Discontinuous fiber-reinforced composite for dental reconstructions - Studies of the fracture resistance and the mechanical properties of the material used for extensive direct restorations

Earlier developed low aspect ratio dental discontinuous-FRC are micrometer-scale discontinuous-FRCs, which lack sufficient strength and fracture toughness to reinforce structures reinforced with them. The aim of this thesis was to evaluate the fracture resistance, the bonding properties as well as some mechanical properties of newly developed millimeter-scale discontinuous-FRC. Fiber- and matrix related properties were also analyzed. Four studies were designed to evaluate the fracture resistance and the failure mode of anterior restorations reinforced with millimeter-scale discontinuous-FRC, to assess the shear bonding strength between incrementally placed layers of this fibrous composite, to measure the thickness and the effect of the oxygen inhibition layer (OIL) on the interlayer bonding characteristics as well as to determine various physicomechanical properties. In addition, fiber related properties, including fiber volume fraction, fiber length, critical fiber length and fiber diameter, and matrix related properties, fiber orientation were computed. The results of these studies show that the use of millimeter-scale discontinuous-FRC post-core-crown structure was advantageous in terms of both provided reinforcement and failure mode. Furthermore, it was found that OIL presence improves the interlayer connection. The protruding fibers ends at the interface between the fibrous composite layers and the semi-IPN were considered to promote the durable adhesion upon OIL removal. Millimeter-scale fibers substantially improved the fracture toughness owing to the fibers ability to bridge the crack, blunt the crack tip and carry the load, accompanied with the semi-IPN aided plasticity. However, fibers shorter than 0.4 mm most likely behave as reinforcing filler particles instead of reinforcing fibers. Furthermore, fiber orientation was found to be important for impeding the crack progression. These studies suggest that millimeter-scale discontinuous-FRC should accompany the individually FRC post insertion and should fill the pulp chamber and extend coronally as core material, to provide retention and to strengthen the cervical portion of the tooth. Alternatively, it could be used as post-core structure. In both cases homogenous unit is assumed, due to the identical composition of the materials. Upon curing, the OIL should be left on the surface of the composite and should not be contaminated. This could improve the bonding and improve the inherent fracture resistance of the material. This was observed also in the ability of the material to resist the fracture propagation, which approached the toughness value of dentin. These studies indicate that the benefits of using millimeter-scale discontinuous-FRC are especially the improved fracture toughness and resistance to fracture, as well as improved interlayer bonding compared to conventional composites. Moreover, using of millimeter-scale discontinuous-FRC changes the fracture pattern and more reparable fractures were found for this material.Siirretty Doriast

Exploring Nurse Leader Self-Efficacy, Burnout, and Intent to Leave

Nurse leader turnover is an emerging issue in healthcare services. Considerable research has been done over the last decade revealing that nurse leaders are experiencing an increased rate of burnout with an intent to leave their jobs. Less research has been done to understand how to mitigate the rate of nurse leader burnout and retain nurse leaders in the workforce. Higher levels of self-efficacy have mediated the effects of work stress on job burnout in other service related fields. The purpose of this quantitative, non-experimental, cross-sectional study was to explore the possible mediating effect of leader self-efficacy between burnout and intent to leave. This research was grounded in Maslach’s burnout theory and Bandura’s self-efficacy theory. The tools included the Maslach Burnout Inventory Human Services Survey (MBI-HSS), the Leader Effectiveness Questionnaire (LEQ), and a 3-item intent to leave job subscale from Cohen’s Turnover Intention Scale (TIS). A total of 325 nurse leaders participated in the study. Statistical analyses included descriptive statistics and correlational mediation analyses. The findings showed that components of leader self-efficacy have a mediating relationship between burnout and intent to leave for nurse leaders. The results provided initial findings on how leadership self-efficacy can stabilize the nursing leadership workforce while influencing the delivery of care to patients. United States leaders rely on the nursing workforce to resolve the health care delivery crisis. Strong nurse leaders are needed to continue to influence positive social change

Mycobacterium smegmatis is a suitable cell factory for the production of steroidic synthons

13 p.-3 fig.-3 tab.A number of pharmaceutical steroid synthons are currently produced through the microbial side-chain cleavage of natural sterols as an alternative to multistep chemical synthesis. Industrially, these synthons have been usually produced through fermentative processes using environmental isolated microorganisms or their conventional mutants. Mycobacterium smegmatis mc2155 is a model organism for tuberculosis studies which uses cholesterol as the sole carbon and energy source for growth, as other mycobacterial strains. Nevertheless, this property has not been exploited for the industrial production of steroidic synthons. Taking advantage of our knowledge on the cholesterol degradation pathway of M. smegmatis mc2155 we have demonstrated that the MSMEG_6039 (kshB1) and MSMEG_5941 (kstD1) genes encoding a reductase component of the 3-ketosteroid 9a-hydroxylase (KshAB) and a ketosteroid D1-dehydrogenase (KstD), respectively, are indispensable enzymes for the central metabolism of cholesterol. Therefore, wehave constructed a MSMEG_6039 (kshB1) gene deletion mutant of M. smegmatis MS6039 that transforms efficiently natural sterols (e.g. cholesterol and phytosterols) into 1,4-androstadiene-3,17-dione. In addition,we have demonstrated that a double deletion mutant M. smegmatis MS6039-5941 [DMSMEG_6039 (DkshB1)and DMSMEG_5941 (DkstD1)] transforms natural sterols into 4-androstene-3,17-dione with high yields.These findings suggest that the catabolism of cholesterol in M. smegmatis mc2155 is easy to handle and equally efficient for sterol transformation than other industrial strains, paving the way for valuating this strain as a suitable industrial cell factory to develop à la carte metabolic engineering strategies for the industrial production of pharmaceutical steroids.This study was supported by grants from the Ministry of Science and Innovation (BFU2006-15214-C03-01, BFU2009-11545-C03-03) and Ministry of Economy and Competitiveness (BIO2012-39695-C02-01).Peer reviewe

Effective Contract in Higher Education: Intentions and Outcomes

The issue of the academic contract in the Russian higher education is associated with the salary systems reform in social sector and scientific field according to the adoption of the Decree of the President of the Russian Federation from May 7, 2012 No. 597 “On Measures for the Implementation of the State Social Policy”. Institutional project of the effective contract was aimed to solve two problems. Firstly, to raise the level of wages. Secondly, to its orientation to increase performance (i.e. outcomes-based payment). Over the past ten years in practice an effective contract evolved from innovation to university routine. On the other hand, researchers moved from substantiating approaches and elaborating methodologies to analyzing the experience of implementing an academic contract and then to evaluating its outcomes. The purpose of this study is to show the outcomes of the implementation of the effective contract project in the higher education system in two directions. Firstly, the achievement of target indicators for increasing the level of salaries of university teachers. Secondly, stimulating more efficient activities.Data from the Monitoring of higher education institutions effectiveness in 2021 is used in the study, and it includes data on 1222 universities. There is information on the average salary of university teachers (excluding part-time workers and civil contract staff) for 2020 for each educational institution, as well as on the ratio of teaching staff salary to the average salary in the region’s economy for 2016-2020. It was revealed that the task of introducing an effective contract for the increasing of salaries is generally being fulfilled but with significant difficulties due to the economic factors. The stimulating impact of an effective contract on the activities of university teachers is realized in conjunction with the solution of the tasks of increasing the effectiveness of the functioning of the universities themselves

Bergarbeiterproteste im Kuzbass: das Jahr des Schienenkrieges in Fallstudien

'Der vorliegende Bericht befaßt sich mit den Bergarbeiterprotesten im Kuzbass, dem Kohlenrevier des Gebiets Kemerovo. Die politische Rolle der Bergarbeiter ist zwiespältig. Erst kämpften sie für die Abschaffung des sowjetischen Verwaltungssystems und erfüllten so die Rolle eines 'demokratischen Vortrupps' für Reformpolitiker um Boris Jelzin. Einige Jahre später protestierten sie dann gegen den Präsidenten und liberale Reformen und unterstützten statt dessen kommunistische Politiker. Hier soll nun der Versuch unternommen werden, die Bergarbeiterproteste auf ihr Ausmaß, ihre Formen und ihre politische Bedeutung hin zu untersuchen. Mit Hilfe von Methoden der qualitativen Sozialforschung sollen die wesentlichen Züge der Problematik erfaßt werden.' (Textauszug)'The present report is concerned with the miners' protests in the Kuzbass, the coal-mining region of Kemerovo oblast. The political role of the miners is an ambivalent one. Initially they fought for the abolition of the Soviet system and thus played the role of a kind of 'democratic vanguard' for the reformist politicians surrounding Boris Yeltsin. A few years later, however, they began to protest against the president and the liberal reforms and transferred their support to communist politicians. The report examines the extent of the miners' protests, the form they have taken and their political significance. The most important aspects of the issue are outlined using the methods of qualitative social research.' (extract

Creation and Characterization of Mycolicibacterium Smegmatis mc2155 with Deletions in Genes Encoding Sterol Oxidation Enzymes

The fast-growing saprotrophic strain Mycolicibacterium smegmatis mc2155 is capable of utilizing plant and animal sterols and can be used for creation of genetically engineered strains producing biologically active steroids. Oxidation of the 3β-hydroxyl group and Δ5(6)→Δ4(5) double bond isomerization followed by formation of stenones from sterols are considered as the initial stage of steroid catabolism in some actinobacteria. The study of the mechanism of steroid nucleus 3β-hydroxyl group oxidation is relevant for the creation of a method of the microbiological production of valuable 3β-hydroxy-5-en-steroids. A mutant strain of M. smegmatis with deletions in three genes (MSMEG_1604, MSMEG_5228 and MSMEG_5233) encoding known enzymes exhibiting 3β-hydroxysteroid dehydrogenase activity was constructed by homologous recombination coupled with double selection. The resulting mutant retained macromorphological properties and the ability to convert cholesterol. 3-Keto-4-en-steroids were found among the sterol catabolism intermediates. Experimentally obtained data indicate the presence of a previously undetected intracellular enzyme that performs the function of 3β-hydroxysteroid dehydrogenase/Δ5(6)→Δ4(5) isomerase