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Enhancement of thermal stability and chemical reactivity of phenolic resin ameliorated by nanoSiO2
Yajun Guo,Lihong Hu,Puyou Jia,Baofang Zhang,Yonghong Zhou 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.1
Phenolic resin has unsatisfactory thermal stability owing to the poor anti-oxidation property of methylene and phenol groups. To overcome this defect, a series of phenolic resin modified by nanoSiO2 based on the tetraethoxysilane (TEOS) was successfully prepared via sol-gel method using phenol as solvent. The effect of nanoSiO2 on the structures and properties of phenolic resin/foam was investigated. TGA and DTG indicated that the initial decomposition temperature of PR-0.5 (TEOS accounted for 0.5% of phenolic resin) was 41.8 oC higher than the neat PR-0. DSC revealed that the peak temperature presented a parabolic shape with the dosage of the TEOS, its maximal value resting on the PR-0.5. FT-IR and XRD demonstrated that chemical crosslink was reacted between PR and nanoSiO2 hydrolyzed by the TEOS, forming new chemical bands. Reactivity analysis illustrated that the free phenol content and the hydroxymethyl group content changed sharply in PF-0.5, implying it has highest reactivity.
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Genetic Variation and Evolution of the Pi9 Blast Resistance Locus in the AA Genome Oryza Species
Jinling Liu,Yajun Hu,Yuese Ning,Nan Jiang,Jun Wu,전종성,Yinghui Xiao,Xionglun Liu,Liangying Dai,Guo-Liang Wang 한국식물학회 2011 Journal of Plant Biology Vol.54 No.5
The rice nucleotide-binding site–leucine-rich repeat (NBS-LRR)-encoding resistance (R) gene Pi9 confers broad-spectrum resistance to the fungal pathogen Magnaporthe oryzae. The Pi9 locus comprises many NBS-LRR-like genes and is an ancient locus that is highly conserved in cultivated and wild rice species. To understand the genetic variation and molecular evolutionary mechanism of the Pi9 alleles in different rice species, we studied five AA genome Oryza species including two cultivated rice species (Oryza sativa and Oryza glaberrima) and three wild rice species (Oryza nivara, Oryza rufipogon, and Oryza barthii). A 2.9-kb fragment spanning the NBS-LRR core region of the Pi9 gene was amplified and sequenced from 40 accessions. Sequence comparison revealed that the Pi9 alleles had an intermediate-diversified nucleotide polymorphism among the AA genome Oryza species. Sequence variations were more abundant in the LRR region than in the NBS region, indicating that the LRR region has played a more important role for the evolution of the Pi9alleles. Furthermore, positive selection was found to be the main force promoting the divergence of the Pi9 alleles,especially in the LRR region. Our results reveal the characteristics and evolutionary dynamics of the Pi9 alleles among the two cultivated and three wild rice species.
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Yubao Zhang,Yajun Wang,Zhongkui Xie,Ruoyu Wang,Zhihong Guo,Yuhui He 한국식물병리학회 2020 Plant Pathology Journal Vol.36 No.2
The Lily mottle virus (LMoV) impedes the growth and quality of lily crops in Lanzhou, China. Recently Arabis mosaic virus (ArMV) has been detected in LMoV- infected plants in this region, causing plant stunting as well as severe foliar symptoms, and likely posing a threat to lily production. Consequently, there is a need to develop simple, sensitive, and reliable detection methods for these two viruses to prevent them from spreading. Reverse transcription (RT) loop-mediated isothermal amplification (LAMP) assays have been de- veloped to detect LMoV and ArMV using two primer pairs that match six conserved sequences of LMoV and ArMV coat proteins, respectively. RT-LAMP assay results were visually assessed in reaction tubes using green fluorescence and gel electrophoresis. Our assays successfully detected both LMoV and ArMV in lily plants without the occurrence of viral cross-reactivity from other lily viruses. Optimal conditions for LAMP reactions were 65°C and 60°C for 60 min for LMoV and ArMV, respectively. Detection sensitivity for both RT-LAMP assays was a hundredfold greater than that of our comparative RT-polymerase chain reaction as- says. We have also found this relatively rapid, target specific and sensitive method can also be used for samples collected in the field and may be especially useful in regions with limited or no laboratory facilities.
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Saeed Jerban,,Nikolaus Szeverenyi,Yajun Ma,Tan Guo,Behnam Namiranian,Sarah To,장형석,Eric Y. Chang,Jiang Du 대한자기공명의과학회 2019 Investigative Magnetic Resonance Imaging Vol.23 No.3
Purpose: To investigate the temperature-based differences of cortical bone ultrashort echo time MRI (UTE-MRI) biomarkers between body and room temperatures. Investigations of ex vivo UTE-MRI techniques were performed mostly at room temperature however, it is noted that the MRI properties of cortical bone may differ in vivo due to the higher temperature which exists as a condition in the live body. Materials and Methods: Cortical bone specimens from fourteen donors (63 ± 21 years old, 6 females and 8 males) were scanned on a 3T clinical scanner at body and room temperatures to perform T1, T2*, inversion recovery UTE (IR-UTE) T2* measurements, and two-pool magnetization transfer (MT) modeling. Results: Single-component T2*, IR-T2*, short and long component T2*s from bicomponent analysis, and T1 showed significantly higher values while the noted macromolecular fraction (MMF) from MT modeling showed significantly lower values at body temperature, as compared with room temperature. However, it is noted that the short component fraction (Frac1) showed higher values at body temperature. Conclusion: This study highlights the need for careful consideration of the temperature effects on MRI measurements, before extending a conclusion from ex vivo studies on cortical bone specimens to clinical in vivo studies. It is noted that the increased relaxation times at higher temperature was most likely due to an increased molecular motion. The T1 increase for the studied human bone specimens was noted as being significantly higher than the previously reported values for bovine cortical bone. The prevailing discipline notes that the increased relaxation times of the bound water likely resulted in a lower signal loss during data acquisition, which led to the incidence of a higher Frac1 at body temperature.
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Ke Chen,Hongyang Shi,Yajun Guo,Lei Yin,Ziwei Bao,Hongmei Zheng 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.4
Due to its unique characteristic of non-contact torque transmission between its permanent magnetic rotor and conductorrotor, permanent magnet eddy current coupling (PMECC) is preferable in transmitting torque from the outside to the insideof a sealed container, which can effectively avoid the tricky problem of dynamic seals. To mix non-uniform liquid solutionsor gas mixtures in sealed containers more effectively, a sinusoidal torque is also required. Thus, permanent magnet eddy current coupling with a slotted conductor is proposed in this paper, which can adaptively output sinusoidal torque under a real-time load when the input rotational speed is constant. Based on the equivalent magnetic circuit method, an analytical model for calculating torque is proposed. When establishing the equivalent magnetic circuit model of the PMECC, the radial magnetic flux leakage circuit is added to the equivalent magnetic circuit diagram, and the cross-sectional shape of the eddy current region is equivalent to an octagon, which simplifies the torque calculation process. The analytical model is verified by finite element method (FEM) simulation and experiments. According to a comparison, the peak and lowest values of output torque obtained by the experiments, the analytical model, and the FEM simulation are consistent. The output torque waveform obtained by the analytical model and FEM simulation are also consistent.
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Role of Ubiquitination in Plant Innate Immunity and Pathogen Virulence
Gautam Shirsekar,Liangying Dai,Yajun Hu,Xuejun Wang,Lirong Zeng,Guo-Liang Wang 한국식물학회 2010 Journal of Plant Biology Vol.53 No.1
Plant diseases are a major constraint for stable crop production in the world. Plants are constantly threatened by different pathogens and have developed an array of mechanisms to defend themselves. A growing body of evidence indicates that ubiquitination, which is one of the most important cellular processes for protein modification in eukaryotic organisms, is involved in the regulation of host defense signaling. Pathogens also exploit ubiquitination to block or interfere with plant defenses. Recent studies in a few model plants have demonstrated that ubiquitination plays a critical role in plant–pathogen interactions that lead either to plant resistance or to successful pathogen invasion of the plant host. This review discusses recent findings about the functions of ubiquitination in host defense and pathogen invasion.
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Yubao Zhang,Zhongkui Xie,John D Fletcher,Yajun Wang,Ruoyu Wang,Zhihong Guo,Yuhui He 한국식물병리학회 2020 Plant Pathology Journal Vol.36 No.1
Cucumber mosaic virus (CMV) is damaging to the growth and quality of lettuce crops in Lanzhou, China. Recently, however, for the first time an isolate of lettuce necrotic yellows virus (LNYV) has been detected in lettuce crops in China, and there is concern that this virus may also pose a threat to lettuce production in China. Consequently, there is a need to develop a rapid and efficient detection method to accurately identify LNYV and CMV infections and help limit their spread. Reverse transcription loop-mediated isothermal amplification (RT-LAMP) assays were developed to detect the nucleoprotein (N) and coat protein (CP) genes of LNYV and CMV, respectively. RT-LAMP amplification products were visually assessed in reaction tubes separately using green fluorescence and gel electrophoresis. The assays successfully detected both viruses in infected plants without cross reactivity recorded from either CMV or LNYV or four other related plant viruses. Optimum LAMP reactions were conducted in betaine-free media with 6 mM Mg2+ at 65°C for LNYV and 60°C for 60 min for CMV, respectively. The detection limit was 3.5 pg/ml and 20 fg/ml using RT-LAMP for LNYV and CMV plasmids, respectively. Detection sensitivity for both RT-LAMP assays was greater by a factor of 100 compared to the conventional reverse transcription polymerase chain reaction assays. This rapid, specific, and sensitive technique should be more widely applied due to its low cost and minimal equipment requirements.
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Jerban, Saeed,Szeverenyi, Nikolaus,Ma, Yajun,Guo, Tan,Namiranian, Behnam,To, Sarah,Jang, Hyungseok,Chang, Eric Y.,Du, Jiang Korean Society of Magnetic Resonance in Medicine 2019 Investigative Magnetic Resonance Imaging Vol.23 No.3
Purpose: To investigate the temperature-based differences of cortical bone ultrashort echo time MRI (UTE-MRI) biomarkers between body and room temperatures. Investigations of ex vivo UTE-MRI techniques were performed mostly at room temperature however, it is noted that the MRI properties of cortical bone may differ in vivo due to the higher temperature which exists as a condition in the live body. Materials and Methods: Cortical bone specimens from fourteen donors ($63{\pm}21$ years old, 6 females and 8 males) were scanned on a 3T clinical scanner at body and room temperatures to perform T1, $T2^*$, inversion recovery UTE (IR-UTE) $T2^*$ measurements, and two-pool magnetization transfer (MT) modeling. Results: Single-component $T2^*$, $IR-T2^*$, short and long component $T2^*s$ from bi-component analysis, and T1 showed significantly higher values while the noted macromolecular fraction (MMF) from MT modeling showed significantly lower values at body temperature, as compared with room temperature. However, it is noted that the short component fraction (Frac1) showed higher values at body temperature. Conclusion: This study highlights the need for careful consideration of the temperature effects on MRI measurements, before extending a conclusion from ex vivo studies on cortical bone specimens to clinical in vivo studies. It is noted that the increased relaxation times at higher temperature was most likely due to an increased molecular motion. The T1 increase for the studied human bone specimens was noted as being significantly higher than the previously reported values for bovine cortical bone. The prevailing discipline notes that the increased relaxation times of the bound water likely resulted in a lower signal loss during data acquisition, which led to the incidence of a higher Frac1 at body temperature.
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