稀土在硫酸盐木浆氧漂中的应用

在阔叶木硫酸盐浆的氧漂处理中，对稀土络合物的应用进行了试验和研究。确定了稀土助剂用于硫酸盐浆氧漂的工艺条件，并研究了稀土的行为。结果表明，稀土具有阻抑碳水化合物降解的作用，漂后纸浆白度和得率提高、强度性能有所改善。     

H13模具钢表面处理和热疲劳—热熔损性能

对Ｈ１３钢进行了硫氮碳（ＳＮＣ）共渗加氧化处理，稀土（ＲＥ）－ＳＮＣ共渗及稀土（ＲＥ）－ＳＮＣ共渗加氧化处理等表面处理工艺试验，并对处理试样分别进行了热疲劳性能和在合金铝液中的热熔损性能试验，结果表明，在空气氧化条件下，添加稀土的ＳＮＣ共渗加氧化复合处理试验的渗层热疲劳性能比未添加稀土（ＲＥ）的ＳＮＣ共渗加氧化得事处理及随后未经氧化处理的ＲＥ－ＳＮＣ共渗的试样高，在本试验条件下，加稀土进行处理的试     

稀土对MoSi2低温氧化行为的影响

利用热重量分析法（简称ＴＧＡ法）、Ｘ－射线衍射（Ｘ－Ｒａｙ）和扫描电镜观察（ＳＥＭ）分析了稀土在ＭｏＳｉ２低温下氧化中的作用。结果表明，稀土的加入促进了ＭｏＳｉ２的氧化程度，但未发现“ＰＥＳＴ”现象。     

硫酸钠复盐法分离Ce（Ⅳ）和RE（Ⅲ）过程中影响分离效果的因素的研究

在硫酸稀土溶液中，用Ｎａ２ＳＯ４复盐法分离Ｃｅ（Ⅳ）和ＲＥ（Ⅲ）时，研究了溶液中Ｆ－浓度、Ｎａ２ＳＯ４加入量、反应时间、温度和溶液的酸度对Ｃｅ（Ⅳ）提取率的影响，以及复盐沉淀洗涤情况对Ｃｅ（Ⅳ）和ＲＥ（Ⅲ）分离效果的影响。确立了在稀土溶液中用Ｎａ２ＳＯ４复盐法提取铈和少铈稀土的合理工艺条件。     

ICp－AES法同时直接测定氟碳铈精矿中稀土和部分非稀土元素

ＩＣｐ－ＡＥＳ法同时直接测定氟碳铈精矿中稀土和部分非稀土元素张义东,曾,刘贵标,韩英辉,赖娟,夏禹谟（赣加稀土有限公司,江西赣县,３４１１００）ＩＣｐ─ＡＥＳ法在混合稀土分析中已有报道（１～３）,但直接测定氟碳铈矿中全部稀土和部分非稀土元素未见报道。...     

氧化钇标准物质中CeO_2，Pr_6O_（11），Dy_2O_3，PbO，NiO

氧化钇标准物质中ＣｅＯ_２，Ｐｒ_６Ｏ_（１１），Ｄｙ_２Ｏ_３，ＰｂＯ，ＮｉＯ，ＣａＯ的ＩＣＰ－ＡＥＳ测定江瑞源（福建省测试技术研究所，福州，３５０００３）高纯稀土中杂质测定有控制气氛电弧法、色层分离电弧法及ＩＣＰ－ＡＥＳ法等。而ＩＣＰ－ＡＥＳ法对高纯?..     

镧系元素高氯酸盐苯丁基亚砜配合物的合成与表征

本文以稀土高氯酸盐ＲＥ（ＣｌＯ_４）_３ｎＨ_２Ｏ（ＲＥ＝Ｌａ~（３＋）、Ｃｅ~（３＋）、Ｐｒ~（３＋）、Ｎｄ~（３－）、Ｓｍ~（３－）、Ｅｕ（３＋），ｎ＝６～７）与苯丁基亚砜ＰＢＳＯ（Ｃ_６Ｈ_５Ｃ_４Ｈ_９）在无水乙醇体系中合成出六个新配合物，并对配合物进行了元素分析，稀土离子含量测定，配体ＰＢＳＯ含量测定ＣｌＯ_４~－含量测定、ＩＲ谱、导电、ＴＧ－ＤＴＡ分析及Ｘ－射线粉末衍射。确定了配合物的组成为［ＲＥ（ＢＰＳＯ）_７（ＣｌＯ_４）］（ＣｌＯ_４）_２，配位数为８，电解质类型为１：２。     

50%稀土精矿配稀土富渣冶炼稀土硅铁合金

本文研究了包头５０％稀土精矿配稀土富渣，采用硅热法成功地冶炼出ＦｅＳｉＲＥ（２４－３２）不粉化合金。     

ICP—MS测定高纯氧化铒中14个稀土杂质

研究了用电感耦合等离子质谱法（ＩＣＰ—ＭＳ）测定高纯氧化铒中１４个稀土杂质的方法。本文比较了５种内标元素，研究了产生氢化铒时，氢化铒的量与铒丰度之间的关系，从而有效地扣除了ＥｒＨ（１６９）对Ｔｍ（１６９）的干扰。确定了在正常分辨率下，以Ｃｓ作内标，标准曲线校正，扣除ＥｒＨ（１６９）后，测定氧化铒中１４个稀土杂质的方法。对于５ＮＥｒ２Ｏ３，ＲＳＤ＜１５％，回收范围７０～１５０％，与标准加入法校正结果吻合。     

电化学在稀土湿法冶金中的应用──Ⅱ．铕的电解还原及分离工艺

电化学在稀土湿法冶金中的应用──Ⅱ．铕的电解还原及分离工艺刘建刚（包钢稀土研究院包头０１４０１０）铕是稀土中稀少元素之一。Ｅｕ（Ⅲ）离子与其周围元素离子Ｓｍ（Ⅲ）、Ｇｄ（Ⅲ）性质及其相似，很难用萃取法和离子交换法将它们分离。铕及其化合物用于重要的发光...     

稀土助漂时硫酸盐木浆中纤维素结晶度的研究

稀土应用于混合阔叶材硫酸盐浆的氧碱漂白中，引起纸浆质量和性能的变化。本文介绍了用Ｒｕｌａｎｄ法分析纸浆的绝对结晶度，研究了稀土氧碱处理后纸浆结晶度的变化，对稀土在纸浆氧漂中的行为及其对纸浆纤维素的作用进行了探讨。     

Molecular analysis of bacterial isolates and total community DNA from kraft pulp mill effluent treatment systems

Chloroaliphatics are major components of bleached kraft mill effluents. Gene probes and oligonucleotide primers were developed to monitor kraft pulp mill effluent treatment systems for the presence of key genes (dehalogenases) responsible for the dehalogenation of chloroaliphatic organics. The primers were used for polymerase chain reaction (PCR) analysis of genomic DNA extracted from dehalogenating bacterial isolates and from total community DNA extracted from water and sediments of mill effluent treatment system. PCR amplification with oligonucleotide primers designed from dhlB, encoding the haloacid dehalogenase from Xanthobacter autotrophicus, revealed the presence of dehalogenase genes in both aerated lagoons and stabilization basins. Similarly, positive results were obtained with mmoX primers designed from the soluble methane monooxygenase gene of Methylococcus capsulatus Bath. The haloacetate dehalogenase encoding gene (dehH2) from Moraxella sp. was typically not detected in mill effluent treatment systems unless the biomass was selectively enriched. DNA sequence analysis of several PCR fragaments revealed significant similarity to known dehalogenase amd methane monooxygenase genes. The results indicated a broad distribution of known dehalogenation genes and bacteria with chloroorganic-degrading potential in the mill effluent treatment systems.     

Contaminants in ospreys from the Pacific Northwest: I. Trends and patterns in polychlorinated dibenzo-p-dioxins and -dibenzofurans in eggs and plasma

Osprey (Pandion haliaetus) eggs were collected from 1991 to 1997 at nests (n = 121) upstream and downstream of bleached kraft pulp mills and at reference sites in the Fraser and Columbia River drainage systems of British Columbia, Washington, and Oregon. Blood samples were collected from nestling ospreys during the 1992 breeding season on the Thompson River. Samples were analyzed for polychlorinated dibenzo-p-dioxins (PCDDs) and -dibenzofurans (PCDFs). Mean concentrations of 2,3,7,8-TCDD were significantly higher in eggs collected in 1991 at downstream compared to upstream nests near pulp mills at Kamloops and Castlegar, British Columbia. There were no significant temporal trends in 2,3,7,8-TCDD, -TCDF or other measured compounds at a sample of nests monitored between 1991 and 1994 downstream of the Castlegar pulp mill, despite changes in bleaching technology (CIO2 substitution). However, by 1997 concentrations of 2, 3,7,8-TCDD and -TCDF were significantly lower than previous years in nests sampled downstream at both Castlegar and Kamloops. An unusual pattern of higher chlorinated PCDDs and PCDFs was found in many of the osprey eggs collected in this study, and considerable individual variation in the pattern existed among eggs from the same site. For example, eggs from four different nests at one study area (Quesnel) on the Fraser River had concentrations of 1,2,3,4,6,7,8-HpCDD ranging from <1 to 1,100 ng/kg and OCDD from <1 to 7,000 ng/kg wet weight. Higher mean concentrations of HpCDD and OCDD were found in eggs from the Thompson River, a tributary of the Fraser, compared to the Columbia River, and concentrations were generally higher at nests upstream of pulp mills. In plasma samples, 1,2,3,4,6,7,8-HpCDD and OCDD were the main compounds detected, with no significant differences measured between samples upstream versus downstream or earlier versus later in the breeding season. Use of chlorophenolic wood preservatives by lumber processors was considered the main source of higher chlorinated PCDD/Fs throughout the systems, based on patterns of trace PCDFs in eggs and significant correlations between egg concentrations of pentachlorophenol and both HpCDD (r = 0.891, p < 0.01) and OCDD (r = 0.870, p < 0.01).     

Intestinal mast cell response and mucosal defence against Strongyloides venezuelensis in interleukin-3-hyporesponsive mice

Mineralization in the pulp is a common finding in permanent as well as primary teeth and is associated with caries, aging, traumatic injuries and systemic conditions. This article describes an unusual pattern of pulpal calcification. A tube-like calcified structure formed in the dental pulp of primary incisors following mild traumatic injuries. It was studied by clinical, radiographic and histologic evaluation and by scanning electron microscopy. The tube-like structure was found to extend along the entire length of the pulp canal. Generally it was separated from the root dentin by normal pulp tissue, but was connected to the dentin in some sites. It had the histologic appearance of osteodentin with cell inclusions in a ring-like formation that was incomplete in places. The scanning electron microscope study showed rough inner and outer surfaces of a tube-like structure with openings that seemed to be dentinal tubules.     

Cloning, sequencing and overexpression in Escherichia coli of a xylanase gene, xynA from the thermophilic bacterium Rt8B.4 genus Caldicellulosiruptor

A genomic library of the extremely thermophilic eubacterial strain Rt8B.4 was constructed in lambda ZapII and screened for the expression of xylanase activity. One recombinant bacteriophage showed xylanase, xylosidase and arabinosidase activity. Sequence analysis and homology comparisons showed that this plasmid derivative, pNZ2011, was composed of 6.7 kb thermophilic DNA and contained what appeared to be an operon-like structure involving genes associated with xylose metabolism. The xylanase gene, xynA was shown to code for a multi-domain protein. Xylanase activity was shown to be associated with the carboxy-terminal domain (domain 2) by deletion analysis and also by selective polymerase chain reaction (PCR) amplification and expression of the individual domains. Denaturing polyacrylamide gel analysis of the protein encoded by the PCR product showed three main overexpressed proteins to be present in cell extracts, presumably caused by proteolytic degradation in the Escherichia coli host. The xylanase activity from domain 2 is associated with a 36-kDa protein, which is stable at 70 degrees C for at least 12 h at pH 7. The small size of this active enzymatic domain and its temperature stability suggest that it may be of value in the enzyme-enhanced bleaching of kraft pulp.     

Root resorption and pulpal changes due to intrusive force

Intrusion has been regarded as a controversial topic in the literature. It is apparent from many studies that excessive forces applied in orthodontic treatment might lead to undesirable results such as circulatory disturbances, pulp degeneration, calcification and even necrosis. This study was performed to observe the reaction of pulp and roots following tooth intrusion. Material consisted of four first premolar teeth of two adult patients. One premolar of each patient was intruded orthodontically and the other premolars were taken as controls. The palatal roots of the experimental teeth were cut and examined in scanning electron microscope (SEM) and the pulps of the teeth were examined in transmission electron microscope (TEM). At SEM examination, root surfaces of intruded teeth showed resorption cavities of different diameters and depths. At TEM examination, vascular degeneration was the main change in the pulps of experimental teeth.     

Patterns, trends, and toxicological significance of chlorinated hydrocarbon and mercury contaminants in bald eagle eggs from the Pacific coast of Canada, 1990-1994

Bald eagle (Haliaeetus leucocephalus) eggs were collected during incubation, 1990-1992, from 16 nests near three bleached-kraft pulp mills, from six nests in the Fraser River estuary and from seven nests at a reference site on the Pacific coast of Canada. Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were present in all eggs in a qualitatively similar pattern among sites. Mean concentrations of 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) were significantly higher in eggs collected from near three kraft pulp mill sites in the Strait of Georgia (44, 45, 84 ng/kg) than from the reference area in Johnstone Strait (15 ng/kg). There were few differences among sites in mean organochlorine pesticide levels, indicating the diffuse distribution of those chemicals and the domination of atmospheric inputs. Mean concentrations of total polychlorinated biphenyls (PCBs) were highest in eggs from the Strait of Georgia (4.86 mg/kg) and the PCB congener pattern was significantly different between that area and both the lower Fraser valley and Johnstone Strait. Mean mercury concentrations, which were mainly methyl-mercury, were significantly higher in eggs collected from the lower Fraser Valley (0.258 mg/kg) and Johnstone Strait (0.294 mg/kg) compared to the Strait of Georgia (0.188 mg/kg). Individual and regional variation in concentrations of organochlorine pesticides, PCBs and mercury in eagle eggs were thought to be influenced mainly by dietary differences. Toxicologically, in 1990, mean TCDD-toxic equivalents (TEQs) in bald eagle eggs were about two-fold greater than a lowest-observed-effect level, suggested elsewhere for this species, of 210 ng/kg TEQs. In the Strait of Georgia, PCCDs and PCDFs made a greater contribution to TEQs than non-ortho and mono-ortho PCBs, whereas the reverse was true for eggs outside the strait. Mean eggshell thickness was less than the pre-1947 value at all sites, although there was no significant relationship between eggshell thickness and DDE concentrations. Levels of other organochlorine pesticides and mercury were below those considered to be toxic.     

CMAP: a novel cystatin-like gene involved in liver metastasis

The distribution and ultrastructure of class II major histocompatibility complex (MHC)-positive cells were investigated in human dental pulp, employing immunohistochemistry using an anti-human leukocyte antigen (HLA)-DR-monoclonal antibody. HLA-DR-immunopositive cells, appearing spindle-like or dendritic in profile, were densely distributed throughout the dental pulp. Under the electron microscope, these cells exhibited various sizes of vesicles containing clear or opaque contents, multivesicular bodies and characteristic fine tubulovesicular structures in their cytoplasm. Some reactive cells possessed coated pits and vesicles including electron-dense materials, indicating an active endocytosis. At the periphery of the pulp tissue, the HLA-DR-immunopositive cells were predominantly situated in the subodontoblastic layer, with some located in the odontoblast layer and/or predentin and extending their cytoplasmic processes into the dentinal tubules. Cell processes of these cells occasionally made contact with several odontoblast processes in the same way as the nerve fibers in the predentin. These cells never contained the typical phagosomes frequently observed in the HLA-DR-immunoreactive macrophages in the subodontoblastic layer and the pulp core. The results suggest that the HLA-DR-immunopositive cells in the odontoblast layer and/or predentin have some regulatory function on the odontoblasts under physiological conditions, in addition to their involvement in the initial defense reaction after tooth injury.     

Metabolism of caffeine to nucleic acid precursors in mammalian cells

The mission of this study was to determine whether or not arteriovenous connections, indicative of a "closed" type of circulation, existed in the human spleen. Spleens from four patients requiring therapeutic splenectomy were the basis for this report. Scanning electron microscopy of plastic corrosion casts, prepared from these four spleens, revealed direct vascular conduits between splenic pulp arteries or arterial capillaries and the venous sinuses in the red pulp. Also demonstrated were a few arteriovenous shunts between pulp arteries or arterial capillaries and pulp or trabecular veins. Inclusion of sized microspheres in low-viscosity perfusion plastic illustrated that some diameters of the connecting shunts were 7-10 mum, with other shunts even smaller. Not only do arteriovenous connections exist in human spleens, but their frequency, as revealed by methods accentuating three-dimensional aspects of the splenic microcirculation, justify future reconsiderations of the functional significance of this closed type of circulation. Examination of samples of the same intact spleens, prepared by freeze-fracture and conventional critical-point drying, also revealed an "open" type circulation structure, namely, pore-patterned sinus walls that could facilitate blood cell movement from pulp cords into venous sinuses. Scanning electron microscopy thus has provided direct evidence that human spleens have both "open" and "closed" circulatory pathways in their microvasculature.