Cavity evacuation

In tumour cases after the pharyngeal incision it is usually easy to enter the tumour itself, which is then removed with tumour forceps, microcurettes (Fig. 10) and suction. In one of our C2 tumour eases (osteoclastoma) an interbody fusion was performed using iliac autograft and smaller bone chips placed into the cavity evacuated in the vertebral body. 

Die castings produced in a cavity which has been evacuated contain significantly less porosity and hence, are more ductile. Such castings were produced on an experimental basis in the 1980s. In the 1990s, this process is expected to compete with components either fabricated from sheet metal or... 

This technique is based on the Dewar flask, which is a donble-walled vessel with reflective surfaces on the evacuated side to reduce radiation losses. Figure 11-66 shows a typical laboratory-size Dewar. Figure 11-67 shows a semiportable type. Radiation losses can be further reduced by filling the cavity with powders such as perlite or silica prior to pulling the vacuum. 

A series of CoSx-MoSx/NaY catalysts was synthesized by intoducing Co(CO)3NO into MoSx/NaY evacuated at 673 K for 1 h, followed by second programmed sulfidation procedures. MoSx-CoSx/NaY catalysts were prepared in the reversed order of the metal sulfide accommodations into the zeolite cavities. When Co2(CO)g was used as the Co precursor, MoSx/NaY was impregnated with COj(CO)g dispersed in n-hexane, followed by evacuation at room temperature to remove the solvent. Co2(CO)g/MoSx/NaY was subsequently sulfided at 673 K to give CoSx/MoSx/NaY. The catalyst composition was determined by AAS and ICP. 

Strictly defined, cavitation refers only to the completely evacuated bubble or cavity, a true void, but since dissolved gases are present unless special steps are taken to remove them, and the vapor of the liquid can also penetrate the cavity, the term cavitation most often encompasses the three kinds of bubbles. 

A thin zirconia membrane is sealed to a stainless cup of about one inch diameter (Figure 5.9). The stainless cup has a feed tube welded to it. The inside cavity is evacuated to about 5 psi and sealed off. One can calculate the leak rate by monitoring the pressure decay as a function of time (see Section 5.2.1). 

While core formation during hydrolysis of Fe(III) produces electrically neutral ferri-hydrite, it also produces protons two per Fe(II) oxidized and hydrolysed, whether due to iron oxidation and hydrolysis at the ferroxidase centre, followed by further hydrolysis and migration to the core nucleation sites or by direct Fe(II) oxidation and hydrolysis on the mineral surface of the growing core. These protons must either be evacuated from the cavity or else their charges must be neutralized by incoming anions, and it... 

The Eulr2 alloy was prepared by direct combination of the metals. Europium chips, % in. on edge were placed in a V4 in.-diameter cavity of a die. Iridium metal powder, —325 mesh and 99.9% pure, was sprinkled over the rare earth element, and the mixture was compressed at 5000 psi. The compressed pellet was placed in a molybdenum boat, which then was transferred to a quartz sleeve, followed by insertion into a quartz reaction tube. The tube was attached to a glass vacuum line and evacuated. Argon was added to approximately 1 atm and the compressed pellet was heated to 900° C and held at the temperature for 14 hr. The product was air quenched to room temperature. The product was crushed in an agate ball mill, compressed into a pellet again, and reheated in the same manner as before. 

Temperature Sensing. As shown in Fig. 16, a layer of silicon (whose refractive index changes with temperature) is placed in the optical path in place of the evacuated cavity, as previously described. The second reflector (glass) is rigid. The effective path length thus changes with temperature. 

The sample to be analyzed, say C60 fullerene, is mixed with an appropriate amount of KBr in an agate mortar and then transferred into a press and compressed at 4,000 Kg into a pellet with a diameter of 1.2 cm and a thickness of 0.2 cm. The pellet was mounted into the sample holder of the Specac variable temperature cell and inserted into the cell. The cell was then evacuated with the aid of a pump to a vacuum of 0.1 torr and then heated gradually at 120°C in order to permit the humidity absorbed on the internal surfaces of the cell and in the KBr pellet to evaporate. The sample was then cooled to the desired temperature to record the infrared spectrum. In order to go below room temperature, use was made of liquid nitrogen, added cautiously and in small amount in the cavity present inside the cell. Such cavity is connected with the sample holder and permits to cool the sample to the desired temperature. The temperature of the sample was monitored with adequate thermocouples. The lowest temperature reached with this apparatus was -180°C (93K) while the highest temperature was +250°C. Heating is provided by the Joule effect and an external thermal control unit. 

RTM involves the pumping of the thermoset precursors into a heated mold cavity containing preplaced fiber mats. Mold filling and fiber impregnation may be assisted by partial evacuation of the mold. 

Ip is degassed and then distilled into a previously evacuated 23 cm long quartz cell with wedged (1.5°) anti-reflection coated windows epoxied on the ends. The cell is mounted in the laser cavity on X-Y-Z translation stages, and the I2 is frozen into the sidearm by dipping it in+a cold bath. The dye lasing threshold is measured, and the Ar laser is then set to the desired power. For one set of experiments, threshold pump power is near ( 11%) 550 mW, while for a second set the threshold is near 790 mW. 

All of the systematic tests [l, 10] to date support the results of reference [1]. The 1900 ppm difference with theory remains unresolved at this time. A new and systematically very different experiment designed to reach 100 ppm accuracy [12] using a slow positron beam with Ps formation in an evacuated cavity is now underway. Results are expected within one year. 

A schematic diagram of the spectrometer is shown in figure 10.16 its successfid operation depends critically upon the ability to achieve accurate timing for a sequence of several events. First, a short pulse of gas is produced from a pulsed-nozzle source, the gas travelling in a direction perpendicular to the axis of an evacuated Fabry Perot cavity, described later. This gas pulse lasts for about 1 ms, and the expansion in the cavity is in an essentially collision-free environment... 

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