Droplet Measurement Technologies (United States)

<strong class="journal-contentHeaderColor">Abstract.</strong> Air pollution and fog are closely connected, influencing both visibility and human health. As relative humidity rises, aerosol particles absorb water and grow hygroscopically, potentially activating into fog droplets when supersaturation is reached. However, distinguishing between hydrated (non-activated) aerosols and activated droplets is critical, as their differing thermodynamic states influence fog chemistry and dissipation. This study quantifies the impact of hydrated aerosol particles on fog microphysical properties and visibility in the Po Valley, one of Europe&rsquo;s most polluted regions. We analyzed detailed aerosol&ndash;fog observations from the 2021/22 FAIRARI campaign at San Pietro Capofiume, Italy, using <em>&kappa;</em>-K&ouml;hler theory and the Large Eddy Simulation (LES) model MIMICA. The median hygroscopicity <em>&kappa;</em>-value of fog residuals (0.45) exceeded that of interstitial particles (0.40) and out-of-fog aerosols (0.34), reflecting enhanced inorganic content in fog droplets. Hygroscopic growth calculations show that hydrated particles can reach several micrometers in diameter, significantly influencing inferred fog microphysical properties. Excluding hydrated aerosols led to an 81 % increase in effective diameter (from 11.6 <em>&mu;</em>m to 21.0 <em>&mu;</em>m) and an 87 % decrease in cloud droplet number concentration (from 97.4 to 12.4 cm^-3). Hydrated particles contributed on average 21 % to liquid water content and accounted for 36 % of sub-kilometer visibility events without droplet activation. LES results emphasize that fog prediction depends strongly on the largest dry aerosol particles. Our findings demonstrate the need to distinguish between hydrated and activated particles when interpreting fog observations and modeling fog development in polluted environments.

Chronic ulcers that damage muscle and bone and result in limb amputations are a major disease burden that costs over $25 billion/year. Despite major advances in understanding the factors that cause non-healing ulcers, currently there are no effective treatments that can heal such ulcers and mitigate associated morbidity and mortality. Changing the gene expression in all affected tissues (skin, vasculature, muscle and bone) via gene or protein therapy to attenuate the inflammatory microenvironment in the non-healing ulcer and activate new cell growth is critical for effective wound healing. Current approaches to deliver gene and protein therapy to deep tissues that are damaged via local transdermal delivery depends on medicated topical creams that contain these large molecular weight therapeutics and/or microneedle arrays or various skin substitutes that carry stem cells or growth factors and placed on top of wound. However, microneedle arrays can deliver molecules only few millimeters below wound surface and transdermal injection is painful. Moreover, degradation by wound enzymes, washout by wound exudates, and inability to enter cells in deep tissues that are located a few centimeters below wound surface substantially reduce the efficacy of these approaches. Therefore, there is an urgent, unmet, medical need to develop a new treatment based on delivery for growth factors, cytokines and reparative gene or protein therapy to the deep wound beds of chronic ulcers that can reach not only deep skin, but also the damaged muscle and bone tissues, to repair deep tissue damage and expedite healing of chronic ulcers. The goal of this study was to test new prototypes of Droplette Micromist Technology Device (DMTD) to enable needle-free localized transdermal delivery of DNA, siRNA and protein to regulate gene expression in deep tissues. Two new DMTD prototypes were used to test our hypothesis that DMTD-delivered plasmid DNA and siRNA would change gene expression in deep tissues, and Insulin like Growth Factor 1 (IGF-1) would promote wound healing. Both ex vivo (pig skin and human skin from amputated limbs of consented and deidentified patients at Tufts Medical Center) and in vivo (Zucker diabetic fatty (ZDF) rat wound model, Wistar rat, and FVB-Tg(CAG-luc,-GFP)L2G85Chco/J strain #:008450 transgenic mice that expresses green fluorescent protein (GFP)) preclinical models were used (n=5; p&lt;0.001-0.05). Animals studies were approved by IACUCs of Tufts and University of Missouri and handled as per the US National Institutes of Health standards. Human studies were performed after Tufts IRB approval. Robust expression of de novo Red Fluorescent Protein (RFP) was achieved by delivery of 300µL of DMTD micromist containing 10µg and 2.5µg pCMV-AC-RFP plasmid DNA using 15volt and 18volt DMTD prototypes in human and pig skin and live Wistar rat. The 18-volt DMTD micromist with 10µg DNA expressed RFP in muscle layer and in an area 7.5cm wide and 4cm deep. The 18-volt DMTD micromist containing anti-GFP siRNA (1µMolar) significantly suppressed GFP expression in ear, shoulder and paw of GFP transgenic mice compared to scrambled siRNA micromist. Finally, DMTD-micromist with IGF-1 (200ng) delivered daily reduced re-epithelialization times of 4mm full thickness wounds on ZDF rats faster (40%) than topical application (20%). In conclusion, DMTD micromist is a novel, needle-free and painless transdermal delivery stem that can successfully deliver plasmids and siRNA to change gene expression in deep tissues and expedite diabetic wound healing. We propose that DMTD micromist containing gene and peptide therapeutics offer a much needed treatment for chronic ulcer healing. This work is supported by DoD grant PR220947 to LP This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Parameter tuning based adapter methods have achieved notable success in vision-language models (VLMs). However, they face challenges in scenarios with insufficient training samples or limited resources. While leveraging image modality caching and retrieval techniques can reduce resource requirements, these approaches often overlook the significance of textual modality and cross-modal cues in VLMs. To address this, we propose a Conditional Cross-Modal learning model, which is abbreviated as CoCM. CoCM builds separate cache models for both the text and image modalities and embedding textual knowledge conditioned on image information. It dynamically adjusts the cross-modal fusion affinity ratio and disentangles similarity measures across different modalities. Additionally, CoCM incorporates intra-batch image similarity loss as a regularization term to identify hard samples and enhance fine-grained classification performance. CoCM surpasses existing methods in terms of accuracy, generalization ability, and efficiency, achieving a 0.28% accuracy improvement over XMAdapter across 11 datasets and demonstrating 44.79% generalization performance on four cross-domain datasets.

Regular, low-cost Decadal-class science missions to planetary destinations will be enabled by high-ΔV small spacecraft, such as the high-energy Photon, and small launch vehicles, such as Electron, to support expanding opportunities for scientists and to increase the rate of science return. The Rocket Lab mission to Venus is a small direct entry probe planned for baseline launch in May 2023 with accommodation for a single ~1 kg instrument. A backup launch window is available in January 2025. The probe mission will spend about 5 min in the Venus cloud layers at 48–60 km altitude above the surface and collect in situ measurements. We have chosen a low-mass, low-cost autofluorescing nephelometer to search for organic molecules in the cloud particles and constrain the particle composition.

Black (EBC) and Brown (BrC) Carbon are ubiquitous constituents of atmospheric particulate matter that affect people’s health, disrupt ecosystems, and modulate local and global climate. Tracking the local deposition and sources of these aerosol particles is essential to better understanding their multidimensional environmental impact. The main goal of the current study is to measure the absorption coefficient (Babs) of particles within the Planetary Boundary Layer (PBL) of the El Paso (US)–Ciudad Juárez (Mexico) airshed and assess the contribution of black and brown carbon particles to the optical absorption. Measurements were taken during a summer, wildfire, and winter season to evaluate the optical properties of BC and non-volatile BrC. The winter season presented a variation from the background Babs in the late evening hours (3:00 PM to midnight) due to an increase in biomass burning driven by lower temperatures. The wildfire season presents the greatest variation in the Babs from the background absorption due to EBC- and BrC-rich smoke plumes arriving at this region from the US West seasonal wildfires. It was found that the international bridges’ vehicular traffic, waiting time to cross back and forth between both cities, added to other local anthropogenic activities, such as brick kiln emissions in Ciudad Juarez, have created a background of air pollution in this region. These pollutants include carbon monoxide, sulfur dioxide, nitrogen and nitric oxides, coarse and fine particulate matter dominated by BC and BrC. The absorption coefficients due to EBC and BrC of this background constitute what we have called a baseline EBC and BrC. Aided by two photoacoustic Extinctiometers (PAX), operating at 405 nm and 870 nm wavelengths, connected to a 340 °C thermal denuder to remove volatile organics, the optical properties were documented and evaluated to identify the impact of long-range transported emissions from western wildfires. The Single Scattering Albedo and the Absorption Ångstrom exponent were calculated for the winter and summer season. The Angstrom exponent showed a decrease during the wildfire events due to the aging process. The High-Resolution Rapid Refresh Smoke model, HRRR, and the Hybrid Single-Particle Lagrangian Integrated Trajectory model, HYSPLIT, were used to estimate the sources of the particles. In addition, a Vaisala Ceilometer was employed to study the vertical profile of particulate matter within the planetary boundary layer.

&amp;lt;p&amp;gt;The presence of ice in mixed-phase clouds has a vital impact on their radiative properties, lifetime, and&amp;amp;#160; ability to precipitate. Ice crystal formation is initially induced by a rare subset of ambient aerosol&amp;amp;#160; particles called ice-nucleating particles (INPs). Despite the importance of INPs on aerosol-cloud interactions and century-long research efforts, the knowledge about their nature and atmospheric&amp;amp;#160; abundance still needs improvement. Recent instrument developments allow more automated and&amp;amp;#160; continuous INP measurements with a high time resolution, to gain a better understanding of the natural variability of INPs in different locations, and to investigate the identity and source regions of them.&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Here we present long-term observations of INPs at Storm Peak Laboratory (SPL) located in the Rocky Mountains of Colorado. SPL is at an altitude of 3200 m a.s.l. within the lower free troposphere, and in winter it is a location where mixed-phase clouds frequently occur. Therefore, the present aerosol particles are directly relevant for ice formation in such clouds. The ongoing INP measurements started in October 2021, and are conducted with the Portable Ice Nucleation Experiment (PINE) at conditions resembling the formation of mixed-phase clouds at temperatures between -22&amp;amp;#176;C and -32&amp;amp;#176;C. Results on the short-term and inter-seasonal variability will be presented, with a focus on parallel measurements of aerosol particle properties and meteorology. During the winter months of January and February 2022, we characterized the size of the INPs by selecting ice crystal residuals downstream of PINE using a pumped-counterflow virtual impactor and a novel optical particle counter. As this setup operates continuously, it is capable to investigate INP properties for longer time periods and to improve sampling statistics. In the future, it will be used with other diagnostic instruments, such as a single particle mass spectrometer, giving insights into the size and chemical composition of INPs, and thus allows to have a direct measure of the nature of INPs in ambient air.&amp;lt;/p&amp;gt;

<strong class="journal-contentHeaderColor">Abstract.</strong> Eight years of upper-tropospheric (UT) ice crystal measurements with the backscatter cloud probe (BCP), installed on commercial aircraft operated as part of the In-Service Aircraft for a Global Observing System (IAGOS), have been analyzed to assess the frequency and characteristics of extreme ice crystal events (EIEs), defined in this study as encounters with clouds that have number concentrations exceeding 5000 L<span class="inline-formula">^−1</span>. A total of 3196 events, in clouds of horizontal extent <span class="inline-formula">≥</span> 2.5 km, were identified during the period from December 2011 to March 2020 in the latitude band between 30<span class="inline-formula">^∘</span> S and 30<span class="inline-formula">^∘</span> N. Regions of anthropogenic sources of carbon monoxide, with particles that can alter cloud microphysics, were attributed to these EIEs in UT clouds using the SOFT-IO model. The evaluation of low- and upper-level kinematic variables from the European Centre for Medium-Range Weather Forecasts (ERA5) reanalysis, combined with spatial distributions of aerosol optical depth and regions of biomass burning, highlights the physical mechanisms by which the particles are lofted to flight levels in regions of deep convection. The maps of lightning frequency, derived from the World Wide Lightning Location Network (WWLLN), provide additional evidence of the role of deep convection in transporting aerosol particles, cloud hydrometeors and carbon monoxide to aircraft cruising altitudes. The evaluation of aerosol particle mass concentrations and composition from the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) contributes additional evidence for a link between regions of EIEs and surface emissions of dust, black carbon (BC), organic carbon (OC) and sulfate particles. Given the composition of the source aerosols and the role of deep convection in their transport to the UT, the sampled ice clouds likely originate from the homogeneous or heterogeneous freezing of droplets formed on these particles, as has been reported in previous studies. The results from this study, which have been obtained from a large sample of measurements, have ramifications related to satellite measurement validation, weather forecasting and climate change. In addition, over 2000 of the randomly sampled clouds had derived ice water contents larger than 1 g m<span class="inline-formula">^−3</span>, a concentration that is considered potentially hazardous to commercial aircraft operations.

<strong class="journal-contentHeaderColor">Abstract.</strong> African aerosol particles, traveling thousands of kilometers before reaching the Americas and the Caribbean, directly scatter and absorb solar radiation and indirectly impact climate by serving as cloud condensation nuclei (CCN) or ice-nucleating particles (INPs) that form clouds. These particles can also affect the water budget by altering precipitation patterns that subsequently affect ecosystems. As part of the NSF-funded Luquillo Critical Zone Observatory, field campaigns were conducted during the summers of 2013 (23 <span class="inline-formula">d</span>), 2014 (11 <span class="inline-formula">d</span>), and 2015 (92 <span class="inline-formula">d</span>) at Pico del Este, a site in a tropical montane cloud forest on the Caribbean Island of Puerto Rico. Cloud microphysical properties, which included liquid water content, droplet number concentration, and droplet size, were measured. Using products from models and satellites, as well as in situ measurements of aerosol optical properties, periods of high- and low-dust influence were identified. The results from this study suggest that meteorology and air mass history have a more important effect on cloud processes than aerosols transported from Africa. In contrast, air masses that arrived after passing over the inhabited islands to the southeast led to clouds with much higher droplet concentrations, presumably due to aerosols formed from anthropogenic emissions.

Abstract. African aerosol particles, traveling thousands of kilometers before reaching the Americas and the Caribbean, directly scatter and absorb solar radiation and indirectly impact climate by serving as cloud condensation nuclei (CCN) or ice nuclei (IN) that form clouds. These particles can also affect the water budget by altering precipitation patterns that subsequently affect ecosystems. As part of the NSF-funded Luquillo Critical Zone Observatory, field campaigns were conducted during the summers of 2013, 2014, and 2015 at Pico del Este, a site in a tropical montane cloud forest on the Caribbean island of Puerto Rico. Cloud microphysical properties, which included liquid water content, droplet number concentration, and droplet size, were measured. Using products from models and satellites, as well as in-situ measurements of aerosol optical properties, periods of high and low dust influence were identified. The results from this study suggest that meteorology and air mass history have a more important effect on cloud processes than aerosols transported from Africa. In contrast, air masses that arrived after passing over the inhabited islands to the southeast led to clouds with much higher droplet concentrations, presumably due to aerosols formed from anthropogenic emissions.

Measurements of primary biological aerosol particles (PBAPs) have been conducted worldwide using ultraviolet light-induced fluorescence (UV-LIF) spectrometers. However, how these instruments detect and respond to known biological and non-biological particles, and how they compare, remains uncertain due to limited laboratory intercomparisons. Using the Defence Science and Technology Laboratory, Aerosol Challenge Simulator (ACS), controlled concentrations of biological and non-biological aerosol particles, singly or as mixtures, were produced for testing and intercomparison of multiple versions of the Wideband Integrated Bioaerosol Spectrometer (WIBS) and Multiparameter Bioaerosol Spectrometer (MBS). Although the results suggest some challenges in discriminating biological particle types across different versions of the same UV-LIF instrument, a difference in fluorescence intensity between the non-biological and biological samples could be identified for most instruments. While lower concentrations of fluorescent particles were detected by the MBS, the MBS demonstrates the potential to discriminate between pollen and other biological particles. This study presents the first published technical summary and use of the ACS for instrument intercomparisons. Within this work a clear overview of the data pre-processing is also presented, and documentation of instrument version/model numbers is suggested to assess potential instrument variations between different versions of the same instrument. Further laboratory studies sampling different particle types are suggested before use in quantifying impact on ambient classification.