True minimum Subject

The Alexander model and its descendants impose strong restrictions on the allowed chain configurations within the tethered assembly. The equilibrium state thus found is subject to constraints and may not attain the true minimum free energy of the constraint-free system. In particular, the Alexander model constrains the segment density to be uniform and all the chain ends to be at the same distance from the grafting surface. Related treatments of curved systems retain only the second... 

In the meantime several theoretical101 and experimental102 papers dealing with this subject have been published. Recent calculations101 c have shown that oxirene (76) is a true minimum on the C2H2O energy surface. An unequivocal verification of this prediction, however, is still missing.103... 

The initial guess structure is subjected to a total energy minimisation by slightly modifying the internal rotation angles in order to reach a microscopic structure in a mechanical equilibrium, i.e. corresponding to a true potential energy minimum. 

The foregoing conclusion is subject to another constraint for gas chromatography a substantial pressure drop is sometimes needed to force the gas phase through the column. In this case the mean pressure, unable to approach zero, should at least be reduced to a minimum, which for true optimization will require vacuum outlet conditions [31]. 

A minimum of 15 subjects per group is recommended, as is the use of a control product. Hence, if one test product is used, a minimum of 30 subjects should be employed (15 for the test product and 15 for the control product). This is a statistically adequate number, in most cases, to detect true differences between the test and control products after washes 1 and 5, as well as the microbial reduction counts from baseline after washes 1 and 5. A caveat is that the baseline standard deviation value must be less than 0.5 log. If the standard deviation is greater, it will be difficult to detect a true difference between the test and control products after washes 1 and 5. It will also be more difficult to detect true microbial reductions from the baseline values after wash samples 1 and 5. Hence, using a larger sample size is in the best interest of the product manufacturers. 

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