Rheological,mechanical, thermal and electrical properties of UHMWPE/CNC composites

Cellulose - In this work, composites of ultra high molecular weight polyethylene (UHMWPE) and various loadings of cellulose nanocrystals (CNCs) were prepared exploiting different methods. Besides,...     

Quadratic Bolza Problems in Static Spacetimes with Critical Asymptotic Behavior

The aim of this paper is to investigate the existence of trajectories under the action of an external field in a (standard) static spacetime when both the growth of the potential and that one of the coefficient of the metric are critical. Supported by M.I.U.R. (research funds ex 40% and 60%).     

Microfluidic biofunctionalisation protocols to form multi‐valent interactions for cell rolling and phenotype modification investigations

In this study, we propose a fast, simple method to biofunctionalise microfluidic systems for cellomic investigations based on micro‐fluidic protocols. Many available processes either require expensive and time‐consuming protocols or are incompatible with the fabrication of microfluidic systems. Our method differs from the existing since it is applicable to an assembled system, uses few microlitres of reagents and it is based on the use of microbeads. The microbeads have specific surface moieties to link the biomolecules and couple cell receptors. Furthermore, the microbeads serve as arm spacer and offer the benefit of the multi‐valent interaction. Microfluidics was adapted together with topology and biochemistry surface modifications to offer the microenvironment for cellomic studies. Based on this principle, we exploit the streptavidin–biotin interaction to couple antibodies to the biofunctionalised microfluidic environment within 5 h using 200 μL of reagents and biomolecules. We selected the antibodies able to form complexes with the MHC class I (MHC‐I) molecules present on the cell membrane and involved in the immune surveillance. To test the microfluidic system, tumour cell lines (RMA) were rolled across the coupled antibodies to recognise and strip MHC‐I molecules. As result, we show that cell rolling performed inside a microfluidic chamber functionalised with beads and the opportune antibody facilitate the removal of MHC class I molecules. We showed that the level of median fluorescent intensity of the MHC‐I molecules is 300 for cells treated in a not biofunctionalised surface. It decreased to 275 for cells treated in a flat biofunctionalised surface and to 250 for cells treated on a surface where biofunctionalised microbeads were immobilised. The cells with reduced expression of MHC‐I molecules showed, after cytotoxicity tests, susceptibility 3.5 times higher than normal cells.     

The viscoelasticity of thermotropic liquid crystalline polymers: effects of the chemical composition

In this work, the rheological properties of the wholly aromatic random copolyester HBA/HNA (60/40), the commercial copolyesteramide Vectra B950, and the semiflexible commercial copolyester Rodrun 3000, PET/HBA 40/60, were investigated. All the thermotropic liquid crystalline polymers (TLCPs) show linear viscoelastic behavior at small strain amplitudes. The strain sweep experiments have clearly indicated that the onset for non linearity significantly decreases as the applied frequency increases in all the TLCPs here studied, independent of chemical composition and flexibility. In the case of the Vectra B950, a strain-hardening effect occurred at a strain of about 40% for all the applied frequencies. The frequency behavior showed that the HBA/HNA 60/40 TLCP is characterized by the leveling off of G′ and by a dominant elastic behavior at low frequencies. The inclusion of the flexible PET determines the disappearance of the plateau value for G′ with a viscous response at low frequencies.Paper presented at the Annual Meeting of the European Society of Rheology, Grenoble, April 2005.     

Periodic trajectories with fixed energy on Riemannian and Lorentzian manifolds with boundary

We state some existence and multiplicity results for periodic solutions with prescribed energy of a Lagrangian system and for closed geodesics on Riemannian manifolds convex close to their boundary. As an application we get the existence and multiplicity of periodic trajectories with fixed energy on a class of physically important Lorentzian manifolds with boundary. Entrata in Redazione il 23 aprile 1998. Part of the Ph.D. thesis of this author is contained in this paper. Partially supported by MEC grant PB97-0784-C03-01.