Corrections to the theory and the optimal line in the swimming diagram of Taylor (1952).

The analysis of undulatory swimming gaits requires knowledge of the fluid forces acting on the animal body during swimming. In his classical 1952 paper, Taylor analysed this problem using a 'resistive-force' theory. The theory was used to characterize the undulatory gaits that result in the smallest energy dissipation to the fluid for a given swim velocity.

Surface force spectroscopic point load measurements and viscoelastic modelling of the micromechanical properties of air flow sensitive hairs of a spider (Cupiennius salei).

The micromechanical properties of spider air flow hair sensilla (trichobothria) were characterized with nanometre resolution using surface force spectroscopy (SFS) under conditions of different constant deflection angular velocities theta (rad s(-1)) for hairs 900-950 microm long prior to shortening for measurement purposes. In the range of angular velocities examined (4 x 10(-4) - 2.6 x 10(-1) rad s(-1)), the torque T (Nm) resisting hair motion and its time rate of change (Nm s(-1)) were found to vary with deflection velocity according to power functions.

Drag force acting on a neuromast in the fish lateral line trunk canal. I. Numerical modelling of external-internal flow coupling.

Fishes use a complex, multi-branched, mechanoreceptive organ called the lateral line to detect the motion of water in their immediate surroundings. This study is concerned with a subset of that organ referred to as the lateral line trunk canal (LLTC). The LLTC consists of a long tube no more than a few millimetres in diameter embedded immediately under the skin of the fish on each side of its body.

Drag force acting on a neuromast in the fish lateral line trunk canal. II. Analytical modelling of parameter dependencies.

In Part I of this two-part study, the coupled flows external and internal to the fish lateral line trunk canal were consecutively calculated by solving the Navier-Stokes (N-S) equations numerically in each domain. With the external flow known, the solution for the internal flow was obtained using a parallelepiped to simulate the neuromast cupula present between a pair of consecutive pores, allowing the calculation of the drag force acting on the neuromast cupula. While physically rigorous and accurate, the numerical approach is tedious and inefficient since it does not readily reveal the parameter dependencies of the drag force.

Analytical and numerical investigation of the flow past the lateral antennular flagellum of the crayfish Procambarus clarkii.

Analytical and numerical methodologies are combined to investigate the flow fields that approach and pass around the lateral flagellum of the crayfish Procambarus clarkii. Two cases are considered, the first being that of a free-flicking flagellum and the second corresponding to a flagellum fixed inside a small bore tube. The first case is the natural one while the second corresponds to the experimental configuration investigated by Mellon and Humphrey in the accompanying paper.

Directional asymmetry in responses of local interneurons in the crayfish deutocerebrum to hydrodynamic stimulation of the lateral antennular flagellum.

We have recorded spiking responses from single, bimodally sensitive local interneurons (Type I) in the crayfish deutocerebrum to hydrodynamic and odorant stimuli flowing in two directions past the lateral antennular flagellum. Changing the direction of seamless introductions (meaning, with minimal variations of fluid velocity magnitude) of odorant flow past the flagellum, from proximal-->distal to distal-->proximal, did not consistently affect the dose-dependent responses of Type I neurons. By contrast, changing the direction of an abruptly initiated flow of water (or odorant) past the flagellum resulted in consistently larger numbers of spikes in response to this hydrodynamic stimulation when the flow direction was proximal-->distal.

Infrared temperature control system for a completely noncontact polymerase chain reaction in microfluidic chips.

A completely noncontact temperature system is described for amplification of DNA via the polymerase chain reaction (PCR) in glass microfluidic chips. An infrared (IR)-sensitive pyrometer was calibrated against a thermocouple inserted into a 550-nL PCR chamber and used to monitor the temperature of the glass surface above the PCR chamber during heating and cooling induced by a tungsten lamp and convective air source, respectively. A time lag of less than 1 s was observed between maximum heating rates of the solution and surface, indicating that thermal equilibrium was attained rapidly.

Interstitial transport and transvascular fluid exchange during infusion into brain and tumor tissue.

A model of convection-enhanced delivery in brain and neoplastic tissue is presented that includes transvascular fluid exchange in addition to interstitial fluid transport. Measured values for the relevant material parameters are compiled from published literature. The transient distributions of interstitial fluid pressure and fluid velocity resulting from infusion into brain tissue and into a tissue-isolated tumor are derived, in addition to the steady-state distribution of interstitial fluid pressure and fluid velocity resulting from infusion into a tumor with a necrotic core.

Positive pressure infusion of therapeutic agents into brain tissues: mathematical and experimental simulations.

Positive pressure infusion is a clinical means of achieving convection-enhanced delivery of therapeutic agents within the tissues of the central nervous system for the treatment of glioblastoma multiforme and other diseases of the brain. We have developed a mathematical model of the technique and an in vitro gelatin surrogate for it, which provide biophysical insights into the performance characteristics of candidate infusion systems and drug delivery protocols. We present a brief overview of the clinical problems that are being addressed, succinctly describe the mathematical and in vitro models used in our laboratories, and highlight some representative results from our studies.

Viscosity-mediated motion coupling between pairs of trichobothria on the leg of the spider Cupiennius salei.

Arachnids and insects use long, thin hairs as motion sensors to detect signals contained in the movement of the surrounding air. These hairs often form groups with a small spacing of tens to hundreds of micrometers between them. For air oscillation frequencies of biological interest, the potential exists for viscosity-mediated coupling among hairs in a group affecting their response characteristics.