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X Xing

Publications and source records attributed to X Xing.

At least 19 recordsLinked to original sources
PubMed2006

Vacuum ultraviolet laser pulsed field ionization-photoelectron study of cis-dichloroethene.

The vacuum ultraviolet (VUV) laser pulsed field ionization photoelectron (PFI-PE) spectrum of cis-dichloroethene (cis-ClCH[Double Bond]CHCl) has been measured in the energy region of 77 600-79 500 cm(-1). On the basis of the semiempirical simulation of the origin PFI-PE band, we have obtained the IE(cis-ClCH[Double Bond]CHCl) to be 77 899.5+/-2.0 cm(-1) (9.658 39+/-0.000 25 eV). The assignment of the vibrational bands resolved in the VUV-PFI-PE spectrum are guided by high-level ab initio calculations of the vibrational frequencies for cis-ClCH[Double Bond]CHCl(+) and the Franck-Condon factors for the ionization transitions. Combining the results of the present VUV-PFI-PE measurement and the recent VUV-infrared-photoinduced Rydberg ionization study, the vibrational frequencies for eleven of the twelve vibrational modes of cis-ClCH[Double Bond]CHCl(+) have been experimentally determined: nu(1) (+)(a(1))=181 cm(-1), nu(2) (+)(a(2))=277 cm(-1), nu(3) (+)(b(2))=580 cm(-1), nu(4) (+)(b(1))=730 cm(-1), nu(5) (+)(a(1))=810 cm(-1), nu(6) (+)(a(2))=901 cm(-1), nu(8) (+)(a(1))=1196 cm(-1), nu(9) (+)(b(2))=1348 cm(-1), nu(10) (+)(a(1))=1429 cm(-1), nu(11) (+)(b(2))=3067 cm(-1), and nu(12) (+)(a(1))=3090 cm(-1)). These values are compared to theoretical anharmonic vibrational frequencies obtained at the MP2/6-311G(2df,p) and CCSD(T)/6-311G(2df,p) levels. The IE prediction for cis-ClCH[Double Bond]CHCl has also been calculated with the wave function based CCSD(T)/CBS method, which involves the approximation to the complete basis set (CBS) and the high-level correlation corrections. The theoretical IE(cis-ClCH[Double Bond]CHCl)=9.668 eV thus obtained is found to have a deviation of less than 10 meV with respect to the experimental IE value.

Journal Article↗
PubMed2006

Infrared vibrational spectroscopy of cis-dichloroethene in Rydberg states.

We have measured the infrared (IR) vibrational spectrum for cis-dichloroethene (cis-ClCH[Double Bond]CHCl) in excited Rydberg states with the effective principal quantum numbers n(*)=9, 13, 17, 21, 28, and 55 using the vacuum ultraviolet-IR-photoinduced Rydberg ionization (VUV-IR-PIRI) scheme. Although the IR frequencies observed for the vibrational bands nu(11) (*) (asymmetric C-H stretch) and nu(12) (*) (symmetric C-H stretch) are essentially unchanged for different n(*) states, suggesting that the IR absorption predominantly involves the ion core and that the Rydberg electron behaves as a spectator; the intensity ratio for the nu(11) (*) and nu(12) (*) bands [R(nu(11) (*)nu(12) (*))] is found to decrease smoothly as n(*) is increased. This trend is consistent with the results of a model ab initio quantum calculation of R(nu(11) (*)nu(12) (*)) for excited cis-ClCH[Double Bond]CHCl in n(*)=3-18 states and the MP26-311++G(2df,p) calculations of R(nu(11)nu(12)) and R(nu(11) (+)nu(12) (+)), where R(nu(11)nu(12))[R(nu(11) (+)nu(12) (+))] represents the intensity ratio of the nu(11)(nu(11) (+)) asymmetric C-H stretching to the nu(12)(nu(12) (+)) symmetric C-H stretching vibrational bands for cis-ClCH[Double Bond]CHCl (cis-ClCH[Double Bond]CHCl(+)). We have also measured the IR-VUV-photoion (IR-VUV-PI) and IR-VUV-pulsed field ionization-photoelectron depletion (IR-VUV-PFI-PED) spectra for cis-ClCH[Double Bond]CHCl. These spectra are consistent with ab initio calculations, indicating that the IR absorption cross section for the nu(12) band is negligibly small compared to that for the nu(11) band. While the VUV-IR-PIRI measurements have allowed the determination of nu(11) (+)=3067+/-2 cm(-1), nu(12) (+)=3090+/-2 cm(-1), and R(nu(11) (+)nu(12) (+)) approximately 1.3 for cis-ClCH=CHCl(+), the IR-VUV-PI and IR-VUV-PFI-PED measurements have provided the value nu(11)=3088.5+/-0.2 cm(-1) for cis-ClCH=CHCl.

Journal Article↗
PubMed2004

Rovibrational-state-selected pulsed field ionization-photoelectron study of methyl iodide using two-color infrared-vacuum ultraviolet lasers.

The preparation of methyl iodide (CH(3)I) in selected rovibrational states [nu(7)=1 (C-H stretch); J] by infrared (IR) excitation prior to vacuum ultraviolet (VUV) photoionization has greatly simplified the observed pulsed field ionization-photoelectron (PFI-PE) spectra, allowing the direct determination of the rotational constants B(+)(C(+))=0.254+/-0.003 cm(-1) for CH(3)I(+)(X (2)E(3/2);nu(7) (+)) and the ionization energy (76 896.9+/-0.2 cm(-1)) for CH(3)I(+)(X (2)E(3/2);nu(7) (+)=1,J(+)=3/2)<--CH(3)I(X (1)A(1);nu(7)=1,J=0). The IR-VUV-PFI-PE and IR-VUV-photoion measurements also provide relative state-to-state (nu(7) (+)=1, J(+)<--nu(7)=1, J) cross sections for the photoionization process.

Journal Article↗
PubMed2004

Single-photon vacuum-ultraviolet laser-pulsed-field ionization-photoelectron studies of trans- and cis-1-bromopropenes.

The vacuum-ultraviolet (VUV) pulsed-field ionization-photoelectron (VUV-PFI-PE) spectra of trans-1-bromopropene (trans-CH(3)CH[Double Bond]CHBr) and cis-1-bromopropene (cis-CH(3)CH[Double Bond]CHBr) have been measured in the energy region of 74 720-76 840 cm(-1). The simulation of fine structures observed in the origin VUV-PFI-PE vibrational bands of these molecules has provided the ionization energies (IEs) of trans-1-bromopropene and cis-1-bromopropene to be 74 779.3+/-2.0 cm(-1) (9.2715+/-0.0002 eV) and 75 140.2+/-2.0 cm(-1) (9.3162+/-0.0002 eV), respectively. The vibrational bands resolved in these VUV-PFI-PE spectra at energies 0-1700 cm(-1) above the IEs of trans-1-bromopropene and cis-1-bromopropene have been assigned based on theoretical vibrational frequencies and calculated Franck-Condon factors for the ionization transitions.

Journal Article↗
PubMed2004

Vacuum ultraviolet-infrared photo-induced Rydberg ionization spectroscopy: C-H stretching frequencies for trans-2-butene and trichloroethene cations.

We have demonstrated the two-color vacuum ultraviolet (VUV)-infrared (IR) photoinduced Rydberg ionization (PIRI) experiment. Trichloroethene (ClCH=CCl2) and trans-2-butene (trans-CH3CH=CHCH3) were prepared in Rydberg states in the range of effective principal quantum number n* approximately 7-93 by VUV excitation prior to IR-induced autoionization. The observed VUV-IR-PIRI spectra are found to be independent of n*, suggesting that the electron Rydberg orbital is conserved, i.e., the Rydberg electron is behaving as a spectator during the excitation process. The observed IR active C-H stretching vibrational frequencies nu12+ = 3072+/-5 cm(-1) for ClCH=CCl2+ and nu23+ =2908+/-3 cm(-1), nu25+ =2990+/-10 cm(-1) and nu30+ =3022+/-10 cm(-1) for trans-CH3CH=CHCH3+ are compared with predictions based on ab initio quantum-chemical procedures and density functional calculations.

Journal Article↗
PubMed2002

Obesity, coronary heart disease risk factors and diabetes in Chinese: an approach to the criteria of obesity in the Chinese population.

The aim of this work was to study the relationship between excess body weight and the risks of hypertension and diabetes in the population of northeastern China. Subsections of a cross-sectional survey in Da Qing City were used to assess the relationship of excess weight to risk factors for coronary heart disease (CHD). A 6-year prospective study also assessed the probability of developing Type 2 diabetes. A total of 2856 adults (25-70 years of age) were assessed cross-sectionally and 629 non-diabetic subjects of similar age were followed-up for 6 years. Blood pressure, plasma fasting glucose, triglycerides, high-density lipoporotein (HDL) cholesterol and fibrinogen levels were measured as well as weight, height and waist and hip circumferences. About 45% of adults had a body mass index (BMI) of > or =25.0. Risk factors increased with increasing BMI from a baseline value of 21.0: at a BMI of 23.0-24.9, the risk of hypertension and hypertriglyceridaemia doubled; the risk increased threefold at a BMI of 25.0-26.9. The prevalence of Type 2 diabetes increased progressively in women within the normal BMI range and in men from a BMI of 25.0. Type 2 diabetes was four times as common if the BMI was >27.0. Increasing waist measurements predicted 10-fold increases in hypertension and a three-to-five times increased risk of diabetes. Suitable waist cut-off points were 85cm for men and 80cm for women, with statistical analysis showing waist as the more dominant predictor of risk than age, waist-to-hip ratios or BMIs. Hence, small increases in BMI, and particularly in waist circumference, predict a substantial increase in the risk of diabetes and risk for CHD, especially hypertension, in Chinese adults.

Adult↗
PubMed2001

Pharmacological differences between immunoisolated native brain and heterologously expressed rat alpha4beta2 nicotinic receptors.

Native brain and heterologously expressed rat alpha4beta2 nicotinic receptors (in Xenopus oocytes and CV-1 cells) were immunoisolated with the anti-alpha4 antibody mAb 299 and their pharmacological properties were compared using [3H](+/-)epibatidine, the novel N-alkylnicotinium analog N-n-octylnicotinium iodide (NONI), and the ganglionic antagonist trimethaphan (TRM). The equilibrium dissociation constant (K(d)) for [3H](+/-)epibatidine binding to the native and heterologously expressed receptors ranged from 13 to 21 pM. The Hill coefficients for [3H](+/-)epibatidine binding to the native and expressed receptors ranged from 0.8 to 1.1 and were consistent with a single high-affinity site. NONI inhibited 30 pM [3H](+/-)epibatidine binding to the native and expressed receptors with similar potency (IC(50) values of 6-7 microM). However, [3H](+/-)epibatidine dissociated 2-3 times more slowly from the native, than from the expressed receptors and TRM inhibited 30 pM [3H](+/-)epibatidine binding to the native receptors (IC(50) value of 330 microM) less potently than it did to the receptors expressed in oocytes (IC(50) value of 16 microM) or CV-1 cells (IC(50) value of 55 microM). The differences between the native and expressed [3H](+/-)epibatidine dissociation rate constants and IC(50) values for TRM were significant for both host cell types, although the values for the CV-1-expressed receptors were closer to the native ones than were those for the oocyte-expressed receptors. Thus, the epibatidine and trimethaphan binding sites in native and expressed alpha4beta2 receptors appear to have significantly different structural or chemical properties.

Animals↗
PubMed2001

A novel synthesis of enantiomerically pure 5,5,5,5',5',5'-hexafluoroleucine.

[reaction in text] A novel, short, and efficient synthesis of (S)-5,5,5,5',5',5'-hexafluoroleucine (6) in greater than 99% ee starting from the protected oxazolidine aldehyde 1 is described. The enantiomeric excess of the product was calculated from an NMR analysis of a dipeptide formed by reaction with a protected L-serine derivative. Furthermore, a racemic sample of N-acylated hexafluoroleucine was enzymatically resolved by treatment with porcine kidney acylase I and was found to have the same optical rotation as a synthetic sample of 6.

Amidohydrolases↗
PubMed2001

Reactions of first-row transition metal ions with propargyl alcohol in the gas phase.

The gas-phase reactions with propargyl alcohol (PPA) of all the singly charged ions of the first-row transition metals, generated by laser ablation in an external ion source, were studied by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICRMS.). The reactivities of the metal ions change irregularly across the periodic table, and the reactivity of each ion is a function of its electronic configuration and corresponding metal-oxygen (M-O) bond energies. The 10 metal ions were classified into three categories according to their reactivities: Sc(+), Ti(+) and V(+) are the most reactive ions which react with PPA to give many kinds of oxygen-rich products due to stronger M-O bonds; Fe(+), Co(+) and Ni(+) are less reactive; Cr(+), Mn(+), Cu(+) and Zn(+) are the most unreactive ions, due to the half and completely occupied valence electronic configurations. The order of reactivity is Ti(+) > V(+) > Sc(+) >> Co(+) > Fe(+) approximately Ni(+) > Zn(+) > Cr(+) approximately Mn(+) approximately Cu(+).

Journal Article↗
PubMed2001

Formation of binary alloy cluster ions from group-14 elements and cobalt and comparison with solid-state alloys.

By using laser ablation on mixtures of transition metal cobalt and group-14 elements, binary alloy cluster anions were produced while no binary alloy cluster cations were detected, and the homocluster cations of group-14 elements appeared at very low abundance. The differences between clustering abilities of germanium, tin and lead with cobalt are described, and the chemical bonds in the binary alloy cluster anions appear to indicate a transition from covalent to metal bonds. The cluster anion [CoPb10](-) appears in very high abundance (magic number), and an endohedral structure is proposed for this cluster. The cluster anion [CoPb12](-), also representing a magic number, probably has an icosahedral structure. Compared with solid-state Co/Ge binary alloys, the compositions of most binary alloy cluster anions are germanium-rich, in which the covalent bonds are predominant.

Journal Article↗
PubMed2001

[Reconstruction of digital avulsion with pre-fabricated subdermal vascular network skin flap by ultrasonic liposuction].

OBJECTIVE: To investigate the clinical application of subdermal vascular network skin flap pre-fabricated by ultrasonic liposuction in reconstruction of digital avulsion. METHODS: Forty-seven injured fingers of 23 cases were treated from June 1997 to February 2000. Conventional abdominal skin flap was elevated, according to the size of digital avulsion, and subcutaneous fat was removed with scissors. Ultrasonic liposuction technology was adopted, in order to minimize the injury of subdermal vascular vessels, to remove the fat particles close to the vascular network. Finally, the pre-fabricated skin flap was used to repair the digital avulsion. The vascular pedicle was severed in 5 to 7 days after operation. The range of skin flap was 4 cm x 3 cm to 8 cm x 7 cm, and the ratio of length and width was (2 to 3) to 1. RESULTS: All the skin flaps were survived. Twenty-one patients were available for postoperative follow-up for 6 to 24 months. The motion of interphalangeal joint achieved functional recovery, and the sensation of pain, temperature and taction recovered well. CONCLUSION: Ultrasonic liposuction does not obviously injure the subdermal vascular network skin flap, it is a simple and safe method for treatment of digital avulsion.

Adolescent↗
PubMed2001

[Effect of grazing rate on biomass and element composition of Xanthoparmelia camtschadalis].

Xanthoparmelia camtschadalis is widely distributed in grassland area of Mongolian Plateau. There are few studies on the relationships between biomass, element composition and stocking rate. The relationships of biomass and element composition of Xanthoparmelia camtschadalis to grazing rates in Leymus chinensis steppe in Inner Mongolia were investigated. The results indicated that the biomass of the lichen was highest under light grazing, while the lowest under extremely overgrazing treatment. The C, N and Ca concentrations were higher than 1%, P, Mg, K and Fe were between 0.1% and 1%, and Na, Mn, Cu, Zn, and B were less than 0.1%. The Ca content in Xanthoparmelia camtschadalis was much higher than that in vascular plant. With an increasing grazing rate, the C concentration decreased, while N increased. The C/N ratio was the lowest under moderate and heavy grazing treatments. Ca, Mg, K, Fe, Mn and Cu contents were higher under grazing treatments. The changes of biomass and element composition of Xanthoparmelia camtschadalis had a good response to grazing rate, and hence, it was a good indicator to indicate the healthy condition and changes of biogeochemistry cycles in grassland ecosystems.

Animals↗
PubMed2001

[The application of air-lift loop column filling with porous carrier in wastewater treatment].

An air lift loop reactor filling with porous carrier particles was utilized as aeration column. Experiments were carried out in wide operating conditions. The experimental results showed that in the range of gas flow rate from 0.117 to 0.156 m3/(min.m3), a higher efficiency of removal of ammonium-N was achieved, and when the gas flow rate was above 0.039 m3/(min.m3), the COD was completely degraded in about 1 h. The filling ratio of the porous carriers in the column was an important factor for the removal of C and N compounds, and a filling ratio of 15% was proved to be most suitable in the operation ranges. The experimental results also indicated that the effect of aeration temperature on the removal efficiency was significant and the highest efficiency was obtained at around 25 degrees C.

Nitrogen↗
PubMed2001

[Clinical observation of phacoemulsification with foldable intraocular lens implantation through a limbus incision].

OBJECTIVE: To investigate the clinical therapeutic effects of phaco-emulsification with foldable intraocular lens implantation through a limbus tunnel incision. METHODS: Eighty-six patients (107 eyes) with senile cataract underwent phacoemulsification with acrylic foldable posterior chamber intraocular lens implantation through a 4 mm superior limbus tunnel incision. RESULTS: The corrected visual acuity of 0.5 or better was 62.6% at the 1st day, and 76.6%, 92.5% and 88.8% respectively at the 1st week, 1st month and 3rd month postoperatively. CONCLUSION: Phacoemulsification with foldable intraocular lens implantation through a limbus tunnel incision has advantages of both scleral tunnel incision and clear corneal tunnel incision. The postoperative therapeutic effects are satisfactory.

Adult↗
PubMed2001

[An experimental study on the construction of composite graft with epithelia and fibroblasts on collagen sponge].

OBJECTIVE: Primarily cultured human epithelia and fibroblasts were inoculated on collagen sponge to construct composite skin substitute. METHODS: Epithelia and fibroblast asts from human foreskin were primarily cultured. Fibroblasts (1 x 10(5)/cm(2)) were inoculated on collagen sponge after digestion and cultured for 3 days prior to inoculation of epithelial cells (2 x 10(5)/cm(2)) to construct composite skin grafting substitute, and it was then grafted onto full skin loss (FSL) wounds of nude mice. Collagen sponge membrane lacking cell inoculation was used as control. The wound healing was evaluated by measuring the residual wound area. Tissue samples were harvested and examined by means of histology, immunohistochemistry and electron microscopy. RESULTS: Epithelia and fibroblasts could be cultured in vitro on the carrier collagen sponge. After being grafted onto the wound, the epithelia and fibroblasts wound further proliferated and differentiated. The composite skin could stick to the carrier fairly well. There exhibited less epidermal scar proliferation and satisfactory contour of the neoskin. Integral basal membrane of the skin could be identified by immunohistochemical staining. The quality and speed of wound healing with the composite skin substitute were superior to that with collagen sponge only. CONCLUSION: The composite grafts constructed by epithelia and fibroblasts on collagen sponge could be a potential neotype composite skin substitute for the repair of FSL.

Animals↗
PubMed2001

[Effects of estradoil valerate on osteoporosis in ovariectomized rats].

OBJECTIVE: Compared with 17beta-estradiol, to evaluate the effects of estradiol valerate on osteopenia in ovariectomized rats. METHODS: Forty two six months old female Wistar rats were randomly divided into 5 groups performed ovariectomy (OVX) or sham-operation. (1) 6 weeks after OVX (Ovxb, n = 8): sacrificed at 6 weeks after OVX; (2) Sham ovariectomized (n = 8); (3) 14 weeks after OVX (Ovxe, n = 8); (4) 17beta-estradoil treated group (O + E, n = 9, with 17beta-estradiol 20 microg x kg(-1) x d(-1) Sc.); (5) Estradoil valerate treated group (O + EV, n = 9, with estradiol valerate 800 microg x kg(-1) x d(-1) po). Treatment started 6 weeks after OVX and lasted for 8 weeks. Histomorphometry analysis of tibia, peripheral quantitative computed tomography (pQCT) scanning of femur, bone biomechanical test in femur were performed. RESULTS: OVX induced osteopenia and increase of bone turnover. Compared with Ovxe, O + E and O + EV caused an evident reduction of urinary deoxypyridinoline/creatinine, a bone resorption marker, by 54.6% and 77.4% respectively (all P < 0.01). Both O + E and O + EV lowered the high level of eroded surface, mineral surface and bone formation rate induced by OVX. An increase of 122.3% and 119.7% in trabecular bone volume respectively in O + E and O + EV group, compared with Ovxe group. Microarchitecture of trabeculea also improved in those two groups. The trabeculae bone mineral density determined by pQCT were significantly increased in O + E and O + EV compared with Ovxe group (99.5% and 128.4% P < 0.01). Similarly, significant increases were found in cancellouse maximal load and canceallous stiffness of distal femur in O + E, but not O + EV. There was no significant difference in these changes between the group O + E and O + EV. CONCLUSION: Oral estradiol valerate performed effects similar to those of 17beta-estradiol Sc. in inhibiting bone turnover, protecting bone loss and increasing bone mineral density of trabecular bone.

Animals↗