Tube Width Research Articles

Association Between Floral Traits and Rewards in Erysimum mediohispanicum (Brassicaceae)

Floral rewards may be associated with certain morphological floral traits and thus act as underlying factors promoting selection on these traits. This study investigates whether some traits that are under pollinator-mediated selection (flower number, stalk height, corolla diameter, corolla tube length and corolla tube width) in the Mediterranean herb E. mediohispanicum (Brassicaceae) are associated with rewards (pollen and nectar). During 2005 the phenotypic traits and the visitation rate of the main pollinator functional groups were quantified in 720 plants belonging to eight populations in south-east Spain, and during 2006 the same phenotypic traits and the reward production were quantified in 400 additional plants from the same populations. A significant correlation was found between nectar production rate and corolla tube length, and between pollen production and corolla diameter. Visitation rates of large bees and butterflies were significantly higher in plants exhibiting larger flowers with longer corolla tubes. The association between reward production and floral traits may be a factor underlying the pattern of visitation rate displayed by some pollinators.

Probing the ground state in gauge theories

We consider two very different models of the flux tube linking two heavy quarks: a string linking the matter fields and a Coulombic description of two separately gauge invariant charges. We compare how close they are to the unknown true ground state in compact U(1) and the SU(2) Higgs model. Simulations in compact U(1) show that the string description is better in the confined phase but the Coulombic description is best in the deconfined phase; the last result is shown to agree with analytical calculations. Surprisingly in the nonabelian theory the Coulombic description is better in both the Higgs and confined phases. This indicates a significant difference in the width of the flux tubes in the two theories.

Behavior of thin walled steel tube confined concrete stub columns subjected to axial local compression

The behavior of thin walled steel tube confined concrete (STCC) stub columns subjected to axial local compression was experimentally investigated in this paper. A total of 46 specimens, including 36 STCC specimens and 10 plain concrete specimens, were tested. The main parameters varied in the tests are: (1) sectional types: circular and square; (2) local compression area ratio (concrete cross-sectional area to local compression area): from 1 to 25; (3) steel tube width (or diameter)-to-wall thickness ratio, B(or D)/ t, from 52.1 to 104.7. It was found that the ultimate bearing strength of the composite sections decreases with increase local compression area ratio. The confinement action of the steel tube to core concrete and the ultimate strength of the locally loaded STCC specimens decrease with increase in steel tube width (or diameter)-to-thickness ratio. It was also found that, generally, circular steel tubes have higher confinement to their concrete core than those of the tubes with square sections when the composite members are subjected to axially local compression.

Quantitative tube model for semiflexible polymer solutions

We develop an analytical and quantitative theory of the tube model concept for entangled networks of semiflexible polymers. The absolute value of the tube diameter L perpendicular is derived as a function of the polymers' persistence length lp and mesh size xi of the network. To leading order, we find L perpendicular = 0.31xi 6/5 lp (-1/5) , which is consistent with known asymptotic scaling laws. Additionally, our theory provides finite-length corrections that can account for effects of polydispersity. We support our analytical studies by extensive computer simulations. These allow to verify assumptions essential to our theoretical description and provide an excellent agreement with the analytically calculated tube diameter. Furthermore, we present simulation data for the distribution function of tube widths in the network.

Energy dissipation via electron energization in standing shear Alfvén waves

A two-dimensional hybrid magnetohydrodynamic-kinetic electron model in dipolar coordinates is used to study the case of a fundamental mode toroidal field line resonance (FLR) centered on an L=10 closed dipolar magnetic field line. The model is initialized via a perturbation of the azimuthal shear Alfvén velocity so that only upward field aligned currents (corresponding to downwelling electrons) are present at the ionospheric boundaries during the first half wave period. It is found that the acceleration of the electrons to carry the field aligned currents can be a significant sink of Alfvén wave energy depending on the width of the flux tube. For a FLR with an equatorial perpendicular wavelength of 0.25 RE about 20% of the wave energy is dissipated over a half cycle. This varies inversely with the width of the flux tube increasing to 40% by a width of 0.15 RE, which, unless the system is driven, can completely damp the resonance in about 2–3cycles.

Combined pedicled antropyloroplasty and gastric pull-up reconstruction for corrosive esophagogastric stricture

Combined pedicled antropyloroplasty and gastric pull-up reconstruction for corrosive esophagogastric stricture

Flame–sound interaction in tubes with nonslip walls

Flame interaction with sound is studied for a premixed flame propagating to the closed end of a tube with nonslip walls. The flow geometry is similar to that in the classical Searby experiments on flame–acoustic interaction [Combust. Sci. Technol. 81 (1992) 221]. The problem is solved by direct numerical simulations of the combustion equations. The flame–sound interaction strongly influences oscillations of the flame front. Particularly, sound noticeably increases the oscillation amplitude in comparison with that in an open tube with nonreflecting boundary conditions at the ends studied previously. Oscillations become especially strong in the second part of the tube, where flame pulsations are in resonance with the acoustic wave. Parameters of the flame oscillations are investigated for different values of the tube width and length. It is demonstrated that the oscillations are stronger in wider tubes, though the investigated tube width is limited by the computational facilities. In sufficiently wide tubes, violent folding of a flame front is observed because of the flame–acoustic resonance. By increasing the Lewis number, one also increases the oscillation amplitude.

Analytical Solutions to Evaluate the Stream Tube Approach for Field‐Scale Modeling of Evaporation

Quantifying upward flow across larger areas of the landscape is important for water resources management and research involving global exchange processes. The stream tube or parallel column model may be used for this purpose. Columns should be narrow enough to account for variability of local parameters and wide enough to minimize the effect of lateral flow. To provide guidance with the selection of minimum column width, an approximate analytical solution was obtained for steady flow in a medium composed of two vertical soil columns. The normalized matric flux potential, Φ, was used as a dependent variable. The two‐dimensional solution consisted of a one‐dimensional term and a perturbation term to ensure continuity in water flux and soil pressure head, h Comparison of two‐dimensional and one‐dimensional stream tube results showed little difference in h and Φ, except near the interface. The greatest effect was found for finer textured soils. An analytical expression for the lateral flux was obtained from the solution for Φ. For “wet” conditions involving a shallow water table and high surface water contents, the lateral flux was found to be no more than 5% of the evaporative flux. For “dry” conditions with miniscule fluxes, the evaporative and lateral fluxes may be of the same order of magnitude; application of the stream tube model could involve considerable error. The analytical solutions are convenient to evaluate the impact of stream tube width for different evaporation scenarios and also to verify more elaborate numerical schemes.

Flame oscillations in tubes with nonslip at the walls

A laminar premixed flame front propagating in a two-dimensional tube is considered with nonslip at the walls and with both ends open. The problem of flame propagation is solved using direct numerical simulations of the complete set of hydrodynamic equations including thermal conduction, diffusion, viscosity, and chemical kinetics. As a result, it is shown that flame interaction with the walls leads to the oscillating regime of burning. The oscillations involve variations of the curved flame shape and the velocity of flame propagation. The oscillation parameters depend on the characteristic tube width, which controls the Reynolds number of the flow. In narrow tubes the oscillations are rather weak, while in wider tubes they become stronger with well-pronounced nonlinear effects. The period of oscillations increases for wider tubes, while the average flame length scaled by the tube diameter decreases only slightly with increasing tube width. The average flame length calculated in the present work is in agreement with that obtained in the experiments. Numerical results reduce the gap between the theory of turbulent flames and the experiments on turbulent combustion in tubes.

A New Species of Freshwater Tardigrades from Disko Island (Greenland) Increases an Unsolved Paradox in Tardigrade Systematics

During the “Workshop on Arctic tardigrades” at the Danish Arctic Station (Qeqertarsuaq, Disko Island, Greenland) an undescribed species of Dactylobiotus was found in freshwater sediments of the Isunngua spring. We have the honour and pleasure to describe this new taxon that we dedicate to all participants of that symposium, naming the species Dactylobiotus octavi sp. n. The animals appear similar to Dactylobiotus dispar and Dactylobiotus haplonyx with the presence of a very short secondary branch in the claws of the first three pairs of legs, but they differ from these species in the size of claw and buccal tube width. This new species also has peculiar ornamented eggs. The eggshell consists of bowl-like processes, each one surrounded by a band of fine pores. A morphological parsimony analysis to identify phylogenetic relationships among D. octavi sp. n. and the other Dactylobiotus species was performed, obtaining inconclusive results. The discovery of this new species increases an unsolved paradox in tardigrade systematics related to the presence of closely related species which share a very similar morphology of the animals but clearly differ in their egg morphology, while, conversely, there are species belonging to different evolutionary lines that have similar eggs, but very different adult morphology. The finding of D. octavi sp. n. increases the already high number of species found in Disko Island and once again underlines the importance of tardigrades in the biodiversity of the Arctic area.

One-step method for the self-assembly of metal nanoparticles onto facetted hollow silica tubes

An optimized synthetic approach has been developed for the exclusive formation of facetted silica tubes using a simple organic molecule i.e. ammonium tartrate as a template. The synergy of two phenomena: (a) aggregation of ammonium tartrate and (b) interaction of a hydrolysed TEOS intermediate with the ammonium tartrate aggregate, was achieved under optimized conditions (i.e. 0 °C and pH ca. 11) which resulted in the complete formation of facetted silica tubes as the sole morphology. The typical length and width of these facetted tubes were of the order of 60–100 µm and 0.4–1.2 µm, respectively. Furthermore, a novel one-step method has been developed to anchor Au and Ag nanoparticles onto these tubes. This involves surfactant coated nanoparticles and the anchoring does not necessitate the pre-functionalization of the silica walls. The method is fast, economic and in addition it can be adapted for the synthesis of other hybrid nanomaterials.

Flame dynamics in thin semi-closed tubes at different heat loss conditions

The results of detailed 2D numerical simulation of non-steady methane–air flame propagation in semi-closed tubes after ignition near the closed end are presented. Flame dynamics dependence on the tubes width for adiabatic and non-adiabatic walls is obtained. It is shown that main mechanism of front acceleration is flame surface perturbation due to hydrodynamic drag near the walls, which grows due to gas thermal expansion and flow acceleration. The mechanism of vortex formation in vicinity of the front bow point is demonstrated. The vortex is generated at the flame front velocities of the order of S l ∼ 20 m/s and may become precursor for flow turbulization at later instants. The new theoretically possible regime of gas combustion in adiabatic conditions in narrow capillary is found. It is characterized by relatively low propagation velocity and incomplete combustion.

Invited commentary

Invited commentary

The SAR train concept: An along-track formation of sar satellites for diluting the antenna area over [formula omitted] smaller satellites, while increasing performance by [formula omitted

This concept implements the coherent combination of N separate SAR flying along the same orbital arc as seen from ground. A particular case is when the N SAR are in visibility with a single one that transmits. A “signal cleaning” class of trains keeps the antenna area requirement of each individual SAR unchanged and brings a factor N advantage that applies on SNR and ambiguity protection. The main formation flying constraint is the width of the tube containing the satellite trajectories. The multiplication by N of the total antenna area is the other counterpart to these advantages. An “antenna dilution” class of train enables the distribution of an unchanged total antenna area into N smaller elementary antennas, together with multiplication by N of the SAR merit factor (swath over resolution ratio). With respect to the first class, the tube width constraint is increased and the space–time separation along the track has to be very accurate. Use of appropriate spread spectrum waveforms instead of conventional pulse waveforms removes the major part of the extra orbit constraints introduced by the “antenna dilution” class. A train of N SAR in visibility makes the concept more robust against loss of coherence and eases the metrology of the formation (DGPS). Moreover, the global energy efficiency is increased by N since with only a single transmit SAR the same performance is achieved. However, the along-track separation constraints for antenna dilution are made more stringent because of being restrained to the space domain, which reinforces the spread spectrum interest. As part of its applications, the concept can circumvent the matter of huge antenna size for SAR mission in very low frequency (P band) or at high altitude (surveillance).

Tests and calculations for hollow structural steel (HSS) stub columns filled with self-consolidating concrete (SCC)

The behaviour of self-consolidating concrete (SCC) filled hollow structural steel (HSS) stub columns subjected to an axial load was investigated experimentally. A total of 50 specimens were tested. The main parameters varied in the tests are: (1) sectional types: circular and square; (2) steel yielding strength: from 282 to 404 MPa; and (3) tube diameter or width to wall thickness ratio ( D / t or B / t ): from 30 to 134. A mechanics model is developed in this paper for concrete-filled HSS stub columns. A unified theory is described whereby a confinement factor ( ξ ) is introduced to describe the composite action of the steel tube and the filled concrete. The predicted load versus deformation relationship was in good agreement with test results. The theoretical model was used to investigate the influence of important parameters that determine the ultimate strength of the composite columns. The parametric and experimental studies provide information for the development of formulae for the calculation of the ultimate strength and the axial load versus axial strain curves of the composite columns. Comparisons are made with predicted stub column strengths using the existing codes, such as ACI-1999, AISC-LRFD-1999, AIJ-1997, BS5400-1979 and EC4-1994.

Response rate of a uniformly accelerated source in the presence of boundaries

We investigate, from the point of view of an inertial frame, the response rate of a uniformly accelerated point source interacting with a massless real scalar field in Minkowski vacuum submitted to boundary conditions on a surface of general shape with walls parallel to the source moving direction. Following the procedure developed by Higuchi, Matsas, and Sudarsky, we show that the same response rate is obtained in the coaccelerated frame assuming the existence of the Fulling-Davies-Unruh thermal bath and imposing the same boundary conditions to the thermal field. We compute the explicit form of the response rate for the case of a rectangular waveguide where Dirichlet boundary conditions are imposed to the field, obtaining a considerable inhibition of this rate for realistic tube width and particle acceleration.

Biserovus xiae sp. n. and Doryphoribius qinlingense sp. n., new species of eutardigrades from China

Two new species of tardigrades are described from China (Biserovus xiae sp. n. and Doryphoribius qinlingense sp. n.). B. xiae sp. n. is the second species of this genus. It differs from B. bindae in shorter and wider bucco-pharyngeal tube with buccal tube width pt 15.0, in relatively shorter pharyngeal tube, and in narrower and shorter common tract and much longer principal and secondary branches of the double claws. D. qinlingense differs from other species of the genus in having a smooth cuticle, or in the number of placoids, or in having claws with a well-developed common tract or with a relatively longer secondary branch.

Static potential, force, and flux-tube profile in 4D compact U(1) lattice gauge theory with the multi-level algorithm

The long range properties of four-dimensional compact U(1) lattice gauge theory with the Wilson action in the confinement phase is studied by using the multi-level algorithm. The static potential, force and flux-tube profile between two static charges are successfully measured from the correlation function involving the Polyakov loop. The universality of the coefficient of the 1/ r correction to the static potential, known as the Lüscher term, and the transversal width of the flux-tube profile as a function of its length are investigated. While the result supports the presence of the 1/ r correction, the width of the flux tube shows an almost constant behavior at a large distance.

Tubed flap interpolation in reconstruction of helical and ear lobe defects.

A useful reconstructive tool, as a delayed method, for marginal defects of the ear of more than 2.5 cm wide with no deficit of the cartilaginous frame and low scapha involvement, consists of tubed flaps raised from neighboring areas. The patients treated with this technique sustained a dog bite in three cases, a human bite in one case, a motorcycle accident in one case, and finally, a burn trauma in two cases. Three different cases of acquired marginal defects, namely ascending superior helix, descending helix, and cauda elicis with lobule involvement, are shown. In the helix reconstruction, the tube width has not to be more than 15 mm, and the tube length has to be 1 cm longer than the defect. There was no conditioning of the flaps. No pedicle bridge was interposed along the major tube. The interval between two divisions was on average approximately 5 weeks. Seven patients were treated with this technique: In all cases, we had no infections or skin necrosis. To avoid a shrinkage of the tube, a correct ratio between flap dimensions and helical defect has to be estimated. Although it is considered an old technique and it is a multistage reconstructive sequence, this procedure could be the first preference in cases of marginal defects more than 2.5 cm wide. This is because it restores naturally the anatomy of the helix.

The width of a gastric tube has no impact on outcome after esophagectomy

Background We evaluated the impact of the size of gastric tubes on tissue blood flow of the anastomotic site, the frequency of leakage and the postoperative nutritional status. Methods Forty-four patients were randomly allocated to either reconstruction using subtotal stomach (n = 22) or to reconstruction using slender gastric tube (n = 22) after esophagectomy. The tissue blood flow at the anastomotic site was measured. The postoperative nutritional status of 17 patients without recurrence was examined. Possible correlations between the type of esophageal substitute and the tendency to leakage as well as postoperative nutritional status were examined. Results There was no significant difference in the tissue blood and the frequency of leakage between the types of gastric tubes. There was no significant difference noted between the two in the postoperative nutritional status at 6 and 12 months after operation. Conclusions The width of gastric tube has no impact on tissue blood flow, the frequency of leakage, and the postoperative nutritional status after esophagectomy.