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Most ultrasound imaging techniques necessitate the fundamental step of converting temporal signals received from transducer elements into a spatial echogenecity map. This beamforming (BF) step requires the knowledge of speed-of-sound (SoS) value in the imaged medium. An incorrect assumption of BF SoS leads to aberration artifacts, not only deteriorating the quality and resolution of conventional brightness mode (B-mode) images, hence limiting their clinical usability, but also impairing other ultrasound modalities such as elastography and spatial SoS reconstructions, which rely on faithfully beamformed images as their input. In this work, we propose an analytical method for estimating BF SoS. We show that pixel-wise relative shifts between frames beamformed with an assumed SoS is a function of geometric disparities of the transmission paths and the error in such SoS assumption. Using this relation, we devise an analytical model, the closed form solution of which yields the difference between the assumed and the true SoS in the medium. Based on this, we correct the BF SoS, which can also be applied iteratively. Both in simulations and experiments, lateral B-mode resolution is shown to be improved by ≈ 25% compared to that with an initial SoS assumption error of 3.3% (50 m/s), while localization artifacts from beamforming are also corrected. After 5 iterations, our method achieves BF SoS errors of under 0.6 m/s in simulations. Residual time-delay errors in beamforming 32 numerical phantoms are shown to reduce down to 0.07 µs, with average improvements of up to 21 folds compared to initial inaccurate assumptions. We additionally show the utility of the proposed method in imaging local SoS maps, where using our correction method reduces reconstruction root-mean-square errors substantially, down to their lower-bound with actual BF SoS.

Objectives: The aim is to assess the feasibility and accuracy of a novel quantitative ultrasound (US) method based on global speed-of-sound (g-SoS) measurement using conventional US machines, for breast density assessment in comparison to mammographic ACR (m-ACR) categories.

Materials and methods: In a prospective study, g-SoS was assessed in the upper-outer breast quadrant of 100 women, with 92 of them also having m-ACR assessed by two radiologists across the entire breast. For g-SoS, ultrasonic waves were transmitted from varying transducer locations and the image misalignments between these were then related analytically to breast SoS. To test reproducibility, two consecutive g-SoS acquisitions each were taken at two similar breast locations by the same operator.

Results: Measurements were found highly repeatable, with a mean absolute difference +/- standard deviation of 3.16 +/- 3.79 m/s. Multiple measurements were combined yielding a single g-SoS estimate per each patient, which strongly correlated to m-ACR categories (Spearman's = 0.773). The g-SoS values for categories A-D were 1459.6 +/- 0.74, 1475.6 +/- 15.92, 1515.6 +/- 27.10, and 1545.7 +/- 20.62, with all groups (except A-B) being significantly different from each other. Dense breasts (m-ACR C&D) were classified with 100% specificity at 78% sensitivity, with an area under the curve (AUC) of 0.931. Extremely dense breasts (m-ACR D) were classified with 100% sensitivity at 77.5% specificity (AUC = 0.906).

Conclusion: Quantitative g-SoS measurement of the breast was shown feasible and repeatable using conventional US machines, with values correlating strongly with m-ACR assessments.

Key Points: Breast density is a strong predictor of risk for breast cancer, which frequently develops in dense tissue regions. Therefore, density assessment calls for refined non-ionizing methods.

Findings: Quantitative global speed-of-sound (g-SoS) measurement of the breast is shown to be feasible using conventional US machines, repeatable, and able to classify breast density with high accuracy.

Clinical relevance: Being effective in classifying dense breasts, where mammography has reduced sensitivity, g-SoS can help stratify patients for alternative modalities. Ideal day for mammography or MRI can be determined by monitoring g-SoS. Furthermore, g-SoS can be integrated into personalized risk assessment.

Speed of sound (SoS) is an emerging quantitative biomechanical marker for tissue characterization. It is also used for beamforming in various ultrasound imaging solutions, the success of which hence depend critically on the accuracy of SoS assumption. Several robust global (single-value) SoS estimation techniques have been proposed. However, in heterogeneous in-vivo tissue, localized SoS estimation is desired. In this work, we propose a meta-method that extends beamforming-based global SoS estimation approaches to enable windowed SoS estimation within a desired region of interest (ROI) that is SoS-wise homogeneous. By dividing the ROI into sub-windows, we introduce a differential formulation that eliminates the influence of superficial layers for deducing the SoS within the ROI. We demonstrate this based on a recent beamforming-based SoS estimator using simulations and phantom experiments, showing that our method can accurately estimate ROI-window SoS under varying superficial layer conditions. Our window-based correction method reduces the SoS errors by over 80% in numerical simulations and over 60% in phantom experiments compared to applying global SoS estimation naively within the ROI. Our window-correction meta-method can extend to other beamforming-based global SoS estimators that are robust enough within sub-windows of a ROI.

Speed-of-sound (SoS) is an emerging ultrasound contrast modality, where pulse-echo techniques using conventional transducers offer multiple benefits. For estimating tissue SoS distributions, spatial domain reconstruction from relative speckle shifts between different beamforming sequences is a promising approach. This operates based on a forward model that relates the sought local values of SoS to observed speckle shifts, for which the associated image reconstruction inverse problem is solved. The reconstruction accuracy thus highly depends on the hand-crafted forward imaging model. In this work, we propose to learn the SoS imaging model based on data. We introduce a convolutional formulation of the pulse-echo SoS imaging problem such that the entire field-of-view requires a single unified kernel, the learning of which is then tractable and robust. We present least-squares estimation of such convolutional kernel, which can further be constrained and regularized for numerical stability. In experiments, we show that a forward model learned from k-Wave simulations reduces the contrast error of SoS reconstruc- tions by 38%, compared to a conventional hand-crafted line-based wave-path model. This simulation-learned model generalizes successfully to acquired phantom data, reducing the contrast error compared to the conventional hand-crafted alternative. We successfully demonstrate the feasibility of learning machine-specific kernels as well as one-shot learning from a single image. On in-vivo data of a cancerous breast tumor, the phantom-learned model exhibits an SoS contrast of 34.6 m/s, as an impressive improvement over the conventional model contrast of merely 3.4 m/s.

Medical imaging aims to recover underlying tissue properties, using inexact (simplified/linearized) imaging models and often from inaccurate and incomplete measurements. Analytical reconstruction methods rely on hand-crafted regularization, sensitive to noise assumptions and parameter tuning. Among deep learning alternatives, plug-and-play (PnP) approaches learn regularization while incorporating imaging physics during inference, outperforming purely data-driven methods. The performance of all these approaches, however, still strongly depends on measurement quality and imaging model accuracy. In this work, we propose DenOiS, a framework that denoises both input observations and resulting solution in their respective domains. It consists of an observation refinement strategy that corrects degraded measurements while compensating for imaging model simplifications, and a diffusion-based PnP reconstruction approach that remains robust under missing measurements. DenOiS enables generalization to real data from training only in simulations, resulting in high-fidelity image reconstruction with noisy observations and inexact imaging models. We demonstrate this for speed-of-sound imaging as a challenging setting of quantitative ultrasound image reconstruction.

New research indicates that genetic variants related to educational attainment influence individuals’ political participation. This suggests that political inequality of opportunity is partially rooted in an inequality in genetic resources. However, the possibility that these genetic influences are contingent on individuals’ environments, such that they are amplified or reduced by certain environmental characteristics, remains unexplored. Using longitudinal and geo-coded register data for a large sample of genotyped twins in the Swedish Twin Registry, this paper explores whether early-life proximal environments that are conducive to participation modifies the effects of individuals’ education-related genetic resources on voting, as measured by a polygenic index for educational attainment. The results suggest that the level of political engagement, and of SES, both within the family and within the neighbourhood, can reduce the effects of genetic resources on voting. This has implications for how we can direct policy to ameliorate genetic inequalities in political participation.

For half a century, scholars have debated the societal implications of research that suggests genetic explanations for socioeconomic disparities. However, studies of whether and how such genetic explanations affect the attitudes of citizensare surprisingly limited. Using two identical, pre-registered survey experiments fielded in the United States (N=2003) and Sweden (N=2005), this study tests whether a short, twin study-based genetic explanation for income and education differencesleads to citizens adopting a lower perceived possibility, as well as a lower perceived fairness, of the government reducing socioeconomic differences. The results do not provide systematic evidence to this effect. Rather, there are indications that citizens increase their belief in the effectiveness, as well as in the fairness of government intervention. Most clearly, the treatment increased citizens’ support for a set of redistributive policy proposals, particularly in Sweden. Overall, however, the treatment effects appear to have been limited. This is likely attributable to the experimental manipulationbeing inadequate in magnitude. This study suggests that genetic explanations for socioeconomic differences do not necessarily have to cause a naturalization of inequality among citizens, but further research on this important topic is needed.

Interest in the role of genetics in influencing key life outcomes such as educational attainment has grown quickly. However, the question of whether genetic influences on educational attainment, on average as well as in conjunction with socioeconomic circumstances, are moderated by macro-level factors has not yet received sufficient attention. This study combines polygenic indices for educational attainment (EA PGI) with high-quality register data in a large sample of Swedish twins of European ancestry born 1920–1999. Employing both conventional between-family and within-family models, the analyses suggest that the influences of education-related genetic propensities on educational attainment have increased in Sweden during the twentieth century, a period featuring major expansions of the Swedish educational system, and decreasing economic inequality. The analyses also suggest that the degree to which socioeconomic background enhances genetic influences on education has decreased across cohorts. Genetic influences on education do not appear to have translated into increased genetic influences on income. Additionally, there is some evidence of floor and ceiling effects in the analyses of dichotomous educational outcomes.

Pathogenic multidrug-resistant bacteria with hybrid chromosomes have emerged as a significant global healthcare threat. These include the pandemic Escherichia coli ST1193, the product of homologous recombination events involving two phylogenetically distant strains of E. coli, in which mutant alleles of the widely separated genes, gyrA and parC, generating high-level fluoroquinolone resistance were acquired. The mechanisms and frequency of hybrid formation are poorly understood. We developed a robust hybrid selection procedure and applied it to 118 clinical UTI isolates of E. coli mixed with suitable recipient strains. Hybrids were selected from 39% of isolates. All hybrids were recombinants of donor and recipient chromosomal DNA (median length of donor DNA 367 kb), with 90% also acquiring conjugative mobile genetic elements (MGE) from the donor. We showed that individual conjugative plasmids, and integrative conjugative elements (ICE), from donors were sufficient to drive hybrid formation. These observations strongly support conjugative chromosomal DNA transfer as the major mechanism underlying hybrid formation. ICE are genome-integrated and passively propagated but when transferring to recipients they normally do so by excising and producing their own conjugation machinery. We found that ICE were responsible for the highest frequencies of hybrid chromosome formation. They could mobilize DNA around the full length of the chromosome, including the simultaneous acquisition of mutant variants of gyrA and parC, separated by ∼826 kb, generating highly fluoroquinolone-resistant bacteria in a single event. Bacterial hybrid chromosome formation driven by conjugative MGE may be an important and widespread mechanism in the emergence and evolution of high-risk bacterial pathogens.

Horizontal gene transfer (HGT) between bacterial species is an important contributor to the development of multidrug-resistant (MDR) clinical pathogens. One example is the transfer of MDR conjugative plasmids from Klebsiella pneumoniae into Escherichia coli occurring within co-infected human hosts. Here, we asked whether, in mixed-species bacterial populations, we could also detect the transfer of chromosomal DNA. To address this, we screened 50 K. pneumoniae clinical isolates for their ability to generate chromosomal hybrids with E. coli as recipient. We found that 7/50 (14%) generated chromosomal hybrids at frequencies above our limit of detection (~10-11) up to a frequency of 5x10-10. Genome sequence analysis of 28 hybrids revealed multiple underlying mechanisms of DNA transfer and recombination. These included two different mechanisms by which a region of the E. coli chromosome was replaced with K. pneumoniae chromosomal DNA (Hfr-like mechanisms, with up to 586 kb of K. pneumoniae DNA acquired), and three different mechanisms by which F’-like plasmids carrying K. pneumoniae chromosomal DNA were created and transferred into E. coli. Accordingly, clinical isolates of K. pneumoniae have the ability to transfer, not just plasmids, but also intrinsically non-mobile chromosomal DNA into E. coli to create novel hybrid strains. Several of the isolated hybrids acquired genes related to virulence or antibiotic resistance. Chromosomal hybrids were stable after evolution in rich media and had a 70-95% fitness compared to MG1655. The results provide insights into the mechanisms involved in creating bacteria with novel hybrid chromosomes, which may have important implications for bacterial evolution, and the spread of antibiotic resistance and virulence genes.

Integrated conjugative elements can drive the transfer of chromosomal DNA from one Escherichia coli strain into another, generating strains with hybrid chromosomes. Several pandemic virulent multidrug-resistant strains of E. coli are chromosomal hybrids. Here we show that the frequency of hybrid formation can differ by orders of magnitude depending on the parental combination. However, the donor-recipient characteristics affecting hybridization efficiency are poorly understood. The laboratory workhorse strain E. coli MG1655 is significantly more proficient as a recipient in hybrid generation than E. coli ATCC25922, the strain used for quality control in antibiotic susceptibility testing. Focusing on these two strains we tested several hypotheses to identify barriers to hybrid formation. Among these, we found that relative conjugation efficiency correlated with hybrid formation frequency. To explore this, we used transposon mutagenesis to identify genes in ATCC25922 whose inactivation relieves a conjugation barrier. Among the first 1500 mutants tested we isolated and identified one that was 500-fold more conjugation-permissive than the parental strain. Whole genome sequencing identified this candidate ‘barrier’ gene as a protein-coding sequence on plasmid 3. Understanding the barrier mechanism will require further study. We are currently testing whether inactivation of this gene also increases chromosomal hybrid formation. The importance of this work is that it could significantly deepen our understanding of preferred pathways of HGT, something that will have broad application in both clinical and evolutionary biology.

Escherichia coli is a prototroph and can synthesize all twenty proteinogenic amino acids when required to grow in minimal medium. There are approximately sixty protein-coding genes individually essential for amino acid synthesis. This is a large mutational target for the accumulation of detrimental mutations. E. coli can rewire biosynthetic pathways in response to mutational damage but the limits of this capacity are poorly understood. Here, to address evolutionary robustness, we asked whether and how the phenotypes of irreversible mutations causing auxotrophy could be suppressed or bypassed in the absence of horizontal gene transfer (HGT). Spontaneous suppressors could be selected for only ten of fifty-nine mutants tested (detection limit ~7x10^-11). Mechanisms of suppression included: regional amplifications; mutations increasing gene or operon expression; mutations relaxing enzyme specificity; and mutations causing biochemical pathway diversions. Overall, the data show that spontaneous suppression of auxotrophy caused by an irreversible mutation is an evolutionary survival mechanism relevant only to a minority of the genes essential for amino acid synthesis. As a consequence, the essential genetic foundations for amino acid prototrophy are expected to be degraded over time by mutations (Muller’s ratchet) and metabolic rewiring alone will be insufficient to counteract this effect. This implies that maintaining phenotypes, including prototrophy in E. coli, and potentially other bacterial species, is likely to be reliant on HGT of housekeeping genes to counteract the effects of inevitable mutational inactivation. Accordingly, chromosomal HGT in bacteria may be critical for survival across diverse environmental niches. 

Nature-Based Solutions (NBS) are growing in popularity to mitigate and adapt to climate change, enhance biodiversity, and secure human well-being. However, the emergence of NBS has not generated equal attention for all ecosystems. One such neglected ecosystem are ponds and pondscapes (i.e. groups of ponds in a landscape), which are deteriorating in quality and diminishing in quantity. As the European Union (EU) is regarded as influential in the conceptualisation and operationalisation of NBS, we conducted a qualitative content analysis of 38 EU policies to identify opportunities and limitations for the implementation of ponds and pondscapes as NBS. We focus our analysis on ponds and pondscapes, but their prevalence in different landscapes and their multitude of benefits allows us to also make some inferences about the implications of the EU policy context for NBS at large. We find that EU policies strengthen NBS linked to existing and potential Natura 2000 sites, as well as to ecosystems protected through the EU's Birds and Habitats Directives and Water Framework Directive. However, if ecosystems fall outside of these already established policies - as is the case with the vast majority of ponds and pondscapes - their implementation as NBS may be hampered. We also find that the EU emphasises natural water retention measures and carbon-rich ecosystems for climate change adaptation and mitigation, but mostly does not explicitly include ponds and pondscapes despite their potential contributions. Other findings are that the EU's Horizon Europe research policy will likely influence which ecosystems will be used and financed as NBS, while the exact ambition and selection of NBS rests with lower-level authorities or individuals. Therefore, further studies tracing the impact of the supra-national EU policy framework at lower governance levels are vital.

Nature-based solutions (NBS) are increasingly suggested to address biodiversity decline and climate change. However, many ecosystems are hardly used as NBS, including ponds and pondscapes. We therefore examine how policies and practices affect their implementation as NBS. Using a content analysis of policy documents and stakeholder inputs, we assess the policy context in eight countries but also zoom in on policies and practices in seventeen pondscapes. We derive three key insights: first, a protective status for a pond or pondscape interlinks with other enabling factors for NBS implementation, and protection and conservation should therefore be considered more often as NBS. Second, there is a shortage of, especially long-term, financing. Third, local leadership should be nurtured to overcome a lack of institutional cooperation and stakeholder awareness as well as fragmented land ownership. Beyond that, we show that implementation barriers interlink and interventions should therefore address several barriers simultaneously.

Low-carbon transitions are essential but contested, particularly regarding what constitutes a ‘just transition’. To grasp their political nature, adopting a spatial perspective becomes indispensable, as different actors hold different views on how to allocate burdens and benefits across scales. In this study, we examine how notions of ‘justice’ are expressed and manifested spatially, negotiated between conflicting parties, and undergo changes, delving into the conflict surrounding an electric vehicle (EV) factory near Berlin, Germany. To do so, we leverage the theoretical lens of ‘hydrosocial territories’. This framework helps to understand how beliefs about desirable societal development (‘imaginaries’) interlink with actors’ perceptions of just distribution of water-related benefits and burdens, as well as decision-making power across spatial scales. We identify one territory supporting the factory and two counter-territories challenging its legitimacy. Actors of one counter-territory question the net benefit for in situ communities due to water challenges, while the other casts doubt on the legitimacy of the capitalist systems as such and considers the EV technology and its supply chains exemplary of exploitative relations in the water sector. We derive three key insights for the conceptualisation of ‘justice’: Firstly, divergence in the underlying values of desired societal development and the spatial scales at which transitions are conceptualised can affect the possibilities for compromise. Secondly, justice, as viewed by actors negotiating transitions, requires continuous reassessment due to its fluid nature. Thirdly, localities where low-carbon transitions occur are perceived at multiple spatial scales simultaneously, adding complexity to how actors understand justice. Our research holds value for the study of low-carbon transitions, illuminating the complexity, spatiality, and fluidity of justice and offering a heuristic device to capture it.

This study explores the production of coherence between Uruguay’s agricultural, environmental and water policies amidst growing tensions, which are particularly manifested in conflicts between an expanding agricultural sector and water insecurity for the broader public. We apply a novel mixed-method approach, combining a political discourse analysis of key sectoral policies, the ruling party’s programme and workshop discussions with a survey of implementing technical staff, thus capturing both the discursive nature of coherence and perceptions of its practical implementation - extending thereby beyond instrumental and even existing critical policy coherence analysis frameworks. Our findings reveal divergent views on policy coherence, with agricultural sector staff generally viewing it more positively than their counterparts in the environmental and water sectors. We also identified two distinct discourses: the hegemonic discourse, which promotes agricultural growth with minimal environmental safeguards, and the counter-hegemonic discourse, which advocates for a cultural shift that challenges the capitalist structures underpinning large-scale agriculture. Our study highlights how prevailing discourses shape both the perception and practice of policy coherence. However, we also found that vagueness in policy objectives and instruments allow powerful actors to maintain the status quo, making policy objectives appear coherent while diverging from the discursive ideals of a strong sustainability in practice. The gap between discursive ideals and real-world outcomes illustrates that coherence, to a degree, is a choice shaped and limited by power dynamics and institutional capacities. Overall, our approach and findings bear relevance for an ever-increasing number of contexts in which economic and environmental priorities intersect and compete.

FemTech, technology often in the forms of apps developed to specifically target female health issues, have billions of users globally. Yet, despite the popularity of e.g., period trackers or pregnancy apps, we know little about the potential impact of these technologies, often developed outside controlled and regulated healthcare. How interactive technology is designed, and in our case the cycle represented through the design, has the potential to shape women's understanding of menstruation. In this study we analyse the interaction design of nine of the most downloaded menstruation apps, asking how commercial menstruation apps represent the cycle through their interaction design. While previous research has criticized these types of apps for lacking privacy and for enforcing normative ideals on women, they are often marketed in terms of female empowerment and users do indeed seem to find them very useful for period and fertility tracking. However, the term 'empowerment' is today used broadly and is known for having many potential meanings. Even within the field of Human Computer Interaction (HCI), 'empowerment' is used frequently but rarely explicitly defined. The question then becomes what empowerment could mean for menstruation tracking. In order to begin exploring the way menstruation and the period is represented in current apps and the way that future apps could design for empowerment, we engage in a comparative design investigation using what we call critical app-walkthrough methodology where an app's design is explored comprehensibly at one point in time and apps interacted with over a longer time period through researcher use-diares. Our results center around three ways in which these apps represent the cycle to users through design. We analyse; (1) interface metaphors used to represent the temporality of bleeding, (2) datafication of menstruation through input and output for intimate data tracking, and (3) the ways fertility predictions convey certainty over uncertainty. In a second step, we then explore what empowerment could mean for period trackers and how design could support empowering experiences. Finally, we present four design sensitivities meant to inspire designers to design for other types of period tracking experiences that might better empower bleeders. These are: support lived temporalities, embrace uncertainty, empower the self, and design less.

Digital applications for tracking pregnancy and fetal development are increasingly popular, yet we know little of how these technologies shape individual pregnancy experiences. This empirical study investigates how 17 expectants in Sweden use such apps to make sense of their pregnancies. It is grounded in feminist perspectives, highlighting the need to focus on women's health. Drawing on entanglement and flat ontology, we show how apps are part of socio-material configurations where they contribute to pregnancy meaning-making. We show how users experience a gradual realization that apps model ideal pregnancies and not the participants' own, how the app's commercial nature conflicts with many participants' ideals of pregnancy, and how participants continue to use apps despite this but engage in selective use. All to support ways of making pregnancy in desired ways. Finally, we outline how users engage with pregnancy apps and the resulting natureculture arrangements where bodies and technology are intertwined and co-constructed. We argue that entanglement should be seen as a process, not a state, as users continually negotiate their use, engaging in what could be called processes of untangling.

AgBiS2 nanocrystals have been shown to be a promising material for solar cell applications due to their high absorption coefficient, solution-processability and stability. However, detailed and systematic insight into how different surface passivation agents affect the overall material properties and corresponding device performance is still limited. Herein, a study about AgBiS2 nanocrystals treated with five different halide-based compounds - TBAI, TMAI, TBABr, TMABr and TMACl - is presented, with the nanocrystals themselves being synthesised via a newly adapted route under atmospheric conditions. For the differently passivated samples, variation in the ligand uptake, as well as shifts in the position of the valence and conduction bands could be observed. Incorporating these ligand-treated thin films into solar cell devices allowed for further investigation of their overall performance as well as into their respective charge carrier dynamics. Markedly longer charge carrier lifetimes were observed for the bromide- and chloride-passivated samples through transient photovoltage and photocurrent measurements as well as impedance spectroscopy. The effect of the surface modification on the charge carrier transport behaviour, on the other hand, was found to be less pronounced. Overall, this work demonstrates the importance of better understanding how different ligands affect nanocrystal properties, showcasing how it influences a wide variety of parameters controlling final device performance.