Xinguo Hong - Academia.edu (original) (raw)
Papers by Xinguo Hong
Review of Scientific Instruments, 2007
We describe an x-ray absorption method for in situ density measurement of non-crystalline materia... more We describe an x-ray absorption method for in situ density measurement of non-crystalline materials in the diamond anvil cell using a monochromatic synchrotron x-ray microbeam. Sample thickness, which is indispensable in the absorption method, can be determined precisely by extrapolating the thickness profile of the gasket obtained by x-ray absorption and diffraction measurements. Diamond deformation across the sample chamber becomes
Journal of Non-crystalline Solids, 2002
X-ray diffraction measurements for expanded fluid selenium have been carried out in a wide densit... more X-ray diffraction measurements for expanded fluid selenium have been carried out in a wide density region from the liquid to the dense vapor using synchrotron radiation at SPring-8. We have developed a new high pressure vessel with seven windows to measure scattered X-rays and the reliability of the structure factors becomes much better. The measurements were made in the semiconductor–metal
Physical Review B, 2003
ABSTRACT X-ray-diffraction measurements for fluid mercury up to the supercritical region have bee... more ABSTRACT X-ray-diffraction measurements for fluid mercury up to the supercritical region have been carried out using synchrotron radiation at SPring-8. We obtained the structure factor S(Q) with good signal-to-noise ratio, and the pair distribution functions g(r) for expanded fluid Hg from the liquid to the dense vapor. To see the volume dependence of the local structure in fluid Hg in detail, we tried to reproduce 4πn0r2g(r) of fluid Hg using Gaussian peaks. The optimized parameters show that the asymmetrical first peak in g(r) of liquid Hg consists of atomic distributions at short and long distances of about 3Å and 3.5Å. Volume dependence of the parameters suggests that decrease of the atoms coordinated at the short distance is strongly correlated with the metal-nonmetal transition in fluid Hg.
Applied Physics Letters, 2014
ABSTRACT We report a pressure-induced dense tetrahedral intermediate state via Ge–O–Ge rotation f... more ABSTRACT We report a pressure-induced dense tetrahedral intermediate state via Ge–O–Ge rotation formed at 3–5 GPa and the polyhedral relations in GeO2 glass up to 17.5 GPa using in situ X-ray total scattering and X-ray absorption (XAFS) techniques. It was found that the nearest-neighbor Ge-Ge correlations show a decrease reaching a minimum between 4 and 6 GPa, and exhibit negative compression behavior at 7–17.5 GPa. The Ge–Ge distance determined by XAFS shows a substantial reduction, i.e., normal compression behavior, at 7–17.5 GPa. The comparison with the theoretical g(r) function for rutile-type GeO2 (16.1 GPa) indicates that the negative compression of intermediate range order reflects the direct formation of GeO6 octahedral units. Results of coordination number analysis show that GeO2 glass undergoes a transition from tetrahedral GeO4, to GeO5 units (possibly triangular bipyramidal), and finally to octahedral GeO6 units. The present investigation provides the structural details of the polyhedral units and their relationships in GeO2 glass at high pressure.
Structure, 2010
Ibalizumab is a humanized, anti-CD4 monoclonal antibody. It potently blocks HIV-1 infection and t... more Ibalizumab is a humanized, anti-CD4 monoclonal antibody. It potently blocks HIV-1 infection and targets an epitope in the second domain of CD4 without interfering with immune functions mediated by interaction of CD4 with major histocompatibility complex (MHC) class II molecules. We report here the crystal structure of ibalizumab Fab fragment in complex with the first two domains (D1-D2) of CD4 at 2.2 Å resolution. Ibalizumab grips CD4 primarily by the BC-loop (residues 121-125) of D2, sitting on the opposite side of gp120 and MHC-II binding sites. No major conformational change in CD4 accompanies binding to ibalizumab. Both monovalent and bivalent forms of ibalizumab effectively block viral infection, suggesting that it does not need to crosslink CD4 to exert antiviral activity. While gp120-induced structural rearrangements in CD4 are probably minimal, CD4 structural rigidity is dispensable for ibalizumab inhibition. These results could guide CD4-based immunogen design and lead to a better understanding of HIV-1 entry.
Review of Scientific Instruments, 2009
Review of Scientific Instruments, 1995
A new method of measuring the viscosity of liquid, which is named the double-wire torsion pendulu... more A new method of measuring the viscosity of liquid, which is named the double-wire torsion pendulum method in contrast to the conventional torsion pendulum method, is described in this paper. It was found that the damping factor αl changes nearly linearly with the kinematical viscosity &eegr;/&rgr; of the standard oil in the range from 1.55 to 1.15×104 cp. An empirical
Review of Scientific Instruments, 2009
Journal of Synchrotron Radiation, 2001
Journal of Physics: Condensed Matter, 2014
The structural behavior of GeO2 glass has been investigated up to 64 GPa using results from x-ray... more The structural behavior of GeO2 glass has been investigated up to 64 GPa using results from x-ray absorption spectroscopy in a diamond anvil cell combined with previously reported density measurements. The difference between the nearest Ge-O distances of glassy and rutile-type GeO2 disappears at the Ge-O distance maximum at 20 GPa, indicating completion of the tetrahedral-octahedral transition in GeO2 glass. The mean-square displacement σ(2) of the Ge-O distance in the first Ge-O shell increases progressively to a maximum at 10 GPa, followed by a substantial reduction at higher pressures. The octahedral glass is, as expected, less dense and has a higher compressibility than the corresponding crystalline phase, but the differences in Ge-O distance and density between the glass and the crystals are gradually eliminated over the 20-40 GPa pressure range. Above 40 GPa, GeO2 forms a dense octahedral glass with a compressibility similar to that of the corresponding crystalline phase (α-PbO2 type). The EXAFS and XANES spectra show evidence for subtle changes in the dense glass continuing to occur at these high pressures. The Ge-O bond distance shows little change between 45-64 GPa, and this may reflect a balance between bond shortening and a gradual coordination number increase with compression. The density of the glass is similar to that of the α-PbO2-type phase, but the Ge-O distance is longer and is close to that in the higher-coordination pyrite-type phase which is stable above ∼60 GPa. The density data provide evidence for a possible discontinuity and change in compressibility at 40-45 GPa, but there are no major changes in the corresponding EXAFS spectra. A pyrite-type local structural model for the glass can provide a reasonable fitting to the XAFS spectra at 64 GPa.
Journal of Physics: Conference Series, 2013
ABSTRACT Although coupling the X-ray absorption fine structure (XAFS) technique to the diamond an... more ABSTRACT Although coupling the X-ray absorption fine structure (XAFS) technique to the diamond anvil cell (DAC) has long been recognized as potentially important for understanding the behavior and evolution of the local and electronic structure of matter under extreme conditions, the DAC has been regarded as poorly suited for XAFS due to the DAC imposed glitches. Recently, an iterative method was proposed to distinguish and eliminate the serious interference of the diamond Bragg peaks, and succeeded in acquiring high quality 'reflection-free' XAFS spectra at high pressure under the DAC environment. In this paper, we use this method and present demonstration XAFS spectra for GeO2 glass, which is the archetype of network forming glasses with important geophysical implications, at pressures to 64 GPa. This is far above the change in coordination from tetrahedra to octahedra occurring at 6-13 GPa. The results provide important insight into the structural polymorphism of GeO2 glass at high pressure.
Journal of Non-Crystalline Solids, 1999
Journal of Non-Crystalline Solids, 2001
Journal of Non-Crystalline Solids, 2002
Journal of Non-Crystalline Solids, 2002
Journal of Crystal Growth, 1999
Journal of Crystal Growth, 1998
Journal of Crystal Growth, 1995
The density and surface tension of the K2ONb2O5 molten system between 50 and 56 mol% K2O melts w... more The density and surface tension of the K2ONb2O5 molten system between 50 and 56 mol% K2O melts were measured from 1080 to 1180°C. Excess K2O in the melt can reduce both density and surface tension, and there is a minimum both in the composition dependence and in the temperature dependence of the density within this composition range. It was found
Review of Scientific Instruments, 2007
We describe an x-ray absorption method for in situ density measurement of non-crystalline materia... more We describe an x-ray absorption method for in situ density measurement of non-crystalline materials in the diamond anvil cell using a monochromatic synchrotron x-ray microbeam. Sample thickness, which is indispensable in the absorption method, can be determined precisely by extrapolating the thickness profile of the gasket obtained by x-ray absorption and diffraction measurements. Diamond deformation across the sample chamber becomes
Journal of Non-crystalline Solids, 2002
X-ray diffraction measurements for expanded fluid selenium have been carried out in a wide densit... more X-ray diffraction measurements for expanded fluid selenium have been carried out in a wide density region from the liquid to the dense vapor using synchrotron radiation at SPring-8. We have developed a new high pressure vessel with seven windows to measure scattered X-rays and the reliability of the structure factors becomes much better. The measurements were made in the semiconductor–metal
Physical Review B, 2003
ABSTRACT X-ray-diffraction measurements for fluid mercury up to the supercritical region have bee... more ABSTRACT X-ray-diffraction measurements for fluid mercury up to the supercritical region have been carried out using synchrotron radiation at SPring-8. We obtained the structure factor S(Q) with good signal-to-noise ratio, and the pair distribution functions g(r) for expanded fluid Hg from the liquid to the dense vapor. To see the volume dependence of the local structure in fluid Hg in detail, we tried to reproduce 4πn0r2g(r) of fluid Hg using Gaussian peaks. The optimized parameters show that the asymmetrical first peak in g(r) of liquid Hg consists of atomic distributions at short and long distances of about 3Å and 3.5Å. Volume dependence of the parameters suggests that decrease of the atoms coordinated at the short distance is strongly correlated with the metal-nonmetal transition in fluid Hg.
Applied Physics Letters, 2014
ABSTRACT We report a pressure-induced dense tetrahedral intermediate state via Ge–O–Ge rotation f... more ABSTRACT We report a pressure-induced dense tetrahedral intermediate state via Ge–O–Ge rotation formed at 3–5 GPa and the polyhedral relations in GeO2 glass up to 17.5 GPa using in situ X-ray total scattering and X-ray absorption (XAFS) techniques. It was found that the nearest-neighbor Ge-Ge correlations show a decrease reaching a minimum between 4 and 6 GPa, and exhibit negative compression behavior at 7–17.5 GPa. The Ge–Ge distance determined by XAFS shows a substantial reduction, i.e., normal compression behavior, at 7–17.5 GPa. The comparison with the theoretical g(r) function for rutile-type GeO2 (16.1 GPa) indicates that the negative compression of intermediate range order reflects the direct formation of GeO6 octahedral units. Results of coordination number analysis show that GeO2 glass undergoes a transition from tetrahedral GeO4, to GeO5 units (possibly triangular bipyramidal), and finally to octahedral GeO6 units. The present investigation provides the structural details of the polyhedral units and their relationships in GeO2 glass at high pressure.
Structure, 2010
Ibalizumab is a humanized, anti-CD4 monoclonal antibody. It potently blocks HIV-1 infection and t... more Ibalizumab is a humanized, anti-CD4 monoclonal antibody. It potently blocks HIV-1 infection and targets an epitope in the second domain of CD4 without interfering with immune functions mediated by interaction of CD4 with major histocompatibility complex (MHC) class II molecules. We report here the crystal structure of ibalizumab Fab fragment in complex with the first two domains (D1-D2) of CD4 at 2.2 Å resolution. Ibalizumab grips CD4 primarily by the BC-loop (residues 121-125) of D2, sitting on the opposite side of gp120 and MHC-II binding sites. No major conformational change in CD4 accompanies binding to ibalizumab. Both monovalent and bivalent forms of ibalizumab effectively block viral infection, suggesting that it does not need to crosslink CD4 to exert antiviral activity. While gp120-induced structural rearrangements in CD4 are probably minimal, CD4 structural rigidity is dispensable for ibalizumab inhibition. These results could guide CD4-based immunogen design and lead to a better understanding of HIV-1 entry.
Review of Scientific Instruments, 2009
Review of Scientific Instruments, 1995
A new method of measuring the viscosity of liquid, which is named the double-wire torsion pendulu... more A new method of measuring the viscosity of liquid, which is named the double-wire torsion pendulum method in contrast to the conventional torsion pendulum method, is described in this paper. It was found that the damping factor αl changes nearly linearly with the kinematical viscosity &eegr;/&rgr; of the standard oil in the range from 1.55 to 1.15×104 cp. An empirical
Review of Scientific Instruments, 2009
Journal of Synchrotron Radiation, 2001
Journal of Physics: Condensed Matter, 2014
The structural behavior of GeO2 glass has been investigated up to 64 GPa using results from x-ray... more The structural behavior of GeO2 glass has been investigated up to 64 GPa using results from x-ray absorption spectroscopy in a diamond anvil cell combined with previously reported density measurements. The difference between the nearest Ge-O distances of glassy and rutile-type GeO2 disappears at the Ge-O distance maximum at 20 GPa, indicating completion of the tetrahedral-octahedral transition in GeO2 glass. The mean-square displacement σ(2) of the Ge-O distance in the first Ge-O shell increases progressively to a maximum at 10 GPa, followed by a substantial reduction at higher pressures. The octahedral glass is, as expected, less dense and has a higher compressibility than the corresponding crystalline phase, but the differences in Ge-O distance and density between the glass and the crystals are gradually eliminated over the 20-40 GPa pressure range. Above 40 GPa, GeO2 forms a dense octahedral glass with a compressibility similar to that of the corresponding crystalline phase (α-PbO2 type). The EXAFS and XANES spectra show evidence for subtle changes in the dense glass continuing to occur at these high pressures. The Ge-O bond distance shows little change between 45-64 GPa, and this may reflect a balance between bond shortening and a gradual coordination number increase with compression. The density of the glass is similar to that of the α-PbO2-type phase, but the Ge-O distance is longer and is close to that in the higher-coordination pyrite-type phase which is stable above ∼60 GPa. The density data provide evidence for a possible discontinuity and change in compressibility at 40-45 GPa, but there are no major changes in the corresponding EXAFS spectra. A pyrite-type local structural model for the glass can provide a reasonable fitting to the XAFS spectra at 64 GPa.
Journal of Physics: Conference Series, 2013
ABSTRACT Although coupling the X-ray absorption fine structure (XAFS) technique to the diamond an... more ABSTRACT Although coupling the X-ray absorption fine structure (XAFS) technique to the diamond anvil cell (DAC) has long been recognized as potentially important for understanding the behavior and evolution of the local and electronic structure of matter under extreme conditions, the DAC has been regarded as poorly suited for XAFS due to the DAC imposed glitches. Recently, an iterative method was proposed to distinguish and eliminate the serious interference of the diamond Bragg peaks, and succeeded in acquiring high quality 'reflection-free' XAFS spectra at high pressure under the DAC environment. In this paper, we use this method and present demonstration XAFS spectra for GeO2 glass, which is the archetype of network forming glasses with important geophysical implications, at pressures to 64 GPa. This is far above the change in coordination from tetrahedra to octahedra occurring at 6-13 GPa. The results provide important insight into the structural polymorphism of GeO2 glass at high pressure.
Journal of Non-Crystalline Solids, 1999
Journal of Non-Crystalline Solids, 2001
Journal of Non-Crystalline Solids, 2002
Journal of Non-Crystalline Solids, 2002
Journal of Crystal Growth, 1999
Journal of Crystal Growth, 1998
Journal of Crystal Growth, 1995
The density and surface tension of the K2ONb2O5 molten system between 50 and 56 mol% K2O melts w... more The density and surface tension of the K2ONb2O5 molten system between 50 and 56 mol% K2O melts were measured from 1080 to 1180°C. Excess K2O in the melt can reduce both density and surface tension, and there is a minimum both in the composition dependence and in the temperature dependence of the density within this composition range. It was found