Axial Intervals Research Articles

Interactions of coherent structures in a film flow: Simulations of a highly nonlinear evolution equation

Numerical simulations of the evolution equation [14] for thickness of a film flowing down a vertical fiber are presented. Solutions with periodic boundary conditions on extended axial intervals develop trains of pulse-like structures. Typically, a group of several interacting pulses (or a solitary pulse) is bracketed by spans of nearly uniform thinned film and is virtually isolated: The evolution of such a “section” is modeled as a solution with periodic boundary conditions on the corresponding, comparatively short, interval. Single-pulse sections are steady-shape traveling waveforms (“cells” of shorter-period solutions). The collision of two pulses can be either a particle-like “elastic” rebound, or—and only if a control parameter S (proportional to the average thickness) exceeds a certain critical value, S c ≈ 1—a “deeply inelastic” coalescence. A pulse which grows by a cascade of coalescences is associated with large drops observed in experiments by Quere [39] and our S c is in excellent agreement with its laboratory value.

Quantitative morphologic study of intimal thickening at the human carotid bifurcation: II. The compensatory enlargement response and the role of the intima in tensile support

Arteries enlarge where intimal plaques form, tending to preserve lumen cross sectional area but causing an increase in mural tangential tension due to the increase in radius. To characterize the compensatory enlargement process at the carotid bifurcation and to evaluate the possible contribution of intima thickening to mural tensile support during the enlarging process, we assessed the relationships among intimal thickening, artery size and estimated tensile stress at 9 sequential axial levels in 42 human carotid bifurcations obtained during post-mortem examinations of 36 adults with no clinical or anatomical evidence of cerebrovascular disease. Right and left bifurcations were available for 6 patients. The arteries were fixed under conditions of controlled pressure distention and histologic sections were prepared at 0.5 cm axial intervals. We determined vessel radius ( r), intima thickness (IT), media thickness (MT), intima area (IA), lumen area (LuA) and the area encompassed by the internal elastic lamina (IELA), i.e. the lumen area if there were no intimal thickening. Although IT, IA and r were greatest in the proximal sinus region, there was a highly significant linear relationship between IA and IELA at each axial level; correlation coefficients ranged from 0.64 to 0.97 with P < 0.001 at each level. Stenosis (IA/IELA × 100) ranged from 10.8 ± 8.0% at the common carotid level immediately proximal to the bifurcation angle to 22.3 ± 17.9% at the level immediately distal to the angle, but LuA remained nearly constant at each level regardless of IA. When wall tensile stress (TS) was computed using only media thickness (MT), values ranged from 8.2 ± 2.5 to 17 ± 7.0 × 10 5 dyn/cm 2 (1 dyn = 10 −5 N) with the maximum occurring at the proximal sinus. When, however, total wall thickness (IT + MT) was used, TS was similar at all levels with a mean of 6.5 ± 2.5 × 10 5 dyn/cm 2, (range, 5.5 ± 1.8 to 7.3 ± 2.7 × 10 5 dyn/cm 2) with no significant differences among the 9 levels, including those with little or no intimal thickening. We conclude that during stages of minimal or moderate intimal thickening and plaque formation at the carotid bifurcation, artery size (IELA) at each level increases with IA, thereby preserving LuA. The sum of intima and media thickness corresponds to the increase in radius such that estimated tangential mural tensile stress remains normal at each level.

Intermediate filament structure

In a previous communication (Biosci. Rep. 3, 517-525, 1983) we described quantitative X-ray diffraction studies of alpha-keratin which were shown to be consistent with the presence of finite arrays of repeating units, successive arrays being set down at axial intervals of 470 A. In addition the axial interval between repeating units in an array was shown to be 197.9 A. It was suggested that this could most readily be explained by supposing that a surface lattice was present which contained a dislocation along a helical path with unit height h = 470 A and unit twist magnitude of t = 49.1 degrees. The number of repeating units was shown to be in the range 7-9. With 7 repeats the mismatch of the lattice along the dislocation is small and this choice was used to develop a detailed model for the filament. Subsequent studies of molecular interactions have shown however that the coiled-coil rope segments in the rod domain of the molecule are most probably oriented parallel to the dislocation, and so minimization of lattice mismatch may be less important than originally supposed. In the present communication it is shown that the choice of 8, rather than 7, for the number of repeating units yields a model which is more compatible with estimates of the linear density and also provides the basis for a general model for polymorphism in intermediate filament lattices.

円筒形状の離散測定におけるサンプリング間隔

Sampling interval in a measurement of cylindrical form by means of the discrete data is studied in this research from the viewpoints of form error, wave length to be analysed and measuring accuracy. Namely, circumferential and axial sampling intervals of the cylinder surface are proposed from the analysis of auto-correlation function with considering the ratio of the difference between the original profile and the linear-interpolated profile of neighboring discrete data to the magnitude of the original form errors as a criterion.

Plain and Complex Flagella of Pseudomonas rhodos : Analysis of Fine Structure and Composition

Cells of Pseudomonas rhodos 9-6 produce two morphologically distinct flagella termed plain and complex, respectively. Fine structure analyses by electron microscopy and optical diffraction showed that plain flagellar filaments are cylinders of 13-nm diameter composed of globular subunits like normal bacterial flagella. The structure comprises nine large-scale helical rows of subunits intersecting four small-scale helices of pitch angle 25 degrees . Complex filaments have a conspicuous helical sheath, 18-nm wide, of three close-fitting helical bands, each about 4.7-nm wide, separated by axial intervals, 4.7 nm wide, running at an angle of 27 degrees . The internal core has similar but not identical substructure to plain filaments. Unlike plain flagella, the complex species is fragile and does not aggregate in bundles. Mutants bearing only one of two types of flagellum were isolated. Cells with plain flagella showed normal translational motion, and cells with complex flagella showed rapid spinning. Isolated plain flagella consist of a 37,000-dalton subunit separable into two isoproteins. Complex filaments consist of a 55,000-dalton protein; a second 43,000-dalton protein was assigned to complex flagellar hooks. The results indicate that plain and complex flagella are entirely different in structure and composition and that the complex type represents a novel flagellar species. Its possible mode of action is discussed.