The highest member of the series of normal dibasic acids hitherto obtained by electrosynthesis is hexadecane dicarboxylic acid, HOOC.(CH2)16. COOH. In attempts to synthesise by this means dicarboxylic acids of still higher molecular weight, the following difficulties are encountered:—(1) The temperature of the liquid undergoing electrolysis must be kept above the melting point of the synthetic di-ester, in order that the latter may not solidify on the anode and prevent the passage of the current; (2) the alkali ethyl salts of the higher dibasic acids are of a soapy nature, and cannot readily be dealt with in concentrated solution. Two of the conditions favourable to electrosynthesis, high concentration of the electrolyte and low temperature, are thus unattainable.

In an operator algebra, the general element of the connected component of the unitary group can beexpressed as a finite product of exponential unitary elements. The recently introduced concept of exponential rank is defined in terms of the number of exponentials required for this purpose. The present paper is concerned with a concept of exponential length, determined not by the number of exponentials but by the sum of the norms of their self-adjoint logarithms. Knowledge of the exponential length of an algebra provides an upper bound for its exponential rank (but not conversely). This is used to estimate the exponential rank of certain algebras of operator-valued continuous functions.

Two eigenvalue problems associated with steady rotations of a chain are considered. To compare the spectra of these two problems, let σK(n) denote the set of all angular velocities with which a chain of unit length with one end fixed and the other free can rotate in a vertical plane so as to have exactly n nodes on thevertical axis (including the fixed end). In a linearised theory σK(n) is a single point, i.e.

In the full non-linear theory σK(n) is an infinite interval lying to the right of ⍵n. Indeed,

This is established in [1].

Next, let σM(β, n) denote the set of all angular velocities with which a chain, having ends fixed at unit distance apart on the vertical axis, can rotate in a vertical plane so as to have exactly n+l nodes on the vertical axis (including the ends) and so that the tension takes the value β at the lower end. This problem, in which the length of the chain is not prescribed is a model for a spinning process in which the ‘chain’ is continuously created in a rotating configuration. For β>0, we again have in the linearised theory that σM(β, n) is a singleton, i.e.

In the full non-linear theory σM(β, n) lies to the left of λn(β). Although unable to determine exactly σM(β, n) for β>0, we have

where ⍵n λn(β), and are all characterised as the nth zeros of known combinations of Bessel functions.

After a brief introduction and physical motivation, we show how the nonlinear Schrödinger (NLS) equation can be derived from a general class of nonlinear hyperbolic systems. Its purpose is to describe the behaviour of high-frequency oscillating wave packets over a large time-scale that requires us to take into account diffractive effects. We then show that the NLS approximation fails for short pulses and propose some alternative models, including a modified Schrödinger equation with improved frequency dispersion. It turns out that these models have better properties and are quite accurate for short pulses. For ultrashort pulses, however, they must also be abandoned for more complex approaches. We give the main steps for such an analysis and explain one striking fact about ultrashort pulses: their dynamics in dispersive media is linear.

For bounded domains Ω, we prove that the Lp-norm of a regular function with compact support is controlled by weighted Lp-norms of its gradient, where the weight belongs to a class of symmetric non-negative definite matrix-valued functions. The class of weights is defined by regularity assumptions and structural conditions on the degeneracy set, where the determinant vanishes. In particular, the weight A is assumed to have rank at least 1 when restricted to the normal bundle of the degeneracy set S. This generalization of the classical Poincaré inequality is then applied to develop a robust theory of first-order Lp-based Sobolev spaces with matrix-valued weight A. The Poincaré inequality and these Sobolev spaces are then applied to produce various results on existence, uniqueness and qualitative properties of weak solutions to boundary-value problems for degenerate elliptic, degenerate parabolic and degenerate hyperbolic partial differential equations (PDEs) of second order written in divergence form, where A is calibrated to the matrix of coefficients of the second-order spatial derivatives. The notion of weak solution is variational: the spatial states belong to the matrix-weighted Sobolev spaces with p = 2. For the degenerate elliptic PDEs, the Dirichlet problem is treated by the use of the Poincaré inequality and Lax–Milgram theorem, while the treatment of the Cauchy–Dirichlet problem for the degenerate evolution equations relies only on the Poincaré inequality and the parabolic and hyperbolic counterparts of the Lax–Milgram theorem.

We present an existence and stability theory for gravity–capillary solitary waves with constant vorticity on the surface of a body of water of finite depth. Exploiting a rotational version of the classical variational principle, we prove the existence of a minimizer of the wave energy 𝓗 subject to the constraint 𝓘 = 2µ, where 𝓘 is the wave momentum and 0 < µ ≪ 1. Since 𝓗 and 𝓘 are both conserved quantities, a standard argument asserts the stability of the set Dµ of minimizers: solutions starting near Dµ remain close to Dµ in a suitably defined energy space over their interval of existence. In the applied mathematics literature solitary water waves of the present kind are described by solutions of a Korteweg–de Vries equation (for strong surface tension) or a nonlinear Schrödinger equation (for weak surface tension). We show that the waves detected by our variational method converge (after an appropriate rescaling) to solutions of the appropriate model equation as µ ↓ 0.

The classification of orientable vector bundles over CW-complexes of dimension ≦8 is given in terms of characteristic classes using elementary homotopy theoretic methods and relations among characteristic classes.

We consider the three-dimensional viscous primitive equations with periodic boundary conditions. These equations arise in the study of ocean dynamics and generate a dynamical system in a Sobolev H1-type space. Our main result establishes the so-called squeezing property in the Ladyzhenskaya form for this system. As a consequence of this property we prove the finiteness of the fractal dimension of the corresponding global attractor, the existence of a finite number of determining modes and the ergodicity of a related random kick model. All these results provide new information concerning the long-time dynamics of oceanic motion.

Existence and uniqueness of large, boundary blow-up solutions are obtained for the quasilinear elliptic problem −Δpu = λf(u) in Ω, u = ∞ on ∂Ω via good boundary layer estimates for large λ, where Δp is the p-Laplacian (1 < p < ∞) and Ω ⊂ ℝ N (N ≥ 2) is a bounded smooth domain. The nonlinear term f satisfies f(0) = f(z1) = f(z2) = 0 with 0 < z1 < z2, with z2 a zero of f of order k. It is shown that, if k ≥ p −1, the unique large solution ūλ is a boundary-layer solution which satisfies ūλ > z2 in Ω; if 0 < k < p −1, the unique large solution ūλ is a boundary-layer solution, but a flat core of ūλ occurs. Furthermore, for sufficiently large λ a small positive boundary blow-up solution uλ is obtained and its asymptotic behaviour as λ → ∞ is discussed.

We study nonlinear measure data elliptic problems involving the operator of generalized Orlicz growth. Our framework embraces reflexive Orlicz spaces, as well as natural variants of variable exponent and double-phase spaces. Approximable and renormalized solutions are proven to exist and coincide for arbitrary measure datum and to be unique when for a class of data being diffuse with respect to a relevant nonstandard capacity. A capacitary characterization of diffuse measures is provided.

1. The integration of systems of linear partial differential equations of hypergeometric type has been the subject of a great number of recent investigations (e.g. Appell, 1925; Appell-Kampé de Fériet, 1926). Especially Professor Horn (see references) and his pupils, for instance Borngässer (1933), have done much valuable work in this field.

The first method that suggests itself for integrating systems of this type is to try power-series expansions of the solutions in the neighbourhood of the singular points of the system. This method, however, does not yield in general a complete set of solutions. Those singular points of the system in which more than n singular manifolds intersect, n being the number of independent variables, give rise to considerable difficulties.

Associated with the volcanic rocks of Tertiary age that bulk so largely in the Mull, Morvern, and Ardnamurchan districts of Argyllshire, western Scotland, are occasional sedimentary deposits of insignificant proportions. The sediments, for the most part, consist of sandstones and conglomerates, but there may also be shaly bands and thin, impersistent seams of lignites (Mull Memoir, 1924, Chap. III). These lignites have been found to possess an abundant pollen-content of great interest and considerable variety, and this paper is a preliminary account of some of the forms isolated. It has not yet been possible to make a detailed examination of each seam throughout its entire thickness and thus get a complete picture of its pollen-aspect—but it is hoped to attempt this interesting task in the near future.

We study to what extent the known results concerning the behaviour of Hopf vector fields, with respect to volume, energy and generalized energy functionals, on the round sphere are still valid for the metrics obtained by performing the canonical variation of the Hopf fibration.

Existence and uniqueness of large, boundary blow-up solutions are obtained for the quasilinear elliptic problem −Δpu = λf(u) in Ω, u = ∞ on ∂Ω via good boundary layer estimates for large λ, where Δp is the p-Laplacian (1 < p < ∞) and Ω ⊂ R N (N ≥ 2) is a bounded smooth domain. The nonlinear term f satisfies f(0) = f(z1) = f(z2) = 0 with 0 < z1 < z2, with z2 a zero of f of order k. It is shown that, if k ≥ p −1, the unique large solution ūλ is a boundary-layer solution which satisfies ūλ > z2 in Ω; if 0 < k < p −1, the unique large solution ūλ is a boundary-layer solution, but a flat core of ūλ occurs. Furthermore, for sufficiently large λ a small positive boundary blow-up solution is obtained and its asymptotic behaviour as λ → ∞ is discussed.

We are concerned with the multiplicity of solutions to the system driven by a fractional operator with homogeneous Dirichlet boundary conditions. Namely, using fibering maps and the Nehari manifold, we obtain multiple solutions to the following fractional elliptic system:

where Ω is a smooth bounded set in ℝn , n > 2s, with s ∈ (0, 1); (–Δ)s is the fractional Laplace operator;, λ, μ > 0 are two parameters; the exponent n/(n – 2s) ⩽ q < 2; α > 1, β > 1 satisfy is the fractional critical Sobolev exponent.

In this paper, we prove the existence of the global smooth solution for the equation of a viscoelastic model with relaxation in time under the only assumption that the C0-norm of the initial data is small, without smallness hypothesis for the C1-norm.

For Banach spaces X and Y, we consider bifurcation from the line of trivial solutions for the equation F (λ, u) = 0, where F : ℝ × X → Y with F (λ, 0) = 0 for all λ ∈ ℝ. The focus is on the situation where F (λ, ·) is only Hadamard differentiable at 0 and Lipschitz continuous on some open neighbourhood of 0, without requiring any Fréchet differentiability. Applications of the results obtained here to some problems involving nonlinear elliptic equations on ℝN, where Fréchet differentiability is not available, are presented in some related papers, which shed light on the relevance of our hypotheses.

In the first part of the paper a variational characterisation of the periodic eigenvalues (the so-called Fučik spectrum) of a semilinear, positive homogeneous Sturm–Liouville equation is given. The proof relies on the S1-invariance of the equation.

In the second part a nonlinear Sturm–Liouville equation with, typically, an exponential nonlinearity is considered. It is proved that under certain conditions this equation is solvable for arbitrary forcing terms. The proof uses a comparison of the minimax levels of the functional associated to this equation with suitable values in the Fučik spectrum.

We consider the problem

where u ∊ Rn, n ≧ 2, and V ∊ C2(Rn∖e, R) is a potential having an absolute maximum at 0 and such that V(x) → − ∞ as x → e. We prove that, under some conditions on V, this problem has at least n − 1 geometrically distinct solutions.

A quadratic functional Q is considered which is defined by an integral on a subset of functions in a weighted Hilbert space. The functional Q is minimized subject to the Dirichlet index of the associated differential operator being minimal. The infimum of Q is shown to be the least point in the spectrum of a certain self-adjoint operator which arises as a Friedrichs extension.