• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 308
  • 272
  • 78
  • 69
  • 19
  • 14
  • 13
  • 10
  • 8
  • 8
  • 6
  • 6
  • 5
  • 4
  • 4
  • Tagged with
  • 939
  • 107
  • 103
  • 82
  • 63
  • 61
  • 53
  • 52
  • 49
  • 47
  • 40
  • 39
  • 38
  • 38
  • 37
  • 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

Hepatic adaptations to maintain metabolic homeostasis in response to fasting and refeeding in mice

Geisler, C. E., Hepler, C., Higgins, M. R., Renquist, B. J. 26 September 2016 (has links)
Background: The increased incidence of obesity and associated metabolic diseases has driven research focused on genetically or pharmacologically alleviating metabolic dysfunction. These studies employ a range of fasting-refeeding models including 4-24 h fasts, "overnight" fasts, or meal feeding. Still, we lack literature that describes the physiologically relevant adaptations that accompany changes in the duration of fasting and re-feeding. Since the liver is central to whole body metabolic homeostasis, we investigated the timing of the fast-induced shift toward glycogenolysis, gluconeogenesis, and ketogenesis and the meal-induced switch toward glycogenesis and away from ketogenesis. Methods: Twelve to fourteen week old male C57BL/6J mice were fasted for 0, 4, 8, 12, or 16 h and sacrificed 4 h after lights on. In a second study, designed to understand the response to a meal, we gave fasted mice access to feed for 1 or 2 h before sacrifice. We analyzed the data using mixed model analysis of variance. Results: Fasting initiated robust metabolic shifts, evidenced by changes in serum glucose, non-esterified fatty acids (NEFAs), triacylglycerol, and beta-OH butyrate, as well as, liver triacylglycerol, non-esterified fatty acid, and glycogen content. Glycogenolysis is the primary source to maintain serum glucose during the first 8 h of fasting, while de novo gluconeogenesis is the primary source thereafter. The increase in serum a-OH butyrate results from increased enzymatic capacity for fatty acid flux through beta-oxidation and shunting of acetyl-CoA toward ketone body synthesis (increased CPT1 (Carnitine Palmitoyltransferase 1) and HMGCS2 (3-Hydroxy-3-Methylglutaryl-CoA Synthase 2) expression, respectively). In opposition to the relatively slow metabolic adaptation to fasting, feeding of a meal results in rapid metabolic changes including full depression of serum a-OH butyrate and NEFAs within an hour. Conclusions: Herein, we provide a detailed description of timing of the metabolic adaptations in response to fasting and re-feeding to inform study design in experiments of metabolic homeostasis. Since fasting and obesity are both characterized by elevated adipose tissue lipolysis, hepatic lipid accumulation, ketogenesis, and gluconeogenesis, understanding the drivers behind the metabolic shift from the fasted to the fed state may provide targets to limit aberrant gluconeogenesis and ketogenesis in obesity.
22

The impact of credit and debt on wealth accumulation

Leitz, Linda Y. January 1900 (has links)
Doctor of Philosophy / School of Family Studies and Human Services / Sonya L. Britt / This study explored whether the use of debt, specifically mortgages and student loans, has a negative relationship with wealth accumulation over a consumer’s lifetime. The analysis looked at whether exploration questioned whether consumer debt is incongruent with good personal financial management and consumers should hold a philosophy of avoidance of debt in order to accumulate more wealth. Some financial planners believe in leveraging current assets in hopes of accelerating wealth accumulation. The latter approach is more congruent with a behavioral life-cycle hypothesis perspective (Shefrin & Thaler, 1988), which posits that consumers are the happiest when consumption remains relatively constant over a lifetime through use of debt and savings. To account for wealth accumulation across the lifespan, a measure of relative net worth was constructed by taking current net worth divided by current annual income divided by age. Relative net worth was used rather than net worth in order to allow comparisons between consumers of different ages and income. Data were collected from a sample of convenience, recruited from social media, friends and their acquaintances, and the clients of financial advisors who agreed to distribute the survey. Four ordinary least squares (OLS) regression analyses were conducted to determine the influence of current mortgage relative to the value of the home, mortgage obtained at the time of home purchase as a multiple of income, and student loans at graduation as a multiple of income on relative net worth accumulations. Results suggested that current mortgage debt that is 80% or less of home value, lack of a mortgage, and completing higher education without student debt are associated with higher relative net worth. Using a sample of convenience, the respondent pool was not nationally representative. In comparison to the United States population, the sample population is more highly educated, has a higher percentage of married and individuals in a committed relationship, contains more adults over the age of 50, and does not reflect the ethnic diversity of the United States. This study did not provide deep new insight into the factors contributing to wealth accumulation. It showed that mortgages and student loans alone do not have a large impact on wealth accumulation. This is evidenced by the low R² for all regressions (ranging from .00 to .07). Of the independent variables chosen for regression, the impact was not large and statistical significance for those factors was not present in all regressions. The results of this study do not provide direct support to the ability to use mortgages and student loans as part of wealth accumulation strategies. Future studies may be able to incorporate other elements with debt decisions as well as the impact of financial advice on the use and levels of debt as part of an integrated wealth accumulation strategy. The level of debt to positively impact socioeconomic status is also another area for future study.
23

Transgenic Overexpression of CTRP3 Prevents Alcohol-Induced Hepatic Triglyceride Accumulation

Trogen, Greta, Bacon, Joshua, Li, Ying, Wright, Gary L., Degroat, Ashley, Hagood, Kendra L., Warren, Zachary, Forsman, Allan, Kilaru, Aruna, Clark, W. Andrew, Peterson, Jonathan M. 15 May 2018 (has links)
This study tested the ability of a novel adipose tissue derived cytokine, C1q TNF Related Protein 3 (CTRP3), to prevent alcohol-induced hepatic lipid accumulation, or alcoholic fatty liver disease (ALD). Previous work has demonstrated that CTRP3 is effective at preventing high fat diet-induced fatty liver, however, the potential of CTRP3 to inhibit ALD has not been explored. To test the potential protective effects of CTRP3, transgenic mice overexpressing CTRP3 (Tg) or wildtype littermates (WT) were subjected to one of two different models of ALD. In the first model, known as the NIAAA model, mice were fed control or alcohol-containing liquid diets (5% v/v) for 10 days followed by a single gavage of ethanol (5 g/kg). In the second model, the chronic model, mice were fed control or alcohol-containing diets for 6 weeks with no gavage. This study found that CTRP3 reduced triglyceride accumulation in the chronic model of alcohol consumption by ~50%, whereas no reduction was observed in the NIAAA model. Further analysis of isolated primary hepatocytes from WT and Tg mice demonstrated that CTRP3 increased oxygen consumption in the presence of fatty acids, indicating that CTRP3 increases hepatic fatty acid utilization. In conclusion, this study indicates that CTRP3 attenuates hepatic triglyceride accumulation in response to long-term chronic but not short-term alcohol consumption.
24

Knowledge and commitment in innovation processes

Waters, John Frederick, University of Western Sydney, College of Law and Business, School of Management January 2004 (has links)
This study was aimed at achieving an understanding of the role of knowledge and commitment in the process of innovation. To do that, the study confronted several intractable problems of innovation research that have created barriers to knowledge accumulation. Theoretical models were developed based on organizational knowledge and commitments and aimed at overcoming the shortcomings of the traditional research models. Theoretical models of organizational change were investigated through multiple case studies of innovation projects that compared organizations of different types and size, and change processes of both technological and administrative character. A conclusion from this research is that innovation research should learn to live with the dialectic that innovation is unrelated to knowledge or outcomes. This would help to focus research attention on the means by which knowledge is transformed into action, the central problem of the management of innovation. / Doctor of Philosophy (PhD)
25

Dietary accumulation of hexabromocyclododecane diastereoisomers in juvenile rainbow trout (Oncorhynchus mykiss): bioaccumulation/depuration parameters and evidence of bioisomerization

Law, Kerri L 29 March 2006 (has links)
The major objectives of this research were to examine the bioaccumulation parameters [depuration rates (kd), half life (t1/2) and biomagnification factor (BMF)] of individual isomers of hexabromocyclododecane (HBCD, C12H18Br6) in fish and to test the hypothesis of in vivo bioisomerization. This was done by exposing three groups of juvenile rainbow trout (Oncorhynchus Mykiss) to food fortified with known concentrations of an individual diastereoisomer (α, β, γ) for 56 days (uptake phase) followed by 112 days (depuration phase) of unfortified food. A fourth group of fish were exposed to unfortified food for the duration of the experiment. Fish (n=4) from all four aquaria were sacrificed on days 0, 7, 14, 56, 63, 70, 112 and 168 and muscle tissue was extracted and analyzed for diastereoisomer concentrations by high performance liquid chromatography tandem mass spectrometry (LC/MS/MS). Bioaccumulation of the γ diastereoisomer was linear during the uptake phase while the α and β diastereoisomers were found to increase exponentially with respective doubling times of 14.1 and 20.5 days. Both the β and γ diastereoisomers followed first order depuration kinetics with calculated t1/2’s of 94 ± 25 and 84 ± 51 (± 1 × standard error) days, respectively. The BMF for the α diastereoisomer (BMF = 4.1) was one and a half times greater than the β-diastereoisomer (BMF = 2.6) and about one fifth larger than the γ-diastereoisomer (BMF = 3.6). The large BMF for the α diastereoisomer is consistent with this diastereoisomer dominating higher trophic level organisms in wildlife. Although the BMF of the β diastereoisomer suggests that it will biomagnify, because it is present in small quantities in commercial mixtures it is rarely detected in environmental samples. Results from these studies also provide evidence of bioisomerization of the β and γ diastereoisomers. Most importantly, the α diastereoisomer which was recalcitrant to bioisomerization by juvenile rainbow trout in this study and known to be the dominant diastereosiomer in fish, was bioformed from both the β and γ diastereoisomers. To our knowledge, this is the first report of bioisomerization of a halogenated organic pollutant in biota. / May 2006
26

Effect of Harvest Dates on Biomass Accumulation and Composition in Bioenergy Sorghum

Borden, Dustin Ross 2011 December 1900 (has links)
Sorghum (Sorghum bicolor) has the potential to be used as a cellulosic feedstock for ethanol production due to its diversity and wide adaptation to many different climates. With a wide range of diversity, this crop could be tailored specifically for use as a feedstock for ethanol production. Other factors such as water use efficiency, drought tolerance, yield potential, composition, and established production systems also make sorghum a logical choice as a feedstock for bioenergy production. The objectives of this study were to better understand the biomass potential of different types of sorghum that may be used for energy production, and determine the composition of these sorghums over the season to better understand biomass yield and composition over time. Six commercial sorghum cultivars or hybrids that represent sorghum types from grain to energy were evaluated near College Station, Texas during the 2008 and 2009 cropping years. An optimal harvest window (defined by maximum yield) was established for all genotypes, and significant variation was seen among the genotypes for fresh and dry biomass production. The later maturity genotypes, including the photo-period sensitive and modified photo-period sensitive type sorghums, produced the highest yields (up to 24 dry Mg/ha). Compositional analysis using near infrared reflectance spectroscopy (NIR) for lignin, hemicellulose, and cellulose was performed on a dry matter basis for the optimal harvest window for each genotype. Significant differences were seen in 2009 between the genotypes for lignin, hemicellulose, cellulose, ash and protein; with the earlier genotypes having higher percentage of lignin, and the later genotypes having lower percentages of lignin. Genotype x Environment interactions were also seen, and show the significance that rainfall can have. Based on this research, grain sorghum could be harvested first, followed by photo-period insensitive forage varieties, then moderately photo-period sensitive forage varieties followed by dedicated bioenergy sorghums (that are full photo-period sensitive), allowing for a more constant supply of feedstock to processing plants. Sweet sorghums would also allow the end user to obtain biomass when needed, however these types of sorghum may be much better suited to a different end application (i.e. crushing the stalks to obtain the juice).
27

On The resource accumulation and industry differentiation of fastener industry in Taiwan

Wu, Tsung-Yea 06 July 2000 (has links)
Fastener industry has developed for forty years in Taiwan, and it created significant contribution to so-called "Economic Miracle". This research was operated via grounded theory, and we practically visited seven firms in South Taiwan to trace the track on development of fastener industry in Taiwan, investigating the industrial features influenced by interaction of strategy and resource accumulation. The research revealed that the process of resource accumulation and the changes of industry surroundings stimulated the mechanism of industry differentiation, forming two directions of industry development mass production style and delicate production style. Two kinds of firms took different strategic actions and formed divergent features of development. This research also forecasts future development of fastener industry, and offers some suggestions to the participant in the industry.
28

Topics on Mean Value Theorems

Huang, Gen-Ben 19 January 2001 (has links)
Please read the PDF file of my thesis.
29

SOME EFFECTS OF CADMIUM ON SELECT CRAYFISH IN THE FAMILY CAMBARIDAE

Wigginton, Andrew Joseph 01 January 2005 (has links)
A series of acute (96h) toxicity tests were conducted on six species of crayfish inthe family Cambaridae. Toxicity values fell into a sensitive group comprising Orconectesplacidus and Procambarus acutus (LC 50= 0.368mg Cd/L - 0.487mg Cd/L; LC10= 0.048mg Cd/L - 0.092 mg Cd/L) and tolerant group comprising O. juvenilis, O. virilis, P.alleni, and P. clarkii (LC 50= 2.44 mg Cd/L - 3.30 mg Cd/L; LC10= 0.386 mg Cd/L -0.947 mg Cd/L). For juvenile crayfish, the LC50 and LC10 values were as follows: O.juvenilis, 0.060 and 0.014 mg Cd/L; O. placidus, 0.037 and 0.002 mg Cd/L; P. clarkii,0.624 and 0.283 mg Cd/L. Cd exposure decreased molting success highlighting theimportance of this sensitive process. Behavioral responses were assessed in O. placidus,O. virilis, P. acutus, P. alleni, and P. clarkii. The tail-flip predator avoidance behaviorwas significantly reduced by cadmium exposure. In most species tested, the claw raisedefensive behavior was significantly increased by Cd exposure. Between species, as bodymass increased, the tail-flip response frequency decreased, and the claw-raise responseincreased in frequency. P. clarkii was also analyzed for the effect of Cd exposure onheart rate and response to two stimuli. The data indicate that heart rate may be a usefulphysiological marker of Cd toxicity. The major organ systems were dissected fromsurvivors of four adult crayfish toxicity tests (O. juvenilis, O. placidus, P. acutus, P.clarkii) and analyzed for metal content. Cadmium tissue content correlated with Cdexposure. Cadmium accumulated more in the hepatopancreas, gills and green glands ofsensitive species than in tolerant species. Zn showed negative correlations with Cdexposure in the hepatopancreas. Cu increased in green glands, gills, and hemolymph and,in some cases, decreased in the hepatopancreas. Ca, Fe, Mg, and Zn also showedsignificant trends. Zn accumulated in the exposure water over 24h. These data indicatethat Cd may displace Cu and/or Zn in the hepatopancreas and the displaced metal thenmay move into other tissues, especially the gills and green glands, possibly to beexcreted.
30

Short-term effects of forest harvesting on CO2 and CH4 accumulation in small boreal lakes.

Landström, Emelie January 2014 (has links)
The purpose of the study was to examine how forest harvesting affects the accumulation of carbon dioxide (CO2) and methane (CH4) under the ice-cover. Dissolved organic carbon (DOC) was hypothesized to increases post-harvest, this supplementation would in turn lead to an increased accumulation of CO2 and CH4 under the ice-cover. Four small boreal lakes, (two treatment lakes, two reference lakes) were sampled once a year during winter, under a three-year period (2012-2014). The sampling was performed using a headspace equilibration technique. During the three study years (2012-2014), the CO2 concentration increased in both the reference lakes and the harvested lakes (percentage increase; 18 % and 89 % respectively). The mean CH4-concentration in the reference lakes increased during the years 2012-2014, (2, 6, 7.5 μM). While the concentrations in the harvested lakes showed a slightly different pattern, with a peak during year 2013 which latter decreased until year 2014, (6, 12.5, 8.5 μM). The result of this study suggests that harvest in the catchment area increases the accumulation of CO2 and possible CH4 under the ice. Inflow of supersaturated surface water was found to be a more important source to the increased accumulation under ice than DOC, contradicting the previous hypothesis that DOC would be a more important factor controlling the CO2 and CH4 production. Moreover this study indicates that the dimension of the edge-zone left in connection to the inlets can be of crucial importance, possible reducing the amount of supersaturated surface water reaching the lakes.

Page generated in 0.1031 seconds