10081 research outputs found
Sort by
Understanding the metrology challenges and variability of black carbon properties from urban to remote environments
Get PDFBlack carbon (BC) is an important short-lived climate forcer, which overall impact is still uncertain in climate models. A better estimate requires the accurate characterization of fundamental properties such as BC size and mixing state, and climate-relevant properties (i.e. BC mass concentration and mass absorption cross-section) in different environments. Here, we integrated field observations from European and South American urban and remote sites with chamber experiments in the CESAM simulation chamber to assess the metrology limits of widely used measurement techniques and the variability of BC properties, both at the emission and after ageing in the atmosphere. Our findings reveal site and technique-dependent metrology limitations and the impact of different correction methods on mass concentration and absorption coefficient measurements. The combined biases from these factors may inflate the estimate of the mass absorption cross-section by up to 90%. Urban environments displayed rapid responses of BC properties to diurnal changes in emissions and meteorology, with traffic sources dominating in summer and biomass burning contributing more in colder months. Mass concentration exhibited significant variations with traffic intensity, leading to sharp increases during rush hours in both European and Bolivian cities. Concurrently, BC particle size increased from urban traffic sites to background locations, reflecting direct source proximity and rapid BC modification. Ventilated conditions promoted dispersion of traffic emissions and dilution with background air, altering BC properties compared to stagnant periods in an urban coastal site (Barcelona). In contrast, BC properties at the remote mountain site of Chacaltaya were influenced by long-range transport, with pollution injection from the boundary layer systematically modifying climate-relevant properties while negligibly impacting particle size. This study contributes to reducing uncertainty in BC observations, offering insights into fundamental and climate-relevant BC properties in urban and remote environments essential for refining BC direct radiative forcing estimates in models
Exploring dark energy and modified gravity with Euclid-CMB cross-correlation
Get PDFIn this thesis we study the synergy between observations of the cosmic microwave background (CMB) and large scale structure of the Universe, in the context of the ESA mission Euclid. The Euclid mission aims at building the largest galaxy catalogue to date, observing galaxies in about a third of the sky, and providing high quality data for the study of dark energy, dark matter and gravity. In this context we first discuss modified gravity theories that can be targeted by Euclid and provide original cosmological constraints with existing datasets on a subset of scalar-tensor theories of gravity, discussing also their implications for the Hubble tension. We then forecast for Euclid capabilities in further constraining this class of models in combination with CMB experiments. In the forecasts we initially focus on the combination of CMB lensing with
Euclid observables showing its relevance for extended cosmological models, and then provide forecasts for the full CMB-Euclid joint analysis. This study shows the striking complementarity of these datasets, which breaks degeneracies between cosmological parameters, guaranteeing the largest constraining power, both on the standard cosmological parameters and on the parameters of the extended models, such as the sum of the neutrino masses or the modified gravity parameters. In order to provide these constraints and fulfill the forecasts it is necessary to build an end-to-end pipeline for the joint analysis of Euclid and CMB data, we explore this topic as well by presenting the results of the validation and implementation of the likelihood module for the cross-correlation observables. In particular we delve into the details of the likelihood for the detection of the integrated Sachs-Wolfe effect through the correlation of the CMB temperature field
and galaxy number counts; and also discuss the implementation of CMB lensing in the official Euclid likelihood code
Navigating the landscape of EU sustainable finance regulation: challenges and imperatives to enforce sustainability financial promises in the EU through harmonized private enforcement mechanisms
Get PDFSustainability financial disputes against financial firms have emerged as a focal point within legal discourse in the absence of other private enforcement mechanisms. This study explores the strategic implications of sustainability financial disputes, intertwining individual interests with broader societal concerns, and offers a novel methodology rooted in case law analysis. Despite the absence of explicit private enforcement mechanisms in EU capital markets laws, our examination highlights the crucial role of private enforcement in supplementing public regulatory frameworks. The proposal calls for regulatory reforms to harmonize obligations and enforcement measures at the EU level, extending to exploring corporate governance, fiduciary duties, and the role of not-for-profit organizations in boosting sustainable finance. Looking ahead, we advocate for the use of standardized technical sustainability standards to streamline dispute resolution processes and enhance clarity and consistency in sustainability financial disputes and a unified cause of action, taking as reference point the language of the civil liability provision included in the EU Credit Rating Agencies Regulation . This study sheds light on the complex enforcement landscape surrounding sustainability financial disputes and offers practical insights for policymakers and legal practitioners alike, addressing varying interpretations by national adjudicators on sustainability criteria that may lead to market fragmentation. In summary, the proposal offers a novel examination of tensions between issuers and investors in green securities offerings, emphasizing the integration of sustainability considerations, and reorients the legal focus to address emerging challenges in the rapidly expanding green investment market, providing an innovative perspective on the critical issue of advancing lending to green finance while harmonizing enforcement measures to ensure market integrity, legal certainty and investor protection
Carbapenemase producing enterobacteriacae rectal colonization in dialysis patients: a large monocentric retrospective analysis
Get PDFCarbapenemase-producing Enterobacteriaceae (CPE) represent a growing global public health concern due to their increasing prevalence and resistance to carbapenems, a group of last-resort antibiotics. Dialysis patients, who often have compromised immune systems, are particularly vulnerable to infections that represent the second cause of death in dialysis’ cohorts. Presenting a rectal colonization by CPE has a significative impact on patients in dialysis? Are there factors that can help us understand which patients are at a higher risk of developing CPE colonization? How can we treat a CPE colonized patient who develop fever? Our study aim to reviews the challenges posed by CPE in dialysis settings and explores current diagnostic, therapeutic, and infection control strategies on a large cohort of dialyzed patients
Non-invasive detection of acute cell-mediated graft rejection in paediatric heart transplant recipients: the role of cardiovascular magnetic resonance
Get PDFBackground and Aim: Acute cardiac rejection is currently diagnosed by endomyocardial biopsy (EMB), but multiparametric cardiac magnetic resonance (CMR) may be a non-invasive alternative by its capacity for myocardial structure and function characterization. Our primary aim was to determine the utility of multiparametric CMR in identifying acute graft rejection in paediatric heart transplant recipients. The second aim was to compare textural features of parametric maps in cases of rejection versus those without rejection.
Methods: Fifteen patients were prospectively enrolled for contrast-enhanced CMR followed by EMB and right heart catheterization.
Images were acquired on a 1,5 Tesla scanner including T1 mapping (modified Look-Locker inversion recovery sequence – MOLLI) and T2 mapping (modified GraSE sequence). The extracellular volume (ECV) was calculated using pre- and post-gadolinium T1 times of blood and myocardium and the patient’s hematocrit. Markers of graft dysfunction including hemodynamic measurements from echocardiography, catheterization and CMR were collated. Patients were divided into two groups based on degree of rejection at EMB: no rejection with no change in treatment (Group A) and acute rejection requiring new therapy (Group B). Statistical analysis included student’t t test and Pearson correlation.
Results: Acute rejection was diagnosed in five patients. Mean T1 values were significantly associated with acute rejection. A monotonic, increasing trend was noted in both mean and peak T1 values, with increasing degree of rejection. ECV was significantly higher in Group B. There was no difference in T2 signal between two groups.
Conclusion: Multiparametric CMR serves as a noninvasive screening tool during surveillance encounters and may be used to identify those patients that may be at higher risk of rejection and therefore require further evaluation. Future and multicenter studies are necessary to confirm these results and explore whether multiparametric CMR can decrease the number of surveillance EMBs in paediatric heart transplant recipients
Application of augmented reality in craniofacial surgery: a feasibility study
Get PDFAugmented Reality (AR) is a novel promising technology, which is gaining success in the medical field. A number of applications in surgery have been described, but few studies have been focusing on pediatric craniofacial surgery. In this research project, the Authors have been implementing a system for intraoperative surgical navigation by means of HoloLens 2 by Microsoft, applied to pediatric craniofacial surgery. The Authors tested the device in a preclinical setting first, and then moved to patients. The Authors assessed the accuracy of the HoloLens 2 by performing 36 procedures in vitro on a printed 3D model of a patient. In clinical setting, 10 patients were prospectively enrolled in the study. The virtual surgical planning was designed for each patient and uploaded onto the software which allows for the AR interface and the standard neurosurgical navigator. For each patient, the surgeon has been drawing osteotomy lines both under the guidance of HoloLens2 and of the neurosurgical navigator. The Author then checked the accuracy with calibrated CAD CAM cutting guides with different grooves, in order to assess the accuracy of the osteotomies performed. We tested levels of accuracy of ±1.5 mm and ±1mm .
In the preclinical setting, the HoloLens 2 performed with levels of accuracy of 1.5 mm, whereas in the real setting, surgeons were able to trace the osteotomy lines under the AR guidance for an amount of 45% (0.4 SD) of the entire line, with an accuracy level of ±1.5 mm. This percentage lowers to 34% (0.4 SD) when assessing accuracy level of ±1 mm. The results of the same tasks for the standard navigator are 36% and 16%, for ±1.5 mm and ± 1 mm accuracy level, respectively.
The Authors reported encouraging results both in the preclinical and the clinical setting
Kinetics of photogenerated carriers in nanostructured semiconductor heterojunctions for solar water splitting
Get PDFThis thesis aims to investigate the fundamental processes governing the performance of different types of photoelectrodes used in photoelectrochemical (PEC) applications, such as unbiased water splitting for hydrogen production. Unraveling the transport and recombination phenomena in nanostructured and surface-modified heterojunctions at a semiconductor/electrolyte interface is not trivial. To approach this task, the work presented here first focus on a hydrogen-terminated p-silicon photocathode in acetonitrile, considered as a standard reference for PEC studies. Steady-state and time-resolved excitation at long wavelength provided clear evidence of the formation of an inversion layer and revealed that the most optimal photovoltage and the longest electron-hole pair lifetime occurs when the reduction potential for the species in solution lies within the unfilled conduction band states. Understanding more complex systems is not as straight-forward and a complete characterization that combine time- and frequency-resolved techniques is needed. Intensity modulated photocurrent spectroscopy and transient absorption spectroscopy are used here on WO3/BiVO4 heterojunctions. By selectively probing the two layers of the heterojunction, the occurrence of interfacial recombination was identified. Then, the addition of Co-Fe based overlayers resulted in passivation of surface states and charge storage at the overlayer active sites, providing higher charge separation efficiency and suppression of recombination in time scales that go from picoseconds to seconds. Finally, the charge carrier kinetics of several different Cu(In,Ga)Se2 (CIGS)-based architectures used for water reduction was investigated. The efficiency of a CIGS photocathode is severely limited by charge transfer at the electrode/electrolyte interface compared to the same absorber layer used as a photovoltaic cell. A NiMo binary alloy deposited on the photocathode surface showed a remarkable enhancement in the transfer rate of electrons in solution. An external CIGS photovoltaic module assisting a NiMo dark cathode displayed optimal absorption and charge separation properties and a highly performing interface with the solution
A comprehensive study of the AGN feedback cycle in galaxy clusters from high resolution X-ray and radio observations
Get PDFAt the center of galaxy clusters, a dramatic interplay known as feedback cycle occurs between the hot intracluster medium (ICM) and the active galactic nucleus (AGN) of the central galaxy. The footprints of this interplay are evident from X-ray observations of the ICM, where X-ray cavities and shock fronts are associated with radio lobe emission tracing energetic AGN outbursts. While such jet activity reduces the efficiency of the hot gas to cool to lower temperatures, residual cooling can generate warm and cold gas clouds around the central galaxy. The condensed gas parcels can ultimately reach the core of the galaxy and be accreted by the AGN. This picture is the result of tremendous advances over the last three decades. Yet, a deeper understanding of the details of how the heating–cooling regulation is achieved and maintained is still missing. In this Thesis, we delve into key aspects of the feedback cycle. To this end, we leverage high-resolution (sub-arcsecond), multifrequency observations (mainly X-ray and radio) of several top-level facilities (e.g., Chandra, JVLA, VLBA, LOFAR). First, we investigate which conditions trigger a feedback response to gas cooling, by studying the properties of clusters where feedback is just about to start. Then, we focus on the details of how the AGN–ICM interaction progresses by examining cavity and shock heating in the cluster RBS797, an exemplary case of the jet feedback paradigm. Furthermore, we explore the importance of shock heating and the coupling of distinct jet power regimes (i.e., FRII, FRI and FR0 radio galaxies) to the environment. Ultimately, as heating models rely on the connection between the direct evidence (the jets) and the smoking gun (the X-ray cavities) of feedback, we examine the cases in which these two are dramatically misaligned
Mind the gaps: cognitive-inspired AI for high-level visual sensemaking. Towards abstract concept image classification
Get PDFThe abundance of visual data and the push for robust AI are driving the need for automated visual sensemaking. Computer Vision (CV) faces growing demand for models that can discern not only what images "represent," but also what they "evoke." This is a demand for tools mimicking human perception at a high semantic level, categorizing images based on concepts like freedom, danger, or safety. However, automating this process is challenging due to entropy, scarcity, subjectivity, and ethical considerations. These challenges not only impact performance but also underscore the critical need for interoperability. This dissertation focuses on abstract concept-based (AC) image classification, guided by three technical principles: situated grounding, performance enhancement, and interpretability. We introduce ART-stract, a novel dataset of cultural images annotated with ACs, serving as the foundation for a series of experiments across four key domains: assessing the effectiveness of the end-to-end DL paradigm, exploring cognitive-inspired semantic intermediaries, incorporating cultural and commonsense aspects, and neuro-symbolic integration of sensory-perceptual data with cognitive-based knowledge. Our results demonstrate that integrating CV approaches with semantic technologies yields methods that surpass the current state of the art in AC image classification, outperforming the end-to-end deep vision paradigm. The results emphasize the role semantic technologies can play in developing both effective and interpretable systems, through the capturing, situating, and reasoning over knowledge related to visual data. Furthermore, this dissertation explores the complex interplay between technical and socio-technical factors. By merging technical expertise with an understanding of human and societal aspects, we advocate for responsible labeling and training practices in visual media. These insights and techniques not only advance efforts in CV and explainable artificial intelligence but also propel us toward an era of AI development that harmonizes technical prowess with deep awareness of its human and societal implications
Combining molecular alterations and functional imaging in metastatic castration resistant prostate cancer treated with taxanes
Get PDFThe treatment of metastatic castration-resistant prostate cancer (mCRPC) is currently characterized by several drugs with different mechanisms of action, such as new generation hormonal agents (abiraterone, enzalutamide), chemotherapy (docetaxel, cabazitaxel), PARP inhibitors (olaparib) and radiometabolic therapies (radium-223, LuPSMA). There is an urgent need to identify biomarkers to guide personalized therapy in mCRPC. In recent years, the status of androgen receptor (AR) gene detected in liquid biopsy has been associated with outcomes in patients treated with abiraterone or enzalutamide. More recently, plasma tumor DNA (ptDNA) and its changes during treatment have been identified as early indicators of response to anticancer treatments. Recent works also suggested a potential role of tumor-related metabolic parameters of 18Fluoro-Choline Positron Emission Tomography (F18CH-PET)-computed tomography (CT) as a prognostic tool in mCRCP. Other clinical features, such as the presence of visceral metastases, have been correlated with outcome in mCRPC patients.
Recent studies conducted by our research group have designed and validated a prognostic model based on the combination of molecular characteristics (ptDNA levels), metabolic features found in basal FCH PET scans (metabolic tumor volume values, MTV), clinical parameters (absence or presence of visceral metastases), and laboratory tests (serum lactate dehydrogenase levels, LDH).
Within this PhD project, 30 patients affected by mCRPC, pre-treated with abiraterone or enzalutamide, candidate for taxane-based treatments (docetaxel or cabazitaxel), have been prospectively evaluated. The prognostic model previously described was applied to this population, to interrogate its prognostic power in a more advanced cohort of patients, resulting in a further external validation of the tool