Formation and structure of LaNi2 intermetallic compound under high pressure

The Cubic LaNi2 Laves phase has been synthesized under high pressure. The effects of temperature and pressure on the stability of the Laves phase have been studied. High pressure also induces the phase transitions from intermetallic compounds La2Ni3 and LaNi2.286 to the Laves phase.

Chemical characteristic of bioactive polysaccharides isolated from Ornithogalum caudatum Ait.

A water-soluble crude extract prepared from Ornithogalum caudatum Ait. (OCA) showing a high immunomodulating activitiy was isolated and characterized by virtue of get filtration and column chromatography. The presence of the monosaccharides has been established by the chemical analysis. The quantitative analysis of the alditol acetate derivatives of them showed the ratios of the monosaccharides analyzed by means of GC respectively. The concentrations of protein(280 nm) and carbohydrate (496 nm) were detected respectively. The information of the molecular weight from the pure polysaccharide was obtained by several standard Dextrans from the Sephadex chromatography.

聚砜齐聚物的激光质谱分析

MALDI-TOF-MS是20世纪80年代末发展起来的一种先进的软电离技术,由于它具有质量范围宽、碎片少的优点,能够用来直接观察到一些聚合物离子,它已被成功地应用在生物高分子如蛋白质、核苷酸以及PS,PEG、树枝状聚脂、树枝状聚醚等合成高分子的表征中[1,2].另外,它也成功地应用到了芳香环状聚酯[3]、芳香环状聚酰胺[4]等芳香环状齐聚物结构表征中.本文应用了MALDI-TOF-MS法对聚砜齐聚物结构进行了表征与确认,获得了满意的结果.研究结果表明该方法是测定聚砜齐聚物结构的有效方法.

Formation of ordered arrays of gold nanoparticles from CTAB reverse micelles

In this presentation, a reverse micelle technique was described to create colloid gold nanoparticles and their self-organization into superlattices. Gold nanoparticles were prepared by the reduction of HAuCL4 in CTAB/octane + 1-butanol/H2O reverse micelle system using NaBH4 as reducing agent. Dodecanethiol (C12H25SH) was used to passivate the gold nanoparticles immediately after formation of the gold colloid. After re-dispersing in toluene under ultrasonication, a supernatant containing nearly monodispersed dodecanethiol-capped gold nanoparticles was obtained. Self-organization of the gold nanoparticles into 1D, 2D and 3D superlattices was observed on the carbon-coated copper grid by TEM. UV-vis absorption spectra were also used to characterize the gold colloids with and without dodecanethiol capping. (C) 2001 Elsevier Science B.V. All rights reserved.

二苯基四硫富瓦烯-十二钨杂多酸自由基盐的合成、性质和结构

用电结晶法合成了二苯基四硫富瓦烯（ＤＢＴＴＦ）－十二钨杂多酸自由基盐，（ＤＢＴＴＦ）６ＨＳｉＷ１２Ｏ４０·２Ｈ２Ｏ和（ＤＢＴＴＦ）６ＰＷ１２Ｏ４０·５Ｈ２Ｏ，并用红外光谱、电子光谱和ＥＳＲ谱进行了表征。测定了两个盐的磁化率、电导率和（ＤＢＴＴＦ）６ＨＳｉＷ１２Ｏ４０·２Ｈ２Ｏ的单晶结构以及Ｘ－射线粉末衍射图。晶体属三斜晶系，Ｐ１空间群；晶胞参数为：ａ＝１３．７７４（２），ｂ＝１４．１９６（２），ｃ＝１５．６２８（３），α＝１０４．４８（１）°，β＝１０３．９７（１）°，γ＝９５．８２（１）°，Ｖ＝２８２８．４（８）３，Ｚ＝１，Ｄｃ＝２．７８９ｍｇ／ｍ３，Ｒ＝０．０６１５。两种盐均为顺磁性物质，具有半导体的电传导性。

Direct deposition and characterization of Langmuir-Blodgett monolayers of soluble polyimides

Langmuir-Blodgett (LB) monolayers of three kinds of soluble polyimides were prepared with the direct deposition method, The monolayer structures were characterized with W-vis absorption spectroscopy, the wide angle X-ray scattering method and electrochemical techniques. The polyimide molecules in the LB monolayers lie orderly on the substrate surfaces with the orientation in which the dianhydride group is normal to the substrate surface and two carbonyl oxygen groups close to the surface. Therefore, the thickness of the three kinds of polyimide LB monolayers are the same because it depends on the distance between the two carbonyl oxygen groups in the same ring. The area of monomeric units are dependent on the length of the diamine group. The model of the molecular packing proposed from the quantomechanical calculation is in good agreement with the experimental results. (C) 1997 Elsevier Science S.A.

UNIMOLECULAR DISSOCIATION REACTIONS OF DOUBLY-CHARGED IONS [C12H12N2O](2+) AND [C12H12N2S](2+) IN GAS-PHASE

The unimolecular dissociation reactions of doubly charged ions were reported, which resulted from a tandem mass spectrometer and a reversed geometry double focusing mass spectrometer by electron impact, Mass analyzed ion kinetic energy spectrometry (MIKES) was used to obtain the kinetic energy releases in charge separation reactions of doubly charged ions, The intercharge distances between the two charges at transition states can be calculated from the kinetic energy releases, Transition structures of unimolecular dissociation reactions were infered from MIKES and MS/MS.

STUDIES ON THE SYNTHETIC, STRUCTURAL, ELECTRICAL, AND MAGNETIC-PROPERTIES OF THE NEW LAYERED OXIDES LN(2)MCO(2)O(7) (LN=SM, GD, M=SR, BA)

Three new oxides Ln(2)MCo(2)O(7) (Ln = Sm, Gd; M = Sr, Ba) have been synthesized in solid state reaction method. The powder X-ray diffraction spectra show that they are all isostructural with Sr3Ti2O7. The electrical resistivities in the temperature range 300-1100 K show that they are all semiconductors, and a transition to metals is observed at 1053, 1053, and 573 K for Sm2SrCo2O7, Gd2SrCo2O7, and Sm2BaCo2O7, respectively. The magnetic suspectivities of Gd2SrCo2O7 in the temperature range 300-673 K fit the Curie-Weiss law well. A plateau is observed in the curves of Sm(2)MCo(2)O(7) (M = Sr, Ba) which is attributed to the configuration state change of Co(III) from low spin to high spin. (C) 1995 Academic Press, Inc.

双电荷离子［C_（12）H_（12）N_2O］~（2＋）和［C_（12）H_（12

双电荷离子［Ｃ_（１２）Ｈ_（１２）Ｎ_２Ｏ］~（２＋）和［Ｃ_（１２）Ｈ_（１２）Ｎ_２Ｓ］~（２＋）的气相单分子分解反应研究任达，贾维平，李智立，刘淑莹（中国科学院长春应用化学研究所，长春，１３００２２）关键词双电荷离子，质量分析离子动能谱，串联质谱，４...

MgCl_2·EB／TiCl_4高效载体催化剂的乙烯／1－丁烯共聚反应研究

以ＭｇＣｌ＿３．ＥＢ／ＴｉＣｌ＿４高效载体催化剂，在工业条件下进行了乙烯／１－丁烯共聚合。探讨了１－丁烯的存在及浓度对催化剂效率及聚合动力学的影响。用ＦＴ－ＩＲ和１３ＣＮＭＲ测定了共聚物的组成和序列分布。

COMPARATIVE-STUDY OF KALMAN FILTERING, SYNCHRONOUS EXCITATION AND NUMERICAL DERIVATIVE TECHNIQUES IN FLUOROMETRY

The performance of Kalman filtering, synchronous excitation and numerical derivative techniques for the resolution of overlapping emission spectra in spectrofluorimetry was studied. The extent of spectrum overlap was quantitatively described by the separation degree D(s), defined as the ratio of the peak separation to the full width at half-maximum of the emission spectrum of the interferent. For the system of Rhodamine B and Rhodamine 6G with a large D(s) of about 0.4, both Kalman filtering and synchronous techniques are able to resolve the overlapping spectra well and to give satisfactory results while the derivative spectra are still overlapped with each other. Moreover, the sensitivities are greatly decreased in derivative techniques. For more closely spaced spectra emitted by the complexes of Al and Zn with 7-iodo-8-hydroxyquinoline-5-sulphonic acid (Ferron)-hexadecyltrimethylammonium bromide, the synchronous excitation technique cannot completely separate the overlapping peaks, although it increases the separation degree from 0.25 in the conventional spectra to 0.37 in the synchronous spectra. On the other hand, Kalman filtering is capable of resolving this system. When the Al/Zn intensity ratio at the central wavelength of Al was > 1, however, the accuracy and precision of the estimates for Zn concentration produced by the Kalman filter became worse. In this event, the combination of synchronous excitation and Kalman filtering can much improve the analytical results.

几种反丁烯二酸酯的自由基聚合反应研究

以 AIBN及BPO为引发剂,对几种自制的反丁烯二酸酯(DRFs)单体,如反丁烯二酸二环已酯(DCHCF)、反丁烯二酸二仲丁酯(DsBF)、反丁烯二酸二仲戊酯(DsAF)、反丁烯二酸甲基异丙基酯(MiPF)等单体的自由基聚合反应进行了研究。研究了它们的自由基聚合反应动力学,并求得它们的聚合反应表现活化能值在80.0～95KJ/mol之间。采用IR,~1H-NMR,~(13)C-NMR等手段对所得到的聚合物结构进行了表征。还对聚合物的溶解性及热性能进行了研究。

希土永磁材料Nd—Fe—B氧化过程及抗氧化新体系的研究

Nd-Fe-B永磁体的热稳定性较差,易氧化,氧化使材料的结构受到破坏,永磁性能受到不可恢复的损失。氧化过程是分阶段的,在室温和干燥的空气中是稳定的,150℃左右受到破坏的主要原因是体系中钕的氧化,230℃以上铁开始氧化,温度升高使氧化加快,800℃左右氧化基本结束,最终产物主要是Fe_2O_3、Nd_2O_3和NdBO_3。新研制的Nd-Fe-B-Si四元体系的抗氧化能力有较大的提高,居里温度也提高了许多,是一种大有发展前途的新材料。

Genome-wide survey of putative serine/threonine protein kinases in cyanobacteria

Background: Serine/threonine kinases (STKs) have been found in an increasing number of prokaryotes, showing important roles in signal transduction that supplement the well known role of two-component system. Cyanobacteria are photoautotrophic prokaryotes able to grow in a wide range of ecological environments, and their signal transduction systems are important in adaptation to the environment. Sequence information from several cyanobacterial genomes offers a unique opportunity to conduct a comprehensive comparative analysis of this kinase family. In this study, we extracted information regarding Ser/Thr kinases from 21 species of sequenced cyanobacteria and investigated their diversity, conservation, domain structure, and evolution. Results: 286 putative STK homologues were identified. STKs are absent in four Prochlorococcus strains and one marine Synechococcus strain and abundant in filamentous nitrogen-fixing cyanobacteria. Motifs and invariant amino acids typical in eukaryotic STKs were conserved well in these proteins, and six more cyanobacteria- or bacteria-specific conserved residues were found. These STK proteins were classified into three major families according to their domain structures. Fourteen types and a total of 131 additional domains were identified, some of which are reported to participate in the recognition of signals or substrates. Cyanobacterial STKs show rather complicated phylogenetic relationships that correspond poorly with phylogenies based on 16S rRNA and those based on additional domains. Conclusion: The number of STK genes in different cyanobacteria is the result of the genome size, ecophysiology, and physiological properties of the organism. Similar conserved motifs and amino acids indicate that cyanobacterial STKs make use of a similar catalytic mechanism as eukaryotic STKs. Gene gain-and-loss is significant during STK evolution, along with domain shuffling and insertion. This study has established an overall framework of sequence-structure-function interactions for the STK gene family, which may facilitate further studies of the role of STKs in various organisms.