A Novel Dimeric Eremophilane from Ligularia virgaurea spp. oligocephala

A novel dimeric eremophilane, ligulolide B, was isolated from the alcoholic extract of the whole plant of Ligularia virgaurea spp. oligocephala. The structure was elucidated by various spectroscopic methods including intensive 2D NMR techniques （^1H-^1H COSY, gHMQC, gHMBC and ^1H-^1H NOESY） and HR-ESI-MS.     

Development of a new analytical method for the evaluation of hazards from slow decomposition of waste streams and process solutions

A wide variety of liquid streams are generated as part of the process research and development effort. Frequently these streams are drummed off, either as intermediates that must be held for processing or as wastes that must be sent off-site for disposal. Because of the long times and low concentrations often involved, current thermoanalytical techniques were inadequate to detect the potential of streams to generate gas. A custom-made apparatus, the gas evolution test cell (GETC), was developed in the Merck Research Laboratories to measure the gas generation potential of various streams under precisely defined conditions, is the key innovation for the development of a quantitative gas-generation test method.     

一类齐次对称多项式上的切比雪夫不等式

本文借助于控制不等式及数学归纳法，将著名的切比雪夫不等式推广到m次一般齐次对称多项式上(如文中定理及引理7)，并将此结果用于对称平均等．旨在展示证明解析不等式的一些有效的方法和技巧，同时为数学研究特别是高维几何研究提供一些新的有趣而有用的解析不等式．     

Experimental techniques for the determination of the dynamic responses of structures to wind

Summary The paper reviews the limitations and advantages of various experimental techniques available for the determination of the dynamic effects of wind on structures. The prime causes of dynamic action (i.e. incident turbulence, wake effects and motion) are described with particular attention being given to the nature and importance of the forces induced by structural motion. Also discussed briefly are the modelling requirements and the compromises that must be made in the design of models. The techniques discussed include the use of aeroelastic models of various types, the base balance approach to the assessment of dynamic response, the use of surface pressure measurements and the direct measurement of motion-induced forces on vibrating models.The base balance technique provides a rapid low-cost method which yields data within a time frame that permits integration of the wind tunnel data into the design process. The method does, however, have serious deficiencies if motion-induced forces are of significance or if the geometry of the structure or its mode shapes is unduly complex. High speed external pressure measurements offer a method capable of dealing with complex geometries and mode shapes but, again, care must be taken in regard to the role played by motion-induced forces. For structures expected to perform at wind speeds in the vicinity of the so-called critical speed, motion-induced forces are likely to be of great significance and aeroelastic testing or direct measurement of these forces should form part of the experimental program.

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Sommario Si passano in rassegna i limiti ed i vantaggi di varie tecniche sperimentali attualmente disponibili per la determinazione degli effetti dinamici del vento sulle strutture. Si descrivono le principali cause dell'azione dinamica (cioè turbolenza, effetti scia e moto della struttura stessa), dando particolare attenzione alla natura e all'importanza delle forze indotte dal moto della struttura. Vengono anche brevemente discussi i requisiti e i compromessi che devono essere soddisfatti nella modellazione. Le tecniche discusse includono modelli aeroelastici di vari tipi, modelli rigidi con dinamometro alla base, misure di pressioni superficiali e misurazioni dirette delle forze indotte dal moto in modelli deformabili.La tecnica del dinamometro alla base è un metodo rapido e di basso costo che fornisce dati in un tempo che permette lo sfruttamento dei risultati delle prove in galleria del vento nella progettazione, ma che ha serie limitazioni se le forze indotte dal moto sono significative o se la geometria della struttura o delle sue forme modali è complicata. Misure rapide della pressione esterna sono un metodo capace di affrontare complicate geometrie e forme modali, ma anche in questo caso è necessario fare attenzione al ruolo giocato dalle forze indotte dal moto. Per strutture che possono venir sottoposte a venti con velocità prossime alla cosiddetta velocità critica, è prevedibile che le forze indotte dal moto abbiano grande influenza; perciò in tali casi, il programma sperimentale dovrebbe includere prove aeroelastiche o la misura diretta di queste forze.

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Keynote lecture presented at the 1st Italian National Conference on Wind Engineering, Florence, Italy, 28–30 October 1990; to be included in the Conference Proceedings Volume. Reprinted here courtesy of National Association for Wind Engineering (ANIV).     

Tabakuntersuchung und Nicotinbestimmung

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