Given a variety we study the existence of a class such that S1 every A can be represented as a global subdirect product with factors in and S2 every non-trivial A is globally indecomposable. We show that the following varieties (and its subvarieties) have a class satisfying properties S1 and S2: p-algebras, distributive double p-algebras of a finite range, semisimple varieties of lattice expansions such that the simple members form a universal class (bounded distributive lattices, De Morgan algebras, etc) and arithmetical varieties in which the finitely subdirectly irreducible algebras form a universal class (f-rings, vector groups, Wajsberg algebras, discriminator varieties, Heyting algebras, etc). As an application we obtain results analogous to that of Nachbin saying that if every chain of prime filters of a bounded distributive lattice has at most length 1, then the lattice is Boolean.We wish to thank Lic. Alfredo Guerin and Dr. Daniel Penazzi for helping us with linguistics aspects. We are indebted to the referee for several helpful suggestions. We also wish to thank Professor Mick Adams for providing us with several reprints and useful e-mail information on the subject.Suported by CONICOR and SECyT (UNC). 相似文献
There are approximately one million cases oftype 1 diabetes in the US, and the incidenceis increasing worldwide. Given that two-thirdsof cases present in childhood, it is criticalthat prediction and prevention research involvechildren. In this article, I examine whethercurrent research methodologies conform to theethical guidelines enumerated by the NationalCommission for the Protection of Human Subjectsof Biomedical and Behavioral Research, andadopted into the federal regulations thatprotect research subjects. I then offer twopolicy recommendations to help researchersdesign studies that conform to these ethicalrequirements. 相似文献
This research describes and evaluates a workshop aimed at promoting career specialty choice and examines relationships between measured career specialty interests, work values, and personality type. Three consecutive classes of second-year medical students (N = 161) participated in a two-session specialty choice workshop. All participants in the study rated the usefulness of the workshop and reported their level of specialty choice certainty and satisfaction. They also responded to measures of medical specialty preference, work values, and personality type. Results indicated two distinct student subgroups of career-specialty-decided and -undecided students. The former subgroup evidenced more stability and certainty of specialty choice as well satisfaction with their choice. Both groups of students reported having benefited from the workshop. Significant gender differences in the relationships between scores on a measure of medical specialty preference and scores on measures of work values and personality emerged. Implications are discussed in terms of the differential career counseling needs of students either decided or undecided about their career specialty choices. 相似文献
This paper aims at creating an adequate theoretical basis for a systematic integration of institutional insights into the
pragma-dialectical analysis of argumentative exchanges that occur in institutionalised contexts. The argumentative practice
of Prime Minister’s Question Time in the British House of Commons is examined, as a case in point, in order to illustrate
how the knowledge of the characteristics of an institution, its rules and conventions can be integrated into the pragma-dialectical
analysis. The paper highlights the role that theoretical concepts and tools such as strategic manoeuvring, argumentative activity
types and dialectical profiles play in this integration.
This paper presents Automath encodings (which are also valid in LF/λP) of various kinds of foundations of mathematics. Then it compares these encodings according to their size, to find out which foundation is the simplest.
The systems analyzed in this way are two kinds of set theory (ZFC and NF), two systems based on Church's higher order logic (Isabelle/Pure and HOL), three kinds of type theory (the calculus of constructions, Luo's extended calculus of constructions, and Martin-Löf's predicative type theory) and one foundation based on category theory.
The conclusions of this paper are that the simplest system is type theory (the calculus of constructions), but that type theories that know about serious mathematics are not simple at all. In that case the set theories are the simplest. If one looks at the number of concepts needed to explain such a system, then higher order logic is the simplest, with twenty-five concepts. On the other side of the scale, category theory is relatively complex, as is Martin-Löf's type theory.
(The full Automath sources of the contexts described in this paper are one the web at http://www.cs.ru.nl/~freek/zfc-etc/.) 相似文献