Dewars, composite

Among the radical cations derived from strained ring hydrocarbons those of composition (CH)6, the valence isomers of benzene (128) (Scheme 11), have attracted considerable interest. In addition to the one-electron oxidation products of Dewar benzene (126) [360-368), bicylopropenyl (129) [369], benzvalene (130)... 

The entire system is fully purged with the diluent gas and then the glass trap is cooled with a Dewar flask containing liquid nitrogen. A mixture of sulfur(IV) oxide and diluent gas containing about 80% sulfur(IV) oxide is then passed through the reaction system at a rate of 0.3 to 0.8 l./min. Neither the gas composition nor the gas flow rate is critical here. The course of the reaction is determined by following the relatively narrow hot reaction... 

Foam films are usually used as a model in the study of various physicochemical processes, such as thinning, expansion and contraction of films, formation of black spots, film rupture, molecular interactions in films. Thus, it is possible to model not only the properties of a foam but also the processes undergoing in it. These studies allow to clarify the mechanism of these processes and to derive quantitative dependences for foams, O/W type emulsions and foamed emulsions, which in fact are closely related by properties to foams. Furthermore, a number of theoretical and practical problems of colloid chemistry, molecular physics, biophysics and biochemistry can also be solved. Several physico-technical parameters, such as pressure drop, volumetric flow rate (foam rotameter) and rate of gas diffusion through the film, are based on the measurement of some of the foam film parameters. For instance, Dewar [1] has used foam films in acoustic measurements. The study of the shape and tension of foam bubble films, in particular of bubbles floating at a liquid surface, provides information that is used in designing pneumatic constructions [2], Given bellow are the most important foam properties that determine their practical application. The processes of foam flotation of suspensions, ion flotation, foam accumulation and foam separation of soluble surfactants as well as the treatment of waste waters polluted by various substances (soluble and insoluble), are based on the difference in the compositions of the initial foaming solution and the liquid phase in the foam. Due ro this difference it is possible to accelerate some reactions (foam catalysis) and to shift the chemical equilibrium of some reactions in the foam. The low heat... 

As an example, it will be permitted to assume the shape of kerosene charged in the Dewar flask used in the BAM test to be a composite of a cylinder and a hemisphere (see Fig. 47 in Subsection 5.5.2). 

Before the apparatus was assembled, the volume of the U-tube was determined as a function of the distance from a reference mark at the bottom of the tube. The volume of liquid ozone collected was then determined by reading the liquid level with a cathetometer. The liquid level was viewed through an unsilvered strip in the Dewar flask and the boiling liquid oxygen (or nitrogen) which was used as a refrigerant. The distortions inherent in these readings limited the accuracy, but the compositions at the liquid phase boundaries were reproducible within 0.5%. 

For CHONS compounds with up to 40 carbons, see G. H. Stout, Composition Tables, New York, W. A. Benjamin, Inc., 1963 for compounds of these elements plus phosphorus and the halogens, with up to 30 carbons, see M. J. S. Dewar and R. Jones, loc. cit. 

This principle, used by the National Accelerator Laboratory to support superconducting magnets through the walls of a dewar, achieves dimensional stability because the thermal contraction of the aluminum intermediate tube equals the sum of the contractions of the outer and inner G-10 composite tubes. 

The composite struts also act as electric and thermal insulators between the helium dewar and rock. 

The designs presented are for a laminated composite structure fastened to the vertical rock tunnel wall. This structure is 1.5 m wide radially, 3.7 m long axially, and carries magnetically induced compressive radial forces of 17.3 MN and axial shearing forces of -30.5 MN. These forces are applied via the aluminum bulkhead to the free edge of the strut. The bulkhead is a load-carrying member between the strut and the liquid helium dewar. The strut is... 

Resistance-Temperature Scaling of Carbon-Composition Thermometers (2) 104 TRANSFER OF LIQUEFIED GASES [see also DEWARS, LINES, PUMPING SYSTEMS]... 

Hust, J. G., Thermal Conductivity of Glass Fiber/Epoxy Composite Support Bands for Cryogenic Dewars, Phase II, NBSIR 84-3003, National Bureau of Standards, Boulder, CO, 1984. [G-10]... 

Since ortho and parahydrogen have different vapor pressures, an ortho-para analyzer was connected to sample gas from both the vapor bulb and the dewar, to measure any differences in vapor composition. 

After the transfer tube has been assembled and evacuated, the vapor-pressure system is filled. Since it is important that the composition of the substance in the vapor-pressure system be identical to that flowing through the test orifice, the vapor-pressure system is filled with gas obtained by vaporizing liquid from the supply dewar. The final pressure of the vapor-pressure system is fixed because during testing the liquid-vapor interface must be in the bulb and not in the pressure line. 

THERMOMETRY. Twelve matched 2 Allen-Bradley carbon-composition resistors were installed on 5% in. centers on a thin-walled stainless steel tube in one of our 6000-liter supply dewars. The objective of this was measurement of gas and possibly liquid temperatures in order to obtain a better idea on pressurization gas requirements, and the amount of heat transferred to the liquid. The resistors were selected to match at room temperature (33 ohms) and in liquid nitrogen (40 ohms). They remained matched in liquid hydrogen(70 ohms). Within our accuracy requirements their resistance R(T) is described by the simple inverse temperature law... 

Answer by Author No, it does not. The composition by weight of the chamber gas is the same as that in the dewar regardless of the flow rate. The only exception is the small amount of oxygen consumed by the animals in the chamber. This amounts to only about. 0014 pounds per minute. 

Demorest M, Mooberry D, Danforth JD (1951) Decomposition of ketones and fatty acids by silica-alumina composites. Ind Eng Chem 43 2560-2572 Dewar MJ, Krull KL (1990) Acidity of carboxylic acids due to delocalization or induction J Chem Soc Chem Commun 333-334... 

Early calorimetric investigations were performed on pupae of the wax moth Galleria mellonella by means of a differential adiabatic setup [92]. Galleria represents an important pest for weak honeybee colonies where it feeds on wax, honey, pollen and other organic material. Individual pupae were kept in small Dewar flasks of 5 cm for measurements of 10 to 60 min, which were repeated in regular intervals through the whole pupal metamorphosis of about 7 days. The calorimetric experiments alternated with manometry (indirect calorimetry) to evaluate the RQ and to find hints about the type of metabolism. Heat dissipation was monitored by electrical heating of the reference flask to keep the temperature difference between both Dewars close to zero. In this way composite curves for male and female moths and both direct and indirect calorimetry were established. 

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