Geometrical constraints in the construction of graptolite stipes

Paleobiology ◽  
1983 ◽  
Vol 9 (2) ◽  
pp. 116-125 ◽  
Author(s):  
Richard A. Fortey
Keyword(s):  
Growth Curves ◽  
Dorsal Wall ◽  
Sine Curve ◽  
Growth Increments ◽  
Independent Variation ◽  
Exponential Decrease ◽  
Geometrical Constraints ◽  
Definition Of ◽  
Stipe Width

The geometry of the simpler types of graptolite stipes can be quantified by assuming them to consist of stacked cylinders representing the thecal tubes. It can be shown that specification of any three characters, for example, thecal inclination, thecal spacing, and stipe width, effectively defines the others (thecal overlap, thecal length and width, thecal “density”); hence the parameters commonly used in the definition of species are not independent. Variation within and between species can be represented by three-character plots. The effects of altering the apertural angle from 90° on such characters as thecal spacing can also be represented geometrically. If thecae are considered as cones rather than cylinders, it follows that as stipe width increases, thecal curvature will describe a sine curve if the thecae are to remain in contact; this observation is matched on real graptolites. Thecal curvature beyond 90° to the dorsal wall is generally impossible without thecae detaching from their neighbors to produce thecal isolation. Growth of thecae along a stipe can be represented graphically. Computer fits to growth curves for five dichograptids show that they can be closely described by an exponential decrease in growth increments along the stipe, and that this model is more accurate than two possible alternatives.

scholarly journals An ontology for the generalisation of the bathymetry on nautical charts

2014 ◽  
Vol II-2 ◽  
pp. 1-7 ◽  
Author(s):  
J. Yan ◽  
E. Guilbert ◽  
E. Saux
Keyword(s):  
Large Scale ◽  
Feature Representation ◽  
The Other ◽  
Central Concept ◽  
Semantic Constraints ◽  
Nautical Chart ◽  
Database Server ◽  
Geometrical Constraints ◽  
Definition Of

On nautical charts, undersea features are portrayed by sets of soundings (depth points) and isobaths (depth contours) from which map readers can interpret landforms. Different techniques were developed for automatic soundings selection and isobath generalisation from a sounding set. These methods are mainly used to generate a new chart from the bathymetric database or from a large scale chart through selection and simplification however a part of the process consists in selecting and emphasising undersea features on the chart according to their relevance to navigation. Its automation requires classification of the features from the set of isobaths and soundings and their generalisation through the selection and application of a set of operators according not only to geometrical constraints but also to semantic constraints. <br><br> The objective of this paper is to define an ontology formalising undersea feature representation and the generalisation process achieving this representation on a nautical chart. The ontology is built in two parts addressing on one hand the definition of the features and on the other hand their generalisation. The central concept is the undersea feature around which other concepts are organised. The generalisation process is driven by the features where the objective is to select or emphasise information according to their meaning for a specific purpose. The ontologies were developed in Protégé and a bathymetric database server integrating the ontology was implemented. A generalisation platform was also developed and examples of representations obtained by the platform are presented. Finally, current results and on-going research are discussed.

Ring-Width Chronologies of the Alpine Dwarf Shrub Empetrum Hermaphroditum FROM THE NORWEGIAN MOUNTAINS

IAWA Journal ◽  
2007 ◽  
Vol 28 (3) ◽  
pp. 325-338 ◽  
Author(s):  
Annette Bär ◽  
Achim Bräuning ◽  
Jörg Löffler
Keyword(s):  
Ring Width ◽  
Growth Curves ◽  
Growth Period ◽  
Snow Accumulation ◽  
Growth Patterns ◽  
Dwarf Shrub ◽  
Tree Line ◽  
Growth Variability ◽  
Empetrum Hermaphroditum ◽  
Growth Increments

In this study, we present the first ring-width chronologies of the dwarf shrub species Empetrum hermaphroditum. For a proper synchronization of the growth rings, serial sectioning was applied in order to deal with the high intern al growth variability and the high proportion of discontinuous rings. The plants were collected from three micro-sites in the middle alpine belt of the Norwegian Scandes wh ich differed regarding solar insolation, snow accumulation and wind exposure. The constructed ringwidth chronologies cover aperiod of max. 80 years. Irrespective of microclimatic differences, the chronologies are highly correlated among each other and with temperatures during the growth period (June-August). However, ecological differences between the micro-sites are reflected by the mean annual growth increments of the plants. We compared the Empetrum chronologies with a ring-width chronology of Betula pubescens trees from the local tree line. Despite the differences in life form and local site conditions, the growth patterns are very similar, an observation which underscores the dominant influence of temperature on growthring formation. Due to the strong climatic signal recorded in the growth curves of E. hermaphroditum, this dwarf shrub provides a significant potential for climate-growth studies in arctic and alpine regions beyond the tree line.

Morphology and classification of some Early Silurian monograptids (Graptoloidea) from the Cape Phillips Formation, Canadian Arctic Islands

1997 ◽  
Vol 34 (8) ◽  
pp. 1128-1149 ◽  
Author(s):  
Jeff J. Lukasik ◽  
Michael J. Melchin
Keyword(s):  
Canadian Arctic ◽  
Canadian Arctic Archipelago ◽  
Dorsal Wall ◽  
Wall Structures ◽  
Morphological Criteria ◽  
Cape Phillips Formation ◽  
Upward Growth ◽  
Definition Of ◽  
Simultaneous Evolution

Exquisitely preserved early to mid-Llandovery monograptids have been chemically isolated from calcareous concretions sampled from the Cape Phillips Formation, central Canadian Arctic Archipelago. They provide morphological information critical in refining the definition of four of the earliest known monograptid genera, and in the elucidation of their phylogenetic dispersal through the Llandovery monograptid radiation. These primitive monograptid genera are defined primarily on the basis of derived thecal form. The specific, derived thecal and thecal apertural character states used in generic diagnoses are as follows: species of Atavograptus possess simple, geniculate to slightly sigmoidal thecae with a large dorsoventral overlap; species of Pribylograptus possess thecae bearing lateral apertural lappets that may occur with Atavograptus-style thecae proximally; species of Coronograptus possess flared thecal apertures at least part way along the rhabdosome; species of Lagarograptus have conspicuous, tongue-like, ventral apertural processes developed as ventral apertural margin outgrowths. Species of all of these genera may possess hoods that are genicular in origin, with the exception of those of Lagarograptus inexpeditus, which are dorsal wall structures. These earliest monograptid genera possess a pattern Mr astogeny, characterized by the outward, then upward growth of theca 1 from a sicular resorption porus (pattern Mr, different from younger monograptids that possess a primary porus developed during sicular astogeny (pattern Mp)). Through analysis of their defining morphological criteria in conjunction with sicular dimensions and thecal uniformity, each of these early monograptid genera is considered to be monophyletic, arising from the primitive Atavograptus stock. Atavograptus thecal morphology provided a simple template for the derivation of thecal form leading to the nearly simultaneous evolution of Pribylograptus, Coronograptus, and Lagarograptus in the lower Rhuddanian. Fourteen species belonging to four genera are described, including six new species.

scholarly journals Parametric Hull Design with Rational Bézier Curves

2021 ◽  
pp. 221-227
Author(s):  
Antonio Mancuso ◽  
Antonio Saporito ◽  
Davide Tumino
Keyword(s):  
Graphical User Interface ◽  
Early Stage ◽  
Bezier Curves ◽  
Bézier Curves ◽  
Rational Bézier Curves ◽  
Hull Design ◽  
Geometrical Constraints ◽  
Sailing Yacht ◽  
Definition Of ◽  
Different Characteristics

AbstractIn this paper, a tool able to support the sailing yacht designer during the early stage of the design process has been developed. Quadratic and cubic Rational Bézier curves have been selected to describe the main curves defining the hull of a sailing yacht. The adopted approach is based upon the definition of a set of parameters, say the length of water line, the beam of the waterline, canoe body draft and some dimensionless coefficients according to the traditional way of the yacht designer. Some geometrical constraints imposed on the curves (e.g. continuity, endpoint angles) have been conceived aimed to avoid unreasonable shapes. These curves can be imported in any commercial CAD software and used as a frame to fit with a surface. The algorithm and the related Graphical User Interface (GUI) have been written in Visual Basic for Excel. To test the usability and the precision of the tool, two sailboats with different characteristics have been replicated. The rebuilt version of the hulls is very close to the original ones both in terms of shape and dimensionless coefficients.

Determination of Cutter Trajectories for Contoured Turbine Buckets

1960 ◽  
Vol 82 (3) ◽  
pp. 200-203
Author(s):  
R. G. DeBiase
Keyword(s):  
Cross Sections ◽  
Complex Surface ◽  
Entire Surface ◽  
Unequally Spaced ◽  
Part Surface ◽  
Geometrical Constraints ◽  
Machining System ◽  
Definition Of ◽  
Turbine Bucket

The advent of numerically controlled machine-tool systems introduces the serious problem of suitably employing them for part fabrication. To numerically contour the complex surface of a large turbine bucket with this type of machining system, it is necessary to determine the geometrical constraints on the motion of the cutter, which will sweep out the desired part surface as an envelope of the cutter surface. A definition of the turbine-bucket surface is given in terms of unequally spaced cross sections along the length of the part, and an interpolating procedure is employed to define the entire surface with properly faired transitions between the specified cross sections. The procedures outlined in this paper have been used to program an IBM 704 computer for the preparation of digital control tapes, which instruct the motions of the machining system.

Quantitative analysis of functional reconstructions reveals lateral and axial zonation in the renal inner medulla

2008 ◽  
Vol 294 (6) ◽  
pp. F1306-F1314 ◽  
Author(s):  
Thomas L. Pannabecker ◽  
Cory S. Henderson ◽  
William H. Dantzler
Keyword(s):  
Surface Area ◽  
Three Dimensional ◽  
Outer Zone ◽  
Vasa Recta ◽  
Collecting Ducts ◽  
Exponential Decrease ◽  
Renal Inner Medulla ◽  
Distance Mapping ◽  
Definition Of ◽  
Quantitative Definition

Three-dimensional functional reconstructions of descending thin limbs (DTLs) and ascending thin limbs (ATLs) of loops of Henle, descending vasa recta (DVR), ascending vasa recta (AVR), and collecting ducts (CDs) permit quantitative definition of lateral and axial zones of probable functional significance in rat inner medulla (IM). CD clusters form the organizing motif for loops of Henle and vasa recta in the initial 3.0–3.5 mm of the IM. Using Euclidean distance mapping, we defined the lateral boundary of each cluster by pixels lying maximally distant from any CD. DTLs and DVR lie almost precisely on this independently defined boundary, placing them in the intercluster interstitium maximally distant from any CD. ATLs and AVR lie in a nearly uniform pattern throughout intercluster and intracluster regions, which we further differentiated by a polygon around CDs in each cluster. Loops associated with individual CD clusters show a similar axial exponential decrease as all loops together in the IM. Because ∼3.0–3.5 mm below the IM base CD clusters cease to form the organizing motif, all DTLs lack aquaporin 1 (AQP1), and all vasa recta are fenestrated, we have designated the first 3.0–3.5 mm of the IM the “outer zone” (OZ) and the final 1.5–2.0 mm the “inner zone” (IZ). We further subdivided these into OZ-1, OZ-2, IZ-1, and IZ-2 on the basis of the presence of completely AQP1-null DTLs only in the first 1 mm and on broad transverse loop bends only in the final 0.5 mm. These transverse segments expand surface area for probable NaCl efflux around loop bends from ∼40% to ∼140% of CD surface area in the final 100 μm of the papilla.

scholarly journals Growth and development of the third permanent molar in Paranthropus robustus from Swartkrans, South Africa

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Christopher Dean ◽  
Clément Zanolli ◽  
Adeline Le Cabec ◽  
Mirriam Tawane ◽  
Jan Garrevoet ◽  
...  
Keyword(s):  
South Africa ◽  
Growth Curves ◽  
Daily Growth ◽  
Tooth Formation ◽  
Dental Maturation ◽  
X Ray ◽  
Permanent Molar ◽  
Growth Increments ◽  
Micro Tomography ◽  
Late Maturation

Abstract Third permanent molars (M3s) are the last tooth to form but have not been used to estimate age at dental maturation in early fossil hominins because direct histological evidence for the timing of their growth has been lacking. We investigated an isolated maxillary M3 (SK 835) from the 1.5 to 1.8-million-year-old (Mya) site of Swartkrans, South Africa, attributed to Paranthropus robustus. Tissue proportions of this specimen were assessed using 3D X-ray micro-tomography. Thin ground sections were used to image daily growth increments in enamel and dentine. Transmitted light microscopy and synchrotron X-ray fluorescence imaging revealed fluctuations in Ca concentration that coincide with daily growth increments. We used regional daily secretion rates and Sr marker-lines to reconstruct tooth growth along the enamel/dentine and then cementum/dentine boundaries. Cumulative growth curves for increasing enamel thickness and tooth height and age-of-attainment estimates for fractional stages of tooth formation differed from those in modern humans. These now provide additional means for assessing late maturation in early hominins. M3 formation took ≥ 7 years in SK 835 and completion of the roots would have occurred between 11 and 14 years of age. Estimated age at dental maturation in this fossil hominin compares well with what is known for living great apes.

Introductory paper

1966 ◽  
Vol 24 ◽  
pp. 3-5
Author(s):  
W. W. Morgan
Keyword(s):  
Line Intensity ◽  
Classification Scheme ◽  
Two Dimensional ◽  
Spectral Classification ◽  
Dimensional Array ◽  
Rr Lyrae ◽  
Metallic Line ◽  
Introductory Paper ◽  
Parameter Varying ◽  
Definition Of

1. The definition of “normal” stars in spectral classification changes with time; at the time of the publication of theYerkes Spectral Atlasthe term “normal” was applied to stars whose spectra could be fitted smoothly into a two-dimensional array. Thus, at that time, weak-lined spectra (RR Lyrae and HD 140283) would have been considered peculiar. At the present time we would tend to classify such spectra as “normal”—in a more complicated classification scheme which would have a parameter varying with metallic-line intensity within a specific spectral subdivision.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

2.2. Working Group 2: Conceptual Definitions of Reference Coordinate Systems for Earth Dynamics

1975 ◽  
Vol 26 ◽  
pp. 21-26
Keyword(s):  
Coordinate System ◽  
Working Group ◽  
General Character ◽  
Coordinate Systems ◽  
Reference Coordinate System ◽  
Group 2 ◽  
Definition Of ◽  
Earth Dynamics

An ideal definition of a reference coordinate system should meet the following general requirements:1. It should be as conceptually simple as possible, so its philosophy is well understood by the users.2. It should imply as few physical assumptions as possible. Wherever they are necessary, such assumptions should be of a very general character and, in particular, they should not be dependent upon astronomical and geophysical detailed theories.3. It should suggest a materialization that is dynamically stable and is accessible to observations with the required accuracy.

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