Search

Sixty-two samples from 62 donors were investigated to determine the significance of warm IgG autoantibodies that were detected using a gel system during compatibility testing. The presence of autoantibodies on the red cells was confirmed by elution studies. Twelve of 23 strongly positive samples, 7 of 19 moderately positive samples, and 6 of 11 weakly positive samples were studied. The remaining nine samples were found positive during crossmatching, then negative when it was repeated. These nine samples were not included in this study. With a tube test, most of the antibodies had titers from 4 to 8. IgG subclass studies showed that 14 of 25 samples with reactive eluates contained IgG1, one contained IgG1+IgG2, one contained IgG1+IgG4, and two contained IgG1+IgG3 weak. The frequency of donors with a positive direct antiglobulin test (DAT) was ~ 1 in 3000 and males were twice as likely to be DAT positive (8 females vs.17 males in this study). None of the donors had hemolysis. Two donors showed low-titer anticardiolipin antibodies. We conclude that DAT-positive donors can be a problem during compatibility testing when sensitive methods are used. Immunohematology2002;18:78–81.

In this paper we define a two-rule reduction system for the lazy computation of unification on first-order terms. The computation consists of a sequence of reductions which is almost linear with the size of the input. Every reduction transforms the problem into an equivalent one which is a better approximation of the solution. The approach is based on a combinatorial system which provides abstractions for terms and term unification, and does not resort to any specific reduction control strategy. The abstraction on both data and control makes our system suitable in any applicative context where unification is required.

Abstract: The experience in designing large software systems shows that even the definitions of a programming language can be seen as the application of specific implementation and formalization techniques rather than as the result of a designing art. In this context, a formalism is proposed here as a tool for defining conventional high level programming languages. The formalism is an algebraic model supporting the definition of representational entities such as types. A Type is a set of data and operations on them. An isomorphism between language components and types realizes an isomorphism between the language and its specification on the model. Then, the definition of a language can be performed by stepwise definitions of the types representing the language components. So the model is also a language development tool. Stepwise definition methodologies are also investigated and two are the proposed ones: the horizontal, methodology and the vertical methodology. In particular, the vertical methodology defines languages by the development of a hierarchy of abstraction levels, each corresponding to one class of languages: The last class only contains the language being defined.

We discuss an algebra of open formulas, SOAF. The algebra is equipped with the operator mgi-o, which computes suprema of sets of open formulas, ordered according to a weak form of instance ordering. Rules to compute such points are provided. These rules supply a computation procedure to unify open formulas. Next, we consider an algebra of closed formulas, SCAF. It has an operator mgi-c, which computes suprema of set of formulas ordered according to the instance preordering. We give rules to compute such points. These rules supply a computation procedure to unify closed formulas. Relations between these operators and unification in open and closed formulas, and weak unification in closed formulas, are addressed. Also, we consider clausal formulas and apply these considerations to the resolution process. This provides a rule alternative to resolution and shows that resolvents can be expressed and effectively obtained as suprema of closed formulas. The new rule need not resort to renaming, unification. and instantiation as first class operations. Finally, applications to resolution in Horn clause logic and logic programming are discussed. This leads to a more compact theory of logic programming, in which, for instance, the domain of substitutions is eliminated.