China is facing serious haze problems due to the levels of fine particulate matter (PM2.5). Therefore, source apportionment of PM2.5 is required for formulating effective air pollution control strategies. The fast increase of the vehicle population, especially in the megacities of China in recent years, makes vehicular emissions one of the most important sources of PM2.5 and has led to it receiving great attention and concern. There is an urgent need to accurately and quantitatively estimate the contribution of vehicular emissions. A growing number of studies have been conducted for source apportionment of PM2.5 in China and report the contribution from vehicular emissions using different methods. However, it is still a big challenge as to how vehicular emissions can be accurately quantified.
This study summarizes the various methods that have been used to identify and quantify the vehicular emissions contribution to PM2.5 in published literature by international and domestic scientists, lists advantages and disadvantages of each method, and proposes ways to reduce its uncertainty. In general, methods for estimating vehicular emission contributions in previous studies include emission inventory based methods, chemical transport models, receptor models, hybrid models etc. The receptor model based method is the most commonly applied method in China. Source profiles of vehicular emissions based on source testing in China, and organic and inorganic tracers used for diagnosing vehicular emissions, which are two key factors for quantifying vehicular exhaust in receptor models, are also summarized here.
Contributions of vehicular emissions to ambient PM2.5 reported in different areas in China, especially Beijing, are listed and compared. It can be seen that the contribution of vehicular emissions to PM2.5 varies significantly with the study area, year of the study, as well as the methods in use. The vehicular emissions contribution to PM2.5 in Beijing is reported to be in the range of 4%–36% based on previous studies from 1989 to 2014, primarily using the receptor model method.
This work also points out challenges in the current studies, provides suggestions in order to better quantify the contribution from vehicular emissions in China, and proposes ways to optimize the methods. For example, besides primary emissions from vehicular exhaust, quantifying secondary organic and inorganic aerosols formed from gaseous and particulate precursors from vehicular emissions, as well as traffic related sources (e. g., resuspended road dust) is also a big concern and challenge for accurately estimating vehicular emissions. In addition, there is still a pressing need to develop more detailed and comprehensive chemical profiles and an emissions inventory of vehicular emissions, with standardized sampling and analytical protocols in the future. An improved emission inventory with high time, spatial and species resolutions should be established. A hybrid model, which integrates emission inventory, chemical transport model, receptor model and observational data is a promising direction to provide an accurate estimate of vehicular emissions in the future. In addition, there is a need to develop a system to verify the results obtained from a source apportionment study.
The discovery of sodium taurocholate cotransporting polypeptide (NTCP) as the hepatitis B virus (HBV) receptor enabled researchers to create hepatoma cell lines susceptible to HBV infection. Infection in current systems, however, is inefficient and virus fails to spread. Infection efficiency is enhanced by treating cells with polyethylene glycol 8000 (PEG) during infection. However, this alone does not promote virus spread. Here we show that maintaining PEG in culture medium increases the rate of infection by at least one order of magnitude, and, most importantly, promotes virus spread. To demonstrate the utility of this system, we show that two interferon-stimulated genes (ISGs), ISG20 and tetherin, restrict HBV spread in NTCP-expressing hepatoma cells. Thus, this protocol can be easily applied to existing cell culture systems to study the complete HBV life cycle, including virus spread.
Practical and optimal reduction of watershed loads under deep uncertainty requires sufficient search alternatives and direct evaluation of robustness. These requirements contribute to the understanding of the tradeoff between cost and robustness; while they are not well addressed in previous studies. This study thereby (a) uses preconditioning technique in Evolutionary Algorithm to reduce unnecessary search space, which enables a sufficient search; and (b) derives Robustness Index (RI) as a second-tier optimization objective function to achieve refined solutions (solved by GA) that address both robustness and optimality. Uncertainty-based Refined Risk Explicit Linear Interval Programming is used to generate alternatives (solved by Controlled elitist NSGA-II). The robustness calculation error is also quantified. Proposed approach is applied to Lake Dianchi, China. Results demonstrate obvious improvement in robustness after conducting sufficient search and negative robustness-optimality trade-offs, and provides a detailed characteristic of robustness that can serve as references for decision-making.
The challenge of continuous printing in high-efficiency large-area organic solar cells is a key limiting factor for their widespread adoption. A materials design concept for achieving large-area, solution-coated all-polymer bulk heterojunction solar cells with stable phase separation morphology between the donor and acceptor is presented. The key concept lies in inhibiting strong crystallization of donor and acceptor polymers, thus forming intermixed, low crystallinity, and mostly amorphous blends. Based on experiments using donors and acceptors with different degree of crystallinity, the results show that microphase separated donor and acceptor domain sizes are inversely proportional to the crystallinity of the conjugated polymers. This methodology of using low crystallinity donors and acceptors has the added benefit of forming a consistent and robust morphology that is insensitive to different processing conditions, allowing one to easily scale up the printing process from a small-scale solution shearing coater to a large-scale continuous roll-to-roll (R2R) printer. Large-area all-polymer solar cells are continuously roll-to-roll slot die printed with power conversion efficiencies of 5%, with combined cell area up to 10 cm2. This is among the highest efficiencies realized with R2R-coated active layer organic materials on flexible substrate.
For devices with a 15 micron anode-to-cathode distance, nearly 1.5 times increase in the blocking (breakdown) voltage (from 692 to 1030 V) has been achieved by replacing the alloyed Ohmic contact at the anode electrode of the conventional MOS gated hybrid-anode lateral field-effect rectifier (CMLFER) with a low barrier Schottky contact. The new Schottky-MOS hybrid-anode lateral field-effect rectifier is found to offer comparable low onset voltage (V-ON of 0.68 +/- 0.13 versus 0.65 +/- 0.11 V for CMLFER) independent of the anode-to- cathode distance. The immunity of the punch through caused by drain induced barrier lowering effect is obtained through the low barrier Schottky contact in anode, which is believed to be responsible for the reduction in the leakage current, and the improvement of rectifier breakdown voltage.
53#,a strain of efficient alginate degrading bacteria,is isolated from rotted kelp using sodium alginate as the only carbon resource. Strain 53# is identified as Paenibacillus agaridevorans based on physiological characteristics and 16S rRNA sequencing. The optimaltion yield condition of strain 53# is identified at ${\rm{pH = 8}}$,$T = 25^\circ {\rm{C}}$,NaCl 15 g/L,and sodium alginate 15 g/L by orthogonal experiment and analysis,and the highest enzyme activity is ${\rm{390}}{\rm{.53}} \pm {\rm{17}}{\rm{.32\;U/mL}}$. Strain 53# has the advantages such as being cultivated easily,producing enzyme fast and having high enzyme activity. It can achieve a high efficiency for saccharification of alginate and thus has potential value to be utilized in the production of bioethanol from brown algae.以海藻酸钠为唯一碳源,从天然腐烂海带中筛选得到一株高效褐藻胶降解菌株53#,经形态学观察和16S rRNA鉴定,确定为类芽孢杆菌Paenibacillus agaridevorans。采用正交试验方法,以pH、温度、NaCl浓度和海藻酸钠初始浓度为影响因素,对该菌株的产酶条件进行优化,得到53#菌的 最佳产酶条件: ${\rm{pH = 8}}$,25℃,NaCl浓度15 g/L,海藻酸钠初始浓度15 g/L。在最佳产酶条件下,褐藻胶裂解酶最大酶活可达${\rm{390}}{\rm{.53}} \pm {\rm{17}}{\rm{.32\;U/mL}}$。筛选得到的类芽孢杆菌Paenibacillus agaridevorans 53#具有易于培养、产酶速度快和酶活力高等优点,能够实现褐藻胶的高效糖化,在褐藻生产生物乙醇领域具有潜在利用价值。
The self-assemblies of polycyclic aromatic diimide (PAI) compounds on solid surfaces have attracted great interest because of the versatile and attractive properties for application in organic electronics. Here, a planar guest species (coronene) selectively adsorbs on the helicene-typed PAI1 monolayer strongly, depending on the conjugated cores of these PAIs. PAI1 molecule displays evidently a bowl structure lying on the highly oriented pyrolytic graphite surface due to the torsion of the "C"-shaped fused benzene rings. In combination with density functional theory calculation, the selective inclusion of coronene atop the backbone of the PAI1 array might be attributed to the bowl structure, which provides a groove for immobilizing coronene molecules. On the other planar densely packed arrays, it is difficult to observe the unstable adsorption of coronene. The selective addition of coronene molecules would be a strategic step toward the controllable multicomponent supramolecular architectures.
High-sensitivity plasmonic refractive index sensors show great applications in the areas of the biomedical diagnostics, healthcare, food safety, environmental monitoring, homeland security, and chemical reaction. However, the unstable and complicated environments considerably limit their practical applications. By employing the independent double Fano resonances in a simple metallic grating, we experimentally demonstrated a self-reference plasmonic sensor, which significantly reduces the error contributions of the light intensity fluctuations in the long-distance propagation and local temperature variations at the metallic grating, and the detection accuracy is guaranteed. The numerical simulation shows that the two Fano resonances have different originations and are independent with each other. As a result, the left Fano resonance is quite sensitive to the refractive index variations above the metal surface, while the right Fano resonance is insensitive to that. Experimentally, a high figure of merit (FOM) of 31 RIU-1 and FOM* of 860 RIU-1 are realized by using the left Fano resonance. More importantly, by using the right Fano resonance as a reference signal, the influence of the light intensity fluctuations and local temperature variations are monitored and eliminated in the experiment. This simple self-reference plasmonic sensor based on the double Fano resonances may find important applications in high-sensitive and accurate sensing under the unstable and complicated environments, as well as multi-parameter sensing.
Learning the spatial-temporal representation of motion information is crucial to human action recognition. Nevertheless, most of the existing features or descriptors cannot capture motion information effectively, especially for long-term motion. To address this problem, this paper proposes a long-term motion descriptor called sequential Deep Trajectory Descriptor (sDTD). Specifically, we project dense trajectories into two-dimensional planes, and subsequently a CNN-RNN network is employed to learn an effective representation for long-term motion. Unlike the popular two-stream ConvNets, the sDTD stream is introduced into a three-stream framework so as to identify actions from a video sequence. Consequently, this three-stream framework can simultaneously capture static spatial features, short-term motion and long-term motion in that video. Extensive experiments were conducted on three challenging datasets: KTH, HMDB51 and UCF101. Experimental results show that our method achieves state-of-the-art performance on the KTH and UCF101 datasets, and is comparable to the state-of-the-art methods on the HMDB51 dataset.
