Area of constriction

Recent advances in insulator dielectrophoretic devices have shown wide variety and creativity enabling highly functional electric field gradients. In all cases, highest field intensity occurs at sharp points or areas of highest curvature on the insulator as well as through areas of constriction in channels. 

In orifice and Venturi meters, tite area of constriction is constant, and tite pressure drop increases with the increase in flow rates. In area the meter, the pressure drop is constant, but the area of constriction increases witii increase in flow rate. The rotameter consists of a gradually tapered glass tube moimted vertically in a frame with the large end up. The fluid flows upward and with increase in flow, the float moves upward. 

The pneumatic deposition of the filament bundles onto the moving belt results in formation of the web. A pneumatic gun uses high pressure air to move the filaments through a constricted area of lower pressure but higher velocity, as in a venturi tube. Pneumatic jets used in spunbonded production have been described (17,24). Unfortunately, the exceUent filament uniformity coming out of the spinnerette is lost when the filaments are consoHdated going through a gun. 

In the meters so far described the area of the constriction or orifice is constant and the drop in pressure is dependent on the rate of flow. In the variable area meter, the drop in pressure is constant and the flowrate is a function of the area of the constriction. 

Boyack and Giddings [45] considered the tortuosity effects to be separable from the constriction effects. In their derivation they assumed that the electric field in the constricted channel decreased proportionally to the decrease in cross-sectional area and changes in path length. The field was assumed not to penetrate the barrier. The effect of constriction can be written in terms of porosity and L as... 

Stricture An area of narrowing or constriction of a tubular structure. Strictures may result from long-standing inflammation. 

For pH sensors used in in-vivo applications, especially those in continuous pH monitor or implantable applications, hemocompatibility is a key area of importance [150], The interaction of plasma proteins with sensor surface will affect sensor functions. Thrombus formation on the device surface due to accelerated coagulation, promoted by protein adsorption, provided platelet adhesion and activation. In addition, variation in the blood flow rate due to vasoconstriction (constriction of a blood vessel) and sensor attachment to vessel walls, known as wall effect , can cause significant errors during blood pH monitoring [50, 126],... 

Caffeine has widespread therapeutic use. It is widely used in headache (migraine) remedies such as aspirin and other analgesics. Caffeine is a mild vasoconstrictor and its ability to constrict blood vessels serving the brain explains its use to relieve headache. Individuals who consume caffeine regularly through medications and food are susceptible to what is known as a rebound headache or caffeine rebound. This occurs when regular caffeine intake is suddenly reduced and the vessels dilate. Caffeine is a common substance in medications to treat apnea in premature infants. Apparently, the area of the brain controlling respiration in premature infants is not fully developed and caffeine helps to stimulate this portion of the... 

By constricting the vascular bed, such coadministered vasoactive excipients as epinephrine can reduce the rate of uptake from the SC sites (4a). By contrast, the excipient hyaluronidase breaks down the interstitial barrier by lysing hyaluronic acid, a polysaccharide that helps form the intercellular ground substance of connective tissue (4b). This in effect spreads the injected drug solution over a larger area of connective tissue, increasing the absorption surface, and thereby increasing both the volume that can normally be injected SC (Table 1) and the rate of uptake (6). 

The mechanical stability of PSM and AMM-5 samples was investigated by pressing the sample in a die (having a diameter of 16 mm) under different pressures for 15 min. The effects of compression on the surface areas and pore properties of the materials are shown in Table 1. It can be seen that the surface areas of both PSM and AMM-5 samples decrease under high pressure compression. The decrease of surface area, which is proportional to the pressure exerted on the samples, is accompanied with the decrease of pore volume, with no obvious decrease of the pore diameter for both samples. The results indicate that, under high pressure compression, some of the mesoporous channels of MCM-41 have collapsed completely and not constricted to pores of smaller diameter. 

On a physiological level, Ritalin causes a 23 to 30% decrease of the overall blood flow in all areas of the human brain, as measured by a PET scan. This reduction is believed to be caused by a constriction of the blood vessels, probably... 

One of the areas of greatest interest is the development of synthetic blood vessels. Heart disease is currently the number one cause of death among both men and women in the United States. The most common cause of heart disease, in turn, is atherosclerosis, a condition in which fatty deposits form on the inner walls of blood vessels, constricting the flow of blood. If it were possible to develop an artificial substitute for blood vessels damaged by atherosclerosis or other diseases, it would save the lives of millions of Americans each year. 

The ability to control pain and inflammation is an area of continued interest within the pharmaceutical industry. Sensoneuropeptide tachykinins, distributed in the peripheral and central nervous systems, are known to be involved in neurologic inflammation, pain transmission, and broncho-constriction.39 The activation of NK-1 (neurokinin-1), NK-2, and NK-3 receptors can mediate the effects of these tachykinins, resulting in a search for new antagonists as a means of controlling... 

An additional form of air-conditioning is concerned with the removal of particulates, such as dust, microorganisms and allergens, from the inspired air. The large cross-sectional area of the nasal cavity and relatively low air velocities are ideal for particle deposition, as is the turbulence caused beyond constrictions where changes in air flow direction occur. The efficiency of particle removal from the air-stream is dependent on a number of factors including the aerodynamic diameter of the inhaled particles ... 

Semi-quantitative results may be obtained by the use of the Yagoda confined-spot-test papers (Schleicher and Schuell, U.S.A., Nos. 211Y and 597Y) these are prepared with a chemically inert, water-repelling barrier which constricts the spot reaction to a uniform area of fixed dimensions. 

The area of the mesophyll cell walls across which CO2 can diffuse is considerably larger than the surface area of the leaf (Figs. 1-2 and 8-4). For the constricting effect caused by the stomata, we used Ast/A, the fraction of the leaf surface area that is occupied by stomatal pores. Here we will use the ratio Am s/A to indicate the increase in area available for CO2 diffusion into cells within a leaf compared to the leaf surface area, where Ames is the total area of the cell walls of mesophyll cells that is exposed to the intercellular air spaces, and A is the area of one side of the same leaf. More conveniently, A mesM can refer to the internal and the external areas of a part of the leaf that is examined microscopically. 

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