A controllable synthetic route to Cu,Cu2O,and CuO nanotubes and nanorods

Reducing Cu(OH)4(2-) with hydrazine hydrate and glucose in the presence of a structure-directing surfactant at room temperature gave Cu and Cu2O nanotubes/nanorods, respectively, whereas facile hydrothermal treatment of Cu(OH)4(2-) precursor resulted in CuO nanotubes/nanorods.     

差示扫描量热法对芝麻酚纯度标准物质的定值

建立了采用差示扫描量热法对芝麻酚纯度标准物质的定值及不确定度评价的数学模型、有效检测技术和分析方法.采用差示扫描量热法测量芝麻酚样品纯度的实验条件为升温速率3.0 K/min,称样量3.4～4.7 mg,炉内气体为静态空气.对通过均匀性检验和长期稳定性考察的芝麻酚纯度标准物质进行定值和不确定度评价,同时采用高效液相色谱...     

Degenerative transfer living Ziegler-Natta polymerization: application to the synthesis of monomodal stereoblock polyolefins of narrow polydispersity and tunable block length

The neutral dimethyl pentamethylcyclopentadienylzirconium acetamidinate, (eta(5)-C(5)Me(5))ZrMe(2)[N(t-Bu)C(Me)N(Et)], can serve as a highly active initiator for the living Ziegler-Natta polymerization of alpha-olefins to produce polyolefins of narrow polydispersity (D < or = 1.05) when "activated" through mono demethylation by a substoichiometric amount of the borate, [PhNMe(2)H][B(C(6)F(5))(4)]. The mechanism by which this living polymerization proceeds is through a process of degenerative transfer involving rapid and reversible methyl group exchange between cationic (active) zirconium propagating centers and neutral (dormant) methyl, polymeryl zirconium end groups. Facile metal-centered epimerization of the dormant species is responsible for a loss of stereocontrol during propagation that produces iso-rich material in contrast to the pure isotactic polymer microstructure obtained when degenerative transfer is not present. By turning degenerative transfer "on" and "off" between successive monomer polymerizations, a successful strategy for the production of monomodal stereoblock polyolefins of narrow polydispersity and tunable block length has been demonstrated.     

The catalytic performance study of polymerized ionic liquid synthesized in different conditions on alkylation of o‐Xylene with styrene

In this work, a series of novel acidic polymerized ionic liquids were used as heterogeneous catalyst for alkylation of o‐Xylene with styrene. And the effect of the amount of initiator and the type of acid used for ion exchange on catalyst structure and the catalytic performance of catalysts for alkylation were studied thoroughly. The experiment results show: when the percentage of the amount of initiator in the total material is 3%, the polymerized ionic liquid catalyst MPM‐SO₃H‐[C₃V][SO₃CF₃] has the most uniform with a specific surface area of 97.30 m²/g and a pore volume of 0.35 cm³/g. Benefiting from the unique structure features, MPM‐SO₃H‐[C₃V][SO₃CF₃] manifested an excellent catalytic performance for alkylation of o‐Xylene with styrene, along with the conversion of styrene was 96.8% and the yield of 1‐Phenyl‐1‐ortho‐xylene ethane was 94.7%. Therefore, this work provides a novel reference to the synthesis of polymerized ionic liquids and clearly explains the advantage of novel acidic polymerized ionic liquids on alkylation.     

Preparation and characterization of core–shell polymer particles with protonizable shells prepared by oxyanionic polymerization

A series of polystyrene (PS)/poly(vinyl acetate) (PVAc) crosslinked particles (240, 210, or 90 nm) with different concentrations of PS (75, 50, or 25 wt %) were prepared by soap‐free emulsion polymerization. Based on the crosslinked polymer particles, three series of monodisperse core–shell particles with pH‐sensitive poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA) shells were synthesized by oxyanionic polymerization. During the oxyanionic polymerization, the acetate groups of PVAc were hydrolyzed, and the hydroxyl groups that formed on the surfaces of the particles, acting as initiators, were transferred to ? O^?K⁺ by DMSO^?K⁺ (where DMSO is dimethyl sulfoxide) at the same time; then, ? O^?K⁺ initiated the polymerization of 2‐(dimethylamino)ethyl methacrylate. ¹H NMR and Fourier transform infrared studies confirmed the existence of PDMAEMA shells, and the contents of PDMAEMA were measured by elemental analysis. Because the PDMAEMA chain could be protonated at a low pH, these core–shell particles could adsorb negatively charged modified magnetite particles, and at higher pHs, the magnetite particles could be released again; this process was reversible. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6081–6088, 2004     

Fusopoltide A and fusosterede A,A polyketide with a pentaleno[1,2-c]pyran ring system and A degraded steride,from the fungus Fusarium solani

Fusopoltide A (1), a novel polyketide featured a pentaleno[1,2-c]pyran ring, and fusosteride A (2), a new steride with A/B-ring degraded, together with a known ergosterol peroxide (3), were isolated from a solid culture extract of Fusarium solani. The structures of 1 and 2 were elucidated by detailed interpretation of their HRESIMS and NMR spectroscopic data and their absolute configurations were determined by X-ray crystallographic analysis and the electronic circular dichroic (ECD) method, respectively. The postulated biogenetic pathways of 1 and 2 were also discussed. Compound 1 exhibits inhibitory activity against cyclooxygenase-2 (COX-2) with an IC₅₀ value of 3.45?μM.     

A new diarylheptanoid from Alpinia officinarum promotes the differentiation of 3T3-L1 preadipocytes

A new diarylheptanoid, namely trans-(4R,5S)-epoxy-1,7-diphenyl-3-heptanone (1), and a new natural product, 7-(4″-hydroxy-3″-methoxyphenyl)-1-phenyl-hepta-4E,6E-dien-3-one (2), were obtained from the aqueous extract of Alpinia officinarum Hance, together with three other diarylheptanoids, 5-hydroxy-1,7-diphenyl-3-heptanone (3), 1,7-diphenyl-4E-en-3-heptanone (4) and 5-methoxy-1,7-diphenyl-3-heptanone (5). The structures were characterised mainly by analysing their physical data including IR, NMR and HRMS. This study highlights that the 4,5-epoxy moiety in 1 is rarely seen in diarylheptanoids. In addition, the five isolates were tested for their differentiation activity of 3T3-L1 preadipocytes. The results showed that these compounds could dose-dependently promote adipocyte differentiation without cytotoxicity (IC₅₀ > 100 μM).     

Existence and nonexistence of global positive solutions to nonlinear diffusion problems with nonlinear absorption through the boundary

This paper deals with the existence and nonexistence of global positive solutions to in ,

and in . Here is a parameter, is a bounded smooth domain. After pointing out the mistakes in Global behavior of positive solutions to nonlinear diffusion problems with nonlinear absorption through the boundary, SIAM J. Math. Anal. 24 (1993), 317-326, by N. Wolanski, which claims that, for the ball of , the positive solution exists globally if and only if , we reconsider the same problem in general bounded domain and obtain that every positive solution exists globally if and only if .

     

Measurement of mobility of adsorbed colloids by lateral force microscopy

The surface mobility of colloidal latex particles adsorbed on mica was measured by moving the particles with an AFM tip in the lateral force microscopy mode. The same particle was repeatedly scanned while the normal force was gradually increased, until the particle was displaced from its location on the substrate. The lateral (friction) force curve obtained for that scan was then used to determine the force needed to displace the particle. The data accumulated for approximately 100 particles indicate a wide distribution in the lateral force required. However, the data show that the mean lateral force is proportional to the particle diameter, with the effect of electrostatic interactions on the mobility of adsorbed particles seen to be weak. These results are consistent with classical theories of friction in macroscopic systems.