Source origins, modeled profiles, and apportionments of halogenated hydrocarbons in the greater Pearl River Delta region, southern China

We analyze 16-month data of 13 major halocarbons measured at a southern China coastal site in the greater Pearl River Delta (PRD). A total of 188 canister air samples were collected from August 2001 to December 2002. Overall inspection indicated that CH2Cl2, C2Cl 4, and C2HCl3 had similar temporal variations while CFC-11, CFC-12, and CFC-113 showed the same emission patterns during the sampling period. Diurnal variations of halocarbons presented different patterns during ozone episode days, mainly related to emission strength, atmospheric dispersion, and photochemical lifetimes. For further statistics and source appointment, Lagrangian backward particle release simulations were conducted to help understand the potential source regions of all samples and classify them into different categories, including local Hong Kong, inner PRD, continental China, and marine air masses. With the exception of HCFC-142b, the mixing ratios of all halocarbons in marine air were significantly lower than those in urban and regional air (p < 0.01), whereas no significant difference was found between urban Hong Kong and inner PRD regional air, reflecting the dominant impact of the greater PRD regional air on the halocarbon levels. The halocarbon levels in this region were significantly influenced by anthropogenic sources, causing the halocarbon mixing ratios in South China Sea air to be higher than the corresponding background levels, as measured by global surface networks and by airborne missions such as Transport and Chemical Evolution Over the Pacific. Interspecies correlation analysis suggests that CHCl3 is mainly used as a solvent in Hong Kong but mostly as a feedstock for HCFC-22 in the inner PRD. Furthermore, CH3Cl is often used as a refrigerant and emitted from biomass/biofuel burning in the inner PRD. A positive matrix factorization receptor model was applied to the classified halocarbon samples in the greater PRD for source profiles and apportionments. Seven major sources were identified and quantified. Emissions from solvent use were the most significant source of halocarbons (71 ± 9%), while refrigeration was the second largest contributor (18 ± 2%). By further looking at samples from the inner PRD and from urban Hong Kong separately, we found that more solvent was used in the dry cleaning industry in Hong Kong, whereas the contribution of cleaning solvent in the electronic industry was higher in the inner PRD. Besides the two common sources of solvent use and refrigeration, the contributions of biomass/biofuel burning and feedstock in chemical manufacturing was remarkable in the inner PRD but negligible in Hong Kong. These findings are of help to effectively control and phase out the emissions of halocarbons in the greater PRD region of southern China Copyright 2009 by the American Geophysical Union

Relationships of trace gases and aerosols and the emission characteristics at Lin'an, a rural site in eastern China, during spring 2001

We present measurements of trace gases and fine aerosols obtained from a rural site in eastern China during 18 February to 30 April 2001. The field program aimed to characterize the variations in aerosol and gaseous pollutant concentrations and the emission signatures from the inland region of eastern China in the spring season. The data included O3, CO, NO, NOy*, SO2, methane, C2-C8 nonmethane hydrocarbons (NMHCs), C 1-C2 halocarbons, and the chemical composition of PM2.5. The average hourly mixing ratios (±standard deviation) of CO, SO2, and NOy* were 677 (±315) ppbv, 15.9 (±14.6) ppbv, and 13.8 (±7.2) ppbv, respectively. The mean daytime ozone mixing ratio was 41 (± 19) ppbv. The most abundant NMHC was ethane (3189 ± 717 pptv), followed by ethyne (2475 ± 1395 pptv), ethene (1679 ± 1455 pptv), and toluene (1529 ± 1608 pptv). Methyl chloride was the most abundant halocarbon (1108 ± 653 pptv). The average concentrations of particulate organic matter (POM, as organic carbon, OC, times 1.4) and elemental carbon (EC) in PM2.5 were 21.5 (±7) μg/m3 and 2.5 (±0.7) μg/m3, respectively, and sulfate and nitrate levels were 17.3 (±6.6) and 6.5 (±4) μg/m3, respectively. CO showed moderate to good correlation with NOy* (r2 = 0.59), OC (r2 = 0.65), CH3Cl (r2 = 0.59), soluble potassium (r2 = 0.53), and many NMHCs, indicating contributions from the burning of biofuel/biomass. CO also correlated with an industrial tracer, C2Cl4, indicative of some influence from industrial sources. SO2, on the other hand, correlated well with EC (r2 = 0.56), reflecting the contribution from the burning of coal. Ammonium was sufficiently abundant to fully neutralize sulfate and nitrate, indicating that there were strong emissions of ammonia from agricultural activities. Silicon and calcium had poor correlations with iron and aluminum, revealing the presence of source(s) for Si and Ca other than from soil. Examination of C2H2/CO, C3H8/C 2H6, nitrate/(nitrate + NOy* , and sulfate/(SO2 + sulfate) suggested that relatively fresh air masses had been sampled at the study site in the spring season. Comparison of the observed ratios/slopes with those derived from emission inventories showed that while the observed SO2/NO y* ratio (1.29 ppbv/ppbv) in March was comparable (within 20%) to the inventory-derived ratio for the study region, the measured CO/NOy* slope (37 ppbv/ppbv) was about 200% larger. The observed slope of CO relative to NMHC (including ethane, propane, butanes, ethene, and ethyne) also indicated the presence of excess CO, compared to the ratios from the inventories. These results strongly suggest that emissions of CO in eastern China have been underrepresented. The findings of this study highlight the importance of characterizing trace gases and aerosols within source regions of the Asian continent. The springtime results were also compared with data previously collected at the site in 1999-2000 and with those obtained on the Transport and Chemical Evolution over the Pacific (TRACE-P) aircraft and from a coastal site in South China for the same study period. Copyright 2004 by the American Geophysical Union

Broadband High-Gain SIW Cavity-Backed Circular-Polarized Array Antenna

© 2016 IEEE. A circularly polarized (CP) 4 × 4 array antenna based on substrate integrated waveguide (SIW) technology is presented. Circular polarization is achieved by applying the sequential rotation technique (SRT) with a well-designed sequential feed network and linear-polarized array elements. The proposed 4 × 4 array has a wide axial ratio (AR) bandwidth of 14% from 18.3 to 21.1 GHz with gain > 13 dBic. Then, the array is expanded to achieve higher gains. A 16 × 16-element array is designed, fabricated, and tested. Test results show that the 16 × 16 array has an AR bandwidth of 13.8% from 18.5 to 21.25 GHz and a peak gain of 25.9 dBic at 20.5 GHz

Cation-swapped homogeneous nanoparticles in perovskite oxides for high power density

Exsolution has been intensively studied in the fields of energy conversion and storage as a method for the preparation of catalytically active and durable metal nanoparticles. Under typical conditions, however, only a limited number of nanoparticles can be exsolved from the host oxides. Herein, we report the preparation of catalytic nanoparticles by selective exsolution through topotactic ion exchange, where deposited Fe guest cations can be exchanged with Co host cations in PrBaMn1.7Co0.3O5+delta. Interestingly, this phenomenon spontaneously yields the host PrBaMn1.7Fe0.3O5+delta, liberating all the Co cations from the host owing to the favorable incorporation energy of Fe into the lattice of the parent host (Delta E-incorporation = -0.41 eV) and the cation exchange energy (Delta E-exchange = -0.34 eV). Remarkably, the increase in the number of exsolved nanoparticles leads to their improved catalytic activity as a solid oxide fuel cell electrode and in the dry reforming of methane

International Veterinary Epilepsy Task Force recommendations for a veterinary epilepsy-specific MRI protocol

Epilepsy is one of the most common chronic neurological diseases in veterinary practice. Magnetic resonance imaging (MRI) is regarded as an important diagnostic test to reach the diagnosis of idiopathic epilepsy. However, given that the diagnosis requires the exclusion of other differentials for seizures, the parameters for MRI examination should allow the detection of subtle lesions which may not be obvious with existing techniques. In addition, there are several differentials for idiopathic epilepsy in humans, for example some focal cortical dysplasias, which may only apparent with special sequences, imaging planes and/or particular techniques used in performing the MRI scan. As a result, there is a need to standardize MRI examination in veterinary patients with techniques that reliably diagnose subtle lesions, identify post-seizure changes, and which will allow for future identification of underlying causes of seizures not yet apparent in the veterinary literature. There is a need for a standardized veterinary epilepsy-specific MRI protocol which will facilitate more detailed examination of areas susceptible to generating and perpetuating seizures, is cost efficient, simple to perform and can be adapted for both low and high field scanners. Standardisation of imaging will improve clinical communication and uniformity of case definition between research studies. A 6–7 sequence epilepsy-specific MRI protocol for veterinary patients is proposed and further advanced MR and functional imaging is reviewed

3D printing of twisting and rotational bistable structures with tuning elements

Three-dimensional (3D) printing is ideal for the fabrication of various customized 3D components with fine details and material-design complexities. However, most components fabricated so far have been static structures with fixed shapes and functions. Here we introduce bistability to 3D printing to realize highly-controlled, reconfigurable structures. Particularly, we demonstrate 3D printing of twisting and rotational bistable structures. To this end, we have introduced special joints to construct twisting and rotational structures without post-assembly. Bistability produces a well-defined energy diagram, which is important for precise motion control and reconfigurable structures. Therefore, these bistable structures can be useful for simplified motion control in actuators or for mechanical switches. Moreover, we demonstrate tunable bistable components exploiting shape memory polymers. We can readjust the bistability-energy diagram (barrier height, slope, displacement, symmetry) after printing and achieve tunable bistability. This tunability can significantly increase the use of bistable structures in various 3D-printed components

Aggregated impact of allowance allocation and power dispatching on emission reduction

Climate change has become one of the most important issues for the sustainable development of social well-being. China has made great efforts in reducing CO2 emissions and promoting clean energy. Pilot Emission Trading Systems (ETSs) have been launched in two provinces and five cities in China, and a national level ETS will be implemented in the third quarter of 2017, with preparations for China’s national ETS now well under way. In the meantime, a new round of China’s electric power system reform has entered the implementation stage. Policy variables from both electricity and emission markets will impose potential risks on the operation of generation companies (GenCos). Under this situation, by selecting key variables in each domain, this paper analyzes the combined effects of different allowance allocation methods and power dispatching models on power system emission. Key parameters are set based on a provincial power system in China, and the case studies are conducted based on dynamic simulation platform for macro-energy systems (DSMES) software developed by the authors. The selected power dispatching models include planned dispatch, energy saving power generation dispatch and economic dispatch. The selected initial allowance allocation methods in the emission market include the grandfathering method based on historical emissions and the benchmarking method based on actual output. Based on the simulation results and discussions, several policy implications are highlighted to help to design an effective emission market in China

Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente

Observation of a ppb mass threshoud enhancement in \psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p}) decay

The decay channel $\psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p})$ is studied using a sample of $1.06\times 10^8$ $\psi^\prime$ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the $p\bar{p}$ invariant mass spectrum. The enhancement can be fit with an $S$-wave Breit-Wigner resonance function with a resulting peak mass of $M=1861^{+6}_{-13} {\rm (stat)}^{+7}_{-26} {\rm (syst)} {\rm MeV/}c^2$ and a narrow width that is $\Gamma<38 {\rm MeV/}c^2$ at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with those of any known meson resonance.Comment: 5 pages, 3 figures, submitted to Chinese Physics