Direkte Bestimmung der Additivelemente Ca, Ba und Zn in Schmier?len

Zusammenfassung Lösungen von CaCl₂ · 2 H₂O, BaCl₂ · 2 H₂O und Zn(CH₃CO₂)₂ · 2 H₂O in Dimethylsulfoxid lassen sich anstelle metallorganischer Verbindungen als Standards zur direkten Bestimmung der Additivelemente Ca, Ba und Zn in Schmierölen mittels Atomabsorptionsspektroskopie verwenden. In 10 verschiedenen Ölen wurden die Additive bestimmt. Die mit Atomabsorption erhaltenen Meßergebnisse weichen von den naßchemisch ermittelten um maximal 5% ab.

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Direct determination of the additive elements Ca, Ba and Zn in lubricating oilsSolutions of inorganic salts in dimethyl sulphoxide as standards in atomic absorption spectroscopy

For the determination of the additive elements Ca, Ba and Zn in oils by atomic absorption spectroscopy, solutions of CaCl₂ · 2 H₂O, BaCl₂ · 2 H₂O and Zn(CH₃CO₂)₂ · 2 H₂O in dimethyl sulphoxide can be used as standards instead of metallorganic compounds. The additives in 10 different oil samples have been determined. The results obtained by atomic absorption differ from those gained by conventional analytical methods by 5% at most.

     

Cesium's Off‐the‐Map Valence Orbital

The T_d ‐symmetric [CsO₄]⁺ ion, featuring Cs in an oxidation state of 9, is computed to be a minimum. Cs uses outer core 5s and 5p orbitals to bind the oxygen atoms. The valence Cs 6s orbital lies too high to be involved in bonding, and contributes to Rydberg levels only. From a molecular orbital perspective, the bonding scheme is reminiscent of XeO₄: an octet of electrons to bind electronegative ligands, and no low‐lying acceptor orbitals on the central atom. In this sense, Cs⁺ resembles hypervalent Xe.     

Pre-B?tzinger复合体的从簇到峰放电的同步转迁及分岔机制

Pre-Bötzinger复合体是兴奋性耦合的神经元网络,通过产生复杂的放电节律和节律模式的同步转迁参与调控呼吸节律.本文选用复杂簇和峰放电节律的单神经元数学模型构建复合体模型,仿真了与生物学实验相关的多类同步节律模式及其复杂转迁历程,并利用快慢变量分离揭示了相应的分岔机制.当初值相同时,随着兴奋性耦合强度的增加,复合体模型依次表现出完全同步的“fold/homoclinic”,“subHopf/subHopf”簇放电和周期1峰放电.当初值不同时,随耦合强度增加,表现为由“fold/homoclinic”,到“fold/fold limit cycle”、到“subHopf/subHopf”与“fold/fold limit cycle”的混合簇放电、再到“subHopf/subHopf”簇放电的相位同步转迁,最后到反相同步周期1峰放电.完全(同相)同步和反相同步的周期1节律表现出了不同分岔机制.反相峰同步行为给出了与强兴奋性耦合容易诱发同相同步这一传统观念不同的新示例.研究结果给出了preBötzinger复合体的从簇到峰放电节律的同步转迁规律及复杂分岔机制,反常同步行为丰富了非线性动力学的内涵.