环大西洋显生宙造山带中的前中生代地体

环大西洋显生宙造山带内前中生代地体已经由IGcP第233项工作组成员收集了一张二叠纪复原再造图上,即一个封闭的大西洋。最初提出在环太平洋造山带应用地体概念需要对环大西洋造山带的概念作某些修改。因而,地体重新定义为这样的一种地区,其内部地质特点具有连续性(包括地层、生物群、构造、变质作用、火成岩、成矿作用、地球物理特点及古地磁记录),它被断层或代表海沟杂岩的混杂岩,或一条隐地缝合线所圈定,穿过这种界限,相邻地体(1)具有用相变不能解释的一些截然不同的地质记录(外来地体);或(2)可以具有类似的地质记录(近源地体),只有根据代表叠生大洋岩石圈的地体边界的存在才能识别它们。地体可以依据年龄和构造背景划分:原地叠瓦状基底/冒地斜、陆隆、大洋岩石圈、大洋岩系、岩浆弧杂岩、弧缘盆地、海沟杂岩、断裂(disruptes)地体(构造混杂岩)、原岩不明的变质岩、源地不明     

BRI 0021-0214: Another Surprise at the Bottom of the Main Sequence

We report the detection of an Halpha flare on the low-luminosity M9.5 dwarf BRI 0021-0214. This star has rapid rotation, vsin&parl0;i&parr0; approximately 40 km s-1, but generally shows no significant chromospheric emission. Our detection of the flare shows that a magnetic field is present, although the level of activity at maximum is 3 times lower than the mean quiescent level in early- and mid-type M dwarfs. Based on data available in the literature, we estimate that the star is in outburst for no more than 7% of the time.     

The infrared emission bands. II. A spatial and spectral study of the Orion Bar

We have studied the spectral and spatial distribution across the Orion Bar of the 3-14 micrometers emission, including hydrogen Brackett alpha and 12.8 micrometers [Ne II] emission lines and several "dust" emission features. The data indicate that the "dust" consists of three components; (1) "classical" dust with a temperature of approximately 60 K accounting for emission longward of 20 micrometers, (2) amorphous carbon particles or polycyclic aromatic hydrocarbon (PAH) clusters (approximately 400 C atoms) which produce broad emission features in the 6-9 and 11-13 micrometers bands, and (3) free PAHs which emit in sharper bands (most strongly at 3.3, 6.2, 7.7, 8.6, and 11.3 micrometers). The 3.3 and 11.3 micrometers features, which are due to C-H modes, are well correlated spatially, while the 7.7 micrometers band, due to C=C modes, has a different distribution than the 3.3 and 11.3 micrometers bands. We conclude that the sharp emission bands arise in the photodissociation transition region between the H II region and the molecular cloud and are not present in the H II region. The broad continuum feature extending from 11-13 micrometers is strong in both regions. Previous broad-band observations of the 10 and 20 micrometers flux distributions, which show that the 10 micrometers radiation extends farther into the neutral gas to the south than the 20 micrometers radiation, suggest that some of the 10 micrometers flux is supplied via a nonthermal mechanism, such as fluorescence.     

The influence of sediment resuspension on the degradation of phenanthrene in flow-through microcosms

The effect of sediment resuspension on the mineralization of phenanthrene was examined in microcosms and sediment slurries. In computer-controlled, flow-through microcosms, 14C-phenanthrene-amended sediments were resuspended into overlying oxic water at frequencies of 12, 4, 1, 0.25 and 0 d(-1). In slurry bottle experiments 14C-phenanthrene-amended sediments were continuously resuspended under oxic (excess air headspace) and anoxic (N2 headspace) conditions and mineralization was measured at periods from 2 h to 7 days. Our main findings were: (1) mineralization rate constants from the microcosms ranged from 0.001 to 0.01 d(-1) and increased with frequency of resuspension, (2) these rates fell between those measured in oxic and anoxic slurries and were predicted within a factor of 2.5 by a model in which mineralization depended on the degree of oxygen exposure, and (3) the phenanthrene-degrading bacterial community was more active in resuspended sediments incubated in the microcosms than in sediments which were not resuspended, or which were stored under refrigeration. We conclude from these experiments that the effects of sediment resuspension on phenanthrene degradation are consistent with a primary role of average oxygen exposure, and also an alteration in the PAH-degrading activity of microbial populations.     

对称指数地形水槽内纵波和横波解析解研究

水槽实验通常用于波浪传播变形及防波堤护面块体稳定性等研究,涉及的波要素沿水槽纵向变化且在垂直于水槽的横向保持不变。然而实验中当波长与水槽宽度满足一定关系时,可能出现明显的横向波动现象。本文针对对称指数型隆起地形,基于线性长波方程分别推导了其内沿水槽方向的纵波与垂直于水槽方向的横波的解析表达。水槽内对称指数地形上的纵波可以表示为第一类和第二类一阶贝塞尔函数的形式,并结合自由水面及速度连续条件最终得到其完整解。对称指数地形上分别存在偶对称和奇对称模态的横波,可表示为第一类ν阶贝塞尔函数的形式。偶对称模态(n, m)沿水槽方向有n条波节线,在垂直于水槽方向存在2m条波节线;奇对称模态(n, m)沿水槽方向存在n条波节线而在垂直方向有2m-1条波节线。     

Uptake and distribution of N, P and heavy metals in three dominant salt marsh macrophytes from Yangtze River estuary, China

We examined the variation in aboveground biomass accumulation and tissue concentrations of nitrogen (N), phosphorus (P), copper (Cu), zinc (Zn) and lead (Pb) in Phragmites australis (common reed), Spartina alterniflora (salt cordgrass), and Scirpus mariqueter throughout the growing season (April-October 2005), in order to determine the differences in net element accumulation and distribution between the three salt marsh macrophytes in the Yangtze River estuary, China. The aboveground biomass was significantly greater in the plots of S. alterniflora than in the plots of P. australis and S. mariqueter throughout the growing season (P<0.05). In August, the peak aboveground biomass was 1246+/-89 gDW/m(2), 2759+/-250 gDW/m(2) and 548+/-54 gDW/m(2) for P. australis, S. alterniflora and S. mariqueter, respectively. The concentrations of nutrients and heavy metals in plant tissues showed similar seasonal patterns. There was a steady decline in element concentrations of the aboveground tissues from April to October. Relative element concentrations in aboveground tissues were at a peak during the spring sampling intervals with minimum levels during the fall. But the concentrations of total nitrogen and total phosphorus in the belowground tissues were relatively constant throughout growing season. Generally, trace metal concentrations in the aboveground tissues of S. mariqueter was the highest throughout the growing season, and the metal concentrations of S. alterniflora tissues (aboveground and belowground) were greater than those of P. australis. Furthermore, the aboveground pools of nutrients and metals were consistently greater for S. alterniflora than for P. australis and S. mariqueter, which suggested that the rapid replacement of native P. australis and S. mariqueter with invasive S. alterniflora would significantly improve the magnitude of nutrient cycling and bioavailability of trace metals in the salt marsh and maybe transport more toxic metals into the water column and the detrital food web in the estuary.