Corrosion-fatigue life of commercially pure titanium and Ti-6Al-4V alloys in different storage environments

Statement of problem. Removable partial dentures are affected by fatigue because of the cyclic mechanism of the masticatory system ansi frequent insertion and removal. Titanium and its alloys have been used in the manufacture of denture frameworks; however, preventive agents with fluorides are thought to attack titanium alloy surfaces.Purpose. This study evaluated, compared, analyzed the corrosion-fatigue life of commercially pure titanium and Ti-6Al-4V alloy in different storage environments.Material and methods. For each metal, 33 dumbbell rods, 2.3 mm in diameter at the central segment, were cast in the Rematitan system. Corrosion-fatigue strength test was carried out through a universal testing machine with a load 30% lon er than the 0.2% offset yield strength and a combined influence of different: environments: in air at room temperature, with synthetic saliva, and with fluoride synthetic saliva. After failure, the number of cycles were recorded, and fracture surfaces were examined with on SEM.Results. ANOVA and Tukey's multiple comparison rest indicated that Ti-6Al-4V alloy achieved 21,269 cycles (SD = 8,355) against 19,157 cycles (SD = 3,624) for the commercially purr Ti. There were no significant differences between either metal in the corrosion-fatigue life for dry specimens, but when the solutions were present, the fatigue life was significantly reduced, probably because of the product-ion of corrosion pits caused by superficial reactions.

The Estimation of the Ecological Condition of the City Environment by Methods of Phytoindication (as Applied to the Vasileostrovsky District of St. Petersburg)

The project aimed to use results of contamination of city vegetation with heavy metals and sulphur compounds as the basis for analysing the integral response of trees and shrubs to contamination, through a complex method of phytoindication. The results were used to draw up recommendations on pollution reduction in the city and to develop the method of phytoindication as a means of monitoring environmental pollution in St. Petersburg and other large cities. Field investigations were carried out in August 1996, and 66 descriptions of green areas were made in order to estimate the functional state of plants in the Vasileostrovsky district. Investigations of the spectrum reflecting properties of plants showed considerable variation of albedo meanings of leaves under the influence of various internal and external factors. The results indicated that lime trees most closely reflect the condition of the environment. Practically all the green areas studied were in poor condition, the only exceptions being areas of ash trees, which are more resistant to environmental pollution, and one lime-tree alley in a comparatively unpolluted street. The study identified those types of trees which are more or less resistant to complex environmental pollution and Ms. Terekhina recommends that the species in the present green areas be changed to include a higher number of the more resistant species. The turbidimetric analysis of tree barks for sulphates gave an indication of the level and spatial distribution of each pollutant, and the results also confirmed other findings that electric conductivity is a significant feature in determining the extent of sulphate pollution. In testing for various metals, the lime tree showed the highest contents for all elements except magnesium, copper, zinc, cadmium and strontium, again confirming the species' vulnerability to pollution. Medium rates of concentration in the city and environs showed that city plants concentrate 3 times as many different elements and 10 times more chromium, copper and lead than do those in the suburbs. The second stage of the study was based on the concept of phytoindication, which presupposes that changes in the relation of chemical elements in regional biological circulation under the influence of technogenesis provide a criterion for predicting displacements in people's health. There are certain basic factors in this concept. The first is that all living beings are related ecologically as well as by their evolutionary origin, and that the lower an organism is on the evolutionary scale, the less adaptational reserve it has. The second is that smaller concentrations of chemical elements are needed for toxicological influence on plants than on people and so the former's reactions to geochemical factors are easier to characterise. Visual indicational features of urban plants are well defined and can form the basis of a complex "environment - public health" analysis. Specific plant reactions reflecting atmospheric pollution and other components of urbogeosystems make it possible to determine indication criteria for predicting possible disturbances in the general state of health of the population. Thirdly the results of phytoindication investigations must be taken together with information about public health in the area. It only proved possibly to analyse general indexes of public health based on statistical data from the late 1980s and early 1990s as the data of later years were greatly influenced by social factors. These data show that the rates of illness in St. Petersburg (especially for children) are higher than in Russia as a whole, for most classes of diseases, indicating that the population there is more sensitive to the ecological state of the urban environment. The Vasileostrovsky district had the second highest sick rate for adullts, while the rate of infant mortality in the first year of life was highest there. Ms. Terekhina recommends further studies to more precisely assess the effectiveness of the methods she tested, but has drawn up a proposed map of environmental hazard for the population, taking into account prevailing wind directions.

The confessions of St. Augustine.

Mode of access: Internet.

The life of the right Reverend Monsignor Weedall, D.D. ... including incidentally the early history of Oscott College /

Mode of access: Internet.

The life of Richard Steele,

Appendices (v. 2, p. [347]-428): I. The Steeles of Cheshire, and others. II. Fords of St. Michael's parish, Barbadoes. III. Performances of Steele's plays. IV. Music for Steele's songs.

The remains of Henry Kirke White, of Nottingham : late of St. John's College, Cambridge /

Portrait of White in vol. 1 and 3.

Wild life on the plains and horrors of Indian warfare : By a corps of competent authors and artists. Being a complete history of Indian life, warfare and adventure in America. Making specially prominent the late Indain war, with full descriptions of the Messiah craze, ghost dance, life of Sitting Bull ...

A reprint, with additional chapters, of Custer's "My life on the plains."

The life of Catherine Booth : the mother of the Salvation Army /

Mode of access: Internet.

The goodness of St. Rocque, and other stories.

Mode of access: Internet.

St. Patrick, his writings and life,

Contains a translation of Muirchu's Life of St. Patrick.

The life of Granville George Leveson Gower, second earl Granville, K.G., 1815-1891,

Appendix (From the Tablet, September 27, 1884) St. Augustine's cross in the Isle of Thanet.

A narrative of the life of David Crockett, of the state of Tennessee /

Crockett's attempt (ghost-written by Thomas Chilton) to correct erroneous impressions produced by Mathew St. Clair Clarke's The life and adventures of Colonel David Crockett of West Tennessee, which was published anonymously in 1833, and later reissued as Sketches and eccentricities of Colonel David Crockett of West Tennessee. Cf. introduction to the facsimile edition of the Narrative, edited by J.A. Shackford and S.J. Folmsbee, and published by the University of Tennessee Press.

The life of Saint Patrick, Apostle of Ireland, to which is added Saint Fiech's Irish Hymn; also a copious appendix of the various ecclesiastical institutions, &c. in Ireland,

Includes a hymn on the life, virtues and miracles of St. Patrick, composed by St. Fiech.

John Bachman, the pastor of St. John's Lutheran Church, Charleston.

Life and letters, ed. by C.L. Bachman.

The Confessions of St. Augustine /

Mode of access: Internet.