Gas permeation performance of cellulose hollow fiber membranes made from the cellulose/N-methylmorpholine-N-oxide/H2O system

Cellulose hollow fiber membranes (CHFM) were prepared using a spinning solution containing N-methylmorpholine-N-oxide as solvent and water as a nonsolvent additive. Water was also used as both the internal and external coagulant. It was demonstrated that the phase separation mechanism of this system was delayed demixing. The CHFM was revealed to be homogeneously dense structure after desiccation. The gas permeation properties of CO2, N-2, CH4, and H-2 through CHFM were investigated as a function of membrane water content and operation pressure. The water content of CHFM had crucial influence on gas permeation performance, and the permeation rates of all gases increased sharply with the increase of membrane water content. The permeation rate of CO2 increased with the increase of operation pressure, which has no significant effect on N-2, H-2, and CH4. At the end of this article a detailed comparison of gas permeation performance and mechanism between the CHFM and cellulose acetate flat membrane was given. (C) 2003 Wiley Periodicals, Inc.

长白山四种森林土壤呼吸的影响因素

2004年5-10月,研究了非生物因素(温度、土壤含水量)和生物因素(微生物量碳和植被类型)对长白山北坡四个垂直植被带阔叶红松(Pinus koraiensis)林、红松云冷杉(Picea jezoensis,Abies nephrolepis)林、岳桦(Betula ermani)云冷杉林和岳桦林的土壤呼吸的影响。结果表明:4种森林的土壤呼吸与土壤温度、大气温度之间都呈极显著(p<0.01)指数相关关系;土壤呼吸与土壤含水量没有明显的相关关系;土壤微生物量碳随季节变化有相似的变化规律,即单峰型曲线,峰值出现在8月份;土壤呼吸的月平均值和土壤微生物量碳之间都呈线性相关,但均未达到显著水平;不同月份植被类型对土壤呼吸的影响没有明显的规律。

Bulk ultrafine binderless (W0.4Al0.6)C prepared by high pressure sintering

Pure (W0.4Al0.6)C powder of about 1 mu m in diameter was sintered by the high pressure sintering (HPS) process without the addition of any binder phase. The microstructure, Vickers micro hardness and density versus the sintering time and temperature are well described. The most suitable sintering condition under pressure of 4.5 GPa is 1873 K for 8 min. Under this sintering condition, the hardness can reach 2295 kg mm(-2) and the relative density can reach 98.6%.

碳薄膜电极材料在电分析化学中的应用

由于具有一系列的优点,碳材料被广泛应用于电分析化学。新型碳电极材料的开发及其性质研究对电分析化学的发展起着重要的推动作用。最近报道了一些制备新型碳薄膜电极材料的方法,因为制备方法不同,这些碳薄膜材料的电化学性质如电位窗、稳定性、导电性也存在显著的差异。目前电位窗宽、背景电流低、稳定性高、表面不易被电极产物钝化的碳薄膜电极材料的研究非常活跃。本文综述了采用不同方法制备的一些碳薄膜电极材料如硼掺杂的金刚石薄膜、无定形碳和纳米晶体碳薄膜材料等在电分析化学中应用。

Synthesis, reactive mechanism and thermal stability of W1-xAlxC (x=0.33, 0.5, 0.75, 0.86) nanocrystalline

W1-xAlxC (x = 0.33, 0.50, 0.75, 0.86) solid solutions have been synthesized directly by ball-milling tungsten powder, aluminum powder and activated carbon. The structural development of W0.5Al0.5C phase with the milling times up to 160 h has been followed using X-ray diffraction. X-ray photoelectron spectra demonstrate that Al atom takes the place of W. High temperature annealing experiment reveals that Al is stable in hexagonal structure to 1873 K. Transmission electron microscopy image shows that the grain size of the prepared powders is about 5 nm.

Hydrothermal synthesis and spectral properties of the Eu doped KZnF3

The polycrystals of KZnF3 : Eu have been synthesized by hydrothermal method at 220 degreesC, The product was characterized by XRD, XPS and SEM. The emission and excitation spectra of europium ion were measured. The existence of Eu2+ ion was confirmed by ESR and spectroscopy. The sites were possibly occupied by Eu2+ ions, charge compensation in this crystal were also discussed.

KZnF_3∶Eu的水热合成及其光谱性质

采用中温水热法合成了立方钙钛矿单相 KZn F3 及 KZn F3 ∶ Eu,通过 SEM观察了产物形态 ;XPS测定结果表明 ,产物含氧量不高 ;荧光光谱及 ESR谱表明 ,KZn F3 ∶ Eu体系中 Eu2 +与 Eu3 +共存 ,进一步讨论了不等价取代中的电荷补偿途径

Ce3+ -> Eu2+ energy transfer in BaLiF3 phosphor

Photoluminescence characteristics and the energy transfer between Ce3+ and Eu2+ in BaLiF3 host lattice have been investigated. A series of concentrations of Ce3+ ion with a fixed Eu2+ concentration in doubly doped BaLiF3:Ce3+,Eu2+ have been studied. According to the defects forming after Eu2+ and Ce3+ entering the host lattice, cerium ions occupy the positions of nearest neighbors of the europium ions. The energy transfer probability and critical distance are calculated. (C) 1999 Elsevier Science Ltd. All rights reserved.

Synthesis, extraction and electronic structure of Ce@C-2n

In view of the growing interest in endohedral lanthanide fullerenes, Ce, as a typical +4 oxidation state lanthanide element, has been systematically studied. The synthesis, extraction and electronic structure of Ce@C-2n are investigated. Soot containing Ce@C-2n was synthesized in high yield by carbonizing CeO2-containing graphite rods and are back-burning the CeC2-enriched cathode deposit in a DC are plasma apparatus. Ce@C-2n, dominated by Ce@C-82, can be efficiently extracted from the insoluble part of the soot after toluene Soxhlet extraction by pyridine at high temperature and high pressure in a closed vessel. About 60% Ce@C-2n (2n = 82,80,78,76) and 35% Ce@C-82 can be enriched in the pyridine extract. This fact is identified by desorption electron impact mass spectrometry (DEI MS). The electronic structure of Ce@C-2n is analyzed by using X-ray photoemission spectroscopy (XPS) of pyridine-free film. It is suggested that the encapsulated Ce atom is in a charge state close to +3 and was effectively protected from reaction with water and oxygen by the enclosing fullerene cage. Unlike theoretical expectation, the electronic state of Ce@C-82 is formally described as Ce+3@C-82(3-). (C) 1997 Elsevier Science Ltd.

(η~5-C_9H_7)_3Ln·OC_4H_8(Ln=Nd、Gd、Er)的合成及晶体结构

合成了三茚基稀土配合物(η~5-C_9H_7)_3Ln·OC_4H_8(Ln=Nd、Gd、Er),经元素分析、红外光谱、水解产物核磁共振谱及质谱表征,并测得了(η~5-C_9H_7)_3Nd·OC_4H_8(1)及(η~5-C_9H_7)_3Gd·OC_4H_8(2)的晶体结构。(1)、(2)均属六方晶系,P6_3空间群,Z=2。(1)的晶体学参数为a=b=1.1843(3)nm,c=1.0304(4)nm,V=1.25165(87)nm~3,D_c=1.49g·cm~(-3),最后一致性因子R=0.049;(2)的晶体学参数a=b=1.1805(2)nm,c=1.0236(2)nm,V=1.23536(56)nm~3,D_c=1.54 g·cm~(-3),R=0.023。平均Nd-C=0.2812nm,Gd-C=0.2795nm;Nd-O=0.2557(21)nm,Gd—O=0.2459(13)nm。配合物中四氢呋喃的四个碳原子处于完全无序状态。

Halogenated Sesquiterpenes from the Marine Red Alga Laurencia saitoi (Rhodomelaceae)

Four new halogenated sesquiterpenes, 10-bromo-3-chloro-2,7-epoxychamigr-9-en-8a-of (1), 2,10 beta-dibromochamigra-2,7-dien-9 alpha-ol (2), (9S)-2-bromo-3-chloro-6,9-epoxybisabola-7(14),10-diene (3), and (9R)-2-bromo-3-chloro-6,9-epoxybisabola-7(14),10-diene (4), were characterized from the marine red alga Laurencia saitoi. In addition, two known halosesquiterpenes, 2,10-dibromo-3-chlorochamigr-7-en-9 alpha-ol (5) and isolaurenisol (6), were also isolated and identified. Their structures were established on the basis of extensive analysis of spectroscopic data.

Life history strategies of Calanus sinicus in the southern Yellow Sea in summer

Ecological and physiological features of the planktonic copepod Calanus sinicus in the southern Yellow Sea in summer were studied to reveal its life history strategy. From the coastal shallow waters to the central part of the southern Yellow Sea, a shift of the stage composition occurs from being dominated by the egg-nauplius stage to being dominated by the fifth copepodite (CV) stage. Most CVs reside in the Yellow Sea Cold Water Mass (YSCWM), where both temperature and food abundance are low. CVs in the YSCWM have longer body lengths, heavier body weights and higher carbon contents than those outside the YSCWM. Onboard incubations show that the development of CVs in the YSCWM is suspended. Energy conservation, development suspension and lack of diel vertical migration (DVM) behavior suggest a diapause status for the CVs in the YSCWM, although vertical distribution patterns indicate the CV individuals are not fully synchronous in physiology and development. This adaptive oversummering strategy would help C. sinicus to live through the warm and food-limited summer in the central part of the southern Yellow Sea; both low temperature and low food supply are necessary for CV to maintain the resting state in the YSCWM. Calanus sinicus exhibits different life history strategies in different regions of the southern Yellow Sea in summer.

A close phylogenetic relationship between Sipuncula and Annelida evidenced from the complete mitochondrial genome sequence of Phascolosoma esculenta

Background: There are many advantages to the application of complete mitochondrial (mt) genomes in the accurate reconstruction of phylogenetic relationships in Metazoa. Although over one thousand metazoan genomes have been sequenced, the taxonomic sampling is highly biased, left with many phyla without a single representative of complete mitochondrial genome. Sipuncula (peanut worms or star worms) is a small taxon of worm-like marine organisms with an uncertain phylogenetic position. In this report, we present the mitochondrial genome sequence of Phascolosoma esculenta, the first complete mitochondrial genome of the phylum. Results: The mitochondrial genome of P. esculenta is 15,494 bp in length. The coding strand consists of 32.1% A, 21.5% C, 13.0% G, and 33.4% T bases (AT = 65.5%; AT skew = -0.019; GC skew = -0.248). It contains thirteen protein-coding genes (PCGs) with 3,709 codons in total, twenty-two transfer RNA genes, two ribosomal RNA genes and a non-coding AT-rich region (AT = 74.2%). All of the 37 identified genes are transcribed from the same DNA strand. Compared with the typical set of metazoan mt genomes, sipunculid lacks trnR but has an additional trnM. Maximum Likelihood and Bayesian analyses of the protein sequences show that Myzostomida, Sipuncula and Annelida (including echiurans and pogonophorans) form a monophyletic group, which supports a closer relationship between Sipuncula and Annelida than with Mollusca, Brachiopoda, and some other lophotrochozoan groups. Conclusion: This is the first report of a complete mitochondrial genome as a representative within the phylum Sipuncula. It shares many more similar features with the four known annelid and one echiuran mtDNAs. Firstly, sipunculans and annelids share quite similar gene order in the mitochondrial genome, with all 37 genes located on the same strand; secondly, phylogenetic analyses based on the concatenated protein sequences also strongly support the sipunculan + annelid clade (including echiurans and pogonophorans). Hence annelid "key-characters" including segmentation may be more labile than previously assumed.