Fringe Type Research Articles

Convergent evolution of lizard toe fringes

Lizard toe fringes are composed of laterally projecting elongated scales and have arisen independently at least 26 times in seven families of lizards. Four different fringe types are identified: triangular, projectional, conical and rectangular. To determine if variation in fringe morphology can be attributed to environmental differences, each independent evolution of a fringe type is identified; correlation of substrate types with evolutionary independent fringe morphologies are then studied. Variation in fringe morphology shows a strong association with substrate type: triangular, projectional and conical fringes with windblown sand; and rectangular fringes with water. Some aspects of fringe morphology may result from differences in functional requirements, and others may have no adaptive significance. This example of convergent evolution points out difficulties inherent to comparative studies of adaptation and underscores the value of broad comparative surveys which provide an alternative to ad hoc adaptive explanations of similarity.

Flame focussing of laser beams and refractive fringe formation

Two flat oxy-acetylene flames focus a pulsed ruby laser which burns a hole in a polythene target. The formation of two types of fringes, fine and coarse is observed and explained.

Review of the principal contrast effects observed at interphase boundaries using transmission electron microscopy

SUMMARYThis review is concerned with the interpretation of contrast features observed at interphase interfaces using conventional transmission electron microscopy. The principal features which arise are interfacial dislocations and steps, four types of fringes, namely thickness, Δw, displacement and moiré fringes, and lattice images. The contrast mechanisms leading to these features are discussed in the framework of the dynamical theory of electron diffraction. In particular, the influence on image contrast of the cyrstal composition and structure, the interfacial configuration and the crystallographic relationship of the two phases in the specimen is considered. In general, electron diffraction in bi‐crystalline specimens is complicated, and reliable interpretation can only be carried out when the diffraction conditions have been carefully established. The diffraction conditions most widely used are discussed, and their relative merits compared.

Cementation of Upper Miocene Reefs in Western Mediterranean: ABSTRACT

Coral reefs in the western Mediterranean (southeast Spain, Balearic Island, northern Morocco, Sicily, and Italy) show a wide variety of cement types, ranging from completely tight, well-cemented, to poorly cemented reefs with most of the primary porosity still preserved. Cementation processes in those coral reefs appear to be controlled to a great extent by repeated changes of relative sea levels and regional variations of seawater chemistry. Reef progradation occurred during four to six (or more) important sea level changes, resulting in complicated geometric relationships of reef complexes and their freshwater lenses. Progradation occurred during sea level rises and falls and is reflected in abrupt escarpments in some field localities, generally separated by important t rraced erosional surfaces. Various types of aragonitic isopachous cement fringes of marine origin, 0.1 to 1.5 cm (.04 to .6 in.) thick, are well preserved in some localities. This is probably due to subsequent plugging by gypsum cement during the Messinian salinity crises. Another possible effect of salinity fluctuations is the abundance of thick crusts of peletoidal, micrite cement of marine origin, locally forming about three-fourths of the volume of the reef core. End_of_Article - Last_Page 457------------

Nachstrommessungen an einem Schiffsmodell im Windkanal

Three component measurements in the wake of a double ship model without propeller in a wind tunnel are presented. The Reynolds number is 4.65 × 106. In the plane of the propeller turbulence intensities of more than 80% are found. The signal of the one channel fringe type laser anemometer is processed by autocorrelation. The correlograms are evaluated by curve fitting assuming gaussian velocity distribution. It is shown how the results compare with a pressure tube investigation.The statistical errors of the LDA data are studied evaluating a large number of simulated correlograms. It is found that the errors in velocity and turbulence are described by two two-dimensional functions.

Community structure and species diversity of hermatypic corals at Eilat, Red Sea

This study investigates the community structure of reefbulding corals in terms of species composition, zonation and diversity patterns, as well as possible factors affecting the observed distributions. The study was carried out by a series of line transects run underwater with SCUBA apparatus from the reef flat to a depth of 30 m. The reefs of Eilat are of the fringing type, with seleractinian corals as the most important hermatypic organisms. The different zones of the reef are analyzed on the basis of topographical characteristics of the reef, as well as from the numerical data on abundance and living coverage, using cluster analysis of all transects surveyed. The present knowledge concerning species diversity is reviewed and analyzed in the context of hermatypic coral data. Three different diversity indices (the species count, Simpson's index and Shannon and Weaver's index) were calculated for estimating the diversity obtained on different zones of the reef. It was found that there is a successive increase in diversity of hermatypic corals from shallow water to a depth of 30 m. Species diversity and living voverage of corals were significantly greater in steeper zones as compared to flatter zones of the reef. A possible explanation for this phenomenon is the accumulation of sediments in the flat zones. It is proposed that the severe and umpredictable nature of the reef flat may account for low abundance and living coverage of corals. It is also proposed that deep-water species which do not invade shallow water are species which have developed high specialization to their local environment. The idea that light intensity is a significant factor in calcium-carbonate deposition by scleractinian corals is supported by field measurements of individual colonies at different depths.

X‐Ray Dynamical Contrast of a Planar Defect

AbstractThe presence of a non‐diffracting lamella in an otherwise perfect crystal results in particular interference fringes on X‐ray topographs. The form and contrast of these fringes as found on section topographs have been calculated using the basic assumptions of the dynamical theory. Two different types of fringes can be distinguished: those independent of the gap thickness which are similar to stacking fault fringes, and those characteristic of a gap, whose shape depends sharply on the gap thickness. It is shown that among these interference systems some fringes of high contrast exist even in absorbing crystals. The experimental results obtained with various geometric arrangements are in good agreement with the theoretical predictions.

Crystallization of isotactic polystyrene from toluene solution

Synopsis The overall rate of crystallization of isotactic polystyrene from dilute solutions, 1% by weight, in trans-decalin and benzyl alcohol was studied as a function of temperature using dilatometry. These solvents were chosen because the dissolution temperatures of crystalline isotactic polystyrene are practically the same in both solvents. The overall rate of crystallization as a function of crystallization temperature showed a maximum in both solvents at about 50°C. At lower crystallization temperatures the rate of crystallization is much lower. The overall rate of crystallization of isotactic polystyrene in benzyl alcohol is far larger than in trans-decalin at the same undercooling throughout the temperature range, which is in apparent contradiction to present crystallization theories. At very large undercooling (T, lower than about OOC) the solutions of isotactic polystyrene in both solvents quickly become “rigid” gels. Surface replicas of freeze-etched gels indicate that a fringed micelle type of crystallization takes place at these low temperatures. The transition from folded chain crystallization to fringed micelle crystallization may be due to a stiffening of the polymer chain below about 5OoC, with a reduced rotational mobility of the phenyl groups on the chain. If very dilute solutions, below 0.5% by weight, are crystallized at these low temperatures no gels were formed but fibrous crystals are produced which could be observed under the polarizing microscope.

Measurement of Thickness and Refractive Index of Oxide Films on Silicon

Optical interference methods for determining the thickness and refractive index of oxide films on silicon are described. The treatment is confined to those methods in which a portion of the film is dissolved with , and measurements are made on the height of the step thus created. For thick films (>3000Aå) two‐beam interference is used, and for thin films (>3000Aå) multiple‐beam interference is used. The different types of fringes are explained, and the accuracies of the methods are given. The emphasis is on the development of simple, practical procedures which can be applied in a routine manner.

Fringe Populations of the European Corn Borer, Pyrausta nubilalis: Their Characteristics and Problems1

The distribution of animals is often limited or isolated into populations. Whenever a population has a boundary, there exist fringes. Five major types of population fringes—climatic, topographic, biotic, advancing, and artificial—are briefly discussed. The Minnesota and South Dakota populations of the European corn borer show a climatic fringe in the north, and an advancing and a topographic fringes in the west. The characteristics of the three types of fringe populations are described, and the practical difficulties in insecticidal control of this insect that resulted from the fringe characteristics are considered. More knowledge on fringe populations is needed and would be valuable in practical fields such as game and fishery biology and biological and chemical control of insects. It also may elucidate the basic ecological principles involved in the natural control of animal populations, and in the adaptive variation and hybridization among animal populations.

Secondary Interference Fringes

A dissonance phenomenon is observed to occur between two types of interference fringes: (1) those produced by stationary light waves formed in front of a mirror and made visible on a thin translucent film and (2) the fringes of equal thickness formed by the wedge of air enclosed between the thin film and the mirror.

Barrier Reefs as a Sign of a Subsiding Coast Line

IN my letter on the recession of the Tahitian coral reefs published in NATURE of April 23, proof is given of the original continuity of the present barrier reef from shore to ocean slope. The absence of a lagoon from parts of the coasts of both Tahiti and Moorea should alone prove that barrier reefs can no longer be taken as an index of subsidence without independent proof from the adjacent land, and the completion of the proof that barriers may be formed from broad reefs of the fringing type should be decisive. Further, I propose shortly to publish proof that in the adjacent but older island of Moorea there has been a tilting, resulting in subsidence of the south coast, which, though it took place during the growth of the reefs, has not made any difference to their form off that part of the island. The investigation of reef problems owes much to the numerous papers by Prof. Davis, which insist upon, and explain, the geological factors which it is essential to take into account. The biologist must, however, join in these researches, and it is much to be regretted that this side has been entirely neglected in Davis's work. One also misses any detailed local descriptions of the great series of reefs, old and new, which he has visited, that of Tahiti being the only one I have seen; this appears in French in Annales de Geographic, 1918. In this Prof. Davis gives reasons for believing that the island has undergone a large subsidence, with which conclusion, after much consideration given to the subject on the spot, I am quite unable to agree.

Types of Achromatic Fringes

Types of Achromatic Fringes