40 research outputs found
Excellent Catalytic Effects of Graphene Nanofibers on Hydrogen Release of Sodium alanate
One of the most technically challenging barriers to the
widespread commercialization of hydrogen-fueled
devices and vehicles remains hydrogen storage. More environmentally
friendly and effective nonmetal catalysts are required to improve
hydrogen sorption. In this paper, through a combination of experiment
and theory, we evaluate and explore the catalytic effects of layered
graphene nanofibers toward hydrogen release of light metal hydrides
such as sodium alanate. Graphene nanofibers, especially the helical
kind, are found to considerably improve hydrogen release from NaAlH<sub>4</sub>, which is of significance for the further enhancement of
this practical material for environmentally friendly and effective
hydrogen storage applications. Using density functional theory, we
find that carbon sheet edges, regardless of whether they are of zigzag
or armchair type, can weaken Al–H bonds in sodium alanate,
which is believed to be due to a combination of NaAlH<sub>4</sub> destabilization
and dissociation product stabilization. The helical form of graphene
nanofibers, with larger surface area and curved configuration, appears
to benefit the functionalization of carbon sheet edges. We believe
that our combined experimental and theoretical study will stimulate
more explorations of other microporous or mesoporous nanomaterials
with an abundance of exposed carbon edges in the application of practical
complex light metal hydride systems
Role of interleukin-12 in the regulation of CD4(+) T cell apoptosis in a mouse model of asthma
Allergic asthma, a chronic inflammatory disease of the airways, is characterized by the presence of T helper 2 cells and eosinophils in sputum, bronchoalveolar lavage, and mucosal biopsy specimens. Although the T helper 1-promoting cytokine, interleukin-12, is capable of inhibiting the T helper 2-driven asthma symptoms and bronchial responsiveness, the specific mechanisms underlying these interleukin-12 actions are unclear. The anti-allergic response to interleukin-12 is only partially dependent on interferon-γ, which induces apoptosis by enhancing expression of Fas antigen. We therefore investigated in vivo whether the anti-allergic action of interleukin-12 is mediated through induction of apoptosis. C57BL/6 mice immunized to ovalbumin by intraperitoneal injection were challenged three times with an ovalbumin aerosol every second day for 7 days. Recombinant interleukin-12 was administered intravenously after the final challenge. After the last ovalbumin challenge, mice were examined for effects of interleukin-12 on inflammatory cell infiltration and apoptosis in the lung as detected by terminal deoxynucleotidyl transferase-mediated deoxyribonucleoside triphosphate nick end-labelling. Administration of interleukin-12 reduced ovalbumin-induced pulmonary eosinophilia (P < 0·01) and CD4(+) T cell infiltration (P < 0·01). Moreover, treatment with interleukin-12 shortly after ovalbumin inhalation resulted in both increased interferon-γ production (P < 0·01) and enhanced apoptosis of CD4(+) T cells in allergic airway infiltrates (P < 0·05). These results suggest that the beneficial effects of interleukin-12 in asthma may include enhancement of apoptosis of CD4(+) T cells in airways
Graphyne and graphdiyne: versatile catalysts for dehydrogenation of light metal complex hydrides
The interaction between new two-dimensional carbon allotropes, i.e., graphyne (GP) and graphdiyne (GD), and light metal complex hydrides LiAlH 4, LiBH4, and NaAlH4 was studied using density functional theory (DFT) incorporating long-range van der Waals dispersion correction. The interaction of light metal complex hydrides with GP and GD is much stronger than that with fullerene because of the well-defined pore structure of GP and GD. Such strong interactions greatly affect the degree of charge donation from the alkali metal atom to AlH4 or BH4, consequently destabilizing the Al-H or B-H bonds. Compared to the isolated light metal complex hydride, the presence of GP or GD can lead to a significant reduction of the hydrogen removal energy. Most interestingly, the hydrogen removal energies for LiBHx on GP and with GD are found to be lowered at all the stages (x from 4 to 1), whereas the H-removal energy in the third stage is increased for LiBH4 on fullerene. In addition, the presence of uniformly distributed pores on GP and GD is expected to facilitate the dehydrogenation of light metal complex hydrides. The present results highlight new interesting materials to catalyze light metal complex hydrides for potential application as media for hydrogen storage. Because GD has been successfully synthesized in a recent experiment, we hope the present work will stimulate further experimental investigations in this direction
CD14 is Expressed by Subsets of Murine Dendritic Cells and Upregulated by Lipopolysaccharide
Mahnke K, Becher E, Ricciardi-Castagnioli P, Schwarz T, Luger T, Grabbe S. CD14 is Expressed by Subsets of Murine Dendritic Cells and Upregulated by Lipopolysaccharide. In: Ricciardi-Castagnoli P, ed. Dendritic Cells in Fundamental and Clinical Immunology. Advances in Experimental Medicine and Biology. Vol 417. Boston, MA: Springer US; 1997: 145-159