• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 355
  • 256
  • 59
  • 38
  • 36
  • 20
  • 16
  • 16
  • 13
  • 13
  • 7
  • 6
  • 6
  • 6
  • 3
  • Tagged with
  • 1024
  • 131
  • 114
  • 97
  • 95
  • 92
  • 67
  • 64
  • 57
  • 57
  • 54
  • 52
  • 52
  • 51
  • 50
  • 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.
221

Human vaginal epithelial immunity and influences of hormonal contraceptive usage

Ildgruben, Anna January 2005 (has links)
The vagina is the port of entry for sexually transmitted diseases in women. Its epithelium constitutes the luminal border, thus comprising an important defence barrier. The objective of this work was to investigate the mechanisms of importance in the immune defence of the vaginal epithelium of healthy, fertile women, and possible menstrual cycle changes. Effects of hormonal contraceptive usage on oestrogen receptor (ER) and progesterone receptor (PR) expression were studied. The contribution of epithelial cell to the immune defence was estimated by assaying their expression of antimicrobial defensins and the epithelial thickness. Vaginal biopsies and serum samples were collected during the follicular and luteal phases in regularly menstruating women (controls) and in users of combined oral contraceptives (COCs), levonorgestrel implants (LNGs), or depot-medroxyprogesterone acetate injections (DMPAs). Fifteen healthy women (aged 20–34 years) were enrolled in each group. Morphometry was performed on vaginal tissue stained with haematoxylin/eosin and by immunohistochemistry using monoclonal antibodies against immune cell markers, PR, and ER. Expression of mRNA for human α-defensins HD-5 and HD-6, and human β-defensins (HBD) 1 to 4 were determined by real-time qRT-PCR and in situ hybridization. In controls, the epithelium was 261 ± 16 μm thick and harboured 241 ± 35 leukocytes (CD45+) per mm2. T lymphocytes (CD3+) dominated. Both αβ T cells and γδ T cells were present with an approximate 4-fold dominance of αβ T cells. Cytotoxic T cells (CD8+) were more frequent than T helper cells (CD4:CD8 ratio: 0.7 ± 0.1). Macrophages (CD68+) constituted the second-largest population, followed by Langerhans cells (CD1a+). B cells, natural killer cells, monocytes and granulocytes were generally absent. No differences were found between the follicular and luteal phase. All four β-defensins analysed for were detected in vaginal epithelium and most samples expressed at least two. HBD-2 and HBD-3 were most frequent. HBD-3 and HBD-4 expressing cells were localized in the parabasal and intermediate cell layers. α-defensins were not detected. The epithelium was significantly thicker (333 ± 9 μm) in COC, LNG, and DMPA users than in controls, and commonly showed hyperplasia. In DMPA and LNG users the frequency of intraepithelial leukocytes (CD45+) was increased, explained by increased frequencies of both αβ and γδ T cells. In DMPA users there was also a selective increase in CD8+ T cells. PR expression was significantly reduced in DMPA users compared with controls, COC and LNG users. COC and particularly DMPA users often had undetectable levels of serum E2. In conclusion, both adaptive immunity, i.e. intraepithelial T cells, and innate defence mechanisms, i.e. intraepithelial macrophages and β-defensins, are believed to contribute to the immune defence in the human female lower genital tract. These parameters did not change during the menstrual cycle but hormonal contraceptive usage, especially DMPA, affected the quality of the epithelium. The use of DMPA and LNG was correlated with the accumulation of T cells within the epithelium. The effects of these changes on the risk of contracting infections are yet to be determined.
222

Sagittal abdominal diameter is a more independent measure compared with waist circumference to predict arterial stiffness in subjects with type 2 diabetes - a prospective observational cohort study

Dahlén, Elsa, Bjarnegård, Niclas, Länne, Toste, Nyström, Fredrik H., Östgren, Carl Johan January 2013 (has links)
Background Anthropometric measurements are useful in clinical practice since they are non-invasive and cheap. Previous studies suggest that sagittal abdominal diameter (SAD) may be a better measure of visceral fat depots. The aim of this study was to prospectively explore and compare how laboratory and anthropometric risk markers predicted subclinical organ damage in 255 patients, with type 2 diabetes, after four years. Methods Baseline investigations were performed in 2006 and were repeated at follow-up in 2010. Carotid intima-media thickness (IMT) was evaluated by ultrasonography and aortic pulse wave velocity (PWV) was measured with applanation tonometry over the carotid and femoral arteries at baseline and at follow-up in a cohort of subjects with type 2 diabetes aged 55–65 years old. Results There were significant correlations between apolipoprotein B (apoB) (r = 0.144, p = 0.03), C - reactive protein (CRP) (r = 0.172, p = 0.009) at baseline and IMT measured at follow-up. After adjustment for sex, age, treatment with statins and Hba1c, the associations remained statistically significant. HbA1c, total cholesterol or LDL-cholesterol did not correlate to IMT at follow-up. Baseline body mass index (BMI) (r = 0.130, p = 0.049), waist circumference (WC) (r = 0.147, p = 0.027) and sagittal Abdominal Diameter (SAD) (r = 0.184, p = 0.007) correlated to PWV at follow-up. Challenged with sex, SBP and HbA1c, the association between SAD, not WC nor BMI, and PWV remained statistically significant (p = 0.036). In a stepwise linear regression, entering both SAD and WC, the association between SAD and PWV was stronger than the association between WC and PWV. Conclusions We conclude that apoB and CRP, but not LDL-cholesterol predicted subclinical atherosclerosis. Furthermore, SAD was more independent in predicting arterial stiffness over time, compared with WC, in middle-aged men and women with type 2 diabetes. / <p>Funding Agencies|Medical Research Council of Southeast Sweden||Center for Medical Image Science and Visualization (CMIV)||Linkoping University||Futurum||King Gustaf V and Queen Victoria Freemason Foundation||GE Healthcare||Swedish Heart-Lung Foundation||Swedish Research Council Grant|12661|</p>
223

Cortical Morphology in Children with Alcohol-related Neurodevelopmental Disorder

Rajaprakash, Meghna 26 November 2012 (has links)
Individuals exposed to alcohol in utero have reduced cortical grey matter volumes. However, the underlying determinants of these reductions have not been investigated exclusively in alcohol-related neurodevelopmental disorder (ARND). Using magnetic resonance imaging scans from 121 participants (57 ARND and 64 controls) aged 8 to 16 years, cortical morphology was analyzed. Results revealed the ARND group had reduced cortical grey matter volumes, but did not differ from controls in cortical thickness. Rather, the cortical abnormalities reflected reductions in global surface area, local surface area reductions in the right occipital-temporal area and right superior temporal gyrus, as well as reduced gyrification. A significant interaction between sex and group was observed, with females showing greater reductions than males in cortical volume and surface area. Results suggest that ARND is characterized by global reductions in cortical surface area and gyrification and females are more vulnerable than males to the teratogenic effects of alcohol.
224

Cortical Morphology in Children with Alcohol-related Neurodevelopmental Disorder

Rajaprakash, Meghna 26 November 2012 (has links)
Individuals exposed to alcohol in utero have reduced cortical grey matter volumes. However, the underlying determinants of these reductions have not been investigated exclusively in alcohol-related neurodevelopmental disorder (ARND). Using magnetic resonance imaging scans from 121 participants (57 ARND and 64 controls) aged 8 to 16 years, cortical morphology was analyzed. Results revealed the ARND group had reduced cortical grey matter volumes, but did not differ from controls in cortical thickness. Rather, the cortical abnormalities reflected reductions in global surface area, local surface area reductions in the right occipital-temporal area and right superior temporal gyrus, as well as reduced gyrification. A significant interaction between sex and group was observed, with females showing greater reductions than males in cortical volume and surface area. Results suggest that ARND is characterized by global reductions in cortical surface area and gyrification and females are more vulnerable than males to the teratogenic effects of alcohol.
225

Correlation and Stratigraphic Analysis of the Bakken and Sappington Formations in Montana

Adiguzel, Zeynep 1986- 14 March 2013 (has links)
The Upper Devonian-Lower Mississippian (Late Fammenian-Tournaisian) Bakken Formation in the Williston Basin is one of the largest continuous oil fields in the U.S. The upper and the lower shale members are organic rich source rocks that supplied oil to the middle member, which is reservoir rock. Although the oil-producing Bakken Formation has been intensely studied in the Williston Basin, the lateral relationship between the Bakken Formation and the coeval Sappington Formation in western Montana remains cryptic. This study correlates the Sappington Formation in western Montana with the Bakken Formation in the Williston Basin in northeastern Montana. It clarifies the lateral relationship between these two units, and extent of their members across Montana and, the causes of these thickness variations. This study utilized 675 well logs (mostly gamma ray, caliper, sonic, density, neutron, resistivity logs) to make multiple E-W and N-S cross sections and isopach maps. Also, seven outcrops of the Sappington Formation in southwestern Montana and five Bakken Formation cores in the Williston Basin were tied to the subsurface data. Variations in the distribution of the Bakken/Sappington Formation were caused by eustatic changes and local epeirogenic uplifts. The Bakken/Sappington Formation is thickest in the depressions in southwestern and the northeastern Montana, the Central Montana Trough and the Williston Basin in Montana. The Bakken/Sappington Formation is thin coincident with major structural uplifts that were active during the Late Devonian, such as Yellowstone Park Uplift, Bearpaw Anticline, Scapegoat-Bannatyne Anticline and Nesson Anticline. Devonian strata are difficult to identify in the subsurface of south-central Montana making the Bakken/Sappington correlation problematic in this area. The Lower Bakken/Sappington Member thickness is 15 ft (4.6 m) in northeastern and southwestern Montana. The Lower Bakken/Sappington Member is more continuous in western Montana than the other Bakken/Sappington Members. The Middle Bakken/Sappington Member is thickest (~55 ft; 16.7 m) in the northeastern Williston Basin and in the Central Montana Trough (~50 ft; 15.2 m). The Middle Bakken/Sappington Member was less affected by the tectonics and it is present from northwestern to northeastern Montana, except in far northwestern and central Montana. The Upper Bakken Member (~5-15 ft; 1.5 m-4.6 m) is the most continuous unit in the Williston Basin, as the Bakken Members show onlapping relationship that makes the distribution of each younger member greater. However, the Upper Bakken/Sappington Member is absent west of the Central Montana Trough due to basin inversion and it is also absent in far northwestern and central Montana as a result of the erosion or nondeposition caused by the local uplifts. Transgressions were responsible for the deposition of the upper and the lower black shales in offshore marine environments, whereas the Middle Bakken/Sappington Member was deposited during regression and records multiple offshore marine to tidal environments.
226

A Methodology For Lining Design Of Circular Mine Shafts In Different Rock Masses

Guler, Erdogan 01 March 2013 (has links) (PDF)
The objective of this thesis is to predict lining thickness inside circular mine shafts. A numerical study with different rock mass strengths and different in-situ non-hydrostatic stresses are carried out in 2D shaft section models to predict pressures that develop on lining support. An iterative process of applying support pressure until observing no failure zone around shaft is used to simulate lining support pressure for each individual model. Later, regression and fuzzy logic analyses are carried out to find a pressure equation for all of the models. Finally, the pressure equation derived is used in elastic &ldquo / thick-walled cylinder&rdquo / equation to calculate the lining thickness required to prevent the development of a failure zone around shafts. At the end of this research, a computer program &ldquo / Shaft 2D&rdquo / is developed to simplify the lining thickness calculation process.
227

Construction Of A Collagen-based, Split Thickness Cornea Substitute

Acun, Aylin 01 January 2013 (has links) (PDF)
Cornea is the transparent outermost layer of the eye. It is a thin (500 &micro / m) multilayer tissue which performes around 75% of the total refraction in the eye. It also protects the inner layers against any type of damage. Since it is avascular, the three cellular layers of cornea always need transport of nutrients and other materials in and out of the tissue via diffusion. Any change in shape, transparency or thickness of cornea, or physical damages and infections, may cause serious defects. The conventional methods are satisfactory in the treatment of mild injuries but severe cases require the substitution of the tissue with an equivalent. Keratoprosthesis and donor corneas that are used as replacements do not completely meet requirements. Tissue engineering can be an alternative method for preparing a biocompatible and stable cornea equivalent. The ability to choose from a variety of materials and the ability to incorporate bioactive agents allow the researchers to tailor make the construct. The structure needs to be seeded with the patient&rsquo / s own cells and cultured in vitro to yield an optimal corneal replacement. In this study a novel, split thickness cornea replacement is proposed to substitute the two upper cellular layers (epithelium and stroma) of the native cornea. The design includes a chondroitin sulfate impregnated collagen type I (isolated from rat tail) foam (CSXLF) produced by lyophilization carrying electrospun fibers of the same polymer collected directly on top of the foam, forming the bilayer structure (Fo-Fi). The fiber layer was intended to separate the epithelium and the stroma of the reconstructed cornea yet to allow material transfer in between. The foam layer (bottom) was crosslinked by N-ethyl-N-[3-dimethylaminopropyl] carbodiimide (EDC), and N-hydroxy succinimide and after fiber deposition the bilayer was further stabilized with physical crosslinking (DHT method). The physical characterization of the foam showed that their pore sizes (10-200 &micro / m) and porosities (around 70%) were well within the desired range for typical tissue engineering applications. The cell free wet thicknesses of both single and bilayer constructs were close to that of the native stroma and light transmittance through these scaffolds was quite high (around 82% in the 500-700 nm range). The scaffolds were also tested for their stability and shown to be suitable for in vitro testing. In vitro studies were performed using retinal pigment epithelial cells (RPE, D407 cell line) and isolated human corneal keratocytes (HK) to reconstruct the epithelium and the stroma, respectively. Three types of constructs were prepared / only HK seeded Fo-Fi constructs, RPE-HK seeded CSXLFs, and RPE-HK seeded Fo-Fi constructs. All were shown to support cell attachment and promoted cell proliferation as was shown by the cells that covered the inner and outer spaces of the scaffolds. The fiber layer prevented the mixing of the two cell types, without hindering material exchange between them. Moreover, when co-cultured for 14 days, the keratocytes started to deposit collagen type I, a specific marker of these cells. In contrast, ECM deposition could not be observed in the single type cell seeded samples. The co-cultured bilayer construct was tested for suturability at the end of 31 days of in vitro incubation and it was shown that it could be successfully sutured without any major tears. Under the light of these results it was concluded that both the single layer and the bilayer constructs show promise for use as split thickness cornea replacements.
228

Analysis of Antarctic Sea Ice Thickness: A Newly Created Database for 2000-2009

Morgan, Benjamin Patrick 2011 August 1900 (has links)
Observations of Antarctic sea ice thickness are sporadic in space and time, hindering knowledge of its variability. A proxy based on stage of development data from the National Ice Center (NIC) weekly operational charts is used to create a high-resolution time series of sea ice concentration, thickness and volume for 2000-2009. Record-length mean thickness and volume of Antarctic sea ice are 66.7 cm and 7.7 x10^3 km^3. The mean growth and decay seasons in the Southern Ocean and in the Ross sector are 210 days and 155 days, but at least at least one week shorter (growth) and longer (decay) in the Amundsen/Bellingshausen sector. Over 90% of the Antarctic continental shelf is covered with sea ice for 3-5 months, and for 2 to 4 months longer periods in the Amundsen/Bellingshausen and Ross sectors. Yearly mean sea ice area (extent) in the Southern Ocean increased at a rate of 0.71 x 10^6 km^2/decade (0.70 x 10^6 km^2/decade), equivalent to a 7.7 %/decade (6.3 %/decade) rise. A comparable trend of 9.1 %/decade (8.5 %/decade) is estimated in the Ross sector, at 0.21 x 10^6 km2/decade (0.23 x 10^6 km2/decade). The opposite trend is found in the Amundsen/Bellingshausen sector: a -0.15 x 10^6 km^2/decade (-0.17 x 10^6 km^2/decade) decline, or -14.6 %/decade (-13.4 %/decade). The estimated annual increase of Antarctic sea ice thickness is 22.6 cm/decade (49.2 %/decade) and of volume is 3.78 x 10^3 km^3/decade (68.3 %/decade). The Ross sector showed similar trends for thickness, at 23.8 cm/decade (47.0 %/decade), and volume, at 1.11 x 10^3 km^3/decade (75.8 %/decade). Thickness has increased in the Amundsen/Bellingshausen sector, 20.7 cm/decade (44.8 %/decade), but with a less pronounced volume rise of 0.17 x10^3 km^3/decade (26.0 %/decade). Monthly sea ice thickness anomalies show a weak response to the El Nino Southern Oscillation (ENSO) index. A strong positive response is observed in 2008 when a negative a negative ENSO index compounded to a positive Southern Annular Mode (SAM) index. Therefore the estimated increase of sea ice thickness in the Southern Ocean could be attributed to the prevailing atmospheric conditions with a positive SAM phase over the past decade.
229

き裂エネルギ密度による安定成長き裂の破壊抵抗評価 (第3報, 薄板延性き裂破壊抵抗の板厚効果)

渡辺, 勝彦, Watanabe, Katsuhiko, 畔上, 秀幸, Azegami, Hideyuki, 平野, 八州男, Hirano, Yasuo 08 1900 (has links)
No description available.
230

Vascular Aging: Influences on cerebral blood flow and executive function

Robertson, Andrew Donald January 2007 (has links)
An age-related decline in cerebral blood flow (CBF) is widely acknowledged. However, uncertainty exists as to whether this reduction is the result of a reduced metabolic demand (cerebral atrophy) or an impaired delivery system (cerebrovascular disease). The purpose of these experiments was to examine the relationship of CBF and dynamic cerebrovascular regulation with changes in common carotid intima-media thickness (cIMT), brachial-ankle pulse wave velocity (baPWV) and common carotid distensibility. Additionally, we took an exploratory view into the effect of vascular aging and CBF reduction on brain function, as expressed through the performance of motor and cognitive tasks. An important finding in elderly participants was that seated anterior CBF declined as a function of arterial stiffness, independently of age. Linear regression analysis developed a model that predicts CBF drops 22 ml/min (95% confidence interval (CI): 6, 38) for each 100 cm/s increase in baPWV and 8 ml/min (95% CI: 1, 15) for each additional year in age. The effect of baPWV appears to be mediated through an increase in cerebrovascular resistance (r2 = 0.84, p < 0.0001). Additionally, CBF showed postural dependency and the volume of the drop in CBF between supine and seated positions was greatest in elderly participants (YOUNG: 65 ± 81 ml/min; ELDERLY: 155 ± 119 ml/min; p = 0.001). Despite this negative impact of vascular aging on steady state flow, dynamic regulation does not appear to be affected. Cerebrovascular responses to an acute drop in blood pressure or to activation of the motor cortex were not attenuated in the elderly participants. Finally, seated CBF had modest directionally relevant relationships with perceptuo-motor and complex sequencing processes; while cIMT appeared to influence performance on initiation and inhibition tasks.

Page generated in 0.0589 seconds