Synthesis and in vitro properties of dexamethasone 21-sulfate sodium as a colon-specific prodrug of dexamethasone

We synthesized dexamethasone 21-sulfate sodium (DS) as a colon-specific prodrug of dexamethasone and investigated its properties. Introduction of a sulfate group to dexamethasone lowered the apparent partition coefficient from 52.5 to 0.27 in 1-octanol/pH 6.8 phosphate buffer at 37°C. DS was stable on incubation with buffer solutions of varied pH or with the upper intestinal contents of rats at 37°C for 24 h. On incubation with the cecal contents, DS was hydrolyzed by producing dexamethasone over 80% of the dose at 10 h. When DS was incubated with the cecal contents collected from trinitrobenzenesulfonic acid (TNBS)-induced colitic rats, the degree of prodrug hydrolysis and production of dexamethasone amounted to 70% of healthy rats. In comparison with prednisolone, hydrocortisone, and cortisone, dexamethasone was stable against bioinactivation by the cecal contents, a desirable property for the development of a colon-specific prodrug. These results demonstrated that DS might be delivered specifically to the colon as an intact form to produce dexamethasone in high yield, suggesting DS as a potential colon-specific prodrug of dexamethasone.     

Energy absorption of gold nanoshells in hyperthermia therapy

The unique optical characteristics of a gold nanoshell motivate the application of nanoshell-based hyperthermia in drug delivery and cancer treatment. However, most of our understanding on energy absorption and heat transfer is still focused on individual particles, which may not be accurate for nanoshell aggregates in a real application due to the strong optical interaction of nanoshells. This paper investigates the relationship between the optical interaction and the interparticle distance in the visible and near-infrared regions by means of a finite-difference time-domain (FDTD) method. The objective is to explore the energy transportation mechanism, which is critical for hyperthermia therapy. From the numerical simulation results of different forms of nanoshell aggregates, including individual nanoshells, 1-D chains, 2-D arrays, and 3-D clusters, it was found that the interparticle distance plays a crucial role from the maximal absorption point of view. The interparticle distance affects both field enhancement and surface plasmon resonance position. The accurate prediction of energy absorption also helps the way nanoshells are populated in the tumor cell so as to prevent heat damage to healthy tissues in clinic applications. In the case of 3-D clusters, the laser energy decays exponentially along the wave propagation, and the penetration depth greatly depends on the interparticle distance. The closer the nanoshells are placed, the shorter the penetration depth is. The maximal total length for the laser penetration through the shell of gold nanoparticles is about a few hundred to several nanometers. The actual penetration depth primarily depends not only on the interparticle distance, but also on the size of the nanoshells as well as other factors. Since the absorption energy is concentrated on the surface clusters of nanoparticles, heat transfer mechanisms in metal-nanoparticles-based hyperthermia will differ from that in other hyperthermia. The information obtained from this paper will serve as a basis for further study of heat transfer in metal-nanoparticles-based hyperthermia.     

Evaluation of gold nanoparticles as the additive in real-time polymerase chain reaction with SYBR Green I dye

Gold nanoparticles (AuNPs) have been proven to be able to improve the specificity or increase the efficiency of a polymerase chain reaction (PCR) when a suitable amount of AuNPs was used. However, there is still a lack of systematic evaluation of AuNPs in real-time PCR. In this study, DNA degradation and the fluorescence quenching effect of AuNPs were first tested in real-time PCR. Then two different kinds of Taq DNA polymerase, native and recombinant Taq polymerase, were employed to evaluate the AuNPs' effect on the threshold cycle (C(T)) values, standard curves and melting curves in real-time PCR. Different ratios of the amount of native Taq DNA polymerase to the amount of AuNPs were also tested. It was found that AuNPs could be applied in real-time PCR with correlation coefficient R(2)>0.989. The combination of 2.09?nM AuNPs with 3.75?U of native Taq DNA polymerase could make the amplification curves shift to the left and enhance the efficiency of the real-time PCR (0.628?39 without AuNPs compared with 0.717?89 with 2.09?nM AuNPs), thus enabling faster detection in comparison with those of control samples. However, no improvement ability of AuNPs was found in real-time PCR based on recombinant rTaq DNA polymerase. Besides, the results suggest that a complex interaction exists between AuNPs and native Taq DNA polymerase.     

Analytical design of permanent-magnet traction-drive motors

This paper presents an analytical method for the design of permanent-magnet (PM) traction-drive motors with emphasis on calculation of the magnet's volume and size. The method uses a set of formulas to properly size the magnets without the high effort of finite-element analysis (FEA). The formulas not only give optimized magnet sizes, but also provide quick solutions for the preliminary designs. The method can be used in the initial design stage to set up the base for FEA and optimization, as well as throughout the entire design and optimization process to validate a PM motor design. Numerical methods and experiments confirm the accuracy of the proposed method.     

Synthesis,characterization and magnetic performance of Co-incorporated ordered mesoporous carbons

Co-incorporated ordered mesoporous carbon (Co-OMC) with magnetic frameworks has been synthesized via a one-pot self-assembly strategy. The effects of cobalt loading on carbon matrix, adsorption properties and magnetic properties of the resultant mesostructured cobalt/carbon composites were investigated by nitrogen sorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TG) and magnetometer measurements. The results show that the mesoporous composites with a high cobalt content (such as 18.0 wt%) possess an ordered and uniform mesoporous structure (5.3 nm), high surface areas (up to 687 m²/g) and high pore volumes (up to 0.54 cm³/g). Cobalt nanoparticles of size 4–9 nm are confined inside the mesopores or walls of the mesoporous carbon. These materials exhibit typical ferromagnetic characteristics. The saturation magnetization strength can be easily adjusted by changing the content of cobalt. The carbonization temperatures have significant effects on the structure and magnetic properties of Co-OMC also.     

长效直接使用型1,2-丙二醇防冻冷却液的研制

丙二醇替代乙二醇用作防冻冷却液具有低毒、环保、防腐蚀性能更佳等优点,目前,国内对其研究尚不够深入。研制了长效直接使用型1,2-丙二醇防冻冷却液的防腐蚀添加剂配方,讨论了缓蚀剂的选择与复配关系,确定了添加剂A、癸二酸、琥珀酸等主要添加剂的最佳使用量和配比,并进行了性能测试。结果表明,性能较优的冷却液配方为:钼酸钠、硅酸钠组合物0.17%,苯并三氮唑0.12%,安息香酸钠0.7%,1,2-丙二醇30.00%,添加剂A 1.0%～1.2%,癸二酸0.2%,琥珀酸0.1%。对6种金属材质的恒温静态挂片腐蚀试验和长效耐久腐蚀试验表明,该类冷却液对多种金属具有协同防腐蚀效果和5年以上长效防护性能,且低毒、环保,适用于车船等设备。     

Tunable luminescence and energy transfer properties in YVO<Subscript>4</Subscript>:Bi<Superscript>3+</Superscript>,Ln<Superscript>3+</Superscript> (Ln = Dy,Sm, Eu) phosphors prepared by microwave sintering method

YVO₄:Bi³⁺,Ln³⁺ (Ln?=?Dy, Sm, Eu) phosphors were successful synthesized by microwave sintering method, and characterized by X-ray powder diffraction, scanning electron microscope, photoluminescence spectra, lifetime, quantum efficiency and general structure analysis system structure refinement. Refinement results indicated that the introduced ions occupy the sites of Y³⁺. Under 275 nm excitation, the luminescent intensity of YVO₄:Bi³⁺ samples reach the maximum when Bi³⁺ concentration is 0.02, the broad excitation spectrum of YVO₄:Bi³⁺ has a strongest peak at near 343 nm. Doped Bi³⁺ can effectively improve the emission intensity of YVO₄:Ln³⁺. The energy transfer mechanism of Bi³⁺?→?Ln³⁺ was dipole-quadrupole mechanism of electric multipole interaction. The critical distance (R_c) between Ln³⁺ and Bi³⁺ were calculated by concentration quenching method. Emitting color of YVO₄:Bi³⁺,Ln³⁺ phosphors were tunable by adjusting Ln³⁺ content. In a word, the material has a good application prospects on light emitting diodes.     

FeCoSi合金磁粉磷化处理及高频电磁性能

采用快淬甩带和高能球磨工艺制备了成分为Fe70Co12Si18(合金名称中数字为原子百分数)的片状合金磁粉,并用磷酸酒精溶液对磁粉进行了磷化处理.重点研究了磷化前后及不同磷酸浓度对FeCoSi磁粉电磁参数和微波吸收性能的影响.结果 表明,随着磷酸浓度的提高,FeCoSi合金吸波材料的介电常数实部和虚部均减小,磁导率实部...     

Co-coating effect of GdPO4 and carbon on LiFePO4 cathode surface for lithium ion batteries

The electronic conductivity enhanced has been extensively studied and reported in lithium iron phosph-ate (LiFePO₄). However, only few existing literatures are available for researchers to enhance simultaneously the ion and electronic conductivity of LiFePO₄. Herein, we disclose that the LiFePO₄ is co-coated with novel GdPO₄ and Carbon via a hydrothermal-assisted solid-phase method, contributing to particle size and dispersibility. What surprising is that the ionic and electronic conductivity of the material is significantly enhanced, and the interfacial side reaction is effectively inhibited between the materials and the electrolytes. The diverse proportions of the mixed coating (LiFePO₄/C&xGdPO₄ (x = 0, 1 wt%, 2 wt%, 3 wt%, 4 wt%)) are synthesized compared with bare LiFePO₄. The experimental results suggest that LiFePO₄/C&0.03GdPO₄ exhibits the most excellent electrochemical performance. There is discharge capacity of 158, 148.8, 141.6, 134.9, 121.8, 104.9, and 86.7mAh/g at 0.1, 0.2, 0.5, 1, 2, 5, and 10 C rates, respectively.