Coagulation mechanisms

Dismption of the endothehal surface of blood vessels expose coUagen fibers and connective tissue. These provide surfaces that promote platelet adherence, platelet release reaction, and subsequent platelet aggregation. Substances Hberated from the platelets stimulate further platelet aggregation, eg, adenosine diphosphate maintain vasoconstriction, eg, serotonin and participate in blood coagulation, eg, platelet Factors III and IV. In addition, the release reaction modifies platelet membranes in a manner that renders phosphoHpid available for coagulation. The thrombin [9002-04-4] elaborated by the coagulation mechanism is a potent agent in the induction of the platelet release reaction. 

Destruction of the casein micelles in the milk with subsequent precipitation of the casein can be accomplished in a number of ways. The action of heat or the action of alcohols, acids, salts and the enzyme rennet all bring about precipitation. In commercial practise the two techniques used employ either acid coagulation or rennet coagulation mechanisms. 

Prindle and Ray (ZB.) have recently analyzed the same styrene data using a hybrid model consisting of the micellar nucleation mechanism above the CMC and of the homogeneous nucleation and coagulation mechanism below the CMC. Their simulations show a much steeper rise in the particle number concentration precisely at the CMC than predicted by EPM. Their hybrid model does not appear to predict that the particle concentration levels off at high surfactant concentrations. 

The schlieren experiments employing solutions with THF and dloxane as solvents proved that at least two different coagulation mechanisms exist in an unstirred bath. It is evident that Case B applied for the THF solution, while Case A applied for the dloxane solution. The depletion and removal of the THF from the cast layer Interface via convection flow (rather than diffusive exchange with water molecules) is instantaneous, and the rapid accumulation of the solvent on the surface of the aqueous coagulation bath is notable. As for the dloxane solution (Figure 7), schlieren patterns could not be observed even after 1000 seconds - even when phase... 

This implies that the selective layer of reverse osmosis membranes may have a different origin from that of the micelles. Such a case is clearly identified by examination of the skin structure of cellulose acetate/poly(bromophenylene oxide phosphonate) alloy membranes (1 ), which exhibit a high flux and high salt separation (Figure 13). The skin rests on an assembly of giant spheres (up to 1 pm in diameter) and is certainly originated by a different coagulation mechanism than that of the spheres. 

If possible, discontinue or reduce the dosage of drugs interfering with coagulation mechanisms (eg, salicylates, antibiotics) as an alternative to phytonadione. The severity of the coagulation disorder should determine whether the immediate administration of phytonadione is required in addition to discontinuation or reduction of interfering drugs. 

Adverse effects include anaphylactoid reactions, manifesting as itching, chills, urticaria, shock and bronchospasm. In rising doses it can influence coagulation mechanism without triggering clinical haemorrhage. 

Unknown regimen for 2 mos Female/7 8 Coronary artery bypass and progressive dementia Warfarin for 5 yrs None mentioned Intracerebral hemorrhage Additive effect on coagulation mechanisms... 

It is also important to note that the coagulation mechanism in vivo does not occur in solution, but is localized to activated cell surfaces expressing anionic phospholipids such as phosphatidylserine, and is mediated by Ca2+ bridging between the anionic phospholipids and 7-carboxyglutamic acid residues of the clotting factors. This is the basis for using calcium chelators such as ethylenediamine tetraacetic acid (EDTA) or citrate to prevent blood from clotting in a test tube. 

Merlini PA, Bauer KA, Oltrona L, et al. Persistent activation of the coagulation mechanism in unstable angina and myocardial infarction. Circulation 1994 90 61-68. 

Only one coagulation mechanism is dominant for each particle size considered. 

Each coagulation mechanism can be represented by a single parameter. 

Tang, W., et al. (1997). Study on coagulate mechanism of polyaluminium chloride. J. Nanjing Univ. Science Technol. 21, 4, 325-328. 

Concerning the fourth type of pattern, Ni (and REE) are relatively more depleted in the Negro waters than in the Solimoes waters. These elements have a very limited solubility and are transported mainly in the particulate form. Following Gaillardet et al. (1997), pH strongly controls the transport phase of these elements. Adsorption-desorption processes and coagulation mechanisms may explain their low temporal variations. U and Rb are more soluble, but the narrow... 

The equations for dN/dt and dRj/dt, as well as for dV dt [Eq. (39)] are solved by numerical integration for the polymerization stem MMA-K2S20e water, with rate constants obtained from the literature. The initiator efficiency was set equal to unity. Particle numbers between 10 and 10 were drained for initiator concentrations of 10 -10 mol/dm. The calculations showed that N should be almost independent of the chosen value offor values between 5 and 70 (in strong contrast to our calculations). The reason for this is probably that aqueous-phase termination with subsequent precipitation is the dominant particle-formation mechanism in Aral s model, even more so with increasing initiator concentration. The theoretical particle-formation time was on the order of 2 sec, a veiy low value compared to the experimental results of Fitch and Tsai. Aral et at. found that their calculated particle numbers were approximately in accordance with the experimental results of Yamazaki et al. (1968) for emulsifier-free polymerizations. Aral s model does not inclnde any coagulation mechanisms. It will therefore have the same shortcomings as most other models, namely that the strongly increased particle number in... 

Platelets are contractile blood elements with a specialized task in the arrest of bleeding. The fundamental mechanisms of this specific hmction involve adhesion, aggregation, internal contraction and secretion. Furthermore, the phospholipids present in the platelet membranes play a key role in the development of coagulation mechanisms. 

A6. Alexander, B., Some biochemical, physiological and pathological aspects of the coagulation mechanism. In Blood Cells and Plasma Proteins (J. R. Tullis, ed.), pp. 75-92. Academic Press, New York, 1953. 

Therapy for the control or prevention of the acute events in death due to vascular disease can be approached in several ways. One general approach would be to control the interaction of blood components with the diseased blood vessel or with each other. In both these cases antithrombotic agents of diverse mechanism should be helpful. Whether control of fibrin formation, fibrinolysis or platelet function is desirable, each patient s problem would dictate the therapy best suited. Several reviews are available in which the different blood coagulation mechanisms that may be helpful in such therapy are discussed s " Reviews have also been published in which methodology is discussed for the testing of compounds and for the determination of abnormalities in platelet function. ... 

Thus there is a lai e discrepancy between the theoretical predictions of the collision efficiency for aerosol coagulation by differential sedimentation (taking into account inter-particie fluid motion) and experimental measurements for coagulation by turbulent shear in aqueous suspensions. We do not know whether this discrepancy is due to the ba.sic difference in the coagulation mechanisms (differential sedimentation vs. turbulent shear), different phenomena operating in the different fluid media, or some other as yet unidentified effect. 

Figure 7.7 Comparison of coagulation mechanisms for particles of 1 -/rra diameter interacting with panicles of diameter between 0.1 and 10 jam. Coagulation by shear based on 1000...

The contribution of the coagulation term [dtft/di]co3g vanishes identically no matter what the form of the collision frequency function. The coagulation mechanism only shifts matter up the distribution function from small to large sizes and does not change the local volumetric concentration of aerosol. 

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