Diagnosis of ultrafast surface dynamics of thin foil targets irradiated by intense laser pulses.

The temporal modulation of an electron bunch train accelerated from a foil target irradiated by an intense laser pulse is studied by measuring the coherent transition radiation (CTR) from the rear surface of a target. We experimentally obtained CTR spectra from a 1 µm thick foil target irradiated at a maximum intensity of 6.5 × 1019 W/cm2. Spectral redshifts of the emitted radiation corresponding to increases in laser intensity were observed. These measurements were compared with the theoretical calculation of CTR spectra considering ultrafast surface dynamics, such as plasma surface oscillation and relativistically induced transparency. Plasma surface oscillations induce a spectral redshift, while relativistic transparency causes a spectral blueshift. Both effects are required to find reasonable agreement with the experiment over the entire range of laser intensities.

Diagnosis of warm dense conditions in foil targets heated by intense femtosecond laser pulses using Kα imaging spectroscopy.

Warm dense conditions in titanium foils irradiated with intense femtosecond laser pulses are diagnosed using an x-ray imaging spectroscopy technique. The line shapes of radially resolved titanium Kα spectra are measured with a toroidally bent GaAs crystal and an x-ray charge-coupled device. Measured spectra are compared with the K-shell emissions modeled using an atomic kinetics - spectroscopy simulation code. Kα line shapes are strongly affected by warm (5-40 eV) bulk electron temperatures and imply multiple temperature distributions in the targets. The spatial distribution of temperature is dependent on the target thickness, and a thin target shows an advantage to generate uniform warm dense conditions in a large area.

The role of Phe181 in the hexamerization of Helicobacter pylori quinolinate phosphoribosyltransferase.

Quinolinic acid phosphoribosyltransferase (QAPRTase; NadC) catalyzes an indispensable step in NAD biosynthesis, one that is essential for cell survival in prokaryotes, which makes it an attractive target for antibacterial drug therapy. We recently reported the crystal structures of Helicobacter pylori QAPRTase with bound quinolinic acid, nicotinamide mononucleotide, and phthalic acid. The enzyme exists as a hexamer organized as a trimer of dimers, which is essential for full enzymatic activity. The loop between helix alpha7 and strand beta8 contributes significantly to the hydrophobic dimer-dimer interactions. Phe181Pro mutation within the alpha7-beta8 loop disrupts the hexamerization of QAPRTase, and the resultant dimer shows dramatically reduced protein stability and no activity. Our findings thus suggest that compounds able to disrupt its proper oligomerization could potentially function as selective inhibitors of Helicobacter pylori QAPRTase and represent a novel set of antibacterial agents.

[Studies of molecular marker-assisted-selection for resistance to Fusarium wilt in watermelon (Citrullus lanatus) breeding].

The RAPD marker OPP01/700 proved to be linked to the Fusarium wilt resistant gene in watermelon wild germplasm PI296341 was cloned and sequenced, and transferred into a SCAR marker. The linked marker was tested to be one copy by Southern blotting. The technique of detection of the SCAR-amplified products was simplified. These techniques were applied in selecting resistant plants in F3 of the introgression of the disease resistant gene. It is the first report in this field of transfer ring a RAPD marker linked to disease resistance gene into SCAR marker, and establishing the technique of molecular marker-assisted-selection for breeding Fusarium wilt resistance cultivars.

[Identification of quantitative trait loci associated with fruit traits in watermelon [Citullus lanantus (Thanb) Mansf] and analysis of their genetic effects].

In this study, we mapped and characterized quantitative trait loci (QTL) affecting watermelon fruit traits. A total of 118 F2 progenies derived from the cross 97103 (which is a cultivar with higher total soluble solids concentration, thin rind, susceptible to Fusarium wilt disease) x PI296341(which is a wild germplasm with lower total soluble solids concentration, thick rind, resistant to Fusarium wilt disease) were used to construct a 96-markers map in watermelon. By using interval mapping 4 QTLs for total soluble solids concentration, 5 QTLs for hardness of rind, 2 QTLs for thickness of rind, 3 QTLs for weight of simple fruit, and 6 QTLs for weight of one thousand grain seeds were identified. In addition, the explained variations, additive effects and dominance effects for all detected QTLs were analyzed.