Graphene nanoribbon electrical decoupling from metallic substrates

We address the structural and electronic properties of graphene nanoribbons (GNRs) covalently immobilized on a metallic substrate by means of an organic layer. The GNR–organic layer and organic layer–metal interfaces can be thought of as constituents of a nanodevice and have been accurately studied using large-scale density functional theory calculations. Our results demonstrate the possibility of combining nanopatterned metal–organic layer substrates with selected GNRs to obtain well ordered and stable structures while preserving the GNR energy band gap, an essential requirement for any switching nanodevice

Spontaneous polarization and piezoelectricity in polar molecular crystals

Molecular materials with a polar arrangement of the constituent dipoles are good candidates for exhibiting piezoelectric properties directly related to the strain-induced polarization. We assess, from first principles, the properties of the metal-organic molecular crystal (4-dimethylaminopyridyl)bis(acetylacetato)zinc(II) in presence of strain. The spontaneous polarization and the piezoelectric properties are studied by means of the modern theory of polarization. The cooperative interaction among molecular chains is shown to lead to a collective polarization enhancement effect. Some theoretical issues concerning the multivalued behavior of the Berry phase are also illustrated

Ab initio study of electron affinity variation induced by organic molecule adsorption on the silicon (001) surface

The effect of organic adsorbates on the silicon (001) surface is investigated using first-principles calculations. Ethylene and a class of cyclopentene derivatives, containing different functional groups, are considered, all anchoring to the surface through the same [2+2] cycloaddition mechanism. Because they all show similar bonding properties, any variation in the surface properties must be related to the functional group. The structural relaxation induced by the adsorption is discussed, elucidating the effect of both the adsorbate species and coverage. It turns out that different distortions occur in the molecular geometry, depending on both the species and the surface coverage, while molecule-to-surface bonding does show very similar features for all the considered molecules. We show that the presence of the adsorbate can modify the surface charge density, thus giving rise to an induced dipolar layer that modifies the electrostatic potential outside the surface. Such a dipole layer can, in turn, be related to surface electron affinity and work function changes. A careful analysis of the dipole moment and of the electrostatic potential changes is carried out discussing the correlations with the properties of the isolated molecules. All the results indicate how the surface properties can be tuned through a suitable choice of the adsorbate

Functional analysis via standardized whole-blood stimulation systems defines the boundaries of a healthy immune response to complex stimuli.

International audienceStandardization of immunophenotyping procedures has become a high priority. We have developed a suite of whole-blood, syringe-based assay systems that can be used to reproducibly assess induced innate or adaptive immune responses. By eliminating preanalytical errors associated with immune monitoring, we have defined the protein signatures induced by (1) medically relevant bacteria, fungi, and viruses; (2) agonists specific for defined host sensors; (3) clinically employed cytokines; and (4) activators of T cell immunity. Our results provide an initial assessment of healthy donor reference values for induced cytokines and chemokines and we report the failure to release interleukin-1α as a common immunological phenotype. The observed naturally occurring variation of the immune response may help to explain differential susceptibility to disease or response to therapeutic intervention. The implementation of a general solution for assessment of functional immune responses will help support harmonization of clinical studies and data sharing