Yufei Li - Academia.edu (original) (raw)

Papers by Yufei Li

Polymer Bulletin, 1999

A novel category of polyamides with precisely pendant Percec-type dendritic fragments has been su... more A novel category of polyamides with precisely pendant Percec-type dendritic fragments has been successfully synthesized. Their structures were confirmed by FT-IR and 1H-NMR spectra. The solubilities of these polyamides were greatly improved, especially the one with second generation dendritic blocks can be dissolved in normal organic solvents such as ethyl acetate, acetone, ether, hexane, etc.

Bioresource Technology, 2008

A continuous fixed bed study was carried out by using rice husk as a biosorbent for the removal o... more A continuous fixed bed study was carried out by using rice husk as a biosorbent for the removal of congo red (CR) from aqueous solution. The effects of important factors, such as the value of initial pH, existing salt, the flow rate, the influent concentration of CR and bed depth, were studied. Data confirmed that the breakthrough curves were dependent on flow rate, initial dye concentration and bed depth. Thomas, Adams-Bohart, and Yoon-Nelson models were applied to experimental data to predict the breakthrough curves using non-linear regression and to determine the characteristic parameters of the column useful for process design, while bed depth/service time analysis (BDST) model was used to express the effect of bed depth on breakthrough curves. The results showed that Thomas model was found suitable for the normal description of breakthrough curve at the experimental condition, while Adams-Bohart model was only for a initial part of dynamic behavior of the rice husk column. The data were in good agreement with BDST model. It was concluded that the rice husk column can remove CR from solution.

Macromolecular Rapid Communications, 1999

Journal of Polymer Science Part A-polymer Chemistry, 2000

The polycondensation of polymerizable diamines bearing two generations of Percec-type dendritic b... more The polycondensation of polymerizable diamines bearing two generations of Percec-type dendritic blocks with dianhydrides led to the formation of novel aromatic polyamic acids that then were converted into a series of novel aromatic polyimides jacked with dendritic fragments. Their solubility in organic solvents was improved remarkably by the introduction of the dendritic fragments, especially in the case of the polyamides and polyamic acids, and the polymers were soluble in normal solvents such as ethyl acetate, acetone, and chloroform. Their thermal properties were investigated with differential scanning calorimetry and thermogravimetric analysis. The glasstransition temperatures of these polyamides were lower than those of the conventional aramids. All of the polyamides, polyamic acids, and polyimides bearing the dendritic fragments showed two decomposition stages.

Polymers for Advanced Technologies, 2007

A polymeric waveguide film was manufactured by spinning the materials on quartz substrate. Two-ph... more A polymeric waveguide film was manufactured by spinning the materials on quartz substrate. Two-photon-initiated photopolymerization was carried out by tight-focusing femtosecond laser pulses in the two-mode planar waveguide. A typical index-modulated grating of 2.5 × 2 mm areas without morphology was fabricated. The results show that peak-to-peak modulation depth of the surface profile of grating region was only about 7 nm. The diffraction efficiency (DE) of the grating with a spacing period 2 µm was 0.17% and the corresponding index modulation reached 5.7 × 10−3. Copyright © 2007 John Wiley & Sons, Ltd.

Optics and Laser Technology, 2000

The phase matching angle of GdCOB crystal is calculated. By using Xenon¯ash lamp as pump source, ... more The phase matching angle of GdCOB crystal is calculated. By using Xenon¯ash lamp as pump source, we have realized the free run from 1.06 mm to 0.53 mm in self-frequency-doubling Cr:Nd:GdCOB (bi-doped) crystal and Nd:GdCOB (uni-doped) crystal. The experimental results show that the threshold energies for bi-doped crystal and uni-doped crystal are 0.92 J and 1.00 J, respectively; when the pump energy is 10 J, the output energies of green laser for two kinds of crystals are 2.46 mJ and 1.96 mJ, respectively. The output energy of Cr:Nd:GdCOB crystal has an increase of 25% in comparison to that of Nd:Gd:COB crystal. In addition, we discuss ways to improve eciency. 7

Applied Surface Science, 2004

Optical emission spectra of the plasma produced by 1.06 mm Nd:YAG laser irradiation of a potassiu... more Optical emission spectra of the plasma produced by 1.06 mm Nd:YAG laser irradiation of a potassium titanium phosphate (KTP) crystal in vacuum and in air were recorded and analyzed in a spatially resolved manner. Electron temperatures and densities in the plasma in vacuum were determined with the Boltzmann plot method using five Ti(II) emission lines and the Stark-broadened linewidths of neutral K atoms, respectively. The dependence of the electron densities and temperatures on distance from the target surface and on laser irradiance were manifested. In order to see the effect of backing gas, we also performed laser ablation of a KTP crystal in air and compared the results with that of the ablation in vacuum. Gas dynamical parameters of the laser-induced KTP evaporation wave were simulated using a hydrocode developed in our group based on the self-similar solutions of the gas dynamical equations. Moreover, the velocity of the evaporating wave and the vapor pressure were calculated under different laser power densities. #

Optics and Laser Technology, 2007

Passively Q-switched output of a flashlamp-pumped 1.319 mm Nd:YAG laser is realized by using Co 2... more Passively Q-switched output of a flashlamp-pumped 1.319 mm Nd:YAG laser is realized by using Co 2+ :LaMgAl 11 O 19 (Co:LMA) as saturable absorber. When initial transmission of the saturable absorber T 0 is 78%, a Q-switched output pulse with pulse width (FWHM) 44.8 ns and pulse energy 17.4 mJ is obtained, corresponding to $19.3% of the free-running energy under the equal pumping energy of 45.4 J. The experimental results show that the higher T 0 will result in a lower pumping threshold of the laser, but lower T 0 can make the laser generate pulses with higher single-pulse energy, narrower pulse width, and accordingly higher peak power. r

Optics Communications, 2009

We have demonstrated an efficient diode-pumped passively Q-switched Nd: GdVO4 laser working at 13... more We have demonstrated an efficient diode-pumped passively Q-switched Nd: GdVO4 laser working at 1342nm by using an uncoated V3+: YAG crystal as the saturable absorber, in which both a-cut and c-cut Nd: GdVO4 crystals are employed. At the maximum absorbed ...

Optics Communications, 2004

A laser-diode pumped Nd:Y x Gd 1 − x VO 4 laser passively Q-switched with a GaAs saturable absorb... more A laser-diode pumped Nd:Y x Gd 1 − x VO 4 laser passively Q-switched with a GaAs saturable absorber has been realized. Both continuous wave (CW) and Q-switched laser performances at l.06 μm are investigated. At the incident pump power of 4.4 W and with the output ...

Laser and Particle Beams, 2003

The optical emission spectra of the plasma generated by a 1.06-[mu]m Nd:YAG laser irradiation of ... more The optical emission spectra of the plasma generated by a 1.06-[mu]m Nd:YAG laser irradiation of Al target in air was recorded and analyzed in a spatially resolved manner. Electron temperatures and densities in the plasma were obtained using the relative emission intensities and the Stark-broadened linewidths of Al(I) emission lines, respectively. The dependence of the electron density and temperature on

Optics Express, 2007

Passively Q-switched output of a flashlamp-pumped 1.319 mm Nd:YAG laser is realized by using Co 2... more Passively Q-switched output of a flashlamp-pumped 1.319 mm Nd:YAG laser is realized by using Co 2+ :LaMgAl 11 O 19 (Co:LMA) as saturable absorber. When initial transmission of the saturable absorber T 0 is 78%, a Q-switched output pulse with pulse width (FWHM) 44.8 ns and pulse energy 17.4 mJ is obtained, corresponding to $19.3% of the free-running energy under the equal pumping energy of 45.4 J. The experimental results show that the higher T 0 will result in a lower pumping threshold of the laser, but lower T 0 can make the laser generate pulses with higher single-pulse energy, narrower pulse width, and accordingly higher peak power. r

Optics and Laser Technology, 2003

By using the calculation theory of the phase-matching direction and e ective nonlinear coe cient ... more By using the calculation theory of the phase-matching direction and e ective nonlinear coe cient of frequency doubling in biaxial crystal, we calculate the e ective nonlinear coe cients at di erent frequency-doubling phase-matching directions of the three main uorescent lines (936, 1060, 1331 nm) of Nd:GdCOB crystal. The space distribution curves of e ective nonlinear coe cient are drawn. Two crystal specimens are cut at the optimal type I phase matching angles: for specimen 1, Â = 65 • , = 34:6 • (the ÿrst octant); for specimen 2, Â = 66:5 • , = 145:5 • (the second octant). When pumped by Datachroom-5000 pulsed dye laser, the output self-frequency-doubling red laser in specimen 2 is 0:62 mJ, and the corresponding conversion e ciency is 2.5%. Under the same pumping condition, the output red laser of specimen 1 is much smaller than that of specimen 2, which is well in agreement with the theoretical calculation. ?

Optics and Laser Technology, 2004

A xenon ash-lamp-pumped, passively Q-switched Nd:GdVO4 laser with GaAs semiconductor saturable ab... more A xenon ash-lamp-pumped, passively Q-switched Nd:GdVO4 laser with GaAs semiconductor saturable absorber is demonstrated. The static laser performance is investigated and the static output is 52 mJ when the pump energy is 9:45 J. The dynamic laser has the highest slope e ciency when the GaAs wafer is both the saturable absorber and output coupler. Pulses with duration of 64 ns and dynamic output of 47:6 mJ are obtained when the pump energy is 9:45 J. The highest dynamic-static ratio is 0.9:1. The coupled rate equations are used to simulate the Q-switched process of laser. The theoretical and experimental results are compared and discussed. ?

Optics Express, 2006

The static and dynamic 1.34 mum laser output performance of the Nd:Y(x)Gd(1-x)VO(4) mixed crystal... more The static and dynamic 1.34 mum laser output performance of the Nd:Y(x)Gd(1-x)VO(4) mixed crystal pumped by flash-lamp is investigated with different transmissions of output couplers (T=15%, 30% and 40%) in a plano-concave laser cavity. With the output coupler transmission of T=30%, the static output energy of 62 mJ is obtained when the pump energy is 24.2 J, and the corresponding electric-optical conversion efficiency is 0.26%. By using a new saturable absorber: Co(2+):LaMgAl(11)O(19) (Co:LMA), the passive Q-switching at 1.34 mum is realized when the second threshold condition of passive Q-switching is satisfied. With the cavity length of 245 mm and pump energy of 24.2 J, the single-pulse output energy, pulse width and peak power are obtained to be 3.5 mJ, 45 ns and 77.8 kW, respectively.

Polymer International, 2000

Journal of Molecular Catalysis A-chemical, 2002

A series of aryl-substituted tetramethylcyclopentadienyl zirconocenes (C 5 Me 4 C 6 H 4 X-4)Cp MC... more A series of aryl-substituted tetramethylcyclopentadienyl zirconocenes (C 5 Me 4 C 6 H 4 X-4)Cp MCl 2 [Cp = C 5 H 5 , X = H (5), Me (6), Cl (7) or OMe (8); Cp = Ind, X = H (9), Me (10) or Cl (11); Cp = 2-Ph-Ind, X = H (12)] and (C 5 Me 4 C 6 H 4 X-4) 2 ZrCl 2 [X = H (13), Me (14), Cl (15)], with different substituents at the 4-position of phenyl, have been prepared by the reaction of the corresponding ligands (C 5 Me 4 HC 6 H 4 X-4) [X = H (1), Me (2), Cl (3) or OMe (4)] with n-BuLi, ZrCl 4 and Cp Li or with n-BuLi and ZrCl 4 . Ethylene polymerization with these complexes in combination with MAO has been studied. The electron donor (Me) at the 4-position of phenyl led to an increase in catalytic activity while the electron-withdrawing group (Cl) and the strong donor (OMe) led to its decrease. Complexes 5, 6, 9 and 10 exhibited very high activities, but 13-15 showed much lower activities due to the bulky steric effect. The molecular structure of 5 has been determined by X-ray diffraction. The relationship between structures of catalysts and catalytic activities were discussed.

Macromolecular Rapid Communications, 2001

Journal of Polymer Science Part A-polymer Chemistry, 2000

Two new silolene-bridged metallocenes for isotactic polypropylene, racemic (1,4-butanediyl) silyl... more Two new silolene-bridged metallocenes for isotactic polypropylene, racemic (1,4-butanediyl) silylene-bis (1-5 -2-methyl-indenyl) dichlorozironium and racemic diphenyl silylene-bis (1-5 -2-methyl-indenyl) dichlorozironium, were designed in terms of the mechanism and concept of the activity and selectivity of metallocenes. The predictions on which the designs were based were carried out for four metallocene catalysts through molecular modeling methods such as molecular mechanics and charge equilibrium. In a comparison of the data from three of the catalysts that were successfully synthesized, the predicted orders of the activity and selectivity were consistent. This shows that classical methods such as charge equilibrium are useful in predicting the activity of catalysts.

Toxicology, 2009

Perfluorooctanoic acid (PFOA) is a ligand for peroxisome proliferator-activated receptor (PPAR) α... more Perfluorooctanoic acid (PFOA) is a ligand for peroxisome proliferator-activated receptor (PPAR) α, which exhibits marked species differences in expression and function, especially between rodents and humans. We investigated the functional difference in PFOA response between mice and humans, using a humanized PPARα transgenic mouse line. Three genotyped mice, 129/Sv wild-type (mPPARα), Pparα-null mice and humanized PPARα (hPPARα) mice (8-week-old males) were divided into three groups: the first was treated with water daily for 2 weeks by gavage (control group), and the remaining two groups were treated with 0.1 and 0.3 mg/kg ammonium perflurooctanate (APFO), respectively, for 2 weeks by gavage. The APFO dosages used did not influence the plasma triglyceride or total cholesterol levels in any mouse line, but the high dose increased both hepatic lipid levels only in mPPARα mice. APFO increased mRNA and/or protein levels of PPARα target genes cytochrome P450 Cyp4a10, peroxisomal thiolase and bifunctional protein only in the liver of mPPARα mice, but not in Pparα-null or hPPARα mice. This chemical also increased expression of mitochondrial very long chain acyl-CoA dehydrogenase only in the liver of mPPARα mice. Taken together, human PPARα may be less responsive to PFOA than that of mice when a relatively low dose is applied. This information may be very valuable in considering whether PFOA influences the lipid metabolism in humans.

Polymer Bulletin, 1999

A novel category of polyamides with precisely pendant Percec-type dendritic fragments has been su... more A novel category of polyamides with precisely pendant Percec-type dendritic fragments has been successfully synthesized. Their structures were confirmed by FT-IR and 1H-NMR spectra. The solubilities of these polyamides were greatly improved, especially the one with second generation dendritic blocks can be dissolved in normal organic solvents such as ethyl acetate, acetone, ether, hexane, etc.

Bioresource Technology, 2008

A continuous fixed bed study was carried out by using rice husk as a biosorbent for the removal o... more A continuous fixed bed study was carried out by using rice husk as a biosorbent for the removal of congo red (CR) from aqueous solution. The effects of important factors, such as the value of initial pH, existing salt, the flow rate, the influent concentration of CR and bed depth, were studied. Data confirmed that the breakthrough curves were dependent on flow rate, initial dye concentration and bed depth. Thomas, Adams-Bohart, and Yoon-Nelson models were applied to experimental data to predict the breakthrough curves using non-linear regression and to determine the characteristic parameters of the column useful for process design, while bed depth/service time analysis (BDST) model was used to express the effect of bed depth on breakthrough curves. The results showed that Thomas model was found suitable for the normal description of breakthrough curve at the experimental condition, while Adams-Bohart model was only for a initial part of dynamic behavior of the rice husk column. The data were in good agreement with BDST model. It was concluded that the rice husk column can remove CR from solution.

Macromolecular Rapid Communications, 1999

Journal of Polymer Science Part A-polymer Chemistry, 2000

The polycondensation of polymerizable diamines bearing two generations of Percec-type dendritic b... more The polycondensation of polymerizable diamines bearing two generations of Percec-type dendritic blocks with dianhydrides led to the formation of novel aromatic polyamic acids that then were converted into a series of novel aromatic polyimides jacked with dendritic fragments. Their solubility in organic solvents was improved remarkably by the introduction of the dendritic fragments, especially in the case of the polyamides and polyamic acids, and the polymers were soluble in normal solvents such as ethyl acetate, acetone, and chloroform. Their thermal properties were investigated with differential scanning calorimetry and thermogravimetric analysis. The glasstransition temperatures of these polyamides were lower than those of the conventional aramids. All of the polyamides, polyamic acids, and polyimides bearing the dendritic fragments showed two decomposition stages.

Polymers for Advanced Technologies, 2007

A polymeric waveguide film was manufactured by spinning the materials on quartz substrate. Two-ph... more A polymeric waveguide film was manufactured by spinning the materials on quartz substrate. Two-photon-initiated photopolymerization was carried out by tight-focusing femtosecond laser pulses in the two-mode planar waveguide. A typical index-modulated grating of 2.5 × 2 mm areas without morphology was fabricated. The results show that peak-to-peak modulation depth of the surface profile of grating region was only about 7 nm. The diffraction efficiency (DE) of the grating with a spacing period 2 µm was 0.17% and the corresponding index modulation reached 5.7 × 10−3. Copyright © 2007 John Wiley & Sons, Ltd.

Optics and Laser Technology, 2000

The phase matching angle of GdCOB crystal is calculated. By using Xenon¯ash lamp as pump source, ... more The phase matching angle of GdCOB crystal is calculated. By using Xenon¯ash lamp as pump source, we have realized the free run from 1.06 mm to 0.53 mm in self-frequency-doubling Cr:Nd:GdCOB (bi-doped) crystal and Nd:GdCOB (uni-doped) crystal. The experimental results show that the threshold energies for bi-doped crystal and uni-doped crystal are 0.92 J and 1.00 J, respectively; when the pump energy is 10 J, the output energies of green laser for two kinds of crystals are 2.46 mJ and 1.96 mJ, respectively. The output energy of Cr:Nd:GdCOB crystal has an increase of 25% in comparison to that of Nd:Gd:COB crystal. In addition, we discuss ways to improve eciency. 7

Applied Surface Science, 2004

Optical emission spectra of the plasma produced by 1.06 mm Nd:YAG laser irradiation of a potassiu... more Optical emission spectra of the plasma produced by 1.06 mm Nd:YAG laser irradiation of a potassium titanium phosphate (KTP) crystal in vacuum and in air were recorded and analyzed in a spatially resolved manner. Electron temperatures and densities in the plasma in vacuum were determined with the Boltzmann plot method using five Ti(II) emission lines and the Stark-broadened linewidths of neutral K atoms, respectively. The dependence of the electron densities and temperatures on distance from the target surface and on laser irradiance were manifested. In order to see the effect of backing gas, we also performed laser ablation of a KTP crystal in air and compared the results with that of the ablation in vacuum. Gas dynamical parameters of the laser-induced KTP evaporation wave were simulated using a hydrocode developed in our group based on the self-similar solutions of the gas dynamical equations. Moreover, the velocity of the evaporating wave and the vapor pressure were calculated under different laser power densities. #

Optics and Laser Technology, 2007

Passively Q-switched output of a flashlamp-pumped 1.319 mm Nd:YAG laser is realized by using Co 2... more Passively Q-switched output of a flashlamp-pumped 1.319 mm Nd:YAG laser is realized by using Co 2+ :LaMgAl 11 O 19 (Co:LMA) as saturable absorber. When initial transmission of the saturable absorber T 0 is 78%, a Q-switched output pulse with pulse width (FWHM) 44.8 ns and pulse energy 17.4 mJ is obtained, corresponding to $19.3% of the free-running energy under the equal pumping energy of 45.4 J. The experimental results show that the higher T 0 will result in a lower pumping threshold of the laser, but lower T 0 can make the laser generate pulses with higher single-pulse energy, narrower pulse width, and accordingly higher peak power. r

Optics Communications, 2009

We have demonstrated an efficient diode-pumped passively Q-switched Nd: GdVO4 laser working at 13... more We have demonstrated an efficient diode-pumped passively Q-switched Nd: GdVO4 laser working at 1342nm by using an uncoated V3+: YAG crystal as the saturable absorber, in which both a-cut and c-cut Nd: GdVO4 crystals are employed. At the maximum absorbed ...

Optics Communications, 2004

A laser-diode pumped Nd:Y x Gd 1 − x VO 4 laser passively Q-switched with a GaAs saturable absorb... more A laser-diode pumped Nd:Y x Gd 1 − x VO 4 laser passively Q-switched with a GaAs saturable absorber has been realized. Both continuous wave (CW) and Q-switched laser performances at l.06 μm are investigated. At the incident pump power of 4.4 W and with the output ...

Laser and Particle Beams, 2003

The optical emission spectra of the plasma generated by a 1.06-[mu]m Nd:YAG laser irradiation of ... more The optical emission spectra of the plasma generated by a 1.06-[mu]m Nd:YAG laser irradiation of Al target in air was recorded and analyzed in a spatially resolved manner. Electron temperatures and densities in the plasma were obtained using the relative emission intensities and the Stark-broadened linewidths of Al(I) emission lines, respectively. The dependence of the electron density and temperature on

Optics Express, 2007

Passively Q-switched output of a flashlamp-pumped 1.319 mm Nd:YAG laser is realized by using Co 2... more Passively Q-switched output of a flashlamp-pumped 1.319 mm Nd:YAG laser is realized by using Co 2+ :LaMgAl 11 O 19 (Co:LMA) as saturable absorber. When initial transmission of the saturable absorber T 0 is 78%, a Q-switched output pulse with pulse width (FWHM) 44.8 ns and pulse energy 17.4 mJ is obtained, corresponding to $19.3% of the free-running energy under the equal pumping energy of 45.4 J. The experimental results show that the higher T 0 will result in a lower pumping threshold of the laser, but lower T 0 can make the laser generate pulses with higher single-pulse energy, narrower pulse width, and accordingly higher peak power. r

Optics and Laser Technology, 2003

By using the calculation theory of the phase-matching direction and e ective nonlinear coe cient ... more By using the calculation theory of the phase-matching direction and e ective nonlinear coe cient of frequency doubling in biaxial crystal, we calculate the e ective nonlinear coe cients at di erent frequency-doubling phase-matching directions of the three main uorescent lines (936, 1060, 1331 nm) of Nd:GdCOB crystal. The space distribution curves of e ective nonlinear coe cient are drawn. Two crystal specimens are cut at the optimal type I phase matching angles: for specimen 1, Â = 65 • , = 34:6 • (the ÿrst octant); for specimen 2, Â = 66:5 • , = 145:5 • (the second octant). When pumped by Datachroom-5000 pulsed dye laser, the output self-frequency-doubling red laser in specimen 2 is 0:62 mJ, and the corresponding conversion e ciency is 2.5%. Under the same pumping condition, the output red laser of specimen 1 is much smaller than that of specimen 2, which is well in agreement with the theoretical calculation. ?

Optics and Laser Technology, 2004

A xenon ash-lamp-pumped, passively Q-switched Nd:GdVO4 laser with GaAs semiconductor saturable ab... more A xenon ash-lamp-pumped, passively Q-switched Nd:GdVO4 laser with GaAs semiconductor saturable absorber is demonstrated. The static laser performance is investigated and the static output is 52 mJ when the pump energy is 9:45 J. The dynamic laser has the highest slope e ciency when the GaAs wafer is both the saturable absorber and output coupler. Pulses with duration of 64 ns and dynamic output of 47:6 mJ are obtained when the pump energy is 9:45 J. The highest dynamic-static ratio is 0.9:1. The coupled rate equations are used to simulate the Q-switched process of laser. The theoretical and experimental results are compared and discussed. ?

Optics Express, 2006

The static and dynamic 1.34 mum laser output performance of the Nd:Y(x)Gd(1-x)VO(4) mixed crystal... more The static and dynamic 1.34 mum laser output performance of the Nd:Y(x)Gd(1-x)VO(4) mixed crystal pumped by flash-lamp is investigated with different transmissions of output couplers (T=15%, 30% and 40%) in a plano-concave laser cavity. With the output coupler transmission of T=30%, the static output energy of 62 mJ is obtained when the pump energy is 24.2 J, and the corresponding electric-optical conversion efficiency is 0.26%. By using a new saturable absorber: Co(2+):LaMgAl(11)O(19) (Co:LMA), the passive Q-switching at 1.34 mum is realized when the second threshold condition of passive Q-switching is satisfied. With the cavity length of 245 mm and pump energy of 24.2 J, the single-pulse output energy, pulse width and peak power are obtained to be 3.5 mJ, 45 ns and 77.8 kW, respectively.

Polymer International, 2000

Journal of Molecular Catalysis A-chemical, 2002

A series of aryl-substituted tetramethylcyclopentadienyl zirconocenes (C 5 Me 4 C 6 H 4 X-4)Cp MC... more A series of aryl-substituted tetramethylcyclopentadienyl zirconocenes (C 5 Me 4 C 6 H 4 X-4)Cp MCl 2 [Cp = C 5 H 5 , X = H (5), Me (6), Cl (7) or OMe (8); Cp = Ind, X = H (9), Me (10) or Cl (11); Cp = 2-Ph-Ind, X = H (12)] and (C 5 Me 4 C 6 H 4 X-4) 2 ZrCl 2 [X = H (13), Me (14), Cl (15)], with different substituents at the 4-position of phenyl, have been prepared by the reaction of the corresponding ligands (C 5 Me 4 HC 6 H 4 X-4) [X = H (1), Me (2), Cl (3) or OMe (4)] with n-BuLi, ZrCl 4 and Cp Li or with n-BuLi and ZrCl 4 . Ethylene polymerization with these complexes in combination with MAO has been studied. The electron donor (Me) at the 4-position of phenyl led to an increase in catalytic activity while the electron-withdrawing group (Cl) and the strong donor (OMe) led to its decrease. Complexes 5, 6, 9 and 10 exhibited very high activities, but 13-15 showed much lower activities due to the bulky steric effect. The molecular structure of 5 has been determined by X-ray diffraction. The relationship between structures of catalysts and catalytic activities were discussed.

Macromolecular Rapid Communications, 2001

Journal of Polymer Science Part A-polymer Chemistry, 2000

Two new silolene-bridged metallocenes for isotactic polypropylene, racemic (1,4-butanediyl) silyl... more Two new silolene-bridged metallocenes for isotactic polypropylene, racemic (1,4-butanediyl) silylene-bis (1-5 -2-methyl-indenyl) dichlorozironium and racemic diphenyl silylene-bis (1-5 -2-methyl-indenyl) dichlorozironium, were designed in terms of the mechanism and concept of the activity and selectivity of metallocenes. The predictions on which the designs were based were carried out for four metallocene catalysts through molecular modeling methods such as molecular mechanics and charge equilibrium. In a comparison of the data from three of the catalysts that were successfully synthesized, the predicted orders of the activity and selectivity were consistent. This shows that classical methods such as charge equilibrium are useful in predicting the activity of catalysts.

Toxicology, 2009

Perfluorooctanoic acid (PFOA) is a ligand for peroxisome proliferator-activated receptor (PPAR) α... more Perfluorooctanoic acid (PFOA) is a ligand for peroxisome proliferator-activated receptor (PPAR) α, which exhibits marked species differences in expression and function, especially between rodents and humans. We investigated the functional difference in PFOA response between mice and humans, using a humanized PPARα transgenic mouse line. Three genotyped mice, 129/Sv wild-type (mPPARα), Pparα-null mice and humanized PPARα (hPPARα) mice (8-week-old males) were divided into three groups: the first was treated with water daily for 2 weeks by gavage (control group), and the remaining two groups were treated with 0.1 and 0.3 mg/kg ammonium perflurooctanate (APFO), respectively, for 2 weeks by gavage. The APFO dosages used did not influence the plasma triglyceride or total cholesterol levels in any mouse line, but the high dose increased both hepatic lipid levels only in mPPARα mice. APFO increased mRNA and/or protein levels of PPARα target genes cytochrome P450 Cyp4a10, peroxisomal thiolase and bifunctional protein only in the liver of mPPARα mice, but not in Pparα-null or hPPARα mice. This chemical also increased expression of mitochondrial very long chain acyl-CoA dehydrogenase only in the liver of mPPARα mice. Taken together, human PPARα may be less responsive to PFOA than that of mice when a relatively low dose is applied. This information may be very valuable in considering whether PFOA influences the lipid metabolism in humans.