生物植入用碳纳米管增强混合功能梯度材料的力学性能(英文)

利用羟基磷灰石(HA)、不锈钢316L(SS316L)和碳纳米管(CNT)制备生物医学植入体用混合功能梯度材料(FGM)。加入SS316L和CNT增强功能梯度材料离散层的HA制成三种不同类型的功能梯度材料。第一种功能梯度材料加入10%~40%(质量分数)的SS316L强化微米HA,浓度梯度为10%。第二种功能梯度材料,在第一种功能梯度材料的基础上加入0.5%(质量分数)的功能化碳纳米管。第三种功能梯度材料在第二种功能梯度材料的基础上加入微米HA和纳米HA(1:1)的混合物。所有类型的功能梯度材料在相似的压缩参数和烧结参数下,进行单轴压缩实验,并采用无压烧结技术进行烧结。结果表明,加入碳纳米管和纳米晶体HA提高了功能梯度材料的致密度。碳纳米管增强的功能梯度材料的硬度和断裂韧性增加,但是微米和纳米晶体HA增强的功能梯度材料的硬度和断裂韧性的增加更明显。     

Repurposing of FDA-Approved drugs to predict new inhibitors against key regulatory genes in <i>Mycobacterium tuberculosis</i>

Tuberculosis (TB) disease has become one of the major public health concerns globally, especially in developing countries. Numerous research studies have already been carried out for TB, but we are still struggling for a complete and quick cure for it. The progress of Mycobacterium tuberculosis (MTB) strains resistant to existing drugs makes its cure and control very complicated. Therefore, it is the need of the hour to search for newer and effective drugs that can inhibit an increasing number of putative drug targets. We applied the drug repurposing concept to identify promising FDA-approved drugs against five key-regulatory genes (FurB, IdeR, KstR, MosR, and RegX3) of the MTB. The FDA drugs were virtually screened using a structure-based approach by GOLD versions 5.2, and subjected to rigid docking followed by an induced-fit docking algorithm to enhance the accuracy and prioritize drugs for repurposing. We found 11 candidate drugs (including ZINC03871613, ZINC03871614, ZINC03871615 as top scorer candidate drugs) that were frequently present within the top 20 GoldScore ranks and showed promising results. Furthermore, molecular dynamics simulation was performed to monitor the effect of the top scorer drugs on the structural stability of all the five targets, indicating that inhibitors preferentially bind to the active site of the targets. This work suggests that these known FDA-approved drugs open new application domains in the form of anti-tuberculosis agents.

     

喀麦隆里奥—德雷盆地泥岩底辟构造与油气分布规律

里奥-德雷（Rio del Rey）盆地位于喀麦隆境内、尼日尔三角洲（Niger Delta）东北缘,油气资源十分丰富,已有30余年油气勘探开发历史。古新世以来发生的长期海退和三角洲沉积作用,形成了现今的里奥-德雷被动大陆边缘盆地,其主要发育3个地层单元,自下而上分别为阿卡塔（Akata）组、阿格巴达（Agbada）组和贝宁（Benin）组。在三角洲进积推进过程中,由于大陆边缘的重力作用和三角洲泥岩的塑性推覆作用,由陆向海、自北向南形成了3个构造区,即伸展构造区、泥岩底辟构造区和逆冲推覆构造区。其中,在泥岩底辟构造区形成了许多与泥岩底辟或泥岩脊相关的辟顶背斜、断背斜构造圈闭或辟边岩性遮挡圈闭,现今已发现的大型油气田主要与这些圈闭有关。同时,泥岩底辟的活动也形成了储集和运移方面的优势条件,促使油气在泥岩底辟构造区富集高产。因此,未来泥岩底辟构造区以及与泥岩底辟相关的圈闭仍然是里奥-德雷盆地进一步寻找勘探潜力的主要地区。     

基于轨迹系数特征空间表示法的含有异常情况的自动运动学习

Techniques for understanding video object motion activity are becoming increasingly important with the widespread adoption of CCTV surveillance systems. Motion trajectories provide rich spatiotemporal information about an object's activity. This paper presents a novel technique for clustering of object trajectory-based video motion clips using basis function approximations. Motion cues can be extracted using a tracking algorithm on video streams from video cameras. In the proposed system, trajectories are treated as time series and modelled using orthogonal basis function representation. Various function approximations have been compared including least squares polynomial, Chebyshev polynomials, piecewise aggregate approximation, discrete Fourier transform (DFT), and modified DFT (DFT-MOD). A novel framework, namely iterative hierarchical semi-agglomerative clustering using learning vector quantization (Iterative HSACT-LVQ), is proposed for learning of patterns in the presence of significant number of anomalies in training data. In this context, anomalies are defined as atypical behavior patterns that are not represented by sufficient samples in training data and are infrequently occurring or unusual. The proposed algorithm does not require any prior knowledge about the number of patterns hidden in unclassified dataset. Experiments using complex real-life trajectory datasets demonstrate the superiority of our proposed Iterative HSACT-LVQ-based motion learning technique compared to other recent approaches.     

Nanohydroxyapatite synthesis using optimized process parameters for load-bearing implant

In this study, nanohydroxyapatite (NHA) was synthesized using calcium nitrate tetrahydrate and diammonium hydrogen phosphate via the precipitation method assisted with ultrasonication. Three independent process parameters: temperature (T) (70, 80 and 90°C), ultrasonication time (t) (20, 25 and 30 min), and amplitude (A) (60, 65 and 70%) were studied and optimized using response surface methodology based on 3 factors and 5 level central composite design. The responses of the model were analysed with the help of the particle size measured from field-emission scanning electron microscopy and Brunauer–Emmett–Teller (BET). The surface area of particle was measured with BET and the thermal stability of the powder was measured using thermogravimetric analysis. Finally, with the optimized process parameters obtained from the model, the NHA powder was synthesised and validated against the predicted value. The results show a good agreement with an average error 8% between the actual and predicted values. Moreover, the thermal stability and porosity of synthesized NHA was further improved after calcination. This improvement could be due to the removal of impurities from the NHA powder after calcination as indicated by the Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy.     

Oblique propagation of nonlinear ion-acoustic cnoidal waves in magnetized electron–positron–ion plasmas with nonextensive electrons

Theoretical investigation of nonlinear electrostatic ion-acoustic cnoidal waves(IACWs) is presented in magnetized electron–positron–ion plasma with nonextensive electrons and Maxwellian positrons. Using reductive perturbation technique, Korteweg–de Vries equation is derived and its cnoidal wave solution is analyzed. For given plasma parameters, our model supports only positive potential(compressive) IACW structures. The effect of relevant plasma parameters(viz., nonextensive parameter q, positron concentration p, temperature ratio σ,obliqueness l_3) on the characteristics of IACWs is discussed in detail.     

Mechanical properties of CNT reinforced hybrid functionally graded materials for bioimplants

The hybrid functionally graded materials (FGM) of hydroxyapatite (HA), stainless steel 316L (SS316L) and carbon nanotubes (CNT) were synthesized for biomedical implants. Three different types of FGM were produced by the combination of SS316L and CNT to reinforce HA in discrete layers of FGM. In the first type of FGM, concentration of SS316L was varied from 10% to 40% (mass fraction) with an increment of 10% to reinforce micro HA. In the second type of FGM, 0.5% (mass fraction) functionalized CNT was added by maintaining the rest of composition as that of the first type of FGM. In the third type of FGM, mixture of micro and nano HA (mass ratio1:1) was used, keeping rest of composition similar to the second type of FGM. All types of FGM were subjected to uniaxial compaction and sintered by pressureless sintering technique at similar compaction and sintering parameters. The results show that the densification is enhanced with the addition of CNT and nanocrystalline HA in the FGM. Hardness and fracture toughness increase in both FGM reinforced with CNT, but the increase of the hardness and fracture toughness are more pronounced in FGM with micro and nanocrystalline HA.