9H-xanthene-2,7-diols as antioxidants for autoxidation of linoleic acid

The antioxidant activities of 9H-xanthene-2,7-diols and α-tocopherol were studied during the oxidation of linoleic acid in a homogeneous solution and in an aqueous micelle dispersion. The antioxidant activities of 9H-xanthene-2,7-diols for both systems were 1.0–2.4 times greater relative to α-tocopherol. In addition, the 1,3,4,5,6,8-hexamethylxanthene-2,7-diol showed less cytotoxicity toward human fibroblasts than did 2,6-di-t-butyl-4-methylphenol.     

Induction of granulomas in interferon-gamma gene-disrupted mice by avirulent but not by virulent strains of Mycobacterium tuberculosis

Tumor necrosis factor-alpha (TNF-alpha) levels were measured in the serum (sTNF-alpha) or bone marrow (BM) biopsies of 43 patients with myelodysplastic syndromes (MDS) who subsequently received therapy with a combination of pentoxifylline and ciprofloxacin (PC) with or without dexamethasone (PCD). All 43 patients received only PC therapy for 12 weeks, after which 18 of 36 nonresponders received PCD. A total of 18 of 43 patients showed a hematologic or cytogenetic response or both. BM TNF-alpha levels were semiquantitatively assessed using immunohistochemistry on a scale of 0-8+ and in the serum using enzyme linked immunoassay. The median TNF-alpha for the entire group was 3.0 in BM and 6.9 pg/ml in the serum, and 14 patients had no detectable levels. Responders had higher BM levels (median 3.5 vs. 2.0) than nonresponders, although this was not statistically significant. During PC therapy, a decline in BM TNF-alpha level was seen in the entire group, which was significant at 2 weeks (p = 0.02), 8 weeks (p = 0.001), and 12 weeks (p = 0.0001). Both responders (p = 0.01) and nonresponders (p = 0.03) had a decline at 8 weeks, but at 12 weeks, only the responders continued to show a significant decline (p = 0.03). We conclude that MDS patients with high BM TNF-alpa levels have a better chance of responding to PCD therapy and that the therapy is quite successful in reducing the TNF-alpha levels in a sustained fashion. Future studies need to be directed at identifying agents that would be more potent suppressors of the proapoptotic cytokines in these patients.     

Ultrasonic attenuation of the excitonic state in pure bismuth in high magnetic fields

The ultrasonic attenuation of the excitonic state in pure Bi in high magnetic fields is studied theoretically. Use is made of the mean-field approximation to describe the excitonic state in pure Bi in the extreme quantum limit, where the motion of the electron and the hole is limited only in the direction parallel to the magnetic field. The attenuation constant of the longitudinal sound has a broad peak below the excitonic transition temperatureT _c and then decreases rapidly as the temperature decreases, which agrees qualitatively with a recent observation by Sakaiet al.     

Application of rigid polyurethane integral-skin foams to thermal insulating unit cases for car air conditioners

Integral-skin foams of rigid polyurethane are sandwich structures consisting of a core layer of closed cells enclosed in rigid surface layers on both sides. We examined the layer composition of integral-skin foam with the objective of maximum flexural strength, and then studied possibilities of reconciling the strength and thermal insulating properties in housings for evaporators in car air conditioners; i.e., unit cases. This examination showed that the most practical density range (250 ≦ ρ_pall ≦ 500 kg/m³) provides vibratile resistance and thermal insulating properties. In actual car-running tests, a maximum 0.1 MPa stress was generated on unit cases with overall densities of 350 kg/m³, We found this to be 0.4% of the flexural strength of an integral-skin foam and 2% of the fatigue strength. In the forcible vibratile test, a stress of 0.5 to 1.0 MPa was generated at the resonance point of a unit case with 250 to 500 kg/m³ overall density. We found that these values are 2 to 5% of integral-skin foam's flexural strength and 10 to 25% of its fatigue strength. These values are of the same level as the conventional unit case made of polypropylene blended with talc. An integral-skin foam with an overall density of 250 kg/m³, nearly equal to half the weight of polypropylene, has the same level of resistance to vibration.     

Fluctuation phenomena below the superconducting transition

The fluctuation propagator for the superconducting order parameter belowT _c is derived for a gapless superconductor. The fluctuation of the order parameter consists of two distinct modes: the fluctuations of the phase and the modulus of the order parameter. The former fluctuation obeys a phononlike dispersion, while the latter fluctuation is described by a damping diffusion type equation. The present theory gives an account of the fluctuation-induced Josephson effect belowT _c observed recently by Carlson and Goldman.     

Calculation of Age-Replacement with Weibull Failure Times

An age-replacement policy with Weibull failure times is considered. It is troublesome to compute an optimum replacement time numerically. Upper and lower bounds of an optimum time are given in simple terms of replacement costs and parameters of a Weibull distribution. A numerical example shows that the approximation can be used when the ratio of the replacement cost for a failed unit to that for a nonfailed unit is large. The approximation is best when the optimum age of replacement is small.     

Microwave response of superconducting thin films in magnetic fields

We calculate the complex conductivity of a superconducting thin film in a tilted magnetic field. Use is made of the time-dependent Ginzburg-Landau equations to deal with the dynamical behavior of the order parameter associated with the vortex motion in response to the microwave. The reactive part of the conductivity at zero frequency vanishes identically due to the vortex motion and the conductivity resembles that in the flux-flow regime of the type-II superconductor, unless the dc magnetic field is parallel to the film surface with high precision.     

Inelastic neutron scattering from the vortex lattice in type-II superconductors. I

The inelastic neutron scattering from the vortex lattice in dirty type-II superconductors is considered. In the high-field region, the correlation function for the local magnetization is given in terms of the fluctuation propagator of the superconducting order parameter. In particular it is shown that the Fourier transform of the correlation function for the local magnetization diverges as /q –G _i /^–2, when the transverse transfered momentumq approaches the reciprocal lattice vectorG _i of the Abrikosov lattice. This term gives rise to tails around each Bragg peak in the inelastic neutron-scattering cross section.     

Magnetic resonances of helical textures in 3He-A

The NMR frequencies of the helical texture in ³He-A in the presence of a magnetic field parallel to the superflow are reexamined in the entire stability region. The effects of the anisotropic contribution to the spin susceptibility are explicitly included and are shown to leave previous results qualitatively unchanged. On the other hand, we find that the anisotropic contribution gives rise to quantitative corrections of maximally 20% at T/T _c = 0.95, while its contribution in the immediate vicinity of T _c is negligibly small.Work supported in part by the National Science Foundation under grant number DMR 76-21032.Guggenheim Fellow 1979–1980.