Secondary mechanisms

Nucleation is initiated by secondary mechanisms involving the seed crystals or low super-saturation and high surface area of seed crystals eliminate or minimize nucleation seed crystals grow... 

Nucleation continues by secondary mechanisms and growth continues throughout the run until the batch achieves equilibrium and/or is dumped... 

Where feed lines have short pipe runs, where hot wells or FW tanks are of small volume, or when FW is too cold, there often is insufficient time for full DO scavenging to take place, even when using catalyzed scavengers. The inevitable result of this lack of contact time is the formation of oxygen-induced corrosion products, which by various secondary mechanisms may settle out to form permanent deposits within the boiler system. These deposits may develop in several forms (e.g., where DO removal is particularly poor, they often appear as reddish tubercles of hematite covering sites where pitting corrosion is active). Active pitting corrosion combined with the presence of waterside deposits ultimately may lead to tube failure in a boiler or other item of system equipment and result in a system shutdown. 

Where very effective steam-water separation is required, primary functional control lies in the efficiency and operating condition of the mechanical devices employed. As pressure increases, the density differences between water and steam decrease, so in order to ensure good separation, large HP boilers may employ several types and designs of both primary and secondary mechanical separation devices. 

Additional Investigation Is required to determine If effects on these pathways are primary or secondary mechanisms of action and If the same mechanisms are applicable to more anatomically complex plants and under a range of environmental conditions. 

Goodman JI, Watson RE. Altered DNA methylation a secondary mechanism involved in carcinogenesis. Annu Rev Pharmacol Toxicol 2002 42 501-525. 

The design-base particle diameter to be separated in the vapor space should not exceed the pad-disengage-mt-nt droplet diameter. 1). To be on the safe side, a maximum droplet diameter should be limited to 400 pm. In horizontal drum design, the mesh pad should be regarded as a polisher for removing small droplets not separated in the vapor space—i.e., as a secondary mechanism in vapor-liquid separation... 

Fig. 32 shows the effect of varying the frequency. In this case the secondary mechanical y process normally considered characteristic of a chain containing four or more methylenes is clearly visible. 

Another way in which gene expression is regulated is by translational control, where the rate of protein synthesis is controlled at the point of transcription of mRNA into polypeptides (Appendix 5.6). Generally, the majority of the control mechanisms in bacteria is at the transcriptional level. Translational control is less well understood and appears to be a secondary mechanism in bacteria, but it is thought to be very important in eukaryotic organisms. 

According to Coura and Dias (2009), the transmission mechanisms for Chagas infection can be divided into two groups (i) the principal mechanisms, by means of vectors (triatomines), blood transfusion, oral transmission, contaminated food and placental, or birth canal transmission and (ii) secondary mechanisms, by means of laboratory accidents, management of infected animals, organ transplants, sexual transmission, wounds, contact with sperm or menstrual fluid contaminated with T. cruzi and, hypothetically, deliberate criminal inoculation or contamination of food with the parasite (Coura and Dias, 2009). 

Park E., Velumian A. A., and Fehlings M. G. (2004). The role of excitotoxicity in secondary mechanisms of spinal cord injury a review with an emphasis on the implications for white matter degeneration. J. Neurotrauma 21 754-774. 

Each of the types of SPE sorbents discussed retains analytes through a primary mechanism, such as by van der Waals interactions, polar dipole-dipole forces, hydrogen bonding, or electrostatic forces. However, sorbents often exhibit retention by a secondary mechanism as well. Bonded silica ion-exchange sorbents primarily exhibit electrostatic interactions, but the analyte also experiences nonpolar interaction with the bonded ligand. Nonpolar bonded silicas primarily retain analytes by hydrophobic interactions but exhibit a dual-retention mechanism, due to the silica backbone and the presence of unreacted surface silanol groups [72], Recognition that a dual-... 

I) Absorption of the laser energy and ablation of the target material. According to [26], the laser ablation (also called photon induced sputtering) can be classified into the following primary and secondary mechanisms that take place simultaneously. The share of each particular process is hardly to determine. 

Kara T. Primary and secondary mechanisms of action of visible to near-IR radiation on cells. J Photochem Photobiol B Biol 1999 49 1-17. 

Thermodynamical calculations are helpful in deciding between various secondary mechanisms taking place in photochemical reactions. A given intermediate product can exist in equilibrium with the reactants only if there is a decrease in free energy, but even then the rate of formation of the intermediate compound may be too slow to be an appreciable factor. Another basis for reaching a decision as to intermediate steps and the mechanism of the reaction rests on the quantum calculations of reaction rate. It will be shown in Chapter IX that many reactions which appear possible on paper may be definitely excluded on the basis of these theoretical calculations. 

Fig. 18. Secondary mechanical dispersion peaks of Thomel 300/Fiberite 934 composites as influenced by thermal history...

An extensive study by Koppelmann (1958) of viscoelastic functions through one of the secondary mechanisms in Poly(methyl methacrylate) is shown in Fig. 13.15. Dynamic storage moduli and tan <5 s near 25 °C are plotted vs. angular frequency. It shows first, that a secondary mechanism is present, secondly that E and G are not completely parallel, because the Poisson constant is not a real constant, but also dependent on frequency (the numbers in between both moduli are the actual, calculated Poisson constants) and thirdly that tan <5E is practically equal to tan <5G. 

An alternate method of classification of damage mechanisms in terms of environmental conditions such as stress, temperature, corrosion, wear, radiation is known as the failure wheel. In this representation secondary mechanisms are underlined as opposed to primary damage mechanisms. The boiler tube failure discussed can be represented in terms of failure wheel, as shown in Figure 2.31. The aim in any case is to identify definitively the underlying mechanism of failure to enable one to undertake remedial action such that future failures do not occur. 

Furthermore, the secondary mechanism then causes the pit propagation to become autocatalytic where one of the products formed in the reaction serves to accelerate it. Figure 7.104 describes the following mechanism. Pitting occurs in three stages initiation, propagation and termination. 

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