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1.
Noemi Roman 《Dimensions of critical care nursing》2005,24(6):275-278
The pediatric intensive care unit at a community hospital successfully implemented the use of standardized concentrations. The process included deciding the standardized concentrations, use of titration charts, and integration of smart pump technology. Since the implementation of standardized concentrations, there has been no signal or sentinel events reported. It is safe and efficacious to use standardized concentrations combined with smart pump technology and abandon the use of the rule of 6 in the pediatric population. 相似文献
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Incoronata Tritto Maria Carmela Sacchi Paolo Locatelli 《Macromolecular chemistry and physics.》1986,187(9):2145-2151
A 13C NMR analysis of the methyl and ethyl end-groups in isotactic polypropylene, prepared in the presence of TiCl3- and Til3-based catalysts, was performed and the isotactic regularity of the first propylene unit added to the Ti—alkyl bond was measured. In the presence of the catalyst Til3/Al(13CH2CH3)3 the stereoregulating effects derived from the ethyl and iodine ligands are cooperative, so that the addition of the first monomeric unit is as isotactic as the following propagation steps. A comparison of the chain end-groups of polypropylene obtained in the presence of different catalysts shows that the extent of steric control upon insertion of the first monomer molecule results not only from the presence of alkyl titanium ligands larger than methyl and of titanium halide ligands larger than chlorine, but also from mutual ligand interactions. 相似文献
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Johannes Carolus Jansen Raniero Mendichi Maria Carmela Sacchi Incoronata Tritto 《Macromolecular chemistry and physics.》2003,204(3):522-530
Copolymers of ethylene (E) with norbornene (N) were synthesized using the catalysts rac‐Et(Ind)2ZrCl2/MAO ( 1 ), 90%rac/10%meso‐Et(4,7‐Me2Ind)2ZrCl2/MAO ( 2 ), and rac‐H2C(3‐t‐BuInd)2ZrCl2/MAO ( 3 ). Catalyst activity, molar mass (MM), and copolymer composition were studied as a function of time. The polymers showed an unusually narrow molar mass distribution (MMD) and a significant increase of their MM with time for up to one hour, suggesting a “quasi‐living” polymerization at 30 °C. The experimental data were fitted to kinetic equations and the propagation and transfer reactions were described in quantitative terms. Norbornene greatly depressed the propagation rate, along with the chain transfer rate. The more sterically hindered catalysts of the series showed lower propagation and chain transfer turnover frequency than 1 and yielded polymers with a low ( 2 ) to very low ( 3 ) norbornene content. The presence of norbornene in solution seemed to be one of the main factors responsible for the observed “quasi‐living” character of the copolymerization, probably due to coordination of norbornene to the active site. Time‐resolved kinetic studies also allowed for the calculation of the fraction of active metal centers, ranging from 56% ( 3 ) and 66–68% ( 1 ) to 94% ( 2 ) of the total zirconium present, depending on catalyst structure.
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Incoronata Tritto San Xi Li Laura Boggioni Maria Carmela Sacchi Paolo Locatelli Aideen O'Neill 《Macromolecular chemistry and physics.》1997,198(5):1347-1361
Ethylene polymerizations and norbornene oligomerizations catalysed by Cp2Ti13CH3Cl/MAO (Cp: cyclopentadienyl; MAO: methylaluminoxane) mixtures have been carried out at different temperatures (from -20°C to 20°C), in order to test the validity of carbene mechanisms in α-olefin polymerizations. Depending on the temperature, different ratios of the cationic species [Cp2Ti13CH3]+[Cl · MAO]? and precursors of the alkylidene Cp2Ti = 13CH2 exist. The in situ polymerization of 13C enriched ethylene was monitored by 13C NMR spectroscopy. Moreover, catalytic activity was determined and polyethylene samples were analyzed by 13C NMR and gel permeation chromatography (GPC). The following evidence has been provided against the carbene mechanism in the α-olefin polymerization with titanocene based catalysts: (a) in the in situ ethylene polymerization experiments the appearance of polyethylene signals is concurrent with the decrease of cationic [Cp2Ti13CH3]+[Cl · MAO]? signals and is not related to the intensity of the alkylidene Cp2Ti = 13CH2 signals; (b) from the 13C NMR analysis of polyethylene chain-end groups the 13C enrichment of Cp2Ti13CH3Cl has only been found in the methyl chain-end group and not in the methylene of the propyl chain-end group, as should have been the case if the carbene mechanism had been valid; (c) from norbornene oligomerization (at 0°C) the addition product 2-13C enriched methyl-norbornane has been identified. Moreover, the identification of a 13C enriched methylidene-norbornane dimer at higher temperatures has revealed the possibility of norbornene addition to titanium carbenes through the formation of titanacyclobutane without the opening of the norbornene ring. However, this process requires higher energies with respect to the Cossee type insertion. 相似文献