Detection of bioaerosols, or primary biological aerosol particles (PBAPs), has become increasingly important for a wide variety of research communities and scientific questions. In particular, ...real-time (RT) techniques for autonomous, online detection and characterization of PBAP properties in both outdoor and indoor environments are becoming more commonplace and have opened avenues of research. With advances in technology, however, come challenges to standardize practices so that results are both reliable and comparable across technologies and users. Here, we present a critical review of major RT instrument classes that have been applied to PBAP research, especially with respect to environmental science, allergy monitoring, agriculture, public health, and national security. Eight major classes of RT techniques are covered, including the following: (i) fluorescence spectroscopy, (ii) elastic scattering, microscopy, and holography, (iii) Raman spectroscopy, (iv) mass spectrometry, (v) breakdown spectroscopy, (vi) remote sensing, (vii) microfluidic techniques, and (viii) paired aqueous techniques. For each class of technology we present technical limitations, misconceptions, and pitfalls, and also summarize best practices for operation, analysis, and reporting. The final section of the article presents pressing scientific questions and grand challenges for RT sensing of PBAP as well as recommendations for future work to encourage high-quality results and increased cross-community collaboration.
Inflammation is a feature of pulmonary arterial hypertension (PAH), and increased circulating levels of cytokines are reported in patients with PAH. However, to date, no information exists on the ...significance of elevated cytokines or their potential as biomarkers. We sought to determine the levels of a range of cytokines in PAH and to examine their impact on survival and relationship to hemodynamic indexes.
We measured levels of serum cytokines (tumor necrosis factor-alpha, interferon-gamma and interleukin-1beta, -2, -4, -5, -6, -8, -10, -12p70, and -13) using ELISAs in idiopathic and heritable PAH patients (n=60). Concurrent clinical data included hemodynamics, 6-minute walk distance, and survival time from sampling to death or transplantation. Healthy volunteers served as control subjects (n=21). PAH patients had significantly higher levels of interleukin-1beta, -2, -4, -6, -8, -10, and -12p70 and tumor necrosis factor-alpha compared with healthy control subjects. Kaplan-Meier analysis showed that levels of interleukin-6, 8, 10, and 12p70 predicted survival in patients. For example, 5-year survival with interleukin-6 levels of >9 pg/mL was 30% compared with 63% for patients with levels < or = 9 pg/mL (P=0.008). In this PAH cohort, cytokine levels were superior to traditional markers of prognosis such as 6-minute walk distance and hemodynamics.
This study illustrates dysregulation of a broad range of inflammatory mediators in idiopathic and familial PAH and demonstrates that cytokine levels have a previously unrecognized impact on patient survival. They may prove to be useful biomarkers and provide insight into the contribution of inflammation in PAH.
•UV intensities in virions in particles can be reduced by refraction and absorption.•Virions in dry particles are modeled with the Multi-Sphere T-Matrix method (MSTM).•UV intensity in a virion in a ...particle is compared to a single virion on a surface.•In 9µm droplets at 260nm, 18% of virions had intensity< 0.01 the single virion UV.•Shielding is reduced by illuminating a droplet from separated incident directions.
UV radiation can inactivate viruses such as SARS-CoV-2. However, designing effective UV germicidal irradiation (UVGI) systems can be difficult because the effects of dried respiratory droplets and other fomites on UV light intensities are poorly understood. Numerical modeling of UV intensities inside virus-containing particles on surfaces can increase understanding of these possible reductions in UV intensity. We model UV intensities within spherical approximations of virions randomly positioned within spherical particles. The model virions and dried particles have sizes and optical properties to approximate SARS-CoV-2 and dried particles formed from respiratory droplets, respectively. In 1-, 5- and 9-µm diameter particles on a surface, illuminated by 260-nm UV light from a direction perpendicular to the surface, 0%, 10% and 18% (respectively) of simulated virions are exposed to intensities less than 1/100th of intensities in individually exposed virions (i.e., they are partially shielded). Even for 302-nm light (simulating sunlight), where absorption is small, 0% and 11% of virions in 1- and 9-µm particles have exposures 1/100th those of individually exposed virions. Shielding is small to negligible in sub-micron particles. Results show that shielding of virions in a particle can be reduced by illuminating a particle either from multiple widely separated incident directions, or by illuminating a particle rotating in air for a time sufficient to rotate through enough orientations. Because highly UV-reflective paints and surfaces can increase the angular ranges of illumination and the intensities within particles, they appear likely to be useful for reducing shielding of virions embedded within particles.
The effects of winds and local mineralogy on ambient aerosol composition are poorly understood. We measured the Raman spectra (RS) of ambient aerosol particles on the Jornada Experimental Range, a ...desert location in southern New Mexico, used these RS to group spectra by composition or spectral features, and compared the numbers of RS with the winds and minerology. An aerosol Raman hyperspectral imager was used to collect particles onto a tape and measure a hyperspectral Raman image in 15‐ or 20‐min intervals. Over a 48 h period, 6306 RS were above the thresholds used and were analyzed further. Multiple RS may originate from the same particle. Of these 6306 RS, 2567 were classified as luminescence; 2647 contained the D and G peaks of DG Carbon (DGC, which includes soots, black carbon, and similar materials); 43 exhibited peaks consistent with CH stretching; and 130, 102, and 29 RS were consistent with quartz, carbonates (calcite and dolomite), and potassium feldspar, respectively. A convective dust event was concurrent with an increase in the number of RS of luminescent particles >20X the median; numbers of DGC RS in the interquartile range of DGC for the entire measurement period; RS consistent with quartz, calcite, iron oxides, feldspar, and anatase; and no RS consistent with oxalates or nitrates. This work shows that hyperspectral Raman imaging can help understand the time‐dependent composition of ambient aerosol particles at time resolutions below an hour.
An aerosol Raman hyperspectral imager collected and measured Raman spectra (RS) of particles in a desert in 15 or 20 min. Periods. RS were consistent with black carbon (DGC), carbonates, quartz, and luminescent matter. A convective dust event was concurrent with changes in numbers of some RS.
SARS-CoV-2 and other microbes within aerosol particles can be partially shielded from UV radiation. The particles refract and absorb light, and thereby reduce the UV intensity at various locations ...within the particle. Previously, we demonstrated shielding in calculations of UV intensities within spherical approximations of SARS-CoV-2 virions within spherical particles approximating dried-to-equilibrium respiratory fluids. The purpose of this paper is to extend that work to survival fractions of virions (i.e., fractions of virions that can infect cells) within spherical particles approximating dried respiratory fluids, and to investigate the implications of these calculations for using UV light for disinfection. The particles may be on a surface or in air. Here, the survival fraction (S) of a set of individual virions illuminated with a UV fluence (F, in J/m
2
) is assumed described by S(kF) = exp(-kF), where k is the UV inactivation rate constant (m
2
/J). The average survival fraction (S
p
) of the simulated virions in a group of particles is calculated using the energy absorbed by each virion in the particles. The results show that virions within particles of dried respiratory fluids can have larger S
p
than do individual virions. For individual virions, and virions within 1-, 5-, and 9-µm particles illuminated (normal incidence) on a surface with 260-nm UV light, the S
p
= 0.00005, 0.0155, 0.22, and 0.28, respectively, when kF = 10. The S
p
decrease to <10
−7
, <10
−7
, 0.077, and 0.15, respectively, for kF = 100. Results also show that illuminating particles with UV beams from widely separated directions can strongly reduce the S
p
. These results suggest that the size distributions and optical properties of the dried particles of virion-containing respiratory fluids are likely important to effectively designing and using UV germicidal irradiation systems for microbes in particles. The results suggest the use of reflective surfaces to increase the angles of illumination and decrease the S
p
. The results suggest the need for measurements of the S
p
of SARS-CoV-2 in particles having compositions and sizes relevant to the modes of disease transmission.
After sunset, a stable boundary layer (SBL) develops close to the ground, while the upper region of the daytime mixed layer becomes the residual layer (RL). Mixing between the SBL and RL is often ...quite limited and the RL is thought to be a reservoir for daytime mixed-layer pollutants under such conditions. However, ozone (O3) profiles observed in Maryland, U.S. suggest that the RL is not always a reservoir of O3 in that region. Nocturnal low-level jets (LLJs) and/or other mechanisms are speculated to enhance vertical mixing between the SBL and RL, which influences the vertical O3redistribution. Nocturnal surface O3 maxima, an RL with reduced O3 levels, and a concurrent strong LLJ were observed in Maryland on the night of August 9–10, 2010. Surface O3 measurements in the region and three-dimensional air quality simulations suggest that horizontal advection cannot explain the nocturnal O3 maxima and concurrent decrease of O3 levels within the RL. A sensitivity study with a single column (1D) chemistry model was performed to investigate the role of LLJs in generating turbulent mixing within the nighttime boundary layer and to identify related impacts on O3 concentrations at night and on the following day. The strong shear associated with the LLJ enhanced turbulent mixing and weakened the decoupling of the RL and SBL substantially. Ozone was actively mixed down from the RL to the surface, causing secondary nocturnal surface O3 maxima. Near the surface, O3 was efficiently removed by chemical reactions and dry deposition, which resulted in lower O3 peak values on the next day.
► The nocturnal O3 maxima occurred concurrently at multiple sites along the corridor. ► The residual layer (RL) is leaky in the presence of a strong low-level jet (LLJ). ► The role of LLJ-induced vertical mixing on boundary layer O3 is identified. ► Mixed-layer O3 concentration on the next day is reduced as a result of a leaky RL.
Although much research has focused on daytime ozone (O
3) distribution in the atmospheric boundary layer, there remain many unresolved processes related to O
3 transport in the residual layer. To ...address such unresolved questions, a field study was conducted in Beltsville, MD during the summer of 2010 to study the spatial and temporal distribution of O
3 and other pollutants using ground-based gas analyzers and ozonesondes. During elevated pollution events in the daytime, the convective boundary layer, which reached a maximum depth of about 2 km, had nearly uniform O
3 levels of almost 100 parts per billion (ppbv). Due to intermittent and intense vertical turbulent motion, the residual layer became “leaky” and permitted vertical transport to enhance ground-level O
3 mixing ratios by as much as 10–30 ppbv in a span of 0.5–3 h. Model simulations, using the Weather Research and Forecasting model with Chemistry (WRF/Chem), were carried out to investigate the impact of different treatments of vertical mixing on the simulation of O
3 in the nocturnal boundary layer and residual layer. WRF/Chem model simulations provided realistic O
3 vertical distribution during the daytime. During the nighttime, in the residual layer, model outputs resulted in higher O
3 levels compared with the
in-situ observations. Model sensitivity analyses showed that increasing the turbulent length scales and improved stability functions yielded improvements in the vertical transport of O
3 within the residual layer. One key conclusion of this study is that models such as WRF/Chem require improved numerical algorithms to properly account for the nocturnal vertical transport of O
3 in the residual region of the atmospheric boundary layer.
► At times, the residual layer became leaky and permitted vertical transport to enhance surface O
3. ► Ozone in the residual layer is highly variable. ► The current implementation of the ACM2 PBL scheme in WRF/Chem does not properly simulate the mixing of pollutants. ► Increasing the asymptotic length and using “long-tails” stability function improved the nighttime simulation.
Background Abnormalities of cardiac structure and function are common in patients undergoing dialysis, and cardiovascular disease is the major cause of mortality in this group. Heart failure is a ...common clinical manifestation of cardiovascular disease and is preceded by left ventricular hypertrophy (LVH). There are variable reports about the impact of dialysis on LVH, both deleterious and beneficial. Our study investigated whether the timing of the initiation of dialysis therapy had an impact on cardiac structure and function. Study Design Randomized controlled trial. Setting & Participants This is a cardiac substudy involving 182 patients with stage 5 chronic kidney disease in the IDEAL (Initiating Dialysis Early and Late) trial. Intervention The IDEAL trial randomly assigned patients on the basis of estimated glomerular filtration rate (eGFR), calculated using the Cockcroft-Gault equation, to start dialysis therapy early (GFR, 10-14 mL/min/1.73 m2 ), with the others starting late (GFR, 5-7 mL/min/1.73 m2 ). Outcomes & Measurements Echocardiograms were obtained at baseline and 12 months after randomization. Primary outcomes were change in left ventricular mass indexed for height (LVMi) between baseline and 12 months, left ventricular ejection fraction, left ventricular systolic annular velocity, ratio of mitral inflow velocity (E) to mitral annular velocity (Ea) (E/Ea), and left atrial volume indexed for height (LAVi). Results LVMi at baseline was elevated, but similar in both groups, with no significant change within or between groups at 12 months. E/Ea and LAVi were increased at baseline, consistent with significant diastolic dysfunction; there were no differences between groups at 12 months and no changes were observed for left ventricular volumes, left ventricular ejection fraction, stroke volume, and other echocardiographic parameters. Limitations Small multicenter study using echocardiography. Conclusions Advanced cardiac disease in these patients with stage 5 chronic kidney disease did not progress during the 12-month study period and planned early initiation of dialysis therapy did not result in differences in any echocardiographic variables of cardiac structure and function.
Aims The study evaluated the use of age-related decision limits for N-terminal pro-B-type natriuretic peptide (NT-proBNP), for ruling out suspected systolic dysfunction in symptomatic patients in ...primary care, compared with the present standards. Methods and results Data were obtained from 5508 patients from 10 studies in the UK, New Zealand, Europe, and USA. All have had NT-proBNP analysis and echocardiography. The median age was 62 years (range 18–100 years) with a prevalence of reduced left ventricular systolic function (left ventricular ejection fraction ≤40%) of 18%. In a receiver operating characteristic curve analysis, overall area under the curve (AUC) was 0.89. When looking at different age groups, AUC was highest (0.95) for <50 years, intermediate (0.90) for 50–75 years, and lowest (0.82) for >75 years. Using optimized decision limits, sensitivity, specificity, and negative predictive values (NPVs) were: <50 years (50 ng/L): 99.2, 57.2, and 99.7%; 50–75 years (75 ng/L): 95.9, 51.0, and 96.8%; and >75 years (250 ng/L): 87.9, 53.7, and 92.4%, respectively. Using only a single decision value (125 ng/L for all ages) gave sensitivities of 89.1, 91.9, and 94.3%; specificities of 84.0, 69.1, and 29.3% and NPVs of 97.7, 97.6, and 93.4%. A decision value of 400 ng/L for all ages gave much lower sensitivities. Conclusion In a large population of patients in primary care, the use of age-stratified NT-proBNP decision limits considerably improves performance over current standards, with an excellent NPV for exclusion of reduced left ventricular systolic function.
•Raman spectra (RS) of atmospheric aerosol particles were measured with a semi-continuous system.•Of the 100,320 RS measured in 22.5 h, approximately 9000 had intensities above the thresholds.•RS ...were consistent with soots, carbonates, silicates, sulfates, iron oxides and biomaterials.•RS consistent with calcium oxalate hydrates (C2O4)Ca·(1 + x)H2O where 0<= x <=1 were seen.•Particles were charred infrequently by the laser, more often during daytime.
Raman spectroscopy can be used to determine the vibrational frequencies of materials and from these the chemical compositions. Raman microspectroscopy (RMS) can help in understanding the chemistry of atmospheric and other aerosols. This paper describes the use of an automated Aerosol Raman Spectrometer (ARS) from Battelle to collect approximately 100,000 RS in 15-min intervals over 22.5 h in Maryland, USA. Approximately 9000 of these RS have intensities exceeding the thresholds used in this analysis. This paper describes and illustrates processing techniques used for the RS, including detection and removal of RS exhibiting charring, and estimation and removal of fluorescence and other broad features. RS exhibiting the D and G bands of soots and other black carbons (labeled DG Carbon or DGC), are especially common in the data, probably because the particles are charged to increase the collection efficiency of small particles; the Raman cross sections of DGC are large; and the sampling location is near major roads. RS consistent with calcium oxalate hydrates (C2O4)Ca·(1 + x)H2O where x = 0 (whewellite) and x = 1 (weddellite) are observed. RS with the ν(CO) frequency intermediate between the x = 0 and 1 extremes are also observed, possibly suggesting calcium oxalates with x between 0 and 1, or mixed oxalates including other metals, e.g., Fe or Mg. Other materials consistent with the measured RS are calcite, dolomite, gypsum, anhydrite, quartz, orthoclase, jadeite or muscovite, biological materials, and iron oxides. The measured RS data set and code to process these are provided.
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