Mechanical universe

The authors [35] emphasize that their result regarding the first HgS monolayer, which involves reversible underpotential adsorption, suggests that nucleation cannot be considered as a universal mechanism for the formation of anodic films. Analogous conclusions have been inferred for cathodic HgSe films electrodeposited on mercury electrode by the reduction of selenous acid [37] the first monolayer appeared to be reversibly adsorbed, while formation of the following two layers was preceded by nucleation. 

Asymmetric cell division is a universal mechanism utilized for the generation of cellular diversity during development (for reviews see Horvitz Herskowitz 1992, Guo Kemphues 1996, Shapiro Losick 1997, Jan Jan 1998). Asymmetric cell divisions during Drosophila embryonic development involve both extrinsic cues mediated through Notch and Delta and intrinsic cell fate determinants and play a major role in producing the distinct cell types which are... 

Even that most sacred of mechanisms, the S ICB for base hydrolysis, established after a long and fruitful rivalry (21), is under some attack, at least as a universal mechanism (22-24). A concerted E2 mechanism is suggested for the base hydrolysis... 

Ma B, Nussinov R (2004) Release factors eRFl and RF2 a universal mechanism controls die large conformational changes. J Biol Chem 279 53875—53885... 

James M Gere, Prof Emeritus, Stanford University, Mechanics of Materials 5lh edition, page 22, Brookes/Cole, Ca, 93950, USA. 

ABSTRACT The acid-catalysed epimerization reaction of bioactive indole alkaloids and their derivatives is reviewed. The three mechanisms, which have been proposed for the (J-carboline-type indole alkaloids, are discussed. Through recent developments, evidence for all three mechanisms has been obtained, which shows the complexity of the epimerization reaction. The epimerization seems to depend on structural features and reaction conditions making it difficult to define one universal mechanism. On the other hand, the isomerization mechanism of oxindole alkaloids has been widely accepted. The acid-catalysed epimerization reaction provides a powerful tool in selectively manipulating the stereochemistry at the epimeric centre and it can also have a marked effect on the pharmacology of any epimerizable compound. Therefore, examples of this reaction in die total synthesis of indole alkaloids are given and pharmacological activities of some C-3 epimeric diastereomers are compared. Finally, literature examples of acid-catalysed epimerization reactions are presented. 

Structural features, reaction conditions and acid strength also influence the acid-catalysed epimerization reaction. For example, Mechanism 1 requires protonation at C-7, which seems to occur under strongly acidic conditions. When a P-carboline derivative was treated with a weakly acidic solution (TFA-d, 2.9 equiv., rt), deuterium incorporation did not occur, whereas refluxing of a similar compound in a DCl/MeOH solution resulted in deuterium incorporation at the epimeric centre. Therefore, it is impossible to define one universal mechanism to explain the epimerization reaction for any given compound. On the contrary, each compound type must be separately investigated under different conditions. Clearly, then, the acid-catalysed epimerization reaction of indole alkaloids is a fruitful research area. 

In this case the Birc/i-reduction system (sodium in liquid ammonia) is used. Normally this system is employed to reduce aromatic rings to 1,4-dihydrobenzenes. Here it is advantageous because in contrast to catalytic hydrogenation it does not touch olefinic double bonds and the expected alcohol is generated in 95 % yield (see universal mechanism on the left). 

Stress condition where oxygen (radical) reacts with internal components in cells (e.g., lipids and DNA) and produces damages that eventually kill or destroy tissues. Considered as a universal mechanism of toxic damage in cells. Vol. 1(14). 

After 40 years of descriptive work on the behavior of ion-coupled transport systems and the establishment of the near universal mechanism of energy transduction by coupling to ion flows, there is a sense that the next decade will see an information explosion on the mechanism of action of the transporters and their structures at the molecular level. 

It is remarkable that the series of peaks that appear after corona treatment is also observed in corona treatment of other polymers, e.g. polyester, polyethylene, and polystyrene. The nature of the low-molecular weight material thus seems to be independent of the type of polymer, suggesting a rather universal mechanism of formation. This mechanism is still unclear, but a pertinent observation may be that at very short treatment times the surfaces of many polymers indicate a high degree of unsaturation. This is seen in Table II, which shows the ratio 27/29, which is a measure of unsaturation. In corona as well as plasma treatments, the unsaturation increases steeply and then decreases with increasing time or dose. It is thus possible that many polymers initially form some sort of graphite-like structure which then reacts at a slower rate with oxygen. This would explain the similarity in the behavior of these polymers. 

Billings, R.E. Colorado State University Mechanisms of toxic chemical interaction in the liver-hepatotoxicity NIEHS... 

Another subclass of pharmacological chaperones includes compounds that act through other mechanisms. This subclass includes generalized chaperones—those that rescue the trafficking defects of many or all ER-retained proteins through a universal mechanism. Many different mechanisms of correction are possible. Examples of this subclass of chaperones are described below. 

Although many oscillating reactions have been studied experimentally, as many or perhaps even more models describing the oscillatory behavior have been discussed. At present there is no universal mechanism that explains oscillations in all heterogeneously catalyzed reactions. Every reaction has to be thoroughly investigated to discover its specific oscillation mechanism. There are, nevertheless, certain classes of models under which several oscillating systems can be considered. 

There are two reasons why so much is unknown. First, at high densities three (and even four) body forces are important. This is particularly so when chemically reactive atoms are present. Then, even for two-body forces, the strongly repulsive regime is not well understood and, in addition, close in, as one approaches the united atom limit, there is considerable promotion of molecular orbitals. This is a universal mechanism for electronic excitation which means a breakdown of the Born-Oppenheimer approximation for close collisions. 

Numerous compounds can provide general cryoprotection to proteins, when used at concentrations of several hundred millimolar. These include sugars, polyols, amino acids, methylamines, and salting-out salts (e.g., ammonium sulfate) [59,61,68-70]. Based on the results of freeze-thawing experiments with LDH and PFK and a review of the literature on protein freezing. Carpenter and Crowe [59] have proposed that this cryoprotection can be explained by the same universal mechanism that Timasheff and Arakawa have defined for solute-induced protein stabilization in nonfrozen, aqueous solution (reviewed in [4,70,78,79]). 

This class of biomarkers measures actual toxic effects at the molecular, cellular and physiological levels. It is more closely related to pathological conditions (morbidity) that could lead to death. The oxidative status of cells has been proposed as a universal mechanism leading to cell dysfunction. The normal metabolism (e.g. (3-oxidation, pentose shunt pathway, immune function) produces oxidizing precursors such as hydrogen peroxide (H2O2), nitric oxide (NO) and peroxynitrite (ONOO) that are rapidly eliminated by non-enzymatic and enzymatic antioxidants to prevent tissue damage. 

Collisional decoherence is a universal mechanism which occurs for objects of any size. In contrast to that, the following section describes a mechanism which only appears for complex quantum systems, namely decoherence,thermal due to the emission of their own heat radiation. 

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