An Experimental Investigation of the Mechanism of Hygrothermal Aging and Low-Velocity Impact Performance of Resin Matrix Composites.

Resin matrix composites (RCs) have better thermal and chemical stability, so they are widely used in engineering fields. In this study, the aging process and mechanism of two different types of resin-based three-dimensional four-way braided composites (H15 and S15) under different hygrothermal aging conditions were studied. The effect of aging behavior on the mechanical properties of RCs was also studied. Three different aging conditions were studied: Case I, 40 °C Soak; Case II, 70 °C Soak; and Case III, 70 °C-85% relative humidity (RH). It was found that the hygroscopic behavior of RCs in the process of moisture-heat aging conforms to Fick's second law. Higher temperatures and humidity lead to higher water absorption. The equilibrium hygroscopic content of H15 was 1.46% (Case II), and that of S15 was 2.51% (Case II). FT-IR revealed the different hygroscopic mechanisms of H15 and S15 in terms of aging behavior. On the whole, the infiltration behavior of water molecules is mainly exhibited in the process of wet and thermal aging. At the same time, the effect of the aging process on resin matrices was observed using SEM. It was found that the aging process led to the formation of microchannels on the substrate surface of S15, and the formation of these channels was the main reason for the better moisture absorption and lower mechanical strength of S15. At the same time, this study further found that temperature and oxygen content are the core influences on post-aging strength. The LVI experiment also showed that the structural changes and deterioration effects occurring after aging reduced the strength of the studied material.

The complete chloroplast genome and phylogenetic analysis of Acalypha hispida Burm. f. (Euphorbiaceae), an ornamental and medicinal plant.

Acalypha hispida Burm. f. (1768) is an evergreen shrub native to New Guinea and the Bismarck Archipelago. Currently, it is widely cultivated as an ornamental and medicinal plant in tropical and subtropical areas worldwide. This study characterized the complete chloroplast genome of A. hispida, which is 172,122 bp in length and consists of large single-copy (LSC) and small single-copy (SSC) regions of 97,025 bp and 19,787 bp, respectively, that are separated by a pair of 27,655 bp inverted repeat (IR) regions. The overall GC content of the genome is 34.22%. The genome contains 131 genes, including 86 protein-coding, 37 tRNA, and eight rRNA genes. Phylogenetic analysis indicates that A. hispida is closely related to Ricinus communis and Cleidiocarpon cavaleriei in the Euphorbiaceae family. The complete chloroplast genome of A. hispida provides genomic resources and potential markers suitable for future species identification and speciation studies of the genus Acalypheae and will also provide important information on the phylogenetic relationships of the Euphorbiaceae family.

[Analysis of ethambutol drug-resistance gene mutation in Mycobacterium tuberculosis by specific endonuclease].

OBJECTIVE: Surveyor nuclease is a member of the family of plant endonucleases that cleave heteroduplexes DNA with high specificity at sites of base substitution mismatch and DNA distortion. Heteroduplex analysis by Surveyor nuclease is a relatively new method. The purpose of this study was to explore the application of this method in analysis of drug-resistance gene mutation in Mycobacterium tuberculosis. METHODS: Surveyor nuclease was used to analyze embB gene mutation of 60 Mycobacterium tuberculosis isolates, among which 45 were EMB-resistant and embB gene mutation was found by sequencing, and 15 EMB-susceptible isolates without embB mutation. PCR amplification was carried out first, and then hybridized with products of H37Rv to form heteroduplex, cleaved by Surveyor nuclease, and lastly the results were shown by polyacrylamide gel electrophoresis and mutation was judged according to electrophoresis profile. RESULTS: Forty-five EMB-resistant isolates were found harboring embB gene mutation, while in the 15 EMB-susceptible isolates no mutation was found. All the 45 EMB-resistant isolates were revealed to harbor embB gene hotspot codon 306 mutation, among which 33 with ATG-->GTG, 3 with ATG-->ATT, 5 with ATG-->ATA, 2 with ATG-->ATC, 2 with ATG-->CTG. These results from Surveyor nuclease method was completely parallel to those of sequencing. CONCLUSION: Heteroduplex analysis by Surveyor nuclease may become a useful method for drug-resistance gene mutation analysis for Mycobacterium tuberculosis because of its simplicity, stability, low-cost, and high sensitivity and specificity.

[Impact of anti-tuberculosis drug resistance on treatment outcome of pulmonary tuberculosis patients receiving directly observed treatment strategy in Henan Province, China].

OBJECTIVE: To study the impact of anti-tuberculosis drug resistance on treatment outcome of pulmonary tuberculosis (TB) patients receiving directly observed treatment strategy (DOTS) in Henan Province, China. METHODS: From Aug. 2001 to Jun. 2002, the second round surveillance of anti-TB drug resistance was carried out in cooperation with WHO in Henan Province, China. The proportion method was used for drug susceptibility test and all enrolled patients were administrated with DOTS. RESULTS: The treatment success rate of smear-positive patients was 85.5% (1,343/1,571), of which the treatment success rate of initial-treatment cases was 89.6% (1,159/1,293). The treatment success rates among 565 anti-TB drug resistant cases and 215 multi-drug-resistant-TB (MDR-TB) cases were 76.6% (433/565), (initial treatment cases: 86.8%, 341/393; re-treated cases: 53.5%, 92/172; being significantly different), 58.6% (126/215), (initial treatment cases: 75.4%, 83/110; re-treated cases: 41.0%, 43/105; being significantly different), respectively. For the cases being resistant to 2, 3 or 4 drugs, the treatment success rates in initial treatment cases were all higher than those in re-treatment cases. Multivariate analysis showed that re-treatment, resistance to 2 plus drugs or MDR were the significant risk factors for treatment failure, and that re-treatment, older age and MDR were the significant risk factors for TB death. CONCLUSION: The treatment outcome of initial treatment of smear-positive patients with DOTS in Henan was satisfying, but that of retreated patients, especially retreated patients of MDR was very poor. Re-treatment, older age, resistance to 2 anti-TB drugs or MDR were the risk factors for the poor outcome of treatment with DOTS.

[Epidemiological survey on bronchial asthma in Henan province].

OBJECTIVE: To survey asthma prevalence, correlation factors for prevention, treatment, and for policy decision of asthma control. METHODS: Done with TB epidemiological survey synchronously, sampling by stratified-cluster-random method. 43 points were selected and distributed in all 18 prefectures in Henan province. Sampling population was 75 134, and 65 033 (97.0%) were investigated actually. RESULTS: In this survey, 682 asthma patients were found. The total prevalence rate was 1.05%, the rate for children was 1.71%, and that for adult was 0.82%; the rates for male and female were 1.16%, 0.94% respectively. The ratio of male to female was 1.23:1. When asthmatic chronic bronchitis cases were regarded as asthma cases and included in total asthma cases, the overall prevalence rate of asthma would increase up to 1.73%, raised by 65%. The higher prevalence were in 0 approximately 3 years old age group (4.48%) and >/= 65 years old age group (1.43%), the lowest prevalence was in 15 approximately 24 years old age group (0.36%). For 90% of asthmatic children, the initiative age of asthma was before 7 years old, and for 1/3 adult patient, it was in childhood. The prevalence of asthma in rural area was higher than that of urban area. Cold air, common cold, stimulation of smoking and cooking, and room dust were the 4 main inducing factors. Seasonal attack of asthma accounted for 67.2%, and that in winter and spring was 65.4%. 60.6% of asthma cases showed history of allergic diseases including allergic rhinitis, dermatitis, and drug allergy; 34.3% asthma family history. CONCLUSIONS: The rate of prevalence and inducing factors of asthma in Henan province were gained in this survey. The results may basically reflect the present status and be provided for asthma control as reference. According to the prevalence, asthma cases would be up to 0.98 approximately 1.6 million in whole Henan province and more attention should be paid to this situation.

Genotypic analysis of multidrug-resistant Mycobacterium tuberculosis isolates recovered from central China.

DNA sequencing analysis was used to investigate genetic alterations in the rpoB, katG, and inhA regulatory region and embB in 66 Mycobacterium tuberculosis isolates recovered from Central China. Of the 36 multidrug-resistant isolates, 33 (92%) had mutations in the amplified region of rpoB. The most frequent mutation (58%, 19/36) was S531L (TCG-->TTG). At least one mutation was found in the katG and inhA regulatory region in 83% (30/36) of the multidrug-resistant isolates, and mutations at katG codon 315 were identified in 78% (28/36). Alterations at embB306 may not confer resistance to EMB, and embB306 mutants were more frequently accompanied by rpoB mutations (100%, 16/16) than by katG 315 mutations (75%, 12/16). Our results show that geographic variation in the molecular genetic mechanism is responsible for drug resistance in multidrug-resistant M. tuberculosis. This observation will facilitate the development of a rapid molecular drug resistance screening approach for drug-resistant M. tuberculosis.