PriorVAE: encoding spatial priors with variational autoencoders for small-area estimation

Gaussian processes (GPs), implemented through multivariate Gaussian distributions for a finite collection of data, are the most popular approach in small-area spatial statistical modelling. In this context, they are used to encode correlation structures over space and can generalize well in interpolation tasks. Despite their flexibility, off-the-shelf GPs present serious computational challenges which limit their scalability and practical usefulness in applied settings. Here, we propose a novel, deep generative modelling approach to tackle this challenge, termed PriorVAE: for a particular spatial setting, we approximate a class of GP priors through prior sampling and subsequent fitting of a variational autoencoder (VAE). Given a trained VAE, the resultant decoder allows spatial inference to become incredibly efficient due to the low dimensional, independently distributed latent Gaussian space representation of the VAE. Once trained, inference using the VAE decoder replaces the GP within a Bayesian sampling framework. This approach provides tractable and easy-to-implement means of approximately encoding spatial priors and facilitates efficient statistical inference. We demonstrate the utility of our VAE two-stage approach on Bayesian, small-area estimation tasks.     

Synthesis of mesoporous tungsten oxide nanofibers using the electrospinning method

Mesoporous tungsten oxide nanofibers were synthesized via a 500 °C thermal treatment of composite nanofibers prepared by electrospinning an ethanol solution consisting of tungsten ethoxide, P123 triblock copolymer, and polyvinylpyrrolidone. The as-electrospun composites exhibited unwoven nanofibers with an average diameter of 233 nm and a smooth surface morphology. During the calcination process, the composite nanofibers were shrunk to 85 nm in diameter and converted into rough, wormhole-like nanofibers. These were formed by agglomerating polycrystalline WO₃ particles of 10–30 nm along the axial direction. Furthermore, a measured pore-size distribution indicated that this nanofiber mat had different types of meso-sized porosities, which may have resulted from their wormhole-like structures and inter-fiber voids. In addition, it was observed to have the intra-grain porosity with the diameter of about 1.0 nm.     

Tree colonization trends on a sediment bar after a major flood

Tree mortality and regeneration in riparian areas are greatly influenced by flooding. The elevational distribution of Salix spp. and Robinia pseudoacacia were investigated by observing densities and standing conditions before and after a major flood on a sediment bar in the middle reaches of the Arakawa River in Kumagaya, Japan. The subsequent tree recruitment was also examined. R. pseudoacacia was easily washed away with the eroded sediment, whereas Salix spp. was found to be more tolerant. Both species were able to survive even after collapsing, provided that their roots were fully or partially embedded in the sediment. Re‐shooting of collapsed trees, rather than emergence from saplings (either by seeds or vegetative fragments), was observed to be the major method of recruitment after the flood. Therefore, tree density before the flood was unchanged, unless the trees were subject to washing away. Salix spp. recruitment was mainly observed in low‐lying areas and R. pseudoacacia in elevated areas. Recruitment from saplings was species‐specific. Salix spp. at high elevations originated mainly from shoot fragments as they need high levels of moisture for seed germination and at higher elevations, sediment moisture content is very low. R. pseudoacacia, on other hand, originated mainly from roots and seeds. At a given elevation, past recruitment patterns indicated that the annual recruitment of trees increased with tree density up to a particular threshold of recruitment density. Further increases in tree density beyond that optimum value resulted in a decline in recruitment. Furthermore, threshold density was observed to increase along with elevation for R. pseudoacacia while declining with Salix spp. Copyright © 2010 John Wiley & Sons, Ltd.     

乌兹别克斯坦水资源变化及其对供给压力的影响

梳理文献资料,结合农业、遥感和气象水文产品数据,分析乌兹别克斯坦水资源变化及水资源供给压力。分析表明:自1980年以来,乌兹别克斯坦年平均取水量由59亿m~3增至102亿m~3,灌溉农业消耗了90%以上的水资源;尽管1992年以来耕地面积总体呈下降态势(200km~2/a),且高耗水作物种植比重下降(-3.24%),但受气候变暖的影响(0.31℃/(10a)),单位面积作物需水量持续增加(3.27mm/a),导致总的需水量仍呈增加态势(2.75亿m~3/a);与此同时,上游来水量减少以及上游国家用水的增加,将进一步加剧区域水资源短缺及供给压力。为应对水资源问题,乌兹别克斯坦需加强水管理,改进灌溉技术,提高用水效率,同时,需寻求完善跨境河流水资源分配与管理的途径。该研究有助于增进对乌兹别克斯坦水资源问题的认识,并为应对该问题提供科学依据,以及为"一带一路"合作发展提供支撑。     

The Carboxyl Terminal Regions of P0 Protein Are Required for Systemic Infections of Poleroviruses

P0 proteins encoded by poleroviruses Brassica yellows virus (BrYV) and Potato leafroll virus (PLRV) are viral suppressors of RNA silencing (VSR) involved in abolishing host RNA silencing to assist viral infection. However, other roles that P0 proteins play in virus infection remain unclear. Here, we found that C-terminal truncation of P0 resulted in compromised systemic infection of BrYV and PLRV. C-terminal truncation affected systemic but not local VSR activities of P0 proteins, but neither transient nor ectopic stably expressed VSR proteins could rescue the systemic infection of BrYV and PLRV mutants. Moreover, BrYV mutant failed to establish systemic infection in DCL2/4 RNAi or RDR6 RNAi plants, indicating that systemic infection might be independent of the VSR activity of P0. Partially rescued infection of BrYV mutant by the co-infected PLRV implied the functional conservation of P0 proteins within genus. However, although C-terminal truncation mutant of BrYV P0 showed weaker interaction with its movement protein (MP) when compared to wild-type P0, wild-type and mutant PLRV P0 showed similar interaction with its MP. In sum, our findings revealed the role of P0 in virus systemic infection and the requirement of P0 carboxyl terminal region for the infection.     

Environmental Kuznets Curve for carbon emissions in Pakistan: An empirical investigation

This study investigates the relationship between carbon emissions, income, energy consumption, and foreign trade in Pakistan for the period 1972–2008. By employing the Johansen method of cointegration, the study finds that there is a quadratic long-run relationship between carbon emissions and income, confirming the existence of Environmental Kuznets Curve for Pakistan. Moreover, both energy consumption and foreign trade are found to have positive effects on emissions. The short-run results have, however, denied the existence of the Environmental Kuznets Curve. The short-run results are unique to the existing literature in the sense that none of the long-run determinants of emissions is significant. The contradictory results of short- and long-run give policy makers the opportunity to formulate different types of growth policies for the two terms taking environmental issues into consideration. In addition, the uni-directional causality from growth to energy consumption suggests that the policy makers should not only focus on forecasting future demand for energy with different growth scenarios but also on obtaining the least cost energy. Furthermore, the absence of causality from emissions to growth suggests that Pakistan can curb its carbon emissions without disturbing its economic growth.     

Exhaust emission profiling of fatty acid methyl esters and NOx control studies using selective synthetic and natural additives

Clean Technologies and Environmental Policy - The present study was focused on the optimized biodiesel production using Moringa oleifera (M. oleifera) and rice bran oils, characterization, and...     

Downlink Radio Resource Management Through CoMP and Carrier Aggregation for LTE-Advanced Network

Long Term Evolution-Advanced (LTE-A) offers several new technologies to improve the performance of the user. However, poor received signal and interference from adjacent cells in the cell-edge area can reduce the efficiency of using individual technology. Therefore, the cell-edge users have lower throughput compared to the other users in the cell and LTE-A standard. An efficient downlink radio resource management scheme is proposed in this paper by combining the coordinated multipoint transmission and reception technique along with carrier aggregation technique to achieve higher throughput for the cell-edge user and better overall performance. The proposed method jointly transmits multiple component carriers to the cell-edge user from different cells to increase the bandwidth, strengthen the received signal, and reduce the interference while it satisfies several constraints. Modified largest weighted delay first packet scheduling algorithm is deployed for resource allocation, which takes into account the delay parameters, the probability of packet loss, and data rates of the user. The obtained system-level simulation results show that the proposed method significantly enhances the throughput performances, spectral efficiency, and fairness index, compared with the existing conventional methods.