Curvature Pattern Research Articles

Structural changes in the lyrate feathers in the development of the tail plumage of the Superb Lyrebird, Menura novaehollandiae

The tail plumage of the Superb Lyrebird, Menura novaehollandiae, proceeds through a succession of annual moults over about eight years for the male and about seven for the female in which the feathers change in dimensions, shape, structure and pigmentation. Male lyrates increase in length from 245 mm to ∼700 mm, and in weight from 0.37 g to 2.4 g; adult female lyrates are ∼305 mm long and weigh 0.55 g; but details vary from bird to bird. The asymmetry (defined in paper) of the first two generations of lyrates is low, but increases at each generation. The shape of the feather is determined by the lengths of the barbs in both vanes and the angle of growth, and the curvature pattern of the shaft, which is curved concave to the long axis of the bird over the proximal part and convex over the distal part. The degree of curvature is greatest in the distal part and increases as the bird matures. Lyrates have yellow-orange-brown bars along the inner vane; the number increases from 16 for the second generation to 20–25 at maturity; adult female lyrates have 8–12 bars. Lyrebirds from Sherbrooke Forest differ from one another in the details of the properties studied; lyrates from other districts had characteristics that fell within the ranges of values for the Sherbrooke birds. The data for a particular mature male bird from Healesville indicate that, once a male bird has matured, the dimensions and structural details remain (practically) unchanged. The lyrates of adult females from different districts differed in some respects, but were similar in others.

Study on Digital Style Design

This paper deals with a style design system developed for creating shapes with required highlight lines input by the computer mouse. Highlight lines are a very important parameter for evaluating the aesthetic shape of products. The system allows simple construction of high quality surfaces in a virtual space by evaluating the shapes of highlight lines. This paper also proposes methods to define an evolute representing the curvature centers of a section of a surface by using highlight line information, and clarifies that an involute of an evolute is the section having a shape with the required highlight lines. Process methods to define an evolute of the shape of a modified section are classified according to the changing patterns of curvature. The system was developed by implementing the algorithm based on the proposed method, and the usefulness of the system was confirmed by basic tests.

Curvature analysis of the mandibular condyle.

To determine whether curvature analysis on high resolution CT images can be used as a tool for evaluation of mandibular condyle morphology. Curvature analysis was performed on reconstructed oblique coronal CT images of 634 normal condyles from 317 patients (144 men and 173 women; age range 4-89 years) with inner or middle ear disease. The condyles were scanned with 1 mm collimation using helical CT. The CT images were analysed manually on a personal computer. The condyle CT images could be categorized into five curvature profile patterns: (1) bi-peak; (2) no peak; (3) tri-peak; (4) bi-peak with an intervening bottom above the base line (bi-peak with a col); and (5) bi-peak with an intervening negative phase. A separate evaluation using computer graphic condyle models indicated that these curvature patterns corresponded to flat (bi-peak), round (no peak), convex (bi-peak with a col), concave (bi-peak with a negative phase) and angled (tri-peak) contours of the condyle's superior surface. The curvature profiles were identical between bilateral condyles in 40% (126/317) of the patients. Gender-related differences in the incidence of the curvature profiles were also found, the bi-peak with a col profile being more frequently observed in women and the bi-peak with a negative phase profile being observed more frequently in men. Curvature analysis on CT images depicts condyle morphology effectively and may be an adjunctive tool for condyle morphometry.

Generic and non-generic conditions for the perception of surface shape from texture

Li and Zaidi (Vision Research 40 (2000) 217; 41 (2001) 1519) have recently argued that there are two necessary conditions for the perception of 3D shape from texture: (1) the texture pattern must have a disproportionate amount of energy along directions of principal curvature; and (2) the surface must be viewed with a noticeable amount of perspective. In the present article we present evidence that these conclusions are only valid under a limited set of non-generic viewing conditions. Other relevant factors that need to be considered in this context include the distribution of curvature on an object's surface and the set of possible viewing directions from which it can be observed. For generic viewing directions and patterns of curvature, the perception of surface curvature from texture is only minimally affected by the orientation spectrum of the texture pattern or the amount perspective in its optical projection. Li and Zaidi (Vision Research 41 (2001) 1519) have also identified two characteristic patterns of image contours, which they claim to be the only possible source of information within textured images for determining the direction of surface slant or the sign of surface curvature. In the present article we attempt to show that these characteristic patterns can only arise in natural vision for a limited set of non-generic viewing directions. We also review several other factors that can influence the perceived direction of slant or the perceived sign of curvature, which have been identified previously by other investigators.

A Comparative Analysis of Wet and Dry Ashing Techniques for the Extraction of Phytoliths from Plant Material

Two methods are commonly used for the extraction of phytoliths from plant material to be used as reference in the analysis of archaeological phytolith samples: (1) spodograms or dry ashings; and (2) acid digestions or wet ashing. It has been suggested that these techniques may modify the resultant samples in different ways. Dry ashing, in particular, has been implicated as a cause of shrinkage and warping in phytolith assemblages when incineration occurs at ≥450°C. The results of a morphometric comparative analysis between the dry ashing and wet ashing methods do not support these claims. This study establishes that differences in patterns of dimension and curvature of short bilobate phytoliths and of elongate phytoliths both subjected to dry and wet ash preparation are not statistically significant. There is, therefore, no detectable evidence of morphological impact as a result of these methods. This finding implies that any differences that do occur in phytolith size and curvature are typical, possibly random permutation within assemblages, or that they are the result of variation in leaf cell structure rather than the consequence of a particular extraction procedure. This suggests that the practice of using different methods of preparation of reference samples for fossil analysis can be reliably continued.

Prevention of corneal ectasia in laser in situ keratomileusis.

Ectasia after laser in situ keratomileusis (LASIK) is a rare but serious complication. Prevention includes proper patient selection with detection of those at particular risk. Causes of ectasia include predisposition, excessive ablation with less than 250 microm of residual stromal bed, thicker than normal flap, irregular corneal thickness, and different ablation rates. We evaluated corneal curvature patterns and their relationship to corneal topography and pachymetry maps. Corneal topography (axial, tangential, and altimetric) and pachymetry map characteristics of normally astigmatic corneas, keratoconus, false-positive and false-negative cases, as well as contact lens-induced warpage are discussed. Preoperative pachymetry maps for LASIK surgery allow accurate case selection through detection of borderline cases, and provide important documentation of preoperative status, as well as useful information for improving surgical strategy. Another important parameter is the asphericity index.

Prism adaptation produces neglect-like patterns of hand path curvature in healthy adults

Visuospatial neglect is a common consequence of brain injury in which patients fail to respond appropriately to stimuli or events occurring within their contralesional hemispace and may restrict eye and hand movements to objects or events occurring within ipsilesional space. Emerging evidence suggests, however, that neglect is a syndrome consisting of several components, including the impaired representation of corporeal and extrapersonal space. To better understand the neglect syndrome it is important to develop experimental models of each of these components. Here we develop an experimental model of the spatial impairment associated with visuospatial neglect based upon adaptation to laterally displacing optical prisms. We demonstrate that after a short period spent adapting to rightward displacing prisms, healthy subjects exhibit increases in hand-path curvature during reaches executed under visual guidance, but, not during reaches executed to proprioceptively-defined targets without vision.

ChemInform Abstract: Molecular-Dynamics Studies of Single-Stranded Hexitol, Altritol, Mannitol, and Ribose Nucleic Acids (HNA, MNA, ANA, and RNA, Resp.) and of the Stability of HNA×RNA, ANA×RNA, and MNA×RNA Duplexes.

The influence of the orientation of a 3′-OH group on the conformation and stability of hexitol oligonucleotides in complexes with RNA and as single strands in aqueous solution was investigated by molecular-dynamics (MD) simulations with AMBER 4.1. The particle mesh Ewald (PME) method was used for the treatment of long-range electrostatic interactions. An equatorial orientation of the 3′-OH group in the single-stranded D-mannitol nucleic acid (MNA) m(GCGTAGCG) and in the complex with the RNA r(CGCAUCGC) has an unfavorable influence on the helical stability. Frequent H-bonds between the 3′-OH group and the O−C(6′) of the phosphate backbone of the following nucleotide explain the distorted conformation of the MNA⋅RNA complex as well as that of the single MNA strand. This is consistent with experimental results that show lowered hybridization potentials for MNA⋅RNA complexes. An axial orientation of the 3′-OH group in the D-altritol nucleic acid (ANA) a(GCGTAGCG) leads to a stable complex with the complementary RNA r(CGCAUCGC), as well as to a more highly preorganized single-stranded ANA chain. The averaged conformation of the ANA⋅RNA complex is similar to that of A-RNA, with only minor changes in groove width, helical curvature, and H-bonding pattern. The relative stabilities of ANA⋅RNA vs. HNA⋅RNA (HNA=D-hexitol nucleic acid without 3′-OH group) can be explained by differences in restricted movements, H-bonds, and solvation effects.

The influence of multiple-exposure recording on curvature pattern using multi-aperture speckle shear interferometry

A method based on multiple exposures in binomial mode of recording and its influence on curvature pattern is presented in this paper. Since the curvature information is obtained as a beat moiré between two sets of slope patterns, the multiple-exposure technique proposed in this paper can be implemented to sharpen the background slope fringes to enhance the visibility of the curvature fringes.

Clinical results of the new cervico-thoracic orthosis 'Neck-Chest brace'

The efficacy of a new cervico-thoracic Neck-Chest brace (N-C brace) prepared for post- operative patients of cervical canal expansive laminoplasty was assessed. The orthosis is light in weight (300 g) and easy to fit. The effect of the orthosis to restrict the neck motion was studied in 10 normal young males by using lateral view radiographs in extension and flexion positions. The average range of the neck motion for the N-C brace was 24.4% of the values obtained without the orthosis. The restriction of the motion was significantly better than that without orthosis. Then, the clinical efficacy of the N-C brace was assessed in 40 patients of cervical spondylotic myelopathy who underwent expansive laminoplasty. Alignment changes of the postoperative cervical spine was found only in 10% of the patients who had a straight and kyphotic curvature pattern in the cervical spine before operation. The cervical alignments in the other 90% of patients were not changed post-operatively. These data clearly demonstrated that the N-C brace effectively controls the neck motion and is recommended for patients who have a lordotic curvature pattern in the cervical spine to prevent the post-surgical changes in the alignment after expansive laminoplasty.

Congenitally blind individuals rapidly adapt to coriolis force perturbations of their reaching movements.

Reaching movements made to visual targets in a rotating room are initially deviated in path and endpoint in the direction of transient Coriolis forces generated by the motion of the arm relative to the rotating environment. With additional reaches, movements become progressively straighter and more accurate. Such adaptation can occur even in the absence of visual feedback about movement progression or terminus. Here we examined whether congenitally blind and sighted subjects without visual feedback would demonstrate adaptation to Coriolis forces when they pointed to a haptically specified target location. Subjects were tested pre-, per-, and postrotation at 10 rpm counterclockwise. Reaching to straight ahead targets prerotation, both groups exhibited slightly curved paths. Per-rotation, both groups showed large initial deviations of movement path and curvature but within 12 reaches on average had returned to prerotation curvature levels and endpoints. Postrotation, both groups showed mirror image patterns of curvature and endpoint to the per-rotation pattern. The groups did not differ significantly on any of the performance measures. These results provide compelling evidence that motor adaptation to Coriolis perturbations can be achieved on the basis of proprioceptive, somatosensory, and motor information in the complete absence of visual experience.

Simultaneous measurement of pure curvature and twist distribution fields by a five-aperture shearing and two-Fourier filtering technique

A five-aperture shearing and two-Fourier filtering technique to measure simultaneously pure curvature and twist distribution fields of a deformed object is proposed. In this method the slope fringes that are contained in the patterns of curvature and twist fringes can be completely eliminated. Thus patterns of pure curvature and twist fringes with a good contrast can be obtained. A theoretical analysis and experimental results are given.

Observations of lattice curvature near the interface of a deformed aluminium bicrystal

Abstract Reported here is a study of the pattern of lattice curvature near the interface of deformed high-purity aluminium (99.9999%) bicrystals of specified crystallographic character (large-angle random). Curvature data are obtained from electron back-scattering diffraction pattern observations using orientation imaging microscopy. The concept of geometrically necessary dislocations (GNDs) is used as the central tool in the description of the observations. The samples studied were channel-die compressed perpendicular to the interface to plastic strain levels of 0.1 and 0.3. At a strain level of 0.1 the primary observation is the development of a pile-up of GNDs (i.e. lattice curvature) near the interface. At the higher strain level of 0.3, however, a dramatic change in the distribution is observed. The nature of this change suggests that the interface has absorbed (or emitted) some components of the nearby GND field. with an accompanying change in the local character of the interface towards a broader dispersion of misorientation character.

Lines of principal curvature around umbilics and Whitney umbrellas

In this paper is studied the configuration of lines of curvature near a Whitney umbrella which is the unique stable singularity for maps of surfaces into R 3. The pattern of such configuration is established and characterized in terms of the 3-jet of the map. The result is used to establish an expression for the Euler-Poincare characteristic in terms of the number of umbilics and umbrellas. 1. Introduction. The bending or curvature pattern of a smooth mapping a : M -» R3, where M is a compact oriented two dimensional manifold, will be represented here by singular points, Sa, at which the mapping has rank less than 2 and the bending can be re- garded to be infinite; the umbilic points, Ua, at which the bending is finite but equal in all directions: and by the family of lines of principal curvature T\,a and Ti,a defined on M (Ua U 4. They showed that Darbouxian umbilic points characterize those with local structurally stable configuration, under small C3 deformations of the surface. See also the work of Bruce and Fidal (B-F). A study of principal foliations near the set Sa of singular points, aiming to characterize their local stability, was carried out by Gutierrez and Sotomayor (GS2). To this end they gave two sufficient conditions, the first of which is the Whitney singularity condition for stability of mappings in the sense of Singularity Theory (G-G). However, in this paper, an erroneous

A Chondral Modeling Theory Revisited

The mechanical environment of limb joints constantly changes during growth due to growth-related changes in muscle and tendon lengths, long bone dimensions, and body mass. The size and shape of limb joint surfaces must therefore also change throughout post-natal development in order to maintain normal joint function. Frost's (1979, 1999) chondral modeling theory proposed that joint congruence is maintained in mammalian limbs throughout postnatal ontogeny because cartilage growth in articular regions is regulated in part by mechanical load. This paper incorporates recent findings concerning the distribution of stress in developing articular units, the response of chondrocytes to mechanically induced deformation, and the development of articular cartilage in order to expand upon Frost's chondral modeling theory. The theory presented here assumes that muscular contraction during post-natal locomotor development produces regional fluctuating, intermittent hydrostatic pressure within the articular cartilage of limb joints. The model also predicts that peak levels of hydrostatic pressure in articular cartilage increase between birth and adulthood. Finally, the chondral modeling theory proposes that the cell–cell and cell–extracellular matrix interactions within immature articular cartilage resulting from mechanically induced changes in hydrostatic pressure regulate the metabolic activity of chondrocytes. Site-specific rates of articular cartilage growth are therefore regulated in part by the magnitude, frequency, and orientation of prevailing loading vectors. The chondral modeling response maintains a normal kinematic pathway as the magnitude and direction of joint loads change throughout ontogeny. The chondral modeling theory also explains ontogenetic scaling patterns of limb joint curvature observed in mammals. The chondral modeling response is therefore an important physiological mechanism that maintains the match between skeletal structure, function, and locomotor performance throughout mammalian ontogeny and phylogeny.

A Theoretical Perusal of the Satellite DNA Curvature in Tenebrionid Beetles

The curvature patterns of seven satellite DNAs taken from beetles belonging to the family Tenebrionidae (Coleoptera) were modelled utilising a number of computer programs that describe and plot the curvature profiles of DNA. The theoretical analysis agreed with the experimentally observed curvature of most of these satellite DNAs, and its absence in Tribolium freemani and Tenebrio obscurus satellite I. In many cases, the tenebrionid satellite DNAs lack periodically repeated runs of phased-A-tracts, yet they represent a clear example of cuved DNA. The macroscopic curvature of satellites from these closely related organisms confirmed that other sequence elements must be participating in the bending of these DNAs. Our modelling approaches are discussed, together with previous experimental results, in terms of the role played by DNA curvature in the organisation of satellite DNA and the tight compacting of heterochromatin.

Unique translational positioning of nucleosomes on synthetic DNAs.

A computational study was previously carried out to analyze DNA sequences that are known to position histone octamers at single translational sites. A conserved pattern of intrinsic DNA curvature was uncovered that was proposed to direct the formation of nucleosomes to unique positions. The pattern consists of two regions of curved DNA separated by preferred lengths of non-curved DNA. In the present study, 11 synthetic DNAs were constructed which contain two regions of curved DNA of the form [(A5.T5)(G/C)5]4 separated by non-curved regions of variable length. Translational mapping experiments of in vitro reconstituted mononucleosomes using exonuclease III, micrococcal nuclease and restriction enzymes demonstrated that two of the fragments positioned nucleosomes at a single site while the remaining fragments positioned octamers at multiple sites spaced at 10 base intervals. The synthetic molecules that positioned nucleosomes at a single site contain non-curved central regions of the same lengths that were seen in natural nucleosome positioning sequences. Hydroxyl radical and DNase I digests of the synthetic DNAs in reconstituted nucleosomes showed that the synthetic curved element on one side of the nucleosomal dyad assumed a rotational orientation where narrow minor grooves of the A-tracts faced the histone surface with all molecules. In contrast, the curved element on the other side of the nucleosome displayed variable rotational orientations between molecules which appeared to be related to the positioning effect. These results suggest that asymmetry between the two halves of nucleosomal DNA may facilitate translational positioning.

Spatio-temporal curvature pattern of the caudal body axis for non-mutant and curly tail mouse embryos during the period of caudal neural tube closure.

During the period of early organogenesis the mouse embryo has a curved body shape, which is thought to interact with ongoing developmental processes. Curly tail is a mouse mutant causing spina bifida, in which aberrant axial curvature is considered to be responsible for a delay in the closure of the posterior neuropore (PNP). Since detailed descriptions of axial curvature have never been made in either the normal or the mutant embryo, the onset and development of the aberrant axial curvature in the curly tail embryo are unknown. In the present study, axial curvature and segmental growth during closure of the PNP are described using circle segments at each somite level in two non-mutant mouse strains. Using the radius and angle of the segments as parameters, CD-1 and Balb/c mouse embryos showed maxima of curvature at the levels of the limb buds. Throughout development, a general axial unbending occurred that was due to a level-specific combination of general outgrowth and other factors. A marked additional decrease in the axial curvature was spatially and temporally related to the final closure of the PNP, indicating that this decrease of curvature facilities the final closure of the PNP. In the curly tail embryo the segment parameter radius was used to relate the axial curvature to an aberrant neural tube closure pattern. These embryos exhibited an enhanced curvature over the entire neuropore region as soon as a delay in the PNP closure could be distinguished. A steep decrease in curvature during final closure of the PNP did also occur, but at a more caudal level. Both the axial level of straightening and the rate of curvature were normalized at advanced developmental stages. The aberrant spatio-temporal curvature pattern in the curly tail mouse embryo indicates that both the rate of curvature and the axial level of unbending are important for a correct PNP closure.

Gravitropic responses of the Avena coleoptile in space and on clinostats. III. Hypogravity effects on coleoptile curvatures

The precise description of the gravitropic curvature response of plants is often difficult due to the presence of gravity when the response is recorded. Therefore, unambiguous results on the gravitropic reactions in differents segments of coleoptiles, the participation of auxin transport in the curvature development and the reactions to hypogravity stimulations can only be achieved in weightlessness. To answer these questions, curvatures of Avena coleoptiles at different distances from the apex were studied after transverse, hypogravity stimulations. The experiments were conducted in Spacelab on the Shuttle in earth orbit.Test plants were cultivated on 1.0 g‐centrifuges in Spacelab. The stimulation accelerations, were between 0.1 and 1.0 g, and duration varied between 2 and 130 min. All plant responses were recorded in weightlessness by a video cassette recorder for analysis.The gravitropic curvature started almost simultaneously in apical segments, and occurred later in the basal ones. After maximum response, the curvature in the top segments showed a clear autotropic reaction, that was not seen in the basal segments. Initial wrong‐way curvatures were recorded in the basal part of the coleoptiles at several g‐levels.The further down along the coleoptile, the later the occurrence of the maximum gravitropic curvature of each segment. For example, after a stimulus of 25 g min the maxima appeared to travel down the coleoptile with a speed of about 50 mm h−1 in the upper and 20 mm h−1 in the lower part of the coleoptiles. It is concluded that the basipetal auxin transport can contribute only marginally to the gravitropic curvature pattern due to its much lower transport rate. Local reactions control the curvature pattern in each segment (even if the basipetal auxin transport must add to the reactions).Extrapolations from stimulus response data curves allowed some determinations of threshold stimulation times for different segments along the coleoptiles. Data for the individual segments along the coleoptiles were not at variance with the reciprocity law.

Shape-similarity analysis of 20 stable conformations of neutral β-alanine

The family of 20 stable conformations of neutral β-alanine are analyzed in terms of their shape similarities using the topological Shape Group Method, a general molecular shape analysis technique as applied to the three-dimensional electronic density. Molecular electron densities are calculated using the 6-31G** basis set, followed by the determination of the shape groups of local curvature patterns for the entire chemically relevant range of electron density contour surfaces. The results of the shape group analysis are represented by two-dimensional shape maps. Discretized grids of these maps generate numerical shape codes, and comparisons of these numerical codes serve as measures of shape similarity of the various conformers of β-alanine. This technique is based on direct comparisons of the intrinsic shape features of molecules and requires no superposition of molecules for comparisons. Mathematically well-defined and unbiased similarity measures are obtained by this non-visual, computer-based method, useful for the detection, quantification, and analysis of electronic charge distribution similarities. The family of 20 stable conformers of β-alanine serves as a test case for the application of the methodology for a large number of conformers, representing a level of complexity analogous to that of typical conformational problems in computer-aided drug design and the screening of potential drug molecules for shape similarity. Key words: similarity measures, shape groups, β-alanine, conformation analysis, molecular shape, electron density.