Search

Two miniature inverted-repeat transposable elements (MITEs), MCLas-A and MCLas-B, were recently identified from ‘CandidatusLiberibacter asiaticus’ known to be associated with citrus Huanglongbing (HLB, yellow shoot disease). MCLas-A was suggested as an active MITE because of its mobility. The immediate upstream gene of the two MITEs was predicted to be a putative transposase. The goal of this study is to analyze the sequence variation in the upstream putative transposase of MITEs and explore the possible correlation between sequence variation of transposase gene and MITE activity. PCR and sequence analysis showed that 12 sequence types were found in six major amplicon types from 43 representative ‘Ca. L. asiaticus’ isolates from China, the United States and Brazil. Out of the 12 sequence types, three (T4, T5-2, T6) were reported for the first time. Recombination events were found in the two unique sequence types (T5-2 and T6) which were detected in all Brazilian isolates. Notably, no sequence variation or recombination events were detected in the upstream putative transposase gene of MCLas-A, suggesting the conservation of the transposase gene might be closely related with the MITE activity. Phylogenetic analysis demonstrated two well supported clades including five subclades were identified, clearly reflecting the geographical origins of isolates, especially that of Ruili isolates, São Paulo isolates and a few Florida isolates.

Citrus Huanglongbing (HLB, yellow shoot disease) was first observed in the coastal Chaoshan Plain of Guangdong Province, China, in the late 19th century based on descriptions of yellow shoot symptoms. “CandidatusLiberibacter asiaticus” has been considered as a putative pathogen associated with HLB since 1994. Information about the curent prevalence of this bacterium is important for HLB control in Guangdong and also provides useful reference for HLB study elsewhere. In 2007, we collected HLB symptomatic citrus samples from 16 cultivars in 12 prefecture cities, mostly in the north and west regions of Guangdong, where major citrus fruits are currently produced. Among the 359 samples collected, 241 (67.1%) were positive for “Ca. L. asiaticus”, distributed in 15 out of the 16 cultivars from all 12 cities, indicating the widespread prevalence of “Ca. L. asiaticus” in Guangdong Province. The detection rates varied from 16.7 to 100% depending on location and cultivar. Lower detection rates were found in newer citrus cultivation cities among the previously less popular but now promoted cultivars. In reviewing the citrus management and pest control practice, we believe that infected nursery stocks play a key role in the current spread of “Ca. L. asiaticus”.

up-buying activities based on the characteristics of the rural market and online group-buying. Then it presents a rural online group-buying model based on the contacts. Finally, it analyses this mode based on the SWOT approach. Generally speaking, this paper provides an inspiration and reference for the development of the group-buying online industry, by the exploring study on the online group-buying of the rural areas.

The objective of this study is to determine the optimal ball grinding parameters of the bio-ceramics ZrO2 by executing the Taguchi’s L18 orthogonal array experiment, analysis of variation (ANOVA), and the full factorial experiment on a PC-based multi-axis CNC engraving machine. The manufacture of a ZrO2 coping using the optimal ball grinding parameters has also been studied based on a tooth plaster model via reverse engineering technique. The 3D data points of a tooth plaster model were digitized by the developed on-machine measurement system on a PC-based CNC multi-axis engraving machine by integrating a circular triangulation laser probe with the machine and a PC. A CAD model of a coping could then be constructed by Pro/Engineer software, based on the digitized 3D data points. With the help of the PowerMill CAM software, the machining path of a coping has been simulated, and the correspondent NC codes have been generated to fabricate the ZrO2 coping using the determined optimal ball grinding parameters, on the CNC multi-axis engraving machine. The average surface roughness of Ra=0.49 um for the ground ZrO2 ceramics coping could be obtained by utilizing the optimal flat surface grinding parameters.

In this article, the structural properties and pH sensing characteristics of Nd2O3sensing films deposited on Si(100) substrates through reactive sputtering were reported. X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy were used to explore the structural and morphological features of these films with annealing at various temperatures. We found that the Nd2O3films annealed at 700°Cexhibit a higher sensitivity of 56.01 mV/pH, a lower hysteresis voltage of 4.71 mV, and a smaller drift rate of 1.34 mV/h than that of the other thermal annealing conditions.