Windmill rotation

Samples are transferred to a separatory funnel, surrogates are added, and an immiscible solvent (dichloromethane, hexane, etc.) is added. The liquids are shaken vigorously for a few minutes and then allowed to rest until a separation between the two phases occurs. The solvent is removed and the extraction process is repeated twice more. The extracts are combined, dried over anhydrous sodium sulphate, and processed further (cleanup) as required. Some laboratories have automated this tedious procedure by performing extractions in bottles. In this case, solvent and water are placed in a bottle and rotated (windmill rotators) or shaken (platform shakers) for 1—2 h. The lack of vigorous shaking is replaced by an extended time for extraction. Liquiddiquid extraction is used for all semivolatile analysis (hydrocarbons >C12, PAH, pesticides, PCB, dioxins). By lowering the pH, extraction of phenols (pentachlorophenol) and acidic compounds (2,4-dichlorophenoxyacetic acid—2,4-D) will be enhanced. Increasing the pH will increase extractability of basic (aromatic amines) and neutral compounds (PAH). 

One of the special rotary atomizers worth mentioning is the windmill type atomizer. In this atomizer, radial cuts are made at the periphery of a disk and the tips of segments are twisted, so that the disk is actually converted into a windmill that can rotate rapidly when exposed to an air flow at aircraft flight speed. The windmill type atomizer has been demonstrated 1171 to be an ideal rotary atomizer for generating a narrow spectrum of droplet sizes in the range most suitable for aerial applications of pesticides at relatively high liquid flow rates. 

As important to biochemists as configurations, the stable arrangements of bonded atoms, are conformations, the various orientations of groups that are caused by rotation about single bonds.5 8 In many molecules such rotation occurs rapidly and freely at ordinary temperatures. We can think of a -CH3 group as a kind of erratic windmill, turning in one direction, then another. However, even the simplest molecules have preferred conformations, and in more complex structures rotation is usually very restricted. 

Although, as we have already stressed, analogies between the macroscopic and the molecular world often lead to misunderstandings and must be used carefully, it is tempting to compare the relationship between chirality and motion in Feringa s systems with that seen in a macroscopic example the windmill. When the wind blows at the vanes of a windmill, its rotor immediately knows which direction to rotate in. When blown at by the same wind, two enantiomeric windmills will rotate in opposite directions, and if the vanes were symmetric with respect to the axis of rotation, the windmill just... 

The basic principles of wind energy have been used for centuries. Windmills existed in the 7th century in Persia. An older image closely associated with wind power is Don Quixote and the wooden towers with cloth-covered sails turning in the wind. Today s wind turbines use a giant propeller on a tall metal pole. As it rotates, the propeller drives a generator to supply nearby users or send power to the grid. 

Figure 2-21. Examples of sixfold rotational symmetry (a) Star of David, New York photograph by the authors (b) six-blade windmill.

The way in which rotary nozzles are classified usually relates to the type of surface the liquid will be rolled on. These include flat disk, disk with vanes, windmill (slotted wheel) and rotating cups. Often rotary nozzles mix the liquid with gas to improve the atomization, creating a twin fluid rotary nozzle. 

Current meters are hydrodynamic instruments with rotating vanes or buckets. The speed of their rotation is proportional to the flow velocity. The forerunners of current meters were the paddle wheels developed in the early 18 century. These were applied by Francesco Domenico Michelotti (1710-1777) in 1767, or by Pierre-Louis Du Buat (1734-1809) in 1786. There are two principal types of current meters, namely the screw and the cup types. The first was conceived by the famous British engineer Robert Hooke in 1783 to measure wind velocity with four vanes similar to a windmill. This type was developed by Reinhard Woltman (1757-1837) in 1790, Andre Baumgarten (1808-1859), Albert Ott (1847-1895), Alphonse Fteley (1837-1903) and Haskell, among many others. The other type meter has several cups on spokes rotating around an axis oriented transverse to the current. These anemometers were first applied around 1850 to measure wind velocities, and then were developed by Theodore Gunville Ellis (1829-1883), or William G. Price (1853-1928) to record flow velocity in rivers. 

Figure 12 (a) Molecular structure of OPV3-CHO. High-resolution STM images with CW rotation (b) Self-assembly of chiral windmill... 

Air velocities can be measmed by a variety of instruments but vane anemometers and heated head (hot wire or thermistor) air meters are the most common. Vane anemometers Figure 3.6.7) have a rotating windmill type head coupled to a meter and are most suitable for use in open... 

Compared to the last two technologies, (i) the push-pull method doesn t need designing machine to create special shapes, which is needed by the windmill driving mechanism, and (ii) the actuating isn t limited to rotating, but to any random 3D movement. As an example, a micro-oscillator system was driven by this mechanism, which will be discussed in the following section. 

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