Nonuniform-to-uniform structural transitions induced by ultrasonic vibrations.

Recent millimetre-scale studies proposed that ultrasonic vibrations (UVs) promote material flow in welding joints via acting on dislocations. Here, we report atomic-scale results from molecular dynamics simulations of Mg-Al nanolayers joined by two means: only heat and heat accompanied by UVs (vibration amplitude, B = 0.1-10 nm and vibration frequency, f = 5.7-100 GHz) over the temperature range of 600-800 K. Comparative and quantitative analyses were performed on the structural evolution (including atomic diffusion, arrangements and distributions) of the joining Mg/Al interfaces and motions of dislocations, as well as on the influences of the vibration amplitude and vibration frequency on these two features. The results show that the applied UV with large vibration amplitudes (B ≥ 5 nm) and a low vibration frequency (f = 5.7 GHz) significantly facilitates atomic diffusion (10-1000 times as fast as that in the case free of UVs) and formations and motions of dislocations, resulting in nonuniform-to-uniform structural transitions and increases in the thicknesses of the joined Mg/Al interfaces. These results provide a way to understand how the applied UV acts on dislocations and atomic diffusion during the UV-assisted welding processes of Mg-Al and other systems.

Coherent-interface-induced second hardening deformation of Al-Mg-Al nanolayers by molecular dynamics simulations.

Thermal diffusion plays an important role in the determination of the structures and properties of interfaces and nanolayers. Here we report results from molecular dynamics simulations of the tensile behavior of Al-Mg-Al nanolayers with their Al/Mg interfaces being joined by the thermal diffusion of atoms. We find that a different deformation mechanism applies in each case: low thermal diffusion temperatures (300 ≤ T1 < 664 K) and high thermal diffusion temperatures (664 ≤ T1 ≤ 846 K). The formation of coherent Al/Mg interfaces in the case of high T1 induces the second hardening deformation of Al-Mg-Al nanolayers before the stress reaching the tensile strength, significantly enhancing the tensile properties of Al-Mg-Al nanolayers in comparison to the case of low T1. This difference would provide guidance on the improvement of the mechanical properties of Al-Mg layered systems.

Melting at Mg/Al interface in Mg-Al-Mg nanolayer by molecular dynamics simulations.

The melting at the magnesium/aluminum (Mg/Al) interface is an essential step during the fabrications of Mg-Al structural materials and biomaterials. We carried out molecular dynamics simulations on the melting at the Mg/Al interface in a Mg-Al-Mg nanolayer via analyzing the changes of average atomic potential energy, Lindemann index, heat capacity, atomic density distribution and radial distribution function with temperature. The melting temperatures (Tm) of the nanolayer and the slabs near the interface are significantly sensitive to the heating rate (vh) over the range ofvh ≤ 4.0 K ps-1. The distance (d) range in which the interface affects the melting of the slabs is predicted to be (-98.2, 89.9) Å atvh→0,if the interface is put atd = 0 and Mg (Al) is located at the left (right) side of the interface. TheTmof the Mg (Al) slab just near the interface (e.g.d=4.0Å) is predicted to be 926.8 K (926.6 K) atvh→0,with 36.9 K (37.1 K) below 963.7 K for the nanolayer. These results highlight the importance of regional research on the melting at an interface in the nanolayers consisting of two different metals.

Expression of GADD153 in follicular tumors of thyroid and comparison with CK19, Galectin-3 and HBME-1 / 中华病理学杂志

<p><b>OBJECTIVE</b>To study immunohistochemical expression of GADD153 and assess its usefulness as markers in the differential diagnoses in follicular tumors of the thyroid.</p><p><b>METHODS</b>Immunohistochemical staining was performed on formalin-fixed paraffin-embedded tissue of 34 cases of follicular thyroid adenomas (FTA), 46 cases of follicular thyroid carcinomas (FTC), 29 cases of follicular variant papillary carcinomas (FVPC).</p><p><b>RESULTS</b>(1) GADD153 was expressed in cell nucleus with positive or strong positive expression in FTC, and no or weak expression in FTA and FVPC. The positive expressions of GADD153 were present in 38 of 46(82.6%) in FTC, 11 of 34(32.4%) in FTA and three of 29(10.3%) in FVPC, the positive expression rate in FTC was obviously higher than that in FTA and in FVPC, the differences were statistically significant (χ² = 20.80 and 37.48; P < 0.01). (2) CK19, Galectin-3 (Gal-3) and HBME-1 were all expressed in the cytoplasm, the positive expressions of CK19, Gal-3 and HBME-1 were present in 54.3% (25/46), 67.4% (31/46) and 58.7% (27/46) in FTC; 50.0% (17/34), 29.4% (10/34) and 32.4% (11/34) in FTA; 100% (29/29), 93.1% (27/29) and 89.7% (26/29) in FVPC, the differences were statistically significant as well (χ² = 21.20 and 8.22; P < 0.01). (3) According to the expressions of CK19, Gal-3, HBME-1 and GADD153, we divided the results into low expression group (0 or 1+) and high expression group (2+ or 3+), the sensitivity and the specificity were calculated. in FTA, the sensitivity were 26.5%, 8.8%, 2.9% and 11.8%; the specificity were 50.7%, 52.0%, 54.7% and 58.7%. in FTC, the sensitivity were 19.6%, 26.1%, 23.9% and 65.2%; the specificity were 41.3%, 57.1%, 62.0% and 92.1%. in FVPC, the sensitivity were 96.6%, 82.8%, 79.3% and 3.4%; the specificity were 77.5%, 81.3%, 85.0% and 57.5%.</p><p><b>CONCLUSIONS</b>The sensitivity and the specificity of GADD153 expression are well for diagnosing FTC, and CK19, Gal-3, HBME-1 are well for FVPC. The four markers when used in combination, are better to identify the follicular tumors of the thyroid.</p>

[Fingerprints identification of Gynostemma pentaphyllum by RAPD and cloning and analysis of its specific DNA fragment].

OBJECTIVE: To identify the resources of Gynostemma pentaphyllum and its spurious breed plant Cayratia japonica at level of DNA. METHODS: Two random primers ( WGS001, WGS004) screened were applied to do random amplification with genomic DNA extracted from Gynostemma pentaphyllum and Cayratia japonica which were collected from different habitats. After amplificated with WGS004, one characteristic fragment about 500 bp which was common to all Gynostemma pentaphyllum samples studied but not to Cayratia japonica was cloned and sequenced. Then these sequences obtained were analyzed for identity and compared by Blastn program in GenBank. RESULTS: There were obvious different bands amplified by above two primers in their fingerprints of genomic DNA. On the basis of these different bands of DNA fingerprints, they could distinguish Gynostemma pentaphyllum and Cayratia japonica obviously. Sequence alignment of seven cloned bands showed that their identities ranged from 45.7% - 94.5%. There was no similar genome sequences searched in GenBank. This indicated that these seven DNA fragments had not been reported before and they should be new sequences. CONCLUSION: RAPD technique can be used for the accurate identification of Gynostemma pentaphyllum and its counterfeit goods Cayratia japonica. Besides, these specific DNA sequences for Gynostemmna pentaphyllum in this study are useful for the further research on identification of species and assisted selection breeding in Gynostemma pentaphyllum.

[Molecular characters of Centella asiatica found with RAPD technology].

OBJECTIVE: To analyze the DNA molecular characters of Centella asiatica with RAPD technology. METHODS: With the genomic DNA as templates extracted from various source of Centella asiatica samples, optimized RAPD PCR reaction systems had been used. The random promers had been screened to amplify the specific molecular fragments of Centella asiatica. RESULTS: The specific genetic bands of Centella asiatica species from various habitats were established which were highly stable and repeatable and obviously different from those of other families, genuses of plants such as Gynostemma pentaphylum, Tobacco, Cayratia japonica. CONCLUSION: The developed method of RAPD analysis for the genetic character bands of Centella asiatica could be applied to identify real Centella asiatica from its spurious breed plants. The genetic character bands of Centella asiatica amplified with the RAPD method show high homogeneous in several samples from different habitats.