Profile of inhalable bacteria in PM2.5 at Mt. Tai, China: Abundance, community, and influence of air mass trajectories

Bacteria are ubiquitous in the near-surface atmosphere where they constitute an important component of aerosols with the potential to affect climate change, ecosystems, atmospheric process and human health. Limitation in tracking bacterial diversity accurately has thus far prevented the knowledge of airborne bacteria and their pathogenic properties. We performed a comprehensive assessment of bacterial abundance and diverse community in PM_2.5 collected at Mt. Tai, via high-throughput sequencing and real-time PCR. The samples exhibited a high microbial biodiversity and complex chemical composition. The dominating populations were gram-negative bacteria including Burkholderia, Delftia, Bradyrhizobium, and Methylobacterium. The PM mass concentration, chemical composition, bacterial concentration and community structure varied under the influence of different air-mass trajectories. The highest mass concentration of PM_2.5 (61 μg m^-3) and major chemical components were recorded during periods when marine southeasterly air masses were dominant. The local terrestrial air masses from Shandong peninsula and its adjacent areas harbored highest bacterial concentration loading (602 cells m^-3) and more potential pathogens at the site. In contrast, samples influenced by the long-distance air flow from Siberia and Outer Mongolia were found to have a highest richness and diversity as an average, which was also marked by the increase of dust-associated bacteria (Brevibacillus and Staphylococcus). The primary research may serve as an important reference for the environmental microbiologist, health workers, and city planners.

Responses of seed germination and shoot metabolic profiles of maize (Zea maysL.) to Y2O3nanoparticle stress

The potential risks of rare-earth nanoparticles (RENPs) to plants in the environment are attracting increasing attention due to their wide-spread application. In this regard, little is known about the effects of Y₂O₃ NPs as an important member of RENPs on crop plants. Seed germination is vulnerable to environmental stress, which determines the growth and yield of crops. Here, maize seeds were exposed to a Y₂O₃ NP suspension (0–500 mg L⁻¹) in the dark for 6 days. It was found that the Y₂O₃ NPs had no significant effect on the germination rates (>93%) in all treatments, but they could reduce seed vitality, delay germination, and inhibit seedling growth in a dose-dependent manner. Further, the inhibition effect of Y₂O₃ NPs on root elongation was much stronger than that on shoot elongation. Meanwhile, the activities of peroxidase (POD) and catalase (CAT) in shoots were enhanced with the increase in the Y₂O₃ NP concentration. A high-concentration (≥300 mg L⁻¹) of Y₂O₃ NPs induced a significant increase in the malondialdehyde (MDA) level in shoots compared to the control, indicating that the membrane lipid peroxidation and permeability were enhanced. ¹H NMR-based analysis showed that the polar metabolic profiles were altered significantly after treatment with 0, 10, and 500 mg L⁻¹ of Y₂O₃ NPs, but there was no marked alteration observed for the non-polar metabolic profiles. The polar metabolites (e.g., sugars, amino acids, and most organic acids) showed a dose-dependent increase to Y₂O₃ NP stress, indicating that the metabolic pathways of carbohydrate metabolism, the tricarboxylic acid cycle (TCA), and amino acid synthesis were disturbed. There were significantly positive correlations found among the metabolites related with the antioxidant response and osmotic adjustment. The simultaneous accumulation of these metabolites possibly indicated the adaptation of the seedlings to stress at the cost of retarding glycolysis, TCA, and protein synthesis. The retarded effects finally inhibited the apparent growth of the seedlings. These findings reveal the phytotoxicity of Y₂O₃ NPs and provide physiological and biochemical and molecular-scale perspectives on the response of seedlings to stress.

A hypothetic model for the adaptation of maize to Y₂O₃ NPs stress during seed germination.

A density functional theory study of the molecular interactions between a series of amides and sulfuric acid

Amides, a class of nitrogen-containing organic pollutants in the atmosphere, may affect the formation of atmospheric aerosols by the interactions with sulfuric acid. Here, the molecular interactions of sulfuric acid with formamide, methylformamide, dimethylformamide, acetamide, methylacetamide and dimethylacetamide was investigated by density functional theory. Geometry optimization and Gibbs free energy calculation were carried out at M06-2X/6-311++G(3df,3pd) level. The results indicate that the addition of amides to H₂SO₄ might have a promoting effect on atmospheric new particle formation at 298.15 K and 1 atm. In the initial stage of new particle formation, the binding capacity of amides and sulfuric acid is stronger than ammonia, but weaker than methylamine. It is worth noting that the trans-methylacetamide could have similar capabilities of stabilizing sulfuric acid as dimethylamine. In the presence of water, amides are found to only have a weak enhancement capability on new particle formation. In addition, we can infer from evaporation rate that the small molecule clusters of formamide and sulfuric acid may be more energetically favorable than macromolecule clusters.

Six sources mainly contributing to the haze episodes and health risk assessment of PM2.5 at Beijing suburb in winter 2016

Aiming to a better understanding sources contributions and regional sources of fine particles, a total of 273 filter samples (159 of PM_2.5 and 114 of PM_1.0) were collected per 8 h during the winter 2016 at a southwest suburb of Beijing. Chemical compositions, including water soluble ions, organic carbon (OC), and elemental carbon (EC), as well as secondary organic carbon (SOC), were systematically analyzed and estimated. The total ions concentrations (TIC), OC, and SOC of PM_2.5 were with the following order: 16:00-24:00 > 08:00-16:00 > 00:00-08:00. Since primary OC and EC were mainly attributed to the residential combustion in the night time, their valley values were observed in the daytime (08:00-16:00). However, the highest ratio value of SOC/OC was observed in the daytime. It is because that SOC is easily formed under sunshine and relatively high temperature in the daytime. Positive matrix factorization (PMF), clustering, and potential source contribution function (PSCF) were employed for apportioning sources contributions and speculating potential sources spatial distributions. The average concentrations of each species and the source contributions to each species were calculated based on the data of species concentrations with an 8 h period simulated by PMF model. Six likely sources, including secondary inorganic aerosols, coal combustion, industrial and traffic emissions, road dust, soil and construction dust, and biomass burning, were contributed to PM_2.5 accounting for 29%, 21%, 17%, 16%, 9%, 8%, respectively. The results of cluster analysis indicated that most of air masses were transported from West and Northwest directions to the sampling location during the observation campaign. Several seriously polluted areas that might affect the air quality of Beijing by long-range transport were identified. Most of air masses were transported from Western and Northwestern China. According to the results of PSCF analysis, Western Shandong, Southern Hebei, Northern Henan, Western Inner Mongolia, Northern Shaanxi, and the whole Shanxi provinces should be the key areas of air pollution control in China. The exposure-response function was used to estimate the health impact associated with PM_2.5 pollution. The population affected by PM_2.5 during haze episodes reached 0.31 million, the premature death cases associated with PM_2.5 reached 2032. These results provided important implication for making environmental policies to improve air quality in China.

Experimental demonstration of high sensitivity refractive index sensing based on magnetic plasmons in a simple metallic deep nanogroove array

A high-performance wide-angle refractive index sensor based on a simple one-dimensional (1D) metallic deep nanogroove array with a high aspect ratio is experimentally fabricated and demonstrated. The 1D deep groove array is featured by the excitation of magnetic plasmon (MP), referring to an effective coupling of incident electromagnetic waves with a strong magnetic response induced inside the deep grooves. Utilizing the MP resonances that are extremely sensitive to the surrounding dielectric medium, we successfully achieve a refractive index sensitivity (RIS) up to ∼1300 nm/RIU, which is higher than that of most experimentally designed plasmonic sensors in the infrared region. Importantly, benefiting from angle-independent MP resonances with strong confinement of the magnetic field inside the deep grooves and strong electric field localization at the groove openings, we demonstrate wide-angle sensing capability valid in a broadband infrared region with an excellent linear dependence on the change of refractive index. Such a MP-based sensor, together with its simple 1D flat nature and ease of fabrication, has great potential for the practical design of high sensitive, cost-effective and compact sensing devices.

Combination of the Searches for Pair-Produced Vectorlike Partners of the Third-Generation Quarks at sqrt[s]=13 TeV with the ATLAS Detector

A combination of the searches for pair-produced vectorlike partners of the top and bottom quarks in various decay channels (T→Zt/Wb/Ht, B→Zb/Wt/Hb) is performed using 36.1  fb^{-1} of pp collision data at sqrt[s]=13  TeV with the ATLAS detector at the Large Hadron Collider. The observed data are found to be in good agreement with the standard model background prediction in all individual searches. Therefore, combined 95% confidence-level upper limits are set on the production cross section for a range of vectorlike quark scenarios, significantly improving upon the reach of the individual searches. Model-independent limits are set assuming the vectorlike quarks decay to standard model particles. A singlet T is excluded for masses below 1.31 TeV and a singlet B is excluded for masses below 1.22 TeV. Assuming a weak isospin (T,B) doublet and |V_{Tb}|≪|V_{tB}|, T and B masses below 1.37 TeV are excluded.

Observation of Centrality-Dependent Acoplanarity for Muon Pairs Produced via Two-Photon Scattering in Pb+Pb Collisions at sqrt[s_{NN}]=5.02 TeV with the ATLAS Detector

This Letter presents a measurement of γγ→μ^{+}μ^{-} production in Pb+Pb collisions recorded by the ATLAS detector at the Large Hadron Collider at sqrt[s_{NN}]=5.02  TeV with an integrated luminosity of 0.49  nb^{-1}. The azimuthal angle and transverse momentum correlations between the muons are measured as a function of collision centrality. The muon pairs are produced from γγ through the interaction of the large electromagnetic fields of the nuclei. The contribution from background sources of muon pairs is removed using a template fit method. In peripheral collisions, the muons exhibit a strong back-to-back correlation consistent with previous measurements of muon pair production in ultraperipheral collisions. The angular correlations are observed to broaden significantly in central collisions. The modifications are qualitatively consistent with rescattering of the muons while passing through the hot matter produced in the collision.

Search for Resonant and Nonresonant Higgs Boson Pair Production in the bb[over ¯]τ^{+}τ^{-} Decay Channel in pp Collisions at sqrt[s]=13 TeV with the ATLAS Detector

A search for resonant and nonresonant pair production of Higgs bosons in the bb[over ¯]τ^{+}τ^{-} final state is presented. The search uses 36.1  fb^{-1} of pp collision data with sqrt[s]=13  TeV recorded by the ATLAS experiment at the LHC in 2015 and 2016. Decays of the τ-lepton pairs with at least one τ lepton decaying to final states with hadrons and a neutrino are considered. No significant excess above the expected background is observed in the data. The cross-section times branching ratio for nonresonant Higgs boson pair production is constrained to be less than 30.9 fb, 12.7 times the standard model expectation, at 95% confidence level. The data are also analyzed to probe resonant Higgs boson pair production, constraining a model with an extended Higgs sector based on two doublets and a Randall-Sundrum bulk graviton model. Upper limits are placed on the resonant Higgs boson pair production cross-section times branching ratio, excluding resonances X in the mass range 305  GeV<m_{X}<402  GeV in the simplified hMSSM minimal supersymmetric model for tanβ=2 and excluding bulk Randall-Sundrum gravitons G_{KK} in the mass range 325  GeV<m_{G_{KK}}<885  GeV for k/M[over ¯]_{Pl}=1.

Stabilizing mixed fatty acid and phthalate ester monolayer on artificial seawater

Phthalate esters which are widely used as industrial chemicals have become widespread contaminants in the marine environment. However, little information is available on the interfacial behavior of phthalate esters in the seawater, where contaminants generally occur at elevated concentrations and have the potential to transfer into the atmosphere through wave breaking on sea surface. We used artificial seawater coated with fatty acids to simulate sea surface microlayer in a Langmuir trough. The interactions of saturated fatty acids (stearic acid (SA) and palmitic acid (PA)) with one of the most abundant phthalate esters (di-(2-ethylhexyl) phthalate (DEHP)), were investigated under artificial seawater and pure water conditions. Pure DEHP monolayer was not stable, while more stable mixed monolayers were formed by SA and DEHP on the artificial seawater at relatively low surface pressure. Sea salts in the subphase can lower the excess Gibbs free energy to form more stable mixed monolayer. Among the ten components in the sea salts, Ca²⁺ ions played the major role in condensation of mixed monolayer. The condensed characteristic of the mixed SA (or PA)/DEHP monolayers suggested that the hydrocarbon chains were ordered on artificial seawater. By means of infrared reflection-absorption spectroscopy (IRRAS), we found that multiple sea salt mixtures induced deprotonated forms of fatty acids at the air-water interface. Sea salts can improve the stability and lifetime of mixed fatty acid and phthalate ester monolayer on aqueous droplets in the atmosphere. Interfacial properties of mixed fatty acid and phthalate ester monolayers at the air-ocean interface are important to help understand their behavior and fate in the marine environment.

[Relationship between FGF23/FGFR4 expression in atrial tissue and atrial fibrosis in patients with atrial fibrillation]

Objective: To observe the expression of fibroblast growth factor 23 (FGF23) and FGFR4 in patients with atrial fibrillation (AF) and its relationship with atrial fibrosis. Methods: Fifty-one patients with rheumatic heart disease undergoing cardiac surgery at the Second Affiliated Hospital of Nanchang University from October 2016 to April 2017 were divided into two groups according to whether they were complicated with atrial fibrillation: 39 patients with persistent AF(AF group), and 12 patients with sinus rhythm (SR group). The right atrial appendage was cut out during cardiac surgery. The expression of FGF23 and FGFR4 mRNA was detected by quantitative real-time PCR. The expression of FGFR4 protein was detected by Western blot. Atrial structure was evaluated by echocardiography. Masson staining was used to evaluate the degree of atrial fibrosis. The expression of FGF23 and FGFR4 was compared between the two groups.Additionally, the relationship between FGF23 and FGFR4 expression and atrial fibrosis was evaluated. Results: AF group had significantly higher right and left atrial diameter than SR group((40.1±1.6 )mm vs (34.1±1.5)mm, (52.4±2.9)mm vs (41.3±2.4)mm, all P<0.05) . There were no statistically significant differences in age, gender, ejection fraction between the two groups. The expression of FGF23 and FGFR4 mRNA in AF group were significantly higher than those in SR group (1.93±0.32 vs 0.93±0.14, 1.89±0.17 vs 0.91±0.11, both P<0.05). Compared with the SR group, the protein expression of FGFR4 in the AF group was significantly higher(1.76±0.21 vs 0.84±0.12). In AF group, there was no correlation between FGF23 mRNA and atrial diameter (r=0.274 (left atrial), r=0.238 (right atrium), both P>0.05). Meanwhile, FGFR4 mRNA and protein expression had no correlation with atrial diameter either. There was positive correlation between FGF23 mRNA and atrial collagen volume fraction in AF group (r=0.42, P<0.05). The expression of FGFR4 mRNA and protein were positively correlated with the atrial collagen volume fraction (r=0.573, r=0.478, all P<0.05). Conclusion: The expression of FGF23 and FGFR4 in atrial fibrillation patients is increased, which is positively correlated with atrial fibrosis, suggesting that FGF23/FGFR4 pathway may play an important role in atrial fibrillation by promoting atrial fibrosis.

Source Contribution Analysis and Collaborative Assessment of Heavy Metals in Vegetable-Growing Soils

Source quantification of heavy metals in farmland is essential for developing and implementing restoration strategies. We used various data analyses to identify and quantify sources of arsenic, cadmium, chromium, copper, mercury, nickel, lead, and zinc in vegetable-growing soils. A new method of collaborative assessment, combining soil environmental quality and agricultural product safety, showed that approximately 5.20% of cultivation systems were multi-contaminated by heavy metals. The nonlinear relationship between pollution sources and the comprehensive contamination situation was established, deriving from a fitted bivariate model. The model revealed that anthropogenic sources and natural origins accounted for 65.8-86.0 and 34.2-14.0% of the comprehensive pollution, respectively. These results suggested that both human activities and natural factors contributed to the decline of local soil quality and the influence of the former was more substantial than that of the latter.

Probing the Quantum Interference between Singly and Doubly Resonant Top-Quark Production in pp Collisions at sqrt[s]=13 TeV with the ATLAS Detector

This Letter presents a normalized differential cross-section measurement in a fiducial phase-space region where interference effects between top-quark pair production and associated production of a single top quark with a W boson and a b-quark are significant. Events with exactly two leptons (ee, μμ, or eμ) and two b-tagged jets that satisfy a multiparticle invariant mass requirement are selected from 36.1  fb^{-1} of proton-proton collision data taken at sqrt[s]=13  TeV with the ATLAS detector at the LHC in 2015 and 2016. The results are compared with predictions from simulations using various strategies for the interference. The standard prescriptions for interference modeling are significantly different from each other but are within 2σ of the data. State-of-the-art predictions that naturally incorporate interference effects provide the best description of the data in the measured region of phase space most sensitive to these effects. These results provide an important constraint on interference models and will guide future model development and tuning.

Diurnal concentrations, sources, and cancer risk assessments of PM2.5-bound PAHs, NPAHs, and OPAHs in urban, marine and mountain environments

Ambient measurements of PM_2.5-bounded polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), and oxy-PAHs (OPAHs) were conducted during the summer in Jinan, China, an urban site, and at Tuoji island and Mt. Tai, two background locations. 3.5 h and 11.5 h sampling intervals in daytime and nighttime were utilized to research the diurnal variations of PAHs, NPAHs, and OPAHs. The concentrations of PAHs, NPAHs, and OPAHs were highest at the urban site and lowest at the marine site. The diurnal patterns of PAHs and NPAHs at the urban and marine sites were dissimilar to those observed at the mountain site partly due to the influence of the boundary layer. Vehicle emissions at the urban site made a large contribution to high molecular weight PAHs. 1N-PYR and 7N-BaA during morning and night sampling periods in JN were relatively high. Fossil fuel combustion and biomass burning were the main sources for all three sites during the sampling periods. The air masses at the marine and mountain sites were strongly impacted by photo-degradation, and the air masses at the marine site were the most aged. Secondary formation of NPAHs was mainly initiated by OH radicals at all the three sites and was strongest at the marine site. Secondary formation was most efficient during the daytime at the urban and mountain sites and during morning periods at the marine site. The average excess cancer risk from inhalation (ECR) for 70 years' life span at the urban site was much higher than those calculated for the background sites.

Insights into the catalytic mechanism of dehydrogenase BphB: A quantum mechanics/molecular mechanics study

The present study delineated the dehydrogenation mechanism of cis-2,3-dihydro-2,3-dihydroxybiphenyl (2,3-DDBPH) and cis-2,3-dihydro-2,3-dihydroxy-4,4'-dichlorobiphenyl (2,3-DD-4,4'-DBPH) by Pandoraea pnomenusa strain B-356 cis-2,3-dihydro-2,3-dihydroxybiphenyl dehydrogenase (BphB) in atomistic detail. The enzymatic process was investigated by a combined quantum mechanics/molecular mechanics (QM/MM) approach. Five different snapshots were extracted and calculated, which revealed that the Boltzmann-weighted average barriers of 2,3-DDBPH and 2,3-DD-4,4'-DBPH dehydrogenation processes are 10.7 and 11.5 kcal mol^-1, respectively. The established dehydrogenation mechanism provides new insight into the degradation processes of other chlorinated 2,3-DDBPH. In addition to Asn115, Ser142, and Lys149, the importance of Ile 89, Asn143, Pro184, Met 187, Thr189, and Lue 191 during the dehydrogenation process of 2,3-DDBPH and 2,3-DD-4,4'-DBPH were also highlighted to search for promising mutation targets for improving the catalytic efficiency of BphB.

[Factors affecting stability after fixed orthodontic treatment]

Objective: To analyze factors affecting stability after fixed orthodontic treatment. Methods: Five hundred and forty-four patients who had finished fixed orthodontic treatment more than two years in First Department of Orthodontics, China Medical University from January, 2000 to December, 2017 were investigated and the rate of regular revisit was counted. The data of 288 patients were successfully collected by calling or sending text messages and the rate of standard use of retainers as prescribed (patients wore retainers for 24 months or longer) was counted. According to the variation of peer assessment rating (PAR) index at the start of retention and the time the data collected, the patients were divided into relapse group (variation of PAR index >5) and non-relapse group (variation of PAR index ≤5). Difference significance analysis and multiple-factor logistic regression analysis were used. Sixty patients wearing retainers well were collected and the curative effects of Hawley retainer and vacuum formed retainer (VFR) were compared, which included overbite, overjet, maxillary irregularity index, mandibular irregularity index, width betwenn canine and width between first molar. Results: The rate of regular revisit was 41.0% (223/544). Two hundred and one of 288 patients (69.8%) who were visited successfully had regular revisit, and 60.4%(174/288) of the patients wore retainers well; 30.2% (87/288) of the patients who were visited successfully didn't have regular revisit, and 10.4% (30/288) of the patients wore retainers well. Difference significance analysis showed that there was highly significant difference between relapse group and non-relapse group in the type of retainer and duration of retention (P<0.01). One hundred and forty of 224 patients (62.5%) in non-relapse group and 37.5% (24/64) of the patients in relapse group used VFR, and the duration of retention in non-relapse group was significantly longer than that in relapse group (P<0.01). Multiple-factor Logistic regression analysis showed that wearing Hawley retainers (OR=3.067, P<0.05) was the risk factor influencing relapse. The duration of retention (OR=0.832, P<0.01) was the protective factor influencing relapse. Independent-sample t test indicated that the variations of maxillary [(0.82±0.36) mm] and mandibular [(1.05±0.22) mm] irregularity index in Hawley retainer group were larger than maxillary [(0.64±0.29) mm] and mandibular [(0.72±0.35) mm)] irregularity index in VFR group, respectively. The differences between the two groups were significant (P<0.05). Conclusions: Duration of retention was implicated in stability after orthodontic treatment. VFR had better effect in the aspects of irregularity index than Hawley retainer.

Strong ozone production at a rural site in theNorth China Plain: Mixed effects of urban plumesand biogenic emissions

Regional ozone (O₃) pollution has drawn increasing attention in China over the recent decade, but the contributions from urban pollution and biogenic emissions have not been clearly elucidated. To better understand the formation of the regional O₃ problem in the North China Plain (NCP), intensive field measurements of O₃ and related parameters were conducted at a rural site downwind of Ji'nan, the capital city of Shandong province, in the summer of 2013. Markedly severe O₃ pollution was recorded, with the O₃ mixing ratios exceeding the Chinese national ambient air quality standard on 28 days (a frequency of 78%) and with a maximum hourly value of 198 ppbv. Extensive regional transport of well-processed urban plumes to the site was identified. An observation-constrained chemical box model was deployed to evaluate in situ photochemical O₃ production on two episodes. The results show that the in situ formation accounted for approximately 46% of the observed O₃ accumulation, while the remainder (~54%) was contributed by regional transport of the O₃-laden urban plumes. The in situ ozone production was in a mixed controlled regime that reducing either NOx or VOCs would lead to a reduction of ozone formation. Biogenic VOCs played an important role in the local ozone formation. This study demonstrates the significant mixed effects of both anthropogenic pollution from urban zones and biogenic emission in rural areas on the regional O₃ pollution in the NCP region, and may have general applicability in facilitating the understanding of the formation of secondary pollution over China.

Understanding unusually high levels of peroxyacetyl nitrate (PAN) in winter in Urban Jinan, China

Peroxyacetyl nitrate (PAN), as a major secondary pollutant, has gained increasing worldwide attentions, but relevant studies in China are still quite limited. During winter of 2015 to summer of 2016, the ambient levels of PAN were measured continuously by an automatic gas chromatograph equipped with an electron capture detector (GC-ECD) analyzer at an urban site in Jinan (China), with related parameters including concentrations of O₃, NO, NO₂, PM_2.5, HONO, the photolysis rate constant of NO₂ and meteorological factors observed concurrently. The mean and maximum values of PAN concentration were (1.89 ± 1.42) and 9.61 ppbv respectively in winter, and (2.54 ± 1.44) and 13.47 ppbv respectively in summer. Unusually high levels of PAN were observed during severe haze episodes in winter, and the formation mechanisms of them were emphatically discussed. Study showed that high levels of PAN in winter were mainly caused by local accumulation and strong photochemical reactions during haze episodes, while mass transport played only a minor role. Accelerated photochemical reactions (compared to winter days without haze) during haze episodes were deduced by the higher concentrations but shorter lifetimes of PAN, which was further supported by the sufficient solar radiation in the photolysis band along with the high concentrations of precursors (NO₂, VOCs) and HONO during haze episodes. In addition, significant PAN accumulation during calm weather of haze episodes was verified by meteorological data.

Search for Low-Mass Dijet Resonances Using Trigger-Level Jets with the ATLAS Detector in pp Collisions at sqrt[s]=13 TeV

Searches for dijet resonances with sub-TeV masses using the ATLAS detector at the Large Hadron Collider can be statistically limited by the bandwidth available to inclusive single-jet triggers, whose data-collection rates at low transverse momentum are much lower than the rate from standard model multijet production. This Letter describes a new search for dijet resonances where this limitation is overcome by recording only the event information calculated by the jet trigger algorithms, thereby allowing much higher event rates with reduced storage needs. The search targets low-mass dijet resonances in the range 450-1800 GeV. The analyzed data set has an integrated luminosity of up to 29.3  fb^{-1} and was recorded at a center-of-mass energy of 13 TeV. No excesses are found; limits are set on Gaussian-shaped contributions to the dijet mass distribution from new particles and on a model of dark-matter particles with axial-vector couplings to quarks.

The effect of continuous perfusion of esmolol on cardiovascular risk in elderly patients undergoing noncardiac surgery

We evaluated the effect of continuous perfusion of esmolol on cardiovascular risk during curative laparoscopic surgery for gastrointestinal cancer in elderly patients. Sixty patients with gastrointestinal cancer, aged from 60 to 80 years, were divided into an esmolol group (ES, n = 30) and a control group (NS, n = 30). ES patients were treated with esmolol at a dose of 0.3 mg/kg 3 min before tracheal intubation, and received continuous perfusion of esmolol at a dose of 50 μg/kg/min during operation. In NS, esmolol was replaced by saline. SBP/DBP, MAP, HR, SPO2, PETCO2, the depth of anesthesia and the value of RPP were recorded before anesthesia (T0), during intubation (T1), 10 min before pneumoperitoneum (T2), during pneumoperitoneum (T3), 30 min after incision (T4), at the end of surgery (T5), during extubation (T6) and 30 min after extubation (T7). The serum levels of cTnI, CK, CK-MB and LDH were measured before anesthesia, 6 and 30 h after surgery. HR, MAP, RPP at T1, T3, T6 in ES were obviously decreased compared with NS (P < 0.05). There were no significant differences between both groups at different time points with respects to the serum levels of cTnI, CK, CK-MB and LDH. No major adverse cardiocerebral event was observed in both groups in three postoperative months. The present study indicated that the application of esmolol during curative laparoscopic surgery for gastrointestinal cancer can effectively reduce the cardiovascular responses in intubation, operation and extubation, sustain hemodynamic stable, reduce myocardial oxygen consumption, and prevent perioperative adverse cardiovascular events, but had no significant myocardial protective effect.

Computational evidence for the degradation mechanism of haloalkane dehalogenase LinB and mutants of Leu248 to 1-chlorobutane

The catalytic degradation ability of the haloalkane dehalogenase LinB toward 1-chlorobutane (1-CB) was studied using a combined quantum mechanics/molecular mechanics (QM/MM) approach. Two major processes are involved in the LinB-catalyzed removal of halogens: dechlorination and hydrolyzation. The present study confirmed the experimentally proposed reaction path at the molecular level. Moreover, based on nucleophilic substitution mechanism (SN2 reaction), dechlorination was found to be the rate-determining step of the entire reaction process. In this study, the Boltzmann-weighted average barrier for dechlorination was determined to be 17.0 kcal mol-1, which is fairly close to the experimental value (17.4 kcal mol-1). The state of His107 and the influence of Leu248 on the dechlorination process were also explored. In addition, an intriguing phenomenon was discovered: the potential energy barrier decreased by 7.5 kcal mol-1 when the Leu248 residue was mutated into Phe248. This discovery might be of great help to design new mutant enzymes or novel biocatalysts.

Polycyclic aromatic hydrocarbons (PAHs) associated with PM2.5 within boundary layer: Cloud/fog and regional transport

A study of PM_2.5-associated PAHs analysis at Mount Lushan (1165m) was conducted to investigate the distributions of PAHs in PM_2.5 and influences of cloud/fog. The main purpose was to quantify the main emission sources of PAHs and estimate regional transport effects within the boundary layer. Mount Lushan is located between the boundary layer and troposphere, which is an ideal site for atmosphere transport investigation. The concentrations of PAHs in PM_2.5 were analyzed with GC-MS. The results showed that the volume concentration was 6.98ng/m³ with a range from 1.47 to 25.17ng/m³ and PAHs mass were 160.24μg/g (from 63.86 to 427.97μg/g) during the sampling time at Mount Lushan. The dominant compounds are BbF, Pyr and BP. In terms of aromatic-ring PAHs distributions, 4-6-ring PAHs are predominant, indicating that the high-ring PAHs tend to contribute more than low-ring PAHs in particulates. Due to frequent cloud/fog days at Mount Lushan, PAHs concentrations in the PM_2.5 were determined before and after cloud/fog weather. The results demonstrated that the cloud/fog and rain conditions cause lower PAHs levels. Regression analysis was used for studying the relationship of PAHs distributions with meteorological conditions like temperature, humidity and wind. The results showed that the temperature and wind speed were inversely related with PAHs concentration but humidity had no significant relationship. Furthermore, backward trajectories and PCA combined with DR (diagnostic ratio analysis) were employed to identify the influences of regional transport and main emission sources. The results revealed that PAHs in PM_2.5 were mainly affected by regional transport with the main emissions by mobile vehicle and steel industry, which contributed about 56.0% to the total PAHs in the area of Mount Lushan. In addition, backward trajectories revealed that the dominant air masses were from the northwest accounting for about one third of total PAHs.

Abundance and origin of fine particulate chloride in continental China

Particulate chloride can be converted to nitryl chloride (ClNO₂) through heterogeneous reactions with dinitrogen pentoxide (N₂O₅), and photolysis of ClNO₂ affects atmospheric oxidative capacity. However, the characteristics and sources of chloride, especially those with an anthropogenic origin, are poorly characterized, which makes it difficult to evaluate the effects of ClNO₂ on radical chemistry and air quality in polluted regions. Aerosol composition data from the literature were compiled to derive the spatial distributions of particulate chloride across China, and hourly aerosol composition data collected at a highly polluted inland urban site in eastern China and at a coastal site in southern China were analysed to gain further insights into non-oceanic sources of chloride. The results show that particulate chloride is concentrated mainly in fine particles and that high chloride loadings are observed in the inland urban areas of northern and western China with higher Cl^-/Na⁺ mass ratios (2.46 to 5.00) than sea water (1.81), indicative of significant contributions from anthropogenic sources. At the inland urban site, the fine chloride displays distinct seasonality, with higher levels in winter and summer. Correlation analysis and positive matrix factorization (PMF) results indicate that coal combustion and residential biomass burning are the main sources (84.8%) of fine chloride in winter, and open biomass burning is the major sources (52.7%) in summer. The transport of plumes from inland polluted areas leads to elevated fine chloride in coastal areas. A simulation with WRF-Chem model confirmed a minor contribution of sea-salt aerosol to fine chloride at the inland site during summer with winds from the East Sea. The widespread sources of chloride, together with abundant NOx and ozone, suggest significant ClNO₂ production and subsequent enhanced photochemical processes over China.