EFFECT OF ELECTRON CORRELATION AND SOLVENT ON THE CONFORMATIONAL TRANSITION OF DNA

The conformational transition of DNA is studied by considering electron–electron interaction and coupling to the environment. It is shown that the effect of counterions on DNA can be expressed approximately by the change of elasticity constant of the DNA backbone. We set up the coupled nonlinear equations to describe the interaction between the longitudinal displacement of DNA backbone and the electronic wave function as well as the solvent effect. It is also proved that the longitudinal displacement of DNA statistics the ϕ4 field form. With the help of the ϕ4 statistics properties, it is illustrated that the salt concentration and electron correlation plays an important role in the structural phase transition of DNA.

Structural and functional characteristics of peripheral pulmonary parenchyma in golden hamsters

Mechanical properties of the peripheral pulmonary parenchyma of freshly excised hamster lung tissue were examined to evaluate determinants of displacement-tension relationships with regard to structural constituents of the alveolar wall. A tissue segment measuring 50 x 50 x 400–600 microns and consisting mostly of the alveolar wall was prepared from the lung parenchyma adjacent to the pleura. By use of a constant speed maneuver for extension and relaxation of this minute preparation, displacement-tension relationships of peripheral pulmonary parenchyma were examined in a bath filled with 37 degrees C physiological buffer solution. The specimen was repeatedly extended up to 20–40 mg, a little above a point resembling “yield” in displacement-tension relationships. Analyses of displacement-tension relationships constantly showed double exponential relations. The first component at the lower strain was approximated by sigma 1 = A1(e alpha 1 epsilon - 1) and the second component beyond the inflection (yield) point was sigma = s1 + s2 = A1(e alpha 1 epsilon - 1) + A2(e alpha 2 epsilon - 1), where sigma, A, alpha, and epsilon represent stress, constant determined by tissue quantity, elasticity constant, and strain, respectively. Immersion of the lung specimen into elastase resulted in decreases of only alpha 1, and collagenase reduced alpha 2 but not alpha 1. Hyaluronidase, acetylcholine, ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, and norepinephrine did not alter alpha 1 or alpha 2. These observations suggest that alpha 1 and alpha 2 of the peripheral pulmonary parenchyma are mechanical indexes of elastin and collagen characters, respectively.

Theory of the Formation of Arches in Bins

The flowing of the granular materials in bins is governed, particularly in the case of small ratios of aperture diameter to particle size, by the constant formation and breaking down of arches, known as dynamical arches. In unfavorable circumstances the arches may become stable and the aperture clogged. By building up a mechanical model of the arch the fields have been found in which a stable and a dynamical arch, respectively, may be formed, enabling a bin to be judged with respect to the danger of stable arch formation. A stable field allows of studying the interaction of arch stresses and deformation of materials starting from the stress curve of the arch as a function of the curvature, and from the curve of deformation of the material as a function of the stress. It is, therefore, possible that the elasticity of the material diminishes the stable field or even reduces it to zero. In the case of nonelastic materials, the collapse of the arch may be introduced by making the lower part of the aperture wall elastic. Stable arches can now be prevented from forming by choosing the elasticity of the resilient aperture wall in such a way that if the stress increases the wall expands sufficiently to cause the required collapse. The theory underlying this solution enables the elasticity constant and the required expansion to be calculated.

Pattern of function of left ventricle of mammals

Since, over a limited range, rubber has elastic properties similar to contracted cardiac muscle, a method for determining the elasticity constant of rubber left ventricle models has been developed and used to determine the elasticity constant of the contracted mammalian left ventricle. Serial determinations of left ventricular end-systolic pressure, enddiastolic volume, end-systolic volume, and stroke volume were carried out following increased blood volume and stepwise hemorrhages in rabbits, dogs, swine, horses, and cattle. The end-systolic pressure-volume relationship of the ventricle of these animals was found to be similar to that of rubber ventricle models, hemiprolate spheroids, and thick-walled spheres; evidence is presented that the contracted left ventricle, and rubber models of it, function as an equivalent thick-walled sphere having the same wall mass and internal volume. From the linear relationship between "average" wall stress and "average" circumference, equations are derived relating chamber internal volume and: systolic pressure, total potential energy, and energy dissipated in ejection of the stroke volume.