Periodicity of Holocene climatic variations in the Huguangyan Maar Lake

There exist five primary periods of 2 930, 1 140, 490, 250 and 220 a in the Holocene climatic variations in the Huguangyan Maar Lake, according to the energy-spectrum and filter analyses of high-resolution time sequences (10–15 a) of the sediment dry density. The peak values of the three temperature-decreasing periods with the 2 930 a cycle occur at about 7 300, 4 250 and 1 200 Cal. aBP. There are 7–8 temperature-decreasing periods with the 1 140 a cycle, and the climate fluctuation range is largest in the early Holocene, and reduces gradually in the middle and late Holocene. The millennial-scale climatic change in the Holocene may adjust the global water cycle and the thermohaline circulation intensity through the harmonic tones of the earth’s precession cycle, which in turn influences the global climate change.     

Optimized use of MgO flux in the agglomeration of high-chromium vanadium-titanium magnetite

The optimized use of MgO flux in the agglomeration of high-chromium vanadium-titanium magnetite was investigated systematically through sinter and pellet experiments. MgO was added in the form of magnesite. When the content of MgO in the sinter was increased from 1.95wt% to 2.63wt%, the low-temperature reduction degradation index increased from 80.57% to 82.71%. When the content of MgO in the pellet was increased from 1.14wt% to 2.40wt%, the reduction swelling index decreased from 15.2% to 8.6%; however, the compressive strength of the oxidized pellet decreased dramatically and it was 1985 N with an MgO content of 1.14wt%. This compressive strength does not satisfy the requirements for blast-furnace production. When all of the aforementioned results were taken into account, the sinter with a high MgO content (2.63wt%) matching the pellet with a low MgO content (less than 1.14wt%) was the rational burden structure for smelting high-chromium vanadium-titanium magnetite in blast furnaces.     

不同磷营养水平对重金属Cu、Zn、Cd生物毒性效应的影响

运用水溞趋光行为的抑制试验,研究了水体中不同磷营养水平和重金属（Cu、Zn、Cd）共同存在时的联合生物毒性效应.结果表明,在较低浓度下,水体中无机磷的生物毒性很小;当浓度较高时,不同形态的无机磷对水溞生物毒性存在显著差异,大小顺序为：PO4^3-〉H2PO4-≈HPO4^2-.在富营养化的水体中,重金属的生物毒性与水体中磷的营养水平有关,磷的存在可一定程度地减轻重金属污染的生物毒害作用.研究结果可为进一步了解富营养化状态下的重金属毒性变化以及富营养化和重金属污染的相互关系及生态毒性效应提供理论依据,为淡水资源的保护及水生生态系统的健康质量评价和恢复提供理论依据和手段.     

含锰钢液在真空有渣精炼过程中的锰蒸发和脱氮行为研究

Considering the precise composition control on the vacuum refining of high-Mn steel, the behaviors of both Mn evaporation and nitrogen removal from molten Mn steel were investigated via vacuum slag refining in a vacuum induction furnace. It was found that the reaction interfaces of denitrification and Mn evaporation tend to migrate from the surface of slag layer to the surface of molten steel with the gradual exposure of molten steel during the vacuum slag refining process. Significantly, compared with the experimental group without slag addition, the addition of slag into steel can result in a lower Mn evaporation rate constant of 0.0192 cm·min?1 at 370 Pa, while the denitrification rate is almost not affected. Besides, the slag has a stronger inhibitory effect on Mn evaporation than the reduced vacuum pressure. Moreover, the inhibitory effect of the slag layer on Mn evaporation can be weakened with the increase of the initial Mn content in molten steel. The slag layer can work as an inhibitory layer to reduce the Mn evaporation from molten steel, the evaporation reaction of Mn mainly proceeds on the surface of the molten steel. This may be attributed to the Mn mass transfer coefficient for one of reaction at steel/slag interface, mass transfer in molten slag, and evaporation reaction at slag/gas interface is lower than that of evaporation reaction at steel/gas interface. The introduction of slag is proposed for both denitrification and manganese control during the vacuum refining process of Mn steels.     

单纯二重有向三元系的相交数

解决了单纯二重有向三元系的相交数问题，即证明了对于任一正整数ｕ≥３，ｖ≡０，１（ｍｏｄ ３），存在两个单纯二重有向三元系相交于ｓ个公共区组的充要条件是：当ｖ≥４时，ｓ∈（０，１，２，．．．，２ｖ（ｖ－１）／３），ｓ≠（２ｖ（ｖ－１）／３）－１当ｖ＝３时，ｓ∈（０，２，４）。     

A SISO mixed H2／l1 optimal control problem and its solution

Study of the SISO mixed H2/l1 problem for discrete time systems showed that there exists a unique optimal solution which can be approximated within any prescribed missing error bound in l2 norm with solvable suboptimal solutions and solvable superoptimal solutions.     

Functional profiling of the Saccharomyces cerevisiae genome

Determining the effect of gene deletion is a fundamental approach to understanding gene function. Conventional genetic screens exhibit biases, and genes contributing to a phenotype are often missed. We systematically constructed a nearly complete collection of gene-deletion mutants (96% of annotated open reading frames, or ORFs) of the yeast Saccharomyces cerevisiae. DNA sequences dubbed 'molecular bar codes' uniquely identify each strain, enabling their growth to be analysed in parallel and the fitness contribution of each gene to be quantitatively assessed by hybridization to high-density oligonucleotide arrays. We show that previously known and new genes are necessary for optimal growth under six well-studied conditions: high salt, sorbitol, galactose, pH 8, minimal medium and nystatin treatment. Less than 7% of genes that exhibit a significant increase in messenger RNA expression are also required for optimal growth in four of the tested conditions. Our results validate the yeast gene-deletion collection as a valuable resource for functional genomics.     

三角形内部两个动点的一个不等式

运用三角形的基本不等式及Stewart定理,建立涉及三角形内部两个动点的一个不等式,且应用该不等式导出一些已知和新的不等式,最后提出两个猜想。     

传染性肝炎对糖代谢负荷异常的研究

到目前为止国内外对传染性肝炎还未有特效药治疗,最近试用的免疫治疗还在试验中,一般以休养、营养和中西医结合护肝治疗为主。因此临床上常供给大量葡萄糖,甚至无期限与无限度地使用。作者鉴于临床上不少病例,因供糖过多,而出现糖尿病对此问题曾对各型传染性肝炎作葡萄糖代谢负荷的研究,目的是探讨肝炎患者是否有必要长期及大量供应葡萄糖,其结果作为临床家的参考。材料选择