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2001 Volume 17 Issue 5
2001, 17(05): 385-388
doi: 10.3866/PKU.WHXB20010501
Abstract:
Two expressions are introduced to calculate the lithium ion diffusion coefficients in graphite anode as a function of potentials when potentiostatic intermittent titration technique(PITT) is used. The lithium ion diffusion coefficients in graphite derived from effective surface area, which is measured by electrochemical method, are more reliable than those derived simply from radius of graphite particles(calculated from equation (3) and equation (2) respectively). The curves of dQ/dE vs E demonstrate that there are three reversible phase transitions during intercalation or deintercalation of lithium ion in graphite. In the vicinity of the potentials where phase transitions take place, the lithium ion diffusion coefficients in graphite material have three minima in the potential range 10～600 mV.
Two expressions are introduced to calculate the lithium ion diffusion coefficients in graphite anode as a function of potentials when potentiostatic intermittent titration technique(PITT) is used. The lithium ion diffusion coefficients in graphite derived from effective surface area, which is measured by electrochemical method, are more reliable than those derived simply from radius of graphite particles(calculated from equation (3) and equation (2) respectively). The curves of dQ/dE vs E demonstrate that there are three reversible phase transitions during intercalation or deintercalation of lithium ion in graphite. In the vicinity of the potentials where phase transitions take place, the lithium ion diffusion coefficients in graphite material have three minima in the potential range 10～600 mV.
2001, 17(05): 389-392
doi: 10.3866/PKU.WHXB20010502
Abstract:
The development of human genome project calls for more rapid and accurate protein structure prediction method to assign the structure and function of gene products. Threading has been proved to be successful in protein fold assignment,although difficulties remain for low homolo us sequences. We have developed a method for solving the sequence rearrangement problem in threading. By reshuffling secondary elements,protein structures with the same spatial arrangement of secondary structures but different connections can be predicted. This method has been proved to be useful in fold recognition for proteins of different evolutionary origin and converge to the same fold.
The development of human genome project calls for more rapid and accurate protein structure prediction method to assign the structure and function of gene products. Threading has been proved to be successful in protein fold assignment,although difficulties remain for low homolo us sequences. We have developed a method for solving the sequence rearrangement problem in threading. By reshuffling secondary elements,protein structures with the same spatial arrangement of secondary structures but different connections can be predicted. This method has been proved to be useful in fold recognition for proteins of different evolutionary origin and converge to the same fold.
2001, 17(05): 393-396
doi: 10.3866/PKU.WHXB20010503
Abstract:
Patterned arrays of shortened singlewalled carbon nanotubes(sSWNTs) on ld were prepared using a surface reaction method. Under the existence of a condensation reagent, dicyclohexyl carbodiimide (DCC), sSWNTs terminated with carboxylic groups were found to react with the NH2(CH2)11SH selfassembled monolayers (SAMs) on ld readily, but could rarely be adsorbed on a CH3terminated surface. Thus by using a patterned surface with both NH2 and CH3 groups, sSWNTs were immobilized only on NH2 areas, resulting in a patterned array of sSWNTs.
Patterned arrays of shortened singlewalled carbon nanotubes(sSWNTs) on ld were prepared using a surface reaction method. Under the existence of a condensation reagent, dicyclohexyl carbodiimide (DCC), sSWNTs terminated with carboxylic groups were found to react with the NH2(CH2)11SH selfassembled monolayers (SAMs) on ld readily, but could rarely be adsorbed on a CH3terminated surface. Thus by using a patterned surface with both NH2 and CH3 groups, sSWNTs were immobilized only on NH2 areas, resulting in a patterned array of sSWNTs.
2001, 17(05): 397-399
doi: 10.3866/PKU.WHXB20010504
Abstract:
The isopropylation of naphthalene with isopropanol over AlMCM48 mesoporous molecular sieves was studied. AlMCM48 showed high activity and shape selectivity to the isopropylation of naphthalene. Grafting aluminum on MCM48 improved its acidity. It was found that with the increasing of Al content, the performance of AlMCM48 catalysts for naphthalene conversion was enhanced. High naphthalene conversion of 89.5 ％ was achieved over AlMCM48 with Si/Al=5.3 under the reaction conditions:n(isopropanol) /n(naphthalene)=2, temperature T=250 ℃, time t=4 h.
The isopropylation of naphthalene with isopropanol over AlMCM48 mesoporous molecular sieves was studied. AlMCM48 showed high activity and shape selectivity to the isopropylation of naphthalene. Grafting aluminum on MCM48 improved its acidity. It was found that with the increasing of Al content, the performance of AlMCM48 catalysts for naphthalene conversion was enhanced. High naphthalene conversion of 89.5 ％ was achieved over AlMCM48 with Si/Al=5.3 under the reaction conditions:n(isopropanol) /n(naphthalene)=2, temperature T=250 ℃, time t=4 h.
2001, 17(05): 400-405
doi: 10.3866/PKU.WHXB20010505
Abstract:
Densities have been determined for ternary aqueous solutions containing glycine, ethylene glycol or glycerol(cosolvent), with mass fractions of the polyols in cosolventwater mixtures ranging from 0 to 0.50. The apparent molar volumes, the limiting partial molar volumes and hydration numbers of glycine zwitterion have been calculated. The transfer volumes from water to polyolwater mixtures have been obtained and discussed in terms of the structural hydration interaction model. The results obtained have been compared with that in ethanolwater mixtures. It is concluded that the magnitude of enhancement effect on volume is somewhat related to the number of OH groups on alcohol molecules. However, the most important factor that influences volumes is the structural shapes of hydration shells of alcohol molecules. The unusual enhancement effect on volume in ethanolwater mixtures is considered to be related to the fact that the microstructure of the mixtures is heterogeneous and discontinuous.
Densities have been determined for ternary aqueous solutions containing glycine, ethylene glycol or glycerol(cosolvent), with mass fractions of the polyols in cosolventwater mixtures ranging from 0 to 0.50. The apparent molar volumes, the limiting partial molar volumes and hydration numbers of glycine zwitterion have been calculated. The transfer volumes from water to polyolwater mixtures have been obtained and discussed in terms of the structural hydration interaction model. The results obtained have been compared with that in ethanolwater mixtures. It is concluded that the magnitude of enhancement effect on volume is somewhat related to the number of OH groups on alcohol molecules. However, the most important factor that influences volumes is the structural shapes of hydration shells of alcohol molecules. The unusual enhancement effect on volume in ethanolwater mixtures is considered to be related to the fact that the microstructure of the mixtures is heterogeneous and discontinuous.
2001, 17(05): 406-411
doi: 10.3866/PKU.WHXB20010506
Abstract:
The resonance scattering spectra of orange ulcer germs have been studied. There are four resonance scattering peaks at 330, 425, 465 and 695 nm. When the excitation wavelength (λex) is set at 330 nm(9.09 1014 Hz), the orange ulcer germs in solution exhibit a resonance scattering peak at 330 nm and two 1/2, 1/3 fraction frequency scattering peaks at 465 nm（1/2×9.09×1014 Hz） and 990 nm（1/3×9.09×1014 Hz）respectively. A resonance scattering peak at 465 nm(6.45×1014 Hz) and a 1/2 fraction frequency scattering peak at 930 nm(1/2×6.45×1014 Hz) are observed as λex =465 nm. There are a 3/2 fraction frequency scattering peak at 465 nm(2 3.23 1014 Hz), a three times frequency scattering peak at 310 nm(3 3.23 1014 Hz) and a resonance scattering peak at 930 nm(3.23 1014 Hz) observed for the excitation wavelength of 930 nm. Orange ulcer is a nonlinear scattering medium. Experiments showed that the fraction frequency peak and the multiple frequency peak have similar scattering behaviour to that of the resonance scattering peak.
The resonance scattering spectra of orange ulcer germs have been studied. There are four resonance scattering peaks at 330, 425, 465 and 695 nm. When the excitation wavelength (λex) is set at 330 nm(9.09 1014 Hz), the orange ulcer germs in solution exhibit a resonance scattering peak at 330 nm and two 1/2, 1/3 fraction frequency scattering peaks at 465 nm（1/2×9.09×1014 Hz） and 990 nm（1/3×9.09×1014 Hz）respectively. A resonance scattering peak at 465 nm(6.45×1014 Hz) and a 1/2 fraction frequency scattering peak at 930 nm(1/2×6.45×1014 Hz) are observed as λex =465 nm. There are a 3/2 fraction frequency scattering peak at 465 nm(2 3.23 1014 Hz), a three times frequency scattering peak at 310 nm(3 3.23 1014 Hz) and a resonance scattering peak at 930 nm(3.23 1014 Hz) observed for the excitation wavelength of 930 nm. Orange ulcer is a nonlinear scattering medium. Experiments showed that the fraction frequency peak and the multiple frequency peak have similar scattering behaviour to that of the resonance scattering peak.
2001, 17(05): 412-415
doi: 10.3866/PKU.WHXB20010507
Abstract:
Low energy ion implantation has been widely used for mutation breeding,DNA delivery and microbe improvement et al.since 1980′s,but for a long time such kind of implantation was performed only to dry samples because it needed a vacuum chamber,for this reason,a new apparatus (see Fig.1)was designed in this paper to induce chemical reactions by introducing low energy ions into aqueous solution.In order to explore the origin of life induced by low energy ions and prebiotic synthesis of nucleotide via reaction between low energy ions and aqueous solution under primitive earth conditions,low energy N＋ was implanted into aqueous solution containing adenine,D ribose,and NH4H2PO4.HPLC analysis showed that a new substance was synthesized which was eluted as 5′AMP (to see Fig.2),then it was separated from the sample and analyzed by 1HNMR spectrum.It was confirmed that 5′AMP was formed in the experiment by 1HNMR spectrum (see Fig.3).The relation between yield of 5′AMP and irradiated time was obtained (see Fig.4).Mechanism of the production of 5′AMP was also discussed.The result is interesting for the formation and accumulation of nucleotide in the primitive oceans on the early earth.
Low energy ion implantation has been widely used for mutation breeding,DNA delivery and microbe improvement et al.since 1980′s,but for a long time such kind of implantation was performed only to dry samples because it needed a vacuum chamber,for this reason,a new apparatus (see Fig.1)was designed in this paper to induce chemical reactions by introducing low energy ions into aqueous solution.In order to explore the origin of life induced by low energy ions and prebiotic synthesis of nucleotide via reaction between low energy ions and aqueous solution under primitive earth conditions,low energy N＋ was implanted into aqueous solution containing adenine,D ribose,and NH4H2PO4.HPLC analysis showed that a new substance was synthesized which was eluted as 5′AMP (to see Fig.2),then it was separated from the sample and analyzed by 1HNMR spectrum.It was confirmed that 5′AMP was formed in the experiment by 1HNMR spectrum (see Fig.3).The relation between yield of 5′AMP and irradiated time was obtained (see Fig.4).Mechanism of the production of 5′AMP was also discussed.The result is interesting for the formation and accumulation of nucleotide in the primitive oceans on the early earth.
2001, 17(05): 416-421
doi: 10.3866/PKU.WHXB20010508
Abstract:
A model for the freely jointed square well chain fluid is developed based on the thermodynamic perturbation theory of BarkerHenderson,Zhang and Wertheim.The analytic representations of squarewell monomer by Zhang are extended to obtain a series of representations for thermodynamic properties of squarewell chain fluids using the incorporating structural information for squarewell monomer of Wertheim's TPT1 model.The same work has been done using incorporating structural information for the diatomic squarewell fluid of TPTD model.The calculated results of compressibility factor,residual internal energy and constantvolume heat capacity of 4mer,8mer and 16mer chain fluids are tested against the MC results and a careful comparison between the model from TPT1 and that from TPTD has been made.The former agree with MC results much better than the later,especially for internal energy.To obtain the constantvolume heat capacity,NVT MC simulations have been performed.
A model for the freely jointed square well chain fluid is developed based on the thermodynamic perturbation theory of BarkerHenderson,Zhang and Wertheim.The analytic representations of squarewell monomer by Zhang are extended to obtain a series of representations for thermodynamic properties of squarewell chain fluids using the incorporating structural information for squarewell monomer of Wertheim's TPT1 model.The same work has been done using incorporating structural information for the diatomic squarewell fluid of TPTD model.The calculated results of compressibility factor,residual internal energy and constantvolume heat capacity of 4mer,8mer and 16mer chain fluids are tested against the MC results and a careful comparison between the model from TPT1 and that from TPTD has been made.The former agree with MC results much better than the later,especially for internal energy.To obtain the constantvolume heat capacity,NVT MC simulations have been performed.
2001, 17(05): 422-426
doi: 10.3866/PKU.WHXB20010509
Abstract:
The endtoend vector distribution P(R) of a linear randomflight polymer chain with one end attached to an infinite large flat surface is investigated by Monte Carlo method.The meansquare endtoend distance can be given by=(4/3)n,and the mean angle by <θ>=45 ,where n is the chain length, θ is the angle between the endtoend vector R and Z axis normal to the surface.The radial distribution is P(R)dR=2A4 exp (－A2R2)R3 dR and the angular distribution isP(θ)dθ =sin 2θdθ ,here A2=3/(2n).The shape factor :: is about 1:2.73:12.5.The distribution of angle ,the angle between the longest principal axis L3 and Z axis,is approximately P(α)dα =sinαdα ,and its mean value <α> is nearly equal to 55.5 .
The endtoend vector distribution P(R) of a linear randomflight polymer chain with one end attached to an infinite large flat surface is investigated by Monte Carlo method.The meansquare endtoend distance can be given by
2001, 17(05): 427-431
doi: 10.3866/PKU.WHXB20010510
Abstract:
Bucky onions were fabricated by DC discharge method and their behaviors and electric properties on Highly Oriented Pyrolytic Graphite(HOPG) were studied using Atomic Force Microscope (AFM), Scanning Tunneling Microscope(STM) and Transmission Electron Microscope (TEM). Scanning Tunneling Spectroscopy showed that Bucky onions pocessed nonlinear electric properties similar to those of singlewall carbon nanotubes. Smallsized Bucky onions demonstrated the properties of semiconductors and as the size increased their metallicity became stronger. AFM and STM images revealed the tendency of Bucky onions to form dimers. Due to their nonlinear electric properties, Bucky onion is considered as a promising candidate for the future single electron devices.
Bucky onions were fabricated by DC discharge method and their behaviors and electric properties on Highly Oriented Pyrolytic Graphite(HOPG) were studied using Atomic Force Microscope (AFM), Scanning Tunneling Microscope(STM) and Transmission Electron Microscope (TEM). Scanning Tunneling Spectroscopy showed that Bucky onions pocessed nonlinear electric properties similar to those of singlewall carbon nanotubes. Smallsized Bucky onions demonstrated the properties of semiconductors and as the size increased their metallicity became stronger. AFM and STM images revealed the tendency of Bucky onions to form dimers. Due to their nonlinear electric properties, Bucky onion is considered as a promising candidate for the future single electron devices.
2001, 17(05): 432-437
doi: 10.3866/PKU.WHXB20010511
Abstract:
In an acidic aqueous solution of acetonitrile,the catalytic activity of the catalysts consisted of Pd(OAc)2/hydroquinone(HQ) with iron phthalocyanine (FePc) from various sources was obviously different in the oxidation of cyclohexene to cyclohexanone.The analysis of the FePc using IR spectroscopy,Mssbauer spectroscopy,Xray photoelectron spectroscopy (XPS),Xray powder diffraction (XRD),scanning electron microscopy(SEM) and BET surface area measurement indicated that the catalytic activity of the multicomponent catalytic system composed of iron phthalocyanines depends on the amount of μ-oxo FePc,the crystallinity and the surface structure of iron phthalocyanine.
In an acidic aqueous solution of acetonitrile,the catalytic activity of the catalysts consisted of Pd(OAc)2/hydroquinone(HQ) with iron phthalocyanine (FePc) from various sources was obviously different in the oxidation of cyclohexene to cyclohexanone.The analysis of the FePc using IR spectroscopy,Mssbauer spectroscopy,Xray photoelectron spectroscopy (XPS),Xray powder diffraction (XRD),scanning electron microscopy(SEM) and BET surface area measurement indicated that the catalytic activity of the multicomponent catalytic system composed of iron phthalocyanines depends on the amount of μ-oxo FePc,the crystallinity and the surface structure of iron phthalocyanine.
2001, 17(05): 438-442
doi: 10.3866/PKU.WHXB20010512
Abstract:
AGNTO was prepared by mixing aminocarbamidine bicarbonate and 3nitro1,2,4triazol5one. The product was characterized by element analysis and IR measurement. The crystal structure of AGNTO was determined by single crystal diffraction analysis. The crystal belongs to monoclinic space group P21/n. Crystallographic data are:a=0.67870(10)nm， b=2.7915(4)nm， c=1.2739(2)nm； β=96.930(10) V=2.3959(6)nm3， Z=12， Dc=1.698 g•cm－3， μ(Mo K )=1.47 cm－1， F(000)=1272, R=0.0352， wR=0.0718. This salt would be a very promising energetic material, and it might be used as new gas generate agent.
AGNTO was prepared by mixing aminocarbamidine bicarbonate and 3nitro1,2,4triazol5one. The product was characterized by element analysis and IR measurement. The crystal structure of AGNTO was determined by single crystal diffraction analysis. The crystal belongs to monoclinic space group P21/n. Crystallographic data are:a=0.67870(10)nm， b=2.7915(4)nm， c=1.2739(2)nm； β=96.930(10) V=2.3959(6)nm3， Z=12， Dc=1.698 g•cm－3， μ(Mo K )=1.47 cm－1， F(000)=1272, R=0.0352， wR=0.0718. This salt would be a very promising energetic material, and it might be used as new gas generate agent.
2001, 17(05): 443-447
doi: 10.3866/PKU.WHXB20010513
Abstract:
Dispersion of B2O3 on zirconia surface with load levels up to 20％B2O3 was explored with samples that were prepared by impregnation of boric acid onto porous ZrO2 obtained by precalcination of ZrO(OH)2 at different temperatures (110－700 ℃). After calcination at 350 ℃, the B2O3/ZrO2 samples were characterized with FTIR, XPS and FTRaman techniques to determine the interaction state of B2O3 on the surface. Both tetrahedral BO4 and tri nal BO3 were detected as the basic units of the dispersed B2O3. The ratio of BO4 to BO3 units depended strongly on the temperature of the precalcination and the load level of boria. At lower precalcination temperature for the support and at low levels of boria load, B2O3 interacts directly with the support surface in BO4 units and forms monolayer dispersion. Inversely,multilayer dispersion with BO3 as the structural unit forms over the support precalcined at high temperature. The XPS and Raman data also provide od measurements for monolayer dispersion capacity of boria; with ZrO2 precalcined at 500 ℃, this capacity is 0.05 g/g(or mass fraction of B2O3 w=4.7 6 ％). A model for the dispersion structure of B2O3/ZrO2 has been proposed.
Dispersion of B2O3 on zirconia surface with load levels up to 20％B2O3 was explored with samples that were prepared by impregnation of boric acid onto porous ZrO2 obtained by precalcination of ZrO(OH)2 at different temperatures (110－700 ℃). After calcination at 350 ℃, the B2O3/ZrO2 samples were characterized with FTIR, XPS and FTRaman techniques to determine the interaction state of B2O3 on the surface. Both tetrahedral BO4 and tri nal BO3 were detected as the basic units of the dispersed B2O3. The ratio of BO4 to BO3 units depended strongly on the temperature of the precalcination and the load level of boria. At lower precalcination temperature for the support and at low levels of boria load, B2O3 interacts directly with the support surface in BO4 units and forms monolayer dispersion. Inversely,multilayer dispersion with BO3 as the structural unit forms over the support precalcined at high temperature. The XPS and Raman data also provide od measurements for monolayer dispersion capacity of boria; with ZrO2 precalcined at 500 ℃, this capacity is 0.05 g/g(or mass fraction of B2O3 w=4.7 6 ％). A model for the dispersion structure of B2O3/ZrO2 has been proposed.
2001, 17(05): 448-452
doi: 10.3866/PKU.WHXB20010514
Abstract:
Based on the principle of the sum of inducted polarity vectors proposed by us and its successful applications in explanations of the stabilities of isomers and design of a new scheme for calculation of the enthalpies of formation of alkanes, we have designed a new scheme with 5 parameters for the calculation of the standard enthalpies of formation of polychloroalkanes. Compared with the Group Additivity Scheme with 9 parameters, this new scheme has a higher calculation accuracy(its prediction errors are even lower than the experimental deviations). This new scheme contains less parameters and thus can be extended to calculate theoretically the standard enthalpies of formation of alkane derivatives with some different hetero atoms on a carbon atom.
Based on the principle of the sum of inducted polarity vectors proposed by us and its successful applications in explanations of the stabilities of isomers and design of a new scheme for calculation of the enthalpies of formation of alkanes, we have designed a new scheme with 5 parameters for the calculation of the standard enthalpies of formation of polychloroalkanes. Compared with the Group Additivity Scheme with 9 parameters, this new scheme has a higher calculation accuracy(its prediction errors are even lower than the experimental deviations). This new scheme contains less parameters and thus can be extended to calculate theoretically the standard enthalpies of formation of alkane derivatives with some different hetero atoms on a carbon atom.
2001, 17(05): 453-456
doi: 10.3866/PKU.WHXB20010515
Abstract:
The growth characteristic of intermetallics during the reaction of solid (Cu,Ag,Au,Fe,Co,Ni,etc) with liquid (Sn,Sb,Bi,Zn) within a very short time of 1～2 s at different temperatures has been studied by metallographic method for explaining the process in the fillet during soldering. It is indicated that the incongruent compourds often grow up as bamboo shoot form. But congruent compounds grow up basically just by spreading out as a layer along the solid border. Base on these facts,the influence of intermetallics in the fillet during soldering has been discussed.
The growth characteristic of intermetallics during the reaction of solid (Cu,Ag,Au,Fe,Co,Ni,etc) with liquid (Sn,Sb,Bi,Zn) within a very short time of 1～2 s at different temperatures has been studied by metallographic method for explaining the process in the fillet during soldering. It is indicated that the incongruent compourds often grow up as bamboo shoot form. But congruent compounds grow up basically just by spreading out as a layer along the solid border. Base on these facts,the influence of intermetallics in the fillet during soldering has been discussed.
2001, 17(05): 457-459
doi: 10.3866/PKU.WHXB20010516
Abstract:
A niobate was synthesized by doping Bi3＋ in the ternary system BaONa2ONb2O5. The crystal structure was determined by Xray powder diffraction,and it belongs to tetra nal tungsten bronze structure at room temperature with unit cell parameters a=1.24777 (2) nm,c=0.39266(1) nm, = = =90 .Measurements of dielectric properties indicate that phase transitions of Ba3NaBiNb10O30 from paraelectric to ferroelectric occurs at 400℃,which is lower than that of Ba2NaNb5O30.
A niobate was synthesized by doping Bi3＋ in the ternary system BaONa2ONb2O5. The crystal structure was determined by Xray powder diffraction,and it belongs to tetra nal tungsten bronze structure at room temperature with unit cell parameters a=1.24777 (2) nm,c=0.39266(1) nm, = = =90 .Measurements of dielectric properties indicate that phase transitions of Ba3NaBiNb10O30 from paraelectric to ferroelectric occurs at 400℃,which is lower than that of Ba2NaNb5O30.
2001, 17(05): 460-464
doi: 10.3866/PKU.WHXB20010517
Abstract:
An apparatus was set up for in situ UVVis determintion of ethylene polymerization under atmospheric pressure. In three different solvents, tetrahydrofuran(THF), chlorobenzene and dimethyl formamide (DMF), and using MAO as cocatalyst, α-iimine/nickel catalytic system was prepared for ethylene polymerization with the UVVis testing system. In THF, active peak at 545 nm and inactive peak at 660 nm were observed. In chlorobenzene, active peak at 520 nm, 570 nm, and inactive peak at 660 nm were also observed. The regularities of growth and disappearence of active peaks were investigated. The structure of active species and solvent effect were discussed.
An apparatus was set up for in situ UVVis determintion of ethylene polymerization under atmospheric pressure. In three different solvents, tetrahydrofuran(THF), chlorobenzene and dimethyl formamide (DMF), and using MAO as cocatalyst, α-iimine/nickel catalytic system was prepared for ethylene polymerization with the UVVis testing system. In THF, active peak at 545 nm and inactive peak at 660 nm were observed. In chlorobenzene, active peak at 520 nm, 570 nm, and inactive peak at 660 nm were also observed. The regularities of growth and disappearence of active peaks were investigated. The structure of active species and solvent effect were discussed.
2001, 17(05): 465-470
doi: 10.3866/PKU.WHXB20010518
Abstract:
By defining a polyhaloalkyl and a polyhaloalcohol, using recurrence method, the generating functions for counting staggered conformations of polyhaloalkyls and polyhaloalcohols have been obtained. The numerical results in Table 1－3 are given. According to the results obtained, using graphtheoretical method, the generating functions for counting staggered conformations of polyhaloalkanes have been devived. Some numerical results are given in Table 4. Furthermore, the staggered conformations of polyhaloalkanes according to their symmetry groups have been classified and the generating function of counting the staggered conformations belong to each group have been derived. The numerical results are given in Table 5.
By defining a polyhaloalkyl and a polyhaloalcohol, using recurrence method, the generating functions for counting staggered conformations of polyhaloalkyls and polyhaloalcohols have been obtained. The numerical results in Table 1－3 are given. According to the results obtained, using graphtheoretical method, the generating functions for counting staggered conformations of polyhaloalkanes have been devived. Some numerical results are given in Table 4. Furthermore, the staggered conformations of polyhaloalkanes according to their symmetry groups have been classified and the generating function of counting the staggered conformations belong to each group have been derived. The numerical results are given in Table 5.
2001, 17(05): 471-476
doi: 10.3866/PKU.WHXB20010519
Abstract:
The solution property of amphiphilic graft copolymer has been examined by means of NMR,TEM and viscometry. It is found that water and toluene are selective solvent for PStgPEO. When it is dissolved in water, micelle can be formed with hydrophobic PSt backbone as the core and hydrophilic PEO side chains as the shell. On the other hand, in selective solvent toluene, the reversedmicelle can be formed with PEO as core and PSt as the shell. In toluene, with an increase in concentration, the conformation of PStgPEO can be transformed from stretched single molecule to spherical reversedmicelle. The critical micelle concentration(CMC) is determined at different temperature and with the increase of temperature and the content of PEO the reversedmicelle can be formed in lower concentrations.
The solution property of amphiphilic graft copolymer has been examined by means of NMR,TEM and viscometry. It is found that water and toluene are selective solvent for PStgPEO. When it is dissolved in water, micelle can be formed with hydrophobic PSt backbone as the core and hydrophilic PEO side chains as the shell. On the other hand, in selective solvent toluene, the reversedmicelle can be formed with PEO as core and PSt as the shell. In toluene, with an increase in concentration, the conformation of PStgPEO can be transformed from stretched single molecule to spherical reversedmicelle. The critical micelle concentration(CMC) is determined at different temperature and with the increase of temperature and the content of PEO the reversedmicelle can be formed in lower concentrations.
2001, 17(05): 477-480
doi: 10.3866/PKU.WHXB20010520
Abstract:
Preliminary study on the mechanism of nonenzymatic bioreduction of ld,silver,platinum,palladium and rhodium ions by Bacillus megatherium D01 biomass has been carried out by means of TEM,XRD,XPS and FTIR methods. The results showed that after contacted with D01 biomass,Au3＋ has been completely reduced to elemental,cell bound Au0 for 2h and about 45％ Rh3＋ to Rh0 for 2 d at 30℃ and pH 3.5 without biochemical or chemical cofactors; the cardinal mechanism of D01 cell accumulating metal ions was biosorption,and the primary location where biosorption occurred was the D01 cell wall; active groups such as carbonyl of amido bond and carboxyl on the cell wall may complex or chelate with the precious metal ions; and aldose and ketose,i.e.,hydrolysate of part polysaccharide on the cell wall in acidic medium,served as the election donor,and reduced soluble precious metal ions to atoms.
Preliminary study on the mechanism of nonenzymatic bioreduction of ld,silver,platinum,palladium and rhodium ions by Bacillus megatherium D01 biomass has been carried out by means of TEM,XRD,XPS and FTIR methods. The results showed that after contacted with D01 biomass,Au3＋ has been completely reduced to elemental,cell bound Au0 for 2h and about 45％ Rh3＋ to Rh0 for 2 d at 30℃ and pH 3.5 without biochemical or chemical cofactors; the cardinal mechanism of D01 cell accumulating metal ions was biosorption,and the primary location where biosorption occurred was the D01 cell wall; active groups such as carbonyl of amido bond and carboxyl on the cell wall may complex or chelate with the precious metal ions; and aldose and ketose,i.e.,hydrolysate of part polysaccharide on the cell wall in acidic medium,served as the election donor,and reduced soluble precious metal ions to atoms.
