Single-scan 2D DOSY NMR spectroscopy

Spatial encoding is a particular kind of spin manipulation that enables the acquisition of multidimensional NMR spectra within a single scan. This encoding has been shown to possess a general applicability and to enable the completion of arbitrary nD NMR acquisitions within a single transient. The present study explores its potential towards the acquisition of 2D DOSY spectra, where the indirect dimension is meant to encode molecular displacements rather than a coherent spin evolution. We find that in its simplest form this extension shows similarities with methods that have been recently discussed for the single-scan acquisition of this kind of traces; still, a number of advantageous features are also evidenced by the “ultrafast” modality hereby introduced. The principles underlying the operation of this new single-scan 2D DOSY approach are discussed, its use is illustrated with a variety of sequences and of samples, the limitations of this new experiment are noted, and potential extensions of the methodology are mentioned.     

基于高精度定位的卫星导航板卡性能对比路测

高精度定位与精细化导航的实现,至少需要具备两个条件:高精度定位网络、终端定位芯片或板卡。在高精度定位网络准备之际,终端板卡的能力成了重要关注点。基于此,文章依托中移智行的高精度定位精品网络,选择了三款主流板卡进行测试,对板卡接入中国移动高精度定位网后的功效与性能进行验证。测试表明,在中国移动高精度定位网络的良好支撑下,K700(三系统单频)、K706(三系统六频)、K803(四系统十三频)均能很好地支撑交通参与者获得良好的高精度定位服务。     

New massive gravity domain walls

The properties of the asymptotic AdS₃${\mathit{AdS}}_3$ space–times representing flat domain walls (DW's) solutions of the new massive 3D gravity with scalar matter are studied. Our analysis is based on first order BPS-like equations involving an appropriate superpotential. The Brown–York boundary stress-tensor is used for the calculation of DW's tensions as well as of the CFT₂${\mathit{CFT}}_2$ central charges. The holographic renormalization group flows and the phase transitions in specific deformed CFT₂${\mathit{CFT}}_2$ dual to 3D massive gravity model with quadratic superpotential are discussed.     

Significant effects of transport on nanoparticles during new particle formation events in the atmosphere of Beijing

The mechanisms of new particle formation (NPF) events that occurred under high aerosol loadings (“polluted” NPF) in the atmosphere have been unclear, which has inhibited the precision of particle pollution control. To deepen the understanding of how the “polluted” NPF events occur, a one-month comprehensive measurement was conducted in the atmosphere of Beijing during the summer of 2016. The “clean” NPF events (frequency = 22%) (condensation sink, CS < 0.015 s⁻¹) were found to be caused by local nucleation and growth. The “polluted” NPF events (frequency = 28%) (CS > 0.015 s⁻¹) were influenced by both local nucleation-growth and regional transport, and the contributions from the two factors to 6–25 nm particle number concentration were 60% and 40%, respectively. This study emphasized the importance of the transport for nanoparticles in relatively polluted atmospheres, and for that the regional joint particle pollution control would be an essential policy.