Voltammetric determination of boron by using Alizarin Red S

Cordycepin is the main active metabolite of Cordyceps militaris extracts; according to recent studies it has interesting therapeutic activities. A new capillary electrophoresis (CE) procedure with UV detection at 254 nm for determination of cordycepin was developed and optimized. Optimal conditions found were 20 mM sodium borate buffer with 28.6% methanol, pH 9.5, separation voltage 20 kV, hydrodynamic injection time 10 s and temperature 25 °C. Linearity was found over the 20-100 μg/mL concentration ranges of cordycepin. The developed method has been applied for determination of cordycepin in various pharmaceutical products. A comparison was made between CE and a high performance liquid chromatography (HPLC) method. Both of these methods gave comparable results. The shorter analysis time and low running cost are the main advantages of CE method.     

Viscoelasticity of mono- and polydisperse inverse ferrofluids

We report on measurements of a magnetorheological model fluid created by dispersing nonmagnetic microparticles of polystyrene in a commercial ferrofluid. The linear viscoelastic properties as a function of magnetic field strength, particle size, and particle size distribution are studied by oscillatory measurements. We compare the results with a magnetostatic theory proposed by De Gans et al. [Phys. Rev. E 60, 4518 (1999)] for the case of gap spanning chains of particles. We observe these chain structures via a long distance microscope. For monodisperse particles we find good agreement of the measured storage modulus with theory, even for an extended range, where the linear magnetization law is no longer strictly valid. Moreover we compare for the first time results for mono- and polydisperse particles. For the latter, we observe an enhanced storage modulus in the linear regime of the magnetization.     

Radial-type complete solutions for a class of partial differential equations

We give some fundamental solutions of a class of iterated elliptic equations including Laplace equation and its iterates.     

一个解剖基人体下肢的生物动力模型--第三部分:肌肉效应

本将人体下肢的肌肉根据其解剖特征，分为５个肌群，并在由本第一部分所建立的基本的解剖基模型的基础上，计入其对人体下肢动力运动的效应。本所建立的５个肌群，则主要代表着膝关节处的运动和稳定肌。最后，作为应用，研究了一个献中的特例。     

One-Step Synthesis of Triblock Copolymers via Simultaneous Reversible-Addition Fragmentation Chain Transfer (RAFT) and Ring-Opening Polymerization Using a Novel Difunctional Macro-RAFT Agent Based on Polyethylene Glycol

One-step synthesis of the triblock copolymers was carried out by reversible addition–fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) and ring-opening polymerization (ROP) of β-butyrolactone (BL) or ?-caprolactone (CL) using a novel difunctional macro-RAFT agent. For this purpose, primarily PEG-Br (polyethylene glycol bromine) was obtained by using 3-bromopropanoyl chloride and PEGs (polyethylene glycols) with different molecular weights. Then, macro-RAFT agent was synthesized by the reaction of potassium ethyl xanthogenate and PEG-Br. By using macro-RAFT agent, poly(MMA-b-EG-b-BL), and poly(MMA-b-EG-b-CL) triblock copolymers were synthesized by changing some polymerization conditions such as monomer/initiator concentration, polymerization time. The effect of the reaction conditions on the polydispersity and molecular weights were also investigated. The block lengths of the triblock copolymers were calculated by using ¹H-nuclear magnetic resonance (¹H-NMR) spectra. It was observed that the block length could be altered by varying the monomer and initiator concentrations. The characterization of the products were achieved using ¹H-NMR, Fourier-transform infrared spectroscopy (FTIR), gel-permeation chromatography (GPC), thermogravimetric analysis (TGA), and fractional precipitation (γ) techniques.     

Synthesis,Spectroscopic Studies and Crystal Structure of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-bis((thiophene-2-carboxamido)propyl)piperazine

Abstract  A new multidentate ligand N,N′-bis((thiophene-2-carboxamide)propyl)piperazine has been synthesized from the reaction of thiophene-2-carbonylchloride and 1,4-bis(3-aminopropyl)piperazine. The title compound has been characterized by elemental analysis, FT-IR, ¹H-NMR and ¹³C-NMR spectroscopic techniques. The crystal structure of the title compound (C₂₀H₃₀N₄O₂S₂Cl₂) has also been determined by X-ray analysis. The title compound crystallize in the monoclinic space group P2₁/c with a = 9.768(1), b = 12.895(1), c = 10.083(1) ?, β = 115.12(1)°, V = 1149.9(2) ?³, D _x = 1.425 g cm⁻³ and Z = 2. The crystal structure was solved by direct methods and refined by full-matrix least squares to a find R = 0.039 [I > 2σ (I)] for 2,786 observed reflections. Graphical Abstract  The (N,N’–bis((thiophene-2- carboxamido)propyl)piperazine) molecule has been synthesized and its molecule structure has been investigated by using , FT-IR, 13C NMR and 1H-NMR spectroscopic and crystallographic techniques.

Holditch Theorem and Steiner Formula for the Planar Hyperbolic Motions

The Steiner formula and the Holditch Theorem for one-parameter closed planar Euclidean motions [1, 7] were expressed by H.R. Müller [9] under the one-parameter closed planar motions in the complex sense. In this paper, in analogy with complex motions as given by Müller [9], the Steiner formula and the mixture area formula are obtained under one parameter hyperbolic motions. Also Holditch theorems were expressed in the hyperbolic sense. The classical Holditch Theorem: If the endpoints A, B of a segment of fixed length are rotated once on an oval, then a given point X of this segment, with , describes a closed, not necessarily convex, curve. The area of the ring-shaped domain bounded by the two curves is πab, [1, 7].     

Distribution of eigenvalues for the discontinuous boundary-value problem with functional-manypoint conditions

In this study, we investigate the boundary-value problem with eigenvalue parameter generated by the differential equation with discontinuous coefficients and boundary conditions which contains not only endpoints of the considered interval, but also a point of discontinuity, a finite number of internal points and abstract linear functionals. So our problem is not a pure boundary-value one. We single out a class of linear functionals and find simple algebraic conditions on the coefficients which guarantee the existence of an infinite number of eigenvalues. Also, the asymptotic formulas for the eigenvalues are found. The results obtained in this paper are new, even in the case of boundary conditions either without internal points or without linear functionals.     

Natural radioactivity and hazard-level assessment of Portland cements in Turkey

The natural radioactivity levels and some radiological parameters of Turkish Portland cements (PC) originated in various regions were determined in this study. The activity concentration of cement samples for ²²⁶Ra, ²³²Th, and ⁴⁰K were measured using a gamma-ray spectrometer with high purity germanium radiation detector. The PC samples had activity concentrations of 33.0, 16.7, and 239.5 Bq kg⁻¹ for ²²⁶Ra, ²³²Th, and ⁴⁰K, respectively. The mean value of radium equivalent value (Ra_eq) was found to be 75.4 Bq kg⁻¹. The radium equivalent values in the cement samples were lower than the acceptable level of 370 Bq kg⁻¹. The calculated radiological parameters were found to be below the acceptance levels.

     

Area-selective growth of amorphous carbon nanofibers via catalytic decomposition of polyimide thin film

A dense layer of amorphous carbon nanofibers was fabricated by pyrolyzing a thin film of polyimide using a monolayer of gold nanoparticles as a catalyst.