151
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Yin Y, Zech M, Williams TL, Wang XF, Wu G, Chen XH, Hoffman JE. Scanning tunneling spectroscopy and vortex imaging in the iron pnictide superconductor BaFe1.8Co0.2As2. PHYSICAL REVIEW LETTERS 2009; 102:097002. [PMID: 19392555 DOI: 10.1103/physrevlett.102.097002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Indexed: 05/27/2023]
Abstract
We present an atomic resolution scanning tunneling spectroscopy study of superconducting BaFe1.8Co0.2As2 single crystals in magnetic fields up to 9 T. At zero field, a single gap with coherence peaks at Delta=6.25 meV is observed in the density of states. At 9 and 6 T, we image a disordered vortex lattice, consistent with isotropic, single flux quantum vortices. Vortex locations are uncorrelated with strong-scattering surface impurities, demonstrating bulk pinning. The vortex-induced subgap density of states fits an exponential decay from the vortex center, from which we extract a coherence length xi=27.6+/-2.9 A, corresponding to an upper critical field Hc2=43 T.
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152
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Sun RS, Chen XH, Sui JF, Liu RQ, Cheng TM, Ran XZ, Yang T. Detecting anti-FcepsilonRI autoantibodies in patients with asthma by flow cytometry. J Int Med Res 2009; 36:1214-9. [PMID: 19094429 DOI: 10.1177/147323000803600607] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Autoimmune diseases have been implicated in the development of intrinsic asthma, however little data are available on the role of autoimmunity in the pathogenesis of asthma. The purpose of this study was to investigate circulating autoantibodies against the high-affinity receptor for immunoglobulin E, FcepsilonRI, in patients with asthma. Seventy-eight patients with asthma and 32 healthy control subjects were included. All individuals were tested using a triple-staining flow cytometry-based basophil activation test (BAT) for the potential presence of autoantibodies against FcepsilonRI. Of the 78 asthma patients, 29 (37.2%) had a positive BAT result, indicating that their serum was able to activate basophils, compared with only four (12.5%) of the control group, a statistically significant between-group difference. These data suggest that some asthma patients have aberrant anti-FcepsilonRI autoantibodies, which implies that autoimmunity may be one factor involved in the pathogenesis of intrinsic asthma.
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153
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Ou HW, Zhao JF, Zhang Y, Xie BP, Shen DW, Zhu Y, Yang ZQ, Che JG, Luo XG, Chen XH, Arita M, Shimada K, Namatame H, Taniguchi M, Cheng CM, Tsuei KD, Feng DL. Novel electronic structure induced by a highly strained oxide interface with incommensurate crystal fields. PHYSICAL REVIEW LETTERS 2009; 102:026806. [PMID: 19257306 DOI: 10.1103/physrevlett.102.026806] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2008] [Indexed: 05/27/2023]
Abstract
The misfit oxide, Bi2Ba1.3K0.6Co2.1O7.94, made of alternating rocksalt-structured [BiO/BaO] layers and hexagonal CoO2 layers, was studied by angle-resolved photoemission spectroscopy, revealing the electronic structure of a highly strained oxide interface. We found that low-energy states are confined within individual sides of the interface, but scattered by the incommensurate crystal field from the other side. Furthermore, the high strain on the rocksalt layer induces large charge transfer to the CoO2 layer, and a novel effect, the interfacial enhancement of electron-phonon interactions, is discovered.
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154
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Chen H, Wu T, Xie YL, Liu RH, Wu G, Wang XF, Chen XH. Magnetotransport properties in K(0.50)CoO(2) single crystals. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:016004. [PMID: 21817241 DOI: 10.1088/0953-8984/21/1/016004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We have measured susceptibility and angle-dependent magnetoresistance (AMR) on K(0.50)CoO(2) single crystals. A possible magnetic structure similar to that of Na(0.5)CoO(2), a G-type anti-ferromagnetic (AF) structure (both in-plane and inter-plane are AF), is proposed. At ∼20 K, a loop is observed between zero-field-cooled (ZFC) and field-cooled (FC) susceptibility. The absolute value of magnetoresistance (MR) at 20 K is much larger than other cases with H applied within the ab plane. This could arise from the magnetic field being applied in the ab plane, leading to spin-flop of the small magnetic moment of Co(3.5-δ) sites at 20 K to form in-plane ferromagnetic ordering, as observed in Na(0.52)CoO(2).
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155
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Huang Q, Qiu Y, Bao W, Green MA, Lynn JW, Gasparovic YC, Wu T, Wu G, Chen XH. Neutron-diffraction measurements of magnetic order and a structural transition in the parent BaFe2As2 compound of FeAs-based high-temperature superconductors. PHYSICAL REVIEW LETTERS 2008; 101:257003. [PMID: 19113744 DOI: 10.1103/physrevlett.101.257003] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Indexed: 05/27/2023]
Abstract
The recent discovery of superconductivity in (Ba,K)Fe2As2, which crystallizes in the ThCr2Si2 (122) structure as compared with the LnFeAsO (Ln is lanthanide) systems that possess the ZrCuSiAs (1111) structure, demonstrates the exciting potential of the FeAs-based materials for high-T{C} superconductivity. Here we report neutron diffraction studies that show a tetragonal-to-orthorhombic distortion associated with the onset of q=(101) antiferromagnetic order in BaFe2As2, with a saturation moment 0.87(3)micro {B} per Fe that is orientated along the longer a axis of the ab planes. The simultaneous first-order structural and magnetic transition is in contrast with the separated transitions previously reported in the 1111-type materials. The orientational relation between magnetic alignment and lattice distortion supports a multiorbital nature for the magnetic order.
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156
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Qiu Y, Bao W, Huang Q, Yildirim T, Simmons JM, Green MA, Lynn JW, Gasparovic YC, Li J, Wu T, Wu G, Chen XH. Crystal structure and antiferromagnetic order in NdFeAsO1-xFx (x=0.0 and 0.2) superconducting compounds from neutron diffraction measurements. PHYSICAL REVIEW LETTERS 2008; 101:257002. [PMID: 19113743 DOI: 10.1103/physrevlett.101.257002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Indexed: 05/27/2023]
Abstract
The transition temperature T{C} approximately 26 K of the recently discovered superconductor LaFeAsO1-xFx is extremely sensitive to the lanthanide ion, reaching 55 K for the Sm containing oxypnictides. Therefore, it is important to determine how the moment on the lanthanide affects the overall magnetism in these systems. Here we report a neutron diffraction study of the Nd oxypnictides. Long-ranged antiferromagnetic order is apparent in NdFeAsO below 1.96 K. Rietveld refinement shows that both Fe and Nd magnetic ordering are required to describe the observed data with the staggered moment 1.55(4)micro{B}/Nd and 0.9(1)micro{B}/Fe at 0.3 K. The other structural properties such as the tetragonal-orthorhombic distortion are found to be very similar to those in LaFeAsO. Neither the magnetic ordering nor the structural distortion occur in the superconducting sample NdFeAsO0.80F0.20 at any temperatures down to 1.5 K.
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157
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Peng HF, Zhang ZF, Wu B, Chen XH, Zhang GQ, Zhang ZM, Wan BH, Lu YP. Molecular mapping of two reverse photoperiod-sensitive genic male sterility genes (rpms1 and rpms2) in rice (Oryza sativa L.). TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2008; 118:77-83. [PMID: 18810384 DOI: 10.1007/s00122-008-0877-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2008] [Accepted: 08/23/2008] [Indexed: 05/26/2023]
Abstract
The reverse photoperiod-sensitive genic male sterility (PGMS) and thermo-sensitive genic male sterility (TGMS) lines have an opposite phenotype compared with normal PGMS and TGMS lines widely used by the two-line system in current hybrid rice seed production. Thus, the application of reverse PGMS and TGMS lines can compensate PGMS and TGMS lines in hybrid rice production. YiD1S is a reverse PGMS line, in which pollen fertility is mainly regulated by day-length, but also influenced by temperature. Genetic analysis indicated that male sterility of YiD1S was controlled by two recessive major genes. An F(2) population from a cross between YiD1S and 8528 was developed and used for molecular mapping of the two reverse PGMS genes which were first named rpms1 and rpms2. Both simple sequence repeat (SSR) markers and bulked segregant analysis (BSA) were used in this study. As a result, one reverse PGMS gene (rpms1) was mapped to the interval between SSR markers RM22980 (0.9 cM) and RM23017 (1.8 cM) on chromosome 8. Eight SSR markers, YDS818, RM22984, RM22986, RM22997, YDS816, RM23002, RM339 and YDS810 completely co-segregated with the rpms1 gene. Another reverse PGMS gene (rpms2) was mapped to the interval between SSR markers RM23898 (0.9 cM) and YDS926 (0.9 cM) on chromosome 9. The physical mapping information from publicly available resources shows that the rpms1 and rpms2 loci are located in a region of 998 and 68 kb, respectively. The analysis based on marker genotypes showed that the effect of rpms1 was slightly larger than that of rpms2 and that the two genes interacted in controlling male sterility.
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158
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Chen XH, Scholz R, Borriss M, Junge H, Mögel G, Kunz S, Borriss R. Difficidin and bacilysin produced by plant-associated Bacillus amyloliquefaciens are efficient in controlling fire blight disease. J Biotechnol 2008; 140:38-44. [PMID: 19061923 DOI: 10.1016/j.jbiotec.2008.10.015] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2008] [Revised: 09/19/2008] [Accepted: 10/21/2008] [Indexed: 10/21/2022]
Abstract
Representatives of Bacillus amyloliquefaciens were shown to possess biocontrol activity against fire blight, a serious disease of orchard trees caused by Erwinia amylovora. Genome analysis of B. amyloliquefaciens FZB42 identified gene clusters responsible for synthesis of several polyketide compounds with antibacterial action. We show here that the antibacterial polyketides difficidin and to a minor extent bacillaene act efficiently against E. amylovora. Surprisingly, a mutant strain blocked in the production of difficidin (CH8 Deltadfn) inhibited growth of E. amylovora and suppressed fire blight disease nearly in the same range as the wild type. In addition, a sfp mutant (CH3 Deltasfp) unable to synthesize non-ribosomally lipopeptides and polyketides did still suppress growth of E. amylovora, suggesting that besides action of polyketides another antagonistic principle exist. A double mutant (RS06 Deltasfp Deltabac) devoid in polyketide and bacilysin synthesis was unable to suppress growth of E. amylovora indicating that the additional inhibitory effect is due to production of bacilysin, a dipeptide whose synthesis does not depend on Sfp. We propose to use B. amyloliquefaciens strains with enhanced synthesis of difficidin and/or bacilysin for development of biocontrol agents efficient against fire blight disease.
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159
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Drew AJ, Pratt FL, Lancaster T, Blundell SJ, Baker PJ, Liu RH, Wu G, Chen XH, Watanabe I, Malik VK, Dubroka A, Kim KW, Rössle M, Bernhard C. Coexistence of magnetic fluctuations and superconductivity in the pnictide high temperature superconductor SmFeAsO1-xFx measured by muon spin rotation. PHYSICAL REVIEW LETTERS 2008; 101:097010. [PMID: 18851648 DOI: 10.1103/physrevlett.101.097010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Indexed: 05/26/2023]
Abstract
Muon spin rotation experiments were performed on the pnictide high temperature superconductor SmFeAsO1-xFx with x=0.18 and 0.3. We observed an unusual enhancement of slow spin fluctuations in the vicinity of the superconducting transition which suggests that the spin fluctuations contribute to the formation of an unconventional superconducting state. An estimate of the in-plane penetration depth lambda ab(0)=190(5) nm was obtained, which confirms that the pnictide superconductors obey an Uemura-style relationship between Tc and lambda ab(0);(-2).
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160
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Dubroka A, Kim KW, Rössle M, Malik VK, Drew AJ, Liu RH, Wu G, Chen XH, Bernhard C. Superconducting energy gap and c-axis plasma frequency of (Nd,Sm)FeAsO0.82F0.18 superconductors from infrared ellipsometry. PHYSICAL REVIEW LETTERS 2008; 101:097011. [PMID: 18851649 DOI: 10.1103/physrevlett.101.097011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Indexed: 05/26/2023]
Abstract
We present far-infrared ellipsometric measurements of polycrystalline samples of the pnictide superconductor RFeAsO0.82F0.18 (R=Nd and Sm). We find evidence that the electronic properties are strongly anisotropic such that the optical spectra are dominated by the weakly conducting c-axis response similar to the cuprate high-temperature superconductors. We deduce an upper limit of the c-axis superconducting plasma frequency of omega pl,c(SC)< or =260 cm(-1) corresponding to a lower limit of the c-axis magnetic penetration depth of lambda c > or =6 microm and lambda c/lambda ab > or =30 as compared to lambda ab=185 nm from muon spin rotation [A. Drew, arXiv:0805.1042 [Phys. Rev. Lett. (to be published)]]. We also observe a gaplike suppression of the conductivity in the superconducting state with a shoulderlike feature at omegaSC* approximately 300 cm(-1) and spectral shape which is consistent with an unconventional order parameter with 2Delta approximately omegaSC* approximately 37 meV.
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161
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Liu RH, Wu G, Wu T, Fang DF, Chen H, Li SY, Liu K, Xie YL, Wang XF, Yang RL, Ding L, He C, Feng DL, Chen XH. Anomalous transport properties and phase diagram of the FeAs-based SmFeAsO1-xFx superconductors. PHYSICAL REVIEW LETTERS 2008; 101:087001. [PMID: 18764649 DOI: 10.1103/physrevlett.101.087001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2008] [Indexed: 05/26/2023]
Abstract
We report the detailed phase diagram and anomalous transport properties of Fe-based high-T_{c} superconductors SmFeAsO1-xFx. It is found that superconductivity emerges at x approximately 0.07, and optimal doping takes place in the x approximately 0.20 sample with the highest T_{c} approximately 54 K. T_{c} increases monotonically with doping; the anomaly in resistivity from structural phase or spin-density-wave order is rapidly suppressed, suggesting a quantum critical point around x approximately 0.14. As manifestations, a linear temperature dependence of the resistivity shows up at high temperatures in the x<0.14 regime but at low temperatures just above T_{c} in the x>0.14 regime; a drop in carrier density evidenced by a pronounced rise in the Hall coefficient is observed below the temperature of the anomaly peak in resistivity. A scaling behavior is observed between the Hall angle and temperature: cottheta_{H} proportional, variantT;{1.5} for all samples with different x in SmFeAsO1-xFx system.
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162
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Wu T, Wang CH, Wu G, Fang DF, Luo JL, Liu GT, Chen XH. Giant anisotropy of the magnetoresistance and the 'spin valve' effect in antiferromagnetic Nd(2-x)Ce(x)CuO(4). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2008; 20:275226. [PMID: 21694387 DOI: 10.1088/0953-8984/20/27/275226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We have studied anisotropic magnetoresistance (MR) and magnetization with a rotating magnetic field (B) within the CuO(2) plane in lightly doped AF Nd(2-x)Ce(x)CuO(4). A giant anisotropy in the MR is observed at low temperature, below 5 K. The c-axis resistivity can be tuned over about one order of magnitude just by changing the B direction within the CuO(2) plane, and a scaling behavior for the out-of-plane and in-plane MR is found. A 'spin valve' effect is proposed for explaining the giant anisotropy of the out-of-plane MR and the evolution of the scaling parameters with the external field. It is found that the field-induced spin-flop transition of the Nd(3+) layer under high magnetic field is the key to understanding the giant anisotropy. These results suggest that a novel entanglement of charge and spin dominates the underlying physics.
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163
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Long YZ, Yin ZH, Chen ZJ, Jin AZ, Gu CZ, Zhang HT, Chen XH. Low-temperature electronic transport in single K(0.27)MnO(2)·0.5H(2)O nanowires: enhanced electron-electron interaction. NANOTECHNOLOGY 2008; 19:215708. [PMID: 21730587 DOI: 10.1088/0957-4484/19/21/215708] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The current-voltage (I-V) characteristics and electrical resistivity of isolated potassium manganese oxide (K(0.27)MnO(2)·0.5H(2)O) nanowires prepared by a simple hydrothermal method were investigated over a wide temperature range from 300 to 4 K. With lowering temperature, a transition from linear to nonlinear I-V curves was observed around 50 K, and a clear zero bias anomaly (i.e., Coulomb gap-like structure) appeared on the differential conductance (dI/dV) curves, possibly due to enhanced electron-electron interaction at low temperatures. The temperature dependence of resistivity, [Formula: see text], follows the Efros-Shklovskii (ES) law, as expected in the presence of a Coulomb gap. Here we note that both the ES law and Coulomb blockade can in principle lead to a reduced zero bias conductance at low temperatures; in this study we cannot exclude the possibility of Coulomb-blockade transport in the measured nanowires, especially in the low-temperature range. It is still an open question how to pin down the origin of the observed reduction to a Coulomb gap (ES law) or Coulomb blockade.
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164
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Chen XH, Wu T, Wu G, Liu RH, Chen H, Fang DF. Superconductivity at 43 K in SmFeAsO1-xFx. Nature 2008; 453:761-2. [PMID: 18500328 DOI: 10.1038/nature07045] [Citation(s) in RCA: 1530] [Impact Index Per Article: 95.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Accepted: 04/29/2008] [Indexed: 11/09/2022]
Abstract
Since the discovery of high-transition-temperature (high-T(c)) superconductivity in layered copper oxides, extensive effort has been devoted to exploring the origins of this phenomenon. A T(c) higher than 40 K (about the theoretical maximum predicted from Bardeen-Cooper-Schrieffer theory), however, has been obtained only in the copper oxide superconductors. The highest reported value for non-copper-oxide bulk superconductivity is T(c) = 39 K in MgB(2) (ref. 2). The layered rare-earth metal oxypnictides LnOFeAs (where Ln is La-Nd, Sm and Gd) are now attracting attention following the discovery of superconductivity at 26 K in the iron-based LaO(1-x)F(x)FeAs (ref. 3). Here we report the discovery of bulk superconductivity in the related compound SmFeAsO(1-x)F(x), which has a ZrCuSiAs-type structure. Resistivity and magnetization measurements reveal a transition temperature as high as 43 K. This provides a new material base for studying the origin of high-temperature superconductivity.
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165
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Wang GY, Chen XH, Wu T, Luo XG, Zhang WT, Wu G. Novel dynamical effects and glassy response in a strongly correlated electronic system. PHYSICAL REVIEW LETTERS 2008; 100:146402. [PMID: 18518056 DOI: 10.1103/physrevlett.100.146402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2007] [Revised: 09/13/2007] [Indexed: 05/26/2023]
Abstract
We find an unconventional nucleation of a low-temperature paramagnetic metal phase with a monoclinic structure from the matrix of a high-temperature antiferromagnetic insulator phase with a tetragonal structure in a strongly correlated electronic system BaCo0.9Ni0.1S1.97. Such unconventional nucleation leads to a decrease in resistivity by several orders with relaxation at a fixed temperature. The novel dynamical process could arise from the competition of strain fields, Coulomb interactions, magnetic correlations, and disorders. Such competition may frustrate the nucleation, giving rise to a slow, nonexponential relaxation and "physical aging" behavior.
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166
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Zeng YH, Chen XH, Jiao NZ. Genetic diversity assessment of anoxygenic photosynthetic bacteria by distance-based grouping analysis of pufM sequences. Lett Appl Microbiol 2007; 45:639-45. [PMID: 17922815 DOI: 10.1111/j.1472-765x.2007.02247.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM To assess how completely the diversity of anoxygenic phototrophic bacteria (APB) was sampled in natural environments. METHODS AND RESULTS All nucleotide sequences of the APB marker gene pufM from cultures and environmental clones were retrieved from the GenBank database. A set of cutoff values (sequence distances 0.06, 0.15 and 0.48 for species, genus, and (sub)phylum levels, respectively) was established using a distance-based grouping program. Analysis of the environmental clones revealed that current efforts on APB isolation and sampling in natural environments are largely inadequate. Analysis of the average distance between each identified genus and an uncultured environmental pufM sequence indicated that the majority of cultured APB genera lack environmental representatives. CONCLUSIONS The distance-based grouping method is fast and efficient for bulk functional gene sequences analysis. The results clearly show that we are at a relatively early stage in sampling the global richness of APB species. Periodical assessment will undoubtedly facilitate in-depth analysis of potential biogeographical distribution pattern of APB. SIGNIFICANCE AND IMPACT OF THE STUDY This is the first attempt to assess the present understanding of APB diversity in natural environments. The method used is also useful for assessing the diversity of other functional genes.
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167
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Zhao JF, Ou HW, Wu G, Xie BP, Zhang Y, Shen DW, Wei J, Yang LX, Dong JK, Arita M, Namatame H, Taniguchi M, Chen XH, Feng DL. Evolution of the electronic structure of 1T-Cu(x)TiSe(2). PHYSICAL REVIEW LETTERS 2007; 99:146401. [PMID: 17930690 DOI: 10.1103/physrevlett.99.146401] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2007] [Indexed: 05/25/2023]
Abstract
The electronic structure of a new charge-density-wave system or superconductor, 1T-Cu(x)TiSe(2), has been studied by photoemission spectroscopy. A correlated semiconductor band structure is revealed for the undoped case, which resolves a long-standing controversy in the system. With Cu doping, the charge-density wave is suppressed by the raising of the chemical potential, while the superconductivity is enhanced by the enhancement of the density of states, and possibly suppressed at higher doping by the strong scattering.
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168
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Li SY, Wu G, Chen XH, Taillefer L. Single-gap s-Wave superconductivity near the charge-density-wave quantum critical point in CuxTiSe2. PHYSICAL REVIEW LETTERS 2007; 99:107001. [PMID: 17930404 DOI: 10.1103/physrevlett.99.107001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2007] [Indexed: 05/25/2023]
Abstract
The in-plane thermal conductivity kappa of the layered superconductor CuxTiSe2 was measured down to temperatures as low as Tc/40, at x=0.06 near where the charge-density-wave order vanishes. The absence of a residual linear term at T-->0 is strong evidence for conventional s-wave superconductivity in this system. This is further supported by the slow magnetic field dependence, also consistent with a single gap, of uniform magnitude across the Fermi surface. Comparison with the closely related material NbSe2, where the superconducting gap is 3 times larger on the Nb 4d band than on the Se 4p band, suggests that in Cu0.06TiSe2 the Se 4p band is below the Fermi level and Cu doping into the Ti 3d band is responsible for the superconductivity.
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169
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Chen XH, Moskovits M. Observing catalysis through the agency of the participating electrons: surface-chemistry-induced current changes in a tin oxide nanowire decorated with silver. NANO LETTERS 2007; 7:807-12. [PMID: 17269831 DOI: 10.1021/nl062467z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Conductometric measurements were performed on single tin oxide nanowires with and without Ag nanoparticle surface decoration, in flowing oxygen/ethylene mixtures of varying composition. Ag-decorated nanowires showed a significant ethylene effect, which we explain in terms of the modification of the Schottky junction formed between the Ag particles and the tin oxide, resulting from the surface chemical processes involving ethylene and oxygen occurring exclusively on the silver nanoparticles' surface. Assuming the observed temperature dependence of these ethylene-induced current decrements reflect changes in the steady-state concentration of ethylene, oxygen, and a surface intermediate that ultimately leads to ethylene oxide, one calculates the enthalpy for the production of the reaction intermediate to be approximately -4.6 kcal/mol, of the right order of magnitude as the calculated value reported in the literature for the formation of a putative ethylene oxametallacycle intermediate in the ethylene epoxidation reaction. Our results illustrate how fundamental catalytic processes occurring at metal nanoparticle surfaces can significantly influence the electronic properties of oxide nanowires used as metal particle supports.
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170
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Chen Q, Zou H, Xu XH, Luo M, Wang J, Zuo YQ, Chen YH, Chen XH, Chen XL, Yao ZQ, Song N, Zeng J, Mi XY, Sun SX, Wang JX, Zhao TM. Characterization of HLA-B*5516, -B*1313, -B*9512, and -DRB1*1457 alleles identified in a southwest Chinese population. ACTA ACUST UNITED AC 2007; 68:339-43. [PMID: 17026471 DOI: 10.1111/j.1399-0039.2006.00669.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The human leukocyte antigen (HLA)-B*5516 allele differs from the B*5502 by a single 97 T --> C substitution (His to Tyr at position 33) in exon 2. The B*1313 allele results from 419 T --> A and 420 A --> C substitutions, encoding a Leu to Tyr substitution at 140 in exon 2 of the B*1301 allele. The B*9512 allele differs from B*1502 by a single 360 G --> C substitution (Gln to His at 120) in exon 3. The DRB1*1457 allele appears to be a hybrid molecule generated by recombination between the DRB1*13 and DRB1*14 alleles. The serological equivalents of these new alleles are HLA-B22, -B13, -B15, and DR13, respectively. Family studies detected two rare haplotypes: A*11, B*9512, DRB1*14 and A*24, B*52, Cw*07, DRB1*1457, DRB3*020201, DQB1*050301. The gene frequencies of these alleles in the Chinese population are less than 0.0001.
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171
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Meng H, Cui FY, Chen XH, Pan YC. Inhibition of gene expression directed by small interfering RNAs in infectious bronchitis virus. Acta Virol 2007; 51:265-269. [PMID: 18197734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
In this study, fourteen small interfering RNAs (siRNAs) were synthesized for targeting of coding gene sequences, specific 5'-leader sequence of mRNA and 3'-end sequence of the Infectious bronchitis virus (IBV) genome. The expression of viral genes in Vero-E6 cells was detected by real-time PCR. Obtained results indicated that the majority of siRNAs could effectively inhibit the expression of viral genes. The inhibition effect of siRNAs significantly differed among various genes and sites on the virus genome.
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Chen XH, Zhang JZH. Molecular fractionation with conjugated caps density matrix with pairwise interaction correction for protein energy calculation. J Chem Phys 2006; 125:44903. [PMID: 16942188 DOI: 10.1063/1.2218341] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Pairwise interaction correction (PIC) is introduced to account for electron density polarization due to short-range interactions such as hydrogen bonding and close contact between molecular fragments in the molecular fractionation with conjugated caps density matrix (MFCC-DM) approach for energy calculation of protein and other polymers [Chen et al., J. Chem. Phys. 122, 184105 (2005)]. With this PIC, the accuracy of the calculated protein energy and other electronic properties are improved, and the MFCC approach can be applied to study real proteins with short-range structural complexity. In the present MFCC-DM-PIC approach, the short-range interresidual interactions are represented by a pair of small molecules (interacting units) which are made from the two residues that fall within a certain distance criterion. The density matrices of fragments, concaps, interacting units and pairs are calculated by conventional Hartree-Fock or density functional theory methods and are combined to construct the full density matrix which is finally employed to calculate the total energy, electron density, electrostatic potential, dipole moment, etc., of the protein. Numerical tests on seven conformationally varied peptides are presented to demonstrate the accuracy of the MFCC-DM-PIC method.
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173
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Wang CH, Chen XH, Wu T, Luo XG, Wang GY, Luo JL. In-plane ferromagnetism in charge-ordering Na0.55CoO2. PHYSICAL REVIEW LETTERS 2006; 96:216401. [PMID: 16803257 DOI: 10.1103/physrevlett.96.216401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2005] [Indexed: 05/10/2023]
Abstract
The magnetic and transport properties are systematically studied on the single crystal Na(0.55)CoO2 with the resistivity divergence below 50 K. A weak ferromagnetic ordering is observed in susceptibility below 20 K with the magnetic field parallel to the Co-O plane, while no such ferromagnetic ordering is observed with the field perpendicular to the Co-O plane. It gives evidence for the existence of in-plane ferromagnetism below 20 K. The observed magnetoresistance of 30% at the field of 6 T at low temperatures indicates an unexpectedly strong spin-charge coupling in the triangle lattice NaxCoO2 system.
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174
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Li SY, Taillefer L, Wang CH, Chen XH. Ballistic magnon transport and phonon scattering in the antiferromagnet Nd2CuO4. PHYSICAL REVIEW LETTERS 2005; 95:156603. [PMID: 16241747 DOI: 10.1103/physrevlett.95.156603] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2005] [Indexed: 05/05/2023]
Abstract
The thermal conductivity of the antiferromagnet Nd2CuO4 was measured down to 50 mK. Using the spin-flop transition to switch on and off the acoustic Nd magnons, we can reliably separate the magnon and phonon contributions to heat transport. We find that magnons travel ballistically below 0.5 K, with a thermal conductivity growing as T3, from which we extract their velocity. We show that the rate of scattering of acoustic magnons by phonons grows as T3, and the scattering of phonons by magnons peaks at twice the average Nd magnon frequency.
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175
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Li QY, Zhang SX, Liu ZJ, Tan LW, Qiu MG, Li K, Cui GY, Guo YL, Yang XP, Zhang WG, Chen XH, Chen JH, Ding SY, Chen W, You J, Wang YS, Deng JH, Tang ZS. The pre-styloid compartment of the parapharyngeal space: a three-dimensional digitized model based on the Chinese Visible Human. Surg Radiol Anat 2005; 26:411-6. [PMID: 15300412 DOI: 10.1007/s00276-004-0252-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
To build a digitized visible model of the parapharyngeal space of the Chinese Visible Human and to provide a sectional anatomic basis for radiological and clinical diagnosis of the parapharyngeal space, sectional anatomy data of the parapharyngeal space were selected from the Chinese Visible Human male and female to compare with MR imaging findings in the axial planes. From these data the parapharyngeal space and surrounding structures were segmented. They were then reconstructed in three dimensions on PC. In the axial planes of the sectional anatomy and MR imaging, the shape, content and relations of the parapharyngeal space were clearly displayed and the dominant plane for showing the parapharyngeal space was elicited. The three-dimensional reconstructed images displayed perfectly the anatomic relationships of the parapharyngeal space, parotid, muscles, mandible and vessels. All reconstructed structures can be displayed singly, in groups or as a whole; any diameter or angle of the reconstructed structures can be easily measured. The Chinese Visible Human male and female data set can provide complete and accurate data. The digitized model of the parapharyngeal space and its surroundings offers unique insights into the complex anatomy of the area, providing morphologic data for imaging diagnosis and surgery of the parapharyngeal space.
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Wang NL, Wu D, Li G, Chen XH, Wang CH, Luo XG. Infrared spectroscopy of the charge ordering transition of Na0.5CoO2. PHYSICAL REVIEW LETTERS 2004; 93:147403. [PMID: 15524841 DOI: 10.1103/physrevlett.93.147403] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2004] [Indexed: 05/24/2023]
Abstract
We report infrared reflectivity study of charge ordering in a Na0.5CoO2 single crystal. In comparison with x=0.7 and 0.85 compounds, we found that the effective carrier density increases systematically with decreasing Na contents. The charge ordering transition only affects the optical spectra below 1000 cm(-1). A hump near 800 cm(-1) develops below 100 K, which is accompanied by the appearance of new lattice modes as well as the strong antiresonance feature of phonon spectra. These observations signify a polaronic characteristic of charge carriers. Below T(co), an optical gap develops at the magnitude of 2Delta approximately 3.5k(B)T(co) (T<<T(co)), evidencing an insulating charge density wave ground state.
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177
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Li SY, Taillefer L, Hawthorn DG, Tanatar MA, Paglione J, Sutherland M, Hill RW, Wang CH, Chen XH. Giant electron-electron scattering in the Fermi-liquid state of Na0.7CoO2. PHYSICAL REVIEW LETTERS 2004; 93:056401. [PMID: 15323717 DOI: 10.1103/physrevlett.93.056401] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2003] [Indexed: 05/24/2023]
Abstract
The in-plane resistivity rho and thermal conductivity kappa of single crystal Na0.7CoO2 were measured down to 40 mK. Verification of the Wiedemann-Franz law, kappa/T=L(0)/rho as T-->0, and observation of a T2 dependence of rho at low temperature establish the existence of a well-defined Fermi-liquid state. The measured value of coefficient A reveals enormous electron-electron scattering, characterized by the largest Kadowaki-Woods ratio A/gamma(2) encountered in any material. The rapid suppression of A with magnetic field suggests a possible proximity to a magnetic quantum critical point. We also speculate on the possible role of magnetic frustration and proximity to a Mott insulator.
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Zhu ZG, Yu YY, Zhang Y, Ji J, Zhang J, Liu BY, Chen XH, Lu Y, Jiang HS, Bu L, Hu LD, Kong XY. Germline mutational analysis of CDH1 and pathologic features in familial cancer syndrome with diffuse gastric cancer/breast cancer proband in a Chinese family. Eur J Surg Oncol 2004; 30:531-5. [PMID: 15135482 DOI: 10.1016/j.ejso.2004.03.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/04/2004] [Indexed: 01/29/2023] Open
Abstract
AIMS Hereditary non-polyposis colorectal cancer, thyroid medullary carcinoma, breast/ovarian cancer and gastric cancer/breast cancer syndrome are encountered in surgery. Some gastric cancer/breast cancer syndrome may be the result of a CDH1 germline mutation. This is the first report of CDH1 germline mutations gastric cancer/breast cancer syndrome in Chinese patients. METHODS Peripheral blood from the proband, as well as, her first and second degree relatives was collected and CDH1 gene exon 1-16 mutations were screened. E-cadherin/beta-catenin proteins expression and histopathologic features were examined on gastric cancer/breast cancer tissues from the proband. RESULTS A C-->T nucleotide substitution at exon 13 (mRNA 2200 locus, Accession number NM-004360) was found. This was a transition from GCC-->GCT in DNA sequence (Ala154Ala). Diffuse-type gastric cancer and infiltrating ductal breast carcinoma were present. Both tumours preserved E-cadherin/beta-catenin expression immunohistochemically. CONCLUSIONS Familial cancer syndrome with diffuse-type gastric cancer/breast cancer proband in Chinese has a propensity of early onset during lifespan. No truncating or splice-site CDH1 mutations had been identified in this family. A silent nucleotide variation in exon 13 of the CDH1 gene may contribute to some forms of cancer susceptibility.
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179
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Zhang DW, Chen XH, Zhang JZH. Molecular caps for full quantum mechanical computation of peptide-water interaction energy. J Comput Chem 2004; 24:1846-52. [PMID: 14515367 DOI: 10.1002/jcc.10346] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We present a systematic study of numerical accuracy of various forms of molecular caps that are employed in a recently developed molecular fractionation scheme for full quantum mechanical computation of protein-molecule interaction energy. A previously studied pentapeptide (Gly-Ser-Ala-Asp-Val) or P5 interacting with a water molecule is used as a benchmark system for numerical testing. One-dimensional potential energy curves are generated for a number of peptide-water interaction pathways. Our study shows that various forms of caps all give consistently accurate energies compared to the corresponding full system calculation with only small deviations. We also tested the accuracy of cutting peptide backbone at different positions and comparisons of results are presented.
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180
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Chen XH, Zhang DW, Zhang JZH. Fractionation of peptide with disulfide bond for quantum mechanical calculation of interaction energy with molecules. J Chem Phys 2004; 120:839-44. [PMID: 15267920 DOI: 10.1063/1.1630964] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a computational study of a recently developed molecular fractionation with conjugated caps (MFCC) method for application to peptide/protein that has disulfide bonds. Specifically, we employ the MFCC approach to generate peptide fragments in which a disulfide bond is cut and a pair of conjugated caps are inserted. The method is tested on two peptides interacting with a water molecule. The first is a dipeptide consisting of two cysteines (Cys-Cys) connected by a disulfide bond and the second is a seven amino acid peptide consisting of Gly-Cys-Gly-Gly-Gly-Cys-Gly with a disulfide cross link. One-dimensional peptide-water potential curves are computed using the MFCC method at various ab initio levels for a number of interaction geometries. The calculated interaction energies are found to be in excellent agreement with the results obtained from the corresponding full system ab initio calculations for both peptide/water systems. The current study provides further numerical support for the accuracy of the MFCC method in full quantum mechanical calculation of protein/peptide that contains disulfide bonds.
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181
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Chen XH, Lin KB, Wang XW. Outbreaks of an iridovirus disease in maricultured large yellow croaker, Larimichthys crocea (Richardson), in China. JOURNAL OF FISH DISEASES 2003; 26:615-619. [PMID: 14653319 DOI: 10.1046/j.1365-2761.2003.00494.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
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182
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Liu X, Lin WM, Yan XH, Chen XH, Hoidal JR, Xu P. Improved method for measurement of human plasma xanthine oxidoreductase activity. J Chromatogr B Analyt Technol Biomed Life Sci 2003; 785:101-14. [PMID: 12535843 DOI: 10.1016/s1570-0232(02)00860-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The XOR activity in human plasma was measured by quantifying the XOR-derived uric acid (UA) in plasma using the high-performance liquid chromatography (HPLC) equipped with a UV detector. Chromatographic separation consisted of the mobile phase (a mixture of 0.1% trifluoroacetic acid in Milli-Q water and 0.085% trifluoroacetic acid in acetonitrile in a mix ratio of 99:1) running through a Zorbax StableBond SB-C(18) column at a flow-rate of 1 ml/min. Deproteinization with heat-treatment of plasma samples after the reaction was used in the assay to avoid splitting of the UA and xanthine peaks caused by acid deproteinization that could interfere the accurate determination of human plasma XOR activity in our case. Based on the examination of the dependence of XOR activity on added amounts of xanthine and reaction times, the amount of xanthine and reaction time for XOR activity assay were determined to prevent the errors caused by the limiting effect of substrates and plateau phase of the reaction. Using this method, human plasma XOR activities of 25 healthy people were measured. The average human plasma XOR activity was 2.1+/-0.8 (x10(-3) U/ml).
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183
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Nishida Y, Minatoguchi S, Arai M, Takemura G, Uno Y, Hashimoto K, Wang N, Chen XH, Fujiwara T, Fujiwara H. N-methyl-1-deoxynojirimycin (MOR-14), an alpha-glucosidase inhibitor, markedly improves postischemic left ventricular dysfunction. Heart Vessels 2002; 15:268-73. [PMID: 11766064 DOI: 10.1007/s003800070004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We examined whether pharmacological inhibition of glycogenolysis by N-methyl-1-deoxynojirimycin (MOR-14), a new compound which reduces the glycogenolytic rate by inhibiting the alpha-1,6-glucosidase activity of the glycogen-debranching enzyme, can protect the heart against postischemic left ventricular dysfunction. The hearts of male Sprague-Dawley rats were excised, and perfused on a Langendorff apparatus with Krebs-Henseleit solution with a gas mixture of 95% O2 and 5% CO2. The hearts were paced at 320 beats/min except during the ischemia. Left ventricular developed pressure (LVDP, mmHg), +/-dP/dt (mmHg/s), and coronary flow (ml/min) were continuously monitored. All hearts were perfused for a total of 120 min including a 30-min preischemic period followed by a 30-min episode of global ischemia and 60 min reperfusion. with or without 0.5 or 2 mM of MOR-14 during the 30-min preischemic period or the first 30 min of reperfusion. In another series of experiments, the myocardial content of glycogen and lactate was measured during the 30-min episode of ischemia in groups treated with and without 2mM of MOR-14. Preischemic but not postischemic treatment with MOR-14 significantly improved LVDP and +/-dP/dt without altering coronary flow during reperfusion in a dose-dependent manner. MOR-14 significantly preserved the glycogen content and significantly attenuated the lactate accumulation during the 30-min episode of ischemia. Preischemic treatment with MOR-14 is protective against postischemic left ventricular dysfunction through the inhibition of glycogenolysis in the isolated rat heart.
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184
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Shen ZY, Xu LY, Chen XH, Cai WJ, Shen J, Chen JY, Huang TH, Zeng Y. The genetic events of HPV-immortalized esophageal epithelium cells. Int J Mol Med 2001; 8:537-42. [PMID: 11605024 DOI: 10.3892/ijmm.8.5.537] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We studied cytogenesis, telomere and telomerase, and c-myc, ras, bcl-2, and p53 genes of cells in the progressive process of immortal epithelial cells from embryonic esophagus induced by human papillomavirus (HPV). The SHEE cell line, established by us, consist of immortalized epithelial cells from the embryonic esophagus induced by genes E6E7 of HPV type 18. It was in initial malignant transformation when cultivated over 60 passages without co-carcinogens. Cells of the 10th, 31st, and 60th passages were represented in the progressive process within the immortal period. In these three stages of the cell line, the modal number of chromosome and karyotypes were analyzed. The telomere length was assayed by Southern blot methods, and the telomerase activity was analyzed by hTR and hTERT assay. C-myc, p53, bcl-2, ras genes were assayed by the multi-PCR method. The morphology of the 10th passage cells exhibited good differentiation, the 60th passage cells were relatively poorly differentiated, and the 31st passage cells differentiated in two distinct ways. The growth characteristics of the 31st and 60th passage cells were weakened at contact-inhibition and anchorage-dependent growth. Karyotypes of three cell passages belonged to hyperdiploid and hypotriploid with abnormal chromosomes +1, +3, +7, +9, +17, +18; del(1)(p32); der(4), t(4;?)(q31;?); der(5),t(5;?)(q31;?); der(13),t(13;13)(p11;q11) and others. Bimodal distribution of chromosomes with more aberrant chromosomes appeared in the 31st and 60th passage cells. Telomere length sharply shortened from normal fetal esophagus to the 10th and 31st passage step by step, but was stable from the 31st to the 60th passage and the telomerase activities measured were expressed at late two passages. p53 mutant was positive in three passages, c-myc was positive in the 31st and the 60th passage K-ras only in the last. The results reveal that changes of chromosomes, telomere length, telomerase activity and certain gene expressions are important events of HPV-immortalized esophageal epithelium cells. All of these changes occurred in dynamic progressive process. This cell line may be useful for the elucidation of the genetic mechanism of cellular immortalization.
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185
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Chen XH, Yuan ZN. [Determination of micro Pb in preserved egg by flame atomic absorption spectrometry]. GUANG PU XUE YU GUANG PU FEN XI = GUANG PU 2001; 21:668-669. [PMID: 12945326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The method for the determination of micro Pb in preserved egg by flame atomic absorption spectrometry was studied in this paper. These samples are treated with ammonium persulfate, it is not necessary to preconcentrate the lead by extraction, the method is sensitive, easy to operate and has good precision and accuracy. The detection limit was 0.016 microgram.mL-1, the relative standard deviation of Pb was 3.2%, and the rates of recovery were 94.0%-98.0%.
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186
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Lai JP, Tao ZD, Xiao JY, Chen XH, Zhao SP, Tian YQ, Betz CS. Microinvasive Nd:YAG laser therapy of early glottic carcinoma and its effect on soluble interleukin-2 receptor, interleukin-2, and natural killer cells. Laryngoscope 2001; 111:1585-8. [PMID: 11568609 DOI: 10.1097/00005537-200109000-00017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To investigate the effectiveness of microinvasive Nd:YAG laser therapy in human glottic Tis and T1 carcinomas, as well as its effect on the cellular immune function of the tumor-bearing hosts. STUDY DESIGN We treated 34 patients with microinvasive Nd:YAG laser therapy and evaluated its effect on the cellular immune function of the host. METHODS Thirty-four patients with glottic Tis or T1 squamous cell carcinoma were treated with fiberoptic laryngoscopic Nd:YAG laser surgery. Both before and after therapy, serum levels of soluble interleukin-2 receptor (SIL-2R) and interleukin-2 (IL-2), as well as natural killer (NK) cell activity, were determined by means of double-antibody sandwich technique, tritiated thymidine-deoxyribonucleoside incorporation, and iodine 125-uridine-deoxyribonucleoside release technique, respectively. RESULTS All 34 patients tolerated the procedure well. A 3- to 7-year follow-up in a subgroup of 27 patients resulted in an estimated cure rate of 85.2% (23 of 27 patients). In all 27 patients with a regular follow-up, a subjective improvement of phonation was noted after therapy to various degrees. In 74% (20 of 27 patients), voice and speech subjectively recovered to almost normal levels. The post-therapy serum levels of SIL-2R were significantly declined (P <.001), whereas those of IL-2 and the NK activity were significantly elevated (P <.001) as compared with those detected before therapy. CONCLUSIONS Therapy with fiberoptic laryngoscopic Nd:YAG laser surgery is simple, safe, effective and only minimally invasive for patients with glottic Tis or T1 carcinoma. At the same time, it has an immunoenhancing effect on its host.
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187
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Bross PF, Beitz J, Chen G, Chen XH, Duffy E, Kieffer L, Roy S, Sridhara R, Rahman A, Williams G, Pazdur R. Approval summary: gemtuzumab ozogamicin in relapsed acute myeloid leukemia. Clin Cancer Res 2001; 7:1490-6. [PMID: 11410481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
PURPOSE Gemtuzumab ozogamicin (Mylotarg; Wyeth Laboratories, Philadelphia, PA) consists of a semisynthetic derivative of calicheamicin, a cytotoxic antibiotic linked to a recombinant monoclonal antibody directed against the CD33 antigen present on leukemic myeloblasts in most patients with acute myeloid leukemia (AML). In this study, we review the preclinical and clinical profiles of this immunoconjugate and the regulatory review that led to marketing approval by the United States Food and Drug Administration. EXPERIMENTAL DESIGN From the literature and manufacturer's data, we review the activity, tolerability, and pharmacokinetics of gemtuzumab ozogamicin in preclinical and Phase I studies and its activity, efficacy, and side effects in three Phase 2 trials of 142 patients with relapsed AML. RESULTS In Phase I studies, the major toxicity was myelosuppression, especially neutropenia and thrombocytopenia, resulting from the expression of CD33 on myeloid progenitor cells. The Phase 2 dose was 9 mg/m(2) infused i.v. over 4 h, repeated on day 14. A minority of patients experienced acute infusion-related symptoms, usually transient and occasionally requiring hospitalization. The complete response (CR) rate with full recovery of hematopoiesis was 16%. A subset of patients [CRs with incomplete platelet recovery (CRps)] was identified with blast clearance and neutrophil recovery but incomplete platelet recovery. The duration of responses of CRps appeared to be similar to those of the CRs, although the numbers were small. The question of the equivalence of these response groups was a central issue in the review of this new drug application (NDA). After considerable discussion, the Oncology Drugs Advisory Committee recommended allowing inclusion of CRps resulting in an overall response rate in the Phase 2 studies of 30%. In the subgroup of patients over 60 years of age, the overall response rate was 26%. Response duration was difficult to establish because of the high prevalence of postremission therapies. Tolerability and ease of administration may be improved compared with conventional chemotherapy, except for hepatotoxicity, with 31% of patients exhibiting abnormal liver enzymes. One patient died of liver failure in the Phase 2 trials. CONCLUSIONS Marketing approval of gemtuzumab ozogamicin was granted on May 17, 2000 by the United States Food and Drug Administration under the Accelerated Approval regulations. Gemtuzumab ozogamicin is indicated for the treatment of patients with CD33 positive AML in first relapse who are 60 years of age or older and who are not considered candidates for cytotoxic chemotherapy. The approved dose was 9 mg/m(2) i.v. over 4 h and repeated in 14 days. Completion of the ongoing studies of gemtuzumab ozogamicin in relapsed AML and initiation of randomized clinical trials comparing the effects of gemtuzumab ozogamicin in combination with conventional induction chemotherapy to conventional chemotherapy alone on survival are mandated to confirm clinical benefit under the accelerated approval Subpart H regulations. Postmarketing reports of fatal anaphylaxis, adult respiratory distress syndrome (ARDS), and hepatotoxicity, especially venoocclusive disease (VOD) in patients treated with gemtuzumab ozogamicin, with and without associated hematopoietic stem cell transplantation (HSCT), have required labeling revisions and the initiation of a registration surveillance program. Tumor lysis and ARDS have been reported in patients with leukocytes above 30,000/ml treated with gemtuzumab ozogamicin; therefore, the reduction of leukocyte counts to below 30,000/ml is recommended prior to treatment. Patients should be carefully monitored for acute hypersensitivity, hypoxia, and delayed hepatotoxicity following treatment with gemtuzumab ozogamicin.
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Chen XH, Kim CS, Kashiwagi T, Tebayashi S, Horiike M. Antifeedants against Acusta despesta from the Japanese cedar, Cryptomeria japonica II. Biosci Biotechnol Biochem 2001; 65:1434-7. [PMID: 11471750 DOI: 10.1271/bbb.65.1434] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Cryptomeria japonica against Acusta despesta. This hexane soluble-fraction was used to isolate and identify two sesquiterpenols, (-)-cubebol and (+)-2,7(14),10-bisabolatrien-1-ol-4-one, as the active compounds. Both compounds strongly inhibited the feeding behavior of A. despesta at 120 microg/cm2 and 80 microg/cm2 concentrations, respectively.
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189
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Zhao J, Zhang ZP, Chen HS, Chen XH, Zhang XQ. [Preparation and anti-HIV activity study of baicalien and its benzylated derivatives]. YAO XUE XUE BAO = ACTA PHARMACEUTICA SINICA 2001; 32:140-3. [PMID: 11243200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
Baicalein (1) was prepared from baicalin by acid hydrolysis with yield of 24%. 5, 6-Dibenzyl-7-hydroxyl-flanone (4) and 6-benzyl-5, 7-dihydroxyl-flanone (5) were obtained by using different benzylating agents, and then hydrolyzing those benzylated compounds. The total yield of (4) and (5) were 5.9% and 5%, respectively. Both 4 and 5 were less effective than baicalien on inhibition of HIV-1 RT in vitro.
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190
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Li Y, Wang SB, Liu C, Li HX, Hu HY, Liu H, Liu CH, Chen XH. [Genetic studies of 13 loci in Guangdong Han population by two multiplex PCR systems and its forensic application]. FA YI XUE ZA ZHI 2001; 17:82-5. [PMID: 12533862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
Abstract
OBJECTIVE The genetic studies of 13 short tandem repeats(STRs) loci in two multiplex amplification systems were carried out on Chinese Han population in Guangdong. METHODS DNA samples from 328 unrelated individuals were screened. The 13 loci were D3S1358, vWA, FGA, D8S1179, D21S11, D18S51, D5S818, D13S317, D7S820, D16S539, TH01, TPOX and CSF1PO. The PCR products were analyzed and genotyped by ABI 377-96 Sequencer. RESULTS The combined power of discrimination (DP) was 0.999999999999993 and the combined paternity of exclusion(PE) was 99.999%. These 13 loci met the Hardy-Weinberg expectations. CONCLUSION The two multiplex amplification systems were very useful in forensic case investigation.
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191
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Luo ZY, Zhou G, Chen XH, Lu QH, Hu WX. [Isolation of high-quality genomic DNA from plants]. HUNAN YI KE DA XUE XUE BAO = HUNAN YIKE DAXUE XUEBAO = BULLETIN OF HUNAN MEDICAL UNIVERSITY 2001; 26:178-80. [PMID: 12536665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
Abstract
In order to isolate high-quality genomic DNA from medicinal plant tissues enriching polyphenols and polysaccharides, a simple and rapid method based on CTAB extraction for isolating high-quality intact DNA was established by modifying several existing methods. With this technique, the absorbance ratio (A260/A280) of DNAs obtained from fresh and/or dried roots of Panax ginseng, P. Quinquefolius and P. notoginseng was 1.8 approximately. The restriction fragments of DNAs were directly digested with restriction enzyme (EcoR I/Mse I), linked up by T4 DNA ligase and amplified by nested PCR. Reproducible amplified fragment length polymorphism (AFLP) genomic DNA fingerprinting profiles were established with the isolated DNAs. The results demonstrate that the modified technique may be efficient and reliable in isolating high-quality and high-molecular-weight DNAs from fresh and/or dried medicinal plants containing a high content of polyphenols and polysaccharides. We expect that this method can also be applied to other plants.
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192
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He Y, Ma WY, Chen XH, Zhang CN. [Synthesis and activities of 4-deoxy-4 beta-arylmehtylene sulfonylamido-4'-demethylpodophyllotoxins]. YAO XUE XUE BAO = ACTA PHARMACEUTICA SINICA 2001; 36:105-7. [PMID: 12579874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
Abstract
AIM To find new anticancer drug based on the structure of podophyllotoxin. METHODS AND RESULTS 4-Deoxy-4-beta-arylmethylenesulfonylamido-4'- demethylpodophyllotoxins were (1-15) synthesized and their antitumour activities against KB cells and L1210 leukemia cells were tested. CONCLUSION These compounds are new compounds. Among them, compounds 2, 3, 8, 9, 11 and 12 showed antitumour activities. When halides exist on the aryl ring of substituted sulfonyl group, the corresponding compound has relatively higher activities. The stereo factor is important for the activities.
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Chen XH, Gao RL, Xu WH. [Effect of ginsenosides in inducing proliferation and transcription factor of erythrocytic, granulo-monocytic and megakarocytic cell lines]. ZHONGGUO ZHONG XI YI JIE HE ZA ZHI ZHONGGUO ZHONGXIYI JIEHE ZAZHI = CHINESE JOURNAL OF INTEGRATED TRADITIONAL AND WESTERN MEDICINE 2001; 21:40-2. [PMID: 12577377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
Abstract
OBJECTIVE To investigate the action of Ginsenosides (GS) in inducing transcription factor c-fos and GATA-1 to explore the mechanism of GS in hematopoietic cells. METHODS The proliferation effects of GS on granulocytic (HL-60), monocytic (U937), erythrocytic (K562) and megaryocytic (Meg-01) cell lines were observed by using proliferation test of MTT and colony formation of progenitor cells. The combining reaction of transcription factors c-fos and GATA-1 with nuclear protein antigen were analyzed by Western Blot after being treated by GS. RESULTS (1) GS (10 micrograms/ml) could stimulate and promote proliferation of 3 cell lines with significant difference between GS and non-GS control (P < 0.05 in all) in both MTT test and colony assay. (2) After treatment with GS, c-fos protein in HL-60, K562 and Meg-01 cell lines was increased by 1.5, 2.0 and 2.5 fold respectively, while U937 cell did not express c-fos. (3) Except that U937 cell hadn't expressed GATA-1, the other cell lines after the treatment by GS, the GATA-1 protein level was elevated to 1.5, 2.1 and 1.3 fold of that before treatment. CONCLUSION The proliferation of three lines initiated by GS was involved in transcription factor c-fos or GATA-1, which could pay the role in the GS induced up-regulation correlated with proliferation and differentiation of hematopoiesis.
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Leoni MJ, Chen XH, Mueller AL, Cheney J, McIntosh TK, Smith DH. NPS 1506 attenuates cognitive dysfunction and hippocampal neuron death following brain trauma in the rat. Exp Neurol 2000; 166:442-9. [PMID: 11085909 DOI: 10.1006/exnr.2000.7513] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although several noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonists have been shown to be substantially efficacious in experimental models of brain trauma, side effects associated with this class of compounds have impeded clinical application. Therefore, new noncompetitive NMDA receptor antagonists have been developed, including NPS 1506, that appear to be nontoxic but retain efficacy. In the present study, we evaluated the efficacy of NPS 1506 in a model of parasagittal fluid percussion brain trauma in the anesthetized rat. Administration of 1 mg/kg NPS 1506 at both 10 min and 4 h posttrauma induced no changes in brain temperature, mean arterial pressure, pulse, or arterial blood gasses. At 1 week postinjury, animals treated with the same dosing regimen of NPS 1506 demonstrated a dramatic attenuation of memory dysfunction evaluated by a water maze task (P < 0.02) and had greatly reduced neuron death in the CA3 subfield of the hippocampus (P < 0.01). However, NPS 1506 treatment did not significantly affect the extent of cortical tissue loss following injury. Since memory dysfunction and hippocampal damage are common and potentially related consequences of brain trauma in humans, our results suggest that NPS 1506 treatment may have clinical utility.
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Koopman C, Gore-Felton C, Marouf F, Butler LD, Field N, Gill M, Chen XH, Israelski D, Spiegel D. Relationships of perceived stress to coping, attachment and social support among HIV-positive persons. AIDS Care 2000; 12:663-72. [PMID: 11218551 DOI: 10.1080/095401200750003833] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The purpose of this study was to examine the relationships of coping, attachment style and perceived social support to perceived stress within a sample of HIV-positive persons. Participants were 147 HIV-positive persons (80 men and 67 women). Multiple regression analysis was used to examine the relationships of the demographic variables, AIDS status, three coping styles, three attachment styles and perceived quality of general social support with total score on the Perceived Stress Scale (PSS). PSS score was significantly associated with less income, greater use of behavioural and emotional disengagement in coping with HIV/AIDS, and less secure and more anxious attachment styles. These results indicate that HIV-positive persons who experience the greatest stress in their daily lives are those with lower incomes, those who disengage behaviourally/emotionally in coping with their illness, and those who approach their interpersonal relationships in a less secure or more anxious style.
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Wen HH, Chen XH, Yang WL, Zhao ZX. Same superconducting criticality for underdoped and overdoped La2-xSrxCuO4 single crystals. PHYSICAL REVIEW LETTERS 2000; 85:2805-2808. [PMID: 10991238 DOI: 10.1103/physrevlett.85.2805] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2000] [Indexed: 05/23/2023]
Abstract
By measuring the superconducting diamagnetic moments for an underdoped and an overdoped La2-xSrxCuO4 single crystal with equal quality and roughly equal transition temperatures, it is found that the underdoped sample has only one transition which corresponds to H(c2), but the overdoped sample has two transitions with the higher one at H(c2). Further investigation reveals the same upper-critical field H(c2) for both samples although the overall charge densities are very different, indicating the possibility of a very direct and detailed equivalence of the superconducting condensation process in the two doping limits. The second transition for the overdoped sample can be understood as the bulk coupling between the superconducting clusters produced by macroscopic phase separation.
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Smith DH, Nonaka M, Miller R, Leoni M, Chen XH, Alsop D, Meaney DF. Immediate coma following inertial brain injury dependent on axonal damage in the brainstem. J Neurosurg 2000; 93:315-22. [PMID: 10930019 DOI: 10.3171/jns.2000.93.2.0315] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT Immediate and prolonged coma following brain trauma has been shown to result from diffuse axonal injury (DAI). However, the relationship between the distribution of axonal damage and posttraumatic coma has not been examined. In the present study, the authors examine that relationship. METHODS To explore potential anatomical origins of posttraumatic coma, the authors used a model of inertial brain injury in the pig. Anesthetized miniature swine were subjected to a nonimpact-induced head rotational acceleration along either the coronal or axial plane (six pigs in each group). Immediate prolonged coma was consistently produced by head axial plane rotation, but not by head coronal plane rotation. Immunohistochemical examination of the injured brains revealed that DAI was produced by head rotation along both planes in all animals. However, extensive axonal damage in the brainstem was found in the pigs injured via head axial plane rotation. In these animals, the severity of coma was found to correlate with both the extent of axonal damage in the brainstem (p < 0.01) and the applied kinetic loading conditions (p < 0.001). No relationship was found between coma and the extent of axonal damage in other brain regions. CONCLUSIONS These results suggest that injury to axons in the brainstem plays a major role in induction of immediate posttraumatic coma and that DAI can occur without coma.
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Li SM, Chen XH, Gross RA, McCarthy SP. Hydrolytic degradation of PCL/PEO copolymers in alkaline media. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2000; 11:227-233. [PMID: 15348037 DOI: 10.1023/a:1008920326988] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
PCL/PEO copolymers with different compositions were obtained from ring opening polymerization of epsilon-caprolactone in the presence of ethylene oxide and characterized by various analytical techniques. Data collected from DSC and X-ray diffractometry suggested that the copolymer chains possess a blocky structure, leading to both PCL and PEO-type crystalline structures. Hydrolytic degradation of these copolymers was carried out in a pH=10.6 carbonate buffer solution at 37 degrees C. Comparison was made with a PCL homopolymer and a PCL/PEG blend which had the same gross composition as one of the copolymers. The results showed that the presence of PEO sequences considerably enhanced the hydrophilicity of the copolymers as compared with PCL homopolymer. Nevertheless, the degradability of PCL chains was not enhanced due to the phase separation between the two components. These materials should be of great interest for biomedical uses such as matrices for sustained drug delivery because of the presence of both hydrophilic and hydrophobic microdomains.
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Nonaka M, Chen XH, Pierce JE, Leoni MJ, McIntosh TK, Wolf JA, Smith DH. Prolonged activation of NF-kappaB following traumatic brain injury in rats. J Neurotrauma 1999; 16:1023-34. [PMID: 10595819 DOI: 10.1089/neu.1999.16.1023] [Citation(s) in RCA: 137] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Activation of transcription factor, nuclear factor kappa B (NF-kappaB), has been shown to play a key role in inflammatory response, neuronal survival and signaling. We investigated the regional and temporal distribution of activated NF-kappaB in rats at 1 h, 2 h, 24 h, 48 h, 1 week, 2 weeks, 1 month, 2 months, 6 months, and 1 year following brain injury in rats. Early after trauma (1-2 h), activated NF-kappaB was detected in axons, and subsequently found in the cytoplasm and nucleus of neurons by 24 h and lasting up to 1 week. In addition, by 24 h posttrauma, activated NF-kappaB was detected in microglia/macrophages and astrocytes in injured cortex. Surprisingly, this activation persisted for at least 1 year following injury in the cortex, primarily at the margins of progressively enlarging ventricle. Activated NF-kappaB was also detected in endothelial cells, as early as 1 h, and persisted for up to 1 year. These results suggest that a neuronal response to brain trauma includes the activation of NF-kappaB first in the axon with subsequent translocation to the nucleus. Furthermore, these results demonstrate that remarkably prolonged activation of NF-kappaB in glia is found in the same regions undergoing persistent atrophy, suggesting NF-kappaB activation may play a role in long-term inflammatory processes following brain trauma.
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Jiang JD, Wang Y, Wang ZZ, Chen XH, Guo ZM, Pan HL, Bekesi GJ, Wang AX, Chen HS. Low frequency of the ccr5delta32 HIV-resistance allele in mainland China: identification of the first case of ccr5delta32 mutation in the Chinese population. SCANDINAVIAN JOURNAL OF INFECTIOUS DISEASES 1999; 31:345-8. [PMID: 10528870 DOI: 10.1080/00365549950163752] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
A 32-bp deletion on the CCR5 gene (ccr5delta32) confers resistance to HIV-1 infection. This deletion is common in Caucasians, but rare in Asians. Since the frequency of the ccr5delta32 allele of Chinese in mainland China has been unknown we investigated the ccr5delta32 mutation in a cohort of 407 Chinese people in this area. A 225-bp fragment of CCR5 encompassing the 32-bp region was analysed by PCR, hybridization and sequencing. Only 1 out of 407 subjects was heterozygous for ccr5delta32 and no homozygotes were detected. The frequency of ccr5delta32 in this cohort is thus 0.00123, i.e. much lower than that of Caucasians. The ccr5delta32 heterozygote is a healthy young man. To our knowledge this is the first ccr5delta32 mutant found in Chinese people. The results indicate that ccr5delta32 does exist in Chinese people, but at very low frequency. This suggests that ccr5delta32 is not a significant factor for the genetic resistance to HIV-1 in Chinese people.
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