Elimination of Interface Energy Barriers Using Dendrimer Polyelectrolytes with Fractal Geometry.

In this work we study conjugated polyelectrolyte (CPE) films based on polyamidoamine (PAMAM) dendrimers of generations G1 and G3. These fractal macromolecules are compared to branched polyethylenimine (b-PEI) polymer using methanol as the solvent. All of these materials present a high density of amino groups, which protonated by methoxide counter-anions create strong dipolar interfaces. The vacuum level shift associated to these films on n-type silicon was 0.93 eV for b-PEI, 0.72 eV for PAMAM G1 and 1.07 eV for PAMAM G3. These surface potentials were enough to overcome Fermi level pinning, which is a typical limitation of aluminium contacts on n-type silicon. A specific contact resistance as low as 20 mΩ·cm2 was achieved with PAMAM G3, in agreement with the higher surface potential of this material. Good electron transport properties were also obtained for the other materials. Proof-of-concept silicon solar cells combining vanadium oxide as a hole-selective contact with these new electron transport layers have been fabricated and compared. The solar cell with PAMAM G3 surpassed 15% conversion efficiency with an overall increase of all the photovoltaic parameters. The performance of these devices correlates with compositional and nanostructural studies of the different CPE films. Particularly, a figure-of-merit (Vσ) for CPE films that considers the number of protonated amino groups per macromolecule has been introduced. The fractal geometry of dendrimers leads to a geometric increase in the number of amino groups per generation. Thus, investigation of dendrimer macromolecules seems a very good strategy to design CPE films with enhanced charge-carrier selectivity.

Immunoglobulin production in man stimulated by an orally administered bacterial lysate.

The concentrations of secretory immunoglobulins in the saliva, and of immunoglobulin in the serum, have been measured by the radial immunodiffusion method in 12 healthy volunteers, before and after oral administration of Broncho-Vaxom which is a lysate of bacteria that usually cause infection in the upper respiratory tract. The mean concentration of secretory IgA in the saliva was increased by over 100% after the 10-day administration of the product. This increase was statistically significant between the 20th and 33rd day after the beginning of the treatment (p < 0.05). It fell to a normal level after a month in 4 subjects who received one treatment course only. In 8 subjects who received a second treatment course beginning 1 month after termination of the first course, the high concentration of IgAs in the saliva persisted for at least 3 months. A significant increase in the serum concentrations of IgG of about 50% and of IgM of at least 100% above the initial level was observed in the treated subjects in the time between day 35 and 5 months after the beginning of the experiment (p < 0.05).

Immunologic impairment in patients with non-lymphoid cancer: correlation with the tumoral stage, response to treatment and survival.

The cellular immunity has been studied in 121 patients by solid nonlymphoid tumors, and in 50 healthy patients, 11 with benign tumors, with the use of techniques of in vivo dinitrochlorobenzene (DNCB) and in vitro lymphocyte response to phytohemagglutinin to observe the correlation between both tests and the clinical stage of the disease, the response to chemotherapy and surgery, prognosis, and survival. Patients with anergy presented tumoral irresectability, lack of response to chemotherapy, advanced disease, and limited survival. In the patients with good immune response, the disease was limited, responding with greater frequency to therapy and presenting a higher rate of survival. Consequently, the immunologic study of a neoplastic patient can guide us toward a therapeutic behavior and a prognosis.