191026 Clocked Atom Delivery to a Photonic Crystal Waveguide

Title:
Clocked Atom Delivery to a Photonic Crystal Waveguide

Speaker:
彭陸 (Lucas Sky Peng), PhD, AOSense, Inc.

Time:
10/26 (Sat.) 7 pm PDT, 8 pm MDT, 9 pm CDT, 10 pm EDT
10/27 (Sun.) 10 am Taiwan

Keywords:
Physics, Atomic physics, Quantum optics, Nanophotonics, Photonic crystal waveguide, Many body physics

Abstract:
Experiments and numerical simulations are described that develop quantitative understanding of atomic motion near the surfaces of nanoscopic photonic crystal waveguides (PCWs). Ultracold atoms are delivered from a moving optical lattice into the PCW. Synchronous with the moving lattice, transmission spectra for a guided-mode probe field are recorded as functions of lattice transport time and frequency detuning of the probe beam. By way of measurements such as these, we have been able to validate quantitatively our numerical simulations, which are based upon detailed understanding of atomic trajectories that pass around and through nanoscopic regions of the PCW under the influence of optical and surface forces. The resolution for mapping atomic motion is roughly 50 nm in space and 100 ns in time. By introducing auxiliary guided-mode (GM) fields that provide spatially varying AC Stark shifts, we have, to some degree, begun to control atomic trajectories, such as to enhance the flux into the central vacuum gap of the PCW at predetermined times and with known AC Stark shifts. Applications of these capabilities include enabling high fractional filling of optical trap sites within PCWs, calibration of optical fields within PCWs, and utilization of the time-dependent, optically dense atomic medium for novel nonlinear optical experiments.

191012 Coupling Cell-Cell Adhesion to Cell Polarization

Title:
Coupling Cell-Cell Adhesion to Cell Polarization

Speaker:
王成禾 (Chen-Ho Wang), PhD student, Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG)

Time:
10/12 (Sat.) 11 am PDT, 12 pm MDT, 1 pm CDT, 2 pm EDT
10/13 (Sun.) 2 am Taiwan

Keywords:
Biology, Biophysics, Cell polarization, Reaction diffusion, Cell-cell adhesion, Live-cell imaging

Abstract:

Cell polarization is an essential process which is key to morphology and function of tissues. Cells in tissue polarize and align their polarization axis to create functional, tissue specific architecture. A prominent example is the organization of epithelial tissues. Here, single cells polarize into three distinct cell membrane domains: apical (free surface), lateral (cell-cell contact) and basal (cell-matrix contact). Adhesion contacts of cell-cell versus cell-matrix interface are the most obvious external cues to align polarization axis of single cells such that apical domains are forming a single closed surface or cavity. Much is still unknown about the role of cell-cell contact interface with its homophilic adhesion receptors. Even less is known about the feedback and interplay of basal and lateral domains and how this is connected to apical-basal polarization of epithelial cells.

In this research, we combine two approaches: 1) a minimal organ approach which comprising of MDCK doublets cultured in array of microcavities to precisely control the spatial organization of cellular adhesions in three dimensions, 2) To provide a minimum model of cell polarization in epithelium, computational simulation will be involved for examining sufficiency of the model.