A new three-stage evolution model for millimeter to centimeter wavelength outbursts in BL Lacertae

The multi-frequency light curves of BL Lacertae during 1997.5 – 1999.5 have been modeled by four outbursts,each having a 3-stage evolution in the (S m,νm) plane with distinct rising–plateau–decaying phases.It is shown that the observed light curves can be well fitted for the eight frequencies from 350GHz to 4.8GHz.The main characteristics of the model-fitting are: (1) the outbursts are found to have very flat spectra with an optically thin spectral index α (defined as Sν∝ν-α) of about 0.15.This is consisten...     

氟与环境健康——综述

100多年以来,各领域的学者一直在研究着环境中的氟化物与人类健康的关系。大多数学者认为,摄入少量的氟有助于预防龋齿、强健骨骼,而长期摄入大剂量的氟会给健康带来不利的影响,包括氟斑牙、氟骨症,骨折机率增加;生育能力下降;尿结石机率增加;甲状腺机能下降;儿童智力下降。长期接触氟灰尘和气体,膀胱癌和呼吸系统疾病患病率增高。另据报道,摄入氟化钠杀虫剂和护牙用品会患急性氟中毒,严重者甚至死亡。自然环境中氟化物的分布非常不均一,主要是氟元素的地球化学特征所致。氟元素最先选择岩浆和热液释放地带富集,这就可以解释为什么正长岩、花岗类岩、火成岩、碱性火山岩和热液沉积岩的氟化物浓度一般比较高的原因。氟化物还常存在于沉积地层,该层包括来自原生岩的含氟化物矿物、富集氟化物的粘土、或者磷灰石。溶解的氟化物浓度一般受萤石（CaF2）的溶解度控制,因此,氟化物浓度高常常与软、碱性和钙含量不足的水体有关。尽管人们对氟化物的形成和其对健康的影响已经有很高的认识,但是,仍有很多氟化物与环境健康问题存在于第三世界国家,这些国家的居民几乎不能选择自己的饮用水和食物。即便是在发达国家,如果忽略了饮用水源之外的水源,那么,居民摄入的氟化物的含量也超过了推荐的剂量。     

Two-Dimensional Variational Analysis of Near-Surface Moisture from Simulated Radar Refractivity-Related Phase Change Observations

Because they are most sensitive to atmospheric moisture content, radar refractivity observations can provide high-resolution information about the highly variable low-level moisture field. In this study, simulated radar refractivity-related phase-change data were created using a radar simulator from realistic highresolution model simulation data for a dryline case. These data were analyzed using the 2DVAR system developed specifically for the phase-change data. Two sets of experiments with the simulated observations were performed, one assuming a uniform target spacing of 250 m and one assuming nonuniform spacing between 250 m to 4 km. Several sources of observation error were considered, and their impacts were examined. They included errors due to ground target position uncertainty, typical random errors associated with radar measurements, and gross error due to phase wrapping. Without any additional information, the 2DVAR system was incapable of dealing with phase-wrapped data directly. When there was no phase wrapping in the data, the 2DVAR produced excellent analyses, even in the presence of both position uncertainty and random radar measurement errors. When a separate pre-processing step was applied to unwrap the phase-wrapped data, quality moisture analyses were again obtained, although the analyses were smoother due to the reduced effective resolution of the observations by interpolation and smoothing involved in the unwrapping procedure. The unwrapping procedure was effective even when significant differences existed between the analyzed state and the state at a reference time. The results affirm the promise of using radar refractivity phase-change measurements for near-surface moisture analysis.     

Trophic ecology of the sea urchin Spatangus purpureus elucidated from gonad fatty acids composition analysis

Irregular sea urchins such as the spatangoid Spatangus purpureus are important bioturbators that contribute to natural biogenic disturbance and the functioning of biogeochemical cycles in soft sediments. In the coastal waters of the Balearic Islands S. purpureus occurs in soft red algal beds, and can reach high densities. The diet of S. purpureus is unknown and it is particularly difficult to analyze the stomach contents of this group; therefore, we analyzed the fatty acid (FA) composition of the gonads and potential food resources in order to assess the trophic relationships of this species. The FA profiles of the gonads of S. purpureus agree well with the FA composition of the potential trophic resources (algae and sediment) and reveals changes between localities with different available resources. Three polyunsaturated FAs mainly contributes in the composition in the S. purpureus gonads: eicosapentaenoic acid (C20:5n-3) and arachidonic acid (C20:4n-6), both abundant in the macroalgal material, and palmitoleic acid (C16:1n-7), which is characteristic of sediment samples. Trophic markers of bacterial input and carnivorous feeding were significantly more abundant in sea urchins caught on bottoms with less vegetation. The current study demonstrates that the FA content of S. purpureus gonads is a useful marker of diet, as differences in the profiles reflected the variations in detritus composition. The results of this study show that this species has omnivorous feeding behavior; however, viewed in conjunction with available abundance data the results suggest that phytodetritus found within algal beds is an important carbon source for this species.     

A Photometric Study of the W UMa-type Eclipsing Binary System GSC 0445-1993

Several new light minimum times for the eclipsing binary GSC 0445-1993 have been determined from the observations by Koppelman et al. and the orbital period of this system was revised. A photometric analysis was carried out using the 2003 version of the Wilson-Devinney code. The results reveal that GSC 0445-1993 is a W-type eclipsing binary with a mass ratio of q = 0.323(±0.002) and an over-contact degree of f = 22.8%(±4.2%). A small temperature difference between the components of △T = 135 K and an orbital inclination of i = 65.7°(±0.3°) were obtained. The asymmetry of its light curve (i.e., the O'Connell effect) for this binary star is explained by the presence of a dark spot on the more massive component.     

Interaction of Waves, Surface Currents, and Turbulence： the Application of Surface-Following Coordinate Systems

Surface waves comprise an important aspect of the interaction between the atmosphere and the ocean, so a dynamically consistent framework for modelling atmosphere-ocean interaction must take account of surface waves, either implicitly or explicitly. In order to calculate the effect of wind forcing on waves and currents, and vice versa, it is necessary to employ a consistent formula- tion of the energy and momentum balance within the airflow, wave field, and water column. It is very advantageous to apply sur- face-following coordinate systems, whereby the steep gradients in mean flow properties near the air-water interface in the cross-interface direction may be resolved over distances which are much smaller than the height of the waves themselves. We may account for the waves explicitly by employing a numerical spectral wave model, and applying a suitable theory of wave–mean flow interaction. If the mean flow is small compared with the wave phase speed, perturbation expansions of the hydrodynamic equations in a Lagrangian or generalized Lagrangian mean framework are useful: for stronger flows, such as for wind blowing over waves, the presence of critical levels where the mean flow velocity is equal to the wave phase speed necessitates the application of more general types of surface-following coordinate system. The interaction of the flow of air and water and associated differences in temperature and the concentration of various substances (such as gas species) gives rise to a complex boundary-layer structure at a wide range of vertical scales, from the sub-millimetre scales of gaseous diffusion, to several tens of metres for the turbulent Ekman layer. The bal- ance of momentum, heat, and mass is also affected significantly by breaking waves, which act to increase the effective area of the surface for mass transfer, and increase turbulent diffusive fluxes via the conversion of wave energy to turbulent kinetic energy.     

地核探索——一项并不过分的建议

对我们这颗行星的内部运作情况进行探索——这不是科幻小说，而是一项在技术上行得通的方案。