Narrowband microwave generation with tuneable frequency is demonstrated by illuminating a photoconductive semiconductor switch (PCSS) with a burst-mode fibre laser. The whole system is composed of a high-power linearly polarized burst-mode pulsed fibre laser and a linear-state PCSS. To obtain a high-performance microwave signal, a desired envelope of burst is necessary and a pulse pre-compensation technique is adopted to avoid envelope distortion induced by the gain-saturation effect. Resulting from the technique, homogenous peak power distribution in each burst is ensured. The maximum energy of the laser burst pulse reaches 200 μJ with a burst duration of 100 ns at the average power of 10 W, corresponding to a peak power of 4 kW. When the PCSS is illuminated by the burst-mode fibre laser, narrowband microwave generation with tuneable frequency (0.80–1.12 GHz) is obtained with a power up to 300 W. To the best of the authors’ knowledge, it is the first demonstration of frequency-tuneable narrowband microwave generation based on a fibre laser. The high-power burst-mode fibre laser reported here has great potential for generating high-power arbitrary microwave signals for a great deal of applicable demands such as smart adaptive radar and intelligent high-power microwave systems.

A useful procedure is described to rapidly obtain Bragg-reflection intensities from the FULLPROF suite, and the Bragg intensities can then be input into the GEST and the PECKCRYST programs for crystal-structure determination of small molecules. An example on using the new procedure for the structure determination from powder diffraction determination of hydrochlorothiazide (C7H8ClN3O4S2) is presented, and the powder-structure results obtained by the PECKCRYST program are in good agreement with previously reported single-crystal results.

CdS nanocrystals embedded in sodium borosilicate glass were synthesized through sol-gel process. The CdS nanocrystals were usually 10 to 20 nm in size. The microstructure of CdS nanocrystals was determined to be of the hexagonal phase. The morphology and microstructure of the glass were examined using diverse techniques including scanning-probe microscopy (SPM), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), energy dispersion x-ray spectra (EDAX), and high-resolution TEM (HRTEM). The linear optical absorption spectrum of the glass showed a blue shift as a result of quantum-size effect. Furthermore, the third-order optical nonlinearities of the glass were studied by Z-scan technique at a wavelength of 770 nm. The results showed that the third-order optical nonlinear refractive index γ, absorption coefficient β, and susceptibility χ(3) were determined to be −2.16 × 10−16 m2/W, 6.32 × 10−11 m/W, and 1.20 × 10−10 esu, respectively, which were greater than those reported previously for CdS nanocrystals embedded in different matrices.

In plants, acid invertases are known to be the key enzymes cleaving sucrose into reducing sugars (RS) (glucose and fructose). To improve the quality of potato (Solanum tuberosum L.) chips, which is largely influenced by RS accumulation in tubers stored at low temperature, a part of acid invertase cDNA with hairpin RNA (hpRNA) structure was transformed into potato cv. N2. Detection of polymerase chain reaction (PCR) amplification and Northern blotting suggested that the RNA interference (RNAi) vector was successfully transformed into cv. N2. The analysis of acid invertase activity in the plantlets and microtubers of RNAi transgenic lines indicated that the expression of the acid invertase was significantly repressed by the activity of RNAi of plantlets by an average 69.8% (with the exception of line Ni-1) with a maximal decrease of 78% (line Ni-4), and the highest decrease of activity in microtubers of 68%. Compared with that of well-inhibited antisense inv transgenic plants, the comparative downregulation of RNAi suggests a distinct alteration of endogenous acid invertase activity and a potential strategy for post-transcriptional gene silencing (PTGS) in modulation of cold-sweetening in potato.

A nonlinear analysis of the interaction between a water wave and a floating ice cover in river channels is presented. The one-dimensional weakly nonlinear equation for shallow water wave propagation in a uniform channel with a floating ice cover is derived. The ice cover is assumed to be a thin uniform elastic plate. The weakly nonlinear equation is a fifth-order KdV equation. Analytical solutions of the nonlinear periodic wave equation are obtained. These solutions show that the shape, wavelength and celerity of the nonlinear waves depend on the wave amplitude. The wave celerity is slightly smaller than the open water wave celerity. The wavelength decreases as the wave amplitude increases. Based on these solutions the fracture of the ice cover is analysed. The spacing between transverse cracks varies form 50 m to a few hundred metres with the corresponding wave amplitude varying from 0.2 to 0.8 m, depending on the thickness and strength of the cover. These results agree well with limited field observations.