Monoterpene Photooxidation in a Continuous-Flow Chamber: SOA Yields and Impacts of Oxidants, NOx, and VOC Precursors

Monoterpene photooxidation plays an important role in secondary organic aerosol (SOA) formation in the atmosphere. The low-volatility products can enhance new particle formation and particle growth and thus influence climate feedback. Here, we present the results of α-pinene and Δ-3-carene photooxidation experiments conducted in continuous-flow mode in an environmental chamber under several reaction conditions. The roles of oxidants, addition of NO, and VOC molecular structure in influencing SOA yield are illustrated. SOA yield from α-pinene photooxidation shows a weak dependence on H₂O₂ concentration, which is a proxy for HO₂ concentration. The high O/C ratios observed in the α-pinene photooxidation products suggest the production of highly oxygenated organic molecules (HOM). Addition of ozone to the chamber during low-NO_x photooxidation experiments leads to higher SOA yield. With the addition of NO, the production of N-containing HOMs is enhanced and the SOA yield shows a modest, nonlinear dependence on the input NO concentration. Carene photooxidation leads to higher SOA yield than α-pinene under similar reaction conditions, which agrees with the lower volatility retrieved from evaporation kinetics experiments. These results improve the understanding of SOA formation from monoterpene photooxidation and could be applied to refine the representation of biogenic SOA formation in models.

Engineering Models of the Heart Left Ventricle

Despite capturing the imagination of scientists for decades, the goal of creating an artificial heart for transplantation proved to be significantly more challenging than initially anticipated. Toward this goal, recent ground-breaking studies demonstrate the development of functional left ventricular (LV) models. LV models are artificially constructed 3D chambers that are capable of containing liquid within the engineered cavity and exhibit the functionality of native LV including contraction, ejection of fluid, and electrical impulse propagation. Various hydrogels and polymers have been used in manufacturing of LV models, relying on techniques such as electrospinning, bioprinting, casting, and molding. Most studies scaled down the models based on the dimensions of the human or rat ventricle. Initially, neonatal rat cardiomyocytes were the cell type of choice for construction the LV models. Yet, as the stem cell biology field advanced, recent studies focused on the use of cardiomyocytes derived from human induced pluripotent stem cells. In this review, we first describe the physiological characteristics of the human heart, to establish the parameter space for modeling. We then elaborate on current advances in the field and compare recently developed LV models among themselves and with the native human left ventricle. Fabrication methods, cell types, biomaterials, functional properties, and disease modeling capability are some of the major parameters that have distinguished these models. We also highlight some of the current challenges in this field, such as vascularization, cell composition and fidelity, and discuss potential solutions to overcome them.

Variability in Aromatic Aerosol Yields under Very Low NOx Conditions at Different HO2/RO2 Regimes

Current chemical transport models generally use a constant secondary organic aerosol (SOA) yield to represent SOA formation from aromatic compounds under low NO_x conditions. However, a wide range of SOA yields (10 to 42%) from m-xylene under low NO_x conditions is observed in this study. The chamber HO₂/RO₂ ratio is identified as a key factor explaining SOA yield variability: higher SOA yields are observed for runs with a higher HO₂/RO₂ ratio. The RO₂ + RO₂ pathway, which can be increasingly significant under low NO_x and HO₂/RO₂ conditions, shows a lower SOA-forming potential compared to the RO₂ + HO₂ pathway. While the traditional low-NO_x chamber experiments are commonly used to represent the RO₂ + HO₂ pathway, this study finds that the impacts of the RO₂ + RO₂ pathway cannot be ignored under certain conditions. We provide guidance on how to best control for these two pathways in conducting chamber experiments to best obtain SOA yield curves and quantify the contributions from each pathway. On the global scale, the chemical transport model GEOS-Chem is used to identify regions characterized by lower surface HO₂/RO₂ ratios, suggesting that the RO₂ + RO₂ pathway is more likely to prove significant to overall SOA yields in those regions. Current models generally do not consider the RO₂ + RO₂ impacts on aromatic SOA formation, but preliminary sensitivity tests with updated SOA yield parameters based on such a pathway suggest that without this consideration, some types of SOA may be overestimated in regions with lower HO₂/RO₂ ratios.

Chamber-Specific Protein Expression during Direct Cardiac Reprogramming

Forced expression of core cardiogenic transcription factors can directly reprogram fibroblasts to induced cardiomyocyte-like cells (iCMs) in vitro and in vivo. This cardiac reprogramming approach provides a proof of concept for induced heart regeneration by converting a fibroblast fate to a cardiomyocyte fate. However, it remains elusive whether chamber-specific cardiomyocytes can be generated by cardiac reprogramming. Therefore, we assessed the ability of the cardiac reprogramming approach for chamber specification in vitro and in vivo. We found that in vivo cardiac reprogramming post-myocardial infarction exclusively induces a ventricular-like phenotype, while a major fraction of iCMs generated in vitro failed to determine their chamber identities. Our results suggest that in vivo cardiac reprogramming may have an inherent advantage of generating chamber-matched new cardiomyocytes as a potential heart regenerative approach.

Particle-Phase Photoreactions of HULIS and TMIs Establish a Strong Source of H2O2 and Particulate Sulfate in the Winter North China Plain

During haze periods in the North China Plain, extremely high NO concentrations have been observed, commonly exceeding 1 ppbv, preventing the classical gas-phase H₂O₂ formation through HO₂ recombination. Surprisingly, H₂O₂ mixing ratios of about 1 ppbv were observed repeatedly in winter 2017. Combined field observations and chamber experiments reveal a photochemical in-particle formation of H₂O₂, driven by transition metal ions (TMIs) and humic-like substances (HULIS). In chamber experiments, steady-state H₂O₂ mixing ratios of 116 ± 83 pptv were observed upon the irradiation of TMI- and HULIS-containing particles. Correspondingly, H₂O₂ formation rates of about 0.2 ppbv h^-1 during the initial irradiation periods are consistent with the H₂O₂ rates observed in the field. A novel chemical mechanism was developed explaining the in-particle H₂O₂ formation through a sequence of elementary photochemical reactions involving HULIS and TMIs. Dedicated box model studies of measurement periods with relative humidity >50% and PM_2.5 ≥ 75 μg m^-3 agree with the observed H₂O₂ concentrations and time courses. The modeling results suggest about 90% of the particulate sulfate to be produced from the SO₂ reaction with OH and HSO₃^- oxidation by H₂O₂. Overall, under high pollution, the H₂O₂-caused sulfate formation rate is above 250 ng m^-3 h^-1, contributing to the sulfate formation by more than 70%.

A safe and reusable imaging chamber compatible with organic solvents

High refractive index organic solvents are commonly used as an imaging medium in tissue clearing approaches. While effective, such solvents provide serious concerns for the safety of users and the equipment, especially in a central microscopy unit. To overcome these concerns, we have developed a large and reusable imaging chamber compatible with the universal mounting frame AK (PeCon GmbH). This chamber is easy to assemble and significantly improves the working environment in a central microscopy unit, where hazardous chemicals could negatively affect equipment and people. To encourage the uptake of these chambers, the design is made publicly available for download.

An increase in dietary lipid content from different forms of double-low rapeseed reduces enteric methane emission in Datong yaks on the Qinghai-Tibetan Plateau

Enteric methane (CH₄ ) emission in cattle generally decreases by approximately 1 g/g dry matter intake (DMI) with an increase in dietary lipids of 10 g/kg dry matter (DM). The effect of dietary lipids on CH₄ emission in yaks has not been reported and is the subject of this study. Four Datong yaks were used in a 4 × 4 Latin-square design in which the four treatments included restricted intakes of double-low rapeseed differing in form and lipid (ether extract-EE) content: (a) rapeseed meal (EE 32.6 g/kg DM); (b) rapeseed meal and rapeseed cake (EE 45.8 g/kg DM); (c) rapeseed meal and whole cracked rapeseed (EE 54.5 g/kg DM) and (d) rapeseed meal and rapeseed oil (EE 62.7 g/kg DM). The digestibility of feed components did not differ among treatments. The ruminal total volatile fatty acids (p = .082) and acetic acid (p = .062) concentrations tended to be lowest in yaks consuming the diet with highest lipid content. In addition, CH₄ production was lowest in this group (p = .004), and declined by 1.75 g/g DMI per 10 g/kg DM reduction in dietary lipid content, a rate substantially faster than in cattle.

Cardiac Magnetic Resonance Imaging and Transthoracic Echocardiography: Investigation of Concordance between the Two Methods for Measurement of the Cardiac Chamber

Background and objectives: Cardiac magnetic resonance (CMR) imaging is the gold standard method for the detection of ventricular volumes and myocardial edema/scar. Transthoracic echocardiography (TTE) imaging is primarily used in the evaluation of cardiac functions and chamber dimensions. This study aims to investigate whether the chamber diameter measurements are concordant with each other in the same patient group who underwent TTE and CMR. Materials and Methods: The study included 41 patients who underwent TTE and CMR imaging. Ventricular and atrial diameter measurements from TTE-derived standard parasternal long axis and apical four-chamber views and CMR-derived three- and four-chamber views were recorded. The concordance between the two methods was compared using intra-class correlation coefficients (ICC) and Bland–Altman plots. Results: Of the patients, 25 (61%) were male and the mean age was 48.12 ± 16.79. The mean ICC for LVDD between CMR observers was 0.957 (95% CI: 0.918–0.978), while the mean ICC between CMR and TTE measurements were 0.849 (95% CI: 0.709–0.922) and 0.836 (95% CI: 0.684–0.915), respectively. The mean ICC for the right ventricle between CMR observers was 0.985 (95% CI: 0.971–0.992), while the mean ICC between CMR and TTE measurements were 0.869 (95% CI: 0.755–0.930) and 0.892 (95% CI: 0.799–0.942), respectively. Passing–Bablok Regression and Bland–Altman plots indicated high concordance between the two methods. Conclusions: TTE and CMR indicated high concordance in chamber diameter measurements for which the CMR should be considered in patients for whom optimal evaluation with TTE could not be performed due to their limitations.

Greenhouse gas fluxes over managed grasslands in Central Europe

Central European grasslands are characterized by a wide range of different management practices in close geographical proximity. Site-specific management strategies strongly affect the biosphere-atmosphere exchange of the three greenhouse gases (GHG) carbon dioxide (CO₂ ), nitrous oxide (N₂ O), and methane (CH₄ ). The evaluation of environmental impacts at site level is challenging, because most in situ measurements focus on the quantification of CO₂ exchange, while long-term N₂ O and CH₄ flux measurements at ecosystem scale remain scarce. Here, we synthesized ecosystem CO₂ , N₂ O, and CH₄ fluxes from 14 managed grassland sites, quantified by eddy covariance or chamber techniques. We found that grasslands were on average a CO₂ sink (-1,783 to -91 g CO₂  m^-2  year^-1 ), but a N₂ O source (18-638 g CO₂ -eq. m^-2  year^-1 ), and either a CH₄ sink or source (-9 to 488 g CO₂ -eq. m^-2  year^-1 ). The net GHG balance (NGB) of nine sites where measurements of all three GHGs were available was found between -2,761 and -58 g CO₂ -eq. m^-2  year^-1 , with N₂ O and CH₄ emissions offsetting concurrent CO₂ uptake by on average 21 ± 6% across sites. The only positive NGB was found for one site during a restoration year with ploughing. The predictive power of soil parameters for N₂ O and CH₄ fluxes was generally low and varied considerably within years. However, after site-specific data normalization, we identified environmental conditions that indicated enhanced GHG source/sink activity ("sweet spots") and gave a good prediction of normalized overall fluxes across sites. The application of animal slurry to grasslands increased N₂ O and CH₄ emissions. The N₂ O-N emission factor across sites was 1.8 ± 0.5%, but varied considerably at site level among the years (0.1%-8.6%). Although grassland management led to increased N₂ O and CH₄ emissions, the CO₂ sink strength was generally the most dominant component of the annual GHG budget.

Revisiting the choice of the driving temperature for eddy covariance CO2 flux partitioning

So-called CO₂ flux partitioning algorithms are widely used to partition the net ecosystem CO₂ exchange into the two component fluxes, gross primary productivity and ecosystem respiration. Common CO₂ flux partitioning algorithms conceptualize ecosystem respiration to originate from a single source, requiring the choice of a corresponding driving temperature. Using a conceptual dual-source respiration model, consisting of an above- and a below-ground respiration source each driven by a corresponding temperature, we demonstrate that the typical phase shift between air and soil temperature gives rise to a hysteresis relationship between ecosystem respiration and temperature. The hysteresis proceeds in a clockwise fashion if soil temperature is used to drive ecosystem respiration, while a counter-clockwise response is observed when ecosystem respiration is related to air temperature. As a consequence, nighttime ecosystem respiration is smaller than daytime ecosystem respiration when referenced to soil temperature, while the reverse is true for air temperature. We confirm these qualitative modelling results using measurements of day and night ecosystem respiration made with opaque chambers in a short-statured mountain grassland. Inferring daytime from nighttime ecosystem respiration or vice versa, as attempted by CO₂ flux partitioning algorithms, using a single-source respiration model is thus an oversimplification resulting in biased estimates of ecosystem respiration. We discuss the likely magnitude of the bias, options for minimizing it and conclude by emphasizing that the systematic uncertainty of gross primary productivity and ecosystem respiration inferred through CO₂ flux partitioning needs to be better quantified and reported.

Evaluation of automatic exposure control system chamber for the dose optimization when examining pelvic in digital radiography

We found a way to optimize the image quality and reduce the exposure dose of patients through the proper activity combination of the automatic exposure control system chamber for the dose optimization when examining the pelvic anteroposterior side using the phantom of the human body standard model. We set 7 combinations of the chamber of automatic exposure control system. The effective dose was yielded by measuring five times for each according to the activity combination of the chamber for the dose measurement. Five radiologists with more than five years of experience evaluated the image through picture archiving and communication system using double blind test while classifying the 6 anatomical sites into 3-point level (improper, proper, perfect). When only one central chamber was activated, the effective dose was found to be the highest level, 0.287 mSv; and lowest when only the top left chamber was used, 0.165 mSv. After the subjective evaluation by five panel members on the pelvic image was completed, there was no statistically meaningful difference between the 7 chamber combinations, and all had good image quality. When testing the pelvic anteroposterior side with digital radiography, we were able to reduce the exposure dose of patients using the combination of the top right side of or the top two of the chamber.

Capturing the efficiency of vibrating mesh nebulizers: minimizing upper airway deposition

BACKGROUND

Vibrating mesh devices are portable nebulizer systems with reported high efficiency. Losses occur during expiration, and particle size distributions vary. We describe an aerosol chamber designed to capture and condition aerosols from a typical vibrating mesh nebulizer, the Omron U22. The goal was to improve inhaled mass (IM) and respirable fraction (RF) and shorten treatment time.

METHODS

With test solutions of radiolabeled saline, we characterized the Omron U22 (three examples) vibrating mesh nebulizer measuring aerosol output with different breathing patterns, with and without manual breath synchronization. Particle size distributions were measured by cascade impaction as a "standing cloud" and during ventilation with a piston respirator. IM (percentage of nebulizer charge), respirable mass (RM), particle size distribution, and breathing time were measured with and without use of the chamber. Breathing patterns were designed to simulate tidal breathing with a "COPD" (chronic obstructive pulmonary disease) pattern (450 mL, rate 15, duty cycle 0.35) and "slow and deep" breathing for maximal lung deposition (1,500 mL, rate 5, duty cycle 0.70). Patterns of deposition were confirmed in a human volunteer using a gamma camera.

RESULTS

IM was significantly affected by breathing pattern and averaged 30.0±2.91% and 53.9±7.99% for COPD and slow and deep patterns, respectively. With the chamber, IM was less sensitive to breathing pattern (57.4±6.97%, 57.9±4.69%, respectively). Particle size distributions varied widely between devices and were markedly affected by both ventilating the device and addition of the chamber. With the chamber, RF and RM increased, and differences in particle size distributions between individual devices were minimized. Compared with breath synchronization, treatment time was reduced. Gamma camera images revealed reduced upper airway deposition consistent with predictions from in vitro cascade distributions.

CONCLUSIONS

Our prototype chamber allowed for capture and conditioning of nebulized aerosol by mixing with room air and removal of large particles by impaction, providing better control of IM, RF, RM, and lung deposition, without the need for breath synchronization.

Individual reference values for 2D echocardiographic measurements. The Stockholm - Umeå Study

OBJECTIVES

Improved reference values for 2D echocardiographic measurements are required, even when more recent echocardiographic technology is employed. In addition, it may be preferable to individualize reference values from age, gender and body characteristics of any subject.

DESIGN

A material of 180 healthy subjects was collected and investigated, aiming for an even distribution of sex and age (from 20 to 80 years of age; the Stockholm material). For atrial areas, material from another 216 healthy subjects with similar sex and age distribution was added (the Umeå material). The 2D measures determined were the left and right ventricular diameters in diastole, the left ventricular diameter in systole, the thickness of septum and posterior wall, the diameters of the aortic root (sinotubular junction) and the left atrium (all in parasternal view), together with the left and right ventricular diameters in diastole and left and right atrial areas in end-systole (apical four-chamber view). The width of the inferior vena cava (from subcostal view) was also determined.

RESULTS

Confidence intervals for females and males are presented for each of these measures. Multiple linear regression analyses with age, sex and measures of body characteristics as predictors were also performed, and for eight of the 12 measurements, such equations are presented.

CONCLUSIONS

It is possible to obtain more highly individualized reference values for these cardiac dimensions, which may clinically be a better way of distinguishing pathological states from normal states.

Tobacco smoke induced COPD/emphysema in the animal model-are we all on the same page?

Chronic Obstructive Pulmonary Disease (COPD) is one of the foremost causes of death worldwide. It is primarily caused by tobacco smoke, making it an easily preventable disease, but facilitated by genetic α-1 antitrypsin deficiency. In addition to active smokers, health problems also occur in people involuntarily exposed to second hand smoke (SHS). Currently, the relationship between SHS and COPD is not well established. Knowledge of pathogenic mechanisms is limited, thereby halting the advancement of new treatments for this socially and economically detrimental disease. Here, we attempt to summarize tobacco smoke studies undertaken in animal models, applying both mainstream (direct, nose only) and side stream (indirect, whole body) smoke exposures. This overview of 155 studies compares cellular and molecular mechanisms as well as proteolytic, inflammatory, and vasoreactive responses underlying COPD development. This is a difficult task, as listing of exposure parameters is limited for most experiments. We show that both mainstream and SHS studies largely present similar inflammatory cell populations dominated by macrophages as well as elevated chemokine/cytokine levels, such as TNF-α. Additionally, SHS, like mainstream smoke, has been shown to cause vascular remodeling and neutrophil elastase-mediated proteolytic matrix breakdown with failure to repair. Disease mechanisms and therapeutic interventions appear to coincide in both exposure scenarios. One of the more widely applied interventions, the anti-oxidant therapy, is successful for both mainstream and SHS. The comparison of direct with indirect smoke exposure studies in this review emphasizes that, even though there are many overlapping pathways, it is not conclusive that SHS is using exactly the same mechanisms as direct smoke in COPD pathogenesis, but should be considered a preventable health risk. Some characteristics and therapeutic alternatives uniquely exist in SHS-related COPD.

Method for Evaluating Germicidal Ultraviolet Inactivation of Biocontaminated Surfaces

Safety issues related to work-site conditions often deal with potential worker exposure to infectious airborne microorganisms due to their dissemination in indoor air and contamination of surfaces. Germicidal ultraviolet (GUV) radiation is used in health-care settings and other occupational environments for microbial inactivation. In this study, a new methodology for determining the efficiency of GUV microbial inactivation of surfaces was developed and evaluated. The method utilizes identical chambers in which test microorganisms are irradiated on agar surfaces at different humidity and irradiation intensity levels. The effects of GUV intensity and exposure time on microbial inactivation were examined for Micrococcus luteus and Serratia marcescens. It was found that at low humidity levels (20-25%) both organisms can be inactivated with at least 95% efficiency if the GUV intensity exceeds 50 μW/cm² for at least 3-5 min (corresponding to a dose of ~ 10 mJ/cm²). The radiation dose needed for effective inactivation of S. marcescens, as measured by a UV meter near the microbial sample, was found not to be affected by the humidity level, whereas that of M. luteus increased at higher humidities. The findings of this study can be used to determine sufficient GUV inactivation doses for occupational environments with various microbial contaminations.