Bleeding, permeability

Damp-proofing admixtures include soaps and fatty acids which react with the cement hydrates to modify workability, bleeding and settlement, air content, compressive strength and durability characteristics. Mix proportions, mix consistency, admixture dosage and poor mixing influence the effects produced by the admixture. In cement-rich mixes void content is often increased, resulting in increased permeability. Since the admixture... 

The rate of bleeding is dependent on several factors, including the permeability of the fiber bed, both vertically and horizontally, and the viscosity of the liquid resin. The permeability of the fiber bed will depend on the weave of the fabric, the fiber diameter, and the fiber volume fraction. The resin viscosity is determined by the chemistry of the resin and the thermal profile of the cure cycle. The cure cycle greatly affects resin viscosity and the flow process, both directly through the pressure application and indirectly through the effect of the thermal profile on resin viscosity. 

Vasopressin [vay soe PRESS in] (antidiuretic hormone, ADH), is structurally related to oxytocin (Figure 25.5). The chemically-synthesized nonapeptide has replaced that extracted from animal posterior pituitaries. Vasopressin has both antidiuretic and vasopressor effects. In the kidney it binds to the V2 receptor to increase water permeability and resorption in the collecting tubules. Thus the major use of vasopressin is to treat diabetes insipidus. It also finds use in controlling bleeding due to esophageal varices or colonic diverticula. Other effects of vasopressin are mediated by the Vi receptor, found in vascular smooth muscle, liver and other tissues. As might be expected the major toxicity is water intoxication and hyponatremia. Headache, bronchoconstriction and tremor also can occur. Caution must be used in treating patients with coronary artery disease, epilepsy and asthma. 

Figure 28. Relationship between permeability and bleed through for acid-activated montmorillonite (AAM) and activated hormite (AH). (This figure is available in full color at http //www.mrw.interscience.wiley.com/biofp.)...

The essential element, hypoperfusion of vital organs, is present whatever the cause, whether pump failure (myocardial infarction), maldistribution of blood (septic shock) or loss of total intravascular volume (bleeding or increased permeability of vessels damaged by bacterial cell products, bums or anoxia). Fimction of vital organs, brain (consciousness, respiration) and kidney (urine formation) are clinical indicators of adequacy of perfusion of these organs. 

It is preferable to apply the phenol before dermabrasion, as the dermabrasion might cause the phenol to penetrate too quickly and too deeply through skin whose permeability has been significantly altered by the abrasion. Also, the diffuse bleeding that accompanies the abrasion would partially neutralize the phenol. 

Dicoumarin is a white crystalline substance of slightly bitter taste. Its biological action is twofold. On the one hand, it is an antagonist of vitamin K, reducing the production of prothrombin in liver cells, which results in a decrease of blood coagulability. On the other hand, dicoumarin makes vein walls permeable, so that blood may penetrate the tissues of internal organs. As a result of this double action, animals bleed to death or die from cerebral haemorrhage. 

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