Publications by authors named "Charles Bernando"

Objectives: The number of deaths from cardiovascular disease is projected to reach 23.3 million by 2030. As a contribution to preventing this phenomenon, this paper proposed a machine learning (ML) model to predict patients with arteriosclerotic heart disease (AHD).

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Strong-field ionization of nanoscale clusters provides excellent opportunities to study the complex correlated electronic and nuclear dynamics of near-solid density plasmas. Yet, monitoring ultrafast, nanoscopic dynamics in real-time is challenging, which often complicates a direct comparison between theory and experiment. Here, near-infrared laser-induced plasma dynamics in ∼600  nm diameter helium droplets are studied by femtosecond time-resolved x-ray coherent diffractive imaging.

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Advancements in x-ray free-electron lasers on producing ultrashort, ultrabright, and coherent x-ray pulses enable single-shot imaging of fragile nanostructures, such as superfluid helium droplets. This imaging technique gives unique access to the sizes and shapes of individual droplets. In the past, such droplet characteristics have only been indirectly inferred by ensemble averaging techniques.

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The angular momentum of rotating superfluid droplets originates from quantized vortices and capillary waves, the interplay between which remains to be uncovered. Here, the rotation of isolated submicrometer superfluid ^{4}He droplets is studied by ultrafast x-ray diffraction using a free electron laser. The diffraction patterns provide simultaneous access to the morphology of the droplets and the vortex arrays they host.

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Silver clusters were assembled in helium droplets of different sizes ranging from 10 to 10 atoms. The clusters were heated upon laser irradiation at 355 nm, and evaporation dynamics of He atoms were studied by quadrupole mass spectroscopy using signals from He, He, and He splitter ions. We found that for droplets containing less than 10 atoms the laser irradiation leads to evaporation of He atoms.

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Article Synopsis
  • Lensless x-ray microscopy relies on recovering the phase of scattered radiation from a specimen, which is crucial for creating images.
  • Researchers introduced a new phase retrieval method by encasing objects in superfluid helium nanodroplets, which supports the specimen and aids in image reconstruction.
  • The technique is effective and produces detailed images, as demonstrated with xenon clusters showing transient quantum vortices within the delicate helium droplets.
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Helium nanodroplets are considered ideal model systems to explore quantum hydrodynamics in self-contained, isolated superfluids. However, exploring the dynamic properties of individual droplets is experimentally challenging. In this work, we used single-shot femtosecond x-ray coherent diffractive imaging to investigate the rotation of single, isolated superfluid helium-4 droplets containing ~10(8) to 10(11) atoms.

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