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91.
A Chelex-100 resin column has been employed for the preliminary concentration of trace elements in water samples before their determination by neutron-activation analysis. The column, filled with a 1:1 mixture of the resin (50-100 mesh) and Pyrex glass powder of the same mesh-size, is shown to maintain a constant flow-rate and give reproducible results. By a combination of preconcentration and neutron-activation analysis it is possible to determine Ba, Ca, Cd, Ce, Co, Cr, Cu, Fe, La, Mg, Mn, Sc, U, V and Zn in sea-water and/or fresh water simultaneously at the parts per milliard level. 相似文献
92.
The novel atrane-like six-coordinate (RO)(2)TaL complexes [where R = Me or Et and L = tris(2-oxy-3,5-dimethylbenzyl)amine] containing three six-membered rings have been synthesized and characterized. The R = Me complex is the first group 5 representative of this class of compounds structurally characterized by X-ray means. Somewhat surprisingly, these compounds failed to function as single-site initiators for the polymerization of l-LA to isotactic PLA and rac-LA to atactic PLA, whereas Ta(OEt)(5) and two titanium analogues ROTiL (where R = 2,6-di-i-PrC(6)H(3) and i-Pr) as well as Ti(O-i-Pr)(4) were effective catalysts for both polymerizations. 相似文献
93.
In association with microtubules, a variety of kinesins play important roles in cellular functions such as intracellular transport of organelles or vesicles, signal transduction, and cell division. In a previous study we revealed that human kinesin superfamily protein member 4 (KIF4) is a chromokinesin that binds to chromosomes. Since localization of several kinds of kinesin at midzone called central spindle, or midbody that connects two daughter cells, or both, suggests their implication in cell division, we investigated KIF4 localization of during mitosis and cytokinesis in Hela cells. In addition to association with segregating chromosomes through entire mitosis, it also localized to the midzone and to midbody at ana/telophase through cytokinesis. Especially in cells at cytokinesis, KIF4 appeared as a doublet facing each other at the apical ends of two daughter cells. Three- dimensional analysis of architectural relationship between microtubule bundles and KIF4 indicated that KIF4 forms a ring structure wrapping around the microtubule bundles. These results suggest that KIF4 is involved in cytokinesis, although direct evidence was not provided in this study. 相似文献
94.
In contrast to lower phosphorylation states (e.g. the tryptic monophosphopeptide FQpSEEQQQTEDELQDK from bovine beta-casein), the specific detection of multi-phosphorylated peptides (e.g. the tetraphosphopeptide RELEELNVPGEIVEpSLpSpSpSEESITR from tryptic digestion of bovine beta-casein) has often been problematic for liquid chromatographic mass spectrometric (LC/MS) analysis owing to their high affinity for adsorption to exposed surfaces. We observed an enhancement in the overall detection of phosphopeptides on addition of phosphoric acid (0.1-1.0%) to the sample solution; a 10-fold increase in sensitivity was determined for the detection of two tryptic phosphopeptides and also a significant improvement in the detection of the tetraphosphopeptide. Using capillary LC with ion trap tandem MS for detection and identification, the achievable detection limits were 50 fmol and 50 pmol for the monophosphopeptide and the tetraphosphopeptide, respectively. Phosphoric acid is believed to act as a blocking agent to available silanol groups on both the silica capillary surface and the C(18)-bonded stationary phase silica surface. 相似文献
95.
GITR (glucocorticoid-induced TNF receptor) is a recently identified member of the TNF receptor superfamily. The receptor is preferentially expressed on CD4(+)CD25(+) regulatory T cells and GITR signals break the suppressive activity of the subset. In this study, we wanted to reveal the in vivo function of GITR in herpes simplex virus type 1 (HSV-1) infection. A single injection of anti-GITR mAb (DTA-1) immediately after viral infection significantly increased the number of CD4(+) and CD8(+) T cells expressing CD25, an activation surface marker, and secreting IFN-gamma. We confirmed these in vivo observations by showing ex vivo that re-stimulation of CD4(+) or CD8(+) T cells with a CD4(+) or CD8(+) T-cell-specific HSV-1 peptide, respectively, induced a significant elevation in cell proliferation and in IFN-gamma secretion. Our results indicate that GITR signals play a critical role in the T-cell immunity to HSV-1. 相似文献
96.
V. Kim A. G. Shostenko V. E. Myshkin N. I. Kartashev 《Reaction Kinetics and Catalysis Letters》1979,11(3):241-245
The kinetics of CCl3 radical addition to 1-hexene in CCl3Br and CCl4 media has been studied. The rate constant of CCl3 addition to the double bond is shown to be independent of the solvent. The ratios between the rate constants of transfer and allyl chain termination for the alkyl and polychloroalkyl radicals have been estimated by competition methods. Activation parameters for the calculated rate constants are given.
CCl3- 1- CCCl3Br CCl4. , . . .相似文献
97.
Thermal properties of bio flour-filled polypropylene bio-composites with different pozzolan contents
H. -S. Kim S. -W. Choi B. -H. Lee S. Kim H. -J. Kim C. W. Cho D. Cho 《Journal of Thermal Analysis and Calorimetry》2007,89(3):821-827
In this study, the thermal properties of bio-flour-filled, polypropylene (PP) bio-composites with different pozzolan contents
were investigated. With increasing pozzolan content, the thermal stability, 5% mass loss temperature and derivative thermogravimetric
curve (DTGmax) temperatures of the bio-composites slightly increased. The coefficient of thermal expansion (CTE) and thermal expansion
of the bio-composites decreased as the pozzolan content increased. The glass transition temperature (T
g), melting temperature (T
m) and percentage of crystallinity (X
c) of the bio-composites were not significantly changed. The thermal stability, thermal expansion and X
c of the maleic anhydride-grafted PP (MAPP)-treated bio-composites were much higher than those of non-treated bio-composites
at 1% pozzolan content due to enhanced interfacial adhesion. X-ray diffraction (XRD) analysis confirmed the crystallinity
of pozzolan-added bio-composites. From these results, we concluded that the addition of pozzolan in the bio-composites was
an effective method for enhancing the thermal stability and thermal expansion. 相似文献
98.
To isolate epigallocatechin gallate (EGCG) of catechin compounds from Korean green tea (Bosung, Chonnam), a C18 reversed-phase preparative column (250x22 mm) packed with packings of three different sizes (15, 40-63, and 150 microm) was used. The sample extracted with water was partitioned with chloroform and ethyl acetate to remove the impurities including caffeine. The mobile phases in this experiment were composed of 0.1% acetic acid in water, acetonitrile, methanol and ethyl acetate. The injection volume was fixed at 400 microl and the flow rate was increased as the particle size becomes larger. The isolation of EGCG with particle size was compared at a preparative scale and the feasibility of separation of EGCG at larger particle sizes was confirmed. The optimum mobile phase composition for separating EGCG was experimentally obtained at the particle sizes of 15 and 40-63 microm in the isocratic mode, but EGCG was not purely separated at the particle size of 150 microm. 相似文献
99.
A novel chemical cyclization method using BBr3 has been successfully developed to prepare ladder-type conjugated systems. The cyclized ladder compounds revealed an extended conjugation due to planarization of the structures. The extended ladder polymer can also be easily prepared by our chemical cyclization method using a soluble precursor. 相似文献