Open ends gradients

The checkers used a Hoskins tube furnace, type FD303A (Central Scientific Co.), 17 in. long. The heater for the sublimation vessel was wound in two sections with heating wire in such a way that a decreasing temperature gradient in the direction of the pyrolysis oven was maintained. The open end of the heater was closed by an asbestos end plate which could be heated independently by a small nichrome coil. 

The dendrimer tubes prepared by this multilayer process have only one open end and probably show a mechanical stability gradient, indicating that the effective number of layer-deposition steps in the proximity of the closed end is lower than elsewhere because the ionic dendrimer to be precipitated has limited access there. Production of uniform tubes would therefore require templates with two openings. 

Thermal cycling will be lessened if the control (but not the measuring) thermocouple is placed between the liner and the furnace wall. It is highly advisable that the fused silica jacket about the welded container be sufficiently long to extend from the end of the furnace to permit condensation of the tetrahalide, should a leak develop. Unless a thermal gradient is required, the tantalum tube itself should be centered in the furnace. Although the explosion hazard is very slight if these procedures are followed, the open ends of the furnace should still be shielded from workers. 

Momentum Equation of Liquid-Liquid Flow We now consider a transient, fully developed, laminar, liquid-liquid stratified electroosmotic flow through a rectangular channel as illustrated in Fig. 2. For electroosmotic flow in an open-end channel, it is assumed that there is no pressure gradient along the microchannel. 

In uniform systems spiral waves usually appear as a pair when a break of a wave front creates two open ends of the front [2, 3] in nonuniform systems single spirals emerge frequently [44]. Only one open end of the wave front can form a spiral under some asymmetric spatial distributions of parameters (Figure 3). Single spirals can emerge at nonuniformities situated near a boundary of the system. In other cases, one spiral from a pair can be brought by gradient-induced drift to the medium boundary where it perishes. 

Thermocouples are primarily based on the Seebeck effect In an open circuit, consisting of two wires of different materials joined together at one end, an electromotive force (voltage) is generated between the free wire ends when subject to a temperature gradient. Because the voltage is dependent on the temperature difference between the wires (measurement) junction and the free (reference) ends, the system can be used for temperature measurement. Before modern electronic developments, a real reference temperature, for example, a water-ice bath, was used for the reference end of the thermocouple circuit. This is not necessary today, as the reference can be obtained electronically. Thermocouple material pairs, their temperature-electromotive forces, and tolerances are standardized. The standards are close to each other but not identical. The most common base-metal pairs are iron-constantan (type J), chomel-alumel (type K), and copper-constantan (type T). Noble-metal thermocouples (types S, R, and B) are made of platinum and rhodium in different mixing ratios. 

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