A structural theorem for Kleene algebras is proved, showing that an element of a Kleene algebra can be looked upon as an ordered pair of sets. Further, we show that negation with the Kleene property (called the 'Kleene negation') always arises from the set theoretic complement. The corresponding propositional logic is then studied through a 3-valued and rough set semantics. It is also established that Kleene negation can be considered as a modal operator, and enables giving a perp semantics to the logic. One concludes with the observation that all the semantics for this logic are equivalent.

Chironomus circumdatus is one of the most common and wide-spread species in India. Cytogenetic studies pertaining to the mitotic and polytene chromosomes, nucleolar organizer regions, C-banding and naturally occurring chromosomal polymorphism have been carried out for the first time in this Indian species. Altogether seven inversions comprising six paracentric and one pericentric are detected in the Indian populations. The distribution of inversions in relation to different environmental conditions is discussed.

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Highlights d Retroviral silencing precedes acquisition of pluripotency during reprogramming d The primer-binding site in retrovirus is essential for retroviral silencing d OCT4, SOX2, and c-MYC are required for retroviral silencing d TAF-Ia is induced during reprogramming to facilitate retroviral silencing

Chromosomal polymorphisms in Drosophila nasuta populations from the north and northeastern parts of India were studied. A total of 22 heterozygous inversions were detected. Among them, 16 were previously undescribed gene arrangements. The X chromosome has one inversion, the 2L chromosome arm has two, the 2R chromosome arm has four, and chromosome 3 has 15 inversions. Three heterozygous inversions, 2L-2, 3-2, and 3-35, were very common and detected in high frequencies In all populations examined. Several rare inversions were detected only once. Further, the mean number of heterozygous inversions per individual varies from 1.70 to 2.76. The highest frequency of heterokaryotypes Is on chromosome 2L, and the lowest Is on the X chromosome.