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Experimental investigation on gas-liquid two-phase flow patterns and vibration characteristics of an inducer pump
No full textInducers typically enhance centrifugal pump performance in two-phase flow regimes by producing more uniform mixtures and increasing pressure before the impeller. Their impact is most pronounced under part-load conditions compared to overload situations. This study experimentally investigates air-water two-phase flow behavior within a pump inducer. Using high-speed photography and grayscale image processing, five distinct gas-liquid flow patterns were identified: bubble flow, strip bubble flow, agglomerated bubble flow, gas pocket flow, and segregated flow. The inducer's head and vibration characteristics were also measured. Results show that flow pattern transitions significantly affect performance degradation and vibration. Specifically, the head decreases as the liquid flow rate increases at a constant gas volume fraction (λ) and generally follows a downward trend as λ increases at a constant liquid flow rate. Bubble flow, representing minimal λ, has a negligible effect on performance. However, with higher λ, a sharp decline in head occurs within the agglomerated bubble flow range, followed by a gradual decrease during gas pocket flow under both optimal and overload conditions. In part-load conditions, the head decreases sharply during strip bubble and segregated flow. While bubble flow mitigates vibration fluctuations, increasing GVF leads to higher vibration amplitude, particularly in the range of 2–8 times the inducer's rotational frequency, due to flow pattern instability
Subjective appearance and objective discrimination of shapes in the periphery of the visual field
No full textThis thesis focuses on three different yet related phenomena, in the framework of the interplay between foveal and peripheral vision. Three exceptions to traditional visual models are discussed, illustrating three scenarios: 1) foveal vision aids peripheral discrimination, 2) foveal vision does not interact with peripheral vision, and 3) foveal vision hinders peripheral discrimination. This thesis also explores the difference between subjective and objective precepts, illustrating the presence of dissociations between the two. Part I reviews literature on the visual system and models of visual perception. Part II discusses Foveal Feedback, a mechanism where foveal retinotopic cortex recruitment enhances peripheral discrimination. Foveal Feedback challenges the traditional retinotopic model of visual perception. In this part, different aspects of Foveal Feedback are investigated: 1) first, a more precise estimate of the timing of the feedback; second, the existence of this mechanism for different types of stimuli and tasks, along with its modulation by task and stimuli complexity; 3) third, a possible relation with visual imagery. Part III presents a study on the Honeycomb Illusion, a particular stimulus where mechanisms usually employed when looking at pattern (uniformity assumption, extrapolation) do not occur. The Honeycomb Illusion represents a situation in which there is no interaction between foveal and peripheral vision, thus being an exception to the traditional view of peripheral information inferred from foveal vision. Part IV introduces the Central Region Interference with Periphery (CRIP) effect, illustrating how central vision can hinder peripheral discrimination, and challenging predictive processing models. Through two different studies, it is demonstrated that we do not always rely on central vision to disambiguate elements in the periphery. The final section summarises findings, addresses open questions, and suggests future research directions
Robotic Thymectomy for Myasthenia Gravis: Analysis of the Surgical and Neurological Outcomes After a 20 Years' Experience
Full text linkBackground: Evidence supporting robotic thymectomy for myasthenia gravis is generally based on small sample-size studies, heterogeneous in patient selection and in reporting outcomes. Therefore, this study was conducted to assess the surgical and neurological outcomes of robotic thymectomy in myasthenic patients and to identify prognostic factors associated with symptoms' remission through a large cohort of patients operated in a 20 years' period. Methods: A retrospective analysis of a prospectively maintained database was conducted for all patients undergoing robotic thymectomy for myasthenia gravis between 2002 and 2022. Myasthenia Gravis Foundation of America (MGFA) recommendations were used to report the neurological outcomes. Complete remission and overall improvement were evaluated using Cumulative Incidence Functions, while the effect of preoperative variables on the probability of remission was estimated with Cox models. Results: In total, 267 patients underwent robotic thymectomy. Median operative time was 135 min and there were 7 (2.6%) open conversions. Clinical follow-up (median 83 months) showed a 5-year probability of complete remission of 18% and of overall improvement of 84%. Complete remission was negatively associated with age (HR 0.97, 95% CI 0.95–0.99, p = 0.001) and preoperative use of pyridostigmine (HR 0.34, 95% CI 0.15–0.81, p = 0.014), while severe MGFA class did not reach significance (HR 0.55, 95% CI 0.3–1.01, p = 0.052). Instead, there was a benefit in patients operated on in later years (HR 1.11, 95% CI 1.04–1.18, p = 0.01). Comment: Robotic thymectomy is a safe procedure. Long-term neurological follow-up demonstrated an improvement in most patients, also in subgroups that historically showed worse outcomes
Differences in autoimmune thyroid diseases between females and males: the result of a complex interconnection of factors
No full textPurpose: The aim of this paper is to review the scientific evidence for the link between autoimmune thyroid diseases (AITDs) and sex, and the plausible causes of the female prevalence in AITDs. Methods: An extensive literature search of published articles was conducted using online search engines. Results: AITDs are more frequent in the female sex. Numerous studies have focused on the differences between males and females in their presentation of AITD and their response to therapy, sometimes with conflicting results. Several factors are considered to be responsible for the higher incidence of AITDs in females, crucial among which is the relationship between sex hormones and the immune system. In addition to hormones, there is also evidence that sex chromosomes, epigenetic factors, foetal microchimerism, the microbiota and endocrine-disrupting chemicals (EDCs) play an important role in the predisposition of females to AITDs. Conclusion: The prevalence of AITDs in the female sex appears to be attributable to numerous factors, the most important being the influence of sex hormones on the immune system
Light intensity activation of alternative electron transport mechanisms in the moss Physcomitrium patens
Full text linkPhotosynthetic organisms exploit sunlight to drive an electron transport chain and obtain the chemical energy supporting their metabolism. In highly dynamic environmental conditions, excitation energy and electron transport need to be continuously modulated to prevent over-reduction and the consequent damage. An essential role in the regulation of electron transport is played by alternative electron transport mechanisms such as cyclic electron transport (CET) facilitated by PGRL1/PGR5 and NDH complex and pseudo-cyclic electron transport (PCET) mediated by the flavodiiron proteins (FLV) and the Mehler reaction. In this work mutant lines of the moss Physcomitrium patens depleted in PCET (flva KO) or CET (pgrl1/ndhm KO) were compared to wild-type plants for their ability to regulate photosynthetic electron transport in response to light fluctuations of different intensities. FLV activity enables a very fast increase in electron transport capacity but its impact is transient and becomes undetectable after 3 min from a light change. The FLV electron transport capacity is saturated at 100 μmol photons m−2 s−1 and does not increase even if exposed to stronger illumination. On the other hand, CET activation after an increase in illumination has a smaller contribution on electron transport capacity, but it provides a steady contribution for several minutes after a change in illumination intensity. Overall, these results demonstrate that light adapted plants CO2 fixation capacity needs approx. 3 min to adjust to different illumination intensities. In this interval CET and PCET enable adjusting temporary unbalances in electron transport, fully responding to 2–4 time increases in illumination. In case of larger increases, these mechanisms still contribute to protection from light damage by reducing the accumulation of electrons at PSI acceptor side. While the two mechanisms play an overlapping function, their activity shows distinctive kinetics and electron transport capacity thus they are complementary in ensuring optimal photoprotection
Stepanov differentiability theorem for intrinsic graphs in Heisenberg groups
Full text linkWe prove a Stepanov differentiability type theorem for intrinsic graphs in sub-Riemannian Heisenberg groups
A natural indirect adaptive controller for a satellite-mounted manipulator
No full textThe work considers the design of an indirect adaptive controller for a satellite equipped with a robotic arm manipulating an object. Model uncertainty on the manipulated object can considerably impact the overall behavior of the system. In addition, the dynamics of the actuators of the base satellite are non-linear and can be affected by malfunctioning. Neglecting these two phenomena may lead to excessive control effort or to performance degradation. To deal with these issues, an indirect adaptive control approach is pursued in this paper, which allows consideration of relevant features of the actuators’ dynamics, such as loss of effectiveness. Furthermore, an adaptive law that preserves the physical consistency of the inertial parameters of the various rigid bodies comprising the system is employed. The performance and robustness of the controller are first analyzed and then validated in a realistic simulation study
Rescue Project of the University of Heidelberg’s Archaeological Expedition at Nineveh in the Southwest Palace on Tell Kuyunjik, Seasons 2021–2023
No full textStatistics of Climate Change: Three Advanced Econometric Essays
No full textThis thesis addresses one of the most critical challenges for humanity in the short to medium term: climate change mitigation. The success of this process requires coordination across all sectors of society and effective management of global warming, which poses both environmental and economic threats. The impacts of climate change may destabilize the financial system, trigger recessions, and interfere with the transition itself.
Climate finance is the field that studies climate-related risks to the economic and financial system, categorized into three main types: physical risk, transition risk, and liability risk. These risks are incorporated into economic models to assess exposure to climate change. However, financial institutions have shown significant shortcomings in integrating these risks into their internal models. Another emerging concern is the potential formation of a speculative bubble in green sectors (i.e. green bubble), whose effects on financial stability remain unclear. An additional layer of complexity arises from the significant variation in climate policies across countries, which has profound implications for energy production and carbon-intensive industries.
The thesis is structured into three chapters. The first chapter introduces an innovative framework for studying and detecting green bubbles. The second chapter presents an algorithmic approach to enhance climate scenarios and macroeconomic forecasts. Finally, the third chapter explores the potential impacts of implementing the European Union’s Carbon Border Adjustment Mechanism (CBAM) on the Indian iron and steel sector