Impacts of wildfire-season air quality on park and playground visitation in the Northwest United States.

A significant cost of wildfires is the exposure of local and regional populations to air pollution from smoke, which can travel hundreds of miles from the source fire and is associated with significant negative health consequences. Wildfires are increasing in frequency and intensity in the United States, driven by historic fire management approaches and global climate change. These influences will take many decades or longer to reverse, so the main opportunities for mitigating health effects involve minimizing human exposure through changes in behavior or infrastructure. One key recommendation for reducing pollution exposures during wildfire smoke events is to limit time and physical activity outdoors, but there is limited evidence on the extent to which people make this change. We estimate how use of parks and playgrounds changes with air quality during wildfire season in the northwest United States. We find small reductions in park and playground visits on moderately polluted days, and large reductions, to 50-60% of baseline visits, when pollution levels are high. Disaggregating results by neighborhood characteristics, we find a significantly greater behavioral response to moderate levels of air pollution in neighborhoods with higher socio-economic status, although responses to high levels of pollution are similar across neighborhood types.

Applying location quotient methodology to urban park settings with mobile location data: Implications for equity and park planning.

In this study, we pilot a novel use of location quotient and proportional comparison methodology paired with mobile device location data. Specifically, we sought to understand visitation patterns in an urban park context based on visitor home locale socio-demographics, using an example from Fairmount Park in Philadelphia, PA, USA. We examined visitors' home locale demographics (i.e., percent African American and median household income) across a variety of park amenities (e.g., playgrounds, ball fields, splashpads), using location quotients and proportional analyses to compare the home locale demographics of visitors to specific amenities to park visitors as a whole. Findings illustrate amenities with over- or underrepresentation of visitors from certain socio-demographic groups, with bivariate analyses documenting intersectionality between race and income. Results of such analyses can aid park managers in understanding use of particular amenities and service gaps among historically underserved populations, and in turn, support more equitable resource allocation.

Practical Characterization Strategies for Comparison, Qualification, and Selection of Cell Viability Detection Methods for Cellular Therapeutic Product Development and Manufacturing.

Cellular therapy development and manufacturing has focused on providing novel therapeutic cell-based products for various diseases. The International Organization for Standardization (ISO) has provided guidance on critical quality attributes (CQAs) that shall be considered when testing and releasing cellular therapeutic products. Cell count and viability measurements are two of the CQAs that are determined during development, manufacturing, testing, and product release. The ISO Cell Counting Standard Part 1 and 2 addressed the needs for improving the quality of cell counting results. However, there is currently no guidance on the qualification and selection of a fit-for-purpose cell viability detection method. In this work, we present strategies for the characterization and comparison of AO/PI and AO/DAPI staining methods using the heat-killed (HK) and low temperature/nutrient-deprived (LT/ND) cell death models to evaluate the comparability of cell viability measurements and identify potential causes of differences. We compared the AO/PI and AO/DAPI staining methods using HK and LT/ND-generated dead cells, investigated the staining time effects on cell viability measurements, and determined their viability linearity with different mixtures of live and dead cells. Furthermore, we validated AO/PI and AO/DAPI cell viability measurement with a long-term cell proliferation assay. Finally, we demonstrate a practical example of cell viability measurement comparison using AO/PI and AO/DAPI on antibiotic-selected transduced Jurkat and THP-1 cells to select a fit-for-purpose method for functional genomics screening. The proposed strategies may potentially enable scientists to properly characterize, compare, and select cell viability detection methods that are critical for cellular therapeutic product development and manufacturing.

Big data spatial analysis of campers' landscape preferences: Examining demand for amenities.

Outdoor recreation decision-making has received significant research interest over the last fifty years. In the context of campsite choice, this previous research has almost exclusively used stated preference data and aspatial methods to understand decision-making. This present research seeks to understand how recreationists reach decisions on the selection of campsites and what aspects of the recreational setting drive demand through an examination of a big dataset of revealed preference data using a spatial regression. Specifically, we examine which managerial, social, and ecological aspects of the setting influence demand for campsites in Zion National Park's (USA) Watchman Campground using reservation data from the Recreation Information Database (RIDB). Results indicate that price, access to electricity, ease of access, and proximity to the Virgin River are significantly predictive of demand. Study implications for park management, including campsite allocation and distributive justice, are provided. Additionally, implications for future research methodology, including the use of transaction-style big data in protected area management research, are discussed.

Tomographic lifetime imaging using combined early- and late-arriving photons.

We present a novel, hybrid approach for time domain fluorescence tomography that efficiently combines lifetime multiplexing using late-arriving or asymptotic photons, with the high spatial resolution capability of early photon tomography. We also show that a decay amplitude-based asymptotic approach is superior to direct inversion of late-arriving photons for tomographic lifetime imaging within turbid media. The hybrid reconstruction approach is experimentally shown to recover fluorescent inclusions separated as close as 1.4 mm, with improved resolution and reduced cross talk compared to just using early photons or the asymptotic approach alone.

Fire suppression makes wildfires more severe and accentuates impacts of climate change and fuel accumulation.

Fire suppression is the primary management response to wildfires in many areas globally. By removing less-extreme wildfires, this approach ensures that remaining wildfires burn under more extreme conditions. Here, we term this the "suppression bias" and use a simulation model to highlight how this bias fundamentally impacts wildfire activity, independent of fuel accumulation and climate change. We illustrate how attempting to suppress all wildfires necessarily means that fires will burn with more severe and less diverse ecological impacts, with burned area increasing at faster rates than expected from fuel accumulation or climate change. Over a human lifespan, the modeled impacts of the suppression bias exceed those from fuel accumulation or climate change alone, suggesting that suppression may exert a significant and underappreciated influence on patterns of fire globally. Managing wildfires to safely burn under low and moderate conditions is thus a critical tool to address the growing wildfire crisis.

Experimental recreationist noise alters behavior and space use of wildlife.

Providing outdoor recreational opportunities to people and protecting wildlife are dual goals of many land managers. However, recreation is associated with negative effects on wildlife, ranging from increased stress hormones1,2 to shifts in habitat use3,4,5 to lowered reproductive success.6,7 Noise from recreational activities can be far reaching and have similar negative effects on wildlife, yet the impacts of these auditory encounters are less studied and are often unobservable. We designed a field-based experiment to both isolate and quantify the effects of recreation noise on several mammal species and test the effects of different recreation types and group sizes. Animals entering our sampling arrays triggered cameras to record video and broadcast recreation noise from speakers ∼20 m away. Our design allowed us to observe and classify behaviors of wildlife as they were exposed to acoustic stimuli. We found wildlife were 3.1-4.7 times more likely to flee and were vigilant for 2.2-3.0 times longer upon hearing recreation noise compared with controls (natural sounds and no noise). Wildlife abundance at our sampling arrays was 1.5 times lower the week following recreation noise deployments. Noise from larger groups of vocal hikers and mountain bikers caused the highest probability of fleeing (6-8 times more likely to flee). Elk were the most sensitive species to recreation noise, and large carnivores were the least sensitive. Our findings indicate that recreation noise alone caused anti-predator responses in wildlife, and as outdoor recreation continues to increase in popularity and geographic extent,8,9 noise from recreation may result in degraded or indirect wildlife habitat loss.

Resolution below the point spread function for diffuse optical imaging using fluorescence lifetime multiplexing.

We show that asymptotic lifetime-based fluorescence tomography can localize multiple-lifetime targets separated well below the diffuse point spread function of a turbid medium. This is made possible due to a complete diagonalization of the time domain forward problem in the asymptotic limit. We also show that continuous wave or direct time gate approaches to fluorescence tomography are unable to achieve this separation, indicating the unique advantage of a decay-amplitude-based approach for tomographic lifetime multiplexing with time domain data.

The PEG-fluorochrome shielding approach for targeted probe design.

We provide a new approach for fluorescent probe design termed "PEG-fluorochrome shielding", where PEGylation enhances quantum yields while blocking troublesome interactions between fluorochromes and biomolecules. To demonstrate PEG-fluorochrome shielding, fluorochrome-bearing peptide probes were synthesized, three without PEG and three with a 5 kDa PEG functional group. In vitro, PEG blocked the interactions of fluorochrome-labeled peptide probes with each other (absorption spectra, self-quenching) and reduced nonspecific interactions with cells (by FACS). In vivo, PEG blocked interactions with biomolecules that lead to probe retention (by surface fluorescence). Integrin targeting in vivo was obtained as the differential uptake of an (111)In-labeled, fluorochrome-shielded, integrin-binding RGD probe and a control RAD. Using PEG to block fluorochrome-mediated interactions, rather than synthesizing de novo fluorochromes, can yield new approaches for the design of actively or passively targeted near-infrared fluorescent probes.

Exclusionary Effects of Campsite Allocation through Reservations in U.S. National Parks: Evidence from Mobile Device Location Data.

Campsites represent highly sought after recreational amenities in the national parks of the United States. Equitable allocation of scarce recreational resources has long been a key management issue in U.S. national parks, but has become increasingly difficult in an era of increasing demand. At present, a growing number of national park campsites are allocated through an online reservation system well in advance of a camper's arrival at a park. Compounding the challenge of allocating these campsites is a long history of exclusivity within national park camping-institutionalized through campground design and predicated on a legacy of the leisure class's affinity for camping in national parks. Given national park camping's history of exclusivity, this exploratory study seeks to explore how online reservation systems may impact the demographics of national park campers. Using mobile device location data, estimated demographics were calculated for campers in five national park campgrounds in the U.S. that each contained some sites requiring reservations and some sites available on a first-come, first-served basis. We detail results from analyses of variance between campsites requiring reservations and those that are available on a first-come, first-served basis. Results suggest that for each of the five campgrounds, those campers camping in sites that require reservations came from areas with higher median household incomes, on average. In three of the five campgrounds, this difference was significant. Additionally, in an urban-proximate setting, those camping in sites requiring reservations came from areas with a higher portion of White residency than those campers in campsites not requiring reservations, on average. We conclude with discussion that includes management implications concerning the growing prominence of online reservation systems for outdoor recreation amenities, and a brief research agenda for diversity, equity, and inclusion (DEI) as they relate to campgrounds. Principally, the former group of implications includes the realization that online reservation systems present the unintended consequence of excluding low-income, and perhaps non-White, would-be campers-a conclusion drawn from the results of this exploratory study. This discussion includes an analysis of the distributive justice of online reservation systems.

COVID-19's impact on visitation behavior to US national parks from communities of color: evidence from mobile phone data.

The widespread COVID-19 pandemic fundamentally changed many people's ways of life. With the necessity of social distancing and lock downs across the United States, evidence shows more people engage in outdoor activities. With the utilization of location-based service (LBS) data, we seek to explore how visitation patterns to national parks changed among communities of color during the COVID-19 pandemic. Our results show that visitation rates to national parks located closer than 347 km to individuals have increased amidst the pandemic, but the converse was demonstrated amongst parks located further than 347 km from individuals. More importantly, COVID-19 has adversely impacted visitation figures amongst non-white and Native American communities, with visitation volumes declining if these communities are situated further from national parks. Our results show disproportionately low-representations amongst national park visitors from these communities of color. African American communities display a particularly concerning trend whereby their visitation to national parks is substantially lower amongst communities closer to national parks.

Rapid cell counting and viability detection method of Escherichia coli Nissle using image cytometry.

The improvement of cell enumeration methods for the counting of Escherichia coli (E. coli) is important as E. coli gains in popularity as a basis for biopharmaceutical applications. In the biopharmaceutical industry, enumerating, characterizing, and dosing the accurate number of cells is imperative. In this work, we demonstrate the utilization of a chip-based image cytometer using a thin-gap, low volume counting chamber consumable to directly enumerate E. coli in bright field and fluorescence, and measure their viability using SYTOX™ Green. The total E. coli particles can be counted accurately label-free by adjusting the focus and targeting the linear range of the instrument. The E. coli are stained with SYTOX™ Green to count the membrane-compromised dead bacterial cells in the green fluorescence channel, while the total cells are counted using the bright field channel. Optimization of the system settings, image focus, cell counting range, and staining conditions have yielded a precise, rapid, and accurate E. coli cell enumeration and viability measurement.

Osteoblastic differentiation and stress response of human mesenchymal stem cells exposed to alternating current electric fields.

BACKGROUND: Electric fields are integral to many biological events, from maintaining cellular homeostasis to embryonic development to healing. The application of electric fields offers substantial therapeutic potential, while optimal dosing regimens and the underlying mechanisms responsible for the positive clinical impact are poorly understood. METHODS: The purpose of this study was to track the differentiation profile and stress response of human bone marrow derived mesenchymal stem cells (hMSCs) undergoing osteogenic differentiation during exposure to a 20 mV/cm, 60 kHz electric field. Morphological and biochemical changes were imaged using endogenous two-photon excited fluorescence (TPEF) and quantitatively assessed through eccentricity calculations and extraction of the redox ratio from NADH, FAD and lipofuscin contributions. Real time reverse transcriptase-polymerase chain reactions (RT-PCR) were used to track osteogenic differentiation markers, namely alkaline phosphatase (ALP) and collagen type 1 (col1), and stress response markers, such as heat shock protein 27 (hsp27) and heat shock protein 70 (hsp70). Comparisons of collagen deposition between the stimulated hMSCs and controls were examined through second harmonic generation (SHG) imaging. RESULTS: Quantitative differences in cell morphology, as described through an eccentricity ratio, were found on days 2 and days 5 (p < 0.05) in samples exposed to the electric field. A delayed but two fold increase in ALP and col1 transcript was detected by week 2 (p < 0.05) in differentiating hMSCs exposed to an electric field in comparison to the nonstimulated controls. Upregulation in stress marker, hsp27, and type 1 collagen deposition were correlated with this response. Increases in NADH, FAD, and lipofuscin were traced in the stimulation group during the first week of field exposure with differences statistically significant on day 10 (p < 0.05). Changes in hsp27 expression correlate well with changes in lipofuscin detected in the stimulation group, suggesting a connection with oxidative stress. Both differentiation factors and electrical stimulation improved hMSC differentiation potential to bone based on calcium deposition on day 28. CONCLUSIONS: Electrical stimulation is a useful tool to improve hMSC osteogenic differentiation, while heat shock proteins may reveal underlying mechanisms, and optical non-invasive imaging may be used to monitor the induced morphological and biochemical changes.

Understanding changes in park visitation during the COVID-19 pandemic: A spatial application of big data.

In the spring of 2020, the COVID-19 pandemic changed the daily lives of people around the world. In an effort to quantify these changes, Google released an open-source dataset pertaining to regional mobility trends-including park visitation trends. Changes in park visitation are calculated from an earlier baseline period for measurement. Park visitation is robustly linked to positive wellbeing indicators across the lifespan, and has been shown to support wellbeing during the COVID-19 pandemic. Therefore, this dataset offers vast application potential, containing aggregated information from location data collected via smartphones worldwide. However, empirical analysis of these data is limited. Namely, the factors influencing reported changes in mobility and the degree to which these changes can be directly attributable to COVID-19 remain unknown. This study aims to address these gaps in our understanding of the changes in park visitation, the causes of these changes (e.g., safer-at-home orders, amount of COVID-19 cases per county, climate, etc.) and possible impacts to wellbeing by constructing and testing a spatial regression model. Results suggest that elevation and latitude serve as primary influences of reported changes in park visitation from the baseline period. Therefore, it is surmised that Google's reported changes in park-related mobility are only partially the function of COVID-19.

Observation and quantification of the morphological effect of trypan blue rupturing dead or dying cells.

Trypan blue has long been the gold standard for staining dead cell to determine cell viability. The dye is excluded from membrane-intact live cells, but can enter and concentrate in membrane-compromised dead cells, rendering the cells dark blue. Over the years, there has been an understanding that trypan blue is inaccurate for cell viability under 80% without scientific support. We previously showed that trypan blue can alter the morphology of dead cells to a diffuse shape, which can lead to over-estimation of viability. Here, we investigate the origin of the dim and diffuse objects after trypan blue staining. Utilizing image and video acquisition, we show real-time transformation of cells into diffuse objects when stained with trypan blue. The same phenomenon was not observed when staining cells with propidium iodide. We also demonstrate the co-localization of trypan blue and propidium iodide, confirming these diffuse objects as cells that contain nuclei. The videos clearly show immediate cell rupturing after trypan blue contact. The formation of these diffuse objects was monitored and counted over time as cells die outside of the incubator. We hypothesize and demonstrate that rapid water influx may have caused the cells to rupture and disappear. Since some dead cells disappear after trypan blue staining, the total can be under-counted, leading to over-estimation of cell viability. This inaccuracy could affect the outcomes of cellular therapies, which require accurate measurements of immune cells that will be infused back into patients.

Non-invasive characterization of structure and morphology of silk fibroin biomaterials using non-linear microscopy.

Designing biomaterial scaffolds remains a major challenge in tissue engineering. Key to this challenge is improved understanding of the relationships between the scaffold properties and its degradation kinetics, as well as the cell interactions and the promotion of new matrix deposition. Here we present the use of non-linear spectroscopic imaging as a non-invasive method to characterize not only morphological, but also structural aspects of silkworm silk fibroin-based biomaterials, relying entirely on endogenous optical contrast. We demonstrate that two photon excited fluorescence and second harmonic generation are sensitive to the hydration, overall beta sheet content and molecular orientation of the sample. Thus, the functional content and high resolution afforded by these non-invasive approaches offer promise for identifying important connections between biomaterial design and functional engineered tissue development. The strategies described also have broader implications for understanding and tracking the remodeling of degradable biomaterials under dynamic conditions both in vitro and in vivo.

Tomographic fluorescence lifetime multiplexing in the spatial frequency domain.

The ability to simultaneously recover multiple fluorophores within biological tissue (multiplexing) can have important applications for tracking parallel disease processes in vivo. Here we present a novel method for rapid and quantitative multiplexing within a scattering medium, such as biological tissue, based on fluorescence lifetime contrast. This method employs a tomographic inversion of the asymptotic (late) portion of time-resolved spatial frequency (SF) domain measurements. Using Monte Carlo simulations and phantom experiments, we show that the SF-asymptotic time domain (SF-ATD) approach provides a several-fold improvement in relative quantitation and localization accuracy over conventional SF-time domain inversion. We also show that the SF-ATD approach can exploit selective filtering of high spatial frequencies to dramatically improve reconstruction accuracy for fluorophores with subnanosecond lifetimes, which is typical of most near-infrared fluorophores. These results suggest that the SF-ATD approach will serve as a powerful new tool for whole-body lifetime multiplexing.

Quantitative biomarkers of stem cell differentiation based on intrinsic two-photon excited fluorescence.

We present the use of two-photon excited fluorescence (TPEF) as a noninvasive means to monitor differentiation of human mesenchymal stem cells (hMSCs) into an adipogenic pathway relying entirely on endogenous sources of contrast. Specifically, we demonstrate that TPEF can be used to reveal quantitative differences in the biochemical status and the shape of differentiating and nondifferentiating stem cells in two-dimensional (2-D) cultures. We find that even in simple 2-D cultures, not all cells are undergoing differentiation at the same rate. Last, such noninvasive approaches may also ultimately allow for determination of the lineage toward which the cells are differentiating (e.g., fat versus bone). Thus, intrinsic TPEF imaging provides quantitative morphological and biochemical biomarkers associated with stem cell differentiation and could serve as an important enabling technology in tissue engineering applications.

In vivo flow cytometry: a new method for enumerating circulating cancer cells.

The fate of circulating tumor cells is an important determinant of their ability to form distant metastasis. Here, we demonstrate the use of in vivo flow cytometry as a powerful new method for detecting quantitatively circulating cancer cells. We specifically examine the circulation kinetics of two prostate cancer cell lines with different metastatic potential in mice and rats. We find that the cell line and the host environment affect the circulation kinetics of prostate cancer cells, with the intrinsic cell line properties determining the initial rate of cell depletion from the circulation and the host affecting cell circulation at later time points.

Substrate-based near-infrared imaging sensors enable fluorescence lifetime contrast via built-in dynamic fluorescence quenching elements.

Enzymatic activity sensing in fluorescence lifetime (FLT) mode with "self-quenched" macromolecular near-infrared (NIR) sensors is a highly promising strategy for in vivo imaging of proteolysis. However, the mechanisms of FLT changes in such substrate-based NIR sensors have not yet been studied. We synthesized two types of sensors by linking the near-infrared fluorophore IRDye 800CW to macromolecular graft copolymers of methoxy polyethylene glycol and polylysine (MPEG-gPLL) with varying degrees of MPEGylation and studied their fragmentation induced by trypsin, elastase, plasmin and cathepsins (B,S,L,K). We determined that the efficiency of such NIR sensors in FLT mode depends on sensor composition. While MPEG-gPLL with a high degree of MPEGylation showed rapid (τ1/2=0.1-0.2 min) FLT increase (Δτ=0.25 ns) upon model proteinase-mediated hydrolysis in vivo, lower MPEGylation density resulted in no such FLT increase. Temperature-dependence of fluorescence de-quenching of NIR sensors pointed to a mixed dynamic/static-quenching mode of MPEG-gPLL-linked fluorophores. We further demonstrated that although the bulk of sensor-linked fluorophores were de-quenched due to the elimination of static quenching, proteolysis-mediated deletion of a fraction of short (8-10kD) negatively charged fragments of highly MPEGylated NIR sensor is the most likely event leading to a rapid FLT increase phenomenon in quenched NIR sensors. Therefore, the optimization of "built-in" dynamic quenching elements of macromolecular NIR sensors is a potential avenue for improving their response in FLT mode.