Stem formation

There is some hierarchy in the formation of RNA secondary structure. A rate of single helix (stem) formation depends mostly on the energy barrier of a loop which is formed while the reverse reaction of stem melting is determined by its stacking energy (16-18) ... 

Energy Barriers of Refolding. Thus every mutation operation of the GA started with a disruption of some stems in a given structure (an individual of the genetic algorithm population). Then after calculation of a list of stems compatible with the remaining structure, new stems were added by stepwise selection from the list, using a probability distribution for stem formation. The procedure continued until no stem could be added. 

It is clear that such a manipulation of an RNA structure in GA is equivalent to climbing some energy barrier due to stem disruption, followed by descending to a (probably new) local minimum of free energy determined by stem formation. Repeated GA mutations represent a walk in a free energy landscape for a given sequence, that is, RNA folding pathway (44). As mentioned in the first section, the... 

Stem layer adsorption was involved in the discussion of the effect of ions on f potentials (Section V-6), electrocapillary behavior (Section V-7), and electrode potentials (Section V-8) and enters into the effect of electrolytes on charged monolayers (Section XV-6). More speciflcally, this type of behavior occurs in the adsorption of electrolytes by ionic crystals. A large amount of wotk of this type has been done, partly because of the importance of such effects on the purity of precipitates of analytical interest and partly because of the role of such adsorption in coagulation and other colloid chemical processes. Early studies include those by Weiser [157], by Paneth, Hahn, and Fajans [158], and by Kolthoff and co-workers [159], A recent calorimetric study of proton adsorption by Lyklema and co-workers [160] supports a new thermodynamic analysis of double-layer formation. A recent example of this is found in a study... 

Electrica.1 Properties. The electrical properties of SF stem primarily from its effectiveness as an electron scavenger. To accomplish electrical breakdown in a dielectric gas, primary electrons must gain sufficient energy to generate appreciable numbers of secondary electrons on molecular impact. Sulfur hexafluoride interferes with this process by capturing the primary electrons, resulting in the formation of SF or SF ions and F atoms (29) ... 

Polymer and chain formation is another property of chalcogen-nitrogen compounds that distinguishes them from their oxygen analogues. In addition to the unique, superconducting poly(sulfur nitride) (SN) (1.24) (Section 14.2), a variety of poly(thiazyl) chains such as RS5N4R (1.25) (Section 14.3) have been characterized. Interest in these chains stems from their possible use as models for the behaviour of (SN) and as components in molecular materials, e.g., as molecular wires. 

Silyl ethers are among the most frequently used protective groups for the alcohol function. This stems largely from the fact that their reactivity (both formation and cleavage) can be modulated by a suitable choice of substituents on the silicon atom. Both steric and electronic effects are the basic controlling elements that regulate the ease of cleavage in multiply functionalized substrates. In plan-... 

Interaction of iron(II) chloride with the lithium salt of R4B2NJ (R = Me, Et) gives sandwiches 61 (R = Me, Et) (67ZAAC1, 96MI4), resembling in electronic properties those of ferrocene (99ICA(288)17). The n- rf-) complex stems from the further complex-formation of 61 (R = Me, Et) with mercury(II) salts via the unsubstituted nitrogen atom. 

The proportion of essential oil sensibly diminishes in the stems, in the leaves, and especially in the inflorescences, and in the whole plant. The most active formation of essential oil is, therefore, in the early part of the plant s life up to the commencement of flowering. 

The drill pipe itself can be used for formation evaluation (Drill Stem Testing— DST), well stimulation (fracturing, acidizing), and fishing operations. 

---