Chiral recognition in solution and the gas phase. Experimental and theoretical studies of aromatic D- and L-amino acid–Cu(II)–chiragen complexes Jennifer L. Seymour František Tureček Andrei V. Malkov Pavel Kočovský Journal of Mass Spectrometry 2004; 39: 1044–1052

The original article to which this Erratum refers was published in Journal of Mass Spectrometry 2004; 39: 1044–1052.     

Calorimetric investigations on mound-building birds

Megapodes, and mound-building birds of the Pacific, incubate their eggs underground where the heat is supplied by organic decomposition, solar radiation, or geothermal sources. The incubation biology of the Australian mound builders has been examined from the standpoints of (1) the energetic requirements of malleefowl (Leipoa ocellata) to construct and maintain incubation mounds and (2) the physics, physiology, and behavior concerning mound thermoregulation of the brush turkey (Alectura lathami).

The energetic cost of mound tending in malleefowl is estimated by indirect calorimetry. The power required for digging into the mound to reach the eggs is approximately 20 W, or 3.8 times the basal metabolic rate of the bird. About 850 kg of sand has to be removed and replaced on the mound every time it is opened, a task requiring about 5 h. The overall energy investment for incubation for the entire 9 month season is 2.5 times that expected in similarly sized birds.

Brush turkey mounds become homeothermic because of (1) the high thermal inertia of their 3–11 t mass and (2) a stable equilibrium that is reached between heat production and heat loss. The mound tends to seek the equilibrium, but the bird adjusts the temperature by subtle manipulation of the mound. At an equilibrium temperature of 33°C, the mound produces about 110 W. Empirical data from natural mounds, set in the context of a numerical model of heat production and heat flux in the mound, indicate that equilibrium temperature is extremely sensitive to ambient temperature and mound size, but not water content. Wet or dry mounds can maintain appropriate incubation temperature, but the dry ones have low thermal conductivity, retain the heat well, and minimize the amount of forest litter collected during the incubation season.     

Solutions to the Navier-Stokes Equations Describing Local Flows of Stratified and Compressible Fluids

A family of exact solutions of the Navier-Stokes equations is used to describe local flows of incompressible stratified and compressible fluids. For some of the flows, the coefficient of viscosity can depend on the temperature. An example of an incompressible stratified flow for which the analysis is applicable is the sheared swirling flow that is produced between two parallel plates that translate with different velocities and rotate with different angular velocities about different, but parallel, axes. The fluid may be stratified in the direction normal to the plates. These generalized von Karman flows are relevant to the study of strong local atmospheric disturbances, such as might be produced by the passage of a tornado. Also, when the coefficient of viscosity depends on the temperature, they can be used to analyze the flow of molten metals between surfaces that are in relative motion. An example of a compressible flow for which the analysis is applicable is that produced by a plane shock wave as it traverses a layer where the fluid is sheared in a direction normal to the shock.     

Exact Solutions for Large Amplitude Waves in Dispersive and Dissipative Systems

This paper describes some applications of a transformation which takes a system of two, first order, quasilinear, partial differential equations in two dependent and two independent variables into a similar system. Typically, the equations govern wave propagation in dispersive and dissipative systems. It is shown that certain nonlinear equations which are of current practical interest can be transformed into linear equations.     

Laterally stabilized complexes of DNA with linear reducible polycations: strategy for triggered intracellular activation of DNA delivery vectors.

Target-specific DNA delivery requires vectors that combine stability in the biological milieu, receptor-mediated uptake into target cells, and intracellular activation to mediate transgene expression. This is achieved here using polymer-coated vectors based on plasmid DNA complexed with a reductively degradable polycation (RPC), designed for intercellular degradation. The RPC were prepared by oxidation of the terminal cysteinyl thiol groups of Cys(Lys)10Cys. The complexes were coated and surface-cross-linked using multivalent reactive copolymers of N-(2-hydroxypropyl)methacrylamide (PHPMA), providing a unique combination of steric and reversible lateral stabilization, known to promote extended circulation in the bloodstream. Coated complexes containing RPC exhibited lateral stabilization that was reversible by treatment with 2.5 mM dithiothreitol, releasing free DNA after incubation with a polyanion. In contrast, coated complexes containing nonreducible poly(l-lysine) (PLL) were not destabilized by reduction. The biological usefulness of this trigger mechanism was examined by measuring transfection activity in human retinoblast 911 cells of coated complexes, based on PLL or RPC, targeted to cell surface receptors by covalent linkage of basic fibroblast growth factor. The levels of transgene expression observed for RPC-based targeted vectors indicated efficient intracellular activation, authenticating the concept that lateral stabilization introduced by surface coating with PHPMA can be reversed by intracellular reduction.     

Counting negative eigenvalues of a Hilbert-Schmidt operator via sign changes of a determinant

In this paper a continuous analogue of the Jacobi-Sturm rule for counting the number of negative eigenvalues of a Hermitian matrix is derived.     

Subgraphs of large connectivity and chromatic number in graphs of large chromatic number

For each pair k, m of natural numbers there exists a natural number f(k, m) such that every f(k, m)-chromatic graph contains a k-connected subgraph of chromatic number at least m.