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971.
Background
Low concentrations of free magnesium in the intracellular environment can present critical limitations for hammerhead ribozymes, especially for those that are designed for intermolecular (trans) cleavage of a host or pathogen RNA. Tertiary stabilizing motifs (TSM's) from natural and artificial ribozymes with a "type I" topology have been exploited to stabilize trans-cleaving hammerheads. Ribozymes with "type II" or "type III" topologies might seem incompatible with conversion to trans-cleavage designs, because opening the loop at the end of stem 1 or stem 2 to accommodate substrate binding is expected to disrupt the TSM and eliminate tertiary stabilization. 相似文献972.
Nan Wang Li Hua Zhu Jing Li He Qing Tang 《中国化学快报》2007,18(10):1261-1264
A very simple and controllable approach was proposed to synthesize novel Fe(OH)_3/TiO_2 nanoparticles.Compared with neat TiO2,the Fe(OH)_3/TiO_2 increased the rate of the photocatalytic degradation of methyl orange at pH 6.0 by more than five times, showing photocatalytic activity as excellent as P25.This enhancing effect is mainly attributed to the ferric hydroxide deposits as the electron scavenger and the enriched surface hydroxyl groups. 相似文献
973.
974.
Bo?AndreassonEmail author Jennie?Forsstr?m Lars?W?gberg 《Cellulose (London, England)》2005,12(3):253-265
It has been shown, in the present investigation, that the two methods used to investigate the pore size distribution of unbleached
chemical pulps, i.e. inverse size exclusion chromatography (ISEC) and nuclear magnetic resonance (NMR), give different average
pore radius for the pores inside the fibre wall. This is due to the way in which these experiments are performed and the sensitivity
of the methods to different types of pores in the cell wall. It was also shown that the two methods gave different results
when changing the pH and the ionic strength of the pulp suspension. The pore radius, as detected with ISEC, decreased with
both increasing ionic strength and decreasing pH, indicating a loose structure of the exterior of the fibrillar network. However,
the pore radius as detected with NMR, was virtually unaffected when increasing the ionic strength, indicating a very rigid
structure of the interior of the fibre wall. Decreasing pH though, lead to a decrease in pore radius indicating that upon
protonation of the carboxylic groups in the fibre wall, the electrostatic repulsion is diminished and the average pore radius
decreases. The NMR technique was also used to study wet strength aid penetration into the fibre wall. It was shown that wet
strength aids with a small molecular weight, penetrated the fibre wall, as detected by a decrease in pore radius. It was also
shown that addition of different wet strength aids increased the tensile index of the sheet and decreased the fibre strength,
measured as zero span-strength of the sheets. 相似文献
975.
Autoverification is a process in which computer software will automatically evaluate laboratory test results, verify result integrity, and then release the results to the hospital interface without any technologist intervention. Autoverify release criteria are user defined and can be customized. The process of developing, implementing, and monitoring autoverify is achievable for most test results in laboratory medicine. The use of autoverification will improve result quality, increase revenue, and create faster turn-around times. All of this put together will ultimately lead to improved customer satisfaction. Computers and autoverification are survival tools in the competitive market of laboratory diagnostics services.Presented at the 8th Conference on Quality in the Spotlight, 17–18 March 2003, Antwerp, Belgium 相似文献
976.
Hui-Ning D Wen-Chen Z Shao-Yi W Sheng T 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(3):489-492
In this paper, we calculate the EPR parameters (g factors g parallel, g perpendicular and hyperfine structure constants A parallel, A perpendicular) of rare earth ion Sm3+ in fluoride crystals KY3F10 and LiYF4 from the perturbation formulas of EPR parameters for a 4f5 ion in tetragonal symmetry. In these formulas, the crystal-field J-mixing of the first and second excited-state multiplets 6H(7/2) and 6H(9/2) into the ground state multiplet 6H(5/2), the mixtures among the states with the same J value via spin-orbit coupling interaction and the interactions between the ground Kramers doublet Gammagamma and the same irreducible representation as Gammagamma in other 11 Kramers doublets Gammax within 6HJ (J=5/2, 7/2, 9/2) states via crystal-field and orbital angular momentum (or hyperfine structure) are considered. The calculated results (which are in agreement with the observed values) are discussed. 相似文献
977.
IntroductionItiswellknownthatyttriumcanbeusedinmanyfields ,suchasmetallurgy ,ceramics ,lasersandelectron ics ,especiallyinfluorescentmaterialswhoseneedforhighpurityyttriumoxideisincreasing .InChina ,there sourceofyttriumisrich ,andthehighpureyttriumisbe ingo… 相似文献
978.
Villareal V Kaddis J Azad M Zurita C Silva I Hernandez L Rudolph M Moran J Gomez FA 《Analytical and bioanalytical chemistry》2003,376(6):822-831
Partial-filling affinity capillary electrophoresis (PFACE) is used to examine the binding interactions between two model biological systems: D-Ala-D-Ala terminus peptides to the glycopeptide antibiotic vancomycin (Van) from Streptomyces orientalis, and arylsulfonamides to carbonic anhydrase B (CAB, EC 4.2.1.1, bovine erythrocytes). Using these two systems, modifications in the PFACE technique are demonstrated including flow-through PFACE (FTPFACE), competitive flow-through PFACE (CFTPFACE), on-column ligand synthesis PFACE (OCLSPFACE), and multiple-step ligand injection PFACE (MSLIPFACE). In PFACE small plugs of sample are injected into the capillary column and an equilibrium is established between receptor and ligand during electrophoresis. Binding constants are then obtained by Scatchard analysis using changes in the migration time of the receptor/ligand on changing the concentration of the ligand/receptor. Data demonstrating the quantitative potential of these methods are presented. This review focuses on the unique capabilities of the different PFACE techniques as applied to two model biological systems. 相似文献
979.
Lindsey?Gillian?MackayEmail author C.?Peter?Taylor Richard?Bruce?Myors Ruth?Hearn Bernard?King 《Accreditation and quality assurance》2003,8(5):191-194
The selection of an appropriate isotope dilution mass spectrometry technique for the practical application of this potentially primary method of analysis is highly important. The NARL approach for the application of the exact matching double isotope dilution mass spectrometry technique developed by Henrion is presented. NARL's approach utilises exact matching to minimise the effect of measurement biases within the method but also includes the thorough examination of all other biasing factors. The approach has been successfully tested in international CCQM intercomparisons with other national metrology institutes. 相似文献
980.
The aim of the present work was to improve the discriminatory potential, and hence the probative value, of Y-STR-based testing by extending the set of Y chromosome STR loci available for forensic casework. In accordance with the requirements of a Y chromosome multiplex analytical system developed specifically for forensic casework use, we have sought to maximize the number of loci able to be co-amplified, ensure appropriate assay sensitivity (1–2 ng of input genomic DNA), balance inter-locus signals and minimize confounding female DNA artifacts. Two Y chromosome STR systems, multiplex I (MPI) and multiplex II (MPII), have been developed which permit the robust co-amplification of 18 Y-STRs. The loci include DYS19, DYS385(a) and (b), DYS388, DYS389I and II, DYS390, DYS391, DYS392, DYS393, DYS425, DYS434, DYS437, DYS438, DYS439, Y-GATA-C4, Y-GATA-A7.1 (DYS460) and Y-GATA-H4. The two multiplex systems are robust over a wide range of primer, magnesium, and DNA polymerase concentrations and perform well under a variety of cycling conditions. Complete male haplotypes can be obtained with as little as 100–250 pg of template DNA. Although a limited number of female DNA artifacts are observed in mixed stains in which the male DNA comprises 1/100 of the total, the male profile is easily discernible. Slightly modified versions of MPI and MPII demonstrate a significant reduction in female artifacts. Thus, it may not be necessary to employ a differential extraction strategy to obtain a male haplotype (or haplotypes in the case of multiple male donors) in cases of sexual assault. The potential utility of MPI and MPII for forensic casework is exemplified by their ability to dissect out the male haplotype in post-coital vaginal swabs and to determine the number of male donors in mixed semen stains.This study has emphasized the need for novel Y-STR multiplexes developed for forensic use to undergo a series of validation exercises that go beyond simply optimizing the PCR reaction conditions. Specifically, stringent performance checks on their efficacy need to be carried out using casework-type specimens in order to determine potential confounding effects from female DNA. 相似文献