Vacuum backing

Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs used to treat serotonin imbalances. Drugs such as Prozac, Cymbalta, Lexapro, and Zoloft are in this class. Normally the sending neuron vacuums back up the excess serotonin so that it can be released again. These drugs block or inhibit that reuptake, leaving more serotonin available in the synapses of the brain. 

In order to prevent overpressurization of the annular space due to a leak in the inner vessel, the outer vessel should also be equipped with a pressure relief device. If the device is a rupture disk, the disk should be reinforced with a vacuum backing disk to prevent its collapse during evacuation of the insulation space. The annular space safety disk serves to prevent collapsing of the inner vessel due to external pressure, as well as to prevent damage to the outer vessel from internal pressure. This burst-disk assembly is normally designed to rupture if the annular space pressure exceeds about 35-50 kPa gauge. 

Each newly cleaved mica surface is very clean. Flowever, it is known that mica has a strong tendency to spontaneously adsorb particles [45] or organic contaminants [46], which may affect subsequent measurements. The mica sheets are cut into 10 nun x 10 nun sized samples using a hot platinum wire, then laid down onto a thick and clean 100 nun x 100 nun mica backing sheet for protection. On the backing sheet, the mica samples can be transferred into a vacuum chamber for themial evaporation of typically 50-55 mn thick silver mirrors. 

For all vacuum distillations, a trap (cf. K, Fig. 14, p, 31) should be fitted near the pump, in ease the water sucks back . 

When constructing a manometer of the type shown in Fig. 12(c), it is impor tant to apply a very high vacuum (e.g., with a Hy-Vac pump) to the manometer while the mercury in the left-hand (sealed) limb is heated until it boils unless this is done, traces of air will remain in this limb and cause inaccurate readings. During a distillation, the tap I should be kept closed except when a pressure reading is being taken if it is left open indefinitely, a sudden default by the distillation apparatus or by the pump may cause the mercury in the sealed limb of G to fly back and fracture the top of the limb. 

The high-pressure water supply service is employed for the operation of the ordinary filter pump, which finds so many applications in the laboratory. A typical all metal filter pump is illustrated in Fig. 11, 21, 1. It is an advantage to have a non-return valve fitted in the side arm to prevent sucking back if the water is turned off or if the water pressure is suddenly reduced. Theoretically, an efficient filter pump should reduce the pressure in a system to a value equal to the vapour pressure of the water at the temperature of the water of the supply mains. In practice this pressure is rarely attained (it is usually 4 10 mm. higher) because of the leakage of air into the apparatus and the higher temperature of the laboratory. The vapour pressures of water at 5°, 10°, 15°, 20° and 25° are respectively 6-5, 9-2,12-8, 17 5 and 23 8 mm. respectively. It is evident that the vacuum obtained with a water pump will vary considerably with the temperature of the water and therefore with the season of the year in any case a really good vacuum cannot be produced by a filter pump. 

Preparation of silver maleate. Dissolve 65 g. of pure maleic acid (Section 111,143) in the calculated quantity of carefully standardised 3-5N aqueous ammonia solution in a 1-htre beaker and add, whilst stirring mechanically, a solution of 204 g. of silver nitrate in 200 ml. of water. Filter oflf the precipitated silver maleate at the pump, wash it with distilled water, and press well with the back of a large flat glass stopper. Dry in an electric oven at 50-60° to constant weight. The yield of the dry silver salt is 150 g. Store in a vacuum desiccator in the dark. 

It will be a little tricky but one can also try to purify by freezing I The sassafras oil is thrown into the freezer to chill. Safrole itself freezes at -14°C so anything that starts to freeze prior to that can be cold filtered in a prechilled vacuum filtration setup. The filtrate goes back in the freezer until -14°C is reached and the mother lode of safrole freezes up. This again is filtered cold but this time the frozen mass of safrole crystals are washed with some ice cold methanol or ethanol (preferably at -14°C) to wash away the unfrozen high-boiling constituents. 

After 5 hours the reaction is stopped and the flask cooled. The formyl-MDA can be isolated and hydrolyzed by any of the ways Strike just mentioned a few paragraphs back, but this method offers a third, very convenient way which should be tried. What the chemist does is forget about letting the flask and its contents cool. Instead, she removes the oil bath, places the flask back on the stirplate (distillation setup still attached), attaches a vacuum and distills off all the formamide. What remains is a dark, heavy formyl-MDA precipitate that is allowed to cool down while the chemist makes up a solution of 150g potassium hydroxide (KOH), 500mL ethanol and 125mL dH20. This solution is poured into the... 

As the solution cools a big old mass of unreacted ammonium chloride will form. The chemist removes this by vacuum filtration and saves the crystals for reuse at another time. The golden colored filtrate is placed back in the flask and distilled (with vacuum now ) to reduce its volume by about a third. Temperature is not so much a problem now as the chemist will let the stuff distill over at whatever temperature is necessary. Sometimes the reducing solution is so concentrated that the remaining ammonium chloride crystals... 

If a particularly parallel beam is required in the chamber into which it is flowing the beam may be skimmed in the region of hydrodynamic flow. A skimmer is a collimator which is specially constructed in order to avoid shockwaves travelling back into the gas and increasing 7). The gas that has been skimmed away may be pumped off in a separate vacuum chamber. Further collimation may be carried out in the region of molecular flow and a so-called supersonic beam results. When a skimmer is not used, a supersonic jet results this may or may not be collimated. 

Dislodging of Cake by Reverse Flow. Intermittent back-flushing of the filter medium can also be used to control cake growth, leading to filtration through thin cakes in short cycles. Conventional vacuum or pressure filters can be modified to counter the effects of the forces during the back-flush (23,24). 

In the extraction of citms juices it is desirable to have as gende an extraction pressure as possible. There should be minimal contact time between juice and pulp to reduce the amount of bitter substances expressed from the peel into the juice. The amount of suspended soHds in citms juice is controlled in a subsequent separation in a finisher. A screw action is used to force the juice through a perforated screen and separate the larger pulp particles from the juice. The oil level in the juice is adjusted by vaporizing under a vacuum (10). The separated pulp is washed and finished several times to produce a solution which is then either added back to the juice to increase juice yield, or concentrated to produce pulp wash soHds, also called water extract of orange soHds, which can be used as a cloudy beverage base. 

The reactor effluent is separated by conventional distillation into recycle solvent, light gases, to 537°C bp distillate, and a heavy vacuum bottoms stream containing unconverted coal and ash. The recycle solvent is hydrogenated in a separate reactor and sent back to the Hquefaction reactor. 

The rigidi d thermoplastic sheet - Tiocess combines thermoplastic sheet vacuum forming with a spray-up or cold press molding process to add a thermoset composite stmctural backing to a decorative thermoplastic skin. Large parts such as bathtubs, hot tubs, recreation vehicle components, and camper tops have been produced by this process. 

For low pressure pipelines that have ports open to the atmosphere, eg, sewers or closed effluent culverts, samplers are designed to sample through manholes. In a typical system, the Hquid is lifted through a suction line into the sampling chamber under vacuum. When filled, the vacuum shuts off, and the sample drains into a sample jar. A secondary float prevents any Hquid from reaching the vacuum pump. The suction line then drains by gravity back to the source. 

Another PVC siding is an extmded product of an internally ribbed, dual-wall profile. A conventional screw extmder, with a vacuum sizer cooled with water and air, forms a product about 20 cm wide with 160 mm walls and 80 mm ribs on 25 cm centers. The total thickness is about 0.64 cm. The ribs provide rigidity and strength and the dual-wall constmction adds thermal insulation. No backing or core is used. 

---