The Influence of Certain Processing Factors on the Durability of Yttrium Stabilized Zirconia Used As Dental Biomaterial

In dentistry, yttrium partially stabilized zirconia (ZrO2) has become one of the most attractive ceramic materials for prosthetic applications. The aim of this series of studies was to evaluate whether certain treatments used in the manufacturing process, such as sintering time, color shading or heat treatment of zirconia affect the material properties. Another aim was to evaluate the load-bearing capacity and marginal fit of manually copy-milled custom-made versus prefabricated commercially available zirconia implant abutments. Mechanical properties such as flexural strength and surface microhardness were determined for green-stage milled and sintered yttrium partially stabilized zirconia after different sintering time, coloring process and heat treatments. Scanning electron microscope (SEM) was used for analyzing the possible changes in surface structure of zirconia material after reduced sintering time, coloring and heat treatments. Possible phase change from the tetragonal to the monoclinic phase was evaluated by X-ray diffraction analysis (XRD). The load-bearing capacity of different implant abutments was measured and the fit between abutment and implant replica was examined with SEM. The results of these studies showed that the shorter sintering time or the thermocycling did not affect the strength or surface microhardness of zirconia. Coloring of zirconia decreased strength compared to un-colored control zirconia, and some of the colored zirconia specimens also showed a decrease in surface microhardness. Coloring also affected the dimensions of zirconia. Significantly decreased shrinkage was found for colored zirconia specimens during sintering. Heat treatment of zirconia did not seem to affect materials’ mechanical properties but when a thin coating of wash and glaze porcelain was fired on the tensile side of the disc the flexural strength decreased significantly. Furthermore, it was found that thermocycling increased the monoclinic phase on the surface of the zirconia. Color shading or heat treatment did not seem to affect phase transformation but small monoclinic peaks were detected on the surface of the heat treated specimens with a thin coating of wash and glaze porcelain on the opposite side. Custom-made zirconia abutments showed comparable load-bearing capacity to the prefabricated commercially available zirconia abutments. However, the fit of the custom-made abutments was less satisfactory than that of the commercially available abutments. These studies suggest that zirconia is a durable material and other treatments than color shading used in the manufacturing process of zirconia bulk material does not affect the material’s strength. The decrease in strength and dimensional changes after color shading needs to be taken into account when fabricating zirconia substructures for fixed dental prostheses. Manually copy-milled custom-made abutments have acceptable load-bearing capacity but the marginal accuracy has to be evaluated carefully.

Doubly fed induction generator versus direct drive permanent magnet synchronous generator in wind power applications

The objective of this master's thesis is to compare two different generator systems for wind turbines. It is the doubly fed induction generator system with three stage gearbox and the direct drive permanent magnet generator system. The comparison of generator systems is based on annual energy production for a given wind climate. For comparison a 3 MW, 15 rpm wind turbine is used. Modelling of a turbine rotor, gearbox and converters were done. Design of two generators was done and their performance was examined.

Virtual Professional Network as a Value Creator in the Dental Business

The research of virtual professional networks has been enormous but the lack of research in the dental field was obvious. This study focuses on those uses and gratifications, and motives of participants that a virtual pro-fessional network should fulfil. The aim of this study is to understand the factors behind the successful virtual professional network, and motives of participants that support a particular business network’s building up for contributing its further success. In this study the focus is on particular mo-tives, needs and benefits of participants that are significant for the net-work’s further development. The study will explore relevant scientific research and theory that is char-acteristic in networking, and theories of user’s needs and motives. Empiri-cal data was collected from dental professionals by net based question-naire that was sent by e-mail. Data analysis was done by quantitative fac-tor analysis. The findings of this study were obvious that virtual knowledge of implantology is inadequate and knowledge is rather difficult to find in the Internet. Sharing of virtual knowledge, net-learning and communication were seen to improve the quality of impolantological professionalism and also the development of these areas was experienced essential. On the grounds of this study a host of a virtual professional network can focus on those aspects that serve the users at best, can develop professionalism in implantology and can profit in its own business operations.

Carbohydrate intake in children - associations with dietary intakes, growth, serum lipids,and dental health. The STRIP Project

This study is part of the STRIP study, which is a long-term, randomized controlled trial, designed to decrease the exposure of children in the intervention group (n=540) to known risk factors of atherosclerosis. The main focus of the intervention was the quality of dietary fat. The control group (n=522) did not receive any individualized counselling. Food consumption was evaluated with food records, and blood samples were drawn and growth was measured regularly for all participating children from 13 months to 9 years. A subsample of 66 children participated in a dental health survey. The number of studies on children’s carbohydrate intake, especially fibre intake, is insufficient. The current international recommendations for fibre intake in children are based on average assumptions and data extrapolated from intakes in adults and intake recommendations for adults. Finnish nutrition recommendations lack strict recommendations for dietary fibre in children. Due to fibre’s high bulk volume, excessive dietary fibre is considered to decrease energy density and hence it may have an adverse effect on growth. If fats are reduced from the diet, the low-fat diet may become high in sucrose. Therefore, especially in the STRIP study, it is important to determine the use of fibre and sucrose in children and possible associations with growth and nutrition as well as dental health. The results of the present study indicate that a high fibre intake does not displace energy or disturb growth in children and that children with high fibre intake have better quality of diet than those with low fibre intake. Additionally, dietary fibre intake associated inversely with serum cholesterol concentration. Other carbohydrates also affected serum lipid levels as well, since total carbohydrates, sucrose, and fructose increased serum triglyceride concentration. Total carbohydrate intake reduced HDL cholesterol concentration only in children with apoE3 or apoE4 phenotype. Over the period from the 1970s to the 1990s the dental health of children in Finland has substantially improved despite an increase in sucrose intake. The improvement was thought to be due to improved dental hygiene and the use of fluorine. However, during the past twenty years improvement in dental health has stopped. The present study showed that high long-term sugar intake increases risk of caries in children. High intake of sugar had also negative effects on the diet of children, because it worsens dietary quality by displacing essential nutrients. Furthermore, the quality of dietary fat was worse in children with high sucrose intake. In this study the children’s high sucrose intake was not associated with overweight, but interestingly, it associated inversely with growth.

Use data from permanent sampling points in growth and yield modeling

This study was carried to evaluate the efficiency of the Bitterlich method in growth and yield modeling of the even-aged Eucalyptus stands. 25 plots were setup in Eucalyptus grandis cropped under a high bole system in the Central Western Region of Minas Gerais, Brazil. The sampling points were setup in the center of each plot. The data of four annual mesurements were colleted and used to adjust the three model types using the age, the site index and the basal area as independent variables. The growths models were fitted for volume and mass of trees. The efficiency of the Bitterlich method was confirmed for generating the data for growth and yield modeling.

A comparative study of four tree species used in riparian forest restoration along Uruguay River, Brazil

Silvicultural and ecological knowledge about tree species is basic to restoration planning, particularly in high diversity regions. Here we present a comparison of four native tree species from the middle Uruguay River basin, Brazil-Argentine frontier: Heliocarpus americanus L. (Malvaceae), Maclura tinctoria (L.) D. Don ex Steud. (Moraceae), Schinus terebinthifolius Raddi (Anacardiaceae) and Cordia trichotoma (Vell.) Arrab. ex Steud. (Boraginaceae). We obtained data on initial growth, light interception, litterfall and litter mineral contents. H. americanus presented the greatest height and the lowest value of height/crown width ratio. H. americanus and M. tinctoria presented the highest light interception rate (>94 %) and highest litterfall (879 ± 151 and 792 ± 164 g·m-2·year-1, respectively). For the set of species, the lowest litterfall occurred between July and September. H. americanus presented the highest K concentration (1.13%) in the litter, while C. trichotoma had the highest values of Ca and Mg (6.35 and 2.02 %, respectively). S. terebinthifolius had the lowest light interception rate and litter mineral content.

Influence of pioneer-species combinations on restoration of disturbed ecosystems in the Atlantic Forest, Rio de Janeiro, Brazil

The analysis of species composition and its effects on sustainability restoration processes in the Atlantic Forest with poor environmental attributes is important to improve rehabilitation techniques for disturbed ecosystems. Reforestation projects were used as Biological Measures (BM) of rehabilitation, where treatments differ in the composition of exotic species, utilized as anthropic pioneers: BM1 - 82% (73% Mimosa caesalpiniifolia Benth, 9% Eucalyptus citriodora Hook.); BM2 - 91% (9%, 82%); and BM3 - 25% (15%, 10%). The monitoring of spontaneous regeneration was evaluated in three 12-year-old reforestation sites between thr rainy season of 2004 and 2005, and compared with an approximately 100-year-old native forest fragment and a grassland: ecosystems with inertial tendency toward recuperation and degradation, respectively. It was detected that exotic species used as anthropic pioneers strongly influenced regeneration: BM1 (75%), BM2 (85%), BM3 (55%), Forest (0%) and Grassland (50%). The highest similarity of species with forest regeneration (5%) was found for treatment BM3.

What can and should be legalized in ecological restoration?

After listing the five key elements of ecological restoration, ecology, economics, social values, cultural values, and politics, I celebrate the fact that in Brazil there is legislation on how to perform ecological restoration of degraded tropical forests, as well as an ongoing dialogue among legislators and scientists about this legislation, and also a lively debate among scientists as the best way forward, referring to articles by Brancalion et al. (2010) and Durigan et al. (2010) in this issue of Revista Árvore. Legislators elsewhere, especially megadiversity countries, should take note. I do not take sides in the debate; I think both groups of authors make very good points. Instead I call on the scientists and legislators concerned with restoration to ponder five strategic tools: A. Start with clear concepts. B. Decide where you want to go and why. C. Negotiate who should benefit & how, and who should pay, how, & why. D. Work out how an honest cost-benefit analysis of restoration would look, regardless of the biome in which you are working. Finally, figure out how to make the restoration immediately attractive for private landowners. Otherwise, they will not cooperate as fully as they could or should, and restoration efforts will not achieve its full potential.

The role of arbuscular mycorrhizal fungi on the early-stage restoration of seasonally dry tropical forest in Chamela, Mexico

It was evaluated the effect of two different sources of local inocula from two contrasting sites (mature forest, pasture) of arbuscular mycorrhizae fungi (AMF) and a non-mycorrhizal control on the plant growth of six woody species differing in functional characteristics (slow-, intermediate- and fast-growth), when introduced in a seasonally tropical dry forest (STDF) converted into abandoned pasture. Six plots (12 X 12m) were set as AMF inoculum source. Six replicates of six different species arranged in a Latin Square design were set in each plot. Plant height, cover area and the number of leaves produced by individual plant was measured monthly during the first growing season in each treatment. Species differed in their ability to benefit from AMF and the largest responsiveness in plant height and leaf production was exhibited by the slow-growing species Swietenia humilis, Hintonia latiflora and Cordia alliodora. At the end of the growing season (November), the plant height of the fast growing species Tabebuia donnel-smithii, Ceiba pentandra and Guazuma ulmifolia were not influenced by AMF. However, inocula of AMF increased leaf production of all plant species regardless the functional characteristics of the species, suggesting a better exploitation of above-ground space and generating a light limited environment under the canopy, which contributed to pasture suppression. Inoculation of seedlings planted in abandoned pasture areas is recommended for ecological restoration due to the high responsiveness of seedling growth in most of species. Use of forest inoculum with its higher diversity of AMF could accelerate the ecological restoration of the above and below-ground comunities.

Field Weakening, Parameters and Operation Range of the Permanent Magnet Traction Motors

The main focus of this thesis is to define the field weakening point of permanent magnet synchronous machine with embedded magnets in traction applications. Along with the thesis a modelling program is made to help the designer to define the field weakening point in practical applications. The thesis utilizes the equations based on the current angle. These equations can be derived from the vector diagram of permanent magnet synchronous machine. The design parameters of the machine are: The maximum rotational speed, saliency ratio, maximum induced voltage and characteristic current. The main result of the thesis is finding out the rated rotational speed, from which the field weakening starts. The action of the machine is estimated at a wide speed range and the changes of machine parameters are examined.

Design Aspects of Megawatt-Range Direct-Driven Permanent MagnetWind Generators

Direct-driven permanent magnet synchronous generator is one of the most promising topologies for megawatt-range wind power applications. The rotational speed of the direct-driven generator is very low compared with the traditional electrical machines. The low rotational speed requires high torque to produce megawatt-range power. The special features of the direct-driven generators caused by the low speed and high torque are discussed in this doctoral thesis. Low speed and high torque set high demands on the torque quality. The cogging torque and the load torque ripple must be as low as possible to prevent mechanical failures. In this doctoral thesis, various methods to improve the torque quality are compared with each other. The rotor surface shaping, magnet skew, magnet shaping, and the asymmetrical placement of magnets and stator slots are studied not only by means of torque quality, but also the effects on the electromagnetic performance and manufacturability of the machine are discussed. The heat transfer of the direct-driven generator must be designed to handle the copper losses of the stator winding carrying high current density and to keep the temperature of the magnets low enough. The cooling system of the direct-driven generator applying the doubly radial air cooling with numerous radial cooling ducts was modeled with a lumped-parameter-based thermal network. The performance of the cooling system was discussed during the steady and transient states. The effect of the number and width of radial cooling ducts was explored. The large number of radial cooling ducts drastically increases the impact of the stack end area effects, because the stator stack consists of numerous substacks. The effects of the radial cooling ducts on the effective axial length of the machine were studied by analyzing the crosssection of the machine in the axial direction. The method to compensate the magnet end area leakage was considered. The effect of the cooling ducts and the stack end area effects on the no-load voltages and inductances of the machine were explored by using numerical analysis tools based on the three-dimensional finite element method. The electrical efficiency of the permanent magnet machine with different control methods was estimated analytically over the whole speed and torque range. The electrical efficiencies achieved with the most common control methods were compared with each other. The stator voltage increase caused by the armature reaction was analyzed. The effect of inductance saturation as a function of load current was implemented to the analytical efficiency calculation.

NATURAL REGENERATION STRATUM AS AN INDICATOR OF RESTORATION IN AREA OF ENVIRONMENTAL COMPENSATION FOR MINING LIMESTONE, MUNICIPALITY OF BARROSO, MG, BRAZIL

ABSTRACT This study was conducted in a forest under restoration process, which belongs to the company Holcim Brasil S/A, in the municipality of Barroso, state of Minas Gerais (21º00'to 22º00'S and 43º00' to 44º00'W), where 40 plots (2 x 2 m) were set, spaced at 10 m, forming eight strata parallel to the watercourse present in the area. Floristic composition and natural regeneration stratum were characterized, and the formed strata allowed evaluating whether the riparian vegetation and watercourse influence on the local regeneration. It was found 162 individuals of 13 families, 18 genera and 22 species, and 10,125 individuals/ha were estimated. Successional classes from pioneer and early secondary and zoochory dispersion syndrome prevailed among species and individuals. The watercourse and riparian vegetation did not exercise significant influence (p> 0.05) on the number of species and regenerating individuals among the different strata of the forest. The diversity index of Shannon-Wiener (H') and equability of Pielou (J') were 2.691 and 0.870, respectively. The species Psidium guajava and Myrtaceae families presented the highest VI (value of importance). Natural regeneration analysis showed the low floristic diversity in the area, suggesting that corrective management actions should be adopted.

METHODOLOGY FOR AUTOMATICALLY DELIMITING PERMANENT PRESERVATION AREAS ALONG WATER COURSES - THE USE OF GIS IN THE HYDROLOGICAL BASIN OF THE SERGIPE RIVER, BRAZIL

ABSTRACT Permanent Preservation Areas (PPAs) along watercourses have been the focus of numerous studies, not only because of the fragility and ecological relevance of riverine vegetation, but also because of the inefficiency demonstrated in conforming to the legislation protecting it. One of the major difficulties encountered in terms of guaranteeing the effective conservation of these riverside areas is the absence of methodologies that can be used to define them rapidly and accurately without manually determining the widths of the rivers or assigning only uniform linear values for the entire watercourse. The present work sought to develop a spatial analysis methodology capable of automatically defining permanent preservation areas along watercourses using geographic information system (GIS) software. The present study was undertaken in the Sergipe River basin, "considering the river itself and its principal affluents. We used the database of the Digital Atlas of Hydrological Resources (SEMARH/SE), and the delimitations of the PPAs were performed using ArcGIS 10.1 and the XToolPro 9.0 extension. A total of 5,003.82 hectares of Permanent Preservation Areas were delimited along the margins of the rivers analyzed, with a margin of error of <1% in delimiting the widths of the rivers within the entire area considered. The methodology described here can be used to define PPAs efficiently, relatively rapidly, and with very small margins of error, thus representing a technological advance in terms of using GIS for land management.

Analysis of land use and occupancy in permanent preservation areas according to the hydrography of Ribeirão Água Fria - Bofete, SP - Brazil

The use conflicts are determined by the inadequate occupations of the soil, as it is the case of soil occupation inside of permanent preservation areas. This study aimed to determine the classes of the soil use and if there are conflicts inside of permanent preservation areas along the drainage network of the Água Fria Stream watershed, located in Bofete city - São Paulo, Brazil. It locates geographically between the coordinates: 48°09'30" to 48°18'30" longitude WGr., 22°58'30" to 23°04'30" latitude S, with an area of 15242.84 ha. The map of soil use was elaborated through the interpretation directly in the computer screen of satellite digital image. In the orbital data, the study area is inserted in the quadrant A, of image TM/Landsat - 5, orbit 220, point 76, passage 9/8th/2007. The Geographical Information System used was CartaLinx. The conflict areas of the watershed were obtained from the crossing between the maps of soil use and of PPAs. The results allowed the conclusion that more than half of the area (51.09%) is occupied by pastures, reflex of sandy soils and low fertility. It was also verified that although almost half of the watershed is covered with some type of vegetation (48.78% of natural forest /reforestation), it has approximately a third of permanent preservation areas used inappropriately by pastures (88.15%), reforestation (10.42%) and exposed soil (1.43%), totaling 343.07ha of conflicting areas, in a total of 993.26 ha of PPAs.

Evaluation of sediment production and siltation in a small earth dam in Fernandópolis, SP

The siltation is a natural process, but can be accelerated by human actions and results in major problems for the reservoirs, reducing its useful volume for irrigation. An example of this problem was the reduction of the area of mirror water of Fernandópolis municipal dam in 48.3% during 20 years. Therefore, this study aimed to evaluate the production of sediments and siltation of Fernandópolis municipal dam from a methodology that can be applied to small earth dams for agricultural purposes. For this, it was monitored, monthly throughout the year, the volume of sediment deposited in the reservoir. The percentage of retention sediment in Fernandópolis municipal dam ranged from 53.9 to 94.5%, that associated with a high specific sediment yield, will cause its full silting in at most 57 years. It is recommended to minimize this process the restoration of permanent preservation areas and the removal of 17,500 m³ of sediment from the riverbed of the dam.