Planar Body Research Articles

A central role for microvillous receptor presentation in leukocyte adhesion under flow

Leukocyte adhesion to endothelium requires specialized mechanisms for contact initiation under flow. L-selectin (CD62L), an efficient initiator of adhesion, is clustered on the tips of leukocyte microvilli. To test whether microvillous presentation is critical for contact formation (“tethering”), we transfected lymphoid cells with chimeras of L-selectin and CD44, an adhesion molecule that is excluded from microvilli. CD44 transmembrane and intracellular (TM-IC) domains targeted the L-selectin ectodomain to the planar body, whereas L-selectin TM-IC segments conferred CD44 ectodomain clustering on microvilli. Wild-type and chimeric transfectants bound similarly to anti-ectodomain MAbs in static assays, but MAb binding under flow was much more efficient in the context of microvillous presentation. Similarly, wild-type and chimeric L-selectin possessed equivalent lectin activity, but microvillous presentation dramatically enhanced contact initiation on a native ligand. These findings demonstrate a critical role for receptor topography in leukocyte adhesion and suggest a novel regulatory mechanism of leukocyte trafficking.

Cooling of a 2-dimensional intrusion

Descriptions of the processes of crystallization and cooling of a planar intrusion body and its environs are compared by applying the frequently used Jaeger-Carslaw, adjusted Feoktistov-Feoktistova nad modified Lovering methods.

Stability analysis of a rotating flexible system

We analyse here the equations of motion of a planar body consisting of a rigid body with attached flexible rod. These equations take the form of coupled ordinary and partial differential equations. We analyse the equations both with and without centrifugal stiffening effects. Using the ‘energy-momentum’ method, we analyse nonlinear stability of the equilibria in each case. We also analyse the Hamiltonian and Poisson bracket structure of the system as well as the energy-momentum map and associated relative equilibria.

Some Experimental Results Using Heuristics for Solving the Find-Path Problem in C-Space

The problem of moving a rigid planar body in a 2D environment with fixed obstacles is discussed. In spite of being a simple instance of the general find-path problem, the computational complexity of the existing algorithms to solve it are still too high for practical purposes. A new approach improving the efficiency of the solution to this problem, when viewed as a search problem in configuration space, is introduced. It is based on the use of a reduced model of the connectivity of free-space to globally guide the search process towards the more promising directions in configuration space. The search time savings obtained when using this heuristic are shown to be important and justify its interest for real time applications. Some examples comparing the efficiency of classical search methods with the efficiency of the proposed search procedure are included.

Numerical solutions for stresses near crack tips in time-dependent inelastic fracture mechanics

The boundary element method is used in this paper to calculate the stresses in a finite planar body with a traction free crack present in it. The body is assumed to undergo time-dependent inelastic deformation and is described by an elastic-power law creep constitutive model. A stationary crack is modelled as a very thin ellipse and numerical solutions to the complete transient problem are obtained by step-wise integration in time. The numerical results for stresses near a crack tip are compared with the asymptotic analytical results obtained by other researchers. These asymptotic results are those for a plate with a line crack where the elastic strain rates are neglected relative to the nonelastic strain rates near the crack tips. Both Mode III and Mode I deformation, under time-independent and time-dependent remote loading, are considered in the calculations.

Calculation of initial stage of heating a planar body with variable properties

A method is presented for calculation of upper and lower limits of the temperature field of a planar body with temperature-dependent thermophysical properties.

Random Torsional Oscillation Model for Rotational Molecular Motion. Cold Neutron Scattering Investigation of Cholesteryl Propionate, Nonanoate, and Myristate

AbstractThe incoherent scattering function for the case of simple translation of the centre of mass and the random torsional oscillations of the rigid planar body along the long molecular axes of an amplitude φ of perfectly ordered molecules in nematic phase, is calculated. The model of a random molecular torsional motion is built on the assumption that each proton in the molecule suffers a large number of equal angular displacements between two perfectly reflecting barriers at φ and −φ. The dynamics of molecular tail is described by uniaxial free rotational diffusion and freely rotating spherical top models, respectively. The predictions of the calculations are tested on measured time of flight spectra, obtained on three members of a homologous series of cholesteric liquid crystals and agreement is obtained.

Temperature distribution in a planar body with circular boundary and thermally insulated cracks

Stationary heat-conduction problems are analyzed for infinite plates with a circular hole or for a circular disk weakened by straight-line thermally insulated cracks of arbitrary direction if boundary conditions of the first or second kind are specified on the domain boundary.

Constraint Coordination for the Single Motion State

The methods of constraint coordination are derived and applied to an industrial problem to synthesize a mechanism solution. The motion of an input constraint of unknown proportions is coordinated with the motion of a planar body to yield constraint dimensions. The motion of a secondary constraint is chosen to optimize the transmission angle over a cycle of motion.

Conditions equivalent to central symmetry of convex curves

In this paper we establish that a convex planar body C is centrally symmetric provided either one of the following conditions hold:(1) Each line halving the circumference of the boundary γ of C is a diametral line.(A diametral line is a line intersecting C in a chord of maximal length in the family of parallel chords.)(2) Each line halving the area of C is a diametral line.

Inviscid Hypersonic Flow Over Blunt-Nosed Slender Bodies

At hypersonic speeds the drag/area of a blunt nose is much larger than the drag/area of a slender afterbody, and the energy contained in the flow field in a plane at right angles to the flight direction is nearly constant over a downstream distance many times greater than the characteristic nose dimension. The transverse flow field exhibits certain similarity properties directly analogous to the flow similarity behind an intense blast wave found by G. I. Taylor and S. C. Lin. Conditions for constant energy show that the shape of the bow shock wave R(x) not too close to the nose is given by R/d = K_1 (γ)(d/c)^(1/2) for a body of revolution, and by R/d = K_0(γ) (x/d)^(2/3) for a planar body, where d is nose diameter, or leading-edge thickness. A comparison with the experiments of Hammitt, Vas, and Bogdonoff on a flat plate with a blunt leading-edge at M_∞ = 13 in helium shows that the shock wave shape is predicted very accurately by this analysis. The predicted surface pressure distribution is somewhat less satisfactory. Energy considerations combined with a detailed study of the equations of motion show that flow similarity is also possible for a class of bodies of the form r_b ~ x^m, provided that m' ≤ m ≤ 1, where m' = 3/4 for a planar body and m' = (3/2(γ+1))/(3γ + 2) for a body of revolution. When m < m' the shock shape is not similar to the body shape, and except for the constant energy flows the entire flow field some distance from the nose must depend to some extent on the details of the nose geometry. Be again again utilizing energy and drag considerations one finds that at hypersonic speeds the inviscid surface pressures generated by a blunt nose are larger than the pressures produced by boundary layer growth on a flat surface over a distance from the nose of order l, where l/d ≃ 1/15 ((Re_d)/M_∞^2))^3 (Here Re_d is free-stream Reynolds number based on leading-edge thickness.) Thus at M_∞ = 15 the viscous interaction effects should be important for Re_d 3000 the inviscid pressure field is dominant and determines the boundary layer development, skin friction and heat transfer over the forward portion of the body. These rough estimates are in qualitative agreement with the experimental results of References 7 and 9.