First countable extensions of regular spaces

We investigate feebly compact extensions of first countable regular locally feebly compact spaces. Solutions of problems posed by R. M. Stephenson, Jr. and G. M. Reed are given.

     

Detecting functional magnetic resonance imaging activation in white matter: Interhemispheric transfer across the corpus callosum

Background  

It is generally believed that activation in functional magnetic resonance imaging (fMRI) is restricted to gray matter. Despite this, a number of studies have reported white matter activation, particularly when the corpus callosum is targeted using interhemispheric transfer tasks. These findings suggest that fMRI signals may not be neatly confined to gray matter tissue. In the current experiment, 4 T fMRI was employed to evaluate whether it is possible to detect white matter activation. We used an interhemispheric transfer task modelled after neurological studies of callosal disconnection. It was hypothesized that white matter activation could be detected using fMRI.     

Pseudoradial Spaces: Results and Problems

In this paper it is given a survey of principal results (old and new) concerning the class of pseudoradial spaces. In this class cardinal invariants and their inequalities are considered. The behaviour of pseudoradial spaces under the operations of taking topological products and subspaces are examined and a typical proof is given. A particular attention is dedicated to the so called “small cardinals” in connection with pseudoradiality. Pseudoradiality of 2^{ω 2} is also examined. It is proved that pseudoradiality can be ω¹ productive for spaces of weight at most ω². Finally, several open problems are presented. This work was supported by the National Group “Real Analysis, Measure Theory with Applications to Economy” of the Italian Ministery of Education, University and Research.     

Nefness of adjoint bundles for ample vector bundles of corank 3

Let be an ample vector bundle of rank on a smooth complex projective variety X of dimension n. The aim of this paper is to describe the structure of pairs as above whose adjoint bundles are not nef for . Furthermore, we give some immediate consequences of this result in adjunction theory.     

On two upper bounds for hypersurfaces involving a Thas’ invariant

Let $X^n$ be a hypersurface in ${\mathbb{P}}^{n+1}$ with $n\ge 1$ defined over a finite field ${\mathbb{F}}_q$ of $q$ elements. In this note, we classify, up to projective equivalence, hypersurfaces $X^n$ as above which reach two elementary upper bounds for the number of ${\mathbb{F}}_q$-points on $X^n$ which involve a Thas’ invariant.     

Varieties with a reducible hyperplane section whose two components are hypersurfaces

We classify smooth complex projective varieties of dimension admitting a divisor of the form among their hyperplane sections, both and of codimension in their respective linear spans. In this setting, one of the following holds: 1) is either the Veronese surface in or its general projection to , 2) and is contained in a quadric cone of rank or , 3) and .

     

Thermal analysis to assess pozzolanic activity of calcined kaolinitic clays

The use of calcined clays as partial replacement of cement is encouraged since it promotes the reduction of the green-house gas emission and the energy requirement of cement-based material, maintaining or enhancing the mechanical properties and the durable performance of these materials. In this paper, the use of thermal methods—DTA/TG and calorimetry—to select and to evaluate two kaolinitic clays for their use as pozzolanic materials was explored. The content and crystallinity of kaolinite in clays can be determined by DTA/TG analysis, and this technique is also suitable to select the calcination temperature for complete kaolinite dehydroxylation. Calorimetric analysis on blended cements (30 % by mass of replacement) can differentiate the reactivity of calcined kaolinitic clays. Results show that more reactive calcined kaolinitic clay develops the second and third peaks earlier than those of PC with great intensity and high acceleration. The reactivity of calcined clays is associated to raw materials containing kaolinite with high structural disorder that determines calcined clays with large specific surface area, high grindability, and small mean particles size (d ₅₀) for the same grinding objective. Finally, the DTA/TG analysis can determine the type and the amount of hydrated phases obtained at different ages to evaluate the pozzolanic reaction of calcined clay in accordance with the standardized pozzolanic activity index.