This paper contains two traditions of diagrammatic studies namely one, the Euler–Venn–Peirce diagram and the other, following tradition of Aristotle, the square of oppositions. We put together both the traditions to study representations of singular propositions, their negations and the inter relationship between the two. Along with classical negation we have incorporated negation of another kind viz. absence. We have also considered the changes that take place in the context of open universe.

Venn diagram system has been extended by introducing names of individuals and their absence. Absence gives a kind of negation of singular propositions. We have offered here a non-classical interpretation of this negation. Soundness and completeness of the present diagram system have been established with respect to this interpretation.

A new diagram system \ where properties are fundamental and an object exists only w.r.t a property is presented. This work modifies both in syntax and semantics the system \ proposed by Choudhury and Chakraborty to picturise and address issues connected with open universe. Semantics for the current system is given. Soundness and completeness w.r.t the semantics are established.

The National Blood Policy in India relies heavily on voluntary blood donors, as they are usually assumed to be associated with low levels of transfusion-transmitted infections . In India, it is mandatory to test every unit of blood collected for hepatitis B, hepatitis C, HIV/AIDS, syphilis and malaria. Donors come to the blood bank with altruistic intentions. If donors test positive to any of the five infections, their blood is discarded. Although the blood policy advocates disclosure of TTI status, donors (...) are not, in practice, informed about their results. The onus is on the donor to contact the blood bank. Out of approximately 16 000 donations in the past 2 years, 438 tested positive for TTI, including 107 for HIV. Only 20% of the donors contacted the blood bank; none of them were HIV positive. Disclosure by blood banks of TTI status by telephone or mail has resulted in serious consequences for some donors. Health providers face an ethical dilemma, in the absence of proper mechanisms in place for disclosure of test results, regarding notification to donors who may test positive but remain ignorant of their TTI status. Given the high cost of neglecting to notify infected donors, the authors strongly recommend the use of rapid tests before collecting blood, instead of the current practice, which takes 3 h to obtain results, and disclosure of results directly to the donor by a counsellor, to avoid dropouts and to ensure confidentiality. (shrink)