six three-spheres. The full partition function on the ${\mathbb S}^7$ is well-defined even when the square of the effective Yang-Mills coupling is negative. We show for an $SU(2)$ gauge theory in this regime that the bare negative tension of the instanton membranes is canceled off by contributions from the instanton partition function, indicating the existence of tensionless membranes. We provide evidence that this phase is distinct from the usual weakly coupled super Yang-Mills and, in fact, is gravitational., Comment: 22 pages + 2 appendices, v3: minor revisions

Reducing the energy loss of sub-cells is critical for high performance tandem organic solar cells, while it is limited by the severe non-radiative voltage loss via the formation of non-emissive triplet excitons. Herein, we develop an ultra-narrow bandgap acceptor BTPSeV-4F through replacement of terminal thiophene by selenophene in the central fused ring of BTPSV-4F, for constructing efficient tandem organic solar cells. The selenophene substitution further decrease the optical bandgap of BTPSV-4F to 1.17 eV and suppress the formation of triplet exciton in the BTPSV-4F-based devices. The organic solar cells with BTPSeV-4F as acceptor demonstrate a higher power conversion efficiency of 14.2% with a record high short-circuit current density of 30.1 mA cm(-2) and low energy loss of 0.55 eV benefitted from the low non-radiative energy loss due to the suppression of triplet exciton formation. We also develop a high-performance medium bandgap acceptor O1-Br for front cells. By integrating the PM6:O1-Br based front cells with the PTB7-Th:BTPSeV-4F based rear cells, the tandem organic solar cell demonstrates a power conversion efficiency of 19%. The results indicate that the suppression of triplet excitons formation in the near-infrared-absorbing acceptor by molecular design is an effective way to improve the photovoltaic performance of the tandem organic solar cells. Reducing energy loss of sub-cells is critical for high performance tandem organic solar cells. Here, the authors design and synthesize an ultra-narrow bandgap acceptor through replacement of terminal thiophene by selenophene in the central fused ring, achieving efficiency of 19% for tandem cells. Funding Agencies|National Key Research and Development Program of China - MOST [2019YFA0705900]; National Natural Science Foundation of China [51820105003, 21734008, 61904181, 52173188]; Basic and Applied Basic Research Major Program of Guangdong Province [2019B030302007]; ONR [N000142012155]; U.S. DOE Office of Science User Facility [DE-AC02-05CH11231]

In this paper, we design and propose a compact label-free microfluidic lab-on-a-chip device to separate circulating tumor cells (CTCs) from red blood cells (RBCs) at low voltage to minimize cell damage. With the aim of developing a mm-long device to perform cell separation, we used 3D finite element simulation modeling and investigated separation efficiency for different electrode configurations, electrode shapes, and channel heights. Our results show that configuring the electrodes as two arrays, consisting of only five pairs of top and bottom planar electrodes shifted relative to each other and energized with ± 6 V at 70 kHz, generates sufficient non-uniform electric fields to separate CTCs and RBCs in a 2 mm long channel. The advantage of the proposed design is the simplicity of the electrode arrangement and that the electrodes do not cover the central part of the channel, thus allowing for brightfield imaging of the channel. In addition, the low voltage needed and the 50 µm high channel reduce the Joule heating effect and improve the device's separation and throughput efficiency. We suggest that the proposed design would be effective for separating CTCs and RBCs and, thus, used as a device for the early detection of CTCs.

Thinking About English-Medium Instruction: Do We Need Everything Everywhere All at Once? Around the world, more and more university courses are being taught in English. Although there are sound economic, social and political reasons for this trend, many questions remain about the pedagogical effects of EMI at university level: How can teachers be prepared for EMI teaching? Will students cope? Are some forms of teaching less suited to EMI? Do different disciplines have different needs? Etc. etc. In this workshop, I present some of the research I have carried out in Sweden that addresses these questions and make a number of recommendations. I finish the workshop by proposing a disciplinary literacy discussion matrix (Airey, 2011) as a tool for carrying out disciplinary needs analysis for EMI. References Airey, J. (2011). The disciplinary literacy discussion matrix: A heuristic tool for initiating collaboration in higher education. Across the disciplines, 8(3), 1-9.

Luminescent solar concentrators (LSCs) are large-area sunlight collectors for efficient solar-to-electricity conversion. The key point for highly efficient LSCs is the choice of fluorophores, which need to have broad absorption, high quantum yield and large Stokes shift. Among various fluorophores, carbon quantum dots (C-dots) hold great promise as eco-friendly alternatives to heavy-metal-containing quantum dots (QDs) due to their adjustable absorption and emission spectra, non-toxicity, low cost and eco-friendly synthetic methods. However, due to the limited absorption band and relatively low quantum yield in the red region, it is a challenge to obtain efficient LSCs based on C-dots. Here, we demonstrated highly efficient LSCs based on red-emissive C-dots. The as-synthesized C-dots have a cubic structure, broad absorption covering 300-600 nm, and red emission (peak located at 595 nm), with a high quantum yield of ∼65% and a large Stokes shift of 0.45 eV. Transient absorption experiments of the C-dots revealed the ultrafast formation of the broad emissive state (1 ps). Based on the excellent optical properties of the C-dots, the as-prepared large-area LSC (10 × 10 × 0.52 cm3) exhibited an optimized external optical efficiency of 4.81% and a power conversion efficiency of 2.41% under natural sun irradiation (70 mW cm−2). Furthermore, a tandem LSC using green-emissive C-dots (top layer) and red-emissive C-dots (bottom layer) as fluorophores exhibited an external optical efficiency as high as 6.78%. These findings demonstrate the possibility of using eco-friendly carbon-based nanomaterials for highly efficient large-area LSCs. Funder: Ca‘ Foscari University of Venice; Shandong Natural Science Funds for Distinguished Young Scholar (ZR2020JQ20); ÅFORSK Foundation; National Key Research and Development Program of China (2019YFE0121600)

Fluorescence methods have developed very strongly in the last decade, allowing single- molecule detection sensitivity, high specificity, high time- and spatial resolution, as well as high readout speeds. Together, this makes fluorescencea very central readout modality for biomolecular and cellular studies. The photophysics of the fluorescence emitters, fluorophores, used is of central importance or the performance. Here, the photostability and brightness ofthe fluorophores, but also their blinking properties set the limits of the performance. Fluorophore blinking, arising from photo-induced, non-fluorescent transient states of fluorophores, can however also be taken advantage of cellular and biomolecular studies. Blinking is a prerequisite for essentially allso-called fluorescence-based super-resolution techniques. Moreover, blinkingis often sensitive to micro-environmental parameters such as pH, oxygen concentrations,redox conditions and viscosity. This follows from the fact that the underlying, non-luminescent, dark transient states typically have 103 to 106 longer lifetimes than the fluorescent excited states of the fluorophores, thereby giving fluorescent molecules in the dark states more time to interactwith their surrounding in biological environment. It can thus be utilized as an alternative readout parameter to provide useful information on molecules and cells and their environments, beyond what can be monitored by traditional fluorescence methods. This thesis takes as one starting point the transient state (TRAST) spectroscopy technique, designed to monitor such long-lived, dark transient states, including triplet, photo-oxidation, photo-reduction and photo-isomerized states of fluorophores, by measuring how the time-averaged fluorescence signal detected in the sample is changed upon systematically varying the excitation modulation. The major focus of the present thesis work is to further extent the use of long-lived dark transient states of fluorescence emitters in solution, lipid membranes and live cells. For this different TRAST modalities were adapted and developed, and then demonstrated as useful characterization methods. First, we showed how the relaxed brightness requirements of TRAST made it possible to characterize the photo-physical properties of the high triplet yield carboxy-fluorescein dye and its brominated derivatives (paper I). By widefield TRAST measurements, we demonstrated its capability to sense heavy atom effect of bromine and iodide atoms, and how they affected the triplet and long-lived photo-oxidation states and their transitions rates. Next, we developed and demonstrated a concept based on TRAST method and its ability to distinguish fluorophores with different blinking properties as a way to perform fluorescence-based barcoding and multiplexing. This concept, demonstrated by exploiting the by TRAST well distinguishable photophysical transitions of two fluorescent dyes, which emit in the same spectral range, was demonstrated in paper II. In the same work, we also developed a TRAST modality for microfluidic measurements of molecules and lipid vesicles, on which the bar-coding concept could be demonstrated on-the-fly, as the molecules and vesicles passed through the microfluidic channel. Furthermore, with TRAST implemented in camera-based wide-field microscopy, multicolor barcoded images of cells with high spatial resolution could be further investigated for the first time due to the specific blinking dynamics of these labels. The last two papers of this thesis describe further extensions of the TRAST concept, and the monitoring of fluorescence blinking to live cell studies. In paper III, TRAST in a widefield microscopy setting was employed in combination with FCS to study the folding of dye-labelled RNA strands into G-quadruplex structures in solution and live cells using photo-isomerization kinetics of cyanine dye as a readout parameter. Here, we took advantage of the high sensitivity of cyanine dye photoisomerization, to viscosity and steric constraints,and the resulting blinking of the cyanines, to monitor conformation changes of RNAs in live cells. Finally, in paper IV, we demonstrated how it by TRAST imaging, taking advantage of the photo-induced dark states of a mitochondrial localization fluorophore (n-Nonyl Acridine Orange, NAO), is possible to give this localization probe environmental sensing properties as well. To sum up, the experimental findings and papers included in this thesis show that fluorescence blinking represent a rich source of information for biomolecular and cellular studies. By the TRAST technique, and the variants further adapted and developed in this work, it is shown that it possible tocapture this rich source of complementary information in a broad range of samples. The work in this thesis suggest that further combination of classical fluorescence readouts and a continued development of different TRAST modalities will open yet new windows and provide insights into molecular interaction studies in biological research. Fluorescensmetoder har utvecklats mycket starkt under det senaste decenniet, vilket har möjliggjort detektion av enstaka molekyler, med hög specificitet, hög upplösning i tid och rum, samt snabba avläsningshastigheter. Sammantaget gör detta fluorescens till en mycket central avläsningsmodalitet för biomolekylära och cellulära studier. Fotofysiken för de fluorescensmarkörer, fluoroforer, som används är av central betydelse hur fluorescensmetoder presterar. Här sätter fluoroforernas fotostabilitet och ljusstyrka, men också deras blinknings- egenskaper tydliga gränser för prestandan. Fluoroforblinkande, som härrör från fotoinducerade, icke-fluorescerande övergående tillstånd av fluoroforer, kan emellertid också utnyttjas inom cellulära och biomolekylära studier. Blinkande är en förutsättning för i stort sett alla så kallade fluorescensbaserade superupplösningstekniker. Dessutom är fluorophorers blinkningsbeteenden ofta känsliga för mikromiljöparametrar som pH, syrekoncentrationer, redoxförhållanden och viskositet. Detta följer av det faktum att de underliggande, icke-luminescerande, mörka transienta tillstånden vanligen har 103 till 106 gånger längre livslängder än de fluorescerande exciterade tillstånden hos fluoroforerna. Detta ger fluorescerande molekyler i mörka tillstånd mer tid att interagera med sin omgivning i biologiska miljöer. Blinkningskineitk hos fluoroforer kan således användas som en alternativ avläsningsparameter för att ge användbar information om molekyler, celler och deras miljöer, utöver vad som kan erhållas med traditionella fluorescensmetoder. Denna avhandling utgår från en spektroskopiteknik, s.k. transient state (TRAST) spectroscopy, utformad för att övervaka sådana långlivade, mörka transienta tillstånd, inklusive triplett, fotooxidation, fotoreduktion och fotoisomeriserade tillstånd av fluoroforer. Principen med TRAST bygger på att mäta hur den tidsgenomsnittliga fluorescenssignalen som detekteras i ett prov ändras vid systematisk variation av excitationsmoduleringen. Huvudfokus för denna avhandling är att utvidga möjligheterna med TRAST att monitorera långlivade mörka transienta tillstånd hos fluoroforer i lösning, lipidmembran och levande celler. För detta anpassade och utvecklade vi olika TRAST-modaliteter och visade sedan deras användbarhet i olika applikationer. Först visade vi hur de relativt låga krav på ljusemission från fluoroforer studerade med TRAST gjorde det möjligt att karakterisera de fotofysikaliska egenskaperna hos karboxy-fluorescein, en fluorofor med hög tripletformering (artikel I). Vi visade även metodens förmåga att känna av hur brom- och jodidatomer påverkade bildningen av långlivade triplett-tillstånd och fotooxidation hos karboxyfluorescein, samt de inblandade övergångshastigheterna. Därefter utvecklade och demonstrerade vi ett koncept baserat på TRAST-metoden och visade dess förmåga att särskilja fluoroforer med olika blinkningsegenskaper, som ett sätt att utföra fluorescensbaserad streckkodning och multiplexering. Detta koncept, demonstrerat genom att utnyttja de av TRAST väl urskiljbara fotofysiska övergångarna hos två olika fluoroforer som emitterar i samma spektralområde, demonstrerades i artikel II. I samma arbete utvecklade vi också en TRAST-modalitet för mikrofluidik-mätningar av molekyler och lipidvesiklar, i vilka streckkodningskonceptet kunde demonstreras när molekylerna och vesiklarna passerade genom mikrofluidkanalen. Dessutom, med TRAST implementerad i kamerabaserad widefield mikroskopi, visade vi att flerfärgade bilder av celler kan erhållas med hög rumslig upplösning, där för första gången blinkningsegenskaperna hos de olika fluorforerna kunde användas för att särskilja dem i cellerna. De två sista artiklarna i denna avhandling beskriver ytterligare utvidgningar av TRAST-konceptet, byggande på monitorering av fluorescensblinkningar i levande celler. I artikel III användes TRAST tillsammans med widefield mikroskopi samt FCS för att studera veckningen av färgämnesmärkta RNA-strängar till s.k. G-quadruplex-strukturer, i lösning samt i levande celler. Här utnyttjade vi fotoisomeriseringskinetiken och resulterande fluorescensblinkningar hos ett cyaninfärgämne som avläsningsparameter, och den höga känsligheten hos denna fotoisomerisering för viskositet och steriska begränsningar, för att övervaka konformationsförändringar av RNA i cellerna. Slutligen, i artikel IV, visade vi hur TRAST-avbildning gör det möjligt att utnyttja fotoinducerade mörka tillstånd hos en mitokondriell lokaliseringsfluorofor (n-Nonyl Acridine Orange, NAO), för att ge denna lokaliseringsprob även omgivnings-avkännande egenskaper. Sammanfattningsvis visar de experimentella resultaten och artiklarna som ingår i denna avhandling att fluorescensblinkningar representerar en rik källa till information för biomolekylära och cellulära studier. Genom TRAST-tekniken, och de varianter som ytterligare anpassats och utvecklats i detta arbete, visar vi att det är möjligt att utnyttja denna rika källa av kompletterande information i ett brett urval av prover. Arbetet i denna avhandling tyder på att ytterligare kombinationer av klassiska fluorescensavläsningar och en fortsatt utveckling av olika TRAST-modaliteter kommer att kunna öppna nya möjligheter för molekylära interaktionsstudier inom biologisk forskning. QC 2023-05-22

Scanning Electron Microscopy combined with Energy Dispersive X-ray Spectroscopy (SEM-EDS) is a widely applied elemental microanalysis method. The integration of silicon drift detectors (SDDs) has notably enhanced EDS performance, enabling precise elemental identification due to its large sensitive area and low output capacitance. Accurate simulations of SDDs can provide insights that enable the design and optimization of future models without the need for costly and time-consuming experimental iterations. Moreover, the current model-based quantification methods for EDS applications have reached their maximum predictive accuracy. As such, creating a more accurate simulation model could help achieve a higher level of precision in these quantification models, which would be immensely valuable for all EDS applications. With this objective in mind, a simulation framework for modeling SDDs in EDS was developed based on Geant4, Allpix Squared, and COMSOL Multiphysics. The simulation encompasses the entire physics pipeline, including characteristic X-ray emission from the target sample and its absorption in the detector. The generated charge carriers within the detector are propagated through the internal electric field of the SDD, and their individual charge contribution is measured to simulate EDS spectra. The simulated model was compared to existing literature and in-house experimental measurements, showing strong agreement in the case of a well-tuned SDD. Limitations of the simulation framework are discussed, and further research to enhance accuracy and speed is explored.

This paper presents a study on the optimization of floating offshore wind farms. The aim of this study is mainly to create a tool that can help determine the most profitable layout option for the floating offshore wind power company Windeed. This report contains an overview of wind power theory including wind roses, wake losses, fatigue loading, and construction theory. The methodology used for modeling and optimization is the programming language Python together with additional tools such as TopFarm and PyWake. Challenges in the process of designing the layout of a floating wind farm are discussed and the two mathematical models, Bastankhah Gaussian and NOJ, are compared for their ability to recreate wake effects. In the results, the discoveries of the study and the tool created for the company are presented. It was found that allowing freely placed turbines rather than placing the turbines in a strict hexagonal pattern, with shared anchors, gave notably higher annual power production for examined wind farms. Although the levelized cost of energy of the farms with hexagonal patterns were lower for some of the investigated scenarios. Some of the key factors that need to be considered when choosing layout for an off shore wind farm, as well as the potential improvements of the tool are also highlighted in the discussion chapter. Overall, this study provides valuable insights into the design and optimization of floating offshore wind farms.

Laboratory work and student motivation are two lead roles in physics education. Laboratory work provides a strategy to help students conceptualise about physical phenomena while student motivation is a more general but no less crucial part of all education and education research. Cognitive processes alone can not entirely explain how students understand things. Due to both these parts' importance in physics education it is important to not only examine them separately but to examine the relationship between the two, which prompts the purpose of this project. This project aims to examine the effect of laboratory work on student motivation. 15 university students' perspectives on this were qualitatively explored through semi-structured interviews. The participants were restricted to students at Uppsala University and KTH Royal Institute of Technology who had chosen a bachelor's, teacher's, or master's programme in physics or engineering. The interviews were transcribed, translated, and analysed. The theoretical framework for this project was attribution theory and the methodological framework was phenomenography. Through the analysis six categories of how laboratory work affects motivation emerged; inquiry, lab partner, teacher, use of time, structure, level of difficulty, and interest. From this, ten major conclusions were drawn; verifying the theory can be motivating, a higher level of inquiry is more motivating, external causes perceived as controllable decreases motivation, lab assistants may increase motivation, the time pressure may be unmotivating, attributing success to structure is motivating, the low level of difficulty is unmotivating, individual interest in physics is motivating, and a high level of inquiry could stimulate situational interest which in time may increase motivation. This provides an overview of how laboratory work affects motivation, partially explaining the relationship between these two lead roles. Laborativt arbete och studiemotivation är två huvudroller inom fysikutbildning. Laborativt arbete utgör en strategi för att hjälpa elever konceptualisera kring fysikaliska fenomen medan studiemotivation är en mer generell men inte mindre viktig del av all utbildning och utbildningsforskning. Kognitiva processer kan inte i sig självt fullkomligt förklara hur elever förstår saker. På grund av båda dessa delars betydelse i fysikutbildning så är det viktigt att inte bara undersöka dem separat utan att också undersöka sambandet mellan dem, vilket uppmanar till syftet med det här projektet. Det här projektet syftar till att undersöka effekten laborativt arbete har på studiemotivationen. 15 universitetsstudenters perspektiv på detta utforskades kvalitativt genom semistrukturerade intervjuer. Deltagarna begränsades till studenter vid Uppsala universitet och Kungliga Tekniska Högskolan som har valt ett kandidat-, lärar-, eller masterprogram inom fysik eller ingenjörsteknik. Intervjuerna transkriberades, översattes, och analyserades. Det teoretiska ramverket för det här projektet var attributionsteori och det metodologiska ramverket var fenomenografi. Genom analysen kunde sex kategorier av hur laborativt arbete påverkar motivation klargöras; inquiry, laborationspartner, lärare, tidsfördelning, struktur, svårighetsgrad, och intresse. Utifrån dessa så kunde tio huvudsakliga slutsatser dras; det kan vara motiverande att verifiera teorin, det är mer motiverande med en högre grad av inquiry, yttre faktorer som uppfattas kontrollerbara minskar motivationen, labbassistenter kan vara motiverande, tidspressen kan vara omotiverande, att tillskriva lyckade utfall till stuktur är motiverande, en låg svårighetsgrad är omotiverande, individuellt intresse för fysik är motiverande, och att en högre nivå av inquiry kan stimulera ett situationellt intresse vilken kan öka motivationen över tid. Det här ger en överblick över hur laborativt arbete påverkar motivation, vilket delvis förklarar sambandet mellan dessa två huvudroller.

We study four-point functions of spinning operators in the flavor current multiplet in four dimensional N = 2 SCFTs, using superspace techniques. In particular we explicitly construct the differential operators relating the different components of the super-correlator. As a byproduct of our analysis, we report the computation of the four-point amplitudes of gluons in bosonic Yang-Mills theories on AdS(5) and we give evidence of an AdS double copy relation between the gluon amplitude and its gravitational counterpart.

Complex systems research seeks to explain emergent properties in social, technological, and biological systems that result from interactions between their components. As data on the intricate relationships within these systems become increasingly available, there is a growing need for more sophisticated models to describe them accurately and offer deeper insights. This thesis addresses challenges in incorporating higher-order interactions and dynamics into the analysis of complex systems that go beyond standard network approaches. It covers mapping changing network organizations, modeling higher-order dynamics on ordinary networks, integrating network structure and metadata, and modeling multibody interactions. The thesis offers new tools and models to enhance our understanding of how higher-order dynamics and interactions shape the organization and give rise to the function of complex systems by providing more accurate representations than traditional network models. These findings pave the way for new research in network science. Forskning om komplexa system strävar efter att förklara egenskaper som uppstår i sociala, teknologiska och biologiska system genom samspel mellan deras delar. När allt mer data om dessa relationer blir tillgänglig ökar behovet av mer avancerade modeller för att beskriva systemen korrekt och ge djupare insikter. Den här avhandlingen tar upp utmaningar med att inkludera högre ordningens interaktioner och dynamik i analysen av komplexa system, genom att använda högre ordningens nätverksmodeller. Den behandlar kartläggning av förändrade nätverksstrukturer, modellering av högre ordningens dynamik i vanliga nätverk, kombinering av nätverksstruktur och metadata samt modellering av flerkroppsinteraktioner. De nya verktygen och modellerna ökar vår förståelse för hur högre ordningens dynamik och interaktioner påverkar organisationen och funktionen hos komplexa system. Detta görs genom att erbjuda mer precisa representationer än traditionella nätverksmodeller. Dessa resultat öppnar upp för framtida forskning inom nätverksvetenskap.

Dielectrophoresis is an electric field-based technique for moving neutral particles through a fluid. When used for particle separation, dielectrophoresis has many advantages compared to other methods, providing label-free operation with greater control of the separation forces. In this paper, we design, build, and test a low-voltage dielectrophoretic device using a 3D printing approach. This lab-on-a-chip device fits on a microscope glass slide and incorporates microfluidic channels for particle separation. First, we use multiphysics simulations to evaluate the separation efficiency of the prospective device and guide the design process. Second, we fabricate the device in PDMS (polydimethylsiloxane) by using 3D-printed moulds that contain patterns of the channels and electrodes. The imprint of the electrodes is then filled with silver conductive paint, making a 9 pole comb electrode. Lastly, we evaluate the separation efficiency of our device by introducing a mixture of 3 $\mu$m and 10 $\mu$m polystyrene particles and tracking their progression. Our device is able to efficiently separate these particles when the electrodes are energized with $\pm$12 V at 75 kHz. Overall, our method allows the fabrication of cheap and effective dielectrophoretic microfluidic devices using commercial off-the-shelf equipment., Comment: 1 supporting information file

The use of heavy vehicles in rough terrain is vital in the industry but has negative implications for the climate and ecosystem. In addition, the demand for improved efficiency underscores the need to enhance these vehicles' navigation capabilities. Navigating rough terrain presents distinct challenges, including deformable soil, surface roughness, and spatial and temporal terrain variability. Focusing on forestry, this thesis aims to improve navigation using machine learning and physics simulations. Without considering the vehicle-terrain dynamics, methods for navigation can result in unsafe or unnecessarily challenging situations. Specifically, we address route planning, control for autonomous vehicles, and soilde formations. We simulate soil using the discrete element method and vehicles using multibody dynamics. To enhance route planning, we train a predictor model that uses a height map of the terrain to predict measures of traversability. The model has a directional dependency, couples geometric terrain features with vehicle design and dynamics, and allows for swift evaluations over large areas. The proposed method facilitates detailed route planning, using multiple objectives to yield efficient solutions. We address autonomy in rough terrain navigation by training a controller through deep reinforcement learning. The control policy uses a local height map for perception to plan and control a forwarder with actively articulated suspensions. The controller adapts to overcome various obstacles and demonstrates skilled driving in rough terrain. Extending beyond simulation, we address the simulation-to-reality gap of vehicles with complex hydraulic drivelines through system identification and domain randomization. The results show that having an accurate model of the actuators, modelling system delays, and preventing bang-bang control yields successful transfer. Controllers that train in simulation and transfer to reality are a step toward autonomous vehicles. While the previously mentioned studies assume rigid terrain, we also answer if the discrete element method can capture large soil deformations due to heavy traffic. The results show that the discrete element method can represent a wide variety of natural soil and that the resulting rut depths agree well with empirical models and experimental data, including multipass scenarios.

Materials 16(11), 4113 (2023). doi:10.3390/ma16114113, Published by MDPI, Basel

The aim of this study is to contribute to more knowledge about how pedagogical link-making can be used to make the subject content of physics visible in systematic investigations. The method used is a didactic exemplification in a design study, where pupils have been observed in the teaching through audio recording and field notes. The study was carried out in two teaching cycles and the sample of pupils consisted of two classes in 4th grade. We studied whether the subject content in a systematic investigation could be made visible to the pupils through specific pedagogical link-making processes. The result showed that link-making was less favorable in the practical aspects of a systematic investigation, but it created opportunities for feedback that promoted learning, together with emotional involvement. It turned out that the emotional involvement of the pupils does not alone lead to learning. Feedback on subject content was required to be able to lead the pupils towards new knowledge. It is therefore important that the teaching is not only planned based on creating an emotional commitment but also to link back to the subject content in different ways. Based on this insight, the original didactic model was revised, and a new draft of a didactic model was produced. The teacher needs to take responsibility for meeting the pupils in their emotions about the teaching and try to connect these with different types of knowledge to promote pupil learning, which was made visible in the new model. Syftet med denna studie är att bidra med mer kunskap om hur pedagogiskt länkskapande kan användas för att synliggöra fysikens ämnesinnehåll i systematiska undersökningar. Metoden som använts är en didaktisk exemplifiering i en designstudie, där elever har observerats i undervisningen genom ljudupptagning och fältanteckning. Undersökningen genomfördes i två undervisningscykler och elevurvalet bestod av två klasser i årskurs 4. Studien undersökte, om ämnesinnehållet i en systematisk undersökning kunde synliggöras för eleverna genom olika pedagogiskt länkskapande processer. Undersökningen visade att länkskapning var mindre gynnsamt i de praktiska momenten i en systematisk undersökning, men att det skapade möjligheter för en återkoppling som tillsammans med känslomässigt engagemang främjade ett lärande. Det visade sig att känslomässigt engagemang hos eleverna inte ensamt leder till ett lärande, utan det krävdes en återkoppling till någon form av ämnesinnehåll för att kunna leda eleverna vidare mot nya kunskaper. Det blir därmed av betydelse, att undervisningen inte enbart planeras utifrån att skapa ett känslomässigt engagemang, utan även för att koppla tillbaka till ämnesinnehållet på olika sätt. Utifrån denna insikt reviderades den ursprungliga didaktiska modellen och ett nytt utkast till en didaktisk modell togs fram. Läraren behöver ta ett ansvar i att möta eleverna i deras känslor för undervisningen och försöka koppla samman dessa med olika typer av kunskaper för att främja lärandet hos eleverna, detta synliggjordes i den nya modellen.

During interventional cardiology (IC), medical staff are exposed to scattered ionizing radiation from the patient, potentially leading to various radiation-induced health effects. Therefore, shielding devices are routinely used to reduce occupational exposure during IC procedures. This study explores how the positioning of shielding devices impacts radiation protection efficiency in clinical scenarios. The study aims to determine optimal setups and potential pitfalls that might significantly reduce the efficiency of the shielding devices. It also explores the relationship between DICOM-based production data, clinical observations, and phantom-based measurements to add knowledge to the research field of radiation protection in IC. Clinical DICOM-based production data from 4976 procedures were analyzed to identify C-arm projection angles used during different procedure types. This data and the results of an observational study were used to determine a scattered radiation measurement setup. A survey meter was used to measure air kerma at seven heights in the operator position while an anthropomorphic phantom was irradiated. The measurements were distributed over seven projections with 56 position combinations of the shielding devices. A total of 3171 measurements were performed. The measurements suggest significant variations in the operator dose depending on the projection and how the shielding devices are positioned. The most optimal combination of shielding devices was achieved when placing the table-mounted shield along the table, the ceiling-suspended shield caudal close to the phantom, and without the patient drape. Conversely, the least optimal combination was achieved when placing the table-mounted shield flared out, the ceiling-suspended shield cranial 10 cm above the phantom, and without the patient drape. The air kerma rate for these two shielding setups with the LAO25/CAUD30 projection was reduced from 0.19 μGy/s to 0.05 μGy/s at 110 cm from the floor. This height was shown to be the hardest to properly shield. Despite the implementation of the most optimal shielding combination, it is evident that certain heights present difficulties in effectively protecting the operator from scattered radiation.

When submerged under a liquid, the microstructure of a SuperHydrophobic Surface (SHS) traps a lubricating layer of gas pockets, which has been seen to reduce the skin friction of the overlying liquid flow in both laminar and turbulent regimes. More recently, spatially homogeneous SHS have also been shown to delay laminar–turbulent transition in channel flows, where transition is triggered by modal mechanisms. In this study, we investigate, by means of topology optimization, whether a spatially inhomogeneous SHS can be designed to further delay transition in channel flows. Unsteady direct numerical simulations are conducted using the spectral element method in a 3D periodic wall-bounded channel. The effect of the SHS is modelled using a partial slip length on the walls, forming a 2D periodic optimization domain. Following a density-based approach, the optimization procedure uses the adjoint-variable method to compute gradients and a checkpointing strategy to reduce storage requirements. This methodology is adapted to optimizing over an ensemble of initial perturbations. This study presents the first application of topology optimization to laminar–turbulent transition. We show that this method can design surfaces that delay transition significantly compared to a homogeneous counterpart, by inhibiting the growth of secondary instability modes. By optimizing over an ensemble of streamwise phase-shifted perturbations, designs have been found with comparable mean transition time and lower variance.

The machined surface integrity in the turning of hardened steels is adversely influenced by heat generation and friction which requires pacification of the temperature by the effective cooling-lubrication approach and cutting tool performance. The present research analyzes the surface integrity of hardened AISI 4140 steel during turning with recently developed scalable pulsed power plasma SPPP-AlTiSiN coated carbide tool under nanofluid-assisted minimum quantity lubrication (MQL). Zinc oxide nanoparticles and environmentally friendly radiator coolant are mixed to prepare the nano cutting fluid. This analysis addresses the various aspects of surface integrity concerning surface morphology, machined surface hardness, residual stress and white layer development, and machined surface finish under varying cutting parameters (depth of cut, speed, feed, nose radius). Response surface methodology (RSM) is suggested to predict and to optimize the surface roughness in hard turning. Thereafter, the predictive modelling and optimization results are implemented for economic analysis. According to the findings of the experiments, with a contribution of 58.18%, the feed rate possesses a high impact on the surface finish, followed by the nose radius (12.32%) and speed (0.85%). Consequently, the machined surface quality improved with the increase of the nose radius because of the minimum tool wear and due to the increase of the effective length of the cutting edge. At optimum cutting conditions, the tool life of SPPP-AlTiSiN coated carbide insert is noted as 46 minutes under nanofluid-MQL and consequently, it estimated the overall machining cost per component as Rs.23.12 in Indian currency.

Hollow microstructured-and nanostructured-materials (also known as core-shell particles) have got great attention as advanced materials due to their fascinating physicochemical properties and favourable application prospects in many fields. In recent years, a variety of synthesis strategies have been explored to fabricate core-shell particles with different morphologies, compositions, microstructures, and thereby versatile functionalities. Among the synthesis strategies, soft-templating with the usage of nanobubbles is a feasible and effective one. Many inorganic core-shell particles have been prepared by using nanobubbles as a template. Nevertheless, studies in this field have not been reviewed comprehensively yet. Herein, the paper firstly reviewed several critical aspects of nanobubbles, such as the formation methods, stability and stabilization strategies of nano-bubbles; Secondly, characteristics of core-shell particles prepared by using nanobubbles soft template were summarized, including formation mechanisms, morphologies, etc.; Lastly, concerns regarding nanobubbles as soft templates were also briefly discussed. De två första författarna delar förstaförfattarskapet

In this review study, we ask ourselves if decoherence theory can solve the problems of measurement in quantum mechanics. After an introduction to decoherence theory, we present the problem of preferred basis, the problem of non-observability of interference and the problem of definite outcomes. We present Zurek's theory of environment induced superselection rules and find that the problem of preferred basis and the problem of non-observability of interference can be solved through decoherence theory, but not the problem of outcomes, if we accept the eigenstate-eigenvalue link and the Born statistical interpretation. We reveal that these two concepts are essential in the Copenhagen interpretations of quantum mechanics, and give an account for von Neumann's and Wigner's conscious collapse interpretation as well as a detailed description of Bohr's and Heisenberg's interpretation. We discuss how Bohr's and Heisenberg's interpretation relates to decoherence with a special emphasis on the irreducibility of classical concepts as interpreted by Don Howard. During the discussion, we critique Wigner's use of the word "consciousness" as opposed to von Neumann's use, as well as Howard's decisively ontological approach to Bohr through an antithetical Kantian approach. We conclude by stating that decoherence theory cannot decisively solve the problem of definite outcomes of quantum mechanics, even when considering it in relation to the Copenhagen interpretation.

The black hole information paradox, which states that the evaporation of black holes due to Hawking radiation results in a violation of the conservation of quantum information, is arguably one of the most fundamental problems in all of modern physics. Through the equivalence principle, the essence of the problem can be understood and studied in the context of much simpler flat spacetime (described by the theory of special relativity); in this context the Hawking radiation takes the form of the so-called Unruh effect, a thermal effect in the vacuum of a Minkowski quantum field theory that can be measured by accelerated observers. In this essay, the Unruh effect is reviewed and derived from the first principles of special relativity and quantum field theory -- we emphasize the importance of horizon effects in this derivation. Moreover, its connection with black hole physics and applications to the information paradox is discussed and explored in the context of cosmological horizons. Informationsparadoxen handlar om hur avdustningen av svarta hål till följd av Hawkingstrålning bryter mot bevarandet av kvantinformation, och är ett av de mest fundamentala olösta problemen inom modern fysik. Genom ekvivalensprincipen kan problemet förstås och studeras i en en mycket enklare kontext, nämligen i en platt rumtid som beskrivs av speciell relativitetsteori. I denna kontext tar Hawkingstrålningen formen av den så kallade Unruhstrålningen, en termisk effekt i vakumet av en Minkowski-kvantfältteori som kan mätas av accelererande observatörer. Denna uppsats diskuterar och härleder Unruh-effekten från grundprinciper inom speciell relativitetsteori och kvantfältteori -- vi understryker framförallt påverkan av horisonteffekter. Slutligen diskuteras även Unruh-effektens koppling till svarta hål och informationsparadoxen.

With the growing need for secure and high-capacity communications, innovative solutions are needed to meet the demands of tomorrow. One such innovation is to make use of the still unutilized spatial dimension of light in communications, which has promising applications in both enabling higher data traffic as well as the security protocols of the future in quantum communications. The perhaps most promising way of realizing this technology is through spatial division multiplexing (SDM) in optical fibers. There are many challenges and open questions in implementing this, such as how perturbations to the signal should be kept under control and which type of optical fiber to use. Consequently, this thesis focuses on the implementation of SDM in few-mode fibers where the perturbation effects on the spatial distribution have been investigated. Following this investigation, an implementation of adaptive spatial mode control using a motorized polarization controller has been implemented. The mode control has been done with the focus on having relevance for quantum technology applications such as Quantum Key Distribution (QKD) and quantum random number generation (QRNG) but also for spatial division multiplexing (SDM) for general communications. For this reason, two evaluation metrics have been optimized for: extinction ratio and equal amplitude. The control algorithm used is an adaptation of the optimization algorithm Stochastic Parallel Gradient Descent (SPGD). Control has been achieved in stabilizing the extinction ratio of LP11a and LP11b over 12 hours with an average extinction ratio of 98 %. Additionally, equal amplitude between LP11a and LP11b has been achieved over 1 hour with an average relative difference of 0.42 % and 0.45 %. Out of the perturbation effects investigated; temperature caused large disturbances to the signal which later is corrected for with the implemented algorithm.

Bioprinting nerve conduits supplemented with glial or stem cells is a promising approach to promote axonal regeneration in the injured nervous system. In this study, we examined the effects of different compositions of bioprinted fibrin hydrogels supplemented with Schwann cells and mesenchymal stem cells (MSCs) on cell viability, production of neurotrophic factors, and neurite outgrowth from adult sensory neurons. To reduce cell damage during bioprinting, we analyzed and optimized the shear stress magnitude and exposure time. The results demonstrated that fibrin hydrogel made from 9 mg/mL of fibrinogen and 50IE/mL of thrombin maintained the gel’s highest stability and cell viability. Gene transcription levels for neurotrophic factors were significantly higher in cultures containing Schwann cells. However, the amount of the secreted neurotrophic factors was similar in all co-cultures with the different ratios of Schwann cells and MSCs. By testing various co-culture combinations, we found that the number of Schwann cells can feasibly be reduced by half and still stimulate guided neurite outgrowth in a 3D-printed fibrin matrix. This study demonstrates that bioprinting can be used to develop nerve conduits with optimized cell compositions to guide axonal regeneration.

Neutron detectors in the form of liquid organic scintillators are widely used for nuclear disarmament purposes. The main purpose of this thesis is to characterize the neutron detection efficiency of the organic liquid scintillator EJ-309 using Monte Carlo based simulations in the simulation program Geant4. The Monte Carlo simulation code was benchmarked using recorded light output data from a laboratory experiment and it was confirmed that the simulation code could reproduce data from this experiment. In order to characterize the efficiency of the neutron detector, the benchmarked code was used to simulate light output distributions of 241-Am-Be and Cf-252, an (α, n) and a spontaneous fission source respectively, where it was found that the two different types of sources could be distinguished. However, distinguishment between two different spontaneous fission sources was not possible, as simulations of the light output distribution of another spontaneous fission source, Pu-240, was similar to the one for Cf-252. The light output distributions from the simulations were compared to earlier research where good agreements were obtained. A quantitative study was also performed to determine how many detected neutrons were needed to properly be able to distinguish between the two sources 241-Am-Be and Cf-252, and the number was found to be 560. This value was considered low relative to the number of detected neutrons in the simulations, and hence, more quantitative studies are needed in order to verify this result. The absolute and intrinsic detection efficiency were also determined for varying threshold values of neutron energy.

The discovery of integrability in the planar limit of the AdS5/CFT4 correspondence has led to impressive progress in the study of string theory and four-dimensional N=4 Super-Yang-Mills. In particular, with the formulation of the Quantum Spectral Curve (QSC) the spectral problem is now solved. The QSC has demonstrated its versatility and usefulness in various other applications, including the study of Wilson lines, conformal bootstrap, and the calculation of structure constants. It would be highly desirable to extend the QSC from AdS5/CFT4 to other instances of the AdS/CFT correspondence, a program so far only fully completed for AdS4/CFT3. Achieving this objective requires a solid understanding of the foundation of the QSC, a so-called analytic Q-system. In this thesis and the included papers, we investigate Q-systems and their algebraic and analytic properties. Inspired by the ODE/IM correspondence we propose Q-systems that encode the conserved charges of integrable models with a simply-laced symmetry algebra. In particular, for the case of D(r) a powerful parameterization of the Q-system using pure spinors is employed to efficiently solve compact rational spin chains and find T-functions solving Hirota equations. The extension from D(r) to the non-simply laced algebra B(2)/C(2) is explained and detailed. While many features are similar the relation between the symmetry of the Q-system and that of the integrable model becomes more intricate. By introducing a new method dubbed Monodromy Bootstrap we construct new Quantum Spectral Curves based on gl(2|2). In particular, one curve is conjectured to describe planar string theory on AdS3 with pure RR-flux. We solve the curve in a weak coupling limit both analytically and numerically. We also discuss the problem of finding the eigenvalue spectrum of operators on the squashed seven-sphere coming from the compactification of eleven-dimensional supergravity. These eigenvalues are of importance for the mass spectrum of fields in AdS4.

The usage of neural networks to derive physical laws without any kind of pre-existing bias is a promising but relatively new field with the long-term goal to construct an artificial intelligence physicist that is able to derive physical laws from experimental data. In this project, a step is taken in the direction of solving complex problems by tackling the double pendulum, the simplest chaotic system. To do so, a neural network architecture, adapted from previous work, is used to find the relevant parameters of the system in multiple configurations of the pendulum. Afterwards, the possibility of a neural network derived general solution of the problem is discussed through the relevant aspects that increase its complexity.

High-grade gliomas (HGGs) are a type of malignant brain cancer, which include glioblastomas (GBMs). In adults, GBM is the most common malignant primary brain cancer. Attempts to treat patients with GBMs have been conducted for over a century, but the prognosis has only marginally improved. Current standard treatment involves surgical resection of the gross tumor volume (GTV), followed by radiotherapy and chemotherapy. Despite the efforts, the median survival for patients diagnosed with GBMs is less than 15 months. The inability to accurately determine the full extent of the tumor invaded regions in the brain is assumed to be the reason for the incurability of GBMs. In radiotherapy, the microscopic infiltration of normal tissue by tumor cells in the vicinity of the GTV is accounted for by extending the target into a clinical target volume (CTV). Current recommended margin widths for GBMs range from 15 to 30 mm. Despite a generous margin, the persistent recurrence of GBMs following treatment indicates that the CTV delineations currently used might fail to encompass the entirety of the tumor cell distribution, leaving clonogenic tumor cells untreated. To improve the CTV delineation and possibly treatment of GBMs, novel approaches in determining the tumor infiltrated regions have been suggested in the form of mathematical modeling. The aim of this project is to develop a mathematical model for the infiltration of glioma cells into normal brain tissue and implement it into a framework for predicting the full extent of tumor-invaded tissue for HGGs. This thesis is comprised of papers I–II, an overview of the methodology, results, and discussion of the work. The work herein is presented in order of: 1) model development; 2) model verification. Paper I explores the robustness and results of a mathematical model for tumor spread in terms of its input parameters. By applying the model to a large dataset, the behavior of the model could be investigated statistically, and optimal input parameters determined. The results of the tumor invasion simulations were compared in terms of volumes to the conventionally delineated CTVs, which were found not to adhere to the pathways of the simulated spread. Paper II used the resulting simulated invasions from paper I to predict the overall survival (OS) of the same cohort of cases. OS prediction was better predicted by the simulated volumes of the tumor spread than the size of the GTV. The results showed the potential of improving OS prediction and furthermore demonstrated a new methodology for indirect model verification that does not rely on histopathological data. Planned future work will revolve around dose prescription and plan optimization based on the simulated tumor spread, model investigation using artificial intelligence methods, and finally, practical implementation of the model into research versions of treatment planning systems.

In this study, the effect of AlN buffer layer structure and morphology on the GaN films deposited on Si (111) substrate by reactive DC magnetron sputtering have been studied. For structural and morphological characterization X-ray diffraction (XRD) and Scanning electron microscope (SEM) were used. It is found that AlN films without Al pre-deposition on Si have a poor crystalline quality due to the formation of an amorphous layer at Si/AlN interface. Various initial Al sputtering durations on Si substrate result in changing the AlN buffer layer’s quality and morphology and choosing proper deposition duration can improve AlN buffer layer and the subsequent GaN layer quality. It is found that more than 15 s Al pre deposition can suppress the amorphous layer formation and enhance the film quality. The Rocking curve FWHM for both in-plane and out-of-plane orientation decreased from 1.86 and 1.56 to 0.4 and 0.3 , respectively, by 4 minutes Al pre-deposition on Si, however, overlong Al deposition results in poor surface morphology. It is found that 15s Al deposition is sufficient to enhance the quality as well as keeping the surface relatively smooth. In addition, AlN films deposited at 1000 showed the best film quality. GaN films directly grown on Si showed a poor crystalline quality and surface morphology, improvement of quality and morphology was observed for GaN samples deposited on AlN buffer layer. Also, melt-back etching observed on the surface of GaN grown on Si without AlN buffer layer. It is found that duration of Al deposition has a significant effect on GaN surface morphology, Al layer deposition more than 15 s result in a rough surface for GaN films. With choosing the optimum duration of Al pre-deposition and proper growth temperature a good quality GaN with a smooth surface morphology can be produced.

This master’s thesis explores a space-division-multiplexing (SDM) platform fora delayed-choice experiment. SDM is a multiplexing technique for optical datatransmission that employs spatial modes in a multi- or few-mode fiber to increasethe transmission capacity. The spatial modes can thus be used as separate channels. SDM have shown great potential for quantum information systems, making it intriguing to investigate its broad applications by examining its use in adelayed-choice experiment. The delayed-choice experiment was proposed by J.A.Wheeler in 1978 explored the particle- and wave-like behavior of quantum particles and observe if the particle knows in advance if it should propagate as a waveor a particle through the experimental platform. Hence, it was suggested thatthe experiment should be changed after the particle entered the experimentalplatform. The experiment has afterward been realized in many different constellations but previous wave-particle delayed-choice experiments have not beendemonstrated with SDM nor with an all in fiber platform. The research involved modeling and constructing a SDM fiber-optic platform,only utilizing commercially available fiber optical telecommunication components. The platform was constructed with photonic lanterns, used as spatial division multiplexer and demultiplexer, and a two-input fiber Sagnac Interferometer,as a removable beam splitter. The system was tested with classical light but without difficulties, the platform could move to the quantum domain for performingthe delayed-choice experiment with single photons on the platform. The thesis resulted in a SDM platform with good performance for future measurement of bothparticle- and wave-like behavior of photons in a delayed-choice experiment.

LiDAR is a remote sensing technology that uses a laser to map the surrounding environment. With its many applications, for example in autonomous vehicles, LiDAR is a growing field within technology and research. The silicon photomultiplier (SiPM) is a solid state device commonly used in the receiving system of a LiDAR. However, ambient light from sun or other light sources is also seen by the photodetector which creates noise in the receiving system. The purpose of this work is to examine how the performance of a 1D LiDAR with a SiPM receiver can be predicted, given a certain level of ambient light, target reflectance and measuring distance. This was carried through by working with mathematical models and comparing the outcomes to lab measurements of a certain LiDAR model. The outcome showed that describing the performance of the particular LiDAR by a model based on incident photon rate was difficult mainly due to the unknown relation between how the voltage signal threshold in the receiving electric circuit for when the LiDAR stops the time measurement relates to the number of microcells activated in the SiPM during a time span. However, the results obtained suggest a threshold value of between around 20 and 60 microcells activated within a 1 ns time interval, but further tests are needed in order to confirm or reject this. Of the two other approaches tried, the signal voltage model gave reasonable results for the values tested but in a rather indirect way. The other approach, describing the connection between DC noise and AC RMS noise in the receiving system gave results deviating between 40% and 320% from the lab results, i.e. not so good match. LiDAR är en fjärranalysteknik som använder laser för att kartlägga ett geografiskt område. Med flertalet användningsområden, bland annat inom industrin för självstyrande fordon, är LiDAR ett växande teknik- och forskningsområde. Kisel-fotomultiplikatorn är en halvledarapparat som ofta används i LiDAR-mottagarsystemet. Bakgrundsljus från omgivningen detekteras dock också av fotodetektorn vilket orsakar brus i mottagarsystemet. Detta arbete syftar till att testa metoder för hur prestandan hos en 1D LiDAR med en kisel-fotomultiplikator i mottagaren kan estimeras, i en viss nivå av bakgrundsljus, med en viss målreflektans på ett visst mätavstånd. Detta utfördes genom att arbeta med matematiska modeller och jämföra dess resultat med resultat från laborativa tester på en viss LiDAR-modell. Det visade sig vara svårt att beskriva prestandan för denna LiDAR enligt en modell baserad på fotonflöde, huvudsakligen på grund av den okända kopplingen mellan tröskelnivån i termer av voltsignal i mottagarkretsen då tidmätningen stoppas och antalet aktiverade mikroceller i kisel-fotomultiplikatorn under ett visst tidsintervall. De resultat som erhölls visar dock på en träskelnivå någonstans mellan 20 och 60 mikroceller inom ett 1 ns tidsintervall, men ytterligare tester bör genomföras för att konfirmera eller förkasta detta. Av de övriga två angreppssätten prövade, gav modellen baserad på voltsignal rimliga resultat för värdena testade men på ett relativt indirekt sätt. Försök till beskrivning av sambandet mellan DC brus och AC RMS brus i mottagarsystemet gav resultat med mellan 40% och 320% avvikelse från de laborativa mätningarna, relativt dåligt alltså.

The investigation to understand the subsurface and its features has long been asubject of interest for various fields, including fields such as archaeology and infras-tructure projects. However, traditional excavation methods are often costly and time-consuming. In their place, alternative techniques such as borehole drilling, which isitself expensive, and ground-penetrating radar (GPR), which produces a good butdistorted image, have gained popularity. Nonetheless, the limitations of each methodimpede them from meeting the requirements of subsurface exploration. This Mas-ter’s thesis introduces an approach combining these two methods to overcome theirlimitations and enhance their accuracy to understand the subsurface.This thesis aims to demonstrate the feasibility and effectiveness of integratingborehole drilling and GPR for subsurface exploration. Specifically, the integrationof borehole with GPR-profiles will be examined to enhance their practicality andaccuracy, meaning that this thesis will investigate the utilization of borehole datato update and adjust GPR-profiles, thereby providing more precise and informativedata for further analysis.The findings of this work indicate that combining borehole drilling and GPR-profiling to improve and update the accuracy of the GPR-profiles is entirely feasibleand results in a substantially improved subsurface exploration capability. Further,the outcomes of this thesis suggest that the integrated approach can generate amore precise representation of the underground structure. Ultimately, the proposedintegration of borehole drilling and GPR-profiling presents a promising approach toenhance the accuracy and efficiency of subsurface exploration and has the potentialto be valuable in a wide range of fields.i

Understanding the interaction of water waves with winds and marine currents is a fundamental problem in geophysical fluid dynamics. From the point of view of hydrodynamic stability, surface waves are regarded as perturbations of an inviscid parallel shear flow modeling the wind in the air and the current in the water. For small two-dimensional perturbations, the linearization of the Euler equation of motion yields an eigenvalue problem to be solved for a given wavenumber k. The eigenfunction is a streamfunction obeying the so-called Rayleigh equation. The eigenvalue is a complex phase speed, c, whose real part is the actual phase speed of sheared waves while the imaginary part of kc is the growth rate of the wave amplitude. Using the smallness of the air/water density ratio and assuming no flow in the water, Miles solved this eigenvalue problem perturbatively in 1957. He uncovered an instability of the wind field due to a critical layer in the air, where the wind speed equals the phase speed of free surface waves, and showed that the growth rate of wind-waves is proportional to the square modulus of the solution of the Rayleigh equation at the critical level. This level is a regular singular point, which makes the resolution of the Rayleigh equation challenging. For that reason, an explicit expression of the growth rate of the Miles instability as a function of the wavenumber was lacking. Firstly, I designed a numerical scheme to solve the Rayleigh equation for an arbitrary monotonic wind profile. Secondly, I solved it analytically using asymptotic methods for long and short waves. In physical oceanography, a standard model for the mean turbulent wind field is the logarithmic profile, which contains only one length scale: the roughness length, z0 ~1 mm, accounting for the presence of waves on the water surface. I am interested in waves propagating due to gravity and surface tension, which have wavelengths ranging from a few millimeters to hundreds of meters. Hence, a natural small parameter is kz0, which I used to obtain long wave solutions of the Rayleigh equation, and subsequently the growth rate of the Miles instability. The comparison with both numerical and measured growth rates is excellent. Furthermore, I approximated the maximum growth rate in the strong wind limit, and inferred that the fastest growing wave is such that the aerodynamic pressure is in phase with the wave slope. I also considered the short wave limit of the eigenvalue problem. Using 1/(kL) as a small parameter, where L is a characteristic length scale of the shear, I found general asymptotic solutions for interfacial waves in presence of a wind and a current, where the density ratio does not need to be small. One application concerns the mixing of elements at the surface of white dwarfs. Moreover, short wave asymptotics provide insights on another instability. When waves have a phase speed that matches the current speed, there is another critical layer, in the water, which is responsible for the so-called rippling instability. I obtained a general asymptotic formula for the growth rate of this instability. Finally, I used my experience in solving eigenvalue problems to study, in collaboration with other researchers, wrinkles in thin elastic sheets floating on a liquid foundation. We had to solve a fourth order eigenvalue problem where the eigenvalue is the compressive load imposed on the sheet and the eigenfunction is the vertical displacement. For homogeneous sheets, the bending stiffness of the sheet is constant and the eigenvalue problem could be solved analytically. We found that the buckling shape has a symmetric and an antisymmetric mode. The mode associated with the minimum compressive load depends on the size of the confined sheet. Hence, there are changes of symmetry at certain confinement sizes for which the buckling shape is degenerate. We numerically showed that this degeneracy disappears for composite sheets, whose bending stiffness depends on space due to the presence of liquid inclusions.

As part of the development of the beam imaging system at the European Spallation Source, luminescent screens have been fabricated by the flame spraying of scintillating materials onto stainless steel backings. A total of seven screens were produced, three of chromia alumina (Al2O3:Cr), two of YAG (Y3Al5O12:Ce) and two of a 50/50 mix of these. The properties of these screens under proton irradiation were evaluated using a 2.55 MeV proton beam at currents of up to 10 A. Irradiation times were up to 25 h per sample, during which luminescence-, spectrographic-, thermal- and current-data was sampled at a rate of 1 Hz. Preliminary results of these measurements are reported here; with a quantitative analysis presented for one of the chromia alumina screens and a qualitative comparison of all three material types. The luminescent yield for chromia alumina was determined to be around 2000 photons/MeV for a virgin screen, and was found to drop to 1.5% after 167 mC of proton irradiation. A recovery of the luminescence of chromia alumina to >60% was observed after beam current was reduced for an 8 h period. Observations indicate that the YAG and mixed composition screens retain higher luminescence than the chromia alumina even at temperatures of over 200 °C. It is indicated that the luminescence from YAG feeds the R-lines of chromia alumina in the mixed composition screens.

Nanomaterials : open access journal 13(8), 1341 (2023). doi:10.3390/nano13081341, Published by MDPI, Basel