Micro arc oxidized HAp-TiO2 nanostructured hybrid layers-part I: Effect of voltage and growth time

Micro arc oxidation was employed to grow hydroxyapatite-TiO₂ nanostructured porous composite layers. The layers were synthesized on the titanium substrates in the electrolytes consisting of calcium acetate and sodium β-glycerophosphate salts under different applied voltages for various times. SEM and AFM investigations revealed a porous structure and rough surface where the pores size and the surface roughness were respectively determined as 70-650 nm and 9.8-12.7 nm depending on the voltage and time. Chemical composition and phase structure of the layers were evaluated using EDX, XPS, and XRD methods. The layers consisted of the hydroxyapatite, anatase, α-TCP, and calcium titanatephases with a varying fraction depending on the growth conditions. The hydroxyapatite crystalline size was also determined as ∼42 nm. The sample fabricated under the voltage of 350 V for 3 min exhibited the most appropriate Ca/P ratio (∼1.60) as well as the highest amount of the hydroxyapatite phase. This sample had a fine surface morphology and a high pores density.     

DLC nano-dot surfaces for tribological applications in MEMS devices

With the invention of miniaturized devices like micro-electro-mechanical systems (MEMS), tribological studies at micro/nano-scale have gained importance. These studies are directed towards understanding the interactions between surfaces at micro/nano-scales, under relative motion. In MEMS devices, the critical forces, namely adhesion and friction restrict the smooth operation of the elements that are in relative motion. These miniaturized devices are traditionally made from silicon (Si), whose tribological properties are not good. In this paper, we present a short investigation of nano- and micro-tribological properties of diamond-like carbon (DLC) nano-dot surfaces. The investigation was undertaken to evaluate the potential of these surfaces for their possible application to the miniaturized devices. The tribological evaluation of the DLC nano-dot surfaces was done in comparison with bare Si (1 0 0) surfaces and DLC coated silicon surfaces. A commercial atomic force microscope (AFM) was used to measure adhesion and friction properties of the test materials at the nano-scale, whereas a custom-built micro-tribotester was used to measure their micro-friction property. Results showed that the DLC nano-dot surfaces exhibited superior tribological properties with the lowest values of adhesion force, and friction force both at the nano- and micro-scales, when compared to the bare Si (1 0 0) surfaces and DLC coated silicon surfaces. In addition, the DLC nano-dot surfaces showed no observable wear at the micro-scale, unlike the other two test materials. The superior tribological performance of the DLC nano-dot surfaces is attributed to their hydrophobic nature and the reduced area of contact projected by them.     

First X-ray fluorescence CT experimental results at the SSRF X-ray imaging beamline

X-ray fluorescence CT is a non-destructive technique for detecting elemental composition and distribution inside a specimen. In this paper, the first experimental results of X-ray fluorescence CT obtained at the SSRF X-ray imaging beamline (BL13W1) are described. The test samples were investigated and the 2D elemental image was reconstructed using a filtered back-projection algorithm. In the sample the element Cd was observed. Up to now, the X-ray fluorescence CT could be carried out at the SSRF X-ray imaging beamline.     

哑型急性肺栓塞的临床研究

目的 探讨哑型急性肺栓塞（APE）患者的临床特点和预后。方法 51 例经肺动脉增强CT确诊,但无明显肺栓塞常见临床特征的哑型APE患者予以低分子肝素钠、华法林抗凝治疗。分析患者D- 二聚体、血管彩超、心脏彩超、心电图检查结果,并观察治疗后情况,了解哑型APE患者的临床特点及预后。结果 51 例患者均痊愈出院,4 例患者因出现活动性出血停止抗凝治疗。31 例患者在3个月后复查肺动脉增强CT 未见明显栓塞征象,其余16 例患者在4~6 月后肺栓塞征象消失。结论 哑型APE患者临床表现不典型,肺动脉增强CT 检查是明确诊断的金标准,D-二聚体、心电图等可作为相应的补充,经过恰当及时的治疗,患者预后良好。     

气泡对沉积物声学特性影响研究:以东海沉积物为例

气泡对海底沉积物的声学物理特性的影响在海洋学、海洋地质学和海洋地球物理学等领域中都有着重要的研究意义. 利用Micro-CT扫描仪对沉积物样品进行无损检测扫描, 根据沉积物样品中水、气和固体颗粒对X射线吸收率的不同, 提取了沉积物的气体体积(气泡)含量. 利用智能非金属超声检测仪对沉积物样品进行超声无损测定, 得到沉积物声速与衰减. 通过回归分析, 建立了样品采集海域沉积物孔隙填充气体与流体含量与沉积物声学特性之间的相关关系. 结果表明: 含气量的少许增大就会引起声速的急剧降低和声衰减的急剧上升, 但含气量超过10%后, 这种上升和降低的幅度明显减小.     

基于对数解调的递变能量CT成像方法

复杂结构件由于有效厚度差异大和成像系统动态范围受限, 单一能量下的投影数据信息不完整, 常用CT重建算法及不完全数据重建算法无法在数据缺失严重的情况, 有效实现复杂结构件的CT重建. 为此论文提出基于对数解调的递变能量CT成像方法. 该方法在分析直接高动态CT成像所存在问题的基础上, 提出利用对数变换压缩递变能量投影序列动态范围, 并利用现有的基于图像灰度一致性的融合方法, 计算融合加权系数, 再经常规重建算法实现复杂构件的CT成像. 论文并以某复杂仪表为对象, 进行实验, 相比传统的固定能量成像方式, CT信息完整, 质量高. 从而说明论文所提出的方法, 能够实现CT系统动态范围的扩展, 实现复杂结构件的高动态CT成像.     

B,N-codoped 3D micro-/mesoporous carbon nanofibers web as efficient metal-free catalysts for oxygen reduction

B, N-codoped carbon nanofibers were massively prepared by heat treatment of electrospun carbon nanofibers with the mixture of boric acid/urea in N₂ (BNC_f-N) and subsequently activated in NH₃ (BNC_f-NA). The directly electrospun self-standing 3D non woven structure with void spaces between each fiber facilitates the mass transport of reactant and resulted molecules. Further NH₃ activation gives BNC_f-NA a high surface area of 306.3 m² g⁻¹ with micro/mesoporous structure, providing abundant passageway for proton transfer. Simultaneously, NH₃ activation also realizes the optimization of surface functionalities, such as more B–N–C and pyridinic-N. These intriguing features render BNC_f-NA excellent catalytic behavior with nearly four-electron oxygen reduction reaction (ORR) process in alkaline media, especially much better stability and methanol tolerance than the commercial Pt/C catalyst. Our work provides a large-scale preparation method for efficient metal-free catalysts toward ORR, thus further intensifying the commercial application of fuel cells.     

A simple chip free‐flow electrophoresis for monosaccharide sensing via supermolecule interaction of boronic acid functionalized quencher and fluorescent dye

Here, a simple micro free‐flow electrophoresis (μFFE) was developed for fluorescence sensing of monosaccharide via supermolecule interaction of synthesized boronic acid functionalized benzyl viologen (ο‐BBV) and fluorescent dye. The μFFE contained two open electrode cavities and an ion‐exchange membrane was sandwiched between two polymethylmethacrylate plates. The experiments demonstrated the following merits of developed μFFE: (i) up to 90.5% of voltage efficiency due to high conductivity of ion‐exchange membrane; (ii) a strong ability against influence of bubble produced in two electrodes due to open design of electrode cavities; and (iii) reusable and washable separation chamber (45 mm × 17 mm × 100 μm, 77 μL) avoiding the discard of μFFE due to blockage of solute precipitation in chamber. Remarkably, the μFFE was first designed for the sensing of monosaccharide via the supermolecule interaction of synthesized ο‐BBV, fluorescent dye, and monosaccharide. Under the optimized conditions, the minimum concentration of monosaccharide that could be detected was 1 × 10^?11 M. Finally, the developed device was used for the detection of 0.3 mM glucose spiked in human urine. All of the results demonstrated the feasibility of monosaccharide detection via the μFFE.     

Mechanisms of Non-Newtonian Polymer Flow Through Porous Media Using Navier–Stokes Approach

This study includes solving non-Newtonian Navier–Stokes equation in three-dimensions (real rock images) and two-dimensions (simplified pore geometries) using the finite-difference method. The purpose of this study is to improve understanding of local phenomena leading to the mobilization of residual oil. This involves local pressure variations for non-Newtonian polymers and compares it with Newtonian fluid behavior. When a higher degree of shear thickening is induced, more flow diversion to side channels perpendicular to the main flow path and larger drag on fluids inside side channels will occur. This is consistent with oil mobilization and lowering of residual oil saturation.     

Plasma pharmacochemistry combined with microdialysis to screen potential bioactive components and their metabolites in Anemarrhena asphodeloides saponin extract using ultrahigh‐performance liquid chromatography/quadrupole‐time‐of‐flight mass spectrometry

Although various techniques have been employed to analyze drug metabolites, the metabolism of multicomponent herbal medicine has seldom been fully addressed. In contrast to chemical drugs, a number of compounds in herbal medicine could get into circulation and then be metabolized. Metabolism study on active constituents in herbal medicine is a good way for us to explain and predict a variety of events related to the efficacy and toxicity of herbal medicine. The present work aims to elucidate the multicomponent metabolic characteristics of a herbal medicine by the combination of plasma pharmacochemistry and microdialysis sampling. Anemarrhena asphodeloides, a well‐known traditional Chinese medicine, was chosen as a model. After oral administration of A. asphodeloides saponin extract to rats, microdialysis samples were collected continuously in the jugular vein and analyzed by ultrahigh‐performance LC/quadrupole‐TOF MS. The identification of compounds in biosamples was achieved by accurate mass measurement and detailed fragmentation pathway analysis. The results showed that unbound constituents in blood circulation of the rat included seven parent saponins and six metabolites, which might be the potential active components in vivo. Among which, three metabolites have not been previously reported and were identified in this study. It is the first report on systemic metabolism of total saponins of A. asphodeloides in mammalian plasma.