Search

Enhanced CO2 mineralization and geologic CO2 storage have received increasing attention as two prominent approaches in combating climate change and fostering sustainable development of human society. This paper aims to explore three emerging areas of research within the realm of enhanced CO2 mineralization and geologic CO2 storage, including enhanced rock weathering, numerical modeling and validation of CO2 storage accounting for the interplay of various trapping mechanisms, and the examination of how reservoir heterogeneity influences the migration of CO2-brine multiphase flow. Discussions highlight the effectiveness of the spectrum induced polarization for monitoring changes in petrophysical and geochemical properties of rocks during enhanced rock weathering. Additionally, the multi-scale heterogeneity of geological formations needs to be carefully characterized, due to the fact that it plays a vital role in CO2 migration. Further research is required to achieve accurate and reliable simulations of convective mixing for field-scale applications. [ABSTRACT FROM AUTHOR]

With the rapid development of vehicular networks, there is an increasing demand for extensive networking, computting, and caching resources. How to allocate multiple resources effectively and efficiently for dynamic vehicular networks is extremely important. Most existing works on resource management in vehicular networks assume static network conditions. In this paper, we propose a general framework that can enable fast-adaptive resource allocation for dynamic vehicular environments. Specifically, we model the dynamics of the vehicular environment as a series of related Markov Decision Processes (MDPs), and we combine hierarchical reinforcement learning with meta-learning, which makes our proposed framework quickly adapt to a new environment by only fine-tuning the top-level master network, and meanwhile the low-level sub-networks can make the right resource allocation policy. Extensive simulation results show the effectiveness of our proposed framework, which can quickly adapt to different scenarios, and significantly improve the performance of resource management in dynamic vehicular networks. [ABSTRACT FROM AUTHOR]

The lipid dependence of the nicotinic acetylcholine receptor from the Torpedo electric organ has long been recognized, and one of the most consistent experimental observations is that, when reconstituted in membranes formed by zwitterionic phospholipids alone, exposure to agonist fails to elicit ion-flux activity. More recently, it has been suggested that the bacterial homolog ELIC (Erwinia chrysanthemi ligand-gated ion channel) has a similar lipid sensitivity. As a first step toward the elucidation of the structural basis of this phenomenon, we solved the structures of ELIC embedded in palmitoyl-oleoyl-phosphatidylcholine- (POPC-) only nanodiscs in both the unliganded (4.1-Å resolution) and agonist-bound (3.3 Å) states using single-particle cryoelectron microscopy. Comparison of the two structural models revealed that the largest differences occur at the level of loop C--at the agonist-binding sites--and the loops at the interface between the extracellular and transmembrane domains (ECD and TMD, respectively). On the other hand, the transmembrane pore is occluded in a remarkably similar manner in both structures. A straightforward interpretation of these findings is that POPC-only membranes frustrate the ECD-TMD coupling in such a way that the "conformational wave" of liganded-receptor gating takes place in the ECD and the interfacial M2-M3 linker but fails to penetrate the membrane and propagate into the TMD. Furthermore, analysis of the structural models and molecular simulations suggested that the higher affinity for agonists characteristic of the open- and desensitized-channel conformations results, at least in part, from the tighter confinement of the ligand to its binding site; this limits the ligand's fluctuations, and thus delays its escape into bulk solvent. [ABSTRACT FROM AUTHOR]

The memristor device based on graphene/Nb-doped SrTiO 3 heterojunction was fabricated. The device exhibits obvious resistive switching between high resistance state and low resistance state. By using the graphene as the transparent electrode, remarkable photocurrent and photovoltage was achieved in the heterojunction. The photovoltage shows a clear dependence on the resistance state, whereas the photocurrent keeps unchanged. Based on these features, a new non-destructive photovoltaic reading method of the memristor was demonstrated. The photovoltaic reading method is free of external driving voltage, thereby avoiding the perturbation of the stored data. Moreover, the photovoltage output signal instead of the current is more compatible with the IC technologies. [ABSTRACT FROM AUTHOR]

HFO-1234yf (2,3,3,3-tetrafluoropropene) was proposed as an automobile air conditioner (MAC) refrigerant worldwide. However, its atmospheric degradation product is the highly soluble and phytotoxic trifluoroacetic acid (TFA), which persists in aquatic environments. We used a global three-dimensional chemical transport model to assess the potential environmental effects resulting from complete future conversion of the refrigerant in all MAC to HFO-1234yf in China, the United States, and Europe. The annual mean atmospheric concentrations of HFO-1234yf were 2.62, 2.20, and 2.73 pptv, and the mean deposition rates of TFA were 0.96, 0.45, and 0.52 kg km-2 yr-1, in three regions. The regional TFA deposition sources mainly came from emissions within the same region. The annual TFA deposition in the North Pole region was lower than the global average and mainly originated from European emissions. A potential doubling in the future HFO-1234yf emissions in China mainly affected the local TFA depositions. The TFA concentrations in rainwater were strongly affected by the regional precipitation rates. North Africa and the Middle East, regions with scant rainfall, had extremely high TFA concentrations. The rainwater concentrations of TFA during individual rain events can exceed the level considered to be safe, indicating substantial potential regional risks from future HFO-1234yf use. [ABSTRACT FROM AUTHOR]

With the improved spatial resolution than earlier instruments and more than ten years of service, tropospheric NO2 retrievals from the Ozone Monitoring Instrument (OMI) have led to many influential studies on the relationships between socioeconomic activities and NOx emissions. This study focuses on how to improve OMI NO2 retrievals for more reliable trend analysis. We retrieve OMI tropospheric NO2 vertical column densities (VCDs) and obtain the NO2 seasonal trends over the United States, which are compared with coincident in situ surface NO2 measurements from the Air Quality System (AQS) network. The Mann-Kendall method is applied to derive the NO2 seasonal and annual trends for four regions at coincident sites during 2005-2014. The OMI-based NO2 seasonal relative trends are generally biased high compared to the in situ trends by up to 3.7 % yr-1, except for the underestimation in the Midwest and Northeast during Dec-Jan-Feb (DJF). We improve the OMI retrievals for trend analysis by removing the ocean trend, using the MODerate-resolution Imaging Spectroradiometer (MODIS) albedo data in air mass factor (AMF) calculation, and applying a lightning flash filter to exclude lightning affected OMI NO2 retrievals. These improvements result in close agreement (within 0.3 % yr-1) between in situ and OMI-based NO2 regional annual relative trends. Thus, we recommend future studies to apply these procedures to ensure the quality of satellite-based NO2 trend analysis, especially in regions without reliable long-term in situ NO2 measurements. We derive optimized OMI-based NO2 regional annual relative trends using all available data for the West (-2.0 % ± 0.3 yr-1), the Midwest (-1.8 % ± 0.4 yr-1), the Northeast (-3.1 % ± 0.5 yr-1), and the South (-0.9 % ± 0.3 yr-1). The OMI-based annual mean trend over the contiguous United States is -1.5 % ± 0.2 yr-1. It is a factor of 2 lower than that of the AQS in situ data (-3.9 % ± 0.4 yr-1); the difference is mainly due to the fact that the locations of AQS sites are concentrated in urban and suburban regions. [ABSTRACT FROM AUTHOR]

Remarkable advances have been made toward the structural characterization of ion channels in the last two decades. However, the unambiguous assignment of well-defined functional states to the obtained structural models has proved challenging. In the case of the superfamily of nicotinic-receptor channels (also referred to as pentameric ligand-gated ion channels [pLGICs]), for example, two different types of model of the open-channel conformation have been proposed on the basis of structures solved to resolutions better than 4.0 Å. At the level of the transmembrane pore, the open-state models of the proton-gated pLGIC from Gloeobacter violaceus (GLIC) and the invertebrate glutamate-gated Cl- channel (GluCI) are very similar to each other, but that of the glycine receptor (GlyR) is considerably wider. Indeed, the mean distances between the axis of ion permeation and the Ca atoms at the narrowest constriction of the pore (position -2 ') differ by ~2 Å in these two classes of model, a large difference when it comes to understanding the physicochemical bases of ion conduction and charge selectivity. Here, we take advantage of the extreme open-channel stabilizing effect of mutations at pore-facing position 9'. We find that the !9'A mutation slows down entry into desensitization of GLIC to the exte n t that macroscopic currents decay only slightly by the end of pH 4.5 solution applications to the extracellular side for several minutes. We crystallize (at pH 4.5) two variants of GLIC carrying this mutation and solve their structures to resolutions of 3.12 Å and 3.36 Å. Furthermore, we perform all-atom molecular dynamics simulations of ion permeation and picrotoxinin block, using the different open-channel structural models. On the basis of these results, we favor the notion that the open-channel structure of pLGICs from animals is much closer to that of the narrow models (of GLIC and GluCI) than it is to that of the GlyR. [ABSTRACT FROM AUTHOR]

Ground-level ozone is adverse to human and vegetation health. High ground-level ozone concentrations usually occur over the United States in the summer, often referred to as the ozone season. However, observed monthly mean ozone concentrations in the southeastern United States were higher in October than July in 2010. The October ozone average in 2010 reached that of July in the past three decades (1980-2010). Our analysis shows that this extreme October ozone in 2010 over the Southeast is due in part to a dry and warm weather condition, which enhances photochemical production, air stagnation, and fire emissions. Observational evidence and modeling analysis also indicate that another significant contributor is enhanced emissions of biogenic isoprene, a major ozone precursor, from water-stressed plants under a dry and warm condition. The latter finding is corroborated by recent laboratory and field studies. This climate-induced biogenic control also explains the puzzling fact that the two extremes of high October ozone both occurred in the 2000s when anthropogenic emissions were lower than the 1980s and 1990s, in contrast to the observed decreasing trend of July ozone in the region. The occurrences of a drying and warming fall, projected by climate models, will likely lead to more active photochemistry, enhanced biogenic isoprene and fire emissions, an extension of the ozone season from summer to fall, and an increase of secondary organic aerosols in the Southeast, posing challenges to regional air quality management. [ABSTRACT FROM AUTHOR]

Fabricating reliable nano-Ohmic contact on wide gap semiconductors is an important yet difficult step in oxide nanoelectronics. We fabricated Ohmic contact on the n-type wide gap oxide Nb-doped SrTiO3 in nanoscale by mechanically scratching the surface using an atomic force microscopy tip. Although contacted to high work function metal, the scratched area exhibits nearly linear IV behavior with low contact resistance, which maintains for hours in vacuum. In contrast, the unscratched area shows Fowler-Nordheim tunneling dominated Schottky rectifying behavior with high contact resistance. It was found that the Ohmic conductivity in the scratched area was drastically suppressed by oxygen gas indicating the oxygen vacancy origin of the Ohmic behavior. The surface oxygen vacancy induced barrier width reduction was proposed to explain the phenomena. The nanoscale approach is also applicable to macroscopic devices and has potential application in all-oxide devices. [ABSTRACT FROM AUTHOR]

The epitaxial 200-nm-thick FeV2O4(110) films on (110)-oriented SrTiO3, LaAlO3 and MgAl2O4 substrates were fabricated for the first time by pulsed laser deposition, and the structural, magnetic, and magnetoresistance anisotropy were investigated systematically. All the films are monoclinic, whereas its bulk is cubic. Compared to FeV2O4 single crystals, films on SrTiO3 and MgAl2O4 are strongly compressively strained in [001] direction, while slightly tensily strained along normal [110] and in-plane [110] directions. In contrast, films on LaAlO3 are only slightly distorted from cubic. The magnetic hard axis is in <001> direction, while the easier axis is along normal [110] direction for films on SrTiO3 and MgAl2O4, and in-plane [110] direction for films on LaAlO3. Magnetoresistance anisotropy follows the magnetization. The magnetic anisotropy is dominated by the magnetocrystalline energy, and tuned by the magneto-elastic coupling. [ABSTRACT FROM AUTHOR]

Current knowledge of daytime HONO sources remains incomplete. A large missing daytime HONO source has been found in many places around the world, including polluted regions in China. Conventional understanding and recent studies attributed this missing source mainly to ground surface processes or gas-phase chemistry, while assuming aerosols to be an insignificant media for HONO production. We analyze in situ observations of HONO and its precursors at an urban site in Beijing, China, and report an apparent dependence of the missing HONO source strength on aerosol surface area and solar ultraviolet radiation. Based on extensive correlation analysis and process-modeling, we propose that the rapid daytime HONO production in Beijing can be explained by enhanced hydrolytic disproportionation of NO2 on aqueous aerosol surfaces due to catalysis by dicarboxylic acid anions. The combination of high abundance of NO2, aromatic hydrocarbons, and aerosols over broad regions in China likely leads to elevated HONO levels, rapid OH production, and enhanced oxidizing capacity on a regional basis. Our findings call for attention to aerosols as a media for daytime heterogeneous HONO production in polluted regions like Beijing. This study also highlights the complex and uncertain heterogeneous chemistry in China, which merits future efforts of reconciling regional modeling and laboratory experiments, in order to understand and mitigate the regional particulate and O3 pollutions over China. [ABSTRACT FROM AUTHOR]

Vanadium oxide is considered as a potential cathode material for lithium-ion batteries, while its performance is significantly restricted by its poor Li+ ion diffusion rate and low electric conductivity. These ion and charge transport rates, however, are also well correlated with the 3-dimensional (3D) morphologies/structures of the electroactive materials. Herein, we synthesized three different nanostructured vanadium oxides on Ti foils. The comparison of electrochemical properties of these materials shows that the structures of electrodes have great influences on their performances. Among these structures, the nanoribbons are most beneficial for fast charge transfer and reduced contact resistance. In addition, the spaces between each nanoribbon provide efficient ion transport pathways and sufficient electrolyte penetration. The initial discharge and charge capacities of vanadium oxide nanoribbon reach to 322 and 310 mA h g-¹, with a reversible discharge/charge capacity of 200 mA h g-¹ at the current rate of 1C (1C = 300 mA g-¹). [ABSTRACT FROM AUTHOR]

The layout of urban buildings shows significant heterogeneity, which leads to the significant spatial inhomogeneity of the wind field in and over the canopy of urban street canyons. However, most of the current urban canopy models do not fully consider the heterogeneity of the urban canopy. Large discrepancies thus exist between the wind speeds simulated by the current urban canopy models and those observed in the street canyon. In this study, a parameterization scheme for wind field, Inhomogeneous Wind Scheme for Urban Street (IWSUS), is developed to better characterize the heterogeneity of the urban canopy. We use a Computational Fuild Dynamics method to generate the IWSUS scheme and compare with observations of wind profile and turbulent flux in and over the street canyon for validation. In IWSUS, the wind speed vertical profiles at six representative positions located in a typical street canyon (i.e., the windward or leeward side of a long straight street, or the inflow or outflow end) are parameterized separately. The wind profile by IWSUS thus can better describe the horizontal heterogeneity of the urban near-surface wind field, e.g., the dynamic drag effect of building in the lower atmosphere layer over the urbanized land use. The validation based on observations shows that the performance of simulation results by IWSUS is better than that by logarithmic-exponential (exp-log) law widely used in the current urban schemes. As we consider typical building arrangement and specific street orientations in IWSUS for wind field simulations, which can better match the distribution characteristics of street canyons around the observation point in the street canyon. The averaged wind profiles and turbulence energy fluxes in the model grids of urban area by IWSUS are also more approach to the observation than those by exp-log law. The normalized mean errors (NME) between the simulated and the observed vertical average wind speed are 49.0% for IWSUS and 56.1% for exp-log law in the range from the ground to four times the average height of the building, and 70% for IWSUS and 285.8% for exp-log law in the street canyon (range from the ground to building top). This study proves that the accuracy of land surface process and near-grounded meteorological process simulations over urban canopy can be improved by fully considering the heterogeneity of the urban canopy layout structures and the inhomogeneous of wind field distributions in and over the street canyon. The IWSUS is expected to be coupled with mesoscale atmospheric models to improve the accuracy of the wind field, land surface energy budget, meteorological, and atmospheric chemistry simulations. [ABSTRACT FROM AUTHOR]

We analyzed satellite observations of nitrogen dioxide (NO,) columns by the Ozone Monitoring Instrument (OMI) over China from 2005 to 2010 in order to estimate the top-down anthropogenic nitrogen oxides (NOiV) emission trends. Since NOv emissions were affected by the economic slowdown in 2009, we removed one year of abnormal data in the analysis. The estimated average emission trend is 4.01 ± 1.39% yr-1, which is slower than the trend of 5.8-10.8% yr-1 reported for previous years. We find large regional, seasonal, and urban-rural variations in emission trends. The average NOx emission trend of 3-47 ± 1.07% yr-1 in warm season (June-September) is less than the trend of 5.03 ± 1.92% yr-1 in cool season (October-May). The regional annual emission trends decrease from 4.76 + 1.61% yr-1 in North China Plain to 3.11 ± 0.98% yr-1 in Yangtze River Delta and further down to -4.39 ± 1.81% yr-1 in Pearl River Delta. The annual emission trends of the four largest megacities, Shanghai, Beijing, Guangzhou, and Shenzhen are -0.76 ± 0.29%, 0.69 ± 0.27%, -4.46 ± 1.22%, and -7.18 ± 2.88% yr-1, considerably lower than the regional averages or surrounding rural regions. These results appear to suggest that a number of factors, including emission control measures of thermal power plants, increased hydro-power usage, vehicle emission regulations, and closure or migration of high-emission industries, have significantly reduced or even reversed the increasing trend of NOA. emissions in more economically developed megacities and southern coastal regions, but their effects are not as significant in other major cities or less economically developed regions. [ABSTRACT FROM AUTHOR]

Vaccinia Tian Tan (VTT) was attenuated by deletion of the TC7L-TK2L and TA35R genes to generate MVTT3. The mutant was generated by replacing the open reading frames by a gene encoding enhanced green fluorescent protein (EGFP) flanked by loxP sites. Viruses expressing EGFP were then screened for and purified by serial plaque formation. In a second step the marker EGFP gene was removed by transfecting cells with a plasmid encoding cre recombinase and selecting for viruses that had lost the EGFP phenotype. The MVTT3 mutant was shown to be avirulent and immunogenic. These results support the conclusion that TC7L-TK2L and TA35R deletion mutants can be used as safe viral vectors or as platform for vaccines. [ABSTRACT FROM AUTHOR]

We analyze the observations of near-surface peroxy acetyl nitrate (PAN) and its precursors in Beijing, China in August of 2007. The levels of PAN are remarkably high (up to 14 ppbv), surpassing those measured over other urban regions in recent years. Analyses employing a 1-D version of a chemical transport model (Regional chEmical and trAnsport Model, REAM) indicate that aromatic non-methane hydrocarbons (NMHCs) are the dominant (55-75%) PAN source. The major oxidation product of aromatics that produces acetyl peroxy radicals is methylglyoxal (MGLY). PAN and O3 in the observations are correlated at daytime; aromatic NMHCs appear to play an important role in O3 photochemistry. Previous NMHC measurements indicate the presence of reactive aromatics at high levels over broad polluted regions of China. Aromatics are often ignored in global and (to a lesser degree) regional 3D photochemical transport models; their emissions over China as well as photochemistry are quite uncertain. Our findings suggest that critical assessments of aromatics emissions and chemistry (such as the yields of MGLY) are necessary to understand and assess ozone photochemistry and regional pollution export in China. [ABSTRACT FROM AUTHOR]

Economic growth and associated pollution emissions in China are concentrated over three connected plains to the east. In this work, we analyze an episode of highly elevated ozone over East China on June 9-14, 2004, using a 3-D chemical transport model. During this episode, the East China plains were under a high-pressure system, which suppressed the ventilation of pollutants from the boundary layer. Simulated ozone concentrations over a major fraction of East China reached high levels, all the way down to the Pearl River Delta region in the southern border. The convergence of pollutant emissions and population over the vast stretch of the geographically flat plains of East China makes the region susceptible to high-ozone exposure. During this episode, the high-O3 region extended over an area >1 million km², which hosts a population of >800 million people. Model results indicate that controlling anthropogenic NOx emissions effectively reduces the area with high-ozone exposure. [ABSTRACT FROM AUTHOR]

Prescribed burning is a large aerosol source in the southeastern United States. Its air quality impact is investigated using 3-D model simulations and analysis of ground and satellite observations. Fire emissions for 2002 are calculated based on a recently developed VISTAS emission inventory. March was selected for the investigation because it is the most active prescribed fire month. Inclusion of fire emissions significantly improved model performance. Model results show that prescribed fire emissions lead to ∼50% enhancements of mean OC and EC concentrations in the Southeast and a daily increase of PM2.5 up to 25 μg m-3, indicating that fire emissions can lead to PM2.5 nonattainment in affected regions. Surface enhancements of CO up to 200 ppbv are found. Fire count measurements from the moderate resolution imaging spectroradiometer (MODIS) onboard the NASA Terra satellite show large springtime burning in most states, which is consistent with the emission inventory. These measurements also indicate that the inventory may underestimate fire emissions in the summer. [ABSTRACT FROM AUTHOR]

Large amounts of air pollutants are emitted during prescribed forest fires. Such emissions and corresponding air quality impacts can be modulated by different forest management practices. The impacts of changing burning seasons and frequencies and of controlling emissions during smoldering on regional air quality in Georgia are quantified using source-oriented air quality modeling, with modified emissions from prescribed fires reflecting effects of each practice. Equivalent fires in the spring and winter are found to have a greater impact on PM2.5 than those in summer, though ozone impacts are larger from spring and summer fires. If prescribed fires are less frequent more biofuel is burnt in each fire, leading to larger emissions and air quality impacts per fire. For example, emissions from a fire with a 5-year fire return interval (FRI) are 72% larger than those from a fire of the same acreage with a 2-year FRI. However, corresponding long-term regional impacts are reduced with the longer FRI since the annual burned area is reduced. Total emissions for fires in Georgia with a 5-year FRI are 32% less than those with a 2-year FRI. Smoldering emissions can lead to approximately 1.0 or 1.9 µg/m³ of PM2.5 in the Atlanta PM2.5 nonattainment area during March 2002. [ABSTRACT FROM AUTHOR]

To synthesize good diamond-like carbon (DLC) films on the inner surface of a cylinder, C2H2 plasma should be generated uniformly in the cylinder. In this study, glow discharge C2H2 plasma was generated by a high pulsed bias voltage applied on the cylinder, and ions were accelerated and implanted into the sample by the same bias. The effect of pulse frequency of the bias and working pressure on the discharge characteristics was investigated. In addition, the ball-on-disk test and Raman spectroscopy were used to characterize the as-deposited DLC films. The test results show that wear resistance of samples increases with the applied voltage, and the friction coefficient of DLC films lies in the range of 0.15-0.20. [ABSTRACT FROM AUTHOR]

Background and Objective: Colorectal cancer is one of the most common malignant tumors in the world. The prognosis of colorectal cancer is thus variable despite the rapid development of treatment methods in recent years, the prognosis of colorectal cancer is still not satisfactory. Therefore, it is important to understand pathogenesis and development for more accurate prognostic methods. The present study aimed to identify a long non-coding (lnc) RNAs-based signature for prognosis in colon cancer patients. Methods: Datasets from the GEO and TCGA databases were used, differential expression of lncRNA was analyzed, and a 6-lncRNA signature was identified. KEGG and GO was used to enrich the signal pathway to determine the biological effects of these 6-lncRNA. Results: This study has established a prognosis model containing "LINC01494", "TRPM2-AS", "ATP1A1-AS1", "FRY-AS1", "LINC01360", and "RBFADN" based on data set of colorectal cancer patients available in the TCGA and GEO databases. The prognostic model of lncRNAs can predict the prognosis of patients with colorectal cancer. Conclusion: The present study identified a 6-lncRNA signature that could predict the survival rate for colon cancer patients. [ABSTRACT FROM AUTHOR]

Background and Objective: Colorectal cancer is one of the most common malignant tumors in the world. The prognosis of colorectal cancer is thus variable despite the rapid development of treatment methods in recent years, the prognosis of colorectal cancer is still not satisfactory. Therefore, it is important to understand pathogenesis and development for more accurate prognostic methods. The present study aimed to identify a long non-coding (lnc) RNAs-based signature for prognosis in colon cancer patients. Methods: Datasets from the GEO and TCGA databases were used, differential expression of lncRNA was analyzed, and a 6-lncRNA signature was identified. KEGG and GO was used to enrich the signal pathway to determine the biological effects of these 6-lncRNA. Results: This study has established a prognosis model containing "LINC01494", "TRPM2-AS", "ATP1A1-AS1", "FRY-AS1", "LINC01360", and "RBFADN" based on data set of colorectal cancer patients available in the TCGA and GEO databases. The prognostic model of lncRNAs can predict the prognosis of patients with colorectal cancer. Conclusion: The present study identified a 6-lncRNA signature that could predict the survival rate for colon cancer patients. [ABSTRACT FROM AUTHOR]

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) glycoprotein mediates viral entry and membrane fusion. Its cleavage at S1/S2 and S29 sites during the biosynthesis in virus producer cells and viral entry are critical for viral infection and transmission. In contrast, the biological significance of the junction region between both cleavage sites for S protein synthesis and function is less understood. By analyzing the conservation and structure of S protein, we found that intrachain contacts formed by the conserved tyrosine (Y) residue 756 (Y756) with three α-helices contribute to the spike's conformational stability. When Y756 is mutated to an amino acid residue that can provide hydrogen bonds, S protein could be expressed as a cleaved form, but not vice versa. Also, the L753 mutation linked to the Y756 hydrogen bond prevents the S protein from being cleaved. Y756 and L753 mutations alter S protein subcellular localization. Importantly, Y756 and L753 mutations are demonstrated to reduce the infectivity of the SARS-CoV-2 pseudoviruses by interfering with the incorporation of S protein into pseudovirus particles and causing the pseudoviruses to lose their sensitivity to neutralizing antibodies. Furthermore, both mutations affect the assembly and production of SARS-CoV-2 virus-like particles in cell culture. Together, our findings reveal for the first time a critical role for the conserved L753-LQ-Y756 motif between S1/S2 and S29 cleavage sites in S protein synthesis and processing as well as virus assembly and infection. [ABSTRACT FROM AUTHOR]

The problem of vibration in turnout zones caused by passing trains has become increasingly serious due to the complexity of the structure and force of metro turnouts. However, there are only a few studies focusing on the vibration transmission characteristics in turnout zones. In this paper, three typical turnouts in a city were studied to test the vibration responses of track slabs and a tunnel wall in the switch zone and the crossing zone when a train was passing a turnout. First, the short-time Fourier transform, wavelet transform, and constant-Q nonstationary Gabor transform (CQ-NSGT) were applied to the typical time-domain signal of tunnel wall respectively. The comparison results showed that CQ-NSGT delivered a higher time resolution and a higher frequency resolution. Based on this, the CQ-NSGT was used to analyze the vibration signal of the track slabs and specifically study the vertical vibration characteristics of the track slabs in the turnout zone toward the tunnel at the time when a train was passing. The result showed the vibration signal transmitted to the tunnel wall from the track slabs in both the switch and crossing zones will experience high-frequency vibration attenuation. It was noted that different train types have no effects on the vibration signal transmission rule, but an increase in the train speed will increase the vibration energy and expand the frequency band when the signal was transmitted to the tunnel wall. [ABSTRACT FROM AUTHOR]

Global climate models (GCMs) are the state-of-the-art tool for understanding climate change and predicting future. However, little research has been reported on the latest NEX-GDDP-CMIP6 product in China. The purpose of this study was to evaluate the simulated performance and drought capture utility of the NEX-GDDP-CMIP6 over China. First, the simulation skills of the 16 GCMs in NEX-GDDP-CMIP6 was evaluated by the 'DISO', a big data evaluation method. Second, the DISO framework for drought identification was constructed by coupling the Correlation Coefficient (CC), False Alarm Rate (FAR) and Probability of Detection (POD). Then, it was combined with SPI and SPEI to evaluate the drought detection capability of NEX-GDPD-CMIP6. The result shows that: (1) NEX-GDPD-CMIP6 can reproduce the spatial distribution pattern of historical precipitation and temperature, which performs well in simulating warming trend but fails to capture precipitation's fluctuation characteristics. (2) The best performing model in precipitation is ACCESS-CM2 (DISO 1.630) and in temperature is CESM2 (DISO 3.246). (3) The 16MME performs better than the best single model, indicating that multi-model ensemble can effectively reduce the uncertainty inherent in models. (4) The SPEI calculated by 16MME identifying drought well in arid, while SPI is recommended for other climate classifications of China. [ABSTRACT FROM AUTHOR]

Human herpesvirus 6 (HHV-6) belongs to the betaherpesvirus subfamily and is divided into two distinct species, HHV-6A and HHV-6B. HHV-6 can infect nerve cells and is associated with a variety of nervous system diseases. Recently, the association of HHV-6A infection with Alzheimer's disease (AD) has been suggested. The main pathological phenomena of AD are the accumulation of β-amyloid (Aβ), neurofibrillary tangles, and neuroinflammation; however, the specific molecular mechanism of pathogenesis of AD is not completely clear. In this study, we focused on the effect of HHV-6A U4 gene function on Aβ expression. Coexpression of HHV-6A U4 with amyloid precursor protein (APP) resulted in inhibition of ubiquitin-mediated proteasomal degradation of APP. Consequently, accumulation of β-amyloid peptide (Aβ), insoluble neurofibrillary tangles, and loss of neural cells may occur. Immunoprecipitation coupled with mass spectrometry (IP-MS) showed that HHV-6A U4 protein interacts with E3 ubiquitin ligase composed of DDB1 and cullin 4B, which is also responsible for APP degradation. We hypothesize that HHV-6A U4 protein competes with APP for binding to E3 ubiquitin ligase, resulting in the inhibition of APP ubiquitin modification and clearance. Finally, this leads to an increase in APP expression and Aβ deposition, which are the hallmarks of AD. These findings provide novel evidence for the etiological hypothesis of AD, which can contribute to the further analysis of the role of HHV-6A in AD. IMPORTANCE The association of HHV-6A infection with Alzheimer's disease has attracted increasing attention, although its role and molecular mechanism remain to be estsblished. Our results here indicate that HHV-6A U4 inhibits amyloid precursor protein (APP) degradation. U4 protein interacts with CRLs (cullin-RING E3 ubiquitin-protein ligases), which is also responsible for APP degradation. We propose a model in which U4 competitively binds to CRLs with APP, resulting in APP accumulation and Aβ generation. Our findings provide new insights into the etiological hypothesis of HHV-6A in AD that can help further analyses. [ABSTRACT FROM AUTHOR]

We demonstrate a facile, two-step coating/calcination approach to grow a uniform MnO nanoparticle@ mesoporous carbon (MnO@C) composite on conducting substrates, by direct coating of the Mn-oleate precursor solution without any conducting/binding reagents, and subsequent thermal calcination. The monodispersed, sub-10 nmMnOnanoparticles offer high theoretical energy storage capacities and catalytic properties, and the mesoporous carbon coating allows for enhanced electrolyte transport and charge transfer towards/from MnO surface. In addition, the direct growth and attachment of the MnO@C nanocomposite in the supporting conductive substrates provide much reduced contact resistances and efficient charge transfer. These excellent features allow the use of MnO@C nanocomposites as lithium-ion battery and supercapacitor electrodes for energy storage, with high reversible capacity at large current densities, as well as excellent cycling and mechanical stabilities. Moreover, this MnO@C nanocomposite has also demonstrated a high sensitivity for H2O2 detection, and also exhibited attractive potential for the tumor cell analysis. [ABSTRACT FROM AUTHOR]

Biomass burning is a major and growing contributor to particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5). Such impacts (especially individual impacts from each burning source) are quantified using the Community Multiscale Air Quality (CMAQ) Model, a chemical transport model (CTM). Given the sensitivity of CTM results to uncertain emission inputs, simulations were conducted using three biomass burning inventories. Shortcomings in the burning emissions were also evaluated by comparing simulations with observations and results from a receptor model. Model performance improved significantly with the updated emissions and speciation profiles based on recent measurements for biomass burning: mean fractional bias is reduced from 22% to 4% for elemental carbon and from 18% to 12% for organic matter; mean fractional error is reduced from 59% to 50% for elemental carbon and from 55% to 49% for organic matter. Quantified impacts of biomass burning on PM2.5 during January, March, May, and July 2002 are 3.0, 5.1, 0.8, and 0.3 μg m-3 domainwide on average, with more than 80% of such impacts being from primary emissions. Impacts of prescribed burning dominate biomass burning impacts, contributing about 55% and 80% of PM2.5 in January and March, respectively, followed by land clearing and agriculture field burning. Significant impacts of wildfires in May and residential wood combustion in fireplaces and woodstoves in January are also found. [ABSTRACT FROM AUTHOR]

A two-dimensional (2-D) particle-in-cell (PIC) model was used to study plasma immersion ion implantation (PIII) process of the ball bearing. In the simulation, distributions of the normalized potential and the accumulated incident dose were calculated. In addition, the relationship among the minimum distance between neighboring ball bearings without sheath overlap, the implantation voltage, the plasma density, and the pulsewidth was obtained. When the voltage is –10 kV, the plasma density is 2.95 × 108 cm-3 and the pulsewidth is 10 μs; the minimum distance without sheath overlap is 38.0 cm. To evaluate the model, the potential in the sheath was measured using a probe. Experimental results are in agreement with the calculated values. The simulation results reveal that a large number of ions are implanted into the top part of the ball bearing, which shows bad dose uniformity. When the ball bearing is revolved during PIII treatment, the dose uniformity can be improved to 91.25% at least. [ABSTRACT FROM AUTHOR]

The ability to produce outer membrane projections in the form of tubular membrane extensions (MEs) and membrane vesicles (MVs) is a widespread phenomenon among diderm bacteria. Despite this, our knowledge of the ultrastructure of these extensions and their associated protein complexes remains limited. Here, we surveyed the ultrastructure and formation of MEs and MVs, and their associated protein complexes, in tens of thousands of electron cryo- tomograms of ~90 bacterial species that we have collected for various projects over the past 15 years (Jensen lab database), in addition to data generated in the Briegel lab. We identified outer MEs and MVs in 13 diderm bacterial species and classified several major ultrastructures: (1) tubes with a uniform diameter (with or without an internal scaffold), (2) tubes with irregular diameter, (3) tubes with a vesicular dilation at their tip, (4) pearling tubes, (5) connected chains of vesicles (with or without neck- like connectors), (6) budding vesicles and nanopods. We also identified several protein complexes associated with these MEs and MVs which were distributed either randomly or exclusively at the tip. These complexes include a secretin- like structure and a novel crown- shaped structure observed primarily in vesicles from lysed cells. In total, this work helps to characterize the diversity of bacterial membrane projections and lays the groundwork for future research in this field. [ABSTRACT FROM AUTHOR]

Carbonaceous aerosols have great influence on the air quality, human health and climate change. Except for organic carbon (OC) and elemental carbon (EC), brown carbon (BrC), mainly originates from biomass burning, as a group of OC with strong absorption from the visible to near ultraviolet wavelengths, makes a considerable contribution to global warming. Large amounts of studies have reported long-term observation of OC and EC concentrations throughout the word, but studies of BrC based on long-term observations are rather limited. In this study, we established two-wavelength method (658 nm and 405 nm) applied in the Sunset thermo/optical carbon analyzer. Based on one-year observation, we firstly investigated the characteristics, meteorological impact and transport process of OC and EC. Due to BrC absorbs light at 405 nm more effectively than 658 nm, we defined the enhanced concentrations (dEC =EC405 nm—EC658 nm) and gave the possibility to provide an indicator of BrC. The receptor model and MODIS fire information were used to identify the presence of BrC aerosols. Our results showed that the carbonaceous aerosols concentrations were highest in winter and lowest in summer. Traffic emission was an important source of carbonaceous aerosols in Nanjing. Receptor model results showed that strong local emissions were found in OC and EC aerosols, however dEC aerosols were significantly affected by regional or long-range transport. The dEC/OC and OC/EC ratios showed similar diurnal patterns and the dEC/OC increased when the OC/EC ratios increased, indicating strong secondary sources or biomass burning contributions to dEC. Two biomass burning events both in summer and winter were analyzed and the results showed that the dEC concentrations were obvious higher in biomass burning days, however, no similar levels of the OC and EC concentrations were found both in biomass burning days and normal days in summer, suggesting that biomass burning emission made a great contribution to dEC and the sources of OC and EC were more complicated. Large number of open fire counts from the northwest and southwest areas of the study site were monitored in winter, significantly contributed to OC, EC and dEC. In addition, the near-by YRD area was one of the main potential source areas of dEC, suggesting that anthropogenic emissions could also be important sources of dEC. The results proved that dEC can be an indicator of BrC in biomass burning days. Our modified two-wavelength instrument provided more information than traditional single-wavelength thermo/optical carbon analyzer and gave a new idea about the measurement of BrC, the application of dEC data need to be further investigated. [ABSTRACT FROM AUTHOR]

A new ion source (IS) utilizing vacuum ultraviolet (VUV) light is developed and characterized for use with iodide-chemical ionization mass spectrometers (I−-CIMS). The VUV-IS utilizes a compact krypton lamp that emits light in two wavelength bands corresponding to energies of ~10.0 and 10.6 eV. The VUV light photoionizes either methyl iodide (ionization potential, IP = 9.54 ± 0.02 eV) or benzene (IP = 9.24378 ± 0.00007 eV) to form cations and photoelectrons. The electrons react with methyl iodide to form I− which serves as the reagent ion for the CIMS. The VUV-IS is characterized by measuring the sensitivity of a quadrupole CIMS (Q-CIMS) to formic acid, molecular chlorine, and nitryl chloride under a variety of flow and pressure conditions. The sensitivity of the Q-CIMS, with the VUV-IS, reached up to ~700 Hz pptv−1, with detection limits of less than 1 pptv for a one minute integration period. The reliability of the Q-CIMS with a VUV-IS is demonstrated with data from a month long ground-based field campaign. The VUV-IS is further tested by operation on a high resolution time-of-flight CIMS (TOF-CIMS). Sensitivities greater than 25 Hz pptv−1 were obtained for formic acid and molecular chlorine, which were similar to that obtained with a radioactive source. In addition, the mass spectra from sampling ambient air was cleaner with the VUV-IS on the TOF-CIMS compared to measurements using a radioactive source. These results demonstrate that the VUV lamp is a viable substitute for radioactive ion sources on I−-CIMS systems for most applications. In addition, the VUV-IS can likely be extended to other reagent ions, such as SF6− which are formed from high IP electron attachers, by the use of absorbers such as benzene to serve as a source of photoelectrons. [ABSTRACT FROM AUTHOR]

The study showed the synthesis of nickel-molybdenum binary metal complex Ni(en)3MoO4 with high purity from the impregnating solution. The complex was characterized and confirmed by single-crystal XRD, FT-IR and TGA. The binary transition metal complex was impregnated to γ-Al2O3 to prepare hydrodesulfurization catalyst. The catalyst was characterized by low temperature N2 adsorption-desorption isotherms, XRD and HRTEM. No molybdenum and nickel species were observed over the hydrodesulfurization catalyst surface, and the average slab length and layer number of the MoS2 crystallites in the catalyst are 2.6 nm and 2.3, respectively. The results indicated the high dispersion of active metal species over support. The DBT conversion of the catalyst can reach 91.4%, and the overall pseudo-first order rate constant kDBT is 3.1×10-4 gcat-1 s-1. The result showed the catalyst possessed good catalytic activity and Ni(en)3MoO4 can make efficient precursor to produce hydrotreating catalyst. [ABSTRACT FROM AUTHOR]

Hydroperoxyl radical (HO2) is a key species to atmospheric chemistry. At warm temperatures, the HO2 and NO2 come to a rapid steady state with pernitric acid (HO2NO2). This paper presents the derivation of HO2 from observations of HO2NO2 and NO2 in metropolitan Atlanta, US, in winter 2014 and summer 2015. HO2 was observed to have a diurnal cycle with morning concentrations suppressed by high NO from the traffic. At night, derived HO2 levels were nonzero and exhibited correlations with O3 and NO3, consistent with previous studies that ozonolysis and oxidation by NO3 are sources of nighttime HO2. Measured and model calculated HO2 were in reasonable agreement: Without the constraint of measured HO2NO2, the model reproduced HO2 with a model-to-observed ratio (M/O) of 1.27 (r = 0.54) for winter, 2014, and 0.70 (r = 0.80) for summer, 2015. Adding measured HO2NO2 as a constraint, the model predicted HO2 with M/O = 1.13 (r = 0.77) for winter 2014 and 0.90 (r = 0.97) for summer 2015. These results demonstrate the feasibility of deriving HO2 from HO2NO2 measurements in warm regions where HO2NO2 has a short lifetime. [ABSTRACT FROM AUTHOR]

Objective: To investigate the reperfusion time in patients with ST-segment elevation myocardial infarction (STEMI) in Henan Province, China, and discuss the strategies for shortening that period. Methods: The reperfusion times of 1556 STEMI cases in 30 hospitals in Henan Province were analyzed from January 2008 to August 2012, including 736 cases from provincial hospitals, 462 cases from municipal hospitals and 358 cases from country hospitals. The following data: Time period 1 (from symptom onset to first medical contact), Time period 2 (from first medical contact to diagnosis), Time period 3 (from the diagnosis to providing consent), Time period 4 (from the time of providing consent to the beginning of treatment) and Time period 5 (from the beginning of treatment to the patency) were recorded and analyzed. Results: In patients receiving primary percutaneous coronary intervention, the door-to-balloon time of provincial hospitals and municipal hospitals was 172±13 minutes and 251±14 minutes, respectively. The hospitals at both levels had a delay comparison of 90 minutes largely caused by the delay in the time for obtaining consent. In patients receiving thrombolysis treatment, the door-to-needle times of provincial hospitals, municipal hospitals and country hospitals were 86±7, 91±7 and 123±11 minutes, respectively. The hospitals at all levels had delays lasting more than 30 minutes, which was mainly attributed to the delay in the time for providing consent. Compared with the time required by the guidelines, the reperfusion time of patients with STEMI in China is evidently delayed. In terms of China's national conditions, the door-toballoon time is too general. Therefore, we suggest refining this time as the first medical contact-diagnosis time, consent provision time, therapy preparation time and the start of therapy balloon time. Conclusion: Compared to the time required by the guidelines, the reperfusion time of patients with STEMI in China was obviously greater. In terms of China's national conditions, the door to balloon time is not applicable. So it is suggested to refine it as the first medical contact-diagnosis time, providing consent time, therapy prepare time and the start of therapy - balloon time. [ABSTRACT FROM AUTHOR]

Composites of styrene butadiene rubber (SBR), hydrogenated acrylonitrile-butadiene rubber (HNBR) and silica were prepared. Sulfur (S), dicumyl peroxide (DCP) and a combination of S and DCP (M) were used as curing agents, respectively. The morphology of the composites with different blend ratio was examined to correlate with observations on mechanical properties by scanning electron microscopy. The effects of blend ratio and curing systems on the curing characteristics and mechanical properties, such as stress-strain behavior, tensile strength, elongation at break and hardness of SBR/HNBR/Silica composites, were studied. Composites prepared by M curing systems showed comparatively better mechanical properties, wet traction and rolling resistance than S and D curing systems. The tensile strength, tear strength, and elongation at break were improved by adding HNBR for M curing systems. The wet traction of the vulcanizates containing HNBR was better than that of the vulcanizates without HNBR. A relatively uniform dispersion of silica was observed for SBR/HNBR/silica compositions compared with SBR/silica composites. [ABSTRACT FROM AUTHOR]