We develop an explicit covering theory for complexes of groups, parallel to that developed for graphs of groups by Bass. Given a covering of developable complexes of groups, we construct the induced monomorphism of fundamental groups and isometry of universal covers. We characterize faithful complexes of groups and prove a conjugacy theorem for groups acting freely on polyhedral complexes. We a...

We extend the notion of ‘homomorphism-homogeneity’ to a wider class of kinds of maps than previously studied, and we investigate the relations between the resulting notions of homomorphism-homogeneity, giving several examples. We also give further details on related work reported in [Deborah Lockett and John K. Truss, Generic endomorphisms of homogeneous Structures,in ‘Groups and model theory’,...

The category k-BFAlg of all k-algebras with a bilinear form, whose objects are pairs (R,b) where R is k-algebra and b:R×R→k mapping, equivalent to the unital A for which canonical homomorphism (k,1)→(A,1A) splitting monomorphism in k-Mod. Call left inverses this “weak augmentations” algebra. There isomorphism between weak augmentation (A,bA) form bA compatible multiplication A, i.e., such that ...

Assumption 2 (Condition I) Let K be a class of L-structures which admit a monotone idempotent closure operation cl taking subsets of M ∈ K to substructures of M such that cl has finite character. Strictly speaking, we should write clM (X) rather than cl(X) but we will omit the M where it is clear from context. Definition 3 Let A be a subset of H, H ′ ∈ K. A map from X ⊂ H − A to X ′ ⊂ H ′ − A i...

Triatoma rubrovaria has become the most frequently captured triatomine species since the control of T. infestans in the State of Rio Grande do Sul (RS), Brazil. In order to evaluate the genetic variability of this species, field collections were performed in four municipalities where it has been reported and distant from 75 to 322 km. Specimens were analyzed by color pattern and isoenzymes. Nin...

Papillary thyroid carcinoma (PTC) in children and adolescents is a medical problem that attracts attention of investigators and clinicians primarily because of the high incidence of this malignancy in individuals exposed to radioactive isotopes of iodine in case of nuclear reactor emergencies. New facts uncovered by various research groups make it possible to see the clinical and pathological p...

is a monomorphism for all collections of right R-modules {Ni : i ∈ I} . Restricting the Ni to certain classes of modules one obtains various relativized concepts. For instance, Goodearl investigated this notion relativized to flat modules. The present study provides a uniform background for such relativizations and thus covers and generalizes, among others, a number of known results about such ...

We consider a symmetric monoidal closed category V = (V ,⊗, I, [−,−]) together with a regular injective object Q such that the functor [−, Q] : V → V op is comonadic and prove that in such a category, as in the monoidal category of abelian groups, a morphism of commutative monoids is an effective descent morphism for modules if and only if it is a pure monomorphism. Examples of this kind of mon...

LetX be a compact metric space and let Λ be a Z (k ≥ 1) action onX.We give a solution to a version of Voiculescu’s problem of AF-embedding: The crossed product C(X) ⋊Λ Z k can be embedded into a unital simple AF-algebra if and only if X admits a strictly positive Λ-invariant Borel probability measure. Let C be a unital AH-algebra, let G be a finitely generated abelian group and let Λ : G → Aut(...