A novel H(2)O(2) amperometric biosensor based on gold nanoparticles/self-doped polyaniline nanofibers

A new kind of gold nanoparticles/self-doped polyaniline nanofibers (Au/SPAN) with grooves has been prepared for the immobilization of horseradish peroxidase (HRP) on the surface of glassy carbon electrode (GCE). The ratio of gold in the composite nanofibers was up to 64%, which could promote the conductivity and biocompatibility of SPAN and increase the immobilized amount of HRP molecules greatly. The electrode exhibits enhanced electrocatalytic activity in the reduction of H₂O₂ in the presence of the mediator hydroquinone (HQ). The effects of concentration of HQ, solution pH and the working potential on the current response of the modified electrode toward H₂O₂ were optimized to obtain the maximal sensitivity. The proposed biosensor exhibited a good linear response in the range from 10 to 2000 μM with a detection limit of 1.6 μM (S/N = 3) under the optimum conditions. The response showed Michaelis–Menten behavior at larger H₂O₂ concentrations, and the apparent Michaelis–Menten constant K_m was estimated to be 2.21 mM. The detection of H₂O₂ concentration in real sample showed acceptable accuracy with the traditional potassium permanganate titration.     

Attractors for non-autonomous parabolic problems with singular initial data

In this paper, we study the asymptotic behavior of solutions of non-autonomous parabolic problems with singular initial data. We first establish the well-posedness of the equation when the initial data belongs to Lr(Ω) (1<r<∞) and W1,r(Ω) (1<r<N), respectively. When the initial data belongs to Lr(Ω), we establish the existence of uniform attractors in Lr(Ω) for the family of processes with external forces being translation bounded but not translation compact in . When we consider the existence of uniform attractors in , the solution of equation lacks the higher regularity, so we introduce a new type of solution and prove the existence result. For the long time behavior of solutions of the equation in W1,r(Ω), we only obtain the uniform attracting property in the weak topology.     

A Criterion of Normality Concerning Holomorphic Functions Whose Derivative Omits a Function

The authors discuss the normality concerning holomorphic functions and get the following result. Let F be a family of holomorphic functions on a domain D ⊂ ℂ, all of whose zeros have multiplicity at least k, where k ≥ 2 is an integer. And let h(z) ≢ 0 be a holomorphic function on D. Assume also that the following two conditions hold for every f ∈ F: (a) f(z) = 0 ⇒ |f ^(k)(z)| < |h(z)|; (b) f ^(k)(z) ≠ h(z). Then F is normal on D.     

Computation of generalized differentials in nonlinear complementarity problems

Let f and g be continuously differentiable functions on R ⁿ . The nonlinear complementarity problem NCP(f,g), 0≤f(x)⊥g(x)≥0, arises in many applications including discrete Hamilton-Jacobi-Bellman equations and nonsmooth Dirichlet problems. A popular method to find a solution of the NCP(f,g) is the generalized Newton method which solves an equivalent system of nonsmooth equations F(x)=0 derived by an NCP function. In this paper, we present a sufficient and necessary condition for F to be Fréchet differentiable, when F is defined by the “min” NCP function, the Fischer-Burmeister NCP function or the penalized Fischer-Burmeister NCP function. Moreover, we give an explicit formula of an element in the Clarke generalized Jacobian of F defined by the “min” NCP function, and the B-differential of F defined by other two NCP functions. The explicit formulas for generalized differentials of F lead to sharper global error bounds for the NCP(f,g).     

Tetrazole-Functionalized Silica for Hydrophilic Interaction Chromatography of Polar Solutes

In this work, tetrazole-functionalized stationary phase was prepared with nitrile-modified silica by an ammonium-catalyzed (3 + 2) azide-nitrile cycloaddition reaction. The prepared stationary phase was used for separation of nucleobases and nucleosides by hydrophilic interaction chromatography (HILIC) mode. A typical HILIC mechanism was observed at higher content of acetonitrile (>85%, v/v) in the mobile phase. The retention mechanism of the column was investigated by the models used for describing partitioning and surface adsorption through adjustment ratio of water in the mobile phase, and by the influence of salt concentration, buffer pH, and temperature on the retention of solutes. The results illustrated that the surface adsorption through hydrogen bonding dominated the retention behavior of nucleobases/nucleosides under HILIC mode. From the separation ability, the tetrazole-functionalized stationary phase could become a valuable alternative for the separation of the compounds concerned.     

Theoretical study on the smallest endohedral metallofullerenes: TM@C20 (TM = Ce and Gd)

The structure, electronic property, and infrared spectroscopy of endohedral metallofullerenes TM@C₂₀ (TM = Ce and Gd) have been systematically investigated with the aid of the hybrid DFT‐B3LYP functional. It is found that in the endohedral metallofullerenes the average C? C bond lengths are obvious longer than those of empty cage. The frontier orbital analyses show that the endohedral metallofullerene Gd@C₂₀ has the high‐thermodynamic stability. Natural population analysis also tells us that only in the Ce@C₂₀, the Ce atom acts as an electron acceptor with the negative charges, and the 4f orbitals of Ce and Gd atoms have a significant contribution in the formation of chemical bonding. Additionally, the analyses of harmonic vibrational frequencies reveal that when the TM atoms are encapsulated into the C₂₀ cage, the strongest absorption peaks are characterized by a mixture of TM?C bending and C? C stretching vibrations. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Nanotubular metal-organic frameworks with high porosity based on T-shaped pyridyl dicarboxylate ligands

Two nanotubular metal-organic frameworks (MOFs), {Cu(L1)·2H(2)O·1.5DMF}(∞) (1) and {Cu(2)(L2)(2)(H(2)O)(2)·7H(2)O·3DMF}(∞) (2), with novel topologies have been constructed based on Cu(2+), 5-(pyridin-4-yl)isophthalic acid (L1) and 5-(pyridin-3-yl)isophthalic acid (L2), respectively. Two MOFs were characterized by IR spectroscopy, thermogravimetry, single-crystal, and powder X-ray diffraction methods. Network analysis reveals a two-nodal (3,6)-connected (4·6(2))(2)(4(2)·6(10)·8(3)) net and a three-nodal (3,4)-connected (4·8(2))(4)(4(2)·8(2)·10(2))(2)(8(4)·12(2)) net. Interpenetration is inherently prevented by both of the topologies of the frameworks. The porosity of MOF 1 was confirmed by N(2) and CO(2) gas adsorption investigations. MOF 1 exhibits remarkable hydrogen sorption hysteresis at low pressure and a H(2) uptake capacity of 1.05 wt% at 77 K and 1 atm.     

Tunable full-color-emitting Ca3Sc2Si3O12:Ce3+, Mn2+ phosphor via charge compensation and energy transfer

A tunable full-color-emitting Ca(3)Sc(2)Si(3)O(12):Ce(3+), Mn(2+) (CSS:Ce(3+),Mn(2+)) phosphor is obtained by addition of doped ions as charge compensation. White LEDs with high R(a) (> 90) are achieved using the single CSS:Ce(3+),Mn(2+) phosphor.     

小变形轴力杆件的变形位移方程

从杆件变形量的定义出发,利用两点间距离公式,导出了小变形轴力杆件的变形位移方 程. 此方程形式简洁,计算方便,对线性和非线性材料的小变形问题都可应用,也不必区分静定 结构和超静定结构,还可以方便地处理支座沉陷问题,因而广泛适用于桁架结构的受力分析.