Onset Of Branching Research Articles

Variability in reproductive effort of a keystone species: age and height of branch establishment

Carnegiea gigantea (saguaro, Cactaceae) is a protected and keystone species in the Sonoran Desert upon which nearly all of the ecosystem’s fauna rely. Little is known about its branching habits, which are particularly important as branching is directly related to seed production. This study assessed the ages and heights of plants when branching commenced under four different environmental regimes. Significant variations were observed in the onset of branching across the populations by both age (78–139 years) and height (4.4–5.5 m), likely related to the interplay between summer precipitation (and thus growth rate) and winter precipitation, which increases branching in any given individual. In all four populations, branches developed from areoles that are themselves reproductive (past or present); i.e., the lower areoles that pre-date the start of reproduction do not appear to contribute to branch production. Further, unlike the wide range of ages at the start of branching, the delay between the start of fruiting and the production of branches appears to be relatively consistent across populations, hovering around a 30-year time lag. Of greatest concern is the advanced age (around 140 years) at which branching begins at the most marginal, arid site, which is around the same time that old-age mortality may set in for the species (generally), dramatically diminishing reproductive output in an already marginal population. If this keystone species declines in this already arid to hyper-arid environment, it would have dramatic and irreversible consequences for the fauna and the ecosystem in this region.

A comparison of 3D particle, fluid and hybrid simulations for negative streamers

Modeling individual free electrons can be important in the simulation of discharge streamers. Stochastic fluctuations in the electron density can accelerate the branching of streamers. In negative streamers, energetic electrons can even ‘run away’ and contribute to processes such as terrestrial gamma-ray and electron flashes. To track energies and locations of single electrons in relevant regions, we have developed a 3D hybrid model that couples a particle model for single electrons in the region of high fields and low electron densities with a fluid model in the rest of the domain. Here we validate our 3D hybrid model on a 3D (super-)particle model for negative streamers without photoionization in overvolted gaps. We show that the extended fluid model approximates the particle and the hybrid model well until stochastic fluctuations become important, while the classical fluid model underestimates velocities and ionization densities. We compare density fluctuations and the onset of branching between the models, and we compare the front velocities with an analytical approximation.

A strong discontinuity approach on multiple levels to model solids at failure

This paper presents a modification of the well established strong discontinuity approach to model failure phenomena in solids by extending it to multiple levels. This is achieved by the resolution of the overall problem to be solved into a main boundary value problem and identified sub-domains based on the concepts of domain decomposition. The initiation of those sub-domains is based on the detection of failure onset within finite elements of the main boundary value problem which takes place at the process zone in front of the propagating cracks. Those sub-domains are subsequently adaptively discretized during run-time and comprise the so called sub-boundary value problem to be solved simultaneously with the main boundary value problem. To model failure, only the sub-elements of those sub-boundary value problems are treated by the strong discontinuity approach which, depending on their state of stress, may develop strong discontinuities to be understood as jumps in the displacement field to model cracks and shear bands. Due to its resolution into many sub-elements, the single finite element of the main boundary value problem can therefore simulate a single propagating strong discontinuity arising in quasi-static problems as well as the propagation of multiple propagating strong discontinuities arising for simulations of crack branching in brittle materials undergoing dynamic failure. Whereas the advantages of the strong discontinuity approach in the form of its efficiency by statically condensing out the degrees of freedom related to the failure zone as well as its applicability to use standard displacement based, mixed, and enhanced formulations for the underlying finite element are kept, new challenges arise due to its proposed modification. Firstly, the solutions of the different sub-boundary value problems must be transferred to the main boundary value problem, which is achieved in this work based on concepts of domain decomposition. Secondly, since multiple strong discontinuities might propagate over the boundaries of the sub-boundary value problem, the applied boundary conditions must take into account the appearance of possible jumps in the displacement fields arising from the solution of the sub-boundary value problem itself. It is shown that for single propagating cracks arising in problems of quasi-static failure only minor differences are obtained through the proposed modification. For the simulation of solids undergoing dynamic fracture the modification allows though to predict the onset of crack branching without the need for any artificial crack branching criterion. A close agreement with experiments of the simulation results in terms of micro- and macro branching in addition to studying certain key parameters like critical velocity, dynamic stress intensity factor, and the strain energy release rate at branching is found.

The effect of secondary arm growth on thermoelectric magnetohydrodynamics

Direct numerical simulations of 3D dendritic growth in the presence of moderate-high magnetic fields have shown that significant fluid flow can be driven in the mushy interdendritic region. The onset of secondary branches caused by the heat and mass transport of fluid flow causes thermoelectric microcirculations to form, which act to amplify the Lorentz force. However magnetic damping will dominate when a region lacks thermoelectric currents.

“Raining c_ _ _ and _o_ _” - The role of the syllable onset in word recognition in reading in Portuguese

The aim of this study was to confirm on new data whether the syllable onset, especially in word initial position, enables more efficient word recognition in reading. Many researchers have suggested the importance of the syllable onset. The consonantal skeleton of words is the first to be activated in the reading process in English, according to Lee, Rayner & Pollatsek (2001). Moreover, it was shown that the onset is preserved whereas other graphemes are suppressed in chat discourse in Portuguese (Silva, 2006). An experimental study was conducted based on a word recognition task in the context of a sentence. One or two graphemes belonging either to the onset or the rime, or its constituents, the nucleus or the coda, were represented. We reached the conclusion that the branching onset in word initial position favours lexical recognition.

Node‐specific branching and heterochronic changes underlie population‐level differences in Mimulus guttatus (Phrymaceae) shoot architecture

Shoot architecture is a fundamentally developmental aspect of plant biology with implications for plant form, function, reproduction, and life history evolution. Mimulus guttatus is morphologically diverse and becoming a model for evolutionary biology. Shoot architecture, however, has never been studied from a developmental perspective in M. guttatus. We examined the development of branches and flowers in plants from two locally adapted populations of M. guttatus with contrasting flowering times, life histories, and branch numbers. We planted second-generation seed in growth chambers to control for maternal and environmental effects. Most branches occurred at nodes one and two of the main axis. Onset of branching occurred earlier and at a greater frequency in perennials than in annuals. In perennials, almost all flowers occurred at the fifth or more distal nodes. In annuals, most flowers occurred at the third and more distal nodes. Accessory axillary meristems and higher-order branching did not influence shoot architecture. We found no evidence for trade-offs between flowers and branches because axillary meristem number was not limiting: a large number of meristems remained quiescent. If, however, quiescence is a component of meristem allocation strategy, then meristems may be limited despite presence of quiescent meristems. At the two basalmost nodes, branch number was determined by mechanisms governing either meristem initiation or outgrowth, rather than flowering vs. branching. At the third and more distal nodes, heterochronic processes contributed to flowering time and branch number differences between populations.

Propagation Structure of a 13.56-MHz Asymmetric Surface Barrier Discharge Plasma in Atmospheric-Pressure Air

The global structure of a pulse-modulated 13.56-MHz asymmetric surface barrier discharge plasma has been investigated in atmospheric-pressure air. Intensified-CCD images were exposed over 20- μs radio-frequency pulses for three input power cases. The discharges do not appear to move significantly during the pulses, even though they are integrated over more than 200 oscillations of the applied voltage, and this allows for the observation of organized filamentary structures. The quantity and propagation length of the discharges are observed to increase with increasing input power, and the onset of branching occurs at a uniform propagation length. Subsequent to branching, a distinct decrease in luminosity is observed as the branches realign to propagate parallel to the original discharge. The spacing between the tips of the filaments is very similar to that of small indentations present on the surface of the dielectric barrier.

Dynamic Fracture of Concrete–3D Numerical Study of Compact Tension Specimen

The behavior of concrete structures is strongly influenced by the loading rate. Compared to quasi-static loading concrete loaded by impact loading acts in a different way. First, there is a strain-rate influence on strength, stiffness, and ductility, and, second, there are inertia forces activated. Both influences are clearly demonstrated in experiments. For concrete structures, which exhibit damage and fracture phenomena, the failure mode and cracking pattern depend on loading rate. Moreover, theoretical and experimental investigations indicate that after the crack reaches critical speed of propagation there is crack branching. The present paper focuses on 3D finite-element study of the crack propagation of the concrete compact tension specimen. The rate sensitive microplane model is used as a constitutive law for concrete. The strain-rate influence is captured by the activation energy theory. Inertia forces are implicitly accounted for through dynamic finite element analysis. The results of the study show that the fracture of the specimen strongly depends on the loading rate. For relatively low loading rates there is a single crack due to the mode-I fracture. However, with the increase of loading rate crack branching is observed. Up to certain threshold (critical) loading rate the maximal crack velocity increases with increase of loading rate, however, for higher loading rates maximal velocity of the crack propagation becomes independent of the loading rate. The critical crack velocity at the onset of crack branching is found to be approximately 500 to 600 m/s.

Dynamic fracture of concrete – compact tension specimen

The behavior of concrete structures is strongly influenced by the loading rate. Compared to quasi-static loading concrete loaded by impact loading acts in a different way. First, there is a strain-rate influence on strength, stiffness, and ductility, and, second, there are inertia forces activated. Both influences are clearly demonstrated in experiments. Moreover, for concrete structures, which exhibit damage and fracture phenomena, the failure mode and cracking pattern depend on loading rate. In general, there is a tendency that with the increase of loading rate the failure mode changes from mode-I to mixed mode. Furthermore, theoretical and experimental investigations indicate that after the crack reaches critical speed of propagation there is crack branching. The present paper focuses on 3D finite-element study of the crack propagation of the concrete compact tension specimen. The rate sensitive microplane model is used as a constitutive law for concrete. The strain-rate influence is captured by the activation energy theory. Inertia forces are implicitly accounted for through dynamic finite element analysis. The results of the study show that the fracture of the specimen strongly depends on the loading rate. For relatively low loading rates there is a single crack due to the mode-I fracture. However, with the increase of loading rate crack branching is observed. Up to certain threshold (critical) loading rate the maximal crack velocity increases with increase of loading rate, however, for higher loading rates maximal velocity of the crack propagation becomes independent of the loading rate. The critical crack velocity at the onset of crack branching is found to be approximately 500 m/s.

Native range variation in Capsella bursa-pastoris (Brassicaceae) along a 2500 km latitudinal transect

Capsella bursa-pastoris (L.) Medik. is a self compatible tetraploid annual species which has successfully spread to most continents and is mostly confined to man-made habitats. The colonising success may be associated with fine-scaled ecotypic differentiation, and regional adaptation. Seeds of 377 individuals from 40 provenances were collected over a distance of more than 2500 km from the Kola Peninsula in the north to the Caspian Sea in the south in Russia and from northern to southern Scandinavia. 3558 progenies were investigated in common garden field experiments in order to distinguish between phenotypic variability and genetic variation of quantitative life-history traits (onset of flowering, rosette diameter, leaf type, plant height, and branching and fruit characters). Genetic diversity and population structure was examined with isozyme analysis. Along both transects, Capsella showed clinal differentiation in phenotypic traits: e.g., the most northern and most southern provenances flowered earlier than the provenances from in between. A highly significant quadratic correlation exists between morphological traits and the degree of latitude. Distribution of leaf types showed no geographical pattern, unlike that observed for other regions. Allozyme variation follows a pattern of isolation by distance.

Architecture of inner medullary descending and ascending vasa recta: pathways for countercurrent exchange

Pathways and densities of descending vasa recta (DVR) and ascending vasa recta (AVR) in the outer zone of the inner medulla (IM) were evaluated to better understand medullary countercurrent exchange. Nearly all urea transporter B (UT-B)-positive DVR, those vessels exhibiting a continuous endothelium, descend with little or no branching exclusively through the intercluster region. All DVR have a terminal fenestrated (PV-1-positive) segment that partially overlaps with the UT-B-positive segment. This fenestrated segment descends a distance equal to approximately 15% of the length of the connecting UT-B-positive segment before formation of the first branch. The onset of branching is indicative of vessel entry into the intracluster region. The number density of UT-B-positive DVR at 3,000 mum below the OM-IM boundary is approximately 60% lower than the density at 400 mum below the OM-IM boundary, a result of DVR joining to fenestrated interconnecting vessels and an overall decline in UT-B expression. AVR that lie in the intercluster region (designated AVR(2)) lie distant from CDs and ascend to the OM-IM boundary with little or no branching. AVR(2a) represent a subcategory of AVR(2) that abut DVR. The mean DVR length (combined UT-B- and PV-1-positive segments) nearly equals the mean AVR(2a) length, implying a degree of overall equivalence in fluid and solute countercurrent exchange may exist. The AVR(2)/DVR ratio is approximately 2:1, and the AVR(2a)/DVR ratio is approximately 1:1; however, the AVR/DVR ratio determined for the full complement of fenestrated vessels is approximately 4:1. The excess fenestrated vessels include vessels of the intracluster region (designated AVR(1)). Countercurrent exchange between vasa recta occurs predominantly in the intercluster region. This architecture supports previous functional estimates of capillary fluid uptake in the renal IM.

Limited plasticity of shoot preformation in response to light by understorey saplings of common walnut (Juglans regia)

Background and aims Analysis of the variability of organogenesis and extension (two basic processes of primary growth) is needed to improve our understanding of architectural plasticity in trees. An example of such plasticity is the difference in size between fully grown shoots found at different positions on the tree. The contribution of preformation processes to these differences was explored by determining the intraspecific variability of shoot preformation of main stems of understorey saplings of Juglans regia. Methodology In 2007, two samples of annual shoots that differentiated in 2006 were taken from saplings growing in a Mediterranean mixed forest in the south of France. At the first sampling, the terminal winter bud of each parent shoot was dissected and the nodes of these buds were counted. For the second sampling, annual shoot growth was measured after the 2008 growing season. The percentage of light transmitted through the understorey was determined by hemispherical photographs. Principal results The effect of plant development (ontogeny) on the number of preformed leaves and the annual shoot extension was strong. Light availability also contributed to explaining differences in the length of annual shoots. The impact of light on the number of preformed leaves was minimal. Conclusions Ontogeny (onset of branching) and reduced irradiance both affected leaf preformation in buds of annual shoots, with ontogeny being the more influential. The results suggest that the shoot preformation did not contribute to the plasticity of morphology of annual shoots. Light availability was more influential and promoted annual shoot extension.

Complexidade prosódica e segmentação de palavras em crianças dos 4 aos 6 anos de idade

The main goal of the current study is to identify the impact of specific linguistic aspects in the task of word syllabic segmentation. Three prosodic variables were considered: syllabic complexity, word extension and word stress. The instruments for the evaluation of phonological awareness are normally conceived without underlying criteria constraining the shape of the phonological stimuli used for data collection. The present study contributes for the discussion on the relevant variables to be taken into account for the proposal of a linguistically controlled evaluation instrument in the field of phonological awareness. The syllabic segmentation task used contains 42 words and it was presented to a group of 80 Portuguese children with of mean age of 64 months. For the ‘syllabic complexity’ variable, the Onset of the first syllable of the word was controlled (CV, V, CCV). The results showed that children reach a higher rate of success for word-initial CV and V than for branching Onset. The reaction time values obtained show that the segmentation for word-initial V and CV forms are lower than the ones for word-initial CCV. As for the variable ‘word extension’, the success rates depended on this aspect: disyllabic words are easier to segment than disyllabic ones. Finally, the ‘word stress’ variable showed that the penultimate stress pattern in trisyllabic words promote the success in the children’s performance.

On the backward Lamb waves near thickness resonances in anisotropic plates

A closed-form expression for the leading-order dispersion coefficient, describing the trend of Lamb-wave branches at their onset from thickness resonances, is derived for an arbitrary anisotropic plate. The sign of this coefficient and hence of the in-plane group velocity near cutoffs decides the existence or non-existence of the backward Lamb waves without a necessity to calculate the dispersion branches. A link between the near-cutoff dispersion of Lamb waves and the curvature of bulk-wave slowness curves in a sagittal plane is analyzed. It is established that a locally concave slowness curve of a bulk mode entails the backward Lamb waves at the onset of branches emerging from this bulk mode resonances of high enough order. A simple sufficient condition for no backward Lamb waves near the resonances associated with a convex slowness curve is also noted. Two special cases are discussed: the first involves the coupled resonances of degenerate bulk waves, and the second concerns quasi-degenerate resonances which give rise to pairs of dispersion branches with a quasilinear positive and negative onset. Occasions of the backward Lamb waves in isotropic plate materials are tabulated.

Vortical structures and heat transfer in a round impinging jet

In order to gain a better insight into flow, vortical and turbulence structure and their correlation with the local heat transfer in impinging flows, we performed large-eddy simulations (LES) of a round normally impinging jet issuing from a long pipe at Reynolds number Re = 20000 at the orifice-to-plate distance H = 2D, where D is the jet-nozzle diameter. This configuration was chosen to match previous experiments in which several phenomena have been detected, but the underlying physics remained obscure because of limitations in the measuring techniques applied. The instantaneous velocity and temperature fields, generated by the LES, revealed interesting time and spatial dynamics of the vorticity and eddy structures and their imprints on the target wall, characterized by tilting and breaking of the edge ring vortices before impingement, flapping, precessing, splitting and pairing of the stagnation point/line, local unsteady separation and flow reversal at the onset of radial jet spreading, streaks pairing and branching in the near-wall region of the radial jets, and others. The LES data provided also a basis for plausible explanations of some of the experimentally detected statistically-averaged flow features such as double peaks in the Nusselt number and the negative production of turbulence energy in the stagnation region. The simulations, performed with an in-house unstructured finite-volume code T-FlowS, using second-order-accuracy discretization schemes for space and time and the dynamic subgrid-scale stress/flux model for unresolved motion, showed large sensitivity of the results to the grid resolution especially in the wall vicinity, suggesting care must be taken in interpreting LES results in impinging flows.

The Structure of Branching Onsets and Rising Diphthongs: Evidence from the Acquisition of French and Spanish

Consonant-glide-vowel (CGV) sequences are represented differently across languages. In some languages, the CG sequence is represented as a branching onset; in other languages, the GV sequence is represented as a rising diphthong. Given variable syllabification across languages, this study examines how young children represent CGV sequences. In particular, we evaluate Rose's (2000) proposal, based on French acquisition data, that CGV sequences are initially represented as rising diphthongs. To do this, we examined children's acquisition of CGV sequences in cross-sectional data from 14 French-speaking children (aged 1;10–2;10 years) and longitudinal data from five Spanish-speaking children (aged 1;3–3;0 years). Across several different measures (order of acquisition, style of acquisition, positional faithfulness, error patterns), children's production of rising diphthongs and branching onsets patterned similarly. The results suggest that at least for these children, CGV sequences are represented as branching onsets during the early stages of acquisition.

Branching onsets and syncope in English

English abounds in lexical consonant clusters, and morpheme-internal consonant clusters can also be created postlexically, by syncope (the deletion of a schwa within a word). In theories that do not recognize empty nuclei, the consonant clusters thus created are usually analysed as coda-onset clusters. This article argues that such syncope-created consonant clusters in English bear a much closer resemblance to so-called branching onsets. I argue that these two categories are not entirely distinct; rather, branching onsets are a special type of the set that includes all syncope-created clusters. I consider the three types of consonant cluster that are often distinguished in English, which I label ‘onset clusters’, ‘medial clusters’ and ‘coda clusters’, and argue, instead, for an alternative system of cluster types which has only two types, each with two subtypes; the main aim of this article is thus to question long-accepted, apparent truisms about consonant clusters.

Are children’s grammars rogue grammars? Glide substitution in branching onsets

Dans cet article nous traitons de l’existence d’un stade consonne + glide lors de l’acquisition des attaques doubles, quand le glide remplace systematiquement la liquide dans les clusters consonne + liquide. Il est generalement envisage dans la litterature que ces productions consonne + glide sont des attaques branchantes alors que de telles syllabifications ne sont attestees dans les grammaires adultes que si l’on trouve simultanement consonne + liquide en attaque branchante. D’autres possibilites de syllabification du glide sont ici discutees et l’analyse proposee est que le glide n’a pas a ce stade d’ancrage prosodique. A partir de la, nous demontrons que le type de representation proposee a des paralleles dans les grammaires adultes.

Reavaliando o estatuto silábico das seqüências obstruinte+lateral em português europeu

Segundo as descrições fonológicas e as normas ortográficas do português, todas as sequências Obstruinte+Líquida constituiriam, nesta língua, sequências tautossilábicas (Ataques ramificados), sendo heterossilábicas todas as restantes sequências C1C2. Porém, aplicando às sequências Obstruinte+Lateral alguns dos critérios que levam à classificação à parte das sequências heterossilábicas - origem histórica e certas manifestações externas do conhecimento fonológico (CF) dos falantes -, verificamos que as sequências Obstruinte+Lateral se comportam frequentemente como as sequências heterossilábicas, sobretudo quando, no tocante às manifestações do CF, se olha a dados obtidos com sujeitos sem conhecimento ortográfico. Esta verificação leva-nos a caracterizar as sequências Obstruinte+Lateral do português europeu como genuinamente heterossilábicas e, paralelamente, a aceitar a interferência do conhecimento ortográfico sobre o conhecimento fonológico dos falantes.

Branching, biomass distribution, and light capture efficiency in a pioneer tree, Rhus trichocarpa, in a secondary forest

Crown architecture and biomass distribution patterns were investigated in relation to branching and tree size in a pioneer species, Rhus trichocarpa Miq. (Anacardiaceae), in a Japanese secondary forest. Crown architecture changed with tree size and with branching. Crown depth and area were greater in taller trees. In addition, branched trees had crowns of greater depth, and crown area increased more rapidly with increasing height in branched trees as compared with unbranched trees. In contrast, biomass distribution to nonphotosynthetic and photosynthetic organs changed only with tree size and was similar in unbranched and branched trees of similar size. Light capture efficiency was related to neither height nor branching status for trees with heights of 1–2.5 m. Coexistence of unbranched and branched trees at the height around the onset of branching is possible because these trees realize similar biomass distribution patterns and light capture efficiencies. Individual leaf area and leaf area index increased with tree size in unbranched trees but decreased with tree size in branched trees. These results suggest that several leaf clusters of limited size are sparsely arranged in a large three-dimensional space in tall trees.