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151.
152.
The best operating conditions that yield maximum sensitivity at minimum source pressure have been evaluated for the chemical ionization source in a Kratos MS-25 mass spectrometer. The best reagent gas pressure is shown to be different for each gas and is significantly lower than is usually reported in the literature. 相似文献
153.
154.
We find numerical solutions for symmetic Bianchi type IX universes. These numerical solutions coincide almost exactly with diagrammatic solutions found previously. 相似文献
155.
C.G. Ryan I. Morrison D.L. Kennedy A.E. Stuchbery H.H. Bolotin 《Nuclear Physics A》1980,342(3):373-384
The lifetimes of 9 states in 63Cu up to an excitation energy of 2092 keV have been determined by means of the Doppler-shift attenuation method using the reaction. A search was made for a suitable set of M1 and E2 single-particle matrix elements for use with shell-model eigenstates throughout the Ni, Cu and Zn isotopes. The theoretical predictions for the level spectroscopy and electromagnetic transitions and static moments in 63Cu are in satisfactory agreement with the experimental findings. 相似文献
156.
Yang Y Nesterenko DV Trump RP Yamaguchi K Bartlett PA Drueckhammer DG 《Journal of chemical information and modeling》2005,45(6):1820-1823
Three new virtual databases have been developed for use with the bond-orientation-based database searching program CAVEAT. These consist of a database of trisubstituted monocyclic hydrocarbons having ethyl, vinyl, and phenyl substituents; a database of unsubstituted bicyclic hydrocarbons; and a database of core structures from established combinatorial synthetic methods having hydrogen, ethyl, vinyl, and phenyl substituents at the readily varied positions. Each collection of molecules was subjected to a batch conformational search, minimization, and conversion to a vector database for use with CAVEAT. 相似文献
157.
Cobb SL Deng H Hamilton JT McGlinchey RP O'Hagan D 《Chemical communications (Cambridge, England)》2004,(5):592-593
5'-Fluoro-5'-deoxy-D-ribose-1-phosphate (FDRP) is identified as a biosynthetic intermediate during fluorometabolite biosynthesis in Streptomyces cattleya. 相似文献
158.
Despite Nature's longstanding ability to use a proton, the most prevalent Lewis acid, to both activate and orient a substrate during an enantioselective reaction, this work represents the first example of this phenomenon outside of a protein. A chiral, nonracemic BisAMidine (BAM) ligand was designed, synthesized, and complexed to the proton of a Br?nsted acid. The resulting coordination compound catalyzed the production of enantioenriched product from the combination of a Schiff base and nitroalkane (the aza-Henry reaction). This particular reaction is also considered a model for many analogous carbon-carbon bond-forming reactions catalyzed by enzymes (e.g., the Mannich reaction). This discovery suggests the use of ionic hydrogen bonds in asymmetric catalysis may not only be more general than previously thought, but also a viable "green" approach to single-enantiomer organic compounds. 相似文献
159.
Lee JN Jiang X Ryan D Whitesides GM 《Langmuir : the ACS journal of surfaces and colloids》2004,20(26):11684-11691
This paper describes the influence of the composition of poly(dimethylsiloxane) (PDMS) on the attachment and growth of several different types of mammalian cells: primary human umbilical artery endothelial cells (HUAECs), transformed 3T3 fibroblasts (3T3s), transformed osteoblast-like MC3T3-E1 cells, and HeLa (transformed epithelial) cells. Cells grew on PDMS having different ratios of base to curing agent: 10:1 (normal PDMS, PDMSN), 10:3 (PDMSCA), and 10:0.5 (PDMSB). They were also grown on "extracted PDMS" (normal PDMS that has reduced quantities of low molecular-weight oligomers, PDMSN,EX) and normal PDMS that had been extracted and then oxidized (PDMSN,EX,OX); all surfaces were exposed to a solution of fibronectin prior to cell attachment. Generally, fibronectin-coated PDMS is a suitable substrate for culturing mammalian cells. Compatibility of cells on some surfaces, however, was dependent on the cell type: PDMSN,EX,OX caused cell detachment of 3T3 fibroblasts and MC3T3-E1 cells, and PDMSCA caused detachment of HUAECs and HeLa cells. Growth of cells on PDMSN, PDMSN,EX, and PDMSB was comparable to growth on tissue culture-treated polystyrene for most of the cell types. All cells grew at similar rates on PDMS substrates regardless of the stiffness of the substrate, for substrates having Young's moduli ranging from E=0.60 +/- 0.04 to 2.6 +/- 0.2 MPa (for PDMSB and PDMSN,EX, respectively). 相似文献
160.
Frankel BA Bentley M Kruger RG McCafferty DG 《Journal of the American Chemical Society》2004,126(11):3404-3405
Several small molecule vinyl sulfones were found to exhibit irreversible time-dependent inhibition of the Staphylococcus aureus sortase SrtA in vitro. A representative of these compounds was shown to impair the ability of S. aureus bacteria to bind fibronectin-coated surfaces through in vivo inhibition of SrtA-mediated linkage of fibronectin to the cell surface. These data highlight the potential use of small molecule vinyl sulfones as chemotherapeutics to prevent adhesion to and colonization of host tissues during S. aureus infection. 相似文献