The cooperative role of membrane skeleton and bilayer in the mechanical behaviour of red blood cells

Red blood cell (RBC) shape, behaviour and deformability can be consistently accounted for by a model for the elastic properties of the RBC membrane that includes the elasticity of the membrane skeleton in dilation and shear, and the local and nonlocal resistance of the bilayer to bending. The role of the corresponding energy terms in different RBC shape and deformation situations is analyzed. RBC shape transformations are compared to the shape transformations of phospholipid vesicles that are driven by the difference between the equilibrium areas of the bilayer leaflets (DeltaA0). It is deduced that the skeleton energy contributions play a crucial role in the formation of an echinocyte. The effect of a transformation of the natural biconcave RBC shape into an echinocyte on its resistance to entry into capillary-sized cylindrical tubes is analyzed. It is shown that, during the aspiration of an echinocyte into a pipette, there are two competing skeleton deformation effects, which arise due to skeleton density changes, one due to spicule formation and the other due to deformation induced by micropipette aspiration. Furthermore, the shift of the observed dependence of the projection length on the aspiration pressure of more crenated cells towards higher aspiration pressures can be accounted for by an increase of the equilibrium area difference DeltaA0 and consequent modification of the nonlocal contribution to the cell elastic energy.     

Spectral Properties of the Cauchy Operator and Its Product with Bergman's Projection on a Bounded Domain

In this paper exact asymptotic formulae are found for singularvalues of the Cauchy operator and the logarithmic potentialtype operator (on a bounded domain), as well as their productswith Bergman's projection. It is shown that these spectral characteristicsdetect geometric properties of a domain (area and the lengthof the boundary). The hypothesis "can we hear the shape of adrum", from a paper by J.M. Anderson, D. Khavinson, and V. Lomonosov[‘Spectral properties of some integral operators arisingin potential theory’, Quart. J. Math. Oxford (2) 43 (1992)387-407], is correct in the above sense. 1991 Mathematics SubjectClassification: 47B10.     

The association of laryngoceles with ventricular phonation

Laryngoceles represent dilatations of the laryngeal saccule that may extend internally into the airway, or externally through the thyrohyoid membrane. Unilateral laryngoceles are uncommon clinical entities and bilateral laryngoceles are rare. Certain activities like glass blowing and playing a wind instrument are associated with laryngocele development, as is laryngeal carcinoma in the ventricular area. This case describes development of bilateral laryngoceles in a patient who chronically uses ventricular phonation during speech. The pathogenesis involves repetitive elevation of intralaryngeal pressure during false vocal cord approximation, exposing the ventricles to abnormally high air pressures. The pathogenesis in this case, as well as in laryngoceles associated with occupational or anatomic risk factors, is discussed.     

Absolute Intensities of the 10-µm Bands of (16)O(3)

Two hundred ninety experimental absolute intensities of nu(1) and nu(3) transitions of ozone have been measured, with good accuracy (<2%). They are used to derive the transition-moment parameters for these bands. The agreement between our observed and calculated line intensities is satisfactory. This work shows that the intensities of these two bands are on average 4% smaller than those used in the literature. In addition, 20 intensities of the nu(2) + nu(3) - nu(2) band confirm this value. Also, 42 line intensities of the 2nu(1)-nu(3) band are reported. Copyright 2001 Academic Press.     

Semileptonic (Λ b → Λcev) decay in a field theoretic quark model

The semileptonic decay width of heavy baryons such as (Λ _b → Λcev) has been estimated in the framework of a nonrelativistic field theoretic quark model where four component quark field operators along with a harmonic oscillator wave function are used to describe translationally invariant hadronic states. The present estimation does not make an explicit use of heavy quark symmetry and has a reasonable agreement with the experimentally measured decay width, polarisation ratio and form factors with the harmonic oscillator radii and quark momentum distribution inside the hadron as free parameters.     

Far downstream analysis for the Blasius boundary-layer stability problem

In this paper, we examine the large Reynolds number (Re) asymptoticstructure of the wave number in the Orr–Sommerfeld regionfor the Blasius boundary layer on a semi-infinite flat plategiven by Goldstein (1983, J. Fluid Mech., 127, 59–81).We show that the inclusion of the term which contains the leading-ordernon-parallel effects, at O(Re^{– 1/2}), leads to a non-uniformexpansion. By considering the far downstream form of each termin the asymptotic expansion, we derive a length scale at whichthe non-uniformity appears, and compare this position with theposition seen in plots of the wave number.     

Upper Bounds in Affine Weyl Groups under the Weak Order

Björner and Wachs proved that under the weak order every quotient of a Coxeter group is a meet semi-lattice, and in the finite case is a lattice. In this paper, we examine the case of an affine Weyl group W with corresponding finite Weyl group W ₀. In particular, we show that the quotient of W by W ₀ is a lattice and that up to isomorphism this is the only quotient of W which is a lattice. We also determine that the question of which pairs of elements of W have upper bounds can be reduced to the analogous question within a particular finite subposet.     

The effect of structural changes in the molecular core and periphery on the liquid-crystalline properties of some chiral 4-n-alkoxyphenylpropiolates

The thermotropic liquid-crystalline properties of several homologous series of chiral 4-n-alkoxyphenylpropiolates were correlated with chemical structural modification on the periphery of the rigid, aromatic, molecular core. The temperature ranges of the most disordered mesophase in each series were shown to be inversely proportional with respect to the number of carbon atoms in the terminal alkoxy moiety. The type of mesophase exhibited by an homologous series is determined by the number of carbons in the chiral alkyl substituent. Homologous series containing short chain chiral alkyl substituents formed mesophases that had higher degrees of disorder (i.e. cholesteric phases) than did those that contained long chain chiral alkyl substituents.     

Crystal and molecular structure of tetrachlorophosphorus(V) hexachlorouranate(V)

The crystal structure of tetrachlorophosphorus(V) hexachlorouranate(V), PCl⁺₄.UCl^?₆, has been solved with 2492 independent F(hkl) collected by necessity from one component of a bicrystal; all crystals prepared were twinned. The structure is triclinic, space group P$\text{1}$, with a = 7.038(4), b = 7.373(4), c = 13.706(8) Å, α = 89.38(3), β = 88.80(3), γ = 105.20(3)°, with Z = 2. The two components of the bicrystal, in the volume ratio of 2.5 to 1, had their reciprocal lattice spots sufficiently separated to allow collection of the data set from component 1 with AgKα radiation (λ = 0.5608 Å). A model was derived from the Patterson synthesis and refined by least squares to R = Σ(|Fo|-|F_C|)/Σ|Fo| = 0.146. The structure was confirmed by a final (ρ_o-ρ_c) synthesis. The structure is an assembly of octahedral U(1)Cl^?₆, U(2)Cl^?₆ and tetrahedral PCl⁺₄ groups. The chlorine atom array is hexagonal close-packed, while the polyhedra are regular within the experimental errors. The structure is isomorphous with the transition metal analogues PCl₅.NbCl₅ and PCl₅.TaCl₅.