Direct capillary action

In Section 4.1.3 (Figure 91) it was already demonstrated that direct capillary action may be used to produce more or less spherical agglomerates in and from a bed of powder. Similar methods are conceivable. 

Another technology, which was also mentioned previously in Section 4.1.3 (Figure 86), finds considerable interest in recent times and can also be classified as a method based on direct capillary action. Details may be gleaned from publications. ... 

Directed Oxidation of a Molten Metal. Directed oxidation of a molten metal or the Lanxide process (45,68,91) involves the reaction of a molten metal with a gaseous oxidant, eg, A1 with O2 in air, to form a porous three-dimensional oxide that grows outward from the metal/ceramic surface. The process proceeds via capillary action as the molten metal wicks into open pore channels in the oxide scale growth. Reinforced ceramic matrix composites can be formed by positioning inert filler materials, eg, fibers, whiskers, and/or particulates, in the path of the oxide scale growth. The resultant composite is comprised of both interconnected metal and ceramic. Typically 5—30 vol % metal remains after processing. The composite product maintains many of the desirable properties of a ceramic however, the presence of the metal serves to increase the fracture toughness of the composite. 

We will cover a simple drying model to examine the radiation drier of coated paper. We assume there are no major temperature or humidity variations in the direction of the paper web thickness, and that temperature T and humidity u are constant in the direction of thickness. This assumption requires that the capillary action be ignored, and the pressure gradient of water is zero on the assumption hu/dx = dT/dx = 0. How is it possible that the humidity distribution remains uniform ... 

An indwelling catheter is commonly used in various health care settings, and is associated with UTIs. Bacteria may be introduced into the bladder via the catheter in several ways. These include direct infection introduction during catheterization (via colonization and subsequently traveling the length of the catheter through bacterial motility or capillary action). UTIs as a result of an indwelling catheter are common and occur at a rate of 5% per day of catheter presence.25... 

Chromatography techniques can be further classified according to configuration—how the stationary phase is contained, how the mobile phase is configured with respect to the stationary phase in terms of physical state (gas or liquid) and positioning, and how and in what direction the mobile phase travels in terms of gravity, capillary action, or other forces. 

Water flow through unsaturated soil is controlled by the same forces as capillary action and water retention (i.e., adhesion, gravity, and surface tension). Flow can occur only when the water phase is continuous from pore to pore. If gravity is the controlling force, downward flow will occur according to Darcy s law in direct proportion to the percentage of water-filled, connected pores. For example, if only half the pores in a cross section are water filled, the flow through that section will be half of that predicted by Q- K1A. 

Aravamudhan, Rahman, and Bhansali. [70] developed a micro direct ethanol fuel cell with silicon diffusion layers. Each silicon substrate had a number of straight micropores or holes that were formed using microelec-tromechanical system (MEMS) fabrication techniques. The pores acted both as microcapillaries/wicking structures and as built-in fuel reservoirs. The capillary action of the microperforations pumps the fuel toward the reaction sites located at the CL. Again, the size and pattern of these perforations could be modified depending on the desired properties or parameters. Lee and Chuang [71] also used a silicon substrate and machined microperforations and microchannels on it in order to use it as the cathode diffusion layer and FF channel plate in a micro-PEMFC. 

In this approach, NAs are directly deposited onto a glass support using a robot able to deliver with high precision a sample to a specific x y programmed location. The NA sample is loaded into a spotting pin (highly miniaturized stainless-steel fountain-pen nibs with a gap) by capillary action, and small volumes are transferred to a solid surface, such as a microscope slide, by direct physical contact between the pin and the solid substrate. Spot size depends on the acceleration of the pen towards and away from the slide, and the surface tension of the slide. After the first spotting cycle, the pin is washed and a second sample is then transferred to an adjacent address. A robotic control system and multiplexed print heads allow the automated immobilization of many different probes simultaneously onto the slide [29]. 

The most commonly used form of refractometer is the Abbe refractometer, shown schematically in Fig. 11. This differs from the immersion refractometer in two important respects. First, instead of dipping into the liquid, the refractometer contains only a few drops of the liquid held by capillary action in a thin space between the refracting prism and an illuminating prism. Second, instead of reading the position of the critical-ray boundary on a scale, one adjusts this boundary so that it is at the intersection of a pair of cross-hairs by rotating the refracting prism until the telescope axis makes the required angle 8 with the normal to the air interface of the prism. The index of refraction is then read directly from a scale associated with the prism rotation. 

The origin is generally marked on the paper (with pencil) at 3j inches from one end for electrophoresis at pH 1.9 and at 9-10 inches for electrophoresis at pH 3.6, 4.7 or 6.5, although certain procedures may require a shift in the position of the origin. Samples are usually applied to the dry paper, and if volumes larger than 10-20 pi are to be applied at the same point, the paper should be dried (with a hair dryer or other type of fan) between applications. In some instances, the samples (in less than 25 pi) may be applied directly to papers saturated with the electrophoresis buffer (after air drying for 5-10 min). If the samples are applied to dry papers, the papers are then placed on the electrophoresis racks and saturated with a stream of buffer (a squeeze bottle is convenient) in such a way that the solvent will approach the sample areas by capillary action at about the same rate from both sides. 

The two-phase boride/carbide layer described in item 1 extends downward by reaction as the boron-rich liquid below it is drawn into the porous boron carbide by capillary action. Boron and carbon rapidly diffuse through this thin B-rich liquid layer, causing the two-phase layer to thicken as the directed reaction proceeds. 

The use of an indwelling catheter frequently is associated with infection of the urinary tract and represents the most common cause of hospital-acquired infection. The incidence of catheter-associated infection is related to a variety of factors, including method and duration of catheterization, the catheter system (open or closed), the care of the system, the susceptibility of the patient, and the technique of the health care personnel inserting the catheter. The incidence of infection from a single catheterization in a healthy ambulatory patient is 1%. Bacteria may enter the bladder in a number of ways. During the catheterization, bacteria may be introduced directly into the bladder from the urethra. Once the catheter is in place, bacteria may pass up the lumen of the catheter via the movement of air bubbles, by motility of the bacteria, or by capillary action. In addition, bacteria may reach the bladder from around the exudative sheath that surrounds... 

Hoyland (2) contends that aqueous liquids penetrate paper more by this process than by capillary action. Commencing with Fick s second law of diffusion which relates the diffusion coefficient D to a function of the concentration change of diffusing liquid in time t at any point x along the direction of diffusion ... 

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