Crown wheels

Initially at rest, a disc with a radius r = 10 cm begins to revolve with constant angular acceleration s = 0.5 rad/sec. Find the tangent (a ), normal (a ) and total (a) acceleration of the points on the wheel crown at the end of 2 sec of movement. 

Eranz, m. wreath crown corona ring border, rim, brim lid (of a furnace) rim (of a wheel). 

Template effects have been used in rotaxane synthesis to direct threading of the axle through the wheel. Since macrocycHc compounds such as cyclodextrins, crown ethers, cyclophanes, and cucurbiturils form stable complexes with specific guest molecules, they have been widely used in the templated synthesis of rotax-anes as ring (wheel) components. Here, we briefly discuss macrocycles used in the synthesis of rotaxane dendrimers and their important features. 

The Fe6 rings have also been extensively studied. [Fe6(p2-OMe)12(dbm)6] (32,33) is a neutral species but in the solid state it crystallizes with NaCl to give [Na c Fe6(p2-OMe)12(dbm)6]+. The Na+ ion is trapped in the center of the iron wheel, which acts like a crown ether complexing an alkaline ion. 

The big wheel is structurally complete without any defect in the skeleton of the crown. The cavity measures about 20 A in diameter,... 

A ferris wheel assembly involving a 1 1 complex of 19 and metallated [18]crown-6 is found in the cationic supermolecule [La(H20)3([ 18]crown-6)] (19+2H) + [48]. The lanthanum ion is coordinated by one calixarene sulfonate group, the [18] crown-6 and three aquo ligands, and the metallated crown sits inside the calixarene cavity. A helical hydrogen bonded chain structure is formed between the cationic assembly, water and chloride ions. The ferris wheel structural motif is also found in Ce3+ complex which simultaneously contains a Russian Doll assembly [44]. 

Electrocatalytic devices Poly(allyl-amine) (PAH) Wheel-shaped (Mo36 and Mo46) crown-shaped (Mo54) sphere-shaped M08V2O28.7H2O [81-84]... 

By contrast, a crown wheel is one of the simplest fireworks to set up. It resembles a flying saucer and rests, without ceremony, on a nail fixed in the top of a post. Although it spins at about the same speed as a Catherine wheel and uses a similar pyrotechnic composition, the crown wheel is not fixed in any way. 

Rockets should similarly be located at the rear of the site, along with other aerial fireworks such as crown wheels and maroons, again in positions of safety with respect to the spectators. 

Assembling [2] rotaxanes (wheel and axle) can involve three basic processes (Scheme 13). One of these (93CC1269) involves slippage, in which the axle (115) is linked by a 4,4 -bipyridine, and the wheel (116) is a bisparaphenylene-34-crown-10 ether. Heating the two components in acetonitrile at 60°C yields the rotaxane, which can be characterized by FABMS and H and l3C NMR, but extrusion of the wheel occurs at 100°C. In other developments (94NAT(369)133), the pyridine component may be incorporated in the wheel, as in structure (117), where two bipyridinium units are connected by p-xylyl groups, and here the rotaxane acts as molecular switch. At room temperature in acetonitrile the wheel... 

Fig. 4.57. Ferris-wheel structure formed with lanthanum chloride interacting with p-sulfonatocalix[4]arene and 18-crown-6. Redrawn from A. Drljaca et al., Chem. Commun. 1135, 1999.

T. Takata, H. Kawasaki, N. Kihara, Y. Furusho, Synthesis of Side-Chain Polyrotaxane by Radical Polymerizations of Pseudorotaxane Monomers Consisting of Crown Ether Wheel and Acrylate Axle Bearing Bulky End-Cap and Ammonium Group , Macromolecules, 34, 5449 (2001)... 

While the above studies are representative of the area, it should be noted that a considerable number of other [2]-pseudorotaxanes have been investigated. These include a system exhibiting enantioselective self-assembly during its formation as well as systems incorporating a new structural motif involving a l,2-bis(pyridini-um)ethane axle and a 24-crown-8 ether wheel .A number of poly-pseudoro-taxanes (and related poly-rotaxanes) as well as constitutionally asymmetric and chiral [2]-pseudorotaxanes have been reported. New, multiply-stranded and multiply-encircled systems have also been prepared. The solid state structure of... 

Main Chain-Type Polyrotaxanes Bearing Crown Ethers as The Wheel Components... 

Slipping approach is effective for the preparation of oligorotaxane based on crown ether and secondary ammonium salt because the inclusion complex is fairly stable. When dibenzo-30-crown-10 (DB30C10) was used as the wheel component, 3,5-di-ferf-butylphenyl group is the complementary end-cap to the crown ether. DB30C10 slips over the 3,5-di-ferf-butylphenyl group... 

Tantric, like Taoist, alchemy is mainly internal. It aims to effect a transmutation in the body by producing certain bodily fluids thatwill enable the Tantrist to be at one with the Universe, and to acquire supernatural powers. According to the Tantrist, the body has seven main centers of supernormal psychic energy. They have no physical existence, but can be identified by the Tantrist as being situated along a line between the bottom of the spine and the crown of the head. These centers are known as chakras or wheels. The lowest chakra is inhabited by the kundalini, which in the normal person lies curled up, asleep, like a small serpent, its head blocWng the path of ascent to the next chakra. 

Clinch-on applies a simultaneous bending action over the total circumference of a skirt. Crimped-on applies both flutes and a bending action in the case of closures—the prime example is a crown cork closure invented by W.Painter of Baltimore in 1882. The word crimped is frequently misused when clinched is correct. Rolled-on and spun-on use wheels to bend in a... 

---