Long-term stability of phase-separated half-Heusler compounds.

Half-Heusler (HH) compounds have shown high figure of merit up to 1.5. Here, we address the long-term stability of n- and p-type HH materials. For this purpose, we investigated HH materials based on the Ti0.3Zr0.35Hf0.35NiSn-system after 500 cycles (1700 h) from 373 to 873 K. Both compounds exhibit a maximum Seebeck coefficient of |α|≈ 210 µV K(-1) and a phase separation into two HH phases. The dendritic microstructure is temperature resistant and upon cycling the changes in the microstructure are so marginal that the low thermal conductivity values (κ < 4 W m(-1) K(-1)) could be maintained. Our results emphasize that phase-separated HH compounds are suitable low cost materials and can lead to enhanced thermoelectric efficiencies beyond the set benchmark for industrial applications.

Depth-profiling of nickel nanocrystal populations in a borosilicate glass - A combined TEM and XRM study.

Populations of nickel nanocrystals in a borosilicate glass were studied by TEM and XRM. It is found that XRM, which is applied for the first time to this type of material, is superior for the precise determination of the depth-dependent number densities and volume fractions of precipitated Ni crystals. Statistical precision is gained by imaging 3D data of up to 60 times larger volumes as compared to the volume of the electron transparent rim that a standard TEM wedge specimen provides. Depth-dependent particle-size distributions of XRM were in agreement with those of TEM as the mean sizes of the Ni crystal populations were considerably larger than the XRM resolution limit.

Human fibroblasts release low amounts of reactive oxygen species in response to the potent phagocyte stimulants, serum-treated zymosan, N-formyl-methionyl-leucyl-phenylalanine, leukotriene B4 or 12-O-tetradecanoylphorbol 13-acetate.

Cell lines of human fibroblasts from primary cultures released reactive oxygen species, and displayed an increase in low-level chemiluminescence when stimulated with serum-treated zymosan, N-formyl-methionyl-leucyl-phenylalanine, leukotriene B4, or 12-O-tetradecanoylphorbol 13-acetate, all of which are known stimulants of respiratory burst in phagocytic cells. Non-serum-treated zymosan, interleukin-6, interleukin-2, interferon-gamma or complement factor C3b were ineffective. The primary radical species produced was O theta.2. Radical formation was continuous for up to 4 h, and it did not occur as an oxidative burst. The low level chemiluminescence probably arose from the excitation of carbonyl groups, since it remained unchanged in the presence of azide and 1,4-diazabicyclo[2.2.2]octane. While the release of reactive oxygen species in phagocytes has a function in defense mechanisms, the sustained production of such species in tissue cells may have a role in signaling mechanisms. The amounts of reactive oxygen species released by the fibroblasts upon stimulation with the stimulants mentioned above were low in comparison with the known stimulatory effects of cytokines [Meier et al. (1989) Biochem. J. 263, 539-545].

Human fibroblasts release reactive oxygen species in response to interleukin-1 or tumour necrosis factor-alpha.

Human fibroblasts in primary culture released reactive oxygen species upon stimulation with cytokines such as interleukin-1 alpha (IL-1) or tumour necrosis factor-alpha (TNF). The primary radical produced was O2.- as determined by e.s.r. spin trapping and cytochrome c reduction. In contrast to the oxidative burst in granulocytes and monocytes, radical formation took place continuously for at least 4 h. Low-level chemiluminescence was increased by stimulation with IL-1 and TNF. Spectral characteristics and tests with azide led to the conclusion that the photoemissive species were excited carbonyls and not singlet oxygen. Further, there was a liberation of ethane from the cells. Radical production and light emission were not altered by either xanthine or allopurinol, nor by azide, cyanide or rotenone. O2.- production increased in the presence of NADH or NADPH, making an NAD(P)H oxidase a likely source.

Human fibroblasts release reactive oxygen species in response to treatment with synovial fluids from patients suffering from arthritis.

Human fibroblasts in primary culture released reactive oxygen species upon exposure to synovial fluid obtained by joint aspiration from twelve patients suffering from rheumatoid arthritis. The primary radical produced was O2- as determined by ESR spin trapping and cytochrome c reduction. In contrast to the oxidative burst in granulocytes and monocytes, radical formation proceeded continuously for at least four hours. Low-level chemiluminescence was increased upon exposure to inflammatory human synovial fluids. Spectral characteristics and effects of azide and 1,4-diazabicyclo-(2,2,2)-octane led to the conclusion that the photoemissive species were excited carbonyls. Radical production and light emission were not altered either by xanthine or allopurinol, nor by azide, cyanide or rotenone. The O2- production increased in the presence of NADH or NADPH, making an NAD(P)H oxidase a likely source. The liberation of reactive oxygen species correlated with the number of leukocytes present in the inflammatory joint fluids, but not with the concentrations of immunoglobulins and complement factor C3.