Microstructure,texture evolution and mechanical properties of cold rolled Ti-32.5Nb-6.8Zr-2.7Sn biomedical beta titanium alloy

Ti-32.5 Nb-6.8 Zr-2.7 Sn(TNZS,wt%) alloy was produced by using vacuum arc melting method,followed by solution treatment and cold rolling with the area reductions of 50% and 90%.The effects of cold rolling on the microstructure,texture evolution and mechanical properties of the experimental alloy were investigated by optical microscopy,X-ray diffraction,transmission electron microscopy and universal material testing machine.The results showed that the grains of the alloy were elongated along rolling direction and stress-induced α' martensite was not detected in the deformed samples.The plastic deformation mechanisms of the alloy were related to {112} 111 type deformation twinning and dislocation slipping.Meanwhile,the transition from γ-fiber texture to α-fiber texture took place during cold rolling and a dominant {001} 110_(α-fiber) texture was obtained after 90% cold deformation.With the increase of cold deformation degree,the strength increased owing to the increase of microstrain,dislocation density and grain refinement,and the elastic modulus decreased owing to the increase of dislocation density as well as an enhanced intensity of {001} 110_(α-fiber)texture and a weakened intensity of {111} 112_(γ-fiber)texture.The 90% cold rolled alloy exhibited a great potential to become a new candidate for biomedical applications,since it possesses low elastic modulus(47.1 GPa),moderate strength(883 MPa) and high elastic admissible strain(1.87%),which are superior than those of Ti-6 Al-4 V alloy.     

Inhomogeneous softening during annealing of ultrafine-grained silver processed by HPT

The softening in ultrafine-grained silver processed by high-pressure torsion (HPT) was studied during annealing using differential scanning calorimetry (DSC). Two separate exothermic peaks were observed in the DSC thermogram of the HPT-processed sample. It is shown that the first and the second peaks are related to the recrystallization of the middle volume and the surface regions of the HPT-processed disk, respectively. Therefore, a very inhomogeneous sandwich-like microstructure develops during annealing with a soft interior and hard surface layers. The lower thermal stability of the middle region appears to be related to the stronger twinning activity since the twinned volumes can act as nuclei for recrystallized grains. The higher twin-fault probability in the interior is attributed to the larger strain due to the outflow of material between the anvils of the HPT facility during quasi-constrained processing.     

A Smoothed Finite Element Method for Mechanics Problems

In the finite element method (FEM), a necessary condition for a four-node isoparametric element is that no interior angle is greater than 180° and the positivity of Jacobian determinant should be ensured in numerical implementation. In this paper, we incorporate cell-wise strain smoothing operations into conventional finite elements and propose the smoothed finite element method (SFEM) for 2D elastic problems. It is found that a quadrilateral element divided into four smoothing cells can avoid spurious modes and gives stable results for integration over the element. Compared with original FEM, the SFEM achieves more accurate results and generally higher convergence rate in energy without increasing computational cost. More importantly, as no mapping or coordinate transformation is involved in the SFEM, its element is allowed to be of arbitrary shape. Hence the restriction on the shape bilinear isoparametric elements can be removed and problem domain can be discretized in more flexible ways, as demonstrated in the example problems.     

Integrated label-free protein detection and separation in real time using confined surface plasmon resonance imaging

We demonstrate a label-free protein detection and separation technology for real-time monitoring of proteins in micro/nanofluidic channels, confined surface plasmon resonance imaging (confined-SPRi). This was achieved by fabricating ultrathin fluidic channels (500 nm high, 500 microm wide) directly on top of a specialized SPRi sensor surface. In this way, SPRi is uniquely used to detect proteins deep into the fluidic channel while maintaining high lateral accuracy of separated products. The channel fluid and proteins were driven electrokinetically under an external electric field. For this to occur, the metallic SPR sensor (46 nm of Au on 2 nm of Cr) was segmented into an array of squares (each 200 microm x 200 microm in size and spaced 8 microm apart) and coated with 30 nm of CYTOP polymer. In this work, we track label-free protein separation in real time through a simple cross-junction fluidic device with an 8-mm separation channel length under 30 V/cm electric field strength.     

The emergence of spin electronics in data storage

Electrons have a charge and a spin, but until recently these were considered separately. In classical electronics, charges are moved by electric fields to transmit information and are stored in a capacitor to save it. In magnetic recording, magnetic fields have been used to read or write the information stored on the magnetization, which 'measures' the local orientation of spins in ferromagnets. The picture started to change in 1988, when the discovery of giant magnetoresistance opened the way to efficient control of charge transport through magnetization. The recent expansion of hard-disk recording owes much to this development. We are starting to see a new paradigm where magnetization dynamics and charge currents act on each other in nanostructured artificial materials. Ultimately, 'spin currents' could even replace charge currents for the transfer and treatment of information, allowing faster, low-energy operations: spin electronics is on its way.     

Enhanced protein affinity and selectivity of clustered-charge anion-exchange adsorbents

In this work, we examined the possibility of improving ion-exchange adsorbent performance by nanoscale structuring of ligands into clusters of fixed size rather than a random distribution of individual charges. The calcium-depleted form of the protein alpha-lactalbumin, which displays a cluster of acidic amino acid residues, showed enhanced adsorption affinity and capacity on clustered-charge pentalysinamide and pentaargininamide adsorbents as compared to single-charge lysinamide and argininamide adsorbents of matched total charge. Two differently charge-clustered mutants of rat microsomal cytochrome b(5), E11Q and E44Q, with the same total charge also were well differentiated by clustered-charge adsorbents. Thus, an organized rather than random distribution of charges may produce adsorbents with higher capacity and selectivity, especially for biomolecules with inherent charge clustering.     

GaN-based light-emitting diodes prepared on vicinal sapphire substrates

Thin InGaN epitaxial layers and GaN-based light-emitting diodes (LEDs) on conventional and vicinal cut sapphire substrates are prepared. It is found that indium atoms are distributed much more uniformly in the samples prepared on vicinal cut sapphire substrates. It is also found that stronger electroluminescence intensity can be achieved without the band-filling effect of localised states from the LEDs with vicinal cut sapphire substrate. With 20 mA current injection, it is found that 44% electroluminescence intensity enhancement can be achieved by using the 1deg tilted sapphire substrate     

On the elastic plastic initial-boundary value problem and its numerical integration

An interative approach is proposed for the numerical analysis of elastic–plastic continua. This approach gives after convergence an implicit scheme of integration of the evolution problem, and is concerned with elastic-perfectly plastic materials and with hardening standard materials. Under a generalized assumption of positive hardening, the proof of convergence of the iterative solutions is given. Some numerical examples by the finite element method are also discussed.     

预测DEB-TACE治疗肝细胞肝癌术后生存率的放射组学列线图

【摘要】 目的 探讨CT放射组学列线图模型预测CalliSpheres药物洗脱微球- 经导管动脉栓塞术（DEB- TACE）治疗肝细胞癌（HCC）生存期的价值。方法 回顾性分析2016年1月至2018年12月经穿刺病理或临床诊断为HCC,且巴塞罗那临床肝癌B期（BCLC- B）行DEB- TACE的100例患者（训练组60例,测试组40例）。利用A.K.软件进行术前CT影像组学特征提取,并将选定的特征与相应的非零系数相乘的线性组合来计算每个患者的放射组学评分（Rad- score）。Cox回归分析与术后生存相关的独立危险因素。根据独立危险因素,共建立5个预测模型,并进行模型间AUC比较,选出最佳预测模型。以最佳预测模型生成影像组学列线图,并用校准图形法直观表示其预测符合度。结果 100例患者中,存活52例,死亡48例。肿瘤数目、GGT、Rad-score值是影响DEB- TACE治疗HCC术后生存期的独立危险因素,临床- 静脉期影像组学联合模型在训练组和验证组中的AUC及准确率最高（训练组AUC=0.921,准确率84.4%;验证组AUC=0.904,准确率81.5%）,为最佳模型。该模型在训练组和验证组中都显示出良好的校正能力。结论 术前CT影像组学列线图模型对预测DEB- TACE治疗BCLC- B期HCC生存期具有价值。