Periodical mixing of MORB magmas near East Pacific Rise 13N: evidence from modeling and zoned plagioclase phenocrysts

Thirty-six basalt samples from near East Pacific Rise 13N are analyzed for major and trace elements. Different types of zoned plagioclase phenocrysts in basalts are also backscatter imaged, and major element profiles scanned and analyzed for microprobe. Basalts dredged from a restricted area have evolved to different extents (MgO=9.38wt%-6.76wt%). High MgO basalts are modeled for crystallization to MgO of about 7wt%, and resulted in the Ni contents (28 ppm) that are generally lower than that in observed basalts (> 60 ppm). It suggests that low MgO basalts may have experienced more intensive magma mixing. High MgO (9.38wt%) basalt is modeled for self-"mixing-crystallization", and the high Ni contents in low MgO basalts can be generated in small scale and periodical self-mixing of new magma (high MgO). "Mixing-crystallization" processes that low MgO magmas experienced accord with recent 226Ra/230Th disequilibria studies for magma residence time, in which low MgO magmas have experienced more circles of "mixing-crystallization" in relatively longer residence time. Magma mixing is not homogeneous in magma chamber, however, low MgO magmas are closer to stable composition produced by periodical "mixing-crystallization", which is also an important reason for magma diversity in East Pacific Rise. Zoned plagioclase phenocrysts can be divided into two types: with and without high An# cores, both of which have multiple reversed An# zones, suggesting periodical mixing of their host magmas. Cores of zoned plagioclase in low MgO (7.45wt%) basalt differ significantly with their mantle in An#, but are similar in An# with microlite cores (products of equilibrium crystallization) in high MgO (9.38wt%) basalt, which further shows that plagioclase phenocryst cores in low MgO basalts may have formed in their parental magmas before entering into the magma chamber.

Origin and Pathway of Equatorial 13 degrees C Water in the Pacific Identified by a Simulated Passive Tracer and Its Adjoint

The origin and pathway of the thermostad water in the eastern equatorial Pacific Ocean, often referred to as the equatorial 13 degrees C Water, are investigated using a simulated passive tracer and its adjoint, based on circulation estimates of a global general circulation model. Results demonstrate that the source region of the 13 degrees C Water lies well outside the tropics. In the South Pacific, some 13 degrees C Water is formed northeast of New Zealand, confirming an earlier hypothesis on the water's origin. The South Pacific origin of the 13 degrees C Water is also related to the formation of the Eastern Subtropical Mode Water (ESTMW) and the Sub-Antarctic Mode Water (SAMW). The portion of the ESTMW and SAMW that eventually enters the density range of the 13 degrees C Water (25.8 < sigma(theta) < 26.6 kg m(-3)) does so largely by mixing. Water formed in the subtropics enters the equatorial region predominantly through the western boundary, while its interior transport is relatively small. The fresher North Pacific ESTMW and Central Mode Water (CMW) are also important sources of the 13 degrees C Water. The ratio of the southern versus the northern origins of the water mass is about 2 to 1 and tends to increase with time elapsed from its origin. Of the total volume of initially tracer-tagged water in the eastern equatorial Pacific, approximately 47.5% originates from depths above sigma(theta) = 25.8 kg m(-3) and 34.6% from depths below sigma(theta) = 26.6 kg m(-3), indicative of a dramatic impact of mixing on the route of subtropical water to becoming the 13 degrees C Water. Still only a small portion of the water formed in the subtropics reaches the equatorial region, because most of the water is trapped and recirculates in the subtropical gyre.

Characterization of a homogeneous taxonomic group of marine magnetotactic cocci within a low tide zone in the China Sea

Magnetotactic bacteria are a heterologous group of motile prokaryotes, ubiquitous in aquatic habitats and cosmopolitan in distribution. Here, we studied the diversity of magnetotactic bacteria in a seawater pond within an intertidal zone at Huiquan Bay in the China Sea. The pond is composed of a permanently submerged part and a low tide subregion. The magnetotactic bacteria collected from the permanently submerged part display diversity in morphology and taxonomy. In contrast, we found a virtually homogenous population of ovoid-coccoid magnetotactic bacteria in the low tide subregion of the pond. They were bilophotrichously flagellated and exhibited polar magnetotactic behaviour. Almost all cells contained two chains of magnetosomes composed of magnetite crystals. Intriguingly, the combination of restriction fragment length polymorphism analysis (RFLP) and sequencing of cloned 16S rDNA genes from the low tide subregion samples as well as fluorescence in situ hybridization (FISH) revealed the presence of a homogenous population. Moreover, phylogenetic analysis indicated that the Qingdao Huiquan low tide magnetotactic bacteria belong to a new genus affiliated with the alpha-subclass of Proteobacteria. This finding suggests the adaptation of the magnetotactic bacterial population to the marine tide.

Divergent selection and realized heritability for growth in the Japanese scallop, Patinopecten yessoensis Jay

In order to improve the production and accurately estimate response to selection, divergent selection for growth in shell height was conducted in a cultured population of the Japanese scallop Patinopecten yessoensis. Applying the same selection intensity +/- 1.756 in upward and downward directions, three groups including two selected groups of Fast and Slow and one non-selected Control group were created, which were reared under the same environmental conditions at any stage. Differences always significantly existed among the three groups (P < 0.05), except for larvae at day 1 and at day 5, and in the order of Fast > Control > Slow. The average standardized response to selection (SR), realized heritability (h(R)2) and genetic gain (GG) was 0.473%, 0.269% and 7.85% for the Fast group and 0.381%, 0.217% and 6.60% for the Slow group respectively. Moreover, significant differences (P < 0.05) were detected between the fast and the slow lines in both SR and h(R)2, providing evidence for an asymmetric response in two directions. Performance in shell height is improved by 7.85% in the fast line after one generation selection, suggesting that mass selection for faster growth in a cultured population of the Japanese scallop is effective.

A new species of Bryodema (Orthoptera : Acridoidea) from China, with a key to the described species

A new species Bryodema nigrofrascia of the genus Bryodema Fieber, 1853 (Orthoptera, Acridoidea, Acrididae Oedipodinae) from China is described. A key to known species of the genus is given. The type specimens are deposited in the Northwest Plateau Institute of Biology, Chinese Academy of Sciences, Xining, Qinghai.

烟厂MIS中成本核算子系统实现时的几个重要问题

针对工厂企业中用微机实现管理信息系统(MIS)时,数据量大与数据处理速度慢、存储空间小之间的矛盾,本文论述了在不更新设备和不增加投资的条件下如何用软件方法来解决问题.在延吉卷烟厂成本核算子系统中的实践结果是:数据处理速度可提高到原来的2.24倍,所节省的存储空间相当于目前实际占用数的56%.

不可提取态有机质对菲和萘的吸附过程的影响

土壤对疏水性有机污染物的吸附实际上是土壤中矿物和有机质两部分共同作用的结果。土壤有机质的作用相当重要，因为与矿物相比，它通常对疏水性有机污染物具有较大的热力学亲合力。因此，土壤吸附有机污染物机理的研究主要是从土壤有机质的角度进行的。土壤有机质组成复杂，主要包括非特异性有机质和腐殖质，其中腐殖质约占有机质总量的50％-80％，包括胡敏酸、富里酸和胡敏素。早期的实验研究认为疏水性有机污染物在土壤有机质相中表现为线性分配，可以用平衡分配系数来描述。但是，随着实验研究的深入，平衡分配模型不能合理解释疏水性有机污染物的一些吸附特征，如非线性吸附、溶质竞争吸附以及解吸过程的滞后现象等。后来，Weber和Huang提出土壤吸附有机污染物的三端元模型。同时Pignatello和Xing提出双模式吸附模型。都认为土壤有机质存在明显的不均匀性，并且提出了“软碳”与“硬碳”的概念.

石灰土物质来源的判别—以黔北、黔中几个剖面为例

传统看法认为石灰土是碳酸盐岩风化作用的产物，然而由于碳酸盐岩风化成土的特殊性，在宏观上难以直接甄别土层与母岩的关联性，以至引发出了很大的物源争议。因此，物质来源判别将是石灰土研究的关键内容。基于此，本文选择黔北遵义官坝、安顺天龙和贵阳花溪上水村4个石灰土剖面为实例，进行矿物组合、地球化学特征和粒度分布特征对比分析，旨在对分布十分广泛的贵州省石灰土的物质来源进行判别。结果显示：各剖面土层与下伏的碳酸盐岩具有明显的物源继承关系，石灰土是碳酸盐岩风化作用．酸不溶物残留、堆积的产物。