The Anticancer Activity of Organotelluranes: Potential Role in Integrin Inactivation

Organic Te^IV compounds (organotelluranes) differing in their labile ligands exhibited anti‐integrin activities in vitro and anti‐metastatic properties in vivo. They underwent ligand substitution with l ‐cysteine, as a thiol model compound. Unlike inorganic Te^IV compounds, the organotelluranes did not form a stable complex with cysteine, but rather immediately oxidized it. The organotelluranes inhibited integrin functions, such as adhesion, migration, and metalloproteinase secretion mediation in B16F10 murine melanoma cells. In comparison, a reduced derivative with no labile ligand inhibited adhesion of B16F10 cells to a significantly lower extent, thus pointing to the importance of the labile ligands of the Te^IV atom. One of the organotelluranes inhibited circulating cancer cells in vivo, possibly by integrin inhibition. Our results extend the current knowledge on the reactivity and mechanism of organotelluranes with different labile ligands and highlight their clinical potential.     

Comparative Study of Microwave Sintering of Zinc Oxide at 2.45, 30, and 83 GHz

Temperature gradients that develop in ceramic materials during microwave heating are known to be strongly dependent on the applied microwave frequency. To gain a better understanding of this dependence, identical samples of ZnO powder compacts were microwave heated at three distinct widely separated frequencies of 2.45, 30, and 83 GHz and the core and surface temperatures were simultaneously monitored. At 2.45 GHz, the approximately uniform volumetric heating tends to raise the temperature of the sample as a whole, but the interior becomes hotter than the exterior because of heat loss from the surface. At 30 and 83 GHz, this interior to exterior temperature difference was found to be reversed, especially for high heating rates. This reversal resulted from increased energy deposition close to the sample's surface associated with reduced skin depth. A model for solving Maxwell's equations was incorporated into a newly developed two-dimensional (2-D) heat transport simulation code. The numerical simulations are in agreement with the experimental results. Simultaneous application of two or more widely separated frequencies is expected to allow electronic tailoring of the temperature profile during sintering.     

Bond to Concrete of FRP Rebars after Cyclic Loading

The bond mechanism of fiber-reinforced polymer (FRP) rebars to concrete was studied to evaluate the effect of cyclic loading. Five different types of 12.0- and 12.7-mm rebars were tested. The FRP rods were embedded in concrete blocks and were subjected to up to 450,000 cycles at service stress level. The loading was accompanied by immersion in water at 60 and 20°C to accelerate deterioration effects. Pullout behavior of the rods was determined at the end of the loading period. The results indicated a reduction in the bond strength after loading. Three mechanisms of failure were identified: (1) Abrasion of the surface of the rod, which, in the case of uniform resin throughout the rod, may lead to a reduction of 20–30% in the bond strength; (2) delamination of the outer layer of the resin at the surface of the rod, which may lead to a reduction of up to 60% in the bond strength; and (3) abrasion of cement particles entrapped between the rod and the concrete, which serves as the main source of “bond” for smooth rods leading to approximately 70% of reduction in the bond strength. There was no significant change in the effect of curing temperature on the loss of bond.     

The combined effect of radiation and carbonation on the immobilization of Sr and Cs ions in cementitious pastes

In the present study the effect of gamma irradiation on the transport of immobilized Sr and Cs ions in cementitious paste samples is described. During the irradiation process, the samples were exposed to atmospheric conditions. Hence, atmospheric carbonation of samples could takes place. Cementitious pastes, differing in their w/c ratio (0.3, 0.45), were exposed to an integral dose of 10⁷ grays (Gy) of γ irradiation during a period of approximately 6 months. The effect of irradiation on the transport properties of the immobilized Sr and Cs ions was studied by leaching experiments. The carbonation depth of the different samples was measured and found to markedly increase in the case of irradiated samples compared to samples not exposed to irradiation. The enhanced carbonation is associated with the dehydration due to radiolysis of pore water in the paste. It was found that the irradiation resulted in a marked decrease in the leached fraction of Sr ions. This is related to the increased carbonation found for the irradiated samples. On the other hand, a small increase in Cs diffusivity was found for irradiated samples. This increase in leachability might be associated with the formation of microcracks in the irradiated sample.     

Facilitating data exploration with query previews: a study of user performance and preference

Networked and local data exploration systems that use command languages, menus, or form fill-in interfaces rarely give users an indication of the distribution of data. This often leads users to waste time, posing queries that have zero-hit or mega-hit results. Query previews are a novel visual approach for browsing databases. Query previews supply users with data distribution information for selected attributes of the database, and give continuous feedback about the size of the result set as the query is being formed. Subsequent refinements might be necessary to narrow the search. As there is a risk that query previews are an additional step, leading to a more complex and slow search process, a within-subjects empirical study was ran with 12 subjects who used interfaces with and without query previews and with minimized network delays. Even with 12 subjects and minimized network delays statistically significant differences were found, showing that query previews could speed up performance 1.6 to 2.1 times and lead to higher user satisfaction.     

The role of floor control and of ontology in argumentative activities with discussion-based tools

Argumentative activity has been found beneficial for construction of knowledge and evaluation of information in some conditions. Many theorists in CSCL and some empiricists have suggested that graphical representations may help in this endeavor. In the present study, we examine effects of type of ontology and of synchronicity in students that engage intuitively, without training, in e-discussions. Fifty-four Grade 7 students from two classes participated in the study. We tested the effects of using an informal argumentative ontology and control over turn taking on the average number of claims and arguments relevant to the issue at stake, the average number of different types of references to peers (productive. etc.), and on the number of chat expressions (nicknames, swear words, etc.). We found that when providing both an informal argumentative ontology and control over turn taking, students express less chat expressions and fewer references that are not new relevant claims or arguments to their peers, but express more relevant claims and arguments. These findings suggest the immediate beneficial role of the combination of an informal ontology and control over turn taking in the co-elaboration of knowledge.     

On the Relationship Between the Support Vector Machine for Classification and Sparsified Fisher's Linear Discriminant

We show that the orientation and location of the separating hyperplane for 2-class supervised pattern classification obtained by the Support Vector Machine (SVM) proposed by Vapnik and his colleagues, is equivalent to the solution obtained by Fisher's Linear Discriminant on the set of Support Vectors. In other words, SVM can be seen as a way to sparsify Fisher's Linear Discriminant in order to obtain the most generalizing classification from the training set.