1,720,993 research outputs found
Hybrid RANS-LES Modeling of the Aerothermal Field in an Annular Hot Streak Generator for the Study of Combustor–Turbine Interaction
No full textThe adoption of lean-burn technology in modern aero-engines influences the already critical aerothermal conditions at turbine entry, where the absence of dilution holes preserves the swirl component generated by burners and prevents any control on pattern factor. The associated uncertainty and lack of confidence entail the application of wide safety margins in turbine cooling design, with a detrimental effect on engine efficiency. Computational fluid dynamics (CFD) can provide a deeper understanding of the physical phenomena involved in combustor-turbine interaction, especially with hybrid Reynolds-averaged Navier-Stokes (RANS) large eddy simulation (LES) models, such as scale adaptive simulation (SAS), which are proving to overcome the well-known limitations of the RANS approach and be a viable approach to capture the complex flow physics. This paper describes the numerical investigation on a test rig representative of a lean-burn, effusion cooled, annular combustor developed in the EU Project Full Aerothermal Combustor-Turbine interactiOns Research (FACTOR) with the aim of studying combustor-turbine interaction. Results obtained with RANS and SAS were critically compared to experimental data and analyzed to better understand the flow physics, as well as to assess the improvements related to the use of hybrid RANS-LES models. Significant discrepancies are highlighted for RANS in predicting the recirculating region, which has slight influence on the velocity field at the combustor outlet, but affects dramatically mixing and the resulting temperature distribution. The accuracy of the results achieved suggests the exploitation of SAS model with a view to the future inclusion of the nozzle guide vanes in the test ri
Modelling Strategies for the Prediction of Hot Streak Generation in Lean Burn Aeroengine Combustors
No full textThe accurate prediction of the fluid dynamic conditions at the exit of gas turbine combustors are of paramount importance in the aero-thermal design of the aero-engine. In fact, both the heat loads and the aerodynamic performance of the high pressure turbine (HPT) are substantially affected by the entry conditions, such as velocity components, temperature and turbulence intensity. The problem is particularly serious in new generation devices based on a lean burn concept. Compared to standard Rich–Quench–Lean (RQL) scheme, the absence of dilution jets and the use of highly swirled flows for flame stabilization make the control of combustor exit temperature distribution a complex task. Therefore, the high-fidelity prediction of the hot streak formation within the combustor, as well as its propagation through the HPT, are becoming key aspects. In this work, different strategies for turbulence modelling are tested, mainly focusing on scale-resolving approaches such as Large-Eddy Simulation (LES) and Scale Adaptive Simulations (SAS), which are becoming increasingly popular with the availability of more powerful computational resources. At the same time, classical eddy-viscosity models based on RANS approach are considered, as they still represent the standard simulation strategy in the industrial framework, when a fast response is required in a preliminary design phase. The different methodologies are benchmarked on an experimental test article representative of an aeronautical lean burn combustor cooled by means of effusion. The benchmark performed at engine-relevant conditions allowed to draw interesting conclusions for the purposes of the aero-thermal simulation. SAS proved to be a valid alternative to LES, returning on the whole the same level of accuracy. As expected, the disagreement obtained with RANS was significant. The sensitivity to the turbulent Prandtl number was investigated to provide an insight on its reliability in compensating the underestimation in turbulence mixing
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Molecular modulators of anti-VEGF response in neovascular age-related macular degeneration: aqueous humor dynamics of CD93 and endocannabinoids
No full textBackground: Neovascular age-related macular degeneration (nvAMD) represents a leading cause of legal blindness in the elderly population of developed countries. Although anti-vascular endothelial growth factor (VEGF) therapy has significantly improved visual outcomes, treatment efficacy is highly variable, with a considerable proportion of patients exhibiting incomplete or transient responses. This variability underscores the need to identify additional molecular players that modulate disease progression and therapeutic response. In this context, CD93 has emerged as a promising candidate. CD93 is a transmembrane glycoprotein involved in endothelial cell adhesion, migration, and angiogenesis. Recent studies have shown that CD93 is upregulated in pathological retinal vasculature and promotes ocular neovascularization in preclinical models. However, its behavior in human aqueous humor during anti-VEGF therapy and its potential role as a therapeutic target remain to be elucidated. Parallel to this, the endocannabinoid system (ECS)—comprising bioactive lipids such as anandamide (AEA) and 2-arachidonoylglycerol (2-AG), and their receptors (CB1, CB2) has gained attention for its regulatory role in angiogenesis and inflammation. Experimental evidence suggests that endocannabinoids can modulate VEGF signaling and influence endothelial cell behavior. Moreover, the ECS interacts with immune mediators and oxidative stress pathways that are known to be involved in nvAMD pathogenesis. Despite this, the intraocular ECS dynamics in the setting of nvAMD and their interactions with anti-VEGF blockage have not been previously characterized. This study aims to address these gaps by investigating the intraocular concentrations of CD93 and endocannabinoids in nvAMD eyes undergoing intravitreal anti-VEGF treatment. By analyzing their longitudinal changes and associations with therapeutic response, the study seeks to identify novel molecular markers of treatment efficacy and to shed light on alternative pathways contributing to disease persistence or incomplete response.
Methods: This prospective study involved aqueous humor sampling from two cohorts: patients affected by nvAMD undergoing anti-VEGF therapy, and healthy controls undergoing cataract surgery. Samples in nvAMD eyes were collected at the time of four consecutive monthly intravitreal bevacizumab injections (baseline, week 4, 8 and 12), and once in control eyes at the beginning of cataract surgery.
CD93 concentrations were assessed by enzyme-linked immunosorbent assay (ELISA) in aqueous humor samples from 17 nvAMD eyes and 9 healthy control eyes across all timepoints. Protein normalization was performed to account for intersample variability. Endocannabinoids—anandamide (AEA) and 2-arachidonoylglycerol (2-AG) were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in 10 nvAMD eyes at baseline, week 4, and week 12, and in 10 control eyes at the time of cataract extraction.
Statistical analysis included repeated-measures ANOVA and the Friedman test for within-group longitudinal comparisons, with Wilcoxon signed-rank tests for post-hoc analysis. Between-group differences were tested using the Mann–Whitney U test. Bonferroni correction was applied where appropriate, and significance was set at p < 0.05.
Results: At baseline, CD93 concentrations in the aqueous humor did not significantly differ between nvAMD and control eyes (0.431 ± 0.35 ng/mL vs 0.359 ± 0.25 ng/mL; p=0.55). Anti-VEGF treatment induced a significant overall reduction of raw CD93 levels over time in nvAMD eyes (repeated-measures ANOVA: F=2.97, df=3,48; p=0.041), with pairwise reductions at week 4 (p=0.015) and week 12 (p=0.003) compared to baseline. Normalized CD93 concentrations showed a similar trend (F=2.46, df=3,48; p=0.074), with a significant decrease at week 4 (p=0.007). Stratification based on response to therapy revealed that CD93 reduction was restricted to good responders (F=3.86, p=0.020), while poor responders showed stable CD93 levels over time (F=1.21, p=0.335).
Baseline concentrations of AEA and 2-AG were markedly lower in nvAMD eyes compared to controls (AEA: 0.046 ± 0.040 vs 1.530 ± 0.293 μmol/mL; 2-AG: 0.336 ± 0.293 vs 11.204 ± 6.497 μmol/mL; both p<0.001). Anti-VEGF treatment significantly increased AEA and 2-AG levels over time (Friedman test, p<0.001 for both). Pairwise comparisons showed significant changes between all timepoints (all p=0.006). Notably, AEA levels normalized after a single injection (week 4 vs controls, p=0.97) but decreased again at week 12 (p<0.001). Conversely, 2-AG levels increased progressively, remaining significantly higher than controls at both week 4 (p<0.001) and week 12 (p=0.017).
Conclusions: This study provides novel insights into the molecular modifications induced by anti-VEGF therapy within the aqueous humor of nvAMD eyes. CD93 concentrations significantly decrease during treatment, particularly in patients achieving a favorable anatomical response. In parallel, anti-VEGF administration is associated with a progressive restoration of intraocular endocannabinoid levels, suggesting a potential interaction between VEGF inhibition and ECS homeostasis. These findings expand the understanding of the molecular dynamics in nvAMD and may open new perspectives for biomarker discovery and adjunctive therapeutic strategies
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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