Microstructure of Surface Layer Formed at Low Temperature and High Carbon Concentration Carburizing with Rare Earth Element

A suitable carburized microstructure with fine granular dispersed carbides in hypereutectoid zone,ultra fine martensite in matrix and recrystallized austenite to be refined to the grain size of 12～14 has been obtained by a new process,which is a high carbon concentration carburizing with rare earth element at low temperature(860～880℃)in a discontinuous gas carburization furnace.There was not much difference for the microstructure in eutectic zone between this and conventional process.Forming mechanism of granular carbides has been also studied in this paper.

Thermodynamic Foundation for High Temperature Electrochemistry

Thermodynamic concepts required for the thermodynamic calculation of the potentials of electrodes for high temperature applications are briefly reviewed. A thermodynamic approach to the calculation of half cell potentials and the standard chemical potential of an electron at high temperatures which are related to the Standard Hydrogen Electrode(SHE) is discussed. As examples, an external Ag/AgCl reference electrode and a YSZ(Ag|O_2) pH sensor for high temperature applications are analyzed by using the thermodynamic approach to derive a high temperature pH measurement equation. The two electrodes are employed to measure high temperature pH and the measured pH was compared with the calculated pH by using a solution chemistry method. Concepts and principles for electrode kinetics are also briefly introduced and a modification to the Tafel equations is suggested.

Mechanisms of Swelling of Iron Ore Oxidized Pellets in High Reduction Potential Atmosphere

The influences of the time, temperature and atmosphere on the reduction swelling of oxidized pellets were investigated by single factor experiments. The mechanisms of reduction swelling of oxidized pellets were analyzed and investigated by SEM （scanning electron microscopy） and XRD （X-ray diffractometer） analysis. The results show that the change rules of reduction swelling index of oxidized pellets in different reduction atmospheres are very similar. With the increase of reduction time, the reduction swelling index moves up firstly and then down. When the reduction temperature is above 900 ℃, α-quartz turns into α-tridymite, and the transition generates additional volume expansion effect. The reduction swelling index changes faster in H2 atmosphere than in CO atmosphere. Increasing Ha content in the reduction atmosphere is useful to decrease the reduction swelling index, but it is also easy to cause oxidized pellets cracking.

Magnetic Resonance Gd？RGD Imaging Study of Hepatocellular Carcinoma with High and Low Metastatic Potential before and after Human Bone Marrow？derived Mesenchymal Stem Cell Intervention

Background： Biotherapy based on human bone marrow-derived mesenchymal stem cells （BMSCs） is currently the focus of research, especially in the field of autologous stem cell transplantation. A novel type of metastasis-associated magnetic resonance （MR） molecular imaging probe was constructed, and the changes in metastasis and proliferation of hepatocellular carcinoma （HCC） before and after BMSC intervention were observed through MR imaging （MRI）. Methods：Metastasis-associatedMRmolecularimagingprobe,integrin αvβ3 ligandcRGD-PEG-DGL-DTPA-Gd （Gd-RGD）,wereconstructed. After human BMSC intervention was performed for 6weeks, tumor weight inhibition rates were calculated, and the RGD molecular probe was imaged through MRI with molecular imaging agent Gd-DTPAas control.The signal-to-noise ratio （SNR） and contrast-to-noise ratio （CNR） in the MRI experiment were used as semi-quantitative indicators. Polymerase chain reaction method was performed to detect proliferation- and metastasis-associated indicators, transforming growth factor β-1 （TGFβ1）, osteopontin （OPN）, and integrin subunit αv and β3. Results： The highest tumor weight inhibition rates were observed 3 weeks after the BMSC transplantation. The MR Gd-RGD in the HCC tissues after the BMSC intervention showed less enhancement than Gd-DTPA. The Gd-DTPAMRI of control group had higher SNR and CNR than Gd-RGD MRI in the experimental groups （P 〈 0.05）. For high metastatic potential hepatocellular carcinoma （MHCC97-H）, significant differenceswereobservedintheSNRsandCNRsofGd-RGDMRIbeforeandaftertheBMSCintervention（P〈0.05）.Forlowmetastaticpotential hepatocellular carcinoma （MHCC97-L）, the CNRs of Gd-RGD MRI were statistically different before and after BMSC intervention （P 〈 0.05）. With regard to MHCC97-H, OPN, β3, and TGFβ1 expression significantly decreased after BMSC intervention （P 〈 0.05）. In MHCC97-L and OPN, β3, TGFβ1, and αv expression after BMSC intervention decreased, and the difference was statistically significant （P 〈 0.05）. Conclusions： The CNR index of MRI is a good indicator for distinguishing high- and low-metastatic potential HCC tissues.After BMSC transplantation of MRI through the two kinds of tracer, the SNR and CNR indexes can distinguish two kinds of high and low metastatic potential HCC tissues, and Gd-RGD imaging is more suitable in distinguishing the metastatic potential changes through BMSC intervention.

Characteristics of Landslides Induced by the Great Wenchuan Earthquake

The great Wenchuan （汶川） earthquake induced a large quantity of landslides. They are widely distributed and caused tremendous damages. The sliding mechanism and characteristics of these earthquake-induced landslides are different from those of conventional gravity landslides. Their occurrences are apparently controlled by the powerful earthquake, and they are characterized by high potential energy sliding and ejection sliding. In this article, the earthquake-induced landslides are classified, the characteristics of the sliding and destruction of these landslides are described, and the rela- tionship between the earthquake and the landslides is analyzed. The Donghekou （东河口） landslide is used as an example to characterize fast-moving long-distance earthquake-induced ejection slippage and landslide. This research suggests that many phenomena and issues related to earthquake-induced land- slide are beyond current recognition and knowledge, and new methodologies should be adopted to consider the effect of the earthquake as the paramount factor in the development of landslides. Furthermore, the study of fast-moving long-distance earthquake-induced landslides can also shed light on the formation of old and ancient landslides.