25 research outputs found
A limit model for thermoelectric equations
We analyze the asymptotic behavior corresponding to the arbitrary high
conductivity of the heat in the thermoelectric devices. This work deals with a
steady-state multidimensional thermistor problem, considering the Joule effect
and both spatial and temperature dependent transport coefficients under some
real boundary conditions in accordance with the Seebeck-Peltier-Thomson
cross-effects. Our first purpose is that the existence of a weak solution holds
true under minimal assumptions on the data, as in particular nonsmooth domains.
Two existence results are studied under different assumptions on the electrical
conductivity. Their proofs are based on a fixed point argument, compactness
methods, and existence and regularity theory for elliptic scalar equations. The
second purpose is to show the existence of a limit model illustrating the
asymptotic situation.Comment: 20 page
Apoptosis Inducing Effect of Plumbagin on Colonic Cancer Cells Depends on Expression of COX-2
Plumbagin, a quinonoid found in the plants of the Plumbaginaceae, possesses
medicinal properties. In this study we investigated the anti-proliferative and
apoptotic activity of plumbagin by using two human colonic cancer cell lines,
HT29 and HCT15. IC50 of Plumbagin for HCT15 and HT29 cells (22.5 µM and
62.5 µM, respectively) were significantly different. To study the response
of cancer cells during treatment strategies, cells were treated with two
different concentrations, 15 µM, 30 µM for HCT15 and 50 µM, 75
µM for HT29 cells. Though activation of NFκB, Caspases-3, elevated
levels of TNF-α, cytosolic Cytochrome C were seen in both
HCT15 cells HT29 treated with plumbagin, aberrant apoptosis with decreased level
of pEGFR, pAkt, pGsk-3β, PCNA and Cyclin D1was observed only in 15 µM
and 30 µM plumbagin treated HCT15 and 75 µM plumbagin treated HT29
cells. This suggests that plumbagin induces apoptosis in both HCT15 cells and
HT29 treated, whereas, proliferation was inhibited only in 15 µM and 30
µM plumbagin treated HCT15 and 75 µM plumbagin treated HT29 cells,
but not in 50 µM plumbagin treated HT29 cells. Expression of COX-2 was
decreased in 75 µM plumbagin treated HT29 cells when compared to 50
µM plumbagin treated HT29 cells, whereas HCT15 cells lack COX. Hence the
observed resistance to induction of apoptosis in 50 µM plumbagin treated
HT29 cells are attributed to the expression of COX-2. In conclusion, plumbagin
induces apoptosis in colonic cancer cells through TNF-α mediated pathway
depending on expression of COX-2 expression
High levels of microRNA-21 in the stroma of colorectal cancers predict short disease-free survival in stage II colon cancer patients
Approximately 25% of all patients with stage II colorectal cancer will experience recurrent disease and subsequently die within 5 years. MicroRNA-21 (miR-21) is upregulated in several cancer types and has been associated with survival in colon cancer. In the present study we developed a robust in situ hybridization assay using high-affinity Locked Nucleic Acid (LNA) probes that specifically detect miR-21 in formalin-fixed paraffin embedded (FFPE) tissue samples. The expression of miR-21 was analyzed by in situ hybridization on 130 stage II colon and 67 stage II rectal cancer specimens. The miR-21 signal was revealed as a blue chromogenic reaction, predominantly observed in fibroblast-like cells located in the stromal compartment of the tumors. The expression levels were measured using image analysis. The miR-21 signal was determined as the total blue area (TB), or the area fraction relative to the nuclear density (TBR) obtained using a red nuclear stain. High TBR (and TB) estimates of miR-21 expression correlated significantly with shorter disease-free survival (p = 0.004, HR = 1.28, 95% CI: 1.06–1.55) in the stage II colon cancer patient group, whereas no significant correlation with disease-free survival was observed in the stage II rectal cancer group. In multivariate analysis both TB and TBR estimates were independent of other clinical parameters (age, gender, total leukocyte count, K-RAS mutational status and MSI). We conclude that miR-21 is primarily a stromal microRNA, which when measured by image analysis identifies a subgroup of stage II colon cancer patients with short disease-free survival
PREPARATION OF ULTRA FINE GRAINED MAGNESIA CERAMICS AND THE TEMPERATURE AND POROSITY DEPENDENCE OF THEIR FRACTURE BEHAVIOUR
Des polycristaux de magnésie à grains fins ont été élaborés à 900°C, à partir d'une poudre d'hydroxyde de magnésium, par une technique de frittage réaction sous charge. La vitesse de densification est discutée en termes de déformation superplastique. La résistance à la flexion ainsi que l'énergie effective de surface pour l'initiation de la fracture, γi, ont été déterminées en fonction de la porosité entre la température ambiante et 1200°C. On observe une augmentation rapide de γi avec la température au dessus de 800°C. Ce comportement est à rapprocher de l'observation d'une déformation de type superplastique dans ces domaines de température et taille de grain.Fine grain polycrystals of MgO have been prepared from a Mg (OH)2 powder by reactive hot-pressing at 900°C. The densification rate is discussed in terms of superplastic deformation. The bend strength and the effective surface energy for fracture initiation γi have been determined as a function of porosity between room temperature and 1200°C. A rapid increase in γi with temperature is observed above 800°C. This behaviour is related to the observation of a superplastic deformation in these temperature and grain size ranges
Etude de la redistribution des phases dans des Matériaux Duplex Alumine-Zircone Déformés Superplastiquement
Au cours de la déformation superplastique de matériaux biphasés alumine-zircone, le mécanisme d'intercalation de grains entre les deux types de phases a été mis en évidence. Il se produit par formation d'une protubérance, au niveau d'un nœud triple, sur un grain d'une phase et pénétration de celle-ci dans un joint séparant deux grains de l'autre phase. La séparation complète des deux grains conduit à un changement de voisinage des grains qui a été étudié pour chaque phase. On montre en particulier que ces intercalations entraîne la croissance d'aggrégats de grains d'alumine.During the superplastic deformation of alumina-zirconia ceramics, the way how the intercalation mechanism between grains of the two phases occurred has been put forward. It correspond to the formation of a protuberance on a grain of one of the phases, located at a triple junction, which grew by penetrating in the boundary separating two grains of the other phase. When these grains are completely separated, a change in the grain surroundings has occurred that has been studied. It has been observed that the intercalations favoured the growth of alumina clusters