One-dimensional Bi<Subscript>2</Subscript>Mo<Subscript>x</Subscript>W<Subscript>1-x</Subscript>O<Subscript>6</Subscript> sosoloids: controllable synthesis by electrospinning process and enhanced photocatalytic performance

One-dimensional Bi₂Mo_xW_1-xO₆ (x = 0, 0.2, 0.5, 0.67, and 1) photocatalysts have been successfully synthesized for the first time by a straightforward electrospinning technique with a calcination process. The as-formed Bi₂Mo_xW_1-xO₆ nanofibers are composed of inter-linked nanosheets of 30–50 nm in size and characterized by thermogravimetric and differential scanning calorimetric, Fourier transform infrared, Raman spectra, X-ray powder diffraction, scanning electron microscope, Brunauer-Emmett-Teller, transmission electron microscope, UV-Vis spectroscopy, photoluminescence, HPLC, and EIS. The photodegradation behaviors towards organic dyes, including rhodamine B (RhB) and methylene blue (MB) are investigated, and the results illustrate that Bi₂Mo_0.25W_0.75O₆ nanofibers exhibit the highest photocatalytic performance under visible light irradiation than Bi₂Mo_xW_1-xO₆ (x = 0, 0.2, 0.5, 0.67, and 1) samples. The possible mechanisms of the enhanced photocatalytic properties are discussed in detail.     

Effect of ZnS layers on optical properties of prepared CdS/TiO<Subscript>2</Subscript> nanotube arrays for photocatalyst

The TiO₂ nanotube arrays (TiO₂ NTAs) prepared by re-oxidation were chosen as basement. The NTAs prepared through re-oxidation show smoother surface and more uniform tube mouth on large scale compared with the first as-grown one. We use successive ionic layer adsorption and reaction method to deposit quantum dots (ZnS and CdS) onto the sample successively. The findings reveal that two kinds of quantum dots (～10 nm) distribute regularly and the nanotube mouth is open. From the UV–Vis absorption spectrum of samples, the red shift occurs after the sedimentation of the two quantum dots, which proves that the double modification can expand the absorption to 650 nm. Among all specimens, the sample produced by co-deposition has the highest speed of catalytic efficiency of 90.7% compared with bare TiO₂ NTAs (52.9%) and just CdS QDs sensitized sample (65.8%). In the test of photocatalysis durability, the decay percentages of CdS/TiO₂ NTAs and ZnS/CdS/TiO₂ NTAs were 35.8 and 48.4%, respectively, which means that the ZnS passivation layer plays a crucial role in enhancing photocatalytic activities.     

Pharmacokinetic analysis and drug delivery efficiency of the focused ultrasound-induced blood-brain barrier opening in non-human primates

PurposeFocused Ultrasound (FUS) in conjunction with systemically administered microbubbles has been shown to open the Blood-Brain Barrier (BBB) locally, non-invasively and reversibly in rodents and non-human primates (NHP), suggesting the immense potential of this technique. The objective of this study entailed the investigation of the physiologic changes in the brain following the FUS-induced BBB opening and their relationship with the underlying anatomy.Materials and methodsPharmacokinetic analysis was implemented in NHP's that received FUS at various acoustic pressures. Relaxivity mapping enabled the robust quantitative detection of the BBB opening as well as grey and white matter segmentation. Drug delivery efficiency was measured for pre-clinical validation of the technique.ResultsBased on our results, the opening volume and the amount of the gadolinium delivered were found mostly contained in the grey matter, while FUS-induced permeability and drug concentration varied depending upon the underlying brain inhomogeneity, and increased with the acoustic pressure.ConclusionsOverall, apart from the in vivo protocols for BBB analysis developed here, this study also suggests the important role that FUS can have in efficient drug delivery via localized and transient BBB opening.     

The inelastic electron tunneling spectroscopy of edge-modified graphene nanoribbon-based molecular devices

The inelastic electron tunneling spectroscopy(IETS) of four edge-modified finite-size grapheme nanoribbon(GNR)-based molecular devices has been studied by using the density functional theory and Green's function method. The effects of atomic structures and connection types on inelastic transport properties of the junctions have been studied. The IETS is sensitive to the electrode connection types and modification types. Comparing with the pure hydrogen edge passivation systems, we conclude that the IETS for the lower energy region increases obviously when using donor–acceptor functional groups as the edge modification types of the central scattering area. When using donor–acceptor as the electrode connection groups, the intensity of IETS increases several orders of magnitude than that of the pure ones. The effects of temperature on the inelastic electron tunneling spectroscopy also have been discussed. The IETS curves show significant fine structures at lower temperatures. With the increasing of temperature, peak broadening covers many fine structures of the IETS curves.The changes of IETS in the low-frequency region are caused by the introduction of the donor–acceptor groups and the population distribution of thermal particles. The effect of Fermi distribution on the tunneling current is persistent.     

A generalized model of TiO_x-based memristive devices and its application for image processing

Memristive technology has been widely explored, due to its distinctive properties, such as nonvolatility, high density,versatility, and CMOS compatibility. For memristive devices, a general compact model is highly favorable for the realization of its circuits and applications. In this paper, we propose a novel memristive model of TiO_x-based devices, which considers the negative differential resistance(NDR) behavior. This model is physics-oriented and passes Linn's criteria. It not only exhibits sufficient accuracy(IV characteristics within 1.5% RMS), lower latency(below half the VTEAM model),and preferable generality compared to previous models, but also yields more precise predictions of long-term potentiation/depression(LTP/LTD). Finally, novel methods based on memristive models are proposed for gray sketching and edge detection applications. These methods avoid complex nonlinear functions required by their original counterparts. When the proposed model is utilized in these methods, they achieve increased contrast ratio and accuracy(for gray sketching and edge detection, respectively) compared to the Simmons model. Our results suggest a memristor-based network is a promising candidate to tackle the existing inefficiencies in traditional image processing methods.     

利用Pr_(70)Cu_(30)晶界扩散改善烧结钕铁硼废料矫顽力的研究

钕铁硼磁体制备过程中出现的部分块体废料由于矫顽力较低,性能难以满足使用要求.本文主要通过晶界扩散技术来提高废料磁体的矫顽力.采用Pr_(70)Cu_(30)合金作为扩散介质,对烧结钕铁硼废料磁体进行了晶界扩散处理,研究了扩散温度、扩散时间和回火时间对扩散后的磁体性能的影响.结果显示,800℃下扩散3 h,磁体的矫顽力从原来的7.88 kOe(1 Oe=79.5775 A/m)提升至11.55 kOe,提升幅度为46.6%,同时剩磁没有明显降低.扩散后回火对矫顽力的提升有一定的作用.800℃下扩散4h后的磁体在500℃回火3h后,最高矫顽力可达11.97 kOe,比原磁体废料提高了51.9%,接近成品磁体的水平.显微组织分析证实了晶界扩散的作用.扩散处理后的磁体中,主相晶粒间形成了连续晶间相,起到有效的磁隔离作用,有利于矫顽力的提高.研究还发现,Pr_(70)Cu_(30)晶界扩散虽然可以使磁体腐蚀电位上升,但也会增加腐蚀电流密度,不利于磁体抗腐蚀性的改善.本文工作对于提高材料的成品率具有重要意义.     

无铅四方相钙钛矿短周期超晶格压电效应机理研究

超晶格压电行为与内部正离子之间的内在联系尚缺乏相关的研究.本文基于密度泛函理论的第一性原理方法,研究了三种无铅四方相钙钛矿铁电超晶格(BaTiO_3/SrTiO_3,KNbO_3/KTaO_3和BaTiO_3/KNbO_3)中A,B位正离子对整体的极化和压电贡献.通过计算超晶格不同轴向应变条件下原子结构和Born有效电荷,获得了超晶格和各个正离子的极化值和压电系数.结果表明,在轴向压缩应变条件下(-0.15—0 A),无铅超晶格中的正离子位移D(A)和D(B)受到抑制,在拉应变时位移才显著增大,因此极化和压电行为不明显.在轴向拉伸应变作用下(0—0.15 A),无铅超晶格中各原子的极化贡献显著增大,特别是B位原子Ti,Nb和Ta的极化贡献使得总的极化强度也显著提高,并当拉应变达到一定值,超晶格才会出现明显的压电行为.无铅超晶格的极化和压电行为主要由B位正离子贡献.     

空心Fe_3O_4纳米微球的制备及超顺磁性

采用水热控制合成法,以六水三氯化铁、柠檬酸三钠和尿素为原料,聚丙烯酰胺为稳定剂, 200?C下反应12 h制备得到了超顺磁性空心Fe_3O_4纳米微球.通过X射线衍射仪、扫描电子显微镜、透射电子显微镜对样品的结构和形貌进行表征,并采用振动样品磁强计测试了样品的磁性能.结果表明:所得样品为具有尖晶石结构的Fe_3O_4纳米微球,尺寸为160 nm左右,呈分等级结构,即整个微球由粒径约18 nm的初级晶粒自组装堆叠而成;室温下表现为典型的超顺磁性,且饱和磁化强度为73.3 emu/g (1 emu/g=1 A·m~2/kg),这种高饱和磁化强度可以由其初级晶粒晶化程度高且粒径较大以及这种特殊的二次自组装结构进行解释.这种Fe_3O_4纳米微球为疏松多孔的空心球状结构,具有粒径分布均匀、分散性良好和超顺磁性的特点,在药物靶向输运和肿瘤热疗中有潜在的应用.     

Electrical and structural properties enhancement in plasticized high Tg polymers using metal salts

Plasticized polymer electrolyte composite has been prepared in the form of a film by solution casting method. Poly (ethyl methacrylate) (PEMA) acts as a host polymer and is doped with Sodium Iodide (NaI). Ethylene carbonate (EC) added as a plasticizer and also enhances amorphicity of the polymer electrolyte. The electrical conductivity of the PEMA+NaI was evaluated using complex impedance spectroscopy. Maximum ionic conductivity obtained at room temperature was 8.75 × 10^?6 S/cm with the composition of PEMA: NaI (30%) + 60% EC. The conductivity further increased with increase in temperature and moved up to 5.8 × 10^?5 S/cm. Scanning electron microscopy was used to study the surface morphology of the composite film. Fourier transform infrared ray and X-ray diffraction data confirmed the complexation of material.     

Laser transmission welding of poly(ethylene terephthalate) and biodegradable poly(ethylene terephthalate) – Based blends

Joining of Poly(Ethylene Terephthalate) PET and its biodegradable derivatives is of high relevance to ensure good productive rate, low cost and operational safety for fabrication of medical and electronic devices, sport equipments as well as for manufacturing of food and drug packaging solutions. In the present investigation, granules of PET and PETs modified by organic additives, which promote biodegradation of the polymeric chains, were prepared by extrusion compounding. The achieved granules were subsequently re-extruded to shape thin (330 μm) flat sheets. Substrates cut from these sheets were joined by Laser Transmission Welding (LTW) with a continuous wave High Power Diode Laser (cw-HPDL). First, based on a qualitative evaluation of the welded joints, the most suitable operational windows for PETs laser joining were identified. Second, characterization of the mechanical properties of the welded joints was performed by tensile tests. Accordingly, Young's modulus of PET and biodegradable PET blends was studied by Takayanagi's model and, based on the experimental results, a novel predicting analytical model derived from the mixture rule was developed. Lastly, material degradation of the polymeric joints was evaluated by FT-IR analysis, thus allowing to identify the main routes to thermal degradation of PET and, especially, of biodegradable PET blends during laser processing.