Whispering gallery mode single nanoparticle detection and sizing: the validity of the dipole approximation.

Interactions between whispering gallery modes (WGMs) and small nanoparticles are commonly modeled by treating the particle as a point dipole scatterer. This approach is assumed to be accurate as long as the nanoparticle radius, a, is small compared to the WGM wavelength λ. In this Letter, however, we show that the large field gradients associated with the evanescent decay of a WGM causes the dipole theory to significantly underestimate the interaction strength and, hence, the induced WGM resonance shift, even for particles as small as a∼λ/10. To mitigate this issue, we employ a renormalized Born approximation to more accurately determine nanoparticle-induced resonance shifts and, hence, enable improved particle sizing. The domain of validity of this approximation is investigated, and supporting experimental results are presented.

Label-free detection of single protein using a nanoplasmonic-photonic hybrid microcavity.

Recently we reported the detection and sizing of the smallest RNA virus MS2 with a mass of 6 ag from the resonance frequency shift of a whispering gallery mode-nanoshell hybrid resonator (WGM-h) upon adsorption on the nanoshell and anticipated that single protein above 0.4 ag should be detectable but with considerably smaller signals. Here, we report the detection of single thyroid cancer marker (Thyroglobulin, Tg) and bovine serum albumin (BSA) proteins with masses of only 1 ag and 0.11 ag (66 kDa), respectively. However, the wavelength shifts are enhanced beyond those anticipated in our earlier work by 240% for Tg and 1500% for BSA. This surprising sensitivity is traced to a short-range reactive field near the surface of our Au nanoshell receptor due to intrinsic random bumps of protein size, leading to an unanticipated increase in sensitivity to single protein, which grows larger as the protein diminishes in size. As a consequence of the largest signal-to-noise ratio in our BSA experiments (S/N ≈ 13), we conservatively estimated a new protein limit of detection for our WGM-h of 5 kDa.

Bioinspired optofluidic FRET lasers via DNA scaffolds.

Optofluidic dye lasers hold great promise for adaptive photonic devices, compact and wavelength-tunable light sources, and micro total analysis systems. To date, however, nearly all those lasers are directly excited by tuning the pump laser into the gain medium absorption band. Here we demonstrate bioinspired optofluidic dye lasers excited by FRET, in which the donor-acceptor distance, ratio, and spatial configuration can be precisely controlled by DNA scaffolds. The characteristics of the FRET lasers such as spectrum, threshold, and energy conversion efficiency are reported. Through DNA scaffolds, nearly 100% energy transfer can be maintained regardless of the donor and acceptor concentration. As a result, efficient FRET lasing is achieved at an unusually low acceptor concentration of micromolar, over 1,000 times lower than that in conventional optofluidic dye lasers. The lasing threshold is on the order of µJ/mm(2). Various DNA scaffold FRET lasers are demonstrated to illustrate vast possibilities in optofluidic laser designs. Our work opens a door to many researches and applications such as intracavity bio/chemical sensing, biocontrolled photonic devices, and biophysics.

Periodic plasmonic enhancing epitopes on a whispering gallery mode biosensor.

We propose the attachment of a periodic array of gold nanoparticles (epitopes) to the equator of a Whispering Gallery Mode Biosensor for the purpose of plasmonically enhancing nanoparticle sensing in a self-referencing manner while increasing the capture rate of analyte to antibodies attached to these plasmonic epitopes. Our approach can be applied to a variety of whispering gallery mode resonators from silicon/silica rings and disks to capillaries. The interpretation of the signals is particularly simple since the optical phase difference between the epitopes is designed to be an integer multiple of ?, allowing the wavelength shift from each binding event to add independently.

Emission Sector Impacts on Air Quality and Public Health in China From 2010 to 2020.

Anthropogenic emissions and ambient fine particulate matter (PM2.5) concentrations have declined in recent years across China. However, PM2.5 exposure remains high, ozone (O3) exposure is increasing, and the public health impacts are substantial. We used emulators to explore how emission changes (averaged per sector over all species) have contributed to changes in air quality and public health in China over 2010-2020. We show that PM2.5 exposure peaked in 2012 at 52.8 µg m-3, with contributions of 31% from industry and 22% from residential emissions. In 2020, PM2.5 exposure declined by 36% to 33.5 µg m-3, where the contributions from industry and residential sources reduced to 15% and 17%, respectively. The PM2.5 disease burden decreased by only 9% over 2012 where the contributions from industry and residential sources reduced to 15% and 17%, respectively 2020, partly due to an aging population with greater susceptibility to air pollution. Most of the reduction in PM2.5 exposure and associated public health benefits occurred due to reductions in industrial (58%) and residential (29%) emissions. Reducing national PM2.5 exposure below the World Health Organization Interim Target 2 (25 µg m-3) would require a further 80% reduction in residential and industrial emissions, highlighting the challenges that remain to improve air quality in China.

Public Health Measures to Address the Impact of Climate Change on Population Health-Proceedings from a Stakeholder Workshop.

BACKGROUND: The World Health Organization identified climate change as the 21st century's biggest health threat. This study aimed to identify the current knowledge base, evidence gaps, and implications for climate action and health policymaking to address the health impact of climate change, including in the most underserved groups. METHODS: The Horizon-funded project ENBEL ('Enhancing Belmont Research Action to support EU policy making on climate change and health') organised a workshop at the 2021-European Public Health conference. Following presentations of mitigation and adaptation strategies, seven international researchers and public health experts participated in a panel discussion linking climate change and health. Two researchers transcribed and thematically analysed the panel discussion recording. RESULTS: Four themes were identified: (1) 'Evidence is key' in leading the climate debate, (2) the need for 'messaging about health for policymaking and behaviour change' including health co-benefits of climate action, (3) existing 'inequalities between and within countries', and (4) 'insufficient resources and funding' to implement national health adaptation plans and facilitate evidence generation and climate action, particularly in vulnerable populations. CONCLUSION: More capacity is needed to monitor health effects and inequities, evaluate adaptation and mitigation interventions, address current under-representations of low- or middle-income countries, and translate research into effective policymaking.

Sensitivity of Air Pollution Exposure and Disease Burden to Emission Changes in China Using Machine Learning Emulation.

Machine learning models can emulate chemical transport models, reducing computational costs and enabling more experimentation. We developed emulators to predict annual-mean fine particulate matter (PM2.5) and ozone (O3) concentrations and their associated chronic health impacts from changes in five major emission sectors (residential, industrial, land transport, agriculture, and power generation) in China. The emulators predicted 99.9% of the variance in PM2.5 and O3 concentrations. We used these emulators to estimate how emission reductions can attain air quality targets. In 2015, we estimate that PM2.5 exposure was 47.4 µg m-3 and O3 exposure was 43.8 ppb, associated with 2,189,700 (95% uncertainty interval, 95UI: 1,948,000-2,427,300) premature deaths per year, primarily from PM2.5 exposure (98%). PM2.5 exposure and the associated disease burden were most sensitive to industry and residential emissions. We explore the sensitivity of exposure and health to different combinations of emission reductions. The National Air Quality Target (35 µg m-3) for PM2.5 concentrations can be attained nationally with emission reductions of 72% in industrial, 57% in residential, 36% in land transport, 35% in agricultural, and 33% in power generation emissions. We show that complete removal of emissions from these five sectors does not enable the attainment of the WHO Annual Guideline (5 µg m-3) due to remaining air pollution from other sources. Our work provides the first assessment of how air pollution exposure and disease burden in China varies as emissions change across these five sectors and highlights the value of emulators in air quality research.

Whispering-gallery-mode biosensing: label-free detection down to single molecules.

Optical label-free detectors, such as the venerable surface plasmon resonance (SPR) sensor, are generally favored for their ability to obtain quantitative data on intermolecular binding. However, before the recent introduction of resonant microcavities that use whispering gallery mode (WGM) recirculation, sensitivity to single binding events had not materialized. Here we describe the enhancement mechanisms responsible for the extreme sensitivity of the WGM biosensor, review its current implementations and applications, and discuss its future possibilities.

Acute Pain Management for Patients with Substance Use Disorder Receiving Buprenorphine or Methadone Compared to Patients without Opioid-Dependence Disorder.

This single-center retrospective study assessed pain management between patients being treated for SUD and compared them to those without SUD who underwent orthopedic surgery. Patients with SUD could be admitted for any reason, while the control arm consisted of patients undergoing total knee arthroplasty or hip arthroplasty surgery. Primary endpoints were average pains scores and morphine milligram equivalents (MME) over the first 48h. Secondary endpoints include adjuvant pain medications and the average MME prescribed upon discharge. A total of the 60 patients were enrolled, 30 patients had history of SUD and 30 patients in the control arm. Average MME between the SUD and control was not significantly different (139.9 mg vs. 96.6 mg, p = 0.889). Average pain scores between the groups were significantly different (7.46 vs. 5.94, p = 0.002). Patients with SUD were not given a statistically different amount of MME for acute pain and experienced higher pain scores than patients without SUD. However, this study had a small population size, and further case-control studies are needed to confirm this result.

Dynamic Light Scattering Study of a Laser-Induced Phase-Separated Droplet of Aqueous Glycine.

Tightly focusing a continuous-wave, near-infrared laser beam at the air/solution interface of a millimeter-thick layer of glycine in D2O forms a crystal through a polymorphically and spatially controlled nucleation process known as gradient-force laser-induced nucleation or optical-tweezer laser-induced nucleation. However, when this same beam is focused at the glass/solution interface of a film of aqueous glycine, a highly concentrated laser-induced phase-separated (LIPS) solution droplet is formed that does not nucleate while the focusing beam remains on. Two competing theories have emerged about the nature of the LIPS droplet: one proposes that it is a merger of prenucleation metastable nanodroplets and clusters into one large homogeneous "dense liquid droplet", and the other stipulates that it is the result of the partitioning of larger droplets into the new phase, but not a merging of droplets, around the focal point of the beam. In order to determine the nature of the LIPS droplet, dynamic light scattering was used to detect the presence of nanodroplets undergoing Brownian motion within the droplet and to measure their relative size following a range of laser exposure times. The observation of nanodroplets in motion in the center of the LIPS droplet revealed that the application of optical tweezers at the glass/solution interface forms a relatively monodisperse collection of large nanodroplets (>700 nm) concentrated around the focal point of the beam with smaller particles (<100 nm) depleted within the first 2 min of laser exposure. The LIPS droplet quickly reaches a steady state and is not affected by increasing focusing times. These findings allow for a better understanding of the interactions of optical tweezers with aqueous glycine nanodroplets. This understanding will help in studying the fundamental nature of metastable nanodroplets. More practically, laser-induced phase separation makes possible the nucleation-free separation of large nanodroplets from small clusters, facilitating materials technologies such as high purity, polymorphically selective nucleation of crystals and co-crystals used for pharmaceuticals, dyes, and photovoltaics.

Air Pollution From Forest and Vegetation Fires in Southeast Asia Disproportionately Impacts the Poor.

Forest and vegetation fires, used as tools for agriculture and deforestation, are a major source of air pollutants and can cause serious air quality issues in many parts of Asia. Actions to reduce fire may offer considerable, yet largely unrecognized, options for rapid improvements in air quality. In this study, we used a combination of regional and global air quality models and observations to examine the impact of forest and vegetation fires on air quality degradation and public health in Southeast Asia (including Mainland Southeast Asia and south-eastern China). We found that eliminating fire could substantially improve regional air quality across Southeast Asia by reducing the population exposure to fine particulate matter (PM2.5) concentrations by 7% and surface ozone concentrations by 5%. These reductions in PM2.5 exposures would yield a considerable public health benefit across the region; averting 59,000 (95% uncertainty interval (95UI): 55,200-62,900) premature deaths annually. Analysis of subnational infant mortality rate data and PM2.5 exposure suggested that PM2.5 from fires disproportionately impacts poorer populations across Southeast Asia. We identified two key regions in northern Laos and western Myanmar where particularly high levels of poverty coincide with exposure to relatively high levels of PM2.5 from fires. Our results show that reducing forest and vegetation fires should be a public health priority for the Southeast Asia region.

Regional Policies Targeting Residential Solid Fuel and Agricultural Emissions Can Improve Air Quality and Public Health in the Greater Bay Area and Across China.

Air pollution exposure is a leading public health problem in China. The majority of the total air pollution disease burden is from fine particulate matter (PM2.5) exposure, with smaller contributions from ozone (O3) exposure. Recent emission reductions have reduced PM2.5 exposure. However, levels of exposure and the associated risk remain high, some pollutant emissions have increased, and some sectors lack effective emission control measures. We quantified the potential impacts of relevant policy scenarios on ambient air quality and public health across China. We show that PM2.5 exposure inside the Greater Bay Area (GBA) is strongly controlled by emissions outside the GBA. We find that reductions in residential solid fuel use and agricultural fertilizer emissions result in the greatest reductions in PM2.5 exposure and the largest health benefits. A 50% transition from residential solid fuel use to liquefied petroleum gas outside the GBA reduced PM2.5 exposure by 15% in China and 3% within the GBA, and avoided 191,400 premature deaths each year across China. Reducing agricultural fertilizer emissions of ammonia by 30% outside the GBA reduced PM2.5 exposure by 4% in China and 3% in the GBA, avoiding 56,500 annual premature deaths across China. Our simulations suggest that reducing residential solid fuel or industrial emissions will reduce both PM2.5 and O3 exposure, whereas other policies may increase O3 exposure. Improving particulate air quality inside the GBA will require consideration of residential solid fuel and agricultural sectors, which currently lack targeted policies, and regional cooperation both inside and outside the GBA.

Statistical Emulation of Winter Ambient Fine Particulate Matter Concentrations From Emission Changes in China.

Air pollution exposure remains a leading public health problem in China. The use of chemical transport models to quantify the impacts of various emission changes on air quality is limited by their large computational demands. Machine learning models can emulate chemical transport models to provide computationally efficient predictions of outputs based on statistical associations with inputs. We developed novel emulators relating emission changes in five key anthropogenic sectors (residential, industry, land transport, agriculture, and power generation) to winter ambient fine particulate matter (PM2.5) concentrations across China. The emulators were optimized based on Gaussian process regressors with Matern kernels. The emulators predicted 99.9% of the variance in PM2.5 concentrations for a given input configuration of emission changes. PM2.5 concentrations are primarily sensitive to residential (51%-94% of first-order sensitivity index), industrial (7%-31%), and agricultural emissions (0%-24%). Sensitivities of PM2.5 concentrations to land transport and power generation emissions are all under 5%, except in South West China where land transport emissions contributed 13%. The largest reduction in winter PM2.5 exposure for changes in the five emission sectors is by 68%-81%, down to 15.3-25.9 µg m-3, remaining above the World Health Organization annual guideline of 10 µg m-3. The greatest reductions in PM2.5 exposure are driven by reducing residential and industrial emissions, emphasizing the importance of emission reductions in these key sectors. We show that the annual National Air Quality Target of 35 µg m-3 is unlikely to be achieved during winter without strong emission reductions from the residential and industrial sectors.

Impact of the 2019/2020 Australian Megafires on Air Quality and Health.

The Australian 2019/2020 bushfires were unprecedented in their extent and intensity, causing a catastrophic loss of habitat, human and animal life across eastern-Australia. We use a regional air quality model to assess the impact of the bushfires on particulate matter with a diameter less than 2.5 µm (PM2.5) concentrations and the associated health impact from short-term population exposure to bushfire PM2.5. The mean population Air Quality Index (AQI) exposure between September and February in the fires and no fires simulations indicates an additional ∼437,000 people were exposed to "Poor" or worse AQI levels due to the fires. The AQ impact was concentrated in the cities of Sydney, Newcastle-Maitland, Canberra-Queanbeyan and Melbourne. Between October and February 171 (95% CI: 66-291) deaths were brought forward due to short-term exposure to bushfire PM2.5. The health burden was largest in New South Wales (NSW) (109 (95% CI: 41-176) deaths brought forward), Queensland (15 (95% CI: 5-24)), and Victoria (35 (95% CI: 13-56)). This represents 38%, 13% and 30% of the total deaths brought forward by short-term exposure to all PM2.5. At a city-level 65 (95% CI: 24-105), 23 (95% CI: 9-38) and 9 (95% CI: 4-14) deaths were brought forward from short-term exposure to bushfire PM2.5, accounting for 36%, 20%, and 64% of the total deaths brought forward from all PM2.5. Thus, the bushfires caused substantial AQ and health impacts across eastern-Australia. Climate change is projected to increase bushfire risk, therefore future fire management policies should consider this.

Functionalized Ga2O3 nanowires as active material in room temperature capacitance-based gas sensors.

We report the first evidence for functionalization of Ga(2)O(3) nanowires (NWs), which have been incorporated as the active material in room temperature capacitance gas-sensing devices. An adsorbed layer of pyruvic acid (PA) was successfully formed on Ga(2)O(3) NWs by simple room temperature vapor transport, which was confirmed by Fourier transform infrared spectroscopy. The effect of the adsorbed PA on the surface properties was demonstrated by the change in the response of the NW gas-sensing devices. Results indicate that the adsorption of PA reduced the sensitivity of the Ga(2)O(3) NW device to common hydrocarbons such as nitromethane and acetone while improving the response to triethylamine by an order of magnitude. Taking into account the simplicity of this functionalization together with the ease of producing these capacitance-based gas-sensing devices, this approach represents a viable technique for sensor development.

Constraining remote oxidation capacity with ATom observations.

The global oxidation capacity, defined as the tropospheric mean concentration of the hydroxyl radical (OH), controls the lifetime of reactive trace gases in the atmosphere such as methane and carbon monoxide (CO). Models tend to underestimate the methane lifetime and CO concentrations throughout the troposphere, which is consistent with excessive OH. Approximately half of the oxidation of methane and non-methane volatile organic compounds (VOCs) is thought to occur over the oceans where oxidant chemistry has received little validation due to a lack of observational constraints. We use observations from the first two deployments of the NASA ATom aircraft campaign during July-August 2016 and January-February 2017 to evaluate the oxidation capacity over the remote oceans and its representation by the GEOS-Chem chemical transport model. The model successfully simulates the magnitude and vertical profile of remote OH within the measurement uncertainties. Comparisons against the drivers of OH production (water vapor, ozone, and NO y concentrations, ozone photolysis frequencies) also show minimal bias, with the exception of wintertime NO y . The severe model overestimate of NO y during this period may indicate insufficient wet scavenging and/or missing loss on sea-salt aerosols. Large uncertainties in these processes require further study to improve simulated NO y partitioning and removal in the troposphere, but preliminary tests suggest that their overall impact could marginally reduce the model bias in tropospheric OH. During the ATom-1 deployment, OH reactivity (OHR) below 3 km is significantly enhanced, and this is not captured by the sum of its measured components (cOHRobs) or by the model (cOHRmod). This enhancement could suggest missing reactive VOCs but cannot be explained by a comprehensive simulation of both biotic and abiotic ocean sources of VOCs. Additional sources of VOC reactivity in this region are difficult to reconcile with the full suite of ATom measurement constraints. The model generally reproduces the magnitude and seasonality of cOHRobs but underestimates the contribution of oxygenated VOCs, mainly acetaldehyde, which is severely underestimated throughout the troposphere despite its calculated lifetime of less than a day. Missing model acetaldehyde in previous studies was attributed to measurement uncertainties that have been largely resolved. Observations of peroxyacetic acid (PAA) provide new support for remote levels of acetaldehyde. The underestimate in both model acetaldehyde and PAA is present throughout the year in both hemispheres and peaks during Northern Hemisphere summer. The addition of ocean sources of VOCs in the model increases cOHRmod by 3% to 9% and improves model-measurement agreement for acetaldehyde, particularly in winter, but cannot resolve the model summertime bias. Doing so would require 100 Tg yr-1 of a long-lived unknown precursor throughout the year with significant additional emissions in the Northern Hemisphere summer. Improving the model bias for remote acetaldehyde and PAA is unlikely to fully resolve previously reported model global biases in OH and methane lifetime, suggesting that future work should examine the sources and sinks of OH over land.