Search

Atmospheric aerosol particles play an important role for air quality and climate. Secondary organic aerosol (SOA) make up a significant mass fraction of these particles. SOA particles mostly forms from oxidation of gases, followed by gas-particle conversion of the oxidation products. Due to the variety of precursors and oxidation pathways involved in SOA formation, atmospheric SOA rank among the least understood aerosol types. To assess the impacts of SOA particles on air pollution and climate, knowledge of the number of phases in internal mixtures of different SOA types is critical. For example, gas-particle partitioning of organic species, and thus ultimately ambient SOA mass concentration, strongly depend on the number of phases in SOA particles. Atmospheric models traditionally assumed that different SOA types form a single condensed organic phase when internally mixed in individual particles. In case of mixed SOA particles with a single condensed phase uptake of semi-volatile vapors are enhanced, due to a lowering of the activities in the organic aerosol phase, and hence a lowering of the equilibrium partial pressure. By contrast, the equilibrium partial pressure is greater if the different SOA types form separate phases due to repulsive intermolecular forces between immiscible organic molecules. Consequently, enhancement of vapor uptake and ambient SOA mass concentrations will be smaller or absent in the case of phase-separated SOA particles.Here, using fluorescence microscopy, we directly observed the number of phase in individual particles containing mixtures of different SOA types. A total of 6 different SOA types were generated in environmental chambers from oxidation of single precursors. This included both biogenic and anthropogenic SOA types, having elemental oxygen-to-carbon (O/C) ratios between 0.34 and 1.05, covering values characteristic for aged and fresh atmospheric SOA. The number of phases of all possible internal mixtures of two different SOA types, termed SOA+SOA particles, was investigated as a function of humidity between 90% and 0% relative humidity (RH). We found that the number of phases was independent of RH within the range investigated and that 6 out of 15 SOA+SOA mixtures resulted in particles with two condensed organic phases. The observation of phase separated SOA+SOA particles challenges the approach of assuming a single condensed organic phase when representing SOA formation in atmospheric models. Specifically, we demonstrate that the difference in the average O/C ratio between the two SOA types of a mixture (ΔO/C) is a good predictor of the number of phases in particles that are internal mixtures of different SOA types: two-phase SOA+SOA particles formed for ΔO/C ≥ 0.47, while one-phase SOA+SOA particles formed for ΔO/C < 0.47. This threshold ΔO/C provides a simple, yet powerful parameter to predict whether mixtures of fresh and aged SOA particles form one- or two-phase particles in models.

The COVID lockdown presented a unique opportunity to study the anthropogenic emissions from different sectors under relatively cleaner conditions in India. The complex interplays of power production, industry, and transport could be dissected due to the significantly reduced influence of the latter two emission sources. Here, based on measurements of cloud condensation nuclei (CCN) activity and chemical composition of atmospheric aerosols during the lockdown, we report an episodic event showing rapid growth and high hygroscopicity of new aerosol particles formed in the SO2 plume from a large coal-fired power plant. These sulfate-rich particles had high CCN activity and number concentration, indicating high cloud-forming potential. Examining the sensitivity of CCN properties under relatively clean conditions over India provides important new clues to delineate contributions of different anthropogenic emission sectors and further to understand their perturbations of past and future climate forcing.

The chemical pathways for the production of secondary organic aerosols (SOA) are influenced by the concentration of nitrogen oxides (NO

Background As the proportion of anatomic total shoulder arthroplasty (aTSA) operations performed at outpatient surgical sites continue to increase, it is important to evaluate the clinical implications of this evolution in care. Methods Patients who underwent TSA for glenohumeral osteoarthritis from 2007 to 2019 were identified in the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) registry. Demographic data and 30-day outcomes were collected, and patients were separated into inpatient and outpatient (defined as same day discharge) groups. To control for confounding variables, a propensity score-matching algorithm was utilized. Outcomes included 30-day adverse events, readmission, and operative time. Results A total of 20,035 patients who underwent aTSA between 2007-2019 were identified: 18,707 inpatient aTSAs and 1,328 outpatient aTSAs. Upon matching, there were no significant differences in patient characteristics between inpatient and outpatient cohorts. Patients who underwent outpatient aTSA were less likely to experience a serious adverse event when compared to their matched inpatient aTSA counterparts (outpatient: 1.1% vs. inpatient: 2.1%, p=0.03). Outpatient aTSA was associated with similar rates of all specific individual complications and readmissions (1.5% vs. 1.9%, p=0.31). Conclusion When compared to a propensity score-matched cohort of inpatient counterparts, the current study found outpatient aTSA was associated with significantly reduced severe adverse events and similar readmission rates. These findings support the growing use of outpatient aTSA in appropriately selected patients.

The interaction of aerosols and the planetary boundary layer (PBL) plays an important role in deteriorating urban air quality. Aerosols from different sources may have different effects on regulating PBL structures owing to their distinctive dominant compositions and vertical distributions. To characterize the complex feedback of aerosols on PBL over the Beijing megacity, multiple approaches, including in situ observations in the autumn and winter of 2016–2019, backward trajectory clusters, and large-eddy simulations, were adopted. The results revealed notable distinctions in aerosol properties, vertical distributions and thermal stratifications among three types of air masses from the West Siberian Plain (Type-1), Central Siberian Plateau (Type-2) and Mongolian Plateau (Type-3). Low loadings of 0.28 ± 0.26 and 0.15 ± 0.08 of aerosol optical depth (AOD) appeared in the Type-1 and Type-2, accompanied by cool and less stable stratification, with a large part (80%) of aerosols concentrated below 1500 m. For Type-3, the AOD and single scattering albedo (SSA) were as high as 0.75 ± 0.54 and 0.91 ± 0.05, demonstrating severe pollution levels of abundant scattering aerosols. Eighty percent of the aerosols were constrained within a lower height of 1150 m owing to the warmer and more stable environment. Large-eddy simulations revealed that aerosols consistently suppressed the daytime convective boundary layer regardless of their origins, with the PBL height (PBLH) decreasing from 1120 m (Type-1), 1160 m (Type-2) and 820 m (Type-3) in the ideal clean scenarios to 980 m, 1100 m and 600 m, respectively, under polluted conditions. Therefore, the promotion of absorbing aerosols below the residual layer on PBL could be greatly hindered by the suppression effects generated by both absorbing aerosols in the upper temperature inversion layer and scattering aerosols. Moreover, the results indicated the possible complexities of aerosol-PBL interactions under future emission-reduction scenarios and in other urban regions.

Local atmospheric recirculation flows (i.e., river winds) induced by thermal contrast between wide Amazon rivers and adjacent forests could affect pollutant dispersion, but observational platforms for investigating this possibility have been lacking. Here we collected daytime vertical profiles of meteorological variables and chemical concentrations up to 500 m with a copter-type unmanned aerial vehicle during the 2019 dry season. Cluster analysis showed that a river-forest recirculation flow occurred for 23% (13 of 56) of the profiles. In fair weather, the thermally driven river winds fully developed for synoptic wind speeds below 4 m s−1, and during these periods the vertical profiles of carbon monoxide and total oxidants (defined as ozone and nitrogen dioxide) were altered. Numerical modeling shows that the river winds can recirculate pollution back toward the riverbank. There are implications regarding air quality for the many human settlements along the rivers throughout northern Brazil. Atmospheric pollutants recirculated by river winds reduce air quality for riverbank communities in the Amazon, according to unmanned aerial vehicle measurements and large eddy simulations.

The influence of relative humidity (RH) on the condensational growth of organic aerosol particles remains incompletely understood. Herein, the RH dependence was investigated via a series of experiments for α-pinene ozonolysis in a continuously mixed flow chamber in which recurring cycles of particle growth occurred every 7 to 8 h at a given RH. In 5 h, the mean increase in the particle mode diameter was 15 nm at 0% RH and 110 nm at 75% RH. The corresponding particle growth coefficients, representing a combination of the thermodynamic driving force and the kinetic resistance to mass transfer, increased from 0.35 to 2.3 nm2 s-1. The chemical composition, characterized by O:C and H:C atomic ratios of 0.52 and 1.48, respectively, and determined by mass spectrometry, did not depend on RH. The Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) was applied to reproduce the observed size- and RH-dependent particle growth by optimizing the diffusivities Db within the particles of the condensing molecules. The Db values increased from 5 α-1 × 10-16 at 0% RH to 2 α-1 × 10-12 cm-2 s-1 at 75% RH for mass accommodation coefficients α of 0.1 to 1.0, highlighting the importance of particle-phase properties in modeling the growth of atmospheric aerosol particles.

Purpose To investigate the association between intrauterine device (IUD) use and hip pain, orthopaedic visits for hip pain, and arthroscopic hip surgery. Methods This was a retrospective cohort study of patients aged 18-44 years old using either IUDs or subdermal implants for contraception in a large commercial claims database (MarketScan) from 2012 to 2015. All patients had at least 12 months of continuous enrollment both before and after contraceptive placement. Patients with a history of hip pain or surgery were excluded. The primary outcome was new hip pain. Secondary outcomes included visiting an orthopaedic or sports medicine provider for a hip complaint, intra-articular hip injection, and arthroscopic hip surgery. Outcomes were analyzed with Cox proportional-hazard models. Results We identified a total of 242,383 patients, including 216,541 (89.3%) with IUDs and 25,842 (10.7%) with subdermal contraceptive implants. In time-to-event analysis, IUDs (vs implants) were not associated with increased risk of new hip pain diagnoses (hazard ratio [HR] 0.95, 95% confidence interval [CI] 0.87-1.03, P = .21). In contrast, both age (P < .001) and region (P < .001) were associated with increased risk of new hip pain. Similar results were seen for the secondary outcomes, including risk of orthopaedic visits for hip complaints (HR 1.06, 95% CI 0.83-1.35, P = .63), intra-articular injections of the hip (HR 0.94, 95% CI 0.63-1.41, P = .77), and hip arthroscopy procedures (HR 1.13, 95% CI 0.53-2.40, P = .75). Conclusions In this study, we found no evidence that IUDs were associated with hip pain or surgery. Level of Evidence Level III, retrospective cohort.

Background The most comprehensive health care policy changes aimed at reducing racial disparities were implemented in 2011 and continue today. It is unknown if these initiatives have led to a decrease in racial differences among patients undergoing total shoulder arthroplasty. The purpose of this study is to examine racial differences in procedural rates, complications, and mortality in patients undergoing total shoulder arthroplasty. Methods National rates of utilization of primary anatomic (TSA) and reverse total shoulder arthroplasty (RTSA) were analyzed from 2012 to 2017. Population-adjusted and gender-adjusted procedural rates were trended over time and standardized based on insurance status. Multivariable logistic regression was used to determine racial differences in complications and mortality. Results In 2012, the incidence of TSA and RTSA among white patients was 18.7/100,000 compared to 5.1/100,000 among black patients (difference: 13.6/100,000) and increased to 36.9/100,000 in white patients and 10.8/100,000 in black patients in 2017 (difference: 26.1/100,000). This equated to an increase in the race disparity by 12.5/100,000 over the study period. Blacks underwent lower rates of TSA and RTSA than whites regardless of insurance status. Black patients had a longer length of hospital stay and a higher rate of discharge to facility. Black patients had increased odds of complications, including acute myocardial infarction (odds ratio [OR] 1.43), pulmonary embolism (OR 1.97), acute renal failure (OR 1.40), sepsis (OR 1.68), and surgical site infection (OR 2.19). Black patients had increased odds of mortality compared with white patients (OR 2.88). Conclusion Racial disparities in patients undergoing TSA and RTSA are worsening over time. Black patients undergo TSA and RTSA at lower rates than white patients regardless of insurance status and have increased odds of complications and mortality. Improved initiatives are needed to reduce these racial disparities and further research is warranted to understand their root causes.

Background: There is a paucity of literature on arthroscopic capsular autograft labral reconstruction. Purpose: To report midterm functional outcomes for patients undergoing acetabular labral repair with capsular autograft labral reconstruction. Study Design: Case series; Level of evidence, 4. Methods: This is a retrospective case series of prospectively collected data on patients who underwent arthroscopic acetabular labral repair by the senior surgeon between March 2013 and August 2018. The inclusion criteria for this study were adult patients aged 18 years or older who underwent primary hip arthroscopy for arthroscopic capsular autograft labral reconstruction. Exclusion criteria were Results: A total of 97 hips (94 patients) met the inclusion criteria with a mean final follow-up of 28.2 months (95% CI, 26.0-30.4). Patients had a mean age of 39.0 years (95% CI, 36.8-41.2) with a mean body mass index of 25.8 (95% CI, 24.9-26.7). When compared with baseline (40.4 [95% CI, 36.7-44.2]), the mean international Hip-Outcome Tool-33 (iHOT-33) scores were significantly greater at 3-month (60.9 [95% CI, 56.8-64.9]; P < .001), 6-month (68.8 [95% CI, 64.7-72.9]; P < .001), 12-month (73.2 [95% CI, 68.9-77.5]; P < .001), and final (76.6 [95% CI, 72.4-80.8]; P < .001) follow-up. At 2-year follow-up, 76.3%, 65.5%, and 60.8% of patients’ iHOT-33 scores exceeded clinically meaningful outcome thresholds for minimally clinically important difference (MCID), patient-acceptable symptomatic state, and substantial clinical benefit, respectively. Conclusions: In this study of 97 hips undergoing arthroscopic labral repair with capsular autograft labral reconstruction, we found favorable outcomes that exceeded the MCID thresholds in the majority of patients at a mean 28.2 months’ follow-up. Future studies should compare outcomes between this technique and other methods of autograft and allograft reconstruction to determine differences in patient-reported outcomes, donor-site morbidity, and complications.

Background: Although intra-articular injections are important in the management of patients who may later undergo hip arthroscopy, conflicting data are available regarding the safety of such injections when administered within 3 months of surgery. Furthermore, despite the increasing use of image-guided intra-articular hip injections, it is unknown whether the type of imaging modality used is associated with infection after hip arthroscopy. Purpose: To assess the risk of infection associated with image-guided intra-articular injections before hip arthroscopy and, secondarily, compare that risk between ultrasound (US) and fluoroscopic (FL) guidance. Study Design: Cohort study; Level of evidence, 3. Methods: This was a retrospective cohort study of patients in a large national insurance database who underwent hip arthroscopy between 2007 and 2017. Patients were required to have continuous enrollment from at least 1 year before to 6 months after hip arthroscopy. Patient age, sex, geographic region, medical history, surgical details, and hip injections were collected. Patients who underwent injection ≤3 months preoperatively and >3 to ≤12 months preoperatively were compared with patients who did not undergo preoperative injection. Bivariate analyses and multivariable logistic regressions were used to assess the association between ipsilateral preoperative hip injection and surgical site infection within 6 months of surgery. Results: We identified 17,987 patients (36.3% female; mean ± SD age, 37.6 ± 14.0 years) undergoing hip arthroscopy, 2276 (12.7%) of whom had an image-guided hip injection in the year preceding surgery (53.0% FL). Patients who underwent intra-articular injection ≤3 months preoperatively had similar infection rates to patients who did not undergo preoperative injection in the year before surgery for both the FL (0.46% vs 0.46%; P≥ .995) and the US cohorts (0.50% vs 0.46%; P = .76). Results persisted in adjusted analysis (FL ≤3 months: OR, 1.04; 95% CI, 0.32-3.37; P = .94; US ≤3 months: OR, 1.19; 95% CI, 0.36-3.90; P = .78). Similar results were seen for patients undergoing injections >3 to ≤12 months preoperatively. Conclusion: Postoperative infection was rare in patients undergoing intra-articular hip injection ≤3 months before hip arthroscopy and was no more common than in patients not undergoing preoperative injection. Moreover, no differences were seen in infection risk between US and FL guidance. Although intra-articular hip injections should always be administered with careful consideration, these results do not suggest that these injections are uniformly contraindicated in the 3 months preceding hip arthroscopy.

Covid lockdown presented an important opportunity to study relatively cleaner conditions in India. The complex factors of power production, industry, and transportation could be more carefully dissected because of the extreme reduction in the influence of the latter two emission sources. Measurements of cloud condensation nuclei (CCN) activity and other chemical properties of atmospheric aerosols showed that newly formed aerosol particles were produced in the SO2 plume from a large coal-fired power plant, contrary to normal conditions of heavy pollution. The sulfate-rich particles had high CCN activity and number concentration, indicating high cloud-forming potential. Examining the sensitivity of CCN properties under relatively clean conditions over India provides important new constraints on the perturbations of past and future climate forcing by anthropogenic emissions. Because most sensitive regime of aerosol climate forcing on cloud development is the midpoint of relatively clean conditions afforded by the Covid lockdown between background and polluted conditions.

Secondary organic aerosol (SOA) constitutes a large fraction of atmospheric aerosol. To assess its impacts on cli-mate and air pollution, knowledge of the number of phases in internal mixtures of different SOA types is required. Atmospheric models often assumed that different SOA types form a single phase when mixed. Here, we present visual observations of the number of phases formed after mixing different anthropogenic and biogenic SOA types. Mixing SOA types generated in environmental chambers with oxygen-to-carbon (O / C) ratios between 0.34 to 1.05, we found six out of fifteen mixtures of two SOA types to result in two phase particles. We demonstrate that the number of phases depends on the difference in the average O / C ratio between the two SOA types (Δ(O / C)). Using a threshold Δ(O / C) of 0.47, we can predict the phase behavior of over 90 % of our mixtures, with one- and two-phase particles predicted for Δ(O / C) < 0.47 and Δ(O / C) ≥ 0.47, respectively. This Δ(O / C) threshold further allows to predict if mixtures of fresh and aged SOA form one- or two-phase particles in the atmos-phere. In addition, we show that phase separated SOA particles form when mixtures of volatile organic compounds emitted from real trees are oxidized.

Volatile organic compounds (VOCs) emitted from forests are important chemical components that affect ecosystem functioning, atmospheric chemistry, and regional climate. Temperature differences between a forest and an adjacent river can induce winds that influence VOC fate and transport. Quantitative observations and scientific understanding, however, remain lacking. Herein, daytime VOC datasets were collected from the surface up to 500 m over the “Rio Negro” river in Amazonia. During time periods of river winds, isoprene, α-pinene, and β-pinene concentrations increased by 50, 60, and 80% over the river, respectively. The concentrations at 500 m were up to 80% greater compared to those at 100 m because of the transport path of river winds. By comparison, the concentration of methacrolein, a VOC oxidation product, did not depend on river winds or height. The differing observations for primary emissions and oxidation products can be explained by the coupling of timescales among emission, reaction, and transport. This behavior was captured in large-eddy simulations with a coupled chemistry model. The observed and simulated roles of river winds in VOC fate and transport highlight the need for improved representation of these processes in regional models of air quality and chemistry–climate coupling.

The phase behavior of atmospheric aerosol particles influences processes like gas-particle partitioning, solar light scattering, and cloud formation, ultimately affecting atmospheric air quality an...

Background: Previous observational studies have suggested poor results of arthroscopic surgery for the treatment of acetabular labral tears in patients older than 40 years. Purpose: To compare hip arthroscopy versus nonoperative management for symptomatic labral tears in patients older than 40 years who have limited radiographic osteoarthritis. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: In this single-surgeon, parallel randomized controlled trial, patients older than 40 years who had symptomatic, MRI-confirmed labral tears and limited radiographic osteoarthritis (Tönnis grades 0-2) were randomized 1:1 to arthroscopic surgery with postoperative physical therapy (SPT) or physical therapy alone (PTA) using an electronic randomization program. PTA patients who achieved unsatisfactory improvement were permitted to cross over to SPT after completing ≥14 weeks of physical therapy. The primary outcomes were International Hip Outcome Tool (iHOT-33) and modified Harris Hip Score (mHHS) at 12 months after randomization, and secondary outcomes included other patient-reported outcome measures and the visual analog scale. Outcomes were assessed at baseline and at 3, 6, and 12 months after randomization. Primary analysis was performed on an intention-to-treat basis using linear mixed-effect models. Sensitivity analyses included modified as-treated analysis and treatment-failure analysis. Due to infeasibility, patients and health care providers were both unblinded. Results: The study enrolled 90 patients (46 [51.1%] SPT; 44 [48.9%] PTA); of these, 81 patients (42 [51.9%] SPT; 39 (48.1%) PTA) completed 12-month follow-up. A total of 28 of the 44 PTA patients crossed over to SPT within the study period (63.6% crossover). Intention-to-treat analysis revealed significantly greater iHOT-33 scores (+12.11; P = .007) and mHHS scores (+6.99 points; P = .04) in the SPT group than the PTA group at 12 months. Modified as-treated analysis revealed that these differences exceeded the minimal clinically important difference of 10.0 points (SPT-PTA iHOT-33, +11.95) and 8.0 points (SPT-PTA mHHS, +9.76), respectively. Conclusion: In patients older than 40 years with limited osteoarthritis, arthroscopic acetabular labral repair with postoperative physical therapy led to better outcomes than physical therapy alone. Thus, age over 40 years should not be considered a contraindication to arthroscopic acetabular labral repair. Registration: NCT03909178 (ClinicalTrials.gov identifier)

Volatile organic compounds (VOCs) are important pollutants that affect air quality and atmosphere–ecosystem interactions. Atmospheric sampling onboard a multicopter unmanned aerial vehicle (UAV), s...

Many cities in India experience severe deterioration of air quality in winter. Particulate matter is a key atmospheric pollutant that impacts millions of people. In particular, the high mass concentration of particulate matter reduces visibility, which has severely damaged the economy and endangered human lives. But the underlying chemical mechanisms and physical processes responsible for initiating haze and fog formation remain poorly understood. Here we present the measurement results of chemical composition of particulate matter in Delhi and Chennai. We find persistently high chloride in Delhi and episodically high chloride in Chennai. These measurements, combined with thermodynamic modelling, suggest that in the presence of excess ammonia in Delhi, high local emission of hydrochloric acid partitions into aerosol water. The highly water-absorbing and soluble chloride in the aqueous phase substantially enhances aerosol water uptake through co-condensation, which sustains particle growth, leading to haze and fog formation. We therefore suggest that the high local concentration of gas-phase hydrochloric acid, possibly emitted from plastic-contained waste burning and industry, causes some 50% of the reduced visibility. Our work implies that identifying and regulating gaseous hydrochloric acid emissions could be critical to improve visibility and human health in India. Half of the reduced visibility due to haze formation in cities in India is attributed to local emission of gas-phase hydrochloric acid from waste-burning and industry, according to measurements of particulate matter and thermodynamic modelling.

Semivolatile oxygenated organic compounds (SV-OVOCs) are important atmospheric species, in particular for the production and chemistry of atmospheric particulate matter and related impacts on air quality and climate. In this study, SV-OVOCs were collected in the horizontal plane of the roughness layer over the tropical forest in the central Amazon during the wet season of 2018. A sampler mounted to a copter-type, hovering unmanned aerial vehicle was used. Underlying the collection region, a plateau forest transitioned into a slope forest across several hundred meters. The concentrations of pinonic and pinic acids, which are monoterpene oxidation products, had no statistical difference over the two forests. By comparison, across the study period, differences in the concentration of 2-methyltetrols, which are products of isoprene oxidation, ranged from −70% to +480% over the two forests. The chemical lifetime of 2-methyltetrols in the atmosphere is sufficiently long that heterogeneity in the isoprene emission rate from the two forests followed by atmospheric oxidation does not explain the concentration heterogeneity of 2-methyltetrols. Standing waves and local meteorology also cannot account for the heterogeneity. Of the possibilities considered, the most plausible explanation is the direct emission from the forest of 2-methyltetrols produced through biological processes within the plants. Under this explanation, the rate of direct SV-OVOC emissions should be modulated by forest type and related environmental stressors. Direct emissions of SV-OVOCs should be more broadly considered for constraining and improving models of atmospheric composition, transport, and chemistry over tropical forests.

The concentration of nitrogen oxides (NOx) and their reservoir species, the organonitrates (ON), impacts on the secondary organic aerosol (SOA) production. To estimate the effect of different NOx levels on SOA, we carried out a series of laboratory experiments at the Harvard Environmental Chamber (HEC) investigating the production and partitioning of total organonitrates from α-pinene photo-oxidation in a NOx range varying between 1 ppb and 24 ppb. We measured not only the aerosol mass concentration by using a Scanning Mobility Particle Sizer (SMPS) and composition by an on-line aerosol mass spectrometry (AMS), but also the gas phase and particle-phase organonitrates (gON and pON, respectively) by a thermal dissociation laser-induced fluorescence (TDLIF). In our experimental conditions, we found the presence of crossover point of 6 ppb of NOx between clean and polluted conditions that affect the SOA production: in fact, the SOA yield for 1 to 6 ppb NOx increased, and for >6 ppb NOx steadily dropped. The ON partitioning ratio (pON/(pON+gON)) has been estimated, identifying that also this ratio is strongly affected by the NOx concentrations; in fact, it decreased from 0.27 to 0.13 as the NOx increased from

Black carbon (BC) particles in Beijing summer haze play an important role in the regional radiation balance and related environmental processes. Understanding the factors that lead to variability of the impacts of BC remains limited. Here, we present observations by a soot-particle aerosol mass spectrometer (SP-AMS) of BC-containing submicron particulate matter (BC−PM1) in Beijing, China, during summer 2017. These observations were compared to concurrently measured total non-refractory submicron particulate matter (NR−PM1) by a high-resolution aerosol mass spectrometer (HR-AMS). Distinct properties were observed between NR−PM1 and BC−PM1 relevant to organic aerosol (OA) composition. Hydrocarbon-like OA (HOA) in BC−PM1 was found to be up to 2-fold higher than that in NR−PM1 in fresh vehicle emissions, suggesting that a part of HOA in BC−PM1 may be overestimated, likely due to the change of collection efficiency of SP-AMS. Cooking-related OA was only identified in NR−PM1, whereas aged biomass burning OA (A-BBOA) was a unique factor only identified in BC−PM1. The A-BBOA was linked to heavily coated BC, which may lead to enhancement of the light absorption ability of BC by a factor of 2 via the “lensing effect”. More-oxidized oxygenated OA identified in BC-containing particles was found to be slightly different from that observed by HR-AMS, mainly due to the influence of A-BBOA. Overall, these findings highlight that BC in urban Beijing is partially of agricultural fire origin and that a unique biomass-burning-related OA associated with BC may be ubiquitous in aged BC−PM1, and this OA may play a role in affecting air quality and climate that has not previously been fully considered.

Background Traditional shoulder physical examination (PE) tests have suboptimal sensitivity for detection of supraspinatus full-thickness tears (FTTs). Therefore, clinicians may continue to suspect FTTs in some patients with negative rotator cuff PE tests and turn to magnetic resonance imaging (MRI) for definitive diagnosis. Consequently, there is a need for a secondary screening test that can accurately rule out FTTs in these patients to better inform clinicians which patients should undergo MRI. The purpose of this study was to assess the ability of two new dynamic PE tests to detect supraspinatus pathology in patients for whom traditional static PE tests failed to detect pathology. Methods We prospectively enrolled 171 patients with suspected rotator cuff pathology with negative findings on traditional rotator cuff PE, who underwent two new dynamic PE tests: first, measurement of angle at which the patient first reports pain on unopposed active abduction and, second, the dynamic isotonic manipulation examination (DIME). Patients then underwent shoulder magnetic resonance arthrogram (MRA). Data from the new PE maneuvers were compared to outcomes collected from MRA reports. Results Pain during DIME testing had a sensitivity of 96.3% and 92.6% and negative predictive value (NPV) of 96.2% and 94.9% in the coronal and scapular planes, respectively. DIME strength ≤86.0 N had a sensitivity of 100% and 96.3% and NPV of 100% and 95.7% in the coronal and scapular planes, respectively. Pain at ≤90° on unopposed active abduction in the coronal plane had a specificity of 100% and positive predictive value of 100% for supraspinatus pathology of any kind (i.e. tendinopathy, “fraying”, or tearing). Conclusion DIME is highly sensitive for supraspinatus FTTs in patients with negative traditional rotator cuff PE tests for whom there is still high clinical suspicion of FTTs. Thus, this test is an excellent secondary screening tool for supraspinatus FTTs in patients for whom clinicians suspect rotator cuff pathology despite negative traditional static PE tests. Given its high sensitivity, a negative DIME test rules out supraspinatus FTT well in these patients, and can therefore better inform clinicians which patients should undergo MRI. In addition, the angle at which patients first report pain on unopposed active shoulder abduction is highly specific for supraspinatus pathology. Study Design Level II; Diagnosis Study