PubMed Health⌕ Search

Biomedical subjects

Hongxing Xu

Publications and source records attributed to Hongxing Xu.

11 recordsLinked to original sources
PubMed2006

Genetic mapping of two powdery mildew resistance genes in einkorn (Triticum monococcum L.) accessions.

Powdery mildew is a severe foliar disease for wheat and could cause great yield loss in epidemic years. To explore new powdery mildew resistance genes, two einkorn accessions including TA2033 and M80, both resistant to this disease, were studied for the inheritance of resistance. Each accession possessed a single but different dominant resistance gene that was designated as Mlm2033 and Mlm80, respectively. Marker mapping indicated that they are both linked to Xgwm344 on the long arm of chromosome 7A. To establish their genetic relationship with Pm1 on 7AL, five RFLP markers previously reported to co-segregate with Pm1a were converted to STS markers. Three of them detected polymorphism between the mapping parents and were mapped close to Mlm2033 or Mlm80 or both. Xmag2185, the locus determined by the STS marker derived from PSR680, one of the RFLP markers, was placed less than 2 cM away from them. The allelism test indicated that Mlm2033 and Mlm80 are likely allelic to each other. In addition, through comparative and EST mapping, more markers linked to these two genes were identified. The high density mapping of Mlm2033 and Mlm80 will contribute to map-based cloning of the Pm1 locus. The markers for both genes will also facilitate their transfer to wheat.

Ascomycota↗
PubMed2006

One-dimensional arrays of nanoshell dimers for single molecule spectroscopy via surface-enhanced Raman scattering.

The optical properties of one-dimensional arrays of metal nanoshell dimers are studied systematically using the T-matrix method based on Mie theory, within the context of surface enhanced Raman scattering (SERS). It is shown that the local electromagnetic enhancement can be as high as approximately 4.5 x 10(13) for nanoshell dimer arrays with optimal geometry, and sensitive tunability in the resonant frequency can be gained by varying the geometrical parameters, making such structures appealing templates for SERS measurements with single molecule sensitivity. The extraordinarily high enhancement is attributed to a collective photonic effect constructively superposed onto the intrinsic enhancement associated with an isolated nanoshell dimer.

Journal Article↗
PubMed2006

Creating hot nanoparticle pairs for surface-enhanced Raman spectroscopy through optical manipulation.

We use optical tweezers to move single silver nanoparticles into near-field contact with immobilized particles, forming isolated surface-enhanced Raman spectroscopy (SERS) active Ag particle dimers. The surface-averaged SERS intensity increases by a factor approximately 20 upon dimerization. Electrodynamics calculations indicate that the final approach between the particles is due to "optical binding". The described methodology may facilitate controlled single molecule SERS analysis.

Metal Nanoparticles↗
PubMed2004

Unified treatment of fluorescence and raman scattering processes near metal surfaces.

We present a general model study of surface-enhanced resonant Raman scattering and fluorescence focusing on the interplay between electromagnetic effects and the molecular dynamics. Our model molecule is placed close to two Ag nanoparticles and has two electronic levels. A Franck-Condon mechanism provides electron-vibration coupling. Using realistic parameter values for the molecule we find that an electromagnetic enhancement by 10 orders of magnitude can yield Raman cross sections sigma(R) of the order 10(-14) cm(2). We also discuss the dependence of sigma(R) on incident laser intensity.

Journal Article↗
PubMed2004

Calculation of the near field of aggregates of arbitrary spheres.

We study a numerical method of calculating the near field of ensembles of arbitrary spheres by extending Mie theory. A recursive method based on the orders of scattering is presented. This method represents a concise way to calculate the near field of aggregates of any number of arbitrary spheres, Numerical examples are given to show its validity.

Journal Article↗
PubMed2003

[Effects of different nutritional resources on the longevity and parasitic ability of egg parasitoid Anagrus nilaparvatae].

This paper dealt with the effects of honey, corn pollen, soybean flower, and honeydews excreted by Nilaparavatae lugens and Toya spp. on the longevity and parasitic ability of A. nilaparvatae. The results showed that the longevity of A. nilaparvatae was obviously extended, and its egg production on N. lugens was significantly increased when fed with those nutrient-rich diets except the honeydew excreted by Toya spp. Corn pollen and the honeydew excreted by N. lugens worked only in the forms of pollen (water and honeydew) water. The longevity of N. lugens was not affected by its parasitic behaviors, but its survival rate was higher within 40-48 hours, and then decreased rapidly. About ten species of plant hopper, the host of Anagrus spp., were found in non-rice habitats, which provided shelter and afforded foods to the parasitoids of rice pests, and contributed to protecting the natural enemies and enhancing the biological control in the rice system.

Animals↗
PubMed2003

[Adaptation of Sogatella furcifera to insect-resistant rice variety N22].

The adaptation of whitebacked planthopper (WBPH) Sogatella furcifera to insect-resistant rice variety N22 and the variation of its protective enzyme were studied by rearing it successively two generations on N22 and insect-susceptible rice variety TN1 in laboratory. The results showed that after reared on TN1 or N22 for one or two generations, its egg period, nymphal duration, and total generation period had no significant difference. The ecological parameters, e.g., nymphal survival rate, body weight, amount of honey dew, egg number, and innate increasing rate of WBPH transferred from TN1 to N22 and reared for one generation were lower than those of WBPH reared on N22 successively for two generations, and the latter was lower than that reared on TN1. The activities of superoxide dismutase (SOD) and catalase (CAT) in protective enzyme system of the 2nd generation WBPH on N22 were similar to those of the pest on TN1, indicating that S. furcifera could adapt to insect-resistant variety N22 after rearing it successively for several generations.

Adaptation, Physiological↗
PubMed2003

[Tolerance of rice varieties to whitebacked planthopper Sogatella furcifera and variation of nutrient components in rice plants].

The study showed that the rice varieties N22, Luyuanzhan No. 1 and 94D-22 had a stronger tolerance to Sogatella furcifera, while Mudgo and K89-B5 had a weaker tolerance. The varieties Ptb33 and Zhongzu 74 were of antibiosis, and susceptible varieties Xiushui 11, Shanyou 63 and susceptible check varieties TN1 had no tolerance. After rice plants were infested by S. furcifera, the percentages of nitrogen content (N%) and soluble sugar content (S%) in tolerant varieties increased, but the ratio of nitrogen content to soluble sugar content (N/S) decreased obviously. For susceptible varieties, the variations of N%, S% and N/S were opposite to those of the tolerant varieties. In different varieties the contents of most kinds of free amino acid increased at various degrees, but those of alanine in susceptible variety TN1, alanine, threonine and methionine in tolerant varieties N22, and arginine in resistant variety Ptb33 decreased.

Amino Acids↗
PubMed2002

Surface-plasmon-enhanced optical forces in silver nanoaggregates.

We use extended Mie theory to investigate optical forces induced by and acting on small silver nanoparticle aggregates excited at surface plasmon resonance. It is shown that single molecules can be trapped at junctions between closely spaced nanoparticles, which are simultaneously pulled together by optical forces. These effects could significantly influence surface-enhanced Raman scattering and related spectroscopies under normal experimental conditions and contribute to single-molecule sensitivity.

Journal Article↗