Investigation of electrostatically tunable adhesion and instability of flying head slider

The interfacial adhesion between microstructures is inevitable in a micro-electro-mechanical system(e.g.,hard disk drive(HDD)),which may lead to complicated microtribodynamics problems.This research has investigated the effect of surface potential on the interfacial adhesion and microtribodynamics of the head–disk interface(HDI)in an HDD.A dynamic continuum surface force model,where the electrowetting is considered,is proposed to evaluate the interfacial interaction,and then employed into a two-degree-of-freedom(2DOF)model to theoretically analyze the potential influence mechanism on the microtribodynamics.The results confirm that the elimination of potential can effectively repress the adhesion retention,which is further proved by the measured slider response with a laser Doppler vibrometer(LDV).Moreover,the effect of the potential on the adhesion-induced instability is also analyzed through the phase portrait.It tells that the critical stable flying height can be lowered with the elimination of potential.

Malignant transformation by oncogenic K-ras requires IDH2-mediated reductive carboxylation to promote glutamine utilization

Dear Editor,Oncogenic K-ras mutation plays a major role in malignant transformation and induces significant alterations in cancer cell metabolism[1–4].However,the major molecular players mediating metabolic alterations during K-ras-driven cancer development remain elusive.The observations that tumorigenesis often requires multiple hits suggest that K-ras mutation likely needs the coordination of other molecular events that enable adaptive cellular metabolism for a full malignant transformation.Based on our previous study on the impact of K-ras onmitochondrial metabolism[1,5]and our recent findings that mitochondrial isocitrate dehydrogenase 2(IDH2)could promote the“reverse”flow of the tricarboxylic acid(TCA)cycle fromα-KG to isocitrate and enhance the survival and proliferation of acute myeloid leukemia cells[6],we investigated the potential role of IDH2 in metabolic adaptation during K-ras-driven tumorigenesis.

Development of extruded Mg-6Er-3Y-1.5Zn-0.4Mn(wt.%) alloy with high strength at elevated temperature

A new Mg-6 Er-3 Y-1.5 Zn-0.4 Mn(wt.%) alloy with high strength at high temperature was designed and extruded at 350℃. The as-extruded alloy exhibits ultimate tensile strength of 301 MPa, yield strength(along ED) of 274 MPa and thermal conductivity of 73 W/m·K at 300℃. Such outstanding hightemperature strength is mainly attributed to the formation of nano-spaced solute-segregated basal plane stacking faults(SFs) with a large aspect ratio throughout the entire Mg matrix, fine dynamically recrystallized(DRXed) grains of 1–2μm and strongly textured un-DRXed grains with numerous sub-structures.Microstructural examination unveils that long period stacking ordered(LPSO) phases are formed in Mg matrix of the as-cast alloy when rational design of alloy composition was employed, i.e.(Er + Y): Zn = 3:1 and Er: Y = 1: 1(at.%). It is worth mentioning that it is the first report regarding the formation of nano-spaced basal plane SFs throughout both DRXed and un-DRXed grains in as-extruded alloy with well-designed compositions and processing parameters. The results provide new opportunities to the development of deformed Mg alloys with satisfactory mechanical performance for high-temperature services.

Optimizing yield and chemical compositions of dimethylsulfoxide-extracted birchwood xylan

Dimethylsulfoxide(DMSO)extraction is commonly used to study the chemical structures of orig-inal xylan in the plant cell wall,since the DMSO can preserve the original structure of the xylan as much as possible during the extracting process.In addition,the DMSO-extracted xylans have unique properties allowing their potential applications in emulsifying or filming materials.How-ever,the yield of DMSO-extracted xylan is always low and the effects of different DMSO extraction conditions on the chemical compositions of xylan have not been fully studied,which greatly hin-ders its researches and applications.In this study,we have found that extensive delignification before DMSO extraction results in destruction of lignin-carbohydrate complex(LCC),leading to xylan yield and xylose unit content increased by up to 220%and 20%,respectively.Tert-butanol washing of the holocellulose can further increase the DMSO extracted xylan yield by∼10%.The yield of xylan extracted by the DMSO at 80°C for 7 h was obviously higher than that at room temperature for 3 d by 30%-40%.Thermal analysis showed that the xylans extracted at differ-ent conditions had thermal stability without obvious differences.The results indicate that the DMSO-extracted xylan with a high yield,a high purity and a high degree of acetylation can be ex-tracted at a high delignification level,a high reaction temperature and a short reaction time.This study is of great significance for studying xylan structure-property relationships and promoting the applications of DMSO-extracted xylan.