23 resultados para Dimensional effects
em Université de Lausanne, Switzerland
Resumo:
Surface geological mapping, laboratory measurements of rock properties, and seismic reflection data are integrated through three-dimensional seismic modeling to determine the likely cause of upper crustal reflections and to elucidate the deep structure of the Penninic Alps in eastern Switzerland. Results indicate that the principal upper crustal reflections recorded on the south end of Swiss seismic line NFP20-EAST can be explained by the subsurface geometry of stacked basement nappes. In addition, modeling results provide improvements to structural maps based solely on surface trends and suggest the presence of previously unrecognized rock units in the subsurface. Construction of the initial model is based upon extrapolation of plunging surface. structures; velocities and densities are established by laboratory measurements of corresponding rock units. Iterative modification produces a best fit model that refines the definition of the subsurface geometry of major structures. We conclude that most reflections from the upper 20 km can be ascribed to the presence of sedimentary cover rocks (especially carbonates) and ophiolites juxtaposed against crystalline basement nappes. Thus, in this area, reflections appear to be principally due to first-order lithologic contrasts. This study also demonstrates not only the importance of three-dimensional effects (sideswipe) in interpreting seismic data, but also that these effects can be considered quantitatively through three-dimensional modeling.
Resumo:
In order to study peptide growth factor action in a three-dimensional cellular environment, aggregating cell cultures prepared from 15-day fetal rat telencephalon were grown in a chemically defined medium and treated during an early developmental stage with either bovine fibroblast growth factor (bFGF) or platelet-derived growth factor (PDGF homodimers AA and BB). A single dose (5-50 ng/ml) of either growth factor given to the cultures on day 3 greatly enhanced the developmental increase of the two glia-specific enzyme activities, 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNP) and glutamine synthetase (GS), whereas it had relatively little effect on total protein and DNA content. Distinct patterns of dose-dependency were found for CNP and GS stimulation. At low concentrations of bFGF (0.5-5 ng/ml) and at all PDGF concentrations applied, the oligodendroglial marker enzyme CNP was the most affected. A relatively small but significant mitogenic effect was observed after treatment with PDGF, particularly at higher concentrations or after repetitive stimulation. The two PDGF homodimers AA and BB were similar in their biological effects and potency. The present results show that under histotypic conditions both growth factors, bFGF and PDGF, promote the maturation rather than the proliferation of immature oligodendrocytes and astrocytes.
Resumo:
The aim of the present study is to determine the level of correlation between the 3-dimensional (3D) characteristics of trabecular bone microarchitecture, as evaluated using microcomputed tomography (μCT) reconstruction, and trabecular bone score (TBS), as evaluated using 2D projection images directly derived from 3D μCT reconstruction (TBSμCT). Moreover, we have evaluated the effects of image degradation (resolution and noise) and X-ray energy of projection on these correlations. Thirty human cadaveric vertebrae were acquired on a microscanner at an isotropic resolution of 93μm. The 3D microarchitecture parameters were obtained using MicroView (GE Healthcare, Wauwatosa, MI). The 2D projections of these 3D models were generated using the Beer-Lambert law at different X-ray energies. Degradation of image resolution was simulated (from 93 to 1488μm). Relationships between 3D microarchitecture parameters and TBSμCT at different resolutions were evaluated using linear regression analysis. Significant correlations were observed between TBSμCT and 3D microarchitecture parameters, regardless of the resolution. Correlations were detected that were strongly to intermediately positive for connectivity density (0.711≤r(2)≤0.752) and trabecular number (0.584≤r(2)≤0.648) and negative for trabecular space (-0.407 ≤r(2)≤-0.491), up to a pixel size of 1023μm. In addition, TBSμCT values were strongly correlated between each other (0.77≤r(2)≤0.96). Study results show that the correlations between TBSμCT at 93μm and 3D microarchitecture parameters are weakly impacted by the degradation of image resolution and the presence of noise.
Resumo:
The potential of ochratoxin A (OTA) to damage brain cells was studied by using a three-dimensional cell culture system as model for the developing brain. Aggregating cell cultures of foetal rat telencephalon were tested either during an early developmental period, or during a phase of advanced maturation, over a wide range of OTA concentrations (0.4 nM to 50 microM). By monitoring changes in activities of cell type-specific enzymes (ChAt and GAD, for cholinergic and GABAergic neurones, respectively, GS for astrocytes and CNP for oligodendrocytes), the concentration-dependent toxicity and neurodevelopmental effects of OTA were determined. OTA proved to be highly toxic, since a 10-day treatment at 50 nM caused a general cytotoxicity in both mature and immature cultures. At 10 nM of OTA, cell type-specific effects were observed: in immature cultures, a loss in neuronal and oligodendroglial enzyme activities, and an increase in the activity of the astroglial marker glutamine synthetase were found, Furthermore, at 2 and 10 nM of OTA, a clustering of microglial cells was observed. In mature cultures, OTA was somewhat less potent, but caused a similar pattern of toxic effects. A 24 h-treatment with OTA resulted in a concentration-dependent decrease in protein synthesis, with IC50 values of 25 nM and 33 nM for immature and mature cultures respectively. Acute (24 h) treatment at high OTA concentrations (10 to 50 microM) caused a significant increase in reactive oxygen species formation, as measured by the intracellular oxidation of 2',7'-dichlorofluorescin. These results suggest that OTA has the potential to be a potent toxicant to brain cells, and that its effects at nanomolar concentrations are primarily due to the inhibition of protein synthesis, whereas ROS seem not to be involved in the toxicity mediated by a chronic exposure to OTA at such low concentrations.
Resumo:
Several groups have demonstrated the existence of self-renewing stem cells in embryonic and adult mouse brain. In vitro, these cells proliferate in response to epidermal growth factor, forming clusters of nestin-positive cells that may be dissociated and subcultured repetitively. Here we show that, in stem cell clusters derived from rat embryonic striatum, cell proliferation decreased with increasing number of passages and in response to elevated concentrations of potassium (30 mM KCl). In monolayer culture, the appearance of microtubule-associated protein type-5-immunoreactive (MAP-5(+)) cells (presumptive neurons) in response to basic fibroblast growth factor (bFGF) was reduced at low cell density and with increasing number of passages. In the presence of bFGF, elevated potassium caused a more differentiated neuronal phenotype, characterized by an increased proportion of MAP-5(+) cells, extensive neuritic branching, and higher specific activity of glutamic acid decarboxylase. Dissociated stem cells were able to invade cultured brain cell aggregates containing different proportions of neurons and glial cells, whereas they required the presence of a considerable proportion of glial cells in the host cultures to become neurofilament H-positive. The latter observation supports the view that astrocyte-derived factors influence early differentiation of the neuronal cell lineage.
Resumo:
South Peak is a 7-Mm3 potentially unstable rock mass located adjacent to the 1903 Frank Slide on Turtle Mountain, Alberta. This paper presents three-dimensional numerical rock slope stability models and compares them with a previous conceptual slope instability model based on discontinuity surfaces identified using an airborne LiDAR digital elevation model (DEM). Rock mass conditions at South Peak are described using the Geological Strength Index and point load tests, whilst the mean discontinuity set orientations and characteristics are based on approximately 500 field measurements. A kinematic analysis was first conducted to evaluate probable simple discontinuity-controlled failure modes. The potential for wedge failure was further assessed by considering the orientation of wedge intersections over the airborne LiDAR DEM and through a limit equilibrium combination analysis. Block theory was used to evaluate the finiteness and removability of blocks in the rock mass. Finally, the complex interaction between discontinuity sets and the topography within South Peak was investigated through three-dimensional distinct element models using the code 3DEC. The influence of individual discontinuity sets, scale effects, friction angle and the persistence along the discontinuity surfaces on the slope stability conditions were all investigated using this code.
Resumo:
Combustion-derived and manufactured nanoparticles (NPs) are known to provoke oxidative stress and inflammatory responses in human lung cells; therefore, they play an important role during the development of adverse health effects. As the lungs are composed of more than 40 different cell types, it is of particular interest to perform toxicological studies with co-cultures systems, rather than with monocultures of only one cell type, to gain a better understanding of complex cellular reactions upon exposure to toxic substances. Monocultures of A549 human epithelial lung cells, human monocyte-derived macrophages and monocyte-derived dendritic cells (MDDCs) as well as triple cell co-cultures consisting of all three cell types were exposed to combustion-derived NPs (diesel exhaust particles) and to manufactured NPs (titanium dioxide and single-walled carbon nanotubes). The penetration of particles into cells was analysed by transmission electron microscopy. The amount of intracellular reactive oxygen species (ROS), the total antioxidant capacity (TAC) and the production of tumour necrosis factor (TNF)-a and interleukin (IL)-8 were quantified. The results of the monocultures were summed with an adjustment for the number of each single cell type in the triple cell co-culture. All three particle types were found in all cell and culture types. The production of ROS was induced by all particle types in all cell cultures except in monocultures of MDDCs. The TAC and the (pro-)inflammatory reactions were not statistically significantly increased by particle exposure in any of the cell cultures. Interestingly, in the triple cell co-cultures, the TAC and IL-8 concentrations were lower and the TNF-a concentrations were higher than the expected values calculated from the monocultures. The interplay of different lung cell types seems to substantially modulate the oxidative stress and the inflammatory responses after NP exposure. [Authors]
Resumo:
To make a comprehensive evaluation of organ-specific out-of-field doses using Monte Carlo (MC) simulations for different breast cancer irradiation techniques and to compare results with a commercial treatment planning system (TPS). Three breast radiotherapy techniques using 6MV tangential photon beams were compared: (a) 2DRT (open rectangular fields), (b) 3DCRT (conformal wedged fields), and (c) hybrid IMRT (open conformal+modulated fields). Over 35 organs were contoured in a whole-body CT scan and organ-specific dose distributions were determined with MC and the TPS. Large differences in out-of-field doses were observed between MC and TPS calculations, even for organs close to the target volume such as the heart, the lungs and the contralateral breast (up to 70% difference). MC simulations showed that a large fraction of the out-of-field dose comes from the out-of-field head scatter fluence (>40%) which is not adequately modeled by the TPS. Based on MC simulations, the 3DCRT technique using external wedges yielded significantly higher doses (up to a factor 4-5 in the pelvis) than the 2DRT and the hybrid IMRT techniques which yielded similar out-of-field doses. In sharp contrast to popular belief, the IMRT technique investigated here does not increase the out-of-field dose compared to conventional techniques and may offer the most optimal plan. The 3DCRT technique with external wedges yields the largest out-of-field doses. For accurate out-of-field dose assessment, a commercial TPS should not be used, even for organs near the target volume (contralateral breast, lungs, heart).
Resumo:
This dissertation aims to investigate empirical evidence on the importance and influence of attractiveness of nations in global competition. The notion of country attractiveness, which has been widely developed in the research areas of international business, tourism and migration, is a multi-dimensional construct to measure a country's characteristics with regard to its market or destination that attract international investors, tourists and migrants. This analytical concept provides an account of the mechanism as to how potential stakeholders evaluate more attractive countries based on certain criteria. Thus, in the field of international sport-event bidding, do international sport event owners also have specific country attractiveness for their sport event hosts? The dissertation attempts to address this research question by statistically assessing the effects of country attractiveness on the success of strategy for hosting international sports events. Based on theories of signaling and soft power, country attractiveness is defined and measured as the three dimensions of sustainable development: economic, social, and environmental attractiveness. This thesis proceeds to examine the concept of sport-event-hosting strategy and explore multi-level factors affecting the success in international sport-event bidding. By exploring past history of the Olympic Movement from theoretical perspectives, the thesis proposes and tests the hypotheses that economic, social and environmental attractiveness of a country may be correlated with its bid wins or the success of sport-event-hosting strategy. Quantitative analytical methods with various robustness checks are employed with using collected data on bidding results of major events in Olympic sports during the period from 1990 to 2012. The analysis results reveal that event owners of international Olympic sports are likely to prefer countries that have higher economic, social, and environmental attractiveness. The empirical assessment of this thesis suggests that high country attractiveness can be an essential element of prerequisites for a city/country to secure in order to bid with an increased chance of success.
Resumo:
Brain inflammatory response is triggered by the activation of microglial cells and astrocytes in response to various types of CNS injury, including neurotoxic insults. Its outcome is determined by cellular interactions, inflammatory mediators, as well as trophic and/or cytotoxic signals, and depends on many additional factors such as the intensity and duration of the insult, the extent of both the primary neuronal damage and glial reactivity and the developmental stage of the brain. Depending on particular circumstances, the brain inflammatory response can promote neuroprotection, regeneration or neurodegeneration. Glial reactivity, regarded as the central phenomenon of brain inflammation, has also been used as an early marker of neurotoxicity. To study the mechanisms underlying the glial reactivity, serum-free aggregating brain cell cultures were used as an in vitro model to test the effects of conventional neurotoxicants such as organophosphate pesticides, heavy metals, excitotoxins and mycotoxins. This approach was found to be relevant and justified by the complex cell-cell interactions involved in the brain inflammatory response, the variability of the glial reactions and the multitude of mediators involved. All these variables need to be considered for the elucidation of the specific cellular and molecular reactions and their consequences caused by a given chemical insult.
Resumo:
Aim of the present article was to perform three-dimensional (3D) single photon emission tomography-based dosimetry in radioimmunotherapy (RIT) with (90)Y-ibritumomab-tiuxetan. A custom MATLAB-based code was used to elaborate 3D images and to compare average 3D doses to lesions and to organs at risk (OARs) with those obtained with planar (2D) dosimetry. Our 3D dosimetry procedure was validated through preliminary phantom studies using a body phantom consisting of a lung insert and six spheres with various sizes. In phantom study, the accuracy of dose determination of our imaging protocol decreased when the object volume decreased below 5 mL, approximately. The poorest results were obtained for the 2.58 mL and 1.30 mL spheres where the dose error evaluated on corrected images with regard to the theoretical dose value was -12.97% and -18.69%, respectively. Our 3D dosimetry protocol was subsequently applied on four patients before RIT with (90)Y-ibritumomab-tiuxetan for a total of 5 lesions and 4 OARs (2 livers, 2 spleens). In patient study, without the implementation of volume recovery technique, tumor absorbed doses calculated with the voxel-based approach were systematically lower than those calculated with the planar protocol, with average underestimation of -39% (range from -13.1% to -62.7%). After volume recovery, dose differences reduce significantly, with average deviation of -14.2% (range from -38.7.4% to +3.4%, 1 overestimation, 4 underestimations). Organ dosimetry in one case overestimated, in the other underestimated the dose delivered to liver and spleen. However, both for 2D and 3D approach, absorbed doses to organs per unit administered activity are comparable with most recent literature findings.
Resumo:
Previous work has shown that aggregating fetal brain cell cultures are able to attain a highly differentiated state, and that their development is greatly enhanced by growth and/or differentiation factors such as epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), and the protein kinase C-activating tumor promoter mezerein. The present study shows that in these 3-dimensional cultures the peptide growth factors EGF and bFGF as well as mezerein are able to induce the expression of the proto-oncogene c-fos. This induction was rapid and transient, in good agreement with observations reported from a wide variety of cell types in vitro. The maximal levels of c-fos mRNA found after stimulation were low in immature cultures and increased greatly as maturation progressed. Of the three factors tested, mezerein was the most potent inducer of c-fos. In contrast to the peptide growth factors EGF and bFGF which were found to induce c-fos only in glial cells, mezerein was stimulatory in glial cells as well as in neurons. A similar cell type specificity has been observed previously for the maturation-enhancing response in immature aggregate cultures. However, in the present study no correlation was found between the degree of c-fos induction and the extent of the maturation-enhancing stimulation. Immature cultures known to be most sensitive and responsive to these maturation-enhancing agents required relatively high doses of peptide growth factors for the induction of c-fos, and the maximal levels of c-fos mRNA elicited were much lower than those in differentiated cultures which did not show any long-term response to these stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)
Resumo:
RÉSUMÉ : Le bullying est un type de comportement agressif qu'un élève (ou plusieurs) fait subir à un autre et qui se manifeste par des agressions verbales, physiques et/ou psychologiques. Les caractéristiques du bullying sont la répétitivité d'actions négatives sur le long terme et une relation de pouvoir asymétrique. Pour la victime, ce type de comportement peut avoir des conséquences graves telles qu'échec scolaire, dépression, troubles alimentaires, ou idées suicidaires. De plus, les auteurs de bullying commettent plus de comportements déviants au sein de l'école ou à l'extérieur de cette dernière. La mise en place d'actions ciblées auprès des auteurs de bullying pourrait donc non seulement prévenir une victimisation, mais aussi réduire les actes de délinquance en général. Hormis quelques études locales ou cantonales, aucune recherche nationale auprès d'adolescents n'existait dans le domaine. Ce travail propose de combler cette lacune afin d'obtenir une compréhension suffisante du phénomène qui permet de donner des pistes pour définir des mesures de prévention appropriées. Afin d'appréhender la problématique du bullying dans les écoles secondaires suisses, deux sondages de délinquance juvénile autoreportée ont été effectués. Le premier a eu lieu entre 2003 et 2005 dans le canton de Vaud auprès de plus de 4500 écoliers. Le second a été administré en 2006 dans toute la Suisse et environ 3600 jeunes y ont participé. Les jeunes ont répondu au sondage soit en classe (questionnaire papier) soit en salle d'informatique (questionnaire en ligne). Les jeunes ayant répondu avoir sérieusement harcelé un autre élève est d'environ 7% dans le canton de Vaud et de 4% dans l'échantillon national. Les analyses statistiques ont permis tout d'abord de sélectionner les variables les plus fortement liées au bullying. Les résultats montrent que les jeunes avec un bas niveau d'autocontrôle et ayant une attitude positive envers la violence sont plus susceptibles de commettre des actes de bullying. L'importance des variables environnementales a aussi été démontrée: plus le jeune est supervisé et encadré par des adultes, plus les autorités (école, voisinage) jouent leur rôle de contrôle social en faisant respecter les règles et en intervenant de manière impartiale, moins le jeune risque de commettre des actes de bullying. De plus, l'utilisation d'analyses multiniveaux a permis de montrer l'existence d'effets de l'école sur le bullying. En particulier, le taux de bullying dans une école donnée augmente lorsque les avis des jeunes divergent par rapport à leur perception du climat scolaire. Un autre constat que l'on peut mettre en évidence est que la réaction des enseignants lors de bagarres a une influence différente sur le taux de bullying en fonction de l'établissement scolaire. ABSTRACT : Bullying is the intentional, repetitive or persistent hurting of one pupil by another (or several), where the relationship involves an imbalance of power. Bullying is a type of aggressive behaviour and the act can be verbal, physical and/or psychological. The consequences on the victims are serious: school failure, depressive symptomatology, eating disorders, or suicidal ideation. Moreover, the authors of bullying display more delinquent behaviour within or outside the school. Thus, preventive programmes targeting bullying could not only prevent victimisation, but also reduce delinquency in general. Very little data concerning bullying had been collected in Switzerland and, except some local or cantonal studies, no national research among teenagers existed in the field. This work intends to fill the gap in order to provide sufficient understanding of the phenomenon and to suggest some tracks for defining appropriate measures of prevention. In order to understand the problems of bullying in Swiss secondary schools better, two surveys of self-reported juvenile delinquency were carried out. The first one took place between 2003 and 2005 in the canton Vaud among more than 4500 pupils, the second in 2006 across Switzerland with about 3600 youths taking part. The pupils answered to the survey either in the classroom (paper questionnaire) or in the computer room (online questionnaire). The youths that answered having seriously bullied another pupil are about 7% in canton Vaud and 4% in the national sample. Statistical analyses have selected the variables most strongly related to bullying. The results show that the youths with a low level of self-control and adopting a positive attitude towards violence are more likely to bully others. The importance of the environmental variables was also shown: the more that youth is supervised and monitored by adults, and the more the authorities (school, neighbourhood) play their role of social control by making the rules be respected through intervening in an impartial way, the less the youth bully. Moreover, the use of multilevel analyses permitted to show the existence of effects of the school on bullying. In particular, the rate of bullying in a given school increases when there is a wide variation among students of the same school in their perception of their school climate. Another important aspect concerns teachers' reactions when pupils fight: this variable does not influence the bullying rate to the same extent, and depends on the school.
Resumo:
BACKGROUND: We retrospectively reviewed the long-term outcome and late side effects of endometrial cancer (EC) patients treated with different techniques of postoperative radiotherapy (PORT). METHODS: Between 1999 and 2012, 237 patients with EC were treated with PORT. Two-dimensional external beam radiotherapy (2D-EBRT) was used in 69 patients (30 %), three-dimensional EBRT (3D-EBRT) in 51 (21 %), and intensity-modulated RT (IMRT) with helical Tomotherapy in 47 (20 %). All patients received a vaginal brachytherapy (VB) boost. Seventy patients (29 %) received VB alone. RESULTS: After a median of 68 months (range, 6-154) of follow-up, overall survival was 75 % [95 % confidence interval (CI), 69-81], disease-free survival was 72 % (95% CI, 66-78), cancer-specific survival was 85 % (95 % CI, 80-89), and locoregional control was 86 % (95 % CI, 81-91). The 5-year estimates of grade 3 or more toxicity and second cancer rates were 0 and 7 % (95 % CI, 1-13) for VB alone, 6 % (95 % CI, 1-11) and 0 % for IMRT + VB, 9 % (95 % CI, 1-17) and 5 % (95 % CI, 1-9) for 3D-EBRT + VB, and 22 % (95 % CI, 12-32) and 12 % (95 % CI, 4-20) for 2D-EBRT + VB (P = 0.002 and P = 0.01), respectively. CONCLUSIONS: Pelvic EBRT should be tailored to patients with high-risk EC because the severe late toxicity observed might outweigh the benefits. When EBRT is prescribed for EC, IMRT should be considered, because it was associated with a significant reduction of severe late side effects.
Resumo:
We performed an analysis of a substudy of the randomized Tamoxifen Exemestane Adjuvant Multinational trial to determine the effects of exemestane (EXE) and tamoxifen (TAM) adjuvant treatment on bone mineral density (BMD) measured by dual-energy X-ray absorptiometry compared with the trabecular bone score, a novel grey-level texture measurement that correlates with 3-dimensional parameters of bone texture in postmenopausal women with hormone receptor-positive breast cancer for the first time. In total, 36 women were randomized to receive TAM (n = 17) or EXE (n = 19). Patients receiving TAM showed a mean increase of BMD in lumbar spine from baseline of 1.0%, 1.5%, and 1.9% and in trabecular bone score of 2.2%, 3.5%, and 3.3% at 6-, 12-, and 24-mo treatment, respectively. Conversely, patients receiving EXE showed a mean decrease from baseline in lumbar spine BMD of -2.3%, -3.6%, and -5.3% and in trabecular bone score of -0.9%, -1.7%, and -2.3% at 6-, 12-, and 24-mo treatment, respectively. Changes in trabecular bone score from baseline at spine were also significantly different between EXE and TAM: p = 0.05, 0.007, and 0.006 at 6, 12, and 24mo, respectively. TAM induced an increase in BMD and bone texture analysis, whereas EXE resulted in decreases. The results were independent from each other.