中国对虾(Penaeus chinensis)消化系统发生的研究   总被引：2，自引：2，他引：2  

王海林  廖承义  张志峰  马英杰 《中国海洋大学学报(自然科学版)》1997,(3)

本文对中国对虾消化道和中肠腺的发生进行了研究。完整的中肠管形成于Ｎ３期，它是由幼虫腹面的内胚层板向背中线上卷合拢而形成。在Ｚ１期消化道完全贯通。至Ｍ１期，胃分化为贲门胃和幽门胃两部分，中肠前盲囊和中肠后盲囊也在此期出现，同时胃磨的雏形发生，但完整的胃磨形成于Ｐ期。另外，中肠腺始于Ｎ４－５期中肠前端突出的两对中肠腺盲囊。第一对中肠腺盲囊于Ｍ３期退化消失，而第二对中肠腺盲囊则发育为成体的中肠腺。中肠腺小管由４种不同类型的细胞（胚性细胞、吸收细胞、纤维细胞和泡状细胞）所组成  相似文献   

高速摄影对散体振动的研究     

王树林 《中国海洋大学学报(自然科学版)》1995,(Z1)

以现代高速摄影技术和图像分析以及数据处理方法，针对高效振动磨机中弹性散体工质（如钢棒、球体等）的振动力学进行了深入的探讨和分析，为研究散体动力学和振动超细粉碎过程中的能量分布和传递规律以及能量与物质的相互转换机理奠定了基础，也为相关学科的发展提供了一种可以借鉴的方法。  相似文献   

Some breakage characteristics of ultra-fine wet grinding with a centrifugal mill     

Heechan Cho  Hoon LeeYeongwoo Lee 《International Journal of Mineral Processing》2006

A centrifugal mill is a high-power intensity media mill that can be used for ultra-fine grinding, employing centrifugal forces generated by gyration of the axis of the mill tube in a circle. The mill charge motion is quite different depending on the ratio of the gyration diameter to the mill diameter (G / D ratio), varying from a motion similar to that of a conventional tumbling media mill to that of a vibration mill. In this study, a centrifugal mill was constructed with an arrangement where the gyration diameter could be readily adjusted. The batch grinding characteristics of three different minerals (limestone, talc and illite) in water with dispersing agent were investigated at various G / D ratios. It was found that the optimum G / D ratio in terms of the specific energy consumption to give a desired fineness of product was different for the three minerals. This was due to their different reactions to the breakage mechanisms provided by the mill charge motion at varying G / D ratios. The size distributions became progressively narrower at increased grinding times, and particles finer than about 0.1 μm were not detected even for prolonged grinding times. Measurement of specific surface areas indicated that this was not due to an artifact of the size measurements by laser diffractometry. This implies that there is a limitation in which particles finer than 0.1 μm are not produced under the conditions tested in this type of mill, but further investigation is needed for experimental verification of this limit of comminution.  相似文献   

Production of carbonate and silica nano-particles in stirred bead milling     

Yanmin Wang  Eric Forssberg 《International Journal of Mineral Processing》2006

This paper presents the experimental results of the mechanical production of silica and carbonate colloidal particles below 100 nm using two types of stirred bead mills (i.e., DCP Superflow 12 and PML H/V). It is shown that the stirred bead mill with very small beads can be used as an efficient equipment for the production of the colloidal particles in nanoscale from the feed materials of several microns in sizes at high energy consumptions. The DCP Superflow mill with high power densities is superior for the effective size reduction and production rate, compared to the conventional PML H/V mill with lower power densities. The smaller particles could be produced by the DCP Superflow mill at the same level of high energy inputs as from the PML H/V mill. The “grinding limit” for the processes in the mills has been discussed.  相似文献   

关于求解碾磨机运动问题的相关讨论     

饶黄云  饶瑞昌 《华东地质学院学报》2006,29(3):298-300

针对关于求解碾磨机上一点运动的速度及加速度的问题展开讨论,从运动的不同角度考虑,给出了n种不同的解法。并将此问题拓展到一般情况下进行讨论,得出正确结论。并就一些相关问题进行了分析和解释。  相似文献   

Pollution history and recovery of a boreal lake exposed to a heavy bleached pulping effluent load   总被引：4，自引：0，他引：4  

Juhani Hynynen  Arja Palomäki  Jarmo J. Meriläinen  Allan Witick  Keijo Mäntykoski 《Journal of Paleolimnology》2004,32(4):351-374

We examined the effects of heavy pulp mill discharges on the Lake Lievestuoreenjärvi ecosystem and the later recovery of diatom and chironomid communities from age-dated short core samples. Beginning in 1927 the lake received a heavy effluent load from a sulphite pulp mill. Except for the recession during the Second World War and the temporary closure of the mill from 1967 to 1971, the industrial load, containing large quantities of nutrients, organic matter and toxic compounds, increased continuously. In the early 1980s, laboratory documents were falsified by the directors of the mill and the systematic illegal effluent overload led to a collapse of the whole lake ecosystem. In 1985, the outdated plant was finally closed down. Based on the assessment of chemical properties and biological remains of the sediment, we distinguished five developmental phases in the ecological state of the lake. In the pre-industrial phase, the pelagic and profundal benthic communities were dominated by species preferring ultraoligotrophic or oligotrophic lakes. Concomitant with the increasing discharge and deposition of chlorine compounds, resin acids, and mercury, as well as strong acidity and hypolimnetic and epilimnetic anoxia, the ecological status changed in a short period from excellent to bad. Finally, in the early 1960s, the majority of the lake was virtually dead and the aquatic life survived only in the uppermost littoral zone. Since 1985, a fast recovery in the water quality has led to a strong, but temporary eutrophy in pelagic communities. The main peak of eutrophication was caused by the invasion of a species new to the lake,Aulacoseira granulata var.angustissima. Later, the pelagic communities shifted towards oligotrophy, but the original, pre-industrial status has not been re-established. The profundal benthic communities have not achieved the pre-industrial structure, but at present indicate mesotrophy.  相似文献   

A comparative mineralogical and geochemical study of sulfide mine tailings at two sites in New Mexico, USA   总被引：5，自引：0，他引：5  

Michelle P. Boulet  A. C. L. Larocque 《Environmental Geology》1998,33(2-3):130-142

A comparative study of sulfide mine tailings from two sites near Silver City in southwest New Mexico has shown the need for environmental monitoring in a geological context. The Cyprus-Piños Altos and Cleveland deposits consist of Cu and Zn skarn mineralization in the Piños Altos Mountains of New Mexico. Primary ore minerals in both deposits include chalcopyrite, sphalerite, and galena. The Cyprus-Piños Altos Mine ceased operation in 1995 and the Cleveland Mill closed in 1950. The deposits have similar mineralogical characteristics; however, the tailings are different in terms of age, degree of oxidation and method of disposal. The Cyprus-Piños Altos tailings (CPAT) are stored in a lined, bermed impoundment. They are dominantly water-saturated and exhibit no secondary-phase formation. The grains are not cemented and show no evidence of primary-mineral dissolution. The geochemical data show a predominantly primary signature. The tailings pond water is neutral to slightly alkaline (pH?from 7 to 8.3), partly as a result of processing methods. The Cleveland mill tailings (CMT) were deposited in a valley at the headwaters of an ephemeral stream. They are highly oxidized and differentially cemented. They have undergone numerous wet/dry cycles resulting in extensive oxidation. Secondary minerals predominate, and consist mainly of jarosite, goethite, hematite, and Fe-oxyhydroxides and -oxyhydroxysulfates. The pH of the stream draining the CMT is as high as 2.15. Maximum metal contents in the stream immediately downstream from the tailings are 5305?ppm Zn, 454?ppm Cu, 1.16?ppm Pb, 17.5?ppm Cd, 1.4?ppm As, and 0.01?ppm Hg.  相似文献   

Hooker's sea lions in southern New Zealand     

Graham J. Wilson 《新西兰海洋与淡水研究杂志》2013,47(3):373-375

The discovery at Stewart Island of a hauling‐out ground regularly used by Hooker's sea lions (Phocarctos hooked) is described, and recent sightings of sea lions in southern New Zealand are reported. An attempted copulation between a male Hooker's sea lion and a dead female fur seal (Arctocephalus forsteri) is also described.  相似文献   

Survey of estrogenic and androgenic disruption in Swedish coastal waters by the analysis of bile fluid from perch and biomarkers in the three-spined stickleback   总被引：1，自引：0，他引：1  

Pettersson M  Hahlbeck E  Katsiadaki I  Asplund L  Bengtsson BE 《Marine pollution bulletin》2007,54(12):1868-1880

The potential for endocrine disruption close to sewage treatment plant and pulp mill effluent discharge points along the Swedish Baltic Sea coast was explored using a dual survey strategy employing two stationary fish species. The levels of vitellogenin and spiggin as biomarkers of endocrine disruption were determined in juvenile three-spined sticklebacks (Gasterosteus aculeatus L.) together with the sex ratios and the presence of intersex. As an indication of exposure, estrogenic and androgenic substances were analysed by GC–MS in bile from perch (Perca fluviatilis L.). Spiggin and vitellogenin levels in juvenile three-spined sticklebacks were generally low, and, for most sampling sites no deviation in gonad type ratios were observed. No remarkable levels of natural or synthetic estrogens or androgens were observed in bile fluid from perch, while bisphenol A and 4-nonylphenol were detected in perch from both reference sites and exposed sites. Taken together, the results did not indicate estrogenic or androgenic disruption in the investigated waters.  相似文献   

四川锦屏山隧道岩爆综合防治施工技术     

侯景德 《探矿工程》2010,37(6):75-80

锦屏山隧道工程是锦屏水电枢纽工程的关键性控制施工项目,隧道地处我国西南高地应力区,全长约17.5km,隧道最大埋深约为2375 m,埋深大于1500 m的地段长度约12875 m。通过对锦屏山隧道现场岩爆特征的分析总结和研究,介绍了锦屏山隧道岩爆独特的工程特点和综合防治施工技术。  相似文献