Enamel decalcification caused by poor oral hygiene is a significant problem in orthodontics. Bioactive glass-containing resins have been shown to release Ca2+ ions into surrounding solution. The purpose of this study was to determine the shear bond strength of four different compositions of orthodontic resin prepared with bioactive glass (N=20). Premolars were bonded using one of four BAG-BOND compositions. Brackets were debonded and ARI scores were given. The mean shear bond strength was 7.23 ± 2.47 MPa (62 BAG-BOND), 8.25 ± 2.87 MPa (65 BAG-BOND), 8.78 ± 3.08 MPa (81BAG-BOND) and 5.80 ± 2.27 MPa (85 BAG-BOND). 65 and 81 BAG-BOND were significantly higher than 85 BAG-BOND. The 62 BAG-BOND group was not statistically significantly different from any other group. All groups exhibited a cohesive bond failure and were not statistically significant from each other. Three compositions of the novel orthodontic adhesive exhibited adequate bond strength for clinical applications.

There is a paucity of longitudinal data investigating the role of vitamin D in the maintenance of health in ethnic minority groups. Specifically, little is known about the role of vitamin D on muscle strength, how this affected by emigrating from low to high latitudes. This PhD thesis provides insight into the relationship between vitamin D status and muscle strength in healthy adults migrating from sunny climates (45°N to 45°S to the equator) to higher latitude (Aberdeen, 57°N) (first study) and also sunlight behaviours in both low and high latitudes (second study). A total of 71 people of ethnic minority aged 19-42 years took part in the first study with 56% were seen within 3 months of arriving in Aberdeen (newcomers) and the remainder having been resident for any longer period than this (residents). Participants attended visits every 3 months for 15 months. At each visit, fasted blood samples were collected for analysis of serum 25-hydroxyvitamin D [25(OH)D] by dual tandem-mass spectrometry, parathyroid hormone (PTH), carboxy-terminal collagen crosslinks (CTX) and N-terminal propeptide of type I collagen (P1NP) by electrochemiluminescent immunoassay. Maximal voluntary contraction (MVC) was measured using a Takei digital grip dynamometer (both arms) and a Biodex dynamometer (right knee) for isometric knee extension and isokinetic knee extension and flexion. Mean baseline 25(OH)D concentrations were higher in the newcomers (35.2 nmol/L) than the residents (25.0 nmol/L, p<0.01). After adjusting for the season of measurement at baseline, there was a trend for higher vitamin D status only between newcomers arriving in spring (33.5 nmol/L) and residents (26.8 nmol/L, p=0.09), but not between the newcomers arriving in autumn (36.1 nmol/L) and residents in autumn (35.2 nmol/L, p=0.81). Notably, few newcomers (13%) and residents (7%) had 25OHD concentrations >50 nmol/L. There was a small seasonal variation in 25(OH)D concentration with the difference between zenith (summer/autumn) and nadir (winter/spring) was 5 nmol/L, 6 nmol/L, and 12 nmol/L among the newcomers arriving in spring, autumn and residents, respectively. There was no seasonal variation in bone turnover markers. There was a positive, albeit small, association between vitamin D and knee extensor isometric torque. Mixed modelling predicted that each 1 nmol/L increase in 25(OH)D would increase peak torque by 1 Nm (p=0.04). If extrapolated to higher 25(OH)D, the change in muscle strength would be clinically meaningful. In the second study, 117 Asians in Kuala Lumpur (3°N) and 110 non-Europeans (78% Asians) in Aberdeen were recruited and monitored for one year [every 3 months for participants in Aberdeen and during Southwest monsoon (SWM; July-Sept) and Northeast monsoon (NEM; Nov-Feb) in Kuala Lumpur]. Personal sunlight exposures were assessed by polysulphone film badges and a web-based questionnaire. Asians living in their usual environment (Kuala Lumpur) had similar sunlight behaviours to Asians living in Aberdeen. Sunlight was the major source of vitamin D in Kuala Lumpur during both seasons (median % cutaneous in SWM = 61%; NEM = 59%), but only during summer in Aberdeen (52%). Dietary intakes provided the most source of vitamin D in Aberdeen during autumn (94%), winter (97%) and spring (56%). This thesis has added evidence to the current limited observations on vitamin D and muscle strength, particularly in the cohort of young adults migrating from low to high latitudes. Intervention studies are yet to be conducted with a speculation that an increase in vitamin D status may show a positive impact on muscle strength. The extent of low sunlight behaviour among healthy adults in Kuala Lumpur is of concern.

Title: Effect of arm position on finger flexor strength in sport climbers Objectives: The main purpose of this study was to assess the effect of arm position on finger flexor strength in sport climbers. Methods: Twenty-one women (age 24,5 ± 2,7 years, body weight 59,5 ± 8,3 kg, height 166,4 ± 6 cm) and twenty-five men (age 26,9 ± 5,3 years, body weight 71,7 ± 7,7 kg, height 177,2 ± 5,3 cm) volunteered to be a part of the study. The RP performance varied from the 3rd to 10th degree UIAA (Union International des Assocoation d'Alpinisme) scale. A specially manufactured tool was used to measure the finger flexor force with different positions of an arm. During the study, measurements were taken as the arm was adjusted into four different positions: Handgrip (0ř shoulder and elbow in full extension), Flexion90 (90ř shoulder flexion and external rotation of 45ř and the elbow in 90ř flexion supported by a board), Flexion130 (the arm 130ř abduction and elbow flexion 50ř) and Flexion180 (180ř shoulder flexion and elbow in full extension). The open grip was used for all positions, except for the Handgrip position where the thumb was in opposition. Results: The highest relation between the relative strength and RP climbing performance was found in the Flexion130 (r = 0,81) in women and in Flexion180 (r =...

Title: Reliability of isometric and isokinetic strength testing in the knee flexion and extension Objectives: To compare the reliability of isometric and isokinetic testing of the knee strength in flexion and extension Methods: I used intraclass correlation coefficient and Pearson's correlation coefficient. Results: I have discovered that the reliability measured on isokinetic and isometric dynamometer is high. Furthermore the reliability of the maximum strength measurement was higher with-using the isokinetic dynamometer. Keywords: reliability, intraclass correlation coefficient, isometric dynamometry, maximal isometric strength, isokinetic dynamometry, knee strength, Cybex Humac Norm

Title: Stimulation of strength abilities by short home exercise for women at the age of 50-65 years. Objectives: The objective of this work is to provide information about the influence of the short home exercise on muscle strength by a case study. Methods: Individually designed intervention program is based on the objective of this work and on a diagnosis of musculoskeletal system/locomotor system. Strength of the subject was measured through fourteen different strength tests by the isokinetic dynamometer. Subject's body composition was also measured by the bioimpedance method. Key words: muscle strength, Sarcopenia, age

Title: The effect of alcohol drinking on the isokinetic knee strength Objectives: The objective of this thesis is to assess the effect of alcohol on isokinetic knee strength during extension and flexion. Methods: Fifteen volunteers participated in this study. Their age was 23,9 ± 1,9 years, height 179,5 ± 7,2cm and weight 78,5 ± 7,95kg. They were all students from sports faculty. One group of volunteers was given alcohol with juice (0,8g of alcohol to 1kg of fat-free mass), the second group drank only juice. We used the switch design study. We measured isokinetic knee strenght on dynamometer Cybex Humac Norm (Cybex NORM ®, Humac, CA, USA) in three types of angular velocity (6Oř/s, 180ř/s, 240ř/s). The parametrs were peak torque, muscular work, average muscular power and time to peak. Results: We registered statistically significant increase of peak torque, muscular work and average muscular powers when measuring flexion in all the three angular velocities (60ř/s, 180ř/s, 240ř/s). We did not register statistically or effect size significant diference readings of time needed for maximal peak torque when measuring flexion and extension. The only exception was angular speed 240ř/s where we registered a factually significant change in time needed for extensors to reach the maximal peak torque....

Natural fibre composites (NFCs), which are polymers reinforced with cellulosic bast fibres, have the potential to be applied into a range of building products. They are seen as an alternative to glass fibre reinforced plastics (GFRP) in some applications, because of natural fibres (NF) relatively high strength and low density. Moreover, natural fibres have a set of beneficial traits, such as thermal insulation, thermal stability, biodegradability, and are inherently renewable. Those characteristics are of importance when NF are used as reinforcements in polymer composites, but developments in mechanical performance, reliability and economic viability are still required in order to be adopted fully by industry. The goal of this thesis was the development of a processing methodology for NFC laminate and subsequent material characterisation to assess the developed material suitability for building applications. Research objectives included materials selection, processing route development for laminates and tubes, manufacture of NFC laminates and analysis of mechanical properties in order to find an optimal composition. Hemp and flax fibres were selected as the reinforcement, because both have high mechanical properties and are important bast fibre crops in the European region with established cultivation and processing methods. As a matrix, fossil-fuel based and partially bio-derived thermoset resin systems were used. Handling and processing methodologies were developed for laminates and composite tubes based on filament winding and compression moulding techniques. The effects of the selected factors, namely material composition, volume fraction, processing parameters, reinforcement linear density, yarn twist, lamination sequence, yarn waviness and hybrid hemp-wool reinforcement were subsequently described in mechanical properties analysis of laminates. The influence of weathering conditions on the mechanical performance of the NFCs was examined. Furthermore, a study of NFC tubes under compression was performed. Results showed that the developed laminates reinforced with NF yarns have sufficient mechanical properties to be utilised in sandwich panels and/or tubes. However, a low resistance to moisture-related weathering restricts the developed NFCs for indoor applications.

The objective of the report is to investigate the feasibility and reliability of additive friction stir manufacturing of 7055 aluminum alloy. This is a technique in which multiple lap welds are performed to create a three-dimensional part out of relatively thin plate aluminum. To accomplish this, a four inch stack of 7055 aluminum alloy lap welds must be created. The solid weld nugget is then machined out of the center of the welded stack to create ASTM approved subsize tensile coupons. Rockwell hardness, yield strength, ultimate tensile strength, and percent elongation information is gathered from the tensile coupons to investigate the effectiveness of the additive friction stir manufacturing process. The data shows that the additive manufactured material experiences a significant reduction in strength and percent elongation while not showing any significant response to heat treatment. Suggestions are made regarding possible changes to the weld schedule that could improve the material properties of the additive manufactured aluminum.

[pt] Os aços de alta resistência avançados estão sendo desenvolvidos e usados para a indústria automotiva devido à sua excelente combinação de alta resistência e ductilidade, acarretando na minimização de custo e peso e maximização da segurança. A soldagem por fricção e mistura mecânica a ponto (Friction Stir Spot Welding – FSSW) é uma nova variante do processo de fricção e mistura mecânica (Friction Stir Welding – FSW), que é um processo de soldagem no estado sólido, e pode ser aplicada em uma variedade de indústrias que necessitam de soldagem a ponto como a indústria aeroespacial, automotiva, nuclear, óleo e gás, transporte e outras indústrias que necessitam fazer a junção dos metais usando, geralmente, uma configuração de sobreposição. O presente trabalho é um estudo exploratório para melhor compreensão da soldagem por fricção e mistura mecânica a ponto do aço TRIP 800. Diferentes corpos de prova foram produzidos usando velocidades de rotação da ferramenta de 1600, 2000 e 2400 rpm e tempos de espera de 2s e 3s. Além da caracterização metalúrgica e determinação de microdureza, ensaios de cisalhamento e cross-tension foram realizados para avaliar o desempenho mecânico das juntas. / [en] Advanced high strength steels (AHSS) are being developed and are being used for the automotive industry due to their exceptional combination of high strength and ductility, which leads to cost and weight savings and better safety. Friction Stir Spot Welding (FSSW) is a novel variant of Friction Stir Welding (FSW), which is a solid-state joining process without bulk melting and can be applied in a variety of industries that require spot welding such as aerospace, automotive, marine, nuclear, oil and gas, transportation industries and other industries that need to join metals together, generally using an overlap configuration. The present contribution is an exploratory study to a better understanding of a TRIP 800 friction stir spot welding. Different samples were produced using tool rotational speeds of 1600, 2000 and 2400 rpm and dwell time of 2s and 3s. Besides the metallurgical characterization and microhardness determination, lap-shear and cross-tensile tests were carried out to evaluate the mechanical performance of the joints.

This research study is conducted on one bay-one story non-sway frames where the effects of the rotational restraint and slenderness ratio on the post-buckling strength of the axially restraint column under thermal load are studied. Geometric non-linear analysis of the structures is performed using a research program based on the beam-column theory. A total 32 models are created considering two different bottom end conditions: fixed and hinged, slenderness ratios: 50 and 125, and the beam to column length ratios: 0.5,1,1.5 and 2, to account for the variation in the rotational restraint. All models are subjected to thermal loads and numerical results are obtained to study the post-buckling behavior of the columns of the frames under thermal loads.