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  • 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.
21

Relationships Between Serum Leptin and Bone Mineral with Eating Restraint or Weight Loss

Volpe, Joanne Jackson 23 August 2005 (has links)
High body weight seems protective of bone mass, specifically bone mineral content (BMC) and bone mineral density (BMD), thereby reducing the risk of osteoporosis. Cognitive eating restraint (CER), diet composition, and the satiety hormone, leptin, produced by adipocytes, are associated with body mass and may also influence bone mass. Few studies have examined these relationships. To investigate the relationship between leptin and CER score, 36 premenopausal, healthy weight women, as defined by body mass index (BMI) of 18-25 kg/m<sup>2</sup>, aged 18-25 years were studied. Women were categorized by baseline Eating Inventory questionnaire scores into either the high CER group (score > 9, n = 20) or low CER group (score < 9, n = 16). Serum leptin concentration was significantly lower in the low CER group versus high CER group at baseline. A positive relationship between serum leptin concentration and body fat mass and body fat % in normal weight women despite differences in CER scores was observed. In a separate study, overweight and obese women, (BMI > 25 to < 43 kg/m<sup>2</sup>), aged 32-45 years, were randomly assigned to either a low-carbohydrate, high-protein (LCHP) or low-fat, high-carbohydrate (LFHC) diet for 12 weeks. Serum leptin concentration was significantly greater in the LCHP versus the LFHC diet group at 12 weeks (p < 0.05). Over time, significant decreases in serum leptin concentration, BMI, body weight, total lean mass, total fat mass, and body fat % were observed in both diet groups. Serum leptin concentration was positively associated with body weight, fat mass, and body fat % regardless of diet consumed. Both studies are novel in their respective populations and show no direct link between leptin and bone mass when considered in the context of CER or diet composition. / Master of Science
22

Growth, mineral content and essential oil quality of buchu (Agathosma betulina) in response to ph under controlled conditions in comparison with plants from its natural habitat

Ntwana, Babalwa 12 1900 (has links)
Thesis (MScAgric (Agronomy)--University of Stellenbosch, 2007. / The Cape Floristic Region is a highly distinctive phytogeographical unit which is recognized as a floral Kingdom on its own. Buchu (Agathosma betulina) plants fall under this important Kingdom. Buchu is one of the traditional medicinal plants originating in the Western Cape province of South Africa and the essential oil derived from the leaves is exported in large volumes. Due to high demand, under supply, restrictions of wild harvesting and high prices for Buchu essential oil, growers have started to introduce and commercialize this species as a crop. This commercialization of Buchu necessitated agronomic research to optimize production techniques. The objective of this study was to determine the optimum pH range for the cultivation of high yielding Buchu with acceptable essential oil quality under controlled conditions and compare this with the conditions in the natural habitat. Plant, soil and climatic data were gathered from eleven sites in the natural habitat of Buchu (A. betulina) in the Cederberg Mountains. At all sites most rainfall occurred from May to September, while high temperatures were recorded in summer. Soil analyses indicated low levels of nutrients and low soil pH, ranging from 3.7 to 5.3 at all the sites studied. Low levels of nutrients were also obtained from foliar analysis collected from plants at each of the different sites. Chemical analyses of the essential oil indicated that the plants were from a high quality diosphenol chemotype. In the greenhouse experiment, five different pH levels (pH 33.99, 4-4.99, 5-5.99, 6-6.99 and 7-7.99) were evaluated to determine the effect on growth, yield and quality of A. betulina. Complete nutrient solutions were used to irrigate the plants grown in pots filled with a sand and coco peat mixture. Although the plants subjected to the pH treatment of 4-4.99 tended to have the highest growth rate and yield, this did not differ significantly (P=0.05) from plants subjected to pH values between 3 and 6.99. In contrast, the pH 7-7.99 treatment lead to reduced growth and lower vegetative yields. Levels of nutrients obtained from the leaf mineral analysis differed significantly with different pH treatments. High pH levels resulted in high nitrogen, phosphorus, sodium, manganese and boron contents, but lower contents of copper. Nitrogen, phosphorus, calcium and zinc were higher than those recorded for plants from their natural habitat, but still within the norm reported for most plants. Levels of manganese, sodium, magnesium and copper were found to be more or less similar to the values obtained in plants from the natural habitat. No significant differences were found in essential oil quality in response to the pH treatments. However, high pulegone levels (10.8 to 13.2 %) were obtained from all the treatments in the greenhouse experiment. The high levels of this essential oil constituent could have a negative effect on the marketability of the oil and this aspect may need some attention in future studies.
23

Base-cations in relation to weathering of phyllosilicates and forest management in Swedish forest ecosystems /

El Make, Mahmoud, January 1900 (has links) (PDF)
Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2000. / Härtill 4 uppsatser.
24

Caracterização multiescalar petrofísica e mineralógica de folhelhos da Bacia do Araripe.

RODRIGUES, Isis da Silva. 31 July 2018 (has links)
Submitted by Marcos Wanderley (marcos.wanderley@ufcg.edu.br) on 2018-07-31T22:01:32Z No. of bitstreams: 1 ISIS DA SILVA RODRIGUES - DISSERTAÇÃO(PPGEPM) 2018.pdf: 3596359 bytes, checksum: f406a5fc51f5d3e3cd2686f11093f8b5 (MD5) / Made available in DSpace on 2018-07-31T22:01:32Z (GMT). No. of bitstreams: 1 ISIS DA SILVA RODRIGUES - DISSERTAÇÃO(PPGEPM) 2018.pdf: 3596359 bytes, checksum: f406a5fc51f5d3e3cd2686f11093f8b5 (MD5) Previous issue date: 2018-02-27 / Os reservatórios não convencionais vêm sendo amplamente estudados, devido ao aumento da demanda energética mundial e são reservatórios complexos. Um dos grandes desafios da indústria do petróleo é viabilizar a produção de reservatórios não convencionais de forma econômica e segura. A Bacia do Araripe é uma das bacias terrestres brasileiras que apresentam esse tipo de reservatório, e poucos estudos foram desenvolvidos naquela bacia até o momento. Nesta pesquisa foram estudadas 4 amostras de folhelhos negros com o objetivo de avaliar a porosidade, a densidade total, a densidade de grãos, a conectividade de poros e a composição mineral. Os métodos utilizados na pesquisa são a microtomografia de raios X (μCT) e a nanotomografia de raios X (nCT), métodos não destrutivos e avançados para a caracterização petrofísica, além da integração destes com a técnica de difração de raios X (DRX) e petrografia de lâmina delgada para a identificação mineralógica. Os resultados da análise indicam que as amostras possuem uma porosidade relativamente alta, sendo a conectividade considerada boa apenas para os microporos. Os resultados demonstram que a caracterização dos minerais, pelos diversos métodos, converge para os principais minerais (teores elevados) e diverge para aqueles com pequenos teores (minerais acessórios). Os folhelhos analisados apresentam um alto teor de matéria orgânica, evidenciando o seu potencial gerador de hidrocarbonetos. / Unconventional reservoirs have been widely studied due to the increase in world energy demand and are complex reservoirs. One of the great challenges of the oil industry is to make the production of non-conventional reservoirs economical and safe. The Araripe Basin is one of the Brazilian basins that present this type of reservoir, and few studies has been developed in that basin to date. In this research, 4 samples of black shales were studied in order to evaluate the porosity, total density, grain density, pore connectivity and mineral composition. The methods used in the research are X-ray microtomography (μCT) and X-ray nanotomography (nCT), non-destructive and advanced methods for petrophysical characterization, as well as their integration with X-ray diffraction (XRD) and thin-seition petrography for mineralogical identification. The results of the analyses indicate that the samples have a relatively high porosity, and the connectivity were considered good only for the micropores. The results show that the characterization of the minerals, by the different methods, converges to the main minerals (high contents) and diverges for those with small levels (accessory minerals). The shales analyzed have a high content of organic matter, evidencing their hydrocarbon potential.
25

Medindo a produtividade total dos fatores da indústria extrativa brasileira

Leão, Débora Carneiro 29 May 2013 (has links)
Submitted by MFEE Mestrado Profissional em Finanças e Economia Empresarial da EPGE (mfee@fgv.br) on 2015-02-24T19:56:53Z No. of bitstreams: 1 TESE FINAL Débora.pdf: 3098662 bytes, checksum: 2c28fd9275298b66bf5b3a7405f356d9 (MD5) / Approved for entry into archive by GILSON ROCHA MIRANDA (gilson.miranda@fgv.br) on 2015-03-25T20:32:36Z (GMT) No. of bitstreams: 1 TESE FINAL Débora.pdf: 3098662 bytes, checksum: 2c28fd9275298b66bf5b3a7405f356d9 (MD5) / Approved for entry into archive by Marcia Bacha (marcia.bacha@fgv.br) on 2015-03-26T18:30:54Z (GMT) No. of bitstreams: 1 TESE FINAL Débora.pdf: 3098662 bytes, checksum: 2c28fd9275298b66bf5b3a7405f356d9 (MD5) / Made available in DSpace on 2015-03-26T18:31:09Z (GMT). No. of bitstreams: 1 TESE FINAL Débora.pdf: 3098662 bytes, checksum: 2c28fd9275298b66bf5b3a7405f356d9 (MD5) Previous issue date: 2013-05-29 / The aim o f this study is to measure and analyze the productivity o f Brazilian mining industry as a whole and its subsectors. We first estimate multifactor productivity using the classic method proposed by Robert Solow where there was a drop in productivity in the period between 1997 and 2009. After a new estimation of productivity was made that corrects changes in the quality of the minerais extracted. It was observed that the drop in productivity in the period analyzed was even more pronounced. / O objetivo desse trabalho é medir e analisar a produtividade da indústria extrativa brasileira como um todo e seus subsetores. Primeiramente foi feita a estimação da produtividade multifatorial utilizando o método clássico proposto por Robert Solow de onde se verificou uma queda na produtividade do setor no período entre 1997 e 2009. Posteriormente foi feita uma nova estimação dessa produtividade que corrige as mudanças na qualidade dos minerais extraídos. Observou-se que a queda na produtividade, no período analisado, foi ainda mais acentuada.
26

Selective Serotonin Reuptake Inhibitors and Bone Mineral Density in a Population of U. S. Premenopausal Women

Peterson, Lori J 01 January 2011 (has links) (PDF)
Selective Serotonin Reuptake Inhibitors and Bone mineral Density in a Population of U.S. Premenopausal Women May 2011 M.S., UNIVERSITY of Massachusetts Amherst Directed by: Professor Elizabeth R. Bertone-Johnson Low bone mineral density (BMD) in post-menopausal women is a risk factor for bone fractures and osteoporosis development. Prior studies in post-menopausal women have shown the use of antidepressant medications, specifically selective serotonin reuptake inhibitors (SSRIs) to be inversely related to BMD. However, the association has not been studied in pre-menopausal women. Current SSRI use is widespread with 8% of U.S. women age 18-44 reporting use. We evaluated the association between SSRIs and BMD and bone mineral content (BMC) cross-sectionally using data from the University of Massachusetts Vitamin D Status Study. SSRI use, diet, and lifestyle factors were assessed by questionnaire. BMD and BMC were measured using dual-energy x-ray absorptiometry (DEXA). The study included 256 women aged 18-30 (mean=21.6 years, SD=4.3 years). In this population, SSRI use was 5%, BMD values ranged from 0.97-1.38 g/cm2 (mean 1.16, SD 0.08), and BMC values ranged from 1833g to 3682g (mean 2541.5, SD=349.2). After adjustment for age, body mass index, and physical activity, mean BMD in the 13 users of SSRIs was 1.15g/cm2 (SD=0.06) compared to 1.16g/cm2 (SD=0.77) in the 243 non-users (p =0.66). After the same adjustments, mean BMC in the 13 users was 2467.1g (SD=285.0) compared to 2547.6g (SD=352.6) in the 243 non-users (p=0.94). Our findings do not support an inverse association between SSRI use and BMD or BMC. However, given the prevalence of SSRI use in young women and the potential for adverse effects on bone health, further study of this association is warranted.
27

Skeletal Status and Bone Turnover in Overweight Young Men with and without Sleep Apnea Syndrome

Guignel, Nadine Joëlle 07 July 2005 (has links)
Obesity is a worldwide epidemic increasing at an alarming rate among youth who are facing similar health problems as adults. Sleep Apnea Syndrome (SAS) is an underdiagnosed comorbidity of obesity, characterized by repetitive nocturnal interruptions in breathing. Obesity is associated with delayed skeletal maturation in overweight youth, but mechanisms contributing to this problem are unclear. Obesity and SAS both have been shown to disrupt regulatory hormones and cytokines that influence bone accretion during adolescence. PURPOSE: The purpose of this study was to assess the combined effects of excess body weight and SAS on bone mineral density (BMD) and content (BMC), bone turnover, and on the regulatory hormones leptin and IGF-1 known to potentially influence bone accretion during adolescence. METHODS: Men aged 18-28 years were assigned to groups as follows: normal weight controls (CON: AHI <3, n=8); overweight without SAS (OWT: BMI < 26 kg/m2 and AHI <3, n=9); and overweight with SAS (SAS: BMI >26 kg/m2 and AHI >5, n=8). The apnea/hypopnea index (AHI) expresses the score for disrupted nighttime breathing events/hr and was obtained in this study with results from a home sleep screening test. Health history and Epworth Sleepiness Scale (ESS) questionnaires also were administered. Bone mineral parameters and body composition variables were measured with dual-energy X-ray absorptiometry. Serum osteocalcin, leptin, IGF-1, and NTx-1 were measured, respectively, by radioimmunoassay and enzyme-linked immunoabsorbent assay. RESULTS: Fat-free mass, intra-abdominal fat, and fat mass were higher in the SAS and OWT groups (p<0.03). ESS scores revealed that SAS individuals were sleepier than CON and OWT groups (p<0.009). Total body and site-specific BMD and BMC values (lumbar spine, hip, and forearm) were similar between groups and did not relate to the estimated AHI score. Serum OC and NTx-1 did not differ between groups. Leptin levels were 30% higher in OWT and SAS than in the CON group (p<0.02), but did not correlate with the AHI score. Across all subjects (n=25), only lumbar spine BMC (p<0.005) was correlated to AHI (r=-.52; p<0.01). The preponderance of this relationship between AHI and lumbar spine BMC was attributable to the close inverse association of these two variables within the SAS group (r = -.81; p<0.001). CONCLUSION: The effects of SAS were not influenced by the amount of whole-body, intra-abdominal adiposity or lean body mass. Neither leptin nor IGF-1 predicted bone status across all groups. Daytime fatigue and sleepiness, a cardinal symptom of SAS, combined with overweight may contribute to lower lumbar BMC by chronically reducing weight-bearing physical activity and thereby reduce exposure time for mechanical loading of the spine in affected individuals. Further research is needed to explore the biochemical, physiological, and apparently the physical activity implications of SAS on skeletal status and turnover. / Master of Science
28

Efeitos da perda de peso na massa óssea e alterações metabólicas em adolescentes obesos pós-púberes / Weight loss metabolic effects on bone mass in post-pubertal adolescents

Santos, Luana Caroline dos 15 October 2007 (has links)
A obesidade encontra-se associada a uma série de alterações metabólicas que podem elevar o risco de doenças crônicas não-transmissíveis. Em contraste, o excesso de peso apresenta-se como um fator protetor para a ocorrência de fraturas e baixa densidade óssea. Considerando que a adolescência é um período crucial para aquisição da massa óssea e minimização do risco de osteoporose na maturidade e os efeitos da perda de peso sobre a massa óssea, neste estágio de vida, não são completamente elucidados, o presente estudo foi desenvolvido. Objetivou-se investigar os efeitos da perda de peso sobre a massa óssea e as alterações metabólicas em adolescentes obesos pós-púberes. Realizou-se a revisão bibliográfica sobre o tema e um estudo longitudinal contemplando um período de 9 meses de intervenção baseada em dieta hipocalórica e orientações nutricionais. Foram incluídos 55 adolescentes pós-púberes, 43 meninas, com média de idade de 16,6 (1,4) anos, com índice de massa corporal por idade superior ao percentil 95. Os participantes foram monitorados a cada três semanas por meio de avaliação antropométrica (aferição do peso, estatura e circunferência) e do consumo alimentar (recordatório alimentar de 24 horas). Realizaram-se avaliações da composição corporal e da densidade mineral óssea de corpo total por meio da DXA (dual energy X-ray absorptiometry), do consumo alimentar (registro alimentar de 3 dias) e de parâmetros metabólicos (colesterol total e frações, tricilgliceróis, glicemia de jejum, insulina, leptina e grelina) no início do estudo, após 3 meses e ao fim da intervenção. Verificou-se que 44,4 por cento dos participantes não apresentavam redução do peso. O grupo que respondeu à intervenção apresentou média de perda de peso de 6,2 (4,6) por cento ao fim do estudo. Neste grupo, houve significativa redução do consumo energético, de 2105,4 (537,6) Kcal/dia na primeira avaliação para 1738,8 (608,4) Kcal/dia ao fim do estudo. Observou-se incremento da atividade física entre os participantes e melhora dos parâmetros metabólicos entre adolescentes que perderam peso. / Obesity is associated with several metabolic changes that may increase the risk of chronic diseases. Body weight is recognized as a protective factor against fractures and lower bone density. Considering that adolescence is a crucial period for bone mass acquisition and osteoporosis risk reduction in maturity and the effects of weight loss on bone mass in this life stage are not completely elucidated, the present study was performed. The objective was to investigate the effects of weight loss as well the metabolic changes related to bone mass in post-puberal adolescents. Bibliographic review and a longitudinal study, with adolescents submitted to nutritional intervention based on hipocaloric diet and nutritional advice during 9 months, were realized. Fifty-five subjects, 43 girls, mean age of 16.6 (1.4) years, with body mass index by age superior than 95 percentile, were recruited. Subjects were monitored every three weeks with anthropometric (weight, height and circumferences) and dietary intake (24h food intake recall) evaluation. Body composition and total-body bone mineral density. (assessed by dual-energy X-ray absorptiometry), metabolic parameters (plasma lipids, glucose, insulin, leptin and ghrelin concentrations) and dietary intake (3-day food records) were evaluated at the baseline, after 3-months and at the end of the study. Sixteen participants thatcompleted the study did not lost weight. The group that adhered to intervention nutritional had mean weight loss of 6.2 (4.6) %. In this group, there was a significant decrease in energy intake, from 2105.4 (537.6) Kcal/day to 1738.8 (608.4) Kcal/day. Physical activity pratice increased between participants and there were metabolic parameters improvement in adolescents who lose weight. In these subjects, hypercholesterolemia and insulin resistance decreased, 7,9% and 27.2% (p<0.05) respectively, after 3 months of intervention. There was a significant increase of total bone mineral density and bone mineral content (BMC) in adolescents did not lost weight. Increased BMC and bone area was verified in participants that adhered to intervention nutritional. Bone parameters changes were associated with body fat alterations. The increment in bone mineral density even under weight loss showed no negative effect of bone mass. Dietary intake change and weight control contributed to metabolic parameters improvement of obese adolescents.
29

Bone and Aluminium

Hellström, Hans-Olov January 2007 (has links)
<p>Osteoporosis is a major health care problem, by reason of its devastating consequences, in particular hip fractures. Worldwide it has been estimated that the incidence of hip fracture will increase to more than 6 million per year by 2050 compared to 1.7 million per year in 1990. Osteoporosis can be caused by various factors namely, genetic, lifestyle and environmental factors, and since the rising incidence of its consequences is not fully explained by the growing age of the population, there is an urgent need to identify individual causal factors of this condition. </p><p>The present research has focused on aluminium, one potential environmental factor of importance for bone disease, and its possible relation to osteoporosis, since it is known to cause osteoporosis-like bone disease and has been associated with induction of progressive central nervous system diseases.</p><p>Aluminium is the third most common element in the earth’s crust and the most abundant metal (8%). It is widely utilized industrially and it is also naturally present in many foods. Although aluminium is ubiquitous in the human environment, evolution has not given it an essential biological function.</p><p>The aluminium content of bone was measured by inductively coupled mass spectrometry in a large group of patients suffering from hip fractures, high energy fractures and osteoarthrosis. An exponential increase in aluminium content of bone with age was found (p=0.0004). However, no significant association of aluminium in bone with occurrence of hip fracture or dementia could be found, and no indirect evidence was obtained, e.g. through bone mineral density or biomechanical properties, that aluminium is involved in the pathogenesis of osteoporosis. Although we accumulate aluminium in bone throughout our lives, and there are experimental suggestions that aluminium induces premature cell death, the body content of this metal does not seem to influence the overall mortality risk. </p>
30

Bone and Aluminium

Hellström, Hans-Olov January 2007 (has links)
Osteoporosis is a major health care problem, by reason of its devastating consequences, in particular hip fractures. Worldwide it has been estimated that the incidence of hip fracture will increase to more than 6 million per year by 2050 compared to 1.7 million per year in 1990. Osteoporosis can be caused by various factors namely, genetic, lifestyle and environmental factors, and since the rising incidence of its consequences is not fully explained by the growing age of the population, there is an urgent need to identify individual causal factors of this condition. The present research has focused on aluminium, one potential environmental factor of importance for bone disease, and its possible relation to osteoporosis, since it is known to cause osteoporosis-like bone disease and has been associated with induction of progressive central nervous system diseases. Aluminium is the third most common element in the earth’s crust and the most abundant metal (8%). It is widely utilized industrially and it is also naturally present in many foods. Although aluminium is ubiquitous in the human environment, evolution has not given it an essential biological function. The aluminium content of bone was measured by inductively coupled mass spectrometry in a large group of patients suffering from hip fractures, high energy fractures and osteoarthrosis. An exponential increase in aluminium content of bone with age was found (p=0.0004). However, no significant association of aluminium in bone with occurrence of hip fracture or dementia could be found, and no indirect evidence was obtained, e.g. through bone mineral density or biomechanical properties, that aluminium is involved in the pathogenesis of osteoporosis. Although we accumulate aluminium in bone throughout our lives, and there are experimental suggestions that aluminium induces premature cell death, the body content of this metal does not seem to influence the overall mortality risk.

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