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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.
521

Aneuploidy and DNA fragmentation in morphologically abnormal sperm

Tang, Steven Siu Yan 11 1900 (has links)
Introduction: Intracytoplasmic sperm injection (ICSI) has been a successful assisted reproductive technique for men with severe male-factor infertility. However, ICSI requires the subjective selection of normal looking sperm, which does not preclude the transmission of genetically abnormal sperm. Correlation between abnormal sperm morphology and chromosomal abnormalities has been suggested but not been conclusive and less is known about the connection between sperm morphology and DNA integrity. Sperm morphology will be evaluated on its ability to identify the level of chromosomal abnormalities or fragmented DNA in sperm. To further focus this investigation on sperm morphology, men with infertility isolated to abnormal sperm morphology (isolated teratozoopsermia) are examined. Materials and Methods: Sperm from isolated teratozoopsermic men (n=10) were analysed by fluorescent in situ hybridization (FISH) and terminal dUTP nick-end labelling (TUNEL) assays to determine the level of aneuploidy and DNA fragmentation, respectively. These results were also compared to that of sperm from control men (n=9) of proven fertility and normal seminal parameters. Results: Sperm from teratozoospermic men, compared to control men, had higher rates of total chromosomal abnormality (5.90±3.74% vs. 2.35±0.87%, P=0.0128), total aneuploidy (4.90±2.82% vs. 1.99±0.65%, P=0.0087), and chromosome 13 disomy (0.77±0.50% vs. 0.20±0.14%, P=0.0046). In control samples, incidence of tapered heads associated with supernumerary chromosomal abnormalities (rs=0.9747, P=0.0167). In teratozoospermic samples, incidence of amorphous heads associated to chromosome 13 disomy and sex chromosome aneuploidy (rs=0.6391, P= 0.0466; rs=0.8049, P=0.0050, respectively). Tail abnormalities were associated with chromosomal abnormalities (bent tail-disomy 13: rs=0.7939, P=0.0061; 2-tailed-disomy 13: rs=0.8193, P=0.0037; 2-tailed-supernumerary chromosomal abnormalities: rs=0.7534, P=0.0119). Levels of DNA fragmented sperm were higher in teratozoospermic men than control men (60.28±21.40% vs. 32.40±17.20%, P=0.0121). DNA fragmentation in sperm positively correlated with the incidence of sperm with bent necks in control samples (rs=0.8571, P=0.0238) and round headed sperm in teratozoospermic samples (rs=0.6727, P=0.0390). Conclusions: Sperm of isolated teratozoospermic men have elevated rates of chromosomal abnormalities and DNA fragmentation compared to that of fertile controls. Specific abnormal sperm morphology can be correlated wiht chromosomal abnormalities and level of DNA fragmentation in sperm and this may prove useful in sperm selection for ICSI when applied to isolated teratozoospermic patients.
522

The morphology and structure of intercalated and pillared clays

Duong, Loc V. January 2008 (has links)
This thesis is submitted in a format of published papers by the candidate. Advanced methods of electron microscopy and X-ray spectroscopy have been used to study the relationship between the pillars and the silicate structure ranging from Al13 and Ga13 complexes to the final products Al- and Ga-pillared clays. The Al13 and Ga13 pillared montmorillonites have been prepared by conventional and ultrasonic methods. The ultrasonic method has been proven to be effective and showed very good catalytically activity. Transmission electron microscopy combined with elemental mapping by EDS showed the distribution of the Ga and Al pillars in the clay structure. The use of gallium allowed the independent observation of the Ga pillar distribution from the Al distribution in the clay structure. XPS spectra of the Ga13 pillared montmorillonites showed that the pillars has been changed from the original Keggin structure with a 7+ charge to something more stable with a lower charge upon intercalation. No direct evidence of the inverted silicon tetrahedron structure bonding to the pillar structure, as suggested by Plee in his original thesis, was observed. For comparative reasons the major aluminium hydroxide minerals in bauxite (gibbsite, bayerite and (pseudo-) boehmite) were studied. Detailed information about the Al13 structure was obtained by studying the basic sulphate and nitrate salts with XPS. The XPS results of a set of starting clays in comparison to the pillared clays indicated that small changes in the binding energy could explain the changes in the pillar structure and the formation of chemical bonds to the clay tetrahedral sheets during the calcination leading to the final products.
523

Word Structure in Ngalakgan

Baker, Brett Joseph January 1999 (has links)
Ngalakgan is an Australian language of the Gunwinyguan family, spoken fluently by just a few people in the mid Roper River area of the Top End. The thesis is a description and examination of the phonology, prosody, and morphology of Ngalakgan, based on several years of fieldwork. Ngalakgan is a language with a rich inventory of classically Gunwinyguan morphological features, including noun class agreement for all major and some minor word classes, compounding of both nouns and verbs, and a rich array of modifying and inflectional prefixes and suffixes. In Ngalakgan, there is a distinction between two kinds or 'levels' of morphology: 'root'-level and 'word'-level. Root-level morphology is lexicalised and unproductive. It is restricted to the tense/aspect/mood inflection of the small closed class of 'finite' verb roots, and to the large closed class of compounds of these roots. Word-level morphology is productive, and includes almost all prefixes, all (non-tensed) suffixes and all clitics. Only word-level structure is consistently reflected in prosodic structure; forms which are complex only at the root-level are treated as prosodic units. I show that all word-level morphemes constitute prosodic domains: every word-level stem, affix and clitic potentially begins a new domain for metrical foot structure. Geminates and glottal stops are over-represented at morpheme boundaries in complex words. In addition, they are subject to complex, non-local alternations with simple stops and zero, respectively, in Ngalakgan and related languages. The alternations are conditioned by preceding geminates and voiceless obstruent clusters, as well as by prosodic and morphological structure. I propose that voiceless obstruent clusters constitute 'boundary signals' to morphological structure, in a similar fashion to stress and, like stress, are 'licensed' by the organisation of intonation. Ngalakgan displays a quantitive-sensitive stress system in roots which is apparently unique to languages of this area. Heavy syllables in Ngalakgan are those which are articulatorily and perceptually complex: those in which the coda is followed by a consonant with a distinct place of articulation. Geminates, homorganic nasal+stop clusters and glottal stops interact with this distinction in ways which are not predicted by current prosodic theories.
524

Ecology and ecophysiology of southwestern Australian hakea species with contrasting leaf morphology and life forms.

Groom, Philip K. January 1996 (has links)
Members of the genus Hakea (Proteaceae) are sclerophyllous, evergreen perennial shrubs or small trees endemic to Australia, with 65% of species confined to the South-West Botanical Province (southwestern Australia). Southwestern Australian Hakea species possess two contrasting leaf morphologies (broad or terete leaves) and fire-related life forms (non-sprouting (fire-killed) or resprouting (fire-surviving)), with each species representing one of four leaf morphology-life form groups.Representative species within each group were studied to determine whether they display similar distribution and ecophysiological patterns at both the adult and seedling stages. The distribution of species within these groups was best based on averages and variations in annual temperature and rainfall. The highest percentage of terete leaved non-sprouters (25 species) occurred in areas of low-moderate rainfall with large annual temperature ranges, whereas terete leaved resprouters (14 species) displayed a patchy distribution. Broad leaved resprouters (28 species) dominated areas of strongly seasonal rainfall, with few species occurring in the drier regions. Broad leaved non-sprouters (33 species) were best represented in areas of low annual temperature. The distribution of non-sprouters/resprouters may be due to the effect of climatic factors on seedling recruitment and/or fire frequencies. Leaf morphology appears to have a more direct influence on species distribution, as broad leaves are favoured in regions of medium-high, seasonal rainfall (less stressful habitats) while terete leaves are better adapted to tolerate hot, dry environments.Terete leaves are either simple (needle-like) or 2-3 pronged, and, apart from their narrow width, are characterised by their greater leaf thickness (> 1 mm), smaller projected area and mass, higher leaf mass per area (a measure of sclerophylly) and a ++ / lower density than broad leaves. Broad leaves are much more variable in their shape. Increased leaf thickness and sclerophylly in terete leaves can be partially attributed to the presence of a central parenchyma core and increased palisade thickness. This core is surrounded a compact network of fibre-capped vascular bundles. Thickness and sclerophylly were good indicators of relative nutrient content in terete, but not broad leaves. Both leaf types have a thick cuticle (> 20 mu m) and sunken stomates, with terete leaves possessing a greater stomatal density than broad leaves. Broad leaves are bilateral and hence amphistomatous. Adult and seedling leaves (of a similar leaf type) differed in morphology, but not anatomy, with some species producing broad seedling leaves and terete adult leaves.Seedlings growing under optimal growth conditions (full sunlight, well watered) in pots showed no relationship between rate of growth and ecophysiology with respect to the four species groupings, although seedlings of non-sprouters and broad leaved species had higher transpiration and photosynthetic rates than seedlings of resprouters and terete leaved species respectively. In response to high air temperatures (> 35°C), leaf temperatures close to or lower than the surrounding air temperature only occurred for terete leaved species possessing small individual and total leaf areas. By maintaining leaf photosynthesis rates during periods of relatively high air temperatures, terete leaved seedlings were able to produce more biomass per leaf area while retaining a low leaf area per seedling mass. When subjected to periods of water stress (withholding water), differences in water relations were most evident between seedlings of non-sprouters and resprouters, with resprouter seedlings showing an ability to minimise the decrease in relative water content for a given decrease in XPP. ++ / Although terete leaves possess many xeromorphic attributes, terete leaved seedlings were not necessarily superior at avoiding/tolerating drought. Terete leaves in seedlings may have alternative heat dissipation and/or anti-herbivore properties.Seasonal water relations of adult plants were monitored for over a year, including a period of prolonged summer drought at four sites (two on laterite (rocky substrate) and two on deep sand). The eight species inhabiting the lateritic sites were more stressed (more negative xylem pressure potentials (XPP)) in summer than the eight species on sandy soils, with lower conductances and higher leaf specific resistivity (XPP/area-based transpiration, LSR). Broad leaved species had higher transpiration rates and LSR, and more negative midday XPP throughout the study than terete leaved species. When spring (predrought) and summer (drought) data were compared, non-sprouters had lower XPP in summer, and lower transpiration rates and conductances in both seasons than resprouters. Non-sprouters on lateritic sites had the lowest water relations values in summer (drought tolerators). There was a tendency for broad leaved resprouters on sandy soils to have higher summer water relations values (drought avoiders). Broad leaved non-sprouters on lateritic soils could be considered the most water stressed group, with substantial plant death during the summer period. Terete leaved species on sandy soils were the most conservative in their water usage.
525

A biomechanical study on the hoof impact at the trot /

Gustås, Pia, January 2005 (has links) (PDF)
Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv. / Härtill 4 uppsatser.
526

Structural growth in mountain birch, Betula pubescens ssp. czerepanovii /

Borg, Christina, January 2005 (has links)
Diss. (sammanfattning) Uppsala : Univ., 2005. / Härtill 5 uppsatser.
527

The Morphology of Leitneria floridana ... /

Pfeiffer, Wanda May. January 1912 (has links)
Thesis (PH. P.)--University of Chicago, 1908. / "Reprinted from the Botanical gazette, vol. LIII, no. 3, March 1912." "Literature cited": p. 202. Also available on the Internet. Also issued online.
528

Variation in size and form of the cranial base thesis submitted as partial fulfillment ... orthodontics ... /

Ash, Allan A. January 1959 (has links)
Thesis (M.S.)--University of Michigan, 1959.
529

Habitat associations of the long-nosed potoroo (potoroos tridactylus) at multiple spatial scales

Norton, Melinda A. January 2009 (has links)
Thesis (M.Sc. (Res.))--University of Wollongong, 2009. / Typescript. Includes bibliographical references: leaf 147-159.
530

Distribution of 14C-labeled assimilates from two leaf positions in Zea mays L. during different stages of grain development

Tripathy, Prafulla Chandra, January 1970 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves 79-88).

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