New Iron-based SiC Spherical Composite Magnetic Abrasive for Magnetic Abrasive Finishing

SiC magnetic abrasive is used to polish surfaces of precise, complex parts which are hard, brittle and highly corrosion-resistant in magnetic abrasive finishing（MAF）. Various techniques are employed to produce this magnetic abrasive, but few can meet production demands because they are usually time-consuming, complex with high cost, and the magnetic abrasives made by these techniques have irregular shape and low bonding strength that result in low processing efficiency and shorter service life. Therefore, an attempt is made by combining gas atomization and rapid solidification to fabricate a new iron-based SiC spherical composite magnetic abrasive. The experimental system to prepare this new magnetic abrasive is constructed according to the characteristics of gas atomization and rapid solidification process and the performance requirements of magnetic abrasive. The new iron-based SiC spherical composite magnetic abrasive is prepared successfully when the machining parameters and the composition proportion of the raw materials are controlled properly. Its morphology, microstructure, phase composition are characterized by scanning electron microscope（SEM） and X-ray diffraction（XRD） analysis. The MAF tests on plate of mold steel S136 are carried out without grinding lubricant to assess the finishing performance and service life of this new SiC magnetic abrasive. The surface roughness（Ra） of the plate worked is rapidly reduced to 0.051 μm from an initial value of 0.372 μm within 5 min. The MAF test is carried on to find that the service life of this new SiC magnetic abrasive reaches to 155 min. The results indicate that this process presented is feasible to prepare the new SiC magnetic abrasive; and compared with previous magnetic abrasives, the new SiC spherical composite magnetic abrasive has excellent finishing performance, high processing efficiency and longer service life. The presented method to fabricate magnetic abrasive through gas atomization and rapid solidification presented can significantly improve the finishing performance and service life of magnetic abrasive, and provide a more practical approach for large-scale industrial production of magnetic abrasive.

Review of nuclear magnetic resonance studies on iron-based superconductors

The newly discovered iron-based superconductors have triggered renewed enormous research interest in the condensed matter physics community. Nuclear magnetic resonance （NMR） is a low-energy local probe for studying strongly correlated electrons, and particularly important for high-Tc superconductors. In this paper, we review NMR studies on the structural transition, antiferromagnetic order, spin fluctuations, and superconducting properties of several iron-based high-Tc superconductors, including LaFeAsOl_xFx, LaFeAsOl_x, BaFe2As2, Bal_xKxFe2As2, Cao.23Nao.67Fe2As2, BaFe2（Asl_xPx）2, Ba（Fel_xRux）2As2, Ba（Fel_xCox）2As2, Lil＋xFeAs, LiFel_xCoxAs, NaFeAs, NaFel_xCoxAs, KyFe2_xSe2, and （T1,Rb）yFe2_xSe2.

Modeling of removal of an organophosphorus pesticide from aqueous solution by amagnetic metal–organic framework composite

Today,a variety of pesticides are used to fight plant pests in the world.The entry of these resistant pollutants into water resources can have devastating effects on human health and the environment,hence their removal from the environment is a vital task.In the present work,the magnetic iron-based metalorganic framework(Fe_(3) O_(4)/MIL-101(Fe)) was synthesized by a simple and feasible method and characterized by FT-IR,XRD,BET,FESEM,TEM,TGA,and VSM techniques.The synthesized nanocom posite was successfully applied for the removal of fenitrothion(FEN) pesticide from the aqueous solutions.The isothermal and kinetic models were also investigated.The Langmuir isotherm model(type I) and pseudo-second-order kinetic model were more consistent in the adsorption process.The thermodynamic parameters of fenitrothion sorption were also calculated.The results revealed that the adsorption of fenitrothion onto Fe_(3) O_(4)/MIL-101(Fe) was spontaneous and endothermic under optimized conditions.Moreover,the removal efficiency of FEN was predicted using the developed fuzzy logic model.Four input variables including the initial concentration of FEN(mg·L^(-1)),pH of the solution,adsorbent dosage(mg).and contact time(min) versus removal efficiency as output were fuzzified by the usage of an artificial intelligence-based method.The fuzzy subsets consisted of Triangular and Trapezoidal membership functions(MFs) with six levels and a total of 23 rules in IF-THEN format which was applied on a Mamdani inference system.The obtained coefficient of determination value(R_(pred)^(2)=0.98205) proved the excellent accuracy of the fuzzy logic model as a powerful tool for the prediction of FEN removal efficiency.

Effect of niobium on glass-formation ability and soft magnetic properties of Gd-doping glassy alloys

The effect of niobium on glass-formation ability and soft magnetic properties were studied in Fe-Gd-B glassy alloys. The glassy alloys exhibited high glass-formation ability when the element of Nb was added. Bulk glassy rod （Fe0.87Co0.13）68.5Gd3.5Nb3B25 with a diameter up to 3 mm was produced by copper mold casting. The size of the atom might play an important role in increasing glass-formation ability. The coercive force of glassy （Fe0.87Co0.13）71.5.xGd3.sNbxB25 （x=1.2, 1.5, 2, 2.5, 3, 4） alloys decreased after the addition of niobium element and was in the range of 1.5-2.9 A/m. The permeability spectrum of （Fe0.87Co0.13）70.3Gd3.5Nb1.5B25 glassy ribbon showed that the relaxation frequency （f0） was 6.1 MHz.

Spin, charge, and orbital orderings in iron-based superconductors

In this article, we briefly review spin, charge, and orbital orderings in iron-based superconductors, as well as the multi-orbital models. The interplay of spin, charge, and orbital orderings is a key to understand the high temperature superconductivity. As an illustration, we use the two-orbital model to show the spin and charge orderings in iron-based superconductors based on the mean-field approximation in real space. The typical spin and charge orderings are shown by choosing appropriate parameters, which are in good agreement with experiments. We also show the effect of Fe vacancies, which can introduce the nematic phase and interesting magnetic ground states. The orbital ordering is also discussed in iron-based superconductors. It is found that disorder may play a role to produce the superconductivity.

Preparation and Photodynamic Anti-tumor Activity of Magnetic Polylactic Acid Nanoparticles Loaded with Photosensitizer

A novel magnetic nanocarrier was strategically designed and successfully prepared.Photosensitizer 2,7,12,18-tetramethyl-3,8-di-(1-propoxyethyl)-13,17-bis-(3-hydroxypropyl)porphyrin(PHPP)was encapsulated into polylactic acid(PLA)-coated Fe3O4 nanoparticles.The diameter of nanocarrier is 30-50 nm by transmission electron micrograph(TEM).The encapsulation efficiency of photosensitizer is 27.98% calculated from UV-vis absorption spectra.The nanocarrier shows obvious photocytotoxic activity to Hela299 tumor cells in vitro.

In vitro Anticancer Efficacy by Magnetic Targeted Nanocarrier with Local Delivery of Paclitaxel

A magnetic nanoparticles-loaded polymeric nanocarrier was developed. Amphiphilic copolymer, methoxy polyethylene glycol-poly（D,L-lactide-co-glycolide）（MPEG-PLGA） could self-assemble to form nanomicelle with the help of emulsion-solvent evaporation technique. This nanocarrier with core-shell structure was loaded with magnetic iron oxide nanoparticles（IONPs） and anticancer drug paclitaxel（PTX）. The hydrodynamic diameter of IONPs-PTX-loaded nanocarrier showed an average size of 110 nm with a polydispersity index（PDI） of 0.136, and its zeta potential was （-4.76±0.36） mV. The drug-loading content and encapsulation efficiency were 4.47% and 31.28%, respectively. In vitro drug release experiment was performed and a sustained release profile was observed. 3-（4,5-Dimethyl-2-thiazolyl）-2,5-diphenyl-2-H-tetrazolium bromide（MTT） assay indicated that IONPs-PTX-loaded nanocarrier showed comparable cytotoxicity with free paclitaxel. When an external magnetic field was applied, the nanocarrier significantly localized at the target area, demonstrating that the nanocarrier could be used for potential magnetic targeted drug delivery.

丁烯二酸单酯化-β-环糊精修饰的磁性纳米颗粒制备及性能研究

以可聚合的β-环糊精衍生物丁烯二酸单酯化-β-环糊精为功能单体,在一定的条件下,与采用含有乙烯基的偶联剂进行表面改性的Fe_3O_4纳米颗粒,通过自由基共聚法,制备一种带有环糊精基团的磁性纳米颗粒。通过扫描电子显微镜和透射电子显微镜表征其形貌;红外光谱和X-射线衍射表征结构;振动样品磁强计表征其磁性;热重分析仪表征热稳定性。随后对其在不同表面活性剂中的分散稳定性进行测定,并通过细胞毒性试验对含有表面活性剂的分散体系的生物相容性进行研究。在此基础上,以抗癌药物卡莫氟为模型药物考察载体的载药性能。实验结果表明该磁性纳米颗粒有望作为药物载体应用在抗肿瘤药物靶向给药领域。

多功能纳米载体靶向传输Survivin siRNA抑制肝细胞癌增殖

【目的】研究RGD修饰、MRI可视的纳米载体(RGD-PEG-g-PEI-SPION)靶向传输Survivin siRNA至肝细胞癌抑制裸鼠肝癌生长的作用;探讨RGD-PEG-g-PEI-SPION对裸鼠肝癌的MRI显像功能。【方法】经皮下注射Bel-7402细胞构建裸鼠皮下荷瘤模型;经肿瘤生长抑制实验、肿瘤组织HE染色、免疫组织化学染色和肿瘤组织细胞凋亡试验评估RGD-PEG-g-PEI-SPION靶向传输Survivin siRNA对裸鼠肝癌的治疗功能;利用MRI成像分析RGD-PEG-g-PEI-SPION对肝细胞癌的靶向显像功能。【结果】裸鼠皮下荷瘤模型成功建立并经裸鼠尾静脉首次注射25 d后,RGD-PEG-g-PEI-SPION/siRNA、PEG-g-PEI-SPION/siRNA、RGD-PEG-g-PEI-SPION/siNC、PEG-g-PEI-SPION/siNC和PBS溶液裸鼠的皮下移植瘤体积分别为:59±8、156±7、202±7、212±9和220±8(mm3),肿瘤组织学检查显示RGD-PEG-g-PEI-SPION/siRNA实验组肿瘤坏死范围最广,Survivin蛋白表达量最低,凋亡的肿瘤细胞数量明显增多;在尾静脉注射RGD-PEG-g-PEI-SPION载体、PEG-g-PEI-SPION载体3 h后,较载体注射前皮下移植瘤的标准化MRI信号强度分别下降为原来的(51.6±4.3)%和(88.5±3.2)%。【结论】RGD-PEG-g-PEI-SPION靶向传输Survivin siRNA至肝细胞癌,促进肿瘤细胞凋亡,抑制肿瘤生长,取得了较好的抗肿瘤疗效;RGD-PEG-g-PEI-SPION对裸鼠肝癌组织具备良好的靶向MRI显像功能。

一种磁性介孔硅纳米复合物的制备及其对顺铂前药的释放研究

文章通过在Fe3O4纳米粒外层包覆实心的nSiO2后,再包裹一层mSiO2,制备了一种MMSN,并将其负载顺铂前药Pt(Ⅳ),连结GnRH-a,成功制备了一种能靶向GnRH受体的磁性介孔硅纳米复合物,其对顺铂前药的负载量高,具有良好的超顺磁性以及磁靶向性能,并能够有效的实现药物释放。

Magnetic labeling of natural lipid encapsulations wit ron-based nanoparticles

With superior biocompatibility and unique magnetic properties, iron-based nanoparticles （IBNP） are commonly encapsulated in cells and extracellular vesicles （EV） to allow for magnetic force controlled drug delivery and non-invasive tracking. Based on their natural source and similar morphologs; we classify both cells and EVs as being natural lipid encapsulations （NLEs）, distinguishing them from synthetic liposomes. Both their imaging contrast and drug effects are dominated by the amount of iron encapsulated in each NLE, demonstrating the importance of magnetic labeling efficiency. It is known that the membranes function as barriers to ensure that substances pass in and out in an orderly manner. The most important issue in increasing the cellular uptake of IBNPs is the interaction between the NLE membrane and IBNPs, which has been found to be affected by properties of the IBNPs as well as NLE heterogeneity. Two aspects are important for effective magnetic labelling： First, how to effectively drive membrane wrapping of the nanoparticles into the NLEs, and second, how to balance biosafety and nanoparticle uptake. In this review, we will provide a systematic overview of the magnetic labeling of NLEs with IBNPs. This article provides a summary of the applications of magnetically labeled NLEs and the labeling methods used for IBNPs. The review also analyzes the role of IBNPs physicochemical properties, especially their magnetic properties, and the of NLEs in the internalization pathway. At the same time, the future of magnetically labeled NLEs is also discussed. development

NMR and NQR studies on transition-metal arsenide superconductors LaRu2As2,KCa2Fe4As4F2,and A2Cr3As3

We report 75As-nuclear magnetic resonance(NMR)and nuclear quadrupole resonance(NQR)measurements on transition-metal arsenides LaRu2As2,KCa2Fe4As4F2,and A2Cr3As3.In the superconducting state of LaRu2As2,a Hebel–Slichter coherence peak is found in the temperature dependence of the spin-lattice relaxation rate 1/T1 just below Tc,which indicates that LaRu2As2 is a full-gap superperconducor.For KCa2Fe4As4F2,antiferromagnetic spin fluctuations are observed in the normal state.We further find that the anisotropy rate RAF=Tc 1/Tab 1 is small and temperature independent,implying that the low energy spin fluctuations are isotropic in spin space.Our results indicate that KCa2Fe4As4F2 is a moderately overdoped iron-arsenide high-temperature superconductor with a stoichiometric composition.For A2Cr3As3(A=Na,K,Rb,Cs),we calculate the electric field gradient by first-principle method and assign the 75As-NQR peaks to two crystallographically different As sites,paving the way for further NMR investigation.

Microstructures and soft magnetic properties of Fe_(73.5)Cu_(1)Nb_(3-x)Si_(13.5)B_(9)Yx(x=0-1.5)alloys

Based on composition of Finemet alloy,structures and soft magnetic properties of Fe_(73.5)Cu_(1)Nb_(3-x)Si_(13.5)B_(9)Yx(x=0,0.5,1.0,1.5)alloys formed by replacing Nb(niobium)by Y(yttrium)were studied in this paper.The research results show that when x=0 or 0.5,rapidly solidified as-cast alloy is Fe amorphous single-phase structure,and Y atoms are dispersed in matrix;when x=1.0 or 1.5,crystalline phase precipitates.Fe_(73.5)Cu_(1)Nb_(3-x)Si_(13.5)B_(9)Yx(x=0,0.5,1.0,1.5)alloys begin to precipitateα-Fe(Si)solid solution phase after crystallization annealing above 480℃,when x=0.5,grain size is 12.6 nm,which shows that Y can replace Nb in small amount and refine grain size.Fe_(73.5)Cu_(1)Nb_(2.5)Si_(13.5)B_(9)Y_(0.5)alloy has excellent soft magnetic properties:μm value is 813.1×10^(3),which is 36%higher than that of Finemet alloy;μi value is 154.6×10^(3),close to that of Finemet alloy,and BS and Hc values are 1.24 T and 0.56 A/m,respectively,better than those of Finemet alloy.In addition,Fe_(73.5)Cu_(1)Nb_(2.5)Si_(13.5)B_(9)Y_(0.5)alloy has excellent soft magnetic properties at high temperature,μe value only reduces by 8.8%at 1 kHz with ambient temperature increased from 30 to150℃,andμe value is 128.02×10^(3)in 150℃,which is 15.74%higher than that of Finemet alloy.

磁性纳米颗粒负载质粒DNA的研究

【目的】研究磁性纳米颗粒(MNP)负载质粒DNA形成的纳米载体−基因复合物的生物物理学特性、负载形态与负载机理,为基于磁性纳米载体定向编辑技术的应用奠定基础。【方法】以MNP作为基因载体,与质粒DNA pRGEB32制备纳米载体−基因复合物MNP−pRGEB32,分析MNP负载、保护pRGEB32的能力,并对其粒度分布、Zeta电位、结合形态进行研究。【结果】MNP通过静电作用压缩、吸附、聚集pRGEB32,形成纳米载体−基因复合物。MNP能有效负载并保护pRGEB32。【结论】MNP可作为一种理想的基因转移载体。

Gal和PEI修饰磁性纳米颗粒载体介导的c-Met siRNA构建及其抗肝癌细胞效应观察

目的构建半乳糖(Gal)和聚乙烯亚胺(PEI)修饰磁性纳米颗粒(SPIO)载体介导的c-MetsiRNA,并观察其抗肝癌细胞效应。方法制备Gal-PEI-SPIO纳米载体,以琼脂糖凝胶电泳检测载体与siRNA的结合情况,采用CCK-8试验检测纳米载体复合物的细胞毒性;分别采用q-PCR和Westernblotting法检测纳米载体携带c-MetsiRNA在细胞中的沉默效率,使用Transwell法观察Gal-PEI-SPIO/c-MetsiRNA纳米复合物对肝癌细胞MHCC-97H迁移和侵袭能力的影响。结果琼脂糖凝胶电泳结果显示,Gal-PEI-SPIO和siRNA以SPIO、siRNA质量比≥4∶1时两者可紧密结合;细胞毒性分析显示,当SPIO、siRNA质量比≥4∶1时细胞活性迅速降低;q-PCR、Westernblotting结果显示,Gal-PEI-SPIO/c-MetsiRNA纳米复合物有效降低了MHCC-97H细胞中c-MetmRNA及蛋白表达(P均<0.01);在细胞侵袭、迁移实验中,Gal-PEI-SPIO/c-MetsiRNA纳米复合物使MHCC-97H侵袭、迁移的穿膜细胞减少(P均<0.05)。结论Gal-PEI-SPIO纳米载体能够与siRNA紧密结合,并能携带c-MetsiRNA进入肝癌细胞发挥对c-Met的沉默作用,从而抑制肝癌细胞MHCC-97H的侵袭和迁移能力。

Mitochondrion targeting peptide-modified magnetic graphene oxide delivering mitoxantrone for impairment of tumor mitochondrial functions

In this study,we prepared mitochondrion targeting peptide-grafted magnetic graphene oxide(GO)nanocarriers for efficient impairment of the tumor mitochondria.The two-dimensional GOMNP-MitP nanosheets were synthesized by grafting magnetic y-Fe_(2)O_(3)to the surface of GO,followed by covalent modification of mitochondrion targeting peptide(MitP).GOMNP-MitP exhibited the high capacity of loading the anticancer drug mitoxantrone(MTX),and preferentially targeted the tumor mitochondria.With the aid of alternating magnetic field(AMF),the MTX-loading GOMNP-MitP released MTX to the mitochondria,severely impairing mitochondrial functions,including attenuation of ATP production,decrease in mitochondrial membrane potential(MMP),and further leading to activation of apoptosis.This study realized high-efficient mitochondrion-ta rgeting drug delivery for anticancer therapy by twodimensional nanoplatforms.

Nodal superconducting gap in LiFeP revealed by NMR:Contrast with LiFeAs

Identifying the uniqueness of FeP-based superconductors may shed new lights on the mechanism of superconductivity in iron-pnictides.Here,we report nuclear magnetic resonance(NMR) studies on LiFeP and LiFeAs which have the same crystal structure but different pnictogen atoms.The NMR spectrum is sensitive to inhomogeneous magnetic fields in the vortex state and can provide the information on the superconducting pairing symmetry through the temperature dependence of London penetration depth λ_(L).We find that λ_(L) saturates below T~0.2 T_(C) in LiFeAs,where T_(C) is the superconducting transition temperature,indicating nodeless superconducting gaps.Furthermore,by using a two-gaps model,we simulate the temperature dependence of λ_(L) and obtain the superconducting gaps of LiFeAs,as Δ_(1)=1.2 kB T_(C) and Δ_(2)=2.8 k_(B)T_(C),in agreement with previous result from spin-lattice relaxation.For LiFeP,in contrast,λ_(L) does not show any saturation down to T~0.03 T_(C),indicating nodes in the superconducting gap function.Finally,we demonstrate that strong spin fluctuations with diffusive characteristics exist in LiFeP,as in some cuprate high temperature superconductors.

Dispersion of neutron spin resonance mode in Ba_(0.67)K_(0.33)Fe_(2)As_(2)

We report an inelastic neutron scattering investigation on the spin resonance mode in the optimally hole-doped ironbased superconductor Ba_(0.67)K_(0.33)Fe_(2)As_(2)with T_c=38.2 K.Although the resonance is nearly two-dimensional with peak energy ER≈14 meV,it splits into two incommensurate peaks along the longitudinal direction([H,0,0])and shows an upward dispersion persisting to 26 meV.Such dispersion breaks through the limit of total superconducting gaps△_(tot)=|△k|+|△k+Q|(about 11-17 meV)on nested Fermi surfaces measured by high resolution angle resolved photoemission spectroscopy(ARPES).These results cannot be fully understood by the magnetic exciton scenario under s^(±)-pairing symmetry of superconductivity,and suggest that the spin resonance may not be restricted by the superconducting gaps in the multi-band systems.

Constraint Cooling of Hot Rolled Coil

Amorphous ribbons of Fe 74Al 4Sn 2(PSiB) 20 alloy have been synthesized by melt spinning and axial design method. The thermal properties of the amorphous ribbons have been measured by differential scanning calorimeter (DSC). The DSC results show that the Fe 74Al 4Sn 2P 12Si 4B 4 amorphous alloy has relatively wider supercooled liquid region with a temperature interval of 40 38 K (ΔT x=T x-T g). The alloys with a higher phosphorous content in the metalloid element composition triangle of Fe 74Al 4Sn 2(PSiB) 20 have high glass forming ability. The amorphous alloys also show good magnetic properties in which Fe 74Al 4Sn 2P 6 67Si 6 67B 6 67 alloy has a large maximum permeability (μ m), Fe 78Al 4Sn 2P 3Si 3B 10 alloy exhibits a high square ratio (B r/B 10) and Fe 74Al 4Sn 2P 4Si 12B 4 shows a low core loss (P 0 5/1 3T). High glass forming ability and good magnetic properties make Fe 74Al 4Sn 2(PSiB) 20 amorphous alloys valuable in future research.

Universal behavior of the upper critical field in iron-based superconductors

The newly discovered iron-based high temperature superconductors have demonstrated rich phys- ical properties. Here we give a brief review on the recent studies of the upper critical field and its anisotropy in a few typical series of the iron-based superconductors （FeSCs）. In spite of their characters of a layered crystal structure, all the FeSCs possess an extremely large upper critical field and a weak anisotropy of superconductivity, being unique among the layered superconductors. These particular properties indicate potential applications of the FeSCs in the future. Based on the experimental facts of the FeSCs, we will discuss the possible mechanisms of pair breaking in high magnetic fields and its restrictions on the theoretical analysis of the superconducting pairing mechanisms.