Enhanced Thermal Object Imaging by Photon Addition or Subtraction

Long-baseline interferometry (LBI) is used to reconstruct the image of faint thermal objects. The image quality, for a given exposure time, is in general limited by a low signal-to-noise ratio (SNR). We show theoretically that a significant increase of the SNR, in a LBI, is possible by adding or subtracting photons to the thermal beam. At low photon counts, photon addition-subtraction technology strongly enhances the image quality. We have experimentally realized a nondeterministic physical protocol for photon subtraction. Our theoretical predictions are supported by experimental results.Comment: 4 pages, 5 figure

Genetic Manipulation of Neural Progenitors Derived from Human Embryonic Stem Cells

Human embryonic stem cell–derived neural progenitors (NP) present an important tool for understanding human development and disease. Optimal utilization of NP cells, however, requires an enhanced ability to monitor these cells in vitro and in vivo. Here we report production of the first genetically modified self-renewing human embryonic stem cell–derived NP cells that express fluorescent proteins under constitutive as well as lineage-specific promoters, enabling tracking and monitoring of cell fate. Nucleofection, transfection, and lentiviral transduction were compared for optimal gene delivery to NP cells. Transduction was most efficient in terms of transgene expression (37%), cell viability (39%), and long-term reporter expression (>3 months). Further, the constitutive gene promoters, cytomegalovirus, elongation factor 1α, and ubiquitin-C, exhibited comparable silencing (20–30%) in NP cells over a 2-month period, suggesting their suitability for long-term reporter expression studies. Transduced NP cells maintained their progenitor state and differentiation potential, as demonstrated by expression of endogenous NP markers and neuronal markers after differentiation. We also detected reporter expression in astrocytes generated from NP cells transduced with an astrocyte-specific gene promoter, glial fibrillary acidic protein, demonstrating the usefulness of this approach. The genetically manipulated NP cells described here offer great potential for live cell–tracking experiments, and a similar approach can as well be used for expression of proteins other than reporters