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Showing papers by "Xiang Zhang published in 2000"


Journal ArticleDOI
TL;DR: In this paper, the authors studied the possible correlation between flux densities (FR, FK, FO, FX, and Fγ) in the radio, infrared, optical, X-ray, and γ-ray wave bands, in both the low and high states.
Abstract: Using multi-wave band data for 61 γ-ray-loud blazars (17 BL Lacertae objects and 44 flat-spectrum radio quasars [FSRQs]), we have studied the possible correlation between flux densities (FR, FK, FO, FX, and Fγ) in the radio, infrared, optical, X-ray, and γ-ray wave bands, in both the low and high states. For some blazars, it is hard to determine whether they are in a low or a high state because only one data point is available for each of them; initially, we exclude these blazars in our analysis. However, we include these blazars in later analysis by temporarily assuming them to be in a low state or a high state. Our main results are as follows. There are very strong correlations between FX and FO and between FO and FK in both low and high states. However, a strong correlation between FX and FK exists only in the low state. No definite correlation is found between γ-ray flux density and those of lower energy bands; however, there are hints of anticorrelation between Fγ and FX as well as Fγ and FO and a positive correlation between Fγ and FR. From these results we suggest that (1) photons from infrared to X-rays are emitted by the same particles via synchrotron radiation and (2) if γ-rays are mainly produced by an inverse Compton scattering mechanism, it seems that the up-scattered soft photons are from external photons rather than synchrotron photons.

63 citations


Journal ArticleDOI
TL;DR: In this article, the authors demonstrate the effects of NH3 flow modulation on the lateral growth rate and morphology of GaN stripes employing lateral epitaxial overgrowth (LEO) by metalorganic chemical vapor deposition.
Abstract: We demonstrate the effects of NH3 flow modulation on the lateral growth rate and morphology of GaN stripes employing lateral epitaxial overgrowth (LEO) by metalorganic chemical vapor deposition. The self-limiting growth mechanism, enhanced Ga diffusion on the (0001) plane, and Ga lateral supply are used to explain our observations. A lateral overgrowth rate to a vertical growth rate ratio of 2.1 and fully coalesced LEO GaN stripes after 1 h growth have been achieved.

48 citations


Journal ArticleDOI
Xiaoning Jiang1, Cheng Sun1, Xiang Zhang1, Baomin Xu1, Y.H Ye1 
TL;DR: In this paper, the microstereolithography mSL of lead zirconate titanate PZT thick films on platinum-buffered silicon substrates is reported for the first time.
Abstract: The microstereolithography mSL of lead zirconate titanate PZT thick films on platinum-buffered silicon substrates is reported for . the first time in this paper. Crack-free PZT thick films 80-130 mm thick have been fabricated by laser direct-write UV polymerization from the HDDA-based UV curable PZT suspensions. The characterization of the fired films shows dielectric permittivities of 120-200, 2 . tangent loss of 0.92-2.5% and remnant polarization of 0.9-1.7 mCrcm . The field-induced longitudinal piezoelectric coefficient d of 33 . y3 an 84-mm thick film is 100 pCrN and the piezoelectric voltage coefficient g is about 59.5 = 10 V mrN. These results 33 demonstrated the potential for mSL of advanced piezoelectric microsensors and microactuators. q 2000 Elsevier Science B.V. All rights reserved.

39 citations


Journal ArticleDOI
TL;DR: In this article, a sparse nucleation process on sapphire (0001) substrates has been developed for the growth of GaN thin films, where the density of nucleation sites is reduced to only 4×104 cm−2.
Abstract: A sparse nucleation process on sapphire (0001) substrates has been developed for the growth of GaN thin films. The density of nucleation sites is reduced to only 4×104 cm−2. Based on this process, we performed direct lateral epitaxial overgrowth (LEO) of GaN by metalorganic chemical vapor deposition on patterned SiO2/sapphire (0001) substrates. An aggregate lateral to vertical growth rate ratio of around 2:1 was achieved after the coalescence of the GaN stripes. Cathodoluminescence imaging shows strong and uniform near-band gap luminescence from LEO regions and confirms the improved quality of LEO GaN, which is further supported by atomic force microscopy analysis.

15 citations


Journal ArticleDOI
TL;DR: Relativistic discrete-variational local density functional calculations on endohedral Gd@C60, La@C 60,Gd@ C74, and La-C74 are performed in this paper.
Abstract: Relativistic discrete-variational local density functional calculations on endohedral Gd@C60, La@C60,Gd@C74, and La@C74 are performed. All the C60- and C74-derivedlevels are lowered upon endohedral Gd and La doping. Both the Gd (4f75d16s2) and La (5d16s2) atoms only donate their two 6s valence electrons to the cages, leaving behind their 5d electrons when they are placed at the cage centers. Compared with large-band-gap C60, small-band-gap C74 and Gd (La)-metallofullerenes have strong both electron-donating and electron-accepting characters, and the calculated ionization potentials and electron affinities for them agree well with the available experimental data.

15 citations


Journal ArticleDOI
01 May 2000
TL;DR: In this article, the benefits of cold expanding fastener holes at various stages of the fatigue life in a 2024-T351 low-load transfer joint were examined and the results were pre-cycled to 25, 50 and 7...
Abstract: This paper examines the benefits of cold expanding fastener holes at various stages of the fatigue life in a 2024-T351 low-load transfer joint. The specimens were pre-cycled to 25, 50 and 7...

10 citations


Journal ArticleDOI
TL;DR: In this article, a three-component effective medium model was proposed to characterize the quality of thin gallium nitride (GaN) films grown on silicon substrates by IR spectroscopy and scanning electron microscopy (SEM).

8 citations


Journal ArticleDOI
TL;DR: In this paper, the problem of low velocity impact damage in fabricated structures made of laminated carbon-epoxy composites was addressed and it was shown that the threshold energy for onset of delamination can be predicted using a dynamic finite element code.
Abstract: This paper addresses the problem of the complex nature of low velocity impact damage in fabricated structures made of laminated carbon-epoxy composites. The structures chosen are stiffened compression panels since these are the most vulnerable to delamination and debonding. Four ‘top-hat’ stiffened panels were tested and predicted using a dynamic finite element code. The panels all had considerable postbuckling strength so the impact sites were carefully chosen to inflict maximum loss of strength. It was shown that the threshold energy for onset of delamination can be predicted using a dynamic finite element code. The amount of delamination or debonding is also predicted using a crude strength-based criterion, which seems to work only because the maximum impact force is a transient phenomenon of short duration.

6 citations


Journal Article
Wu Q1, Guo X, Fan H, Zhou T, Tan G, Guo Q, Chen P, Xiang Zhang, Gengxin Luo, Xu M 
TL;DR: Hypermethylation of P(15)(INK4B) gene is one of the main causes of its inactivation and was closely related to the development of malignant hematopoietic diseases.
Abstract: OBJECTIVE To study the effect of operative region hypermethylation gene in human malignant hematopoietic tumors. METHODS The abnormal methylation rate of P(15)(INK4B) gene 5'CpG island in 68 cases of malignant hematopoietic tumor samples were determined by methylation specific PCR using bisulfite modified DNA. RESULTS The methylation rates of P(15)(INK4B) were 84%, 0, 50% and 75%, respectively, for 25 cases of acute myeloid leukemia (AML), 15 chronic myeloid leukemia (CML), 16 myelodysplastic syndrome (MDS) and 12 multiple myeloma (MM). P(15)(INK4B) gene was frequently methylated in patients with high risk MDS and early stage of MM. CONCLUSION Hypermethylation of P(15)(INK4B) gene is one of the main causes of its inactivation. Hypermethylation of CpG island was closely related to the development of malignant hematopoietic diseases.

5 citations


01 Jan 2000
TL;DR: Author(s): Olson, Arthur J.
Abstract: Author(s): Olson, Arthur J.; Pailthorpe, B. A.; Toga, A. W.; Wunsch, C. I.; Genetti, J. D.; Nadeau, D. R.; Sanner, M. F.; Bajaj, C.; Bordes, N.; De Castro, A. G.; Charles, R. D.; Moreland, J. L.; Omelchenko, A.; Shamir, A.; Parks, S.; Zhang, X.; Hamann, Bernd; Takanashi, Ikuko; Thompson, P. M.; Baden, S. B.; Stammer, D.; Saltz, J. H.; Meyer, Joerg

2 citations


Journal Article
TL;DR: The visible spectra of forty-five synthesized polyaluminium ferric chloride aqueous solutions with different [OH]/[Al + Fe] (B) and nAl/nFe(molar ratio) were investigated and it was thought that these points stand for the dynamic equilibrium of OH- between the polynucleus hydroxyl Fe(III) and Al(III).
Abstract: The visible spectra of forty-five synthesized polyaluminium ferric chloride (PAFC) aqueous solutions with different [OH]/[Al + Fe] (B) and nAl/nFe(molar ratio) were investigated. The results showed that their absorbances A of shoulder at 460 nm are all linear interrelationship with their B. We made the curve of absorbance A of PAFC with same B vs. nAl/nFe, there was a turning point. All of these points just located at the places of pH value rising higher in pH- nAl/nFe diagrams. For these reason, we thought that these points stand for the dynamic equilibrium of OH- between the polynucleus hydroxyl Fe(III) and Al(III). These points made certain relationship among the absorbance A at 460 nm, basicities and total Fe(III) concentration of PAFC solutions.

01 Feb 2000
TL;DR: In this article, a strategy is developed for predicting easily the threshold energy for delamination caused by impact, whatever the nature of the laminated structure, and actual delamination and fibre damage is also predicted and the consequent compression-after-impact strengths.
Abstract: : A strategy is developed for predicting easily the threshold energy for delamination caused by impact, whatever the nature of the laminated structure. The actual delamination and fibre damage is also predicted and the consequent compression-after- impact strengths. The latter strategies may be approximate but current research is pointing the way to more accurate solutions based on finding energy-release-rates around the delamination front.

Journal Article
Yungui Wang, Wanzhuo Xie, Qiu Y, Gu Z, Xiang Zhang 
TL;DR: The proliferation of CD(4)(+) cells after cultured with DC may become an indicator for the function of antigen loaded DC and for the efficiency of DC immunotherapy.
Abstract: OBJECTIVE To study the effect of antigen loading on dendritic cells (DC). METHODS DCs collected from peripheral blood monocytes were loaded with a tumor antigen from XG-7 cell line. These DCs were then co-cultured with allogeneic T cells and were compared with those DCs without antigen exposure. RESULTS Although DCs showed no change in their phenotypes after cultured with the antigen, they secreted more IL-12, and became more powerful in allogenic mixed lymphocyte reaction (MLR). Antigen-loaded DC stimulated more CD(4)(+) cells to proliferate than nonantigen-loaded DCs did. These CD(4)(+) cells did not kill XG-7 cells, but promoted CD(8)(+) cells' ability to inhibit the XG-7 proliferation. CONCLUSION The proliferation of CD(4)(+) cells after cultured with DC may become an indicator for the function of antigen loaded DC and for the efficiency of DC immunotherapy.

Journal ArticleDOI
TL;DR: InGaN thin films were grown by low-pressure metalorganic-vapor-phaseepitaxy (MOVPE) and characterized by cathodoluminescence (CL) and scanning electron microscopy (SEM).
Abstract: InGaN thin films were grown by low-pressure metalorganic-vapor-phase-epitaxy (MOVPE) and characterized by cathodoluminescence (CL) and scanning electron microscopy (SEM). SEM images showed that InGaN samples have inverted hexagonal pits which are formed by the In segregation on the (1011) surfaces. Room temperature CL at the wavelengths corresponding to the GaN band edge, the In-poor and In-rich regions showed that the In–rich regions formed at the periphery of the hexagonal pits.