Lauren Mason – Page 2

Quantitative Assessment of Collagen Remodeling during a Murine Pregnancy

Uterine cervical remodeling is a fundamental feature of pregnancy, facilitating the delivery of the fetus through the cervical canal. Yet, we still know very little about this process due to the lack of methodologies that can quantitatively and unequivocally pinpoint the changes the cervix undergoes during pregnancy. We utilize polarization-resolved second harmonic generation to visualize the alterations the cervix extracellular matrix, specifically collagen, undergoes during pregnancy with exquisite resolution. This technique provides images of the collagen orientation at the pixel level (0.4 μm) over the entire murine cervical section. They show tight and ordered packing of collagen fibers around the os at the early stage of pregnancy and their disruption at the later stages. Furthermore, we utilize a straightforward statistical analysis to demonstrate the loss of order in the tissue, consistent with the loss of mechanical properties associated with this process. This work provides a deeper understanding of the parturition process and could support research into the cause of pathological or premature birth.

The hierarchical structure of organic mixed ionic–electronic conductors as revealed with 4D-STEM

Polymeric organic mixed ionic–electronic conductors (OMIECs) underpin several technologies where their electrochemical properties are desirable. These properties however depend on the microstructure that develops in their aqueous operational environment. In relevant experimental conditions, electrolyte-induced swelling amounts to up 20% in volume. We investigated the structure of a model OMIEC across multiple length-scales using cryogenic four-dimensional scanning transmission electron microscopy (cryo-4D-STEM) in both dry and hydrated states. 4D STEM allows us to identify the prevalent defects in the polymer crystalline regions and to analyze the liquid-crystalline nature of the polymer. The orientation maps of the dry and hydrated polymer show that swelling-induced disorder is mostly localized within discrete regions, thus largely preserving liquid crystalline order. Therefore, the liquid crystalline mesostructure makes electronic transport robust to electrolyte ingress. This study demonstrates that cryo-4D-STEM provides multiscale structural insights into complex, hierarchical structures such as polymeric OMIECs, even in their hydrated operating state.

Deep-learning phase retrieval with low radiation doses

Phase retrieval is fundamentally important in scientific imaging and is crucial for nanoscale techniques like coherent diffractive imaging (CDI). Low radiation dose imaging is essential for applications involving radiation-sensitive samples. However, most phase retrieval methods struggle in low-dose scenarios due to high shot noise. Recent advancements in optical data acquisition setups, such as in-situ CDI, have shown promise for low-dose imaging, but they rely on a time series of measurements, making them unsuitable for single-image applications. Similarly, data- driven phase retrieval techniques are not easily adaptable to data-scarce situations. Zero-shot deep learning methods based on pre-trained and implicit generative priors have been effective in various imaging tasks but have shown limited success in PR. In this work, we propose low-dose deep image prior (LoDIP), which combines in-situ CDI with the power of implicit generative priors to address single-image low-dose phase retrieval. Quantitative evaluations demonstrate LoDIP’s superior performance in this task and its applicability to real experimental scenarios. We expect the LoDIP method to find applications in X-ray imaging of dose-sensitive samples across diverse fields including organic semiconductors and biological specimens.

Reduced-Dimensionality Al Nanocrystals: Nanowires, Nanobars, and Nanomoustaches

Aluminum nanocrystals created by catalyst-driven colloidal synthesis support excellent plasmonic properties, due to their high level of elemental purity, monocrystallinity, and controlled size and shape. Reduction in the rate of nanocrystal growth enables the synthesis of highly anisotropic Al nanowires, nanobars, and singly twinned “nanomoustaches”. Electron energy loss spectroscopy was used to study the plasmonic properties of these nanocrystals, spanning the broad energy range needed to map their plasmonic modes. The coupling between these nanocrystals and other plasmonic metal nanostructures, specifically Ag nanocubes and Au films of controlled nanoscale thickness, was investigated. Al nanocrystals show excellent long-term stability under atmospheric conditions, providing a practical alternative to coinage metal-based nanowires in assembled nanoscale devices.

Congratulations to Neerja Aggarwal for Receiving a Second Place Poster Award at the Advanced Imaging Methods Workshop at the University of California Berkeley

Neerja Aggarwal’s poster titled “Spectral DiffuserScope: Compact Hyperspectral Imager for Fluorescence Microscopy” received a Second Place Poster Award at the Advanced Imaging Methods Workshop at the University of California Berkeley.

Congratulations to Laura Waller for Being Selected as the 2024 AFOSR Chief Scientist Distinguished Lecturer

The AFRL/AFOSR Chief Scientist Distinguished Lecture Series selected Dr. Laura Waller, the Charles A. Desoer Professor of Electrical Engineering and Computer Sciences at UC Berkeley, as the 2024 AFOSR Chief Scientist Distinguished Lecturer. On March 21, 2024, from 11:30 AM – 12:30 PM ET, Dr. Waller delivered a talk titled “Computational Imaging, from Microscopes to Telescopes,” exploring the joint design of imaging system hardware and software for optimized data acquisition and reconstruction.

Congratulations to Tristan O’Neill for Receiving a 2024 M&M Student Poster Award

Congratulations to Tristan O’Neill for receiving a 2024 M&M Student Poster Award for his poster titled, “Mapping Moiré Potentials with STEM EBIC Imaging.”

Congrats to Ho Leung Chan for Being Selected as a 2024 M&M Student Scholar

Graduate student Ho Leung Chan from Prof. Chris Regan’s research group at UCLA received a 2024 M&M Student Scholar Award! Her presentation is titled “Nano-PUND and STEM EBIC Imaging for Ferroelectric Polarization Mapping.”

The award consists of free registration for the meeting, $1000 travel support, and invitations to the Presidential Reception. Applicants must be bona fide students at a recognized college or university at the time of the meeting. Awards are based on the quality of the paper submitted for presentation at the meeting. The applicant must be the first author of the submitted paper. Successful applicants must present their papers personally at the meeting in order to receive the award.

Congrats to Chris Regan and William Hubbard for Receiving the 2023 Microscopy Today Innovation Award

Congratulations to Prof. Chris Regan and Dr. William Hubbard for receiving the 2023 Microscopy Today Innovation Award for Low Noise, Two Channel STEM EBIC System.

NEI’s STEM EBIC system enables straightforward imaging of electronic and thermal features that are otherwise difficult, if not impossible, to visualize in the TEM. Electron beam-induced current (EBIC) is a measure of the current generated in a sample as it is raster-scanned by a focused electron beam. Associating the measured EBIC with the beam position produces an EBIC image. First implemented in the 1960s, EBIC imaging is usually performed in a scanning electron microscope (SEM) to map electric fields in microelectronic devices. For instance, the built-in electric field of a p-n junction separates electron-hole pairs generated by the beam, producing a strong EBIC signal. Recently, thousand-fold improvements in current measurement sensitivity have led to practical EBIC imaging in scanning transmission electron microscopes (STEMs). This improved sensitivity reveals previously undetectable EBICs. In particular, the EBIC generated by secondary electron emission (SEEBIC) can now be routinely visualized.

Standard TEM-based techniques excel at determining the physical structure of a sample—the atomic locations and elemental identities—but they struggle to distinguish a metal from an insulator, or a warm interconnect from a cold one. In microelectronic devices, such electronic and thermal structure is generally of greater interest than the physical structure. STEM SEEBIC-based imaging of micro- and nano-electronic devices reveals these signals at high resolution. It can, for instance, quantitatively map conductivity, electric field, temperature, SE yield, active dopant concentration, and work function.

NEI’s STEM EBIC system is a turn-key solution for measuring extremely small EBICs. Low-noise STEM EBIC images of sub-pA signals, including SEEBIC, can be acquired in under two minutes. Extrinsic noise (for example, line noise) is nearly undetectable, so image filtering and post-processing are not necessary. The system—featuring a sample holder, custom substrates, and electronics optimized for EBIC in the TEM—is equipped with two independent EBIC amplifier channels for acquiring EBIC from different electrodes simultaneously. Two-channel EBIC can definitively separate SEEBIC from standard EBIC in situations where both are present, which greatly facilitates analysis and interpretation. NEI’s STEM EBIC system is designed to work with other in situ techniques, including heating and biasing on either custom-fabricated test devices or FIB-extracted cross-sectional samples.

Congratulations to Max Krauss for Being Awarded 2024 Computer Engineering Senior of the Year at Fort Lewis College

Max Krauss, an undergraduate student and Fort Lewis College, was awarded 2024 FLC Computer Engineering Senior of the Year. Congratulations, Max!

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About Lauren Mason