ABSTRACT
Dust storms have great impacts on air quality and climate. Dust can influence cloud microphysical properties and determine their radiative forcing and precipitation. Asian dust storms (ADS) are important sources of global aerosol. However, the physiochemical characteristics of dust from ADS at a single particle level are less understood, and the exact particles that can serve as ice nucleating particles (INPs) remain unclear. Here, we present the physicochemical properties and ice nucleation ability of dust particles collected in Beijing during two major ADS in March 2021. The particles from two ADS were classified into Illite, Kaolinite, Feldspar, Quartz, Chlorite, Mixed-dust, and Non-dust particles, which contributed 28.6 % ± 3.3 %, 20.0 % ± 3.9 %, 12.3 % ± 2.3 %, 11.1 % ± 2.8 %, 9.8 % ± 0.8 %, 13.7 % ± 1.8 %, and 4.4 % ± 1.7 % in number, respectively. On average, the ADS particles formed ice crystals via deposition ice nucleation from relative humidity with respect to ice (RHice) of 112 % ± 1 % at 250 K to 154 % ± 15 % RHice at 205 K. Part of the samples also formed ice via immersion freezing between 230 K and 250 K. Among the 149 identified INPs, Clay-like particles (Chlorite, Illite, and Kaolinite) contributed 71.1 % ± 6.2 % in number and followed by Mixed-dust-like particles (16.9 % ± 8.7 %) and Feldspar-like particles (10.4 % ± 6.3 %). Enrichment factor of each particle type in INPs is calculated as the ratio of its number fractions in INPs and the aerosol population. It ranges from 0.6 ± 0.7 to 1.3 ± 2.2. The contribution of each particle type to INP was correlated with its fraction in the population. These results imply that each particle type can serve as INP. Clay-like particles are the dominant INPs during the ADS. We conducted ice nucleation kinetic analysis and provided parameterizations of heterogeneous ice nucleation rate coefficient and contact angle for ADS. These parameterizations can be used in the modeling study to evaluate the impact of ADS in atmospheric ice crystal formation in clouds.
ABSTRACT
Seasonal variations in black carbon (BC) pollution characteristics during haze episodes in Benxi city, Liaoning province, were analyzed using year-long measurements of BC, carbon monoxide (CO), and PM2.5. Haze frequencies were recorded to be 0.07, 0.03 and 0.14 in spring, autumn, and winter respectively. Solid fuel contributions increased notably by 7%-8% during haze events compared to clean periods in all seasons. Transitioning from clean to haze periods led to ΔBC/ΔCO increases of 16% in spring and autumn, and 6.8% in winter, while BC/PM2.5 ratios decreased by approximately 33%, 50%, and 24% for spring, autumn, and winter respectively, likely indicating enhanced residential and industrial contributions. These further led to an increase in BC absorption capacities by factors of around 2.2 in spring and autumn, and up to 2.6 in winter during haze periods. Despite liquid fuel sources dominating BC emissions, certain haze episodes (frequency <10%) showed solid fuel contributions of up to 65%, highlighting BC pollution complexity in the region during haze. Backward trajectories analysis revealed local air masses from Liaoning province arrived consistently with the most occurrence of haze events across all seasons, while long-range air masses from Mongolian regions, though with less frequent occurrence during haze periods, significantly elevated BC loadings from solid fuel sources, particularly in spring and autumn due to biomass burning. Despite higher BC wet scavenging rates (WSR) in long-range air masses (0.072 ng m-3 ppbv-1 mm-1) compared to local air masses (0.039 ng m-3 ppbv-1 mm-1), significant BC transport persisted due to limited precipitation along transport pathways, especially during haze periods. These findings provide crucial insights for policymakers, highlighting the need for targeted haze prevention and control strategies focusing on mitigating BC emissions in Northeast China.
Subject(s)
Air Pollutants , Environmental Monitoring , Particulate Matter , Seasons , Soot , China , Air Pollutants/analysis , Soot/analysis , Particulate Matter/analysis , Carbon Monoxide/analysis , Air Pollution/statistics & numerical data , Atmosphere/chemistryABSTRACT
Hyaluronic acid (HA), an endogenous polysaccharide comprising alternating D-glucuronic acid and N-acetylglucosamine units, is renowned for its high hydrophilicity, biocompatibility, and biodegradability. These attributes have rendered HA invaluable across medical and drug delivery fields. HA can be altered through physical, chemical, or enzymatic methods to improve the properties of the modified substances. In this work, we synthesized a derivative via the esterification of HA with poly(glyceryl)10-stearate (PG10-C18), designated as HA-PG10-C18. This novel derivative was employed to fabricate a nano co-delivery system (HA-PG10-C18@Res-NE) for fish oil and resveratrol (Res), aiming to enhance their stability and bioaccessibility. An exhaustive investigation of HA-PG10-C18@Res-NE revealed that the HA-modified system displayed superior physicochemical stability, notably in withstanding oxidation and neutralizing free radicals. Moreover, in vitro simulated digestion underscored the system's enhanced bioaccessibility of Res and more efficient release of free fatty acids. These outcomes underscore the strategic advantage of HA in modifying PG10-C18 for nanoemulsion formulation. Consequently, HA-PG10-C18 stands as a promising emulsifier for encapsulating lipophilic bioactives in functional foods, nutraceuticals, and pharmaceuticals.
Subject(s)
Antioxidants , Emulsions , Fish Oils , Hyaluronic Acid , Resveratrol , Resveratrol/chemistry , Resveratrol/pharmacokinetics , Fish Oils/chemistry , Hyaluronic Acid/chemistry , Emulsions/chemistry , Antioxidants/chemistry , Antioxidants/pharmacology , Antioxidants/pharmacokinetics , Nanoparticles/chemistry , Drug Carriers/chemistry , Drug Delivery Systems , Biological AvailabilityABSTRACT
Chiral epichlorohydrin (ECH) is an attractive intermediate for chiral pharmaceuticals and chemicals preparation. The asymmetric synthesis of chiral ECH using 1,3-dicholoro-2-propanol (1,3-DCP) catalyzed by a haloalcohol dehalogenase (HHDH) was considered as a feasible approach. However, the reverse ring opening reaction caused low optical purity of chiral ECH, thus severely restricts the industrial application of HHDHs. In the present study, a novel selective conformation adjustment strategy was developed with an engineered HheCPS to regulate the kinetic parameters of the forward and reverse reactions, based on site saturation mutation and molecular simulation analysis. The HheCPS mutant E85P was constructed with a markable change in the conformation of (S)-ECH in the substrate pocket and a slight impact on the interaction between 1,3-DCP and the enzyme, which resulted in the kinetic deceleration of the reverse reactions. Compared with HheCPS, the catalytic efficiency (kcat(S)-ECH/Km(S)-ECH) of the reversed reaction dropped to 0.23-fold (from 0.13 to 0.03 mM-1 s-1), while the catalytic efficiency (kcat(1,3-DCP)/Km(1,3-DCP)) of the forward reaction only reduced from 0.83 to 0.71 mM-1 s-1. With 40 mM 1,3-DCP as substrate, HheCPS E85P catalyzed the synthesis of (S)-ECH with the yield up to 55.35% and the e.e. increased from 92.54 to >99%. Our work provided an effective approach for understanding the stereoselective catalytic mechanism as well as the green manufacturing of chiral epoxides.
Subject(s)
Epichlorohydrin , Hydrolases , Epichlorohydrin/chemistry , Epichlorohydrin/metabolism , Hydrolases/genetics , Hydrolases/metabolism , Hydrolases/chemistry , Kinetics , Stereoisomerism , Escherichia coli/genetics , Escherichia coli/enzymology , Protein Engineering/methods , alpha-Chlorohydrin/analogs & derivativesABSTRACT
Hydroxyl radicals (·OH) generated during the flooding-drought transformation process play a vital role in affecting nutrient cycles at riparian zone. However, information on the processes and mechanisms for ·OH formation under the influence of microplastics (MPs) remains unclear. In this study, the effects of MPs on ·OH production from riparian sediments with different biomass [e.g., vegetation lush (VL) and vegetation barren (VB)] were studied. The results showed that presence of MPs inhibited the production of ·OH by 27 % and 7.5 % for VB and VL sediments, respectively. The inhibition was mainly resulted from the MP-induced reduction of the biotic and abiotic mediated Fe redox processes. Spectral analysis revealed that VL sediments contained more high-molecular-weight humic-like substances. Presence of MPs increased the abundances and activities of Proteobacteria, Acidobacteria and Actinobacteria, which were conducive to the changes in humification and polar properties of organic matters. The reduced humic- and fulvic-like substances were accumulated in the flooding period and substantially oxidized during flooding/drought transformation due to the enhanced MP-mediated electron transfer abilities, thus mitigated the MP-induced inhibition effects. Therefore, in order to better understanding the biogeochemical cycling of contaminants as influenced by ·OH and MPs in river ecosystems, humic substances should be considered systematically.
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RATIONALE: Kaposiform hemangioendothelioma is an aggressive vascular tumor that is often associated with life-threatening coagulopathies and Kasabach-Merritt phenomenon. Pathologic biopsies can provide a good basis for diagnosis and treatment. Therapy with srolimus combined with glucocorticoids may offer patients a favorable prognosis. PATIENT CONCERNS: A large purplish-red mass on the knee of a child with extremely progressive thrombocytopenia and refractory coagulation abnormalities. Conventional doses of glucocorticoids alone failed to improve coagulation abnormalities and the child developed large cutaneous petechiae and scalp hematomas. DIAGNOSIS: Kaposiform hemangioendothelioma combined with Kasabach-Merritt phenomenon. INTERVENTIONS: The patient received prednisolone 2.0 mg/kg*d for 4 days. Blood products were transfused to ensure vital signs and to complete the pathologic biopsy. Sirolimus combined with prednisolone was given after clarifying the diagnosis of Kaposiform hemangioendothelioma. OUTCOMES: The tumor basically disappeared on examination and the ultrasound showed a subcutaneous hyperechoic mass with normal blood flow. LESSONS: Sirolimus combined with glucocorticoids is effective in controlling Kasabach-Merritt phenomenon and pathologic biopsy is important for definitive diagnosis.
Subject(s)
Blood Coagulation Disorders , Hemangioendothelioma , Kasabach-Merritt Syndrome , Sarcoma, Kaposi , Humans , Infant, Newborn , Blood Coagulation Disorders/complications , Glucocorticoids/therapeutic use , Hemangioendothelioma/complications , Hemangioendothelioma/drug therapy , Hemangioendothelioma/diagnosis , Kasabach-Merritt Syndrome/drug therapy , Prednisolone/therapeutic use , Sarcoma, Kaposi/pathology , Sirolimus/therapeutic useABSTRACT
Objective: This study explores the 22-year evolution of Infantile Hemangiomas (IHs) treatment strategies at a single-center hospital, aiming to establish an individualized IHs management protocol. Methods: Retrospective review of IHs infants 2000-2022 at the Department of Plastic Surgery, Jiangxi Provincial Children's Hospital. Results: In our study of 27,513 IHs cases, 72.2% were female, with the median age at first hospital visit being 25 days. The majority of cases had localized and superficial lesions primarily on the head, face, and neck (67.5%). Ulceration rates fell from 21.1% to 12.6% with the introduction of propranolol. Management strategies have shifted over time, with the proportion of cases undergoing expectant management dropping from 32.9% to 12.4%. Since 2008, 26.1% of patients were treated with oral propranolol, largely replacing corticosteroids. Topical ß-blockers have been used in 12.1% of cases, leading to a reduction in local injection therapy from 20.8% to 13.2%. Laser therapy, introduced in 2016, has been used in 13.8% of cases, while surgical excision has dropped from 25.0% to 8.5% due to alternative treatment options. Combination therapy was used in 8.8% of cases post-2015, indicating a rising trend. Drawing from the evolution of IHs management strategies, an individualized protocol for the management of IHs was successfully established. Conclusion: Treatment for IHs has evolved over recent decades, with less invasive medical interventions increasingly replacing more invasive methods. Furthermore, a personalized treatment protocol established in this study could boost the cure rate of IHs while minimizing potential side effects and complications.
ABSTRACT
This study aimed to synthesize a novel emulsifier, hyaluronic acid-poly(glyceryl)10-stearate (HA-PG10-C18), and employ it for the fabrication of nanoemulsions incorporating deep-sea fish oil to improve their apparent solubility and physicochemical stability. 1H NMR and FT-IR analyses indicated successful synthesis of HA-PG10-C18. Nanoemulsions of deep-sea fish oil loaded with HA-PG10-C18 (HA-PG10-C18@NE) were successfully fabricated by ultrasonic emulsification. The fixed aqueous layer thickness (FALT) of PG10-C18@NE and HA-PG10-C18@NE was determined and the FALT of both nanoemulsions was similar, while the surface density of HA-PG10-C18@NE (4.92 × 10-12 ng/nm2) is 60 % higher than that of PG10-C18@NE (3.07 × 10-12 ng/nm2). Notably, HA-PG10-C18@NE demonstrated an exceptional physicochemical stability when exposed to various stressed environmental conditions, especially its freeze-thaw stability. Moreover, after simulated in vitro digestion, the HA-PG10-C18@NE exhibited a comparatively greater liberation of free fatty acids (94.0 ± 1.7 %) when compared to the release observed in PG10-C18@NE (85.5 ± 2.2 %).
Subject(s)
Fish Oils , Stearates , Hyaluronic Acid , Emulsions/chemistry , Spectroscopy, Fourier Transform InfraredABSTRACT
The application of (R)-ω-transaminases as biocatalysts for chiral amine synthesis has been hampered by inadequate stereoselectivity and narrow substrate spectrum. Herein, an effective evolution strategy for (R)-ω-transaminase designing for the asymmetric synthesis of sitagliptin intermediate is presented. Since natural transaminases lack activity toward bulky prositagliptin ketone, transaminase scaffolds with catalytic machinery and activity toward the truncated prositagliptin ketone were firstly screened based on substrate walking principle. A transaminase chimera was established synchronously conferring catalytic activity and (R)-selectivity toward prositagliptin ketone through motif swapping, followed by stepwise evolution. The process resulted in a "best" engineered variant MwTAM8, which exhibited 79.2-fold higher activity than the chimeric scaffold MwTAMc. Structural analysis revealed that the heightened activity is mainly due to the enlarged and adaptive substrate pocket and tunnel. The novel (R)-transaminase exhibited unsatisfied industrial operation stability, which is expected to further modify the protein to enhance its tolerance to temperature, pH, and organic solvents to meet sustainable industrial demands. This study underscores a useful evolution strategy of engineering biocatalysts to confer new properties and functions on enzymes for synthesizing high-value drug intermediates.
Subject(s)
Sitagliptin Phosphate , Transaminases , Transaminases/chemistry , Catalytic Domain , Catalysis , Ketones/chemistry , Substrate Specificity , Amines/chemistryABSTRACT
Based on in-situ measurement of black carbon (BC) and carbon monoxide (CO), the characteristics of BC emissions and wet scavenging were comprehensively investigated in Nanning, South China. The average annual BC concentration was 1.02 ± 0.53 µg m-3 with higher pollution levels during winter. In winter, a higher net BC/CO (ΔBC/ΔCO) ratio of 3.3 ± 0.3 ng m-3 ppb-1 along with an increased absorption Ångström exponent (AAE) and BC mass from biomass burning (BCbb), indicated a significant contribution of biomass burning to BC emissions. However, emissions from the traffic sector consistently exerted a dominant influence throughout the year. Cluster analysis of backward trajectories identified three types of air masses with distinct origins. Cluster #1 originated from Guangxi province and its vicinity, intermittently influencing the sampling site throughout the year with varying effects between winter and summer. This air mass brought in clean sea breeze in summer whereas transported a higher proportion of BCbb to the site during wintertime due to local open biomass burning. Cluster #3 primarily arrived in autumn and winter (October-December) from polluted central China, resulting in substantially high BC mass at the site. Cluster #2 coincided with the period (January-March) when extensive surface open biomass burning events occurred in Southeast Asia (SEA) regions. These BC aerosols in cluster#2 initially rose to higher altitudes above SEA before being regionally transported, but were significantly scavenged by clouds and precipitation during vertical uplift. The remaining BC exhibited a notably lower BC loss rate on relative humidity (RH) of -0.01 ng m-3 ppb-1 %-1 compared to cluster #1 (-0.03) and cluster #3 (-0.06), corresponding to an average BC transport efficiency of 0.85, 0.73, and 0.53, respectively. Nonetheless, air masses in cluster #2 could still transport considerably high BC mass to Nanning due to dry conditions and less wet scavenging along trajectory pathways. These findings provide valuable insights for policymakers and government officials in regulating and mitigating BC pollution in South China.
ABSTRACT
Fish oils are a rich source of polyunsaturated fatty acids, including eicosapentaenoic acid and docosahexaenoic acid, which are reported to exhibit therapeutic effects in a variety of human diseases. However, these oils are highly susceptible to degradation due to oxidation, leading to rancidity and the formation of potentially toxic reaction products. The aim of this study was to synthesize a novel emulsifier (HA-PG10-C18) by esterifying hyaluronic acid with poly(glyceryl)10-stearate (PG10-C18). This emulsifier was then used to formulate nanoemulsion-based delivery systems to co-deliver fish oil and coenzyme Q10 (Q10). Q10-loaded fish oil-in-water nanoemulsions were fabricated, and then their physicochemical properties, digestibility, and bioaccessibility were measured. The results indicated that the environmental stability and antioxidant activity of oil droplets coated with HA-PG10-C18 surpassed those coated with PG10-C18 due to the formation of a denser interfacial layer that blocked metal ions, oxygen, and lipase. Meanwhile, the lipid digestibility and Q10 bioaccessibility of nanoemulsions formulated with HA-PG10-C18 (94.9 and 69.2%) were higher than those formulated with PG10-C18 (86.2 and 57.8%), respectively. These results demonstrated that the novel emulsifier synthesized in this study could be used to protect chemically labile fat-soluble substances from oxidative damage, while still retaining their nutritional value.
Subject(s)
Hyaluronic Acid , Stearates , Humans , Emulsions/chemistry , Emulsifying Agents/chemistry , Fish Oils/chemistryABSTRACT
Although the efficacy of propranolol in the treatment of infantile hemangioma (IH) has been well established, clinical data on the safety and tolerability of propranolol in neonates are still lacking. In this work, clinical data of 112 neonates with IH were analyzed retrospectively. All of the patients were evaluated in the hospital at the beginning of the treatment and later in outpatient settings during the treatment. Each time, the following monitoring methods were applied: physical examination, ultrasound echocardiography (UCG), electrocardiography (ECG), blood pressure (BP), heart rate (HR), and basic laboratory tests including blood glucose (BG), liver function, blood potassium, thyroid function. There was a significant reduction in BP and HR at the initiation of treatment. The incidences of bradycardia and hypoglycemia were observed to be increased with the prolong duration of treatment, but not prolonged PR interval. During the course of the therapy, the risk of hyperkalemia and hypothyroidism was reached maximum at the 2 months and 3 months, respectively. Physical growth index including average height, weight and head circumference was not influenced by the treatment. The observed adverse effects were majority mild and only 3 patients needed to rest for 7 days due to severe diarrhea before restarting treatment. This study demonstrated that propranolol is safe and well-tolerated by properly selected young infants with IH. No serious adverse events were observed.
Subject(s)
Hemangioma, Capillary , Hemangioma , Skin Neoplasms , Infant , Infant, Newborn , Humans , Propranolol/adverse effects , Retrospective Studies , Adrenergic beta-Antagonists/therapeutic use , Hemangioma/drug therapy , Hemangioma, Capillary/drug therapy , Treatment Outcome , Administration, Oral , Skin Neoplasms/drug therapyABSTRACT
We study the denial-of-service (DoS) attack power allocation optimization in a multiprocess cyber-physical system (CPS), where sensors observe different dynamic processes and send the local estimated states to a remote estimator through wireless channels, while a DoS attacker allocates its attack power on different channels as interference to reduce the wireless transmission rates, and thus degrading the estimation accuracy of the remote estimator. We consider two attack optimization problems. One is to maximize the average estimation error of different processes, and the other is to maximize the minimal one. We formulate these problems as Markov decision processes (MDPs). Unlike the majority of existing works where the attacker is assumed to have complete knowledge of the CPS, we consider an attacker with no prior knowledge of the wireless channel model and the sensor information. To address this uncertainty issue and the curse of dimensionality, we provide a learning-based attack power allocation algorithm stemming from the double deep Q-network (DDQN) method. First, with a defined partial order, the maximal elements of the action space are determined. By investigating the characteristic of the MDP, we prove that the optimal attack allocations of both problems belong to the set of these elements. This property reduces the entire action space to a smaller subset and speeds up the learning algorithm. In addition, to further improve the data efficiency and learning performance, we propose two enhanced attack power allocation algorithms which add two auxiliary tasks of MDP transition estimation inspired by model-based reinforcement learning, i.e., the next state prediction and the current action estimation. Experimental results demonstrate the versatility and efficiency of the proposed algorithms in different system settings compared with other algorithms, such as the conventional value iteration, double Q-learning, and deep Q-network.
ABSTRACT
Ammonia (NH3) measurements were performed with a mobile platform deploying a cavity ring-down spectroscopy NH3 analyzer in Beijing. The transect and loop sampling strategy revealed that the Beijing urban area is more strongly affected by NH3 emissions than surrounding areas. Although average enhancements of on-road NH3 were small compared to background levels, traffic emissions clearly dominated city enhancements of NH3, carbon dioxide (CO2), acetaldehyde and acetone. Increments of on-road NH3 ranged between 5.1 ppb and 11.4 ppb in urban areas, representing an enhancement of 20.6 % to 47.9 % over the urban background. The vehicle NH3:CO2 emission ratio was 0.26 ppb/ppm, about a factor of 1.5 higher than the value derived from the available emission inventory. The obtained NH3 emission factor was approximately 306.9 mg/kg. If the annual gasoline consumption in Beijing is accurate, annual NH3 emissions from vehicles are estimated at 1.5 Gg. The influx and outflux of NH3 in Beijing during monitoring periods fluctuated due to variations of wind direction (WD), wind speed (WS), and planetary boundary layer height (PBLH). Net fluxes at the 4th Ring Road were larger than zero, suggesting that local emissions were important in urban Beijing. Negative net fluxes at the 6th Ring Road reveal a large amount of NH3 transported from agricultural regions south of Beijing lost during transport across the city, for example by deposition or particle formation in the city. Our analyses have important implications for regional NH3 emission estimates and for improving vehicular NH3 emission inventory allocations.
ABSTRACT
Volatile organic compounds (VOCs) are precursors for ozone and secondary organic aerosol (SOA) formation, thereby playing a vital role in atmospheric chemistry and urban air quality. To characterize the relationship between VOCs and SOA, organics both in gas and particulate phases were concurrently measured in urban Beijing. The VOCs and organic aerosol (OA) were apportioned into factors with different oxidation levels by applying the factorization analysis on their detailed mass spectra. Six factors of VOCs were identified, including four primary VOCs (PVOC) factors and two secondary VOCs (SVOC) factors. The PVOC factors dominated the total VOCs when the air mass originated in the cleaner northern areas, while SVOC factors dominated for polluted southern air masses. The normalized concentrations of PVOC and primary OA factors showed consistent diurnal variations regardless of air mass directions, owing to the relatively stable local emissions during the experimental period. This contrasted with the secondary factors due to more complex transformation processes. The traffic-related VOCs and solid fuel combustion VOCs negatively correlated with SOA, implying that they may have contributed to the SOA formation through photooxidation. The VOCs in lower oxidation levels were found to have poor correlations with the less oxidized SOA, whereas they correlated strongly to the more oxidized SOA. This implied that the less oxidized SOA may be in a transition state, where its production and loss rates were balanced. These served as products of VOCs oxidation and reactants of more oxidized SOA formation, playing important roles on the VOC to SOA transformation. The identified VOC emission sources and their photochemical production of SOA should be considered in air quality policy planning.
Subject(s)
Air Pollutants , Ozone , Volatile Organic Compounds , Volatile Organic Compounds/analysis , Air Pollutants/analysis , Beijing , Ozone/analysis , Aerosols/analysis , China , Environmental MonitoringABSTRACT
The light-absorbing organic aerosol (OA) constitutes an important fraction of absorbing components, counteracting major cooling effect of aerosols to climate. The mechanisms in linking the complex and changeable chemistry of OA with its absorbing properties remain to be elucidated. Here, by using solvent extraction, ambient OA from an urban environment was fractionated according to polarity, which was further nebulized and online characterized with compositions and absorbing properties. Water extracted high-polar compounds with a significantly higher oxygen to carbon ratio (O/C) than methanol extracts. A transition O/C of about 0.6 was found, below and above which the enhancement and reduction of OA absorptivity were observed with increasing O/C, occurring on the less polar and high polar compounds, respectively. In particular, the co-increase of nitrogen and oxygen elements suggests the important role of nitrogen-containing functional groups in enhancing the absorptivity of the less polar compounds (e.g., forming nitrogen-containing aromatics), while further oxidation (O/C > 0.6) on high-polar compounds likely led to fragmentation and bleaching chromophores. The results here may reconcile the previous observations about darkening or whitening chromophores of brown carbon, and the parametrization of O/C has the potential to link the changing chemistry of OA with its polarity and absorbing properties.
Subject(s)
Air Pollutants , Methanol , Aerosols/analysis , Air Pollutants/analysis , Carbon/analysis , Nitrogen , Oxygen , Particulate Matter/analysis , Solvents , Water/chemistryABSTRACT
Black carbon (BC) aerosols have effects on the atmospheric thermal vertical structure due to its radiation absorption characteristics, hereby influencing the boundary layer characteristics and pollutant diffusion. This study focuses on the BC effects under different atmospheric conditions on air quality and vertical meteorological conditions. Four days flight observation combined with surface wind profiler radar data were used to investigate the vertical profiles of BC and wind speed over Beijing urban area in early summer. The vertical profiles of BC concentration and wind speed in the boundary layer had a negative correlation, both having abrupt changes near the boundary layer height under stagnant weather conditions. The chemical transport model showed the increase of BC under stagnant conditions could cause aggravation of the stability of the boundary layer, thereby increasing the accumulation of pollutants. In particular, BC leads to the changes in the temperature profile, which will modify relative humidity and indirectly lead to the changes in the vertical profile of aerosol optical properties. However, if the early accumulation of BC was absent under more turbulent conditions, the effects of BC on air quality and meteorological conditions were limited.
Subject(s)
Air Pollutants , Air Pollution , Aerosols/analysis , Air Pollutants/analysis , Air Pollution/analysis , Beijing , Carbon/analysis , Environmental Monitoring , Meteorological Concepts , Particulate Matter/analysis , SootABSTRACT
ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION: Bourouni S, Dritsas K, Kloukos D, Wierichs RJ. Efficacy of resin infiltration to mask post-orthodontic or non-post-orthodontic white spot lesions or fluorosis - a systematic review and meta-analysis. Clin Oral Investig. 2021 Aug;25(8):4711-4719. SOURCE OF FUNDING: University of Bern. TYPE OF STUDY/DESIGN: Systematic review with meta-analysis.
Subject(s)
Dental Caries , Fluorosis, Dental , Dental Enamel/pathology , Fluorosis, Dental/pathology , HumansABSTRACT
Subgroup A avian leukosis virus (ALV-A) invades cells through gp85-encoded surface glycoprotein (SU) via specifically recognizing the cellular receptor Tva. To identify the key residues of ALV-A SU that determine the Tva binding affinity and infectivity in DF-1 cells, a strategy of substituting corresponding residues of SU between ALV-A RSA and ALV-E ev-1 (using Tvb as the receptor) was adopted. A series of chimeric soluble gp85 proteins were expressed for co-immunoprecipitation (co-IP) analysis and blocking analysis of viral entry, and various recombinant viruses based on replication-competent avian retrovirus vectors containing Bryan polymerase (RCASBP) were constructed for transfection into DF-1 cells and measurement of the percentage of GFP-positive cells. The results revealed that the substitution of residues V138, W140, Y141, L142, S145, and L154 of host range region 1 (hr1), residues V199, G200, Q202, R222, and R223 of host range region 2 (hr2), and residue G262 of variable region 3 (vr3) reduced the viral infectivity and Tva binding affinity, which was similar to the effects of the -139S, -151N, -155PWVNPF, -201NFD, Δ214-215, and -266S mutations. Our study indicated that hr1 and hr2 contain the principal receptor interaction determinants, with new identified-vr3 also playing a key role in the receptor binding affinity of ALV-A.
ABSTRACT
In order to investigate the chemical composition and source apportionment of aerosols during winter in the Beijing-Tianjin-Heibei region, the particular matter (PM) and aerosol chemical composition at Mt. Haituo were observed by using a GRIMM 180, a single-particle soot photometer (SP2), and a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) from December 28, 2020 to February 3, 2021. Combining these observations with meteorological data and the HYSPLIT model, we calculated the potential source contribution factor (PSCF) and concentration weighted trajectory (CWT) and analyzed the temporal evolution and potential sources apportionment of PM and aerosol chemical composition under different pollution processes. The results showed that the dust storm process mainly affected PM10 and PM2.5 in Mt. Haituo during the winter and had a small impact on PM1; by contrast, haze pollution mainly affected PM1. Chemical components of aerosol accounted for 85.0% and 73.4% of PM1 on clean and haze days, respectively, but only 47.4% of PM1 in dust storm processes. NO3- was the chemical component with the largest mass concentration in haze, accounting for 25.2% of PM1; black carbon (BC) had the largest mass concentration on clean and dust storm days, accounting for 24.1% and 12.8% of PM1, respectively. The median diameters of BC were 209.7, 207.5, and 204.7 nm on clean, dust storm, and haze days, respectively. Dp/Dc was 2.15 in haze pollution, which was 1.38 and 1.39 times that on dust storm and clean days, respectively. Diurnal variations in PM and aerosol chemical components were different during the different processes. PM10 and PM2.5had high mass concentrations at night and low mass concentrations during the daytime on clean and dust storm days and had a unimodal distribution with a peak at 14:00 in haze. Diurnal variations in chemical composition had a unimodal distribution on clean days and a bimodal distribution on dust storm and haze days. The chemical compositions of the BC coating layer were different under different processes. The coating layers of BC were mainly NH4NO3, (NH4)2SO4, and organic matter on the clean, dust storm, and haze days, respectively. The distribution of potential sources of PM1 and its chemical components were different under different processes. The high-value area of the potential sources was mainly concentrated in the Beijing-Baoding-Shijiazhuang-Yangquan area in the southwestern portion of the site during dust storms and was mainly concentrated in Yanqing, Huailai, and Changping in the areas around the site during haze.