251 research outputs found
Editorial: Extracellular vesicles as modulators of cancer cell adaptive responses linked to therapy resistance
No full textNo abstract availabl
Interview with Falone Serna Regarding Student Enrollment
No full textThese responses from Falone Serna, Vice President for Enrollment Management, discuss changes to enrollment for the 2020-2021 year as a result of the COVID-19 pandemic. This interview was performed through email correspondence. He reports that the college experienced a 40% decline in applications and many students decided to take leaves of absence or delayed their enrollment. Online learning also meant that campus tours could not be held, which Mr. Serna notes is important for incoming students. He also mentions the challenges that student athletes, international students, and low-income and first-generation students. Student athletes make up approximately a third of the Whittier student body. Low-income and first-generation students make up a significant amount of the population, and international students face additional complications regarding the status of their visas. This is an insight into how Whittier College handled its enrollment strategies during the pandemic
Trasporto di fluidi organici e di fluttuazioni di pressione: un approccio numerico alla termofluidodinamica.
No full textI temi affrontati nella ricerca in ambito termofluidodinamico richiedono spesso un approccio multidisciplinare e tecniche di indagine non tradizionali. Una delle strategie più utilizzate, vista anche la sempre crescente disponibilità di risorse computazionali, è quella di operare con modelli numerici per la simulazione di fenomeni complessi, multifisici e multiscala. Una tematica di forte interesse ingegneristico è lo studio delle fluttuazioni di pressione derivanti dall’interazione tra un corpo e una corrente d’aria che lo investe: tale disturbo può ricadere nel campo dell’udibile e la sua diffusione può contribuire all’aumento dell’inquinamento acustico. Ne è un esempio il rumore prodotto dalle turbine eoliche di grande taglia per le quali sono state già state adottate tecniche di abbattimento del rumore, come l’impiego di bordi di uscita dentellati (trailing edge serration). Un altro tema di estrema rilevanza è quello del trasporto di fluidi organici veicolanti virus o batteri: la recente pandemia da SARS–CoV–2 ha messo in evidenza quanto sia importante valutare accuratamente la dinamica delle micro–gocce di saliva e la loro interazione termofluidodinamica con l’ambiente al fine di fornire corrette linee guida sulla distanza sociale e sulle buone pratiche da seguire nella quotidianità all’interno del contesto pandemico. In questo lavoro di tesi viene utilizzato un approccio numerico per lo studio dell’emissione aeroacustica prodotta da oggetti investiti da un flusso d’aria e della diffusione aerea di micro–particelle di fluido organico veicolanti virus. Viene sviluppato un solutore in grado di condurre simulazioni dirette (Direct Numerical Simulation – DNS) del campo aeroacustico, utilizzando condizioni al contorno non riflettive e schemi di integrazione temporale Runge–Kutta espliciti di alto ordine, e indagata la possibilità di adottare il riscaldamento localizzato quale tecnica di smorzamento delle fluttuazioni di pressione caratteristiche di un’onda sonora. Viene, inoltre, presentato un modello con approccio Euleriano–Lagrangiano multiscala, che permetta di valutare la diffusione in ambiente di particelle di fluido muco–salivare, nonché il processo di cristallizzazione della quota–parte salina delle droplet accoppiando il metodo Particle–Source–In–cell (PSI–cell) alla Population Balance Equation (PBE). Viene indagata anche la possibilità di ridurre la trasmissione di SARS–CoV–2 utilizzando la radiazione ultravioletta di tipo C quale tecnica di disinfezione real–time. I modelli sono sviluppati adottando il metodo di discretizzazione ai volumi finiti non strutturati e co–locati disponibile all’interno della libreria OpenFOAM.The new issues addressed in scientific research in the thermal and fluid dynamic field often require a multidisciplinary approach and non–traditional investigation techniques. One of the most used strategies, also because of increasing availability of computational resources, is to operate with numerical models that allow the simulation of complex, multiphysics and multiscale phenomena. A cutting-edge topic is certainly the study of fluctuating pressure resulting from a body and air interaction: this disturbance can be such that to be in the hearing range and its diffusion can contribute to the increase in noise pollution and have a significant impact on our daily life. As an example, we can refer to the noise produced by multi–megawatt wind turbines that are often equipped with trailing edge serration in order to reduce the aeroacouistic emission. Another crucial topic in this moment is related to the organic fluids, carrying viruses or bacteria, diffusion: SARS–CoV–2 pandemic has highlighted how important is to understand and rigorous study saliva droplets dynamics and their interaction with the environment in order to provide guidelines on social distance and good practices to be followed in daily life. In this PhD thesis a numerical approach is used to study the aeroacoustic emission radiated by objects in a flow as well as to investigate airborne diffusion of organic fluid micro - particles carrying viruses. A new solver is developed in order to perform Direct Numerical Simulation of the aeroacoustic fields. Explicit high–order Runge–Kutta schemes are employed for time integration and non–reflective boundary conditions are adopted. The local wall heating effect fluctuating pressure is also investigated, in order to give an insight on a new method for active controlling the noise emission. Furthermore, a new computational model, developed in a multiscale Eulerian - Lagrangian framework, is presented. This approach allows to evaluate the spreading of micro–droplets emitted in respiratory activities, as well as their thermal and fluid dynamic interaction with the surrounding environment, taking also into account the droplet dry nuclei formation. Saliva sodium chloride crystallization kinetics is modelled by coupling Particle–Source–In–cell (PSI–cell) method with Population Balance Equation (PBE). Moreover, a real–time disinfection strategy is studied: biological inactivation of SARS–CoV–2 using ultraviolet–C radiation is addressed. The aforementioned models are developed adopting the unstructured, co–located, finite volume method available in the well-known OpenFOAM library
Design and RF measurements of an X-band accelerating structure for the SPARC project
No full textThe paper presents the design of an X-band accelerating section for linearizing the longitudinal phase space in the Frascati Linac Coherent Light Source (SPARC). The nine cells structure, operating on the π standing wave mode, is fed by a central coupler and has been designed to obtain a 42 MV/m accelerating gradient. The 2D profile has been obtained using the electromagnetic codes Superfish and Oscar2D while the coupler has been designed using HFSS. Bead-pull measurements made on a copper prototype have been performed and the results are illustrated and compared with the numerical predictions
Direct computation of aeroacoustic fields in laminar flows: Solver development and assessment of wall temperature effects on radiated sound around bluff bodies
No full textThis work presents results of a direct computation of acoustic fields produced by several laminar flow configurations. A solver specifically developed for compressible mass, momentum and energy equations, named caafoam, is presented. Low–storage high-order Runge-Kutta schemes were used for time integration, and an unstructured colocated finite–volume method for space discretization. A sponge-layer-type non-reflective boundary treatment was adopted to avoid spurious numerical reflections at the far-field boundaries. These techniques were chosen and tested to see if they enable a broad range of physical phenomena, with a particular emphasis on aeroacoustic problems, to be solved. The reliability, efficiency and robustness of caafoam was demonstrated by computing several benchmarks concerning far-field aerodynamic sound. After proving the direct simulation capabilities of caafoam, it was used to analyze the effect of the wall temperature conditions on the aeroacoustic sound produced by laminar flows over bluff bodies
A Novel Framework for Unstructured Finite-Volume Methods with Optimized Hamiltonian Path Cell Ordering and Parallel Efficiency
No full textA novel optimized framework for unstructured finite-volume methods is presented, with an emphasis on memory bandwidth optimizations and parallel efficiency. The same numerical methods as an OpenFOAM-based solver named caafoam are used, which was recently developed for direct computation of aeroacoustic simulations. The current work presents a bottom-up optimization of caafoam. The mesh cells are ordered using Hamiltonian paths, where two consecutive cells in the path are guaranteed to be contiguous in memory, greatly reducing the failed data requests inherent to unstructured grids. To further reduce the memory footprint from the CPU, efficient data structures and compute kernel fusion are used. For optimal parallel efficiency, boundary and interior cells are treated separately to take full advantage of asynchronous MPI communication. Furthermore, the latest MPI-4 persistent neighborhood collective framework was implemented for optimal communications of ghost cells. A series of benchmark is used to validate the accuracy and performance of the novel solver. For this preliminary study, relatively small grids of up to 648,000 cells were run. A comparative performance study shows a speed-up of 1.8x-6.6x when compared to the original caafoam solver
A low—storage Runge—Kutta OpenFOAM solver for compressible low—Mach number flows: aeroacoustic and thermo—fluid dynamic applications
No full textA solver for compressible Navier–Stokes equations is presented in this paper. Low-storage RungeKutta schemes were adopted for time integration; on the other hand the finite volume approach available within OpenFOAM library has been adopted for space discretization. Kurganov-Noelle-Petrova approach was used for convective terms, while central schemes for diffusive ones. The aforementioned techniques were selected and tested in order to allow the possibility of solving a broad range of physical phenomena with particular emphasis to aeroacoustic and thermo-fluid dynamic problems. Indeed, that standard OpenFOAM solution techniques produce an unacceptable dissipation for acoustic phenomena computations. Non–reflective boundary treatment was also considered to avoid spurious numerical reflections. The reliability and the robustness of the solver is proved by computing several benchmarks. Lastly, the impact of the thermal boundary conditions on the sound propagation was analyzed
Thermal Behaviour of a Cylindrical Li-Ion Battery
No full textThis paper presents an experimental evaluation of thermal and electrical performances of a 26650 cylindrical Lithium Iron Phosphate/graphite battery cell. Thermal management of Lithium batteries is a fundamental issue of electric mobility, where batteries are subjected to severe operating conditions. Therefore, battery heat generation is a very important characteristic to be studied. In this work cell performances were assessed during battery discharge at ambient temperature over a wide range of discharge rates. The cell surface temperature was measured both with thermocouples and infrared thermography. Furthermore, also the open circuit potential and entropic heat coefficient were experimentally measured. Based on this experimental data, a simplified battery thermal model was used to evaluate the battery heat generation. The results show a substantial increase of battery surface temperature especially at high discharge rates. During discharge, the heat generated is greater at low battery state of charge due to the sudden decrease of cell potential. The contributions to heat generation are also carefully evaluated
Late-onset running biphasically improves redox balance, energy- and methylglyoxal-related status, as well as SIRT1 expression in mouse hippocampus
No full text"Despite the active research in this field, molecular mechanisms underlying exercise- induced beneficial effects on brain physiology and functions are still matter of debate, especially with regard to biological processes activated by regular exercise affecting the onset and progression of hippocampal aging in individuals unfamiliar with habitual physical activity. Since such responses seem to be mediated by changes in antioxidative, antiglycative and metabolic status, a possible exercise-induced coordinated response involving redox, methylglyoxal- and sirtuin-related molecular networks may be hypothesized.. In this study, hippocampi of CD1 mice undergoing the transition from mature to middle age were analyzed for redox-related profile, oxidative and methylglyoxal-dependent damage patterns, energy metabolism, sirtuin1 and glyoxalase1 expression after a 2- or 4-mo treadmill running program. Our findings suggested that the 4-mo regular running lowered the chance of dicarbonyl and oxidative stress, activated mitochondrial catabolism and preserved sirtuin1-related neuroprotection. Surprisingly, the same cellular pathways were negatively affected by the first 2 months of exercise, thus showing an interesting biphasic response.. In conclusion, the duration of exercise caused a profound shift in the response to regular running within the rodent hippocampus in a time-dependent fashion. This research revealed important details of the interaction between exercise and mammal hippocampus during the transition from mature to middle age, and this might help to develop non-pharmacological approaches aimed at retarding brain senescence, even in individuals unfamiliar with habitual exercise.
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