Narrow Branches Research Articles

Phylogenetic position and systematics of the bryozoan Tennysonia: further evidence for convergence and plasticity in skeletal morphology among cyclostome bryozoans

Cyclostomes are an ancient order of marine bryozoans with a fossil record extending back over 450 million years into the Ordovician. The current taxonomy of both fossil and modern cyclostomes is based almost entirely on skeletal characters but newly available sequence data are beginning to reveal rampant convergence of some of them. An unusual combination of skeletal characters in the South African cyclostome Tennysonia stellata Busk, 1867 has made this genus difficult to classify. After revising the taxonomy of Tennysonia, we use almost complete small and large ribosomal subunits (ssrDNA and lsrDNA) to demonstrate its close phylogenetic affinity with the tubuliporine genus Idmidronea (family Tubuliporidae) with which it shares a similar colony form, despite the presence of skeletally open kenozooids between the autozooids, reminiscent of cerioporine cyclostomes such as Favosipora. The spaces between the transverse rows of autozooidal apertures, occupied by exterior autozooidal frontal walls in Idmidronea, are occupied by kenozooids in Tennysonia, thereby maintaining the spacing between lophophores necessary for efficient suspension feeding. Sympatric colonies of T. stellata with narrow and broad branches are identical or almost identical on the basis of ssrDNA and lsrDNA sequences, respectively, suggesting within-species ecophenotypic plasticity in this aspect of colony form.

POPULATION PARAMETERS OF INTERMEDIATE-AGE STAR CLUSTERS IN THE LARGE MAGELLANIC CLOUD. II. NEW INSIGHTS FROM EXTENDED MAIN-SEQUENCE TURNOFFS IN SEVEN STAR CLUSTERS

We discuss new photometry from high-resolution images of 7 intermediate-age (1-2 Gyr) star clusters in the Large Magellanic Cloud taken with the Advanced Camera for Surveys on board the Hubble Space Telescope. We fit color-magnitude diagrams (CMDs) with several different sets of theoretical isochrones, and determine systematic uncertainties for population parameters when derived using any one set of isochrones. The cluster CMDs show several interesting features, including extended main sequence turnoff (MSTO) regions, narrow red giant branches, and clear sequences of unresolved binary stars. We show that the extended MSTOs are not caused by photometric uncertainties, contamination by field stars, or the presence of binary stars. Enhanced helium abundances in a fraction of cluster stars are also ruled out as the reason for the extended MSTOs. Quantitative comparisons with simulations indicate that the MSTO regions are better described by a spread in ages than by a bimodal age distribution, although we can not formally rule out the latter for the three lowest-mass clusters in our sample (which have masses lower than about 3E4 solar masses). This conclusion differs from that of some previous works which suggested that the age distribution in massive clusters in our sample is bimodal. This suggests that any secondary star formation occurred in an extended fashion rather than through short bursts. We discuss these results in the context of the nature of multiple stellar populations in star clusters.

Arbuscular mycorrhizal‐like fungi in Carboniferous arborescent lycopsids

Arbuscular mycorrhizal‐like fungi in Carboniferous arborescent lycopsids

Torque around the center of mass: dynamic stability during quadrupedal arboreal locomotion in the Siberian chipmunk ( Tamias sibiricus)

When animals travel on tree branches, avoiding falls is of paramount importance. Animals swiftly running on a narrow branch must rely on movement to create stability rather than on static methods. We examined how Siberian chipmunks ( Tamias sibiricus) remain stable while running on a narrow tree branch trackway. We examined the pitch, yaw, and rolling torques around the center of mass, and hypothesized that within a stride, any angular impulse (torque during step time) acting on the center of mass would be canceled out by an equal and opposite angular impulse. Three chipmunks were videotaped while running on a 2 cm diameter branch trackway. We digitized the videos to estimate center of mass and center of pressure positions throughout the stride. A short region of the trackway was instrumented to measure components of the substrate reaction force. We found that positive and negative pitch angular impulse was by far the greatest in magnitude. The anterior body was pushed dorsally (upward) when the forelimbs landed simultaneously, and then the body pitched in the opposite direction as both hindlimbs simultaneously made contact. There was no considerable difference between yaw and rolling angular impulses, both of which were small and equal between fore- and hindlimbs. Net angular impulses around all three axes were usually greater than or less than zero (not balanced). We conclude that the chipmunks may balance out the torques acting on the center of mass over the course of two or more strides, rather than one stride as we hypothesized.

The Climate Change Debate: A Greater and More Varied Voice from the Social Sciences

As the debate on climate change in North America and Europe has heated up, the full voice of the social sciences, for the most part, has not been heard. Indeed, the relatively small representation of academic scholarship in this debate has come predominately from the physical sciences in defining the problem, and from one narrow branch of social science – neo-classical economics – in generating solutions. Both disciplines focus heavily on the quantitative and “rational” treatments of the climate change issue, rather than on its more qualitative and less rational dimensions. In this paper, we will provide a brief overview of the ways in which a broader array of social sciences can inform the debate over the problem of climate change, and, more importantly help refine solutions. We then summarize these benefits by offering a modified model of problem and solution assessment in risk and science communication; one that moves beyond their present focus on the “rational weigher” or “irrational weigher” models for describing social responses to scientific information. We expand upon the “cultural evaluator” model in which individuals do not engage in expected-utility “weighing” of information; but rather use affective and related faculties of perception to discern the nature of the problem and what stance they should adopt toward a particular risk. Affective features, in turn, depend directly on cultural outlooks and commitments. This cultural evaluator model offers several adjustments to current approaches to climate change problem definition and solutions, particularly around the array of communication strategies to be used.

On surfaces and soreness

The objective of this study was to use a pressure plate to quantify the toe–heel load redistribution in the forelimbs of sound warmblood horses with normal shoes and shoes with a wide toe and narrow branches, used empirically in the treatment of superficial digital flexor tendon or suspensory ligament injuries. In a crossover-design study, six horses, randomly shod with normal shoes and shoes with a wide toe, were led over a dynamically calibrated pressure plate to record data from both forelimbs. There were no significant differences between both shoes in the toe–heel index of stance time, peak vertical force and vertical impulse. For the adapted shoe, the peak vertical pressure was slightly lower and was exerted slightly earlier in the stance phase, albeit not significantly. However, the significantly larger toe contact area of the adapted shoe resulted in a significantly lower total vertical pressure in the toe region. Hence, the pressure plate adequately visualised the individual loading of the toe and heel region, and clearly demonstrated the altered pressure distribution underneath the shoe with a wide toe. Although further research on a deformable surface is needed to confirm this hypothesis, the pressure redistribution from the toe to the heels could promote sinking of the heels in arena footing, thereby mimicking the biomechanical effects of a toe wedge and providing a rationale for its application in the treatment of SDFT or SL injuries. The pressure measuring equipment used in this study can offer to the clinician a diagnostic tool for the evaluation of the load distribution underneath the equine hoof and for the fine-tuning of corrective shoeing.

WHAT WAS “IT” THAT ROBBINS WAS DEFINING?

This paper argues that Robbins’ famous definition of economics was of “economic science” which he saw as only a narrow branch of the field of economics. The field of economics included both economic science—which his definition dealt with, and political economy--which his essay did not deal with. His prescriptive message was that policy belonged in the “political economy” branch of economics. He believed that while the science of economics should avoid value judgments as much as possible, the political economy (applied policy) branch of economics should, and must, include value judgments. That prescriptive message has been lost. (This abstract was borrowed from another version of this item.)

Extended Phase Field Higher-Order Active Contour Models for Networks

This paper addresses the segmentation from an image of entities that have the form of a `network', i.e. the region in the image corresponding to the entity is composed of branches joining together at junctions, e.g. road or vascular networks. We present new phase field higher-order active contour (HOAC) prior models for network regions, and apply them to the segmentation of road networks from very high resolution satellite images. This is a hard problem for two reasons. First, the images are complex, with much `noise' in the road region due to cars, road markings, etc., while the background is very varied, containing many features that are locally similar to roads. Second, network regions are complex to model, because they may have arbitrary topology. In particular, we address a limitation of a previous model in which network branch width was constrained to be similar to maximum network branch radius of curvature, thereby providing a poor model of networks with straight narrow branches or highly curved, wide branches. We solve this problem by introducing first an additional nonlinear nonlocal HOAC term, and then an additional linear nonlocal HOAC term to improve the computational speed. Both terms allow separate control of branch width and branch curvature, and furnish better prolongation for the same width, but the linear term has several advantages: it is more efficient, and it is able to model multiple widths simultaneously. To cope with the difficulty of parameter selection for these models, we perform a stability analysis of a long bar with a given width, and hence show how to choose the parameters of the energy functions. After adding a likelihood energy, we use both models to extract the road network quasi-automatically from pieces of a QuickBird image, and compare the results to other models in the literature. The state-of-the-art results obtained demonstrate the superiority of our new models, the importance of strong prior knowledge in general, and of the new terms in particular.

The Tendinous Patterns in the Palmar Surface of the Lizard Manus: Functional Consequences for Grasping Ability

In lizards, distinct patterns of the tendinous structures associated with the forearm flexors have been described. In most lizards, the m. flexor digitorum longus ends in a tendinous plate with an embedded sesamoid, from which tendons run to the terminal phalanx of each digit. This structure is known as the flexor plate. In many polychrotid lizards, however, the flexor digitorum longus muscle is continuous with individual tendons running to each digit, and no complete flexor plate is present. In most geckos, the flexor plate is reduced to a tendinous plate without sesamoid. To evaluate the consequences of these differences in morphology on locomotion and grasping, we compared the use of the fore-arm and hand in lizards exhibiting three different tendon patterns (Pogona vitticeps, an agamid with a well-developed flexor plate; Gekko gecko, a gekkonid with a flexor plate, but without an embedded sesamoid; Anolis equestris, a polychrotid without flexor plate, but showing independent tendons running to each digit) while moving on different substrates. We found that the presence of a flexor plate with sesamoid bone prevents digital flexion and creates a rather stiff palmar surface in P. vitticeps. This configuration makes it impossible for P. vitticeps to grasp narrow branches and results in a strongly impaired locomotor performance on narrow substrates. Both G. gecko and A. equestris can flex the palms of their hands and their fingers more extensively, and do so when moving on narrow substrates. We suggest that the reduction of the flexor plate in both G. gecko and A. equestris allows these animals to move effectively on narrow substrates.

Influence of the branches width on the nonlinear output characteristics of InAlAs/InGaAs-based three-terminal junctions

In this work, the influence of the geometry of the different branches on the output characteristics of InAlAs/InGaAs three-branch junctions is analyzed. At room temperature experimental measurements show that when increasing the width of the horizontal branches, the nonlinear behavior persists, even if less pronounced. This implies a reduction in the (typically high) impedance of these nanodevices, which is quite interesting in order to minimize the influence of parasitic capacitances on their cutoff frequency and to decrease the reflected power due to the mismatch with the 50 Ω standard equipment. The width of the vertical branch is also a relevant parameter, nonlinear effects being more important for narrow branches. In both cases surface charges at the etched boundaries of the branches play a key role. Monte Carlo simulations (performed with a self-consistent surface charge model recently proposed by the authors) are used to explain the physical origin of the observed behavior and to improve the device performance. We focus on the enhancement of their efficiency as a way to develop their promising functionalities in various analog and digital circuits.

Molecular analyses reveal high levels of eukaryotic richness associated with enigmatic deep-sea protists (Komokiacea)

Komokiaceans are testate agglutinated protists, extremely diverse and abundant in the deep sea. About 40 species are described and share the same main morphological feature: a test consisting of narrow branching tubules forming a complex system. In some species, the interstices between the tubules are filled by sediment, creating a mudball structure. Because of their unusual and sometimes featureless appearance, komokiaceans were frequently ignored or overlooked until they formal description in 1977. The most recent taxonomy places the Komokiacea within the Foraminifera based on general morphological features. To examine their taxonomic position at the molecular level, we analysed the SSU rDNA sequences of two species, Normanina conferta and Septuma ocotillo, obtained either with specific foraminiferal or universal eukaryotic primers. Many different sequences resulted from this investigation but none of them could clearly be attributed to komokiaceans. Although our study failed to confirm univocally that Komokiacea are foraminiferans, it revealed a huge eukaryotic richness associated with these organisms, comparable with the richness in the overall surrounding sediment. These observations suggest strongly that komokiaceans, and probably many other large testate protists, provide a habitat structure for a large spectrum of eukaryotes, significantly contributing to maintaining the biodiversity of micro- and meiofaunal communities in the deep sea.

Molecular systematics of the genus Actinotrichia (Galaxauraceae, Rhodophyta) from Taiwan, with a description of Actinotrichia taiwanica sp. nov.

Three species of Actinotrichia from Taiwan (Galaxauraceae, Rhodophyta) are described on the basis of morphological and molecular evidence, including A. fragilis, the generitype, A. robusta, a new record for Taiwan, and A. taiwanica sp. nov. Actinotrichia fragilis can be distinguished from the other two species by having a wider branching angle (usually > 40°), persistent and distinctly whorled assimilatory filaments and paraphyses issuing from the pericarp, which do not intermix with the gonimoblasts. Actinotrichia robusta can be distinguished from A. taiwanica by its narrower branches, thinner cortex, more obvious whorled assimilatory filaments and smaller fusion cell that is usually indistinguishable in the mature cystocarp. Recognition of these three species was also supported by rbcL sequence analysis. While A. fragilis is distributed in the pantropical regions of the Indian and Pacific oceans, A. robusta and A. taiwanica sp. nov. are only found along the Kuroshio Current in the northwestern Pacific Ocean.

CFD modelling and wind tunnel validation of airflow through plant canopies using 3D canopy architecture

The efficiency of pesticide application to agricultural fields and the resulting environmental contamination highly depend on atmospheric airflow. A computational fluid dynamics (CFD) modelling of airflow within plant canopies using 3D canopy architecture was developed to understand the effect of the canopy to airflow. The model average air velocity was validated using experimental results in a wind tunnel with two artificial model trees of 24 cm height. Mean air velocities and their root mean square (RMS) values were measured on a vertical plane upstream and downstream sides of the trees in the tunnel using 2D hotwire anemometer after imposing a uniform air velocity of 10 m s −1 at the inlet. 3D virtual canopy geometries of the artificial trees were modelled and introduced into a computational fluid domain whereby airflow through the trees was simulated using Reynolds-Averaged Navier–Stokes (RANS) equations and k-ε turbulence model. There was good agreement of the average longitudinal velocity, U between the measurements and the simulation results with relative errors less than 2% for upstream and 8% for downstream sides of the trees. The accuracy of the model prediction for turbulence kinetic energy k and turbulence intensity I was acceptable within the tree height when using a roughness length ( y 0 = 0.02 mm) for the surface roughness of the tree branches and by applying a source model in a porous sub-domain created around the trees. The approach was applied for full scale orchard trees in the atmospheric boundary layer (ABL) and was compared with previous approaches and works. The simulation in the ABL was made using two groups of full scale orchard trees; short ( h = 3 m) with wider branching and long ( h = 4 m) with narrow branching. This comparison showed good qualitative agreements on the vertical profiles of U with small local differences as expected due to the spatial disparities in tree architecture. This work was able to show airflow within and above the canopy in 3D in more details.

The Design and Performance of a Novel Square-Loop Patch Frequency Selective Surface

A novel stop-band Frequency selective surface (FSS) is presented. By adding four narrow branches to conventional square-loop FSS, the proposed FSS can achieve a good frequency stability for different oblique angles and a high frequency selective ability. An equivalent circuit model is used to simply analyze its transmission property. The good agreement between simulated and measured results shows the validation of our design.

CFD and PTV Steady Flow Investigation in an Anatomically Accurate Abdominal Aortic Aneurysm

There is considerable interest in computational and experimental flow investigations within abdominal aortic aneurysms (AAAs). This task stipulates advanced grid generation techniques and cross-validation because of the anatomical complexity. The purpose of this study is to examine the feasibility of velocity measurements by particle tracking velocimetry (PTV) in realistic AAA models. Computed tomography and rapid prototyping were combined to digitize and construct a silicone replica of a patient-specific AAA. Three-dimensional velocity measurements were acquired using PTV under steady averaged resting boundary conditions. Computational fluid dynamics (CFD) simulations were subsequently carried out with identical boundary conditions. The computational grid was created by splitting the luminal volume into manifold and nonmanifold subsections. They were filled with tetrahedral and hexahedral elements, respectively. Grid independency was tested on three successively refined meshes. Velocity differences of about 1% in all three directions existed mainly within the AAA sack. Pressure revealed similar variations, with the sparser mesh predicting larger values. PTV velocity measurements were taken along the abdominal aorta and showed good agreement with the numerical data. The results within the aneurysm neck and sack showed average velocity variations of about 5% of the mean inlet velocity. The corresponding average differences increased for all velocity components downstream the iliac bifurcation to as much as 15%. The two domains differed slightly due to flow-induced forces acting on the silicone model. Velocity quantification through narrow branches was problematic due to decreased signal to noise ratio at the larger local velocities. Computational wall pressure and shear fields are also presented. The agreement between CFD simulations and the PTV experimental data was confirmed by three-dimensional velocity comparisons at several locations within the investigated AAA anatomy indicating the feasibility of this approach.

Stability of the annular Poiseuille flow of a Newtonian liquid with slip along the walls

The annular Poiseuille flow a Newtonian fluid is studied assuming that slip occurs along the walls. Different slip models relating the wall shear stress to the slip velocity are employed. In the case of non-monotonic slip models with a maximum followed by a minimum, there exist linearly unstable steady-state solutions with one or both the slip velocities along the inner and outer cylinders of the annulus corresponding to the (unstable) negative-slope branch of the slip equation. The resulting flow curve is non-monotonic with one or even two narrow unstable branches corresponding to the stick–slip instability regime. The sizes of these two unstable regimes are reduced as the radii ratio is reduced. It is demonstrated that the second unstable branch may not be observed at all due to the presence of stable steady-states. These results provide a partial explanation for the absence of the stick–slip instability in annular extrusion experiments.

QRS Alternans with 2:1 Atrioventricular Conduction Block: What Is the Mechanism?

An 81-year-old woman was admitted for symptomatic bradycardia. On admission, the ECG exhibited QRS alternans, narrow QRS complex and left bundle branch block with 2:1 AV block. The patient soon had complete AV block and underwent a pacemaker implantation. An appropriate mechanism for explaining those ECG findings might be 4:1 conduction over the left bundle branch and 2:1 conduction over the right bundle branch. An ECG pattern exhibiting QRS alternans with a narrow QRS complex and bundle branch block with 2:1 AV block may suggest the coexistence of both bundle branch blocks and a high risk of complete AV block.

Distribution and morphological variation of colonies of the bryozoan Pentapora fascialis (Bryozoa: Cheilostomata) along the western coast of Italy

Bathymetric range, substrate, colony density, colony size, and some zoarial features (form of the colony and branches) of the carbonate reef building cheilostome bryozoan Pentapora fascialis (Pallas) were recorded from 15 localities along the western coast of Italy. A wide range in the depth distribution of colonies was observed (11 to 60 m). Colonies occurred on several different types of substrate including gorgonians, sponges, bedrock and rock boulders, in current swept areas. Density was approximately 1 colony/m2. The most frequent colony size-class was 10 to 20 cm in diameter and was typically found growing epizoically on gorgonians. Ellipsoidal colony forms with expanded, foliaceous laminae were characteristic of larger colonies; these frequently grew on rock substrates. Subspherical colonies with a diameter less than 20 cm grew as epizoans and had a narrow branches structure. This information will help to inform decisions on taxonomic discrepancies within the Pentaporidae. In addition the data provide a useful baseline for the future estimation of a carbonate budget in the region.

A Suprime-Cam study of the stellar population of the Ursa Major I dwarf spheroidal galaxy

We present deep and wide V , I CCD photometry of the Ursa Major I (UMa I) dwarf spheroidal galaxy (dSph) in the Local Group. The images of the galaxy were taken with the Subaru/Suprime-Cam wide field camera, covering a field of 34´ $\times$ 27´ located at the centre of the galaxy. The colour-magnitude diagram (CMD) of the UMa I dSph shows a steep and narrow red giant branch (RGB), blue and red horizontal branch (HB), and main sequence (MS) stars. A well-defined main sequence turn-off (MSTO) is found to be located at $V_{0,\rm MSTO}$ ~ 23.5 mag. The distance modulus is derived as $(m-M)_0$ = 19.93 ± 0.1 (corresponding to a distance D = 96.8 ± 4 kpc) from the V -band magnitude of the horizontal branch ($V_{0,\rm HB}$ = 20.45 ± 0.02). The mean metallicity of the RGB stars is estimated by the $V-I$ colour as [Fe/H] ~ -2.0. The turn-off age estimated by overlaying the theoretical isochrones reveals that most of stars in the UMa I dSph are formed at a very early epoch (~12 Gyr ago). The isopleth map of stellar number density of the UMa I dSph, based upon the resolved star counts of MS, RGB, HB stars as well as blue stragglers (BS), shows that the morphology of the UMa I dSph is quite irregular and distorted, suggesting that the galaxy is in a process of disruption. The very old and metal-poor nature of the stellar population implies that the star formation history of this newly discoverd faint dSph may have been different from other well-known “classical” dSphs, which show significant stellar populations of intermediate age. The stellar population of the UMa I dSph closely resembles that of Galactic old metal-poor globular clusters, but its size is typical of Galactic dSphs ( r e = 188 [pc], $r_{1/2}$ = 300 [pc]), and the shape of its spatial density contours suggests that it is undergoing tidal disruption. These characteristics of stellar population and spatial distribution of the faint galaxies help us to understand how they formed and evolved, and give a hint to the nature of the building blocks of hierarchical galaxy formation.

Drop-Size Soda Lakes: Transient Microbial Habitats on a Salt-Secreting Desert Tree

We describe a hitherto unrecognized bacterial community, inhabiting the leaf surfaces of the salt-excreting desert tree Tamarix. High temperatures, strong radiation, and very low humidity dictate a daytime existence in complete desiccation, but damp nights allow the microbial population to proliferate in a sugar-rich, alkaline, and hypersaline solution, before drying up again after sunrise. The exclusively bacterial population contains many undescribed species and genera, but nevertheless appears to be characterized by relatively limited species diversity. Sequences of 16S rRNA genes from either isolates or total community DNA place the identified members of the community in five bacterial groups (Actinobacteria, Bacteroidetes, Firmicutes, alpha-, and gamma-Proteobacteria); in each of these, they concentrate in a very narrow branch that in most cases harbors organisms isolated from unrelated halophilic environments.