Tools for micropatterning epithelial cells into microcolonies on transwell filter substrates

Despite the importance of epithelial tissue in most major organs there have been limited attempts to tissue engineer artificial epithelium. A key feature of mature epithelium is the presence of an apical-basal polarization, which develops over 7-20 days in culture. Currently, the most widely used 2D system to generate polarized epithelium in vitro involves the filter insert culture system, however this system is expensive, laborious and requires large numbers of cells per sample. We have developed a set of micropatterning techniques to spatially control the organization of epithelial cells into microsheets on filter inserts under the culture conditions necessary to induce epithelial cell polarization. Micropatterning improves cell uniformity within each microsheet, allows multiple sheet analysis on one filter insert, and reduced cell number requirements. We describe an agarose patterning method that allows maintenance of cell patterns for over 15 days, the time necessary to induce apical-basal polarization. We also describe a Parafilm? patterning method that allows patterning for 5 to 15 days depending on cell type and only allows the generation of stripes and circular microsheets. The parafilm? method however is extremely straightforward and could be easily adopted by any laboratory without the need of access to specialized microfabrication equipment. We also demonstrate that micropatterning epithelial cells does not alter the localization of the apical-basal marker ZO-1 or the formation of cilia, a marker of epithelium maturation. Our methods provide a novel tool for studying epithelial biology in polarized epithelium microsheets of controlled size.     

Relaxation times effects on the four wave-mixing signal for π-conjugated push-pull molecules within the two-state valence-bond charge-transfer model

We have theoretically studied the four wave-mixing signal for π-conjugated push-pull molecules in the context of the simple valence-bond charge-transfer model. In particular, we address the effect of modify the rate between the longitudinal and transversal relaxation times on this signal considering the variation of the parameter f (fraction of the charge-transfer resonance structure of the ground state). Our results show notable changes in intensity of the peaks of the four wave-mixing (FWM) spectrum with relation to the variation in the ratio of the relaxation times.     

Linear Key Predistribution Schemes

In a key predistribution scheme, some secret information is distributed among a set of users. For a given family of privileged groups, this secret information must enable every user in a privileged group to compute a common key associated with that group. Besides, this common key must remain unknown to some specified coalitions of users outside the privileged group. We present in this paper a new model, based on linear algebraic techniques, for the design of key predistribution schemes that unifies all previous proposals. This new model provides a common mathematical formulation and a better understanding of key predistribution schemes. Two new families of key predistribution schemes that are obtained by using this model are presented. Those families provide, for some specification structures, schemes that have better information rates than the ones given in previous proposals or fit in situations that have not been considered before.     

Graph-theoretic and algebraic characterizations of some Markov processes

An algebraic decidable condition for a stationary Markov chain to consist of a single ergodic set, and a graph-theoretic decidable condition for a stationary Markov chain to consist of a single ergodic noncyclic set are formulated. In the third part of the paper a graph-theoretic condition for a nonstationary Markov chain to have the weakly-ergodic property is given. The paper is based on part of the author’s work towards the D. Sc. degree.     

Sur un probleme d'optimisation de domaine

Let Ω be a bounded open subset of R ⁿ; with every measurable subset A of Ω is associated the real number En(A), related to capacity (for electrostatic problems) or to heat flux (for problems of thermal conduction). One investigates the minimization of En(A) when the measure of A is imposed. Penalty methods allows one to apply some techniques of convex analysis.     

Straightforward α‐Amino Nitrile Synthesis Through Mo(CO)6‐Catalyzed Reductive Functionalization of Carboxamides

The selective reduction of amides into an intermediate hemiaminal catalyzed by Mo(CO)₆ together with the inexpensive and easy to handle TMDS (1,1,3,3‐tetramethyldisiloxane) as reducing agent, followed by subsequent trapping of the hemiaminal with a cyanide source, allows for the straightforward synthesis of α‐amino nitriles. The methodology presented here, displays high levels of chemoselectivity allowing for the reduction of amides in the presence of functional groups such as ketones, imines, aldehydes, and acids, which affords a simple route for the synthesis of α‐amino nitriles with a broad scope of functionalities in high yields. Furthermore, the applicability of this methodology is demonstrated by scale up experiments and by derivatization of the target compounds into synthetically interesting products. The selective cyanation is successfully applied in late stage functionalizations of amide containing drugs and prolinol derivatives.     

Heterobimetallic Catalysis: Platinum‐Gold‐Catalyzed Tandem Cyclization/C−X Coupling Reaction of (Hetero)Arylallenes with Nucleophiles

Heterobimetallic catalysis offers new opportunities for reactivity and selectivity but still presents challenges, and only a few metal combinations have been explored so far. Reported here is a Pt‐Au heterobimetallic catalyst system for the synthesis of a family of multi‐heteroaromatic structures through tandem cyclization/C?X coupling reaction. Au‐catalyzed 6‐endo‐cyclization takes place as the first fast step. Pt‐Au clusters are proposed to be responsible for the increased reactivity in the second step, that is, the intermolecular nucleophilic addition which occurs through an outer‐sphere mechanism by hybrid homogeneous‐heterogeneous catalysis.     

Excess enthalpies of ternary mixture consisting of tert-butyl methyl ether, ethanol and heptane

Excess molar enthalpies, measured at 298.15 K in a Calvet microcalorimeter, are reported for {x ₁ tert-butyl methyl ether (MTBE)+x ₂ethanol (EtOH)+(1?x ₁?x ₂)heptane}. Smooth representations of the results are presented and used to construct contant excess molar enthalpy contours on Roozeboom diagrams.