Disjunctive databases for representing repairs

This paper addresses the problem of representing the set of repairs of a possibly inconsistent database by means of a disjunctive database. Specifically, the class of denial constraints is considered. We show that, given a database and a set of denial constraints, there exists a (unique) disjunctive database, called canonical, which represents the repairs of the database w.r.t. the constraints and is contained in any other disjunctive database with the same set of minimal models. We propose an algorithm for computing the canonical disjunctive database. Finally, we study the size of the canonical disjunctive database in the presence of functional dependencies for both subset-based repairs and cardinality-based repairs.     

Cross section measurements of the 23Na(n, 2n)22Na, 58Ni(n, 2n)57Ni and 115In(n,n′)115mIn reactions

Cross sections for two high energy threshold reactions ²³Na(n, 2n)²²Na and ⁵⁸Ni(n, 2n)⁵⁷Ni were measured by the activation method in the neutron energy range from 14 to 18 MeV. Inelastic scattering cross section for ¹¹⁵In was measured in the threshold region, i.e. from 0.5 to 1.3 MeV. The results of measurements are compared with scarce and divergent earlier data.     

Systemic vasculitis: classification and serologic diagnosis

Cardiovascular morbidity and mortality in hemodialyzed patients are increased due to the frequently abnormal lipid metabolism. It has been reported that this abnormal lipid metabolism could be partially corrected by some highly permeable membranes, such as polysulfone or cellulose triacetate. We investigated the influence of 4 months of dialysis with a polyamide membrane upon the course of lipid parameters in 6 patients presenting a hypertriglyceridemia > 2 mmol/l while on bicarbonate dialysis with a cellulose membrane. Lipid parameters improved after 4 months of hemodialysis with a polyamide membrane. Serum triglyceride and cholesterol levels decreased, while HDL cholesterol and HDL levels rose significantly (p < 0.05). Apolipoprotein B decreased significantly (p < 0.05). Following heparin administration, lipoprotein lipase activity improved (p < 0.02), associated with a decrease apolipoprotein C3 (p < 0.05). The fractional clearance rate of triglycerides rose significantly (p < 0.01). The use of highly permeable polyamide membranes results in a significant improvement in lipid disturbances of dialysis patients due to an increased lipoprotein lipase activity, induced perhaps by the removal of circulating inhibitors such as apolipoprotein C3.     

Influence of long-term human recombinant erythropoietin treatment on secretion of pancreatic polypeptide and gastrin in hemodialysed patients with chronic renal failure

The study aimed to assess the influence of long-term rhu-EPO treatment on secretion of pancreatic polypeptide (PP) and gastrin. A total of 27 haemodialysed patients and nine healthy subjects were examined. Nine patients with uraemic anaemia were treated with rhu-EPO for 12 months (EPO group), while another nine patients did not receive rhu-EPO (non-EPO group), but were monitored biochemically and clinically as patients of the EPO group. The third group (HD) comparised nine haemodialysed patients with a haematocrit value > or = 30% without rhu-EPO therapy. In all subjects plasma levels of PP and gastrin were estimated before and after administration of a test meal. Patients of the EPO and non-EPO group were examined before and after 6 and 12 months of rhu-EPO therapy (EPO group) or clinical monitoring (non-EPO group) respectively, while only one test was performed in patients of the HD group and healthy subjects. Six months rhu-EPO therapy was followed by an decrease of basal plasma level of PP and increased response of gastrin to the test meal. After 12 months of rhu-EPO therapy basal plasma level of PP was still lower, the response of PP secretion to a test meal was higher, while that of gastrin secretion lower that the pretreatment ones. Our results suggest, that rhu-EPO treatment exerts effect on secretion of PP and gastrin. These alterations seem not to be related to improvement of the haematological status.     

Discrete dislocation analysis of a plastic shear crack

A detailed discrete dislocation analysis has been carried out in order to understand the behavior of a shear crack. It is found that a shear crack can be classified broadly into four categories based on its elastic and plastic behavior. The realistic growth of a plastic crack is found to take place by emission of lattice dislocations whenever the crack can reduce its energy, otherwise it expands elastically. The elastic energy released when the plastic crack forms is related to the self energy and interaction energy of the dislocations along with the frictional energy expended in creating the plastic zone. The plastic work for a plastic crack defined earlier by Orowan is obtained as a function of the energy terms contributing to the total energy of the plastic crack, namely the frictional work and the work done by the applied stress in creating the plastic zone.

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Résumé Une analyse discrète détaillée des dislocations a été effectuée en vue de comprendre le comportement d'une fissure de cisaillement. On a trouvé qu'une fissure de cisaillement peut être généralement classée en quatre catégories, selon son comportement élastique ou plastique. On trouve que la croissance réaliste d'une fissure dans des conditions plastiques peut se produire par l'émission de dislocations dans le réseau, lesquelles produisent une réduction de l'énergie de la fissure, qui se propageait précédemment de manière élastique. L'énergie élastique libérée lorsque se forme la fissure plastique est mise en relation avec l'énergie propre et l'énergie d'interaction des dislocations ainsi qu'avec l'énergie de friction dépensée pour créer la zône plastique. Le travail plastique associé à une fissure plastique et défini précédemment par Orowan est obtenu en fonction des termes d'énergie contribuant à l'énergie totale de la fissure plastique, notamment le travail de friction et le travail effectué par la contrainte appliquée pour créer la zône plastique.

     

Differential geometry of phase transformations

The foundations have been laid with respect to a generalized theory of phase transformations in solids. In particular, the methods of differential geometry have been employed and such important tensor quantities as distortion, metric, torsion, and anholonomic object have been developed with respect to such transformations. It is further shown that both Riemannian as well as non-Riemannian (dislocation) geometries are needed to describe these transformations properly.     

Study of polyethylene spherulites using scanning electron microscopy

A detailed scanning electron microscopy study has been made of spherulites in meltcrystallized polyethylene. In particular, unetched, ion etched, nitric acid etched and plastically deformed polyethylene samples have been examined. It appears that the spherulites visible on the surface of these samples consist of lamellae which possess alternate right- and left-handed partial twists. It is quite possible that enough material was removed from the surfaces of the samples by ion etching that the spherulites visible on etched samples could be representative of bulk samples. While questions remain both about the half twist model and about the current full twist model, the half twist model deserves consideration as an alternate model for spherulite structure.Now deceased, formerly with the Chemistry Department, University of Maryland.     

The relationship between cracks,holes and surface dislocations

International Journal of Fracture - It has been shown that surface cracks as well as holes can be represented in terms of surface dislocations. These surface dislocations exist in order to insure...