Recognition of DNA three-way junctions by metallosupramolecular cylinders: gel electrophoresis studies

The interaction of metallosupramolecular cylinders with DNA three-way junctions has been studied by gel electrophoresis. A recent X-ray crystal structure of a palindromic oligonucleotide forming part of a complex with such a cylinder revealed binding at the heart of a three-way junction structure. The studies reported herein confirm that this is not solely an artefact of crystallisation and reveal that this is a potentially very powerful new mode of DNA recognition with wide scope. The cylinders are much more effective at stabilizing three-way junctions than simple magnesium di-cations or organic or metallo-organic tetra-cations, with the M cylinder enantiomer being more effective than P. The recognition is not restricted to three-way junctions formed from palindromic DNA with a central AT step at the junction; non-palindromic three-way junctions and those with GC steps are also stabilised. The cylinder is also revealed to stabilise other Y-shaped junctions, such as that formed at a fraying point in duplex DNA (for example, a replication fork), and other DNA three-way junction structures, such as those containing unpaired nucleotides, perhaps by opening up this structure to access the central cavity.     

Analytical approximate 3D solution for the longitudinally vibrating cylinder

Summary The paper presents a three-dimensional approximate solution of a longitudinally vibrating cylinder. It is based on the frequency equation for free waves travelling along an infinitely long cylinder which follows from the radial boundary condition on the lateral surface of the cylinder. An equivalent longitudinal traction is calculated by integration of the normal stresses over the end cross section. The full solution of the longitudinally vibrating rod adapted to given axial boundary conditions is derived. The solution is compared to numerical results, and good agreement is obtained.     

Constitutive equations for non-affine polymer networks with slippage of chains

A model is derived for isothermal three-dimensional deformation of polymers with finite strains. A polymer fluid is treated as a permanent network of chains bridged by junctions (entanglements). Macro-deformation of the medium induces two motions at the micro-level: (i) sliding of junctions with respect to their reference positions that reflects non-affine deformation of the network, and (ii) slippage of chains with respect to entanglements that is associated with unfolding of back-loops. Constitutive equations are developed by using the laws of thermodynamics. Three important features characterize the model: (i) the symmetry of relations between the elongation of strands and an appropriate configurational tensor, (ii) the strong nonlinearity of the governing equations, and (iii) the account for the volumetric deformation of the network induced by stretching of chains. The governing equations are applied to the numerical analysis of extensional and shear flows. It is demonstrated that the model adequately describes the time-dependent response of polymer melts observed in conventional rheological tests.     

薄壁加筋肋圆柱壳稳定性分析的参数化研究

针对在轴向载荷作用下的正置、正交网格形式的薄壁加筋肋圆柱壳结构，利用有限元程序，对薄壁加筋肋圆柱壳稳定性分析进行了参数化研究，得到了进行结构优化设计的准则，对于给定的设计载荷，当结构参数位于某一个局部失稳与整体失稳的临界区域时，结构的重量最轻。提出了基于有限元分析进行结构优化设计的策略，利用优化策略，获得了一薄壁加筋肋圆柱壳结构的优化设计结果，同时给出了粘合刚度简化模型与有限元计算结果的比较。     

Stress Analysis of Orthotropic Hollow Noncircular Cylinders

The paper proposes an approach to solving three-dimensional stress problems for hollow orthotropic cylinders with noncircular cross section and certain end conditions. The approach is based on the method of separation of generatrix and directrix variables, discrete Fourier series, and the stable method of discrete orthogonalization. The results of analysis of an orthotropic cylinder are presented     

Near-wake flow structure of elliptic cylinders close to a free surface: effect of cylinder aspect ratio

The flow fields behind elliptic cylinders adjacent to a free surface were investigated experimentally in a circulating water channel. A range of cylinder aspect ratios (AR=2, 3, 4) were considered, while the cross-sectional area of the elliptical cylinder was kept constant. The main objective of this study was to investigate the effect of cylinder aspect ratio and a free surface on the flow structure in the near-wake behind elliptic cylinders. For each elliptic cylinder, the flow structure was analyzed for various values of the submergence depth of the cylinder beneath the free surface. The flow fields were measured using a single-frame double-exposure PIV (Particle Image Velocimetry) system. For each experimental condition, 350 instantaneous velocity fields were obtained and ensemble-averaged to obtain the mean velocity field and spatial distribution of the mean vorticity statistics. The results show that near-wake can be classified into three typical flow patterns: formation of a Coanda flow, generation of substantial jet-like flow, and attachment of this jet flow to the free surface. The general flow structure observed behind the elliptic cylinders resembles the structure previously reported for a circular cylinder submerged near a free surface. However, the wake width and the angle of downward deflection of the shear layer developed from the lower surface of the elliptic cylinder differ from those observed for a circular cylinder. These trends are enhanced as cylinder aspect ratio is increased. In addition, the free surface distortion is also discussed in the paper.     

Intrinsic Permeability Evolution in High Temperature Concrete: An Experimental and Numerical Analysis

This paper presents an experimental and thermo-hydro-chemical-mechanical numerical analysis of concrete at high temperatures, aiming at the definition of a law describing the evolution of intrinsic permeability. The evaluation of heat and mass transfers, evolution of the phases composing the porous medium, and mechanical performances of concrete are taken into account in a full three phases coupled analysis. An experimental set-up and a numerical simulation are then presented. A hollow cylinder has been heated up to 523.15 K (250 °C) on the internal side and subjected to gas pressure/temperature measurements; the experience has been then simulated by means of a numerical code. The analysis has allowed for the definition of an original relationship describing intrinsic permeability evolution. Finally, the law has been validated measuring the actual value of intrinsic permeability on heated concrete.     

A simple extensional viscometer

An extensional viscometer is described in which the liquid filament leaving a capillary is subjected to a stretching deformation. In order to keep the flow rate through the capillary unaltered upon inception of stretching, the pressure head at the capillary entrance has to be reduced by an amount equal to the extensional viscoelastic stress at the capillary exit. This affords a simple means of measuring small fluid forces such as those that occur in the stretching of dilute polymer solutions. Since stretch rates can be obtained from a knowledge of the mass flow rate and the filament diameter profile, extensional viscosities can be computed. The efficacy of the technique is demonstrated by obtaining the anticipated results for Newtonian liquids.     

Raman spectroscopy and magnetic properties of KMCr(CN)6 under pressure

We study the effect of pressure on Raman spectra as well on magnetic properties of molecule-based magnets KNiCr(CN)₆ and KMnCr(CN)₆. The effect of pressure on the ν[C≡N] vibration band which is located in the 2100–2200?cm^?1 spectral range is relatively weak. Hydrostatic pressure has small almost a negligible effect on the Curie temperature of ferromagnetic KNiCr(CN)₆ while leads to a pronounced reversible Curie temperature increase occurrence of new magnetic phase under pressure in the case of KMnCr(CN)₆. Applied pressure affects magnetization curves only marginally. All pressure-induced changes are reversible.     

A plane problem of uncoupled thermomagnetoelasticity for an infinite,elliptical cylinder carrying a steady axial current by a boundary integral method

A boundary integral method earlier proposed by two of the authors is used to solve a problem of uncoupled magnetothermoelasticity for an infinite, elliptical cylindrical conductor carrying a steady axial, uniform electric current. The cylinder is placed in a variable ambient temperature and is allowed to exchange heat with the surrounding medium.