Elongated Ribbons Research Articles

ROAD NETWORK EXTRACTION USING GPS TRAJECTORIES BASED ON MORPHOLOGICAL AND SKELETONIZATION ALGORITHMS

Abstract. In this article, a method for road network extraction is proposed, based on GPS (Global Positioning System) trajectories. Unlike existing methods, it is not necessary to resample the GPS trajectories into a raster structure; instead, all analyses are based on the polylines that represent the GPS trajectories. Basically, a morphological analysis and a skeletonization technique are used by the proposed method. Two main steps of the method can be identified: the first step consists in generating an elongated polygon (that delimitates an elongated ribbon) that represents the selected road; and the second step aims at reconstructing the road network. The proposed method was evaluated based on four GPS trajectory datasets and the results obtained can be considered good, but some inconsistencies were noted, as for example: extraction failures occur in places with very low trajectory density (such as 3–4 trajectories); merging of very close and parallel roads; some road crossings that are close to one another have been merged into a single point. The proposed method was also compared with existing methods in the literature and the obtained results showed good consistency between them.

Knifefish turning control and hydrodynamics during forward swimming.

Rapid turning and swimming contribute to ecologically important behaviors in fishes such as predator avoidance, prey capture, mating and the navigation of complex environments. For riverine species, such as knifefishes, turning behaviors may also be important for navigating locomotive perturbations caused by turbulent flows. Most research on fish maneuvering focuses on fish with traditional fin and body morphologies, which primarily use body bending and the pectoral fins during turning. However, it is uncertain how fishes with uncommon morphologies are able to achieve sudden and controllable turns. Here, we studied the turning performance and the turning hydrodynamics of the black ghost knifefish (Apteronotus albifrons, N=6) which has an atypical elongated ribbon fin. Fish were filmed while swimming forward at ∼2 body lengthss-1 and feeding from a fixed feeder (control) and an oscillating feeder (75 Hz) at two different amplitudes. 3D kinematic analysis of the body revealed the highest pitch angles and lowest body bending coefficients during steady swimming. Low pitch angle, high maximum yaw angles and large body bending coefficients were characteristic of small and large turns. Asynchrony in pectoral fin use was low during turning; however, ribbon fin wavelength, frequency and wave speed were greatest during large turns. Digital particle image velocimetry (DPIV) showed larger counter-rotating vortex pairs produced during turning by the ribbon fin in comparison to vortices rotating in the same direction during steady swimming. Our results highlight the ribbon fin's role in controlled rapid turning through modulation of wavelength, frequency and wave speed.

The origin of quasi-periodicities during circular ribbon flares

Context. Solar flares with a fan-spine magnetic topology are able to form circular ribbons. A previous study based on Hα line observations of the solar flares on 5 March 2014 revealed a uniform and continuous rotation of the magnetic fan-spine. A preliminary analysis of the flare time profiles revealed quasi-periodic pulsations (QPPs) with similar properties in hard X-rays, Hα, and microwaves. Aims. In this work, we address the question of whether the observed periodicities are related to periodic acceleration of electrons or plasma heating. Methods. We analysed QPPs in the Hα emission from the centre of the fan (inner ribbon R1), a circular ribbon (R2), a remote source (R3), and an elongated ribbon (R4) located between R2 and R3. We used methods of correlation, Fourier, wavelet, and empirical mode decomposition. We compared the QPPs in Hα emission with those in microwave and X-ray emission. Results. We found multi-wavelength QPPs with periods around 150 s, 125 s, and 190 s. The 150 s period is seen to co-exist in Hα, hard X-rays, and microwave emissions, which allowed us to connect it with flare kernels R1 and R2. These kernels spatially coincide with the site of the primary flare energy release. The 125 s period is found in the Hα emission of the elongated ribbon R4 and the microwave emission at 5.7 GHz during the decay phase. The 190 s period is present in the emission during all flare phases in the Hα emission of both the remote source, R3, and the elongated ribbon, R4, in soft X-rays and in microwaves at 4–8 GHz. Conclusions. We connected the dominant 150 s QPPs with the slipping reconnection mechanism occurring in the fan. We suggested that the period of 125 s in the elongated ribbon can be caused by a kink oscillation of the outer spine, connecting the primary reconnection site with the remote footpoint. The period of 190 s is associated with the three-minute sunspot oscillations.

Observations of a Footpoint Drift of an Erupting Flux Rope

Abstract We analyze the imaging observations of an M-class eruptive flare of 2015 November 4. The pre-eruptive Hα filament was modeled by the nonlinear force-free field model, which showed that it consisted of two helical systems. Tether-cutting reconnection involving these two systems led to the formation of a hot sigmoidal loop structure rooted in a small hook that formed at the end of the flare ribbon. Subsequently, the hot loops started to slip away from the small hook until it disappeared. The loops continued slipping and the ribbon elongated itself by several tens of arcseconds. A new and larger hook then appeared at the end of the elongated ribbon with hot and twisted loops rooted there. After the eruption of these hot loops, the ribbon hook expanded and later contracted. We interpret these observations in the framework of the recent three-dimensional (3D) extensions to the standard solar flare model predicting the drift of the flux rope footpoints. The hot sigmoidal loop is interpreted as the flux rope, whose footpoints drift during the eruption. While the deformation and drift of the new hook can be described by the model, the displacement of the flux rope footpoint from the filament to that of the erupting flux rope indicate that the hook evolution can be more complex than those captured by the model.

<p><strong>The first fossil Nemopteridae from the Oligocene of Céreste (France) (Insecta: Neuroptera)</strong></p>

Nemopteridae are a small family of myrmeleontoid lacewings characterized by elongated ribbon- or thread-like hindwings. Extant Nemopteridae comprise two subfamilies, viz. Crocinae (thread-wings) and Nemopterinae (spoon- and ribbon-wings). They are distributed in all zoogeographical regions except the Nearctic region in the extant fauna. However, the major species diversity of Nemopteridae is confined to the southern part of Africa. The fossil record of the family is scarce, with five Lower Cretaceous fossils, one from the lowermost Cenomanian, two fossils from the Upper Eocene, and two from the Oligocene (Lu et al., 2019; Nel & Jarzembowski, 2019). Here we describe a new, nearly complete fossil from the Oligocene of Lubéron in France. It was found in the Konservat Lagerstätte of Céreste, in finely laminated lacustrine limestones. It is the only specimen of this family found in this outcrop, among more than 30000 fossil insects. Neuroptera are extremely rare in this outcrop; only one adult Ascalaphidae (Ascaloptynx oligocenicus Nel, 1991) and two Mantispidae (Prosagittalata oligocenica Nel, 1988 and an undescribed specimen) have been discovered there (Nel, 1988, 1991).

Extração automatica de segmentos lineares de rodovias em imagens de resoluções variadas

In this paper a methodology for automatic extraction of road segments from images with different resolutions (low, middle and high resolution) is presented. It is based on a generalized concept of lines in digital images, by which lines can be described by the centerlines of two parallel edges. In the specific case of low resolution images, where roads are manifested as entities of 1 or 2 pixels wide, the proposed methodology combines an automatic image enhancement operation with the following strategies: automatic selection of the hysteresis thresholds and the Gaussian scale factor; line length thresholding; and polygonization. In medium and high resolution images roads manifest as narrow and elongated ribbons and, consequently, the extraction goal becomes the road centerlines. In this case, it is not necessary to apply the previous enhancement step used to enhance roads in low resolution images. The results obtained in the experimental evaluation satisfied all criteria established for the efficient extraction of road segments from different resolution images, providing satisfactory results in a completely automatic way.

The crystal structure of the influenza matrix protein M1 at neutral pH: M1-M1 protein interfaces can rotate in the oligomeric structures of M1.

The influenza matrix protein (M1) forms a protein layer under the viral membrane and is essential for viral stability and integrity. M1 mediates the encapsidation of the viral RNPs into the viral membrane by its membrane and RNP-binding activities. In order to understand the roles of M1-M1 protein interactions in forming the M1 layer, X-ray crystallographic studies of a M1 fragment (1-162) were carried out at neutral pH and compared with an acidic pH structure. At neutral pH the asymmetric unit was a stacked dimer of M1. A long molecular ribbon of neutral stacked dimers was formed by translation as dictated by the P1 space group. The elongated ribbon had a positively charged stripe on one side of the ribbon. A similar M1-M1 stacking interface was also found in the acidic asymmetric unit. However, within the acidic stacked dimer the molecules were not straight, but rotated in relation to each other by slightly changing the M1-M1 stacking interface. The acidic structure possessed an additional M1-M1 twofold interface. Protein docking confirmed that the M1-M1 stacking and M1-M1 twofold interfaces could be used to form a double ribbon of M1 molecules. By iterative repetition of the rotated relationship among the M1 molecules, a helix of M1 was generated. These studies suggest that M1 has the ability to form straight or bent elongated ribbons and helices. These oligomers are consistent with previous electron microscopic studies of M1, which demonstrated that isolated M1 formed elongated and flexible ribbons when isolated from what appeared to be a helical shell of M1 in the influenza virus.

Fibres from polypropylene and liquid crystal polymer blends: 3. A comparison of polyblend fibres containing Vectra A900, Vectra B950 and Rodrun LC3000

Polyblend fibres were made of polypropylene (PP) and three thermotropic liquid crystal polymers (LCPs). The LCPs were found to exist in different morphological structures; the Vectra A900 and Vectra B950 LCPs existed mainly as fibrils, while the Rodrun LC3000 existed as short elongated ribbons. The tensile properties of the as-spun fibres were improved on addition of the LCPs, with the properties of the drawn polyblend fibres varying with the drawing procedure. In one-stage drawing, the polyblend fibres gave poorer tensile properties than the pure PP fibre. However in two-stage drawing, the Vectra A900 blend showed an increase in initial modulus over that of the pure PP fibre, while the Rodrun LC3000 blend produced an improvement in fibre tenacity.

Microstructure Development in a High Current Density NbTi Superconducting Composite

Several features of the metallurgy of superconducting composites of Nb-Ti in a Cu matrix are of interest. The cold drawing strains are generally of order 8-10, producing a very fine grain structure of diameter 30-50 nm. Heat treatments of as little as 3 hours at 300 C (∼ 0.27 TM) produce a thin (1-3 nm) Ti-rich grain boundary film, the precipitate later growing out at triple points to 50-100 nm dia. Further plastic deformation of these larger a-Ti precipitates by strains of 3-4 produces an elongated ribbon morphology (of order 3 x 50 nm in transverse section) and it is the thickness and separation of these precipitates which are believed to control the superconducting properties. The present paper describes initial attempts to put our understanding of the metallurgy of these heavily cold-worked composites on a quantitative basis. The composite studied was fabricated in our own laboratory, using six intermediate heat treatments. This process enabled very high critical current density (Jc) values to be obtained. Samples were cut from the composite at many processing stages and a report of the structure of a number of these samples is made here.

Pectin Enzymes

Background: Microbial pectin and pectate lyases are virulence factors that degrade the pectic components of the plant cell wall. The homogalacturan backbone of pectin varies in its degree of methylation from the highly methylated and relatively hydrophobic form known as pectin, to the fully demethylated and highly charged form known as pectate. Methylated and demethylated regions of pectin are cleaved by pectin lyase and calcium-dependent pectate lyases, respectively. Protein engineering of lyases specific for particular patterns of methylation, will yield modified pectins of high value to the food and pharmaceutical industries.Results: The crystal structures of pectin lyase A from two strains of Aspergillus niger, N400 and 4M-147, have been determined at pH 6.5 (2.4 Å resolution) and pH 8.5 (1.93 Å resolution), respectively. The structures were determined by a combination of molecular replacement, multiple isomorphous replacement and intercrystal averaging. Pectin lyase A folds into a parallel β helix and shares many of the structural features of pectate lyases, despite no more than 17% sequence identity after pairwise structure-based alignment. These shared structural features include amino acid stacks and the asparagine ladder. However, the differences in the substrate-binding clefts of these two enzymes are striking. In pectin lyase A, the cleft is dominated by aromatic residues and is enveloped by negative electrostatic potential. In pectate lyases, this cleft is rich in charged residues and contains an elongated ribbon of positive potential when Ca2+ is bound. The major difference between the two pectin lyase A structures from the two strains is in the conformation of the loop formed by residues 182–187. These observed differences are due to the different pH values of crystallization.Conclusions: The substrate-binding clefts and catalytic machinery of pectin and pectate lyases have diverged significantly. Specificity is dictated by both the nature of the protein–carbohydrate interaction and long-range electrostatic forces. Three potential catalytic residues have been identified in pectin lyase, two of these are common to pectate lyases. Pectin lyase A does not bind Ca2+ but an arginine residue is found in an equivalent position to the Ca2+ ion in pectate lyase, suggesting a similar role in catalysis. The activity of pectin lyase A is pH -dependent with an optimum activity at pH 5.5. The activity drops above pH 7.0 due to a conformational change at the binding cleft, triggered by the proximity of two buried aspartate residues.