Project description:When small quantum systems, atoms or molecules, absorb a high-energy photon, electrons are emitted with a well-defined energy and a highly symmetric angular distribution, ruled by energy quantization and parity conservation. These rules are based on approximations and symmetries which may break down when atoms are exposed to ultrashort and intense optical pulses. This raises the question of their universality for the simplest case of the photoelectric effect. Here we investigate photoionization of helium by a sequence of attosecond pulses in the presence of a weak infrared laser field. We continuously control the energy of the photoelectrons and introduce an asymmetry in their emission direction, at variance with the idealized rules mentioned above. This control, made possible by the extreme temporal confinement of the light-matter interaction, opens a road in attosecond science, namely, the manipulation of ultrafast processes with a tailored sequence of attosecond pulses.

| S-EPMC7245115 | biostudies-literature

Human Lymphatic Architecture and Dynamic Transport Imaged Using Near-infrared Fluorescence.

Project description:BackgroundAlthough the importance of lymphatic function is well recognized, the lack of real-time imaging modalities limits our understanding of its role in many diseases. In a phase 0 exploratory study, we used dynamic, near-infrared (NIR) fluorescence imaging to assess the extremes of lymphatic architecture and transport in healthy human subjects and in subjects clinically diagnosed with unilateral lymphedema (LE), a disease that can be prevalent in cancer survivors.Methods and resultsActive lymphatic propulsion was imaged after intradermal injections of 25 µg of indocyanine green (total maximum dose ?400 µg) bilaterally in the arms or legs of control and subjects. Images show well-defined lymphatic structures with propulsive dye transport in limbs of healthy subjects. In LE subjects, we observed extravascular dye accumulation, networks of fluorescent lymphatic capillaries, and/or tortuous lymphatic vessels in all symptomatic and some asymptomatic limbs. Statistical models indicate that disease status and/or limb significantly affect parameters of apparent lymph propagation velocity and contractile frequency.ConclusionsThese clinical research studies demonstrate the potential of NIR fluorescence imaging as a diagnostic measure of functional lymphatics and as a new tool in translational research studies to decipher the role of the lymphatic system in cancer and other diseases.

| S-EPMC3000461 | biostudies-literature

Polymeric Membranes Doped with Halloysite Nanotubes Imaged using Proton Microbeam Microscopy.

Project description:Polymeric membranes are useful tools for water filtration processes, with their performance strongly dependent on the presence of hydrophilic dopants. In this study, polyaniline (PANI)-capped aluminosilicate (halloysite) nanotubes (HNTs) are dispersed into polyether sulfone (PES), with concentrations ranging from 0.5 to 1.5 wt%, to modify the properties of the PES membrane. Both undoped and HNT-doped PES membranes are investigated in terms of wettability (static and time-dependent contact angle), permeance, mechanical resistance, and morphology (using scanning electron microscopy (SEM)). The higher water permeance observed for the PES membranes incorporating PANI-capped HNTs is, finally, assessed and discussed vis-à-vis the real distribution of HNTs. Indeed, the imaging and characterization in terms of composition, spatial arrangement, and counting of HNTs embedded within the polymeric matrix are demonstrated using non-destructive Micro Particle Induced X-ray Emission (µ-PIXE) and Scanning Transmission Ion Microscopy (STIM) techniques. This approach not only exhibits the unique ability to detect/highlight the distribution of HNTs incorporated throughout the whole thickness of polymer membranes and provide volumetric morphological information consistent with SEM imaging, but also overcomes the limits of the most common analytical techniques exploiting electron probes. These aspects are comprehensively discussed in terms of practical analysis advantages.

| S-EPMC10674683 | biostudies-literature

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