首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 182 毫秒
1.
The accumulation and deposition of β-amyloid (Aβ) plaques in the brain is considered a potential pathogenic mechanism underlying Alzheimer's disease (AD). Chiral l/d -FexCuySe nanoparticles (NPs) were fabricated that interfer with the self-assembly of Aβ42 monomers and trigger the Aβ42 fibrils in dense structures to become looser monomers under 808 nm near-infrared (NIR) illumination. d -FexCuySe NPs have a much higher affinity for Aβ42 fibrils than l -FexCuySe NPs and chiral Cu2−xSe NPs. The chiral FexCuySe NPs also generate more reactive oxygen species (ROS) than chiral Cu2−xSe NPs under NIR-light irradiation. In living MN9D cells, d -NPs attenuate the adhesion of Aβ42 to membranes and neuron loss after NIR treatment within 10 min without the photothermal effect. In-vivo experiments showed that d -FexCuySe NPs provide an efficient protection against neuronal damage induced by the deposition of Aβ42 and alleviate symptoms in a mouse model of AD, leading to the recovery of cognitive competence.  相似文献   

2.
The accumulation and deposition of β‐amyloid (Aβ) plaques in the brain is considered a potential pathogenic mechanism underlying Alzheimer's disease (AD). Chiral l/d ‐FexCuySe nanoparticles (NPs) were fabricated that interfer with the self‐assembly of Aβ42 monomers and trigger the Aβ42 fibrils in dense structures to become looser monomers under 808 nm near‐infrared (NIR) illumination. d ‐FexCuySe NPs have a much higher affinity for Aβ42 fibrils than l ‐FexCuySe NPs and chiral Cu2?xSe NPs. The chiral FexCuySe NPs also generate more reactive oxygen species (ROS) than chiral Cu2?xSe NPs under NIR‐light irradiation. In living MN9D cells, d ‐NPs attenuate the adhesion of Aβ42 to membranes and neuron loss after NIR treatment within 10 min without the photothermal effect. In‐vivo experiments showed that d ‐FexCuySe NPs provide an efficient protection against neuronal damage induced by the deposition of Aβ42 and alleviate symptoms in a mouse model of AD, leading to the recovery of cognitive competence.  相似文献   

3.
In the present study, chiral CuxCoyS nanoparticles (NPs) were developed to selectively induce apoptosis of senescent cells using both an alternating magnetic field (AMF) and near infrared (NIR) photon illumination. The chiral effects on living cells were investigated, and d ‐CuxCoyS NPs showed about 2.5 times higher of internalized ability than l ‐NPs. By modifying beta 2 macroglobulin (MG), senescent cells were effectively eliminated by d ‐CuxCoyS NPs without damaging the activities of normal cells under AMF and photon illumination. Compared to the individual application of NIR illumination and AMF, their synergistic effect induced the production of caspase‐3 with a much shorter treatment time and higher efficiency due to the more serious photon‐induced cellular redox and mechanical damage of cellular skeleton. Moreover, the developed strategy was successfully used to remove senescent cells in vivo. This study developed a controllable way of regulating cell activities using chiral NPs, which will provide a valuable way for treating diseases and promoting health.  相似文献   

4.
The mutual miscibility of random poly (styrene-co-methylmethacrylate)s with different compositions but a constant molecular weight of Mw ? 150,000 was studied at room temperature and at 180°C. Compatibility was analyzed with films cast from solutions with different solvents. The reliability of the analytical technique is discussed. The miscibility windows {x, yx}, which define the limits of miscibility of the blends of a given copolymer P (SxMMA1?x) with other copolymers P (SyMMA1?y), were determined for all x. The widths |x ? yx| of these windows are, contrary to the predictions of the Flory–Huggins model, different for yx > x and yx > x, and depend strongly on x. Miscibility is better for blends with a high MMA content. The windows are markedly wider at room temperature. Many blends are, therefore, “semicompatible,” i.e., have a critical point of the LCST type between room temperature and 180°C.  相似文献   

5.
The synthesis of filled skutterudite compounds (Ce or Y)yFexCo4-xSb12, through a solid state reaction using chloride of Ce or Y, high purity powder of Co, Fe, and Sb as starting materials, was investigated. (Ce or Y)yFexCo4-xSb12 (x = 0 1.0,y = 0 0.15) compounds were obtained at 850 1 123 K. The results of Rietveld analysis demonstrate that (Ce or Y)yFexCo4-xSb12 synthesized by a solid state reaction possesses a filled skutterudite structure. The filling fraction of Ce or Y obtained by Rietveld analysis agrees well with the composition obtained by chemical analysis. The lattice constant of CeyFexCo4-xSb12 increases with increasing substitution of Fe at Co sites, and with an increasing Ce filling fraction in the Sb-dodecahedron voids. The lattice thermal conductivity of (Ce or Y)yFexCo4-xSb12 decreases significantly with an increasing Ce or Y filling fraction in the voids and with substitution of Fe at Co sites.  相似文献   

6.
Ions produced by the 1064 nm Nd:YAG laser ablation of various Si–C samples include mixed silicon carbon (SixCy) cluster ions of low molecular mass. Unique SixCy cluster ion distributions are observed. A charge state effect for SixCy clusters is evident from differences between the respectively charged distributions. This may be accounted for by either differing energetics and/or differing formation mechanisms for positive and negative SixCy cluster ions. Several specific SixCy clusters of probable high stability consistently dominate the mass spectra. The chemistry of the more abundant SixCy ions was probed by collision-induced dissociation and ion–molecule reactivity experiments. Similar SixCy+˙ dissociation results in the common loss of an Si ion. Parent SixCy ion and small neutral reagent reactants give rise to oxidation, addition and exchange reactions.  相似文献   

7.
Three pairs of enantiopure chiral triangular Ln3 clusters, [Ln3LRRRRRR/SSSSSS3‐OH)2(H2O)2(SCN)4]?xCH3OH?yH2O ( R ‐Dy3 , Ln=Dy, x=6, y=0; S ‐Dy3 , Ln=Dy, x=6, y=1; R ‐Ho3 , Ln=Ho, x=6, y=1; S ‐Ho3 , Ln=Ho, x=6, y=1; R ‐Er3 , Ln=Er, x=6, y=0; S ‐Er3 , Ln=Er, x=6, y=1), have been successfully synthesized by a rational enantioselective synthetic strategy. The core of triangular Ln3 is bound in the central N6O3 of the macrocyclic ligand, and the coordination spheres of Ln ions are completed by four SCN? anions and two H2O molecules in axial positions of the macrocycle. The circular dichroism (CD) and vibrational circular dichroism (VCD) spectra of the enantiomers demonstrate that the chirality is successfully transferred from the ligands to the resulting Ln3 clusters. Ac susceptibility measurements reveal that single‐molecule magnet behavior occurs for both enantiopure clusters of R ‐Dy3 and S ‐Dy3 . This work is one of the few examples of the successful design of a pair of triangular Dy3 clusters showing simultaneously slow magnetic relaxation and optical activity, and this might open up new opportunities to develop novel multifunctional materials.  相似文献   

8.
Unsymmetrical and symmetrical mononuclear and insoluble polynuclear oxo-vanadium(IV) Schiff-base complexes were prepared and characterized. The complexes [VO(5-x-6-y-Sal)(5-x′-6-y′-Sal)en)] (where x, x′ = H, Br and y, y′ = H, OMe) were obtained in monomeric form while for x or x′ = NO2 polymers were produced. In the case of [VO(5-x-6-y-Sal)(5-x′-6-y′-Sal)pn)] with a six-member N–N chelating ring, oxo-vanadium(IV) complexes were polynuclear. The tetradentate N2O2-Schiff-base ligands are coordinated in the equatorial plane of oxo-vanadium(IV). Electrochemical and spectroscopic data (UV–Vis and IR) suggest importance of coordination geometry and the substiuents on phenyl rings and the bridge group. Electron density of the vanadium center decreases by the electron-withdrawing groups on the ligand while electron density on vanadium increases via σ-donation of phenolic oxygen.  相似文献   

9.
Ti1−x V x O2−y C y (0 ≤ x ≤ 0.10 and x = 0.50) whiskers having the anatase structure were synthesized via thermolysis of vanadium-doped titanium glycolate of composition Ti1−x V x (OCH2CH2O)2 (0 ≤ x ≤ 0.10 and x = 0.50). The starting reagents used to prepare Ti1−x V x (OCH2CH2O)2 were mixtures of coprecipitated titanium and vanadyl hydroxides, which were heated in ethylene glycol at T ≤ 200°C: (1 − x)TiO(OH)2 + xVO(OH)2 + 2HOCH2CH2OH = Ti1−x V x (OCH2CH2O)2 + 3H2O↑. Thermolysis of vanadium-doped titanium glycolate in various gas media over a wide range of temperatures is useful to prepare titania samples doped with both vanadium and carbon to form a phase of the general composition Ti1 − x V x O2 − y C y whiskers prepared by thermolyzing Ti1 − x V x (OCH2CH2O)2 in air at 450°C were found to have a high photocatalytic activity in hydroquinone oxidation in aqueous solutions irradiated in the UV spectral range; the photocatalyst’s activity increases with increasing vanadium concentration. When hydroquinone was irradiated in the blue, the maximal catalytic activity was discovered in a sample of composition Ti0.50V0.50O2−y C y . Quantum-chemical calculations support experimental data that the double doping of titania (Ti1−x V x O2−y C y ) enhances its photocatalytic activity compared to undoped anatase or anatase doped in one sublattice: Ti1−x V x O2 and TiO2−y C y .  相似文献   

10.
Electrochemical and spectroscopic data of unsymmetrical and symmetrical mononuclear oxo-vanadium(IV)salicyldiimine complexes [VO(x,y-Sal)(x′,y′-Sal)Phen)] and [VO(x, y-Sal)(x′, y′-Sal)iPr)], where x, x′ =?5-H, 5-Br, 5-NO2 and y, y′ =?4-H, 4-MeO, were prepared and studied. Our results show tetradentate SalPhen or SaliPr coordinated in the equatorial plane. The electrochemical behavior is related to UV–Vis and IR spectra. Electron-withdrawing groups affected vanadium through π-acceptor properties of imine and electron-donation groups through π- and σ-donation via phenolic oxygen.  相似文献   

11.
The method of isotopic exchange was used to study the kinetics of oxygen exchange and diffusion in complex oxides of La1 − x Sr x Co1 − y Fe y O3 − δ (x = 0.0, y = 0.0; x = 0.6, y = 0.2, 0.4). The rates of oxygen interfacial exchange and its diffusion coefficient were determined for LaCoO3 − δ at the pressure of 5 torr in the temperature range of 600–850°C and at the temperature of 700°C in the pressure range of 1–70 torr. The contributions of the three exchange types were calculated. The order of the dependence of the interfacial exchange rate on the oxygen pressure was 0.51 ± 0.01. In the case of La0.4Sr0.6Co1 − y Fe y O3 − δ (y = 0.2, 0.4) in the temperature range of 600–900°C at the oxygen pressure of 10 torr, the oxygen exchange rates and diffusion coefficients were determined in the material bulk and in the subsurface region; contributions of the three types of exchange were calculated. The paper considers the mechanism of oxygen exchange and diffusion as compared to nonstoichiometry in the oxygen sublattice of the La1 − x Sr x Co1 − y Fe y O3 − δ oxides.  相似文献   

12.
Oxygen states in the La1 – x Ca x FeO3 – y perovskites prepared using different procedures are studied by temperature-programmed reduction (TPR). Results are compared to data on the catalytic activity in the oxidation of methane and carbon monoxide. The activity of the samples in the CO and CH4 oxidation over a wide temperature range (200–600°C) is shown to correlate with the amount of reactive surface and subsurface oxygen removable during TPR below 420°C. These oxygen states in the samples of the La1 – x Ca x FeO3 – y series can be associated with the domain or intergrain boundaries. No correlation is found between the amount of lattice oxygen removable during TPR and the activity of the La1 – x Ca x FeO3 – y samples in the complete oxidation of methane at temperatures of 450–600°C. It is suggested that catalytic complete oxidation is determined by the most reactive surface and subsurface oxygen states located at the interphase boundaries, whereas the lattice oxygen does not participate in these reactions.  相似文献   

13.
目的:建立刺激胰岛素分泌的新型降糖药物(-)-2 (S)-苄基-4-酮-4-(顺式-全氢化异吲哚-2-基)丁酸钙对映体的HPLC拆分方法。方法:采用Sumichiral OA-3300手性柱(250 × 4.6 mm I.D., 5 μm), 柱温35℃,以0.05 mol·L-1醋酸铵的甲醇溶液为流动相,检测波长为210 nm。结果:本品两对映体在22分钟内实现良好分离,分离度达3以上,S-异构体分别在0.028 ~ 5.6 μg mL-1和0.03 ~ 6.0 μg mL-1范围内线性关系良好,回归方程分别为:Y=1.32×103x-2.54 (r=0.9997)和Y=1.15×103x-1.78 (r=0.9998),最低检测限分别为0.15 ng和0.10 ng,方法精密度RSD低于1.0% (n=5)。结论:建立的对映体分离方法可用于本品光学异构体的质量控制。  相似文献   

14.
FeOxHy and Fe-containing Ni/Co oxyhydroxides are the most-active catalysts for the oxygen evolution reaction (OER) in alkaline media. However, the activity of Fe sites appears strongly dependent on the electrode-substrate material and/or the elemental composition of the matrix in which it is embedded. A fundamental understanding of these interactions that modulate the OER activity of FeOxHy is lacking. We report the use of cyclic voltammetry and chronopotentiometry to assess the substrate-dependent activity of FeOxHy on a number of commonly used electrode substrates, including Au, Pt, Pd, Cu, and C. We also evaluate the OER activity and Tafel behavior of these metallic substrates in 1 M KOH aqueous solution with Fe3+ and other electrolyte impurities. We find that the OER activity of FeOxHy varies by substrate in the order Au>Pd≈Pt≈Cu>C. The trend may be caused by differences in the adsorption strength of the Fe oxo ion on the substrate, where a stronger adhesion results in more adsorbed Fe at the interface during steady-state OER and possibly a decreased charge-transfer resistance at the FeOxHy-substrate interface. These results suggest that the local atomic and electronic structure of [FeO6] units play an important role in catalysis of the OER as the activity can be tuned substantially by substrate interactions.  相似文献   

15.
A new series of iron(III) complexes with different fourth generation of quinolone drugs of the type [Fe(L)n(Cl)x]?yH2O (( 1 ) L: nalidixic acid, n = 3, x = 3, y = 3; ( 2 ) L: oxolonic acid, n = 3, x = 3, y = 0; ( 3 ) L: pipemidic acid, n = 3, x = 3, y = 2; ( 4 ) L: lomefloxacin, n = 3, x = 3, y = 0; ( 5 ) L: pefloxacin mesylate, n = 3, x = 3, y = 2; ( 6 ) L: levofloxacin, n = 3, x = 3, y = 6) were synthesized and identified using microanalysis, Fourier transform infrared spectroscopy, conductance data, effective magnetic moments and electronic UV–visible spectra. In these six complexes, the quinolone drug chelates act in a unidentate manner via nitrogen atom of pyridone/piperazyl moiety. Electronic spectroscopic data are in agreement with an octahedral geometrical structure. Thermal degradation analyses in nitrogen gas were used to investigate the number and location of water molecules. The thermal decomposition process is completed in 3?5 steps, the first step being responsible for loss of uncoordinated water molecules and the steady state of all complexes occurs at around 500 °C with oxide forms as residual products. The stabilities of iron(III) complexes 1 – 6 were studied in terms of activation energy E*, entropy ΔS*, enthalpy ΔH* and Gibbs free energy ΔG* that were estimated using Coats–Redfern and Horowitz–Metzger non‐isothermal methods. Molecular docking was used to predict the binding between some of the quinolone drugs and the receptor of prostate cancer 2q7k hormone.  相似文献   

16.
Substitutional solid solutions (Cu1−y Zn y )2(OH)PO4·xH2O (0 ≤ y ⩽ 0.26, x = 0.1−0.2), (Cu1−y Co y )2(OH)PO4·xH2O (0 ≤ y ≤ 0.10, x = 0.1−0.2), and (Cu1−y Ni y )2(OH)PO4·xH2O (0 ≤ y ≤ 0.08, x = 0.1−0.2) were synthesized. The unit cell parameters of the resulting phosphates were determined, and their IR absorption spectra were measured. The reactants were H3PO4 and mixtures of hydrous carbonates of the appropriate metals. Thermolysis of the solid solutions was examined with (Cu1−y Co y )2(OH)PO4·xH2O (0 ≤ y ≤ 0.10, x = 0.1−0.2) as an example.  相似文献   

17.
Angle‐resolved XPS data (elemental quantification and high‐energy‐resolution C 1s) are presented for ten polymers with side‐chains of the form ? OCO(CF2)yF, ? COO(CH2)2OCO(CF2)yF (y = 1, 2, 3) and ? COO(CH2)x(CF2)yF (x = 1, y = 1, 2, 3; x = 2, y = 8). Particular attention was paid to charge compensation and speed of data acquisition, with co‐addition from multiple fresh samples to give spectra with good energy resolution and good signal‐to‐noise ratio free from the effects of x‐ray‐induced degradation. Water contact angles for the polymers are also reported. The XPS data demonstrate preferential surface segregation of fluorine‐containing groups for all but the shortest side‐chain polymer, where the ? OCOCF3 side‐chain either does not surface segregate or is too short for surface segregation to be detectable by angle‐resolved XPS. In the other polymers studied the relative positions of functional groups in the side‐chains correlate with the angle‐resolved behaviour of the corresponding C 1s components. This shows that the surface side‐chains are oriented towards the polymer surface. For the ? COO(CH2)2OCO(CF2)yF (y = 1) side‐chain, the angle‐resolved C 1s data suggest reduced ordering and linearity compared with y = 2 and 3. For any particular series of polymers, e.g. ? COO(CH2)x(CF2)yF, the water contact angles increase with y, consistent with burying of the hydrophilic ester groups as y increases. For any particular value of y the sequence of water contact angles is ? COO(CH2)x(CF2)yF > ? OCO(CF2)yF ~ ? COO(CH2)2OCO(CF2)yF, suggesting greater ordering and density of fluorocarbon species at the surface of the ? COO(CH2)x(CF2)yF side‐chain polymers compared with the other polymers studied. For the ? COO(CH2)2(CF2)8F polymer a water contact angle of 124° is measured, which is greater than that of poly(tetrafluoroethene). The ? COO(CH2)2OCO(CF2)F polymer is unusual in that it shows a particularly low water contact angle (83° ), suggesting that the probe fluid is able to sense both ester groups, consistent with the reduced ordering of the side‐chain detected by angle‐resolved XPS. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

18.
Phase composition, electroconductivity, oxygen ion transport number, and microhardness of samples of Ln1 − x SrxGa0.5 − y/2Al0.5 − y/2MgyO3 − δ (Ln = La, Pr, Nd; x, y = 0.10, 0.15) synthesized by a ceramic methods are studied. Methods of x-ray diffraction analysis and scanning electron microscopy reveal the La-containing samples to be homogeneous and have a perovskite structure. Magnesium does not dissolve in Pr-and Nd-containing systems but forms an individual phase based on magnesium oxide. Apart from magnesium oxide, in these systems there form extrinsic phases, specifically, LnSrGa3O7 and an unknown phase. The electroconductivity of La1 − x SrxGa1 − y MgyO3 − δ decreases after substituting Al for Ga. Ceramic La1 − x SrxGa0.5 − y/2Al0.5 − y/2MgyO3−δ is a purely ionic conductor in the temperature interval 500 to 1000°C; NdxSrxGa0.5 − y/2Al0.5 − y/2MgyO3 − δ has predominantly ionic conduction; and the predominant type of conduction in Pr1 − x SrxGa0.5 − y/2Al0.5 − y/2MgyO3 − δ is electronic below 700–800°C, with the contribution of ionic conduction increasing at higher temperatures. Substituting Al for Ga raises the hardness of ceramics under study. Among the compositions studied, La0.85Sr0.15Ga0.45Al0.45Mg0.10O3 − δ and La0.85Sr0.15Ga0.425Al0.425Mg0.15O3 − δ exhibit a combination of electroconductivity and hardness that is optimal for application as electrolyte at reduced temperatures (600–800°C). The Pr1 − x SrxGa0.5 − y/2Al0.5 − y/2MgyO3 − δ system possesses mixed ionic-electronic conduction and high hardness, which makes it appealing for application as oxygen-penetrable membranes. Original Russian Text ? Yu.V. Danilov, A.D. Neuimin, L.A. Dunyushkina, L.A. Kuz’mina, N.S. Zybko, Z.S. Martem’yanova, A.A. Pankratov, 2007, published in Elektrokhimiya, 2007, Vol. 43, No. 1, pp. 57–65.  相似文献   

19.
The crystal structure and magnetic properties of orthomanganitesA1−xMnO3+y(A=La, Eu;x≤0.2;y≤0.13) were investigated. It was shown that the increase of oxygen content leads to the transformation from the weak ferromagnetic to the ferromagnetic state in these compounds. The Curie temperatures of La1−xMnO3+yand freezing temperatures of magnetic clusters for Eu1−xMnO3+yin the samples with a deficit ofAcations are higher than those in parent compounds (withx=0). A mixed magnetic state involving ferro- and antiferromagnetic domains is suggested in the intermediate range ofx,yvalues. Arguments are presented to support the assumption that the magnetic properties in the lightly doped insulating regime are governed by superexchange via anions rather than by exchange via charge carriers.  相似文献   

20.
A series of five l ‐di‐p‐toluoyl‐tartaric acid (l ‐DTTA) lanthanide coordination polymers, namely {[Ln4K4 L6(H2O)x]?yH2O}n, [Ln=Dy ( 1 ), x=24, y=12; Ln=Ho ( 2 ), x=23, y=12; Ln=Er ( 3 ), x=24, y=12; Ln=Yb ( 4 ), x=24, y=11; Ln=Lu ( 5 ), x=24, y=12] have been isolated by simple reactions of H2L (H2L= L ‐DTTA) with LnCl3?6 H2O at ambient temperature. X‐ray crystallographic analysis reveals that complexes 1 – 5 feature two‐dimensional (2D) network structures in which the Ln3+ ions are bridged by carboxylate groups of ligands in two unique coordinated modes. Luminescent spectra demonstrate that complex 1 realizes single‐component white‐light emission, while complexes 2 – 4 exhibit a characteristic near‐infrared (NIR) luminescence in the solid state at room temperature.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号