Subject water column

To this solution was added at one time the above-obtained ethyl acetate solution at -15°C, and the resulting mixture was stirred for 1 hour at -10°C to -15°C. The reaction mixture was cooied to -30°C, and water (80 ml) was added thereto. The aqueous layer was separated, adjusted to pH 4.5 with sodium bicarbonate and subjected to column chromatography on Diaion HP-20 resin (Mitsubishi Chemical Industries Ltd.) using 25% aqueous solution of isopropyl alcohol as an eluent. The eluate was lyophilized to give 7-[2-methoxyimino-2-(2-amino-1,3-thiazol-4-yl)acetamido] cephalosporanic acid (syn isomer) (1.8 g), MP 227°C (decomp.). 

The Waters system uses a plastic cartridge which is inserted into a device (the Z-module) that subjects the column to radial compression, ie pressure is applied along the radial axis of the column tube. The flexible wall of the column then moulds itself into the voids that are present in the wall regions of the column. This method is claimed to produce an improvement in the packed bed structure, better column performance and longer useful column life. 

Paraquat is used to control aquatic weeds. It also passes into aquatic environments through rain, where it is rapidly accumulated by aquatic organisms, especially fish (Gabryelak and Klekot 1985). Paraquat applied to control aquatic weeds is accumulated by aquatic macrophytes and algae, and it is adsorbed to sediments and suspended materials. Initial applications of 1 to 5 mg/L in the water column are usually not detectable under field conditions after 8 to 27 days (Summers 1980). The half-time persistence of paraquat in water column at normal doses for weed control (i.e., 0.5 to 1.0 mg/L) was 36 h less than 0.01 mg/L was detectable in 2 weeks (Calderbank 1975). In solution, paraquat was subject to photodecomposition and microbial metabolism, degrading to methylamine... 

Fixed-Roof Tanks. The effect of internal pressure on plate structures, including tanks and pressure vessels, is important to tank design. If a flat plate is subjected to pressure on one side, it must be made quite thick to resist bending or deformation. A shallow cone-roof deck on a tank approximates a flat surface and is typically built of 3/ 16-in. (4.76-mm) thick steel (Fig. 4a). This is unable to withstand more than a few inches of water column pressure. The larger the tank, the more severe the effect of pressure on the structure. As pressure increases, the practicality of fabrication practice and costs force the tank builder to use shapes more suitable for internal pressure. The cylinder is an economic and easily fabricated shape for pressure containment. Indeed, almost all large tanks are cylindrical. The problem, however, is that the ends must be closed. The relatively flat roofs and bottoms or closures of tanks do not lend themselves to much internal pressure. As internal pressure increases, tank builders use roof domes or spheres. The spherical tank is the most economic shape for internal pressure storage in terms of required thickness, but it is generally more difficult to fabricate than a dome- or umbrella-roof tank because of its compound curvature. 

Briggs (B12) was able to subject water at room temperature to a negative pressure of nearly 270 atm. The experimental technique consisted of spinning a horizontal glass tube ( scrupulous cleanliness is necessary ) about a vertical axis located at its center. The tubing contained the liquid and was open at both ends. The centrifugal force needed to break the liquid column was observed. The experimental results are shown in Fig. 24. 

The fate of fenitrothion in the environment has been a subject of great interest in Canada since the late 1960 s because of its use for control of the Spruce Budworm (Chorlstoneura fumiferana). Laboratory and field experiments have established that fenitrothion persists for only 1 to several days in natural waters and is degraded primarily by photolysis and microbial activity (1-4). Sorption by sediments, aquatic macrophytes and microphytes are also important paths of loss of the insecticide from the water column (2-5). 

A solution of S-iodomethyl-6a,9a-difluoro-lip-hydroxy-16a-methyl-3-oxo-17a-propionyloxyandrosta-l,4-diene-17p-carbothioate (310 mg) in acetonitrile (10 ml) was stirred with silver fluoride (947 mg) for 3 days at room temperature in the dark. Ethyl acetate (100 ml) was added and the mixture was filtered through kieselguhr. The filtrate was washed successively with 2 N hydrochloric acid, water, saturated brine, then dried. The solvent was removed and the residue was subjected to column chromatography in chloroform then chloroform-acetone (19 1). The product was eluted with ethyl acetate and crystallised on concentration of the solution to give S-fluoromethyl 6a,9a-difluoro-lip-hydroxy-16a-methyl-3-oxo-17a-propionyloxyandrosta-l,4-diene-17p-carbothioate (0.075 g) melting point 272-273°C (dec.), [a]D= +30° (c 0.35). 

To 1.17 g of (-)-7,8-difluoro-2,3-dihydro-3-hydroxymethyl-4H-[l,4] benzoxazine was added 2.77 g of thionyl chloride in pyridine. The reaction mixture was concentrated and the concentrate was subjected to column chromatography using 40 g of silica gel and eluted with chloroform to obtain 1.18 g of the reaction product as a colorless oily product. This product was dissolved in 30 ml of dimethyl sulfoxide, and 0.41 g of sodium borohydride was added thereto, followed by heating at 80-90°C for 1 hour. The reaction mixture was dissolved in 500 ml of benzene, washed with water to remove the dimethyl sulfoxide, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The concentrate was subjected to column chromatography using 40 g of silica gel and eluted with benzene to obtain 0.80 g of (-)-7,8-difluoro-2,3-dihydro-3-methyl-4H-[l,4]benzoxazine as a colorless oily product [a]D25 = -9.6° (c = 2.17, CHCI3). Optical Purity >99% e.e. 

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