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In this paper, a fully non-contact second harmonic generation (SHG) technique using a pair of air-coupled ultrasonic transducers is developed and the feasibility of the technique is investigated through the evaluation of surface cracks of concrete beams subjected to the bending load. The reliability of developed technique is subsequently validated by comparing the non-contact nonlinear ultrasonic measurements with measurement results based on contact-type sensors, where the coefficient of variation of non-contact measurements is averagely about 46% of the contact measurements. The defined nonlinear parameter is found to have a monotonically increasing trend with the growth of concrete crack, and the nonlinear parameter corresponding to the largest crack increases about 7 times from its initial value corresponding to the sample in intact state. In contrast, the increase of linear parameter namely the time-of-flight of surface wave is only about 40%. The difference as high as one order of magnitude verifies the high sensitivity of developed air-coupled SHG technique. With consideration of the easily removable characteristic of air-coupled ultrasonic measurements, the developed SHG technique could be promising for the large scale quality control of concrete structures in engineering practice.

The plant Na+/H+ antiporter (NHX) plays a significant role in cellular ion homeostasis. Herein, an Na+/H+ antiporter gene, SpNHX1 from the Sesuvium portulacastrum plant, was obtained by homology-cloning method. The SpNHX1 gene contains 2113 bp with an open-reading frame encoding a polypeptide of 554 amino acid residues with an estimated molecular mass of 61.27 kDa and an isoelectric point of 7.24. The amino acid sequences of SpNHX1 shared a high similarity with Arabidopsis thaliana AtNHX1 (75.81%), AtNHX2 (77.12%) and Oryza sativa OsNHX1 (73.10%). SpNHX1 contains an amiloride-binding region (FFIYLLPPI), which is a highly-conserved domain in plant Na+/H+ antiporters. RT-PCR (reverse transcriptional PCR) analysis showed that the SpNHX1 gene had a high expression level in roots compared to other tissues under normal conditions. The qRT-PCR (quantitative real-time PCR) results indicated that NaCl treatment induced the expression of SpNHX1 gene in the roots, but its transcriptional levels were not influenced by the ABA, PEG, H2O2, heat (42 °C) or cold (4 °C) stresses. The growth of yeast cells expressing SpNHX1 was better than the non-transgenic control cells in the presence of 30 mM NaCl, 0.4 M KCl, or 0.5 mM LiCl. Furthermore, transgenic yeast cells with SpNHX1 accumulated more Na+ relative to control cells under salinity stress. These results suggested that SpNHX1 was a key determinant in the salt-stress response in Sesuvium portulacastrum.

Cassava (Manihot esculenta Crantz) is a tropical and subtropical plant and susceptible to chilling injury. In this research, a C-repeat binding factor (CBF)-like gene (GenBank accession number JQ339740) has been isolated from cassava, and named as MeCBF1. The full-length DNA of MeCBF1 is 1,037 base pair (bp), without intron. The 5′ untranslated region is 102 bp, the 3′ untranslated region is 239 bp, and the open reading frame is 696 bp encoding 231 amino acids. The deduced amino acid sequence of MeCBF1 contains two CBF conserved motifs of PKK(P/R)AGRxKFxETRHP and DSxWR. The MeCBF1 shows 83 % homology to the CRT/DRE binding factor 1 from Hevea brasiliensis (Accession no. AAY43213.1). However, in cassava, the MeCBF1 target genes showed low similarity to the CBF/DREB regulated genes in Arabidopsis thaliana. Quantitative real-time PCR showed that the MeCBF1 was highly expressed in stems and leaves, and lowly expressed in roots. In addition, the expression of the MeCBF1 quickly responded to low temperature stress (4 °C). These results suggest that, the MeCBF1 is functional in cassava. Further studies on the MeCBF1 might be helpful to reveal molecular mechanism of cassava’s high sensitivity to low temperature.

Palladium salts can be used as a coprecipitation carrier for the preconcentration of trace elements from natural water prior to their measurement by atomic spectrometry (AAS). The palladium is subsequently reduced by the introduction of hydrogen gas into the sample solution. The procedure is applied to the determination of Cu, Pb and Cd in seawater (enrichment factor 50) and synthetic water samples. Operating conditions have been optimized for the analysis of real samples. With the technique established an enrichment factor (500 fold) is feasible in synthetic samples. The recoveries of Cu, Cd and Pb from seawater are 95, 103 and 100%, respectively. This simple and rapid method can be applied in a wide pH-range and with complex matrices.

The purpose of this paper is to discuss the physical properties of diffractionless beams, their propagation and transformation through optical systems. We start from the analysis of Durnin’s experiment to present a useful idea for the design of Bessel beam convertors. Then, the propagation of Bessel beams through ABCD optical systems are studied, and numerical calculations are performed to illustrate and compare the characteristics of truncated Bessel beams propagating through a sharp-edged aperture and a soft-edged one.