Correlation between dynamic recrystallization and formation of rare earth texture in a Mg-Zn-Gd magnesium alloy during extrusion.

The trace addition of rare earth (RE) elements in Mg alloys can modify the extrusion texture, leading to the formation of RE texture and thus improved formability. The interrupted extrusion experiment as well as electron back-scatter diffraction (EBSD) characterization was conducted in Mg-1.5Zn-0.5Gd (wt.%) alloy to unveil the dominant dynamic recrystallization (DRX) mechanism and its correlation with the formation of RE texture during extrusion. The results indicate that continuous DRX (CDRX) dominated the microstructural development. Fresh DRXed grains with 30° [0001] grain boundaries preferentially nucleated in unDRXed grains with [10[Formula: see text]0] basal fiber orientation via CDRX, showing preferred selection of [2[Formula: see text][Formula: see text]0] basal fiber orientation rather than RE texture orientation. Consequently, CDRX contributed to the weakening of [10[Formula: see text]0] basal fiber texture and had a more significant effect on the formation of [2[Formula: see text][Formula: see text]0] basal fiber component than that of RE texture component. Besides, the preferred growth of recrystallized grains with RE texture orientation was confirmed to occur during static annealing after extrusion, which is inferred as the key reason for the formation of RE texture in dilute Mg-RE alloys.

Identification and analysis of the jnk1 gene in polyploid hybrids of red crucian carp (Carassius auratus red var.) and common carp (Cyprinus carpio L.).

c-Jun N-terminal kinase (JNK) is an important member of the mitogen-activated protein kinase superfamily. The allotetraploid crucian carp is a product of distant hybridization of female red crucian carp with male common carp. It is the first natural case of an allotetraploid with stable genetic characters, including fertility of both female and male animals. In this study, 2 jnk1 cDNAs (including jnk1a and jnk1b) have been cloned from the polyploid crucian carp system, consisting of the allotetraploid crucian carp, the triploid crucian carp, and their original parents (red crucian and common carp). We show that jnk1a and jnk1b represent 2 splice forms arising from the jnk1 gene. On the basis of the genetic structure of jnk1a gene in the polyploid crucian carp system, we demonstrated that the allotetraploid crucian carp is phylogenetically closer to its paternal parent (common carp) than to its maternal parent. We further show a similarity between the triploid crucian carp and its original female parent (red crucian carp). Comparisons of genetic structures indicated that the jnk1b genes of allotetraploid and triploid crucian carp are more similar to those of the original paternal parent rather than the original female parent (red crucian carp). RT-PCR analysis indicated that both the jnk1a and jnk1b genes are widely expressed in fish embryos and in the adult organs, displaying distinct features of embryonic-stage and organ specificity in the polyploid crucian carp system.

[Second sampled survey on the distribution of human parasites in Zhejiang Province].

OBJECTIVE: Twenty-six species of human parasites were recorded in Zhejiang Province in 1987-1989 as a part of the national investigation on the distribution of human parasites, and the total prevalence was 80.2%. In order to find out possible changes on the composition of parasite species and decrease of prevalence after control intervention particularly mass chemotherapy in the past years and provide evidence for an improved control strategy, the second sampled survey was carried out from 1998 to 1999. METHODS: Ten counties were identified randomly out of 28 counties where the last survey was conducted following the same sampling method. Same technics were used for case detection and data processing. RESULTS: The total infection rate in a sample of 15,698 was 22.84% was 22.84% in 30 investigation spots in 10 counties, and 17 species of parasites were revealed. The overall prevalence was reduced by 71.51% in comparison to that of 1989, and the number of parasite species was 17, 9 less than that of the last investigation. CONCLUSIONS: The prevalence of human parasites has greatly declined in this province due to the socioeconomic development and adoption of comprehensive control measures focusing on mass chemotherapy in the past decade.

Study of simplified measures for malaria surveillance in the late consolidation phase in China.

This paper presents the results of a study on simplified surveillance methods conducted in 23 pilot counties in 11 provinces and municipalities in China where reside 15 million people and malaria control has been in the late consolidation phase. Two simplified surveillance Schemes (A and B) taking treatment of clinical cases as the main measure were implemented in 1992-1994. The rate of annual blood examination for case detection was 1.0% in pilot Scheme A, while in areas of scheme B it was 0.3%. The implementation of both Scheme A and Scheme B, simplified or without treatment of infection foci and management of mobile populations, acquired satisfactory effects against malaria. Consequently, malaria incidence was declining steadily, only a few indigenous and introduced cases were detected. The parasite rate in residents and the IFA positive rate in children were very low. The results of pilot studies and cost-effectiveness analysis indicated that Scheme B is effective, rational and economic, and can be implemented to replace the routine surveillance measures in areas where malaria has been at the late consolidation phase in China.