[Mineral nitrogen accumulation and its spatial distribution in soils in dense planting dwarf rootstock apple orchard on the Weibei dry plateau, Northwest China]. / æ¸­åŒ—æ—±å¡¬çŸ®ç §å¯†æ¤è‹¹æžœå›­åœŸå£¤çŸ¿è´¨æ°®ç§¯ç´¯ä¸Žç©ºé—´åˆ†å¸ƒç‰¹å¾.

With the rapid development of dense apple tree plantings with the dwarf rootstock cultivation method, determining accumulation and distribution characteristics of soil mineral nitrogen in densely planted orchards with dwarf rootstock is important to enable scientific fertilization of apple orchards. We investigated densely planted apple orchards with dwarf rootstocks and different plant ages (6 a, 9 a, and 12 a). We collected soil samples under trees, between trees, between rows, and at the midpoints between the trees and rows, and examined the accumulation and distribution characteristics of nitrate, ammonium, and mineral nitrogen. The cumulative amount of nitrate in the 0-300 cm soil layer increased with plant age. The difference between orchards with different plant ages was significant and showed the trend 6 a<9 a<12 a. The cumulative amount of nitrate increased from 1729 kg·hm-2 to 3771 kg·hm-2 with increasing plant age. The ammonium content was low for orchards of all plant ages and had little effect on the accumulation and spatial distribution of mineral nitrogen. There were two accumulation peaks of nitrate nitrogen in the vertical direction. The depth of soil layer where the second accumulation peak was located decreased from 180 cm to 220 cm with increasing plant age. In the horizontal direction, soil nitrate nitrogen content between rows increased from 27 mg·kg-1 to 138 mg·kg-1 with increasing plant age, representing a more than 400% increase. The difference between orchards with different plant ages was significant. In summary, excessive usage of nitrogen fertilizer and serious leaching of nitrate were problematic in all orchards with different ages. Less nitrogen fertilizer should be applied, and anti-seepage measures should be used at the fertilization location to prevent the leaching of nitrate to deep layers.

Irradiation stent insertion for distal biliary obstruction secondary to primary common biliary cancer.

PURPOSE: To assess the effectiveness and safety of irradiation stent insertion for patients with distal biliary obstruction (DBO) secondary to primary common biliary cancer. MATERIAL AND METHODS: Eighty-two consecutive patients with DBO secondary to primary common biliary cancer were treated via either normal (n = 45) or irradiation stenting (n = 37) between January 2013 and December 2019. The instant and long-term outcomes were compared. RESULTS: Technical success rates of normal and irradiation stenting were both 100%. Clinical success rates of normal and irradiation stenting were 91.1 and 100%, respectively (p = .179). Stent reobstruction was observed in 13 and 7 patients in the normal and irradiation stenting groups, respectively (p = .295). The median stent patency was 162 and 225 days in the normal and irradiation stenting groups, respectively (p < .001). The median survival was 178 and 250 days in the normal and irradiation stenting groups, respectively (p < .001). Cholangitis was, respectively, observed in 8 and 12 patients in normal and irradiation stenting groups (p = .124). CONCLUSION: Irradiation stenting is effective and safe for patients with DBO secondary to primary common biliary cancer and can prolong stent patency and survival.

Palladium-catalyzed allylation of aminophenol with alkynes to construct C-N bonds.

A method for the allylic alkylation of aminophenol with alkynes was developed using a palladium-catalysed allylation reaction with 100% atom economy. A series of structurally diverse N-allylic substituted allylamines were synthesized in good yields with high chemo-, regio-, and stereoselectivities under mild conditions.

Palladium-catalyzed allylation of tautomerizable heterocycles with alkynes.

A method for the allylic amidation of tautomerizable heterocycles was developed by a palladium catalyzed allylation reaction with 100% atom economy. A series of structurally diverse N-allylic substituted heterocycles can be synthesized in good yields with high chemo-, regio-, and stereoselectivities under mild conditions.

Palladium-catalyzed allylation of sulfonyl hydrazides with alkynes to synthesize allylic arylsulfones.

A novel method for the construction of allyl arylsulfone derivatives was developed by palladium catalyzed allylation of sulfonyl hydrazides with alkynes. A series of structurally diverse allyl arylsulfones can be regioselectively synthesized in high yields under mild conditions.

Observations of three-dimensional Richtmyer-Meshkov instability on a membraneless gas bubble.

We investigate the three-dimensional evolution of shock impact on a membraneless gas bubble. When a shock wave impacts a gas interface, gas layer is generally perturbed via the Richtmyer-Meshkov instability. We show the vortex structure evolves from the merging process of the extending spikes on the compressed D-shaped surface via the Richtmyer-Meshkov instability. The spikes are found to have a linear growth before 11 µs (of 1.4 mm). A ripple-typed fluctuating ring structure is observed and discussed with the scaling relation. We also notice that a thin layer exists in the intersection of the counterpropagating shock shells. The superposition of the rarefaction waves from both sides of the intersection is suspected to be responsible for the density change.