Through the analysis of peak broadening of energy‐dispersive diffraction lines from a powdered sample, the yield strength of α‐Si3N4 was investigated at a pressure of 9 GPa and temperatures up to 1234°C. During compression at room temperature, the lattice strain deduced from peak broadening increased linearly with pressure up to 9.2 GPa, with no clear indication of strain saturation. While heating at 9 GPa, diffraction peaks narrowed and significant stress relaxation was observed at temperatures above 400°C, indicating the onset of yielding. The yield strength of α‐Si3N4 decreases rapidly with increasing temperature: from 8.7 GPa at 400°C to 4.0 GPa at 1234°C. The low temperature for the onset of yielding and decrease of yield strength upon further heating bring up concern regarding the performance of α‐Si3N4 as an engineering material. Finally, the grain size variation is also outlined together with the dependence of differential strain on pressure and on temperature. This provides crucial information for clarifying the “fine structure” of the evolution of the differential strain.

During the 2004 growing season in the Liaoning Province in China, where there was large population of whiteflies, several sweet potato (Ipomoea batatas) breeding lines showed leaf curl symptoms. A survey was conducted to determine the incidence of Sweet potato leaf curl virus (SPLCV) in China. Sixteen plants were collected and stem scions from those plants were graft inoculated to Ipomoea nil. Three weeks later, the indicator developed symptoms of leaf curling, interveinal chlorosis, and stunting. Total nucleic acid was extracted from young leaves of sweet potato and then evaluated using polymerase chain reaction (PCR). Primers, developed by Briddon and Markham (1) and used as universal primers for amplification of the geminivirus DNA fragment, were BM-V (5′-KSG GGT CGA CGT CAT CAA TGA CGT TRT AC-3′) and BM-C (5′-AAR GAA TTC ATK GGG GCC CAR ARR GAC TGG C-3′). Amplified fragments with BM primers theoretically should have sizes almost equal to the full length of the DNA A component of the bipartite genome (2). Expected DNA fragments of 2.8 kb that contained the AV1, AV2, AC1, AC2, AC3, and AC4 open reading frames were obtained from symptomatic, but not from symptomless (uninfected) plants. The 2.8-kb fragments obtained by amplification were purified and cloned into the PMD18-T vector. Recombinant plasmids were then transformed into competent cells of Escherichia coli strain DH5(. The fragment was sequenced (GenBank Accession No. DQ512731), and nucleotide sequence of corresponding regions were compared with a published sequence of SPLCV available in GenBank (Accession No. AF104036). The AC4 and AC2 genes showed the highest (92%) and the lowest (83%) identity, respectively. This virus has been reported in the United States, Taiwan, Japan, and Peru. To our knowledge, this is the first report of the natural occurrence of SPLCV in China. References: (1) R. W. Briddon and P. G. Markham. Mol. Biotechnol. 1:202, 1994. (2) M. Onuki and K. Hanada. Ann. Phytopathol. Soc. Jpn. 64:116, 1998.

The anti-tarnish film was formed on brass for coinage by 1-phenyl-5-mercaptotetrazole (PMTA), which was studied by accelerated corrosion test (metallic coatings-thioacetamide corrosion test), polarization curves and electrochemical impedance spectroscopy (EIS) in synthetic sweat solution. The accelerated corrosion test showed that PMTA exhibited better anti-tarnish performance on brass than that of traditional anti-tarnish agent benzotriazole (BTA). The polarization measurements showed that PMTA could be classified as a mixed inhibitor for it could restrain both anodic and cathodic reactions. EIS measurements indicated that the inhibition efficiency of PMTA on brass was over 98.4% in synthetic sweat solution. All these results showed that PMTA was an excellent anti-tarnish agent of the brass for coinage, the optimum treating conditions of which were 0.5 gL À1 , pH ¼ 3, 55 C-85 C, 7 min.