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Su ZQ, Wu XL, Bao MJ, Li CW, Kong SZ, Su ZR, Lai XP, Li YC, Chen JN. Isolation of (-)-Patchouli Alcohol from Patchouli Oil by Fractional Distillation and Crystallization. TROP J PHARM RES 2014. [DOI: 10.4314/tjpr.v13i3.7] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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Wu XL, Wang JH, Hu SH, Tao J. Serum prolactin levels and the acute-phase efficacy in drug-naïve schizophrenia treated with ziprasidone and olanzapine (translated version). East Asian Arch Psychiatry 2012; 22:7-11. [PMID: 22447799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
OBJECTIVES. To study the efficacy and associated serum prolactin levels of ziprasidone and olanzapine treatment in drug-naïve schizophrenia patients. METHODS. All 78 inpatients with drug-naïve schizophrenia were recruited from the Department of Psychology, The Third Affiliated Hospital of Sun Yat-sen University. They were divided into either olanzapine group (n = 49 [24 men, 25 women]; mean [standard deviation] age, 24 [6] years) or ziprasidone group (n = 29 [14 men, 15 women]; mean [standard deviation] age, 23 [7] years), all of whom were treated for 4 weeks. The serum prolactin level, the Positive and Negative Syndrome Scale (PANSS), Clinical Global Impression-Severity (CGI-S), and Clinical Global Impression-Improvement scores were measured before and at the end of treatment. RESULTS. In the olanzapine group, the respective mean (standard deviation) PANSS and CGI-S scores after the treatment (62 ± 15 and 3 ± 1) were significantly lower than those before the treatment (104 ± 14 and 6 ± 1) [p < 0.01]. In the ziprasidone group, the corresponding scores after the treatment (75 ± 20 and 4 ± 1) were also significantly lower than those before the treatment (104 ± 17 and 6 ± 1) [p < 0.01]. The decreases in mean (standard deviation) PANSS total (42 ± 17) and PANSS positive scores (12 ± 6) in the olanzapine group were significantly higher than those in the ziprasidone group (29 ± 12 and 6 ± 4, respectively) [p < 0.01]. The increase of serum prolactin in the ziprasidone female group (47 ± 51 µg/L) was significantly higher than that in the ziprasidone male group (17 ± 11 µg/L), the olanzapine male group (5 ± 16 µg/L), and the olanzapine female group (21 ± 34 µg/L) [p < 0.05]. CONCLUSIONS. Both ziprasidone and olanzapine are effective for treating drug-naïve acute schizophrenia, but olanzapine was superior to ziprasidone in terms of positive and general psychopathological symptoms. In women, ziprasidone was associated with greater changes in prolactin level than olanzapine.
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Huang R, Song J, Wang X, Guo YQ, Song C, Zheng ZH, Wu XL, Chu PK. Origin of strong white electroluminescence from dense Si nanodots embedded in silicon nitride. OPTICS LETTERS 2012; 37:692-4. [PMID: 22344150 DOI: 10.1364/ol.37.000692] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Strong white electroluminescence (EL) from SiN-based devices containing Si nanodots with a density of more than 4.6×10(12)cm(2) was investigated. The white EL illustrates enhanced light emission with increasing applied voltage and can be divided into two components, a dominant peak at ~710 nm and weak one at ~550 nm, which are close to those of the PL spectra optically pumped by the 325 and 488 nm lines, respectively. Based on the PL characteristics, we propose that the dominant EL band arises from the band-to-band recombination in the dense Si nanodots where quantum confinement plays a decisive role in the light emission, whereas the weak EL band originates from the radiative Si dangling bond (K0) centers in the silicon nitride matrix.
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Su WN, Wu XL, Wang X, Zhang YY, Shen JC, Zhu JM. Synthesis of crystalline beta-FeSi2 under high-temperature and high-pressure. JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 2011; 11:10963-10966. [PMID: 22409035 DOI: 10.1166/jnn.2011.4067] [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
In this paper, we report the synthesis of crystalline beta-FeSi2 via the reaction of Si and Fe powders under high-temperature and high-pressure. X-ray diffraction and Raman scattering results confirm formation of the beta-FeSi2 phase. Scanning electron microscopy, high-resolution transmission electron microscopy, and selected-area electron diffraction patterns show that the beta-FeSi2 phase coexists with Si phase with small nanocrystal sizes. The formation of the beta-FeSi2 phase is a result of Si diffusion into Fe region. The obtained results suggest that the removal of Si phase can be reached through increasing Fe content and prolonging the duration of high-pressure thermal treatment.
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Li TH, Liu LZ, Li XX, Wu XL, Chen HT, Chu PK. Oxygen vacancy density-dependent transformation from infrared to Raman active vibration mode in SnO2 nanostructures. OPTICS LETTERS 2011; 36:4296-4298. [PMID: 22048396 DOI: 10.1364/ol.36.004296] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Raman spectra acquired from spherical, cubic, and cuboid SnO2 nanocrystals (NCs) reveal a morphologically independent Raman mode at ∼302 cm(-1). The frequency of this mode is slightly affected by the NC size, but the intensity increases obviously with decreasing NC size. By considering the dipole changes induced by oxygen vacancies and derivation based on the density functional theory and phonon confinement model, an oxygen vacancy density larger than 6% is shown to be responsible for the transformation of the IR to Raman active vibration mode, and the intensity enhancement is due to strong phonon confinement.
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Gan ZX, Xiong SJ, Wu XL, He CY, Shen JC, Chu PK. Mn²+-bonded reduced graphene oxide with strong radiative recombination in broad visible range caused by resonant energy transfer. NANO LETTERS 2011; 11:3951-3956. [PMID: 21848298 DOI: 10.1021/nl202240s] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The photoluminescence (PL) characteristics of Mn(2+)-bonded reduced graphene oxide (rGO) are studied in details. The Mn(2+)-bonded rGO is synthesized using MnO(2)-decorated GO as the intermediate products and ideal tunable PL is obtained by enhancing the long-wavelength (450-550 nm) emission. The PL spectra excited by different wavelengths are analyzed to elucidate the mechanism, and the resonant energy transfer between Mn(2+) and sp(2) clusters of the rGO appears to be responsible for the enhanced long-wavelength emission. To examine the effect of Mn(2+) on the long-wavelength emission from the Mn(2+)-bonded rGO, the PL characteristics of Mn(2+)-bonded rGO with smaller Mn concentrations are studied and weaker emission is observed. Our theoretical calculation corroborates the experimental results.
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Chen L, Li DQ, Zhong J, Wu XL, Chen Q, Peng H, Liu SQ. IL-17RA aptamer-mediated repression of IL-6 inhibits synovium inflammation in a murine model of osteoarthritis. Osteoarthritis Cartilage 2011; 19:711-8. [PMID: 21310253 DOI: 10.1016/j.joca.2011.01.018] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2010] [Revised: 01/28/2011] [Accepted: 01/31/2011] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Generate DNA aptamers to inhibit IL-17RA-mediated synovial inflammation in an experimental mouse model of osteoarthritis (OA). METHODS A novel cell-SELEX method was applied to obtain DNA aptamers specific for IL-17RA. A single-stranded (ss) DNA library with four(30) probes was synthesised. By incubating this library with NIH3T3 cells, we collected DNA ligands that could bind the cell surface. The collected ligands were incubated with IL-17RA-deficient NIH3T3 cells, and unbound ssDNA was harvested from the supernatant for the next round of selection. After 12 cycles, specific aptamers against IL-17RA were generated. For animal experiments, a meniscectomy was performed on Balb/C mice to generate an animal model of OA. Mice received weekly intra-articular (i.a.) injections of aptamers or control treatments for 6 weeks. Synovial membranes were evaluated by histomorphology and the mRNAs of critical inflammatory cytokines were measured by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS An aptamer termed RA10-6 was obtained that could efficiently block IL-17 binding to IL-17RA in a dose-dependent manner in vitro. Histological examination and quantitative RT-PCR results showed that OA mice that injected with RA10-6, especially in combination with celecoxib demonstrated inhibition of synovial thickening and reduction in IL-6 levels in the synovial tissue. CONCLUSION Our results suggest that RA10-6 can inhibit synovial inflammation by blocking IL-17/IL-17RA-mediated IL-6 expression. RA10-6 acted synergistically with celecoxib to inhibit IL-6 expression in synovial tissues. Thus, aptamers targeting IL-17RA might serve as potent adjunctive agents for the early treatment of OA.
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Wu XL, Xiong SJ, Liu Z, Chen J, Shen JC, Li TH, Wu PH, Chu PK. Green light stimulates terahertz emission from mesocrystal microspheres. NATURE NANOTECHNOLOGY 2011; 6:103-6. [PMID: 21240282 DOI: 10.1038/nnano.2010.264] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Accepted: 11/30/2010] [Indexed: 05/12/2023]
Abstract
The discovery of efficient sources of terahertz radiation has been exploited in imaging applications, and developing a nanoscale terahertz source could lead to additional applications. High-frequency mechanical vibrations of charged nanostructures can lead to radiative emission, and vibrations at frequencies of hundreds of kilohertz have been observed from a ZnO nanobelt under the influence of an alternating electric field. Here, we observe mechanical resonance and radiative emission at ∼ 0.36 THz from core-shell ZnO mesocrystal microspheres excited by a continuous green-wavelength laser. We find that ∼ 0.016% of the incident power is converted into terahertz radiation, which corresponds to a quantum efficiency of ∼ 33%, making the ZnO microspheres competitive with existing terahertz-emitting materials. The mechanical resonance and radiation stem from the coherent photo-induced vibration of the hexagonal ZnO nanoplates that make up the microsphere shells. The ZnO microspheres are formed by means of a nonclassical, self-organized crystallization process, and represent a straightforward route to terahertz radiation at the nanoscale.
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Liu LZ, Wang J, Wu XL, Li TH, Chu PK. Longitudinal optical phonon-plasmon coupling in luminescent 3C-SiC nanocrystal films. OPTICS LETTERS 2010; 35:4024-4026. [PMID: 21124600 DOI: 10.1364/ol.35.004024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Glycerol-passivated 3C-SiC nanocrystal (NC) solid films with tunable blue photoluminescence show abnormal longitudinal optical (LO) phonon behavior. As the NC size increases, the LO phonon intensity increases in the Raman spectra of the solid films and is even larger than that of the transverse optical mode. The Raman spectra cannot be fitted by using only the phonon confinement model. When further considering the coupling between the LO phonon and plasmon induced by the surface deformation potential in the glycerol layer, good agreement is achieved between the experiments and theory. This indicates that the coupled LO phonon-plasmon effect arising from the surface bonding structure plays a crucial role in the modified LO phonon behavior.
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Han SL, Wu XL, Jia ZR, Wang PF. Adult hepatic cavernous haemangioma with highly elevated alpha-fetoprotein. Hong Kong Med J 2010; 16:400-402. [PMID: 20890007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023] Open
Abstract
A 35-year-old Chinese man presented with dull pain in the right hypochondrial region for the previous 2 months. Laboratory examination revealed that his serum alpha-fetoprotein level was 1890 microg/L (reference range, 0-20 microg/L), and computed tomographic scan showed a hypodense lesion in the left liver lobe. At laparotomy, a dark reddish soft tumour (3.0 x 3.5 cm in diameter) was found in the medial segment of the liver (segment III). The tumour became markedly smaller than that before resection, and a vessel-like structure was found on the cut surface. Intra-operative pathology and postoperative histopathology examinations revealed that the tumour was a cavernous haemangioma of the liver. The serum alpha-fetoprotein level decreased to 3.5 microg/L by the fourth postoperative week. Clinicians should be aware that some rare tumours besides hepatocellular carcinoma and endodermal sinus tumours (yolk sac tumour), for example, hepatic haemangioma, can produce alpha-fetoprotein.
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Zeng DX, Wu XL, Li YH. First Report of Root and Stem Rot Caused by Phytophthora nicotianae on Peperomia tetraphylla in China. PLANT DISEASE 2010; 94:1171. [PMID: 30743707 DOI: 10.1094/pdis-94-9-1171c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Peperomia tetraphylla, an evergreen herb, is becoming increasingly popular as a potted ornamental plant in southern China. In the summer of 2008, in some commercial flower nurseries in Shenzhen, Guangdong Province, P. tetraphylla showed extensive black stem and root rot, with leaves dropping from the rotten stem. Small pieces (approximately 3 mm2) of stems and leaves were excised from the margins of the black lesions, surface disinfected for 30 s to 1 min in 0.1% HgCl2, plated onto potato dextrose agar (PDA), and incubated at 25°C in the dark. All the plated samples yielded Phytophthora, and microscopic examination of pure cultures grown on PDA plates showed arachnoid colonies with abundant aerial mycelium, chlamydospores, and a few sporangia. Numerous sporangia were formed in sterile soil extract. Sporangia were ovoid or obpyriform, noncaducous, with prominent solitary papillae, and measured 31 to 52 μm (average 38 μm) × 21 to 34 μm (average 27 μm). Chlamydospores were spherical and 21 to 34 μm in diameter (average 28 μm). The internal transcribed spacer (ITS) region of rDNA of a single isolate was amplified using primers ITS4/ITS5 and sequenced (2). The ITS sequence, when submitted for a BLAST search in the NCBI database, showed 100% homology with the sequences of two reference isolates of Phytophthora nicotianae (Accession Nos. AY833526 and EU433396) and the consensus ITS sequence was deposited in the NCBI as Accession No. GQ499373. The isolate was identified as Phytophthora nicotianae on the basis of morphological and molecular characteristics (1). Pathogenicity of the isolate was confirmed by inoculating 1-year-old plants of P. tetraphylla growing in pots. The isolate was grown for 7 days on PDA plates and mycelial plugs, 5 mm in diameter and taken from the advancing margins of the colonies, were buried approximately 1 cm deep near the base of the stem in such a way that the mycelium on the plugs was in contact with the surface of the stem, which had been wiped earlier with 70% ethanol and gently wounded with a needle. Plants treated the same way but inoculated with sterile PDA plugs served as control plants. Three plants in each pot were inoculated and there were five replications each for the treatment and the control. All plants were kept in a greenhouse at 22 to 32°C. After 6 to 7 days, the inoculated plants showed black lesions around the mycelial plugs; symptoms of root and stem rot developed rapidly thereafter and the plants collapsed within 2 weeks. All symptoms on the inoculated plants were identical to those observed in naturally diseased plants, whereas the control plants remained healthy. The same fungus was consistently reisolated from the inoculated plants. To our knowledge, this is the first report of Phytophthora nicotianae on P. tetraphylla in China. References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (2) J. B. Ristaino et al. Appl. Environ. Microbiol. 64:948, 1998.
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Liu LZ, Wu XL, Zhang ZY, Xu LL, Li TH, Chu PK. Crystalline core/shell Si/SiO2 nanotubes formed via interfacial stress imbalance. JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 2010; 10:5583-5586. [PMID: 21133077 DOI: 10.1166/jnn.2010.2443] [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
Crystalline core/shell Si/SiO2 nanotubes (NTs) with outer diameters of 130-220 nm and lengths of approximately 1 microm have been synthesized using thermal evaporation. High resolution scanning electron microscopy reveals that the NT formation stems from the intrinsic interfacial stress imbalance in the strained Si/SiO2 bilayered film, consequently leading to NTs with different orifice levels. The NT diameters depend strongly on the bilayer film thicknesses and crystal orientations of the Si and SiO2 layers. A modified Timoshenko formula is derived to calculate the dependence of the tube diameter on the bilayer film thickness. The obtained results are consistent well with experimental data.
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Kim I, Wu XL. Tunneling of micron-sized droplets through soap films. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 82:026313. [PMID: 20866911 DOI: 10.1103/physreve.82.026313] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Revised: 06/08/2010] [Indexed: 05/29/2023]
Abstract
When a micron-sized water droplet impacts on a freely suspended soap film with speed v(i), there exists a critical impact velocity of penetration v(C). Droplets with v(i)<v(C) merge and flow with the film after impacts, whereas droplets with v(i)>v(C) tunnel through it. In all cases, the film remains intact despite the fact that the droplet radius (R_{0}=26 μm) is much greater than the film thickness (0<h≲10 μm) . The critical velocity v(C) is measured as a function of h , and interestingly v(C) approaches an asymptotic value v(C0)≃520 cm/s in the limit h→0 . This indicates that in addition to an inertial effect, a deformation or stretching energy of the film is required for penetration. Quantitatively, we found that this deformation energy corresponds to the creation of ∼14 times of the cross-sectional area of the droplet (14πR(0)(2)) or a critical Weber number We(C)}(≡2ρ(w) v(C0)(2) R(0)/σ)≃44 , where ρ(w) and σ are, respectively, the density and the surface tension of water.
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Wu XL, Lieber CM. Hexagonal Domain-Like Charge Density Wave Phase of TaS2 Determined by Scanning Tunneling Microscopy. Science 2010; 243:1703-5. [PMID: 17751279 DOI: 10.1126/science.243.4899.1703] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The structure of the room-temperature charge density wave (CDW) phase in octahedrally coordinated tantalum disulfide, 1T-TaS2, has been a controversial issue for over 15 years. Large-scale scanning tunneling microscope images of the intralayer structure of this phase exhibit a domain-like pattern defined by a variation in the maximum CDW amplitude. The circular domains, consisting of high-amplitude CDWs, are arranged in a regular hexagonal lattice (period 73+/-3 angstroms) that is rotated relative to the CDWs. In addition, from the analysis of atomic resolution images it was determined that there is a well-defined phase shift between the CDWs in adjacent domains, and that within a domain the CDW superlattice is commensurate with the atomic lattice. These results provide evidence for the hexagonal discommensurate CDW phase in 1T-TaS2 and also suggest an explanation for the long-standing controversy concerning the structure of this phase.
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Wang J, Xiong SJ, Wu XL, Li TH, Chu PK. Glycerol-bonded 3C-SiC nanocrystal solid films exhibiting broad and stable violet to blue-green emission. NANO LETTERS 2010; 10:1466-1471. [PMID: 20210349 DOI: 10.1021/nl100407d] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We have produced glycerol-bonded 3C-SiC nanocrystal (NC) films, which when excited by photons of different wavelengths, produce strong and tunable violet to blue-green (360-540 nm) emission as a result of the quantum confinement effects rendered by the 3C-SiC NCs. The emission is so intense that the emission spots are visible to the naked eyes. The light emission is very stable and even after storing in air for more than six months, no intensity degradation can be observed. X-ray photoelectron spectroscopy and absorption fine structure measurements indicate that the Si-terminated NC surfaces are completely bonded to glycerol molecules. Calculations of geometry optimization and electron structures based on the density functional theory for 3C-SiC NCs with attached glycerol molecules show that these molecules are bonded on the NCs causing strong surface structural change, while the isolated levels in the conduction band of the bare 3C-SiC NCs are replaced with quasi-continuous bands that provide continuous tunability of the emitted light by changing the frequencies of exciting laser. As an application, we demonstrate the potential of using 3C-SiC NCs to fabricate full-color emitting solid films by incorporating porous silicon.
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Liu LZ, Wu XL, Gao F, Yang YM, Li TH, Chu PK. Size-independent low-frequency Raman scattering in Ge-nanocrystal-embedded SiO2 films. OPTICS LETTERS 2010; 35:1022-1024. [PMID: 20364204 DOI: 10.1364/ol.35.001022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The peak position and linewidth of the low-frequency Raman mode observed from amorphous silica films embedded with Ge nanocrystals doped with Si show a size-independent behavior. Spectral analysis reveals the formation of a thin amorphous GeSi layer on the surface of the Ge nanocrystal. Theoretical calculation based on a modified three-region model discloses that the acoustic impedance of the interfacial GeSiO layer is responsible for the size-independent behavior. During high-temperature annealing, Ge atoms are segregated from the interface into the core, and the GeSiO interface layer is converted to SiO(2), leading to disappearance of the size-independent vibration mode.
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Weigel KA, de los Campos G, González-Recio O, Naya H, Wu XL, Long N, Rosa GJM, Gianola D. Predictive ability of direct genomic values for lifetime net merit of Holstein sires using selected subsets of single nucleotide polymorphism markers. J Dairy Sci 2009; 92:5248-57. [PMID: 19762843 DOI: 10.3168/jds.2009-2092] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The objective of the present study was to assess the predictive ability of subsets of single nucleotide polymorphism (SNP) markers for development of low-cost, low-density genotyping assays in dairy cattle. Dense SNP genotypes of 4,703 Holstein bulls were provided by the USDA Agricultural Research Service. A subset of 3,305 bulls born from 1952 to 1998 was used to fit various models (training set), and a subset of 1,398 bulls born from 1999 to 2002 was used to evaluate their predictive ability (testing set). After editing, data included genotypes for 32,518 SNP and August 2003 and April 2008 predicted transmitting abilities (PTA) for lifetime net merit (LNM$), the latter resulting from progeny testing. The Bayesian least absolute shrinkage and selection operator method was used to regress August 2003 PTA on marker covariates in the training set to arrive at estimates of marker effects and direct genomic PTA. The coefficient of determination (R(2)) from regressing the April 2008 progeny test PTA of bulls in the testing set on their August 2003 direct genomic PTA was 0.375. Subsets of 300, 500, 750, 1,000, 1,250, 1,500, and 2,000 SNP were created by choosing equally spaced and highly ranked SNP, with the latter based on the absolute value of their estimated effects obtained from the training set. The SNP effects were re-estimated from the training set for each subset of SNP, and the 2008 progeny test PTA of bulls in the testing set were regressed on corresponding direct genomic PTA. The R(2) values for subsets of 300, 500, 750, 1,000, 1,250, 1,500, and 2,000 SNP with largest effects (evenly spaced SNP) were 0.184 (0.064), 0.236 (0.111), 0.269 (0.190), 0.289 (0.179), 0.307 (0.228), 0.313 (0.268), and 0.322 (0.291), respectively. These results indicate that a low-density assay comprising selected SNP could be a cost-effective alternative for selection decisions and that significant gains in predictive ability may be achieved by increasing the number of SNP allocated to such an assay from 300 or fewer to 1,000 or more.
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Wu XL, Xiong SJ, Zhu J, Wang J, Shen JC, Chu PK. Identification of surface structures on 3C-SiC nanocrystals with hydrogen and hydroxyl bonding by photoluminescence. NANO LETTERS 2009; 9:4053-4060. [PMID: 19894694 DOI: 10.1021/nl902226u] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
SiC nanocrystals (NCs) exhibit unique surface chemistry and possess special properties. This provides the opportunity to design suitable surface structures by terminating the surface dangling bonds with different atoms thereby boding well for practical applications. In this article, we report the photoluminescence properties of 3C-SiC NCs in water suspensions with different pH values. Besides a blue band stemming from the quantum confinement effect, the 3C-SiC NCs show an additional photoluminescence band at 510 nm when the excitation wavelengths are longer than 350 nm. Its intensity relative to the blue band increases with the excitation wavelength. The 510 nm band appears only in acidic suspensions but not in alkaline ones. Fourier transform infrared, X-ray photoelectron spectroscopy, and X-ray absorption near-edge structure analyses clearly reveal that the 3C-SiC NCs in the water suspension have Si-H and Si-OH bonds on their surface, implying that water molecules only react with a Si-terminated surface. First-principle calculations suggest that the additional 510 nm band arises from structures induced by H(+) and OH(-) dissociated from water and attached to Si dimers on the modified (001) Si-terminated portion of the NCs. The size requirement is consistent with the observation that the 510 nm band can only be observed when the excitation wavelengths are relatively large, that is, excitation of bigger NCs.
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Wu XL, Xiong SJ, Sun LT, Shen JC, Chu PK. Low-frequency Raman scattering from nanocrystals caused by coherent excitation of phonons. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2009; 5:2823-2826. [PMID: 19882689 DOI: 10.1002/smll.200901579] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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Wu XL, Zhu YT, Wei YG, Wei Q. Strong strain hardening in nanocrystalline nickel. PHYSICAL REVIEW LETTERS 2009; 103:205504. [PMID: 20365992 DOI: 10.1103/physrevlett.103.205504] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Indexed: 05/29/2023]
Abstract
Low strain hardening has hitherto been considered an intrinsic behavior for most nanocrystalline (NC) metals, due to their perceived inability to accumulate dislocations. In this Letter, we show strong strain hardening in NC nickel with a grain size of approximately 20 nm under large plastic strains. Contrary to common belief, we have observed significant dislocation accumulation in the grain interior. This is enabled primarily by Lomer-Cottrell locks, which pin the lock-forming dislocations and obstruct dislocation motion. These observations may help with developing strong and ductile NC metals and alloys.
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Zhu J, Xiong X, Chen HT, Wu XL, Zhang WC, Chu PK. Syntheses and growth mechanisms of 3C-SiC nanostructures from carbon and silicon powders. JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 2009; 9:6648-6654. [PMID: 19908579 DOI: 10.1166/jnn.2009.1323] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Cubic silicon carbide (3C-SiC) nanostructures such as needle- and Y-shaped nanowhiskers, smooth and pagoda-shaped nanorods are synthesized on a large scale from activated carbon and silicon powders at 1250 degrees C under atmospheric pressure. The use of ball-milled silicon powders results in the formation of nanowires and nanowhiskers, whereas non-milled silicon powders lead to nanorods together with unreacted silicon powders. Residual oxygen in the growth chamber initiates the carburization reactions which can proceed without further oxygen consumption. The size and morphology of the as-synthesized 3C-SiC nanostructures are observed to be related to the size and morphology of the starting silicon particles. An oxygen-assisted gas-solid model is proposed to explain the observed nanostructures.
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Zhu J, Xiong X, Wu XL, Chen HT, Zhang WC, Chu PK. Synthesis and characteristics of cubic silicon carbide nanospheres with smooth surfaces. JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 2009; 9:6643-6647. [PMID: 19908578 DOI: 10.1166/jnn.2009.1318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Large quantities of cubic silicon carbide (3C-SiC) nanospheres are synthesized on silicon wafer using zinc sulphide (ZnS) and activated carbon powder. The synthesized nanospheres have smooth surfaces and their diameters range from 20 to 430 nm. The growth of these nanospheres can be explained by a gas-solid model. ZnS powder plays a key role in the formation of activated Si and SiOx. Carburization of the activated Si and SiOx by CO gas leads to the formation of the 3C-SiC nanospheres. Special three-dimensional structure of the product is related to high concentrations of the reactants.
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Chen HT, Xiong SJ, Wu XL, Zhu J, Shen JC, Chu PK. Tin oxide nanoribbons with vacancy structures in luminescence-sensitive oxygen sensing. NANO LETTERS 2009; 9:1926-1931. [PMID: 19435379 DOI: 10.1021/nl900075f] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Vacancy structures in tin oxide nanoribbons fabricated via thermal evaporation and post-processing are probed by luminescence spectroscopy, and interesting properties that bode well for oxygen sensing are observed. Besides a broad 620-nm band, the fabricated tin oxide nanoribbons show a photoluminescence band at 480 nm when the measurement temperature is <100 K. The blue band appears from nanoribbons synthesized under high oxygen pressure or annealed under oxygen. The dependence suggests that the oxygen interstitial and vacancy densities determine the electronic states that produce the blue band. Calculation of the electron structures based on the density functional theory shows that decreased oxygen vacancies or increased oxygen interstitials enhance the 480-nm band but suppress the 620-nm band. The results reported here indicate that the tin oxide nanoribbons with vacancy structures have potential applications in luminescence-sensitive oxygen sensing.
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Zhang J, Wu XL. Persistent skewness of a strongly active scalar. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 79:045301. [PMID: 19518286 DOI: 10.1103/physreve.79.045301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2009] [Indexed: 05/27/2023]
Abstract
We present a skewness measurement of the density fluctuations deltarho[over ]_{l} on scales l in a vertical turbulent soap film driven by a temperature gradient. Unlike the temperature difference deltaT_{l} in Rayleigh-Bénard convection, the density difference in the film is strongly active because deltarho[over ]_{l}/rho[over ]>>deltaT_{l}T[over ] , where the over-bar indicates the mean. Our results show persistent nonzero skewness S_{y}(l) identical with <deltarho[over ]_{l};{3}>/<deltarho[over ]_{l};{2};{3/2}> on different scales along the gravity direction y[over ]; S_{y}(l) is positive for small l and negative for large l. The sign switch occurs approximately at the Bolgiano length scale l_{B}. The simultaneous presence of positive and negative skewnesses is interpreted here as a result of the structures of rising and falling plumes in a strongly stratified medium.
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Wu XL, Zhu YT. Inverse grain-size effect on twinning in nanocrystalline Ni. PHYSICAL REVIEW LETTERS 2008; 101:025503. [PMID: 18764195 DOI: 10.1103/physrevlett.101.025503] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2008] [Revised: 05/25/2008] [Indexed: 05/26/2023]
Abstract
A long-standing controversy exists between molecular dynamics simulations and experiments on the twinning propensity of nanocrystalline (NC) face-centered-cubic metals. For example, three-dimensional molecular dynamics simulations rarely observed twins in NC Ni, whereas experiments readily observed them. Here this discrepancy is resolved by experimental observation of an inverse grain-size effect on twinning. Specifically, decreasing the grain size first promotes twinning in NC Ni and then hinders twinning due to the inverse grain-size effect. Interestingly, no inverse grain-size effect exists on stacking fault formation. These observations are explained by generalized planar fault energies and grain-size effect on partial emissions.
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