The conservation of weathered historic sandstone with apatite was studied.Based on the growth mechanism of bone,calcium and phosphorus were introduced into weathered sandstone and then mineralized at room temperature....The conservation of weathered historic sandstone with apatite was studied.Based on the growth mechanism of bone,calcium and phosphorus were introduced into weathered sandstone and then mineralized at room temperature.The conservation efficiency was investigated by scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDX),transmission electron microscopy(TEM),selected area electron diffraction(SAED),X-ray diffraction(XRD),and compressive strength,capillary water uptake,water vapor permeability and weather resistance tests.The SEM,EDX,TEM,SAED and XRD results showed that the produced hydroxyapatite could reunite the weathered stone blocks and provide sufficient reinforcement to hold them together.The results of the various tests indicated that the compressive strength and weather resistance of the treated samples was improved significantly.In addition,because of the porous nature of apatite,the water vapor permeability of the treated stone was not affected and its breathability was maintained.展开更多
The weak intermolecular interactions between 2-F-tetrahydrofuran and imidazole, pyrimidine, adenine, and guanine were studied theoretically using density functional B3LYP/6-311++G** and HF/6-311++G** methods. The resu...The weak intermolecular interactions between 2-F-tetrahydrofuran and imidazole, pyrimidine, adenine, and guanine were studied theoretically using density functional B3LYP/6-311++G** and HF/6-311++G** methods. The results showed that both conven- tional N···H hydrogen bond and C-F···H-C pseudohydrogen bond (PHB) structures coexist in the four complexes. The weak intermolecular interaction energies indicate that the relative stabilities of the four complexes are in the order guanine···F > imidazole···F > adenine···F > pyrimidine···F. The characteristics of the four PHBs were determined using geometry optimizations, stretching vibrational frequencies, and natural bond orbital and electron density topological properties calculations. The most important result is that the F group of 2-F-tetrahydrofuran can activate the C-H to accept electrons from another molecule, and C-F···H-C PHB formation is relatively favorable.展开更多
Fluorapatite protective films were prepared on marble substrates using a biomimetic method. By mimicking the mineralization mechanism of enamel, phosphorus and fluorine were introduced on the surface of the marble sub...Fluorapatite protective films were prepared on marble substrates using a biomimetic method. By mimicking the mineralization mechanism of enamel, phosphorus and fluorine were introduced on the surface of the marble substrate. In the presence of a biological template, namely collagen, an integrated fluorapatite film was produced and the marble substrate was entirely covered. The prepared fluorapatite films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) spectroscopy. The performances of the fluorapatite films were evaluated by color changes, capillary water absorption, and acid resistance tests. The results revealed that the fluorapatite films had good compatibility with the marble substrate; the physical properties such as color and capillary water adsorption of the marble substrates were unchanged. The fluorapatite films also had good acid resistance and were stable even in heavy acid rain.展开更多
We used density functional calculations to investigate the electronic origins of the magnetic properties of the high-spin ferric enzyme-substrate complex protocatechuate 3,4-dioxygenase(3,4-PCD).The calculated g-tenso...We used density functional calculations to investigate the electronic origins of the magnetic properties of the high-spin ferric enzyme-substrate complex protocatechuate 3,4-dioxygenase(3,4-PCD).The calculated g-tensors show that ligand-to-metal charge transfer transitions are from the protocatechuate(PCA) and Tyr408 orbitals to the Fe d orbitals,which lead to x-and y-polarized transitions.These polarized transitions require a spin-orbit coupling(SOC) matrix element in the z-direction,Lz(z=z'),resulting in a g z value of 2.0158,significantly deviating from 2.0023.A large zero-field splitting parameter value of+1.147cm-1 is due to △S =-1 spin-orbit mixing with the quartet states for the sextet ground state,accounting for around 73% of the SOC contribution.The SOC matrix elements indicate that the high-spin d 5 system Fe(Ⅲ),3,4-PCD-PCA is a weak spin-crossover compound with an SOC of 31.56 cm-1.展开更多
The optimized geometries of the three complexes between MeH,~ （Me=Na, Mg, Be; n=1 or 2） and Sill4 have been calculated at the B3LYP/6-31 1＋＋g＊＊, MP2/6-31 1＋＋g（3df,3pd） and MP2/aug-cc-pvtz levels, respectivel...The optimized geometries of the three complexes between MeH,~ （Me=Na, Mg, Be; n=1 or 2） and Sill4 have been calculated at the B3LYP/6-31 1＋＋g＊＊, MP2/6-31 1＋＋g（3df,3pd） and MP2/aug-cc-pvtz levels, respectively. The red-shift inverse hydrogen bonds （IHBs） based on Si-H, an electron donor, were reported. The calculated binding energies with basis set super-position error （BSSE） correction of the three complexes are -5.98, -8.65 and -3.96 kJ mol^-1 （MP2/6-311＋＋g（3df, 3pd））, respectively, which agree with the results obtained via MP2/aug-cc-pvtz （-6.18, -9.12 and -4.28 kJ mol^-1, respectively）. The relative stabilities of the three complexes are in the order of SiH4...MgH2 〉 SiH4...NaH 〉 SiH4...BeH2. Natural bond orbital theory （NBO） analysis and the chemical shift calculation of the related atoms revealed that the charges flow from Sill4 to MeHn and the chemical shifts of the interacting H shift to downfield. Here, the Sil-H3 of Sill4 acts as both a bond hydrogen donor and an electron donor. Therefore, compared with conventional hydrogen bonds, they formed IHB complexes. Atoms in molecules （AIM） theory have been used to investigate the topological properties of the critical points in the three IHB structures.展开更多
Iodine-involved single-electron halogen bonds (SEXBs) weak interactions in the systems of CH3···I-Y(Y = BH2, H, CH3, CH==CH2, C≡CH, CN, NC) were investigated for the first time using B3LYP/6-311++G(d,p...Iodine-involved single-electron halogen bonds (SEXBs) weak interactions in the systems of CH3···I-Y(Y = BH2, H, CH3, CH==CH2, C≡CH, CN, NC) were investigated for the first time using B3LYP/6-311++G(d,p) and MP2/aug-cc-pVTZ computational levels (the relativistic effective core potential basis set of Lanl2dz was used on iodine atom). The interaction energies between two moieties with basis set super-position error corrections for the seven complexes are -0.57, -1.36, -3.80, -2.17, -4.49,-6.33 and -8.64 kJ mol-1 (MP2/aug-cc-pVTZ ), respectively, which shows that SEXBs interactions are all weak. Natural bond orbital theory analysis revealed that charges flow from CH3 to the I-Y moiety. The total amount of natural bond orbital charge transfer (ΔNC) from the CH3 radical to I-Y increases in the order CH3…IBH2 < CH3…IH ≈ CH3…ICH3 ≈ CH3···IC2H3 < CH3…ICCH< CH3…ICN< CH3…INC. Atoms-in-molecules theory was used to investigate the topological properties of the bond critical points in the seven SEXB structures.展开更多
基金supported by the Key Project of the Chinese Ministry of Education (211189)"QingLan" Talent Engineering Funds of Tianshui Normal University
文摘The conservation of weathered historic sandstone with apatite was studied.Based on the growth mechanism of bone,calcium and phosphorus were introduced into weathered sandstone and then mineralized at room temperature.The conservation efficiency was investigated by scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDX),transmission electron microscopy(TEM),selected area electron diffraction(SAED),X-ray diffraction(XRD),and compressive strength,capillary water uptake,water vapor permeability and weather resistance tests.The SEM,EDX,TEM,SAED and XRD results showed that the produced hydroxyapatite could reunite the weathered stone blocks and provide sufficient reinforcement to hold them together.The results of the various tests indicated that the compressive strength and weather resistance of the treated samples was improved significantly.In addition,because of the porous nature of apatite,the water vapor permeability of the treated stone was not affected and its breathability was maintained.
基金supported by the Key Project of the Chinese Ministry of Education (211189)the National Natural Science Foundation of China(51063006)the "QingLan" Talent Engineering Funds of Tianshui Normal University
文摘The weak intermolecular interactions between 2-F-tetrahydrofuran and imidazole, pyrimidine, adenine, and guanine were studied theoretically using density functional B3LYP/6-311++G** and HF/6-311++G** methods. The results showed that both conven- tional N···H hydrogen bond and C-F···H-C pseudohydrogen bond (PHB) structures coexist in the four complexes. The weak intermolecular interaction energies indicate that the relative stabilities of the four complexes are in the order guanine···F > imidazole···F > adenine···F > pyrimidine···F. The characteristics of the four PHBs were determined using geometry optimizations, stretching vibrational frequencies, and natural bond orbital and electron density topological properties calculations. The most important result is that the F group of 2-F-tetrahydrofuran can activate the C-H to accept electrons from another molecule, and C-F···H-C PHB formation is relatively favorable.
基金supported by the key Project of Chinese Ministry of Education (211189)"QingLan" Talent Engineering Funds of Tianshui Normal University
文摘Fluorapatite protective films were prepared on marble substrates using a biomimetic method. By mimicking the mineralization mechanism of enamel, phosphorus and fluorine were introduced on the surface of the marble substrate. In the presence of a biological template, namely collagen, an integrated fluorapatite film was produced and the marble substrate was entirely covered. The prepared fluorapatite films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) spectroscopy. The performances of the fluorapatite films were evaluated by color changes, capillary water absorption, and acid resistance tests. The results revealed that the fluorapatite films had good compatibility with the marble substrate; the physical properties such as color and capillary water adsorption of the marble substrates were unchanged. The fluorapatite films also had good acid resistance and were stable even in heavy acid rain.
基金supported by the "QingLan" Talent Engineering Fundsthrough Tian Shui Normal Universitythe Key Project of the Chinese Ministry of Education (211189)
文摘We used density functional calculations to investigate the electronic origins of the magnetic properties of the high-spin ferric enzyme-substrate complex protocatechuate 3,4-dioxygenase(3,4-PCD).The calculated g-tensors show that ligand-to-metal charge transfer transitions are from the protocatechuate(PCA) and Tyr408 orbitals to the Fe d orbitals,which lead to x-and y-polarized transitions.These polarized transitions require a spin-orbit coupling(SOC) matrix element in the z-direction,Lz(z=z'),resulting in a g z value of 2.0158,significantly deviating from 2.0023.A large zero-field splitting parameter value of+1.147cm-1 is due to △S =-1 spin-orbit mixing with the quartet states for the sextet ground state,accounting for around 73% of the SOC contribution.The SOC matrix elements indicate that the high-spin d 5 system Fe(Ⅲ),3,4-PCD-PCA is a weak spin-crossover compound with an SOC of 31.56 cm-1.
基金supported by the National Natural Science Foundation of China (50975273)the "QingLan" Talent Engineering Funds of Tianshui Normal University
文摘The optimized geometries of the three complexes between MeH,~ （Me=Na, Mg, Be; n=1 or 2） and Sill4 have been calculated at the B3LYP/6-31 1＋＋g＊＊, MP2/6-31 1＋＋g（3df,3pd） and MP2/aug-cc-pvtz levels, respectively. The red-shift inverse hydrogen bonds （IHBs） based on Si-H, an electron donor, were reported. The calculated binding energies with basis set super-position error （BSSE） correction of the three complexes are -5.98, -8.65 and -3.96 kJ mol^-1 （MP2/6-311＋＋g（3df, 3pd））, respectively, which agree with the results obtained via MP2/aug-cc-pvtz （-6.18, -9.12 and -4.28 kJ mol^-1, respectively）. The relative stabilities of the three complexes are in the order of SiH4...MgH2 〉 SiH4...NaH 〉 SiH4...BeH2. Natural bond orbital theory （NBO） analysis and the chemical shift calculation of the related atoms revealed that the charges flow from Sill4 to MeHn and the chemical shifts of the interacting H shift to downfield. Here, the Sil-H3 of Sill4 acts as both a bond hydrogen donor and an electron donor. Therefore, compared with conventional hydrogen bonds, they formed IHB complexes. Atoms in molecules （AIM） theory have been used to investigate the topological properties of the critical points in the three IHB structures.
基金supported by the Key Project of the Chinese Ministry of Education(211189)the National Natural Science Foundation of China(51063006)the"QingLan"Talent Engineering Funds of Tianshui Normal University
文摘Iodine-involved single-electron halogen bonds (SEXBs) weak interactions in the systems of CH3···I-Y(Y = BH2, H, CH3, CH==CH2, C≡CH, CN, NC) were investigated for the first time using B3LYP/6-311++G(d,p) and MP2/aug-cc-pVTZ computational levels (the relativistic effective core potential basis set of Lanl2dz was used on iodine atom). The interaction energies between two moieties with basis set super-position error corrections for the seven complexes are -0.57, -1.36, -3.80, -2.17, -4.49,-6.33 and -8.64 kJ mol-1 (MP2/aug-cc-pVTZ ), respectively, which shows that SEXBs interactions are all weak. Natural bond orbital theory analysis revealed that charges flow from CH3 to the I-Y moiety. The total amount of natural bond orbital charge transfer (ΔNC) from the CH3 radical to I-Y increases in the order CH3…IBH2 < CH3…IH ≈ CH3…ICH3 ≈ CH3···IC2H3 < CH3…ICCH< CH3…ICN< CH3…INC. Atoms-in-molecules theory was used to investigate the topological properties of the bond critical points in the seven SEXB structures.
