中性糖对古糖酯含量测定的影响   总被引：2，自引：0，他引：2  

张真庆  赵峡  于广利  管华诗 《中国海洋大学学报(自然科学版)》2004,34(3):377-380

采用硫酸-苯酚法、硫酸-咔唑法和硫酸-间羟联苯3种方法分别对古糖酯的含量测定进行了研究，并考察了3种方法中加入8种单糖即阿拉伯糖(Ara)、半乳糖(Gal)、葡萄糖(Glc)、果糖(Fru)、木糖(Xyl)、甘露糖(Man)、鼠李糖(Rha)和岩藻糖(Fuc)后对古糖酯含量测定的影响。结果表明3种方法测定古糖酯含量时，其吸收值与古糖酯浓度(在0.1～0.5mg／mL范围内)都呈良好的线性关系，不同的中性糖对3种测定方法影响不同。样品回收率亦不相同。  相似文献   

N阶中立型泛函微分方程新的振动准则     

夏青 《中国海洋大学学报(自然科学版)》2001,31(3):448-454

作者对一类N阶中立型泛函微分方程给出了新的区间振动准则。文中的结果推广和改进了由Lalli等人得到的广义Kamenev型准则及其它已知结果。  相似文献   

Immunotoxicity Effect of Benzo[α]Pyrene on Scallop Chlamys farreri     

ZHANG Lin  PAN Luqing  LIU Jing 《中国海洋大学学报(英文版)》2009,8(1)

The toxic effects of benzo[α]pyrene (B[α]P) at different concentrations (0.1, 0.5, 1, 2.5 and 7.5 ugL-1) on scallop (Chla-mys farreri) immune system were studied. The results showed that B[a]P had significant toxic effects on the haemocyte counts, neu-tral red uptake, phagocytosis, bacteriolytic and antibacterial activity (P<0.05), while the seawater control and acetone control had no significant differences. The haemocyte counts, neutral red uptake, phagocytosis and bacteriolvtic activity in all B[α]P treatment groups as well as antibacterial activity, in groups of 0.5, 1, 2.5 and 7.5 ugL-1 B[α]P decreased significantly (P<0.05). Some of these indices tended to be stable on the sixth day and others on the ninth day, and the indices showed clear time- and concentra-tion-response to B[α]P. Bacteriolytic activity in 0.1ugL-1 B[α]P treatment group and antibacterial activity in 0.1 ugL-1 and 0.5 ugL-1 B[α]P treatment groups increased at the beginning of exposure and reached their peaks on day 1 and day 6, respectively. Following that, both activities decreased gradually and became stable after day 9. When all the indices reached stability, they were significantly lower than those in control group (P<0.05), except for antibacterial activity in 0.1 ugL-1 B[α]P treatment group (P<0.05). Thus, B[α]P has evident toxic effects on scallop immune system, which supports the view that a relationship exists between pollution and immu-nomodulation in aquatic organisms.  相似文献   

中性厌氧环境中硫酸盐还原菌导致锌的腐蚀行为研究     

全雨  窦雯雯  韩晓梅  蒲亚男  宋翼  陈守刚 《海洋科学》2020,44(11):28-35

以锌为研究对象，使用表面表征方法和电化学测试，研究了一个培养周期内硫酸盐还原菌（Sulfate-reducing bacteria，SRB）Desulfovibrio vulgaris（D.vulgaris）引起锌（Zn）试样腐蚀行为的影响。实验结果表明，SRB导致Zn试样发生了严重的均匀腐蚀和点蚀。浸泡7天后，SRB体系中的Zn试样平均失重为32.2 mg/cm²，是无菌培养基中试样平均失重的42倍，腐蚀产物主要为ZnS。生物膜和腐蚀产物膜的累积在培养初期可以减缓金属基体与溶液界面的电子传输过程，导致腐蚀速率减缓。培养中后期，由于生物膜和腐蚀产物膜的阻隔作用，导致混合膜层底部有机碳源缺乏，SRB转向Zn获取自身所需电子，表现为腐蚀速率上升。  相似文献   

Mapping of an Approximate Neutral Density Surface with Ungridded Data     

YOU Yuzhu 《中国海洋大学学报(英文版)》2008,7(1):1-9

A neutral density surface is a logical study frame for water-mass mixing since water parcels spread along such a surface without doing work against buoyancy restoring force. Mesoscale eddies are believed to stir and subsequently mix predominantly along such surfaces. Because of the nonlinear nature of the equation of state of seawater, the process of accurately mapping a neutral density surface necessarily involves lateral computation from one conductivity, temperature and depth （CTD） cast to the next in a logical sequence. By contrast, the depth of a potential density surface on any CTD cast is found solely from the data on this cast. The lateral calculation procedure causes a significant inconvenience. In a previous paper by present author published in this journal （You, 2006）, the mapping of neutral density surfaces with regularly gridded data such as Levitus data has been introduced. In this note, I present a new method to find the depth of a neutral density surface from a cast without having to specify an integration path in space. An appropriate reference point is required that is on the neutral density surface and thereafter the neutral density surface can be determined by using the CTD casts in any order. This method is only approximate and the likely errors can be estimated by plotting a scatter diagram of all the pressures and potential temperatures on the neutral density surfaces. The method assumes that the variations of potential temperature and pressure （with respect to the values at the reference point） on the neutral density surface are proportional It is important to select the most appropriate reference point in order to approximately satisfy this assumption, and in practice this is found by inspecting the θ-p plot of data on the surface. This may require that the algorithm be used twice. When the straight lines on the θ-p plot, drawn from the reference point to other points on the neutral density surface, enclose an area that is external to the cluster of θ-p points of the neutral density surface, errors will occur, and these errors can be quantified from this diagram. Examples showing the use of the method are presented for each of the world＇s main oceans.  相似文献   

Particle diffusion and adiabatic expansion of plasmoids     

M. S. Sindhu  G. Renuka  C. Venugopal 《Journal of Earth System Science》1995,104(1):37-47

In this paper neutral point (coalescence) instability (NPI) of plasmoids (PMD) associated with tailward streaming O⁺, H⁺ and e⁻ particles and diffusion region (spatial extent and particle life time) are studied. Also, radial and pitch angle diffusion studies have been carried out in the near-earth region (10 and 11 R_E during substorm onset. Our study revealed that coalescence instability is favoured by a heavier ion like O⁺ and the time required for a heavier ion to reach from one X point to an adjacent X point is minimum. Near an X type neutral line (diffusion region) ions spend a fairly long time and gain a significant amount of energy. Radial and pitch angle diffusion studies showed that higher energy particles are largely confined near the reconnection region (near-earth region) and lower energy particles are rapidly depleted from the near-earth region during substorm onset.  相似文献   

Arsenic fixation on iron-hydroxide-rich and plant litter-containing sediments in natural environments   总被引：2，自引：0，他引：2  

Andreas Fritzsche  Holger Dienemann  Ernst Gert Dudel 《Environmental Geology》2006,51(1):133-142

Iron-hydroxide-rich and plant litter-containing sediments from natural sites contaminated with uranium mine tailing leachates were examined for their ability to adsorb arsenic. The samples with high contents of iron hydroxides (Fe_total concentration, >300 g kg⁻¹) exhibited remarkable fixation of arsenic (up to 40 g As kg⁻¹). This value corresponded approximately to the supersaturation point for natural iron hydroxides under the present conditions, and it was significantly lower than the value found for synthetic iron hydroxides. There was a strong correlation (R=0.8999) between the concentration of iron and that of arsenic at low arsenic contents, indicating adsorption on strong binding sites. Although all the samples had noticeable contents of organic carbon (plant litter), calcium, and manganese, no obvious effect of these elements on arsenic fixation could be detected. The amount of iron hydroxides was found the only fixation-controlling parameter immediately below a leaching water source.  相似文献   

Neutral Points at the Cometary Diamagnetic Cavity Boundary as Possible Source of Cometary Rays     

Israelevich  P. L.  Ershkovich  A. I. 《Earth, Moon, and Planets》1998,81(2):123-133

The point source of neutral gas undergoing ionization and expanding into an uniform magnetic field is considered. Friction between the neutral and ionized particles results in the formation of the magnetic field barrier and diamagnetic cavity surrounding the source. At least one neutral point inevitably arises at the boundary of the cavity. When the neutral gas production rate grows, two neutral points may arise at this boundary. In the vicinity of these points magnetic field lines converge, along with the plasma flow which is magnetic field aligned in the steady state. As a result, two plasma jets originate from the neutral points. Possible relation of these jets to cometary rays is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

彩色图像的层次复制函数     

朱元泓  王永宁 《武汉大学学报(信息科学版)》1996,(3)

以现代彩色复制理论为基础，根据原稿、分色过程、油墨、印刷过程对印刷品层次的影响，建立了彩色复制各环节之间图像层次传递的函数关系，并用Ｃ语言编写了计算机程序，用以计算彩色分色所需要的分色数据和绘制分色曲线  相似文献   

米曲霉产中性蛋白酶的适宜条件   总被引：3，自引：0，他引：3  

杨世平  邱德全 《广东海洋大学学报》2005,25(3):47-51

研究了米曲霉产蛋白酶的分布,优化了米曲霉产中性蛋白酶的适宜培养条件以及培养基的最优组成。研究发现米曲霉产中性蛋白酶的能力为最强。米曲霉产中性蛋白酶的适宜培养条件为:m(麸皮)∶m(豆粕粉)=4∶1,水的质量分数为60%,培养基中各无机盐质量分数为:KNO30.2%,MgSO40.05%,Na2HPO40.13%,pH值为6.0,接种量为每10 g培养基接种1.0×108个孢子,最佳培养温度为30℃,最佳培养时间为48 h。在此培养条件下,最高酶活力达3 999.2 U.g-1。  相似文献