We prove the following three theorems on the enumeration degrees of Σ2 sets. Theorem A: There exists a nonzero noncuppable Σ 0 2 enumeration degree. Theorem B: Every nonzero ∆2 enumeration degree is cuppable to 0e by an incomplete total enumeration degree. Theorem C: There exists a nonzero low ∆2 enumeration degree with the anticupping property.

We prove that a sequence of sets containing representatives of cupping partners for every nonzero ∆2 enumeration degree cannot have a ∆ 0 2 enumeration. We also prove that no subclass of the Σ 2 enumeration degrees containing the nonzero 3-c.e. enumeration degrees can be cupped to 0e by a single incomplete Σ 2 enumeration degree.

Participation in external quality assessment is an integral part of laboratory work and mandatory when the results have a clinical application, which is one of the requirements of standard 15189 for accreditation of medical laboratories. Institute of Clinical Chemistry, the first laboratory accredited for clinical cell analysis by flow cytometry in Croatia, participated in UKNEQAS for Leukocyte...

Zeilberger’s enumeration schemes can be used to completely automate the enumeration of many permutation classes. We extend his enumeration schemes so that they apply to many more permutation classes and describe the Maple package WilfPlus, which implements this process. We also compare enumeration schemes to three other systematic enumeration techniques: generating trees, substitution decomposi...

My half-century journey started from synthetic organic chemistry. During the first stage of my journey, my interest in stereochemistry was initiated through the investigation on the participation of steric effects in reactive intermediates, cylophanes, strained heterocycles, and organic compounds for photography. In chemoinformatics as the next stage of the journey, I proposed the concept of im...

We give an alternative definition of the enumeration jump operator. We prove that the class of total enumeration degrees and the class of low enumeration degrees are first order definable in the local structure of the enumeration degrees.