Vacuum closures

Water Sorption. The water vapor sorption isotherm (293 K) is given in Figure 3. The general sigmoidal shape is evident, and the hysteretic phenomenon is quite pronounced, even when desorption is instigated from intermediate pressures (about 0.6 Pq), and vacuum closure... 

Loss of External Load Turbine Trip Loss of Condenser Vacuum Closure of Main Steam... 

The slot in the interfaces for passage of the belt is formed by two "L"-shaped sapphire pieces which are attached to the stainless-steel flange or vacuum closure bar by epoxy cement. The belts used are either 0.05 or 0.075 mm thick and the slot tolerance is set to be 0.075 mm greater than the belt thickness (i.e., either 0.125 or 0.15 mm). The belt width is 0.317 cm and the slot width is 0.325 cm. A ribbon 0.32 cm wide travelling at a speed of 2.5 cm/sec will carry away a liquid film 0.2 mm thick from a solvent flow of 1 ml/min and if the solvent film can be evaporated without loss of solute, then the ribbon will transport virtually 100% of the solute into the mass spectrometer. Sample utilization will then depend only on the efficiency of the flash vaporization step. In practice, some sample is lost by spray processes and the flash vaporization cannot be fully efficient for all compounds. Nevertheless, yields in the range of 25-40% have been attained with an LC/MS ribbon interface system. It follows that the quantity of column eluent taken from the ribbon will be twenty times greater than that taken by the wire and provide significantly improved sensitivity. 

Turbine trip, loss of condenser vacuum, closure of the main steam isolation valves (in BWRs) and failure of the steam pressure regulator ... 

Although formally it could be classified with the ring transformations (Section 4.04.3.2.2), conversion of 2,4-diphenyl-l,3,4-oxadiazol-2-one (593) by flash vacuum pyrolysis at 500 °C into 3-phenylindazole (595) involves a C(3)—C(3a) ring closure of the diphenylnitrilimine (594) (79AG(E)721). 

Partial MSIV closure y. Loss of normal condenser vacuum... 

Figure 19 illustrates one type of compression mold suitable for molding lip type shaft seals with a metal outside diameter (O.D.). Figure 19a shows the compound preform resting on the shelf and the mold beginning to close. The mold continues to close until it gets to the position shown in Fig. 19b. Finally, the mold opens as shown in Fig. 19c. It can be seen that this molding technique produces a molded lip seal with the flash already removed. In general, when using a vacuum chamber on the press, to ensure that all the air and/or gases are evacuated from the mold after closure, one or...

The base-catalysed reaction of a-bromo-a,P-unsaturated ketones with aliphatic nitro compounds leads to 2-isoxazoline A-oxides by tandem conjugate addition-ring closure (Scheme 5) <95JOC6624>. A -Acyl-3-isoxazolin-5-ones are transformed into oxazoles by photolysis or by flash vacuum pyrolysis (Scheme 6) <96TL675>. 

Whelan C, Stewart J, Schwartz BF (2005) Mechanics of wound healing and importance of vacuum assisted closure in urology. J Urol 173(5) 1463-1470... 

Bottles and vials are not subjected to such a vacuum test because of the flexibility of the rubber closure. However, bottles that are sealed under vacuum may be tested for vacuum by striking the base of the bottle sharply with the heel of the hand to produce a water hammer sound. Another test is the spark test, in which a probe is applied outside the bottle. When it reaches the air space of the bottle, a spark discharge occurs if the headspace is evacuated. 

Vacuum retention determines the ability of an elastomeric closure to maintain vacuum in a container-closure system when vacuum retention is a requirement. In certain instances it impacts on the long-term stability of a parenteral system. 

A series of transformations via nitrene formation similar to the previously discussed case was also found under flash vacuum thermolytic (FVT) conditions by the same team as shown in Scheme 8 <2003JOC1470>. 9-Phenyltetrazolo[l,5- ]quinoline 29 underwent nitrene 30 and cyclic carbodiimide 31 formation, and this intermediate - similar to the previous case - could open up to the isoquinoline nitrene 32 in which, however, proximity of the nitrene to the phenyl substituents allowed the ring closure to the stable tetracyclic ring system 33 which was obtained in 73% yield. 

In Equation 12.13, N is the number density of molecules in the beam of radiation (and is thus inversely proportional to the molar volume, Vm), and o is the permittivity of the vacuum. A useful and widely employed method to evaluate the sum in Equation 12.13 leads via the closure approximation to a one-term equation commonly known as the dispersion relation,... 

The first synthesis of a semibuckminsterfullerene was accomplished by a procedure analogous to the preparation of corannulene except that 1,2,5,6-tetrake-topyracene served as the starting material (Scheme 5). Flash vacuum pyrolysis of the tetrachloro compound led to a remarkable quadruple ring closure to produce the semi-buckminsterfullerene 27. The NMR shows three methine carbons and five quaternary carbons at 125.5, 126.8, 127.3, 128.6, 136.7, 137.3, 142.0, and 145.4 ppm. The latter signals compare favorably to the single resonance observed at 143 ppm for buckminsterfullerene. 

The strain of cycloproparenes is the principal obstacle that must be overcome in their synthesis. Cycloproparenes decompose usually at moderate temperatures, and they undergo ring-opening in the presence of electrophilic or metallic reagents. In contrast, they support even strongly basic conditions quite well. Accordingly, most successful cycloproparene syntheses use some base-induced elimination in the last step. Alternatively, flash vacuum pyrolytic or photochemical extrusion of a neutral fragment, followed by biradical closure or flash vacuum pyrolysis may be used. In these latter approaches the reaction conditions are neutral, and reactive products may be trapped at low temperatures. 

Sharp and co-workers (32) observed that carbonyl ylides can participate in electrocyclic ring closures. Flash vacuum pyrolysis of epoxy ester 101 led initially... 

In a typical experiment the metal vacuum line and connections to the hexafluoride and HF storage tubes are pumped to at least KT4 torr over several hours. A 30-mL Kel-F reaction tube9 fitted with a metal valve closure is charged with silicon powder and a Teflon-covered stirring bar. The reaction tube is attached to the vacuum system and evacuated. 

Bottle closure properly closed (torque force, vacuum test)... 

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