The purpose of this study was to determine duration time, breakage and apical displacement, whilst using six different endodontic filing systems to prepare molar teeth. A total of 96 molar teeth were used in the study, divided equally, ie 16 teeth per system selected randomly, totalling 48 canals per system. A standardised access cavity was prepared for all the teeth before selection. The canals were filed according to the manufacturers&rsquo / guidelines. The result showed that PROTAPER&reg / , K3&trade / and the combination of: HERO Shaper&reg / , HERO Apical&reg / and Endoflare&reg / (Referred from hereon as HERO System for convenience) were statistically faster than PROFILE&reg / and FlexMaster&reg / , which were in turn faster than AETTM. Although breakage did occur in K3&trade / and HERO System this was not deemed statistically significant. Apical displacement occurred in the form of Type 1 in the AETTM, PROFILE&reg / and HERO System, but once again this was not statistically significant. It was concluded that more aggressive cutting features such as a positive rake<br /> angle, pyramidal shaped tip, progressive taper and absence of radial lands, if present, could have enabled K3&trade / , HERO System and PROTAPER&reg / to have faster times, and in addition these features did not compromise these systems with regard to apical foramina transportation and breakage.

The Swedish Environment Protection Act (SEPA) was implemented in 1969 and constituted the first comprehensive Swedish regulation of industry-induced environmental externalities. In keeping with a longstanding corporatist tradition, Swedish policymakers aimed to establish a cooperative climate with industrial producers and instructed the regulatory authorities to strive to reach consensual agreements with affected firms. Despite such accommodations, the environmental adaptation of Swedish industrial production proceeded at a greater pace, during the 1970’s and 1980’s, than in most comparable countries, many of which had implemented seemingly more stringent environmental regulations than had Sweden. This thesis seeks to identify the firm level incentives behind this process, by examining the economic impact of the SEPA upon one of the more pollution-intensive branches of Swedish industrial production, the pulp and paper industry. Guided by previous research, an hypothesis is proposed in which the implementation of the SEPA came to aid the structural rationalization of this industry during the 1970’s and 1980’s, by inducing the exit of marginal, small-scale pulp and paper mills, thereby relaxing the prevailing competition over wood resources and available market space and creating more room for expansion within the surviving mills. As larger firms tend to operate larger mills, the hypothesized effects are suggested to have benefited large-scale producers within the industry, at the expense of their smaller rivals.   The findings of the thesis show that the economic effects of the SEPA were more severe for small as compared to large-scale mills and that regulatory requirements for pollution abatement did contribute to the shutdown of several small-scale mills during the 1970’s and 1980’s. No conclusive evidence could, however, be found for the validity of the thesis’ hypothesis as a whole, as these shutdowns were not predominantly administered by small-scale firms, as predicted by the hypothesis. Rather, the vast majority of these shutdowns were accounted for by some of the largest firms within the industry. Some tentative evidence was found, however, that the implementation of the SEPA may have benefitted certain large-scale producers within the industry, by facilitating acquisitions of smaller firms with valuable assets.

In this thesis, the effectiveness of microparticle retention aid systems comprising of different cationic starches (tapioca and waxy maize), cationic flocculants (flocculant 1, linear with low charge density and flocculant 2, branched with medium charge density polyacrylamides) and anionic colloidal silica in improving retention and drainage of thermomechanical pulp (TMP) suspensions loaded with precipitated calcium carbonate (PCC) is studied. While starch is primarily added as dry strength agent in PCC-filled TMP suspensions, it also has a significant role in improving retention and drainage. Tapioca starch, which has both amylose and amylopectin, is found to be a better retention and drainage aid than waxy maize starch, which only contains amylopectin. In the absence of starch, both flocculants are ineffective in improving retention and drainage. With starch, both flocculant and silica are significant in enhancing retention and drainage further. Increasing the dosage of either flocculant or silica generally increases retention as well as drainage. Flocculant 2 is found to give slightly worse total and filler retention but better drainage compared to flocculant 1. The dosage of flocculant 2 is only half that of flocculant 1 though – for this reason overall flocculant 2 is deemed more effective in improving retention and drainage than flocculant 1. Split starch addition, where a portion of the starch is premixed with PCC and the rest added to the pulp, causes a slight decrease in both retention and drainage. Therefore, should the papermaker decide to use this approach, the starch should be split in a 25:75 ratio between PCC and the pulp to minimize the negative effects. Due to the cost benefits of using increased amounts of PCC, it is desirable to increase PCC content beyond the standard currently used (250 kg/t OD pulp for communications-grade paper). However, at very high dosages of PCC (500 kg/t OD pulp), the best combination identified in this work (tapioca starch, flocculant 2 and silica) is unable to maintain good retention and drainage. Increasing retention aid dosages may help retain more PCC, however this tactic can rapidly become uneconomical. A new approach is thus needed to achieve such highly-filled papers.

Diss. (sammanfattning) Stockholm : Tekn. högsk., 2004. / Härtill 7 uppsatser. I häftet felaktigt ISBN: KTH/FTP/R--2004/37--SE.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 86-89).

Thesis (M.Sc. Biological Sciences)--University of Waikato, 2008. / Title from PDF cover (viewed February 25, 2009) Includes bibliographical references (p. 70-78)

Thesis (M.App.Sc.) - Carleton University, 2005. / Includes bibliographical references (p. 146-152). Also available in electronic format on the Internet.

Thesis (M.S.)--University of Michigan, 1970.

Thesis (M.S.)--University of Michigan, 1969.

Thesis(M.S.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references (p.97-102).