3D tracking of extracellular vesicles by holographic fluorescence imaging

Fluorescence microscopy is the method of choice in biology for its molecular specificity and super-resolution capabilities. However, it is limited to a narrow z range around one observation plane. Here, we report an imaging approach that recovers the full electric field of fluorescent light with single-molecule sensitivity. We expand the principle of digital holography to fast fluorescent detection by eliminating the need for phase cycling and enable three-dimensional (3D) tracking of individual nanoparticles with an in-plane resolution of 15 nm and a z-range of 8 mm. As a proof-of-concept biological application, we image the 3D motion of extracellular vesicles (EVs) inside live cells. At short time scales (<4 s), we resolve near-isotropic 3D diffusion and directional transport. For longer lag times, we observe a transition toward anisotropic motion with the EVs being transported over long distances in the axial plane while being confined in the horizontal dimension.

Research on a medium-tracked omni-vehicle

Existing omnidirectional vehicles have disadvantages of poor load capacities and practicability. Based on the omnidirectional mobile track and an adapted symmetrical layout, a novel medium-tracked omni-vehicle was designed. The kinematic and dynamic model of the vehicle was established, and the anisotropy of the velocity and acceleration of the vehicle was analyzed. With a counterbalanced forklift as the design goal, a virtual prototype and real prototype of the vehicle were established. The prototype had a no-load weight of 5 t and a full-load weight of 7 t. Simulations and experiments were carried out for various omnidirectional movements of the prototype, such as longitudinal, lateral, multi-angle diagonal, and center-point steering motions. The simulation and experimental results showed that the vehicle performed omnidirectional motion in the plane under no-load and full-load conditions. The translational motion of the prototype exhibited anisotropic motion. The causes of the trajectory and velocity deviation during the motion of the prototype were analyzed.

Simultaneous determination of deuteron quadrupole coupling constants and rotational correlation times: the model case of hydrogen bonded ionic liquids

We show that deuteron quadrupole coupling constants, and reorientational correlation times of molecular bonds N–D that are involved in hydrogen bonding, can be determined from NMR T1 relaxation time experiments simultaneously by assuming anisotropic motion.