Controlling Near-Surface Ni Composition in Octahedral PtNi(Mo) Nanoparticles by Mo Doping for a Highly Active Oxygen Reduction Reaction Catalyst.

We report and study the translation of exceptionally high catalytic oxygen electroreduction activities of molybdenum-doped octahedrally shaped PtNi(Mo) nanoparticles from conventional thin-film rotating disk electrode screenings (3.43 ± 0.35 A mgPt-1 at 0.9 VRHE) to membrane electrode assembly (MEA)-based single fuel cell tests with sustained Pt mass activities of 0.45 A mgPt-1 at 0.9 Vcell, one of the highest ever reported performances for advanced shaped Pt alloys in real devices. Scanning transmission electron microscopy with energy dispersive X-ray analysis (STEM-EDX) reveals that Mo preferentially occupies the Pt-rich edges and vertices of the element-anisotropic octahedral PtNi particles. Furthermore, by combining in situ wide-angle X-ray spectroscopy, X-ray fluorescence, and STEM-EDX elemental mapping with electrochemical measurements, we finally succeeded to realize high Ni retention in activated PtNiMo nanoparticles even after prolonged potential-cycling stability tests. Stability losses at the anodic potential limits were mainly attributed to the loss of the octahedral particle shape. Extending the anodic potential limits of the tests to the Pt oxidation region induced detectable Ni losses and structural changes. Our study shows on an atomic level how Mo adatoms on the surface impact the Ni surface composition, which, in turn, gives rise to the exceptionally high experimental catalytic ORR reactivity and calls for strategies on how to preserve this particular surface composition to arrive at performance stabilities comparable with state-of-the-art spherical dealloyed Pt core-shell catalysts.

The virus susceptibility of skin-derived fibroblasts from families with insulin-dependent diabetes mellitus.

We have studied the growth of eight different viruses on skin fibroblasts from three families each having one or more diabetic members and appropriate controls. The haplotypes of all of the family members had been previously characterized. In addition, we have investigated the growth of mumps virus on the lymphoblast cultures from four families of the same type. Our results show no difference between the growth of these viruses in cells derived from juvenile diabetics and cells derived from nondiabetic siblings and parents even when the haplotypes were identical. However, we noted a striking resistance of human skin fibroblast cultures from both normal and diabetic individuals to Coxsackie B virus infection.

Human skin fibroblasts are nonpermissive to coxsackie B4 infection: an age-dependent phenomenon.

Human skin fibroblasts were previously shown to be resistant to coxsackie B4 virus infection. We have cultured fibroblasts from skin and lung tissues of donors of various ages. By a novel method for direct assay of virus absorption and penetration, we have shown that skin fibroblasts from young fetuses are susceptible to coxsackie B4 infection, whereas those from older fetuses, children and adults are not and that this refractoriness is caused by a tissue-specific block to virus penetration.

Demonstration of immunoglobulin G receptors induced by human cytomegalovirus.

Human cytomegalovirus induced a new immunoglobulin G receptor in human fibroblasts. The immunoglobulin G receptor was well localized in the perinuclear region at 48 h postinfection, and antiviral agents blocked its synthesis. The immunoglobulin G receptor bound immunoglobulin G of man and several other species. It may be a source of error in the performance of indirect fluorescence tests for human cytomegalovirus antibody.