Effects of chromium on the corrosion and electrochemical behaviors of ultra high strength steels

The effects of chromium on the corrosion and the electrochemical behaviors of ultra high strength steels were studied by the salt spray test and electrochemical methods. The results show that ultra high strength steels remain martensite structures and have anodic dissolution characteristic with an increase of chromium content. There is no typical passive region on the polarization curves of an ultra high strength stainless steel, AerMet 100 steel, and 300M steel. However, chromium improves the corrosion resistance of the stainless steel remarkably. It has the slowest corrosion rate in the salt spray test, one order of magnitude less than that of AerMet 100 and 300M steels. With the increase of chromium content, the polarization resistance becomes larger, the corrosion potential shifts towards the positive direction with a value of 545 mV, and the corrosion current density decreases in electrochemical measures in 3.5wt% NaCl solutions. Because of the higher content of chromium, the ultra high strength stainless steel has a better corrosion resistance than AerMet 100 and 300M steels.

Heavy-ion and pulsed-laser single event effects in 130-nm CMOS-based thin/thick gate oxide anti-fuse PROMs

Single event effects of 1-T structure programmable read-only memory(PROM) devices fabricated with a 130-nm complementary metal oxide semiconductorbased thin/thick gate oxide anti-fuse process were investigated using heavy ions and a picosecond pulsed laser. The cross sections of a single event upset(SEU) for radiationhardened PROMs were measured using a linear energy transfer(LET) ranging from 9.2 to 95.6 MeV cm^2mg^(-1).The result indicated that the LET threshold for a dynamic bit upset was ～ 9 MeV cm^2mg^(-1), which was lower than the threshold of ～ 20 MeV cm^2mg^(-1) for an address counter upset owing to the additional triple modular redundancy structure present in the latch. In addition, a slight hard error was observed in the anti-fuse structure when employing209 Bi ions with extremely high LET values(～ 91.6 MeV cm^2mg^(-1)) and large ion fluence(～ 1×10~8 ions cm^(-2)). To identify the detailed sensitive position of a SEU in PROMs, a pulsed laser with a 5-μm beam spot was used to scan the entire surface of the device.This revealed that the upset occurred in the peripheral circuits of the internal power source and I/O pairs rather than in the internal latches and buffers. This was subsequently confirmed by a ^(181)Ta experiment. Based on the experimental data and a rectangular parallelepiped model of the sensitive volume, the space error rates for the used PROMs were calculated using the CRèME-96 prediction tool. The results showed that this type of PROM was suitable for specific space applications, even in the geosynchronous orbit.

Verification of SEU resistance in 65 nm high-performance SRAM with dual DICE interleaving and EDAC mitigation strategies

A dual double interlocked storage cell(DICE)interleaving layout static random-access memory(SRAM)is designed and manufactured based on 65 nm bulk complementary metal oxide semiconductor technology.The single event upset(SEU)cross sections of this memory are obtained via heavy ion irradiation with a linear energy transfer(LET)value ranging from 1.7 to 83.4 MeV/(mg/cm^(2)).Experimental results show that the upset threshold(LETth)of a 4 KB block is approximately 6 MeV/(mg/cm^(2)),which is much better than that of a standard unhardened SRAM with an identical technology node.A 1 KB block has a higher LETth of 25 MeV/(mg/cm^(2))owing to the use of the error detection and correction(EDAC)code.For a Ta ion irradiation test with the highest LET value(83.4 MeV/(mg/cm^(2))),the benefit of the EDAC code is reduced significantly because the multi-bit upset proportion in the SEU is increased remarkably.Compared with normal incident ions,the memory exhibits a higher SEU sensitivity in the tilt angle irradiation test.Moreover,the SEU cross section indicates a significant dependence on the data pattern.When comprehensively considering HSPICE simulation results and the sensitive area distributions of the DICE cell,it is shown that the data pattern dependence is primarily associated with the arrangement of sensitive transistor pairs in the layout.Finally,some suggestions are provided to further improve the radiation resistance of the memory.By implementing a particular design at the layout level,the SEU tolerance of the memory is improved significantly at a low area cost.Therefore,the designed 65 nm SRAM is suitable for electronic systems operating in serious radiation environments.

Prediction of proton-induced SEE error rates for the VATA160 ASIC

We predict proton single event effect(SEE)error rates for the VATA160 ASIC chip on the Dark Matter Particle Explorer(DAMPE) to evaluate its radiation tolerance.Lacking proton test facilities,we built a Monte Carlo simulation tool named PRESTAGE to calculate the proton SEE cross-sections.PRESTAGE is based on the particle transport toolkit Geant4.It adopts a location-dependent strategy to derive the SEE sensitivity of the device from heavy-ion test data,which have been measured at the HI-13 tandem accelerator of the China Institute of Atomic Energy and the heavy-ion research facility in Lanzhou.The AP-8,SOLPRO,and August 1972 worst-case models are used to predict the average and peak proton fluxes on the DAMPE orbit.Calculation results show that the averaged proton SEE error rate for the VATA160 chip is approximately 2.17×10^(-5)/device/day.Worst-case error rates for the Van Allen belts and solar energetic particle events are 1-3 orders of magnitude higher than the averaged error rate.

Clinical stages of recurrent hepatocellular carcinoma: A retrospective cohort study

BACKGROUND Hepatocellular carcinoma(HCC)is the second leading cause of cancer-related death worldwide,and has relatively high recurrence rates.Few studies have been published on the clinical stages of recurrent HCC.AIM To assess the applicability of the Barcelona Clinic Liver Cancer(BCLC)staging for recurrent HCC and the need to establish clinical stage criteria for recurrent HCC.METHODS The clinicopathological data of 81 patients with recurrent HCC who were admitted to the Hospital of Guangxi Zhuang Autonomous Region from January 2013 to December 2017 were collected.The patients were divided into three groups according to the BCLC staging system as follows:(1)Group A with BCLC stage A,51 patients;(2)Group B with BCLC stage B,14 patients;and(3)Group C with BCLC stage C,16 patients.The median time to tumor recurrence and the median overall survival were compared.RESULTS The median time to tumor recurrence in groups A,B,and C was 16±1.5 mo,10±2.8 mo,and 6±0.5 mo,respectively,with a statistically significant difference among them(χ^(2)=70.144,P<0.05);no statistically significant difference was noted between group A and group B(χ^(2)=2.659,P>0.05),although there were statistically significant differences between group A and group C and between group B and group C(χ^(2)=62.110,and 19.972,P<0.05).The median overall survival in groups A,B,and C were 42±5.1 mo,22±3.1 mo,and 13±1.8 mo,respectively,with a statistically significant difference among them(χ2=38.949,P<0.05);there were statistically significant differences between group A and group B,group A and group C,and group B and group C(χ2=9.577,37.172,and 7.183,respectively;P<0.05).CONCLUSION There are different prognoses in recurrent HCC patients according to the BCLC staging.Therefore,BCLC staging is applicable to recurrent HCC and it is essential to formulate clinical stage criteria for recurrent HCC.

Experimental study on heavy ion single-event effects in flash-based FPGAs

With extensive use of flash-based field-programmable gate arrays(FPGAs) in military and aerospace applications, single-event effects(SEEs) of FPGAs induced by radiations have been a major concern. In this paper, we present SEE experimental study of a flash-based FPGA from Microsemi Pro ASIC3 product family. The relation between the cross section and different linear energy transfer(LET) values for the logic tiles and embedded RAM blocks is obtained. The results show that the sequential logic cross section depends not too much on operating frequency of the device. And the relationship between 0 →1 upsets(zeros) and 1 →0 upsets(ones) is different for different kinds of D-flip-flops. The devices are not sensitive to SEL up to a LET of 99.0 Me V cm2/mg.Post-beam tests show that the programming module is damaged due to the high-LET ions.

Influences of total ionizing dose on single event effect sensitivity in floating gate cells

The influences of total ionizing dose （TID） on the single event effect （SEE） sensitivity of 34-nm and 25-nm NAND flash memories are investigated in this paper. The increase in the cross section of heavy-ion single event upset （SEU） in memories that have ever been exposed to TID is observed, which is attributed to the combination of the threshold voltage shifts induced by 7-rays and heavy ions. Retention errors in floating gate （FG） cells after heavy ion irradiation are observed. Moreover, the cross section of retention error increases if the memory has ever been exposed to TID. This effect is more evident at a low linear energy transfer （LET） value. The underlying mechanism is identified as the combination of the defects induced by 7-rays and heavy ions, which increases the possibility to constitute a multi-trap assisted tunneling （m- TAT） path across the tunnel oxide.

Differences in MBUs induced by high-energy and medium-energy heavy ions in 28 nm FPGAs

Multiple-bit upsets(MBUs)have become a threat to modern advanced field-programmable gate arrays(FPGAs)applications in radiation environments.Hence,many investigations have been conducted using mediumenergy heavy ions to study the effects of MBU radiation.However,high-energy heavy ions(HEHIs)greatly affect the size and percentage of MBUs because their ionizationtrack structures differ from those of medium-energy heavy ions.In this study,the different impacts of high-energy and medium-energy heavy ions on MBUs in 28 nm FPGAs as well as their mechanisms are thoroughly investigated.With the Geant4 calculation,more serious energy effects of HEHIs on MBU scales were successfully demonstrated.In addition,we identified worse MBU responses resulting from lowered voltages.The MBU orientation effect was observed in the radiation of different dimensions.The broadened ionization tracks for tilted tests in different dimensions could result in different MBU sizes.The results also revealed that the ionization tracks of tilted HEHIs have more severe impacts on the MBU scales than mediumenergy heavy ions with much higher linear energy transfer.Therefore,comprehensive radiation with HEHIs is indispensable for effective hardened designs to apply highdensity 28 nm FPGAs in deep space exploration.

Investigation of flux dependent sensitivity on single event effect in memory devices

Heavy-ion flux is an important experimental parameter in the ground based single event tests. The flux impact on a single event effect in different memory devices is analyzed by using GEANT4 and TCAD simulation methods. The transient radial track profile depends not only on the linear energy transfer （LET） of the incident ion, but also on the mass and energy of the ion. For the ions with the energies at the Bragg peaks, the radial charge distribution is wider when the ion LET is larger. The results extracted from the GEANT4 and TCAD simulations, together with detailed analysis of the device structure, are presented to demonstrate phenomena observed in the flux related experiment. The analysis shows that the flux effect conclusions drawn from the experiment are intrinsically connected and all indicate the mechanism that the flux effect stems from multiple ion-induced pulses functioning together and relies exquisitely on the specific response of the device.

Strategy to mitigate single event upset in 14-nm CMOS bulk FinFET technology

Three-dimensional(3 D)TCAD simulations demonstrate that reducing the distance between the well boundary and N-channel metal-oxide semiconductor(NMOS)transistor or P-channel metal-oxide semiconductor(PMOS)transistor can mitigate the cross section of single event upset(SEU)in 14-nm complementary metal-oxide semiconductor(CMOS)bulk Fin FET technology.The competition of charge collection between well boundary and sensitive nodes,the enhanced restoring currents and the change of bipolar effect are responsible for the decrease of SEU cross section.Unlike dualinterlock cell(DICE)design,this approach is more effective under heavy ion irradiation of higher LET,in the presence of enough taps to ensure the rapid recovery of well potential.Besides,the feasibility of this method and its effectiveness with feature size scaling down are discussed.

聚合物微针药物经皮递送应用研究进展

微针是一种新型的药物经皮递送技术,能穿透皮肤角质层,形成微孔通道,促进药物的渗透和吸收,在药物递送中有重要作用.本文从微针的结构和功能特点,系统阐述了聚合物微针的结构和功能设计,以及制造聚合物微针的材料和方法、微针的给药方式;综述了微针经皮递送技术近年来在抗肿瘤、疫苗递送、血糖调控、组织液提取和检测,以及生物传感等领域中的研究进展,并对其优势及存在的问题进行分析,总结了微针技术发展需要解决的关键问题,展望了微针疫苗未来的发展方向.

Fabrication of h-Mn0_(2)@PDA composite nanocarriers for enhancement of anticancer cell performance by photo-chemical synergetic therapies

The development of functional nanocarriers with multifunctional ability and expected degradability is of great significance for efficient drug delivery on tumor therapy.The release of non-specific drugs and serious side effects severely limit their therapeutic effectiveness,although chemotherapy has been far and widely used in clinical practice[1-4].In the past few decades,nanosized drug carriers integrated with multi-responsive properties have emerged as promising candidates for anticancer treatment due to their long circulation in the bloodstream,high drug loading capacity,and“passive”targeting capability on account of the enhanced permeability and retention(EPR)effect[5-8].

Mechanically Strong Janus Poly(N-isopropylacrylamide)/Graphene Oxide Hydrogels as Thermo-responsive Soft Robots

Simple preparation of stimuli-responsive hydrogels with good mechanical properties and mild stimuliresponsiveness is essential for their applications as smart soft robots. Mechanically strong Janus poly（Nisopropylacrylamide）/graphene oxide（PNIPAM/GO） nanocomposite hydrogels with stimuli-responsive bending behaviors are prepared through a simple one-step method by using molds made of a Teflon plate and a glass plate. Residual oxygen in the air bubbles on the Teflon plate surface affects the polymerization and hence the cross-linking density, leading to the different swelling/deswelling rates of the two sides of the gels. Therefore, the hydrogels exhibit bending/unbending behaviors upon heating/cooling in water. The incorporation of GO nanosheets dramatically enhances the mechanical properties of Janus hydrogels. Meanwhile, the photo-responsive property of the GO nanosheets also imparts the hydrogels with remotecontrollable deformation under IR irradiation. The application of the Janus PNIPAM/GO hydrogels as thermo-responsive grippers is demonstrated.