Based on the Eigen and Crow-Kimura models with a single-peak fitness landscape, we propose the fitness values of all sequence types to be Gausslan distributed random variables to incorporate the effects of the fluctua...Based on the Eigen and Crow-Kimura models with a single-peak fitness landscape, we propose the fitness values of all sequence types to be Gausslan distributed random variables to incorporate the effects of the fluctuations of the fitness landscapes （noise of environments） and investigate the concentration distribution and error threshold of quasispecies by performing an ensemble average within this theoretical framework. We find that a small fluctuation of the fitness landscape causes only a slight change in the concentration distribution and error threshold, which implies that the error threshold is stable against small perturbations. However, for a sizable fluctuation, quite different from the previous deterministic models, our statistical results show that the transition from quasi-species to error catastrophe is not so sharp, indicating that the error threshold is located within a certain range and has a shift toward a larger value. Our results are qualitatively in agreement with the experimental data and provide a new implication for antiviral strategies.展开更多
Thiol-stabilized PbS quantum dots （QDs） with dimensions 3-5 nm capped with a mixture of 1-thioglycerol/dithioglycerol （TGL/DTG） were coUoidally prepared at room temperature. Room temperature photoluminescence quan...Thiol-stabilized PbS quantum dots （QDs） with dimensions 3-5 nm capped with a mixture of 1-thioglycerol/dithioglycerol （TGL/DTG） were coUoidally prepared at room temperature. Room temperature photoluminescence quantum efficiency of freshly prepared PbS QDs （7%-11%） remained higher than 5% upon aging for three weeks when the nanocrystals （NCs） were stored in an ice-bath in the dark, and higher than 5%for at least five weeks when extra DTG ligands were introduced into the nanocrystal solution followed by stirring every two weeks. Poly（N-isopropyl acrylamide） （PNIPAM） microgels were produced via precipitation polymerization with dimensions of ca. 230 nm and polydispersity of 3-5%. Incorporation of PbS QDs into PNIPAM microgels indicated that PbS can be incorporated into the interior of microgel particles and not at the microgel interface. The combination of reasonable room temperature quantum efficiency and strong, efficient luminescence covering the 1.3-1.55 μm telecommunication window makes these nanoparticles promising materials in optical devices and telecommunications.展开更多
The progress on the molecular design, synthesis and characterizations of some kinds of pyridine-containing heteroaromatic polymers in main chain were reviewed in this paper, they would include polyimides （Pls）, poly...The progress on the molecular design, synthesis and characterizations of some kinds of pyridine-containing heteroaromatic polymers in main chain were reviewed in this paper, they would include polyimides （Pls）, polypyrrolones （PPYs）, poly（pyrrolane-imide）s （PPIs）, and poly（pyrrolane-benzimidazone）s （PPBs） containing pyridine moieties. The pyridine-cantaining polymers reported all exhibit good processability, excellent thermal properties and mechanical properties. However, the contribution of pyridine ring to polymers properties is still need to research further, the heteroaromatic polymers containing pyridine moieties have focused by more and more researchers.展开更多
In this paper a modified two-step procedure for synthesis of N-（1-naphthyl） suecinimide （NaS） was developed, and the molecular structure of NaS was properly characterized by XRD, FT-IR, 1H NMR, DSC, etc. The resul...In this paper a modified two-step procedure for synthesis of N-（1-naphthyl） suecinimide （NaS） was developed, and the molecular structure of NaS was properly characterized by XRD, FT-IR, 1H NMR, DSC, etc. The results show that the melting point of our product is 159 ℃-160.5 ℃, and the characteristic infrared absorption band of carbonyl group splits into two peaks （1705cm^-3/1779cm^-3）, which are found to be quite different from the documented data （rap 147℃ -149℃; IR C=0-1700cm^-3）. Besides, photophysical spectroscopy was found to be powerful to study the molecular structure and crystal morphology of NaS compound.展开更多
Polymer-bound Schiff-base ligand (PS-Sal-Cys) was prepared from the polystyrene-bound salicylaldehyde and L-cysteine, its complex (PS-Sal-Cys-Mn) was also synthesized. The polymer ligand and its complex were character...Polymer-bound Schiff-base ligand (PS-Sal-Cys) was prepared from the polystyrene-bound salicylaldehyde and L-cysteine, its complex (PS-Sal-Cys-Mn) was also synthesized. The polymer ligand and its complex were characterized by infrared spectra (IR), small area X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma-atomic emission spectro (ICP-AES). In the presence of complex, cyclohexane can be effectively oxidized by molecular oxygen without a reductant. The major products of the reaction are 2-cyclohexen-1-ol, 2-cyclohexen-1-one, and 2-cyclohexen-1-hydroperoxide, which is different from the typical oxidation of cyclohexene. The mechanism of cyclohexene oxidation is also discussed.展开更多
In fitting the double-differential measurements thelevelwidth broadening effect should be taken into account properly due to Heisenberg uncertainty.Besides level width broadening effect the energy resolution in the me...In fitting the double-differential measurements thelevelwidth broadening effect should be taken into account properly due to Heisenberg uncertainty.Besides level width broadening effect the energy resolution in the measurements is also needed in this procedure.In general,the traditional normal Gaussian expansion is employed.However,the research indicates that to do so in this way the energy balance could not hold.For this reason,the deformed Gaussian expansion functions with exponential form for both the single energy point and continuous spectrum are introduced,with which the normalization and energy balance conditions could hold exactly in the analytical form.展开更多
We study the localization properties of electrons in a two-dimensional system in a random magnetic field with the average and the amplitude of the magnetic field fluctuations δB. The localization length of the syst...We study the localization properties of electrons in a two-dimensional system in a random magnetic field with the average and the amplitude of the magnetic field fluctuations δB. The localization length of the system is calculated by using the finite-size scaling method combined with the transfer-matrix technique. In the case of weak δB, we find that the random magnetic field system is equivalent to the integer quantum Hall effect system, namely, the energy band splits into a series of disorder broadened Landau bands, at the centers of which states are extended with the localization length exponent . With increasing δB, the extended states float up in energy, which is similar to the levitation scenario proposed for the integer quantum Hall effect.展开更多
Non-absorbed macromolecular binders as sequestrants for phosphate ions offer an effective approach to treat hyperphosphatemia in ESRD （end-stage renal disease） patients. RenaGel has been an example with remarkable s...Non-absorbed macromolecular binders as sequestrants for phosphate ions offer an effective approach to treat hyperphosphatemia in ESRD （end-stage renal disease） patients. RenaGel has been an example with remarkable success of a polymer synthesized to prevent the absorption of dietary phosphate for ESRD patients. Electrostatic interaction is the primary driving force for complexation of phosphate-based anions with these amino groups in the polymer backbone. Chitosan is a deacetylation product of chitin, which is the structural element in the exoskeleton of crustaceans and cell walls of fungi. The amino groups in the backbone give the phosphate binding ability to chitosan. This article has demonstrated that chitosan exhibited a phosphate binding effect indeed. Thus, it has potential applications in environmental management and wastewater treatment, as well as treatment of hyperphosphatemia patients.展开更多
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10475008, 10675170, and 10435020, and the Department of Nuclear Physics of China Institute of Atomic Energy under Grant Nos. 11SZZ-200501 and 11SZZ-200601
文摘Based on the Eigen and Crow-Kimura models with a single-peak fitness landscape, we propose the fitness values of all sequence types to be Gausslan distributed random variables to incorporate the effects of the fluctuations of the fitness landscapes （noise of environments） and investigate the concentration distribution and error threshold of quasispecies by performing an ensemble average within this theoretical framework. We find that a small fluctuation of the fitness landscape causes only a slight change in the concentration distribution and error threshold, which implies that the error threshold is stable against small perturbations. However, for a sizable fluctuation, quite different from the previous deterministic models, our statistical results show that the transition from quasi-species to error catastrophe is not so sharp, indicating that the error threshold is located within a certain range and has a shift toward a larger value. Our results are qualitatively in agreement with the experimental data and provide a new implication for antiviral strategies.
基金NSFC(No.50543007)Scientific Research Foundation for the Returned Overseas Chinese Scholars (State Education Ministry)+1 种基金NSF of Guangdong Province (No.07006838)Tianhe Bureau of Sci. & Techno., Guangzhou.
文摘Thiol-stabilized PbS quantum dots （QDs） with dimensions 3-5 nm capped with a mixture of 1-thioglycerol/dithioglycerol （TGL/DTG） were coUoidally prepared at room temperature. Room temperature photoluminescence quantum efficiency of freshly prepared PbS QDs （7%-11%） remained higher than 5% upon aging for three weeks when the nanocrystals （NCs） were stored in an ice-bath in the dark, and higher than 5%for at least five weeks when extra DTG ligands were introduced into the nanocrystal solution followed by stirring every two weeks. Poly（N-isopropyl acrylamide） （PNIPAM） microgels were produced via precipitation polymerization with dimensions of ca. 230 nm and polydispersity of 3-5%. Incorporation of PbS QDs into PNIPAM microgels indicated that PbS can be incorporated into the interior of microgel particles and not at the microgel interface. The combination of reasonable room temperature quantum efficiency and strong, efficient luminescence covering the 1.3-1.55 μm telecommunication window makes these nanoparticles promising materials in optical devices and telecommunications.
文摘The progress on the molecular design, synthesis and characterizations of some kinds of pyridine-containing heteroaromatic polymers in main chain were reviewed in this paper, they would include polyimides （Pls）, polypyrrolones （PPYs）, poly（pyrrolane-imide）s （PPIs）, and poly（pyrrolane-benzimidazone）s （PPBs） containing pyridine moieties. The pyridine-cantaining polymers reported all exhibit good processability, excellent thermal properties and mechanical properties. However, the contribution of pyridine ring to polymers properties is still need to research further, the heteroaromatic polymers containing pyridine moieties have focused by more and more researchers.
基金Natural Science Foundation of China (50273014, 29928003)Natural Science Foundation of Tianjin (03380261).
文摘In this paper a modified two-step procedure for synthesis of N-（1-naphthyl） suecinimide （NaS） was developed, and the molecular structure of NaS was properly characterized by XRD, FT-IR, 1H NMR, DSC, etc. The results show that the melting point of our product is 159 ℃-160.5 ℃, and the characteristic infrared absorption band of carbonyl group splits into two peaks （1705cm^-3/1779cm^-3）, which are found to be quite different from the documented data （rap 147℃ -149℃; IR C=0-1700cm^-3）. Besides, photophysical spectroscopy was found to be powerful to study the molecular structure and crystal morphology of NaS compound.
基金The National Natural Science Foundation of China(20274034)
文摘Polymer-bound Schiff-base ligand (PS-Sal-Cys) was prepared from the polystyrene-bound salicylaldehyde and L-cysteine, its complex (PS-Sal-Cys-Mn) was also synthesized. The polymer ligand and its complex were characterized by infrared spectra (IR), small area X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma-atomic emission spectro (ICP-AES). In the presence of complex, cyclohexane can be effectively oxidized by molecular oxygen without a reductant. The major products of the reaction are 2-cyclohexen-1-ol, 2-cyclohexen-1-one, and 2-cyclohexen-1-hydroperoxide, which is different from the typical oxidation of cyclohexene. The mechanism of cyclohexene oxidation is also discussed.
文摘In fitting the double-differential measurements thelevelwidth broadening effect should be taken into account properly due to Heisenberg uncertainty.Besides level width broadening effect the energy resolution in the measurements is also needed in this procedure.In general,the traditional normal Gaussian expansion is employed.However,the research indicates that to do so in this way the energy balance could not hold.For this reason,the deformed Gaussian expansion functions with exponential form for both the single energy point and continuous spectrum are introduced,with which the normalization and energy balance conditions could hold exactly in the analytical form.
文摘We study the localization properties of electrons in a two-dimensional system in a random magnetic field with the average and the amplitude of the magnetic field fluctuations δB. The localization length of the system is calculated by using the finite-size scaling method combined with the transfer-matrix technique. In the case of weak δB, we find that the random magnetic field system is equivalent to the integer quantum Hall effect system, namely, the energy band splits into a series of disorder broadened Landau bands, at the centers of which states are extended with the localization length exponent . With increasing δB, the extended states float up in energy, which is similar to the levitation scenario proposed for the integer quantum Hall effect.
文摘Non-absorbed macromolecular binders as sequestrants for phosphate ions offer an effective approach to treat hyperphosphatemia in ESRD （end-stage renal disease） patients. RenaGel has been an example with remarkable success of a polymer synthesized to prevent the absorption of dietary phosphate for ESRD patients. Electrostatic interaction is the primary driving force for complexation of phosphate-based anions with these amino groups in the polymer backbone. Chitosan is a deacetylation product of chitin, which is the structural element in the exoskeleton of crustaceans and cell walls of fungi. The amino groups in the backbone give the phosphate binding ability to chitosan. This article has demonstrated that chitosan exhibited a phosphate binding effect indeed. Thus, it has potential applications in environmental management and wastewater treatment, as well as treatment of hyperphosphatemia patients.
