Alpha postulate

This has been referred to as the alpha postulate. There is a sense in which this is true also Look at Figure 13.3. Here, instead of displaying the scaled likelihood for that alternative hypothesis which corresponds to the clinically relevant difference, the alternative hypothesis for which the true treatment effect corresponds to the critical value is illustrated. For P = 0.05, the ratio of this likelihood is the same for the trial with 10 patients per group as for the trial with 200 as, indeed, it is for any trial whatsoever. But we do not know which value of the alternative hypothesis is true if the null hypothesis is false. It thus follows that for a P-value of exactly 0.05, there is always one value of the alternative hypothesis for which the likelihood is 1/0.15 or more than six times as high as for the null hypothesis. The evidence in favour of this alternative hypothesis (which hypothesis changes according to the size of the trial) is always the same. 

When the reaction was run at 100°C in MeOH H20, isotopic exchange was observed (the product from PhCDO had lost some of its deuterium) Swain, C.G. Powell, A.L. Lynch, T.J. Alpha, S.R. Dunlap, R.P. J. Am. Chem. Soc., 1979, 101, 3584. Side reactions were postulated to account for the loss of deuterium. See, however, Chung, S. J. Chem. Soc., Chem. Commun., 1982, 480. 

It used to be postulated that the magnitude of the alpha-carbon KIE in an Sn2 reaction is an indication of the transition state symmetry. The expectation was that this KIE reaches maximal value for a symmetric transition state and drops back to unity for extremely early or late transition states. That expected behavior is marked by the solid line in Fig. 10.10. However, recent calculations of the nucleophilic substitution of chloride from methyl chloride by a broad variety of nucleophiles... 

Postulate 8 defines the beta relationship from the alpha predicate (alphaCx, y) is true if bondCx, y) is true). The term ".not. Identity (x,z) must be included in axiom 8 to prevent an atom from being beta to itself (x=z). 

Approximately 30 years ago, Schildkraut postulated that noradrenaline may play a pivotal role in the aetiology of depression. Evidence in favour of this hypothesis was provided by the observation that the antihypertensive drug reserpine, which depletes both the central and peripheral vesicular stores of catecholamines such as noradrenaline, is likely to precipitate depression in patients in remission. The experimental drug alpha-methyl-paratyrosine that blocks the synthesis of noradrenaline by inhibiting the rate-limiting enzyme tyrosine hydroxylase was also shown to precipitate depression in patients during remission. While such findings are only indirect indicators that noradrenaline plays an important role in human behaviour, and may be defective in depression, more direct evidence is needed to substantiate the hypothesis. The most obvious approach would be to determine the concentration of noradrenaline and/or its major central... 

Rutherford decided that the best way to proceed was to bombard the atoms with rapidly moving alpha particles. If Thomson s theory was correct, the paths of the particles would be deviated only slightly. Electrons were thousands of times lighter than alpha particles they couldn t possibly deflect the paths of the alpha particles significantly. Neither could the hypothetical sphere of positive electricity that Thomson had postulated it was too diffuse. So Rutherford and his assistants directed the particles at sheets of thin gold foil, approximately 0.00004 centimeters thick. After the particles passed through... 

The mechanisms by which 2-PAM exerts its cardiac effects have been studied in experimental animals. At least three classes of action have been attributed to the effects of altered calcium metabolism on autonomic ganglia. A sympathomimetic action of 2-PAM was postulated to explain the increase in blood pressure and the augmented myocardial contractility by one or more of the following mechanisms 2-PAM may not block the release of the endogenous compounds, but may prevent the uptake of catecholamine 1 it may stimulate the release of norepinephrine it Increases myocardial contractility by directly stimulating beta receptors and it increases blood pressure by directly stimulating alpha receptors. 5... 

FIGURE 12-6. Postsynaptic alpha 2 adrenergic receptors are postulated to mediate cognitive effects of norepinephrine in the frontal cortex. Direct-acting alpha 2 agonists such as clonidine and guanfacine can be helpful in attention deficit disorder, perhaps because of actions at this site. 

Parry, D. A. D. (1978). Fibrinogen A preliminary analysis of the amino acid sequences of the portions of the alpha, beta and gamma-chains postulated to form the interdomainal link between globular regions of the molecule. J. Mol. Biol. 120, 545-551. 

The mechanical dispersion peaks in low-Tg epoxies such as Bisphenol-A based resin (Epon 828, products from Shell Development Company) have been the subject of numerous studies 143,145148,152 "155, l59>. The alpha-dispersion peak related to the glass transition can undoubtly be attributed to the large-scale cooperative segmental motion of the macromolecules. The eta-relaxation near —55 °C, however, has been the subject of much controversy 146,153). One postulated origin of the dispersion peak is the crankshaft mechanism at the junction point of the network epoxies (Fig. 17). The crankshaft motion for linear macromolecules was first propos-ed 163 166> as the molecular origin for secondary relaxations which involved restricted motion of the main chain requiring at least 5 and as many as 7 bonds 167>. This kind of... 

Various theoretical models have been proposed to account for the distribution of products obtained on a-amylolysis. A comparison of experimental yields with those calculated for completely random hydrolysis shows that the action of higher-plant alpha-amylases cannot be explained in this way (see Table VII). The postulate that the enzymes degrade randomly to give small products (hexaose and shorter), which are resistant to further attack, does not predict yields in good agreement with experimental observation. If, however, certain bonds are assumed to be resistant to attack, whilst others are more susceptible, better agreement is obtained. For example, it has been proposed that cereal alpha-amylases do not readily attack the... 

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