Coordination Dynamics of the Bipedal Galloping Pattern

A motion equation in relative phase was developed that incorporates the spatial-temporal pattern of the bipedal gallop along with the more commonplace patterns of the bipedal jump and walk-run. In 3 experiments, human participants (N = 6 per experiment) simulated the bipedal gait patterns through the rhythmic motions of hand-held pendulums. Predictions of the motion equation for coordination equilibria and their respective degrees of stability were confirmed. In particular, the gallop pattern was less stable than the fundamental in-phase and antiphase patterns but changed in qualitatively similar ways to those gaits as a function of limb asymmetry and movement frequency. The relation between the modeled coordination dynamics and the kinematic characteristics of real bipedal galloping is discussed.

Transforming growth factor-alpha (TGF alpha) concentrations increase in regenerating rat liver: evidence for a delayed accumulation of mature TGF alpha

Changes in the concentration of transforming growth factor-alpha (TGF alpha) protein were measured in regenerating liver. TGF alpha stimulates both DNA and protein synthesis in various liver-derived cells, and its mRNA levels increase in liver after partial hepatectomy (PH), suggesting that it may be an important autocrine regulator of liver regeneration. Using a sheep antiserum raised against mature rat TGF alpha, we developed a sensitive TGF alpha RIA. TGF alpha was extracted from livers in a detergent-containing buffer with protease inhibitors. Liver extracts, to a volume of 10 microliters/tube, produced a displacement curve of [125I]TGF alpha that was parallel to the pure standard. The TGF alpha content of normal liver was 57.04 +/- 26.25 pg/mg protein, 5.24 +/- 2.61 ng/mg DNA, and 10.33 +/- 4.47 ng/g liver (n = 5; mean +/- SD). Between 13-17 h after operation, TGF alpha concentrations in the livers of PH animals increased over those in sham-operated (SH) controls (P < 0.05) and remained twice those in SH controls for more than 96 h, returning to control values by 8 days. In unoperated liver, gel chromatography showed all TGF alpha immunoactivity to be in fractions corresponding to known TGF alpha precursors (15-30 kilodaltons). Mature 5.6-kilodalton TGF alpha was not detected until 48 h after PH and was still present at 96 h. These data support a role for TGF alpha in the response to PH in the rat. However, the presence of TGF alpha precursors in normal liver, the short (< 4-h) interval between the increase in TGF alpha concentrations and the onset of hepatocyte DNA synthesis, the sustained elevation of TGF alpha levels after DNA synthesis has ceased, and the lack of detectable processing to the mature form until DNA synthesis has subsided all suggest that the membrane-anchored precursor and the mature forms of TGF alpha may have different functions, cellular sources, or target cells in regenerating liver.

Soil-Water Potential: Direct Measurement by a New Technique

Current methods of measuring the potential of water in soil are inadequate. It is proposed to depress the reference free energy of water by a predetermined amount from the standard level of pure free water at atmospheric pressure by use of a solute. The specific free-energy difference of soil water from the depressed reference can be measured as a pressure.

On the Cylindrical Probe Method of Measuring Thermal Conductivity with Special Reference to Soils. I. Extension of Theory and Discussion of Probe Characteristics

The theory of cylindrical probes for measuring thermal conductivity is extended to the case of a probe of finite conductivity containing a line source at its centre. This provides a more realistic approximation to most actual probes than the theory for a probe of infinite conductivity developed by other authors. New experimental results are presented which are in complete agreement with theory It is shown how an estimate can be obtained of the magnitude of a possible thermal contact resistance between the probe and the medium and how its influence on the measured conductivity can be assessed.

On the Cylindrical Probe Method of Measuring Thermal Conductivity with Special Reference to Soils. II. Analysis of Moisture Effects

Thermal conductivity measurements in unsaturated moist porous media are complicated by the action of gravity on the moisture and by moisture movement caused by temperature gradients. The effects of these factors are discussed for the cylindrical probe method.