Dissertations / Theses on the topic 'Secondary ageing'
To see the other types of publications on this topic, follow the link: Secondary ageing.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 27 dissertations / theses for your research on the topic 'Secondary ageing.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Marvier, Allison Christina. "Effects of ageing on primary and secondary transport processes in red beet (Beta vulgaris) storage tissue." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295952.
Full text
2
Buha, Joka School of Materials Science & engineering UNSW. "Interrupted ageing of Al-Mg-Si-Cu alloys." Awarded by:University of New South Wales. School of Materials Science and engineering, 2005. http://handle.unsw.edu.au/1959.4/20794.
Full textAbstract:
This thesis systematically investigates the effects of a recently developed modified ageing procedure of aluminium alloys, termed the T6I6 temper, on the microstructural development and mechanical properties of the Al ??? Mg ??? Si - Cu alloy 6061. For the T6I6 temper, a conventional single stage T6 temper is interrupted by an ageing period at a reduced temperature (65??C) to facilitate secondary precipitation, before resuming the final ageing at the temperature of the initial T6 treatment. The T6I6 temper was found to cause simultaneous increases in tensile properties, hardness, and toughness as compared with 6061 T6. Al ??? Mg ??? Si ??? Cu alloys are medium strength alloys widely used in the automotive industry and their further improvement is underpinned by stringent demands for weight reduction placed on the transportation industry in recent years. The potential for further improvement of the mechanical properties was found in the control of secondary precipitation that may take place even in some fully aged alloys when exposed to reduced temperatures. The overall improvement in the mechanical properties of 6061 T6I6 was attributed to the formation of finer and more densely dispersed precipitates in the final microstructure. The refinement of precipitates was facilitated by control of the precipitation processes and gradual evolution of the microstructure throughout each stage of the T6I6 treatment. The results indicated that the concentration and the chemical environment of the vacancies controlled the precipitation processes in this alloy. Findings also show that the proportion of the different precipitate phases present in the final microstructure, as well as the amount of the solute in these precipitates, can be controlled and modified utilizing secondary precipitation. A number of analytical techniques were used in this study. The evolution of the microstructure was studied using Transmission Electron Microscopy (TEM), High Resolution TEM (HRTEM) and Three Dimensional Atom Probe (3DAP). Vacancy-solute interactions were studied using Positron Annihilation Lifetime Spectroscopy (PALS) and 3DAP. The distribution of the solute was studied using 3DAP and Nuclear Magnetic Resonance (NMR). Differential Scanning Calorimetry (DSC) was used to identify precipitation reactions and to determine the stability of vacancy-associated aggregates.
3
Xu, Dapeng. "Time effects on soil behavior : a particulate-scale study on the mechanisms of secondary consolidation and ageing /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202006%20XU.
Full text
4
Marceau, Ross Kevin William. "Design in Light Alloys by Understanding the Solute Clustering Processes During the Early Stages of Age Hardening in Al-Cu-Mg Alloys." University of Sydney, 2008. http://hdl.handle.net/2123/4008.
Full textAbstract:
Doctor of Philosophy (PhD)The evolution of atomistic-level nanostructure during the early stages of both standard, high-temperature T6 heat treatment, and low-temperature secondary ageing after interruption of the former (T6I4), has been investigated in rapid hardening Al-Cu-Mg alloys using a variety of microscopy and microanalytical techniques, including transmission electron microscopy (TEM), positron annihilation spectroscopy (PAS) and atom probe tomography (APT). In order to carry out this objective, quantitative data-analysis methods were developed with respect to new cluster-finding algorithms, specifically designed for use with three-dimensional APT data. Prior to this detailed characterisation work, the actual thermal impact from both heat treatment and quenching of small, lab-scale specimens was determined through correlation of both experimental results and calculations that modelled the heat transfer conditions using the lumped capacitance method. Subsequently, the maximum diffusion distance by random walk of the solute atoms was calculated for these periods, bearing significance on the propensity for these atoms to have the ability to cluster together, rather than segregate to the dislocation loops in the microstructure, which have a relatively larger interspacing distance. Age-hardening curves for the Al-1.1Cu-xMg (x = 0, 0.2, 0.5, 0.75, 1.0, 1.7 at.%) alloys at 150ºC show that the rapid hardening phenomenon (RHP) exists for Mg compositions ≥ 0.5Mg. Given that zone-like precipitate structures were unable to be detected by TEM or APT during the early stages of ageing at 150ºC, and that statistically significant dispersions of clusters were found in the APT data after ageing for 60 s, the RHP is attributed to these clustering reactions. Identification of clusters in the APT data has been achieved using the core-linkage algorithm and they have been found to be quite small, containing only a few atoms up to a couple of tens of atoms. The RHP is governed by some critical number density of both Mg clusters and Cu-Mg co-clusters of a critical size, whereas Cu clusters do not contribute significantly to the hardening mechanism. Significance testing indicates that Mg clusters are more significant at smaller clusters sizes and Cu-Mg co-clusters more important at larger cluster sizes. Hardness results also confirm the existence of rapid early hardening during secondary ageing at 65ºC in Al-1.1Cu-1.7Mg. The mechanism of secondary rapid hardening involves a combination of both secondary clustering from solute (mainly Mg atoms) residual in solution, and pre-existing amorphous primary clusters that have slower growth kinetics at the lower secondary ageing temperature. The latter occurs mainly by vacancy-assisted diffusion of Mg atoms as evidenced by the gradual increase of the Mg:Cu ratio of co-clusters. From an alloy design point of view it is important to fully understand the solute distribution in the microstructure to be able to subsequently optimise the configuration for enhanced material properties. The change in dispersion of solute atoms during ageing was determined by combining calculations of % vacancy-solute associations with detailed measurements of the dislocation loops to estimate the solute distribution within the microstructure. The implication of the balance of solute atoms segregated to the loops compared with that in the matrix is then discussed in the context of hardnening mechanisms.
5
Remes, T. (Tiina). "Signs of radiation-induced accelerated ageing in survivors of childhood brain tumors:the incidence of cerebrovascular disease, neurocognitive impairment, secondary neoplasms, and low bone mineral density after 18 years of follow-up." Doctoral thesis, Oulun yliopisto, 2019. http://urn.fi/urn:isbn:9789526224305.
Full textAbstract:
Abstract Background: Childhood brain tumors (CBTs) are the most common solid tumors in childhood. CBT survivors have a high risk of several late-effects, including cerebrovascular disease (CVD), neurocognitive impairment, secondary neoplasms, and low bone mineral density; however, only a few studies have clinically investigated the late-sequelae in young-adult CBT survivors. Aim: To determine the prevalence of CVD, neurocognitive impairment, secondary neoplasms, and bone mineral density in a national cohort of radiotherapy-treated long-term survivors of CBT. Subjects and Methods: Radiotherapy-treated CBT survivors diagnosed between 1970–2008 were selected based on the following inclusion criteria: follow-up ≥5 years since the cessation of therapy and age of ≥16 years at the time of the study. Survivors were clinically and neuropsychologically examined, and investigated by magnetic resonance imaging (MRI), bone mineral densitometry, and laboratory analysis. Results: We included 74 survivors after a mean follow-up time of 18.9 ± 6.1 years. The mean age at follow-up was 28.4 ± 6.8 years and at diagnosis 8.3 ± 4.3 years. At the 20-year follow-up, the cumulative prevalence of CVD, along with small- and large-vessel disease was 52%, 38%, and 16%, respectively. Ischemic infarcts or transient ischemic attacks were diagnosed in 11% of the survivors, lacunar infarcts in 10%, and cerebral hemorrhage in 3%. White matter lesions (WMLs) were noted in 49% of the survivors. Higher blood pressure was associated with CVD, large-vessel disease, WMLs, and lacunar infarcts. Survivors had lower cognitive performance in all neuropsychological domains than controls. Mean verbal intelligence quotient was 89 ± 14 and mean performance intelligence quotient 87 ± 19. Executive functions (Z-score -5.0 ± 5.3 SD) and processing speed (Z-score -4.3 ± 5.4 SD) were extensively impaired. Executive functions and processing speed were associated with everyday life skills. Cumulative incidence of secondary meningiomas was 10.2% at the 25-year follow-up using the clinical data, and that of secondary neoplasms was 2.4% using the Finnish Cancer Registry data. We observed low bone mineral density in 23.6% of the survivors, which was associated with fractures in long bones. Conclusions: Young adult CBT survivors experienced late-consequences typically associated with ageingTiivistelmä Taustaa: Suomessa sairastuu vuosittain 46-60 lasta aivokasvaimeen, joka on lapsuusiän yleisin, kiinteä kasvain. Selviytyneillä on todettu lisääntynyt hoitojen myöhäisvaikutuksien riski. Kuitenkin nuorten aikuisten haittavaikutuksia on toistaiseksi tutkittu melko vähän. Tutkimuksen tarkoitus: Tarkoituksena oli selvittää sädehoidon jälkihaittoina esiintyvien sairauksien, kuten aivoverisuonisairauksien, älyllisten ongelmien, sekundaaristen kasvainten ja luustonhaurastumisen yleisyyttä ja riskitekijöitä suomalaisessa, kansallisessa kohortissa. Aineisto ja Menetelmät: Tutkimukseen kutsuttiin kaikki Suomessa lapsuusiällä aivokasvaimen sairastaneet aikuiset, jotka oli hoidettu sädehoidolla vuosina 1970-2008. Tutkittavat olivat yli 16-vuotiaita ja hoitojen päättymisestä oli yli 5 vuotta. Osallistuneille tehtiin kliininen ja neuropsykologinen tutkimus, pään magneettikuvaus, luustontiheysmittaus ja laboratoriotutkimuksia. Tulokset: Tutkimukseemme osallistui 74 nuorta aikuista 18,9 ± 6,1 vuotta hoitojen päättymisen jälkeen. Tutkittavat olivat iältään 28,4 ± 6,8 -vuotiaita osallistuessaan, ja 8,3 ± 4,3 -vuotiaita diagnoosihetkellä. Aivoverisuonisairaus todettiin 52% tutkimukseen osallistuneella 20 vuoden seurannan jälkeen, pienten suonten tauti oli 38 %:lla ja suurten suonten tauti 16 %:lla. Aivoinfarktin oli sairastanut 9 % tutkituista, lakuunainfarktin 10 % ja aivoverenvuodon 3 % tutkituista. Valkean aivoaineen muutoksia todettiin 49 %:lla magneettikuvauksessa. Korkea verenpaine lisäsi aivoverisuonisairauden, suurten suonten taudin, valkoisen aivoaineen muutoksien sekä lakuunainfarktien riskiä. Selviytyjien keskimääräinen kielellinen älykkyysosamäärä oli 89 ± 14 ja ei-kielellinen 87 ± 19. Suurimmat vaikeudet todettiin toiminnanohjauksessa (Z-luku -5,0 ± 5,3 SD) ja prosessointinopeudessa (Z-luku -4,3 ± 5,4 SD). Toiminnanohjauksen ja prosessointinopeuden vaikeudet olivat yhteydessä arkielämän haasteisiin. Sekundaaristen aivokalvokasvainten kumulatiivinen esiintyvyys oli 25 vuoden seuranta-aikana 10,2 % kliinisessä tutkimuksessa ja sekundaaristen kasvainten 2,4 % Syöpärekisteriaineistossa. Matala luustontiheys todettiin 23,6%:lla selviytyneistä. Johtopäätökset: Nuorilla aikuisilla, jotka ovat lapsena aivokasvaimen vuoksi saaneet sädehoitoa, esiintyy useita sellaisia jälkihaittoja, jotka yleensä liittyvät ikääntymiseen
6
Jacumasso, Sheila Cristina. "CARACTERIZAÇÃO MICROESTRUTURAL DAS PARTÍCULAS DE SEGUNDA FASE DE UMA LIGA DE ALUMÍNIO AA7050 NAS CONDIÇÕES T7451, T6 E T6I4-65." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2014. http://tede2.uepg.br/jspui/handle/prefix/1460.
Full textAbstract:
Made available in DSpace on 2017-07-21T20:43:44Z (GMT). No. of bitstreams: 1
Sheila Cristina Jacumasso.pdf: 3640428 bytes, checksum: 9f48682e159a5b7129a15abc7bb73945 (MD5)
Previous issue date: 2014-06-02Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The AA7050 class from the 7XXX series alloys based on Al-Zn-Mg-Cu are widely used in aerospace structures and fuselage components, when the same are subjected to high stress loading due to its high ratio mechanical strength to density, in addition, to its corrosion resistance. The increased resistance of these alloys is obtained by heat treatment that involves solution treatment and ageing followed precipitation of a fine and homogeneous phase from the own chemical composition. In this, the present study aimed to perform the of AA7050 aluminum alloy microstructural characterization with different ageing heat treatment from the T7451, T6 and T6I4-65 conditions. Thus, different characterization techniques from the Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Extraction of second phase particles, X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) were used. It was evaluated which condition results is higher precipitation hardening phases that are responsible for the increased resistance of the alloy. The most significant results were obtained by TEM where it was possible to determine the morphology of the GPII zones in needles form with approximate size of 30nm and 10nm for both T6 and T6I4-65 conditions, respectively. Moreover, the metastable η' phase was identified in platelets form in the T7451, T6 and T6I4-65 conditions with approximate size of 50nm, 20nm and 10nm, respectively. The surface roughness analyses obtained by AFM have revealed that the T6I4-65 condition has higher surface roughness (Ra=14,87nm) when compared to the T7451 (Ra=7,65nm) and T6 (Ra=8,35nm) conditions. Indicating in this case, a higher density of small particles homogeneously distributed in the T6I4-65 aluminum alloy matrix.
As ligas da série 7XXX, da classe AA7050, à base de Al-Zn-Mg-Cu, são muito utilizadas na indústria aeroespacial, em estruturas de fuselagem e componentes sob alta tensão de carregamento, devido à sua alta relação entre resistência mecânica e densidade, além de sua resistência à corrosão. O aumento da resistência destas ligas é obtido por tratamento térmico de solubilização e envelhecimento, através da precipitação de uma fase fina e homogênea, proveniente da própria composição química. Neste contexto, o presente trabalho teve como objetivo principal realizar a caracterização microestrutural de uma liga de alumínio AA7050, submetida a diferentes tratamentos térmicos de envelhecimento nas condições T7451, T6 e T6I4-65. Desse modo, fez-se o uso de diferentes técnicas de caracterização entre elas Microscopia Ótica (MO), Microscopia Eletrônica de Varredura (MEV), Microscopia de Força Atômica (AFM), Extração de Partículas de segunda fase, Difração de Raios X (DRX) e Microscopia Eletrônica de Transmissão. Consequentemente, avaliou-se qual condição apresenta maior precipitação de fases endurecedoras que são responsáveis pelo aumento de resistência da liga. Os resultados mais significativos foram obtidos por MET onde foi possível determinar a morfologia das zonas GPII presentes na forma acicular (needles) com tamanho aproximado de 30nm na condição T6 e 10nm na condição T6I4-65. A fase metaestável η’ foi identificada na forma de plaquetas finas (platelets) nas condições T7451, T6 e T6I4-65 com tamanho aproximado de 50nm, 20nm e 10nm respectivamente. A rugosidade superficial obtida por AFM revelou que a condição T6I4-65 apresenta maior rugosidade superficial (Ra=14,87nm) quando comparado às condições T7451(Ra=7,65nm) e T6 (Ra=8,35nm), indicando maior densidade de partículas de pequena dimensão distribuída homogeneamente na matriz da liga de alumínio.
7
Martinez, Jessica. "Exploring the Long-Term Impact of an Institutional Agent| Success of the Freedom Writers." Thesis, California State University, Long Beach, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=13425593.
Full textAbstract:
Demonstrated by this study, teachers as institutional agents can make a significant difference in the lives of their students during their educational endeavors and beyond. However, institutional agents remain rare within urban education, and adolescents’ access to these individuals in low-income communities is particularly low. This study used Stanton-Salazar’s theory of social capital and construct of institutional agents as a lens to understand the experiences of 14 individuals who participated in the Freedom Writers program. By giving a voice to students two decades after completing high school, this study conveys a critical perspective to the urban educational field. With there being a limited understanding of the lasting impact of such individuals on students as they transition onto adulthood participants’ personal accounts were explored to better understand their experiences.
As a qualitative study, this research inquired into the actions that guided the participants at the individual and situational level to having successful experiences. Data collection occurred through the utilization of an in-depth, semi-structured interviewing method, which provided rich data of the roles and functions of their high school teacher, Erin Gruwell, as an institutional agent. Additionally, providing data of their use of certain supports as provided by or made possible through Gruwell, four themes emerged from the findings of this study: (1) survival mode, (2) journey to Freedom Writers, (3) finding support, and (4) life after Freedom Writers. Within these themes, an in-depth exploration of the findings indicated the careful attention Gruwell placed in assessing the needs of students in order to provide the necessary supports as permitted by her social network and available resources, which involved access to additional institutional agents or other networks; significant forms of information; and other supportive forms of resources. The findings further indicated there being a critical impact to participants’ social development, and academic and career success. Through positive teacher-student relationships teachers can provide positive educational experiences that can have lifelong implications to empower students and create opportunities for life changes. Through the perspectives of the 14 participants, this study can influence the work of practitioners and policymakers in focusing on the needs and concerns of students attending urban high schools as well as in supporting teachers as institutional agents at the high school level.
8
Tones, Megan Jane. "Patterns of engagement in workplace learning amongst employees from social sectors." Thesis, Queensland University of Technology, 2009. https://eprints.qut.edu.au/31248/1/Megan_Tones_Thesis.pdf.
Full textAbstract:
Continuous learning and development has become increasingly important in the information age. However, employees with limited formal education in lower status occupations may be disadvantaged in their opportunities for development, as their jobs tend to require more limited knowledge and skills. In mature age, such workers may be subject to cumulative disadvantage with respect to work related learning and development, as well as negative stereotyping. This thesis concerns work related learning and development from a lifespan development psychology perspective. Development across the lifespan is grounded in biocultural co-constructivism. That is, the reciprocal influences of the individual and environment produce change in the individual. Existing theories and models of adaptive development attempt to explain how developmental resources are allocated across the lifespan. These included the Meta- theory of Selective Optimisation with Compensation, Dual Process Model of Self Regulation, and Developmental Regulation via Optimisation and Primary and Secondary Control. These models were integrated to create the Model of Adaptive Development for Work Related Learning.
The Learning and Development Survey (LDS) was constructed to measure the hypothesised processes of adaptive development for work related learning, which were individual goal selection, individual goal engagement, individual goal disengagement, organisational opportunities (selection and engagement), and organisational constraints. Data collection was undertaken in two phases: the pilot study and the main study. The objective of the pilot study was to test the LDS on a target population of 112 employees from a local government organisation. Exploratory factor analysis reduced the pilot version of the survey to 38 items encompassing eight constructs which covered the processes of the model of adaptive development for work related learning.
In the main study, the Revised Learning and Development Survey (R-LDS) was administered to another group of 137 employees from the local government organisation, as well as 110 employees from a private healthcare organisation. The purpose of the main study was to validate the R-LDS on two different groups to provide evidence of stability, and compare survey scores according to age and occupational status to determine construct validity. Findings from the main study indicated that only four constructs of the R-LDS were stable, which were organisational opportunities – selection, individual goal engagement, organisational constraints – disengagement and organisational opportunities – engagement. In addition, MANOVA studies revealed that the demographic variables affected organisational opportunities and constraints in the workplace, although individual goal engagement was not influenced by age.
The findings from the pilot and main study partially supported the model of adaptive development for work related learning. Given that only four factors displayed adequate reliability in terms of internal consistency and stability, the findings suggest that individual goal selection and individual goal disengagement are less relevant to work related learning and development. Some recent research which emerged during the course of the current study has suggested that individual goal selection and individual goal disengagement are more relevant when goal achievement is impeded by biological constraints such as ageing. However, correlations between the retained factors support the model of adaptive development for work related learning, and represent the role of biocultural co-constructivism in development. Individual goal engagement was positively correlated with both opportunity factors (selection and engagement), while organisational constraints – disengagement was negatively correlated with organisational opportunities – selection. Demographic findings indicated that higher occupational status was associated with more opportunities for development. Age was associated with fewer opportunities or greater constraints for development, especially for lower status workers.
9
Sivan, Atara. "Attitudes of secondary school students and teachers towards the aim of school as a socialising agent for leisure /." Thesis, [Hong Kong : University of Hong Kong], 1990. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13009515.
Full text
10
Dussart, François Mathieu Didier. "Genomic analysis of secondary metabolism in Ramularia collo-cygni, causative agent of Ramularia leaf spot disease of barley." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28829.
Full textAbstract:
In the past two decades a new barley threat has emerged as the disease Ramularia leaf spot (RLS) became more prevalent in temperate regions worldwide. This disease, first identified in the late 19th century, is caused by the filamentous fungus Ramularia collo-cygni (Rcc) and can cause substantial yield losses as well as reduce grain quality. RLS typically occurs late in the growing season and characteristic disease symptoms are usually seen after the crop has flowered. Expression of RLS lesions is thought to be associated with the action of fungal secondary metabolism products. The one group of secondary metabolites (SMs) characterised to date from Rcc, the anthraquinone toxins rubellins, are known to cause necrosis to plant tissues in a non-host specific manner. Therefore, it appears that fungal secondary metabolism might be a key component in understanding the interaction between Rcc and its host. In this study, more than 23 core genes involved in the biosynthesis of SMs belonging to the polyketide and non-ribosomal peptide pathways were identified in the genome of Rcc. Putative clusters containing genes with a predicted function relating to secondary metabolism were identified by in silico genome walking in the genetic loci adjacent to Rcc SM core genes. Two gene clusters containing no SM core gene were also identified. Five of the putative SM clusters exhibited similarity to the known fungal SM biochemical pathways involved in gliotoxin, monodictyphenone, ferricrocin, betaenone and chaetoglobosins biosynthesis. Several gene clusters exhibited similarity to SM clusters from fungal species where the SM pathway is uncharacterised. Changes in transcript abundance of selected SM core genes during RLS development in artificially inoculated barley seedlings were tested. Transcript levels were found to be the highest at an early stage of disease development, typically during the asymptomatic and early lesions formation stages and declined over time, suggesting that the associated SMs in Rcc, may not necessarily be involved in symptoms appearance. The in planta mode of action of the non-host specific photoactivated toxin rubellin D was studied in the model plant Arabidopsis thaliana. Rubellin-induced cell death appeared phenotypically reminiscent of programmed cell death (PCD). Full expression of rubellin D-induced cell death required the host salicylic acid (SA) pathway and the host proteasome supporting the PCD response to this fungal SM. However, a clear correlation between toxin sensitivity and disease susceptibility could not be found, suggesting a potential alternative role for rubellin in disease symptom development.
11
Moushey, Douglas Lee. "Formation of Mesoporosity in Zeolite and Mesoporous Molecular Sieve Structures through use of Carbon as a Secondary Templating Agent." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1218657179.
Full text
12
Chatzikos, Nikolaos. "Influence of fluxing agent on the quality of recycled Aluminium billets." Thesis, KTH, Materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231166.
Full textAbstract:
The quality of aluminium cast billets is highly dependent on the cleanliness of the material. Hydro Extruded Solutions are casting billets in Sjunnen that are delivered for extrusion within the same company. In order to produce extruded profiles of high quality and also maintain the pressing tools, it is a good method to keep the billets as free from inclusions as possible. A fluxing agent in form of salt compounds is used to purify the material during melting, but also to protect it from further oxidation. Another task of fluxing agents is to minimize the aluminium amount in the dross phase. The purpose of this project was to investigate if the fluxing agent that is used by the cast house is having any impact on the quality of the billets. Therefore, for that purpose, samples with a variating amount of fluxing agent were processed by the cast house in order to be investigated. These samples were investigated with the Optical Microscopy-method in order to determine the area fraction of non-metallic inclusions inside them. The results did not reveal any significant difference in the quality of the different samples since most samples obtained a low OM-index after the investigation. That can be explained by the type of scrap that was used since new scrap is usually very clean and contains smaller amounts of inclusions.Kvaliteten hos aluminiumgöt är starkt beroende av renheten i materialet. Hydro Extruded Solutions gjuter rundgöt i Sjunnen, som sedan levereras för strängpressning inom samma företag. För att producera strängpressade profiler av hög kvalitet och även upprätthålla pressverktygen, är en bra metod att hålla göten så fria från inneslutningar som möjligt. Ett flussmedel, i form av saltföreningar, används för att rena materialet under smältningen, men också för att skydda den från vidare oxidation. En annan uppgift som flussmedel har är att minimera mängden aluminium i slaggfasen. Syftet med detta projekt var att undersöka om flussmedelet som används av omsmältverket har någon inverkan på götkvaliteten. Därför, för detta ändamål har prover med en varierande mängd av flussmedel tillverkats i omsmältverket för att bli undersökta. Dessa prover undersöktes med den Optiskt Mikroskopiska-metoden för att bestämma areafraktionen av icke-metalliska inneslutningar inuti dem. Resultaten avslöjade inte någon signifikant skillnad i kvaliteten hos de olika proverna eftersom de flesta prover erhöll ett lågt OM-index efter undersökningen. Detta kan förklaras av vilken typ av skrot som användes, då process-skrot oftast är väldigt rent och består av mindre mängder innseslutningar.
13
Bahi, Muhammad [Verfasser], Hartmut [Akademischer Betreuer] Laatsch, and Axel [Akademischer Betreuer] Zeeck. "Bandamycin as New Antifungal Agent and further Secondary Metabolites from Terrestrial and Marine Microorganisms / Muhammad Bahi. Gutachter: Hartmut Laatsch ; Axel Zeeck. Betreuer: Hartmut Laatsch." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2012. http://d-nb.info/1043991387/34.
Full text
14
Svalmark, Per. "Ta parti! : Gymnasieelevers uppfattade påverkan inför riksdagsvalet 2010." Thesis, Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-6798.
Full textAbstract:
In this examination project I look into what ways upper secondary school students conceive themselves as politically influenced before they voted for the general election of 2010. The purpose is to examine which influences the upper secondary school surroundings and the classes of civic education are contributing with to students before they voted. As a method, I have used personal, semi-structural interviews on eight upper secondary school students who all voted for a party represented in the parliament. I have asked questions about how they believe their parents, the surroundings of their school and the classes of civic education have influenced them. To separate which influences primarily the upper secondary school and the classes of civic educations have had on the students, I have selected two comparison groups of four students in each. One group contains only parent-influenced students whereas the other group contains only not parent-influenced students. My findings show that the upper secondary school surroundings have played an important part to both student groups and the outcome may be theoretically generalized to all upper secondary school students studying natural science. The influences related to the classes of civic education have had a diversified outcome, mostly on not parent-influenced students. Therefore, this piece of result cannot be theoretically generalized to all natural science students. Not parent-influenced students also perceive themselves as more influenced by miscellaneous meaningful people, than do parent-influenced students. I understand the results as students not concurring with their parents politically, are more inclined to chase their political identity among their peer friends and other meaningful people. They are also more open-minded in the teaching moments of political parties, also during the political debate throughout the civic education. Finally, I discuss how the results should be viewed by teachers in civic education and what role the upper secondary school continues to play, as a political socialization agent.
15
Persson, Ingrid. "Fritidshuset som planeringsdilemma." Doctoral thesis, Karlskrona : Blekinge Institute of Technology, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00483.
Full textAbstract:
The thesis The Vacation House as a Planning Dilemma deals with how the processes that generate meaning in space proceed in parallel both in everyday life and in the planning realm. Multiple dwelling, or having two homes, can be seen as a dilemma—one in which the planning system’s attempts to conquer an unruly reality conflicts with the ways people live. The vacation house phenomenon is not a neutral concept, but rather influences and is influenced by a variety of contexts. This ambiguity is problematic for practitioners of spatial planning, a field that strives for unequivocal concepts. My interest is primarily directed at the relationship between the intentions in Swedish legislation and their practical application in planning. These legislative and planning spheres are also influenced by what actually happens in a physical space and by the conceptions we have of the life to be lived in it. The purpose of the thesis is to create the conditions for a discussion of how a planning dilemma like multiple dwelling can be understood based on how the various actors in a space create meaning and on the internal competition among them for the preferential right of interpretation over concepts. The thesis actualizes several scientific issues for us to address: How is the concept of multiple dwelling contextualized in material space? How does the housing market portray conceptions of vacation living? How do municipal planners view having two homes? How do environmental and urban planning laws view multiple dwelling? I use Henri Lefebvre’s three-part dialectic of spatial theory in this thesis as a tool for general classification, to analyze spatial processes over time, and to clarify the relationships between the different elements of a space and different actors’ actions in a space. The focus of my analysis of the field of planning is the various kinds of representations made by experts. My analysis of such constructions is conducted at the level of discourse. In order to understand how such spatial representations are constructed and how they compete with one another, I have taken a discourse analytical perspective inspired by Ernesto Laclau and Chantal Mouffe. The results of my thesis have shown that problem solutions lead to different planning constructions depending on the underlying conception of the vacation house, whether the vacation house is conceived as the Other Home or the secondary home. My analyses have shown that modernism’s striving for systematization and functional separation doesn’t work, at least as applied to housing. We must question the premise of functionally distinguishing between housing forms as a means to conserving natural resources.fritidshus, planeringsdilemma, fysisk planering, lagstiftning, dubbel bosättning, miljöbalken, annonser, fastighetsmäklare, Lefebvre, Laclau, Mouffe
16
Boarman, McKaila J. S. "Trade-offs and Temporal Variation in Predator-Mediated Natural Selection and Sexual Selection on the Wings of the Damselfly Calopteryx splendens." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1491746850419119.
Full text
17
El-Tayeb, El-Sayed Mohamed. "Rétention d'alpha-oléfinésulfonates de sodium dans un sable argilo-calcaire : étude expérimentale et modélisation du transport en présence de cations divalents et d'asphalte." Vandoeuvre-les-Nancy, INPL, 1994. http://www.theses.fr/1994INPL149N.
Full textAbstract:
L’utilisation de tensioactifs de type alpha-oléfinésulfonate dans les procédés de récupération améliorée du pétrole apparait comme une solution à des gisements pétroliers possédant une eau de gisement moyennement salée contenant des cations divalents. L’optimisation du procédé passe par l'élaboration d'un modèle de transport traduisant l'évolution de la concentration du tensioactif, donc de son efficacité, lors de son transit au sein du milieu poreux que constitue le gisement. La modélisation s'est appuyée sur une méthode expérimentale reposant sur la chromatographie réactive, qui permet à partir de l'analyse de la réponse d'un milieu poreux à un signal de concentration de déduire qualitativement et quantitativement les interactions qui contrôlent le transport de l'espèce étudiée. Les expériences ont été effectuées sur un sable argilo-calcaire, le sable de gue et sur un mélange artificiel de sable d'argile, imprégné par de l'asphalte. Le mélange de tensioactif utilisé est une alphaoléfinésulfonate de sodium commerciale en C14-C16. Trois phénomènes prépondérants contrôlent le transport de ce tensio-actif au-dessus de la concentration micellaire critique: (1) l'adsorption est essentiellement contrôlée par la concentration en magnésium qui n'est pas contrôlée par les équilibres calcocarboniques (ii) la séparation chromatographique du mélange en trois classes de produits lors de l'adsorption (iii) le partage du à la présence d'asphalte sur la surface qui augmente notablement la capacité de rétention du milieu. À partir de ces observations un modèle global a été développé pour simuler le comportement du tensioactif dans un large domaine (10-4 à 10-1 mole/l) et de quantité injectée. Ce modèle est utilisable pour évaluer à la fois le comportement des alphaoléfinésulfonates commerciaux en milieu poreux et la faisabilité du procédé
18
Smirnova, Maria. "Contrats de travail et problèmes d'allocation des ressources dans les universités russes - Une approche en termes des modèles multitâches." Phd thesis, Université Panthéon-Sorbonne - Paris I, 2010. http://tel.archives-ouvertes.fr/tel-00510024.
Full textAbstract:
Dans cette étude, nous cherchons à examiner l'influence de la nature multitâche du travail des professeurs universitaires sur leur performance d'enseignants et de chercheurs. Nous nous intéressons au cas particulier des universitaires russes. Le multitasking est un trait caractéristique du travail universitaire partout dans le monde. Pourtant dans le cas russe, le nombre de tâches intra-universitaires est souvent augmenté par un nombre encore plus important de tâches externes, provenant de multiples emplois externes dans lesquels la grande majorité des universitaires russes est engagée. Les tâches internes et externes constituent entre elles des liens complexes. D'un côté, ces liens sont déterminés par la fonction d'utilité des professeurs (par la nature de leurs motivations intrinsèques et la forme de leur fonction de coût personnel). D'autre côté, les systèmes d'incitation et les formes contractuelles qui encadrent le travail universitaire et les activités externes entrent en ligne de compte dans la détermination de ces liens. En nous munissant de l'instrumentaire des modèles multitâches et du concept de l'agent partagé, nous analysons la façon dont telle ou telle relation inter-tâche influence la performance universitaire. Nous le faisons d'abord dans le contexte statique et passons ensuite à l'analyse dynamique. Nous tâchons ensuite de comprendre quelle structure de contrats universitaires pourrait favoriser les externalités positives entre les tâches internes et externes, tout en améliorant la performance intra-universitaire des enseignants et en résolvant le problème de la sélection adverse, qui persiste dans le secteur de l'enseignement supérieur en Russie.
19
Soutif, Jean-Claude. "Etude de l'addition des acides carboxyliques sur les structures oxiranne : application aux polymeres epoxydes." Le Mans, 1987. http://www.theses.fr/1987LEMA1010.
Full textAbstract:
La modification chimique au deuxieme degre de polymeres epoxydes a ete etudiee pour developper une methode de fixation de principes actifs (medicaments, colorants, complexants) comportant des fonctions acides, sur des supports macromoleculaires. Le catalyseur est un sel de tetramethylammonium de l'acide a fixer. Epoxydation de polyisoprene et polybutadiene
20
Zhou, Yu-Xiang, and 周煜翔. "Secondary Voltage Control in Power Systems Using Multi-Agent Reinforcement Learning." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/10683077823926962493.
Full textAbstract:
碩士國立清華大學
資訊工程學系
102
To protect power systems against different severe disturbances, the ways to effectively control voltage have become the important issue in power systems. In light of that, a Multi-Agent System (MAS) structure has been proposed to deal with the issue of voltage regulation. With our system, once the voltage violations occur, the agents would detect the abnormality and try to eliminate these voltage violations by injecting the reactive power. Besides, to make a good decision under abnormal conditions, a reinforcement learning scheme has been proposed to provide better and faster regulation. Based on the concept of distributed control, there are two parts in our reinforcement learning scheme, self-regulated learning and cooperative learning. On the other hand, an altruistic rate has been proposed to consider the impact of other neighbor agents. The performance of the proposed multi-agent reinforcement learning are demonstrated using various conditions in a benchmark of power networks.
21
Bahi, Muhammad. "Bandamycin as New Antifungal Agent and further Secondary Metabolites from Terrestrial and Marine Microorganisms." Doctoral thesis, 2012. http://hdl.handle.net/11858/00-1735-0000-000D-F047-B.
Full text
22
Verdy, Julie. "Le savoir professionnel des conseillers pédagogiques québécois des ordres primaire et secondaire : analyse descriptive." Thèse, 2005. http://hdl.handle.net/1866/17799.
Full text
23
Tessier-Jasmin, Jean-Michel. "Analyse exploratoire de la délinquance scolaire et de l'implication policière dans les écoles secondaires défavorisées de Montréal." Thèse, 2006. http://hdl.handle.net/1866/18163.
Full text
24
Almeida, Ana Paula Fagulha de. "Formação do ozono troposférico: simulação e modelação por agentes - identificação de áreas críticas nos municípios de Porto e Matosinhos." Master's thesis, 2018. http://hdl.handle.net/10362/43437.
Full textAbstract:
Dissertation presented as the partial requirement for obtaining a Master's degree in Geographic Information Systems and ScienceEste trabalho pretende fornecer um método complementar de determinação das zonas mais afetadas pelo poluente ozono dentro da área do município do Porto e de Matosinhos, tendo em vista ser um elemento de apoio à decisão com utilidade na aplicação de medidas de adaptação às alterações climáticas. Para tal são efetuadas análises de distribuição espacial de poluentes a partir das medições existentes validadas oficialmente pela Agência Portuguesa do Ambiente, para determinar quais as áreas onde estes atingem concentrações mais elevadas. A análise espacial foi efetuada primeiro numa fase exploratória dos dados e representada num sistema de informação geográfica. Nesta fase foram efetuadas interpolações espaciais que permitiram concluir os níveis de exposição da população dentro da área de estudo. Seguidamente foi programada uma modelação por agentes, uma vez que a formação do ozono se trata de um sistema complexo (formado por reação fotoquímica a partir de poluentes primários e as condições ambientais adequadas), onde interagem diversos agentes. Os resultados permitiram um estudo mais detalhado ao nível da seção estatística, identificando aquelas onde o aparecimento do ozono pode ser mais problemático, sendo um complemento aos mapas de previsão existentes para este tipo de poluente, atualmente existentes apenas para a escala regional.
This work intends to provide a complementary method to determine the zones most affected by the pollutant ozone within the area of the city of Porto and Matosinhos, in order to be a useful decision support element in the application of climate change adaptation measures. For this purpose, analyses of the spatial distribution of pollutants are carried out, from existing measurements officially validated by the Portuguese Environment Agency, to determine the areas where this pollutant reaches higher concentrations. Spatial analysis was performed, first in an exploratory phase of the data and represented in the ArcGIS geographic information system. In this phase, spatial interpolations were carried out to conclude the exposure levels of the population within the study area. Ozone formation is a complex system (it is a secondary pollutant formed by photochemical reaction from primary pollutants) with multiple agents interacting with each other over time. An agent based model was coded to simulate this phenomenon. The results allowed a more detailed study at a level of the statistical block group, being a complement to the existing forecast maps for this type of pollutant, currently available only at the regional scale.
25
Burns, C. J., E. Fantino, A. K. Powell, Steven D. Shnyder, Patricia A. Cooper, S. Nelson, C. Christophi, et al. "The microtubule depolymerizing agent CYT997 causes extensive ablation of tumor vasculature in vivo." 2011. http://hdl.handle.net/10454/5902.
Full textAbstract:
The orally active microtubule-disrupting agent (S)-1-ethyl-3-(2-methoxy-4-(5-methyl-4-((1-(pyridin-3-yl)butyl)amino)pyrimidin-2- yl)phenyl)urea (CYT997), reported previously by us (Bioorg Med Chem Lett 19:4639-4642, 2009; Mol Cancer Ther 8:3036-3045, 2009), is potently cytotoxic to a variety of cancer cell lines in vitro and shows antitumor activity in vivo. In addition to its cytotoxic activity, CYT997 possesses antivascular effects on tumor vasculature. To further characterize the vascular disrupting activity of CYT997 in terms of dose and temporal effects, we studied the activity of the compound on endothelial cells in vitro and on tumor blood flow in vivo by using a variety of techniques. In vitro, CYT997 is shown to potently inhibit the proliferation of vascular endothelial growth factor-stimulated human umbilical vein endothelial cells (IC(50) 3.7 +/- 1.8 nM) and cause significant morphological changes at 100 nM, including membrane blebbing. Using the method of corrosion casting visualized with scanning electron microscopy, a single dose of CYT997 (7.5 mg/kg i.p.) in a metastatic cancer model was shown to cause destruction of tumor microvasculature in metastatic lesions. Furthermore, repeat dosing of CYT997 at 10 mg/kg and above (intraperitoneally, b.i.d.) was shown to effectively inhibit development of liver metastases. The time and dose dependence of the antivascular effects were studied in a DLD-1 colon adenocarcinoma xenograft model using the fluorescent dye Hoechst 33342. CYT997 demonstrated rapid and dose-dependent vascular shutdown, which persists for more than 24 h after a single oral dose. Together, the data demonstrate that CYT997 possesses potent antivascular activity and support continuing development of this promising compound.
26
Adam, Kathija. "The role of department heads as change agents in the implementation of educational reform in the United Arab Emirates." Thesis, 2005. http://hdl.handle.net/10500/2382.
Full textAbstract:
The implementation of educational reform in the United Arab Emirates (UAE) imposes a change agent role on secondary school department heads however the assistance-intensive process is inhibited by the current educational structure. As the concept of teacher empowerment becomes accepted, some department heads have the ability to develop a professional learning community while others are unable to do so. The present study considers the present and ideal role of the department head as a change agent facilitating the implementation of educational reform in the UAE. A sequential mixed method mode of inquiry with two phases was employed. In phase one, department heads were profiled from a self, superior and subordinate perspective and a conceptual framework related to patterns of effective change agent behaviour was developed. Findings show that effective change agent characteristics of department heads included priorities related to change implementation and teacher support, a collaborative leadership style, seven strategies related to a participatory, supportive and facilitative approach and ten skills that motivate, energise and encourage teachers. The identification of two ineffective department heads by teacher informants in phase one provided an opportunity to study the work of effective and ineffective department heads as cases in-depth. Case study findings confirm the conceptual framework because effective heads were rated high for all characteristics identified, while ineffective heads were rated low. All department heads accepted the change agent role unofficially with no additional time release, but effective heads took ownership of the process and empowered teachers while ineffective heads provided assistance on request. Effective heads used interpersonal skills and asserted themselves as technical experts while ineffective heads were passive and were considered to be traditional teachers. Strategies and skills employed by effective heads included resource linking, collaborative problem solving, facilitation, support and administration/organisation while ineffective department heads used resolution giving and providing technical assistance. Time constraints, restrictive school schedules and role ambiguity were identified as major impediments to the change agent role of department heads in his study. Nevertheless, the new curriculum is being implemented in all of the departments studied verifying that the department head is an untapped resource in the change process.Educational Studies
D.Ed (Education Management)
27
Rezková, Aneta. "Vliv rodiny na výběr povolání u žáků ZŠ." Master's thesis, 2012. http://www.nusl.cz/ntk/nusl-306906.
Full textAbstract:
RESUME The times based on one individual's decision about which school to study to be able to choose further continuous and smooth career path has been over. As a result of current global and local social changes everybody should be prepared to the every possible change in career. Nevertheless the first choice of career is still an important milestone and can direct the individual career, but it is not the only key milestone, that determines the individual career once and for ever. People in contemporary world should be able to respond quickly to constant changes, evaluate new situations and be able to make the right decisions. The widespread myth is that success means to raise money as quickly as possible to guarantee the freedom and happiness. But a real success is a contented life, which is a long way over such values as for example certainty that we are doing the work that we like and which fills us with satisfaction. Individual goal is to focus on the abilities and skills so that the decision directs to such a career path where one will be able to optimally exploit one's potential in a future career. In the beginning of a career path a family as a primary socializing agent and the closest partner institution in the life of the pupil should fulfil its role in close cooperation with the school that...