Soliton microcomb based spectral domain optical coherence tomography

Spectral domain optical coherence tomography (SD-OCT) is a widely used and minimally invaive technique for bio-medical imaging [1]. SD-OCT typically relies on the use of superluminescent diodes (SLD), which provide a low-noise and broadband optical spectrum. Recent advances in photonic chipscale frequency combs [2, 3] based on soliton formation in photonic integrated microresonators provide an chipscale alternative illumination scheme for SD-OCT. Yet to date, the use of such soliton microcombs in OCT has not yet been analyzed. Here we explore the use of soliton microcombs in spectral domain OCT and show that, by using photonic chipscale Si3N4 resonators in conjunction with 1300 nm pump lasers, spectral bandwidths exceeding those of commercial SLDs are possible. We demonstrate that the soliton states in microresonators exhibit a noise floor that is ca. 3 dB lower than for the SLD at identical power, but can exhibit significantly lower noise performance for powers at the milliWatt level. We perform SD-OCT imaging on an ex vivo fixed mouse brain tissue using the soliton microcomb, alongside an SLD for comparison, and demonstrate the principle viability of soliton based SD-OCT. Importantly, we demonstrate that classical amplitude noise of all soliton comb teeth are correlated, i.e. common mode, in contrast to SLD or incoherent microcomb states [4], which should, in theory, improve the image quality. Moreover, we demonstrate the potential for circular ranging, i.e. optical sub-sampling [5, 6], due to the high coherence and temporal periodicity of the soliton state. Taken together, our work indicates the promising properties of soliton microcombs for SD-OCT

Visible spectrum extended-focus optical coherence microscopy for label-free sub-cellular tomography

We present a novel extended-focus optical coherence microscope (OCM) attaining 0.7 {\mu}m axial and 0.4 {\mu}m lateral resolution maintained over a depth of 40 {\mu}m, while preserving the advantages of Fourier domain OCM. Our method uses an ultra-broad spectrum from a super- continuum laser source. As the spectrum spans from near-infrared to visible wavelengths (240 nm in bandwidth), we call the method visOCM. The combination of such a broad spectrum with a high-NA objective creates an almost isotropic 3D submicron resolution. We analyze the imaging performance of visOCM on microbead samples and demonstrate its image quality on cell cultures and ex-vivo mouse brain tissue.Comment: 15 pages, 7 figure

Letters Re: Section 126 Problem

https://egrove.olemiss.edu/aicpa_guides/2617/thumbnail.jp

Community dimensions and HPSA practice location: 30 years of family medicine training

BACKGROUND AND OBJECTIVES: Our objective was to assess practicing family physicians\u27 confidence and participation in a range of community-related activities. Additionally, we assessed the strength of the relationship between the physicians\u27 reported medical school and residency training in community-related activities and their current community activities, as well as whether they were practicing in an underserved location. METHODS: All 347 graduates of the University of Massachusetts Family Medicine Residency were surveyed about practice location and type, involvement and training in community work, confidence in community-related skills, and sociodemographic characteristics. Analyses were conducted by residency graduation decade (1976-1985, 1986-1995, and 1996-2005). RESULTS: Earlier graduates (19761985) were significantly more likely to engage in an array of community-related activities, but recent graduates (1996-2005) were more likely to report having been trained in these skills. There was a significant positive association between practice in an underserved area and confidence in issues related to sociocultural aspects of care. While recent graduates were more likely to locate both initial and current practices in a Health Professions Shortage Area (HPSA), 20.6% of all graduates reported an initial practice in a HPSA. CONCLUSIONS: While family physician involvement in community-related activities increases with years out of residency, a higher proportion of recent graduates report having learned community-related skills while in medical school. Physician relocation tends to be away from HPSA toward non-HPSA sites

Family medicine residency characteristics associated with practice in a health professions shortage area

BACKGROUND AND OBJECTIVES: While some family medicine residency programs are designed to train residents in community health centers (CHCs) for future careers serving underserved populations, there are few outcome studies on such programs. Our residency program provides three options for ambulatory health center training, but otherwise residents participate in the same curriculum. We analyzed relationships between ambulatory training site and likelihood of practice in health professions shortage areas (HPSAs). METHODS: We sent a mail survey to all graduates of one family medicine residency about practice locations, types, and populations; influences on practice choice; and sociodemographic characteristics. RESULTS: Training in a CHC had a statistically significant association with the likelihood of practice in an HPSA for both initial and current practice. Training in a rural residency site was associated with initial and current rural practice. Logistic regression analysis showed that physicians who completed ambulatory training in the CHC were nearly six times more likely to report having practiced initially and four times more likely to cite current practice in an HPSA. CONCLUSIONS: Outpatient CHC residency training increases the likelihood of practice in an underserved setting. This finding has policy implications for supporting workforce training in practice settings that care for underserved populations

In vivo imaging of murine endocrine islets of Langerhans with extended-focus optical coherence microscopy

Aims/hypothesis: Structural and functional imaging of the islets of Langerhans and the insulin-secreting beta cells represents a significant challenge and a long-lasting objective in diabetes research. In vivo microscopy offers a valuable insight into beta cell function but has severe limitations regarding sample labelling, imaging speed and depth, and was primarily performed on isolated islets lacking native innervations and vascularisation. This article introduces extended-focus optical coherence microscopy (xfOCM) to image murine pancreatic islets in their natural environment in situ, i.e. in vivo and in a label-free condition. Methods: Ex vivo measurements on excised pancreases were performed and validated by standard immunohistochemistry to investigate the structures that can be observed with xfOCM. The influence of streptozotocin on the signature of the islets was investigated in a second step. Finally, xfOCM was applied to make measurements of the murine pancreas in situ and in vivo. Results: xfOCM circumvents the fundamental physical limit that trades lateral resolution for depth of field, and achieves fast volumetric imaging with high resolution in all three dimensions. It allows label-free visualisation of pancreatic lobules, ducts, blood vessels and individual islets of Langerhans ex vivo and in vivo, and detects streptozotocin-induced islet destruction. Conclusions/interpretation: Our results demonstrate the potential value of xfOCM in high-resolution in vivo studies to assess islet structure and function in animal models of diabetes, aiming towards its use in longitudinal studies of diabetes progression and islet transplant

Surface and subsurface characterisation of salt pans expressing polygonal patterns

The data set described here contains information about the surface, subsurface and environmental conditions of salt pans that express polygonal patterns in their surface salt crust (Lasser et al., 2020b), DOI: 10.5880/fidgeo.2020.037. Information stems from 5 field sites at Badwater Basin and 21 field sites at Owens Lake – both in central California. All data was recorded during two field campaigns, from between November and December, 2016, and in January 2018. Crust surfaces, including the mean diameter and fluctuations in the height of the polygonal patterns, were characterised by terrestrial laser scanner. The data contains the resulting three dimensional point clouds, which describe these surfaces. The subsurface is characterised by grain size distributions of samples taken from depths between 5 cm and 100 cm below the salt crust, and measured with a laser particle size analyser. Subsurface salinity profiles were recorded and the ground water density was also measured. Additionally, the salts present in the crust and pore water were analysed to determine their compo- sition. To characterise the environmental conditions at Owens Lake, including the differences between nearby crust features, records were made of the temperature and relative humidity during one week in November 2016. The field sites are characterised by images, showing the general context of each site, such as pictures of selected salt polygons, including any which were sampled, a typical core from each site at which core samples were taken and close-ups of the salt crust morphology. Finally, two videos of salt crust growth over the course of spring 2018 and reconstructed from time-lapse images are included

Complexity, transparency and time pressure: practical insights into science communication in times of crisis

A global crisis such as the COVID-19 pandemic that started in early 2020 poses significant challenges for how research is conducted and communicated. We present four case studies from the perspective of an interdisciplinary research institution that switched to “corona-mode” during the first two months of the crisis, focussing all its capacities on COVID-19-related issues, communicating to the public directly and via media, as well as actively advising the national government. The case studies highlight the challenges posed by the increased time pressure, high demand for transparency, and communication of complexity and uncertainty. The article gives insights into how these challenges were addressed in our research institution and how science communication in general can be managed during a crisis