The effect of Al3+ coordination structure on the propane dehydrogenation activity of Pt/Ga/Al2O3 catalysts

The effect of the Al2O3 structure on the performance of Pt/Ga/Al2O3 catalysts is investigated for the direct dehydrogenation of propane. The study unveils that the structure of Al3+determines the bulk structure of catalysts, particularly a high content of coordinatively unsaturated Al3+sites(penta-coordinated Al3+,denoted as Al3+penta) could lead to a remarkably improved dehydrogenation activity of the catalyst. The bulk characterization reveals that the sufficient amount of Al3+pentain Al2O3 benefit the dispersion of Pt and Ga2O3 on the Al2O3 support. At the same time, TPR results reveal that the presence of Pt facilitates the reduction of Ga2O3, likely due to the hydrogen spillover between the well dispersed Pt and Ga2O3,which consequently enhances the synergistic function between Pt and Ga2O3 in the dehydrogenation of propane. Recyclability tests demonstrate that the dehydrogenation activity stabilizes after three cycles over the Pt/Ga/Al2O3 catalyst.

Chemical components of PM_(2.5)in different seasons in Harbin,China

The seasonal characteristics of fine particulate matter(PM_(2.5))were investigated from October 2020 to April 2021(spreading fall,winter and spring)in Harbin,a city located in northeast China.The mass concentrations of PM_(2.5)in winter were significantly higher than those in fall and spring.Moreover,our results indicated that various aerosol species had obvious seasonality.The proportions of secondary components were higher in winter than other two seasons.In contrast,the ratios of nitrate to sulfate(NO_(3)^(-)/SO_(4)^(2-))showed lower levels in winter,which was because both the ratios of nitrogen dioxide to sulfur dioxide(NO_(2)/SO_(2))and the ratios of nitrogen oxidation ratio to sulfur oxidation ratio(NOR/SOR)exhibited lower values in winter than in fall and spring.With PM_(2.5)increased,the NO_(3)^(-)/SO_(4)^(2-)ratios showed increasing trends in all three seasons,which was mainly attributed to the increase of NOR/SOR ratios in fall and spring,and the increase of both NO_(2)/SO_(2)and NOR/SOR ratios in winter.This result highlighted that nitrate was more important than sulfate as a driver for the growth of PM_(2.5)during the period of heavy air pollution.Additionally,the sources of organic aerosol(OA)in different seasons were also distinctly different.Overall,the sum of biomass burning OA(BBOA)and secondary OA(SOA)contributed>70%of OA in three seasons.The fractional contributions of BBOA to total OA,notably,exhibited higher levels in fall and spring,because of intensive open agricultural fires.The SOA fractions in OA were larger in winter,likely due to higher relative humidity which facilitated the secondary for-mation.A large increase in the proportions of BBOA was observed during polluted days in fall and spring compared to clean days.In comparison,during heavily-polluted periods,secondary formation made a dominant contribution to organic matter in winter.

Clathrin-Mediated Auxin Efflux and Maxima Regulate Hypocotyl Hook Formation and Light- Stimulated Hook Opening in Arabidopsis

The establishment of auxin maxima by PIN-FORMED 3 （PIN3）- and AUXIN RESISTANT l/LIKE AUX1 （LAX） 3 （AUX1/LAX3）-mediated auxin transport is essential for hook formation in Arabidopsis hypocotyls. Until now, however, the underlying regulatory mechanism has remained poorly understood. Here, we show that loss of function of clathrin light chain CLC2 and CLC3 genes enhanced auxin maxima and thereby hook curvature, alleviated the inhibitory effect of auxin overproduction on auxin maxima and hook curva- ture, and delayed blue light-stimulated auxin maxima reduction and hook opening. Moreover, pharmaco- logical experiments revealed that auxin maxima formation and hook curvature in clc2 clc3 were sensitive to auxin efflux inhibitors 1-naphthylphthalamic acid and 2,3,5-triiodobenzoic acid but not to the auxin influx inhibitor 1-naphthoxyacetic acid. Live-cell imaging analysis further uncovered that loss of CLC2 and CLC3 function impaired PIN3 endocytosis and promoted its lateralization in the cortical cells but did not affect AUX1 localization. Taken together, these results suggest that clathrin regulates auxin maxima and thereby hook formation through modulating PIN3 localization and auxin efflux, providing a novel mechanism that integrates developmental signals and environmental cues to regulate plant skotomorphogenesis and photomorphogenesis.

Formation of secondary inorganic aerosol in a frigid urban atmosphere

Formation of secondary inorganic aerosol(SIA)was investigated during a six-month long heating season in Harbin,China.Enhanced sulfate formation was observed at high relative humidity(RH),with the same threshold RH(80%)for both colder and warmer measurement periods.Compared to wintertime results from Beijing,the threshold RH was considerably higher in Harbin,whereas the RH-dependent enhancement of sulfur oxidation ratio(SOR)was less significant.In addition,the high RH events were rarely encountered,and for other periods,the SOR were typically as low as~0.1.Therefore,the sulfate formation was considered inefficient in this study.After excluding the several cases with high RH,both SOR and the nitrogen oxidation ratio(NOR)exhibited increasing trends as the temperature increased,with the increase of NOR being sharper.The nitrate to sulfate ratio tended to increase with increasing temperature as well.Based on a semi-quantitative approach,this trend was attributed primarily to the temperature-dependent variations of precursors including SO_(2) and NO_(2).The influence of biomass burning emissions on SIA formation was also evident.With stronger impact of biomass burning,an enhancement in NOR was observed whereas SOR was largely unchanged.The different patterns were identified as the dominant driver of the larger nitrate to sulfate ratios measured at higher concentrations of fine particulate matter.