1,721,016 research outputs found
Numerical simulations of the cerebrospinal flow through the Sylvius aqueduct modeled as a diffuser/nozzle pump
Full text linkThe circulation of the cerebrospinal fluid is rhythmic with a preferential flow direction. In the present study, we performed a series of numerical simulations demonstrating that the shape of the Sylvius aqueduct is functional to this characteristic circulation acting as a diffuser/nozzle pump
Local analysis of the gas exchange in a step-and-pool configuration via numerical simulation
Full text linkScaling strategies for Brinkman penalization in fluid topology optimization
Full text linkTopology optimization provides a rigorous framework for determining optimal flow-path designs in fluid mechanics. A popular technique is the density-based approach, which treats fluid-solid interfaces by considering the solid phase as a porous medium with low permeability. Mathematically, such a problem is governed by the Navier-Stokes equations combined with the Brinkman penalization. To consistently solve the optimization problem, this study examines the theoretical foundations of the method, focusing on dimensionless parameters such as the Reynolds number and a specific Darcy number, D a * . Through dimensional analysis, we derive scaling guidelines for the Brinkman penalization in relation to fluid properties and domain geometry. Numerical simulations show that incorrect scaling can yield nonphysical results, including excessive fluid penetration into solid regions, undermining the optimization. Our findings demonstrate that the invariance of the solution can be maintained by appropriately scaling D a * with the relative velocity in the porous region, ensuring accurate and reliable results in different scenarios. This work provides a systematic framework for parameter selection in fluid topology optimization, addressing key modeling and computational challenges. By emphasizing the importance of dimensional analysis, it contributes to a broader understanding of topology optimization, paving the way for its more robust and consistent application in fluid mechanics
In Vitro and Ex Vivo Hemodynamic Testing of an Innovative Occluder for Paravalvular Leak After Transcather Aortic Valve Implantation
Full text linkThis study aims at achieving a proof-of-concept for a novel device designed to occlude the orifices that may form between transcatheter valves and host tissues after TAVI. The device effect on the performance of a SAPIEN XT with a paravalvular gap was assessed into an in vitro and ex vivo pulse duplicator. The in vitro tests were performed complying with the standard international regulations, measuring the trasvalvular pressure and regurgitant volumes with and without the paravalvular gap, and with the occluder correctly positioned into the gap. In the second series of tests, the leakage reduction due to the presence of the occluder was assessed for the same setup, into a beating swine heart. The occluder implantation decreased the regurgitant fraction of about 50% for the in vitro assessment and 75% for the ex vivo test, under rest operating conditions. These results suggest that suitably designed occluders can lead to important benefit in the PVL treatment
Occupational exposure and lung cancer risk in a coastal area of Northeastern Italy
No full textA case-control study of lung cancer and occupational exposure was conducted in a coastal area of Northeastern Italy where metallurgical and mechanical industries, docks and shipyards are located. Cases comprised 756 men who died of primary lung cancer in a 5-year period. Controls comprised 756 male subjects dying from other causes during the same period. Occupational exposures to lung carcinogens were assessed according to a job title-based approach, using two separate lists of industries/occupations recognized as being causally associated (list A) or suspected of being causally associated (list B) with lung cancer in humans. Exposure to asbestos was classified as absent, possible, or definite. After adjustment for cigarette smoking and place of residence, a significant association was found between lung cancer and occupations in both list A [relative risk (RR) = 2.25, 95% confidence interval (CI) = 1.68-3.03] and list B (RR = 1.33, 95% CI = 1.03-1.71). A significant excess risk was found for workers with definite exposure to asbestos as compared to those with no exposure to lung carcinogens (RR = 1.98, 95% CI = 1.42-2.75). Among occupations with recognized exposure to lung carcinogens other than asbestos, a significant excess risk for lung cancer was observed in iron and metalware workers. In occupational groups with definite exposure to asbestos, elevated risk estimates were found for shipyard workers, dockworkers, carpenters, and electricians. The combined effect of smoking and asbestos was found to be compatible with that expected under a multiplicative model. The overall population-attributable risk (ARp) for cigarette smoking was found to be 87.5%. The ARp estimate for occupations in list A was 16.0%. The estimate increased to 25.3% (95% CI = 16.2-34.4) when occupations in list B were included. The ARp estimate for possible or definite exposure to asbestos was 20.0% (95% CI= 11.5-28.5). With regard to the histologic types of lung cancer, significant associations were found between definite exposure to asbestos and squamous cell carcinoma (RR = 2.00, 95% CI = 1.28-3.11), small cell carcinoma (RR = 2.11, 95% CI = 1.31-3.39). and adenocarcinoma (RR = 2.16, 95% CI = 1.32-3.53)
La rottura di cuore come complicanza dell'infarto acuto del miocardio. Considerazioni anatomoistopatologiche sulla base di 154 osservazioni autoptiche
No full textGoing 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
Alterazione della mucosa laringea in pazienti deceduti per carcinoma polmonare (studio anatomoistologico)
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