14 results on '"Xi-Bin Gu"'
Search Results
2. Photofragment translational spectroscopy of 1-bromo-3-fluorobenzene and 1-fluorobenzene at 266 nm
- Author
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Xi-Bin Gu, Guang-Jun Wang, Ke-Li Han, Jian-Hua Huang, Guo-Zhong He, and Nan-Quan Lou
- Subjects
Fluorocarbons -- Chemical properties ,Chemical reactions -- Research ,Chemicals, plastics and rubber industries - Abstract
The ultraviolet photodissociation of 1-bromo-3-fluorobenzene and 1-fluorobenzene at 266 nm are performed. The observed translational energy distributions of photofragments indicated significant change caused by the fluorine atom substitution. more...
- Published
- 2001
Catalog
3. Photodissociation of m-bromotoluene at 266 nm
- Author
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Nan-Quan Lou, Guang-Jun Wang, Xi-Bin Gu, Jian-Hua Huang, Guo-Zhong He, and Ke-Li Han
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Absorption spectroscopy ,Chemistry ,Photodissociation ,Analytical chemistry ,Ab initio ,General Physics and Astronomy ,Chemical reaction ,Spectral line ,Dissociation (psychology) ,Crossed molecular beam ,medicine ,Physical and Theoretical Chemistry ,medicine.symptom ,Spectroscopy - Abstract
The photodissociation of m-bromotoluene at 266 nm has been investigated on the universal crossed molecular beam machine, and the time-of-flight (TOF) spectra of recoiling photofragment at different angles were measured with the photofragment translational spectroscopy (PTS) detecting technique. The observed TOF spectra indicate that there are two different dissociation channels, one is channel (A) β=0.7±0.1 and 〈Et〉=3.76±0.5 kcal/mol, the other is channel (B) β=0.2±0.15 and 〈Et〉=12.13±0.5 kcal/mol. To better interpret the experimental results and primary photodissociation mechanism, the ultraviolet–visible (UV) absorption spectra of m-, o- and p-bromotoluene were measured, and the geometries of m-bromotoluene were optimized at the CASSCF(8,7)/6-311G** level. Two probable photodissociation mechanisms are suggested based upon the experimental results and the ab initio calculation. more...
- Published
- 2003
- Full Text
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4. Substitution effects of methyl: photodissociation of m-, o- and p-chlorotoluene at 266 nm
- Author
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Guang-Jun Wang, Xi-Bin Gu, Jian-Hua Huang, Guo-Zhong He, Nan-Quan Lou, and Ke-Li Han
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Chemistry ,Photodissociation ,General Physics and Astronomy ,Spectral line ,Dipole ,Excited state ,Physics::Atomic and Molecular Clusters ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Triplet state ,Atomic physics ,Spectroscopy ,Ground state ,Anisotropy - Abstract
The photodissociation dynamics of m-, o- and p-chlorotoluene at 266 nm was studied using the universal crossed molecular beams machine and photofragment translational spectroscopy (PTS) technique. The time-of-flight (TOF) spectra of Cl and C7H7 photofragments were measured at different angles. By employing both forward convolution method and least-squares fitting method, the TOF spectra of photofragments (Cl and C7H7) and the angular distribution of Cl are fitted, at the same time the translational energy distributions of photofragment and anisotropy parameters (β) have been derived. The geometries of the ground state, the first excited state and the triplet state have been optimized using CASSCF(8,7)/6-311G** method. The transition electronic dipole moments were calculated at the CIS/6-311G* level. The calculation results are in good agreement with the experiment. Plausible photodissociation mechanisms are proposed and the substitution effects of methyl are discussed. more...
- Published
- 2002
- Full Text
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5. Three new species of Bredia (Sonerileae, Melastomataceae) from the Sino-Vietnamese border area
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Jin-Hong Dai, Shi-Yue Nong, Xi-Bin Guo, Truong Van Do, Yan Liu, Ren-Chao Zhou, and Ying Liu
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Botany ,QK1-989 - Abstract
Bredia bullata, B. enchengensis, and B. nitida (Sonerileae, Melastomataceae), three species occurring in Sino-Vietnamese limestone karst regions, are described as new. Molecular phylogenetic analyses and morphological divergence indicate that these species are well separated from their close relatives in Bredia, justifying their recognition as distinct species. Bredia bullata is unique in its interveinal areas prominently bullate each with an apical seta, a character otherwise never recorded in the genus. Bredia nitida resembles B. malipoensis in habit, leaf shape, and inflorescence morphology, but differs in the glabrescent and nitid adaxial leaf surface (vs. densely pubescent and subvelvety), ovate-elliptic or elliptic calyx lobes (vs. triangular to semiorbicular), and white petals (vs. purplish-red). Bredia enchengensis is closest to B. longiradiosa, but easily recognized by its prostrate habit (vs. erect), the yellowish-green, membranous and fragile leaves (vs. green or dark green, papery), and white anthers (vs. pink to purplish). These new discoveries show that further botanical exploration is warranted in the remote Sino-Vietnamese bordering region. more...
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- 2022
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6. Photofragment Translational Spectroscopy of 1-Bromo-3-fluorobenzene and 1-Bromo-4-fluorobenzene at 266 nm
- Author
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Guo-Zhong He, Xi-Bin Gu, Ke-Li Han, Guang-Jun Wang, Nan-Quan Lou, and Jian-Hua Huang
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Fluorobenzene ,Photodissociation ,chemistry.chemical_element ,medicine.disease_cause ,Spectral line ,chemistry.chemical_compound ,chemistry ,Ab initio quantum chemistry methods ,Bromobenzene ,Fluorine ,medicine ,Physical chemistry ,Physical and Theoretical Chemistry ,Atomic physics ,Spectroscopy ,Ultraviolet - Abstract
The ultraviolet photodissociation of 1-bromo-3-fluorobenzene and 1-bromo-4-fluorobenzene at 266 nm has been performed on a universal crossed molecular beams machine combined with the photofragment translational spectroscopy (PTS) detection technique. The time-of-flight (TOF) spectra of Br and FC6H4 photofragments have been measured. The observed translational energy distributions P(E-t) of photofragments revealed that about 46.8 +/- 3.3% and 41.7 +/- 3.0% of the available energy are partitioned into translational energy and the anisotropy parameter beta is 0.7 +/- 0.1 and -0.4 +/- 0.1 for 1-bromo-3-fluorobenzene and 1-bromo-4-fluorobenzene, in accord with that of bromobenzene (-0.7), indicating significant change caused by the fluorine atom substitution. To better interpret the experimental results, ab initio calculations have been performed and the calculation results are in good agreement with the experimental results. A plausible photodissociation mechanism is suggested, and the substitution effect of the fluorine atom is discussed. more...
- Published
- 2000
- Full Text
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7. Photodissociation of Nitrosobenzene (C6H5NO) at 266 nm
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Jian-Hua Huang, Guang-Jun Wang, Guo-Zhong He, Xi-Bin Gu, and Ke-Li Han
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Chemistry ,Photodissociation ,medicine.disease_cause ,Spectral line ,Nitrosobenzene ,Wavelength ,chemistry.chemical_compound ,Ab initio quantum chemistry methods ,Physics::Atomic and Molecular Clusters ,medicine ,Perpendicular ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Atomic physics ,Anisotropy ,Ultraviolet - Abstract
The ultraviolet photodissociation of nitrosobenzene at 266 nm has been performed on a universal crossed molecular beams machine with a TOFMS detector. The time-of-flight spectra of the NO and C6H5 photofragments have been measured. The TOF spectra evidence only one component. The measured photofragment translational energy distribution P(E-t) reveals that about 29% of the available energy is partitioned into translational energy. The anisotropy parameter beta at this wavelength is -0.64. From P(E-t) and beta, we deduce that during the photodissociation of C6H5NO, a perpendicular transition dominates over a parallel transition. Ab initio calculations were also performed to interpret the mechanism of the photodissociation. more...
- Published
- 2000
- Full Text
- View/download PDF
8. Photodissociation of o-bromotoluene at 266 nm
- Author
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Nan-Quan Lou, Ke-Li Han, Xi-Bin Gu, Hong Zhang, Guo-Zhong He, Guang-Jun Wang, and Rong-Shun Zhu
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Photodissociation ,Translational energy ,Available energy ,Analytical chemistry ,General Physics and Astronomy ,Physical and Theoretical Chemistry ,Anisotropy ,Dissociation (chemistry) ,Spectral line - Abstract
The photodissociation of o-bromotoluene at 266 nm has been investigated using the universal crossed laser-molecular beam technique. The angle-resolved time-of-flight (TOF) spectra corresponding to Br photofragment are measured at different lab angles. The observed translational energy distribution and anisotropy parameters of the Br photofragment indicate that o-bromotoluene dissociates via two channels. In the first channel, the anisotropy parameter beta is determined to be 0.5 +/- 0.2 and the average translational energy is only 9% of the available energy. In the other photofragmentation channel, beta is determined to be - 0.4 +/- 0.2 and 44% of the available energy is assigned to translational energy. Possible mechanisms are discussed. (C) 1999 Elsevier Science B.V. All rights reserved. more...
- Published
- 1999
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9. Photodissociation of o-dichlorobenzene at 266 nm
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Rong-Shun Zhu, Ke-Li Han, Guang-Jun Wang, Guo-Zhong He, Nan-Quan Lou, Hong Zhang, and Xi-Bin Gu
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Chemistry ,Photodissociation ,Ab initio ,General Physics and Astronomy ,Molecular physics ,Dissociation (chemistry) ,Crossed molecular beam ,Dichlorobenzene ,Excited state ,Physics::Atomic and Molecular Clusters ,Molecule ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Ground state - Abstract
The photodissociation o -dichlorobenzene at 266 nm has been investigated using the universal crossed molecular beam technique. Photofragment translational energy distribution P ( E t ) and angular distribution of photofragments have been obtained and it is estimated that 23% of the available energy is assigned to translational energy. The anisotropy parameter is determined to be 0.4. From P ( E t ) and β we deduce that o -C 6 H 4 Cl 2 photodissociation is a slow process. Ab initio calculation has been performed and it shows that the parent molecule has a larger geometry deformation in its excited states comparing with that of the ground state. The possible dissociation mechanism has also been proposed. more...
- Published
- 1999
- Full Text
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10. [Relations between ALT level and count of HBV special CTL and non-specific CTL in patients with chronic hepatitis B]
- Author
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Xi-bin, Gu, Xiao-juan, Yang, Dong, Wang, Zhong, Hua, Hang-yuan, Wu, Yue-qin, Xu, and Zhong-hua, Lu
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Adult ,Male ,Hepatitis B virus ,Young Adult ,Hepatitis B, Chronic ,Humans ,Alanine Transaminase ,Female ,Lymphocyte Count ,Virus Replication ,T-Lymphocytes, Cytotoxic - Abstract
To explore relations between ALT level and hepatitis B virus (HBV) specific CTL and non-specific CTL in patients with chronic hepatitis B (CHB).148 cases of CHB were divided into three groups according to ALT level. 35 cases in group A, ALTor =2 x upper limit of normal value (ULN)--5 x ULN (100-250 IU/L); 53 cases in group B, ALT5 x ULN--or =10 x ULN (251-500 IU/L); 60 cases in group C, ALT10 x ULN (500 IU/L). Flow cytometry is used to determine non-specific CTV. HBV specific CTL was tested on 74 cases of CHB (17 in group A, 27 in group B and 30 in group C) with positive (HLA)-A2. Compare HBV specific CTL, non-specific CTL, HBV DNA levels and positive rate of HBeAg.HBV specific CTL: Group A (0.42 +/- 0.10)% is higher than group B (0.25 +/- 0.08)%, t = 6.37, P0.01, group B is higher than group C (0.17 +/- 0.004)%, t = 5.14, P0.01; Non-specific CTL: Group A (15.01 +/- 3.01)% is lower than group B (18.1 +/- 5.02)%, t = 2.81, P0.01, group B is lower than group C (21.5 +/- 6.11)%, t = 3.07, P0.01; HBV DNA level: Group A [(4.97 +/- 0.86) log10 copies/ml] is lower than group B [(5.92 +/- 0.92) log10 copies/ml], t = 4.87, P0.01. Group B is lower than group C [(6.37 +/- 0.71) log10 copies/ml], t = 2.92, P0.01; Positive HBeAg: Group A (15 cases, 42.86%) is lower than group B (32 cases, 60.38%), chi2 = 2.59, P0.05. Group B is lower than group C (41 cases, 68.33%), chi2 = 0.78, P0.05. Group A is lower than group C, chi2 = 5.929, P0.05.The higher the non-specific CTL of patients with CHB is, the higher the ALT level would be, whereas the lower the HBV specific CTL is, the stronger the HBV replication would be. more...
- Published
- 2010
11. Design and characteristics of a high-precision chopper wheel motor driver
- Author
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Ying Guo, Ralf I. Kaiser, Henry Chan, Ed Kawamura, and Xi Bin Gu
- Subjects
Electric motor ,Chopper ,Braking chopper ,Motor controller ,Computer science ,Power electronics ,Supersonic speed ,Network synthesis filters ,Instrumentation ,Automotive engineering ,Circuit diagram - Abstract
The circuit diagram and design principles of a high-stability chopper wheel motor driver are presented. Experimental results show that this unit can be interfaced to molecular-beam machines to generate supersonic beams with extremely stable root-mean-square and peak velocities fluctuating on a day-to-day basis by less than 0.2%. more...
- Published
- 2005
- Full Text
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12. Design of a convection-cooled, cluster-based voltage divider chain for photomultiplier tubes
- Author
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Ed Kawamura, Xi Bin Gu, Ying Guo, and Ralf I. Kaiser
- Subjects
Photomultiplier ,Materials science ,Physics::Instrumentation and Detectors ,business.industry ,Voltage divider ,Ion current ,Signal ,law.invention ,Capacitor ,Outgassing ,law ,Electromagnetic shielding ,Optoelectronics ,Resistor ,business ,Instrumentation - Abstract
A highly stable convection-cooled, cluster-based voltage divider chain for photomultiplier tubes has been designed and tested in single ion counting detection systems. Contrasting currently existing voltage divider chains, our unit does not require a cooling liquid to transfer the heat from the resistors and provides safer operation conditions inside ultrahigh vacuum systems utilized in the reaction dynamics community. The unit is enclosed in an air pocket inside an ultrahigh vacuum system so that outgassing of the photomultiplier tubes, resistors, and capacitors can be eliminated completely. The measured resistor chain currents of ±2% lie well within the tolerances of the resistors (±5%) and power supply (±1%) demonstrating that the convective cooling is actually efficient to sustain a stable signal. The monitored total ion current also depicts extremely low fluctuation of only 1.5%. The day-to-day reproducibility has been tested, too. We also demonstrate that a magnetic shielding of the photomultiplier ... more...
- Published
- 2005
- Full Text
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13. Design of a convection-cooled, cluster-based voltage divider chain for photomultiplier tubes.
- Author
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Xi Bin Gu, Ying Guo, Kawamura, Ed, and Kaiser, Ralf I.
- Subjects
DETECTORS ,ENGINEERING instruments ,PHOTOMULTIPLIERS ,VACUUM technology ,ELECTRIC resistors ,DIELECTRIC devices - Abstract
A highly stable convection-cooled, cluster-based voltage divider chain for photomultiplier tubes has been designed and tested in single ion counting detection systems. Contrasting currently existing voltage divider chains, our unit does not require a cooling liquid to transfer the heat from the resistors and provides safer operation conditions inside ultrahigh vacuum systems utilized in the reaction dynamics community. The unit is enclosed in an air pocket inside an ultrahigh vacuum system so that outgassing of the photomultiplier tubes, resistors, and capacitors can be eliminated completely. The measured resistor chain currents of ±2% lie well within the tolerances of the resistors (±5%) and power supply (±1%) demonstrating that the convective cooling is actually efficient to sustain a stable signal. The monitored total ion current also depicts extremely low fluctuation of only 1.5%. The day-to-day reproducibility has been tested, too. We also demonstrate that a magnetic shielding of the photomultiplier tube and the resistor chain enhances the signal by about 15%. [ABSTRACT FROM AUTHOR] more...
- Published
- 2005
- Full Text
- View/download PDF
14. Design and characteristics of a high-precision chopper wheel motor driver.
- Author
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Xi Bin Gu, Ying Guo, Chan, Henry, Kawamura, Ed, and Kaiser, Ralf I.
- Subjects
ELECTRONIC circuit design ,LOGIC design ,DIGITAL electronics ,MOLECULAR beams ,ULTRASONIC waves ,SCIENTIFIC apparatus & instruments - Abstract
The circuit diagram and design principles of a high-stability chopper wheel motor driver are presented. Experimental results show that this unit can be interfaced to molecular-beam machines to generate supersonic beams with extremely stable root-mean-square and peak velocities fluctuating on a day-to-day basis by less than 0.2%. [ABSTRACT FROM AUTHOR] more...
- Published
- 2005
- Full Text
- View/download PDF
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