PCN-Fe(III)-PTX nanoparticles for MRI guided high efficiency chemo-photodynamic therapy in pancreatic cancer through alleviating tumor hypoxia

As nanomedicine-based clinical strategies have continued to develop, the possibility of combining chemotherapy and singlet oxygen-dependent photodynamic therapy (PDT) to treat pancreatic cancer (PaC) has emerged as a viable therapeutic modality. The efficacy of such an approach, however, is likely to be constrained by the mechanisms of drug release and tumor oxygen levels. In the present study, we developed an Fe(III)-complexed porous coordination network (PCN) which we then used to encapsulate PTX (PCN-Fe(III)-PTX) nanoparticles (NPs) in order to treat PaC via a combination of chemotherapy and PDT. The resultant NPs were able to release drug in response to both laser irradiation and pH changes to promote drug accumulation within tumors. Furthermore, through a Fe(III)-based Fenton-like reaction these NPs were able to convert H₂O₂ in the tumor site to O₂, thereby regulating local hypoxic conditions and enhancing the efficacy of PDT approaches. Also these NPs were suitable for use as a T₁-MRI weighted contrast agent, making them viable for monitoring therapeutic efficacy upon treatment. Our results in both cell line and animal models of PaC suggest that these NPs represent an ideal agent for mediating effective MRI-guided chemotherapy-PDT, giving them great promise for the clinical treatment of PaC.

     

Synthesis and transformation of zero-dimensional Cs3BiX6 (X = Cl,Br) perovskite-analogue nanocrystals

The unique structure of zero-dimensional (0D) perovskite-analogues has attracted a great amount of research interest in recent years. To date, the current compositional library of 0D perovskites is largely limited to the lead-based Cs₄PbX₆ (X = Cl, Br, and I) systems. In this work, we report a new synthesis of lead-free 0D Cs₃BiX₆ (X = Cl, Br) perovskite-analogue nanocrystals (NCs) with a uniform cubic shape. We observe a broad photoluminescence peak centered at 390 nm for the 0D Cs₃BiCl₆ NCs at low temperatures. This feature originates from a self-trapped exciton mechanism. In situ thermal stability studies show that Cs₃BiX₆ NCs remain stable upon heating up to 200 °C without crystal structural degradation. Moreover, we demonstrate that the Cs₃BiX₆ NCs can transform into other bismuth-based perovskite-analogues via facile anion exchange or metal ion insertion reactions. Our study presented here offers the opportunity for further understanding of the structure-property relationship of 0D perovskite-analogue materials, leading toward their future optoelectronic applications.

     

用于矿山等极端环境中的高精度定位算法

高精度室内定位技术在矿山、建筑、施工等多种极端环境下都有需求。基于超宽带通信(Ultra Wideband,UWB)的室内定位技术能够提供较高的定位精度,但超宽带信号易受到障碍物的干扰,并且在类似矿山等极端环境中,障碍物不可避免。因此,超宽带非视线传输(Non-Line-of-Sight,NLoS)测距成为当前的一个研究热点。当前研究大多集中在识别和消除非视线传输对超宽带测距的影响上,实际应用中,大多数情形下超宽带信号根本无法穿透障碍物,会导致定位标签只能够与2个或1个信标节点通信,但完成三边定位至少需要3个信标节点。为此,提出了一种基于目标行为分析的定位算法,该算法能够在短时间内仅剩余一个信标节点与标签通信时,也可实现高精度定位。该算法以超宽带通信为基础,使用信号飞行时间(Time of Flight,TOF)算法测距并定位。通过分析信号正常时的目标运动轨迹来判断其速度和方向,当信号不正常时(可通信的信标节点减少),可利用预测的速度和方向参数来实现辅助定位。将该算法部署在一个基于超宽带定位的系统中进行了测试,结果表明:当能够与标签通信并完成TOF算法的信标节点数量少于3个时,基于NLoS传输识别和消除的算法无法完成定位,而基于目标行为分析的定位算法依然能够实现定位,在单信标节点区域的平均定位误差为0.93 m,最大误差为1.41 m,在2个信标节点测距的区域,平均定位误差为0.64 m,最大误差为1.2 m。     

煤矿井下探测中影响不含水断层视电阻率变化的单一主控因素分析

选取晋城矿区典型3号无烟煤试样，在实验室进行单轴加载条件下的电阻率测试实验，并开展矿井瞬变电磁法探测不含水断层现场试验，研究了不含水断层的视电阻率变化特征。结果表明:煤样加载全过程，经过压密阶段、弹性变形阶段、塑性变形阶段、峰值后破裂阶段、残余变形阶段5个阶段；煤样应力应变曲线表现为由低到高再到低的特征，煤样电阻率曲线表现为由高到低再到高的特征；加载过程中，压密阶段、弹性变形阶段应力越大电阻率越小，应力为影响电阻率变化的主控因素；塑性变形阶段，电阻率先减小后增大，应力和裂隙共同影响电阻率变化，由应力为主要因素逐渐转变到裂隙为主要因素；峰值后破裂阶段和残余变形阶段电阻率急速增大，裂隙为影响电阻率变化的主控因素；通过瞬变电磁法探测不含水断层试验，发现不含水断层导致视电阻率明显升高，表明裂隙为影响断层视电阻率单一变化的主要因素。     

Evaluation of Ca-doped BaZrO3 as the crucible refractory for melting TiAl alloys

In this study, a new Ca-doped BaZrO₃ refractory was designed by using thermodynamics approaches and tested for its applicability for vacuum induction melting (VIM) of TiAl alloys. The influence of CaO on the BaZrO₃ phase constitution and microstructure, as well as the key features of the TiAl melt interaction with the Ca-doped BaZrO₃ crucibles were investigated by X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). Results revealed that the Ca-doped BaZrO₃ refractory consisted of Ba_1-xCa_xZrO₃ and CaO phases. An obvious interaction occurred during the melting of the TiAl alloy in the Ca-doped BaZrO₃ crucible along with the generation of BaAl₂O₄ as a reaction product, with formation of a reaction layer up to 5?µm thick. Dissolution of Ca-doped BaZrO₃ refractory in the TiAl melt was the main reason for the alloy-crucible reaction. Moreover, the Ca-doped BaZrO₃ crucible was found to substantially reduce the contamination of the TiAl alloy, with lower oxygen concentration as compared with other conventional oxide crucibles. Overall results confirmed that vacuum induction melting using the Ca-doped BaZrO₃ refractory can be considered as an appropriate method for the fabrication of TiAl alloys.     

Preparation and corrosion resistance of cordierite–spodumene composite ceramics using zircon as a modifying agent

To prolong the service life of cordierite–spodumene composite ceramics applied to the solar heat transmission pipeline, the zircon modifier was introduced to improve the corrosion resistance of the ceramics. The effects of zircon on the density, bending strength, crystalline phase, microstructure and chemical stability were studied. The results showed that the sintering temperature range of the composite ceramics was broadened to 40–60?°C with the introduction of 5–15?wt% zircon. Moreover, the mechanical strength and corrosion resistance of the ceramic materials were improved with the zircon introduction. In particular, sample C3 containing 15?wt% of zircon and sintered at 1360?°C exhibited the best performance, which had the 0.03% Wa, 0.07% Pa, 2.34?g?cm^?3 Db and 100.17?MPa bending strength. After acid and alkali corrosion, the water absorption was still less than 0.5% and the strength loss rate decreased to less than 5.3%. The XRD and SEM analyses demonstrated that the ZrSiO₄ grains dispersed at the grain boundaries could enhance the mechanical properties. Furthermore, the existence of the Zr⁴⁺ ions not only reduced the cationic solubility of the glassy phases but also led to a reaction with OH^? to form Zr(OH)₄ on the surfaces. This improved the corrosion resistance of the composite ceramics and endowed it with a high residual strength after the acid and alkali corrosion.     

Microstructure and properties of a graphene platelets toughened boron carbide composite ceramic by spark plasma sintering

A kind of B₄C/SiC composite ceramic toughened by graphene platelets and Al was fabricated by spark plasma sintering. The effects of graphene platelets and Al on densification, microstructure and mechanical properties were studied. The sintering temperature was decreased about 125–300?°C with the addition of 3–10?wt% Al. Al can also improve fracture toughness but decrease hardness. The B₄C/SiC composite ceramic with 3?wt%Al and 1.5?wt% graphene platelets sintered at 1825?°C for 5?min had the optimal performances. It was fully densified, and the Vickers hardness and fracture toughness were 30.09?±?0.39?GPa and 5.88?±?0.49?MPa?m^1/2, respectively. The fracture toughness was 25.6% higher than that of the composite without graphene platelets. The toughening mechanism of graphene platelets was also studied. Pulling-out of graphene platelets, crack deflection, bridging and branching contributed to the toughness enhancement of the B₄C-based ceramic.     

Negative magnetization and exchange bias effect in Fe-doped CoCr2O4

Polycrystalline ceramics of Co(Cr_1-xFe_x)₂O₄ (0?≤?x?≤?0.12) were experimentally studied based on a series of temperature and time-dependent dc magnetic measurements using different magnetic field histories. Magnetization in field cooling process was continuously decreased for doping content x in the range of 0?≤?x?≤?0.04. Remarkable negative magnetization is observed when x reaches to 0.06 and persists up to x?=?0.1. Two-sublattice model is established and competition of the two magnetic sublattices is responsible for the phenomenon. The magnetic switching effect is realized just by changing the magnitude of the applied magnetic field and double magnetocaloric effects are obtained. These unique features under low magnetic fields show attractive for application in spintronic devices due to that the magnetic state can effectively be tuned through magnetic field or temperature. Besides, the system exhibits both positive and negative exchange bias fields which are considered to be originating from the unidirectional anisotropy of exchange coupling of antiferromagnetic/ferromagnetic phases and spin reorientation of the two sublattices magnetic moments, respectively.     

A preliminary study on the preparation of nanostructured Ti-doped Li4SiO4 pebbles by two-step sintering process

Li₄SiO₄ has been widely studied as attractive tritium breeding materials due to its innate merits. Considering the potential advantages of nanostructure in tritium breeding materials, a distinctive process was developed to obtain nanostructured Li₄SiO₄ pebbles. In brief, ultrafine precursor powders were synthesized by solvothermal method without using surfactants, and then indirect wet method was adopted to generate the green spheres with homogeneous microstructure. After that, the suitable sintering conditions were defined by studying the effects of sintering parameters on the grain size evolution, and nanostructured Ti-doped Li₄SiO₄ pebbles were first obtained by two-step sintering method. This study will be expected to provide references for fabricating other Li-based tritium breeding materials.