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.     

Magnetic flux distribution in type II superconductors with large demagnetization and a high edge barrier

The trapped flux distribution in thin wafers of both polycrystalline and granular superconductors having large demagnetization and edge barriers of different heights is measured by means of polarized neutrons. It is shown that the nature of the critical state in polycrystalline wafers, unlike that in a ceramic wafer, is not described by the Bean model. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 12, 771–775 (25 December 1999)     

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.     

Solubility of bromine derivatives of C<Subscript>60</Subscript>Br<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> fullerene in α-chloro- and α-bromonaphthalene in the temperature range 10–60°C

Isothermal saturation in ampoules was used to study the solubility of bromine derivatives of fullerene C₆₀Br _n (n = 6, 8, 24) in α-C₁₀H₇Cl and α-C₁₀H₇Br in the temperature range of 10–60°C. The corresponding solubility polytherms were characterized, and the compositions of the equilibrium crystal solvates and the density of the saturated solutions of C₆₀Br _n were determined.     

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].     

Neutron Guide System for Ultracold and Cold Neutrons at the WWR-M Reactor

Technical Physics - The results of calculation of fluxes of ultracold (UCNs), very cold, and cold neutrons at the output of neutron guides of the UCN source with superfluid helium at the WWR-M...     

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.