Generation of Mild Recombinants of Papaya Ringspot Virus to Minimize the Problem of Strain-Specific Cross-Protection.

Papaya ringspot virus (PRSV) causes severe damage to papaya (Carica papaya L.) and is the primary limiting factor for papaya production worldwide. A nitrous acid-induced mild strain, PRSV HA 5-1, derived from Hawaii strain HA, has been applied to control PRSV by cross-protection for decades. However, the problem of strain-specific protection hampers its application in Taiwan and other geographic regions outside Hawaii. Here, sequence comparison of the genomic sequence of HA 5-1 with that of HA revealed 69 nucleotide changes, resulting in 31 aa changes, of which 16 aa are structurally different. The multiple mutations of HA 5-1 are considered to result from nitrous acid induction because 86% of nucleotide changes are transition mutations. The stable HA 5-1 was used as a backbone to generate recombinants carrying individual 3' fragments of Vietnam severe strain TG5, including NIa, NIb, and CP3' regions, individually or in combination. Our results indicated that the best heterologous fragment for the recombinant is the region of CP3', with which symptom attenuation of the recombinant is like that of HA 5-1. This mild recombinant HA51/TG5-CP3' retained high levels of protection against the homologous HA in papaya plants and significantly increased the protection against the heterologous TG-5. Similarly, HA 5-1 recombinants carrying individual CP3' fragments from Thailand SMK, Taiwan YK, and Vietnam ST2 severe strains also significantly increase protection against the corresponding heterologous strains in papaya plants. Thus, our recombinant approach for mild strain generation is a fast and effective way to minimize the problem of strain-specific protection.

Development of the Heterodyne Laser Encoder System for the X-Y Positioning Stage.

This investigation develops a laser encoder system based on a heterodyne laser interferometer. For eliminating geometric errors, the optical structure of the proposed encoder system was carried out with the internal zero-point method. The designed structure can eliminate the geometric errors, including positioning error, straightness error, squareness error, and Abbe error of the positioning stage. The signal processing system is composed of commercial integrated circuits (ICs). The signal type of the proposed encoding system is a differential signal that is compatible with most motion control systems. The proposed encoder system is embedded in a two-dimensional positioning stage. By the experimental results of the positioning test in the measuring range of 27 mm × 27 mm, with a resolution of 15.8 nm, the maximum values of the positioning error and standard deviation are 12.64 nm and 126.4 nm, respectively, in the positioning experiments. The result shows that the proposed encoder system can fit the positioning requirements of the optoelectronic and semiconductor industries.

Multi-interferometric displacement measurement system with variable measurement mirrors.

Laser interferometers have been widely implemented for the displacement sensing and positioning calibration of the precision mechanical industry, due to their excellent measuring features and direct traceability to the dimensional definition. Currently some kinds of modified Fabry-Perot interferometers with a planar mirror or a corner cube prism as the measurement mirror have been proposed. Each optical structure of both models has the individual particularity and performance for measuring applications. In this investigation, a multi-interferometric displacement system has been proposed whose measurement mirror can be quickly and conveniently altered with a planar mirror or a corner cube reflector depending on the measuring demand. Some experimental results and analyses about the interpolation error and displacement measurements with both reflectors have been demonstrated. According to the results, suggestions about the choice of a measuring reflector and interpolation model have been presented. With the measuring verifications, the developed system with a maximum standard deviation less than 0.2081 µm in measuring range of 300 mm would be a compact and robust tool for sensing or calibrating the linear displacement of mechanical equipment.

A Novel Analog Interpolation Method for Heterodyne Laser Interferometer.

Laser interferometer technology is used in the precision positioning stage as an encoder. For better resolution, laser interferometers usually work with interpolation devices. According to the interpolation factor, these devices can convert an orthogonal sinusoidal signal into several square-wave signals via digital processing. The bandwidth of the processing will be the limitation of the moving speed of the positioning stage. Therefore, the user needs to make a trade-off between the interpolation factor and the moving speed. In this investigation, a novel analog interpolation method for a heterodyne laser interferometer has been proposed. This method is based on the principle of the lock-in amplifier (LIA). By using the proposed interpolation method, the bandwidth of the laser encoder system can be independent of the interpolation factor. This will be a significant benefit for the ultra-high resolution encoder system and the laser interferometers. The concept, design, and experiment are revealed in this manuscript. The experimental results show that the proposed interpolation method can reach nanometer resolution with a heterodyne laser interferometer, and the bandwidth of the signal is independent of the resolution.

The comparison of environmental effects on michelson and fabry-perot interferometers utilized for the displacement measurement.

The optical structure of general commercial interferometers, e.g., the Michelson interferometers, is based on a non-common optical path. Such interferometers suffer from environmental effects because of the different phase changes induced in different optical paths and consequently the measurement precision will be significantly influenced by tiny variations of the environmental conditions. Fabry-Perot interferometers, which feature common optical paths, are insensitive to environmental disturbances. That would be advantageous for precision displacement measurements under ordinary environmental conditions. To verify and analyze this influence, displacement measurements with the two types of interferometers, i.e., a self-fabricated Fabry-Perot interferometer and a commercial Michelson interferometer, have been performed and compared under various environmental disturbance scenarios. Under several test conditions, the self-fabricated Fabry-Perot interferometer was obviously less sensitive to environmental disturbances than a commercial Michelson interferometer. Experimental results have shown that induced errors from environmental disturbances in a Fabry-Perot interferometer are one fifth of those in a Michelson interferometer. This has proved that an interferometer with the common optical path structure will be much more independent of environmental disturbances than those with a non-common optical path structure. It would be beneficial for the solution of interferometers utilized for precision displacement measurements in ordinary measurement environments.

Nucleotide sequence-homology-independent breakdown of transgenic resistance by more virulent virus strains and a potential solution.

Controlling plant viruses by genetic engineering, including the globally important Papaya ringspot virus (PRSV), mainly involves coat protein (CP) gene mediated resistance via post-transcriptional gene silencing (PTGS). However, the breakdown of single- or double-virus resistance in CP-gene-transgenic papaya by more virulent PRSV strains has been noted in repeated field trials. Recombination analysis revealed that the gene silencing suppressor HC-Pro or CP of the virulent PRSV strain 5-19 is responsible for overcoming CP-transgenic resistance in a sequence-homology-independent manner. Transient expression assays using agro-infiltration in Nicotiana benthamiana plants indicated that 5-19 HC-Pro exhibits stronger PTGS suppression than the transgene donor strain. To disarm the suppressor from the virulent strain, transgenic papaya lines were generated carrying untranslatable 5-19 HC-Pro, which conferred complete resistance to 5-19 and other geographic PRSV strains. Our study suggested the potential risk of the emergence of more virulent virus strains, spurred by the deployment of CP-gene-transgenic crops, and provides a strategy to combat such strains.

Modified Fabry-Perot interferometer for displacement measurement in ultra large measuring range.

Laser interferometers have demonstrated outstanding measuring performances for high precision positioning or dimensional measurements in the precision industry, especially in the length measurement. Due to the non-common-optical-path structure, appreciable measurement errors can be easily induced under ordinary measurement conditions. That will lead to the limitation and inconvenience for in situ industrial applications. To minimize the environmental and mechanical effects, a new interferometric displacement measuring system with the common-optical-path structure and the resistance to tilt-angle is proposed. With the integration of optomechatronic modules in the novel interferometric system, the resolution up to picometer order, high precision, and ultra large measuring range have been realized. For the signal stabilization of displacement measurement, an automatic gain control module has been proposed. A self-developed interpolation model has been employed for enhancing the resolution. The novel interferometer can hold the advantage of high resolution and large measuring range simultaneously. By the experimental verifications, it has been proven that the actual resolution of 2.5 nm can be achieved in the measuring range of 500 mm. According to the comparison experiments, the maximal standard deviation of the difference between the self-developed Fabry-Perot interferometer and the reference commercial Michelson interferometer is 0.146 µm in the traveling range of 500 mm. With the prominent measuring characteristics, this should be the largest dynamic measurement range of a Fabry-Perot interferometer up till now.

Influence of intensity loss in the cavity of a folded Fabry-Perot interferometer on interferometric signals.

Fabry-Perot interferometer is often used for the micro-displacement, because of its common optical path structure being insensitive to the environmental disturbances. Recently, the folded Fabry-Perot interferometer has been investigated for displacement measurements in large ranges. The advantages of a folded Fabry-Perot interferometer are insensitive to the tilt angle and higher optical resolution. But the design of the optical cavity has become more and more complicated. For this reason, the intensity loss in the cavity will be an important parameter for the distribution of the interferometric intensity. To obtain a more accurate result of such interferometer utilized for displacement measurements, the intensity loss of the cavity in the fabricated folded Fabry-Perot interferometer and the modified equation of the folded Fabry-Perot interferometer will be described. According to the theoretical and experimental results, the presented model is available for the analysis of displacement measurements by a folded Fabry-Perot interferometer.

Fabry-Pérot interferometer utilized for displacement measurement in a large measuring range.

The optical configuration of a Fabry-Pérot interferometer is uncomplicated. This has already been applied in different measurement systems. For the displacement measurement with the Fabry-Pérot interferometer, the result is significantly influenced by the tilt angles of the measurement mirror in the interferometer. Hence, only for the rather small measuring range, the Fabry-Pérot interferometer is available. The goal of this investigation is to enhance the measuring range of Fabry-Pérot interferometer by compensating the tilt angles. To verify the measuring characteristic of the self-developed Fabry-Pérot interferometer, some comparison measurements with a reference standard have been performed. The maximum deviation of comparison experiments is less than 0.3 µm in the traveling range of 30 mm. The experimental results show that the Fabry-Pérot interferometer is highly stable, insensitive to environment effects, and can meet the measuring requirement of the submicrometer order.

Lexical tone identification and consonant recognition in acoustic simulations of cochlear implants.

CONCLUSION: Cochlear implant (CI) recipients' performance of lexical tone identification and consonant recognition can be enhanced by providing greater spectral details. OBJECTIVE: To evaluate the effects of increasing the number of total spectral channels on the lexical tone identification and consonant recognition by normally hearing listeners who are native speakers of Mandarin Chinese. SUBJECTS AND METHODS: Lexical tone identification and consonant recognition were measured in 15 Mandarin-speaking, normal-hearing (NH) listeners with varied numbers of total spectral channels (i.e. 4, 6, 8, 10, 12, 16, 20, and 24), using acoustic simulations of CIs. RESULTS: The group of NH listeners' performance of lexical tone identification ranged from 44.53% to 66.60% with 4-24 spectral channels. The performance of tone identification between channels 4 and 16 remained similar; between channels 16 and 20 performance improved significantly. As regards consonant recognition, the NH listeners' overall accuracy ranged from 73.17% to 95.33% with 4-24 channels. Steady improvement in consonant recognition accuracy was observed as a function of increasing the spectral channels. With about 12-16 spectral channels, the NH listeners' overall accuracy in consonant recognition began to be comparable to their accuracy with the unprocessed stimuli.