We have applied a dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) to sensitively detect concentrations of boron and lithium in aqueous solution. Sequential laser pulses from two separate Q-switched Nd:YAG lasers at 532 nm wavelength have been employed to generate laser-induced plasma on a water jet. For achieving sensitive elemental detection, the optimal timing between two laser pulses was investigated. The optimum time delay between two laser pulses for the B atomic emission lines was found to be less than 3 μs and approximately 10 μs for the Li atomic emission line. Under these optimized conditions, the detection limit was attained in the range of 0.8 ppm for boron and 0.8 ppb for lithium. In particular, the sensitivity for detecting boron by excitation of laminar liquid jet was found to be excellent by nearly 2 orders of magnitude compared with 80 ppm reported in the literature. These sensitivities of laser-induced breakdown spectroscopy are very practical for the online elemental analysis of boric acid and lithium hydroxide serving as neutron absorber and pH controller in the primary coolant water of pressurized water reactors, respectively.

It has been shown that CA repeats in the 3'-untranslated region (UTR) of bcl-2 mRNA contribute the constitutive decay of bcl-2 mRNA and that hnRNP L (heterogenous nuclear ribonucleoprotein L) interacts with CA repeats in the 3'-UTR of bcl-2 mRNA, both in vitro and in vivo. The aim of this study was to determine whether the alteration of hnRNP L affects the stability of bcl-2 mRNA in vivo. Human breast carcinoma MCF-7 cells were transfected with hnRNP L-specific shRNA or hnRNP L-expressing vector to decrease or increase hnRNP L levels, respectively, followed by an actinomycin D chase. An RT-PCR analysis showed that the rate of degradation of endogenous bcl-2 mRNA was not affected by the decrease or increase in the hnRNP L levels. Furthermore, during apoptosis or autophagy, in which bcl-2 expression has been reported to decrease, no difference in the degradation of bcl-2 mRNA was observed between control and hnRNP L-knock down MCF-7 Cells. On the other hand, the levels of AUF-1 and nucleolin, transacting factors for ARE in the 3'UTR of bcl-2 mRNA, were not significantly affected by the decrease in hnRNP L, suggesting that a disturbance in the quantitative balance between these transacting factors is not likely to interfere with the effect of hnRNP L. Collectively, the findings indicate that the decay of bcl-2 mRNA does not appear to be directly controlled by hnRNP L in vivo.

The application of laser-induced breakdown spectroscopy (LIBS) to elemental depth profile analysis of high temperature oxidation behavior of Ni-based superalloys is presented. An oxidation test of two Ni-base superalloys, Alloy 617 and Haynes 230, to be considered as the most promising candidates for very high temperature reactor (VHTR), was carried out in dry air at 900 C. A duplex external oxide layer of MnCr 2 O 4 and Cr 2 O 3 with internal Al 2 O 3 oxides was mainly formed in both alloys. In addition, in Alloy 617, Ni and Ti enriched oxides were observed at the surface unlike in Haynes 230, and Alloy 617 was more susceptible to intergranular oxidation. Generally, the oxidation of Alloy 617 was more extensive than that of Haynes 230, i.e. Alloy 617 formed a thicker oxide layer of $8 mm, compared with Haynes 230 with an oxide layer of $5 mm in thickness after 1000 h. Depth profiles obtained by LIBS are found to be in broad agreement with those obtained by established techniques such as X-ray diffraction (XRD), scanning electron microscopy coupled to energy dispersive X-ray spectrometry (SEM-EDS), and secondary ion mass spectrometry (SIMS).

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