镉对鲫非特异性免疫力的影响

采用毒性实验方法研究了镉对鲫非特异性免疫力的影响,确定镉诱导免疫毒性效应及其毒性参数。在试验剂量和时间范围内的结果显示,镉对鲫白细胞数量(WBC)、中性粒细胞的吞噬率(PR)和补体50%溶血活性(CH50)均有剂量-效应关系、时间-效应关系和Hormesis现象,1.25mg·kg-1注射染Cd2+胁迫时对WBC、PR和CH50有激活作用,2.5和3.75mg·kg-1注射染Cd2+胁迫时对WBC、PR和CH50有抑制作用;WBC顶点所对应的时间为染Cd2+后4d,PR顶点所对应的时间为染Cd2+后2d,CH50顶点所对应的时间为染Cd2+后1d。所以Cd2+对鲫具有明显的免疫毒性。     

Negative linear compressibility and massive anisotropic thermal expansion in methanol monohydrate

The vast majority of materials shrink in all directions when hydrostatically compressed; exceptions include certain metallic or polymer foam structures, which may exhibit negative linear compressibility (NLC) (that is, they expand in one or more directions under hydrostatic compression). Materials that exhibit this property at the molecular level--crystalline solids with intrinsic NLC--are extremely uncommon. With the use of neutron powder diffraction, we have discovered and characterized both NLC and extremely anisotropic thermal expansion, including negative thermal expansion (NTE) along the NLC axis, in a simple molecular crystal (the deuterated 1:1 compound of methanol and water). Apically linked rhombuses, which are formed by the bridging of hydroxyl-water chains with methyl groups, extend along the axis of NLC/NTE and lead to the observed behavior.     

An iridium abundance anomaly at the palynological cretaceous-tertiary boundary in northern new Mexico

An iridium abundance anomaly, with concentrations up to 5000 parts per trillion over a background level of 4 to 20 parts per trillion, has been located in sedimentary rocks laid down under freshwater swamp conditions in the Raton Basin of northeastern New Mexico. The anomaly occurs at the base of a coal bed, at the same stratigraphic position at which several well-known species of Cretaceous-age pollen became extinct.     

Stimulated Raman scattering in hydrogen-filled hollow-core photonic crystal fiber

We report on stimulated Raman scattering in an approximately 1-meter-long hollow-core photonic crystal fiber filled with hydrogen gas under pressure. Light was guided and confined in the 15-micrometer-diameter hollow core by a two-dimensional photonic bandgap. Using a pulsed laser source (pulse duration, 6 nanoseconds; wavelength, 532 nanometers), the threshold for Stokes (longer wavelength) generation was observed at pulse energies as low as 800 +/- 200 nanojoules, followed by a coherent anti-Stokes (shorter wavelength) generation threshold at 3.4 +/- 0.7 microjoules. The pump-to-Stokes conversion efficiency was 30 +/- 3% at a pulse energy of only 4.5 microjoules. These energies are almost two orders of magnitude lower than any other reported energy, moving gas-based nonlinear optics to previously inaccessible parameter regimes of high intensity and long interaction length.     

Soliton self-frequency shift cancellation in photonic crystal fibers

We report the cancellation of the soliton self-frequency shift in a silica-core photonic crystal fiber with a negative dispersion slope. Numerical and experimental results show that stabilization of the soliton wavelength is accompanied by exponential amplification of the red-shifted Cherenkov radiation emitted by the soliton. The spectral recoil from the radiation acts on the soliton to compensate for the Raman frequency shift. This phenomenon may find applications in the development of a family of optical parametric amplifiers.     

Geologic framework of nonmarine cretaceous-tertiary boundary sites, raton basin, new Mexico and colorado

Iridium concentrations are anomalously high at the palynological Cretaceous-Tertiary boundary in fluvial sedimentary rocks of the lower part of the Raton Formation at several localities in the Raton Basin of New Mexico and Colorado. The iridium anomaly is associated with a thin bed of kaolinitic claystone in a discontinuous carbonaceous shale and coal sequence.