A clean empty vial was used as a control sample to be certain that E-β-ocimene originated from the bees.
These variants remain unclassified because in the majority of cases it is not possible to follow variants by cosegregation analysis, and the number of appropriate controls required to be certain that a variant is absent in unaffected individuals is prohibitive.
The charge is thought to relate to Document Number 9, which attacked western democratic ideals and called for tighter ideological controls, but it is impossible to be certain because the evidence is classified as a state secret.
The interpretation of these results is inevitably limited by the lack of control group which makes it impossible to be certain that the observed changes were due to the intervention.
To be certain that controls were free of (yet undetected) cancer at the index date, controls with a history of cancer up to 2 years after the index date were excluded.
It is, however, impossible to be certain of adequate control for confounding factors with observational designs.
Temperature can be effectively controlled to be below a certain maximum point that causes hot spots, or thermal run-away behaviour.
It does not help that the Clean Air Act does not allow the cost of pollution controls to be taken into account when setting certain standards.
Injection molding process is a typical repetitive process, where key process variables are controlled to follow certain profiles repetitively to ensure the product quality [22, 38].
The scenes of bloodshed in Hama and Deir al-Zour, cities that had slipped beyond the government's control this summer, were certain to put more pressure on other countries, in particular the United States, to take a harder line against Mr. Assad.
