Advances in computational wide field imaging

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THE EFFECTS OF HOUSING PRICES, WAGES, AND COMMUTING TIME ON JOINT RESIDENTIAL AND JOB LOCATION CHOICES

A utility maximizing framework is used to model how wages, housing prices, and commuting time affect joint decisions of where to live and where to work. The implied multinomial logit model yields plausible estimates of the role of economic variables on joint residence/job location choices.Labor and Human Capital,

Quantifying the Dynamics of Bacterial Secondary Metabolites by Spectral Multiphoton Microscopy

Phenazines, a group of fluorescent small molecules produced by the bacterium Pseudomonas aeruginosa, play a role in maintaining cellular redox homeostasis. Phenazines have been challenging to study in vivo due to their redox activity, presence both intra- and extracellularly, and their diverse chemical properties. Here, we describe a noninvasive in vivo optical technique to monitor phenazine concentrations within bacterial cells using time-lapsed spectral multiphoton fluorescence microscopy. This technique enables simultaneous monitoring of multiple weakly fluorescent molecules (phenazines, siderophores, NAD(P)H) expressed by bacteria in culture. This work provides the first in vivo measurements of reduced phenazine concentration as well as the first description of the temporal dynamics of the phenazine-NAD(P)H redox system in Pseudomonas aeruginosa, illuminating an unanticipated role for 1-hydroxyphenazine. Similar approaches could be used to study the abundance and redox dynamics of a wide range of small molecules within bacteria, both as single cells and in communities

Three-dimensional super-resolution high-throughput imaging by structured illumination STED microscopy

Stimulated emission depletion (STED) microscopy is able to image fluorescence labeled samples with nanometer scale resolution. STED microscopy is typically a point-scanning method, limited by the high intensity requirement of the depletion beam. With the development of high peak power lasers, two dimensional parallel STED microscopy has been developed. Here, we develop the theoretical basis for extending STED microscopy to three dimensional imaging in parallel. This method uses structured illumination (SI) to generates a three dimensional depletion pattern. Compared to the two dimensional parallel STED microscopy, the 3D SI-STED microscopy generates intensity modulation along the light propagation direction without requiring higher laser power. This method not only achieves axial super-resolution of STED microscopy but also greatly reduces photobleaching and photodamage for 3D volumetric imaging.National Institutes of Health (U.S.) (NIH 1-U01-NS090438-01)National Institutes of Health (U.S.) (NIH 5-P41-EB015871)Hamamatsu Corporatio

Improving femtosecond laser pulse delivery through a hollow core photonic crystal fiber for temporally focused two-photon endomicroscopy

In this paper, we present a strategy to improve delivery of femtosecond laser pulses from a regenerative amplifier through a hollow core photonic crystal fiber for temporally focused wide-field two-photon endomicroscopy. For endomicroscope application, wide-field two-photon excitation has the advantage of requiring no scanning in the distal end. However, wide-field two-photon excitation requires peak power that is 10[superscript 4]–10[superscript 5] times higher than the point scanning approach corresponding to femtosecond pulses with energy on the order of 1–10 μJ at the specimen plane. The transmission of these high energy pulses through a single mode fiber into the microendoscope is a significant challenge. Two approaches were pursued to partially overcome this limitation. First, a single high energy pulse is split into a train of pulses with energy below the fiber damage threshold better utilizing the available laser energy. Second, stretching the pulse width in time by introducing negative dispersion was shown to have the dual benefit of reducing fiber damage probability and compensating for the positive group velocity dispersion induced by the fiber. With these strategy applied, 11 fold increase in the two photon excitation signal has been demonstrated.National Institutes of Health (U.S.) (9P41EB015871-26A1)National Institutes of Health (U.S.) (5R01EY017656-02)National Institutes of Health (U.S.) (5R01 NS051320)National Institutes of Health (U.S.) (4R44EB012415-02)National Science Foundation (U.S.) (CBET-0939511)Singapore-MIT AllianceSingapore-MIT Alliance for Research and TechnologySkolkovo Institute of Science and TechnologyHamamatsu CorporationDavid H. Koch Institute for Integrative Cancer Research at MIT. Bridge Project Initiativ

High-throughput three-dimensional lithographic microfabrication

A 3D lithographic microfabrication process has been developed that is high throughput, scalable, and capable of producing arbitrary patterns. It offers the possibility for industrial scale manufacturing of 3D microdevices such as photonic crystals, tissue engineering scaffolds, and microfluidics chips. This method is based on depth-resolved wide-field illumination by temporally focusing femtosecond light pulses. We characterized the axial resolution of this technique, and the result is consistent with the theoretical prediction. As proof-of-concept experiments, we demonstrated photobleaching of 3D resolved patterns in a fluorescent medium and fabricating 3D microstructures with SU-8 photoresist.Deshpande Center for Technological Innovation (Massachusetts Institute of Technology. School of Engineering)Singapore-MIT Alliance for Research and Technology (SMART