• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1272
  • 1022
  • 503
  • 104
  • 104
  • 104
  • 104
  • 104
  • 104
  • 83
  • 59
  • 59
  • 39
  • 24
  • 20
  • Tagged with
  • 3800
  • 1344
  • 586
  • 518
  • 493
  • 487
  • 330
  • 328
  • 328
  • 309
  • 279
  • 249
  • 249
  • 214
  • 203
  • 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.
41

Microbial contamination of enteral feeds

Lee, Cheuk-hung, 李卓雄 January 2004 (has links)
published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy
42

The incidence and duration of breast feeding among women in the greater metropolitan area of Portland, Oregon

Marshall, Joyce M. 02 May 1983 (has links)
The incidence and duration of breast feeding were determined via telephone questionnaires from a sample of 95 women who delivered healthy infants during the month of September 1982, in the greater metropolitan area of Portland, Oregon. This sample was limited in that the women were married, predominately white, over 25 years of age, and well-educated. According to the literature, these factors have a positive correlation with the incidence and duration of breast feeding. Consequently, the reported values for the incidence of breast feeding in the hospital of 88 percent and the duration of breast feeding for six months of 44 percent is higher than reported values on a national level. However, the average duration of breast feeding by women who had weaned their babies at the time of this survey (6.2 weeks) is consistent with other studies. The information obtained from the questionnaires was used to measure the association between the incidence of breast feeding and the amount of information women received during their pregnancy; the duration of breast feeding and support system(s); and the relationship between the incidence and duration of breast feeding to the social factors of income, education, age, and race. Chi Square was the statistic used to compare the distribution, of responses among the three subgroups: women who breast fed only, formula fed only, or both breast and formula fed. Significant associations were not observed between the incidence of breast feeding and information or between the duration of breast feeding and support system(s). There was, however, an observed significant association between the incidence of breast feeding and the social factor of income. Additional findings revealed that women most likely to breast feed had themselves been breast fed as a baby, had breast fed their other children, and did not smoke cigarettes. Possible explanations for these results are discussed. / Graduation date: 1983
43

Induction of hepatic microsomal enzymes in rainbow trout by dietary aroclor 1254 and the effect of cyclopropene fatty acids

Voss, Sherri Denise 05 May 1980 (has links)
A dietary level of Aroclor 1254 (100 ppm) was fed to rainbow trout (Salmo gairdneri) for 15 weeks to determine the effects on hepatic microsomal enzyme induction. Fish were also fed combined polychlorinated biphenyl (PCB) (100 ppm) and cyclopropene fatty acids (CPFA) (50 ppm) to determine the effects on mixed function oxidase (MFO) induction. Dietary PCBs markedly induced the microsomal activities of 7-ethoxyresorufin O-deethylase, 7-ethoxy-coumarin O-deethylase, and benzo(a)-pyrene monooxygenase. Ethoxyresorufin O-deethylase activity continued to increase to a level 77-fold higher than control at week 15. Ethoxycoumarin O-deethylase and benzo(a)-pyrene monooxygenase activities increased to 7.1-fold and 48-fold over control at week 9 and then slightly decreased to 6.8-fold and 45-fold over control at week 15, respectively. Cytochrome P450 values remained approximately 2-fold above controls from week 5 through week 15. At weeks 1 and 3, cytochrome P450 levels were not significantly different from control. Ethoxyresorufin O-deethylase, ethoxycoumarin O-deethylase, and benzo(a)pyrene monooxygenase activities in the combined PCB and CPFA-fed trout were significantly higher than in controls and CPFA-fed fish, and significantly lower than in PCB-fed fish. There was no significant difference in cytochrome P450 levels after week 5. This is the first time dietary PCBs have been shown to induce the MFC system in PCB-fed rainbow trout. / Graduation date: 1980
44

Provisioning strategies, intraspecific parasitism and guild structure in solitary wasps (Hymenoptera: Sphecidae, Pompilidae)

Field, J. P. January 1987 (has links)
Group-living, within the Hymenoptera, is restricted to taxa in which females return to their nests repeatedly with food for their offspring (multiple provisioning), increasing the opportunities for helping (e.g. by guarding the nest). Some solitary wasps provide only one large prey item per cell (single provisioning). <i>Ammophila sabulosa</i> (Sphecidae) females provision half of their cells singly and half multiply. The costs and benefits of these two alternatives are compared in terms of : a. Total weight of prey (caterpillars) provided. b. Time taken to capture and transport prey. c. The probability of intraspecific theft of prey from cells. d. The incidence of parasitism by miltogrammine flies. There is no evidence that either strategy is more successful than the other. An advantage of flexible provisioning is suggested by a study of <i>Anoplius viaticus</i> (Pompilidae), females of which provision all cells singly with spiders. Despite provisioning prey of a smaller size range than does <i>Ammophila</i>, total prey weight in <i>Anoplius</i> cells is more variable and dependent upon seasonal changes in prey availability. <i>Ammophila</i> females steal caterpillars from each others' nests, and both they and <i>Anoplius</i> females brood-parasitize cells of conspecifics. Intraspecific parasitism as an alternative nesting strategy is discussed and compared with work on other solitary wasps. Patterns of resource utilization are documented for the guild of spider-hunting pompilid wasps at one site. Data were collected on : a. Microhabitat utilization. b. Seasonal occurrence. c. Female size distributions. d. Prey species and sizes. Observed patterns of utilization and overlap are compared with 'neutral' models of guild structure in which various aspects of the species x resources utilized matrix are randomized. Some of the results are consistent with the idea that interspecific competition has partly determined pompilid guild structure, but problems of methodology and interpretation are discussed.
45

Feeding and optimization : The foraging behaviour of Nereis diversicolor (Polychaeta)

Pashley, H. E. January 1985 (has links)
No description available.
46

Behavioural development in two species of hyrax living in the Serengeti National Park, Tanzania

Magin, Christopher David January 1987 (has links)
No description available.
47

Phytoplankton and planktonic rotifer populations of Abbot's Pond, Northwest Avon, U.K : Ecological and laboratory feeding studies

Al-Shihab, S. A. January 1987 (has links)
No description available.
48

The effect of feeding on live weight change, carcass composition and quality of cull cows

Phoya, R. K. D. January 1984 (has links)
No description available.
49

EFFECTS OF LYSINE, TOTAL SULFUR AMINO ACIDS, AND TALLOW ON LAYING HEN PERFORMANCES.

SADIK, HAITHAM LOTFY. January 1986 (has links)
An experiment was conducted with laying hens to evaluate the effects of added lysine, methionine and tallow on laying hen performances. Twenty-four treatments were obtained as a result of supplementing the basal diets, which contained either 13.86% or 13.5% protein, with 4 levels of synthetic L-lysine Hcl and with 3 levels of DL-methionine. Each treatment was fed to 5 neplicates of four birds each for ten 28-day periods. Tallow was added at a level of 4% to the 13.5% protein diet. Significant improvements were obtained in egg production and in egg mass as a result of lysine and methionine supplementation. However, 4% added tallow significantly decreased egg production and egg mass. On the other hand, tallow exerted positive effects upon the efficiency of feed utilization only when the diets were adequate in both lysine and TSAA. Three response criteria were used to measure the daily intake of lysine and total sulfur amino acids which are methionine and cysteine (TSAA) required by laying hens; percent egg production, egg mass, and plasma free lysine and TSAA levels. The pattern of response suggested that the dietary lysine requirements were 718 and 709 mg/hen/day for egg production and egg mass respectively; and the dietary TSAA requirements were 616 and 626 mg/hen/day for egg production and egg mass respectively. Multiple regression analysis, which related the intake of these amino acids with hen performances showed numerical, but non-significant, differences than the above requirement values. Using plasma free lysine and TSAA as criteria, the requirements for lysine and TSAA obtained from regression analysis were 674.8 and 561.6 mg/hen/day respectively. Feed intakes and protein intakes were not significantly affected by either lysine or methionine supplementation. However, 4% added tallow significantly decreased feed intakes and protein intakes.
50

FORAGING CHOICE IN THREE SPECIES OF PIPILO (AVES: PASSERIFORMES): A TEST OF THE THRESHOLD CONCEPT (BAYESIAN, TOWHEE).

DUNNING, JOHN BARNARD, JR. January 1986 (has links)
Foraging by captive individuals of three species of towhees (Pipilo:Emberizinae) was investigated to determine if patch choice was associated with critical threshold levels of foraging success. Birds were offered a choice of feeding in three litter types. Once individual preferences for litter type were determined, I reduced the amount of food (millet seed) under a preferred litter each day, while maintaining high levels under a non-preferred litter. Thus, birds experienced a declining resource gradient under their preferred litter. During the bird's initial foraging period each day, I noted number of seeds taken and number of double-scratches made in each litter type, until the bird abandoned its preferred litter and shifted to the other patch. Foraging theory assumes that patch choice is made when foraging success declines as resources decline to some threshold level. I estimated success using information potentially available for decision-making by the birds. One of four success variables, mean seeds/scratch, best conformed to the expected pattern, providing supportive evidence for the threshold assumption. The three species changed patches at species-specific thresholds. Pipilo fuscus, a foraging generalist, switched to its non-preferred litter when food levels under the preferred litter were high. Pipilo aberti and P. erythrophthalmus, two foraging specialists, foraged in their preferred litters until food levels were much lower. Optimal Foraging Theory predicts that shifts in patch use are determined by between-patch comparisons of foraging success. Timing of towhee patch changes was not consistent with between-patch comparisons. An alternative expectation theory, Status-quo Foraging, which emphasizes comparisons of within-patch success, was more consistent with observed results. The rapid patch switching shown by P. fuscus may reflect greater flexibility of this species' foraging repertoire in its natural habitat. This result suggests that foragers with imperfect knowledge may use recent past experience to make foraging decisions. Optimal Foraging Theory provided a useful null model for comparing foraging theories. Deviations from predictions indicated how more realistic hypotheses can be constructed. The nature of available information plays an increasingly important role in modeling decision-making by imperfect foragers.

Page generated in 0.0626 seconds