Optimal preparation of Bose and Fermi atomic gas mixtures of ^(87)Rb and ^(40)K in a crossed optical dipole trap

We report on the optimal production of the Bose and Fermi mixtures with ^(87) Rb and ^(40)K in a crossed optical dipole trap(ODT).We measure the atomic number and lifetime of the mixtures in combination of the spin state |F=9/2,m_(F)=9/2> of^(40)K and |1,1>of ^(87) Rb in the ODT,which is larger and longer compared with the combination of the spin state |9/2,9/2> of^(40)K and 12,2) of ^(87)Rb in the ODT.We observe the atomic numbers of ^(87)Rb and ^(40)K shown in each stage of the sympathetic cooling process while gradually reducing the depth of the optical trap.By optimizing the relative loading time of atomic mixtures in the MOT,we obtain the large atomic number of ^(40)K(~6 ×10^(6)) or the mixtures of atoms with an equal number(~1.6 × 10^(6)) at the end of evaporative cooling in the ODT.We experimentally investigate the evaporative cooling in an enlarged volume of the ODT via adding a third laser beam to the crossed ODT and found that more atoms(8 × 10^(6)) and higher degeneracy(T/T_(F)=0.25) of Fermi gases are obtained.The ultracold atomic gas mixtures pave the way to explore phenomena such as few-body collisions and the Bose-Fermi Hubbard model,as well as for creating ground-state molecules of ^(87)Rb^(40)K.

Parameter Scaling of the Aerodynamic Breakup of the Acoustic Levitated Droplets in an Air Jet Flow

The aerodynamic breakup of the droplet has been intensely studied in this paper.We aim to establish a unified relationship between dimensionless kinematic parameters such as displacement,spreading diameter,Weber num-ber,time,and so on.The breakup characteristics of the acoustic levitated ethanol droplet are experimentally inves-tigated when exposed to an air jetflow.The breakup phenomenons were recorded with a high-speed camera.The breakup characteristics were analyzed,and the physical models of the moving and transforming behaviors were established to explain the breakup mechanisms.We found that the displacement of the windward side of the dro-plet follows free acceleration rule,with the displacement,acceleration,and time in the dimensionless form.The spreading of the diameter during deformation can also be written in a simple equation as a function of Weber number and displacement.We also discussed more details.

Diffusion of a Nonvolatile Fuel Spray in Swirl Flow

The diffusion of fuel spray in swirl flow is vital for the combustion of diesel engine,however,the researches on this is still mysterious due to the obstacles on direct investigations on a real engine.The research of intake swirl in engine at present normally use CFD simulation or based on data analysis of combustion and exhaust emission,the specific mixing process of fuel in swirl flow still not very clear.In this paper,a rapid compression machine(RCM)with an optical combustion chamber was established with the mean compression velocity of 7.55 m/s.Three kinds of flow fields,including intense swirl field,weak swirl field and turbulent field,were conducted to investigate the diffusion characteristics of injected fuel,the mixing processes of fuel spray in the swirl flow fields were recorded by the high-speed camera.Experimental results show that the mixing of fuel spray in air consists of four stages:fuel injection,wall approaching,rapid diffusion and final diffusion.The fuel spray is firstly bended by the lateral flow of the swirl field,then liquid fuel is blown onto,and coats on,the sidewall.The fuel on the sidewall is finally enrolled into the chamber plenum afterwards in gaseous phase via the spiral arms(in swirl fields)or random routes(in turbulent field)At last the fuel disperses all over the chamber.The results give an intuitive observation and help better understand the air-fuel mixing process in diesel and direct inject gasoline engines.

微生物菌群协同提高水稻秸秆转化机制的解析

单一微生物降解水稻秸秆效果不明显,多种微生物组合在一起的微生物菌群能够有效降解水稻秸秆,是当前降解秸秆类废物的首要选择。【目的】探究微生物菌群比单一菌株转化秸秆效率提高的种间协作机制,为改善秸秆类物质的生物降解过程提供理论参考。【方法】通过菌种组合,以水稻秸秆减重率为指标人工构建出降解效果优于单菌培养的微生物群体组合,利用分子生物学方法对实验菌株进行鉴定,结合纤维素酶活性、发酵产物GC-MS分析等指标得出水稻秸秆降解时微生物群体的种间协作机制。【结果】菌株B(Bacillus cereus)在30℃培养8 d水稻秸秆降解率为50.9%,菌株B与菌株D_(2)(Bacillus amyloliquefaciens)、W_(1)(Ochrobactrum intermedium)、G_(1)降解(Bacillus licheniformis)组合构成4株菌BD_(2)W_(1)G_(1)的复合菌群,在30℃培养8 d水稻秸秆降解率为73.3%,比B单菌株分解能力提高22.4%。发酵产物分析结果表明,菌株B单独培养产生大量酸、酚等物质。B+D_(2)联合培养,发酵液内酸类相对减少87.4%,酚类相对减少61.9%(十五烷酸、正十六烷酸、2,4二叔丁基酚和6-叔丁基对甲酚减少明显),水稻秸秆降解率为64.6%。当B+D_(2)+W_(1)联合培养,发酵液内酚类进一步减少15.7%(6-叔丁基对甲酚减少明显),水稻秸秆降解率为71.0%。当B+D_(2)+W_(1)+G_(1)联合培养,酚类继续减少10.7%,水稻秸秆降解率为73.3%。【结论】十五烷酸、正十六烷酸、2,4二叔丁基酚和6-叔丁基对甲酚等酸、酚类物质会抑制菌株B分解水稻秸秆的效率,菌株D_(2)、W_(1)、G_(1)能够减少包括4种物质在内的酸、酚类含量(酸类共减少82.9%,酚类共减少88.2%),来提高分解效率(共提升22.4%的分解效果)。水稻秸秆成分复杂,具有不同功能的菌种组合成复合菌剂,减少反馈抑制形成代谢互补,能有效提高水稻秸秆生物降解效果。

Valsalva动作致近视儿童视盘内出血伴视盘旁视网膜下出血一例

患者,女,10岁,主诉右眼前小片状黑影3 d。2019年9月15日就诊于同济大学附属东方医院门诊,黑影无明显飘动,无眼胀及眼痛,无明显视力下降,无眼球转动痛。既往史:右眼屈光不正;否认外伤史及其他眼病史,无家族遗传史。专科检查:双眼瞳孔等大正圆,直径3 mm,光反射灵敏,右眼视盘表面上方、下方及鼻侧火焰状出血灶,出血区下方可见玻璃体腔相连的凝血块,视盘鼻侧视网膜下可见半月形出血灶,视网膜在位,血管走行正常,黄斑中心凹反射阳性(见图1)。