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This paper describes the creation and description of a nuclear fuel isotopics dataset for irradiated fuel salt from a Molten Salt Reactor (MSR). The dataset has been created using the Monte-Carlo particle transport code, Serpent 2.1.32 (released February 24, 2021) and the calculation code SOURCES 4C (released October 09, 2002). The dataset comprises isotopic mass densities of 1362 isotopes (including fission products and major and minor actinides) and their corresponding contributions to decay heat, gamma activity, and spontaneous fission rates computed by Serpent 2.1.32 as well as overall neutron emission rates from spontaneous fission and (ɑ, n) reactions computed by SOURCES 4C. These quantities are computed for a model MSR core utilizing a full-core 3D model of the Seaborg Compact Molten Salt Reactor (CMSR) . The dataset spans a wide range of values of burnup (BU), initial enrichment (IE) and cooling time (CT) over which the above-mentioned quantities are reported. The structure of the dataset includes isotopic mass densities (in g/cm3), followed by isotope-wise contributions to decay heat (denoted by suffix ‘DH’ and reported in Watts), gamma photon emission rates (denoted by suffix ‘GS’ and reported photos per second), and spontaneous fission rates (denoted by suffix ‘SF’ and reported in fissions per second). In addition to these columns, the data also includes total neutron emission rates from 1) spontaneous fission (denoted by ‘SF’ and reported in neutrons per second per cm3), and 2) (ɑ, n) reactions (denoted by ‘AN’ and reported in neutrons per second per cm3). In total, the dataset has 310,575 rows of different combinations of fuel burnup, initial enrichment, and cooling time (BIC) values spanning the realistic possible range of these parameters. The dataset is made available for public use in a comma-separated value file that can be easily read using one of the numerous popular data analysis tools such as NumPy or Pandas.

Electron magnetic circular dichroism (EMCD) is a powerful technique for estimating element-specific magnetic moments of materials on nanoscale with the potential to reach atomic resolution in transmission electron microscopes. However, the fundamentally weak EMCD signal strength complicates quantification of magnetic moments, as this requires very high precision, especially in the denominator of the sum rules. Here, we employ a statistical resampling technique known as bootstrapping to an experimental EMCD dataset to produce an empirical estimate of the noise-dependent error distribution resulting from application of EMCD sum rules to bcc iron in a 3-beam orientation. We observe clear experimental evidence that noisy EMCD signals preferentially bias the estimation of magnetic moments, further supporting this with error distributions produced by Monte-Carlo simulations. Finally, we propose guidelines for the recognition and minimization of this bias in the estimation of magnetic moments.

Density Functional Theory (DFT) is the prevalent first principles computational method for determining the stacking fault energy (SFE) of face centered cubic (fcc) metals and alloys. Due to several theoretical and computational challenges, SFE determination for interstitial alloys with alloying elements such as carbon, nitrogen, and hydrogen, has so far been limited to few studies at relatively high interstitial content. We propose a new method, rooted in the axial interaction model, that allows rapid and robust mapping of SFE for virtually arbitrary interstitial contents. Instead of computing the total energy of a very large supercell to represent dilute interstitial solutions, representative interstitial-affected and bulk regions are treated separately at the equivalent volume. The SFE is obtained by balancing the SFE values of the regions with a lever rule approach. The method matches SFE values from the axial interaction model within ≤4 mJ.m−2 error, as validated for non-magnetic fcc Fe-N and paramagnetic fcc Fe-N and AISI 304 alloys. The significantly reduced computational workload and equidistant SFE mapping vs. interstitial content down to extremely low values allows accurate fitting of the SFE vs. interstitial content with only few datapoints. This further improves the computational efficiency. So far DFT-based SFE mapping was limited to purely substitutional alloys; we demonstrate the first-time DFT-based SFE mapping in fcc AISI 304 vs. N and Ni, revealing a non-additive contribution of N and Ni to the SFE. Finally, the remaining challenges and future application for high-throughput DFT SFE computation in interstitial alloys is discussed.

Long-term durability is becoming increasingly relevant for capacitive deionization (CDI) as the technology emerges on the commercial scale. Short-term deionization studies have suggested that Faradaic leakages could be a major factor in electrode degradation, but the long-term effects are still unclear. In this study, we probe the degradation process of the desalination efficiency in commercial CDI modules for up to 52 days of non-stop operation. This corresponds to a little more than 100 m3 of water treated, and the lifetime production volume of the modules is estimated between 150,000–250,000 L of purified water. Surprisingly, the results demonstrate that the absolute long-term loss is largely linear with the cumulative charge leakage. This suggests short-term leakage currents could reasonably predict long-term degradation. Interestingly, the absolute loss mechanisms mean devices with higher total capacitance are more degradation resistant. Finally, shortening cycle times and other methods of reducing leakage would lead to a proportionally longer lifetime. Notably, the first 2 min of the 10 min operation retained 50 % of the performance with only 10 % of the leakage (10-fold reduction). In conclusion, the work provides a method for understanding, predicting, and reducing degradation in long-term operations with commercial CDI modules., QC 20240209

We report investigations of the magnetic textures in periodic multilayers [Pt(1 nm)/(CoFeB(0.8 nm)/Ru(1.4 nm)]10 using polarised neutron reflectometry (PNR) and small-angle neutron scattering (SANS). The multilayers are known to host skyrmions stabilized by Dzyaloshinskii-Moriya interactions induced by broken inversion symmetry and spin–orbit coupling at the asymmetric interfaces. From depth-dependent PNR measurements, we observed well-defined structural features and obtained the layer-resolved magnetization profiles. The in-plane magnetization of the CoFeB layers calculated from fitting of the PNR profiles is found to be in excellent agreement with magnetometry data. Using SANS as a bulk probe of the entire multilayer, we observe long-period magnetic stripe domains and skyrmion ensembles with full orientational disorder at room temperature. No sign of skyrmions is found below 250 K, which we suggest is due to an increase of an effective magnetic anisotropy in the CoFeB layer on cooling that suppresses skyrmion stability. Using polarised SANS at room temperature, we prove the existence of pure Néel-type windings in both stripe domain and skyrmion regimes. No Bloch-type winding admixture, i.e. an indication for hybrid windings, is detected within the measurement sensitivity, in good agreement with expectations according to our micromagnetic modelling of the multilayers. Our findings using neutron techniques provide valuable microscopic insights into the rich magnetic behavior of skyrmion-hosting multilayers, which are essential for the advancement of future skyrmion-based spintronic devices.

We study the EFT of a spinning compact object and show that with appropriate gauge fixing, computations become amenable to worldline quantum field theory techniques. We use the resulting action to compute Compton and one-loop scattering amplitudes at fourth order in spin. By matching these amplitdes to solutions of the Teukolsky equations, we fix the values of Wilson coefficients appearing in the EFT such that it reproduces Kerr black hole scattering. We keep track of the spin supplementary condition throughout our computations and discuss alternative ways to ensure its preservation.

Social semiotic discussions about the role played by representations in effective teaching and learning in areas such as physics have led to theoretical proposals that have a strong common thread: in order to acquire an appropriate understanding of a particular object of learning, access to the disciplinary relevance aspects in the representations used calls for the attainment of representational competence across a particular critical constellation of systematically used semiotic resources (which are referred to as modes, see more on this later). However, an affirming empirical investigation into the relationship between a particular object of learning and different representational formulations, particularly with large numbers of students, is missing in the literature, especially in the context of university -level physics education. To start to address, this research shortfall the positioning for this article is that such studies need to embrace the complexities of student thinking and application of knowledge. To achieve this, both factor and network analyses were used. Even though both approaches are grounded in different frameworks, for the task at hand, both approaches are useful for analyzing clustering dynamics within the responses of a large number of participants. Both also facilitate an exploration of how such clusters may relate to the semiotic resource formulation of a representation. The data were obtained from a questionnaire given to 1368 students drawn from 12 universities across 7 countries. The questionnaire deals with the refraction of light in introductorylevel physics and involves asking students to give their best prediction of the relative visual positioning of images and objects in different semiotically constituted situations. The results of both approaches revealed no one-to-one relationship between a particular representational formulation and a particular cluster of student responses. The factor analysis used correct answer responses to

Many strains among spore-forming bacteria species are associated with food spoilage, foodborne disease, and hospital-acquired infections. Understanding the impact of environmental conditions and decontamination techniques on the metabolic activity, viability, and biomarkers of these spores is crucial for combatting them. To distinguish and track spores and to understand metabolic mechanisms, spores must be labeled. Staining or genetic modification are current methods for this, however, these methods can be time-consuming, and affect the viability and function of spore samples. In this work, we investigate the use of heavy water for permanent isotope labeling of spores and Raman spectroscopy for tracking sporulation/germination mechanisms. We also discuss the potential of this method in observing decontamination. We find that steady-state deuterium levels in the spore are achieved after only ∼48 h of incubation with 30% D2O-infused broth and sporulation, generating Raman peaks at cell silent region of 2200 and 2300 cm−1. These deuterium levels then decrease rapidly upon spore germination in non-deuterated media. We further find that unlike live spores, spores inactivated using various methods do not lose these Raman peaks upon incubation in growth media, suggesting these peaks may be used to indicate the viability of a spore sample. We further observe several Raman peaks exclusive to deuterated DPA, a spore-specific chemical biomarker, at e.g. 988 and 2300 cm−1, which can be used to track underlying changes in spores involving DPA. In conclusion, permanent spore labeling using deuterium offers a robust and non-invasive way of labeling bacterial spores for marking, viability determination, and characterising spore activity.

Statistical mechanics has received limited attention in physics education research and remains a relatively underrepresented topic even in research on upper-division physics courses. The purpose of this study was to explore potential challenges that physics students encounter when they solve statistical mechanics problems in groups. Adopting a grounded approach, we video recorded and analyzed nine small student groups engaging in collaborative problem solving on the topic. The analysis involved iterative thematic coding, which gave rise to ten emergent categories of challenges. These were later divided into two broad groupings: challenges with concepts and challenges with problem-solving strategies. In the first grouping, we list seven identified categories related to the concepts of macrostates and microstates, distinguishable and indistinguishable particles, temperature, entropy, energy, equilibrium, heat bath, the Boltzmann distribution, and the partition function. In the second grouping, we list three categories related to the inappropriate application of common relations, difficulty managing tensions between calculated results and qualitative reasoning, and coming up with definitions of new and inconsistent concepts. Some of our findings are supported by existing research on the topic, and others are previously unreported. Based on our findings, we propose that future research should investigate the relations between the identified challenges on one hand, and students’ epistemological framing, reasoning, and use of multiple representations on the other. Finally, we suggest that teachers should spend time engaging students in a conceptual discussion of the central ideas of statistical mechanics, motivating the choice and pointing out limitations of commonly used toy models, and linking course content to real-world phenomena.

Absorbed radiation doses are essential in assessing the effects, e.g. safety and efficacy, of radiopharmaceutical therapy (RPT). Patient-specific absorbed dose calculations in the target or the organ at risk require multiple inputs. These include the number of disintegrations in the organ, i.e. the time-integrated activities (TIAs) of the organs, as well as other parameters describing the process of radiation energy deposition in the target tissue (i.e. mean energy per disintegration, radiation dose constants, etc). TIAs are then estimated by incorporating the area under the radiopharmaceutical's time-activity curve (TAC), which can be obtained by quantitative measurements of the biokinetics in the patient (typically based on imaging data such as planar scintigraphy, SPECT/CT, PET/CT, or blood and urine samples). The process of TAC determination/calculation for RPT generally depends on the user, e.g., the chosen number and schedule of measured time points, the selection of the fit function, the error model for the data and the fit algorithm. These decisions can strongly affect the final TIA values and thus the accuracy of calculated absorbed doses. Despite the high clinical importance of the TIA values, there is currently no consensus on processing time-activity data or even a clear understanding of the influence of uncertainties and variations in personalised RPT dosimetry related to user-dependent TAC calculation. As a first step towards minimising site-dependent variability in RPT dosimetry, this work provides an overview of quality assurance and uncertainty management considerations of the TIA estimation.

MoS2 is widely praised as a promising replacement for Pt as an electrocatalyst for the hydrogen evolution reaction (HER), but even today, it still suffers from low performance. This issue is tackled by using Mn3+ as a surface modifier to trigger sulfur vacancy formation and enhance electron transport in few-layered 2H MoS2. Only 10% of Mn is sufficient to transform the semiconductive MoS2 into an active HER electrocatalyst. The insertion of Mn reduces both HER onset potential and Tafel slope which allows reaching 100 mA/cm2 at an overpotential of 206 mV, ten times larger of what undoped MoS2 can achieve. The enhanced activity arises because Mn3+ introduces electronic states near the conduction band, promotes sulfur vacancies, and increases the hydrogen adsorption. In addition to its facile production and extended shelf-life, Mn–MoS2 exhibits an efficiency of 73% at 800 mA/cm2 and 2.0 V when used in proton exchange membrane water electrolyzers.

We consider the relationship between symmetries of two-dimensional autonomous dynamical systems in two common formulations; as a set of differential equations for the derivative of each state with respect to time, and a single differential equation in the phase plane representing the dynamics restricted to the state space of the system. Both representations can be analysed with respect to their symmetries, and we establish the correspondence between the set of infinitesimal generators of the respective formulations. We show that every generator of a symmetry of the autonomous system induces a well-defined vector field generating a symmetry in the phase plane and, conversely, that every symmetry generator in the phase plane can be lifted to a generator of a symmetry of the original system, which is unique up to constant translations in time. We exemplify the lift of symmetries in two cases; a mass conserved linear model and a non-linear oscillator.

Researchers generally agree that physics experts use mathematics in a way that blends mathematical knowledge with physics intuition. However, the use of mathematics in physics education has traditionally tended to focus more on the computational aspect (manipulating mathematical operations to get numerical solutions) to the detriment of building conceptual understanding and physics intuition. Several solutions to this problem have been suggested; some authors have suggested building conceptual understanding before mathematics is introduced, while others have argued for the inseparability of the two, claiming instead that mathematics and conceptual physics need to be taught simultaneously. Although there is a body of work looking into how students employ mathematical reasoning when working with equations, the specifics of how physics experts use mathematics blended with physics intuition remain relatively underexplored. In this presentation, we describe some components of this blending, by analyzing how physicists perform the rearrangement of a specific equation in cosmology. Our data consist of five consecutive forms of rearrangement of the equation, as observed in three separate higher education cosmology courses. This rearrangement was analyzed from a conceptual reasoning perspective using Sherin’s framework of symbolic forms. Our analysis demonstrates how the number of potential symbolic forms associated with each subsequent rearrangement of the equation decreases as we move from line to line. Drawing on this result, we suggest an underlying mechanism for how physicists reason with equations. This mechanism seems to consist of three components: narrowing down meaning potential, moving aspects between the background and the foreground and purposefully transforming the equation according to the discipline’s questions of interest. Finally, we discuss how being aware of the components of this underlying mechanism can potentially affect physics teachers’ practice when

Objective. To enable practical interferometry-based phase contrast CT using standard incoherent x-ray sources, we propose an imaging system where the analyzer grating is replaced by a high-resolution detector. Since there is no need to perform multiple exposures (with the analyzer grating at different positions) at each scan angle, this scheme is compatible with continuous-rotation CT apparatus, and has the potential to reduce patient radiation dose and patient motion artifacts. Approach. Grating-based x-ray interferometry is a well-studied technique for imaging soft tissues and highly scattering objects embedded in such tissues. In addition to the traditional x-ray absorption-based image, this technique allows reconstruction of the object phase and small-angle scattering information. When using conventional incoherent, polychromatic, hard x-ray tubes as sources, three gratings are usually employed. To sufficiently resolve the pattern generated in these interferometers with contemporary x-ray detectors, an analyzer grating is used, and consequently multiple images need to be acquired for each view angle. This adds complexity to the imaging system, slows image acquisition and thus increases sensitivity to patient motion, and is not dose efficient. By simulating image formation based on wave propagation, and proposing a novel phase retrieval algorithm based on a virtual grating, we assess the potential of a analyzer-grating-free system to overcome these limitations. Main results. We demonstrate that the removal of the analyzer-grating can produce equal image contrast-to-noise ratio at reduced dose (by a factor of 5), without prolonging scan duration. Significance. By demonstrating that an analyzer-free CT system, in conjuction with an efficient phase retrieval algorithm, can overcome the prohibitive dose and workflow penalties associated grating-stepping, an alternative path towards realizing clinical inteferometric CT appears possible., QC 20240219

The ability to detect and inactivate spore-forming bacteria is of significance within, for example, industrial, healthcare, and defense sectors. Not only are stringent protocols necessary for the inactivation of spores but robust procedures are also required to detect viable spores after an inactivation assay to evaluate the procedure’s success. UV radiation is a standard procedure to inactivate spores. However, there is limited understanding regarding its impact on spores’ spectral and morphological characteristics. A further insight into these UV-induced changes can significantly improve the design of spore decontamination procedures and verification assays. This work investigates the spectral and morphological changes to Bacillus thuringiensis spores after UV exposure. Using absorbance and fluorescence spectroscopy, we observe an exponential decay in the spectral intensity of amino acids and protein structures, as well as a logistic increase in dimerized DPA with increased UV exposure on bulk spore suspensions. Additionally, using micro-Raman spectroscopy, we observe DPA release and protein degradation with increased UV exposure. More specifically, the protein backbone’s 1600–1700 cm–1 amide I band decays slower than other amino acid-based structures. Last, using electron microscopy and light scattering measurements, we observe shriveling of the spore bodies with increased UV radiation, alongside the leaking of core content and disruption of proteinaceous coat and exosporium layers. Overall, this work utilized spectroscopy and electron microscopy techniques to gain new understanding of UV-induced spore inactivation relating to spore degradation and CaDPA release. The study also identified spectroscopic indicators that can be used to determine spore viability after inactivation. These findings have practical applications in the development of new spore decontamination and inactivation validation methods., Published as part of The Journal of Physical Chemistry B virtual special issue “Advances in Cellular Biophysics”.

This study investigated the irradiation-induced microstructure evolution in Fe, employing the Creation-Relaxation Algorithm and different interatomic potentials. The influence of self-interstitial atoms (SIAs), which were either locally or uniformly being distributed during the creation of the Frenkel pairs, was investigated on the evolving microstructure. The spatially localized distribution of SIAs, mimicking the low-energy transfer irradiation conditions, moderated the microstructure development, compared to uniform distribution of SIAs, delaying the nucleation of dislocation for higher irradiation doses. Introducing multiple Frenkel pairs facilitated a cumulative irradiation dose of 5 dpa in large supercells. In small supercells, the accumulation of SIAs led to the formation of an artificially stabilized self-interacting planar interstitial cluster, suggesting a minimum cell dimension of 10 nm for an accurate modeling of microstructure evolution when the development of the dislocation network is of interest. The formation and evolution of the C15 Laves phase structure were explored. The evolving C15 structure developed larger clusters with uniformly distributed SIAs, and their sizes depended on the interatomic potential employed. Finally, a comparison with experimental measurements demonstrated that the density and the average size of interstitial dislocation loops aligned well with those observed in experimentally irradiated ultra-high purity Fe at low and room temperatures., QC 20240223

This work is the second of a series of papers devoted to revisiting the properties of Heterotic string compactifications on ALE spaces. In this project we study the geometric counterpart in F-theory of the T-dualities between Heterotic ALE instantonic Little String Theories (LSTs) extending and generalising previous results on the subject by Aspinwall and Morrison. Since the T-dualities arise from a circle reduction one can exploit the duality between F-theory and M-theory to explore a larger moduli space, where T-dualities are realised as inequivalent elliptic fibrations of the same geometry. As expected from the Heterotic/F-theory duality the elliptic F-theory Calabi-Yau we consider admit a nested elliptic K3 fibration structure. This is central for our construction: the K3 fibrations determine the flavor groups and their global forms, and are the key to identify various T-dualities. We remark that this method works also more generally for LSTs arising from non-geometric Heterotic backgrounds. We study a first example in detail: a particularly exotic class of LSTs which are built from extremal K3 surfaces that admit flavor groups with maximal rank 18. We find all models are related by a so-called T-hexality (i.e. a 6-fold family of T-dualities) which we predict from the inequivalent elliptic fibrations of the extremal K3.

In this paper we consider classical and quantum versions of the critical long-range O(N) model, for which we study finite-size and finite-temperature effects, respectively, at large N. First, we consider the classical (isotropic) model, which is conformally invariant at criticality, and we introduce one compact spatial direction. We show that the finite size dynamically induces an effective mass and we compute the one-point functions for bilinear primary operators with arbitrary spin and twist. Second, we study the quantum model, mapped to a Euclidean anisotropic field theory, local in Euclidean time and long-range in space, which we dub fractional Lifshitz field theory. We show that this model admits a fixed point at zero temperature, where it displays anisotropic Lifshitz scaling, and show that at finite temperature a thermal mass is induced. We then compute the one-point functions for an infinite family of bilinear scaling operators. In both the classical and quantum model, we find that, as previously noted for the short-range O(N) model in [1], the large-N two-point function contains information about the one-point functions, not only of the bilinear operators, but also of operators that appear in the operator product expansion of two fundamental fields only at subleading order in 1/N, namely powers of the Hubbard-Stratonovich intermediate field., QC 20240226

Optical nanoscopy, also known as super-resolution optical microscopy, has provided scientists with the means to surpass the diffraction limit of light microscopy and attain new insights into nanoscopic structures and processes that were previously inaccessible. In recent decades, numerous studies have endeavored to enhance super-resolution microscopy in terms of its spatial (lateral) resolution, axial resolution, and temporal resolution. In this review, we discuss recent efforts to push the resolution limit of stimulated emission depletion (STED) optical nanoscopy across multiple dimensions, including lateral resolution, axial resolution, temporal resolution, and labeling precision. We introduce promising techniques and methodologies building on the STED concept that have emerged in the field, such as MINSTED, isotropic STED, and event-triggered STED, and evaluate their respective strengths and limitations. Moreover, we discuss trade-off relationships that exist in far-field optical microscopy and how they come about in STED optical nanoscopy. By examining the latest developments addressing these aspects, we aim to provide an updated overview of the current state of STED nanoscopy and its potential for future research., QC 20240122

The accurate description of non-ideal quantum many-body systems is of prime importance for a host of applications within physics, quantum chemistry, materials science, and related disciplines. At finite temperatures, the gold standard is given by ab initio path integral Monte Carlo (PIMC) simulations, which do not require any empirical input but exhibit an exponential increase in the required computation time for Fermionic systems with an increase in system size N. Very recently, computing Fermionic properties without this bottleneck based on PIMC simulations of fictitious identical particles has been suggested. In our work, we use this technique to perform very large (N <= 1000) PIMC simulations of the warm dense electron gas and demonstrate that it is capable of providing a highly accurate description of the investigated properties, i.e., the static structure factor, the static density response function, and the local field correction, over the entire range of length scales., QC 20240223

We revisit the space of gapped quantum field theories with a global O(N) symmetry in two spacetime dimensions. Previous works using S-matrix bootstrap revealed a rich space in which integrable theories such as the non-linear sigma model appear at special points on the boundary, along with an abundance of unknown models hinting at a non conventional UV behaviour. We extend the S-matrix set-up by including into the bootstrap form factors and spectral functions for the stress-energy tensor and conserved O(N) currents. Sum rules allow us to put bounds on the central charges of the conformal field theory (CFT) in the UV. We find that a big portion of the boundary can only flow from CFTs with infinite central charges. We track this result down to a particular behaviour of the amplitudes in physical kinematics and discuss its physical implications., QC 20240208

Using recent results in mathematics, I point out that free energies and scale-dependent central charges away from criticality can be represented in compact form where modular invariance is manifest. The main example is the near-critical Ising model on a thermal torus, but the methods are not restricted to modular symmetry, and apply to automorphic symmetries more generally. One application is finite-size effects., QC 20240206

Using recent results in mathematics, I point out that free energies and scale-dependent central charges away from criticality can be represented in compact form where modular invariance is manifest. The main example is the near-critical Ising model on a thermal torus, but the methods are not restricted to modular symmetry, and apply to automorphic symmetries more generally. One application is finite-size effects.

We investigate false vacuum decay of a relativistic scalar field initialized in the metastable minimum of an asymmetric double-well potential. The transition to the true ground state is a well-defined initial-value problem in real time, which can be formulated in nonequilibrium quantum field theory on a closed time path. We employ the nonperturbative framework of the two-particle irreducible (2PI) quantum effective action at next-to-leading order in a large-N expansion. We also compare to classical-statistical field theory simulations on a lattice in the high-temperature regime. By this, we demonstrate that the real-time decay rates are comparable to those obtained from the conventional Euclidean (bounce) approach. In general, we find that the decay rates are time dependent. For a more comprehensive description of the dynamics, we extract a time-dependent effective potential, which becomes convex during the nonequilibrium transition process. By solving the quantum evolution equations for the one- and two-point correlation functions for vacuum initial conditions, we demonstrate that quantum corrections can lead to transitions that are not captured by classical-statistical approximations., QC 20240118Nordita, Stockholm University

The present study reports the synthesis and physico-chemical characterization of Mn1−xZnxFe2O4 (x = 0.5, 0.4, 0.3, 0.2, 0.1) nanoparticles-based magnetic fluids with reference to magnetic fluid hyperthermia. The properties of these fluids are studied using XRD, FTIR, TGA, VSM and the induction heating equipment operated at 330 kHz. The heating response of the fluids is investigated within the safety limit of H·f (4.8 *108 A/m-s). The study is also extended to simulate it for the agarose gel phantom system. The power absorption by these samples in distilled water and in agarose gel is calculated to compare with the experimentally observed value. To the best of the author's knowledge, no study of temperature sensitive magnetic fluid is reported on agarose gel, which simulates or phantom an in vivo condition. Results analysis show that the control of hyperthermia temperature is possible at lower fields and frequencies for the A91 sample with the smallest possible concentration, which can be acceptable for in vitro study., QC 20240125

Natural pigments are sustainable compounds that can be employed as emitters, sensors and sensitisers in optoelectronics. The most abundant pigment, chlorophyll, offers advantages of easily available and plentiful feedstock, biodegradability and non-toxicity. However, strenuous extraction and separation limit its application on larger scale. In this work, a practically mild and scalable extraction and separation method for rapid isolation of chlorophyll a from spinach is presented. Three different stationary phases for column chromatography were evaluated, and a new solvent system was developed for the elution of chlorophyll a on a neutral alumina chromatography column. The purified product was obtained with a yield of 0.98 mg ⋅ g−1 with respect to the dry leaves. A first light-emitting electrochemical cell (LEC) based on chlorophyll a as the emitter is reported, using the extracted chlorophyll a as the guest compound dispersed in a blend-host matrix in a concentration of 2.5 or 5 mass %. The higher-chlorophyll-concentration LEC exhibits emission solely from the chlorophyll emitter, with the main emission peak located at 675 nm. The lower-chlorophyll-concentration LEC features two distinct emission bands, one in the red region that is originating from the chlorophyll guest and one in the blue region (main peak at 430 nm) that stems from the blend host. This combined red:blue emission can be attractive for, e. g., greenhouse applications, since it matches the action spectrum of plant photosynthesis.

We explore multi-log grasping using reinforcement learning and virtual visual servoing for automated forwarding in a simulated environment. Automation of forest processes is a major challenge, and many techniques regarding robot control pose different challenges due to the unstructured and harsh outdoor environment. Grasping multiple logs involves various problems of dynamics and path planning, where understanding the interaction between the grapple, logs, terrain, and obstacles requires visual information. To address these challenges, we separate image segmentation from crane control and utilise a virtual camera to provide an image stream from reconstructed 3D data. We use Cartesian control to simplify domain transfer to real-world applications. Because log piles are static, visual servoing using a 3D reconstruction of the pile and its surroundings is equivalent to using real camera data until the point of grasping. This relaxes the limits on computational resources and time for the challenge of image segmentation, and allows for data collection in situations where the log piles are not occluded. The disadvantage is the lack of information during grasping. We demonstrate that this problem is manageable and present an agent that is 95% successful in picking one or several logs from challenging piles of 2–5 logs., Mistra Digital Forest

This work explains the anomalously high runaway electron (RE) pitch angles inferred in the flat-top of dedicated Tokamak a Configuration Variable (TCV) experiments. Kinetic modelling shows that the resonant interaction between the gyromotion of the electrons and the toroidal magnetic field ripple will give rise to strong pitch angle scattering in TCV. The resulting increase in synchrotron radiation power losses acts as a RE energy barrier. These observations are tested experimentally by a magnetic field ramp-down, which gradually reduces the resonant parallel momentum at which the REs interact with the ripple. Resulting changes in synchrotron emission geometry and intensity are observed using three multi-spectral camera imaging systems, viewing the RE beam at distinct spatial angles in multiple wavelength ranges. Experimental reconstructions of the RE distribution in momentum- and real-space are consistent with kinetic model predictions., QC 20231211

Fabry–Pérot-based refractometry has demonstrated the ability to assess gas pressure with high accuracy and has been prophesized to be able to realize the SI unit for pressure, the pascal, based on quantum calculations of the molar polarizabilities of gases. So far, the technology has mostly been limited to well-controlled laboratories. However, recently, an easy-to-use transportable refractometer has been constructed. Although its performance has previously been assessed under well-controlled laboratory conditions, to assess its ability to serve as an actually transportable system, a ring-type comparison addressing various well-characterized pressure balances in the 10–90 kPa range at several European national metrology institutes is presented in this work. It was found that the transportable refractometer is capable of being transported and swiftly set up to be operational with retained performance in a variety of environments. The system could also verify that the pressure balances used within the ring-type comparison agree with each other. These results constitute an important step toward broadening the application areas of FP-based refractometry technology and bringing it within reach of various types of stakeholders, not least within industry., Originally included in thesis in manuscript form with title "Demonstration of a transportable refractometer by a ring-type comparison of dead-weight pressure balances at four European national metrology institutes".

It is crucial to develop functional electronic materials that can be processed from green solvents to achieve environmentally sustainable and cost-efficient printing fabrication of organic electronic devices. Here, the design and cost-efficient synthesis of two hydrophilic and emissive conjugated polymers, TQ-OEG and TQ2F-OEG, are presented, which are rendered hydrophilic through the grafting of oligo(ethylene glycol) (OEG) solubilizing groups onto the thiophene-quinoxaline conjugated backbone and thereby can be processed from a water:ethanol solvent mixture. It is shown that the introduction of the OEG groups enables for a direct dissolution of salts by the neat polymer for the attainment of solid-state ion mobility. These properties are utilized for the design and development of light-emitting electrochemical cells (LECs), the active materials of which can be solution cast from a water:ethanol-based ink. It is specifically shown that such an LEC device, comprising an optimized blend of the TQ2F-OEG emitter and a Li salt as the active material positioned between two air-stabile electrodes, delivers deep-red emission (peak wavelength = 670 nm) with a radiance of 185 µW m−2 at a low drive voltage of 2.3 V. This study contributes relevant information as to how polymers and LEC devices can be designed and fabricated to combine functionality with sustainability.

The concept of a color-kinematics duality is an important driving force in advancing the modern understanding of scattering amplitudes, in both field theory and string theory. Yet, open questions remain that motivate the need for a deeper understanding of the duality. A central open question is: do the kinematic numerators admit a Lie-algebraic origin, just like the corresponding color factors? The answer may be intimately related to a detailed understanding of the duality at the level of the Lagrangian. For pure Yang-Mills theory, a cubic Lagrangian which directly computes color-dual numerators is not yet known. In this thesis, we make progress in this direction by constructing a cubic Lagrangian in terms of the ordinary gauge field and a set of auxiliary fields. The contributions to the numerators are split into independent sectors specified by the number of contractions between polarization vectors. We find a novel Lagrangian with a finite number of fields and interactions that computes color-dual Yang-Mills numerators to any multiplicity, valid for sectors with up to two polarization contractions. In the context of string theory, insights from the color-kinematics duality have revealed interesting relations between string and field theory amplitudes. The sector of open bosonic string amplitudes where transcendental numbers are absent is known to be described by a higher-derivative field theory. The spectrum of this theory includes a massless gauge field and extra massive modes: by integrating the latter out from the Lagrangian, we obtain an expansion in the inverse string tension, which is a low-energy effective description of the dynamics of the massless modes of the bosonic string. This thesis develops the general method and explicitly writes down the operators entering the effective Lagrangian through fourth order in the inverse string tension.

Protons in low-barrier superstrong hydrogen bonds are typically delocalized between two electronegative atoms. Conventional methods to characterize such superstrong hydrogen bonds are vibrational spectroscopy and diffraction techniques. We introduce soft X-ray spectroscopy to uncover the electronic fingerprints for proton sharing in the protonated imidazole dimer, a prototypical building block enabling effective proton transport in biology and high-temperature fuel cells. Using nitrogen core excitations as a sensitive probe for the protonation status, we identify the X-ray signature of a shared proton in the solvated imidazole dimer in a combined experimental and theoretical approach. The degree of proton sharing is examined as a function of structural variations that modify the shape of the low-barrier potential in the superstrong hydrogen bond. We conclude by showing how the sensitivity to the quantum distribution of proton motion in the double-well potential is reflected in the spectral signature of the shared proton.

Metal-organic frameworks (MOFs) are a rapidly growing class of materials that offer great promise in various applications. However, the synthesis remains challenging: for example, a range of crystal structures can often be accessed from the same building blocks, which complicates the phase selectivity. Likewise, the high sensitivity to slight changes in synthesis conditions may cause reproducibility issues. This is crucial, as it hampers the research and commercialization of affected MOFs. Here, it presents the first-ever interlaboratory study of the synthetic reproducibility of two Zr-porphyrin MOFs, PCN-222 and PCN-224, to investigate the scope of this problem. For PCN-222, only one sample out of ten was phase pure and of the correct symmetry, while for PCN-224, three are phase pure, although none of these show the spatial linker order characteristic of PCN-224. Instead, these samples resemble dPCN-224 (disordered PCN-224), which has recently been reported. The variability in thermal behavior, defect content, and surface area of the synthesised samples are also studied. The results have important ramifications for field of metal-organic frameworks and their crystallization, by highlighting the synthetic challenges associated with a multi-variable synthesis space and flat energy landscapes characteristic of MOFs. It performed an interlaboratory study of the synthesis of the metal-organic frameworks (MOFs) PCN-222 and PCN-224. Ten participants independently synthesized the two MOFs and the products are analyzed, primarily by X-ray diffraction. The success rates are low (one-three samples corresponding to a pure sample of the correct phase), thus highlighting the problems with irreproducibility in MOF synthesis. image

This work is a preliminary study of the background of a search for dark, long-lived particles in the IceCube detector. The high flux of atmospheric muons in IceCube is considered background to the detector's primary science goal, which is to detect astrophysical neutrinos through the emission of Cherenkov radiation. However, high muon rates may break fresh ground for the detection of hypothetical dark particles. These could be created during the Bremsstrahlung-like interaction of an energetic muon and decay into a muon and an electron. Such an event is expected to produce a characteristic signal in the detector: A track-like signal produced by the Cherenkov-photon emitting muon, followed by a gap due to the electric neutrality of the dark particle. The subsequent decay of the dark particle into a muon produces a further track-like signal. In order to probe the success rate of this endeavor, two precursory statistical analyses are made using simulated data provided by CORSIKA. In order to obtain a clear track-gap signature that is not diluted by other particles, atmospheric muons should preferably travel in a bundle of few to no other muons. The muon multiplicity in incident bundles is estimated. The study reveals that 50% of all muons are single muons at the point of production, while their relative number increases to 70% by the time they reach the detector boundary. A possible background to this search is assumed to be produced by a collinear neutrino interacting after a stop of the muon. The muon may stop due to energy loss or spontaneous decay. In that case, the resulting signal is expected to be identical to the desired track-gap signature. A preliminary background rate is obtained by performing an event selection. The resulting background rate after the selection process is 5e-5 Hz, which is a reasonable result given a neutrino flux of mHz. A more thorough selection taking into account the particle energies as well as IceCube's limited energy resolution is exp

Syftet med studien är att synliggöra förskollärares uppfattningar och erfarenheter av att implementera fysikundervisning med utgångspunkt i barnlitteratur. För att synliggöra pedagogernas uppfattningar användes kvalitativa semistrukturerade intervjuer, där informanterna bestod av sju aktiva legitimerade förskollärare. Analysen utgick från en fenomenografisk teoriansats i kombination med litterära föreställningsvärldar. Resultatet i studien visar att förskollärarna har goda förutsättningar för att implementera barnlitteratur i förskolans undervisning, men att uppkomna tillfällen inte alltid utnyttjas. Samtidigt visar resultatet att förskollärarna upplever sina egna fysikkunskaper som bristfälliga, vilket begränsade fysikundervisningen tillsammans med barnen. Förutsättningar såsom kompetens och självsäkerhet med avseende på fysikämnet har betydelse för hur och i vilken omfattning pedagogerna använder barnlitteraturen som pedagogiskt verktyg. I samband med intervjuerna ombads informanterna att exemplifiera möjlig eller befintlig fysikundervisning med utgångspunkt i barnlitteratur. Frågor som detta togs emot positivt då samtliga uttryckte att de utmanades men också inspirerades att fånga upp de fysikaliska fenomen som uppstår i vardagen och i alla typer av litteratur. Litteraturen i förskolan uppfattades ha en central plats på grund av gott samarbete med bibliotek, region och tillgänglig bokbuss. Dock hade inte fysiken en lika självklar plats i barnens utbildning som barnlitteraturen., The purpose of the study is to visualize preschool teachers' perceptions and experiences of implementing physics education based on children's literature. In order to make perceptions visible, qualitative semi-structured interviews were used where the informants who participated consisted of seven active licensed preschool teachers. The analysis was based on a phenomenographic theory approach in combination with envisioning literature. The results of the study show that preschool teachers have good conditions for implementing children's literature in preschool teaching, but that opportunities are not always used. At the same time, the results show that the preschool teachers perceive their own physics knowledge as deficient, which limited the teaching of physics together with the children. Prerequisites such as competence and self-confidence with regard to the subject of physics are important for the teachers use children's literature as a pedagogical tool. In connection with the interviews, the informants were asked to exemplify possible or existing physics teaching based on children's literature. Questions like this were received positively as everyone expressed that they were challenged but also inspired to capture the physical phenomena that occur in everyday life and in all types of literature. Literature in the preschool was perceived to have a central place due to good cooperation with the library, the region and the available book bus. However, physics did not have as obvious a place in children's education as children's literature.

Quantum holonomies are non-Abelian Geometric Phases predominantly observed in adiabatic, non-adiabatic, or measurement-based quantum evolutions. Their significance lies in their potential utility within quantum computing due to their robustness against noise throughout the parameter path. In this report, we detail the foundational methods necessary for constructing holonomic non-Abelian gates specifically designed for tripartite states and , which serve as the logical qubits in our project. Given that the existence of a universal set of gates has already been demonstrated for each of these evolution types, our project delves into the advantages of applying these basis states across the three evolution categories. We have reformulated the Nuclear Quadrupole Resonance (NQR) Hamiltonian to be exclusively composed of two-body terms, thus rendering it more experimentally feasible. Furthermore, we have connected the W states with the remaining tripartite states to construct a four-level model system and generalized gates within this framework. Lastly, we introduce a measurement-based method that maintains its non-Abelian attributes even in the Zeno limit, where the process of projective measurement gradually approaches the adiabatic model., Icke-Abelska geometriska faser, så kallade kvantholonomier, observeras huvudsakligen i adiabatiska, icke-adiabatiska eller mätningsbaserade manipulationer av kvanttillstånd. De har stor potential till användning inom kvantdatorberäkningar på grund av deras robusthet mot olika typer av brus. I den här rapporten beskriver vi de grundläggande metoderna som är nödvändiga för att konstruera holonoma kvantgrindar som är speciellt utformade för trekroppstillstånden och , som fungerar som de logiska kvantbitarna i projektet, givet att det är redan bevisat att alla dessa modeller kan klara kraven för universalitet. Den här rapporten fokuserar på fördelarna med att tillämpa dessa logiska kvantbitar för tre olika evolutionskategorier. Vi har omformulerat kärnkvadrupolresonans Hamiltonianen så att den uteslutande består av tvåkroppstermer, vilket gör den mer experimentellt genomförbar för att realisera adiabatiska holonoma kvantgrindar. Vidare har vi kopplat -tillstånden med andra trekroppstillstånden för att konstruera ett så kallat sammanflätat -system och icke-adiabatiska holonoma kvantgrindar inom detta ramverk. Slutligen introducerar vi en mätningsbaserad metod som, till skillnad från tidigare resultat, bibehåller sina icke-Abelska attribut även i Zeno-gränsen, där processen med projektiv mätning gradvis närmar sig den adiabatiska kärnkvadrupolresonans-modellen.

Att planera en laboration i skolan är en central del i sin lärarprofession, speciellt om man undervisar i de naturvetenskapliga ämnena. Denna undersökning har varit ett försök till att kartlägga vilka beslut lärare tar i beaktande när de planerar en laboration samt vilka konsekvenser dessa olika beslut får. För att kunna kategorisera laborationer kan man använda sig av frihetsgrader. Frihetsgrader beskriver hur mycket information som ges till eleverna när de ska genomföra en laboration. Detta har varit ett av flera användbara verktyg för att analysera olika laborationer. I denna undersökning har sex fysiklärare intervjuats där de fick svara på olika frågor om laborationer som de själva använt sig av. Dessa intervjuer har analyserats fenomenografiskt och från denna analys var det möjligt att manifestera sju huvudkategorier. Dessa huvudkategorier är en konkretisering av svaret på frågeställningen: Vilka beslut tar läraren när hen planerar sin laboration med avseende på öppenheten i laborationen? Dessa huvudkategorier är unika där lärarnas olika uttalanden enbart passar in i en av kategorierna. Ett exempel på en huvudkategori är om läraren väljer att ha med tabeller/rader som eleverna fyller i, i laborationsinstruktionen. Tabeller/rader bildar bland annat ett förtydligande i instruktionerna. Ett annat exempel är var läraren väljer att placera utrustningen. Att ha utrustningen framplockad som stationer där eleverna ska laborera gör att man sparar tid men eleverna får inte sätta ihop utrustningen på egen hand.

The recent ability of ChatGPT-4 to process image data as input led us to test its performance in interpreting graphs, one of the most common representations used in physics. We tested ChatGPT’s performance on the well-established Test of Understanding Graphs in Kinematics (TUG-K). The study shows that ChatGPT's responses are quantitatively similar to those of students. However, an in-depth analysis reveals how they qualitatively differ. The chatbot often succeeded in devising strategies for the tasks and accurate “reasoning,” but failed in correctly “seeing” graphs. On the contrary, students typically do not have problems interpreting graphs but struggle with correctly reasoning. The findings suggest that ChatGPT’s abilities are not human-like, and this represents a challenge for its use in physics education.

The well-known artificial intelligence-based chatbot ChatGPT-4 has become able to process image data as input in October 2023. We investigated its performance on the test of understanding graphs in kinematics to inform the physics education community of the current potential of using ChatGPT in the education process, particularly on tasks that involve graphical interpretation. We found that ChatGPT, on average, performed similarly to students taking a high-school level physics course, but with important differences in the distribution of the correctness of its responses, as well as in terms of the displayed “reasoning” and “visual” abilities. While ChatGPT was very successful at proposing productive strategies for solving the tasks on the test and expressed correct reasoning in most of its responses, it had difficulties correctly “seeing” graphs. We suggest that, based on its performance, caution and a critical approach are needed if one intends to use it in the role of a tutor, a model of a student, or a tool for assisting vision-impaired persons in the context of kinematics graphs.

This work presents a collection of scientific research results in the field of quantum information. The first paper describes the mathematical properties of a particular type of state of light, called the two-mode squeezed state (TMSS). We have shown that it is possible to generate a superposition of such states with particular probability distributions, making them suitable for applications in quantum information. In particular, such states are effectively phase insensitive, a property that enables a larger extraction of information regarding a dynamical process. The second paper deals with an extensive discussion on the complexity of quantum algorithms. It was observed that while quantum algorithms can, under certain conditions, outperform classical algorithms in time or space complexity, some key steps such as state preparation and information retrieval are not always taken into account when analysing the complexity of quantum algorithms. For this reason, the aim of this study was to provide a complete complexity analysis for the implementation of quantum algorithms, considering different alternatives in terms of state preparation, quantum gate implementation and measurement techniques. We provide an asymptotic analysis of different algorithm implementation strategies. Finally, the last paper deals with the Hong-Ou-Mandel interference visibility of photons emitted in a cascade process. As a result of a two-photon excitation process, an entangled photon pair is emitted. This unwanted entanglement affects the coherence of the reduced single photon state, i.e. one of the photons emitted in the cascade process. As a result, the visibility of the Hong-Ou-Mandel interference is reduced. We show that, under certain conditions, it is possible to circumvent the restriction imposed by the time-energy entanglement by applying a post-selection method. The experimental results together with the theoretical framework are presented to provide a complete analysis of the method., Este trabalho apresenta uma coleção de resultados de pesquisas científicas no campo da informação quântica. O primeiro artigo descreve as propriedades matemáticas de um tipo específico de estado da luz, chamado de estado comprimido de dois modos (TMSS). Mostramos que é possível gerar uma superposição de tais estados com distribuições de probabilidade específicas, o que os torna adequados para aplicações em informação quântica. Em particular, esses estados são efetivamente insensíveis à fase, propriedade que torna possível aumentar a quantidade de informação que pode ser extraída a respeito de um processo dinâmico. O segundo artigo aborda uma extensa discussão sobre a complexidade de algoritmos quânticos. Foi observado que embora, sob certas condições, os algoritmos quânticos possam superar os algoritmos clássicos em termos de tempo ou espaço, algumas etapas importantes como a preparação do estado e a recuperação de informação nem sempre são contabilizados na análise da complexidade dos algoritmos quânticos. Por esse motivo, o objetivo do estudo é fornecer uma análise completa da complexidade para a implementação de algoritmos quânticos, considerando diferentes alternativas com relação à preparação do estado, à implementação de portas quânticas e técnicas de medição. Apresentamos uma análise assintótica de diferentes estratégias para a implementação de algoritmos. Por fim, o último trabalho está relacionado à visibilidade da interferência de Hong-Ou-Mandel de fótons emitidos em um processo em cascata. Como resultado de um processo de excitação de dois fótons, um par de fótons emaranhados é emitido. Esse emaranhamento indesejado afeta a coerência do estado reduzido de um único fóton, ou seja, de um dos fótons emitidos no processo de cascata. Como resultado, a visibilidade da interferência de Hong-Ou-Mandel é reduzida. Mostramos que, sob certas condições, é possível contornar a restrição imposta pelo emaranhamento tempo-energia aplicando um método de pós-seleção. Os re

We investigate how well a physics-based simulator can replicate a real wheel loader performing bucket filling in a pile of soil. The comparison is made using field-test time series of the vehicle motion and actuation forces, loaded mass, and total work. The vehicle was modeled as a rigid multibody system with frictional contacts, driveline, and linear actuators. For the soil, we tested discrete-element models of different resolutions, with and without multiscale acceleration. The spatiotemporal resolution ranged between 50–400 mm and 2–500 ms, and the computational speed was between 1/10,000 to 5 times faster than real time. The simulation-to-reality gap was found to be around 10% and exhibited a weak dependence on the level of fidelity, e.g., compatible with real-time simulation. Furthermore, the sensitivity of an optimized force-feedback controller under transfer between different simulation domains was investigated. The domain bias was observed to cause a performance reduction of 5% despite the domain gap being about 15%.

Super-oxidized porous carbons produced from reduced graphene oxide have been demonstrated recently to show unique sorption properties. Here we report experiments with identical oxidative treatment applied to four very different types of porous carbon materials with extremely broad range of specific surface area (SSA) ∼350–3400 m2g−1. It is demonstrated that KOH-activated carbons can be oxidized to the same degree as graphene oxide (GO) while preserving a larger part of SSA. Prolonged oxidation with ammonium persulfate resulted in extraordinary high degree of oxidation with C/O ratio reaching 2.1. Precursor carbons with largest share of micropores are found to be more stable against oxidative treatment, while single-walled carbon nanotubes (SWCNT's) are oxidized to much less extent. While mesopores collapse, micropores survive strong oxidation treatment providing materials with rather narrow pore size distribution and high (for given oxidation degree) BET SSA up to ∼1150 m2g−1. Super-oxidized porous carbons (SOPC's) show a high abundance of hydroxyl, epoxide, carbonyl, and carboxyl functional groups (similar to GO). As a result of oxidation, the hydrophobic carbons are converted into hydrophilic materials. Characterization shows that many properties of SOPC (e.g. degree of oxidation, type of functional groups, thermal stability etc.) are rather similar to GO, except for three-dimensional porous structure which can be considered an advantage for sorbent applications. SOPC's demonstrate superior sorption capacity for Cu(II) (up to ∼105 mgg−1), which is 8-fold higher than the value for non-oxidized precursor.

Scanning electron microscopy (SEM) can reveal the ultrastructure of bacterial spores, including morphology, surface features, texture, spore damage, germination, and appendages. Understanding these features can provide a basis for adherence, how physical and environmental stressors affect spore viability, integrity, and functionality, as well as the distribution and function of surface appendages. However, the spore sample preparation method can significantly impact the SEM images' appearance, resolution, and overall quality. In this study, we compare different spore preparation methods to identify optimal approaches for preparation time, spore appearance and resolved features, including the exosporium and spore pili, for SEM imaging. We use Bacillus paranthracis as model species and evaluate the efficacy of preparation protocols using different fixation and drying methods, as well as imaging under room- and cryogenic temperatures. We compare and assess method complexity to the visibility of the spore exosporium and spore appendages across different methods. Additionally, we use Haralick texture features to quantify the differences in spore surface appearance and determine the most suitable method for preserving spore structures and surface features during SEM evaluation. The findings from this study will help establish protocols for preparing bacterial spores for SEM and facilitating accurate and reliable analysis of spores' characteristics.

This paper presents a method for learning world models for wheel loaders performing automatic loading actions on a pile of soil. Data-driven models were learned to output the resulting pile state, loaded mass, time, and work for a single loading cycle given inputs that include a heightmap of the initial pile shape and action parameters for an automatic bucket-filling controller. Long-horizon planning of sequential loading in a dynamically changing environment is thus enabled as repeated model inference. The models, consisting of deep neural networks, were trained on data from a 3D multibody dynamics simulation of over 10,000 random loading actions in gravel piles of different shapes. The accuracy and inference time for predicting the loading performance and the resulting pile state were, on average, 95% in 1.21.2 ms and 97% in 4.54.5 ms, respectively. Long-horizon predictions were found feasible over 40 sequential loading actions.

We explore sim-to-real transfer of deep reinforcement learning controllers for a heavy vehicle with active suspensions designed for traversing rough terrain. While related research primarily focuses on lightweight robots with electric motors and fast actuation, this study uses a forestry vehicle with a complex hydraulic driveline and slow actuation. We simulate the vehicle using multibody dynamics and apply system identification to find an appropriate set of simulation parameters. We then train policies in simulation using various techniques to mitigate the sim-to-real gap, including domain randomization, action delays, and a reward penalty to encourage smooth control. In reality, the policies trained with action delays and a penalty for erratic actions perform nearly at the same level as in simulation. In experiments on level ground, the motion trajectories closely overlap when turning to either side, as well as in a route tracking scenario. When faced with a ramp that requires active use of the suspensions, the simulated and real motions are in close alignment. This shows that the actuator model together with system identification yields a sufficiently accurate model of the actuators. We observe that policies trained without the additional action penalty exhibit fast switching or bang–bang control. These present smooth motions and high performance in simulation but transfer poorly to reality. We find that policies make marginal use of the local height map for perception, showing no indications of predictive planning. However, the strong transfer capabilities entail that further development concerning perception and performance can be largely confined to simulation., Mistra Digital Forest

Carbon dots (CDs) are an emerging class of nanomaterials with attractive optical properties, which promise to enable a variety of applications. An important and timely question is whether CDs can become a functional and sustainable alternative to incumbent optical nanomaterials, notably inorganic quantum dots. Herein, the current CD literature is comprehensively reviewed as regards to their synthesis and function, with a focus on sustainability aspects. The study quantifies why it is attractive that CDs can be synthesized with biomass as the sole starting material and be free from toxic and precious metals and critical raw materials. It further describes and analyzes employed pretreatment, chemical-conversion, purification, and processing procedures, and highlights current issues with the usage of solvents, the energy and material efficiency, and the safety and waste management. It is specially shown that many reported synthesis and processing methods are concerningly wasteful with the utilization of non-sustainable solvents and energy. It is finally recommended that future studies should explicitly consider and discuss the environmental influence of the selected starting material, solvents, and generated byproducts, and that quantitative information on the required amounts of solvents, consumables, and energy should be provided to enable an evaluation of the presented methods in an upscaled sustainability context., This article also appears in:Hot Topic: Biomass UpgradingHot Topic: Carbon, Graphite, and Graphene

Quicklime, rich in CaO(s), is generated by calcining limestone at high temperatures. Parallel-flow regenerative lime kilns are the most energy-effective industrial method available today. To prevent major disruptions in such kilns, a high raw material quality is necessary. Under some conditions, impurity-enriched material may adhere to limestone pebbles and enter the kiln. In this study, limestone and corresponding quicklime were analyzed to evaluate the extent and composition of surface impurities and assess the effect on quicklime product quality, here defined as free CaO. This was performed by sampling and analyzing limestone, quarry clay, laboratory-produced quicklime, and industrially produced quicklime with XRF, SEM/EDX, and XRD; interpretations were supported by thermodynamic equilibrium calculations. In the laboratory-produced quicklime, the surface impurities reacted with calcium forming Larnite, Gehlenite, Åkermanite and Merwinite, reducing the quicklime quality. The results showed that the limestone surface layer comprised 1.2 wt.-% of the total mass but possessed 4 wt.-% of the total impurities. The effect on industrially produced quicklime quality was lower; this indicated that the limestone surface impurities were removed while the material moved through the kiln. Multicomponent chemical equilibrium calculations showed that the quarry clay was expected to be fully melted at 1170 °C, possibly leading to operational problems.

Multilayered metal-dielectric nanostructures display both a strong plasmonic behavior and hyperbolic optical dispersion. The latter is responsible for the appearance of two separated radiative and nonradiative channels in the extinction spectrum of these structures. This unique property can open plenty of opportunities toward the development of multifunctional systems that simultaneously can behave as optimal scatterers and absorbers at different wavelengths, an important feature to achieve multiscale control of light-matter interactions in different spectral regions for different types of applications, such as optical computing or detection of thermal radiation. Nevertheless, the temperature dependence of the optical properties of these multilayered systems has never been investigated. In this work, we study how radiative and nonradiative processes in hyperbolic meta-antennas can probe temperature changes of the surrounding medium. We show that, while radiative processes are essentially not affected by a change in the external temperature, the nonradiative ones are strongly affected by a temperature variation. By combining experiments and temperature-dependent effective medium theory, we find that this behavior is connected to enhanced damping effects due to electron-phonon scattering. Contrary to standard plasmonic systems, a red-shift of the nonradiative mode occurs for small variations of the environment temperature. Our study shows that, to probe temperature changes, it is essential to exploit nonradiative processes in systems supporting plasmonic excitations, which can be used as very sensitive thermometers via linear absorption spectroscopy.

The inverse spin-galvanic effect or current-induced spin-polarization is mainly associated with interfaces between different layers in semiconducting heterostructures, surfaces of metals, and bulk semiconducting materials. Here, we theoretically predict that the inverse spin-galvanic effect should also be present in chiral molecules, as a result of the chiral induced spin selectivity effect. As proof-of-principle, we calculate the nonequilibrium properties of a model system that previously has been successfully used to explain a multitude of aspects related to the chiral induced spin selectivity effect. Here we show that current driven spin-polarization in a chiral molecule gives rise to a magnetic moment that is sensitive to external magnet field. The chiral molecule then behaves like a soft ferromagnet. This, in turn, suggests that magnetic permeability measurement in otherwise nonmagnetic systems may be used noninvasively to detect the presence of spin-polarized currents.

Covariant conserved 2-form currents for linearised gravity are constructed by contracting the linearised curvature with conformal Killing-Yano tensors. The corresponding conserved charges were originally introduced by Penrose and have recently been interpreted as the generators of generalised symmetries of the graviton. We introduce an off-shell refinement of these charges and find the relation between these improved Penrose charges and the linearised version of the ADM momentum and angular momentum. If the graviton field is globally well-defined on a background Minkowski space then some of the Penrose charges give the momentum and angular momentum while the remainder vanish. We consider the generalisation in which the graviton has Dirac string singularities or is defined locally in patches, in which case the conventional ADM expressions are not invariant under the graviton gauge symmetry in general. We modify them to render them gauge-invariant and show that the Penrose charges give these modified charges plus certain magnetic gravitational charges. We discuss properties of the Penrose charges, generalise to toroidal Kaluza-Klein compactifications and check our results in a number of examples.