• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 107
  • 47
  • 39
  • 11
  • 9
  • 8
  • 4
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • Tagged with
  • 273
  • 46
  • 38
  • 38
  • 32
  • 30
  • 28
  • 27
  • 23
  • 20
  • 20
  • 20
  • 20
  • 19
  • 18
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Factors Influencing Salmonella Survival in Agricultural Soils and Internalization through Solanaceous Crop Roots

Bardsley, Cameron 28 April 2020 (has links)
Solanaceous crops such as peppers and more commonly tomatoes have been linked to Salmonella outbreaks that have occurred in the United States. The source of contamination for some of these outbreaks was traced back to the preharvest environment. Sources of contamination at the preharvest level of production often include irrigation water, soil, and the use of biological soil amendments of animal origin (BSAAO). This dissertation aims to (i) determine how factors such as the use of BSAAO's, Salmonella strain, soil type, and irrigation influence the survival of Salmonella in agricultural soils and (ii) determine the risk of Salmonella internalization in to transplanted solanaceous crops (tomatoes and bell peppers) and identify factors that influence internalization through the roots such as mode of contamination, soil contamination level, and root damage. Sandy loam (SL) and clay loam (CL) soils both unamended and amended with poultry litter (PL), irrigated either daily or weekly were inoculated with one of twelve strains of Salmonella enterica and monitored for growth and survival until no longer detected. Tomato plants were transplanted into one of three contamination treatments: contaminated soil (A) or irrigation water administered either once (B, single exposure event) or for 7 d following transplantation (C, repeated exposure event). Plants were sampled 1, 2, 3, 7 and 90 d post-transplantation for Salmonella internalization. Pepper plant roots were left intact, damaged, or removed and placed in inoculated water (6.2 log CFU/ml). Pepper plants in the soil contamination study, were transplanted into soil inoculated with Salmonella at different contamination levels (High, Mid, and Low). Samples were collected 1, 2, 3, and 7d post-transplant. Plants were surface sanitized and enumerated for Salmonella internalization by plant section. Strains in soils treated with PL survived significantly (P<0.05) longer (56 and 112 days for SL and CL respectively), than Salmonella strains in unamended soils. In PL amended SL and CL soils, most strains grew significantly (P<0.05) within the first week following inoculation and ranged from 84 to 210 days in the point it was last detected. Strains survival increased significantly (P<0.05) in soil irrigated weekly compared to soils irrigated daily, weekly irrigation increased survival by 140 to 224 and 42 to 168 days in SL and CL soils respectively depending on the strain. Root sections in the tomato plants of treatment A had significantly (P<0.05) higher recovery of Salmonella internalization compared to the other treatments. No tomato fruit sampled were positive for Salmonella internalization. Pepper plants with damaged roots had significantly higher (P<0.05) Salmonella internalization in the stem than plants with intact roots, while plants with no root stalk had significantly higher (P<0.05) Salmonella internalization in the stem and leaves of plants with intact and damaged roots. Pepper plants exposed to high concentrations of Salmonella had significantly more internalization occur in the roots than plants exposed to mid and low concentrations of Salmonella. Due to the results of these studies assessing the risk of using PL and irrigation regime should be considered in the Salmonella growth and survival in agricultural soils. Though it is unlikely, steps should be considered to limit Salmonella contamination of soil and irrigation water and root damage to prevent the internalization of Salmonella in tomato and bell pepper plants through intervention measures such as composting, water treatment, and effective transplanting techniques. / Doctor of Philosophy / Produce such as tomatoes and peppers has commonly been associated with Salmonella outbreaks in the United States. Fresh produce may be contaminated during the growing period by irrigation water, soil, or manure contaminated with Salmonella. This dissertation aims to (i) determine how factors such as poultry litter, Salmonella strain, soil type, and irrigation affects the survival of Salmonella in agricultural soils and (ii) identify the capability of Salmonella uptake through the roots of tomato and bell pepper plants, and identify factors that facilitate the uptake of Salmonella such as how the plant is contaminated, the Salmonella population level in the soil, and root damage. Sandy loam and clay loam soils untreated and treated with poultry litter, irrigated daily or weekly, were contaminated with one of twelve strains of Salmonella and tested for Salmonella levels until it was no longer detected in the soils. Tomato plants were planted into one of three treatments: Salmonella contaminated soil (A) or irrigated with Salmonella contaminated water once after planting (B, single exposure event) or for 7 days following planting (C, repeated exposure event). Tomato plants were tested for Salmonella uptake within the first week or 90 days following planting. The roots of pepper plants were either left intact, damaged, or removed and placed into Salmonella contaminated water. Pepper plants in the Salmonella contaminated soil study were planted into soil containing one of three different Salmonella contamination levels (high, mid and low). Plants were tested for Salmonella uptake within the first week following planting. Factors such as the use of poultry litter and irrigation influenced the growth and presence of Salmonella in both soil types. The uptake of Salmonella of tomato plants in contaminated soil was observed in the roots more than the roots of plants irrigated with contaminated irrigation water. No tomatoes tested were found positive for Salmonella internalizing. The uptake of Salmonella in the stems and leaves of pepper plants was highly dependent on root damage and the presence of the roots. Pepper plants that were exposed to high levels of Salmonella in the soil had more instances of Salmonella uptake than plants with lower levels of Salmonella in the soil. Based on these results, the use of poultry litter and irrigation should be considered in the potential risk of Salmonella contamination during the growing stage of produce. Though the uptake of Salmonella in tomato and pepper plants is unlikely, precautions should be taken to limit the potential contamination of soil and irrigation water with Salmonella and prevent root damage from occurring to prevent possible uptake of Salmonella.
62

Effects of Apple Development and Damage on the Internalization of Escherichia coli O157:H7 as Observed Under Field and Laboratory Conditions

Hereford, Megan Lee 03 October 2003 (has links)
The number of food borne illnesses associated with the consumption of fresh fruits and vegetables and their minimally processed products (juices) has increased over the past years. Of particular interest is the ability of microbial pathogens to internalize and survive in fresh produce that are commonly used for juices. This research project addresses the issue of the ability of Escherichia coli O157:H7 to internalize and survive in whole apples before and after harvest. Four cultivars of apples, Redfree, Red Delicious, Golden Delicious, and York, were inoculated under field conditions with a surrogate strain of E. coli, Escherichia coli ATCC 25922. The Redfree cultivar was inoculated at the beginning of its growth stage (day 0), and again 30 days later, and sampled for two weeks, until E. coli was not recoverable through microbiological methods after three successive sampling days. Red Delicious, Golden Delicious, and York cultivars were spray inoculated with the surrogate strain two weeks before their anticipated harvest date and sampled every other day until E. coli was not recoverable for three successive sampling days. For each cultivar, the presence of E. coli ATCC 25922 was not detectable after 7 to 9 days. In the laboratory study the Red Delicious, Golden Delicious, Rome, and York cultivars received one of three treatments; unblemished control, bruising, or puncturing. The apples were inoculated by immersion in cold water containing E. coli O157:H7 GFP, incubated for three days then microbiologically analyzed for presence of the bacteria. In all cases, the punctured apples of each cultivar showed the greatest uptake of E. coli O157:H7 GFP. Escherichia coli O157:H7 GFP was visualized in flesh and core sections of untreated, bruised, and punctured apples of all cultivars. The microbe was found in between cells, but not within cells of the apple. Internalization of Escherichia coli in whole apples on the tree is not likely, and leads to the conclusion that internalization is a post-harvest problem. Internalization may occur before pressing or processing of apples, leading to an increased risk of infection with E. coli for consumers of apple products that are not properly treated to destroy pathogens. Internalization does occur when apples are immersed in solutions containing the pathogen Escherichia coli O157:H7, and better post harvest controls need to be implemented in order to prevent this in whole apples that are used for cider and juice production. / Master of Science
63

Internalization of Escherichia Coli in Apples Under Field and Laboratory Conditions

Seeman, Brooke Kettler 03 September 2002 (has links)
The main objective of this project is to gain an understanding of the internalization of Escherichia coli in the tissues of apples. This broad statement includes the rate of internalization in young versus mature apples as well as injured versus non-injured apples. Five apple varieties, Redfree, Red Delicious, Golden Delicious, Rome Beauty and York Imperial, were used to compare differences and similarities in structure and ability to internalize the pathogen. Both the surrogate species, E. coli ATCC 25922, and the pathogen, E. coli O157:H7, were used for field and lab studies, respectively. Internalization of E. coli in apples under natural environmental conditions was addressed in the first study using a controlled outdoor setting. Escherichia coli species (ATCC 25922) was used as an alternative to the pathogenic species. The bacterial culture was applied to topsoil and spread evenly on a 6x6-foot area. Red Delicious, Golden Delicious, and Rome Beauty apples were placed randomly on the soil much like a drop or windfall apple. The position was noted as to whether the apple fell calyx up, down or on its side. Apples were examined for the presence of E. coli and sampled on days 1, 3, 8, and 10. Skin, flesh, inner, and outer core samples were plated on MacConkey agar supplemented with cycloheximide and MUG to ease in identification. Escherichia coli was found in the inner core and flesh samples of all apple varieties, indicating the potential for infiltration by the organism outside laboratory conditions. The second study determined the rate of internalization in immature apples. Redfree was used in a long-term study in which individual apples were spray inoculated at the beginning of the growing season with E. coli ATCC 25922 at 104 cfu/apple. The apples were picked on days 1, 30 and 60, and sectioned into skin, flesh, inner and outer cores. The remaining four apples species were used in an intensive, two-week study. In the long-term study, apples were inoculated two weeks prior to harvest and picked every other day until harvest. The surrogate E. coli was not found in the apples after day 1. Other coliforms, such as E. vulneris, Klebsiella pneumoniae and Kl. ozaenae were present in each pick. The two-week study showed higher rates of internalization in Red and Golden Delicious than in Rome and York, with the E. coli present in all four sections of the apples. Red Delicious apples showed a trend of increasing counts of bacteria over the two-week period with initial counts ranging from less than one cfu/ml to final counts as high as 2.64±1.90 log cfu/ml. Again Klebsiella species and E. vulneris were found in the apples. Microscopy was used for imaging of the apples tissues. Morphological differences were found in the skin, where lenticel presence or absence may affect internalization. Differences were also shown in the flesh where cell wall thickness was shown to vary depending on variety. Imaging thick sections of skin showed cuticle cracks and thickness, which also vary depending on the apple variety. This study indicates that internalization occurs at a high degree in drop apples and to a limited extent in tree apples. However, with the low infective dose required for illness, it is necessary to instate strict regulations to ensure safety. The most effective treatment involves the inclusion of a five-log reduction of the target organism, E. coli O157:H7. This reduction can be obtained through one step or the combination of two or more steps. / Master of Science
64

Influences of general self-efficacy and weight bias internalization on physical activity in bariatric surgery candidates

Hübner, Claudia, Baldofski, Sabrina, Zenger, Markus, Tigges, Wolfgang, Herbig, Beate, Jurowich, Christian, Kaiser, Stefan, Dietrich, Arne, Hilbert, Anja 24 May 2016 (has links) (PDF)
Background: Physical activity (PA) seems to be important for long-term weight loss following bariatric surgery, however, studies provide evidence for insufficient PA levels in bariatric patients. Research found self-efficacy to be associated with PA and weight bias internalization, whose influence on mental and physical health has been shown in recent studies. Objectives: The purpose of the present study was to investigate the influence of general self-efficacy on PA, mediated by weight bias internalization. Setting: Consecutive multicenter registry study conducted in six German bariatric surgery centers. Methods: In N = 179 bariatric surgery candidates, general self-efficacy, weight bias internalization, and different intensities of PA were assessed by self-report questionnaires. Structural equation modeling was used to analyze the assumed mediational relationship. Results: After controlling for sociodemographic variables, weight bias internalization fully mediated the association between general self-efficacy and moderate-intense as well as vigorous-intense PA. Lower general self-efficacy predicted greater weight bias internalization, which in turn predicted lower levels of moderate-intense and vigorous-intense PA. Conclusions: The results suggest an influence of weight bias internalization on preoperative PA in bariatric surgery candidates. Subsequently, implementation of interventions addressing weight bias internalization in the usual treatment of bariatric surgery candidates might enhance patients’ preoperative PA, while longitudinal analyses are needed in order to further examine its predictive value on PA following bariatric surgery.
65

HOW ASSESSMENT PRACTICES INFLUENCE THE ACADEMIC ACCULTURATION PROCESS OF INTERNATIONAL GRADUATE STUDENTS

Zyuzin, ANNA 09 October 2012 (has links)
Previous research studies have demonstrated that international graduate students experience various challenges adapting to academic situations within a new university community. This thesis reports on an interview study with six international graduate students who use English as a second language studying Master’s degree at one Canadian university. This study addresses the academic assessment and evaluation experience of international graduate students in the following four aspects: (1) their enjoyable and challenging assessment practices; (2) understanding of assessment expectations; (3) reflections on previous educational experience; and (4) psychological and physical factors in relation to assessment and evaluation. The findings indicate that these students’ experiences of assessment and evaluation procedures are varied and the academic acculturation process towards assessment depends on different yet interrelated factors: English language competence, cultural and educational awareness, and assessment literacy. All six research participants adapted to the host academic assessment practices and procedures fairly well despite the fact that they were not familiar with the expectations and requirements regarding assessment and evaluation at the beginning of their studies. These students learned about the host academic culture regarding assessment and evaluation through their own examination failure, instructors’ feedback, and peers’ observation. The findings also indicate that international graduate students need more coordinated support from university supportive services and easier access to information about assessment and evaluation expectations and requirements. Implications of the findings for effective learning and positive academic experience for L2 international graduate students, faculty and supportive staff, and for future research are discussed. It is suggested to organize workshops and seminars devoted to assessment literacy for international and domestic graduate students, instructors and supporting staff in order to enhance learning experience and outcomes. / Thesis (Master, Education) -- Queen's University, 2012-10-09 17:43:27.833
66

Acculturation Through Education : A qualitative study on learning strategies of adult immigrants in Romania

Dobre, Adrian January 2016 (has links)
The purpose of the thesis is to examine how adult immigrants in Romania describe the learning strategies that have helped them integrate in the new culture. To be able to draw conclusions about migrants' learning strategies and what has made them work, I have looked at the experience of five immigrants who speak Romanian and who have successfully integrated in the Romanian culture. The study employs a qualitative methodology, information has been collected through semi-structured interviews and analyzed using thematic analysis and a framework approach to data analysis. The key findings of the thesis are that integration through education, specifically through language learning, takes place more effectively if migrants are driven by intrinsic goals or if they internalize the extrinsic rewards that they expect upon completion of their goals. These findings can be put into practice to form better strategies and actions steps in organizational programs that aim at integrating migrants. They can also be brought to the knowledge of migrants looking to successfully integrate, to make them aware of how their choices and goals, even those apparently unrelated, can impact the outcome of their integration efforts.
67

The Rules of the Game : A comparative case study on the conditions for the socialization of permanent representatives in the EU and NATO

Danielson, August January 2017 (has links)
Cooperation in international organizations is to a large degree driven and sustained by socialization – the process of inducting actors into the norms and rules of a given community. In the context of international organizations, the most influential state agents are the permanent representatives, the member states’ ambassadors to an international organization. However, systematic studies on the conditions for the socialization of permanent representatives are conspicuously absent in the literature. Instead, most previous research has focused on the conditions for socialization of “high-level officials” in the European Commission. This quite narrow perspective has led to a “N=1” problem and the generalizability of these studies have suffered as a result. In this thesis, I have aimed to broaden this perspective by testing six hypotheses on the conditions for socialization within two committees of permanent representatives in two different international organizations, the PSC (EU) and the NAC (NATO). This has been done by conducting elite interviews with 21 permanent representatives and deputies in Brussels. In contrast to previous research, the results of this thesis suggest that four of the six tested hypotheses should be disregarded, while two hypotheses – the representative’s relation to its MFA and the ambiguity of the international organization’s norms– should be given more theoretical consideration in future research. In addition, the interviews have shown that the degree of “internalization”, which can be understood as the goal and outcome of socialization, is stronger in the NAC than in the PSC. This outcome also contests the conventional wisdom that the EU is a sui generis case of socialization. On the basis of these results, I argue that the socialization of permanent representatives in international organizations is likely to occur if the organization’s norms have unambiguous, existential and materialistic consequences.
68

Development of Disordered Eating in Undergraduate Women: a Test of the Re-conceptualized Objectification Process

Hasbrouck, Whitney Neal 08 1900 (has links)
The eating disorder literature has long suggested that sociocultural experiences specific to women influence development of bulimic pathology; however, models have differed on the type of experiences that are important and what other variables interact with these experiences to lead to eating pathology. Broader sociocultural theory and objectification theory represent two such differing models, and more recently Moradi hypothesized that integrating elements from both models would provide a better picture of eating disorder development. The present study, therefore, sought to compare these three different models of bulimic pathology development to determine which one provides the best explanation for bulimic outcomes. The sample consisted of 682 undergraduate women between the ages of 18 and 24, recruited from a large southwestern university. Data were collected on-line using a series of questionnaires to measure the constructs of interest and analyzed using structural equation modeling. All three models fit the data well and explained approximately 50% of bulimic outcomes; however, the model based on Moradi’s integrated model provided the most information about the relationships between constructs within the model. The development of bulimic symptomatology appears best explained by a model that focuses on the sociocultural experience of pressures about weight and body size, but also integrates aspects of objectification theory as well. Future research, however, is needed to determine if sexually objectifying experiences, if measured differently, affect women’s development of eating pathology along with pressures.
69

The Relationships of Locus of Control and Perceived Contingency of Teacher Rewards and Punishments to Academic Achievement

Kinley, Shirley J. 12 1900 (has links)
The purpose of the present investigation was to assess the relationships among the contingency of teachers' reactions as perceived by the pupils, the pupils' academic performance, and internality. One might expect that children who perceive their teacher as contingently rewarding and punishing would achieve higher grades and test scores than those who view their teachers' reactions as unrelated to their behavior. It is believed that children's perceptions of the contingencies of their teacher's responses may be more highly related to achievement behavior than the teacher's actual distribution of rewards and punishments. Perceived contingency of punishments and rewards may be important determiners of achievement. The perception of punishments as noncontingent is likely to be negatively related to achievement; however, the same may not be true of noncontingent reward. Indiscriminate dispersion of rewards could have a motivating effect or, as one might infer from Paris & Cairns (1972), no effect at all. Internality and achievement are expected to be positively related, perhaps more so for boys than for girls, as the trend of previous evidence suggests. Because of conflicting reports, no firm expectation can be formulated with regard to sex differences and the effectiveness of IAR+ versus IAR- scores.
70

A dimensão subjetiva da dominação social: a recepção de Nietzsche na teoria crítica de Horkheimer nas décadas de 1930 e 1940 / The subjective aspect of social domination: Nietzsches reception in Horkheimers critical theory from the 1930s and 1940s

Fernandes, Simone Bernardete 17 June 2019 (has links)
Esta dissertação examina a recepção de Nietzsche na teoria crítica de Horkheimer explicitando o modo como a sua filosofia é apropriada nos quadros teóricos das décadas de 1930 e 1940 para a investigação dos bloqueios à emancipação de ordem subjetiva, com foco sobre a noção de interiorização [Verinnerlichung]. Nos anos 1930, para compreender a fixação dos indivíduos pela autoridade e a manipulação das massas, são analisados os efeitos das renúncias e da interiorização dos instintos no contexto de uma antropologia da sociedade burguesa. Na década de 1940, está em jogo o vínculo da razão esclarecida com a dominação, relacionado à dominação de si e dos outros que permearam a formação da subjetividade desde a sua pré-história e compreendido com referência à ideia de interiorização do sacrifício. Pretende-se determinar o papel da filosofia de Nietzsche no pensamento de Horkheimer argumentando-se, em primeiro lugar, que esta aproximação remonta aos anos 1930 e não à influência de Adorno na elaboração da Dialética do esclarecimento e, em segundo lugar, que as contradições internas desta filosofia e as suas contradições com a teoria crítica são profícuas para a filosofia de Horkheimer. / This dissertation thematizes the reception of Nietzsche\'s philosophy in Horkheimer\'s critical theory from the 1930s and 1940s, investigating how it is appropriated for an analysis of the obstacles to social emancipation situated in subjectivity, with reference to the concept of internalization [Verinnerlichung]. In the 1930s, the fixation of the individuals on authority and the manipulation of the masses are investigated through an analysis of the effects of the renunciation and the internalization of instincts, in the context of an anthropology of the bourgeois society. In the 1940s, Horkheimer and Adorno explicit the entailment of enlightened reason on domination, arising from the domination of oneself and of others that permeated the subjective formation since its pre-history, described with the resource to the idea of internalization of sacrifice. This dissertation intends to disclose the role of Nietzsche\'s philosophy in Horkheimer\'s thought, arguing, in the first place, that it goes back to the 1930s and it is not a consequence of Adorno\'s influence in the process of elaboration of the Dialects of Enlightenment, and, secondly, that the contradictions internal to this philosophy and its contradictions with critical theory are productive for Horkheimers philosophy.

Page generated in 0.1348 seconds